WO2025149508A1

WO2025149508A1 - Removal of the unpleasant smell in calcium carbonate filled polymer compositions

Info

Publication number: WO2025149508A1
Application number: PCT/EP2025/050314
Authority: WO
Inventors: Joris BARANGER; Matthias Welker; Louise MCCULLOCH; Fabio Ippolito; Samuel Rentsch; Craig Deporter; René Vinzenz Blum
Original assignee: Omya International AG
Current assignee: Omya International AG
Priority date: 2024-01-10
Filing date: 2025-01-08
Publication date: 2025-07-17
Anticipated expiration: 2026-07-10
Also published as: MX2026002156A

Abstract

The present invention relates to a manufacturing process comprising the reaction of an oxidizable sulfur impurity of a natural calcium carbonate with at least one inorganic peroxide and the use of at least one inorganic peroxide for reducing the odor of a calcium carbonate-containing polymer compound.

Description

Removal of the unpleasant smell in calcium carbonate filled polymer compositions

The present invention relates to a manufacturing process comprising mixing at least one inorganic peroxide with a (ground) natural calcium carbonate comprising an oxidizable sulfur impurity and the use of at least one inorganic peroxide for reducing the odor of a calcium carbonate-containing polymer compound.

Calcium carbonate is widely used as a filler component in a variety of applications, such as in papers, coatings, paints and plastics. Calcium carbonate can be used as a “functional” filler to provide advantageous properties in such applications, for example, improved whiteness, improved mechanical properties, improved breathability and/or improved barrier properties. One of the advantages of calcium carbonate, compared to other conventionally employed fillers, such as titanium dioxide, kaolin, carbon black, barium sulfate, or silica, is its relatively low price, because calcium carbonate is a relatively abundant naturally occurring mineral. It is found, e.g., in mineral form as chalk, limestone, marble or dolomite, and in biological form as eggshells, oyster shells or seashells.

The quality and purity of natural calcium carbonate minerals mined in different quarries may vary greatly. For example, calcium carbonate is most often associated with several gangue minerals, such as iron, magnesium or silicate minerals. Additionally, since natural calcium carbonate deposits can have a biological origin, associated contaminants, such as sulfur compounds, may be present. Sulfur compounds, such as hydrogen sulfide, are known to have a very intense unpleasant smell. Still, such unpleasant smell may not be noticeable in a natural calcium carbonate contaminated with such sulfur compounds, because, e.g., the sulfur compounds are present in very small amounts, present as inclusions in the mineral structure or are adsorbed onto the surface of the calcium carbonate.

Similarly, calcium carbonate of biological origin may contain a variety of organic residues, among them sulfur compounds.

However, if the natural calcium carbonate is comminuted or is heated to higher temperatures, the sulfur compounds, such as hydrogen sulfide, may be liberated, such that the unpleasant smell becomes noticeable. Both comminution and heating are required in order to incorporate natural calcium carbonate into a polymer matrix, because the calcium carbonate must have a suitable particle size to be incorporated into the matrix, and because compounding the calcium carbonate with the polymer requires heating the polymer beyond its softening point. Accordingly, during production of a filled polymer compound, the unpleasant smell evolves and may remain noticeable in the product, i.e. the filled polymer compound. Manufacturers or consumers may not accept odorous polymer compounds.

Therefore, there is a need for reducing or removing the unpleasant smell that can be associated with calcium carbonate-filled polymers. However, at the same time, the costs should not increase or increase only slightly.

Accordingly, it is one objective of the present invention to provide a process that is able to reduce or remove the unpleasant smell that can be associated with calcium carbonate-filled polymers at acceptable costs and without adding too much complexity to the process.

One or more of the foregoing objectives are achieved by the subject-matter as defined in the independent claims. Summary of the Invention

According to one aspect of the present invention, a manufacturing process is provided. The process comprises the steps of a) providing a natural calcium carbonate comprising an oxidizable sulfur impurity, b) providing at least one inorganic peroxide, c) grinding the natural calcium carbonate of step a) to a desired particle size to obtain a ground natural calcium carbonate, wherein

- the at least one inorganic peroxide of step b) is mixed with the natural calcium carbonate of step a) prior to grinding step c) and/or during grinding step c), and/or

- the at least one inorganic peroxide of step b) is mixed with the ground natural calcium carbonate of step c).

The present inventors found that the presence of oxidizable sulfur impurities, such as hydrogen sulfide, may lead to the evolution of an unpleasant smell during or after incorporation of the calcium carbonate into a polymer matrix, e.g. by extrusion, even though the smell may not be noticeable in the natural calcium carbonate. Moreover, it was surprisingly found that the smell could be reduced or even avoided, if the natural calcium carbonate is treated with at least one inorganic peroxide before the calcium carbonate is incorporated into the polymer matrix, for example already during the grinding process or during a surface-treatment process. Thus, the at least one inorganic peroxide can be used as an additive during the production of the final ground natural calcium carbonate or surface-treated natural calcium carbonate without the need for any additional process step. According to the inventive process, there is also no need to remove said additive or potential reaction products prior to further processing. Finally, the inventive process may even improve grinding efficiency and/or throughput.

According to a preferred embodiment of the present invention, the process further comprises the steps of d) providing at least one surface-treatment agent, and e) mixing the at least one surface-treatment agent of step d) with the ground natural calcium carbonate of step c) to obtain a surface-treated natural calcium carbonate.

In such embodiment, the at least one inorganic peroxide of step b) is preferably mixed with the ground natural calcium carbonate of step c) before and/or during mixing step e).

According to a further preferred embodiment of the present invention, the process further comprises the steps of f) providing at least one polymer, and g) compounding the ground natural calcium carbonate of step c) and/or the surface-treated calcium carbonate of step e) with the at least one polymer of step f) to obtain a calcium carbonate- containing polymer compound.

According to yet another preferred embodiment of the present invention, the natural calcium carbonate of step a) is a natural calcium carbonate-containing mineral, preferably selected from the group consisting of chalk, limestone, marble, dolomite and mixtures thereof. The natural calcium carbonate of step a) may have an oxidizable sulfur impurity content of at least 0.7 mg/kg, preferably at least 2 mg/kg, more preferably at least 5 mg/kg, even more preferably at least 10 mg/kg and most preferably at least 25 mg/kg, based on the total weight of the natural calcium carbonate.

The oxidizable sulfur impurity may be selected from the group consisting of sulfides, polysulfides, elemental sulfur, sulfites, thiosulfates, mercaptans, dialkyl mercaptans and mixtures thereof, preferably selected from the group consisting of sulfides, polysulfides, elemental sulfur and mixtures thereof and most preferably the oxidizable sulfur impurity is a sulfide.

According to still another preferred embodiment of the present invention, the at least one inorganic peroxide is mixed with the natural calcium carbonate of step a) and/or the ground natural calcium carbonate of step c) in a total amount of at least 100 ppm by weight, preferably in a total amount from 100 to 5000 ppm by weight, more preferably in a total amount from 200 to 2000 ppm by weight, based on the total dry weight of the respective calcium carbonate.

According to a preferred embodiment of the present invention, the at least one inorganic peroxide is selected from the group consisting of hydrogen peroxide, alkali metal peroxides, alkaline earth metal peroxides, peroxyborates, peroxycarbo nates, peroxysulfates and mixtures thereof, preferably selected from the group consisting of hydrogen peroxide, alkali metal peroxides, alkaline earth metal peroxides and mixtures thereof, more preferably selected from the group consisting of hydrogen peroxide, alkaline earth metal peroxides and mixtures thereof, and most preferably wherein the at least one inorganic peroxide is hydrogen peroxide.

According to another preferred embodiment of the present invention, in step c) a grinding aid is present, preferably wherein the grinding aid is selected from at least one polyol, optionally wherein the polyol comprises amine groups, more preferably wherein the grinding aid is selected from at least one diol or triol, optionally comprising amine groups, even more preferably wherein the grinding aid is selected from the group consisting of ethanediol, propanediol, glycerol, diethanolamine, triethanolamine and mixtures thereof, and most preferably wherein the grinding aid is 1 ,2-propanediol.

Preferably, the grinding aid is present in an amount of at least 50 ppm, preferably at least 100 ppm, more preferably at least 200 ppm and most preferably at least 500 ppm, based on the total dry weight of the natural calcium carbonate. For example, the grinding aid may be present in an amount ranging from 50 ppm to 20,000 ppm, preferably 100 to 10,000 ppm, and most preferably 200 to 8,000 ppm, e.g., 500 to 7,000 ppm, based on the total dry weight of the natural calcium carbonate.

According to yet another preferred embodiment of the present invention, the ground natural calcium carbonate of step c) has i) a weight median particle size dso value in the range from 0.1 pm to 25 pm, preferably from 0.25 pm to 5 pm and most preferably from 0.5 pm to 4 pm, and/or ii) a top cut (cfos) of < 100 pm, preferably < 40 pm, more preferably < 25 pm and most preferably < 15 pm, and/or iii) a specific surface area (BET) of from 0.5 to 150 m²/g, preferably from 0.5 to 50 m²/g, more preferably from 0.5 to 35 m²/g and most preferably from 0.5 to 10 m²/g as measured by the BET nitrogen method, and/or iv) a residual total moisture content of from 0.01 wt.-% to 1 wt.-%, preferably from 0.01 to 0.2 wt.-%, more preferably from 0.02 to 0.2 wt.-% and most preferably from 0.03 to 0.2 wt.-%, based on the total dry weight of the at least one calcium carbonate-containing filler material.

According to still another preferred embodiment of the present invention, the surface-treatment agent is selected from i. a phosphoric acid ester blend of one or more phosphoric acid monoester and/or one or more phosphoric acid di-ester and/or a salt thereof, and/or ii. at least one saturated aliphatic linear or branched carboxylic acid preferably having a total amount of carbon atoms from C4 to C24 and/or a salt thereof, and/or

Hi. at least one aliphatic aldehyde, and/or iv. at least one mono-substituted succinic anhydride consisting of succinic anhydride mono-substituted with a group selected from a linear, branched, aliphatic and cyclic group having a total amount of carbon atoms from at least C2 to C30 in the substituent and/or a salt thereof, and/or v. at least one polydialkylsiloxane, and/or vi. mixtures of the materials according to i. to v..

Preferably, the surface-treatment agent is added in an amount from 0.1 to 2 wt.-%, preferably from 0.2 to 1 .5 wt.-% and most preferably from 0.4 to 1 .2 wt.-%, based on the total dry weight of the ground natural calcium carbonate and/or wherein the surface-treatment agent is added in an amount from 0.5 to 5 mg/m², preferably from 1 to 4 mg/m² and most preferably from 1 .3 to 3 mg/m², based on the total surface area of the ground natural calcium carbonate.

A second aspect of the present invention relates to the use of at least one inorganic peroxide for reducing the odor of a calcium carbonate-containing polymer compound, wherein the at least one inorganic peroxide is contacted with a particulate natural calcium carbonate comprising an oxidizable sulfur impurity prior to compounding it with the polymer.

Preferably, the at least one inorganic peroxide is contacted with the particulate natural calcium carbonate before and/or during a grinding step and/or before and/or during a surface-treatment step.

According to a preferred embodiment of the present aspect, the particulate natural calcium carbonate is a particulate natural calcium carbonate-containing mineral, preferably selected from the group consisting of chalk, limestone, marble, dolomite and mixtures thereof.

According to another preferred embodiment of the present aspect, the at least one inorganic peroxide is contacted with the particulate natural calcium carbonate in an amount of at least 100 ppm by weight, preferably in an amount from 100 to 5000 ppm by weight, more preferably in an amount from 200 to 3000 ppm by weight, based on the total dry weight of the particulate natural calcium carbonate.

According to still another preferred embodiment of the present aspect, the at least one inorganic peroxide is selected from the group consisting of hydrogen peroxide, alkali metal peroxides, alkaline earth metal peroxides, peroxyborates, peroxycarbo nates, peroxysulfates and mixtures thereof, preferably selected from the group consisting of hydrogen peroxide, alkali metal peroxides, alkaline earth metal peroxides and mixtures thereof, more preferably selected from the group consisting of hydrogen peroxide, alkaline earth metal peroxides and mixtures thereof, and most preferably wherein the at least one inorganic peroxide is hydrogen peroxide.

It should be understood that for the purposes of the present invention, the following terms have the following meanings.

The term “oxidizable sulfur impurity” in the meaning of the present invention refers to a chemical compound comprising at least one sulfur atom, which is able to react with the at least one inorganic peroxide in an oxidation reaction, for example, by ‘replacing’ a free electron pair of the sulfur atom by an oxygen atom, optionally by additionally breaking sulfur-sulfur bonds.

A “natural calcium carbonate” refers to a calcium carbonate of natural origin.

The term “ground natural calcium carbonate” (GNCC) as used herein refers to a particulate material obtained from natural calcium carbonate-containing sources (e.g. from minerals such as chalk, limestone, marble or dolomite, or from biological sources, such as eggshells, oyster shells or seashells) which has been processed in a wet and/or dry comminution step, such as crushing and/or grinding, and optionally has been subjected to further steps such as screening and/or fractionation, for example, by a cyclone or a classifier.

An “inorganic peroxide” is understood to be a chemical compound or mixture of compounds comprising an oxygen-oxygen single bond and not comprising a hydrocarbon-based moiety.

The “particle size” of particulate materials herein is described by its distribution of particle sizes c/x(wt). Therein, the value c/_x(wt) represents the diameter relative to which x % by weight of the particles have diameters less than c/_x(wt). This means that, for example, the c/2o(wt) value is the particle size at which 20 wt.% of all particles are smaller than that particle size. The cfeo(wt) value is thus the weight median particle size, i.e. 50 wt.% of all particles are smaller than that particle size and the c/9s(wt) value, referred to as weight-based top cut, is the particle size at which 98 wt.% of all particles are smaller than that particle size. Alternatively, the “particle size” can be described as volume-based particle size distribution c/_x(vol). Therein, the value c/_x(vol) represents the diameter relative to which x % by volume of the particles have diameters less than c/_x(vol). This means that, for example, the c/2o(vol) value is the particle size at which 20 vol.% of all particles are smaller than that particle size. The cfeo(vol) value is thus the volume median particle size, i.e. 50 vol.% of all particles are smaller than that particle size and the cfo8(vol) value, referred to as volume-based top cut, is the particle size at which 98 vol.% of all particles are smaller than that particle size.

In case of particle sizes of 45 pm or greater, fractional sieving according to the ISO 3310-1 :2000(E) standard can be used in all cases to determine particle size distributions.

Throughout the present document, the term “specific surface area” (in m²/g), which is used to define calcium carbonate or other materials, refers to the specific surface area as determined by using the BET method (using nitrogen as adsorbing gas), as measured according to ISO 9277:2010.

Unless indicated otherwise, the “residual total moisture content” of a material refers to the percentage of moisture (i.e. water) which may be desorbed from a sample upon heating to 220 °C. The “residual total moisture content” is determined according to the Coulometric Karl Fischer measurement method, wherein the filler material is heated to 220°C, and the water content released as vapor and isolated using a stream of nitrogen gas (at 100 ml/min) is determined in a Coulometric Karl Fischer unit (e.g. Mettler-Toledo coulometric KF Titrator C30, combined with Mettler-Toledo oven DO 0337).

The “dry weight” of any calcium carbonate disclosed herein can be determined using a Moisture Analyser MJ33 (Mettler-Toledo, Switzerland), with the following settings: drying temperature of 160 °C, automatic switch off if the mass does not change more than 1 mg over a period of 30 s, standard drying of 5 g of suspension.

A “surface-treatment agent” in the meaning of the present invention is a compound that is able to react with or adsorb onto the surface of the ground natural calcium carbonate, such that the ground natural calcium carbonate is at least partially coated with the surface-treatment agent.

As used herein, the term “polymer” generally includes homopolymers and co-polymers such as, for example, block, graft, random and alternating copolymers, as well as blends and modifications thereof. The polymer can be an amorphous polymer, a crystalline polymer, or a semi-crystalline polymer, i.e. a polymer comprising crystalline and amorphous fractions. The degree of crystallinity is specified in percent and can be determined by differential scanning calorimetry (DSC). An amorphous polymer may be characterized by its glass transition temperature and a crystalline polymer may be characterized by its melting point. A semi-crystalline polymer may be characterized by its glass transition temperature and/or its melting point.

A “grinding aid” as used herein is an additive that is present in the grinding step, facilitates grinding, and/or assists in particle size reduction and may increase capacity and effectiveness of the grinding process.

Where an indefinite or definite article is used when referring to a singular noun, e.g., “a”, “an” or “the”, this includes a plural of that noun unless anything else is specifically stated.

Where the term “comprising” is used in the present description and claims, it does not exclude other elements. For the purposes of the present invention, the term “consisting of’ is considered to be a preferred embodiment of the term “comprising”. If hereinafter a group is defined to comprise at least a certain number of embodiments, this is also to be understood to disclose a group, which preferably consists only of these embodiments.

Terms like “obtainable” or “definable” and “obtained” or “defined” are used interchangeably. This, for example, means that, unless the context clearly dictates otherwise, the term “obtained” does not mean to indicate that, for example, an embodiment must be obtained by, for example, the sequence of steps following the term “obtained” though such a limited understanding is always included by the terms “obtained” or “defined” as a preferred embodiment.

Whenever the terms “including” or “having” are used, these terms are meant to be equivalent to “comprising” as defined hereinabove.

In the following, details and preferred embodiments of the inventive process and the inventive use will be set out in more detail. It is to be understood that the technical details and embodiments, which are described for any one of the aspects of the present invention, also apply to each of the remaining aspects of the invention.

Step a) - Providing a natural calcium carbonate comprising an oxidizable sulfur impurity

In step a) of the inventive process, a natural calcium carbonate is provided. The type of natural calcium carbonate is not particularly limited. The natural calcium carbonate may be, e.g., a natural calcium carbonate-containing mineral, preferably selected from the group consisting of chalk, limestone, marble, dolomite and mixtures thereof.

Such natural calcium carbonate can be distinguished from, e.g., precipitated calcium carbonate. A “precipitated calcium carbonate” (PCC) in the meaning of the present invention is a synthesized material, obtained by precipitation following a reaction of carbon dioxide and calcium hydroxide (hydrated lime) in an aqueous environment. Alternatively, precipitated calcium carbonate can also be obtained by reacting calcium- and carbonate salts, for example calcium chloride and sodium carbonate, in an aqueous environment. PCC may have a vateritic, calcitic or aragonitic crystalline form. PCCs are described, for example, in EP 2 447 213 A1 , EP 2 524 898 A1 , EP 2 371 766 A1 , EP 2 840 065 A1 , or WO 2013/142473 A1 . Thus, it is appreciated that the natural calcium carbonate is not a precipitated calcium carbonate.

Alternatively, the natural calcium carbonate may be from biological sources, such as eggshells, oyster shells or seashells. The eggshell may be a bird eggshell, preferably a quail eggshell, a chicken eggshell, a duck eggshell, a goose eggshell, or an ostrich eggshell. The chicken eggshell may be a white chicken eggshell, a brown chicken eggshell, or a combination of both.

According to one embodiment of the present invention, the natural calcium carbonate is at least 80 wt.-%, e.g. at least 95 wt.-%, preferably between 97 and 100 wt.-%, more preferably between 98.5 and 99.95 wt.-% pure, based on the total dry weight of the natural calcium carbonate. Accordingly, it is preferred that the natural calcium carbonate comprises at most 20 wt.-%, preferably at most 5 wt.-%, more preferably from 0 to 3 wt.-% and most preferably from 0.05 to 1 .5 wt.-% of compounds (e.g., minerals) other than calcium carbonate CaCCh (or dolomite CaMg(CC>3)2), based on the total dry weight of the natural calcium carbonate.

As the natural calcium carbonate is ground in step c), the form and particle size of the natural calcium carbonate is not particularly limited. For example, the natural calcium carbonate may have a particle size in the range from 0.1 to 10 mm, preferably from 0.2 to 5 mm, and most preferably from 0.5 to 4 mm. The natural calcium carbonate may have undergone one or more pre-treatment steps, such as a crushing step or a beneficiation step. If the initial particle size of the crude natural calcium carbonate is above the specified range, i.e., above 10 mm, preferably above 5 mm, more preferably above 4 mm, a crushing step is performed as a pre-treatment step.

The natural calcium carbonate to be used in the present invention comprises an oxidizable sulfur impurity.

The present inventors surprisingly found that such oxidizable sulfur impurity may cause an undesired odor during processing of natural calcium carbonate, e.g. during compounding of the same with a polymer, which requires heating the natural calcium carbonate and the polymer to above the softening point of the polymer. The smell may not be noticeable in the natural calcium carbonate as such, because the oxidizable sulfur impurity may be present in very small amounts, may be encapsulated in the natural calcium carbonate and/or may be adsorbed onto the surface of the natural calcium carbonate. However, once the natural calcium carbonate is processed, even very small amounts of oxidizable sulfur impurity may cause a noticeable unpleasant smell. The present inventive process is able to remove such oxidizable sulfur impurity before an eventual compounding step, thereby reducing or removing the unpleasant smell that is encountered during processing of the natural calcium carbonate.

Accordingly, in a preferred embodiment, the natural calcium carbonate of step a) has an oxidizable sulfur impurity content of at least 0.7 mg/kg, preferably at least 2 mg/kg, more preferably at least 5 mg/kg, even more preferably at least 10 mg/kg and most preferably at least 25 mg/kg, based on the total weight of the natural calcium carbonate.

The oxidizable sulfur impurity content may be measured by any method known to the skilled person, for example, by ion-exchange chromatography or colorimetric methods. For example, the presence and amount of hydrogen sulphide may be determined with a colorimetric analysis using methylene blue as coloration reagent. Preferably, this method involves dissolving the samples with HCI and passing the resulting gases (CO2 and H2S) into a zinc acetate solution where the H2S is trapped. The coloration reagent is added and the absorbance of this solution is then measured at 666nm (UV-VIS). As another example, the total sulfur content may be determined, e.g., by ICP-OES, by XRF spectrometry (e.g. ASTM E1621-21 or ISO 29581-2:2010), by elemental analysis (also termed CHNS analysis), by UV fluorescence or microcoulometry, and the amount of non-oxidizable sulfur impurities that may additionally be present, i.e., sulfate, may be subtracted. The sulfate content may be determined, e.g. by ASTM C1580-20. A representative method is provided by Mahanta et al., Atomic Spectroscopy 2017, 38, pages 99-105. If the sample does not contain sulfur impurities other than the oxidizable sulfur impurity, the total sulfur content corresponds to the oxidizable sulfur impurity content.

In a preferred embodiment, the oxidizable sulfur impurity is selected from the group consisting of sulfides, polysulfides, elemental sulfur, sulfites, thiosulfates, mercaptans, dialkyl mercaptans and mixtures thereof, preferably selected from the group consisting of sulfides, polysulfides, elemental sulfur and mixtures thereof.

Sulfides are understood to include hydrogen sulfide (H2S) and salts with an S^2- or HS- anion, e.g., alkali sulfide salts, such as sodium or potassium sulfide, or alkaline earth sulfide salts, e.g., calcium or magnesium sulfide.

Polysulfides are understood to be anions comprising S-S bonds, e.g., S_n ^2-. Elemental sulfur is understood to encompass all allotropes of sulfur, preferably a-, p- and/or y-Sa. Sulfites are understood to be salts with the anion SOa^2- or HSO3" Thiosulfates are understood to include salts with the anion S2O3^2- or HS2O3-. A mercaptan in the meaning of the present invention is an organic compound including a sulfur atom bound to at least one carbon atom, i.e., R¹-S_n-R², with R¹ being an organyl group, R² being hydrogen, a cation (such as an alkali or alkaline earth metal cation), or an organyl group, and n being 1 , 2 or more, preferably 1 . A “thioalcohol” is understood to be a mercaptan, wherein R²=H. Examples of mercaptans include dimethyl sulfide, dimethyl disulfide, methanethiol, ethanethiol, tert-butylthiol, propanethiol, thiophenol, and benzyl mercaptane. A dialkyl mercaptan, accordingly, is understood to be a compound R¹-S-R² with R¹ and R² being independently from another alkyl groups.

Most preferably, the oxidizable sulfur impurity is a sulfide, e.g., hydrogen sulfide or a salt thereof. For example, the natural calcium carbonate may comprise hydrogen sulfide, sodium sulfide and/or calcium sulfide. Step b) - Providing at least one inorganic peroxide

In step b) of the inventive process, at least one inorganic peroxide is provided. The peroxide is capable of reacting with the oxidizable sulfur impurity, which is transformed into an oxidized sulfur impurity. For example, organic sulfides such as dialkyl mercaptanes can be oxidized to the corresponding sulfoxide or sulfone, and elemental sulfur or sulfides can be oxidized to sulfites and/or sulfates. As a specific example, calcium sulfide can be oxidized to calcium sulfate, which may remain in the product, as it is a non-odorous mineral.

The use of an inorganic peroxide has several advantages over the use of odor absorbing compounds, such as zeolites, of odor masking agents, such as fragrances, and of other oxidizing agents. More precisely, odor absorbing compounds, especially zeolites, are comparatively coarse and may be incompatible with applications requiring very fine calcium carbonate particle sizes. Moreover, they also tend to be expensive and to absorb surface-treatment agents, thereby reducing both the efficiency of the zeolite and of the surface treatment. Odor masking agents, such as fragrances, e.g. menthol or vanillin, merely cover, but do not remove the unpleasant smell, and have an intense smell by themselves, which may be undesirable or even perceived as obnoxious. Not least, odor masking agents are volatile compounds, such that their efficiency is only of short duration. Other oxidizing agents, such as metals, e.g., iron(ll) or copper(l) salts, tend to discolor the calcium carbonate and the polymer compounds comprising the same. Odor scavengers, such as cyclodextrins, tend to be prohibitively expensive.

Moreover, common odor absorbing compounds or fragrances are usually added during compounding of the polymer compound, whereas the at least one inorganic peroxide can be added already during the grinding and/or surface-treatment step. Thus, a ready-to-use (surface-treated) ground natural calcium carbonate is obtained by the inventive process. A polymer compound comprising the same has similar or identical optical and mechanical properties as a polymer compound comprising a calcium carbonate that has not been treated with the at least one inorganic peroxide.

Another advantage of the use of an inorganic peroxide is the fact that excess inorganic peroxide, which is not required for complete oxidation of the oxidizable sulfur impurity, decomposes during the inventive process. Accordingly, the at least one inorganic peroxide does not negatively affect the properties of the ground natural calcium carbonate, e.g., when it is compounded with a polymer. Therefore, the amount of the at least one inorganic peroxide is not particularly limited. The minimum amount is selected such that the content of the oxidizable sulfur impurity is reduced to an extent that the odor is effectively reduced, and the maximum amount is mainly determined by economic considerations.

Accordingly, in a preferred embodiment of the present invention, the at least one inorganic peroxide is mixed with the natural calcium carbonate of step a) in a total amount of at least 100 ppm by weight, preferably in a total amount from 100 to 5000 ppm by weight, more preferably in a total amount from 200 to 2000 ppm by weight, even more preferably in a total amount from 200 to 1000 ppm by weight or from 200 to 500 ppm based on the total dry weight of the natural calcium carbonate. Additionally or alternatively, the at least one inorganic peroxide is mixed with the ground natural calcium carbonate of step c) in a total amount of at least 100 ppm by weight, preferably in a total amount from 100 to 5000 ppm by weight, more preferably in a total amount from 200 to 2000 ppm by weight, even more preferably in a total amount from 200 to 1000 ppm by weight, based on the total dry weight of the ground natural calcium carbonate.

Alternatively, the at least one inorganic peroxide is mixed with the natural calcium carbonate of step a) in a total amount of at least 100 ppm by weight, preferably in a total amount of at least 200 ppm, more preferably in a total amount of at least 300 ppm by weight, and most preferably in a total amount of at least 500 ppm by weight. Additionally or alternatively, the at least one inorganic peroxide is mixed with the ground natural calcium carbonate of step c) in a total amount of at least 100 ppm by weight, preferably in a total amount of at least 200 ppm, more preferably in a total amount of at least 300 ppm by weight, and most preferably in a total amount of at least 500 ppm by weight.

Additionally or alternatively, it is preferred that the at least one inorganic peroxide is selected from the group consisting of hydrogen peroxide (H2O2), alkali metal peroxides, alkaline earth metal peroxides, peroxyborates, peroxycarbonates, peroxysulfates and mixtures thereof, preferably selected from the group consisting of hydrogen peroxide, alkali metal peroxides, alkaline earth metal peroxides and mixtures thereof, more preferably selected from the group consisting of hydrogen peroxide, alkaline earth metal peroxides (such as calcium peroxide) and mixtures thereof, and most preferably wherein the at least one inorganic peroxide is hydrogen peroxide. The hydrogen peroxide is preferably added as an aqueous solution comprising from 1 to 50 wt.-%, e.g., from 3 to 30 wt.-% H2O2. The calcium peroxide may be used as a solid with about 75% purity.

Suitable alkali metal peroxides include lithium peroxide, sodium peroxide and potassium peroxide. Suitable alkaline earth metal peroxides include calcium peroxide, magnesium peroxide, strontium peroxide and barium peroxide. Suitable peroxyborates include sodium perborate. Suitable peroxycarbonates include sodium percarbonate. Suitable peroxysulfates include sodium peroxo mo nosulfate, potassium peroxomonosulfate, sodium persulfate, ammonium persulfate and potassium persulfate.

The at least one inorganic peroxide can be used in pure form or dissolved or suspended in a solvent, preferably water. If the at least one inorganic peroxide is used in pure or suspended form and is a solid, it is added before and/or during grinding step c). If the at least one inorganic peroxide is dissolved in a solvent and/or is a liquid, it can be added either before and/or during grinding step c) or after grinding step c), e.g., before and/or during mixing step e), as outlined in detail below.

In a particularly preferred embodiment, the at least one inorganic peroxide is hydrogen peroxide, which is mixed with the natural calcium carbonate of step a) and/or the ground natural calcium carbonate of step c) in a total amount of at least 100 ppm by weight, preferably in a total amount from 100 to 5000 ppm by weight, more preferably in a total amount from 200 to 2000 ppm by weight, based on the total dry weight of the respective natural calcium carbonate.

Even more preferably, the at least one inorganic peroxide is hydrogen peroxide, which is mixed with the natural calcium carbonate of step a) and/or the ground natural calcium carbonate of step c) in a total amount of at least 100 ppm by weight, preferably in a total amount from 100 to 5000 ppm by weight, more preferably in a total amount from 200 to 2000 ppm by weight, based on the total dry weight of the ground natural calcium carbonate, and the oxidizable sulfur impurity is selected from the group consisting of sulfides, polysulfides, elemental sulfur and mixtures thereof, preferably the oxidizable sulfur impurity is a sulfide.

Step c) - Grinding

In step c) of the inventive process, the natural calcium carbonate of step a) is ground to a desired particle size to obtain a ground natural calcium carbonate.

The ground natural calcium carbonate may be obtained by dry grinding or by wet grinding and optionally subsequent drying. Preferably, the ground natural calcium carbonate is obtained by dry grinding.

In general, the grinding step can be carried out with any conventional grinding device, for example, under conditions such that comminution predominantly results from impacts with a secondary body, i.e. in one or more of: a ball mill, a rod mill, a vibrating mill, a roll crusher, a centrifugal impact mill, a vertical bead mill, an attrition mill, a pin mill, a hammer mill, a pulveriser, a shredder, a de-clumper, a knife cutter, or other such equipment known to the skilled man, preferably in a ball mill and/or a pin mill.

In case the natural calcium carbonate is wet ground, the grinding step may be performed under conditions such that autogenous grinding takes place and/or by horizontal ball milling, and/or other such processes known to the skilled man. The wet processed ground natural calcium carbonate thus obtained may be washed and dewatered by well-known processes, e.g. by flocculation, filtration or forced evaporation prior to drying. During the wet grinding process, the total solids content of the slurry preferably is in the range from 20 to 80 wt.-%, more preferably from 30 to 70 wt.-%. The subsequent step of drying may be carried out in a single step such as spray drying, or in at least two steps.

During drying, the associated moisture content may be reduced to a level which is not greater than about 0.5 wt.-%, based on the total dry weight of the GNCC. The residual total moisture content of the filler can be measured by the Karl Fischer coulometric titration method, desorbing the moisture in an oven at 195°C and passing it continuously into the KF coulometer (Mettler Toledo coulometric KF Titrator C30, combined with Mettler oven DO 0337) using dry N2 at 100 ml/min, e.g. for 10 min. The residual total moisture content may be further reduced by applying a second heating step to the GNCC. In case said drying is carried out by more than one drying steps, the first step may be carried out by heating in a hot current of air, while the second and further drying steps are preferably carried out by an indirect heating in which the atmosphere in the corresponding vessel comprises a surface treatment agent.

It is also common that the (ground) natural calcium carbonate is subjected to a beneficiation step (such as a flotation, bleaching or magnetic separation step) to remove impurities either before or after grinding step c). Moreover, a crushing step using, for example, a jaw crusher or a hammer mill, can be employed before grinding step c) (either before or after the optional beneficiation step) in order to provide the natural calcium carbonate with an optimal particle size for grinding the same. Preferably, the natural calcium carbonate is crushed to a particle size in the range from 0.1 to 10 mm, preferably from 0.2 to 5 mm, and most preferably from 0.5 to 4 mm. In a preferred embodiment of the present invention, step c) is a dry grinding step. In another embodiment, step c) is a wet grinding step comprising grinding in a horizontal ball mill, and subsequently drying using the well-known process of spray drying.

During grinding, a grinding aid may be present. The type of grinding aid is not particularly limited as long as it assists in the grinding process and facilitates grinding of the natural calcium carbonate. The grinding aid should be selected such that it does not react with the at least one inorganic peroxide to a large extent, if the latter is present during the grinding process.

Preferably, the grinding aid is selected from at least one polyol, optionally wherein the polyol comprises amine groups. More preferably, the grinding aid is selected from at least one diol or triol, optionally comprising amine groups. Even more preferably, the grinding aid is selected from the group consisting of ethanediol, propanediol, glycerol, diethanolamine, triethanolamine and mixtures thereof. Most preferably, the grinding aid is 1 ,2-propanediol.

The grinding aid may be present during grinding step c) in an amount of at least 50 ppm, preferably at least 100 ppm, more preferably at least 200 ppm and most preferably at least 500 ppm. Specifically, the grinding aid may be present in an amount ranging from 50 ppm to 20,000 ppm preferably 100 to 10,000 ppm, and most preferably 200 to 8,000 ppm, e.g., 500 to 7,000 ppm, based on the total dry weight of the natural calcium carbonate.

The inventors surprisingly found that the use of a grinding aid in the inventive process can assist in reducing the odor of the calcium carbonate.

Accordingly, in a particularly preferred embodiment, the grinding aid is at least one diol or triol, optionally comprising amine groups, preferably 1 ,2-propanediol, and is present during grinding step c) in an amount from 50 ppm to 20,000 ppm preferably 100 to 10,000 ppm, and most preferably 200 to 8,000 ppm, based on the total dry weight of the natural calcium carbonate.

As mentioned above, the natural calcium carbonate is ground to obtain a ground natural calcium carbonate (GNCC) with a desired particle size. The particle size is not particularly limited and depends on the intended application of the GNCC. For example, if the GNCC is to be incorporated into thin films or fibers or breathable films, the GNCC should be ground to a relatively small particle size. For other polymer applications, such as injection molded parts, the particle size may be greater.

Preferably, the ground natural calcium carbonate of step c) has a weight median particle size c o value in the range from 0.1 pm to 25 pm, preferably from 0.25 pm to 5 pm and most preferably from 0.5 pm to 4 pm.

Additionally or alternatively, the ground natural calcium carbonate of step c) has a top cut (daa) of < 100 pm, preferably < 40 pm, more preferably < 25 pm and most preferably < 15 pm.

Additionally or alternatively, the ground natural calcium carbonate of step c) has a specific surface area (BET) of from 0.5 to 150 m²/g, preferably from 0.5 to 50 m²/g, more preferably from 0.5 to 35 m²/g and most preferably from 0.5 to 10 m²/g as measured by the BET nitrogen method.

Additionally or alternatively, the ground natural calcium carbonate of step c) has a residual total moisture content of from 0.01 wt.-% to 1 wt.-%, preferably from 0.01 to 0.2 wt.-%, more preferably from 0.02 to 0.2 wt.-% and most preferably from 0.03 to 0.2 wt.-%, based on the total dry weight of the at least one calcium carbonate-containing filler material. For example, in case the GNCC is a wet ground and spray dried marble, the residual total moisture content of the calcium carbonate-comprising filler material is preferably from 0.01 to 0.1 wt.- %, more preferably from 0.02 to 0.08 wt.-%, and most preferably from 0.04 to 0.07 wt.-%, based on the total dry weight of the GNCC.

Addition of the at least one inorganic peroxide

In the inventive manufacturing process, the at least one inorganic peroxide provided in step b) is

- mixed with the natural calcium carbonate of step a) prior to grinding step c) and/or during grinding step c), and/or

- is mixed with the ground natural calcium carbonate of step c).

Thus, in one embodiment, the at least one inorganic peroxide provided in step b) is mixed with the natural calcium carbonate of step a) prior to grinding step c) and/or during grinding step c). For example, the at least one inorganic peroxide may be mixed with or added simultaneously with the grinding aid, if present.

Accordingly, the at least one inorganic peroxide is present during grinding step c), such that it can directly react with the oxidizable sulfur impurity once the latter is liberated from the natural calcium carbonate. Grinding is an energy-intensive process, such that the mixture of the natural calcium carbonate and the at least one inorganic peroxide is autogenously heated, typically to above room temperature, for example, up to 80°C and more. Excess inorganic peroxide may be decomposed during the grinding step, inter alia due to the temperature increase, such that a ready-to-use ground natural calcium carbonate is obtained.

In another embodiment, the at least one inorganic peroxide provided in step b) is mixed with the ground natural calcium carbonate of step c), i.e., after the grinding step. In this embodiment, it is preferred that the at least one inorganic peroxide is mixed with the ground natural calcium carbonate of step c) before and/or during a surface-treatment step e), as will be described further below. Alternatively, the at least one inorganic peroxide is mixed with the ground natural calcium carbonate in a separate mixing step, preferably with heating to remove excess inorganic peroxide. For example, the separate mixing step may be carried out in suspension, e.g., at a solids content from 10 to 85 wt.-%, preferably from 30 to 75 wt.-%. Preferably, mixing is carried out in the dry state, for example, in a high shear mixer, a ploughshare mixer or a pin mill. By “mixing in the dry state”, it is meant that no water is added other than the residual amount of moisture present in the ground natural calcium carbonate and in the at least one inorganic peroxide. For example, the total moisture content of the mixture may be less than 10 wt.-%, preferably less than 5 wt.-%, more preferably less than 2 wt.-% and most preferably less than 1 wt.-%, based on the total weight of the mixture.

The separate mixing step may be performed by any conventional means known to the skilled person. For example, the separate mixing step may be performed with a Pendraulik-type stirrer, for example, with a toothed disk with a diameter of 3.5 cm as the stirrer. Alternatively, the mixing step may be carried out by using a ploughshare mixer. Ploughshare mixers function according to the principle of the mechanically produced fluidized bed. Ploughshare blades rotate close to the inside wall of a horizontal cylindrical drum and convey the components of the mixture out of the product bed into the open mixing space. The mechanically produced fluidized bed ensures an intense mixing effect even with large batches in a very short period of time. Choppers and/or dispersers are used to disperse lumps when operating dry. The equipment used is available from the company Gebruder Lbdige Maschinenbau GmbH, Paderborn, Germany. Alternatively, the mixing step is performed in a tubular mixing apparatus through an intake tube. Such a tubular mixing apparatus is available, for example from Ystral GmbH, Ballrechten-Dottingen, Germany. However, mixing may also be carried out in a ball mill, a rod mill, a vibrating mill, a roll crusher, a centrifugal impact mill, a vertical bead mill, an attrition mill, a pin mill, a hammer mill, a pulveriser, a shredder, a de-clumper, a knife cutter, a ribbon blender or other such equipment known to the skilled man.

The separate mixing step may be carried out in dry state or in suspension, preferably in dry state. If the separate mixing step is carried out in suspension, a suitable solids content is from 20 to 80 wt.-%.

During the separate mixing step, the mixture may be heated to a temperature above roomtemperature, e.g. to a temperature from 30 to 90 °C, preferably from 50 to 85 °C, e.g. to about 80 °C. Heating may take place autogenously and/or by external heating.

It is appreciated that the inventive process leads to a reduction of the amount of oxidizable sulfur impurities in the natural calcium carbonate. Thus, in a preferred embodiment, the ground natural calcium carbonate of step c) has an oxidizable sulfur impurity content which is lower than that of the natural calcium carbonate of step a). Preferably, the ground natural calcium carbonate of step c) has an oxidizable sulfur impurity content of less than 25 mg/kg, preferably less than 5 mg/kg, more preferably less than 2 mg/kg and most preferably less than 0.7 mg/kg, based on the total weight of the ground natural calcium carbonate.

In view of the foregoing, a preferred embodiment of the present invention relates to a process comprising the steps of a) providing a natural calcium carbonate comprising an oxidizable sulfur impurity, b) providing at least one inorganic peroxide, c) grinding the natural calcium carbonate of step a) to a desired particle size to obtain a ground natural calcium carbonate, wherein the at least one inorganic peroxide of step b) is mixed with the natural calcium carbonate of step a) prior to grinding step c).

Alternatively, a process is provided comprising the steps of a) providing a natural calcium carbonate comprising an oxidizable sulfur impurity, b) providing at least one inorganic peroxide, c) grinding the natural calcium carbonate of step a) to a desired particle size to obtain a ground natural calcium carbonate, wherein the at least one inorganic peroxide of step b) is mixed with the natural calcium carbonate of step a) during grinding step c).

Thus, preferably, the inventive process comprises the steps of a) providing a natural calcium carbonate comprising an oxidizable sulfur impurity, b) providing at least one inorganic peroxide, c) grinding the natural calcium carbonate of step a) to a desired particle size to obtain a ground natural calcium carbonate, wherein the at least one inorganic peroxide of step b) is present during grinding step c).

Alternatively, the process comprises the steps of a) providing a natural calcium carbonate comprising an oxidizable sulfur impurity, b) providing at least one inorganic peroxide, c) grinding the natural calcium carbonate of step a) to a desired particle size to obtain a ground natural calcium carbonate, wherein the at least one inorganic peroxide of step b) is mixed with the ground natural calcium carbonate of step c).

Step d) - Providing at least one surface-treatment agent

During step d) of a preferred embodiment of the inventive process, at least one surfacetreatment agent is provided.

A “surface-treatment agent” in the meaning of the present invention is any material, which is capable of reacting and/or forming an adduct with the surface of the ground natural calcium carbonate, thereby forming a surface-treatment layer on at least a part of the surface of the ground natural calcium carbonate, which preferably renders its surface more hydrophobic. It should be understood that the present invention is not limited to any particular surface-treatment agents, since the type of surface treatment will depend on the intended application of the ground natural calcium carbonate. For example, hydrophobizing surface-treatment agents such as stearic acid or mono-substituted succinic anhydride may improve dispersion of the ground natural calcium carbonate in a polymer matrix, which is beneficial for the mechanical properties of the obtained polymer compound. The skilled person knows how to select suitable materials for use as surface-treatment agents.

Preferably, the surface-treatment agent is added in an amount from 0.1 to 2 wt.-%, preferably from 0.2 to 1 .5 wt.-% and most preferably from 0.4 to 1 .2 wt.-%, based on the total dry weight of the ground natural calcium carbonate.

Additionally or alternatively, the surface-treatment agent is added in an amount from 0.5 to 5 mg/m², preferably from 1 to 4 mg/m² and most preferably from 1 .3 to 3 mg/m², based on the total surface area of the ground natural calcium carbonate.

In a preferred embodiment, the surface-treatment agent is selected from i. a phosphoric acid ester blend of one or more phosphoric acid monoester and/or one or more phosphoric acid di-ester and/or a salt thereof, and/or ii. at least one saturated aliphatic linear or branched carboxylic acid preferably having a total amount of carbon atoms from C4 to C24 and/or a salt thereof, and/or

Hi. at least one aliphatic aldehyde, and/or iv. at least one mono-substituted succinic anhydride consisting of succinic anhydride mono-substituted with a group selected from a linear, branched, aliphatic and cyclic group having a total amount of carbon atoms from at least C2 to C30 in the substituent and/or a salt thereof, and/or v. at least one polydialkylsiloxane, and/or vi. mixtures of the materials according to i. to v.. According to one embodiment of the present invention, the at least one surface-treatment agent is at least one mono-substituted succinic anhydride consisting of succinic anhydride monosubstituted with a group selected from a linear, branched, aliphatic and cyclic group having a total amount of carbon atoms from at least C2 to C30 in the substituent and/or a salt thereof.

In one embodiment of the present invention, the at least one mono-substituted succinic anhydride consists of succinic anhydride mono-substituted with a group selected from a linear, branched, aliphatic, and cyclic group having a total amount of carbon atoms from C3 to C20 in the substituent. For example, the at least one mono-substituted succinic anhydride consists of succinic anhydride mono-substituted with a group selected from a linear, branched, aliphatic, and cyclic group having a total amount of carbon atoms from C4 to C18 in the substituent.

For example, the at least one mono-substituted succinic anhydride consists of succinic anhydride mono-substituted with one group being a linear alkyl group having a total amount of carbon atoms from C2 to C30, preferably from C3 to C20 and most preferably from C4 to C18 in the substituent. Alternatively, the at least one mono-substituted succinic anhydride consists of succinic anhydride mono-substituted with one group being a branched alkyl group having a total amount of carbon atoms from C2 to C30, preferably from C3 to C20 and most preferably from C4 to C18 in the substituent.

In one embodiment of the present invention, the at least one mono-substituted succinic anhydride is at least one linear or branched alkyl mono-substituted succinic anhydride. For example, the at least one alkyl mono-substituted succinic anhydride is selected from the group comprising ethylsuccinic anhydride, propylsuccinic anhydride, butylsuccinic anhydride, triisobutyl succinic anhydride, pentylsuccinic anhydride, hexylsuccinic anhydride, heptylsuccinic anhydride, octylsuccinic anhydride, nonylsuccinic anhydride, decyl succinic anhydride, dodecyl succinic anhydride, hexadecyl succinic anhydride, octadecyl succinic anhydride, and mixtures thereof.

In a preferred embodiment of the present invention, the at least one mono-substituted succinic anhydride consists of succinic anhydride mono-substituted with one group being a linear or branched alkenyl group having a total amount of carbon atoms from C2 to C30, preferably from C3 to C20 and most preferably from C4 to C20 in the substituent.

In one embodiment of the present invention, the at least one mono-substituted succinic anhydride is at least one linear or branched alkenyl mono-substituted succinic anhydride. For example, the at least one alkenyl mono-substituted succinic anhydride is selected from the group comprising ethenylsuccinic anhydride, propenylsuccinic anhydride, butenylsuccinic anhydride, triisobutenyl succinic anhydride, pentenylsuccinic anhydride, hexenylsuccinic anhydride, heptenylsuccinic anhydride, octenylsuccinic anhydride, nonenylsuccinic anhydride, decenyl succinic anhydride, dodecenyl succinic anhydride, hexadecenyl succinic anhydride, octadecenyl succinic anhydride, and mixtures thereof.

In one embodiment of the present invention, the at least one mono-substituted succinic anhydride is a mixture of two or more kinds of alkenyl mono-substituted succinic anhydrides. For example, the at least one mono-substituted succinic anhydride is a mixture of two or three kinds of alkenyl mono-substituted succinic anhydrides. If the at least one mono-substituted succinic anhydride is a mixture of two or more kinds of alkenyl mono-substituted succinic anhydrides, it is appreciated that one alkenyl mono-substituted succinic anhydride is present in an amount of from 20 to 60 wt.-% and preferably of from 30 to 50 wt.- %, based on the total weight of the at least one mono-substituted succinic anhydride provided.

For example, if the at least one mono-substituted succinic anhydride is a mixture of two or more kinds of alkenyl mono-substituted succinic anhydrides comprising one or more hexadecenyl succinic anhydride(s), like linear or branched hexadecenyl succinic anhydride(s), and one or more octadecenyl succinic anhydride(s), like linear or branched hexadecenyl succinic anhydride(s), it is preferred that the one or more octadecenyl succinic anhydride(s) is present in an amount of from 20 to 60 wt.-% and preferably of from 30 to 50 wt.-%, based on the total weight of the at least one monosubstituted succinic anhydride.

Preferred alkenyl mono-substituted succinic anhydrides include branched hexadecenyl succinic anhydrides (CAS No. 32072-96-1), branched octadecenyl succinic anhydrides (CAS No. 28777-98-2) and 2,5-furandione, dihydro-, mono-Ci5-2o-alkenyl derivatives (CAS No. 68784-12-3). According to a preferred embodiment of the present invention the at least one mono-substituted succinic anhydride is 2,5-furandione, dihydro-, mono-Ci5-2o-alkenyl derivatives (CAS No. 68784-12-3).

It is also appreciated that the at least one mono-substituted succinic anhydride may be a mixture of at least one alkyl mono-substituted succinic anhydride as described hereinabove and at least one alkenyl mono-substituted succinic anhydride as described hereinabove.

If the at least one mono-substituted succinic anhydride is a mixture of at least one alkyl monosubstituted succinic anhydrides and at least one alkenyl mono-substituted succinic anhydride, the weight ratio between the at least one alkyl mono-substituted succinic anhydride and the at least one alkenyl mono-substituted succinic anhydride is between 90:10 and 10:90 (wt.-%/wt.-%). For example, the weight ratio between the at least one alkyl mono-substituted succinic anhydride and the at least one alkenyl mono-substituted succinic anhydride is between 70:30 and 30:70 (wt.-% / wt.-%) or between 60:40 and 40:60 (wt.-% / wt.-%).

The at least one mono-substituted succinic anhydride may be provided in the present invention in combination with at least one mono-substituted succinic acid and/or a salt thereof. Alternatively, the surface treatment agent may comprise at least one mono-substituted succinic acid and/or a salt thereof.

It is appreciated that the at least one mono-substituted succinic acid and/or a salt thereof represents a surface treatment agent and consists of succinic acid and/or its salt mono-substituted with a group selected from any linear, branched, aliphatic and cyclic group having a total amount of carbon atoms from C2 to C30 in the substituent.

In one embodiment of the present invention, the at least one mono-substituted succinic acid and/or a salt thereof consists of succinic acid and/or its salt mono-substituted with a group selected from a linear, branched, aliphatic and cyclic group having a total amount of carbon atoms from C3 to C20 in the substituent. For example, the at least one mono-substituted succinic acid and/or a salt thereof consists of succinic acid and/or its salt mono-substituted with a group selected from a linear, branched, aliphatic and cyclic group having a total amount of carbon atoms from C4 to C18 in the substituent. It is appreciated that the at least one mono-substituted succinic anhydride and the at least one mono-substituted succinic acid and/or a salt thereof may comprise the same or different substituent. In one embodiment of the present invention, the succinic acid molecule and/or its salt of the at least one mono-substituted succinic acid and/or a salt thereof and the succinic anhydride molecule of the at least one mono-substituted succinic anhydride are mono-substituted with the same group selected from any linear, branched, aliphatic and cyclic group having a total amount of carbon atoms from C2 to C30, preferably from C3 to C20 and most preferably from C4 to C18 in the substituent.

If the at least one mono-substituted succinic anhydride is provided in combination with at least one mono-substituted succinic acid and/or a salt thereof, the at least one mono-substituted succinic acid is present in an amount of < 10 mol.-%, based on the molar sum of the at least one monosubstituted succinic anhydride and the at least one mono-substituted succinic acid and/or its salt. For example, the at least one mono-substituted succinic acid is present in an amount of < 5 mol.-%, preferably of < 2.5 mol.-% and most preferably of < 1 mol.-%, based on the molar sum of the at least one mono-substituted succinic anhydride and the at least one mono-substituted succinic acid and/or its salt.

Additionally or alternatively, the at least one mono-substituted succinic acid is provided in a blend together with the at least one mono-substituted succinic anhydride.

In a particularly preferred embodiment, the surface-treatment agent forms a surface-treatment layer on the surface of the ground natural calcium carbonate. Preferably, the surface-treatment agent is a mixture of alkenyl succinic anhydrides and/or alkenyl succinic acids, wherein the alkenyl succinic anhydrides and/or alkenyl succinic acids are mono-substituted with a group selected from any linear or branched mono-alkenyl group having a total amount of carbon atoms from C12 to C20, preferably from C15 to C20. In this case, the alkenyl succinic anhydride will typically comprise at least 80 wt.-% of the mixture, based on the total weight of the mixture, preferably at least 85 wt.-%, more preferably at least 90 wt.-% and most preferably at least 93 wt.-%.

The surface treatment of inorganic particles with mono-substituted succinic acids and methods for the production thereof are described in WO 2014/060286 A1 , WO 2014/128087 A1 , and WO 2016/087286 A1.

In another embodiment of the present invention, the surface-treatment agent is at least one saturated aliphatic linear or branched carboxylic acid and/or a salt thereof, preferably at least one saturated aliphatic linear or branched carboxylic acid having a total amount of carbon atoms from C4 to C24 and/or a salt thereof, more preferably at least one saturated aliphatic linear or branched carboxylic acid having a total amount of carbon atoms from C12 to C20 and/or a salt thereof, most preferably at least one saturated aliphatic linear or branched carboxylic acid having a total amount of carbon atoms from C16 to Cis and/or a salt thereof.

In one embodiment of the present invention, the at least one carboxylic acid is selected from saturated unbranched carboxylic acids, that is to say the aliphatic carboxylic acid and/or salt thereof is preferably selected from the group of carboxylic acids consisting of pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, heptadecanoic acid, stearic acid, nonadecanoic acid, arachidic acid, heneicosylic acid, behenic acid, tricosylic acid, lignoceric acid, their salts, their anhydrides and mixtures thereof.

In another embodiment of the present invention, the at least one carboxylic acid is selected from the group consisting of octanoic acid, decanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid and mixtures thereof. Preferably, the aliphatic carboxylic acid is selected from the group consisting of myristic acid, palmitic acid, stearic acid, their salts, and mixtures thereof.

Preferably, the aliphatic carboxylic acid and/or salt thereof is stearic acid and/or a stearic acid salt or stearic anhydride.

The at least one carboxylic acid and/or a salt thereof may be combined with alkenyl carboxylic acids and/or salts thereof, preferably selected from the group consisting of pentenoic acid, hexenoic acid, heptenoic acid, octenoic acid, nonenoic acid, decenoic acid, undecenoic acid, dodecenoic acid, tridecenoic acid, myristoleic acid, pentadecenoic acid, palmitoleic acid, sapienic acid, heptadecenoic acid, oleic acid, elaidic acid, vaccenic acid, nonadecenoic acid, paullinic acid, gadoleic acid, gondoic acid, erucic acid, nervonic acid, linoleic acid, their salts, their anhydrides and isomers and/or mixtures thereof.

Alternatively, the alkenyl carboxylic acid and/or salt thereof is selected from the group consisting of decenoic acid, dodecenoic acid, myristoleic acid, palmitoleic acid, oleic acid, paullinic acid, their salts, and isomers and/or mixtures thereof.

More preferably, the alkenyl carboxylic acid and/or salt thereof is selected from the group consisting of myristoleic acid, palmitoleic acid, sapienic acid, oleic acid, elaidic acid, vaccenic acid, linoleic acid, a-linolenic acid and mixtures thereof. Most preferably, the alkenyl carboxylic acid and/or salt thereof is oleic acid and/or linoleic acid, preferably oleic acid or linoleic acid, most preferably linoleic acid.

Additionally or alternatively, the surface treatment agent is a salt of a carboxylic acid.

The term “salt of a carboxylic acid” refers to a carboxylic acid, wherein the active acid group is partially or completely neutralized. The term “partially neutralized” carboxylic acid refers to a degree of neutralization of the active acid groups in the range from 40 and 95 mol-%, preferably from 50 to 95 mol-%, more preferably from 60 to 95 mol-% and most preferably from 70 to 95 mol-%. The term “completely neutralized” carboxylic acid refers to a degree of neutralization of the active acid groups of > 95 mol-%, preferably of > 99 mol-%, more preferably of > 99.8 mole-% and most preferably of 100 mol-%. Preferably, the active acid groups are partially or completely neutralized.

The salt of the carboxylic acid is preferably a compound selected from the group consisting of sodium, potassium, calcium, magnesium, lithium, strontium, primary amine, secondary amine, tertiary amine and/or ammonium salts thereof, whereby the amine salts are linear or cyclic. For example, the surface treatment agent is a salt of oleic acid and/or linoleic acid, preferably oleic acid or linoleic acid, most preferably linoleic acid. Additionally or alternatively, the at least one surface treatment agent is a phosphoric acid ester blend of one or more phosphoric acid mono-ester and/or salts thereof and/or one or more phosphoric acid di-ester and/or salts thereof.

Thus, the phosphoric acid ester blend may be a blend of one or more phosphoric acid monoesters and one or more phosphoric acid di-esters and optionally one or more phosphoric acid triesters. In one embodiment, said blend further comprises phosphoric acid.

For example, the phosphoric acid ester blend is a blend of one or more phosphoric acid monoester and one or more phosphoric acid di-ester. Alternatively, the phosphoric acid ester blend is a blend of one or more phosphoric acid mono-ester and one or more phosphoric acid di-ester and phosphoric acid. Alternatively, the phosphoric acid ester blend is a blend of one or more phosphoric acid mono-ester and one or more phosphoric acid di-ester and one or more phosphoric acid tri-ester. Alternatively, the phosphoric acid ester blend is a blend of one or more phosphoric acid mono-ester and one or more phosphoric acid di-ester and one or more phosphoric acid tri-ester and phosphoric acid.

For example, said blend comprises phosphoric acid in an amount of < 8 mol.-%, preferably of < 6 mol.-%, and more preferably of < 4 mol.-%, like from 0.1 to 4 mol.-%, based on the molar sum of the compounds in the blend.

The term "phosphoric acid mono-ester" in the meaning of the present invention refers to an o- phosphoric acid molecule mono-esterified with one alcohol molecule selected from branched or linear, aliphatic or aromatic alcohols having a total amount of carbon atoms from Ce to C30, preferably from Ca to C22, more preferably from Ca to C20 and most preferably from Ca to Cia in the alcohol substituent.

The term "phosphoric acid di-ester" in the meaning of the present invention refers to an 0- phosphoric acid molecule di-esterified with two alcohol molecules selected from the same or different, branched or linear, aliphatic or aromatic alcohols having a total amount of carbon atoms from Cato C30, preferably from Ca to C22, more preferably from Ca to C20 and most preferably from Ca to Cia in the alcohol substituent.

The term "phosphoric acid tri-ester" in the meaning of the present invention refers to an 0- phosphoric acid molecule tri-esterified with three alcohol molecules selected from the same or different, branched or linear, aliphatic or aromatic alcohols having a total amount of carbon atoms from Ca to C30, preferably from Ca to C22, more preferably from Ca to C20 and most preferably from Ca to Cia in the alcohol substituent.

Additionally or alternatively, the surface treatment agent is a salt of a phosphoric acid ester. In one embodiment, the salt of a phosphoric acid ester may further comprise minor amounts of a salt of phosphoric acid.

According to one embodiment of the present invention, the surface-treatment composition comprises a phosphoric acid ester blend of one or more phosphoric acid mono-ester and/or salts thereof and/or one or more phosphoric acid di-ester and/or salts thereof.

In one embodiment of the present invention, the one or more phosphoric acid mono-ester consists of an o-phosphoric acid molecule esterified with one alcohol selected from saturated, branched or linear, aliphatic or aromatic alcohols having a total amount of carbon atoms from C6 to C30 in the alcohol substituent. For example, the one or more phosphoric acid mono-ester consists of an o-phosphoric acid molecule esterified with one alcohol selected from saturated, branched or linear, aliphatic or aromatic alcohols having a total amount of carbon atoms from C8 to C22, more preferably from C8 to C20 and most preferably from C8 to C18 in the alcohol substituent.

Alkyl esters of phosphoric acid are well known in the industry especially as surfactants, lubricants and antistatic agents (Die Tenside; Kosswig und Stache, Carl Hanser Verlag Munchen, 1993).

The synthesis of alkyl esters of phosphoric acid by different methods and the surface treatment of minerals with alkyl esters of phosphoric acid are well known to the skilled man, e.g. from Pesticide Formulations and Application Systems: 17th Volume; Collins HM, Hall FR, Hopkinson M, STP1268; Published: 1996, US 3,897,519 A, US 4,921 ,990 A, US 4,350,645 A, US 6,710,199 B2, US 4, 126, 650 A, US 5,554,781 A, EP1092000 B1 and WO 2008/023076 A1 .

In one embodiment of the present invention, the one or more phosphoric acid mono-ester consists of an o-phosphoric acid molecule esterified with one alcohol selected from saturated and linear or branched and aliphatic alcohols having a total amount of carbon atoms from Ce to C30 in the alcohol substituent. For example, the one or more phosphoric acid mono-ester consists of an 0- phosphoric acid molecule esterified with one alcohol selected from saturated and linear or branched and aliphatic alcohols having a total amount of carbon atoms from C8 to C22, more preferably from C8 to C20 and most preferably from C8 to C18 in the alcohol substituent.

In one embodiment of the present invention, the one or more phosphoric acid mono-ester consists of an o-phosphoric acid molecule esterified with one alcohol selected from saturated and linear and aliphatic alcohols having a total amount of carbon atoms from C6 to C30, preferably from C8 to C22, more preferably from C8 to C20 and most preferably from C8 to C18 in the alcohol substituent. Alternatively, the one or more phosphoric acid mono-ester consists of an o-phosphoric acid molecule esterified with one alcohol selected from saturated and branched and aliphatic alcohols having a total amount of carbon atoms from C6 to C30, preferably from C8 to C22, more preferably from C8 to C20 and most preferably from C8 to C18 in the alcohol substituent.

In one embodiment of the present invention, the one or more phosphoric acid di-ester consists of an o-phosphoric acid molecule esterified with two alcohols selected from saturated, branched or linear, aliphatic or aromatic alcohols having a total amount of carbon atoms from C6 to C30 in the alcohol substituent. For example, the one or more phosphoric acid di-ester consists of an 0- phosphoric acid molecule esterified with two fatty alcohols selected from saturated, branched or linear, aliphatic or aromatic alcohols having a total amount of carbon atoms from C8 to C22, more preferably from C8 to C20 and most preferably from C8 to C18 in the alcohol substituent.

It is appreciated that the two alcohols used for esterifying the phosphoric acid may be independently selected from the same or different saturated, branched or linear, aliphatic or aromatic alcohols having a total amount of carbon atoms from C6 to C30 in the alcohol substituent. In other words, the one or more phosphoric acid di-ester may comprise two substituents being derived from the same alcohols or the phosphoric acid di-ester molecule may comprise two substituents being derived from different alcohols.

In one embodiment of the present invention, the one or more phosphoric acid di-ester consists of an o-phosphoric acid molecule esterified with two alcohols selected from the same or different, saturated and linear or branched and aliphatic alcohols having a total amount of carbon atoms from C6 to C30 in the alcohol substituent. For example, the one or more phosphoric acid di-ester consists of an o-phosphoric acid molecule esterified with two alcohols selected from the same or different, saturated and linear or branched and aliphatic alcohols having a total amount of carbon atoms from C8 to C22, more preferably from C8 to C20 and most preferably from C8 to C18 in the alcohol substituent.

In one embodiment of the present invention, the one or more phosphoric acid di-ester consists of an o-phosphoric acid molecule esterified with two alcohols selected from the same or different, saturated and linear and aliphatic alcohols having a total amount of carbon atoms from C6 to C30, preferably from C8 to C22, more preferably from C8 to C20 and most preferably from C8 to C18 in the alcohol substituent. Alternatively, the one or more phosphoric acid di-ester consists of an o-phosphoric acid molecule esterified with two alcohols selected from the same or different, saturated and branched and aliphatic alcohols having a total amount of carbon atoms from C6 to C30, preferably from C8 to C22, more preferably from C8 to C20 and most preferably from C8 to C18 in the alcohol substituent.

The term “salt of phosphoric acid ester” refers to a phosphoric acid ester, wherein the active acid group(s) is/are partially or completely neutralized. The term “partially neutralized” phosphoric acid esters refers to a degree of neutralization of the active acid group(s) in the range from 40 and 95 mole-%, preferably from 50 to 95 mole-%, more preferably from 60 to 95 mole-% and most preferably from 70 to 95 mole-%. The term “completely neutralized” phosphoric acid esters refers to a degree of neutralization of the active acid group(s) of > 95 mole-%, preferably of > 99 mole-%, more preferably of > 99.8 mole-% and most preferably of 100 mole-%. Preferably, the active acid group(s) is/are partially or completely neutralized.

The salt of the phosphoric acid ester is preferably a compound selected from the group consisting of sodium, potassium, calcium, magnesium, lithium, strontium, primary amine, secondary amine, tertiary amine and/or ammonium salts thereof, whereby the amine salts are linear or cyclic.

According to another embodiment of the present invention, the surface-treatment composition comprises at least one aliphatic aldehyde.

In this regard, the at least one aliphatic aldehyde represents a saturated surface treatment agent and may be selected from any linear, branched or alicyclic, substituted or non-substituted, saturated or aliphatic aldehyde. Said aldehyde is preferably chosen such that the number of carbon atoms is greater than or equal to 6 and more preferably greater than or equal to 8. Furthermore, said aldehyde has generally a number of carbon atoms that is lower or equal to 14, preferably lower or equal to 12 and more preferably lower or equal to 10. In one preferred embodiment, the number of carbon atoms of the aliphatic aldehyde is between 6 and 14, preferably between 6 and 12 and more preferably between 6 and 10. Suitable aldehydes suitable for use in the present invention are known to the skilled person, e.g., from WO 2011/147802 A1 .

Additionally or alternatively, the at least one surface treatment agent is abietic acid (also named: abieta-7,13-dien-18-oic acid, CAS-No.: 514-10-3).

Additionally or alternatively, the surface treatment agent is a salt of abietic acid.

The term “salt of abietic acid” refers to abietic acid, wherein the active acid groups are partially or completely neutralized. The term “partially neutralized” abietic acid refers to a degree of neutralization of the active acid groups in the range from 40 and 95 mol-%, preferably from 50 to 95 mol-%, more preferably from 60 to 95 mol-% and most preferably from 70 to 95 mol-%. The term “completely neutralized” abietic acid refers to a degree of neutralization of the active acid groups of > 95 mol-%, preferably of > 99 mol-%, more preferably of > 99.8 mol-% and most preferably of 100 mol- %. Preferably, the active acid groups are partially or completely neutralized, more preferably completely neutralized.

The salt of abietic acid is preferably a compound selected from the group consisting of sodium, potassium, calcium, magnesium, lithium, strontium, primary amine, secondary amine, tertiary amine and/or ammonium salts thereof, whereby the amine salts are linear or cyclic.

According to one embodiment the at least one surface-treatment agent is a polydialkylsiloxane. Preferred polydialkylsiloxanes are, e.g., described in US 2004/0097616 A1. Most preferred are polydialkylsiloxanes selected from the group consisting of polydimethylsiloxane, preferably dimethicone, polydiethylsiloxane and polymethylphenylsiloxane and/or mixtures thereof.

According to another embodiment of the present invention, the at least one surface-treatment agent is an a trialkoxysilane, which is represented by the formula R³-Si(OR⁴)3. Therein, the substituent R³ represents any kind of substituent, i.e., any branched, linear or cyclic moiety having a total amount of carbon atoms from C2 to C30, such as a methyl, ethyl, propyl, butyl, decyl, dodecyl, hexadecyl, octadecyl, allyl, propargyl, butenyl, crotyl, prenyl, pentenyl, hexenyl, cyclohexenyl or vinylphenyl moiety. OR⁴ is a hydrolyzable group, wherein substituent R⁴ represents any saturated or unsaturated, branched, linear, cyclic or aromatic moiety from having a total amount of carbon atoms from C1 to C30, such as a methyl, ethyl, propyl, allyl, butyl, butenyl, phenyl or benzyl group. According to a preferred embodiment, R⁴ is a linear alkyl group having a total amount of carbon atoms from C1 to C15, preferably from C1 to C8 and most preferably from C1 to C2. According to an exemplified embodiment of the present invention, the hydrolysable alkoxy group is a methoxy or an ethoxy group. Thus, specific or preferred examples of trialkoxysilanes suitable for use in the present invention include vinyltrimethoxysilane, vinyltriethoxysilane, allyltrimethoxysilane or allyltriethoxysilane.

Further suitable surface-treatment agents are disclosed in WO 2022/013336 A1 and are incorporated herein by reference.

Preferably, the surface-treatment agent is selected from i. at least one saturated aliphatic linear or branched carboxylic acid preferably having a total amount of carbon atoms from C4 to C24 and/or a salt thereof, and/or ii. at least one mono-substituted succinic anhydride consisting of succinic anhydride mono-substituted with a group selected from a linear, branched, aliphatic and cyclic group having a total amount of carbon atoms from at least C2 to C30 in the substituent and/or a salt thereof, and/or

Hi. mixtures of the foregoing.

Most preferably, the surface-treatment agent is at least one mono-substituted succinic anhydride consisting of succinic anhydride mono-substituted with a group selected from a linear, branched, aliphatic and cyclic group having a total amount of carbon atoms from at least C2 to C30 in the substituent and/or a salt thereof. Step e) - Surface-treatment step

During step e) of a preferred embodiment of the inventive process, the at least one surfacetreatment agent of step d) is mixed with the ground natural calcium carbonate of step c) to obtain a surface-treated natural calcium carbonate.

The so-obtained surface-treated natural calcium carbonate comprises a surface-treatment layer formed from the reaction of the surface-treatment agent with the ground natural calcium carbonate.

It is appreciated that the surface-treatment layer is formed on at least a part of the ground natural calcium carbonate by contacting the ground natural calcium carbonate with the surfacetreatment agent as described hereinabove. A chemical reaction may take place between the ground natural calcium carbonate and the surface treatment agent. In other words, the surface-treatment layer may comprise the surface treatment agent and/or salty reaction products thereof.

The term "salty reaction products" of the surface-treatment agent refers to products obtained by contacting the ground natural calcium carbonate with the surface-treatment composition comprising the surface-treatment agent. Said reaction products are formed between at least a part of the applied surface-treatment agent and reactive molecules located at the surface of the ground natural calcium carbonate.

For example, if the surface-treatment layer is formed by contacting the ground natural calcium carbonate with the mono- or di-substituted succinic anhydride, the surface-treatment layer may further comprise a salt formed from the reaction of the mono- or di-substituted succinic anhydride with the ground natural calcium carbonate. Likewise, if the surface-treatment layer is formed by contacting the ground natural calcium carbonate with stearic acid, the surface-treatment layer may further comprise a salt formed from the reaction of stearic acid with the ground natural calcium carbonate. Analogous reactions may take place when using alternative surface treatment agents according to the present invention.

According to one embodiment, the salty reaction product(s) of the mono- or di-substituted succinic anhydrides are one or more calcium and/or magnesium salts thereof.

According to one embodiment the salty reaction product(s) of the mono- or di-substituted succinic anhydrides formed on at least a part of the surface of the ground natural calcium carbonate are one or more calcium salts and/or one or more magnesium salts thereof.

According to one embodiment the molar ratio of the mono- or di-substituted succinic anhydrides to the salty reaction product(s) thereof is from 99.9:0.1 to 0.1 :99.9, preferably from 70:30 to 90:10.

According to one embodiment of the present invention, the ground natural calcium carbonate comprises, and preferably consists of, an untreated ground natural calcium carbonate and a treatment layer comprising mono- or di-substituted succinic anhydride containing compounds comprising unsaturated carbon moieties and/or salt reaction products thereof. The treatment layer is formed on at least a part of the surface, preferably on the whole surface, of said ground natural calcium carbonate.

In one embodiment of the present invention, the treatment layer formed on the surface of the ground natural calcium carbonate comprises the at least one mono-substituted succinic anhydride and/or salty reaction products thereof obtained from contacting the untreated ground natural calcium carbonate with the at least one mono-substituted succinic anhydride.

Methods for preparing a surface-treatment layer with at least one phosphoric acid ester blend and suitable compounds for coating are described, e.g., in EP 2 770 017 A1 , which is thus incorporated herewith by reference.

Methods for preparing a surface-treatment layer with at least one mono-substituted succinic anhydride consisting of succinic anhydride mono-substituted with a group selected from a linear, branched, aliphatic and cyclic group having a total amount of carbon atoms from at least C2 to C30 in the substituent and suitable compounds for coating are described e.g. in WO 2016/023937 A1 , which is thus incorporated herewith by reference.

If the surface-treatment layer is formed by contacting the ground natural calcium carbonate with a surface-treatment composition comprising two or more surface-treatment agents, it is to be understood that the two or more surface-treatment agents may be provided as a mixture prior to contacting the ground natural calcium carbonate with the surface-treatment composition. Alternatively, the ground natural calcium carbonate may be contacted with a surface-treatment composition comprising the first surface-treatment agent, and the second surface-treatment agent is added subsequently, that is, the surface-treatment composition is formed upon contacting the mixture of the ground natural calcium carbonate and the first surface-treatment agent with the second surfacetreatment agent.

In one embodiment of the present invention, the surface treatment is carried out in the wet state, i.e. the surface treatment is carried out in the presence of an aqueous solvent, preferably water.

Thus, the ground natural calcium carbonate may be provided in form of an aqueous suspension having a solids content in the range from 5 to 80 wt.-%, based on the total weight of the aqueous suspension. According to a preferred embodiment, the solids content of the aqueous suspension is in the range from 10 to 70 wt.-%, more preferably in the range from 15 to 60 wt.-% and most preferably in the range from 15 to 40 wt.-%, based on the total weight of the aqueous suspension.

The term “aqueous” suspension refers to a system, wherein the liquid phase comprises, preferably consists of, water. However, said term does not exclude that the liquid phase of the aqueous suspension comprises minor amounts of at least one water-miscible organic solvent selected from the group comprising methanol, ethanol, acetone, acetonitrile, tetrahydrofuran and mixtures thereof. If the aqueous suspension comprises at least one water-miscible organic solvent, the liquid phase of the aqueous suspension comprises the at least one water-miscible organic solvent in an amount of from 0.1 to 40.0 wt.-% preferably from 0.1 to 30.0 wt.-%, more preferably from 0.1 to 20.0 wt.-% and most preferably from 0.1 to 10.0 wt.-%, based on the total weight of the liquid phase of the aqueous suspension. For example, the liquid phase of the aqueous suspension consists of water. Suitable wet surface-treatment processes are known to the skilled person, and taught, e.g., in EP 3 192 837 A1.

In a preferred embodiment, the surface-modification is performed in the dry state, i.e. the surface treatment is carried out in the absence of solvents. In this embodiment, the untreated ground natural calcium carbonate, which may contain a residual amount of moisture, e.g., less than 10 wt.-%, preferably less than 5 wt.-%, more preferably less than 2 wt.-%, is contacted with the surfacetreatment composition, and subsequently mixed. Suitable dry surface-treatment processes are known to the skilled person and are taught, e.g., in WO 2014/060286 A1 and WO 2018/229061 A1 .

Optionally, the at least one inorganic peroxide of step b) is mixed with the ground natural calcium carbonate of step c) before and/or during mixing step e). Accordingly, the at least one inorganic peroxide may be present during surface-treatment step e). In this embodiment, the at least one inorganic peroxide is not only capable of reacting with the oxidizable sulfur impurity comprised in the (ground) natural calcium carbonate, but can also react with (oxidizable sulfur) impurities contained in the surface-treatment agent, thus further reducing the odor of such surface-treated calcium carbonate, once incorporated into a polymer compound. Moreover, the reaction of the surfacetreatment agent with the ground natural calcium carbonate may liberate the oxidizable sulfur impurity or remaining amounts thereof, such that the at least one inorganic peroxide can scavenge amounts of the oxidizable sulfur impurity liberated thereby.

If the at least one inorganic peroxide of step b) is mixed with the ground natural calcium carbonate of step c) during mixing step e), it may be provided separately from the surface-treatment agent, e.g., in that the at least one inorganic peroxide and the surface-treatment agent are added subsequently or simultaneously. Additionally or alternatively, the at least one inorganic peroxide may be mixed with the surface-treatment agent.

In a preferred embodiment, the at least one inorganic peroxide is mixed with the ground natural calcium carbonate of step c) in a total amount of at least 100 ppm by weight, preferably in a total amount from 100 to 5000 ppm by weight, more preferably in a total amount from 200 to 2000 ppm by weight, even more preferably in a total amount from 200 to 1000 ppm by weight, for example from 200 to 500 ppm by weight, based on the total dry weight of the respective ground natural calcium carbonate. Additionally or alternatively, the at least one inorganic peroxide is mixed with the ground natural calcium carbonate of step c) in a total amount of at least 100 ppm by weight, preferably at least 200 ppm by weight, more preferably at least 300 ppm by weight and most preferably at least 500 ppm by weight.

The surface-treatment step may be performed by any conventional means known to the skilled person, e.g., those described above with respect to the separate mixing step.

Preferably, the surface-treatment step is performed under heating. The temperature during the surface-treatment step may be equal to or higher than the melting point of the at least one hydrophobizing agent. For example the temperature may range from 30 to 150 °C, preferably 40 to 140 °C and most preferably from 50 to 130 °C, e.g., at about 80 °C. The heating facilitates decomposition of excess inorganic peroxide.

Accordingly, the at least one inorganic peroxide may be added prior to grinding step c) and/or during grinding step c), and/or before and/or during mixing step e). Preferably, the at least one inorganic peroxide is added prior to grinding step c) and/or during grinding step c) (so that it is present during grinding step c)), or the at least one inorganic peroxide is added during prior to grinding step c) and/or during grinding step c), and before and/or during mixing step e) (so that it is present during grinding step c) and mixing step e)). It is appreciated that the inventive process leads to a reduction of the amount of oxidizable sulfur impurities in the natural calcium carbonate. Thus, in a preferred embodiment, the surface- treated natural calcium carbonate of step e) has an oxidizable sulfur impurity content which is lower than that of the natural calcium carbonate of step a). Preferably, the surface-treated natural calcium carbonate of step c) has an oxidizable sulfur impurity content of less than 25 mg/kg, preferably less than 5 mg/kg, more preferably less than 2 mg/kg and most preferably less than 0.7 mg/kg, based on the total weight of the surface-treated natural calcium carbonate.

Thus, a preferred embodiment of the present invention relates to a manufacturing process, comprising the steps of a) providing a natural calcium carbonate comprising an oxidizable sulfur impurity, b) providing at least one inorganic peroxide, c) grinding the natural calcium carbonate of step a) to a desired particle size to obtain a ground natural calcium carbonate, d) providing at least one surface-treatment agent, and e) mixing the at least one surface-treatment agent of step d) with the ground natural calcium carbonate of step c) to obtain a surface-treated natural calcium carbonate, wherein

- the at least one inorganic peroxide of step b) is mixed with the ground natural calcium carbonate of step c) before and/or during mixing step e).

Accordingly, in one embodiment, the inventive process comprises the steps of a) providing a natural calcium carbonate comprising an oxidizable sulfur impurity, b) providing at least one inorganic peroxide, c) grinding the natural calcium carbonate of step a) to a desired particle size to obtain a ground natural calcium carbonate, d) providing at least one surface-treatment agent, and e) mixing the at least one surface-treatment agent of step d) with the ground natural calcium carbonate of step c) to obtain a surface-treated natural calcium carbonate, wherein the at least one inorganic peroxide of step b) is mixed with the natural calcium carbonate of step a) prior to grinding step c) and/or during grinding step c).

Preferably, the inventive process comprises the steps of a) providing a natural calcium carbonate comprising an oxidizable sulfur impurity, b) providing at least one inorganic peroxide, c) grinding the natural calcium carbonate of step a) to a desired particle size to obtain a ground natural calcium carbonate, d) providing at least one surface-treatment agent, and e) mixing the at least one surface-treatment agent of step d) with the ground natural calcium carbonate of step c) to obtain a surface-treated natural calcium carbonate, wherein the at least one inorganic peroxide of step b) is mixed with the natural calcium carbonate of step a) during grinding step c). Thus, a process is provided, comprising the steps of a) providing a natural calcium carbonate comprising an oxidizable sulfur impurity, b) providing at least one inorganic peroxide, c) grinding the natural calcium carbonate of step a) to a desired particle size to obtain a ground natural calcium carbonate, d) providing at least one surface-treatment agent, and e) mixing the at least one surface-treatment agent of step d) with the ground natural calcium carbonate of step c) to obtain a surface-treated natural calcium carbonate, wherein the at least one inorganic peroxide of step b) is present during grinding step c).

Alternatively, the process comprises the steps of a) providing a natural calcium carbonate comprising an oxidizable sulfur impurity, b) providing at least one inorganic peroxide, c) grinding the natural calcium carbonate of step a) to a desired particle size to obtain a ground natural calcium carbonate, d) providing at least one surface-treatment agent, and e) mixing the at least one surface-treatment agent of step d) with the ground natural calcium carbonate of step c) to obtain a surface-treated natural calcium carbonate, wherein the at least one inorganic peroxide of step b) is mixed with the ground natural calcium carbonate of step c) before and/or during mixing step e).

Preferably, the process comprises the steps of a) providing a natural calcium carbonate comprising an oxidizable sulfur impurity, b) providing at least one inorganic peroxide, c) grinding the natural calcium carbonate of step a) to a desired particle size to obtain a ground natural calcium carbonate, d) providing at least one surface-treatment agent, and e) mixing the at least one surface-treatment agent of step d) with the ground natural calcium carbonate of step c) to obtain a surface-treated natural calcium carbonate, wherein the at least one inorganic peroxide of step b) is mixed with the ground natural calcium carbonate of step c) during mixing step e).

Thus, a process is provided, comprising the steps of a) providing a natural calcium carbonate comprising an oxidizable sulfur impurity, b) providing at least one inorganic peroxide, c) grinding the natural calcium carbonate of step a) to a desired particle size to obtain a ground natural calcium carbonate, d) providing at least one surface-treatment agent, and e) mixing the at least one surface-treatment agent of step d) with the ground natural calcium carbonate of step c) to obtain a surface-treated natural calcium carbonate, wherein the at least one inorganic peroxide of step b) is present during mixing step e).

A further preferred embodiment of the present invention relates to a manufacturing process, comprising the steps of a) providing a natural calcium carbonate comprising an oxidizable sulfur impurity selected from the group consisting of sulfides, polysulfides, elemental sulfur, sulfites, thiosulfates, mercaptans, dialkyl mercaptans and mixtures thereof, preferably selected from the group consisting of sulfides, polysulfides, elemental sulfur and mixtures thereof and most preferably the oxidizable sulfur impurity is a sulfide, b) providing at least one inorganic peroxide selected from the group consisting of hydrogen peroxide, alkali metal peroxides, alkaline earth metal peroxides, peroxyborates, peroxycarbo nates, peroxysulfates and mixtures thereof, most preferably hydrogen peroxide, c) grinding the natural calcium carbonate of step a) to a desired particle size to obtain a ground natural calcium carbonate, d) providing at least one surface-treatment agent, and e) mixing the at least one surface-treatment agent of step d) with the ground natural calcium carbonate of step c) to obtain a surface-treated natural calcium carbonate, wherein

A further preferred embodiment of the present invention relates to a manufacturing process, comprising the steps of a) providing a natural calcium carbonate comprising an oxidizable sulfur impurity selected from the group consisting of sulfides, polysulfides, elemental sulfur, most preferably a sulfide, in an amount of at least 2 mg/kg, preferably at least 5 mg/kg, based on the total weight of the natural calcium carbonate, b) providing at least one inorganic peroxide selected from the group consisting of hydrogen peroxide, alkaline earth metal peroxides and mixtures thereof, most preferably hydrogen peroxide, c) grinding the natural calcium carbonate of step a) to a desired particle size to obtain a ground natural calcium carbonate, preferably wherein the ground natural calcium carbonate has a weight median particle size dso value in the range from 0.1 pm to 25 pm, preferably from 0.25 pm to 5 pm and most preferably from 0.5 pm to 4 pm, d) providing at least one surface-treatment agent being at least one saturated aliphatic linear or branched carboxylic acid, at least one mono-substituted succinic anhydride consisting of succinic anhydride mono-substituted with a group selected from a linear, branched, aliphatic and cyclic group having a total amount of carbon atoms from at least C2 to C30 in the substituent, or a mixture thereof, and e) mixing the at least one surface-treatment agent of step d) with the ground natural calcium carbonate of step c) to obtain a surface-treated natural calcium carbonate, preferably in an amount from 0.1 to 2 wt.-%, more preferably from 0.2 to 1 .5 wt.-%, wherein

- the at least one inorganic peroxide of step b) is mixed with the natural calcium carbonate of step a) prior to grinding step c) and/or during grinding step c) in a total amount of at least 100 ppm by weight, preferably in a total amount from 100 to 5000 ppm by weight, based on the total dry weight of the natural calcium carbonate, and/or

- the at least one inorganic peroxide of step b) is mixed with the ground natural calcium carbonate of step c) before and/or during mixing step e) in a total amount of at least 100 ppm by weight, preferably in a total amount from 100 to 5000 ppm by weight, based on the total dry weight of the ground natural calcium carbonate.

Step f) - Providing at least one polymer

During step f) of a preferred embodiment of the inventive process, at least one polymer is provided.

In practice, filler materials and especially calcium carbonate-containing filler materials are often used as particulate fillers in thermoplastic polymer products, fibers, filaments, films, threads, sheets, pipes, profiles, molds, injection molds and/or blow molds, usually made of polyethylene (PE), polypropylene (PP), polyurethane (PU), polyvinylchloride (PVC), polycarbonate (PC), polyester (PES) and/or polyamide (PA). Thus, the type of polymer is not particularly limited and depends on the intended application of the final products.

The polymer may be composed of one type of homo- or copolymer or may be a blend of two or more homo- or copolymers.

In a preferred embodiment, the polymer is selected from the group consisting of polyolefins, halogen-containing polymers, polyesters, polypeptides, polyethers, poly(meth)acrylates, polysaccharides and derivatives thereof, polyurethanes, polyimides, polyamides, polycarbonates, polyethylene imine), poly(acrylonitrile), poly(vinyl pyrrolidone), poly(vinyl alcohol), polyaniline, poly(vinylidene fluoride), aryl polysulfones, elastomers, and mixtures and co-polymers of the foregoing.

The polymer may be selected from hydrocarbon polymers, i.e., polymers being composed essentially of carbon and hydrogen atoms, e.g., comprising more than 95 mol-% of carbon and hydrogen atoms. Examples include polyolefins and polystyrene.

For example, the polyolefin can be polyethylene and/or polypropylene and/or polybutylene homopolymers or copolymers. Accordingly, if the polyolefin is polyethylene, the polyolefin is selected from the group comprising homopolymers and/or copolymers of polyethylene like high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), very low-density polyethylene (VLDPE), linear low-density polyethylene (LLDPE) and ultra-high molecular weight polyethylene (UHMWPE).

In case the polymer comprises a copolymer of polyethylene, the polyethylene preferably contains units derivable from ethylene as major components. The copolymer of polyethylene preferably comprises, more preferably consists of, units derived from ethylene and C2 and/or at least one C4 to C10 a-olefin. In one embodiment of the present invention, the copolymer of polyethylene comprises, preferably consists of, units derived from ethylene and at least one a-olefin selected from the group consisting of propylene, 1 butene, 1 pentene, 1 -hexene and 1 -octene.

In case the polymer comprises a copolymer of polypropylene, the polypropylene preferably contains units derivable from propylene as major components. The copolymer of polypropylene preferably comprises, preferably consists of, units derived from propylene and C2 and/or at least one C4 to C10 a-olefin. In one embodiment of the present invention, the copolymer of polypropylene comprises, preferably consists of, units derived from propylene and at least one a-olefin selected from the group consisting of ethylene, 1 -butene, 1 -pentene, 1 -hexene and 1 -octene.

Alternatively, the polymer may be a halogen-containing polymer, i.e. hydrocarbon polymers additionally comprising chlorine, bromine, fluorine and iodine moieties. The halogen-containing polymer preferably is selected from polyvinylchloride (PVC), polyvinylidene chloride (PVDC), polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE).

The polyesters may be selected from aromatic polyesters, such as polyethylene terephthalate), aliphatic polyesters, such as polylactones, and/or biodegradable polyesters, such as poly(lactic acid). In a preferred embodiment, the polyesters are selected from the group consisting of polyethylene terephthalate) (PET), poly(ethylene naphthalate), poly(trimethylene terephthalate), poly(butylene terephthalate), poly(lactic acid) (PLA), poly-(L-lactide), poly(glycolic acid), poly-s- caprolactone, poly(3-hydroxy butyrate-co-3-hydroxyvalerate), and mixtures thereof.

The polyethers may be selected from polyalkylene glycols, preferably polyethylene glycols. The term polyethylene oxide is considered synonymous to polyethylene glycol.

The poly(meth)acrylates may be selected from the group consisting of poly(alkyl acrylates), poly(alkyl methacrylates), poly(methyl acrylate), poly(ethyl acrylate), poly(methyl methacrylate), poly(ethyl methacrylate), copolymers thereof, and copolymers of the foregoing with acrylic acid and/or methacrylic acid and/or salts thereof.

The polyimides may be selected from the group consisting of poly(succinimide) (PSI), poly(bismaleic imide) (PBMI), poly(imidosulfone) (PISO), poly(methacrylimide) (PMI), and mixtures thereof.

The polyamides may be selected from the group consisting of aliphatic polyamides, polyphthalamides, aramids, and mixtures thereof, preferably polyamide-6, polyamide-6,6, polyamide- 10, polyamide-11 , polyamide-12, poly-N-isopropylacrylamide and mixtures thereof.

Polycarbonate is a polymer that contains carbonate groups (-O-(C=O)-O-) and is also known under the trade names Lexan, Makrolon, Hammerglass and others. Polycarbonate can be obtained by the reaction of bisphenol A (BPA) with NaOH and afterwards with phosgene COCI2. An alternative route to polycarbonates entails the transesterification from BPA and diphenyl carbonate, wherein the diphenyl carbonate can be derived in part from carbon monoxide.

The aryl polysulfones may be selected from the group consisting of poly(phenylene sulfone), poly(arylene sulfone) (PAS), poly(bisphenol-A sulfone) (PSF), polyether sulfone (PES), polyphenylenesulfone (PPSU), poly(oxy-1 ,4-phenylenesulfonyl-1 ,4-phenylene), and mixtures thereof.

The copolymers may be selected from the group consisting of polyethylene terephthalate)-co- poly(ethylene imine), poly(dioxanone-co-L-lactide)-block-poly(ethylene glycol), poly(ethylene-co-vinyl alcohol) and mixtures thereof.

The polymer may be biocompatible. Non-limiting examples of such biocompatible polymers include, e.g., poly(glycolic acid), poly(lactic acid), poly(s-caprolactone), poly(lactic-co-glycolic acid), poly(N-isopropylacrylamide), chitin, chitosan, alginate, collagen, gelatin, cellulose, poly(vinyl alcohol), polyethylene glycol), albumen, poly(glycerol-co-sebacate), and poly(dimethylsiloxane). The elastomer may comprise an ethylene-propylene rubber, ethylene-propylene-diene rubber, nitrile-butadiene rubber, acrylonitrile-butadiene rubber, butyl rubber, styrene-butadiene rubber, polyisoprene, hydrogenated nitrile-butadiene rubber, polychloroprene, isobutene-isoprene rubber, chloro-isobutene-isoprene rubber, brominated isobutylene-isoprene rubber, acrylic rubbers, butadiene rubbers, epichlorhydrin rubbers, silicone rubbers, fluorocarbon rubbers, polyurethane rubbers, polysulfide rubbers, thermoplastic rubbers, and mixtures thereof. These types of rubber are well- known to the skilled person (see Winnacker/Kuchler, “Chemische Technik. Prozesse und Produkte”, 5^th vol., 5^th Ed., Wiley-VCH 2005, Ch. 4, pp. 821 to 896). Suitable elastomers include those disclosed in WO 2022/013336 A1 , incorporated herein by reference as to the specification of the elastomers.

Preferably, the at least one polymer is a polyolefin, such as polyethylene or polypropylene, and/or a polyester, such as PET or PLA.

Step g) - compounding

According to step g) of a preferred embodiment of the present invention, the ground natural calcium carbonate of step c) and/or the surface-treated calcium carbonate of step e) is compounded with the at least one polymer of step f) to obtain a calcium carbonate-containing polymer compound. Thus, depending on whether the inventive process comprises a surface-treatment step e), the calcium carbonate-containing polymer compound of step g) comprises the ground natural calcium carbonate or the surface-treated natural calcium carbonate. Preferably, the calcium carbonate-containing polymer compound of step g) comprises the surface-treated natural calcium carbonate. However, the calcium carbonate-containing polymer compound of step g) may also comprise a mixture of a ground natural calcium carbonate and a surface-treated natural calcium carbonate.

The compounding step g) may be performed by any compounding method known to the skilled person. Preferably, compounding is performed by a kneading process, wherein a premix of the ground natural calcium carbonate of step c) and/or the surface-treated calcium carbonate of step e) and the at least one polymer of step f) is continuously fed to an extruder, such as a single screw or twin screw extruder. The extruder is heated to a temperature sufficiently high to allow for efficient mixing of all components, which depends on the type of polymer used. A suitable temperature range is 160 to 280 °C, preferably 180 to 250°C.

Alternatively, the ground natural calcium carbonate of step c) and/or the surface-treated calcium carbonate of step e) may be added during compounding to the at least partially molten polymer, e.g., at any split-feed inlet port along the kneading screw of the extruder.

The calcium carbonate-containing polymer compound of step g) may be obtained as a material having a defined shape, such as pellets, spheres, pearls, beads, prills, flakes, chips or slugs, or a non-defined shape, such as, for example, crumbles. Alternatively, the polymer composition may be a mixture of both defined and non-defined shape materials.

Preferably, a pelletizing step is performed after the kneading process to provide the calcium carbonate-containing polymer compound of step g) in the form of pellets.

The amount of the ground natural calcium carbonate of step c) and/or the surface-treated calcium carbonate of step e) in the calcium carbonate-containing polymer compound of step g) depends on the intended application of the polymer compound. For example, the calcium carbonate- containing polymer compound can be a masterbatch, i.e., the masterbatch comprises a high concentration of the ground natural calcium carbonate of step c) and/or the surface-treated calcium carbonate of step e) and is ‘diluted’ with a certain amount of unfilled polymer to arrive at a polymeric compound comprising the desired amount of the ground natural calcium carbonate of step c) and/or the surface-treated calcium carbonate of step e).

If the calcium carbonate-containing polymer compound is a masterbatch, the ground natural calcium carbonate of step c) and/or the surface-treated calcium carbonate of step e) is contained in the same in a (combined) amount from 50 to 85 wt.-%, preferably from 60 to 83 wt.-% and more preferably from 65 to 80 wt.-%, based on the total weight of the masterbatch.

Alternatively, the ground natural calcium carbonate of step c) and/or the surface-treated calcium carbonate of step e) may be contained in the calcium carbonate-containing polymer compound in a (combined) amount from 1 to 50 wt.-%, preferably from 2 to 40 wt.-%, more preferably from 5 to 35 wt.-%, based on the total weight of the calcium carbonate-containing polymer compound.

During compounding step g), optionally one or more additives, which are well known to the skilled person, may be added to the mixture in an amount of up to 5 wt.-%, preferably up to 2 wt.-%, based on the total weight of the masterbatch. Such additives comprise, without being limited to, UV- absorbers, light stabilizers, processing stabilizers, antioxidants, heat stabilizers, nucleating agents, metal deactivators, impact modifiers, plasticizers, lubricants, rheology modifiers, processing aids, pigments, dyes, optical brighteners, antimicrobials, antistatic agents, slip agents, anti-block agents, coupling agents, dispersants, compatibilizers, oxygen scavengers, acid scavengers, markers, antifogging agents, surface modifiers, flame retardants, blowing agents, smoke suppressors, or mixtures of the foregoing additives. Preferred pigments are titanium dioxide as white pigment and color pigments, such as blue, green and red pigments. The additives may be provided in pure form, in dissolved form or in form of a masterbatch. However, it should be understood that preferably no further or other filler materials are added during compounding step g).

Additionally or alternatively, it is possible to add fragrances, such as vanilla or menthol and/or odor masking agents such as zeolites, diethanolamine, and/or odor scavenging agents such as cyclodextrins. However, in a preferred embodiment of the present invention, the calcium carbonate- containing polymer compound does not comprise fragrances and/or odor masking agents and/or odor scavenging agents. Accordingly, it is especially preferred that the calcium carbonate-containing polymer compound comprises neither fragrances, nor odor masking agents, nor odor scavenging agents.

Preferably, the at least one inorganic peroxide is not added before and/or during compounding step g). Instead, as described in detail before, the at least one inorganic peroxide is present during grinding step c) and/or surface-treatment step e). Inorganic peroxides tend to react with the polymers during compounding, which can affect their mechanical properties and/or their stability, as it can lead to chain scissions and/or the formation of crosslinks in the polymers. Peroxide compounds, such as dicumyl peroxide, are sometimes added on purpose in orderto modify the properties of the polymer. However, from the perspective that the ground natural calcium carbonate obtained by the inventive process should be ready to use and should maintain the properties of a ground calcium carbonate that has not undergone a treatment with an inorganic peroxide as far as possible, the at least one inorganic peroxide should be absent during compounding step g). However, it is possible to add crosslinking agents, such as peroxide compounds other than the at least one inorganic peroxide, during compounding step g), if the intended application of the calciumcarbonate containing polymer compound so requires.

The calcium carbonate-containing polymer compound may be formed into a fiber and/or filament and/or film and/or thread and/or sheet and/or pipe and/or profile and/or mold and/or, injection mold and/or blow mold, depending on the intended application.

Thus, the process of the present invention may comprise a further step of forming a fiber and/or filament and/or film and/or thread and/or sheet and/or pipe and/or profile and/or mold and/or injection mold and/or blow mold, which comprises the ground and/or surface-treated natural calcium carbonate and/or the calcium carbonate-containing polymer compound. The so-obtained products are suitable for use as articles, e.g., selected from the group comprising hygiene products, medical and healthcare products, filter products, geotextile products, agriculture and horticulture products, clothing, footwear and baggage products, household and industrial products, packaging products, construction products and the like. It is preferred that the article is a packaging product selected from the group comprising carrier bags, waste bags, transparent foils, hygiene films, agriculture foils, paper like foils, bottles, (thermoform) foils, extrusion coated papers and boards, boxboards, paperboard cartons, paper bags, sacks, corrugated boxes, flexible tubes, such as for cremes, e.g. dermal cremes, and cosmetics, bags, such as for household waste and crates, oriented and bi-oriented films, trays and the like.

The inventive use

In another aspect of the present invention, the use of at least one inorganic peroxide for reducing the odor of a calcium carbonate-containing polymer compound is provided, wherein the at least one inorganic peroxide is contacted with a particulate natural calcium carbonate comprising an oxidizable sulfur impurity prior to compounding it with the polymer.

As outlined above, the unwanted odor may not be noticeable in the (ground) natural calcium carbonate, but only become apparent during compounding step g) and/or in the final calcium carbonate-containing polymer compound. Thus, the present invention is able to reduce or even avoid the evolution of such odor by treating the (ground) natural calcium carbonate before it is incorporated into the polymer compound.

It is appreciated that the calcium carbonate-containing polymer compound, and the at least one inorganic peroxide are as described hereinabove. The term particulate natural calcium carbonate is understood to refer to the natural calcium carbonate and/or the ground natural calcium carbonate as described hereinabove. Moreover, the oxidizable sulfur impurity is as described hereinabove.

Thus, in a preferred embodiment, the at least one inorganic peroxide is contacted with the particulate natural calcium carbonate before and/or during a grinding step and/or before and/or during a surface-treatment step. It is appreciated that the grinding step and the surface-treatment step are as described hereinabove.

In a further preferred embodiment, the particulate natural calcium carbonate is a natural calcium carbonate-containing mineral, preferably selected from the group consisting of chalk, limestone, marble, dolomite and mixtures thereof, as described hereinabove. Alternatively, the particulate natural calcium carbonate is of biological origin, as described hereinabove. The particulate natural calcium carbonate may have an oxidizable sulfur impurity content of at least 0.7 mg/kg, preferably at least 2 mg/kg, more preferably at least 5 mg/kg, even more preferably at least 10 mg/kg and most preferably at least 25 mg/kg, based on the total weight of the natural calcium carbonate.

According to another preferred embodiment of the present invention, a grinding aid is present during the grinding step, preferably wherein the grinding aid is selected from at least one polyol, optionally wherein the polyol comprises amine groups, more preferably wherein the grinding aid is selected from at least one diol or triol, optionally comprising amine groups, even more preferably wherein the grinding aid is selected from the group consisting of ethanediol, propanediol, glycerol, diethanolamine, triethanolamine and mixtures thereof, and most preferably wherein the grinding aid is 1 ,2-propanediol.

According to yet another preferred embodiment, the particulate natural calcium carbonate has i) a weight median particle size dso value in the range from 0.1 pm to 25 pm, preferably from 0.25 pm to 5 pm and most preferably from 0.5 pm to 4 pm, and/or ii) a top cut (cfos) of < 100 pm, preferably < 40 pm, more preferably < 25 pm and most preferably < 15 pm, and/or iii) a specific surface area (BET) of from 0.5 to 150 m²/g, preferably from 0.5 to 50 m²/g, more preferably from 0.5 to 35 m²/g and most preferably from 0.5 to 10 m²/g as measured by the BET nitrogen method, and/or iv) a residual total moisture content of from 0.01 wt.-% to 1 wt.-%, preferably from 0.01 to 0.2 wt.-%, more preferably from 0.02 to 0.2 wt.-% and most preferably from 0.03 to 0.2 wt.-%, based on the total dry weight of the at least one calcium carbonate-containing filler material.

According to still another preferred embodiment, the surface-treatment agent is selected from i. a phosphoric acid ester blend of one or more phosphoric acid monoester and/or one or more phosphoric acid di-ester and/or a salt thereof, and/or ii. at least one saturated aliphatic linear or branched carboxylic acid preferably having a total amount of carbon atoms from C4 to C24 and/or a salt thereof, and/or iii. at least one aliphatic aldehyde, and/or iv. at least one mono-substituted succinic anhydride consisting of succinic anhydride mono-substituted with a group selected from a linear, branched, aliphatic and cyclic group having a total amount of carbon atoms from at least C2 to C30 in the substituent and/or a salt thereof, and/or v. at least one polydialkylsiloxane, and/or vi. mixtures of the materials according to i. to v..

Preferably, the surface-treatment agent is added in an amount from 0.1 to 2 wt.-%, preferably from 0.2 to 1 .5 wt.-% and most preferably from 0.4 to 1 .2 wt.-%, based on the total dry weight of the ground natural calcium carbonate and/or wherein the surface-treatment agent is added in an amount from 0.5 to 5 mg/m², preferably from 1 to 4 mg/m² and most preferably from 1 .3 to 3 mg/m², based on the total surface area of the particulate natural calcium carbonate.

In another preferred embodiment, the at least one inorganic peroxide is contacted with the particulate natural calcium carbonate in an amount of at least 100 ppm by weight, preferably in an amount from 100 to 5000 ppm by weight, more preferably in an amount from 200 to 2000 ppm by weight, even more preferably in a total amount from 200 to 1000 ppm by weight, based on the total dry weight of the particulate natural calcium carbonate.

An exemplary embodiment of the present invention relates to the use of at least one inorganic peroxide for reducing the odor of a calcium carbonate-containing polymer compound, wherein the at least one inorganic peroxide is used in a process as described hereinabove. Thus, the use of at least one inorganic peroxide for reducing the odor of a calcium carbonate-containing polymer compound manufacturing process is provided, wherein the manufacturing process comprises the steps of a) providing a natural calcium carbonate comprising an oxidizable sulfur impurity, b) providing at least one inorganic peroxide, c) grinding the natural calcium carbonate of step a) to a desired particle size to obtain a ground natural calcium carbonate.

In a preferred embodiment of the present use, the calcium carbonate-containing polymer compound has a melt flow index (MFI) that does not substantially differ from the MFI of a polymer compound containing a calcium carbonate that has not undergone treatment with at least one inorganic peroxide. Preferably, the MFI differs by less than 5 g/10min, more preferably less than 2 g/10 min, even more preferably less than 1 .5 g/10 min. Additionally or alternatively, the MFI differs by less than 50%, more preferably by less than 30%, even more preferably by less than 20%, and most preferably by less than 10%.

The MFI (5 kg, 190°C) of the calcium carbonate-containing polymer compound may be in the range from 0.3 to 150 g/10 min, preferably from 1 to 100 g/10min, more preferably from 2 to 50 g/10min, and most preferably from 3 to 30 g/10min.

The term “melt flow rate” (MFR) or “melt flow index” (MFI) as used herein refers to the mass of the polymer, given in g/10 min, which is discharged through a defined die under specified temperature and pressure conditions. For polypropylene, the MFI is commonly measured under a load of 2.16 kg at 230 °C, according to EN ISO 1133:2011 . For polyethylene, the MFI is commonly measured under a load of 2.16 kg or 5 kg at 190°C. The MFI is a measure of the viscosity of the polymer, which is mainly influenced by the molecular weight of the polymer, but also by the degree of branching or the polydispersity.

In a preferred embodiment of the present use, the calcium carbonate-containing polymer compound has an impact strength that does not substantially differ from the impact strength of a polymer compound containing a calcium carbonate that has not undergone treatment with at least one inorganic peroxide. Preferably, the impact strength differs by less than 30%, more preferably by less than 20%, and most preferably by less than 10%.

The impact strength of the calcium carbonate-containing polymer compound may be at least 1 kJ/m², preferably at least 2 kJ/m², more preferably at least 5 kJ/m². As the calcium carbonate- containing polymer compound may not break, there is no particular upper limit of the impact strength. However, the impact strength may be in the range from 1 to 50 kJ/m², preferably from 3 to 40 kJ/m², and most preferably from 5 to 30 kJ/m².

The impact strength can be determined according to ISO 179-1eA.

In a preferred embodiment of the present use, the calcium carbonate-containing polymer compound has an E modulus that does not substantially differ from the E modulus of a polymer compound containing a calcium carbonate that has not undergone treatment with at least one inorganic peroxide. Preferably, the E modulus differs by less than 30%, more preferably by less than 20%, and most preferably by less than 10%.

The E modulus of the calcium carbonate-containing polymer compound may be in the range from 200 to 5000 N/mm², preferably from 400 to 4000 N/mm², most preferably from 600 to 3000 N/mm².

In a preferred embodiment of the present use, the calcium carbonate-containing polymer compound has a yield strength that does not substantially differ from the yield strength of a polymer compound containing a calcium carbonate that has not undergone treatment with at least one inorganic peroxide. Preferably, the yield strength differs by less than 30%, more preferably by less than 20%, and most preferably by less than 10%.

The yield strength of the calcium carbonate-containing polymer compound may be in the range from 5 to 50 N/mm², preferably from 10 to 30 N/mm², most preferably from 12 to 25 N/mm².

In a preferred embodiment of the present use, the calcium carbonate-containing polymer compound has an elongation at break that does not substantially differ from the elongation at break of a polymer compound containing a calcium carbonate that has not undergone treatment with at least one inorganic peroxide. Preferably, the elongation at break differs by less than 30%, more preferably by less than 20%, and most preferably by less than 10%.

The elongation at break of the calcium carbonate-containing polymer compound may be in the range from 100% to 800%, preferably from 125 to 500%, most preferably from 150% to 250%.

The tensile properties (e.g., E modulus, yield strength, elongation at break) may be determined according to ISO527-1 Type BA(1 :2). Examples

I. Analytical methods

BET specific surface area of a material

Throughout the present document, the specific surface area (in m²/g) of the mineral filler is determined using the BET method (using nitrogen as adsorbing gas), which is well known to the skilled man (ISO 9277:2010). The total surface area (in m²) of the mineral filler is then obtained by multiplication of the specific surface area and the mass (in g) of the mineral filler prior to treatment.

Amount of surface-treatment layer

The amount of the treatment layer on the calcium carbonate-comprising filler material is calculated theoretically from the values of the BET of the untreated calcium carbonate-containing filler material and the amount of at least one hydrophobizing agent that are used for the surface-treatment.

Particle size distribution

Volume determined median particle size cfeo(vol) and the volume determined top cut particle size cfei(vol) as well as the volume particle sizes cfoo(vol) and c/io(vol) may be evaluated in a wet (Hydro LV) or dry (Aero S) unit using a Malvern Mastersizer 3000 Laser Diffraction System (Malvern Instruments Pic., Great Britain). The cfeo(vol) or cfo8(vol) value indicates a diameter value such that 50 % or 98 % by volume, respectively, of the particles have a diameter of less than this value. The raw data obtained by the measurement was analyzed using the Mie theory, with a particle refractive index of 1 .57 and an absorption index of 0.005. The methods and instruments are known to the skilled person and are commonly used to determine particle size distributions of fillers and pigments. Determination of sulfide content via the UV-VIS method:

The calcium carbonate sample is dissolved using hydrochloric acid. The hydrogen sulfide that is encapsulated in the stone is liberated, flowed and captured in a solution of N,N-dimethyl-p- phenyldiamine dihydrochloride and iron ammonium sulfate. The amount of H2S is then quantified by colorimetric analysis with a spectrophotometer. The method may be carried out in an instrument as shown in Fig. 1 and/or using a method as follows:

2 to 4 g of sample 5 are added to 40 mL of ultrapure water in a reaction vessel 4. 8 drops of an anti-foaming agent (e.g., Etingal S from BASF) are added. A flow of nitrogen gas 1 (40 mL/min) is applied to the reaction vessel, such that the gas is bubbled through 40 mL of a zinc acetate solution 7 (concentration: 10.00 g zinc acetate dihydrate/ 500 mL). Excess gas is released to the fume hood 8. After 5 minutes, 20 to 40 mL of 4M hydrochloric acid 3 (depending on the mass of sample) are added dropwise via a dropping funnel 2 over the duration of approximately 20 minutes. The nitrogen gas flow 1 is maintained until 5 minutes after the reaction is finished (no more evolving bubbles are visible). The nitrogen flow is closed. 10 mL of coloration reagent solution and 1 mL of iron ammonium sulfate (III) solution are added to the absorption glassware 6. After shaking and letting react for 10 minutes, the solution is transferred into a 100 mL volumetric flask and filled to 100 mL with ultrapure water.

The solution is analysed with a spectrophotometer at a wavelength of 666nm and calibrated against a calibration curve using six standard solutions (40 mL of the above-mentioned zinc acetate solution + 0 pL, 50 pL, 250 pL, 500 pL, 1000 pL, 1500 pL and 2000 pL, respectively, of a main solution).

The coloration reagent solution is prepared as follows: Weigh 0.50 g N,N-dimethyl-p- phenyldiamine dihydrochloride in a fared volumetric flask of 250 mL. Add 50mL of ultrapure water. Add gently 50 mL of concentrated sulfuric acid. Fill the flask to the mark with ultrapure water.

The iron ammonium sulfate (III) solution is prepared as follows: Weigh 5.00 g of iron ammonium sulfate (III) in a fared volumetric flask of 50 mL. Add 1 mL of concentrated sulfuric acid. Fill the flask to the mark with ultrapure water.

The main solution is prepared as follows: Weigh 0.355 g of sodium sulfide nonahydrate, Na2S • 9 H2O, in a fared volumetric flask of 100 mL. Fill the flask to the mark with ultrapure water to obtain the stock solution. Take 1.3 mL of the stock solution in a 25 mL volumetric flask. Fill the flask to the mark with ultrapure water to obtain the main solution.

Determination of sulfide content via X-Ray Fluorescence (XRF) spectroscopy

The elemental sulfur specified as SO3 is measured by XRF following the standard norm ISO 29581- 2:2010 using a XRF spectrometer Perform’X from Thermo Fischer Scientific. Samples are prepared as fused bead(s) with a LOI-free ratio flux material : sample of 9:0.9 (g/g). The LOI (Loss On Ignition) is determined prior to each measurement (using TGA or oven). As flux material a 66:34 mixture of Li Tetraborate and Li Metaborate (purity of the mixture 99.98%), to which 0.20% LiBr is added, is used. The prepared fused bead(s) is/are measured by XRF (X-Ray Fluorescence) using external calibration. The result represents the average of two measurements. The calibration procedure is a standard calibration commonly used for XRF instruments. The calibration is made by 26 certified reference materials (CRM) prepared as fused beads. The drift of the XRF signal occurring with time is corrected by drift monitors (also CRM, also a standard method in XRF). The system is regularly controlled by standard samples with well-known concentrations.

Smell evaluation

The pellets were stored after the extrusion process inside a closed glass container for one day at room temperature, then a testing panel of 7 people assessed the smell intensity of each sample based on the following table:

Table 1 : Smell evaluation ranking

In the case of powder evaluation, they were just stored in their container overnight and evaluated following the same ranking table. II. Experimental part

Part 1 : Materials

1 . Polymer resin

The polymer resin used is a Linear Low Density Polyethylene (CAS No. 9002-88-4) Dowlex 2631.10UE (MFI = 7 g/10min at 190 °C with 2.16 kg) commercially available from Dow.

2. Natural Calcium carbonate CC1

The calcium carbonate CC1 is an untreated marble from Gebze (Turkey) pre-crushed with a particle size d5o of 4 mm containing 25 mg/kg of H2S measured via the UV-VIS method as explained in the description.

3. Natural Calcium carbonate CC2

The calcium carbonate CC2 is based on untreated oyster shells having a dao of 2.6 pm and a dga of 60.5 pm (measured by Malvern 3000, dry) containing elemental sulfur in an amount of 0.58%, specified as SO3 as measured by XRF.

4. Natural Calcium carbonate CC3

The calcium carbonate CC3 is an untreated dry-ground eggshells, with a dao of 21 .9 pm and a dga of 219 pm (measured by Malvern 3000, dry), containing oxidizable sulfur impurities.

5. Natural Calcium carbonate CC4

The calcium carbonate CC4 is an untreated wet-ground eggshells, then dried at 220°C, with a dao of 1 .79 pm and a dga of 10.5 pm (measured by Malvern 3000, dry), containing oxidizable sulfur impurities.

6. Natural Calcium carbonate CC5

The calcium carbonate CC5 is based on untreated eggshells, with a dao of 11 .7 pm and a dga of 46 pm (measured by Malvern 3000, dry), containing oxidizable sulfur impurities.

7. Grinding aid GA-01 :

The grinding aid GA-01 is a 60% monopropylene glycol solution (CAS No. 57-55-6).

8. Grinding aid GA-02:

The grinding aid GA-02 is a 60% food grade monopropylene glycol solution (CAS No. 57-55-6).

9. Hydrophobizing agent HA-01 : Fatty acid mixtures

The hydrophobizing agent HA-01 is a fatty acid mixture consisting of about 40% stearic acid and about 60% palmitic acid. 10. Hydrophobizing agent HA-02:

The hydrophobizing agent HA-02 is a mono-substituted alkenyl succinic anhydride (2,5- Furandione, dihydro-, mono-Ci5-2o-alkenyl derivs., CAS No. 68784-12-3). It is a blend of mainly branched octadecenyl succinic anhydrides (CAS #28777-98-2) and mainly branched hexadecenyl succinic anhydrides (CAS #32072-96-1). More than 80% of the blend is branched octadecenyl succinic anhydrides. The purity of the blend is > 95wt%. The residual olefin content is below 3 wt%.

11 . Inorganic peroxide:

The inorganic peroxide agent is a hydrogen peroxide solution 30% (w/w) (CAS No. 7722-84-1) from Honeywell.

Part 2: Results

Example 1 : Use of hydrogen peroxide during the surface treatment process of GCC

Grinding process:

CC1 was first ground in a ball mill in presence of grinding aid to produce a ground calcium carbonate GCC 1 and GCC 2 with the following specifications: (dso = 1 .9 pm, dgs = 7.5 pm (measured with Malvern 3000, dry)).

The compositions used for the grinding process of GCC 1 and GCC 2 are presented in Table 2:

Table 2: Preparation and composition of ground calcium carbonates GCC 1 and GCC 2

Surface treatment process:

Surface treatment was carried out in a high shear mixer (Somakon MP-LB Mixer, Somakon Verfahrenstechnik, Germany), and conditioned by stirring for 10 minutes at the treatment temperature (80°C, 600-1000 rpm). After that time, the hydrophobizing agent and hydrogen peroxide were successively added to the mixture, stirring and heating is then continued for another 15 minutes. After that time, the mixture is allowed to cool and the powder is collected.

Table 3: Preparation of the surface treated filler material product:

Extrusion process:

Compounds CP-1 to CP-9 were produced on a lab twin-screw extruder from Three-Tec GmbH (Lab Extruder ZE12 - 25:1 , die: 0.5 mm) with the following line settings: - Extruder temperatures: 190°C / 210 °C / 210 °C / 190 °C

Screw speed: 80 rpm

The polymer matrix used is a linear low density polyethylene that can be obtained from Dow under the tradename Dowlex 2631.10UE. Table 4: Preparation and composition of Compounds CP-1 to CP-9

Smell evaluation:

Smell properties were studied as described in the analytical methods and presented in Table 5.

Data presented in Table 5 are average values obtained from the panel evaluation.

Table 5: Smell evaluation results As can be seen in Table 5, the use of hydrogen peroxide leads to a significant decrease of the unpleasant smell, matching the low-smell level of unfilled resin.

Example 2: Use of hydrogen peroxide during the grinding process of GCC

Grinding process:

CC1 was first ground in a ball mill in presence of grinding aid and optionally hydrogen peroxide solution to produce a ground calcium carbonate with the following specifications: (dso = 1 .9 pm, dgs = 7.5 pm (measured with Malvern 3000, dry)).

The compositions used for the grinding process are presented in Table 6:

Table 6: Preparation and composition of ground calcium carbonates GCC 3 and GCC 4

Surface treatment process:

Surface treatment was carried out in a high shear mixer (Somakon MP-LB Mixer, Somakon Verfahrenstechnik, Germany), and conditioned by stirring for 10 minutes at the treatment temperature (80°C, 600-1000 rpm). After that time, the hydrophobizing agent was added to the mixture, stirring and heating is then continued for another 15 minutes. After that time, the mixture is allowed to cool and the powder is collected.

Table 7: Preparation of the surface treated filler material product:

Extrusion process:

Compounds CP-10 and CP-11 were produced on a lab twin-screw extruder from Three-Tec GmbH (Lab Extruder ZE12 - 25:1 , die: 0.5 mm) with the following line settings:

Extruder temperatures: 190°C / 210 °C / 210 °C / 190 °C

Screw speed: 80 rpm

The polymer matrix used is a linear low density polyethylene that can be obtained from Dow under the tradename Dowlex 2631.10UE.

Table 8: Preparation and composition of Compounds CP-10 and CP-11

Smell evaluation:

Smell properties were studied as described in the analytical methods and presented in Table 9.

Data presented in Table 9 are average values obtained from the panel evaluation.

Table 9: Smell evaluation results

As can be seen in Table 9, the use of hydrogen peroxide during the grinding process also leads to a significant decrease of the unpleasant smell.

Example 3: Use of hydrogen peroxide after the grinding process of renewable calcium carbonate (eggshells or oystershells)

After the grinding process, hydrogen peroxide was used to remove the unpleasant smell of CC2, CC3 and CC4.

A 1 L glass beaker with a large magnetic stirring bar was used. CC2, CC3 or CC4, 500ml deionized water and 1 wt% of a hydrogen peroxide 30% solution were added in the beaker and mixed for 30 minutes at 60 °C. Then, the solution was filtered on filter press, washed with water and filtered again. Finally, the powder was dried overnight in the oven at 100°C and deagglomerated on a IKA hand mixer.

Samples are summarized in Table 10:

Smell evaluation:

Smell properties were studied as described in the analytical methods and presented in Table 11 .

Data presented in Table 11 are average values obtained from the panel evaluation. Table 11 : Smell evaluation results

As can be seen in Table 11 , the use of hydrogen peroxide on renewable calcium carbonate after the grinding process also leads to a significant decrease of the unpleasant smell.

Example 4: Use of hydrogen peroxide during the grinding process of renewable calcium carbonate (eggshells):

Grinding process:

CC5 was ground on the Hosokawa Multi Process Unit. The pin mill is a UPZ 100 and the classifier is an ATP 50. The air flow used was 40 m³/h. The grinding was made in presence of hydrogen peroxide solution. Two passes were necessary and the material from the second pass was classified at 14 000 rpm to produce a ground calcium carbonate with the following specifications: (dso = 3.7 pm, dgs = 9.1 pm (measured with Malvern 3000)).

The composition used for the grinding process is presented in Table 12:

Table 12: Preparation and composition of ground calcium carbonate GCC 11

Smell evaluation:

Smell properties were studied as described in the analytical methods and presented in Table 13.

Data presented in Table 13 are average values obtained from the panel evaluation.

Table 13: Smell evaluation results

As can be seen in Table 13, the use of hydrogen peroxide during the grinding process of renewable calcium carbonate also leads to a significant decrease of the unpleasant smell. Example 5: Use of calcium peroxide

Samples of calcium carbonate from Marmara, Turkey, with a size from 0.5 to 1 mm were ground in a ball mill to a target particle size dso of 1 .9 pm and dga of 7.5 pm. The following samples were prepared:

A commercially available material C1 (a calcium carbonate with a dso of 1 .9 pm and dga of 7.5 pm with a surface-treatment of a mixture of stearic and palmitic acid; OFM 750-GZ with Omyacid 39) was used for comparison.

The ground calcium carbonates were compounded as in Example 1 . Smell evaluation was performed as above. The results are as follows:

Example 6: Influence of peroxide treatment on the properties of the polymer compound

Samples of calcium carbonate as in example 5 were ground in a ball mill and subsequently in a pin mill. Thereafter, the obtained calcium carbonates were compounded as in Example 1 in the indicated amounts. The following samples were prepared:

Melt flow index was performed on a CEAST instrument equipped with the software CEAST view 6.15 4C using 5kg loading at 190°C. The polymer is preheated at 190°C for 300s before the start of the measurement. The melt flow rate is then measured along 20mm. The following results are obtained: - M -

The treatment with hydrogen peroxide tends to increase the MFR of a polymer compound incorporating the treated calcium carbonate. However, the corresponding effect is rather small (absolute MFR difference of about 1 .5 g/10 min or less).

The impact properties are measured according to ISO 179-1eA on a HIT5.5P device from Zwick Roell. Measurements are performed on 30% filled LLDPE notched samples with a hammer of 4J. All measurements were performed on samples that have been stored under similar conditions after preparation. All given values are averaged over at least 8 measurements of the same material. The following results were obtained:

The peroxide treatment had a slightly positive influence on the impact properties of the polymer compounds.

The tensile properties are measured according to ISO527-1 Type BA(1 :2) on a Allround Z020 traction device from Zwick Roell. Measurements are performed with an initial load of 0.1 MPa. For the measurement of the E-modulus a speed of 1 mm/min is used, then it is increased to 100 mm/min. The tensile strain at break is obtained under standard conditions. All measurements are performed on samples that have been stored under similar conditions after preparation. All given values are averaged over at least 8 measurements of the same material. The following results were obtained:

The peroxide treatment had a negligible influence on the E modulus and the Yield strength of the polymer compounds. The elongation at break was slightly reduced.

Claims

1 . A manufacturing process, comprising the steps of a) providing a natural calcium carbonate comprising an oxidizable sulfur impurity, b) providing at least one inorganic peroxide, c) grinding the natural calcium carbonate of step a) to a desired particle size to obtain a ground natural calcium carbonate, wherein

2. The process of claim 1 , further comprising the steps of d) providing at least one surface-treatment agent, and e) mixing the at least one surface-treatment agent of step d) with the ground natural calcium carbonate of step c) to obtain a surface-treated natural calcium carbonate.

3. The process of claim 2, wherein the at least one inorganic peroxide of step b) is mixed with the ground natural calcium carbonate of step c) before and/or during mixing step e).

4. The process of any one of the foregoing claims, further comprising the steps of f) providing at least one polymer, and g) compounding the ground natural calcium carbonate of step c) and/or the surface-treated calcium carbonate of step e) with the at least one polymer of step f) to obtain a calcium carbonate- containing polymer compound.

5. The process of any one of the foregoing claims, wherein the natural calcium carbonate of step a) is a natural calcium carbonate-containing mineral, preferably selected from the group consisting of chalk, limestone, marble, dolomite and mixtures thereof.

6. The process of any one of the foregoing claims, wherein the natural calcium carbonate of step a) has an oxidizable sulfur impurity content of at least 0.7 mg/kg, preferably at least 2 mg/kg, more preferably at least 5 mg/kg, even more preferably at least 10 mg/kg and most preferably at least

25 mg/kg, based on the total weight of the natural calcium carbonate.

7. The process of any one of the foregoing claims, wherein the oxidizable sulfur impurity is selected from the group consisting of sulfides, polysulfides, elemental sulfur, sulfites, thiosulfates, mercaptans, dialkyl mercaptans and mixtures thereof, preferably selected from the group consisting of sulfides, polysulfides, elemental sulfur and mixtures thereof and most preferably the oxidizable sulfur impurity is a sulfide.

8. The process of any one of the foregoing claims, wherein the at least one inorganic peroxide is mixed with the natural calcium carbonate of step a) and/or the ground natural calcium carbonate of step c) in a total amount of at least 100 ppm by weight, preferably in a total amount from 100 to 5000 ppm by weight, more preferably in a total amount from 200 to 3000 ppm by weight, based on the total dry weight of the respective calcium carbonate.

9. The process of any one of the foregoing claims, wherein the at least one inorganic peroxide is selected from the group consisting of hydrogen peroxide, alkali metal peroxides, alkaline earth metal peroxides, peroxyborates, peroxycarbonates, peroxysulfates and mixtures thereof, preferably selected from the group consisting of hydrogen peroxide, alkali metal peroxides, alkaline earth metal peroxides and mixtures thereof, more preferably selected from the group consisting of hydrogen peroxide, alkaline earth metal peroxides and mixtures thereof, and most preferably wherein the at least one inorganic peroxide is hydrogen peroxide.

10. The process of any one of the foregoing claims, wherein in step c) a grinding aid is present, preferably wherein the grinding aid is selected from at least one polyol, optionally wherein the polyol comprises amine groups, more preferably wherein the grinding aid is selected from at least one diol or triol, optionally comprising amine groups, even more preferably wherein the grinding aid is selected from the group consisting of ethanediol, propanediol, glycerol, diethanolamine, triethanolamine and mixtures thereof, and most preferably wherein the grinding aid is 1 ,2-propanediol.

11 . The process of claim 10, wherein the grinding aid is present in an amount of at least 50 ppm, preferably at least 100 ppm, more preferably at least 200 ppm and most preferably at least 500 ppm, based on the total dry weight of the natural calcium carbonate.

12. The process of any one of the foregoing claims, wherein the ground natural calcium carbonate of step c) has i) a weight median particle size dso value in the range from 0.1 pm to 25 pm, preferably from 0.25 pm to 5 pm and most preferably from 0.5 pm to 4 pm, and/or ii) a top cut (cfos) of < 100 pm, preferably < 40 pm, more preferably < 25 pm and most preferably < 15 pm, and/or iii) a specific surface area (BET) of from 0.5 to 150 m²/g, preferably from 0.5 to 50 m²/g, more preferably from 0.5 to 35 m²/g and most preferably from 0.5 to 10 m²/g as measured by the BET nitrogen method, and/or iv) a residual total moisture content of from 0.01 wt.-% to 1 wt.-%, preferably from 0.01 to 0.2 wt.-%, more preferably from 0.02 to 0.2 wt.-% and most preferably from 0.03 to 0.2 wt.-%, based on the total dry weight of the at least one calcium carbonate-containing filler material.

13. The process of any one of claims 2 to 12, wherein the surface-treatment agent is selected from i. a phosphoric acid ester blend of one or more phosphoric acid monoester and/or one or more phosphoric acid di-ester and/or a salt thereof, and/or ii. at least one saturated aliphatic linear or branched carboxylic acid preferably having a total amount of carbon atoms from C4 to C24 and/or a salt thereof, and/or

14. The process of any one of claims 2 to 13, wherein the surface-treatment agent is added in an amount from 0.1 to 2 wt.-%, preferably from 0.2 to 1 .5 wt.-% and most preferably from 0.4 to

1 .2 wt.-%, based on the total dry weight of the ground natural calcium carbonate and/or wherein the surface-treatment agent is added in an amount from 0.5 to 5 mg/m², preferably from 1 to 4 mg/m² and most preferably from 1 .3 to 3 mg/m², based on the total surface area of the ground natural calcium carbonate.

15. Use of at least one inorganic peroxide for reducing the odor of a calcium carbonate-containing polymer compound, wherein the at least one inorganic peroxide is contacted with a particulate natural calcium carbonate comprising an oxidizable sulfur impurity prior to compounding it with the polymer.

16. The use of claim 15, wherein the at least one inorganic peroxide is contacted with the particulate natural calcium carbonate before and/or during a grinding step and/or before and/or during a surface-treatment step.

17. The use of any one of claims 15 or 16, wherein the particulate natural calcium carbonate is a particulate natural calcium carbonate-containing mineral, preferably selected from the group consisting of chalk, limestone, marble, dolomite and mixtures thereof.

18. The use of any one of claims 15 to 17, wherein the at least one inorganic peroxide is contacted with the particulate natural calcium carbonate in an amount of at least 100 ppm by weight, preferably in an amount from 100 to 5000 ppm by weight, more preferably in an amount from 200 to 2000 ppm by weight, based on the total dry weight of the particulate natural calcium carbonate.

19. The use of any one of claims 15 to 18, wherein the at least one inorganic peroxide is selected from the group consisting of hydrogen peroxide, alkali metal peroxides, alkaline earth metal peroxides, peroxyborates, peroxycarbo nates, peroxysulfates and mixtures thereof, preferably selected from the group consisting of hydrogen peroxide, alkali metal peroxides, alkaline earth metal peroxides and mixtures thereof, more preferably selected from the group consisting of hydrogen peroxide, alkaline earth metal peroxides and mixtures thereof, and most preferably wherein the at least one inorganic peroxide is hydrogen peroxide.