DE102008000811A1 - Preparing paper, paperboard and cardboard, comprises shearing the paper material, adding ultrasound treated microparticle system and fine-particle inorganic component to the paper material and dewatering the paper material to form sheets - Google Patents

Abstract

Method for the preparation of paper, paperboard and cardboard, comprises shearing the paper material, adding ultrasound treated microparticle system made of cationic polymers and a fine-particle inorganic component to the paper material following the last shearing step before agglomerating the material, dewatering the paper material to form sheets, and drying the sheets, where the inorganic component of the micro particle system is in the form of an aqueous suspension with a solid concentration of maximum 10 wt.%.

Description

The The invention relates to a process for the production of paper by Draining a stock in the presence of a retention aid system from a cationic polymer and a finely divided inorganic Component.

The use of combinations of nonionic or anionic polymers and bentonite as a retention agent in the production of paper is known, cf. US-A-3,052,595 and EP-A-0 017 353 ,

From the EP-A-0 223 223 discloses a method of producing paper and board by dewatering a stock by first adding bentonite to a stock having a fabric concentration of 2.5 to 5 wt%, then diluting the stock, a highly cationic polymer having a charge density of at least 4 meq / g and a high molecular weight polyacrylamide added, mixed the pulp and then dewatered sheet formation.

Also known is a process for the production of paper which comprises initially adding to an aqueous fiber slurry a substantially linear synthetic cationic polymer having a molecular weight greater than 500,000 in an amount greater than 0.03% by weight, based on dry stock metered, the mixture is then subjected to the action of a shear field, then adding bentonite and dewatering the pulp thus obtained without further action of shear forces, cf. EP-A-0 235 893 , Another method in which a microparticle system of a combination of cationic polymers and bentonite is used is known from US Pat EP-A-0 335 557 known. In addition, this method employs a low molecular weight polymer as a fixing agent and a high molecular weight cationic polymer, also subjecting the pulp to the action of shear forces, then adding bentonite and dewatering the stock to form sheets.

Other methods of making paper using a microparticle system include, for example EP-A-0 885 328 . EP-A-0 711 371 . EP-A-0 910 701 . EP-A-0 608 986 and US-A-6,103,065 known. In US Patent No. 5,393,381 . WO-A-99/66130 and WO-A-99/63159 also a microparticle system is described as a retention agent for the production of paper, wherein the cationic polymer used is a water-soluble, branched polyacrylamide.

After the out of the WO-A-01/34910 In known processes, a polysaccharide or a synthetic polymer is metered into the paper stock in papermaking, the paper stock then sheared and dewatered after the addition of an inorganic compo nents such as silica, bentonite or clay and a water-soluble polymer with formation of leaves.

In the from the DE-A-102 36 252 known method for the production of paper, the paper stock is first sheared, then - before the headbox - mixed with a microparticle system of a cationic polymer and a finely divided inorganic component and then dehydrated. The microparticle system is free of polymers with a charge density of more than 4 meq./g.

As from the above State of Technology and Technical Information, Paper Industry, Microfloc ® S, August 2005 issue, BASF Aktiengesellschaft Ludwigshafen, the inorganic component of the retention aid system is converted into an aqueous suspension. This requires high shear forces. In addition, a sufficient swelling time must be maintained. For the preparation of bentonite suspension, for example, a bentonite dissolving dosing system is recommended in which the suspension is pumped, filtered, diluted and fed to the metering point of the paper machine by means of progressing cavity pumps, cf. Page 3 of the Technical Information Microfloc ® , The solids content of the suspensions is for example 3 to 5 wt .-%.

Of the Invention is based on the object in the production of paper the effectiveness of the known microparticle systems, in particular to further improve the retention of fines and fillers.

The Task is solved according to the invention a process for the production of paper, cardboard and cardboard Shearing a stock, adding a microparticle system a cationic polymer and a finely divided inorganic Component to the pulp, dewatering of the pulp under leaf formation and drying of the leaves, if you put the inorganic component of the microparticle system prior to addition to the paper stock in the form of an aqueous suspension a solids concentration up to at most 10 wt .-% of a Ultrasound treatment subjects.

To the method of the invention can all paper qualities are produced, z. As cardboard, single / multilayer carton, single / multilayer Liner, corrugated medium, papers for newspaper printing, so-called medium fine writing and printing papers, natural gravure papers and lightweight coating papers. To make such papers, For example, you can use wood pulp, thermomechanical material (TMP), chemo-thermo-mechanical substance (CTMP), pressure ground (PGW), Wood pulp and sulphite and sulphate pulp go out. The pulps can be short fiber as well as long fiber. Preferably be wood-free by the novel process Produced grades that yield high-white paper products.

The Papers may optionally be up to 40% by weight, usually 5 to 35 wt .-% fillers. Suitable fillers are z. As titanium dioxide, natural and precipitated Chalk, talc, kaolin, satin white, calcium sulfate, barium sulfate, Clay or alumina.

The Microparticle system is known to consist of a cationic polymer and a finely divided anionic component. As cationic polymers come cationic polyacrylamides, Vinylamineinheiten containing Polymers, polydiallyldimethylammonium chlorides or mixtures thereof with an average molecular weight Mw of at least 500,000 daltons each and a charge density of at most 4.0 meq./g in each case Consideration. Particularly preferred are cationic polyacrylamides with a mean molecular weight Mw of at least 3 million daltons and a charge density of 0.1 to 3.5 meq./g and polyvinylamines, the polymers containing by hydrolysis of vinylformamide units are available, wherein the degree of hydrolysis of vinylformamide units 5 to 100 mol% and the average molecular weight of the polyvinylamines at least 2 million daltons. The polyvinylamines are preferred produced by hydrolysis of homopolymers of vinylformamide, wherein the degree of hydrolysis is, for example, 5 to 20 mol%.

Cationic polyacrylamides are, for example, copolymers prepared by copolymerizing acrylamide and at least one di-C ₁ - to C ₂ -alkylamino-C ₂ - to C ₄ -alkyl (meth) acrylate or a basic acrylamide in the form of the free bases, the salts with organic or inorganic acids or the alkyl halides quaternized compounds are available. Examples of such compounds are dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl acrylate, diethylaminoethyloacrylyl, dimethylaminopropyl methacrylate, dimethylaminopropyl acrylate, diethylaminopropyl methacrylate, diethylaminopropyl acrylate and / or dimethylaminoethylacrylamide. Further examples of polymers containing cationic polyacrylamides and vinylamine units may be the references cited in the prior art, such as EP-A-0 910 701 and US-A-6,103,065 be removed. One can use both linear and branched polyacrylamides. Such polymers are commercial products. Branched polymers, the z. Example, by copolymerization of acrylamide or methacrylamide with at least one cationic monomer in the presence of small amounts of crosslinking agents can be produced, for example, in the references cited in the prior art US Patent No. 5,393,381 . WO-A-99/66130 and WO-A-99/63159 described.

Further suitable cationic polymers are polydiallyldimethylammonium chlorides (PolyDADMAC) with an average molecular weight of at least 500,000 Dalton, preferably at least 1 million daltons. Polymers of this Type are commercial products.

The cationic polymers of the microparticle system become the pulp in an amount of 0.005 to 0.5% by weight, preferably in an amount from 0.005 to 0.2% by weight.

Suitable inorganic components of the microparticle system are, for example, bentonite, colloidal silicic acid, silicates and / or calcium carbonate. Colloidal silicic acid should be understood as meaning products based on silicates, e.g. As silica microgel, silical sol, polysilicates, aluminum silicates, boron silicates, polyborosilicates, clay or zeolites. Calcium carbonate can be used, for example, in the form of chalk, ground calcium carbonate or precipitated calcium carbonate as the inorganic component of the microparticle system. Bentonite is generally understood to be phyllosilicates which are swellable in water. These are mainly the clay mineral montmorillonite and similar clay minerals such as nontronite, hectorite, saponite, sauconite, beidellite, allevardite, illite, halloysite, attapulgite and sepiolite. These phyllosilicates are preferably activated before use, ie converted into a water-swellable form in which the phyllosilicates are treated with an aqueous base such as aqueous solutions of sodium hydroxide solution, potassium hydroxide solution, soda or potash. Bentonite in the form treated with sodium hydroxide solution is preferably used as the inorganic component of the microparticle system. The platelet diameter of the water-dispersed bentonite in the sodium hydroxide-treated form is, for example, 1 to 2 μm, the thickness of the platelets is about 1 nm. Depending on the type and activation, the bentonite has a specific surface area of 60 to 800 m ² / g. Typical bentonites are z. B. in the EP-B-0235893 described. In the Pa pieronite process, bentonite is added to the cellulosic suspension, typically in the form of an aqueous slurry. This bentonite slurry may contain up to 10% by weight of bentonite. The aqueous slurries contain the inorganic component of the microparticle system, for example in an amount of 1 to 6, preferably 3 to 5 wt .-%. Bentonite is preferably used as the inorganic component of the microparticle system.

As colloidal silica, products from the group of silicon-based particles, silica microgels, silica sols, aluminum silicates, borosilicates, polyborosilicates or zeolites can be used. These have a specific surface area of 50-1000 m ² / g and an average particle size distribution of 1-250 nm, usually in the range 40-100 nm. The preparation of such components is e.g. In EP-A-0041056 . EP-A-0185068 and US-A-5176891 described.

Clay or kaolin is a hydrous aluminum silicate with platelet-shaped Structure. The crystals have a layer structure and an aspect ratio (diameter to thickness ratio) of up to 30: 1. The particle size is at least 50% smaller 2 mm.

As carbonates, preferably calcium carbonate, natural calcium carbonate (ground calcium carbonate, GCC) or precipitated calcium carbonate (PCC) can be used. GCC is produced by grinding and visual processes using grinding aids. It has a particle size of 40-95% less than 2 mm, the specific surface area is in the range of 6-13 m ² / g. PCC is made by passing carbon dioxide into calcium hydroxide solution. The average particle size is in the range of 0.03-0.6 mm, the specific surface area can be greatly influenced by the choice of precipitation conditions. It is in the range of 6-13 m ² / g.

The inorganic component of the microparticle system becomes the pulp in an amount of 0.01 to 1.0% by weight, preferably in an amount from 0.1 to 0.5% by weight.

Treated according to the invention the aqueous suspension of the inorganic component with ultrasound. The ultrasonic treatment of the aqueous Suspension of the inorganic component of the microparticle system For example, it may be carried out batchwise. The frequency of the ultrasound is at least for example 20 kHz.

The Sonication of the aqueous suspension of inorganic However, the component of the microparticle system can also be continuous be performed. The aqueous suspension of inorganic component of the microparticle system is then, for example passed through a cell in which the ultrasound treatment takes place. The aqueous suspension can under atmospheric pressure or under increased pressure by the treatment center be guided. When higher pressures applied are, for example, they are 1 to 10 bar, preferably at 1 to 5 bar.

These continuous performance of the ultrasonic treatment has the advantage of being integrated directly into the papermaking process can be. The thus treated aqueous suspension at least an inorganic component then becomes continuous to the papermaking process fed. The ultrasonic treatment of the aqueous Suspension of the inorganic component of the microparticle system is performed at least as long as that during the application Such a suspension in the papermaking process a Improved drainage and retention a corresponding untreated aqueous suspension is achieved. For example, the amount supplied to the system Energy (energy / volume) at least 20 Ws / ml, mostly at least 70 Ws / ml and is preferably at least 100 Ws / ml, z. B. 100 to 500 Ws / ml.

The ultrasound treatment of aqueous suspensions of phyllosilicates of a microparticle system leads to a delamination, ie a separation of silicate layers. The most necessary treatment of an aqueous bentonite suspension using an Ultra-Turrax ^® device or a high-speed stirrer for finely dispersing and / or delamination of bentonite in water can be omitted in the inventive method. Rather, it is already sufficient to disperse the inorganic particles in water first with the aid of a stirrer and then treat the suspension with ultrasound.

object The invention is also the use of aqueous Suspensions containing up to 10 wt .-% of at least one layered silicate and which have been ultrasonicated, as inorganic Component of a microparticle system in the manufacture of paper, Cardboard and cardboard.

The Density of the pulp is for example 1 to 100 g / l, preferably 4 to 30 g / l. The aqueous fiber slurry is subjected to at least one shear stage. She goes through at least one cleaning, mixing and / or pumping stage. The Shearing the pulp can be done, for example, in a pulper, classifier or done in a refiner. After the last shearing stage and before the Headbox on the screen is metered according to the invention Microparticle system. Particularly preferred is an operation, first using the cationic polymer and then the ultrasonically treated inorganic component of the microparticle system dosed to the pulp, which was previously sheared. You can, however also initially the ultrasonically treated inorganic Component of the microparticle system and then the cationic polymer or add both components to the stock at the same time. Thereafter, the dehydration of the pulp is carried out without further Influence of shear forces on a sieve under sheet formation. The paper sheets are then dried.

Except the microparticle system can be the stock usually process chemicals used in papermaking in the usual amounts enforce, for. Fixative, dry and wet strength agents, engine sizes, biocides, and / or Dyes.

With the method according to the invention is compared the known method, an improvement in drainage and an improvement in the ash retention, without the formation and deteriorate paper properties. Also achieved a significant improvement in fiber recovery and thus relieving the water cycle of the paper machine.

The Percentages in the examples mean weight percent, if the context does not indicate otherwise.

The Viscosity of aqueous suspensions of bentonite was in a Brookfield viscometer (spindle 3, 20 rpm) at a Temperature of 20 ° C determined.

The Particle size of the bentonite suspended in water was using a Beckmann Coulter LS 130 by light scattering determined, where the specified particle size the median particle size (D50) is.

The Drainage time was in a Schopper-Riegler test equipment determined by adding in each case 1 l of the pulp to be tested dehydrated in it and time determined for the passage of 600 ml of filtrate was necessary.

The FPA retention (first-pass ash retention) was determined by determination the ratio of the solids content in the white water to Solids content determined in the headbox. Only the ash content was considered. The information is given in percent.

Examples 1-5

Production of bentonite suspensions

First there was prepared a aqueous suspension of bentonite prepared by mixing 1200 g of bentonite (Mikrofloc ^® S, BASF Aktiengesellschaft, Ludwigshafen) earned in 30 liters of deionized water and the mixture was stirred for 30 minutes with a blade stirrer with 120-150 rpm. The suspension thus obtained was pumped continuously by means of a centrifugal pump through an ultrasonic cell (Hielscher Ultrasonics GmbH, UIP 1000, Sonotrode BS2d22, 3.8) under the flow rates and pressures indicated in Table 1. The energy used is also given in the table. The aqueous suspensions of bentonite thus obtained were each collected, and the viscosity and particle size were determined. Table 1 example Flow rate [l / h] Recorded energy [Ws / ml] Pressure [bar] Viscosity of Bentonite-SusPension [mPas] Particle size (D50) [μm] 1 60 26 2 310 4.47 2 7.5 106 conveyed without pressure 795 4.34 3 7.5 230 2 1160 4.08 4 7.5 332 4 1600 3.44 5 5 323 2 1555 3.52

The sonicated aqueous bentonite suspensions were subsequently evaluated for their effectiveness tested in a microparticle system in papermaking. The results are shown in Table 2.

papermaking

The paper production took place in each case in a Britt-Jar test device. For all examples, a paper furnish of 100% woodfree uncoated paper, 30% woodfree coated paper, 0.06% of C ₁₈ alkyl diketene, 0.6% cationic starch and 20% ground calcium carbonate was used. The stock was diluted to a solids content of 0.77% and each with a retention aid system of (i) a cationic polyacrylamide having an average molecular weight M _w of 9 million and a charge density of 1.7 meq./g in the form of a water-in -oil emulsion (Polymin ^® 540) and (ii) each of the above sonicated aqueous bentonite suspension was added to give first (i) the cationic polyacrylamide and then (ii) dose the inorganic component. The amount of cationic polyacrylamide was 0.01%, the amount of bentonite 0.2%. The results for drainage and FPA retention are given in Table 2. Table 2 Aqueous bentonite suspension obtained according to Example Drainage time [s] FPA retention [%] 1 34 56.6 2 34 56.6 3 33 57.7 4 32 58.5 5 32 59.5

Comparative Example 1

A 4% strength aqueous suspension of bentonite was prepared by stirring in bentonite (Mikrofloc ^® S, BASF Aktiengesellschaft, Ludwigshafen) in the specified amount of water and the mixture was then stirred for 4 hours at room temperature. The viscosity of the bentonite suspension was 110 mPas, the particle size (D50) was 11.05 μm.

The Papermaking according to Example 1 was the only exception repeated that now as an inorganic component of the microparticle system the prepared according to Comparative Example 1 bentonite suspension in used the same amount. The drainage time was 41 s, the FPA retention 55.9%.

Comparative Example 2

A 4% strength aqueous suspension of bentonite was prepared by stirring in bentonite (Mikrofloc ^® S, BASF Aktiengesellschaft, Ludwigshafen) in the specified amount of water and the mixture followed End 20 minutes at room temperature, treated with an Ultra-Turrax ^®. The viscosity of the bentonite suspension was 650 mPas, the particle size (D50) was 5 microns.

The Papermaking according to Example 1 was the only exception repeated that now as an inorganic component of the microparticle system the prepared according to Comparative Example 2 bentonite suspension in used the same amount. The drainage time was 36 s, the FPA retention 56.3%.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - US 3052595 A [0002]
• - EP 0017353 A [0002]
• - EP 0223223 A [0003]
• - EP 0235893 A [0004]
• - EP 0335557 A [0004]
• EP 0885328 A [0005]
• - EP 0711371 A [0005]
• - EP 0910701 A [0005, 0014]
• EP 0608986 A [0005]
• - US 6103065 A [0005, 0014]
• - US 5393381 A [0005, 0014]
• WO 99/66130 A [0005]
• WO 99/63159 A [0005, 0014]
• WO 01/34910 A [0006]
• - DE 10236252 A [0007]
• WO 99/66130 [0014]
• - EP 0235893 B [0017]
• - EP 0041056 A [0018]
• EP 0185068 A [0018]
• - US 5176891 A [0018]

Cited non-patent literature

• - State of Technology and Technical Information, Paper Industry, Microfloc ® S, August 2005 Edition, BASF Aktiengesellschaft [0008]
• - Page 3 of the Technical Information Microfloc ® [0008]

Claims (12)

A process for the production of paper, paperboard and cardboard by shearing a pulp, adding a microparticle system comprising a cationic polymer and a finely divided inorganic component to the pulp, dewatering the pulp to form sheets and drying the leaves, which comprises introducing the inorganic component of the microparticle system the addition to the paper stock in the form of an aqueous suspension having a solids concentration of at most 10 wt .-% subjected to an ultrasonic treatment. Method according to claim 1, characterized in that that the solids concentration of the aqueous suspension of the inorganic component of the microparticle system 1 to 6% by weight is. Method according to claim 1 or 2, characterized that the solids concentration of the aqueous suspension of the inorganic component of the microparticle system 3 to 5% by weight is. Method according to one of claims 1 to 3, characterized in that the ultrasonic treatment of aqueous suspension of the inorganic component of the microparticle system discontinuously. Method according to one of claims 1 to 3, characterized in that the ultrasonic treatment of aqueous suspension of the inorganic component of the microparticle system performs continuously and the thus treated aqueous Suspension continuously fed to the papermaking process. Method according to one of claims 1 to 5, characterized in that the ultrasonic treatment of the aqueous Suspension of the inorganic component of the microparticle system at least as long as that is carried out in the application an improvement in drainage in the papermaking process and the retention against a corresponding untreated aqueous suspension is achieved. Method according to one of claims 1 to 6, characterized in that as an inorganic component of the microparticle system is a naturally occurring phyllosilicate starts. Method according to one of claims 1 to 7, characterized in that as an inorganic component microparticle system bentonite, colloidal silica, Clay, kaolin and / or calcium carbonate. Method according to one of claims 1 to 8, characterized in that at least one cationic polyacrylamide having an average molecular weight M _w of at least 3 million daltons, at least one vinylamine units containing polymer having an average molecular weight M _w of at least 2 as the organic component of the microparticle system Millions and / or at least one Polydiallyldimethylammoniumchlorid having an average molecular weight M _w of at least 500,000 sets. Method according to one of claims 1 to 9, characterized in that the cationic polymer of the microparticle system the stock in an amount of 0.005 to 0.2 wt .-%, based on dry stock, is added. Method according to one of claims 1 to 10, characterized in that the inorganic component of Microparticle system the stock in an amount of 0.01 to 1.0 wt .-%, based on dry pulp, is added. Use of aqueous suspensions, containing up to 10 wt .-% of at least one layered silicate and which have been sonicated as inorganic Component of a microparticle system in the manufacture of paper, Cardboard and cardboard.