WO2025132392A1

WO2025132392A1 - A process for producing rosin esters

Info

Publication number: WO2025132392A1
Application number: PCT/EP2024/086850
Authority: WO
Inventors: Jussi Laitio; Ville Nevanlinna
Original assignee: Neste Oyj
Current assignee: Neste Oyj
Priority date: 2023-12-22
Filing date: 2024-12-17
Publication date: 2025-06-26
Anticipated expiration: 2026-06-22
Also published as: FI131246B1; FI20237213A1

Abstract

A process for producing rosin ester comprises preparing a reaction mixture comprising alcohol and rosin, where the rosin is gum rosin, wood rosin, or tall oil rosin. The process comprises spreading the reaction mixture on a heated surface to form a thin layer (201) of the reaction mixture where the esterification reaction takes place. The process comprises removing, from a gas space adjacent to the layer of the reaction mixture, water and other substances evaporated from the reaction mixture, and removing, from the heated surface, product in which the esterification reaction has produced the rosin ester. As the layer (201) of the reaction mixture is thin, mass transfer paths of water molecules leaving the reaction mixture are short and correspondingly an evaporation surface is large. This makes it possible to maintain a low water concentration in the reaction mixture and thereby to increase reaction speed.

Description

A process for producing rosin esters

Field of the disclosure

The disclosure relates generally to rosin esters. More particularly, the disclosure relates to a process for producing rosin esters based on an esterification reaction between alcohol, such as polyol, and gum rosin, wood rosin, or tall oil rosin.

Background

As well known, esterification is a chemical reaction between acid and alcohol to form ester and water. Many alcohols can react with rosin acids to make resinous products, but glycerol and pentaerythritol (PE) dominate the commercial market. The esterification of rosins is advantageously carried out in the presence of a catalyst, such as p-toluene sulfonic acid, hypo-phosphorous acid, calcium- bis[monoethyl(3,5-di-tertiary butyl-4-hydroxybenzyl)phosphonate], and 4,4'- thiobis[2-(1 ,1 -dimethylethyl)-5-methylphenol]). Newer catalysts such as titanates and organotin compounds have been introduced recently. Rosin esters are commonly used as tackifiers for hotmelt adhesives and pressure-sensitive adhesives, modifiers for rubbers and various plastics, base materials for chewing gum, and raw materials such as resins for traffic paints, sizing agents for paper making, emulsifiers for synthetic rubbers, resins for inks, and resins for coatings, and the like.

Typically, production of rosin ester is carried out as a batch process in a reaction vessel. The esterification takes place in a liquid state and at high temperature e.g. from 250°C to 300°C, and typically in the presence of one or more catalysts. To achieve a sufficiently complete esterification, an excess of from 15 to 20 % of alcohol relative to its stoichiometric amount is generally used. The progress of the esterification reaction is typically monitored by determining the acid number, which is typically in the order of 160-180 mg KOH/g for rosin and within the range of 5-15 mg KOH/g for the rosin ester. The residence time in industrial-scale ester production is typically 20-30 hours, which includes a water-vapor stripping of a few hours which is commonly carried out as a last process step. The purpose of the stripping is, in the manner of water-vapor distillation, or inert gas, like N2, distillation, to remove from the reaction product neutrals and odor components present in the rosin. It also causes the softening point of the product to rise, which is often regarded as a desirable property.

Publication EP0872528A2 describes a process for producing tall oil rosin ester with a low odor level. The process comprises an esterification step in a reaction vessel, where a tall oil rosin is esterified with polyol to form a product which contains the tall oil rosin ester. Furthermore, the process comprises an evaporation step carried out on this product to remove odor components and other volatile components from the product. The evaporation is carried out in a short-path evaporator “SPE” which has an evaporation surface and, in the vicinity of this surface, a condenser on which the vaporized components to be removed condense. Tall oil rosin ester with a low odor level is recovered from the short-path evaporator.

To make production of rosin esters more efficient and more beneficial with regards to product quality, flexibility for different types of rosin esters, and/or controllability of a production process, there is a desire to shorten the above-mentioned residence time needed by an esterification reaction as well as to implement a continuous, or at least semicontinuous, ester production process instead of the above-mentioned batch process.

Summary

The following presents a simplified summary to provide a basic understanding of some embodiments of the invention. The summary is not an extensive overview of the invention. It is neither intended to identify key or critical elements of the invention nor to delineate the scope of the invention. The following summary merely presents some concepts of the invention in a simplified form as a prelude to a more detailed description of exemplifying embodiments of the invention.

In accordance with the invention, there is provided a new process for producing rosin esters such as glycerol esters which are commonly called ester gums and pentaerythritol “PE” esters which are often called PE ester gums.

A process according to invention for producing rosin ester comprises: preparing a reaction mixture comprising alcohol, e.g. polyol, and rosin, the rosin being gum rosin, wood rosin, or tall oil rosin,

- spreading the reaction mixture on a heated surface to form a layer of the reaction mixture on the heated surface, an esterification reaction between the alcohol and rosin acids of the rosin taking place in the reaction mixture,

- removing, from a gas space adjacent to the layer of the reaction mixture, substances, including water, evaporated from the reaction mixture, and

- removing, from the heated surface, product in which the esterification reaction has produced the rosin ester.

The thickness of the above-mentioned layer of the reaction mixture can be for example from 0.1 mm to 10 mm, e.g. 5 mm. As the layer of the reaction mixture is thin, mass transfer paths of water molecules leaving the reaction mixture are short and correspondingly an evaporation surface ratio to the reaction mixture volume is larger than in conventional batch vessel type stirred reactor. This makes it possible to maintain a low and even water concentration in the reaction mixture throughout the volume of the reaction mixture and thereby to increase reaction speed, resulting in smaller equipment and shorter residence time compared to a typical batch process. Thus, better quality control and thereby higher quality grades can be achieved compared to a typical batch process. Reaction between rosin and alcohol is equilibrium reaction, which means that when concentration of the reaction products increases in the reaction mixture, produced rosin ester starts to hydrolyze back to rosin in presence of the water. Thus, in a process according to the invention, the residence time reaching the same conversion level in the ester production as in conventional batch vessel type can be low, e.g. from few minutes to few tens of minutes. This is significantly less than residence times of many hours which are typical in industrial-scale ester production at the date of invention of the process described in this document.

The reaction mixture can be fed for example to a thin film evaporator “TFE” to form the layer of the reaction mixture on an interior surface of a cylinder of the thin film evaporator acting as the heated surface. In this exemplifying case, the substances evaporated from the layer of the reaction mixture are removed in a vapor form from the cylinder of the thin film evaporator, and the product is taken out from a bottom part of the thin film evaporator. For another example, the reaction mixture can be fed to a short-path evaporator “SPE” to form the layer of the reaction mixture on an interior surface of a cylinder of the short-path evaporator acting as the heated surface. In this exemplifying case, the substances evaporated from the layer of the reaction mixture are condensed and removed by a condenser inside the cylinder of the short-path evaporator, and the product is taken out from a bottom part of the short-path evaporator. For a third example, the reaction mixture can be fed to a falling film evaporator “FFE” to form the layer of the reaction mixture on interior surfaces of pipes of the falling film evaporator acting as the heated surface.

The layer of the reaction mixture can be arranged to move along the heated surface which is the case when using the above-mentioned thin film evaporator, short-path evaporator, or falling film evaporator. Alternatively, the heated surface can be arranged to continuously move between a feeding point of the reaction mixture and an outlet point of the product which is the case with a conveyor belt type arrangement. Therefore, a continuous ester production process can be provided.

Exemplifying and non-limiting embodiments are described in accompanied dependent claims.

Various exemplifying and non-limiting embodiments both to constructions and to process of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific exemplifying embodiments when read in connection with the accompanying drawings.

The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in the accompanied dependent claims are mutually freely combinable unless otherwise explicitly stated.

Furthermore, it is to be understood that the use of “a” or “an”, i.e. a singular form, throughout this document does not, as such, exclude a plurality. Brief description of figures

Exemplifying and non-limiting embodiments and their advantages are explained in greater details below in the sense of examples and with reference to the accompanying drawings, in which: figure 1 shows a flowchart of a process according to an exemplifying and nonlimiting embodiment for producing rosin ester, figure 2 illustrates a process system for running a process according to an exemplifying and non-limiting embodiment for producing rosin ester, figure 3 illustrates a process system for running a process according to an exemplifying and non-limiting embodiment for producing rosin ester, figure 4 illustrates a process system for running a process according to an exemplifying and non-limiting embodiment for producing rosin ester, figure 5 illustrates a process system for running a process according to an exemplifying and non-limiting embodiment for producing rosin ester, figure 6 illustrates a process system for running a process according to an exemplifying and non-limiting embodiment for producing rosin ester, figure 7 illustrates a process system for running a process according to an exemplifying and non-limiting embodiment for producing rosin ester, figure 8 illustrates a process system for running a process according to an exemplifying and non-limiting embodiment for producing rosin ester, and figure 9 illustrates a process system for running a process according to an exemplifying and non-limiting embodiment for producing rosin ester.

Description of exemplifying embodiments

The specific examples provided in the description below should not be construed as limiting the scope and/or the applicability of the accompanied claims. Lists and groups of examples provided in the description are not exhaustive unless otherwise explicitly stated.

Figure 1 shows a flowchart of a process according to an exemplifying and nonlimiting embodiment for producing rosin ester, such as e.g. glycerol ester or pentaerythritol “PE” ester. The process comprises the following actions:

- action 101 : preparing a reaction mixture comprising alcohol and rosin, wherein the rosin is gum rosin, wood rosin, or tall oil rosin,

- action 102: spreading the reaction mixture on a heated surface to form a layer of the reaction mixture on the heated surface, an esterification reaction between the alcohol and rosin acids of the rosin taking place in the reaction mixture,

- action 103: removing, from a gas space adjacent to the layer of the reaction mixture, substances, including water, evaporated from the reaction mixture, and

- action 104: removing, from the heated surface, product in which the esterification reaction has produced the rosin ester.

In a process according to an exemplifying and non-limiting embodiment, the thickness of the layer of the reaction mixture can be e.g. from 0.1 mm to 10 mm, and more preferably from 1 mm to 5 mm. The temperature of the heated surface is advantageously from 190°C to 350°C, and more advantageously from 250°C to 300°C. As the layer of the reaction mixture is thin, mass transfer paths of water molecules leaving the reaction mixture are short and correspondingly an evaporation surface ratio to the reaction mixture volume is large. This makes it possible to maintain a low water concentration in the reaction mixture and thereby to increase reaction speed. Reaction between rosin and alcohol is equilibrium reaction, which means that when concentration of the reaction products increases in the reaction mixture, produced rosin ester starts to hydrolyze back to rosin in presence of the water. Thus, the residence time in the ester production reaching the same conversion level as in conventional batch vessel type can be low, e.g. from few minutes to few tens of minutes. Typically, the acid number of the reaction mixture decreases during the esterification to a level of 35-15 mg KOH/g, preferably 28-15 mg KOH/g. The acid number can be determined by using e.g. one or more of the standard test methods ASTM D465-15(2020) for Acid Number of Pine Chemical Products Including Tall Oil and Other Related Products.

In a process according to an exemplifying and non-limiting embodiment, the alcohol is polyol that can be for example pentaerythritol, glycerol, or glycol.

In a process according to an exemplifying and non-limiting embodiment, the reaction mixture comprises one or more catalysts. In a process according to an exemplifying and non-limiting embodiment, the one or more catalysts may comprise for example one or more of the following: p-toluene sulfonic acid, hypo-phosphorous acid, calcium-bis[monoethyl(3,5-di-tertiary butyl-4-hydroxybenzyl)phosphonate], 4,4'- thiobis[2-(1 ,1 -dimethylethyl)-5-methylphenol]), titanates compounds, and organotin compounds. It is also possible that no catalyst is used in a process according to an exemplifying and non-limiting embodiment.

In a process according to an exemplifying and non-limiting embodiment, the amount of the alcohol with respect to the rosin in the reaction mixture is from 10% to 300%, more preferably from 90% to 130%, of the stoichiometric amount of the alcohol with respect to the rosin in the esterification reaction.

Figure 2 illustrates a process system for running a process according to an exemplifying and non-limiting embodiment for producing rosin ester. In this exemplifying case, a reaction mixture is fed to a thin film evaporator “TFE” 202 to form a layer 201 of the reaction mixture on an interior surface of a cylinder 213 of the thin film evaporator 202. The thin film evaporator 202 comprises a mechanical agitator 211 comprising wipers at several levels along the path downwards for spreading the reaction mixture to form the thin layer 201 on the interior surface of the cylinder 213, keeping the reaction mixture even and enabling its surface to be renewed over and over again. The mechanical agitator 211 is run with an electric drive 212. The temperature of the interior surface of the cylinder 213 is controlled with a heating fluid, e.g. oil, jacket 207 surrounding the cylinder 213 and with a temperature control system 209. The temperature of the interior surface of the cylinder 213 can be e.g. from 190°C to 350°C, and more advantageously from 250°C to 300°C. Water and other substances evaporated from the layer 201 of the reaction mixture are removed in a vapor form from the cylinder 213 of the thin film evaporator 202 and supplied to a reflux system 250. The other evaporated substances may comprise for example CO2, terpenes, possible unreacted feed materials, and/or impurities of the feed materials. In the reflux system 250, at least part of materials other than water, including possible unreacted feed materials, are condensed and the condensed materials are fed back to the cylinder 213. The reflux system 250 reduces a loss of the feed materials.

Pressure in the gas space adjacent to the layer 201 of the reaction mixture can be e.g. from 900 mbar to 16000 mbar. The layer 201 of the reaction mixture flows downwards along the interior surface of the cylinder 213 due to the gravity simultaneously when the esterification reaction takes place in the reaction mixture. The product comprising the rosin ester is taken out from a bottom part of the thin film evaporator 202. Thus, the esterification process can be a continuous process.

In a process according to an exemplifying and non-limiting embodiment, the rosin is preprocessed prior to preparing the reaction mixture. The preprocessing 217 of the rosin may comprise for example disproportionation carried out by hydrotreating the rosin in presence of a disproportionation catalyst. Examples of the disproportionation catalyst are various known catalysts, for example, metal- supported catalysts such as palladium carbon, rhodium carbon and platinum carbon, powder of metals such as nickel and platinum, iodine, iodides such as iron iodide, and the like. Disproportionation removes conjugated double bonds and thereby increases the stability of the rosin. The major chemical effect of disproportionation is the conversion of abietic acid to dehydroabietic acid.

In a process according to an exemplifying and non-limiting embodiment, the alcohol is preprocessed prior to preparing the reaction mixture. The preprocessing 218 of the alcohol may comprise for example purification of the alcohol.

In a process according to an exemplifying and non-limiting embodiment, the product comprising the rosin ester is postprocessed. The postprocessing 219 of the product ester may comprise for example evaporation to remove unreacted raw materials, possible one or more catalysts, odor components, and/or other unwanted components from the product.

In a process according to an exemplifying and non-limiting embodiment, a part 204 of the product is recycled to the esterification reaction so that the reaction mixture supplied to the thin film evaporator 202 comprises the part 204 of the product in addition to the alcohol, the rosin, and possible one or more catalysts. The product may comprise non-reacted alcohol and rosin acids, and the recycling may decrease the amount of non-reacted alcohol and rosin acids in the product. The recycling can be used for example to keep the feed to the thin film evaporator 202 more even and/or to expand the operating window of the process and/or to preheat the feed.

Figure 3 illustrates a process system for running a process according to an exemplifying and non-limiting embodiment for producing rosin ester. In this exemplifying case, a reaction mixture is fed to a thin film evaporator “TFE” 302 to form a layer 301 of the reaction mixture on an interior surface of a cylinder 313 of the thin film evaporator 302. The thin film evaporator 302 comprises a mechanical agitator 311 comprising wipers at several levels along the path downwards for spreading the reaction mixture to form the thin layer 301 on the interior surface of the cylinder 313, keeping the reaction mixture even and enabling its surface to be renewed over and over again. The temperature of the interior surface of the cylinder 313 is controlled with a heating fluid, e.g. oil, jacket 307 surrounding the cylinder 313 and with a temperature control system 309. The temperature of the interior surface of the cylinder 313 can be e.g. from 190°C to 350°C, and more advantageously from 250°C to 300°C. Water and other substances evaporated from the layer 301 of the reaction mixture are removed in a vapor form from the cylinder 313 of the thin film evaporator 302. Pressure in the gas space adjacent to the layer 301 of the reaction mixture can be e.g. from 900 mbarto 16000 mbar. The layer 301 of the reaction mixture flows downwards along the interior surface of the cylinder 313 due to the gravity simultaneously when the esterification reaction takes place in the reaction mixture. Product_1 comprising the rosin ester is taken out from a bottom part of the thin film evaporator 302. In the exemplifying process system illustrated in figure 3, the product_1 is subjected to evaporation to remove e.g. unreacted raw materials, odor components, possible one or more catalysts, and/or other components from the product_1. In this exemplifying case, the product_1 coming out from the thin film evaporator 302 is fed to a short-path evaporator “SPE” 306 in order to subject the product_1 to the above- mentioned evaporation. The short-path evaporator 306 comprises a mechanical agitator 314 comprising wipers for spreading the product_1 to form a thin layer 315 on the interior surface of a cylinder 316 of the short-path evaporator 306. The thickness of the layer 315 can be from 0.1 mm to 10 mm, and more preferably from 0.1 mm to 5 mm. The temperature of the interior surface of the cylinder 316 is controlled with a heating fluid, e.g. oil, jacket 308 surrounding the cylinder 316 and with a temperature control system 309a. The temperature of the interior surface of the cylinder 316 can be e.g. from 250°C to 300°C. Water and other substances evaporated from the layer 315 are condensed and removed by a condenser 303 that is inside the cylinder 316 of the short-path evaporator 306. The temperature of the condenser 303 is controlled with a cooler 310 that circulates coolant, e.g. water, through the condenser 303. Evaporation-processed product_2 is taken out from a bottom part of the short-path evaporator 306. Neutrals, fatty acids, and rosin can be removed from the product_1 during the evaporation in the short-path evaporator 306. The acid number of the product_2 containing the rosin ester and coming out from the evaporation can be e.g. from 0.2 to 10, preferably from 2 to 6. As the substances evaporated from the layer 315 condense in the vicinity of the layer 315, pressure in a gas space adjacent to the layer 315 can be low. This, in turn, intensifies the evaporation from the layer 315. The pressure in the gas space adjacent to the layer 315 can be as low as from e.g. 0.1 mbar to 20 mbar.

In a process according to an exemplifying and non-limiting embodiment, a part 305 of the condensate coming out from the condenser 303 of the short-path evaporator 306 is recycled to the thin film evaporator 302 so that the reaction mixture supplied to the thin film evaporator 302 comprises the part 305 of the condensate in addition to the alcohol, the rosin, and possible one or more catalysts. The part 305 of the condensate may comprise non-reacted alcohol and rosin acids, and thus the recycling may decrease the loss of the alcohol and rosin acids. Figure 4 illustrates a process system for running a process according to an exemplifying and non-limiting embodiment for producing rosin ester. In this exemplifying case, a reaction mixture is fed to a short-path evaporator “SPE” 402 to form a layer 401 of the reaction mixture on an interior surface of a cylinder 413 of the short-path evaporator 402. The short-path evaporator “SPE” 402 comprises a mechanical agitator 411 comprising wipers for spreading the reaction mixture to form the thin layer 401 on the interior surface of the cylinder 413, keeping the reaction mixture even, and enabling its surface to be renewed over and over again. The temperature of the interior surface of the cylinder 413 is controlled with a heating fluid, e.g. oil, jacket 408 surrounding the cylinder 413 and with a temperature control system 409. The temperature of the interior surface of the cylinder 413 can be e.g. from 190°C to 350°C, and more advantageously from 250°C to 300°C. Water and other substances evaporated from the layer 401 of the reaction mixture are condensed and removed by a condenser 403 inside the cylinder 413 of the shortpath evaporator 402. The temperature of the condenser 403 is controlled with a cooler 410 that circulates coolant, e.g. water, through the condenser 403. The temperature of the condenser 403 can be selected so that water is not condensed whereas materials such as unreacted feed materials are condensed. The condensed materials are returned from a condensate collection system 450 back to the cylinder 413 and water is removed from the condensate collection system 450 in the vapor form. This arrangement reduces a loss of the feed materials.

The layer 401 of the reaction mixture flows downwards along the interior surface of the cylinder 413 due to the gravity simultaneously when the esterification reaction takes place in the reaction mixture. The product comprising the rosin ester is taken out from a bottom part of the short-path evaporator 402. As the substances evaporated from the layer 401 of the reaction mixture condense in the vicinity of the layer 401 , pressure in a gas space adjacent to the layer 401 can be low, e.g. from 0.1 mbar to 20 mbar. This, in turn, intensifies the evaporation from the layer 401 and thereby increases the reaction speed and thus reduces the required residence time needed for the esterification.

In a process according to an exemplifying and non-limiting embodiment, a part 404 of the product is recycled to the esterification reaction so that the reaction mixture supplied to the short-path evaporator 402 comprises the part 404 of the product in addition to the alcohol, the rosin, and possible one or more catalysts. The product may comprise non-reacted alcohol and rosin acids, and the recycling may decrease the amount of the non-reacted alcohol and rosin acids in the product.

Figure 5 illustrates a process system for running a process according to an exemplifying and non-limiting embodiment for producing rosin ester. In this exemplifying case, a reaction mixture is fed to a chain of series connected thin film evaporators “TFE” 502a, 502b, and 502c where an outlet at a bottom part of a preceding thin film evaporator is connected to an inlet of a following thin film evaporator in the chain of the series connected thin film evaporators 502a-502c. In this exemplifying case, amount of non-reacted alcohol and rosin acids decreases in each of the series connected thin film evaporators 502a-502c so that the amount of non-reacted alcohol and rosin acids is smaller in product_3 than in product_2 and smaller in the product_2 than in product_1 . The number of the series connected thin film evaporators is not necessarily three, but the number can be as well two or greater than three. Each of the thin film evaporators 502a-502c comprises a mechanical agitator that comprises wipers for spreading the reaction mixture to form the thin layer on the interior surface of the cylinder of the thin film evaporator under consideration. As illustrated in figure 5, the wipers of the thin film evaporators 502a- 502c are different from the wipers illustrated in figures 2, 3, and 7. Embodiments of the invention based on thin film evaporators are not limited to any specific type of wipers.

Figure 6 illustrates a process system for running a process according to an exemplifying and non-limiting embodiment for producing rosin ester. In this exemplifying case, a reaction mixture is fed to a chain of series connected shortpath evaporators “SPE” 602a, 602b, and 602c where an outlet at a bottom part of a preceding short-path evaporator is connected to an inlet of a following short-path evaporator in the chain of the series connected short-path evaporators 602a-602c. In this exemplifying case, amount of non-reacted alcohol and rosin acids decreases in each of the series connected short-path evaporators 602a-602c so that the amount of non-reacted alcohol and rosin acids is smaller in product_3 than in product_2 and smaller in the product_2 than in product_1 . The number of the series connected short-path evaporators is not necessarily three, but the number can be as well two or greater than three.

Figure 7 illustrates a process system for running a process according to an exemplifying and non-limiting embodiment for producing rosin ester. In this exemplifying case, a batch of reaction mixture is fed to a container tank 750 from which the reaction mixture is fed to a thin film evaporator “TFE” 702. The output of the thin film evaporator 702 is recycled back to the container tank 750 so that material constituted by non-reacted raw materials and formed rosin ester is circulated via the container tank 750 and the thin film evaporator 702 until the proportion of the rosin ester is high enough in the material contained by the container tank 750, i.e. the acid number is sufficiently low. After this, the product is taken out from the container tank 750 via an outlet 751. Capital expenses “CAPEX” of the process system illustrated in figure 7 are typically lower than those of the process system illustrated in figure 5, because in the process system illustrated in figure 7 the same thin film evaporator 702 is used many times for achieving sufficient esterification whereas in the process system illustrated in figure 5 there are many series connected thin film evaporators for achieving sufficient esterification. On the other hand, the exemplifying process illustrated with the aid of figure 7 is a semi batch process in which quality control is more laborious than in a continuous process that can be carried out e.g. in the process system illustrated in figure 5. In an exemplifying embodiment, the process system comprises two or more container tanks such that, when the content of one of the container tanks is under processing, another one of the container tanks can be loaded or emptied, or its content can be analyzed. Thus, the thin film evaporator “TFE” 702 can be used more continuously and with lesser breaks than when having only one container tank.

Figure 8 illustrates a process system for running a process according to an exemplifying and non-limiting embodiment for producing rosin ester. The process system illustrated in figure 8 is otherwise like the process system illustrated in figure 7, but the esterification takes place in a short-path evaporator “SPE” 802 instead of a thin film evaporator. In an exemplifying embodiment, the process system comprises two or more container tanks such that, when the content of one of the container tanks is under processing, another one of the container tanks can be loaded or emptied, or its content can be analyzed. Thus, the short-path evaporator “SPE” 802 can be used more continuously and with lesser breaks than when having only one container tank.

In an exemplifying embodiment, each of the container tanks is provided with a water removing channel for removing water vapor from the container tank.

In an exemplifying embodiment, each of the container tanks is provided with an agitator for stirring the reaction mixture contained by the container tank.

In a process according to an exemplifying and non-limiting embodiment, the above- mentioned container tank 750 is a first one of two or more container tanks, the above-mentioned reaction mixture that has been fed to the first one of the container tanks is a first batch of the reaction mixture, and a second batch of the reaction mixture is fed to a second one of the container tanks when the first batch of the reaction mixture is being circulated via the first one of the container tanks and a reactor that is the thin film evaporator 702 or the short-path evaporator 802, and the second batch of the reaction mixture is being circulated via the second one of the container tanks and the reactor when the product is taken out from the first one of the container tanks and when a next batch of the reaction mixture is subsequently fed to the first one of the container tanks, and so on.

In a process according to an exemplifying and non-limiting embodiment, water vapor is removed from each of the container tanks when the container tank contains the reaction mixture.

In a process according to an exemplifying and non-limiting embodiment, the reaction mixture contained by each of the container tanks is stirred with an agitator.

Figure 9 illustrates a process system for running a process according to an exemplifying and non-limiting embodiment for producing rosin ester. In this exemplifying case, a reaction mixture is fed to a falling film evaporator “FFE” 902 to form layers of the reaction mixture on interior surfaces of pipes of the falling film evaporator 902. In figure 9, one of the layers is denoted with a reference 901 . The temperature of the interior surface of the pipes of the falling film evaporator 902 is controlled with a heating fluid, e.g. oil, jacket surrounding the pipes and with a temperature control system 909. The temperature can be e.g. from 190°C to 350°C, and more advantageously from 250°C to 300°C. Pressure in gas spaces adjacent to the layers of the reaction mixture can be e.g. from 900 m bar to 16000 mbar. Water and other substances evaporated from the layers of the reaction mixture are removed via a bottom area of the falling film evaporator 902. The layers of the reaction mixture flow downwards along the interior surfaces of the pipes due to the gravity simultaneously when the esterification reaction takes place in the reaction mixture. The product comprising the rosin ester is taken out from a bottom part of the falling film evaporator 902. In the exemplifying process system illustrated in figure 9, a part 904 of the product is recycled to the esterification reaction so that the reaction mixture supplied to the falling film evaporator 902 comprises the part 904 of the product in addition to the alcohol, the rosin, and possible one or more catalysts. The product may comprise non-reacted alcohol and rosin acids, and the recycling may decrease the amount of non-reacted alcohol and rosin acids in the product. The recycling can be used for example to keep the feed to the falling film evaporator 902 more even and/or to expand the operating window of the process and/or to preheat the feed.

The specific examples provided in the description given above should not be construed as limiting. For example, in the embodiments presented in the accompanying drawings, each of the thin film evaporators can be replaced with a short-path evaporator or a falling film evaporator, and vice versa. Furthermore, the single thin film evaporator in the semi batch process, i.e. the semicontinuous process, illustrated in figure 7 can be replaced by e.g. a series connection of two or more evaporators each of which can be a thin film evaporator, a short-path evaporator, or a falling film evaporator. Correspondingly, the single short-path evaporator in the semi batch process, i.e. the semicontinuous process, illustrated in figure 8 can be replaced by e.g. a series connection of two or more evaporators each of which can be a thin film evaporator, a short-path evaporator, or a falling film evaporator. Therefore, the invention is not limited merely to the exemplifying and non-limiting embodiments described above. Lists and groups of examples provided in the description are not exhaustive unless otherwise explicitly stated.

Claims

What is claimed is:

1 . A process for producing rosin ester, the process comprising:

- preparing (101 ) a reaction mixture comprising alcohol and rosin, the rosin being gum rosin, wood rosin, or tall oil rosin, characterized in that the process comprises:

- spreading (102) the reaction mixture on a heated surface to form a layer (201 , 301 , 401 , 901 ) of the reaction mixture on the heated surface, an esterification reaction between the alcohol and rosin acids of the rosin taking place in the reaction mixture,

- removing (103), from a gas space adjacent to the layer of the reaction mixture, substances, including water, evaporated from the reaction mixture, and

- removing (104), from the heated surface, product in which the esterification reaction has produced the rosin ester.

2. A process according to claim 1 , wherein a thickness of the layer (201 , 301 , 401 ) of the reaction mixture is from 0.1 mm to 10 mm.

3. A process according to claim 1 or 2, wherein the alcohol is polyol.

4. A process according to claim 3, wherein the polyol is one of following: pentaerythritol, glycerol, and glycol.

5. A process according to any one of claims 1-4, wherein temperature of the heated surface is from 190°C to 350°C.

6. A process according to any one of claims 1-5, wherein the reaction mixture comprises one or more catalysts.

7. A process according to claim 6, wherein the one or more catalysts comprise at least one of following: p-toluene sulfonic acid, hypo-phosphorous acid, calcium- bis[monoethyl(3,5-di-tertiary butyl-4-hydroxybenzyl)phosphonate], 4,4'-thiobis[2- (1 ,1 -dimethylethyl)-5-methylphenol]), titanates compounds, and organotin compounds.

8. A process according to any one of claims 1 -7, wherein an amount of the alcohol with respect to the rosin in the reaction mixture is from 10% to 300%, more preferably from 90% to 130%, of a stoichiometric amount of the alcohol with respect to the rosin in the esterification reaction.

9. A process according to any one of claims 1-8, wherein the reaction mixture is fed to a thin film evaporator (202, 302, 502a, 702) to form the layer (201 , 301 ) of the reaction mixture on an interior surface of a cylinder of the thin film evaporator acting as the heated surface or to a falling film evaporator (902) to form the layer of the reaction mixture on interior surfaces of pipes of the falling film evaporator acting as the heated surface, substances evaporated from the layer of the reaction mixture are removed in a vapor form from the cylinder of the thin film evaporator, and the product is taken out from a bottom part of the thin film evaporator or the falling film evaporator.

10. A process according to claim 9, wherein pressure in a gas space adjacent to the layer (201 , 301 ) of the reaction mixture is from 900 mbar to 16000 mbar.

11. A process according to claim 9 or 10, wherein the thin film evaporator (502a) is a first one in a chain of series connected two or more thin film evaporators (502a- 502c) where an outlet at a bottom part of a preceding thin film evaporator is connected to an inlet of a following thin film evaporator in the chain of the series connected thin film evaporators.

12. A process according to claim 9 or 10, wherein the reaction mixture is fed to a container tank (750) from which the reaction mixture is fed to the thin film evaporator (702), an output of the thin film evaporator is recycled back to the container tank so that material constituted by non-reacted raw materials and formed rosin ester is circulated via the container tank and the thin film evaporator until a proportion of the rosin ester exceeds a limit proportion in material contained by the container tank, and thereafter the product is taken out from the container tank.

13. A process according to any one of claims 1-8, wherein the reaction mixture is fed to a short-path evaporator (402, 602a, 802) to form the layer (401 ) of the reaction mixture on an interior surface of a cylinder of the short-path evaporator acting as the heated surface, substances evaporated from the layer of the reaction mixture are condensed and removed by a condenser (403) that is inside the cylinder of the shortpath evaporator, and the product is taken out from a bottom part of the short-path evaporator.

14. A process according to claim 13, wherein pressure in a gas space adjacent to the layer (401 ) of the reaction mixture is from 0.1 mbar to 20 mbar.

15. A process according to claim 13 or 14, wherein the short-path evaporator (602a) is a first one in a chain of series connected two or more short-path evaporators (602a-602c) where an outlet at a bottom part of a preceding short-path evaporator is connected to an inlet of a following short-path evaporator in the chain of the series connected short-path evaporators.

16. A process according to claim 13 or 14, wherein the reaction mixture is fed to a container tank (750) from which the reaction mixture is fed to the short-path evaporator (802), an output of the short-path evaporator is recycled back to the container tank so that material constituted by non-reacted raw materials and formed rosin ester is circulated via the container tank and the short-path evaporator until a proportion of the rosin ester exceeds a limit proportion in material contained by the container tank, and thereafter the product is taken out from the container tank.

17. A process according to claim 12 or 16, wherein the container tank (750) is a first one of two or more container tanks, the reaction mixture fed to the first one of the container tanks is a first batch of the reaction mixture, and a second batch of the reaction mixture is fed to a second one of the container tanks when the first batch of the reaction mixture is being circulated via the first one of the container tanks and a reactor being the thin film evaporator (702) or the short-path evaporator (802), and the second batch of the reaction mixture is being circulated via the second one of the container tanks and the reactor when the product is taken out from the first one of the container tanks and when a next batch of the reaction mixture is subsequently fed to the first one of the container tanks.

18. A process according to claim 12 or 16 or 17, wherein water vapor is removed from each container tank when the container tank contains the reaction mixture.

19. A process according to claim 12 or 16 or 17 or 18, wherein the reaction mixture contained by each container tank is stirred with an agitator.

20. A process according to any one of claims 1 -19, wherein a part (204, 404, 904) of the product is recycled to the esterification reaction so that the reaction mixture spread on the heated surface comprises the part of the product in addition to the alcohol and the rosin.

21 . A process according to any one of claims 1-20, wherein the product in which the esterification reaction has produced the rosin ester is subjected to evaporation to remove volatile components from the product.

22. A process according to claim 21 , wherein at least some of the volatile components are condensed to form a condensate, and a part (305) of the condensate is recycled to the esterification reaction so that the reaction mixture spread on the heated surface comprises the part of the condensate in addition to the alcohol and the rosin.

23. A process according to claim 21 or 22, wherein the product is fed to a shortpath evaporator (306) to subject the product to the evaporation.