WO2025248168A1

WO2025248168A1 - Method for producing dispersion comprising polysaccharide and rosin and dispersion thereof

Info

Publication number: WO2025248168A1
Application number: PCT/FI2025/050275
Authority: WO
Inventors: Joonas SIIRILÄ; Anneli Lepo; Elisabeth LACKINGER-CSARMANN
Original assignee: Kemira Oyj
Current assignee: Kemira Oyj
Priority date: 2024-05-28
Filing date: 2025-05-26
Publication date: 2025-12-04
Anticipated expiration: 2026-11-28

Abstract

There is provided a method for producing a dispersion comprising a polysaccharide, such as cellulose ester, and rosin. Additionally is provided a dispersion comprising a polysaccharide, such as cellulose ester and rosin.

Description

METHOD FOR PRODUCING DISPERSION COMPRISING POLYSACCHARIDE

AND ROSIN AND DISPERSION THEREOF

TECHNICAL FIELD

The present disclosure generally relates to a method for producing aqueous dispersion comprising polysaccharide and rosin, and to a dispersion thereof.

BACKGROUND

This section illustrates useful background information without admission of any technique described herein representative of the state of the art.

Currently there is increasing interest for sustainable packing solutions. Cellulosic substrates are appealing as these are largely derived from renewable sources and recyclable.

Cellulose is, however, hygroscopic and cellulosic substrates are susceptible to lose their integrity and properties when in contact with water. Thus, hydrophobic compounds such as polymers and resins need to be added during the production of paper and board to decrease the water sensitivity. In production of paper and board the process is called sizing or coating.

One of the most appealing methods to coat or size paper or board during production is by applying the protective component as a water based dispersion. Water based dispersions are preferred as water is environmentally benign and abundant and already used in the production of cellulosic substrates.

Hydrophobic polysaccharide derivates are one potential coating material for paper and board due to similarity with the base material, which is useful in considering recycling. Polysaccharides are generally renewable and biodegradable, saccharide derivatives, such as cellulose ester can also be.

The preparation of water based dispersions of hydrophobic polysaccharide derivates, such as cellulose esters is difficult due to low water solubility, high melt viscosity and high melting temperature range of the derivates. In the art, small molecular weight additives , i.e. solvent and additives have been used to lower the required processing temperatures. The small molecular weight additives are, however, unwanted in the final application and need to be removed during processing or processed to become incorporated as part of the coating.

Rosin is a small molecular weight additive (mostly Mn < 500 g/mol). It, however, does not need to be removed or processed to become part of a coating or a product. It is an active component, commonly used in sizing, especially internal sizing.

Based on above, there is a need for more efficient methods for producing aqueous saccharide dispersions, such as cellulose ester dispersions.

SUMMARY

The appended claims define the scope of protection. Any examples and technical descriptions of apparatuses, products and/or methods in the description and/or drawings not covered by the claims are presented not as embodiments of the invention but as background art or examples useful for understanding the invention.

In a first aspect the present invention provides an aqueous dispersion comprising polysaccharide and rosin, wherein amount of the polysaccharide is at most 95 wt.%, based on the total dry weight of the aqueous dispersion, wherein zero shear rate viscosity of the polysaccharide is equal or less than 500000 mPa s at 160 °C

In a second aspect the present invention provides a method for producing aqueous dispersion comprising polysaccharide and rosin, wherein the method comprises (i) providing polysaccharide and rosin;

(ii-a) mixing the polysaccharide and the rosin to obtain a mixture comprising polysaccharide and rosin, and melting the mixture to obtain a mixture comprising polysaccharide melt and rosin melt;

(ii-b) melting the polysaccharide and melting the rosin, and mixing the polysaccharide melt and the rosin melt to obtain a mixture comprising polysaccharide melt and rosin melt;

(ii-c) melting the polysaccharide, and mixing the rosin to the polysaccharide melt to obtain a mixture comprising polysaccharide melt and rosin melt; or

(ii-d) melting the rosin, and mixing the polysaccharide to the rosin melt to obtain a mixture comprising polysaccharide melt and rosin melt; and

(iii) mixing aqueous phase and the mixture comprising polysaccharide melt and rosin melt to obtain the aqueous composition comprising polysaccharide and rosin. In a third aspect the present invention provides a fiber based substrate comprising the aqueous dispersion according to the present invention or the aqueous composition produced with the method according to the present invention.

In a fourth aspect the present invention provides use of the aqueous dispersion according to the present invention or the aqueous composition produced with the method according to the present invention as a surface sizing agent, an adhesive or a tackifier

It has been surprisingly found that rosin and rosin derivates, such as fortified rosin and rosin esters with polyols, mix with hydrophobic saccharides, such as cellulose esters as melt and the melt can be processed to form an aqueous dispersion. Thus, the present invention enables use of hydrophobic polysaccharides, such as cellulose esters in dispersions.

Cellulose esters itself tend to be viscous at industrial relevant temperatures (90-250 °C). It has been surprisingly found that rosin lowers the viscosity of cellulose esters and makes the melt of cellulose esters and rosin more feasible to be processed, pumped and dispersed in to water. This removes the need for solvent and additional plasticizers and lowers the need for high mechanical force processing methods.

It has been surprisingly found that by increasing the amount of the rosin in polysaccharide/rosin mixtures zero shear rate viscosity decreases.

The hydrophobic polysaccharide / rosin aqueous dispersion can be used in surface treatment of various materials, including cellulosic surfaces, such as paper and board.

The appended claims define the scope of protection.

DETAILED DESCRIPTION

In a first aspect the present invention provides an aqueous dispersion comprising polysaccharide and rosin, wherein amount of the polysaccharide is at most 95 wt.%, based on the total dry weight of the aqueous dispersion., wherein zero shear rate viscosity of the polysaccharide is equal or less than 500000 mPa s such as 2000 mPa s-500000 m Pa s at 160 °C In one embodiment the amount of the polysaccharide is from 5 wt.% to 95 wt.%, preferably from 7 wt.% to 80 wt.%, more preferably from 20 wt.% to 60 wt.%, based on the total dry weight of the aqueous dispersion.

In one embodiment the amount of the rosin is from 5 wt.% to 95 wt.%, preferably from 8 wt.% to 80 wt.% based on the total dry weight of the aqueous dispersion.

In one embodiment the polysaccharide has glass transition temperature (T_g) -20 °C-200 °C, preferably 25 °C-200 °C more, preferably 60 °C-195 °C, such as 75 °C- 195 °C or 60 °C-100 °C.

The glass transition temperature values are measured with differential scanning calorimeter from a dry (non-water containing) sample. The value is taken from the onset of glass transition temperature from the second heating cycle. First heating cycle is used to diminish the effect of thermal history. The heating rate is 10 °C/min.

In one embodiment the polysaccharide has zero shear rate viscosity of equal or less than 500000 mPa s, such as 2000 mPa s-500000 mPa s, preferably equal or less than 400000 mPa s, such as 2000 mPa s-400000 mPa s, more preferably equal or less than 300000 mPa s, such as 2000 mPa s-300000 mPa s at 160 °C.

The zero shear rate viscosity value is measured by using a modular compact rheometer 302e from Anton Paar equipped with a plate-plate i.e. parallel plate geometry at 160 °C and using a heating hood accessory or an oven. Moderate N2 flow is applied during the measurement. First sample is completely melted in the instrument. Then the mixture is equilibrated at least 10 min at the measuring temperature. Complex viscosity at different shear rates are obtained from a frequency sweep with 1 % strain. Zero shear rate viscosity is obtained by extrapolating to zero shear rate.

In one embodiment the polysaccharide/rosin 50/50 by weight mixture has zero shear rate viscosity of 25000-40000 mPa s, such as 33000 mPa s at 140 °C.

In one embodiment the polysaccharide/rosin 20/80 by weight mixture has zero shear rate viscosity of 4000-10000 mPa, such as 7000 mPa s at 140 °C.

In one embodiment the polysaccharide/rosin 10/90 by weight mixture has zero shear rate viscosity of 200-500 mPa s, such as 380 mPa s at 140 °C. By term “polysaccharide” is meant molecules consisting of more than four monosaccharide residual units connected to each other via glycosidic bonds. Examples of polysaccharides are dextran, amylopectin, amylose, starch, glycogen, cellulose, hemicellulose, glucans, lignin-carbohydrate complexes, starch, chitin, chitosan, hyaluronan and a mixture thereof. By the term “polysaccharide” is meant also derivates of said polysaccharides, where part or all of the hydroxyl groups are substituted with alkyl esters or ethers or amides or a mixture thereof.

By term “hydrophobic polysaccharide” is meant water resistant, non-soluble, minimal swelling polysaccharides, mainly derivates of polysaccharides.

In one embodiment the polysaccharide is a polysaccharide, a polysaccharide derivative or a mixture thereof. The polysaccharide and the polysaccharide derivative are preferably substantially water-insoluble, more preferably waterinsoluble.

In one embodiment the polysaccharide comprises dextran, amylopectin, amylose, starch, glycogen, cellulose, hemicellulose, glucans, lignin-carbohydrate complexes, starch, chitin, chitosan, hyaluronan, a derivative thereof or a mixture thereof.

In one embodiment the polysaccharide derivative is linear or branched alkyl ester or ether or amide derivative of polysaccharide. The polysaccharide derivative may carry functional groups, such as hydroxyl and/or carboxylic acid.

In one embodiment the polysaccharide derivate is an ester, preferably the polysaccharide derivative is cellulose ester.

In one embodiment the cellulose ester is cellulose ester with acetic acid, propionic acid, butyric acid or a mixture thereof.

In one embodiment the polysaccharide derivative comprises cellulose ester C1-C18 acyl, cellulose ether C1-C18 alkyl or a mixture thereof. Preferably the polysaccharide derivative is cellulose ester C2-C4 acyl, cellulose ether C2-C4 alkyl, such as cellulose acetate butyrate or a mixture thereof, preferably cellulose acetate butyrate. In one embodiment number average molecular weight (Mn) of the cellulose ester is 5000 g/mol-2000000 g/mol, preferably 10000 g/mol-250000 g/mol, more preferably 16000 g/mol-75000 g/mol, even more preferably 10000 g/mol-25000 g/mol. The number average molecular weight (Mn) are polystyrene-equivalent weights determined using size-exclusion chromatography.

Crude tall oil is produced as a side product in kraft pulping. Through distillation crude tall oil can be fractionated into tall oil fatty acids, rosin and to some additional fractions. Tall oil rosin (TOR) is a bioderived starting material for the product development. TOR and TOR derivates are used in sizing by the industry, especially in internal sizing. TOR mainly consist of various rosin acids like, but not limited to, abietic acid, dehydroabietic acid, palustric acid, neoabietic acid, levopimaric acid and pimaric acids. Upon heating TOR will gradually soften and finally become a liquid. TORs and TOR derivates are usually described using a softening point (SP) which is a temperature where the material exhibits softness according to an agreed level and determined by a standardized test. TOR and TOR derivates may crystallize at temperatures below 140 °C. Heating above 160 °C will melt the crystals. TOR derivates include TOR fortified with maleic anhydride / fumaric acid and TOR esters.

By term “rosin” is meant rosin and its derivatives. The rosin may even be a mixture of different rosins.

In one embodiment the rosin comprises rosin, rosin derivatives, such as rosin esters, dimerised rosins, polymerised rosins, hydrogenated rosins, saponified rosins, fortified rosins and unfortified rosins or a mixture thereof, preferably fortified rosin.

By term “fortified rosin” is meant an adduct of unsaturated carboxylic acid or unsaturated carboxylic acid anhydride and rosin. Suitable fortification carboxylic acids are, for example, fumaric acid, acrylic acid, maleic acid, itaconic acid, and maleic acid anhydride. Fortified rosins obtained by adducting maleic acid anhydride or fumaric acid to the rosin are being preferred. In one embodiment the fortified rosin may comprise 0.2-80 wt.% of the carboxylic acid rosin acid adducts. In one embodiment the rosin may be selected from a group consisting of tall oil rosin, wood rosin, gum rosin, their derivatives and a mixture thereof.

In one embodiment the rosin comprises tall oil rosin, wood rosin, gum oil rosin, their derivative or a mixture thereof. Preferably the rosin is tall oil rosin, more preferably fortified tall oil rosin.

In one embodiment the aqueous dispersion comprises additionally a first stabilization agent, such as polyamine, starch, starch derivative such as degraded starch, cationic starch, anionic starch or non-ionic starch, glucan derivative such as cationic or anionic glucan, carboxymethyl cellulose, hydroxy ethyl cellulose, polyvinyl alcohol, polyethylene glycol, copolymer of ethylene and propylene glycol or a mixture thereof. Preferably the first stabilization agent is polyamine, starch, polyvinyl alcohol or a mixture thereof. The polyvinyl alcohol is preferably be derived from poly(vinyl acetate) and have a degree of hydrolysis equal or less than 90%, more preferably equal or higher than 70%, such as 70-90%.

In one embodiment the aqueous dispersion comprises additionally a second stabilization agent, such as sodium lignosulfonate, naphthalene sulfonate, starch derivative, such as degraded starch, cationic starch, anionic starch, non-ionic starch or a mixture thereof, preferably sodium lignosulfonate.

In one embodiment amount of the first stabilization agent is 0.1 wt.%-30 wt.%, preferably 5 wt.%-20 wt.%, based on the total dry weight of the aqueous dispersion.

In one embodiment amount of the second stabilization agent is 0 wt.%-20 wt.%, preferably 0 - 10 wt.%, more preferably from 0.5 - 5 wt.% based on the total dry weight of the aqueous dispersion.

In one embodiment pH of the aqueous dispersion is 3-9, preferably 3-8, more preferably 4-7.

In one embodiment the aqueous dispersion is substantially free of organic solvents, preferably free of organic solvents. By the term “substantially free of organic solvent” is meant that the amount of the organic solvent is less than 1 wt.%, based on the total weight of the aqueous dispersion. In one embodiment the aqueous dispersion is substantially free of additional plasticizers. By term “additional plasticizers” is meant other plasticizers know in the art than the rosin and polysaccharide, preferably free of additional plasticizers. By term “substantially free of additional plasticizer” is meant that the amount of the additional plasticizer is less than 1 wt.%, based on the total weight of the aqueous dispersion.

Instead of the aqueous dispersion the aqueous form can be aqueous composition, aqueous suspension or aqueous emulsion depending on the production method of the aqueous form.

In one embodiment solid content of the aqueous dispersion is 5-80 %, preferably 10-70 %, more preferably 20-60 %.

In one embodiment viscosity of the aqueous dispersion is less than 1500 mPa s, such as 1-1000 mPa s or 1-500 mPa s or 1-100 mPa s. The viscosity values are measured at 25 °C, with Brookfield LVDV viscometer at solids content of 35-40 wt.%.

In one embodiment D50 particle size of the aqueous polysaccharide/rosin dispersion, such as cellulose acetate butyrate/fortified rosin aqueous dispersion is equal or less than 1 .0 pm, such as 0.5-1 pm or 0.5-0.9 pm.

In one embodiment D90 particle size of the aqueous polysaccharide/rosin dispersion, such as cellulose acetate butyrate/fortified rosin aqueous dispersion is equal or less than 2.5 pm, such as 1 .0-2.5 pm or 1 .5-2.4 pm.

In one embodiment D95 particle size of the aqueous polysaccharide/rosin dispersion such as cellulose acetate butyrate/fortified rosin aqueous dispersion is equal or less than 3.0 pm, such as 2.6-3.0 pm or 2.5-3.0 pm.

The particle sizes are measured by using Malvern Mastersizer 3000. In the present context the particle size D50 refers to the value for 50th percentile of a volume based distribution, the particle size D90 refers to the value for 90th percentile of a volume based distribution and the particle size D95 refers to the value for 95th percentile of a volume based distribution.

The aqueous dispersion may be cationic, anionic or non-ionic. In one embodiment charge density of the aqueous polysaccharide/rosin dispersion at pH 3.5 is +5-+11 peq/g, preferably +5.5-+10.5 peq/g, more preferably +6.0- +10.5 peq/g.

Charge density was measured by using particle charge detector, Mutek™ PCD-05. The samples were diluted with deionized water and the pH adjusted to pH 3.5. The cationic samples were titrated with an anionic titrant. The results were calculated based on dry content.

In one embodiment the aqueous dispersion is produced with the method according to the present invention.

(iii) mixing aqueous phase and the mixture comprising polysaccharide melt and rosin melt to obtain the aqueous dispersion comprising polysaccharide and rosin.

In the option (ii-c) temperature of the polysaccharide melt is high enough to melt the rosin.

In the option (ii-d) temperature of the rosin melt is high enough to melt the polysaccharide.

Instead of the aqueous dispersion the aqueous form can be aqueous composition, aqueous suspension or aqueous emulsion depending on the production method of the aqueous form. In one embodiment the aqueous phase is water, aqueous suspension, aqueous dispersion or aqueous emulsion.

In one embodiment the aqueous phase is water, aqueous suspension, aqueous dispersion or aqueous emulsion containing a first stabilization agent and/or a second stabilization agent.

In one embodiment a first stabilization agent or a second stabilization agent is introduced to the aqueous dispersion comprising polysaccharide and rosin.

In one embodiment a first stabilization agent and a second stabilization agent are introduced to the aqueous dispersion comprising polysaccharide and rosin. In one embodiment the method additionally comprises homogenizing the aqueous dispersion comprising polysaccharide and rosin.

In a third aspect the present invention provides a fiber based substrate comprising the aqueous dispersion according to the present invention or the aqueous dispersion produced with the method according to the present invention.

In a fourth aspect the present invention provides use of the aqueous dispersion according to the present invention or the aqueous dispersion produced with the method according to the present invention as a surface sizing agent, an adhesive or a tackifier

EXAMPLES

Methods pH: measured with laboratory pH meter at 25 °C.

Particle size: measured by using Malvern Mastersizer 3000. In the present context the particle size D50 refers to the value for 50th percentile of a volume based distribution, the particle size D90 refers to the value for 90th percentile of a volume based distribution and the particle size D95 refers to the value for 95th percentile of a volume based distribution.

Dry content: measured using a Mettler Toledo Halogen moisture analyser, or in standard drying oven at 125°C for 1 hour. Viscosity: measured at 25 °C, with Brookfield LVDV viscometer from an aqueous dispersion as is.

Charge density: measured by using particle charge detector, Mutek™ PCD-05. The samples were diluted with deionized water and the pH adjusted to pH 3.5. The catinic samples were titrated with an anionic titrant. The results were calculated based on dry content.

Example 1. Producing an aqueous dispersion in a glass reactor-according to the present invention.

Table 1. Materials used in example 1.

Polysaccharide (cellulose acetate butyrate with 52 wt.% butyryl, 2 wt.% acetyl and 2 wt.% hydroxyl content and with T_g of 85 °C) and rosin (tall oil rosin) were charged in to a 250 ml round bottom flaks mounted in a metal heating element. The mixture was melted by heating the element to 195 °C. Mixing was started as the mixture started to melt. After complete melting and mixing (visually uniform and clear mixture), the heating element was cooled to 160 °C. Mixing was done with an overhead mixer at 160 rpm speed.

60 g of 10 wt.% a first stabilizer (poly(vinyl alcohol) i.e. poly(vinyl acetate) with 80 % degree of hydrolysis) was combined with 10.5 g of a second stabilizer aqueous solution (0.5 g sodium lignosulfonate, 10 g H2O). The stabilizer mix was heated to 95 °C and added to the polysaccharide rosin mixture during 1 h to from an aqueous dispersion. The heating element and the aqueous dispersion were allowed to cool during the process. After the addition, 30 g of H2O was added to dilute the aqueous dispersion. The aqueous dispersion was allowed to cool to room temperature during the additions. Mixing speed was kept at 670 rpm during cooling.

Example 2. Producing an aqueous dispersion in a pressurized system - according to the present invention.

Table 2. Materials used in example 2.

The aqueous dispersion comprising a polysaccharide and rosin was produced in a suitable 1 L pressure reactor with a window. The reactor was connected to a feed vessel which could be heated with an electric heater and pressurized separately. Mixing was done with a mixing head connected through a magnet coupling (Buchi bmd 300) to a F63M-2 ATEX classified motor. Pressure was applied from a N2 bottle.

Polysaccharide (cellulose acetate butyrate with 52 wt.% butyryl, 2 wt. acetyl and 2 wt.% hydroxyl content and with T_g of 85 °C) and rosin (tall oil rosin) were mixed together and charged to the reactor. The mixture was melted by heating to 165 °C and mixing for 30 min. Pressure was set to 9 bar with nitrogen.

Aqueous phase containing a first stabilizer (poly(vinyl alcohol i.e. poly(vinyl acetate) with 80 % degree of hydrolysis)) and a second stabilizer (sodium lignosulfonate) were heated to 155 °C and set to 11 bar pressure.

The aqueous stabilizer was added to the reactor during 1 h 15 min while mixing to from an aqueous dispersion. After the addition, the aqueous dispersion was cooled while mixing to room temperature.

The aqueous dispersion was collected at room temperature. Solid content was 32.5 % by weight. Solid content was measured by drying at 150 °C using a Mettler Toledo HC103 Halogen Moisture Analyzer. Example 3. Rosin-cellulose acetate butyrate (CAB) blends - according to the present invention.

A rosin cellulose acetate butyrate (CAB) blend was prepared and compared to CAB. The rosin was fumaric acid fortified tall oil rosin (TOR). The CAB used had 53 wt.% butyryl content, 2 wt.% acetyl content and 1 .6 wt. % hydroxyl content and T_g of 75 °C.

For the preparation of the rosin CAB blend, fortified TOR was molten at 180°C in a three neck round bottom flask blanketed with nitrogen and equipped with a mechanical stirrer and temperature sensor. The amount of CAB was added and stirred until the rosin CAB melt was homogeneous.

To evaluate the suitability of the rosin CAB blend, viscosities were determined with an Anton Paar Rheometer MCR 72. Together with disposable plates the Cone Plate CP25-2 (D: 25mm + Angle: 2°) was used to conduct the measurements. A constant shear rate of 800 1/s was used to determine 60 measurement points at one set temperature. The mean values of the measurements at certain temperatures are given in the table 3.

Table 3. Viscosities (in millipascal seconds (mPa s)) of a rosin CAB blend and CAB at different temperatures.

Example 4. aqueous dispersions containing fortified TOR and TOR-CAB blends - according to the present invention.

The fortified TOR as well as the blend of fortified TOR with CAB as described in the example 3 and a more TOR rich blend, were dispersed in an aqueous phase consisting of a first stabilizer (cooked starch (maize)) and a second stabilizer (sodium lignosulfonate) by the use of a standard rosin size plant known in the art. There liquified rosin was added to the preheated water phase (>100°C) under pressure and subsequently mixed and emulsified in order to obtain a narrow and small enough particle size distribution (D90 < 3 pm). The aqueous composition was cooled down and pressure was released. The aqueous compositions were stabilized with suitable additives such as biocides and then characterized and checked for their storage stability. The results are presented in table 4 and 5.

Table 4. Characteristics of aqueous dispersions containing fortified TOR and TOR CAB blends .

The stability of the produced sizes was monitored over four weeks at room temperature (23°C). The results are presented at table 5. Table 5. Characteristics of the aqueous dispersions containing fortified TOR and

TOR CAB blends after over the four weeks.

All samples remained stable over the four weeks.

Example 5. Effect of rosin content on the viscosity - according to the present invention. Tall oil rosin and polysaccharide (here cellulose acetate butyrate with 52 wt.% butyryl, 2 wt. acetyl and 2 wt.% hydroxyl content and with T_g of 85 °C) were mixed together as dry powder, pressed to a disc and melted in an advanced rotational rheometer (Anton Paar modular compact rheometer 302e) with a plate-plate geometry at and equipped with a heating hood.. Moderate N2 was applied during the measurement. The mixture was equilibrated 10 min at the measuring temperature and the complex viscosity at different shear rates were obtained from a frequency sweep with 1 % strain. Zero shear rate viscosity was obtained by extrapolating to zero shear rate. Different ratios of the two components were tested and results are presented in table 6.

Table 6. Effect of rosin content on the viscosity.

Various embodiments have been presented. It should be appreciated that in this document, words comprise, include, and contain are each used as open-ended expressions with no intended exclusivity.

The foregoing description has provided by way of non-limiting examples of particular implementations and embodiments a full and informative description of the best mode presently contemplated by the inventors for carrying out the invention. It is however clear to a person skilled in the art that the invention is not restricted to details of the embodiments presented in the foregoing, but that it can be implemented in other embodiments using equivalent means or in different combinations of embodiments without deviating from the characteristics of the invention.

Furthermore, some of the features of the afore-disclosed example embodiments may be used to advantage without the corresponding use of other features. As such, the foregoing description shall be considered as merely illustrative of the principles of the present invention, and not in limitation thereof. Hence, the scope of the invention is only restricted by the appended patent claims.

Claims

1 . An aqueous dispersion comprising polysaccharide and rosin, wherein amount of the polysaccharide is at most 95 wt.%, based on the total dry weight of the aqueous dispersion, wherein zero shear rate viscosity of the polysaccharide is equal or less than 500000 mPa s such as 2000 mPa s-500000 mPa s at 160 °C.

2. The aqueous dispersion according to claim 1 , wherein the polysaccharide is polysaccharide, polysaccharide derivative or a mixture thereof.

3. The aqueous dispersion according to claim 1 or 2, wherein the polysaccharide comprises dextran, amylopectin, amylose, starch, glycogen, cellulose, hemicellulose, glucans, lignin-carbohydrate complexes, starch, chitin, chitosan, hyaluronan, a derivative thereof or a mixture thereof.

4. The aqueous dispersion according to any one of claims 1-3, wherein the polysaccharide derivative is linear or branched alkyl ester or ether or amide derivative of polysaccharide, preferably the polysaccharide derivative is cellulose ester C2-C4 acyl, cellulose ether C2-C4 alkyl, such as cellulose acetate butyrate or a mixture thereof, preferably cellulose acetate butyrate.

5. The aqueous dispersion according to any one of claims 1-4, wherein the rosin comprises rosin, rosin derivatives, such as rosin esters, dimerised rosins, polymerised rosins, hydrogenated rosins, saponified rosins, fortified rosins and unfortified rosins, or a mixture thereof.

6. The aqueous dispersion according to any one of claims 1-5, wherein the polysaccharide has glass transition temperature (T_g) -20 °C-200 °C, preferably 25 °C-200 °C more, preferably 60 °C-195 °C, such as 75 °C-195 °C or 60 °C-100 °C.

7. The aqueous dispersion according to any one of claims 1-6, wherein the zero shear rate viscosity of the polysaccharide is less than 400000 mPa s, such as 2000 mPa s-400000 mPa s, more preferably equal or less than 300000 mPa s, such as 2000 mPa s-300000 mPa s at 160 °C.

8. The aqueous dispersion according to any one of claims 1-7, wherein the amount of the polysaccharide is from 5 wt.% to 95 wt.%, preferably from 7 wt.% to 80 wt.%, more preferably from 20 wt.% to 60 wt.%, based on the total dry weight of the aqueous dispersion.

9. The aqueous dispersion according to any one of claims 1-8, wherein the amount of the rosin is from 5 wt.% to 95 wt.%, preferably from 8 wt.% to 80 wt.%, based on the total dry weight of the aqueous dispersion.

10. The aqueous dispersion according to any one of claims 1-9, wherein the aqueous composition comprises additionally a first stabilization agent, such as polyamine, starch, starch derivative, such as degraded starch, cationic starch, anionic starch, or non-ionic starch, glucan derivative, such as cationic or anionic glucan, glucan, carboxymethyl cellulose, hydroxy ethyl cellulose, polyvinyl alcohol, polyethylene glycol, copolymer of ethylene and propylene glycol or a mixture thereof, preferably the first stabilization agent is polyamine, starch, polyvinyl alcohol or a mixture thereof.

11. The aqueous dispersion according to any one of claims 1-10, wherein the aqueous dispersion comprises additionally a second stabilization agent such as sodium lignosulfonate, naphthalene sulfonate, starch derivative, such as degraded starch, cationic starch, anionic starch, non-ionic starch or a mixture thereof, preferably sodium lignosulfonate.

12. The aqueous dispersion according to any one of claims 1-11 , wherein pH of the aqueous dispersion is 3-9, preferably 3-8, more preferably 4-7.

13. The aqueous dispersion according to any one of claims 1-12, wherein solid content of the aqueous dispersion is 5-80 %, preferably 10-70 %, more preferably 20-60 %.

14. The aqueous dispersion according to any one of claims 1-13, wherein number average molecular weight (Mn) of the cellulose ester is 5000 g/mol-2000000 g/mol, preferably 16000 g/mol-75000 g/mol, preferably 10000 g/mol-25000 g/mol.

15. The aqueous dispersion according to any one of claims 1-14, wherein the aqueous dispersion is substantially free of organic solvents, preferably free of organic solvents and/or substantially free of additional plasticizers excluding the rosin and polysaccharide, preferably free of additional plasticizers excluding the rosin and polysaccharide.

16. A method for producing aqueous dispersion comprising polysaccharide and rosin, wherein the method comprises

(i) providing polysaccharide and rosin;

(ii-a) mixing the polysaccharide and melting the rosin to obtain a mixture comprising polysaccharide and rosin, and melting the mixture to obtain a mixture comprising polysaccharide melt and rosin melt;

(ii-b) melting the polysaccharide and the rosin, and mixing the polysaccharide melt and the rosin melt to obtain a mixture comprising polysaccharide melt and rosin melt;

(ii-c) melting the polysaccharide, and mixing the rosin to the polysaccharide melt to obtain a mixture comprising polysaccharide melt and rosin melt; or (ii-d) melting the rosin, and mixing the polysaccharide to the rosin melt to obtain a mixture comprising polysaccharide melt and rosin melt; and

17. The method according to claim 16, wherein the aqueous phase is water, aqueous suspension, aqueous dispersion, aqueous emulsion or aqueous emulsion comprising a first stabilization agent and/or a second stabilization agent.

18. The method according to claim 16 or 17, wherein a first stabilization agent and/or a second stabilization agent is introduced to the aqueous dispersion comprising polysaccharide and rosin.

19. A fiber based substrate comprising the aqueous dispersion according to any one of claims 1-15 or the aqueous dispersion produced with the method according to any one of claims 16-18.

20. Use of the aqueous dispersion according to any one of claims 1-15 or the aqueous dispersion produced with the method according to any one of claims 16-18 as a surface sizing agent, an adhesive or a tackifier.