An aqueous dispersion for binding and coating applications

Abstract

According to an example aspect of the present invention, here is provided an aqueous dispersion, and a film thereof, comprising an extract comprising suberin, and a dispersant comprising carboxymethyl hemicellulose. Further, there is provided a method of manufacturing such aqueous dispersion or film. In addition, the present invention relates to the use of such aqueous dispersion or film.

Description

AN AQUEOUS DISPERSION FOR BINDING AND COATING APPLICATIONSFIELD

[0001] The present invention relates to an aqueous dispersion, and a film thereof. In particular, the present invention concerns a novel aqueous dispersion comprising suberin and a hemicellulose-based dispersant, especially a carboxymethyl hemicellulose.

[0002] The present invention also concerns a method of producing such an aqueous dispersion and its use for binding and coating applications.BACKGROUND

[0003] Paper and paperboard are renewable packaging materials but they do not as such have the required barrier properties to provide protection for example against moisture, oxygen, volatile aroma, grease and oil, as well as impact of light. At present, the required barrier properties are achieved especially by extrusion plastics (e.g. polyethylene), aluminium, and / or fluorochemicals, resulting in poor end-product recyclability and increasing safety concerns in food packaging materials. Typically, such barriers used are multilayer structures.

[0004] Also latexes are commonly used as coating materials. Latexes (elastomers) are soft amorphous polymers, which typically are formulated as water-based dispersions (latexes) and used in numerous products, e.g., converted paper, packaging materials, coatings, textiles and car tyres. However, the commercial products are mainly oil-based, such as styrene-butadiene, styrene-acrylate, and polyvinyl-acetate copolymers.

[0005] Currently, fossil fuel-based polymer materials for coating applications put a great threat to the environment and human health. Thus, there is a pressing need for alternative bio-based polymer materials to replace the source of fossil-based materials.

[0006] For example, suberin is a complex and wax-like biopolymer that consists of long-chain fatty acids and glycerol. In particular, suberin is a mixture of hydrophobic and lipophilic biopolymers and is one of major components of outer cell walls of certain plant tissues, such as the bark of trees, and can be derived from waste generated by agriculturalindustries. Suberin is known to provide barrier properties in plants due to its high hydrophobicity, making it a promising material for use in barrier coatings on fibre-based packaging. However, such use has not been yet implemented commercially.

[0007] In the preparation of water based suberin dispersions for coating applications, there have been some problems encountered with agglomeration in the wet dispersions when subjected to shear forces. Agglomeration occurring in the dispersion will disturb the coating process. The dispersion is exposed to continuous share forces during coating, which can result in visible and severe agglomeration that accumulate near the metering element. Furthermore, any agglomerates present on the coated surface will cause defects, both due to the agglomerates as such and due to the agglomerates causing disturbances in the flow of the coating dispersion during the coating process. Due to the characteristics of suberin, the agglomerates that develop in the wet dispersion are a bit sticky, and tend to block any grooves in the metering element of the coater. In a continuous coating process, accumulation of agglomerates will impact the overall coating quality negatively, resulting in coatings that gradually becomes poorer in quality.

[0008] A further challenge encountered with suberin coatings is limited wet strength, such that the dry coating can be rubbed of a coated surface, such as a fibrous surface, upon contact with water. This naturally weakens the moisture resistance of the coated surface when the surface is subjected to prolonged contact with moisture or upon repeated touch.

[0009] A further problem that has been encountered for aqueous suberin dispersions is the formation of gas bubbles during the preparation, and in particular during pH adjustment. The presence of gas bubbles will cause defects in the final coating, and thus deteriorate its performance, for example, as a barrier coating.

[0010] Consequently, there is a need to improve the functional properties of biopolymer dispersions for more demanding packaging applications. In particular, there is a clear need for alternative biobased coating and binding agents to replace the petroleum- derived synthetic polymers which are the main ones currently in use.SUMMARY OF THE INVENTION

[0011] It is an aim of the present invention to reduce or even completely to eliminate the above-mentioned problems of fossil-based raw material use encountered in the art.

[0012] The present invention provides an aqueous dispersion comprising suberin and a hemicellulose-based dispersant. The hemicellulose-based dispersant is in particular carboxymethyl hemicellulose. By mixing carboxymethyl hemicellulose, i.e., hemicellulose modified by carboxymethylation, with suberin in an aqueous medium, an aqueous dispersion can be provided which is suitable for various end-use applications. Thus, it has been surprisingly found in the present invention that the combination of the carboxymethyl hemicellulose and suberin provides improved barrier and binding properties, and in particular improved coating quality when compared to alternative biobased suberin coatings.

[0013] The aqueous dispersion of the present invention finds uses in the paper, paperboard and packaging industry, in particular to provide barrier properties to fibrous surfaces, as well as broader in coating and surface treatment products. Among others, it can be used in adhesives, composites, varnishes, and paint applications, as well as in printing inc.

[0014] According to a first aspect of the present invention, there is provided an aqueous dispersion comprising suberin and a dispersant comprising carboxymethyl hemicellulose.

[0015] According to a second aspect of the present invention, there is provided a method of producing an aqueous dispersion, comprising the steps of providing a hemicellulose, providing a carboxymethylation reagent, and reacting the hemicellulose by a carboxymethylation reaction with the carboxymethylation reagent to obtain carboxymethyl hemicellulose as a hemicellulose-based dispersant, and mixing the obtained hemicellulosebased dispersant in an aqueous medium with suberin.

[0016] According to a third aspect of the present invention, there is provided a film formed from the aqueous dispersion according to the first aspect of the present invention or by the method according to the second aspect of the present invention.

[0017] According to a fourth aspect of the present invention there is provided uses for such an aqueous dispersion and film. In particular, there is provided use of the dispersionaccording to the first aspect of the present invention, or the dispersion obtained in the second aspect of the present invention, or the film according to the third aspect of the present invention in coating applications, such as coatings for paper, paperboard or sand paper, preferably in food packaging, in pharmaceutical packaging, in cosmetic packaging, or in water treatment as a membrane. Further uses provided are as a binder in pigment coatings or paints, or as an adhesive, such as adhesive for gluing wood and wood products, or composites.

[0018] More specifically the present invention is characterized by what is stated in the independent claims. Some specific embodiments are defined in the dependent claims.

[0019] Thus, the present invention is at least partly based on the idea that a hemicellulose-based dispersant, in particular surfactant, is used to stabilize suberin into an aqueous dispersion. Due to the hydrophobic nature of suberin and the suberin acids contained therein, it is challenging to provide stable dispersions of suberin in water. In the present invention, it was found that stable aqueous dispersions of suberin can be obtained through a charge stabilization mechanism provided for by the presence of carboxymethyl hemicellulose. Suberin dispersion with carboxymethyl hemicellulose as dispersant has been found to provide high quality bio-based coatings with improved water stability properties when compared to biobased suberin dispersions prepared using alternative dispersants. That is, it was found that the carboxymethyl hemicellulose does not impair the hydrophobicity properties of the suberin in the formed coating to the same extent as, for example, polyvinyl alcohol (PVOH) does.

[0020] The present invention provides a sustainable and safe barrier coating and binder composition comprised of hemicellulose-based dispersant and suberin, especially for fiber-based packaging materials. Suberin is a natural binder and barrier material that is usually burnt for energy in a pulp mill, whereas in the present invention it has been utilized in producing stable aqueous dispersions. Hemicellulose, in turn, is an under-utilized sidestream from paper pulping process. Use of hemicellulose to replace fossil-based chemicals reduces the environmental footprint of the packaging material or binder composition thereof, and further improves recyclability of fiber-based packaging materials. Both suberin and hemicellulose are bio-based materials.

[0021] In general, aqueous dispersion coatings have several benefits, including increased barrier properties and solvent-free production. Thus, compared to conventionalextrusion coatings, dispersion coatings also have lower environmental impact and are often suitable for re-pulping or composting when using bio-based polymer.

[0022] The present invention overcomes the challenges of the prior art with a unique dispersion morphology, wherein the hemicellulose-based dispersant allows for generating sufficiently small suberin particle size in the dispersion to enable applying it as a thin barrier layer. Thus, the carboxymethyl hemicellulose indirectly improves the coating by acting as a dispersant, in particular as a surfactant, creating a homogeneous dispersion between suberin and water.

[0023] The material of the present invention satisfies both the demand of a low film formation temperature and a sufficient flexibility of the barrier layer, thus providing required binding and barrier properties for a wide range of end-use purposes.

[0024] In an environmental perspective, one advantage of the dispersion of the present invention is that it utilizes side streams from pulping and biorefinery industries to produce alternative bio-based and biodegradable aqueous dispersions for barrier coatings and paints, as well as for use as binders or adhesives.

[0025] Further features and advantages of embodiments will become evident from the following description of preferred embodiments in which reference is made to the attached drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIGURE 1 shows a reaction scheme for the carboxymethylation of galactoglucomannan (GGM) according to one embodiment of the present disclosure. Figure 1 presents three steps, step 1 showing spruce GGM in its native form, which is partially acetylated. In step 2, after reacting with NaOH, the GGM becomes deacetylated and mercerized. In the step 3, reaction between the mercerized GGM and monochloroacetic acid (MCA) results in the sodium salt of carboxymethylated galactoglucomannan.

[0027] FIGURE 2 shows the results of Turbiscan analyses carried out to determine the storage stability of the dispersion.

[0028] FIGURE 3 presents the results of water contact angle measurement carried out on suberin based dispersions comprising carboxymethyl hemicellulose.

[0029] FIGURE 4 shows the results of Cobb tests carried out on coated and uncoated fibrous surfaces. The contact time between water and the test surface is 60 seconds.

[0030] FIGURE 5 shows the results of Cobb tests carried out on coated and uncoated fibrous surfaces. The contact time between water and the test surface is five minutes.EMBODIMENTS

[0031] DEFINITIONSIn the present context, the term "bio-based" refers to a material that comprises, consists or essentially consists of a substance (or substances) derived from living matter (biomass) and either occur naturally or are synthesized. In some embodiments, a part or all of the biobased material or bio-based raw-materials are obtained from renewable sources, such as from biomass, in particular wood derived biomass.

[0032] In the present context, the term ’’degree of substitution”, abbreviated ”DS”, refers to the average amount of substituent groups (mmol) attached per gram of the derivative of hemicellulose.

[0033] As used herein, the term “about” refers to the actual given value, and also to an approximation to such given value that would reasonably be inferred to one of ordinary skill in the art, including approximations due to the experimental and / or measurement conditions for such given value.

[0034] Unless otherwise stated, properties that have been experimentally measured or determined herein have been measured or determined at room temperature.

[0035] Unless otherwise indicated, room temperature is 23 °C.

[0036] Unless otherwise stated, properties that have been experimentally measured or determined herein have been measured or determined at atmospheric pressure.

[0037] According to a first aspect of the present disclosure, there is provided an aqueous dispersion comprising suberin, and a dispersant comprising carboxymethylhemicellulose. In particular, there is provided an aqueous dispersion comprising an extract comprising suberin, and a dispersant comprising carboxymethyl hemicellulose.

[0038] Suberin is a complex polyester biopolymer found in the inner face of the primary cell walls in aerial and root parts of plants. In particular, suberin is found in the outermost layer of bark. Main molecular components of suberin are polyaliphatics and polyaromatics. The aliphatic domain is an insoluble polyester largely comprised of fatty acids and glycerol, whereas the aromatic domain is derived from phenylpropanoid. Thus, suberin is typically derived from bark by extraction, such as from birch bark or cork, wherein it is part of a bark extract that may also comprise other components of bark, such as betulin, tannins and / or glucose. Thus, the suberin in the dispersion can be in the form of such an extract, which optionally have been further processed, for example by purification.

[0039] Thus, in some embodiments, the aqueous dispersion comprises suberin in the form of a bark extract comprising suberin. In one embodiment, the extract may consist of suberin, such as isolated suberin.

[0040] Suberin is mixed with a dispersant, preferably surfactant, in order to be able to provide a suberin-based aqueous dispersion by improving separation of the suberin particles in water to prevent their settling and / or clumping. Typically, the dispersant acts as a surfactant lowering the surface tension between two phases, i.e. suberin particles and water in this case. Preferably, the dispersant enables forming a homogeneous aqueous dispersion comprising suberin with small average particle size.

[0041] According to one embodiment, suberin has an average particle size of less than 10 pm, preferably 0.05 to 5 pm, in the aqueous dispersion. The average particle size being measured by laser diffraction particle size analyser (Mastersizer, Malvern Panalytical).

[0042] The dispersion of the present disclosure comprises suberin as well as a hemicellulose derivative, in particular carboxymethyl hemicellulose, i.e., carboxymethylated hemicellulose, which is a hemicellulose comprising carboxymethyl side groups or a salt thereof. Chemically, the carboxymethyl hemicellulose could be described as a hemicellulose ether, as the carboxymethyl groups are linked to some of the functional hydroxyl groups on the hemicellulose, thereby providing side groups with a carboxylate end group, which in turn can provide a negative charge in the aqueous medium. Preferably, the carboxymethyl side groups are in the form of a salt, such as a sodium salt, to induce an ionexchange and negative charges on the hemicellulose. This in turn makes the carboxymethyl group more stable in the aqueous medium. Remaining, unreacted hydroxyl groups on the hemicellulose enable hydrogen bonding of the polymer. The reaction mechanism of the carboxymethylation reaction according to an embodiment is shown in Figure 1.

[0043] Carboxymethyl hemicellulose stabilizes suberin into dispersion through a charge stabilization mechanism, i.e., electrostatic stabilization mechanism. This forms a suberin dispersion with lower viscosity than corresponding dispersions stabilized through steric stabilization. The lower viscosity does in turn enable the formation of dispersions with higher solid content, and thus the inclusion of higher amounts of suberin, which provides for the water repellent properties in a coating formed. This makes the suberin dispersions stabilized with carboxymethyl hemicellulose well suited for coating applications, in which the viscosity can be a limiting factor. Furthermore, a higher solids content reduces the volume of the dispersion and thus transport costs. Likewise, due to the lower water content, the energy required for the drying of the dispersion will also be reduced. Thus, the possibility to obtain dispersion with higher solid content provides for advantages in a wide range of uses, such as in coating and binding applications.

[0044] When compared to suberin dispersions obtained by alternative dispersants, such as polyvinyl alcohol (PVOH), or hemicelluloses modified with carboxylic acids, such as galactoglucomannan modified with fatty acid grafting (FA-g-GGM), the suberin dispersions stabilized with carboxymethyl hemicellulose provides for higher water contact angle and better water barrier properties upon coating of a fibrous surface. This was concluded in tests carried out in the context of the present disclosure, wherein the coated surface otherwise was subjected to identical processing steps, such as oven curing, and the suberin content of the dispersion used was the same. In part, the coating being less water sensitive can be attributed to a higher quality dispersion. The suberin dispersion with carboxymethyl hemicellulose as dispersant had a more uniform character, for example, with less gas bubbles therein. When the dispersion contains gas bubbles, these tend to form pinholes in the final coating. The formation of gas within the dispersion is in particular a problem with hemicellulose grafted with organic acids through ester bonds, as saponification of the organic acids occurs in the presence of strong alkali. Furthermore, in the tests carried out, it was found that the dispersion stabilized with carboxymethyl hemicellulose provides for even further improved storage stability when compared to hemicellulose grafted with fatty acids.

[0045] Hemicelluloses are branched polysaccharides found in plant cell walls. They play an important role in the structural integrity of the plant cell wall and can be isolated from a variety of plant sources. According to some embodiments any hemicellulose can be used. In particular, wood-derived hemicellulose is used.

[0046] According to some embodiments, the carboxymethyl hemicellulose is prepared from galactoglucomannan (GGM), xylan, arabinogalactan, arabino-gluronoxylan, xyloglucan, betaglucan, alpha-glucan or a combination thereof, preferably GGM or xylan. Thus, the hemicellulose-based dispersant can be a carboxymethyl hemicellulose, wherein the hemicellulose is selected from said group of hemicelluloses.

[0047] In preferred embodiments, the carboxymethyl hemicellulose is prepared from galactoglucomannan (GGM) or xylan, especially GGM. Galactoglucomannan is a hemicellulose that is predominantly found in softwoods, and it exhibits desirable properties, such as high solubility in water and possesses emulsifying capacity, which makes it highly suitable for use as a surfactant. Compared to conventional dispersants, GGM-based dispersants has several advantages, such as reduced environmental impact, low toxicity and improved biodegradability.

[0048] According to some embodiments, the carboxymethyl hemicellulose is prepared from hemicellulose that is derived from spruce, preferably by using a spruce extract that is rich in galactoglucomannans. Spruce extract can be produced through pressurized hot water extraction, for example.

[0049] In some embodiments, the carboxymethyl hemicellulose is prepared from isolated hemicellulose, preferably obtained by extraction, membrane filtration, hydrolysis, biosynthesis routes or by the combination thereof.

[0050] According to further some embodiments, the carboxymethyl hemicellulose is obtained from hemicellulose in its native form. In other embodiments, the carboxymethyl hemicellulose is obtained from purified hemicellulose, which increases the weight percentage of the hemicellulose in the hemicellulose composition by removal of impurities. In some embodiments, hemicellulose is purified by an ethanol precipitation method.

[0051] After mixing the carboxymethyl hemicellulose dispersant with suberin in an aqueous solution, in particular with an extract comprising suberin, a stable aqueous dispersion is obtained comprising suberin evenly dispersed in water, and carboxymethylhemicellulose acting at the interface of suberin and water. The carboxymethyl hemicellulose dispersant, preferably acting as a surfactant, facilitates breakdown of suberin aggregates into smaller and more uniform particles in the water phase. The carboxymethyl hemicellulose can act as a bridge between water and suberin, simultaneously interacting with the water phase and the suberin particles due to its partially grafted structure, comprising both unreacted hydroxyl groups and hydroxyl groups that have been transferred into ether bonded carboxymethyl side groups.

[0052] According to some embodiments, the amount of the hemicellulose-based dispersant depends on the degree of substitution on the hemicellulose as well as the suberin content in dispersion. Since the carboxymethylation reaction introduces carboxymethyl side groups (grafts) on the hemicellulose, the degree of substitution corresponds to the number of charged sites on the hemicellulose, which in turn can interact electrostatically with the other components of the dispersion, in particular suberin.

[0053] Carboxymethyl hemicellulose is typically present in the dispersion in an amount that is less or equal the amount of suberin. Thus, the content of carboxymethyl hemicellulose can be from 0.1, 0.5, 1, 3, 5 or 8 wt.% up to 10, 15, 20, 25, 35, 50, 75 or 100 wt.% with respect to the weight of suberin, when calculated based on the dry weight. According to some embodiments, the amount of carboxymethyl hemicellulose is 0.1 to 50 wt.%, preferably 0.5 to 20 wt.%, more preferably 1 to 10 wt.% with respect to weight of suberin, when calculated based on the dry weight of each compound. The amounts of hemicellulose-based dispersant provided in the preferred ranges are typically sufficient to obtain a stable dispersion and enable inclusion of suberin in amounts disclosed herein without reaching a viscosity level that limits the use of the dispersion in coating applications or for use as binders or adhesives.

[0054] The total amount of carboxymethyl hemicellulose in the dispersion can be, for example, 1 to 10 wt.%, such as 1 to 5 wt.%, when calculated based on the dry weight of the carboxymethyl hemicellulose. A content of carboxymethyl cellulose in said ranges is typically sufficient to obtain a uniform dispersion, in particular for coating applications. It should, however, be noted that said ranges are provided as non-limiting examples. In particular in applications where a high viscosity of the dispersion is allowable or even desired, such as when used in adhesives or composite materials, the total amount of carboxymethyl hemicellulose can be higher.

[0055] In some embodiments, the suberin content of the dispersion is 3-40 wt.%, when calculated based on the dry weight of suberin. Thus, the suberin content of the dispersion is from 3, 5, 10, 15, 20, or 25 wt. % up to 10, 15, 20, 25, 30, 35 or 40 wt.%, when calculated based on the dry weight of suberin. Depending on the application and end use, the suberin content can be, for example, 5 to 20 wt.% or 10-35 wt.%, when calculated based on the dry weight of suberin. In coating applications where high moisture resistance is desired, the amount of suberin can be, for example 25-35 wt.%, without being limited thereto. The desired suberin content naturally depends on the intended end use of the coated product, and thus, also the lower ranges for the suberin content are suitable for coating applications, in particular when functionalization of the surface is desired without the need to obtain water barrier properties. Likewise, in some applications, such as in the use of suberin dispersions in adhesives or in the manufacture of composite materials, the viscosity may not be a limiting factor to the same degree as in coating applications. The suberin, or the extract comprising suberin, is preferably the main solid component of the dispersion, as a high suberin content contributes to improved water stability and thus better barrier properties of the treated material, in particular a suberin containing film obtained thereon. The good stabilization properties of the carboxymethyl hemicellulose thus provides for the possibility to increase the solids content, still having appropriate rheological properties for coating applications. A 35 wt.% suberin dispersion (dry suberin / total weight of dispersion) stabilized with carboxymethyl hemicellulose, in particular carboxymethyl GGM is well suited for coating applications and provides for high quality films. In prior art solutions, such as when using PVOH as dispersant, the suberin content has been limited to below 25 wt.% in coating applications, as the viscosity otherwise becomes too high. In some further embodiments of the present disclosure, the suberin content of the dispersion can be up to 50 wt.%, such as from 3, 5, 10, 15, 20, or 25 wt.% up to 50 wt.%, when calculated based on the dry weight of suberin.

[0056] According to some embodiments, the total solid content of the aqueous dispersion is in the range of 5 to 55 wt.%, preferably 15 to 50 wt.%, more preferably 20 to 40 wt.%, calculated from the total weight of the dispersion, the rest preferably being water. A high solids content is desirable in terms of productivity. This reduces the volume of water being transported to the facility of use, such as a coating facility, as well as the energy required for drying. On the other hand, a higher solids content typically results in higherviscosity, whereby the preferred ranges as presented above provide dispersions that are versatile in use.

[0057] In some embodiments, the dispersion comprises further solid components, such as mineral pigments.

[0058] The liquid phase of the aqueous dispersion, i.e., the dispersion medium, is preferably comprised of or essentially comprised of water. Thus, in some embodiments, the percentage of water is at least 90 wt.%, preferably at least 95 wt.%, most suitably at least 97 wt.%, based on the total weight of the liquid phase.

[0059] According to some embodiments, the carboxymethyl hemicellulose has a degree of substitution from 0.1 to 1.5, or 0.5 to 1.5. The degree of substitution is in part dependent on the type of hemicellulose, as for example GGM has a theoretical maximum degree of substitution of 3, while xylan has a theoretical maximum degree of substitution of 2. In practice, it might not be beneficial to aim for the maximum theoretical degree of substitution, as more reagent will be needed and thus also wasted, as complete reaction is difficult to obtain. Furthermore, remaining, unreacted hydroxyl groups on the hemicellulose enable hydrogen bonding of the polymer. Thus, the degree of substitution can to some extent affect the dispersion properties and thus the amount of dispersant used. In some embodiments, the degree of substitution is from 0.1, 0.2, 0.4 or 0.5 up to 0.4, 0.5, 0.7, 0.8, 1.0, 1.5, or 2.0, such as from 0.4 tol.5 The degree of substitution is measured by proton nuclear magnetic resonance.

[0060] In some embodiments, the pH of the dispersion is from 5.5 to 8, preferably from 6 to 7, more preferably 6 to 6.5. Thereby, in some preferred embodiments, the pH can be 5.5-6.5. Thus, the pH can be, for example, from 5.5, 5.8 or 6 up to 6.5, 7 or 8. In some further preferred embodiments, the pH of the dispersion can be up to 6, such as, from 5.5-6.0. Without pH adjustment, the pH may become lower than 5.5, which in turn tend to increase the degree of shear induced agglomeration. Agglomerates formed at a low pH can block the grooves in the metering rod of a coater, or other metering element, resulting in poor coating quality. Any agglomerates present on the coated surface will also cause defects. Furthermore, a too low pH is corrosive for the equipment. However, since suberin has high acidic strength, and thus, a relatively large amount of alkali is needed to neutralize the pH ofthe dispersion upon suberin addition, it might not be motivated to increase the pH above the upper limits disclosed.

[0061] According to a second aspect of the present disclosure, there is provided a method of producing an aqueous dispersion, comprising the steps of:- providing a hemicellulose,- providing a carboxymethylation reagent, and reacting the hemicellulose by a carboxymethylation reaction with the carboxymethylation reagent to obtain carboxymethyl hemicellulose as a hemicellulose-based dispersant, and mixing the obtained hemicellulose-based dispersant in an aqueous medium with suberin.

[0062] Thus, the present invention also concerns a method of producing an aqueous dispersion, in particular an aqueous dispersion described by the embodiments of the first aspect of the present disclosure. Thus, the embodiments presented in the context of the first aspect of the present disclosure also relate to the present method.

[0063] The method comprises reacting hemicellulose through a carboxymethylation reaction, thus providing a hemicellulose comprising carboxymethyl side groups or salts thereof, and mixing such dispersant with suberin, in particular an extract comprising suberin, to obtain an aqueous dispersion. Preferably, the thus obtained carboxymethyl hemicellulose is dispersed in an aqueous medium, whereafter suberin is mixed into the aqueous dispersion comprising carboxymethyl hemicellulose.

[0064] By preparing the hemicellulose dispersant separately, the reaction conditions can be optimized to, for example, reach a desired degree of substitution. An optional purification step can be carried out on the carboxymethyl hemicellulose, whereafter it can be isolated and dissolved in water to obtain pure dispersion. In this way, the ratio of dispersant to suberin can be optimized for the intended end use of the dispersion and the process will become more reliable. Since both suberin and hemicellulose are natural products, the properties thereof can be affected by any residues of other components present in the isolated suberin or hemicellulose fraction, whereby the use of isolates or purified fractions can be preferred.

[0065] According to some embodiments the method comprises a step providing isolated hemicellulose, preferably obtained by extraction, membrane filtration, hydrolysis,biosynthesis routes or by the combination thereof. Also, other known synthesis routes or isolation routes of hemicellulose can be used.

[0066] According to some embodiments, the method comprises providing hemicellulose in dispersed form, preferably dissolved in an aqueous medium or in alcohol, such as in isopropanol, or mixtures thereof. Thus, the hemicellulose can be dispersed in water or in organic solvent. Any suitable aqueous or organic solvent can be used. However, according to a preferred embodiment, hemicellulose is dispersed in low-toxic solvents, or mixtures of those, such as water or alcohols, preferably isopropanol.

[0067] In some embodiments, the method comprises the step of subjecting the hemicellulose to a mercerization reaction under alkaline conditions, preferably in the presence of NaOH. Typically, the mercerization reaction is carried out prior to contacting the hemicellulose with the carboxymethylation reagent. The mercerization reaction can be carried out with alkali treatment, such as by treatment with sodium hydroxide (NaOH). In the mercerization step, alkali can be added in a molar ratio of hemicellulose / alkali of from 0.5:10 to 2:3, such as 1 :7 to 1 :4. Native forms of hemicelluloses, such as native spruce galactoglucomannan, can be partially acetylated. After alkali treatment, in particular after reacting with NaOH, the hemicellulose becomes deacetylated and mercerized. In a mercerization reaction carried out with NaOH, the hydroxyl groups of the hemicellulose will comprise sodium counterions on the hydroxyl sites. By further reaction with a carboxymethylation reagent, typically monochloroacetic acid, a sodium salt of carboxymethylated galactoglucomannan is obtained. The mercerization reaction can be carried out at a temperature of, for example, 20 to 50°C. Preferably the reaction is carried out at room temperature. The total reaction time, from the initiation of the alkali addition, can be, 20 to 90 min, preferably 30 to 70 min, without being limited thereto. In the preferred range of the reaction time, the mercerization can be carried out at room temperature, which is energy efficient.

[0068] In some embodiments, the carboxymethylation reagent is a haloacetic acid, preferably monochloroacetic acid. Monochloroacetic acid is also referred to as monochloroacetate, which is the solid sodium salt of chloroacetic acid. The carboxymethylation reagent is preferably added to the alkaline hemicellulose solution obtained in the mercerization step. The molar ratio of hemicellulose to carboxymethylation reagent in solution can be, for example from 1 :5 to 6.25:5, preferably around 1 :3 to 1 :1.

[0069] According to one embodiment, the carboxymethylation of the hemicellulose is carried out in a solvent, such as an aqueous solvent or an organic solvent, such as an alcohol, or mixtures thereof. Preferably the solvent is similar or the same that was used in the mercerization step, such as water or an alcohol, or mixtures thereof, and then the carboxymethylation reagents are added for the carboxymethylation reaction.

[0070] In further embodiments, the carboxymethylation reagent is allowed to react with the hemicellulose at a temperature of 20 to 65°C, such as at a slightly elevated temperature of 40 to 55°C. The total reaction time, including the time of addition of the carboxymethylation reagent, can be from 60 to 360 min, without being limited thereto. At slightly elevated temperatures, the total reaction time can be, for example 90 to 120 min. Further increased temperatures can result in undesired alkaline degradation of the hemicellulose.

[0071] According to an embodiment the hemicellulose has a number average molecular weight of 2,000-500,000 g / mol, preferably 3,000-50,000 g / mol, more preferably 5,000-20,000 g / mol, in particular 3,000-10,000 g / mol and a weight average molecular weight of 3,000-1,000,000 g / mol, preferably 4,000-50,000 g / mol, in particular 5,000- 30,000 g / mol as measured by a high-performance size exclusion chromatography.

[0072] According to an embodiment the hemicellulose-based dispersant, i.e. grafted hemicellulose, has a number average molecular weight of 2,000-500,000 g / mol, preferably 3,000-50,000 g / mol, more preferably 3,000-20,000 g / mol, in particular 3,000-10,000 g / mol, and a weight average molecular weight of 3,000-1,000,000 g / mol, as measured by a high- performance size exclusion chromatography.

[0073] According to some embodiments, possible organic solvent(s) are removed from the formed dispersion by any known method, such as evaporation or distillation. Preferably, organic solvent(s) are removed before mixing the formed hemicellulose-based dispersant with the suberin, in particular an extract comprising suberin.

[0074] According to some embodiments, the formed hemicellulose-based dispersant is pre-treated and / or isolated before mixing with the suberin. That is, the reaction mixture containing carboxymethyl hemicellulose can be filtered at room temperature to separate the carboxymethyl hemicellulose from the reaction solvent. In one embodiment, the hemicellulose-based dispersant, i.e., the carboxymethyl hemicellulose, is purified and / orneutralized prior to mixing with the suberin. In some embodiments, the obtained hemicellulose-based dispersant is mixed with alcohol, in particular primary alcohols, such as methanol or ethanol. The alcohol can be added as a dissolving step and / or a washing step. The hemicellulose-based dispersant, i.e., the carboxymethyl hemicellulose, can upon competition of the carboxymethylation reaction be neutralized with acid, for example with organic acids such as acetic acid. In a further embodiment, the thus obtained hemicellulosebased dispersant can be optionally isolated through filtration, and / or optionally dried. Drying is preferably performed in a vacuum desiccator, such as in a vacuum oven. Alternatively, the drying can be performed by freeze drying.

[0075] According to some embodiments, the hemicellulose-based dispersant is dispersed in and / or diluted with water before mixing with the suberin. In one embodiment, the hemicellulose-based dispersant is diluted in water to a solids content of 1 to 25 wt.%, such as 1 to 5 wt.%, calculated based on the dry weight of the hemicellulose-based dispersant. A solid content of carboxymethyl hemicellulose in the range of 1 to 5 wt.% in aqueous dispersion is typically sufficient for the formation of suberin dispersions for coating applications, i.e., with suberin content in the ranges as disclosed herein.

[0076] In some embodiments, the amount of hemicellulose-based surfactant is 0.1 to 50 wt.%, preferably 0.5 to 20 wt.%, more preferably 1 to 10 wt.% with respect to the weight of dry suberin. The amount of hemicellulose-based surfactant can be selected from ranges disclosed in the context of the first aspect of the present disclosure, that is, the content of carboxymethyl hemicellulose can be from 0.1, 0.5, 1, 3, 5 or 8 wt.% up to 10, 15, 20, 25, 35, 50, 75 or 100 wt.% with respect to the weight of suberin, when calculated based on the dry weight of each compound.

[0077] In some further embodiments, suberin is added into a suberin content of the dispersion of 3-40 wt.%, or 3-50 wt.%, when calculated based on the dry weight of suberin. That is, the weight of dry suberin in relation to the total weight of the dispersion. Thus, suberin can be added into a suberin content of the dispersion of, for example, from 3, 5, 10, 15, 20, or 25 wt. % up to 10, 15, 20, 25, 30, 35, 40 wt.%, when calculated based on the dry weight of suberin. In some embodiments, the suberin content can be up to 50 wt.%.

[0078] In some embodiments, the pH of the dispersion is adjusted. The pH is preferably adjusted prior to the addition of suberin, for example by addition of alkaline solution to an aqueous dispersion of carboxymethylated hemicellulose. In preferredembodiments, the pH of the suberin dispersion is adjusted to from 5.5 to 8, preferably from 6 to 7, and more preferably from 6 to 6.5. Thereby, in some preferred embodiments, the pH can be adjusted to 5.5-6.5. Thus, the pH can be adjusted to, for example from 5.5, 5.8 or 6 up to 6.5, 7 or 8. In some further preferred embodiments, the pH of the dispersion can be up to 6, such as, from 5.5-6.0. Without pH adjustment, the pH may become lower than 5.5, which can increase the degree of shear induced agglomeration. Agglomerates formed at a low pH can block any grooves in the metering element of the coater and form defects on the coated surface, resulting in poor coating quality. Furthermore, a too low pH is corrosive for the coating equipment.

[0079] Carboxymethyl hemicellulose can be referred to as a hemicellulose ether. One benefit of the carboxymethyl hemicellulose over hemicelluloses grafted with organic acids, such as fatty acids, is that in the presence of strong bases, such as NaOH, the hemicellulose grafted with organic acids will undergo a saponification reaction. The saponification reaction is a reaction of the ester bond and a strong base, which in turn produces foam. The resulting gas bubbles within the dispersion will lead to pinholes in the final coating layer, and the saponified dispersant will thus reduce the water stability of the finished coated product. Since the hemicellulose of the present disclosure comprises carboxymethyl side groups, which are linked to the hemicellulose through ether bonds instead of ester bonds in case of the hemicellulose grafted with carboxylic acids, the foam formation problem will not occur, or only to a much lesser extent. Any foam produced upon pH adjustment in the dispersion containing carboxymethyl hemicellulose is expected to be due to the suberin fatty acids, if the pH is adjusted after the addition of the same. Thus, the pH is preferably adjusted in an aqueous dispersion of carboxymethyl hemicellulose prior to the addition of suberin, such as an extract comprising suberin. For example, the pH of the aqueous dispersion of comprising carboxymethyl hemicellulose can be increased up to around 12.5, as a nonlimiting example, and then neutralized upon addition of suberin. The absence of the saponification reaction is a benefit of using carboxymethyl hemicellulose as dispersant. Since no gas bubbles are formed in the dispersion, the quality of the obtained coating will be improved, and it also enables the possibility to adjust the pH at a later stage, for example as a complementary pH adjustment to reach a desired final pH of the dispersion. With suberin dispersions stabilized with hemicellulose grafted with fatty acids, an increase in viscosity is observed when the pH is adjusted as a last stage after the addition of suberin. With carboxymethyl hemicellulose as dispersant, an additional final pH adjustment does not increase the viscosity to an observabledegree. Furthermore, as no gas bubbles are formed due to saponification, the mixing speed can be chosen more freely.

[0080] A further benefit when compared to hemicellulose grafted with carboxylic acid is the simplified reaction scheme, which makes the carboxymethyl hemicellulose more cost efficient and suitable for large scale applications. Thus, in addition to the preparation of the suberin dispersion being simplified due to the reduced risk of saponification, also the preparation of the dispersant per se requires less complex reaction conditions.

[0081] In the method of the present disclosure, the hemicellulose-based dispersant and the suberin are mixed in an aqueous medium, in particularly mixed until a homogeneous, and preferably transparent, dispersion is obtained. In one embodiment, while mixing, preferably with a mixer with an emulsification screen, suberin is slowly added to ensure that no lumps are formed. The hemicellulose-based dispersant is preferably being dispersed in water prior to addition of suberin.

[0082] In sone embodiments, suberin is added into a carboxymethyl hemicellulose dispersion diluted with water. In particular, suberin is gradually added into such a dispersion.

[0083] In further some embodiments, suberin, or an extract comprising suberin, is added in solid form, preferably suberin is used in the form of freeze dried suberin or as a wet suberin cake.

[0084] In some other embodiments, suberin is melted prior to adding into a dispersion of carboxymethyl hemicellulose. In one embodiment, suberin is melted at about 80 °C (at a temperature higher than melting temperature of suberin) and then added into an aqueous dispersion of carboxymethyl hemicellulose.

[0085] According to some embodiments, the mixing is continued for about 10 to 60 minutes, such as 20 to 30 minutes.

[0086] According to some embodiments, the mixing speed is over 10 000 rpm, for example 10 000 rpm to 14 000 rpm, such as 12 000 rpm. The reduced risk of foaming allows for relatively high mixing speeds.

[0087] Further, the present invention concerns a film formed from the aqueous dispersion or by the described method. In some embodiments of the present disclosure, thefilm is a coating formed from the aqueous dispersion or by the described method on a porous substrate, such as a fibrous substrate.

[0088] Thus, according to some embodiments the method further comprises casting and drying the aqueous dispersion into a film.

[0089] According to one embodiment, there is provided a bio-based film formed by the aqueous dispersion described above, comprising suberin together with a carboxymethyl hemicellulose, or by the method described above, comprising the steps of providing hemicellulose, providing carboxymethylation reagents, reacting the hemicellulose by a carboxymethylation reaction to obtain a hemicellulose-based dispersant, and mixing the hemicellulose-based dispersant in aqueous medium with suberin.

[0090] In some embodiments, the method further comprises curing the film at a temperature of 75 to 130°C, such as from 75, 80, 90, or 100°C up to 110, 115, 120 or 130°C. In particular, a curing temperature of 90 to 120°C, more preferably 100 to 115°C, was found to reduce the water sensitivity of the film.

[0091] In some embodiments, the method further comprises curing the film during a curing time of 0.2 to 96 hours. Thus, the curing time can be from 0.2, 0.5, 1, 2, 4, 8, 16 or 24 h up to 4, 12, 24, 48, 72 or 96 h. A prolonged curing time, such as a curing time of from 4 to 96 h, preferably 8 to 48 hours, was found to in combination with a temperature in the above disclose range to further reduce the water sensitivity of the film.

[0092] According to a third aspect of the present disclosure, there is provided a film obtained from the dispersion of the first aspect of the present disclosure, or any embodiments thereof, or by the method of the second aspect of the present disclosure, or any embodiments thereof.

[0093] In some embodiments, the film has been cured at a temperature of 75 to 130°C, preferably 90 to 120°C, more preferably 100 to 115°C. Particularly in the preferred ranges, a high-quality film can be obtained, thus producing coatings with improved wet strength.

[0094] In further some embodiments, the film has been cured during a curing time as disclosed above. Thus, in some preferred embodiments, the film has been cured during a curing time of 4 to 96 h, preferably from 8 to 48 h. In particular in combination with the curing temperatures as disclosed herein, such a prolonged curing time results in improvedquality of the film obtained in coating applications. Especially, the wet strength of the dry film is improved under such treatment.

[0095] According to some embodiments, the thickness of the film is 30-300 pm, preferably 50-150 pm, in particular 80-150 pm.

[0096] According to a fourth aspect of the present disclosure there is provided uses for an aqueous dispersion as disclosed herein, or a film obtained therefrom. According to some embodiments of the present disclosure, there is provided use of the aqueous dispersion according to the first aspect of the present disclosure, or any embodiment thereof, the aqueous dispersion obtained by the method according to the second aspect of the present disclosure, or any of embodiment thereof, or the film according to the third aspect of the present disclosure, or any embodiment thereof, for coating applications, such as coatings for paper, paperboard or sand paper, preferably in food packaging, in pharmaceutical packaging, in cosmetic packaging, or in water treatment as a membrane. In further some embodiments, there is provided use of said dispersion, a dispersion obtained by said method, or said film as a binder in pigment coatings or paints, or as an adhesive, such as adhesive for gluing wood and wood products, or composites.

[0097] It is to be understood that the embodiments of the invention disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.

[0098] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment.

[0099] As used herein, a plurality of items, structural elements, compositional elements, and / or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on theirpresentation in a common group without indications to the contrary. In addition, various embodiments and example of the present invention may be referred to herein along with alternatives for the various components thereof It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention.

[0100] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

[0101] While the forgoing examples are illustrative of the principles of the present invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below.

[0102] 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 depending 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 exclude a plurality.

[0103] The following non-limiting example illustrates an embodiment.EXAMPLESExample 1 : Preparation of suberin based dispersion using carboxymethyl hemicellulose as dispersantPreparation of hemicellulose derivative

[0104] Spruce extract rich in galactoglucomannans was used as a source of hemicellulose. The spruce extract was produced through pressurized hot water extraction. The spruce extract was first precipitated in ethanol to remove potential impurities and to ensure proper modification. The extract was then filtered and re-dissolved in water before undergoing two additional rounds of precipitation in ethanol. After purification, the extract was dried in a vacuum oven at 40 °C.

[0105] The weight percentage (wt.%) of the GGM composition increased slightly (from 75 wt.% to 82 wt.%) during the purification process, which indicates that impurities were effectively removed through EtOH precipitation step, resulting in a higher concentration of hemicellulose in the purified sample.

[0106] The GGM obtained in the above-described process was dissolved into isopropanol, resulting in a solution with 4 wt.% concentration of GGM. The thus obtained GGM solution was then mercerized by slowly adding sodium hydroxide (NaOH) while mixing during a 20-minute period. After the addition, the final molar ratio of GGM / NaOH in the solution was 1 :5.5. After the NaOH had been added, the mercerization reaction was allowed to take place in room temperature for 20 minutes.

[0107] As a next step, monochloroacetic acid (MCA) was slowly added into the alkali GGM solution in room temperature. After the addition, the final GGM / MCA molar ratio of the reaction solution was 1 :2. The temperature of the reaction solution was then raised to 55°C and the reaction was allowed to continue for 90 minutes. After that, the reaction mixture was cooled to room temperature and filtered through a Buchner funnel.

[0108] The solid material obtained in the previous step was dissolved into 70 wt.% methanol and neutralized with 90 wt.% acetic acid. The neutralized suspension was filtered, and then washed three times with 70 wt.% ethanol. A final washing was carried out with 100 % methanol, after which the material was dried overnight at 30°C in a vacuum desiccator.

[0109] The obtained carboxymethylated galactoglucomannan (CM-GGM) had a degree of substitution of around 0.4.Preparation of a suberin-based aqueous dispersion and a coating thereof

[0110] The hemicellulose-based dispersant of example 1 was used to disperse suberin which was extracted from bark (suberin hydrolysate from outer birch bark). The hemicellulose was added in a concentration of 5 wt.% with respect to the weight of dry suberin, and the final solid content of the suberin dispersion comprising carboxymethyl hemicellulose was adjusted to 30 wt.%, calculated from the total weight of the dispersion.

[0111] The dry hemicellulose-based dispersant obtained in Example 1 was first added to dilution water under vigorous stirring until a clear homogeneous solution was obtained. The pH of the dispersion was adjusted by NaOH addition to around 12.5. Suberin (freeze- dried or aqueous cake) was then added in small amounts to this solution under vigorous stirring to avoid formation of clumps and the stirring was continued until a homogenous dispersion was obtained. A mixer (stirrer) with a fine emulsification screen running at over 10 000 rpm is preferred to obtain a homogeneous dispersion. The final pH of the dispersion after the addition of suberin was around 6.

[0112] This hemicellulose stabilized suberin dispersion was coated onto a paper or paperboard using a sheet coater and dried in the oven at 80-120 °C. For the tests carried out in the context of the present disclosure, a curing temperature of 115°C and a curing time of 24 h was used. The resulting paper or paperboard had approximately 10-25 g / m2of dry suberin coating. The water vapor transmission rate for paperboard samples were in the range of 9-14 g / m2 / 24h. The tests were carried out at 23°C and 50% relative humidity (RH).Example 2: Stability of suberin dispersionsTurbiscan analyses were carried out to determine the stability of the obtained suberin dispersion containing carboxymethylated GGM as dispersant. Comparative tests were run using GGM grafted with fatty acids (Cl 4 and Cl 8) as dispersant.By the Turbiscan analyses, the storage stability of the dispersion is measured using static multiple light scattering (SMLS). Changes in the transmission and backscattering of light is recorded along the height of a vial containing the sample. Sedimentation, aggregation, andcreaming will result in changes that are detectable by the instrument before they can be seen by the human eye. From the recorded data, a value called Turbiscan index is obtained, which can be used in evaluation of the stability of the sample. The lower the index, the better the stability. The index is given as a function of time. Figure 2 shows that the suberin dispersion stabilized with CM-GGM is more stable during a four-hour period than the samples stabilized with fatty acid grafted GGMs, i.e., C14-0.14 fa-g-GGM, which represent galactoglucomannan grafted with C14 (acid equivalent of 0.14), and C18-0.14 fa-g-GGM being galactoglucomannan grafted with Cl 8 (acid equivalent of 0.14). The suberin dispersions stabilised with hemicellulose-based dispersant, i.e., CM-GGM and fa-g-GGM, respectively, had a solid content of 30 wt.%, calculated as the total dry weight of suberin and hemicellulose-based dispersant, wherein thehemicellulose-based dispersant was present in a concentration of 5 wt.% with respect to the weight of dry suberin.However, in the context of the stability tests, it should be noted that the suberin dispersions remained stable during much longer periods, although the tests were limited to a four-hour analysis. No visible phase separation or sedimentation could be observed even after several months of storing. Without being bound by theory, it is likely that the hemicellulose creates a network structure in the suberin dispersion, preventing sedimentation and creaming. During storage, the dispersions tend to form a gel, which can be made fluid again with mild agitation. The FA-g-GGM-stabilized suberin dispersions form a more solid-like gel, while CM-GGM-stabilized suberin dispersions remain in a flowing state.Example 3: Water contact angle

[0113] The water contact angle of suberin-based dispersions was measured using Kruss Mobile Surface Analyzer. The measurements were carried out for the suberin dispersion obtained according to Example 1. Measurements on reference samples were carried out with GGM grafted with C18-fatty acid, with an acid equivalent of 0.14 (FA- GGM, Cl 8 (0.14)), an ethanol-based suberin dispersion, as well as an uncoated reference. The suberin dispersions stabilised with hemicellulose-based dispersant, i.e., CM-GGM and FA-g-GGM, respectively, had a solid content of 30 wt.%, calculated as the total dry weight of suberin and hemicellulose-based dispersant, wherein the hemicellulose-based dispersant was present in a concentration of 5 wt.% with respect to the weight of dry suberin.The results are presented in Figure 3. From the results it can be seen that both aqueous suberin dispersions performed better than the ethanol-suberin dispersion in which no surfactant was present. The best results were obtained with CM-GGM as dispersant.Example 4: Water barrier (Cobb)

[0114] The water barrier properties (water absorption) were measured with the so- called Cobb analysis. A paper sample was placed under a metal ring with an area of 0.1 m2and 100 ml of water was poured into the ring while it was pressed against the paper. Thus, in the test, a one-centimetre-thick layer of water was left resting on top of the sample for a predetermined time period (herein 1 minute and 5 minutes), and the result was measured as the difference between the weight before and after contact with water. The one-minute Cobb test is in the results referred to as Cobb60s and the five-minute Cobb test is in the results referred to as Cobb300s.

[0115] An aqueous suberin dispersion containing CM-GGM dispersant as prepared in Example 1 was applied to a commercial paperboard. The paperboard had a pigment coating on one side, which was intended for printing, and no coating on the other side. Separate samples were prepared by applying suberin containing dispersions on one of these sides.

[0116] The results for the 60 second Cobb test are presented in Figure 4, showing that the suberin coating provides a barrier against water. The CM-GGM stabilized suberin gave the best result when it was coated to the pre-coated side of the paper board.

[0117] The results for the five-minute Cobb test were conducted to see clearer differences between the samples, and the results of which are presented in Figure 5. Without pre-coating, the CM-GGM-stabilized suberin performed equally well as the FA-g-GGM- stabilized suberin. When coated on the pre-coated side, the CM-GGM-stabilized suberin worked much better, even slightly better than the ethanol dispersed suberin which had no dispersant in it at all. The results implies that CM-GGM can be used as a dispersant without any negative impact on the water barrier of the suberin dispersion. In addition, two commercial water barrier latexes, one purchased from Trinseo (styrene-butadiene latex), and another one from BASF (polyolefin) were tested to give reference values for commercial, fossil-based barrier latexes. Hence, these commercial references were not suberin based dispersions, and cannot fully be compared to the biobased CM-GGM and FA-g-GGMdispersions. Instead, the impact of the dispersant in suberin coatings can only be seen as differences between the barriers obtained with the suberin dispersions containing PVOH, CM-GGM, and FA-g-GGM as dispersant.INDUSTRIAL APPLICABILITY

[0118] The aqueous dispersion according to the current invention can be used as glues, adhesives and binders. Particularly, they can be used as glues and adhesives in wood-based products such as plywood or as binders in applications such as pigment coatings and paints. The films according to the current invention can be used as films in packaging materials, such as to replace aluminum foil, PE, PP, PVDC or EVOH, for food, cosmetics and pharmaceuticals or as barrier coatings for paper and paperboard.ACRONYMS LISTCM-GGM Carboxymethylated galactoglucomannanDS Degree of substitutionGGM GalactoglucomannanFA-g-GGM Fatty acid grafted galactoglucomannan

Claims

CLAIMS:

1. An aqueous dispersion comprising suberin, and a dispersant comprising carboxymethyl hemicellulose.

2. The aqueous dispersion according to claim 1, wherein the carboxymethyl hemicellulose is prepared from galactoglucomannan (GGM), xylan, arabinogalactan, arabino- gluronoxylan, xyloglucan, betaglucan, alpha-glucan or a combination thereof, preferably GGM or xylan.

3. The aqueous dispersion according to claim 1 or 2, wherein the carboxymethyl hemicellulose is prepared from isolated hemicellulose, preferably obtained by extraction, membrane filtration, hydrolysis, biosynthesis routes or by the combination thereof.

4. The aqueous dispersion according to any of the preceding claims, wherein the amount of carboxymethyl hemicellulose is 0.1 to 50 wt.%, preferably 0.5 to 20 wt.%, more preferably 1 to 10 wt.% with respect to weight of dry suberin.

5. The aqueous dispersion according to any of the preceding claims, wherein the suberin content of the dispersion is 3-40 wt.%, such as 5-40 wt.%, or 10-40 wt.%, when calculated based on the dry weight of suberin.

6. The aqueous dispersion according to any of the preceding claims, wherein the total solid content of the aqueous dispersion is in the range of 5 to 55 wt.%, preferably 15 to 50 wt.%, more preferably 20 to 40 wt.%, calculated from the total weight of the dispersion, the rest preferably being water.

7. The aqueous dispersion according to any of the preceding claims, wherein the carboxymethyl hemicellulose has a degree of substitution from 0.1 to 1.5, or 0.5-1.5.

8. The aqueous dispersion according to any of the preceding claims, wherein the pH of the dispersion is from 5.5 to 8, preferably from 6 to 7, more preferably 6 to 6.5, or 5.5 to 6.5.

9. A method of producing an aqueous dispersion, comprising the steps of- providing a hemicellulose,- providing a carboxymethylation reagent, and- reacting the hemicellulose by a carboxymethylation reaction with the carboxymethylation reagent to obtain carboxymethyl hemicellulose as a hemicellulose-based dispersant, and mixing the obtained hemicellulose-based dispersant in an aqueous medium with suberin.

10. The method according to claim 9, wherein the carboxymethylation reagent is an haloacetic acid, preferably monochloroacetic acid.

11. The method according to claim 9 or 10, comprising providing isolated hemicellulose, preferably obtained by extraction, membrane filtration, hydrolysis, biosynthesis routes or by the combination thereof.

12. The method according to claim 9 to 11, comprising providing hemicellulose in dispersed form, preferably dissolved in an aqueous medium or in alcohol, such as in isopropanol, or mixtures thereof.

13. The method according to any of claims 9 to 12, comprising the step of subjecting the hemicellulose to a mercerization reaction under alkaline conditions, preferably in the presence of NaOH.

14. The method according to any of claims 9 to 13, wherein the amount of hemicellulosebased dispersant is 0.1 to 50 wt.%, preferably 0.5 to 20 wt.%, more preferably 1 to 10 wt.% with respect to the weight of dry suberin.

15. The method according to any of claims 9 to 14, wherein the pH of the dispersion is adjusted to from 5.5 to 8, preferably from 6 to 7, more preferably 6 to 6.5, or 5.5 to 6.5.

16. The method according to any of claims 9 to 15, wherein the method further comprises casting and drying the aqueous dispersion into a film.

17. A film obtained from the dispersion of any one of claims 1 to 8, or the method of any one of claims 9 to 16.

18. The film according to claim 17, wherein the film has been cured at a temperature of 75 to 130°C, preferably 90 to 120°C, more preferably 100 to 115°C.

19. The film according to any one of claims 17 to 18, wherein the film has been cured during a curing time of 4 to 96 h, preferably from 8 to 48 h.

20. Use of the aqueous dispersion according to any of claims 1 to 8, the aqueous dispersion obtained by the method according to any of claims 9 to 16, or the film according to claim 17-19, for coating applications, such as coatings for paper, paperboard or sand paper, preferably in food packaging, in pharmaceutical packaging, in cosmetic packaging, or in water treatment as a membrane.

21. Use of the aqueous dispersion according to any of claims 1 to 8, the aqueous dispersion obtained by the method according to any of claims 9 to 16, or the film according to claim 17-19, as a binder in pigment coatings or paints, or as an adhesive, such as adhesive for gluing wood and wood products, or composites.

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