Method for preparing a bonding resin

Abstract

The present invention relates to a method for preparing a bonding resin, in which lignin is provided in the form of an ammonia and / or organic base solution and mixed with one or more crosslinking agents and, optionally, one or more additives. The bonding resin is useful, for example, in the production of laminates, mineral wool insulation, and wood products such as plywood, oriented strand board (OSB), laminated veneer lumber (LVL), medium density fiberboard (MDF), high density fiberboard (HDF), parquet flooring, curved plywood, veneered particleboard, veneered MDF, or particleboard. The bonding resin is also useful, for example, in composites, molding compounds, and foundry applications.

Description

[Technical Field]

[0001] The present invention relates to a method for preparing a joint resin, comprising providing lignin in the form of an ammonia and / or organic base solution, and using a glycerol diglycidyl ether, polyglycerol diglycidyl ether, polyglycerol polyglycidyl ether, glycerol triglycidyl ether, sorbitol polyglycidyl ether, alkoxylated glycerol polyglycidyl ether, trimethylolpropane triglycidyl ether, trimethylolpropane diglycidyl ether, polyoxypropylene glycol diglycidyl ether, polyoxypropylene glycol triglycidyl ether, diglycidyl ether of cyclohexanedimethanol, resorcinol diglycidyl ether, isosorbide diglycidyl ether, pentaerythritol tetraglycidyl ether, ethylene glycol diglycidyl ether, 2-9 alkyl glycerol ... polyethylene glycol diglycidyl ethers having 1 to 5 ethylene glycol units, propylene glycol diglycidyl ethers having 1 to 5 propylene glycol units, diglycidyl-, triglycidyl-, or polyglycidyl ethers of carbohydrates, diglycidyl-, triglycidyl-, or polyglycidyl esters of carbohydrates, diglycidyl ethers or diglycidyl esters of salicylic acid, vanillic acid, or 4-hydroxybenzoic acid, epoxidized or glycidyl-substituted plant phenolic compounds (e.g., tannin, cardanol, cardol, anacardic acid) or epoxidized plant oils (e.g., rapeseed oil, linseed oil, soybean oil), tris(4-hydroxyphenyl)methane triglycidyl ether, N,N-bis(2,3-epoxypropyl)aniline, p-(2,3-epoxypropoxy-N,N-bis(2,and optionally one or more additives; and optionally one or more crosslinkers selected from crosslinkers having a functional group selected from glycidyl amine, diglycidyl amine, triglycidyl amine, polyglycidyl amine, glycidyl amide, diglycidyl amide, triglycidyl amide, polyglycidyl amide, glycidyl ester, diglycidyl ester, triglycidyl ester, polyglycidyl ester, glycidyl azide, diglycidyl azide, triglycidyl azide, polyglycidyl azide, glycidyl methacrylate, diglycidyl methacrylate, triglycidyl methacrylate, or polyglycidyl methacrylate. Bonding resins are useful, for example, in the manufacture of laminates, mineral wool insulation, and wood products such as plywood, oriented strand board (OSB), laminated veneer lumber (LVL), medium density fiberboard (MDF), high density fiberboard (HDF), parquet flooring, curved plywood, veneered particleboard, veneered MDF, or particleboard. Bonding resins are also useful, for example, in composites, molding compounds, and foundry applications. [Background technology]

[0002] Lignin, an aromatic polymer, is the main component of wood, for example, and is the most abundant carbon source on Earth after cellulose. In recent years, with the development and commercialization of techniques to extract lignin in a highly pure, solid, and specialized form from the pulp manufacturing process, lignin has attracted considerable attention as a possible renewable alternative to the predominantly aromatic chemical precursors currently supplied by the petrochemical industry.

[0003] Lignin, a polyaromatic network, has been widely investigated as a suitable substitute for phenol in the production of phenol-formaldehyde adhesives. These are used in the production of laminates and structural wood products, such as plywood, oriented strand board, and fiberboard. During the synthesis of such adhesives, phenol, which may be partially replaced by lignin, reacts with formaldehyde in the presence of either a basic or acidic catalyst to form highly crosslinked aromatic resins called novolacs (when an acidic catalyst is used) or resols (when a basic catalyst is used). Currently, due to the lower reactivity of lignin, only a limited amount of phenol can be replaced by lignin.

[0004] One problem with preparing resins containing lignin is the use of formaldehyde, especially when lignin is used in formaldehyde-containing resins, such as lignin-phenol-formaldehyde resins. Formaldehyde-based resins emit formaldehyde, a toxic volatile organic compound. Current and proposed legislation targeting the reduction or elimination of formaldehyde emissions has led to the development of formaldehyde-free resins for wood adhesive applications.

[0005] Jingxian Li R. et al. (Green Chemistry, 2018, 20, 1459-1466) describe the preparation of a resin containing glycerol diglycidyl ether and lignin, where the lignin is provided in solid form. One problem with the technique described in this paper is the long pressing time and high pressing temperature. Three-ply plywood samples were pressed at a temperature of 150°C for 15 minutes to allow the resin to fully cure.

[0006] Engelmann G. and Ganster J. (Holzforschung, 2014, 68, 435-446) describe the preparation of bio-based epoxy resins using low molecular weight kraft lignin and pyrogallol, where the lignin component consists of acetone extraction from kraft lignin. Summary of the Invention

[0007] Surprisingly, it has now been found that a readily prepared joint resin is possible in which the use of formaldehyde can be avoided. It has also been found that an improved joint resin can be achieved by providing the lignin in the form of an aqueous solution containing ammonia and / or an organic base. By providing the lignin in the form of an aqueous solution containing ammonia and / or an organic base, the step of grinding the lignin particles can be avoided, and the formation of lignin clumps and the use of dispersants can be avoided.

[0008] It has been found that providing lignin in the form of an aqueous solution containing ammonia and / or an organic base deprotonates the phenolic hydroxyl groups in the lignin structure, freeing them to react with epoxide groups. This improves the reactivity and performance of the binder. Therefore, providing lignin in the form of an aqueous solution containing ammonia and / or an organic base significantly accelerates the reaction, thereby reducing press times and allowing for the use of lower press temperatures to cure the bonding resin, for example, in the production of laminates, mineral wool insulation, glass wool insulation, and wood products such as plywood, oriented strand board (OSB), laminated veneer lumber (LVL), medium-density fiberboard (MDF), high-density fiberboard (HDF), parquet flooring, curved plywood, veneered particleboard, veneered MDF, or particleboard. Bonding resins are also useful in composites, molding compounds, and foundry applications.

[0009] Furthermore, by providing the lignin in the form of an aqueous solution of the lignin with ammonia and / or an organic base, the risk of degrading, for example, glass wool and mineral wool fibers is minimized.

[0010] The present invention therefore relates to a method for preparing a joint resin, comprising the step of: mixing an aqueous solution of lignin containing ammonia and / or an organic base with a solution of glycerol diglycidyl ether, polyglycerol diglycidyl ether, polyglycerol polyglycidyl ether, glycerol triglycidyl ether, sorbitol polyglycidyl ether, alkoxylated glycerol polyglycidyl ethers, trimethylolpropane triglycidyl ether, trimethylolpropane diglycidyl ether, polyoxypropylene glycol diglycidyl ether, polyoxypropylene glycol triglycidyl ether, diglycidyl ether of cyclohexanedimethanol, resorcinol diglycidyl ether, isosorbide diglycidyl ether, pentaerythritol tetraglycidyl ether, ethylene glycol diglycidyl ether, 2-hydroxybenzoyl benzoate ... Polyethylene glycol diglycidyl ethers having up to 9 ethylene glycol units, propylene glycol diglycidyl ethers having 1 to 5 propylene glycol units, diglycidyl-, triglycidyl-, or polyglycidyl-ethers of carbohydrates, diglycidyl-, triglycidyl-, or polyglycidyl esters of carbohydrates, diglycidyl ethers or esters of salicylic acid, vanillic acid, or 4-hydroxybenzoic acid, epoxidized or glycidyl-substituted plant phenolic compounds (e.g., tannin, cardanol, cardol, anacardic acid) or epoxidized plant oils (e.g., rapeseed oil, linseed oil, soybean oil), tris(4-hydroxyphenyl)methane triglycidyl ether, N,N-bis(2,3-epoxypropyl)aniline, p-(2,3-epoxypropoxy-N,N-bis(2,and mixing the diglycidyl ether of 3-epoxypropyl)aniline, bis-hydroxymethylfuran, and / or a diglycidyl ether of a terminal diol having a linear carbon chain of 3 to 6 carbon atoms with one or more crosslinkers selected from crosslinkers having a functional group selected from glycidyl amine, diglycidyl amine, triglycidyl amine, polyglycidyl amine, glycidyl amide, diglycidyl amide, triglycidyl amide, polyglycidyl amide, glycidyl ester, diglycidyl ester, triglycidyl ester, polyglycidyl ester, glycidyl azide, diglycidyl azide, triglycidyl azide, polyglycidyl azide, glycidyl methacrylate, diglycidyl methacrylate, triglycidyl methacrylate, or polyglycidyl methacrylate.

[0011] One aspect of the present invention is a method for preparing a bonding resin by mixing an aqueous solution of lignin containing ammonia and / or an organic base with one or more crosslinkers and / or one or more glycidyl ethers, wherein the crosslinkers have an epoxy index greater than 4 eq / kg. The epoxy index can be determined according to ISO 3001. Preferably, the crosslinkers have an epoxy index greater than 5 eq / kg. The crosslinkers are aliphatic or, preferably, aromatic glycidyl ethers. Preferably, the crosslinkers are aliphatic.

[0012] The glycidyl ether may be a multifunctional epoxide and the process according to the invention may use mixtures of mono-, di-, tri- and / or tetra-functional epoxides.

[0013] Thus, the present invention is also directed to bonding resins obtainable using the methods described herein, and to the use of the bonding resins in the manufacture of laminates, mineral wool insulation, and wood products, such as plywood, oriented strand board (OSB), laminated veneer lumber (LVL), medium-density fiberboard (MDF), high-density fiberboard (HDF), parquet flooring, curved plywood, veneered particleboard, veneered MDF, or particleboard. The present invention is also directed to such laminates, mineral wool insulation, and wood products, such as plywood, oriented strand board (OSB), laminated veneer lumber (LVL), medium-density fiberboard (MDF), high-density fiberboard (HDF), parquet flooring, curved plywood, veneered particleboard, veneered MDF, or particleboard, manufactured using the bonding resins. The bonding resins according to the present invention can also be used in the manufacture of composites, molding compounds, and foundry applications. DETAILED DESCRIPTION OF THE INVENTION

[0014] Throughout this description, the term "lignin" is intended to encompass any type of lignin, for example, lignin derived from hardwoods, softwoods, or annular plants. Preferably, the lignin is alkaline lignin, for example, produced by the Kraft process. Preferably, the lignin has been purified or isolated before being used in the process according to the invention. The lignin may be isolated from black liquor and, optionally, further purified before being used in the process according to the invention. Purification typically results in a lignin purity of at least 90%, preferably at least 95%. Thus, the lignin used in accordance with the process of the invention preferably contains less than 10%, preferably less than 5%, of impurities. The lignin may then be separated from the black liquor using the method disclosed in WO2006031175. The lignin may then be separated from the black liquor using a method known as the LignoBoost process. The lignin may be provided in the form of particles, for example, particles having an average particle size of 50 to 500 micrometers.

[0015] The glycerol diglycidyl ether, polyglycerol diglycidyl ether, polyglycerol polyglycidyl ether, glycerol triglycidyl ether, sorbitol polyglycidyl ether, alkoxylated glycerol polyglycidyl ether, trimethylolpropane triglycidyl ether, trimethylolpropane diglycidyl ether, polyoxypropylene glycol diglycidyl ether, polyoxypropylene glycol triglycidyl ether, diglycidyl ether of cyclohexanedimethanol, etc. may be used according to the present invention. ether, resorcinol diglycidyl ether, isosorbide diglycidyl ether, pentaerythritol tetraglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ethers having 2 to 9 ethylene glycol units, propylene glycol diglycidyl ethers having 1 to 5 propylene glycol units, diglycidyl-, triglycidyl-, or polyglycidyl-ethers of carbohydrates, diglycidyl-, triglycidyl-, or polyglycidyl esters of carbohydrates, salicylic acid, vanillic acid or diglycidyl ethers or diglycidyl esters of 4-hydroxybenzoic acid, epoxidized or glycidyl-substituted plant phenolic compounds (e.g., tannins, cardanol, cardol, anacardic acid) or epoxidized plant oils (e.g., rapeseed oil, linseed oil, soybean oil), tris(4-hydroxyphenyl)methane triglycidyl ether, N,N-bis(2,3-epoxypropyl)aniline, p-(2,3-epoxypropoxy-N,N-bis(2,3-epoxypropyl)aniline, diglycidyl ethers of bis-hydroxymethylfuran diglycidyl ethers of terminal diols having a linear carbon chain of 3 to 6 carbon atoms, as well as glycidyl amines, diglycidyl amines, triglycidyl amines, polyglycidyl amines, glycidyl amides, diglycidyl amides, triglycidyl amides, polyglycidyl amides, glycidyl esters, diglycidyl esters, triglycidyl esters, polyglycidyl esters, glycidyl azides, diglycidyl azides, triglycidyl azides, polyglycidyl azides, glycidyl methacrylates, diglycidyl methacrylates,A crosslinker with functional groups selected from triglycidyl methacrylate or polyglycidyl methacrylate acts as the crosslinker. Glycidyl ethers with more epoxide functionality, such as glycerol diglycidyl ether, glycerol triglycidyl ether, and sorbitol polyglycidyl ether, can be used. Other glycidyl ethers with 2 to 9 alkylene glycol groups (e.g., 2 to 4 alkylene glycol groups or 2 to 6 alkylene glycol groups), such as diethylene glycol diglycidyl ether, triethylene glycol diglycidyl ether, dipropylene glycol diglycidyl ether, and tripropylene diglycidyl ether, can be used. As the chain length between the two glycidyl ether groups increases, the resin becomes more flexible, but this can adversely affect its performance. The resulting resin becomes adhesive during curing. Other suitable crosslinkers include crosslinkers having functional groups selected from glycidyl amine, diglycidyl amine, triglycidyl amine, polyglycidyl amine, glycidyl amide, diglycidyl amide, triglycidyl amide, polyglycidyl amide, glycidyl ester, diglycidyl ester, triglycidyl ester, polyglycidyl ester, glycidyl azide, diglycidyl azide, triglycidyl azide, polyglycidyl azide, glycidyl methacrylate, diglycidyl methacrylate, triglycidyl methacrylate, and polyglycidyl methacrylate. Typically, the bonding resin according to the present invention is applied to the surface of, for example, veneers in the manufacture of plywood. When the veneers are pressed together under heat, crosslinking occurs in the bonding resin to form an adhesive.

[0016] The aqueous solution of lignin containing ammonia and / or an organic base can be prepared by methods known in the art, for example, by mixing lignin and ammonia and / or an organic base with water. The pH of the aqueous solution of lignin containing ammonia and / or an organic base is preferably in the range of 10 to 14. Examples of organic bases include amines, such as primary, secondary, and tertiary amines, and mixtures thereof. Preferably, the organic base is selected from the group consisting of methylamine, ethylamine, propylamine, butylamine, ethylenediamine, methanolamine, ethanolamine, aniline, cyclohexylamine, benzylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, dimethanolamine, diethanolamine, diphenylamine, phenylmethylamine, phenylethylamine, dicyclohexylamine, piperazine, imidazole, 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-isopropylimidazole, 2-phenylimidazole, 2-methylimidazoline, 2-phenylimidazoline, trimethylamine, triethylamine, dimethylhexylamine, N-methylpiperazine, dimethylbenzylamine, aminomethylpropanol, tris(dimethylaminomethyl)phenol, and dimethylaniline, or a mixture thereof. The total amount of ammonia and / or organic base in the aqueous solution is preferably 0.1% to 20% by weight, preferably 0.1% to 10% by weight, of the total weight of the aqueous solution containing water, lignin, and ammonia and / or organic base. The amount of lignin in the aqueous solution of lignin containing ammonia and / or organic base is preferably 1% to 60% by weight, for example 10% to 30% by weight of the solution. The aqueous solution of lignin containing ammonia and / or organic base does not contain alkali.

[0017] The weight ratio between the lignin (dry weight) and the total amount of crosslinker is preferably in the range of 0.1:10 to 10:0.1, such as 1:10 to 10:0.3, such as 5:10 to 5:0.3, such as 1:10 to 10:1. The amount of lignin in the bonding resin is preferably 5% to 50% by weight, calculated as the dry weight of lignin and the total weight of the bonding resin.

[0018] The jointing resin may also contain additives such as urea, tannin, surfactants, dispersants, and fillers. The jointing resin may also contain a plasticizer. As used herein, the term "plasticizer" refers to an agent that, when added to lignin, makes the lignin softer and more flexible, increasing its plasticity by lowering its glass transition temperature (Tg) and improving its flow behavior. Examples of plasticizers include polyols, alkyl citrates, organic carbonates, phthalates, adipates, sebacates, maleates, benzoates, trimellitates, and organic phosphates. Polyols include, for example, polyethylene glycol, polypropylene glycol, glycerol, diglycerol, polyglycerol, butanediol, sorbitol, and polyvinyl alcohol. Alkyl citrates include, for example, triethyl citrate, tributyl citrate, acetyltriethyl citrate, and trimethyl citrate.

[0019] Examples of organic carbonates include ethylene carbonate, propylene carbonate, glycerol carbonate, and vinyl carbonate. Further examples of plasticizers include solvents used as coalescing agents, such as polyethylene glycol ethers, polyethers, hydrogenated sugars, triacetin, and alcohol ethers. In one embodiment of the present invention, the plasticizer is a polyol, such as a polyol selected from the group consisting of polyethylene glycol and polypropylene glycol. The weight ratio between the plasticizer and lignin, calculated based on the dry weight of each component, is 0.1:10 to 10:1. Preferably, the weight ratio between the plasticizer and lignin, calculated based on the dry weight of each component, is 0.1:10 to 10:10, e.g., 1:10 to 5:10. The bonding resin may also contain a coupling agent, such as a silane-based coupling agent.

[0020] The amount of urea in the bonding resin is 0 to 40%, preferably 5 to 20%, calculated as the dry weight of urea and the total weight of the bonding resin.

[0021] Fillers and / or hardeners may also be added to the bonding resin, examples of which include limestone, cellulose, sodium carbonate, and starch.

[0022] The reactivity of lignin with glycidyl ethers can be increased by modifying the lignin by glyoxylation, etherification, esterification, or any other method that increases the lignin hydroxyl, carboxylic acid, amine, or thiol content. Preferably, the lignin used in accordance with the present invention is not chemically modified.

[0023] The aqueous solution of lignin containing ammonia and / or an organic base is preferably mixed with the glycidyl ether at room temperature, for example, at a temperature of 15° C. to 30° C. Mixing is preferably carried out for about 5 seconds to 2 hours. The viscosity of the mixture is preferably monitored continuously during mixing or by taking samples and determining their viscosity.

[0024] In the manufacture of mineral wool insulation, curing of the bonding resin to form the adhesive occurs when the components used in preparing the mineral wool insulation are exposed to heat. [Example]

[0025] Example 1 First, a lignin solution was prepared by adding 243 g of powdered lignin (95% solids) and 619 g of water to a 1 L glass reactor at ambient temperature and stirring until the lignin was completely and uniformly dispersed. Next, 138 g of a 28-30% ammonia solution was added to the lignin dispersion. The composition was stirred for 60 minutes, ensuring that the lignin was completely dissolved.

[0026] Example 2 3-Aminopropyltrimethoxysilane was diluted to a 1% aqueous solution. A binder composition was prepared by weighing 31.2 g of the lignin-ammonia solution from Example 1, 7.8 g of polyglycerol polyglycidyl ether, and 3 g of 1% 3-aminopropyltrimethoxysilane into a 250 ml plastic container and stirring with a wooden stick for 2 minutes. Quartz sand was weighed into a bowl, and the lignin mixture was poured onto the sand and mixed with an electric hand mixer for 2 minutes. Sand bars were then prepared by placing the sand-binder mixture into a mold and baking it in an oven at 200°C for 2 hours. All sand bars were hard and stable after curing in the oven. The size of each test bar was 23 mm x 22 mm x 84 mm (height x thickness x length).

[0027] The sand bars were conditioned for 2 hours in a water bath at 80° C. The sand bars were post-cured for 24 hours and then immersed in a water bath at 80° C. for 2 hours.

[0028] The sand bars were evaluated by a three-point bending test. The bending strength before and after immersion in water is shown in Table 1.

[0029] Example 3 A binder composition was prepared by weighing 37.8 g of the lignin-ammonia solution from Example 1, 7.6 g of polyglycerol polyglycidyl ether, and 3 g of 1% 3-aminopropyltrimethoxysilane into a 250 ml plastic container and stirring with a wooden rod for 2 minutes. Silica sand was weighed into a bowl, and the lignin mixture was poured onto the sand and mixed with an electric hand mixer for 2 minutes. Sand bars were then prepared by placing the sand-binder mixture into a mold and baking it in an oven at 180°C for 2 hours. All sand bars were hard and stable after curing in the oven.

[0030] The sand bars were conditioned in a water bath at 80°C for 2 hours. After post-curing for 24 hours, they were immersed in a water bath at 80°C for 2 hours. The sand bars were evaluated using a three-point bending test. The bending strength before and after water immersion is shown in Table 1. TIFF0007805295000001.tif60170

[0031] Example 4 First, a lignin solution was prepared by adding 211 g of powdered lignin (95% solids) and 685 g of water to a 1 L glass reactor at ambient temperature and stirring until the lignin was completely and uniformly dispersed. Next, 104 g of a 28-30% ammonia solution was added to the lignin dispersion. The composition was stirred for 60 minutes, ensuring that the lignin was completely dissolved.

[0032] Example 5 3-Aminopropyltrimethoxysilane was diluted to a 1% aqueous solution. A binder composition was prepared by weighing 43.5 g of the lignin-ammonia solution from Example 4, 1.3 g of polyglycerol polyglycidyl ether, 1.3 g of polyethylene glycol 300, 1.9 g of water, and 2 g of 1% 3-aminopropyltrimethoxysilane into a 250 ml plastic container and stirring with a wooden stick for 2 minutes. 250 g of silica sand was weighed into a bowl, and the lignin mixture was poured onto the sand and mixed with an electric hand mixer for 2 minutes. Sand bars were then prepared by placing the sand-binder mixture into a mold and baking it in an oven at 180°C for 2 hours. All sand bars were hard and stable after curing in the oven. The size of each test bar was 23 mm x 22 mm x 84 mm (height x thickness x length).

[0033] The sand bars were post-cured for 24 hours and then immersed in a water bath at 80°C for 2 hours.

[0034] The sand bars were evaluated by a three-point bending test. The bending strength before and after immersion in water is shown in Table 1.

[0035] Example 6 A binder composition was prepared by weighing 47.6 g of the lignin-ammonia solution from Example 4, 0.5 g of polyglycerol polyglycidyl ether, 0.5 g of polyethylene glycol 300, and 2 g of 1% 3-aminopropyltrimethoxysilane into a 250 ml plastic container and stirring with a wooden rod for 2 minutes. 250 g of silica sand was weighed into a bowl, and the lignin mixture was poured onto the sand and mixed with an electric hand mixer for 2 minutes. Sand bars were then prepared by placing the sand-binder mixture into a mold and baking it in an oven at 180°C for 2 hours. All sand bars were hard and stable after curing in the oven.

[0036] After post-curing for 24 hours, the sand bars were immersed in a water bath at 80°C for 2 hours. The sand bars were evaluated using a three-point bending test. The bending strength before and after water immersion is shown in Table 2. TIFF0007805295000002.tif61170

[0037] In view of the above detailed description of the invention, other modifications and variations will be apparent to those skilled in the art, but it is evident that such other modifications and variations can be made without departing from the spirit and scope of the invention.

Claims

1. 1. A method for preparing a joint resin, comprising mixing an aqueous solution of lignin containing ammonia and / or an organic base with one or more crosslinkers selected from glycerol diglycidyl ether, polyglycerol diglycidyl ether, polyglycerol polyglycidyl ether, glycerol triglycidyl ether, sorbitol polyglycidyl ether, alkoxylated glycerol polyglycidyl ethers, trimethylolpropane triglycidyl ether, trimethylolpropane diglycidyl ether, polyoxypropylene glycol diglycidyl ether, polyoxypropylene glycol triglycidyl ether, diglycidyl ether of cyclohexanedimethanol, resorcinol diglycidyl ether, isosorbide diglycidyl ether, pentaerythritol tetraglycidyl ether, ethylene glycol diglycidyl ether, or propylene glycol diglycidyl ether having 1 to 5 propylene glycol units; Lignin is produced by the Kraft process. The aqueous solution of lignin containing ammonia and / or an organic base is alkali-free; the total amount of ammonia and / or organic base in the aqueous solution is 0.1% by weight to 20% by weight of the aqueous solution; The method, wherein the lignin is not chemically modified prior to use in the method.

2. 10. The method of claim 1, wherein the cross-linking agent is a polyglycerol polyglycidyl ether.

3. 3. The method of claim 1 or 2, wherein the aqueous solution of lignin containing ammonia and / or an organic base contains at least 5 wt. % lignin.

4. 3. The method according to claim 1 or 2, wherein the weight ratio between the lignin calculated on dry lignin and the total amount of cross-linking agent is from 0.1:10 to 10:0.

1.

5. 3. The method of claim 1 or 2, wherein the method further comprises mixing one or more additives selected from urea, tannins, surfactants, dispersants, plasticizers, coupling agents, and fillers.

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