阅读说明：本技术 用于处理木质素和制备粘合剂组合物的方法 (Method for treating lignin and preparing binder composition ) 是由 S·皮耶塔里宁 S·瓦尔科宁 O·林格那 于 2014-11-25 设计创作，主要内容包括：本发明涉及用于处理木质素的方法,其中所述方法包括以下步骤：a)将木质素溶解在水性组合物中,所述组合物包含选自酚类的化合物和碱,同时将所述组合物的温度保持在40-85℃,其中所述碱包括碱金属的氢氧化物；以及b)在某一温度下加热组合物,所述温度高于步骤a)中组合物的温度,限制条件是组合物的温度不超过100℃,同时将组合物的pH值保持为6-14。(The present invention relates to a method for treating lignin, wherein the method comprises the steps of: a) dissolving lignin in an aqueous composition comprising a compound selected from the group consisting of phenols and a base, while maintaining the temperature of the composition at 40-85 ℃, wherein the base comprises a hydroxide of an alkali metal; and b) heating the composition at a temperature which is higher than the temperature of the composition of step a), provided that the temperature of the composition does not exceed 100 ℃, while maintaining the pH of the composition in the range of 6 to 14.)

1. A method for treating lignin, characterized in that the method comprises the steps of:

a) dissolving lignin in an aqueous composition comprising a compound selected from the group consisting of phenols and a base while maintaining the temperature of the composition at 40-85 ℃ and the pH of the composition at a pH value of 4-10, wherein the base is a hydroxide of an alkali metal, the lignin being selected from the group consisting of kraft lignin, steam explosion lignin, biorefinery lignin, supercritical separation lignin, hydrolysis lignin, flash precipitation lignin, lignin from biomass, lignin from alkaline pulping, lignin from soda pulping, lignin from organosolv pulping and combinations thereof; and

b) for alkalizing the lignin, the composition obtained in step a) is heated at a temperature which is higher than the temperature of the composition in step a), with the proviso that the temperature of the composition does not exceed 100 ℃, while maintaining the pH of the composition in the range of from 6 to 10, and the concentration of alkali is in the range of from 0.1 to 11 weight-%, based on the total weight of the composition in step b).

2. The method of claim 1, wherein the compound selected from the group consisting of phenols is selected from the group consisting of: phenol, cresol, resorcinol, and combinations thereof.

3. The method of any one of claims 1-2, wherein the temperature of the composition is maintained in the range of 65-80 ℃ in step a).

4. The method of claim 3, wherein the temperature of the composition is maintained in the range of 70 to 75 ℃ in step a).

5. The method of any one of claims 1-2, wherein step b) comprises heating the composition at a temperature that is at least 5 ℃ higher than the temperature of the composition in step a).

6. The method of claim 5, wherein the temperature is at least 10 ℃ higher than the temperature of the composition in step a).

7. The method of claim 6, wherein the temperature is at least 20 ℃ higher than the temperature of the composition in step a).

8. The method of any one of claims 1-2, wherein the pH of the composition is maintained at a pH value of 4.5-9.5 in step a).

9. The method of claim 8, wherein the pH of the composition is maintained at a pH of 5-9 in step a).

10. The method of claim 9, wherein the pH of the composition is maintained at a pH of 5.5 to 8.5 in step a).

11. The method of claim 8, wherein the pH of the composition in step b) is preferably maintained at a pH value of 6.5-9.5.

12. The method of claim 11, wherein the pH of the composition in step b) is preferably maintained at a pH value of 7-9.

13. The method of any one of claims 1-2, wherein in step b), the composition is heated at a temperature of 60-100 ℃.

14. The method of claim 13, wherein in step b), the composition is heated at a temperature of 70-95 ℃.

15. The method of claim 14, wherein in step b), the composition is heated at a temperature of 75-90 ℃.

16. A process for preparing an adhesive composition, characterized in that it comprises the steps of:

a) dissolving lignin in an aqueous composition comprising a compound selected from the group consisting of phenols and a base while maintaining the temperature of the composition at 40-85 ℃ and the pH of the composition at a pH value of 4-10, wherein the base is a hydroxide of an alkali metal, the lignin being selected from the group consisting of kraft lignin, steam explosion lignin, biorefinery lignin, supercritical separation lignin, hydrolysis lignin, flash precipitation lignin, lignin from biomass, lignin from alkaline pulping, lignin from soda pulping, lignin from organosolv pulping and combinations thereof;

b) for alkalizing the lignin, heating the composition obtained in step a) at a temperature which is higher than the temperature of the composition in step a), with the proviso that the temperature of the composition does not exceed 100 ℃, while maintaining the pH of the composition at a pH value of 6-10, and with the concentration of alkali being 0.1-11 weight-%, based on the total weight of the composition in step b); and

c) mixing the composition formed in step b) with a cross-linking agent and heating the composition at a temperature of 60-100 ℃ while maintaining the pH of the composition at a pH value of 6-10.

17. The method of claim 16, wherein step b) comprises heating the composition at a temperature that is at least 5 ℃ greater than the temperature of the composition in step a).

18. The method of claim 17, wherein the temperature is at least 10 ℃ higher than the temperature of the composition in step a).

19. The method of claim 18, wherein the temperature is at least 20 ℃ higher than the temperature of the composition in step a).

20. The method of any one of claims 16-17, wherein step c) comprises heating the composition at a temperature of 65-95 ℃.

21. The method of claim 20, wherein step c) comprises heating the composition at a temperature of from 70 ℃ to 90 ℃.

22. The method of claim 21, wherein step c) comprises heating the composition at a temperature of 75-85 ℃.

23. The method of any one of claims 16-17, wherein the pH of the composition is maintained at a pH of 4.5-9.5 in step a).

24. The method of claim 23, wherein the pH of the composition is maintained at a pH of 5-9 in step a).

25. The method of claim 24, wherein the pH of the composition is maintained at a pH of 5.5 to 8.5 in step a).

26. The method of claim 23, wherein the pH of the composition in step b) is preferably maintained at a pH value of 6.5-9.5.

27. The method of claim 26, wherein the pH of the composition is maintained at a pH of 7-9 in step b).

28. The method of any one of claims 16-17, wherein the pH of the composition is maintained at a pH of 6.5-9.5 in step c).

29. The method of claim 28, wherein the pH of the composition in step c) is at a pH of 7-9.

30. The method of any one of claims 16-17, wherein the crosslinking agent is an aldehyde.

31. The method of claim 30, wherein the crosslinking agent is formaldehyde, paraformaldehyde, or a combination thereof.

32. Use of lignin treated using the method of any one of claims 1-15 for the preparation of a binder composition.

33. An adhesive composition obtainable by the method of any one of claims 16-32.

34. An adhesive composition comprising the adhesive composition of claim 34.

35. Use of an adhesive composition obtainable by the process of claim 26 or 28 for the preparation of a laminate.

36. The use according to claim 35, wherein the laminate is a high pressure laminate.

37. Use of the binder composition obtainable by the process of claim 26 or 28 for the preparation of foundry materials, protective coatings, friction materials, abrasive materials, glass wool, asbestos, prepregs, masking films, coverings, molding components or fiber-reinforced composites.

Technical Field

The present invention relates to a method for treating lignin and its use for preparing a binder composition, and also to different applications of said binder composition.

Background

Lignin is a natural polymer which can be extracted from, for example, wood. Since lignin is a natural biopolymer, lignin has been investigated to replace synthetic materials as a component in glue to obtain more environmentally friendly glue compositions. In particular, it is an object of the prior art to be able to replace synthetic phenols in phenolic resins, such as phenol formaldehyde resins. Lignin can be used to reduce the amount of synthetic phenols in the resin composition. In the past, lignin has been used in place of phenol in the production of lignin-phenol-formaldehyde resins.

However, currently known lignin-based resins are not suitable for all applications using traditional phenolic resins. For example, currently known lignin-based resins are not suitable for high pressure laminates. High-pressure laminates (HPLs), also known as plasticized laminates, can be prepared by fusing together multiple layers of paper, fabric or other core material under the influence of heat and pressure using a thermosetting resin as an adhesive. The present inventors have recognized that there is a need for a process that results in higher phenol substitution in the resin, resulting in a more environmentally friendly adhesive composition having properties suitable for use in different applications, such as high pressure laminates.

Disclosure of Invention

The object of the present invention is to provide a new method for treating lignin and to provide a method for preparing a binder composition for different applications. The object of the present invention is to provide new adhesive compositions and their use.

The method for treating lignin according to the present invention is characterized by claim 1.

The method for preparing the adhesive composition according to the invention is characterized by what is stated in claim 10.

The adhesive composition obtainable by the method according to the invention is characterized by what is stated in claim 21.

The adhesive composition according to the invention is characterized by what is stated in claim 22.

The use according to the invention is characterized by what is stated in claims 20, 23, 24 and 25.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate some embodiments of the invention and together with the description help to explain the principles of the invention. In the drawings:

FIG. 1 is a flow diagram illustrating a method for treating lignin according to one embodiment of the present invention; and is

Fig. 2 is a flow chart illustrating a method for preparing an adhesive composition according to one embodiment of the present invention.

Detailed Description

The present invention relates to a method for treating lignin, said method comprising the steps of:

a) dissolving lignin in an aqueous composition comprising a compound selected from the group consisting of phenols and a base, while maintaining the temperature of the composition at 40-85 ℃, wherein the base comprises a hydroxide of an alkali metal; and

b) heating the composition at a temperature which is higher than the temperature of the composition in step a), provided that the temperature of the composition does not exceed 100 ℃, while maintaining the pH of the composition at a pH of 6 to 14.

The invention also relates to a method of preparing an adhesive composition, the method comprising the steps of:

a) dissolving lignin in an aqueous composition comprising a compound selected from the group consisting of phenols and a base, while maintaining the temperature of the composition at 40-85 ℃, wherein the base comprises a hydroxide of an alkali metal;

b) heating the composition at a temperature which is higher than the temperature of the composition in step a), provided that the temperature of the composition does not exceed 100 ℃, while maintaining the pH of the composition at a pH of 6 to 14; and

c) mixing the composition formed in step b) with a cross-linking agent and heating the composition at a temperature of 60-100 ℃ while maintaining the pH of the composition at a pH value of 6-14.

In one embodiment of the invention, the compound selected from phenols is selected from the group consisting of: phenol, cresol, resorcinol, and combinations thereof. In one embodiment of the present invention, the compound selected from phenols is phenol.

In one embodiment of the invention, in step a), the lignin is dissolved in a composition consisting of water, at least one compound selected from phenols and a base. In one embodiment of the invention, the lignin is dissolved in an aqueous composition of a compound selected from the group consisting of phenols and a base.

In one embodiment of the invention, the temperature of the composition is maintained in step a) at a temperature of 65-80 ℃, preferably 70-75 ℃.

In one embodiment of the invention, step b) comprises heating the composition at a temperature which is at least 5 ℃, preferably at least 10 ℃ and more preferably at least 20 ℃ higher than the temperature of the composition in step a).

In one embodiment of the invention, the composition is heated in step b) at a temperature of 60 to 100 ℃, preferably at a temperature of 70 to 95 ℃, more preferably at a temperature of 75 to 90 ℃.

In one embodiment of the invention, step b) is carried out to react the lignin with a compound selected from phenols and a base.

In one embodiment of the invention, a base is also added to the composition in step b). In one embodiment of the invention, a base is added to the composition in step a) and step b).

The present inventors have surprisingly found that dissolving lignin into a composition of, for example, phenol, alkali and water at the particular temperatures used, will beneficially affect the time required to dissolve the lignin in the composition. The present inventors have found that treating lignin according to step a) and step b) enables the preparation of binder compositions having a low pH value, as desired. The inventors of the present invention have found that by the method of the present invention a lignin based adhesive composition can be prepared which is suitable for use in e.g. the preparation of structural wood board articles and impregnated covering materials. The inventors have also found that different types of lignin, which are often challenging and time consuming to dissolve, can be more easily dissolved by the method of the invention, e.g. dried or condensed lignin. In addition, the present inventors have noted that the alkali used to activate the lignin is not consumed in the step of dissolving the lignin, thereby requiring less chemicals to reduce overall chemical costs.

In one embodiment of the invention, step b) is carried out for alkalizing (alkalating) the lignin. The alkalization (alkalation) step causes the lignin to be activated. Without limiting the invention to any particular theory as to why the alkalization of lignin results in the formation of more activated or reactive lignin compared to non-alkalized lignin, it should be considered that the alkalization opens up the lignin macromolecular structure, thereby removing the steric hindrance in the lignin structure that normally disables reactive groups. Alkalization can also add charged groups to the lignin macromolecules. In one embodiment of the invention, lignin is treated with a method according to the invention to activate the lignin. The benefit of using alkalized lignin, for example, to prepare a binder composition, is that the binder composition compatibility and reaction behavior is much better than in the conventional case where untreated lignin has been used in the cooking or polymerization stage of the preparation process.

In the present specification, unless otherwise indicated, the term "lignin" is to be understood as lignin derived from any suitable lignin source.

The lignin used may be substantially pure lignin. The term "substantially pure lignin" is understood to mean lignin which is at least 90% pure, preferably at least 95% pure. In one embodiment of the invention, the substantially pure lignin contains at most 10% of other components, preferably at most 5% of other components. Extracts and carbohydrates, such as hemicellulose, may be exemplified as the other ingredients. In one embodiment of the invention, the carbohydrate content of the lignin is less than 10 weight-%, preferably less than 6 weight-%, more preferably less than 4 weight-%. The amount of carbohydrates in the lignin can be determined by using high performance anion exchange chromatography and a pulsed current analyzer (HPAE-PAD) according to SCAN-CM 71 standard.

In one embodiment of the invention, the ash percentage of the lignin is less than 7.5 weight-%, preferably less than 5 weight-%, more preferably less than 3 weight-%. The ash content can be determined by carbonizing or rapidly burning the lignin sample to avoid melting of the alkaline salts before the organic matter burns out (e.g., 30 minutes at 20-200 ℃, then adjusting the temperature to 200-. The ash content of the lignin sample refers to the mass remaining after ignition and combustion of the sample, expressed as a percentage relative to the dry content of the sample.

In one embodiment of the present invention, the weight average molecular weight (Mw) of the lignin is 1000-. The molecular weight of lignin can be determined by high performance size exclusion chromatography in the following manner: two parallel measurements were performed. 0.1M NaOH was used as eluent. Calibration was performed using a sodium polystyrene sulfonate standard with a molecular weight of 1100-73900 g/mol. Standard quality kraft lignin and PSS molecular weight standards were used to control quality. The column is PSS MCX front-end column filled with sulfonated styrene-divinylbenzene copolymer matrixAndand (5) separating the column. The program is run isocratically. Run time was 45 minutes. The injection volume was 50. mu.l. The flow rate was 0.5 ml/min. The temperature was 25 ℃. As a result of chromatography, the number average molecular weight (Mn), weight average molecular weight (Mw), peak molecular weight (Mp), and polydispersity index (PDI) can be reported.

In one embodiment of the present invention, the number average molecular weight (Mn) of the lignin is 700-.

In one embodiment of the invention, the polydispersity of the lignin is from 1.0 to 7, preferably from 1.2 to 6, more preferably from 1.4 to 4.5.

In one embodiment of the invention, the normalized group scavenging index (NRSI) of the lignin is from 0.01 to 20, preferably from 0.05 to 10, more preferably from 0.1 to 6. The antioxidant activity of the extract can be evaluated in methanol extracts by the DPPH-method. The basis for the radical scavenging method is described in Malterud et al (Pharmacol. Toxicol.1996,78: 111-116). The method is based on the ability of the extract and pure components to react with 1, 1-diphenyl-m-trinitrophenyl-2-hydrazyl (DPPH) -molecules when DPPH loses its radical character. The decrease in radical form was observed with a spectrophotometer as the solution color changed from violet to yellow (absorbance measured at 515nm wavelength). RSI (group scavenging index) is defined as the reciprocal concentration that gives 50% inhibition in DPPH absorption at 515 nm. The results (NRSI) can then be "normalized" by dividing the sample RSI by the RSI value for the Butylated Hydroxytoluene (BHT) control.

In one embodiment of the invention, the dry solids content of the lignin is less than 98%, preferably 40-80%, more preferably 50-70%. The dry solids content can be measured by drying a 1-5g sample of lignin in a vacuum oven at a temperature of 60 ℃ or higher for 4 hours.

In one embodiment of the invention, the lignin contains aliphatic hydroxyl groups in an amount of 0.1 to 6mmol, preferably 0.3 to 3.5mmol, per gram of dry lignin.

In one embodiment of the invention, the lignin contains phenolic hydroxyl groups in an amount of 0.1 to 5mmol, preferably 1.5 to 4.5mmol, per gram of dry lignin. The aliphatic hydroxyl group and the phenolic hydroxyl group can be determined by the following methods: the lignin samples were characterized by 31P NMR spectra after phosphitylation (phosphorylation), and the aliphatic hydroxyl groups could then be quantitatively determined. For 31P NMR analysis, 40mg of lignin may be weighed and dissolved in 300. mu. l N, N-dimethylformamide. After complete dissolution, 200. mu.l pyridine, 400. mu.l (0.05M) in pyridine/CDCl was added₃Internal standard solution (ISTD) of endo-N-hydroxy-5-norbornene-2, 3-dicarboximide in (1) and 100. mu.l in pyridine/CDCl₃Cr (acac) in (C)₃And (3) solution. Subsequently, 200. mu.l of the phosphorlylation reagent 2-chloro-4, 4,5, 5-tetramethyl-1, 3, 2-dioxaphospholane (dioxaphospholane) was added dropwise. Finally, 600. mu.l CDCl was added to the solution₃A clear brown to black solution was obtained. Freshly prepared samples can then be tested at room temperature using 31P NMR. A Bruker 500MHz NMR spectrometer can be used for the test. The 31P NMR test is based on the method developed by Grannat and Argyropoulos (Grannat A. and Argyropoulos D.S., 2-chloro-4, 4,5, 5-tetramethyl-1, 3, 2-dioxaphospholane, a reagent used for the accurate determination of the uncondensed and condensed phenolic moieties in lignin J.Agric.food Chem,1995,43: 1538-one 1544). The results are calculated as mmol/g lignin.

In one embodiment of the invention, the lignin is selected from the group consisting of kraft lignin, steam explosion lignin, biorefinery lignin, supercritical separation lignin, hydrolysis lignin, flash precipitation lignin, lignin from biomass, lignin from alkaline pulping, lignin from soda pulping, lignin from organosolv pulping and combinations thereof. In one embodiment of the invention, the lignin is a wood-based lignin. The lignin may be derived from softwood, hardwood, annual plants, and combinations thereof.

Different lignin components may have different properties, such as molecular weight, molar mass, polydispersity, hemicellulose and extract content and composition.

In the present invention "kraft lignin" is understood to be, unless otherwise stated, lignin derived from kraft black liquor. The black liquor refers to an alkaline aqueous solution consisting of lignin residues, hemicellulose and inorganic chemicals used in the kraft pulping process. The black liquor derived from the pulping process contains components from various species of softwood and hardwood in various proportions. Lignin can be separated from the black liquor by different techniques including, for example, precipitation and filtration. Lignin generally begins to precipitate at a pH below 11-12. Different pH values may be used to precipitate lignin components with different properties. The molecular weight distribution, e.g., Mw and Mn, polydispersity, hemicellulose and extract content of these lignin components differ from one another. The molar mass of lignin precipitated at higher pH values is higher than the molar mass of lignin precipitated at lower pH values. Further, the molecular weight distribution of the lignin component precipitated at lower pH values is broader than the molecular weight distribution of the lignin component precipitated at higher pH values.

The precipitated lignin can be purified from inorganic impurities, hemicellulose and wood extracts by using an acid wash step. Further purification can be carried out by filtration.

In one embodiment of the invention, the lignin is flash precipitated lignin. In the present specification the term "flash precipitated lignin" is to be understood as lignin precipitated from black liquor in a continuous process by lowering the pH of the black liquor stream to lignin precipitation level using a carbon dioxide based acidifying agent, preferably carbon dioxide, under the influence of an overpressure of 200-. The method for manufacturing flash precipitated lignin is disclosed in patent application FI 20106073. The residence time in the process is less than 300 seconds. The flash precipitated lignin particles, having a particle size of less than 2 μm and forming agglomerates, can be separated from the black liquor using, for example, filtration. The advantage of flash precipitating lignin is that it is more reactive than normal kraft lignin. If desired, the flash precipitated lignin may be purified and/or activated for further processing.

In one embodiment of the invention, the lignin is separated from the pure biomass. The biomass may be liquefied by using a strong base or a strong acid to start the separation process, followed by a neutralization process. The lignin after alkaline treatment can be precipitated in a similar manner as described above. In one embodiment of the present invention, the process step of separating lignin from biomass comprises the step of enzymatic treatment. The enzymatic treatment modifies the lignin to be extracted from the biomass. The lignin separated from the pure biomass is free of sulphur and therefore has value in subsequent processes.

In one embodiment of the invention, the lignin is steam explosion lignin. Steam explosion is a pulping and extraction technique that can be applied to wood and other cellulosic organic materials.

Unless otherwise indicated, "biorefinery lignin" in the present invention is understood to be lignin recoverable from refining equipment and processes, wherein biomass is converted into fuels, chemicals and other materials.

Unless otherwise indicated, "supercritical separation of lignin" in the present invention is understood to be lignin that can be recovered from biomass using supercritical fluid separation or extraction techniques. The supercritical state corresponds to the temperature and pressure of a given substance above the critical point. In the supercritical state, there are no distinct liquid and gas phases. Supercritical water or liquid extraction is a process for decomposing or converting biomass into cellulosic sugars using water or liquid under supercritical conditions. The water or liquid acts as a solvent to extract the sugars from the cellulosic vegetable matter and the lignin remains in the form of solid particles.

In one embodiment of the invention, the lignin is a hydrolyzed lignin. The hydrolyzed lignin can be recovered from pulp or wood chemicals processes.

In one embodiment of the present invention, the lignin is derived from an organosolv process. The organosolv process is a pulping technique that uses an organic solvent to solubilize lignin and hemicellulose.

The pH of the compositions in step a) and step b) may be selected according to the end use of the binder composition to be prepared.

In one embodiment of the invention, the pH of the composition in step a) is maintained at a pH value of 4-10, preferably at a pH value of 4.5-9.5, more preferably at a pH value of 5-9, even more preferably at a pH value of 5.5-8.5. In one embodiment of the invention, the pH of the composition in step b) is preferably maintained at a pH value of 6-10, more preferably at a pH value of 6.5-9.5, even more preferably at a pH value of 7-9. Such pH ranges may be used in step a) and step b) when preparing adhesive compositions for high pressure laminates.

In one embodiment of the invention, the pH of the composition in step a) is maintained at a pH value of 4-14, preferably at a pH value of 7-13.5, more preferably at a pH value of 8.5-13. In one embodiment of the invention, the pH of the composition in step b) is preferably maintained at a pH value of 7-14, more preferably at a pH value of 9-13.5, even more preferably at a pH value of 10-13. Such pH ranges may be used in step a) and step b) when preparing an adhesive composition for plywood.

In one embodiment of the invention, step b) is carried out for 10 minutes to 2 hours, preferably for 1 to 1.5 hours.

In one embodiment of the invention, the base is sodium hydroxide, potassium hydroxide, or a combination thereof.

In one embodiment of the present invention, the concentration of the base is 0.1 to 11 weight-%, preferably 0.5 to 9 weight-%, based on the total weight of the composition in step b). In one embodiment of the present invention, the concentration of the base is 0.1 to 5 weight-%, preferably 0.5 to 2 weight-%, based on the total weight of the composition in step b). In one embodiment of the present invention, the concentration of the base is 3 to 15 weight-%, preferably 5 to 12 weight-%, more preferably 6 to 10 weight-%, based on the total weight of the composition in step b).

In one embodiment of the present invention, the concentration of lignin in step a) is 10-40 weight-%, preferably 20-30 weight-%, based on the total weight of the composition in step a).

In one embodiment of the present invention, the concentration of the compound selected from phenols in step a) is 10 to 50 weight-%, preferably 20 to 50 weight-%, more preferably 20 to 45 weight-%, based on the total weight of the composition in step a).

The step of heating the formed composition in step c) is performed in order to polymerize the reactant components, i.e. lignin, compounds selected from phenols and cross-linking agents, thereby increasing the viscosity of the adhesive composition. The heating may continue until a predetermined viscosity value is established. The predetermined viscosity value of the final adhesive composition may vary depending on the particular application for which the adhesive composition is to be used.

In one embodiment of the invention, the predetermined viscosity value of the final adhesive composition is at least 40cP, preferably at least 50cP, more preferably at least 80 cP. In one embodiment of the invention, the predetermined viscosity value of the final adhesive composition is at least 40cP but not higher than 250cP, preferably at least 50cP but not higher than 150cP, more preferably at least 80cP but not higher than 120 cP.

In one embodiment of the invention, the predetermined viscosity value of the final adhesive composition is at least 250cP, preferably at least 300cP, more preferably at least 500 cP. In one embodiment of the invention, the predetermined viscosity value of the final adhesive composition is at least 250cP but not higher than 1500cP, preferably at least 300cP but not higher than 1200cP, more preferably at least 500cP but not higher than 1000 cP.

The viscosity was measured at 25 ℃ with a rotational viscometer.

In one embodiment of the invention, step c) comprises heating the composition preferably at a temperature of 65-95 ℃, more preferably at a temperature of 70-90 ℃, even more preferably at a temperature of 75-85 ℃.

In one embodiment of the invention, the cross-linking agent is selected from the group consisting of: aldehydes, derivatives of aldehydes, aldehyde-forming compounds, and combinations thereof. In one embodiment of the invention, the derivative of the aldehyde is hexamethylenetetramine, paraformaldehyde or trioxane. In one embodiment of the invention, the cross-linking agent is selected from the group consisting of: aromatic aldehydes, glyoxal, furfuryl alcohol, caprolactam, and ethylene glycol compounds. The aldehyde may be formaldehyde. The aromatic aldehyde may be furfural. In one embodiment of the invention, the crosslinking agent is an aldehyde, preferably formaldehyde, paraformaldehyde, or a combination thereof.

In one embodiment of the invention, step c) is carried out in the presence of a catalyst. In one embodiment of the invention, the catalyst is selected from the group consisting of: sodium hydroxide, potassium hydroxide, and any mixture thereof.

In one embodiment of the invention, the pH of the composition in step c) is preferably maintained at a pH value of 6-10, more preferably at a pH value of 6.5-9.5, even more preferably at a pH value of 7-9.

In one embodiment of the invention, the pH of the composition in step c) is preferably maintained at a pH value of 7-14, more preferably at a pH value of 9-13.5, more preferably at a pH value of 10-13.

The invention also relates to the use of lignin treated by the method for preparing a binder composition according to the invention.

The invention also relates to an adhesive composition obtainable by the method according to the invention.

The invention also relates to an adhesive composition comprising the adhesive composition according to the invention. The adhesive composition may further comprise one or more adhesive components selected from the group consisting of: other binders, extenders, additives, catalysts and fillers.

The invention also relates to the use of an adhesive composition obtainable by the process according to the invention, wherein the pH of the composition is maintained at a value of 4 to 10 in step a) and at a value of 6 to 10 in step b), for the preparation of a laminate, preferably a high pressure laminate.

The invention also relates to the use of an adhesive composition obtainable by the method according to the invention, wherein the pH of the composition is maintained in step c) at a value of 6 to 10, for the preparation of a laminate, preferably a high pressure laminate.

The invention also relates to the use of a binder composition obtainable by the process according to the invention, wherein the pH of the composition is maintained at a value of 4 to 10 in step a) and at a value of 6 to 10 in step b) for the preparation of foundry materials, protective coatings, friction materials, abrasive materials, glass wool, asbestos, prepregs, masking films (shutteringfilm), coverings, molding components or fiber-reinforced composites.

The invention also relates to the use of a binder composition obtainable by the process according to the invention, wherein the pH of the composition is maintained in step c) at a value of 6 to 10 for the preparation of foundry materials, protective coatings, friction materials, abrasive materials, glass wool, asbestos, prepregs, masking films, coverings, molding components or fiber-reinforced composites.

The invention also relates to the use of an adhesive composition obtainable by the process according to the invention, wherein the pH of the composition is maintained at a value of 4 to 14 in step a) and at a value of 7 to 14 in step b) for the preparation of chipboard, oriented chipboard, particle board, allergy resistant laminated wood (intercallam), glued laminated wood, cardboard, waferboard (waferboard), fibreboard, plywood or wood adhesive.

The invention also relates to the use of an adhesive composition obtainable by the process according to the invention, wherein the pH of the composition is preferably maintained in step c) at a value of 7 to 14, for the preparation of particle board, oriented strand board, particle board, anti-sensitive laminated wood, glued laminated wood, cardboard, waffle board, fiberboard, plywood or wood adhesives.

The embodiments described in the present invention can be used in any combination with each other. Several of which may be combined to further form embodiments of the invention. The methods, compositions or uses of the invention may comprise at least one embodiment of the invention.

One advantage of the process of the present invention is that the time required to dissolve the lignin in the aqueous composition is reduced when using a specific temperature.

The advantage of the process of the invention is that the lignin can be treated in such a way that a low pH binder composition can be prepared, i.e. the binder composition is in the neutral or acidic pH range. The lignin treated by the method of the invention has an open structure that makes it more reactive, so that a low pH binder composition can be prepared from lignin.

An advantage of the present invention is that bio-based adhesive compositions suitable for use in the preparation of high pressure laminates can be prepared by the process according to the present invention. An advantage of the present invention is that a more environmentally friendly adhesive composition for high pressure laminates can be prepared.