Phenol-free binder composition

Abstract

The present invention relates to a method for producing a binder composition without using a compound selected from the class of phenols, the method comprising the steps of (i) heating an aqueous composition comprising lignin in the presence of a catalyst, (ii) mixing a crosslinker with the aqueous composition from (i) and heating it at a temperature between 60 and 95°C to prepolymerize the lignin and the crosslinker, and (iii) mixing a tannin with the aqueous composition from (ii) and polymerizing the tannin with the prepolymerized lignin and the crosslinker until a binder composition having a predetermined viscosity value is formed, the molar ratio of the crosslinker to the lignin and the tannin being between 0.5 and 1.7.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a binder composition.Furthermore, the present invention relates to a binder composition, an adhesive composition, and uses. [Background technology]

[0002] Tannins and lignins are natural components that can be extracted from, for example, bark and wood. For example, the tannin content of Nordic coniferous species such as pine and spruce is about 5-20%.

[0003] Because tannins and lignins are biological components, their use in glues to replace synthetic materials, for example, has been investigated with the aim of developing more environmentally friendly adhesive compositions. In particular, their ability to replace synthetic phenols derived from fossil resources in final phenolic resins, such as phenol-formaldehyde resins, has been the subject of prior art research. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent application FI20106073 [Non-patent literature]

[0005] [Non-Patent Document 1] Granata, A., Argyropoulos, D., J. Agric. Food Chem. 1995, 43:1538-1544 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the present inventors have recognized a need for a method that results in phenol-free binder compositions for additional applications. [Means for solving the problem]

[0007] A method for producing a binder composition without the use of a compound selected from the class of phenols is disclosed, the method comprising: (i) heating an aqueous composition containing lignin in the presence of a catalyst at a temperature of 50 to 95°C for 0.25 to 5 hours; (ii) mixing the crosslinking agent with the aqueous composition from (i) and heating it at a temperature of 60 to 95°C to prepolymerize the lignin and the crosslinking agent; (iii) mixing tannin with the aqueous composition from (ii) until a binder composition having a predetermined viscosity value is formed; The molar ratio of the crosslinking agent to the lignin and tannin is 0.5 to 1.7.

[0008] Further disclosed is a binder composition obtainable by the method defined herein.

[0009] Additionally, an adhesive composition comprising the binder composition is disclosed.

[0010] Further disclosed is the use of the binder composition in impregnation applications for gluing wood products or laminated wood products or wood panels, for the production of laminates, shuttering films, mineral wool, nonwoven textiles, molded textiles or extruded textiles. DETAILED DESCRIPTION OF THE INVENTION

[0011] A method for producing a binder composition without the use of a compound selected from the class of phenols is disclosed, the method comprising: (i) heating an aqueous composition containing lignin in the presence of a catalyst at a temperature of 50 to 95°C for 0.25 to 5 hours; (ii) mixing the crosslinking agent with the aqueous composition from (i) and heating it at a temperature of 60 to 95°C to prepolymerize the lignin and the crosslinking agent; (iii) mixing tannin with the aqueous composition from (ii) and polymerizing the tannin with the pre-polymerized lignin and cross-linking agent until a binder composition having a predetermined viscosity value is formed; The molar ratio of the crosslinking agent to the lignin and tannin is 0.5 to 1.7.

[0012] Further disclosed is a binder composition obtainable by the method defined herein.

[0013] In one embodiment, the amount of free crosslinker, e.g., free formaldehyde monomer, of the binder composition is at most 1% by weight, or at most 0.5% by weight, or at most 0.3% by weight, or at most 0.1% by weight, or at most 0.06% by weight. The amount of free crosslinker, e.g., free formaldehyde, can be determined according to the standard EN-ISO 11402 and the procedure for hydroxylamine hydrochloride, except that the sample is diluted in 20 ml of distilled water and 70 ml of 94% ethanol.

[0014] In one embodiment, the binder composition has an amount of free phenol of less than 0.01% by weight as determined by the gas chromatography-flame ionization detector (GC-FID) method according to standard SFS-EN ISO 8974:2002, except that the alkaline sample solution is diluted before neutralization.

[0015] In one embodiment, the water miscibility (tolerance) of the binder composition, as determined according to standard EN ISO 8989, is greater than 500%, or greater than 700%, or greater than 900%, or infinite.

[0016] In one embodiment, the viscosity value of the binder composition increases by at most 400 cP / 7 days, or at most 300 cP / 7 days, or at most 200 cP / 7 days, or at most 100 cP / 7 days when stored at 25° C. after its preparation. The binder compositions disclosed herein have the additional utility of exhibiting good storage stability.

[0017] The inventors have surprisingly found that the specific amount of crosslinker and the molar ratio of crosslinker to the polymerized components, i.e., lignin and tannin, influence the properties of the produced binder composition, such that binder compositions having the above-mentioned properties can be prepared.

[0018] Additionally, an adhesive composition comprising the binder composition is disclosed.

[0019] Further disclosed is the use of the binder composition in impregnation applications for gluing wood products or laminated wood products or wood panels, for the production of laminates, shuttering films, mineral wool, nonwoven, molded or extruded textiles.

[0020] Products produced by using the binder compositions disclosed herein may have one or more of the following properties: - formaldehyde emission is between 0.01 and 0.5 mg / l or between 0.1 and 0.35 mg / l, as measured in a desiccator according to EN ISO 12460-4; - Formaldehyde emission is between 0.01 and 0.40 mg / m when measured according to gas analysis method EN ISO 12460-3 2 *h, or 0.05 to 0.30 mg / m 2 *h, or 0.1 to 0.2 mg / m 2 *h, - Meets minimum bond class 1-4 or 2-4 or 3-4 when measured according to bond quality test methods EN314-1 and EN314-2.

[0021] The present inventors have surprisingly found that the method disclosed herein allows for the preparation of binder compositions without the use of compounds selected from the class of phenols.

[0022] In this specification, unless otherwise specified, the term "compounds selected from the class of phenols" should be understood to mean fossil compounds of the phenolic class, i.e., phenols are compounds consisting of a single aromatic ring to which one or more hydroxyl (-OH) groups are attached.

[0023] Such compounds selected from the class of phenols can be, for example, phenol, cresol, or resorcinol. Such phenols are toxic compounds. In one embodiment, the method includes the proviso that no compounds selected from the class of phenols are used to prepare the binder composition. The methods disclosed herein have the additional advantage of providing a method for preparing a binder composition that does not contain fossil-derived materials. Thus, the binder composition produced may be free of fossil-based phenolic compounds. In particular, the polymerizable materials used in the method, i.e., lignin and tannin, are derived from biomass or living organisms. Thus, the binder compositions disclosed herein may be prepared as non-toxic binder compositions. That is, binder compositions with a reduced proportion of toxic or harmful compounds may be prepared. The binder compositions disclosed herein may be prepared as 100% biological binder compositions.

[0024] The total amount of crosslinker used to prepare the binder composition may be 3 to 7 wt.%, or 3 to 6 wt.%, or 4 to 5 wt.%, based on the total weight of the binder composition. The methods disclosed herein have the additional benefit of allowing for reduced or lower amounts of crosslinker, such as formaldehyde, to be used without detrimentally affecting the properties of the binder composition.

[0025] The crosslinking agent may be an aldehyde, such as formaldehyde or paraformaldehyde. In one embodiment, the aldehyde is prepared from biomethanol. Thus, the aldehyde may be bio-based. Alternatively, the aldehyde may be fossil-derived, i.e., produced from fossil materials. In one embodiment, the aldehyde is prepared from methanol.

[0026] "Total mass" in this specification should be understood as the mass of both the dry matter and the liquid portion, e.g., water, of the binder composition, unless otherwise specified.

[0027] The molar ratio of the crosslinker to the lignin and tannin may be 0.9 to 1.7, or 1.0 to 1.6, or 1.1 to 1.7, or 1.2 to 1.6. As used herein, the molar ratio (MR) is defined as follows: MR=n(Fa) / (n(T)+n(L)) (In the formula, n = amount of substance in moles Fa = cross-linking agent T = tannin L = lignin) It is calculated as follows:

[0028] The amount of a substance in moles is: n=M / m (In the formula, M = molar mass of the substance in g / mol m = mass of substance in grams) It is calculated as follows:

[0029] As used herein, the following values ​​are used in the above calculations: M (tannin) = 320 g / mol (estimated based on literature and assumed chemical structure) M(lignin) = 180 g / mol (estimated based on literature and assumed chemical structure)

[0030] The mass ratio of tannin to lignin may be 0.05 to 1.0, or 0.1 to 0.43, or 0.15 to 0.33.

[0031] The mass ratio of catalyst to lignin and tannin may be 0.20 to 0.37, or 0.22 to 0.35, or 0.26 to 0.33. The molar ratio of catalyst to lignin and tannin may be 1.0 to 1.8, or 1.1 to 1.7, or 1.2 to 1.6. The amount of catalyst can beneficially affect the properties of the produced binder composition.

[0032] The catalyst may comprise an alkali metal or alkaline earth metal salt or hydroxide. In one embodiment, the catalyst is selected from the group consisting of sodium hydroxide, potassium hydroxide, barium hydroxide, and combinations thereof. In one embodiment, the catalyst is sodium hydroxide.

[0033] The aqueous composition of step (i) may comprise, consist of or consist essentially of lignin in the presence of a catalyst.

[0034] Step (i) may comprise heating the aqueous composition containing lignin in the presence of a catalyst at a temperature of 50 to 95°C, 55 to 95°C, 60 to 95°C, 65 to 90°C, or 70 to 85°C. Step (i) may last for 0.25 to 5 hours, 0.25 to 4 hours, 0.25 to 3 hours, 0.5 to 2 hours, or 0.75 to 1.5 hours. During step (i), the lignin used is dissolved in the aqueous composition.

[0035] The temperature can be controlled during preparation of the binder composition by cooling and / or heating the aqueous composition.

[0036] The aqueous composition of step (ii) may comprise, consist of, or consist essentially of the aqueous composition of (i) and a crosslinker.

[0037] Step (ii) may include heating at a temperature of 70 to 90°C, or 75 to 80°C. Heating in step (ii) may be continued until the aqueous composition has a viscosity value of 100 to 1200 cp, or 200 to 1000 cp, or 300 to 800 cP, or 400 to 500 cP, or 100 to 500 cP, or 400 to 800 cP, measured at a temperature of 25°C. The viscosity can be measured at a temperature of 25°C by using a rotational viscometer (Brookfield Digital Viscometer LVDV-II+Pro; cone spindle). In one embodiment, step (ii) continues for 1 to 8 hours, or 2 to 6 hours, or 3 to 5 hours.

[0038] In one embodiment, in step (ii), the molar ratio of crosslinker to lignin is from 1.2 to 1.9, or from 1.4 to 1.8, or from 1.5 to 1.7.

[0039] In one embodiment, the heating in step (ii) is continued until the amount of free crosslinking agent, e.g., free formaldehyde, is at most 1% by weight, or at most 0.5% by weight, or at most 0.2% by weight, based on the total weight of the aqueous composition in step (ii). The amount of free crosslinking agent, e.g., free formaldehyde, is determined according to standard EN-ISO 11402 and the procedure for hydroxylamine hydrochloride, except that the sample is diluted in 20 ml of distilled water and 70 ml of 94% ethanol. That is, tannin should not be added to the aqueous composition of step (ii) before the desired level of free crosslinking agent, e.g., formaldehyde, is achieved.

[0040] Step (ii) may include adding the catalyst in a staged manner. That is, an additional amount of catalyst may be added during step (ii) in addition to that used in step (i). Staged catalyst addition has the added benefit of allowing the lignin and crosslinker to be prepolymerized in a controlled manner. In one embodiment, step (ii) includes adding the catalyst in a staged manner and heating the resulting aqueous composition to prepolymerize the lignin and crosslinker in a controlled manner.

[0041] In one embodiment, the tannin is mixed with the aqueous composition in step (iii) while maintaining the temperature of the composition at 15 to 90°C, or 20 to 80°C, or 40 to 60°C. In one embodiment, the tannin is mixed with the aqueous composition in step (iii) while maintaining the temperature of the composition at 55 to 95°C, or 60 to 90°C, or 70 to 80°C. In one embodiment, the tannin is mixed with the aqueous composition in step (iii) while maintaining the temperature of the composition at 15 to 60°C, or 20 to 40°C, or 15 to 25°C, or 30 to 60°C. Therefore, the temperature of the aqueous composition in step (ii) may be cooled as necessary, and then the tannin may be mixed therewith.

[0042] In one embodiment, the mixing in step (iii) continues until a binder composition having a viscosity value of 150 to 800 cP, or 200 to 600 cP, is formed. In one embodiment, the mixing in step (iii) continues until a binder composition having a viscosity value of 150 to 500 cP, or 200 to 500 cP, or 250 to 400 cP, or 300 to 350 cP, is formed. In one embodiment, the mixing in step (iii) continues until a binder composition having a viscosity value of 500 to 800 cP, or 550 to 750 cP, or 600 to 700 cP, is formed. In one embodiment, step (iii) continues for 0.15 to 6 hours, or 0.25 to 5 hours, or 0.5 to 3.5 hours.

[0043] In one embodiment, step (iii) includes mixing tannin with the aqueous composition of (ii) and polymerizing the tannin with the prepolymerized lignin and crosslinker until a binder composition having a predetermined viscosity value is formed. In this manner, the tannin can react or polymerize with the prepolymerized lignin and crosslinker. The polymerization reaction can proceed by increasing the temperature of the composition to which the tannin is added. Alternatively, the tannin can simply be mixed with the aqueous composition containing the prepolymerized lignin and crosslinker. In step (iii), if the tannin is mixed with the aqueous composition at a low temperature, such as room temperature, the tannin may not polymerize with the prepolymerized lignin and crosslinker.

[0044] In the context of this specification, the term "lignin" may refer to lignin derived from any suitable lignin source. In one embodiment, the lignin is essentially pure lignin. The expression "essentially pure lignin" should be understood as at least 70% pure lignin, or at least 90% pure lignin, or at least 95% pure lignin, or at least 98% pure lignin. Essentially pure lignin may contain at most 30%, or at most 10%, or at most 5%, or at most 2% of other components and / or impurities. Examples of such other components may include extractives and carbohydrates such as hemicellulose.

[0045] Furthermore, in the context of this specification, the term "tannin" may refer to a tannin derived from any suitable tannin source. In one embodiment, the tannin is an essentially pure tannin. The expression "essentially pure tannin" should be understood as at least 70% pure tannin, or at least 90% pure tannin, or at least 95% pure tannin, or at least 98% pure tannin. An essentially pure tannin may contain at most 30%, or at most 10%, or at most 5%, or at most 2% of other components and / or impurities.

[0046] Lignin may contain less than 30%, or less than 10%, or less than 5%, or less than 3%, or less than 2.5%, or less than 2% by weight of carbohydrates. Tannin may contain less than 20%, or less than 15%, or less than 10% by weight of carbohydrates. The amount of carbohydrates present in lignin or tannin can be measured by high performance anion exchange chromatography with pulsed amperometric detection (HPAE-PAD) according to standard SCAN-CM71.

[0047] The ash content of lignin can be less than 7.5% by mass, or less than 5% by mass, or less than 3% by mass, or less than 1.5% by mass. The ash content of tannin can be less than 10% by mass, or less than 5% by mass, or less than 3% by mass. The ash content can be determined as follows: First, the dry solids content of the sample is determined in an oven at 105°C for 3 hours. A ceramic crucible is preheated to 700°C for 1 hour and weighed after cooling. A sample (1.5g-2.5g) is weighed into the ceramic crucible. The lipped crucible is placed in a low-temperature oven. The oven temperature is increased: 20-200°C for 30 minutes → 200-600°C for 60 minutes → 600-700°C for 60 minutes.

[0048] Continue burning uncovered at 700°C for 60 minutes. Cool the crucible in a desiccator, add a few drops of hydrogen peroxide (H2O2, 30%) to the sample, and then burn in an oven at 700°C for 30 minutes. If there are still black spots in the ash, repeat the hydrogen peroxide treatment and burning. Cool the crucible and weigh. All weighing is done to an accuracy of 0.1 mg after cooling in a desiccator.

[0049] Calculating the results Ash content%=(100 ax 100) / (bxc) During the ceremony, a = mass of ash, g b = mass of the sample, g c = dry solids content of sample, %

[0050] The ash content of a sample refers to the mass remaining after combustion and annealing of the sample, expressed as a percentage of the dry content of the sample.

[0051] In one embodiment, the lignin is technical lignin. In the context of this specification, the term "technical lignin" may refer to lignin derived from lignin in any biomass by any technological process. In one embodiment, technical lignin is lignin obtained from an industrial process.

[0052] The lignin used to prepare the binder composition may be selected from the group consisting of kraft lignin, steam explosion lignin, biorefinery lignin, supercritically separated lignin, hydrolyzed lignin, flash precipitation lignin, biomass-derived lignin, lignin from an alkaline pulping process, lignin from a soda process, lignin from organosolv pulping, lignin from an alkaline process, lignin from an enzymatic hydrolysis process, and any combination thereof. In one embodiment, the lignin is wood-based lignin. The lignin may be derived from softwoods, hardwoods, annual grasses, or any combination thereof.

[0053] As used herein, "kraft lignin" refers to lignin derived from kraft black liquor, unless otherwise specified. Black liquor is an alkaline aqueous solution of lignin residue, hemicellulose, and inorganic chemicals used in the kraft pulping process. Black liquor from the pulping process contains components derived from different softwood and hardwood species in varying proportions. Lignin can be separated from black liquor by different techniques, including precipitation and filtration. Lignin typically begins to precipitate at pH values ​​below 11-12. Different pH values ​​can be used to precipitate lignin fractions with different properties. These lignin fractions differ from each other by molecular weight distribution, e.g., Mw and Mn, polydispersity, hemicellulose, and extractives content. The molar mass of lignin precipitated at higher pH values ​​is higher than that of lignin precipitated at lower pH values. Furthermore, the molecular weight distribution of lignin fractions precipitated at lower pH values ​​is broader than that of lignin fractions precipitated at higher pH values. The precipitated lignin can be purified from inorganic impurities, hemicellulose, and wood extractives using an acidic washing step. Further purification can be achieved by filtration.

[0054] As used herein, the term "flash precipitated lignin" refers to lignin precipitated from black liquor in a continuous process by using a carbon dioxide-based acidifying agent, preferably carbon dioxide, to lower the pH of the black liquor stream to a lignin precipitation level under the influence of an overpressure of 200 to 1000 kPa, followed by a sudden release of the pressure to precipitate the lignin. A method for producing flash precipitated lignin is disclosed in patent application FI20106073. The residence time in the process is less than 300 seconds. Flash precipitated lignin particles with a particle size of less than 2 μm form agglomerates that can be separated from the black liquor using, for example, filtration. An advantage of flash precipitated lignin is its increased reactivity compared to conventional kraft lignin. Flash precipitated lignin can be purified and / or activated as needed for further processing.

[0055] Lignin may be derived from an alkaline process, which begins with liquefying the biomass with strong alkali, followed by a neutralization process. After alkaline treatment, the lignin can be precipitated in a similar manner as presented above.

[0056] Lignin may also be derived from steam explosion, a pulping and extraction technique that can be applied to wood and other fibrous organic materials.

[0057] As used herein, "biorefinery lignin," unless otherwise specified, should be understood to be lignin that can be recovered from a refinery facility or process in which biomass is converted into fuels, chemicals, and other materials.

[0058] As used herein, "supercritically separated lignin," unless otherwise specified, should be understood as lignin that can be recovered from biomass using supercritical fluid separation or extraction techniques. Supercritical conditions correspond to temperatures and pressures above the critical point of a given substance. At supercritical conditions, distinct liquid and gas phases do not exist. Supercritical water or liquid extraction is a method that utilizes water or liquid under supercritical conditions to break down biomass and convert it into cellulosic sugars. The water or liquid, acting as a solvent, extracts the sugars from the cellulose plant matter, leaving the lignin as solid particles.

[0059] The lignin may be derived from a hydrolysis process. Lignin derived from a hydrolysis process may be recovered from paper pulp or wood chemical processes.

[0060] The lignin may be derived from an organosolv process, which is a pulping technique that uses organic solvents to solubilize lignin and hemicellulose.

[0061] In one embodiment, the lignin comprises softwood kraft lignin. In one embodiment, the lignin is softwood kraft lignin. In one embodiment, the lignin is a combination of softwood and hardwood lignin. In one embodiment, at most 30% by weight of the lignin is derived from hardwood, or at most 25% by weight, or at most 10% by weight, or at most 5% by weight.

[0062] The weight average molecular weight of the softwood kraft lignin may be 2500 to 9000 Da, or 3000 to 8000 Da, or 3500 to 7000 Da. The polydispersity index of the lignin, for example kraft lignin, may be 2.9 to 6.0, or 3.0 to 5.0, or 3.2 to 4.5.

[0063] The weight-average molecular weight can be determined by gel permeation chromatography (GPC) with a UV detector (280 nm) using the following method: Dissolve the sample in 0.1 M NaOH. Filter the sample solution through a 0.45 micron PTFE filter. Measurements are performed using a PSS MCX precolumn, 1000 Å and 100,000 Å columns with a sulfonated styrene-divinylbenzene copolymer matrix, in 0.1 M NaOH eluent (0.5 ml / min, T = 30 °C). The molecular weight distribution of the sample is calculated relative to six polystyrene sulfonate sodium standards (MW 891-65,400). Values ​​Mw (weight-average molecular weight) and Mn (number-average molecular weight), as well as the polydispersity index (PDI, Mw / Mn), are reported based on two parallel measurements.

[0064] The amount of alkali-insoluble matter in softwood kraft lignin may be less than 10%, or less than 5%, or less than 0.5%. The amount of alkali-insoluble matter can be determined by the following method: First, the dry solids content of the sample is determined in an oven at 105°C for 3 hours. 100 g of the sample is dissolved in 277 g of an aqueous NaOH solution (pH 12-13) and mixed at 50-60°C for 30 minutes. The solution is filtered through a glass filter in a Büchner funnel. The residue on the filter is washed with 0.1 M NaOH and finally with water. The filter containing the residue is dried in an oven and weighed. The amount of alkali-insoluble matter is then calculated as follows: Alkali insolubles, % = [mass of filter (dry) including residue (g) - mass of filter] / [mass of sample (g) * dry solids content of sample (%)]

[0065] The amount of condensed and syringyl groups in the softwood kraft lignin may be less than 3.0 mmol / g, or less than 2.5 mmol / g, or less than 2.0 mmol / g, as determined by 31P NMR. The amount of aliphatic OH groups in the softwood kraft lignin may be less than 3.0 mmol / g, or less than 2.5 mmol / g, as determined by 31P NMR. The amount of guaiacyl OH groups in the softwood kraft lignin may be at least 1.5 mmol / g, as determined by 31P NMR.

[0066] Measurements performed by 31P NMR spectroscopy after phosphitylation can be used to quantify functional groups (aliphatic and phenolic hydroxyl groups, and carboxylic acid groups). Sample preparation and measurements are performed according to the method by Granata and Argyropoulos (Granata, A., Argyropoulos, D., J. Agric. Food Chem. 1995, 43:1538-1544). An accurately weighed sample (approximately 25 mg) is dissolved in N,N-dimethylformamide and mixed with pyridine and the internal standard (ISTD) endo-N-hydroxy-5-norbornene-2,3-dicarboximide (e-HNDI). The phosphitylation reagent (200 μL) 2-chloro-4,4,5,5-tetramethyl-1,3,2-dioxaphopholane is slowly added, followed by the final addition of 300 μL of CDCl3. NMR measurements are performed immediately after addition of the reagents. Spectra are measured on a spectrometer equipped with a probehead optimized for broadband detection.

[0067] In one embodiment, the tannins used are derived from any wood species. They may be derived, for example, from bark or heartwood. Examples of possible sources of tannins include the species of Quebracho, Beech, Oak, Chestnut, Pine, Spruce and Acacia.

[0068] In one embodiment, the tannins used are derived from coniferous bark. The tannins can be separated from coniferous bark in a debarking unit in a sawmill or pulp mill. The separation process can be combined with an ethanol extraction process, a hot water extraction process, a hot steam extraction process, or a water-ethanol extraction process of the coniferous bark.

[0069] In one embodiment, the tannin is a condensed tannin. Condensed tannins have a high dry matter content and are therefore suitable for use in the methods disclosed herein. The dry matter content of the condensed tannin may vary between 40 and 100%, preferably between 60 and 90% or between 70 and 80%. Tannins with such a dry matter content can be easily dispersed, thereby achieving good reactivity with other reaction components. The tannin may also be a hydrolyzable tannin.

[0070] The weight average molecular weight (Mw) of the tannin may be 1500 to 5000 Da, or 2000 to 4500 Da, or 2500 to 4000 Da. The polydispersity index of the tannin may be 2.8 to 1.0, or 2.6 to 1.3, or 2.4 to 1.5.

[0071] In one embodiment, the method includes dispersing the tannin prior to mixing with the aqueous composition. The tannin can be dispersed in an aqueous solution or an aqueous alkaline solution prior to mixing with the aqueous composition. The alkaline solution can be the same as that used as the catalyst. The pH of the formed dispersion can be 4 to 10, or 7 to 9. The concentration of the tannin in the dispersion can be 30 to 50%.

[0072] Tannins are somewhat reactive and may react rapidly with cross-linking agents such as formaldehyde to form cross-linked polymer structures. The inventors have surprisingly found that the polymerization reaction can be controlled by adjusting the temperature in step (iii) and / or by simply adding tannin to the aqueous composition after pre-polymerizing the lignin and cross-linking agent in step (ii).

[0073] The exact order of combining and / or adding the components required to produce the binder composition may vary depending, for example, on the desired properties of the resulting binder composition. Selection of the order of combining and / or adding the required components is within the knowledge of one of ordinary skill in the art based on this specification. The exact amounts of the components used to produce the binder composition may vary, and selection of the amounts of the different components is within the knowledge of one of ordinary skill in the art based on this specification.

[0074] When determining the order of mixing and combining the components used to prepare the binder composition, it is taken into consideration that tannin is a more reactive component than lignin. Therefore, the lignin is mixed with the crosslinking agent in the aqueous composition and heated before adding the tannin. In this way, it is ensured that the lignin has sufficient time to react with the crosslinking agent, e.g., aldehyde.

[0075] Also disclosed herein is an adhesive composition comprising the binder composition disclosed herein. The adhesive composition may contain, in addition to the binder composition, one or more adhesive components selected from the group consisting of other binders, extenders, additives, catalysts, and fillers. A binder is a substance that primarily functions to cause polymer growth and crosslinking, thus assisting in the curing of polymer systems. A binder may also provide adhesive properties to the binder composition. An extender is a substance that assists the binder by adjusting physical properties, for example, by binding moisture. An additive may be a polymer or inorganic compound that assists in properties such as filling, softening, cost reduction, moisture management, increased stiffness, and increased flexibility. A catalyst is generally a substance that enhances and adjusts the curing rate. As used herein, "substance" should be understood to include compounds or compositions. The binder composition may function as a binder, extender, additive, catalyst, and / or filler in the adhesive composition.

[0076] The binder composition, like the adhesive composition, can be used to glue wood products, in one embodiment, the wood products are selected from the group consisting of wood boards, wood veneers, and wood rods.

[0077] The methods disclosed herein have the additional utility of allowing for the production of binder compositions without the use of, for example, phenol or any other compound selected from the class of phenols. The methods disclosed herein have the additional utility of allowing for the production of phenol-free binder compositions having properties suitable for industrial applications, such as weight average molecular weight and viscosity.

[0078] Additionally, the binder compositions disclosed herein have the added utility of providing water resistance, stable adhesion, and / or low formaldehyde emissions to final products produced using said binder compositions. [Example]

[0079] Reference will now be made in detail to various embodiments.

[0080] In the following description, some embodiments are disclosed in sufficient detail to enable those skilled in the art to utilize the embodiments based on the present disclosure. Not all steps or features of the embodiments are disclosed in detail, as many of the steps or features will be apparent to those skilled in the art based on this specification.

[0081] Example 1 Preparation of the binder composition In this example, a lignin-tannin-formaldehyde binder composition was prepared.

[0082] The following ingredients and amounts were used: 100% water 1362kg NaOH (Part I) 50% 420kg Kraft lignin 74% 1460kg NaOH (Part II) 50% 320kg Formaldehyde 37.5% 893kg Tannin 40% (in alkaline solution) 545kg

[0083] The percentages of the ingredients (by total weight) used in this example were: NaOH approx. 8.1% Kraft lignin approx. 21.6% Tannins: Approximately 3.8% Formaldehyde: approx. 6.70%

[0084] The molar ratio of NaOH to lignin and tannin was 1.5, and the molar ratio of formaldehyde to lignin and tannin was 1.70.

[0085] First, water and the first part of NaOH were mixed at room temperature, and heating was initiated. When the temperature reached 72°C, lignin was added to the aqueous composition. Heating and mixing of the composition was continued for 30 minutes while maintaining the temperature at approximately 80-90°C. The aqueous composition was then cooled to 65°C, and formaldehyde was added.

[0086] Mixing and heating of the formed aqueous composition was continued for 1 hour, the second part of the NaOH was added in two portions, and mixing and heating was again continued until the viscosity of the formed composition reached 770 cP (measured at 25°C).

[0087] The aqueous composition was then cooled to a temperature of about 35°C, the tannin was added thereto, and the resulting aqueous composition was mixed for about 45 minutes.

[0088] The binder composition formed had the following measured properties: Solids content, % 37.1 (3 hours at 105°C) pH 12.8 Viscosity, cp 420 (at 25°C) Alkalinity, % 5.4 Free formaldehyde, % 0.13

[0089] Example 2 Preparation of the binder composition In this example, a lignin-tannin-formaldehyde binder composition was prepared.

[0090] The following ingredients and amounts were used: 100% water 1241kg NaOH (Part I) 50% 470kg Kraft lignin 65% 1592kg NaOH (Part II) 50% 170kg Formaldehyde 40.57% 604kg NaOH (Part III) 50% 60kg Tannin 40% (in alkaline solution) 922kg

[0091] The percentages of the ingredients (by total mass) used in this example were: NaOH approx. 7.0% Kraft lignin approx. 20.7% Tannins: Approximately 6.9% Formaldehyde: approx. 4.9%

[0092] The molar ratio of NaOH to lignin and tannin was 1.3, and the molar ratio of formaldehyde to lignin and tannin was 1.2.

[0093] First, water and the first part of NaOH were mixed at room temperature and heating was initiated. When the temperature reached 70°C, lignin was added to the aqueous composition, and mixing and heating of the composition was continued for 30 minutes while maintaining the temperature at approximately 90°C. The temperature of the aqueous composition was then cooled to 60°C, and formaldehyde was added.

[0094] Mixing and heating of the resulting aqueous composition was continued for 44 minutes at a temperature of about 70-76°C. Next, part II of the NaOH was added, and mixing and heating was continued for 70 minutes at a temperature of about 75-80°C. Next, the second part of the NaOH II was added, and mixing and heating was continued for 2 hours and 14 minutes at a temperature of about 70-75°C. The viscosity of the resulting composition reached about 500 cP (measured at 25°C), after which the tannin was added. Mixing of the aqueous composition continued, and the temperature was increased from about 75°C to about 90°C until the viscosity reached about 290 cP. The composition was then cooled to 30°C.

[0095] The binder composition formed had the following measured properties: Solids, % 35.3 (3 hours at 105°C) pH 13.1 Viscosity, cp 280 (at 25°C) Alkalinity, % 5.1 Free formaldehyde, % 0.03 Phenols, GC mass% <0.010 Water tolerance 900%

[0096] Example 3 Manufacturing of plywood products An adhesive composition was prepared using the binder composition prepared in Example 2. The adhesive composition was prepared by mixing the binder composition with wheat flour and limestone (1:1) to achieve a target viscosity of 70-100 seconds at 6 mm FC at 25°C. 3% sodium carbonate was used as a hardening agent in this adhesive composition.

[0097] The resulting adhesive composition was used to manufacture wood veneer plywood products. 1.5 mm thick wood veneers were bonded with the adhesive composition to form 4.5 mm thick plywood panels. The dry matter content of the adhesive composition was 35-50%. The wood veneers containing the adhesive composition were pressed using a hot press technique at temperatures of 130-170°C. The adhesive composition was simultaneously cured. The adhesive composition was found to be suitable for gluing wood veneers and therefore for manufacturing plywood. The results showed that the gluing effect of the adhesive composition was sufficiently good for gluing wood veneers and met the requirements of bonding class 3 according to EN 314-1 and EN 314-2 standards and formaldehyde emission class 1 as measured by EN ISO 12460-3.

[0098] [Table 1]

[0099] It is obvious to those skilled in the art that with the advancement of technology, the basic idea can be implemented in various ways, therefore the embodiments are not limited to the above examples but may instead vary within the scope of the claims.

[0100] The embodiments described herein above can be used in any combination with each other. Several embodiments may be combined together to form further embodiments. The methods, binder compositions, adhesive compositions, or uses disclosed herein may include at least one of the embodiments described herein above. It is understood that the benefits and advantages described above may relate to one embodiment or to multiple embodiments. The embodiments are not limited to those that solve any or all of the stated problems or have any or all of the stated benefits and advantages. It is further understood that a reference to "an" item refers to one or more of those items. As used herein, the term "comprising" is used to mean including the features or acts that follow it without excluding the presence of one or more additional features or acts.

Claims

1. 1. A method for producing a binder composition without using a compound selected from the class of phenols, comprising: (i) heating an aqueous composition comprising lignin in the presence of a catalyst at a temperature of 50 to 95°C for 0.25 to 5 hours; (ii) mixing a crosslinking agent with the aqueous composition from (i) and heating it at a temperature of 60-95°C to prepolymerize the lignin and crosslinking agent, wherein the crosslinking agent is formaldehyde or paraformaldehyde; (iii) mixing tannin with the aqueous composition from (ii) until a binder composition having a predetermined viscosity value is formed; The method wherein the molar ratio of the crosslinking agent to the lignin and tannin is from 0.5 to 1.

7.

2. The method of claim 1, wherein the total amount of crosslinking agent used to prepare the binder composition is 3 to 7% by weight, based on the total weight of the binder composition.

3. 3. The method according to claim 1, wherein the molar ratio of the crosslinking agent to the lignin and tannin is from 0.9 to 1.

7.

4. 4. The method according to claim 1, wherein the mass ratio of catalyst to lignin and tannin is from 0.20 to 0.

37.

5. 5. The method according to any one of claims 1 to 4, wherein the mass ratio of tannin to lignin is 0.05 to 1.

0.

6. 6. The method of any one of claims 1 to 5, wherein step (ii) comprises heating at a temperature of from 75 to 90°C.

7. 7. The method of any one of claims 1 to 6, wherein the heating in step (ii) is continued until the aqueous composition has a viscosity value of from 100 to 1200 cp measured at a temperature of 25°C.

8. 8. The method according to any one of claims 1 to 7, wherein in step (ii), the molar ratio of crosslinker to lignin is from 1.2 to 1.

9.

9. 9. The method of any one of claims 1 to 8, wherein the tannin is mixed with the aqueous composition while maintaining the temperature of the composition at 15 to 90°C.

10. 10. The method of any one of claims 1 to 9, wherein step (iii) comprises mixing the tannin with the aqueous composition of (ii) and polymerizing the tannin with the pre-polymerized lignin and the cross-linking agent until a binder composition having a predetermined viscosity value is formed.

11. 11. The method of any one of claims 1 to 10, wherein the lignin is softwood kraft lignin.

12. 12. The method of any one of claims 1 to 11, wherein the cross-linking agent is an aldehyde prepared from biomethanol.

13. 13. The method of any one of claims 1 to 12, comprising dispersing the tannin before mixing with the aqueous composition.

14. 14. The method of any one of claims 1 to 13, wherein the mixing in step (iii) is continued until a binder composition is formed having a viscosity value of 150 to 800 cp.

15. Use of a binder composition obtained by the method according to any one of claims 1 to 14 in an impregnation application for gluing wood products or laminated wood products or wood panels, the impregnation application being intended for the production of laminates, shuttering films, mineral wool, nonwoven textiles, moulded textiles or extruded textile products.

16. A step of obtaining a binder composition by the method according to any one of claims 1 to 14; using the obtained binder composition; The following characteristics: - formaldehyde emission, measured in a desiccator according to EN ISO 12460-4, of 0.01 to 0.5 mg / l; Formaldehyde emissions of 0.01 to 0.40 mg / m, as measured by gas analysis method EN ISO 12460-3. ２ * h - Meets minimum bond class 1 to 4 when measured by bond quality test methods EN314-1 and EN314-2 A method for manufacturing a product comprising one or more of the following:

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