Method for producing lignin-modified resol-type phenolic resin

Abstract

A method for producing a lignin-modified resol-type phenolic resin, the method comprising: a step for obtaining a first mixture containing phenols, water, and lignin, the ratio of the phenols to the water being 1: 0.03 to 1: 1.5 in terms of the mass ratio of the phenols to the water; a step for obtaining a second mixture by heating the first mixture at a pH of 7 or less and a temperature of 70-120 DEG C to dissolve the lignin in the phenols and the water; a step for obtaining a third mixture by adding an aldehyde and a basic catalyst to the second mixture and adjusting the pH to 7.5-12; and a step for obtaining a lignin-modified resole phenolic resin by heating the third mixture at a temperature of 60-105 DEG C and reacting the lignin, the phenol, and the aldehyde in the presence of the basic catalyst.

Description

Technical Field

[0001] The invention relates to a method for preparing a lignin-modified resol-type phenolic resin. Background Art

[0002] Among thermosetting resins, phenolic resins are excellent in heat resistance, mechanical properties, formability, cost and other aspects, and are used for various purposes such as molding materials and laminated boards. However, phenolic resins are manufactured using petroleum as raw materials. Therefore, the manufacture of phenolic resins may cause global warming due to the emission of carbon dioxide. In addition, petroleum is a depleting resource, which becomes a big problem in the future stable supply of phenolic resins.

[0003] In order to solve such environmental problems and the problem of stable supply, in recent years, as a substitute for petroleum-derived products, biomass has been sought to be converted into phenolic resin products, etc. In order to meet this demand, lignin-modified phenolic resins obtained by replacing part of the phenolic resin with lignin, a resin derived from plants, have been studied.

[0004] For example, Patent Document 1 discloses, as a method for synthesizing a lignin-modified phenolic resin, the following steps of carrying out the following steps under conditions of a predetermined temperature and a predetermined pH: a) a step of dissolving lignin in an aqueous composition containing a compound selected from phenol, cresol, resorcinol, and a combination thereof; b) a step of reacting the composition in which the lignin is dissolved with an alkali to alkalize the lignin; and c) a step of reacting the composition formed in step b) with aldehydes.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent No. 6588433 Summary of the invention

[0008] Technical problem to be solved by the invention

[0009] The present inventors have studied and found that the method for producing a lignin-modified phenolic resin described in Patent Document 1 has room for improvement in terms of yield.

[0010] Means for solving technical problems

[0011] The present invention has been made in view of the above-mentioned technical problems, and has been completed based on the finding of the inventors that a lignin-modified resol-type phenolic resin can be obtained at a high yield by adjusting the production conditions.

[0012] According to the present invention, there is provided a method for producing a lignin-modified resol-type phenolic resin as shown below.

[0013] [1] A method for producing a lignin-modified resol-type phenolic resin, comprising: a step of obtaining a first mixture containing phenols, water and lignin, wherein the ratio of the phenols to the water is 1:0.03 to 1:1.5 in terms of the mass ratio of phenols to water; a step of heating the first mixture at a temperature of 70°C to 120°C at a pH of 7 or less to dissolve the lignin in the phenols and the water, thereby obtaining a second mixture; a step of adding an aldehyde and an alkaline catalyst to the second mixture to adjust the pH to 7.5 to 12 to obtain a third mixture; and a step of heating the third mixture at a temperature of 60°C to 105°C to react the lignin, the phenols and the aldehydes in the presence of the alkaline catalyst to obtain a lignin-modified resol-type phenolic resin.

[0014] [2] The method for producing a lignin-modified resol-type phenolic resin according to item [1], wherein the step of obtaining the first mixture includes: a step of preparing a hydrous lignin composed of water and lignin; and a step of mixing the hydrous lignin and the phenol to obtain the first mixture.

[0015] [3] The method for producing a lignin-modified resol-type phenolic resin according to item [1] or [2], further comprising: after the step of obtaining the first mixture and before the step of obtaining the second mixture, a step of reducing the water from the first mixture by distilling the first mixture.

[0016] [4] The method for producing a lignin-modified resol-type phenolic resin according to any one of items [1] to [3], wherein the weight average molecular weight of the lignin is 2,000 to 100,000.

[0017] [5] A method for producing a lignin-modified resol-type phenolic resin according to any one of items [1] to [4], wherein the step of obtaining the third mixture includes the step of further adding a phenolic compound and / or a vegetable oil to the second mixture, and the step of obtaining the lignin-modified resol-type phenolic resin includes the step of heating the third mixture at a temperature of 60°C to 105°C to react the phenolic compound and / or the vegetable oil, the lignin, the phenols and the aldehydes in the presence of the alkaline catalyst to obtain the lignin-modified resol-type phenolic resin.

[0018] [6] The method for producing a lignin-modified resol-type phenolic resin according to item [5], wherein the step of adding a phenol compound, an aldehyde and an alkaline catalyst to the second mixture and adjusting the pH to 7.5 to 12 to obtain a third mixture comprises: mixing the phenol compound into the second mixture and then heating it to dissolve the phenol compound and / or vegetable oil in the phenols and the water to obtain a mixed solution; adding the alkaline catalyst to the mixed solution to adjust the pH to 7.5 to 12; and mixing the aldehyde into the mixed solution having the adjusted pH to obtain the third mixture.

[0019] [7] The method for producing a lignin-modified resol-type phenolic resin according to item [5] or [6], wherein the phenol compound contains an alkylphenol.

[0020] [8] The method for producing a lignin-modified resol-type phenolic resin according to any one of items [5] to [7], wherein the vegetable oil comprises at least one selected from cashew nut oil, castor oil, soybean oil, tung oil, linseed oil, tannin, pyrogallol and tall oil.

[0021] [9] A method for producing a lignin-modified resol-type phenolic resin, comprising: obtaining a first mixture containing phenols, water and lignin, wherein the ratio of the phenols to the water is 1:0.03 to 1:1.5 in terms of the mass ratio of phenols to water; heating the first mixture at a temperature of 70°C to 120°C at a pH of 7 or less to dissolve the lignin in the phenols and the water, thereby obtaining a second mixture; adding a strong acid when or after obtaining the second mixture and heating the mixture to react the lignin with the phenols, thereby obtaining a third mixture containing phenolated lignin; adding an aldehyde and an alkaline catalyst to the third mixture to adjust the pH to 7.5 to 12, thereby obtaining a fourth mixture; and heating the fourth mixture at a temperature of 60°C to 105°C to react the phenolated lignin with the aldehyde in the presence of the alkaline catalyst, thereby obtaining a lignin-modified resol-type phenolic resin.

[0022]

[10] The method for producing a lignin-modified resol-type phenolic resin according to item [9], further comprising: after the step of obtaining the second mixture and before the step of obtaining the third mixture, a step of reducing the water from the second mixture by distilling the second mixture.

[0023]

[11] The method for producing a lignin-modified resol-type phenolic resin according to item [9] or

[10] , wherein the step of obtaining the third mixture includes: a step of adding a strong acid and heating when or after obtaining the second mixture to react the lignin with the phenol, thereby obtaining a third mixture containing phenolized lignin; a step of dehydrating the third mixture by distillation and solvating it with alcohols or ketones; and a step of adding aldehydes and an alkaline catalyst to a solution containing the alcohols or ketones and adjusting the pH to 7.5 to 12, thereby obtaining the third mixture.

[0024] Effects of the Invention

[0025] According to the present invention, a method for producing a lignin-modified resol-type phenolic resin with improved yield can be provided. DETAILED DESCRIPTION

[0026] Hereinafter, embodiments of the present invention will be described.

[0027] [First embodiment]

[0028] The method for producing a lignin-modified resol-type phenolic resin according to the first embodiment of the present invention includes the following (step a) to (step d).

[0029] (Step a) A step of mixing phenols, water, and lignin to obtain a first mixture.

[0030] (Step b) A step of heating the first mixture obtained in the above (Step a) at a pH of 7 or less and a temperature of 70° C. to 120° C. to dissolve lignin in phenols and water, thereby obtaining a second mixture.

[0031] (Step c) A step of adding aldehydes and a basic catalyst to the second mixture obtained in the above (Step b) and adjusting the pH to 7.5 to 12 to obtain a third mixture.

[0032] (Step d) A step of heating the third mixture obtained in the above (step c) at a temperature of 60° C. to 105° C. to react the lignin and phenols contained in the third mixture with aldehydes in the presence of a basic catalyst to obtain a lignin-modified resol-type phenolic resin.

[0033] Hereinafter, each step will be described in detail.

[0034] (Process a)

[0035] In (step a) of the method of this embodiment, a first mixture containing phenols, water, and lignin is prepared.

[0036] In the first mixture obtained in the above (step a), the ratio of phenols to water is 1:0.03 to 1:1.5 in terms of the mass ratio of phenols to water.

[0037] The first mixture containing phenols, water and lignin in the above (step a) can be obtained by the following methods: (a1) putting phenols, water and lignin prepared separately into a container and mixing them; (a2) first mixing phenols and water to obtain a phenols / water mixed solvent, and then mixing lignin into the mixed solvent; (a3) ​​first obtaining a mixture obtained by mixing phenols and lignin, and then mixing the mixture with water; or (a4) preparing aqueous lignin composed of water and lignin, and then mixing the aqueous lignin into phenols. Here, the lignin in the above methods (a1) to (a3) ​​can be in any form of solid, dispersion, or solution. The aqueous lignin in the above method (a4) can be in the form of a solid or an aqueous solution.

[0038] The phenols and water used in the above (step a) are used in an amount in which the ratio of phenols to water contained in the obtained first mixture is 1:0.03 to 1:1.5 in terms of phenols: water (mass ratio). The ratio of phenols to water in the first mixture is preferably 1:0.1 to 1:1.0, and more preferably 1:0.2 to 1:0.6 in terms of phenols: water (mass ratio). By making the ratio of phenols to water contained in the first mixture within the above range, lignin can be easily dispersed in phenols and water and dissolved, and as a result, the reaction efficiency with lignin and aldehydes in the subsequent (step d) can be improved.

[0039] Here, the amount of water contained in the first mixture is the amount obtained by adding the water contained in the lignin and the water used as the solvent.

[0040] In (step a), lignin and phenols are used in an amount of, for example, 1:10 to 2:1, and preferably 1:4 to 4:3, in terms of the mass ratio of lignin:phenols.

[0041] The phenols used in the above-mentioned (step a) not only function as a solvent, but also function as a raw material monomer of the resol type phenolic resin. In addition, lignin is easily soluble in phenols and poorly soluble in water under the condition of pH 7 or less. Therefore, in the (step b) after the (step a), the lignin can be appropriately dispersed in the mixed solvent and easily dissolved. As a result, a reaction solution having good compatibility with lignin and phenols and being homogenized can be obtained, which can improve the reaction efficiency of the lignin in the (step d).

[0042] As the phenols used in the above (step a), phenol, phenol derivatives and combinations thereof can be mentioned. As the phenol derivative, phenol having a molecular weight of 150 or less with an arbitrary substituent introduced into the benzene ring can be used. As the substituent, hydroxyl groups; lower alkyl groups such as methyl, ethyl, propyl, and butyl groups; halogen atoms such as fluorine, chlorine, bromine, and iodine; amino groups; nitro groups; carboxyl groups, etc. can be mentioned. Specific examples of phenols that can be used in the method of the present embodiment include phenol, catechol, resorcinol, hydroquinone, o-cresol, m-cresol, p-cresol, ethylphenol, propylphenol, isopropylphenol, butylphenol, sec-butylphenol, tert-butylphenol, o-fluorophenol, m-fluorophenol, p-fluorophenol, o-chlorophenol, m-chlorophenol, p-chlorophenol, o-bromophenol, m-bromophenol, p-bromophenol, o-iodophenol, m-iodophenol, p-iodophenol, o-aminophenol, m-aminophenol, p-aminophenol, o-nitrophenol, m-nitrophenol, p-nitrophenol, 2,4-dinitrophenol, 2,4,6-trinitrophenol, salicylic acid, p-hydroxybenzoic acid, etc. Phenols can be used alone or in combination of two or more. Among them, phenol, cresol, resorcinol, and xylenol are preferably used as the phenols because of good handling properties.

[0043] The lignins used in the above (step a) include lignin or a lignin derivative, or a combination thereof.

[0044] Lignin is a main component that forms the structure of plants together with cellulose and hemicellulose, and is one of the most abundant aromatic compounds in nature. Lignin exists as lignocellulose in plants with a part of the bond. Therefore, lignin mostly refers to lignin obtained from plants through decomposition, etc. Examples include pulp lignin such as sulfate lignin, lignin sulfonic acid, alkali lignin, soda-anthraquinone lignin, etc.; organic solvent lignin; lignin phenol added with phenol when extracting lignin with concentrated sulfuric acid in high-temperature and high-pressure water treatment or blasting lignin; phenolized lignin, etc. The source of lignin is not particularly limited, and examples include wood or herbs that contain lignin and can form xylem, and examples include conifers such as cedar, pine, cypress and spruce, broad-leaved trees such as beech, birch, oak, beech and eucalyptus, and grasses (herbs) such as rice, wheat, corn and bamboo.

[0045] In this embodiment, "lignin derivative" refers to a compound having a unit structure constituting lignin or a structure similar to the unit structure constituting lignin. The lignin derivative has a phenol derivative as a unit structure. The unit structure has a chemically and biologically stable carbon-carbon bond or carbon-oxygen-carbon bond, and is therefore not susceptible to chemical degradation and biological decomposition.

[0046] As lignin derivatives, guaiacylpropane (ferulic acid) represented by formula (A) of the following formula (1), syringylpropane (sinapic acid) represented by the following formula (B), and 4-hydroxyphenylpropane (coumaric acid) represented by the following formula (C) can be cited. The composition of lignin derivatives varies depending on the biomass used as the raw material. Lignin derivatives containing a guaiacylpropane structure are mainly extracted from coniferous trees. Lignin derivatives containing a guaiacylpropane structure and a syringylpropane structure are mainly extracted from broad-leaved trees. Lignin derivatives containing a guaiacylpropane structure, a syringylpropane structure, and a 4-hydroxyphenylpropane structure are mainly extracted from herbs.

[0047]

[0048] Lignin derivatives are preferably substances obtained by decomposing biomass. Biomass is a biomass obtained by taking carbon dioxide in the atmosphere and fixing it during photosynthesis. Therefore, biomass helps to suppress the increase of carbon dioxide in the atmosphere. By utilizing biomass in industry, it can help to suppress the global warming effect. As biomass, lignocellulosic biomass can be cited. As lignocellulosic biomass, leaves, bark, branches and wood of plants containing lignin and their processed products can be cited. As plants containing lignin, the above-mentioned broad-leaved trees, coniferous trees, herbs, etc. can be cited.

[0049] As a method for decomposing biomass, chemical treatment methods, hydrolysis treatment methods, steam explosion methods, supercritical water treatment methods, subcritical water treatment methods, mechanical treatment methods, sulfuric acid cresol methods, pulp manufacturing methods, etc. can be cited. From the perspective of environmental load, steam explosion methods, subcritical water treatment methods, and mechanical treatment methods are preferred. From the perspective of cost, pulp manufacturing methods are preferred. In addition, from the perspective of cost, it is preferred to use by-products that utilize biomass. Lignin derivatives can be prepared, for example, by decomposing biomass under the conditions of 150 to 400°C, 1 to 40MPa, and 8 hours or less in the presence of various cooking liquids or solvents. In addition, lignin derivatives can be prepared by the methods disclosed in Japanese Patent Publication No. 2009-084320 and Japanese Patent Publication No. 2012-201828.

[0050] As lignin derivatives, there can be cited lignin derivatives obtained by decomposing lignocellulose formed by bonding lignin, cellulose and hemicellulose, etc. Lignin derivatives can include lignin decomposition products, cellulose decomposition products and hemicellulose decomposition products, etc., which are mainly composed of compounds having a lignin skeleton. In addition, lignin derivatives can also include inorganic substances derived from biomass or from processes, but in the case of the use of the present embodiment, the content of inorganic substances is preferably 10% by mass or less relative to the entire lignin derivative used.

[0051] The lignin derivative preferably has a plurality of reaction sites that allow the curing agent to function by electrophilic substitution reactions on the aromatic ring. From the viewpoint of excellent reactivity of sites with less steric hindrance near the reaction site, at least one of the ortho and para positions of the aromatic ring containing a phenolic hydroxyl group is preferably unsubstituted, and as the aromatic unit of the lignin, it is preferably a lignin derived from conifers or herbs containing a structure of a plurality of guaiacyl cores or 4-hydroxyphenyl cores. As the lignin derivative, the lignin derivatives disclosed in Japanese Patent Laid-Open No. 2009-084320 Gazette and Japanese Patent Laid-Open No. 2012-201828 Gazette, etc. can be used.

[0052] Furthermore, the lignin derivative may be a lignin derivative having a functional group in addition to the above-mentioned basic structure (lignin secondary derivative).

[0053] As the functional group possessed by the secondary derivative of lignin, it is not particularly limited, for example, it is preferably a functional group that can react with each other or a functional group that can react with other functional groups that are the same as 2 or more functional groups. Specifically, in addition to epoxy and methylol, vinyl, acetylene, maleimide, cyanate, isocyanate, etc. with carbon-carbon unsaturated bonds can also be cited. Among them, it is preferred to use a lignin derivative (methylolated) into which methylol is introduced. Such secondary derivatives of lignin produce self-crosslinking by the self-condensation reaction of methylol groups, and are crosslinked with alkoxymethyl or hydroxyl groups in the following crosslinking agents. As a result, a lignin-modified novolac type phenolic resin having a particularly homogeneous and rigid skeleton and excellent solvent resistance can be obtained.

[0054] Moreover, the lignin derivative used in the present embodiment may have a carboxyl group. Lignin obtained by pulping process or high temperature and high pressure water treatment may have a carboxyl group. The lignin modified novolac type phenolic resin obtained from the lignin derivative having a carboxyl group has a plurality of crosslinking points with the curing agent described below, and therefore, the crosslinking density of the obtained crosslinked body can be increased, and as a result, a crosslinked body with excellent solvent resistance can be obtained.

[0055] In addition, when the above-mentioned lignin derivative has a carboxyl group, the carboxyl group is provided to the 13 In C-NMR analysis, the presence or absence of absorption of a peak at 172 to 174 ppm can be confirmed.

[0056] The weight average molecular weight of the lignin used in the present embodiment is, for example, 2,000 or more and 100,000 or less. The lower limit of the weight average molecular weight is preferably 3,000 or more, more preferably 4,000 or more, and further preferably 5,000 or more. The upper limit of the weight average molecular weight is preferably 90,000 or less, more preferably 80,000 or less, and further preferably 60,000 or less. Lignins with a weight average molecular weight in the above range are easily dissolved in the above-mentioned mixed solvent and have excellent handling properties. In addition, the weight average molecular weight is a number average molecular weight calculated by polystyrene measured by gel permeation chromatography, and can be obtained by the method of the embodiment.

[0057] Here, an example of a method for measuring the molecular weight by the above-mentioned gel permeation chromatography will be described.

[0058] In the method of measuring molecular weight by gel permeation chromatography, first, lignin derivatives are dissolved in a solvent to prepare a measurement sample. The solvent used at this time is not particularly limited as long as it can dissolve the lignin derivatives. From the viewpoint of the measurement accuracy of gel permeation chromatography, for example, tetrahydrofuran and N-methyl-2-pyrrolidone are preferred. The lignin used in the manufacture of the lignin-modified novolac type phenolic resin used in the present embodiment may include insolubles formed by biomass, inorganic substances derived from processes, and high molecular weight organic substances derived from plants. Therefore, the molecular weight of the lignin is obtained by selecting an appropriate solvent and filtering the insolubles. In addition, in order to improve the lignin modification rate of the obtained lignin-modified resol type phenolic resin, the insolubles of the lignin used are preferably less than 30% by mass in an appropriate solvent.

[0059] Next, "TSKgelSuperAW4000 (manufactured by TOSOH CORPORATION)", "TSKgel SuperAW3000 (manufactured by TOSOH CORPORATION)", "TSKgel SuperAW2500 (manufactured by TOSOH CORPORATION)" and "TSKgel SuperAW2500 (manufactured by TOSOH CORPORATION)" which are general organic columns filled with styrene-based polymer fillers are connected in series with the GPC system "HLC-8420GPC EcoSEC Elite (manufactured by TOSOH CORPORATION)". 30 μL of the aforementioned measurement sample is injected into the GPC system, and the eluent N-methyl-2-pyrrolidone is developed at 40°C at 0.3 mL / min, and the retention time is measured using the differential refractive index (RI) and ultraviolet absorbance (UV). Based on a calibration curve separately prepared to show the relationship between the retention time and the molecular weight of a standard polystyrene, the number average molecular weight and the weight average molecular weight of the target lignin can be calculated. As a detection mode, the refractive index is preferred.

[0060] The molecular weight of the standard polystyrene used for preparing the calibration curve is not particularly limited, and for example, standard polystyrenes having a weight average molecular weight of 2,110,000, 1,090,000, 427,000, 190,000, 37,900, 18,100, 5,970, 2,420, and 500 (manufactured by Tosoh Corporation) can be used.

[0061] The volatile components of lignin are preferably 60% by mass or less, more preferably 50% by mass or less, and further preferably 40% by mass or less. By making the volatile components of lignin within the above range, the reactivity of lignin can be increased, thereby increasing the reactivity of the obtained lignin-modified novolac-type phenolic resin. The main volatile components are mostly water, which can be calculated, for example, by spreading 4 g in an aluminum cup and drying it at 80° C. for 20 hours.

[0062] When using lignin obtained by decomposing biomass, there is a case where a large amount of low molecular weight components are mixed in, and there is a case where volatile components and odors during heating and softening point reduction may occur. These components can be used directly or removed by heating, drying, etc. of lignin to adjust the softening point and odor.

[0063] The lignin used in the above-mentioned (step a) can be used in the form of a solid, a dispersion or a solution, as described above, or can be used as a hydrous lignin in the form of a solid or an aqueous solution. When using the lignin in the form of an aqueous solution, the lignin aqueous solution can also be distilled to reduce the amount of water contained in the lignin aqueous solution.

[0064] The first mixture containing phenols, water and lignin obtained in the above (step a) can be subjected to a step of reducing the amount of water contained in the first mixture before (step b). The step of reducing the amount of water contained in the first mixture can be implemented, for example, using a distillation method. The step of reducing the amount of water in the first mixture is preferably implemented until the ratio of phenols to water in the first mixture finally obtained becomes 1:0.01 to 1:0.5 in terms of the mass ratio of phenols:water. By making the amount of water within the above range, the yield of the lignin-modified resol-type phenolic resin in (step d) can be increased.

[0065] (Process b)

[0066] In (step b) of the method of this embodiment, the first mixture obtained in (step a) is heated at a pH of 7 or less and a temperature of 70° C. to 120° C. to dissolve lignin in phenols and water, thereby obtaining a second mixture.

[0067] In (step b), the first mixture containing lignin, phenols and water obtained in the above (step a) is adjusted to a pH of less than 7, and then heated at a temperature of 70°C to 120°C. The pH of the first mixture can be adjusted by adding any acid or base. The pH of the first mixture is preferably 1 to 7, more preferably 2 to 6. By adjusting to such a pH, lignin can be dissolved and dissolved in phenols and water. In addition, in order to dissolve lignin in phenols and water, heating is performed at a temperature of 70°C to 120°C, preferably 80°C to 100°C. By heating at a temperature within the above range, lignin is easily dissolved in the mixed solvent.

[0068] (Process c)

[0069] In (step c) in the method of the present embodiment, aldehydes and a basic catalyst are added to the second mixture obtained in (step b) above, and the pH is adjusted to 7.5 to 12, thereby obtaining a third mixture.

[0070] As the aldehydes used in (process c), formaldehyde, paraformaldehyde, trioxane, acetaldehyde, propionaldehyde, polyoxymethylene, chloral, hexamethylenetetramine, furfural, glyoxal, n-butyraldehyde, hexanal, allyl aldehyde, benzaldehyde, crotonaldehyde, acrolein, tetracarboxaldehyde, phenylacetaldehyde, o-tolualdehyde, salicylaldehyde, p-xylene dimethyl ether, etc. can be mentioned. Preferably, formaldehyde, paraformaldehyde, trioxane, polyoxymethylene, acetaldehyde, p-xylene dimethyl ether and their combination can be mentioned. Aldehydes can be used alone or in combination of two or more. Wherein, from the viewpoint of productivity and low price, formaldehyde or acetaldehyde is preferably used.

[0071] Examples of the alkaline catalyst used in (step c) include hydroxides of alkali metals or alkaline earth metals such as sodium hydroxide, potassium hydroxide, and calcium hydroxide; carbonates such as sodium carbonate and calcium carbonate; oxides such as lime; sulfites such as sodium sulfite; phosphates such as sodium phosphate; amines such as ammonia, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, hexamethylenetetramine, and pyridine.

[0072] In one embodiment, in (step c), in addition to the aldehydes and the alkaline catalyst, a phenolic compound and / or a vegetable oil different from the phenols and lignins used in (step a) may be added. When a phenolic compound or a vegetable oil is added, in the subsequent (step d), a resol type phenolic resin is produced by the reaction of the lignins and phenols used in (step a), and the phenolic compound or the vegetable oil with the aldehydes.

[0073] As the phenol compound that can be used in (step c), alkylphenols can be mentioned. As the alkylphenols, phenols having an alkyl group with a molecular weight exceeding 150 are preferably used, and as specific examples, amylphenol, tertiary aminophenol, hexylphenol, heptylphenol, octylphenol, tertiary octylphenol, nonylphenol, tertiary nonylphenol, decylphenol, undecylphenol, dodecylphenol, tridecylphenol, tetradecylphenol, pentadecylphenol, cardanol, cardol, urushiol, hexadecylphenol, methyl cardol, heptadecylphenol, laccol, mercaptan, octadecylphenol, etc. can be mentioned. The phenol compound can be used alone or in combination of two or more.

[0074] Examples of the vegetable oil that can be used in (step c) include cashew nut oil, castor oil, soybean oil, tung oil, linseed oil, tannin, pyrogallol, tall oil, etc. The vegetable oil can be used alone or in combination of two or more. In addition, any one of the phenolic compound and the vegetable oil can be used or they can be used in combination.

[0075] When a phenolic compound and / or a vegetable oil is added to the second mixture in (step c), the following steps are preferably performed: first, the phenolic compound and / or the vegetable oil are mixed with the second mixture, and then heated to dissolve the phenolic compound and / or the vegetable oil in the solvent (mixed solvent of phenols and water) in (step a) to obtain a mixed solution (step c-1), then the above-mentioned alkaline catalyst is added to the mixed solution to adjust the pH to 7.5 to 12 (step c-2), and then the above-mentioned aldehyde is mixed with the pH-adjusted mixed solution to obtain a third mixture (step c-3). When a phenolic compound and / or a vegetable oil is used, the phenolic compound and / or the vegetable oil can be easily dissolved in the second mixture by adding the phenolic compound and / or the vegetable oil to the second mixture before adding the alkaline catalyst.

[0076] When both the phenolic compound and the vegetable oil are used, the order of adding them to the second mixture in (step c) may be arbitrary. Alternatively, a mixture obtained by mixing the phenolic compound and the vegetable oil in advance may be added to the second mixture.

[0077] The aldehyde used in step (c) is used in an amount such that the molar ratio (F / P) of the phenol (P) to the aldehyde (F) is 0.8 or more, preferably 0.8 or more and 5.0 or less, more preferably 1.0 or more and 3.5 or less, and further preferably 1.2 or more and 2.5 or less.

[0078] The basic catalyst used in (step c) is used in an amount of 1 to 30% by mass based on the total amount of phenols, lignins, aldehydes, and, when a phenol compound and / or a vegetable oil is used, the phenol compound and / or the vegetable oil.

[0079] When the above-mentioned phenolic compound and / or vegetable oil is used in (step c), the amount thereof is preferably 1 to 200% by mass relative to the phenols used in (step a). When both the phenolic compound and the vegetable oil are used, it is preferred that the total amount thereof be within the above range.

[0080] (Process d)

[0081] In the method of this embodiment, in the step (d), the third mixture obtained in the step (c) is heated at a temperature of 60°C to 105°C, and the lignin, phenols and aldehydes contained in the third mixture are reacted in the presence of an alkaline catalyst to obtain a lignin-modified resol-type phenolic resin. In the case where a phenolic compound and / or a vegetable oil is used in the step (c), in the step (d), lignin, phenols, phenolic compounds and / or vegetable oils and aldehydes are reacted in the presence of an alkaline catalyst to obtain a lignin-modified resol-type phenolic resin.

[0082] In (step d), the third mixture is heated at a temperature of 60°C to 105°C. The heating temperature in (step d) can be appropriately selected according to the types of lignin, phenols, and phenolic compounds and / or vegetable oils contained in the third mixture, and the physical properties of the target resol type phenolic resin. The heating time in (step d) is, for example, 10 minutes to 100 minutes, preferably 30 minutes to 60 minutes. By heating the third mixture at a temperature and time within the above range, the lignin, phenols, phenolic compounds (when used), vegetable oils (when used) and aldehydes contained therein react to generate a resol type phenolic resin.

[0083] The lignin modified resol type phenolic resin obtained by the method of the present embodiment, wherein the amount of free phenol contained therein is preferably 5.0% by mass or less, more preferably 4.0% by mass or less relative to the lignin modified resol type phenolic resin. The lower limit of the amount of free phenol contained in the lignin modified resol type phenolic resin is not particularly limited, but relative to the lignin modified resol type phenolic resin, for example, is 0.1% by mass or more, preferably 0.5% by mass or more. By making the amount of free phenol below the above upper limit, the lignin modified resol type phenolic resin has excellent handleability and has a wide range of applications. In addition, by making the amount of free phenol above the above lower limit, there is no need for a special device or process for completely removing free aldehydes, so the manufacturing cost can be suppressed.

[0084] [Second Embodiment]

[0085] The method for producing a lignin-modified resol-type phenolic resin according to the second embodiment of the present invention includes the following (step i) to (step iv).

[0086] (Step i) A step of obtaining a first mixture containing phenols, water, and lignin.

[0087] (Step ii) A step of heating the first mixture obtained in the above (Step i) at a pH of 7 or less and a temperature of 70° C. to 120° C. to dissolve lignin in phenols and water, thereby obtaining a second mixture.

[0088] (Step iii-1) A step of adding a strong acid and heating the mixture during or after obtaining the second mixture obtained in the above (Step ii) to react lignin with phenols to obtain a reaction mixture containing phenolated lignin.

[0089] (Step iii-2) A step of adding aldehydes and a basic catalyst to the reaction mixture containing phenolated lignin obtained in the above (Step iii-1) and adjusting the pH to 7.5 to 12 to obtain a third mixture.

[0090] (Step iv) A step of heating the third mixture obtained in the above (Step iii-2) at a temperature of 60° C. to 105° C. to react phenolated lignin and aldehydes in the presence of a basic catalyst to obtain a lignin-modified resol-type phenolic resin.

[0091] Hereinafter, each step will be described in detail.

[0092] (Process i)

[0093] The (step i) in this embodiment is the same as the (step a) in the above-mentioned first embodiment.

[0094] (Process ii)

[0095] The (step ii) in this embodiment is the same as the (step b) in the above-mentioned first embodiment.

[0096] In (step iii-1) of the method of this embodiment, when or after obtaining the second mixture as an aqueous solution containing lignin and phenols obtained in (step ii), a strong acid is added and then heated to react lignin with phenols to obtain phenolated lignin.

[0097] In one embodiment, the aqueous solution (second mixture) in which lignin and phenols are dissolved obtained in (step ii) may be distilled to remove water contained therein before (step iii-1) is performed. The dehydration step can improve the reaction efficiency of lignin and phenols.

[0098] Examples of strong acids used in the reaction between lignin and phenols include sulfuric acid with a concentration of 65% by mass or more, phosphoric acid with a concentration of 85% by mass or more, hydrochloric acid with a concentration of 38% by mass or more, p-toluenesulfonic acid, trifluoroacetic acid, trichloroacetic acid, formic acid, etc., but are not limited thereto.

[0099] The reaction of lignin and phenols can be carried out by heating the second mixture at a temperature of 90°C to 120°C, preferably 100°C to 115°C.

[0100] The phenolic lignin obtained by the above method has a lignin skeleton and a plurality of phenolic hydroxyl groups as reactive groups. Therefore, the phenolic lignin can react with aldehydes using the phenolic hydroxyl groups as reactive groups to generate a phenolic resin containing a lignin skeleton (lignin-modified phenolic resin).

[0101] In one embodiment, after obtaining the phenolic lignin, the reaction mixture containing the phenolic lignin may be subjected to a dehydration treatment and solvated with alcohols, ketones, etc., thereby performing solvent replacement. As the dehydration treatment, for example, a distillation method may be used. In addition, examples of the alcohols used include methanol, ethanol, propanol, 1-methoxy-2-propanol, etc., and examples of the ketones include acetone, methyl ethyl ketone, etc.

[0102] In (step iii-2) of the method of the present embodiment, aldehydes and a basic catalyst are added to the reaction mixture containing phenolic lignin obtained in (step iii-1) above, and the pH is adjusted to 7.5 to 12 to obtain a third mixture.

[0103] The (step iii-2) of the present embodiment is the same as the (step c) of the above-mentioned first embodiment.

[0104] (Process iv)

[0105] In (step iv) of the present embodiment, the third mixture obtained in (step iii-2) is heated at a temperature of 60°C to 105°C to react the phenolic lignin and the aldehydes in the presence of an alkaline catalyst, thereby obtaining a phenolic resin containing a lignin skeleton (lignin-modified resol-type phenolic resin).

[0106] The (step iv) of the present embodiment can be carried out under the same conditions as the (step d) of the above-mentioned first embodiment.

[0107] As mentioned above, although embodiment of this invention was described, these are only illustrations of this invention, and various structures other than the above-mentioned can also be adopted.

[0108] Example

[0109] Hereinafter, the present invention will be described with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

[0110] (Example 1)

[0111] (Preparation of lignin derivatives)

[0112] First, a lignin derivative used for the synthesis of a lignin-modified novolac-type phenolic resin was prepared by the following steps.

[0113] 1500 parts by weight of cedar wood powder with a moisture content of 50% by weight, 5000 parts by weight of pure water, 180 parts by weight of sodium hydroxide, 120 parts by weight of sodium carbonate, and 7.5 parts by weight of 9,10-anthraquinone as a cooking aid were placed in a 10L stainless steel autoclave, and a cooking reaction was carried out at 170°C for 3 hours under stirring. The cooking liquid after the reaction was cooled to room temperature, and the pulp component was removed with a sieve, and the black liquor containing lignin was separated. Dilute sulfuric acid was added to the separated black liquor to adjust the pH to 8, and the resulting precipitate was centrifuged. After washing twice with 500 parts by weight of water, the precipitate was suspended in 5 times the amount of water and readjusted to pH 2 with dilute sulfuric acid. The precipitated lignin is centrifuged again, washed with water, filtered, spread out on a large barrel for air drying, and dried in a reduced pressure oven below 70°C to obtain 140 to 150 parts by weight (solid content conversion) of brown powdered alkali lignin (water-containing lignin) with a solid content of 59% by weight.

[0114] A portion of the obtained hydrous lignin was further dried in a reduced pressure oven at 80°C or less, thereby obtaining an alkali lignin having a solid content of 99% by mass. The solid content was calculated based on the residual rate after 4 g of the sample was placed in an aluminum cup and heated and dried at 135°C for 1 hour. The number average molecular weight (Mn) of the obtained lignin derivative was 2,000, and the weight average molecular weight (Mw) was 14,000.

[0115] (Synthesis of lignin-modified phenolic resin)

[0116] Next, using the prepared alkali lignin having a solid content of 99% by mass, a lignin-modified phenol resin was synthesized according to the following procedure.

[0117] (First step) 100 parts by weight of phenol and 69.5 parts by weight of water were added to a four-necked flask including a stirrer, a cooling tube and a thermometer to prepare a mixed solvent. Then, the temperature of the mixed solvent was adjusted to 60° C. Then, 100 parts by weight of alkali lignin having a solid content of 99% by mass was added in batches while stirring to obtain a first mixture. The ratio of phenol to water in the first mixture was 1:0.7 in terms of phenol:water (mass ratio).

[0118] (Second step) The first mixture obtained in the first step was heated to 90°C and stirred for 20 minutes to dissolve 99% by mass of alkali lignin in the phenol / water mixed solvent, and the absence of floating matter was visually confirmed. The obtained mixture was referred to as the second mixture.

[0119] (Third Step) The second mixture obtained in the second step was cooled to 60°C, and then 20 parts by weight of a 50% aqueous sodium hydroxide solution was added, followed by adding 146.4 parts by weight of 37% formaldehyde while paying attention to raising the temperature, thereby obtaining a third mixture.

[0120] (Fourth step) The third mixture obtained in the third step is reacted at 60°C for 60 minutes, and then the temperature is further raised to 85°C and reacted for 80 minutes. After that, it is quenched and adjusted to an arbitrary viscosity by adding pure water. After that, a trace amount of fibrous insoluble matter is removed by a 200-mesh filter, thereby obtaining a lignin-modified resol-type phenolic resin. The non-volatile component of the obtained lignin-modified phenolic resin is 55% by mass, the water solubility is more than 25 times, the solution resin viscosity is 756 mPa·s, the free phenol is 4.9% by mass, and the free formaldehyde content is 0.6% by mass.

[0121] (Example 2)

[0122] (First step) 100 parts by weight of phenol was added to a four-necked flask including a stirrer, a cooling tube and a thermometer. Then, the temperature of the phenol was adjusted to 60°C. Then, 169.5 parts by weight of brown powdery hydrous lignin having a solid content of 59% by mass prepared in Example 1 was added in batches while stirring to obtain a first mixture. The ratio of phenol to water in the first mixture was 1:0.7 in terms of phenol:water (mass ratio).

[0123] (Second step) The first mixture obtained in the first step was treated under the same conditions as in the second step of Example 1 to dissolve the aqueous lignin, thereby obtaining a second mixture.

[0124] (Third step) The second mixture was treated under the same conditions as the third step of Example 1 to obtain a third mixture.

[0125] (Fourth step) The third mixture obtained in the third step was reacted at 60°C for 60 minutes, and then the temperature was further raised to 85°C and reacted for 80 minutes. Thereafter, the mixture was rapidly cooled and adjusted to an arbitrary viscosity by adding pure water. Thereafter, a trace amount of fibrous insoluble matter was removed by a 200-mesh filter, thereby obtaining a lignin-modified resol-type phenolic resin.

[0126] The non-volatile components, water solubility, solution resin viscosity, free phenol content and free formaldehyde content of the obtained lignin-modified phenolic resin are shown in Table 1.

[0127] (Example 3)

[0128] (First Step) A first mixture was obtained in the same manner as in the first step of Example 1 except that water was changed to 42.9 parts by weight. The quantitative ratio of phenol to water in the first mixture was 1:0.44 in terms of phenol:water (mass ratio).

[0129] Next, the obtained first mixture was distilled to remove water until the mass ratio of phenol to water in the first mixture became phenol:water=1:0.05.

[0130] (Second step) The first mixture after water reduction obtained in the first step was treated under the same conditions as the second step of Example 1 to obtain a second mixture.

[0131] (Third step) The second mixture was treated under the same conditions as the third step of Example 1 to obtain a third mixture.

[0132] (Fourth step) The third mixture obtained in the third step was reacted at 60°C for 60 minutes, and then the temperature was further raised to 85°C and reacted for 40 minutes. Thereafter, the mixture was rapidly cooled and adjusted to an arbitrary viscosity by adding pure water. Thereafter, a trace amount of fibrous insoluble matter was removed by a 200-mesh filter, thereby obtaining a lignin-modified resol-type phenolic resin.

[0133] The non-volatile components, water solubility, solution resin viscosity, free phenol content and free formaldehyde content of the obtained lignin-modified phenolic resin are shown in Table 1.

[0134] (Example 4)

[0135] (First step) A first mixture was obtained in the same manner as in the first step of Example 2. The quantitative ratio of phenol to water in the first mixture was 1:0.7 in terms of phenol:water (mass ratio).

[0136] Next, the obtained first mixture was distilled to remove water until the mass ratio of phenol to water in the first mixture became phenol:water=1:0.05.

[0137] (Second step) The first mixture after water reduction obtained in the first step was treated under the same conditions as the second step of Example 1 to obtain a second mixture.

[0138] (Third step) The second mixture was treated under the same conditions as the third step of Example 1 to obtain a third mixture.

[0139] (Fourth step) The third mixture obtained in the third step was reacted at 60°C for 60 minutes, and then the temperature was further raised to 85°C and reacted for 40 minutes. Thereafter, the mixture was rapidly cooled and adjusted to an arbitrary viscosity by adding pure water. Thereafter, a trace amount of fibrous insoluble matter was removed by a 200-mesh filter, thereby obtaining a lignin-modified resol-type phenolic resin.

[0140] The non-volatile components, water solubility, solution resin viscosity, free phenol content and free formaldehyde content of the obtained lignin-modified phenolic resin are shown in Table 1.

[0141] (Example 5)

[0142] (First step) 100 parts by weight of phenol was added to a four-necked flask including a stirrer, a cooling tube and a thermometer. Then, the temperature of the phenol was adjusted to 60° C. Then, 153.9 parts by weight of brown powdery hydrous lignin having a solid content of 59% by mass prepared in Example 1 was added in batches while stirring to obtain a first mixture. The ratio of phenol to water in the first mixture was 1:0.79 in terms of phenol:water (mass ratio).

[0143] Next, the obtained first mixture was distilled to remove water until the mass ratio of phenol to water in the first mixture became phenol:water=1:0.05.

[0144] (Second step) The first mixture after water reduction obtained in the first step was treated under the same conditions as the second step of Example 1 to obtain a second mixture.

[0145] (Third Step) The second mixture obtained in the second step was cooled to 60°C, and then 20 parts by weight of a 50% aqueous sodium hydroxide solution was added, followed by adding 124.2 parts by weight of 37% formaldehyde while paying attention to raising the temperature, thereby obtaining a third mixture.

[0146] (Fourth step) The third mixture obtained in the third step was reacted at 60°C for 60 minutes, and then the temperature was further raised to 85°C and reacted for 80 minutes. Thereafter, the mixture was rapidly cooled and adjusted to an arbitrary viscosity by adding pure water. Thereafter, a trace amount of fibrous insoluble matter was removed by a 200-mesh filter, thereby obtaining a lignin-modified resol-type phenolic resin.

[0147] (Example 6)

[0148] (First step) 100 parts by weight of phenol was added to a four-necked flask including a stirrer, a cooling tube and a thermometer. Then, the temperature of the phenol was adjusted to 60°C. Then, 169.5 parts by weight of brown powdery hydrous lignin having a solid content of 59% by mass prepared in Example 1 was added in batches while stirring to obtain a first mixture. The ratio of phenol to water in the first mixture was 1:0.7 in terms of phenol:water (mass ratio).

[0149] (Second step) The first mixture obtained in the first step was treated under the same conditions as in the second step of Example 1 to dissolve the aqueous lignin, thereby obtaining a second mixture.

[0150] (Third step) The second mixture was dehydrated by distillation. 98% sulfuric acid was added to the dehydrated second mixture, and the mixture was heated at 110° C. for 30 minutes. Next, the obtained reaction mixture was cooled to 60° C., and then 20.5 parts by weight of a 50% aqueous sodium hydroxide solution was added, and then 137.7 parts by weight of 37% formaldehyde was added while paying attention to the temperature increase, thereby obtaining a third mixture.

[0151] (Fourth step) The third mixture obtained in the third step was reacted at 60°C for 60 minutes, and then the temperature was further raised to 85°C and reacted for 80 minutes. Thereafter, the mixture was rapidly cooled and adjusted to an arbitrary viscosity by adding pure water. Thereafter, a trace amount of insoluble matter was removed by a 200-mesh filter, thereby obtaining a lignin-modified resol-type phenolic resin.

[0152] The non-volatile components, water solubility, solution resin viscosity, free phenol content and free formaldehyde content of the obtained lignin-modified phenolic resin are shown in Table 1.

[0153] (Example 7)

[0154] (First step) 100 parts by weight of phenol was added to a four-necked flask including a stirrer, a cooling tube and a thermometer. Then, the temperature of the phenol was adjusted to 60°C. Then, 169.5 parts by weight of brown powdery hydrous lignin having a solid content of 59% by mass prepared in Example 1 was added in batches while stirring to obtain a first mixture. The ratio of phenol to water in the first mixture was 1:0.7 in terms of phenol:water (mass ratio).

[0155] (Second step) The first mixture obtained in the first step was treated under the same conditions as in the second step of Example 1 to dissolve the aqueous lignin, thereby obtaining a second mixture.

[0156] (Third step) Dehydrate the second mixture by distillation. Add 98% sulfuric acid to the dehydrated second mixture and heat at 110°C for 30 minutes. Then, dehydrate the obtained reaction mixture by distillation and add 201.4 parts by weight of methanol. Next, cool the obtained methanol solution to 60°C, then add 30.0 parts by weight of triethylamine, and then add 86.2 parts by weight of 37% formaldehyde while paying attention to raising the temperature.

[0157] (Fourth step) The third mixture obtained in the third step was reacted at 60°C for 60 minutes, and then the temperature was further raised to 85°C and reacted for 80 minutes. Thereafter, the mixture was rapidly cooled and adjusted to an arbitrary viscosity by adding methanol. Thereafter, a trace amount of insoluble matter was removed by a 200-mesh filter, thereby obtaining a lignin-modified resol-type phenolic resin.

[0158] The non-volatile components, water solubility, solution resin viscosity, free phenol content and free formaldehyde content of the obtained lignin-modified phenolic resin are shown in Table 1.

[0159] (Comparative Example 1)

[0160] (First step) 100 parts by weight of phenol was added to a four-necked flask including a stirrer, a cooling tube and a thermometer. Then, the temperature of the phenol was adjusted to 60° C. Then, 100 parts by weight of alkali lignin having a solid content of 99% by mass prepared in Example 1 was added in batches while stirring to obtain a first mixture. The ratio of phenol to water in the first mixture was 1:0.01 in terms of phenol:water (mass ratio).

[0161] (Second step) The first mixture was treated under the same conditions as in the second step of Example 1 to obtain a second mixture.

[0162] (Third step) The second mixture obtained in the second step is treated under the same conditions as the third step of Example 1 to obtain a third mixture.

[0163] (Fourth step) The third mixture obtained in the third step was reacted at 60°C for 60 minutes, and then the temperature was further raised to 85°C and reacted for 80 minutes. Thereafter, the mixture was rapidly cooled and adjusted to an arbitrary viscosity by adding pure water. Thereafter, the mixture was filtered through a 200-mesh filter to remove fibrous insolubles and block-shaped insolubles, thereby obtaining a lignin-modified resol-type phenolic resin.

[0164] The non-volatile components, water solubility, solution resin viscosity, free phenol content and free formaldehyde content of the obtained lignin-modified phenolic resin are shown in Table 1.

[0165] (Comparative Example 2)

[0166] (First step) A first mixture was obtained in the same manner as in the first step of Example 2.

[0167] (Second step) The first mixture obtained in the first step was heated to 55°C and stirred for 20 minutes to dissolve 59% by mass of the solid content of hydrous lignin in phenol, and the absence of floating matter was visually confirmed. The obtained mixture was referred to as the second mixture.

[0168] (Third step) The second mixture was treated under the same conditions as the third step of Example 1 to obtain a third mixture.

[0169] (Fourth step) The third mixture obtained in the third step was reacted at 60°C for 60 minutes, and then the temperature was further raised to 85°C and reacted for 80 minutes. Thereafter, the mixture was rapidly cooled and adjusted to an arbitrary viscosity by adding pure water. Thereafter, the mixture was filtered through a 200-mesh filter to remove fibrous insolubles and block-shaped insolubles, thereby obtaining a lignin-modified resol-type phenolic resin.

[0170] The non-volatile components, water solubility, solution resin viscosity, free phenol content and free formaldehyde content of the obtained lignin-modified phenolic resin are shown in Table 1.

[0171] [Table 1]

[0172]

[0173] In the lignin-modified resol-type phenolic resin manufactured by the method of the embodiment, the content of unreacted free phenol is reduced, and the content of unreacted free formaldehyde is also reduced. In addition, the reaction mixture obtained in the fourth step in the method of the embodiment contains a small amount of fibrous insoluble matter. On the other hand, the reaction mixture obtained in the fourth step in the method of the comparative example contains fibrous insoluble matter and block-like insoluble matter. In Examples 3 and 4, in which the first mixture is subjected to distillation and dehydration treatment, the reaction time of the fourth step can be shortened. In Example 5, in which the first mixture is subjected to distillation and dehydration treatment, a uniformly solubilized third mixture can be obtained even if cashew nut shell oil is mixed in the third step.

[0174] This application claims priority based on Japanese patent application No. 2022-090308, filed on June 2, 2022, the disclosure of which is incorporated herein in its entirety.

Claims

1. A method for producing a lignin-modified resol-type phenolic resin, characterized in that: include: A step of obtaining a first mixture containing phenols, water and lignin, wherein the ratio of the phenols to the water is 1:0.03 to 1:1.5 in terms of the mass ratio of phenols to water; The step of heating the first mixture at a temperature of 70° C. to 120° C. and below pH 7 to dissolve the lignin in the phenols and the water, thereby obtaining a second mixture; A step of adding aldehydes and a basic catalyst to the second mixture and adjusting the pH to 7.5 to 12 to obtain a third mixture; and A step of heating the third mixture at a temperature of 60° C. to 105° C. to react the lignin, the phenols and the aldehydes in the presence of the alkaline catalyst to obtain a lignin-modified resol-type phenolic resin.

2. The method for producing a lignin-modified resol-type phenolic resin according to claim 1, wherein: The process of obtaining the first mixture comprises: A step of preparing a hydrous lignin composed of water and lignin; and A step of mixing the aqueous lignin and the phenols to obtain a first mixture.

3. The method for producing a lignin-modified resol-type phenolic resin according to claim 1 or 2, characterized in that: Also includes: After the step of obtaining the first mixture and before the step of obtaining the second mixture, a step of reducing the water from the first mixture by distilling the first mixture.

4. The method for producing a lignin-modified resol-type phenolic resin according to any one of claims 1 to 3, characterized in that: The weight average molecular weight of the lignin is 2,000 to 100,000.

5. The method for producing a lignin-modified resol-type phenolic resin according to any one of claims 1 to 4, characterized in that: The step of obtaining the third mixture includes the step of further adding a phenolic compound and / or a vegetable oil to the second mixture, The process of obtaining the lignin-modified resol-type phenolic resin includes heating the third mixture at a temperature of 60°C to 105°C, allowing the phenolic compound and / or vegetable oil, the lignin, the phenols and the aldehydes to react in the presence of the alkaline catalyst to obtain the lignin-modified resol-type phenolic resin.

6. The method for producing a lignin-modified resol-type phenolic resin according to claim 5, characterized in that: The step of adding a phenol compound, an aldehyde and an alkaline catalyst to the second mixture and adjusting the pH to 7.5 to 12 to obtain a third mixture comprises: A step of mixing the phenol compound into the second mixture and then heating the mixture to dissolve the phenol compound and / or the vegetable oil in the phenols and the water to obtain a mixed solution; A step of adding the alkaline catalyst to the mixed solution to adjust the pH to 7.5 to 12; and A step of mixing the aldehydes into the mixed solution having the pH adjusted to obtain the third mixture.

7. The method for producing a lignin-modified resol-type phenolic resin according to claim 5 or 6, characterized in that: The phenolic compound comprises alkylphenols.

8. The method for producing a lignin-modified resol-type phenolic resin according to any one of claims 5 to 7, characterized in that: The vegetable oil comprises at least one selected from the group consisting of cashew nut oil, castor oil, soybean oil, tung oil, linseed oil, tannin, pyrogallol and tall oil.

9. A method for producing a lignin-modified resol-type phenolic resin, characterized in that: include: A step of obtaining a first mixture containing phenols, water and lignin, wherein the ratio of the phenols to the water is 1:0.03 to 1:1.5 in terms of the mass ratio of phenols to water; The step of heating the first mixture at a temperature of 70° C. to 120° C. and below pH 7 to dissolve the lignin in the phenols and the water, thereby obtaining a second mixture; A step of adding a strong acid and heating the mixture when or after the second mixture is obtained to react the lignin with the phenol to obtain a reaction mixture containing phenolated lignin, and adding an aldehyde and an alkaline catalyst to the reaction mixture to adjust the pH to 7.5 to 12 to obtain a third mixture; and The third mixture is heated at a temperature of 60° C. to 105° C. to react the phenolic lignin and the aldehyde in the presence of the alkaline catalyst to obtain a lignin-modified resol-type phenolic resin.

10. The method for producing a lignin-modified resol-type phenolic resin according to claim 9, characterized in that: Also includes: After the step of obtaining the second mixture and before the step of obtaining the third mixture, a step of reducing the water from the second mixture by distilling the second mixture.

11. The method for producing a lignin-modified resol-type phenolic resin according to claim 9 or 10, characterized in that: The process of obtaining the third mixture includes: when or after obtaining the second mixture, adding a strong acid and heating to react the lignin with the phenols, thereby obtaining a third mixture containing phenolic lignin; dehydrating the third mixture by distillation and solvating it with alcohols or ketones; and adding aldehydes and an alkaline catalyst to a solution containing the alcohols or ketones and adjusting the pH to 7.5-12, thereby obtaining the third mixture.

Images