Enzymatic hydrolysis lignin-based epoxy resin, glass fiber board glue solution, glass fiber board and preparation method

Abstract

The invention belongs to the technical field of epoxy resin, and particularly relates to enzymatic hydrolysis lignin-based epoxy resin, a glass fiber board glue solution, a glass fiber board and a preparation method. The preparation method of the enzymatic hydrolysis lignin-based epoxy resin comprises the following steps: 1) mixing enzymatic hydrolysis lignin with organic phenol and a sulfuric acid solution, and heating for reaction to obtain phenolated lignin; 2) dissolving the phenolated lignin, C3-C5 sulfydryl fatty acid and a Lewis acid catalyst in a solvent in an inert atmosphere, and heating for reaction to obtain sulfhydrylated lignin; and 3) carrying out sulfydryl and alkenyl addition reaction on the sulfhydrylated lignin and an unsaturated epoxy compound under the action of an initiator to prepare the enzymatic hydrolysis lignin-based epoxy resin. Phenolation treatment prepares more active sites for Friedel-Crafts acylation reaction; the Friedel-Crafts acylation reaction utilizes phenolic hydroxyl groups to react at ortho-para positions, so that the number of active sites is maximized; the addition reaction conditions of sulfydryl and alkenyl are milder, the reaction efficiency is higher, and the epoxy value of the final product is increased under the synergistic effect of the three-step reaction.

Description

Technical Field

[0001] This invention belongs to the field of epoxy resin technology, specifically relating to an enzymatic hydrolysis of lignin-based epoxy resin, a fiberglass board adhesive, a fiberglass board, and a preparation method thereof. Background Technology

[0002] Epoxy resin is a thermosetting resin containing epoxy groups. Due to its excellent mechanical properties, adhesive properties, electrical insulation properties, and chemical stability, it is commonly used as the core resin matrix in electronic packaging materials, printed circuit board (PCB) substrates, insulating coatings, structural adhesives, and composite material matrices. It has wide applications in the structural fixation, insulation protection, and encapsulation of 3C electronic products. However, epoxy resin originates from non-renewable petrochemical products. With the scarcity of petroleum resources and their continuously rising prices, finding and utilizing renewable resources to replace petrochemical products as raw materials for epoxy resin production is an urgent problem that needs to be solved.

[0003] Lignin is the second most abundant renewable resource in the plant kingdom after cellulose. In the industrial system of producing bioethanol from agricultural waste via enzymatic hydrolysis, it is often generated in large quantities as a byproduct. Thanks to the mild hydrolysis conditions of this process, the activity of various functional groups in the lignin molecule is well preserved, giving it the advantage of easy modification. This characteristic also makes its high-value utilization possible, and it is currently widely used in the modification and preparation of epoxy resins, becoming an important direction for promoting the resource utilization of agricultural waste and expanding the sources of epoxy resin raw materials. For example, the raw material formulation and preparation method of enzymatic hydrolyzed lignin epoxy resin disclosed in patent CN100528926C are as follows: the formulation consists of enzymatic hydrolyzed lignin or its derivatives, bisphenol A type compound, epichlorohydrin or a mixture thereof with an organic solvent, catalyst, curing agent, and filler; the preparation method is to add enzymatic hydrolyzed lignin or its derivatives to an epichlorohydrin solution or a mixture thereof with an organic solvent, stir to dissolve, then add the catalyst, and simultaneously add the curing agent or a mixture of curing agent and filler, and heat to make the reaction complete. Finally, the excess epichlorohydrin or organic solvent is distilled off under reduced pressure to obtain a brown solid that is insoluble in water, which is then washed with water and dried to obtain enzymatic hydrolyzed lignin epoxy resin. The preparation method of enzymatically hydrolyzed lignin-based epoxy resin disclosed in patent CN106883376B includes the following steps: adding 10-20 parts by weight of enzymatically hydrolyzed lignin and 2-5 parts by weight of phase transfer agent to 118-302 parts by weight of epichlorohydrin solution, heating to 50-100℃, stirring thoroughly to mix evenly, adding 7-15 parts by weight of catalyst, reflux reaction for 3-8 hours, after the reaction is completed, washing the reactants with water 3-5 times, taking the organic layer, and distilling under reduced pressure at a temperature of 20-100℃ to remove residual epichlorohydrin and deionized water to obtain enzymatically hydrolyzed lignin-based epoxy resin.

[0004] The above method successfully introduced epoxy groups into the lignin molecules using enzymatically hydrolyzed lignin as raw material to prepare epoxy resin. However, due to the limited activity and content of hydroxyl groups in the enzymatically hydrolyzed lignin, the epoxidation reaction could not be fully carried out, resulting in a low epoxy value of the epoxy resin. The composite material made from this epoxy resin has poor mechanical properties after curing and is difficult to replace conventional petrochemical epoxy resin in the field of 3C electronic products. Summary of the Invention

[0005] To address the technical problem of low epoxy value in epoxy resins prepared using enzymatically hydrolyzed lignin as raw material, resulting in poor mechanical properties of composite materials made from it after curing, this invention first treats the enzymatically hydrolyzed lignin with organic phenols to obtain phenolic lignin. Then, under the action of a Lewis acid catalyst, the phenolic lignin undergoes a Friedel-Crafts acylation reaction with thiol fatty acids, introducing thiol groups at the ortho or para positions of the phenolic hydroxyl groups in the phenolic lignin to obtain thiolized lignin. Finally, through a thiol-alkenyl addition reaction, the thiol groups of the thiolized lignin are covalently linked to the carbon-carbon double bonds of the unsaturated epoxy compound to obtain an enzymatically hydrolyzed lignin-based epoxy resin with a high epoxy value. This is beneficial for improving the mechanical properties of composite materials using it as the main base resin.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for preparing enzymatically hydrolyzed lignin-based epoxy resin includes the following steps:

[0008] 1) Mix enzymatically hydrolyzed lignin with organic phenol and sulfuric acid solution, and heat to react to obtain phenolic lignin;

[0009] 2) Under an inert atmosphere, phenolic lignin, C3-C5 thioglycolic acid, and Lewis acid catalyst are dissolved in a solvent and reacted by heating to obtain thioglycolic lignin;

[0010] 3) Thiolized lignin and unsaturated epoxy compounds undergo a thiol-alkenyl addition reaction under the action of an initiator to obtain enzymatically hydrolyzed lignin-based epoxy resin.

[0011] In step 1), the mass ratio of the enzymatically hydrolyzed lignin, organic phenols, and sulfuric acid solution is 1:1.5-3:0.1-0.15.

[0012] In step 1), the enzymatically hydrolyzed lignin is a natural polymer material extracted from the enzymatic hydrolysis residue of plant straw and corn cob fermentation to produce fuel ethanol and functional polysaccharides using a solvent method. The organic phenol is selected from one or a combination of two of phenol, p-cresol, o-cresol, and m-cresol.

[0013] In step 1), the concentration of the sulfuric acid solution is 65-75 wt%.

[0014] In step 1), the heating reaction is carried out at 80-100℃ for 1-4 hours.

[0015] In step 1), after the heating reaction is completed, the process further includes dissolving in an organic solvent, precipitating in ice water, washing with hot water, filtration, and drying. The organic solvent is selected from ethanol, methanol, acetone, methyl ethyl ketone, and dioxane. The hot water is at 65-85°C. The hot water washing is performed 2-5 times. The drying is carried out at 40-60°C under a vacuum of 0.01-0.1 MPa for 1-3 hours.

[0016] In step 2), the molar amount of the C3-C5 thioglycolic acid, the mass of the phenolic lignin, and the mass ratio of the Lewis acid catalyst are 0.01-0.02 mol: 1 g: 0.05-0.08 g.

[0017] In step 2), the C3-C5 thioglycolic acid is selected from one or more combinations of mercaptopropionic acid, 4-mercaptobutyric acid, 3-mercaptobutyric acid, 3-mercaptoisobutyric acid, 2-mercaptobutyric acid, and 5-mercaptovalerate. The Lewis acid catalyst is selected from one or more combinations of titanium tetrachloride, aluminum chloride, ferric chloride, tin chloride, and boron trifluoride.

[0018] In step 2), the solvent is selected from one or more of acetone, methyl ethyl ketone, and dioxane.

[0019] In step 2), the heating reaction is carried out by heating to reflux for 5-8 hours.

[0020] Step 2) further includes distillation and concentration, precipitation in ice water, water washing, filtration, and drying after the heating reaction is completed. The drying is carried out at 40-60℃ and a vacuum of 0.01-0.1MPa for 1-3 hours.

[0021] In step 3), the mass ratio of the thiolized lignin, unsaturated epoxy compound, and initiator is 1:1.6-2.0:0.05-0.15.

[0022] In step 3), the solvent is selected from one or more of acetone, methyl ethyl ketone, and dioxane.

[0023] In step 3), the initiator is selected from photoinitiators or thermal initiators; when it is a photoinitiator, the reaction conditions are ultraviolet irradiation at -5℃ to 40℃ and a power of 800-3000W for 10-30 minutes; when it is a thermal initiator, the reaction conditions are reaction at 60-80℃ for 2-5 hours.

[0024] The photoinitiator is selected from one or more of the following: benzoin dimethyl ether, 1-hydroxycyclohexylphenyl ketone, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, 2-hydroxy-2-methylphenylacetone, isooctyl p-dimethylaminobenzoate, and methyl benzoylformate; the thermal initiator is selected from one or more of the following: azobisisobutyronitrile, azobisisoheptanenitrile, azodicyanovalerate, dimethyl azobisisobutyrate, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), potassium persulfate, and ammonium persulfate.

[0025] The unsaturated epoxy compound is selected from one or more combinations of glycidyl acrylate, (3,4-epoxycyclohexyl) methyl acrylate, allyl glycidyl ether, and glycidyl methacrylate.

[0026] Step 3) After the addition reaction is completed, the process also includes vacuum distillation, resolution, water washing, separation and combination of organic phases, drying, and vacuum distillation again.

[0027] The vacuum distillation is carried out at 50-80℃ and a vacuum degree of 0.08-0.095 MPa for 0.5-2 hours. The solvent for redissolution is selected from one or a combination of two of ethyl acetate and petroleum ether. The water washing is performed with hot water at 30-40℃ 1-3 times. The drying is performed by absorbing water with anhydrous magnesium sulfate or anhydrous sodium sulfate. The second vacuum distillation is carried out at 40-60℃ and a vacuum degree of 0.09-0.1 MPa for 1-3 hours.

[0028] A fiberglass board adhesive comprises the following raw materials in parts by weight: 30-40 parts of enzymatically hydrolyzed lignin-based epoxy resin prepared by the above method, 10-20 parts of linear phenolic epoxy resin, 2-4 parts of curing agent, 0.5-1.5 parts of accelerator, and 40-60 parts of organic solvent.

[0029] The linear phenolic epoxy resin has an epoxy value of 0.46-0.60.

[0030] The linear phenolic epoxy resin is selected from one or more combinations of BNE200, F-51, EPN1179, EPN1138, and GY289.

[0031] The curing agent is selected from one or a combination of two or more of amine curing agents, acid anhydride curing agents, and dicyandiamide curing agents.

[0032] The amine curing agent is selected from one or more of 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenyl ether, and 4,4′-diaminodiphenyl sulfone.

[0033] The anhydride curing agent is selected from one or more of phthalic anhydride, maleic anhydride, tetrahydrophthalic anhydride, and methyltetrahydrophthalic anhydride.

[0034] The dicyandiamide curing agent is dicyandiamide.

[0035] The accelerator is selected from one or a combination of two of substituted urea curing accelerators and imidazole curing accelerators.

[0036] The substituted urea curing accelerator is selected from one or a combination of two of ECURE 20, DYHARD UR400, DYHARD UR300, DYHARD UR400, DYHARD UR500, DYHARD URACC 57, DYHARD UR700, DYHARD UR800, and DYHARD MCA10.

[0037] The imidazole curing accelerator is selected from one or a combination of two of 2-methylimidazole, 2-phenylimidazole, 2-ethyl-4-methylimidazole, and 1-cyanoethyl-2-methylimidazole.

[0038] The organic solvent is selected from one or more of acetone, methyl ethyl ketone, butanone, DMF, and propylene glycol methyl ether.

[0039] The present invention also provides a method for preparing the above-mentioned glass fiberboard adhesive, comprising the following steps:

[0040] The enzymatically hydrolyzed lignin-based epoxy resin, linear phenolic epoxy resin, curing agent, accelerator, and organic solvent are mixed to obtain a fiberglass board adhesive containing the enzymatically hydrolyzed lignin-based epoxy resin.

[0041] A method for preparing a fiberglass board includes the following steps:

[0042] The fiberglass base fabric is impregnated in the above fiberglass board adhesive solution, and then extruded, dried and cut to obtain a semi-cured sheet; N semi-cured sheets are stacked, hot-pressed and cooled to obtain a fiberglass board.

[0043] The fiberglass-based fabric has a basis weight of 50-220 g / m². 2 The thickness is 0.05-0.2mm.

[0044] The drying process is carried out at 150-170℃ for 2-5 minutes.

[0045] N is an integer.

[0046] The hot pressing is performed at 140-180℃ and 0.5-3MPa for 30-120 minutes.

[0047] The hot pressing is segmented hot pressing, 140-160℃ / 0.5-3MPa / 10-60min, 160-180℃ / 0.5-3MPa / 20-60min.

[0048] The cooling process involves natural cooling to 15-30°C.

[0049] The fiberglass base fabric in the prepreg comprises 50-60 wt%.

[0050] A fiberglass board is prepared by the above-described method for preparing fiberglass boards.

[0051] The present invention also provides applications of the above-mentioned fiberglass board for the preparation of mobile phone covers, back covers or laptop shells.

[0052] Compared with the prior art, the beneficial effects of the present invention are:

[0053] This invention first treats enzymatically hydrolyzed lignin with organic phenols to obtain phenolic lignin. Then, under the action of a Lewis acid catalyst, the phenolic lignin undergoes a Friedel-Crafts acylation reaction with thiol fatty acids, introducing thiol groups at the ortho or para positions of the phenolic hydroxyl groups in the phenolic lignin to obtain thiolized lignin. Finally, through a thiol-alkenyl addition reaction, the thiol groups of the thiolized lignin are covalently linked to the carbon-carbon double bonds of an unsaturated epoxy compound to obtain a high epoxy value enzymatically hydrolyzed lignin-based epoxy resin. In this preparation method, the phenolic treatment increases the number of phenolic hydroxyl groups, preparing more active sites for the Friedel-Crafts acylation reaction. The Friedel-Crafts acylation reaction utilizes phenolic hydroxyl groups, allowing the reaction to occur at the ortho or para positions, thereby maximizing the number of active sites, avoiding ineffective reactions, and providing more thiol groups for the subsequent thiol-alkenyl addition reaction. Thiol groups are highly reactive functional groups; their addition reaction with alkenyl groups is milder and more efficient than the reaction between hydroxyl groups and epichlorohydrin. Ultimately, the synergistic effect of the three-step reaction increases the epoxy value of the final product. Detailed Implementation

[0054] The present invention will be further described below with reference to specific embodiments, but is not limited to the contents of the specification. Unless otherwise specified, all "parts" mentioned in the embodiments of the present invention are parts by weight. All reagents used are commercially available in the art.

[0055] The enzymatically hydrolyzed lignin was obtained from Hubei Shouding Industrial Co., Ltd., using a solvent method to extract it from the enzymatic hydrolysis residue of functional polysaccharides prepared by fermentation of reed straw.

[0056] The linear phenolic epoxy resin BNE200, sourced from Jining Fangyu Chemical Co., Ltd., has an epoxy value of 0.48.

[0057] The accelerator DYHARD UR400 is from Meryan Chemical.

[0058] Fiberglass base fabric 2116, weight 105g / m² 2 It has a thickness of 0.1mm and comes from Taishan Fiberglass Co., Ltd.

[0059] Example 1

[0060] 1) Mix 1 part by mass of enzymatically hydrolyzed lignin with 3 parts by mass of phenol and 0.15 parts by mass of 72wt% sulfuric acid solution, heat to 90℃ and react for 2 hours. Dissolve the resulting mixture in acetone, pour into ice water to precipitate, wash three times with hot water at 65℃, filter, and dry at 40℃ and vacuum degree of 0.02MPa for 2 hours to obtain phenolic lignin.

[0061] 2) Under a nitrogen atmosphere, 1 part by mass of phenolic lignin, 0.02 moles of mercaptopropionic acid, and 0.08 parts by mass of boron trifluoride were dissolved in 4 parts by mass of methyl ethyl ketone. The mixture was heated to reflux and reacted for 6 hours. The mixture was then concentrated by distillation, poured into ice water to precipitate, washed three times with water, filtered, and dried at 40°C and a vacuum of 0.02 MPa for 2 hours to obtain mercapto-substituted lignin.

[0062] 3) Dissolve 1 part by mass of mercapto-modified lignin, 2.0 parts by mass of glycidyl methacrylate, and 0.15 parts by mass of azobisisobutyronitrile in 5 parts by mass of dioxane. Perform mercapto-alkenyl addition reaction at 80℃ for 3 h. Distill under reduced pressure at 50℃ and 0.08 MPa for 1 h. Redissolve in ethyl acetate, wash 3 times with hot water at 40℃, separate and combine the organic phases, dry with anhydrous magnesium sulfate, and distill under reduced pressure at 40℃ and 0.09 MPa for 2 h to obtain enzymatically hydrolyzed lignin-based epoxy resin.

[0063] 4) Mix 40 parts by weight of enzymatically hydrolyzed lignin-based epoxy resin, 10 parts by weight of linear phenolic epoxy resin BNE200, 4 parts by weight of dicyandiamide, 1.5 parts by weight of accelerator DYHARD UR400, and 50 parts by weight of an organic solvent composed of acetone and propylene glycol methyl ether in a volume ratio of 1:1 to obtain a glass fiberboard adhesive containing enzymatically hydrolyzed lignin-based epoxy resin.

[0064] 5) Impregnate the fiberglass base fabric 2116 in a fiberglass board adhesive solution containing enzymatically hydrolyzed lignin-based epoxy resin, extrude it, dry it at 160℃ for 5 min, and cut it into 20cm×20cm pieces to obtain a semi-cured sheet with a fiberglass base fabric content of 60wt%; stack 4 semi-cured sheets, hot press them in sections: 140℃ / 1.5MPa / 20min, 180℃ / 3MPa / 30min, and cool them naturally to room temperature to obtain a 0.48mm fiberglass board.

[0065] Example 2

[0066] The rest is the same as in Example 1, except that in step 2), 4-mercaptobutyric acid is used instead of mercaptopropionic acid in an equimolar amount.

[0067] Example 3

[0068] The rest is the same as in Example 1, except that in step 2), 5-mercaptovalerate is used instead of mercaptopropionic acid.

[0069] Example 4

[0070] The rest is the same as in Example 1, except that in step 1), the amount of phenol used is 1.5 parts by mass.

[0071] Example 5

[0072] The rest is the same as in Example 1, except that in step 2), the amount of 4-mercaptobutyric acid used is 0.01 moles.

[0073] Example 6

[0074] The rest is the same as in Example 1, except that in step 3), the amount of glycidyl methacrylate used is 1.6 parts by weight.

[0075] Example 7

[0076] The rest is the same as in Example 1, except that in step 3), glycidyl acrylate is used instead of glycidyl methacrylate in equal mass.

[0077] Example 8

[0078] The rest is the same as in Example 1, except that in step 4), the amount of enzymatically hydrolyzed lignin-based epoxy resin used is 30 parts by weight.

[0079] Example 9

[0080] The rest is the same as in Example 1, except that in step 3), 1 part by mass of mercapto-modified lignin, 2.0 parts by mass of glycidyl methacrylate, and 0.05 parts by mass of dimethyl benzoate are dissolved in 5 parts by mass of dioxane and reacted under ultraviolet light irradiation at 40°C and 1500W for 20 minutes to carry out mercapto-alkenyl addition reaction. The mixture is then distilled under reduced pressure at 50°C and 0.08MPa for 1 hour, redissolved in ethyl acetate, washed three times with hot water at 40°C, the organic phases are separated and combined, dried with anhydrous magnesium sulfate, and distilled under reduced pressure at 40°C and 0.09MPa for 2 hours to obtain enzymatically hydrolyzed lignin-based epoxy resin.

[0081] Example 10

[0082] 1) Mix 1 part by mass of enzymatically hydrolyzed lignin with 3 parts by mass of o-cresol and 0.15 parts by mass of 72wt% sulfuric acid solution, heat to 80℃ and react for 4 hours. Dissolve the resulting mixture in acetone, pour into ice water to precipitate, wash three times with hot water at 65℃, filter, and dry at 40℃ and vacuum degree of 0.02MPa for 2 hours to obtain phenolic lignin.

[0083] 2) Under a nitrogen atmosphere, 1 part by mass of phenolic lignin, 0.02 moles of 4-mercaptobutyric acid, and 0.05 parts by mass of boron trifluoride were dissolved in 4 parts by mass of methyl ethyl ketone. The mixture was heated to reflux and reacted for 6 hours. The mixture was then concentrated by distillation, poured into ice water to precipitate, washed three times with water, filtered, and dried at 40°C and a vacuum of 0.02 MPa for 2 hours to obtain mercapto-substituted lignin.

[0084] 3) Dissolve 1 part by mass of mercapto-modified lignin, 2.0 parts by mass of glycidyl methacrylate, and 0.15 parts by mass of azobisisobutyronitrile in 5 parts by mass of dioxane. Perform mercapto-alkenyl addition reaction at 80℃ for 3 h. Distill under reduced pressure at 50℃ and 0.08 MPa for 1 h. Redissolve in ethyl acetate, wash 3 times with hot water at 40℃, separate and combine the organic phases, dry with anhydrous magnesium sulfate, and distill under reduced pressure at 40℃ and 0.09 MPa for 2 h to obtain enzymatically hydrolyzed lignin-based epoxy resin.

[0085] 4) Mix 40 parts by weight of enzymatically hydrolyzed lignin-based epoxy resin, 20 parts by weight of linear phenolic epoxy resin BNE200, 4 parts by weight of dicyandiamide, 1.5 parts by weight of accelerator DYHARD UR300, and 50 parts by weight of an organic solvent composed of acetone and propylene glycol methyl ether in a volume ratio of 1:1 to obtain a glass fiberboard adhesive containing enzymatically hydrolyzed lignin-based epoxy resin.

[0086] 5) Impregnate the fiberglass base fabric 2116 in a fiberglass board adhesive solution containing enzymatically hydrolyzed lignin-based epoxy resin, extrude it, dry it at 160℃ for 5 min, and cut it into 20cm×20cm pieces to obtain a semi-cured sheet with a fiberglass base fabric content of 60wt%; stack 4 semi-cured sheets, hot press them in sections: 140℃ / 1.5MPa / 20 min, 180℃ / 3MPa / 30 min, and cool them naturally to room temperature to obtain a 0.47mm fiberglass board.

[0087] Comparative Example 1

[0088] The rest is the same as in Example 1, except that in step 2), 6-mercaptohexanoic acid is used instead of mercaptopropionic acid.

[0089] Comparative Example 2

[0090] The rest is the same as in Example 1, except that steps 1)-3) are not used, and the epoxy resin prepared in Example 1 of patent CN106883376B is used to replace the enzymatic hydrolysis of lignin-based epoxy resin in step 4).

[0091] The materials prepared in the above examples and comparative examples were subjected to the following performance tests:

[0092] Epoxy value: The prepared enzymatically hydrolyzed lignin-based epoxy resin was tested according to the standard GB / T1677-1981 "Determination of epoxy value of plasticizer (hydrochloric acid-acetone method)".

[0093] Tensile strength: For fiberglass boards, the test shall be conducted in accordance with the standard GB / T 1447-2005 Test Method for Tensile Properties of Fiber Reinforced Plastics.

[0094] Bending strength: For fiberglass boards, the bending properties test shall be conducted in accordance with the standard GB / T 1447-2005 Test Method for Fiber Reinforced Plastics.

[0095] Table 1 Performance Test Results

[0096] .

[0097] As can be seen from the performance test results in Table 1, the enzymatic hydrolyzed lignin-based epoxy resin prepared by this invention has a high epoxy value, and the fiberglass board prepared with it as the main material has excellent mechanical properties.

[0098] Furthermore, the bending performance test results of Examples 1-4 and Comparative Example 1 show that when the number of carbon atoms in the thiol fatty acid is C3-C5, the bending modulus decreases with the increase of the number of carbon atoms, that is, the resistance to deformation weakens and the bending strength decreases. When the number of carbon atoms continues to increase to C6, the bending strength of the fiberglass board decreases significantly, and the bending modulus is low, indicating poor resistance to deformation. It is speculated that the flexible carbon chain has hindered the transfer of load, weakening the reinforcing effect and resistance to deformation of the enzymatically hydrolyzed lignin-based epoxy resin.

[0099] The above detailed description is a specific description of one of the feasible embodiments of the present invention. This embodiment is not intended to limit the patent scope of the present invention. All equivalent implementations or modifications that do not depart from the present invention should be included within the scope of the technical solution of the present invention.

Claims

1. A method for preparing an enzymatically hydrolyzed lignin-based epoxy resin, characterized in that, Includes the following steps: 1) Mix enzymatically hydrolyzed lignin with organic phenol and sulfuric acid solution, and heat to react to obtain phenolic lignin; 2) Under an inert atmosphere, phenolic lignin, C3-C5 thioglycolic acid, and Lewis acid catalyst are dissolved in a solvent and reacted by heating to obtain thioglycolic lignin; 3) Thiolized lignin and unsaturated epoxy compounds undergo a thiol-alkenyl addition reaction under the action of an initiator to obtain enzymatically hydrolyzed lignin-based epoxy resin.

2. The method for preparing enzymatically hydrolyzed lignin-based epoxy resin according to claim 1, characterized in that, In step 2), the molar amount of the C3-C5 thioglycolic acid, the mass of the phenolic lignin, and the mass ratio of the Lewis acid catalyst are 0.01-0.02 mol: 1 g: 0.05-0.08 g.

3. The method for preparing enzymatically hydrolyzed lignin-based epoxy resin according to claim 1, characterized in that, In step 2), the C3-C5 thioglycolic acid is selected from one or more combinations of mercaptopropionic acid, 4-mercaptobutyric acid, 3-mercaptobutyric acid, 3-mercaptoisobutyric acid, 2-mercaptobutyric acid, and 5-mercaptovalerate. The Lewis acid catalyst is selected from one or more combinations of titanium tetrachloride, aluminum chloride, ferric chloride, tin chloride, and boron trifluoride.

4. The method for preparing enzymatically hydrolyzed lignin-based epoxy resin according to claim 1, characterized in that, In step 3), the mass ratio of the thiolized lignin, unsaturated epoxy compound, and initiator is 1:1.6-2.0:0.05-0.

15.

5. The method for preparing enzymatically hydrolyzed lignin-based epoxy resin according to claim 1, characterized in that, In step 3), the initiator is selected from photoinitiators or thermal initiators; the photoinitiator reaction conditions are ultraviolet irradiation at -5℃ to 40℃ and a power of 800-3000W for 10-30 minutes; preferably, the photoinitiator is selected from one or more combinations of benzoin dimethyl ether, 1-hydroxycyclohexylphenyl ketone, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, 2-hydroxy-2-methylphenylacetone, isooctyl p-dimethylaminobenzoate, and methyl benzoylformate; or The thermal initiation reaction is carried out at 60-80℃ for 2-5 hours; preferably, the thermal initiator is selected from one or more combinations of azobisisobutyronitrile, azobisisoheptanenitrile, azobiscyanopentanoic acid, dimethyl azobisisobutyrate, 2,2'-azobis(4-methoxy-2,4-dimethylpentanenitrile), potassium persulfate, and ammonium persulfate.

6. The method for preparing enzymatically hydrolyzed lignin-based epoxy resin according to claim 1, characterized in that, In step 3), the unsaturated epoxy compound is selected from one or more combinations of glycidyl acrylate, (3,4-epoxycyclohexyl) methyl acrylate, allyl glycidyl ether, and glycidyl methacrylate.

7. A fiberglass board adhesive, comprising the following raw materials in parts by weight: 30-40 parts of enzymatically hydrolyzed lignin-based epoxy resin prepared by any one of claims 1-6, 10-20 parts of linear phenolic epoxy resin, 2-4 parts of curing agent, 0.5-1.5 parts of accelerator, and 40-60 parts of organic solvent.

8. The fiberglass board adhesive according to claim 7, characterized in that, The linear phenolic epoxy resin has an epoxy value of 0.46-0.60; the curing agent is selected from one or more of amine curing agents, acid anhydride curing agents, and dicyandiamide curing agents.

9. The method for preparing the fiberglass board adhesive according to claim 7 or 8, characterized in that, Includes the following steps: The enzymatically hydrolyzed lignin-based epoxy resin, linear phenolic epoxy resin, curing agent, accelerator, and organic solvent are mixed to obtain a fiberglass board adhesive containing the enzymatically hydrolyzed lignin-based epoxy resin.

10. A method for preparing a fiberglass board, characterized in that, Includes the following steps: The fiberglass base fabric is impregnated in the fiberglass board adhesive as described in any one of claims 7 or 8, and then extruded, dried, and cut to obtain a semi-cured sheet; N semi-cured sheets are stacked, hot-pressed, and cooled to obtain a fiberglass board.