A high-strength mildew-proof plant protein adhesive and its preparation method and application

Abstract

The present invention belongs to the technical field of adhesives, and specifically relates to a high-strength mildew-proof plant protein adhesive and its preparation method and application. It includes the following components: 10-30% plant protein, 50-80% water, 1-6% thickener, 0.25-2.5% activator, 0.25-2.5% stabilizer, 1-4% polymer mildew-proof agent, 0.25-0.5% nano-enhancer and 0-7% pH regulator. The plant protein adhesive of the present invention can be cured under ambient temperature conditions and achieve water-resistant bonding, and has high viscosity, and the adhesive does not contain toxic and harmful substances such as free formaldehyde and free benzene compounds, so that the adhesive is completely green, effectively solving the volatile organic pollution problem caused by artificial boards and their wood products; and the present invention effectively utilizes agricultural and forestry biomass raw materials, realizes green energy conservation and emission reduction in the plywood industry, and has great application value.

Description

Technical Field

[0001] The invention relates to the technical field of adhesives, and in particular to a high-strength mildew-proof plant protein adhesive and a preparation method and application thereof. Background Art

[0002] With the reduction of forest resources and the shortage of wood, artificial boards have become an indispensable material in human production and life. The artificial board industry has developed rapidly. In 2023, my country's artificial board production has exceeded 330 million cubic meters, ranking first in the world. At present, formaldehyde-based synthetic resins are widely used as adhesives in the production of artificial boards, especially urea-formaldehyde resins and their modified products. However, artificial boards and their derivatives made with these resin adhesives will continuously release formaldehyde, pollute indoor air, and pose a threat to human health, becoming the focus of social attention.

[0003] In recent years, my country's wood-based panel production technology has made significant progress, and a lot of research has been conducted on controlling formaldehyde emissions. For example, by adjusting the molar ratio of formaldehyde to urea, adding resorcinol, melamine modification, and using formaldehyde scavengers, the free formaldehyde content of urea-formaldehyde resin has been successfully reduced. In addition, post-treatment of wood-based panels with active molecules such as ammonia and ozone has also achieved certain results. However, these measures have only reduced formaldehyde emissions to a certain extent and have failed to fundamentally solve the formaldehyde pollution problem. The main reason is that as long as resin adhesives containing toxic chemical raw materials such as formaldehyde are used, the products will inevitably contain harmful gases such as formaldehyde. No matter what kind of modification is performed, it is only a temporary solution. At present, the raw materials of formaldehyde-based resin adhesives used in wood-based panels mainly come from petrochemical resources. With concerns about the non-renewable nature of petrochemical resources and the pursuit of a green ecological environment, sustainable development has received increasing attention from society. Therefore, how to use biomass resources to develop environmentally friendly bio-based adhesives has become a research hotspot and development trend in the field of wood-based panel adhesives. Among them, adhesives made from non-toxic soybean protein are one of the important biomass adhesives. Since the 1980s, a lot of research has been done on soybean protein adhesives at home and abroad, and significant progress has been made. It is reported that some modified soybean protein adhesives have been industrialized and applied in plywood-type artificial board products.

[0004] Due to the large molecular weight, complex structure and components of soy protein, it is difficult to chemically modify or modify it. Traditional modification methods cannot ensure that soy protein adhesives have good water resistance and bonding strength; however, the use of cross-linking agent enhanced modification methods can significantly improve the performance of soy protein adhesives. These cross-linking agents can be added during the preparation of the adhesive or directly mixed with soy protein; common effective cross-linking agents include various epoxy-containing glycidyl ethers, epoxides, epoxy resins, etc., various isocyanate substances containing isocyanate groups, acrylic or acrylamide compounds, and various aldehydes and their derivatives such as hydroxymethyl urea, sodium formaldehyde disulfide, glutaraldehyde, glyoxal, glyceraldehyde, urea-formaldehyde resin, phenolic resin, hydroxymethyl phenol, etc.; for example: Application No. 201210277 The composite crosslinking agent used in the invention patent No. 994.2 contains polyvinyl alcohol, isocyanate and amide polymers; in the invention patent No. 201210381979.2, the crosslinking agent is polymethylene polyphenyl isocyanate; in the invention patent No. 201310336430.6, the crosslinking agent is melamine-formaldehyde resin; in the invention patent No. 201610372058.8, the crosslinking agent used is aldehyde derivative resin (tannin-resorcinol-glutaraldehyde prepolymer); and the application No. 201210480566.X uses glutaraldehyde as the crosslinking agent; however, in the above-mentioned technologies, due to the low reactivity of plant protein raw materials, most plant protein adhesives need to be cured at high temperatures to promote covalent crosslinking reactions and achieve strong wet bonding strength. At present, most room temperature cross-linking methods for protein-based adhesives involve free radical polymerization of olefins and aldehyde-amine condensation reactions; however, these methods inevitably leave residual organic solvents or toxic aldehydes; in addition, since residual moisture that is difficult to evaporate quickly at ambient temperature will accelerate the mold growth rate of plant protein adhesives, it is still difficult to achieve green water-resistant bonding curing and mildew resistance of plant protein adhesives under ambient temperature conditions. Summary of the invention

[0005] One object of the present invention is to provide a high-strength mildew-proof plant protein adhesive to solve the problems that existing plant protein adhesives need to be prepared at high temperatures, have low bonding strength, and have residual toxic substances and low toughness. The plant protein adhesive of the present invention can be cured at ambient temperature and has high bonding strength, no toxic substances remain, and realizes green and environmentally friendly production in the wood-based panel industry.

[0006] The second object of the present invention is to provide a method for preparing a high-strength mildew-proof plant protein adhesive.

[0007] The third object of the present invention is to provide a high-strength mildew-proof plant protein adhesive for use in the preparation process of artificial boards.

[0008] In order to achieve the first object of the invention, the present invention can be implemented by the following technical scheme: a high-strength mildew-proof plant protein adhesive, which comprises the following components in terms of mass percentage:

[0009] 10-30% vegetable protein, 50-80% water, 1-6% thickener, 0.25-2.5% activator, 0.25-2.5% stabilizer, 1-4% polymer mildew inhibitor, 0.25-0.5% nano enhancer and 0-7% pH adjuster.

[0010] The beneficial effects of adopting the above technical scheme are as follows: (1) The formula components contained in the high-strength mildew-proof plant protein adhesive of the present invention can enable the adhesive to cure under ambient temperature conditions and achieve water-resistant bonding without the need for heating equipment, which is beneficial to energy conservation and emission reduction in the plywood industry.

[0011] (2) The raw materials used in the plant protein adhesive of the present invention do not contain harmful substances such as formaldehyde, benzene compounds, organic solvents, etc., and the activators, stabilizers, mildew inhibitors and thickeners used in the raw materials are all conventional non-toxic chemical reagents; therefore, the artificial boards prepared with the plant protein adhesive will not release volatile organic compounds such as formaldehyde and organic benzene compounds, which completely solves the volatile organic compound pollution problem caused by artificial boards and their wood products in indoor environments.

[0012] (3) The polymer mildew preventers used in the plant protein adhesive of the present invention have excellent antibacterial and mildew proof properties, and can effectively inhibit the growth of mold and bacteria, thereby extending the service life of the artificial board; the polymer mildew preventers are relatively environmentally friendly, have little impact on the human body and the environment, and meet the requirements of green production; these polymer mildew preventers can form a good composite effect with the adhesive, and improve the performance of the adhesive, including enhancing the bonding strength, water resistance and initial adhesion.

[0013] (4) In the plant protein adhesive of the present invention: first, the carboxyl group of the carboxyl-containing plant protein is activated by an activator to form an easily hydrolyzed ester, and then the stabilizer and the ester undergo an ester exchange reaction to generate a stable active intermediate ester; the active intermediate ester has high activity and can react with the amino group of the plant protein itself at ambient temperature to form a covalent cross-linked bond constructed by an amide bond. At the same time, a thickener with a negative charge or hydrogen bond donor and a polymer mildew inhibitor with a positive charge or hydrogen bond acceptor are introduced into the adhesive. The thickener and the polymer mildew inhibitor quickly form a non-covalent cross-linked structure through hydrogen bonds or electrostatic interactions. This structure not only provides a certain binding force for the uncured adhesive, but also promotes the discharge of moisture, thereby further enhancing the water-resistant bonding performance of the plant protein adhesive under ambient temperature curing conditions. In addition, the nano-enhancer is introduced into the adhesive system structure through the hydrogen bond and electrostatic interaction provided by the thickener or polymer mildewproof agent. On the one hand, the embedding of the high-strength nano-enhancer can reinforce the structure of the adhesive. On the other hand, the nano-enhancer and the adhesive form a microphase separation system, which can dissipate energy and thus improve the toughness of the adhesive. The water-resistant bonding strength of the plywood prepared by the plant protein adhesive of the present invention under ambient temperature curing conditions meets the requirements of Class II plywood specified in the national standard GB / T9846-2015 "Ordinary Plywood".

[0014] In a specific embodiment of the present invention, the plant protein comprises biomass raw materials with a protein content of not less than 20% and their processing residues, which is a mixture of one or more of defatted soybean flour, defatted soybean meal, soy protein isolate, defatted peanut flour, defatted cottonseed meal, defatted tea cake meal or defatted biofuel almond flour.

[0015] In a specific embodiment of the present invention, the thickener is one or a mixture of polyvinyl alcohol, polyethylene glycol, gelatin, xanthan gum, sodium hyaluronate or hyaluronic acid.

[0016] In a specific embodiment of the present invention, the activator is one or a mixture of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, N,N'-dicyclohexylcarbodiimide, N,N,N,N'-tetramethyl-O-(7-azabenzotriazole-1-yl)urea hexafluorophosphate, 2-(1H-benzotriazol L-1-yl)-1,1,3,3-tetramethyluronium tetrafluoroborate or (2-oxime-ethyl cyanoacetate)-N,N-dimethyl-morpholinyluronium hexafluorophosphate.

[0017] In a specific embodiment of the present invention, the stabilizer is one or a mixture of 1-hydroxybenzotriazole, 4-dimethylaminopyridine or diisopropylethylamine.

[0018] In a specific embodiment of the present invention, the polymer mildew inhibitor is one or a mixture of tannic acid, chitosan or polyethyleneimine.

[0019] In a specific embodiment of the present invention, the nano-enhancing agent is one or a mixture of nano-cellulose, nano-silicon dioxide, nano-calcium carbonate or nano-montmorillonite, and its particle size is 50-500 nm.

[0020] In a specific embodiment of the present invention, the pH adjuster is one or a mixture of hydrochloric acid, citric acid, acetic acid, formic acid, sulfuric acid or phosphoric acid.

[0021] In order to achieve the second invention object, the present invention can be implemented by the following technical scheme: providing a method for preparing a high-strength mildew-proof plant protein adhesive, comprising the following steps:

[0022] (1) Add thickener and water into the reactor according to the mass ratio, stir and react at 5-40°C for 30-60 minutes, then add activator and stabilizer, and stir at 5-40°C for 5-20 minutes;

[0023] (2) Add the nano-enhancer and water into a reaction kettle according to the mass ratio, homogenize at 5-40°C for 30-60 minutes, adjust the pH value of the solution to 4-5 when the mildew inhibitor is chitosan, and do not need to adjust the pH value when other mildew inhibitors are used, then add the polymer mildew inhibitor, and stir the reaction at 5-40°C for 30-60 minutes;

[0024] (3) Add the mixture obtained in step (1), the mixture obtained in step (2) and the plant protein into a reaction kettle, stir them uniformly at 5-40° C. and 60-100 r / min to obtain a high-strength mildew-proof plant protein adhesive.

[0025] The beneficial effect of adopting the above technical solution is that the plant protein adhesive of the present invention can replace conventional formaldehyde-containing artificial board adhesives without changing the existing artificial board production equipment and production processes; therefore, there is no need to increase equipment investment or retrain technical workers, and it is suitable for industrial production and wide application.

[0026] In order to achieve the third invention objective, the present invention provides the use of a high-strength mildew-proof plant protein adhesive in a process for preparing artificial boards.

[0027] The beneficial effects of adopting the above technical solution are as follows: the plant protein adhesive of the present invention can replace conventional formaldehyde-containing artificial board adhesives without changing the existing artificial board production equipment and production process; therefore, there is no need to increase equipment investment, and it is suitable for industrial production and wide application. The water-resistant bonding strength of the plywood prepared by the plant protein adhesive of the present invention under ambient temperature curing conditions meets the requirements of Class II plywood specified in the national standard GB / T9846-2015 "Ordinary Plywood", and has good performance and application prospects. DETAILED DESCRIPTION

[0028] To make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0029] The main reagents used in the following examples of the present invention are as follows: polyvinyl alcohol, polyethylene glycol, gelatin, xanthan gum, sodium hyaluronate, hyaluronic acid, tannic acid, chitosan, polyethyleneimine, nanocellulose, nano-calcium carbonate, nano-silicon dioxide, nano-montmorillonite, industrial grade, commercially available.

[0030] 1-Ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, N,N'-dicyclohexylcarbodiimide, N,N,N',N'-tetramethyl-O-(7-azabenzotriazol-1-yl) uron hexafluorophosphate, 2-(1H-benzotriazol L-1-yl)-1,1,3,3-tetramethyluronium tetrafluoroborate, (2-hydroxy-ethyl cyanoacetate)-N,N-dimethyl-morpholinyluronium hexafluorophosphate, 1-hydroxybenzotriazole, 4-dimethylaminopyridine, diisopropylethylamine, and hydrochloric acid were all analytically pure and purchased from Sinopharm Chemical Reagent Co., Ltd.

[0031] The names, models and manufacturers of the instruments used in the present invention are shown in Table 1.

[0032] Table 1 Main instruments and equipment

[0033]

[0034] Example 1

[0035] A high-strength mildew-proof plant protein adhesive, with the total mass of the adhesive raw material being 100%, the components and mass percentages in the raw material are as follows: 25% plant protein, 68% water, 3% polyvinyl alcohol, 0.5% 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride, 0.25% 1-hydroxybenzotriazole, 3% tannic acid and 0.25% nanocellulose;

[0036] The preparation method of the above-mentioned plant protein adhesive comprises the following steps: (1) adding 3 g of polyvinyl alcohol and 30 g of water into a reaction kettle, stirring at 20°C for 30 minutes, and then adding 0.5 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 0.25 g of 1-hydroxybenzotriazole, and stirring at 20°C for 5 minutes.

[0037] (2) 0.25 g of nanocellulose and 38 g of water were placed in a reactor and homogenized at 20°C for 60 minutes without adjusting the pH. Subsequently, 3 g of tannic acid was added and stirred at 20°C for 30 minutes.

[0038] (3) The mixture obtained in step (1), the anti-mold solution obtained in step (2) and 25 g of defatted soybean meal were put into a reactor and mechanically stirred at 100 r / min at 20° C. to obtain a high-strength anti-mold plant protein adhesive that cures at ambient temperature. The main technical indicators of the obtained plant protein adhesive are shown in Table 2.

[0039] Example 2

[0040] A high-strength mildew-proof plant protein adhesive, taking the total mass of the adhesive raw material as 100%, the components and mass percentages in the raw material are as follows: 30% plant protein, 60.25% water, 4% polyethylene glycol,

[0041] N,N'-dicyclohexylcarbodiimide 1%, 1-hydroxybenzotriazole 0.25%, tannic acid 4%, and nanocellulose 0.5%;

[0042] The preparation method of the plant protein adhesive comprises the following steps: (1) adding 4 g of polyethylene glycol and 30 g of water into a reaction kettle, stirring at 20° C. for 30 minutes, and then adding 1 g of N,N'-dicyclohexylcarbodiimide and 0.25 g of 1-hydroxybenzotriazole, stirring at 20° C. for 5 minutes.

[0043] (2) 0.5 g of nanocellulose and 30.25 g of water were placed in a reactor and homogenized at 20°C for 60 minutes without adjusting the pH. Subsequently, 4 g of tannic acid was added and stirred at 20°C for 30 minutes.

[0044] (3) The mixture obtained in step (1), the anti-mold solution obtained in step (2) and 30 g of defatted peanut powder were put into a reactor and mechanically stirred at 100 r / min at 20° C. to obtain a high-strength anti-mold plant protein adhesive that cures at ambient temperature. The main technical indicators of the obtained plant protein adhesive are shown in Table 2.

[0045] Example 3

[0046] A high-strength mildew-proof plant protein adhesive, taking the total mass of the adhesive raw material as 100%, the components and mass percentages in the raw material are as follows: 10% plant protein, 84.25% water, 2% gelatin,

[0047] N,N'-dicyclohexylcarbodiimide 1%, 1-hydroxybenzotriazole 0.5%, tannic acid 2%, and nanocellulose 0.25%;

[0048] The preparation method of the above-mentioned plant protein adhesive comprises the following steps: (1) adding 2 g of gelatin and 30 g of water into a reaction kettle, stirring at 20°C for 60 minutes, and then adding 1 g of N,N'-dicyclohexylcarbodiimide and 0.5 g of 1-hydroxybenzotriazole, stirring at 20°C for 5 minutes.

[0049] (2) 0.25 g of nanocellulose and 54.25 g of water were placed in a reactor and homogenized at 20°C for 60 minutes without adjusting the pH. Subsequently, 2 g of tannic acid was added and stirred at 20°C for 30 minutes.

[0050] (3) The mixture obtained in step (1), the anti-mold solution obtained in step (2) and 10 g of soy protein isolate were put into a reactor and mechanically stirred at 100 r / min at 20° C. to obtain a high-strength anti-mold plant protein adhesive that cures at ambient temperature. The main technical indicators of the obtained plant protein adhesive are shown in Table 2.

[0051] Example 4

[0052] A high-strength mildew-proof plant protein adhesive. Taking the total mass of the adhesive raw materials as 100%, the components and mass percentages in the raw materials are as follows: 25% plant protein, 69.25% water, 2% xanthan gum, 1% N,N,N,N′-tetramethyl-O-(7-azabenzotriazole-1-yl)urea hexafluorophosphate, 0.5% 1-hydroxybenzotriazole, 2% chitosan, 0.25% nano calcium carbonate and an appropriate amount of hydrochloric acid.

[0053] The preparation method of the plant protein adhesive comprises the following steps: (1) adding 2 g of xanthan gum and 30 g of water into a reaction kettle, stirring at 20° C. for 30 minutes, and then adding 1 g of N,N,N,N′-tetramethyl-O-(7-azabenzotriazole-1-yl)urea hexafluorophosphate and 0.5 g of 1-hydroxybenzotriazole, stirring at 20° C. for 5 minutes.

[0054] (2) 0.25 g of nano calcium carbonate and 39.25 g of water were placed in a reactor and homogenized at 20°C for 60 minutes. Hydrochloric acid was added to adjust the pH to 4.0-5.0, and then 2 g of chitosan was added. The mixture was stirred at 20°C for 60 minutes.

[0055] (3) The mixture obtained in step (1), the anti-mold solution obtained in step (2) and 25 g of defatted camellia oleifera cake powder were placed in a reactor and mechanically stirred at 100 r / min at 20° C. to obtain a high-strength anti-mold plant protein adhesive that cures at ambient temperature. The main technical indicators of the obtained plant protein adhesive are shown in Table 2.

[0056] Example 5

[0057] A high-strength mildew-proof plant protein adhesive. Taking the total mass of the adhesive raw materials as 100%, the components and mass percentages in the raw materials are as follows: 25% plant protein, 71% water, 1% sodium hyaluronate, 0.5% 2-(1H-benzotriazol L-1-yl)-1,1,3,3-tetramethyluronium tetrafluoroborate, 0.25% 4-dimethylaminopyridine, 2% chitosan, 0.25% nano calcium carbonate and an appropriate amount of hydrochloric acid.

[0058] The preparation method of the above-mentioned plant protein adhesive comprises the following steps: (1) adding 1 g of sodium hyaluronate and 30 g of water into a reaction kettle, stirring at 20°C for 30 minutes, and then adding 0.5 g of 2-(1H-benzotriazol L-1-yl)-1,1,3,3-tetramethyluronium tetrafluoroborate and 0.25 g of 4-dimethylaminopyridine, and stirring at 20°C for 5 minutes.

[0059] (2) 0.25 g of nano calcium carbonate and 41 g of water were placed in a reaction kettle and homogenized at 20°C for 60 minutes. Hydrochloric acid was added to adjust the pH to 4.0-5.0, and then 2 g of chitosan was added. The mixture was stirred at 20°C for 60 minutes.

[0060] (3) The mixture obtained in step (1), the anti-mold solution obtained in step (2) and 25 g of defatted soybean meal were put into a reactor and mechanically stirred at 100 r / min at 20° C. to obtain a high-strength anti-mold plant protein adhesive that cures at ambient temperature. The main technical indicators of the obtained plant protein adhesive are shown in Table 2.

[0061] Example 6

[0062] A high-strength mildew-proof plant protein adhesive. Taking the total mass of the adhesive raw materials as 100%, the components and mass percentages in the raw materials are as follows: 18% plant protein, 75% water, 2% sodium hyaluronate, 0.5% (2-oxime-ethyl cyanoacetate)-N,N-dimethyl-morpholinyl urea hexafluorophosphate, 0.25% 1-hydroxybenzotriazole, 4% polyethyleneimine and 0.25% nano-silicon dioxide.

[0063] The preparation method of the above-mentioned plant protein adhesive comprises the following steps: (1) adding 2 g of sodium hyaluronate and 30 g of water into a reaction kettle, stirring at 20°C for 30 minutes, and then adding 0.5 g of (2-hydroxy-ethyl cyanoacetate)-N,N-dimethyl-morpholinyl urea hexafluorophosphate and 0.25 g of 1-hydroxybenzotriazole, and stirring at 20°C for 5 minutes.

[0064] (2) 0.25 g of nano-silicon dioxide and 45 g of water were placed in a reaction kettle and homogenized at 20°C for 30 minutes without adjusting the pH. Subsequently, 4 g of polyethyleneimine was added and stirred at 20°C for 30 minutes.

[0065] (3) The mixture obtained in step (1), the anti-mold solution obtained in step (2) and 18 g of defatted biofuel almond powder were put into a reactor and mechanically stirred at 100 r / min at 20°C to obtain a high-strength anti-mold plant protein adhesive that cures at ambient temperature. The main technical indicators of the obtained plant protein adhesive are shown in Table 2.

[0066] Example 7

[0067] A high-strength mildew-proof plant protein adhesive. Taking the total mass of the adhesive raw materials as 100%, the components and mass percentages in the raw materials are as follows: 20% plant protein, 74.75% water, 2% sodium hyaluronate, 0.5% 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride, 0.5% diisopropylethylamine, 2% polyethyleneimine and 0.25% nano-silicon dioxide.

[0068] The preparation method of the above-mentioned plant protein adhesive comprises the following steps: (1) adding 2 g of sodium hyaluronate and 30 g of water into a reaction kettle, stirring at 20°C for 30 minutes, and then adding 0.5 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 0.5 g of diisopropylethylamine, stirring at 20°C for 5 minutes.

[0069] (2) 0.25 g of nano-silicon dioxide and 44.75 g of water were added to a reaction kettle and homogenized at 20°C for 30 minutes without adjusting the pH. Subsequently, 2 g of polyethyleneimine was added and stirred at 20°C for 30 minutes.

[0070] (3) The mixture obtained in step (1), the anti-mildew solution obtained in step (2) and 20 g of defatted cottonseed meal were placed in a reactor and mechanically stirred at 100 r / min at 20° C. to obtain a high-strength anti-mildew plant protein adhesive that cures at ambient temperature. The main technical indicators of the obtained plant protein adhesive are shown in Table 2.

[0071] Example 8

[0072] A high-strength mildew-proof plant protein adhesive. Taking the total mass of the adhesive raw materials as 100%, the components and mass percentages in the raw materials are as follows: 22% plant protein, 70.25% water, 3% sodium hyaluronate, 1% 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride, 0.5% 1-hydroxybenzotriazole, 3% polyethyleneimine and 0.25% nano silicon dioxide.

[0073] The preparation method of the above-mentioned plant protein adhesive comprises the following steps: (1) adding 3 g of sodium hyaluronate and 30 g of water into a reaction kettle, stirring at 20° C. for 30 minutes, then adding 0.5 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 0.5 g of diisopropylethylamine, and stirring at 20° C. for 5 minutes.

[0074] (2) 0.25 g of nano-silicon dioxide and 40.25 g of water were added to a reaction kettle and homogenized at 20°C for 30 minutes without adjusting the pH. Subsequently, 3 g of polyethyleneimine was added and stirred at 20°C for 30 minutes.

[0075] (3) The mixture obtained in step (1), the anti-mildew solution obtained in step (2) and 20 g of defatted cottonseed meal were placed in a reactor and mechanically stirred at 100 r / min at 20° C. to obtain a high-strength anti-mildew plant protein adhesive that cures at ambient temperature. The main technical indicators of the obtained plant protein adhesive are shown in Table 2.

[0076] Example 9

[0077] A high-strength mildew-proof plant protein adhesive. Taking the total mass of the adhesive raw materials as 100%, the components and mass percentages in the raw materials are as follows: 12% plant protein, 82.25% water, 2% hyaluronic acid, 1% 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, 0.5% diisopropylethylamine, 2% polyethyleneimine and 0.25% nano-montmorillonite.

[0078] The preparation method of the above-mentioned plant protein adhesive comprises the following steps: (1) adding 2 g of sodium hyaluronate and 40 g of water into a reaction kettle, stirring at 20°C for 30 minutes, and then adding 1 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 0.5 g of diisopropylethylamine, stirring at 20°C for 5 minutes.

[0079] (2) 0.25 g of nano-montmorillonite and 42.25 g of water were placed in a reaction kettle and homogenized at 20°C for 30 minutes without adjusting the pH. Subsequently, 2 g of polyethyleneimine was added and stirred at 20°C for 30 minutes.

[0080] (3) The mixture obtained in step (1), the anti-mold solution obtained in step (2) and 12 g of soy protein isolate were put into a reactor and mechanically stirred at 100 r / min at 20° C. to obtain a high-strength anti-mold plant protein adhesive that cures at ambient temperature. The main technical indicators of the obtained plant protein adhesive are shown in Table 2.

[0081] Comparative Example 1

[0082] The ambient temperature curing type mildew-proof plant protein adhesive was prepared in the same manner as in Example 1. The difference was that no activator and stabilizer were added during the preparation process. The main technical indicators of the obtained plant protein adhesive are shown in Table 2.

[0083] Comparative Example 2

[0084] The ambient temperature curing type mildew-proof plant protein adhesive was prepared in the same manner as in Example 1. The difference was that no thickener and nano-enhancer were added during the preparation process. The main technical indicators of the obtained plant protein adhesive are shown in Table 2.

[0085] Comparative Example 3

[0086] The ambient temperature curing type mildew-proof plant protein adhesive was prepared in the same manner as in Example 1. The difference was that no polymer mildew-proof agent was added during the preparation process. The main technical indicators of the obtained plant protein adhesive are shown in Table 2.

[0087] Test example

[0088] In order to verify the performance of the ambient temperature curing mildew-proof plant protein adhesive of the present invention, its application effect on plywood products, and the advantages of the product being green and environmentally friendly and harmless to the human body, the present application conducted the following tests, the specific contents of which are as follows:

[0089] The adhesives prepared using the above Examples 1-9 and Control Examples 1-3 were respectively tested for performance such as solid content, pH value, viscosity and total volatile organic compounds. The application effect of the plant protein adhesive on plywood products was evaluated by preparing 5 layers of eucalyptus plywood and measuring its cold pressing bonding strength and hot pressing bonding strength.

[0090] Among them, the tests of solid content, pH value and viscosity are carried out in accordance with the corresponding test methods specified in GB / T 14074-2006 "Test methods for wood adhesives and resins", and the test of total volatile organic compound content is carried out in accordance with Appendix D.7 of GB / T 33372-2020 "Limits of volatile organic compounds in adhesives". The cured adhesive is placed in a constant temperature and humidity chamber at 30℃ / 95% relative humidity, and the mold growth on the adhesive surface is observed every 24 hours to determine the mildew-proof period of the adhesive.

[0091] The test results are shown in Table 2. The cold pressing time of the slab reflects the curing time of the adhesive. After the plywood is cold pressed for a certain period of time, if there is no debonding after 2 hours of placement, it is considered that the adhesive has been effectively cured. The cold pressing time gradient is set to 10, 20, 30, 40...120 minutes. The veneer used to prepare the 5-layer plywood is a 5-year-old fast-growing eucalyptus veneer (length 600 mm, width 600 mm, thickness 2.0 mm), with a moisture content of 10-20%. The preparation process parameters of the 5-layer plywood are: (1) Gluing: double-sided gluing, the glue amount is 300-350g / m 2 ;(2) Cold pressing parameters: 1h, pressure 0.9MPa, room temperature;

[0092] According to the test method for bonding strength of Class II plywood and the dryer method for formaldehyde emission determination specified in GB / T 17657-2013 "Test methods for physical and chemical properties of wood-based panels and veneer wood-based panels", the bonding strength and formaldehyde emission of five-layer plywood prepared with the plant protein adhesives obtained by the nine example methods and the adhesives obtained by the three comparative example methods were tested, and the results are shown in Table 3.

[0093] Table 2

[0094]

[0095] It can be seen from Table 2 that since the raw materials of the protein adhesive are mainly derived from biomass such as regenerated plant protein, sodium alginate, sodium hyaluronate, etc., the plant protein adhesive prepared by the methods of Examples 1-9 of the present invention and the methods of Comparative Examples 1-3 does not contain toxic and harmful substances such as free formaldehyde and free benzene compounds, making the adhesive completely green.

[0096] The viscosity of the plant protein adhesive prepared by the methods of Examples 1-9 of the present invention is between 9314 and 14241 mPa·s, which is significantly greater than the viscosity of the adhesive prepared by the methods of Control Examples 1, 2 and 3. This is because no activator and stabilizer are used in the method of Control Example 1, and the protein fails to form effective covalent crosslinks at ambient temperature. The methods of Control Examples 2 and 3 lack thickeners or polymer mildew inhibitors, thereby lacking non-covalent crosslinks formed by thickeners and polymer mildew inhibitors. Therefore, the prepared plant protein adhesives have low viscosity and do not form a bulk network molecule with a water-resistant structure.

[0097] When conventional formaldehyde resin is used as an adhesive to prepare plywood, the adhesive needs to be adjusted to improve the initial viscosity of the adhesive. Usually, 30%-40% of the weight of the resin is added to the resin. The protein adhesive prepared by the method of Examples 1-9 of the present invention has a higher viscosity, so that it does not need to add additional flour to have good initial viscosity, further reducing the cost of using the protein adhesive as a glue for plywood. The mildew-proof period of Examples 1-9 is more than 3 times that of Control Example 3. This is because tannic acid, chitosan and polyethyleneimine can inhibit the growth of microorganisms by binding to cell membranes, destroying cell structures, inhibiting metabolic activities and affecting enzyme activity. The adhesives prepared by the methods of Examples 1-9 are all effectively cured within 60 minutes, while the adhesive of Control Group 1 is not effectively cured after 120 minutes because it does not form a covalent cross-linked structure at ambient temperature. Control Groups 2 and 3 lack non-covalent cross-linked structures, and the moisture in the adhesive is discharged slowly, and its curing time is longer than 60 minutes.

[0098] Table 3

[0099]

[0100] As shown in Table 3, the plywood prepared by the plant protein adhesive prepared by the methods of Examples 1-9 of the present invention all have high cold pressing bonding strength, meeting the Class II plywood bonding strength (not less than 0.70 MPa) specified in the national standard GB / T 17657-2013 "Test methods for physical and chemical properties of wood-based panels and veneer wood-based panels". Among them, the adhesives prepared by the methods of Examples 1, 2, and 8 have high cold pressing wet bonding strength, while the cold pressing bonding strength of the plywood prepared by the resin adhesive prepared by the control example method is lower than 0.70 MPa, which does not meet the national standard for Class II plywood.

[0101] The above comprehensive comparative analysis shows that the plant protein adhesives prepared by the methods of Examples 1-9 of the present invention do not contain toxic and harmful substances such as free formaldehyde and free benzene compounds, and the adhesives are completely green and can produce green and environmentally friendly plywood without releasing harmful substances under ambient temperature curing conditions.

[0102] The raw materials used in the present invention are all commonly used raw materials in production in this field, can be obtained from the market, and will not affect the production results; the various equipment used are all conventional equipment used in the production process in this field, and the operation and parameters of each equipment are carried out in accordance with conventional operations, and there is nothing special.

[0103] In summary, the high-strength mildew-proof plant protein adhesive based on ambient temperature curing of the present invention can be cured under ambient temperature conditions and achieve water-resistant bonding, and has high viscosity. The adhesive does not contain toxic and harmful substances such as free formaldehyde and free benzene compounds, making the adhesive completely green and effectively solving the volatile organic compound pollution problem caused by artificial boards and their wood products in indoor environments. In addition, the present invention effectively utilizes the residues generated in the processing of agricultural and forestry biomass raw materials to produce edible oils, biofuels, etc., realizes the comprehensive utilization of resources, effectively increases the added value of agricultural and forestry biomass raw materials, and realizes green energy conservation and emission reduction in the plywood industry, which has huge application value.

Claims

1. A high-strength mildew-proof plant protein adhesive, characterized in that: Calculated by mass percentage, it includes the following components: Plant protein 10-30%, water 50-80%, thickener 1-6%, activator 0.25-2.5%, stabilizer 0.25-2.5%, polymer mildew inhibitor 1-4%, nano-enhancer 0.25-0.5% and pH regulator 0-7%; The thickener is one or a mixture of polyvinyl alcohol, polyethylene glycol, gelatin, xanthan gum, sodium hyaluronate or hyaluronic acid; The activator is one or a mixture of N,N'-dicyclohexylcarbodiimide, N,N,N',N'-tetramethyl-O-(7-azabenzotriazole-1-yl)urea hexafluorophosphate, 2-(1H-benzotriazol L-1-yl)-1,1,3,3-tetramethyluronium tetrafluoroborate or (2-oxime-ethyl cyanoacetate)-N,N-dimethyl-morpholinyluronium hexafluorophosphate; The stabilizer is one or a mixture of 1-hydroxybenzotriazole, 4-dimethylaminopyridine or diisopropylethylamine; The polymer mildew inhibitor is one or a mixture of tannic acid, chitosan or polyethyleneimine; The nano-enhancer is one or a mixture of nano-silicon dioxide, nano-calcium carbonate or nano-montmorillonite, and its particle size is 50-500 nm; The pH adjuster is one or a mixture of hydrochloric acid, citric acid, acetic acid, formic acid, sulfuric acid or phosphoric acid; The preparation method of the high-strength mildew-proof plant protein adhesive comprises the following steps: (1) Add thickener and water into the reactor according to the mass ratio, stir and react at 5-40°C for 30-60 minutes, then add activator and stabilizer, and stir at 5-40°C for 5-20 minutes; (2) Add the nano-enhancer and water into a reaction kettle according to the mass ratio, homogenize at 5-40°C for 30-60 minutes, adjust the pH value of the solution to 4-5, then add the polymer mildew inhibitor, and stir and react at 5-40°C for 30-60 minutes; (3) Add the mixture obtained in step (1), the mixture obtained in step (2) and the plant protein into a reaction kettle, stir them uniformly at 5-40° C. and 60-100 r / min to obtain a high-strength mildew-proof plant protein adhesive.

2. The high-strength mildew-proof plant protein adhesive according to claim 1, characterized in that: The plant protein includes biomass raw materials with a protein content of not less than 20% and processing residues thereof, which is a mixture of one or more of defatted soybean powder, defatted soybean meal, soy protein isolate, defatted peanut powder, defatted cottonseed meal, defatted tea cake meal or defatted biofuel almond powder.

3. Application of the high-strength mildew-proof plant protein adhesive according to claims 1-2 in the preparation process of artificial boards.

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