Preparation method and application of reinforcing and toughening bio-based adhesive based on double dynamic covalent bonds

Abstract

The invention relates to the technical field of bio-based formaldehyde-free adhesives, and aims to provide a preparation method and application of a high-strength and high-toughness bio-based adhesive. Through interface molecular structure design, a boron nitride nanosheet based on sulfydryl click chemical function modification is constructed, an interface mechanical interlocking and chemical multi-network cross-linking reinforcing and toughening integrated technology is innovated, and the preparation method of the boron nitride nanosheet intercalation modified reinforcing and toughening plant protein adhesive is provided. The characteristic of poor interfacial adhesion between the adhesive and the wood surface is obviously improved, and the bio-based adhesive with good water resistance, high strength, excellent toughness and wider application range is obtained. According to the present invention, the dry shear strength of the plywood prepared by using the high-performance, high-strength and high-toughness bio-based adhesive through hot pressing can achieve 2.56 MPa, the wet shear strength can achieve 1.32 MPa, the wet debonding work can achieve 1800 mJ, excellent strength and excellent toughness can be represented, the thermal stability and the fire resistance of the adhesive can be significantly enhanced, and the wide industrial application prospect can be provided.

Description

Technical Field

[0001] The present invention relates to the technical field of bio-based formaldehyde-free adhesives, and particularly relates to a preparation method and application of a high-performance, high-strength and high-toughness bio-based adhesive. Background Art

[0002] Formaldehyde-free protein-based adhesives can solve the problems of formaldehyde pollution in the human living environment caused by wood-based panels and their products and the dependence on fossil resources for the raw materials of wood adhesives. Therefore, with the improvement of people's environmental protection awareness and the pursuit of high-quality living standards, formaldehyde-free protein-based adhesives have received increasing attention in the field of wood science and technology research and wood-based panel production. Among them, plant protein adhesives show great development potential due to their rich raw materials, low price, and environmental protection and convenience in production, transportation, and use. However, traditional plant protein adhesives have a hard and brittle cured adhesive layer and poor bonding at the adhesive interface, resulting in low dry bonding strength of bonded products such as wood-based panels and poor impact resistance at the adhesive interface. Problems such as delamination and deformation during actual production and processing and easy chipping during sawing often occur, which limits the further application and promotion of plant protein adhesives. Therefore, improving the strength and toughness of the cured adhesive layer of plant protein adhesives is of great significance and research value for the development of high-performance, high-strength and high-toughness plant protein adhesives. Summary of the Invention

[0003] The present invention overcomes the problems of poor water resistance of ordinary plant protein adhesives and large brittleness of the cured adhesive layer after crosslinking modification, such as easy chipping during sawing in the actual production, processing and application of industrial plywood of wood-based panels. The purpose is to provide a preparation method and application of a high-performance, high-strength and high-toughness plant protein adhesive. Through the design of the interfacial molecular structure, the present invention constructs a boron nitride nanosheet based on thiol click chemistry functional modification, innovates the integrated technology of interfacial mechanical interlocking and chemical multi-network crosslinking for reinforcement and toughening, provides a preparation method for modifying and enhancing the toughness of plant protein adhesives by intercalating and modifying boron nitride nanosheets, significantly improves the characteristic of poor interfacial adhesion between the adhesive and the wood surface, obtains a bio-based adhesive with good water resistance, high strength, excellent toughness and a wider application range, and the thermal stability and flame retardancy of the adhesive are significantly enhanced, having broad industrial application prospects.

[0004] Technical Problems to be Solved

[0005] Aiming at the problems of poor water resistance of ordinary plant protein adhesives and large brittleness of the cured adhesive layer after crosslinking modification in the prior art, through the design of the interfacial molecular structure, the present invention constructs a boron nitride nanosheet based on thiol click chemistry functional modification, and provides a preparation method for modifying and enhancing the toughness of plant protein adhesives by intercalating and modifying boron nitride nanosheets, solving the problems of poor mechanical properties and hard and brittle cured adhesive layer of plant protein adhesives.

[0006] Technical Solutions

[0007] In view of the deficiencies of the prior art, the present invention provides the following technical solution: a bio-based adhesive enhanced and toughened by thiol click chemistry-functionalized boron nitride nanosheets. The high-performance high-strength and high-toughness plant protein adhesive of the present invention is made of the following components: soybean meal, water, functionally modified boron nitride nanosheets, epoxy crosslinking agent, catalyst;

[0008] The preparation method of the present invention utilizes the functionally modified boron nitride nanosheets to form a stable mechanical interlocking structure with the plant protein matrix, and can also undergo covalent / non-covalent interactions with the plant protein matrix, thereby forming a firm physical locking and multiple chemical cross-linking network structure, which is beneficial to improving the bonding strength and toughness of the plant protein adhesive.

[0009] The preparation method of the high-performance high-strength and high-toughness plant protein adhesive of the present invention is as follows:

[0010] (1) Preparation of functionally modified boron nitride nanosheets. The specific steps are as follows. Hexagonal boron nitride is stirred and mixed evenly with isopropanol and deionized water, and hydroxyl-functionalized boron nitride nanosheets are obtained by ultrasonic-assisted liquid-phase exfoliation, which are well dispersed in the aqueous solution to form a colloidal solution. Subsequently, (3-mercaptopropyl)trimethoxysilane is added to the above colloidal solution by an improved sol-gel technique and heated under reflux. After cooling to room temperature, the mixture is washed with ethanol and filtered to obtain mercapto-functionalized boron nitride nanosheets.

[0011] (2) Preparation of high-performance high-strength and high-toughness plant protein adhesive. To ensure the dispersion of mercapto-functionalized boron nitride nanosheets in the soybean meal matrix, first, mercapto-functionalized boron nitride nanosheets are added to water, stirred evenly, and then ultrasonicated to make them disperse evenly. The soybean meal matrix is pretreated with 2-mercaptoethanol to expose more mercapto groups. Then, an appropriate amount of crosslinking agent and pretreated soybean meal are added to the reaction vessel, stirred evenly, and citric acid is added and stirred continuously to promote the formation of disulfide bonds between the protein chains and mercapto boron nitride nanosheets in the adhesive, and a mercapto-functionalized boron nitride nanosheet-modified plant protein adhesive sample is prepared.

[0012] Preferably, in the step (1), the mass ratio of hexagonal boron nitride, isopropanol and deionized water is 1-5:10-50:50-200.

[0013] Preferably, in the step (1), the ultrasonic-assisted liquid-phase exfoliation time is 1-10 h.

[0014] Preferably, in the step (1), the mass ratio of (3-mercaptopropyl)trimethoxysilane to the colloidal solution is 1-10:80-150.

[0015] Preferably, in the step (1), the heating reflux temperature is 80-150 °C and the time is 0.5-3 h.

[0016] Preferably, the hexagonal boron nitride in the step (1) can be one or more of graphene, graphene oxide, molybdenum disulfide, tungsten disulfide, boron nitride, mica, and hydrotalcite.

[0017] Preferably, in the step (2), the mass ratio of the soybean meal matrix to 2-mercaptoethanol is 20-50:1-5.

[0018] Preferably, the addition amount of the crosslinking agent in the step (2) is 1-10% of the mass of the adhesive.

[0019] Preferably, the addition amount of citric acid in the step (2) is 0.1-5% of the mass of the adhesive.

[0020] Preferably, in the step (2), the mass ratio of the soybean meal, the thiol-functionalized boron nitride nanosheets, and the dispersion medium water is 10-30:0.001-0.01:30-100.

[0021] Preferably, the soybean meal matrix in the step (2) can be one or more of low-temperature soybean meal, high-temperature soybean meal, peanut meal, rapeseed meal, high-temperature cottonseed meal, and low-temperature cottonseed meal.

[0022] Preferably, the crosslinking agent in the step (2) is one or more of ethylene glycol diglycidyl ether, trimethylolpropane triglycidyl ether, bisphenol A diglycidyl ether, and epoxy hyperbranched polymer.

[0023] Preferably, the citric acid in the step (2) can be one or more of citric acid, caffeic acid, gallic acid, and tartaric acid.

[0024] Beneficial technical effects

[0025] Compared with the prior art, the present invention has the following beneficial technical effects:

[0026] 1. The high-performance high-strength and high-toughness plant protein adhesive developed by the present invention is based on the thiol-epoxy "click" chemistry, amino-epoxy, and dynamic disulfide multi-network synergistic effect. The functionalized boron nitride nanosheets can form a stable mechanical interlocking structure and enhanced covalent / non-covalent interactions with the plant protein matrix, which is beneficial to the stress transfer and energy dissipation of the adhesive system, endows the plant protein adhesive with excellent bonding strength and toughness, and has good environmental benefits, economic benefits, and good industrial application prospects.

[0027] 2. The mixing of traditional plant protein adhesives with boron nitride nanosheets can improve the performance of the adhesives. However, the practical application of boron nitride nanosheets is still limited by their high surface energy and strong aggregation tendency. The physical and chemical properties of boron nitride nanosheets are completely different from those of the plant protein matrix, and good compatibility and strong interfacial adhesion cannot be formed between them and the protein matrix. If the boron nitride nanosheets are simply physically mixed with the plant protein, problems such as phase separation are likely to occur, resulting in the inability of the boron nitride nanosheets to play the role of enhancing and toughening the plant protein adhesive. In the present invention, appropriate functionalization promotes the uniform dispersion of boron nitride nanosheets in the plant protein adhesive and increases their interfacial interaction, thereby improving the mechanical, thermal, and electrochemical properties and promoting the further application and popularization of the plant protein adhesive.

[0028] 3. The present invention uses inexpensive and green agricultural and forestry waste soybean meal as the raw material of the adhesive, and boron nitride nanosheets as the reinforcing item, which is conducive to making full use of agricultural and forestry waste resources, alleviating the problem of shortage of petrochemical resources brought about by traditional formaldehyde-based adhesives, and conforming to the development concept of sustainable development. In addition, the plant protein adhesive does not have problems such as formaldehyde release, and solves the problems of organic volatiles and formaldehyde in traditional wood-based panels that harm human health and pollute the environment.

[0029] 4. The process of ordinary modified bio-based adhesives is relatively cumbersome, and the cured adhesive layer is hard and brittle. The process of the present invention is simple, has high bonding strength, good water resistance, and can also improve the flame retardant performance, mildew proof performance, etc. of the bio-based adhesive, solving the following problems of the prior arts CN118562443A and CN118222244A: large amount of filler added, high cost, low bonding strength, hard and brittle cured adhesive layer, complex production process, and relatively harsh reaction conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 and Figure 2 is the bonding strength of the high-strength and high-toughness plant protein adhesive obtained by using examples and control examples in the present invention for pressing plywood. DETAILED DESCRIPTION OF THE INVENTION

[0031] The experimental methods used in the following examples are all conventional operation methods unless otherwise specified.

[0032] General scheme:

[0033] A high-performance high-strength and high-toughness plant protein adhesive is made from the following components: soybean meal, water, functionally modified boron nitride nanosheets, epoxy crosslinking agent, catalyst;

[0034] Example 1

[0035] A modified plant protein adhesive, comprising the following steps:

[0036] (1) Preparation of plant protein adhesive. Add 28 g of soybean meal to 72 g of water and stir for 10 min until the solution becomes a uniform and stable state; add 4 g of ethylene glycol diglycidyl ether to the system and continue stirring for 10 min to obtain the modified plant protein adhesive.

[0037] (2) Press a three-layer poplar plywood and test its performance. The results are listed in Figure 1 and Figure 2 .

[0038] Example 2

[0039] A high-performance high-strength and high-toughness plant protein adhesive, comprising the following steps:

[0040] (1) Preparation of functionalized boron nitride nanosheets. Mix 5 g of hexagonal boron nitride with 100 g of isopropanol and deionized water and stir evenly, and use ultrasonic-assisted liquid-phase exfoliation to obtain hydroxylated boron nitride nanosheets, which are well dispersed in the aqueous solution to form a colloidal solution. Subsequently, 0.5 g of (3-mercaptopropyl) trimethoxysilane is added to the above colloidal solution by using an improved sol-gel technique, and heated under reflux at 90 °C for 0.5 h. After cooling to room temperature, the mixture is washed with ethanol and filtered to obtain mercapto-functionalized boron nitride nanosheets, and the mercapto grafting rate is 0.1%.

[0041] (2) Preparation of a high-performance high-strength and high-toughness plant protein adhesive. To ensure the dispersion of mercapto-functionalized boron nitride nanosheets in the soybean meal matrix, first, add 0.1 g of mercapto-functionalized boron nitride nanosheets to 72 g of water, stir evenly, and then perform ultrasonic treatment for 0.5 h to make it disperse evenly. First, 100 g of soybean meal matrix is pretreated with 10 g of 2-mercaptoethanol to expose more mercapto groups. Then, add 2 g of crosslinking agent and the pretreated 28 g of soybean meal to the reaction vessel containing mercapto-functionalized boron nitride nanosheets, stir evenly, and then continue to add 0.3 g of citric acid and stir to promote the formation of disulfide bonds between the protein chains and mercapto boron nitride nanosheets in the adhesive, and prepare a mercapto-functionalized boron nitride nanosheet modified plant protein adhesive sample.

[0042] (3) Press a three-layer poplar plywood and test its performance. The results are listed in Figure 1 and Figure 2 .

[0043] Example 3

[0044] A high-performance high-strength and high-toughness plant protein adhesive, comprising the following steps:

[0045] (1) Preparation of functionalized boron nitride nanosheets. 5 g of hexagonal boron nitride was stirred and mixed evenly with 100 g of isopropanol and deionized water, and hydroxylated boron nitride nanosheets were obtained by ultrasonic-assisted liquid-phase exfoliation. They were well dispersed in the aqueous solution to form a colloidal solution. Subsequently, 0.5 g of (3-mercaptopropyl)trimethoxysilane was added to the above colloidal solution using an improved sol-gel technique, and the mixture was heated under reflux at 90 °C for 0.5 h. After cooling to room temperature, the mixture was washed with ethanol and filtered to obtain mercapto-functionalized boron nitride nanosheets, and the mercapto grafting rate was 0.1%.

[0046] (2) Preparation of a high-performance, high-strength and high-toughness plant protein adhesive. To ensure the dispersion of mercapto-functionalized boron nitride nanosheets in the soybean meal matrix, first, 0.3 g of mercapto-functionalized boron nitride nanosheets was added to 72 g of water, stirred evenly, and then ultrasonicated for 0.5 h to make it disperse evenly. 100 g of soybean meal matrix was pretreated with 10 g of 2-mercaptoethanol to expose more mercapto groups. Then, 2 g of crosslinking agent and 28 g of pretreated soybean meal were added to the reaction vessel containing mercapto-functionalized boron nitride nanosheets, stirred evenly, and then 0.3 g of citric acid was added and stirred continuously to promote the formation of disulfide bonds between the protein chains and mercapto boron nitride nanosheets in the adhesive, and a sample of mercapto-functionalized boron nitride nanosheet-modified plant protein adhesive was prepared.

[0047] (3) Pressing three-layer poplar plywood and testing its properties, and the results are listed in Figure 1 and Figure 2 .

[0048] Example 4

[0049] A high-performance, high-strength and high-toughness plant protein adhesive, comprising the following steps:

[0050] (1) Preparation of functionalized boron nitride nanosheets. 5 g of hexagonal boron nitride was stirred and mixed evenly with 100 g of isopropanol and deionized water, and hydroxylated boron nitride nanosheets were obtained by ultrasonic-assisted liquid-phase exfoliation. They were well dispersed in the aqueous solution to form a colloidal solution. Subsequently, 0.5 g of (3-mercaptopropyl)trimethoxysilane was added to the above colloidal solution using an improved sol-gel technique, and the mixture was heated under reflux at 90 °C for 0.5 h. After cooling to room temperature, the mixture was washed with ethanol and filtered to obtain mercapto-functionalized boron nitride nanosheets, and the mercapto grafting rate was 0.1%.

[0051] (2) Preparation of a high-performance high-strength and high-toughness plant protein adhesive. To ensure the dispersion of mercapto-functionalized boron nitride nanosheets in the soybean meal matrix, first, 0.5 g of mercapto-functionalized boron nitride nanosheets was added to 72 g of water, stirred evenly, and then ultrasonicated for 0.5 h to make it disperse evenly. 100 g of soybean meal matrix was pretreated with 10 g of 2-mercaptoethanol to expose more mercapto groups. Then, 2 g of crosslinking agent and 28 g of pretreated soybean meal were added to the reaction vessel containing mercapto-functionalized boron nitride nanosheets, stirred evenly, and then 0.3 g of citric acid was added and stirred continuously to promote the formation of disulfide bonds between the protein chains and mercapto boron nitride nanosheets in the adhesive, and a mercapto-functionalized boron nitride nanosheet-modified plant protein adhesive sample was prepared.

[0052] (3) Press three-layer poplar plywood and test its performance. The results are listed in Figure 1 and Figure 2 .

[0053] Example 5

[0054] A high-performance high-strength and high-toughness plant protein adhesive, comprising the following steps:

[0055] (1) Preparation of functionalized boron nitride nanosheets. 5 g of hexagonal boron nitride was stirred and mixed evenly with 100 g of isopropanol and deionized water, and hydroxyl-functionalized boron nitride nanosheets were obtained by ultrasonic-assisted liquid-phase exfoliation, which were well dispersed in the aqueous solution to form a colloidal solution. Subsequently, 0.5 g of (3-mercaptopropyl)trimethoxysilane was added to the above colloidal solution using an improved sol-gel technique, and heated under reflux at 90 °C for 0.5 h. After cooling to room temperature, the mixture was washed with ethanol and filtered to obtain mercapto-functionalized boron nitride nanosheets, and the mercapto grafting rate was 0.3%.

[0056] (2) Preparation of a high-performance high-strength and high-toughness plant protein adhesive. To ensure the dispersion of mercapto-functionalized boron nitride nanosheets in the soybean meal matrix, first, 0.7 g of mercapto-functionalized boron nitride nanosheets was added to 72 g of water, stirred evenly, and then ultrasonicated for 0.5 h to make it disperse evenly. 100 g of soybean meal matrix was pretreated with 10 g of 2-mercaptoethanol to expose more mercapto groups. Then, 2 g of crosslinking agent and 28 g of pretreated soybean meal were added to the reaction vessel containing mercapto-functionalized boron nitride nanosheets, stirred evenly, and then 0.3 g of citric acid was added and stirred continuously to promote the formation of disulfide bonds between the protein chains and mercapto boron nitride nanosheets in the adhesive, and a mercapto-functionalized boron nitride nanosheet-modified plant protein adhesive sample was prepared.

[0057] (3) Press three-layer poplar plywood and test its performance. The results are listed in Figure 1 and Figure 2 .

[0058] Example 6

[0059] A high-performance high-strength and high-toughness plant protein adhesive, comprising the following steps:

[0060] (1) Preparation of functionalized boron nitride nanosheets. 5 g of hexagonal boron nitride is stirred and mixed evenly with 100 g of isopropanol and deionized water, and hydroxyl-functionalized boron nitride nanosheets are obtained by ultrasonic-assisted liquid-phase exfoliation. They are well dispersed in the aqueous solution, forming a colloidal solution. Subsequently, 1 g of (3-mercaptopropyl)trimethoxysilane is added to the above colloidal solution using an improved sol-gel technique, and the mixture is heated under reflux at 90 °C for 0.5 h. After cooling to room temperature, the mixture is washed with ethanol and filtered to obtain mercapto-functionalized boron nitride nanosheets, and the mercapto grafting rate is 0.5%.

[0061] (2) Preparation of a high-performance high-strength and high-toughness plant protein adhesive. To ensure the dispersion of mercapto-functionalized boron nitride nanosheets in the soybean meal matrix, first, 0.3 g of mercapto-functionalized boron nitride nanosheets is added to 72 g of water, stirred evenly, and then ultrasonicated for 0.5 h to make it disperse evenly. 100 g of soybean meal matrix is pretreated with 10 g of 2-mercaptoethanol to expose more mercapto groups. Then, 2 g of crosslinking agent and 28 g of pretreated soybean meal are added to the reaction vessel containing mercapto-functionalized boron nitride nanosheets, stirred evenly, and then 0.3 g of citric acid is added and stirred continuously to promote the formation of disulfide bonds between the protein chains and mercapto boron nitride nanosheets in the adhesive, and a mercapto-functionalized boron nitride nanosheet-modified plant protein adhesive sample is prepared.

[0062] (3) Pressing three-ply poplar plywood and testing its performance, and the results are listed in Figure 1 and Figure 2 .

[0063] Example 7

[0064] A high-performance high-strength and high-toughness plant protein adhesive, comprising the following steps:

[0065] (1) Preparation of functionalized boron nitride nanosheets. 5 g of hexagonal boron nitride is stirred and mixed evenly with 100 g of isopropanol and deionized water, and hydroxyl-functionalized boron nitride nanosheets are obtained by ultrasonic-assisted liquid-phase exfoliation. They are well dispersed in the aqueous solution, forming a colloidal solution. Subsequently, 1.5 g of (3-mercaptopropyl)trimethoxysilane is added to the above colloidal solution using an improved sol-gel technique, and the mixture is heated under reflux at 90 °C for 0.5 h. After cooling to room temperature, the mixture is washed with ethanol and filtered to obtain mercapto-functionalized boron nitride nanosheets, and the mercapto grafting rate is 1%.

[0066] (2) Preparation of a high-performance, high-strength and high-toughness plant protein adhesive. To ensure the dispersion of mercapto-functionalized boron nitride nanosheets in the soybean meal matrix, first, 0.3 g of mercapto-functionalized boron nitride nanosheets was added to 72 g of water, stirred evenly, and then ultrasonicated for 0.5 h to make it evenly dispersed. 100 g of soybean meal matrix was pretreated with 10 g of 2-mercaptoethanol to expose more mercapto groups. Then, 2 g of crosslinking agent and 28 g of pretreated soybean meal were added to the reaction vessel containing mercapto-functionalized boron nitride nanosheets, stirred evenly, and then 0.3 g of citric acid was added and stirred continuously to promote the formation of disulfide bonds between the protein chains and mercapto boron nitride nanosheets in the adhesive, and a sample of mercapto-functionalized boron nitride nanosheet-modified plant protein adhesive was prepared.

[0067] (3) Press three-layer poplar plywood and test its performance. The results are listed in Figure 1 and Figure 2 .

[0068] Example 8

[0069] A high-performance, high-strength and high-toughness plant protein adhesive, comprising the following steps:

[0070] (1) Preparation of functionalized boron nitride nanosheets. 5 g of hexagonal boron nitride was stirred and mixed evenly with 100 g of isopropanol and deionized water, and hydroxy-functionalized boron nitride nanosheets were obtained by ultrasonic-assisted liquid-phase exfoliation. They were well-dispersed in the aqueous solution to form a colloidal solution. Subsequently, 2 g of (3-mercaptopropyl)trimethoxysilane was added to the above colloidal solution using an improved sol-gel technique, and heated under reflux at 90 °C for 0.5 h. After cooling to room temperature, the mixture was washed with ethanol and filtered to obtain mercapto-functionalized boron nitride nanosheets, and the mercapto grafting rate was 1.5%.

[0071] (2) Preparation of a high-performance, high-strength and high-toughness plant protein adhesive. To ensure the dispersion of mercapto-functionalized boron nitride nanosheets in the soybean meal matrix, first, 0.3 g of mercapto-functionalized boron nitride nanosheets was added to 72 g of water, stirred evenly, and then ultrasonicated for 0.5 h to make it evenly dispersed. 100 g of soybean meal matrix was pretreated with 10 g of 2-mercaptoethanol to expose more mercapto groups. Then, 2 g of crosslinking agent and 28 g of pretreated soybean meal were added to the reaction vessel containing mercapto-functionalized boron nitride nanosheets, stirred evenly, and then 0.3 g of citric acid was added and stirred continuously to promote the formation of disulfide bonds between the protein chains and mercapto boron nitride nanosheets in the adhesive, and a sample of mercapto-functionalized boron nitride nanosheet-modified plant protein adhesive was prepared.

[0072] (3) Press three-layer poplar plywood and test its performance. The results are listed in Figure 1 and Figure 2 .

[0073] Comparative Example 1

[0074] A plant protein adhesive, comprising the following steps:

[0075] (1) Preparation of the plant protein adhesive. Add 28 g of soybean meal to 72 g of water and stir for 10 min until the solution becomes a uniform and stable state, thus obtaining the plant protein adhesive.

[0076] (2) Press a three-layer poplar plywood and test its performance. The results are listed in Figure 1 and Figure 2 .

[0077] Comparative Example 2

[0078] A modified plant protein adhesive, comprising the following steps:

[0079] (1) Preparation of the plant protein adhesive. Add 28 g of soybean meal to 72 g of water and stir for 10 min until the solution becomes a uniform and stable state; add 4 g of trimethylolpropane triglycidyl ether to the system and continue to stir for 10 min, thus obtaining the modified plant protein adhesive.

[0080] (2) Press a three-layer poplar plywood and test its performance. The results are listed in Figure 1 and Figure 2 .

[0081] Comparative Example 3

[0082] A modified plant protein adhesive, comprising the following steps:

[0083] (1) Preparation of the plant protein adhesive. Add 28 g of soybean meal to 72 g of water and stir for 10 min until the solution becomes a uniform and stable state; add 0.5 g of unmodified boron nitride to the system, stir for 10 min, then continue to add 4 g of trimethylolpropane triglycidyl ether and continue to stir for 10 min, thus obtaining the modified plant protein adhesive.

[0084] (2) Press a three-layer poplar plywood and test its performance. The results are listed in Figure 1 and Figure 2 .

[0085] Comparative Example 4 (Technical solution of Example 1 in Patent Publication No. CN116622060B)

[0086] The test results of the plywood are listed in Figure 1 and Figure 2 .

[0087] Comparative Example 5 (Technical solution of Example 1 in Patent Publication No. CN118222244A)

[0088] The test results of the plywood are listed in Figure 1 and Figure 2 .

[0089] Comparative Example 6 (Technical solution of Example 1 in Patent Publication No.: CN118562443A)

[0090] The test results of the plywood are listed in Figure 1 and Figure 2 .

[0091] For the high-performance, high-strength and high-toughness plant protein adhesives prepared in Examples 1 to 8 and the adhesives prepared in Comparative Examples 1 to 6, poplar veneers were selected to prepare three-layer plywood with a moisture content of 5-15% and a size of 40 cm * 40 cm * 0.15 cm, and it was prepared according to the following process:

[0092] Gluing: Glue was applied on both sides of the core board, and the glue application amount was 300-400 g / m 2 ;

[0093] Pressing: The pressure was 1 MPa, the temperature was 110-130 °C, and the time was 6 minutes.

[0094] The plywood products produced were tested for their bonding strength performance according to the testing method of GB / T17657-1999 "Test Methods for Physical and Chemical Properties of Wood-Based Panels and Decorative Wood-Based Panels", and the test results are as Figure 1 and Figure 2 shown.

[0095] From Figure 1 and Figure 2 , it can be seen that the high-performance, high-strength and high-toughness plant protein adhesive of the present invention is made of the following components: soybean meal, water, functionally modified boron nitride nanosheets, epoxy crosslinking agent, catalyst. By using the functionally modified boron nitride nanosheets to form a stable mechanical interlocking structure with the plant protein matrix, and can also undergo covalent / non-covalent interactions with the plant protein matrix, thereby forming a firm physical locking and multiple chemical cross-linking network structure, which is beneficial to improving the bonding strength and toughness of the plant protein adhesive. The test results show that the three-layer plywood pressed with the adhesive of the present technical invention has excellent mechanical properties, and the wet shear strength is 0.94-1.61 MPa, and it is superior to the comparative examples.

[0096] From Figure 1 and Figure 2It can be seen that when comparing the plywood prepared with the high-performance high-strength and high-toughness plant protein adhesives prepared in Examples 1 to 4, the dry shear strength and wet shear strength gradually increase. It can be seen that with the addition of the functionalized boron nitride nanosheets, effective active sites can be generated, and strong interfacial interactions can be formed between the protein polymer and the nanosheets, thereby improving the dispersion of the nanosheets in the adhesive. By utilizing the enhanced interfacial interaction and interfacial adhesion force between the nanosheets and the plant protein, the plant protein adhesive is synergistically strengthened and toughened, and the water-resistant adhesive performance of the adhesive is improved.

[0097] When comparing Examples 1, 2 and Examples 5, 6, 7, 8, the dry shear strength and wet shear strength of the adhesive gradually increase. This is because the grafting rate of the functionalized boron nitride nanosheets gradually increases, more active sites are generated, stronger interfacial interactions are formed between the protein and the nanosheets, promoting the formation of a firm physical locking and multiple chemical cross-linking network structure inside the adhesive, and improving the water-resistant adhesive performance of the adhesive.

[0098] When comparing the Examples with Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4 (the technical solution of Example 1 in Patent Publication No. CN116622060B), Comparative Example 5 (the technical solution of Example 1 in Patent Publication No. CN118222244A), and Comparative Example 6 (the technical solution of Example 1 in Patent Publication No. CN118562443A), the water-resistant adhesive performance of the plywood pressed with the bio-based adhesive prepared by enhancing with functionalized boron nitride nanosheets in the present invention is significantly better than that of the existing invention technologies.

[0099] Therefore, the preparation method of the high-performance high-strength and high-toughness plant protein adhesive of the present invention is to use basic raw materials such as soybean meal, water, epoxy cross-linking agent and catalyst. By using the functionalized boron nitride nanosheets, it can not only form a stable mechanical interlocking structure with the plant protein matrix, but also undergo covalent / non-covalent interactions with the plant protein matrix, thereby forming a firm physical locking and multiple chemical cross-linking network structure, and preparing a high-performance high-strength and high-toughness plant protein adhesive with high strength and excellent performance, which has good industrial application prospects.

[0100] The above is only a preferred embodiment of the present invention, and it does not impose any form of limitation on the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art, within the scope of the technical solution of the present invention, can make some changes or modifications to equivalent embodiments by using the above-disclosed technical content. However, as long as it does not depart from the content of the technical solution of the present invention, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A high-strength and high-toughness plant protein adhesive, characterized in that: The method is composed of the following raw materials: soybean meal, water, functionally modified boron nitride nanosheets, an epoxy crosslinking agent, and a catalyst.

2. A high-strength and high-toughness plant protein adhesive according to claim 1, characterized in that: The soybean meal is one or more of low-temperature soybean meal, high-temperature soybean meal, peanut meal, rapeseed meal, high-temperature cottonseed meal, and low-temperature cottonseed meal.

3. A high-strength and high-toughness plant protein adhesive according to claim 1, characterized in that: The crosslinking agent is one or more of ethylene glycol diglycidyl ether, trimethylolpropane triglycidyl ether, bisphenol A diglycidyl ether, and epoxy hyperbranched polymer.

4. The high-strength and high-toughness plant protein adhesive according to claim 1, characterized in that: The functionally modified boron nitride nanosheets can be one or more functionally modified products selected from graphene, graphene oxide, molybdenum disulfide, tungsten disulfide, boron nitride, mica, and hydrotalcite.

5. The high-strength and high-toughness plant protein adhesive according to claim 1, characterized in that: The catalyst is one or more of citric acid, caffeic acid, gallic acid and tartaric acid.

6. The high-strength and high-toughness plant protein adhesive according to claim 1, characterized in that: The method for preparing functionally modified boron nitride nanosheets comprises the following steps: Hexagonal boron nitride was stirred and mixed with isopropanol and deionized water, and hydroxylated boron nitride nanosheets were obtained by ultrasonic-assisted liquid phase exfoliation, which were well dispersed in the aqueous solution to form a colloidal solution. Subsequently, (3-mercaptopropyl)trimethoxysilane was added to the colloidal solution using an improved sol-gel technique, and heated to reflux. After cooling to room temperature, the mixture was washed with ethanol and filtered to obtain mercapto-functionalized boron nitride nanosheets.

7. The high-strength and high-toughness plant protein adhesive according to claim 1, characterized in that: In the preparation method of CoNi2S4-In2O3 nanosheets, CoNi2S4 nanosheets can be replaced by graphene, molybdenum disulfide, tungsten disulfide and porous nanomaterials.

8. The high-strength and high-toughness plant protein adhesive according to claim 1, characterized in that The adhesive preparation method comprises the following steps: To ensure the dispersibility of thiol-functionalized boron nitride nanosheets in soybean meal matrix, first, thiol-functionalized boron nitride nanosheets were added to water and stirred evenly, and then ultrasonicated to make them evenly dispersed. The soybean meal matrix was first pretreated with 2-mercaptoethanol to expose more thiol groups. Then, an appropriate amount of cross-linking agent and pretreated soybean meal were added to the reaction vessel and stirred evenly, and then citric acid was added and stirred continuously to promote the formation of disulfide bonds between the protein chain in the adhesive and the thiol-functionalized boron nitride nanosheets, and a thiol-functionalized boron nitride nanosheet modified plant protein adhesive sample was prepared.

9. The method for preparing a high-strength and high-toughness plant protein adhesive according to claim 8, characterized in that: The mass ratio of soybean meal, thiol-functionalized boron nitride nanosheets and dispersion medium water is 10-30:0.001-0.01:30-100.

10. Use of the high-strength and high-toughness plant protein adhesive as claimed in claim 8 in wood processing and artificial boards.

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