Repeatable processing type vegetable protein adhesive as well as preparation method and application thereof

Abstract

The invention provides a reprocessable vegetable protein adhesive and a preparation method and application thereof, the reprocessable vegetable protein adhesive comprises an organic boric acid derivative, polyvinyl alcohol, vegetable protein and water, and the organic boric acid derivative comprises an aldehyde group and a boric acid group. The adhesive provided by the invention has certain repeatable processability, a multi-cross-linked network structure is easily formed between the organic boric acid derivative and other components in the adhesive system, and the comprehensive properties such as prepressing property, mechanical property, degradability and the like of the adhesive are also improved on the basis of repeatable processability.

Description

Technical Field

[0001] This invention relates to the field of adhesive technology, and in particular to a reprocessable plant protein adhesive, its preparation method, and its application. Background Technology

[0002] Traditional synthetic resin adhesives face challenges such as dependence on petroleum-based raw materials, release of volatile harmful gases, and non-recyclability due to thermosetting cross-linking. Plant protein adhesives based on renewable biomass, with their biodegradable properties, have become an important candidate system to replace aldehyde resins.

[0003] The scientific value of plant protein adhesives lies in the designability of their molecular structures. Abundant active functional groups endow them with the ability to construct controllable networks, and the wide availability of raw materials combined with their biodegradability constitutes a complete life cycle loop, making them demonstrate significant technological substitution potential in fields such as wood processing and flexible packaging. This excellent balance between performance and functionality is driving cross-industry application research.

[0004] However, plant protein adhesives face a significant challenge in the field of wood composites. While the irreversible cross-linking mechanism between molecular chains effectively ensures interfacial bond strength, it also makes it difficult to recycle the cured products through conventional depolymerization pathways. This inherent thermosetting characteristic is fundamentally contradictory to the material renewability required by the circular economy, severely restricting its large-scale application in sustainable wood product manufacturing. Summary of the Invention

[0005] This invention aims to at least partially address one of the technical problems in the prior art. Therefore, one object of this invention is to provide a reprocessable plant protein adhesive, its preparation method, and its application.

[0006] In a first aspect, the present invention provides a reprocessable plant protein adhesive comprising: an organoboronic acid derivative, polyvinyl alcohol, plant protein, and water, wherein the organoboronic acid derivative comprises aldehyde and boric acid groups.

[0007] The reprocessable plant protein adhesive provided by the present invention uses an organoboronic acid derivative that has both aldehyde and boric acid groups. The reaction mechanism can be found in [reference needed]. Figure 1Not only can it form reversible Schiff base dynamic bonds with plant protein molecules, exhibiting excellent cohesiveness, but its boric acid groups also form dynamic borate ester bonds with the hydroxyl groups of plant protein molecules / adhesive fillers. The synergistic effect of Schiff base bonds and borate ester bonds provides the adhesive with reusability, and the dissociation-reorganization mechanism of borate ester bonds in the aqueous environment achieves energy dissipation and molecular chain reconstruction. In addition, the abundant hydroxyl groups in the polyvinyl alcohol chain and the polar groups of plant protein molecules form a multiple hydrogen bond network through hydrogen bonds, further promoting efficient energy dissipation and improving the fracture resistance of reprocessable plant protein adhesives, thereby significantly enhancing their toughness. At the same time, plant proteins have broad industrial application prospects due to their environmental friendliness, non-toxicity, and low cost. By using organoboric acid derivatives in combination with polyvinyl alcohol, chemical cross-linking of the active groups in plant proteins can be promoted, promoting uniform mixing of the system. Through the interaction of dual dynamic covalent bonds with plant proteins / polyvinyl alcohol, a cross-linked network structure with reversible recombination properties can be constructed.

[0008] The reprocessable plant protein adhesive provided by the present invention comprises an organoboronic acid derivative selected from at least one of 5-formaldehyde furan-2-boronic acid, o-formylphenylboronic acid, m-formylphenylboronic acid, 4-formylphenylboronic acid, 4-aldehydethiophene-2-boronic acid, 5-formylthiophene-3-boronic acid, 3-formaldehydethiophene-2-boronic acid, 3,5-diformylphenylboronic acid, 4-methoxy-2-formylphenylboronic acid, 4-formylfuran-2-boronic acid, 2-formylpyridin-5-boronic acid, and (1-formylnaphthalene-2-yl)boronic acid, preferably 4-formylphenylboronic acid. Compared with 9,10-anthracene diboronic acid and o-formylphenylboronic acid, the 4-formylphenylboronic acid used in the present invention exhibits significant advantages in adhesive preparation. Its unique molecular structure, with the coexistence of aldehyde (-CHO) and boronic acid (-B(OH)2) groups at the para position on the benzene ring, endows the crosslinking agent with dual key properties. First, enhanced intermolecular crosslinking ability: the para configuration minimizes steric hindrance and electronic interference between functional groups, significantly improving the reaction efficiency and synergistic effect between the bifunctional groups and the active sites of plant proteins (such as amino and hydroxyl groups), thereby constructing a denser and more stable crosslinking network. Second, excellent dynamic reversibility: this structure promotes the simultaneous formation of boronic acid ester bonds and imine / Schiff base bonds during the crosslinking process, both of which possess dynamic reversibility.

[0009] In some embodiments of the present invention, the molecular weight of the polyvinyl alcohol is 140,000-190,000, preferably 146,000-156,000. Polyvinyl alcohol and organoboric acid derivatives can undergo chemical cross-linking to form borate ester bonds, thereby improving the toughness and pre-compression performance of the plant protein adhesive. High molecular weight polyvinyl alcohol undergoes a directional condensation reaction with the borate groups contained in the organoboric acid derivative through the high-density distribution of vicinal diol structural units in its molecular chain, forming dynamically reversible borate ester bonds; this bonding network interpenetrates with the cross-linking network constructed by the amino functional groups in the plant protein molecule to form a synergistic reinforcement system, which significantly improves the fracture toughness of the material by resisting external impact energy through dynamic bonds. At the same time, the three-dimensional hydrogen bond network constructed by the hydroxyl groups of the polyvinyl alcohol backbone has a highly efficient water molecule trapping ability, effectively promoting the wetting and penetration of the adhesive system to the substrate interface, ensuring uniform spread of the colloid and filling of defects on the substrate surface; together with the plasticizing effect generated by its long-chain polymer characteristics, it optimizes the pre-compression performance and overall mechanical properties of the plant protein adhesive.

[0010] In some embodiments of the present invention, the protein content of the plant protein is 90-98 wt%, preferably 93-95 wt%.

[0011] In some embodiments of the present invention, the plant protein is selected from one or more of soybean meal protein, peanut meal protein, cottonseed meal protein, and corn alcohol meal protein.

[0012] In some embodiments of the present invention, the mass ratio of the plant protein to the organoboronic acid derivative is 1:(0.001~0.1), preferably 1:(0.01~0.05).

[0013] In some embodiments of the present invention, the mass ratio of the plant protein to the polyvinyl alcohol is 1:(0.001~1), preferably 1:(0.005~0.2).

[0014] In some embodiments of the present invention, the mass ratio of the plant protein to the water is 1:(1~12), preferably 1:(5~9).

[0015] More preferably, the mass ratio of the plant protein to the organoboronic acid derivative is 1:(0.01~0.05), the mass ratio of the plant protein to the polyvinyl alcohol is 1:(0.005~0.2), and the mass ratio of the plant protein to the water is 1:(5~9).

[0016] In a second aspect, the present invention provides a method for preparing the above-mentioned reprocessable plant protein adhesive, comprising: Polyvinyl alcohol is mixed with water to obtain a stable homogeneous aqueous solution; The stable homogeneous aqueous solution, organoboronic acid derivative, plant protein and water are mixed.

[0017] In some embodiments of the present invention, in the stable homogeneous aqueous solution, the mass ratio of polyvinyl alcohol to water is 1:(5~200), preferably 1:(9~99).

[0018] In a third aspect, the present invention provides another method for preparing the above-mentioned reprocessable plant protein adhesive, comprising: The first product is obtained by mixing plant protein and water; The first product was mixed with polyvinyl alcohol to obtain the second product; The second product is mixed with a material containing an organoboronic acid derivative to obtain the plant protein adhesive.

[0019] In some embodiments of the present invention, the second product is mixed with the material containing the organoboric acid derivative by mechanical stirring; the mechanical stirring conditions are: 800~1200 rpm / min, 0~40°C, stirring for 0.1~1.5 hours; preferably, the mechanical stirring conditions are: 800~1000 rpm / min, 15~35°C, stirring for 0.5~1 hours.

[0020] In a fourth aspect, the present invention provides a plywood formed by stacking multiple sheets, wherein an adhesive layer is provided between adjacent sheets, the adhesive layer being formed by the aforementioned reprocessable plant protein adhesive.

[0021] The present invention has at least the following beneficial effects: The adhesive provided by this invention has a certain degree of reprocessability. Moreover, the organic boric acid derivative can easily form a multi-crosslinked network structure with other components in the adhesive system, which improves the overall performance of the adhesive, such as pre-compression performance, mechanical properties, and biodegradability, on the basis of reprocessability.

[0022] The organic boric acid derivative used in this invention is more conducive to improving the reprocessability of plant protein adhesives. The adhesive film prepared by this invention has an initial tensile strength of 24.47 MPa, and retains 82.39% of its strength (20.16 MPa) after two thermal cycling regenerations. After closed-loop regeneration, the static bending strength (12.9 MPa) and elastic modulus (1907 MPa) of the second-generation recycled plywood both exceed the requirements of GB / T 4897-2015 "Particleboard" P2 type standard (≥11 MPa / ≥1600 MPa).

[0023] The plant protein adhesive of this invention has excellent overall performance, mild processing conditions, and fast curing. It has been verified that the pre-compression strength of the plywood prepared by it can reach 0.68±0.04 MPa, the dry bonding strength can reach 2.18 MPa, and the water-resistant bonding strength can reach 1.29 MPa. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram illustrating the reaction principle of the plant protein adhesive provided by the present invention; Figure 2 This is the macroscopic structure characterization result of the adhesive film obtained in Example 1 of the present invention after two thermal cycle regenerations; Figure 3 This is the tensile strength characterization result of the adhesive film prepared in Example 1 of the present invention after two thermal cycling regenerations; Figure 4 This is a diagram showing the state of the first and second generation recycled plywood after closed-loop recycling of the plywood prepared in Example 1 of the present invention. Figure 5 These are the mechanical strength characterization results of the first and second generation recycled plywood obtained in Example 1 of the present invention after closed-loop recycling. Figure 6 The results show the pre-compression strength of plywood prepared by cold pressing for 1 hour using the adhesive and pure plant protein adhesive prepared in Example 1 of this invention. Detailed Implementation

[0026] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention. The invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the invention in any way.

[0027] The plant protein used in the embodiments and comparative examples of this invention has a protein content of 95 wt% and a particle size of 250 mesh, and was purchased from Shandong Yuwang Ecological Food Industry Co., Ltd.

[0028] High molecular weight polyvinyl alcohol (molecular weight 146,000-156,000, degree of hydrolysis ≥99%) was purchased from Merck KGaA GmbH, Germany.

[0029] 4-Formylphenylboronic acid, glycerol, and potassium carbonate were purchased from Bid Pharmaceutical Technology Co., Ltd.

[0030] The wood boards and wood pellets with a moisture content of 7% to 10% were purchased from Shandong Qiansen Group Co., Ltd.

[0031] Example 1 (1) This embodiment provides a reprocessable plant protein adhesive, the raw materials for which are prepared as follows: 0.75 kg of organoboronic acid derivative (4-formylphenylboronic acid); 1 kg of polyvinyl alcohol; 15kg of plant protein; Water 84kg.

[0032] (2) This embodiment provides a method for preparing a reprocessable plant protein adhesive, using the raw materials from step (1), and the specific process is as follows: a. Under reflux protection conditions, high molecular weight polyvinyl alcohol and water were added to a three-necked flask at a mass ratio of 1:9. The mixture was mechanically stirred continuously at a constant temperature of 90°C for 24 hours to form a homogeneous pre-dispersion system. The system was then transferred to a sealed container and stored under an inert atmosphere to obtain a stable homogeneous aqueous solution. b. Add the plant protein to the remaining water and mechanically stir for 6 minutes. Then add the above-mentioned stable homogeneous aqueous solution and organoboronic acid derivative and continue mechanically stirring for 30 minutes until a uniform paste is produced, thus obtaining a reprocessable plant protein adhesive.

[0033] Example 2 (1) This embodiment provides a reprocessable plant protein adhesive, the raw materials for which are prepared as follows: 0.75 kg of organoboronic acid derivative (4-formylphenylboronic acid); Polyvinyl alcohol 0.8 kg; 15kg of plant protein; 84.2 kg of water.

[0034] (2) The preparation process of the reprocessable plant protein adhesive in Example 2 is the same as that in Example 1.

[0035] Example 3 (1) This embodiment provides a reprocessable plant protein adhesive, the raw materials for which are prepared as follows: 0.375 kg of organoboronic acid derivative (4-formylphenylboronic acid); Polyvinyl alcohol 0.8 kg; 15kg of plant protein; 84.2 kg of water.

[0036] (2) The preparation process of the reprocessable plant protein adhesive in Example 3 is the same as that in Example 1.

[0037] Example 4 (1) This embodiment provides a reprocessable plant protein adhesive, the raw materials for which are prepared as follows: 0.375 kg of organoboronic acid derivative (4-formylphenylboronic acid); Polyvinyl alcohol 0.5 kg; 15kg of plant protein; 79.5 kg of water.

[0038] (2) The preparation process of the reprocessable plant protein adhesive in Example 4 is the same as that in Example 1.

[0039] Example 5 This embodiment provides a reprocessable plant protein adhesive. The only difference between Example 5 and Example 1 is that Example 5 uses o-formylphenylboronic acid instead of 4-formylphenylboronic acid in Example 1.

[0040] Comparative Example 1 This comparative example provides a plant protein adhesive, and the specific preparation process is as follows: Add 15 kg of plant protein meal (soybean protein meal containing 43% soy protein isolate, but also containing other fibers, minerals, etc., purchased from Shandong Wangyu Ecological Food Industry Co., Ltd. (China)) to 75 kg of dispersion medium water, and mechanically stir for 6 minutes. Then add 10 kg of stable homogeneous aqueous solution prepared in step (2) of Example 1 and 0.75 kg of organoboric acid derivative and continue mechanically stirring for 30 minutes until a uniform paste is produced.

[0041] Comparative Example 2 This comparative example provides a plant protein adhesive. The only difference between Comparative Example 2 and Example 1 is that Comparative Example 2 uses 9,10-anthracite diboronic acid instead of 4-formylphenylboronic acid in Example 1.

[0042] Comparative Example 3 This comparative example provides a plant protein adhesive. The only difference between Comparative Example 3 and Example 1 is that Comparative Example 3 does not contain 4-formylphenylboronic acid.

[0043] Experiment 1 The repeatability of the reprocessable plant protein adhesive prepared in Example 1 was tested, and the specific results are shown in [the table below]. Figure 2-6 .

[0044] Figure 2-3The reusability of adhesive films prepared from the adhesive was demonstrated through multi-cycle tensile strength testing. Visually, the surface and morphology of the adhesive films changed significantly with the number of cycles, indicating that their physical properties are affected by the number of cycles. Particularly in the R2 state, the surface smoothness and density of the film decreased significantly after two cycles of heat treatment. The haze of the film also changed significantly with increasing heat treatment cycles. However, new films could still be formed after cutting the film into small pieces and hot-pressing them. The tensile strength of the first prepared film (R0) was 24.47 MPa, the tensile strength of the film after the first cycle (R1) was 24.11 MPa, which is 98.50% of the R0 film's strength, and the second cycle (R2) still maintained 82.39% (20.16 MPa) of the R0 film's tensile strength. The experiment shows that the strong and weak dynamic covalent bonds formed in the adhesive can rearrange in each hot-pressing cycle, thus ensuring its reusability. This discovery strongly supports the sustainability of thermosetting adhesives in practical applications, particularly in the production of wood adhesives and engineered wood products.

[0045] Figure 4-5 It can be seen that two generations of recycled board preparation experiments were designed. First, the plywood prepared from recycled adhesive was crushed into wood particles with a particle size of 0.5-3.5 mm and a length of 2.0-6.0 mm. The first-generation recycled board was hot-pressed with recycled wood particles in a 1:1 mass ratio of adhesive (180 ℃ / 3 MPa / 15 min), and its bending strength (MOR) and modulus of elasticity (MOE) reached 19.5 MPa and 2892 MPa, respectively. The second-generation recycled board was made by crushing the first-generation recycled board a second time and mixing recycled wood particles in a 1.156 mass ratio with deionized water in a 0.3 mass ratio. Its MOR (12.9 MPa) and MOE (1907 MPa) still meet the P2 type board standard in GB / T 4897-2015 (MOR≥11 MPa, MOE≥1600 MPa). Under the same cycling conditions, the MOR of the first-generation recycled board prepared by the phenolic / urea-formaldehyde resin system after hot pressing (180 ℃ / 3 MPa / 15 min) decreased to less than 20% of the initial value. This clearly indicates that under humid and hot conditions, the secondary cross-linking of the adhesive and wood interface was mainly achieved by a strong and weak dynamic covalent network.

[0046] Figure 6It can be seen that the plywood prepared with the adhesive after 1 hour of cold pressing (1 MPa) exhibits a significant increase in pre-compression strength (0.68 MPa), far exceeding that of plywood prepared with pure plant protein adhesive (95% soybean protein isolate purchased from Shandong Wangyu Ecological Food Industry Co., Ltd. (China)) (0.33 MPa). The strong-weak dynamic covalent bond network plays a major role in improving the pre-compression strength of the plywood prepared with the adhesive. Firstly, the boric acid groups form a weak dynamic borate ester bond network with the hydroxyl groups in the plywood (including those in plant proteins, high molecular weight polyvinyl alcohol, and wood substrates). These dynamic bonds have reversible breaking and recombination characteristics, which can alleviate local stress concentration through energy dissipation during pressing, effectively preventing interfacial separation and thus ensuring the stability of the adhesive layer.

[0047] Experiment 2 (1) Mechanical strength test of adhesive film Add 5.0 g of plant protein to 95.0 g of deionized water, adjust the pH to 9-10 using 10% NaOH solution, and stir the mixture at 85°C for 30 minutes. Next, add 1.25 g of the stable homogeneous aqueous solution from the example or comparative example, and continue heating and stirring at 85°C for 5 minutes. Then add 0.1 g of 4-formylphenylboronic acid, and continue stirring at 85°C for 5 minutes. Finally, add 1 g of glycerol, and stir again at 85°C for 5 minutes. Pour the homogeneous solution into a glass petri dish, remove surface air bubbles with a pipette to form a smooth interface. Then place the petri dish in an oven at 45°C to dry for 24 hours to obtain a cured plant protein film. Cut the film into rectangular strips 50 mm long and 10 mm wide, place them in a desiccator containing saturated potassium carbonate solution, and dry at 25°C and 50% RH for one week.

[0048] The tensile strength of the adhesive film was measured using a universal testing machine (UTM Instron 3365, Norwood, MA) at a stride speed of 5 mm / min. After testing, the film was cut into small pieces and hot-pressed at 120°C and 3 MPa for 6 minutes to prepare new films made with SPI / P / pFB2 adhesive. This process was repeated twice, and the tensile strength was measured again to evaluate the reusability of the films made with SPI / P / pFB2 adhesive.

[0049] Pre-compression test: Using 200 mm × 200 mm × 1.5 mm poplar veneer as the substrate, different adhesive formulations were applied to one side at a rate of 180 g / m². An untreated veneer was sandwiched between two coated veneers (adjacent veneers with perpendicular grain). After pre-compression at 25℃ and 1 MPa for 60 min, the specimen was immediately cut. Using a universal testing machine equipped with a 5 kN sensor, the load was applied at a rate of 10 mm / min until failure. The pre-compression shear strength was calculated according to the above formula. Each group was repeated 6 times.

[0050] Dry / Water-Resistant Bond Strength Test: To evaluate the bonding performance of plywood prepared with adhesives, poplar veneer (200×200×1.5mm³) was used as the substrate for plywood fabrication. Adhesives of different formulations were uniformly applied to one side of the veneer at a coating density of 180 g / m². Uncoated veneers were then stacked between two coated veneers, with adjacent veneers arranged perpendicularly. The plywood assembly was pressed for 6 minutes in a hot press at 120°C and 1.0 MPa. After pressing, the plywood was placed at 20°C for 24 hours and then cut into test specimens. Shear strength tests were performed on the plywood using a universal testing machine (CMT4202, China New Sansi Enterprise Development Co., Ltd.) according to Chinese National Standard GB / T17657-2013. The dry bond strength of three-layer plywood specimens (100×25 mm) was measured at a loading rate of 10 mm / min. In the water-resistant adhesive strength test, the sample was immersed in water at 63°C for 3 hours, then cooled to room temperature for 10 minutes before the test was conducted. Each sample was tested six times, and the average value was recorded.

[0051] The results of the mechanical strength test of the adhesive film are shown in Table 1.

[0052] Table 1

[0053] (2) Film cycling test Bending strength test: The preparation method of the first-generation recycled board (size: 100 × 100 × 5 mm; density: 1.0 g / cm³) is to crush the plywood prepared with adhesive into wood particles with a diameter of 0.5 mm to 3.5 mm and a length of 2 mm to 6 mm. These wood particles are mixed with adhesive at a mass ratio of 1:1. The wood particles are added to the adhesive slurry (solid content of 15.75%) and mechanically stirred at 80±2℃ for a period of time to remove excess moisture, so that the moisture content of the wood shavings is controlled between 8% and 12%. Then, it is hot-pressed for 15 min at 180±2℃ and 3 MPa pressure using a press (CGYJ-100, Shijiazhuang, China) to obtain the finished first-generation recycled board (size: 100 x 100 x 5 mm; density: 1.0 g / cm³).

[0054] The first-generation recycled board was crushed into wood particles. The recycled wood particles, which were 1.156 times the mass of the wood particles used to prepare the first-generation recycled board, were mixed with 0.3 times the mass of deionized water. Under the same preparation conditions, the second-generation recycled board was formed by hot pressing.

[0055] Mechanical properties were evaluated according to GB / T 4897-2015 standard. Samples were left to stand at room temperature (20±2℃, 60% RH) for 24 hours. The bending strength (MOR) and modulus of elasticity (MOE) of the particleboard were determined by a three-point bending test at a loading rate of 10 mm / min. Six measurements were performed on each sample, and the average value was taken.

[0056] The tensile strength of the adhesive film prepared in Example 1 after two cycles of regeneration was compared with the tensile strength of adhesive films prepared with other existing adhesives after two cycles of regeneration. The existing adhesives used were soybean protein / L-cysteine / glycidyl / sodium tetraborate / mineralized calcium phosphate adhesives hydrolyzed by bromelain: prepared using the method disclosed by Huang X. et al. in "A reusable soy protein adhesive with enhanced weather resistance through construction of a cutin-like structure" (Cell Reports Physical Science, 2024, Volume 5, Issue 6, 102024).

[0057] The results are shown in Table 2.

[0058] Table 2

[0059] The bending strength of the second-generation recycled board prepared with the adhesive of Example 1 of this invention is compared with that of the second-generation recycled board prepared with other adhesives. Phenolic adhesive, urea-formaldehyde adhesive, and soybean protein / L-cysteine / glycidyl / sodium tetraborate / mineralized calcium phosphate adhesive hydrolyzed with bromelain were obtained using the preparation method disclosed by Huang X. et al. in "A reusable soy protein adhesive with enhanced weather resistance through construction of a cutin-like structure" (Cell Reports Physical Science, 2024. Volume 5, Issue 6, 102024).

[0060] The results are shown in Table 3.

[0061] Table 3

[0062] Comparing the examples and the comparative examples, it is evident that the materials of the examples exhibit superior performance in several key parameters. In terms of reworkability, Example 1 demonstrates a more significant advantage. Furthermore, the examples show significantly higher pre-compact strength and dry / water-resistant bond strength than the comparative examples, indicating superior material mechanical properties. The adhesive of the present invention demonstrates excellent performance in reworkability, pre-compact strength, and mechanical strength, possessing significant application prospects and technological advantages.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A reprocessable plant protein adhesive, characterized in that, include: The ingredients include an organoboronic acid derivative, polyvinyl alcohol, plant protein, and water, wherein the organoboronic acid derivative comprises an aldehyde group and a boric acid group.

2. The adhesive according to claim 1, characterized in that, The organoboronic acid derivative is selected from at least one of 5-formaldehyde-furan-2-boronic acid, o-formylphenylboronic acid, m-formylphenylboronic acid, 4-formylphenylboronic acid, 4-aldehydethiophen-2-boronic acid, 5-formylthiophen-3-boronic acid, 3-formaldehydethiophen-2-boronic acid, 3,5-diformylphenylboronic acid, 4-methoxy-2-formylphenylboronic acid, 4-formylfuran-2-boronic acid, 2-formylpyridin-5-boronic acid, and (1-formylnaphthalene-2-yl)boronic acid, preferably 4-formylphenylboronic acid.

3. The adhesive according to claim 1, characterized in that, The molecular weight of the polyvinyl alcohol is 140,000-190,000, preferably 146,000-156,000.

4. The adhesive according to claim 1, characterized in that, The plant protein has a protein content of 90-98 wt%, preferably 93-95 wt%. And / or, the plant protein is selected from one or more of soybean meal protein, peanut meal protein, cottonseed meal protein, and corn alcohol meal protein.

5. The adhesive according to any one of claims 1-4, characterized in that, The mass ratio of the plant protein to the organoboronic acid derivative is 1:(0.001~0.1), preferably 1:(0.01~0.05).

6. The adhesive according to any one of claims 1-4, characterized in that, The mass ratio of the plant protein to the polyvinyl alcohol is 1:(0.001~1), preferably 1:(0.005~0.2).

7. The adhesive according to any one of claims 1-4, characterized in that, The mass ratio of the plant protein to the water is 1:(1~12), preferably 1:(5~9).

8. A method for preparing the reprocessable plant protein adhesive according to any one of claims 1-7, characterized in that, include: Polyvinyl alcohol is mixed with water to obtain a stable homogeneous aqueous solution; The stable homogeneous aqueous solution, polyvinyl alcohol, plant protein and water are mixed.

9. The method according to claim 8, characterized in that, In the stable homogeneous aqueous solution, the mass ratio of polyvinyl alcohol to water is 1:(5~200), preferably 1:(9~99).

10. A type of plywood, characterized in that, It is formed by stacking multiple sheets, with an adhesive layer between adjacent sheets, the adhesive layer being formed by the reprocessable plant protein adhesive according to any one of claims 1-7.

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