A water-resistant plant protein adhesive, its preparation method and application

Abstract

This invention discloses a water-resistant plant protein adhesive, its preparation method, and its application. The raw materials for preparing the water-resistant plant protein adhesive include: oilseed cake, oilseed cake protein isolate, choline glyphosate, and a modifier; the raw materials for preparing the modifier include: urea and aminosulfonic acid compounds. This invention proposes a water-resistant plant protein adhesive that avoids the separation of oilseed cake while simultaneously improving the flame retardancy, antibacterial properties, and mechanical properties of engineered wood products.

Description

Technical Field

[0001] This invention pertains to board modifiers, specifically relating to a water-resistant plant protein adhesive, its preparation method, and its application. Background Technology

[0002] Timber and bamboo, such as poplar plantations, have advantages such as high yield and fast growth. However, their low density, poor mechanical strength, low surface hardness, low wear resistance, and poor corrosion resistance limit their use. Compared with natural forest timber, their material properties and decorative appeal are far inferior. Therefore, chemical modification of fast-growing timber is extremely necessary. Currently, the preparation of wood adhesives using chemical raw materials has become the mainstream in the industry, especially formaldehyde-based resins (such as urea-formaldehyde resin (UF), melamine-formaldehyde resin (MF), and phenolic resin (PF). Due to their excellent bonding strength and water and weather resistance, they account for about 90% of wood adhesives. However, a fatal flaw of "formaldehyde-based" resins is the harm of formaldehyde to human health and the environment. With the continuous improvement of domestic economic level and people's quality of life, especially under the background of increasingly strict laws and regulations, the drawbacks of "formaldehyde-based" resin adhesives are attracting more and more attention. Developing non-toxic, green, and environmentally friendly new wood adhesives is of profound significance to the development of the industry. With the increasing environmental awareness of the public and the ever-improving environmental requirements for engineered wood products, environmentally friendly biomass-based adhesives such as plant protein adhesives, lignin adhesives, tannin adhesives, and starch adhesives are receiving more and more attention. Currently, the raw materials for preparing protein-based adhesives are mainly plant proteins and plant protein cakes. The extraction process of plant protein isolates is complex and expensive, limiting industrial application. Therefore, in engineered wood product production, plant protein cakes, which have relatively low protein content and lower cost, are often used as raw materials to prepare protein-based adhesives. To improve the water resistance of protein-based adhesives, existing preparation methods are mostly based on modifying protein molecules in plant protein cakes, with less involvement in carbohydrate modification. Traditionally, the cake needs to be separated to separate the difficult-to-react components (cellulose, hemicellulose, and lignin) from the protein components before the protein components can be used for subsequent adhesive-making processes. This process is complex and difficult to scale up.

[0003] In summary, developing a water-resistant plant protein adhesive with a simple preparation process is of paramount importance. Summary of the Invention

[0004] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a water-resistant plant protein adhesive that avoids the separation of the oil cake and simultaneously improves the flame retardancy, antibacterial properties, and mechanical properties of the engineered wood product.

[0005] According to a first aspect of the present invention, a water-resistant plant protein adhesive is provided, wherein the raw materials for preparing the water-resistant plant protein adhesive include: oilseed cake, oilseed cake protein isolate, choline glyphosate, and a modifier;

[0006] The raw materials for preparing the modifier include urea and aminosulfonic acid compounds.

[0007] According to some embodiments of the present invention, the aminosulfonic acid compound includes at least one of aminosulfonic acid and p-aminobenzenesulfonic acid.

[0008] According to the embodiments of the first aspect of the present invention, at least the following beneficial effects are achieved:

[0009] Traditional processes require separating the cake meal to separate the less reactive components (cellulose, hemicellulose, and lignin) from the protein components before the protein components can be used in subsequent adhesive processing. This is because cellulose, hemicellulose, and lignin have low reactivity and cannot participate in subsequent reactions. In this invention, in the above-mentioned raw materials, aminosulfonic acid compounds react with the hydroxyl groups of the various components in the cake meal (mainly cellulose, hemicellulose, lignin, and protein), enhancing the physical and chemical properties of the cake meal and improving its functional characteristics, making subsequent reactions more effective. Phosphocholine degrades and dissolves the protein components in the cake meal, increasing the availability and biocompatibility of the separated protein. The role of phosphocholine is to react with the protein, causing protein reconstruction and improving the performance of the adhesive.

[0010] Specifically, in the first step, aminosulfonic acid compounds and urea react with cellulose, hemicellulose, and lignin in the oilseed cake to depolymerize the three elements and convert them into water-soluble substances. After adding phosphocholine, due to the treatment in step S1, the three elements are converted into the main water-soluble substances. Therefore, the coated protein components are fully exposed, which is beneficial for further treatment with phosphocholine (without the treatment in step S1, the protein components in the oilseed cake cannot be fully treated and reconstructed by using only phosphocholine or related methods; at the same time, the treatment in step S1 converts and separates the three elements, grafts them, and protects the three elements from participating in subsequent reactions, thus fully preserving their reactivity).

[0011] According to some embodiments of the present invention, the oilseed cake protein isolate includes at least one of tung oil cake protein, camellia oil cake protein, soybean protein, and litsea cubeba cake protein.

[0012] Protein isolate from oilseed cake has high reactivity and can undergo condensation reactions with hydroxyl and amino groups in protein, thereby reducing the water and moisture absorption of adhesives and enhancing the mechanical properties of cured adhesives.

[0013] According to a second aspect of the present invention, a method for preparing a water-resistant plant protein adhesive is provided, comprising the following steps:

[0014] S1. The modifier is dispersed and then heated and mixed with the cake meal under pH conditions of 5.0 to 6.0 to obtain component A;

[0015] S2. Under pH conditions of 10-11, choline phosphate and component A are heated and mixed to react, and then impurities are removed to obtain modified cake meal;

[0016] S3. The modified oilseed cake and oilseed cake protein isolate are mixed and reacted to obtain a modified plant protein-based adhesive.

[0017] In step S1, the pH value is controlled between 5.0 and 6.0. Under a weakly acidic environment, urea and sulfamic acid compounds can react better with the hydroxyl groups on lignin, cellulose, and hemicellulose. A weakly acidic environment also protects the protein components from premature and excessive degradation. If the pH value is outside this range, the reaction cannot proceed, and the reaction should also be avoided from being inhibited.

[0018] According to some embodiments of the present invention, in step S1, the method for preparing the modifier includes:

[0019] The aminosulfonic acid compound and urea are mixed and heated to 120-135°C for reaction.

[0020] According to some embodiments of the present invention, in step S2, the molar ratio of the cake to the modifier is 1:10 to 20.

[0021] According to some embodiments of the present invention, in step S1, the heating temperature is 80-90°C.

[0022] According to some embodiments of the present invention, in step S2, the heating temperature is 120-130°C.

[0023] According to some embodiments of the present invention, in step S2, the mass concentration of the protein isolate from the meal is 5-10% wt.

[0024] According to a third aspect of the present invention, a type of engineered wood panel is provided, wherein the raw materials for preparing the engineered wood panel include the water-resistant plant protein adhesive described herein. Detailed Implementation

[0025] The embodiments of the present invention are described in detail below, with examples of these embodiments shown, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to reference are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0026] All the cake protein in the examples was commercially available.

[0027] Example 1

[0028] This embodiment discloses a method for preparing a water-resistant plant protein adhesive, the specific steps of which are as follows:

[0029] S1. Mix aminosulfonic acid and urea at a mass ratio of 1:2, place in a flask, stir continuously, heat in an oil bath to 120°C until the liquid is homogeneous, then mix with water at a mass ratio of 0.5:1.5, and after complete dissolution, adjust the pH of the mixed solution to between 5.0 and 6.0 using oxalic acid to obtain a modifier. Then mix the cake and the obtained modifier at a mass ratio of 1:10, and stir rapidly for 6 hours under heating conditions (80°C) to obtain a mixture. Add urea at 0.1 wt% of the mixture to terminate the reaction and obtain component A.

[0030] S2. After adjusting the pH of component A to between 10 and 11 using ammonia water, a mixed system is obtained. 0.5 wt% of choline phosphate is added to the mixed system. After mixing and stirring evenly, the mixture is rapidly stirred for 3 hours under heating conditions (120℃) to allow for complete reaction. After heating is stopped, the mixture is rapidly cooled to room temperature and centrifuged. After separation, the mixture is dialyzed with dialysis tube and deionized water to remove excess modifier. The solid component is then obtained by centrifugation and freeze-drying to obtain modified cake.

[0031] S3. Mix the modified cake with water to obtain a 10% wt modified cake mixture. After mixing evenly, add tung oil cake protein at 0.5 wt% of the mixture and continue stirring until uniform to obtain the modified plant protein-based adhesive.

[0032] Example 2

[0033] This embodiment discloses a method for preparing a water-resistant plant protein adhesive, the specific steps of which are as follows:

[0034] S1. Mix aminosulfonic acid and urea at a mass ratio of 1:3, place in a flask, stir continuously, heat in an oil bath to 120°C until the liquid is homogeneous, then mix with water at a ratio of 0.5:1.5. After complete dissolution, adjust the pH of the mixed solution to between 5.0 and 6.0 using oxalic acid to obtain a modifier. Then mix the cake meal with the obtained modifier at a ratio of 1:10, and stir rapidly for 6 hours under heating conditions (80°C). Finally, add an appropriate amount of urea to terminate the reaction to obtain component A.

[0035] S2. After adjusting the pH of component A to between 10 and 11 using ammonia water, add 0.5% wt choline glycine, mix and stir evenly, and then stir rapidly for 3 hours under heating conditions (120℃) to allow the reaction to proceed fully. After the reaction is complete, stop heating, cool rapidly to room temperature, centrifuge and then dialyze with dialysis tube and deionized water to remove excess modifier. After centrifugation and freeze drying, obtain the solid component to obtain the modified cake.

[0036] S3. Mix the modified cake with water to obtain a 10% wt modified cake mixture. After mixing evenly, add 5% wt tung oil cake protein and continue stirring until uniform to obtain the modified plant protein-based adhesive.

[0037] Example 3

[0038] This embodiment discloses a method for preparing a water-resistant plant protein adhesive, the specific steps of which are as follows:

[0039] S1. Mix aminosulfonic acid and urea at a mass ratio of 1:5, place in a flask, stir continuously, heat in an oil bath to 120°C until the liquid is homogeneous, then mix with water at a ratio of 0.5:1.5. After complete dissolution, adjust the pH of the mixed solution to between 5.0 and 6.0 using oxalic acid to obtain a modifier. Then mix the cake meal with the obtained modifier at a ratio of 1:10, and stir rapidly for 6 hours under heating conditions (80°C). Finally, add an appropriate amount of urea to terminate the reaction to obtain component A.

[0040] S2. After adjusting the pH of component A to between 10 and 11 using ammonia water, add 0.5% wt choline glycine, mix and stir evenly, and then stir rapidly for 3 hours under heating conditions (120℃) to allow the reaction to proceed fully. After the reaction is complete, stop heating, cool rapidly to room temperature, centrifuge and then dialyze with dialysis tube and deionized water to remove excess modifier. After centrifugation and freeze drying, obtain the solid component to obtain the modified cake.

[0041] S3. Mix the modified cake with water to obtain a 10% wt modified cake mixture. After mixing evenly, add 5% wt tung oil cake protein and continue stirring until uniform to obtain the modified plant protein-based adhesive.

[0042] Example 4

[0043] This embodiment discloses a method for preparing a water-resistant plant protein adhesive, the specific steps of which are as follows:

[0044] S1. Mix aminosulfonic acid (CAS No.: 226-218-8) and urea at a mass ratio of 1:2, place the mixture in a flask, stir continuously, heat in an oil bath to 120°C until the liquid is homogeneous, then mix with water at a mass ratio of 0.5:1.5, and after complete dissolution, adjust the pH of the mixed solution to between 5.0 and 6.0 using oxalic acid to obtain a modifier. Then mix the cake meal with the obtained modifier at a mass ratio of 1:10, and stir rapidly for 6 hours under heating conditions (80°C). Finally, add an appropriate amount of urea to terminate the reaction to obtain component A.

[0045] S2. After adjusting the pH of component A to between 10 and 11 using ammonia water, add 0.2% wt choline glycine, mix and stir evenly, and then stir rapidly for 3 hours under heating conditions (120℃) to allow the reaction to proceed fully. After the reaction is complete, stop heating, cool rapidly to room temperature, centrifuge and then dialyze with dialysis tube and deionized water to remove excess modifier. After centrifugation and freeze drying, obtain the solid component to obtain the modified cake.

[0046] S3. Mix the modified cake with water to obtain a 10% wt modified cake mixture. After mixing evenly, add 5% wt tung oil cake protein and continue stirring until uniform to obtain the modified plant protein-based adhesive.

[0047] Example 5

[0048] This embodiment discloses a method for preparing a water-resistant plant protein adhesive, the specific steps of which are as follows:

[0049] S1. Mix aminosulfonic acid and urea at a mass ratio of 1:2, place in a flask, stir continuously, heat in an oil bath to 120°C until the liquid is homogeneous, then mix with water at a ratio of 0.5:1.5, and after complete dissolution, use oxalic acid to adjust the pH of the mixed solution to between 5.0 and 6.0 to obtain a modifier. Then mix the cake and the obtained modifier at a ratio of 1:10, and stir rapidly for 6 hours under heating conditions (80°C). Finally, add an appropriate amount of urea to terminate the reaction to obtain component A.

[0050] S2. After adjusting the pH of component A to between 10 and 11 using ammonia water, add 0.9% wt choline glycine, mix and stir evenly, and then stir rapidly for 3 hours under heating conditions (120℃) to allow the reaction to proceed fully. After the reaction is complete, stop heating, cool rapidly to room temperature, centrifuge and then dialyze with dialysis tube and deionized water to remove excess modifier. After centrifugation and freeze drying, obtain the solid component to obtain the modified cake.

[0051] S3. Mix the modified cake with water to obtain a 10% wt modified cake mixture. After mixing evenly, add 5% wt tung oil cake protein and continue stirring until uniform to obtain the modified plant protein-based adhesive.

[0052] Comparative Example 1

[0053] This comparative example discloses a method for preparing a water-resistant plant protein adhesive. The difference between this comparative example and Example 1 is that p-toluenesulfonic acid is used instead of aminosulfonic acid compounds, while the other conditions are the same.

[0054] Comparative Example 2

[0055] This comparative example discloses a method for preparing a water-resistant plant protein adhesive. The difference between this comparative example and Example 1 is that sulfamic acid is not added, while the other conditions are the same.

[0056] Comparative Example 3

[0057] This comparative example discloses a method for preparing a water-resistant plant protein adhesive. The difference between this comparative example and Example 1 is that choline chloride is used instead of choline phosphate, while the other conditions are the same.

[0058] Comparative Example 4

[0059] This comparative example discloses a method for preparing a water-resistant plant protein adhesive. The difference between this comparative example and Example 1 is that no adjustment is made to the pH value in step S1, while the other conditions are the same.

[0060] Comparative Example 5

[0061] This comparative example discloses a method for preparing a water-resistant plant protein adhesive. The difference between this comparative example and Example 1 is that no adjustment is made to the pH value in step S2, while the other conditions are the same.

[0062] Comparative Example 6

[0063] This comparative example discloses a method for preparing a water-resistant plant protein adhesive. The difference between this comparative example and Example 1 is that no adjustment is made to the pH value in steps S1 and S2, while the other conditions are the same.

[0064] Comparative Example 7

[0065] This comparative example discloses a method for preparing a water-resistant plant protein adhesive. The difference between this comparative example and Example 1 is that steps S1 and S2 are interchanged, while the other conditions are the same.

[0066] Comparative Example 8

[0067] This comparative example discloses a method for preparing a water-resistant plant protein adhesive. The difference between this comparative example and Example 1 is that step S1 is omitted, while the other conditions are the same.

[0068] Comparative Example 9

[0069] This comparative example discloses a method for preparing a water-resistant plant protein adhesive. The difference between this comparative example and Example 1 is that step S2 is omitted, while the other conditions are the same.

[0070] Comparative Example 10

[0071] This embodiment discloses a method for preparing a water-resistant plant protein adhesive, the specific steps of which are as follows:

[0072] S1. Mix p-aminobenzenesulfonic acid and urea at a mass ratio of 1:2, place in a flask, stir continuously, heat in an oil bath to 120°C until the liquid is homogeneous, then mix with water at a ratio of 0.5:1.5, and after complete dissolution, adjust the pH of the mixed solution to between 5.0 and 6.0 using oxalic acid to obtain component A. Then mix the cake meal with the obtained component A at a ratio of 1:10, and stir rapidly for 6 hours under heating conditions (80°C). Finally, add an appropriate amount of urea to terminate the reaction to obtain component B.

[0073] S2. After adjusting the pH of component B to between 10 and 11 using ammonia water, add 0.5% wt choline glycine, mix and stir evenly, and then stir rapidly for 3 hours under heating conditions (120℃) to allow the reaction to proceed fully. After the reaction is complete, stop heating, cool rapidly to room temperature, centrifuge and then dialyze with dialysis tube and deionized water to remove excess modifier. After centrifugation and freeze drying, obtain the solid component to obtain the modified cake.

[0074] S3. Mix the modified cake with water to obtain a 10% wt modified cake mixture. After mixing evenly, add 5% wt tung oil cake protein and continue stirring until uniform to obtain the modified plant protein-based adhesive.

[0075] Comparative Example 11

[0076] This comparative example discloses a method for preparing a water-resistant plant protein adhesive. The difference between this comparative example and Example 1 is that the pH value in step S1 is between 3 and 4, while the other conditions are the same.

[0077] Comparative Example 12

[0078] This comparative example discloses a method for preparing a water-resistant plant protein adhesive. The difference between this comparative example and Example 1 is that the pH value in step S1 is between 10 and 11, while the other conditions are the same.

[0079] Test Example 1

[0080] This test case evaluated the performance of the adhesives obtained in the examples and comparative examples when applied to boards. The specific steps are as follows:

[0081] ①Preparation of thin bamboo and wood particleboard:

[0082] Raw materials: bamboo shavings or wood shavings.

[0083] Thin wood shavings refer to boards with a thickness of 2–8 mm, made from wood shavings with a length of 0.8–4 mm, an aspect ratio of 15 mm, and a thickness of 0.2–0.25 mm. These boards are generally produced using a rolling process rather than a flat pressing method. This type of board can replace plywood as furniture baseboards, partitions, or as the core board for plywood.

[0084] Hot pressing conditions: hot pressing temperature 120~135℃, hot pressing time 180~300s, hot pressing pressure 0.8~1.2MPa.

[0085] Table 1. Adhesive Storage Stability Test (15-day Storage Test)

[0086]

[0087] Example 5 increased the amount of choline glyphosate, which allowed for sufficient depolymerization and reconstruction of the meal protein in the S2 treatment. However, it also caused excessive depolymerization and reconstruction of the proteome, resulting in a significant increase in the viscosity of the adhesive product compared to other examples.

[0088] In Comparative Example 1, p-toluenesulfonic acid cannot react with the three major elements (cellulose, lignin, and hemicellulose), so the cellulose, hemicellulose, and lignin in the cake do not change and cannot form a homogeneous emulsion in aqueous solution, resulting in precipitation and stratification during storage testing.

[0089] In Comparative Example 2, no aminosulfonic acid was added in step S1, so simply adjusting the pH value could not react with the cellulose, hemicellulose, and lignin in the cake, resulting in the inability to convert the three elements into the main water-soluble substances. Therefore, in subsequent steps, cellulose, hemicellulose, and lignin existed as water-insoluble particulate matter in the emulsion system of the adhesive. After a certain period of storage, the cellulose, hemicellulose, and lignin particles settled, resulting in stratification.

[0090] Comparative Example 3: Choline chloride is unstable in an alkaline environment and is easily degraded. It cannot react with the protein components in the oilseed cake. Since the protein components in the oilseed cake are relatively stable and generally have low water solubility, the protein particles in the oilseed cake that have not undergone any treatment will also settle and separate as the storage time increases.

[0091] In Comparative Example 4, step S1 did not involve any pH adjustment. The reaction of aminosulfonic acid with the three major elements requires a weakly acidic environment, necessitating the provision of H+. +In an acidic environment, degradation is facilitated, promoting the reaction. However, if the acidity is too low, the reaction will not proceed smoothly. This is because acid treatment with too low a pH value will cause a certain degree of carbonization on the surface of cellulose and hemicellulose particles, hindering the wetting and deep reaction of the modifier on the cake particles. As a result, the cellulose, hemicellulose, and lignin particles in the cake will not react completely and cannot be converted into water-soluble substances. They will remain as water-insoluble particles in subsequent reactions and adhesive emulsion systems, and will settle and separate during long-term storage. If the alkalinity is too strong, it will cause excessive degradation of the protein structure. Some of them may degrade into amino acid structures or further dehydrate and carbonize, thus forming water-insoluble particles, which will gradually settle and separate during long-term storage.

[0092] In Comparative Example 5, no pH adjustment was made in step S2. The reaction of phosphocholine with proteins requires an alkaline environment to achieve optimal treatment and the highest reactivity. Therefore, the protein components in the meal cannot be depolymerized and reconstituted in step S2. Its water solubility is poor, making it difficult to fully dissolve and mix with the adhesive emulsion system. Long-term storage will cause sedimentation and stratification.

[0093] In Comparative Example 6, no pH value was adjusted in steps S1 and S2, which resulted in sulfamic acid and glyphosate choline being unable to convert the three major components and protein components in S1 and S2, maintaining them in a water-insoluble particle state, and causing sedimentation and stratification during long-term storage.

[0094] In Comparative Example 7, the treatment steps were changed. Due to the coating and steric hindrance effects of cellulose, hemicellulose, and lignin in the oilseed cake, the first step of choline phosphate treatment of the protein in the oilseed cake was incomplete, resulting in low reaction efficiency. Most of the protein did not complete the depolymerization and reconstruction reaction and remained in a water-insoluble particle state. As a result, it could not be completely dissolved and mixed in the adhesive emulsion system, and sedimentation and stratification occurred after long-term storage.

[0095] In Comparative Example 8, due to the absence of the S1 step, cellulose, hemicellulose, and lignin remained in a water-insoluble particulate state, which prevented them from being completely dissolved and mixed in the adhesive emulsion system, resulting in sedimentation and stratification after long-term storage.

[0096] In Comparative Example 9, due to the absence of the S2 step, the protein component of the cake meal remained in a water-insoluble particulate state with poor reactivity, which resulted in incomplete dissolution and mixing in the adhesive emulsion system, leading to sedimentation and stratification after long-term storage.

[0097] Comparative Example 10 showed weak reactivity with the three major hydroxyl groups of p-aminobenzenesulfonic acid. Furthermore, p-aminobenzenesulfonic acid has a large molecular structure and poor water solubility. During the reaction, due to steric hindrance and poor solubility, even if a certain degree of reaction occurs, it cannot achieve a complete reaction. Therefore, the reaction of cellulose, hemicellulose, and lignin is incomplete and insufficient, with some remaining in a water-insoluble particle state. Over long-term storage, this leads to sedimentation and stratification.

[0098] In Comparative Example 11, the pH value in step S1 is between 3 and 4. Too low a pH acid treatment will cause a certain degree of carbonization on the surface of cellulose and hemicellulose particles, which will hinder the modification agent from wetting and reacting deeply with the cake particles. As a result, the cellulose, hemicellulose and lignin particles in the cake will not react completely and cannot be converted into water-soluble substances. They will remain as water-insoluble particulate matter in subsequent reactions and adhesive emulsion systems, and will settle and separate after long-term storage.

[0099] Comparative Example 12: Aminosulfonic acid is prone to reactive transformation under alkaline conditions and cannot react with the three major cellulose molecules. Therefore, cellulose, hemicellulose and lignin remain in a water-insoluble particulate state and cannot be dissolved and blended in adhesive emulsion systems. After long-term storage, they are prone to sedimentation and stratification.

[0100] The test results are shown in Table 2:

[0101] Table 2 Performance Tests of Board Modifiers in Bamboo and Wood Thin Particleboard

[0102]

[0103]

[0104] Example 5 increased the amount of choline glyphosate, which allowed for sufficient depolymerization and reconstruction of the meal protein in the S2 treatment. However, it also caused excessive depolymerization and reconstruction of the proteome, resulting in a decrease in some physical and mechanical properties compared to other examples.

[0105] In Comparative Example 1, p-toluenesulfonic acid could not react with the three main components (cellulose, lignin, and hemicellulose). As a result, the cellulose, hemicellulose, and lignin in the cake did not react at all, and they could not form a homogeneous emulsion in the aqueous solution. Furthermore, the cellulose, hemicellulose, and lignin particles were purely physically filled in the subsequent adhesive curing reaction without the formation of covalent bonds, resulting in poor mechanical properties. At the same time, the poor LOI was due to the fact that although relevant substances were added, they did not react and were unevenly distributed in the emulsion system, resulting in a low LOI value.

[0106] In Comparative Example 2, without the addition of aminosulfonic acid, the aminosulfonic acid cannot react with the cellulose, hemicellulose, and lignin in the cake, resulting in the inability to convert the three elements into the main water-soluble substances. Therefore, the cellulose, hemicellulose, and lignin remain in a water-insoluble particle state and cannot participate in the subsequent curing reaction. No covalent bonds are formed between the substances, resulting in poor physical and mechanical properties.

[0107] Comparative Example 3: Choline chloride is unstable in an alkaline environment and is easily degraded, making it unable to react further with proteins. This results in a negative effect of adjusting the pH value in S2, causing the proteins in the cake meal to be unable to depolymerize and reconstruct into active reactive substances. Furthermore, the lack of water solubility makes the cake meal protein components prone to sedimentation in the emulsion system, unable to be evenly distributed, and unable to participate in the subsequent solidification reactions of various substances, thus failing to form cross-linked network structures and resulting in poor physical and mechanical properties of the board.

[0108] In Comparative Example 4, step S1 did not involve any pH adjustment. The reaction of aminosulfonic acid with the three major elements requires a weakly acidic environment, necessitating the provision of H+. + In an acidic environment, degradation is easily promoted, which facilitates the reaction. However, if the acidity is too low, the reaction will not proceed smoothly. Excessive acid treatment will cause a certain degree of carbonization on the surface of cellulose and hemicellulose particles, which will hinder the wetting and full reaction of the modifier on the cake particles. As a result, the cellulose, hemicellulose and lignin particles in the cake components will not react fully and will remain in a water-insoluble particle state. They will not be able to participate in the reaction in the subsequent curing reaction, which will affect the formation of the cross-linked network structure and result in poor physical and mechanical properties of the board.

[0109] In Comparative Example 5, no pH value was adjusted in step S2. The reaction of phosphocholine with proteins requires an alkaline environment to achieve optimal treatment and the highest reactivity. Therefore, the protein components in the cake could not be depolymerized and reconstructed in step S2. Its water solubility was poor, which affected the formation of the cross-linked network structure and resulted in poor physical and mechanical properties of the board.

[0110] In Comparative Example 6, no pH value was adjusted in steps S1 and S2, which prevented aminosulfonic acid and glyphosate choline from converting the three major components and protein components in S1 and S2. As a result, the components could not be connected by covalent bonds in the final curing reaction, and no cross-linked network structure was formed, resulting in poor physical and mechanical properties of the board.

[0111] In Comparative Example 7, the treatment steps were changed. Due to the coating and steric hindrance effects of cellulose, hemicellulose, and lignin in the cake, the first step of glyphosate choline treatment of the protein in the cake was incomplete, resulting in low reaction efficiency. Most of the protein did not complete the depolymerization and reconstruction reaction and could not participate in the subsequent curing reaction, which affected the formation of the cross-linked network structure and resulted in poor physical and mechanical properties of the board.

[0112] In Comparative Example 8, due to the absence of the S1 step, cellulose, hemicellulose, and lignin remained in a water-insoluble particle state and were unable to react with other components in subsequent reactions to form covalent bonds and affect the formation of cross-linked network structures.

[0113] In Comparative Example 9, due to the absence of the S2 step, the protein component of the cake meal remained in a water-insoluble particle state, exhibiting poor reactivity. Consequently, it could not react sufficiently and effectively with other components in subsequent reactions, affecting the formation of the cross-linked network structure.

[0114] Comparative Example 10 showed weak reactivity with the three major hydroxyl groups. Furthermore, the large molecular structure of p-aminobenzenesulfonic acid resulted in poor water solubility. Due to steric hindrance and poor solubility, even if a certain degree of reaction occurred, it could not achieve complete reaction. This led to incomplete and insufficient reaction of cellulose, hemicellulose, and lignin, with some components remaining in a water-insoluble particle state. Consequently, these particles could not react with other components in subsequent reactions to form covalent bonds and hindered the formation of cross-linked network structures.

[0115] In Comparative Example 11, the pH value of step S1 was between 3 and 4. Too low a pH value would cause a certain degree of carbonization on the surface of cellulose and hemicellulose particles, which would hinder the modification agent from wetting and reacting deeply with the cake particles. As a result, the cellulose, hemicellulose and lignin particles in the cake would not react completely and could not be converted into water-soluble substances. In subsequent reactions and adhesive emulsion systems, they would remain as water-insoluble particulate matter, which would hinder the smooth progress of the reaction.

[0116] Comparative Example 12: Aminosulfonic acid is prone to reactive transformation under alkaline conditions, making it unable to process the three major elements. In subsequent reactions, it also cannot react with other components to form covalent bonds and affect the formation of cross-linked network structures.

[0117] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A water-resistant plant protein adhesive, characterized by, The raw materials for preparing the water-resistant plant protein adhesive include: oilseed cake, oilseed cake protein isolate, choline glyphosate, and modifier; The raw materials for preparing the modifier include urea and aminosulfonic acid; The water-resistant plant protein adhesive is prepared by the following method: S1. The modifier is dispersed and then heated and mixed with the cake meal under pH conditions of 5.0~6.0 to obtain component A; S2. Under pH conditions of 10-11, choline phosphate and component A are heated and mixed to react, and then impurities are removed to obtain modified cake meal; S3. The modified oilseed cake and oilseed cake protein isolate are mixed and reacted to obtain a modified plant protein-based adhesive.

2. The water-resistant plant protein adhesive according to claim 1, characterized in that, The protein isolate from the oilseed cake includes at least one of tung oil oilseed cake protein, camellia oilseed cake protein, soybean protein, and litsea cubeba oilseed cake protein.

3. The water-resistant plant protein adhesive according to claim 1, wherein, In step S1, the method for preparing the modifier includes: The aminosulfonic acid compound and urea are mixed and heated to 120~135℃ for reaction.

4. The water-resistant plant protein adhesive according to claim 1, wherein In step S1, the mass ratio of the cake meal to the modifier is 1:(10~20).

5. The water-resistant plant protein adhesive according to claim 1, wherein In step S1, the heating temperature is 80~90℃.

6. The water-resistant plant protein adhesive according to claim 1, wherein In step S2, the heating temperature is 120~130℃.

7. The water-resistant plant protein adhesive according to claim 1, wherein In step S2, the mass concentration of the protein isolate from the meal is 5-10%wt.

8. A wood-based panel, characterized in that The raw materials for preparing the artificial board include the water-resistant plant protein adhesive as described in any one of claims 1 to 7.

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