Preparation method of graft modified PAE resin crosslinking agent, binary system soybean meal adhesive and application

Abstract

The application discloses a grafted modified PAE resin crosslinking agent, a binary system soybean meal adhesive and application thereof, and belongs to the field of adhesives and artificial boards. A preparation method is as follows: first, polyamide is prepared by condensation of adipic acid and diethylenetriamine; then, the PAE resin is synthesized by step-by-step reaction of the polyamide and epichlorohydrin; finally, the target crosslinking agent is obtained by grafting modification of the PAE resin under catalysis of p-toluenesulfonic acid and in the presence of acrylic acid. The crosslinking agent is compounded with soybean meal powder, water and water-soluble cellulose derivatives to obtain the binary system soybean meal adhesive. By introducing active groups into the molecular chain of the PAE resin, the crosslinking density and hydrophobicity of the soybean meal protein are remarkably enhanced, and the water-resistant bonding strength of the adhesive is fundamentally improved. Meanwhile, the modified resin and the cellulose derivatives are synergistic, the water retention, rheological properties and wetting and spreading properties of the adhesive on wood are effectively improved, the sizing process and pre-pressing effect are optimized, and the quality of the board is more uniform, and the application is more suitable for industrial production requirements.

Description

Technical Field

[0001] This invention relates to a method for preparing a grafted modified PAE resin crosslinking agent, a binary soybean meal adhesive and its application, belonging to the technical fields of adhesives and engineered wood products. Background Technology

[0002] With the continuous depletion of fossil energy resources and the increasing demands for ecological environmental protection and energy conservation and emission reduction, the development of green and environmentally friendly adhesives using renewable biomass resources as raw materials has gradually become an important development direction for the wood processing and engineered wood products industry. Among many biomass adhesives, soybean meal adhesives are considered to be the most promising formaldehyde-free adhesives. However, in actual industrial applications, soybean meal adhesives still face some technical challenges.

[0003] Specifically, the water resistance of soybean meal adhesives needs further improvement in practical applications, mainly because soybean meal protein molecules contain many hydrophilic groups, which easily absorb water and swell under damp or soaking conditions, affecting the performance of the boards. Patent CN 116083050 B discloses a soybean meal adhesive composed of soybean meal, a penetrant, a dispersion medium, water, and a crosslinking agent. This method uses a crosslinking modification method in a homogeneous system formed under the synergistic effect of the penetrant and dispersion medium to prepare the soybean meal adhesive, which can improve the water resistance and bonding performance of the adhesive. Patent CN115491174 B discloses a soybean meal adhesive including a crosslinking agent and monolayer montmorillonite nanosheets; the preparation method of the monolayer montmorillonite nanosheets includes: mixing montmorillonite, clay, and water, then centrifuging, collecting the suspension, and separating the nanosheets. This method uses monolayer montmorillonite nanosheets as a reinforcing agent to promote the crosslinking effect between soybean meal and the crosslinking agent, resulting in good water resistance.

[0004] Secondly, soybean meal adhesives suffer from insufficient water retention during production, especially in dry climates. The rapid evaporation of water in the adhesive solution leads to a rapid increase in viscosity, decreased fluidity, and even premature dehydration and drying of the adhesive layer. Furthermore, due to the rigid structure of soybean meal protein molecules, the adhesive solution often exhibits insufficient fluidity and poor wetting properties during application. This results in limited adhesion to the veneer surface, hindering the formation of a uniform and continuous adhesive layer structure. Consequently, it affects the pre-pressing effect after assembly and the final quality of the finished veneer product.

[0005] In existing technologies, the water retention of adhesives is usually improved by adding water-retaining agents or hydrophilic polymers, but these components often lead to a decrease in bonding strength. A key technical problem that urgently needs to be solved is to improve bonding strength while simultaneously enhancing water retention and coating performance through structural design and synergistic system regulation. Summary of the Invention

[0006] The purpose of this invention is to provide a technical system based on grafted modified PAE resin crosslinking agent to solve the technical problem that existing soybean meal adhesives are difficult to balance in terms of water retention and bonding strength in the application of wood-based panels.

[0007] In a first aspect, the present invention provides a method for preparing a graft-modified PAE resin crosslinking agent.

[0008] The technical solution is as follows:

[0009] A method for preparing a graft-modified PAE resin crosslinking agent includes the following steps:

[0010] S1. Polyamide is prepared by condensation reaction of adipic acid and diethylenetriamine;

[0011] S2. Adjust the polyamide to a solid content of 20-30%, then add epichlorohydrin dropwise under stirring, and react at 40-50°C under reflux for 1-1.5 hours; then raise the temperature to 70-75°C and react for 2-3 hours; after the reaction is completed, PAE resin is obtained.

[0012] S3. Acrylic acid is added dropwise to the PAE resin under stirring conditions, and p-toluenesulfonic acid is added as a catalyst. The temperature is controlled at 60~70℃ to carry out the polymerization reaction. After the reaction is completed, the grafted modified PAE resin crosslinking agent is obtained.

[0013] This invention provides a solution for improving the overall performance of soybean meal adhesives. Based on a deep understanding of the inherent defects of soybean meal adhesives and the limitations of traditional modification methods, this solution starts from molecular design and aims to synergistically improve water resistance, water retention, and coating properties to meet the comprehensive performance requirements of adhesives in industrial production.

[0014] Currently, although polyamide polyamine epichlorohydrin (PAE) resin is often used as a crosslinking agent in soybean meal adhesives to improve water resistance, the reaction efficiency and crosslinking network density of ordinary PAE resin with soybean meal protein are still insufficient, and it is difficult to improve the rheological properties of the adhesive during application. Simply adding water-retaining materials will directly exacerbate the decrease in bond strength. To address this, this invention creatively proposes a strategy of "graft-modified PAE resin combined with a binary compound system". The core of this strategy is that it no longer involves simple physical mixing or reliance on a single crosslinking mechanism, but rather chemically grafts and modifies the PAE resin to impart new high reactivity, and then compoundes it with functional rheology modifiers to achieve a synergistic improvement in performance and processing properties.

[0015] First, by using molecular grafting design, crosslinking agents are endowed with new reactivity.

[0016] The key to this invention is the chemical modification of traditional PAE resin. First, a basic PAE resin is synthesized, whose molecular chain contains an active hydroxyl group in its azacyclobutanol structure. Then, under catalytic conditions, this hydroxyl group undergoes an esterification reaction with acrylic acid, thereby grafting acrylic acid molecules onto the PAE backbone. This has the following effects: 1) Through the esterification reaction, highly reactive carbon-carbon double bonds are successfully introduced into the PAE molecule, making the modified PAE not only a crosslinking agent but also a "macromonomer" capable of participating in polymerization; 2) A dual crosslinking network is constructed: During hot pressing, these newly introduced double bonds exhibit multiple reactivity capabilities, reacting with various functional groups in soybean meal protein and also copolymerizing with each other. Thus, a novel, dense polymer network is formed within the original PAE-protein crosslinking network. This interpenetrating dual network structure greatly restricts the hydrophilic swelling of protein molecules, thereby significantly improving the water resistance of the adhesive layer.

[0017] Second, by combining binary components, a clear division of labor can be achieved to increase synergy and efficiency.

[0018] This invention designs a binary system composed of modified PAE resin and water-soluble cellulose derivatives. The water-soluble cellulose derivatives are mainly used to improve the water retention and rheological stability of the adhesive. Their long-chain molecules can effectively lock in water, delay moisture evaporation, and improve the wettability and spreadability of the adhesive during application, thereby enhancing coating performance and workability. However, the addition of cellulose-based water-retaining materials usually increases the hydrophilicity of the system or affects the density of the adhesive layer, posing a risk of decreased bonding strength. To address this issue, the modified PAE resin can form a denser and more stable cross-linked network with soybean meal protein, effectively compensating for the potential adverse effects of the water-retaining components on bonding strength and improving the water retention and coating performance of the adhesive.

[0019] Third, the technological path is clear and easy to implement in industrialization.

[0020] This invention starts with molecular structure design and then optimizes the process through functional compounding to form a complete and systematic performance improvement path. The raw materials used in its preparation method are all common chemicals, the modification and compounding processes are simple, and it has good compatibility with existing adhesive production and usage processes. This ensures that the technology can be applied to existing production lines at a relatively low modification cost, and it has good prospects for industrialization and promotion.

[0021] As a preferred embodiment of the above technical solution, in step S1, the molar ratio of adipic acid to diethylenetriamine is 1:(1.0~1.1).

[0022] This ratio control aims to achieve a slight excess of diethylenetriamine, ensuring that the primary amines at both ends react with the adipic acid carboxyl groups to form a linear polyamide, while preserving the secondary amine active sites in the middle of the molecular chain for subsequent reaction with epichlorohydrin. This is crucial for forming a polyamide precursor with the ideal molecular weight.

[0023] As a preferred embodiment of the above technical solution, in step S2, the amount of epichlorohydrin added is 1.2 to 1.6 times that of diethylenetriamine, in molar proportions.

[0024] This precise control of the epichlorohydrin dosage aims to introduce sufficient epoxy groups into the polyamide backbone and form aziridine-onium ion crosslinking active centers, while avoiding excessive epichlorohydrin leading to excessive self-polymerization or side reactions, which would affect the resin's stability and performance.

[0025] As a preferred embodiment of the above technical solution, in step S2, after the reaction has been going on for 2 to 3 hours, the pH value of the system is adjusted to 3.5 to 4 with concentrated sulfuric acid or concentrated hydrochloric acid to terminate the reaction.

[0026] As a preferred embodiment of the above technical solution, in step S3, the reaction ends after 50-60 minutes, heating is stopped, and the mixture is cooled to room temperature to obtain the grafted modified PAE resin crosslinking agent.

[0027] As a preferred embodiment of the above technical solution, in step S3, the amount of acrylic acid added is 1 / (1.8~2.4) of the amount of epichlorohydrin, in molar proportions.

[0028] This ratio is crucial for graft modification. It controls the number of grafted carboxyl groups. If the ratio is too low, the modification effect is not obvious; if the ratio is too high, it may excessively consume the epoxy groups of PAE or lead to self-homogenization, affecting its main function as a crosslinking agent. This range aims to achieve the optimal balance between water retention / rheology improvement and maintaining crosslinking efficiency.

[0029] Secondly, the present invention provides a binary soybean meal adhesive.

[0030] The technical solution is as follows:

[0031] A binary soybean meal adhesive comprises soybean meal powder, water, a water-soluble cellulose derivative, and a graft-modified PAE resin crosslinking agent prepared according to the above method.

[0032] As a preferred embodiment of the above technical solution, the binary soybean meal adhesive has the following components in parts by mass: 36-44 parts grafted modified PAE resin crosslinking agent, 56-64 parts water, 28-35 parts soybean meal powder, and 0.5-2 parts water-soluble cellulose derivative.

[0033] This formulation range reflects an optimized synergistic ratio. Modified PAE serves as the continuous phase and functional host, while the water content ensures suitable solids content and viscosity. A small amount of cellulose derivative significantly improves water retention and rheology, and soybean meal acts as a filler matrix and reactant. This ratio ensures the adhesive solution exhibits good sizing properties, sufficient open time, and ultimately excellent bond strength.

[0034] As a preferred embodiment of the above technical solution, the water-soluble cellulose derivative is selected from at least one of methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, carboxymethylhydroxyethylcellulose, hydroxypropylcellulose, and hydroxypropylmethylcellulose.

[0035] Thirdly, the present invention provides an application of the above-mentioned binary soybean meal adhesive.

[0036] The technical solution is as follows:

[0037] The application of the above-mentioned binary soybean meal adhesive in impregnated paper-faced plywood.

[0038] In summary, the present invention has the following beneficial effects:

[0039] 1. A fundamental improvement in water-resistant bonding strength: By grafting modification, PAE resin is given more reactive groups, forming a denser and more hydrophobic cross-linking network with soybean meal protein, which fundamentally inhibits the damage to the adhesive layer caused by water absorption by hydrophilic groups.

[0040] 2. Significantly improved adhesive application and processing performance: The addition of cellulose derivatives effectively improves the water retention capacity of the adhesive and extends its pot life; at the same time, it optimizes the rheological properties of the adhesive, improves the wettability and spreadability of the wood surface, and facilitates the formation of a uniform adhesive layer, thereby improving the pre-pressing effect and the uniformity of board quality; at the same time, the grafted modified PAE resin can effectively compensate for the possible decrease in bonding strength caused by the addition of water-retaining components, thereby achieving synergistic optimization of water retention performance, coating performance and bonding strength;

[0041] 3. Highly compatible with existing industrial systems: All raw materials are readily available, the preparation and compounding processes are simple, no special equipment is required, and it is easy to promote and apply in existing adhesive production and use systems, with significant industrialization potential. Attached Figure Description

[0042] Figure 1 It is the structural formula of a representative segment in modified PAE resin crosslinking agents;

[0043] Figure 2 This is the Fourier transform infrared spectrum of the modified PAE resin crosslinking agent;

[0044] Figure 3 This is a comparison chart of the coating performance of Example 4 and Comparative Example 2. Detailed Implementation

[0045] The present invention will be further explained and described below with reference to the accompanying drawings.

[0046] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. Any changes made by those skilled in the art after reading this specification, as long as they fall within the scope of the claims, will be protected by patent law.

[0047] Example 1

[0048] A grafted modified PAE resin crosslinking agent and a binary soybean meal adhesive are composed of the following components in parts by weight: 36 parts modified PAE resin crosslinking agent, 64 parts water, 28 parts low-temperature soybean meal powder and 0.5 parts carboxymethyl cellulose.

[0049] The grafted modified PAE resin crosslinking agent is prepared by a method comprising the following steps:

[0050] S1. 20 g of adipic acid, 14.1 g of diethylenetriamine, and 20 g of water were added to a three-necked flask equipped with a stirrer. A condensation reaction was carried out under the action of a catalyst (water). The reaction temperature was set to 90°C for 30 min, then to 150°C for 80 min, and then to 180°C for 140 min. After the reaction was completed, the system was cooled to 100°C, and then 34.1 g of distilled water at 60°C was added to adjust the solid content of the system to 50%. A reddish-brown intermediate of about 68.2 g was prepared.

[0051] S2. In a three-necked flask equipped with a stirrer, take about 68.2 g of the intermediate prepared in S1, add 17.7 g of epichlorohydrin through a dropping funnel under stirring, with the dropping rate controlled at about 5 drops / 2s, and then add 155.4 g of distilled water to adjust the solid content to 25%. First, reflux at 40℃ for 1 h, then raise the temperature to 70℃ and react for 3 h. After the reaction is completed, cool to room temperature, adjust the pH value to about 3.5 with concentrated hydrochloric acid to terminate the reaction, and continue to add distilled water to adjust the solid content to 12.5%, thus obtaining about 414.4 g of PAE resin.

[0052] S3. In a three-necked flask equipped with a stirrer, take 207 g of the PAE resin prepared in S2, and then slowly add 3.42 g of acrylic acid dropwise into the three-necked flask under stirring conditions through a dropping funnel. The dropping rate is controlled at about 5 drops / 2s. At the same time, a small amount of p-toluenesulfonic acid is added as a catalyst to initiate the polymerization reaction. The reaction temperature is controlled at about 60℃ and the time is controlled at 60min. After the reaction is completed, stop heating and cool to room temperature to obtain about 210.42 g of modified PAE resin crosslinking agent.

[0053] Figure 1 This is the structural formula of a representative segment in modified PAE resin crosslinking agents. For example... Figure 1 As shown, in representative fragments, acrylic acid molecules are mainly grafted onto the active hydroxyl groups contained in the azacyclobutanol structure. Meanwhile, other structures also exist in the modified PAE resin crosslinking agent, such as uncyclic (azacyclobutanol ionic ring) epichlorohydrin units (ring-opening grafted onto the secondary amine group of the main chain).

[0054] Chemical structure analysis (Fourier transform infrared spectroscopy, FTIR)

[0055] Figure 2 The Fourier transform infrared spectrum of the modified PAE resin crosslinking agent is shown. As can be seen from the figure, the modified PAE resin exhibits a broad and strong absorption peak at approximately 3400 cm⁻¹, attributed to the stretching vibrations of O–H and N–H, indicating the presence of hydrogen-bonded functional groups such as carboxyl, amide, and amine groups in the sample. A significant absorption peak appears near 1700–1730 cm⁻¹, which can be attributed to the C=O stretching vibrations in carboxyl or ester groups, belonging to the carbonyl stretching vibration peaks of unsaturated acrylate esters. Simultaneously, characteristic absorptions related to amide groups are observed in the range of approximately 1550–1650 cm⁻¹, indicating that the modified resin retains the characteristics of the PAE main chain structure. The enhanced absorption of C–O stretching vibrations near 1170 cm⁻¹ further indicates that acrylic acid has been successfully introduced into the PAE molecular structure, increasing the content of carboxyl / ester-related functional groups in the resin molecule, thus proving the successful grafting modification of PAE resin with acrylic acid.

[0056] Preparation of a binary soybean meal adhesive: By mass, 36 parts of modified PAE resin crosslinking agent, 64 parts of water, 28 parts of low-temperature soybean meal powder and 0.5 parts of carboxymethyl cellulose were stirred and mixed evenly to prepare a binary soybean meal adhesive.

[0057] Comparative Example 1

[0058] The difference from Example 1 is that the PAE resin crosslinking agent is not modified by S3, and the PAE resin obtained by S2 is used directly.

[0059] Two types of impregnated paper-faced plywood were prepared using the adhesives from Example 1 and Comparative Example 1, respectively. Details are as follows:

[0060] Step 1: Apply glue to the poplar core, with a glue application rate of 220 g / m². 2After applying the adhesive, eucalyptus or poplar veneers are glued together to form a board blank. The board blank is cold-pressed at a unit pressure of 0.6 MPa for 40 minutes, and then hot-pressed under a three-stage hot-pressing pressure to obtain the substrate. The specific hot-pressing parameters are: first stage unit pressure 0.65~0.6 MPa, holding pressure for 540 s; second stage unit pressure 0.5~0.4 MPa, holding pressure for 180 s; third stage unit pressure 0.3~0.25 MPa, holding pressure for 420 s.

[0061] Step Two: After the substrate undergoes edge sawing, puttying, curing, and sanding, a second layer of adhesive is applied, and the substrate is then bonded to the ultra-thin fiberboard on both the top and bottom. The ultra-thin fiberboard has a high density and strong covering power, ensuring surface quality and enhancing surface crack resistance. The second layer of adhesive is applied as before. After sanding and edge sawing, the substrate is pressed with impregnated paper to prepare the finished board. The hot-pressing temperature is 130℃, the unit pressure is 0.8 MPa, and the hot-pressing time is 500 s, ultimately yielding impregnated paper-faced plywood.

[0062] The Class II immersion peel performance of the corresponding specimens of Example 1 and Comparative Example 1 was tested according to the methods specified in GB / T 17657-2022 "Test Methods for Physical and Chemical Properties of Wood-based Panels and Decorative Wood-based Panels". Meanwhile, to more intuitively compare the bonding performance of the adhesives prepared in Example 1 and Comparative Example 1, three-layer plywood was prepared in the laboratory using conventional processes, and the Class II bond strength of the corresponding specimens of Example 1 and Comparative Example 1 was tested according to the methods specified in GB / T 17657-2022 "Test Methods for Physical and Chemical Properties of Wood-based Panels and Decorative Wood-based Panels". The comparative test results are shown in Table 1.

[0063] Table 1 Test results of Example 1 and Comparative Example 1

[0064] Type II immersion stripping Class II bond strength / MPa Example 1 qualified 1.2 Comparative Example 1 Unqualified 0.6

[0065] Table 1 shows that the specimen prepared in Comparative Example 1 failed the Class II immersion peel performance test, and the average Class II adhesive strength decreased to 0.6 MPa, significantly lower than that of Example 1. This indicates that directly introducing water-retaining components leads to a sharp decrease in adhesive strength. In Example 1, after acrylic acid grafting modification, highly reactive carbon-carbon double bonds were introduced into the PAE molecule. The reactivity of the resin was significantly enhanced after grafting, improving the cohesive strength and water resistance of the adhesive layer, thus achieving a balance between water retention and adhesive strength.

[0066] Example 2

[0067] The difference from Example 1 is that the amount of acrylic acid added in S3 is based on a molar ratio of epichlorohydrin to acrylic acid of 1.8:1 (approximately 2:1 in Example 1).

[0068] Example 3

[0069] The difference from Example 1 is that the amount of acrylic acid added in S3 is 2.4:1 (2:1 in Example 1).

[0070] Three types of impregnated paper-faced plywood were prepared using the adhesives from Examples 1-3, respectively. Meanwhile, to more intuitively compare the bonding performance of the adhesives prepared in Examples 1-3, three-layer plywood was prepared in the laboratory using conventional processes. The preparation and testing methods were the same as described above, and the test results are shown in Table 2.

[0071] Table 2 Test results of Examples 1-3

[0072] Type II immersion stripping Class II bond strength / MPa Example 1 qualified 1.2 Example 2 qualified 0.8 Example 3 qualified 1

[0073] Table 2 shows that the Class II immersion peel performance of the specimens prepared in Examples 1-3 all passed, indicating that the adhesives obtained under different acrylic acid addition conditions all possess a certain degree of water resistance. However, judging from the average Class II bonding strength, the bonding strength of Example 1 was the highest, indicating that the amount of acrylic acid grafting has a significant impact on the bonding performance of the adhesive, and that more is not necessarily better, but rather there is an appropriate range. Analysis suggests that when the molar ratio of epichlorohydrin to acrylic acid is 2:1, the amount of acrylic acid grafting is moderate, which is beneficial for forming a relatively dense and uniform adhesive network structure, resulting in optimal cohesive strength and interfacial bonding strength, thus exhibiting the highest bonding strength.

[0074] Example 4

[0075] The difference from Example 1 is that the amount of carboxymethyl cellulose added is 0.8 parts.

[0076] Example 5

[0077] The difference from Example 1 is that the amount of carboxymethyl cellulose added is 1 part.

[0078] Comparative Example 2

[0079] The difference from Example 1 is that the PAE resin crosslinking agent is not modified by S3, and the PAE resin obtained by S2 is used directly; at the same time, carboxymethyl cellulose is not added, and the PAE resin, low-temperature soybean meal powder and water are directly mixed and stirred evenly.

[0080] Four types of impregnated paper-faced plywood were prepared using the adhesives from Examples 1, 4-5, and Comparative Example 2, respectively. The preparation and testing methods were the same as described above, and the test results are shown in Table 3. Figure 2 As shown.

[0081] Table 3 Test results of Examples 1, 4-5, and Comparative Example 2

[0082] Type II immersion stripping Drying time / min Coating performance Adhesive fluidity Example 1 qualified 50 uniform Good liquidity Example 4 qualified 60 uniform Good liquidity Example 5 qualified 65 Uneven Poor liquidity Comparative Example 2 qualified 40 Uneven Liquid

[0083] Table 3 shows that the Class II immersion peel performance of the specimens prepared in Examples 1, 4-5, and Comparative Example 2 all passed, indicating that each adhesive system can meet the basic water-resistant bonding requirements. However, there are significant differences among the examples in terms of drying time, coating performance, and adhesive flowability. Among them, Comparative Example 2 had the shortest drying time, only 40 minutes, and the coating performance was uneven. This indicates that without the addition of carboxymethyl cellulose and using ungrafted modified PAE resin, the water retention capacity of the adhesive is weak, and the water evaporates quickly, which easily leads to premature water loss of the adhesive layer during the application process, thus hindering the formation of a uniform and continuous adhesive layer structure. In contrast, the drying time of Examples 1, 4, and 5 was extended after the addition of carboxymethyl cellulose, indicating that the introduction of carboxymethyl cellulose can effectively improve the water retention performance of the adhesive and delay water evaporation. Further comparison of Examples 1, 4, and 5 shows that as the amount of carboxymethyl cellulose added increases from 0.5 parts to 0.8 parts, the drying time of the adhesive is prolonged, while maintaining good fluidity and uniform coating performance. This indicates that appropriately increasing the amount of carboxymethyl cellulose is beneficial to improving the water retention and workability of the adhesive. However, when the amount of carboxymethyl cellulose is further increased to 1 part, although the drying time continues to be prolonged, the fluidity of the adhesive decreases significantly, and the coating performance changes from uniform to uneven. This indicates that excessive addition of carboxymethyl cellulose will lead to excessive viscosity of the adhesive, affecting the spreading and leveling of the adhesive on the substrate surface and hindering uniform application.

[0084] Figure 2 The figure shows a comparison of the coating performance of Example 4 and Comparative Example 2 (left figure is Comparative Example 2, right figure is Example 4). It can be clearly seen from the figure that the addition of carboxymethyl cellulose significantly improves the water retention and coating performance of the adhesive. Combined with... Figure 2 As can be seen from Table 3, 0.8 parts of carboxymethyl cellulose achieved a good balance between water retention and workability, making it the optimal addition amount.

Claims

1. A method for preparing a graft-modified PAE resin crosslinking agent, comprising the following steps: S1. Polyamide is prepared by condensation reaction of adipic acid and diethylenetriamine; S2. Adjust the polyamide to a solid content of 20-30%, then add epichlorohydrin dropwise under stirring, and react at 40-50°C under reflux for 1-1.5 hours; then raise the temperature to 70-75°C and react for 2-3 hours; after the reaction is completed, PAE resin is obtained. S3. Acrylic acid is added dropwise to the PAE resin under stirring conditions, and p-toluenesulfonic acid is added as a catalyst. The temperature is controlled at 60~70℃ to carry out the polymerization reaction. After the reaction is completed, the grafted modified PAE resin crosslinking agent is obtained.

2. The method for preparing a graft-modified PAE resin crosslinking agent according to claim 1, characterized in that: In step S1, the molar ratio of adipic acid to diethylenetriamine is 1: (1.0~1.1).

3. The method for preparing a graft-modified PAE resin crosslinking agent according to claim 1, characterized in that: In step S2, the amount of epichlorohydrin added is 1.2 to 1.6 times that of diethylenetriamine, based on molar parts.

4. The method for preparing a graft-modified PAE resin crosslinking agent according to claim 1, characterized in that: In step S2, after the reaction has been going on for 2 to 3 hours, the pH of the system is adjusted to 3.5 to 4 with concentrated sulfuric acid or concentrated hydrochloric acid to terminate the reaction.

5. The method for preparing a graft-modified PAE resin crosslinking agent according to claim 1, characterized in that: In step S3, the reaction ends after 50-60 minutes. Heating is stopped, and the mixture is cooled to room temperature to obtain the grafted modified PAE resin crosslinking agent.

6. The method for preparing a graft-modified PAE resin crosslinking agent according to claim 1, characterized in that: In step S3, the amount of acrylic acid added is 1 / (1.8~2.4) of the amount of epichlorohydrin, in molar proportions.

7. A binary soybean meal adhesive, comprising soybean meal powder, water, and a water-soluble cellulose derivative, characterized in that, It also includes a graft-modified PAE resin crosslinking agent prepared according to the method of any one of claims 1 to 5.

8. The binary soybean meal adhesive according to claim 7, characterized in that, The contents of each component by mass are as follows: grafted modified PAE resin crosslinking agent 36~44, water 56~64, soybean meal powder 28~35, water-soluble cellulose derivative 0.5~2.

9. The binary soybean meal adhesive according to claim 8, characterized in that, The water-soluble cellulose derivative is selected from at least one of methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, carboxymethylhydroxyethylcellulose, hydroxypropylcellulose, and hydroxypropylmethylcellulose.

10. The application of the binary soybean meal adhesive according to any one of claims 7 to 9 in impregnated paper-faced plywood.

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