A curing accelerating resin for soybean-based adhesive and its preparation method and application

Abstract

A curing-accelerating resin for soybean-based adhesives, and a preparation method and application thereof. The present invention relates to a curing-accelerating resin, and a preparation method and application thereof. The present invention aims to solve the problem that the existing industrial soybean-based adhesives have low crosslinking rate and insufficient crosslinking density, resulting in slow hot pressing speed and low production efficiency in the production of boards, especially the problem that the conventional use of small molecule alkali solution to increase the pH value of the crosslinking dispersant PAE resin solution to increase the hot pressing speed leads to a significant decrease in the bonding performance of the boards. The curing-accelerating resin for soybean-based adhesives is prepared from aliphatic polyamines and organic dibasic acids; the preparation method is: heating aliphatic polyamines and organic dibasic acids to react, collecting water distilled from the polycondensation of the system, stopping heating to cool the reaction system, then adding water and polycondensation distilled water to the reaction system, continuing stirring and cooling the reaction system to obtain the curing-accelerating resin for soybean-based adhesives; application, it is used to prepare soybean-based adhesives.

Description

Technical Field

[0001] The invention relates to a curing accelerating resin and a preparation method and application thereof. Background Art

[0002] Artificial boards are currently an important wood material that replaces solid wood and is widely used in furniture manufacturing and interior decoration. my country is the world's largest producer and consumer of artificial boards. However, the existing production of artificial boards mostly uses formaldehyde-based synthetic resin adhesives, which is the main source of formaldehyde pollution in the current human living environment. Formaldehyde is a Class I carcinogen, and formaldehyde pollution in the human living environment threatens people's health.

[0003] Soybean-based adhesive is a formaldehyde-free biomass-based adhesive produced with defatted soy flour or soy protein as raw materials. It has the advantages of renewable raw materials, no formaldehyde addition, and high dry bonding strength. It is the most promising biomass-based adhesive that is expected to replace formaldehyde-based synthetic resins and eliminate formaldehyde release from artificial boards and their products from the source. In order to make soy-based adhesives meet the needs of industrial applications, in recent years, domestic and foreign scholars have adopted homogenization modification (CN201910667905.7), cross-linking modification (CN202010065540.3; CN202110638174.0), enzymatic modification (CN201911372733.7), mildew-proof modification (CN202210570650.4), hyperbranching modification (CN202210459) to address the problems of poor water resistance, easy mildew, and high cost of traditional soy-based adhesives. 782.X), inorganic hybrid enhancement (CN202310971725.4; CN202210870421.4), bionic modification (CN201910239171.2), synergistic modification (CN202310971788.X) and other modification technologies have effectively improved the water resistance of soybean-based adhesives, reduced costs, and can prevent mildew and inhibit bacteria, meeting the performance requirements of artificial board users and the need of artificial board manufacturers to control adhesive costs, thereby promoting the industrial application of soybean-based adhesives.

[0004] The soy-based adhesive currently used in industry is mainly prepared by stirring defatted soy flour and a cross-linking dispersant polyamide polyamine-epichlorohydrin (PAE) solution at room temperature. During the hot pressing process, the chemical cross-linking between the residual amino groups of soy protein in defatted soy flour and the azetidinium groups of polyamide polyamine-epichlorohydrin resin, as well as the mutual cross-linking (self-cross-linking) between PAE resin molecules, enables the cured soy-based adhesive to form a three-dimensional network structure, giving it excellent bonding strength and water resistance.

[0005] However, soy protein is a linear macromolecule formed by amino acids connected by peptide bonds, and the number of residual amino groups in its molecules is small, resulting in insufficient cross-linking between soy protein and the cross-linking dispersant PAE resin and a slow cross-linking rate. In addition, in order to improve the storage stability of the cross-linking dispersant PAE resin, the pH value of the PAE resin needs to be adjusted to a weak acid (2.5-3.5) with an acid, and the activity of the azetidinium group is inhibited to avoid the failure of the PAE resin due to self-cross-linking during storage. This also inhibits the cross-linking rate of the PAE resin to soy protein during the hot pressing process and the self-cross-linking efficiency of the PAE resin. The combined effect of the above two situations leads to the slow hot pressing speed and low production efficiency of artificial boards produced by soybean-based adhesives. In order to fully cross-link and cure the soybean-based adhesive to ensure the bonding performance of the board, the hot pressing time is usually more than 40% longer than that of urea-formaldehyde resin adhesive at the same hot pressing temperature. Especially in the winter production in the northern cold regions, the hot pressing efficiency of artificial boards produced by soybean-based adhesives is more significantly reduced due to the low temperature, which limits the widespread application of formaldehyde-free soybean-based adhesives in the industrial production of artificial boards.

[0006] Existing studies (Sun Zongxing et al., Journal of Forestry Engineering, 2021, 6(6): 130-136) have shown that increasing the pH of PAE resin with alkaline solution NaOH can increase the self-crosslinking rate of PAE resin, but it also causes excessive consumption of azetidinyl groups in the self-crosslinking, resulting in a reduction in the crosslinking reaction between PAE resin and soy protein, and a significant decrease in the crosslinking density and bonding performance of the cured adhesive. It can be seen that simply increasing the pH value of PAE resin can increase the hot pressing speed, but it also leads to a significant decrease in the bonding performance of the board, which cannot meet the technical requirements of increasing the hot pressing speed without affecting the bonding performance in industrial production applications. Summary of the invention

[0007] The present invention aims to solve the problem that the existing industrial soybean-based adhesives have low crosslinking rate and insufficient crosslinking density, resulting in slow hot pressing speed and low production efficiency in board production, especially the problem that the conventional use of small molecule alkali solution to increase the pH value of the crosslinking dispersant PAE resin solution to increase the hot pressing speed leads to a significant decrease in the bonding performance of the board, thereby providing a soybean-based adhesive curing promoting resin that can promote curing without affecting the bonding performance, as well as a preparation method and application thereof.

[0008] A curing accelerating resin for soybean-based adhesive is prepared from 100 parts of aliphatic polyamine and 80 to 150 parts of organic dibasic acid by mass; the molar number of the organic dibasic acid is greater than the molar number of the aliphatic polyamine.

[0009] A method for preparing a curing-accelerating resin for a soybean-based adhesive, which is prepared according to the following steps:

[0010] Weigh 100 parts of aliphatic polyamine and 80 to 150 parts of organic dibasic acid by mass, put the 100 parts of aliphatic polyamine and 80 to 150 parts of organic dibasic acid into a reaction kettle to obtain a reaction system, under stirring conditions, first heat the reaction system to 105°C to 130°C, then heat it to 160°C to 165°C, and distill it at a temperature of 160°C to 165°C for 3h to 5h, collect water distilled from the system by polycondensation to obtain polycondensation distilled water, stop heating to cool the reaction system to 90°C to 100°C, then add water and polycondensation distilled water to the reaction system, continue stirring and cool the reaction system to below 40°C, and obtain a curing-promoting resin for a soybean-based adhesive;

[0011] The molar number of the organic dibasic acid is greater than the molar number of the aliphatic polyamine.

[0012] The invention discloses an application of a curing accelerating resin for soybean-based adhesive, which is used for preparing soybean-based adhesive.

[0013] The beneficial effects of the present invention are:

[0014] 1) The present invention, under the condition of excessive molar number of organic dibasic acid, uses aliphatic polyamine and organic dibasic acid to prepare medium and low alkaline resins through polycondensation, which can not only regulate the pH value of the soybean-based adhesive and promote the self-crosslinking rate between polyamide polyamine-epichlorohydrin resin molecules and the co-crosslinking rate between polyamide polyamine-epichlorohydrin resin and defatted soybean powder, thereby effectively improving the crosslinking curing rate of the soybean-based adhesive, and the curing promoting resin itself contains active amino groups, which can produce co-crosslinking reactions with the crosslinking agent polyamide polyamine-epichlorohydrin resin, thereby improving the crosslinking density of polyamide polyamine-epichlorohydrin resin, thereby improving the crosslinking density and bonding performance of the soybean-based adhesive. Therefore, the use of the curing promoting resin of the present invention can avoid the problem of reduced bonding performance caused by small molecule alkaline substances such as NaOH and triethanolamine while increasing the pH value of the soybean-based adhesive to accelerate curing, and achieve the effect of promoting rapid curing of the soybean-based adhesive while improving bonding performance.

[0015] 2) By adding the curing accelerating resin of the present invention, the pH value of the soybean-based adhesive and the co-crosslinking reaction of the curing accelerating resin and the crosslinking agent polyamide polyamine-epichlorohydrin resin are regulated to achieve an increase in the crosslinking curing rate of the soybean-based adhesive, so that the hot pressing time of the formaldehyde-free artificial board produced by the soybean-based adhesive at the same hot pressing temperature is shortened by 35% to 50%, or the curing temperature within the same hot pressing time is reduced by 20° C. to 30° C., thereby effectively reducing the heat consumption of the artificial board during hot pressing and improving its production efficiency, improving the process performance of the soybean-based adhesive, and promoting the larger-scale promotion and application of formaldehyde-free soybean-based adhesive in the production of artificial boards.

[0016] 3) The curing-accelerating resin for soybean-based adhesive prepared by the present invention has the advantages of not generating wastewater or waste liquid during the synthesis process, being convenient and simple to use, significantly improving the cross-linking and curing rate of soybean-based adhesive, and requiring a small amount of use. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The crosslinking density test diagram of the crosslinking agent cured product prepared in Example 1 and Comparative Experiments 1 to 2;

[0018] Figure 2 This is a test diagram of the cross-linking density of the cured products of the soy-based adhesives prepared in Example 1 and Comparative Experiments 1 to 2;

[0019] Figure 3 This is a physical picture of the curing-promoting resin for the soybean-based adhesive prepared in Example 1;

[0020] Figure 4 Schematic diagram of the synthesis reaction of the curing accelerating resin of the soybean-based adhesive of the present invention, m and n are integers between 0 and 11, and a is a value between 10 and 100;

[0021] Figure 5 The schematic diagram of the co-crosslinking reaction of the curing-promoting resin modified soybean-based adhesive of the present invention for simultaneously achieving the improvement of the crosslinking curing rate and the crosslinking density. DETAILED DESCRIPTION

[0022] The technical solution of the present invention is not limited to the specific implementation modes listed below, but also includes any combination of the specific implementation modes.

[0023] Specific implementation method 1: This implementation method is a curing accelerating resin for a soybean-based adhesive, which is prepared by 100 parts of aliphatic polyamine and 80 to 150 parts of organic dibasic acid in parts by mass; the molar number of the organic dibasic acid is greater than the molar number of the aliphatic polyamine.

[0024] The beneficial effects of this specific implementation are:

[0025] 1) In this specific embodiment, under the condition of excessive molar number of organic dibasic acid, the low-medium alkaline resin prepared by polycondensation of aliphatic polyamine and organic dibasic acid can not only regulate the pH value of the soy-based adhesive and promote the self-crosslinking rate between polyamide polyamine-epichlorohydrin resin molecules and the co-crosslinking rate between polyamide polyamine-epichlorohydrin resin and defatted soy flour, thereby effectively improving the crosslinking curing rate of the soy-based adhesive, and the curing promoting resin itself contains active amino groups, which can produce co-crosslinking reaction with the crosslinking agent polyamide polyamine-epichlorohydrin resin, thereby improving the crosslinking density of polyamide polyamine-epichlorohydrin resin, thereby improving the crosslinking density and bonding performance of the soy-based adhesive. Therefore, the use of the curing promoting resin of this specific embodiment can avoid the problem of reduced bonding performance caused by small molecule alkaline substances such as NaOH and triethanolamine when increasing the pH value of the soy-based adhesive to accelerate curing, and achieve the effect of promoting rapid curing of the soy-based adhesive while improving bonding performance.

[0026] 2) By adding the curing accelerating resin of this specific embodiment, the pH value of the soybean-based adhesive and the co-crosslinking reaction of the curing accelerating resin and the crosslinking agent polyamide polyamine-epichlorohydrin resin are regulated to achieve an increase in the crosslinking curing rate of the soybean-based adhesive, so that the hot pressing time of the formaldehyde-free artificial board produced by the soybean-based adhesive is shortened by 35% to 50% at the same hot pressing temperature, or the curing temperature is reduced by 20°C to 30°C within the same hot pressing time, thereby effectively reducing the heat consumption of the artificial board during hot pressing and improving its production efficiency, improving the process performance of the soybean-based adhesive, and promoting the larger-scale promotion and application of formaldehyde-free soybean-based adhesives in the production of artificial boards.

[0027] 3) The curing-accelerating resin for soybean-based adhesive prepared in this specific embodiment has the advantages of not generating wastewater or waste liquid during the synthesis process, being convenient and simple to use, significantly improving the cross-linking and curing rate of soybean-based adhesive, and requiring a small amount of use.

[0028] Specific embodiment 2: This embodiment is different from specific embodiment 1 in that: the aliphatic polyamine is one of diethylenetriamine, triethylenetetramine and tetraethylenepentamine or a mixture of several thereof; the organic dibasic acid is one of succinic acid, adipic acid and sebacic acid or a mixture of several thereof. Others are the same as specific embodiment 1.

[0029] Specific implementation method 3: This implementation method is different from specific implementation method 1 or 2 in that the molar number of the organic dibasic acid is 1% to 10% greater than the molar number of the aliphatic polyamine. The rest is the same as specific implementation method 1 or 2.

[0030] In the feeding process of this specific embodiment, the molar number of the organic dibasic acid is greater than the molar number of the aliphatic polyamine, and the molar number of the organic dibasic acid is greater than the molar number of the aliphatic polyamine by 1% to 10%, thereby obtaining a curing-accelerating resin with carboxyl-terminated molecular ends suitable for promoting cross-linking and curing of soybean-based adhesives and enhancing bonding properties, such as Figure 4 shown.

[0031] Specific embodiment 4: This embodiment is a method for preparing a curing-accelerating resin for a soybean-based adhesive, which is prepared according to the following steps:

[0032] Weigh 100 parts of aliphatic polyamine and 80 to 150 parts of organic dibasic acid by mass, put the 100 parts of aliphatic polyamine and 80 to 150 parts of organic dibasic acid into a reaction kettle to obtain a reaction system, under stirring conditions, first heat the reaction system to 105°C to 130°C, then heat it to 160°C to 165°C, and distill it at a temperature of 160°C to 165°C for 3h to 5h, collect water distilled from the system by polycondensation to obtain polycondensation distilled water, stop heating to cool the reaction system to 90°C to 100°C, then add water and polycondensation distilled water to the reaction system, continue stirring and cool the reaction system to below 40°C, and obtain a curing-promoting resin for a soybean-based adhesive;

[0033] The molar number of the organic dibasic acid is greater than the molar number of the aliphatic polyamine.

[0034] In this specific embodiment, the temperature is raised to 160° C. to 165° C., during which the system will distill out some water, and then distill at a temperature of 160° C. to 165° C. for 3 h to 5 h until no more water is distilled out of the system.

[0035] The product prepared in this specific embodiment based on the raw materials, raw material feed ratio and synthesis conditions, reduces the alkalinity of the product (its pH value is 8.5-9.5) by carboxyl end-capping, avoids the generation of small molecular strong alkaline substances such as NaOH due to excessive alkalinity, which causes the cross-linking agent polyamide polyamine-epichlorohydrin resin to produce rapid pre-crosslinking and insufficient self-crosslinking (manifested by a decrease in self-crosslinking density, such as attached Figure 1More importantly, the curing accelerating resin of the soy-based adhesive synthesized in this specific embodiment contains alkaline secondary amine groups (—CH2—CH2—NH—) in its product molecular chain. When it is added to the cross-linking agent polyamide polyamine-epichlorohydrin resin solution, its pH value (the pH value of the polyamide polyamine-epichlorohydrin resin solution with a mass percentage concentration of 6% is usually between 2.6 and 3.2) can be increased to 3.5-4.5, thereby promoting the self-cross-linking reaction of the cross-linking agent polyamide polyamine-epichlorohydrin resin to a certain extent. Moreover, during the hot pressing process, the secondary amine group can also produce a co-cross-linking reaction with the azetidinium group of the cross-linking agent polyamide polyamine-epichlorohydrin resin, so that the cross-linking agent forms a network-like structure (such as the attached Figure 5 As shown), the cross-linking density and bonding performance of the soybean-based adhesive can be improved while promoting the cross-linking and curing of the soybean-based adhesive.

[0036] Specific implementation method 5: This implementation method is different from specific implementation method 4 in that the solid content of the curing accelerating resin of the soy-based adhesive is 19% to 21% by mass. The rest is the same as specific implementation method 4.

[0037] Specific embodiment 6: This embodiment is different from specific embodiment 4 or 5 in that the pH value of the curing accelerating resin of the soy-based adhesive is 8.5-9.5, and the viscosity is 25mPa.s-100mPa.s. The rest is the same as specific embodiment 4 or 5.

[0038] Specific implementation method seven: This implementation method is an application of a curing-accelerating resin for soybean-based adhesives, which is used to prepare soybean-based adhesives.

[0039] Specific embodiment eight: This embodiment differs from specific embodiment seven in that the preparation of the soybean-based adhesive is specifically carried out according to the following steps:

[0040] Weigh 100 parts of polyamide polyamine-epichlorohydrin resin solution, 1 to 5 parts of curing accelerating resin for soy-based adhesive and 30 to 50 parts of defatted soy flour by mass; first add 1 to 5 parts of curing accelerating resin for soy-based adhesive to 100 parts of polyamide polyamine-epichlorohydrin resin solution, stir and mix evenly to obtain a cross-linking agent polyamide polyamine-epichlorohydrin resin solution containing curing accelerating resin, then add 30 to 50 parts of defatted soy flour, stir at room temperature to obtain a homogeneous and viscous curing accelerating resin modified soy-based adhesive. The rest is the same as the seventh specific implementation method.

[0041] Specific implementation method 4: Under the premise of ensuring equivalent bonding performance, the curing temperature of the prepared soybean-based adhesive curing accelerating resin can be reduced by 20°C to 30°C within the same hot pressing time, or the hot pressing time can be shortened by 35% to 50% at the same hot pressing temperature.

[0042] Specific embodiment 9: This embodiment is different from specific embodiment 7 or 8 in that the solid content of the polyamide polyamine-epichlorohydrin resin solution is 5% to 6.5% by mass. The rest is the same as specific embodiment 7 or 8.

[0043] Specific embodiment 10: This embodiment differs from specific embodiments 7 to 9 in that the pH value of the crosslinking agent polyamide polyamine-epichlorohydrin resin solution containing the curing accelerating resin is 3.5 to 4.5; the pH value of the homogeneous and viscous curing accelerating resin modified soy-based adhesive is less than 5.5. The rest is the same as specific embodiments 7 to 9.

[0044] The following examples are used to verify the beneficial effects of the present invention:

[0045] Embodiment 1:

[0046] A curing accelerating resin for a soybean-based adhesive, which is prepared from 100 parts by mass of an aliphatic polyamine and 120 parts by mass of an organic dibasic acid;

[0047] The aliphatic polyamine is diethylenetriamine; the organic dibasic acid is succinic acid;

[0048] The molar number of the organic dibasic acid is 4.7% greater than the molar number of the aliphatic polyamine;

[0049] A method for preparing a curing-accelerating resin for a soybean-based adhesive, which is prepared according to the following steps:

[0050] Weigh 100 parts of aliphatic polyamine and 120 parts of organic dibasic acid by mass, put the 100 parts of aliphatic polyamine and 120 parts of organic dibasic acid into a reactor to obtain a reaction system, heat the reaction system to 120°C under stirring, then heat it to 160°C-165°C, and distill it at 160°C-165°C for 4.5 hours, collect water distilled from the polycondensation of the system to obtain about 36.3 parts of polycondensation water, stop heating to cool the reaction system to 90°C-100°C, then add 694 parts of water and 36.3 parts of polycondensation water to the reaction system, continue stirring and cool the reaction system to below 40°C, and obtain a curing-promoting resin for a soybean-based adhesive;

[0051] The solid content of the curing-promoting resin of the soy-based adhesive is 20.1% by mass;

[0052] The pH value of the curing-promoting resin of the soybean-based adhesive is 8.7, and the viscosity is 61.4 mPa.s (25° C.).

[0053] An application of a curing-accelerating resin for a soybean-based adhesive, which is used to prepare the soybean-based adhesive, and the preparation of the soybean-based adhesive is specifically carried out according to the following steps:

[0054] Weigh 100 parts of a polyamide polyamine-epichlorohydrin resin solution, 4 parts of a curing accelerating resin for a soy-based adhesive, and 45 parts of defatted soy flour by mass; first add 4 parts of a curing accelerating resin for a soy-based adhesive to 100 parts of a polyamide polyamine-epichlorohydrin resin solution, stir and mix evenly to obtain a cross-linking agent polyamide polyamine-epichlorohydrin resin solution (curing cross-linking agent) containing a curing accelerating resin, then add 45 parts of defatted soy flour, stir at room temperature until homogeneous and viscous, and obtain a curing accelerating resin-modified soy-based adhesive;

[0055] The solid content of the polyamide polyamine-epichlorohydrin resin solution is 6% by mass;

[0056] The pH value of the crosslinking agent polyamide polyamine-epichlorohydrin resin solution containing the curing accelerating resin is 4.4; the pH value of the curing accelerating resin modified soy-based adhesive is 5.1;

[0057] The polyamide polyamine-epichlorohydrin resin solution and defatted soybean powder are both commercially available.

[0058] Embodiment 2:

[0059] A curing accelerating resin for a soybean-based adhesive, which is prepared from 100 parts by mass of an aliphatic polyamine and 89.8 parts by mass of an organic dibasic acid;

[0060] The aliphatic polyamine is tetraethylenepentamine; the organic dibasic acid is a mixed acid of adipic acid and sebacic acid, and the molar ratio of adipic acid to sebacic acid is 4:1;

[0061] The molar number of the organic dibasic acid is 8.1% greater than the molar number of the aliphatic polyamine;

[0062] A method for preparing a curing-accelerating resin for a soybean-based adhesive, which is prepared according to the following steps:

[0063] Weigh 100 parts of aliphatic polyamine and 89.8 parts of organic dibasic acid by mass, put 100 parts of aliphatic polyamine and 89.8 parts of organic dibasic acid into a reactor to obtain a reaction system, heat the reaction system to 110°C under stirring, then heat it to 160°C-165°C, and distill it at 160°C-165°C for 4.5 hours, collect water distilled from the polycondensation of the system to obtain about 20.5 parts of polycondensation water, stop heating to cool the reaction system to 90°C-100°C, then add 656 parts of water and 20.5 parts of polycondensation water to the reaction system, continue stirring and cool the reaction system to below 40°C, and obtain a curing-promoting resin for a soybean-based adhesive;

[0064] The solid content of the curing-promoting resin of the soy-based adhesive is 20.0% by mass;

[0065] The pH value of the curing-promoting resin of the soybean-based adhesive is 9.3, and the viscosity is 92.2 mPa.s (25° C.).

[0066] An application of a curing-accelerating resin for a soybean-based adhesive, which is used to prepare the soybean-based adhesive, and the preparation of the soybean-based adhesive is specifically carried out according to the following steps:

[0067] Weigh 100 parts of a polyamide polyamine-epichlorohydrin resin solution, 2 parts of a curing accelerating resin for a soy-based adhesive, and 45 parts of defatted soy flour by mass; first add 2 parts of the curing accelerating resin for a soy-based adhesive to 100 parts of the polyamide polyamine-epichlorohydrin resin solution, stir and mix evenly to obtain a cross-linking agent polyamide polyamine-epichlorohydrin resin solution (curing cross-linking agent) containing the curing accelerating resin, then add 45 parts of defatted soy flour, stir at room temperature until homogeneous and viscous, and obtain a curing accelerating resin-modified soy-based adhesive;

[0068] The solid content of the polyamide polyamine-epichlorohydrin resin solution is 6% by mass;

[0069] The pH value of the crosslinking agent polyamide polyamine-epichlorohydrin resin solution containing the curing-accelerating resin is 4.5; the pH value of the curing-accelerating resin-modified soy-based adhesive is 5.2;

[0070] The polyamide polyamine-epichlorohydrin resin solution and defatted soybean powder are both commercially available.

[0071] Comparative experiment 1:

[0072] Weigh 100 parts of polyamide polyamine-epichlorohydrin resin solution (curing crosslinking agent) and 45 parts of defatted soy flour by mass; add 45 parts of defatted soy flour to 100 parts of polyamide polyamine-epichlorohydrin resin solution, stir at room temperature until homogeneous and viscous, and obtain a reference soy-based adhesive;

[0073] The solid content of the polyamide polyamine-epichlorohydrin resin solution is 6% by mass;

[0074] The pH value of the reference soy-based adhesive is 4.8;

[0075] The polyamide polyamine-epichlorohydrin resin solution and defatted soybean powder are both commercially available.

[0076] Comparative experiment 2 (adhesive properties of soybean-based adhesive modified by NaOH alkali solution):

[0077] Weigh 100 parts of polyamide polyamine-epichlorohydrin resin solution, 4 parts of NaOH solution and 45 parts of defatted soy flour by mass; first add 4 parts of NaOH solution to 100 parts of polyamide polyamine-epichlorohydrin resin solution, stir and mix evenly to obtain a cross-linking agent polyamide polyamine-epichlorohydrin resin solution (curing cross-linking agent) containing NaOH, then add 45 parts of defatted soy flour, stir at room temperature until homogeneous and viscous, and obtain a NaOH-modified soybean-based adhesive;

[0078] The solid content of the polyamide polyamine-epichlorohydrin resin solution is 6% by mass;

[0079] The solid content of the NaOH solution is 20% by mass;

[0080] The pH value of the cross-linking agent polyamide polyamine-epichlorohydrin resin solution containing NaOH is 4.3; the pH value of the curing-accelerating resin-modified soy-based adhesive is 5.6;

[0081] The polyamide polyamine-epichlorohydrin resin solution and defatted soybean powder are both commercially available.

[0082] Comparative experiment 3 (Verification of the curing acceleration ability of the synthesized polyamide polyamine resin under excess aliphatic polyamine):

[0083] A curing accelerating resin for a soybean-based adhesive, which is prepared from 100 parts by mass of an aliphatic polyamine and 139 parts by mass of an organic dibasic acid;

[0084] The aliphatic polyamine is diethylenetriamine; the organic dibasic acid is adipic acid;

[0085] The molar number of the aliphatic polyamine is 2% greater than the molar number of the organic dibasic acid;

[0086] A method for preparing a curing-accelerating resin for a soybean-based adhesive, which is prepared according to the following steps:

[0087] Weigh 100 parts of aliphatic polyamine and 139 parts of organic dibasic acid by mass, put the 100 parts of aliphatic polyamine and 139 parts of organic dibasic acid into a reactor to obtain a reaction system, heat the reaction system to 110°C under stirring, then heat it to 160°C-165°C, and distill it at 160°C-165°C for 5 hours, collect water distilled from the polycondensation of the system to obtain about 33.2 parts of polycondensation water, stop heating to cool the reaction system to 90°C-100°C, then add 790 parts of water and 33.2 parts of polycondensation water to the reaction system, continue stirring and cool the reaction system to below 40°C, and obtain a curing-promoting resin for a soybean-based adhesive;

[0088] The solid content of the curing-promoting resin of the soy-based adhesive is 19.9% ​​by mass;

[0089] The pH value of the curing-promoting resin of the soybean-based adhesive is 10.9, and the viscosity is 67.4 mPa.s (25° C.).

[0090] An application of a curing-accelerating resin for a soybean-based adhesive, which is used to prepare the soybean-based adhesive, and the preparation of the soybean-based adhesive is specifically carried out according to the following steps:

[0091] Weigh 100 parts of a polyamide polyamine-epichlorohydrin resin solution, 4 parts of a curing accelerating resin for a soy-based adhesive, and 45 parts of defatted soy flour by mass; first add 4 parts of a curing accelerating resin for a soy-based adhesive to 100 parts of a polyamide polyamine-epichlorohydrin resin solution, stir and mix evenly to obtain a cross-linking agent polyamide polyamine-epichlorohydrin resin solution (curing cross-linking agent) containing a curing accelerating resin, then add 45 parts of defatted soy flour, stir at room temperature until homogeneous and viscous, and obtain a curing accelerating resin-modified soy-based adhesive;

[0092] The solid content of the polyamide polyamine-epichlorohydrin resin solution is 6% by mass;

[0093] The pH value of the crosslinking agent polyamide polyamine-epichlorohydrin resin solution containing the curing-accelerating resin is 5.3; the pH value of the curing-accelerating resin-modified soy-based adhesive is 6.1;

[0094] The polyamide polyamine-epichlorohydrin resin solution and defatted soybean powder are both commercially available.

[0095] Take the cross-linking agent polyamide polyamine-epichlorohydrin resin solution containing curing accelerator resin and curing accelerator resin modified soy-based adhesive prepared in Examples 1 and 2, the polyamide polyamine-epichlorohydrin resin solution described in Comparative Experiment 1 and the reference soy-based adhesive prepared, the cross-linking agent polyamide polyamine-epichlorohydrin resin solution containing NaOH and the NaOH-modified soy-based adhesive prepared in Comparative Experiment 2, and the cross-linking agent polyamide polyamine-epichlorohydrin resin solution containing curing accelerator resin and the curing accelerator resin modified soy-based adhesive prepared in Comparative Experiment 3, respectively, and cure them at 120±3°C for 4h, then grind them into particles and sieve them through a 120-mesh sieve to obtain fine powders, boil the fine powders in boiling water for 4 hours, filter and dry them, and weigh the insoluble matter, and calculate the boiling water insoluble matter content (i.e., cross-linking density) of the curing cross-linking agent and the soy-based adhesive, respectively, as shown in the attached Figure 1 and 2 As shown; Figure 1 This is a test chart of the crosslinking density of the cured products of the curing crosslinking agent prepared in Example 1 and Comparative Experiments 1 to 2. Figure 2 This is a test chart of the cross-linking density of the cured products of the soybean-based adhesives prepared in Example 1 and Comparative Experiments 1 to 2.

[0096] Figure 3 This is a physical picture of the curing-promoting resin for the soybean-based adhesive prepared in Example 1;

[0097] The curing-accelerating resin-modified soybean-based adhesives prepared in Examples 1 and 2, the reference soybean-based adhesive prepared in Comparative Experiment 1, the NaOH-modified soybean-based adhesive prepared in Comparative Experiment 2, and the curing-accelerating resin-modified soybean-based adhesive prepared in Comparative Experiment 3 were heated to 400 g / m 2 The double-sided glue is applied to both sides of the 1.7mm thick poplar veneer core layer to form a board embryo in a manner perpendicular to the wood grain direction;

[0098] Example 1 Pre-pressing for 30 min under a veneer pressure of 0.6 MPa, and then hot pressing for 4.5 min (A1), 4 min (A2), 3.5 min (A3), 3 min (A4) and 2.5 min (A5) at a temperature of 120° C. and a veneer pressure of 0.6 MPa, respectively, to obtain three-layer plywood pressed by a curing-promoting resin-modified soy-based adhesive at different hot pressing times;

[0099] Comparative experiment 1: pre-pressing for 30 min under the condition of veneer pressure of 0.6 MPa, and then hot pressing for 4.5 min (B1), 4 min (B2), 3.5 min (B3) and 3 min (B4) at a temperature of 120 ° C and a veneer pressure of 0.6 MPa, respectively, to obtain three-layer plywood pressed by the reference soybean-based adhesive at different hot pressing times;

[0100] In the comparative experiment 2, the pre-pressing was performed for 30 min under the condition of veneer pressure of 0.6 MPa, and then the hot pressing was performed for 4.5 min (C1), 4 min (C2), 3.5 min (C3) and 3 min (C4) at a temperature of 120 °C and a veneer pressure of 0.6 MPa, respectively, to obtain three-layer plywood pressed by NaOH-modified soybean-based adhesive at different hot pressing times;

[0101] Example 2: Pre-pressing for 30 min under a veneer pressure of 0.6 MPa, and then hot pressing for 4.5 min at different hot pressing temperatures of 120°C (D1), 110°C (D2), 100°C (D3), 90°C (D4), 80°C (D5) and a veneer pressure of 0.6 MPa, to obtain three-layer plywood pressed at different hot pressing temperatures by a curing-promoting resin-modified soy-based adhesive;

[0102] In comparative experiment three, the panels were pre-pressed for 30 min at a veneer pressure of 0.6 MPa, and then hot-pressed for 4.5 min at different hot-pressing temperatures of 120°C (E1), 110°C (E2), 100°C (E3), 90°C (E4), and 80°C (E5) and a veneer pressure of 0.6 MPa, to obtain three-layer plywood pressed by a curing-promoting resin-modified soy-based adhesive at different hot-pressing temperatures.

[0103] According to the method specified in the national standard GB / T17657-2015, the dry strength and 63°C blister strength of the plywood were tested respectively (the specimens were immersed in 63±2°C water for 3 h and then immersed in 25°C cold water for 10 min). The results are shown in Tables 1 to 5.

[0104] Table 1 Bonding properties of reference soybean-based adhesives under different hot pressing times in comparative experiment 1

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[0106] Table 2 Comparative bonding performance of NaOH modified soybean-based adhesives under different hot pressing times in experiment 2

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[0108] Table 3 Bonding properties of curing-promoting resin-modified soybean-based adhesives under different hot pressing times in Example 1

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[0110] Table 4 Bonding properties of curing-promoting resin-modified soybean-based adhesives at different hot-pressing temperatures in Example 2

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[0112] Table 5 Comparative experiment on the bonding performance of the soy-based adhesive modified by curing-promoting resin under different hot pressing temperatures under the condition of excess tri-polyamine

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[0114]

[0115] As shown in Table 1, for conventional soybean-based adhesives in the absence of a curing accelerator, as the hot pressing time gradually shortens, its bonding strength gradually decreases significantly. Especially when the hot pressing time is less than 4 minutes, its bonding performance can no longer meet the national standard GB / T9846-2015 for Class II plywood bonding performance requirements (≥0.70MPa). This is attributed to the fact that reducing the hot pressing time fails to fully cure and crosslink the soybean-based adhesive, resulting in reduced bonding performance.

[0116] As shown in Table 2, for the soybean-based adhesive modified by adding NaOH solution, as the hot pressing time gradually shortens, its bonding strength gradually decreases. However, the addition of NaOH solution can shorten the hot pressing time to 3.5 min and still produce plywood with bonding properties that meet the national standard GB / T9846-2015 for Class II plywood bonding properties (≥0.70 MPa), and the bonding properties of the plywood prepared under a shorter hot pressing time (3 min) are also higher than those of the reference soybean-based adhesive without adding NaOH solution. This shows that the use of alkaline NaOH solution can shorten the hot pressing time of soybean-based adhesives to a certain extent to produce plywood and improve production efficiency. However, when comparing the bonding performance of plywood B1 and C1 (hot pressing at 120℃ for 4.5min) or plywood B2 and C2 (hot pressing at 120℃ for 4min), it can be seen that the bonding performance of soybean-based adhesive C1 or C2 modified by adding NaOH solution is significantly lower than that of soybean-based adhesive B1 or B2 without adding NaOH solution at the same hot pressing time, indicating that increasing the pH value of the cross-linking agent amide polyamine-epichlorohydrin resin solution by adding NaOH solution can only accelerate the self-cross-linking of the cross-linking agent and thus shorten the hot pressing time of the board, but cannot increase the cross-linking density of the cured soybean-based adhesive, which has an adverse effect on the bonding performance; Figure 1 The crosslinking density of the crosslinking agent sample "crosslinker + NaOH" cured after pH adjustment with NaOH solution (77.4%) is lower than that of the reference crosslinking agent sample "crosslinker" cured after pH adjustment without NaOH solution (79.2%), which further proves that the use of NaOH solution to adjust pH value only accelerates the self-crosslinking rate of the crosslinker, but cannot improve the degree of crosslinking. Figure 2As shown in the figure, the crosslinking density (67.6%) of the soybean-based adhesive cured sample "NaOH modified adhesive" prepared by adjusting the pH value with NaOH solution is lower than the crosslinking density (71.3%) of the reference soybean-based adhesive cured sample "reference adhesive" prepared without adjusting the pH value with NaOH solution, which makes the Class II water resistance of plywoods C1 and C2 lower than that of the corresponding plywoods B1 and B2.

[0117] As shown in Table 3, the curing-accelerating resin modified soybean-based adhesive of Example 1 is used to gradually shorten the hot pressing time at the same hot pressing temperature. Due to the reduction in the energy provided for cross-linking and curing, the overall bonding strength shows a trend of gradually decreasing. However, compared with comparative experiments 1 and 2, the degree of bonding strength attenuation caused by shortening the hot pressing time from 4.5 min to 3 min is significantly reduced (the curing-accelerating resin is attenuated by 21.5%, the NaOH solution is attenuated by 37.4%, and the reference without curing-accelerating resin or NaOH is attenuated by 70.5%). This fully proves that the curing-accelerating resin of Example 1 can effectively promote the cross-linking and curing of soybean-based adhesives, thereby shortening the hot pressing time, and can shorten the hot pressing time to 2.5 min to still prepare plywood whose bonding performance meets the national standard GB / T9846-2015 for Class II plywood bonding performance requirements (≥0.70 MPa). Moreover, the bonding properties of the plywood prepared at the same hot pressing time (hot pressing at 120°C) are higher than those of the soy-based adhesive using the alkali solution NaOH to adjust the pH value. This shows that the curing accelerating resin in Example 1 not only improves the cross-linking curing speed of the soy-based adhesive, but also improves its cross-linking density and bonding properties. This is attributed to the ability of the curing accelerating resin in Example 1 to adjust the pH value of the soy-based adhesive according to the attached Figure 5 Good co-crosslinking reaction with the crosslinking agent; Figure 1 The crosslinking density of the crosslinking agent sample "crosslinking agent + curing accelerator resin" after adding the curing accelerator resin (88.9%) is significantly higher than the crosslinking density of the crosslinking agent sample "crosslinking agent" without adding NaOH alkali solution and curing accelerator resin (79.2%), and the crosslinking density of the crosslinking agent sample "crosslinking agent + NaOH" with only adding NaOH alkali solution (77.4%). Figure 2 As shown in the figure, the crosslinking density of the curing sample "curing-accelerating resin modified adhesive" (76.4%) of the curing sample of the soy-based adhesive modified with a curing-accelerating resin is significantly higher than the crosslinking density of the "NaOH modified adhesive" (67.6%) of the curing sample of the soy-based adhesive modified with NaOH and the "reference adhesive" (71.3%) of the curing sample of the reference soy-based adhesive not modified with NaOH and a curing-accelerating resin.

[0118] As can be seen from Table 4, the curing-promoting resin modified soybean-based adhesive of Example 2 increases the pH value of the cross-linking agent polyamide polyamine-epichlorohydrin resin solution by the curing-promoting resin, thereby accelerating the cross-linking curing rate. At the same time, the cross-linking density is effectively increased (from 79.2% to 86.1%) by the co-cross-linking reaction of the curing-promoting resin and the cross-linking agent polyamide polyamine-epichlorohydrin resin. The cross-linking density (74.9%) of the cured product of the curing-promoting resin modified soybean-based adhesive of Example 2 is also higher than the cross-linking density (71.3%) of the reference soybean-based adhesive cured sample "reference adhesive". Therefore, under the same hot pressing time, the hot pressing temperature can be reduced from 120°C to 90°C while ensuring the necessary bonding performance (higher than the national standard GB / T9846-2015 for Class II plywood bonding performance requirement of 0.70MPa), thereby effectively reducing the energy consumption of soybean-based adhesive production of plywood.

[0119] As can be seen from Table 5, the polyamide polyamine resin synthesized under the condition of 2% excess of aliphatic polyamine has too many residual alkaline amino groups in the system. On the one hand, the pH value of the resin solution (10.9) and the pH value of the soy-based adhesive (6.1) are significantly higher than the curing-accelerating resin of the present invention (8.5-9.5) and the modified soy-based adhesive (less than 5.5), thereby causing the pH value of the modified soy-based adhesive to be too high, resulting in a similar effect to the modification of small molecule strong alkaline substances (mainly promoting the self-crosslinking of the polyamide polyamine-epichlorohydrin resin by increasing the pH of the adhesive solution); on the other hand, too many residual alkaline amino groups will consume the active azetidinium groups in the crosslinking agent polyamide polyamine-epichlorohydrin resin, resulting in the crosslinking agent polyamide polyamine-epichlorohydrin resin being unable to fully crosslink with defatted soy flour. The crosslinking density of the crosslinking agent polyamide polyamine-epichlorohydrin resin solution containing a curing accelerator resin prepared with an excess of polyamine and its modified soybean-based adhesive cured product was compared with the crosslinking density of the product modified by the small molecule strong base NaOH and the curing accelerator of Example 1 (see Appendix Figure 1 and attached Figure 2) for comparison: the crosslinking density of the crosslinking product of the crosslinking agent polyamide polyamine-epichlorohydrin resin solution containing a curing accelerator resin prepared by excessive polyamine is 89.5%, which is higher than the crosslinking density of the reference crosslinking agent without additive addition (79.2%), the crosslinking agent modified by NaOH (77.4%) and the crosslinking agent modified by the curing accelerator of Example 1 (88.9%), which confirms that the addition of polyamide polyamine resin synthesized by excessive polyamine can make the crosslinking agent polyamide polyamine-epichlorohydrin resin produce obvious crosslinking. ; However, the crosslinking density of the polyamide-polyamine resin modified soybean-based adhesive prepared by excessive polyamine is 69.7%, which is only higher than the soybean-based adhesive modified by NaOH (67.6%), but lower than the crosslinking density of the reference crosslinking agent without additive addition (71.3%) and the crosslinking agent modified by the curing accelerator of Example 1 (76.4%), which proves that its addition reduces the crosslinking degree of the crosslinking agent polyamide-polyamine-epichlorohydrin resin and defatted soybean powder, and finally leads to a significant reduction in the crosslinking degree of the cured soybean-based adhesive. Further comparison of the results in Table 5 and Table 4 shows that it is also fully confirmed that the polyamide-polyamine resin with excessive alkalinity not only fails to promote curing, but also makes the crosslinking agent ineffective, resulting in insufficient crosslinking and curing of the soybean-based adhesive and a significant reduction in bonding performance. Therefore, it is particularly important to regulate the degree of polymerization (dehydration amount) during the curing-promoting resin synthesis and the appropriate excess of organic dibasic acid, so as to obtain a suitable pH-raising effect and a suitable curing accelerator-crosslinking agent co-crosslinking, thereby promoting the crosslinking curing rate of the soybean-based adhesive, and at the same time, the crosslinking agent after co-crosslinking modification can retain enough active crosslinkable groups of azetidinium, so that the defatted soybean powder can be fully crosslinked and have excellent bonding properties.

Claims

1. An application of a curing-accelerating resin for a soybean-based adhesive, characterized in that It is used to formulate soy-based adhesives; The preparation of the soybean-based adhesive is specifically carried out according to the following steps: Weigh 100 parts of a polyamide polyamine-epichlorohydrin resin solution, 1 to 5 parts of a curing-accelerating resin for a soy-based adhesive, and 30 to 50 parts of defatted soy flour by mass; first add 1 to 5 parts of a curing-accelerating resin for a soy-based adhesive to 100 parts of a polyamide polyamine-epichlorohydrin resin solution, stir and mix evenly to obtain a cross-linking agent polyamide polyamine-epichlorohydrin resin solution containing a curing-accelerating resin, then add 30 to 50 parts of defatted soy flour, stir at room temperature, and obtain a homogeneous and viscous curing-accelerating resin-modified soy-based adhesive; The solid content of the polyamide polyamine-epichlorohydrin resin solution is 5% to 6.5% by mass; The pH value of the crosslinking agent polyamide polyamine-epichlorohydrin resin solution containing the curing accelerating resin is 3.5-4.5; the pH value of the homogeneous and viscous curing accelerating resin modified soybean-based adhesive is less than 5.5; The curing accelerating resin of the soy-based adhesive is prepared from 100 parts of aliphatic polyamine and 80 to 150 parts of organic dibasic acid by mass; the molar number of the organic dibasic acid is greater than the molar number of the aliphatic polyamine; The aliphatic polyamine is one of diethylenetriamine, triethylenetetramine and tetraethylenepentamine or a mixture of several thereof; the organic dibasic acid is one of succinic acid, adipic acid and sebacic acid or a mixture of several thereof.

2. The use of a curing accelerating resin for a soybean-based adhesive according to claim 1, characterized in that The molar number of the organic dibasic acid is 1% to 10% greater than the molar number of the aliphatic polyamine.

3. The use of a curing accelerating resin for a soybean-based adhesive according to claim 1, characterized in that The curing accelerating resin of the soy-based adhesive is prepared according to the following steps: Weigh 100 parts of aliphatic polyamine and 80 to 150 parts of organic dibasic acid by mass, put the 100 parts of aliphatic polyamine and 80 to 150 parts of organic dibasic acid into a reaction kettle to obtain a reaction system, under stirring conditions, first heat the reaction system to 105°C to 130°C, then heat it to 160°C to 165°C, and distill it at a temperature of 160°C to 165°C for 3h to 5h, collect water distilled from the system by polycondensation to obtain polycondensation distilled water, stop heating to cool the reaction system to 90°C to 100°C, then add water and polycondensation distilled water to the reaction system, continue stirring and cool the reaction system to below 40°C, and obtain a curing-promoting resin for a soybean-based adhesive; The molar number of the organic dibasic acid is greater than the molar number of the aliphatic polyamine.

4. The use of a curing accelerating resin for a soybean-based adhesive according to claim 3, characterized in that The solid content of the curing accelerating resin of the soybean-based adhesive is 19% to 21% by mass.

5. The use of a curing accelerating resin for a soybean-based adhesive according to claim 3, characterized in that The pH value of the curing accelerating resin of the soybean-based adhesive is 8.5-9.5, and the viscosity is 25mPa.s-100mPa.s.

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