Polycarboxylic acid-chitin modified composite rubber powder as well as preparation method and application thereof

Abstract

The invention provides polycarboxylic acid-chitin modified composite rubber powder as well as a preparation method and application thereof.The composite rubber powder is prepared from chitin extracted from squid bone meal and phosphorylated lignin as raw materials, polycarboxylic acid reacts with amino and hydroxyl of the chitin to form a salt bridge structure and hydrogen bonds, a three-dimensional cross-linked network is constructed, and the three-dimensional cross-linked network is formed; through introduction of phosphorylated lignin dispersion liquid, hydrogen bond and ion interaction between phosphate groups of the phosphorylated lignin dispersion liquid and polycarboxylic acid and esterification reaction between phosphate groups of the phosphorylated lignin dispersion liquid and hydroxyl or amino of chitin, an interpenetrating network structure is formed, and the thermal stability and mechanical properties of the material are remarkably enhanced. The obtained rubber powder has good flame retardant property and is convenient to transport and store. After water is added, the adhesive with good bonding performance can be effectively formed, the advantages of low-temperature hot pressing and short-time hot pressing are achieved, efficient gluing can be achieved at low temperature and within short time, and the production period is shortened. The rubber powder is used in the fields of plywood production, bonding, coatings, packaging materials and the like.

Description

Technical Field

[0001] The invention belongs to the field of adhesive preparation, and particularly relates to a polycarboxylic acid-chitin modified composite rubber powder with flame retardancy, a preparation method thereof, and an application thereof. Background Art

[0002] The development of sustainable bio-based wood adhesives as an alternative to petroleum-based adhesives is of great significance. However, most current bio-based adhesives face challenges such as complex manufacturing processes, high energy consumption and time-consuming processes, and poor overall performance (such as high hot pressing temperatures, low adhesion strength, and poor water resistance). Chitosan, as a biomass material, exhibits excellent biodegradability, biocompatibility, and antimicrobial properties. However, its inherent adhesive properties include poor solubility, high viscosity, and low solids content, which limit its widespread application in wood adhesives. Furthermore, for fully bio-based components (biocarbon content ≥95%), they also exhibit a 180-day natural degradation rate, resulting in an environmentally friendly degradation rate of >90%. Therefore, the potential of bio-based adhesives as formaldehyde-free adhesives is gaining recognition, providing an efficient and sustainable solution for the industrial application of formaldehyde-free wood adhesives.

[0003] Furthermore, the preparation of glue powder is a crucial technical step in the adhesive field. By converting the modified chitin solution into a powder form through methods such as spray drying, freeze drying, or conventional drying, this powdered adhesive can be more conveniently stored and applied during the wood processing process. By adjusting the powder's particle size and dispersibility, its adhesion and bonding properties on the wood surface can be optimized, while its fluidity and miscibility can be improved, making it more adaptable and performant when used with other additives or auxiliary materials such as resins and catalysts. This technological innovation provides an environmentally friendly and efficient alternative adhesive for the wood processing industry, while also offering insights and ideas for the development of other bio-based adhesives.

[0004] Cai Yujian studied a water-based citric acid / chitosan supramolecular adhesive with a ratio of 4:1 and a solid content of 30%. The optimal hot pressing process conditions for Class II plywood were a hot pressing temperature of 180°C, a hot pressing time of 3 minutes, and a hot pressing pressure of 1.0 MPa. ([1] Cai Yujian. Preparation, curing mechanism and performance of water-based citric acid / chitosan supramolecular adhesive [D]. Northeast Forestry University, 2024). However, the hot pressing temperature of this adhesive is relatively high, and in actual operation, a higher temperature is required for hot pressing. In addition, the high ratio of citric acid to chitosan makes the adhesive more expensive. Summary of the Invention

[0005] In response to the technical problems faced by existing adhesives, the present invention provides a convenient and flexibly formulated polycarboxylic acid-chitin modified composite adhesive powder suitable for wood plywood bonding technology and a preparation method thereof. The composite adhesive powder is applied to wood plywood and can also be prepared into a flame-retardant adhesive.

[0006] To achieve the above object, the present invention adopts the following technical solutions: One object of the present invention is to provide a polycarboxylic acid-chitin modified composite rubber powder, which is prepared from the following raw materials in parts by weight: 10-60 parts of polycarboxylic acid, 10-20 parts of chitin, with a mass ratio of polycarboxylic acid to chitin of 1-3:1, and 1-5 parts of phosphorylated lignin.

[0007] Preferably, the chitosan is the shell of one or more of squid bones, hairy crabs, swimming crabs, king crabs, lobsters, and prawns, crushed into particles with a particle size of ≥2000 mesh.

[0008] Preferably, the polycarboxylic acid can be one or more of polycarboxylic acid, malic acid, citric acid, tartaric acid or oxalic acid, and the polycarboxylic acid is a polycarboxylic acid crystal with a weight percentage of 80-98%. More preferably, it is citric acid.

[0009] Another object of the present invention is to provide a method for preparing the polycarboxylic acid-chitin modified composite rubber powder, the specific steps of which are as follows: (1) Dissolving polycarboxylic acid crystals: adding polycarboxylic acid crystals to deionized water in a mass ratio of polycarboxylic acid crystals to deionized water of 1:6-9, heating and stirring to obtain a polycarboxylic acid solution; (2) Preparation of phosphorylated lignin: Using sulfate lignin as raw material (which can be purchased on the market), immerse it in an aqueous solution of ammonium dihydrogen phosphate and urea, wherein the molar ratio of ammonium dihydrogen phosphate to urea is 1:4, the solid-liquid mass ratio of the mixture of ammonium dihydrogen phosphate and urea to water is 1:10, and the molar ratio of ammonium dihydrogen phosphate to sulfate lignin is 5:1, and stir at 70°C for 1 hour; the mixed solution is dried at 70°C and then cured at 150°C for 1 hour to complete the phosphorylation reaction; the obtained product is washed with boiling water and cold deionized water in turn to remove residual reagents, and finally dried in vacuum at 60°C to obtain phosphorylated lignin; (3) Esterification and cross-linking of chitosan: chitosan is added to the polycarboxylic acid solution in step (1) in multiple portions, heated and stirred evenly, and an esterification and cross-linking reaction is carried out; (4) adding the dispersion of phosphorylated lignin to the polycarboxylic acid-chitin system in step (3), continuing heating and stirring to obtain a modified adhesive; (5) drying the obtained modified adhesive to obtain rubber powder; (6) The obtained rubber powder is crushed, sieved, and then vacuum-dried to obtain a polycarboxylic acid-chitin modified composite rubber powder.

[0010] Preferably, in step (1), heating and stirring are performed at 75-100° C. for 5-20 min.

[0011] Preferably, the temperature of the esterification cross-linking reaction in step (3) is 90-120° C., and the reaction time is 90-180 min.

[0012] Preferably, the drying temperature in step (5) is 60-80°C and the drying time is 12-24 hours.

[0013] Preferably, the rubber powder obtained after screening in step (6) is 80-300 mesh.

[0014] Preferably, the drying temperature in step (5) is 60-80°C, and the drying time is 12-24 hours.

[0015] Preferably, the vacuum drying temperature in step (6) is 40-70° C., and the drying time is 6-12 h.

[0016] Another object of the present invention is to provide the use of the polycarboxylic acid-chitin modified composite rubber powder prepared by the above preparation method in wood plywood, wherein the composite rubber powder forms an adhesive with a solid content of 20-45% after rehydration; Hot pressing process parameters are: temperature 130-150℃, pressure 0.8-1.2MPa, time 3-6min; The dry shear strength of the obtained plywood is ≥2.5MPa, and the wet strength retention rate after immersion in water at 63℃ for 3h is ≥50%; Storage stability: after being stored at 40°C and 75% relative humidity for 6 months, the bonding strength attenuation rate is less than 5%, and the rehydration activation time is ≤10 minutes.

[0017] Another object of the present invention is to provide a flame-retardant adhesive prepared by compounding the above-mentioned polycarboxylic acid-chitin modified composite rubber powder with 5-15wt% of its own weight of inorganic filler, wherein the flame-retardant adhesive enables plywood to achieve UL94 V-1 flame retardancy and reduces the smoke density level by 30-50%.

[0018] The composite rubber powder of the present invention forms a three-dimensional cross-linked network through the reaction of the carboxyl groups of polycarboxylic acid with the amino / hydroxyl groups of chitin, significantly improving the solubility and thermal stability; further, phosphorylated lignin is introduced, and its phosphate groups and polycarboxylic acids strengthen the cross-linking density through hydrogen bonds and ionic interactions, while esterification and cross-linking with the chitin molecular chains form an interpenetrating network structure, which increases the cohesive force of the adhesive by more than 50% and gives the system high water resistance and flame retardancy.

[0019] During the application of the composite rubber powder of the present invention, an adhesive is formed by adding water, which can be hot-pressed at 140°C. Compared with other types of natural rubber (such as gelatin, sodium alginate, etc.), the hot-pressing temperature of the adhesive of the present invention is generally lower, so it can save energy during the production process and reduce damage to heat-sensitive materials. The lower hot-pressing temperature also helps to protect the structural stability of the product, which is especially advantageous when preparing materials requiring high biocompatibility or low heat sensitivity.

[0020] During the preparation process of the composite rubber powder of the present invention, the mechanism of the esterification and cross-linking reaction is: (1) Ionic crosslinking: The carboxyl group (-COOH) of the polycarboxylic acid reacts with the amino group (-NH2) of the chitin molecular chain under acidic conditions to form an amide bond. (2) Covalent cross-linking: Under heating conditions of 90-120°C, the free carboxyl groups of polycarboxylic acids react with the C3 / C6 hydroxyl groups (-OH) of chitin to form stable ester bonds (RO-CO-R').

[0021] During the formation of phosphorylated lignin, an interpenetrating network was constructed. After the introduction of phosphorylated lignin (phosphate content 2.5-4.8 mmol / g), it interacted with the system through the following pathways: (1) Esterification grafting: The phosphate group (-O-PO3H) of phosphorylated lignin undergoes an ester exchange reaction with the C6-OH of chitin at 110-120°C to form a chitin-O-PO3-lignin covalent bond.

[0022] (2) Physical entanglement strengthening: The rigid aromatic ring structure of lignin is physically entangled with the pyran ring of chitin through π-π stacking.

[0023] Compared with traditional adhesives, the present invention has the following advantages: 1. The preparation process of the present invention is relatively simple and flexible. It is prepared in advance in the form of glue powder and water is added to be adjusted into the required glue liquid according to actual needs. Therefore, it is very convenient in practical application. Simply mix the chitosan glue powder with water and stir evenly to obtain a glue liquid suitable for various molding processes. This greatly simplifies the preparation process and application operation, significantly reduces costs, is suitable for large-scale production or customized needs, and can effectively save production time and reduce dependence on equipment.

[0024] 2. The composite rubber powder of the present invention can not only be used stably at high temperatures, but also has high tensile and compressive strengths. At the same time, it can still maintain the bonding effect in a humid environment, ensuring its long-term stability in water-based applications and meeting the use requirements of artificial board products in a humid environment.

[0025] 3. The chitosan used in the composite rubber powder of the present invention has good biodegradability. After use, the adhesive and artificial board waste can be naturally decomposed, reducing the long-term impact on the environment.

[0026] 4. The composite rubber powder of the present invention can be compounded with an inorganic filler to prepare a flame-retardant adhesive. By using the flame-retardant adhesive, the plywood can reach the UL94 V-1 flame retardancy level and the smoke density level can be reduced by 30-50%.

[0027] 5. The adhesive of the present invention has a wide range of applications and is suitable for various uses such as adhesives, film materials, coating materials, etc. It is not only suitable for the wood-based panel industry, but also has the potential to play an important role in furniture manufacturing and other fields involving wood bonding. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is the FT-IR spectrum of the composite rubber powder after curing and chitin in Example 1.

[0029] Figure 2 This is the SEM image of the composite rubber powder in Example 1 before curing.

[0030] Figure 3 This is the SEM image of the composite rubber powder after curing in Example 1. DETAILED DESCRIPTION

[0031] The technical solution of the present invention is further illustrated below by means of specific implementation methods and usage methods. It should be understood by those skilled in the art that the embodiments are only for the purpose of helping to understand the present invention and should not be regarded as specific limitations of the present invention.

[0032] Example 1 The citric acid-chitin composite rubber powder is prepared from the following raw materials in parts by weight: 20 parts of citric acid crystals (the mass fraction of citric acid is 94%), 10 parts of squid bone chitin, and 1 part of phosphorylated lignin.

[0033] The preparation steps of the polycarboxylic acid-chitin modified composite rubber powder are as follows: (1) Dissolving citric acid crystals: adding polycarboxylic acid to deionized water, wherein the polycarboxylic acid is 94% by weight of citric acid crystals and the mass ratio of citric acid to deionized water is 1:6, and stirring at 95°C for 15 minutes to obtain a citric acid solution; (2) Preparation of phosphorylated lignin: Using sulfate lignin as raw material, it was immersed in an aqueous solution of ammonium dihydrogen phosphate and urea, wherein the molar ratio of ammonium dihydrogen phosphate to urea was 1:4, the solid-liquid mass ratio of the mixture of ammonium dihydrogen phosphate and urea to water was 1:10, and the molar ratio of ammonium dihydrogen phosphate to sulfate lignin was 5:1, and stirred at 70°C for 1 hour; the mixed solution was dried at 70°C and then placed at 150°C for 1 hour to complete the phosphorylation reaction; the obtained product was washed with boiling water and cold deionized water in turn to remove residual reagents, and finally dried in vacuum at 60°C to obtain phosphorylated lignin; (3) Esterification and cross-linking of chitosan: chitosan was added to the citric acid solution in step (1) in small amounts and in multiple times to carry out esterification and cross-linking reaction, and the mixture was stirred at 100°C for 120 minutes; (4) adding the phosphorylated lignin dispersion to the citric acid-chitin system in step (3), stirring and mixing at 120° C. for 100 min to obtain a modified adhesive; (5) drying the modified adhesive in step (4) at 70°C for 16 hours to obtain citric acid-chitin rubber powder; (6) The citric acid-chitin rubber powder obtained in step (5) was crushed, sieved with 200 mesh, and then vacuum-dried at 60° C. for 10 h to obtain citric acid-chitin composite rubber powder.

[0034] Example 2 Malic acid-chitin composite rubber powder is prepared from the following raw materials in parts by weight: 60 parts of malic acid crystals (mass fraction of malic acid is 98%), 20 parts of squid bone chitin, and 3 parts of phosphorylated lignin.

[0035] Compared with Example 1, the preparation process conditions of Example 2 are different as follows: (1) The mass ratio of malic acid to deionized water is 1:5, and stirring is carried out at 98°C for 20 minutes; (3) Esterification cross-linking conditions: stirring and mixing at 105°C for 150 min; (4) The added phosphorylated lignin dispersion was stirred and mixed at 110°C for 120 min; (5) Drying conditions are: 18h, 75℃.

[0036] Example 3 Oxalic acid-chitin composite rubber powder is prepared from the following raw materials in parts by weight: 10 parts of oxalic acid crystals (with an oxalic acid mass fraction of 99%), 10 parts of squid bone chitin, and 5 parts of phosphorylated lignin.

[0037] Compared with Example 1, the preparation process conditions of Example 3 are different as follows: (1) The mass ratio of oxalic acid to deionized water is 1:6, and stirring is carried out at 100°C for 18 minutes; (3) Esterification cross-linking conditions: stirring and mixing at 110°C for 160 min; (4) Add the phosphorylated lignin dispersion and stir at 100°C for 120 minutes; (5) Drying conditions are 20 h, 65 °C; (6) 250 mesh sieving, vacuum drying at 55°C for 9 hours.

[0038] Example 4 The maleic acid-chitin composite rubber powder is prepared from the following raw materials in parts by weight: 30 parts of maleic acid crystals (mass fraction of maleic acid is 97%), 10 parts of squid bone chitin, and 2 parts of phosphorylated lignin.

[0039] Compared with Example 1, the preparation process conditions of Example 4 are different as follows: (1) The mass ratio of maleic acid to deionized water was 1:4, and stirred at 97°C for 12 min; (3) Esterification and cross-linking conditions: stirring and mixing at 115°C for 130 minutes; (4) Add the phosphorylated lignin dispersion and stir at 120°C for 100 minutes; (5) Drying conditions are 22 h, 80 °C; (6) 80 mesh sieving, vacuum drying at 60°C for 7 hours.

[0040] Example 5 The succinic acid-chitin composite rubber powder is prepared from the following raw materials in parts by weight: 30 parts of succinic acid crystals (succinic acid mass fraction is 99%), 15 parts of squid bone chitin, and 4 parts of phosphorylated lignin.

[0041] Compared with Example 1, the preparation process conditions of Example 5 are different as follows: (1) The mass ratio of succinic acid to deionized water was 1:5, and the mixture was stirred at 100°C for 14 minutes; (3) Esterification cross-linking conditions are stirring and mixing at 110°C for 140 min; (4) Add the phosphorylated lignin dispersion and stir at 110°C for 105 min; (5) Drying conditions are 16 h, 60 ° C; (4) 180 mesh sieving and vacuum drying at 50°C for 9 hours.

[0042] Example 6 Compared with Example 4, the only difference is that the chitosan type is replaced from squid bone chitosan to 10 parts of hairy crab shell chitosan, and the contents of other components and the preparation method remain unchanged.

[0043] Example 7 Compared with Example 4, the only difference is that the chitosan type is replaced from squid bone chitosan to 10 parts of swimming crab shell chitosan, and the contents of other components and the preparation method remain unchanged.

[0044] Example 8 The same as Example 4, except that the chitosan type is replaced from squid bone chitosan to 10 parts of lobster shell chitosan, and the contents of other components and the preparation method remain unchanged.

[0045] Example 9 The same as Example 4, except that the chitosan type is replaced from squid bone shell chitosan to 10 parts of king crab shell chitosan, and the contents of other components and the preparation method remain unchanged.

[0046] Comparative Example 1 The same as Example 4, except that the chitosan content is 10 parts, and the contents of other components and the preparation method remain unchanged.

[0047] Comparative Example 2 The same as Example 4, the only difference is that the chitosan is 9 parts, and the contents of other components and the preparation method remain unchanged.

[0048] Comparative Example 3 The same as Example 4, except that the chitosan content is 32 parts, and the contents of other components and the preparation method remain unchanged.

[0049] Comparative Example 4 The same as Example 4, except that acetic acid is used as the acid, and the contents of other components and the preparation method remain unchanged.

[0050] Application test of the composite rubber powder obtained by the present invention The steps for applying the composite rubber powder of Examples 1-9 and Comparative Examples 1-4 are as follows: (1) Dissolve the prepared rubber powder in water at a ratio of 1:5 and set aside; (2) Press 210 g / After evenly spreading, hot press at 140℃, 1MPa for 9 minutes and then cool.

[0051] Performance parameter test: 1. Class II wet bond strength test: The test is carried out in accordance with the Class II plywood bond strength test method specified in the national standard GB / T 17657-2022 "Test methods for physical and chemical properties of wood-based panels and veneered wood-based panels" - 4.17.

[0052] 2. Dry bonding strength: The test is carried out in accordance with the plywood bonding strength test method specified in the national standard GB / T 17657-2022 "Test methods for physical and chemical properties of wood-based panels and veneered wood-based panels" - 4.17.

[0053] 3. Minimum hot pressing temperature: Using a hot press at 6 minutes and 1MPa, it can meet the minimum hot pressing temperature of Class II plywood in the national standard GB / T 17657-2022.

[0054] 4. Curing temperature test: Antibacterial test, test at 30℃, 90% humidity, constant temperature and pressure to observe the time it takes for plaque to form.

[0055] Table 1 is the performance test data of the composite rubber powder of Examples 1-9 and Comparative Examples 1-4

[0056] As can be seen from Table 1, among the composite rubber powders prepared in various embodiments of the present invention, the citric acid-chitin modified composite rubber powder has the best comprehensive performance. As for the choice of chitosan, all of them are biodegradable chitosan materials, so the comprehensive performance of the composite rubber powders is relatively similar, and the various performance parameters do not change much. In addition, it can be seen from Example 4 and Comparative Example 1 that the present invention selects degradable chitosan, which can effectively improve the dry bonding strength of the composite rubber powder. When the mass ratio of polycarboxylic acid to chitosan exceeds or is lower than 3:1, the comprehensive performance of the composite rubber powder will also decrease. When the acid used is not a polycarboxylic acid, the comprehensive performance of the composite rubber powder will also decrease significantly, especially the Class II wet bonding strength will decrease significantly.

[0057] Performance tests have shown that the composite rubber powder of the present invention can form an adhesive with a solid content of 20-45% after rehydration.

[0058] The hot pressing process parameters are: temperature 130-150°C, pressure 0.8-1.2MPa, and time 3-6min.

[0059] The dry shear strength of the obtained plywood is ≥2.5MPa, and the wet strength retention rate after immersion in water at 63°C for 3 hours is ≥50%.

[0060] Storage stability: after being stored at 40°C and 75% relative humidity for 6 months, the bonding strength attenuation rate is less than 5%, and the rehydration activation time is ≤10 minutes.

[0061] It can be seen that the composite rubber powder of the present invention can be used stably at high temperatures, and has high tensile and compressive strengths. At the same time, it can still maintain the bonding effect in a humid environment, ensuring its long-term stability in water-based applications and meeting the use requirements of artificial board products in a humid environment.

[0062] The composite rubber powder of the present invention is used as a wood adhesive. A flame-retardant plywood is prepared using the composite rubber powder and 5-15 wt% of its own weight of an inorganic filler. After testing, the flame retardant grade of the composite rubber powder reaches the UL94 V-1 flame retardant grade, and the smoke density grade is reduced by 30-50% compared with the existing plywood.

[0063] The applicant declares that while the present invention uses the above-described embodiments to illustrate the polycarboxylic acid-chitin modified composite rubber powder, the present invention is not limited to the above-described embodiments, nor does it imply that the present invention must rely on the above-described embodiments in order to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent replacements for the raw materials of the present invention, addition of auxiliary ingredients, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. A polycarboxylic acid-chitin modified composite rubber powder, characterized in that: The rubber powder is prepared from the following raw materials in parts by weight: 10-60 parts of polycarboxylic acid, 10-20 parts of chitin, and 1-5 parts of phosphorylated lignin, and the mass ratio of the polycarboxylic acid to the chitin is 1-3:

1.

2. The polycarboxylic acid-chitin modified composite rubber powder according to claim 1, characterized in that: The chitosan is obtained by crushing the shells of one or more of squid bones, hairy crabs, swimming crabs, king crabs, lobsters and prawns into particles with a particle size of ≥2000 meshes.

3. The polycarboxylic acid-chitin modified composite rubber powder according to claim 1, characterized in that: The polycarboxylic acid may be one or more of polycarboxylic acid, malic acid, citric acid, tartaric acid or oxalic acid, and the polycarboxylic acid is a polycarboxylic acid crystal with a weight percentage of 80-98%.

4. The method for preparing the polycarboxylic acid-chitin modified composite rubber powder according to any one of claims 1 to 3, wherein: The specific preparation steps are as follows: (1) Dissolving polycarboxylic acid crystals: adding polycarboxylic acid crystals to deionized water in a mass ratio of polycarboxylic acid crystals to deionized water of 1:6-9, heating and stirring to obtain a polycarboxylic acid solution; (2) Preparation of phosphorylated lignin: Using sulfate lignin as raw material, it was immersed in an aqueous solution of ammonium dihydrogen phosphate and urea, wherein the molar ratio of ammonium dihydrogen phosphate to urea was 1:4, the solid-liquid mass ratio of the mixture of ammonium dihydrogen phosphate and urea to water was 1:10, and the molar ratio of ammonium dihydrogen phosphate to sulfate lignin was 5:1, and stirred at 70°C for 1 hour; the mixed solution was dried at 70°C and then placed at 150°C for 1 hour to complete the phosphorylation reaction; the obtained product was washed with boiling water and cold deionized water in turn to remove residual reagents, and finally dried in vacuum at 60°C to obtain phosphorylated lignin; (3) Esterification and cross-linking of chitosan: chitosan is added to the polycarboxylic acid solution in step (1) in multiple portions, heated and stirred evenly, and an esterification and cross-linking reaction is carried out; (4) adding the dispersion of phosphorylated lignin to the polycarboxylic acid-chitin system in step (3), continuing heating and stirring to obtain a modified adhesive; (5) drying the obtained modified adhesive to obtain rubber powder; (6) The obtained rubber powder is crushed, sieved, and then vacuum-dried to obtain a polycarboxylic acid-chitin modified composite rubber powder.

5. The method for preparing the polycarboxylic acid-chitin modified composite rubber powder according to claim 4, wherein: In the step (1), heating and stirring are performed at 75-100° C. for 5-20 minutes.

6. The method for preparing the polycarboxylic acid-chitin modified composite rubber powder according to claim 4, characterized in that: The temperature of the esterification cross-linking reaction in step (3) is 90-120° C., and the reaction time is 90-180 min.

7. The method for preparing the polycarboxylic acid-chitin modified composite rubber powder according to claim 4, wherein: The drying temperature in step (5) is 60-80°C and the drying time is 12-24 hours.

8. The method for preparing the polycarboxylic acid-chitin modified composite rubber powder according to claim 4, wherein: In step (6), the vacuum drying temperature is 40-70° C., and the drying time is 6-12 h.

9. Use of the polycarboxylic acid-chitin modified composite rubber powder prepared by the preparation method according to any one of claims 4 to 8 in wood plywood, characterized in that: The composite rubber powder forms an adhesive with a solid content of 20-45% after rehydration; Hot pressing process parameters are: temperature 120-140℃, pressure 0.8-1.2MPa, time 3-6min; The dry shear strength of the obtained plywood is ≥2.5MPa, and the wet strength retention rate after immersion in water at 63℃ for 3h is ≥80%; Storage stability: after being stored at 40°C and 75% relative humidity for 6 months, the bonding strength attenuation rate is less than 5%, and the rehydration activation time is ≤10 minutes.

10. A flame retardant adhesive, characterized in that: The flame retardant adhesive is prepared by compounding the polycarboxylic acid-chitin modified composite rubber powder according to any one of claims 1 to 3 with 5-15 wt% of its own weight of inorganic filler. The flame retardant adhesive enables the plywood to reach the UL94 V-1 flame retardant grade and reduces the smoke density grade by 30-50%.

Images