Chitosan-based boiling-water-resistant flame-retardant wood adhesive, aerogel with low compression modulus and preparation method of chitosan-based boiling-water-resistant flame-retardant wood adhesive

Abstract

The invention discloses a chitosan-based boiling-water-resistant flame-retardant wood adhesive, low-compression-modulus aerogel and a preparation method, and belongs to the technical field of chitosan-based composite materials. The preparation method of the wood adhesive comprises the following steps: S1, mixing acidified chitosan and acryloyl chloride, and reacting to obtain an AMS material; s2, mixing polyamine, acryloyl chloride and dichloromethane, and reacting to obtain an AHC material; s3, mixing the CS (at) IRMOF-3, phosphonitrilic chloride trimer and tetrahydrofuran, and then reacting to obtain a CS (at) IRMOF-3 (at) P material; s4, AMS, AHC, water and CS-coated IRMOF-3-coated P materials are mixed and react to obtain the boiling-water-resistant flame-retardant wood adhesive, and the boiling-water-resistant flame-retardant wood adhesive has excellent boiling water resistance, thermal stability and fire resistance and is environmentally friendly. In addition, the aerogel prepared from AMS, AHC, water and CS (at) IRMOF-3 (at) P materials shows adjustable compressibility in flexible application.

Description

Technical Field

[0001] The invention belongs to the technical field of chitosan-based composite materials, and particularly relates to a chitosan-based boiling water-resistant flame-retardant wood adhesive, an aerogel with a low compression modulus, and a preparation method thereof. Background Art

[0002] As a natural, renewable and environmentally friendly material, wood is widely used in many fields such as construction, furniture, papermaking and packaging. Wood adhesives are particularly important for maximizing the utilization of wood resources, especially in the production of wood-based panels. Wood adhesives not only play a key role in enhancing the strength and durability of wood, but also have a profound impact on the environmental friendliness and sustainability of wood products. With the enhancement of global environmental awareness and the popularization of the concept of sustainable development, the greening and environmental protection of wood adhesives have become the development trend of the industry. Biomass-based adhesives, as a good substitute for formaldehyde-based resins, have been widely used in the wood industry. Biomass raw materials such as soy protein, starch, tannin, and lignin have been successfully modified through blending, grafting, reaction cross-linking and other methods to prepare wood adhesives with good bonding properties.

[0003] Chitosan, the second most abundant biomass material after cellulose, has been shown to be a highly promising value-added biomass. As an environmentally friendly and renewable biomacromolecule, it possesses many of the physical and chemical properties that make it a good adhesive. Therefore, it can also be used in the preparation of biomass adhesives. Studies have shown that chitosan, as a natural adhesive, has comparable performance to commercial adhesives such as urea-formaldehyde resin and methylene diphenyl isocyanate.

[0004] However, chitosan-based adhesives exhibit poor water resistance and tend to disintegrate after immersion in water, failing to meet current national standards. Furthermore, the flame retardancy of wood-based panels is gaining increasing attention, and market demand for flame-retardant wood-based panels is increasing. However, biomass-based adhesives exhibit poor flame retardancy, requiring the addition of additional flame retardants to enhance their flame retardancy to meet industrial application requirements. Therefore, improving their water resistance and flame retardancy has become a pressing issue for those skilled in the art.

[0005] At the same time, the current chitosan-based aerogel has the problem of high compression modulus, and there is also a need for an aerogel with better adaptability in deformation and pressure buffering. Summary of the Invention

[0006] In light of this, the present invention aims to provide a chitosan-based, boiling-water-resistant, flame-retardant wood adhesive, a low-compression modulus aerogel, and a preparation method. The wood adhesive of the present invention exhibits excellent boiling-water resistance, thermal stability, and fire resistance, while being environmentally friendly. Furthermore, aerogels prepared from AMS, AHC, water, and CS@IRMOF-3@P exhibit tunable compressibility for flexible applications.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] In a first aspect, the present invention provides a method for preparing a chitosan-based boiling water-resistant flame-retardant wood adhesive, comprising the following steps:

[0009] S1. mixing acidified chitosan and acryloyl chloride and reacting them to obtain an AMS material;

[0010] S2. mixing polyamine, acryloyl chloride and dichloromethane and reacting them to obtain an AHC material;

[0011] S3. CS@IRMOF-3, tripolyphosphazene chloride, and tetrahydrofuran were mixed and reacted to obtain CS@IRMOF-3@P material;

[0012] S4. AMS, AHC, water, and CS@IRMOF-3@P were mixed and reacted to obtain a boiling water-resistant flame-retardant wood adhesive.

[0013] The preparation method of the polyamine in S2 comprises the following steps:

[0014] triethyl citrate, 1,6-hexanediamine and methanol are mixed and reacted to obtain polyamine;

[0015] The preparation method of CS@IRMOF-3 in S3 comprises the following steps:

[0016] (a) mixing chitosan and ethanol and reacting them to obtain a reaction solution a;

[0017] (b) dissolving zinc nitrate hexahydrate and 2-aminoterephthalic acid in a mixed solution of ethanol and dimethylformamide to react to obtain a reaction solution b;

[0018] (c) mixing reaction solution a and reaction solution b and reacting them to obtain reaction solution c;

[0019] (d) The reaction solution c and triethylamine were mixed and reacted to obtain CS@IRMOF-3.

[0020] Preferably, the preparation method of the acidified chitosan in S1 is: chitosan, maleic anhydride and acetonitrile are mixed and reacted to obtain the acidified chitosan;

[0021] The mass volume ratio of the chitosan, maleic anhydride and acetonitrile is (5-10) g: (1-10) g: (10-30) mL;

[0022] The reaction temperature is 80-100° C., and the reaction time is 10-15 hours.

[0023] Preferably, the mass ratio of acidified chitosan to acryloyl chloride in S1 is (5-20): (1-5);

[0024] The reaction temperature is -20 to 0°C, and the reaction time is 1 to 3 hours.

[0025] Preferably, in the preparation method of the S2 polyamine, the mass volume ratio of triethyl citrate, 1,6-hexanediamine and methanol is (5-15) g: (15-20) g: (20-40) mL;

[0026] The reaction temperature is 40-80°C, and the reaction time is 10-15 hours.

[0027] Preferably, the mass volume ratio of polyamine, acryloyl chloride and dichloromethane in S2 is (20-40) g: (3-5) g: (10-30) mL;

[0028] The reaction temperature is -20 to 0°C, and the reaction time is 1 to 3 hours.

[0029] Preferably, the preparation method of S3CS@IRMOF-3 includes the following parameters:

[0030] In step (a), the mass volume ratio of chitosan and ethanol is (1-5) g: (10-30) mL; the reaction temperature is 20-25° C., and the reaction time is 0.5-1 h;

[0031] In step (b), the mass volume ratio of zinc nitrate hexahydrate, 2-aminoterephthalic acid solution, ethanol and dimethylformamide is (5-10) g: (1-5) g: (30-50) mL: (10-30) mL; the reaction temperature is 20-25° C., and the reaction time is 0.5-1 h;

[0032] In step (c), the reaction temperature is 20-25° C., and the reaction time is 0.5-1 h;

[0033] In step (d), the mass volume ratio of solution c and triethylamine is (70-90) mL: (5-10) mL; the reaction temperature is 90-110° C., and the reaction time is 22-26 h.

[0034] Preferably, the mass volumes of CS@IRMOF-3, tripolyphosphazene chloride and tetrahydrofuran in S3 are (1-5) g: (1-5) g: (10-30) mL;

[0035] The reaction temperature is 50-70 mL, and the reaction time is 22-26 h.

[0036] Preferably, the mass ratio of AMS, AHC, water and CS@IRMOF-3@P material in S4 is (1-6): (1-5): (25-45): (0.5-2);

[0037] The reaction temperature is 50-90° C., and the reaction time is 0.5-3 h.

[0038] In a second aspect, the present invention provides a method for preparing a chitosan-based aerogel with a low compression modulus, comprising the following steps:

[0039] 1) Select the AMS material, AHC material, and CS@IRMOF-3@P material in claim 1;

[0040] 2) AMS, AHC, water, and CS@IRMOF-3@P material were mixed in a mass volume ratio of (10-16) g: (1-10) g: (100-160) mL: (1-5) g to obtain a mixture;

[0041] 3) reacting the mixture at 60-100° C. for 0-2 hours, and then freeze-drying the mixture to obtain an aerogel with a low compression modulus.

[0042] Furthermore, the freezing temperature of the freeze-drying operation is -70 to 0°C, the freezing time is 10 to 16 hours, and the vacuum time is 46 to 52 hours;

[0043] The drying temperature is 40-80° C., and the drying time is 10-14 hours.

[0044] In a third aspect, the present invention provides a boiling water resistant flame retardant wood adhesive and a low compression modulus aerogel prepared by the above-mentioned preparation method.

[0045] In a fourth aspect, the present invention provides a use of the boiling water resistant flame retardant chitosan-based multifunctional composite material in preparing a laminated plywood. The preparation of the laminated plywood comprises the following steps:

[0046] The poplar veneer is dried, glued, assembled and hot pressed in sequence to obtain laminated plywood;

[0047] During the gluing process, the amount of boiling water resistant flame retardant starch-based wood adhesive used on the poplar veneer is 200-400 g / m 2 ;

[0048] The hot pressing temperature is 130-200° C., the hot pressing pressure is 0.5-2 MPa, and the hot pressing time is 3-10 minutes.

[0049] Furthermore, after drying, the moisture content of the poplar veneer is ≤8%.

[0050] Contains at least the following beneficial technical effects:

[0051] (1) Enhanced boiling water resistance: Chitosan undergoes nucleophilic addition with maleic anhydride, followed by nucleophilic substitution with acryloyl chloride to form "zipper teeth" (AMS) with double bonds and carboxyl groups. Triethyl citrate and 1,6-diaminohexane undergo an amine transesterification reaction to form a polyamine compound (HC), which then reacts with acryloyl chloride to form a "zipper head" (AHC) with double bonds and amino groups. During the hot pressing process, the amino groups of AHC undergo a condensation reaction with the carboxyl groups of AMS (similar to a Schiff base reaction), while the double bonds undergo free radical copolymerization to form a tightly cross-linked network similar to a "zipper". This step-by-step "zipper" reaction (Schiff base reaction + free radical copolymerization) constructs a highly cross-linked three-dimensional network structure, significantly enhancing the mechanical strength and water resistance of the adhesive.

[0052] (2) Significant improvement in flame retardancy: The introduction of a metal organic framework (IRMOF-3) and a phosphorus-containing flame retardant (tripolyphosphazene chloride) improves the flame retardancy of the adhesive. Tripolyphosphazene chloride contains the element P, which decomposes at high temperatures to generate phosphorus oxides and free radicals, which can capture active free radicals during the combustion process and block the combustion chain reaction, thereby achieving flame retardancy. As a metal organic framework compound, IRMOF-3 has a porous structure that can adsorb and capture combustible gases and free radicals during the combustion process, further inhibiting combustion. The limiting oxygen index of the prepared adhesive reached 49.7%, providing a new solution for the fire safety of wood adhesives.

[0053] (3) Innovative synthesis strategy: This strategy combines the natural adhesive properties of chitosan, the structural strengthening effect of IRMOF-3, and the flame retardant function of tripolyphosphazene chloride. This strategy significantly improves the adhesive's water resistance, mechanical properties, flame retardancy, and thermal stability, while maintaining good environmental protection and sustainability. This innovative synthesis method for chitosan-based aerogel materials provides new ideas for the development of multifunctional chitosan-based composite materials.

[0054] In summary, this new boiling water-resistant flame-retardant chitosan-based multifunctional composite material has significant improvements in environmental protection, boiling water resistance, flame retardancy, comprehensive performance and cost-effectiveness compared with existing technologies, highlighting the potential of multifunctional synergistic effects in the design of sustainable application materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1Schematic diagram of the synthesis of AMS materials;

[0056] Figure 2 Schematic diagram of the synthesis of AHC;

[0057] Figure 3 Schematic diagram of the synthesis of boiling water resistant flame retardant chitosan-based multifunctional composite materials. DETAILED DESCRIPTION

[0058] The present invention provides a method for preparing a chitosan-based boiling water-resistant flame-retardant wood adhesive, comprising the following steps:

[0059] S1. mixing acidified chitosan and acryloyl chloride and reacting them to obtain an AMS material;

[0060] S2. mixing polyamine, acryloyl chloride and dichloromethane and reacting them to obtain an AHC material;

[0061] S3. CS@IRMOF-3, tripolyphosphazene chloride, and tetrahydrofuran were mixed and reacted to obtain CS@IRMOF-3@P material;

[0062] S4. A boiling water-resistant flame-retardant wood adhesive was obtained by mixing AMS, AHC, water, and CS@IRMOF-3@P.

[0063] In the present invention, acidified chitosan and acryloyl chloride are mixed and reacted to obtain the AMS material.

[0064] The preparation method of acidified chitosan in the present invention comprises the following steps:

[0065] Chitosan, maleic anhydride and acetonitrile are mixed and reacted to obtain acidified chitosan;

[0066] Through the above technical solution, the present invention introduces carboxyl groups (-COOH) to enhance water solubility: the hydrophilicity of the carboxyl groups makes the modified chitosan easier to disperse in the aqueous phase, facilitating subsequent reactions; providing cross-linking sites, the carboxyl groups can undergo condensation reactions (such as amidation or Schiff base reaction) with the amino groups (-NH2) of AHC to form a cross-linked network; retaining some amino groups (-NH2) to provide active sites for subsequent reactions with acryloyl chloride.

[0067] In the present invention, the usage ratio of chitosan, maleic anhydride and acetonitrile is 5-10 g: 1-10 g: 10-30 mL, preferably 7-10 g: 2-9 g: 15-25 mL, more preferably 9-10 g: 2-3 g: 20 mL;

[0068] The reaction temperature is 80-100° C., preferably 85-95° C., more preferably 90° C.; the reaction time is 10-15 h, preferably 11-14 h, more preferably 12-13 h.

[0069] In the present invention, the usage ratio of acidified chitosan and acryloyl chloride in step S1 is 5-20 g:1-5 g, preferably 10-15 g:2-4 g, and more preferably 12 g:2-3 g. Through the above technical solution, the present invention introduces a double bond (C=C), which can copolymerize with the double bond of AHC under hot pressing conditions to form a covalent cross-linked network. The cross-linked network improves the water resistance and shear strength of the adhesive.

[0070] The reaction temperature is -20 to 0°C, preferably -15 to -5°C, more preferably -15°C; the reaction time is 1 to 3 hours, preferably 1.5 to 2.5 hours, more preferably 1.5 to 2 hours;

[0071] In the present invention, polyamine, acryloyl chloride and dichloromethane are mixed and reacted to obtain an AHC material.

[0072] In the present invention, the polyamine is prepared by mixing triethyl citrate, 1,6-hexanediamine, and methanol and reacting them to obtain the polyamine. This technical solution provides a large number of amino groups (-NH2) for subsequent condensation with the carboxyl groups of AMS. This allows for molecular weight control (Mw = 13498 Da as measured by GPC) to influence crosslink density.

[0073] In the present invention, the usage ratio of triethyl citrate, 1,6-hexanediamine and methanol is 5-15g:15-20g:20-40mL, preferably 8-15g:16-19g:25-35mL, more preferably 10-14g:17-18g:30mL; the reaction temperature is 40-80°C, preferably 50-70°C, more preferably 60°C; the reaction time is 10-15h, preferably 11-14h, more preferably 12-13h.

[0074] In the present invention, the ratio of polyamine, acryloyl chloride, and dichloromethane in step S2 is 20-40 g: 3-5 g: 10-30 mL, preferably 25-35 g: 3.5-4.5 g: 15-25 mL, and more preferably 30-35 g: 4.5 g: 40 mL. Through the above technical solution, the present invention forms a three-dimensional cross-linked network (free radical polymerization) by copolymerizing with the double bond of AMS. The amino group of AHC condenses with the carboxyl group of AMS, and the double bond copolymerizes with the double bond of AMS to synergistically construct a tight network (similar to a zipper closure).

[0075] The reaction temperature is -20 to 0°C, preferably -15 to -5°C, more preferably -15°C; the reaction time is 1 to 3 hours, preferably 1.5 to 2.5 hours, more preferably 1.5 to 2 hours.

[0076] In the present invention, CS@IRMOF-3, tripolyphosphazene chloride and tetrahydrofuran are mixed and reacted to obtain CS@IRMOF-3@P material.

[0077] In the present invention, the preparation method of CS@IRMOF-3 comprises the following steps:

[0078] (a) mixing chitosan and ethanol and reacting them to obtain a reaction solution a;

[0079] (b) dissolving zinc nitrate hexahydrate and 2-aminoterephthalic acid in a mixed solution of ethanol and dimethylformamide to react to obtain a reaction solution b;

[0080] (c) mixing reaction solution a and reaction solution b and reacting them to obtain reaction solution c;

[0081] (d) The reaction solution c and triethylamine are mixed and reacted to obtain CS@IRMOF-3. Through the above technical solution, the present invention forms hierarchical channels between the lattice pores of IRMOF-3 and the micron-scale pores of chitosan, thereby increasing the specific surface area. 2+ The coordination bond with chitosan enhances the thermal stability of the material.

[0082] In step (a), the ratio of chitosan to ethanol is 1-5 g:10-30 mL, preferably 2-4 g:15-25 mL, more preferably 3-4 g:20 mL; the reaction temperature is 20-25° C., preferably 21-24° C., more preferably 21-23° C.; the reaction time is 0.5-1.5 h, preferably 0.5-1 h, more preferably 0.5 h;

[0083] In step (b), the reaction temperature is 20-25° C., preferably 21-24° C., more preferably 21-23° C.; the reaction time is 0.5-1.5 h, preferably 0.5-1 h, more preferably 0.5 h; the amount ratio of zinc nitrate hexahydrate, 2-aminoterephthalic acid solution, ethanol and dimethylformamide is 5-10 g:1-5 g:30-50 mL:10-30 mL, preferably 5-9 g:2-4 g:35-45 mL:15-25 mL, more preferably 5-7 g:3-4 g:40 mL:20 mL;

[0084] In step (c), the reaction temperature is 20-25° C., preferably 21-24° C., more preferably 21-23° C.; the reaction time is 0.5-1.5 h, preferably 0.5-1 h, more preferably 0.5 h;

[0085] In step (d), the amount ratio of solution c and triethylamine is 70-90 mL:5-10 mL, preferably 75-85 mL:5-8 mL, more preferably 80 mL:5-6 mL; the reaction temperature is 90-110 ° C, preferably 95-105 ° C, more preferably 100 ° C; the reaction time is 22-26 h, preferably 23-25 h, more preferably 24 h.

[0086] In the present invention, in step S3, during the preparation of CS@IRMOF-3@P, the ratio of CS@IRMOF-3, trichlorophosphazene, and tetrahydrofuran is 1-5 g:1-5 g:10-30 mL, preferably 2-4 g:2-4 g:15-25 mL, and more preferably 3 g:2 g:20-25 mL. Through this technical solution, the present invention generates PO radicals through the pyrolysis of the phosphorus element, which captures the active free radicals from the combustion chain reaction. The flexible PN bonds of PCT and the pores of the MOF work synergistically, making the aerogel more compressible. The IRMOF-3 pores absorb moisture, the phosphorus and nitrogen synergistic flame retardancy of PCT, and the biocompatibility of chitosan expand the material's potential for applications in sustainable adhesives and flexible devices.

[0087] The reaction temperature is 50-70°C, preferably 55-65°C, more preferably 60°C; the reaction time is 22-26 hours, preferably 23-25 hours, more preferably 24 hours.

[0088] The present invention obtains a boiling water resistant flame retardant wood adhesive by mixing AMS, AHC, water and CS@IRMOF-3@P materials. Through the above technical solution, the present invention utilizes the condensation reaction of the amino group of AHC and the carboxyl group of AMS during the hot pressing process (similar to the Schiff base reaction), and at the same time, the double bonds undergo free radical copolymerization to form a tightly cross-linked network similar to a "zipper". This step-by-step "zipper" reaction (Schiff base reaction + free radical copolymerization) constructs a highly cross-linked three-dimensional network structure, which significantly enhances the mechanical strength and water resistance of the adhesive. CS@IRMOF-3@P provides porous water adsorption, phosphorus element flame retardancy, and Zn 2+ Coordination enhances thermal stability.

[0089] In the present invention, in step S4, the mass ratio of AMS, water and AHC material is 1-6:25-45:1-5, preferably 2-6:26-45:2-5, and more preferably 3-5:26-44:2-4.

[0090] The reaction temperature is 50-90° C., preferably 55-85° C., more preferably 60-80° C.; the reaction time is 0.5-3 h, preferably 0.5-2 h, more preferably 0.5-1 h.

[0091] The present invention also provides a method for preparing a chitosan-based aerogel with a low compression modulus, comprising the following steps:

[0092] 1) Select the AMS material, AHC material, and CS@IRMOF-3@P material in claim 1;

[0093] 2) AMS, AHC, water, and CS@IRMOF-3@P material are mixed in a mass volume ratio of (10-16) g: (1-10) g: (100-160) mL: (1-5) g to obtain a mixture; the mass volume ratio is preferably 11-15 g: 105-150 mL: 2-9 g, and more preferably 11-13 g: 110-130 mL: 5-7 g;

[0094] 3) reacting the mixture at 60-100° C. for 0-2 h, and then freeze-drying to obtain an aerogel with a low compression modulus; the reaction temperature is preferably 70-90° C., more preferably 80° C.; the reaction time is preferably 0-1 h, more preferably 0-0.5 h.

[0095] Among them, low compression modulus is the ability of a material to resist deformation under compressive stress. The lower the modulus, the easier the material is to be compressed, and it exhibits higher flexibility and elasticity. Aerogels with low compression modulus have the following advantages: excellent compressibility and resilience, lightweight porous structure and good pressure dispersion ability. The introduction of CS@IRMOF-3@PCT is the key factor leading to the reduction of compression modulus. IRMOF-3 is a metal-organic framework with a high specific surface area and open pore structure. The modification of PCT further increases the porosity and further reduces the structural rigidity. During the freeze-drying process, the growth of ice crystals will form micron-sized pores, which are easy to collapse when compressed, thereby reducing the modulus.

[0096] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0097] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0098] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0099] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the present invention. The present description and examples are intended to be illustrative only.

[0100] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0101] Unless otherwise specified, the "room temperature" and "normal temperature" mentioned in the present invention are all calculated as 25±2°C.

[0102] Unless otherwise specified, all raw materials and instruments used in the following examples of the present invention are commercially available.

[0103] Example 1

[0104] Preparation of AMS materials:

[0105] In a clean reaction flask, add 8.9 g of chitosan and 2.45 g of maleic anhydride, then add 20 mL of acetonitrile as solvent. Heat and stir at 90°C for 12 hours, then reflux. Then, add 2.25 g of acryloyl chloride and stir at -15°C for 2 hours. After completion of the reaction, rotary evaporation was performed to obtain AMS.

[0106] Preparation of AHC materials:

[0107] First, in a clean reaction flask, mix 13.8 g of triethyl citrate and 17.4 g of 1,6-hexanediamine. Then, add 30 mL of methanol as the solvent. Heat and stir at 60°C for 12 hours and reflux. After the reaction, remove excess methanol with rotary evaporation to obtain a colorless, viscous liquid, HC. Then, add 4.5 g of acryloyl chloride and 20 mL of DCM to the HC prepared above, and stir at -15°C for 2 hours. After the reaction, rotary evaporation is performed to obtain AHC.

[0108] Preparation of CS@IRMOF-3@P material:

[0109] First, in a clean reaction flask, 1 g of chitosan was dispersed in 10 mL of ethanol (Solution A). In a clean reaction flask, 5 g of zinc nitrate hexahydrate and 1 g of 2-aminoterephthalic acid were dissolved in a mixture of 30 mL of ethanol and 10 mL of dimethylformamide (DMF) (Solution B). Solutions A and B were mixed and sonicated for 30 minutes, followed by the dropwise addition of 10 mL of triethylamine. The mixture was then reacted at 100°C for 24 hours. After the reaction, the mixture was cooled to room temperature and filtered to obtain the product. The product was washed three times with anhydrous ethanol and chloroform and dried at 70°C for 12 hours to obtain CS@IRMOF-3. 3 g of CS@IRMOF-3 was dispersed in 20 mL of tetrahydrofuran (THF) under ultrasonication. A solution of PCT (2.0 g) in THF was slowly added to the suspension. The mixture was stirred at 60°C for 24 hours. THF was then recovered by distillation under reduced pressure, and the solid product was washed three times with THF and distilled water and then dried at 70 °C for 10 h to obtain CS@IRMOF-3@P.

[0110] Preparation of AMS-AHC-CS@IRMOF-3@P wood adhesive:

[0111] 4 g of the AMS prepared above was weighed at room temperature, dispersed in 42 g of deionized water, and mixed with 1.5 g of the CS@IRMOF-3@P prepared above, placed in a reaction pot at 70°C, and stirred continuously for 0.5 h to obtain a boiling water-resistant flame-retardant chitosan-based wood adhesive (AMS-AHC-CS@IRMOF-3@P adhesive).

[0112] Example 2

[0113] Preparation of AMS materials:

[0114] In a clean reaction flask, add 8.9 g of chitosan and 2.45 g of maleic anhydride, then add 20 mL of acetonitrile as solvent. Heat and stir at 90°C for 12 hours, then reflux. Then, add 2.25 g of acryloyl chloride and stir at -15°C for 2 hours. After completion of the reaction, rotary evaporation was performed to obtain AMS.

[0115] Preparation of AHC materials:

[0116] First, in a clean reaction flask, mix 13.8 g of triethyl citrate and 17.4 g of 1,6-hexanediamine. Then, add 30 mL of methanol as the solvent. Heat and stir at 60°C for 12 hours and reflux. After the reaction, remove excess methanol with rotary evaporation to obtain a colorless, viscous liquid, HC. Then, add 4.5 g of acryloyl chloride and 20 mL of DCM to the HC prepared above, and stir at -15°C for 2 hours. After the reaction, rotary evaporation is performed to obtain AHC.

[0117] Preparation of CS@IRMOF-3@P material:

[0118] First, in a clean reaction flask, 4g of chitosan was dispersed in 20mL of ethanol (Solution A). In a clean reaction flask, 5.95g of zinc nitrate hexahydrate and 3.62g of 2-aminoterephthalic acid were dissolved in a mixture of 40mL of ethanol and 20mL of dimethylformamide (DMF) (Solution B). Solutions A and B were mixed and sonicated for 30 minutes, followed by the dropwise addition of 5.5mL of triethylamine. The mixture was then reacted at 100°C for 24 hours. After the reaction, the mixture was cooled to room temperature and filtered to obtain the product. The product was washed three times with anhydrous ethanol and chloroform and dried at 70°C for 12 hours to obtain CS@IRMOF-3. 3g of CS@IRMOF-3 was dispersed in 20mL of tetrahydrofuran (THF) under ultrasonication. A solution of PCT (2.0g) in THF was slowly added to the suspension. The mixture was stirred at 60°C for 24 hours. THF was then recovered by distillation under reduced pressure, and the solid product was washed three times with THF and distilled water and then dried at 70 °C for 10 h to obtain CS@IRMOF-3@P.

[0119] Preparation of AMS-AHC-CS@IRMOF-3@P wood adhesive:

[0120] 4 g of the AMS prepared above was weighed at room temperature and dispersed in 39 g of deionized water. 2 g of the AHC material prepared above was added again and mixed with 1.0 g of the CS@IRMOF-3@P prepared above and placed in a reaction pot at 70°C. The mixture was stirred continuously for 0.5 h to obtain a boiling water-resistant flame-retardant chitosan-based wood adhesive (AMS-AHC-CS@IRMOF-3@P adhesive).

[0121] Example 3

[0122] Preparation of AMS materials:

[0123] In a clean reaction flask, add 5g of chitosan and 1g of maleic anhydride, then add 10mL of acetonitrile as solvent. Heat and stir at 80°C for 10 hours and reflux. Then, add 5g of acryloyl chloride and stir at -20°C for 1 hour. After completion of the reaction, rotary evaporation is performed to obtain AMS.

[0124] Preparation of AHC materials:

[0125] First, in a clean reaction flask, mix 5g of triethyl citrate and 15g of 1,6-hexanediamine. Then, add 20mL of methanol as the solvent. Heat and stir at 40°C for 10 hours and reflux. After the reaction, remove excess methanol with rotary evaporation to obtain a colorless, viscous liquid, HC. Then, add 3g of acryloyl chloride and 10mL of DCM to the HC prepared above, and stir at -20°C for 1 hour. After the reaction, rotary evaporation is performed to obtain AHC.

[0126] Preparation of CS@IRMOF-3@P material:

[0127] First, in a clean reaction flask, 1 g of chitosan was dispersed in 10 mL of ethanol (Solution A). In a clean reaction flask, 5 g of zinc nitrate hexahydrate and 1 g of 2-aminoterephthalic acid were dissolved in a mixture of 30 mL of ethanol and 10 mL of dimethylformamide (DMF) (Solution B). Solutions A and B were mixed and sonicated for 30 minutes, followed by the dropwise addition of 10 mL of triethylamine. The mixture was then reacted at 100°C for 24 hours. After the reaction, the mixture was cooled to room temperature and filtered to obtain the product. The product was washed three times with anhydrous ethanol and chloroform and dried at 70°C for 12 hours to obtain CS@IRMOF-3. 3 g of CS@IRMOF-3 was dispersed in 20 mL of tetrahydrofuran (THF) under ultrasonication. A solution of PCT (2.0 g) in THF was slowly added to the suspension. The mixture was stirred at 60°C for 24 hours. THF was then recovered by distillation under reduced pressure, and the solid product was washed three times with THF and distilled water and then dried at 70 °C for 10 h to obtain CS@IRMOF-3@P.

[0128] Preparation of AMS-AHC-CS@IRMOF-3@P wood adhesive:

[0129] Weigh 1 g of the AMS prepared above at room temperature and disperse it in 25 g of deionized water. Add 1 g of the AHC material prepared above again, mix it with 0.5 g of the CS@IRMOF-3@P prepared above, place it in a reaction pot at 70°C, and stir the reaction continuously for 0.5 h to obtain a boiling water-resistant flame-retardant chitosan-based wood adhesive (AMS-AHC-CS@IRMOF-3@P adhesive).

[0130] Comparative Example 1

[0131] Preparation of AMS materials:

[0132] In a clean reaction flask, add 8.9 g of chitosan and 2.45 g of maleic anhydride, then add 20 mL of acetonitrile as solvent. Heat and stir at 90°C for 12 hours, then reflux. Then, add 2.25 g of acryloyl chloride and stir at -15°C for 2 hours. After completion of the reaction, rotary evaporation was performed to obtain AMS.

[0133] Preparation of AHC materials:

[0134] First, in a clean reaction flask, mix 13.8 g of triethyl citrate and 17.4 g of 1,6-hexanediamine. Then, add 30 mL of methanol as the solvent. Heat and stir at 60°C for 12 hours and reflux. After the reaction, remove excess methanol with rotary evaporation to obtain a colorless, viscous liquid, HC. Then, add 4.5 g of acryloyl chloride and 20 mL of DCM to the HC prepared above, and stir at -15°C for 2 hours. After the reaction, rotary evaporation is performed to obtain AHC.

[0135] Preparation of AMS-AHC wood adhesive:

[0136] 4 g of the AMS prepared above was weighed at room temperature and dispersed in 34 g of deionized water. 2 g of the AHC material prepared above was added again, and the mixture was placed in a reaction pot at 70°C. The mixture was stirred continuously for 0.5 h to obtain a boiling water-resistant flame-retardant chitosan-based wood adhesive (AMS-AHC-CS@IRMOF-3@P adhesive).

[0137] Experimental Example 1

[0138] Laminated plywood was prepared using the wood adhesives prepared in Examples 1-2 and Comparative Example 1, respectively.

[0139] (1) Drying: Poplar veneer is dried to a moisture content of less than 8%;

[0140] (2) Gluing: Apply adhesive on both sides of the dried poplar veneer, with a total coating amount of 300g / m 2 ; No need to wait for it to dry after painting;

[0141] (3) Assembly: Arrange and combine the poplar veneers coated with adhesive material in a vertical grain pattern to form a blank of a predetermined shape and size;

[0142] (4) Hot pressing: The assembled product is placed in a hot press for pressing at a temperature of 140°C, a pressure of 1.0 MPa, and a time of 6 min to obtain a laminated plywood.

[0143] Application Example 1

[0144] The adhesive used was prepared in Example 1.

[0145] Application Example 2

[0146] The same as Application Example 1, except that the adhesive used is prepared in Example 2.

[0147] Application Example 3

[0148] The same as Application Example 1, except that the adhesive used is prepared in Comparative Example 1.

[0149] Performance Testing

[0150] The evaluation of bonding strength was carried out in accordance with the provisions of the national standard GB / T17657-2013. First, the laminated plywood samples were cut into the same size (100mm×25mm) and then grooved so that the area of the bonding part was 25mm×25mm. Next, the laminated plywood samples were immersed in a water bath at 23±3℃, 63±3℃ and 93±3℃ for 3 hours. After being taken out, they were placed at room temperature for 10 minutes, and then the bonding strength test was carried out using an electronic universal mechanical testing machine. The test results are detailed in Table 1.

[0151] Table 1 Properties of laminated plywood prepared with different adhesives

[0152]

[0153]

[0154] As shown in Table 1, the dry shear strength of the adhesives prepared in the present invention is not much different. However, in hot water, the adhesive with 1 g of AMS-AHC-CS@IRMOF-3@P added has better bonding performance than the adhesive without AMS-AHC-CS@IRMOF-3@P added.

[0155] Example 4

[0156] The present invention also provides the use of the boiling water resistant flame retardant chitosan-based multifunctional composite material in preparing aerogel, comprising the following steps:

[0157] 1) Select the AMS material, AHC material, and CS@IRMOF-3@P material in the examples;

[0158] 2) A mixture of AMS, AHC, water, and CS@IRMOF-3@P was prepared in a mass-to-volume ratio of 13 g:7 g:130 mL:3 g. AMS (zipper teeth) and AHC (zipper head) formed a dense network through covalent bonds (amide bonds + polymeric double bonds). The flexibility of the P-N bonds and the porosity of the MOF made the aerogel more compressible.

[0159] 3) reacting the mixture at 80° C. for 1 hour, and then freeze-drying the mixture to obtain an aerogel with a low compression modulus.

[0160] The freezing temperature of the freeze-drying operation is -40°C, the freezing time is 12 hours, and the vacuum time is 50 hours;

[0161] The drying temperature is 60° C. and the drying time is 12 hours. Freezing forms an ice crystal template, and vacuum drying removes the ice crystals, retaining the porous structure.

[0162] Comparative Example 2

[0163] The preparation method of this comparative example is the same as that of Example 4, except that the CS@IRMOF-3@P material is not added.

[0164] Experimental Example 2

[0165] The performance of the aerogel materials prepared in Example 4 and Comparative Example 2 was tested.

[0166] Performance testing:

[0167] The resulting aerogel had dimensions of 23 mm in length, 19 mm in width / diameter, and 15 mm in height / thickness. The compression properties of the aerogel were further tested using an electronic universal testing machine. The test results are detailed in Table 2.

[0168] Table 2 Compression modulus of different aerogels

[0169] category Compression modulus / MPa Application Example 1 58.02 Application Example 2 117.82

[0170] As shown in Table 2, the compression modulus of the aerogel prepared by the present invention, including the addition of AMS-AHC-CS@IRMOF-3@P, is significantly lower. This lower compression modulus improves the aerogel's adaptability to deformation and pressure buffering, making it particularly suitable for applications requiring flexibility and lightweight properties.

[0171] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a chitosan-based boiling water-resistant flame-retardant wood adhesive, characterized in that: The following steps are involved: S1. mixing acidified chitosan and acryloyl chloride and reacting them to obtain an AMS material; S2. mixing polyamine, acryloyl chloride and dichloromethane and reacting them to obtain an AHC material; S3. CS@IRMOF-3, tripolyphosphazene chloride, and tetrahydrofuran were mixed and reacted to obtain CS@IRMOF-3@P material; S4. AMS, AHC, water, and CS@IRMOF-3@P were mixed and reacted to obtain a boiling water-resistant flame-retardant wood adhesive. The preparation method of the polyamine in S2 comprises the following steps: triethyl citrate, 1,6-hexanediamine and methanol are mixed and reacted to obtain polyamine; The preparation method of CS@IRMOF-3 in S3 comprises the following steps: (a) mixing chitosan and ethanol and reacting them to obtain a reaction solution a; (b) dissolving zinc nitrate hexahydrate and 2-aminoterephthalic acid in a mixed solution of ethanol and dimethylformamide to react to obtain a reaction solution b; (c) mixing reaction solution a and reaction solution b and reacting them to obtain reaction solution c; (d) The reaction solution c and triethylamine were mixed and reacted to obtain CS@IRMOF-3.

2. The preparation method according to claim 1, characterized in that The preparation method of the acidified chitosan in S1 is: chitosan, maleic anhydride and acetonitrile are mixed and reacted to obtain the acidified chitosan; The mass volume ratio of the chitosan, maleic anhydride and acetonitrile is (5-10) g: (1-10) g: (10-30) mL; The reaction temperature is 80-100° C., and the reaction time is 10-15 hours.

3. The preparation method according to claim 1, characterized in that The mass ratio of acidified chitosan to acryloyl chloride in S1 is (5-20): (1-5); The reaction temperature is -20 to 0°C, and the reaction time is 1 to 3 hours.

4. The preparation method according to claim 1, characterized in that In the preparation method of the S2 polyamine, the mass volume ratio of triethyl citrate, 1,6-hexanediamine and methanol is (5-15) g: (15-20) g: (20-40) mL; The reaction temperature is 40-80°C, and the reaction time is 10-15 hours.

5. The preparation method according to claim 1, characterized in that The mass volume ratio of polyamine, acryloyl chloride and dichloromethane in S2 is (20-40) g: (3-5) g: (10-30) mL; The reaction temperature is -20 to 0°C, and the reaction time is 1 to 3 hours.

6. The preparation method according to claim 1, characterized in that The preparation method of S3CS@IRMOF-3 includes the following parameters: In step (a), the mass volume ratio of chitosan and ethanol is (1-5) g: (10-30) mL; the reaction temperature is 20-25° C., and the reaction time is 0.5-1 h; In step (b), the mass volume ratio of zinc nitrate hexahydrate, 2-aminoterephthalic acid solution, ethanol and dimethylformamide is (5-10) g: (1-5) g: (30-50) mL: (10-30) mL; the reaction temperature is 20-25° C., and the reaction time is 0.5-1 h; In step (c), the reaction temperature is 20-25° C., and the reaction time is 0.5-1 h; In step (d), the mass volume ratio of solution c and triethylamine is (70-90) mL: (5-10) mL; the reaction temperature is 90-110° C., and the reaction time is 22-26 h.

7. The preparation method according to claim 1, characterized in that The mass volumes of CS@IRMOF-3, tripolyphosphazene chloride and tetrahydrofuran in S3 are (1-5) g: (1-5) g: (10-30) mL; The reaction temperature is 50-70 mL, and the reaction time is 22-26 h.

8. The preparation method according to claim 1, characterized in that The mass ratio of AMS, AHC, water and CS@IRMOF-3@P material in S4 is (1-6): (1-5): (25-45): (0.5-2); The reaction temperature is 50-90° C., and the reaction time is 0.5-3 h.

9. A method for preparing a chitosan-based aerogel with low compression modulus, characterized in that: The following steps are involved: 1) Select the AMS material, AHC material, and CS@IRMOF-3@P material in claim 1; 2) AMS, AHC, water, and CS@IRMOF-3@P material were mixed in a mass volume ratio of (10-16) g: (1-10) g: (100-160) mL: (1-5) g to obtain a mixture; 3) reacting the mixture at 60-100° C. for 0-2 hours, and then freeze-drying the mixture to obtain an aerogel with a low compression modulus.

10. The boiling water resistant flame retardant wood adhesive prepared by the preparation method according to any one of claims 1 to 8, and the aerogel with low compression modulus prepared by the preparation method according to claim 9.

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