Formaldehyde-free adhesive for wood-based panels and its preparation method

Abstract

The present invention discloses a formaldehyde-free adhesive for wood-based panels and its preparation method, belonging to the technical field of adhesives. The adhesive is composed of 1-butene-2,3,4-tricarboxylic acid, fumaric acid, acrylate monomers, emulsifiers, water, initiators, silane compounds, bisphenol A epoxy resin and modified fillers. Compared with the prior art, the adhesive of the present invention exhibits high tensile strength and elongation at break after curing, and the peel strength is superior to that of traditional formaldehyde-containing adhesives, having significant advantages in mechanical properties and peel strength, and meeting the environmental protection and performance requirements for the manufacture of wood-based panels.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesives, and particularly to a formaldehyde-free adhesive for wood-based panels and a preparation method thereof. Background Art

[0002] With the development of the modern furniture manufacturing and interior decoration industries, wood-based panels are widely used due to their high cost-effectiveness, easy processing, and environmental friendliness. In the production process of wood-based panels, adhesives are one of the indispensable key materials, which directly affect the strength, durability, and environmental performance of wood-based panels. Traditional wood-based panel adhesives mostly use formaldehyde as the main raw material, but formaldehyde release is harmful to the human body and pollutes the environment. Therefore, the development of formaldehyde-free adhesives has become an urgent need in the industry.

[0003] To solve this problem, researchers and manufacturers have begun to explore and apply various formaldehyde-free adhesives. These adhesives are usually based on bio-based raw materials, synthetic resins, or modified polymers, aiming to provide bonding performance comparable to formaldehyde-containing adhesives while reducing or eliminating formaldehyde emissions. Although certain progress has been made, these formaldehyde-free adhesives still face challenges in terms of mechanical properties, water resistance, heat resistance, and cost-effectiveness.

[0004] Chinese Patent Invention CN117025149A discloses a formaldehyde-free adhesive for non-sticking steel plates and a preparation method thereof. The formaldehyde-free adhesive in this invention is prepared from the following raw materials in parts by weight: 60 - 80 parts of bisphenol A epoxy resin, 2 - 6 parts of antioxidant, 15 - 25 parts of core-shell nanoparticles, 3 - 10 parts of diluent, 2 - 6 parts of defoamer, 6 - 8 parts of amine curing agent, and 4 - 7 parts of curing accelerator. The adhesive prepared by this invention uses bisphenol A epoxy resin as the matrix. By modifying the filler and grafting hyperbranched polymers on the surface of the rigid organometallic framework to form core-shell nanoparticles, it can not only improve the compatibility between the nanoparticles and the matrix, enhance the interfacial bonding force, but also improve the brittleness of the matrix, increase the toughness and mechanical properties of the matrix. In addition, no volatile organic compounds such as formaldehyde are released during this process, which is environmentally friendly. However, the mechanical properties and peel strength of the formaldehyde-free adhesive prepared by this invention still need to be improved. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention aims to provide a formaldehyde-free adhesive for wood-based panels that is both environmentally friendly and has excellent mechanical properties and a preparation method thereof, in order to reduce the impact on the environment and human health while ensuring the quality of wood-based panel products.

[0006] To achieve the above invention purpose, the present invention adopts the following technical solutions:

[0007] A preparation method of a formaldehyde-free adhesive for wood-based panels is as follows, in parts by weight:

[0008] Step 1: Mix 10 - 15 parts of 1 - butene - 2,3,4 - tricarboxylic acid, 5 - 10 parts of fumaric acid, 5 - 10 parts of acrylate monomer, 0.1 - 0.3 part of emulsifier, and 10 - 15 parts of water evenly. After heating to 60 - 70 °C, add 0.3 - 0.5 part of initiator and process for 0.5 - 2 hours to obtain a pretreated product.

[0009] Step 2: Add 2 - 4 parts of silane compound and 1.5 - 2 parts of epoxy resin to the pretreated product prepared in Step 1. After stirring evenly, raise the temperature to 60 - 80 °C, add 0.1 - 0.3 part of emulsifier, 0.05 - 0.2 part of sodium acetate, and 0.3 - 0.5 part of initiator, and continue to process for 1 - 2 hours to obtain a post - treated product.

[0010] Step 3: Mix the post - treated product prepared in Step 2 evenly with 1 - 3 parts of modified filler to obtain a formaldehyde - free binder for wood - based panels.

[0011] The acrylate monomer is at least one of isobutyl acrylate, methyl methacrylate, and cyclohexyl acrylate.

[0012] The silane compound is at least one of decamethyltetrasiloxane, trimethyltriphenylcyclotrisiloxane, hexadecylcyclooctasiloxane, hexamethyl - 1,5 - dihydroxytetrasiloxane, and 3 - (methacryloyloxy)propyltrimethoxysilane.

[0013] The emulsifier is at least one of triglyceride fatty acid ester, sodium dodecylbenzenesulfonate, and Tween 80.

[0014] The epoxy resin is bisphenol A type epoxy resin.

[0015] The initiator is azobisisobutyronitrile.

[0016] The preparation method of the modified filler is as follows, by weight:

[0017] S1: Mix 3 - 5 parts of p - toluenesulfonic acid and 1 - 3 parts of chopped carbon fiber, add them to 25 - 35 parts of toluene, raise the temperature to 55 - 65 °C, keep warm for 0.5 - 2 h, and filter to obtain pretreated fibers.

[0018] S2: Mix 1 - 3 parts of the pretreated fibers prepared in Step S1, 0.3 - 0.5 part of hydroxypropyl deacetylated chitosan, and 40 - 60 parts of water and heat. During stirring, gradually add 5 - 10 parts of benzylidene malonaldehyde solution, and the benzylidene malonaldehyde solution is prepared by mixing benzylidene malonaldehyde and absolute ethanol according to a mass ratio of 1 - 2:8 - 9; adjust the pH value to 4 - 6 with 1 - 3 mol / L hydrochloric acid, then continue to stir for 1 - 3 hours, filter and wash, and finally dry to obtain a reinforcing material.

[0019] S3. Mix and disperse 1 - 3 parts of reinforcing material with 80 - 120 parts of water, add 0.2 - 0.4 parts of isophthalic acid and 5 - 7 parts of 0.4 - 0.6 wt% cobalt nitrate aqueous solution, mix evenly, adjust the pH value to 7 - 8 with 1 - 3 mol / L sodium hydroxide aqueous solution, then treat at 75 - 85 °C for 1 - 3 hours, and obtain the modified filler after filtration, washing and drying.

[0020] Preferably, the preparation method of the modified filler is as follows, by weight:

[0021] S1. Mix 3 - 5 parts of p - toluenesulfonic acid with 1 - 3 parts of chopped carbon fiber and add them to 25 - 35 parts of toluene, heat to 55 - 65 °C and keep warm for 0.5 - 2 h, then filter to obtain the pretreated fiber;

[0022] S2. Mix 1 - 3 parts of the pretreated fiber prepared in step S1, 0.3 - 0.5 parts of hydroxypropyl deacetylated chitosan with 40 - 60 parts of water and heat, gradually add 5 - 10 parts of the compound solution during stirring, and the compound solution is composed of benzylidene malonaldehyde, 2 - hydroxyterephthalaldehyde and absolute ethanol mixed according to the mass ratio of 0.5 - 1:0.5 - 1:8 - 9; adjust the pH value to 4 - 6 with 1 - 3 mol / L hydrochloric acid, then continue stirring for 1 - 3 hours, filter and wash, and finally dry to obtain the reinforcing material;

[0023] S3. Mix and disperse 1 - 3 parts of reinforcing material with 80 - 120 parts of water, add 0.2 - 0.4 parts of isophthalic acid and 5 - 7 parts of 0.4 - 0.6 wt% cobalt nitrate aqueous solution, mix evenly, adjust the pH value to 7 - 8 with 1 - 3 mol / L sodium hydroxide aqueous solution, then treat at 75 - 85 °C for 1 - 3 hours, and obtain the modified filler after filtration, washing and drying.

[0024] The functions of each substance in the present invention are as follows:

[0025] 1 - butene - 2,3,4 - tricarboxylic acid, as one of the main components of the binder, provides the main structure of the resin, increases the intermolecular interaction force, and thus improves the cohesion and adhesion performance of the binder.

[0026] Fumaric acid may be used to adjust the acid value of the resin, affect its cross - linking density and curing speed, and thus affect the mechanical properties of the binder.

[0027] Acrylate monomers, as the active components of the binder, participate in the polymerization reaction, increasing the cross - linking degree and stability of the binder.

[0028] The emulsifier is used to improve the uniformity of the mixture, enable each component to be evenly dispersed, and improve the stability and adhesion performance of the binder.

[0029] Silane compounds may be used to improve the adhesion between adhesives and wood-based panel substrates, and increase the water resistance and weather resistance of adhesives.

[0030] Bisphenol A epoxy resin, as another main component of the adhesive, provides a high-strength crosslinked network, enhancing the mechanical properties and heat resistance of the adhesive.

[0031] Initiators are used to initiate polymerization reactions, causing acrylate monomers and other components to polymerize and form a three-dimensional network structure.

[0032] Modified fillers, through specific preparation methods, enhance the interaction between the filler and the matrix, improving the cohesion and adhesion performance of the adhesive.

[0033] p-Toluenesulfonic acid may be used to treat chopped carbon fibers in the preparation of modified fillers, increasing their surface activity and improving their compatibility with resins.

[0034] Hydroxypropyl deacetylated chitosan may be used to provide additional hydroxyl groups in the preparation of modified fillers, enhancing the crosslinked network of the fillers.

[0035] Benzylidene malonaldehyde is used to enhance the crosslinked network of fillers and improve the performance of adhesives in the preparation of modified fillers.

[0036] Isocaffeic acid reacts with cobalt nitrate to form cobalt isocaffeate in the preparation of modified fillers, enhancing the internal structure of the fillers and improving the overall strength and toughness of the composite material.

[0037] Cobalt nitrate reacts with isocaffeic acid to enhance the crosslinked network of modified fillers.

[0038] Sodium hydroxide is used to adjust the pH value, optimize the reaction conditions, and improve the stability and performance of the adhesive.

[0039] The combination and interaction of these substances enable the formaldehyde-free adhesive of the present invention to have good mechanical properties and peel strength, while maintaining environmental protection characteristics.

[0040] Compared with the prior art, it has the following beneficial effects:

[0041] 1) The formaldehyde-free adhesive for wood-based panels provided by the present invention does not use volatile organic compounds such as formaldehyde during the preparation process, thereby reducing potential hazards to the environment and human health and improving the environmental protection of the product.

[0042] 2) Through specific raw material ratios and preparation methods, the adhesive of the present invention exhibits excellent mechanical properties, including high tensile strength and elongation at break, as well as good peel strength, making the adhesive more reliable and durable in the application of wood-based panels.

[0043] 3) By introducing modified fillers, the present invention enhances the interaction between the fillers and the matrix, improves the cohesion and adhesion properties of the adhesive, thereby providing a stronger bonding effect during the manufacturing process of wood-based panels. Detailed implementation manners

[0044] Main sources of substances:

[0045] Short carbon fiber, tensile strength: 3530 MPA, fiber diameter: 7 μm, length: 6 mm, Jusheng Carbon Fiber (Guangdong) Co., Ltd.

[0046] Hydroxypropyl deacetylated chitosan: product number: PA11877, AR substitution degree ≥ 80.0%, Guangdong Wengjiang Chemical Reagent Co., Ltd.

[0047] Benzylidene malonaldehyde: CAS number: 82700-43-4.

[0048] Isobranched acid: CAS number: 22642-82-6.

[0049] The remaining raw materials in the examples and comparative examples of the present invention are all commercially available products.

[0050] The design idea of the present invention is to provide a formaldehyde-free adhesive for wood-based panels with environmental protection and excellent performance and its preparation method. By carefully selecting and combining various raw materials, including 1-butene-2,3,4-tricarboxylic acid, fumaric acid, acrylate monomers, silane compounds, bisphenol A epoxy resin, and specific emulsifiers and initiators, through a series of refined preparation steps, including pretreatment, post-treatment, and preparation of modified fillers, to ensure that the final product not only has no formaldehyde release, but also has excellent mechanical properties and peel strength. In addition, by introducing specific modified fillers, the interaction between the fillers and the matrix is enhanced, and the cohesion and adhesion properties of the adhesive are improved, thus realizing an adhesive that is both environmentally friendly and high-performance.

[0051] Example 1

[0052] A preparation method of a formaldehyde-free adhesive for wood-based panels is as follows, in parts by weight:

[0053] Step 1: Mix 12 kg of 1-butene-2,3,4-tricarboxylic acid, 8 kg of fumaric acid, 8 kg of methyl methacrylate, 0.2 kg of Tween 80, and 12 kg of water evenly, heat to 65 °C, and then add 0.4 kg of azobisisobutyronitrile, and process for 1 hour to obtain a pretreatment product;

[0054] Step 2: Add 3 kg of 3-(methacryloyloxy)propyltrimethoxysilane and 1.8 kg of bisphenol A epoxy resin to the pretreatment product prepared in Step 1. After stirring evenly, heat it up to 70°C, add 0.2 kg of Tween 80, 0.1 kg of sodium acetate, and 0.4 kg of azobisisobutyronitrile, and continue to process for 1.5 hours to obtain a post-treatment product;

[0055] Step 3: Mix the post-treatment product prepared in Step 2 evenly with 2 kg of modified filler to obtain a formaldehyde-free binder for wood-based panels.

[0056] The preparation method of the modified filler is as follows:

[0057] S1: Mix 4 kg of p-toluenesulfonic acid and 2 kg of chopped carbon fibers and add them to 30 kg of toluene. Heat up to 60°C and keep it warm for 1 h, then filter to obtain pretreated fibers;

[0058] S2: Mix 2 kg of the pretreated fibers prepared in Step S1, 0.4 kg of hydroxypropyl deacetylated chitosan, and 50 kg of water and heat them. Gradually add 8 kg of benzylidene malonaldehyde solution during stirring. The benzylidene malonaldehyde solution is prepared by mixing benzylidene malonaldehyde and absolute ethanol according to a mass ratio of 1.5:8.5; Adjust the pH value to 5 with 2 mol / L hydrochloric acid, then continue to stir for 2 hours, followed by filtration and washing, and finally drying to obtain a reinforcing material;

[0059] S3: Mix 2 kg of the reinforcing material with 100 kg of water and disperse it. Add 0.3 kg of isochorismic acid and 6 kg of 0.5 wt% cobalt nitrate aqueous solution, mix evenly, adjust the pH value to 7 with 2 mol / L sodium hydroxide aqueous solution, then process at 80°C for 2 hours, and after filtration, washing, and drying, obtain the modified filler.

[0060] Example 2

[0061] A preparation method of a formaldehyde-free binder for wood-based panels is basically the same as that of Example 1, and the only difference lies in the different preparation methods of the modified filler.

[0062] The preparation method of the modified filler is as follows:

[0063] S1: Mix 4 kg of p-toluenesulfonic acid and 2 kg of chopped carbon fibers and add them to 30 kg of toluene. Heat up to 60°C and keep it warm for 1 h, then filter to obtain pretreated fibers;

[0064] S2. Mix 2 kg of the pretreated fibers prepared in step S1, 0.4 kg of hydroxypropyl chitosan deacetate with 50 kg of water and heat. Gradually add 8 kg of 2-hydroxyterephthaldehyde solution during stirring. The 2-hydroxyterephthaldehyde solution is prepared by mixing 2-hydroxyterephthaldehyde and absolute ethanol at a mass ratio of 1.5:8.5. Adjust the pH value to 5 with 2 mol / L hydrochloric acid, then continue stirring for 2 hours, followed by filtration and washing, and finally drying to obtain the reinforcing material.

[0065] S3. Mix 2 kg of the reinforcing material with 100 kg of water and disperse. Add 0.3 kg of isocrotonic acid and 6 kg of 0.5 wt% cobalt nitrate aqueous solution, mix evenly. Adjust the pH value to 7 with 2 mol / L sodium hydroxide aqueous solution, then treat at 80 °C for 2 hours. After filtration, washing and drying, obtain the modified filler.

[0066] Example 3

[0067] The preparation method of a formaldehyde-free binder for wood-based panels is basically the same as that of Example 1, and the only difference lies in the preparation method of the modified filler.

[0068] The preparation method of the modified filler is as follows:

[0069] S1. Mix 4 kg of p-toluenesulfonic acid with 2 kg of chopped carbon fibers and add them to 30 kg of toluene. Heat to 60 °C and keep warm for 1 h, then filter to obtain the pretreated fibers.

[0070] S2. Mix 2 kg of the pretreated fibers prepared in step S1, 0.4 kg of hydroxypropyl chitosan deacetate with 50 kg of water and heat. Gradually add 8 kg of 4-methoxycinnamaldehyde solution during stirring. The 4-methoxycinnamaldehyde solution is prepared by mixing 4-methoxycinnamaldehyde and absolute ethanol at a mass ratio of 1.5:8.5. Adjust the pH value to 5 with 2 mol / L hydrochloric acid, then continue stirring for 2 hours, followed by filtration and washing, and finally drying to obtain the reinforcing material.

[0071] S3. Mix 2 kg of the reinforcing material with 100 kg of water and disperse. Add 0.3 kg of isocrotonic acid and 6 kg of 0.5 wt% cobalt nitrate aqueous solution, mix evenly. Adjust the pH value to 7 with 2 mol / L sodium hydroxide aqueous solution, then treat at 80 °C for 2 hours. After filtration, washing and drying, obtain the modified filler.

[0072] Example 4

[0073] The preparation method of a formaldehyde-free binder for wood-based panels is basically the same as that of Example 1, and the only difference lies in the preparation method of the modified filler.

[0074] The preparation method of the modified filler is as follows:

[0075] S1. Mix 4 kg of p-toluenesulfonic acid with 2 kg of chopped carbon fiber, add them to 30 kg of toluene, heat to 60 °C and keep warm for 1 h, then filter to obtain pretreated fiber;

[0076] S2. Mix 2 kg of the pretreated fiber prepared in step S1, 0.4 kg of hydroxypropyl deacetylated chitosan with 50 kg of water and heat. During stirring, gradually add 8 kg of 3,4-dihydroxycinnamaldehyde solution, where the 3,4-dihydroxycinnamaldehyde solution is prepared by mixing 3,4-dihydroxycinnamaldehyde and absolute ethanol according to a mass ratio of 1.5:8.5; adjust the pH value to 5 with 2 mol / L hydrochloric acid, then continue stirring for 2 h, followed by filtration and washing, and finally drying to obtain the reinforcing material;

[0077] S3. Mix 2 kg of the reinforcing material with 100 kg of water and disperse, add 0.3 kg of isochorismic acid and 6 kg of 0.5 wt% cobalt nitrate aqueous solution, mix evenly, adjust the pH value to 7 with 2 mol / L sodium hydroxide aqueous solution, then treat at 80 °C for 2 h, and after filtration, washing and drying, obtain the modified filler.

[0078] Example 5

[0079] The preparation method of the formaldehyde-free binder for wood-based panels is basically the same as that in Example 1, and the only difference lies in the different preparation method of the modified filler.

[0080] The preparation method of the modified filler is as follows:

[0081] S1. Mix 4 kg of p-toluenesulfonic acid with 2 kg of chopped carbon fiber, add them to 30 kg of toluene, heat to 60 °C and keep warm for 1 h, then filter to obtain pretreated fiber;

[0082] S2. Mix 2 kg of the pretreated fiber prepared in step S1, 0.4 kg of hydroxypropyl deacetylated chitosan with 50 kg of water and heat. During stirring, gradually add 8 kg of benzylidene malonaldehyde solution, where the benzylidene malonaldehyde solution is prepared by mixing benzylidene malonaldehyde and absolute ethanol according to a mass ratio of 1.5:8.5; adjust the pH value to 5 with 2 mol / L hydrochloric acid, then continue stirring for 2 h, followed by filtration and washing, and finally drying to obtain the reinforcing material;

[0083] S3. Mix 2 kg of the reinforcing material with 100 kg of water and disperse, add 0.3 kg of 2,5-dimethyl-2,4-hexadienedioic acid and 6 kg of 0.5 wt% cobalt nitrate aqueous solution, mix evenly, adjust the pH value to 7 with 2 mol / L sodium hydroxide aqueous solution, then treat at 80 °C for 2 h, and after filtration, washing and drying, obtain the modified filler.

[0084] Example 6

[0085] The preparation method of the formaldehyde-free binder for wood-based panels is basically the same as that of Example 1, and the only difference lies in the preparation method of the modified filler.

[0086] The preparation method of the modified filler is as follows:

[0087] S1. Mix 4 kg of p-toluenesulfonic acid with 2 kg of chopped carbon fibers, add them to 30 kg of toluene, heat to 60 °C and keep warm for 1 h, then filter to obtain pretreated fibers;

[0088] S2. Mix 2 kg of the pretreated fibers prepared in step S1, 0.4 kg of hydroxypropyl deacetylated chitosan with 50 kg of water and heat. During stirring, gradually add 8 kg of benzylidene malonaldehyde solution, which is prepared by mixing benzylidene malonaldehyde and absolute ethanol according to a mass ratio of 1.5:8.5; Adjust the pH value to 5 with 2 mol / L hydrochloric acid, then continue stirring for 2 hours, followed by filtration and washing, and finally drying to obtain the reinforcing material;

[0089] S3. Mix 2 kg of the reinforcing material with 100 kg of water and disperse it, add 0.3 kg of cis-hexenedioic acid and 6 kg of 0.5 wt% cobalt nitrate aqueous solution, mix evenly, adjust the pH value to 7 with 2 mol / L sodium hydroxide aqueous solution, then treat it at 80 °C for 2 hours, and after filtration, washing and drying, obtain the modified filler.

[0090] Example 7

[0091] The preparation method of the formaldehyde-free binder for wood-based panels is basically the same as that of Example 1, and the only difference lies in the preparation method of the modified filler.

[0092] The preparation method of the modified filler is as follows:

[0093] S1. Mix 4 kg of p-toluenesulfonic acid with 2 kg of chopped carbon fibers, add them to 30 kg of toluene, heat to 60 °C and keep warm for 1 h, then filter to obtain pretreated fibers;

[0094] S2. Mix 2 kg of the pretreated fibers prepared in step S1, 0.4 kg of hydroxypropyl deacetylated chitosan with 50 kg of water and heat. During stirring, gradually add 8 kg of the compound solution, which is prepared by mixing benzylidene malonaldehyde, 2-hydroxyterephthalaldehyde and absolute ethanol according to a mass ratio of 0.75:0.75:8.5; Adjust the pH value to 5 with 2 mol / L hydrochloric acid, then continue stirring for 2 hours, followed by filtration and washing, and finally drying to obtain the reinforcing material;

[0095] S3. Mix 2 kg of reinforcing material with 100 kg of water and disperse them. Add 0.3 kg of isophthalic acid and 6 kg of 0.5 wt% cobalt nitrate aqueous solution, mix evenly, adjust the pH value to 7 with 2 mol / L sodium hydroxide aqueous solution, then treat at 80 °C for 2 hours. After filtration, washing and drying, the modified filler is obtained.

[0096] Comparative Example 1

[0097] The preparation method of a formaldehyde-free binder for wood-based panels is basically the same as that of Example 1, and the only difference is the different preparation method of the modified filler.

[0098] The preparation method of the modified filler is as follows:

[0099] S1. Mix 4 kg of p-toluenesulfonic acid with 2 kg of chopped carbon fibers and add them to 30 kg of toluene. Heat to 60 °C and keep warm for 1 h, then filter to obtain the pretreated fibers.

[0100] S2. Mix 2 kg of the pretreated fibers prepared in step S1, 0.4 kg of hydroxypropyl deacetylated chitosan with 50 kg of water and heat. Gradually add 8 kg of 3-(4-hydroxyphenyl)acrolein solution during stirring. The 3-(4-hydroxyphenyl)acrolein solution is prepared by mixing 3-(4-hydroxyphenyl)acrolein and absolute ethanol according to a mass ratio of 1.5:8.5. Adjust the pH value to 5 with 2 mol / L hydrochloric acid, then continue stirring for 2 hours, followed by filtration and washing, and finally drying to obtain the reinforcing material.

[0101] S3. Mix 2 kg of the reinforcing material with 100 kg of water and disperse them. Add 0.3 kg of isophthalic acid and 6 kg of 0.5 wt% cobalt nitrate aqueous solution, mix evenly, adjust the pH value to 8 with 2 mol / L sodium hydroxide aqueous solution, then treat at 80 °C for 2 hours. After filtration, washing and drying, the modified filler is obtained.

[0102] Comparative Example 2

[0103] The preparation method of a formaldehyde-free binder for wood-based panels is basically the same as that of Example 1, and the only difference is the different preparation method of the modified filler.

[0104] The preparation method of the modified filler is as follows:

[0105] S1. Mix 4 kg of p-toluenesulfonic acid with 2 kg of chopped carbon fibers and add them to 30 kg of toluene. Heat to 60 °C and keep warm for 1 h, then filter to obtain the pretreated fibers.

[0106] S2. Mix 2 kg of the pretreated fibers prepared in step S1, 0.4 kg of hydroxypropyl chitosan and 50 kg of water, and heat the mixture. Gradually add 8 kg of benzylidene malonaldehyde solution during stirring. The benzylidene malonaldehyde solution is prepared by mixing benzylidene malonaldehyde and absolute ethanol at a mass ratio of 1.5:8.5. Adjust the pH value to 5 with 2 mol / L hydrochloric acid, continue stirring for 2 hours, then filter and wash, and finally dry to obtain the reinforcing material.

[0107] S3. Mix 2 kg of the reinforcing material with 100 kg of water and disperse it. Add 0.3 kg of sorbic acid and 6 kg of 0.5 wt% cobalt nitrate aqueous solution, mix evenly, adjust the pH value to 7 with 2 mol / L sodium hydroxide aqueous solution, then treat at 80 °C for 2 hours, and after filtration, washing and drying, obtain the modified filler.

[0108] Comparative Example 3

[0109] A method for preparing a formaldehyde-free binder for wood-based panels is as follows, by weight:

[0110] Step 1. Mix 12 kg of 1-butene-2,3,4-tricarboxylic acid, 8 kg of fumaric acid, 8 kg of methyl methacrylate, 0.2 kg of Tween 80 and 12 kg of water evenly, heat to 65 °C, and then add 0.4 kg of azobisisobutyronitrile, and treat for 1 hour to obtain a pretreatment product.

[0111] Step 2. Add 3 kg of 3-(methacryloyloxy)propyltrimethoxysilane and 1.8 kg of bisphenol A epoxy resin to the pretreatment product prepared in step 1, stir evenly, then raise the temperature to 70 °C, add 0.2 kg of Tween 80, 0.1 kg of sodium acetate and 0.4 kg of azobisisobutyronitrile, and continue to treat for 1.5 hours to obtain a post-treatment product.

[0112] Step 3. Mix the post-treatment product prepared in step 2 evenly with 2 kg of chopped carbon fibers to obtain a formaldehyde-free binder for wood-based panels.

[0113] Test Example 1

[0114] Mechanical property test

[0115] The mechanical properties were determined according to the standard of GB / T 2567-2021 "Test Methods for Properties of Resin Castings". First, cure the formaldehyde-free binders for wood-based panels prepared in the examples and comparative examples of the present invention. The curing conditions are curing at 170 °C for 3 h and then at 200 °C for 1 h. Record the tensile strength and elongation at break. The test results are shown in Table 1.

[0116] Table 1

[0117] Experimental Scheme Tensile Strength (MPa) Elongation at Break (%) Example 1 29.53 89.46 Example 2 28.46 87.82 Example 3 26.41 82.65 Example 4 27.87 84.70 Example 5 28.56 84.82 Example 6 27.09 83.68 Example 7 30.25 90.67 Comparative Example 1 27.40 83.06 Comparative Example 2 26.79 82.74 Comparative Example 3 24.72 76.93

[0118] Test Example 2

[0119] Peeling Strength Test

[0120] The test was carried out in accordance with GB / T 532-2008 "Determination of Adhesion Strength between Vulcanized Rubber or Thermoplastic Rubber and Fabrics". The formaldehyde-free adhesives for wood-based panels prepared in each example and comparative example were evenly coated on the surface of the sanded wood-based panels, placed at 80 °C for activation for 3 min and then bonded. The sampling specification was 100 mm × 25 mm. After pressing for 15 s, the test was carried out on a universal testing machine with a peeling angle of 180° and a tensile rate of 50 mm / min;

[0121] The test results are shown in Table 2.

[0122] Table 2

[0123] Experimental Scheme Peel Strength (KN / m) Example 1 15.7 Example 2 15.4 Example 3 14.3 Example 4 15.1 Example 5 15.3 Example 6 15.1 Example 7 16.0 Comparative Example 1 15.0 Comparative Example 2 14.9 Comparative Example 3 13.6

[0124] It can be seen from the data in Tables 1 and 2 that the mechanical properties and peeling strength of the formaldehyde-free adhesive for wood-based panels prepared in Example 1 are better than those in Examples 2 to 6 and Comparative Examples 1 to 3.

[0125] The superior properties of benzylidenemalonaldehyde in Example 1, compared with other aldehyde compounds, can be attributed to its unique molecular structure and reaction characteristics. Benzylidenemalonaldehyde contains a carbon-carbon double bond and two aldehyde groups, which not only enhance the π-π interaction and hydrogen bond formation ability between molecules, but also increase the intermolecular interaction force. In addition, the aldehyde groups of benzylidenemalonaldehyde can react with carboxyl groups and hydroxyl groups to form stable structures, thereby enhancing the crosslinking degree and stability of the material. The introduction of benzylidenemalonaldehyde may also enhance the interaction between the modified filler and the matrix, improving the cohesion and bonding performance of the adhesive. These factors work together to make benzylidenemalonaldehyde exhibit better mechanical properties and peeling strength in the formaldehyde-free adhesive.

[0126] Isocitric acid exhibits excellent mechanical properties and peeling strength in the present invention, which is mainly attributed to its unique role in the reinforcing material. Isocitric acid contains carboxyl and hydroxyl functional groups, which can react with cobalt nitrate to promote the in-situ formation of cobalt isocitrate on the reinforcing material. This in-situ formed cobalt isocitrate not only enhances the internal structure of the reinforcing material, but also improves the overall strength and toughness of the composite material. In contrast, 2,5-dimethyl-2,4-hexadienedioic acid, cis-hexenedioic acid and sorbic acid may not be able to effectively promote the reinforcement of the reinforcing material and the improvement of the composite material properties due to the insufficient number or reactivity of the functional groups. Therefore, isocitric acid performs more excellently in improving the mechanical properties and peeling strength of the formaldehyde-free adhesive for wood-based panels, which benefits from the efficient reaction of its functional groups with the reinforcing material and the significant effect on the reinforcement of the reinforcing material.

[0127] In Example 7, the method of compounding benzylidene malonaldehyde and 2-hydroxyterephthalaldehyde is adopted. Compared with the examples using only one of the aldehyde compounds alone, better effects can be achieved, mainly due to the comprehensive effect of the compounded solution. Benzylidene malonaldehyde has a carbon-carbon double bond and two aldehyde groups, which can provide strong cross-linking ability and reaction activity; while 2-hydroxyterephthalaldehyde contains a phenolic hydroxyl group and a terephthalaldehyde group, which can provide additional hydrogen bond formation sites and cross-linking points. The compounded use of these two compounds not only enhances the intermolecular interactions, including the formation of π-π interactions, hydrogen bonds and covalent bonds, but also increases the number and types of functional groups available for reaction in the system, thereby improving the cross-linking density and stability of the modified filler. This composite cross-linking structure helps to improve the cohesion and adhesion performance of the adhesive, and further improves the mechanical properties and peel strength of the formaldehyde-free adhesive for wood-based panels. Therefore, in Example 7, by compounding benzylidene malonaldehyde and 2-hydroxyterephthalaldehyde, the advantages of the two compounds are complementary to each other, thus obtaining better comprehensive performance.

Claims

1. A preparation method of a formaldehyde-free adhesive for wood-based panels, characterized in that, The method is as follows, by weight parts: Step 1: Mix 10 - 15 parts of 1-butene-2,3,4-tricarboxylic acid, 5 - 10 parts of fumaric acid, 5 - 10 parts of acrylate monomer, 0.1 - 0.3 part of emulsifier and 10 - 15 parts of water evenly. After heating to 60 - 70 °C, add 0.3 - 0.5 part of initiator and process for 0.5 - 2 hours to obtain a pretreated product. Step 2: Add 2 - 4 parts of silane compound and 1.5 - 2 parts of epoxy resin to the pretreated product prepared in Step 1. After stirring evenly, raise the temperature to 60 - 80 °C, add 0.1 - 0.3 part of emulsifier, 0.05 - 0.2 part of sodium acetate and 0.3 - 0.5 part of initiator, and continue to process for 1 - 2 hours to obtain a post-treated product. Step 3: Mix the post-treated product prepared in Step 2 evenly with 1 - 3 parts of modified filler to obtain a formaldehyde-free binder for wood-based panels. The preparation method of the said modified filler is as follows, by weight parts: S1: Mix 3 - 5 parts of p-toluenesulfonic acid and 1 - 3 parts of chopped carbon fiber, add them to 25 - 35 parts of toluene, raise the temperature to 55 - 65 °C and keep it warm for 0.5 - 2 h, then filter to obtain pretreated fibers. S2: Mix 1 - 3 parts of the pretreated fibers prepared in Step S1, 0.3 - 0.5 part of hydroxypropyl deacetylated chitosan and 40 - 60 parts of water and heat. During stirring, gradually add 5 - 10 parts of a compound solution, which is composed of benzylidene malonaldehyde, 2-hydroxyterephthalaldehyde and absolute ethanol in a mass ratio of 0.5 - 1:0.5 - 1:8 - 9. Adjust the pH value to 4 - 6 with 1 - 3 mol / L hydrochloric acid, then continue to stir for 1 - 3 hours, filter and wash, and finally dry to obtain a reinforcing material. S3: Mix 1 - 3 parts of the reinforcing material with 80 - 120 parts of water and disperse, add 0.2 - 0.4 part of isophthalic acid and 5 - 7 parts of 0.4 - 0.6 wt% cobalt nitrate aqueous solution, mix evenly, adjust the pH value to 7 - 8 with 1 - 3 mol / L sodium hydroxide aqueous solution, then process at 75 - 85 °C for 1 - 3 hours, and after filtration, washing and drying, obtain the modified filler.

2. The preparation method of the formaldehyde-free binder for wood-based panels according to claim 1, characterized in that, The acrylate monomer is at least one of isobutyl acrylate, methyl methacrylate, cyclohexyl acrylate.

3. The preparation method of the formaldehyde-free binder for wood-based panels according to claim 1, characterized in that, The silane compound is at least one of decamethyltetrasiloxane, trimethyltriphenylcyclotrisiloxane, hexadecylcyclooctasiloxane, hexamethyl-1,5-dihydroxytetrasiloxane, 3-(methacryloyloxy)propyltrimethoxysilane.

4. The preparation method of the formaldehyde-free binder for wood-based panels according to claim 1, characterized in that, The emulsifier is at least one of triglyceride fatty acid ester, sodium dodecylbenzenesulfonate, Tween 80.

5. The preparation method of the formaldehyde-free binder for wood-based panels according to claim 1, characterized in that, The epoxy resin is bisphenol A type epoxy resin.

6. The preparation method of the formaldehyde-free binder for wood-based panels according to claim 1, characterized in that, The initiator is azobisisobutyronitrile.

7. A formaldehyde-free adhesive for wood-based panels, characterized in that, Prepared by the preparation method according to any one of claims 1 - 6.