An ethylene-maleic anhydride copolymer and a method for preparing the same

Abstract

The present application relates to the technical field of ethylene-maleic anhydride copolymer, and specifically discloses an ethylene-maleic anhydride copolymer and a preparation method thereof, wherein the ethylene-maleic anhydride copolymer is synthesized by using ethylene and maleic anhydride, then the copolymer is modified by using cyclohexylamine, n-octylamine and diaminodiphenyl ether, and mixed with branched epoxy prepolymer to form an adhesive, so that the heat resistance, thermal stability, mechanical strength, dimensional stability and long-term durability of the adhesive are improved.

Description

Technical Field

[0001] This invention relates to the field of ethylene-maleic anhydride copolymer technology, specifically to an ethylene-maleic anhydride copolymer and its preparation method. Background Technology

[0002] Ethylene-maleic anhydride copolymers are polymers composed of ethylene and maleic anhydride units arranged in a highly regular 1:1 ratio. Their main chain is rich in highly reactive anhydride groups, giving the polymer not only excellent polarity and interfacial affinity but also good chemical modification properties. Based on this characteristic, ethylene-maleic anhydride copolymers can be directly used as components in adhesives, coating resins, and polymer modifiers, and can also serve as key modifying raw materials in dispersants, water treatment agents, and paper sizing agents. However, traditional ethylene-maleic anhydride copolymers, when used as adhesive components, face bottlenecks in terms of adhesive strength, adhesion durability, and adaptability. Therefore, developing ethylene-maleic anhydride copolymers that combine high strength, excellent durability, and superior overall performance is of great significance for breaking through their application in the field of high-performance adhesive composites. Summary of the Invention

[0003] The purpose of this invention is to provide an ethylene-maleic anhydride copolymer and its preparation method, thereby solving the problems of insufficient strength and poor durability of the ethylene-maleic anhydride copolymer as a binder.

[0004] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A method for preparing an ethylene-maleic anhydride copolymer, specifically comprising: Maleic anhydride was added to the solvent and stirred until homogeneous. Initiator was added and stirred until homogeneous again. The mixture was then transferred to a high-pressure reactor. The gas inside the reactor was replaced with nitrogen and ethylene was introduced. The reaction was carried out at 60-120℃ and 300-500 rpm for 10-15 hours. After the reaction was completed, the mixture was cooled and depressurized. The product was filtered, washed with dichloromethane, and dried under vacuum at 60-70℃ for 6-8 hours to obtain the ethylene-maleic anhydride copolymer.

[0005] As a limitation of the present invention, the solvent is one or more of toluene, xylene and acetone, and the solid content of maleic anhydride in the solvent is 10%-30%; the initiator is one of benzoyl peroxide and azobisisobutyronitrile, and the amount used is 0.1%-2% of the mass of maleic anhydride; during the reaction, ethylene is introduced to maintain the pressure inside the reactor at 1-10 MPa.

[0006] As a limitation of the present invention, the molecular weight Mw of the ethylene-maleic anhydride copolymer is 10,000-400,000; and the molar ratio of ethylene to maleic anhydride in the ethylene-maleic anhydride copolymer is 1:1.

[0007] Under heating conditions, the initiator decomposes to generate free radicals that attack ethylene and maleic anhydride monomers, forming chain radicals. According to the charge-transfer complex mechanism, maleic anhydride is a strongly electron-withdrawing monomer, while ethylene is an electron-donating monomer; they form a charge-transfer complex through electron donor-acceptor interactions. The chain radicals attack this charge-transfer complex, causing ethylene and maleic anhydride monomers to alternately insert into the chain, achieving chain growth and forming a copolymer structure with alternating arrangements of ethylene and maleic anhydride.

[0008] Ethylene-maleic anhydride copolymers are formed by alternating arrangements of ethylene and maleic anhydride. The polymerization of ethylene units forms the flexible hydrocarbon chain backbone structure of the copolymer, endowing it with good flexibility, impact resistance, and low-temperature resistance. Maleic anhydride units exist in a high-density, regularly arranged manner within the polymer chain structure. Through their polarity and high reactivity, they transform the non-polar chain structure into a strongly polar structure, giving the ethylene-maleic anhydride copolymer a strong affinity and wettability for polar surfaces, thus significantly improving adhesive strength. They also serve as reaction sites to further enhance various properties of the copolymer. Furthermore, they improve the compatibility between polar and non-polar monomers, enhancing the material's processability.

[0009] A method for preparing an adhesive comprising an ethylene-maleic anhydride copolymer, using the ethylene-maleic anhydride copolymer prepared above, specifically comprising: Step 1: Mix cyclohexylamine, n-octylamine and ethylene-maleic anhydride copolymer to obtain mixed amine modified ethylene-maleic anhydride copolymer; Step 2: Mix the mixed amine-modified ethylene-maleic anhydride copolymer and diaminodiphenyl ether to obtain the mixed amine-modified ethylene-maleic anhydride derivative; Step 3: Mix hydrogenated bisphenol A, hexahydrophthalic anhydride and bisphenol A epoxy resin to obtain a branched epoxy prepolymer; Step 4: Melt-mix the mixed amine-modified ethylene-maleic anhydride derivative, the branched epoxy prepolymer, and dicyandiamide to obtain an adhesive containing the ethylene-maleic anhydride copolymer.

[0010] As a limitation of the present invention, the preparation method of the mixed amine modified ethylene-maleic anhydride derivative is as follows: Cyclohexylamine and n-octylamine were added to toluene and stirred until homogeneous to obtain a mixed amine solution. The ethylene-maleic anhydride copolymer was added to N,N-dimethylformamide and stirred until homogeneous. The mixed amine solution was then added, and the mixture was stirred at 80-90℃ and 300-400rpm for 6-8 hours under nitrogen protection. After the reaction was completed, the mixture was cooled, transferred to methanol to precipitate, centrifuged, washed with methanol, and vacuum dried at 60-70℃ for 8-10 hours to obtain the mixed amine modified ethylene-maleic anhydride copolymer. The mixed amine-modified ethylene-maleic anhydride copolymer was added to N,N-dimethylformamide and stirred until homogeneous. Diaminodiphenyl ether was then added, and the mixture was stirred at 90-100℃ and 300-400rpm for 10-12 hours under nitrogen protection. After the reaction was completed, the mixture was cooled, transferred to methanol to precipitate, centrifuged, washed with methanol, and vacuum dried at 60-70℃ for 8-10 hours to obtain the mixed amine-modified ethylene-maleic anhydride derivative.

[0011] As a limitation of the present invention, the molar ratio of cyclohexylamine, n-octylamine, diaminodiphenyl ether and ethylene-maleic anhydride copolymer is (0.2-0.3):(0.2-0.3):(0.2-0.3):1.

[0012] Cyclohexylamine and n-octylamine, as monofunctional amines, undergo amidation reactions with the anhydride groups in the ethylene-maleic anhydride copolymer structure. The amino group attacks the carbonyl carbon on the maleic anhydride ring, initiating ring-opening and forming an amide bond structure. The alicyclic structure of cyclohexylamine and the aliphatic chain structure of n-octylamine are linked to the ethylene-maleic anhydride copolymer through amide bonds. The alicyclic structure of cyclohexylamine improves the material's rigidity, modulus, and heat resistance, while the aliphatic chain structure of n-octylamine enhances the material's toughness, impact resistance, compatibility with nonpolar materials, wettability at nonpolar interfaces, and resistance to damp heat aging. This synergistic modification enhances the material's mechanical properties at the molecular level.

[0013] Subsequently, diaminodiphenyl ether undergoes an imide reaction with the remaining anhydride group. Specifically, one amino group of diaminodiphenyl ether first undergoes an amidation reaction with the anhydride group to form an amide bond linked to the benzene ring. Due to the strong electron-withdrawing conjugation effect of the benzene ring, the amide bond and carboxyl group are activated. Under heating conditions, the activated amide bond and carboxyl group react to form a five-membered imide ring rigid structure, which greatly improves the material's heat resistance, thermal stability, mechanical strength, dimensional stability, and long-term durability.

[0014] As a limitation of this invention, the method for preparing the branched epoxy prepolymer is as follows: Hydrogenated bisphenol A and hexahydrophthalic anhydride were added to toluene and stirred until homogeneous. Then, p-toluenesulfonic acid was added as a catalyst. The mixture was refluxed at 130-140℃ and 300-400rpm for 4-6 hours under nitrogen protection. After the reaction was completed, the mixture was cooled and added to n-hexane to precipitate the precipitate. The precipitate was filtered, washed with ethanol and deionized water, and dried under vacuum at 60-70℃ for 8-10 hours to obtain a terminal carboxyl dicarboxylic acid. Bisphenol A epoxy resin and terminal carboxyl dicarboxylic acid are mixed evenly, and triphenylphosphine catalyst is added. The mixture is stirred at 120-130℃ and 300-400rpm for 2-3 hours. After the reaction is completed, the mixture is cooled to obtain a branched epoxy prepolymer.

[0015] As a limitation of the present invention, the mass ratio of hydrogenated bisphenol A, hexahydrophthalic anhydride and catalyst p-toluenesulfonic acid is (24-28):(30-34):(0.1-0.3); the mass ratio of bisphenol A epoxy resin, terminal carboxyl dicarboxylic acid and catalyst triphenylphosphine is (90-100):(15-20):(0.1-0.3).

[0016] In the presence of p-toluenesulfonic acid as a catalyst, hydrogenated bisphenol A undergoes an esterification and polycondensation reaction with hexahydrophthalic anhydride. The two hydroxyl groups of hydrogenated bisphenol A react with the anhydride groups in the two hexahydrophthalic anhydride molecules, respectively, to generate a diacid with a rigid aliphatic ring of hydrogenated bisphenol A at its center and carboxyl groups at both ends. In the presence of triphenylphosphine as a catalyst, the carboxyl groups at both ends of the diacid act as nucleophiles, attacking the epoxy groups on different epoxy resin molecular chains, causing them to open their rings and undergo esterification. This forms a branched epoxy prepolymer structure with hydrogenated bisphenol A as the connecting point. The branching points of hydrogenated bisphenol A can hinder the close packing of molecular chains, increase free volume, and absorb a large amount of energy through the orientation of the molecular chains and the deformation of the branching points when the material is subjected to impact, thereby significantly improving the fracture toughness and impact resistance of the adhesive. During the adhesive curing process, the branching points of the epoxy network and the active groups of the ethylene-maleic anhydride copolymer can form a more uniform and robust interpenetrating network structure, which can greatly strengthen the phase interface, improve stress transfer efficiency, and enable the adhesive to have excellent mechanical strength, durability and peel resistance.

[0017] As a limitation of the present invention, the adhesive comprising ethylene-maleic anhydride copolymer includes, by weight, 90-100 parts of mixed amine modified ethylene-maleic anhydride derivative, 30-40 parts of branched epoxy prepolymer and 5-7 parts of dicyandiamide.

[0018] An adhesive comprising an ethylene-maleic anhydride copolymer, prepared by any of the preparation methods described above.

[0019] Compared with the prior art, the beneficial effects of the present invention are: This invention synthesizes an ethylene-maleic anhydride copolymer using ethylene and maleic anhydride. The ethylene units in the copolymer provide good flexibility, impact resistance, and low-temperature resistance, while the maleic anhydride units enhance the wettability of the copolymer to polar surfaces through their own polarity and high activity, thereby significantly improving the adhesive performance.

[0020] This invention involves reacting cyclohexylamine, n-octylamine, and diaminodiphenyl ether with anhydride groups in a copolymer structure. The alicyclic structure of cyclohexylamine enhances the material's rigidity, modulus, and heat resistance, while the alicyclic structure of n-octylamine strengthens its toughness, impact resistance, compatibility with nonpolar materials, wettability at nonpolar interfaces, and resistance to damp heat aging. The diaminodiphenyl ether forms a rigid five-membered imide ring structure with the remaining anhydride groups, significantly improving the material's heat resistance, thermal stability, mechanical strength, dimensional stability, and long-term durability.

[0021] This invention utilizes a branched epoxy prepolymer to modify an ethylene-maleic anhydride copolymer. The branching points of hydrogenated bisphenol A can hinder the close packing of molecular chains, increase free volume, and absorb a large amount of energy through the orientation of molecular chains and the deformation of branching points when the material is subjected to impact, thereby significantly improving the fracture toughness and impact resistance of the adhesive. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. The terminology used in the embodiments is for describing specific implementation schemes, not for limiting the scope of protection of the present invention. The dosages in the embodiments are laboratory-scale tests and can be scaled up proportionally. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Bisphenol A epoxy resin (brand: E-51, epoxy equivalent: 200g / eq).

[0024] Example 1: A method for preparing an adhesive comprising an ethylene-maleic anhydride copolymer, specifically as follows: The preparation method of ethylene-maleic anhydride copolymer is as follows: Maleic anhydride was added to toluene at a solid content of 10%, and stirred until homogeneous. Azobisisobutyronitrile (1% of the mass of maleic anhydride) was then added as an initiator, and the mixture was stirred until homogeneous. The mixture was then transferred to a high-pressure reactor, and the gas inside the reactor was replaced three times with nitrogen. Ethylene was then introduced to raise the pressure of the reactor to 5 MPa. The reactor was then stirred at 100°C and 300 rpm for 12 h. During the reaction, ethylene was continuously introduced to maintain the pressure of the reactor. After the reaction was completed, the reactor was cooled and depressurized. The product was filtered, washed three times with toluene, and dried under vacuum at 60°C for 8 h to obtain the ethylene-maleic anhydride copolymer.

[0025] The preparation method of the adhesive is as follows: Step 1: Add 0.2 mol cyclohexylamine and 0.2 mol n-octylamine to 500 mL toluene and stir until homogeneous to obtain a mixed amine solution. Add 1 mol ethylene-maleic anhydride copolymer to 500 mL N,N-dimethylformamide and stir until homogeneous. Add the mixed amine solution and react under nitrogen protection at 80 °C and 300 rpm for 6 h. After the reaction is complete, cool and transfer to methanol to precipitate. Centrifuge and wash three times with methanol. Dry under vacuum at 60 °C for 8 h to obtain the mixed amine modified ethylene-maleic anhydride copolymer. Step 2: Add the mixed amine-modified ethylene-maleic anhydride copolymer to 500 mL of N,N-dimethylformamide, stir until homogeneous, add 0.3 mol of diaminodiphenyl ether, and react under nitrogen protection at 90 °C and 300 rpm for 10 h. After the reaction is complete, cool, transfer to methanol to precipitate, centrifuge, wash 3 times with methanol, and vacuum dry at 60 °C for 8 h to obtain the mixed amine-modified ethylene-maleic anhydride derivative. Step 3: Add 24g of hydrogenated bisphenol A and 30g of hexahydrophthalic anhydride to 200mL of toluene, stir well, add 0.1g of p-toluenesulfonic acid catalyst, and reflux at 140℃ and 300rpm for 4h under nitrogen protection. After the reaction is completed, cool, add n-hexane to precipitate, filter, wash with ethanol and deionized water, and dry under vacuum at 60℃ for 8h to obtain terminal carboxyl dicarboxylic acid; Step 4: Mix 100g of bisphenol A epoxy resin and 15g of terminal carboxyl dicarboxylic acid evenly, add 0.15g of triphenylphosphine catalyst, stir at 120℃ and 300rpm for 2h, and cool after the reaction is complete to obtain branched epoxy prepolymer. Step 5: Add 100g of mixed amine-modified ethylene-maleic anhydride derivative, 30g of branched epoxy prepolymer, and 5g of dried dicyandiamide to a mixer, mix at 100℃ for 15min, cool and discharge to obtain an adhesive containing ethylene-maleic anhydride copolymer.

[0026] Example 2: A method for preparing an ethylene-maleic anhydride copolymer and an adhesive, specifically as follows: The preparation method of ethylene-maleic anhydride copolymer is as follows: Maleic anhydride was added to toluene at a solid content of 10%, and stirred until homogeneous. Azobisisobutyronitrile (1.2% of the mass of maleic anhydride) was then added as an initiator, and the mixture was stirred until homogeneous. The mixture was then transferred to a high-pressure reactor, and the gas inside the reactor was replaced three times with nitrogen. Ethylene was then introduced to raise the pressure of the reactor to 5 MPa. The reactor was then stirred at 100°C and 300 rpm for 12 h. During the reaction, ethylene was continuously introduced to maintain the pressure of the reactor. After the reaction was completed, the reactor was cooled and depressurized. The product was filtered, washed three times with toluene, and dried under vacuum at 60°C for 8 h to obtain the ethylene-maleic anhydride copolymer.

[0027] The preparation method of the adhesive is as follows: Step 1: Add 0.3 mol of cyclohexylamine and 0.2 mol of n-octylamine to 500 mL of toluene and stir until homogeneous to obtain a mixed amine solution. Add 1 mol of ethylene-maleic anhydride copolymer to 500 mL of N,N-dimethylformamide and stir until homogeneous. Add the mixed amine solution and react under nitrogen protection at 80 °C and 300 rpm for 6 h. After the reaction is complete, cool and transfer to methanol to precipitate. Centrifuge and wash three times with methanol. Dry under vacuum at 60 °C for 8 h to obtain the mixed amine modified ethylene-maleic anhydride copolymer. Step 2: Add the mixed amine-modified ethylene-maleic anhydride copolymer to 500 mL of N,N-dimethylformamide, stir until homogeneous, add 0.3 mol of diaminodiphenyl ether, and react under nitrogen protection at 90 °C and 300 rpm for 10 h. After the reaction is complete, cool, transfer to methanol to precipitate, centrifuge, wash 3 times with methanol, and vacuum dry at 60 °C for 8 h to obtain the mixed amine-modified ethylene-maleic anhydride derivative. Step 3: Add 26g of hydrogenated bisphenol A and 32g of hexahydrophthalic anhydride to 200mL of toluene, stir well, add 0.15g of catalyst p-toluenesulfonic acid, and reflux at 140℃ and 300rpm for 4h under nitrogen protection. After the reaction is completed, cool, add n-hexane to precipitate, filter, wash with ethanol and deionized water, and dry under vacuum at 60℃ for 8h to obtain terminal carboxyl dicarboxylic acid; Step 4: Mix 100g of bisphenol A epoxy resin and 17g of terminal carboxyl dicarboxylic acid evenly, add 0.2g of triphenylphosphine catalyst, stir at 120℃ and 300rpm for 2h, and cool after the reaction is complete to obtain branched epoxy prepolymer. Step 5: Add 100g of mixed amine-modified ethylene-maleic anhydride derivative, 35g of branched epoxy prepolymer, and 5g of dried dicyandiamide to a mixer, mix at 100℃ for 15min, cool and discharge to obtain an adhesive containing ethylene-maleic anhydride copolymer.

[0028] Example 3: A method for preparing an ethylene-maleic anhydride copolymer and an adhesive, specifically as follows: The preparation method of ethylene-maleic anhydride copolymer is as follows: Maleic anhydride was added to toluene at a solid content of 10% and stirred until homogeneous. Azobisisobutyronitrile (1.5% of the mass of maleic anhydride) was then added as an initiator and stirred until homogeneous. The mixture was then transferred to a high-pressure reactor, and the gas inside the reactor was replaced three times with nitrogen. Ethylene was then introduced to raise the pressure of the reactor to 5 MPa. The reactor was then stirred at 100°C and 300 rpm for 12 h. During the reaction, ethylene was continuously introduced to maintain the pressure of the reactor. After the reaction was completed, the reactor was cooled and depressurized. The product was filtered, washed three times with toluene, and dried under vacuum at 60°C for 8 h to obtain the ethylene-maleic anhydride copolymer.

[0029] The preparation method of the adhesive is as follows: Step 1: Add 0.3 mol of cyclohexylamine and 0.3 mol of n-octylamine to 500 mL of toluene and stir until homogeneous to obtain a mixed amine solution. Add 1 mol of ethylene-maleic anhydride copolymer to 500 mL of N,N-dimethylformamide and stir until homogeneous. Add the mixed amine solution and react under nitrogen protection at 80 °C and 300 rpm for 6 h. After the reaction is complete, cool and transfer to methanol to precipitate. Centrifuge and wash three times with methanol. Dry under vacuum at 60 °C for 8 h to obtain the mixed amine modified ethylene-maleic anhydride copolymer. Step 2: Add the mixed amine-modified ethylene-maleic anhydride copolymer to 500 mL of N,N-dimethylformamide, stir until homogeneous, add 0.2 mol of diaminodiphenyl ether, and stir at 90 °C and 300 rpm for 10 h under nitrogen protection. After the reaction is complete, cool, transfer to methanol to precipitate, centrifuge, wash 3 times with methanol, and vacuum dry at 60 °C for 8 h to obtain the mixed amine-modified ethylene-maleic anhydride derivative. Step 3: Add 28g of hydrogenated bisphenol A and 34g of hexahydrophthalic anhydride to 200mL of toluene, stir well, add 0.25g of p-toluenesulfonic acid catalyst, and reflux at 140℃ and 300rpm for 4h under nitrogen protection. After the reaction is completed, cool, add n-hexane to precipitate, filter, wash with ethanol and deionized water, and dry under vacuum at 60℃ for 8h to obtain terminal carboxyl dicarboxylic acid; Step 4: Mix 100g of bisphenol A epoxy resin and 20g of terminal carboxyl dicarboxylic acid evenly, add 0.25g of triphenylphosphine catalyst, stir at 120℃ and 300rpm for 2h, and cool after the reaction is complete to obtain branched epoxy prepolymer. Step 5: Add 100g of mixed amine-modified ethylene-maleic anhydride derivative, 40g of branched epoxy prepolymer, and 5g of dried dicyandiamide to a mixer, mix at 100℃ for 15min, cool and discharge to obtain an adhesive containing ethylene-maleic anhydride copolymer.

[0030] Based on Example 1, the following comparative experiments were conducted, specifically Comparative Example 1, Comparative Example 2, and Comparative Example 3, as described below: Comparative Example 1: This comparative example relates to a method for preparing an ethylene-maleic anhydride copolymer and an adhesive. The difference from Example 1 is that cyclohexylamine is used instead of the mixture of cyclohexylamine and n-octylamine to modify the ethylene-maleic anhydride copolymer. Specifically: The preparation method of the ethylene-maleic anhydride copolymer is the same as in Example 1, and the preparation method of the adhesive is as follows: Step 1: Add 0.4 mol of cyclohexylamine to 500 mL of toluene and stir until homogeneous to obtain a mixed amine solution. Add 1 mol of ethylene-maleic anhydride copolymer to 500 mL of N,N-dimethylformamide and stir until homogeneous. Add the mixed amine solution and react under nitrogen protection at 80 °C and 300 rpm for 6 h. After the reaction is complete, cool and transfer to methanol to precipitate. Centrifuge and wash three times with methanol. Dry under vacuum at 60 °C for 8 h to obtain cyclohexylamine-modified ethylene-maleic anhydride copolymer. Step 2: Add the cyclohexylamine-modified ethylene-maleic anhydride copolymer to 500 mL of N,N-dimethylformamide, stir until homogeneous, add 0.3 mol of diaminodiphenyl ether, and react under nitrogen protection at 90 °C and 300 rpm for 10 h. After the reaction is complete, cool, transfer to methanol to precipitate, centrifuge, wash 3 times with methanol, and vacuum dry at 60 °C for 8 h to obtain the cyclohexylamine-modified ethylene-maleic anhydride derivative. Step 3: Add 24g of hydrogenated bisphenol A and 30g of hexahydrophthalic anhydride to 200mL of toluene, stir well, add 0.1g of p-toluenesulfonic acid catalyst, and reflux at 140℃ and 300rpm for 4h under nitrogen protection. After the reaction is completed, cool, add n-hexane to precipitate, filter, wash with ethanol and deionized water, and dry under vacuum at 60℃ for 8h to obtain terminal carboxyl dicarboxylic acid; Step 4: Mix 100g of bisphenol A epoxy resin and 15g of terminal carboxyl dicarboxylic acid evenly, add 0.15g of triphenylphosphine catalyst, stir at 120℃ and 300rpm for 2h, and cool after the reaction is complete to obtain branched epoxy prepolymer. Step 5: Add 100g of cyclohexylamine-modified ethylene-maleic anhydride derivative, 30g of branched epoxy prepolymer, and 5g of dried dicyandiamide to a mixer, mix at 100℃ for 15min, cool and discharge to obtain an adhesive containing ethylene-maleic anhydride copolymer.

[0031] Comparative Example 2: This comparative example relates to a method for preparing an ethylene-maleic anhydride copolymer and an adhesive. The difference from Example 1 is that it does not use diaminodiphenyl ether modification. Specifically: The preparation method of the ethylene-maleic anhydride copolymer is the same as in Example 1, and the preparation method of the adhesive is as follows: Step 1: Add 0.2 mol cyclohexylamine and 0.2 mol n-octylamine to 500 mL toluene and stir until homogeneous to obtain a mixed amine solution. Add 1 mol ethylene-maleic anhydride copolymer to 500 mL N,N-dimethylformamide and stir until homogeneous. Add the mixed amine solution and react under nitrogen protection at 80 °C and 300 rpm for 6 h. After the reaction is complete, cool and transfer to methanol to precipitate. Centrifuge and wash three times with methanol. Dry under vacuum at 60 °C for 8 h to obtain the mixed amine modified ethylene-maleic anhydride copolymer. Step 2: Add 24g of hydrogenated bisphenol A and 30g of hexahydrophthalic anhydride to 200mL of toluene, stir well, add 0.1g of p-toluenesulfonic acid catalyst, and reflux at 140℃ and 300rpm for 4h under nitrogen protection. After the reaction is completed, cool, add n-hexane to precipitate, filter, wash with ethanol and deionized water, and dry under vacuum at 60℃ for 8h to obtain terminal carboxyl dicarboxylic acid; Step 3: Mix 100g of bisphenol A epoxy resin and 15g of terminal carboxyl dicarboxylic acid evenly, add 0.15g of triphenylphosphine catalyst, stir at 120℃ and 300rpm for 2h, and cool after the reaction is complete to obtain branched epoxy prepolymer. Step 4: Add 100g of mixed amine-modified ethylene-maleic anhydride derivative, 30g of branched epoxy prepolymer, and 5g of dried dicyandiamide to a mixer, mix at 100℃ for 15min, cool and discharge to obtain the adhesive.

[0032] Comparative Example 3: This comparative example relates to a method for preparing an ethylene-maleic anhydride copolymer and an adhesive. The difference from Example 1 is that epoxy resin is directly added to the adhesive. Specifically: The preparation method of the ethylene-maleic anhydride copolymer is the same as in Example 1, and the preparation method of the adhesive is as follows: Step 1: Add 0.2 mol cyclohexylamine and 0.2 mol n-octylamine to 500 mL toluene and stir until homogeneous to obtain a mixed amine solution. Add 1 mol ethylene-maleic anhydride copolymer to 500 mL N,N-dimethylformamide and stir until homogeneous. Add the mixed amine solution and react under nitrogen protection at 80 °C and 300 rpm for 6 h. After the reaction is complete, cool and transfer to methanol to precipitate. Centrifuge and wash three times with methanol. Dry under vacuum at 60 °C for 8 h to obtain the mixed amine modified ethylene-maleic anhydride copolymer. Step 2: Add the mixed amine-modified ethylene-maleic anhydride copolymer to 500 mL of N,N-dimethylformamide, stir until homogeneous, add 0.3 mol of diaminodiphenyl ether, and react under nitrogen protection at 90 °C and 300 rpm for 10 h. After the reaction is complete, cool, transfer to methanol to precipitate, centrifuge, wash 3 times with methanol, and vacuum dry at 60 °C for 8 h to obtain the mixed amine-modified ethylene-maleic anhydride derivative. Step 3: Add 100g of mixed amine-modified ethylene-maleic anhydride derivative, 30g of bisphenol A epoxy resin, and 5g of dicyandiamide (dried) to a mixer and mix at 100℃ for 15 minutes. Cool and discharge to obtain the adhesive.

[0033] Testing experiment: Adhesives were prepared as test samples according to the preparation methods in each embodiment and comparative example, and the following tests were performed.

[0034] Tensile shear strength: The tensile shear strength test of adhesives is conducted in accordance with the "Determination of Tensile Shear Strength of Adhesives (Rigid Material to Rigid Material)" (GB / T 7124-2008). The adhesive test sample is coated on a metal test piece to prepare a single-lapped specimen with dimensions of 100mm × 25mm, a bonding surface length of 12.5mm, and an adhesive layer thickness of 0.2mm. The test is conducted using a universal testing machine, with the shear stress change rate controlled at 9.0MPa / min until the specimen fails. The maximum failure load is recorded, and the tensile shear strength of the adhesive is calculated.

[0035] Shear impact strength: The shear impact strength test of adhesives is conducted in accordance with the "Test Method for Shear Impact Strength of Adhesives" (GB / T 6328-2021). The adhesive test sample is coated between metal test blocks to prepare an impact specimen. The upper metal test block is 25mm×25mm×10mm in size, and the lower metal test block is 45mm×25mm×20mm in size. The test blocks are fixed on the fixture of the pendulum impact testing machine. The pendulum is released to impact the specimen, and the impact energy absorbed by the sample is recorded. The shear impact strength of the adhesive is then calculated.

[0036] Aging resistance test: The aging resistance test of the adhesive is conducted in accordance with the "Guideline for Aging Conditions of Adhesives" (GB / T35489-2017). The adhesive test sample is coated on a metal test piece to prepare a single-lapped sample with a size of 100mm×25mm, a bonding surface length of 12.5mm, and an adhesive layer thickness of 0.2mm. The sample is then placed in an aging chamber and aged for 6 weeks at 90℃ and 90%RH relative humidity. At the same time, a sample that has been naturally aged (25℃ and 50%RH relative humidity) for 6 weeks is used as a control. The tensile shear strength of the sample after aging is measured, and the aging rate of the adhesive is calculated.

[0037]

[0038] Conclusion: The test data show that, compared with Example 1, in Comparative Example 1, without the use of n-octylamine to modify the ethylene-maleic anhydride copolymer, the tensile shear strength, shear impact strength, and aging rate of the adhesive all decreased slightly; in Comparative Example 2, without the use of diaminodiphenyl ether to modify the ethylene-maleic anhydride copolymer, the rigidity of the adhesive was affected, and the tensile shear strength and aging rate of the adhesive decreased partially; in Comparative Example 3, the use of epoxy resin and ethylene-maleic anhydride copolymer resulted in poor interfacial bonding between the epoxy resin and the copolymer, and the tensile shear strength, shear impact strength, and aging rate of the adhesive all decreased significantly. The ethylene-maleic anhydride copolymer and adhesive provided by this invention have good mechanical properties and aging resistance.

[0039] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for preparing an ethylene-maleic anhydride copolymer, characterized in that: Specifically: Maleic anhydride was added to the solvent and stirred until homogeneous. Initiator was added and stirred until homogeneous again. The mixture was then transferred to a high-pressure reactor. The gas inside the reactor was replaced with nitrogen and ethylene was introduced. The reaction was carried out at 60-120℃ and 300-500 rpm for 10-15 hours. After the reaction was completed, the mixture was cooled and depressurized. The product was filtered, washed with dichloromethane, and dried under vacuum at 60-70℃ for 6-8 hours to obtain the ethylene-maleic anhydride copolymer.

2. The method for preparing an ethylene-maleic anhydride copolymer according to claim 1, characterized in that: The solvent is one or more of toluene, xylene, and acetone, and the solid content of maleic anhydride in the solvent is 10%-30%; the initiator is one of benzoyl peroxide and azobisisobutyronitrile, and the amount used is 0.1%-2% of the mass of maleic anhydride; during the reaction, ethylene is introduced to maintain the pressure inside the reactor at 1-10 MPa.

3. The method for preparing an ethylene-maleic anhydride copolymer according to claim 1, characterized in that: The molecular weight (Mw) of the ethylene-maleic anhydride copolymer is 10,000-400,000; the molar ratio of ethylene to maleic anhydride in the ethylene-maleic anhydride copolymer is 1:

1.

4. A method for preparing an adhesive comprising an ethylene-maleic anhydride copolymer, characterized in that: The ethylene-maleic anhydride copolymer prepared according to claim 1 is specifically used as follows: Step 1: Mix cyclohexylamine, n-octylamine and ethylene-maleic anhydride copolymer to obtain mixed amine modified ethylene-maleic anhydride copolymer; Step 2: Mix the mixed amine-modified ethylene-maleic anhydride copolymer and diaminodiphenyl ether to obtain the mixed amine-modified ethylene-maleic anhydride derivative; Step 3: Mix carboxyl-terminated butadiene-acrylonitrile liquid rubber, bisphenol A epoxy resin and catalyst 2-methylimidazole to obtain branched epoxy prepolymer; Step 4: Melt-mix the mixed amine-modified ethylene-maleic anhydride derivative, the branched epoxy prepolymer, and dicyandiamide to obtain an adhesive containing the ethylene-maleic anhydride copolymer.

5. A method for preparing an adhesive comprising an ethylene-maleic anhydride copolymer according to claim 4, characterized in that: The preparation method of mixed amine modified ethylene-maleic anhydride derivatives is as follows: Cyclohexylamine and n-octylamine were added to toluene and stirred until homogeneous to obtain a mixed amine solution. The ethylene-maleic anhydride copolymer was added to N,N-dimethylformamide and stirred until homogeneous. The mixed amine solution was then added, and the mixture was stirred at 80-90℃ and 300-400rpm for 6-8 hours under nitrogen protection. After the reaction was completed, the mixture was cooled, transferred to methanol to precipitate, centrifuged, washed with methanol, and vacuum dried at 60-70℃ for 8-10 hours to obtain the mixed amine modified ethylene-maleic anhydride copolymer. The mixed amine-modified ethylene-maleic anhydride copolymer was added to N,N-dimethylformamide and stirred until homogeneous. Diaminodiphenyl ether was then added, and the mixture was stirred at 90-100℃ and 300-400rpm for 10-12 hours under nitrogen protection. After the reaction was completed, the mixture was cooled, transferred to methanol to precipitate, centrifuged, washed with methanol, and vacuum dried at 60-70℃ for 8-10 hours to obtain the mixed amine-modified ethylene-maleic anhydride derivative.

6. A method for preparing an adhesive comprising an ethylene-maleic anhydride copolymer according to claim 5, characterized in that: The molar ratio of cyclohexylamine, n-octylamine, diaminodiphenyl ether and ethylene-maleic anhydride copolymer is (0.2-0.3):(0.2-0.3):(0.2-0.3):

1.

7. A method for preparing an adhesive comprising an ethylene-maleic anhydride copolymer according to claim 4, characterized in that: The preparation method of branched epoxy prepolymer is as follows: Hydrogenated bisphenol A and hexahydrophthalic anhydride were added to toluene and stirred until homogeneous. Then, p-toluenesulfonic acid was added as a catalyst. The mixture was refluxed at 130-140℃ and 300-400rpm for 4-6 hours under nitrogen protection. After the reaction was completed, the mixture was cooled and added to n-hexane to precipitate the precipitate. The precipitate was filtered, washed with ethanol and deionized water, and dried under vacuum at 60-70℃ for 8-10 hours to obtain a terminal carboxyl dicarboxylic acid. Bisphenol A epoxy resin and terminal carboxyl dicarboxylic acid are mixed evenly, and triphenylphosphine catalyst is added. The mixture is stirred at 120-130℃ and 300-400rpm for 2-3 hours. After the reaction is completed, the mixture is cooled to obtain a branched epoxy prepolymer.

8. A method for preparing an adhesive comprising an ethylene-maleic anhydride copolymer according to claim 7, characterized in that: The mass ratio of hydrogenated bisphenol A, hexahydrophthalic anhydride and catalyst p-toluenesulfonic acid is (24-28):(30-34):(0.1-0.3); the mass ratio of bisphenol A epoxy resin, terminal carboxyl dicarboxylic acid and catalyst triphenylphosphine is (90-100):(15-20):(0.1-0.3).

9. A method for preparing an adhesive comprising an ethylene-maleic anhydride copolymer according to claim 4, characterized in that: By weight, the adhesive comprising ethylene-maleic anhydride copolymer includes 90-100 parts of mixed amine modified ethylene-maleic anhydride derivative, 30-40 parts of branched epoxy prepolymer and 5-7 parts of dicyandiamide.

10. An adhesive comprising an ethylene-maleic anhydride copolymer, characterized in that: It is prepared by the preparation method according to any one of claims 4-9.

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