Hot melt adhesive with high adhesive power

Abstract

The invention relates to the technical field of hot melt adhesives, and particularly discloses a hot melt adhesive with high adhesive power, which is prepared from the following raw materials in parts by mass: 75 to 95 parts of modified polyurethane, 15 to 28 parts of polyamide resin, 10 to 20 parts of tackifying resin, 3 to 5 parts of antioxidant and 1 to 2 parts of plasticizer. Wherein the modified polyurethane comprises a prepolymer obtained through a reaction of dihydric alcohol and toluene diisocynate, a chain extender, modified cellulose and a modified filler, and the modified polyurethane is used as a main film forming substance of the hot melt adhesive and can effectively inhibit high-temperature deformation of a matrix and delay thermal decomposition; flexible chain segments in the modified polyurethane and rigid chain segments in the polyamide resin form an interpenetrating structure through hydrogen bonds, so that the mechanical strength of the hot melt adhesive is enhanced, the heat resistance and adhesive power of a matrix are improved, and the hot melt adhesive is solvent-free, green, environment-friendly and excellent in comprehensive performance.

Description

Technical Field

[0001] The present invention relates to the technical field of hot melt adhesives, and specifically to a hot melt adhesive with high adhesion force. Background Art

[0002] As an environmentally friendly adhesive, hot melt adhesive has been widely used in the fields of packaging, automotive, electronics, etc. due to its solvent-free, rapid curing and reprocessable characteristics. However, with the increasing requirements for the performance of bonding materials in industrial scenarios, the technical bottlenecks of traditional hot melt adhesives have become increasingly prominent. The heat resistance of traditional hot melt adhesives is limited by the softening point of the base resin, and the temperature resistance performance is generally low. Although the bonding performance is excellent at room temperature, problems such as embrittlement, decrease in bonding strength, and interfacial peeling will occur in high-temperature environments, and long-term heat resistance requirements cannot be met.

[0003] Chinese Patent Application CN110951419A discloses a hot melt adhesive, which comprises the following components: ethylene-vinyl acetate copolymer, modified starch, tackifying resin, antioxidant, viscosity regulator, filler. By reasonably selecting the types and ratios of ethylene-vinyl acetate copolymer, tackifying resin and modified starch, the prepared hot melt adhesive has excellent bonding strength, but the heat resistance of this hot melt adhesive is poor, it is easy to peel off under high-temperature conditions, and the added filler has poor dispersibility, affecting the adhesion of the hot melt adhesive. Chinese Patent Application CN108587554A discloses a PA hot melt adhesive and its preparation method. The PA hot melt adhesive comprises PA resin, microcrystalline wax, antioxidant. The PA resin is formed by polycondensation of dibasic acid and diamine. This PA hot melt adhesive can significantly regulate the viscosity during the sizing process, but the high-temperature resistance is insufficient. Under high-temperature conditions, the microcrystalline wax in it is easy to soften and migrate, resulting in debonding and poor thermal stability.

[0004] Therefore, there is an urgent need to develop a high-adhesion hot melt adhesive with excellent bonding performance that can withstand high temperatures. Summary of the Invention

[0005] (I) Technical Problems to be Solved In view of the deficiencies of the prior art, the present invention provides a hot melt adhesive with high adhesion force, which solves the problems of general adhesion performance and heat resistance performance of hot melt adhesives.

[0006] (II) Technical Solutions In order to achieve the above object, the present invention discloses a hot melt adhesive with high adhesion force, comprising the following raw materials in parts by mass: 75-95 parts of modified polyurethane, 15-28 parts of polyamide resin, 10-20 parts of tackifying resin, 3-5 parts of antioxidant, 1-2 parts of plasticizer; The preparation method of the modified polyurethane comprises the following steps: In a nitrogen atmosphere, a diol and toluene diisocyanate are added to a reactor, a catalyst is added dropwise, and the mixture is stirred and heated to react to obtain a prepolymer. Isocyanate-modified cellulose, polyetheramine, 4,4'-diaminodiphenyl disulfide, and N,N-dimethylacetamide are mixed, and after mixing evenly, they are added to the prepolymer. Then, amino-modified calcium carbonate is added, and the mixture is stirred and reacted. After the reaction is completed, the solvent is removed by heating to obtain modified polyurethane.

[0007] Preferably, the tackifying resin includes any one or more of polymerized rosin resin, EVA resin, and terpene resin.

[0008] Preferably, the antioxidant includes any one or more of BHT, antioxidant 1010, and antioxidant 168.

[0009] Preferably, the plasticizer includes any one or more of dioctyl phthalate, dibutyl phthalate, epoxidized soybean oil, and microcrystalline wax.

[0010] Preferably, the specific preparation method of the modified polyurethane includes the following steps: In a nitrogen atmosphere, a diol and toluene diisocyanate are added to a reactor, a catalyst is added dropwise, and the mass ratio of the diol, toluene diisocyanate, and catalyst is 140-160:100:0.5-1. The mixture is stirred and heated, and the reaction occurs at 55-65 °C. After reacting for 1 h, the amount of -NCO is detected by the di-n-butylamine back-titration method during the reaction to obtain a prepolymer. The modified cellulose and chain extender are dissolved in N,N-dimethylacetamide, where the modified cellulose is isocyanate-modified cellulose, and the chain extender is composed of polyetheramine and 4,4'-diaminodiphenyl disulfide. After mixing evenly, a mixture is obtained and added to the prepolymer. Then, amino-modified calcium carbonate is added, and the mass ratio of isocyanate-modified cellulose, polyetheramine, 4,4'-diaminodiphenyl disulfide, N,N-dimethylacetamide, prepolymer, and amino-modified calcium carbonate is 4-9:120-155:3-5:300-350:100:2-6. The mixture is stirred and reacted at 45-55 °C for 1 h. After the reaction is completed, the product is added to a polytetrafluoroethylene mold and heated at 120 °C for 24 h to obtain modified polyurethane.

[0011] Preferably, the diol is heat-resistant diol XC-488, and the polyetheramine is polyetheramine D2000.

[0012] Preferably, the catalyst includes one or several of dibutyltin dilaurate, stannous octoate, and dibutyltin diacetate.

[0013] Preferably, the preparation method of the isocyanate-modified cellulose includes the following steps: The nanocellulose was ultrasonically dispersed in ethyl acetate. After uniform dispersion, triisocyanate and dibutyltin dilaurate were added, and the mixture was stirred and reacted. After the reaction was completed, filtration was carried out, and it was washed with petroleum ether and dried in vacuum at 60 °C for 24 h to obtain isocyanate-modified cellulose.

[0014] Furthermore, the preparation method of the nanocellulose includes the following steps: Prepare a 60% sulfuric acid solution, mix microcrystalline cellulose and the sulfuric acid solution at a mass ratio of 4:1, stir, heat in a water bath at 45 °C for 1 h. After the reaction is completed, centrifuge, wash with deionized water until the pH of the supernatant is 7, dialyze, and freeze-dry to obtain nanocellulose.

[0015] Preferably, in the preparation process of the isocyanate-modified cellulose, the mass ratio of nanocellulose, ethyl acetate, triisocyanate and dibutyltin dilaurate is 100:1400 - 1600:75 - 90:1 - 1.5, the reaction temperature is 45 - 55 °C, and the reaction time is 1 - 2 h.

[0016] Furthermore, the triisocyanate is selected from (2,4,6-trioxotriazine-1,3,5(2H,4H,6H)-triyl)tris(hexamethylene) isocyanate.

[0017] Preferably, the preparation method of the amino-modified calcium carbonate includes the following steps: The nanometer calcium carbonate was ultrasonically dispersed in an ethanol solution. After uniform dispersion, γ-aminopropyltriethoxysilane was added, and the mass ratio of nanometer calcium carbonate, ethanol solution, and γ-aminopropyltriethoxysilane was 100:2400 - 2800:25 - 35. The mixture was stirred and reacted at 25 - 35 °C for 5 - 8 h. After the reaction was completed, filtration was carried out, and it was washed with deionized water and absolute ethanol and dried in vacuum at 60 °C for 12 h to obtain amino-modified calcium carbonate.

[0018] Furthermore, the ethanol solution is a 95wt% ethanol aqueous solution.

[0019] (III) Beneficial technical effects In the present invention, γ-aminopropyltriethoxysilane is used to modify nano calcium carbonate, introducing amino groups onto the nano calcium carbonate to obtain amino-modified calcium carbonate. (2,4,6-Trioxotriazine-1,3,5(2H,4H,6H)-triyl) tris(hexamethylene) triisocyanate is used to modify nano cellulose, introducing isocyanate groups onto the surface of the nano cellulose to obtain isocyanate-modified cellulose. A temperature-resistant diol XC-488 and toluene diisocyanate polymerize under the action of a catalyst to obtain a prepolymer. The isocyanate-modified cellulose contains a large number of isocyanate groups. The isocyanate-modified cellulose, a chain extender, and the filler amino-modified calcium carbonate are added to obtain a modified polyurethane. The modified polyurethane, polyamide resin, tackifying resin, antioxidant, and plasticizer are used as raw materials to obtain a hot melt adhesive with high adhesion.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The nano calcium carbonate in the present invention is inexpensive and has excellent heat resistance. It can improve the hardness and dimensional stability of the matrix, accelerate heat diffusion, delay the thermal decomposition of the hot melt adhesive, delay the failure of the adhesive layer of the hot melt adhesive caused by local overheating, and reduce the raw material cost while improving the performance. Modifying the nano calcium carbonate effectively improves the dispersion performance of the nano calcium carbonate, avoids the agglomeration of the nano calcium carbonate, and reduces the stress concentration of the matrix. The amino groups on the surface of the amino-modified calcium carbonate can react with the isocyanate groups in the prepolymer to form chemical bonding, hinder crack propagation, and reduce interface defects. As a rigid nano filler, nano cellulose can effectively improve the tensile modulus and high-temperature dimensional stability of the matrix. After being modified with isocyanate, it can form a covalent bond with the prepolymer to form a composite structure of a rigid skeleton-flexible matrix, providing rigid support, inhibiting high-temperature deformation, and effectively delaying thermal decomposition at the same time.

[0021] (2) The modified polyurethane in the present invention, as the main film-forming substance of the hot melt adhesive, can effectively provide initial adhesion and cohesive strength. The microphase separation structure of the soft segment and the hard segment in it can well balance elasticity and rigidity. The large number of active groups contained in it can form hydrogen bonds and van der Waals forces with the polar groups (such as metal oxides and plastic hydroxyl groups) on the surface of the substrate, enhancing the interfacial bonding. During the preparation process of the modified polyurethane, the isocyanate-terminated prepolymer reacts with the chain extender to form a three-dimensional crosslinked structure, improving heat resistance. Polyetheramine D2000 can provide a long-chain flexible segment, lower the glass transition temperature, enhance low-temperature toughness, and effectively absorb peeling stress. Adding 4,4'-diaminodiphenyl disulfide to introduce thioether bonds can improve heat and oxidation resistance and inhibit the high-temperature fracture of molecular chains. The isocyanate-modified cellulose and amino-modified calcium carbonate are introduced during the reaction process and can participate in the reaction. Through synergistic effects, the comprehensive performance of the hot melt adhesive is further improved.

[0022] (3) In the present invention, the polyamide resin has excellent high-temperature resistance, which can effectively improve the heat distortion temperature and long-term thermal stability of the hot melt adhesive. Hydrogen bonds are generated between the polyamide resin and the modified polyurethane. The flexible chain segments in the modified polyurethane and the rigid chain segments in the polyamide resin form an interpenetrating structure through hydrogen bonds, which can effectively inhibit the molecular chain slippage at high temperatures, enhance the mechanical strength of the hot melt adhesive, and improve the heat resistance and adhesion of the matrix. At the same time, the crystallinity of the polyamide resin can also hinder the penetration of solvent molecules and improve the oil resistance of the hot melt adhesive. This hot melt adhesive is solvent-free, green and environmentally friendly, and has excellent comprehensive performance. Detailed implementation mode

[0023] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below. Preferred embodiments of the present invention are given below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure content of the present invention more thorough and comprehensive.

[0024] Example 1 A hot melt adhesive with high adhesion includes the following raw materials in parts by mass: 75 parts of modified polyurethane, 15 parts of polyamide resin, 10 parts of terpene resin, 3 parts of antioxidant 1010, and 1 part of plasticizer epoxidized soybean oil; The preparation method of the modified polyurethane includes the following steps: In a nitrogen atmosphere, the heat-resistant diol XC-488 and toluene diisocyanate are added to a reactor, and a catalyst is added dropwise. The mass ratio of the diol, toluene diisocyanate, and catalyst dibutyltin dilaurate is 140:100:0.5. Stir and mix, heat up, and react at 55°C. After reacting for 1 h, the amount of -NCO is detected by the back titration method of di-n-butylamine during the reaction process to obtain a prepolymer. Dissolve isocyanate-modified cellulose, polyetheramine D2000, and 4,4'-diaminodiphenyl disulfide in N,N-dimethylacetamide, mix evenly to obtain a mixture, add it to the prepolymer, and then add amino-modified calcium carbonate. The mass ratio of isocyanate-modified cellulose, polyetheramine D2000, 4,4'-diaminodiphenyl disulfide, N,N-dimethylacetamide, prepolymer, and amino-modified calcium carbonate is 4:120:3:300:100:2. Stir and mix, react at 45°C for 1 h. After the reaction is completed, add the product to a polytetrafluoroethylene mold, heat, and heat at 120°C for 24 h to obtain the modified polyurethane.

[0025] The preparation method of the isocyanate-modified cellulose includes the following steps: The nanocellulose was ultrasonically dispersed in ethyl acetate. After uniform dispersion, (2,4,6-trioxotriazine-1,3,5(2H,4H,6H)-triyl)tris(hexamethylene)triisocyanate and dibutyltin dilaurate were added. The mass ratio of nanocellulose, ethyl acetate, (2,4,6-trioxotriazine-1,3,5(2H,4H,6H)-triyl)tris(hexamethylene)triisocyanate and dibutyltin dilaurate was 100:1400:75:1. They were stirred and mixed, and reacted at 45 °C for 2 h. After the reaction, filtration was carried out, washed with petroleum ether, and vacuum dried at 60 °C for 24 h to obtain isocyanate-modified cellulose.

[0026] The preparation method of amino-modified calcium carbonate comprises the following steps: The nanocalcium carbonate was ultrasonically dispersed in a 95 wt% ethanol aqueous solution. After uniform dispersion, γ-aminopropyltriethoxysilane was added. The mass ratio of nanocalcium carbonate, ethanol solution, and γ-aminopropyltriethoxysilane was 100:2400:25. They were stirred and mixed, and reacted at 25 °C for 8 h. After the reaction, filtration was carried out, washed with deionized water and absolute ethanol, and vacuum dried at 60 °C for 12 h to obtain amino-modified calcium carbonate.

[0027] Example 2 A hot melt adhesive with high adhesion force comprises the following raw materials in parts by mass: 82 parts of modified polyurethane, 20 parts of polyamide resin, 14 parts of terpene resin, 3.5 parts of antioxidant 1010, and 1.5 parts of plasticizer epoxidized soybean oil; The preparation method of the modified polyurethane comprises the following steps: In a nitrogen atmosphere, the heat-resistant diol XC-488 and toluene diisocyanate were added to a reactor, and a catalyst was added dropwise. The mass ratio of diol, toluene diisocyanate, and catalyst dibutyltin dilaurate was 148:100:0.6. They were stirred and mixed, heated up, and reacted at 60 °C. After reacting for 1 h, the amount of -NCO was detected by the back titration method with di-n-butylamine during the reaction to obtain a prepolymer. The isocyanate-modified cellulose, polyetheramine D2000, and 4,4'-diaminodiphenyl disulfide were dissolved in N,N-dimethylacetamide. After mixing evenly, a mixture was obtained and added to the prepolymer. Then, amino-modified calcium carbonate was added. The mass ratio of isocyanate-modified cellulose, polyetheramine D2000, 4,4'-diaminodiphenyl disulfide, N,N-dimethylacetamide, prepolymer, and amino-modified calcium carbonate was 6:135:3.8:340:100:4. They were stirred and mixed, and reacted at 50 °C for 1 h. After the reaction, the product was added to a polytetrafluoroethylene mold, heated, and heated at 120 °C for 24 h to obtain modified polyurethane.

[0028] The preparation method of the isocyanate-modified cellulose comprises the following steps: The nanocellulose was ultrasonically dispersed in ethyl acetate. After uniform dispersion, (2,4,6-trioxotriazine-1,3,5(2H,4H,6H)-triyl)tris(hexamethylene)triisocyanate and dibutyltin dilaurate were added. The mass ratio of nanocellulose, ethyl acetate, (2,4,6-trioxotriazine-1,3,5(2H,4H,6H)-triyl)tris(hexamethylene)triisocyanate and dibutyltin dilaurate was 100:1500:82:1.2. They were stirred and mixed, and reacted at 50 °C for 1.5 h. After the reaction ended, suction filtration was carried out, washed with petroleum ether, and vacuum dried at 60 °C for 24 h to obtain isocyanate-modified cellulose.

[0029] The preparation method of amino-modified calcium carbonate comprises the following steps: The nanometer calcium carbonate was ultrasonically dispersed in an ethanol aqueous solution of 95 wt%. After uniform dispersion, γ-aminopropyltriethoxysilane was added. The mass ratio of nanometer calcium carbonate, ethanol solution, and γ-aminopropyltriethoxysilane was 100:2600:30. They were stirred and mixed, and reacted at 30 °C for 6 h. After the reaction ended, suction filtration was carried out, washed with deionized water and absolute ethanol, and vacuum dried at 60 °C for 12 h to obtain amino-modified calcium carbonate.

[0030] Example 3 A hot melt adhesive with high adhesion force comprises the following raw materials in parts by mass: 82 parts of modified polyurethane, 20 parts of polyamide resin, 14 parts of terpene resin, 3.5 parts of antioxidant 1010, and 1.5 parts of plasticizer epoxidized soybean oil; The preparation method of the modified polyurethane comprises the following steps: In a nitrogen atmosphere, a heat-resistant diol XC-488 and toluene diisocyanate were added to a reactor, and a catalyst was added dropwise. The mass ratio of diol, toluene diisocyanate, and catalyst dibutyltin dilaurate was 155:100:0.8. They were stirred and mixed, heated up, and reacted at 60 °C. After reacting for 1 h, the amount of -NCO was detected by the back titration method with di-n-butylamine during the reaction process to obtain a prepolymer. The isocyanate-modified cellulose, polyetheramine D2000, and 4,4'-diaminodiphenyl disulfide were dissolved in N,N-dimethylacetamide. After mixing evenly, a mixture was obtained and added to the prepolymer. Then amino-modified calcium carbonate was added. The mass ratio of isocyanate-modified cellulose, polyetheramine D2000, 4,4'-diaminodiphenyl disulfide, N,N-dimethylacetamide, prepolymer, and amino-modified calcium carbonate was 8:150:4.5:340:100:5. They were stirred and mixed, and reacted at 50 °C for 1 h. After the reaction ended, the product was added to a polytetrafluoroethylene mold, heated, and heated at 120 °C for 24 h to obtain modified polyurethane.

[0031] The preparation methods of the isocyanate-modified cellulose and nano calcium carbonate are the same as those of the isocyanate-modified cellulose and nano calcium carbonate in Example 2.

[0032] Example 4 A hot melt adhesive with high adhesion force, comprising the following raw materials in parts by mass: 90 parts of modified polyurethane, 25 parts of polyamide resin, 18 parts of terpene resin, 4 parts of antioxidant 1010, and 1.5 parts of plasticizer epoxidized soybean oil; The preparation method of the modified polyurethane is the same as that of the modified polyurethane in Example 3.

[0033] The preparation methods of the isocyanate-modified cellulose and nano calcium carbonate are the same as those of the isocyanate-modified cellulose and nano calcium carbonate in Example 2.

[0034] Example 5 A hot melt adhesive with high adhesion force, comprising the following raw materials in parts by mass: 95 parts of modified polyurethane, 28 parts of polyamide resin, 20 parts of terpene resin, 5 parts of antioxidant 1010, and 2 parts of plasticizer epoxidized soybean oil; The preparation method of the modified polyurethane comprises the following steps: In a nitrogen atmosphere, the temperature-resistant diol XC-488 and toluene diisocyanate are added to a reactor, and a catalyst is added dropwise. The mass ratio of the diol, toluene diisocyanate, and catalyst dibutyltin dilaurate is 160:100:1. Stir and mix, heat up, and react at 65 °C. After reacting for 1 h, the amount of -NCO is detected by the back titration method using di-n-butylamine during the reaction process to obtain a prepolymer. The isocyanate-modified cellulose, polyetheramine D2000, and 4,4'-diaminodiphenyl disulfide are dissolved in N,N-dimethylacetamide, and after mixing evenly, a mixture is obtained and added to the prepolymer. Then, amino-modified calcium carbonate is added. The mass ratio of the isocyanate-modified cellulose, polyetheramine D2000, 4,4'-diaminodiphenyl disulfide, N,N-dimethylacetamide, prepolymer, and amino-modified calcium carbonate is 9:155:5:350:100:6. Stir and mix, and react at 55 °C for 1 h. After the reaction is completed, the product is added to a polytetrafluoroethylene mold and heated at 120 °C for 24 h to obtain the modified polyurethane.

[0035] The preparation method of the isocyanate-modified cellulose comprises the following steps: The nanocellulose was ultrasonically dispersed in ethyl acetate. After uniform dispersion, (2,4,6-trioxotriazine-1,3,5(2H,4H,6H)-triyl)tris(hexamethylene)triisocyanate and dibutyltin dilaurate were added. The mass ratio of nanocellulose, ethyl acetate, (2,4,6-trioxotriazine-1,3,5(2H,4H,6H)-triyl)tris(hexamethylene)triisocyanate and dibutyltin dilaurate was 100:1600:90:1.5. The mixture was stirred and reacted at 55 °C for 1 h. After the reaction, filtration was carried out, and it was washed with petroleum ether and dried in vacuo at 60 °C for 24 h to obtain isocyanate-modified cellulose.

[0036] The preparation method of amino-modified calcium carbonate comprises the following steps: The nanocalcium carbonate was ultrasonically dispersed in an ethanol aqueous solution of 95 wt%. After uniform dispersion, γ-aminopropyltriethoxysilane was added. The mass ratio of nanocalcium carbonate, ethanol solution, and γ-aminopropyltriethoxysilane was 100:2800:35. The mixture was stirred and reacted at 35 °C for 5 h. After the reaction, filtration was carried out, and it was washed with deionized water and absolute ethanol and dried in vacuo at 60 °C for 12 h to obtain amino-modified calcium carbonate.

[0037] Comparative Example 1 A hot-melt adhesive comprises the following raw materials in parts by mass: 90 parts of modified polyurethane, 25 parts of polyamide resin, 18 parts of terpene resin, 4 parts of antioxidant 1010, and 1.5 parts of plasticizer epoxidized soybean oil; Among them, the preparation method of the modified polyurethane comprises the following steps: In a nitrogen atmosphere, the heat-resistant diol XC-488 and toluene diisocyanate were added to a reactor, and a catalyst was added dropwise. The mass ratio of diol, toluene diisocyanate, and catalyst dibutyltin dilaurate was 155:100:0.8. The mixture was stirred and heated, and the reaction occurred at 60 °C. After 1 h of reaction, the amount of -NCO was detected by the back-titration method using di-n-butylamine during the reaction to obtain a prepolymer. The nanocellulose, polyetheramine D2000, and 4,4'-diaminodiphenyl disulfide were dissolved in N,N-dimethylacetamide. After mixing evenly, a mixture was obtained and added to the prepolymer. Then, amino-modified calcium carbonate was added. The mass ratio of nanocellulose, polyetheramine, 4,4'-diaminodiphenyl disulfide, N,N-dimethylacetamide, prepolymer, and amino-modified calcium carbonate was 8:150:4.5:340:100:5. The mixture was stirred and reacted at 50 °C for 1 h. After the reaction, the product was added to a polytetrafluoroethylene mold and heated at 120 °C for 24 h to obtain modified polyurethane.

[0038] The preparation method of amino-modified calcium carbonate comprises the following steps: The nano calcium carbonate was ultrasonically dispersed in an ethanol aqueous solution of 95 wt%, and after uniform dispersion, γ-aminopropyltriethoxysilane was added. The mass ratio of nano calcium carbonate, ethanol solution, and γ-aminopropyltriethoxysilane was 100:2600:30. Stir and mix, react at 30 °C for 6 h. After the reaction, filter by suction, wash with deionized water and absolute ethanol, and dry in vacuum at 60 °C for 12 h to obtain amino-modified calcium carbonate.

[0039] Comparative Example 2 A hot melt adhesive comprises the following raw materials in parts by mass: 90 parts of modified polyurethane, 25 parts of polyamide resin, 18 parts of terpene resin, 4 parts of antioxidant 1010, and 1.5 parts of plasticizer epoxidized soybean oil; The preparation method of the modified polyurethane comprises the following steps: In a nitrogen atmosphere, the heat-resistant diol XC-488 and toluene diisocyanate were added to a reactor, and a catalyst was added dropwise. The mass ratio of diol, toluene diisocyanate, and catalyst dibutyltin dilaurate was 155:100:0.8. Stir and mix, heat up, and react at 60 °C. After reacting for 1 h, the amount of -NCO was detected by the back titration method of di-n-butylamine during the reaction to obtain a prepolymer. Dissolve isocyanate-modified cellulose, polyetheramine D2000, and 4,4'-diaminodiphenyl disulfide in N,N-dimethylacetamide, and after mixing evenly, obtain a mixture, add it to the prepolymer, and then add nano calcium carbonate. The mass ratio of isocyanate-modified cellulose, polyetheramine, 4,4'-diaminodiphenyl disulfide, N,N-dimethylacetamide, prepolymer, and nano calcium carbonate is 8:150:4.5:340:100:5. Stir and mix, react at 50 °C for 1 h. After the reaction, add the product to a polytetrafluoroethylene mold, heat, and heat at 120 °C for 24 h to obtain modified polyurethane.

[0040] The preparation method of the isocyanate-modified cellulose comprises the following steps: The nano cellulose was ultrasonically dispersed in ethyl acetate. After uniform dispersion, (2,4,6-trioxo-1,3,5-triazine-1,3,5(2H,4H,6H)-triyl)tris(hexamethylene) diisocyanate and dibutyltin dilaurate were added. The mass ratio of nano cellulose, ethyl acetate, (2,4,6-trioxo-1,3,5-triazine-1,3,5(2H,4H,6H)-triyl)tris(hexamethylene) diisocyanate, and dibutyltin dilaurate was 100:1500:82:1.2. Stir and mix, react at 50 °C, and the reaction time was 1.5 h. After the reaction, filter by suction, wash with petroleum ether, and dry in vacuum at 60 °C for 24 h to obtain isocyanate-modified cellulose.

[0041] Comparative Example 3 A hot melt adhesive, comprising raw materials in the following parts by mass: 90 parts of modified polyurethane, 25 parts of polyamide resin, 18 parts of terpene resin, 4 parts of antioxidant 1010, and 1.5 parts of plasticizer epoxidized soybean oil; The preparation method of the modified polyurethane comprises the following steps: In a nitrogen atmosphere, a heat-resistant diol XC-488 and toluene diisocyanate are added to a reactor, and a catalyst is added dropwise. The mass ratio of the diol, toluene diisocyanate, and catalyst dibutyltin dilaurate is 155:100:0.8. Stir and mix, heat up, and react at 60 °C. After reacting for 1 h, the amount of -NCO is detected by the back titration method using dibutylamine during the reaction process to obtain a prepolymer. Dissolve nanocellulose, polyetheramine D2000, and 4,4'-diaminodiphenyl disulfide in N,N-dimethylacetamide, mix evenly to obtain a mixture, add it to the prepolymer, and then add nanometer calcium carbonate. The mass ratio of nanocellulose, polyetheramine, 4,4'-diaminodiphenyl disulfide, N,N-dimethylacetamide, prepolymer, and nanometer calcium carbonate is 8:150:4.5:340:100:5. Stir and mix, and react at 50 °C for 1 h. After the reaction is completed, add the product to a polytetrafluoroethylene mold, heat, and heat at 120 °C for 24 h to obtain the modified polyurethane.

[0042] The preparation method of the nanocellulose used in the examples and comparative examples of the present invention comprises the following steps: Prepare a 60% sulfuric acid solution, mix and stir microcrystalline cellulose and the sulfuric acid solution with a mass ratio of 4:1, heat in a water bath at 45 °C, react for 1 h, centrifuge after the reaction is completed, wash with deionized water until the pH of the supernatant is 7, dialyze, and freeze-dry to obtain nanocellulose.

[0043] The high adhesion heat-resistant diol XC-488 used in the examples and comparative examples of the present invention is purchased from Beijing Baiyuan Chemical Co., Ltd., Mn = 500, industrial grade; microcrystalline cellulose is purchased from Tianjin Guangfu Fine Chemical Research Institute; nanometer calcium carbonate is purchased from Guangxi Huana Technology Co., Ltd., with an average particle size of 20 nm; polyamide resin is purchased from Shandong Dengnuo New Materials Technology Co., Ltd., product number HS-J1; terpene resin is purchased from Dezhou Pule Chemical Co., Ltd., model H-5; other raw materials and reagents not specified are commercially available.

[0044] Perform relevant performance tests on the hot melt adhesives prepared in Examples 1-5 and Comparative Examples 1-3, and the tests are as follows: (1) Heat resistance test: Perform thermogravimetric analysis on the hot melt adhesive. The test standard refers to ASTM E1131, and the test is carried out in a nitrogen atmosphere. The heating rate is 10 °C / min, and the temperature range is 25 - 600 °C. Record the initial decomposition temperature T 5% and the maximum decomposition temperature T max, where the initial decomposition temperature is the temperature corresponding to a 5% weight loss; (2) Adhesion test: Conduct a peel strength test. The test standard refers to ASTM D1876 (T-peel). The test substrate is the adhesion between a soft PVC film and a metal plate, and the peel rate is 100 mm / min; The above test results are shown in Table 1: Table 1 According to the test results in Table 1, it can be seen that Examples 1-5 of the present invention have excellent heat resistance and adhesion. In Comparative Example 1, cellulose was not modified, resulting in a decrease in the stability of the hot melt adhesive, poor heat resistance, and easy cracking at the interface. In Comparative Example 2, nano-calcium carbonate was not modified, and the nano-fillers were prone to agglomeration, causing stress concentration and a decline in comprehensive performance. In Comparative Example 3, neither nano-cellulose nor nano-calcium carbonate was modified and was directly added to the prepolymer, resulting in poor dispersibility and compatibility between the raw materials, and a significant decline in the comprehensive performance of the prepared hot melt adhesive.

[0045] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. All equivalent changes and improvements made within the scope of the present invention application shall still fall within the scope covered by the present invention.

Claims

1. A hot melt adhesive with high adhesion, characterized in that: It comprises raw materials in the following parts by mass: 75 - 95 parts of modified polyurethane, 15 - 28 parts of polyamide resin, 10 - 20 parts of tackifying resin, 3 - 5 parts of antioxidant, and 1 - 2 parts of plasticizer; The preparation method of the modified polyurethane comprises the following steps: In a nitrogen atmosphere, a diol, toluene diisocyanate, and a catalyst are mixed and reacted to obtain a prepolymer, and then a chain extender, modified cellulose, and modified filler are added and reacted to obtain the modified polyurethane.

2. The hot melt adhesive with high adhesion according to claim 1, characterized in that: The tackifying resin includes any one or more of polymerized rosin resin, EVA resin, and terpene resin.

3. The hot melt adhesive with high adhesion according to claim 1, wherein: The antioxidant includes any one or more of BHT, antioxidant 1010, and antioxidant 168.

4. The hot melt adhesive with high adhesion according to claim 1, characterized in that: The plasticizer includes any one or more of dioctyl phthalate, dibutyl phthalate, epoxy soybean oil, and microcrystalline wax.

5. The hot melt adhesive with high adhesion according to claim 1, wherein: The specific preparation method of the modified polyurethane comprises the following steps: In a nitrogen atmosphere, the diol and toluene diisocyanate are added to a reactor, and the catalyst is added dropwise. The mass ratio of the diol, toluene diisocyanate, and catalyst is 140 - 160:100:0.5 - 1. Stir and mix, heat up, and react at 55 - 65 °C. After reacting for 1 h, the amount of -NCO is detected by the dibutylamine back - titration method during the reaction process to obtain a prepolymer. The modified cellulose and the chain extender are dissolved in N,N - dimethylacetamide. The modified cellulose is isocyanate - modified cellulose, and the chain extender is composed of polyetheramine and 4,4'-diaminodiphenyl disulfide. After mixing evenly, a mixture is obtained and added to the prepolymer. Then, amino - modified calcium carbonate is added. The mass ratio of the isocyanate - modified cellulose, polyetheramine, 4,4'-diaminodiphenyl disulfide, N,N - dimethylacetamide, prepolymer, and amino - modified calcium carbonate is 4 - 9:120 - 155:3 - 5:300 - 350:100:2 - 6. Stir and mix, and react at 45 - 55 °C for 1 h. After the reaction is completed, the product is added to a polytetrafluoroethylene mold and heated at 120 °C for 24 h to obtain the modified polyurethane.

6. The hot melt adhesive with high adhesion force according to claim 5, characterized in that: The diol is heat - resistant diol XC - 488, and the polyetheramine is polyetheramine D2000.

7. A hot melt adhesive with high adhesion according to claim 5, characterized in that: The catalyst includes one or several of dibutyltin dilaurate, stannous octoate, and dibutyltin diacetate.

8. A hot melt adhesive with high adhesion according to claim 5, characterized in that: The preparation method of the isocyanate - modified cellulose comprises the following steps: The nano - cellulose is ultrasonically dispersed in ethyl acetate. After dispersing evenly, triisocyanate and dibutyltin dilaurate are added, stirred and mixed, and reacted. After the reaction is completed, suction filtration is carried out, washed with petroleum ether, and vacuum - dried at 60 °C for 24 h to obtain the isocyanate - modified cellulose.

9. The hot melt adhesive with high adhesion force according to claim 5, characterized in that: During the preparation process of the isocyanate - modified cellulose, the mass ratio of nano - cellulose, ethyl acetate, triisocyanate, and dibutyltin dilaurate is 100:1400 - 1600:75 - 90:1 - 1.

5. The reaction temperature is 45 - 55 °C, and the reaction time is 1 - 2 h.

10. A hot melt adhesive with high adhesion according to claim 5, characterized in that: The preparation method of the amino - modified calcium carbonate comprises the following steps: The nano calcium carbonate is ultrasonically dispersed in an ethanol solution. After uniform dispersion, γ-aminopropyltriethoxysilane is added, where the mass ratio of nano calcium carbonate, ethanol solution, and γ-aminopropyltriethoxysilane is 100:2400 - 2800:25 - 35. Stir and mix, react at 25 - 35 °C for 5 - 8 h. After the reaction is completed, filter by suction, wash with deionized water and absolute ethanol, and dry in vacuum at 60 °C for 12 h to obtain amino-modified calcium carbonate.

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