Self-repairing polyurethane hot melt adhesive and preparation method thereof

Abstract

The invention particularly relates to a self-repairing polyurethane hot melt adhesive and a preparation method thereof. The preparation method comprises the following steps: mixing polycaprolactone glycol, polycarbonate 1, 6-hexanediol ester glycol and a solvent to obtain a material A; mixing dicyclohexylmethane diisocyanate, isophorone diisocyanate and a solvent, adding a catalyst, and preserving heat to obtain a material B; mixing an end-capping reagent and a solvent to obtain a material C; mixing copper acetylacetonate and stearic acid, adding a solvent, and mixing to obtain a material D; dropwise adding the material B into the material A for reaction, then adding the material C for reaction, and then dropwise adding the material D for reaction; 2, 2 '-dithiodiethanol is added into the first mixture for a reaction, then the material D is dropwise added for a reaction, and then tackifying resin and a compatilizer are added for heat preservation; and adding a filler and silane coupling agent mixture and an auxiliary agent into the mixture II, and carrying out melt blending granulation. The hot melt adhesive has good bonding performance, self-repairing performance and solvent resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of hot melt adhesives, and in particular to a self-repairing polyurethane hot melt adhesive and a preparation method thereof. Background Art

[0002] With the development of society and the advancement of science and technology, industries such as electronics, automobiles, and intelligent manufacturing have developed rapidly. Mobile phones, smart watches, bracelets, tablet computers, etc. are becoming more and more popular in people's lives and work, and their diversified performance and convenient repair and maintenance are also increasingly valued by people. Polyurethane hot melt adhesive has good bonding properties, weather resistance, solvent resistance, and high and low temperature performance. It has been widely used in the production and manufacturing of products such as mobile phones, smart watches, bracelets, and tablet computers. Although traditional polyurethane hot melt adhesives have some bonding properties, their self-healing ability is poor. During use, they are easily damaged by mechanical damage or environmental erosion and fail, resulting in reduced performance and the need for frequent replacement, which leads to high costs, and easily leads to waste of resources and environmental pollution. Therefore, it is of great significance to develop polyurethane hot melt adhesives with good bonding properties and self-healing properties to improve product quality and reliability and reduce costs. Summary of the Invention

[0003] The purpose of the present invention is to address the deficiencies of the above-mentioned prior art and to provide a self-healing polyurethane hot melt adhesive and a preparation method thereof. The hot melt adhesive has good bonding properties, self-healing properties and solvent resistance, which is beneficial to solving the problems of poor repair performance and rapid performance degradation of polyurethane hot melt adhesives in the prior art; the preparation method of the hot melt adhesive has a stable process, easy operation, high production efficiency, and is conducive to industrial production.

[0004] The purpose of the present invention is achieved through the following technical solution: A method for preparing a self-repairing polyurethane hot melt adhesive comprises the following steps:

[0005] (1) Under the protection of inert gas, polycaprolactone diol and polycarbonate diol are mixed with a solvent to obtain material A; dicyclohexylmethane diisocyanate and isophorone diisocyanate are mixed with a solvent, and then a catalyst is added to mix to obtain material B; a blocking agent is mixed with a solvent to obtain material C; copper acetylacetonate and stearic acid are mixed, and then a solvent is added to mix to obtain material D;

[0006] (2) adding material B dropwise to material A to react, and after the residual isocyanate content in the system drops to the target value, adding material C dropwise to react, and removing part of the solvent from the obtained product to obtain a mixture 1;

[0007] (3) adding a mixed solution of 2,2'-dithiodiethanol and a solvent to the mixture 1 to react; then adding material D dropwise to react, and then adding a tackifying resin and a compatibilizer to keep warm to obtain a mixture 2;

[0008] (4) removing the solvent from the obtained mixture, then adding a filler and a silane coupling agent mixture and an auxiliary agent, and performing melt blending and granulation to obtain a self-repairing polyurethane hot melt adhesive.

[0009] The preparation method of the self-repairing polyurethane hot melt adhesive of the present invention adopts polycaprolactone diol, polycarbonate 1,6-hexanediol ester diol combined with dicyclohexylmethane diisocyanate and isophorone diisocyanate, and is compounded with raw materials such as tackifying resin, compatibilizer, filler, silane coupling agent, and combined with dynamic exchange of disulfide bonds and metal coordination, to achieve damage repair of polyurethane hot melt adhesive at room temperature or under heating conditions, extending the service life of the adhesive layer and convenience of use. The present invention makes the prepared polyurethane hot melt adhesive have good bonding properties, self-repairing properties and solvent resistance by regulating the raw material ratio and processing technology, which is conducive to solving the problems of poor repair performance and rapid performance decay of polyurethane hot melt adhesive in the prior art, and can be applied to electronic products, automobile manufacturing, packaging and other fields.

[0010] Furthermore, in step (1), the solvent is at least one of dimethylacetamide and dimethyl sulfoxide.

[0011] Furthermore, in step (1), 40-50 parts of polycaprolactone diol, 30-40 parts of polycarbonate diol and 75-85 parts of solvent are uniformly mixed to obtain material A. The polycarbonate diol is preferably polycarbonate 1,6-hexanediol ester diol.

[0012] Furthermore, in step (1), 15-25 parts of dicyclohexylmethane diisocyanate, 10-20 parts of isophorone diisocyanate and 55-65 parts of solvent are uniformly mixed, and then 0.1-1 parts of catalyst are added, and the mixture is kept at 55-65° C. for 1-10 minutes to obtain material B;

[0013] Furthermore, in step (1), 8-15 parts of a blocking agent and 25-35 parts of a solvent are uniformly mixed to obtain material C. The blocking agent is at least one of 2,4-pentanedione dioxime, methyl ethyl ketoxime, cyclohexanone oxime and dimethylglyoxime.

[0014] Furthermore, in step (1), copper acetylacetonate and stearic acid are mixed, heated and kept warm, and then mixed evenly with a solvent to obtain material D.

[0015] Furthermore, in step (1), 1-3 parts of copper acetylacetonate and 0.9-3.3 parts of stearic acid are mixed evenly, kept warm at 55-65° C. for 40-80 minutes, and then 15-25 parts of solvent are added and mixed evenly to obtain material D.

[0016] Furthermore, in step (2), material B is added dropwise to material A until the residual isocyanate content in the system drops to 3-8%, that is, the target value is 3-8% residual isocyanate content; material C is added dropwise, and the reaction is carried out at 50-60° C. for 4-6 hours. The solvent is removed from the obtained product to obtain mixture 1.

[0017] Further, in step (3), in step (3), a mixture consisting of 2-5 parts of 2,2'-dithiodiethanol and 8-12 parts of a solvent is added to the mixture one, and the mixture is reacted at 55-65°C for 10-30 minutes; material D is then added dropwise, and the mixture is reacted at 55-65°C for 3-5 hours, and then 5-10 parts of a tackifying resin and 3-6 parts of a compatibilizer are added, and the mixture is kept warm for 40-80 minutes to obtain a mixture two;

[0018] Furthermore, in step (3), the tackifying resin is at least one of rosin resin, petroleum resin, and ethylene-vinyl acetate copolymer. The compatibilizer is at least one of maleic anhydride grafted acrylonitrile-butadiene-styrene copolymer, maleic anhydride grafted polypropylene, and maleic anhydride grafted polyethylene.

[0019] Furthermore, in step (4), the solvent is removed from the obtained mixture, and a mixture consisting of 3-10 parts of filler and 2-5 parts of silane coupling agent and 2.5-9 parts of auxiliary agent are added, and then melt-blended and granulated to obtain self-repairing polyurethane hot melt adhesive particles.

[0020] Furthermore, in step (4), each part of the auxiliary agent comprises the following raw materials in parts by weight: 1-3 parts of antioxidant, 1-3 parts of light stabilizer and 0.5-3 parts of defoaming agent.

[0021] Furthermore, in step (4), the silane coupling agent is at least one of γ-mercaptopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloxypropyltrimethoxysilane. The filler is at least one of nano-silicon dioxide, nano-calcium carbonate, and nano-aluminum oxide.

[0022] Furthermore, in step (4), the antioxidant is at least one of antioxidant 1010, antioxidant 1076, antioxidant 168, antioxidant 626, and antioxidant DSTDP. The light stabilizer is at least one of light stabilizer 770, light stabilizer 944, and light stabilizer UV-327. The defoamer is at least one of BYK525 and BYK-088.

[0023] The present invention also provides a self-repairing polyurethane hot melt adhesive, which is prepared by the above-mentioned preparation method of the self-repairing polyurethane hot melt adhesive.

[0024] The beneficial effects of the present invention are as follows: the preparation method of the self-repairing polyurethane hot melt adhesive of the present invention combines flexible polyols with isocyanates, and compounded with raw materials such as tackifying resins, compatibilizers, fillers, silane coupling agents, and combined with dynamic exchange of disulfide bonds and metal coordination, the damage repair of the polyurethane hot melt adhesive at room temperature or under heating conditions is achieved, and the service life and convenience of the adhesive layer are extended. The present invention adjusts the raw material ratio and processing technology so that the prepared polyurethane hot melt adhesive has good bonding properties, self-repairing properties and solvent resistance, which is beneficial to solving the problems of poor repair performance and rapid performance degradation of polyurethane hot melt adhesives in the prior art. The preparation method of the PUR hot melt adhesive has a stable process, convenient control, high production efficiency, and is conducive to industrial production. DETAILED DESCRIPTION

[0025] In order to facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the embodiments. The contents mentioned in the embodiments are not intended to limit the present invention.

[0026] In some embodiments of the present invention, a method for preparing a self-repairing polyurethane hot melt adhesive comprises the following steps:

[0027] (1) Under the protection of inert gas, 40-50 parts of polycaprolactone diol and 30-40 parts of polycarbonate 1,6-hexanediol ester diol are mixed with 75-85 parts of solvent to obtain material A; under the protection of inert gas, 15-25 parts of dicyclohexylmethane diisocyanate, 10-20 parts of isophorone diisocyanate and 55-65 parts of solvent are mixed, and then a catalyst is added, and the mixture is kept warm at 55-65° C. to obtain material B; 8-15 parts of a blocking agent and 25-35 parts of a solvent are mixed to obtain material C; 1-3 parts of copper acetylacetonate, 0.9-3.3 parts of stearic acid and 15-25 parts of a solvent are mixed to obtain material D; wherein, the preparation of material A, material B, material C and material D can be carried out simultaneously or in reverse order;

[0028] (2) adding material B dropwise to material A for 20-60 min, and after the residual isocyanate content in the system is reduced to 3-8%, adding material C dropwise for 20-40 min, and reacting at 50-60° C. for 4-6 h while adding dropwise; removing part of the solvent from the obtained product to make the solvent content less than 10 wt %, to obtain mixture 1;

[0029] (3) adding a mixture consisting of 2-5 parts of 2,2'-dithiodiethanol and 8-12 parts of a solvent to the mixture 1, and reacting at 55-65°C for 10-30 minutes; then adding material D dropwise for 30-60 minutes, and reacting at 55-65°C for 3-5 hours, while adding dropwise, and then adding 5-10 parts of a tackifying resin and 3-6 parts of a compatibilizer, and keeping warm for 40-80 minutes to obtain a mixture 2;

[0030] (4) The obtained mixture 2 is vacuum dried to remove the solvent until the content is less than 0.1%, and then a mixture consisting of 3-10 parts of filler and 2-5 parts of silane coupling agent and 2.5-9 parts of auxiliary agent are added, and then melt blending and granulation are carried out using a twin-screw extruder to obtain a self-repairing polyurethane hot melt adhesive.

[0031] Furthermore, in step (1), 40-50 parts of polycaprolactone diol, 30-40 parts of polycarbonate 1,6-hexanediol ester diol and 75-85 parts of solvent are uniformly mixed to obtain material A. The molecular weight of the polycaprolactone diol is 1000-3000. The molecular weight of the polycarbonate 1,6-hexanediol ester diol is 800-2500.

[0032] Furthermore, in step (1), 15-25 parts of dicyclohexylmethane diisocyanate, 10-20 parts of isophorone diisocyanate and 55-65 parts of solvent are uniformly mixed, and then 0.1-1 parts of catalyst are added, and the mixture is kept warm at 55-65° C. for 1-10 minutes to obtain material B.

[0033] Furthermore, in step (1), the catalyst is at least one of an organic bismuth catalyst, dibutyltin dilaurate and bis(2-dimethylaminoethyl) ether.

[0034] Furthermore, in step (1), the catalyst is composed of an organic bismuth catalyst and bis(2-dimethylaminoethyl) ether in a weight ratio of 2-5:1.

[0035] Furthermore, in step (1), 8-15 parts of a blocking agent and 25-35 parts of a solvent are uniformly mixed to obtain material C; the blocking agent is at least one of 2,4-pentanedione dioxime, methyl ethyl ketoxime, cyclohexanone oxime and dimethylglyoxime.

[0036] Furthermore, in step (1), 1-3 parts of copper acetylacetonate and 0.9-3.3 parts of stearic acid are mixed evenly, kept warm at 55-65° C. for 40-80 minutes, and then 15-25 parts of solvent are added and mixed evenly to obtain material D.

[0037] Furthermore, in step (3), the tackifying resin is at least one of rosin resin, petroleum resin, and ethylene-vinyl acetate copolymer. The compatibilizer is at least one of maleic anhydride grafted acrylonitrile-butadiene-styrene copolymer, maleic anhydride grafted polypropylene, and maleic anhydride grafted polyethylene.

[0038] Furthermore, in step (3), each part of the auxiliary agent comprises the following raw materials in parts by weight: 1-3 parts of antioxidant, 1-3 parts of light stabilizer and 0.5-3 parts of defoaming agent.

[0039] Furthermore, in step (4), the filler is at least one of nano-silicon dioxide, nano-calcium carbonate, and nano-aluminum oxide. The antioxidant is at least one of antioxidant 1010, antioxidant 1076, antioxidant 168, antioxidant 626, and antioxidant DSTDP. The light stabilizer is at least one of light stabilizer 770, light stabilizer 944, and light stabilizer UV-327. The defoamer is at least one of BYK-A 525, BYK-A 535, and BYK-088.

[0040] Example 1

[0041] This embodiment provides a method for preparing a self-repairing polyurethane hot melt adhesive, comprising the following steps:

[0042] (1) Under the protection of inert gas, 45 parts of polycaprolactone diol and 35 parts of polycarbonate 1,6-hexanediol ester diol were mixed with 80 parts of solvent to obtain material A; 20 parts of dicyclohexylmethane diisocyanate and 15 parts of isophorone diisocyanate were mixed with 60 parts of solvent, and then 0.3 parts of catalyst was added, and the mixture was kept warm at 60°C for 5 minutes to obtain material B; 12 parts of end-capping agent and 30 parts of solvent were mixed to obtain material C; 2 parts of copper acetylacetonate and 1.8 parts of stearic acid were mixed to obtain material D; wherein, the preparation of material A, material B, material C and material D can be carried out simultaneously or in reverse order; the solvent is dimethylacetamide;

[0043] (2) Material B was added dropwise to material A for 30 min. After the residual isocyanate content in the system dropped to 5%, material C was added dropwise for 30 min. The mixture was reacted at 55° C. for 5 h. The obtained product was decompressed to reduce the solvent content to less than 10 wt %, to obtain a mixture 1.

[0044] (3) Adding a mixture consisting of 3 parts of 2,2'-dithiodiethanol and 10 parts of a solvent to the mixture 1, and reacting at 60°C for 20 minutes; then adding material D dropwise for 40 minutes, and reacting at 60°C for 4 hours, and then adding 7 parts of a tackifying resin and 5 parts of a compatibilizer, and keeping the temperature for 60 minutes to obtain a mixture 2;

[0045] (4) The obtained mixture 2 is vacuum dried to remove the solvent until the content is less than 0.1 wt %, and then a mixture consisting of 5 parts of filler and 4 parts of silane coupling agent, 1.5 parts of antioxidant, 1 part of light stabilizer and 1 part of defoamer are added, and then melt-blended and granulated using a twin-screw extruder to obtain a self-repairing polyurethane hot melt adhesive; the silane coupling agent and the filler are pre-mixed at 75° C. for 10 minutes.

[0046] Furthermore, in step (1), the catalyst is bismuth neodecanoate and bis(2-dimethylaminoethyl) ether in a weight ratio of 2:1. The end-capping agent is dimethylglyoxime. The polycaprolactone diol is polycaprolactone diol Jining Tangyi Chemical PCL2000. The polycarbonate 1,6-hexanediol ester diol is Ube UH-200 polycarbonate diol.

[0047] Furthermore, in step (3), the tackifying resin is Ganges petroleum resin HH2-1003, and the compatibilizer is ExxonMobil maleic anhydride grafted polypropylene 1015.

[0048] Furthermore, in step (4), the silane coupling agent is composed of γ-mercaptopropyltrimethoxysilane and γ-methacryloxypropyltrimethoxysilane in a weight ratio of 2:1. The filler is composed of nano-silica and nano-alumina in a weight ratio of 2:1. The antioxidant is composed of antioxidant 1010 and antioxidant 168 in a weight ratio of 1:1. The light stabilizer is light stabilizer 944. The defoamer is BYK-A 525.

[0049] Example 2

[0050] This embodiment provides a method for preparing a self-repairing polyurethane hot melt adhesive, comprising the following steps:

[0051] (1) Under the protection of inert gas, 42 parts of polycaprolactone diol and 38 parts of polycarbonate 1,6-hexanediol ester diol were mixed with 80 parts of solvent to obtain material A; 22 parts of dicyclohexylmethane diisocyanate and 13 parts of isophorone diisocyanate were mixed with 60 parts of solvent, and then 0.3 parts of catalyst was added, and the mixture was kept warm at 60°C for 5 minutes to obtain material B; 12 parts of end-capping agent and 30 parts of solvent were mixed to obtain material C; 2 parts of copper acetylacetonate and 1.8 parts of stearic acid were mixed to obtain material D; wherein, the preparation of material A, material B, material C and material D can be carried out simultaneously or in reverse order; the solvent is dimethylacetamide;

[0052] (2) Material B was added dropwise to material A for 30 min. After the residual isocyanate content in the system dropped to 5%, material C was added dropwise for 30 min. The mixture was reacted at 55° C. for 5 h. The obtained product was decompressed to reduce the solvent content to less than 10 wt %, to obtain a mixture 1.

[0053] (3) Adding a mixture consisting of 3 parts of 2,2'-dithiodiethanol and 10 parts of a solvent to the mixture 1, and reacting at 60°C for 20 minutes; then adding material D dropwise for 40 minutes, and reacting at 60°C for 4 hours, and then adding 5 parts of a tackifying resin and 4 parts of a compatibilizer, and keeping the temperature for 60 minutes to obtain a mixture 2;

[0054] (4) The obtained mixture 2 is vacuum dried to remove the solvent until the content is less than 0.1%, and then a mixture consisting of 5 parts of filler and 4 parts of silane coupling agent, 1.5 parts of antioxidant, 1 part of light stabilizer and 1 part of defoaming agent are added, and then melt-blending and granulation are carried out using a twin-screw extruder to obtain a self-repairing polyurethane hot melt adhesive.

[0055] Furthermore, in step (1), the catalyst is composed of bismuth neodecanoate and bis(2-dimethylaminoethyl) ether in a weight ratio of 2:1. The capping agent is dimethylglyoxime.

[0056] Furthermore, in step (3), the tackifying resin is petroleum resin, and the compatibilizer is ExxonMobil maleic anhydride grafted polypropylene 1015.

[0057] Furthermore, in step (4), the silane coupling agent is γ-mercaptopropyltrimethoxysilane, and the filler is composed of nano-silica and nano-alumina in a weight ratio of 1:1.

[0058] The rest of the contents of this embodiment are the same as those of Embodiment 1 and will not be repeated here.

[0059] Example 3

[0060] This embodiment provides a method for preparing a self-repairing polyurethane hot melt adhesive, comprising the following steps:

[0061] (1) Under the protection of inert gas, 48 ​​parts of polycaprolactone diol and 32 parts of polycarbonate 1,6-hexanediol ester diol were mixed with 80 parts of solvent to obtain material A; 18 parts of dicyclohexylmethane diisocyanate and 17 parts of isophorone diisocyanate were mixed with 60 parts of solvent, and then 0.3 parts of catalyst was added, and the mixture was kept warm at 60°C for 5 minutes to obtain material B; 12 parts of end-capping agent and 30 parts of solvent were mixed to obtain material C; 2 parts of copper acetylacetonate and 1.8 parts of stearic acid were mixed, and the mixture was kept warm at 60°C for 60 minutes, and then 20 parts of solvent was added and mixed to obtain material D; wherein, the preparation of material A, material B, material C and material D can be carried out simultaneously or in reverse order; the solvent is dimethylacetamide;

[0062] (2) Material B was added dropwise to material A for 30 min. After the residual isocyanate content in the system dropped to 5%, material C was added dropwise for 30 min. The mixture was reacted at 55° C. for 5 h. The obtained product was decompressed to reduce the solvent content to less than 10 wt %, to obtain a mixture 1.

[0063] (3) Adding a mixture consisting of 3 parts of 2,2'-dithiodiethanol and 10 parts of a solvent to the mixture 1, and reacting at 60°C for 20 minutes; then adding material D dropwise for 40 minutes, and reacting at 60°C for 4 hours, and then adding 7 parts of a tackifying resin and 5 parts of a compatibilizer, and keeping the temperature for 60 minutes to obtain a mixture 2;

[0064] (4) The obtained mixture 2 is vacuum dried to remove the solvent until the content is less than 0.1%, and then a mixture consisting of 7 parts of filler and 6 parts of silane coupling agent, 1.5 parts of antioxidant, 1 part of light stabilizer and 1 part of defoaming agent are added, and then melt blending and granulation are carried out using a twin-screw extruder to obtain a self-repairing polyurethane hot melt adhesive.

[0065] Furthermore, in step (1), the catalyst is composed of bismuth neodecanoate and bis(2-dimethylaminoethyl) ether in a weight ratio of 2:1. The capping agent is dimethylglyoxime.

[0066] Furthermore, in step (3), the tackifying resin is petroleum resin, and the compatibilizer is ExxonMobil maleic anhydride grafted polypropylene 1015.

[0067] Furthermore, in step (4), the silane coupling agent is γ-mercaptopropyltrimethoxysilane, and the filler is composed of nano-silicon dioxide and nano-calcium carbonate in a weight ratio of 2:1.

[0068] The rest of the contents of this embodiment are the same as those of Embodiment 1 and will not be repeated here.

[0069] Comparative Example 1

[0070] This comparative example provides a method for preparing a polyurethane hot melt adhesive, comprising the following steps:

[0071] (1) Under the protection of inert gas, 45 parts of polycaprolactone diol and 35 parts of polycarbonate 1,6-hexanediol ester diol were mixed with 80 parts of solvent to obtain material A; 20 parts of dicyclohexylmethane diisocyanate and 15 parts of isophorone diisocyanate were mixed with 60 parts of solvent, and then 0.3 parts of catalyst was added, and the mixture was kept warm at 60°C for 5 minutes to obtain material B; 12 parts of end-capping agent and 30 parts of solvent were mixed to obtain material C; 2 parts of copper acetylacetonate, 1.8 parts of stearic acid and 20 parts of solvent were mixed to obtain material D; wherein, the preparation of material A, material B, material C and material D can be carried out simultaneously or in reverse order; the solvent is dimethylacetamide;

[0072] (2) Material B was added dropwise to material A for 30 min. After the residual isocyanate content in the system dropped to 5%, material C was added dropwise for 30 min. The mixture was reacted at 55° C. for 5 h. The obtained product was decompressed to reduce the solvent content to less than 10 wt %, to obtain a mixture 1.

[0073] (3) Add 10 parts of solvent to mixture 1, then dropwise add material D for 40 minutes, react at 60°C for 4 hours, then add 7 parts of tackifying resin and 5 parts of compatibilizer, and keep warm for 60 minutes to obtain mixture 2;

[0074] (4) The obtained mixture 2 is vacuum dried to remove the solvent until the content is less than 0.1%, and then a mixture consisting of 5 parts of filler and 4 parts of silane coupling agent, 1.5 parts of antioxidant, 1 part of light stabilizer and 1 part of defoaming agent are added, and then melt-blending and granulation are carried out using a twin-screw extruder to obtain a self-repairing polyurethane hot melt adhesive.

[0075] Comparative Example 2

[0076] This embodiment provides a method for preparing a self-repairing polyurethane hot melt adhesive, comprising the following steps:

[0077] (1) Under the protection of inert gas, 45 parts of polycaprolactone diol and 35 parts of polycarbonate 1,6-hexanediol ester diol were mixed with 80 parts of solvent to obtain material A; 20 parts of dicyclohexylmethane diisocyanate and 15 parts of isophorone diisocyanate were mixed with 60 parts of solvent to obtain material B; 12 parts of end-capping agent and 30 parts of solvent were mixed to obtain material C; wherein, the preparation of material A, material B and material C can be carried out simultaneously or in reverse order; the solvent is dimethylacetamide;

[0078] (2) Material B was added dropwise to material A for 30 min. After the residual isocyanate content in the system dropped to 5%, material C was added dropwise for 30 min. The mixture was reacted at 55° C. for 5 h. The obtained product was decompressed to reduce the solvent content to less than 10 wt %, to obtain a mixture 1.

[0079] (3) Adding a mixture consisting of 3 parts of 2,2'-dithiodiethanol and 10 parts of a solvent to the mixture 1, and reacting at 60°C for 20 minutes; then adding material D dropwise for 40 minutes, and reacting at 60°C for 4 hours, and then adding 7 parts of a tackifying resin and 5 parts of a compatibilizer, and keeping the temperature for 60 minutes to obtain a mixture 2;

[0080] (4) The obtained mixture 2 is vacuum dried to remove the solvent until the content is less than 0.1%, and then a mixture consisting of 5 parts of filler and 4 parts of silane coupling agent, 1.5 parts of antioxidant, 1 part of light stabilizer and 1 part of defoaming agent are added, and then melt-blending and granulation are carried out using a twin-screw extruder to obtain a self-repairing polyurethane hot melt adhesive.

[0081] The rest of the contents of this comparative example are the same as those of Example 1 and will not be repeated here.

[0082] The performance of the polyurethane hot melt adhesives prepared in Examples 1-3 was tested, and the test results are shown in the following table:

[0083]

[0084] The shear strength test was conducted according to ASTM D1002. A PUR hot-melt adhesive was used to overlap the aluminum plate and the inked glass. The adhesive thickness was 0.15mm. The aluminum plate dimensions were 100mm×25mm×1.6mm. After curing for 7 days at 25°C / 50% RH, the aluminum alloy was tested using a universal material testing machine at a loading rate of 5mm / min at 25°C. The aluminum alloy was polished to Ra ≤ 0.8μm. The shear strength retention test after immersion in a 10wt% NaOH solution involved immersing the specimen in a 10wt% NaOH solution for 72 hours, removing it, wiping the surface dry, and drying it at room temperature for 24 hours before testing. The self-healing test involved making a cross-shaped incision in the middle of the adhesive layer with a blade. The incision had a depth of 50μm and a length of 10mm. The shear strength recovery rate within the test was recorded after the specimens were treated at 25°C for 24 hours and at 100°C for 30 minutes and then cooled to 25°C for 2 hours.

[0085] In summary, the preparation method of the self-healing polyurethane hot melt adhesive of the present invention combines polycaprolactone diol, polycarbonate 1,6-hexanediol ester diol with dicyclohexylmethane diisocyanate and isophorone diisocyanate, and compounded with raw materials such as tackifying resin, compatibilizer, filler, silane coupling agent, etc., and combined with the dynamic exchange of disulfide bonds and metal coordination, the raw materials work synergistically to achieve damage repair of the polyurethane hot melt adhesive at room temperature or heated conditions, extend the service life of the adhesive layer and the convenience of use, so that the prepared polyurethane hot melt adhesive has good bonding properties, self-healing properties and solvent resistance.

[0086] The above specific embodiments are further explanations of the technical solutions and beneficial effects of the present invention, and are not intended to limit the implementation methods. For those skilled in the art, any obvious substitutions that do not depart from the concept of the present invention are within the scope of protection of the present invention.

Claims

1. A method for preparing a self-repairing polyurethane hot melt adhesive, characterized in that: The steps include: (1) Under the protection of inert gas, polycaprolactone diol and polycarbonate diol are mixed with a solvent to obtain material A; dicyclohexylmethane diisocyanate and isophorone diisocyanate are mixed with a solvent, and then a catalyst is added to mix to obtain material B; a blocking agent is mixed with a solvent to obtain material C; copper acetylacetonate and stearic acid are mixed, and then a solvent is added to mix to obtain material D; (2) adding material B dropwise to material A to react, and after the residual isocyanate content in the system drops to the target value, adding material C dropwise to react, and removing part of the solvent from the obtained product to obtain a mixture 1; (3) adding a mixed solution of 2,2'-dithiodiethanol and a solvent to the mixture 1 to react; then adding material D dropwise to react, and then adding a tackifying resin and a compatibilizer to keep warm to obtain a mixture 2; (4) removing the solvent from the obtained mixture, then adding a filler and a silane coupling agent mixture and an auxiliary agent, and performing melt blending and granulation to obtain a self-repairing polyurethane hot melt adhesive.

2. The self-repairing polyurethane hot melt adhesive according to claim 1, characterized in that: In step (1), 40-50 parts of polycaprolactone diol, 30-40 parts of polycarbonate diol and 75-85 parts of solvent are uniformly mixed to obtain material A.

3. The self-repairing polyurethane hot melt adhesive according to claim 2, characterized in that: In step (1), 15-25 parts of dicyclohexylmethane diisocyanate, 10-20 parts of isophorone diisocyanate and 55-65 parts of solvent are uniformly mixed, and then 0.1-1 parts of catalyst are added, and the mixture is kept warm at 55-65° C. for 1-10 minutes to obtain material B.

4. The self-repairing polyurethane hot melt adhesive according to claim 1, characterized in that: In step (1), 8-15 parts of a capping agent and 25-35 parts of a solvent are uniformly mixed to obtain material C.

5. The self-repairing polyurethane hot melt adhesive according to claim 1, characterized in that: In step (1), 1-3 parts of copper acetylacetonate and 0.9-3.3 parts of stearic acid are mixed uniformly, kept warm at 55-65° C. for 40-80 minutes, and then 15-25 parts of solvent are added and mixed uniformly to obtain material D.

6. The self-repairing polyurethane hot melt adhesive according to claim 1, characterized in that: In step (2), material B is added dropwise to material A. After the residual isocyanate content in the system drops to 3-8%, material C is added and reacted at 50-60° C. for 4-6 hours. The solvent is removed from the obtained product to obtain mixture 1.

7. The self-repairing polyurethane hot melt adhesive according to claim 1, characterized in that: In step (3), a mixture consisting of 2-5 parts of 2,2'-dithiodiethanol and 8-12 parts of a solvent is added to the mixture one, and the mixture is reacted at 55-65°C for 10-30 minutes; material D is then added dropwise, and the mixture is reacted at 55-65°C for 3-5 hours. Then, 5-10 parts of a tackifying resin and 3-6 parts of a compatibilizer are added, and the mixture is kept warm for 40-80 minutes to obtain a mixture two.

8. The self-repairing polyurethane hot melt adhesive according to claim 1, characterized in that: In step (4), the solvent is removed from the obtained mixture, and a mixture consisting of 3-10 parts of filler and 2-5 parts of silane coupling agent and 2.5-9 parts of auxiliary agent are added, and then melt-blending and granulation are carried out to obtain self-repairing polyurethane hot melt adhesive particles.

9. The self-repairing polyurethane hot melt adhesive according to claim 8, characterized in that: In step (4), each part of the auxiliary agent comprises the following raw materials in parts by weight: 1-3 parts of antioxidant, 1-3 parts of light stabilizer and 0.5-3 parts of defoaming agent.

10. A self-repairing polyurethane hot melt adhesive, characterized by: The self-repairing polyurethane hot melt adhesive is prepared by the preparation method of the self-repairing polyurethane hot melt adhesive according to any one of claims 1 to 9.

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