A moisture-curing reactive polyurethane hot melt adhesive for shoes and its preparation method

Abstract

This application relates to the field of adhesives, and specifically discloses a moisture-curing reactive polyurethane hot melt adhesive for shoes and its preparation method. Among them, the raw materials for preparing the moisture-curing reactive polyurethane hot melt adhesive for shoes include polyester polyol, polyether polyol, isocyanate, composite coupling agent-modified kaolin, chain extender, antioxidant, and catalyst. Among them, the raw materials for preparing the composite coupling agent-modified kaolin include titanate coupling agent, aluminate coupling agent, and nano-kaolin. The nano-kaolin can form a microscopic barrier structure in the hot melt adhesive, reduce the porosity, lower the water penetration, reduce the erosion of water molecules on the internal structure of the adhesive, and through the modification of the composite coupling agent, improve the compatibility of the nano-kaolin, form a dense adhesive layer, thereby improving the water resistance of the hot melt adhesive.

Description

Technical Field

[0001] The present invention relates to the field of adhesives, and particularly to a moisture-curing reactive polyurethane hot melt adhesive for shoes and a preparation method thereof. Background Art

[0002] As a solvent-free and environmentally friendly adhesive, reactive polyurethane (PUR) hot melt adhesive has advantages such as excellent bonding performance, mechanical properties, and low VOC emissions, and has been widely used in various industrial fields. The reactive polyurethane hot melt adhesive is heated and melted under the condition of inhibiting chemical reactions to form a fluid state convenient for coating. Subsequently, when two adherends are bonded together, the adhesive layer will quickly coagulate and play a bonding role. Finally, by reacting with moisture in the air or attached to the surface of the adherend, chain extension occurs to generate a high-polymer polymer with high polymerization force, thereby significantly improving the adhesive force and heat resistance.

[0003] The main raw materials of polyurethane hot melt adhesive are polyisocyanate and polyol. Among them, polyester polyol contains a large number of ester bonds (-COO-), has strong polarity, cohesive strength, and crystallization performance, and the prepared hot melt adhesive often has good bonding performance. However, due to the easy hydrolysis of the ester group at high temperature, the bonding strength is reduced, especially in a humid environment, and its water resistance performance is not good. This problem is particularly prominent in footwear products because shoes often need to withstand tests in humid environments such as washing during use and are prone to delamination. Summary of the Invention

[0004] In order to improve the poor water resistance of polyurethane hot melt adhesive and extend the service life of the hot melt adhesive, the present application provides a moisture-curing reactive polyurethane hot melt adhesive for shoes and a preparation method thereof.

[0005] In the first aspect, a moisture-curing reactive polyurethane hot melt adhesive for shoes provided by the present application adopts the following technical solution: A moisture-curing reactive polyurethane hot melt adhesive for shoes, prepared from the following raw materials by weight: 20-30 parts of polyester polyol, 40-50 parts of polyether polyol, 25-35 parts of isocyanate, 10-20 parts of composite coupling agent-modified kaolin, 2-4 parts of chain extender, 0.5-0.7 part of antioxidant, and 0.02-0.04 part of catalyst;

[0006] The preparation raw materials of the composite coupling agent-modified kaolin include titanate coupling agent, aluminate coupling agent, and nano kaolin, and the weight ratio of the titanate coupling agent, aluminate coupling agent, and nano kaolin is (0.3-0.5):(0.1-0.3):(8-10).

[0007] By adopting the above technical solutions, polyester polyol and polyether polyol serve as the soft segments in polyurethane, and isocyanate serves as the hard segment in polyurethane. Among them, the polyester polyol contains a large number of ester groups, has strong polarity, relatively high cohesive energy, and good adhesion performance. The polyether polyol contains a large number of ether bonds, and the ether bonds are not easily hydrolyzed. Therefore, the polyester polyol and the polyether polyol are compounded and used, so that the hot melt adhesive in this application has better adhesion and water resistance. The end of the isocyanate molecular chain has an -NCO group. The -NCO group can react with the moisture in the air and the adsorbed water on the substrate surface to form urea bonds, resulting in cross-linking and curing. The polar groups can also interact with each other to form strong hydrogen bonds, improving the adhesion strength of the hot melt adhesive. Nano kaolin can form a microscopic barrier structure in the hot melt adhesive, reduce the porosity, can reduce the penetration of moisture, reduce the erosion of water molecules on the internal structure of the adhesive, and the nano kaolin itself has good chemical stability and is not easily reacted with water, which can slow down the chemical degradation of the hot melt adhesive in a humid environment. And under the modification of the composite coupling agent, the compatibility of nano kaolin in the polyurethane hot melt adhesive is improved, and the internal structure of the hot melt adhesive is not easily damaged, thereby improving the hydrolysis stability of the hot melt adhesive.

[0008] Preferably, the titanate coupling agent is at least one of bis(dioctyl pyrophosphate) glycolato titanate and dicarboxylato ethylene titanate; the aluminate coupling agent is at least one of di(isopropyl aluminate bis(distearoyl glycerol ester)), di(isopropyl aluminate bis(distearoyl diglycol ester)), and di(isopropyl aluminate bis(oleoyl diglycol ester)).

[0009] By adopting the above technical solutions, the alkoxy groups in the titanate coupling agent and the aluminate coupling agent are hydrolyzed and combined with the hydroxyl groups on the surface of kaolin to form an organic active monolayer on the surface of kaolin, which is beneficial to improving the compatibility of kaolin in the molten system. The barrier effect of nano kaolin is further exerted, making the surface structure of the adhesive layer more compact, and it is difficult for moisture to diffuse into the interior of the adhesive layer, thereby playing a waterproof role and extending the service life of the hot melt adhesive.

[0010] Preferably, the isocyanate is at least one of isophorone diisocyanate, hexamethylene diisocyanate, and dicyclohexylmethane diisocyanate.

[0011] By adopting the above technical solutions, the hot melt adhesive prepared with the above aliphatic isocyanate has good durability and light stability, making the hot melt adhesive not easily turn yellow, having a long service life, and having less impact on the environment.

[0012] Preferably, the polyester polyol is at least one of polyethylene glycol-propylene glycol adipate diol and polyethylene glycol adipate diglycol.

[0013] By adopting the above technical solution, the combination of the above polyester polyol and isocyanate has a good effect, has strong cohesion and crystallization properties, and the prepared hot melt adhesive has a relatively high bonding strength.

[0014] Preferably, the polyether polyol is at least one of polytetrahydrofuran ether diol and polypropylene glycol.

[0015] By adopting the above technical solution, the hot melt adhesive prepared from the above polyether polyol has a relatively low glass transition temperature, has good flexibility, and has good compatibility with isocyanate and polyester polyol, and has good processing performance.

[0016] Preferably, the chain extender is at least one of ethylenediamine, N,N-dihydroxy(diisopropyl)aniline, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, neopentyl glycol, sorbitol, and diethylaminoethanol.

[0017] By adopting the above technical solution, the chain extender reacts with the functional groups in the polyurethane prepolymer to increase the length of the molecular chain, thereby improving the cohesion of the hot melt adhesive and enhancing the adhesion between the polyurethane and the substrate. At the same time, the chain extender can affect the curing speed of the hot melt adhesive, thereby controlling the transition speed of the hot melt adhesive from liquid to solid.

[0018] Preferably, the antioxidant is at least one of antioxidant 264, antioxidant 1076, and antioxidant 1010.

[0019] By adopting the above technical solution, polyurethane is prone to thermal-oxidative degradation and photo-degradation under light and heat conditions, and the addition of antioxidants can improve the heat resistance of polyurethane, reduce the problem of degradation of polyurethane in a thermal-oxidative environment, and improve the stability of polyurethane. The mechanism of action of the antioxidant is to reduce the cleavage of carbon-hydrogen bonds in the molecular structure and prevent the oxidation reaction from proceeding, thereby achieving the antioxidant effect and helping to maintain the bonding strength and bonding performance of the hot melt adhesive.

[0020] Preferably, the catalyst is an organic zirconium catalyst.

[0021] By adopting the above technical solution, the organic zirconium catalyst has an obvious effect on the -NCO / -OH reaction, stabilizes the intermediate formed during the reaction, reduces the reaction activation energy, and at the same time promotes the formation of ion pairs, thereby accelerating the reaction rate, reducing the occurrence of side reactions, reducing the generation of CO2, thereby reducing the generation of bubbles in the product and improving the mechanical properties of the hot melt adhesive.

[0022] In the second aspect, a preparation method of a wet-curing reactive polyurethane hot melt adhesive for shoes provided by the present application adopts the following technical solution:

[0023] A preparation method of a moisture-curing reactive polyurethane hot melt adhesive for shoes, comprising the following steps:

[0024] Weigh the raw materials according to the component ratio, mix the polyester polyol and polyether polyol in a vacuum environment, stir and react at 120 - 130 °C for 30 - 40 min. Under the protection of nitrogen, cool down to 80 - 90 °C and add isocyanate and chain extender, react for 1 - 2 h. Then add composite coupling agent modified kaolin, chain extender, antioxidant and catalyst, and react at 65 - 75 °C for 2 - 3 h to obtain the moisture-curing reactive polyurethane hot melt adhesive for shoes.

[0025] By adopting the above technical solution, after mixing the polyester polyol, polyether polyol and isocyanate, then adding the composite coupling agent modified kaolin, under the reinforcement of the composite coupling agent modified kaolin, the internal structure of the hot melt adhesive is stabilized to improve the water resistance of the hot melt adhesive.

[0026] Preferably, the preparation method of the composite coupling agent modified kaolin is as follows:

[0027] ① Place kaolin in a NaOH solution, stir at 45 - 55 °C for 2 - 3 h, then alternately wash with deionized water and alcohol, carry out vacuum filtration to remove excess water, and dry to obtain pretreated kaolin;

[0028] ② Mix the titanate coupling agent and aluminate coupling agent to obtain a composite coupling agent. Then add the composite coupling agent to an ethanol solution, adjust the pH to 6.5 - , hydrolyze for 1 - 2 h to obtain a hydrolyzed coupling agent solution. Then add the pretreated kaolin to the hydrolyzed coupling agent solution, stir at 50 - 60 °C for 2 - 3 h, then alternately wash with deionized water and alcohol, filter and dry to obtain the composite coupling agent modified kaolin.

[0029] By adopting the above technical solution, the composite coupling agent modified kaolin prepared by the above preparation method has the characteristics of structural stability and strong surface properties, which is beneficial to giving full play to the hydrolysis stability of the composite coupling agent modified kaolin.

[0030] This application has the following beneficial effects:

[0031] In this application, polyester polyol and polyether polyol serve as the soft segments in polyurethane, and isocyanate serves as the hard segment in polyurethane. Among them, polyester polyol contains a large number of ester groups, has strong polarity, relatively high cohesive energy, and good adhesion performance. While polyether polyol contains a large number of ether bonds, and ether bonds are not easily hydrolyzed. Therefore, polyester polyol and polyether polyol are compounded and used, so that the hot melt adhesive in this application has better adhesion and water resistance. The end of the isocyanate molecular chain has -NCO groups. The -NCO groups can react with the moisture in the air and the adsorbed water on the surface of the substrate to form urea bonds, resulting in crosslinking and curing. The polar groups can also interact with each other to form strong hydrogen bonds, improving the adhesion strength of the hot melt adhesive. Nano kaolin can form a microscopic barrier structure in the hot melt adhesive, reduce the porosity, can reduce the penetration of moisture, reduce the erosion of the internal structure of the adhesive by water molecules, and nano kaolin itself has good chemical stability and is not easily reacted with water, which can slow down the chemical degradation of the hot melt adhesive in a humid environment. And under the modification of the composite coupling agent, the compatibility of nano kaolin in the polyurethane hot melt adhesive is improved, so that the internal structure of the hot melt adhesive is not easily damaged, thereby improving the hydrolysis stability of the hot melt adhesive. Detailed implementation mode

[0032] Preparation example

[0033] Preparation example 1

[0034] Preparation method of composite coupling agent modified kaolin:

[0035] ① Place 8 kg of nano kaolin in NaOH solution, stir at 45 °C for 2 h, carry out vacuum filtration to remove excess moisture, and dry to obtain pretreated kaolin;

[0036] ② Mix 0.3 kg of bis(octylpyrophosphate)glycolato titanate and 0.1 kg of isopropyl bis(distearoylglycerolate) aluminate to obtain a composite coupling agent. Then add the composite coupling agent to an ethanol solution, adjust the pH to 6.5, hydrolyze for 1 h to obtain a hydrolyzed coupling agent solution, and then add the pretreated kaolin to the hydrolyzed coupling agent solution, stir at 50 °C for 2 h, filter and dry to obtain composite coupling agent modified kaolin.

[0037] Preparation example 2

[0038] Preparation method of composite coupling agent modified kaolin:

[0039] ① Place 9 kg of nano kaolin in NaOH solution, stir at 50 °C for 2.5 h, carry out vacuum filtration to remove excess moisture, and dry to obtain pretreated kaolin;

[0040] ② Mix 0.4 kg of dicarboxyethylenedititanate and 0.2 kg of isopropyl bis(diglycol stearate) aluminate to obtain a composite coupling agent. Then add the composite coupling agent to an ethanol solution, adjust the pH to 7.0, and hydrolyze for 1.5 h to obtain a hydrolyzed coupling agent solution. Next, add the pretreated kaolin to the hydrolyzed coupling agent solution, stir at 55 °C for 2.5 h, filter and dry to obtain composite coupling agent-modified kaolin.

[0041] Preparation Example 3

[0042] Preparation method of composite coupling agent-modified kaolin:

[0043] ① Place 10 kg of nano-kaolin in a NaOH solution, stir at 50 °C for 3 h, carry out vacuum filtration under reduced pressure to remove excess moisture, and dry to obtain pretreated kaolin;

[0044] ② Mix 0.5 kg of bis(octylpyrophosphate)glycolato titanate and 0.3 kg of isopropyl bis(diglycol oleate) aluminate to obtain a composite coupling agent. Then add the composite coupling agent to an ethanol solution, adjust the pH to 7.5, and hydrolyze for 2 h to obtain a hydrolyzed coupling agent solution. Next, add the pretreated kaolin to the hydrolyzed coupling agent solution, stir at 60 °C for 3 h, filter and dry to obtain composite coupling agent-modified kaolin.

[0045] Example

[0046] Example 1

[0047] A moisture-curing reactive polyurethane hot melt adhesive for shoes, comprising 20 kg of polyethylene glycol-propylene glycol adipate diol (molecular weight 2000), 40 kg of polytetrahydrofuran ether diol (molecular weight 2000), 25 kg of isophorone diisocyanate, 10 kg of composite coupling agent-modified kaolin (prepared in Preparation Example 1), 2 kg of 1,4-butanediol, 0.5 kg of antioxidant 1076, and 0.02 kg of tetrabutyl zirconate.

[0048] Among them, the preparation method of the moisture-curing reactive polyurethane hot melt adhesive for shoes in this example includes the following steps:

[0049] Weigh the raw materials according to the component ratio, mix polyethylene glycol-propylene glycol adipate diol and polytetrahydrofuran ether diol, and evacuate. Stir and react at 120 °C for 30 min. Under the protection of nitrogen, cool down to 80 °C and add isophorone diisocyanate and 1,4-butanediol, react for 1 h, then add composite coupling agent-modified kaolin, antioxidant 1076 and tetrabutyl zirconate, and react at 65 °C for 2 h to obtain a moisture-curing reactive polyurethane hot melt adhesive for shoes.

[0050] Example 2

[0051] A moisture-curing reactive polyurethane hot melt adhesive for shoes, comprising 25 kg of polyethylene adipate diglycol (molecular weight 3000), 45 kg of polypropylene glycol (molecular weight 2000), 30 kg of hexamethylene diisocyanate, 15 kg of composite coupling agent-modified kaolin (prepared in Preparation Example 2), 3 kg of N,N-dihydroxy(diisopropyl)aniline, 0.6 kg of antioxidant 1010, and 0.03 kg of tetrabutyl zirconate.

[0052] Among them, the preparation method of the moisture-curing reactive polyurethane hot melt adhesive for shoes in this example includes the following steps:

[0053] Weigh the raw materials according to the component ratio, mix the polyethylene adipate diglycol and polypropylene glycol, evacuate, stir and react at 125 °C for 35 min. Under the protection of nitrogen, cool down to 85 °C and add hexamethylene diisocyanate and N,N-dihydroxy(diisopropyl)aniline, react for 1.5 h, then add the composite coupling agent-modified kaolin, antioxidant 1010 and tetrabutyl zirconate, and react at 70 °C for 2.5 h to obtain the moisture-curing reactive polyurethane hot melt adhesive for shoes.

[0054] Example 3

[0055] A moisture-curing reactive polyurethane hot melt adhesive for shoes, comprising 30 kg of polyethylene adipate diglycol (molecular weight 2000), 50 kg of polytetrahydrofuran ether glycol (molecular weight 3000), 35 kg of dicyclohexylmethane diisocyanate, 20 kg of composite coupling agent-modified kaolin (prepared in Preparation Example 3), 4 kg of ethylenediamine, 0.7 kg of antioxidant 264, and 0.04 kg of tetrabutyl zirconate.

[0056] Among them, the preparation method of the moisture-curing reactive polyurethane hot melt adhesive for shoes in this example includes the following steps:

[0057] Weigh the raw materials according to the component ratio, mix the polyethylene adipate diglycol and polytetrahydrofuran ether glycol, evacuate, stir and react at 130 °C for 40 min. Under the protection of nitrogen, cool down to 90 °C and add dicyclohexylmethane diisocyanate and ethylenediamine, react for 2 h, then add the composite coupling agent-modified kaolin, antioxidant 264 and tetrabutyl zirconate, and react at 75 °C for 3 h to obtain the moisture-curing reactive polyurethane hot melt adhesive for shoes.

[0058] Example 4

[0059] A moisture-curing reactive polyurethane hot melt adhesive for shoes, which is different from Example 1 in that isophorone diisocyanate is replaced with an equal amount of diphenylmethane diisocyanate.

[0060] Comparative Example

[0061] Comparative Example 1

[0062] A moisture-curing reactive polyurethane hot melt adhesive for shoes, which is different from that in Example 1 in that the composite coupling agent-modified kaolin is replaced with an equal amount of nano kaolin.

[0063] Comparative Example 2

[0064] A moisture-curing reactive polyurethane hot melt adhesive for shoes, which is different from that in Example 1 in that the composite coupling agent-modified kaolin is replaced with an equal amount of titanate coupling agent-modified kaolin.

[0065] Comparative Example 3

[0066] A moisture-curing reactive polyurethane hot melt adhesive for shoes, which is different from that in Example 1 in that the composite coupling agent-modified kaolin is replaced with an equal amount of aluminate coupling agent-modified kaolin.

[0067] Comparative Example 4

[0068] A moisture-curing reactive polyurethane hot melt adhesive for shoes, which is different from that in Example 1 in that the composite coupling agent-modified kaolin is not added.

[0069] Performance detection test

[0070] 1. Water resistance test: The samples bonded with the hot melt adhesives prepared in Examples 1-4 and Comparative Examples 1-4 were aged in air, hot water (80 °C) and cold water (30 °C) for 7 days respectively, and then dried in an environment with 25% and 50% relative humidity for 1 day. Referring to QJ 1634A-96 "Test Method for Compressive Shear Strength of Adhesives", the compressive shear strength test was carried out on the bonded samples, and the test results are shown in Table 1.

[0071] 2. Water absorption test: The samples bonded with the hot melt adhesives prepared in Examples 1-4 and Comparative Examples 1-4 were placed in an oven at 70 °C and dried to a constant weight. Record their initial mass as m0, then soak the samples in deionized water at room temperature for 24 h, take them out and quickly dry the surface moisture with a paper towel and weigh them, record the mass as m1, then the water absorption rate (η) of the samples after soaking for 24 h is calculated according to formula (1):

[0072]

[0073] The water absorption rate can characterize the ability of water molecules to enter the binder. The larger the water absorption rate, the easier it is for water to cause erosion of the adhesive layer.

[0074] 3. Melting Viscosity Test: Refer to the standard HG / T 3660-1999 to measure the melting viscosity of the sample. Place the sealed hot melt adhesive sample in an oven and heat it for about 30 min until the sample becomes a molten fluid. Subsequently, quickly pour it into the sleeve of an SNB-2 rotational viscometer, set the temperature and keep it for about 2 min to make the internal temperature of the glue sample uniform, and finally measure the constant-temperature melting viscosity of PURHMA.

[0075] Table 1

[0076]

[0077] From the comparison between Example 1 and Comparative Example 1 and the data in Table 1, it can be seen that when nano kaolin is directly added to the raw materials without modification, due to the poor compatibility between nano kaolin and the molten system, the formed cross-linked structure is not stable enough, resulting in the easy hydrolysis of the hot melt adhesive. On the contrary, by modifying nano kaolin with a composite coupling agent, the compatibility of nano kaolin in the polyurethane hot melt adhesive can be improved, making the internal structure of the hot melt adhesive not easily damaged, thereby improving the hydrolysis stability of the hot melt adhesive.

[0078] From the comparison between Example 1 and Comparative Examples 2-3 and the data in Table 1, it can be seen that the modification effect of using a single coupling agent on nano kaolin is not obvious. When using a composite coupling agent to modify nano kaolin, an organic active monomolecular layer can be formed on the surface of kaolin, improving the compatibility of nano kaolin in the molten system, capable of forming a microscopic barrier structure in the hot melt adhesive, reducing the porosity, reducing the penetration of moisture, and reducing the erosion of water molecules on the internal structure of the adhesive, thereby improving the water resistance of the hot melt adhesive. At the same time, it also has a certain promoting effect on improving the bonding performance of the hot melt adhesive.

[0079] From the comparison between Example 1 and Comparative Example 4 and the data in Table 1, it can be seen that when kaolin is not modified with a composite coupling agent, the water resistance of the hot melt adhesive is poor. On the contrary, after adding a composite coupling agent to modify kaolin, the hydrolysis stability of the hot melt adhesive can be improved. Due to the formation of a physical barrier by nano kaolin in the hot melt adhesive, the penetration of water molecules is slowed down, and at the same time, the stability of the cross-linked network structure of the hot melt adhesive can be improved, increasing the bonding performance of the hot melt adhesive.

[0080] From the comparison between Example 1 and Example 4 and the data in Table 1, it can be seen that compared with aliphatic isocyanates, aromatic isocyanates have poor hydrolysis resistance, especially in a humid environment. Aliphatic isocyanates show better chemical stability due to the absence of a benzene ring structure.

[0081] This specific embodiment is only an interpretation of the present application and does not limit the present application. After reading this specification, those skilled in the art can make modifications to this specific embodiment without creative contributions as needed, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A moisture-curing reactive polyurethane hot melt adhesive for shoes, characterized in that, By weight parts, it is prepared from the following raw materials: 20 - 30 parts of polyester polyol, 40 - 50 parts of polyether polyol, 25 - 35 parts of isocyanate, 10 - 20 parts of composite coupling agent - modified kaolin, 2 - 4 parts of chain extender, 0.5 - 0.7 part of antioxidant, and 0.02 - 0.04 part of catalyst; The preparation raw materials of the composite coupling agent - modified kaolin include dicarboxyethylenedi - titanate, isopropyl bis(distearoylglycerolate) aluminate, and nano - kaolin, and the weight ratio of dicarboxyethylenedi - titanate, isopropyl bis(distearoylglycerolate) aluminate, and nano - kaolin is (0.3 - 0.5):(0.1 - 0.3):(8 - 10).

2. The moisture-curing reactive polyurethane hot melt adhesive for shoes according to claim 1, wherein The isocyanate is at least one of isophorone diisocyanate, hexamethylene diisocyanate, and dicyclohexylmethane diisocyanate.

3. The moisture-curing reactive polyurethane hot melt adhesive for shoes according to claim 1, characterized in that, The polyester polyol is at least one of polyethylene glycol - propylene glycol adipate diol and polyethylene glycol adipate diol.

4. The moisture-curing reactive polyurethane hot melt adhesive for shoes according to claim 1, characterized in that, The polyether polyol is at least one of polytetrahydrofuran ether diol and polypropylene glycol.

5. The wet-curing reactive polyurethane hot melt adhesive for shoes according to claim 1, wherein The chain extender is at least one of ethylenediamine, N,N - dihydroxy(diisopropyl)aniline, 1,4 - butanediol, 1,6 - hexanediol, diethylene glycol, neopentyl glycol, sorbitol, and diethylaminoethanol.

6. The wet-curing reactive polyurethane hot melt adhesive for shoes according to claim 1, characterized in that, The antioxidant is at least one of antioxidant 264, antioxidant 1076, and antioxidant 1010.

7. The moisture-curing reactive polyurethane hot melt adhesive for shoes according to claim 1, characterized in that The catalyst is an organic zirconium - based catalyst.

8. The preparation method of a wet-curing reactive polyurethane hot melt adhesive for shoes according to any one of claims 1-7, characterized in that, It includes the following steps: Weigh the raw materials according to the component ratio, mix the polyester polyol and polyether polyol in a vacuum environment, stir - react at 120 - 130 °C for 30 - 40 min. Under the protection of nitrogen, cool down to 80 - 90 °C and add isocyanate and chain extender, react for 1 - 2 h, then add composite coupling agent - modified kaolin, chain extender, antioxidant, and catalyst, and react at 65 - 75 °C for 2 - 3 h to obtain the moisture - curable reaction - type polyurethane hot - melt adhesive for shoes.

9. The preparation method of a wet-curing reactive polyurethane hot melt adhesive for shoes according to claim 8, characterized in that, The preparation method of the composite coupling agent - modified kaolin is as follows: ① Place kaolin in a NaOH solution, stir at 45 - 55 °C for 2 - 3 h, carry out vacuum filtration to remove excess moisture, and dry to obtain pretreated kaolin; ② Mix titanate coupling agent and aluminate coupling agent to obtain a composite coupling agent, then add the composite coupling agent to an ethanol solution, adjust the pH to 6.5 - 7.5, hydrolyze for 1 - 2 h to obtain a hydrolyzed coupling agent solution, and then add the pretreated kaolin to the hydrolyzed coupling agent solution, stir at 50 - 60 °C for 2 - 3 h, filter and dry to obtain the composite coupling agent - modified kaolin.

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