EVA material for making shoe soles and its preparation process

Abstract

This invention relates to the field of shoe sole materials, and more particularly to an EVA material for making shoe soles and its preparation process. The invention uses raw materials including unsaturated alicyclic epoxy compounds, EVA resin, modified hollow epoxy microspheres, polyborosiloxane, foaming agent, vulcanization activator, activating aid, and free radical initiator. These are blended and crosslinked to obtain the EVA material. The cavities contained in the modified hollow epoxy microspheres act as a buffer under pressure, exhibiting strong recovery after deformation. The addition of polyborosiloxane effectively improves the high-temperature aging resistance of the EVA material, while the boron-oxygen bonds can break and recombine under stress, giving it self-healing properties.

Description

Technical Field

[0001] This invention relates to the field of shoe sole materials, specifically to an EVA material for making shoe soles and its preparation process. Background Technology

[0002] Ethylene-vinyl acetate copolymer (EVA) is a type of elastomer with excellent flexibility, elasticity, low-temperature flexural strength, and aging resistance. It can be processed into various products through injection molding, blow molding, extrusion, and compression molding, and has numerous applications, particularly in the midsoles of athletic shoes. EVA soles are lightweight, elastic, and comfortable, effectively mitigating the impact of the ground on the feet during walking and reducing the risk of sports injuries, making them popular with consumers. However, with the improvement of living standards, the tensile strength of traditional EVA sole materials is relatively low, making them prone to damage and cracking over long-term use, affecting the lifespan of the soles. Furthermore, the resilience of traditional EVA materials needs improvement; when subjected to external impact, its energy absorption and release capacity is limited, resulting in a poor feel during walking or exercise, failing to provide effective cushioning and support for the feet, easily causing foot fatigue, and reducing wearing comfort. Heat aging resistance is also a major challenge for EVA shoe sole materials. In high-temperature environments, such as summer sun exposure or prolonged exposure to warm environments, EVA materials are prone to thermo-oxidative aging, which leads to a decline in their mechanical properties, hardening, and brittleness, and loss of their original elasticity and flexibility, thereby affecting the service life and safety of the shoe sole.

[0003] Chinese patent CN118878969B discloses a high-elasticity EVA composite sole material, sole, and its preparation method. It is prepared by mixing thermoplastic polyester elastomer, EVA, stearic acid, zinc oxide, zinc stearate, 1,4-cyclohexanediol, magnesium oxide, crosslinking composite material, and AC foaming agent. Through an aldol ketation reaction, ketone groups are grafted onto silica, and further, a crosslinked molecular network is generated through the condensation reaction of the ketone groups with polyamide, giving the system better tensile strength and elasticity. However, the above-mentioned prior art does not improve the aging resistance of EVA materials; therefore, how to prepare a highly elastic and aging-resistant EVA sole material has become a key focus. Summary of the Invention

[0004] The purpose of this invention is to provide an EVA material for making shoe soles and its preparation process, so as to solve the problems existing in the prior art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0006] A process for preparing EVA material for making shoe soles includes the following steps:

[0007] S100. Using raw materials including unsaturated alicyclic epoxy compounds and EVA resin, unsaturated alicyclic epoxy compound graft-modified EVA resin is prepared.

[0008] S200: Modified epoxy microspheres are prepared using raw materials including hollow epoxy microspheres and aminosilane coupling agents.

[0009] S300: Unsaturated alicyclic epoxy compound grafted modified EVA resin and modified hollow epoxy microspheres are mixed and then kneaded to obtain a blend.

[0010] S400: The blend, polyborosiloxane, foaming agent, vulcanization activator, activating aid, and free radical initiator are mixed and then discharged after internal mixing. The mixture is then mixed with the catalyst on a two-roll mill, sheeted, and placed for molding and foaming to obtain a foamed material. The foamed material is then placed in water for cross-linking and dried to obtain the EVA material.

[0011] Furthermore, step S100 specifically includes:

[0012] S110. After reflux extraction of EVA resin with petroleum ether, the EVA resin is dried to constant weight to obtain purified EVA resin. The purified EVA resin is placed in toluene solution, heated to 75-85℃, and stirred until completely dissolved to obtain a transparent solution.

[0013] S120. Add peroxide initiator to transparent solution and stir until completely dissolved. Then add unsaturated aliphatic epoxy compound. Immediately after addition, add triethylamine and stir for 5-10 minutes. Then add hydroquinone, purge with nitrogen, raise the temperature to 85-95℃, and stir the reaction at a constant temperature for 3-6 hours to obtain the reaction solution.

[0014] S130. Pour the reaction solution into methanol, stir vigorously, filter and collect the precipitate, wash and dry to obtain the unsaturated alicyclic epoxy grafted modified EVA resin.

[0015] Furthermore, step S200 specifically includes:

[0016] S210. Add aminosilane coupling agent to an ethanol aqueous solution, and add glacial acetic acid to adjust the pH to 4.5-5.0 while stirring to obtain silane coupling agent hydrolysate.

[0017] S220. Add hollow epoxy microspheres to anhydrous ethanol and ultrasonically disperse for 20-40 minutes to form a microsphere suspension.

[0018] S230. The hydrolysate of the silane coupling agent is added dropwise to the microsphere suspension, the temperature is raised to 65-75℃ and stirred at a constant temperature for 4-6 hours, then cooled to room temperature, centrifuged and the supernatant is discarded. The precipitate is washed and dried to obtain the modified epoxy microspheres.

[0019] Furthermore, the preparation method of the hollow epoxy microspheres includes the following steps:

[0020] A1. Add epoxy resin, triethylenetetramine, Span-80, and polypropylene glycol diglycidyl ether to the reactor, raise the temperature to 40-50℃ and stir evenly. Then add distilled water dropwise, mix and stir to emulsify, and prepolymerize for 40-60 minutes to obtain W / O emulsion.

[0021] A2. Add distilled water, sodium dodecyl sulfate, emulsifier, and triethylenetetramine to the reactor. Raise the temperature to 60-90℃ and stir until homogeneous to obtain a mixed solution. Add the W / O emulsion dropwise to the mixed solution and stir thoroughly to obtain a W / O / W emulsion. Stir continuously at a constant temperature for 3-5 hours. After filtration and washing, obtain water-containing epoxy microspheres. After drying, obtain hollow epoxy microspheres.

[0022] Further, step S300 specifically includes: adding unsaturated alicyclic epoxy compound-grafted modified EVA resin into a torque rheometer, setting the temperature to 70-90℃ and the rotation speed to 40-60rpm, and after the torque stabilizes, adding modified hollow epoxy microspheres and mixing for 8-10min, increasing the temperature to 110-130℃ and the rotation speed to 60-80rpm, and mixing for 6-10min to obtain a blend.

[0023] Further, step S400 specifically includes: adding the blend to a torque rheometer, setting the temperature to 70-90℃ and the rotation speed to 40-60rpm, and after the torque stabilizes, adding polyborosiloxane, foaming agent, vulcanization activator, activation aid, and free radical initiator, mixing for 8-12 minutes, and then removing the glue. Then, adding a catalyst and mixing on a two-roll mill at 30-50℃, sheeting, and placing for 25-32 hours, followed by molding and foaming to obtain a foamed material. The foamed material is then soaked in water at 80-90℃ for 3-5 hours and dried in a vacuum drying oven to obtain the EVA material.

[0024] Furthermore, the mass ratio of the blend, polyborosiloxane, foaming agent, vulcanization activator, activation aid, free radical initiator, and catalyst is 100:8-10:3-4:4-8:1.5-3:0.5-2:0.1-1.

[0025] Furthermore, the conditions for compression molding foaming are as follows: at 150-160℃, first pre-compress with a pressure of 3-5MPa for 2-4 minutes, and then increase the pressure to 6-8MPa for 3-5 minutes.

[0026] The present invention also provides an EVA material for making shoe soles, which is prepared by the preparation process provided by any of the above technical solutions.

[0027] The present invention has the following beneficial effects:

[0028] This invention uses unsaturated alicyclic epoxy compounds grafted onto modified EVA resin as the sole substrate. The epoxy groups on its surface react with the amino groups on the surface of the added modified hollow epoxy microspheres, which helps to disperse the hollow epoxy microspheres. Furthermore, the modified hollow epoxy microspheres, as organic polymer materials, have better flexibility than inorganic particles. Under pressure, the cavities inside the hollow epoxy microspheres can act as a buffer, and they have strong recovery force after deformation. The addition of polyborosiloxane during blending effectively improves the high-temperature aging resistance of the EVA material. Simultaneously, the siloxane segments can reduce the surface friction coefficient and improve anti-slip performance, while the boron-oxygen bonds can break and recombine under stress, giving it self-healing properties. Detailed Implementation

[0029] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0030] The EVA resin (Aa content 28%) used in this invention was purchased from Arkema, France; toluene (AR, ≥99.5%) and 4-vinylcyclohexane (purity 98%) were purchased from Sinopharm Chemical Reagent Co., Ltd.; epoxy resin (epoxy value 0.51) was purchased from Sinopec Baling Petrochemical Branch; polypropylene glycol diglycidyl ether (V-207) was purchased from Shenzhen Huite Chemical Co., Ltd.; hydroxyl silicone oil (analytical grade) was purchased from Chengdu Kelong Chemical Co., Ltd.; and tetrahydroxydiborane (analytical grade) was purchased from Adamas Reagent Co., Ltd. All reagents used in this invention are commercially available.

[0031] Traditional shoe soles are generally made from high-molecular materials such as animal leather, natural rubber, and polyvinyl chloride (PVC), resulting in heavy soles with poor breathability and comfort. Ethylene-vinyl acetate copolymer (EVA) is a type of elastomer with excellent flexibility, elasticity, low-temperature flexural strength, and aging resistance. It is also lightweight and has excellent processing performance. However, EVA as a shoe material also has disadvantages such as poor abrasion resistance, low mechanical strength, and easy shrinkage and deformation.

[0032] Based on this, the present invention provides a preparation process for EVA material used in making shoe soles, the preparation process comprising the following steps:

[0033] S100. Using raw materials including unsaturated alicyclic epoxy compounds and EVA resin, unsaturated alicyclic epoxy compound graft-modified EVA resin is prepared.

[0034] S200: Modified epoxy microspheres are prepared using raw materials including hollow epoxy microspheres and aminosilane coupling agents.

[0035] S300: Unsaturated alicyclic epoxy compound grafted modified EVA resin and modified hollow epoxy microspheres are mixed and then kneaded to obtain a blend.

[0036] S400: The blend, polyborosiloxane, foaming agent, vulcanization activator, activating aid, and free radical initiator are mixed and then discharged after internal mixing. The mixture is then mixed with the catalyst on a two-roll mill, sheeted, and placed for molding and foaming to obtain a foamed material. The foamed material is then placed in water for cross-linking and dried to obtain the EVA material.

[0037] S100 specifically includes:

[0038] S110. After reflux extraction of EVA resin particles with petroleum ether for 18-34 h, the EVA resin particles are dried in a vacuum drying oven at 50-60℃ to constant weight to obtain purified EVA resin. The purified EVA resin is placed in toluene solution, heated to 75-85℃, and stirred until completely dissolved to obtain a transparent solution.

[0039] S120. Add peroxide initiator to transparent solution and stir until completely dissolved. Then, slowly add unsaturated aliphatic epoxy compound dropwise. After the addition is complete, add triethylamine immediately and stir for 5-10 minutes. Then add hydroquinone, purge with nitrogen, raise the temperature to 85-95℃, and stir the reaction at a constant temperature for 3-6 hours to obtain the reaction solution.

[0040] S130. Pour the reaction solution into methanol, stir vigorously, filter and collect the precipitate, wash it and dry it in a vacuum drying oven at 50-60℃ until constant weight to obtain the unsaturated alicyclic epoxy compound grafted modified EVA resin.

[0041] In step S100, the mass ratio of purified EVA resin, toluene solution, peroxide initiator, unsaturated aliphatic epoxy compound, triethylamine, hydroquinone, and methanol is 10:100-120:0.4-0.8:5-8:0.08-0.12:0.01-0.04:500-550.

[0042] In step S100, the unsaturated aliphatic epoxy compound is any one or a mixture of several of vinyl epoxy compounds, propylene epoxy compounds, and diene epoxy compounds. Further, the unsaturated aliphatic epoxy compound is one or a mixture of several of vinylcyclohexene oxide, 4-vinylcyclohexane oxide, allyl glycidyl ether, methyl allyl glycidyl ether, 1,3-butadiene epoxide, and epoxidized polybutadiene.

[0043] The peroxide initiator is one or a mixture of several of the following: di-tert-butyl peroxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, tert-butyl hydroperoxide, and tert-butyl peroxide.

[0044] In step S100, an epoxy functional group is introduced through the double bond addition of EVA chain free radicals and unsaturated epoxy compounds. At the same time, triethylamine and hydroquinone can play the role of regulating the reaction and terminating free radicals. The introduced epoxy groups provide reaction sites for the subsequent reaction with the hollow microspheres modified with aminosilane coupling agents.

[0045] S200 specifically includes:

[0046] S210. Slowly add aminosilane coupling agent dropwise to 95% ethanol aqueous solution, and add glacial acetic acid to adjust the pH to 4.5-5.0 while stirring. Continue stirring for 2-4 hours to obtain silane coupling agent hydrolysate; wherein the mass ratio of ethanol aqueous solution to aminosilane coupling agent is 100:4-8.

[0047] S220. Add hollow epoxy microspheres to anhydrous ethanol and ultrasonically disperse for 20-40 min to form a microsphere suspension; wherein the mass ratio of anhydrous ethanol to hollow epoxy microspheres is 200:8-12.

[0048] S230. The above-mentioned silane coupling agent hydrolysate is added dropwise to the microsphere suspension, the temperature is raised to 65-75℃ and stirred at a constant temperature for 4-6 hours, then cooled to room temperature, centrifuged and the supernatant is discarded. The precipitate is washed 3-5 times with anhydrous ethanol and then placed in a vacuum drying oven at 40-60℃ to dry to constant weight to obtain the modified hollow epoxy microspheres.

[0049] In step S200, the aminosilane coupling agent is any one or a mixture of several of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, phenylaminomethyltrimethoxysilane, γ-aminopropyltris(methylethoxy)silane, and N-octyl-γ-aminopropyltrimethoxysilane.

[0050] The method for preparing the hollow epoxy microspheres includes the following steps:

[0051] A1. Add epoxy resin, triethylenetetramine, Span-80, and polypropylene glycol diglycidyl ether to a reactor, raise the temperature to 40-50℃ and stir until homogeneous. Then, add distilled water dropwise, mix and emulsify, and prepolymerize for 40-60 minutes to obtain a W / O emulsion. The mass ratio of epoxy resin, triethylenetetramine, Span-80, polypropylene glycol diglycidyl ether, and distilled water is 10:0.8-1.2:1.5-2.8:1.2-1.8:4-8.

[0052] A2. Add distilled water, sodium dodecyl sulfate, emulsifier, and triethylenetetramine to a reactor. Raise the temperature to 70-90℃ and stir until homogeneous to obtain a mixed solution. Add the W / O emulsion dropwise to the mixed solution and stir thoroughly to obtain a W / O / W emulsion. Stir continuously at a constant temperature for 3-5 hours. After filtration and washing, obtain water-containing epoxy microspheres. After drying, obtain hollow epoxy microspheres. The mass ratio of distilled water, sodium dodecyl sulfate, emulsifier, and triethylenetetramine is 100:0.3-0.45:8-12:7-9.

[0053] In step A2, the emulsifier is one or a mixture of several of Tween-80, Tween-60, OP-10, SDBS, NH4DS, and CTAB.

[0054] In step S200, EVA material has low hardness, and pure EVA material is insufficient to meet the deformation resistance requirements of shoe soles. Adding filler allows the filler particles to be evenly dispersed in the EVA matrix, forming a skeletal support that increases hardness. Simultaneously, the filler, acting as an "anti-wear skeleton," can share frictional stress, reducing direct wear on the EVA matrix. Existing technologies often add inorganic particles as fillers, but due to the limited deformation capacity of inorganic materials, their toughening ability is limited. Compared to inorganic materials, organic polymer materials have better flexibility and energy absorption capacity. Therefore, this invention uses epoxy microspheres as fillers. Epoxy powder has excellent mechanical properties; when subjected to pressure, epoxy microspheres can hinder crack development. To further improve the elastic deformation absorption of impact force by epoxy microspheres, this invention further uses hollow epoxy microspheres as fillers. Hollow epoxy microspheres have internal cavities, resulting in low overall density. Under stress, the outer shell can undergo reversible deformation, and the cavities act as buffers, resulting in high energy absorption efficiency and strong recovery force after deformation. To improve its compatibility with EVA materials, an aminosilane coupling agent was used to modify it. The aminosilane coupling agent was grafted onto the surface of hollow epoxy microspheres through Si-O-Si covalent bonds, while the amino groups were exposed on the surface, providing reaction sites for subsequent reactions with unsaturated alicyclic epoxy compounds to modify EVA resin.

[0055] S300 specifically includes: adding unsaturated alicyclic epoxy grafted modified EVA resin into a torque rheometer, setting the temperature to 70-90℃ and the rotation speed to 40-60 rpm, and after the torque stabilizes, adding modified hollow epoxy microspheres and mixing for 8-10 min, increasing the temperature to 110-130℃ and the rotation speed to 60-80 rpm, and mixing for 6-10 min to obtain a blend; wherein the mass ratio of unsaturated alicyclic epoxy grafted modified EVA resin to modified hollow epoxy microspheres is 90-110:10-15.

[0056] S400 specifically includes: adding the blend to a torque rheometer, setting the temperature to 70-90℃ and the rotation speed to 40-60rpm, and after the torque stabilizes, adding polyborosiloxane, foaming agent, vulcanization activator, activation aid, and free radical initiator, mixing for 8-12 minutes, and then removing the glue. Then, adding a catalyst and mixing on a two-roll mill at 30-50℃, sheeting, and placing for 25-32 hours, followed by molding and foaming to obtain a foamed material. The foamed material is then soaked in water at 80-90℃ for 3-5 hours and then dried in a vacuum drying oven to obtain the EVA material.

[0057] In step S400, the preparation method of polyborosiloxane is as follows: under room temperature conditions, hydroxyl silicone oil, tetrahydroxydiborane, methanol and ethyl acetate are added to a reactor, stirred and then dried in a vacuum oven at 95-105℃ for 10-15h to obtain the product. The mass ratio of hydroxyl silicone oil, tetrahydroxydiborane, methanol and ethyl acetate is 100:1-3:200-300:100-150.

[0058] In step S400, the mass ratio of the blend, polyboronsiloxane, foaming agent, vulcanization activator, activation aid, free radical initiator, and catalyst is 100:8-12:3-4:4-8:1.5-3:0.5-2:0.1-0.8; the molding foaming conditions are: at 150-160℃, first pre-compressed at 3-5MPa pressure for 2-4min, then increased to 6-8MPa pressure for 3-5min.

[0059] The foaming agents are azodicarbonamide, sodium bicarbonate, and N,N / - One or a mixture of dinitrospentamethylenetetramine and polybutadiene; the activator is one or a mixture of zinc oxide, magnesium oxide, lead oxide, and zinc carbonate; the activator is one or a mixture of zinc stearate, calcium stearate, paraffin wax, and oleamide; the free radical initiator is one or a mixture of dicumyl peroxide, benzoyl peroxide, and di-tert-butyl peroxide; the catalyst is one or a mixture of dibutyltin dilaurate, dibutyltin dioctanoate, bismuth isooctanoate, bismuth neodecanoate, dibutyltin oxide, tetrabutyl titanate, tetraisopropyl titanate, zinc acetate, zinc chloride, dibutyltin diacetate, dibutyltin oxide, and isopropyltristearate titanate.

[0060] In the above steps, the unsaturated alicyclic epoxy graft modified EVA resin is gradually melted. After the torque stabilizes, the unsaturated alicyclic epoxy graft modified EVA resin forms a uniform molten matrix, providing a stable carrier for the dispersion of modified hollow epoxy microspheres. After modification with an aminosilane coupling agent, the amino groups on the surface of the hollow epoxy microspheres can react with the epoxy groups on the unsaturated alicyclic epoxy compound. EVA materials have poor heat resistance, are prone to aging, and have a low coefficient of friction. However, the thermal stability of the silicon-oxygen bonds in polyboron siloxanes can compensate for the shortcomings of EVA materials, allowing them to withstand high-temperature aging. The siloxane segments can reduce the surface friction coefficient and improve anti-slip performance. At the same time, the boron-oxygen bonds can break and recombine under stress, giving them self-healing properties. In polyboron siloxanes, boron atoms are directly connected through chemical bonds, double bonds, aromatic rings, etc., forming a "boron-bond" structure. Compared with the single boron structure, this significantly increases the crosslinking density. Furthermore, the synergistic effect of the boron-bond structure and the silicon-oxygen bonds results in a higher dynamic bond density and superior self-healing efficiency. In step S400, the polyborosiloxane molecules contain active groups that can interact with the hydroxyl groups in the blend and the ester groups in the EVA material, enhancing the compatibility between the siloxane and the matrix and providing sites for subsequent crosslinking. Furthermore, under the action of the peroxide initiator, C-C covalent bonds are formed between the molecular chains to construct a three-dimensional network structure. Finally, in a water bath, under the action of a catalyst, wet crosslinking is carried out to obtain a peroxide-crosslinked and wet-crosslinked double-crosslinked foam material.

[0061] Example 1

[0062] S1. EVA resin particles were extracted by reflux with petroleum ether for 28 hours and then dried in a vacuum drying oven at 55°C to constant weight to obtain purified EVA resin. 10 parts by weight of purified EVA resin were placed in 110 parts by weight of toluene solution, heated to 80°C and stirred until completely dissolved to obtain a transparent solution.

[0063] S2. Add 0.6 parts by weight of benzoyl peroxide to the transparent solution obtained in step S1, stir until completely dissolved, then slowly add 6 parts by weight of 4-vinylepoxycyclohexane. Immediately after the addition is complete, add 0.1 parts by weight of triethylamine, stir for 8 minutes, then add 0.02 parts by weight of hydroquinone, purge with nitrogen, raise the temperature to 90°C, and stir the reaction at a constant temperature for 4 hours to obtain the reaction solution.

[0064] S3. Pour the reaction solution obtained in step S2 into 500 parts by weight of methanol, stir vigorously, filter and collect the precipitate, wash it 5 times with methanol and dry it in a vacuum drying oven at 55°C until constant weight to obtain unsaturated alicyclic epoxy compound grafted modified EVA resin.

[0065] S4. Add 10 parts by weight of epoxy resin, 1 part by weight of triethylenetetramine, 1.8 parts by weight of Span-80, and 1.6 parts by weight of polypropylene glycol diglycidyl ether to the reactor. Raise the temperature to 45°C and stir until homogeneous. Then add 6 parts by weight of distilled water dropwise and mix and emulsify. Prepolymerize for 50 minutes to obtain a W / O emulsion.

[0066] S5. Add 100 parts by weight of distilled water, 0.4 parts by weight of sodium dodecyl sulfate, 10 parts by weight of Tween-80, and 8 parts by weight of triethylenetetramine to the reactor. Raise the temperature to 80°C and stir until homogeneous to obtain a mixed solution. Add the W / O emulsion obtained in step S4 dropwise to the mixed solution and stir thoroughly to obtain a W / O / W emulsion. Stir continuously at a constant temperature for 4 hours. After filtration and washing, obtain water-containing epoxy microspheres. Place them in a vacuum drying oven at 60°C and dry to constant weight to obtain hollow epoxy microspheres.

[0067] S6. Slowly add 6 parts by weight of γ-aminopropyltriethoxysilane to 100 parts by weight of 95% ethanol aqueous solution, and add glacial acetic acid to adjust the pH to 4.5-5.0 while stirring. Continue stirring for 3 hours to obtain silane coupling agent hydrolysate.

[0068] S7. Add 10 parts by weight of hollow epoxy microspheres to 200 parts by weight of anhydrous ethanol, and disperse by ultrasonication for 30 min to form a microsphere suspension.

[0069] S8. The hydrolysate of the silane coupling agent obtained in step S4 is added dropwise to the microsphere suspension obtained in step S5. The temperature is raised to 70°C and stirred at a constant temperature for 5 hours. After cooling to room temperature, the supernatant is discarded by centrifugation. The precipitate is washed 5 times with anhydrous ethanol and then dried in a vacuum drying oven at 50°C to constant weight to obtain modified hollow epoxy microspheres.

[0070] S9. Add 100 parts by weight of unsaturated alicyclic epoxy grafted modified EVA resin to a torque rheometer, set the temperature to 80℃ and the speed to 50 rpm. After the torque stabilizes, add 12 parts by weight of modified hollow epoxy microspheres and mix for 9 min. Increase the temperature to 120℃ and the speed to 70 rpm, and mix for 8 min to obtain the blend.

[0071] S10. Add 100 parts by weight of the blend to a torque rheometer, set the temperature to 80℃ and the speed to 50 rpm. After the torque stabilizes, add 10 parts by weight of polyborosiloxane, 3.2 parts by weight of foaming agent, 6 parts by weight of vulcanization activator, 2.2 parts by weight of activating aid, and 1.2 parts by weight of free radical initiator. Mix for 10 minutes and then discharge the binder. Then add 0.6 parts by weight of catalyst and mix on a two-roll mill at 40℃. Sheet the mixture and let it stand for 28 hours. Then, perform molding and foaming to obtain the foamed material. Immerse the foamed material in 8... After being dried in water at 5℃ for 4 hours, the material was dried in a vacuum drying oven at 60℃ until constant weight to obtain EVA material. The preparation method of polyborosiloxane is as follows: at room temperature, 100 parts by weight of hydroxyl silicone oil, 1.5 parts by weight of tetrahydroxydiborane, 240 parts by weight of methanol and 80 parts by weight of ethyl acetate are added to a reactor, stirred and then dried in a vacuum oven at 100℃ for 14 hours. The molding foaming conditions are as follows: at 155℃, the material is first pre-compressed at 4MPa for 3 minutes, and then the pressure is increased to 7MPa for 4 minutes.

[0072] Example 2

[0073] Compared with Example 1, the amount of each raw material used in this embodiment is different in the preparation process, but the rest is the same as in Example 1, as follows:

[0074] S1, same as step S1 in Example 1;

[0075] S2. Add 0.4 parts by weight of benzoyl peroxide to the transparent solution obtained in step S1, stir until completely dissolved, then slowly add 5 parts by weight of 4-vinylepoxycyclohexane, and immediately add 0.08 parts by weight of triethylamine. After stirring for 5 minutes, add 0.01 parts by weight of hydroquinone, purge with nitrogen, raise the temperature to 85°C, and stir the reaction at a constant temperature for 3 hours to obtain the reaction solution.

[0076] S3, same as step S3 in Example 1;

[0077] S4. Add 10 parts by weight of epoxy resin, 0.8 parts by weight of triethylenetetramine, 1.5 parts by weight of Span-80, and 1.2 parts by weight of polypropylene glycol diglycidyl ether to the reactor. Raise the temperature to 40°C and stir until homogeneous. Then add 4 parts by weight of distilled water dropwise and mix and emulsify. Prepolymerize for 40 minutes to obtain a W / O emulsion.

[0078] S5. Add 100 parts by weight of distilled water, 0.3 parts by weight of sodium dodecyl sulfate, 8 parts by weight of Tween-80, and 7 parts by weight of triethylenetetramine to the reactor. Raise the temperature to 70°C and stir until homogeneous to obtain a mixed solution. Add the W / O emulsion obtained in step S4 dropwise to the mixed solution and stir thoroughly to obtain a W / O / W emulsion. Stir continuously at a constant temperature for 3 hours. After filtration and washing, obtain water-containing epoxy microspheres. Place them in a vacuum drying oven at 60°C and dry to constant weight to obtain hollow epoxy microspheres.

[0079] S6. Slowly add 4 parts by weight of γ-aminopropyltriethoxysilane to 100 parts by weight of 95% ethanol aqueous solution, and add glacial acetic acid to adjust the pH to 4.5-5.0 while stirring. Continue stirring for 2 hours to obtain silane coupling agent hydrolysate.

[0080] S7. Add 8 parts by weight of hollow epoxy microspheres to 200 parts by weight of anhydrous ethanol, and disperse by ultrasonication for 20 min to form a microsphere suspension.

[0081] S8. The hydrolysate of the silane coupling agent obtained in step S4 is added dropwise to the microsphere suspension obtained in step S5. The temperature is raised to 65℃ and stirred at a constant temperature for 4 hours. After cooling to room temperature, the supernatant is discarded by centrifugation. The precipitate is washed 5 times with anhydrous ethanol and then placed in a vacuum drying oven at 40℃ to dry to constant weight to obtain modified hollow epoxy microspheres.

[0082] S9. Add 90 parts by weight of unsaturated alicyclic epoxy grafted modified EVA resin to a torque rheometer, set the temperature to 70℃ and the speed to 40 rpm. After the torque stabilizes, add 10 parts by weight of modified hollow epoxy microspheres and mix for 8 min. Increase the temperature to 110℃ and the speed to 60 rpm and mix for 6 min to obtain the blend.

[0083] S10. Add 100 parts by weight of the blend to a torque rheometer, set the temperature to 70℃ and the speed to 40 rpm. After the torque stabilizes, add 8 parts by weight of polyborosiloxane, 3 parts by weight of foaming agent, 4 parts by weight of vulcanization activator, 1.5 parts by weight of activating aid, and 0.5 parts by weight of free radical initiator. Mix for 8 minutes and then discharge the glue. Then add 0.1 parts by weight of catalyst and mix on a two-roll mill at 30℃. Sheet the mixture and let it stand for 25 hours. Then, perform compression molding to obtain foamed material. Soak the foamed material in water at 80℃ for 3 hours and then dry it in a vacuum drying oven at 60℃ until constant weight to obtain EVA material. The preparation of polyborosiloxane is as described in Example 1. The compression molding conditions are: at 150℃, first pre-compress at 3MPa pressure for 2 minutes, and then increase the pressure to 6MPa for 3 minutes.

[0084] Example 3

[0085] Compared with Example 1, the amount of each raw material used in this embodiment is different in the preparation process, but the rest is the same as in Example 1, as follows:

[0086] S1, same as step S1 in Example 1;

[0087] S2. Add 0.8 parts by weight of benzoyl peroxide to the transparent solution obtained in step S1, stir until completely dissolved, then slowly add 8 parts by weight of 4-vinylepoxycyclohexane, and immediately add 0.12 parts by weight of triethylamine. After stirring for 10 minutes, add 0.04 parts by weight of hydroquinone, purge with nitrogen, raise the temperature to 95°C, and stir the reaction at a constant temperature for 6 hours to obtain the reaction solution.

[0088] S3, same as step S3 in Example 1;

[0089] S4. Add 10 parts by weight of epoxy resin, 1.2 parts by weight of triethylenetetramine, 2.8 parts by weight of Span-80, and 1.8 parts by weight of polypropylene glycol diglycidyl ether to the reactor. Raise the temperature to 50°C and stir until homogeneous. Then add 8 parts by weight of distilled water dropwise and mix and emulsify. Prepolymerize for 60 minutes to obtain a W / O emulsion.

[0090] S5. Add 100 parts by weight of distilled water, 0.45 parts by weight of sodium dodecyl sulfate, 12 parts by weight of Tween-80, and 9 parts by weight of triethylenetetramine to the reactor. Raise the temperature to 90°C and stir until homogeneous to obtain a mixed solution. Add the W / O emulsion obtained in step S4 dropwise to the mixed solution and stir thoroughly to obtain a W / O / W emulsion. Stir continuously at a constant temperature for 5 hours. After filtration and washing, obtain water-containing epoxy microspheres. Place them in a vacuum drying oven at 60°C and dry to constant weight to obtain hollow epoxy microspheres.

[0091] S6. Slowly add 8 parts by weight of γ-aminopropyltriethoxysilane to 100 parts by weight of 95% ethanol aqueous solution, and add glacial acetic acid to adjust the pH to 4.5-5.0 while stirring. Continue stirring for 4 hours to obtain silane coupling agent hydrolysate.

[0092] S7. Add 12 parts by weight of hollow epoxy microspheres to 200 parts by weight of anhydrous ethanol, and disperse by ultrasonication for 40 min to form a microsphere suspension.

[0093] S8. The hydrolysate of the silane coupling agent obtained in step S4 is added dropwise to the microsphere suspension obtained in step S5. The temperature is raised to 75°C and stirred at a constant temperature for 6 hours. After cooling to room temperature, the supernatant is discarded by centrifugation. The precipitate is washed 5 times with anhydrous ethanol and then dried in a vacuum drying oven at 60°C to constant weight to obtain modified hollow epoxy microspheres.

[0094] S9. Add 110 parts by weight of unsaturated alicyclic epoxy grafted modified EVA resin to a torque rheometer, set the temperature to 90℃ and the speed to 60 rpm. After the torque stabilizes, add 15 parts by weight of modified hollow epoxy microspheres and mix for 10 min. Increase the temperature to 130℃ and the speed to 80 rpm and mix for 10 min to obtain the blend.

[0095] S10. Add 100 parts by weight of the blend to a torque rheometer, set the temperature to 90℃ and the speed to 60 rpm. After the torque stabilizes, add 12 parts by weight of polyborosiloxane, 4 parts by weight of foaming agent, 8 parts by weight of vulcanization activator, 3 parts by weight of activation aid, and 2 parts by weight of free radical initiator. Mix for 8 minutes and then discharge the glue. Then add 0.8 parts by weight of catalyst and mix on a two-roll mill at 32℃. Sheet the mixture and let it stand for 32 hours. Then, perform compression molding to obtain foamed material. Soak the foamed material in water at 90℃ for 5 hours and then dry it in a vacuum drying oven at 60℃ until constant weight to obtain EVA material. The preparation of polyborosiloxane is as described in Example 1. The compression molding conditions are: at 160℃, first pre-compress with a pressure of 5MPa for 4 minutes, and then increase the pressure to 8MPa for 5 minutes.

[0096] Example 4

[0097] Compared with Example 1, in this embodiment, the hollow epoxy microspheres are replaced with solid epoxy microspheres during the preparation process, while the rest is the same as in Example 1, as detailed below:

[0098] Steps S1-S3 are the same as steps S1-S3 in Embodiment 1; Step S4 is the same as step S6 in Embodiment 1;

[0099] S5. Add 10 parts by weight of epoxy microspheres to 200 parts by weight of anhydrous ethanol and sonicate for 30 min to form a microsphere suspension; the epoxy microspheres were purchased from Xi'an Qiyue Biotechnology Co., Ltd. (GMA, particle size 5-10 μm).

[0100] S6. Following the same procedure as step S8 in Example 1, modified epoxy microspheres are obtained.

[0101] S7. Add 100 parts by weight of unsaturated alicyclic epoxy grafted modified EVA resin to a torque rheometer, set the temperature to 80℃ and the speed to 50 rpm. After the torque stabilizes, add 12 parts by weight of modified epoxy microspheres and mix for 9 min. Increase the temperature to 120℃ and the speed to 70 rpm, and mix for 8 min to obtain the blend.

[0102] S8, same as step S10 in Example 1.

[0103] Example 5

[0104] Compared with Example 4, in this embodiment, the solid epoxy microspheres are replaced with SiO2 powder during the preparation process. In Example 4, the SiO2 powder was purchased from Shandong Yanda Chemical Co., Ltd. (model YDHG).

[0105] Example 6

[0106] Compared with Example 1, this embodiment does not modify the hollow epoxy microspheres, but replaces the modified hollow epoxy microspheres with hollow epoxy microspheres. The rest is the same as in Example 1.

[0107] Example 7

[0108] Compared with Example 1, this embodiment replaces polyborosiloxane with polyborosiloxane in the preparation process, while the rest is the same as in Example 1.

[0109] Comparative Example 1

[0110] Compared with Example 1, this comparative example does not add modified hollow microspheres during the preparation process; all other aspects are the same as in Example 1, as detailed below:

[0111] Steps S1-S3 are the same as steps S1-S3 in Embodiment 1;

[0112] S4. 100 parts by weight of unsaturated alicyclic epoxy grafted modified EVA resin were added to a torque rheometer. The temperature was set at 80℃ and the rotation speed at 50 rpm. After the torque stabilized, 10 parts by weight of polyborosiloxane, 3.2 parts by weight of foaming agent, 6 parts by weight of vulcanization activator, 2.2 parts by weight of activating aid, and 1.2 parts by weight of free radical initiator were added and mixed for 10 minutes. The mixture was then discharged. 0.6 parts by weight of catalyst were added and mixed on a two-roll mill at 40℃. The mixture was then sheeted and placed for 28 hours. After that, it was molded and foamed to obtain a foamed material. The foamed material was soaked in water at 85℃ for 4 hours and then dried in a vacuum drying oven at 60℃ until constant weight to obtain EVA material. The preparation of polyborosiloxane and the molding and foaming conditions were as described in Example 1.

[0113] Comparative Example 2

[0114] Compared with Example 1, this comparative example does not add polyborosiloxane during the preparation process, but otherwise follows the same procedure as Example 1.

[0115] Comparative Example 3

[0116] Compared with Comparative Example 1, this comparative example does not add polyborosiloxane during the preparation process, while the rest is the same as Comparative Example 1.

[0117] Related tests:

[0118] Tensile property testing: The test was conducted in accordance with GB / T 6344-2008 standard;

[0119] Aging performance test: The samples prepared in each example and comparative example were placed in an air circulation aging chamber at 150℃ for 4 days. After aging, the samples were taken out and tested according to GB / T 6344-2008 standard; the tensile strength retention rate after aging = (tensile strength after aging / tensile strength before aging) × 100%;

[0120] Resilience test: Refer to the determination method of GB / T 6670-2008 Method A. After conditioning for 72 hours under the conditions of temperature (23±2)℃ and relative humidity (50±5)%, the test was carried out. The sample size was 100mm×100mm×50mm and the steel ball drop height was 460mm.

[0121] Scratch test: The samples prepared in each example and comparative example were scratched with a blade with a depth of 1 mm. They were then left to stand at room temperature for 8 hours to observe whether the cracks of each sample healed.

[0122] The test results are shown in Table 1.

[0123] Table 1 Relevant performance test results

[0124]

[0125] A comparison of the test results from Examples 1 and 4 (replacing hollow epoxy microspheres with solid epoxy microspheres), Example 5 (replacing solid epoxy microspheres with SiO2 powder), and Example 6 (no modification of hollow epoxy microspheres) reveals that the resilience decreases after replacing hollow epoxy microspheres with solid epoxy microspheres. This is because the hollow epoxy microspheres contain cavities that act as buffers under external force, resulting in strong recovery after deformation. Conversely, the resilience decreases after replacing organic polymer microspheres with inorganic powder. This is because organic polymers have better flexibility than inorganic particles, and inorganic materials have limited deformation capacity, thus limiting their toughening ability. Furthermore, when hollow epoxy microspheres are added, those modified with aminosilane coupling agents exhibit better compatibility with the matrix, resulting in better mechanical properties. The test results of Example 1 and Example 7 (where polyboron siloxane was replaced with polyboron siloxane), Comparative Example 2 (where no polyboron siloxane was added during preparation) and Comparative Example 3 (where no polyboron siloxane and modified hollow microspheres were added during preparation) show that the addition of polyboron siloxane gives the prepared material good self-healing properties. Compared with the single boron structure, the boron structure can work synergistically with the silicon-oxygen bond, resulting in better self-healing efficiency.

[0126] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0127] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A preparation process for EVA material used in shoe soles, characterized in that, Includes the following steps: S100. Using raw materials including unsaturated alicyclic epoxy compounds and EVA resin, an unsaturated alicyclic epoxy compound graft-modified EVA resin is prepared; wherein the unsaturated alicyclic epoxy compound is one or a mixture of several of vinylcyclohexene oxide, 4-vinylcyclohexane oxide, allyl glycidyl ether, methyl allyl glycidyl ether, 1,3-butadiene epoxide, and epoxidized polybutadiene. S200: Modified epoxy microspheres are prepared using raw materials including hollow epoxy microspheres and aminosilane coupling agents; the aminosilane coupling agent is grafted onto the surface of the hollow epoxy microspheres through Si-O-Si covalent bonds. S300. Add unsaturated alicyclic epoxy grafted modified EVA resin into a torque rheometer, set the temperature to 70-90℃ and the speed to 40-60rpm. After the torque stabilizes, add modified hollow epoxy microspheres and mix for 8-10min. Increase the temperature to 110-130℃ and the speed to 60-80rpm, and mix for 6-10min to obtain the blend. S400. Add the blend to a torque rheometer, set the temperature to 70-90℃ and the speed to 40-60rpm. After the torque stabilizes, add polyborosiloxane, foaming agent, vulcanization activator, activation aid, and free radical initiator. Mix for 8-12 minutes and then discharge the glue. Then add the catalyst and mix on a two-roll mill at 30-50℃. Sheet the mixture and let it stand for 25-32 hours. Then, mold and foam the mixture to obtain a foamed material. Soak the foamed material in water at 80-90℃ for 3-5 hours and then dry it in a vacuum drying oven to obtain the EVA material. In a water bath, under the action of a catalyst, perform moisture crosslinking to finally obtain a peroxide crosslinked and moisture crosslinked double crosslinked foamed material. The foaming agents are azodicarbonamide, sodium bicarbonate, and N,N / - One or a mixture of dinitrospentamethylenetetramine and polybutadiene; the activator is one or a mixture of zinc oxide, magnesium oxide, lead oxide, and zinc carbonate; the activator is one or a mixture of zinc stearate, calcium stearate, paraffin wax, and oleamide; the free radical initiator is one or a mixture of dicumyl peroxide, benzoyl peroxide, and di-tert-butyl peroxide; the catalyst is one or a mixture of dibutyltin dilaurate, dibutyltin dioctanoate, bismuth isooctanoate, bismuth neodecanoate, dibutyltin oxide, tetrabutyl titanate, tetraisopropyl titanate, zinc acetate, zinc chloride, dibutyltin diacetate, dibutyltin oxide, and isopropyltristearate titanate.

2. The process for preparing EVA material for making shoe soles as claimed in claim 1 wherein, Step S100 specifically includes: S110. After reflux extraction of EVA resin with petroleum ether, the EVA resin is dried to constant weight to obtain purified EVA resin. The purified EVA resin is placed in toluene solution, heated to 75-85℃, and stirred until completely dissolved to obtain a transparent solution. S120. Add peroxide initiator to transparent solution and stir until completely dissolved. Then add unsaturated aliphatic epoxy compound. Immediately after addition, add triethylamine and stir for 5-10 minutes. Then add hydroquinone, purge with nitrogen, raise the temperature to 85-95℃, and stir the reaction at a constant temperature for 3-6 hours to obtain the reaction solution. S130. Pour the reaction solution into methanol, stir vigorously, filter and collect the precipitate, wash and dry to obtain the unsaturated alicyclic epoxy grafted modified EVA resin.

3. The process for preparing EVA material for making shoe soles as claimed in claim 1 wherein, Step S200 specifically includes: S210. Add aminosilane coupling agent to an ethanol aqueous solution, and add glacial acetic acid to adjust the pH to 4.5-5.0 while stirring to obtain silane coupling agent hydrolysate. S220. Add hollow epoxy microspheres to anhydrous ethanol and ultrasonically disperse for 20-40 minutes to form a microsphere suspension. S230. The hydrolysate of the silane coupling agent is added dropwise to the microsphere suspension, the temperature is raised to 65-75℃ and stirred at a constant temperature for 4-6 hours, then cooled to room temperature, centrifuged and the supernatant is discarded. The precipitate is washed and dried to obtain the modified epoxy microspheres.

4. The process for preparing EVA material for making shoe soles as claimed in claim 1 wherein, The method for preparing the hollow epoxy microspheres includes the following steps: A1. Add epoxy resin, triethylenetetramine, Span-80, and polypropylene glycol diglycidyl ether to the reactor, raise the temperature to 40-50℃ and stir evenly. Then add distilled water dropwise, mix and stir to emulsify, and prepolymerize for 40-60 minutes to obtain W / O emulsion. A2. Add distilled water, sodium dodecyl sulfate, emulsifier, and triethylenetetramine to the reactor. Raise the temperature to 60-90℃ and stir until homogeneous to obtain a mixed solution. Add the W / O emulsion dropwise to the mixed solution and stir thoroughly to obtain a W / O / W emulsion. Stir continuously at a constant temperature for 3-5 hours. After filtration and washing, obtain water-containing epoxy microspheres. After drying, obtain hollow epoxy microspheres.

5. The process for preparing EVA material for making shoe soles as claimed in claim 1 wherein, The mass ratio of the blend, polyborosiloxane, foaming agent, vulcanization activator, activation aid, free radical initiator and catalyst is 100:8-10:3-4:4-8:1.5-3:0.5-2:0.1-1.

6. The process for preparing EVA material for making shoe soles as claimed in claim 1 wherein, The conditions for compression molding foaming are as follows: at 150-160℃, first pre-compress with a pressure of 3-5MPa for 2-4 minutes, and then increase the pressure to 6-8MPa for 3-5 minutes.

7. An EVA material for making shoe soles, characterized by, It is prepared using the EVA material preparation process for making shoe soles as described in any one of claims 1-6.

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