Composite shoe material containing bio-based EVA and preparation method thereof

Abstract

The invention relates to the technical field of shoe materials, in particular to a bio-based EVA-containing composite shoe material and a preparation method thereof, and the bio-based EVA-containing composite shoe material is prepared from the following raw materials in parts by weight: a bio-based EVA polymer, bio-based TPU, a cross-linking agent, a compatilizer, a nucleating agent, filler, a foaming agent, a plasticizer, a flexible component, a biodegradation accelerant, a non-polyolefin elastomer and maleic anhydride grafted polyethylene wax. Wherein the compatilizer can be ethylene-vinyl alcohol and the like; the nucleating agent can be nanoscale talcum powder and the like; the filler can be ethyl cellulose and the like; the foaming agent is an azodicarbonamide foaming agent; the biodegradation accelerant is prepared from immobilized lipase, a tannic acid-Fe < 3 + > complex and surface carboxylated TiO2. The preparation method comprises two steps of mixing granulation and supercritical foaming. The composite shoe material provided by the invention has good biodegradability, can reduce environmental pollution, and maintains excellent physical and mechanical properties at the same time.

Description

Technical Field

[0001] The present invention relates to the technical field of shoe materials, and in particular to a composite shoe material containing bio-based EVA and a preparation method thereof. Background Art

[0002] With growing environmental awareness, the footwear industry is actively seeking more environmentally friendly and sustainable material alternatives. While ethylene-vinyl acetate (EVA), widely used in traditional footwear, possesses excellent physical properties, its petroleum-based origin and resistance to degradation no longer meet today's demand for environmentally friendly materials. Bio-based EVA, a new environmentally friendly material derived partially from renewable resources, has become a research hotspot in the footwear industry.

[0003] Currently, there are a variety of technical solutions for EVA-based composite shoe materials on the market. CN116574323B discloses a high-performance foamed sole material that can achieve rapid degradation. Its core is to prepare a degradation-promoting functional masterbatch and add it to the EVA sole material, allowing the sole to be degraded by microorganisms under anaerobic conditions. Testing shows a 360-day degradation rate of 60.1-62.5%. CN110885487A proposes a method for preparing biodegradable foamed soles. By using recycled EVA film, EVA, starch-grafted EVA, and maleic anhydride-grafted POE as components, it solves the incompatibility problem between the hydrophilic surface of starch and EVA, increases interfacial adhesion, and improves the overall performance of the blend.

[0004] In terms of improving the performance of shoe materials, CN117247610B discloses a plain leather sole material. By adding modified terpene resin to solution-polymerized styrene-butadiene rubber and adding diphenylmethane diisocyanate and end-hydroxy polydimethylsiloxane to thermoplastic polyurethane elastomer, the material's moisture-proof, anti-slip, wear-resistant and tear-resistant properties are improved. CN112063036A introduces a protein filler composite EVA foam shoe material. The protein powder filler composite EVA produced with waste leather scraps as raw materials has a certain hygroscopicity and can be used as a substitute for traditional EVA materials. CN102786734B provides a starch dry-grafted polyolefin and polyolefin elastomer composite foam shoe material. It uses abundant and fully degradable starch to carry out dry grafting copolymerization with EVA resin and elastomer in an internal mixer, which better solves the compatibility problem.

[0005] However, there are still some urgent problems to be solved in the bio-based EVA composite shoe materials in the existing technology: First, bio-based EVA has a high melt viscosity and low melt fluidity, which makes it difficult to fully melt and flow during the processing, and has poor compatibility with fillers or reinforcing materials, poor interface bonding, and the traditional EVA foaming process may not be suitable for bio-based EVA; Second, bio-based EVA usually has a high crystallinity and low elasticity, the filler content in the composite material is too high or the hardness is large, and excessive cross-linking or vulcanization during the processing process leads to a high hardness of the final product, affecting wearing comfort; Finally, although bio-based EVA is partially derived from renewable resources, its degradation rate is still relatively slow and it is difficult to degrade under certain circumstances. The fillers or additives in the composite material are not degradable, and cross-linking or vulcanization during the processing process will further reduce the degradation performance of the material.

[0006] Therefore, there is an urgent need to develop a bio-based EVA composite shoe material with good formability, suitable hardness and degradability to meet the footwear industry's demand for environmentally friendly and high-performance materials. Summary of the Invention

[0007] In order to solve the problems of formability, hardness and degradation of composite shoe materials containing bio-based EVA, and to achieve the technical effects of improving interface bonding strength, improving material fluidity, reducing material hardness, improving flexibility and accelerating material degradation, the present invention provides a composite shoe material containing bio-based EVA and a preparation method thereof; the composite shoe material containing bio-based EVA has achieved comprehensive improvements in formability, flexibility and degradability, and achieved a comprehensive balance between environmental protection, comfort and processing performance, providing an effective technical solution for the application of bio-based EVA in the field of shoe materials.

[0008] The objective of the present invention is achieved through the following technical solution: a composite shoe material containing bio-based EVA, comprising the following raw materials in parts by weight: 40-60 parts of bio-based EVA polymer, 10-30 parts of bio-based TPU, 0.1-1.0 parts of a crosslinking agent, 2-6 parts of a compatibilizer, 4-8 parts of a nucleating agent, 3-7 parts of a filler, 1-5 parts of a foaming agent, 3-7 parts of a plasticizer, 5-15 parts of a flexible component, 3-7 parts of a biodegradation accelerator, 6-10 parts of a non-polyolefin elastomer, and 5-10 parts of a maleic anhydride grafted polyethylene wax.

[0009] Preferably, the compatibilizer is one or more of ethylene vinyl alcohol, ethylene vinyl acetate grafted maleic anhydride, and naphthenic oil.

[0010] Preferably, the nucleating agent is one or more of nano-talc, nano-titanium dioxide, nano-zinc oxide and nano-calcium carbonate.

[0011] Preferably, the filler is one or more of ethyl cellulose, organic montmorillonite, nano-SiO2, talc, bagasse fiber, starch, and cellulose.

[0012] Preferably, the foaming agent is an azodicarbonamide foaming agent.

[0013] Preferably, the flexible component is one or more of polyolefin elastomer, thermoplastic polyurethane, and styrene elastomer.

[0014] Preferably, the biodegradation accelerator is composed of immobilized lipase, tannic acid-Fe3+ complex and surface carboxylated TiO2 in a mass ratio of 5:3:01.5-2.5.

[0015] More preferably, the tannic acid-Fe3+ complex is prepared by the following method:

[0016] A1. Dissolve tannic acid in deionized water and stir thoroughly to obtain a tannic acid solution.

[0017] A2. Dissolve ferric chloride hexahydrate in deionized water, then slowly add the ferric chloride hexahydrate solution dropwise to the tannic acid solution, and adjust the pH to 3-7 using NaOH solution; wherein the molar ratio of tannic acid to FeCl3 is 1:1-3;

[0018] A3. Under stirring, maintain the reaction temperature at 60-90°C to react to form a complex, and then obtain tannic acid-Fe by centrifugation. 3+ Complex powder;

[0019] A4. Wash the separated complex powder with appropriate amount of water and ethanol to remove unreacted tannic acid, iron salt and other impurities. Finally, dry the washed complex to obtain pure tannic acid-Fe 3+ complex.

[0020] Preferably, the non-polyolefin elastomer is one or more of styrene elastomer, thermoplastic polyester elastomer, and polyamide elastomer.

[0021] Preferably, the cross-linking agent is a mixture of di(tert-butylperoxyisopropyl)benzene and triallyl isocyanurate.

[0022] The present invention improves the interfacial bonding strength between bio-based EVA and other components by adding a compatibilizer, reduces the melt viscosity and improves fluidity by adding a plasticizer, balances the processing performance and mechanical properties by optimizing the filler type and content, and uses supercritical foaming technology to achieve foaming molding at low temperature and low pressure, effectively solving the problem of difficult processing of bio-based EVA. Compared with traditional EVA composite materials, the composite shoe material of the present invention has a melt fluidity increased by more than 30% and an interface bonding strength increased by more than 25% during the molding process, significantly improving the molding effect of the material; the addition of flexible components and non-polyolefin elastomers increases the flexibility of the material, reduces excessive cross-linking by controlling the amount of cross-linking agent, and reduces the crystallinity of the material through a supercritical foaming process, so that the hardness of the composite shoe material is reduced by 15-20%, the elastic recovery rate is increased by more than 25%, and the compression permanent deformation is reduced by more than 30%, significantly improving the comfort of the shoe material; degradable fillers (such as sugarcane bagasse fiber, starch, cellulose, etc.), the addition of a specific ratio of biodegradation promoters, the controllable degree of cross-linking, and the use of a controllable supercritical foaming process increase the degradation rate of the composite material under standard composting conditions by more than 40%, and the 90-day degradation rate can reach about 65%, which is much higher than the degradation performance of traditional EVA composite materials and significantly reduces the impact on the environment.

[0023] The present invention further discloses a method for preparing a composite shoe material containing bio-based EVA, comprising the following steps:

[0024] S1. Mix the bio-based EVA polymer, bio-based TPU, cross-linking agent, compatibilizer, nucleating agent, filler, plasticizer, flexible component, biodegradation accelerator, non-polyolefin elastomer, foaming agent, and maleic anhydride grafted polyethylene wax in parts by weight, and granulate them through a twin-screw extruder for later use.

[0025] S2. After the granulated material is placed for more than 24 hours, it is placed in a foaming kettle for foaming, nitrogen is introduced, and the temperature is raised to 130-150°C and the pressure is increased to 15-23 MPa to make it reach a supercritical state. After reaching the supercritical state, the temperature and pressure are maintained for 1-3 hours. After the gas is saturated, the pressure is released, the test piece is taken out, and the sample is cut to obtain a composite shoe material.

[0026] The beneficial effects of the present invention are:

[0027] 1) To address moldability issues, the present invention improves the interfacial bonding between bio-based EVA and other components by adding a compatibilizer, reduces melt viscosity and improves fluidity by adding a plasticizer, balances processability and mechanical properties by optimizing filler type and content, and utilizes supercritical foaming technology to achieve foam molding at low temperature and low pressure, effectively resolving the processing difficulties of bio-based EVA. Compared to traditional EVA composite materials, the present invention's composite shoe material exhibits over 30% greater melt fluidity and over 25% greater interfacial bonding strength during molding, significantly improving the material's molding performance.

[0028] 2) To address the problem of hardness, the present invention increases the flexibility of the material by adding flexible components and non-polyolefin elastomers, reduces excessive cross-linking by controlling the amount of cross-linking agent, and reduces the crystallinity of the material through a supercritical foaming process. As a result, the hardness of the composite shoe material is reduced by 15-20%, the elastic recovery rate is increased by more than 25%, and the compression permanent deformation is reduced by more than 30%, significantly improving the comfort of the shoe material.

[0029] 3) To address the degradation problem, the present invention selects degradable fillers (such as sugarcane bagasse fiber, starch, cellulose, etc.), adds a specific ratio of biodegradation promoters, controls the degree of cross-linking, and adopts a controllable supercritical foaming process. This increases the degradation rate of the composite material under standard composting conditions by more than 40%, and the 90-day degradation rate can reach about 65%, which is much higher than the degradation performance of traditional EVA composite materials, significantly reducing the impact on the environment. DETAILED DESCRIPTION

[0030] 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.

[0031] Example 1

[0032] A composite shoe material containing bio-based EVA includes the following raw materials in parts by weight: 50 parts of bio-based EVA polymer, 20 parts of bio-based TPU, 0.5 parts of a cross-linking agent, 4 parts of a compatibilizer, 6 parts of a nucleating agent, 5 parts of a filler, 3 parts of a foaming agent, 5 parts of a plasticizer, 10 parts of a flexible component, 5 parts of a biodegradation accelerator, 8 parts of a non-polyolefin elastomer, and 7 parts of a maleic anhydride grafted polyethylene wax.

[0033] The compatibilizer is a mixture of ethylene vinyl alcohol and ethylene vinyl acetate grafted maleic anhydride, mixed in a mass ratio of 2:2. The addition of the compatibilizer can effectively improve the compatibility between the bio-based EVA polymer and the bio-based TPU, and enhance the uniformity and stability of the material.

[0034] The nucleating agent is a mixture of nano-talc and nano-titanium dioxide, mixed in a mass ratio of 4:2. The addition of the nucleating agent promotes uniform bubble formation during the foaming process, improves foaming efficiency, and results in a more uniform microporous structure in the final product.

[0035] The filler is a mixture of ethyl cellulose and bagasse fiber, mixed in a mass ratio of 2:3. The addition of the filler not only reduces material cost but also enhances the rigidity and dimensional stability of the material. Furthermore, bagasse fiber, as a natural fiber, further increases the bio-based content of the composite shoe material.

[0036] The foaming agent is an azodicarbonamide-based foaming agent, specifically AC foaming agent. This foaming agent decomposes at a temperature between 130°C and 150°C, releasing nitrogen and forming a uniform microporous structure. This gives the composite shoe material excellent lightness and cushioning properties.

[0037] The flexible component is a mixture of polyolefin elastomer and thermoplastic polyurethane, mixed in a mass ratio of 6:4. The addition of the flexible component can improve the flexibility and elasticity of the material, making the composite shoe material more comfortable and provide a better wearing experience.

[0038] The biodegradation promoter is composed of immobilized lipase, tannic acid-Fe3 + The complex and the surface carboxylated TiO2 are composed in a mass ratio of 5:3:2. The addition of the biodegradation accelerator can accelerate the degradation process of the composite shoe material in the natural environment and reduce environmental pollution.

[0039] Wherein, the tannic acid-Fe3+ complex is prepared by the following method

[0040] A1. Dissolve tannic acid in deionized water and stir thoroughly to obtain a tannic acid solution.

[0041] A2. Dissolve ferric chloride hexahydrate in deionized water, then slowly add the ferric chloride hexahydrate solution dropwise to the tannic acid solution, and adjust the pH to 3 using NaOH solution; wherein the molar ratio of tannic acid to FeCl3 is 1:1;

[0042] A3. Under stirring, the reaction temperature is maintained at 60 ° C. to react to form a complex, and then centrifuge to obtain tannic acid-Fe3 + Complex powder;

[0043] A4. Wash the separated complex powder with appropriate amount of water and ethanol to remove unreacted tannic acid, iron salt and other impurities. Finally, dry the washed complex to obtain pure tannic acid-Fe3 + complex.

[0044] The non-polyolefin elastomer is a mixture of a styrene elastomer and a thermoplastic polyester elastomer, mixed in a mass ratio of 5:3. The addition of the non-polyolefin elastomer further enhances the elasticity and durability of the material, extending the service life of the composite shoe material.

[0045] The crosslinking agent is a mixture of di(tert-butylperoxyisopropyl)benzene and triallyl isocyanurate, mixed in a mass ratio of 3:2. The addition of the crosslinking agent can promote the formation of chemical crosslinks between polymer chains, improving the thermal stability and mechanical strength of the material.

[0046] The plasticizer is an environmentally friendly plasticizer, the main component of which is a citric acid ester compound, which can improve the processing performance of the material, reduce the processing temperature, and maintain the flexibility of the material.

[0047] The addition of maleic anhydride grafted polyethylene wax can improve the compatibility and dispersibility of the material, while also playing a role in lubrication and demoulding, making it easier to process and shape composite shoe materials.

[0048] The preparation method of the composite shoe material comprises the following steps:

[0049] S1. According to parts by weight, 50 parts of bio-based EVA polymer, 20 parts of bio-based TPU, 0.5 parts of cross-linking agent, 4 parts of compatibilizer, 6 parts of nucleating agent, 5 parts of filler, 5 parts of plasticizer, 10 parts of flexible component, 5 parts of biodegradation promoter, 8 parts of non-polyolefin elastomer, 3 parts of foaming agent, and 7 parts of maleic anhydride grafted polyethylene wax are mixed evenly, and then granulated by twin-screw extruder for later use; the specific operation is as follows: first, the bio-based EVA polymer, bio-based TPU, compatibilizer, filler, plasticizer, flexible component, non-polyolefin elastomer and maleic anhydride grafted polyethylene wax are mixed evenly, and then the nucleating agent, biodegradation promoter, cross-linking agent and foaming agent are added, and mixed and granulated in a twin-screw extruder. The temperature of the extruder is controlled at 110-120°C and the screw speed is 80-100rpm to ensure that the components are fully mixed and uniform without causing premature decomposition of the foaming agent;

[0050] S2. After the granules are placed for more than 24 hours, they are placed in a foaming kettle for foaming, nitrogen is introduced, and the temperature is raised to 140°C and the pressure is increased to 20 MPa to reach a supercritical state. After reaching the supercritical state, the temperature and pressure are maintained for 2 hours. After the gas is saturated, the pressure is released and the test piece is taken out, and the sample is cut to obtain a composite shoe material; the specific operation is as follows: the granules are placed at room temperature for 24 hours to fully release the internal stress of the material, and then the granules are placed in a foaming kettle, sealed and nitrogen is introduced to replace the air in the kettle, the temperature is raised to 140°C, and the pressure is increased to 20 MPa at the same time to make the system reach a supercritical state, and maintained under this condition for 2 hours to fully dissolve the nitrogen in the polymer matrix, and then the pressure is released at a rate of 5-10 MPa / min to form tiny bubbles of dissolved nitrogen. Finally, the test piece is taken out, cooled to room temperature at room temperature, and cut into the required shape and size to obtain a composite shoe material containing bio-based EVA.

[0051] The resulting composite shoe material exhibits the following characteristics: density of 0.15-0.25 g / cm³, hardness of 45-55 Shore A, tensile strength ≥2.5 MPa, elongation at break ≥150%, and resilience ≥40%. These properties were measured using the latest national testing standards for their respective fields. This composite shoe material is lightweight, soft, elastic, and wear-resistant, making it suitable for use in athletic shoe midsoles, insoles, and insoles. Furthermore, by utilizing bio-based EVA polymer and bio-based TPU as primary raw materials, along with the addition of a biodegradation accelerator, the composite shoe material exhibits a high biobased content and excellent biodegradability, meeting environmental requirements.

[0052] Example 2

[0053] A composite shoe material containing bio-based EVA includes the following raw materials in parts by weight: 45 parts of bio-based EVA polymer, 15 parts of bio-based TPU, 0.3 parts of a cross-linking agent, 3 parts of a compatibilizer, 5 parts of a nucleating agent, 4 parts of a filler, 2 parts of a foaming agent, 4 parts of a plasticizer, 8 parts of a flexible component, 4 parts of a biodegradation accelerator, 7 parts of a non-polyolefin elastomer, and 6 parts of a maleic anhydride grafted polyethylene wax.

[0054] The compatibilizer is cyclohexane oil, the nucleating agent is a mixture of nano zinc oxide and nano calcium carbonate, mixed at a mass ratio of 3:2. The filler is a mixture of organic montmorillonite and nano SiO2, mixed at a mass ratio of 2:2. The foaming agent is an azodicarbonamide foaming agent. The flexible component is a styrene elastomer. The biodegradation accelerator is a mixture of immobilized lipase, tannic acid-Fe 3+ The complex and surface carboxylated TiO2 are composed in a mass ratio of 5:3:1.8. The non-polyolefin elastomer is a polyamide elastomer. The crosslinker is a mixture of di(tert-butylperoxyisopropyl)benzene and triallyl isocyanurate, mixed in a mass ratio of 2:1.

[0055] Wherein, the tannic acid-Fe3+ complex is prepared by the following method

[0056] A1. Dissolve tannic acid in deionized water and stir thoroughly to obtain a tannic acid solution.

[0057] A2. Dissolve ferric chloride hexahydrate in deionized water, then slowly add the ferric chloride hexahydrate solution dropwise to the tannic acid solution, and adjust the pH to 4 using NaOH solution; wherein the molar ratio of tannic acid to FeCl3 is 1:1.5;

[0058] A3. Under stirring, the reaction temperature is maintained at 65 ° C. to react to form a complex, and then centrifuge to obtain tannic acid-Fe3 + Complex powder;

[0059] A4. Wash the separated complex powder with appropriate amount of water and ethanol to remove unreacted tannic acid, iron salt and other impurities. Finally, dry the washed complex to obtain pure tannic acid-Fe3 + complex.

[0060] The preparation method of the composite shoe material comprises the following steps:

[0061] S1. According to parts by weight, 45 parts of bio-based EVA polymer, 15 parts of bio-based TPU, 0.3 parts of cross-linking agent, 3 parts of compatibilizer, 5 parts of nucleating agent, 4 parts of filler, 4 parts of plasticizer, 8 parts of flexible component, 4 parts of biodegradation promoter, 7 parts of non-polyolefin elastomer, 2 parts of foaming agent, and 6 parts of maleic anhydride grafted polyethylene wax are mixed evenly, and the mixture is granulated by twin-screw extruder for later use. The specific operation is as follows: the bio-based EVA polymer, bio-based TPU, compatibilizer, filler, plasticizer, flexible component, non-polyolefin elastomer and maleic anhydride grafted polyethylene wax are first mixed evenly, and then the nucleating agent, biodegradation promoter, cross-linking agent and foaming agent are added, and the mixture is granulated in a twin-screw extruder. The temperature of the extruder is controlled at 105-115° C. and the screw speed is 85-95 rpm.

[0062] S2. After the granules are placed for more than 24 hours, they are placed in a foaming kettle for foaming, nitrogen is introduced, and the temperature is raised to 135°C and the pressure is increased to 18 MPa to make it reach a supercritical state. After reaching the supercritical state, the temperature and pressure are maintained for 1.5 hours. After the gas is saturated, the pressure is released and the test piece is taken out, and the sample is cut to obtain a composite shoe material; the specific operation is as follows: the granules are placed at room temperature and allowed to stand for 30 hours, and then the granules are placed in a foaming kettle. After sealing, nitrogen is introduced to replace the air in the kettle, the temperature is raised to 135°C, and the pressure is increased to 18 MPa at the same time to make the system reach a supercritical state. Under this condition, it is maintained for 1.5 hours, and then the pressure is released at a rate of 7 MPa / min. Finally, the test piece is taken out, cooled to room temperature at room temperature, and cut into the required shape and size.

[0063] The resulting composite shoe material has the following characteristics: density of 0.18-0.28g / cm³, hardness of 48-58 Shore A, tensile strength ≥2.2MPa, elongation at break ≥140%, and resilience ≥38%. These properties were measured using the latest national testing standards in their respective fields. This composite shoe material is suitable for manufacturing components such as midsoles and insoles for casual shoes.

[0064] Example 3

[0065] A composite shoe material containing bio-based EVA includes the following raw materials in parts by weight: 55 parts of bio-based EVA polymer, 25 parts of bio-based TPU, 0.8 parts of a cross-linking agent, 5 parts of a compatibilizer, 7 parts of a nucleating agent, 6 parts of a filler, 4 parts of a foaming agent, 6 parts of a plasticizer, 12 parts of a flexible component, 6 parts of a biodegradation accelerator, 9 parts of a non-polyolefin elastomer, and 9 parts of a maleic anhydride grafted polyethylene wax.

[0066] The compatibilizer is ethylene vinyl acetate grafted maleic anhydride. The nucleating agent is nano-grade talc. The filler is a mixture of talc and cellulose, mixed at a mass ratio of 3:3. The foaming agent is an azodicarbonamide foaming agent. The flexible component is a mixture of polyolefin elastomer and thermoplastic polyurethane, mixed at a mass ratio of 7:5. The biodegradation accelerator is a mixture of immobilized lipase, tannic acid-Fe3 + The complex and surface carboxylated TiO2 are composed in a mass ratio of 5:3:2.2. The non-polyolefin elastomer is a thermoplastic polyester elastomer. The crosslinker is a mixture of di(tert-butylperoxyisopropyl)benzene and triallyl isocyanurate, mixed in a mass ratio of 4:4.

[0067] Wherein, the tannic acid-Fe 3 The complex was prepared by the following method

[0068] A1. Dissolve tannic acid in deionized water and stir thoroughly to obtain a tannic acid solution.

[0069] A2. Dissolve ferric chloride hexahydrate in deionized water, then slowly add the ferric chloride hexahydrate solution dropwise to the tannic acid solution, and adjust the pH to 5 using NaOH solution; wherein the molar ratio of tannic acid to FeCl3 is 1:2;

[0070] A3. Under stirring, the reaction temperature was maintained at 70°C to form a complex, and then tannic acid-Fe was obtained by centrifugation. 3+ Complex powder;

[0071] A4. Wash the separated complex powder with appropriate amount of water and ethanol to remove unreacted tannic acid, iron salt and other impurities. Finally, dry the washed complex to obtain pure tannic acid-Fe3+ complex.

[0072] The preparation method of the composite shoe material comprises the following steps:

[0073] S1. According to parts by weight, 55 parts of bio-based EVA polymer, 25 parts of bio-based TPU, 0.8 parts of cross-linking agent, 5 parts of compatibilizer, 7 parts of nucleating agent, 6 parts of filler, 6 parts of plasticizer, 12 parts of flexible component, 6 parts of biodegradation promoter, 9 parts of non-polyolefin elastomer, 4 parts of foaming agent, and 9 parts of maleic anhydride grafted polyethylene wax are mixed evenly, and then mixed and granulated by twin-screw extruder for later use; the specific operation is as follows: first, the bio-based EVA polymer, bio-based TPU, compatibilizer, filler, plasticizer, flexible component, non-polyolefin elastomer and maleic anhydride grafted polyethylene wax are mixed evenly, and then the nucleating agent, biodegradation promoter, cross-linking agent and foaming agent are added, and mixed and granulated in a twin-screw extruder, and the temperature of the extruder is controlled at 115-125°C and the screw speed is 90-110rpm;

[0074] S2. After the granules are placed for more than 24 hours, they are placed in a foaming kettle for foaming, nitrogen is introduced, and the temperature is raised to 145°C and the pressure is increased to 22 MPa to make it reach a supercritical state. After reaching the supercritical state, the temperature and pressure are maintained for 2.5 hours. After the gas is saturated, the pressure is released and the test piece is taken out, and the sample is cut to obtain a composite shoe material; the specific operation is as follows: the granules are placed at room temperature and allowed to stand for 36 hours, and then the granules are placed in a foaming kettle. After sealing, nitrogen is introduced to replace the air in the kettle, the temperature is raised to 145°C, and the pressure is increased to 22 MPa at the same time to make the system reach a supercritical state. Under this condition, it is maintained for 2.5 hours, and then the pressure is released at a rate of 6 MPa / min. Finally, the test piece is taken out, cooled to room temperature at room temperature, and cut into the required shape and size.

[0075] The composite shoe material has the following characteristics: density is 0.12-0.22g / cm 3 The composite material has a hardness of 42-52 Shore A, a tensile strength of 2.8 MPa or higher, an elongation at break of 160% or higher, and a resilience of 45% or higher. These properties are measured using the latest national testing standards for their respective fields. This composite material is suitable for use in midsoles and outsoles of high-end athletic shoes, offering excellent shock absorption and durability.

[0076] Example 4

[0077] A composite shoe material containing bio-based EVA includes the following raw materials in parts by weight: 40 parts of bio-based EVA polymer, 10 parts of bio-based TPU, 0.1 parts of a cross-linking agent, 2 parts of a compatibilizer, 4 parts of a nucleating agent, 3 parts of a filler, 1 part of a foaming agent, 3 parts of a plasticizer, 5 parts of a flexible component, 3 parts of a biodegradation accelerator, 6 parts of a non-polyolefin elastomer, and 5 parts of a maleic anhydride grafted polyethylene wax.

[0078] The compatibilizer is ethylene vinyl alcohol. The nucleating agent is nano-titanium dioxide. The filler is starch. The foaming agent is azodicarbonamide foaming agent. The flexible component is thermoplastic polyurethane. The biodegradation accelerator is immobilized lipase, tannic acid-Fe 3+ The complex and surface carboxylated TiO2 are composed in a mass ratio of 5:3:1.5. The non-polyolefin elastomer is a styrene elastomer. The crosslinker is a mixture of di(tert-butylperoxyisopropyl)benzene and triallyl isocyanurate, mixed in a mass ratio of 1:1.

[0079] Wherein, the tannic acid-Fe3+ complex is prepared by the following method

[0080] A1. Dissolve tannic acid in deionized water and stir thoroughly to obtain a tannic acid solution.

[0081] A2. Dissolve ferric chloride hexahydrate in deionized water, then slowly add the ferric chloride hexahydrate solution dropwise to the tannic acid solution, and adjust the pH to 6 using NaOH solution; wherein the molar ratio of tannic acid to FeCl3 is 1:2.5;

[0082] A3. Under stirring, the reaction temperature was maintained at 75°C to form a complex, and then tannic acid-Fe3 was obtained by centrifugation. + Complex powder;

[0083] A4. Wash the separated complex powder with appropriate amount of water and ethanol to remove unreacted tannic acid, iron salt and other impurities. Finally, dry the washed complex to obtain pure tannic acid-Fe3 + complex.

[0084] The preparation method of the composite shoe material comprises the following steps:

[0085] S1. According to parts by weight, 40 parts of bio-based EVA polymer, 10 parts of bio-based TPU, 0.1 parts of cross-linking agent, 2 parts of compatibilizer, 4 parts of nucleating agent, 3 parts of filler, 3 parts of plasticizer, 5 parts of flexible component, 3 parts of biodegradation promoter, 6 parts of non-polyolefin elastomer, 1 part of foaming agent, and 5 parts of maleic anhydride grafted polyethylene wax are mixed evenly, and the mixture is granulated by twin-screw extruder for later use. The specific operation is as follows: the bio-based EVA polymer, bio-based TPU, compatibilizer, filler, plasticizer, flexible component, non-polyolefin elastomer and maleic anhydride grafted polyethylene wax are first mixed evenly, and then the nucleating agent, biodegradation promoter, cross-linking agent and foaming agent are added, and the mixture is granulated in a twin-screw extruder. The temperature of the extruder is controlled at 100-110° C. and the screw speed is 75-85 rpm.

[0086] S2. After the granules are placed for more than 24 hours, they are placed in a foaming kettle for foaming, nitrogen is introduced, and the temperature is raised to 130°C and the pressure is increased to 15Mpa to make it reach a supercritical state. After reaching the supercritical state, the temperature and pressure are maintained for 1 hour. After the gas is saturated, the pressure is released and the test piece is taken out, and the sample is cut to obtain a composite shoe material; the specific operation is as follows: the granules are placed at room temperature and allowed to stand for 26 hours, and then the granules are placed in a foaming kettle. After sealing, nitrogen is introduced to replace the air in the kettle, the temperature is raised to 130°C, and the pressure is increased to 15Mpa at the same time to make the system reach a supercritical state. It is maintained under this condition for 1 hour, and then the pressure is released at a rate of 8Mpa / min. Finally, the test piece is taken out, cooled to room temperature at room temperature, and cut into the required shape and size.

[0087] The composite shoe material has the following characteristics: density is 0.22-0.32g / cm 3 The composite material has a hardness of 52-62 Shore A, a tensile strength of ≥2.0 MPa, an elongation at break of ≥130%, and a resilience of ≥35%. These properties are measured using the latest national testing standards for their respective fields. This composite material is suitable for use in the manufacture of insoles and insoles for lightweight shoes, offering excellent lightness and comfort.

[0088] Example 5

[0089] A composite shoe material containing bio-based EVA includes the following raw materials in parts by weight: 60 parts of bio-based EVA polymer, 30 parts of bio-based TPU, 1.0 part of a cross-linking agent, 6 parts of a compatibilizer, 8 parts of a nucleating agent, 7 parts of a filler, 5 parts of a foaming agent, 7 parts of a plasticizer, 15 parts of a flexible component, 7 parts of a biodegradation accelerator, 10 parts of a non-polyolefin elastomer, and 10 parts of a maleic anhydride grafted polyethylene wax.

[0090] Among them, the compatibilizer is a mixture of ethylene vinyl alcohol, ethylene vinyl acetate grafted maleic anhydride and cyclohexane oil, mixed in a mass ratio of 2:2:2. The nucleating agent is a mixture of nano-grade talc, nano-titanium dioxide, nano-zinc oxide and nano-calcium carbonate, mixed in a mass ratio of 2:2:2:2. The filler is a mixture of ethyl cellulose, organic montmorillonite, nano-SiO2, talc, bagasse fiber, starch and cellulose, mixed in a mass ratio of 1:1:1:1:1:1:1. The foaming agent is an azodicarbonamide foaming agent. The flexible component is a mixture of polyolefin elastomer, thermoplastic polyurethane and styrene elastomer, mixed in a mass ratio of 5:5:5. The biodegradation accelerator is a mixture of immobilized lipase, tannic acid-Fe 3+ The complex and surface carboxylated TiO2 are composed in a mass ratio of 5:3:2.5. The non-polyolefin elastomer is a mixture of a styrene elastomer, a thermoplastic polyester elastomer, and a polyamide elastomer, mixed in a mass ratio of 3:3:4. The crosslinker is a mixture of di(tert-butylperoxyisopropyl)benzene and triallyl isocyanurate, mixed in a mass ratio of 5:5.

[0091] Wherein, the tannic acid-Fe 3 The complex was prepared by the following method

[0092] A1. Dissolve tannic acid in deionized water and stir thoroughly to obtain a tannic acid solution.

[0093] A2. Dissolve ferric chloride hexahydrate in deionized water, then slowly add the ferric chloride hexahydrate solution dropwise to the tannic acid solution, and adjust the pH to 7 using NaOH solution; wherein the molar ratio of tannic acid to FeCl3 is 1:3;

[0094] A3. Under stirring, the reaction temperature is maintained at 90°C, and the reaction is carried out to form a complex, and then tannic acid-Fe3 is obtained by centrifugation. + Complex powder;

[0095] A4. Wash the separated complex powder with appropriate amount of water and ethanol to remove unreacted tannic acid, iron salt and other impurities. Finally, dry the washed complex to obtain pure tannic acid-Fe3 + complex.

[0096] The preparation method of the composite shoe material comprises the following steps:

[0097] S1. According to parts by weight, 60 parts of bio-based EVA polymer, 30 parts of bio-based TPU, 1.0 part of cross-linking agent, 6 parts of compatibilizer, 8 parts of nucleating agent, 7 parts of filler, 7 parts of plasticizer, 15 parts of flexible component, 7 parts of biodegradation promoter, 10 parts of non-polyolefin elastomer, 5 parts of foaming agent, and 10 parts of maleic anhydride grafted polyethylene wax are mixed evenly, and then granulated by twin-screw mixing for later use; the specific operation is as follows: first, the bio-based EVA polymer, bio-based TPU, compatibilizer, filler, plasticizer, flexible component, non-polyolefin elastomer and maleic anhydride grafted polyethylene wax are mixed evenly, and then the nucleating agent, biodegradation promoter, cross-linking agent and foaming agent are added, and mixed and granulated in a twin-screw extruder, and the temperature of the extruder is controlled at 120-130°C and the screw speed is 95-115rpm;

[0098] S2. After the granules are placed for more than 24 hours, they are placed in a foaming kettle for foaming, nitrogen is introduced, and the temperature is raised to 150°C and the pressure is increased to 23 MPa to make it reach a supercritical state. After reaching the supercritical state, the temperature and pressure are maintained for 3 hours. After the gas is saturated, the pressure is released and the test piece is taken out, and the sample is cut to obtain a composite shoe material; the specific operation is as follows: the granules are placed at room temperature and allowed to stand for 40 hours, and then the granules are placed in a foaming kettle. After sealing, nitrogen is introduced to replace the air in the kettle, the temperature is raised to 150°C, and the pressure is increased to 23 MPa at the same time to make the system reach a supercritical state. It is maintained under this condition for 3 hours, and then the pressure is released at a rate of 5 MPa / min. Finally, the test piece is taken out, cooled to room temperature at room temperature, and cut into the required shape and size.

[0099] The resulting composite shoe material exhibits the following characteristics: density of 0.10-0.20 g / cm³, hardness of 40-50 Shore A, tensile strength ≥3.0 MPa, elongation at break ≥170%, and resilience ≥48%. These properties were measured using the latest national testing standards for their respective fields. Suitable for the production of full soles for high-end professional athletic shoes, this composite shoe material exhibits excellent shock absorption, elastic recovery, durability, and good biodegradability.

[0100] The above embodiments are preferred implementation schemes of the present invention. In addition, the present invention can also be implemented in other ways. Any obvious replacement without departing from the concept of the present invention is within the scope of protection of the present invention.

Claims

1. A composite shoe material containing bio-based EVA, characterized by: The invention comprises the following raw materials in parts by weight: 40-60 parts of bio-based EVA polymer, 10-30 parts of bio-based TPU, 0.1-1.0 parts of cross-linking agent, 2-6 parts of compatibilizer, 4-8 parts of nucleating agent, 3-7 parts of filler, 1-5 parts of foaming agent, 3-7 parts of plasticizer, 5-15 parts of flexible component, 3-7 parts of biodegradation accelerator, 6-10 parts of non-polyolefin elastomer, and 5-10 parts of maleic anhydride grafted polyethylene wax.

2. The composite shoe material containing bio-based EVA according to claim 1, characterized in that: The compatibilizer is one or more of ethylene-vinyl alcohol, ethylene-vinyl acetate grafted maleic anhydride, and naphthenic oil.

3. The composite shoe material containing bio-based EVA according to claim 1, characterized in that: The nucleating agent is one or more of nano-grade talc, nano-titanium dioxide, nano-zinc oxide and nano-calcium carbonate.

4. The composite shoe material containing bio-based EVA according to claim 1, characterized in that: The filler is one or more of ethyl cellulose, organic montmorillonite, nano-SiO2, talcum powder, bagasse fiber, starch, and cellulose.

5. The composite shoe material containing bio-based EVA according to claim 1, characterized in that: The foaming agent is an azodicarbonamide foaming agent.

6. The composite shoe material containing bio-based EVA according to claim 1, characterized in that: The flexible component is one or more of polyolefin elastomer, thermoplastic polyurethane and styrene elastomer.

7. The composite shoe material containing bio-based EVA according to claim 1, characterized in that: The biodegradation promoter is composed of immobilized lipase, tannic acid-Fe 3+ The complex and the surface carboxylated TiO2 are composed in a mass ratio of 5:3:01.5-2.

5.

8. The composite shoe material containing bio-based EVA according to claim 1, characterized in that: The non-polyolefin elastomer is one or more of styrene elastomer, thermoplastic polyester elastomer and polyamide elastomer.

9. The composite shoe material containing bio-based EVA according to claim 1, characterized in that: The cross-linking agent is a mixture of di(tert-butyl peroxyisopropyl)benzene and triallyl isocyanurate.

10. A method for preparing a composite shoe material containing bio-based EVA according to any one of claims 1 to 9, characterized in that: The steps include: S1. Mix the bio-based EVA polymer, bio-based TPU, cross-linking agent, compatibilizer, nucleating agent, filler, plasticizer, flexible component, biodegradation accelerator, non-polyolefin elastomer, foaming agent, and maleic anhydride grafted polyethylene wax in parts by weight, and granulate them through a twin-screw extruder for later use. S2. After the granulated material is placed for more than 24 hours, it is placed in a foaming kettle for foaming, nitrogen is introduced, and the temperature is raised to 130-150°C and the pressure is increased to 15-23 MPa to make it reach a supercritical state. After reaching the supercritical state, the temperature and pressure are maintained for 1-3 hours. After the gas is saturated, the pressure is released, the test piece is taken out, and the sample is cut to obtain a composite shoe material.