High-elastic wear-resistant EVA foam material and preparation method thereof

Abstract

The invention belongs to the technical field of high polymer material foaming, and particularly relates to a high-elastic wear-resistant EVA foaming material and a preparation method thereof. Through ternary compounding of EVA, metallocene polyolefin and POE elastomer, a high-strength and high-elasticity resin matrix is constructed, and the problem that strength and elasticity of a traditional material are difficult to consider at the same time is solved. The silane coupling agent and the POE are adopted to carry out synergistic surface modification on the calcium carbonate / talcum powder filler to form a tough interface layer, so that the rigidity and the wear resistance are improved, and meanwhile, the high elasticity is kept. Recycled plastics are innovatively used as carrier master batches, efficient dispersion of PTFE micro powder and a compound stabilizer is achieved, and the surface abrasion resistance, the coloring stability and the thermo-oxidative aging resistance are synchronously enhanced. The optimized step-by-step mixing and foaming process ensures that the filler is uniformly dispersed and the foaming agent is prevented from being decomposed in advance through accurate temperature control and sequential charging, and finally a three-dimensional network structure with uniform and fine foam holes is formed, so that the comprehensive performance of the product is excellent and stable.

Description

Technical Field

[0001] This invention belongs to the field of polymer foaming technology, specifically relating to a high-elasticity and wear-resistant EVA foaming material and its preparation method. Background Technology

[0002] Ethylene vinyl acetate (EVA or E / VAC), also known as ethylene / vinyl acetate copolymer, is a synthetic material made by polymerizing ethylene and vinyl acetate. EVA is an important polymer material, and its industrial production typically employs a high-pressure continuous bulk polymerization process, where non-polar ethylene and highly polar vinyl acetate undergo a polymerization reaction under high temperature and pressure conditions. Due to its excellent properties, EVA is processed into a variety of products, including but not limited to foamed materials, functional and packaging films, injection-molded / blow-molded products, adhesives, cable sheaths, and photovoltaic films.

[0003] However, traditional EVA foam materials face numerous technical bottlenecks in pursuing high performance. While single EVA resin exhibits good flexibility after foaming, its tensile strength, tear resistance, and fatigue resistance are insufficient, and its elastic recovery (resilience) is limited, making it prone to permanent deformation. Simply increasing the VA content of EVA to enhance elasticity sacrifices the material's strength and dimensional stability. Although the industry often uses blending with polyolefins (such as PE) or elastomers (such as rubber) for modification, simple blending often leads to poor interfacial compatibility, resulting in materials that are either "rigid and brittle" or "soft and weak," making it difficult to achieve the ideal balance between high elasticity and high strength.

[0004] To reduce costs and improve dimensional stability, rigidity, and wear resistance, existing technologies often require the addition of large amounts of inorganic fillers (such as calcium carbonate and talc) to EVA. However, untreated fillers have poor compatibility with the organic polymer matrix, easily agglomerate, and form stress concentration points. This not only severely damages the integrity of the cell structure, leading to increased material hardness, a sharp drop in elasticity, and increased susceptibility to cracking, but also causes filler particles to easily detach during friction, thus exacerbating wear. While conventional silane coupling agent treatment can improve wettability, its contribution to improving elasticity is limited.

[0005] Furthermore, the performance of EVA foam materials largely depends on their uniform and fine internal cell structure. Traditional one-step mixing processes are prone to partial decomposition or pre-crosslinking of the foaming agent and crosslinking agent due to premature heating and shearing, resulting in uneven foaming and large cells.

[0006] Therefore, it is urgent to research and develop an EVA foam material that simultaneously achieves excellent high elasticity, superior wear resistance, and good mechanical strength, and to establish a stable and efficient preparation method. Summary of the Invention

[0007] The purpose of this invention is to address existing problems by providing a high-elasticity, wear-resistant EVA foam material and its preparation method.

[0008] This invention is achieved through the following technical solution: A high-elasticity, wear-resistant EVA foam material is composed of the following raw materials in parts by weight: 100 parts resin matrix, 20-40 parts surface-modified composite mineral filler, 3-8 parts multifunctional additives, 5-9 parts foaming crosslinking system, and 0.5-1.5 parts lubricant; The surface-modified composite mineral filler is obtained by mixing 1250-mesh ultrafine heavy calcium carbonate and 500-800-mesh flaky talc powder at a mass ratio of 1:(0.5-1), and then synergistically surface-modifying it with a silane coupling agent and an ethylene-octene copolymer. The multifunctional additive is uniformly mixed from the following components by weight percentage: 30-45% polytetrafluoroethylene micro powder, 20-35% coloring-heat resistant composite stabilizer, and 30-40% carrier masterbatch; the carrier masterbatch is obtained by melt extrusion granulation of recycled polyolefin plastic and inorganic filler.

[0009] Furthermore, the resin matrix is ​​composed of ethylene-vinyl acetate copolymer, metallocene polyolefin, and ethylene-octene copolymer elastomer in a ratio of (70~80):(10~20):(10~15); The VA content of the ethylene-vinyl acetate copolymer is 18-28%, and the melt index is 2.5-4.0 g / 10 min. The density of the metallocene polyolefin is 0.90~0.92 g / cm³. 3 The melt flow index is 1.0~3.0 g / 10 min; The ethylene-octene copolymer elastomer has a Shore hardness D of 30-40 and a melt index of 0.5-1.5 g / 10 min.

[0010] Furthermore, in the foaming and crosslinking system, the mass ratio of foaming agent to crosslinking agent is (3~4):1; The foaming agent is azodicarbonamide, which has a decomposition temperature of 160~170℃. The crosslinking agent is dicumyl peroxide, with an active oxygen content of 7.0-7.5%.

[0011] Furthermore, the lubricant is zinc stearate.

[0012] Furthermore, the preparation of the surface-modified composite mineral filler includes the following steps: (1) Dry 1250 mesh ultrafine heavy calcium carbonate and flaky talc powder separately to a moisture content of ≤0.3%, then mix them in proportion to obtain mineral composite powder; (2) Dissolve the ethylene-octene copolymer in toluene, then add the silane coupling agent KH-570, stir to dissolve, and prepare a modification solution; wherein, the amount of KH-570 is 1.0~1.5% of the total mass of the mineral composite powder, and the amount of ethylene-octene copolymer is 2~3% of the total mass of the mineral composite powder; (3) Add the mineral composite powder to the high-speed mixer, heat it to 90°C, rotate it at 800~1000 rpm, spray the modification liquid at a uniform speed for 2~3 min, keep the temperature at 90°C, increase the rotation speed to 1000~1200 rpm, and react for 10~15 min. (4) After the reaction is complete, cool down to 40~50℃, discharge the material, crush it, pass it through an 80-mesh sieve, and seal it for later use.

[0013] Furthermore, the carrier masterbatch in the multifunctional additive is prepared by premixing clean and dried recycled polyethylene or polypropylene plastic fragments with precipitated barium sulfate at a mass ratio of (65~75):(25~35), and then melt-extruding and granulating the mixture using a twin-screw extruder at 170~200℃. Furthermore, the coloring-heat resistant composite stabilizer in the multifunctional additive is composed of a colorant and a heat stabilizer in a mass ratio of 1:(0.5~2).

[0014] Furthermore, the colorant is rutile titanium dioxide or carbon black; the heat stabilizer is hindered phenolic antioxidant or phosphite auxiliary antioxidant.

[0015] A method for preparing a high-elasticity, wear-resistant EVA foam material includes the following steps: S1, First-order plasticizing blend: The resin matrix, lubricant, and 40-60% of the total amount of multifunctional additives are added to an internal mixer and plasticized and mixed at 100-110°C until they are melted and uniform. S2, Second-stage packing composite: Add all the surface-modified composite mineral filler and the remaining multifunctional additives to the internal mixer in step S1, heat to 110~120℃, and continue mixing until the filler is evenly dispersed to obtain a premix. S3, Final Refining with Added Foaming System: The premixed material is transferred to a two-roll mill, cooled to 80-90°C, and the foaming crosslinking system is added. After mixing evenly, the material is sheeted to obtain raw rubber sheets. S4. Compression foaming molding: The raw rubber sheet is placed in a mold and subjected to molding and foaming in two stages on a flat vulcanizing machine: preheating and cross-linking, and high-temperature foaming. Then, the temperature is reduced and the pressure is released to obtain the foamed material blank. S5, Post-ripening: The foamed material preform is placed at room temperature for more than 24 hours to obtain the high-elasticity and wear-resistant EVA foamed material.

[0016] Furthermore, the specific conditions for compression molding foaming in step S4 are as follows: first, the temperature is raised to 120-130°C under a pressure of 5-8 MPa and held for 3-5 minutes for preheating and crosslinking; then, the temperature is raised to 160-170°C under a pressure of 8-10 MPa and foamed for 8-12 minutes.

[0017] The present invention has the following advantages over the prior art: 1. This invention achieves a breakthrough in material performance through a ternary compound of ethylene-vinyl acetate copolymer (EVA), metallocene polyolefin, and ethylene-octene copolymer (POE) elastomer. EVA provides a good foaming base and flexibility, metallocene polyolefin significantly improves the tensile strength and melt uniformity of the material due to its regular molecular structure, and POE elastomer, as a highly efficient elastic recovery component, greatly enhances the material's resilience and resistance to compression set. The complementary advantages of these three components construct a resin matrix with both a high-strength skeleton and a high-elasticity network at the molecular level, fundamentally solving the core contradiction of traditional EVA foam materials where strength and elasticity are difficult to balance.

[0018] 2. The surface-modified composite mineral filler of this invention plays a crucial role in reinforcement and toughening. By synergistically modifying the surface of the calcium carbonate / talc composite filler with a silane coupling agent (KH-570) and POE, a robust and flexible interfacial transition layer is constructed between the inorganic filler and the organic resin matrix. This interfacial layer not only effectively promotes filler dispersion and reduces stress concentration, but also dissipates energy through its own deformation under external forces. Therefore, while significantly improving the material's wear resistance, rigidity, and dimensional stability, it maximizes the preservation of the system's high elasticity, achieving high performance under high filler conditions.

[0019] 3. This invention uses recycled polyolefin plastics as the carrier masterbatch, achieving not only environmental protection and economy, but also serving as a highly efficient dispersion carrier to ensure the uniform distribution of polytetrafluoroethylene (PTFE) micropowder and the coloring-heat-resistant composite stabilizer in the matrix. The PTFE micropowder, acting as a "solid lubricant," greatly improves surface wear resistance, while the composite stabilizer ensures color stability and resistance to thermo-oxidative aging during processing and use. This design avoids compatibility and dispersibility problems that may result from simple mixing of multiple additives, achieving a synergistic effect.

[0020] 4. In terms of the preparation process, the optimized step-by-step preparation process of first-stage plasticization-second-stage filler-final foaming in this invention provides a reliable guarantee for the realization of the above-mentioned material design. This process, through precise control of temperature and feeding sequence, ensures full plasticization of the resin, perfect wetting and dispersion of the filler, and effectively prevents premature decomposition of the foaming agent. Finally, in the molding foaming stage, the precise combination of preheating crosslinking and high-temperature foaming forms a three-dimensional network structure with moderate crosslinking degree and uniform and delicate cell structure. This structure is a direct guarantee for the material to obtain excellent resilience, cushioning performance, and high mechanical strength, ensuring the uniformity and stability of product performance. Detailed Implementation

[0021] To further explain the present invention, the following specific embodiments are described.

[0022] Preparation Example 1 The preparation of surface-modified composite mineral filler I includes the following steps: (1) Dry 1250 mesh ultrafine heavy calcium carbonate and flaky talc powder separately to a moisture content of ≤0.3%, then mix them in proportion to obtain mineral composite powder; (2) Dissolve the ethylene-octene copolymer in toluene, then add the silane coupling agent KH-570, stir to dissolve, and prepare a modification solution; wherein, the amount of KH-570 is 1.0% of the total mass of the mineral composite powder, and the amount of ethylene-octene copolymer is 2% of the total mass of the mineral composite powder; (3) Add the mineral composite powder to the high-speed mixer, heat it to 90°C, rotate it at 800 rpm, spray the modification liquid at a uniform speed for 2 min, keep the temperature at 90°C, increase the rotation speed to 1000 rpm, and react for 10 min. (4) After the reaction is complete, cool down to 40°C, discharge the material, crush it, pass it through an 80-mesh sieve, and seal it for later use.

[0023] Preparation Example 2 The preparation of surface-modified composite mineral filler II includes the following steps: (1) Dry 1250 mesh ultrafine heavy calcium carbonate and flaky talc powder separately to a moisture content of ≤0.3%, then mix them in proportion to obtain mineral composite powder; (2) Dissolve the ethylene-octene copolymer in toluene, then add the silane coupling agent KH-570, stir to dissolve, and prepare a modification solution; wherein, the amount of KH-570 is 1.2% of the total mass of the mineral composite powder, and the amount of ethylene-octene copolymer is 2.5% of the total mass of the mineral composite powder; (3) Add the mineral composite powder to the high-speed mixer, heat it to 90°C, rotate it at 900 rpm, spray the modification liquid at a uniform speed for 2.5 min, keep the temperature at 90°C, increase the rotation speed to 1100 rpm, and react for 12 min. (4) After the reaction is complete, cool down to 45°C, discharge the material, crush it, pass it through an 80-mesh sieve, and seal it for later use.

[0024] Preparation Example 3 The preparation of surface-modified composite mineral filler III includes the following steps: (1) Dry 1250 mesh ultrafine heavy calcium carbonate and flaky talc powder separately to a moisture content of ≤0.3%, then mix them in proportion to obtain mineral composite powder; (2) Dissolve the ethylene-octene copolymer in toluene, then add the silane coupling agent KH-570, stir to dissolve, and prepare a modification solution; wherein, the amount of KH-570 is 1.5% of the total mass of the mineral composite powder, and the amount of ethylene-octene copolymer is 3% of the total mass of the mineral composite powder; (3) Add the mineral composite powder to the high-speed mixer, heat it to 90°C, rotate it at 1000 rpm, spray the modification liquid at a uniform speed for 3 min, keep the temperature at 90°C, increase the rotation speed to 1200 rpm, and react for 15 min. (4) After the reaction is complete, cool down to 50°C, discharge the material, crush it, pass it through an 80-mesh sieve, and seal it for later use. Example 1

[0025] A method for preparing a high-elasticity, wear-resistant EVA foam material includes the following steps: S1. Raw material preparation: Weigh out 100 parts of resin matrix, 20 parts of surface-modified composite mineral filler I, 3 parts of multifunctional additive, 5 parts of foaming crosslinking system, and 0.5 parts of zinc stearate for later use; The resin matrix is ​​composed of ethylene-vinyl acetate copolymer, metallocene polyolefin, and ethylene-octene copolymer elastomer in a ratio of 70:10:10; the ethylene-vinyl acetate copolymer has a VA content of 18% and a melt index of 2.5 g / 10 min; the metallocene polyolefin has a density of 0.90 g / cm³. 3 The melt flow index is 1.0 g / 10 min; the Shore hardness D of the ethylene-octene copolymer elastomer is 30, and the melt flow index is 0.5 g / 10 min. The surface-modified composite mineral filler I is obtained by mixing 1250-mesh ultrafine heavy calcium carbonate and 500-mesh flaky talc powder at a mass ratio of 1:0.5, and then synergistically surface-modifying it with a silane coupling agent and an ethylene-octene copolymer. The multifunctional additive is uniformly mixed from the following components by weight percentage: 40% polytetrafluoroethylene micro powder, 20% coloring-heat resistant composite stabilizer, and 40% carrier masterbatch; the carrier masterbatch is obtained by melt extrusion granulation of recycled polyolefin plastics and inorganic fillers. The carrier masterbatch in the multifunctional additive is prepared by premixing clean and dried recycled polyethylene plastic fragments with precipitated barium sulfate at a mass ratio of 65:35, and then melting and granulating the mixture by extrusion at 170°C using a twin-screw extruder. The coloring-heat resistant composite stabilizer in the multifunctional additive is composed of a colorant and a heat stabilizer in a mass ratio of 1:0.5. The colorant is rutile titanium dioxide; the heat stabilizer is hindered phenolic antioxidant 1010. In the foaming and crosslinking system, the mass ratio of foaming agent to crosslinking agent is 3:1; wherein the foaming agent is azodicarbonamide with a decomposition temperature of 160℃; and the crosslinking agent is dicumyl peroxide with an active oxygen content of 7.0%. S2, First-stage plasticizing blending: The resin matrix, lubricant and 40% of the total amount of multifunctional additives are added to an internal mixer and plasticized and mixed at 100°C until they are melted and uniform; S3, Second-stage filler compound: Add all surface-modified composite mineral filler I and the remaining multifunctional additives to the internal mixer of step S2, heat to 110°C, and continue mixing until the filler is evenly dispersed to obtain a premix. S4. Final mixing and addition of foaming system: Transfer the premix to a two-roll mill, cool it to 80°C, add the foaming crosslinking system, mix evenly and then sheet to obtain raw rubber sheets; S5. Compression foaming: The raw rubber sheet is placed in a mold and subjected to compression foaming in two stages on a flat vulcanizing machine: preheating and cross-linking, and high-temperature foaming. Then, the temperature is reduced and the pressure is released to obtain the foamed material blank. The specific conditions for the compression molding foaming are as follows: First, the temperature is raised to 120°C under a pressure of 5MPa and held for 3 minutes for preheating and cross-linking; then, the temperature is raised to 160°C under a pressure of 8MPa and foamed for 8 minutes. S6. Post-curing: The foamed material blank is placed at room temperature for more than 24 hours to obtain the high-elasticity and wear-resistant EVA foamed material. Example 2

[0026] A method for preparing a high-elasticity, wear-resistant EVA foam material includes the following steps: S1. Raw material preparation: Weigh out 100 parts of resin matrix, 30 parts of surface-modified composite mineral filler II, 5 parts of multifunctional additive, 7 parts of foaming crosslinking system, and 1 part of zinc stearate for later use; The resin matrix is ​​composed of ethylene-vinyl acetate copolymer, metallocene polyolefin, and ethylene-octene copolymer elastomer in a ratio of 75:15:12; the ethylene-vinyl acetate copolymer has a VA content of 22% and a melt index of 3.5 g / 10 min; the metallocene polyolefin has a density of 0.91 g / cm³. 3 The melt flow index is 2.0 g / 10 min; the Shore hardness D of the ethylene-octene copolymer elastomer is 35, and the melt flow index is 1 g / 10 min. The surface-modified composite mineral filler II is obtained by mixing 1250-mesh ultrafine heavy calcium carbonate and 600-mesh flaky talc powder at a mass ratio of 1:0.7, and then synergistically surface-modifying it with a silane coupling agent and an ethylene-octene copolymer. The multifunctional additive is uniformly mixed from the following components by weight percentage: 40% polytetrafluoroethylene micro powder, 30% coloring-heat resistant composite stabilizer, and 30% carrier masterbatch; the carrier masterbatch is obtained by melt extrusion granulation of recycled polyolefin plastics and inorganic fillers. The carrier masterbatch in the multifunctional additive is prepared by premixing clean and dried recycled polyethylene plastic fragments with precipitated barium sulfate at a mass ratio of 70:30, and then melting and granulating the mixture by extrusion at 180°C using a twin-screw extruder. The coloring-heat resistant composite stabilizer in the multifunctional additive is a mixture of colorant and heat stabilizer in a mass ratio of 1:1. The colorant is rutile titanium dioxide; the heat stabilizer is hindered phenolic antioxidant 1010. In the foaming and crosslinking system, the mass ratio of foaming agent to crosslinking agent is 3.5:1; wherein the foaming agent is azodicarbonamide with a decomposition temperature of 165℃; and the crosslinking agent is dicumyl peroxide with an active oxygen content of 7.2%. S2, First-stage plasticizing blending: The resin matrix, lubricant and 50% of the total amount of multifunctional additives are added to an internal mixer and plasticized and mixed at 105°C until they are melted and uniform. S3, Second-stage filler compound: Add all surface-modified composite mineral filler II and the remaining multifunctional additives to the internal mixer of step S2, heat to 115℃, and continue to mix until the filler is evenly dispersed to obtain a premix. S4. Final mixing and addition of foaming system: Transfer the premix to a two-roll mill, cool it to 85°C, add the foaming crosslinking system, mix evenly and then sheet to obtain raw rubber sheets; S5. Compression foaming: The raw rubber sheet is placed in a mold and subjected to compression foaming in two stages on a flat vulcanizing machine: preheating and cross-linking, and high-temperature foaming. Then, the temperature is reduced and the pressure is released to obtain the foamed material blank. The specific conditions for the compression molding foaming are as follows: First, the temperature is raised to 125°C under a pressure of 6MPa and held for 4 minutes for preheating and cross-linking; then, the temperature is raised to 165°C under a pressure of 9MPa and foamed for 10 minutes. S6. Post-curing: The foamed material blank is placed at room temperature for more than 24 hours to obtain the high-elasticity and wear-resistant EVA foamed material. Example 3

[0027] A method for preparing a high-elasticity, wear-resistant EVA foam material includes the following steps: S1. Raw material preparation: Weigh out the following amounts: 100 parts of resin matrix, 40 parts of surface-modified composite mineral filler III, 8 parts of multifunctional additive, 9 parts of foaming crosslinking system, and 1.5 parts of zinc stearate for later use. The resin matrix is ​​composed of ethylene-vinyl acetate copolymer, metallocene polyolefin, and ethylene-octene copolymer elastomer in a ratio of 80:20:15; the ethylene-vinyl acetate copolymer has a VA content of 28% and a melt index of 4.0 g / 10 min; the metallocene polyolefin has a density of 0.92 g / cm³. 3 The melt flow index is 3.0 g / 10 min; the Shore hardness D of the ethylene-octene copolymer elastomer is 40, and the melt flow index is 1.5 g / 10 min. The surface-modified composite mineral filler III is obtained by mixing 1250-mesh ultrafine heavy calcium carbonate and 800-mesh flaky talc powder in a mass ratio of 1:1, and then synergistically surface-modifying it with a silane coupling agent and an ethylene-octene copolymer. The multifunctional additive is uniformly mixed from the following components by weight percentage: 45% polytetrafluoroethylene micro powder, 20% coloring-heat resistant composite stabilizer, and 35% carrier masterbatch; the carrier masterbatch is obtained by melt extrusion granulation of recycled polyolefin plastics and inorganic fillers. The carrier masterbatch in the multifunctional additive is prepared by premixing clean and dried recycled polyethylene plastic fragments with precipitated barium sulfate at a mass ratio of 75:25, and then melting and granulating the mixture by extrusion at 200°C using a twin-screw extruder. The coloring-heat resistant composite stabilizer in the multifunctional additive is composed of a colorant and a heat stabilizer in a mass ratio of 1:2. The colorant is rutile titanium dioxide; the heat stabilizer is hindered phenolic antioxidant 1010. In the foaming and crosslinking system, the mass ratio of foaming agent to crosslinking agent is 4:1; wherein the foaming agent is azodicarbonamide with a decomposition temperature of 170℃; and the crosslinking agent is dicumyl peroxide with an active oxygen content of 7.5%. S2, First-stage plasticizing blending: The resin matrix, lubricant and 60% of the total amount of multifunctional additives are added to an internal mixer and plasticized and mixed at 110°C until they are melted and uniform; S3, Second-stage filler compound: Add all surface-modified composite mineral filler III and the remaining multifunctional additives to the internal mixer of step S2, heat to 120°C, and continue mixing until the filler is evenly dispersed to obtain a premix. S4. Final mixing and addition of foaming system: Transfer the premix to a two-roll mill, cool it to 90°C, add the foaming crosslinking system, mix evenly and then sheet to obtain raw rubber sheets; S5. Compression foaming: The raw rubber sheet is placed in a mold and subjected to compression foaming in two stages on a flat vulcanizing machine: preheating and cross-linking, and high-temperature foaming. Then, the temperature is reduced and the pressure is released to obtain the foamed material blank. The specific conditions for the compression molding foaming are as follows: First, the temperature is raised to 130°C under 8MPa pressure and held for 5 minutes for preheating and crosslinking; then, the temperature is raised to 170°C under 10MPa pressure and foamed for 12 minutes. S6. Post-curing: The foamed material blank is placed at room temperature for more than 24 hours to obtain the high-elasticity and wear-resistant EVA foamed material.

[0028] Comparative Example 1 Compared with Example 2, Comparative Example 1 only uses pure EVA resin matrix. Except for replacing the resin matrix with an equal amount (100 parts) of EVA with the same VA content and MI as in Example 2, the other steps and parameters are the same as in Example 2.

[0029] Comparative Example 2 Compared with Example 2, Comparative Example 2 uses unmodified ordinary mineral filler and replaces the surface-modified composite mineral filler with an equal amount (30 parts) of ordinary mineral filler. The ordinary mineral filler is obtained by mixing 1250 mesh ultrafine heavy calcium carbonate and 600 mesh flaky talc powder at a mass ratio of 1:0.7. Other steps and parameters are the same as in Example 2.

[0030] Comparative Example 3 Compared with Example 2, Comparative Example 3 uses conventional functional additives. The conventional functional additives consist of 1.6 parts of PTFE micro powder, 1.5 parts of rutile titanium dioxide, and 0.5 parts of hindered phenolic antioxidant 1010, which are added directly during the initial mixing of raw materials. Other steps and parameters are the same as in Example 2.

[0031] Comparative Example 4 Compared with Example 2, Comparative Example 4 adopts a conventional one-step mixing process, in which all raw materials are added to the internal mixer at one time, mixed at 110°C for 15 minutes, and then discharged, started to grind, and sheeted. The subsequent molding and foaming process is the same as in Example 2.

[0032] Performance testing 1. Test Methods (1) Apparent density: The apparent density was determined in accordance with GB / T 6343-2009 "Determination of apparent density of foamed plastics and rubber".

[0033] (2) Hardness (Asker C): The Asker C hardness tester was used to measure the hardness in accordance with GB / T 531.1-2008 "Test method for indentation hardness of vulcanized rubber or thermoplastic rubber - Part 1: Shore hardness tester method (Shore hardness)".

[0034] (3) Compression set: According to GB / T 6669-2008 "Determination of compression set of flexible foam polymer materials", the compression set was measured after being compressed by 50% at 70℃ and held for 22 hours. The lower the value, the better the elastic recovery.

[0035] (4) Rebound rate: The rebound rate was determined in accordance with GB / T 6670-2008 "Determination of rebound performance of flexible foam polymer materials by falling ball method".

[0036] (4) Tensile strength and elongation at break: The tensile strength and elongation at break of the polymer porous elastic materials shall be determined in accordance with GB / T 10654-2001.

[0037] (5) Abrasion resistance (DIN abrasion): Refer to GB / T 9867-2008 "Determination of abrasion resistance of vulcanized rubber or thermoplastic rubber (rotary roller abrasion tester method)" and use a DIN abrasion tester to record the volume loss of abrasion. The lower the value, the better the abrasion resistance.

[0038] 2. Experimental Results The performance of the EVA foam materials prepared by the methods of Examples 1-3 and Comparative Examples 1-4 were tested according to the above scheme. Three parallel tests were conducted and the average value was taken as the final test result.

[0039] The test results are shown in Table 1 below.

[0040] Table 1 Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 <![CDATA[Apparent density (g / cm 3 ).]]> 0.21 0.22 0.23 0.21 0.23 0.22 0.25 Hardness (Asker C) 50 55 60 48 62 58 60 Compression set (%) 20 18 22 25 35 28 32 Rebound rate (%) 65 68 63 55 50 60 52 Tensile strength (MPa) 3.2 3.5 3.8 2.2 2.8 3.0 2.6 Elongation at break (%) 300 280 260 320 180 240 200 <![CDATA[DIN wear amount (mm 3 )]]> 140 120 130 180 160 200 150 As can be seen from Table 1 above, compared with Example 2, the compression set of Comparative Example 1 (pure EVA) is significantly higher than that of Example 2, and the rebound rate is greatly reduced, confirming its insufficient elastic recovery ability. At the same time, the significant deterioration of its tensile strength and abrasion resistance comprehensively proves that the contribution of metallocene polyolefin to strength and the contribution of POE elastomer to high elasticity are indispensable, and only through the synergy of the three can the unity of high strength and high elasticity be achieved.

[0041] Comparative Example 2 (unmodified filler) exhibited the worst elastic properties: compression set as high as 35%, rebound rate as low as 50%, and elongation at break sharply reduced to 180%. This is directly attributed to the extremely poor interfacial compatibility between the unmodified filler and the resin matrix, causing filler agglomeration into stress concentration points, which easily lead to cell wall rupture under stress, thus making the material hard, brittle, and losing elasticity. The surface modification treatment of this invention successfully constructs a flexible interfacial layer, which is the key technology for maintaining high elasticity under high filler content.

[0042] The DIN abrasion rate of Comparative Example 3 (with conventional additives) was 67% higher than that of Example 2, and its abrasion resistance decreased sharply. This clearly shows that simple physical mixing cannot effectively disperse PTFE micropowder, resulting in its inability to form a continuous abrasion-resistant network. This invention uses recycled plastic carrier masterbatch to pre-disperse and "encapsulate" PTFE and stabilizers, ensuring their uniform distribution and efficient utilization in the matrix, thus maximizing functionality.

[0043] The material obtained from Comparative Example 4 (one-step mixing) had a higher density and a comprehensive decline in overall performance. This indicates that one-time mixing under high temperature and high shear easily leads to premature decomposition of the foaming agent, uneven consumption of the crosslinking agent, and poor dispersion of the filler, ultimately resulting in uneven cell structure, low foaming efficiency, and impaired mechanical properties. The step-by-step process of this invention, through precise feeding sequence and temperature control, provides a solid process guarantee for obtaining a uniform and fine cell structure and high-performance finished product.

[0044] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-elasticity, wear-resistant EVA foam material, characterized in that, It consists of the following raw materials in parts by weight: 100 parts resin matrix, 20-40 parts surface-modified composite mineral filler, 3-8 parts multifunctional additives, 5-9 parts foaming crosslinking system, and 0.5-1.5 parts lubricant; The surface-modified composite mineral filler is obtained by mixing 1250-mesh ultrafine heavy calcium carbonate and 500-800-mesh flaky talc powder at a mass ratio of 1:(0.5-1), and then synergistically surface-modifying it with a silane coupling agent and an ethylene-octene copolymer. The multifunctional additive is uniformly mixed from the following components by weight percentage: 30-45% polytetrafluoroethylene micro powder, 20-35% coloring-heat resistant composite stabilizer, and 30-40% carrier masterbatch; the carrier masterbatch is obtained by melt extrusion granulation of recycled polyolefin plastic and inorganic filler.

2. The high-elasticity, wear-resistant EVA foam material according to claim 1, characterized in that, The resin matrix is ​​composed of ethylene-vinyl acetate copolymer, metallocene polyolefin, and ethylene-octene copolymer elastomer in a ratio of (70~80):(10~20):(10~15); The VA content of the ethylene-vinyl acetate copolymer is 18-28%, and the melt index is 2.5-4.0 g / 10 min. The density of the metallocene polyolefin is 0.90~0.92 g / cm³. 3 The melt flow index is 1.0~3.0 g / 10 min; The ethylene-octene copolymer elastomer has a Shore hardness D of 30-40 and a melt index of 0.5-1.5 g / 10 min.

3. The high-elasticity, wear-resistant EVA foam material according to claim 1, characterized in that, In the foaming and crosslinking system, the mass ratio of foaming agent to crosslinking agent is (3~4):1; The foaming agent is azodicarbonamide, which has a decomposition temperature of 160~170℃. The crosslinking agent is dicumyl peroxide, with an active oxygen content of 7.0-7.5%.

4. The high-elasticity, wear-resistant EVA foam material according to claim 1, characterized in that, The lubricant is zinc stearate.

5. The high-elasticity, wear-resistant EVA foam material according to claim 1, characterized in that, The preparation of the surface-modified composite mineral filler includes the following steps: (1) Dry 1250 mesh ultrafine heavy calcium carbonate and flaky talc powder separately to a moisture content of ≤0.3%, then mix them in proportion to obtain mineral composite powder; (2) Dissolve the ethylene-octene copolymer in toluene, then add the silane coupling agent KH-570, stir to dissolve, and prepare a modification solution; wherein, the amount of KH-570 is 1.0~1.5% of the total mass of the mineral composite powder, and the amount of ethylene-octene copolymer is 2~3% of the total mass of the mineral composite powder; (3) Add the mineral composite powder to the high-speed mixer, heat it to 90°C, rotate it at 800~1000 rpm, spray the modification liquid at a uniform speed for 2~3 min, keep the temperature at 90°C, increase the rotation speed to 1000~1200 rpm, and react for 10~15 min. (4) After the reaction is complete, cool down to 40~50℃, discharge the material, crush it, pass it through an 80-mesh sieve, and seal it for later use.

6. The high-elasticity, wear-resistant EVA foam material according to claim 1, characterized in that, The carrier masterbatch in the multifunctional additive is prepared by premixing clean and dried recycled polyethylene or polypropylene plastic fragments with precipitated barium sulfate at a mass ratio of (65~75):(25~35), and then melt-extruding and granulating the mixture using a twin-screw extruder at 170~200℃.

7. The high-elasticity, wear-resistant EVA foam material according to claim 1, characterized in that, The coloring-heat resistant composite stabilizer in the multifunctional additive is a compound of colorant and heat stabilizer in a mass ratio of 1:(0.5~2).

8. The high-elasticity, wear-resistant EVA foam material according to claim 7, characterized in that, The colorant is rutile titanium dioxide or carbon black; the heat stabilizer is hindered phenolic antioxidant or phosphite auxiliary antioxidant.

9. A method for preparing the high-elasticity, wear-resistant EVA foam material according to any one of claims 1 to 8, characterized in that, Includes the following steps: S1, First-order plasticizing blend: The resin matrix, lubricant, and 40-60% of the total amount of multifunctional additives are added to an internal mixer and plasticized and mixed at 100-110°C until they are melted and uniform. S2, Second-stage packing composite: Add all the surface-modified composite mineral filler and the remaining multifunctional additives to the internal mixer in step S1, heat to 110~120℃, and continue mixing until the filler is evenly dispersed to obtain a premix. S3, Final Refining with Added Foaming System: The premixed material is transferred to a two-roll mill, cooled to 80-90°C, and the foaming crosslinking system is added. After mixing evenly, the material is sheeted to obtain raw rubber sheets. S4. Compression foaming molding: The raw rubber sheet is placed in a mold and subjected to molding and foaming in two stages on a flat vulcanizing machine: preheating and cross-linking, and high-temperature foaming. Then, the temperature is reduced and the pressure is released to obtain the foamed material blank. S5, Post-ripening: The foamed material preform is placed at room temperature for more than 24 hours to obtain the high-elasticity and wear-resistant EVA foamed material.

10. The method for preparing the high-elasticity, wear-resistant EVA foam material according to claim 9, characterized in that, The specific conditions for compression molding foaming in step S4 are as follows: First, the temperature is raised to 120-130℃ under a pressure of 5-8MPa and held for 3-5 minutes for preheating and crosslinking; then, the temperature is raised to 160-170℃ under a pressure of 8-10MPa and foamed for 8-12 minutes.