Preparation method of lightweight wear-resistant insole material

Abstract

The invention provides a preparation method of a lightweight wear-resistant insole material, which comprises the following steps: S10: carrying out melt grafting blending on thermoplastic polyester elastomer resin, ethylene-vinyl acetate copolymer carrier resin and a maleic anhydride grafted polyolefin elastomer compatilizer to prepare modified thermoplastic polyester elastomer particles; s20, mixing the modified thermoplastic polyester elastomer particles with matrix resin, a functional additive, a cross-linking agent and a foaming agent; s30, the rubber compound is placed in a primary foaming mold, and a primary foaming rough blank is prepared through mold pressing foaming; s40, the primary foaming rough blank is placed in a secondary forming mold; and after mold closing, heating is conducted firstly, then circulating cooling water is introduced into the secondary forming mold for cooling, the mold closing pressure is maintained in the cooling process, and mold opening is conducted till the temperature of the secondary forming mold is reduced. According to the preparation method, the problems that a conventional EVA insole material is prone to collapse and poor in wear resistance can be solved.

Description

Technical Field

[0001] This invention relates to the field of midsole material technology, specifically to a method for preparing a lightweight and abrasion-resistant midsole material. Background Technology

[0002] Ethylene-vinyl acetate copolymer (EVA) is widely used in footwear materials (such as midsoles, insoles, and footbeds), packaging materials, and sports protective equipment due to its excellent cushioning, heat insulation, and processing properties. However, EVA materials also have drawbacks such as limited resilience and significant compression set. During prolonged or high-intensity exercise, EVA midsoles are prone to collapse, leading to decreased cushioning performance and wearing comfort. Furthermore, EVA foam materials have poor abrasion resistance, typically requiring an external rubber outsole to provide grip and abrasion resistance, which increases the overall weight of the footwear and the manufacturing process. Summary of the Invention

[0003] The purpose of this invention is to overcome the above-mentioned defects or problems in the prior art and provide a method for preparing a lightweight and wear-resistant midsole material, which can improve the problems of easy collapse and poor wear resistance of conventional EVA midsole materials.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: Technical Solution 1: A method for preparing a lightweight and wear-resistant midsole material, comprising the following steps: S10: Preparing modified thermoplastic polyester elastomer particles: Thermoplastic polyester elastomer resin, ethylene-vinyl acetate copolymer carrier resin, and maleic anhydride-grafted polyolefin elastomer compatibilizer are melt-grafted and blended at 155℃-165℃ to obtain modified thermoplastic polyester elastomer particles with a softening point of 120℃-130℃; S20: Preparing a compound: The modified thermoplastic polyester elastomer particles are blended with a matrix resin, functional additives, crosslinking agents, and foaming agents at 115℃-125℃, wherein the melt flow rate ratio of the modified thermoplastic polyester elastomer particles to the ethylene-vinyl acetate copolymer in the matrix resin is 1.2:1 to 2.0:1; S30: S1: Foaming: The compound is placed in a primary foaming mold and foamed at 170℃-180℃ to obtain a primary foamed preform with an expansion ratio of 175%-185%; S40: Secondary molding: The primary foamed preform is placed in a secondary molding mold, and the ratio of the volume of the primary foamed preform to the cavity volume of the secondary molding mold is 1.4:1 to 1.5:1; After the mold is closed, it is first heated at 175℃-181℃ for 550 seconds-610 seconds, and then circulating cooling water at 10℃-25℃ is introduced into the secondary molding mold for cooling. During the cooling process, the mold closing pressure is maintained until the temperature of the secondary molding mold drops to 40℃-50℃ before the mold is opened.

[0005] Technical Solution 2 based on Technical Solution 1: In step S10, each component includes, by weight, 50-60 parts of thermoplastic polyester elastomer resin, 40-50 parts of ethylene-vinyl acetate copolymer carrier resin, 2-5 parts of maleic anhydride grafted polyolefin elastomer compatibilizer, and 0.5-1.0 parts of stearic acid.

[0006] Technical Solution 3 based on Technical Solution 1: In step S10, the rotation speed during melt grafting is 280 r / min to 320 r / min, and the melt index of the modified thermoplastic polyester elastomer particles obtained is 4.5-5.5 g / 10 min under the test conditions of 190℃ and 2.16 kg.

[0007] Technical Solution Four based on Technical Solution One: In step S20, the matrix resin comprises, by weight, 30-40 parts of ethylene-vinyl acetate copolymer, 15-20 parts of polyolefin elastomer, 10-20 parts of styrene block copolymer, and 5-10 parts of ethylene propylene diene monomer (EPDM) rubber; wherein, the amount of modified thermoplastic polyester elastomer particles added is 20-30 parts.

[0008] Technical Solution 5 based on Technical Solution 1: In step S20, the functional additive includes a wear-resistant agent, which is an organosilicon masterbatch, and the amount of the organosilicon masterbatch added to the compound is 8-10 parts.

[0009] Technical Solution Six based on Technical Solution One: In step S20, the crosslinking agent is bis(tert-butylperoxyisopropyl)benzene, and the addition amount is 0.6-0.7 parts; the foaming agent is modified azodicarbonamide, and the addition amount is 3.2-3.6 parts.

[0010] Technical solution seven based on technical solution one: between step S30 and step S40, step S35 is also included: the primary foamed preform is left to stand at 20℃-30℃ for 24 to 48 hours, and then the skin layer on the surface of the primary foamed preform is removed by mechanical grinding.

[0011] Technical solution eight based on technical solution one: In step S40, the cooling rate during the cooling stage is 10℃ / min to 15℃ / min.

[0012] Technical Solution Nine based on Technical Solution One: In step S20, the specific steps of the mixing are as follows: S21: Mix the modified thermoplastic polyester elastomer particles and the matrix resin and mix for 20-40 seconds; S22: Add the functional additives and continue mixing until the material temperature reaches 115℃-121℃; S23: Add the crosslinking agent and the foaming agent, mix until the material temperature reaches 123℃-127℃ and then discharge the material; wherein, the total mixing time from steps S21 to S23 is 9 minutes-13 minutes.

[0013] Technical Solution 10 based on Technical Solution 1: After completing step S20 and before entering step S30, it also includes a refining process: the discharged material is placed on a double roller for refining, the temperature of the front roller is controlled at 90℃-100℃ and the temperature of the rear roller is controlled at 80℃-90℃; during the refining process, the material is refining and packaging 4-6 times, and then the roller gap is adjusted until the material output temperature is 115℃-120℃, and the material is output according to the preset thickness specifications.

[0014] As can be seen from the above description of the present invention, compared with the prior art, the present invention has the following beneficial effects: The first technical solution of the present invention provides a method for preparing a lightweight and wear-resistant midsole material. This method improves the problems of easy collapse and poor wear resistance of conventional EVA midsole materials by pre-modifying thermoplastic polyester elastomer and improving specific processes in secondary molding.

[0015] This solution addresses the problem of uneven mixing between thermoplastic polyester elastomer and ethylene-vinyl acetate copolymer due to their vastly different melting points. In conventional techniques, the melting temperature of thermoplastic polyester elastomers is typically above 180°C, while the foaming processing temperature of ethylene-vinyl acetate copolymers usually cannot exceed 130°C, otherwise the foaming agent and crosslinking agent will become ineffective. Direct mixing results in the thermoplastic polyester elastomer existing as solid particles, leading to uneven bubble distribution or easy tearing defects within the foamed material. This solution reduces the softening temperature to below 130°C by pre-melting the thermoplastic polyester elastomer, carrier resin, and grafting material. This allows the modified particles to melt and mix evenly with the ethylene-vinyl acetate copolymer in subsequent processes. By controlling the melt index ratio between 1.2 and 2.0, the thermoplastic polyester elastomer forms a continuous network support structure within the material. This structure utilizes the inherent strength of the elastomer material, providing better support and resilience when the material is repeatedly compressed, thus solving the problem of ordinary foamed materials easily collapsing and deforming after long-term use.

[0016] However, the addition of a higher proportion of thermoplastic polyester elastomer introduces a new problem of surface wrinkling during the molding process. Thermoplastic polyester elastomer crystallizes rapidly during cooling and exhibits significant volume shrinkage. When manufacturing soles with high sidewall structures, this shrinkage leads to irregular wrinkles and unclear patterns on the sides. The usual approach is to reduce the amount of elastomer to avoid wrinkling, but this reduces the material's elasticity and fatigue resistance. This solution addresses this issue by employing a two-stage molding process, specifically limiting the volume compression ratio between the mold and the material to between 1.4 and 1.5, and forcibly cooling the mold to below 50 degrees Celsius using circulating water while the mold is closed. During cooling, the pressure within the mold forces the crystallizing material to adhere tightly to the inner wall of the mold. The crystalline structure formed under pressure acts as a shape stabilizer, counteracting the volume shrinkage force during cooling. This manufacturing process transforms the crystallization characteristic, which would otherwise cause defects, into a means of maintaining shape stability, ensuring smooth sole sides and clear bottom patterns, and solving the problem of achieving a fine appearance and side wrinkling with highly elastic materials.

[0017] Furthermore, this solution, through a specific material combination and a secondary molding process, forms a dense outer skin on the material surface. Under the high temperature and high pressure environment of secondary molding, the wear-resistant components in the formula migrate towards the mold surface. Because the material undergoes more than 1.4 times volume compression in the mold, the pores in the surface layer are squeezed out, forming a solid layer with a density far exceeding that of the inner foam layer. This outer skin is integrally molded with the inner foam material, possessing strong tear resistance and abrasion resistance. This allows the foam material to be used directly as the sole in contact with the ground, eliminating the need for a separate rubber layer. This design improves the durability of the sole while maintaining the material's lightweight properties.

[0018] In technical solution two, the specific proportions of the thermoplastic polyester elastomer resin, the ethylene-vinyl acetate copolymer carrier resin, and the maleic anhydride-grafted polyolefin elastomer compatibilizer are defined to ensure that a sufficient number of chemical grafting sites are generated within the material while lowering the softening point. The added stearic acid acts as an internal lubricant during extrusion, preventing the high-viscosity components from sticking together during processing and ensuring the regularity of the modified particles.

[0019] In technical solution three, the specific process of melt grafting is defined to ensure the fullness of the grafting reaction. The shear force provided by the appropriate rotation speed range allows the active groups in the compatibilizer to be evenly distributed on the polymer molecular chain, avoiding the gelation phenomenon caused by excessive local reaction. The determined melt index range ensures that these modified particles can achieve deeper micro-penetration when they are subsequently mixed with the matrix resin due to their similar fluidity.

[0020] In technical solution four, polyolefin elastomers, styrene block copolymers, and EPDM rubber are introduced into the matrix resin. Together with modified thermoplastic polyester elastomer particles, they form a multi-component resin system. These components fill the gaps in the skeleton formed by the ethylene-vinyl acetate copolymer and the elastomer, which plays a role in toughening and adjusting the feel. This allows the material to maintain stable performance under different temperature environments. In particular, it can prevent the midsole from hardening and becoming brittle under low temperature conditions, further enhancing the overall tear resistance.

[0021] In technical solution five, silicone masterbatch is added to the rubber compound as a wear-resistant agent. During the molding process, the wear-resistant agent can migrate to the surface of the material and form a distribution, reducing the friction coefficient of the finished product surface. Combined with the one-piece molded dense outer skin, when the sole of the shoe contacts the ground and generates friction, the direct mechanical damage to the material surface can be reduced through the micro-slippage of the surface layer, further improving the wear resistance and service life of the material.

[0022] In technical solution six, the type and ratio of foaming agent are limited to ensure that the crosslinking reaction rate and the foaming gas release rate are synchronized, and a uniformly distributed closed-cell structure can be formed inside the material to prevent the bubbles from collapsing or merging.

[0023] In technical solution seven, a stabilization and mechanical grinding step is added between the primary foaming and secondary molding processes. This eliminates residual processing stress inside the preform and prevents irregular deformation of the preform before it enters the secondary mold. Specifically, grinding removes the original skin layer on the surface of the preform, creating an open-pore structure on the material surface. This allows for closer contact between the material and the mold cavity during secondary molding, and promotes the re-entanglement of molecular chains at the interface during secondary heating, thereby forming a denser, higher-strength skin for secondary molding.

[0024] In technical solution eight, limiting the cooling rate during the cooling stage can effectively control the formation and growth process of crystal nuclei inside the material, avoiding coarse grains due to slow cooling and stress accumulation due to excessively rapid cooling.

[0025] In technical solution nine, modified particles, matrix resin and various additives are added in stages, and the total mixing time is controlled to ensure that the high viscosity material is fully melted and to prevent the chemical additives from decomposing or scorching prematurely due to excessive heating time.

[0026] In technical solution ten, before entering the foaming process, the rubber compound is pressed and refined through an open milling process, which further removes the tiny air bubbles that may be trapped in the compound during the internal mixing stage, improves the dispersion uniformity between components, and gives the rubber sheet a regular thickness and uniform density. Detailed Implementation

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are preferred embodiments of the present invention and should not be considered as excluding other embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0028] In the claims and description of this invention, the terms "comprising," "having," and variations thereof are used to mean "including but not limited to."

[0029] This invention relates to a method for preparing a lightweight and abrasion-resistant midsole material, which includes the following steps: S10: Preparation of modified thermoplastic polyester elastomer particles: Thermoplastic polyester elastomer resin, ethylene-vinyl acetate copolymer carrier resin and maleic anhydride grafted polyolefin elastomer compatibilizer are melt-grafted and blended at 155℃-165℃ to obtain modified thermoplastic polyester elastomer particles with a softening point of 120℃-130℃. S20: Preparation of compound: The modified thermoplastic polyester elastomer particles are compounded with a matrix resin, functional additives, crosslinking agents and foaming agents at 115℃-125℃, wherein the melt flow rate ratio of the modified thermoplastic polyester elastomer particles to the ethylene-vinyl acetate copolymer in the matrix resin is 1.2:1 to 2.0:1; S30: Primary foaming: The compound is placed in a primary foaming mold and foamed at 170℃-180℃ to obtain a primary foamed preform with an expansion ratio of 175%-185%. S40: Secondary molding: The primary foamed preform is placed in a secondary molding mold, and the ratio of the volume of the primary foamed preform to the cavity volume of the secondary molding mold is 1.4:1 to 1.5:1; after the mold is closed, it is first heated at 175℃-181℃ for 550 seconds to 610 seconds, and then circulating cooling water at 10℃-25℃ is introduced into the secondary molding mold for cooling. During the cooling process, the mold closing pressure is maintained until the temperature of the secondary molding mold drops to 40℃-50℃ before the mold is opened.

[0030] The following will provide a detailed explanation of each of the above steps.

[0031] In step S10, the modified thermoplastic polyester elastomer particles are first prepared. When preparing the raw materials, 50 to 60 parts by weight of thermoplastic polyester elastomer resin are selected as the main adhesive, and 40 to 50 parts of ethylene-vinyl acetate copolymer are selected as the carrier resin. To promote the grafting reaction and improve the compatibility between components, 2 to 5 parts of maleic anhydride-grafted polyolefin elastomer compatibilizer are added. In addition, 0.5 to 1.0 parts of stearic acid are added as a processing aid to improve flowability during processing and prevent material adhesion. In a specific implementation, 55 parts of thermoplastic polyester elastomer resin, 45 parts of ethylene-vinyl acetate copolymer carrier resin, 3 parts of maleic anhydride-grafted polyolefin elastomer compatibilizer, and 0.8 parts of stearic acid are preferably used.

[0032] The weighed raw materials are pre-mixed in a mixer. After the materials are evenly mixed, the mixture is fed into a twin-screw extruder for melt grafting. During processing, the temperature of the twin-screw extruder is controlled between 155°C and 165°C. Twin-screw extruders are typically divided into multiple heating zones. Based on the material's residence time in the barrel, the temperature of the front conveying zone is set to 155°C, the middle melting and reaction zone to 160°C, and the rear exhaust and extrusion zone to 165°C. To ensure sufficient reaction and uniform material dispersion, the screw's length-to-diameter ratio is set between 40:1 and 48:1.

[0033] During the melt grafting process, the screw rotation speed is adjusted between 280 rpm and 320 rpm. Under the high shear force of the twin screws, the material undergoes physical mixing and chemical grafting reactions, resulting in a chemical bond between the maleic anhydride groups and the elastomer molecular chains. The strip-shaped melt extruded from the extruder die is cooled by a circulating water cooling tank and then enters a pelletizer for pelletizing, thereby producing modified thermoplastic polyester elastomer granules.

[0034] The modified thermoplastic polyester elastomer granules prepared using the specific process parameters and proportions described above have a softening point reduced to 120-130 degrees Celsius, making them compatible with the processing temperature requirements of subsequent foaming processes. Under test conditions of 190 degrees Celsius and a load of 2.16 kg, the melt index of the prepared modified thermoplastic polyester elastomer granules ranges from 4.5 g / 10 min to 5.5 g / 10 min.

[0035] In step S20, the compound is prepared. First, raw materials are weighed according to a preset ratio. The base resin consists of 30 to 40 parts of ethylene-vinyl acetate copolymer, 15 to 20 parts of polyolefin elastomer, 10 to 20 parts of styrene block copolymer, and 5 to 10 parts of ethylene propylene diene monomer (EPDM) rubber. Based on this base resin, 20 to 30 parts of the modified thermoplastic polyester elastomer particles obtained in step S10 are added. Simultaneously, functional additives and a foaming system are prepared. The wear-resistant agent in the functional additives is selected from silicone masterbatch, with an addition amount of 8 to 10 parts. The crosslinking agent is selected from di-tert-butyl peroxide isopropylbenzene, with an addition amount of 0.6 to 0.7 parts. The foaming agent is selected from modified azodicarbonamide, with an addition amount of 3.2 to 3.6 parts.

[0036] The mixing process is carried out in stages. In sub-step S21, the modified thermoplastic polyester elastomer particles and the matrix resin are first fed into an internal mixer for preliminary mixing and compounding, with the time controlled between 20 and 40 seconds. During this stage, it is necessary to ensure that the melt flow rate ratio of the modified thermoplastic polyester elastomer particles to the ethylene-vinyl acetate copolymer in the matrix resin is within the range of 1.2:1 to 2.0:1. This ratio allows the different components to have similar flow properties after softening upon heating, thereby forming a uniform microstructure under mechanical shear force.

[0037] The process then proceeds to sub-step S22, where functional additives, including silicone masterbatch, are added to the material, and mixing continues. By monitoring the shear heating of the material, when the material temperature rises to the range of 115°C to 121°C, it indicates that the resin components have sufficiently softened and encapsulated the additive particles. Next, sub-step S23 is initiated, where a crosslinking agent and a foaming agent are added, and mixing continues until the material temperature reaches 123°C to 127°C. Within this temperature range, the crosslinking agent and foaming agent can disperse rapidly in the compound without undergoing large-scale chemical decomposition. From S21 to the end of S23 (discharge), the total mixing time is controlled between 9 and 13 minutes.

[0038] After the internal mixing and discharge process is completed, the open mixing process begins. The discharged material is placed on a two-roll mill for pressing. To control the physical state of the rubber compound and prevent premature scorching, the temperature of the front roll is controlled at 90 to 100 degrees Celsius, and the temperature of the rear roll is controlled at 80 to 90 degrees Celsius. During the pressing process, the operator performs 4 to 6 tumbling and triangular wrapping operations on the rubber compound to further eliminate residual air bubbles and improve the uniformity of component distribution. Finally, by adjusting the roll gap, the sheeting temperature of the rubber compound is controlled at 115 to 120 degrees Celsius, and the rubber compound is pressed into uniform sheets according to the preset thickness specifications. After the rubber compound cools, it can be used for the subsequent foaming step.

[0039] In step S30, a primary foaming process is performed to prepare a preform. The compounded rubber sheet obtained from the open milling process is cut to a predetermined size and placed in the cavity of a primary foaming mold. After mold closing, pressure is applied, and the temperature of the primary foaming mold is controlled between 170°C and 180°C. Within this temperature range, the foaming agent in the compounded rubber undergoes chemical decomposition to generate gas, while the crosslinking agent initiates chemical crosslinking between polymer chains to form a network structure. After a preset time, the mold is opened, and the material rapidly expands under the action of internal air pressure. The linear expansion ratio of the primary foamed preform in all dimensions is within the range of 175% to 185%, thereby obtaining a preform with a preliminary cell structure.

[0040] After the first foaming and demolding are completed, step S35 is performed to stabilize and surface-treat the primary foamed preform. The primary foamed preform is placed in an indoor environment with a temperature of 20°C to 30°C for 24 to 48 hours. After the preform dimensions have stabilized, each surface of the primary foamed preform is polished using mechanical grinding equipment. The polishing process must completely remove the dense skin layer generated during the first foaming, exposing the internal open-pore structure of the primary foamed preform.

[0041] In step S40, a secondary molding operation is performed. The primary foamed preform, which has undergone surface treatment and cutting in step S35, is placed into the cavity of the secondary molding mold. During this process, the volume ratio of the primary foamed preform to the cavity volume of the secondary molding mold must be within the range of 1.4:1 to 1.5:1. By limiting this volume compression ratio, the material can generate outward expansion pressure after softening due to heat, thereby completely filling the texture within the cavity and forming a dense surface layer. The cavity surface of the secondary molding mold has a pattern with a depth greater than or equal to 1.5 mm, and the sidewalls of the pattern have a draft angle of 3 to 5 degrees to facilitate demolding of the finished product and ensure the integrity of the bottom pattern.

[0042] After mold closing and pressurization, the heating system is activated to raise the temperature of the secondary molding mold to 175°C to 181°C and maintain this temperature for 550 to 610 seconds. After heating, while maintaining the mold closing pressure, the cooling system is activated to circulate cooling water at a temperature of 10°C to 25°C into the cooling channels within the secondary molding mold. By adjusting the flow rate of the circulating cooling water, the cooling rate of the mold is controlled between 10°C and 15°C per minute. The mold closing pressure is maintained until the temperature of the secondary molding mold drops to between 40°C and 50°C, at which point the mold is opened and the finished product is removed.

[0043] This invention relates to a method for preparing a lightweight and wear-resistant midsole material. This method improves the problems of easy collapse and poor wear resistance of conventional EVA midsole materials by pre-modifying thermoplastic polyester elastomer and improving specific processes in secondary molding.

[0044] This solution addresses the problem of uneven mixing between thermoplastic polyester elastomer and ethylene-vinyl acetate copolymer due to their vastly different melting points. In conventional techniques, the melting temperature of thermoplastic polyester elastomers is typically above 180°C, while the foaming processing temperature of ethylene-vinyl acetate copolymers usually cannot exceed 130°C, otherwise the foaming agent and crosslinking agent will become ineffective. Direct mixing results in the thermoplastic polyester elastomer existing as solid particles, leading to uneven bubble distribution or easy tearing defects within the foamed material. This solution reduces the softening temperature to below 130°C by pre-melting the thermoplastic polyester elastomer, carrier resin, and grafting material. This allows the modified particles to melt and mix evenly with the ethylene-vinyl acetate copolymer in subsequent processes. By controlling the melt index ratio between 1.2 and 2.0, the thermoplastic polyester elastomer forms a continuous network support structure within the material. This structure utilizes the inherent strength of the elastomer material, providing better support and resilience when the material is repeatedly compressed, thus solving the problem of ordinary foamed materials easily collapsing and deforming after long-term use.

[0045] However, the addition of a higher proportion of thermoplastic polyester elastomer introduces a new problem of surface wrinkling during the molding process. Thermoplastic polyester elastomer crystallizes rapidly during cooling and exhibits significant volume shrinkage. When manufacturing soles with high sidewall structures, this shrinkage leads to irregular wrinkles and unclear patterns on the sides. The usual approach is to reduce the amount of elastomer to avoid wrinkling, but this reduces the material's elasticity and fatigue resistance. This solution addresses this issue by employing a two-stage molding process, specifically limiting the volume compression ratio between the mold and the material to between 1.4 and 1.5, and forcibly cooling the mold to below 50 degrees Celsius using circulating water while the mold is closed. During cooling, the pressure within the mold forces the crystallizing material to adhere tightly to the inner wall of the mold. The crystalline structure formed under pressure acts as a shape stabilizer, counteracting the volume shrinkage force during cooling. This manufacturing process transforms the crystallization characteristic, which would otherwise cause defects, into a means of maintaining shape stability, ensuring smooth sole sides and clear bottom patterns, and solving the problem of achieving a fine appearance and side wrinkling with highly elastic materials.

[0046] Furthermore, this solution, through a specific material combination and a secondary molding process, forms a dense outer skin on the material surface. Under the high temperature and high pressure environment of secondary molding, the wear-resistant components in the formula migrate towards the mold surface. Because the material undergoes more than 1.4 times volume compression in the mold, the pores in the surface layer are squeezed out, forming a solid layer with a density far exceeding that of the inner foam layer. This outer skin is integrally molded with the inner foam material, possessing strong tear resistance and abrasion resistance. This allows the foam material to be used directly as the sole in contact with the ground, eliminating the need for a separate rubber layer. This design improves the durability of the sole while maintaining the material's lightweight properties.

[0047] To further illustrate the technical effects of the present invention, the following embodiments and comparative examples are provided.

[0048] To ensure the feasibility of this invention and the accuracy of the test results, the raw material specifications used in the examples and comparative examples are as follows (unless otherwise specified, all components are expressed in parts by mass): The thermoplastic polyester elastomer resin used is SKYPEL FP130 granules produced by SK Chemicals, with a Shore hardness of 55D.

[0049] The ethylene-vinyl acetate copolymer in the matrix resin is LG Chem's E280L product, which has a vinyl acetate (VA) content of 26% and a melt index of 2.5 g / 10 min.

[0050] The polyolefin elastomer selected is ENGAGE 8003, manufactured by Dow Chemical.

[0051] The styrene block copolymer used is SEBS of grade YH530P produced by Baling Petrochemical.

[0052] The EPDM rubber used is Keltan 2450, manufactured by Arlanx.

[0053] The maleic anhydride-grafted polyolefin elastomer compatibilizer used was a product manufactured by Ellersen with a grafting rate of 1.0%.

[0054] The wear-resistant agent is an organosilicon masterbatch containing 50% active ingredients.

[0055] The odorless crosslinking agent used is bis-tert-butyl peroxide isopropylbenzene (BIBP).

[0056] The foaming agent used is a surface-modified high-temperature azodicarbonamide (AC).

[0057] Example 1 In step S10, 50 parts of thermoplastic polyester elastomer resin, 50 parts of ethylene-vinyl acetate copolymer carrier resin, 2 parts of maleic anhydride grafted polyolefin elastomer compatibilizer and 0.5 parts of stearic acid are fed into an extrusion device and melt-grafted at 155 degrees Celsius to obtain modified thermoplastic polyester elastomer particles with a softening point of 120 degrees Celsius. The melt index of these particles at 190 degrees Celsius and 2.16 kg is tested to be 4.5 g / 10 min.

[0058] In step S20, 20 parts of the above-mentioned particles are mixed with 40 parts of ethylene-vinyl acetate copolymer, 20 parts of polyolefin elastomer, 20 parts of styrene block copolymer, and 10 parts of ethylene propylene diene monomer (EPDM) rubber. The melt flow rate ratio of the modified particles to the ethylene-vinyl acetate copolymer in the matrix resin is controlled at 1.2:1. The discharge temperature is controlled at 123 degrees Celsius during mixing, and the mixing time is 9 minutes. After the open milling process, the sheeting temperature is controlled at 115 degrees Celsius.

[0059] In step S30, the rubber material is placed in a primary foaming mold and foamed at 170 degrees Celsius to obtain a primary foamed preform with an expansion ratio of 175%.

[0060] In steps S35 and S40, the blank is left at 20 degrees Celsius for 48 hours and then polished. The volume compression ratio is set to 1.4:1, and the mold is heated to 175 degrees Celsius and held for 550 seconds. Then, 25-degree Celsius circulating cooling water is introduced, and the cooling rate is controlled at 10 degrees Celsius per minute. The mold is opened when the mold temperature drops to 50 degrees Celsius.

[0061] Example 2 In step S10, 60 parts of thermoplastic polyester elastomer resin, 40 parts of ethylene-vinyl acetate copolymer carrier resin, 5 parts of maleic anhydride grafted polyolefin elastomer compatibilizer and 1.0 part of stearic acid are blended at 165 degrees Celsius to obtain modified thermoplastic polyester elastomer particles with a softening point of 130 degrees Celsius and a melt index of 5.5 g / 10 min.

[0062] In step S20, 30 parts of the above-mentioned particles are mixed with 30 parts of ethylene-vinyl acetate copolymer, 15 parts of polyolefin elastomer, 10 parts of styrene block copolymer, and 5 parts of ethylene propylene diene monomer (EPDM) rubber. The melt flow rate ratio is controlled at 2.0:1. The mixing discharge temperature is 127 degrees Celsius, and the time is 13 minutes. The open mill sheeting temperature is 120 degrees Celsius.

[0063] In step S30, foaming is performed at 180 degrees Celsius to obtain a single-foamed preform with an expansion ratio of 185%.

[0064] In steps S35 and S40, the blank is left at 30 degrees Celsius for 24 hours and then polished. The volume compression ratio is set to 1.5:1, the heating temperature is 181 degrees Celsius and held for 610 seconds. Then, 10 degrees Celsius circulating water is introduced, the cooling rate is 15 degrees Celsius per minute, and the mold is opened when the mold temperature drops to 40 degrees Celsius.

[0065] Example 3 In step S10, 55 parts of thermoplastic polyester elastomer resin, 45 parts of ethylene-vinyl acetate copolymer carrier resin, 3 parts of maleic anhydride grafted polyolefin elastomer compatibilizer and 0.8 parts of stearic acid are blended at 160 degrees Celsius to obtain modified thermoplastic polyester elastomer particles with a softening point of 125 degrees Celsius and a melt index of 5.1 g / 10 min.

[0066] In step S20, 25 parts of the above-mentioned particles are mixed with 35 parts of ethylene-vinyl acetate copolymer, 18 parts of polyolefin elastomer, 15 parts of styrene block copolymer, and 7 parts of ethylene propylene diene monomer (EPDM) rubber. The melt flow rate ratio is controlled at 1.7:1. The mixing discharge temperature is 125 degrees Celsius, and the total mixing time is 12 minutes.

[0067] In step S30, foaming is performed at 175 degrees Celsius to obtain a single-foamed preform with an expansion ratio of 180%.

[0068] In steps S35 and S40, the blank is left at 25 degrees Celsius for 36 hours and then polished. The volume compression ratio is set to 1.45:1, the heating temperature is set to 178 degrees Celsius and held for 580 seconds. Forced cooling is performed by circulating water at 20 degrees Celsius at a cooling rate of 12 degrees Celsius per minute, and the mold temperature is lowered to 45 degrees Celsius before mold opening.

[0069] Comparative Example 1 The only difference between this comparative example and Example 3 is that, in step S20, 25 parts of unmodified thermoplastic polyester elastomer granules (grade FP130) were used directly instead of the modified granules. Since the unmodified granules have a melting point higher than 180 degrees Celsius, they cannot melt during the mixing process at 125 degrees Celsius.

[0070] Comparative Example 2 The only difference between this comparative example and Example 3 is that in step S40, after heating is completed, forced cooling with water is not performed, and the mold closing pressure is not maintained. Instead, the mold is opened directly to allow the material to cool naturally in room temperature air.

[0071] Comparative Example 3 This comparative example uses a conventional EVA foaming scheme, with the matrix consisting of 70 parts EVA and 30 parts POE. No thermoplastic polyester elastomer is added, and the volume compression ratio and pressurized cooling process in step S40 are not performed.

[0072] The performance of the midsole materials prepared in the above embodiments and comparative examples was tested. The test items and the standards used are as follows: Specific gravity testing was conducted according to GB / T 533-2008; hardness testing was conducted according to HG / T 2489-2007; resilience testing was conducted according to GB / T 1681-2009; compression set testing was conducted according to GB / T 6669-2008 (test conditions: 50% compression, 50℃×6h); abrasion resistance testing was conducted according to GB / T 9867-2008.

[0073] The test results are as follows:

[0074] According to the test data above, the midsole materials prepared in Examples 1 to 3 maintained a low density (0.135 g / cm³-0.142 g / cm³) while keeping the compression set below 31%. This indicates that within the parameter range defined by this invention, by preparing modified elastomer particles with low softening points and controlling a specific melt flow rate ratio, a stable and continuous support network can be formed inside the material, fundamentally solving the problem of poor fatigue resistance in the traditional EVA solution (Comparative Example 3). A comparison between Example 3 and Comparative Example 1 reveals that without the modification treatment in step S10, the high-melting-point elastomer cannot fuse with the matrix during the mixing process. This not only fails to improve resilience (52%) but also leads to a significant decrease in fatigue resistance (45.5%) due to stress concentration. A comparison between Example 3 and Comparative Example 2 verifies the effect of the S40 process. Due to the lack of a pressurized forced cooling process, Comparative Example 2 experienced disordered crystallization and shrinkage of the elastomer components, resulting in significant wrinkles and blurred patterns on the high sidewall areas.

[0075] The foregoing description of the specifications and embodiments is intended to explain the scope of protection of this invention, but does not constitute a limitation on the scope of protection of this invention. Modifications, equivalent substitutions, or other improvements to the embodiments of this invention or a portion thereof that can be obtained by those skilled in the art through logical analysis, reasoning, or limited experimentation, based on the teachings of this invention or the foregoing embodiments, in conjunction with common knowledge, general technical knowledge, and / or existing technology, should all be included within the scope of protection of this invention.

Claims

1. A method of making a lightweight, wear-resistant midsole material, characterized by, The method comprises the following steps: S10: preparing modified thermoplastic polyester elastomer particles: melt grafting and blending thermoplastic polyester elastomer resin, ethylene-vinyl acetate copolymer carrier resin and maleic anhydride grafted polyolefin elastomer compatibilizer at 155-165℃ to prepare modified thermoplastic polyester elastomer particles with a softening point of 120-130℃; S20: preparing a rubber compound: melt blending the modified thermoplastic polyester elastomer particles with a base resin, functional additives, a crosslinking agent and a foaming agent at 115-125℃, wherein the melt flow rate ratio of the modified thermoplastic polyester elastomer particles to ethylene-vinyl acetate copolymer in the base resin is 1.2:1 to 2.0:1; S30: primary foaming: placing the rubber compound in a primary foaming mold and performing mold foaming at 170-180℃ to prepare a primary foaming roughcast with an expansion ratio of 175-185%; S40: secondary mold forming: placing the primary foaming roughcast in a secondary forming mold, wherein the volume ratio of the primary foaming roughcast to the cavity volume of the secondary forming mold is 1.4:1 to 1.5:1; after closing the mold, heating at 175-181℃ for 550-610 seconds, then introducing circulating cooling water at 10-25℃ into the secondary forming mold for cooling, and maintaining the closing pressure during the cooling process until the temperature of the secondary forming mold is reduced to 40-50℃ and the mold is opened.

2. The method for preparing a lightweight and wear-resistant midsole material as described in claim 1, characterized in that, In step S10, the components include, by weight: thermoplastic polyester elastomer resin 50-60 parts, ethylene-vinyl acetate copolymer carrier resin 40-50 parts, maleic anhydride grafted polyolefin elastomer compatibilizer 2-5 parts, and stearic acid 0.5-1.0 parts.

3. The method for preparing a lightweight and wear-resistant midsole material as described in claim 1, characterized in that, In step S10, the rotation speed during melt grafting and blending is 280-320 r / min, and the melt index of the prepared modified thermoplastic polyester elastomer particles under the test conditions of 190℃ and 2.16 kg is 4.5-5.5 g / 10 min.

4. The method for preparing a lightweight and wear-resistant midsole material as described in claim 1, characterized in that, In step S20, the base resin includes, by weight: ethylene-vinyl acetate copolymer 30-40 parts, polyolefin elastomer 15-20 parts, styrene-based block copolymer 10-20 parts, and ethylene-propylene-diene rubber 5-10 parts; wherein the addition amount of the modified thermoplastic polyester elastomer particles is 20-30 parts.

5. The method for preparing a lightweight and wear-resistant midsole material as described in claim 1, characterized in that, In step S20, the functional additives include an anti-wear agent, the anti-wear agent is silicone masterbatch, and the addition amount of the silicone masterbatch in the rubber compound is 8-10 parts.

6. The method for preparing a lightweight and wear-resistant midsole material as described in claim 1, characterized in that, In step S20, the crosslinking agent is bis(tert-butyl peroxyisopropyl) benzene, and the addition amount is 0.6-0.7 parts; the foaming agent is modified azodicarbonamide, and the addition amount is 3.2-3.6 parts.

7. The method for preparing a lightweight and wear-resistant midsole material as described in claim 1, characterized in that, Between step S30 and step S40, step S35 is further included: placing the primary foaming roughcast in an environment of 20-30℃ for 24-48 hours, and then removing the skin layer on the surface of the primary foaming roughcast by mechanical grinding.

8. The method for preparing a lightweight and wear-resistant midsole material as described in claim 1, characterized in that, In step S40, the cooling rate during the cooling stage is 10-15℃ / min.

9. The method of claim 1, wherein the step of applying the first layer of material is performed by applying a first layer of a thermoplastic material. In step S20, the specific steps of the mixing are as follows: S21: mixing and mixing the modified thermoplastic polyester elastomer particles and the base resin for 20-40 seconds; S22: adding the functional auxiliary agent and continuing to mix until the material temperature reaches 115-121℃; S23: adding the crosslinking agent and the foaming agent, and mixing until the material temperature reaches 123-127℃, and then discharging; The total mixing time of steps S21-S23 is 9-13 minutes.

10. The method for preparing a lightweight and wear-resistant midsole material as described in claim 1, characterized in that, After completing step S20 and before entering step S30, the mixing process also includes the following steps: The discharged material is placed on a double roller to perform compression mixing, the front roller temperature is controlled at 90-100℃, and the rear roller temperature is controlled at 80-90℃; during the compression mixing process, 4-6 times of turning and packing are performed, and then the roller gap is adjusted to the material sheet temperature of 115-120℃, and the sheet is discharged according to the preset thickness specification.

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