A modified TPEE material and its application in preparing supercritical foaming sole material

Abstract

The present invention provides a modified TPEE material and its application in the preparation of supercritical foaming sole materials, belonging to the field of preparation and realization of footwear materials. The modified TPEE material is made by blending TPEE with epoxy chain extenders, polyvinyl alcohol short fibers, epoxy coupling agents and flow aids. The foaming sole material is made of materials through a supercritical foaming process, and the materials include: EVA, TPEE components (modified TPEE materials), POE, OBC, SEBS, epoxy compatibilizer, epoxy nucleating agent, cell stabilizer, lubricant and cross-linking agent. The present invention finally obtains a high-performance supercritical foaming sole material through the mutual matching design of the above materials. For example, the foaming sole material includes: density 0.1±0.02g / cm 3 , rebound rate ≥72%, layered tear strength ≥35N / cm; the product has the characteristics of extremely light, extremely elastic, high tearing, etc., and the cost is relatively low.

Description

Technical Field

[0001] The present invention relates to the field of preparation and realization of footwear materials, in particular to a modified TPEE material and application thereof in preparing supercritical foaming sole materials. Background Art

[0002] The traditional chemical foaming method for producing foamed athletic shoe midsoles is plagued by issues such as residual harmful additives, strong odor, and poor environmental performance. In recent years, a growing number of sports brands, both domestically and internationally, have embraced the supercritical physical foaming process for producing foamed shoe sole materials. This is primarily due to the fact that supercritical physical foaming, which typically uses N2 or CO2 supercritical gases as the foaming agent, eliminates the use of chemical foaming agents, leaves the product free of odorous residue, and improves environmental performance.

[0003] Currently, the base resins for supercritical foaming midsoles fall into four main categories: polyamide elastomer (PEBAX), polyester elastomer (TPEE), polyurethane elastomer (TPU), and ethylene-vinyl acetate copolymers (such as EVA / POE / OBC / EPDM / SEBS). Foamed soles made with PEBAX or TPEE, among these high-performance thermoplastic elastomers, can achieve extreme lightness and resilience, but typically suffer from poor tear and compression properties. Furthermore, the raw materials are very expensive (PEBAX is 5-8 times more expensive than EVA-based materials, and TPEE is approximately 3 times more expensive). Therefore, they are only suitable for high-end athletic shoes and have a limited market share. While EVA-based supercritical foaming soles are relatively inexpensive, the raw material's performance is limited, and the resulting foamed soles cannot achieve the same extreme lightness and resilience. Summary of the Invention

[0004] In view of this, the present invention provides a modified TPEE material and its application in the preparation of supercritical foamed sole materials. The present invention can use modified TPEE to prepare supercritical foamed sole materials. The foamed sole product has the characteristics of being extremely light, extremely elastic, and highly tearable, and has a low cost.

[0005] The present invention provides a modified TPEE material, which is prepared by blending TPEE with an epoxy chain extender, polyvinyl alcohol staple fibers, an epoxy coupling agent, and a flow aid; the epoxy chain extender is a styrene-acrylonitrile-glycidyl methacrylate copolymer; and the mass ratio of the TPEE, epoxy chain extender, and polyvinyl alcohol staple fibers is 100:2-7:4-11.

[0006] In an embodiment of the present invention, the epoxy coupling agent is 3-(2,3-epoxypropoxy)propyltrimethoxysilane; the flow aid is a mixture of silicone oil and erucamide; and the mass ratio of TPEE, epoxy coupling agent, and flow aid is 100:2-4:1-2.

[0007] In an embodiment of the present invention, the hard segment in the TPEE is a polyethylene terephthalate segment, and the soft segment is a polyethylene glycol ether segment; the MI index of the modified TPEE material is 3.8-4.9 g / 10min.

[0008] TPEE is a block copolymer formed by alternating two-block copolymerization, generally consisting of polyester segments of varying lengths connected by ester groups. Molecularly, the hard segments in TPEE are primarily composed of short, crystalline aromatic polyester segments, such as polyethylene terephthalate (PET), polypropylene terephthalate (PBT), and polybutylene terephthalate (PTT), providing rigidity. The soft segments, on the other hand, are composed of flexible, amorphous polymer segments, such as polytetramethylene ether (PTMG), polyethylene glycol ether (PEG), and polypropylene glycol ether (PPG), ensuring the material's excellent flexibility and resilience at low temperatures.

[0009] Typical TPEE materials are linear, crystalline polymers with high fluidity. Due to the varying ratios of soft and hard segments, which lead to variations in internal crystallization and microdomain size, their solid-state foaming behavior is significantly influenced by the hard segment content. When pure TPEE is used in supercritical foaming, its melt foaming process can produce high-expansion foam materials. However, due to its linear nature, TPEE has low melt strength. While the resulting foamed soles are extremely light and resilient, they suffer from poor delamination tear strength and compression set performance.

[0010] EVA-based elastomers can improve their melt strength through peroxide micro-crosslinking, but the molecular structure of TPEE prevents it from being cross-linked through peroxide. This results in the TPEE melt strength not being able to support the gas well under the high temperature and high pressure conditions of supercritical foaming, thus affecting the physical properties of the final product.

[0011] Compared to existing technologies, the present invention utilizes an epoxy chain extender, polyvinyl alcohol staple fibers, an epoxy coupling agent, and a flow aid to modify TPEE using a twin-screw granulator, thereby increasing the melt strength of linear TPEE and forming the modified TPEE material. The epoxy chain extender is styrene-acrylonitrile-glycidyl methacrylate, and the mass ratio of TPEE, epoxy chain extender, and polyvinyl alcohol staple fibers is 100:2-7:4-11. Because TPEE is a polycondensation product of an aromatic organic acid and a long-chain polyol, its chain segments contain residual carboxyl (-COOH) and hydroxyl (-OH) groups. Chain extension and branching can be achieved through functional group reactions between the epoxy chain extender and the carboxyl or hydroxyl groups of TPEE. The resulting chain-extended / branched macromolecules significantly increase the number of entanglement points between the melt macromolecular chains and chain segments, significantly improving the melt strength of the TPEE. This can increase the cell density and expansion ratio of the foamed material, thereby reducing the overall density of the foamed shoe sole. The molecular structure of the polyvinyl alcohol staple fiber contains polar hydroxyl groups, which have good compatibility with the polar polyester TPEE. In addition, the polyvinyl alcohol staple fiber is conducive to increasing the crystallization temperature and crystallization rate of TPEE. In the subsequent supercritical foaming process, TPEE crystals can grow uniformly and rapidly, further reducing the energy barrier for bubble nucleation, inducing bubble nucleation and growth, and increasing the bubble density, thereby improving the delamination tear strength of the foamed sole and reducing compression deformation.

[0012] Furthermore, the epoxy coupling agent is 3-(2,3-epoxypropoxy)propyltrimethoxysilane, the epoxy groups in its molecular structure can form strong chemical bonds with the carboxyl groups in TPEE and the hydroxyl groups in the polyvinyl alcohol staple fibers, increasing the connectivity between TPEE and polyvinyl alcohol fibers, thereby significantly improving the mechanical strength of TPEE.

[0013] Furthermore, the flow aid is a mixture of silicone oil and erucamide. As TPEE chains grow and branch, their molecular weight increases, their melt index decreases, and their fluidity tends to deteriorate. Therefore, the flow aids erucamide and silicone oil can improve their fluidity. Silicone oil is more effective in wetting polyvinyl alcohol staple fibers, and their combination enhances processability during twin-screw melt blending.

[0014] The present invention provides a foamed sole material containing a TPEE component, which is made of materials through a supercritical foaming process. The materials include: EVA, TPEE components, POE, OBC, SEBS, epoxy compatibilizer, epoxy nucleating agent, cell stabilizer, lubricant and cross-linking agent;

[0015] The TPEE component is the modified TPEE material described above.

[0016] In an embodiment of the present invention, the materials include, by weight, 30-50 parts of EVA, 20-40 parts of TPEE component, 5-15 parts of POE, 5-15 parts of OBC, 5-10 parts of SEBS, 5-10 parts of epoxy compatibilizer, 2-4 parts of epoxy nucleating agent, 0.3-0.7 parts of cell stabilizer, 1-1.5 parts of lubricant and 0.4-0.7 parts of crosslinking agent.

[0017] In an embodiment of the present invention, the epoxy compatibilizer is an epoxy glycidyl methacrylate graft polymer; the epoxy nucleating agent is an epoxy silane-modified silica material; and the cell stabilizer is polyvinyl alcohol.

[0018] In an embodiment of the present invention, the lubricant is stearic acid; and the cross-linking agent is a peroxide cross-linking agent.

[0019] In an embodiment of the present invention, the density of the foamed sole material is 0.08-0.12 g / cm 3 , the rebound rate is above 70%.

[0020] The present invention provides a method for preparing the foamed sole material as described above, comprising:

[0021] Provide TPEE components;

[0022] The TPEE component, EVA, POE, OBC, SEBS, epoxy compatibilizer, epoxy nucleating agent, cell stabilizer, crosslinking agent and lubricant are weighed separately and mixed to obtain a material;

[0023] The material is granulated and then preliminarily foamed by injection molding to obtain a rough sole blank;

[0024] The shoe sole blank is subjected to autoclave supercritical foaming and then molded to obtain the foamed shoe sole material.

[0025] In an embodiment of the present invention, the autoclave pressure supercritical foaming includes: using a mixed fluid of carbon dioxide and nitrogen to perform high-pressure and high-temperature foaming at 20-30 MPa and 120±5°C.

[0026] In the embodiment of the present invention, the modified TPEE material described above is matched with EVA, POE, OBC, SEBS, epoxy compatibilizer, epoxy nucleating agent, cell stabilizer, lubricant, cross-linking agent, etc., and this formula material is formed into a foamed sole material using a supercritical foaming process. Because general TPEE is a polar polymer and has poor compatibility with non-polar polymers such as OBC, POE, and SEBS, the present invention connects the polymer end of the epoxy compatibilizer with SEBS / EVA / POE / OBC, and the epoxy end reacts with the carboxyl or hydroxyl group of the modified TPEE polyester end, thereby improving the compatibility of each polymer and improving the mechanical properties. The present invention finally obtains a high-performance supercritical foamed sole material through the matching design of the above materials. For example, the density of the foamed sole material is 0.10±0.02g / cm 3 , hardness is 40±3C, rebound rate ≥72%, forefoot rebound performance ≥70%, energy return rate ≥86%, delamination tear strength ≥35N / cm, compression deformation ≤30%, shock absorption G≤10. DETAILED DESCRIPTION

[0027] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0028] The present invention provides a modified TPEE material, which is prepared by a blending reaction of TPEE with an epoxy chain extender, polyvinyl alcohol staple fibers, an epoxy coupling agent, and a flow aid; the epoxy chain extender is a styrene-acrylonitrile-glycidyl methacrylate copolymer; and the mass ratio of the TPEE, epoxy chain extender, and polyvinyl alcohol staple fibers is 100:2-7:4-11.

[0029] The modified TPEE material provided by the present invention has properties such as high melt strength and can be used to prepare extremely light, extremely elastic, and high-tear supercritical foamed sole materials while reducing costs.

[0030] Preferably, the polyester TPEE comprises a polyethylene terephthalate (PET) hard segment and a polyethylene glycol ether (PEG) soft segment. Specifically, the commercially available Hytrel 4056 (Celanese Corporation) is a linear crystalline polymer with high fluidity, such as a melt flow index (MI) of 5.6 g / 10 min. In this embodiment, an epoxy chain extender, high-strength polyvinyl alcohol staple fibers, an epoxy coupling agent, and a flow aid are used to modify the product using a twin-screw pelletizer.

[0031] Specifically, in an embodiment of the present invention, the dried polyester elastomer TPEE can be mixed with an epoxy chain extender, high-strength polyvinyl alcohol staple fibers, an epoxy coupling agent, a flow aid, etc. in a high-speed mixer, and then sent into a twin-screw granulator for blending and modification, preferably melt-processed at a temperature of 200-220°C to obtain modified polyester TPEE particles.

[0032] The epoxy chain extender is a styrene-acrylonitrile-glycidyl methacrylate terpolymer (SAG), preferably commercially available SAG001 (Nantong Rizhisheng New Technology Development Co., Ltd., containing 1-2% glycidyl methacrylate by mass). This epoxy chain extender reacts with the carboxyl or hydroxyl groups of TPEE to achieve chain extension and branching. The resulting extended / branched macromolecules significantly increase the number of entanglement points between macromolecular chains and chain segments in the melt, significantly improving the melt strength of TPEE. The mass ratio of TPEE to epoxy chain extender can be 100:2-7, preferably 100:3-7, for example, 100:3, 100:4, 100:5, 100:6, etc.

[0033] The high-strength polyvinyl alcohol staple fibers offer high strength, high modulus, excellent impact resistance, and toughness. Their molecular structure also contains polar hydroxyl groups, providing good compatibility with polar polyester TPEE. Furthermore, the polyvinyl alcohol fibers help increase the crystallization temperature and rate of TPEE, facilitating uniform and rapid growth of TPEE crystals during supercritical foaming. This further reduces the energy barrier for cell nucleation, inducing cell nucleation and growth, and increasing cell density. The high-strength polyvinyl alcohol staple fibers can have a breaking strength exceeding 1200 MPa and a fiber diameter of, for example, 14 to 16 microns. Commercially available polyvinyl alcohol staple fibers, such as SH-PVA-6 (fiber length 0.4 to 0.6 mm, from Tai'an Haosong Fiber Co., Ltd.), are preferred. The mass ratio of TPEE to polyvinyl alcohol staple fibers can be 100:4-11, preferably 100:5-10, for example, 100:5, 100:7, or 100:10.

[0034] In specific embodiments of the present invention, the mass ratio of TPEE, epoxy chain extender, and polyvinyl alcohol staple fiber is 100:2-7:4-11, preferably 100:3-6:5-10. In some embodiments, the modified polyester TPEE comprises, by weight, 100 parts polyester TPEE, 3-7 parts epoxy chain extender, 5-10 parts high-strength polyvinyl alcohol staple fiber, 2-4 parts epoxy coupling agent, and 1-2 parts flow aid.

[0035] Preferably, the epoxy coupling agent is 3-(2,3-epoxypropoxy)propyltrimethoxysilane; silane coupling agent KH560. The epoxy groups in its molecular structure can form strong chemical bonds with the carboxyl groups in TPEE and the hydroxyl groups in the polyvinyl alcohol staple fibers, enhancing the connectivity between TPEE and the polyvinyl alcohol fibers, thereby significantly improving the mechanical strength of TPEE. The mass ratio of TPEE to epoxy coupling agent is preferably 100:2-4, more preferably 100:3-4.

[0036] Furthermore, the flow aid is preferably a mixture of silicone oil and erucamide; the mass ratio of TPEE to the flow aid can be 100:1-2. The silicone oil is preferably dimethyl silicone oil Si-201, which is beneficial for fiber wetting and improving flowability; its combination with erucamide can improve the flowability and processability of TPEE and other materials.

[0037] Specifically, the modified TPEE material exhibits a melt index (MI) of 3.8-4.9 g / 10 min (tested under the national standard: 190°C, 2.16 kg load), demonstrating high melt strength. This embodiment of the present invention can fully utilize the excellent properties of modified TPEE to prepare high-performance supercritical foaming shoe sole materials.

[0038] The present invention provides a foamed sole material containing a TPEE component, which is made of materials through a supercritical foaming process. The materials include: EVA, a TPEE component, POE, OBC, SEBS, an epoxy compatibilizer, an epoxy nucleating agent, a cell stabilizer, a lubricant and a cross-linking agent; the TPEE component is the modified TPEE material described above.

[0039] By adding modified TPEE material components, the present invention can break through the technical bottleneck of poor tearing and compression performance of extremely light and elastic foam soles. The high tear strength and super compression resistance of the foam sole material are at the leading level in the industry.

[0040] In the foam sole material formulation of the present invention, the EVA (ethylene-vinyl acetate copolymer) molecular chain contains a vinyl acetate (VA) monomer structure. Specifically, the EVA matrix resin contains 18%-40% VA by weight, with EVA28005 (LG Chem, South Korea) being a preferred variety. The EVA content can be 30-50 parts by weight, for example, 30, 40, 45, or 50 parts.

[0041] In parts by weight, the raw materials in the recipe of this embodiment include 5-15 parts POE and 5-15 parts OBC. POE is the abbreviation for polyolefin elastomer, primarily including ethylene-octene random copolymer, which exhibits excellent flexibility and resilience. OBC, which stands for segmented olefin copolymer, has an alternating ethylene-octene block structure and offers superior overall performance compared to other olefin copolymers. Preferably, the POE is a commercially available brand with a hardness of 60A-80A, with Dow's POE8180 being a preferred choice. Specifically, the amount of POE can be 10-15 parts. Commercially available OBCs can include brands with a hardness of 60A-85A, with OBC8530 and OBC9530 (Dow) being preferred. Specifically, the amount of POE can be 10-15 parts.

[0042] SEBS is the abbreviation for a linear triblock copolymer with polystyrene as the terminal segments and an ethylene-butylene copolymer obtained by hydrogenating polybutadiene as the middle elastic block. This refers to hydrogenated styrene-butadiene-styrene copolymer (SEBS), which exhibits excellent aging resistance. The preferred SEBS grade contains 20-33% styrene by weight, such as SEBS P1083 (Asahi Kasei Corporation, Japan). The preferred styrene content is 5-10 parts by weight.

[0043] In some specific embodiments of the present invention, the materials include, by weight, 30-50 parts of EVA, 20-40 parts of TPEE component, 5-15 parts of POE, 5-15 parts of OBC, 5-10 parts of SEBS, 5-10 parts of epoxy compatibilizer, 2-4 parts of epoxy nucleating agent, 0.3-0.7 parts of cell stabilizer, 1-1.5 parts of lubricant and 0.4-0.7 parts of cross-linking agent; wherein the content of the TPEE component is consistent with that of the modified TPEE material described above.

[0044] The epoxy compatibilizer described in the embodiments of the present invention, also known as an epoxy compatibilizer, primarily comprises an epoxy glycidyl methacrylate (GMA) grafted polymer, such as SEBS-g-GMA or EVA-g-GMA. The GMA graft fraction can range from 10-13%. In the embodiments of the present invention, the modified TPEE component is connected to SEBS / EVA / POE / OBC via the polymer end of the epoxy compatibilizer. The epoxy end reacts with the carboxyl or hydroxyl groups on the TPEE polyester end, thereby enhancing the compatibility of the polymers and improving mechanical properties. Specifically, the epoxy compatibilizer is preferably EVA-g-GMA, such as the commercially available product BF-2B (Sumitomo Corporation, Japan, with a GMA fraction of 12%). Its weight ratio can be 5 parts, 7.5 parts, 8 parts, or 10 parts.

[0045] The epoxy nucleating agent described in the present embodiment is preferably epoxysilane-modified silica (also referred to as epoxidized silica). It exhibits excellent compatibility with epoxy-chain-extended modified TPEE and epoxy compatibilizers, providing sufficient micronuclei during the foaming process, accelerating bubble generation and improving foaming efficiency. Furthermore, it reduces foaming temperature and pressure, shortens foaming time, and increases foaming efficiency, further enhancing the rebound, compression, and delamination tear properties of the foamed shoe sole. The epoxy nucleating agent, with an epoxy group mass fraction of 1-2%, can be commercially available product SQNM80300Y (Qinghe Chaotai Metal Materials Co., Ltd.).

[0046] Preferably, the cell stabilizer is polyvinyl alcohol (PVA). Polyvinyl alcohol, with the same molecular structure as the high-strength polyvinyl alcohol staple fibers, can evenly distribute cells, prevent foam shrinkage and collapse, and increase cell stability. By optimizing the cell structure, it avoids localized insufficient or excessive density, significantly improving the various properties of the foamed sole. The cell stabilizer is more preferably polyvinyl alcohol (PVA) 1799, with a molecular weight of 1700-1800 and a melting point of 230-240°C.

[0047] The cross-linking agent described in the embodiment of the present invention preferably includes a peroxide cross-linking agent, specifically one of diisopropylbenzene peroxide and 1,4-bis-tert-butylperoxyisopropylbenzene (BIBP), and the preferred variety is BIBP. If the EVA series foamed soles are not cross-linked, the melt strength of each polymer cannot form a network structure under high temperature and high pressure, and the bubbles are prone to rupture and merger, etc., and the mechanical strength of the final foamed sole is poor. The embodiment of the present invention introduces an appropriate amount of cross-linking agent into the formula, and first performs micro-cross-linking when ejecting the sole embryo, which not only increases the viscosity of the blend; but also helps to form a network cross-linked structure during high temperature and high pressure foaming in a supercritical autoclave, thereby controlling the bubble pore size and reducing the shrinkage of the foamed sole. In addition, the lubricant is preferably stearic acid, and the preferred variety is stearic acid 1801.

[0048] Furthermore, the present invention provides a method for preparing the foamed sole material as described above, comprising:

[0049] Provide TPEE components;

[0050] The TPEE component, EVA, POE, OBC, SEBS, epoxy compatibilizer, epoxy nucleating agent, cell stabilizer, crosslinking agent and lubricant are weighed separately and mixed to obtain a material;

[0051] The material is granulated and then preliminarily foamed by injection molding to obtain a rough sole blank;

[0052] The shoe sole blank is subjected to autoclave supercritical foaming and then molded to obtain the foamed shoe sole material.

[0053] In the present invention, the TPEE polyester elastomer is first modified with an epoxy chain extender, high-strength polyvinyl alcohol staple fibers, an epoxy coupling agent, and a flow aid to provide a TPEE component. In some embodiments, the TPEE modification steps include: drying → stirring → granulation → drying, as follows:

[0054] (1) Drying: First, vacuum dry the TPEE polyester material and high-strength polyvinyl alcohol staple fiber at 80±10°C, preferably for 2-4 hours, to completely remove the adsorbed moisture;

[0055] (2) Stirring: After weighing the raw materials in proportion (the contents of each raw material are as described above), pour them into a high-speed blender and mix for 30 minutes at a stirring speed of 800-1000 rpm and a mixing temperature of 50-60°C;

[0056] (3) Granulation: The particles after high-speed stirring are melt-extended and modified at high temperature by a twin-screw machine, and then extruded into granules. The processing temperature is preferably set at 180±20℃.

[0057] (4) Drying: The modified TPEE particles are vacuum dried at 80±10℃ for 4-6 hours so that they can be sealed for future use. They are suitable for supercritical physical foaming process.

[0058] In the present embodiment, the modified TPEE material obtained is mixed with the EVA, POE, OBC, SEBS, epoxy compatibilizer, epoxy nucleating agent, cell stabilizer, lubricant, and crosslinking agent to prepare the sole material through a supercritical foaming process. The supercritical foaming process includes: weighing → mixing → granulation → IP injection of small embryos → autoclave supercritical foaming → secondary compression molding, as follows:

[0059] Weighing materials: According to the dosage of the formula, weigh the modified polyester TPEE as the first group; weigh the EVA / POE / OBC / SEBS as the second group; weigh the epoxy compatibilizer, epoxy nucleating agent, and foam stabilizer as the third group; weigh the crosslinking agent and lubricant as the fourth group.

[0060] Mixing: First, plasticize the modified polyester TPEE particles on an open mixer. The temperature of the open mixer is preferably set to 100°C. After the modified polyester TPEE particles are pulled into thin sheets, pour them into an internal mixer and turn on the machine for plastication for 8-10 minutes. When the temperature rises to between 120-130°C, pour in the second group of materials and mix for 10-15 minutes. When the temperature rises to 130-140°C, pour in the third group of materials and mix for 8-10 minutes. Then pour in the fourth group of materials and mix for 5-8 minutes, and pour out the mixed materials.

[0061] Granulation: Pour the mixed material into a single-screw granulator. The temperatures of the first, second, third and fourth zones are preferably adjusted to 100, 105, 110 and 115°C respectively. The screw speed is adjusted to 45-55 rpm and the cutting speed is adjusted to 20-25 rpm.

[0062] IP injection of small (rough) embryos: Pour the prepared pellets into the injection foam molding machine, and the temperatures of the first, second, third and fourth feeding zones are preferably adjusted to 104, 106, 108 and 110°C respectively; the injection speed of each zone is 50(±2)-45(±2)-40(±2)-35(±2)-30(±2)%; the injection pressure of each zone is 110(±5)-110(±5)-110(±5)-110(±5)-110(±5)bar; the vacuum time can be 100±20 seconds; the temperature of the upper and lower templates of the molding mold are adjusted to: 176±5°C, 176±5°C respectively. Set the material amount according to the mold usage (mold size 18cm*10cm*1cm, according to the foaming ratio 160%-205%, the material amount can be set to 100±10g), the injection time is 50±10 seconds, the vulcanization time is 300±50 seconds, and then take out the small rough sole and let it cool naturally for 2 hours to set.

[0063] Autoclave supercritical foaming: Place the small rough blank after standing for 12-24 hours into an autoclave supercritical physical foaming tank, first introduce supercritical CO2 gas, and soak at 5-10MPa, 60-80℃ for 20-30min; then introduce supercritical nitrogen N2, at a pressure of 20~30MPa, a foaming temperature of 118±5℃, and maintain the heat and pressure for 90-120min before releasing the pressure. Keep the temperature unchanged during the pressure release process, and the pressure release rate is 1-10MPa / s. After quickly releasing the pressure to normal pressure, take out the foamed sole and cool it to room temperature.

[0064] Secondary compression molding: Place the supercritical foamed semi-finished product that has been left to stand for 72-96 hours into a flat-plate compression mold to complete the finished product compression molding; the hot pressing temperature is preferably: 173±5°C; the hot pressing time is: 700±50 seconds; the cooling water temperature is: 25±3°C, and the cooling time is: 700±50 seconds.

[0065] In a preferred embodiment of the present invention, the autoclave pressure supercritical foaming includes: using a mixed fluid of carbon dioxide and nitrogen to perform high-pressure and high-temperature foaming at 20-30 MPa and 120±5°C; its production efficiency is high and is conducive to mass production.

[0066] In some embodiments, the density of the prepared foamed sole material is 0.10±0.02 g / cm 3, hardness is 40±3C, rebound rate ≥72%, forefoot rebound performance ≥70%, energy return rate ≥86%, delamination tear strength ≥35N / cm, compression deformation ≤30%, shock absorption G ≤10. Compared with some existing TPEE foam soles (generally rebound rate of 60~65%, density 0.14-0.16g / cm 3 ), the foamed sole material containing modified TPEE described in the present invention not only has low density and high rebound, but also has good tear strength and compression resistance, and has broad application prospects.

[0067] In summary, the present invention utilizes a TPEE polyester modified material, EVA, POE, OBC, SEBS, an epoxy compatibilizer, an epoxy nucleating agent, a cell stabilizer, a lubricant, and a crosslinking agent to produce a highly cost-effective supercritical foamed shoe sole. Compared to existing EVA-based supercritical foamed shoe sole materials, the introduction of a TPEE polyester material modified by chain extension and branching mitigates the drawbacks of pure TPEE materials, which suffer from low melt strength due to their linear structure, leading to poor delamination tear strength and compression set performance. This results in a foamed shoe sole with high delamination tear strength and low compression set. Secondly, by connecting the polymer end of the epoxy compatibilizer EVA-g-GMA to SEBS / EVA / POE / OBC, the epoxy end reacts with the carboxyl or hydroxyl group of the TPEE polyester end, thereby improving the compatibility of the polymers and further improving mechanical properties. Furthermore, the addition of an epoxidized silica nucleating agent not only enhances compatibility with the epoxy-extended modified TPEE and epoxy compatibilizer, but also provides sufficient micro-cores during the foaming process, accelerating bubble generation and improving the foaming effect. Furthermore, the foaming temperature and pressure are reduced, the foaming time is shortened, and the foaming efficiency is improved. The overall effect is to enhance the various properties of the foamed sole. Finally, the present invention also adds a small amount of polyvinyl alcohol cell stabilizer to uniformly distribute the cells, prevent foam shrinkage and rupture, and increase cell stability. By optimizing the cell structure, localized insufficient or excessive density is avoided, significantly improving the various properties of the foamed sole.

[0068] In this embodiment of the present invention, pure TPEE polyester material is modified by selecting epoxy chain extenders, high-strength polyvinyl alcohol staple fibers, epoxy coupling agents, and flow aids. First, the epoxy chain extender is styrene-acrylonitrile-glycidyl methacrylate, which reacts with the residual carboxyl (-COOH) and hydroxyl (-OH) groups at the ends of TPEE segments to achieve chain extension and branching. The resulting chain-extended / branched macromolecules significantly increase the number of entanglements between melt macromolecular chains and segments, significantly improving the TPEE melt strength. This helps increase the cell density and expansion ratio of the foamed shoe sole, thereby reducing the overall density of the foamed shoe sole. Secondly, TPEE can be reinforced with high-strength polyvinyl alcohol staple fibers. On the one hand, the molecular structure of high-strength polyvinyl alcohol staple fibers also contains polar hydroxyl groups, which are highly compatible with polar polyester TPEE. Furthermore, they possess high strength, high modulus, and excellent impact resistance / toughness. Furthermore, polyvinyl alcohol fibers help to increase the crystallization temperature and rate of TPEE. During the supercritical foaming process, TPEE crystals grow uniformly and rapidly, further reducing the energy barrier for cell nucleation, inducing cell nucleation and growth, increasing cell density, improving the delamination tear strength of the foamed sole, and reducing the compression set. Furthermore, the addition of an epoxy coupling agent enhances the connectivity between TPEE and polyvinyl alcohol staple fibers. The epoxy groups in the cycloalkane coupling agent's molecular structure can form strong chemical bonds with the carboxyl groups in TPEE and the hydroxyl groups in the polyvinyl alcohol fibers, significantly improving the mechanical strength of TPEE. Finally, the use of flow aids such as erucamide and silicone oil to improve processing fluidity, and the use of silicone oil to wet the polyvinyl alcohol fibers, together, improves processability during twin-screw melt blending. Ultimately, through the above technical means, the embodiment of the present invention obtains a TPEE polyester modified material with stronger mechanical properties such as density, hardness, tensile strength, tear strength, and melting point, which is conducive to breaking through the technical bottleneck of poor tearing and compression performance of extremely light and elastic foam soles. Its technical means are at the industry-leading level.

[0069] To better illustrate the present invention, the following examples are provided to further illustrate the present invention. Unless otherwise specified, the technical means used in the present invention are conventional means well known to those skilled in the art, and the various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0070] In the embodiment of the present invention, a modified TPEE material with high melt strength (referred to as modified material) is first prepared. The modification steps are: drying → stirring → granulation → drying. Specifically:

[0071] (1) Drying: First, vacuum dry the TPEE polyester material and high-strength polyvinyl alcohol staple fiber at 80±10℃ for 2-4 hours;

[0072] (2) Stirring: Weigh the raw materials in the proportions listed in Table 1, pour them into a high-speed blender and mix for 30 min at a stirring speed of 900 rpm and a mixing temperature of 60°C;

[0073] (3) Granulation: The particles after high-speed stirring are melt-extended and modified at high temperature by a twin-screw machine, and then extruded into granules. The processing temperature is set at 180±20℃.

[0074] (4) Drying: The modified TPEE particles are vacuum dried at 80±10°C for 4-6 hours and sealed for later use.

[0075] In Table 1, the modified TPEE materials are respectively recorded as modified material 1, modified material 2, modified material 3 to modified material 8, and modified material 9; including the performance test results (test methods: density: ISO 1183; hardness: ISO 868; tensile strength: ISO 527; tear strength: ISO 34-1; elongation at break: ISO 527; melting point: ISO 3146; MI: ISO 1133).

[0076] Table 1 Raw material ratio of modified TPEE materials

[0077]

[0078] Table 1 shows the performance data for modified materials 1-5: Maintaining the same amount of polyvinyl alcohol staple fiber, increasing the amount of epoxy chain extender gradually increases the density, hardness, tensile strength, tear strength, and melting point of the modified TPEE polyester, while decreasing the elongation at break and melt flow index. This indicates that the epoxy chain extender reacts with the carboxyl or hydroxyl groups of TPEE to achieve chain extension and branching. The resulting extended / branched macromolecules significantly increase the number of entanglement points between macromolecular chains and segments in the melt, leading to significant improvements in the mechanical properties of TPEE. The improvement is minimal at an addition of 2 phr, and diminishes at 8 phr, making an addition of 3-7 phr preferable.

[0079] The performance data for modified materials 3, 6, 7, 8, and 9 show that, while maintaining the same epoxy chain extender dosage, increasing the amount of polyvinyl alcohol fiber added maintains essentially unchanged density, hardness, and melting point of the modified TPEE polyester. However, tensile strength, tear strength, and elongation at break increase slightly, while the melt flow index decreases slightly. The improvement is minimal at 4 phr, and diminishes at 11 phr, so an addition of 5-10 phr is preferred.

[0080] Example 1

[0081] The present invention primarily achieves cost-effective supercritical foaming of shoe soles by introducing modified high-melt-strength TPEE materials into an EVA-based formula. The supercritical foaming process is as follows: weighing → mixing → granulation → IP injection of small embryos → autoclave supercritical foaming → secondary compression molding. The details are as follows:

[0082] Weighing materials: According to the dosage of the formula in Table 2, weigh the modified polyester TPEE as the first group; weigh the EVA / POE / OBC / SEBS as the second group; weigh the epoxy compatibilizer, epoxy nucleating agent, and foam stabilizer as the third group; and weigh the crosslinking agent and lubricant as the fourth group.

[0083] Mixing: First, plasticize the modified polyester TPEE particles on an open mixer. Set the mixer temperature to 100°C. After the modified polyester TPEE particles are pulled into thin sheets, pour them into an internal mixer and turn on the machine for plastication for 8-10 minutes. When the temperature rises to between 120-130°C, pour in the second group of materials and mix for 10-15 minutes. When the temperature rises to 130-140°C, pour in the third group of materials and mix for 8-10 minutes. Then pour in the fourth group of materials and mix for 5-8 minutes, and pour out the mixed materials.

[0084] Granulation: Pour the mixed material into a single-screw granulator, adjust the temperatures of the first, second, third and fourth zones to 100, 105, 110 and 115°C respectively, adjust the screw speed to 45-55 rpm, and adjust the cutting speed to 20-25 rpm.

[0085] IP injection of small rough blanks: pour the prepared pellets into the injection foam molding machine, and adjust the temperatures of the first, second, third and fourth feeding zones to 104, 106, 108 and 110℃ respectively; the injection speed is 50(±2)-45(±2)-40(±2)-35(±2)-30(±2)%; the injection pressure is 110(±5)-110(±5)-110(±5)-110(±5)-110(±5)bar; the vacuum time is 100±20 seconds; the temperature of the upper and lower templates of the molding mold is adjusted to: 176±5℃, 176±5℃ respectively. The material amount is set according to the mold usage (mold size is 18cm*10cm*1cm, according to the foaming ratio of 160%-205%, the material amount can be set to 100±10g), the injection time is 50±10 seconds, the vulcanization time is 300±50 seconds, and then the small rough sole is taken out and naturally cooled for 2 hours to set.

[0086] Autoclave supercritical foaming: Place the rough blank after standing for 12-24 hours into an autoclave supercritical physical foaming tank, first introduce supercritical CO2 gas, and soak at 5-10MPa, 60-80℃ for 20-30min; then introduce supercritical N2, at a pressure of 20~30MPa, a foaming temperature of 118±5℃, and maintain the heat and pressure for 90-120min before releasing the pressure. Keep the temperature unchanged during the pressure release process, and the pressure release rate is 1-10MPa / s. After quickly releasing the pressure to normal pressure, take out the foamed sole and cool it to room temperature.

[0087] Molding: Place the supercritical foamed semi-finished product that has been left to stand for 72-96 hours into a flat-plate molding mold to complete the finished product molding; the hot pressing temperature is: 173±5℃; the hot pressing time is: 700±50 seconds; the cooling water temperature is: 25±3℃, and the cooling time is: 700±50 seconds.

[0088] Examples 2-8

[0089] According to the preparation steps of Example 1, the raw materials are shown in Table 2, and foamed sole samples are obtained respectively.

[0090] Comparative Examples 1-8

[0091] According to the preparation steps of Example 1, the raw materials are shown in Table 3, and foamed sole samples are obtained respectively.

[0092] Table 2 Formulation and performance of the embodiments of the present invention

[0093]

[0094] Table 3 Comparative Examples of the present invention and their performance

[0095]

[0096] Among them, the sources of various raw materials are as follows:

[0097] EVA 28005: hardness 79A, VA content 28%, tensile strength 12MPa, elongation at break 800%, crystallinity 21.8%, melting temperature 72°C, LG Chem, South Korea.

[0098] POE 8180: hardness 63A, tensile strength 6.3MPa, elongation at break 910%, crystallinity 16%, melting point 47°C, Dow Chemical.

[0099] OBC 9530: Hardness 83A, tensile strength 7.3MPa, elongation at break 1000%, crystallinity 24%, melting point 121°C, Dow Chemical.

[0100] SEBS P1083: styrene content 20%, hardness 56A, tensile strength 8.1MPa, elongation at break 817%, Asahi Kasei Co., Ltd., Japan.

[0101] BF-2B: Epoxy compatibilizer EVA-g-GMA, GMA mass fraction is 12%, hardness 36D, melting point 95℃, melt index 7g / 10min, tensile strength 17MPa, elongation at break 750%, Sumitomo Corporation of Japan.

[0102] SQNM80300Y: Epoxidized silica, particle size 0.35±0.1μm, epoxy group mass fraction 1%, specific surface area 20±2m 2 / g, Qinghe County Chaotai Metal Materials Co., Ltd.

[0103] PVA 1799: polyvinyl alcohol, density 1.3g / cm 3 , melting point 230-240℃, Hubei Xinjiecheng Chemical Technology Co., Ltd.

[0104] BIBP: Akzo Nobel.

[0105] Stearic acid 1801: Indonesian Dukuda.

[0106] Hytrel 4056: density 1.15 g / cm 3 , hardness 40D, tensile strength 53MPa, tear strength 101KN / m, elongation at break 324%, melting point 150℃, melt flow index 5.6g / 10min, Celanese Corporation.

[0107] SAG001: Styrene-acrylonitrile-glycidyl methacrylate, including 1-2% glycidyl methacrylate by mass, Nantong Rizhisheng New Technology Development Co., Ltd.

[0108] SH-PVA-6: high-strength polyvinyl alcohol fiber, fiber length 0.5±0.1mm, fiber diameter 15±1μm, breaking strength 1200±10MPa, elastic modulus 35±3GPa, Taian Haosong Fiber Co., Ltd.

[0109] Si-201: viscosity 100,000-1,000,000 mPa.s (25°C), Tai'an Songze Composite Materials Co., Ltd.

[0110] KH-560: Guangzhou Shouzheng Chemical Technology Co., Ltd.

[0111] Erucamide: Nantong Haimen Zhongteng New Material Technology Co., Ltd.

[0112] According to Table 2 and Table 3, from the comparative data of Examples 1 / 2 / 3 / 4 / 5, it can be seen that when the addition amount of TPEE polyester modified material is 30 parts, the modified materials 2 / 3 / 4 / 7 / 8 are tested and the density can be obtained as 0.10±0.02g / cm 3 , high-performance foam sole material with hardness 40±3C, rebound rate ≥72%, energy return rate ≥86%, delamination tear strength ≥35N / cm, compression deformation ≤30%, and shock absorption G ≤10.

[0113] Comparison of the data from Examples 2 / 6 / 7 and Comparative Examples 2 / 3 / 4 reveals that as the addition of the TPEE polyester modified material increases from 10 to 45 parts, the density and compression set of the foamed sole gradually decrease, while the hardness, rebound rate, energy return rate, delamination tear strength, and shock absorption G value gradually increase. This demonstrates that the mechanical properties of the TPEE polyester modified material, modified by chain growth and chain branching, are significantly improved, resulting in a significantly increased melt strength of the foam, increased cell density and expansion ratio, and thus a reduction in the overall density of the foamed sole. Increasing cell density improves properties such as rebound rate, energy return rate, and delamination tear strength of the foamed sole, while also reducing compression set and improving compression resistance. The improvement is minimal at an addition of 10-15 parts, and slows at 45 parts, with the delamination tear strength and compression set slightly deteriorating. Therefore, an addition of 20-40 parts is preferred.

[0114] Comparison of the data between Comparative Example 1 and Examples 1 / 2 / 3 / 4 / 5 shows that the TPEE polyester material in Comparative Example 1, which has not been modified by chain extension and chain branching, exhibits stronger melt strength and mechanical properties than EVA / POE / OBC / SEBS. Therefore, while the hardness, rebound rate, energy return rate, delamination tear strength, and shock absorption G-value of the foamed shoe sole are improved, the improvement is not as significant as that of the modified TPEE polyester material.

[0115] Comparing the data from Comparative Example 5 with Example 2 shows that without the addition of an epoxy compatibilizer, the overall performance of the foamed sole significantly deteriorates. This is primarily due to the poor compatibility of TPEE, a polar polymer, with non-polar polymers such as OBC, POE, and SEBS. In Example 2, the epoxy compatibilizer's polymer end is linked to SEBS / EVA / POE / OBC, allowing the epoxy end to react with the carboxyl or hydroxyl groups at the TPEE polyester end, thereby enhancing the compatibility of the polymers and significantly improving the foamed sole's performance, including rebound, energy return, delamination tear strength, and shock absorption.

[0116] Comparing the data from Comparative Example 6 with Example 2 shows that without the addition of an epoxy nucleating agent, the overall performance of the foamed sole deteriorates. This is primarily due to the poor dispersibility of conventional silica in the polymer matrix. Epoxidizing silica improves compatibility with epoxy-chain-extended modified TPEE and epoxy compatibilizers, providing sufficient micronuclei during the foaming process, accelerating bubble generation and improving the foaming effect. Furthermore, it reduces foaming temperature and pressure, shortens foaming time, and increases foaming efficiency, further enhancing the foamed sole's rebound, compression, and delamination tearing properties.

[0117] Comparison of the data from Comparative Example 7 and Example 2 shows that without the addition of a cell stabilizer, the overall performance of the foamed sole deteriorates. This is primarily due to the polyvinyl alcohol's ability to evenly distribute cells, prevent foam shrinkage and rupture, increase cell stability, and optimize the cell structure, avoiding localized insufficient or excessive density, thereby improving various properties of the foamed sole.

[0118] From the above examples, it can be seen that the density of the supercritical foamed sole prepared in the preferred embodiment of the present invention is 0.10±0.02g / cm 3 , hardness 40±3C, rebound rate ≥72%, energy return rate ≥86%, delamination tear strength ≥35N / cm, compression deformation ≤30%, shock absorption G≤10. It is extremely light and elastic, but also has extremely high delamination tear strength and excellent compression deformation performance. Its excellent comprehensive performance is a first in the industry.

[0119] The foregoing descriptions of specific exemplary embodiments of the present invention are for purposes of illustration and description. These descriptions are not intended to limit the invention to the precise forms disclosed, and it is apparent that many variations and modifications are possible in light of the foregoing teachings. The exemplary embodiments have been selected and described for the purpose of explaining the specific principles of the invention and their practical application, thereby enabling those skilled in the art to realize and utilize a variety of exemplary embodiments of the invention and various options and modifications. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A foamed sole material containing TPEE components, characterized in that: The material is made by supercritical foaming process, and the material includes: EVA, TPEE component, POE, OBC, SEBS, epoxy compatibilizer, epoxy nucleating agent, cell stabilizer, lubricant and cross-linking agent; The TPEE component is a modified TPEE material, which is made by blending TPEE with an epoxy chain extender, polyvinyl alcohol staple fibers, an epoxy coupling agent, and a flow aid. The epoxy chain extender is a styrene-acrylonitrile-glycidyl methacrylate copolymer. The mass ratio of the TPEE, epoxy chain extender, and polyvinyl alcohol staple fibers is 100:2-7:4-11. The epoxy coupling agent is 3-(2,3-epoxypropoxy)propyltrimethoxysilane. The flow aid is a mixture of silicone oil and erucamide. The mass ratio of the TPEE, epoxy coupling agent, and flow aid is 100:2-4:1-2. The hard segment in the TPEE is a polyethylene terephthalate segment, and the soft segment is a polyethylene glycol ether segment. The MI index of the modified TPEE material is 3.8-4.9 g / 10min. The epoxy compatibilizer is an epoxy glycidyl methacrylate graft polymer; the epoxy nucleating agent is an epoxy silane modified silica material; In parts by weight, the materials include: 30-50 parts of EVA, 20-40 parts of TPEE component, 5-15 parts of POE, 5-15 parts of OBC, 5-10 parts of SEBS, 5-10 parts of epoxy compatibilizer, 2-4 parts of epoxy nucleating agent, 0.3-0.7 parts of foam stabilizer, 1-1.5 parts of lubricant and 0.4-0.7 parts of crosslinking agent.

2. The foam sole material according to claim 1, characterized in that: The cell stabilizer is polyvinyl alcohol.

3. The foam sole material according to claim 1, characterized in that: The lubricant is stearic acid; and the cross-linking agent is a peroxide cross-linking agent.

4. The foam sole material according to any one of claims 1 to 3, characterized in that: The density of the foamed sole material is 0.08-0.12 g / cm 3 , the rebound rate is above 70%.

5. The method for preparing the foamed sole material according to any one of claims 1 to 4, wherein: include: Provide TPEE components; The TPEE component, EVA, POE, OBC, SEBS, epoxy compatibilizer, epoxy nucleating agent, cell stabilizer, crosslinking agent and lubricant are weighed separately and mixed to obtain a material; The material is granulated and then preliminarily foamed by injection molding to obtain a rough sole blank; The shoe sole blank is subjected to autoclave supercritical foaming and then molded to obtain the foamed shoe sole material.

6. The preparation method according to claim 5, characterized in that The autoclave pressure supercritical foaming comprises: using a mixed fluid of carbon dioxide and nitrogen to perform high-pressure and high-temperature foaming at 20-30 MPa and 120±5°C.

Images