Modified TPEE material and application thereof in preparation of supercritical foaming sole material

Abstract

The invention provides a modified TPEE material and application thereof in preparation of a supercritical foaming sole material, and belongs to the field of preparation and realization of shoe materials. The modified TPEE material is prepared from TPEE, an epoxy chain extender, polyvinyl alcohol short fibers, an epoxy coupling agent and a flow promoter through a blending reaction. The foaming sole material is prepared from materials through a supercritical foaming process, wherein the materials comprise EVA, a TPEE component (a modified TPEE material), POE, OBC, SEBS, an epoxy compatibilizer, an epoxy nucleating agent, a foam stabilizer, a lubricant and a cross-linking agent. Through the matching design of the materials, the high-performance supercritical foaming sole material is finally obtained. For example, the foaming sole material comprises the components as follows: the density is 0.1 + / -0.02 g / cm < 3 >, the rebound rate is greater than or equal to 72%, and the layered tearing strength is greater than or equal to 35N / cm; the product has the characteristics of being extremely light, extremely elastic, high in tear and the like, and is lower in cost.

Description

Technical Field

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

[0002] The traditional chemical foaming method is used to prepare sports shoe foam midsoles, which mainly has problems such as harmful additive residues, strong odor, and poor environmental protection. In recent years, more and more sports brands at home and abroad are keen to choose supercritical physical foaming process to prepare foamed sole materials, mainly because it is generally based on N 2 or CO 2 Supercritical gas is used as the foaming agent, and no chemical foaming agent is used in the foaming process. There is no residual odorous substance in the product, which also improves environmental protection to a certain extent.

[0003] The base resins of current supercritical foaming midsole materials are mainly divided into four types: polyamide elastomer (PEBAX), polyester elastomer (TPEE), polyurethane elastomer (TPU), and ethylene-vinyl acetate copolymer (such as EVA / POE / OBC / EPDM / SEBS). The foamed soles prepared with PEBAX or TPEE from these high-performance thermoplastic elastomers can be extremely light and elastic, but usually have poor tear and compression properties, and their raw materials are very expensive (PEBAX is 5-8 times that of EVA-based raw materials, and TPEE is about 3 times that of EVA-based raw materials). Therefore, they can only be used to prepare high-end sports shoes and have a limited market share. Although the EVA-based supercritical foamed soles have the lowest price, the performance of the raw materials is limited, and the prepared foamed soles cannot be extremely light and elastic. Summary of the invention

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

[0005] The 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 erucic acid amide; 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 generated by alternating copolymerization of two blocks, generally composed of polyester segments of different lengths and polyether segments connected by ester groups. From the perspective of molecular structure, the hard segment in the TPEE molecular structure is mainly composed of aromatic polyester segments with short chain length and crystalline properties, such as polyethylene terephthalate (PET), polypropylene terephthalate (PBT), polybutylene terephthalate (PTT), etc., to provide the rigidity of the material; while the soft segment is composed of flexible amorphous polymer segments such as polytetramethylene ether (PTMG), polyethylene glycol ether (PEG), polypropylene glycol ether (PPG), etc., to ensure that the material has good flexibility and resilience at low temperatures.

[0009] General TPEE materials are linear crystalline polymers with high fluidity. Due to the difference in the ratio of soft and hard segments, the internal crystallization and micro-area size are different, and its solid-state foaming behavior is significantly affected by the hard segment content. When pure TPEE is used for supercritical foaming, its melt foaming process can prepare high-ratio foaming materials. However, since TPEE is a linear polymer with low melt strength, the prepared foamed soles are extremely light and elastic, but have poor layered tear strength and poor compression deformation performance.

[0010] EVA-based elastomers can improve their melt strength through peroxide micro-crosslinking, but the molecular structure of TPEE makes it impossible to crosslink through peroxide. This will result 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 with the prior art, the present invention uses epoxy chain extenders, polyvinyl alcohol staple fibers, epoxy coupling agents, and flow aids, and can modify TPEE through a twin-screw granulator to improve the melt strength of linear TPEE, thereby forming the modified TPEE material. Among them, the epoxy chain extender is styrene-acrylonitrile-methyl methacrylate, and the mass ratio of the TPEE, epoxy chain extender and polyvinyl alcohol staple fibers is 100:2-7:4-11. Since TPEE is a polycondensation product of aromatic organic acids and long-chain polyols, there are residual carboxyl-COOH and hydroxyl-OH at the ends of its chain segments. Chain growth and chain branching can be achieved by reacting the epoxy chain extender with the carboxyl or hydroxyl of TPEE with functional groups. The generated chain extension / branching macromolecules can significantly increase the number of entanglement points between the melt macromolecular chains and chain segments, so that the melt strength of TPEE is significantly improved, and the foaming cell density and foaming ratio can be improved, thereby reducing the overall density of the foamed 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 improving the crystallization temperature and crystallization rate of TPEE. In the subsequent supercritical foaming process, TPEE crystals can grow uniformly and quickly, further reducing the energy barrier of 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, and 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, thereby increasing the connectivity between TPEE and the polyvinyl alcohol fibers, thereby significantly improving the mechanical strength of TPEE.

[0013] Furthermore, the flow aid is a mixture of silicone oil and erucic acid amide; as the chain of TPEE grows and branches, its molecular weight increases, the melt index decreases, and the fluidity tends to deteriorate, so the flow aid erucic acid amide and silicone oil can improve its fluidity. Silicone oil is more conducive to wetting polyvinyl alcohol staple fibers, and the combination of the two is conducive to the processability of 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, wherein the materials include: EVA, a TPEE component, POE, OBC, SEBS, an epoxy compatibilizer, an epoxy nucleating agent, a cell stabilizer, a lubricant and a crosslinking 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 components, 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.

[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 mold pressing 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] The embodiment of the present invention matches the modified TPEE material described above with EVA, POE, OBC, SEBS, epoxy compatibilizer, epoxy nucleating agent, cell stabilizer, lubricant, cross-linking agent, etc., and uses a supercritical foaming process to form a foamed sole material. 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 at the end of the modified TPEE polyester, thereby improving the compatibility of each polymer and improving 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, the 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 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.

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

[0030] Preferably, in the polyester TPEE, the hard segment is a polyethylene terephthalate PET segment, and the soft segment is a polyethylene glycol ether PEG segment; specifically, it can be the commercially available Hytrel 4056 product (Celanese Corporation), which is a linear crystalline polymer with high fluidity, such as a melt flow index (MI) of 5.6 g / 10 min. The embodiment of the present invention selects epoxy chain extenders, high-strength polyvinyl alcohol staple fibers, epoxy coupling agents, and flow aids, and modifies them through a twin-screw granulator.

[0031] Specifically, in the 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] Among them, the epoxy chain extender is a terpolymer of styrene-acrylonitrile-glycidyl methacrylate (SAG), preferably a commercially available SAG001 chain extender (Nantong Rizhisheng New Technology Development Co., Ltd., including 1-2% glycidyl methacrylate by mass). The epoxy chain extender can react with the carboxyl or hydroxyl groups of TPEE to achieve chain growth and chain branching through functional group reaction, and the generated chain extension / branching macromolecules can significantly increase the number of entanglement points between the melt macromolecular chains and chain segments, so that the melt strength of TPEE is significantly improved. The mass ratio of TPEE to the epoxy chain extender can be 100:2-7, preferably 100:3-7, for example, 100:3, 100:4, 100:5, 100:6, etc.

[0033] At the same time, the high-strength polyvinyl alcohol staple fiber has high strength, high modulus, excellent impact resistance and toughness, and also contains polar hydroxyl groups in the molecular structure, which has good compatibility with polar polyester TPEE. In addition, polyvinyl alcohol fiber is conducive to improving the crystallization temperature and crystallization rate of TPEE, which can facilitate the uniform and rapid growth of TPEE crystals during supercritical foaming, further reduce the energy barrier of cell nucleation, induce cell nucleation and growth, and increase the cell density. The breaking strength of the high-strength polyvinyl alcohol staple fiber can be above 1200MPa, and the fiber diameter is 14~16 microns, preferably commercially available polyvinyl alcohol staple fiber SH-PVA-6 (fiber length 0.4~0.6mm, Tai'an Haosong Fiber Co., Ltd.). In addition, the mass ratio of TPEE and polyvinyl alcohol staple fiber can be 100:4-11, preferably 100:5-10, for example, 100:5, 100:7, 100:10, etc.

[0034] In a specific embodiment 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 raw materials of the modified polyester TPEE are: 100 parts of polyester TPEE, 3-7 parts of epoxy chain extender, 5-10 parts of high-strength polyvinyl alcohol staple fiber, 2-4 parts of epoxy coupling agent, and 1-2 parts of flow aid.

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

[0036] In addition, 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 to fiber wetting and fluidity improvement; its combination with erucamide can improve the fluidity and processability of TPEE and the like.

[0037] Specifically, the MI index of the modified TPEE material is 3.8-4.9 g / 10 min (test conditions are the conditions specified in the national standard: 190° C., load 2.16 kg), and it is a TPEE material with high melt strength after modification. The embodiments of the present invention can make full use of the excellent properties of modified TPEE and be applied to the preparation of high-performance supercritical foaming 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] The present invention can break through the technical bottleneck of poor tearing and compression performance of extremely light and elastic foam soles by adding modified TPEE material components. The high tear strength and super compression resistance of the foam sole material are at the leading level in the industry.

[0040] In the foaming sole material formula of the embodiment of the present invention, the molecular chain of EVA (ethylene-vinyl acetate copolymer) contains a vinyl acetate (VA) monomer structure, specifically, EVA matrix resin with VA=18%-40% by weight, and the preferred variety is EVA28005 (LG Chemical Company, South Korea). The weight parts of the EVA can be 30-50 parts, for example, 30 parts, 40 parts, 45 parts, 50 parts, etc.

[0041] In parts by weight, the raw materials of the formula of the embodiment of the present invention include 5-15 parts of POE and 5-15 parts of OBC, etc.; POE is the English abbreviation of polyolefin elastomer, mainly ethylene-octene random copolymer, etc., which has good flexibility and resilience, and OBC is the full name of block olefin copolymer, which has an ethylene-octene alternating block structure, and its comprehensive performance is better than other olefin copolymers. Preferably, the POE is a commercially available brand product with a hardness of 60A-80A, and the preferred variety is Dow's POE8180, which can be specifically 10-15 parts. The commercially available OBC products may include brands with a hardness of 60A-85A, and the preferred varieties are OBC8530 and OBC9530 (Dow), which can be specifically 10-15 parts.

[0042] SEBS is the abbreviation of a linear triblock copolymer with polystyrene as the terminal segment and ethylene-butene copolymer obtained by hydrogenating polybutadiene as the middle elastic block, that is, hydrogenated styrene-butadiene-styrene copolymer SEBS, which has good aging resistance and other properties. The SEBS preferably includes a variety with a styrene content of 20-33% by mass, which can be SEBS P1083 (Asahi Kasei Corporation, Japan); its mass content is preferably 5-10 parts.

[0043] In some specific embodiments of the present invention, the materials include, by weight: 30-50 parts of EVA, 20-40 parts of TPEE components, 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 the content of the modified TPEE material mentioned above.

[0044] The epoxy compatibilizer described in the embodiment of the present invention is also called an epoxy compatibilizer, which mainly includes epoxy glycidyl methacrylate (GMA) grafted polymers, such as SEBS-g-GMA and EVA-g-GMA, wherein the GMA grafting mass fraction can be 10-13%. In the embodiment of the present invention, the modified TPEE component is connected to SEBS / EVA / POE / OBC through the polymer end of the epoxy compatibilizer, and the epoxy end reacts with the carboxyl or hydroxyl group of the TPEE polyester end, thereby improving the compatibility of each polymer and improving the mechanical properties. Specifically, the epoxy compatibilizer is preferably EVA-g-GMA, such as the commercially available product BF-2B (Sumitomo Corporation of Japan, with a mass fraction of GMA of 12%); its weight parts can be 5 parts, 7.5 parts, 8 parts, and 10 parts.

[0045] The epoxy nucleating agent described in the embodiment of the present invention is preferably epoxysilane modified silica (also referred to as epoxy silica), which has good compatibility with epoxy chain-extended modified TPEE, epoxy compatibilizer, etc., so that it can provide enough tiny cores during the foaming process, accelerate the generation of bubbles during the foaming process, improve the foaming effect, reduce the foaming temperature and pressure, shorten the foaming time, improve the foaming efficiency, and also help to improve the rebound / compression / delamination tearing properties of the foamed sole. The epoxy group mass fraction in the epoxy nucleating agent is 1-2%, and the commercially available product SQNM80300Y (Qinghe County Chaotai Metal Materials Co., Ltd.) can be used.

[0046] Preferably, the cell stabilizer is polyvinyl alcohol (PVA). Polyvinyl alcohol with the same molecular structure as the high-strength polyvinyl alcohol short fibers can make the cells evenly distributed, prevent foam shrinkage and rupture, increase cell stability, and optimize the cell structure to avoid insufficient or excessive local density, which is conducive to significantly improving the various properties of the foamed sole. The cell stabilizer is further preferably polyvinyl alcohol PVA1799, 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-di-tert-butylperoxyisopropylbenzene (BIBP), and the preferred variety is BIBP. If the EVA series of foamed soles are not cross-linked, the melt strength of each polymer cannot form a network structure at high temperature and high pressure, and the foam cells are prone to rupture and merge, 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 in the formula, and first performs micro-cross-linking when the sole embryo is ejected, which can not only increase the viscosity of the blend; and it is also conducive to forming a network cross-linked structure during high temperature and high pressure foaming in a supercritical autoclave, thereby controlling the pore diameter 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 mold pressing to obtain the foamed shoe sole material.

[0053] In the embodiment of the present invention, the TPEE polyester elastomer is first modified by an epoxy chain extender, high-strength polyvinyl alcohol short 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, the TPEE polyester material and the high-strength polyvinyl alcohol staple fiber are vacuum dried at 80±10°C, preferably for 2-4 hours, to completely remove the adsorbed moisture;

[0055] (2) Stirring: After weighing the raw materials in order according to the proportion (the contents of each raw material are as described above), pour them into a high-speed mixer 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 subjected to melt high-temperature chain extension modification and extrusion granulation by a twin-screw machine. The processing temperature is preferably set at 180±20°C.

[0057] (4) Drying: The modified TPEE particles are vacuum dried at 80±10°C for 4-6 hours so as to be sealed for later use, which is suitable for supercritical physical foaming process.

[0058] In the embodiment of the present invention, the obtained modified TPEE material is matched 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, they are poured into an internal mixer and the machine is turned on for plasticization 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, and the temperatures of the first, second, third and fourth zones are preferably adjusted to 100, 105, 110 and 115°C respectively, and 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 foaming 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 is adjusted to: 176±5°C, 176±5°C 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 shape.

[0063] Autoclave supercritical foaming: After standing for 12-24 hours, the small rough embryos are placed in the autoclave supercritical physical foaming tank, and supercritical CO is first introduced. 2 Gas, soak at 5-10MPa, 60-80℃ for 20-30min; then introduce supercritical nitrogen N 2 , at a pressure of 20~30MPa, a foaming temperature of 118±5℃, and a heat preservation and pressure holding time of 90-120min before depressurization. Keep the temperature unchanged during the depressurization process, and the depressurization rate is 1-10MPa / s. After quickly depressurizing 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 standing for 72-96 hours into a flat 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 embodiment of the present invention prepares a cost-effective supercritical foamed sole by matching TPEE polyester modified material, EVA, POE, OBC, SEBS, epoxy compatibilizer, epoxy nucleating agent, cell stabilizer, lubricant, crosslinking agent, etc. Compared with the existing EVA-based supercritical foamed sole material, firstly, the TPEE polyester material modified by chain growth and chain branching is introduced, which improves the disadvantages of the pure TPEE material due to the linear structure and low melt strength, resulting in poor delamination tear strength and poor compression deformation performance of the foamed sole, thereby obtaining a foamed sole with high delamination tear strength and low compression deformation rate. Secondly, the polymer end of the epoxy compatibilizer EVA-g-GMA is connected with SEBS / EVA / POE / OBC, and the epoxy end reacts with the carboxyl or hydroxyl group of the TPEE polyester end, thereby improving the compatibility of each polymer and further improving the mechanical properties; and furthermore, the epoxy silicon dioxide nucleating agent is used to improve the compatibility with the modified TPEE and epoxy compatibilizer of the epoxy chain extension on the one hand, and on the other hand, sufficient tiny cores are provided during the foaming process to accelerate the generation of bubbles during the foaming process, improve the foaming effect, and reduce the foaming temperature and pressure, shorten the foaming time, and improve the foaming efficiency. The overall effect is to enhance the various properties of the foaming sole. Finally, the present invention also adds a small amount of polyvinyl alcohol cell stabilizer to make the cells evenly distributed, prevent foam shrinkage and rupture, increase cell stability, and optimize the cell structure to avoid the occurrence of insufficient or excessive local density, so that the various properties of the foaming sole are significantly improved.

[0068] The embodiment of the present invention modifies the pure TPEE polyester material by selecting epoxy chain extenders, high-strength polyvinyl alcohol staple fibers, epoxy coupling agents, flow aids, etc. First, the epoxy chain extender is styrene-acrylonitrile-glycidyl methacrylate, which can react with the residual carboxyl-COOH and hydroxyl-OH at the end of the TPEE chain segment to achieve chain growth and chain branching through functional group reactions. The generated chain extension / branching macromolecules can significantly increase the number of entanglement points between the melt macromolecular chains and chain segments, so that the TPEE melt strength is significantly improved, which is beneficial to improve the cell density and foaming ratio of the foamed sole, thereby reducing the overall density of the foamed sole. Secondly, TPEE can be reinforced by 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 have good compatibility with polar polyester TPEE. On the other hand, it has high strength, high modulus and excellent impact resistance / toughness. In addition, polyvinyl alcohol fibers are conducive to improving the crystallization temperature and crystallization rate of TPEE. During the supercritical foaming process, TPEE crystals can grow uniformly and quickly, further reducing the energy barrier of cell nucleation, inducing cell nucleation and growth, increasing cell density, improving the delamination tear strength of the foamed sole and reducing the compression deformation rate. Furthermore, the connectivity of TPEE and polyvinyl alcohol staple fibers is increased by epoxy coupling agents. The epoxy groups in the molecular structure of cycloalkane coupling agents can form strong chemical bonds with the carboxyl groups in TPEE and the hydroxyl groups in polyvinyl alcohol fibers, significantly improving the mechanical strength of TPEE. Finally, the processing fluidity is improved by flow aids erucamide and silicone oil, and the polyvinyl alcohol fibers are wetted by silicone oil. The two are mutually compatible and conducive to improving the processability during twin-screw melt blending. Finally, 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, melting point, etc., which is conducive to breaking through the technical bottleneck of poor tearing and compression performance of extremely light and elastic foamed soles. Its technical means are at the leading level in the industry.

[0069] In order to better illustrate the present invention, the following examples are further illustrated. 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, and 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 mixer 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 subjected to melt high-temperature chain extension modification and extrusion granulation through a twin-screw machine. The processing temperature is set at 180±20°C.

[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 performance test results (test method: 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] According to Table 1, it can be seen from the performance data of modified materials 1-5 that: keeping the amount of polyvinyl alcohol staple fibers unchanged, as the amount of epoxy chain extender added gradually increases, the density, hardness, tensile strength, tear strength, melting point of the modified TPEE polyester material gradually increase, while the elongation at break and melt flow index gradually decrease. This shows that the chain growth and chain branching reactions are achieved by the epoxy chain extender and the carboxyl or hydroxyl groups of TPEE through functional group reactions, and the generated chain extension / branching macromolecules can significantly increase the number of entanglement points between the melt macromolecular chains and chain segments, so that the mechanical properties of TPEE are significantly improved. When the addition amount is 2 parts, the improvement effect is very small, and when the addition amount is 8 parts, the improvement effect slows down, so the preferred addition amount is 3-7 parts.

[0079] From the performance data of modified materials 3, 6, 7, 8, and 9, it can be seen that: keeping the amount of epoxy chain extender unchanged, with the increase of the amount of polyvinyl alcohol fiber added, the density, hardness, and melting point of the modified TPEE polyester material remain basically unchanged, but the tensile strength, tear strength, and elongation at break are slightly improved, and the melt flow index is slightly reduced. When the addition amount is 4 parts, the improvement effect is very small, and when the addition amount is 11 parts, the improvement effect slows down, so the preferred addition amount is 5-10 parts.

[0080] Example 1

[0081] The present invention mainly introduces the modified TPEE material with high melt strength into the EVA-based formula to achieve a cost-effective supercritical foaming sole, wherein the supercritical foaming process is: weighing → mixing → granulation → IP injection of small embryos → kettle pressure 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 temperature of the open mixer to 100°C, pour the modified polyester TPEE particles into an internal mixer after being pulled into thin sheets, and turn on the machine for plasticization 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 embryos: 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 mold plates of the molding mold is adjusted to 176±5℃ and 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 shape.

[0086] Autoclave supercritical foaming: After standing for 12-24 hours, the small rough embryos are placed in the autoclave supercritical physical foaming tank, and supercritical CO is first introduced. 2 Gas, immersed at 5-10MPa, 60-80℃ for 20-30min; then supercritical N 2, at a pressure of 20~30MPa, a foaming temperature of 118±5℃, and a heat preservation and pressure holding time of 90-120min before depressurization. During the depressurization process, the temperature is kept unchanged, and the depressurization rate is 1-10MPa / s. After quickly depressurizing to normal pressure, the foamed sole is taken out and cooled to room temperature.

[0087] Molding: Place the supercritical foamed semi-finished product that has been standing for 72-96 hours into a flat-plate molding mold to complete 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] Embodiment 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 Formula 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 Chemical Company of South Korea.

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

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

[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: Dukuda, Indonesia.

[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), Taian Songze Composite Materials Co., Ltd.

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

[0111] Erucic acid amide: Nantong Haimen Zhongteng New Material Technology Co., Ltd.

[0112] According to Table 2 and Table 3, it can be seen from the comparative data of Examples 1 / 2 / 3 / 4 / 5 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, hardness 40±3C, rebound rate ≥72%, energy return rate ≥86%, delamination tear strength ≥35N / cm, compression deformation ≤30%, and shock absorption G≤10 high-performance foam sole material.

[0113] From the comparison data of Example 2 / 6 / 7 and Comparative Example 2 / 3 / 4, it can be seen that as the addition amount of TPEE polyester modified material increases from 10 parts to 45 parts, the density / compression deformation rate of the final foamed sole gradually decreases, and the hardness / rebound rate / energy return rate / layered tear strength / shock absorption G value gradually increases. This shows that the various mechanical properties of the TPEE polyester modified material modified by chain growth and chain branching are significantly improved, so that the melt strength of the foam is significantly improved, the pore density and foaming ratio are improved, thereby reducing the overall density of the foamed sole; with the increase of pore density, it is beneficial to improve the rebound rate / energy return rate / layered tear strength and other properties of the foamed sole, and reduce the compression deformation rate, and improve the compression resistance. When the addition amount is 10-15 parts, the improvement effect is very small, and when the addition amount is 45 parts, the improvement effect slows down, and the layered tear strength and compression deformation are slightly worse, so the preferred addition amount is 20-40 parts.

[0114] From the comparison data between comparative example 1 and examples 1 / 2 / 3 / 4 / 5, it can be seen that the TPEE polyester material of comparative example 1 has not been modified by chain growth and chain branching, and its melt strength and mechanical properties are stronger than those of EVA / POE / OBC / SEBS, etc. Therefore, although the hardness / rebound rate / energy return rate / delamination tear strength / shock absorption G value of the foamed shoe sole are improved, the improvement effect is not as obvious as that of the modified TPEE polyester modified material.

[0115] From the comparison data of Comparative Example 5 and Example 2, it can be seen that if the epoxy compatibilizer is not added, the overall performance of the foamed sole will be greatly reduced. This is mainly because TPEE is a polar polymer and has poor compatibility with non-polar polymers such as OBC, POE, and SEBS. Example 2 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 TPEE polyester end, thereby improving the compatibility of each polymer and greatly improving the rebound rate / energy return rate / delamination tear strength / shock absorption and other properties of the foamed sole.

[0116] From the comparison data of Comparative Example 6 and Example 2, it can be seen that if no epoxy nucleating agent is added, the overall performance of the foamed sole is reduced, which is mainly due to the poor dispersibility of ordinary silica in the polymer matrix. After epoxidation of silica, it has good compatibility with modified TPEE and epoxy compatibilizers of epoxy chain extension, so that it can provide enough tiny cores in the foaming process, accelerate the generation of bubbles in the foaming process, improve the foaming effect, reduce the foaming temperature and pressure, shorten the foaming time, and improve the foaming efficiency, which is also conducive to improving the rebound / compression / delamination tearing properties of the foamed sole.

[0117] From the comparison data of Comparative Example 7 and Example 2, it can be seen that if the cell stabilizer is not added, the overall performance of the foamed sole is reduced. This is mainly because polyvinyl alcohol can make the cells evenly distributed, prevent foam shrinkage and rupture, increase cell stability, and optimize the cell structure to avoid the occurrence of insufficient or excessive local density, so that various properties of the foamed sole are improved.

[0118] It can be seen from the above examples that the density of the supercritical foaming 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, yet has extremely high delamination tear strength and excellent compression deformation performance. Its excellent comprehensive performance is a first in the industry.

[0119] The foregoing description of specific exemplary embodiments of the present invention is for the purpose of illustration and demonstration. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is clear that many changes and variations can be made based on the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different selections and changes. The scope of the present invention is intended to be limited by the claims and their equivalents.

Claims

1. A modified TPEE material, characterized in that: It is made by blending TPEE with epoxy chain extender, polyvinyl alcohol short fiber, epoxy coupling agent and flow aid; The epoxy chain extender is styrene-acrylonitrile-glycidyl methacrylate copolymer; the mass ratio of the TPEE, epoxy chain extender and polyvinyl alcohol staple fiber is 100:2-7:4-11.

2. The modified TPEE material according to claim 1, characterized in that: The epoxy coupling agent is 3-(2,3-epoxypropoxy)propyltrimethoxysilane; the flow aid is a mixture of organic silicone oil and erucamide; The mass ratio of the TPEE, the epoxy coupling agent and the flow aid is 100:2-4:1-2.

3. The modified TPEE material according to claim 1 or 2, characterized in that: 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 / 10 min.

4. 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 the modified TPEE material according to any one of claims 1-3.

5. The foamed sole material according to claim 4, characterized in that: In parts by weight, the materials include: 30-50 parts of EVA, 20-40 parts of TPEE components, 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 cross-linking agent.

6. The foamed sole material according to claim 5, characterized in that: The epoxy compatibilizer is an epoxy glycidyl methacrylate graft polymer; the epoxy nucleating agent is an epoxy silane modified silicon dioxide material; and the cell stabilizer is polyvinyl alcohol.

7. The foamed sole material according to claim 5, characterized in that: The lubricant is stearic acid; and the cross-linking agent is a peroxide cross-linking agent.

8. The foamed sole material according to any one of claims 4 to 7, characterized in that: The density of the foamed sole material is 0.08-0.12 g / cm 3 , the rebound rate is over 70%.

9. The method for preparing the foamed sole material according to any one of claims 4 to 8, characterized in that: 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 mold pressing to obtain the foamed shoe sole material.

10. The preparation method according to claim 9, 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.

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