A foamed shoe sole material and a method for producing the same

Abstract

The present application provides a kind of foamed shoe sole material, which is a low thickness variation rate dynamic fatigue resistant foamed shoe sole material.The present application also provides the application of vinyl-acrylate nanofiber in the preparation of foamed shoe sole material.The present application first designs a modified thermoplastic polyurethane elastomer, which is a rigid crosslinking network copolymer with strong polarity and stable structure, then uses it as a reinforcing skeleton to inhibit cell collapse and improve the compression creep resistance, further composite with EVA, polyolefin elastomer, vinyl-acrylate nanofiber and compatibilizer to form a three-dimensional support network, and prepare a lightweight and high-elastic shoe sole material through foaming process.The present application has excellent dynamic durability, the thickness variation rate is less than or equal to 10% under dynamic compression condition, and the change of resilience / energy return rate / shock attenuation G value before and after fatigue is less than 9%, which can meet the comprehensive performance requirements of high-strength sports shoes for lightweight, high resilience and long-term deformation stability.

Description

Technical Field

[0001] This invention belongs to the field of foamed shoe sole material technology, and relates to the application of vinyl-acrylate nanofibers in the preparation of foamed shoe sole materials, a foamed shoe sole material and its preparation method, and particularly to a dynamic fatigue-resistant foamed shoe sole material with low thickness change rate and its preparation method. Background Technology

[0002] With the rapid development of the athletic shoe market, people have increasingly higher requirements for the wearing experience and appearance of shoe soles and other components. Consumers typically demand that shoes not only be lightweight and comfortable but also have a cool and fashionable look, thus placing higher demands on the performance of sole materials. Among these, softness, comfort, and lightweight are the main development trends. Existing technologies have also disclosed some corresponding technical research solutions, such as patent 201611026985.0, which discloses a low-compression-deformation foamed sole and its preparation method. The prepared low-compression-deformation foamed sole exhibits less than 20% compression deformation under conditions of 50℃, 50% compression ratio, and 6 hours of static compression time, while maintaining a density of 0.20-0.23 g / cm³. 3 The material has a hardness of 54-57C and a resilience of 52-57%. Patent 202310033499.5 discloses a compression-resistant composite foam material, its preparation method, and a shoe sole. By combining modified styrene-ethylene-butene-styrene block copolymers with ethylene-vinyl acetate copolymers, the modified styrene-ethylene-butene-styrene block copolymers possess excellent resistance to compression deformation. Therefore, their addition to the ethylene-vinyl acetate copolymers makes the composite foam material more suitable for secondary foaming and significantly reduces the demand for coupling agents. While maintaining the elasticity and softness of the material, the compression deformation rate can be reduced by 20%-50%. Patent 202311706559.1 provides a compression-resistant masterbatch and its preparation method, as well as a low-compression-deformation foam material and its preparation method. Patent 202010738380.4 provides an extremely lightweight, wear-resistant, low-compression, high-resilience composite foam material for sports shoe soles. Although the composite foam material has a low density and excellent wear resistance, resilience, and compression resistance, there is still room for improvement in the material's wear resistance and resilience.

[0003] However, lightweight, soft, and elastic materials are prone to poor resilience and collapse after prolonged wear, and the sole gradually loses its elasticity, resulting in decreased cushioning performance and severely impacting the wearing experience and structural appearance of the shoe. Especially in high-intensity sports, lightweight, soft, and elastic foam soles deform significantly under dynamic stress, failing to meet the demands of such activities. Therefore, for high-intensity sports, a material that can effectively reduce the rate of change in foam sole thickness under dynamic fatigue is needed to improve the shoe's durability and safety.

[0004] Furthermore, the industry currently uses compression deformation to demonstrate the fatigue resistance of foam shoe soles. The testing standard for compression deformation is the static compression deformation test, which measures the compression deformation rate at 50°C, a compression ratio of 50%, and a static compression time of 6 hours. Static compression deformation obtained from a static test can only indicate the compression deformation performance of a product when it is at rest. However, consumers wearing athletic shoes frequently need to run or walk, so the static compression deformation value obtained using this method is not actually suitable for indicating the shoe's fatigue resistance.

[0005] Therefore, how to develop and design a more suitable foam sole material for sports shoes and solve the above-mentioned technical problems of existing foam sole materials has become one of the urgent problems to be solved by many front-line researchers in the industry, especially for long-distance sports. Summary of the Invention

[0006] In view of this, the technical problem to be solved by the present invention is to provide the application of vinyl-acrylate nanofibers in the preparation of foamed shoe sole materials, a foamed shoe sole material and its preparation method, and in particular, a dynamically fatigue-resistant foamed shoe sole material with low thickness change rate. Through innovation in material formulation and preparation process, the present invention produces a shoe sole material with excellent dynamic durability, which can meet the comprehensive performance requirements of high-intensity sports shoes for lightweight, high rebound, and long-term deformation stability. It is suitable for the high-end sports shoe field, achieving performance optimization and enhanced application value.

[0007] This invention provides the application of vinyl-acrylate nanofibers and maleic anhydride-grafted EVA compatibilizer in the preparation of foamed shoe sole materials;

[0008] The applications include reducing the rate of thickness change of foamed shoe soles during use.

[0009] Preferably, the foamed sole material includes EVA-based foamed sole material;

[0010] The diameter of the vinyl-acrylate nanofibers is 50~100 nm;

[0011] The amount of the vinyl-acrylate nanofiber used in the preparation of foamed shoe sole material is 3 to 7 parts by weight.

[0012] Preferably, the amount of the maleic anhydride-grafted EVA compatibilizer used in the preparation of foamed shoe sole material is 2 to 5 parts by weight;

[0013] The raw materials for preparing the foamed shoe sole material also include a matrix material;

[0014] The matrix material is EVA, polyolefin elastomer, and modified thermoplastic polyurethane elastomer;

[0015] The applications also include one or more of the following: forming a three-dimensional polymer support network structure in foamed shoe soles, enhancing cell stability, and enhancing cell uniformity.

[0016] This invention provides a foamed shoe sole material, comprising, by weight of raw materials: 40-60 parts by weight of EVA, 20-40 parts by weight of polyolefin elastomer, 10-30 parts by weight of modified thermoplastic polyurethane elastomer, 3-7 parts by weight of vinyl-acrylate nanofibers, 2-5 parts by weight of maleic anhydride-grafted EVA compatibilizer, 0.4-0.8 parts by weight of peroxide crosslinking agent, 0-4 parts by weight of AC foaming agent, 0-1.5 parts by weight of zinc oxide, and 1-1.5 parts by weight of stearic acid.

[0017] Preferably, the VA content in the EVA is 15% to 40% by mass;

[0018] The polyolefin elastomer (polyolefin thermoplastic elastomer) includes one or more of ethylene-octene random polymer (POE), ethylene-octene block polymer (OBC), and ethylene-propylene-conjugated diene (EPDM).

[0019] The modified thermoplastic polyurethane elastomer includes a carboxyl-containing acrylate vinyl rubber modified thermoplastic polyurethane elastomer.

[0020] The modified thermoplastic polyurethane elastomer includes one or more of aliphatic polyester TPU, aliphatic polyether TPU, aromatic polyester TPU, aromatic polyether TPU, polycaprolactone-type polyester TPU, and polycarbonate-type polyester TPU.

[0021] The maleic anhydride-grafted EVA compatibilizer includes a maleic anhydride-grafted EVA compatibilizer with a grafting rate ≥1.0%.

[0022] The peroxide crosslinking agent includes dicumyl peroxide and / or 1,4-di-tert-butylperoxide;

[0023] The AC foaming agent includes one or more of azodicarbonamide, sodium bicarbonate, expanded microspheres, 4,4-oxodibenzenesulfonyl hydrazine, supercritical nitrogen, and supercritical carbon dioxide.

[0024] Preferably, the modified thermoplastic polyurethane elastomer comprises, by weight of raw materials: 70-80 parts by weight of thermoplastic polyurethane elastomer, 20-30 parts by weight of highly polar carboxyl-containing acrylate vinyl rubber, 0.5-2 parts by weight of grafting agent, 0.5-1 parts by weight of initiator, and 0.3-1 parts by weight of lubricant.

[0025] The highly polar carboxyl-containing acrylate vinyl rubbers include ACM 2012;

[0026] The grafting agent includes one or more of maleic anhydride, acrylic acid, and methacrylic acid;

[0027] The initiator includes one or more of azobisisobutyronitrile, benzoyl peroxide, and ethane peroxide;

[0028] The lubricant includes stearic acid and / or zinc stearate;

[0029] The thermoplastic polyurethane elastomer and carboxyl-containing acrylate vinyl rubber form a rigid cross-linked network blend with strong polarity and stable structure after being heated and melted.

[0030] This invention also provides a method for preparing a foamed shoe sole material, comprising the following steps:

[0031] 1) Peroxide crosslinking agent, AC foaming agent and zinc oxide are used as the first group of raw materials; vinyl-acrylate nanofibers, stearic acid and maleic anhydride grafted EVA compatibilizer are used as the second group of raw materials; the remaining raw materials are used as the third group of raw materials;

[0032] The third group of raw materials is added into the internal mixer and heated and mixed until the first temperature is reached. Then the second group of raw materials is added and heated and mixed until the second temperature is reached. Then the first group of raw materials is added and heated and mixed until the third temperature is reached, resulting in a mixture. The mixture is then granulated to obtain granules.

[0033] 2) The granules obtained in the above steps are foamed to obtain a semi-finished product, and then molded to obtain foamed shoe sole material; or, the granules obtained in the above steps are injection foamed to obtain foamed material, and then baked to obtain foamed shoe sole material.

[0034] or,

[0035] 1) Peroxide crosslinking agent is used as the first group of raw materials; vinyl-acrylate nanofibers, stearic acid and maleic anhydride grafted EVA compatibilizer are used as the second group of raw materials; the remaining raw materials are used as the third group of raw materials; the raw materials do not contain AC foaming agent and zinc oxide;

[0036] The third group of raw materials is added into the internal mixer and heated and mixed until the first temperature is reached. Then the second group of raw materials is added and heated and mixed until the second temperature is reached. Then the first group of raw materials is added and heated and mixed until the third temperature is reached, resulting in a mixture. The mixture is then granulated to obtain granules.

[0037] 2) After the granules obtained in the above steps are injection molded by IP, a small rough blank is obtained. The small rough blank is then subjected to supercritical foaming and cooled to obtain a semi-finished product. Finally, after finished product molding, foamed shoe sole material is obtained.

[0038] Preferably, the first temperature is 100~110℃;

[0039] The second temperature is 110~120℃;

[0040] The third temperature is 120~125℃;

[0041] The granulation temperature is 100~130℃;

[0042] The temperature of the small foam is 170~180℃;

[0043] The time for the small foaming is 500-560 seconds;

[0044] The molding temperature is 170~180℃;

[0045] The molding time is 400-460 seconds;

[0046] The feeding temperature for injection foaming is 105~120℃;

[0047] The temperature of the molding die for injection foaming is 170~180℃;

[0048] The injection time for the injection foaming process is 180-220 seconds;

[0049] The vulcanization and foaming time for injection molding is 570-630 seconds;

[0050] The baking temperature is 80~100℃;

[0051] The oven speed for baking is 50-60 revolutions per minute;

[0052] The baking time is 30 to 40 minutes.

[0053] Preferably, the molding temperature of the IP injection molding is 170~180℃;

[0054] The injection time for the IP injection molding is 180~220 seconds;

[0055] The vulcanization time for the IP injection molding is 470~530 seconds;

[0056] The pressure of the supercritical foaming is 18~35MPa;

[0057] The supercritical foaming temperature is 115~150℃;

[0058] The heat preservation and pressure holding time for the supercritical foaming is 1.5~2.5h;

[0059] The heating temperature for molding the finished product is 160~170℃;

[0060] The heating time for molding the finished product is 470~530 seconds;

[0061] The cooling temperature for the molded finished product is 20~25℃;

[0062] The cooling time for the molded finished product is 470-530 seconds.

[0063] This invention also provides the application of dynamic impact testing in GB / T 38018-2019 in evaluating the fatigue resistance of foamed shoe sole materials.

[0064] This invention provides the application of vinyl-acrylate nanofibers in the preparation of foamed shoe sole materials. Compared with the prior art, this invention suggests that in the published patents for EVA chemically foamed shoe soles, if thermoplastic polyurethane is used to improve the compression deformation of the foam material, the modified compression-resistant material is obtained by twin-screw blending thermoplastic polyurethane with EVA or thermoplastic polyurethane with high-resilience rubber (one or more of EPDM rubber, styrene-butadiene rubber, butadiene rubber, and brominated butyl butyl rubber). Due to the large polarity difference between thermoplastic polyurethane and EVA or EPDM rubber, styrene-butadiene rubber, butadiene rubber, and brominated butyl butyl rubber, simple twin-screw blending and granulation is difficult to achieve effective compatibility. When this blended material is added to a matrix such as EVA / POE / OBC for foaming, it leads to a decrease in the overall compatibility of the formulation, ultimately affecting the rebound and delamination tear performance of the foamed shoe sole. As can be seen from the example data of 201611026985.0, although the compression deformation of its foamed sole is <20%, its density is 0.20~0.23g / cm³. 3 With a hardness of 54-57C and a resilience of 52-57%, it cannot meet the requirements of being lightweight, soft, and highly elastic.

[0065] If modified styrene-ethylene-butene-styrene block copolymer is used to improve the compression deformation of EVA-based foamed shoe soles, its mass content in the formula is 29%-53%. Since the 1,2 structure accounts for 70%-90% of the modified hydrogenated butadiene and the 1,2 structure of the side groups is high, the flexibility of the molecular chain will decrease, and it will be more inclined to shock absorption. This will lead to a decrease in the rebound performance of the foamed shoe sole, and the rebound performance will decrease significantly with the increase of the amount added.

[0066] If EVA / POE / OBC / EPDM is used to prepare an ultra-lightweight, wear-resistant, and low-compression composite foam material, the poor mechanical properties of EPDM rubber limit its effectiveness in improving compression set. Test data shows that the compression set of the example is 38%-42%, hardness is 50C-55C, rebound is 55%-59%, and tear strength is <20N / cm. The high hardness, low rebound, and poor compression set and tear strength prevent it from achieving the fatigue resistance of a lightweight, soft, and elastic foam sole. Furthermore, the non-polar polymer (polyolefin elastomer POE + olefin block copolymer OBC) in the formulation is as high as 50%-78%, while the weakly polar ethylene-vinyl acetate copolymer is 5-10%. Although 3-6% maleic anhydride-grafted POE is added, the overall polarity of the formulation is poor, which can easily lead to poor adhesion of the foam sole and a risk of delamination.

[0067] Based on this, the present invention specifically uses vinyl-acrylate nanofibers in the preparation of foamed shoe sole materials, and further combines them with maleic anhydride-grafted EVA compatibilizers for use in specific EVA, polyolefin elastomers, and modified thermoplastic polyurethane elastomer matrices. The present invention also provides a foamed shoe sole material, which is a dynamically fatigue-resistant foamed shoe sole material with a low thickness change rate. The present invention first heat-melt blends thermoplastic aliphatic polyether polyurethane (TPU) with carboxyl-containing acrylate vinyl rubber using a twin-screw extruder under the action of a grafting agent and an initiator to form a rigid cross-linked network copolymer with strong polarity and structural stability. This modified thermoplastic polyurethane elastomer copolymer acts as a reinforcing skeleton to inhibit cell collapse and improve compressive creep resistance. It is further combined with EVA, polyolefin elastomers, vinyl-acrylate nanofibers, and compatibilizers to form a three-dimensional support network, and then prepared into a lightweight, highly elastic shoe sole material through a foaming process.

[0068] Experimental results show that the foamed shoe sole material prepared by this invention possesses excellent dynamic durability, with a hardness of 42±3 C and a density of 0.12±0.02 g / cm³. 3 The material exhibits a rebound rate of ≥65%, a thickness change rate of ≤10% under dynamic compression conditions, and changes in rebound rate / energy return rate / shock absorption G-value before and after fatigue of <9%. This material meets the comprehensive performance requirements of high-intensity sports shoes for lightweight, high rebound, and long-term deformation stability. It is particularly suitable for midsole materials in sports shoes, making it ideal for high-end sports footwear and of great value for long-distance athletic events.

[0069] Furthermore, to better align with actual wearing scenarios, compared to the existing technology that uses the static compression deformation test standard in GB / T 38018-2019 to evaluate the fatigue resistance of shoe sole materials (compression deformation rate at 50℃, 50% compression ratio, and 6 hours of static compression), this invention employs dynamic impact testing (GB / T38018-2019) to assess its fatigue resistance. This involves applying pressure to the shoe sole material at a certain rate, approaching the pressure of a human foot during jogging, simulating the repeated compression process of the foot on the material during actual wear. After a certain number of fatigue compression cycles, the fatigue resistance of the shoe sole material is evaluated using indicators such as the thickness change rate and the performance change rate. Typically, the pressure is set at 1200±120N, with a rate of 120±12 times / min, continuously compressed 50,000 to 100,000 times, thereby measuring the thickness change rate ΔH of the foamed shoe sole (ΔH = (d1-d0) / d0*100%, where d1 is the thickness of the sample after fatigue, in millimeters; d0 is the thickness of the sample after fatigue, in millimeters). Attached Figure Description

[0070] Figure 1 A simplified flow diagram of the MD chemical foaming process provided by the present invention;

[0071] Figure 2 A simplified flowchart illustrating the IP process provided by this invention;

[0072] Figure 3 A simplified flowchart illustrating the supercritical physical process provided by this invention. Detailed Implementation

[0073] 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, and not for limiting the scope of the claims.

[0074] There are no particular restrictions on the source of any raw materials used in this invention; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0075] There are no particular restrictions on the purity of any of the raw materials used in this invention. However, this invention preferably uses analytical grade or the purity requirements conventional in the field of foamed shoe sole material preparation.

[0076] All raw materials of this invention are conventional in the field, and each brand name and abbreviation is clear and distinct in its relevant application. Those skilled in the art can purchase them from the market or prepare them by conventional methods based on the brand name, abbreviation and corresponding application.

[0077] This invention provides the application of vinyl-acrylate nanofibers and maleic anhydride-grafted EVA compatibilizer in the preparation of foamed shoe sole materials;

[0078] The applications include reducing the rate of thickness change of foamed shoe soles during use.

[0079] In this invention, the foamed sole material preferably includes EVA-based foamed sole material.

[0080] In this invention, the diameter of the vinyl-acrylate nanofibers can be 50~100 nm, 60~90 nm, or 70~80 nm.

[0081] In this invention, the amount of vinyl-acrylate nanofiber used in the preparation of foamed shoe sole material is 3 to 7 parts by weight, or 3.5 to 6.5 parts by weight, or 4 to 6 parts by weight, or 4.5 to 5.5 parts by weight.

[0082] In this invention, the application preferably includes the application of reducing the thickness change rate of foamed shoe soles during use.

[0083] In this invention, the application is preferably the application of vinyl-acrylate nanofibers and maleic anhydride-grafted EVA compatibilizer in the preparation of foamed shoe sole materials.

[0084] In this invention, the amount of maleic anhydride-grafted EVA compatibilizer used in the preparation of foamed shoe sole materials can be 2-5 parts by weight, more preferably 2.5-4.5 parts by weight, or more preferably 3-4 parts by weight.

[0085] In this invention, the matrix of the foamed shoe sole material is preferably EVA, polyolefin elastomer, or modified thermoplastic polyurethane elastomer.

[0086] In this invention, the application preferably includes one or more of the following: forming a three-dimensional polymer support network structure in a foamed shoe sole, enhancing cell stability, and enhancing cell uniformity; more preferably, it includes the application of forming a three-dimensional polymer support network structure in a foamed shoe sole, enhancing cell stability, or enhancing cell uniformity.

[0087] In this invention, the foamed sole material preferably includes sports shoe midsole material.

[0088] This invention provides a foamed shoe sole material, comprising, by weight of raw materials: 40-60 parts by weight of EVA, 20-40 parts by weight of polyolefin elastomer, 10-30 parts by weight of modified thermoplastic polyurethane elastomer, 3-7 parts by weight of vinyl-acrylate nanofibers, 2-5 parts by weight of maleic anhydride-grafted EVA compatibilizer, 0.4-0.8 parts by weight of peroxide crosslinking agent, 0-4 parts by weight of AC foaming agent, 0-1.5 parts by weight of zinc oxide, and 1-1.5 parts by weight of stearic acid.

[0089] In this invention, the amount of EVA added is 40-60 parts by weight, or 44-56 parts by weight, or 48-52 parts by weight.

[0090] In this invention, the amount of polyolefin elastomer added is 20-40 parts by weight, or 24-36 parts by weight, or 28-32 parts by weight.

[0091] In this invention, the amount of the modified thermoplastic polyurethane elastomer added is 10-30 parts by weight, or 14-26 parts by weight, or 18-22 parts by weight.

[0092] In this invention, the amount of vinyl-acrylate nanofibers added is 3 to 7 parts by weight, or 3.5 to 6.5 parts by weight, or 4 to 6 parts by weight, or 4.5 to 5.5 parts by weight.

[0093] In this invention, the amount of maleic anhydride-grafted EVA compatibilizer added is 2-5 parts by weight, or 2.5-4.5 parts by weight, or 3-4 parts by weight.

[0094] In this invention, the amount of the peroxide crosslinking agent added is 0.4 to 0.8 parts by weight, or 0.45 to 0.75 parts by weight, or 0.5 to 0.7 parts by weight, or 0.55 to 0.65 parts by weight.

[0095] In this invention, the amount of AC foaming agent added is 0-4 parts by weight, preferably 0 or 3-4 parts by weight, and can be 3.2-3.8 parts by weight or 3.4-3.6 parts by weight. When using a supercritical process, the AC foaming agent is not required.

[0096] In this invention, the amount of zinc oxide added is 0 to 1.5 parts by weight, preferably 0 or 1.0 to 1.5 parts by weight, and can be 1.1 to 1.4 parts by weight or 1.2 to 1.3 parts by weight. When using a supercritical process, zinc oxide is not required.

[0097] In this invention, the amount of stearic acid added is 1.0 to 1.5 parts by weight, or 1.1 to 1.4 parts by weight, or 1.2 to 1.3 parts by weight.

[0098] In this invention, the VA content in the EVA can be 15% to 40%, more preferably 20% to 35%, or more preferably 25% to 30%.

[0099] In this invention, the polyolefin elastomer (polyolefin thermoplastic elastomer) preferably includes one or more of ethylene-octene random polymer (POE), ethylene-octene block polymer (OBC), and ethylene-propylene-conjugated diene (EPDM), more preferably ethylene-octene random polymer (POE), ethylene-octene block polymer (OBC), or ethylene-propylene-conjugated diene (EPDM).

[0100] In this invention, the modified thermoplastic polyurethane elastomer preferably includes a carboxyl-containing acrylate vinyl rubber modified thermoplastic polyurethane elastomer.

[0101] In this invention, the thermoplastic polyurethane elastomer preferably includes one or more of aliphatic polyester TPU, aliphatic polyether TPU, aromatic polyester TPU, aromatic polyether TPU, polycaprolactone-type polyester TPU, and polycarbonate-type polyester TPU, more preferably aliphatic polyester TPU, aliphatic polyether TPU, aromatic polyester TPU, aromatic polyether TPU, polycaprolactone-type polyester TPU, or polycarbonate-type polyester TPU.

[0102] In this invention, the modified thermoplastic polyurethane elastomer comprises, by weight of raw materials: 70-80 parts by weight of thermoplastic polyurethane elastomer, 20-30 parts by weight of highly polar carboxyl-containing acrylate vinyl rubber, 0.5-2 parts by weight of grafting agent, 0.5-1 parts by weight of initiator, and 0.3-1 parts by weight of lubricant.

[0103] Specifically, the amount of thermoplastic polyurethane elastomer added can be 70-80 parts by weight, 72-78 parts by weight, or 74-76 parts by weight.

[0104] The amount of the highly polar carboxyl-containing acrylate vinyl rubber added can be 20-30 parts by weight, 22-28 parts by weight, or 24-26 parts by weight.

[0105] The amount of grafting agent added can be 0.5 to 2 parts by weight, 0.8 to 1.7 parts by weight, or 1.1 to 1.4 parts by weight.

[0106] The amount of the initiator added can be 0.5 to 1 part by weight, 0.6 to 0.9 parts by weight, or 0.7 to 0.8 parts by weight.

[0107] The amount of lubricant added can be 0.3 to 1 part by weight, 0.3 to 0.8 parts by weight, or 0.4 to 0.5 parts by weight.

[0108] In this invention, the highly polar carboxyl-containing acrylate vinyl rubber preferably includes ACM 2012.

[0109] In this invention, the grafting agent preferably includes one or more of maleic anhydride, acrylic acid, and methacrylic acid, more preferably maleic anhydride, acrylic acid, or methacrylic acid.

[0110] In this invention, the initiator preferably includes one or more of azobisisobutyronitrile, benzoyl peroxide, and ethane peroxide, more preferably azobisisobutyronitrile, benzoyl peroxide, or ethane peroxide.

[0111] In this invention, the lubricant preferably includes stearic acid and / or zinc stearate, more preferably stearic acid or zinc stearate.

[0112] In this invention, the thermoplastic polyurethane elastomer and the carboxyl-containing acrylate vinyl rubber preferably form a rigid cross-linked network blend with strong polarity and stable structure after being heated and melted.

[0113] In this invention, the maleic anhydride-grafted EVA compatibilizer preferably comprises a maleic anhydride-grafted EVA compatibilizer with a grafting rate ≥1.0%.

[0114] In this invention, the peroxide crosslinking agent preferably includes dicumyl peroxide and / or 1,4-di-tert-butylperoxyisopropylbenzene, more preferably dicumyl peroxide or 1,4-di-tert-butylperoxyisopropylbenzene.

[0115] In this invention, the AC foaming agent preferably includes one or more of azodicarbonamide, sodium bicarbonate, expanded microspheres, 4,4-oxodibenzenesulfonyl hydrazine, supercritical nitrogen, and supercritical carbon dioxide, more preferably azodicarbonamide, sodium bicarbonate, expanded microspheres, 4,4-oxodibenzenesulfonyl hydrazine, supercritical nitrogen, or supercritical carbon dioxide.

[0116] This invention provides a method for preparing a foamed shoe sole material, comprising the following steps:

[0117] 1) Peroxide crosslinking agent, AC foaming agent and zinc oxide are used as the first group of raw materials; vinyl-acrylate nanofibers, stearic acid and maleic anhydride grafted EVA compatibilizer are used as the second group of raw materials; the remaining raw materials are used as the third group of raw materials;

[0118] The third group of raw materials is added into the internal mixer and heated and mixed until the first temperature is reached. Then the second group of raw materials is added and heated and mixed until the second temperature is reached. Then the first group of raw materials is added and heated and mixed until the third temperature is reached, resulting in a mixture. The mixture is then granulated to obtain granules.

[0119] 2) The granules obtained in the above steps are foamed to obtain a semi-finished product, and then molded to obtain foamed shoe sole material; or, the granules obtained in the above steps are injection foamed to obtain foamed material, and then baked to obtain foamed shoe sole material.

[0120] or,

[0121] 1) Peroxide crosslinking agent is used as the first group of raw materials; vinyl-acrylate nanofibers, stearic acid and maleic anhydride grafted EVA compatibilizer are used as the second group of raw materials; the remaining raw materials are used as the third group of raw materials; the raw materials do not contain AC foaming agent and zinc oxide;

[0122] The third group of raw materials is added into the internal mixer and heated and mixed until the first temperature is reached. Then the second group of raw materials is added and heated and mixed until the second temperature is reached. Then the first group of raw materials is added and heated and mixed until the third temperature is reached, resulting in a mixture. The mixture is then granulated to obtain granules.

[0123] 2) After the granules obtained in the above steps are injection molded by IP, a small rough blank is obtained. The small rough blank is then subjected to supercritical foaming and cooled to obtain a semi-finished product. Finally, after finished product molding, foamed shoe sole material is obtained.

[0124] This invention first uses peroxide crosslinking agent, AC foaming agent and zinc oxide as the first group of raw materials; vinyl-acrylate nanofibers, stearic acid and maleic anhydride grafted EVA compatibilizer as the second group of raw materials; and the remaining raw materials as the third group of raw materials.

[0125] The third group of raw materials is added into the internal mixer and heated and mixed until the first temperature is reached. Then the second group of raw materials is added and the mixture is heated and mixed until the second temperature is reached. Then the first group of raw materials is added and the mixture is heated and mixed until the third temperature is reached, resulting in a mixture. The mixture is then granulated to obtain granules.

[0126] In this invention, the first temperature can be 100~110℃, 102~108℃, or 104~106℃.

[0127] In this invention, the second temperature can be 110~120℃, 112~118℃, or 114~116℃.

[0128] In this invention, the third temperature can be 120~125℃, 121~124℃, or 122~123℃.

[0129] In this invention, the granulation temperature can be 100~130℃, 105~125℃, or 110~120℃.

[0130] Finally, the granules obtained in the above steps are foamed to obtain a semi-finished product, which is then molded to obtain foamed shoe sole material.

[0131] In this invention, the temperature of the small foam can be 170~180℃, 172~178℃, or 174~176℃.

[0132] In this invention, the foaming time can be 500-560 seconds, 510-550 seconds, or 520-540 seconds.

[0133] In this invention, the molding temperature can be 170~180℃, 172~178℃, or 174~176℃.

[0134] In this invention, the molding time can be 400-460 seconds, 410-450 seconds, or 420-440 seconds.

[0135] Finally, the granules obtained in the above steps are injection-molded to obtain foamed material, which is then baked to obtain foamed shoe sole material.

[0136] In this invention, the feeding temperature for injection foaming can be 105~120℃, 108~117℃, or 111~114℃.

[0137] In this invention, the temperature of the molding die for injection foaming can be 170~180℃, 172~178℃, or 174~176℃.

[0138] In this invention, the injection time for injection foaming can be 180-220 seconds, 185-215 seconds, 190-210 seconds, or 195-205 seconds.

[0139] In this invention, the vulcanization foaming time of the injection foaming molding can be 570~630 seconds, 580~620 seconds, or 590~610 seconds.

[0140] In this invention, the baking temperature can be 80~100℃, 84~96℃, or 88~92℃.

[0141] In this invention, the oven speed can be 50~60 rpm, 52~58 rpm, or 54~56 rpm.

[0142] In this invention, the baking time can be 30-40 minutes, 32-38 minutes, or 34-36 minutes.

[0143] In addition to the two preparation methods mentioned above, this invention also provides a third preparation method, as described below:

[0144] This invention first uses a peroxide crosslinking agent as the first group of raw materials; vinyl-acrylate nanofibers, stearic acid and maleic anhydride grafted EVA compatibilizer as the second group of raw materials; and the remaining raw materials as the third group of raw materials; wherein, the preparation method adopts a supercritical foaming process, without the need to add AC foaming agent and zinc oxide.

[0145] The third group of raw materials is added into the internal mixer and heated and mixed until the first temperature is reached. Then the second group of raw materials is added and the mixture is heated and mixed until the second temperature is reached. Then the first group of raw materials is added and the mixture is heated and mixed until the third temperature is reached, resulting in a mixture. The mixture is then granulated to obtain granules.

[0146] Finally, the granules obtained in the above steps are injection molded by IP to obtain a small preform. The preform is then subjected to supercritical foaming and cooled to obtain a semi-finished product. Finally, after finished product molding, foamed shoe sole material is obtained.

[0147] In this invention, the molding temperature of the IP injection molding can be 170~180℃, 172~178℃, or 174~176℃.

[0148] In this invention, the injection time of the IP injection molding can be 180~220 seconds, 185~215 seconds, 190~210 seconds, or 195~205 seconds.

[0149] In this invention, the vulcanization time of the IP injection molding can be 470~530 seconds, 480~520 seconds, or 490~510 seconds.

[0150] In this invention, the supercritical foaming pressure can be 18~35MPa, 22~31MPa, or 26~27MPa.

[0151] In this invention, the supercritical foaming temperature can be 115~150℃, 120~145℃, 125~140℃, or 130~135℃.

[0152] In this invention, the heat preservation and pressure holding time of the supercritical foaming can be 1.5~2.5h, 1.7~2.3h, or 1.9~2.1h.

[0153] In this invention, the heating temperature for molding the finished product can be 160~170℃, 162~168℃, or 164~166℃.

[0154] In this invention, the heating time for molding the finished product can be 470~530 seconds, 480~520 seconds, or 490~510 seconds.

[0155] In this invention, the cooling temperature of the finished product molding can be 20~25℃, 21~24℃, or 22~23℃.

[0156] In this invention, the cooling time of the molded finished product can be 470~530 seconds, 480~520 seconds, or 490~510 seconds.

[0157] This invention aims to complete and refine the overall technical solution, better ensure the composition and structure of foamed shoe sole materials, and further improve the low thickness change rate and dynamic fatigue resistance of foamed shoe sole materials. Specifically, the application of the aforementioned vinyl-acrylate nanofibers in the preparation of foamed shoe sole materials, and a dynamic fatigue-resistant foamed shoe sole material with a low thickness change rate and its preparation method, may include the following:

[0158] This invention provides a method for preparing and realizing a dynamic fatigue-resistant foamed shoe sole material with low thickness change rate, comprising, by weight: 40-60 parts EVA, 20-40 parts polyolefin elastomer, 10-30 parts modified thermoplastic polyurethane elastomer, 3-7 parts vinyl-acrylate nanofibers, 2-5 parts maleic anhydride-grafted EVA compatibilizer, 0.4-0.8 parts peroxide crosslinking agent, 3-4 parts AC foaming agent, 1.0-1.5 parts zinc oxide, and 1-1.5 parts stearic acid.

[0159] Specifically, EVA (ethylene-vinyl acetate copolymer): including EVA with VA content of 15% to 40%, with preferred varieties being EVAUE632 and EVAUE659.

[0160] Specifically, the polyolefin elastomer is preferably a polyolefin thermoplastic elastomer, including 1 to 3 types of ethylene-octene random polymers (POE) with a hardness of 50-70A and a crystallinity of <20%, ethylene-octene block polymers (OBC) with a hardness of 50-70A and a crystallinity of <25%, and ethylene-propylene-conjugated diene (EPDM) with a crystallinity of <5%. Preferred varieties include POE LC161, OBC 9107, and EPDM5565.

[0161] Specifically, modified thermoplastic polyurethane elastomer: a mixture of 70-80 parts of thermoplastic aliphatic polyether polyurethane (TPU), 20-30 parts of carboxyl-containing acrylate vinyl rubber, 0.5-2 parts of grafting agent, 0.5-1 parts of initiator, and 0.3-1 parts of lubricant is melted by a twin-screw extruder at a temperature controlled at 150-180°C to form a strongly polar, rigid cross-linked network structure copolymer.

[0162] Among them, ① thermoplastic aliphatic polyether polyurethane (TPU): Thermoplastic polyurethane (TPU) is a type of linear block copolymer composed of alternating hard and soft segments, possessing excellent elasticity, abrasion resistance, oil resistance, and processing performance. Based on different chemical structures and raw materials, TPU copolymer resins can be mainly classified into the following types: aliphatic polyesters, aliphatic polyethers, aromatic polyesters, aromatic polyethers, polycaprolactone-type polyesters, polycarbonate-type polyesters, etc. This invention preferably uses aliphatic polyether polyurethane. Aliphatic polyether polyurethane is a type of polymer material synthesized primarily from aliphatic isocyanates and polyether polyols, possessing the following significant advantages: Because its molecular structure does not contain aromatic rings, aliphatic polyurethane is less prone to yellowing and degradation under light, thus exhibiting excellent weather resistance; the polyether soft segments impart a lower glass transition temperature (Tg) to the material, allowing it to maintain excellent elasticity and flexibility even at low temperatures; compared to polyester-type polyurethane, polyether-type polyurethane has superior dynamic mechanical properties, resilience, and abrasion resistance, making it suitable for applications with high dynamic loads. The preferred variety is Elastollan C 85 A.

[0163] ② Highly polar acrylate vinyl rubbers containing carboxyl groups: These are vinyl rubber elastomers formed through free radical polymerization or copolymerization, with acrylate monomers containing highly polar carboxyl functional groups as the main component. Their main chain is a flexible vinyl structure composed of carbon-carbon bonds, and the side chains contain highly polar carboxyl groups, thus endowing the material with high polarity and special interfacial properties. A preferred variety is ACM 2012.

[0164] ③ Grafting agent: selected from one or more of maleic anhydride, acrylic acid, and methacrylic acid, with maleic anhydride being preferred; ④ Initiator: selected from one or more of azobisisobutyronitrile, benzoyl peroxide, and ethane peroxide, with azobisisobutyronitrile being preferred. Through the action of the grafting agent methacrylic acid and the initiator azobisisobutyronitrile, thermoplastic polyurethane (TPU) and carboxyl-containing acrylate vinyl rubber are melted upon heating to form a rigid cross-linked network blend with strong polarity and stable structure. This blend acts as a "skeleton support," improving the rigidity and compressive strength of the foam cells, comprehensively enhancing the mechanical properties of the foamed shoe sole, while limiting cell wall collapse and deformation, and reducing the thickness change rate of the foamed shoe sole under later dynamic fatigue.

[0165] Specifically, vinyl-acrylate nanofibers are a type of functional elastomer nanofiber material prepared by copolymerization modification based on acrylate monomers. This material has a nanometer-scale diameter of 50-100 nm, possessing both excellent elasticity and flexibility. It combines the stretchability of polymeric elastomers with the unique physical effects of nanostructures (such as high specific surface area, quantum size effect, and high surface activity), exhibiting comprehensive performance far exceeding that of traditional fibers. Due to the presence of polar functional groups in its molecular chain, vinyl-acrylate nanofibers have good compatibility and strong interfacial bonding with polar polymers such as TPU and EVA. In foaming systems, these nanofibers tend to distribute in the interface regions of the cell walls, interacting with modified TPU and EVA through hydrogen bonds and covalent bonds to construct a stable three-dimensional network structure. This structure significantly enhances the mechanical strength of the cell walls, effectively maintaining the stability of the cells during foaming, inhibiting cell collapse under dynamic compression, thereby reducing the thickness change rate of foamed shoe soles during use and improving the material's durability and resilience. A preferred variety is PORE 5145.

[0166] Specifically, maleic anhydride-grafted EVA compatibilizers include: the anhydride groups in maleic anhydride (MAH) molecules have high reactivity and can undergo ring-opening reactions with polar polymers containing functional groups such as amino (-NH2), hydroxyl (-OH), or carboxyl (-COOH) groups to form covalent bonds. In TPU / EVA blend systems, the anhydride in MAH-g-EVA can react chemically to generate grafted or cross-linked structures, thereby forming "molecular bridges" between the two phase interfaces and significantly enhancing interfacial adhesion. MAH-g-EVA retains the skeletal structure of EVA, thus it can dissolve or disperse well in EVA and part of the TPU matrix; at the same time, the grafted maleic anhydride provides polar sites, enabling it to also generate strong van der Waals forces or hydrogen bonds with polar components. This characteristic of "one end favoring the nonpolar phase and the other end favoring the polar phase" makes MAH-g-EVA a highly efficient interfacial compatibilizer. It reduces interfacial tension, promotes uniform dispersion, prevents phase separation, results in more uniform foaming, more stable cell structure, and improved resilience and wear resistance. By enhancing interfacial bonding, MAH-g-EVA effectively transfers stress while reducing the generation of defects such as micropores and cracks, improving the overall uniformity and durability of the material, and increasing the tensile strength, impact strength, and peel strength of the composite material. This invention preferably uses maleic anhydride grafts with a grafting rate ≥1.0%, with C250 being a preferred variety.

[0167] Specifically, the peroxide crosslinking agent includes one of the following: dicumyl peroxide or 1,4-di-tert-butylperoxyisopropylbenzene. A preferred variety is BIBP 14S-FL.

[0168] Specifically, the foaming agent includes one of the following: azodicarbonamide, sodium bicarbonate, expanded microspheres, 4,4-oxodibenzenesulfonyl hydrazine, supercritical nitrogen, and supercritical carbon dioxide. The preferred agent for chemical foaming process is AC JTR-M; the preferred agent for supercritical foaming process is supercritical nitrogen.

[0169] Specifically, zinc oxide: purity ≥ 99.7%, with ZnO 997 being the preferred variety.

[0170] Specifically, stearic acid is a highly efficient lubricant, with 1801 being a preferred variety.

[0171] The present invention also provides corresponding implementation steps: The present invention is applicable to MD chemical foaming process, IP chemical foaming process, and supercritical autoclave foaming process.

[0172] (1) MD chemical foaming process

[0173] See Figure 1 , Figure 1 A simplified flow chart of the MD chemical foaming process provided by the present invention.

[0174] Implementation steps:

[0175] ① Weighing materials: Based on the dosage of the formula, weigh the first group of crosslinking agent, foaming agent, and zinc oxide; weigh the second group of vinyl-acrylate nanofiber, stearic acid, and maleic anhydride grafted EVA compatibilizer; weigh the remaining materials as the third group.

[0176] ② Mixing: First, pour the third batch of material into the internal mixer and turn on the machine. Wait for the temperature to rise to between 100-110℃; then pour in the second batch of material; when the temperature rises to 110-120℃, pour in the first batch of material; when the temperature rises to 120-125℃, pour out the mixed material.

[0177] ③ Granulation: Pour the mixed material into the granulator. Adjust the temperatures of the first, second, third, and fourth zones to 105, 110, 115, and 120℃ respectively. Adjust the screw speed to 60-75 rpm and the cutting speed to 25-35 rpm.

[0178] ④ Small foaming: Pour the prepared granules into a flat mold for small foaming to complete the first foaming. The foaming temperature is 175±5℃ and the foaming time is 530±30 seconds.

[0179] ⑤ Molding: After the small foamed semi-finished product has been left to stand and cool for 24 hours, press the small foamed semi-finished product into a flat molding die to complete the molding of the finished product; the hot pressing temperature is 175±5℃; the hot pressing time is 430±30 seconds; the cooling water temperature is 25℃ and the cooling time is 430±30 seconds.

[0180] (2) IP process implementation steps:

[0181] See Figure 2 , Figure 2 A simplified flowchart illustrating the IP process provided by this invention.

[0182] Implementation steps:

[0183] ①The processes of weighing, mixing, and granulation are consistent with MD processes ①, ②, and ③.

[0184] ② Foaming: Pour the prepared material into the injection molding foaming machine. Adjust the temperatures of the first, second, third, and fourth feeding zones to 105, 110, 115, and 120℃ respectively. Adjust the temperatures of the upper and lower mold plates to 175±5℃ and 175±5℃ respectively. Set the injection time to 200±20 seconds and the vulcanization foaming time to 600±30 seconds.

[0185] Baking: Set the temperatures of the first, second, third, and fourth zones of the oven to 80, 90, 95, and 100℃ respectively, and the rotation speed to 60 revolutions per minute; send the foamed material into the oven opening, and the oven length should be 30 meters; the baking time from start to finish should be 40 minutes.

[0186] (3) Implementation steps of supercritical physical process:

[0187] See Figure 3 , Figure 3 A simplified flowchart illustrating the supercritical physical process provided by this invention.

[0188] Implementation steps:

[0189] ① Weighing materials: Based on the dosage of the formula, weigh BIBP as the first group; weigh vinyl-acrylate nanofibers, stearic acid, and maleic anhydride grafted EVA compatibilizer as the second group; weigh the remaining materials as the third group.

[0190] The mixing and granulation processes are consistent with MD processes ② and ③.

[0191] IP Injection Preform: Pour the prepared granules into the injection molding foam molding machine. Adjust the temperatures of the first, second, third, and fourth feeding zones to 105, 110, 115, and 120℃ respectively. Adjust the temperatures of the upper and lower mold plates to 175±5℃ and 175±5℃ respectively. The injection time is 200±20 seconds, and the vulcanization time is 500±30 seconds. Then, remove the shoe sole preform.

[0192] Supercritical foaming under pressure: Place the small rough blank into a supercritical physical foaming tank under pressure, N2 pressure 18~35MPa, foaming temperature 115~150℃, heat preservation and pressure holding time 1.5~2.5h, then depressurize, and take out the foamed shoe sole and cool it to room temperature.

[0193] Compression molding: After the supercritical foamed semi-finished product has been allowed to stand and cool for 24 hours, it is placed into a flat molding die to complete the molding of the finished product; the hot pressing temperature is 165±5℃; the hot pressing time is 500±30 seconds; the cooling water temperature is 25℃ and the cooling time is 500±30 seconds.

[0194] The present invention provides the application of vinyl-acrylate nanofibers in the preparation of foamed shoe sole materials, a dynamically fatigue-resistant foamed shoe sole material with low thickness change rate, and its preparation method. On one hand, the present invention constructs a modified thermoplastic polyurethane elastomer with a strong polar rigid cross-linked network structure: by melt blending aliphatic polyether-type TPU with carboxyl-containing acrylate vinyl rubber under the action of a grafting agent (such as maleic anhydride) and an initiator (such as azobisisobutyronitrile), a rigid cross-linked network copolymer with strong polarity and structural stability is formed. This structure, acting as a "skeleton support," significantly improves the rigidity and compressive strength of the foam cells, effectively suppresses the thickness change of the foamed shoe sole under dynamic fatigue, and improves the overall mechanical properties and durability of the material. Secondly, vinyl-acrylate nanofibers are introduced to enhance the stability of the foam cell walls. Due to their high specific surface area and polar functional groups, they can be uniformly distributed in the interface region of the foam cell walls, forming a stable three-dimensional network structure with the TPU, EVA, and other matrices through hydrogen bonds and covalent bonds. This design significantly enhances the mechanical strength of the cell walls, maintains cell stability during foaming, prevents collapse and deformation, thereby reducing the thickness change rate and improving resilience. Finally, maleic anhydride-grafted EVA is selected as a compatibilizer to construct an efficient interfacial compatibility system to optimize multiphase blending uniformity and foaming quality. Utilizing its amphiphilic properties (one end attracted to a weakly polar phase (EVA), the other end attracted to a polar phase (TPU, etc.),) "molecular bridges" are formed between the multi-component interfaces, enhancing interfacial adhesion, reducing interfacial tension, promoting uniform dispersion of components, and preventing phase separation. This technology improves foaming uniformity and cell structure stability, enhancing the material's resilience, wear resistance, and overall uniformity.

[0195] This invention achieves a performance breakthrough: Existing technologies suffer from high dynamic fatigue thickness variation rates, decreased resilience, and a tendency to collapse in lightweight, soft, and elastic foam sole materials under high-intensity sports conditions. The dynamic fatigue-resistant foam sole material with low thickness variation rate provided by this invention successfully achieves the following four key indicators simultaneously: hardness of 42±3 C, and density of 0.12±0.02 g / cm³. 3 With a rebound rate of ≥65%, a thickness change rate of ≤10%, and changes in rebound rate / energy return rate / shock absorption G-value before and after fatigue of <9%, it achieves synergistic optimization of "lightweight, soft, elastic + dynamic fatigue resistance", breaking through industry bottlenecks and meeting the dual needs of high-end sports shoes for comfort and durability.

[0196] This invention also employs innovative performance characterization and testing: to better reflect real-world wearing scenarios, a dynamic impact test is introduced for the first time to evaluate the fatigue resistance of materials. This simulates the actual pressure conditions of the foot on the sole during jogging, repeatedly compressing the material at a set frequency and load to realistically replicate the usage scenario. By monitoring the change rate of thickness and key performance parameters before and after fatigue, the dynamic durability of the material is comprehensively evaluated. Compared to existing technologies that use the static compression deformation test standard in GB / T 38018-2019 to evaluate the fatigue resistance of sole materials (compression deformation rate at 50℃, 50% compression ratio, and 6 hours of static compression), this invention uses a dynamic impact test (GB / T38018-2019) to assess its fatigue resistance. This applies pressure values ​​close to those of the foot during jogging to the sole material at a certain rate, simulating the repeated compression process of the foot on the material during actual wear. After a certain number of fatigue compression cycles, the fatigue resistance of the sole material is evaluated using indicators such as the change rate of thickness and the change rate of performance. Typically, the pressure is set at 1200±120N, and the material is continuously compressed 50,000 to 100,000 times at a rate of 120±12 times / min. The thickness change rate ΔH of the foamed shoe sole is then measured (ΔH=(d1-d0) / d0*100%, where d1 is the thickness of the sample after fatigue in millimeters, and d0 is the thickness of the sample after fatigue in millimeters).

[0197] Test results show that the material of this invention exhibits minimal performance fluctuations after undergoing dynamic impact, verifying the feasibility and advancement of its technical solution and demonstrating significant prospects for industrial application and market competitiveness.

[0198] To further illustrate the present invention, the following examples describe in detail the application of the vinyl-acrylate nanofibers provided by the present invention in the preparation of foamed shoe sole materials, a foamed shoe sole material and its preparation method. However, it should be understood that these examples are implemented under the premise of the technical solution of the present invention, and provide detailed implementation methods and specific operating procedures. They are only for further illustrating the features and advantages of the present invention, and are not intended to limit the scope of the claims of the present invention. The scope of protection of the present invention is not limited to the following examples.

[0199] Modified Examples 1-8

[0200] See Table 1, which contains the formulation and performance data of the modified thermoplastic polyurethane elastomer provided by this invention.

[0201] Table 1

[0202]

[0203] in:

[0204] Elastollan C 85 A: Density 1.19 g / cm³3 Hardness 87A, tensile strength 50MPa, tear strength 70KN / m, elongation at break 650%, melting point 135℃, BASF.

[0205] ACM 2012: Mooney viscosity 50±5 (ML1+4@100℃), Dewey Rubber Technology Co., Ltd.

[0206] Maleic anhydride: density 1.48 g / cm³ 3 Melting point 51-56℃, Shandong Longhui Chemical Co., Ltd.

[0207] Azobisisobutyronitrile: density 1.11 g / cm³ 3 Melting point: 102-104℃, Zibo Defeng Chemical Co., Ltd.

[0208] Stearic acid 1801: density 0.84 g / cm³ 3 Melting point 67-72℃, from Dukuda Company, Indonesia.

[0209] Preparation process of modified thermoplastic polyurethane elastomer:

[0210] A mixture of Elastollan C 85 A, ACM 2012, maleic anhydride, azobisisobutyronitrile and stearic acid 1801 was melted by a twin-screw extruder at a temperature controlled at 170±3℃ to form a highly polar, rigid cross-linked network structure copolymer, namely a modified thermoplastic polyurethane elastomer.

[0211] Modification conclusion:

[0212] (1) The performance data of modified materials 1-5 show that: keeping the amount of grafting agent / initiator / lubricant added unchanged, adjusting the amount of TPU-Elastollan C 85A added to 65-85 parts and the amount of carboxyl acrylate vinyl rubber ACM 2012 added to 15-35 parts, as the amount of ACM 2012 added gradually increases, the density, hardness, tensile strength and tear strength of the modified polyurethane material show a trend of first increasing and then decreasing. This indicates that the carboxyl group of ACM 2012 undergoes grafting and chain growth and chain branching reactions with the TPU chain segments. The generated chain extended / branched macromolecules can significantly increase the number of entanglement points between the TPU melt macromolecular chains and chain segments, which significantly improves the mechanical properties of TPU and helps to increase its skeleton stiffness. Adding 15 parts of ACM 2012 has little effect on improving hardness, tensile strength and tear strength. When the addition exceeds 30 parts, the hardness, tensile strength and tear strength decrease. Therefore, the preferred addition amount is 70-80 parts of TPU-Elastollan C 85A and 20-30 parts of ACM 2012.

[0213] (2) From the performance data of modified materials 3, 6, 7 and 8, it can be seen that: keeping the amount of TPU and carboxyl-containing acrylate vinyl rubber added unchanged, the greater the amount of maleic anhydride grafting agent added, the density, hardness, tensile strength and tear strength of the modified TPU polyurethane material gradually increase. When the amount of addition reaches 2 parts, the improvement effect slows down. Therefore, the preferred amount of maleic anhydride grafting agent added is 0.5-2 parts.

[0214] Examples and Comparative Examples

[0215] MD chemical foaming process

[0216] ① Weighing materials: Based on the dosage of the formula, weigh the first group of crosslinking agent, foaming agent, and zinc oxide; weigh the second group of vinyl-acrylate nanofiber, stearic acid, and maleic anhydride grafted EVA compatibilizer; weigh the remaining materials as the third group.

[0217] ② Mixing: First, pour the third batch of material into the internal mixer and turn on the machine. Wait until the temperature rises to 105℃; then pour in the second batch of material; when the temperature rises to 115℃, pour in the first batch of material; when the temperature rises to 125℃, pour out the mixed material.

[0218] ③ Granulation: Pour the mixed material into the granulator. Set the temperatures of the first, second, third, and fourth zones to 105, 110, 115, and 120℃ respectively. Set the screw speed to 70 rpm and the cutting speed to 30 rpm.

[0219] ④ Small foaming: Pour the prepared granules into a flat mold for small foaming to complete the first foaming. The foaming temperature is 175℃ and the foaming time is 530 seconds.

[0220] ⑤ Molding: After the small foamed semi-finished product has been left to stand and cool for 24 hours, press the small foamed semi-finished product into a flat molding die to complete the molding of the finished product; the hot pressing temperature is 175±5℃; the hot pressing time is 430 seconds; the cooling water temperature is 25℃ and the cooling time is 430 seconds.

[0221] See Table 2, which details the raw materials and specific formulas in the embodiments of the present invention.

[0222] Table 2

[0223]

[0224] See Table 3, which details the raw materials and specific formulations in the comparative examples of this invention.

[0225] Table 3

[0226]

[0227] in:

[0228] EVA UE659: VA molar content is 25%, hardness is 84A, melting point is 77℃, melt index is 2.0g / 10min, tensile strength is 21.2MPa, elongation at break is 890%, crystallinity is 20-25%, Formosa Plastics Corporation.

[0229] POE LC161: Hardness 67A, melting point 57℃, melt index 0.5g / 10min, tensile strength 7.3MPa, elongation at break 800%, crystallinity 19%, LG Chem.

[0230] OBC 9107: Hardness 60A, melting point 121℃, melt index 1.0g / 10min, tensile strength 27MPa, elongation at break 1550%, crystallinity 10-12%, DuPont.

[0231] EPDM 5565: Mooney viscosity 65 ML 1+4 / 25℃, ENB content 7.5%, crystallinity <1%, Dow Chemical Company.

[0232] C250: Grafting rate >1.0%, hardness 84A, melt index 1.5g / 10min, melting point 48℃, tensile strength 11.4MPa, DuPont.

[0233] PORE5145: Fiber diameter 50~100 nm, tensile strength 100~200 MPa, Shandong Meideye Co., Ltd.

[0234] BIBP 14S-FL: White granules, AkzoNobel.

[0235] AC JTR-M: Yellow powder, decomposition temperature 150±3℃, gas evolution 170±5ml / g, Fujian Jinlang New Material Technology Co., Ltd.

[0236] ZnO 997: White powder, Shipai zinc oxide, with a relative density of 4.42~4.45.

[0237] The performance of the foamed materials prepared in the embodiments and comparative examples of the present invention was tested.

[0238] Refer to Table 4, which shows the mechanical property data of the foamed materials prepared in the embodiments of the present invention.

[0239] Table 4

[0240]

[0241] Note: After fatigue testing, the foamed sample was first subjected to 100,000 impacts with a force of 1.3KN according to GB / T 38018-2019 standard, and then tested according to GB / T 38012-2019.

[0242] See Table 5, which shows the mechanical properties of the foamed materials prepared in the comparative example of this invention.

[0243] Table 5

[0244]

[0245] in conclusion:

[0246] 1) Test data from Examples 1-3 show that, with the addition of 20 parts of modified material (2 / 3 / 4) and other components remaining unchanged, the density of the prepared foamed shoe sole is approximately 0.13 g / cm³. 3 The material exhibits a hardness of approximately 41-43 C, a springback rate of 68-70%, and a thickness variation rate between 6.1% and 7.4%. The springback rate, energy return rate, and damping G-value show minimal differences before and after fatigue, indicating that the material possesses excellent dynamic fatigue resistance.

[0247] 2) Data from Examples 2, 4, and 5 and Comparative Examples 4 and 5 show that as the amount of modified material 3 added increases from 5 parts to 35 parts, the rebound rate, energy return rate, and shock absorption G-value of the foamed shoe sole before fatigue all show an upward trend, while the thickness change rate gradually decreases. When the amount added is 5 parts, the performance improvement effect is limited; however, when the amount added reaches 35 parts, the rebound performance actually decreases, and the thickness change rate increases. Therefore, the optimal addition range of modified material 3 is 10-30 parts.

[0248] 3) Based on the experimental results of Examples 2, 6, and 7: Under the premise of keeping the polymer matrix dosage constant, gradually increasing the addition of compatibilizer C250 and vinyl-acrylate nanofiber PORE5145 significantly improved the rebound performance, energy return rate, and shock absorption G-value of the foamed shoe sole before fatigue. Comparative Example 6, without the addition of compatibilizer C250, resulted in poor compatibility between the nanofibers and matrices such as TPU and EVA, leading to uneven cell structure and reduced density, ultimately causing a decline in various performance indicators and an increased thickness change rate. Comparative Example 7, without the addition of nanofiber PORE5145, lacked stable support for the cell structure, making it prone to collapse and deformation, similarly leading to performance degradation and an increased thickness change rate. Furthermore, the significant performance differences between Comparative Examples 6 and 7 before and after fatigue indicate poor dynamic fatigue resistance.

[0249] 4) Comparing the data of Example 2 with Comparative Examples 1-3 revealed that if aliphatic polyester TPU and carboxyl-containing acrylate vinyl rubber are used directly in the foaming system without graft modification, an effective "skeleton support" structure cannot be formed. The cell rigidity and compressive strength are insufficient, resulting in a high rate of change in sole thickness. Furthermore, the rebound rate, energy return rate, and shock absorption G-value fluctuate significantly before and after fatigue, indicating poor dynamic fatigue resistance. Comparative Example 3, without the addition of modifier 3, exhibited the largest rate of thickness change and the worst fatigue resistance. The study shows that by melt-blending and grafting aliphatic polyether TPU with carboxyl-containing acrylate vinyl rubber under the action of maleic anhydride grafting agents and initiators such as azobisisobutyronitrile, a rigid cross-linked network copolymer with strong polarity and high structural stability can be formed. This modified product, acting as a "skeleton support," significantly enhances the rigidity and compressive strength of the cell structure, effectively suppressing thickness changes during dynamic fatigue. While ensuring the sole is lightweight, soft, and highly elastic, it greatly improves its dynamic fatigue resistance.

[0250] The application of vinyl-acrylate nanofibers provided by this invention in the preparation of foamed shoe sole materials, a dynamic fatigue-resistant foamed shoe sole material with low thickness change rate, and its preparation method have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this invention. The above descriptions of the embodiments are only for the purpose of helping to understand the method and core ideas of this invention, including the best mode, and also to enable any person skilled in the art to practice this invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those skilled in the art, several improvements and modifications can be made to this invention without departing from the principles of this invention, and these improvements and modifications also fall within the protection scope of the claims of this invention. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements that are not different from the textual description of the claims, or if they include equivalent structural elements that are not substantially different from the textual description of the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. Application of vinyl-acrylate nanofibers and maleic anhydride-grafted EVA compatibilizer in the preparation of foamed shoe sole materials; The applications include reducing the rate of thickness change of foamed shoe soles during use.

2. The application according to claim 1, characterized in that, The foamed sole material includes EVA-based foamed sole material; The diameter of the vinyl-acrylate nanofibers is 50~100 nm; The amount of the vinyl-acrylate nanofiber used in the preparation of foamed shoe sole material is 3 to 7 parts by weight.

3. The application according to claim 1, characterized in that, The amount of the maleic anhydride-grafted EVA compatibilizer used in the preparation of foamed shoe sole material is 2-5 parts by weight. The raw materials for preparing the foamed shoe sole material also include a matrix material; The matrix material is EVA, polyolefin elastomer, and modified thermoplastic polyurethane elastomer; The applications also include one or more of the following: forming a three-dimensional polymer support network structure in foamed shoe soles, enhancing cell stability, and enhancing cell uniformity.

4. A foamed shoe sole material, characterized in that, Based on the weight parts of the raw materials, it includes: 40-60 parts by weight of EVA, 20-40 parts by weight of polyolefin elastomer, 10-30 parts by weight of modified thermoplastic polyurethane elastomer, 3-7 parts by weight of vinyl-acrylate nanofibers, 2-5 parts by weight of maleic anhydride-grafted EVA compatibilizer, 0.4-0.8 parts by weight of peroxide crosslinking agent, 0-4 parts by weight of AC foaming agent, 0-1.5 parts by weight of zinc oxide, and 1-1.5 parts by weight of stearic acid.

5. The foamed shoe sole material according to claim 4, characterized in that, The VA content in the EVA is 15%~40% by mass; The polyolefin elastomer includes one or more of the following: ethylene-octene random polymer (POE), ethylene-octene block polymer (OBC), and ethylene-propylene-conjugated diene (EPDM). The modified thermoplastic polyurethane elastomer includes a carboxyl-containing acrylate vinyl rubber modified thermoplastic polyurethane elastomer. The modified thermoplastic polyurethane elastomer includes one or more of aliphatic polyester TPU, aliphatic polyether TPU, aromatic polyester TPU, aromatic polyether TPU, polycaprolactone-type polyester TPU, and polycarbonate-type polyester TPU. The maleic anhydride-grafted EVA compatibilizer includes a maleic anhydride-grafted EVA compatibilizer with a grafting rate ≥1.0%. The peroxide crosslinking agent includes dicumyl peroxide and / or 1,4-di-tert-butylperoxide; The AC foaming agent includes one or more of azodicarbonamide, sodium bicarbonate, expanded microspheres, 4,4-oxodibenzenesulfonyl hydrazine, supercritical nitrogen, and supercritical carbon dioxide.

6. The foamed shoe sole material according to claim 4, characterized in that, The modified thermoplastic polyurethane elastomer, by weight of raw materials, comprises: 70-80 parts by weight of thermoplastic polyurethane elastomer, 20-30 parts by weight of highly polar carboxyl-containing acrylate vinyl rubber, 0.5-2 parts by weight of grafting agent, 0.5-1 parts by weight of initiator, and 0.3-1 parts by weight of lubricant. The highly polar carboxyl-containing acrylate vinyl rubbers include ACM 2012; The grafting agent includes one or more of maleic anhydride, acrylic acid, and methacrylic acid. The initiator includes one or more of azobisisobutyronitrile, benzoyl peroxide, and ethane peroxide; The lubricant includes stearic acid and / or zinc stearate; The thermoplastic polyurethane elastomer and carboxyl-containing acrylate vinyl rubber form a rigid cross-linked network blend with strong polarity and stable structure after being heated and melted.

7. A method for preparing a foamed shoe sole material, characterized in that, Includes the following steps: 1) Peroxide crosslinking agent, AC foaming agent and zinc oxide are used as the first group of raw materials; Vinyl-acrylate nanofibers, stearic acid, and maleic anhydride grafted EVA compatibilizer were used as the second group of raw materials; the remaining raw materials were used as the third group of raw materials. The third group of raw materials is added into the internal mixer and heated and mixed until the first temperature is reached. Then the second group of raw materials is added and heated and mixed until the second temperature is reached. Then the first group of raw materials is added and heated and mixed until the third temperature is reached, resulting in a mixture. The mixture is then granulated to obtain granules. 2) The granules obtained in the above steps are foamed to obtain a semi-finished product, and then molded to obtain foamed shoe sole material; or, the granules obtained in the above steps are injection foamed to obtain foamed material, and then baked to obtain foamed shoe sole material. or, 1) Use peroxide crosslinking agent as the first group of raw materials; Vinyl acrylate nanofibers, stearic acid, and maleic anhydride grafted EVA compatibilizer were used as the second group of raw materials; the remaining raw materials were used as the third group of raw materials; the raw materials did not contain AC foaming agent or zinc oxide; The third group of raw materials is added into the internal mixer and heated and mixed until the first temperature is reached. Then the second group of raw materials is added and heated and mixed until the second temperature is reached. Then the first group of raw materials is added and heated and mixed until the third temperature is reached, resulting in a mixture. The mixture is then granulated to obtain granules. 2) After the granules obtained in the above steps are injection molded by IP, a small rough blank is obtained. The small rough blank is then subjected to supercritical foaming and cooled to obtain a semi-finished product. Finally, after finished product molding, foamed shoe sole material is obtained.

8. The preparation method according to claim 7, characterized in that, The first temperature is 100~110℃; The second temperature is 110~120℃; The third temperature is 120~125℃; The granulation temperature is 100~130℃; The temperature of the small foam is 170~180℃; The time for the small foaming is 500-560 seconds; The molding temperature is 170~180℃; The molding time is 400-460 seconds.

9. The preparation method according to claim 7, characterized in that, The feeding temperature for injection foaming is 105~120℃; The temperature of the molding die for injection foaming is 170~180℃; The injection time for the injection foaming process is 180-220 seconds; The vulcanization and foaming time for injection molding is 570-630 seconds; The baking temperature is 80~100℃; The oven speed for baking is 50-60 revolutions per minute; The baking time is 30 to 40 minutes.

10. The preparation method according to claim 7, characterized in that, The molding temperature for the IP injection molding is 170~180℃; The injection time for the IP injection molding is 180~220 seconds; The vulcanization time for the IP injection molding is 470~530 seconds; The pressure of the supercritical foaming is 18~35MPa; The supercritical foaming temperature is 115~150℃; The heat preservation and pressure holding time for the supercritical foaming is 1.5~2.5h; The heating temperature for molding the finished product is 160~170℃; The heating time for molding the finished product is 470~530 seconds; The cooling temperature for the molded finished product is 20~25℃; The cooling time for the molded finished product is 470-530 seconds.

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