A high-resilience supercritical foamed midsole material and its preparation method

Abstract

This invention provides a high-resilience supercritical foamed midsole material and its preparation method, relating to the field of supercritical foamed material technology. Using TPU or TPEE as a matrix, reactive chain extension / mild branching is employed to improve melt strength and supercritical fluid solubility, thereby enhancing foaming performance. Preferably, a dual nucleation system is constructed by compounding inorganic nucleating agents and inducing crystallization components, further increasing cell density and suppressing foaming, thus improving the performance of the foamed material. The polymer particles of this invention are injection molded or extruded, then cold-molded for shaping, and finally supercritically foamed.

Description

Technical Field

[0001] This invention belongs to the field of supercritical foaming technology and relates to a high-resilience supercritical foamed midsole material and its preparation method. Background Technology

[0002] Supercritical foaming materials, such as supercritical TPU and supercritical TPEE, have been widely used in various applications, including footwear, cushioning, and medical devices. The melt strength of polymer materials (such as TPU and TPEE) is a key factor determining the performance of supercritical foaming, directly affecting the entire process of cell nucleation, expansion, and stabilization, and ultimately determining the foaming ratio, cell morphology uniformity, mechanical properties, resilience, and other core indicators of the foamed material.

[0003] Therefore, improving the melt strength of polymer materials is of great significance for supercritical foaming. Increasing the molecular weight of polymer materials is an effective way to improve their melt strength. One method is to increase the molecular weight of the polymer material during preparation, and another method is to use chain extenders to perform post-chain extension on the polymer material. Chinese Patent CN119875353A discloses a modified polyurethane elastomer comprising thermoplastic polyurethane elastomer, polyisocyanate-based chain extender, and antioxidant components. The polyisocyanate-based chain extender is used to extend the chain of the thermoplastic polyurethane elastomer and improve its melt strength. Chinese Patent CN120904665A discloses a high melt strength thermoplastic polyurethane elastomer, which incorporates a melt reinforcing composition, namely a composition of hyperbranched polyester, bisphenol F diglycidyl ether, and octadecyl phosphate.

[0004] However, the applicant believes that existing methods for improving the melt strength of supercritical foamed polymer materials need further optimization. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a high-resilience supercritical foamed midsole material and its preparation method.

[0006] The technical solution of the present invention is as follows:

[0007] A high-resilience supercritical foamed midsole material is obtained by supercritical foaming of a polymer composition;

[0008] The polymer composition comprises extended TPU and / or extended TPEE;

[0009] The extended TPU and / or extended TPEE are obtained by extending the chain of TPU and / or TPEE using a reinforcing chain extender.

[0010] The chain extender includes an NCO-terminated chain extender;

[0011] The terminal NCO chain extender contains not less than two NCO groups and is obtained by reacting a terminal hydroxyl compound of formula (1) with a diisocyanate monomer.

[0012] (1)

[0013] Wherein, R1 is selected from C1-C6 alkylene, R2 is selected from H or C1-C4 alkyl, and m=2-4.

[0014] Preferably, the weight ratio of the TPU and / or TPEE to the reinforcing chain extender is 100:0.1-1.

[0015] Preferably, the NCO-terminated chain extender accounts for no less than 50% of the weight of the reinforcing chain extender.

[0016] Preferably, the molar ratio of the terminal hydroxyl compound to the diisocyanate monomer is 1:2-5.

[0017] More preferably, the terminal hydroxyl compound is obtained by reacting an amine compound of formula (2) with a dialkyl oxalate ester of formula (3).

[0018] HOR1R2N(CH2) m NH2(2)

[0019] R3OCOCOOR3 (3)

[0020] R3 is selected from C1-C6 hydrocarbon groups.

[0021] More preferably, the diisocyanate monomer is selected from at least one of IPDI, HDI, HTDI, TMDI and HMDI.

[0022] More preferably, when R2 is selected from C1-C4 alkyl groups, the chain extender further comprises a triisocyanate monomer;

[0023] The triisocyanate monomer accounts for no more than 60% by weight in the reinforcing chain extender.

[0024] Preferably, the weight percentage of the chain-extended TPU and / or chain-extended TPEE in the polymer composition is not less than 95%;

[0025] The polymer composition further comprises an inorganic nucleating agent and a crystallization-inducing component;

[0026] The inorganic nucleating agent is selected from at least one of nano-silicates, nano-carbonates, nano-metal oxides, and nano-layered materials;

[0027] The induced crystallization component is selected from C8-C18 carboxylic acid metal salts.

[0028] More preferably, the weight ratio of the inorganic nucleating agent to the crystallizing component is 1:0.6-2;

[0029] The combined weight percentage of the inorganic nucleating agent and the induced crystallization component in the polymer composition is 1-3%.

[0030] A method for preparing a high-resilience supercritical foamed midsole material as described in any of the above embodiments, comprising the following steps:

[0031] The polymer composition is obtained by injection molding or extrusion, followed by cold molding to form a preform material;

[0032] The preformed material is subjected to supercritical foaming to obtain the high-resilience supercritical foamed midsole material.

[0033] The beneficial effects of this invention are as follows: This invention uses a reinforcing chain extender to directly extend the chain of TPU and / or TPEE, thereby increasing the molecular weight and / or branching degree of TPU and / or TPEE, and obtaining extended TPU and / or extended TPEE with high melt strength. The reinforcing chain extender of this invention contains multiple groups that can form hydrogen bonds, including urea bonds, amino groups, and oxalamide groups, which can further improve melt strength and also increase the solubility of supercritical fluids, thereby improving the foaming performance of the polymer composition and the resilience, mechanical strength, and other properties of the supercritical foam material. Detailed Implementation

[0034] The technical solution of the present invention will be further explained and described below through specific embodiments.

[0035] On the one hand, the present invention proposes a high-resilience supercritical foamed midsole material, which is obtained by supercritical foaming of a polymer composition;

[0036] The polymer composition comprises chain-extended TPU and / or chain-extended TPEE;

[0037] Chain-extended TPU and / or chain-extended TPEE are obtained by chain extension of TPU and / or TPEE using a reinforcing chain extender;

[0038] Chain extenders include terminal NCO chain extenders;

[0039] The terminal NCO chain extender contains not less than two NCO groups and is obtained by reacting a terminal hydroxyl compound as shown in formula (1) with a diisocyanate monomer.

[0040] (1)

[0041] Wherein, R1 is selected from C1-C6 alkylene, R2 is selected from H or C1-C4 alkyl, and m=2-4.

[0042] This invention employs a chain extender to extend the chain of TPU and / or TPEE. The terminal NCO chain extender contains multiple NCO groups, which can react with the terminal hydroxyl and amino groups of TPU and / or TPEE, thereby extending the chain and increasing the molecular weight of TPU and / or TPEE to obtain chain-extended TPU and / or chain-extended TPEE with high melt strength.

[0043] There are no particular restrictions on the reaction conditions for the chain extender to extend the chain in TPU and / or TPEE, and the reaction can be carried out in a twin-screw extruder. For example, in the TPU melt extrusion process, the TPU and the chain extender react in the melt section (the melt section temperature can be 165-190℃) to extend the chain. To improve the stability of TPU at high temperatures, an appropriate amount of antioxidant, such as antioxidant 1010, can be added to the TPU, and the amount added can be 0.1% of the weight of the TPU. In this invention, both TPU and TPEE can be obtained directly from the market.

[0044] The NCO-terminated chain extender is obtained by reacting the terminal hydroxyl compound shown in formula (1) with a diisocyanate monomer. The molecular structure of the NCO-terminated chain extender contains multiple amino, urea, and oxalamide groups that can form hydrogen bonds. It can also improve the solubility of supercritical fluids (such as supercritical CO2 and supercritical N2), thereby improving the foaming performance of the polymer composition, resulting in a higher foaming ratio and greater cell density. The obtained supercritical foamed material has better properties, such as better resilience and mechanical strength. In addition, the molecular size of the NCO-terminated chain extender is more suitable. The NCO-terminated chain extender has high reactivity, but avoids side reactions such as self-polymerization and reaction with water vapor that may occur at high temperatures due to excessive reactivity.

[0045] Therefore, the present invention employs a reinforcing chain extender, which improves both the melt strength of the polymer composition and the solubility in supercritical fluids, thereby improving foaming performance and obtaining supercritical foamed materials with better performance, such as supercritical foamed midsole materials, which have better resilience and higher mechanical strength.

[0046] In some embodiments, the weight ratio of TPU and / or TPEE to the reinforcing chain extender is 100:0.1-1. For example, the weight ratio of TPU and / or TPEE to the reinforcing chain extender can be any value or any value between 100:0.1, 100:0.2, 100:0.3, 100:0.4, 100:0.5, 100:0.6, 100:0.7, 100:0.8, 100:0.9, 100:1, etc., without particular limitation. Further, the weight ratio of TPU and / or TPEE to the reinforcing chain extender can be 100:0.3-1. A sufficient amount of reinforcing chain extender is more beneficial for the chain-extending effect on TPU and / or TPEE, but if too much reinforcing chain extender is used, side reactions such as self-polymerization may occur during the chain extension process due to high temperature, moisture, etc.

[0047] In some embodiments, the weight percentage of the terminal NCO chain extender in the reinforcing chain extender is not less than 50%. If the weight percentage of the terminal NCO chain extender in the reinforcing chain extender is too low, the function of the terminal NCO chain extender cannot be effectively utilized. For example, the weight percentage of the terminal NCO chain extender in the reinforcing chain extender can be any value or any value between 50%, 60%, 70%, 80%, 90%, 90%, 100%, etc., without any particular limitation.

[0048] In some embodiments, the molar ratio of the terminal hydroxyl compound to the diisocyanate monomer is 1:2-5. For example, the molar ratio of the terminal hydroxyl compound to the diisocyanate monomer can be any value or any value between 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, etc., without particular limitation. If too much diisocyanate monomer is used, the reaction efficiency will not be improved, but it will lead to waste of raw materials, more complicated post-processing, and side reactions.

[0049] In some embodiments, the terminal hydroxyl compound is obtained by reacting an amine compound of formula (2) with a dialkyl oxalate ester of formula (3).

[0050] HOR1R2N(CH2) m NH2(2)

[0051] R3OCOCOOR3 (3)

[0052] R3 is selected from C1-C6 hydrocarbon groups.

[0053] The amine compound shown in formula (2) can be N-(2-hydroxyethyl)ethylenediamine, N-methyl-N-(2-hydroxyethyl)-1,3-propanediamine, N-(2-hydroxyethyl)-1,3-propanediamine, etc. Specifically, the terminal hydroxyl compound can be prepared by referring to the method of existing technology CN115785369A, for example, by reacting N-methyl-N-(2-hydroxyethyl)-1,3-propanediamine with diethyl oxalate, or by reacting N-(2-hydroxyethyl)-1,3-propanediamine with diethyl oxalate.

[0054] In some embodiments, the diisocyanate monomer is selected from at least one of isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), hydrogenated toluene diisocyanate (HTDI), trimethylhexane diisocyanate (TMDI), and dicyclohexylmethane diisocyanate (HMDI). The above-mentioned diisocyanate monomers are aliphatic or alicyclic diisocyanate monomers, exhibiting good weather resistance and resistance to yellowing.

[0055] In some embodiments, when R2 is selected from C1-C4 alkyl groups, the chain extender further comprises a triisocyanate monomer;

[0056] The triisocyanate monomer shall not exceed 60% by weight in the reinforcing chain extender.

[0057] When R2 is selected from C1-C4 alkyl groups, the resulting terminal NCO chain extender contains two NCO groups. When extending the chain of TPU and / or TPEE, it primarily yields linear-chain extended TPU and / or extended TPEE. Introducing a triisocyanate monomer can increase the branching degree of the extended TPU and / or extended TPEE, further improving the melt strength of the polymer composition. The triisocyanate monomer contains three NCO groups and can be an HDI trimer, IPDI trimer, etc.

[0058] When R2 is H, the terminal hydroxyl compound contains more than two active hydrogens (H on OH and H on NH), and the molar ratio of the terminal hydroxyl compound to the diisocyanate monomer is greater than 1:2, such as 1:2.5-3, or the ratio of the NCO equivalent of the diisocyanate monomer to the active hydrogen equivalent of the terminal hydroxyl compound is not less than 1, such as 1:1, 1.2:1, 1.5:1, 2:1, etc. The diisocyanate monomer can also react with R2, so that the terminal NCO chain extender contains more than two NCO groups. The terminal NCO chain extender can both extend the chain of TPU and / or TPEE, and introduce branched structures, thereby improving the melt strength of the polymer composition.

[0059] In some embodiments, the weight percentage of chain-extended TPU and / or chain-extended TPEE in the polymer composition is not less than 95%;

[0060] The polymer composition also contains an inorganic nucleating agent and a crystallization-inducing component;

[0061] The inorganic nucleating agent is selected from at least one of nano-silicates, nano-carbonates, nano-metal oxides, and nano-layered materials;

[0062] The induced crystallization components are selected from C8-C18 carboxylic acid metal salts.

[0063] Inorganic nucleating agents can increase the number of nuclei in the cells, refine the cell size, improve cell density and uniformity, inhibit cell merging and collapse, and enhance the foaming effect. Crystallization-inducing components can further enhance the crystallinity of extended-chain TPU and / or extended-chain TPEE, improve melt strength, and enhance the performance of supercritical foam materials. In this invention, extended-chain TPU and / or extended-chain TPEE can form more hydrogen bonds and polar structures, which is more conducive to crystallization. The added inorganic nucleating agents and crystallization-inducing components can work synergistically to further optimize the foaming performance of the polymer composition and improve the resilience, mechanical strength, and other properties of supercritical foam materials.

[0064] The components that induce crystallization can be magnesium laurate, zinc stearate, calcium stearate, zinc laurate, etc.

[0065] In some embodiments, the weight ratio of the inorganic nucleating agent to the crystallizing induction component is 1:0.6-2; for example, the weight ratio of the inorganic nucleating agent to the crystallizing induction component can be any value or any value between 1:0.6, 1:0.8, 1:1, 1:1.2, 1:1.5, 1:1.8, 1:2, etc., without any particular limitation.

[0066] The total weight percentage of the inorganic nucleating agent and the crystallizing inducing component in the polymer composition is 1-3%. For example, the total weight percentage of the inorganic nucleating agent and the crystallizing inducing component in the polymer composition can be any value or any value between 1%, 1.5%, 2%, 2.5%, 3%, etc., without any particular limitation.

[0067] On the other hand, the present invention also proposes a method for preparing a high-resilience supercritical foamed midsole material as described in any of the above embodiments, the steps of which include:

[0068] The polymer composition is injection molded or extruded and then shaped by cold molding to obtain a preformed material;

[0069] Preformed materials are subjected to supercritical foaming to obtain high-resilience supercritical foamed midsole materials.

[0070] The present invention can directly form a mold for shoe material midsole by injection molding or extrusion of polymer composition, and then carry out supercritical foaming to form a supercritical foamed midsole material with high resilience.

[0071] The technical solution of the present invention will be further described and explained below with reference to various preparation examples and embodiments. Unless otherwise specified, the parts mentioned in the following preparation examples and embodiments are parts by weight.

[0072] Preparation Examples 1-3: Preparation of NCO-terminated chain extenders

[0073] Preparation Example 1

[0074] The terminal hydroxyl compound was obtained by reacting diethyl oxalate and N-methyl-N-(2-hydroxyethyl)-1,3-propanediamine according to the method described in CN115785369A.

[0075] The molar ratio of the terminal hydroxyl compound to HDI was 1:2. The terminal hydroxyl compound was dissolved in anhydrous THF to prepare a 20% solution. Under nitrogen protection, HDI was added to the reaction vessel, and the terminal hydroxyl compound solution was added dropwise. After the addition was complete, the mixture was stirred at room temperature for 1 hour, then heated to 60°C and reacted for 1 hour. Finally, THF was removed to obtain the NCO-terminated chain extender.

[0076] Preparation Example 2

[0077] 0.02 mol of diethyl oxalate and 25 g of anhydrous ethanol were added to a reaction flask, and 0.1 mol of N-(2-hydroxyethyl)-1,3-propanediamine was added dropwise. The mixture was stirred at room temperature for 24 hours to obtain a white precipitate. The white precipitate was washed twice with anhydrous ethanol and dried overnight in a vacuum oven at 40 °C to obtain the terminal hydroxyl compound.

[0078] The molar ratio of the terminal hydroxyl compound to HMDI was 1:4 (the equivalent ratio of active hydrogen to NCO was 1:2). The terminal hydroxyl compound was dissolved in anhydrous THF to prepare a 20% solution. Under nitrogen protection, HMDI was added to the reaction vessel, and the terminal hydroxyl compound solution was added dropwise. After the addition was complete, the mixture was stirred at room temperature for 1 hour, then heated to 60°C and reacted for 2 hours to obtain the terminal NCO chain extender.

[0079] Preparation Example 3

[0080] The difference between this preparation example and Preparation Example 2 is that in Preparation Example 2, N-(2-hydroxyethyl)-1,3-propanediamine was replaced with an equimolar amount of N-(2-hydroxyethyl)-ethylenediamine. The remaining steps remained unchanged.

[0081] Example 1

[0082] Commercially available TPU (hardness 85A) is dried in an oven at 110°C until the water content is less than 0.03%.

[0083] Under nitrogen protection, dried and dehydrated TPU and the terminal NCO chain extender of Preparation Example 1 were added to a twin-screw extruder at a weight ratio of 100:0.1, and melt extrusion was carried out at a melt temperature of 170-190°C to obtain chain-extended TPU.

[0084] Example 2

[0085] The difference between this embodiment and Embodiment 1 is that in Embodiment 1, the weight ratio of TPU to NCO-terminated chain extender was adjusted from 100:0.1 to 100:0.3. The remaining steps remain unchanged.

[0086] Example 3

[0087] The difference between this embodiment and Embodiment 1 is that in Embodiment 1, the weight ratio of TPU to NCO-terminated chain extender was adjusted from 100:0.1 to 100:1. The remaining steps remain unchanged.

[0088] Example 4

[0089] The difference between this embodiment and Embodiment 2 is that in Embodiment 2, the terminal NCO chain extender of Preparation Example 1 is replaced with an equal weight of the terminal NCO chain extender of Preparation Example 2. The remaining steps remain unchanged.

[0090] Example 5

[0091] The difference between this embodiment and Embodiment 2 is that in Embodiment 2, the terminal NCO chain extender in Preparation Example 1 is replaced with an equal weight combination of the terminal NCO chain extender from Preparation Example 1 and the terminal NCO chain extender from Preparation Example 2 in a weight ratio of 1:1. The remaining steps remain unchanged.

[0092] Example 6

[0093] The difference between this embodiment and Embodiment 2 is that in Embodiment 2, the terminal NCO chain extender in Preparation Example 1 is replaced with an equal weight of a combination of the terminal NCO chain extender from Preparation Example 1 and HDI trimer in a 1:1 weight ratio. The remaining steps remain unchanged.

[0094] Example 7

[0095] The difference between this embodiment and Embodiment 2 is that in Embodiment 2, 0.6 wt% nano-silica and 0.6 wt% zinc stearate were added to the commercially available TPU. The remaining steps remained unchanged.

[0096] Comparative Example 1

[0097] The difference between this comparative example and Example 2 is that in Example 2, the terminal NCO chain extender in Preparation Example 1 was replaced with an equal weight of HDI. The remaining steps remained unchanged.

[0098] Comparative Example 2

[0099] The difference between this comparative example and Example 2 is that in Example 2, the terminal NCO chain extender in Preparation Example 1 was replaced with an equal weight of HDI trimer. The remaining steps remained unchanged.

[0100] In Comparative Example 2, a significant degree of particulate cross-linking was observed during the experiment. This may be because the HDI trimer is too active and undergoes self-polymerization at high temperatures to form cross-linked particulate impurities.

[0101] Comparative Example 3

[0102] The difference between this comparative example and Example 1 is that in Example 1, the weight ratio of TPU to NCO-terminated chain extender was adjusted from 100:0.1 to 100:1.5. The remaining steps remained unchanged.

[0103] In Comparative Example 3, a significant particulate crosslinking was observed during the experiment. This may be due to an excessive amount of terminal NCO chain extender, which can cause self-polymerization at high temperatures and form crosslinked particulate impurities. Therefore, in this invention, the amount of reinforcing chain extender added should not be excessive, not exceeding 1% of the weight of TPU and / or TPEE.

[0104] Comparative Example 4

[0105] The difference between this comparative example and Example 2 is that in Example 2, the terminal NCO chain extender in Preparation Example 1 was replaced with an equal weight of 1,4-butanediol diglycidyl ether. The remaining steps remained unchanged.

[0106] Comparative Example 5

[0107] The commercially available TPU in Example 1.

[0108] Performance testing

[0109] Melt strength: Tested using a melt strength tester at 190°C. Using the melt strength of the commercially available TPU in Comparative Example 5 as a benchmark, the improvement rate of melt strength for the extended-chain TPUs of Examples 1-7, Comparative Example 1, and Comparative Example 4 was calculated. A greater improvement rate in melt strength indicates higher melt strength.

[0110] Supercritical CO2 solubility: The TPU to be tested was placed in CO2 at 60℃ and 10MPa for 24 hours, and the weight gain rate of the TPU was measured. Using the commercially available TPU of Comparative Example 5 as a benchmark, the increase in supercritical CO2 solubility of the chain-extended TPUs of Examples 1-7, Comparative Example 1, and Comparative Example 4 was calculated. The more supercritical CO2 dissolved, the better for foaming.

[0111] Examples 1-7, the extended-chain TPU of Comparative Examples 1 and 4, and the TPU of Comparative Example 5 were subjected to supercritical foaming according to the following process to obtain supercritical foamed TPU: supercritical CO2, foaming temperature 120℃, foaming pressure 18MPa, foaming time 2.5h, and depressurization pressure 5MPa / s. The performance of the supercritical foamed TPU was tested.

[0112] The results are shown in Table 1 below.

[0113] Table 1

[0114]

[0115] Therefore, as can be seen from the data results in Table 1, the present invention uses a reinforcing chain extender containing terminal NCO chain extender to extend the chain of TPU, which can significantly improve the melt strength and solubility of supercritical CO2 in TPU, and improve the foaming performance of supercritical foamed TPU, resulting in higher cell density, better resilience and tensile strength.

[0116] Example 8

[0117] Commercially available TPEE (hardness 40D) is dried in an oven at 110°C until the water content is less than 0.03%.

[0118] Under nitrogen protection, dried and dehydrated TPEE and the terminal NCO chain extender of Preparation Example 1 were added to a twin-screw extruder at a weight ratio of 100:0.7, and melt extrusion was carried out at a melt temperature of 220-250°C to obtain extended chain TPEE.

[0119] Example 9

[0120] The difference between this embodiment and Embodiment 8 is that in Embodiment 8, the terminal NCO chain extender of Preparation Example 1 is replaced with an equal weight combination of the terminal NCO chain extender of Preparation Example 1 and the terminal NCO chain extender of Preparation Example 3 in a weight ratio of 3:1. The remaining steps remain unchanged.

[0121] Example 10

[0122] The difference between this embodiment and Example 8 is that in Example 8, the terminal NCO chain extender of Preparation Example 1 is replaced with an equal weight of a combination of the terminal NCO chain extender of Preparation Example 1 and IPDI trimer in a weight ratio of 3:1. The remaining steps remain unchanged.

[0123] Comparative Example 6

[0124] Commercially available TPEE in Example 8.

[0125] Comparative Example 7

[0126] The difference between this comparative example and Example 8 is that in Example 8, the terminal NCO chain extender in Preparation Example 1 was replaced with an equal weight of IPDI. The remaining steps remained unchanged.

[0127] Melt strength: Tested using a melt strength tester at 250°C. Using the melt strength of commercially available TPEE from Comparative Example 6 as a benchmark, the improvement rate of melt strength for the extended-chain TPEEs of Examples 8-10 and Comparative Example 7 was calculated. A greater improvement rate indicates higher melt strength.

[0128] Supercritical N2 solubility: The TPEE to be tested was placed in N2 at 70°C and 12 MPa for 24 hours, and the weight gain of the TPEE was measured. Using the commercially available TPEE in Comparative Example 6 as a benchmark, the increase in supercritical N2 solubility of the chain-extended TPEEs in Examples 8-10 and Comparative Example 7 was calculated. The greater the increase in supercritical N2 solubility, the more supercritical N2 is dissolved, which is more beneficial for foaming.

[0129] The extended-chain TPEEs of Examples 8-10 and Comparative Example 7, as well as the TPEE of Comparative Example 6, were subjected to supercritical foaming according to the following process to obtain supercritical foamed TPEEs: supercritical N2, foaming temperature 210℃, foaming pressure 20MPa, foaming time 1.5h, and depressurization pressure 0.5MPa / s. The performance of the supercritical foamed TPEEs was tested.

[0130] The results are shown in Table 2 below.

[0131] Table 2

[0132]

[0133] Therefore, as can be seen from the data in Table 2, the present invention uses a reinforcing chain extender containing terminal NCO chain extender to extend the chain of TPEE, which can significantly improve the melt strength and solubility of TPEE in supercritical N2, and enhance the foaming performance of supercritical foamed TPEE, resulting in higher cell density, better resilience and tensile strength.

[0134] As described above, the basic principles, main features, and advantages of the present invention have been shown and described. Those skilled in the art should understand that the present invention is not limited to the above embodiments, which are merely preferred embodiments and should not be construed as limiting the scope of the invention. All equivalent changes and modifications made in accordance with the scope of the patent and the description should still fall within the scope of the present invention. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A high-resilience supercritical foamed midsole material, characterized in that, Obtained by supercritical foaming of a polymer composition; The polymer composition comprises extended TPU and / or extended TPEE; The extended TPU and / or extended TPEE are obtained by extending the chain of TPU and / or TPEE using a reinforcing chain extender. The chain extender includes an NCO-terminated chain extender; The weight percentage of the terminal NCO chain extender in the reinforcing chain extender is not less than 50%; The terminal NCO chain extender contains not less than two NCO groups and is obtained by reacting a terminal hydroxyl compound of formula (1) with a diisocyanate monomer. （1） Wherein, R1 is selected from C1-C6 alkylene, R2 is selected from H or C1-C4 alkyl, and m=2-4; The weight ratio of the TPU and / or TPEE to the reinforcing chain extender is 100:0.1-1.

2. The high-resilience supercritical foamed midsole material according to claim 1, characterized in that, The molar ratio of the terminal hydroxyl compound to the diisocyanate monomer is 1:2-5.

3. The high-resilience supercritical foamed midsole material according to claim 2, characterized in that, The terminal hydroxyl compound is obtained by reacting an amine compound of formula (2) with a dialkyl oxalate ester of formula (3). HOR1R2N(CH2) m NH2(2) R3OCOCOOR3 (3) R3 is selected from C1-C6 hydrocarbon groups.

4. The high-resilience supercritical foamed midsole material according to claim 2, characterized in that, The diisocyanate monomer is selected from at least one of IPDI, HDI, HTDI, TMDI and HMDI.

5. The high-resilience supercritical foamed midsole material according to claim 2, characterized in that, When R2 is selected from C1-C4 alkyl groups, the chain extender further comprises a triisocyanate monomer; The triisocyanate monomer accounts for no more than 60% by weight in the reinforcing chain extender.

6. The high-resilience supercritical foamed midsole material according to claim 1, characterized in that, The weight percentage of the extended TPU and / or extended TPEE in the polymer composition is not less than 95%; The polymer composition further comprises an inorganic nucleating agent and a crystallization-inducing component; The inorganic nucleating agent is selected from at least one of nano-silicates, nano-carbonates, and nano-metal oxides; The induced crystallization component is selected from C8-C18 carboxylic acid metal salts.

7. The high-resilience supercritical foamed midsole material according to claim 6, characterized in that, The weight ratio of the inorganic nucleating agent to the crystallizing induction component is 1:0.6-2; The combined weight percentage of the inorganic nucleating agent and the induced crystallization component in the polymer composition is 1-3%.

8. A method for preparing a high-resilience supercritical foamed midsole material as described in any one of claims 1-7, characterized in that the step... include: The polymer composition is obtained by injection molding or extrusion, followed by cold molding to form a preform material; The preformed material is subjected to supercritical foaming to obtain the high-resilience supercritical foamed midsole material.

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