TPU (Thermoplastic Polyurethane) composite foaming material with open pore structure and preparation method of TPU composite foaming material

Abstract

The invention relates to the field of open-cell foam materials, in particular to a TPU (thermoplastic polyurethane) composite foam material with an open-cell structure and a preparation method thereof, and the TPU composite foam material comprises the following components in parts by weight: 60-90 parts of TPU, 10-40 parts of EVA (ethylene-vinyl acetate) and 0.5-2.5 parts of a catalyst; the catalyst is a mixture of zinc diethyl dithiocarbamate and bismuth trioxide. Zinc diethyldithiocarbamate and bismuth trioxide are compounded into a catalyst to be added into a system, so that the compatibility between TPU and EVA can be improved through two aspects of physical coordination bridging and catalytic ester exchange, the EVA can be uniformly dispersed in a TPU matrix in a smaller particle form, and the EVA can be used as a pore opening agent, so that the compatibility between TPU and EVA can be improved. The aperture ratio of the TPU composite foaming material is improved, so that the TPU composite foaming material with excellent performance is prepared.

Description

Technical Field

[0001] This application relates to the field of open-cell foamed materials, and in particular to an open-cell TPU composite foamed material and its preparation method. Background Technology

[0002] Thermoplastic polyurethane (TPU) and ethylene-vinyl acetate copolymer (EVA) are two widely used polymers in the field of foam materials. TPU is favored for its excellent abrasion resistance, high elasticity, good mechanical strength, and oil resistance, while EVA has advantages due to its free flexibility, low processing temperature, and inherent foaming properties. Therefore, those skilled in the art often blend TPU and EVA to prepare foam materials.

[0003] However, in the actual blending process, due to the poor compatibility between TPU and EVA, the EVA phase is difficult to form a fine and uniform dispersion. Instead, it exists in the TPU matrix as relatively large particles or agglomerates, resulting in an unsatisfactory open-cell ratio of the TPU composite foam material. This limits its application in high-permeability materials, protective cushioning materials, and sound-absorbing materials.

[0004] To address these challenges, researchers are working to develop novel catalyst systems that can regulate the dispersion of EVA in a TPU matrix by catalyzing transesterification reactions, thereby improving the open-cell ratio of TPU composite foam materials. Summary of the Invention

[0005] To improve the compatibility between TPU and EVA and the open-cell ratio of TPU-EVA composite materials, this application provides an open-cell TPU composite foam material and its preparation method.

[0006] In the first aspect, this application provides a TPU composite foam material with an open-cell structure, which adopts the following technical solution: A TPU composite foam material with an open-cell structure, comprising the following components in parts by weight: 60-90 parts TPU, 10-40 parts EVA, and 0.5-2.5 parts catalyst; The catalyst is a mixture of zinc diethyldithiocarbamate and bismuth trioxide.

[0007] By adopting the above technical solution, during the foaming process of TPU composite foam material, the presence of EVA can act as a stress concentration point, causing the film to tear from around the EVA region, forming a connected open-cell network, increasing the open-cell rate of the TPU composite foam material, and reducing resilience. Furthermore, zinc diethyldithiocarbamate and bismuth trioxide are compounded into a catalyst. The zinc ions in zinc diethyldithiocarbamate and the bismuth ions in bismuth trioxide act as Lewis acids, forming coordination bonds with the carbonyl oxygen and amino nitrogen on the TPU chain and the ester carbonyl oxygen on the EVA chain. This brings the TPU and EVA molecular chains closer together, increases the molecular entanglement and interaction strength at the interface between the two phases, effectively reduces the interfacial tension, and allows the TPU and EVA phases to be more uniformly dispersed. Under conditions close to the melting temperature, zinc diethyldithiocarbamate and bismuth trioxide can catalyze the transesterification reaction between the carbamate groups of TPU and the ester groups of EVA to generate TPU-g-EVA graft copolymer, thereby effectively improving the compatibility of TPU and EVA, enabling EVA to be stably dispersed in the TPU continuous phase with smaller and more uniform particle size.

[0008] Furthermore, the sulfur atoms of zinc diethyldithiocarbamate possess strong coordinating ability, enabling them to coordinate with bismuth ions on the surface of bismuth trioxide, forming stable Bi-S covalent bonds and constructing an "inorganic-organic hybrid catalytic interface." The inorganic phase can activate carbonyl groups through electrostatic or coordination interactions, while the organic phase exhibits van der Waals forces or hydrophobic interactions with the organic molecular chains of TPU and EVA, specifically adsorbing the molecular chains of both substrates. This "dual adsorption" simultaneously immobilizes the ester groups of TPU and the vinyl acetate groups of EVA near the active sites on the catalytic interface, significantly shortening the spatial distance between the two molecular chains, greatly reducing the steric hindrance of the transesterification reaction, and accelerating the transesterification process. Simultaneously, the organic segments of zinc diethyldithiocarbamate create steric hindrance on the surface of bismuth trioxide, hindering the aggregation of bismuth trioxide particles, resulting in a more uniform distribution of active sites on the interface and improving catalytic efficiency.

[0009] Meanwhile, the presence of zinc diethyldithiocarbamate and bismuth trioxide can also inhibit the occurrence of side reactions. The presence of zinc diethyldithiocarbamate can not only delay the thermal degradation of TPU, but also neutralize the acetic acid produced by EVA deacetylation. Bismuth trioxide can also adsorb and partially neutralize the acetic acid produced by EVA deacetylation, effectively reducing the compression set of TPU composite foam materials.

[0010] This application improves the compatibility between TPU and EVA by adding zinc diethyldithiocarbamate and bismuth trioxide as a catalyst to the system through physical coordination bridging and catalytic transesterification. This allows EVA to be uniformly dispersed in the TPU matrix as smaller particles, and the presence of EVA can act as an opener to increase the open cell ratio of the TPU composite foam material, thereby preparing a high-performance TPU composite foam material.

[0011] Preferably, the molar ratio of zinc diethyldithiocarbamate to bismuth trioxide is 0.8-1.2:1.

[0012] By adopting the above technical solution, when the proportion of zinc diethyldithiocarbamate is too low, there is not enough zinc diethyldithiocarbamate to form Bi-S bonds with bismuth trioxide, resulting in insufficient area and discontinuity of the formed "inorganic-organic hybrid catalytic interface", reduced density of active sites, and easy agglomeration of bismuth trioxide particles, which reduces the opening rate of the pores.

[0013] When the proportion of zinc diethyldithiocarbamate is too high, the bismuth ion sites on the surface of bismuth trioxide are limited. Excess zinc diethyldithiocarbamate cannot be fully anchored on its surface through effective Bi-S bonds. Furthermore, the excessively thick organic layer of zinc diethyldithiocarbamate itself will form new and excessive steric hindrance, hindering the diffusion of substrate molecules and their contact with active sites deep in the interface, thus reducing catalytic efficiency and porosity.

[0014] Preferably, the bismuth trioxide has a particle size of 1-3 μm.

[0015] By adopting the above technical solution, when the particle size of bismuth trioxide is too small, the surface energy of small-sized bismuth trioxide particles is extremely high, and they are very easy to agglomerate due to intermolecular forces. The specific surface area is reduced, the effective catalytic sites are reduced, and the unagglomerated nanoparticles migrate too fast and are unevenly distributed in the melt, resulting in excessive breakage of local molecular chains, causing melt collapse and reducing the open cell ratio of TPU composite foam material.

[0016] When the particle size of bismuth trioxide is too large, the large-particle bismuth trioxide is difficult to disperse uniformly in the TPU-EVA matrix. It is easy to settle or float during the processing, resulting in uneven distribution of the catalyst in the system. It cannot effectively bring the molecular chains of the two phases closer together, resulting in poor effect of reducing interfacial tension. The EVA dispersed phase is easy to coarsen and aggregate, which leads to a decrease in the open cell ratio of the TPU composite foam material.

[0017] Preferably, 0.1-1 part of an antioxidant is also added, wherein the antioxidant is a mixture of distearate thiodipropionate and antioxidant 1135.

[0018] By adopting the above technical solution, the thioether bond in distearate can reduce peroxides and convert them into stable alcohols. By eliminating hydroperoxides, it prevents them from decomposing into highly reactive free radicals and cuts off the propagation chain of the oxidation reaction.

[0019] Antioxidant 1135 contains hindered phenols in its molecule. The phenolic hydroxyl groups in the hindered phenols can actively capture free radicals generated in the oxidation reaction. By providing hydrogen atoms to combine with the free radicals, it transforms itself into a stable phenol-oxygen free radical, thereby directly terminating the "chain growth" stage of the free radical chain reaction.

[0020] By combining distearate thiodipropionate and antioxidant 1135 to form an antioxidant, antioxidant 1135 blocks free radical propagation, and distearate thiodipropionate eliminates oxidation intermediates. This comprehensively inhibits the thermal oxidative degradation of materials from the two key stages of the oxidation reaction, namely "initiation" and "diffusion," maintaining the stability of melt strength. Furthermore, the phenolic free radicals generated by antioxidant 1135 can react with distearate thiodipropionate to regenerate phenolic hydroxyl groups, while distearate thiodipropionate is oxidized to stable products such as thioethers, effectively improving the utilization rate of antioxidant 1135.

[0021] Preferably, the mass ratio of the distearate thiodipropionate to antioxidant 1135 is 1:1-2.

[0022] By adopting the above technical solution, when the proportion of distearate thiodipropionate is too high, the antioxidant cannot efficiently capture the free radicals continuously generated during the processing and use of the open-cell foam material, leading to molecular chain breakage, resulting in decreased melt strength, weakened cell wall toughness, and large cell phenomenon in the foamed product, causing product defects. When the proportion of distearate thiodipropionate is too low, its ability to decompose hydrogen peroxide and regenerate auxiliary antioxidant 1135 is insufficient, leading to the accumulation of hydrogen peroxide and rapid consumption of antioxidant 1135, which intensifies the oxidative breakage of molecular chains and increases the resilience and compression set of the TPU composite foam material.

[0023] Preferably, the TPU is a polyester-type TPU.

[0024] By adopting the above technical solution, polyester-based TPU, with its strong polar groups, can interact strongly with the vinyl acetate groups in EVA, thereby improving their compatibility and promoting the uniform dispersion of EVA in the TPU matrix. Furthermore, polyester-based TPU exhibits good chemical stability and high strength during foaming, and can react more effectively with catalysts, further improving the open-cell structure and mechanical properties of the foamed material. Therefore, polyester-based TPU is preferred.

[0025] Secondly, this application provides a method for preparing a TPU composite foam material with an open-cell structure, using the following technical solution: A method for preparing a TPU composite foam material with an open-cell structure includes the following steps: S1. Mix the TPU, EVA and catalyst in the specified amounts to obtain the mixed product. S2. Compress the intensively mixed product into sheets to obtain sheets; S3. The sheet is subjected to high-pressure gas at 125-145℃, and the pressure of the high-pressure gas is 12-15MPa. S4. After the high-pressure gas in the sheet reaches saturation, the pressure is released to obtain a TPU composite foam material with an open-cell structure.

[0026] By adopting the above technical solution, TPU, EVA and catalyst are first fully fused through intensive mixing, so that the catalyst can promote the transesterification reaction between TPU and EVA, improve the compatibility of TPU and EVA, and promote the uniform dispersion of EVA in TPU with smaller particles. Then, a sheet with uniform thickness is obtained by pressing. Then, high-pressure gas is introduced, and the high-pressure gas is uniformly dissolved in the TPU-EVA mixture and reaches saturation. Then, when the pressure is released, the gas expands and breaks through the cell walls to form an interconnected network structure, thereby obtaining a TPU composite foam material with ideal open porosity.

[0027] Preferably, in S1, an appropriate amount of antioxidant is added to mix with TPU, EVA and catalyst to obtain a mixed product.

[0028] By adopting the above technical solution, since the mixing process is often accompanied by high temperature and high shear force, the ester / ether groups in the TPU molecular chain and the vinyl acetate groups in EVA are very prone to free radical chain oxidation reaction, resulting in molecular chain breakage or cross-linking. By adding antioxidants, the molecular weight stability of TPU-EVA can be maintained, and the melt strength can be prevented from decreasing or local cross-linking can be prevented from running out of control.

[0029] In summary, this application includes at least one of the following beneficial technical effects: 1. In this application, zinc diethyldithiocarbamate and bismuth trioxide are combined to form a catalyst and added to the system. This catalyst can improve the compatibility between TPU and EVA through physical coordination bridging and catalytic transesterification. This allows EVA to be uniformly dispersed in the TPU matrix as smaller particles. Furthermore, the presence of EVA can act as an open-cell agent to improve the open-cell ratio of the TPU composite foam material, thereby preparing a high-performance TPU composite foam material. 2. The bismuth trioxide used in this application has a particle size of 1-3 μm. When the particle size of bismuth trioxide is too small, the small-sized bismuth trioxide particles are prone to agglomeration due to intermolecular forces, reducing the effective catalytic sites. Furthermore, the unagglomerated nanoparticles migrate too quickly and are unevenly distributed in the melt, leading to excessive breakage of local molecular chains and causing melt collapse, which reduces the open porosity of the TPU composite foam material. When the particle size of bismuth trioxide is too large, the large-sized bismuth trioxide particles are difficult to disperse uniformly in the TPU-EVA matrix, resulting in uneven distribution of the catalyst in the system. This makes it impossible to effectively bring the molecular chains of the two phases closer together, resulting in poor interfacial tension reduction. The EVA dispersed phase is prone to coarsening and aggregation, leading to a decrease in the open porosity of the TPU composite foam material. 3. This application combines distearate and antioxidant 1135 to form an antioxidant. Antioxidant 1135 blocks free radical propagation, and distearate eliminates oxidation intermediates. It comprehensively inhibits the thermal oxidative degradation of materials from the two key stages of oxidation reaction, namely "initiation" and "diffusion", and maintains the stability of melt strength. Furthermore, the phenolic free radicals generated by antioxidant 1135 can react with distearate to regenerate phenolic hydroxyl groups, while distearate is oxidized to stable products such as thioethers, effectively improving the utilization rate of antioxidant 1135. Detailed Implementation

[0030] The raw materials in this application include the following: Polyester-type TPU: The polyester-type TPU with the grade TPU9063 from Wanhua Chemical Group Co., Ltd. is used; Polyether-type TPU: The polyether-type TPU with the grade TPU9083 from Wanhua Chemical Group Co., Ltd. is used; EVA: Ethylene-vinyl acetate copolymer, using EVA grade Eva28005 from LG Chem Ltd. (LG Chem) in South Korea; Zinc diethyldithiocarbamate: Uses commercially available products with CAS number 14324-55-1; Bismuth trioxide: Bismuth trioxide with a particle size of 2μm was used from Ningbo Luofei Nanotechnology Co., Ltd.; Zinc stearate: Use commercially available product with CAS number 557-05-1; Distearate thiodipropionate: Use the commercially available product with CAS number 693-36-7; Antioxidant 1135: Uses a commercially available product with CAS number 125643-61-0.

[0031] The present application will be further described in detail below with reference to embodiments and comparative examples.

[0032] Example 1

[0033] A method for preparing a TPU composite foam material with an open-cell structure includes the following steps: S1. Add 750g TPU, 250g EVA and 15g catalyst to a mixer and mix at 190℃ for 10 minutes to obtain the mixed product. S2. Compress the intensively mixed product at 180°C for 10 minutes to obtain sheets; S3. The sheet is purged with high-pressure CO2 gas and high-pressure N2 gas at 135°C. The volume ratio of high-pressure CO2 gas to high-pressure N2 gas is 1:2, and the total pressure is 15MPa. S4. After the high-pressure gas in the sheet reaches saturation, the pressure is released to obtain a TPU composite foam material with an open-cell structure.

[0034] The catalyst is a mixture of zinc diethyldithiocarbamate and bismuth trioxide, with a molar ratio of 1:1 between the two.

[0035] Example 2-3 Examples 2-3 are based on the preparation method of Example 1, but the components of the TPU composite foam material are adjusted as shown in Table 1.

[0036] Comparative Example 1 Comparative Example 1 was prepared by removing the catalyst in step S1 and adding only 750g TPU and 250g EVA to a mixer and mixing at 190°C for 10 minutes to obtain the mixed product. All other conditions remained unchanged.

[0037] Performance testing The TPU composite foam materials of Examples 1-3 and Comparative Example 1 were analyzed using the following specific testing methods: 1. Compression permanent deformation Referring to the determination method of GB / T 6669-2008, TPU composite foam material was prepared into a sample with a length and width of (50±1) mm and a thickness of (25±1) mm. After conditioning for 72 h at a temperature of (23±2)℃ and a relative humidity of (50±5)%, its initial thickness d0 was measured. The sample was placed between two plates of the device and compressed by 50%±4% of its thickness. Within 15 min, the compressed sample was placed in an oven at (50±1)℃ and maintained in this state for (6±0.2) h. The device was removed from the oven and the sample was removed within 1 min. It was then placed on a surface of a low thermal conductivity object to cool for (30±5) min, and the final thickness d of the sample was measured. t Calculate the compressive permanent deformation CS=[(d0-d t ) / d0]*100%.

[0038] 2. Rebound rate Following the determination method of Method A in GB / T 6670-2008, TPU composite foam material was prepared into a sample with dimensions of (100±1)mm*(100±1)mm*(50±0.5)mm. The sample was conditioned for 72 hours at a temperature of (23±2)℃ and a relative humidity of (50±5)%. A transparent tube with an inner diameter of 50mm was selected, and graduation lines were drawn on its outer side. A steel ball with a diameter of 16mm±0.5mm and a mass of 16.8g±1.5g was selected. The sample was placed on a reference surface, and the tube was fixed to ensure light contact between the tube and the sample without causing any visible pressure. The steel ball was released using a release device, and the maximum rebound height was recorded, ensuring it did not touch the inner wall of the tube. Multiple measurements were taken, and the median value was used as the rebound rate of the sample.

[0039] 3. Open area ratio After removing the outer skin of the foam sample, the true volume of the foam was measured using a gas displacement density analyzer. The open porosity of the foam was calculated using Formula 1, where V open V close V skeleton V true and V total These represent the open pore volume, closed pore volume, cytoskeleton volume, and actual volume (V), respectively. close and V skeleton (sum of) and total volume (V) open V close and V skeleton The sum of (V). Actual volume (V) true The volume of the cytoskeleton (V) was measured using a gas-displacement density analyzer (AccuPyc II 1340, Micromeritics). skeleton The total volume (V) was determined by the Archimedes displacement method, which was applied to the sample prior to foaming. total The same method was used to measure the volume after foaming. By comparing the volume difference obtained by the two methods, V can be derived. open .

[0040]

[0041] Formula 1:

[0042] Based on the above detection method, the test results of Examples 1-3 and Comparative Example 1 were obtained, as shown in Table 1 below.

[0043] Table 1. Composition and performance test results of TPU composite foam materials in Examples 1-3 and Comparative Example 1

[0044] Referring to Table 1, a comparison of Examples 1-3 and Comparative Example 1 shows that the TPU composite foam materials of Examples 1-3 outperform the TPU composite foam material of Comparative Example 1. This is likely because the addition of the catalyst enables the formation of coordination bonds with TPU and EVA, bringing the molecular chains of TPU and EVA closer together, enhancing the molecular entanglement and interaction strength at the interface between the two phases. Furthermore, near the melting temperature, the catalyst can catalyze transesterification between TPU and EVA, effectively improving the compatibility between TPU and EVA. This allows EVA to be stably dispersed in the continuous TPU phase with smaller and more uniform particle sizes. The presence of EVA also acts as a stress concentration point, significantly increasing the open porosity of the TPU composite foam material and reducing its resilience. In addition, the presence of the catalyst can suppress side reactions, helping to reduce the compression set of the TPU composite foam material.

[0045] Comparative Examples 2-4 Comparative Examples 2-4 were prepared using the same method as in Example 1, but with adjustments made to the catalyst composition, as shown in Table 2.

[0046] The TPU composite foam materials of Comparative Examples 2-4 were subjected to the above performance tests, and the test results are shown in Table 2.

[0047] Table 2 Catalyst composition and performance test results for Examples 1 and Comparative Examples 2-4

[0048] Referring to Table 2, comparing Example 1 and Comparative Examples 2-3, it can be seen that the open-cell ratio of the TPU composite foam material in Example 1 is better than that of the TPU composite foam materials in Comparative Examples 2-3. This may be because the catalyst is composed of zinc diethyldithiocarbamate and bismuth trioxide. The bimetallic coordination of zinc ions in zinc diethyldithiocarbamate and bismuth ions in bismuth trioxide can cover a wider range of coordination sites, further bringing the molecular chains of TPU and EVA closer together, enhancing the molecular entanglement and interaction strength at the interface between the two phases, and effectively reducing the interfacial tension. Under conditions close to the melting temperature, zinc diethyldithiocarbamate and bismuth trioxide can jointly promote the transesterification efficiency of TPU and EVA, making the size of the EVA dispersed phase smaller, the distribution more uniform and stable, thereby significantly improving the open-cell ratio of the TPU composite foam material.

[0049] Comparing Example 1 and Comparative Example 4, it can be seen that the performance of the TPU composite foam material of Example 1 is significantly better than that of the TPU composite foam material obtained in Comparative Example 4. This may be because the sulfur atoms of zinc diethyldithiocarbamate have strong coordination ability and can coordinate with bismuth ions on the surface of bismuth trioxide to form stable Bi-S covalent coordination bonds, constructing an "inorganic-organic hybrid catalytic interface", which reduces the spatial distance between TPU and EVA and effectively accelerates the transesterification reaction process.

[0050] Examples 4-7 Examples 4-7 are based on the preparation method of Example 1, but the molar ratio of zinc diethyldithiocarbamate and bismuth trioxide is adjusted as shown in Table 3.

[0051] The TPU composite foam materials of Examples 4-7 were subjected to the above-mentioned performance tests, and the test results are shown in Table 3.

[0052] Table 3. Molar ratio of zinc diethyldithiocarbamate and bismuth trioxide in Examples 1 and 4-7 and their performance test results.

[0053] Referring to Table 3, comparing Examples 1 and 4-7, it can be seen that when the molar ratio of zinc diethyldithiocarbamate to bismuth trioxide is in the range of 0.8-1.2:1, especially when the molar ratio of zinc diethyldithiocarbamate to bismuth trioxide is 1:1, the resulting TPU composite foam material has the highest open cell ratio. This may be because when the proportion of zinc diethyldithiocarbamate is too low, there is not enough zinc diethyldithiocarbamate to form Bi-S bonds with bismuth trioxide, resulting in a "inorganic-organic hybrid catalytic interface". Insufficient and discontinuous bismuth oxide particles reduce the density of active sites and cause bismuth trioxide particles to agglomerate, resulting in a decrease in the open porosity of the bubbles. When the proportion of zinc diethyldithiocarbamate is too high, the bismuth ion sites on the surface of bismuth trioxide are limited, and the excess zinc diethyldithiocarbamate cannot be fully anchored on its surface through effective Bi-S bonds. Furthermore, the excessively thick organic layer of zinc diethyldithiocarbamate itself will form new and excessive steric hindrance, hindering the diffusion of substrate molecules and their contact with the active sites deep in the interface, thus reducing catalytic efficiency and open porosity.

[0054] Example 8

[0055] Example 8: Based on the preparation method of Example 1, in S1, 5g of antioxidant was added and mixed with TPU, EVA and catalyst to obtain a preliminary mixed product. The antioxidant was a mixture of distearate thiodipropionate and antioxidant 1135. The mass ratio of distearate thiodipropionate to antioxidant 1135 was 1:1.5, and the other conditions remained unchanged.

[0056] Examples 9-10 Examples 9-10 are based on the preparation method of Example 1, but the components of the antioxidant are adjusted as shown in Table 4.

[0057] The TPU composite foam materials of Examples 8-10 were subjected to the above-mentioned performance tests, and the test results are shown in Table 4.

[0058] Table 4. Antioxidant components and performance test results for Examples 1 and 8-10

[0059] Referring to Table 4, a comparison of Example 1 and Examples 8-10 shows that the addition of antioxidants can effectively improve the performance of TPU composite foam materials. This is because antioxidants can quickly capture alkyl free radicals or peroxy free radicals generated by polymers in the early stage of high-temperature oxidation, interrupt the propagation of chain oxidation reaction, and ensure the quality of foam cells.

[0060] Furthermore, by combining distearate and antioxidant 1135 to form an antioxidant, antioxidant 1135 blocks free radical propagation, and distearate eliminates oxidation intermediates. This comprehensively inhibits the thermal oxidative degradation of materials from the two key stages of the oxidation reaction, namely "initiation" and "diffusion," maintaining the stability of melt strength. Moreover, the phenolic free radicals generated by antioxidant 1135 can react with distearate to regenerate phenolic hydroxyl groups, while distearate is oxidized to stable products such as thioethers, effectively improving the utilization rate of antioxidant 1135.

[0061] Examples 11-14 Examples 11-14 are based on the preparation method of Example 8, but the mixing mass ratio of distearate thiodipropionate and antioxidant 1135 is adjusted as shown in Table 5.

[0062] The TPU composite foam materials of Examples 11-14 were subjected to the above-mentioned performance tests, and the test results are shown in Table 5.

[0063] Table 5. Mixed mass ratio and performance test results of distearate and antioxidant 1135 in Examples 8 and 11-14.

[0064] Referring to Table 5, a comparison of Examples 8 and 11-14 shows that the TPU composite foam material exhibits the best performance when the mass ratio of distearate to antioxidant 1135 is 1:1-2, especially when the mass ratio is 1:1.5. This may be because when the proportion of distearate is too high, the antioxidant cannot efficiently capture the free radicals continuously generated during the processing and use of the open-cell foam material, leading to molecular chain breakage, resulting in decreased melt strength, weakened cell wall toughness, and decreased open-cell ratio. When the proportion of distearate is too low, its ability to decompose hydrogen peroxide and assist in the regeneration of antioxidant 1135 is insufficient, leading to the accumulation of hydrogen peroxide and rapid consumption of antioxidant 1135, which intensifies molecular chain oxidation and breaks, resulting in increased resilience and compression set of the TPU composite foam material.

[0065] Example 15

[0066] Example 15 is based on the preparation method of Example 1, but the polyester TPU is replaced with an equal amount of polyether TPU, and the other conditions remain unchanged.

[0067] The TPU composite foam material of Example 15 was subjected to the above-mentioned performance tests, and the test results are shown in Table 6.

[0068] Table 6. TPU and its performance test results in Examples 1 and 15

[0069] Referring to Table 6, a comparison of Example 1 and Example 15 shows that the performance of the TPU composite foam material in Example 1 is significantly better than that in Example 15. This may be because polyester-type TPU has strong polar groups that can interact strongly with the vinyl acetate groups in EVA, thereby improving the compatibility between the two and promoting the uniform dispersion of EVA in the TPU matrix. Furthermore, polyester-type TPU has good chemical stability and high strength during the foaming process, and can react more effectively with the catalyst, further improving the open-cell structure and mechanical properties of the foam material.

[0070] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A TPU composite foam material with an open-cell structure, characterized in that, It includes the following components in parts by weight: 60-90 parts TPU, 10-40 parts EVA, and 0.5-2.5 parts catalyst; The catalyst is a mixture of zinc diethyldithiocarbamate and bismuth trioxide.

2. The TPU composite foam material with an open-cell structure according to claim 1, characterized in that, The molar ratio of zinc diethyldithiocarbamate to bismuth trioxide is 0.8-1.2:

1.

3. The TPU composite foam material with an open-cell structure according to claim 1, characterized in that, The bismuth trioxide has a particle size of 1-3 μm.

4. The TPU composite foam material with an open-cell structure according to claim 1, characterized in that, It also contains 0.1-1 parts of an antioxidant, which is a mixture of distearate thiodipropionate and antioxidant 1135.

5. The TPU composite foam material with an open-cell structure according to claim 4, characterized in that, The mass ratio of the distearate thiodipropionate to antioxidant 1135 is 1:1-2.

6. The TPU composite foam material with an open-cell structure according to claim 1, characterized in that, The TPU is a polyester-type TPU.

7. A method for preparing a TPU composite foam material with an open-cell structure according to any one of claims 1-6, characterized in that, Includes the following steps: S1. Mix the TPU, EVA and catalyst in the specified amounts to obtain the mixed product. S2. Compress the intensively mixed product into sheets to obtain sheets; S3. The sheet is subjected to high-pressure gas at 125-145℃, and the pressure of the high-pressure gas is 12-15MPa. S4. After the high-pressure gas in the sheet reaches saturation, the pressure is released to obtain a TPU composite foam material with an open-cell structure.

8. The method for preparing a TPU composite foam material with an open-cell structure according to claim 7, characterized in that, In S1, antioxidants, TPU, EVA, and catalyst are added in the prescribed amounts and then mixed to obtain the mixed product.

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