A lightweight and wear-resistant foamed shoe sole material and its preparation method

Abstract

This invention belongs to the field of polymer foamed shoe material technology, specifically relating to a lightweight, wear-resistant foamed shoe sole material and its preparation method. The material is obtained by two-stage compression molding and cross-linking foaming of the following components in parts by weight: 75-85 parts ethylene-vinyl acetate copolymer, 15-25 parts polyolefin elastomer, 4-8 parts elastic siloxane shell-fumed silica core coated particles, 0.2-0.4 parts benzoyl peroxide, 0.7-0.9 parts dicumyl peroxide, and 2.8-3.6 parts azodicarbonamide (based on effective components). The coated particles are obtained by partial cross-linking of fumed silica-supported vinyl-terminated polydimethylsiloxane with hydrosilicone oil via hydrosilylation, retaining the vinyl groups. The first stage forms a pre-cross-linked network with a gel fraction of 10%-30%, followed by the second stage of foaming. The apparent density of the material is 0.20-0.23 g / cm³. 3 DIN wear not greater than 250mm 3 The dry dynamic friction coefficient is comparable to that of the matrix material without siloxane components, taking into account lightweight, wear resistance and slip resistance.

Description

Technical Field

[0001] This invention relates to the field of shoe sole material technology, specifically to a lightweight, wear-resistant foamed shoe sole material and its preparation method. Background Technology

[0002] Foamed sole materials are the main sole material for athletic and casual shoes. They are typically made by chemically cross-linking and molding with ethylene-vinyl acetate copolymer as the matrix and polyolefin elastomers. With increasing demands for lightweighting, the apparent density of sole materials needs to be reduced to 0.24 g / cm³. 3 In addition, the outsole working surface must maintain low wear and sufficient anti-slip performance.

[0003] To improve the abrasion resistance of foamed shoe soles, existing technologies often add or replace abrasion-resistant components within the conventional one-stage molding crosslinking foaming process. Patent CN114773658B discloses a wear-resistant, lightweight, and non-slip EVA foamed shoe sole material, using pre-dispersed silicone masterbatch as an abrasion-resistant agent and adding tetra-needle-shaped zinc oxide whiskers to compensate for the decrease in non-slip performance caused by the introduction of silicone. Patent CN113881130B discloses a highly abrasion-resistant EVA foamed material for shoes, using a composite solid precipitated from the blending of polytetrafluoroethylene emulsion and styrene-butadiene rubber emulsion as an abrasion-resistant agent. Patent CN115678154A discloses a processing technology for wear-resistant and non-slip EVA shoe soles, involving surface treatment of silica with hydrogen-containing silicone oil before adding it to the formula.

[0004] However, increasing the foaming ratio thins the cell walls, leading to increased wear. Self-lubricating wear-resistant components rely on migration to the product surface to be effective, reducing surface energy and impairing anti-slip performance while reducing wear, requiring additional compensating components. The silicone oil layer of surface-treated fillers is an inert hydrophobic layer, offering limited improvement in wear. Lightweight, wear-resistant, and anti-slip properties are difficult to achieve simultaneously within existing single-stage molding systems. Summary of the Invention

[0005] The technical problem to be solved by this invention is that after reducing the apparent density of foamed shoe sole materials, the cell walls become thinner and wear increases significantly; although the introduction of self-lubricating and wear-resistant components can reduce wear, the anti-slip performance decreases due to the migration of components to the surface, making it difficult to simultaneously achieve lightweight, wear-resistant and anti-slip properties.

[0006] To solve the above-mentioned technical problems, the present invention provides a lightweight and wear-resistant foamed shoe sole material, which is obtained by two-stage compression cross-linking foaming of a composition comprising the following components in parts by weight: 75-85 parts of ethylene-vinyl acetate copolymer, 15-25 parts of polyolefin elastomer, 4-8 parts of elastic siloxane shell-fumed silica core coated particles, 0.2-0.4 parts of benzoyl peroxide, 0.7-0.9 parts of dicumyl peroxide, and 2.8-3.6 parts of azodicarbonamide (based on effective ingredients), wherein the total weight of the ethylene-vinyl acetate copolymer and the polyolefin elastomer is 100 parts; the coated particles... The foamed sole material is prepared by partial crosslinking of vinyl-terminated polydimethylsiloxane with hydrogen-containing silicone oil supported on precipitated silica via platinum-catalyzed hydrosilylation. The molar ratio of SiH provided by the hydrogen-containing silicone oil to SiVi provided by the vinyl-terminated polydimethylsiloxane is 0.3–0.6. The resulting coating layer is gelled and fixed while retaining the vinyl groups. The two-stage compression molding crosslinking foaming includes a first stage at 125–135°C to form a pre-crosslinked network with a gel fraction of 10%–30%, and a second stage at 168–176°C for compression molding foaming. The apparent density of the foamed sole material is 0.20–0.23 g / cm³. 3 .

[0007] Preferably, in the coated particles, the weight ratio of the total weight of vinyl-terminated polydimethylsiloxane and hydrosilicone oil to the weight of precipitated silica is 0.35–0.55:1. Preferably, the composition further comprises 1.2–1.8 parts zinc oxide, 0.8–1.2 parts stearic acid, 0.5–1.0 parts zinc stearate, and 3–6 parts light calcium carbonate. The polyolefin elastomer is preferably an ethylene-octene copolymer. The BET specific surface area of ​​the precipitated silica is preferably 160–180 m² / g. 2 / g, wherein the vinyl content of the vinyl-terminated polydimethylsiloxane is preferably 0.35-0.45 mmol / g, and the hydrogen content of the hydrogen-containing silicone oil is preferably 0.18%. The coated particles are preferably prepared by the following steps: precipitated silica is kneaded with vinyl-terminated polydimethylsiloxane, hydrogen-containing silicone oil and platinum catalyst until uniform adsorption is achieved, and then subjected to hydrosilylation partial crosslinking at 90-105℃ for 60-90 min, followed by cooling, pulverization and sieving.

[0008] The present invention also provides a method for preparing the above-mentioned lightweight wear-resistant foamed shoe sole material, comprising the following steps: (1) mixing ethylene-vinyl acetate copolymer, polyolefin elastomer, the coated particles, filler, activator and lubricant in an intensive mixing process at a temperature not higher than 110°C, without adding peroxide and foaming agent in this step; (2) transferring the rubber material to an open mill, adding benzoyl peroxide, dicumyl peroxide and azodicarbonamide at 80-90°C, mixing and then extruding the mixture into sheets; (3) pressing the sheet at 125-135°C for 6-10 minutes for the first stage of molding to form a pre-crosslinked network with a gel fraction of 10%-30%; (4) heating to 168-176°C and pressing for 7-9 minutes for the second stage of molding and foaming, and then opening the mold to expand; (5) cutting after curing to obtain the lightweight wear-resistant foamed shoe sole material. Preferably, the mixing temperature in step (1) is 105-110℃ and the mixing time is 8-10 min; the molding pressure in steps (3) and (4) is 10-15 MPa.

[0009] The beneficial effects of this invention are as follows: (1) A foaming matrix is ​​constructed using ethylene-vinyl acetate copolymer and polyolefin elastomer, and elastic siloxane shell-fumed silica core coated particles are introduced, with an apparent density of 0.20-0.23 g / cm³. 3 Reduce DIN wear to 250mm under the following conditions 3 The following reduces the apparent density by more than 45% compared to foamed materials with the same density, without the particle, and conventionally molded in one step; the foamed sole can be molded in one piece and used directly as the ground contact outsole, eliminating the need for a separate rubber outsole bonding process.

[0010] (2) The siloxane coating layer of the coated particles is fixed by hydrosilylation gelation and co-crosslinked with the matrix during molding. The siloxane phase does not migrate to the surface of the product. The siloxane extraction rate is no more than 20%, while when added in the form of free silicone oil or silicone masterbatch, the rate is more than 80%. The dry dynamic friction coefficient is comparable to that of the matrix material without siloxane components. While reducing wear, it maintains anti-slip performance and does not require additional anti-slip compensation components.

[0011] (3) The molding process adopts a two-stage molding process of low-temperature pre-crosslinking and high-temperature foaming. The first stage forms a pre-crosslinked network with a gel fraction of 10% to 30%. Foaming is carried out under the constraint of this network, resulting in fine and uniform pores. The reduction in wear exceeds the sum of the effects of the coating particles and the two molding stages alone.

[0012] (4) Using 15 to 25 parts of polyolefin elastomer as the elastic phase, the material has a rebound rate of not less than 54%, a Shore C hardness of 51 to 55, which is within the suitable range for sports shoes and casual shoes, and a compression set comparable to conventional foamed materials.

[0013] (5) The coated particles are prepared by conventional kneading and heat preservation processes, and the two-stage molding can be carried out on ordinary flat vulcanizing equipment; the SiH to SiVi molar ratio of 0.3 to 0.6 and the pre-crosslinked gel fraction of 10% to 30% can accommodate the fluctuations of conventional batches, which is convenient for stable production. Detailed Implementation

[0014] The ethylene-vinyl acetate copolymer used in the preparation examples, embodiments, and comparative examples was sourced from Hanwha Total, brand name E180F, with a vinyl acetate content of 18%; the polyolefin elastomer was sourced from Dow Chemical, trade name ENGAGE, brand name 8150; and the precipitated silica was sourced from Wuxi Quecheng Silicon Chemical Co., Ltd., brand name 165MP, with a BET specific surface area of ​​160–180 m². 2 / g; Vinyl-terminated polydimethylsiloxane was sourced from Jiangxi Lanxing Xinghuo Organosilicon Co., Ltd., with a viscosity grade of 100 mPa·s and a vinyl content of 0.4 mmol / g; Hydrogen-containing silicone oil was sourced from Jiangxi Lanxing Xinghuo Organosilicon Co., Ltd., and was a side-hydrogen type low-hydrogen silicone oil with a hydrogen content of 0.18%; The platinum catalyst was a Karstedt type vinylsiloxane platinum complex solution with a platinum content of 3000 ppm; Benzoyl peroxide was sourced from Norinon, brand name Perkadox L-W75, with an effective content of 75%, and the amount of this raw material used in the examples and comparative examples was based on the actual weighing value of the product; Dicumyl peroxide was sourced from Norinon, brand name Perkadox BC-FF; the azodicarbonamide foaming agent was sourced from Hangzhou Haihong Fine Chemical Co., Ltd., brand name AC-3000H, with a particle size of 3-5 μm; the pre-dispersed silicone masterbatch used in Comparative Example 3 was sourced from Dow Chemical, brand name MB50-313, using ethylene-vinyl acetate copolymer as a carrier, with a silicone content of 50%. Zinc oxide, stearic acid, zinc stearate, and light calcium carbonate were all commercially available industrial-grade products.

[0015] Preparation Example 1: 500g of precipitated silica was added to a kneader, along with 204.6g of vinyl-terminated polydimethylsiloxane, 20.4g of hydrogen-containing silicone oil, and 0.75g of platinum catalyst solution. The mixture was kneaded for 35 minutes until uniform adsorption was achieved. The temperature was then raised to 95℃ and held for 75 minutes. The silicone oil underwent partial cross-linking via hydrosilylation on the silica surface, forming a non-flowing elastic coating layer. After cooling, the silica was pulverized and passed through a 60-mesh sieve to obtain elastic siloxane-shell-silica core coated particles.

[0016] Preparation Example 2: 500g of precipitated silica was added to a kneader, along with 177.5g of vinyl-terminated polydimethylsiloxane, 12.5g of hydrogen-containing silicone oil, and 0.63g of platinum catalyst solution. The mixture was kneaded for 35 minutes until the adsorption was uniform. The temperature was then raised to 95℃ and held for 75 minutes. After cooling, the mixture was pulverized and passed through a 60-mesh sieve to obtain coated particles.

[0017] Preparation Example 3: 500g of precipitated silica was added to a kneader, along with 235.2g of vinyl-terminated polydimethylsiloxane, 29.8g of hydrogen-containing silicone oil, and 0.88g of platinum catalyst solution. The mixture was kneaded for 35 minutes until uniform adsorption was achieved. The temperature was then raised to 95℃ and held for 75 minutes. After cooling, the mixture was pulverized and passed through a 60-mesh sieve to obtain coated particles.

[0018] Example 1: Step (1): 400g of ethylene-vinyl acetate copolymer, 100g of polyolefin elastomer, 30g of coated particles obtained in Preparation Example 1, 22.5g of light calcium carbonate, 7.5g of zinc oxide, 5g of stearic acid and 4g of zinc stearate were put into a mixer and mixed at 108°C for 9 minutes.

[0019] Step (2): Transfer the rubber compound to a two-roll mill at a roller temperature of 85°C, add 2g benzoyl peroxide, 4g dicumyl peroxide and 16g azodicarbonamide, mix thoroughly 7 times, and then sheet the compound with a sheet thickness of 3.5mm.

[0020] Step (3): Place the film into the mold and press it at 130℃ and 12MPa for 8 minutes to form the first stage of molding and form a pre-crosslinked network.

[0021] Step (4): Raise the mold temperature to 172°C within 12 minutes, and hold the pressure for 8 minutes after the mold temperature reaches 172°C to carry out the second stage of molding and foaming; after the pressure holding is completed, open the mold, the blank expands, and after curing at room temperature for 24 hours, punch cut to obtain foamed shoe sole material.

[0022] Example 2: Step (1): 425g of ethylene-vinyl acetate copolymer, 75g of polyolefin elastomer, 22.5g of coated particles obtained in Preparation Example 1, 22.5g of light calcium carbonate, 7.5g of zinc oxide, 5g of stearic acid and 4g of zinc stearate were put into a mixer and mixed at 108°C for 9 minutes.

[0023] Step (2): Transfer the rubber compound to a two-roll mill at a roller temperature of 85°C, add 2g benzoyl peroxide, 4g dicumyl peroxide and 16g azodicarbonamide, mix thoroughly 7 times, and then sheet the compound with a sheet thickness of 3.5mm.

[0024] Step (3): Place the film into the mold and press it at 130℃ and 12MPa for 8 minutes to form the first stage of molding and form a pre-crosslinked network.

[0025] Step (4): Raise the mold temperature to 172°C within 12 minutes, and hold the pressure for 8 minutes after the mold temperature reaches 172°C to carry out the second stage of molding and foaming; after the pressure holding is completed, open the mold, the blank expands, and after curing at room temperature for 24 hours, punch cut to obtain foamed shoe sole material.

[0026] Example 3: Step (1): 390g of ethylene-vinyl acetate copolymer, 110g of polyolefin elastomer, 37.5g of coated particles obtained in Preparation Example 1, 22.5g of light calcium carbonate, 7.5g of zinc oxide, 5g of stearic acid and 4g of zinc stearate were put into a mixer and mixed at 108°C for 9 minutes.

[0027] Step (2): Transfer the rubber compound to a two-roll mill at a roller temperature of 85°C, add 2g benzoyl peroxide, 4g dicumyl peroxide and 16g azodicarbonamide, mix thoroughly 7 times, and then sheet the compound with a sheet thickness of 3.5mm.

[0028] Step (3): Place the film into the mold and press it at 130℃ and 12MPa for 8 minutes to form the first stage of molding and form a pre-crosslinked network.

[0029] Step (4): Raise the mold temperature to 172°C within 12 minutes, and hold the pressure for 8 minutes after the mold temperature reaches 172°C to carry out the second stage of molding and foaming; after the pressure holding is completed, open the mold, the blank expands, and after curing at room temperature for 24 hours, punch cut to obtain foamed shoe sole material.

[0030] Example 4: Step (1): 410g of ethylene-vinyl acetate copolymer, 90g of polyolefin elastomer, 30g of coated particles obtained in Preparation Example 2, 22.5g of light calcium carbonate, 7.5g of zinc oxide, 5g of stearic acid and 4g of zinc stearate were put into a mixer and mixed at 108°C for 9 minutes.

[0031] Step (2): Transfer the rubber compound to a two-roll mill at a roller temperature of 85°C, add 1.5g benzoyl peroxide, 4g dicumyl peroxide and 16g azodicarbonamide, mix thoroughly 7 times, and then sheet the compound with a sheet thickness of 3.5mm.

[0032] Step (3): Place the film into the mold and press it at 127℃ and 12MPa for 9.5 minutes to form the first stage of molding and form a pre-crosslinked network.

[0033] Step (4): Raise the mold temperature to 172°C within 12 minutes, and hold the pressure for 8 minutes after the mold temperature reaches 172°C to carry out the second stage of molding and foaming; after the pressure holding is completed, open the mold, the blank expands, and after curing at room temperature for 24 hours, punch cut to obtain foamed shoe sole material.

[0034] Example 5: Step (1): 375g of ethylene-vinyl acetate copolymer, 125g of polyolefin elastomer, 30g of coated particles obtained in Preparation Example 3, 22.5g of light calcium carbonate, 7.5g of zinc oxide, 5g of stearic acid and 4g of zinc stearate were put into a mixer and mixed at 108°C for 9 minutes.

[0035] Step (2): Transfer the rubber compound to a two-roll mill at a roller temperature of 85°C, add 2.5g benzoyl peroxide, 4g dicumyl peroxide and 16g azodicarbonamide, mix thoroughly 7 times, and then sheet the compound with a sheet thickness of 3.5mm.

[0036] Step (3): Place the film into the mold and press it at 133℃ and 12MPa for 6.5 minutes to form the first stage of molding and form a pre-crosslinked network.

[0037] Step (4): Raise the mold temperature to 172°C within 12 minutes, and hold the pressure for 8 minutes after the mold temperature reaches 172°C to carry out the second stage of molding and foaming; after the pressure holding is completed, open the mold, the blank expands, and after curing at room temperature for 24 hours, punch cut to obtain foamed shoe sole material.

[0038] Comparative Example 1: Except for the absence of coating particles, the absence of benzoyl peroxide, the change of the amount of dicumyl peroxide to 5g, and the change of the two-stage molding to a single-stage pressing at 172℃ and 12MPa for 9min, the other raw materials, amounts, and preparation conditions are the same as in Example 1, and foamed shoe sole material is obtained.

[0039] Comparative Example 2: Except for replacing 30g of the coated particles obtained in Example 1 with 20.7g of precipitated silica, 8.5g of vinyl-terminated polydimethylsiloxane and 0.8g of hydrogen-containing silicone oil, which were added together with other powders in the mixing stage, the other raw materials, amounts and preparation conditions were the same as in Example 1, and foamed shoe sole material was obtained.

[0040] Comparative Example 3: Except for replacing 30g of the coated particles obtained in Example 1 with 18.6g of predispersed silicone masterbatch and 20.7g of precipitated silica, the other raw materials, dosages and preparation conditions were the same as in Example 1, and foamed shoe sole material was obtained.

[0041] Comparative Example 4: Except for canceling the first stage of molding and changing the molding conditions to a single stage of holding pressure at 172°C and 12MPa for 9 minutes, the other raw materials, dosages and preparation conditions are the same as in Example 1, and foamed shoe sole material is obtained.

[0042] Comparative Example 5: Except for changing the amount of hydrogen-containing silicone oil used in Preparation Example 1 to 50g, obtaining fully cured coated particles and using them in equal amounts, the other raw materials, amounts and preparation conditions are the same as in Example 1, and foamed shoe sole material is obtained.

[0043] Comparative Example 6: Except for changing the amount of hydrogen-containing silicone oil used in Preparation Example 1 to 9.1g and preparing coated particles with incompletely gelled shells and using them in equal amounts, the other raw materials, amounts and preparation conditions were the same as in Example 1, and foamed shoe sole material was obtained.

[0044] Comparative Example 7: Except for changing the amount of benzoyl peroxide to 0.7g, the other raw materials, amounts and preparation conditions are the same as in Example 1, and foamed shoe sole material is obtained.

[0045] Comparative Example 8: Except for changing the amount of benzoyl peroxide to 4g, the other raw materials, amounts and preparation conditions are the same as in Example 1, and foamed shoe sole material is obtained.

[0046] Comparative Example 9: Except for the absence of coating particles, the other raw materials, dosages, and preparation conditions are the same as in Example 1, resulting in foamed shoe sole material.

[0047] Performance testing: Apparent density: determined according to GB / T 6343-2009 "Determination of apparent density of foamed plastics and rubber". Three samples were tested for each sample, and the arithmetic mean of the results was taken.

[0048] DIN abrasion: The relative volumetric abrasion was determined according to Method A of GB / T 9867-2008 "Determination of abrasion resistance of vulcanized rubber or thermoplastic rubber (rotary roller abrasion tester method)". The sample was punched from a self-foamed sheet, and the surface of the foamed sheet was used as the abrasion surface. The volumetric abrasion was calculated based on the actual apparent density of the sample. Three samples were tested for each sample, and the arithmetic mean of the results was taken.

[0049] Dry dynamic friction coefficient: Referring to the sliding method principle of GB / T 10006-2021, the surface of the foam sheet of each sample is used as the test surface. The dynamic friction coefficient between the sample and the stainless steel plate is measured in the dry state. The mass of the slider and the sliding speed are performed according to the standard. Each sample is measured 5 times, and the result is taken as the arithmetic mean.

[0050] Shore C hardness: determined according to HG / T 2489-2018 "Test Method for Hardness of Microporous Materials for Footwear", with 5 points measured for each sample, and the arithmetic mean of the results is taken.

[0051] Rebound rate: Determined according to GB / T 6670-2008 "Determination of rebound performance of flexible foam polymer materials by falling ball method". Each sample was measured 3 times and the result was taken as the arithmetic mean.

[0052] Compression set: The compression set was determined according to GB / T 6669-2008 "Determination of compression set of flexible foam polymer materials". The compression rate was 50%. The sample was kept at 70℃ for 22 hours and unloaded for 30 minutes before measurement. Three samples were measured for each sample, and the arithmetic mean of the results was taken.

[0053] Extractable siloxane rate: The sample was chopped and extracted with toluene under reflux at 80°C for 24 h, and then dried under vacuum to constant weight. The difference between the extraction weight loss rate of the sample and the background weight loss rate of Comparative Example 9 under the same conditions was multiplied by the sample mass and then divided by the amount of siloxane added in the sample according to the formula to calculate the extractable siloxane rate. Three samples were measured for each sample, and the results were taken as the arithmetic mean.

[0054] Pre-crosslinking gel fraction: Parallel films from the same batch were molded under the same first-stage conditions. Samples were taken at the end of the first stage and extracted with xylene at 110°C for 24 hours. The mass of insoluble matter was reduced by the inorganic filler and then divided by the amount of crosslinkable polymer (ethylene-vinyl acetate copolymer, polyolefin elastomer, and the sum of siloxanes in the coated particles) to calculate the pre-crosslinking gel fraction. Three samples were measured for each sample, and the arithmetic mean of the results was taken. The first-stage molding conditions and peroxide dosage in Examples 2 and 3 were the same as in Example 1, and the pre-crosslinking gel fractions were comparable to those in Example 1, as shown by "—" in Table 2. The test results are shown in Tables 1 and 2.

[0055] Table 1. Main properties of the foamed shoe sole materials obtained in each embodiment and comparative example.

[0056] Table 2 Extractable siloxane ratio and pre-crosslinked gel fraction for each example and comparative example.

[0057] Results analysis: As shown in Table 1, the DIN wear of Examples 1 to 5 is 202–240 mm. 3 Compared to Comparative Example 1, which is 451mm 3 The apparent density is reduced by more than 45%; the apparent density is 0.202–0.220 g / cm³. 3 Compared with Comparative Example 1, which has a concentration of 0.203 g / cm³, this figure is significantly lower. 3 The dry-state dynamic friction coefficient was 0.96–0.98, which is no more than 0.05 different from 1.00 in Comparative Example 1. This indicates that the combination of the coated particles and the two-stage molding significantly reduced wear without increasing the apparent density, while maintaining the anti-slip performance. The Shore C hardness of Examples 1 to 5 was 51–55, and the rebound rate was 55%–58%, all within the suitable wear range.

[0058] Comparative Example 2 involved adding silica and silicone oil of the same composition as the coated particles directly in free form. The extractable siloxane rate was 82.5%, the dry-state dynamic friction coefficient decreased to 0.80, and the DIN wear was 382 mm. 3Comparative Example 3, using pre-dispersed silicone masterbatch and silica, achieved an extractable siloxane rate of 90.3% and further reduced the dry dynamic friction coefficient to 0.74. Example 1 showed an extractable siloxane rate of 11.6% and maintained a dry dynamic friction coefficient of 0.98. This indicates that the siloxane coating layer, after partial cross-linking via hydrosilylation and co-cross-linking with the matrix during molding, remains fixed within the cross-linked network and does not migrate to the surface, thus maintaining its anti-slip properties. Free or masterbatch-state silicone migrates to the surface, resulting in a significant decrease in the friction coefficient, but the improvement in wear is weaker than in the examples.

[0059] In Comparative Example 4, after the first stage of molding was removed, the DIN wear increased back to 309 mm. 3 The rebound rate decreased to 51%, the extractable siloxane rate was 11.5%, and the dry dynamic friction coefficient was 0.96, comparable to Example 1; Comparative Example 9 retained the two-stage molding process but did not add coating particles, and the DIN wear was 415 mm. 3 Compared to Comparative Example 1, Comparative Example 4 showed a reduction in wear of 142 mm. 3 Comparative Example 9 is 36mm 3 The sum of the two is 178mm 3 The reduction was significantly less than the 239mm reduction in Example 1. 3 The wear improvement achieved by combining coated particles with two-stage molding exceeds the sum of the effects of either alone.

[0060] Comparative Example 5 showed that the coated particle shell was completely cured with no residual vinyl involved in co-crosslinking, and the DIN abrasion returned to 341 mm. 3 The extractable siloxane rate was 9.1%, and the dry-state dynamic friction coefficient was 0.95, which was still comparable to the example. In Comparative Example 6, the shell was not completely gelled, the extractable siloxane rate increased to 40.2%, the dry-state dynamic friction coefficient decreased to 0.84, and the DIN wear was 264 mm. 3 The proportion of residual vinyl groups in the shell of Comparative Example 6 was higher than that of the Examples, but its wear resistance was limited. This may be related to the fact that the unfree siloxanes were still co-crosslinked with the matrix during molding, and the reinforcing effect of the silica core was partially retained. The performance degradation was mainly due to the decrease in anti-slip properties caused by the migration of free silicone oil to the surface. Comparative Examples 2 and 3, which had the highest amount of free siloxanes, still showed significantly higher wear resistance than the Examples, indicating that the improvement in wear resistance did not come from surface lubrication. It can be seen that when the degree of shell crosslinking is too high, it loses the ability to co-crosslink with the matrix, and the improvement in wear resistance is significantly weakened; when it is too low, some silicone oil migrates freely, and the anti-slip performance is impaired; when the shell is gelled and fixed and retains co-crosslinkable vinyl groups, both wear resistance and anti-slip properties are maintained simultaneously.

[0061] Comparative Example 7 had a pre-crosslinked gel fraction of 6%, resulting in insufficient melt strength, cell coalescence, and an apparent density increase to 0.235 g / cm³ during foaming. 3 DIN wear is 337mm 3The rebound rate decreased to 51%; in Comparative Example 8, the pre-crosslinked gel fraction reached 43%, foaming was suppressed, and the apparent density increased to 0.263 g / cm³. 3 The Shore C hardness reaches 59, the resilience drops to 51%, and the DIN wear is 212mm. 3 However, the apparent density and hardness have exceeded the applicable range for lightweight shoe soles. It can be seen that when the degree of pre-crosslinking in the first stage is too low, the pre-crosslinking network is insufficient to constrain foaming; when it is too high, the foaming expansion is inhibited; when the pre-crosslinking gel fraction is 10% to 30%, it can balance low density and fine pores.

[0062] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A lightweight, wear-resistant foamed shoe sole material, characterized in that, The product is prepared by two-stage compression molding and crosslinking foaming of a composition comprising the following components in parts by weight: 75-85 parts ethylene-vinyl acetate copolymer, 15-25 parts polyolefin elastomer, 4-8 parts elastic siloxane shell-fumed silica core-coated particles, 0.2-0.4 parts benzoyl peroxide, 0.7-0.9 parts dicumyl peroxide, and 2.8-3.6 parts azodicarbonamide (based on active ingredients), wherein the sum of the weight parts of the ethylene-vinyl acetate copolymer and the polyolefin elastomer is 100 parts; the coated particles are vinyl-terminated by precipitated silica. Polydimethylsiloxane is partially crosslinked with hydrogen-containing silicone oil via platinum-catalyzed hydrosilylation. The molar ratio of SiH provided by the hydrogen-containing silicone oil to SiVi provided by the vinyl-terminated polydimethylsiloxane is 0.3–0.

6. The resulting coating layer is gelled and fixed while retaining the vinyl group. The two-stage molding crosslinking foaming includes a first stage molding at 125–135°C to form a pre-crosslinked network with a gel fraction of 10%–30%, and a second stage molding foaming at 168–176°C. The apparent density of the foamed sole material is 0.20–0.23 g / cm³. 3 .

2. The lightweight, wear-resistant foamed shoe sole material according to claim 1, characterized in that, In the coated particles, the total weight ratio of vinyl-terminated polydimethylsiloxane and hydrogen-containing silicone oil to the weight ratio of precipitated silica is 0.35 to 0.55:

1.

3. The lightweight, wear-resistant foamed shoe sole material according to claim 1, characterized in that, The composition further includes 1.2 to 1.8 parts of zinc oxide, 0.8 to 1.2 parts of stearic acid, 0.5 to 1.0 parts of zinc stearate, and 3 to 6 parts of light calcium carbonate.

4. The lightweight, wear-resistant foamed shoe sole material according to claim 1, characterized in that, The polyolefin elastomer is an ethylene-octene copolymer.

5. The lightweight, wear-resistant foamed shoe sole material according to claim 1, characterized in that, The BET specific surface area of ​​the precipitated silica is 160–180 m². 2 / g, wherein the vinyl content of the vinyl-terminated polydimethylsiloxane is 0.35-0.45 mmol / g, and the hydrogen content of the hydrogen-containing silicone oil is 0.18%.

6. The lightweight, wear-resistant foamed shoe sole material according to claim 1, characterized in that, The coated particles are prepared by the following steps: precipitated silica is kneaded with vinyl-terminated polydimethylsiloxane, hydrogen-containing silicone oil and platinum catalyst until the adsorption is uniform, and then subjected to hydrosilylation partial crosslinking at 90-105℃ for 60-90 min. After cooling, the particles are pulverized and sieved.

7. A method for preparing a lightweight, wear-resistant foamed shoe sole material as described in any one of claims 1 to 6, characterized in that, The process includes the following steps: (1) mixing ethylene-vinyl acetate copolymer, polyolefin elastomer, the coated particles, filler, activator and lubricant in an intensive mixing process at a temperature not exceeding 110°C. No peroxide or foaming agent is added in this step; (2) transferring the rubber compound to a two-roll mill and adding benzoyl peroxide, dicumyl peroxide and azodicarbonamide at 80-90°C. After mixing, the mixture is sheeted out; (3) pressing the sheet at 125-135°C for 6-10 minutes to form a pre-crosslinked network with a gel fraction of 10%-30%; (4) heating to 168-176°C and pressing for 7-9 minutes to form a second stage of molding and foaming, followed by mold opening and expansion; (5) cutting after curing to obtain the lightweight wear-resistant foamed shoe sole material.

8. The method for preparing the lightweight, wear-resistant foamed shoe sole material according to claim 7, characterized in that, In step (1), the mixing temperature is 105-110℃ and the mixing time is 8-10 min.

9. The method for preparing the lightweight wear-resistant foamed shoe sole material according to claim 7, characterized in that, The molding pressure in steps (3) and (4) is 10 to 15 MPa.

Images