Supercritical rubber foaming material for soles and preparation process of supercritical rubber foaming material

Abstract

The invention provides a supercritical rubber foaming material for soles, which is prepared from the following components in parts by mass: 50 to 95 parts of rubber, 5 to 50 parts of thermoplastic elastomer, 20 to 60 parts of white carbon black, 1 to 5 parts of flaky filler, 0.5 to 5 parts of active agent, 0.1 to 10 parts of coupling agent, 0.5 to 5 parts of softening agent, 2 to 5 parts of antioxidant, 3 to 5 parts of zinc oxide, 0.5 to 3 parts of stearic acid, 1 to 5 parts of accelerant, 0.5 to 3 parts of sulfur and 0.1 to 0.5 part of bridging agent. The sum of the mass parts of the rubber and the thermoplastic elastomer is 100. The preparation process of the rubber supercritical foaming material comprises preparation of a rubber compound and preparation of the rubber supercritical foaming material. According to the invention, the rubber and the thermoplastic elastomer matrix are used together to form a uniform dispersion system of the rubber / thermoplastic elastomer; the spherical white carbon black and the flaky filler are synergistically used to improve the filler-matrix interface effect, promote heterogeneous nucleation of supercritical gas, increase the cell density and endow the material with the performance characteristic of lighter weight. Through the combination of a material matrix, a formula system and a foaming method, the performance requirements of light weight, wear resistance and slip resistance of the sole rubber are met.

Description

Technical Field

[0001] The invention belongs to the field of sole materials, and in particular relates to a rubber supercritical foaming material for soles and a preparation process thereof. Background Art

[0002] As people are increasingly participating in sports and fitness, sports shoes, as essential sports equipment, have increasingly higher performance requirements. The sole consists of two parts: the midsole and the outsole. The main functions of the midsole are shock absorption, rebound and support, helping to absorb the impact from the ground and reduce the pressure on the joints during exercise. The outsole is designed to provide excellent grip and durability. The combination of the midsole and outsole functions meets the performance requirements of sports shoes such as light weight, shock absorption, rebound, wear resistance and anti-slip.

[0003] Existing shoe midsole products mostly use foaming materials. For example, traditional midsoles are made of a composite system of EVA, SEBS, OBC, POE and other materials through chemical foaming. The foaming agent undergoes chemical decomposition when heated, and the generated gas is partially retained in the EVA pores, producing an unpleasant odor. In addition, the chemical foaming agent is difficult to disperse evenly in the polymer matrix, which will also lead to an uneven pore structure, a low foaming ratio, and average resilience and compression resistance, which cannot meet the performance requirements of high-end shoe materials.

[0004] In order to meet consumers' demand for lightweight shoes, midsole and outsole integrated products have been developed in recent years, using EVA compound systems to replace traditional rubber outsole systems. However, the poor anti-slip performance and wear resistance of the EVA material system have become the main factors restricting its application.

[0005] In addition to chemical foaming, the midsoles or integrated midsoles and outsoles of high-end sports shoes mostly use the more expensive supercritical foaming technology. Supercritical physical foaming uses supercritical fluids such as CO2 and N2 that have been treated with high temperature and high pressure as foaming agents. The bubbles obtained by supercritical foaming technology are more uniform and the material density is lower. The process of supercritical fluid turning into gas under normal temperature and pressure conditions is a physical change, which does not involve chemical reagent residues produced by chemical reactions. It is a more environmentally friendly way to foam shoe materials.

[0006] The outsole is usually made of wear-resistant rubber or synthetic materials. Compared with traditional thermoplastic elastomer materials, rubber materials have excellent elasticity, shock absorption, wear resistance and anti-slip properties. The elasticity of rubber is essentially entropy elasticity. The conformation of the rubber molecular chain changes under the action of force. This elasticity has the characteristic of being recoverable after stretching or compression. The rubber material also has good shock absorption performance, relying on the internal friction between the entangled molecular chains to absorb impact energy. In particular, after the rubber is vulcanized, a chemically cross-linked three-dimensional network structure is formed, and the compression resistance is even better. In order to reduce the specific gravity of the rubber material, the rubber can also be foamed. At present, the industry's rubber material foaming is mainly based on chemical foaming, and there are few reports on supercritical foaming technology of rubber materials.

[0007] Chinese invention patent CN118063836B discloses a method for preparing a wear-resistant rubber foam material using a supercritical foaming process, using an EPDM rubber matrix, modifying diatomaceous earth with maleimide-based polyamide, and compounding it with the EPDM rubber matrix to prepare a wear-resistant rubber foam material using supercritical foaming technology.

[0008] Patent CN118165350B discloses a process for preparing wear-resistant rubber sole materials using supercritical foaming method, using natural rubber and epoxidized natural rubber as the matrix, and adding epoxidized polystyrene and amino-containing polyaryletherketonesulfone to form chemical crosslinks with the matrix to improve the wear resistance and anti-slip properties of the rubber foam material.

[0009] Due to the complexity of rubber material formula and foaming process, the supercritical foaming technology of rubber materials has progressed slower than the thermoplastic elastomer foaming technology. Among the currently disclosed materials, the dimensional stability, density, compression resistance, tear strength, and wear resistance and anti-slip properties of rubber foam materials still cannot meet product requirements.

[0010] Therefore, providing a foaming process that balances the density, rebound, strength, wear resistance and anti-slip properties of rubber is also important for the green environmental protection and sustainable development of rubber foam materials. Summary of the invention

[0011] Aiming at the problem of uneven chemical foaming and poor performance of rubber materials in the prior art, the present invention provides a rubber supercritical foaming material for soles and a preparation process thereof.

[0012] The technical scheme of the present invention is as follows: a rubber supercritical foaming material for soles, which comprises, by mass fraction, 50-95 parts of rubber, 5-50 parts of thermoplastic elastomer, 20-60 parts of white carbon black, 1-5 parts of flaky filler, 0.5-5 parts of active agent, 0.1-10 parts of coupling agent, 0.5-5 parts of softener, 2-5 parts of antioxidant, 3-5 parts of zinc oxide, 0.5-3 parts of stearic acid, 1-5 parts of accelerator, 0.5-3 parts of sulfur and 0.1-0.5 parts of bridging agent, wherein the sum of the mass fractions of rubber and thermoplastic elastomer is 100 parts.

[0013] Furthermore, the rubber is at least one of natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, nitrile rubber, carboxylated nitrile rubber, butyl rubber, chlorosulfonated polyethylene rubber, and ethylene-propylene-diene rubber.

[0014] Furthermore, the thermoplastic elastomer is at least one of styrene-based thermoplastic elastomers SBS, SEBS, SEPS, SIS, polyolefin elastomers POE, OBC, and ethylene-vinyl acetate, and the melt index is 0.1 to 10 g / 10 min.

[0015] Furthermore, the white carbon black is at least one of precipitated white carbon black and fumed white carbon black, and the white carbon black has a specific surface area of ​​100-250m 2 / g.

[0016] Furthermore, the flaky filler is at least one of montmorillonite, hydrotalcite, graphene, and boron nitride, and the thickness of the flaky filler is 1-10 nm.

[0017] Furthermore, the coupling agent is at least one of 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, γ-mercaptopropylethoxybis-(propyl-hexaethoxysiloxane), 3-octanoylthiopropyltriethoxysilane, bis-[γ-(triethoxysilyl)propyl]tetrasulfide, and bis-[3-(triethoxysilyl)propyl]-disulfide.

[0018] Furthermore, the active agent is at least one of diethylene glycol, polyethylene glycol, and triethanolamine;.

[0019] Furthermore, the softener is at least one of cyclohexane oil, paraffin oil, and petroleum resin; the antioxidant is at least one of antioxidant 1010, antioxidant 1076, antioxidant 264, antioxidant SP, antioxidant MB, antioxidant 168, and antioxidant DSPT.

[0020] Furthermore, the accelerator is at least one of accelerator M, accelerator DM, accelerator NS, accelerator NOBS, accelerator TBzTD, and accelerator DPG; and the bridging agent is at least one of diisopropylbenzene peroxide, di-tert-butyl peroxide diisopropylbenzene, trimethylolpropane trimethacrylate, and triallyl isocyanurate.

[0021] The present invention also provides a preparation process of a rubber supercritical foaming material for soles, which is used to prepare the above-mentioned rubber supercritical foaming material for soles, comprising the following steps:

[0022] S1. Preparation of rubber compound

[0023] S11, setting the temperature of the internal mixer to 80-100°C, putting the rubber and thermoplastic elastomer into the internal mixer and mixing for 2 minutes, then adding white carbon black, flaky filler, coupling agent and activator in batches and mixing for 2-5 minutes, then adding zinc oxide, stearic acid, antioxidant and softener and mixing for 2-5 minutes, and when the temperature of the rubber material reaches 120-150°C, the rubber is discharged, and the sheet is discharged by an open mixer, and the sheet is parked for 24 hours to obtain a mixed rubber sheet;

[0024] S12, adding accelerator, sulfur and bridging agent to the first mixed rubber sheet by using an open mixing mill, and mixing evenly to obtain the second final mixed rubber sheet;

[0025] S13, cutting the test piece to the corresponding size and keeping it aside for later use;

[0026] S2. Preparation of rubber supercritical foaming material

[0027] S21, pre-vulcanizing the test piece obtained in S13 on a flat vulcanizer or a drum vulcanizer, the vulcanization temperature is 110-150° C., the vulcanization time is 3-30 min, and a pre-vulcanized sample is obtained;

[0028] S22, putting the pre-vulcanized sample prepared in S21 into a supercritical foaming kettle, setting the temperature in the kettle to 50-100°C, and after the temperature reaches the set temperature and stabilizes, introducing N2 or CO2 or a mixture of the two into the supercritical foaming kettle, adjusting the gas pressure in the kettle to 10-50MPa, and when the gas in the kettle is in a supercritical state, maintaining a constant temperature and pressure for 0.1-3 hours, opening the pressure relief valve to release the pressure to normal pressure, opening the supercritical foaming kettle to take out the sample, and cooling it to room temperature to obtain a foamed rubber material;

[0029] S23, transferring the foamed rubber material obtained in S22 to a vulcanizing tank, an oven or a hot pressing molding device to continue secondary vulcanization and shaping, the vulcanization temperature is 130-180°C, the vulcanization time is 5-30min, and after the sample is cooled, a shaped supercritical rubber foam material is obtained.

[0030] The advantages of the present invention are: in terms of material matrix selection, the high molecular weight rubber component provides entropy elasticity, and the high modulus thermoplastic elastomer component with crystalline characteristics controls the size of the material sample after foaming, provides effective support for the bubbles, maintains the light weight and low density characteristics of the foamed rubber, and controls the shrinkage of the sample; through blending, a uniform dispersion system of rubber / thermoplastic elastomer is formed at the matrix level.

[0031] In the formulation system, an in-situ modification method is adopted to prepare coupling agent-modified functionalized silica / flaky filler. Through mechanical blending, a strong interface bonding effect is formed between the filler system and the polymer chain, which provides a certain rigidity and strength for the material and improves the supporting capacity of the pore structure.

[0032] In terms of the foaming method, the supercritical gas is fully dissolved in the polymer matrix, and the introduced silica particles promote the heterogeneous nucleation of the supercritical gas, increase the cell density, and give the material a lighter performance characteristic. Through the combination of material matrix-formulation system-foaming method, the prepared rubber supercritical foaming material meets the performance requirements of lightweight, soft elasticity, wear resistance and anti-slip of the sole. The supercritical foaming process is located between the two vulcanization processes of the matrix, and the final vulcanization shaping also provides better dimensional stability for the rubber supercritical foaming material. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] The rubber supercritical foaming material for soles of the present invention selects a blending system of rubber and thermoplastic elastomer as a matrix, adopts high elastic rubber and thermoplastic elastomer to blend to form a uniform dispersion system, selects low-cost white carbon black and a small amount of flaky fillers as fillers, forms a hybrid composite filler through in-situ modification, improves the uniform dispersion of filler particles in the rubber matrix, and improves the interface strength between the inorganic component and the rubber matrix. Auxiliary agents such as activators, coupling agents, antioxidants, softeners, zinc oxide, stearic acid, accelerators, sulfur, and bridging agents are also added.

[0035] Specifically, the rubber supercritical foaming material for soles includes, by mass fraction, 50-95 parts of rubber, 5-50 parts of thermoplastic elastomer, 20-60 parts of white carbon black, 1-5 parts of flaky filler, 0.5-5 parts of active agent, 0.1-10 parts of silane coupling agent, 0.5-5 parts of softener, 2-5 parts of antioxidant, 3-5 parts of zinc oxide, 0.5-3 parts of stearic acid, 1-5 parts of accelerator, 0.5-3 parts of sulfur, and 0.1-0.5 parts of bridging agent, wherein the sum of the mass parts of rubber and thermoplastic elastomer is 100 parts.

[0036] The rubber is at least one of natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, nitrile rubber, carboxylated nitrile rubber, butyl rubber, chlorosulfonated polyethylene rubber, and EPDM rubber. The thermoplastic elastomer is at least one of styrene thermoplastic elastomers SBS, SEBS, SEPS, SIS, polyolefin elastomers POE, OBC, and ethylene-vinyl acetate, and the melt index is 0.1 to 10 g / 10 min (2.16 kg @ 190°C).

[0037] The white carbon black is at least one of precipitated white carbon black and fumed white carbon black, with a specific surface area (BET method) of 100-250m 2 / g. The flaky filler is at least one of montmorillonite, hydrotalcite, graphene and boron nitride, and the thickness of the flaky filler is 1-10nm.

[0038] The active agent is at least one of diethylene glycol, polyethylene glycol, and triethanolamine. The coupling agent is at least one of 3-mercaptopropyl trimethoxysilane, 3-mercaptopropyl triethoxysilane, γ-mercaptopropyl ethoxybis-(propyl-hexaethoxysiloxane), 3-octanoylthiopropyl triethoxysilane, bis-[γ-(triethoxysilyl)propyl] tetrasulfide, and bis-[3-(triethoxysilyl)propyl]-disulfide. The softener is at least one of cyclohexane oil, paraffin oil, and petroleum resin. The antioxidant is at least one of antioxidant 1010, antioxidant 1076, antioxidant 264, antioxidant SP, antioxidant MB, antioxidant 168, and antioxidant DSPT. The promoter is at least one of promoter M, promoter DM, promoter NS, promoter NOBS, promoter TBzTD, and promoter DPG. The bridging agent is at least one of diisopropylbenzene peroxide, di-tert-butyl diisopropylbenzene peroxide, trimethylolpropane trimethacrylate, and triallyl isocyanurate.

[0039] The above-mentioned different rubbers and thermoplastic elastomers are selected to synergistically play their respective advantages. The high molecular weight rubber component provides entropy elasticity, and the thermoplastic elastomer component controls the size of the foamed material sample with its high modulus with crystalline characteristics, providing effective support for the bubbles; thereby improving the elasticity, wear resistance and anti-slip properties of the material, and combining the filler modification method and compounding method to strengthen the filler dispersion, ensuring processability in terms of compatibility and melt strength.

[0040] The present invention also provides a preparation process of the above-mentioned supercritical rubber foaming material, comprising the following steps:

[0041] S1. Preparation of rubber compound

[0042] S11, setting the temperature of the internal mixer to 80-100°C, putting the rubber and thermoplastic elastomer into the internal mixer and mixing for 2 minutes, then adding white carbon black, flaky filler, coupling agent and activator in batches and mixing for 2-5 minutes, then adding zinc oxide, stearic acid, antioxidant and softener and mixing for 2-5 minutes, and when the temperature of the rubber material reaches 120-150°C, the rubber is discharged, and the sheet is discharged by an open mixer, and the sheet is parked for 24 hours to obtain a mixed rubber sheet;

[0043] S12, adding accelerator, sulfur and bridging agent to the first mixed rubber sheet by using an open mixing mill, and mixing evenly to obtain the second final mixed rubber sheet;

[0044] S13. Cut the test pieces to the corresponding size according to the performance test standards and keep them aside for later use.

[0045] S2. Preparation of rubber supercritical foaming material

[0046] S21, pre-vulcanizing the test piece obtained in S13 on a flat vulcanizer or a drum vulcanizer, the vulcanization temperature is 110-150° C., the vulcanization time is 3-30 min, and a pre-vulcanized sample is obtained;

[0047] S22. Place the pre-vulcanized sample prepared in S21 into a supercritical foaming kettle, set the temperature in the kettle to 50-100°C, and after the temperature reaches the set temperature and stabilizes, introduce N2 or CO2 or a mixture of the two into the supercritical foaming kettle, and adjust the gas pressure in the kettle to 10-50MPa. When the gas in the kettle is in a supercritical state, maintain a constant temperature and pressure for 0.1-3 hours, then quickly open the pressure relief valve to release the pressure to normal pressure, quickly open the supercritical foaming kettle to take out the sample, and after cooling to room temperature, obtain a foamed rubber material.

[0048] S23, transferring the foamed rubber material obtained in S22 to a vulcanizing tank, an oven or a hot pressing molding device to continue secondary vulcanization and shaping, the vulcanization temperature is 130-180°C, the vulcanization time is 5-30min, and after the sample is cooled, a shaped supercritical rubber foam material is obtained.

[0049] In the above preparation process, the rubber compound preparation process adopts an in-situ modification method to prepare a coupling agent-modified functional reinforced silica / flaky filler. Through mechanical blending with the matrix, a strong interface bonding effect is formed between the filler system and the polymer chain, providing a certain rigidity and strength for the matrix and improving the support of the pore structure. In the supercritical foaming process, the supercritical gas is fully dissolved in the matrix, and the inorganic nanoparticles introduced in the filler system promote the heterogeneous nucleation of the supercritical gas and increase the pore density. The supercritical foaming process is located between the two vulcanization processes of the matrix. The final vulcanization setting provides better dimensional stability for the rubber supercritical foaming material, meeting the demand for soft elasticity of the sole.

[0050] The technical solution of the present invention is further described clearly and completely below in conjunction with several groups of specific embodiments.

[0051] Example 1

[0052] The rubber supercritical foaming material for soles includes, by mass fraction, 50 parts of natural rubber, 10 parts of carboxylated nitrile rubber, 30 parts of butadiene rubber, 5 parts of ethylene-vinyl acetate copolymer (melting index 4g / 10min (2.16kg@190℃)), 5 parts of ethylene-octene block copolymer OBC (melting index 0.5g / 10min (2.16kg@190℃)), 5 parts of precipitated silica (specific surface area 150m 2 / g) 30 parts, montmorillonite flaky filler (thickness of 5nm) 3 parts, polyethylene glycol 2 parts, 3-mercaptopropyltrimethoxysilane 3 parts, cyclohexane oil 1 part, antioxidant 1010 2 parts, antioxidant 1076 3 parts, zinc oxide 3 parts, stearic acid 1 part, accelerator M 1 part, accelerator DM 1 part, accelerator TBzTD 0.5 parts, sulfur 2 parts, dicumyl peroxide 0.3 parts, wherein the sum of the mass parts of natural rubber, carboxylated nitrile rubber, butadiene rubber, ethylene-vinyl acetate copolymer, and ethylene-octene block copolymer OBC is 100 parts.

[0053] The preparation process of the above-mentioned supercritical rubber foaming material comprises the following steps:

[0054] S1. Preparation of rubber compound

[0055] S11, setting the temperature of the internal mixer to 80°C, putting the rubber and thermoplastic elastomer into the internal mixer and mixing for 2 minutes, then adding white carbon black, flaky filler, coupling agent and activator in batches and mixing for 2 minutes, then adding zinc oxide, stearic acid, antioxidant and softener and mixing for 2 minutes, and when the temperature of the rubber material reaches 150°C, the rubber is discharged, and the sheet is discharged by an open mixer, and the sheet is parked for 24 hours to obtain a mixed rubber sheet;

[0056] S12, adding accelerator, sulfur and bridging agent to the first mixed rubber sheet by using an open mixing mill, and mixing evenly to obtain the second final mixed rubber sheet;

[0057] S13. Cut the test pieces to the corresponding size according to the performance test standards and keep them aside for later use.

[0058] S2. Preparation of rubber supercritical foaming material

[0059] S21, pre-vulcanizing the test piece obtained in S13 on a flat vulcanizer or a drum vulcanizer, with the vulcanization temperature being 110° C. and the vulcanization time being 30 min to obtain a pre-vulcanized sample;

[0060] S22. Place the pre-vulcanized sample prepared in S21 into a supercritical foaming kettle, set the temperature in the kettle to 60°C, and after the temperature reaches the set temperature and stabilizes, introduce N2 or CO2 or a mixture of the two into the supercritical foaming kettle, and adjust the gas pressure in the kettle to 50MPa. When the gas in the kettle is in a supercritical state, maintain constant temperature and pressure for 0.1 hour, then quickly open the pressure relief valve to release the pressure to normal pressure, quickly open the supercritical foaming kettle to take out the sample, and after cooling to room temperature, obtain a foamed rubber material.

[0061] S23. Transfer the foamed rubber material obtained in S22 to a vulcanizing tank, an oven or a hot pressing molding device for further secondary vulcanization and shaping. The vulcanization temperature is 150° C. and the vulcanization time is 20 min. After the sample is cooled, a shaped supercritical rubber foam material is obtained.

[0062] Comparative Example 1

[0063] The rubber supercritical foaming materials include: 50 parts of natural rubber, 10 parts of carboxylated nitrile rubber, 30 parts of butadiene rubber, precipitated silica (specific surface area 150m 2 / g) 30 parts, montmorillonite flaky filler (thickness of 5nm) 3 parts, polyethylene glycol 2 parts, 3-mercaptopropyltrimethoxysilane 3 parts, cyclohexane oil 1 part, antioxidant 1010 2 parts, antioxidant 1076 3 parts, zinc oxide 3 parts, stearic acid 1 part, accelerator M 1 part, accelerator DM 1 part, accelerator TBzTD 0.5 parts, sulfur 2 parts, diisopropyl peroxide 0.3 parts, wherein the sum of the mass parts of natural rubber, carboxyl nitrile rubber, and butadiene rubber is 90 parts.

[0064] Compared with the rubber supercritical foaming material in Example 1, no thermoplastic elastomer is added.

[0065] The preparation process of the above-mentioned supercritical rubber foaming material comprises the following steps:

[0066] S1. Preparation of rubber compound

[0067] S11, setting the temperature of the internal mixer to 80°C, putting the rubber into the internal mixer and mixing for 2 minutes, then adding white carbon black, flaky filler, coupling agent, and activator in batches and mixing for 2 minutes, then adding zinc oxide, stearic acid, antioxidant, and softener and mixing for 2 minutes, and when the temperature of the rubber material reaches 150°C, the rubber is discharged, and the sheet is discharged by an open mixer, and the sheet is parked for standby for 24 hours to obtain a mixed rubber sheet;

[0068] The remaining steps are the same as in Example 1.

[0069] Example 2

[0070] The rubber supercritical foaming materials include, by mass fraction, 10 parts of natural rubber, 20 parts of nitrile rubber, 20 parts of butadiene rubber, 20 parts of ethylene-vinyl acetate copolymer (melting index 2g / 10min (2.16kg@190℃)), 10 parts of styrene thermoplastic elastomer SEBS (melting index 0.1g / 10min (2.16kg@190℃)), 20 parts of ethylene-octene random copolymer POE (melting index 3g / 10min (2.16kg@190℃)), precipitated silica (specific surface area 100m 2 / g) 20 parts, hydrotalcite flake filler (thickness of 5nm) 5 parts, diethylene glycol 0.5 parts, 3-mercaptopropyltriethoxysilane 0.1 parts, paraffin oil 0.5 parts, antioxidant 264 is 1 part, antioxidant SP is 1 part, zinc oxide 5 parts, stearic acid 0.5 parts, accelerator M is 1 part, accelerator NS is 0.5 parts, accelerator DPG is 0.5 parts, sulfur 3 parts, di-tert-butyl peroxide diisopropylbenzene 0.5 parts, wherein the sum of the mass parts of natural rubber, nitrile rubber, butadiene rubber, ethylene-vinyl acetate copolymer, styrene thermoplastic elastomer SEBS, and ethylene-octene random copolymer POE is 100 parts.

[0071] The preparation process of the above-mentioned supercritical rubber foaming material comprises the following steps:

[0072] S1. Preparation of rubber compound

[0073] S11, setting the temperature of the internal mixer to 90°C, putting the rubber and thermoplastic elastomer into the internal mixer and mixing for 2 minutes, then adding white carbon black, flaky filler, coupling agent and activator in batches and mixing for 5 minutes, then adding zinc oxide, stearic acid, antioxidant and softener and mixing for 5 minutes, and when the temperature of the rubber material reaches 120°C, the rubber is discharged, and the sheet is discharged by an open mixer, and the sheet is parked for standby for 24 hours to obtain a mixed rubber sheet;

[0074] S12, adding accelerator, sulfur and bridging agent to the first mixed rubber sheet by using an open mixing mill, and mixing evenly to obtain the second final mixed rubber sheet;

[0075] S13. Cut the test pieces to the corresponding size according to the performance test standards and keep them aside for later use.

[0076] S2. Preparation of rubber supercritical foaming material

[0077] S21, pre-vulcanizing the test piece obtained in S13 on a flat vulcanizer or a drum vulcanizer, the vulcanization temperature is 150° C., the vulcanization time is 3 min, and a pre-vulcanized sample is obtained;

[0078] S22. Place the pre-vulcanized sample prepared in S1 into a supercritical foaming kettle, set the temperature in the kettle to 80°C, and after the temperature reaches the set temperature and stabilizes, introduce N2 or CO2 or a mixture of the two into the supercritical foaming kettle, and adjust the gas pressure in the kettle to 15MPa. When the gas in the kettle is in a supercritical state, maintain constant temperature and pressure for 2 hours, then quickly open the pressure relief valve to release the pressure to normal pressure, quickly open the supercritical foaming kettle to take out the sample, and after cooling to room temperature, obtain the foamed rubber material.

[0079] S23. Transfer the foamed rubber material obtained in S22 to a vulcanizing tank, an oven or a hot pressing molding device for further secondary vulcanization and shaping. The vulcanization temperature is 160° C. and the vulcanization time is 30 min. After the sample is cooled, a shaped supercritical rubber foam material is obtained.

[0080] Comparative Example 2

[0081] The supercritical foaming materials include, by mass fraction: ethylene-vinyl acetate copolymer (melting index 2g / 10min (2.16kg@190℃)) 20 parts, styrene thermoplastic elastomer SEBS (melting index 0.1g / 10min (2.16kg@190℃)) 10 parts, ethylene-octene random copolymer POE (melting index 3g / 10min (2.16kg@190℃)) 20 parts, precipitated silica (specific surface area 100m 2 / g) 20 parts, hydrotalcite flake filler (thickness of 5nm) 5 parts, diethylene glycol 0.5 parts, 3-mercaptopropyltriethoxysilane 0.1 parts, paraffin oil 0.5 parts, antioxidant 264 is 1 part, antioxidant SP is 1 part, zinc oxide 5 parts, stearic acid 0.5 parts, accelerator M is 1 part, accelerator NS is 0.5 parts, accelerator DPG is 0.5 parts, sulfur 3 parts, di-tert-butyl peroxide diisopropylbenzene 0.5 parts, wherein the sum of the mass parts of ethylene-vinyl acetate, styrene-based thermoplastic elastomer SEBS, and ethylene-octene random copolymer POE is 50 parts.

[0082] Compared with the rubber supercritical foaming material in Example 2, no rubber is added.

[0083] The preparation process of the supercritical foaming material comprises the following steps:

[0084] S1. Preparation of rubber compound

[0085] S11, setting the temperature of the internal mixer to 90°C, putting the thermoplastic elastomer into the internal mixer and mixing for 2 minutes, then adding white carbon black, flaky filler, coupling agent, and activator in batches and mixing for 5 minutes, then adding zinc oxide, stearic acid, antioxidant, and softener and mixing for 5 minutes, and when the temperature of the rubber material reaches 120°C, the rubber is discharged, and the sheet is discharged by an open mixer, and the sheet is parked for standby for 24 hours to obtain a mixed rubber sheet;

[0086] The remaining steps are the same as in Example 2.

[0087] Example 3

[0088] The rubber supercritical foaming material includes, by mass fraction, 30 parts of natural rubber, 20 parts of styrene-butadiene rubber, 20 parts of butadiene rubber, 5 parts of ethylene-vinyl acetate copolymer (melting index 7g / 10min (2.16kg@190℃)), 5 parts of styrene thermoplastic elastomer SBS (melting index 0.5g / 10min (2.16kg@190℃)), 5 parts of styrene thermoplastic elastomer SIS (melting index 3g / 10min (2.16kg@190℃)), 15 parts of ethylene-octene random copolymer POE (melting index 5g / 10min (2.16kg@190℃)), fumed silica (specific surface area 250m 2 / g) 30 parts, graphene flake filler (thickness of 1nm) 1 part, triethanolamine 5 parts, γ-mercaptopropylethoxybis-(propyl-hexaethoxysiloxane) 10 parts, petroleum resin 3 parts, antioxidant MB 2 parts, antioxidant 168 2 parts, zinc oxide 5 parts, stearic acid 1 part, accelerator NOBS 1.5 parts, accelerator TBzTD 0.2 parts, accelerator DPG 0.5 parts, sulfur 2 parts, trimethylolpropane trimethacrylate 0.4 parts, wherein the sum of the mass parts of natural rubber, styrene-butadiene rubber, butadiene rubber, ethylene-vinyl acetate copolymer, styrene thermoplastic elastomer SBS, SIS, and ethylene-octene random copolymer POE is 100 parts.

[0089] The preparation process of the above-mentioned supercritical rubber foaming material comprises the following steps:

[0090] S1. Preparation of rubber compound

[0091] S11, setting the temperature of the internal mixer to 100°C, putting the rubber and thermoplastic elastomer into the internal mixer and mixing for 2 minutes, then adding white carbon black, flaky filler, coupling agent and activator in batches and mixing for 5 minutes, then adding zinc oxide, stearic acid, antioxidant and softener and mixing for 3 minutes, and when the temperature of the rubber material reaches 140°C, the rubber is discharged, and the sheet is discharged by an open mixer, and the sheet is parked for standby for 24 hours to obtain a mixed rubber sheet;

[0092] S12, adding accelerator, sulfur and bridging agent to the first mixed rubber sheet by using an open mixing mill, and mixing evenly to obtain the second final mixed rubber sheet;

[0093] S13. Cut the test pieces to the corresponding size according to the performance test standards and keep them aside for later use.

[0094] S2. Preparation of rubber supercritical foaming material

[0095] S21, pre-vulcanizing the test piece obtained in S13 on a flat vulcanizer or a drum vulcanizer at a vulcanization temperature of 130° C. for 5 min to obtain a pre-vulcanized sample;

[0096] S22. Place the pre-vulcanized sample prepared in S1 into a supercritical foaming kettle, set the temperature in the kettle to 90°C, and after the temperature reaches the set temperature and stabilizes, introduce N2 or CO2 or a mixture of the two into the supercritical foaming kettle, and adjust the gas pressure in the kettle to 20MPa. When the gas in the kettle is in a supercritical state, maintain constant temperature and pressure for 1 hour, then quickly open the pressure relief valve to release the pressure to normal pressure, quickly open the supercritical foaming kettle to take out the sample, and after cooling to room temperature, obtain the foamed rubber material.

[0097] S23. The foamed rubber material obtained in S22 is transferred to a vulcanizing tank, an oven or a hot pressing molding device for further secondary vulcanization and shaping. The vulcanization temperature is 180° C. and the vulcanization time is 5 min. After the sample is cooled, a shaped supercritical rubber foam material is obtained.

[0098] Comparative Example 3

[0099] The rubber supercritical foaming material includes, by mass fraction, 30 parts of natural rubber, 20 parts of styrene-butadiene rubber, 20 parts of butadiene rubber, 5 parts of ethylene-vinyl acetate copolymer (melting index 7g / 10min (2.16kg@190℃)), 5 parts of styrene thermoplastic elastomer SBS (melting index 0.5g / 10min (2.16kg@190℃)), 5 parts of styrene thermoplastic elastomer SIS (melting index 3g / 10min (2.16kg@190℃)), 15 parts of ethylene-octene random copolymer POE (melting index 5g / 10min (2.16kg@190℃)), fumed silica (specific surface area 250m 2 / g) 30 parts, graphene flake filler (thickness of 1nm) 1 part, triethanolamine 5 parts, petroleum resin 3 parts, antioxidant MB 2 parts, antioxidant 168 2 parts, zinc oxide 5 parts, stearic acid 1 part, accelerator NOBS 1.5 parts, accelerator TBzTD 0.2 parts, accelerator DPG 0.5 parts, sulfur 2 parts, trimethylolpropane trimethacrylate 0.4 parts, wherein the sum of the mass parts of natural rubber, styrene-butadiene rubber, butadiene rubber, ethylene-vinyl acetate copolymer, styrene thermoplastic elastomer SBS, SIS, and ethylene-octene random copolymer POE is 100 parts.

[0100] Compared with the rubber supercritical foaming material in Example 3, no coupling agent is added.

[0101] The preparation process of the above-mentioned supercritical rubber foaming material comprises the following steps:

[0102] S1. Preparation of rubber compound

[0103] S11, setting the temperature of the internal mixer to 100°C, putting the rubber and thermoplastic elastomer into the internal mixer and mixing for 2 minutes, then adding white carbon black, flaky filler and activator in batches and mixing for 5 minutes, then adding zinc oxide, stearic acid, antioxidant and softener and mixing for 3 minutes, and when the temperature of the rubber material reaches 140°C, the rubber is discharged, and the sheet is discharged by an open mixer, and the sheet is parked for standby for 24 hours to obtain a mixed rubber sheet;

[0104] The remaining steps are the same as in Example 3.

[0105] Comparative Example 4

[0106] The rubber supercritical foaming material includes, by mass fraction, 30 parts of natural rubber, 20 parts of styrene-butadiene rubber, 20 parts of butadiene rubber, 5 parts of ethylene-vinyl acetate copolymer (melting index 7g / 10min (2.16kg@190℃)), 5 parts of styrene thermoplastic elastomer SBS (melting index 0.5g / 10min (2.16kg@190℃)), 5 parts of styrene thermoplastic elastomer SIS (melting index 3g / 10min (2.16kg@190℃)), 15 parts of ethylene-octene random copolymer POE (melting index 5g / 10min (2.16kg@190℃)), fumed silica (specific surface area 250m 2 / g) 30 parts, triethanolamine 5 parts, γ-mercaptopropylethoxybis-(propyl-hexaethoxysiloxane) 10 parts, petroleum resin 3 parts, antioxidant MB 2 parts, antioxidant 168 2 parts, zinc oxide 5 parts, stearic acid 1 part, accelerator NOBS 1.5 parts, accelerator TBzTD 0.2 parts, accelerator DPG 0.5 parts, sulfur 2 parts, trimethylolpropane trimethacrylate 0.4 parts, wherein the sum of the mass parts of natural rubber, styrene-butadiene rubber, butadiene rubber, ethylene-vinyl acetate copolymer, styrene thermoplastic elastomer SBS, SIS, and ethylene-octene random copolymer POE is 100 parts.

[0107] Compared with the rubber supercritical foaming material in Example 3, no flake filler is added.

[0108] The preparation process of the above-mentioned supercritical rubber foaming material comprises the following steps:

[0109] S1. Preparation of rubber compound

[0110] S11, setting the temperature of the internal mixer to 100°C, putting the rubber and thermoplastic elastomer into the internal mixer and mixing for 2 minutes, then adding white carbon black, coupling agent and activator in batches and mixing for 5 minutes, then adding zinc oxide, stearic acid, antioxidant and softener and mixing for 3 minutes, and when the temperature of the rubber material reaches 140°C, the rubber is discharged, and the sheet is discharged by an open mixer, and the sheet is parked for 24 hours to obtain a mixed rubber sheet;

[0111] The remaining steps are the same as in Example 3.

[0112] Example 4

[0113] The rubber supercritical foaming material includes, by mass fraction, 50 parts of natural rubber, 10 parts of butyl rubber, 10 parts of chlorosulfonated polyethylene rubber, 10 parts of styrene thermoplastic elastomer SEPS (melting index 8g / 10min (2.16kg@190℃)), 10 parts of ethylene-octene block copolymer OBC (melting index 2g / 10min (2.16kg@190℃)), 10 parts of ethylene-octene random copolymer POE (melting index 1.5g / 10min (2.16kg@190℃)), 10 parts of precipitated silica (specific surface area 180m 2 / g) 60 parts, boron nitride flake filler (thickness of 3nm) 2 parts, triethanolamine 3 parts, 3-octanoylthiopropyl triethoxysilane 8 parts, cyclohexane oil 2 parts, antioxidant MB 2 parts, antioxidant 168 2 parts, antioxidant DSPT 1 part, zinc oxide 5 parts, stearic acid 1 part, accelerator NOBS 1.5 parts, accelerator TBzTD 0.2 parts, accelerator DPG 3 parts, sulfur 1 part, triallyl isocyanurate 0.2 parts, wherein the sum of the mass parts of natural rubber, butyl rubber, chlorosulfonated polyethylene rubber, styrene thermoplastic elastomer SEPS, polyolefin elastomer OBC, and POE is 100 parts.

[0114] The preparation process of the above-mentioned supercritical rubber foaming material comprises the following steps:

[0115] S1. Preparation of rubber compound

[0116] S11, setting the temperature of the internal mixer to 80°C, putting the rubber and thermoplastic elastomer into the internal mixer and mixing for 2 minutes, then adding white carbon black, flaky filler, coupling agent and activator in batches and mixing for 3 minutes, then adding zinc oxide, stearic acid, antioxidant and softener and mixing for 3 minutes, and when the temperature of the rubber material reaches 140°C, the rubber is discharged, and the sheet is discharged by an open mixer, and the sheet is parked for standby for 24 hours to obtain a mixed rubber sheet;

[0117] S12, adding accelerator, sulfur and bridging agent to the first mixed rubber sheet by using an open mixing mill, and mixing evenly to obtain the second final mixed rubber sheet;

[0118] S13. Cut the test pieces to the corresponding size according to the performance test standards and keep them aside for later use.

[0119] S2. Preparation of rubber supercritical foaming material

[0120] S21, pre-vulcanizing the test piece obtained in S13 on a flat vulcanizer or a drum vulcanizer, with the vulcanization temperature being 140° C. and the vulcanization time being 10 min to obtain a pre-vulcanized sample;

[0121] S22. Place the pre-vulcanized sample prepared in S1 into a supercritical foaming kettle, set the temperature in the kettle to 70°C, and after the temperature reaches the set temperature and stabilizes, introduce N2 or CO2 or a mixture of the two into the supercritical foaming kettle, and adjust the gas pressure in the kettle to 25MPa. When the gas in the kettle is in a supercritical state, maintain constant temperature and pressure for 1.5 hours, then quickly open the pressure relief valve to release the pressure to normal pressure, quickly open the supercritical foaming kettle to take out the sample, and after cooling to room temperature, obtain the foamed rubber material.

[0122] S23. Transfer the foamed rubber material obtained in S22 to a vulcanizing tank, an oven or a hot pressing molding device for further secondary vulcanization and shaping. The vulcanization temperature is 140° C. and the vulcanization time is 20 min. After the sample is cooled, a shaped supercritical rubber foam material is obtained.

[0123] The properties of the rubber supercritical foaming materials of Examples 1-4 and Comparative Examples 1-4 are as follows:

[0124] Table 1 Performance of various embodiments and comparative examples of rubber supercritical foaming materials

[0125]

[0126]

[0127] Note: Density test corresponds to GB / T 533-2008, resilience test corresponds to GB / T 2009, DIN abrasion test corresponds to GB / T 9867-2008, Akron abrasion test corresponds to GB / T 1689-2014, anti-slip performance test corresponds to GB / T3903.6-2017, hardness test corresponds to GB / T 533.1-2008, tensile strength and elongation at break test correspond to GB / T528-2009, tear strength test corresponds to GB / T 529-2009. All tests of the present invention adopt GB / T series, which can comprehensively reflect the performance of various indicators of the sole.

[0128] From the performance of the above embodiments and comparative examples, it can be seen that the density, elasticity, strength, wear resistance, anti-slip properties and other properties of the rubber supercritical foaming material are related to the rubber matrix, the type of thermoplastic elastomer, the dispersion of the silica reinforcing filler and the silica-rubber interface.

[0129] Comparing Example 1 with Comparative Example 1, it can be seen that the type and amount of thermoplastic elastomer affect the performance of the foamed material. The thermoplastic elastomer has certain crystallization characteristics. After blending with the rubber matrix, it is beneficial to the shaping of the foamed material, controls the shrinkage of the sample, improves the elasticity of the foamed material, and reduces the material density.

[0130] By comparing Example 2 with Comparative Example 2, it can be seen that the type and amount of the rubber matrix affect the performance of the foamed material. The rubber matrix has a higher molecular weight, forms more complex entanglements between molecules, and the rubber material has stronger entropy elasticity. The combined use and blending of rubber and thermoplastic elastomer materials is beneficial to improving the foaming ratio of the rubber material and improving the elasticity of the foamed material.

[0131] Comparison of Example 3 with Comparative Examples 3 and 4 further verifies the technical advantages of in-situ chemical modification of coupling agents and the coordinated use of multiple fillers. The performance improvement of the system without coupling agent modification and filler combination is limited. The present invention relies on chemical modification of coupling agents to form chemical grafting, and then relies on the spatial physical isolation between the flaky filler and the spherical white carbon black particles to enhance the interface effect between white carbon black and the rubber matrix. The white carbon black particles are evenly dispersed in the rubber matrix, which has a positive effect on improving the strength, wear resistance and anti-slip performance of the rubber material.

[0132] The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment, it is not used to limit the present invention. Any technician familiar with this patent can make some changes or modify the technical contents suggested above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the solution of the present invention.

Claims

1. A supercritical foamed rubber material for soles, characterized in that: The components by mass fraction include: 50-95 parts of rubber, 5-50 parts of thermoplastic elastomer, 20-60 parts of white carbon black, 1-5 parts of flaky filler, 0.5-5 parts of activator, 0.1-10 parts of coupling agent, 0.5-5 parts of softener, 2-5 parts of antioxidant, 3-5 parts of zinc oxide, 0.5-3 parts of stearic acid, 1-5 parts of accelerator, 0.5-3 parts of sulfur and 0.1-0.5 parts of bridging agent, wherein the sum of the mass parts of rubber and thermoplastic elastomer is 100 parts.

2. The supercritical foamed rubber material for soles according to claim 1, characterized in that: The rubber is at least one of natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, nitrile rubber, carboxylated nitrile rubber, butyl rubber, chlorosulfonated polyethylene rubber, and ethylene-propylene-diene rubber.

3. The supercritical foamed rubber material for soles according to claim 1, characterized in that: The thermoplastic elastomer is at least one of styrene-based thermoplastic elastomers SBS, SEBS, SEPS, SIS, polyolefin elastomers POE, OBC, and ethylene-vinyl acetate, and has a melt index of 0.1 to 10 g / 10 min.

4. The supercritical foamed rubber material for soles according to claim 1, characterized in that: The white carbon black is at least one of precipitated white carbon black and fumed white carbon black, and the white carbon black has a specific surface area of ​​100-250m 2 / g.

5. The supercritical foamed rubber material for soles according to claim 1, characterized in that: The flaky filler is at least one of montmorillonite, hydrotalcite, graphene and boron nitride, and the thickness of the flaky filler is 1-10 nm.

6. The supercritical foamed rubber material for soles according to claim 1, characterized in that: The coupling agent is at least one of 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, γ-mercaptopropylethoxybis-(propyl-hexaethoxysiloxane), 3-octanoylthiopropyltriethoxysilane, bis-[γ-(triethoxysilyl)propyl]tetrasulfide, and bis-[3-(triethoxysilyl)propyl]-disulfide.

7. The supercritical foamed rubber material for soles according to claim 1, characterized in that: The active agent is at least one of diethylene glycol, polyethylene glycol and triethanolamine.

8. The supercritical foamed rubber material for soles according to any one of claims 1 to 7, characterized in that: The softener is at least one of cyclohexane oil, paraffin oil and petroleum resin; the antioxidant is at least one of antioxidant 1010, antioxidant 1076, antioxidant 264, antioxidant SP, antioxidant MB, antioxidant 168 and antioxidant DSPT.

9. The supercritical foamed rubber material for soles according to any one of claims 1 to 7, characterized in that: The accelerator is at least one of accelerator M, accelerator DM, accelerator NS, accelerator NOBS, accelerator TBzTD, and accelerator DPG; the bridging agent is at least one of diisopropylbenzene peroxide, di-tert-butyl diisopropylbenzene peroxide, trimethylolpropane trimethacrylate, and triallyl isocyanurate.

10. A process for preparing a rubber supercritical foaming material for shoe soles, characterized in that: The method for preparing the supercritical foamed rubber material for soles as claimed in any one of claims 1 to 9 comprises the following steps: S1. Preparation of rubber compound S11, setting the temperature of the internal mixer to 80-100°C, putting the rubber and thermoplastic elastomer into the internal mixer and mixing for 2 minutes, then adding white carbon black, flaky filler, coupling agent and activator in batches and mixing for 2-5 minutes, then adding zinc oxide, stearic acid, antioxidant and softener and mixing for 2-5 minutes, and when the temperature of the rubber material reaches 120-150°C, the rubber is discharged, and the sheet is discharged by an open mixer, and the sheet is parked for 24 hours to obtain a mixed rubber sheet; S12, adding accelerator, sulfur and bridging agent to the first mixed rubber sheet by using an open mixing mill, and mixing evenly to obtain the second final mixed rubber sheet; S13, cutting the test piece to the corresponding size and keeping it aside for later use; S2. Preparation of rubber supercritical foaming material S21, pre-vulcanizing the test piece obtained in S13 on a flat vulcanizer or a drum vulcanizer, the vulcanization temperature is 110-150° C., the vulcanization time is 3-30 min, and a pre-vulcanized sample is obtained; S22, putting the pre-vulcanized sample prepared in S21 into a supercritical foaming kettle, setting the temperature in the kettle to 50-100°C, and after the temperature reaches the set temperature and stabilizes, introducing N2 or CO2 or a mixture of the two into the supercritical foaming kettle, adjusting the gas pressure in the kettle to 10-50MPa, and when the gas in the kettle is in a supercritical state, maintaining a constant temperature and pressure for 0.1-3 hours, opening the pressure relief valve to release the pressure to normal pressure, opening the supercritical foaming kettle to take out the sample, and cooling it to room temperature to obtain a foamed rubber material; S23, transferring the foamed rubber material obtained in S22 to a vulcanizing tank, an oven or a hot pressing molding device to continue secondary vulcanization and shaping, the vulcanization temperature is 130-180°C, the vulcanization time is 5-30min, and after the sample is cooled, a shaped supercritical rubber foam material is obtained.

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