High temperature resistant anti-cracking rubber material and preparation method thereof

Abstract

This invention relates to the field of rubber materials, specifically to a high-temperature resistant and crack-resistant rubber material and its preparation method. The rubber material, by weight, comprises the following components: 100 parts rubber matrix, 40-80 parts composite reinforcing filler, 3-10 parts crosslinking agent, 5-15 parts antioxidant, 3-8 parts vulcanization activator, and 2-8 parts processing aid; wherein the rubber matrix comprises hydrogenated nitrile butadiene rubber and ethylene propylene diene monomer (EPDM) rubber, with a weight ratio of 60-80:20-40. The rubber material prepared by this invention, when used as a shoe sole, meets the comfort and durability requirements of daily wear, and is also suitable for the higher requirements of abrasion resistance and damage resistance in light outdoor and work scenarios. It solves the problems of limited application scenarios and single performance of existing shoe sole materials, significantly improving the market competitiveness of shoe sole products, and has extremely high practical value and market application prospects.

Description

Technical Field

[0001] This invention relates to the field of rubber materials, specifically to a high-temperature resistant and crack-resistant rubber material and its preparation method. Background Technology

[0002] With increasing health awareness and demand for exercise, the performance requirements for footwear products such as athletic shoes and work safety shoes are becoming increasingly stringent. As the core component that directly contacts the ground and bears all dynamic loads from the human body, the sole's material properties directly determine the durability, safety, and wearing experience of the footwear. Rubber materials are widely used in sole manufacturing due to their excellent comprehensive properties, such as high elasticity, wear resistance, and slip resistance.

[0003] However, in practical use, especially in scenarios such as high-intensity sports, long-term walking, or high-temperature work environments, traditional rubber sole materials face two major challenges: dynamic fatigue cracking and thermo-oxidative aging failure. On the one hand, during walking or running, the forefoot metatarsophalangeal joint area and the outer heel area are subjected to high-frequency cyclic bending, compression, and shear stresses. This complex dynamic mechanical load easily induces micro-cracks within the material, which gradually expand with increasing use, eventually leading to through-cracks in the sole. On the other hand, during dynamic use, the internal friction of rubber molecular chains and the external friction between the sole and the ground generate significant heat accumulation. Especially in summer or during high-speed running, the internal temperature of the sole can rise rapidly. Traditional sole materials primarily composed of natural rubber (NR), styrene-butadiene rubber (SBR), or butadiene rubber (BR) experience accelerated thermo-oxidative aging. This aging not only directly weakens the material's fatigue resistance and accelerates the generation and propagation of cracks, but also causes the sole to harden, lose cushioning performance, severely affecting wearing comfort and increasing the risk of sports injuries.

[0004] Therefore, developing a rubber material specifically for shoe soles that can synergistically address the problems of thermal aging under high-temperature environments and fatigue cracking under dynamic stress, while also ensuring good processability and wearing comfort, has become a technical challenge that urgently needs to be overcome in this field. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention aims to provide a high-temperature resistant and crack-resistant rubber material and its preparation method.

[0006] The objective of this invention is achieved through the following technical solution: In a first aspect, the present invention provides a high-temperature resistant and crack-resistant rubber material, comprising the following components by weight: 100 parts rubber matrix, 40-80 parts composite reinforcing filler, 3-10 parts crosslinking agent, 5-15 parts antioxidant, 3-8 parts vulcanization activator, and 2-8 parts processing aid.

[0007] Preferably, the rubber matrix comprises hydrogenated nitrile butadiene rubber and ethylene propylene diene monomer (EPDM) rubber, wherein the weight ratio of hydrogenated nitrile butadiene rubber to EPDM rubber is 60-80:20-40.

[0008] Preferably, the hydrogenated nitrile rubber has an acrylonitrile content of 35%-40%, a degree of hydrogenation ≥98%, and a Mooney viscosity (ML1+4, 100℃) of 45-55.

[0009] Preferably, the ethylene propylene diene monomer (EPDM) rubber has an ethylene content of 55wt%-65wt%, a propylene content of 30wt%-35wt%, and a Mooney viscosity (ML1+4, 125℃) of 50-60.

[0010] The hydrogenated nitrile butadiene rubber provides excellent oil resistance and basic heat resistance, while the ethylene propylene diene monomer (EPDM) rubber has a high ethylene content, providing excellent vulcanization activity and flexibility. The combination of the two achieves a balance between molecular chain segment flexibility and heat resistance.

[0011] Preferably, the composite reinforcing filler is modified precipitated silica, and the preparation method includes: S1. Take industrial-grade sodium silicate and add deionized water to prepare a sodium silicate solution; adjust the pH to 9.0-10.0 with dilute sulfuric acid, add silane coupling agent KH-792, then add surfactant AEO-9, stir evenly, and keep warm in a water bath at 50-60℃ for 40-60 minutes to obtain a pretreated sodium silicate solution. S2. Add dilute sulfuric acid dropwise to the pretreated sodium silicate solution until the pH reaches 8.0-8.5, adjust the temperature to 50-70℃, and simultaneously add 4-acetoxybenzaldehyde solution and dilute sulfuric acid. Stop adding dilute sulfuric acid when the pH of the reaction system drops to 6.8-7.2, continue stirring the reaction for 90-120 min, and then age at 70-75℃ for 30 min to obtain a composite organic-coated modified silica suspension. S3. Vacuum filter the suspension to obtain a filter cake, wash with water until the washing liquid is neutral; vacuum dry for 4-6 hours, spray in hexamethyldisilazane, stir and passivate at room temperature, and then pulverize by airflow to obtain modified precipitated silica.

[0012] Preferably, in step S1, the sodium silicate solution has a mass concentration of 18-22%; the amount of silane coupling agent KH-792 added is 0.3-0.5% of the mass of the sodium silicate solution; and the amount of surfactant AEO-9 added is 0.1%-0.2% of the mass of the sodium silicate solution.

[0013] Preferably, in step S2, the 4-acetoxybenzaldehyde solution is a 10-12% (w / w) solution of 4-acetoxybenzaldehyde prepared with ethylene glycol dimethyl ether, and contains 2-3% (w / w) of acetic anhydride of 4-acetoxybenzaldehyde.

[0014] Preferably, in step S3, the amount of hexamethyldisilazane injected is 0.1-0.2% of the filter cake particle mass.

[0015] Preferably, the composite reinforcing filler is modified precipitated silica, and the preparation method includes: S1. Take industrial-grade sodium silicate (modulus 3.1-3.4), dilute with deionized water to prepare a sodium silicate solution with a mass concentration of 18-22%; first, slowly adjust the pH to 9.0-10.0 with 12% dilute sulfuric acid, then add silane coupling agent KH-792, the amount of which is 0.3-0.5% of the mass of the sodium silicate solution; then add surfactant AEO-9, accounting for 0.1-0.2% of the mass of the sodium silicate solution, stir at 200-300 r / min until uniform, and keep warm in a water bath at 50-60℃ for 40-60 min to obtain a pretreated sodium silicate solution; In this step, the purpose of adding the coupling agent is to pre-introduce active groups on the surface of sodium silicate molecules, laying the foundation for the strong bonding of the subsequent coating layer; S2. Add the pretreated sodium silicate solution obtained in step 1 to the reaction vessel, add dilute sulfuric acid dropwise until the pH reaches 8.0-8.5, adjust the temperature of the reaction vessel to 50-70℃, and control the stirring speed at 400-500 r / min; slowly add 4-acetoxybenzaldehyde solution (4-acetoxybenzaldehyde solution is prepared by using ethylene glycol dimethyl ether to form a solution with a mass concentration of 10-12%, and adding 2-3% acetic anhydride by mass of 4-acetoxybenzaldehyde), while simultaneously adding dilute sulfuric acid dropwise at a rate of 1.5-2.5 mL / min. Monitor the pH value of the reaction system in real time during the dropwise addition. When the pH value drops to 6.8-7.2, stop adding dilute sulfuric acid, continue stirring the reaction for 90-120 min, and age at 70-75℃ for 30 min to obtain a composite organic-coated modified silica suspension; In this step, dilute sulfuric acid reacts with sodium silicate in situ to produce silica, while simultaneously catalyzing the reaction between 4-acetoxybenzaldehyde and the amino groups on the surface of pretreated sodium silicate, instantly coating the surface of the newly formed silica particles to form an organic coating layer. S3. Vacuum filter the composite organic-coated modified silica suspension at a pressure of 0.06-0.08 MPa to obtain a filter cake. Wash the filter cake with deionized water 3-4 times until the pH of the washing solution is neutral. Place the washed filter cake in a vacuum drying oven and dry it at 95-105℃ and a vacuum of 0.09-0.1 MPa for 4-6 hours. After drying, spray in 0.1-0.2% hexamethyldisilazane (HMDS) by particle mass and passivate it by stirring at room temperature for 10-15 minutes. Place it in an air jet mill and pulverize it to a particle size of 800-1200 mesh to obtain the organic-coated modified precipitated silica product for rubber materials.

[0016] Preferably, the antioxidant is a compound of antioxidant 445 (2,2,4-trimethyl-1,2-dihydroquinoline polymer) and antioxidant MTI (methylbenzotriazole) in a weight ratio of 2:1. This compound system can exert a highly efficient inhibitory effect on both chain breakage and chain crosslinking aging pathways, producing a synergistic protective effect.

[0017] Preferably, the crosslinking agent is a complex of dicumyl peroxide and sulfur, with a weight ratio of 1.5-2.5:1. The peroxide forms stable CC crosslinking bonds between the main chains, and the polysulfide bonds preferentially break and recombine under stress, which can effectively dissipate energy and delay the destruction of the main crosslinking network.

[0018] Preferably, the vulcanizing activator is one or a mixture of zinc oxide, stearic acid and accelerator DPTT (dipentylene thiuram tetrasulfide); more preferably, the vulcanizing activator is zinc oxide, stearic acid and accelerator DPTT in a weight ratio of 3-5:1-3:1.

[0019] Preferably, the processing aid is polyethylene wax and / or liquid polysulfide rubber; more preferably, the processing aid is polyethylene wax and liquid polysulfide rubber in a weight ratio of 1:0.5-1.

[0020] Preferably, the liquid polysulfide rubber has a molecular weight of 1000-4000 and a thiol group content of 1%-3%.

[0021] Secondly, the present invention provides a method for preparing a high-temperature resistant and crack-resistant rubber material, comprising the following steps: Step 1, Raw material pretreatment: Dry the rubber matrix and composite reinforcing filler at 80±5℃ for 2-3 hours until the moisture content is ≤0.5%, and then cool to room temperature; Step 2: Internal mixing: Preheat the internal mixer to 80-90℃, speed 60-80r / min, add the rubber matrix and mix for 3-5min until melted; add the composite reinforcing filler in 2-3 batches, mixing for 2-3min each time; add the antioxidant, processing aid, and vulcanization activator in sequence, mixing for 1.5-2min each; heat to 110-120℃ and mix for 8-12min, then discharge and cool to obtain the first compound; Step 3: Open mill mixing: Preheat the open mill to 70-80℃, with a roller gap of 1-2mm. Pass the first compound through the mill 8-10 times until the surface is smooth. Adjust the roller gap to 3-4mm, add the crosslinking agent and mix for 3-5 minutes. Remove and cool to obtain the second compound. Step 4: Molding and vulcanization: Preheat the mold to 150-160℃, put the second compounded rubber blank into the mold, pre-press 5-8MPa and hold for 5-10 minutes to release the air; put it into a flat vulcanizing machine, vulcanize at 160-170℃ and 15-20MPa for 15-20 minutes; cool to below 100℃ to demold, hold at 80±5℃ for 2-3 hours for secondary vulcanization, and cool to room temperature; Step 5: Post-processing: Trim the edges and remove burrs. Seal the qualified products and store them in a cool, dry place. The preparation is now complete.

[0022] The beneficial effects of this invention are as follows: 1. This invention uses hydrogenated nitrile butadiene rubber and ethylene propylene diene monomer (EPDM) rubber as the rubber matrix, taking into account both molecular chain flexibility and temperature stability; the compounded anti-aging agent targets the aging damage caused by long-term walking and bending of the sole, and the reinforcement effect of the composite reinforcing filler reduces the stress concentration in the forefoot, heel and other stress-bearing parts of the sole during walking, ensuring that the sole does not crack or break after long-term bending and wear, significantly improving the service life of the sole and solving the problem of easy cracking and damage of existing soles.

[0023] 2. The composite reinforcing filler of the present invention adopts in-situ precipitation, organic coating and surface passivation process to solve the problems of uneven coating, weak bonding and poor rubber compatibility of existing modification methods. It realizes the high efficiency compatibility between modified silica and rubber matrix. The prepared modified silica has a three-layer structure of inorganic core-organic shell-passivation layer, which is fully adapted to the reinforcement, high temperature resistance and dynamic crack resistance of rubber materials, and improves the mechanical properties and processing performance of rubber products.

[0024] 3. Since 4-acetoxybenzaldehyde contains aldehyde group, benzene ring and acetoxy group at the same time, in the preparation process of composite reinforcing filler, the aldehyde group reacts with the amino group on the surface of pretreated sodium silicate to form Schiff base covalent bond, realizing the firm bond between the organic layer and the silica; the benzene ring provides a rigid skeleton, which can improve thermal stability and deformation resistance; the acetoxy group, as a hydrophobic ester group, is suitable for non-polar rubber matrix, which can reduce the interfacial polarity difference.

[0025] 4. When the rubber material of this invention is applied to shoe soles, it possesses excellent properties such as crack resistance, abrasion resistance, high and low temperature resistance, and comfort. It can be widely adapted to the preparation of various types of shoe soles, such as casual shoes, sports shoes, outdoor shoes, and work shoes. It can meet the comfort and durability requirements of daily wear, as well as the higher requirements for abrasion resistance and damage resistance in light outdoor and work scenarios. This solves the problems of limited applicability and single performance of existing shoe sole materials, significantly enhancing the market competitiveness of shoe sole products and possessing extremely high practical value and market application prospects. Attached Figure Description

[0026] The present invention will be further described with reference to the accompanying drawings, but the embodiments in the drawings do not constitute any limitation on the present invention. For those skilled in the art, other drawings can be obtained based on the following drawings without creative effort.

[0027] Figure 1 This is a SEM image of the high-temperature resistant and crack-resistant rubber material prepared in Example 1 of this invention; Figure 2 This is a schematic diagram of the high-temperature resistant and crack-resistant rubber material prepared in Example 1 of the present invention. Detailed Implementation

[0028] The technical solution of the present invention is illustrated below through specific examples. It should be understood that the one or more method steps mentioned in the present invention do not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps; it should also be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or defining the scope of the present invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the present invention.

[0029] To better understand the above technical solutions, exemplary embodiments of the present invention are described in more detail below. While exemplary embodiments of the present invention are shown, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the invention to those skilled in the art.

[0030] The present invention will be further described below with reference to the following embodiments.

[0031] Example 1 A high-temperature resistant and crack-resistant rubber material, comprising the following components by weight: 100 parts rubber matrix, 60 parts composite reinforcing filler, 6 parts crosslinking agent, 10 parts antioxidant, 5 parts vulcanization activator, and 5 parts processing aid.

[0032] The rubber matrix is ​​a blend of hydrogenated nitrile butadiene rubber and ethylene propylene diene monomer (EPDM) rubber in a weight ratio of 70:30. The hydrogenated nitrile butadiene rubber has an acrylonitrile content of 37%, a degree of hydrogenation of 99%, and a Mooney viscosity (ML1+4, 100℃) of 50. The EPDM rubber has an ethylene content of 60wt%, a propylene content of 32wt%, and a Mooney viscosity (ML1+4, 125℃) of 55.

[0033] The antioxidant is composed of antioxidant 445 and antioxidant MTI in a weight ratio of 2:1; the crosslinking agent is composed of dicumyl peroxide and sulfur in a weight ratio of 2:1; the vulcanizing activator is composed of zinc oxide, stearic acid and accelerator DPTT in a weight ratio of 4:2:1; and the processing aid is composed of polyethylene wax and liquid polysulfide rubber in a weight ratio of 1:0.8. The polyethylene wax has a molecular weight of 2000, the liquid polysulfide rubber has a molecular weight of 2500, and the mercaptan content is 2%.

[0034] The composite reinforcing filler is organically coated modified precipitated silica, and the specific preparation method is as follows: S1. Take 4.0 kg of industrial-grade sodium silicate (modulus 3.2), dilute it with deionized water to prepare a sodium silicate solution with a mass concentration of 20%; first, slowly adjust the pH to 9.5 with 12% dilute sulfuric acid, then add silane coupling agent KH-792, the amount of which is 0.4% of the mass of the sodium silicate solution; then add surfactant AEO-9, accounting for 0.15% of the mass of the sodium silicate solution, stir evenly at 250 r / min, and keep it in a 55℃ water bath for 50 min to obtain a pretreated sodium silicate solution; S2. Add the pretreated sodium silicate solution obtained in S1 to the reaction vessel, add dilute sulfuric acid dropwise until pH=8.2, adjust the reaction vessel temperature to 60℃, and control the stirring speed at 450r / min; slowly add 4-acetoxybenzaldehyde solution (4-acetoxybenzaldehyde solution is 200g of 4-acetoxybenzaldehyde prepared with ethylene glycol dimethyl ether to a mass concentration of 11%, and add 2.5% acetic anhydride by mass of 4-acetoxybenzaldehyde), while adding dilute sulfuric acid dropwise at a rate of 2.0mL / min. Monitor the pH value of the reaction system in real time during the dropwise addition. When the pH value drops to 7.0, stop adding dilute sulfuric acid, continue stirring the reaction for 105min, and age at 72℃ for 30min to obtain a composite organic-coated modified silica suspension; S3. The composite organic-coated modified silica suspension is vacuum filtered at a pressure of 0.07 MPa to obtain a filter cake. The filter cake is washed three times with deionized water until the pH of the washing solution is neutral. The washed filter cake is placed in a vacuum drying oven and dried at 100℃ and a vacuum of 0.095 MPa for 5 hours. After drying, 0.15% by weight of hexamethyldisilazane (HMDS) is sprayed in and the mixture is stirred and passivated at room temperature for 12 minutes. The mixture is then placed in an air jet mill and pulverized to a particle size of 1000 mesh to obtain the organic-coated modified precipitated silica product for use in rubber materials.

[0035] The preparation method of the above-mentioned high-temperature resistant and crack-resistant rubber material includes the following steps: Step 1, Raw material pretreatment: Dry the rubber matrix and composite reinforcing filler at 80℃ for 2.5h until the moisture content is ≤0.5%, and then cool to room temperature; Step 2: Internal mixing: Preheat the internal mixer to 85℃, speed 70r / min, add the rubber matrix and mix for 4min until melted; add the composite reinforcing filler in 2 batches, mixing for 2.5min each time; add the antioxidant, processing aid and vulcanization activator in sequence, mixing for 1.8min each; heat to 115℃ and mix for 10min, then discharge and cool to obtain the first compound; Step 3: Open mill mixing: Preheat the open mill to 75°C, with a roller gap of 1.5mm. Pass the first compound through the mill 9 times until the surface is smooth. Adjust the roller gap to 3.5mm, add the crosslinking agent and mix for 4 minutes. Remove and cool to obtain the second compound. Step 4: Molding and vulcanization: Preheat the mold to 155℃, put the second compounded rubber blank into the mold, pre-press 6MPa and hold for 8min to release the air; put it into a flat vulcanizing machine, vulcanize at 165℃ and 18MPa for 18min; cool to below 100℃ to demold, hold at 80℃ for 2.5h for secondary vulcanization, and cool to room temperature. Step 5: Post-processing: Trim the edges and remove burrs. Seal the qualified products and store them in a cool, dry place. The preparation is now complete.

[0036] Example 2 A high-temperature resistant and crack-resistant rubber material, comprising the following components by weight: 100 parts rubber matrix, 40 parts composite reinforcing filler, 3 parts crosslinking agent, 5 parts antioxidant, 3 parts vulcanization activator, and 2 parts processing aid.

[0037] The rubber matrix is ​​a blend of hydrogenated nitrile butadiene rubber and ethylene propylene diene monomer (EPDM) rubber in a weight ratio of 60:40. The hydrogenated nitrile butadiene rubber has an acrylonitrile content of 35%, a degree of hydrogenation of 98%, and a Mooney viscosity (ML1+4, 100℃) of 45. The EPDM rubber has an ethylene content of 55wt%, a propylene content of 35wt%, and a Mooney viscosity (ML1+4, 125℃) of 50.

[0038] The types and proportions of antioxidants, crosslinking agents, vulcanizing activators, and processing aids are the same as in Example 1; the molecular weight of the liquid polysulfide rubber is 1000, and the thiol group content is 1%.

[0039] The composite reinforcing filler is organically coated modified precipitated silica, and the specific preparation method is as follows: S1. Take industrial-grade sodium silicate (modulus 3.1), dilute it with deionized water to prepare a sodium silicate solution with a mass concentration of 18%; first, slowly adjust the pH to 9.0 with 12% dilute sulfuric acid, then add silane coupling agent KH-792, the amount of which is 0.3% of the mass of the sodium silicate solution; then add surfactant AEO-9, accounting for 0.1% of the mass of the sodium silicate solution, stir at 200 r / min until uniform, and keep it in a 50℃ water bath for 40 min to obtain a pretreated sodium silicate solution; S2. Add the pretreated sodium silicate solution obtained in step 1 to the reaction vessel, add dilute sulfuric acid dropwise until pH=8.0, adjust the reaction vessel temperature to 50℃, and control the stirring speed at 400r / min; slowly add 4-acetoxybenzaldehyde solution (4-acetoxybenzaldehyde solution is a 10% mass concentration solution prepared with ethylene glycol dimethyl ether, and 2% acetic anhydride by mass of 4-acetoxybenzaldehyde is added at the same time), while adding dilute sulfuric acid dropwise at a rate of 1.5mL / min. Monitor the pH value of the reaction system in real time during the dropwise addition. When the pH value drops to 6.8, stop adding dilute sulfuric acid, continue stirring the reaction for 90min, and age at 70℃ for 30min to obtain a composite organic-coated modified silica suspension; S3. Vacuum filter the composite organic-coated modified silica suspension at a pressure of 0.06 MPa to obtain a filter cake. Wash the filter cake three times with deionized water until the pH of the washing solution is neutral. Place the washed filter cake in a vacuum drying oven and dry it for 4 hours at 95°C and a vacuum of 0.09 MPa. After drying, spray in 0.1% hexamethyldisilazane (HMDS) by particle mass and passivate it by stirring at room temperature for 10 minutes. Place it in an air jet mill and pulverize it to a particle size of 800 mesh to obtain the organic-coated modified precipitated silica product for rubber materials.

[0040] The preparation method of the above-mentioned high-temperature resistant and crack-resistant rubber material is basically the same as that in Example 1, with only the following parameters adjusted: Step 1: Drying temperature 75℃, drying time 2 hours; Step 2: Preheat the internal mixer to 80℃, rotate at 60r / min, and internally mix the rubber matrix for 3min; add the composite reinforcing filler in 2 batches, internally mixing for 2min each time; internally mix each additive for 1.5min; heat to 110℃ and internally mix for 8min. Step 3: Preheat the open mill to 70°C, roll gap 1mm, thin pass 8 times; adjust roll gap to 3mm, add crosslinking agent and mix for 3 minutes; Step 4: Preheat the mold to 150℃, pre-press at 5MPa and hold for 5 minutes; vulcanize at 160℃ and 15MPa for 15 minutes in a flat vulcanizing machine; secondary vulcanization at 75℃ for 2 hours.

[0041] Example 3 A high-temperature resistant and crack-resistant rubber material, comprising the following components by weight: 100 parts rubber matrix, 80 parts composite reinforcing filler, 10 parts crosslinking agent, 15 parts antioxidant, 8 parts vulcanization activator, and 8 parts processing aid.

[0042] The rubber matrix is ​​a blend of hydrogenated nitrile butadiene rubber and ethylene propylene diene monomer (EPDM) rubber in a weight ratio of 80:20. The hydrogenated nitrile butadiene rubber has an acrylonitrile content of 40%, a degree of hydrogenation of 99.5%, and a Mooney viscosity (ML1+4, 100℃) of 55. The EPDM rubber has an ethylene content of 65wt%, a propylene content of 30wt%, and a Mooney viscosity (ML1+4, 125℃) of 60.

[0043] The types and proportions of antioxidants, crosslinking agents, vulcanizing activators, and processing aids are the same as in Example 1; the molecular weight of the liquid polysulfide rubber is 4000, and the thiol group content is 3%.

[0044] The composite reinforcing filler is organically coated modified precipitated silica, and the specific preparation method is as follows: S1. Take industrial-grade sodium silicate (modulus 3.4), dilute it with deionized water to prepare a sodium silicate solution with a mass concentration of 22%; first, slowly adjust the pH to 10.0 with 12% dilute sulfuric acid, then add silane coupling agent KH-792, the amount added is 0.5% of the mass of sodium silicate solution; then add surfactant AEO-9, accounting for 0.2% of the mass of sodium silicate solution, stir at 300 r / min until uniform, and keep it in a 60℃ water bath for 60 min to obtain a pretreated sodium silicate solution; S2. Add the pretreated sodium silicate solution obtained in step 1 to the reaction vessel, add dilute sulfuric acid dropwise until pH=8.5, adjust the temperature of the reaction vessel to 70℃, and control the stirring speed at 500 r / min; slowly add 4-acetoxybenzaldehyde solution (4-acetoxybenzaldehyde solution is a 12% mass concentration solution prepared by ethylene glycol dimethyl ether, with 3% acetic anhydride added by mass of 4-acetoxybenzaldehyde), while adding dilute sulfuric acid dropwise at a rate of 2.5 mL / min. Monitor the pH value of the reaction system in real time during the dropwise addition. When the pH value drops to 7.2, stop adding dilute sulfuric acid, continue stirring the reaction for 120 min, and age at 75℃ for 30 min to obtain a composite organic-coated modified silica suspension; S3. The composite organic-coated modified silica suspension is vacuum filtered at a pressure of 0.08 MPa to obtain a filter cake. The filter cake is washed four times with deionized water until the pH of the washing solution is neutral. The washed filter cake is placed in a vacuum drying oven and dried at 105℃ and a vacuum of 0.1 MPa for 6 hours. After drying, 0.2% by weight of hexamethyldisilazane (HMDS) is sprayed in and the mixture is stirred and passivated at room temperature for 15 minutes. The mixture is then placed in an air jet mill and pulverized to a particle size of 1200 mesh to obtain the organic-coated modified precipitated silica product for use in rubber materials.

[0045] The preparation method of the above-mentioned high-temperature resistant and crack-resistant rubber material is basically the same as that in Example 1, with only the following parameters adjusted: Step 1: Drying temperature 85℃, drying time 3 hours; Step 2: Preheat the internal mixer to 90℃, rotate at 80r / min, and internally mix the rubber matrix for 5min; add the composite reinforcing filler in 3 batches, internally mixing for 3min each time; internally mix each additive for 2min; heat to 120℃ and internally mix for 12min. Step 3: Preheat the open mill to 80°C, with a roll gap of 2mm, and pass through the mill 10 times; adjust the roll gap to 4mm, add the crosslinking agent, and mix for 5 minutes. Step 4: Preheat the mold to 160℃, pre-press at 8MPa and hold for 10 minutes; vulcanize at 170℃ and 20MPa for 20 minutes in a flat vulcanizing machine; secondary vulcanization at 85℃ for 3 hours.

[0046] Comparative Example 1 A rubber material differs from Example 1 only in that the composite reinforcing filler is an unmodified precipitated silica prepared in situ, while the other components and preparation methods remain unchanged. Specifically, no silane coupling agent, surfactant AEO-9, 4-acetoxybenzaldehyde, or hexamethyldisilazane are added during the preparation of the composite reinforcing filler; no modification treatment is performed, and ordinary silica is prepared solely through in-situ precipitation.

[0047] Methods for preparing composite reinforcing fillers include: S1. Take industrial-grade sodium silicate (modulus 3.2), dilute it with deionized water to prepare a sodium silicate solution with a mass concentration of 20%; add the sodium silicate solution to the reaction vessel, add 12% dilute sulfuric acid dropwise until pH=7.0, adjust the temperature of the reaction vessel to 60℃, control the stirring speed at 450r / min, continue stirring and reacting for 105min, and age at 72℃ for 30min to obtain a suspension of unmodified precipitated silica. S2. Vacuum filter the suspension at a pressure of 0.07 MPa to obtain a filter cake. Wash the filter cake three times with deionized water until the pH of the washing liquid is neutral. Place the washed filter cake in a vacuum drying oven and dry it for 5 hours at 100°C and a vacuum of 0.095 MPa. Then, place it in an air jet mill and grind it to a particle size of 1000 mesh to obtain the unmodified precipitated silica product.

[0048] Comparative Example 2 A rubber material differs from Example 1 only in that the composite reinforcing filler is modified precipitated silica without the introduction of 4-acetoxybenzaldehyde; the other components and preparation methods remain unchanged. That is, the preparation of the composite reinforcing filler differs from Example 1 in that, in step S2, no 4-acetoxybenzaldehyde solution is added; modification is performed only by silane coupling agents and surfactants, without the organic coating treatment of 4-acetoxybenzaldehyde.

[0049] Methods for preparing composite reinforcing fillers include: S1. Take industrial-grade sodium silicate (modulus 3.2), dilute it with deionized water to prepare a sodium silicate solution with a mass concentration of 20%; first, slowly adjust the pH to 9.5 with 12% dilute sulfuric acid, then add silane coupling agent KH-792, the amount of which is 0.4% of the mass of the sodium silicate solution; then add surfactant AEO-9, accounting for 0.15% of the mass of the sodium silicate solution, stir evenly at 250 r / min, and keep it in a 55℃ water bath for 50 min to obtain a pretreated sodium silicate solution; S2. Add the pretreated sodium silicate solution obtained in step 1 to the reaction vessel, add dilute sulfuric acid dropwise until pH=7.0, adjust the temperature of the reaction vessel to 60℃, control the stirring speed at 450r / min, continue stirring and reacting for 105min, and age at 72℃ for 30min to obtain a modified precipitated silica suspension. S3. Vacuum filter the composite organic-coated modified silica suspension at a pressure of 0.07 MPa to obtain a filter cake. Wash the filter cake three times with deionized water until the pH of the washing solution is neutral. Place the washed filter cake in a vacuum drying oven and dry it for 5 hours at 100°C and a vacuum of 0.095 MPa. After drying, spray in 0.15% hexamethyldisilazane (HMDS) by particle mass and passivate it by stirring at room temperature for 12 minutes. Place it in an air jet mill and pulverize it to a particle size of 1000 mesh to obtain the modified precipitated silica product.

[0050] Comparative Example 3 A rubber material differs from Example 1 only in that the composite reinforcing filler is a modified precipitated silica prepared in situ using 4-acetoxybenzaldehyde via a non-in-situ method; the other components and preparation methods remain unchanged. That is, the difference in the preparation method of the composite reinforcing filler compared to Example 1 is that ordinary silica is prepared first, followed by silane coupling agent pretreatment and 4-acetoxybenzaldehyde coating (non-in-situ simultaneous coating). In other words, silica formation and organic coating occur stepwise, rather than being completed simultaneously in situ.

[0051] Methods for preparing composite reinforcing fillers include: S1. First, prepare ordinary precipitated silica: Take industrial grade sodium silicate (modulus 3.2), add deionized water to dilute to a mass concentration of 20%, add 12% dilute sulfuric acid dropwise to pH=7.0, stir at 60℃ and 450r / min for 105min, age at 72℃ for 30min, filter, wash, dry at 100℃ for 5h, and pulverize to 1000 mesh to obtain ordinary precipitated silica; S2. Pretreatment: Add ordinary precipitated silica to deionized water to prepare a suspension with a mass concentration of 20%. Add silane coupling agent KH-792 (0.4% of the mass of silica) and surfactant AEO-9 (0.15% of the mass of silica). Stir at 250 r / min until homogeneous, keep warm at 55℃ for 50 min, filter and dry to obtain pretreated silica. S3. Non-in-situ coating: Add pretreated silica to ethylene glycol dimethyl ether and stir to disperse evenly to obtain a suspension; slowly add 4-acetoxybenzaldehyde solution (preparation method is the same as in Example 1), and simultaneously add dilute sulfuric acid to adjust the pH to 7.0. Stir at 60℃ and 450r / min for 105min, filter and dry; spray in 0.15% HMDS for passivation for 12min to obtain the non-in-situ modified precipitated silica product.

[0052] To more clearly illustrate the present invention, the performance standards of the rubber materials obtained in Example 1 and Comparative Examples 1-3 of the present invention were tested respectively.

[0053] The testing items and methods include: Tensile strength: Performed in accordance with GB / T 528-2009, the tensile strength (MPa) of the rubber material in the unaged state is tested. The higher the tensile strength, the better the mechanical properties of the material. Flexural cracking performance: Performed according to GB / T 13934-2006, the test condition is 1 million flexes, and the cracking level is evaluated (level 1 is the best, level 5 is the worst, no cracking is level 1, and severe cracking is level 5). Abrasion resistance: Tested according to GB / T 1689-2014, Akron abrasion rate (cm). 3( / 1.61km), the smaller the value, the better the wear resistance; High temperature resistance: Hot air aging test, performed according to GB / T 3512-2014, test conditions are 150℃×72h, test tensile strength retention rate (%) and elongation at break retention rate (%) after aging. The higher the retention rate, the better the high temperature resistance. Low temperature resistance: Performed in accordance with GB / T 15256-2014, the low temperature brittleness temperature (°C) is tested, and the lower the value, the better the low temperature resistance; Comfort performance: Shore A hardness is tested (GB / T 531.1-2008). The comfort range is between 60 and 70 Shore A. The closer the value is to the middle value, the better the comfort. Long-term high-temperature service temperature: The highest long-term service temperature (°C) at which the rubber material shows no obvious cracking or significant performance degradation (tensile strength retention rate ≥80%) is determined through constant temperature aging test.

[0054] The test results are listed in the table below: The results in the table above show that Example 1 not only has high initial tensile strength, but also retains 92.3% of its tensile strength after aging at 150℃ for 72 hours, indicating that it possesses both excellent initial mechanical properties and high-temperature aging resistance. Example 1 exhibits a flexural cracking grade of 1 (no cracking), while Comparative Examples 1-3 all show varying degrees of cracking. Example 1 has a lower Akron abrasion loss than Comparative Examples 1-3, demonstrating the best abrasion resistance. Example 1 also exhibits excellent high and low temperature resistance, with both its low-temperature brittle temperature (-42℃) and high-temperature long-term service temperature (155℃) being superior to the comparative examples. Example 1 has a Shore A hardness of 65, falling within the comfortable range of 60-70, indicating optimal comfort. Comparative Example 1 has a hardness of 78, feeling somewhat hard; Comparative Example 2 has a hardness of 72, slightly hard; and Comparative Example 3 has a hardness of 68, close to the comfortable range but still inferior to Example 1.

[0055] In summary, the modified precipitated silica prepared by the in-situ synchronous coating method in Example 1 of this invention is used as a composite reinforcing filler, which enables the prepared rubber material to have excellent anti-cracking, wear resistance, high and low temperature resistance and comfort performance. This solves the technical problems of existing rubber materials being prone to aging at high temperatures, cracking, poor wear resistance and poor comfort when used as shoe soles.

[0056] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. The illustrative expressions of the above terms in this specification should not be construed as necessarily referring to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0057] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A high-temperature resistant and crack-resistant rubber material, characterized in that, By weight, it includes the following components: 100 parts rubber matrix, 40-80 parts composite reinforcing filler, 3-10 parts crosslinking agent, 5-15 parts antioxidant, 3-8 parts vulcanization activator, and 2-8 parts processing aid; The rubber matrix comprises hydrogenated nitrile butadiene rubber and ethylene propylene diene monomer (EPDM) rubber, wherein the weight ratio of hydrogenated nitrile butadiene rubber to EPDM rubber is 60-80:20-40.

2. The high-temperature resistant and crack-resistant rubber material according to claim 1, characterized in that, The composite reinforcing filler is modified precipitated silica, and the preparation method includes: S1. Take industrial-grade sodium silicate and add deionized water to prepare a sodium silicate solution; adjust the pH to 9.0-10.0 with dilute sulfuric acid, add silane coupling agent KH-792, then add surfactant AEO-9, stir evenly, and keep warm in a water bath at 50-60℃ for 40-60 minutes to obtain a pretreated sodium silicate solution. S2. Add dilute sulfuric acid dropwise to the pretreated sodium silicate solution until the pH reaches 8.0-8.5, adjust the temperature to 50-70℃, and simultaneously add 4-acetoxybenzaldehyde solution and dilute sulfuric acid. Stop adding dilute sulfuric acid when the pH of the reaction system drops to 6.8-7.2, continue stirring the reaction for 90-120 min, and then age at 70-75℃ for 30 min to obtain a composite organic-coated modified silica suspension. S3. Vacuum filter the suspension to obtain a filter cake, wash with water until the washing liquid is neutral; vacuum dry for 4-6 hours, spray in hexamethyldisilazane, stir and passivate at room temperature, and then pulverize by airflow to obtain modified precipitated silica.

3. The high-temperature resistant and crack-resistant rubber material according to claim 2, characterized in that, In S1, the mass concentration of sodium silicate solution is 18-22%; the amount of silane coupling agent KH-792 added is 0.3-0.5% of the mass of sodium silicate solution, and the amount of surfactant AEO-9 added is 0.1%-0.2% of the mass of sodium silicate solution.

4. The high-temperature resistant and crack-resistant rubber material according to claim 2, characterized in that, In S2, the 4-acetoxybenzaldehyde solution is a 10-12% (w / w) solution of 4-acetoxybenzaldehyde prepared with ethylene glycol dimethyl ether, and contains 2-3% (w / w) of acetic anhydride of 4-acetoxybenzaldehyde.

5. The high-temperature resistant and crack-resistant rubber material according to claim 2, characterized in that, In step S3, the amount of hexamethyldisilazane injected is 0.1-0.2% of the filter cake particle mass.

6. The high-temperature resistant and crack-resistant rubber material according to claim 1, characterized in that, The antioxidant is a compound of antioxidant 445 and antioxidant MTI in a weight ratio of 2:

1.

7. The high-temperature resistant and crack-resistant rubber material according to claim 1, characterized in that, The crosslinking agent is a complex of dicumyl peroxide and sulfur, with a weight ratio of 1.5-2.5:

1.

8. The high-temperature resistant and crack-resistant rubber material according to claim 1, characterized in that, The vulcanizing activator is one or a mixture of zinc oxide, stearic acid and accelerator DPTT.

9. The high-temperature resistant and crack-resistant rubber material according to claim 1, characterized in that, The processing aid is polyethylene wax and / or liquid polysulfide rubber; wherein the liquid polysulfide rubber has a molecular weight of 1000-4000 and a mercaptan content of 1%-3%.

10. A method for preparing the high-temperature resistant and crack-resistant rubber material according to claim 1, characterized in that, Includes the following steps: Step 1, Raw material pretreatment: Dry the rubber matrix and composite reinforcing filler at 80±5℃ for 2-3 hours, and then cool to room temperature; Step 2: Internal mixing: Preheat the internal mixer to 80-90℃, speed 60-80r / min, add the rubber matrix and mix for 3-5min until melted; add the composite reinforcing filler in 2-3 batches, mixing for 2-3min each time; add the antioxidant, processing aid, and vulcanization activator in sequence, mixing for 1.5-2min each; heat to 110-120℃ and mix for 8-12min, then discharge and cool to obtain the first compound; Step 3: Open mill mixing: Preheat the open mill to 70-80℃, with a roller gap of 1-2mm. Pass the first compound through the mill 8-10 times until the surface is smooth. Adjust the roller gap to 3-4mm, add the crosslinking agent and mix for 3-5 minutes. Remove and cool to obtain the second compound. Step 4: Molding and vulcanization: Preheat the mold to 150-160℃, put the second compounded rubber blank into the mold, pre-press 5-8MPa and hold for 5-10 minutes to release the air; put it into a flat vulcanizing machine, vulcanize at 160-170℃ and 15-20MPa for 15-20 minutes; cool to below 100℃ to demold, hold at 80±5℃ for 2-3 hours for secondary vulcanization, and cool to room temperature; Step 5: Post-processing: Trim the edges and remove burrs. Seal the qualified products and store them in a cool, dry place. The preparation is now complete.

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