Heat-resistant ozone-resistant air spring outer layer rubber material and preparation method thereof

Abstract

The invention relates to the technical field of new energy automobile air suspensions, and particularly discloses a heat-resistant ozone-resistant air spring outer layer rubber material. The rubber material is prepared from natural rubber, chlorosulfonated polyethylene rubber, ethylene-vinyl acetate rubber, high-activity magnesium oxide, stearic acid, an anti-aging agent, microcrystalline wax, tert-butylphenol formaldehyde resin, reinforcing filler, a plasticizer, zinc oxide, a vulcanizing agent and an accelerant. The invention also discloses a preparation method of the sizing material. The heat-resistant ozone-resistant air spring outer layer rubber material disclosed by the invention has good heat resistance, cold resistance and ozone aging resistance, and also has the advantages of wide application environment range and long service life.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of new energy vehicle air suspension, in particular to a heat-resistant and ozone-resistant air spring outer rubber material and a preparation method thereof. BACKGROUND

[0002] In the automotive industry, passenger car suspension systems play a crucial role in improving vehicle ride comfort and ride comfort. With the development of new energy vehicles and intelligent driving technology, passenger car suspensions are gradually upgrading from passive suspensions to active suspensions. Among them, air spring suspensions perform well in vehicle safety, driving comfort and energy efficiency, etc., which can significantly improve driving safety and handling stability, such as adjusting the damper control body posture when the car turns or accelerates, and improving tire and ground friction when the vehicle is unstable or emergency braking.

[0003] Air springs as the core elastic element of air suspension, use the compression elasticity of air to realize load bearing, buffering, shock absorption and other functions. Rubber capsule skin is one of the core technical barriers of air spring, and its thermodynamic performance is the key to ensure the normal operation of air suspension. Fatigue resistance and aging resistance determine the service life of air suspension, and it must have sufficient strength and low stiffness to meet the needs of automobile shock absorption and stability.

[0004] Currently, there are many invention patents about air spring rubber material. For example, CN119798801A, CN117683277A, CN119119604A, CN110343303A disclose air spring rubber materials that only focus on improving the fatigue performance and ozone resistance of the rubber material by using different rubber and additives, but do not focus on optimizing the high-temperature heat aging performance of the rubber material. CN106700482A discloses a low-temperature-resistant, high-temperature-resistant and oil-resistant air spring for automobiles and a preparation method thereof, which uses chloroether rubber and butadiene rubber. Although the product is described as having low-temperature resistance, high-temperature resistance and oil resistance, the heat resistance of the rubber material is only tested at 70℃, and the fatigue performance of the product in a high-temperature hot air environment is not tested.

[0005] In practical applications, air springs are often installed on the exterior of automobiles. Some, such as the air springs on the side of the cab of a tractor-trailer, are located near the rear of the engine exhaust pipe and must withstand temperatures as high as 100°C during use. This results in the lifespan of air springs in this location being more than half that of those in other locations. This is because the rubber bladder of the air spring is mainly composed of rubber, polyester fiber, and polyamide fiber materials, which are pre-molded and then vulcanized. Under continuous high temperature, light, and ozone environments, the rubber material ages rapidly, leading to premature cracking and air leakage. While traditional blends of natural rubber and butadiene rubber can impart good mechanical properties to the compound under normal atmospheric conditions, their highly unsaturated nature makes them prone to aging and failure under light, heat, and ozone. Furthermore, the use of chloroprene rubber and butadiene rubber in applications such as CN106700482A results in poor fatigue performance due to the high saturation of chloroprene rubber and poor compatibility with butadiene rubber, with flexural cracking not exceeding 600,000 cycles. While some solutions using chloroprene rubber to improve ozone aging performance can enhance heat aging resistance, their practical application is limited by factors such as poor processing performance, easy self-vulcanization during storage, short shelf life, easy scorching, and poor adhesion to the natural rubber of the cord layer due to the use of thiourea vulcanization system.

[0006] Regarding the aforementioned technologies, the inventors believe it is necessary to improve the heat resistance and ozone aging resistance of air spring rubber materials. Summary of the Invention

[0007] To address the technical deficiencies of existing technologies, this application provides a heat-resistant and ozone-resistant outer layer rubber compound for air springs and its preparation method.

[0008] In a first aspect, this application provides a heat-resistant and ozone-resistant air spring outer layer rubber compound, which adopts the following technical solution: A heat-resistant and ozone-resistant air spring outer layer rubber compound, comprising, by weight fraction: 30-60 parts of natural rubber; 35-55 parts of chlorosulfonated polyethylene rubber; 5-15 parts of ethylene-vinyl acetate rubber; 4-7 parts of highly active magnesium oxide; 0.5-3 parts of stearic acid; 4.5-11 parts of antioxidant; 1-3 parts of microcrystalline wax; 3-6 parts of tert-butylphenol formaldehyde resin; 50-90 parts of reinforcing filler; 10-25 parts of plasticizer; 2-5 parts of zinc oxide; 2.6-5.7 parts of vulcanizing agent; and 0.6-1.8 parts of accelerator.

[0009] By adopting the above technical solution, using natural rubber and chlorosulfonated polyethylene rubber as the main raw rubbers, and ethylene-vinyl acetate rubber as a compatibilizer, the natural rubber ensures the adhesion and processing convenience of the rubber compound to the fabric layer, while the chlorosulfonated polyethylene rubber significantly improves the heat resistance and ozone resistance of the compound. Ethylene-vinyl acetate rubber effectively reduces the interfacial tension between natural rubber and chlorosulfonated polyethylene rubber, solving the compatibility problem caused by their polarity difference, and achieving complementary performance of the raw rubber system. Simultaneously, by incorporating a specific ratio of highly active magnesium oxide, antioxidants, reinforcing fillers, plasticizers, vulcanizing agents, and accelerators, the mechanical properties, anti-aging ability, and processing stability of the compound are synergistically optimized. This ultimately solves the core pain points of existing air springs, such as easy aging and short lifespan under high-temperature environments, and broadens the application range of air springs.

[0010] Preferably, the natural rubber is smoked sheet rubber.

[0011] By adopting the above technical solution and selecting smoked sheet rubber as the natural rubber raw material, smoked sheet rubber has the characteristics of high purity, low impurity content and excellent mechanical strength. It can further improve the core mechanical properties of the rubber compound such as tensile strength and elongation at break. At the same time, it reduces the adverse effects of impurities on the vulcanization reaction, compatibility and adhesion performance with the cord layer of the rubber compound, ensuring the stability and reliability of the rubber compound performance, and laying the foundation for the durability of the outer layer rubber of the air spring.

[0012] Preferably, the iodine value of the highly active magnesium oxide is 150 mg / g.

[0013] By adopting the above technical solution, the iodine value of highly active magnesium oxide is limited to 150 mg / g. A higher iodine value means that magnesium oxide has a larger specific surface area and higher activity, which can more efficiently act as a vulcanizing activator for chlorosulfonated polyethylene rubber, promote the vulcanization crosslinking reaction of chlorosulfonated polyethylene rubber, and increase the crosslinking density of the rubber compound. At the same time, high activity can also enhance the synergistic effect of magnesium oxide with antioxidants and vulcanizing agents, further improve the heat resistance and compression set resistance of the rubber compound, and reduce the performance degradation of the rubber compound at high temperatures.

[0014] Preferably, the antioxidant is a compound of antioxidant 4020, antioxidant NBC and antioxidant BLE; the mass ratio of the three is (1.5-3):(1-3):(2-5).

[0015] By adopting the above technical solution, the antioxidant is limited to a compound system of antioxidant 4020, antioxidant NBC, and antioxidant BLE, and the mass ratio of the three is controlled at (1.5-3):(1-3):(2-5). Among them, antioxidant 4020 can effectively improve the fatigue performance and thermo-oxidative aging performance of the rubber compound, antioxidant NBC is an excellent anti-ozone aging agent, and antioxidant BLE can improve the thermo-oxidative, flexural, and fatigue aging performance of the rubber compound. The compound of the three can achieve multi-dimensional aging protection of "anti-thermal oxidation + anti-ozone + anti-fatigue", and the optimization of the specific ratio maximizes the synergistic effect of the three, avoiding the problem of limited protection range of a single antioxidant, and significantly extending the service life of the rubber compound in the combined environment of heat and ozone.

[0016] Preferably, the plasticizer is diisodecyl ester, which is one or more of diisodecyl phthalate and diisodecyl adipate.

[0017] By adopting the above technical solution, the plasticizer is limited to diisodecyl phthalate, specifically diisodecyl phthalate or diisodecyl adipate, or a combination of both. Diisodecyl phthalate exhibits excellent heat resistance, preventing plasticizer loss at high temperatures that could lead to hardening and brittleness in the rubber compound. Diisodecyl adipate, on the other hand, possesses excellent cold resistance, ensuring the flexibility of the rubber compound in low-temperature environments and preventing low-temperature brittle fracture. The two can be flexibly combined according to application requirements to achieve a balance in the high and low temperature performance of the rubber compound, ensuring that the air spring maintains good elasticity and performance under different climatic conditions such as cold and hot. Furthermore, diisodecyl phthalate has good compatibility with the raw rubber system of this application and will not affect the mechanical properties of the rubber compound due to migration.

[0018] Preferably, the reinforcing filler is N774 carbon black and strong iodine powder; the mass ratio of N774 carbon black to strong iodine powder is (3-5):(2-4).

[0019] By adopting the above technical solution, the reinforcing filler is limited to a compound system of N774 carbon black and strong-coated powder, and the mass ratio is controlled at (3-5):(2-4). N774 carbon black has good reinforcing effect and dispersibility, which can significantly improve the tensile strength, abrasion resistance and processing fluidity of the rubber compound; strong-coated powder can further optimize the weather resistance, heat resistance and dimensional stability of the rubber compound, and also improve the air tightness of the rubber compound. The compounding and optimization of the ratio of the two can ensure the reinforcing effect of the rubber compound while avoiding the problems of excessive hardness and processing difficulties caused by a single filler, thus achieving a balance between the mechanical properties and processing performance of the rubber compound, and providing a guarantee for the molding and durability of the outer layer rubber of the air spring.

[0020] Preferably, the vulcanizing agent is pentaerythritol and sulfur; the mass ratio of pentaerythritol to sulfur is (2-4.5):(0.6-1.2).

[0021] By adopting the above technical solution, the vulcanizing agent is limited to a compound system of pentaerythritol and sulfur, and the mass ratio is controlled at (2-4.5):(0.6-1.2). Pentaerythritol can specifically adapt to the vulcanization requirements of chlorosulfonated polyethylene rubber, promoting its full cross-linking; sulfur can meet the vulcanization reaction of natural rubber, ensuring that natural rubber forms a stable cross-linked structure. The compound can simultaneously adapt to the vulcanization characteristics of the two main raw rubbers, ensuring uniform and sufficient overall cross-linking of the rubber compound, thereby improving the overall strength, heat resistance, and compression set resistance of the rubber compound, and reducing the performance loss of the rubber compound under high temperature environments.

[0022] Preferably, the accelerator is accelerator DM and accelerator DPTT, and the mass ratio of accelerator DM to accelerator DPTT is (0.2-0.8):(0.4-1).

[0023] By adopting the above technical solution, the accelerator is limited to a compound system of accelerator DM and accelerator DPTT, and the mass ratio is controlled at (0.2-0.8):(0.4-1). Accelerator DM can slowly promote the vulcanization reaction, avoiding excessively fast vulcanization and scorching of the rubber compound; accelerator DPTT can efficiently improve vulcanization efficiency, ensuring that the vulcanization reaction proceeds fully. The specific ratio of the two compounds allows for precise control of the vulcanization rate of the rubber compound, avoiding the risk of scorching while ensuring vulcanization uniformity, improving the crosslinking quality of the rubber compound, further optimizing the mechanical properties and heat aging resistance of the rubber compound, and simultaneously ensuring the safety and stability of the processing.

[0024] Secondly, the present invention provides a method for preparing the above-mentioned heat-resistant and ozone-resistant outer layer rubber material of the air spring, which adopts the following technical solution: A method for preparing a heat-resistant and ozone-resistant outer layer rubber compound for an air spring includes the following steps: S1: Put natural rubber into an internal mixer, plasticize for 3-5 minutes, mix to 105-120℃, discharge the rubber, cool and collect the rubber. S2: Put the masticated natural rubber, chlorosulfonated polyethylene rubber, and ethylene-vinyl acetate rubber into an internal mixer and mix for 5-8 minutes until the temperature reaches 85-90℃. S3: Add highly active magnesium oxide, stearic acid, antioxidant, microcrystalline wax and tert-butylphenol formaldehyde resin to the internal mixer and mix for 4-6 minutes to 95-100℃. S4: Add reinforcing filler and mix in an internal mixer for 2-4 minutes to 105-110℃; S5: Add the plasticizer to the internal mixer and mix for 3-6 minutes until the temperature reaches 115-120℃; S6: Lift the top bolt of the internal mixer, clean the powder above and press it down. Mix for 3-5 minutes until the temperature reaches 120°C, then discharge the rubber. Transfer the rubber to the open mill and cool it down to 70-80°C by wrapping the rollers. S7: Add zinc oxide, vulcanizing agent and accelerator to the masterbatch on the open mill, mix for 5-8 minutes and then sheet it. After the temperature drops to room temperature, collect it for later use. S8: The rubber material is calendered into a sheet of a specified thickness, and then the sheet is bonded to the rubber cord fabric on a molding machine to obtain a product blank; S9: The product blank is vulcanized to obtain a heat-resistant and ozone-resistant air spring bladder.

[0025] By adopting the above technical solution, the preparation method involves staged internal mixing and open milling, with strict control over the temperature and time at each stage: first, natural rubber is plasticized separately to ensure uniform plasticization; then, raw rubber, activators, antioxidants, reinforcing fillers, and plasticizers are gradually added to avoid localized overheating or uneven dispersion due to vigorous reactions when different components are mixed; subsequently, zinc oxide, vulcanizing agents, and accelerators are added after cooling in an open mill to prevent premature reaction of the vulcanizing agent at high temperatures, which could lead to scorching. The entire preparation process is logically clear and the parameters are controllable, ensuring that each component is fully dispersed and the vulcanization reaction proceeds stably, ultimately guaranteeing the consistency and stability of the rubber compound's properties; subsequent calendering and vulcanization further ensure the molding quality of the outer layer rubber of the air spring, achieving effective transformation of the rubber compound's properties.

[0026] Preferably, the rubber compound in step S8 is left to stand for more than 24 hours before calendering.

[0027] By adopting the above technical solution, allowing the rubber compound to rest for more than 24 hours before calendering allows for the full release of internal stress within the compound. Simultaneously, it enables the components to further diffuse and distribute evenly within the compound, preventing performance fluctuations or defects in the calendered film caused by uneven component distribution. Furthermore, sufficient resting time enhances the plasticity and flowability of the rubber compound, facilitating subsequent calendering processes, ensuring uniform thickness and a smooth surface of the calendered film, thereby improving the bonding strength between the film and the fabric, reducing issues such as bubbles and delamination during molding, and ensuring the overall quality of the air spring product.

[0028] In summary, this application has the following beneficial effects: This application establishes a complete technical logic of "performance complementarity - efficacy amplification - process adaptation" through deep synergy between the raw rubber system, functional additive system, and preparation process. It addresses the core pain points of existing air spring outer layer adhesives at the molecular and microstructural levels: insufficient heat and ozone resistance, difficulty in balancing mechanical properties and adhesion, and poor processing stability. In the raw rubber system, ethylene-vinyl acetate rubber plays a crucial "bridging role": while natural rubber possesses excellent processing fluidity and adhesion to the fabric layer, it is a non-polar, highly unsaturated rubber, susceptible to heat and ozone aging; chlorosulfonated polyethylene rubber has a temperature limit exceeding 140℃ and outstanding ozone resistance, but it is a polar, saturated rubber with a large difference in interfacial tension compared to natural rubber. Direct use of these materials can easily lead to phase separation and a sharp drop in mechanical properties. The ethylene-vinyl acetate rubber molecular chain contains both non-polar ethylene segments and polar vinyl acetate segments, which can be compatible with natural rubber and chlorosulfonated polyethylene rubber respectively. This effectively reduces the interfacial tension between the two, promotes the uniform dispersion of the two phases to form a stable blend structure, retains the processability and adhesion of natural rubber, and fully utilizes the heat resistance and ozone resistance of chlorosulfonated polyethylene rubber. Its own high temperature resistance of 175℃ further enhances the overall heat resistance limit of the raw rubber system.

[0029] In addition, in the functional additive system, each component works synergistically around the properties of raw rubber: antioxidant 4020 inhibits thermo-oxidative aging by capturing thermo-oxidative free radicals, antioxidant NBC blocks ozone aging by reacting with ozone, and antioxidant BLE alleviates fatigue aging by improving molecular chain flexibility. These three are compounded in a specific ratio to form all-scenario aging protection, and also extend the durability of protection through intermolecular synergistic effects; the vulcanizing agent pentaerythritol is adapted to the crosslinking requirements of chlorosulfonated polyethylene rubber, sulfur is adapted to the vulcanization reaction of natural rubber, and the accelerator... DM slows down the growth rate to prevent scorching, while DPTT efficiently improves crosslinking and ensures full crosslinking. The combination of the two ensures that the two types of raw rubber crosslink simultaneously and uniformly. The reinforcing filler N774 carbon black enhances tensile strength with its high dispersibility, while strong powder enhances weather resistance with its ultrafine silicate structure. The combination of the two balances the reinforcing effect and the hardness of the rubber compound. The plasticizers diisodecyl phthalate are heat-resistant and prevent leakage, while diisodecyl adipate is cold-resistant and prevents brittleness. The combination of the two achieves excellent performance at both high and low temperatures. The additives do not act independently, but rather amplify the overall performance through complementary effects. Detailed Implementation

[0030] The present application will be further described in detail below with reference to the embodiments.

[0031] The natural rubber (smoked sheet rubber) is RSS3 from Thailand's Hongmanli Company; The chlorosulfonated polyethylene rubber is TS530 from Tosoh Corporation of Japan; The ethylene-vinyl acetate rubber is Lanxess's EVM500. The highly active magnesium oxide MgO 150 is STARMAG 150 from Kamishima Corporation of Japan; The stearic acid is SA1801 from Indonesian Sumiassih Oils & Fats Chemical Co., Ltd. (PT. SUMIASIH). Anti-aging agent 4020 was purchased from Shandong Shangshun Company; The antioxidant NBC was purchased from Wuhan Jinghe Company; The antioxidant BLE was purchased from Changzhou Wuzhou Chemical Co., Ltd. The microcrystalline wax used is RW220 from Jinchangsheng Company; The tert-butylphenol formaldehyde resin is SL-1401 from Huachi Company; N774 carbon black was purchased from Jiangxi Black Cat Company; Qiangwei powder was purchased from Jinan Xinno Polymer Company; Diisodecyl phthalate was purchased from ExxonMobil. Diisodecyl adipate was purchased from Weifang Hansheng Chemical Co., Ltd. Zinc oxide was purchased from Yangzhou Huali Zinc Industry Co., Ltd. Pentaerythritol was purchased from Guangdong Xiyuan Chemical Co., Ltd. Accelerator DM was purchased from Weilin New Materials Co., Ltd. The accelerator DPTT was purchased from Weilin New Materials Co., Ltd. The sulfur was purchased from Henan Kailun Chemical Company; The butadiene rubber is Sinopec's BR9000; The trans-butadiene rubber was purchased from Shandong Huaju Polymer Materials Co., Ltd. The chloroprene rubber is CR232 from Changshou Chemical. N550 carbon black was purchased from Jiangxi Black Cat Company; Anti-aging agent RD was purchased from Shandong Shangshun Company; Accelerator CZ was purchased from Tianjin Dongfang Ruichuang Company; Naphthenic oil KN4006 was purchased from a company in Karamay, Xinjiang. N330 carbon black was purchased from Jiangxi Black Cat Company; Example 1 A heat-resistant and ozone-resistant air spring outer layer rubber compound comprises the following components by weight: 30 parts natural rubber (NR); 55 parts chlorosulfonated polyethylene rubber (CSM); 15 parts ethylene-vinyl acetate rubber (EVM); 7 parts high-activity magnesium oxide; 0.5 parts stearic acid; 1.5 parts antioxidant 4020; 1 part antioxidant NBC; 2 parts antioxidant BLE; 1 part microcrystalline wax; 6 parts tert-butylphenol formaldehyde resin; 50 parts N774 carbon black; 20 parts strong phthalate powder; 15 parts diisodecyl phthalate; 10 parts diisodecyl adipate; 5 parts zinc oxide; 4.5 parts pentaerythritol; 0.8 parts accelerator DM; 1 part accelerator DPTT; and 0.6 parts sulfur.

[0032] The heat-resistant and ozone-resistant outer layer rubber material of the air spring in this embodiment is prepared by the following method: S1: Put natural rubber into a 75L internal mixer, masticate for 3 minutes, mix to 105℃, discharge the rubber, cool and collect the rubber. S2: Put the plasticized natural rubber, chlorosulfonated polyethylene rubber, and ethylene-vinyl acetate rubber into a 75L internal mixer and mix them at a speed of 20r / min for 5min until the temperature reaches 90℃. S3: Add high-activity magnesium oxide, stearic acid, antioxidant 4020, antioxidant BLE, microcrystalline wax and tert-butylphenol formaldehyde resin to the internal mixer, and mix at a speed of 20r / min for 4min to raise the temperature to 95℃. S4: Add strong powder and continue mixing in a 75L internal mixer at a speed of 20r / min for 2min until the temperature reaches 105℃; S5: Add N774 carbon black and diisodecyl ester to the internal mixer and mix at 20 r / min for 3 min to raise the temperature to 115℃; S6: Lift the top bolt of the internal mixer, clean the powder above and press it down, mix at 20 r / min for 3 min, and discharge the rubber when the temperature reaches 120℃. Transfer the rubber compound to the open mill and cool it down to 70℃ by wrapping the rollers. S7: Add zinc oxide, antioxidant NBC, pentaerythritol, accelerator DPTT and accelerator DM to the masterbatch on the open mill, mix for 5 minutes, sheet out, and collect for later use after the temperature drops to room temperature.

[0033] Example 2 A heat-resistant and ozone-resistant outer layer rubber compound for air springs comprises the following components by weight: Natural rubber (NR) 60 parts; chlorosulfonated polyethylene rubber (CSM) 35 parts; ethylene-vinyl acetate rubber (EVM) 5 parts; high-activity magnesium oxide 4 parts; stearic acid 3 parts; antioxidant 4020 3 parts; antioxidant NBC 3 parts; antioxidant BLE 5 parts; microcrystalline wax 3 parts; tert-butylphenol formaldehyde resin 3 parts; N774 carbon black 30 parts; strong iodine powder 40 parts; diisodecyl phthalate 5 parts; diisodecyl adipate 5 parts; zinc oxide 2 parts; pentaerythritol 2 parts; accelerator DM 0.2 parts; accelerator DPTT 0.4 parts; sulfur 1.2 parts.

[0034] Among them, the iodine value of highly active magnesium oxide is 150 mg / g.

[0035] The heat-resistant and ozone-resistant outer layer rubber material of the air spring in this embodiment is prepared by the following method: S1: Put natural rubber into a 75L internal mixer, masticate for 5 minutes, mix to 120℃ and then discharge the rubber, cool and collect the rubber. S2: Put the plasticized natural rubber, chlorosulfonated polyethylene rubber, and ethylene-vinyl acetate rubber into a 75L internal mixer and mix them at a speed of 20r / min for 8min until the temperature reaches 90℃. S3: Add high-activity magnesium oxide, stearic acid, antioxidant 4020, antioxidant BLE, microcrystalline wax and tert-butylphenol formaldehyde resin to the internal mixer, and mix at a speed of 20r / min for 6min to raise the temperature to 100℃. S4: Add the strong powder and continue to mix in a 75L internal mixer at a speed of 20r / min for 4 minutes until the temperature reaches 110℃; S5: Add N774 carbon black and diisodecyl ester to the internal mixer and mix at 20 r / min for 6 min to raise the temperature to 120℃; S6: Lift the top bolt of the internal mixer, clean the powder above and press it down, mix at 20 r / min for 5 min, and discharge the rubber when the temperature reaches 120℃. Transfer the rubber compound to the open mill and cool it down to 80℃ by wrapping the rollers. S7: Add zinc oxide, antioxidant NBC, pentaerythritol, accelerator DPTT and accelerator DM to the masterbatch on the open mill, mix for 8 minutes, sheet out, and collect for later use after the temperature drops to room temperature.

[0036] Example 3 A heat-resistant and ozone-resistant outer layer rubber compound for air springs comprises the following components by weight: Natural rubber (NR) 40 parts; chlorosulfonated polyethylene rubber (CSM) 45 parts; ethylene-vinyl acetate rubber (EVM) 15 parts; high-activity magnesium oxide 5.5 parts; stearic acid 1.5 parts; antioxidant 4020 1.8 parts; antioxidant NBC 1.1 parts; antioxidant BLE 3 parts; microcrystalline wax 1.5 parts; tert-butylphenol formaldehyde resin 5.5 parts; N774 carbon black 38 parts; strong phthalate powder 35 parts; diisodecyl phthalate 8 parts; diisodecyl adipate 7 parts; zinc oxide 3 parts; pentaerythritol 3 parts; accelerator DM 0.3 parts; accelerator DPTT 0.6 parts; sulfur 0.7 parts.

[0037] Among them, the iodine value of highly active magnesium oxide is 150 mg / g, and the natural rubber is smoked sheet rubber.

[0038] The heat-resistant and ozone-resistant outer layer rubber material of the air spring in this embodiment is prepared by the following method: S1: Put natural rubber into a 75L internal mixer, masticate for 5 minutes, mix to 110℃ and then discharge the rubber, cool and collect the rubber. S2: Put the plasticized natural rubber, chlorosulfonated polyethylene rubber, and ethylene-vinyl acetate rubber into a 75L internal mixer and mix them at a speed of 20r / min for 6.5min until the temperature reaches 85℃. S3: Add high-activity magnesium oxide, stearic acid, antioxidant 4020, antioxidant BLE, microcrystalline wax and tert-butylphenol formaldehyde resin to the internal mixer, and mix at a speed of 20 r / min for 5.5 min to raise the temperature to 95℃. S4: Add strong powder and continue mixing in a 75L internal mixer at a speed of 20r / min for 2min until the temperature reaches 105℃; S5: Add N774 carbon black and diisodecyl ester to the internal mixer and mix at 20 r / min for 4 min to raise the temperature to 115℃; S6: Lift the top bolt of the internal mixer, clean the powder above and press it down, mix at 20 r / min for 3.5 min, and discharge the rubber when the temperature reaches 120℃. Transfer the rubber compound to the open mill and cool it down to 70℃ by wrapping the rollers. S7: Add zinc oxide, antioxidant NBC, pentaerythritol, accelerator DPTT and accelerator DM to the masterbatch on the open mill, mix for 6 minutes, sheet, and collect for later use after the temperature drops to room temperature.

[0039] Example 4 A heat-resistant and ozone-resistant outer layer rubber compound for air springs comprises the following components by weight: Natural rubber (NR) 50 parts; chlorosulfonated polyethylene rubber (CSM) 38 parts; ethylene-vinyl acetate rubber (EVM) 12 parts; high-activity magnesium oxide 4.5 parts; stearic acid 2 parts; antioxidant 4020 2.2 parts; antioxidant NBC 0.9 parts; antioxidant BLE 3.5 parts; microcrystalline wax 2.1 parts; tert-butylphenol formaldehyde resin 5 parts; N774 carbon black 45 parts; strong phthalate powder 30 parts; diisodecyl phthalate 10 parts; diisodecyl adipate 8 parts; zinc oxide 3.8 parts; pentaerythritol 2.4 parts; accelerator DM 0.5 parts; accelerator DPTT 0.8 parts; sulfur 1.1 parts.

[0040] Among them, the iodine value of highly active magnesium oxide is 150 mg / g, and the natural rubber is smoked sheet rubber.

[0041] The heat-resistant and ozone-resistant outer layer rubber material of the air spring in this embodiment is prepared by the following method: S1: Put natural rubber into a 75L internal mixer and masticate for 4.5 minutes. When the mixing temperature reaches 105℃, discharge the rubber, then cool and collect the rubber.

[0042] S2: Add the masticated natural rubber, chlorosulfonated polyethylene rubber, and ethylene-vinyl acetate rubber to a 75L internal mixer and mix at 20r / min for 8 minutes until the temperature reaches 90℃.

[0043] S3: Add high-activity magnesium oxide, stearic acid, antioxidant 4020, antioxidant BLE, microcrystalline wax and tert-butylphenol formaldehyde resin to a 75L internal mixer, and mix at 20r / min for 5 minutes until the temperature reaches 95℃.

[0044] S4: Add the strong powder to a 75L internal mixer and mix at a speed of 20r / min for 3 minutes until the temperature rises to 105℃.

[0045] S5: Place N774 carbon black and diisodecyl ester into a mixer and mix at a speed of 20 r / min for 5.5 min until the mixing temperature reaches 118℃.

[0046] S6: Lift the top bolt of the internal mixer, clean the powder above, and press it down. Mix at a speed of 20r / min for 3.5min. When the temperature reaches 120℃, discharge the rubber and transfer the rubber to the open mill. Cool it down to 75℃ by wrapping the rollers.

[0047] S7: Add zinc oxide, antioxidant NBC, pentaerythritol, accelerator DPTT and accelerator DM to the masterbatch on the open mill, mix for 8 minutes to make it uniform, then sheet it, and collect it for later use after the temperature drops to room temperature.

[0048] Comparative Example 1 A heat-resistant and ozone-resistant outer layer rubber compound for air springs comprises the following components by weight: Natural rubber (SCR5 standard rubber) 55 parts; butadiene rubber 45 parts; N550 carbon black 20 parts; N774 carbon black 25 parts; environmentally friendly aromatic oil 6 parts; antioxidant RD 1.5 parts; antioxidant 4020 2 parts; microcrystalline wax 2 parts; zinc oxide 5 parts; stearic acid 1.5 parts; sulfur 1.8 parts; accelerator CZ 1.0 part; scorch inhibitor: 0.15 parts.

[0049] The preparation method of the comparative rubber compound is the same as that of Example 3.

[0050] Comparative Example 2 A heat-resistant and ozone-resistant air spring outer layer compound differs from the compound in Example 3 in that, by weight, 60 parts of natural rubber and 40 parts of butadiene rubber are used to replace the original natural rubber (NR), chlorosulfonated polyethylene rubber (CSM), and ethylene-vinyl acetate rubber (EVM).

[0051] Comparative Example 3 A heat-resistant and ozone-resistant air spring outer layer compound differs from the compound in Example 3 in that, by weight, 50 parts of natural rubber, 35 parts of cis-butadiene rubber, and 15 parts of trans-butadiene rubber are used to replace the original natural rubber (NR), chlorosulfonated polyethylene rubber (CSM), and ethylene-vinyl acetate rubber (EVM).

[0052] Comparative Example 4 A heat-resistant and ozone-resistant air spring outer layer compound differs from the compound in Example 3 in that, by weight, 60 parts of natural rubber and 40 parts of chloroprene rubber replace the original natural rubber (NR), chlorosulfonated polyethylene rubber (CSM), and ethylene-vinyl acetate rubber (EVM).

[0053] Comparative Example 5 A heat-resistant and ozone-resistant outer layer rubber compound for air springs comprises the following components by weight: Natural rubber (NR) 40 parts; chlorosulfonated polyethylene rubber (CSM) 45 parts; ethylene-vinyl acetate rubber (EVM) 15 parts; stearic acid 1 part; zinc oxide 3 parts; antioxidant 4020 1.8 parts; antioxidant DTPD (3100) 1.1 parts; antioxidant RD 3 parts; microcrystalline wax 2 parts; N330 carbon black 18 parts; N550 carbon black 35 parts; naphthenic oil KN4006 10 parts; accelerator CZ 0.9 parts; sulfur 0.7 parts.

[0054] Among them, naphthenic oil KN4006 is a plasticizer.

[0055] Performance testing 1. Determination of vulcanization parameters To facilitate data comparison, uncured rubber compounds from Examples 1-4 and Comparative Examples 1-5 were also used, and their curing parameters at 165°C were measured using a vulcanizing apparatus. The results are shown in Table 1.

[0056] Table 1 Test results of vulcanization parameters of rubber compounds As shown in Table 1, the processing time and vulcanization time of the rubber compound of the present invention can meet the normal production requirements of the rubber compound.

[0057] 2. Rubber compound performance parameter testing According to national standards GB / T528, GB / T7759, GB / T531.1, GB / T13934, and GB / T1682, the conventional properties of the air spring rubber compounds in Examples 1-4 and Comparative Examples 1-5 were tested. Based on the performance requirements of GB / T 13061-2017, the acceptable standards for tensile strength are: ≥15 MPa; elongation at break (%): ≥500%; permanent deformation at break: ≤35%; compression set: ≤30%; Shore hardness: 55-65 HA; flexural strength: ≥1 million cycles; and brittle temperature: ≤-40℃.

[0058] The results are shown in Table 2.

[0059] Table 2 Performance Parameter Test Results As shown in Table 2, the conventional performance parameters of the four rubber compounds in the embodiments of the present invention all meet the qualified standards. However, only the conventional performance parameters of the rubber compound in Comparative Example 1 meet the qualified standards. Even so, the number of flexural cracks in Comparative Example 1 is much less than that of the rubber compound in the embodiments of the present invention.

[0060] 3. Heat resistance test The heat resistance of the air spring rubber compound in hot air environment was tested according to national standards GB / T3512 and GB / T528 in Examples 1-4 and Comparative Examples 1-5.

[0061] According to the performance requirements of the rubber compound in GB / T 13061-2017, the acceptable standards for the change rate of tensile strength, the change rate of elongation at break, and the change in hardness after aging in hot air at 70℃ for 96 hours are ±20%. To verify the improvement in the heat aging resistance of the rubber compound, this invention adds more stringent test conditions of aging in hot air at 100℃ for 72 hours and at 120℃ for 48 hours to further confirm the heat aging resistance of the rubber compound. The results are shown in Table 3.

[0062] Table 3 Results of heat resistance test As shown in Table 3, the rubber compounds of Examples 1-4 of the present invention have excellent heat resistance properties, which are significantly better than those of other comparative rubber compounds. This indicates that the components of the formulation of the present invention are irreplaceable and have a significant synergistic effect.

[0063] 4. Ozone resistance test According to the requirements of GB / T 13061-2017 standard, the ozone resistance of the rubber compound must meet the requirement of not cracking after 72 hours of testing under the conditions of ozone concentration of 50 pphm, 20% tensile strength, and temperature of 40℃. The ozone resistance of the air spring rubber compounds in Examples 1-4 and Comparative Examples 1-5 were tested in an ozone environment according to national standard GB / T 7762, and the results are shown in Table 4.

[0064] Table 4 Ozone Resistance Test As shown in Table 4, the ozone resistance of the rubber compounds in Examples 1-4 of this invention is also excellent, while the ozone resistance of Comparative Examples 1-5 is weak. Only Comparative Examples 1, 4, and 5 can perform well under the test conditions of 50 pphm, 20% tensile strength, and 40℃×72h. However, when the test conditions are 100 pphm, 30% tensile strength, and 40℃×120h, these comparative examples will also crack. That is, the ozone resistance of Comparative Examples 1, 4, and 5 is weak under the conditions of 100 pphm, 30% tensile strength, and 40℃×120h.

[0065] Application Example 1 An air spring, prepared using the rubber compound of Example 3, is described in the following specific preparation method: S1: The rubber material is calendered into a sheet of a specified thickness, and then the sheet is bonded to the rubber cord fabric on a molding machine to obtain a product blank; S2: The product blank is vulcanized to obtain a heat-resistant and ozone-resistant air spring bladder.

[0066] S3: Remove the flash from the vulcanized air spring bladder; S4: One end of the air spring bladder is fitted with a metal cap (or metal ring), and the other end is fitted with a metal or plastic piston. At the same time, a buffer rubber block is installed inside to obtain a complete air spring product. S5: After filling the air spring with a certain amount of air through the air nozzle on the metal cover, place it in a water tank so that the entire air spring is completely submerged and check the airtightness of the product.

[0067] S6: Remove the air spring from the water tank without any leaks, dry it, and package it.

[0068] Application Example 2 An air spring, which differs from Application Example 1 in that it uses the rubber compound of Example 4.

[0069] Application Comparative Example 1 An air spring, which differs from Application Example 1 in that it uses the rubber compound of Comparative Example 1.

[0070] Application Comparative Example 2 An air spring, which differs from Application Example 1 in that it uses the rubber compound of Comparative Example 2.

[0071] Application Comparative Example 3 An air spring, which differs from Application Example 1 in that it uses the rubber compound of Comparative Example 3.

[0072] Application Comparative Example 4 An air spring, which differs from Application Example 1 in that it uses the rubber compound of Comparative Example 4.

[0073] Application Comparative Example 5 An air spring, which is different from that in Application Example 1 in that the rubber compound of Comparative Example 5 is used.

[0074] Performance test According to the requirements of the GB / T 13061-2017 standard, it is qualified that the internal pressure drop of the air spring product within 24 hours does not exceed 0.05 MPa, the burst pressure of the air spring is not less than 2.5 times the maximum internal pressure (the maximum internal pressure of the product is 0.8 MPa, that is, the burst pressure requirement is not less than 2.0 MPa), and the room temperature bench fatigue life of the air spring is not less than 3 million times. The adhesion strength between the outer rubber layer and the cord fabric layer of the air spring is required by the enterprise standard and is not less than 6.0 kN / m. To verify the improvement of the heat aging performance of the air spring product, the present invention additionally conducts a hot air aging bench test on the air spring product under the conditions of 80 °C and 100 °C, that is, under more severe conditions, to further confirm the heat aging situation of the air spring product. The laboratory performance parameters of the air springs of Application Examples 1-2 and Application Comparative Examples 1-5 are tested, and the results are shown in Table 5.

[0075] Table 5 Performance test results of air springs As can be seen from Table 5, all the data of the air springs prepared in Embodiment 3 and Embodiment 4 of the present invention are significantly better than those of the air springs prepared with the rubber compounds of Comparative Examples 1-5, indicating that the rubber compound of the present invention can also maintain excellent performance in practical applications.

[0076] This specific embodiment is only an explanation of the present application, and it is not a limitation of the present application. Those skilled in the art can make modifications without creative contributions to this embodiment according to needs after reading this specification, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A heat-resistant and ozone-resistant outer layer rubber material for air springs, characterized in that, The product comprises, by weight fraction: 30-60 parts natural rubber; 35-55 parts chlorosulfonated polyethylene rubber; 5-15 parts ethylene-vinyl acetate rubber; 4-7 parts highly active magnesium oxide; 0.5-3 parts stearic acid; 4.5-11 parts antioxidant; 1-3 parts microcrystalline wax; 3-6 parts tert-butylphenol formaldehyde resin; 50-90 parts reinforcing filler; 10-25 parts plasticizer; 2-5 parts zinc oxide; 2.6-5.7 parts vulcanizing agent; and 0.6-1.8 parts accelerator.

2. The heat-resistant and ozone-resistant outer layer rubber material of an air spring according to claim 1, characterized in that: The natural rubber mentioned is smoked sheet rubber.

3. The heat-resistant and ozone-resistant outer layer rubber material of an air spring according to claim 1, characterized in that: The iodine value of the highly active magnesium oxide is 150 mg / g.

4. The heat-resistant and ozone-resistant outer layer rubber material of an air spring according to claim 1, characterized in that: The antioxidant is a compound of antioxidant 4020, antioxidant NBC and antioxidant BLE; the mass ratio of the three is (1.5-3):(1-3):(2-5).

5. The heat-resistant and ozone-resistant outer layer rubber material of an air spring according to claim 1, characterized in that: The plasticizer is diisodecyl ester, which is one or more of diisodecyl phthalate and diisodecyl adipate.

6. The heat-resistant and ozone-resistant outer layer rubber material of an air spring according to claim 5, characterized in that: The reinforcing filler is N774 carbon black and strong powder; the mass ratio of N774 carbon black to strong powder is (3-5):(2-4).

7. The heat-resistant and ozone-resistant outer layer rubber material of an air spring according to claim 1, characterized in that: The vulcanizing agent is pentaerythritol and sulfur; the mass ratio of pentaerythritol to sulfur is (2-4.5):(0.6-1.2).

8. The heat-resistant and ozone-resistant outer layer rubber material of an air spring according to claim 1, characterized in that: The accelerator is accelerator DM and accelerator DPTT, and the mass ratio of accelerator DM to accelerator DPTT is (0.2-0.8):(0.4-1).

9. A method for preparing the heat-resistant and ozone-resistant outer layer rubber material of an air spring according to any one of claims 1-8, characterized in that, Includes the following steps: S1: Put natural rubber into an internal mixer, plasticize for 3-5 minutes, mix to 105-120℃, discharge the rubber, cool and collect the rubber. S2: Put the masticated natural rubber, chlorosulfonated polyethylene rubber, and ethylene-vinyl acetate rubber into an internal mixer and mix for 5-8 minutes until the temperature reaches 85-90℃. S3: Add highly active magnesium oxide, stearic acid, antioxidant, microcrystalline wax and tert-butylphenol formaldehyde resin to the internal mixer and mix for 4-6 minutes to 95-100℃. S4: Add reinforcing filler and mix in an internal mixer for 2-4 minutes to 105-110℃; S5: Add the plasticizer to the internal mixer and mix for 3-6 minutes until the temperature reaches 115-120℃; S6: Lift the top bolt of the internal mixer, clean the powder above and press it down. Mix for 3-5 minutes until the temperature reaches 120°C, then discharge the rubber. Transfer the rubber to the open mill and cool it down to 70-80°C by wrapping the rollers. S7: Add zinc oxide, vulcanizing agent, and accelerator to the masterbatch on the open mill, mix for 5-8 minutes, then sheet the mixture and collect it for later use after the temperature drops to room temperature.

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