Palm oil-resistant, damp-heat-resistant and gas permeation-resistant tire sidewall rubber composition

Abstract

The invention relates to the technical field of tire production, in particular to a tire sidewall rubber composition resistant to palm oil, damp heat and gas permeation. On the basis of 100 parts by weight of the rubber component, the rubber composition further comprises 30 to 50 parts by weight of carbon black, 5 to 10 parts by weight of silicon dioxide, 5 to 10 parts by weight of superprex, 2 to 5 parts by weight of alkyl styrene resin, 1.0 to 3.0 parts by weight of zinc oxide, 1.0 to 3.0 parts by weight of stearic acid, 0.5 to 1.5 parts by weight of an anti-aging agent, 1.0 to 3.0 parts by weight of protective wax, 2.0 to 3.0 parts by weight of a super vulcanizing agent PSO (Polystyrene Oxide)-35, 0.3 to 0.8 part by weight of sulfur and 1.0 to 2.0 parts by weight of an accelerant DM, wherein the rubber component comprises 45-60 parts by weight of natural rubber, 5-10 parts by weight of rare earth isoprene rubber, 15-25 parts by weight of chlorinated butyl rubber and 15-25 parts by weight of high vinyl polybutadiene rubber. According to the invention, the damp-heat aging resistance of the sidewall is improved, and the palm oil resistance and the gas permeation resistance are improved.

Description

Technical Field

[0001] The invention relates to the technical field of tire production, in particular to a tire sidewall rubber composition which is resistant to palm oil, moisture and heat, and gas penetration. Background Art

[0002] As we all know, Southeast Asia has a tropical rainforest climate, characterized by high temperatures throughout the year, abundant rainfall, and a hot and humid climate that provides a unique natural environment for the production of oil palm, so the region is rich in palm oil. The transportation of palm oil has driven the development of local all-steel truck tires. During the long-term circulation of tires transporting palm oil, palm oil leaks to the tire sidewalls, and the sidewall rubber is corroded by palm oil for a long time and cracks appear. With the increase of speed and load, the cracks gradually expand and extend, and external gas gradually penetrates into the tire body. At the same time, it is attacked by ozone and oxygen. When the continuous driving time is too long, the sidewalls are repeatedly flexed and deformed. When the accumulated heat of the tire is too high, the tire temperature rises rapidly, and it is very easy to cause delamination damage at the stress concentration point. Therefore, higher requirements are put forward for the oil resistance, moisture resistance, and gas permeation resistance of the tire.

[0003] Traditional sidewall formulation technology mainly focuses on how to resist flex fatigue and aging, and the raw rubber system is mainly natural rubber and polybutadiene rubber. Currently, there is no technical report on tire sidewall rubber composition and its evaluation method that is resistant to palm oil, moisture and heat, and gas permeation in the industry. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies of the above-mentioned prior art and to provide a tire sidewall rubber composition that is resistant to palm oil, moisture and heat, and gas permeation, thereby improving the sidewall's resistance to moisture and heat aging, and improving its palm oil resistance and gas permeation resistance.

[0005] The technical solution adopted by the present invention to solve the above technical problems is: a palm oil-resistant, heat-resistant and gas-permeable tire sidewall rubber composition, characterized in that, based on 100 parts by weight of the rubber component, it also contains 30 to 50 parts by weight of carbon black, 5 to 10 parts by weight of silica, 5 to 10 parts by weight of suprex, 2 to 5 parts by weight of alkyl styrene resin, 1.0 to 3.0 parts by weight of zinc oxide, 1.0 to 3.0 parts by weight of stearic acid, 0.5 to 1.5 parts by weight of antioxidant, 1.0 to 3.0 parts by weight of protective wax, 2.0 to 3.0 parts by weight of super vulcanizer PSO-35, 0.3 to 0.8 parts by weight of sulfur, and 1.0 to 2.0 parts by weight of accelerator DM, wherein the rubber component contains 45 to 60 parts by weight of natural rubber, 5 to 10 parts by weight of rare earth isoprene rubber, 15 to 25 parts by weight of chlorinated butyl rubber, and 15 to 25 parts by weight of high vinyl polybutadiene rubber.

[0006] The chlorine content of the chlorinated butyl rubber is ≥1.2%, the weight ratio of rare earth isoprene rubber to natural rubber is ≤20%, the weight ratio of chlorinated butyl rubber to total rubber components is ≥15%, the weight ratio of high vinyl polybutadiene rubber to total rubber components is ≥15%, the total weight ratio of chlorinated butyl rubber and high vinyl polybutadiene rubber to total rubber components is ensured to be ≥30% and ≤50%, the weight ratio of natural rubber to total rubber components is ≥50%, the mass fraction of vinyl side groups of high vinyl polybutadiene rubber (HVBR) is more than 80%, and the 1,2-structure is randomly distributed.

[0007] The beneficial effects of the present invention are that it has excellent palm oil resistance and flexural fatigue resistance, preventing the long-term swelling and corrosion of the sidewall rubber by palm oil during transportation, and at the same time has low gas permeability, preventing gas from penetrating through the sidewall into the tire body, effectively reducing the sidewall delamination problem caused by air infiltration, and has excellent resistance to wet and hot aging, avoiding the reduction of the adhesion performance of the rubber composition in a high temperature and high humidity environment, resulting in sidewall bulging and delamination. DETAILED DESCRIPTION

[0008] The present invention will be further described below in conjunction with embodiments:

[0009] The rubber components involved in the present invention include chlorinated butyl rubber, natural rubber, rare earth isoprene rubber and high vinyl polybutadiene rubber. The chlorine content of the chlorinated butyl rubber is ≥1.2%, the weight ratio of the chlorinated butyl rubber to the total rubber component is ≥15%, the weight ratio of the high vinyl polybutadiene rubber to the total rubber component is ≥15%, and the total weight ratio of the chlorinated butyl rubber and the high vinyl polybutadiene rubber to the total rubber component is ensured to be ≥30% and ≤50%. The chlorine atom group is polar, and palm oil is a non-polar solvent. According to the principle of like dissolves like, the chlorinated butyl rubber needs to be higher than a certain proportion to inhibit the dissolution and corrosion of the sidewall rubber by palm oil, and improve the gas permeation resistance. The high vinyl polybutadiene rubber is selected to utilize the steric hindrance effect of the side group. The high vinyl polybutadiene rubber (HVBR) is required to have a vinyl side group mass fraction of more than 80%, and the 1,2-structure is randomly distributed, which delays the penetration of oil and gas into the tire, and the total The weight proportion of the rubber component must be ≥15% to play a role and improve the fatigue resistance of the sidewall rubber composition. At the same time, it is necessary to ensure that the two do not account for too high a proportion of the total rubber component. If the total amount of chlorinated butyl rubber and high vinyl polybutadiene rubber is high, the physical properties and flexural fatigue properties of the sidewall rubber will deteriorate. The chlorinated butyl rubber is preferably 15 to 25 parts, and the high vinyl polybutadiene rubber is preferably 15 to 25 parts. Natural rubber has poor aging resistance. 5 to 10 parts of rare earth isoprene rubber are selected to improve aging resistance and viscosity. At the same time, it is necessary to ensure that the proportion of natural rubber in the total rubber component is ≥50%, and the comprehensive physical properties such as the tensile strength of the sidewall are ensured. Therefore, the weight ratio of rare earth isoprene rubber to natural rubber is ≤20%, and the proportion of natural rubber in the total rubber component is ≥50%. Preferably, 45 to 60 parts of natural rubber and 5 to 10 parts of rare earth isoprene rubber are used.

[0010] The present invention uses an alkyl styrene resin instead of environmentally friendly oil. On the one hand, the side group benzene ring structure is used to reduce the migration of gas and water small molecules into the tire, thereby improving oil resistance and gas penetration resistance. On the other hand, it can reduce the migration of antioxidants to the outside of the tire, thereby improving the aging resistance of the sidewall rubber composition. The product SL6801 can be purchased from Huaqi (China) Chemical Co., Ltd. If the dosage is too low, no obvious effect can be seen on oil resistance and gas penetration resistance, and if the dosage is too high, it will lead to excessive heat generation.

[0011] The high vinyl polybutadiene rubber HVBR described in the invention is synthesized by coordination polymerization, and the molecular side groups contain rich vinyl, with a mass fraction of more than 80%, and the 1,2-structure is randomly distributed. It is a product of the rubber factory of Sinopec Qilu Co., Ltd. The rare earth isoprene rubber NdIR described in the invention has a cis content of 98% and a relative molecular mass of more than 450,000. It is a product of the Yanshan Branch of Sinopec Beijing Chemical Research Institute.

[0012] The suprex described in the invention has a diameter-to-thickness ratio of 23, a pH value of 4 to 5, and a lamellar structure, which improves the gas barrier performance, reduces the gas penetration into the tire, forms a dense material cross-linking network with the rubber, increases the cross-linking density of the mixed rubber, and can effectively prevent oil molecules from diffusing into the rubber, thereby improving oil resistance. However, if the amount of inorganic filler exceeds a certain level, it will affect the physical properties of the sidewall rubber composition, such as tensile strength. It is produced by Yiruishi North American Ceramic Technology Group.

[0013] The protective wax HG72 described in the present invention is a product of Shandong Yanggu Huatai Chemical Co., Ltd. The carbon number distribution of the wax film at 40° C. is concentrated in C29-C37, and the mass fraction of isoalkanes is large. The wax film has a high density, which inhibits the migration of antioxidants and improves the sidewall's resistance to ozone aging, wet heat aging and flex fatigue.

[0014] The super vulcanizer PSO-35 of the present invention is used in combination with sulfur. Compared with sulfur crosslinking, the Sx of the vulcanized rubber is reduced, that is, the polysulfide bonds are reduced, flexible groups are introduced, the anti-vulcanization reversion and heat aging performances are excellent, and the flex fatigue resistance is improved. If the super vulcanizer PSO-35 is used alone, the crosslinking density is low and the physical properties of the sidewall rubber composition are low. Therefore, it must be used in combination with a small amount of sulfur to ensure the physical properties while improving the heat resistance. Therefore, it is recommended that the amount of PSO-35 is 2.0-3.0 parts and the amount of sulfur is 0.3-0.8 parts. The product is produced by Jiangsu Qixiang High-tech Materials Co., Ltd.

[0015] Table 1: Invention formula table (unit: weight parts)

[0016]

[0017]

[0018] Table 2: Physical properties of tire sidewall test pieces manufactured by formula

[0019]

[0020]

[0021] Test piece vulcanization conditions: 150℃*30min, wet heat aging test conditions: immersed in a sealed container with 100℃ water vapor and aged for 72 hours.

[0022] Evaluation method for oil resistance of tire sidewalls made of sidewall rubber compositions:

[0023] 1. Volume swelling ratio, %: Weigh a fixed weight test piece and place it in a 1000ml beaker, immerse it in a certain volume of palm oil, requiring the palm oil to cover the test piece, place it in a nitrogen and oxygen aging box at 65°C and soak it for 7 days, take out the sample and weigh it, calculate the volume of the sample before oil immersion V0 and the volume of the sample after oil immersion V1, and calculate the volume swelling ratio (V1-V0) / V0. In order to distinguish different test schemes, the test piece can be cut into different shapes to distinguish them. The larger the volume swelling ratio, the more oil the test piece is immersed in, which means the worse the oil resistance is. Therefore, choosing a small volume swelling ratio is conducive to improving oil resistance.

[0024] 2. Change rate of tensile strength after oil immersion, %: Use the standard dumbbell-shaped specimen for tensile strength testing according to the national standard to apply the temperature and oil immersion conditions with the same volume swelling ratio as mentioned above to test the change rate of tensile strength of the specimen after oil immersion. A negative number represents a decrease in tensile strength. The lower the absolute value, the better the oil resistance.

[0025] Evaluation method for gas permeation resistance of tire sidewalls made of sidewall rubber compositions:

[0026] As evaluated from the gas permeability coefficient, the smaller the permeability coefficient of the tire sidewall made of the sidewall rubber composition, the higher the air tightness and the better the gas permeation resistance performance.

[0027] Evaluation method for wet heat aging resistance of tire sidewalls made of sidewall rubber compositions:

[0028] The vulcanized test piece was immersed in a sealed container with water vapor at 100°C for aging for 72 hours, and the change rate of the tensile strength before and after aging was tested. The lower the absolute value of the change rate, the smaller the decrease in tensile strength and the better the moisture and heat aging resistance.

[0029] As can be seen from the table, compared with the comparative example, the volume swelling ratio of the inventive example becomes smaller, and the tensile strength decreases after oil immersion, and the absolute value of the change rate becomes smaller, both of which indicate that the oil resistance of the inventive formula is improved, and the oil resistance performance is improved by more than 40%; the permeability coefficient before and after aging, the inventive example is smaller than that of the comparative example, indicating that the higher the air tightness of the sidewall rubber composition, the better the gas permeation resistance, which can be improved by more than 20% at most; the change in tensile strength after wet heat aging is reduced, indicating that the wet heat aging resistance performance is excellent.

[0030] The raw rubber of the present invention mainly adopts a certain proportion of chlorinated butyl rubber and high vinyl polybutadiene rubber. Since chlorinated butyl rubber contains polar chlorine atom groups and palm oil belongs to non-polar solvents, according to the principle of like dissolves like, chlorinated butyl rubber plays a role in inhibiting palm oil from dissolving and corroding the sidewall rubber. At the same time, the side benzene ring of the alkyl styrene resin reacts synergistically with the chlorinated butyl rubber to form a dense network with large steric hindrance, thereby preventing palm oil from migrating from the outside of the sidewall to the inside of the tire body. At the same time, due to the molecular structure of the molecular chain side groups of the chlorinated butyl rubber being dense and the polybutadiene rubber with 1,2-structured randomly distributed vinyl molecular side chains, external gas is prevented from penetrating into the interior of the tire through rubber molecules, and gas permeation resistance is effectively improved. Suprex with a diameter-to-thickness ratio of 23 and a PH value of 4-5 and a lamellar structure is used to improve gas barrier performance, reduce gas penetration into the interior of the tire, form a dense material cross-linking network with the rubber, increase the cross-linking density of the mixed rubber, effectively prevent oil molecules from diffusing into the interior of the rubber, and improve oil resistance. A certain proportion of rare earth isoprene rubber and natural rubber are used to improve the sidewall's resistance to wet heat aging while ensuring the sidewall's flexural performance. Super vulcanizer PSO-35 is used to form a dense cross-linked network dominated by single and double sulfur bonds with sulfur and DM, which increases the cross-linking density of the rubber compound, increases the cross-linking bond energy, avoids the scission of polysulfide bonds at high temperatures, and reduces the physical properties and adhesion of the sidewall, and improves the resistance to wet heat aging. At the same time, the polar groups in the rubber matrix in the wet and hot environment prevent water from penetrating into the internal rubber and migrating to increase the oxygen concentration on the steel wire surface. Chlorobutyl rubber, natural rubber, rare earth isoprene rubber and high vinyl polybutadiene rubber with specific chlorine content are used. The specific rubber characteristics are combined with the synergistic reaction of various other rubbers. From the two aspects of similar miscibility and steric hindrance effect mechanism, the sidewall's resistance to wet heat aging is improved while ensuring the sidewall's flexural performance, and the palm oil resistance and gas permeation resistance are improved, preventing palm oil and gas from penetrating into the sidewall and causing the sidewall to delaminate.

Claims

1. A palm oil-resistant, heat-resistant, and gas-permeation-resistant tire sidewall rubber composition, characterized in that: Based on 100 parts by weight of the rubber component, it also includes 30 to 50 parts by weight of carbon black, 5 to 10 parts by weight of silica, 5 to 10 parts by weight of suprex, 2 to 5 parts by weight of alkyl styrene resin, 1.0 to 3.0 parts by weight of zinc oxide, 1.0 to 3.0 parts by weight of stearic acid, 0.5 to 1.5 parts by weight of antioxidant, 1.0 to 3.0 parts by weight of protective wax, 2.0 to 3.0 parts by weight of super vulcanizer PSO-35, 0.3 to 0.8 parts by weight of sulfur, and 1.0 to 2.0 parts by weight of accelerator DM, wherein the rubber component includes 45 to 60 parts by weight of natural rubber, 5 to 10 parts by weight of rare earth isoprene rubber, 15 to 25 parts by weight of chlorinated butyl rubber, and 15 to 25 parts by weight of high vinyl polybutadiene rubber.

2. The palm oil-resistant, heat-resistant and gas-permeation-resistant tire sidewall rubber composition according to claim 1, characterized in that The chlorine content of the chlorinated butyl rubber is ≥1.2%, the weight ratio of rare earth isoprene rubber to natural rubber is ≤20%, the weight ratio of chlorinated butyl rubber to total rubber components is ≥15%, the weight ratio of high vinyl polybutadiene rubber to total rubber components is ≥15%, the total weight ratio of chlorinated butyl rubber and high vinyl polybutadiene rubber to total rubber components is ensured to be ≥30% and ≤50%, the weight ratio of natural rubber to total rubber components is ≥50%, the mass fraction of vinyl side groups of high vinyl polybutadiene rubber is more than 80%, and the 1,2-structure is randomly distributed.

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