Sidewall rubber composition for car tire and preparation method thereof

Abstract

The invention discloses a sidewall rubber composition for a car tire and a preparation method of the sidewall rubber composition, and belongs to the technical field of rubber compositions. According to the technical scheme, the high-cis butadiene-isoprene rubber composition comprises high-cis butadiene-isoprene rubber, chlorinated butyl rubber and amine-terminated polybutadiene. According to the rubber composition, the high-cis butadiene-isoprene rubber, the chlorinated butyl rubber and the amine-terminated polybutadiene are combined, so that the high-cis butadiene-isoprene rubber has excellent anti-fatigue performance and high elasticity; the chlorinated butyl rubber has excellent aging resistance and fatigue aging resistance, and due to the excellent aging resistance, the dosage of an anti-aging agent in the sidewall rubber can be reduced, and the appearance of a tire is improved; the amino-terminated polybutadiene plays a role of a compatibilizer of the high cis-butadiene-isoprene rubber and the chlorinated butyl rubber, so that the phase interfacial tension of the high cis-butadiene-isoprene rubber and the chlorinated butyl rubber is reduced, the compatibility of the high cis-butadiene-isoprene rubber and the chlorinated butyl rubber is improved, and the physical properties of the rubber material are greatly improved; therefore, the sidewall rubber has excellent thermo-oxidative aging resistance, ozone aging resistance and flexural fatigue damage resistance, and meets the performance requirements of the sidewall rubber.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of rubber compositions, and particularly relates to a tire side rubber composition for passenger car tires and a preparation method thereof. BACKGROUND

[0002] As a key part directly exposed to the external environment, the tire side of the tire is subjected to harsh environmental factors such as high temperature, ozone and ultraviolet light for a long time, which can easily cause the rubber molecular chain to break, crosslink or oxidize and degrade, resulting in the formation of cracks on the surface of the tire side, and seriously affecting the service life of the tire and driving safety. During driving, the tire side of the tire absorbs the vibration and impact from the road through continuous flexural deformation, and is prone to fatigue aging under periodic strain. The flexural fatigue aging and ozone aging work together to form ozone aging flexural fatigue damage, which gradually reduces the performance of the tire side of the tire, thereby reducing the service life of the tire side of the tire.

[0003] At present, the tire side formula research mainly takes natural rubber and butadiene rubber as the main body. Natural rubber has excellent mechanical properties and fatigue crack propagation resistance, and butadiene rubber has excellent fatigue crack initiation resistance. However, since both natural rubber and butadiene rubber are unsaturated carbon chain rubbers with small intramolecular resistance, their aging resistance is poor, which results in that the tire side rubber cannot have excellent heat-oxygen aging resistance, ozone resistance and flexural fatigue damage resistance. In order to cope with the aging problem, the existing formula mainly adds anti-aging agents (such as amine compounds) and anti-ozone additives (such as protective wax), which migrate and spray out of the rubber surface to delay the aging process. However, the traditional amine anti-aging agent is prone to migration failure under high temperature conditions, which causes the protective effect to gradually decrease with the use time. In addition, under the synergistic action of ozone and ultraviolet light, photo-oxidation and ozone cracking reactions easily occur on the surface of the rubber, and the anti-aging performance of the existing additives is limited, which is difficult to maintain the mechanical properties and weather resistance of the rubber for a long time.

[0004] Chlorinated butyl rubber has excellent anti-aging performance and fatigue aging resistance. Its excellent anti-aging performance can reduce the amount of anti-aging agent in the tire side rubber and improve the appearance of the tire. However, the polarity and molecular chain structure of chlorinated butyl rubber are significantly different from those of most polydiene rubbers, and the compatibility is poor, which finally cannot meet the high requirements of the tire for the tire side. SUMMARY

[0005] In view of the deficiencies of the prior art, the technical problem to be solved by the present application is that the existing tire side rubber cannot have excellent heat-oxygen aging resistance, ozone aging resistance and flexural fatigue damage resistance. A tire side rubber composition for passenger car tires having excellent heat-oxygen aging resistance, ozone aging resistance and flexural fatigue damage resistance and a preparation method thereof are provided.

[0006] To solve the aforementioned technical problem, the technical solution adopted by the present invention is as follows: One aspect of the present invention provides a sidewall rubber composition for passenger car tires, comprising high cis butyl rubber, chlorinated butyl rubber and amine-terminated polybutadiene.

[0007] Preferably, the terminal amine polybutadiene is a polymer with terminal amine groups obtained by end-group conversion method, with a 1,4-structure mass fraction of more than 90% and an amine value of 0.4~0.6 mmol / g.

[0008] Preferably, the high-cis-butadiene-pentadiene rubber is a high-cis-1,4-butadiene-isoprene copolymer rubber, wherein the butadiene and isoprene structural units are randomly arranged, the molar fraction of isoprene is 10-20%, and the number average molecular weight is (10~30)*10. 4 g / mol, molecular weight distribution PDI < 2.

[0009] Preferably, the chlorinated butyl rubber is obtained by chlorinating butyl rubber, with a chlorine content of 1.1~1.3% and a Mooney viscosity [ML(1+8)@125℃] of 38±5.

[0010] Preferably, the sidewall rubber composition for passenger car tires further includes magnesium oxide.

[0011] Preferably, the sidewall rubber composition for passenger car tires further includes carbon black, zinc oxide masterbatch, stearic acid, antioxidant, tackifying resin, vulcanizing agent, and accelerator.

[0012] Preferably, the sidewall rubber composition for passenger car tires comprises 60-90 parts of high cis-butadiene rubber, 10-40 parts of chlorinated butyl rubber, 1-5 parts of amine-terminated polybutadiene, 40-50 parts of carbon black, 0.1-0.5 parts of magnesium oxide, 2.5-3.5 parts of zinc oxide masterbatch, 1-2 parts of stearic acid, 2-4 parts of antioxidant, 2-4 parts of tackifying resin, 1.2-2 parts of vulcanizing agent, and 1-1.4 parts of accelerator.

[0013] Preferably, the carbon black has an iodine absorption value of (30-50) g / kg and a DBP value of (100-130)*10. -5 m 3 / kg.

[0014] Another aspect of the present invention provides a method for preparing the above-mentioned sidewall rubber composition for passenger car tires, including a masterbatch mixing step and a final rubber mixing step. The masterbatch mixing step includes: Add high-cis butyl rubber, chlorinated butyl rubber, amine-terminated polybutadiene, and magnesium oxide to the internal mixer and mix for 30-40 seconds. Add carbon black after lifting the plug and mix for 35-45 seconds. Add antioxidant, stearic acid, and tackifying resin after lifting the plug and mix for 30-40 seconds. Lift the plug and mix again at 135-145℃. Lift the plug and mix again at a constant temperature of 138-142℃ for 30-60 seconds. Lift the plug and discharge the material.

[0015] Preferably, the final rubber compounding step includes: Masterbatch, zinc oxide masterbatch granules, accelerator, and vulcanizing agent are fed into an internal mixer and mixed to 95-105℃. The mixture is then discharged, sheeted, and cooled to obtain the final rubber.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention provides a sidewall rubber composition for passenger car tires. This composition comprises high-cis-butadiene rubber, chlorinated butyl rubber, and amine-terminated polybutadiene. The high-cis-butadiene rubber has a cis content of over 96%, a glass transition temperature close to that of conventional cis-butadiene rubber, and a flexible molecular chain, exhibiting excellent fatigue resistance and high elasticity. The chlorinated butyl rubber possesses excellent anti-aging properties and fatigue aging resistance. The amine-terminated polybutadiene acts as a compatibilizer for both the high-cis-butadiene rubber and chlorinated butyl rubber. On one hand, the polybutadiene portion of the amine-terminated polybutadiene has a macromolecular structure similar to that of the high-cis-butadiene rubber, which can produce… Biophysical entanglement is achieved, and polybutadiene can co-crosslink with high-cis-butadiene rubber, enhancing the bonding effect between amine-terminated polybutadiene and high-cis-butadiene rubber. On the one hand, the amine groups of amine-terminated polybutadiene can chemically react with chlorinated butyl rubber, linking the polybutadiene backbone of amine-terminated polybutadiene with high-cis-butadiene rubber and the amine groups with chlorinated butyl rubber, thus forming a strong phase interface between high-cis-butadiene rubber and chlorinated butyl rubber. Both can exert their advantageous properties, while reducing the amount of antioxidants used in the tire sidewall rubber, making it more environmentally friendly and improving the poor appearance caused by the migration and spraying of antioxidants on the tire sidewall. Detailed Implementation

[0017] The technical solutions in specific embodiments of the present invention will be described in detail and completely below. Obviously, the described embodiments are only some specific implementations of the overall technical solution of the present invention, and not all implementations. Based on the overall concept of the present invention, all other embodiments obtained by those skilled in the art fall within the protection scope of the present invention.

[0018] The present invention provides a sidewall rubber composition for passenger car tires, comprising high cis butyl rubber, chlorinated butyl rubber and amine-terminated polybutadiene.

[0019] It should be noted that chlorinated butyl rubber has excellent anti-aging and fatigue aging resistance. Its excellent anti-aging properties can reduce the amount of antioxidants used in the sidewall rubber and improve the tire's appearance. However, chlorinated butyl rubber differs significantly from most polydiolefin rubbers in polarity and molecular chain structure, resulting in poor compatibility and failing to meet the high requirements of actual tire use for the sidewall.

[0020] To address the aforementioned issues, the present invention provides a sidewall rubber composition for passenger car tires comprising high-cis-butadiene rubber, chlorinated butyl rubber, and terminal amine polybutadiene. The high-cis-butadiene rubber has a cis content exceeding 96%, a glass transition temperature close to that of conventional cis-butadiene rubber, and a flexible molecular chain, exhibiting excellent fatigue resistance and high elasticity. Chlorinated butyl rubber possesses excellent anti-aging and fatigue aging resistance; its superior anti-aging properties reduce the amount of antioxidants required in the sidewall rubber, improving tire appearance. Terminal amine polybutadiene acts as a compatibilizer for both high-cis-butadiene rubber and chlorinated butyl rubber. The main chain of terminal amine polybutadiene is polybutadiene, which is similar to the molecular structure of high-cis-butadiene rubber. During the mixing stage, this results in "like dissolves like" between terminal amine polybutadiene and high-cis-butadiene rubber. During the vulcanization stage, because terminal amine polybutadiene can participate in the vulcanization reaction, it can form a co-vulcanization with high-cis-butadiene rubber, enhancing their bonding effect. The terminal amine-terminated polybutadiene (PPD) molecules, with their highly reactive and polar amine groups (-NH2), can undergo nucleophilic substitution reactions with chlorine atoms on the chlorinated butyl rubber molecular chain, producing stable amine-chlorinated butyl rubber macromolecular bonds. During the mixing stage, a small portion of the PPD reacts with the chlorinated butyl rubber to initially form chemical bonds. During the vulcanization stage, the high temperature significantly accelerates the reaction rate between the amine groups and chlorine atoms, ensuring sufficient bonding of the compatibilizer at the interface between the high-cis butyl ester rubber and the chlorinated butyl rubber. In summary, the PPD backbone of the PPD physically entangles and co-vulcanizes with the high-cis butyl ester rubber through the principle of "like dissolves like," while its terminals bond with the chlorinated butyl rubber through chemical reactions. This effectively reduces the interfacial tension between the high-cis butyl ester rubber and the chlorinated butyl rubber, thus greatly improving their compatibility. Enhanced compatibility significantly improves the physical properties of the rubber compound, meeting the performance requirements of tire sidewall rubber.

[0021] In a preferred embodiment, the amine-terminated polybutadiene is a polymer with amine groups at the end, obtained by the end-group conversion method, with a 1,4-structure mass fraction of more than 90% and an amine value of 0.4~0.6 mmol / g.

[0022] The aforementioned technical solution limits the amine value of terminal amine-terminated polybutadiene to 0.4~0.6 mmol / g. This is because if the amine value is too high, on the one hand, its reaction with chlorinated butyl rubber is too vigorous, causing a sharp increase in the Mooney viscosity of the compound and increasing the difficulty of mixing; on the other hand, the molecular weight of terminal amine-terminated polybutadiene is too low, and the chain segments are too short, making it unable to form effective physical entanglement with high-cis-butadiene rubber. If the amine value is too low, on the one hand, there are not enough terminal amine groups to react with chlorinated butyl rubber, making it difficult to reduce the interfacial forces between the two phases; on the other hand, the molecular chains of terminal amine-terminated polybutadiene are too long, weakening their migration ability and making it difficult to quickly migrate to the interfacial region between the two phases. As a compatibilizer for high-cis-butadiene rubber and chlorinated butyl rubber, terminal amine-terminated polybutadiene exhibits thermodynamic "like dissolves like" and co-curing effects with high-cis-butadiene rubber, and also undergoes a moderate chemical bonding reaction with chlorinated butyl rubber. The amine-terminated polybutadiene acts as a bridge between high cis-butadiene rubber and chlorinated butyl rubber. The amine-terminated groups anchor the chlorinated butyl rubber, while the polybutadiene molecular chains anchor the high cis-butadiene rubber, which greatly increases the compatibility of the two rubber phases and significantly improves the performance of the rubber compound.

[0023] In a preferred embodiment, the high-cis-1,4-butadiene-isoprene copolymer rubber is a high-cis-1,4-butadiene-isoprene copolymer rubber, wherein the butadiene and isoprene structural units are randomly arranged, the molar fraction of isoprene is 10-20%, and the number average molecular weight is (10~30)*10. 4 g / mol, molecular weight distribution PDI < 2.

[0024] By adopting the above technical solutions, high-cis butyl ester rubber has the following effects: First, the molecular chains are flexible. When the sidewall rubber is subjected to cyclic stress, the flexible molecular chains can easily stretch, curl up and reorient, resulting in uniform stress distribution. Second, the high elasticity of butyl ester rubber allows the molecular chain stress to relax quickly. Third, the low intramolecular friction and low hysteresis loss greatly reduce the tendency of thermo-oxidative aging, while heat accumulation will accelerate fatigue flexural failure. Therefore, the low heat generation can enable the sidewall rubber to maintain more stable performance during long-term dynamic use.

[0025] In a preferred embodiment, the chlorinated butyl rubber is obtained by chlorinating butyl rubber, with a chlorine content of 1.1~1.3% and a Mooney viscosity [ML(1+8)@125℃] of 38±5.

[0026] By adopting the above technical solutions, the Mooney viscosity of low Mooney chlorinated butyl rubber is similar to that of high cis-butadiene rubber, which is beneficial to improving the compatibility of the two phases. The saturated main chain of chlorinated butyl rubber gives it excellent resistance to ozone and thermo-oxidative aging. Under cyclic stress and strain, it makes it less prone to initial microcracks on the sidewall rubber surface, fundamentally delaying the initiation of fatigue failure. Furthermore, the more stable carbon-carbon bonds and ether bonds formed after crosslinking of chlorinated butyl rubber create a stable crosslinked network that prevents the propagation of microcracks. Simultaneously, the ether bonds possess a certain degree of flexibility, effectively dispersing local stress throughout the entire rubber network during cyclic flexing.

[0027] In a preferred embodiment, the sidewall rubber composition for passenger car tires further includes magnesium oxide.

[0028] By adopting the above technical solution, since the terminal amino group of polybutadiene has an amino group (-NH2) at the end of the molecule, it has high reactivity and polarity. It can undergo a nucleophilic substitution reaction with the chlorine atom on the chlorinated butyl rubber molecular chain to produce a stable amine-chlorinated butyl rubber macromolecular bond. Since this reaction produces the byproduct HCl, a certain proportion of magnesium oxide is added at the same time to react with the byproduct HCl and consume the byproduct. In addition, magnesium oxide itself acts as an acid absorbent in the system containing chlorinated butyl rubber to inhibit the early crosslinking of chlorinated butyl rubber during the mixing stage.

[0029] In a preferred embodiment, the sidewall rubber composition for passenger car tires further includes carbon black, zinc oxide masterbatch, stearic acid, antioxidant, tackifying resin, vulcanizing agent, and accelerator.

[0030] In a preferred embodiment, the sidewall rubber composition for passenger car tires comprises 60-90 parts of high cis-butadiene rubber, 10-40 parts of chlorinated butyl rubber, 1-5 parts of amine-terminated polybutadiene, 40-50 parts of carbon black, 0.1-0.5 parts of magnesium oxide, 2.5-3.5 parts of zinc oxide masterbatch, 1-2 parts of stearic acid, 2-4 parts of antioxidant, 2-4 parts of tackifying resin, 1.2-2 parts of vulcanizing agent, and 1-1.4 parts of accelerator.

[0031] The above technical solution specifies the dosages of high-cis-butadiene rubber, chlorinated butyl rubber, terminal amine polybutadiene, carbon black, magnesium oxide, zinc oxide masterbatch, stearic acid, antioxidant, tackifying resin, vulcanizing agent, and accelerator. It is understood that the dosage of high-cis-butadiene rubber can also be 70 parts, 75 parts, 80 parts, 85 parts, or any value within this range; the dosage of chlorinated butyl rubber can also be 20 parts, 30 parts, or any value within this range; the dosage of terminal amine polybutadiene can also be 2 parts, 3 parts, 4 parts, or any value within this range; the dosage of carbon black can also be 42.5 parts, 45 parts, 47 parts, or any value within this range; and the dosage of magnesium oxide can also be 0.2 parts, 0.3 parts, or any value within this range. The amount of zinc oxide masterbatch can be 0.4 parts or any value within the range; the amount of zinc oxide masterbatch can also be 2.7 parts, 2.9 parts, 3.1 parts, 3.3 parts or any value within the range; the amount of stearic acid can also be 1.25 parts, 1.5 parts, 1.75 parts or any value within the range; the amount of antioxidant can also be 2.5 parts, 3 parts, 3.5 parts or any value within the range; the amount of tackifying resin can also be 2.5 parts, 3 parts, 3.5 parts or any value within the range; the amount of vulcanizing agent can also be 1.4 parts, 1.6 parts, 1.8 parts or any value within the range; and the amount of accelerator can also be 1.1 parts, 1.2 parts, 1.3 parts or any value within the range.

[0032] In a preferred embodiment, the carbon black has an iodine absorption value of (30-50) g / kg and a DBP value of (100-130)*10. -5 m 3 / kg.

[0033] By adopting the above technical solution, due to the higher structural density, its more complex aggregate chain dendritic structure can capture more rubber molecular chains, resulting in more retained rubber, which is equivalent to effectively increasing the volume fraction of filler. Under the same modulus, fewer filler parts are filled, resulting in lower hysteresis loss of the tire sidewall rubber composition, and it is easier to disperse evenly during mixing, with better processability.

[0034] In another aspect, the present invention provides a method for preparing the above-mentioned sidewall rubber composition for passenger car tires, comprising a masterbatch mixing step and a final rubber mixing step. The masterbatch mixing steps include: Add high-cis butylene terephthalate rubber, chlorinated butyl rubber, amine-terminated polybutadiene, and magnesium oxide to a Banbury mixer and mix for 30-40 seconds. Add carbon black after lifting the Banbury mixer and mix for 35-45 seconds. Add antioxidant, stearic acid, and tackifying resin after lifting the Banbury mixer and mix for 30-40 seconds. Lift the Banbury mixer and mix again at 135-145℃. Lift the Banbury mixer and mix again at a constant temperature of 138-142℃ for 30-60 seconds. Discharge the mixture after lifting the Banbury mixer. By adopting the above technical solution, high cis-butadiene rubber, chlorinated butyl rubber, and amine-terminated polybutadiene are first added during the masterbatch mixing process. Magnesium oxide is mixed and reacted first, and then other materials are added. High-temperature constant-temperature mixing is carried out in the later stage of mixing so that the amine-terminated polybutadiene can fully exert the compatibilizing effect between the two.

[0035] In a preferred embodiment, the final rubber compounding step includes: Masterbatch, zinc oxide masterbatch granules, accelerator, and vulcanizing agent are fed into an internal mixer and mixed to 95-105℃. The mixture is then discharged, sheeted, and cooled to obtain the final rubber.

[0036] To provide a clearer and more detailed description of the sidewall rubber composition for passenger car tires and its preparation method provided in the embodiments of the present invention, the following description will be based on specific embodiments.

[0037] Examples 1-3: A method for preparing a sidewall rubber composition for passenger car tires 1. Raw material composition: The raw material formulations for Examples 1-3 are shown in Table 1.

[0038] Table 1. Formulations of Sidewall Rubber Compositions in Examples 1-3

[0039] Note: The amount of magnesium oxide used is approximately 1% of the amount of chlorinated butyl rubber, and the amount of amine-terminated polybutadiene used is approximately 10% of the amount of chlorinated butyl rubber.

[0040] Preparation method of Example 1: Masterbatch mixing: Add high cis butyl rubber, chlorinated butyl rubber, amine-terminated polybutadiene, and magnesium oxide to an interlocking internal mixer, press and mix for 40 seconds, lift the plug and add carbon black N550, press and mix for 30 seconds, lift the plug and add antioxidants (antioxidant 6PPD, antioxidant TMQ and rubber protective wax), stearic acid, and C5 tackifying resin, press and mix for 30 seconds, lift the plug, press and mix again to 138°C, lift the plug, press and mix again at 140°C for 60 seconds, and then discharge the material. Final rubber compounding: Add appropriate amounts of masterbatch, zinc oxide masterbatch granules, accelerator, and vulcanizing agent to the internal mixer, mix to 105°C, discharge the rubber into sheets and cool to obtain the final rubber compound.

[0041] Preparation method of Example 2: Masterbatch mixing: Add high cis butyl rubber, chlorinated butyl rubber, amine-terminated polybutadiene, and magnesium oxide to an interlocking internal mixer, press and mix for 40 seconds, lift the plug and add carbon black N550, press and mix for 30 seconds, lift the plug and add antioxidants (antioxidant 6PPD, antioxidant TMQ and rubber protective wax), stearic acid, and C5 tackifying resin, press and mix for 30 seconds, lift the plug, press and mix again to 138°C, lift the plug, press and mix again at 140°C for 40 seconds, lift the plug and discharge the material; Final rubber compounding: Add appropriate amounts of masterbatch, zinc oxide masterbatch granules, accelerator, and vulcanizing agent to the internal mixer, mix to 105°C, discharge the rubber into sheets and cool to obtain the final rubber compound.

[0042] Preparation method of Example 3: Masterbatch mixing: Add high cis butyl rubber, chlorinated butyl rubber, amine-terminated polybutadiene, and magnesium oxide to an interlocking internal mixer, press and mix for 40 seconds, lift the plug and add carbon black N550, press and mix for 30 seconds, lift the plug and add antioxidants (antioxidant 6PPD, antioxidant TMQ and rubber protective wax), stearic acid, and C5 tackifying resin, press and mix for 30 seconds, lift the plug, press and mix again to 138°C, lift the plug, press and mix again at 140°C for 25 seconds, lift the plug and discharge the material; Final rubber compounding: Add appropriate amounts of masterbatch, zinc oxide masterbatch granules, accelerator, and vulcanizing agent to the internal mixer, mix to 105°C, discharge the rubber into sheets and cool to obtain the final rubber compound.

[0043] Comparative Examples 1-5 1. Raw material composition: The raw material formulations for Comparative Examples 1-5 are shown in Table 2.

[0044] Table 2. Formulations of Sidewall Rubber Compositions for Comparative Examples 1-5

[0045] Notes: ① The amount of magnesium oxide used above is approximately 1% of the amount of chlorinated butyl rubber, and the amount of amine-terminated polybutadiene is approximately 10% of the amount of chlorinated butyl rubber; ② Due to the different curing methods of chlorinated butyl rubber, the amounts of vulcanizing agent and accelerator in the above formulas are adjusted to different degrees according to the characteristics of the formula.

[0046] Preparation method of Comparative Example 1: Masterbatch mixing: Add natural rubber and nickel-based cis-butadiene rubber to the interlocking internal mixer, press the plug and mix for 20 seconds, lift the plug and add carbon black N550, press the plug and mix for 40 seconds, lift the plug and add antioxidants (antioxidant 6PPD, antioxidant TMQ and rubber protective wax), stearic acid and C5 tackifying resin, press the plug and mix for 40 seconds, lift the plug and press the plug again to mix to 155℃ and discharge. Final rubber compounding: Add appropriate amounts of masterbatch, zinc oxide masterbatch granules, accelerator, and vulcanizing agent to the internal mixer, mix to 105°C, discharge the rubber into sheets and cool to obtain the final rubber compound.

[0047] Preparation method of Comparative Example 2: Masterbatch mixing: Add high cis butyl rubber, chlorinated butyl rubber, and magnesium oxide to the interlocking internal mixer, press and mix for 20 seconds, lift the plug and add carbon black N550, press and mix for 40 seconds, lift the plug and add antioxidants (antioxidant 6PPD, antioxidant TMQ and rubber protective wax), stearic acid, and C5 tackifying resin, press and mix for 40 seconds, lift the plug and press and mix again until 140℃ for discharge; Final rubber compounding: Add appropriate amounts of masterbatch, zinc oxide masterbatch granules, accelerator, and vulcanizing agent to the internal mixer, mix to 105°C, discharge the rubber into sheets and cool to obtain the final rubber compound.

[0048] Preparation method of Comparative Example 3: Masterbatch mixing: Add high cis butyl pentadiene rubber to the interlocking internal mixer, press and mix for 20 seconds, lift the plug and add carbon black N550, press and mix for 40 seconds, lift the plug and add antioxidants (antioxidant 6PPD, antioxidant TMQ and rubber protective wax), stearic acid and C5 tackifying resin, press and mix for 40 seconds, lift the plug and press and mix again until 155℃ for discharge. Final rubber compounding: Add appropriate amounts of masterbatch, zinc oxide masterbatch granules, accelerator, and vulcanizing agent to the internal mixer, mix to 105°C, discharge the rubber into sheets and cool to obtain the final rubber compound.

[0049] Preparation method of Comparative Example 4: Masterbatch mixing: Chlorinated butyl rubber and magnesium oxide are added to the interlocking internal mixer and mixed for 20 seconds. Carbon black N550 is added after lifting the plug and mixed for 40 seconds. Antioxidant (antioxidant 6PPD, antioxidant TMQ and rubber protective wax), stearic acid and C5 tackifying resin are added after lifting the plug and mixing for 40 seconds. The plug is then lifted and mixed again until 140℃ is reached before discharge. Final rubber compounding: Add appropriate amounts of masterbatch, zinc oxide masterbatch granules, accelerator, and vulcanizing agent to the internal mixer, mix to 105°C, discharge the rubber into sheets and cool to obtain the final rubber compound.

[0050] The preparation method of Comparative Example 5 is the same as that of Example 1.

[0051] Test case The performance of the rubber compounds obtained in Examples 1-3 and Comparative Examples 1-5 was tested, and the test results are shown in Table 3 below.

[0052] Table 3 Properties of Sidewall Rubber Compositions

[0053] Note: Static ozone aging test conditions were: temperature: 40℃, humidity: 50%, ozone concentration: 100 pphm, and sample elongation: 25%.

[0054] As can be seen from the data in Table 3, compared with Comparative Example 1, although Comparative Example 2 used highly saturated chlorinated butyl rubber, the physical properties of the sidewall rubber composition deteriorated due to the poor compatibility between high cis-butyl ester rubber and chlorinated butyl rubber. Example 1, based on Comparative Example 2, added a compatibilizer—terminated amine polybutadiene. The physical properties of the vulcanizate before and after thermo-oxidative aging were significantly improved and enhanced. The rate of change of various physical properties after thermo-oxidative aging was greatly reduced, and the vulcanizate exhibited excellent ozone aging resistance. Examples 2 and 3 both reduced the amount of chlorinated butyl rubber and correspondingly increased the amount of high cis-butyl ester rubber. The physical properties of the vulcanizate before aging were comparable to those of Example 1 and Comparative Example 1. After thermo-oxidative aging, the rate of change of various physical properties of the vulcanizate was higher than that of Example 1 but lower than that of Comparative Example 1. Due to the reduced amount of chlorinated butyl rubber, the thermo-oxidative aging resistance of the vulcanizate was worse than that of Example 1, but better than that of Comparative Example 1. Comparative Example 3 used 100 parts of high-cis-butadiene rubber. High-cis-butadiene rubber has poor anti-aging properties. Since the anti-aging system was not reinforced, it can be seen that although the physical properties of the sidewall rubber composition were excellent before aging, the rate of change of various physical properties increased significantly after thermo-oxidative aging, and the ozone aging resistance of the vulcanizate decreased. Comparative Example 4 used 100 parts of chlorinated butyl rubber. Although the rate of change of various physical properties after thermo-oxidative aging was the smallest and the ozone aging resistance was excellent, the high saturation and low crosslinking density of chlorinated butyl rubber made it difficult for the physical properties of the vulcanizate to meet the formulation design requirements of the sidewall rubber. In Comparative Example 5, the ratio of high-cis-butadiene rubber to chlorinated butyl rubber was 4:6. Due to the increased proportion of chlorinated butyl rubber, a gradually complete continuous phase was formed in the system. Compared with Examples 1-3, the rate of change of various physical properties of the vulcanizate after thermo-oxidative aging in Comparative Example 5 was smaller. However, since the physical properties of the vulcanizate decreased significantly, it was not adopted.

[0055] It can be seen that by introducing high-cis butyl rubber and chlorinated butyl rubber, using terminal amine polybutadiene as a two-phase compatibilizer, using magnesium oxide as an acid absorbent, and combining the optimization of the mixing process, it can be inferred that the tire sidewall prepared using this rubber composition has excellent resistance to thermo-oxidative aging, flexural fatigue failure, and ozone aging.

Claims

1. A sidewall rubber composition for passenger car tires, characterized in that, This includes high cis-butadiene rubber, chlorinated butyl rubber, and amine-terminated polybutadiene.

2. The sidewall rubber composition for passenger car tires according to claim 1, characterized in that, The terminal amine polybutadiene is a polymer with terminal amine groups obtained by the end-group conversion method, with a 1,4-structure mass fraction of over 90% and an amine value of 0.4~0.6 mmol / g.

3. The sidewall rubber composition for passenger car tires according to claim 1, characterized in that, The high-cis-1,4-butadiene-isoprene copolymer rubber is a high-cis-1,4-butadiene-isoprene copolymer rubber, in which butadiene and isoprene structural units are randomly arranged, the molar fraction of isoprene is 10-20%, and the number average molecular weight is (10~30)*10. 4 g / mol, molecular weight distribution PDI < 2.

4. The sidewall rubber composition for passenger car tires according to claim 1, characterized in that, The chlorinated butyl rubber is obtained by chlorinating butyl rubber, with a chlorine content of 1.1~1.3% and a Mooney viscosity [ML(1+8)@125℃] of 38±5.

5. The sidewall rubber composition for passenger car tires according to any one of claims 1-4, characterized in that, The sidewall rubber composition for passenger car tires also includes magnesium oxide.

6. The sidewall rubber composition for passenger car tires according to claim 5, characterized in that, The sidewall rubber composition for passenger car tires also includes carbon black, zinc oxide masterbatch, stearic acid, antioxidant, tackifying resin, vulcanizing agent, and accelerator.

7. The sidewall rubber composition for passenger car tires according to claim 6, characterized in that, The sidewall rubber composition for passenger car tires comprises 60-90 parts of high cis-butadiene rubber, 10-40 parts of chlorinated butyl rubber, 1-5 parts of amine-terminated polybutadiene, 40-50 parts of carbon black, 0.1-0.5 parts of magnesium oxide, 2.5-3.5 parts of zinc oxide masterbatch, 1-2 parts of stearic acid, 2-4 parts of antioxidant, 2-4 parts of tackifying resin, 1.2-2 parts of vulcanizing agent, and 1-1.4 parts of accelerator.

8. The sidewall rubber composition for passenger car tires according to claim 6, characterized in that, The carbon black has an iodine absorption value of (30-50) g / kg and a DBP value of (100-130)*10. -5 m 3 / kg.

9. A method for preparing the sidewall rubber composition for passenger car tires according to any one of claims 1-8, characterized in that, This includes the masterbatch mixing step and the final rubber mixing step; The masterbatch mixing step includes: Add high-cis butyl rubber, chlorinated butyl rubber, amine-terminated polybutadiene, and magnesium oxide to the internal mixer and mix for 30-40 seconds. Add carbon black after lifting the plug and mix for 35-45 seconds. Add antioxidant, stearic acid, and tackifying resin after lifting the plug and mix for 30-40 seconds. Lift the plug and mix again at 135-145℃. Lift the plug and mix at a constant temperature of 138-142℃ for 30-60 seconds. Lift the plug and discharge the material.

10. The preparation method according to claim 9, characterized in that, The final rubber mixing step includes: Masterbatch, zinc oxide masterbatch granules, accelerator, and vulcanizing agent are fed into an internal mixer and mixed to 95-105℃. The mixture is then discharged, sheeted, and cooled to obtain the final rubber.

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