Inner support rubber composition for run-flat tire and preparation method thereof

Abstract

The present invention proposes a special inner support rubber composition for run-flat tires and a preparation method thereof, which belongs to the field of tire rubber compositions and can solve the technical problems that the existing inner support rubber compositions for run-flat tires generally have high hardness, strong rigidity, and poor tire comfort. Among them, the flex fatigue life of the vulcanized rubber of the special inner support rubber composition for run-flat tires is not less than 300,000 times, the Shore A hardness at 23°C is 65-69, and the 100% strain modulus at 23°C is 4.0-5.5MPa; at 2MPa static loading pressure, 6.35mm stroke, 30Hz compression frequency and 100°C test temperature, the final dynamic compression rate of the vulcanized rubber of the inner support rubber composition is not higher than 22%, and the temperature rise is not higher than 28°C. The support rubber prepared by the rubber composition has excellent flex fatigue resistance and low heat generation, the tire can travel more than 80km at zero air pressure, the actual vehicle comfort in the inflated state reaches 7.0 level, and the support rubber is not damaged after traveling more than 60,000 kilometers.

Description

Technical Field

[0001] The invention belongs to the field of tire rubber compositions, and in particular relates to an inner support rubber composition dedicated to a run-flat tire and a preparation method thereof. Background Art

[0002] A run-flat tire is a tire that can continue to run even after losing some or all of its air pressure. It mainly maintains its support after the tire loses pressure by adding high-hardness support rubber to the inner sidewall. After a run-flat tire loses pressure, most of the vehicle load is borne by the inner support rubber, which requires the support rubber to have a high hardness and modulus. In addition, in order to cope with the increased deformation of the sidewall and the rapid accumulation of heat caused by the high load when the tire is running with a flat tire, the support rubber is also required to have low hysteresis loss and excellent flex fatigue resistance and other mechanical properties, thereby reducing the dynamic temperature rise under high load and increasing the mileage of the tire when it is deflated.

[0003] In order to maintain a certain stable driving ability of the tire in the deflated state, the overall rigidity of the sidewall of the run-flat tire is higher and the deformation is smaller. Although this ensures the driving safety of the tire in the event of an accidental blowout or zero air pressure, it also causes the run-flat tire to have strong bouncing, poor smoothness, and a bad experience when driving in the daily inflated state. Its ride comfort is much lower than that of conventional pneumatic tires.

[0004] It can be seen that how to ensure the tire's safety when driving at zero air pressure while significantly improving its comfort when inflated has become an urgent problem to be solved in current run-flat tire products. Summary of the invention

[0005] In view of the technical problem that the existing run-flat tires cannot balance the support in the deflated state and the comfort in the inflated state, the present invention proposes a special inner support rubber composition for run-flat tires with excellent flex fatigue resistance, certain support and low hysteresis. The tire prepared by using the rubber composition can travel more than 80km with zero air pressure, and the comfort reaches level 7.0 when driving in the inflated state, and the support rubber will not be damaged after driving for more than 60,000 kilometers, which can provide users with a safer and more comfortable driving experience.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] An inner support rubber composition for a run-flat tire, wherein the flex fatigue life of the vulcanized rubber of the inner support rubber composition is not less than 300,000 times, the Shore A hardness at 23°C is 65-69, and the 100% strain modulus at 23°C is 4.0-5.5MPa;

[0008] Under a static loading pressure of 2 MPa, a stroke of 6.35 mm, a compression frequency of 30 Hz and a test temperature of 100° C., the final dynamic compression rate of the vulcanized rubber of the inner support rubber composition is not higher than 22%, and the temperature rise is not higher than 28° C.

[0009] In one embodiment, the inner support rubber composition for a run-flat tire comprises at least the following components in parts by weight:

[0010] 30-60 parts of natural rubber, 40-70 parts of rare earth butadiene rubber, and 3-15 parts of liquid polybutadiene rubber.

[0011] In one embodiment, the number average molecular weight of the liquid polybutadiene rubber is 3000-8000, wherein 1,2-butadiene structural units account for 20%-40% of the mass of the polybutadiene rubber segment, 1,4-butadiene structural units account for 60%-80% of the mass of the polybutadiene rubber segment, and the molecular chain end modification rate is 50%-80%.

[0012] In one embodiment, the rare earth butadiene rubber is a neodymium-based high-cis butadiene rubber with a weight average molecular weight of 600,000-900,000, a molecular weight distribution width of 2.5-3.5, and a mass fraction of 1,4-butadiene cis structure of not less than 97.5%.

[0013] In one embodiment, the inner support rubber composition for a run-flat tire further comprises the following components in parts by weight:

[0014] 25-45 parts of carbon black, 10-30 parts of highly dispersed white carbon black, 1-3.5 parts of silane coupling agent, 3-5 parts of antioxidant, 3-6 parts of activator, 1-3 parts of insoluble sulfur, 1-2 parts of accelerator, and 1-3 parts of anti-reversion agent.

[0015] In one embodiment, the anti-reversion agent portion M1, the pure sulfur portion M2, and the accelerator portion M3 are set, and M1, M2, and M3 satisfy the following formula:

[0016] 0.30≤M1 / (M1+M2+M3)≤0.50, and the crosslinking density of the vulcanized rubber of the inner support rubber composition satisfies 22≤MH-ML≤26.

[0017] In one embodiment, the carbon black has an iodine absorption value of (30-60) g / kg and a DBP absorption value of (120-150)×10 - 5 m 3 / kg; the nitrogen adsorption specific surface area of ​​the highly dispersed white carbon black is (85-115) m 2 / g.

[0018] In one embodiment, the silane coupling agent is selected from at least one of bis-(γ-triethoxysilylpropyl)tetrasulfide and bis-[γ-(triethoxysilyl)propyl]-disulfide; the anti-reversion agent is selected from at least one of tetrabenzylthiuram disulfide, diisobutylthiuram disulfide, 1,6-bis(N,N′-dibenzylthiocarbamoyl disulfide)hexane, and 1,1′-dithiobiscaprolactam.

[0019] The present invention also provides a method for preparing the inner support rubber composition for a run-flat tire according to any of the above embodiments, comprising the following steps:

[0020] First-stage mixing: adding the natural rubber, rare earth butadiene rubber, liquid polybutadiene rubber, carbon black, highly dispersed white carbon black, silane coupling agent, antioxidant and activator into a closed rubber mixer according to weight proportion, mixing evenly and discharging the rubber to obtain a first-stage masterbatch;

[0021] Second stage mixing: adding the first stage masterbatch, insoluble sulfur, accelerator and anti-reversion agent into a closed rubber mixer, mixing evenly and then discharging the rubber to obtain the final mixed rubber.

[0022] The present invention further provides an inner support rubber for a run-flat tire, which is prepared using the inner support rubber composition for a run-flat tire described in any of the above embodiments.

[0023] Compared with the prior art, the advantages and positive effects of the present invention are:

[0024] 1. The present invention provides a special inner support rubber composition for run-flat tires. The rubber composition introduces liquid polybutadiene rubber into the composition formula, and further optimizes the ratio of other components (for example, anti-reversion agent, pure sulfur, accelerator). The support rubber prepared by using the rubber composition has excellent flex fatigue resistance, and the flex fatigue life is not less than 300,000 times. At the same time, it takes into account certain support and low hysteresis. The final dynamic compression rate of the vulcanized rubber is not higher than 22%, and the temperature rise is not higher than 28°C.

[0025] 2. The present invention provides a special inner support rubber composition for a run-flat tire and a preparation method thereof. The run-flat tire prepared with the inner support of the run-flat tire can travel more than 80 km at zero air pressure, and the comfort level when driving in an inflated state reaches 7.0, and the support rubber is not damaged after driving for more than 60,000 kilometers, which can significantly improve the driving comfort while ensuring that the tire has the ability to continue running at zero air pressure;

[0026] 3. The rubber composition proposed in the present invention is a special inner support rubber composition for run-flat tires, which has low rigidity, excellent flex fatigue resistance, certain support and low heat generation, so as to achieve a balance between support of the run-flat tire in the deflated state and comfort in the inflated state, and can provide users with a safer and more comfortable driving experience. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] The embodiment of the present invention provides an inner support rubber composition for a run-flat tire, wherein the flexural fatigue life of the vulcanized rubber of the inner support rubber composition is not less than 300,000 times, the Shore A hardness at 23° C. is 65-69, and the 100% strain modulus at 23° C. is 4.0-5.5 MPa;

[0029] Under a static loading pressure of 2 MPa, a stroke of 6.35 mm, a compression frequency of 30 Hz and a test temperature of 100° C., the final dynamic compression rate of the vulcanized rubber of the inner support rubber composition is not higher than 22%, and the temperature rise is not higher than 28° C.

[0030] The composition proposed in the above embodiment is a special inner support rubber composition for run-flat tires, which has low rigidity, excellent flex fatigue resistance, certain support and low heat generation, so as to achieve a balance between support of the run-flat tire in the deflated state and comfort in the inflated state, providing users with a safer and more comfortable driving experience.

[0031] Furthermore, it can be seen from the contents described in the above embodiments that this case defines two core properties of the rubber composition, namely comfort and support. Among them, ① the flexural fatigue life of the vulcanized rubber of the inner support rubber composition is not less than 300,000 times, the Shore A hardness at 23°C is 65-69, and the 100% strain modulus at 23°C is 4.0-5.5MPa, which defines comfort. A higher number of flexures can ensure that the support rubber is not damaged when driving in an inflated state. Moderate hardness and modulus are conducive to improving the comfort of the tire while taking into account a certain degree of support; ② Under a static loading pressure of 2MPa, a stroke of 6.35mm, a compression frequency of 30Hz and a test temperature of 100°C, the final dynamic compression rate of the vulcanized rubber of the inner support rubber composition is not higher than 22%, and the temperature rise is not higher than 28°C, which defines support. Through compression fatigue testing under specific test conditions, the stress conditions of the support rubber in the deflated state of the tire are simulated. The lower final dynamic compression rate and temperature rise can ensure that the support rubber has a certain degree of support and lower heat generation, thereby avoiding a decrease in the mechanical properties of the support rubber in the deflated state or even damage.

[0032] In one specific embodiment, the inner support rubber composition for a run-flat tire comprises at least the following components by weight:

[0033] 30-60 parts of natural rubber, 40-70 parts of rare earth butadiene rubber, and 3-15 parts of liquid polybutadiene rubber.

[0034] In the above-mentioned embodiment, liquid polybutadiene rubber and its modified products were originally rubbers specially developed for tire tread rubber. As a reactive plasticizer, it is not easy to migrate and volatilize during the use of the tire, which can reduce the precipitation of small molecules of the plasticizer and extend the service life of the tire. The present invention uses liquid polybutadiene rubber in the support rubber formula, and further defines the molecular structure of the liquid polybutadiene rubber, which is beneficial to greatly improve the flex fatigue resistance of the rubber while maintaining a low hysteresis. In addition, the present invention also defines the use amount of liquid polybutadiene rubber as 3-15 parts. It can be understood that the use amount of liquid polybutadiene rubber can also be 5 parts, 10 parts and any point value within the limited range, which falls within the protection scope of the present invention. After the raw material is used in combination with other targeted and preferred compounding agents, an inner support rubber composition specially used for run-flat tires with greatly improved flex fatigue resistance is finally obtained. The run-flat tire made of the inner support rubber composition has a comfort level of 7.0 when inflated and can travel more than 60,000 kilometers without damaging the support rubber. The tire can travel more than 80 km with zero air pressure, indicating that the solution has excellent driving comfort performance and a certain run-flat running capacity.

[0035] In a specific embodiment, the number average molecular weight of the liquid polybutadiene rubber is 3000-8000, wherein 1,2-butadiene structural units account for 20%-40% of the mass of the polybutadiene rubber segment, 1,4-butadiene structural units account for 60%-80% of the mass of the polybutadiene rubber segment, and the molecular chain end modification rate is 50%-80%.

[0036] In the above embodiment, the present invention further limits the number average molecular weight of the liquid polybutadiene rubber and the proportion of 1,2-butadiene structural units and 1,4-butadiene structural units. The reason is that: a moderate molecular weight can improve the flexural fatigue resistance and hysteresis loss of the rubber compound; a lower content of 1,2-butadiene structural units can reduce the number of vinyl side groups and reduce the steric hindrance of internal rotation, but at the same time a certain 1,2-butadiene structure is beneficial to the rubber matrix to maintain a higher crosslinking density, which has a positive effect on the hardness and hysteresis loss of the vulcanized rubber; a higher molecular chain end modification rate can provide lower hysteresis loss while maintaining its excellent processability and storage properties.

[0037] In a specific embodiment, the rare earth butadiene rubber is a neodymium-based high-cis butadiene rubber with a weight average molecular weight of 600,000-900,000, a molecular weight distribution width of 2.5-3.5, and a mass fraction of 1,4-butadiene cis structure of not less than 97.5%.

[0038] In the above embodiment, the present invention defines key parameters of the rare earth butadiene rubber such as the weight average molecular weight and the molecular weight distribution width. The reason is that a higher molecular weight and a lower molecular weight distribution width are beneficial to improving the mechanical strength of the rubber and reducing the hysteresis loss of the rubber. At the same time, a higher 1,4-butadiene cis-structure content can improve the rubber's resistance to crack initiation.

[0039] In one specific embodiment, the inner support rubber composition for a run-flat tire further comprises the following components in parts by weight:

[0040] 25-45 parts of carbon black, 10-30 parts of highly dispersed white carbon black, 1-3.5 parts of silane coupling agent, 3-5 parts of antioxidant, 3-6 parts of activator, 1-3 parts of insoluble sulfur, 1-2 parts of accelerator, and 1-3 parts of anti-reversion agent.

[0041] In a specific embodiment, the anti-reversion agent portion M1, the pure sulfur portion M2, and the accelerator portion M3 are set, and the M1, M2, and M3 satisfy the following formula:

[0042] 0.30≤M1 / (M1+M2+M3)≤0.50, and the crosslinking density of the vulcanized rubber of the inner support rubber composition satisfies 22≤MH-ML≤26.

[0043] In the above embodiment, the present invention further defines the weight ratio of the anti-reversion agent, pure sulfur and accelerator. When the weight ratios of the three satisfy the above calculation formula, an ideal rubber composition can be prepared. Among them, when the anti-reversion crosslinking agent dosage ratio is lower than 0.3, the polysulfide bonds in the inner support rubber composition are dominant, and the heat resistance is poor. When the tire is running with a flat tire, the support rubber is prone to early damage due to thermal degradation of the crosslinking bonds. When the anti-reversion crosslinking agent dosage ratio is higher than 0.5, the content of single and double sulfur bonds in the inner support rubber composition is too high, the support rubber has a high modulus, strong rigidity, and poor flexibility, which is also not conducive to improving support and comfort. Therefore, a specific content of anti-reversion crosslinking agent can ensure that the content of single and double sulfur bonds in the rubber material reaches the optimal ratio, which can not only improve the thermal stability of the crosslinking bonds, but also balance the flexibility of the composition. Among them, MH-ML can be used to characterize the crosslinking density of the rubber compound. The higher the value, the greater the crosslinking density. When MH-ML is less than 22, the crosslinking density of the support rubber composition is low, the average molecular weight of the rubber segments between adjacent crosslinking points in the vulcanized crosslinking network is large, the molecular chain has strong mobility, high heat generation, and is prone to early damage. When MH-ML is greater than 26, the support rubber is too rigid and the flexibility becomes poor. When the tire is running with a flat tire, the inner support rubber is prone to fracture and damage. Therefore, an appropriate crosslinking density is more conducive to improving the support of the inner support rubber composition.

[0044] In a specific embodiment, the carbon black has an iodine absorption value of (30-60) g / kg and a DBP absorption value of (120-150)×10 -5 m 3 / kg; the nitrogen adsorption specific surface area of ​​the highly dispersed white carbon black is (85-115) m 2 / g.

[0045] In the above embodiment, the carbon black and highly dispersed silica used in the present invention are respectively large particle size high structure carbon black and low specific surface area highly dispersed silica, wherein the large particle size high structure carbon black can reduce the hysteresis loss of the rubber and improve the anti-crack propagation property of the rubber; the low specific surface area highly dispersed silica can further reduce the hysteresis loss of the rubber.

[0046] In a specific embodiment, the silane coupling agent is selected from at least one of bis-(γ-triethoxysilylpropyl)tetrasulfide and bis-[γ-(triethoxysilyl)propyl]-disulfide; the anti-reversion agent is selected from at least one of tetrabenzylthiuram disulfide, diisobutylthiuram disulfide, 1,6-bis(N,N′-dibenzylthiocarbamoyl disulfide)hexane and 1,1′-dithiobiscaprolactam.

[0047] In a specific embodiment, the coupling agent selected in the present invention is a silane coupling agent. The use of such a coupling agent can further reduce the hysteresis loss of the rubber and improve the vulcanization reversion phenomenon; the anti-reversion crosslinking agent can improve the thermal stability of the crosslinking bond and further improve the heat resistance of the rubber.

[0048] The present invention also provides a method for preparing an inner support rubber composition dedicated to a run-flat tire, comprising the following steps:

[0049] S1, one-stage mixing: adding the natural rubber, rare earth butadiene rubber, liquid polybutadiene rubber, carbon black, highly dispersed white carbon black, silane coupling agent, antioxidant and activator into a closed rubber mixer according to weight proportion, mixing evenly and discharging the rubber to obtain a masterbatch;

[0050] S2, second stage mixing: adding the first stage masterbatch, insoluble sulfur, accelerator and anti-reversion agent into a closed rubber mixer, mixing evenly and then discharging the rubber to obtain the final mixed rubber.

[0051] The present invention further provides an inner support rubber for a run-flat tire, which is prepared using the inner support rubber composition for a run-flat tire described in any of the above embodiments. The run-flat tire obtained by the inner support of the run-flat tire can travel more than 80 km with zero air pressure, and the comfort level reaches 7.0 when driving in an inflated state, and the support rubber is not damaged after driving for more than 60,000 kilometers, indicating that the solution takes into account both certain run-flat running continuation performance and excellent comfort performance.

[0052] In order to more clearly and in detail introduce the inner support rubber composition for run-flat tires and the preparation method thereof provided in the embodiments of the present invention, they will be described below in conjunction with specific embodiments.

[0053] Example 1

[0054] This embodiment provides a special inner support rubber composition for a run-flat tire and a preparation method thereof, specifically:

[0055] The inner support rubber composition specially used for run-flat tires comprises the following components in parts by weight:

[0056] 50 parts of natural rubber, 50 parts of neodymium-based butadiene rubber, 5 parts of liquid polybutadiene rubber, 30 parts of N550 carbon black, 25 parts of 1115MP white carbon black, 3.0 parts of TESPT silane coupling agent, 3.5 parts of antioxidant, 4.0 parts of activator, 1.25 parts of HD OT20 insoluble sulfur, 1.3 parts of NS accelerator, and 1.2 parts of TBzTD anti-reversion agent.

[0057] Among them, the number average molecular weight of liquid polybutadiene rubber is 3000, 1,2-butadiene structural units account for 20% of the mass of the butadiene rubber chain segment, 1,4-butadiene structural units account for 80% of the mass of the butadiene rubber chain segment, and the molecular chain end modification rate is 50%. The weight average molecular weight of neodymium-based butadiene rubber is 700,000, the molecular weight distribution width is 2.8, and the mass fraction of 1,4-butadiene cis structure is 97.5%.

[0058] Preparation method:

[0059] (1) mixing in one stage: adding the natural rubber, rare earth butadiene rubber, liquid polybutadiene rubber, carbon black, highly dispersed white carbon black, silane coupling agent, antioxidant and activator into a closed rubber mixer according to the above weight ratio, mixing evenly and discharging the rubber to obtain a masterbatch;

[0060] (2) Second stage mixing: adding the primary masterbatch obtained in step (1), insoluble sulfur, accelerator and anti-reversion agent into a closed rubber mixer, mixing evenly and then discharging the rubber to obtain the final rubber mix.

[0061] Example 2

[0062] This embodiment provides a special inner support rubber composition for a run-flat tire and a preparation method thereof, specifically:

[0063] The inner support rubber composition specially used for run-flat tires comprises the following components in parts by weight:

[0064] 50 parts of natural rubber, 50 parts of neodymium-based butadiene rubber, 10 parts of liquid polybutadiene rubber, 25 parts of N550 carbon black, 30 parts of 1115MP white carbon black, 3.5 parts of TESPT silane coupling agent, 3.0 parts of antioxidant, 5.0 parts of activator, 1.25 parts of HD OT20 insoluble sulfur, 1.1 parts of NS accelerator, and 1.4 parts of TiBTD anti-reversion agent.

[0065] Among them, the number average molecular weight of liquid polybutadiene rubber is 5000, 1,2-butadiene structural units account for 40% of the mass of the butadiene rubber chain segment, 1,4-butadiene structural units account for 60% of the mass of the butadiene rubber chain segment, and the molecular chain end modification rate is 60%. The weight average molecular weight of neodymium-based butadiene rubber is 900,000, the molecular weight distribution width is 3.0, and the mass fraction of 1,4-butadiene cis structure is 98.0%.

[0066] The preparation method is the same as that of Example 1, except that the method is carried out according to the rubber composition formulation defined in this example.

[0067] Example 3

[0068] This embodiment provides a special inner support rubber composition for a run-flat tire and a preparation method thereof, specifically:

[0069] The inner support rubber composition specially used for run-flat tires comprises the following components in parts by weight:

[0070] 60 parts of natural rubber, 40 parts of neodymium-based butadiene rubber, 10 parts of liquid polybutadiene rubber, 40 parts of BC2123 carbon black, 15 parts of 1115MP white carbon black, 1.8 parts of TESPT silane coupling agent, 4.0 parts of antioxidant, 3.0 parts of activator, 1.0 parts of HD OT20 insoluble sulfur, 1.3 parts of NS accelerator, and 1.6 parts of KA9188 anti-reversion agent.

[0071] Among them, the number average molecular weight of liquid polybutadiene rubber is 6000, 1,2-butadiene structural units account for 30% of the mass of the butadiene rubber chain segment, 1,4-butadiene structural units account for 70% of the mass of the butadiene rubber chain segment, and the molecular chain end modification rate is 70%. The weight average molecular weight of neodymium-based butadiene rubber is 800,000, the molecular weight distribution width is 3.5, and the mass fraction of 1,4-butadiene cis structure is 98.0%.

[0072] The preparation method is the same as that of Example 1, except that the method is carried out according to the rubber composition formulation defined in this example.

[0073] Example 4

[0074] This embodiment provides a special inner support rubber composition for a run-flat tire and a preparation method thereof, specifically:

[0075] The inner support rubber composition specially used for run-flat tires comprises the following components in parts by weight:

[0076] 40 parts of natural rubber, 60 parts of neodymium-based butadiene rubber, 15 parts of liquid polybutadiene rubber, 45 parts of BC2123 carbon black, 10 parts of 1085MP white carbon black, 1.2 parts of TESPT silane coupling agent, 5.0 parts of antioxidant, 6.0 parts of activator, 1.0 parts of HD OT20 insoluble sulfur, 1.0 parts of NS accelerator, and 2.25 parts of CLD-80 anti-reversion agent.

[0077] Among them, the number average molecular weight of liquid polybutadiene rubber is 8000, 1,2-butadiene structural units account for 30% of the mass of the butadiene rubber chain segment, 1,4-butadiene structural units account for 70% of the mass of the butadiene rubber chain segment, and the molecular chain end modification rate is 80%. The weight average molecular weight of neodymium-based butadiene rubber is 600,000, the molecular weight distribution width is 2.5, and the mass fraction of 1,4-butadiene cis structure is 98.0%

[0078] The preparation method is the same as that of Example 1, except that the method is carried out according to the rubber composition formulation defined in this example.

[0079] Comparative Example 1

[0080] This comparative example provides a special inner support rubber composition for a run-flat tire and a preparation method thereof, specifically:

[0081] The inner support rubber composition specially used for run-flat tires comprises the following components in parts by weight:

[0082] 50 parts of natural rubber, 50 parts of neodymium-based butadiene rubber, 30 parts of N550 carbon black, 25 parts of 1115MP white carbon black, 3.0 parts of TESPT silane coupling agent, 3.5 parts of antioxidant, 4.0 parts of activator, 1.5 parts of HD OT20 insoluble sulfur, 1.5 parts of NS accelerator, and 0.8 parts of TBzTD anti-reversion agent.

[0083] Among them, the weight average molecular weight of neodymium-based butadiene rubber is 700,000, the molecular weight distribution width is 3.8, and the mass fraction of 1,4-butadiene cis structure is 96.0%.

[0084] Preparation method:

[0085] (1) One-stage mixing: adding natural rubber, neodymium-based butadiene rubber, N550 carbon black, 1115MP white carbon black, silane coupling agent, antioxidant and activator into a closed rubber mixer according to the above weight ratio, mixing evenly and discharging the rubber to obtain a masterbatch;

[0086] (2) Second stage mixing: adding the primary masterbatch obtained in step (1), insoluble sulfur, accelerator and anti-reversion agent into a closed rubber mixer, mixing evenly and then discharging the rubber to obtain the final rubber mix.

[0087] Comparative Example 2

[0088] This comparative example provides a special inner support rubber composition for a run-flat tire and a preparation method thereof, specifically:

[0089] The inner support rubber composition specially used for run-flat tires comprises the following components in parts by weight:

[0090] 50 parts of natural rubber, 50 parts of neodymium-based butadiene rubber, 5 parts of liquid polybutadiene rubber, 30 parts of N550 carbon black, 25 parts of 1115MP white carbon black, 3.0 parts of TESPT silane coupling agent, 3.5 parts of antioxidant, 4.0 parts of activator, 1.5 parts of HD OT20 insoluble sulfur, 1.5 parts of NS accelerator, and 0.8 parts of TBzTD anti-reversion agent.

[0091] Among them, the number average molecular weight of liquid polybutadiene rubber is 2500, 1,2-butadiene structural units account for 5% of the mass of the butadiene rubber chain segment, 1,4-butadiene structural units account for 95% of the mass of the butadiene rubber chain segment, and the molecular chain end is unmodified. The weight average molecular weight of neodymium-based butadiene rubber is 700,000, the molecular weight distribution width is 3.8, and the mass fraction of 1,4-butadiene cis structure is 96.0%.

[0092] The preparation method is the same as that of Comparative Example 1, except that the method is carried out according to the rubber composition formula defined in this comparative example.

[0093] Performance Testing

[0094] The present invention conducted multiple performance tests on the rubber materials prepared in the above-mentioned Examples 1-4 and Comparative Examples 1-2. The specific test methods and test results are as follows:

[0095] (1) Test method:

[0096] The rubber vulcanization condition is 161℃×15min. The rubber hardness test is carried out in accordance with GB / T531, and the rubber tensile performance is carried out in accordance with GB / T528. The compression fatigue temperature rise constant temperature box is 100℃, the static load is 2MPa, the stroke is 6.35mm, the loading frequency is 30Hz, and the test time is 1h. The rubber flexural resistance test is carried out at a temperature of 100℃, and the others are carried out in accordance with GB / T13934, and the crack grade is observed every 10,000 times. The tire test adopts 225 / 45R17 specifications, the test speed is set to 60km / h, and the others are carried out in accordance with GB / T30196.

[0097] (2) The test results are shown in Table 1.

[0098] Table 1 Test results of the performance of the rubber materials obtained in Examples 1-4 and Comparative Examples

[0099]

[0100]

[0101] Based on the rubber composition formulas shown in the embodiments and comparative examples, combined with the performance test data in Table 1, it can be seen that: Comparative Example 1 is an existing commonly used rubber composition formula, the raw rubber system adopts natural rubber and butadiene rubber, the hardness is relatively high, the zero air pressure endurance time of the trial tire is 1.96h, the support is good in the deflated state, but the flexural fatigue resistance is poor, the tire comfort grade is low, and the comfort is poor; Comparative Example 2 adds 5 parts of liquid polybutadiene rubber on the basis of Comparative Example 1, the hardness of the supporting rubber is reduced, and the comfort is improved, but because the liquid butadiene rubber has a low molecular weight and the molecular chain end is not modified, the heat generation of the supporting rubber is high, and the zero air pressure endurance time of the tire is significantly reduced.

[0102] However, Examples 1-4 are rubber materials prepared using the inner support rubber composition for run-flat tires provided by the present invention and the preparation method thereof. They have low hardness and modulus, significantly improved flex fatigue resistance, and a significantly improved tire comfort level. The tires can travel more than 80 km under zero air pressure and have certain run-flat support properties.

[0103] It can be seen that the rubber composition formula provided by the present invention is finally used to prepare a special inner support rubber composition for run-flat tires with extremely excellent flex fatigue resistance, while taking into account certain support and low hysteresis, which can solve the problem in the prior art that the support of the run-flat tire in the deflated state and the comfort in the inflated state cannot be taken into account at the same time.

Claims

1. A special inner support rubber composition for a run-flat tire, characterized in that: The flex fatigue life of the vulcanized rubber of the inner support rubber composition is not less than 300,000 times, the Shore A hardness at 23°C is 65-69, and the 100% strain modulus at 23°C is 4.0-5.5MPa; Under a static loading pressure of 2 MPa, a stroke of 6.35 mm, a compression frequency of 30 Hz and a test temperature of 100° C., the final dynamic compression rate of the vulcanized rubber of the inner support rubber composition is not higher than 22%, and the temperature rise is not higher than 28° C.; The inner support rubber composition dedicated to the run-flat tire comprises at least the following components in parts by weight: 30-60 parts of natural rubber, 40-70 parts of rare earth butadiene rubber, 3-15 parts of liquid polybutadiene rubber; The number average molecular weight of the liquid polybutadiene rubber is 3000-8000, wherein the 1,2-butadiene structural unit accounts for 20%-40% of the mass of the polybutadiene rubber segment, the 1,4-butadiene structural unit accounts for 60%-80% of the mass of the polybutadiene rubber segment, and the molecular chain end modification rate is 50%-80%; The rare earth butadiene rubber is a neodymium-based high-cis butadiene rubber with a weight average molecular weight of 600,000-900,000, a molecular weight distribution width of 2.5-3.5, and a mass fraction of 1,4-butadiene cis structure of not less than 97.5%.

2. The inner support rubber composition for a run-flat tire according to claim 1, characterized in that: In parts by weight, it also contains the following components: Carbon black 25-45 parts, highly dispersed white carbon black 10-30 parts, silane coupling agent 1-3.5 parts, antioxidant 3-5 parts, activator 3-6 parts, insoluble sulfur 1-3 parts, accelerator 1-2 parts, anti-reversion agent 1-3 parts.

3. The inner support rubber composition for a run-flat tire according to claim 2, characterized in that: The anti-reversion agent portion M1, the pure sulfur portion M2, and the accelerator portion M3 are set, and the M1, M2, and M3 satisfy the following formula: 0.30≤ M1 / (M1+M2+M3)≤0.50, and the crosslinking density of the vulcanized rubber of the inner support rubber composition satisfies 22≤MH-ML≤26.

4. The inner support rubber composition for a run-flat tire according to claim 2, characterized in that: The carbon black iodine absorption value is (30-60) g / kg, and the DBP absorption value is (120-150)×10 -5 m 3 / kg; the nitrogen adsorption specific surface area of ​​the highly dispersed white carbon black is (85-115) m 2 / g.

5. The inner support rubber composition for a run-flat tire according to claim 2, characterized in that: The silane coupling agent is selected from at least one of bis-(γ-triethoxysilylpropyl)tetrasulfide and bis-[γ-(triethoxysilyl)propyl]-disulfide; the anti-reversion agent is selected from at least one of tetrabenzylthiuram disulfide, diisobutylthiuram disulfide, 1,6-bis(N,N′-dibenzylthiocarbamoyl disulfide)hexane and 1,1′-dithiobiscaprolactam.

6. The method for preparing the inner support rubber composition for a run-flat tire according to any one of claims 1 to 5, characterized in that: The following steps are involved: First-stage mixing: adding the natural rubber, rare earth butadiene rubber, liquid polybutadiene rubber, carbon black, highly dispersed white carbon black, silane coupling agent, antioxidant and activator into a closed rubber mixer according to weight proportion, mixing evenly and discharging the rubber to obtain a first-stage masterbatch; Second stage mixing: adding the first stage masterbatch, insoluble sulfur, accelerator and anti-reversion agent into a closed rubber mixer, mixing evenly and then discharging the rubber to obtain the final mixed rubber.

7. Special inner support rubber for run-flat tires, characterized by: The tire is prepared using the inner support rubber composition for run-flat tires as described in any one of claims 1 to 5.

Images