Low-temperature-cold-crack-resistant low-rolling-resistance tire sidewall rubber composition and preparation method thereof

Abstract

The invention provides a low-temperature cold-crack-resistant low-rolling-resistance tire sidewall rubber composition and a preparation method thereof, belongs to the technical field of rubber compositions, and can solve the problems that an existing new energy automobile tire sidewall rubber composition is easy to have cold cracks and rolling resistance is increased under a low-temperature condition. The low-temperature cold-crack-resistant low-rolling-resistance tire sidewall rubber composition is prepared from the following raw materials in parts by weight: 30 to 70 parts of natural rubber, 30 to 70 parts of chain segment modified butadiene rubber, 1 to 40 parts of pre-modified negative expansion filler and 1 to 15 parts of modified montmorillonite. The sidewall rubber composition disclosed by the invention not only has excellent low-temperature cold crack resistance, but also has excellent normal-temperature rolling resistance and low-temperature rolling resistance, and can be applied to new energy automobile tire sidewalls.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of rubber compositions, and particularly relates to a low-temperature-resistant and cold-crack-resistant tire sidewall rubber composition and a preparation method thereof. BACKGROUND

[0002] With the promotion of relevant regulations and the change of consumer consumption concept, the new energy vehicle market is rapidly expanding. Correspondingly, new energy vehicle tires face a huge matching and replacement market, becoming an important growth point of the tire industry. Compared with traditional fuel vehicles, new energy vehicles generally face range anxiety, and the range capability is closely related to the rolling resistance of the tire, so it is necessary to further reduce the rolling resistance of the tire; in addition, due to the high output torque of the starting motor of new energy vehicles, higher requirements are put forward for the wear resistance of the tire tread and the flexing resistance of the tire sidewall.

[0003] Tires are a composite material system composed of rubber, fillers, steel wires, polyester cords, etc. Due to the viscoelastic behavior of rubber and the thermodynamic response of the material, which is greatly affected by the environmental temperature, the performance of the tire is closely related to the environmental temperature. In some cold regions, the minimum temperature can reach minus 40℃, and the change of tire performance will affect the use of new energy vehicles in low temperature environment. In the prior art, the sidewall rubber composition often uses high-cis butadiene rubber in combination with natural rubber as the matrix, and carbon black as the reinforcing filler. However, the rubber matrix has a relatively high positive thermal expansion coefficient (usually 100-200×10 -6 / K), and shrinks significantly when cooled; the thermal expansion coefficient (CTE) of carbon black is usually 2-15×10 -6 / K, and the shrinkage when cooled is less than that of the rubber matrix. When the temperature decreases, the thermal expansion coefficients of the rubber matrix and the filler mismatch, resulting in stress concentration at the filler-rubber interface, forming initial microcracks, and since the sidewall component is continuously deformed in flexure during vehicle driving, it is easy to accelerate the propagation of microcracks, becoming one of the main causes of sidewall cold cracking; in addition, high-cis butadiene rubber will crystallize locally at about -20℃, causing the modulus at low temperature to rise, and the crystalline region becomes a stress concentration point, accelerating crack generation. Moreover, as the temperature decreases, the rubber changes from a high-elastic state to a glassy state, the molecular chain segment movement ability decreases sharply, the hysteresis loss increases, and the rolling resistance also increases, affecting the range of new energy vehicles. SUMMARY

[0004] The present application is directed to the technical problem that the new energy automobile tire sidewall rubber composition is prone to cold cracking and increased rolling resistance under low temperature conditions, and proposes a low-temperature cold cracking and low-rolling resistance tire sidewall rubber composition, which not only has excellent low-temperature cold cracking resistance, but also has excellent normal temperature rolling resistance and low-temperature rolling resistance performance. The present application uses chain segment modified butadiene rubber to improve the crystallization of butadiene rubber at low temperature, reduce the low temperature modulus, and improve the low temperature performance. The pre-modified negative expansion filler with negative thermal expansion coefficient and CTE<0 is introduced into the tire sidewall rubber composition, which reduces the shrinkage stress of the rubber matrix and the filler under low temperature environment, reduces the generation of micro cracks, and reduces the low temperature rolling resistance. The modified montmorillonite sheet filler is used in combination to hinder the expansion of micro cracks, thereby realizing the preparation of a low-temperature cold cracking and low-rolling resistance tire sidewall rubber composition.

[0005] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows: a low-temperature cold cracking and low-rolling resistance tire sidewall rubber composition, by weight, comprising the following raw materials: natural rubber 30-70 parts, chain segment modified butadiene rubber 30-70 parts, pre-modified negative expansion filler 1-40 parts, modified montmorillonite 1-15 parts.

[0006] It can be understood that the weight fraction of each component can be adjusted within the above range by those skilled in the art according to the actual situation, for example, the weight fraction of natural rubber can also be 30 parts, 40 parts, 50 parts, 60 parts, 70 parts or any point value within the above range, the weight fraction of chain segment modified butadiene rubber can also be 30 parts, 40 parts, 50 parts, 60 parts, 70 parts or any point value within the above range, the weight fraction of pre-modified negative expansion filler can also be 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts, 21 parts, 22 parts, 23 parts, 24 parts, 25 parts, 26 parts, 27 parts, 28 parts, 29 parts, 30 parts, 31 parts, 32 parts, 33 parts, 34 parts, 35 parts, 36 parts, 37 parts, 38 parts, 39 parts, 40 parts or any point value within the above range, and the weight fraction of modified montmorillonite can also be 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts or any point value within the above range.

[0007] In the above technical solution of the present application, the segment modified butadiene rubber is used to improve the crystallinity of butadiene rubber at low temperature, reduce the low temperature modulus of the tire side rubber composition, and reduce crack generation; the pre-modified negative expansion filler is introduced into the tire side rubber composition to reduce the shrinkage stress of the rubber matrix and the filler under low temperature environment, reduce micro-crack generation, and reduce rolling resistance; the modified montmorillonite sheet filler is used in combination to increase the interaction with the rubber, hinder the expansion of micro-cracks, and prepare a low-temperature cold-crack-resistant low-rolling-resistance tire side rubber composition.

[0008] In one embodiment, the segment modified butadiene rubber is prepared by random copolymerization of isoprene and butadiene, and the mass fraction of isoprene in the segment modified butadiene rubber is 8%-15%.

[0009] In the above technical solution of the present application, the isoprene segment modification can improve the crystallinity of butadiene rubber at low temperature and reduce the low temperature modulus.

[0010] In one embodiment, the pre-modified negative expansion filler is prepared by pre-modification treatment of the negative expansion filler with a silane coupling agent, and the D50 range of the negative expansion filler is 0.05-20 μm.

[0011] In the above technical solution of the present application, the silane coupling agent includes any one of bis(triethoxysilyl) tetrasulfide, bis(triethoxysilyl) disulfide, 3-octanoylthio-1-propyl triethoxysilane, (3-octanoylthio-1-propyl triethoxysilane)-(γ-mercaptopropyl-triethoxysilane) condensation oligomer, and γ-mercaptopropyl-ethoxyl bis(propyl-hexaethoxyl) silane. The surface of the negative expansion filler is pre-modified by the silane coupling agent, which can reduce the shrinkage stress of the rubber matrix and the filler under low temperature environment, reduce micro-crack generation, and reduce rolling resistance. By limiting the D50 particle size of the negative expansion filler, uniform dispersion in the rubber matrix is facilitated, and good crack expansion prevention effect is also achieved.

[0012] In one embodiment, the pre-modification treatment of the negative expansion filler with the silane coupling agent specifically includes the following steps: The negative expansion coefficient filler, the silane coupling agent, and the ethanol are weighed according to the mass ratio of 100:(1-5):(500-800); The silane coupling agent and the ethanol are stirred and mixed, and the stirring time is 5-40 min; The negative expansion coefficient filler is then added, and the reaction is carried out at 40-90°C for 20-80 min; After the reaction is completed, the pre-modified negative expansion filler is obtained by cooling and filtering.

[0013] In the above technical solution of the present application, the negative expansion filler is pre-modified by a silane coupling agent, which can reduce the shrinkage stress of the rubber matrix and the filler in a low-temperature environment, reduce the generation of micro-cracks, and reduce the rolling resistance; by limiting the mass ratio of the negative expansion coefficient filler, the silane coupling agent and ethanol, the surface modification degree of the negative expansion filler is appropriate, and the interaction effect of the filler and the rubber matrix is better.

[0014] In one embodiment, the negative expansion filler is any one or several of spodumene (LiAl(SiO3)2 / Li2O·Al2O3·4SiO2), petalite (β-LiAlSiO4), aluminum titanate (Al2TiO5), cordierite (2MgO·2Al2O3·5SiO2), zirconium tungstate (ZrW2O8), zirconium phosphate (Zr2P2O9), magnesium phosphate (Mg2P4O7), NaZr2(PO4)3 (abbreviated as NZP), and BaZr4(PO4)6.

[0015] In one embodiment, the modified montmorillonite is montmorillonite that is surface-modified by acid treatment and quaternary ammonium salt treatment, and the D50 particle size of the modified montmorillonite is 2-5 μm.

[0016] In the above technical solution of the present application, the montmorillonite is a polar sheet silicate, which, after acid treatment, has a passivated polar bond, an increased specific surface area, and an increased pore size, which can better hinder crack propagation; after quaternary ammonium salt treatment, the compatibility with rubber is enhanced, and the mechanical properties of the rubber compound are improved.

[0017] In one embodiment, the low-temperature-resistant cold-cracking and low-rolling-resistance tire sidewall rubber composition further comprises, by weight fraction, the following raw materials: carbon black 30-80 parts, softening agent 2-6 parts, active agent 3-6 parts, vulcanizing agent 1-4 parts, accelerator 1-3 parts, and antioxidant 3-8 parts.

[0018] In the above technical solution of the present application, the softening agent is preferably octyl tackifying resin; the active agent is preferably zinc oxide and stearic acid; the vulcanizing agent is preferably insoluble sulfur; the accelerator is preferably a sulfenamide accelerator; and the antioxidant is preferably one or more of physical protective wax, antioxidant 6PPD, and antioxidant RD.

[0019] In one embodiment, the nitrogen adsorption value (total specific surface area) of the carbon black ranges from 30-90×10 3 m 2 / kg.

[0020] In the above technical solution of the present application, the rubber composition prepared using the carbon black with the nitrogen adsorption value in the above range has excellent rolling resistance.

[0021] The application also provides a preparation method of the low-temperature cold cracking resistant and low rolling resistance tire sidewall rubber composition. First-stage mixing: according to the weight ratio, natural rubber, chain segment modified butadiene rubber, pre-modified negative expansion filler, carbon black, modified montmorillonite, softener, active agent, antioxidant and the like are added into a closed rubber mixing machine for first-stage mixing, and after uniform mixing, the rubber is discharged to obtain a masterbatch; Second-stage mixing: the masterbatch, vulcanizing agent and accelerator are added into the closed rubber mixing machine for mixing, and after uniform mixing, the rubber is discharged, recovered and cooled to obtain the low-temperature cold cracking resistant and low rolling resistance tire sidewall rubber composition.

[0022] In the above technical solution of the application, the rubber composition is prepared by using a segmented mixing process, the pre-modified negative expansion filler is added into the mixing together with raw rubber, carbon black and modified montmorillonite, so that the mixing is more uniform, and the performance of the rubber compound is improved.

[0023] In one embodiment, in the first-stage mixing step, the mixing temperature is 135-160 DEG C, and the mixing time is 90-140 s; in the second-stage mixing step, the mixing temperature is 90-120 DEG C, and the mixing time is 70-120 s.

[0024] In the above technical solution of the application, the first-stage mixing is carried out by gradually increasing the temperature, which can realize good dispersion and infiltration of carbon black, and at the same time, protect the rubber molecular chain, especially the natural rubber, from excessive thermal oxidative degradation; the second-stage mixing is carried out at low temperature, so as to ensure safe and uniform introduction of the vulcanizing system, avoid scorching, ensure the vulcanization reaction under controllable conditions, and ensure processing safety.

[0025] Compared with the prior art, the low-temperature cold cracking resistant and low rolling resistance tire sidewall rubber composition has the advantages and positive effects that: the low-temperature cold cracking resistant and low rolling resistance tire sidewall rubber composition not only has excellent low-temperature cold cracking resistance, but also has excellent normal-temperature rolling resistance and low-temperature rolling resistance. The chain segment modified butadiene rubber improves the crystallinity of butadiene rubber at low temperature, reduces the low-temperature modulus of the rubber compound, reduces the risk of crack generation, further improves the flexing resistance of the rubber compound, and prevents the occurrence of low-temperature cold cracking; the surface pre-modified negative expansion filler reduces the shrinkage stress between the rubber matrix and the filler, and reduces the rolling resistance; the surface modification improves the dispersion of the negative expansion filler and the interaction between the rubber and the filler, the tensile strength of the rubber compound is gradually increased, the well-dispersed negative expansion filler expands when flexing, buffers the stress, and improves the flexing resistance of the rubber compound; the montmorillonite with a layered nano structure forms a "brick wall" structure in the rubber to hinder crack propagation and reduce the crack propagation rate; the quaternary ammonium salt modification of the surface of the montmorillonite enhances the compatibility with the rubber and improves the tensile strength of the rubber compound; at the same time, the negative expansion coefficient filler is used in combination with the modified montmorillonite to inhibit the crack propagation rate and reduce the low-temperature rolling resistance. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0027] The present application provides a kind of low temperature cold cracking resistant low rolling resistance tire side rubber composition and preparation method thereof, the low temperature cold cracking resistant low rolling resistance tire side rubber composition of the present application reduces the modulus of rubber at low temperature by adding segment modified butadiene rubber, reduces the risk of crack generation;At the same time, by using the compound of negative expansion coefficient filler and modified montmorillonite, the crack propagation rate is inhibited and the low temperature rolling resistance is reduced, the prepared side rubber composition not only has excellent low temperature cold cracking resistance, but also has excellent normal temperature rolling resistance and low temperature rolling resistance performance.

[0028] In order to more clearly and in detail introduce the low temperature cold cracking resistant low rolling resistance tire side rubber composition and preparation method thereof provided by the embodiments of the present application, the following will be described in combination with specific embodiments, wherein the raw material ratio of examples 1-6 and comparative examples 1-4 is shown in table 1, each raw material can be obtained by marketing. In table 1, the segment modified butadiene rubber is butadiene rubber obtained by random copolymerization of 10% mass fraction of isoprene and butadiene;The nitrogen adsorption value (total specific surface area) of carbon black is 30-40×10 3 m 2 / kg, the brand is N660;Pre-modified negative expansion filler is silane coupling agent modified zirconium tungstate (ZrW2O8), D50 is 0.5 μm;Modified montmorillonite is montmorillonite modified by acidification and quaternary ammonium salt modification on the surface, D50 is 3 μm, brand DK4-D;Softener is octyl tackifying resin;The rest of the active agent, vulcanizing agent, accelerator, antioxidant component are all market products.

[0029] Table 1 raw material ratio (by weight fraction) of examples 1-6 and comparative examples 1-3

[0030] Example 1 The low temperature cold cracking resistant low rolling resistance tire side rubber composition of the present application, by weight fraction, includes the following raw materials: natural rubber 60 parts, segment modified butadiene rubber 40 parts, carbon black N660 40 parts, pre-modified negative expansion filler zirconium tungstate (ZrW2O8) 2 parts, modified montmorillonite 2 parts, softener is octyl tackifying resin 2.0 parts, active agent includes zinc oxide 3 parts and stearic acid 1.0 part, vulcanizing agent is insoluble sulfur 2.0 parts, accelerator CZ 1.0 part, antioxidant includes antioxidant 6PPD 3.5 parts, antioxidant RD 1.0 part and bimodal wax 2.0 parts.

[0031] The preparation method of the low-temperature cold cracking and low rolling resistance tire sidewall rubber composition of the embodiment comprises the following steps: The surface of the negative expansion filler is pre-modified: the negative expansion filler zirconium tungstate, the silane coupling agent bis(triethoxysilyl) disulfide and ethanol are weighed according to the mass ratio of 100:4:600; the silane coupling agent bis(triethoxysilyl) disulfide and ethanol are stirred and mixed, and the stirring time is 20 min; after dissolution, the zirconium tungstate with an average particle size of 0.5 μm is added, heated at 70°C for 50 min for reaction, and after cooling, deionized water is used for filtration to obtain the pre-modified negative expansion filler zirconium tungstate; First stage mixing: according to the weight ratio, natural rubber, chain segment modified butadiene rubber, pre-modified negative expansion filler zirconium tungstate, carbon black, modified montmorillonite, softener octyl tackifying resin, zinc oxide, stearic acid, antioxidant 6PPD, antioxidant RD and bimodal wax are added to a closed rubber mixing machine for step-by-step temperature mixing, and the mixing steps are as follows: after pressing the weight for 25 s, lifting the weight, pressing the weight for 30 s or lifting the weight to 135°C, pressing the weight to 155°C and mixing for 100 s to discharge the rubber, to obtain a masterbatch; Second stage mixing: the masterbatch, insoluble sulfur and accelerator CZ are added to the closed rubber mixing machine for low-temperature mixing, the mixing temperature is 110°C, the mixing time is 80 s, and after uniform mixing, the rubber is discharged, recovered and cooled to obtain the low-temperature cold cracking and low rolling resistance tire sidewall rubber composition.

[0032] Example 2 The low-temperature cold cracking and low rolling resistance tire sidewall rubber composition of the embodiment comprises the following raw materials in weight parts: natural rubber 60 parts, chain segment modified butadiene rubber 40 parts, carbon black N660 40 parts, pre-modified negative expansion filler zirconium tungstate (ZrW2O8) 4 parts, modified montmorillonite 2 parts, softener octyl tackifying resin 2.0 parts, active agent including zinc oxide 3 parts and stearic acid 1.0 part, vulcanizing agent insoluble sulfur 2.0 parts, accelerator CZ 1.0 part, antioxidant including antioxidant 6PPD 3.5 parts, antioxidant RD 1.0 part and bimodal wax 2.0 parts.

[0033] The preparation method of the low-temperature cold cracking and low rolling resistance tire sidewall rubber composition of the embodiment comprises the following steps: The surface of the negative expansion filler is pre-modified: the negative expansion filler zirconium tungstate, the silane coupling agent bis(triethoxysilyl) disulfide and ethanol are weighed according to the mass ratio of 100:4:600; the silane coupling agent bis(triethoxysilyl) disulfide and ethanol are stirred and mixed, and the stirring time is 20 min; after dissolution, the zirconium tungstate with an average particle size of 0.5 μm is added, heated at 70°C for 50 min for reaction, and after cooling, deionized water is used for filtration to obtain the pre-modified negative expansion filler zirconium tungstate; First-stage mixing: according to the weight ratio, natural rubber, chain segment modified butadiene rubber, pre-modified negative expansion filler zirconium tungstate, carbon black, modified montmorillonite, softener octyl tackifying resin, zinc oxide, stearic acid, antioxidant 6PPD, antioxidant RD and bimodal wax are added to a closed rubber mixing machine for step-by-step temperature increasing mixing, the mixing steps are: after pressing the weight for 25 s, lifting the weight, pressing the weight for 30 s or lifting the weight to 135 DEG C, pressing the weight to 155 DEG C and mixing for 100 s to discharge the rubber, to obtain a masterbatch; Second-stage mixing: the masterbatch, insoluble sulfur and accelerator CZ are added to the closed rubber mixing machine for low-temperature mixing, the mixing temperature is 110 DEG C, the mixing time is 80 s, the rubber is discharged after uniform mixing, recovered and cooled, to obtain the low-temperature cold cracking and low rolling resistance tire sidewall rubber composition.

[0034] Example 3 The low-temperature cold cracking and low rolling resistance tire sidewall rubber composition of the example includes the following raw materials in weight parts: natural rubber 60 parts, chain segment modified butadiene rubber 40 parts, carbon black N660 40 parts, pre-modified negative expansion filler zirconium tungstate (ZrW2O8) 8 parts, modified montmorillonite 2 parts, softener octyl tackifying resin 2.0 parts, active agent including zinc oxide 3 parts and stearic acid 1.0 part, vulcanizing agent insoluble sulfur 2.0 parts, accelerator CZ 1.0 part, antioxidant including antioxidant 6PPD 3.5 parts, antioxidant RD 1.0 part and bimodal wax 2.0 parts.

[0035] The preparation method of the low-temperature cold cracking and low rolling resistance tire sidewall rubber composition of the example includes the following steps: Surface pre-modification treatment of the negative expansion filler: the negative expansion filler zirconium tungstate, the silane coupling agent bis(triethoxysilyl) disulfide and ethanol are weighed according to the mass ratio of 100:4:600; the silane coupling agent bis(triethoxysilyl) disulfide and ethanol are stirred and mixed, the stirring time is 20 min; after dissolution, the zirconium tungstate with an average particle size of 0.5 μm is added, heated at 70 DEG C for 50 min for reaction, cooled and filtered with deionized water to obtain the pre-modified negative expansion filler zirconium tungstate; First-stage mixing: according to the weight ratio, natural rubber, chain segment modified butadiene rubber, pre-modified negative expansion filler zirconium tungstate, carbon black, modified montmorillonite, softener octyl tackifying resin, zinc oxide, stearic acid, antioxidant 6PPD, antioxidant RD and bimodal wax are added to a closed rubber mixing machine for step-by-step temperature increasing mixing, the mixing steps are: after pressing the weight for 25 s, lifting the weight, pressing the weight for 30 s or lifting the weight to 135 DEG C, pressing the weight to 155 DEG C and mixing for 100 s to discharge the rubber, to obtain a masterbatch; Second stage mixing: add the masterbatch, insoluble sulfur and accelerator CZ to the closed mixer for low temperature mixing, the mixing temperature is 110°C, the mixing time is 80s, after uniform mixing, discharge the rubber, recover and cool, to obtain the low temperature resistant and low rolling resistance tire sidewall rubber composition.

[0036] Example 4 The low temperature resistant and low rolling resistance tire sidewall rubber composition of the present example comprises the following raw materials in parts by weight: natural rubber 60 parts, segment modified butadiene rubber 40 parts, carbon black N660 40 parts, pre-modified negative expansion filler zirconium tungstate (ZrW2O8) 8 parts, modified montmorillonite 4 parts, softener octyl tackifying resin 2.0 parts, active agent including zinc oxide 3 parts and stearic acid 1.0 part, vulcanizing agent insoluble sulfur 2.0 parts, accelerator CZ 1.0 part, antioxidant including antioxidant 6PPD 3.5 parts, antioxidant RD 1.0 part and bimodal wax 2.0 parts.

[0037] The preparation method of the low temperature resistant and low rolling resistance tire sidewall rubber composition of the present example comprises the following steps: Pre-modification treatment of the negative expansion filler: take the negative expansion filler zirconium tungstate, silane coupling agent bis(triethoxysilylpropyl) disulfide and ethanol according to the mass ratio of 100:4:600; mix the silane coupling agent bis(triethoxysilylpropyl) disulfide and ethanol by stirring for 20 min; after dissolving, add the zirconium tungstate with an average particle size of 0.5 μm, heat at 70°C for 50 min for reaction, and after cooling, filter with deionized water to obtain the pre-modified negative expansion filler zirconium tungstate; First stage mixing: add the natural rubber, segment modified butadiene rubber, pre-modified negative expansion filler zirconium tungstate, carbon black, modified montmorillonite, softener octyl tackifying resin, zinc oxide, stearic acid, antioxidant 6PPD, antioxidant RD and bimodal wax to the closed mixer according to the weight ratio for stepwise temperature mixing, the mixing steps are: press the weight for 25 s, then lift the weight, press the weight again for 30 s or heat to 135°C, then lift the weight, press the weight again to 155°C for 100 s mixing and discharging, to obtain the masterbatch; Second stage mixing: add the masterbatch, insoluble sulfur and accelerator CZ to the closed mixer for low temperature mixing, the mixing temperature is 110°C, the mixing time is 80s, after uniform mixing, discharge the rubber, recover and cool, to obtain the low temperature resistant and low rolling resistance tire sidewall rubber composition.

[0038] Example 5 The low-temperature cold cracking and low rolling resistance tire sidewall rubber composition of the embodiment comprises the following raw materials in parts by weight: natural rubber 60 parts, segment modified butadiene rubber 40 parts, carbon black N660 40 parts, pre-modified negative expansion filler zirconium tungstate (ZrW2O8) 8 parts, modified montmorillonite 8 parts, softener octyl tackifying resin 2.0 parts, active agent including zinc oxide 3 parts and stearic acid 1.0 part, vulcanizing agent insoluble sulfur 2.0 parts, accelerator CZ 1.0 part, antioxidant including antioxidant 6PPD 3.5 parts, antioxidant RD 1.0 part and bimodal wax 2.0 parts.

[0039] The preparation method of the low-temperature cold cracking and low rolling resistance tire sidewall rubber composition of the embodiment comprises the following steps: The surface of the negative expansion filler is pre-modified: the negative expansion filler zirconium tungstate, the silane coupling agent bis(triethoxysilylpropyl) disulfide and ethanol are weighed according to the mass ratio of 100:4:600; the silane coupling agent bis(triethoxysilylpropyl) disulfide and ethanol are stirred and mixed, the stirring time is 20 min; after dissolution, the zirconium tungstate with an average particle size of 0.5 μm is added, heated at 70°C for 50 min for reaction, and after cooling, deionized water is used for filtration to obtain the pre-modified negative expansion filler zirconium tungstate; First stage mixing: according to the weight ratio, the natural rubber, the segment modified butadiene rubber, the pre-modified negative expansion filler zirconium tungstate, the carbon black, the modified montmorillonite, the softener octyl tackifying resin, the zinc oxide, the stearic acid, the antioxidant 6PPD, the antioxidant RD and the bimodal wax are added to the closed rubber mixing machine for step-by-step temperature increasing mixing, the mixing steps are that after pressing the weight for 25 s, the weight is lifted, then pressing the weight for 30 s or increasing the temperature to 135°C, lifting the weight, then pressing the weight to 155°C for 100 s of mixing and rubber removal, to obtain the masterbatch; Second stage mixing: the masterbatch, the insoluble sulfur and the accelerator CZ are added to the closed rubber mixing machine for low-temperature mixing, the mixing temperature is 110°C, the mixing time is 80 s, after uniform mixing, the rubber is removed, recovered and cooled, to obtain the low-temperature cold cracking and low rolling resistance tire sidewall rubber composition.

[0040] Example 6 The low-temperature cold cracking and low rolling resistance tire sidewall rubber composition of the embodiment comprises the following raw materials in parts by weight: natural rubber 50 parts, segment modified butadiene rubber 50 parts, carbon black N660 40 parts, pre-modified negative expansion filler zirconium tungstate (ZrW2O8) 8 parts, modified montmorillonite 4 parts, softener octyl tackifying resin 2.0 parts, active agent including zinc oxide 3 parts and stearic acid 1.0 part, vulcanizing agent insoluble sulfur 2.0 parts, accelerator CZ 1.0 part, antioxidant including antioxidant 6PPD 3.5 parts, antioxidant RD 1.0 part and bimodal wax 2.0 parts.

[0041] The preparation method of the low-temperature cold cracking and low rolling resistance tire sidewall rubber composition of the embodiment comprises the following steps: Surface pre-modification treatment was performed on the negative expansion filler: the negative expansion filler zirconium tungstate, silane coupling agent bis(triethoxysilylpropyl) disulfide and ethanol were weighed according to the mass ratio of 100:4:600; the silane coupling agent bis(triethoxysilylpropyl) disulfide was mixed with ethanol by stirring for 20 min; after dissolution, the zirconium tungstate with an average particle size of 0.5 μm was added, and the reaction was carried out at 70°C for 50 min, and then cooled to obtain the pre-modified negative expansion filler zirconium tungstate by filtering with deionized water; First-stage mixing: according to the weight ratio, natural rubber, chain segment modified butadiene rubber, pre-modified negative expansion filler zirconium tungstate, carbon black, modified montmorillonite, softener octyl tackifying resin, zinc oxide, stearic acid, antioxidant 6PPD, antioxidant RD and bimodal wax were added to a closed rubber mixing machine for stepwise temperature increasing mixing, and the mixing steps were as follows: after pressing the weight for 25 s, the weight was lifted, and then the weight was pressed for 30 s or the temperature was increased to 135°C and the weight was lifted, and then the weight was pressed to 155°C and mixed for 100 s to discharge the rubber, to obtain a masterbatch; Second-stage mixing: the masterbatch, insoluble sulfur and accelerator CZ were added to the closed rubber mixing machine for low-temperature mixing, the mixing temperature was 110°C, the mixing time was 80 s, and after uniform mixing, the rubber was discharged, recovered and cooled to obtain the low-temperature cold cracking resistant and low rolling resistance tire sidewall rubber composition.

[0042] Comparative Example 1 The comparative example was a traditional low rolling resistance tire sidewall formula for new energy passenger vehicles, which included the following raw materials in parts by weight: natural rubber 60 parts, high cis-butadiene rubber 40 parts, carbon black N660 40 parts, softener octyl tackifying resin 2.0 parts, active agent including zinc oxide 3 parts and stearic acid 1.0 part, vulcanizing agent insoluble sulfur 2.0 parts, accelerator CZ 1.0 part, antioxidant including antioxidant 6PPD 3.5 parts, antioxidant RD 1.0 part and bimodal wax 2.0 parts.

[0043] The preparation method of the tire sidewall rubber composition of the comparative example included the following steps: First-stage mixing: according to the weight ratio, natural rubber, high cis-butadiene rubber, carbon black, softener octyl tackifying resin, zinc oxide, stearic acid, antioxidant 6PPD, antioxidant RD and bimodal wax were added to a closed rubber mixing machine for stepwise temperature increasing mixing, and the mixing steps were as follows: after pressing the weight for 25 s, the weight was lifted, and then the weight was pressed for 30 s or the temperature was increased to 135°C and the weight was lifted, and then the weight was pressed to 155°C and mixed for 100 s to discharge the rubber, to obtain a masterbatch; Second-stage mixing: the masterbatch, insoluble sulfur and accelerator CZ were added to the closed rubber mixing machine for low-temperature mixing, the mixing temperature was 110°C, the mixing time was 80 s, and after uniform mixing, the rubber was discharged, recovered and cooled to obtain the low-temperature cold cracking resistant and low rolling resistance tire sidewall rubber composition.

[0044] Comparative Example 2 The comparative example is a conventional low rolling resistance tire side formula for new energy passenger vehicles, which comprises the following raw materials in parts by weight: natural rubber 60 parts, chain segment modified butadiene rubber 40 parts, carbon black N660 40 parts, softener octyl tackifying resin 2.0 parts, active agent including zinc oxide 3 parts and stearic acid 1.0 part, vulcanizing agent insoluble sulfur 2.0 parts, accelerator CZ 1.0 part, antioxidant including antioxidant 6PPD 3.5 parts, antioxidant RD 1.0 part and bimodal wax 2.0 parts.

[0045] The preparation method of the tire side rubber composition of the comparative example comprises the following steps: First stage mixing: according to the proportioning by weight, the natural rubber, chain segment modified butadiene rubber, carbon black, softener octyl tackifying resin, zinc oxide, stearic acid, antioxidant 6PPD, antioxidant RD and bimodal wax are added to a closed rubber mixing machine for step-by-step temperature increasing mixing, the mixing steps are that after pressing the weight for 25 s, the weight is lifted, then pressing the weight for 30 s or increasing the temperature to 135 ℃ and lifting the weight, then pressing the weight to 155 ℃ and mixing for 100 s to discharge the rubber, to obtain a masterbatch; Second stage mixing: the masterbatch, insoluble sulfur and accelerator CZ are added to the closed rubber mixing machine for low temperature mixing, the mixing temperature is 110 ℃, the mixing time is 80 s, and after uniform mixing, the rubber is discharged, recovered and cooled, to obtain a low temperature resistant cold cracking and low rolling resistance tire side rubber composition.

[0046] Comparative example 3 The comparative example is a conventional low rolling resistance tire side formula for new energy passenger vehicles, which comprises the following raw materials in parts by weight: natural rubber 60 parts, chain segment modified butadiene rubber 40 parts, carbon black N660 40 parts, modified montmorillonite 2 parts, softener octyl tackifying resin 2.0 parts, active agent including zinc oxide 3 parts and stearic acid 1.0 part, vulcanizing agent insoluble sulfur 2.0 parts, accelerator CZ 1.0 part, antioxidant including antioxidant 6PPD 3.5 parts, antioxidant RD 1.0 part and bimodal wax 2.0 parts.

[0047] The preparation method of the tire side rubber composition of the comparative example comprises the following steps: First stage mixing: according to the proportioning by weight, the natural rubber, chain segment modified butadiene rubber, carbon black, softener octyl tackifying resin, zinc oxide, stearic acid, antioxidant 6PPD, antioxidant RD and bimodal wax are added to a closed rubber mixing machine for step-by-step temperature increasing mixing, the mixing steps are that after pressing the weight for 25 s, the weight is lifted, then pressing the weight for 30 s or increasing the temperature to 135 ℃ and lifting the weight, then pressing the weight to 155 ℃ and mixing for 100 s to discharge the rubber, to obtain a masterbatch; Second stage mixing: add the masterbatch, insoluble sulfur and accelerator CZ to the internal mixer for low temperature mixing, the mixing temperature is 110°C, the mixing time is 80s, after uniform mixing, discharge the rubber, recover and cool, to obtain the low temperature crack resistant and low rolling resistance tire sidewall rubber composition.

[0048] Comparative Example 4 The comparative example is a traditional low rolling resistance tire sidewall formula for new energy passenger vehicles, including the following raw materials in parts by weight: natural rubber 60 parts, chain segment modified butadiene rubber 40 parts, carbon black N660 40 parts, unmodified negative expansion filler zirconium tungstate (ZrW2O8) 2 parts, modified montmorillonite 2 parts, softener octyl tackifying resin 2.0 parts, active agent including zinc oxide 3 parts and stearic acid 1.0 parts, vulcanizing agent insoluble sulfur 2.0 parts, accelerator CZ 1.0 parts, antioxidant including antioxidant 6PPD 3.5 parts, antioxidant RD 1.0 parts and bimodal wax 2.0 parts.

[0049] The preparation method of the tire sidewall rubber composition of the comparative example includes the following steps: First stage mixing: add natural rubber, chain segment modified butadiene rubber, modified montmorillonite, carbon black, unmodified negative expansion filler zirconium tungstate, softener octyl tackifying resin, zinc oxide, stearic acid, antioxidant 6PPD, antioxidant RD and bimodal wax to the internal mixer for stepwise temperature mixing, the mixing steps are: press the weight 25s, then lift the weight, then press the weight for 30s or lift the weight to 135°C, then press the weight to 155°C and mix for 100s to discharge the rubber, to obtain the masterbatch; Second stage mixing: add the masterbatch, insoluble sulfur and accelerator CZ to the internal mixer for low temperature mixing, the mixing temperature is 110°C, the mixing time is 80s, after uniform mixing, discharge the rubber, recover and cool, to obtain the low temperature crack resistant and low rolling resistance tire sidewall rubber composition.

[0050] Performance test The sidewall rubber compositions prepared in Examples 1-6 and Comparative Examples 1-4 were tested for performance, and the specific test results are shown in Table 2. Among them, the tensile strength was determined by a universal material testing machine according to the method specified in GB / T528-2009; the low temperature modulus and the normal temperature rolling resistance were tested by a dynamic mechanical analyzer (DMA) according to GB / T9870.1, generally characterized by E' at -20°C for low temperature modulus and tanδ at 60°C for normal temperature rolling resistance; the low temperature (-7°C) cold cracking performance was tested by a high and low temperature durometer flexing tester according to GB / T 13934, characterized by the flexing times and the crack propagation rate (linear fitting slope da / dN of the crack from 2mm to 5mm interval) reaching level 1.

[0051] Further, the sidewall rubber compositions prepared in Examples 1-6 and Comparative Examples 1-4 were respectively prepared into tires of the same specification and pattern (specification: 205 / 60R16 92V), and the rolling resistance performance of the tires was tested at low temperature environment (-7°C), and the test results are shown in Table 2. The specific method is as follows: first, the tire was mounted on the rim and inflated, then stored at -7°C for 4h, and the air pressure was supplemented to the test air pressure, and then the rolling resistance test was carried out at -7°C environment temperature.

[0052] Table 2 Performance test results of the rubber compositions prepared in Examples 1-6 and Comparative Examples 1-4 and rolling resistance performance test results of the tires

[0053] Note: The performance test data in Table 2 has no unit, which is a relative value, and is calculated based on the sample of Comparative Example 1. The larger the value, the better the corresponding performance.

[0054] Comparative Example 1 is a low rolling resistance sidewall formula special for new energy, and Comparative Example 2 uses a segment modified butadiene rubber to replace the high cis-butadiene rubber in Comparative Example 1. As can be seen from Table 2, the segment modified butadiene rubber introduced in Comparative Example 2 suppresses the low temperature crystallinity of butadiene rubber through isoprene segments, reduces the low temperature modulus by 50%, reduces the probability of crack generation, further improves the flexing performance of the rubber compound, and reduces the risk of low temperature cracking; Comparative Example 3 adds 2 parts of acid modified and quaternary ammonium salt modified montmorillonite to Comparative Example 2, and the crack propagation rate of the rubber compound is reduced by 24%. This is because the layered nano structure of montmorillonite forms a "brick wall" structure in the rubber, forcing the crack to detour. Moreover, due to the quaternary ammonium salt modification on the surface of montmorillonite, the compatibility with rubber is enhanced, and the tensile strength of the rubber compound is also improved; Comparative Example 4 adds 2 parts of unmodified negative expansion filler zirconium tungstate to Comparative Example 3, which reduces the shrinkage stress between the rubber matrix and the filler, and reduces the low temperature rolling resistance of the tire by 7%. However, due to the poor compatibility of the unmodified negative expansion filler zirconium tungstate with rubber, the normal temperature rolling resistance is increased.

[0055] Compared with Comparative Example 4, the surface modification of the negative expansion filler zirconium tungstate in Example 1 is tested, and the results show that the low-temperature rolling resistance is reduced by 18%, the normal-temperature rolling resistance is reduced by 3%, and the tensile strength is increased by 2%, proving the effectiveness of surface modification of the negative expansion filler in promoting the interaction between rubber and filler. In addition, the well-dispersed zirconium tungstate in the rubber matrix expands when flexed, buffers the stress, and the number of times of low-temperature flexing of the compound to level 1 is increased by 13%, and the crack propagation rate is reduced by 7%. In Examples 2 and 3, the amount of surface pre-modified negative expansion filler is further increased to 4 parts and 8 parts, and the results show that the low-temperature rolling resistance of the tire continues to decrease, and the low-temperature rolling resistance in Example 3 is reduced by 42% compared with Comparative Example 1. The tensile strength and flexing performance of the compound are gradually increased, and the prepared tire side rubber composition has excellent comprehensive performance.

[0056] In Examples 4 and 5, the amount of modified montmorillonite is increased to 4 parts and 8 parts based on Example 3, respectively. It can be seen that the crack propagation rate continues to decrease by 21% and 11%, respectively, further proving that the layered nanostructure of montmorillonite has a role in inhibiting crack propagation. However, the tensile strength and the number of times of low-temperature flexing to level 1 all show a trend of first increasing and then decreasing, which may be because when the amount of montmorillonite in the system is too high, agglomeration is easy to occur, and therefore the preferred amount of modified montmorillonite is 4 parts.

[0057] In Example 6, the ratio of natural rubber to chain segment modified butadiene rubber is adjusted based on Example 4, and 10 parts of chain segment modified butadiene rubber are added. As can be seen from Table 2, compared with Comparative Example 1, the low-temperature modulus of the compound is reduced by 58%, greatly reducing the probability of crack occurrence. The flexing performance of the compound is also greatly improved, the number of times of low-temperature flexing to level 1 is increased by 120%, the crack propagation rate is reduced by 75%, and the low-temperature cold crack resistance of the compound is improved. At the same time, the normal-temperature rolling resistance is reduced by 16%, and the low-temperature rolling resistance is reduced by 39%, indicating that the tire side rubber composition prepared in Example 6 has excellent rolling resistance performance, can reduce the rolling resistance of the tire in a wide temperature range, and is beneficial to improving the endurance mileage of new energy vehicles.

[0058] In summary, the low-temperature modulus of the compound is reduced by chain segment modified butadiene rubber, the risk of crack occurrence is reduced, and the crack propagation rate and low-temperature rolling resistance are inhibited by the use of negative expansion coefficient filler and modified montmorillonite, and a low-rolling-resistance tire side rubber composition with low-temperature cold crack resistance is prepared.

[0059] The above described embodiments are merely to describe the preferred embodiments of the present application, and are not intended to limit the scope of the present application. Without departing from the design spirit of the present application, various modifications, modifications, evolutions, improvements of the technical solutions of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.

Claims

1. A low-temperature cold cracking resistant and low rolling resistance tire sidewall rubber composition, characterized in that: The invention comprises the following raw materials in parts by weight: 30-70 parts of natural rubber, 30-70 parts of segment-modified butadiene rubber, 1-40 parts of pre-modified negative expansion filler and 1-15 parts of modified montmorillonite.

2. The low-temperature cold cracking resistant and low rolling resistance tire sidewall rubber composition according to claim 1, characterized in that: The segment-modified butadiene rubber is prepared by random copolymerization of isoprene and butadiene, and the mass fraction of isoprene in the segment-modified butadiene rubber is 8%-15%.

3. The low-temperature cold cracking resistant and low rolling resistance tire sidewall rubber composition according to claim 1, characterized in that: The pre-modified negative expansion filler is prepared by pre-modifying the negative expansion filler with a silane coupling agent.

4. The low-temperature cold cracking resistant and low rolling resistance tire sidewall rubber composition according to claim 3, characterized in that: The negative expansion filler is pre-modified with a silane coupling agent and specifically comprises the following steps: Weigh a negative expansion coefficient filler, a silane coupling agent, and ethanol in a mass ratio of 100:(1-5):(500-800); Stir and mix the silane coupling agent and ethanol for 5-40 minutes; Then add negative expansion coefficient filler and heat at 40-90°C for 20-80 minutes to react; After the reaction is completed, the mixture is cooled and filtered to obtain a pre-modified negative expansion filler.

5. The low-temperature cold cracking resistant and low rolling resistance tire sidewall rubber composition according to claim 3, characterized in that: The negative expansion filler is any one or more of LiAl(SiO3)2 / Li2O·Al2O3·4SiO2, β-LiAISiO4, Al2TiO5, 2MgO·2Al2O3·5SiO2, ZrW2O8, Zr2P2O9, Mg2P4O7, NaZr2(PO4)3, and BaZr4(PO4)6.

6. The low-temperature cold cracking resistant and low rolling resistance tire sidewall rubber composition according to claim 1, characterized in that: The modified montmorillonite is montmorillonite whose surface is treated by acidification modification and quaternary ammonium salt modification, and the D50 particle size of the modified montmorillonite is 2-5 μm.

7. The low-temperature cold cracking resistant and low rolling resistance tire sidewall rubber composition according to claim 1, characterized in that: The low-temperature cold cracking resistant and low rolling resistance tire sidewall rubber composition also includes the following raw materials in parts by weight: 30-80 parts of carbon black, 2-6 parts of softener, 3-6 parts of activator, 1-4 parts of vulcanizer, 1-3 parts of accelerator, and 3-8 parts of antioxidant.

8. The low-temperature cold cracking resistant and low rolling resistance tire sidewall rubber composition according to claim 7, characterized in that: The nitrogen adsorption value of carbon black ranges from 30 to 90 × 10 3 m 2 / kg.

9. A method for preparing the low-temperature cold cracking resistant and low rolling resistance tire sidewall rubber composition according to any one of claims 1 to 8, characterized in that: The following steps are involved: First stage mixing: natural rubber, segment-modified butadiene rubber, pre-modified negative expansion filler, carbon black, modified montmorillonite, softener, activator, antioxidant, etc. are added to a closed rubber mixer according to the weight ratio and mixed for the first time. After mixing evenly, the rubber is discharged to obtain a masterbatch; The second mixing stage: adding the masterbatch, vulcanizing agent and accelerator into a closed rubber mixer, mixing evenly and then discharging the rubber, recovering and cooling to obtain a low-temperature cold cracking resistant and low rolling resistance tire sidewall rubber composition.

10. The method for preparing the low-temperature cold cracking resistant and low rolling resistance tire sidewall rubber composition according to claim 9, characterized in that: In the first mixing step, the mixing temperature is 135-160° C. and the mixing time is 90-140 seconds; in the second mixing step, the mixing temperature is 90-120° C. and the mixing time is 70-120 seconds.

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