JP6000810B2 - Tire sidewall rubber member and pneumatic tire - Google Patents

Description

  The present invention relates to a sidewall rubber member that constitutes a sidewall portion of a pneumatic tire, and a pneumatic tire including the same.

  The demand for lower fuel consumption of automobiles is increasing, and it has been studied to make the rubber composition constituting the tire difficult to generate heat, that is, to improve the low heat generation performance. In order to improve the low heat generation performance, it is conceivable to increase the amount of the vulcanization accelerator. However, when the amount of the vulcanization accelerator is increased, the fatigue resistance, which is one of the characteristics required for the sidewall rubber member, is poor. Become. Moreover, there is a problem that the tear resistance is deteriorated due to the increased rigidity.

  By the way, it is disclosed in Patent Documents 1 to 6 that by adding a thiosulfuric acid compound having a specific structure to a rubber composition, the viscoelastic characteristics of the vulcanized rubber can be improved and the low heat generation performance can be improved. Has been. These documents disclose the use of a butadiene rubber having a high cis-1,4 bond content as a rubber component, but the use of a butadiene rubber containing syndiotactic-1,2-polybutadiene crystals is disclosed. There is no mention of fatigue resistance.

JP 2011-202137 A JP 2011-202138 A JP 2012-012457 A JP 2012-107232 A JP 2012-11681 A JP 2012-117008 A

  The present inventor has found that the fatigue resistance is improved by using a thiosulfuric acid compound having the above specific structure in combination with a butadiene rubber containing syndiotactic-1,2-polybutadiene crystals. That is, an object of the present invention is to provide a tire sidewall rubber member having improved fatigue resistance and a pneumatic tire including the tire sidewall rubber member.

  The tire sidewall rubber member according to the present invention is a rubber containing 20 to 80 parts by mass of natural rubber and / or isoprene rubber and 20 to 70 parts by mass of butadiene rubber containing syndiotactic-1,2-polybutadiene crystals. A rubber composition comprising 0.1 to 2.0 parts by mass of an organic thiosulfuric acid compound containing an amino group and 30 to 100 parts by mass of a filler composed of carbon black and / or silica with respect to 100 parts by mass of the component. It consists of The pneumatic tire according to the present invention includes the sidewall rubber member.

  According to the present invention, there is provided a tire sidewall rubber member having improved fatigue resistance performance by combining an organic thiosulfuric acid compound containing an amino group and a butadiene rubber containing a syndiotactic-1,2-polybutadiene crystal. can do.

  Hereinafter, matters related to the implementation of the present invention will be described in detail.

  The sidewall rubber member of the tire according to the present embodiment includes an amino group with respect to a rubber component containing a butadiene rubber (hereinafter also referred to as SPB-containing BR) containing syndiotactic-1,2-polybutadiene crystals. The rubber composition is composed of an organic thiosulfuric acid compound and a filler made of carbon black and / or silica.

  Specifically, the rubber component contains (A) 20-80% by mass of natural rubber and / or isoprene rubber and (B) 20-70% by mass of SPB-containing BR. That is, 20-80 mass parts (A) component and 20-70 mass parts (B) component are contained in 100 mass parts of rubber components.

  The natural rubber (NR) and isoprene rubber (IR) as the component (A) are not particularly limited, and those generally used in the rubber industry can be used. The component (A) may be natural rubber alone, isoprene rubber alone, or a blend of natural rubber and isoprene rubber.

  As the SPB-containing BR of the component (B), butadiene rubber which is a rubber resin composite in which syndiotactic-1,2-polybutadiene crystals (hereinafter referred to as SPB) are dispersed in a high cis polybutadiene rubber as a matrix is used. Preferably used. Such SPB-containing BR is generally used to improve the rigidity of the vulcanized rubber, but in this embodiment, the fatigue resistance can be improved by using it together with the organic thiosulfuric acid compound. .

  The method for producing the SPB-containing BR is not particularly limited. For example, first, 1,3-butadiene is cis 1,4-polymerized to obtain a high cis polybutadiene rubber (cis-1,4 bond content of 90% or more, more preferably 95% or more), and then the polymerization system is syndiotactic. It can be produced by introducing a tic-1,2 polymerization catalyst and 1,2-polymerizing the remaining 1,3-butadiene. As a result, a highly crystalline syndiotactic-1,2-polybutadiene is chemically bonded to the high cis polybutadiene rubber and dispersed in an SPB-containing BR. In addition, the SPB-containing BR can be produced by previously polymerizing the high cis polybutadiene rubber and SPB separately and blending the respective polymerization solutions, or alternatively, the SPB-containing BR can be solidified in the polymerization solution of the high cis polybutadiene rubber. It can also be produced by blending SPB in the form of a powder.

  The SPB content in the SPB-containing BR is not particularly limited, but is preferably 2.5% by mass or more, and more preferably 10% by mass or more. The upper limit of the content is not particularly limited, but is preferably 30% by mass or less, and more preferably 20% by weight or less. In addition, the content rate of SPB in SPB containing BR is calculated | required by measuring a boiling n-hexane insoluble matter.

  In addition to the components (A) and (B), the rubber component may be blended with butadiene rubber (hereinafter also referred to as a rare earth element catalyst BR) synthesized using a rare earth element catalyst (C). it can. By combining a rare earth element-based catalyst BR with the combination of the organic thiosulfuric acid compound and the SPB-containing BR, the fatigue resistance and the tear resistance can be improved.

As the rare earth element-based catalyst in the synthesis of the rare earth element-based catalyst BR, a neodymium-based catalyst is preferable, and examples thereof include neodymium alone, a compound of neodymium and other metals, and an organic compound. Specific examples include NdCl ₃ , Et-NdCl _{2 and the} like.

Butadiene rubber synthesized with a rare earth element-based catalyst generally has a microstructure with a high cis content and a low vinyl content. In the present embodiment, those having a cis-1,4 bond content of 95% or more are preferably used, and more preferably 97% or more. The vinyl group (1,2-vinyl bond) content of the rare earth element-based catalyst BR is preferably 1.0% or less. In the present specification, the cis-1,4 bond content and the vinyl group content are values calculated by the integration ratio of the ¹ HNMR spectrum.

  The content of each component in 100 parts by mass of the rubber component is such that when the component (C) is not included, the component (A) is 20 to 80 parts by mass, more preferably 30 to 70 parts by mass, and still more preferably 30 to 50 parts. It is a mass part, and (B) component is 20-70 mass parts, More preferably, it is 30-70 mass parts, More preferably, it is 40-60 mass parts. Moreover, when (C) component is included, (A) component is 20-70 mass parts, More preferably, it is 30-50 mass parts, (B) Component is 20-70 mass parts, More preferably, it is 20-50 mass parts. And (C) component is 10-60 mass parts, More preferably, it is 20-50 mass parts.

  The rubber component in the present embodiment is basically composed of a blend of the component (A) and the component (B) or a blend of the component (A), the component (B) and the component (C). You may mix | blend another rubber within the range which is not impaired. Other rubbers are not particularly limited. For example, styrene butadiene rubber (SBR), butadiene rubber (BR) other than components (B) and (C), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), etc. And diene rubber.

  Carbon black and / or silica is used as the filler to be blended in the present embodiment. Carbon black and / or silica can be blended in a total amount of 30 to 100 parts by mass, more preferably 30 to 60 parts by mass with respect to 100 parts by mass of the rubber component. Thus, it becomes advantageous to the improvement of the low heat-generating performance by making it the side wall rubber member of the low filling filler which decreased the compounding quantity of the filler.

  Although it does not specifically limit as said carbon black, Iodine adsorption amount (IA) is 30-100 mg / g and DBP (dibutyl phthalate) oil absorption amount uses 90-160 mL / 100g preferably. It is done. The iodine adsorption amount is a value measured according to JIS K6217, and the tear resistance can be improved by using a value of 30 mg / g or more. Moreover, the effect of improving the low heat generation performance can be enhanced by using an iodine adsorption amount of 100 mg / g or less. Further, the DBP oil absorption is measured according to JIS K6217, and is an index of the structure of carbon black. It is advantageous in maintaining fatigue resistance performance by using this value having a value of 90 mL / 100 g or more. It is.

As silica, for example, wet silica (hydrous silicic acid), dry silica (anhydrous silicic acid), surface-treated silica, and the like can be used. Preferably, wet silica is used. BET specific surface area of the silica (measured according to BET method according to JIS K6430) is not particularly limited, is preferably 90~220m ² / g, more preferably 150~220m ² / g.

  The filler may be carbon black alone, silica alone, or a combination of carbon black and silica. Preferably, carbon black alone or a combination of carbon black and silica is used, and the carbon black is preferably 10 to 60 parts by mass, more preferably 30 to 50 parts by mass with respect to 100 parts by mass of the rubber component. Yes, it is preferable to blend a larger amount than silica.

  When silica is blended, a silane coupling agent may be used in combination in order to improve the dispersibility. It is preferable that the compounding quantity of a silane coupling agent is 5-15 mass parts with respect to 100 mass parts of silica. The silane coupling agent is not particularly limited. For example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis Sulfide silane coupling agents such as (4-triethoxysilylbutyl) disulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) disulfide; 3-mercaptopropyltrimethoxysilane, 3- Mercaptosilane coupling agents such as mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyldimethylmethoxysilane, mercaptoethyltriethoxysilane; Examples thereof include protected mercaptosilane coupling agents such as tanoylthio-1-propyltriethoxysilane and 3-propionylthiopropyltrimethoxysilane. These can be used alone or in combination of two or more.

  The rubber composition according to the present embodiment is blended with an organic thiosulfuric acid compound containing an amino group. By blending such an organic thiosulfuric acid compound in combination with the SPB-containing BR, the affinity between the rubber component and the filler can be improved, and the fatigue resistance performance can be improved. Moreover, by using the organic thiosulfuric acid compound in combination with the SPB-containing BR and the rare earth element-based catalyst BR, it is possible to improve the tear resistance as well as the fatigue resistance.

  The amino group of the organic thiosulfuric acid compound is not limited to an unsubstituted primary amino group, but may be a secondary or tertiary amino group such as a mono- or dialkylamino group, or may be a cyclic amino group.

As the organic thiosulfuric acid compound, it is preferable to use a thiosulfuric acid compound represented by any of the following formulas (1) to (3) or a salt thereof, and one of these thiosulfuric acid compounds and salts thereof: Or 2 or more types can be used. Examples of the salt include alkali metal salts such as lithium salt, sodium salt, potassium salt and cesium salt; transition metal salts such as cobalt salt and copper salt; typical metal salts such as zinc salt; substitution of ammonium salt, trimethylammonium salt and the like Examples thereof include unsubstituted ammonium salts. In these, metal salts, such as lithium, sodium, potassium, cesium, cobalt, copper, or zinc, are preferable, and lithium salt, sodium salt, or potassium salt is especially preferable. Moreover, when using a thiosulfuric acid compound and its salt as a mixture thereof, such a mixture is, for example, a method of mixing a thiosulfuric acid compound and a salt thereof, or a method of metallizing a part of a thiosulfuric acid compound using a metal alkali. A product obtained by a method of neutralizing a part of a metal salt of a thiosulfuric acid compound using a protonic acid can be used.

In Formula (1), n shows the integer of 2-9.

In the formula (2), R represents an alkanediyl group having 3 to 12 carbon atoms, and n represents an integer of 2 to 5. n is more preferably 4 or 5.

  In the formula (3), R represents an alkanediyl group having 1 to 6 carbon atoms, and n represents an integer of 1 to 2.

  Examples of the compound represented by the formula (1) include S- (2-aminoethyl) thiosulfuric acid, S- (3-aminopropyl) thiosulfuric acid, S- (4-aminobutyl) thiosulfuric acid, S- (5-aminopentyl) thiosulfuric acid, S- (6-aminohexyl) thiosulfuric acid and the like.

  The compound represented by the formula (1) can be produced by any known method. For example, a salt of S- (3-aminopropyl) thiosulfuric acid is obtained by reacting 3-halopropylamine with sodium thiosulfate. Or a method of reacting potassium phthalimide with 1,3-dihalopropane, reacting the obtained compound with sodium thiosulfate, and then hydrolyzing the obtained compound. it can. S- (3-aminopropyl) thiosulfuric acid can be produced by neutralizing a salt of S- (3-aminopropyl) thiosulfuric acid with a protonic acid. The S- (3-aminopropyl) thiosulfuric acid and / or its salt thus produced can be isolated by operations such as concentration and crystallization, and the isolated S- (3-aminopropyl) The thiosulfuric acid and / or salt thereof usually contains about 0.1% to 5% of water.

  Examples of the compound represented by the above formula (2) include S-3- (piperidin-1-yl) propylthiosulfuric acid, S-4- (piperidin-1-yl) butylthiosulfuric acid, S-5- (piperidine- 1-yl) pentylthiosulfuric acid, S-6- (piperidin-1-yl) hexylthiosulfuric acid, S-7- (piperidin-1-yl) heptylthiosulfuric acid, S-8- (piperidin-1-yl) octylthiosulfuric acid, S -10- (piperidin-1-yl) decylthiosulfuric acid, S-12- (piperidin-1-yl) dodecylthiosulfuric acid, S-3- (pyrrolidin-1-yl) propylthiosulfuric acid, S-4- (pyrrolidin-1- Yl) butylthiosulfuric acid, S-5- (pyrrolidin-1-yl) pentylthiosulfuric acid, S-6- (pyrrolidin-1-yl) hexylthiosulfuric acid, S-7- (pyrrolidin-1- Le) heptylthio sulfate, S-8- (pyrrolidin-1-yl) octylthio sulfate, S-10- (pyrrolidin-1-yl) decylthio sulfuric acid, S-12-(pyrrolidin-1-yl) dodecylthio sulfate. Among them, S-3- (piperidin-1-yl) propylthiosulfate, S-3- (piperidin-1-yl) propylthiosulfate sodium, S-6- (piperidin-1-yl) hexylthiosulfate or S-6- ( Piperidin-1-yl) hexyl thiosulfate sodium is preferred, and S-3- (piperidin-1-yl) propyl thiosulfate sodium is particularly preferred.

The compound represented by the formula (2) can be produced, for example, by the method represented by the following formula.

In the formula, R and n are the same as in formula (2), and X ₁ and X ₂ each independently represent a chlorine atom, a bromine atom or an iodine atom. According to such a production method, a sodium salt is usually obtained, but a desired compound can be produced by cation exchange if necessary. The obtained compound usually contains about 0.1 to 5% by mass of water.

  Examples of the compound represented by the above formula (3) include S- (4-aminophenyl) methylthiosulfuric acid, S- [2- (4-aminophenyl) ethyl] thiosulfuric acid, S- [3- (4- Aminophenyl) propyl] thiosulfuric acid, S- [4- (4-aminophenyl) butyl] thiosulfuric acid, S- [5- (4-aminophenyl) pentyl] thiosulfuric acid, S- [6- (4-aminophenyl) ) Hexyl] thiosulfuric acid, S-2- (3-aminophenyl) methylthiosulfuric acid, S- [2- (3-aminophenyl) ethyl] thiosulfuric acid, S- [3- (3-aminophenyl) propyl] thiosulfuric acid S- [4- (3-aminophenyl) butyl] thiosulfuric acid, S- [5- (3-aminophenyl) pentyl] thiosulfuric acid, S- [6- (3-aminophenyl) hexyl] thiosulfuric acid, S -(2-Aminophenyl Methylthiosulfuric acid, S- [2- (2-aminophenyl) ethyl] thiosulfuric acid, S- [3- (2-aminophenyl) propyl] thiosulfuric acid, S- [4- (2-aminophenyl) butyl] thiosulfuric acid , S- [5- (2-aminophenyl) pentyl] thiosulfuric acid, S- [6- (2-aminophenyl) hexyl] thiosulfuric acid, S- (3,5-diaminophenyl) methylthiosulfuric acid, S- (3 , 4-Diaminophenyl) methylthiosulfuric acid, S- [2- (3,5-diaminophenyl) ethyl] thiosulfuric acid, S- [2- (3,4-diaminophenyl) ethyl] thiosulfuric acid and the like. Among them, S- [2- (4-aminophenyl) ethyl] thiosulfuric acid and sodium S- [2- (4-aminophenyl) ethyl] thiosulfate are preferable, and S- [2- (4-aminophenyl) ethyl] Sodium thiosulfate is particularly preferred.

The compound represented by the formula (3) can be produced, for example, by the method represented by the following formula.

  In the formula, R and n are the same as in the above formula (3), and X independently represents a chlorine atom, a bromine atom or an iodine atom. According to such a production method, a sodium salt is usually obtained, but a desired compound can be produced by cation exchange if necessary. The obtained compound usually contains about 0.1 to 5% by mass of water.

  The compounding amount of the organic thiosulfuric acid compound is preferably 0.1 to 2.0 parts by mass with respect to 100 parts by mass of the rubber component. By setting it as such a compounding quantity, the improvement effect of fatigue resistance can be heightened. The blending amount is more preferably 0.2 to 2.0 parts by mass.

  In addition to the above components, the rubber composition according to the present embodiment is used for tire sidewall rubber members such as zinc white, stearic acid, anti-aging agent, softener, wax, vulcanizing agent, vulcanization accelerator, etc. Various additives generally used in the rubber composition can be blended. Examples of the vulcanizing agent include sulfur components such as powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur. Although not particularly limited, the blending amount thereof is 100 parts by mass of the rubber component. It is preferable that it is 0.1-10 mass parts with respect to it, More preferably, it is 0.5-5 mass parts. Moreover, as a compounding quantity of a vulcanization accelerator, it is preferable that it is 0.1-7 mass parts with respect to 100 mass parts of said rubber components, More preferably, it is 0.5-5 mass parts.

  The rubber composition can be prepared by kneading according to a conventional method using a commonly used Banbury mixer, kneader, roll, or other mixer. For example, in the first mixing stage, the rubber component is added and mixed with the organic thiosulfuric acid compound and the filler together with other additives except the vulcanizing agent and the vulcanization accelerator, and then the resulting mixture is finally mixed. A rubber composition can be prepared by adding and mixing a vulcanizing agent and a vulcanization accelerator in stages.

  The sidewall rubber member according to this embodiment is produced using the rubber composition, and the rubber composition is extruded into a predetermined cross-sectional shape corresponding to the sidewall portion, or alternatively, A sidewall rubber member according to the embodiment is obtained by winding a ribbon-shaped rubber strip made of a rubber composition in a spiral shape on a drum to form a cross-sectional shape corresponding to the sidewall portion. Such a side wall rubber member is assembled into a tire shape according to a conventional method together with other tire members constituting the tire such as an inner liner, a carcass, a belt, a bead core, a bead filler, and a tread rubber to obtain a raw tire. And the pneumatic tire provided with the side wall rubber member is obtained by carrying out the vulcanization molding of the obtained green tire at 140-180 degreeC, for example according to a conventional method.

  The type of pneumatic tire according to the present embodiment is not particularly limited, and examples thereof include various types of tires such as radial tires for passenger cars and heavy duty tires used for large vehicles such as trucks and buses.

  Examples of the present invention will be described below, but the present invention is not limited to these examples. In addition, the manufacturing method of the thiosulfuric acid compound used by the following example and the comparative example is as follows.

[Thiosulfuric acid compound: production of S- (3-aminopropyl) thiosulfuric acid]
The reaction vessel was purged with nitrogen, and 25 g (0.11 mol) of 3-bromopropylamine bromate, 28.42 g (0.11 mol) of sodium thiosulfate pentahydrate, 125 ml of methanol and 125 ml of water were placed in the reaction vessel. The resulting mixture was refluxed at 70 ° C. for 4.5 hours.

  The reaction mixture was allowed to cool and methanol was removed under reduced pressure. To the reaction mixture from which methanol had been removed, 4.56 g of sodium hydroxide was added and stirred at room temperature for 30 minutes. Thereafter, sodium bromide as a by-product was removed by hot filtration. The filtrate was concentrated under reduced pressure until crystals precipitated, and then allowed to stand. The crystals were collected by filtration and washed with ethanol and hexane, and the crystals obtained were dried under vacuum to obtain sodium salt of S- (3-aminopropyl) thiosulfuric acid.

  The reaction vessel was purged with nitrogen, and 26.0 g of S- (3-aminopropyl) thiosulfuric acid sodium salt and 45 ml of water were charged into the reaction vessel, and 5 mol / l hydrochloric acid was added to adjust the pH of the solution to 5-6. It was adjusted. It concentrated until the crystal | crystallization precipitated under reduced pressure, Then, it stood still. The crystals were collected by filtration and washed with ethanol, and the crystals obtained were vacuum dried to obtain S- (3-aminopropyl) thiosulfuric acid.

[Preparation of rubber composition for sidewall]
Using a Banbury mixer, according to the composition (parts by mass) shown in Table 1 below, first, in the first mixing stage, components other than sulfur and vulcanization accelerator are added and mixed, and then the resulting mixture is finally mixed. In the stage, sulfur and a vulcanization accelerator were added and mixed to prepare a rubber composition for a sidewall. The details of each component in Table 1 are as follows.

・ NR: Natural rubber (SIR-20)
Co-BR: “BR150B” manufactured by Ube Industries, Ltd. (butadiene rubber polymerized with a cobalt-based catalyst)
SPB-containing BR: “VCR617” manufactured by Ube Industries, Ltd. (cis-1,4-bond content of high-cis polybutadiene rubber as a matrix = 98%, SPB content in SPB-containing BR = 17.0% by mass )
Nd-BR: “Buna CB22” manufactured by LANXESS (butadiene rubber polymerized with a neodymium catalyst, cis-1,4 bond content = 97%, vinyl group content = 0.4%)
Carbon black: FEF carbon black (N-550), “Seast SO” manufactured by Tokai Carbon Co., Ltd. (iodine adsorption = 35-53 mg / g, DBP oil absorption = 106-123 mL / 100 g)
Silica: “Nip Seal AQ” manufactured by Tosoh Silica Co., Ltd. (BET specific surface area = 205 m ² / g)
Silane coupling agent: “Si75” manufactured by Degussa
Paraffin oil: “Process P200” manufactured by JOMO Sun Energy Co., Ltd.
・ Stearic acid: “Lunac S-20” manufactured by Kao Corporation
・ Zinc flower: “Zinc flower 1” manufactured by Mitsui Mining & Smelting Co., Ltd.
Anti-aging agent: “Antigen 6C” manufactured by Sumitomo Chemical Co., Ltd.
・ Wax: Nippon Seiwa Co., Ltd. “OZOACE0355”
・ Vulcanization accelerator: “Soxinol CZ” manufactured by Sumitomo Chemical Co., Ltd.
・ Sulfur: “Sulfur Powder” manufactured by Tsurumi Chemical Co., Ltd.

  About each rubber composition, the tear strength and the bending fatigue resistance were measured and evaluated using the test piece of the predetermined shape vulcanized at 150 degreeC for 30 minutes. Each measurement / evaluation method is as follows. The results are shown in Table 1.

Bending fatigue resistance performance: A bending crack generation test based on JIS K6260 (demach bending cracking test) was performed to determine the number of bendings required to reach the third grade, and an index with the value of Comparative Example 1 as 100 was shown. The larger the index, the greater the number of flexing times and the better the bending fatigue resistance.

Tear strength: Tear strength was measured according to JIS K6252 (Crescent test piece), and the value was shown as an index with the value of Comparative Example 1 being 100. The larger the index, the higher the tear strength and the better the tear resistance.

  The results are as shown in Table 1. Compared to Comparative Example 1 as a control, Comparative Example 2 in which butadiene rubber was simply replaced with SPB-containing BR significantly deteriorated fatigue resistance. In Comparative Example 3, although SPB-containing BR and Nd-BR were used in combination, the fatigue resistance performance and tear resistance performance were inferior because no thiosulfate compound was blended.

  On the other hand, in Comparative Example 4, although the thiosulfuric acid compound was blended, the SPB-containing BR was not blended, so that the effect of improving fatigue resistance and tear resistance was not obtained. In Comparative Example 5, the compounding amount of the thiosulfate compound was too large, and the fatigue resistance and tear resistance were deteriorated.

  In contrast, in Examples 1 to 3 in which SPB-containing BR and a thiosulfuric acid compound were combined, fatigue resistance and tear resistance were improved compared to Comparative Example 1, and compared with Comparative Example 2 and Comparative Example 4. As can be seen from the results, an advantageous effect completely different from the case of adding the SPB-containing BR and the thiosulfate compound alone was obtained. In Example 4, a better effect than that of Example 1 was obtained by increasing the blending amount of the thiosulfate compound. In Example 5, the tear resistance performance was significantly improved. As apparent from the comparison with Comparative Example 3, Example 6 is a combination system of SPB-containing BR and Nd-BR. By further blending a thiosulfate compound, fatigue resistance and tear resistance are greatly improved. Was.

Claims (3)

  An amino group is added to 100 parts by mass of a rubber component containing 20 to 80 parts by mass of natural rubber and / or isoprene rubber and 20 to 70 parts by mass of butadiene rubber containing syndiotactic-1,2-polybutadiene crystals. A tire sidewall rubber member comprising a rubber composition in which 0.1 to 2.0 parts by mass of an organic thiosulfuric acid compound is contained and 30 to 100 parts by mass of a filler composed of carbon black and / or silica. The tire sidewall according to claim 1, wherein the organic thiosulfuric acid compound is at least one of a thiosulfuric acid compound represented by any one of the following formulas (1) to (3) and a salt thereof. Rubber member.

(In Formula (1), n shows the integer of 2-9.)

(In the formula (2), R represents an alkanediyl group having 3 to 12 carbon atoms, and n represents an integer of 2 to 5)

(In Formula (3), R shows a C1-C6 alkanediyl group, n shows an integer of 1-2.) A pneumatic tire having a sidewall rubber member according to claim 1 or 2.