JP2010090293A - Rubber composition and pneumatic tire using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire excellent in run flat performance by using a rubber composition having high rigidity and a high melting point in a reinforcing part for a sidewall of a run flat tire. <P>SOLUTION: The rubber composition including a diene rubber and a crystalline resin is provided; wherein (A) the crystalline resin (a) is a syndiotactic polystyrene having 50 wt.% or more of a syndiotactic crystal, (B) assuming that a dispersion obtained by dispersing the crystalline resin (a) in the diene rubber (b1) is a dispersion (c), the crystalline resin (a) is dispersed in the dispersion (c) in amounts of 1-50 wt.%, (C) assuming that a mixture including the dispersion (c) and the diene rubber (b2) is a mixture (d), 5-60 wt.% of the dispersion (c) is included in the mixture (d), and 95-40 wt.% of the diene rubber (b2) is included in the mixture (d). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a rubber composition and a pneumatic tire using the same.

  In recent years, in the automobile industry, from the viewpoint of resource saving and energy saving, it has been studied to further reduce the driving fuel consumption of a passenger car. In order to reduce driving fuel consumption, it is effective to reduce the weight of the automobile and decrease the running resistance. For this purpose, it is effective to reduce the rolling resistance as well as the weight of the tire itself. Therefore, various methods for reducing the weight of the tire and reducing the rolling resistance have been tried.

  In order to reduce tire weight and rolling resistance, it may be possible to reduce carbon black and silica, which are reinforcing agents, but since the hardness of the rubber decreases, the tire stiffness and steering stability deteriorate. End up. Moreover, since the strength of rubber is reduced by the above-described method, wear resistance and cut resistance are also reduced.

  In order to compensate for these drawbacks, an improved polybutadiene rubber in which syndiotactic-1,2-polybutadiene (SPBD) is dispersed in a matrix of high cis-1,4-polybutadiene (hereinafter “high cis polybutadiene”) has been proposed. ing. Since this polybutadiene rubber has a structure in which SPBD is dispersed in a matrix of high cis polybutadiene, the polybutadiene rubber has a characteristic that its hardness is higher than that of conventional rubber such as high cis polybutadiene plain rubber. Therefore, it is possible to compensate for a decrease in hardness due to a reduction in the amount of reinforcing agent.

  On the other hand, even if a run-flat tire having a high-strength side reinforcing layer (reinforcing layer) disposed inside the sidewall portion has been put into practical use and the air pressure has been lost due to puncture (zero internal pressure), the tire Even when subjected to repeated bending, the rubber is less damaged and can travel safely to some extent. As a result, there is no need to always have spare tires, and weight reduction in the entire vehicle can be expected. The high-strength side reinforcing layer disposed inside the sidewall portion of the run-flat tire is desired to have high rigidity and low heat generation, and the improved polybutadiene rubber in which the SPBD is dispersed is suitable. .

  Since the side reinforcing layer of the run flat tire is repeatedly deformed during run flat running, the temperature rises to around 200 ° C. by generating heat and storing heat. For this reason, the thermal deterioration of the rubber proceeds, and the breaking strength of the side reinforcing layer decreases. The melting point of SPBD is about 180 to 215 ° C., but since the SPBD softens from about 160 ° C. before reaching the melting point, the hardness gradually decreases and the deflection increases. The heat generation is further increased, and when the melting point is exceeded, the hardness is remarkably lowered and eventually leads to tire damage. Therefore, a resin that is difficult to soften even at a high temperature of 160 ° C. or higher, that is, a resin having a higher melting point than SPBD is desired.

  Although there is literature which proposes mixing of SPBD slurry and rubber solution, there is no description about syndiotactic polystyrene crystals (SPS).

  Although there is a literature that suggests a mixture of rubber elastic body and SPS, the purpose is to improve the impact resistance of SPS, and SPS is 200 to 5000 parts by weight with respect to 100 parts by weight of rubber component. However, the examples are not intended to disperse SPS in rubber only by dry blending.

  Although there is a literature in which a mixture of SPS, a rubber elastic body, and an inorganic filler is proposed, SPS which has been dried and solidified is used, and is extruded and mixed after the rubber elastic body and dry blend. Although the use of a diene rubber is also described, since SPS dried and solidified has a high melting point, it is very difficult to finely disperse it in the diene rubber by dry blending.

  An object of the present invention is to provide a tire having excellent run-flat performance by being used for a sidewall reinforcing portion of a run-flat tire because of its high rigidity and high melting point.

The present invention is a rubber composition comprising a diene rubber and a crystalline resin,
(A) The crystalline resin (a) is syndiotactic polystyrene having 50% by weight or more of syndiotactic crystals,
(B) When the dispersion of the crystalline resin (a) in the diene rubber (b1) is used as the dispersion (c), the crystalline resin (a) is 1 to 50 weights in the dispersion (c). % Distributed,
(C) When the mixture (d) is composed of the dispersion (c) and the diene rubber (b2), the dispersion (c) is contained in the mixture (d) in an amount of 5 to 60% by weight, and the diene rubber This relates to a rubber composition containing 95 to 40% by weight of (b2) in the mixture (d).

The diene rubber (b1) and the diene rubber (b2) are each a diene rubber (diene rubber) containing at least one selected from the group (D) selected from styrene butadiene rubber, isoprene rubber, natural rubber, and butadiene rubber. The rubber (b1) and the diene rubber (b2) may be the same or different.

The dispersion (c) is:
(E) After mixing a slurry solution in which the crystalline resin (a) is dispersed in an organic solvent and (F) a cement solution in which the diene rubber (b1) is dissolved in the organic solvent,
Those obtained by removing the solvent are preferred.

The present invention also relates to a tire in which the rubber composition is used in (G) a sidewall reinforcing part and / or (H) a bead apex.

  According to the present invention, since it has a high rigidity and a high melting point, it can be expected to provide a tire having excellent run flat performance when used in a sidewall reinforcing portion of a run flat tire.

(1) The rubber composition of the present invention is a rubber composition containing a diene rubber and a crystalline resin,
(A) The crystalline resin (a) is syndiotactic polystyrene having 50% by weight or more of syndiotactic polystyrene crystals,
(B) When the dispersion of the crystalline resin (a) in the diene rubber (b1) is used as the dispersion (c), the crystalline resin (a) is 1 to 50 weights in the dispersion (c). % Distributed,
(C) When the mixture (d) is composed of the dispersion (c) and the diene rubber (b2), the dispersion (c) is contained in the mixture (d) in an amount of 5 to 60% by weight, and the diene rubber (B2) is a rubber composition containing 95 to 40% by weight of the mixture (d) (claim 1 of the present application).

(1-1) (A) It demonstrates that the crystalline resin (a) is a syndiotactic polystyrene which has 50 weight% or more of syndiotactic polystyrene crystals.

  The crystalline resin (a) contained in the rubber composition of the present invention is a resin having crystallinity. The ratio of crystal parts in the resin is called crystallinity.

  Examples of the crystalline resin include syndiotactic polystyrene, polyphenylene sulfide, polyamide, fluororesin, and polyether nitrile. Syndiotactic polystyrene is more preferable from the viewpoint of easy polymerization and excellent adhesion to diene rubber.

に示されるように規則的に交互に配置する構造を取り、普通のポリスチレンとは異なる性質を示す素材である。 Polystyrene ([—CH ₂ —CH (C ₆ H ₅ ) —] _n ) is a polymer of styrene (CH ₂ ═CHC ₆ H ₅ ). The syndiotactic polystyrene crystal (SPS) of the present invention is a polystyrene having a three-dimensional structure different from that of ordinary polystyrene.

As shown in Fig. 1, the material has a structure in which the layers are regularly arranged alternately and exhibits a property different from that of ordinary polystyrene.

  Syndiotactic polystyrene crystal (SPS) is usually a crystallized polystyrene having a Tg (glass transition temperature) of 100 ° C. and a Tm (crystal melting point) of 270 ° C.

  The crystalline resin (a) contained in the rubber composition of the present invention contains a crystalline part and an amorphous part. The crystal part is a syndiotactic polystyrene crystal (that is, having a syndiotactic polystyrene structure), and the amorphous part is a non-syndiotactic polystyrene structure.

  The crystalline resin (a) contained in the rubber composition of the present invention is syndiotactic polystyrene having 50% by weight or more of syndiotactic polystyrene crystals (SPS) because of its high melting point, and syndiotactic polystyrene crystals. Syndiotactic polystyrene having (SPS) of 60% by weight or more, more preferably 80% by weight or more is preferable. Moreover, 100 weight% may be sufficient as a syndiotactic polystyrene crystal (SPS) in crystalline resin (a).

  In the rubber composition of the present invention, the crystalline resin (a) is syndiotactic polystyrene having 50% by weight or more of syndiotactic polystyrene crystals. The content of the syndiotactic polystyrene crystal can be measured from the heat of fusion of the crystalline resin.

やアイソタクチックポリスチレン（通常、Ｔｇは１００℃、Ｔｍは２４０℃である）： Examples of polystyrene other than syndiotactic polystyrene crystals (SPS) include atactic polystyrene (usually Tg is 100 ° C. and Tm is not present):

Or isotactic polystyrene (Tg is usually 100 ° C. and Tm is 240 ° C.):

などがある。

and so on.

  The crystal melting point of the syndiotactic polystyrene crystal (SPS) contained in the rubber composition of the present invention can be measured at an increase rate of 10 ° C./min using an automatic differential scanning calorimeter DSC-60A manufactured by Shimadzu Corporation. it can.

  It is preferable that the melting point of the syndiotactic polystyrene crystal (SPS) is 220 ° C. or higher.

(1-2) (B) When the dispersion (c) is obtained by dispersing the crystalline resin (a) in the diene rubber (b1), the crystalline resin (a) is the dispersion (c). The dispersion of 1 to 50% by weight will be described.

  The dispersion (c) is obtained by dispersing the crystalline resin (a) in the diene rubber (b1).

  Since the crystalline resin (a) contained in the rubber composition of the present invention has crystallinity, when the solvent used for the polymerization is dried, the resins are aggregated and crystals are enlarged. The crystalline resin (a) contained in the rubber composition of the present invention is obtained by being polymerized in a rubber solution and taken out in a state dispersed in fine particles in a rubber (diene rubber (b1)). That is, the main structure of the dispersion (c) contained in the rubber composition of the present invention is rubber (diene rubber (b1)).

  The content of the crystalline resin (a) contained in the rubber composition of the present invention is such that the dispersion (c) is obtained by dispersing the crystalline resin (a) in the diene rubber (b1). 1 to 50% by weight of the conductive resin (a) is dispersed in the dispersion (c).

  If the content of the crystalline resin (a) in the dispersion (c) is less than 1% by weight, a sufficient rubber reinforcing effect cannot be obtained, and if it exceeds 50% by weight, the processability of the rubber deteriorates and molding is performed. Becomes difficult. The crystalline resin (a) is preferably dispersed in the dispersion (c) by 10 to 40% by weight, more preferably 20 to 40% by weight.

The diene rubber (b1) and diene rubber (b2) used in the rubber composition of the present invention each contain at least one selected from the group selected from (D) styrene butadiene rubber, isoprene rubber, natural rubber, and butadiene rubber. The diene rubber is preferably a diene rubber (diene rubber (b1) and diene rubber (b2) may be the same or different).

  Examples of the diene rubber (b1) and diene rubber (b2) in which the crystalline resin (a) is dispersed include natural rubber (NR), butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), isoprene rubber ( IR), acrylonitrile-butadiene copolymer rubber (NBR), chloroprene rubber (CR), styrene-isoprene-butadiene copolymer rubber (SIBR), styrene-isoprene copolymer rubber, isoprene-butadiene copolymer rubber, etc. SBR, IR, NR, and BR are preferable because of their excellent properties and low exothermic properties. Moreover, SBR is more preferable because of its familiarity with syndiotactic polystyrene crystals.

  For example, BR (2) used in the present embodiment described below will be described.

  BR (2) is a butadiene rubber containing syndiotactic polystyrene crystals (SPS). The SPS content of 12% by weight indicates that 12% by weight of SPS is present in the dispersion (c) containing the butadiene rubber (b1). SC 86% by weight indicates that the syndiotactic polystyrene crystal part is 86% by weight in the crystalline resin (a). The mp (melting point) of the syndiotactic polystyrene crystal is 256 ° C.

(1-3) When the mixture (d) is composed of the dispersion (c) and the diene rubber (b2), the dispersion (c) is contained in the mixture (d) in an amount of 5 to 60% by weight. Then, it will be described that the diene rubber (b2) is contained in the mixture (d) by 95 to 40% by weight.

  The rubber composition of the present invention includes the mixture (d) composed of the dispersion (c) and the diene rubber (b2). In order to obtain a sufficient rubber reinforcing effect, the dispersion (c) Is contained in the mixture (d) in an amount of 5 to 60% by weight, and the diene rubber (b2) is contained in the mixture (d) in an amount of 95 to 40% by weight. The dispersion (c) is preferably contained in the mixture (d) in an amount of 10 to 50% by weight (that is, the diene rubber (b2) is contained in the mixture (d) in an amount of 4 to 47.5% by weight. The dispersion (c) is more preferably contained in the mixture (d) in an amount of 30 to 50% by weight (that is, the diene rubber (b2) is contained in the mixture (d) in an amount of 12 to 47.5% by weight. More preferably it is included).

(2) The dispersion (c) contained in the rubber composition of the present invention is:
(E) After mixing a slurry solution in which the crystalline resin (a) is dispersed in an organic solvent and (F) a cement solution in which the diene rubber (b1) is dissolved in the organic solvent,
Those obtained by removing the solvent are preferred (claim 3).

(2-1) (E) A slurry solution in which the crystalline resin (a) is dispersed in an organic solvent will be described.

  Styrene, which is a raw material for synthesizing the crystalline resin (a) (syndiotactic polystyrene crystal), dissolves in an organic solvent. However, as the polymerization of styrene proceeds, the syndiotactic polystyrene crystal is crystallized because it is crystalline. It partially crystallizes) and becomes difficult to dissolve in an organic solvent.

  In the present invention, syndiotactic polystyrene crystal microcrystals are precipitated in a transparent organic solvent, resulting in white turbidity and increased viscosity. In the present invention, this state is called a slurry solution.

  The organic solvent used for the styrene polymerization (crystalline resin (a)) of the slurry solution is not particularly limited. In the present invention, since styrene is polymerized, an organic solvent such as toluene, cyclohexane, or n-hexane is preferable.

(2-2) (F) A cement solution in which the diene rubber (b1) is dissolved in an organic solvent will be described.

  In the present invention, when the diene rubber (b1) is dissolved in an organic solvent, the viscosity becomes very high, and this state is called a cement solution.

  The dispersion (c) in which the crystalline resin (a) is dispersed in the diene rubber (b1) contained in the rubber composition of the present invention is polymerized in a solvent without drying and solidifying the crystalline resin. After the liquid-liquid combination of the slurry solution of the crystalline resin (a) as dispersed in the organic solvent and the cement solution of the diene rubber (b1) dissolved in the organic solvent, the solvent is removed by drying. can get.

  It does not specifically limit about the organic solvent which melt | dissolves the diene rubber (b1) of the said cement solution. In this invention, it may be the same as the organic solvent used for the styrene polymerization (crystalline resin (a)) of the said slurry-like solution, and may differ.

  In general, when the crystalline resin (a) is dried from the slurry after polymerization, the crystals are solidified by agglomeration of crystals, and a large agglomerate is formed. And it is impossible to melt and disperse the aggregate by rubber kneading. Therefore, in order to finely disperse the crystalline resin (a) in the rubber, a method of mixing the slurry solution (crystalline resin (a) solution) with the cement solution (diene rubber (b1) solution) is necessary. It is.

(3) For the rubber composition of the present invention, reinforcing agents, processing aids, vulcanizing agents and the like can be used.

  In the rubber composition of the present invention, as the diene rubber (b2) component, for example, natural rubber (NR), epoxidized natural rubber (ENR), butadiene rubber (BR), styrene butadiene rubber (SBR), isoprene rubber ( IR), butyl rubber (IIR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), styrene isoprene butadiene rubber (SIBR), styrene isoprene rubber, and isoprene butadiene rubber may be used, and these may be used alone. Two or more kinds may be used in combination.

  The rubber composition of the present invention preferably further contains carbon black.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 30 m ² / g or more, and more preferably 35 m ² / g or more, from the viewpoint of obtaining sufficient reinforcement and durability. Also, N ₂ SA of carbon black is from the viewpoint of excellent low heat build-is preferably not more than 100 m ² / g, more preferably not more than ^{80m 2 / g, 60m 2 /} g or less is more preferred.

  The dibutyl phthalate oil absorption (DBP) of carbon black is preferably 50 ml / 100 g or more, more preferably 80 ml / 100 g or more, from the viewpoint that sufficient reinforcing properties can be obtained. The DBP of carbon black is preferably 300 ml / 100 g or less, more preferably 200 ml / 100 g or less, from the viewpoint of excellent fatigue resistance such as elongation at break.

  The content of carbon black is preferably 10 parts by weight or more, more preferably 20 parts by weight or more, and still more preferably 30 parts by weight or more with respect to 100 parts by weight of the diene rubber component from the viewpoint of obtaining sufficient rubber strength. Further, the content of carbon black is preferably 100 parts by weight or less, more preferably 70 parts by weight or less, and even more preferably 60 parts by weight or less from the viewpoint that the viscosity at the time of kneading is appropriately maintained and the processability is excellent.

  Moreover, it is preferable that the rubber composition of the present invention further contains sulfur or a sulfur compound.

  As sulfur or a sulfur compound, insoluble sulfur is preferable because it suppresses surface precipitation of sulfur.

  The average molecular weight of insoluble sulfur is preferably 10,000 or more, more preferably 100,000 or more from the viewpoint that decomposition does not easily occur even at low temperatures and surface precipitation is difficult. The average molecular weight of insoluble sulfur is preferably 500,000 or less, more preferably 300,000 or less, from the viewpoint of excellent dispersibility in rubber.

  The content of sulfur or sulfur compound is preferably 3 parts by weight or more, more preferably 4 parts by weight or more with respect to 100 parts by weight of the diene rubber component, from the viewpoint that sufficient hardness can be obtained, it is difficult to bend and break. Further, the content of sulfur or sulfur compound is preferably 20 parts by weight or less, and more preferably 15 parts by weight or less from the viewpoint that blooming is difficult and sufficient workability is obtained.

  Further, the rubber composition of the present invention preferably further contains a vulcanization accelerator.

  Examples of the vulcanization accelerator include N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N, N′-dicyclohexyl-2- Examples include benzothiazolylsulfenamide (DZ), mercaptobenzothiazole (MBT), dibenzothiazolyl disulfide (MBTS), and diphenylguanidine (DPG). TBBS, CBS, DZ, etc., because they are difficult, have excellent vulcanization characteristics, have excellent low heat buildup against deformation due to external forces, and have a great effect on improving the durability of run-flat tires. Of these, sulfenamide vulcanization accelerators are preferred.

  In addition to the rubber component, carbon black, sulfur or sulfur compound and vulcanization accelerator, the rubber composition of the present invention includes compounding agents conventionally used in the rubber industry, such as stearic acid, zinc oxide, various anti-aging agents. An agent or the like can be appropriately blended as necessary.

  The rubber composition of the present invention is produced by a general method. That is, the rubber composition of the present invention can be produced by kneading the rubber component, filler, and other compounding agents as necessary with a Banbury mixer, kneader, open roll, and then vulcanizing. .

(4) The present invention relates to a tire in which the rubber composition is used for (G) a side wall reinforcing portion and / or (H) a bead apex (claim 4 of the present application).

  The rubber composition of the present invention is preferably used as a sidewall reinforcing part or bead apex of a run-flat tire because it has a high rigidity and a high melting point and is lighter than carbon black.

  FIG. 1 is a right half of a cross-sectional view of a run-flat tire in which the rubber composition of the present invention is used for a sidewall reinforcing part or a bead apex.

  In FIG. 1, a side wall reinforcing portion 2 and a bead apex 3 are shown in the run flat tire 1.

  As shown in FIG. 1, the sidewall reinforcing portion 2 is disposed on the sidewall portion 6 from the bead portion 5 to the shoulder portion in contact with the inside of the carcass ply 4 of the run-flat tire 1, and the thickness gradually decreases in both end directions. To be arranged in a crescent shape. Further, the sidewall reinforcing portion 2 is arranged between the bead portion 5 and the tread portion 7 between the carcass ply 4 main body portion and the folded portion, or arranged in two layers between the plurality of carcass plies 4 or the reinforcing plies. Is done. FIG. 1 shows a belt layer 8 and a bead core 9 in the run flat tire 1.

  The side wall reinforcing part is a lining strip layer disposed between the side wall part and the carcass part of the run flat tire, and the air pressure is lost due to the presence of the side wall part reinforcing rubber in the run flat tire. Even in a broken state, the vehicle can be supported and excellent run-flat durability can be imparted.

  The bead apex is a tire portion located in a bead portion of a tire and surrounded by a carcass and a bead wire. Similarly, the bead apex can impart excellent run-flat durability.

  The run flat tire of the present invention is produced by a usual method using the rubber composition of the present invention. That is, if necessary, the rubber composition of the present invention blended with the above-mentioned compounding agent is extruded in accordance with the shape of the tire sidewall reinforcing rubber layer at an unvulcanized stage, and together with other tire members, the tire An unvulcanized tire is formed by molding by a normal method on a molding machine. This unvulcanized tire is heated and pressurized in a vulcanizer to obtain a run flat tire.

  The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

カーボンブラック（ＦＥＦ）：三菱化学（株）製のダイヤブラックＥ（Ｎ₂ＳＡ：４１ｍ²／ｇ、ＤＢＰ吸油量：１１５ｍｌ／１００ｇ）
ステアリン酸：日本油脂（株）製の椿
酸化亜鉛：三井金属鉱業（株）製の酸化亜鉛２種
老化防止剤：住友化学（株）製のアンチゲン６Ｃ（Ｎ−（１，３−ジメチルブチル）−Ｎ’−フェニル−ｐ−フェニレンジアミン）
不溶性硫黄：四国化成工業（株）製のミュークロンＯＴ
加硫促進剤：大内新興化学工業（株）製のノクセラーＮＳ（Ｎ−ｔ−ブチル−２−ベンゾチアゾリルスルフェンアミド） Various chemicals used in Examples and Comparative Examples will be described together.
Syndiotactic-1,2-polybutadiene is referred to as SPBD.
The syndiotactic polystyrene crystal is expressed as SPS.
NR: natural rubber, RSS # 3
BR (1): butadiene rubber containing SPBD, VCR412 manufactured by Ube Industries, Ltd. (SPBD content: 12% by weight)
BR (2): butadiene rubber containing SPS synthesized by the following <synthesis of BR (2)> (content of SPS 12% by weight, mp = 256 ° C., SC = 86% by weight)
BR (2) is a butadiene rubber containing syndiotactic polystyrene crystals (SPS). The SPS content of 12% by weight indicates that 12% by weight of SPS is present in the dispersion (c) containing the butadiene rubber (b1). Further, SC 86% by weight indicates that the syndiotactic polystyrene crystal part is 86% by weight in the crystalline resin (a). The mp (melting point) of the syndiotactic polystyrene crystal is 256 ° C.
BR (3): butadiene rubber containing SPS synthesized by the following <synthesis of BR (3)> (content of SPS 27 wt%, mp = 254 ° C., SC = 85 wt%)
BR (3) is a butadiene rubber containing syndiotactic polystyrene crystals (SPS). The SPS content of 27% by weight indicates that 27% by weight of SPS is present in the dispersion (c) containing the butadiene rubber (b1). Moreover, SC85 weight% shows that a syndiotactic polystyrene crystal part is 85 weight% in crystalline resin (a). The mp (melting point) of the syndiotactic polystyrene crystal is 254 ° C.
BR (4): butadiene rubber containing SPS synthesized from the following <synthesis of BR (4)> (content of SPS 0.5 wt%, mp = 251 ° C., SC = 84 wt%)
BR (4) is a butadiene rubber containing syndiotactic polystyrene crystals (SPS). The SPS content of 0.5% by weight indicates that 0.5% by weight of SPS is present in the dispersion (c) containing the butadiene rubber (b1). Further, SC 84% by weight indicates that the syndiotactic polystyrene crystal part is 84% by weight in the crystalline resin (a). The mp (melting point) of the syndiotactic polystyrene crystal is 251 ° C.
SBR (1): Styrene butadiene rubber JSR, SL574 manufactured by
SBR (2): Styrene butadiene rubber containing SPS synthesized by the following <Synthesis of SBR (2)> (SPS content 27 wt%, mp = 254 ° C., SC = 85 wt%)
SBR (2) is a styrene butadiene rubber containing syndiotactic polystyrene crystals (SPS). The SPS content of 27% by weight indicates that 27% by weight of SPS is present in the dispersion (c) containing the styrene-butadiene rubber (b1). Moreover, SC85 weight% shows that a syndiotactic polystyrene crystal part is 85 weight% in crystalline resin (a). The mp (melting point) of the syndiotactic polystyrene crystal is 254 ° C.

Carbon Black (FEF): Diamond Black E (N ₂ SA: 41 m ² / g, DBP oil absorption: 115 ml / 100 g) manufactured by Mitsubishi Chemical Corporation
Stearic acid: Zinc oxide manufactured by Nippon Oil & Fats Co., Ltd .: Zinc oxide type 2 manufactured by Mitsui Mining & Smelting Co., Ltd. Anti-aging agent: Antigen 6C (N- (1,3-dimethylbutyl) manufactured by Sumitomo Chemical Co., Ltd. -N'-phenyl-p-phenylenediamine)
Insoluble sulfur: Mukuron OT manufactured by Shikoku Kasei Kogyo Co., Ltd.
Vulcanization accelerator: Noxeller NS (Nt-butyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

  Below, the synthesis method of BR (2), BR (3), BR (4) and SBR (2) used in the present Example is shown in detail.

  A slurry solution of SPS (syndiotactic polystyrene crystal) is obtained by polymerizing styrene in a solvent. The method for polymerizing SPS is not particularly defined, but for example, it can be polymerized by the methods disclosed in JP-A-62-148818 and JP-A-8-134122.

<Synthesis of BR (2)>
Dissolve 10 ml of styrene in 200 ml of toluene, add 1 ml of 0.01 mol / L of cyclopentadienyltitanium trichloride in toluene and 5 ml of methylaminoxane toluene solution with an aluminum content of 7% by weight, and react at 50 ° C. for 3 hours. To obtain a slurry solution of SPS. A polymer cement solution in which 45 g of butadiene rubber is dissolved in 450 ml of toluene is mixed with a slurry solution of SPS, and then the polymer is precipitated with methanol. After drying, a BR (butadiene rubber) composite having an SPS content of 12 w% (weight%) Of 50 g was obtained. As the butadiene rubber, BR150B manufactured by Ube Industries, Ltd. was used.

<Synthesis of BR (3)>
Dissolve 30 ml of styrene in 600 ml of toluene, add successively 3 ml of 0.01 mol / L cyclopentadienyltitanium trichloride in toluene and 15 ml of methylaminoxanthane toluene solution with an aluminum content of 7% by weight, and react at 50 ° C. for 3 hours. To obtain a slurry solution of SPS. A polymer cement solution in which 30 g of butadiene rubber was dissolved in 300 ml of toluene was mixed with a slurry solution of SPS, and then the polymer was precipitated with methanol. After drying, 48 g of BR composite having an SPS content of 27 w% was obtained. As the butadiene rubber, BR150B manufactured by Ube Industries, Ltd. was used.

<Synthesis of BR (4)>
Dissolve 1 ml of styrene in 20 ml of toluene, add 0.1 ml of a 0.01 mol / L cyclopentadienyl titanium trichloride toluene solution and 0.5 ml of a methylaminoxane toluene solution with an aluminum content of 7% by weight, For 3 hours to obtain a slurry solution of SPS. A polymer cement solution in which 120 g of butadiene rubber was dissolved in 1200 ml of toluene was mixed with a slurry solution of SPS, and then the polymer was precipitated with methanol. After drying, 120 g of a BR composite having an SPS content of 0.5 w% was obtained. As the butadiene rubber, BR150B manufactured by Ube Industries, Ltd. was used.

<Synthesis of SBR (2)>
Dissolve 30 ml of styrene in 600 ml of toluene, add 3 ml of a 0.01 mol / L cyclopentadienyltitanium trichloride toluene solution and 15 ml of a methylaminoxane toluene solution with an aluminum content of 7% by weight, and react at 50 ° C. for 3 hours. To obtain a slurry solution of SPS. A polymer cement solution in which 30 g of SBR was dissolved in 300 ml of toluene was mixed with the slurry solution of SPS, and then the polymer was precipitated with methanol. After drying, 48 g of an SBR complex having an SPS content of 27 w% was obtained. SBR used was SL574 manufactured by JSR Corporation.

<Measurement of melting point of SPS (syndiotactic polystyrene crystal) and calculation of SPS content>
The SPS was reprecipitated with methanol from the slurry before blending with the polymer, dried and solidified using an automatic differential scanning calorimeter DSC-60A manufactured by Shimadzu Corporation, and measured at a heating rate of 10 ° C./min. The melting point (mp (onset)) was confirmed.

  The same sample was subjected to Soxhlet extraction using methyl ethyl ketone as a solvent, and the SPS content (SC) was calculated from the extracted residue by analysis by isotope carbon nuclear magnetic resonance (13C-NMR).

<Preparation of unvulcanized rubber composition>
Chemicals other than sulfur and a vulcanization accelerator were added in the amounts shown in Table 1, and kneaded at 150 ° C. for 5 minutes using a 250 cc lab blast mill. Thereafter, sulfur and a vulcanization accelerator are added to the obtained kneaded material in the amounts shown in Table 1, and kneaded at 80 ° C. for 5 minutes using a biaxial open roll. Got.

<Exothermic temperature>
The time until the internal temperature of the vulcanized rubber composition reached 200 ° C. was measured under the conditions of a static load of 30 kgf, a dynamic load of 120 kgf, a test frequency of 25 Hz, and a test start temperature of 35 ° C. using a flexometer FT1260 manufactured by Ueshima Seisakusho.
Specimen size: cylindrical shape with a diameter of 30 mm and a height of 25.4 mm The longer the time, the slower the temperature rise, and the effect of slowing the destruction of rubber or crosslinked structure due to heat is obtained. It shows excellent durability during run-flat running when used in sidewall reinforcing rubber layers and bead apex of run-flat tires.

  The rubber heat generation durability evaluation method of the present invention is based on the constant stress flexometer test in JIS K6265 (2001) “How to determine heat generation and fatigue resistance of vulcanized rubber and thermoplastic rubber by flexometer” It is possible to use a flexometer that complies with this.

  The evaluation results of the above test are shown in Table 1.

It is the right half of the sectional view of the run flat tire which used the rubber composition of the present invention for the side wall reinforcement part or bead apex.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Run flat tire 2 Side wall reinforcement part 3 Bead apex 4 Carcass ply 5 Bead part 6 Side wall part 7 Tread part 8 Belt layer 9 Bead core

Claims (4)

A rubber composition comprising a diene rubber and a crystalline resin,
(A) The crystalline resin (a) is syndiotactic polystyrene having 50% by weight or more of syndiotactic crystals,
(B) When the dispersion of the crystalline resin (a) in the diene rubber (b1) is used as the dispersion (c), the crystalline resin (a) is 1 to 50 weights in the dispersion (c). % Distributed,
(C) When the mixture (d) is composed of the dispersion (c) and the diene rubber (b2), the dispersion (c) is contained in the mixture (d) in an amount of 5 to 60% by weight, and the diene rubber A rubber composition containing 95 to 40% by weight of (b2) in the mixture (d). A diene rubber (diene rubber) in which the diene rubber (b1) and the diene rubber (b2) each contain at least one selected from the group (D) selected from styrene butadiene rubber, isoprene rubber, natural rubber, and butadiene rubber. The rubber composition according to claim 1, wherein (b1) and the diene rubber (b2) may be the same or different. Dispersion (c) is
(E) After mixing a slurry solution in which the crystalline resin (a) is dispersed in an organic solvent and (F) a cement solution in which the diene rubber (b1) is dissolved in the organic solvent,
The rubber composition according to claim 1 or 2 obtained by removing the solvent. The tire which used the rubber composition of Claim 1, 2, or 3 for (G) sidewall reinforcement part and / or (H) bead apex.

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