JP2008291084A - Rubber composition for sidewall and pneumatic tire obtained using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for sidewalls that reduces the used amount of raw materials derived from petroleum resources and can achieve all of weather resistance, cut growth performances and tear strength, and a pneumatic tire using the same. <P>SOLUTION: The rubber composition for sidewalls comprises a rubber component, silica and carbon, where the rubber component comprises a natural rubber component comprised of at least either natural rubber or an epoxidized natural rubber. The compounded amount of the silica is at least 20 pts.mass based on 100 pts.mass of the rubber component; the compounded amount of the carbon is at most 5 pts.mass based on 100 pts.mass of the rubber component; and the BET specific surface area of the carbon is at least 140 m<SP>2</SP>/g. The pneumatic tire is obtained using the same. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a rubber composition for a sidewall and a pneumatic tire including a sidewall rubber made of the rubber composition for a sidewall.

  The sidewall of the pneumatic tire is likely to be distorted by an external force received during traveling, and this distortion causes a crack in the sidewall. In order to prevent the occurrence and growth of cracks in the sidewall, conventionally, for example, a method of blending polybutadiene rubber (BR), carbon black or the like with a rubber composition for sidewall is used. Synthetic rubber and carbon black are both derived from petroleum resources.

  In recent years, methods for reducing the amount of raw materials derived from petroleum resources have been studied in various technical fields due to increasing interest in environmental problems. Currently, commercially available tires are composed of raw materials in which more than half of the total weight is petroleum resources. For example, a general tire for a passenger car contains about 20% by mass of synthetic rubber, about 20% by mass of carbon black, a softener, a synthetic fiber, and the like, so that about 50% by mass or more of the entire tire is derived from raw materials of petroleum resources. It is configured. Therefore, there is a demand for the development of rubber for tires using raw materials derived from natural resources that satisfies the same or more required characteristics as when using raw materials derived from petroleum resources. It is desired to reduce the amount of raw materials derived from petroleum resources while satisfying required properties such as cut gloss performance (that is, flex crack growth resistance) and tear strength.

Patent Document 1 discloses that when used in a tread portion of a pneumatic tire, an NR of 40 to 70 is provided for the purpose of providing a rubber composition for a tire tread capable of maintaining high on-ice driving performance and wear resistance. 15 to 40 parts by weight of carbon black having a nitrogen adsorption specific surface area of 100 to 165 m ² / g and a DBP oil absorption of 90 to 130 ml / 100 g with respect to 100 parts by weight of the diene rubber contained by weight, 20 to 60 parts by weight of precipitated silica having a BET specific surface area of 150 to ²⁰⁰ m ² / g is contained, the total of carbon black and precipitated silica is 40 to 90 parts by weight, and carbon black / precipitated silica is 0.25 to 1 A rubber composition for tire treads of 0.0 is proposed. However, this technique relates to a rubber composition for a tire tread, and does not consider the compatibility between the weather resistance, cut gloss performance and tear strength of the sidewall rubber.

In Patent Document 2, for the purpose of providing a rubber composition for an inner liner with improved rolling resistance performance and processability, a BET specific surface area is 150 m ^{2 with} respect to 100 parts by mass of a rubber component made of natural rubber. A rubber composition for an inner liner containing 30 parts by mass or more of silica less than / g and 5 parts by mass or less of carbon black has been proposed. However, this technique relates to a rubber composition for an inner liner, and does not consider the compatibility between the weather resistance, cut gloss performance and tear strength of the sidewall rubber.

In Patent Document 3, for the purpose of providing a rubber composition for a tire tread having improved rolling resistance characteristics and wet grip performance, nitrogen is added to 100 parts by weight of a rubber component containing 5 to 100% by weight of epoxidized natural rubber. 5 to 150 parts by weight of silica having an adsorption specific surface area of 100 to 300 m ² / g, 1 to 50 parts by weight of plant-derived oil, and 1 to 20 parts by weight of a silane coupling agent with respect to 100 parts by weight of the silica And a rubber for tire tread containing 1 to 20 parts by weight of an anionic surfactant with respect to 100 parts by weight of the silica and 0.1 to 20 parts by weight of an anionic surfactant with respect to 100 parts by weight of the silica. Compositions have been proposed. However, this technique relates to a rubber composition for a tire tread, and does not consider the compatibility between the weather resistance, the cut gloss performance, and the tear strength of the sidewall rubber.

In Patent Document 4, for the purpose of providing a pneumatic tire capable of both reducing rolling resistance and improving durability, a carcass, a bead portion reinforcing layer, a reinforcing layer formed by coating a steel cord with a coating rubber, 30-80 of silica having at least one of a side portion reinforcing layer and a belt, and the coating rubber is 100 parts by mass of diene rubber and the nitrogen adsorption specific surface area is 70 m ² / g or more and 150 m ² / g or less. A pneumatic tire made of a coating rubber composition containing part by mass, 1 to 15 parts by mass of a silane coupling agent, and organic acid cobalt has been proposed. However, this technique does not take into consideration the compatibility between the weather resistance, cut gloss performance and tear strength of the sidewall rubber.

Therefore, depending on the conventional technology, it is difficult to obtain a rubber composition for a sidewall that reduces the amount of a petroleum resource-derived raw material used and satisfies weather resistance, cut gloss performance, and tear strength.
JP 2002-97304 A JP 2006-249147 A JP 2005-263156 A JP 2006-143821 A

  The present invention solves the above-mentioned problems, reduces the amount of raw materials derived from petroleum resources, and uses a rubber composition for a sidewall capable of achieving both weather resistance, cut gloss performance and tear strength. An object is to provide a pneumatic tire.

The present invention contains a rubber component, silica, and carbon, and the rubber component includes a natural rubber component composed of at least one of natural rubber and epoxidized natural rubber. 20 parts by mass or more with respect to parts by mass, the compounding amount of the carbon is 5 parts by mass or less with respect to 100 parts by mass of the rubber component, and the BET specific surface area of the carbon is 140 m ² / g or more. A rubber composition for a sidewall is provided.

  In the rubber composition for a sidewall of the present invention, the content of the natural rubber component in the rubber component is preferably in the range of 30 to 100% by mass.

  The present invention also provides a pneumatic tire provided with a sidewall rubber comprising any one of the rubber compositions for sidewalls described above.

  ADVANTAGE OF THE INVENTION According to this invention, the rubber composition for sidewalls which can reduce the usage-amount of the raw material derived from petroleum resources, and can make weather resistance, cut gloss performance, and tear strength compatible, and a pneumatic tire using the same Provision is possible.

  In the present invention, excellent weather resistance, cut gloss performance and tear strength can be obtained by combining silica and carbon in a rubber composition for a sidewall.

<Rubber component>
The rubber component used in the present invention includes a natural rubber component composed of at least one of natural rubber and epoxidized natural rubber.

  As the natural rubber (NR), those conventionally used in the rubber industry can be used, and examples thereof include natural rubber of grades such as RSS # 3 and TSR.

  Epoxidized natural rubber (ENR) is a kind of modified natural rubber in which unsaturated double bonds of natural rubber are epoxidized, and molecular cohesion is increased by epoxy groups that are polar groups. Therefore, the glass transition temperature (Tg) is higher than that of natural rubber, and the mechanical strength, abrasion resistance, and air permeation resistance are excellent. In particular, when silica is compounded in the rubber composition, due to the reaction between the silanol group on the silica surface and the epoxy group of the epoxidized natural rubber, the same degree as when carbon black is compounded in the rubber composition. The mechanical strength and wear resistance can be obtained.

  As the epoxidized natural rubber (ENR), a commercially available product may be used, or an epoxidized natural rubber (NR) may be used. The method for epoxidizing natural rubber (NR) is not particularly limited, and examples thereof include a chlorohydrin method, a direct oxidation method, a hydrogen peroxide method, an alkyl hydroperoxide method, and a peracid method. Examples of the peracid method include a method of reacting an organic peracid such as peracetic acid or performic acid as an epoxidizing agent with an emulsion of natural rubber.

  The epoxidation rate of the epoxidized natural rubber (ENR) is preferably 5 mol% or more, and more preferably 10 mol% or more. Here, the epoxidation rate means a ratio of the number of epoxidized out of the total number of double bonds in the natural rubber before epoxidation, and is obtained by, for example, titration analysis or nuclear magnetic resonance (NMR) analysis. . When the epoxidation rate of the epoxidized natural rubber (ENR) is less than 5 mol%, the glass transition temperature of the epoxidized natural rubber (ENR) is low, so the rubber hardness of the rubber composition for the sidewall is low, and the sidewall There is a tendency that the weather resistance of a pneumatic tire using the rubber composition for a rubber as a sidewall rubber is lowered. The epoxidation rate of the epoxidized natural rubber (ENR) is preferably 60 mol% or less, and more preferably 50 mol% or less. When the epoxidation rate of the epoxidized natural rubber (ENR) exceeds 60 mol%, the cut gloss performance tends to decrease due to the hardened rubber composition for the sidewall.

  More typical examples of the epoxidized natural rubber (ENR) include an epoxidized natural rubber having an epoxidation rate of 25 mol% and an epoxidized natural rubber having an epoxidation rate of 50 mol%.

  In the present invention, the content of the natural rubber component in the rubber component is preferably 10% by mass or more. When this content rate is less than 10 mass%, there exists a tendency for the reduction effect of the usage-amount of the raw material derived from petroleum resources to become low. The content of the natural rubber component is more preferably 30% by mass or more, and further preferably 40% by mass or more. The content of the natural rubber component is preferably 100% by mass from the viewpoint that the effect of reducing the amount of the raw material derived from petroleum resources is good. For example, the content may be 90% depending on the desired tire characteristics. You may mix | blend rubbers other than a natural rubber component as a remainder in a rubber component, making it into mass% or less and also 80 mass% or less.

  In addition to the natural rubber component defined above, the rubber component of the present invention can contain modified natural rubber such as hydrogenated natural rubber, for example, as rubber derived from non-petroleum resources.

  Further, the rubber component may contain a petroleum resource-derived rubber as long as the effects of the present invention are not impaired. Examples of rubbers derived from petroleum resources include styrene butadiene rubber (SBR), butadiene rubber (BR), styrene isoprene copolymer rubber, isoprene rubber (IR), butyl rubber (IIR), chloroprene rubber (CR), and acrylonitrile butadiene rubber. Examples thereof include (NBR), halogenated butyl rubber (X-IIR), and halides of copolymers of isobutylene and p-methylstyrene. Among these, SBR, BR, and IR are preferable in that the hardness of the rubber composition for the sidewall can be appropriately increased and particularly good weather resistance can be imparted to the pneumatic tire.

  The content of natural rubber (NR) in the rubber component is preferably 10% by mass or more. When the content of natural rubber (NR) is less than 10% by mass, the mechanical strength of the rubber composition for sidewall tends to be low. The content of natural rubber (NR) is more preferably 30% by mass or more, and further preferably 40% by mass or more. The content of natural rubber (NR) in the rubber component is preferably 90% by mass or less. When the content of natural rubber (NR) exceeds 90% by mass, the bending resistance of the rubber composition for sidewall tends to be low. The content of natural rubber (NR) is more preferably 80% by mass or less.

  The content of epoxidized natural rubber (ENR) in the rubber component is preferably 10% by mass or more. When the content of the epoxidized natural rubber (ENR) is less than 10% by mass, the effect of improving the bending resistance tends to be low. The content of the epoxidized natural rubber (ENR) is more preferably 20% by mass or more, and further preferably 30% by mass or more. The content of epoxidized natural rubber (ENR) in the rubber component is preferably 70% by mass or less. When the content of epoxidized natural rubber (ENR) exceeds 70% by mass, the rubber hardness tends to increase and the cut gloss performance tends to decrease. The content of epoxidized natural rubber (ENR) is more preferably 60% by mass or less.

<Silica>
In this invention, the compounding quantity of the silica with respect to 100 mass parts of rubber components shall be 20 mass parts or more. When the blending amount of silica is less than 20 parts by mass, a sufficient reinforcing effect due to silica cannot be obtained, and sufficient mechanical strength cannot be imparted to the rubber composition for sidewalls. As for the compounding quantity of a silica, it is more preferable that it is 30 mass parts or more. In terms of securing mechanical strength, it is preferable that the amount of silica is large. However, if the amount of silica is excessively large, the rubber composition for the sidewall tends to be too hard and the cut gloss performance tends to deteriorate. Therefore, the blending amount of silica is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, and further preferably 40 parts by mass or less.

It is preferable that the BET specific surface area of a silica exists in the range of 40-400 m < ² > / g. When the BET specific surface area of silica is less than 40 m ² / g, the hardness of the rubber composition for the sidewall tends to be too low and the mechanical strength tends to decrease, and when it exceeds 400 m ² / g, the workability tends to decrease. There is. The BET specific surface area of silica is more preferably 80 m ² / g or more, and more preferably 300 m ² / g or less.

  Silica may be prepared by a wet method or may be prepared by a dry method.

<Carbon>
In this invention, the compounding quantity of carbon with respect to 100 mass parts of rubber components shall be 5 mass parts or less. If the amount of carbon exceeds 5 parts by mass, the amount of raw material derived from petroleum resources cannot be reduced sufficiently. From the viewpoint of reducing the amount of raw material derived from petroleum resources, the blending amount of carbon is more preferably 4.5 parts by mass or less, and further preferably 4 parts by mass or less. On the other hand, when the amount of carbon is less than 2 parts by mass, the effect of improving the weather resistance, cut gloss performance and tear strength of the rubber composition for sidewall tends to be small. It is preferably at least part by mass, more preferably at least 2.5 parts by mass, and even more preferably at least 3 parts by mass.

The BET specific surface area of carbon is 140 m ² / g or more. In the present invention, by adding carbon having a large BET specific surface area, the weather resistance, cut gloss performance and tear strength of the sidewall rubber are improved even if the amount of carbon generally derived from petroleum resources is reduced. If the BET specific surface area of carbon is less than 140 m ² / g, the amount of carbon required to ensure weather resistance, cut gloss performance and tear strength will increase, and the amount of raw materials derived from petroleum resources will be reduced. It cannot be reduced sufficiently. The BET specific surface area of carbon is more preferably 150 m ² / g or more. When the BET specific surface area of the carbon is excessively large, the processability tends to be lowered, the BET specific surface area of the carbon is preferably 300 meters ² / g or less, 200 meters ² / g or less, further 180 m ² / g The following is more preferable.

  As a preferable commercial product of carbon, for example, “Show Black N110” manufactured by Cabonet Japan can be exemplified.

<Silane coupling agent>
In the present invention, silica is blended. Therefore, when a silane coupling agent is used in combination, an excellent reinforcing effect is imparted to the sidewall rubber composition, which is preferable. The compounding amount of the silane coupling agent is preferably in the range of 4 to 20% by mass when the compounding amount of silica is 100% by mass. When the amount of the silane coupling agent is less than 4% by mass, the reinforcing effect tends to be low. When the amount exceeds 20% by mass, a significant improvement in the reinforcing effect cannot be expected even if the amount is increased, but the cost is low. It tends to be uneconomical because it rises. The blending amount of the silane coupling agent is more preferably 5% by mass or more, and more preferably 15% by mass or less.

  As the silane coupling agent, a conventionally known silane coupling agent can be used. For example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (4- Triethoxysilylbutyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (4-trimethoxysilylbutyl) tetrasulfide, bis (3-triethoxy Silylpropyl) trisulfide, bis (2-triethoxysilylethyl) trisulfide, bis (4-triethoxysilylbutyl) trisulfide, bis (3-trimethoxysilylpropyl) trisulfide, bis (2-trimethoxysilylethyl) ) Resulfide, bis (4-trimethoxysilylbutyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) disulfide, bis (4-triethoxysilylbutyl) disulfide, bis (3 -Trimethoxysilylpropyl) disulfide, bis (2-trimethoxysilylethyl) disulfide, bis (4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyltetrasulfide, 3-tri Ethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-trimethoxysilylethyl-N, N-dimethylthio Sulfide systems such as rubamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, 3-trimethoxysilylpropyl methacrylate monosulfide; 3-mercaptopropyltrimethoxysilane Mercapto type such as 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane; Vinyl type such as vinyltriethoxysilane, vinyltrimethoxysilane; 3-aminopropyltriethoxysilane 3-aminopropyltrimethoxysilane, 3- (2-aminoethyl) aminopropyltriethoxysilane, 3- (2-aminoethyl) aminopropyltrimethoxy Amino systems such as silane; glycidoxy systems such as γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropylmethyldimethoxysilane Nitro compounds such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane, 2-chloroethyltri Chloro-based compounds such as ethoxysilane; These silane coupling agents may be used alone or in combination of two or more.

  Among the above, Si69 (bis (3-triethoxysilylpropyl) tetrasulfide), Si266 (bis (3-triethoxysilylpropyl) disulfide) manufactured by Degussa and the like are preferably used because of good workability. .

<Other ingredients>
In addition to the above-described components, the side wall rubber composition of the present invention includes other compounding agents conventionally used in the rubber industry, such as vulcanizing agents, stearic acid, vulcanization accelerators, vulcanization acceleration aids, You may mix | blend oil, hardening resin, wax, anti-aging agent, etc. Moreover, as a filler other than the above-mentioned silica and carbon, for example, titanium oxide, magnesium oxide, calcium carbonate, magnesium carbonate, aluminum hydroxide, magnesium hydroxide, clay, talc and the like may be used in combination.

  As the vulcanizing agent, an organic peroxide or a sulfur-based vulcanizing agent can be used. Examples of the organic peroxide include benzoyl peroxide, dicumyl peroxide, and di-t-butyl peroxide. , T-butyl cumyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (benzoyl) Peroxy) hexane, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3 or 1,3-bis (t-butylperoxypropyl) benzene, di-t-butylperoxy- Diisopropylbenzene, t-butylperoxybenzene, 2,4-dichlorobenzoyl peroxide, 1,1-di t- butyl peroxy-3,3,5-trimethyl siloxane, and the like can be used n- butyl-4,4-di -t- butyl peroxy valerate. Of these, dicumyl peroxide, t-butylperoxybenzene and di-t-butylperoxy-diisopropylbenzene are preferred. Moreover, as a sulfur type vulcanizing agent, sulfur, morpholine disulfide, etc. can be used, for example. Of these, sulfur is preferred. These vulcanizing agents may be used alone or in combination of two or more. Further, sulfur may be oil-treated.

  Vulcanization accelerators include sulfenamide, thiazole, thiuram, thiourea, guanidine, dithiocarbamic acid, aldehyde-amine or aldehyde-ammonia, imidazoline, or xanthate vulcanization accelerators. Those containing at least one of them can be used. Examples of the sulfenamide system include CBS (N-cyclohexyl-2-benzothiazylsulfenamide), TBBS (N-tert-butyl-2-benzothiazylsulfenamide), N, N-dicyclohexyl-2- Sulfenamide compounds such as benzothiazylsulfenamide, N-oxydiethylene-2-benzothiazylsulfenamide, and N, N-diisopropyl-2-benzothiazolesulfenamide can be used. Examples of the thiazole group include MBT (2-mercaptobenzothiazole), MBTS (dibenzothiazyl disulfide), sodium salt of 2-mercaptobenzothiazole, zinc salt, copper salt, cyclohexylamine salt, 2- (2,4-dinitro). Thiazole compounds such as phenyl) mercaptobenzothiazole and 2- (2,6-diethyl-4-morpholinothio) benzothiazole can be used. Examples of thiurams include TMTD (tetramethyl thiuram disulfide), tetraethyl thiuram disulfide, tetramethyl thiuram monosulfide, dipentamethylene thiuram disulfide, dipentamethylene thiuram monosulfide, dipentamethylene thiuram tetrasulfide, dipentamethylene thiuram hexasulfide. Further, thiuram compounds such as tetrabutylthiuram disulfide and pentamethylenethiuram tetrasulfide can be used. As the thiourea series, for example, thiourea compounds such as thiacarbamide, diethylthiourea, dibutylthiourea, trimethylthiourea, diortolylthiourea and the like can be used. Examples of guanidine-based compounds include guanidine-based compounds such as diphenylguanidine, diortolylguanidine, triphenylguanidine, orthotolylbiguanide, and diphenylguanidine phthalate. Examples of dithiocarbamate include zinc ethylphenyldithiocarbamate, zinc butylphenyldithiocarbamate, sodium dimethyldithiocarbamate, zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, zinc diamyldithiocarbamate, zinc dipropyldithiocarbamate , Complex salt of zinc pentamethylenedithiocarbamate and piperidine, zinc hexadecyl (or octadecyl) isopropyldithiocarbamate, zinc dibenzyldithiocarbamate, sodium diethyldithiocarbamate, piperidine pentamethylenedithiocarbamate, selenium dimethyldithiocarbamate, tellurium diethyldithiocarbamate, diamyl Di, such as cadmium dithiocarbamate And the like can be used Okarubamin acid compound. As the aldehyde-amine system or aldehyde-ammonia system, for example, an aldehyde-amine system or aldehyde-ammonia system compound such as acetaldehyde-aniline reaction product, butyraldehyde-aniline condensate, hexamethylenetetramine, acetaldehyde-ammonia reaction product, etc. is used. can do. As the imidazoline-based compound, for example, an imidazoline-based compound such as 2-mercaptoimidazoline can be used. As the xanthate type, for example, a xanthate type compound such as zinc dibutylxanthate can be used. These vulcanization accelerators may be used alone or in combination of two or more.

  As the anti-aging agent, amine-based, phenol-based, imidazole-based, carbamic acid metal salts, and the like can be appropriately selected and used.

  Examples of the oil include process oil, vegetable oil and fat, or a mixture thereof. Examples of the process oil include paraffinic process oil, naphthenic process oil, and aromatic process oil. Vegetable oils include castor oil, cottonseed oil, sesame oil, rapeseed oil, soybean oil, palm oil, palm oil, peanut oil, rosin, pine oil, pineapple, tall oil, corn oil, rice bran oil, beet flower oil, sesame oil, Examples include olive oil, sunflower oil, palm kernel oil, cocoon oil, jojoba oil, macadamia nut oil, safflower oil, tung oil, and the like.

  The present invention also provides a pneumatic tire provided with a sidewall rubber comprising the rubber composition for a sidewall of the present invention as described above. Hereinafter, the pneumatic tire of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view illustrating the left half of a pneumatic tire according to the present invention. The pneumatic tire 1 includes a tread portion 2, a pair of sidewall portions 3 extending inward in the tire radial direction from both ends of the tread portion 2, and a bead portion 4 positioned at an inner end of each sidewall portion 3. Prepare. A carcass 6 is bridged between the bead portions 4 and 4, and a belt layer 7 is provided outside the carcass 6 and inside the tread portion 2 to reinforce the tread portion 2 with a tagging effect.

  The carcass 6 is formed of one or more carcass plies in which the carcass cord is arranged at an angle of, for example, 70 to 90 ° with respect to the tire equator CO. The carcass ply extends from the tread portion 2 to the sidewall portion 3. After that, the periphery of the bead core 5 of the bead portion 4 is folded back from the inner side in the tire axial direction to be locked.

  The belt layer 7 is composed of two or more belt plies in which the belt cords are arranged at an angle of, for example, 40 ° or less with respect to the tire equator CO. The belt layers 7 are stacked in different directions so that the belt cords cross each other. is doing. If necessary, a band layer (not shown) for preventing lifting at both ends of the belt layer 7 may be provided at least outside the belt layer 7. At this time, the band layer is formed of a low modulus organic fiber. The cord is formed of a continuous ply spirally wound substantially parallel to the tire equator CO.

  Further, a bead apex rubber 8 extending radially outward from the bead core 5 is disposed in the bead portion 4, and an inner liner rubber 9 forming a tire lumen surface is adjacent to the inside of the carcass 6. The outside of the carcass 6 is protected by clinch rubber 4G and sidewall rubber 3G. The rubber composition for an inner liner of the present invention is used for the side wall rubber 3G of the side wall portion 3 described above.

  Although FIG. 1 illustrates a pneumatic tire for a passenger car, the present invention is not limited to this, and air used for various vehicles such as a passenger car, a truck, a bus, and a heavy vehicle. Provide filled tires.

  The pneumatic tire of the present invention is produced by a conventionally known method using the rubber composition for a sidewall of the present invention. That is, a rubber composition for a sidewall containing the above-described essential components and other compounding agents blended as necessary is kneaded and extruded in accordance with the shape of the tire sidewall at an unvulcanized stage. And an unvulcanized tire is formed by shape | molding with a tire molding machine with a normal method with the other member of a tire. The tire of the present invention can be obtained by heating and pressurizing the unvulcanized tire in a vulcanizer.

  Such a pneumatic tire of the present invention has a reduced content ratio of components derived from petroleum resources, particularly in the sidewall rubber, and sufficient consideration is given to resource saving and environmental protection, as well as weather resistance, cut gloss performance and tearing. Since a rubber composition for a sidewall capable of achieving a high degree of strength is used, it is an “eco-tyre” that is friendly to the global environment and has good weather resistance, cut gloss performance, and tear strength.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in detail, this invention is not limited to these.

<Examples 1 and 2 and Comparative Examples 1 and 2>
In accordance with the formulation shown in Table 1, using a 1.7L Banbury mixer manufactured by Kobe Steel, the components except for sulfur and vulcanization accelerator were kneaded, and then the obtained rubber kneaded with sulfur and vulcanized on an open roll. A sulfur accelerator was added according to the formulation shown in Table 1, kneaded, and extruded to obtain an unvulcanized rubber sheet. The obtained unvulcanized rubber sheet was vulcanized at 150 ° C. for 30 minutes to obtain a test rubber sheet.

(Weatherability)
About the rubber sheet for a test obtained above, the weather resistance was evaluated according to JIS-K6266. That is, after the test rubber sheet was stretched to 120% and exposed outdoors for two months, the occurrence of cracks was visually evaluated. Was recognized as B.

(Cut gloss performance)
For the test rubber sheet obtained above, the flex crack growth rate at 50% strain was evaluated according to JIS-K6260 (Dematcher flex fatigue test method). A case where the number of bendings until a crack of 1 mm or more occurred was 30 million times or more was shown as A, and a case where it was less than 30 million times was shown as B.

(Tear strength)
The tear strength (N / mm) of the test rubber sheet obtained above was measured according to JIS-K6252.

Note 1: Natural rubber is TSR20.
Note 2: The epoxidized natural rubber is “ENR25” (epoxidation rate: 25%) manufactured by Kumphura Langley.
Note 3: Carbon A is “Show Black N220” (BET specific surface area: 111 m ² / g) manufactured by Cabonet Japan.
Note 4: Carbon B is “Show Black N110” (BET specific surface area: 144 m ² / g) manufactured by Cabonet Japan.
Note 5: Silica is Ultrazil VN3 (BET specific surface area: 170 m ² / g) manufactured by Degussa.
Note 6: Silane coupling agent is “Si75” manufactured by Degussa.
Note 7: Wax is “Sannokk Wax” manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Note 8: The anti-aging agent is “NOCRACK 6C” (N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine) manufactured by Ouchi Shinsei Chemical Co., Ltd.
Note 9: Stearic acid is stearic acid manufactured by NOF Corporation.
Note 10: Zinc oxide is “Zinc Hana 1” manufactured by Mitsui Mining & Smelting Co., Ltd.
Note 11: Sulfur is “powder sulfur” manufactured by Tsurumi Chemical Co., Ltd.
Note 12: The vulcanization accelerator is “Noxeller NS” manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

  As shown in Table 1, when Example 1 and Comparative Example 1 in which the compounding amount of carbon is 5 parts by mass with respect to 100 parts by mass of the rubber component are both compared, Example 1 and Comparative Example 1 are both good. Showed good weather resistance and cut gloss performance. On the other hand, in Comparative Example 1 in which carbon having a BET specific surface area outside the range of the present invention was used together with silica, the tearing performance was inferior, whereas carbon having a BET specific surface area within the range of the present invention was combined with silica. In Example 1 used quantitatively, the tear performance was good. Further, when Example 2 and Comparative Example 2 in which the compounding amount of carbon is 3 parts by mass with respect to 100 parts by mass of the rubber component are compared, carbon having a BET specific surface area outside the range of the present invention is used together with silica. In Comparative Example 2, the sufficient weather resistance, cut gloss performance and tearing performance could not be obtained, but in Example 2 in which carbon having a BET specific surface area within the range of the present invention was used together with silica, good weather resistance was obtained. , Cut gloss performance and tear performance were obtained. Therefore, according to the present invention, it can be seen that weather resistance, cut gloss performance, and tear strength can be highly compatible with each other while suppressing the amount of carbon used and reducing the amount of raw material derived from petroleum resources.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The rubber composition for a side wall of the present invention is suitably applied to a side wall rubber of a pneumatic tire for various uses such as for passenger cars, trucks, buses, heavy vehicles, and the like. It can be suitably applied to various uses.

It is sectional drawing which illustrated the left half of the pneumatic tire which concerns on this invention.

Explanation of symbols

  1 tire, 2 tread part, 3 sidewall part, 4 bead part, 5 bead core, 6 carcass, 7 belt layer, 8 bead apex rubber, 9 inner liner rubber, 3G side wall rubber, 4G clinch rubber.

Claims (3)

Contains rubber component, silica and carbon,
The rubber component includes a natural rubber component consisting of at least one of natural rubber and epoxidized natural rubber,
The amount of silica is 20 parts by mass or more with respect to 100 parts by mass of the rubber component,
The compounding amount of the carbon is 5 parts by mass or less with respect to 100 parts by mass of the rubber component,
The rubber composition for a side wall, wherein the carbon has a BET specific surface area of 140 m ² / g or more.   The rubber composition for a sidewall according to claim 1, wherein the content of the natural rubber component in the rubber component is in the range of 30 to 100% by mass.   A pneumatic tire provided with a sidewall rubber comprising the rubber composition for a sidewall according to claim 1.

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