JP2010150412A - Rubber composition for use in insulation or bead apex, and tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for use in insulation or bead apex, the rubber composition having the excellent low heat-build up and simultaneously the high mechanical strengths; and to provide a pneumatic tire which has the insulation and/or bead apex made by using the same. <P>SOLUTION: The rubber composition for use in the insulation or bead apex includes 100 pts.mass of a rubber component and 10-150 pts.mass of silica, wherein the rubber component contains a butadiene rubber modified with a compound expressed by formula (1) (wherein, R<SP>1</SP>, R<SP>2</SP>and R<SP>3</SP>are the same or different and are each alkyl, alkoxy, silyloxy, acetal, carboxyl, mercapto or a derivative thereof; R<SP>4</SP>and R<SP>5</SP>are the same or different and are each a hydrogen atom or an alkyl group; and n is an integer). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a rubber composition for insulation or bead apex, and a pneumatic tire using the same.

Conventionally, in order to reduce the rolling resistance of tires based on social demands for reducing fuel consumption of automobiles, technology using a low exothermic compound in the insulation part and bead apex part has been used. In recent years, there has been an increasing demand for lower fuel consumption, and further lower heat generation is required.

In order to further reduce the heat generation in the insulation portion and the bead apex portion, it is conceivable to reduce the amount of carbon black used as a reinforcing filler or increase the particle size of the carbon black.

However, if the amount of carbon black is reduced or carbon black having a large particle size is used, the strength of the rubber composition is lowered. This decrease in strength is undesirable because it causes a decrease in tire durability and a decrease in lateral rigidity.

Patent Document 1 describes modified polybutadiene obtained by modifying polybutadiene with organoalkoxysilane or organoaloxysilane, and Patent Document 2 describes modified polybutadiene obtained by modifying polybutadiene with a diamine compound, which can improve performance such as wet skid resistance. It is described that it is useful as a rubber material.

However, even if such modified polybutadiene is used, there is still room for improvement in terms of achieving both low heat build-up and mechanical strength of the rubber composition. In addition, application to tire installation and bead apex has not been studied.

Japanese Patent Laid-Open No. 2001-40001 JP 2007-31722 A

The object of the present invention is to solve the above-mentioned problems and to provide a rubber composition for an insulation or bead apex having high mechanical strength while having excellent low exothermic properties. Another object of the present invention is to provide a pneumatic tire having an installation and / or a bead apex produced using the rubber composition.

The present invention provides an insulation or bead containing butadiene rubber containing 10 to 150 parts by mass of silica with respect to 100 parts by mass of the rubber component, wherein the rubber component is modified with a compound represented by the following formula (1). The present invention relates to a rubber composition for apex.

（式中、Ｒ^１、Ｒ^２及びＲ^３は、同一若しくは異なって、アルキル基、アルコキシ基、シリルオキシ基、アセタール基、カルボキシル基、メルカプト基又はこれらの誘導体を表す。Ｒ^４及びＲ^５は、同一若しくは異なって、水素原子又はアルキル基を表す。ｎは整数を表す。）

(Wherein R ¹ , R ² and R ³ are the same or different and each represents an alkyl group, an alkoxy group, a silyloxy group, an acetal group, a carboxyl group, a mercapto group or a derivative thereof. R ⁴ and R ⁵ are (The same or different, and represents a hydrogen atom or an alkyl group. N represents an integer.)

The vinyl content of the modified butadiene rubber is preferably 35% by mass or less.

The present invention also relates to a pneumatic tire having an installation and / or a bead apex produced using the rubber composition.

According to the present invention, the rubber composition contains 10 to 150 parts by mass of silica with respect to 100 parts by mass of the rubber component, and the rubber component includes a butadiene rubber modified with a specific compound. By using the composition as a tire insulation or bead apex, it is possible to provide a pneumatic tire having excellent low heat buildup and high mechanical strength.

The rubber composition for insulation or bead apex of the present invention contains 10 to 150 parts by mass of silica with respect to 100 parts by mass of the rubber component. Moreover, the rubber component used for the said rubber composition contains the butadiene rubber (modified butadiene rubber) modified | denatured with the compound represented by the said Formula (1). By using the modified butadiene rubber and silica, excellent low heat build-up can be obtained while maintaining high mechanical strength in the rubber composition. Therefore, it is possible to achieve both low heat buildup and high mechanical strength in the tire installation portion and bead apex portion.

In the compound represented by the above formula (1), R ¹ , R ² and R ³ are the same or different and are an alkyl group, an alkoxy group, a silyloxy group, an acetal group, a carboxyl group (—COOH), a mercapto group (— SH) or derivatives thereof. As said alkyl group, C1-C4 alkyl groups, such as a methyl group, an ethyl group, n-propyl group, isopropyl group, n-butyl group, t-butyl group, etc. are mentioned, for example. Examples of the alkoxy group include alkoxy groups having 1 to 8 carbon atoms (preferably 1 to 6 carbon atoms) such as methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, and t-butoxy group. More preferably, C1-C4) etc. are mentioned. The alkoxy group includes a cycloalkoxy group (cycloalkoxy group having 5 to 8 carbon atoms such as cyclohexyloxy group) and an aryloxy group (aryloxy group having 6 to 8 carbon atoms such as phenoxy group and benzyloxy group). ) Is also included.

Examples of the silyloxy group include a silyloxy group substituted with an aliphatic group having 1 to 20 carbon atoms and an aromatic group (trimethylsilyloxy group, triethylsilyloxy group, triisopropylsilyloxy group, diethylisopropylsilyloxy group, t- Butyldimethylsilyloxy group, t-butyldiphenylsilyloxy group, tribenzylsilyloxy group, triphenylsilyloxy group, tri-p-xylylsilyloxy group, etc.).

Examples of the acetal group include groups represented by -C (RR ')-OR "and -O-C (RR')-OR". Examples of the former include a methoxymethyl group, an ethoxymethyl group, a propoxymethyl group, a butoxymethyl group, an isopropoxymethyl group, a t-butoxymethyl group, and a neopentyloxymethyl group. The latter includes a methoxymethoxy group, an ethoxy group, and the like. Methoxy group, propoxymethoxy group, i-propoxymethoxy group, n-butoxymethoxy group, t-butoxymethoxy group, n-pentyloxymethoxy group, n-hexyloxymethoxy group, cyclopentyloxymethoxy group, cyclohexyloxymethoxy group, etc. Can be mentioned. R ¹ , R ² and R ³ are preferably alkoxy groups. Thereby, low exothermic property and mechanical strength can be suitably achieved.

Examples of the alkyl group for R ⁴ and R ⁵ include the same groups as the above alkyl group.

As n (integer), 1-5 are preferable. Thereby, low exothermic property and mechanical strength can be suitably achieved. Furthermore, n is more preferably 2 to 4, and most preferably 3. When n is 0, it is difficult to bond a silicon atom and a nitrogen atom, and when n is 6 or more, the effect as a modifier is reduced.

Specific examples of the compound represented by the above formula (1) include 3-aminopropyldimethylmethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylethyldimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, Aminopropyldimethylethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyldimethylbutoxysilane, 3-aminopropylmethyldibutoxysilane, dimethylaminomethyltrimethoxysilane, 2-dimethyl Aminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 4-dimethylaminobutyltrimethoxysilane, dimethylaminomethyldimethoxymethylsilane, 2-dimethylaminoethyldimethoxy Methylsilane, 3-dimethylaminopropyldimethoxymethylsilane, 4-dimethylaminobutyldimethoxymethylsilane, dimethylaminomethyltriethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 4-dimethylaminobutyl Triethoxysilane, dimethylaminomethyldiethoxymethylsilane, 2-dimethylaminoethyldiethoxymethylsilane, 3-dimethylaminopropyldiethoxymethylsilane, 4-dimethylaminobutyldiethoxymethylsilane, diethylaminomethyltrimethoxysilane, 2- Diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 4-diethylaminobutyltrimethoxysilane, diethylamino Tildimethoxymethylsilane, 2-diethylaminoethyldimethoxymethylsilane, 3-diethylaminopropyldimethoxymethylsilane, 4-diethylaminobutyldimethoxymethylsilane, diethylaminomethyltriethoxysilane, 2-diethylaminoethyltriethoxysilane, 3-diethylaminopropyltriethoxysilane 4-diethylaminobutyltriethoxysilane, diethylaminomethyldiethoxymethylsilane, 2-diethylaminoethyldiethoxymethylsilane, 3-diethylaminopropyldiethoxymethylsilane, 4-diethylaminobutyldiethoxymethylsilane, and the like. These may be used alone or in combination of two or more.

Examples of the modification method of butadiene rubber with the compound (modifier) represented by the above formula (1) include conventionally known methods such as methods described in JP-B-6-53768 and JP-B-6-57767. Techniques can be used. For example, the butadiene rubber may be brought into contact with the modifying agent, the butadiene rubber is polymerized, and a predetermined amount of the modifying agent is added to the polymer rubber solution, and the modifying agent is added to the butadiene rubber solution and reacted. Methods and the like.

The butadiene rubber (BR) to be modified is not particularly limited. For example, BR1220 manufactured by Nippon Zeon Co., Ltd., BR130B manufactured by Ube Industries, Ltd., BR150B, and other high cis content BR, Ube Industries, Ltd. BR containing a syndiotactic polybutadiene crystal such as VCR412 and VCR617 manufactured by the same company can be used.

The vinyl content of the modified butadiene rubber is preferably 35% by mass or less, more preferably 25% by mass or less, and still more preferably 20% by mass or less. When the vinyl content exceeds 35% by mass, the low exothermic property tends to be impaired. The lower limit of the vinyl content is not particularly limited.
The vinyl content (1,2-bond butadiene unit amount) can be measured by infrared absorption spectrum analysis.

The content of the modified butadiene rubber in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 15% by mass or more, and further preferably 30% by mass or more. If it is less than 10% by mass, a low exothermic effect cannot be expected. The upper limit of the content of the modified butadiene rubber is not particularly limited, but is preferably 90% by mass or less, more preferably 80% by mass or less, and still more preferably 70% by mass or less. If it exceeds 90% by mass, the rubber strength tends to be insufficient.

Examples of rubber components other than the modified butadiene rubber used in the rubber composition include diene rubbers. For example, natural rubber (NR), epoxidized natural rubber (ENR), butadiene rubber (BR), styrene-butadiene rubber ( SBR), isoprene rubber (IR), ethylene-propylene-diene rubber (EPDM), butyl rubber (IIR), halogenated butyl rubber (X-IIR), chloroprene rubber (CR), acrylonitrile (NBR), isomonoolefin and paraalkyl A halide of a copolymer with styrene can be used. Especially, it is preferable to use natural rubber with the said modified butadiene rubber from the point of an intensity | strength improvement.

The NR is not particularly limited, and for example, those commonly used in the tire industry such as SIR20, RSS # 3, TSR20, and the like can be used.

The content of natural rubber in 100% by mass of the rubber component is preferably 30% by mass or more, more preferably 50% by mass or more, and still more preferably 60% by mass or more. There exists a tendency for intensity | strength to fall that it is less than 30 mass%. The content of natural rubber is preferably 90% by mass or less, more preferably 80% by mass or less, and still more preferably 70% by mass or less. If it exceeds 90% by mass, the flex crack growth tends to deteriorate.

The rubber composition contains silica. By blending silica with the modified butadiene rubber, good low heat buildup and high rubber strength can be obtained. Examples of the silica include, but are not limited to, dry method silica (anhydrous silicic acid), wet method silica (anhydrous silicic acid), and the like, and wet method silica is preferable because it has many silanol groups.

The average primary particle diameter of silica is preferably 10 nm or more, more preferably 15 nm or more. If it is less than 10 nm, it tends to be inferior in low heat build-up and rubber processability. The average primary particle diameter of silica is preferably 40 nm or less, more preferably 30 nm or less. If it exceeds 40 nm, the fracture strength tends to decrease. In addition, the average primary particle diameter of silica can be calculated | required from the average value which observes a silica with an electron microscope, measures a particle diameter about 50 arbitrary particles, for example.

The content of silica is 10 parts by mass or more, preferably 20 parts by mass or more with respect to 100 parts by mass of the rubber component. When the content of silica is less than 10 parts by mass, sufficient effects due to the blending of silica cannot be obtained. The silica content is 150 parts by mass or less, preferably 120 parts by mass or less. If the silica content exceeds 150 parts by mass, it will be difficult to disperse the silica in the rubber, and the processability of the rubber will deteriorate.

The rubber composition preferably contains a silane coupling agent. As the silane coupling agent, any silane coupling agent conventionally used in combination with silica can be used in the rubber industry. For example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-tri Ethoxysilylethyl) tetrasulfide, bis (4-triethoxysilylbutyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (4-trimethoxysilyl) Butyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (2-triethoxysilylethyl) trisulfide, bis (4-triethoxysilylbutyl) trisulfide, bis (3-trimethoxysilylpropyl) Trisulfi Bis (2-trimethoxysilylethyl) trisulfide, 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-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-trime Xylylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3- Sulfide type such as trimethoxysilylpropyl methacrylate monosulfide, mercapto type such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, vinyltri Vinyl series such as ethoxysilane and vinyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysila , Glycidoxy type such as γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, nitro type such as 3-nitropropyltrimethoxysilane, 3-nitropropyltriethoxysilane, 3-chloropropyl Examples include chloro-based compounds such as trimethoxysilane, 3-chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane, and 2-chloroethyltriethoxysilane. Product names include Si69, Si75, Si363 (Degussa), NXT, NXT-LV, NXT-ULV, NXT-Z (GE). Of these, bis (3-triethoxysilylpropyl) disulfide is preferable. These silane coupling agents may be used alone or in combination of two or more.

The content of the silane coupling agent is preferably 5 parts by mass or more and more preferably 8 parts by mass or more with respect to 100 parts by mass of the silica. If it is less than 5 mass parts, there exists a tendency for a fracture strength to fall large. Moreover, 15 mass parts or less are preferable with respect to 100 mass parts of silica content, and, as for content of a silane coupling agent, 10 mass parts or less are more preferable. When the amount exceeds 15 parts by mass, effects such as an increase in fracture strength and a reduction in rolling resistance due to the addition of the silane coupling agent tend not to be obtained.

You may mix | blend carbon black with the said rubber composition. Thereby, the intensity | strength of rubber | gum can be improved. As carbon black, GPF, HAF, ISAF, SAF, etc. can be used, for example.

When carbon black is used, the nitrogen adsorption specific surface area (N ₂ SA) of the carbon black is preferably 30 m ² / g or more, and more preferably 40 m ² / g or more. When N ₂ SA is less than 30 m ² / g, there is a tendency that sufficient reinforcing properties cannot be obtained. Also, _N 2 SA of carbon black is preferably 120 m ² / g or less, more preferably ^90m 2 / g. When N ₂ SA exceeds 120 m ² / g, the viscosity at the time of unvulcanization becomes very high, and the workability tends to deteriorate or the fuel consumption tends to deteriorate. The nitrogen adsorption specific surface area of carbon black is determined by the A method of JIS K6217.

The content of carbon black is preferably 5 parts by mass or more, more preferably 10 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 5 parts by mass, sufficient reinforcing properties tend not to be obtained. Further, the content of carbon black is preferably 60 parts by mass or less, more preferably 50 parts by mass or less with respect to 100 parts by mass of the rubber component. When it exceeds 60 parts by mass, the heat generation tends to increase.

You may mix | blend a thermosetting resin with the said rubber composition, especially the rubber composition for bead apex. Examples of the thermosetting resin include phenolic resins and cresol resins. Of these, phenolic resins are preferred from the viewpoint of obtaining high hardness.

Examples of phenolic resins include phenolic resins obtained by reacting phenols with aldehydes such as formaldehyde, acetaldehyde, furfural and the like with an acid or alkali catalyst; cashew oil, tall oil, linseed oil, various animal and vegetable oils, Examples thereof include a modified phenolic resin modified with unsaturated fatty acid, rosin, alkylbenzene resin, aniline, melamine and the like. Among the phenol-based resins, a modified phenol resin is preferable because a hardness (Hs) can be improved, and a cashew oil-modified phenol resin or a rosin-modified phenol resin is preferable.

The content of the thermosetting resin is preferably 1 part by mass or more and more preferably 3 parts by mass or more with respect to 100 parts by mass of the rubber component from the viewpoint that sufficient hardness is obtained. In addition, the content of the thermosetting resin is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, from the viewpoint that the unvulcanized rubber does not become too hard and the processability is excellent.

In the rubber composition of the present invention, in addition to the rubber component such as the modified butadiene rubber, silica, silane coupling agent, carbon black, thermosetting resin, a compounding agent generally used in the production of a rubber composition, for example, Further, reinforcing fillers such as clay, zinc oxide, stearic acid, various anti-aging agents, oils such as aroma oil, waxes, vulcanizing agents, vulcanization accelerators, and the like can be appropriately blended.

Examples of the vulcanizing agent include sulfur or a sulfur compound.
The content of sulfur or sulfur compound is preferably 0.5 parts by mass or more and more preferably 1 part by mass or more with respect to 100 parts by mass of the rubber component from the viewpoint that sufficient hardness is obtained and it is difficult to break. Further, the content of sulfur or sulfur compound is preferably 5 parts by mass or less, more preferably 3 parts by mass or less from the viewpoint that blooming is difficult and sufficient workability is obtained.

Examples of the vulcanization accelerator that can be used in the present invention include N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N, N ′. -Dicyclohexyl-2-benzothiazolylsulfenamide (DZ), mercaptobenzothiazole (MBT), dibenzothiazolyl disulfide (MBTS), diphenylguanidine (DPG) and the like. Above all, sulfenamide-based vulcanization acceleration such as TBBS, CBS, and DZ is promoted because of excellent vulcanization characteristics, excellent physical properties of rubber after vulcanization, excellent low heat build-up, and great effect of improving mechanical hardness. Agents are preferred. In particular, when used in an insulation part, it is preferable to use CBS and DPG together, and when used for a bead apex part, it is preferable to use TBBS and DPG together.

The content of the vulcanization accelerator is preferably 0.7 parts by mass or more, more preferably 1.0 parts by mass or more, and further preferably 1.2 parts by mass or more with respect to 100 parts by mass of the rubber component. The content is preferably 6 parts by mass or less, more preferably 5 parts by mass or less, and still more preferably 4.5 parts by mass or less. If the amount is less than 0.7 parts by mass, the rubber composition is not sufficiently vulcanized and the required rubber properties tend not to be obtained. If it exceeds 6 parts by mass, the rubber composition tends to be vulcanized too much.

As a method for producing the rubber composition of the present invention, a known method can be used. For example, the above components are kneaded using a rubber kneader such as an open roll or a Banbury mixer, and then vulcanized. Can be manufactured.

The rubber composition of the present invention is used for an insulation disposed between the carcass and the inner liner and / or a bead apex disposed on the inner side of the tire clinch so as to extend radially outward from the bead core. . Specifically, the installation part and the bead apex part are members shown in FIGS. 1-2 of JP-A-2008-150523.

The pneumatic tire of the present invention is produced by a usual method using the rubber composition. That is, if necessary, the rubber composition with various additives is extruded in accordance with the shape of the insulation and bead apex at an unvulcanized stage, and molded by a normal method on a tire molding machine, After bonding together with other tire members to form an unvulcanized tire, the tire can be manufactured by heating and pressing in a vulcanizer.

The tire of the present invention is suitably used as a passenger car tire, bus tire, truck tire, and the like.

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

Hereinafter, various chemicals used in Examples and Comparative Examples will be described together.
NR: TSR20
Butadiene rubber (BR (1)): Nipol BR1220 (vinyl content 1% by mass, non-modified) manufactured by Nippon Zeon Co., Ltd.
Butadiene rubber (BR (2)): Modified butadiene rubber manufactured by Sumitomo Chemical Co., Ltd. (vinyl content 15% by mass, R ¹ , R ² and R ³ = -OCH ₃ , R ⁴ and R ⁵ = -CH ₂ CH ₃ , N = 3)
Silica: ULTRASIL VN3 (average primary particle diameter: 15 nm) manufactured by Degussa
Carbon Black (1): Seast NH (N ₂ SA: 74 m ² / g) manufactured by Tokai Carbon Co., Ltd.
Carbon black (2): Carbon black N330 (N ₂ SA: 80 m ² / g) manufactured by Mitsubishi Chemical Corporation
Silane coupling agent: Si75 (bis (3-triethoxysilylpropyl) disulfide) manufactured by Degussa Huls Co., Ltd.
Zinc oxide: Zinc Hana No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Stearic acid “Kashiwa” manufactured by NOF Corporation
Aroma oil: Process X-140 manufactured by Japan Energy Co., Ltd.
Anti-aging agent: Antigen 6C (N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd.
Adhesive resin: SP1068 manufactured by Nippon Shokubai Co., Ltd.
Cured resin: phenolic cured resin “Sumilite Resin PR12686” (cashew oil modified phenolic resin) manufactured by Sumitomo Duretsu
Wax: Sunnock N manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Sulfur: Powder sulfur vulcanization accelerator manufactured by Karuizawa Sulfur Co., Ltd. (1): Noxeller CZ (N-cyclohexyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Co., Ltd.
Vulcanization accelerator (2): Noxeller D (N, N'-diphenylguanidine) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Vulcanization accelerator (3): Noxeller NS (N-tert-butyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

Examples 1-6 and Comparative Examples 1-4
According to the formulation shown in Tables 1 and 2, chemicals other than sulfur and a vulcanization accelerator were kneaded for 4 minutes using a Banbury mixer to obtain a kneaded product. Next, using an open roll, sulfur and a vulcanization accelerator were added to the obtained kneaded product and kneaded for 4 minutes to obtain an unvulcanized rubber composition. Further, the obtained unvulcanized rubber composition was press vulcanized for 12 minutes at 170 ° C. to obtain a vulcanized rubber composition (vulcanized rubber sheet).

The obtained vulcanized rubber sheet was evaluated as follows. The results are shown in Tables 1-2.

(Viscoelasticity test)
The vulcanized rubber sheet was thermally oxidized and deteriorated at 170 ° C. for 12 minutes, and using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd. The loss tangent tan δ of the vulcanized rubber sheet at 30 ° C. was measured, and the low exothermic index of Comparative Example 1 (Table 1) or Comparative Example 3 (Table 2) was set to 100. displayed. In addition, it shows that heat_generation | fever is so small that a low exothermic index | exponent is large and it is excellent in low exothermic property.
(Low exothermic index) = (tan δ of Comparative Example 1 or 3) / (tan δ of each formulation) × 100

(Tensile test)
In accordance with JIS K 6251 “Vulcanized Rubber and Thermoplastic Rubber-Determination of Tensile Properties”, a tensile test was carried out using a No. 3 dumbbell-shaped test piece made of each vulcanized rubber sheet, and the breaking strength (TB) and The elongation at break (EB) was measured and the fracture energy (TB × EB / 2) was calculated. The strength index of Comparative Example 1 (Table 1) or Comparative Example 3 (Table 2) was set to 100, and the breaking energy of each formulation was indicated by an index according to the following calculation formula. In addition, it shows that it is excellent in mechanical strength, so that an intensity | strength index | exponent is large.
(Strength index) = (Fracture energy of each formulation) / (Fracture energy of Comparative Example 1 or 3) × 100

In the examples in which the modified butadiene rubber and silica were used in combination, a rubber composition having high mechanical strength and excellent low heat buildup was obtained. On the other hand, in Comparative Examples 2 and 4 using butadiene rubber (non-modified) instead of the modified butadiene rubber, the mechanical strength was lowered and the low heat build-up was also inferior. Moreover, in Comparative Examples 1 and 3 using butadiene rubber (non-modified) and not containing silica, the low heat build-up was insufficient and the mechanical strength was also inferior.

Claims (3)

10 to 150 parts by mass of silica with respect to 100 parts by mass of the rubber component,
A rubber composition for an insulation or bead apex, wherein the rubber component comprises a butadiene rubber modified with a compound represented by the following formula (1).

(Wherein R ¹ , R ² and R ³ are the same or different and each represents an alkyl group, an alkoxy group, a silyloxy group, an acetal group, a carboxyl group, a mercapto group or a derivative thereof. R ⁴ and R ⁵ are (The same or different, and represents a hydrogen atom or an alkyl group. N represents an integer.) The rubber composition for an insulation or bead apex according to claim 1, wherein the vinyl content of the modified butadiene rubber is 35% by mass or less. A pneumatic tire having an installation and / or a bead apex produced using the rubber composition according to claim 1.