JP5555599B2 - Rubber composition for tire and pneumatic tire - Google Patents

Description

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

In recent years, due to environmental problems such as global warming, social demands for lower fuel consumption have increased, and development of fuel-efficient tires with reduced rolling resistance has been demanded in response to lower fuel consumption of automobiles. As a method for reducing the rolling resistance of a tire, in terms of materials, a method of substituting carbon black with silica and a method of reducing a filler such as carbon black or silica are known. On the other hand, in terms of the tire structure, a technique for reducing the thickness of the rubber material is known.

Silica can be used in combination with various coupling agents to bond the silica surface and the rubber polymer chain to reinforce the rubber. As a method for enhancing the interaction between silica and the rubber polymer chain, a technique for modifying the polymer chain is known, whereby the rolling resistance of the tire can be further reduced.

Although the rolling resistance characteristics can be improved by the above method, the steering stability of the tire tends to deteriorate. In addition, silica has lower reinforcement and dispersibility than carbon black, so replacing carbon black with silica tends to deteriorate durability (rubber strength, bending fatigue resistance, etc.) and kneadability. there were.

Patent Document 1 discloses a rubber composition in which sepiolite is blended as a sulfur adsorbent. However, the use of sepiolite as a filler, dispersibility of sepiolite, interaction with polymer chains, and the like are described in detail. It was not examined.

Japanese Examined Patent Publication No. 4-61020

The present invention solves the above-mentioned problems, and uses a rubber composition for tires that can improve the rolling resistance characteristics, steering stability, durability (particularly rubber strength, bending fatigue resistance) and kneading workability in a well-balanced manner. An object of the present invention is to provide a pneumatic tire.

（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。）で表される化合物により変性されたジエン系ゴムとを含むタイヤ用ゴム組成物に関する。 The present invention contains a rubber component and rod-like silica having an average width of 3 to 35 nm and an average length of 50 nm to 5 μm. The rubber component is natural rubber and 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 present invention relates to a rubber composition for tires comprising a diene rubber modified with a compound represented by the same or different and each represents a hydrogen atom or an alkyl group, and n represents an integer.

It is preferable that the content of the rod-shaped silica with respect to 100 parts by mass of the rubber component is 2 to 50 parts by mass.

It is preferable to contain 5-100 mass parts silica with respect to 100 mass parts of said rubber components.

The rod-like silica is preferably obtained by defibrating sepiolite mineral.

The rubber composition is preferably a tire cord covering rubber composition.

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

According to the present invention, since the rubber component is a tire rubber composition containing a rubber component and a specific rod-like silica, and the rubber component includes a natural rubber and a diene rubber modified with a specific compound, It is possible to provide a pneumatic tire that is excellent in resistance characteristics, steering stability and durability, and easy to manufacture.

It is a schematic diagram which shows schematic structure of rod-shaped silica (sepiolite).

（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（好ましくは炭素数１〜８、より好ましくは炭素数１〜６、更に好ましくは炭素数１〜４のアルコキシ基）、シリルオキシ基、アセタール基、カルボキシル基（−ＣＯＯＨ）、メルカプト基（−ＳＨ）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（好ましくは炭素数１〜４のアルキル基）を表す。ｎは整数（好ましくは１〜５、より好ましくは２〜４、更に好ましくは３）を表す。）で表される化合物により変性されたジエン系ゴム（変性ジエン系ゴム）とを含む。 The rubber composition for tires of the present invention contains a rubber component and specific rod-like silica, and the rubber component contains natural rubber (NR) and the following formula (1);

(In formula, R < ¹ >, R < ² > and R < ³ > are the same or different, and are an alkyl group and an alkoxy group (preferably C1-C8, More preferably C1-C6, More preferably C1-C4 An alkoxy group), a silyloxy group, an acetal group, a carboxyl group (—COOH), a mercapto group (—SH), or a derivative thereof, and R ⁴ and R ⁵ are the same or different and represent a hydrogen atom or an alkyl group (preferably Represents an alkyl group having 1 to 4 carbon atoms, and n represents an integer (preferably 1 to 5, more preferably 2 to 4, more preferably 3). Rubber (modified diene rubber).

Examples of the compound represented by the above formula (1) include those described in JP 2010-111753 A. R ¹ , R ² and R ³ are preferably alkoxy groups, and R ⁴ and R ⁵ are preferably alkyl groups from the viewpoint that the effects of the present invention can be obtained satisfactorily.

Specific examples of the compound represented by the above formula (1) include 3-aminopropyldimethylmethoxysilane, 3-aminopropylmethyldimethoxysilane, 2-dimethylaminoethyltrimethoxysilane and the like. These may be used alone or in combination of two or more.

Examples of the method for modifying the diene rubber with the compound represented by the above formula (1) (modifier) include conventionally known methods such as the methods described in JP-B-6-53768 and JP-B-6-57767. Can be used.

Examples of the diene rubber modified with the compound represented by the above formula (1) include isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR ), Butyl rubber (IIR), styrene-isoprene-butadiene copolymer rubber (SIBR), and the like. Among these, BR and SBR are preferable, and BR is more preferable from the viewpoint of high bending fatigue resistance.

The amount of bound styrene of the SBR modified with the compound represented by the above formula (1) is preferably 45% by mass or less, more preferably 40% by mass or less. If it exceeds 45 mass%, the glass transition temperature (Tg) becomes too high, the hysteresis loss increases, and the rolling resistance characteristics tend to deteriorate. The amount of bound styrene is preferably 5% by mass or more, more preferably 15% by mass or more. If it is less than 5% by mass, the effect of blending SBR cannot be obtained sufficiently, the modulus (elastic modulus) tends to decrease, and the steering stability tends to deteriorate.

The weight average molecular weight (Mw) of the modified diene rubber is preferably 100,000 or more, more preferably 200,000 or more. If it is less than 100,000, the rubber strength and wear resistance tend to deteriorate. The Mw is preferably 2 million or less, more preferably 1 million or less. If it exceeds 2 million, the kneading processability deteriorates, causing poor dispersion such as rod-like silica, and the rubber strength tends to deteriorate. In addition, hysteresis loss increases and rolling resistance characteristics tend to deteriorate.
In addition, a weight average molecular weight (Mw) is the value measured by the method as described in the below-mentioned Example.

The content of the modified diene rubber in 100% by mass of the rubber component is preferably 15% by mass or more, more preferably 30% by mass or more. If the amount is less than 15% by mass, the improvement effect by the modified diene rubber tends to be insufficient. The content of the modified diene rubber is preferably 90% by mass or less, more preferably 70% by mass or less, and still more preferably 50% by mass or less. When it exceeds 90 mass%, there is a tendency that sufficient rubber strength cannot be obtained. Further, the rubber is not well packed at the time of kneading and tends to deteriorate the productivity.

The rubber composition of the present invention contains natural rubber (NR) as a rubber component together with a modified diene rubber. As NR, those generally used in the tire industry such as SIR20, RSS # 3, and TSR20 can be used. NR includes deproteinized natural rubber (DPNR) and high-purity natural rubber (HPNR). In addition, modified natural rubber such as epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber may be used.

The content of NR of 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 30% by mass or more, and still more preferably 50% by mass or more. If it is less than 10% by mass, rubber strength and kneading workability tend to deteriorate. The NR content is preferably 90% by mass or less, more preferably 80% by mass or less. If it exceeds 90% by mass, the heat-resistant deterioration characteristics are lowered, and the rubber strength after heat deterioration tends to deteriorate.

In the present invention, a specific rod-like silica is used.
Unlike ordinary silica having a spherical shape, rod-shaped silica is an inorganic material (silica) having a rod-like or needle-like shape and having a silanol group on the surface thereof. Examples of the rod-like silica include sepiolite, palygorskite, attapulgite, sirotile, rafrinite, falconite, imogolite and the like. Of these, sepiolite and attapulgite are preferred because they have few impurities and many silanol groups. In this specification, when it is simply described as silica, it means spherical silica unless otherwise specified.

Silanol groups are present on the surface of the rod-like silica. Therefore, by mix | blending a silane coupling agent, a rubber molecule and rod-shaped silica can be couple | bonded through a silane coupling agent, and the effect which mix | blended rod-shaped silica can fully be acquired. Further, by blending the modified diene rubber, a strong interaction can be directly formed between the modified diene rubber and the rod-like silica. Therefore, the effect of blending rod-like silica can be obtained more sufficiently.

Rod-like silica, can be suitably used those obtained by fibrillating sepiolite mineral is fibrous material _{[Mg 8 Si 12 O 30 (} OH) 4 (H 2 O) 4 · 8 (H 2 O)] . The structure of sepiolite mineral is formed by connecting three Si-O tetrahedrons to form a Si-O tetrahedral ribbon parallel to the fiber direction. The ribbons are connected by octahedrally coordinated magnesium ions and resemble a talc structure. Form a 2: 1 mold. These adhere to each other to form a fiber bundle, which can form an aggregate.

The agglomerates can be broken (defibrated) by industrial processes such as pulverization (grinding) or chemical modification (see for example EP 170299), whereby fibers of nanometer diameter, That is, exfoliated (defibrated) rod-like silica (sepiolite) can be produced. In the present invention, the method for defibrating sepiolite minerals is not particularly limited, but it is preferable to defibrate without substantially breaking the shape of rod-like silica (sepiolite) as a fiber. Examples of such a defibrating method include a wet pulverization method (for example, a method described in European Patent No. 170299, Japanese Patent Laid-Open No. 5-97488, European Patent No. 85200094-4, etc.) and the like. .

An example of the wet pulverization method will be specifically described. First, rod-shaped silica (sepiolite) containing water is pulverized to a particle size of 2 mm or less. After pulverization, water is added so that the solid content concentration of the suspension is 5 to 25%, and then a dispersant (for example, an alkali salt of hexametaphosphate) is added. The suspension is then stirred for 5-15 minutes using a stirrer with high shear. At the time of stirring, the mixture is first stirred at a low speed for 2 to 7 minutes, and then at a high speed for 2 to 8 minutes. Next, by separating the supernatant by decantation or centrifugation, rod-shaped silica (sepiolite) that has been defibrated without substantially breaking the shape as a fiber can be obtained.

The sepiolite in the present invention is a concept including attapulgite (also known as palygorskite). Attapulgite is structurally and chemically almost identical to sepiolite, except that the unit cell of attapulgite is slightly smaller (fiber length is shorter).

The average width of the rod-like silica is 3 nm or more, preferably 5 nm or more. If it is less than 3 nm, the surface area tends to be large, and the dispersion into rubber tends to be poor. The average width of the rod-like silica is 35 nm or less, preferably 30 nm or less. If it exceeds 35 nm, the aspect ratio tends to be small, and sufficient rolling resistance characteristics tend not to be obtained.

The average length of the rod-like silica is 50 nm or more, preferably 100 nm or more, more preferably 300 nm or more. If it is less than 50 nm, the aspect ratio tends to be small, and sufficient rolling resistance characteristics tend not to be obtained. The average length of the rod-like silica is 5 μm or less, preferably 3 μm or less, more preferably 2 μm or less. When it exceeds 5 μm, it becomes a starting point of destruction, so that the rubber strength tends to deteriorate.

The aspect ratio (average length / average width) of the rod-like silica is preferably 2 or more, more preferably 5 or more. If it is less than 2, sufficient rolling resistance characteristics tend not to be obtained. The upper limit of the aspect ratio of the rod-like silica is not particularly limited, and it is preferably as large as possible within the range of the above shape.

FIG. 1 is a schematic diagram showing a schematic structure of rod-like silica (sepiolite). As shown in FIG. 1, rod-like silica (sepiolite) has a needle shape or a long fiber shape (rod shape). The width, thickness, and length of sepiolite correspond to X, Y, and Z in FIG. In other words, the sepiolite width (X) is the length of the short side of the main surface (the surface having the largest area when viewed in plan), and the sepiolite thickness (Y) is the normal to the main surface. It is the length in the direction, and the sepiolite length (Z) is the length of the long side of the main surface.

In the present specification, the average width of the rod-shaped silica is an average value of X of the rod-shaped silica measured by a transmission electron microscope (for example, an average value calculated by measuring X of 100 rod-shaped silica). In the present specification, the average length of the rod-shaped silica is an average value of Z of the rod-shaped silica measured by a transmission electron microscope (for example, an average value calculated by measuring Z of 100 rod-shaped silica). .

The content of the rod-like silica is preferably 2 parts by mass or more, more preferably 5 parts by mass or more, and further preferably 10 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 2 parts by mass, the effect of blending rod-like silica may not be sufficiently obtained. Further, the content of the rod-like silica is preferably 50 parts by mass or less, more preferably 30 parts by mass or less. If it exceeds 50 parts by mass, the kneading processability tends to deteriorate.

In the present invention, silica (spherical silica) is preferably blended. Thereby, the effect of this invention is acquired favorably. The silica is not particularly limited, and examples thereof include dry process silica (anhydrous silicic acid), wet process silica (hydrous silicic acid), and the like, but wet process silica is preferable because of its large number of silanol groups. Silica may be used alone or in combination of two or more.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 50 m ² / g or more, more preferably 80 m ² / g or more. If it is less than 50 m ² / g, the reinforcing effect is small and the durability tends to deteriorate. The N ₂ SA of silica is preferably 300 m ² / g or less, more preferably 250 m ² / g or less. When it exceeds 300 m ² / g, dispersibility is poor, hysteresis loss increases, and rolling resistance characteristics tend to deteriorate.
The _N 2 SA of silica is a value measured by the BET method in accordance with ASTM D3037-81.

The content of silica 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 durability tends not to be obtained. The content of silica is preferably 100 parts by mass or less, more preferably 70 parts by mass or less, and still more preferably 50 parts by mass or less. If it exceeds 100 parts by mass, kneading workability tends to deteriorate.

The total content of the rod-like silica and silica is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, and further preferably 50 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 10 parts by mass, sufficient durability tends not to be obtained. The total content is preferably 150 parts by mass or less, more preferably 100 parts by mass or less, and still more preferably 80 parts by mass or less. If it exceeds 150 parts by mass, the kneadability tends to deteriorate.

The rubber composition of the present invention preferably contains a silane coupling agent together with rod-like silica and silica.
Examples of the silane coupling agent include bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, and bis (2-triethoxy). Silylethyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyl Trimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N, N-dimethylthiocarb Moyl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilyl Propyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis (3-diethoxymethylsilylpropyl) tetrasulfide, dimethoxymethylsilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, dimethoxymethylsilylpropylbenzothiazole tetra Sulfide silane coupling agents such as sulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylto Triethoxysilane, 2-mercaptoethyl trimethoxysilane, 2-mercaptoethyl triethoxysilane, and mercapto-type silane coupling agents such as 3-mercaptopropyl dimethoxymethyl silane and the like. Among them, bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide, and mercapto-based silane are preferred because they have good processability and high dispersibility of rod-like silica and silica. Coupling agent is preferable, and combined use of bis (3-triethoxysilylpropyl) tetrasulfide or bis (3-triethoxysilylpropyl) disulfide with other silane coupling agents (preferably mercapto silane coupling agents) is more preferable. preferable.

（式中、ｘ、ｙはそれぞれ１以上の整数である。Ｒ^６は水素、ハロゲン、分岐若しくは非分岐の炭素数１〜３０のアルキル基若しくはアルキレン基、分岐若しくは非分岐の炭素数２〜３０のアルケニル基若しくはアルケニレン基、分岐若しくは非分岐の炭素数２〜３０のアルキニル基若しくはアルキニレン基、又は該アルキル基若しくは該アルケニル基の末端が水酸基若しくはカルボキシル基で置換されたものを示す。Ｒ^７は水素、分岐若しくは非分岐の炭素数１〜３０のアルキレン基若しくはアルキル基、分岐若しくは非分岐の炭素数２〜３０のアルケニレン基若しくはアルケニル基、又は分岐若しくは非分岐の炭素数２〜３０のアルキニレン基若しくはアルキニル基を示す。Ｒ^６とＲ^７とで環構造を形成してもよい。） As a mercapto-based silane coupling agent, the bonding unit A represented by the following general formula (2) and the following general formula (2) can be obtained from the point that the effect of improving rolling resistance characteristics and durability is great and good workability is obtained. What copolymerized the coupling | bonding unit B in the ratio of 1-70 mol% with respect to the total amount with the coupling | bonding unit B shown by 3) is preferable.

(Wherein, x and y are each an integer of 1 or more. R ⁶ is hydrogen, halogen, branched or unbranched C 1-30 alkyl group or alkylene group, branched or unbranched C 2-30 alkenyl or alkenylene group, a branched or unbranched alkynyl or alkynylene group having 2 to 30 carbon atoms, or .R ⁷ showing a the end of the alkyl or alkenyl group is replaced with a hydroxy or carboxyl group Hydrogen, branched or unbranched alkylene group or alkyl group having 1 to 30 carbon atoms, branched or unbranched alkenylene group or alkenyl group having 2 to 30 carbon atoms, or branched or unbranched alkynylene group having 2 to 30 carbon atoms Alternatively, it represents an alkynyl group, and R ⁶ and R ⁷ may form a ring structure.)

The silane coupling agent having the above structure has an increased viscosity during processing as compared with polysulfide silanes such as bis- (3-triethoxysilylpropyl) tetrasulfide because the molar ratio of the bond unit A to the bond unit B satisfies the above conditions. Is suppressed. This is presumably because the increase in Mooney viscosity is small because the sulfide portion of the bond unit A is a C—S—C bond and is thermally stable compared to tetrasulfide and disulfide.

Moreover, when the molar ratio of the bond unit A and the bond unit B satisfies the above conditions, the shortening of the scorch time is suppressed as compared with mercaptosilane such as 3-mercaptopropyltrimethoxysilane. This is because the bonding unit B has a structure of mercaptosilane, but the —C ₇ H ₁₅ part of the bonding unit A covers the —SH group of the bonding unit B, so that it does not easily react with the polymer and scorch is less likely to occur. This is probably because of this.

Examples of the halogen for R ⁶ include chlorine, bromine, and fluorine.

Examples of the branched or unbranched alkyl group having 1 to 30 carbon atoms of R ⁶ and R ⁷ include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an iso-butyl group, and a sec-butyl group. Tert-butyl group, pentyl group, hexyl group, heptyl group, 2-ethylhexyl group, octyl group, nonyl group, decyl group and the like. The number of carbon atoms of the alkyl group is preferably 1-12.

Examples of the branched or unbranched alkylene group having 1 to 30 carbon atoms of R ⁶ and R ⁷ include ethylene group, propylene group, butylene group, pentylene group, hexylene group, heptylene group, octylene group, nonylene group, decylene group, Examples include an undecylene group, a dodecylene group, a tridecylene group, a tetradecylene group, a pentadecylene group, a hexadecylene group, a heptadecylene group, and an octadecylene group. The alkylene group preferably has 1 to 12 carbon atoms.

Examples of the branched or unbranched alkenyl group having 2 to 30 carbon atoms represented by R ⁶ and R ⁷ include a vinyl group, 1-propenyl group, 2-propenyl group, 1-butenyl group, 2-butenyl group, 1-pentenyl group, 2-pentenyl group, 1-hexenyl group, 2-hexenyl group, 1-octenyl group and the like can be mentioned. The alkenyl group preferably has 2 to 12 carbon atoms.

Examples of the branched or unbranched C 2-30 alkenylene group of R ⁶ and R ⁷ include vinylene group, 1-propenylene group, 2-propenylene group, 1-butenylene group, 2-butenylene group, 1-pentenylene group, 2-pentenylene group, 1-hexenylene group, 2-hexenylene group, 1-octenylene group and the like can be mentioned. The alkenylene group preferably has 2 to 12 carbon atoms.

Examples of the branched or unbranched alkynyl group having 2 to 30 carbon atoms represented by R ⁶ and R ⁷ include ethynyl group, propynyl group, butynyl group, pentynyl group, hexynyl group, heptynyl group, octynyl group, noninyl group, decynyl group, An undecynyl group, a dodecynyl group, etc. are mentioned. The alkynyl group preferably has 2 to 12 carbon atoms.

Examples of the branched or unbranched C2-C30 alkynylene group of R ⁶ and R ⁷ include an ethynylene group, a propynylene group, a butynylene group, a pentynylene group, a hexynylene group, a heptynylene group, an octynylene group, a noninylene group, a decynylene group, An undecynylene group, a dodecynylene group, etc. are mentioned. The alkynylene group preferably has 2 to 12 carbon atoms.

In the silane coupling agent having the above structure, the total repeating number (x + y) of the repeating number (x) of the bonding unit A and the repeating number (y) of the bonding unit B is preferably in the range of 3 to 300. Within this range, since the mercaptosilane of the bond unit B is covered by —C ₇ H ₁₅ of the bond unit A, it is possible to suppress the scorch time from being shortened and to have good reactivity with silica and rubber components. Can be secured.

As the silane coupling agent having the above structure, for example, NXT-Z30, NXT-Z45, NXT-Z60 manufactured by Momentive, etc. can be used.

The content of the silane coupling agent is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, with respect to 100 parts by mass of the total content of rod-like silica and silica. If it is less than 3 parts by mass, the rod-like silica and silica cannot be sufficiently dispersed, and the rolling resistance characteristics and rubber strength may be deteriorated. Further, the content of the silane coupling agent is preferably 15 parts by mass or less, more preferably 10 parts by mass or less. When it exceeds 15 parts by mass, an excess silane coupling agent remains, which may cause deterioration of kneading processability and rubber strength of the resulting rubber composition.

In the rubber composition of the present invention, in addition to the above components, compounding agents generally used in the production of rubber compositions, for example, reinforcing fillers such as carbon black, zinc oxide, stearic acid, various anti-aging agents, Oils, waxes, vulcanizing agents, vulcanization accelerators and the like can be appropriately blended.

In the present invention, it is preferable to blend carbon black. Thereby, the effect of the present invention can be obtained well and the durability can be further improved. Carbon black may be used alone or in combination of two or more.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 50 m ² / g or more, more preferably 70 m ² / g or more. If it is less than 50 m < ² > / g, sufficient reinforcement performance cannot be obtained and there exists a tendency for durability to deteriorate. The N ₂ SA of the carbon black is preferably 280 m ² / g or less, more preferably 250 m ² / g or less, and still more preferably 100 m ² / g or less. If it exceeds 280 m ² / g, the dispersibility tends to be poor, and the rolling resistance characteristics tend to deteriorate.
In addition, the nitrogen adsorption specific surface area of carbon black is a value measured by the A method of JIS K6217.

The content of carbon black is preferably 2 parts by mass or more, more preferably 5 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 2 parts by mass, there is a risk of significant deterioration due to ultraviolet rays. The carbon black content is preferably 50 parts by mass or less, more preferably 20 parts by mass or less. If it exceeds 50 parts by mass, the kneading processability tends to deteriorate. In addition, hysteresis loss increases and rolling resistance characteristics tend to deteriorate.

The rubber composition of the present invention is produced by a general method. That is, it can be produced by a method of kneading the above components with a Banbury mixer, a kneader, an open roll or the like and then vulcanizing. The rubber composition can be used for each member of a tire, and in particular, can be suitably used as a rubber composition for covering a tire cord of a member having a tire cord such as a belt or a carcass.

The pneumatic tire of the present invention is produced by a usual method using the rubber composition. That is, a tire cord is coated with an unvulcanized rubber composition containing the above components to form a ply for use in a belt or carcass, and then the ply and another tire member are bonded together to form an unvulcanized tire. Form. The unvulcanized tire is heated and pressurized in a vulcanizer to obtain a tire.

The pneumatic tire of the present invention is preferably used as a tire for passenger cars, a tire for trucks and buses, a tire for motorcycles, a tire for competition, and the like, and more preferably used as a tire for passenger cars.

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 the production examples will be described together.
n-hexane: n-hexane cyclohexane manufactured by Kanto Chemical Co., Ltd .: cyclohexane styrene manufactured by Kanto Chemical Co., Ltd .: styrene 1,3-butadiene manufactured by Kanto Chemical Co., Ltd .: 1, manufactured by Tokyo Chemical Industry Co., Ltd. 3-butadiene p-methoxystyrene: p-methoxystyrene tetramethylethylenediamine manufactured by Tokyo Chemical Industry Co., Ltd .: tetramethylethylenediamine n-butyllithium manufactured by Kanto Chemical Co., Ltd .: 1.6M n manufactured by Kanto Chemical Co., Ltd. -Butyllithium hexane solution modifier: 3- (N, N-dimethylaminopropyl) trimethoxysilane manufactured by AMAX Co. (in formula (1), R ¹ , R ² and R ³ = methoxy group, R ⁴ and R ⁵ = Methyl group, n = 3)
2,6-tert-butyl-p-cresol: NOCRACK 200 manufactured by Ouchi Shinsei Chemical Co., Ltd.

Analysis of the polymer obtained in the production example was performed by the following method.

(Measurement of weight average molecular weight (Mw))
Mw is converted to standard polystyrene using a gel permeation chromatograph (GPC) (GPC-8000 series, manufactured by Tosoh Corporation), detector: differential refractometer, column: TSKGELSUPERMALTPOREHZ-M manufactured by Tosoh Corporation. It was measured.

(Measurement of bound styrene content)
The amount of bound styrene was measured using NMR.

(Production Example 1)
Add 1500 ml of n-hexane, 100 mmol of styrene, 800 mmol of 1,3-butadiene, 5 mmol of p-methoxystyrene, 0.2 mmol of tetramethylethylenediamine, and 0.12 mmol of n-butyllithium to a pressure-resistant container sufficiently purged with nitrogen at 50 ° C. Stir for 48 hours. Thereafter, 0.12 mmol of a modifier was added to stop the reaction, 1 g of 2,6-tert-butyl-p-cresol was added to the reaction solution, and then polymer 1 (modified SBR) was obtained by reprecipitation purification. The Mw of the polymer 1 was 490000 and the amount of bound styrene was 19% by mass.

(Production Example 2)
Into a pressure vessel sufficiently substituted with nitrogen, 1500 ml of cyclohexane, 900 mmol of 1,3-butadiene, 0.2 mmol of tetramethylethylenediamine, and 0.12 mmol of n-butyllithium were added and stirred at 40 ° C. for 48 hours. Thereafter, 0.12 mmol of a modifier was added to stop the reaction, and 1 g of 2,6-tert-butyl-p-cresol was added to the reaction solution, and then polymer 2 (modified BR) was obtained by reprecipitation purification. The Mw of the polymer 2 was 460000.

Hereinafter, various chemicals used in Examples and Comparative Examples will be described together.
NR: TSR20
Modified SBR: Polymer 1 above
BR: BR150B manufactured by Ube Industries, Ltd.
Modified BR: Polymer 2 above
Rod-like silica 1: PANGEL AD manufactured by TOLSA (length: 200 to 2000 nm, width: 5 to 30 nm, wet pulverized product of sepiolite mineral)
Rod-like silica 2: PANSIL manufactured by TOLSA (length: 200 to 5000 nm, width: 5 to 30 nm, dry pulverized product of sepiolite mineral)
Carbon black: Show Black N330 manufactured by Cabot Japan Co., Ltd. (nitrogen adsorption specific surface area: 75 m ² / g)
Silica: ULTRASIL VN3 manufactured by Degussa (nitrogen adsorption specific surface area: 175 m ² / g)
Silane coupling agent 1: Si75 (bis (3-triethoxysilylpropyl) disulfide) manufactured by Degussa
Silane coupling agent 2: NXT-Z45 manufactured by Momentive (copolymer of bonding unit A and bonding unit B, bonding unit A: 55 mol%, bonding unit B: 45 mol%)
Aroma oil: Process X-140 manufactured by Japan Energy Co., Ltd.
Anti-aging agent: Santoflex 13 manufactured by Flexis
Stearic acid: Stearic acid “椿” manufactured by NOF Corporation
Zinc oxide: Zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powdered sulfur vulcanization accelerator manufactured by Tsurumi Chemical Co., Ltd .: Noxera NS, manufactured by Ouchi Shinsei Chemical Co., Ltd.

Examples and Comparative Examples According to the formulation shown in Table 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. The obtained unvulcanized rubber composition was press vulcanized at 170 ° C. for 12 minutes to obtain a vulcanized rubber sheet.
The unvulcanized rubber composition processed into a sheet having a thickness of about 1 mm was pressure-bonded to the top and bottom of the ply cord array shown in Table 1 to obtain a carcass ply. The obtained carcass ply is bonded to another tire member to produce an unvulcanized tire, and vulcanized at 150 ° C., 35 minutes, 25 kgf to obtain a test tire (size: 195 / 65R15). It was.

The following evaluation was performed using the unvulcanized rubber composition, the vulcanized rubber sheet, and the test tire. The results are shown in Table 2.

(Kneading workability index)
According to JIS K6300, the Mooney viscosity of the unvulcanized rubber composition was measured at 130 ° C., and the measurement result was indicated by an index using the following formula. The larger the index, the lower the Mooney viscosity and the better the kneading processability. If the index is 95 or more, there is no problem.
(Kneading workability index) = (Mooney viscosity of Comparative Example 1) / (Mooney viscosity of each formulation) × 100

(Rubber strength index)
A tensile test was performed according to JIS K6251 to measure the elongation at break of the vulcanized rubber sheet, and the measurement result was indicated by an index using the following formula. The larger the index, the higher the rubber strength and the better the durability. If the index is 95 or more, there is no problem.
(Rubber strength index) = (breaking elongation of each compound) / (breaking elongation of Comparative Example 1) × 100

(Low heat generation performance index)
Using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd., the loss tangent tan δ of the vulcanized rubber sheet at 70 ° C. was measured under the conditions of a frequency of 10 Hz, an initial strain of 10% and a dynamic strain of 2%. Was expressed as an index by the following formula. A larger index indicates less heat generation and better rolling resistance characteristics. If the index is 95 or more, there is no problem.
(Low heat generation performance index) = (tan δ of Comparative Example 1) / (tan δ of each formulation) × 100

(Bending fatigue resistance index)
The bending fatigue resistance of the vulcanized rubber sheet was evaluated using a constant stress / constant strain fatigue tester (FT-3100) manufactured by Ueshima Seisakusho Co., Ltd. in accordance with the method of ISO6943. The test piece of dumbbell No. 3 composed of the vulcanized rubber sheet was repeatedly applied with 1 Hz, 30% strain, the number of times until the test piece was broken was measured, and the measurement result was indicated by an index using the following formula. . The larger the index, the higher the bending fatigue resistance and the better the durability. If the index is 95 or more, there is no problem.
(Bending fatigue resistance index) = (Number of times of each blending) / (Number of times of Comparative Example 1) × 100

(Maneuvering stability)
Prototype tires were mounted on all domestic FF2000cc wheels, and the vehicle was run on a test course. The driver's sensory evaluation evaluated steering stability. The evaluation was performed with a maximum of 10 points, with Comparative Example 1 being 6 points, and the driver judged that the performance was clearly improved was 6.5 points or more, which was not seen at all in the same class / size tires so far The score of 7.5 or higher was assigned.

From Table 2, Examples containing NR, a modified diene rubber modified with the compound of the above formula (1), and a specific rod-like silica have rolling resistance characteristics, steering stability, Durability and kneading processability were improved in a well-balanced manner.

Claims (5)

Containing a rubber component and rod-like silica having an average width of 3 to 35 nm and an average length of 50 nm to 5 μm,
The rubber component is natural rubber and 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 A rubber composition for covering a tire cord , comprising a diene rubber modified with a compound represented by: a hydrogen atom or an alkyl group, which are the same or different and each represents a hydrogen atom or an alkyl group. 2. The rubber composition for covering a tire cord according to claim 1, wherein the content of the rod-like silica with respect to 100 parts by mass of the rubber component is 2 to 50 parts by mass. The rubber composition for covering a tire cord according to claim 1 or 2, comprising 5 to 100 parts by mass of silica with respect to 100 parts by mass of the rubber component. The rubber composition for covering a tire cord according to any one of claims 1 to 3, wherein the rod-like silica is obtained by defibrating a sepiolite mineral. A pneumatic tire using the rubber composition according to any one of claims 1-4.

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