JP2012144619A - Method for producing rubber composition for tire, and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a rubber composition for tires, by which kneadability, rolling resistance and durability (in particular, rubber strength, bending fatigue resistance) are improved in a well-balanced manner, and to provide the rubber composition for tires and pneumatic tires using the composition.SOLUTION: The method for producing a rubber composition for tires includes: a step 1 of kneading a rubber component, rod-like silica having an average width of 3-35 nm and an average length of 5 nm to 5 μm, and a silane coupling agent; a step 2 of kneading a kneaded material 1 obtained in the step 1, silica and a silane coupling agent; and a step 3 of kneading the kneaded material 2 obtained in the step 2 and a vulcanization accelerator.

Description

The present invention relates to a method for producing a tire rubber composition, a tire rubber composition, 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. Methods for reducing the rolling resistance of tires include replacing carbon black with silica, reducing the amount of filler such as carbon black and silica, and modifying the polymer chain of the diene rubber to change the silica and rubber polymer chain. Techniques for enhancing interaction are known.

Although the rolling resistance characteristics can be improved by the above method, silica is inferior in reinforcement and dispersibility compared to carbon black, so durability (rubber strength, bending fatigue resistance, etc.) and kneading workability tend to deteriorate. is there.

On the other hand, Patent Document 1 discloses a rubber composition containing sepiolite as a sulfur adsorbent. However, a method for producing a rubber composition that efficiently exhibits the effect of sepiolite as a filler is examined in detail. Was not.

Japanese Examined Patent Publication No. 4-61020

The present invention solves the above-mentioned problems, and provides a method for producing a rubber composition for tires and a rubber composition for tires that can improve kneading processability, rolling resistance characteristics and durability (particularly rubber strength and bending fatigue resistance) in a well-balanced manner. And it aims at providing a pneumatic tire using the same.

As a result of studying the above problems, the present inventors have prepared a master batch by kneading a rubber component, rod-shaped silica such as sepiolite and a silane coupling agent in advance, so that the coupling reaction between the rod-shaped silica and the rubber component is sufficiently performed. The present inventors have found that a rubber composition advanced to 1 can be produced, and have completed the present invention.

The present invention includes a step 1 for kneading a rubber component, rod-like silica having an average width of 3 to 35 nm and an average length of 50 nm to 5 μm, and a silane coupling agent, a kneaded product 1 obtained in the above step 1, silica and a silane coupling The present invention relates to a method for producing a rubber composition for a tire, comprising a step 2 for kneading an agent, and a step 3 for kneading a kneaded product 2 obtained in step 2 and a vulcanization accelerator.

The compounding amount of the silane coupling agent in step 1 is 3 to 15 parts by mass with respect to 100 parts by mass of the rod-like silica compounded in step 1, and the compounding amount of the silane coupling agent in step 2 is in step 2. It is preferable that it is 3-15 mass parts with respect to 100 mass parts of silica mix | blended.

The rubber component preferably contains natural rubber and / or diene synthetic rubber.

In step 1, silica is further kneaded, and the silica content in step 1 is preferably 1 to 30% by mass with respect to 100% by mass of the total silica used for the production of the rubber composition.

（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を含むことが好ましい。 The rubber component is

(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 It is the same or different and represents a hydrogen atom or an alkyl group. N represents an integer.) It is preferable to include a diene rubber modified with a compound represented by:

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

The present invention also relates to a tire rubber composition obtained by the above production method. Here, it is preferable that the content of the rod-like silica is 2 to 50 parts by mass and the content of the silica is 5 to 100 parts by mass with respect to 100 parts by mass of the rubber component.

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

According to the present invention, the step 1 of kneading the rubber component, the specific rod-like silica and the silane coupling agent, the kneaded product 1 obtained in the step 1, the step 2 of kneading the silica and the silane coupling agent, Since it is a manufacturing method of the rubber composition for tires including the kneaded material 2 obtained in the step 2 and the step 3 for kneading the vulcanization accelerator, kneadability, rolling resistance characteristics and durability (particularly rubber strength, Bending fatigue resistance) can be improved in a well-balanced manner.

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

The method for producing a rubber composition for tires of the present invention was obtained in Step 1 of kneading a rubber component, rod-like silica having an average width of 3 to 35 nm and an average length of 50 nm to 5 μm and a silane coupling agent, and the Step 1 above. A kneaded product 1 (master batch), a step 2 for kneading silica and a silane coupling agent, and a step 3 for kneading the kneaded product 2 obtained in step 2 and a vulcanization accelerator are included.

Since the amount of silanol groups in rod-like silica such as sepiolite is less than ordinary silica, kneading rod-like silica and silica at the same time causes the silane coupling agent to preferentially react with silica, resulting in insufficient reaction with rod-like silica. . On the other hand, the present invention is a production method for preparing a master batch in which a rubber component, rod-like silica and a silane coupling agent are kneaded in advance and the coupling reaction has sufficiently progressed. Is obtained. Therefore, a reinforcing effect and a low heat generation effect are effectively exhibited, and rolling resistance characteristics and durability (particularly rubber strength and bending fatigue resistance) can be improved in a well-balanced manner. It is also excellent in kneading processability.

(Process 1)
In step 1, a rubber component, rod-like silica having an average width of 3 to 35 nm and an average length of 50 nm to 5 μm and a silane coupling agent are kneaded.

（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（−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を表す。ｎは整数を表す。 The rubber component usually contains natural rubber (NR) and / or diene synthetic rubber. Diene-based synthetic rubbers include isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), and styrene-isoprene-butadiene. Examples thereof include polymer rubber (SIBR) and diene rubber (modified diene rubber) modified with a compound represented by the following formula (1). These may be used alone or in combination of two or more. Among them, NR is preferable because kneading processability, rolling resistance characteristics and durability (particularly rubber strength and bending fatigue resistance) are obtained in a well-balanced manner, and BR is preferable and preferable because bending fatigue resistance is high. SBR is preferred because it provides excellent processability. In addition, a diene rubber (modified diene rubber) modified with a compound represented by the following formula (1) is preferable because the effect of blending the rod-shaped silica can be sufficiently obtained.

(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 (—COOH), a mercapto group (—SH) or a derivative thereof. R ⁴ and R ⁵ are the same or different and each represents a hydrogen atom or an alkyl group, and n represents an integer.

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 each an alkoxy group (preferably having 1 to 8 carbon atoms, more preferably 1 to 1 carbon atoms) because rod-like silica can be well dispersed and excellent rolling resistance characteristics and rubber strength can be obtained. 6, more preferably an alkoxy group having 1 to 4 carbon atoms), and R ⁴ and R ⁵ are preferably alkyl groups (preferably alkyl groups having 1 to 4 carbon atoms). n is preferably 1 to 5, more preferably 2 to 4, and still more preferably 3.

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.

The diene rubber modified with the compound represented by the above formula (1) is not particularly limited, and examples thereof include the diene rubber. Of these, BR is preferable for the purpose of improving bending fatigue resistance.

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, a weight average molecular weight (Mw) is the value measured by the method as described in the below-mentioned Example.

The blending ratio of the rubber component in Step 1 is preferably 40% by mass or more, more preferably 70% by mass or more, and still more preferably 100% by mass with respect to 100% by mass of the total rubber components used for the production of the rubber composition. . Thereby, the coupling reaction of rod-shaped silica proceeds effectively.

The specific rod-like silica used in the present invention is an inorganic material (silica) having a rod-like or needle-like shape and having a silanol group on its surface, unlike ordinary silica having a spherical shape. 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, rubber molecules and rod-like silica are bonded via a silane coupling agent, and the effect of blending rod-like silica can be sufficiently obtained. In addition, when the modified diene rubber is blended, a strong interaction can be directly formed between the modified diene rubber and the rod-like silica, so that the effect of the blending is further exhibited.

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.). .

An example of the wet pulverization method will be specifically described. First, after pulverizing the rod-like silica (sepiolite) containing water until the particle size is 2 mm or less, water is added so that the solid content concentration of the suspension is 5 to 25%, and then a dispersant (for example, , Hexametaphosphate alkali salt). 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. Subsequently, 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 includes 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-shaped 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 blending ratio of the rod-like silica in Step 1 is preferably 40% by mass or more, more preferably 70% by mass or more, and still more preferably 100% by mass with respect to 100% by mass of the total rod-like silica used for the production of the rubber composition. . Thereby, the coupling reaction of rod-shaped silica proceeds effectively.

In step 1, silica (spherical silica) may be kneaded together with rod-like silica. Although it does not specifically limit as a silica, The thing similar to the process 2 can be used. Here, the compounding ratio of the silica in the step 1 is preferably 1 to 30% by mass, more preferably 1 to 15% by mass with respect to 100% by mass of the total silica used for the production of the rubber composition. When it exceeds 30% by mass, the reaction between the rod-like silica and the silane coupling agent is difficult to proceed, and the effect of improving the rolling resistance characteristic tends to decrease.

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-based silane coupling agents such as sulfide; 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltri Tokishishiran, 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 coupling are preferable because of good processability and high dispersibility of rod-like silica. Agents are preferred.

（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 formula (2) and the following formula (3) can be obtained because the effect of improving rolling resistance characteristics and durability is great and good workability is also obtained. Those obtained by copolymerizing the bonding units B at a ratio of 1 to 70 mol% with respect to the total amount with the bonding units B represented by

(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 undecylene group, dodecylene group, tridecylene group, tetradecylene group, pentadecylene group, hexadecylene group, heptadecylene group, octadecylene group and the like. 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 with —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 the rod-like silica and rubber component. Can be secured.

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

The compounding amount of the silane coupling agent in the step 1 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 rod-like silica compounded in the step 1. Moreover, this compounding quantity becomes like this. Preferably it is 15 mass parts or less, More preferably, it is 12 mass parts or less, More preferably, it is 10 mass parts or less.

When kneading silica in step 1, the amount of the silane coupling agent in step 1 is preferably 3 parts by mass or more, more preferably 100 parts by mass of the total amount of rod-like silica and silica compounded in step 1. Is 5 parts by mass or more. The amount is preferably 15 parts by mass or less, more preferably 12 parts by mass or less, and still more preferably 10 parts by mass or less.

With regard to the blending amount of these silane coupling agents, if the amount is less than the lower limit, the coupling rate of the rod-like silica to the rubber component is low, and there is a possibility that the rolling resistance characteristics and the effect of improving the rubber strength cannot be sufficiently obtained. If the upper limit is exceeded, unreacted silane coupling agent remains and the kneading processability may deteriorate.

The kneading method in step 1 is not particularly limited as long as each component can be kneaded while controlling the temperature. For example, a closed kneader such as a Banbury mixer or a kneader, or an open roll is preferably used. Can do.

The kneading temperature in step 1 is preferably 130 to 170 ° C. If it is lower than 130 ° C., the efficiency of the coupling reaction is poor, and the rolling resistance characteristics and the effect of improving the rubber strength tend not to be sufficiently exhibited. If it exceeds 170 ° C., the workability tends to deteriorate due to a sudden increase in viscosity. The kneading time is preferably 1 to 10 minutes.

In Step 1, components other than the above components may be appropriately blended within a range not impairing the effects of the present invention, or only the above components may be blended.

(Process 2)
In step 2, the kneaded product 1 (masterbatch) obtained in step 1 is mixed with silica and a silane coupling agent.

Examples of the silica include, but are not limited to, dry process silica (anhydrous silicic acid), wet process silica (hydrous silicic acid), and 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, there exists a tendency for a reinforcement effect to be small and for durability to fall. The N ₂ SA is preferably 300 m ² / g or less, more preferably 250 m ² / g or less. When it exceeds 300 m ² / g, the dispersibility is poor, the hysteresis loss increases, and the rolling resistance characteristic tends to be lowered.
The _N 2 SA of silica is a value measured by the BET method in accordance with ASTM D3037-81.

40 mass% or more is preferable, as for the compounding ratio of the silica in process 2, with respect to 100 mass% of all the silica used for manufacture of a rubber composition, 70 mass% or more is more preferable, and 100 mass% is still more preferable. When the blending amount is in the above range, kneading processability, rolling resistance characteristics and durability can be obtained satisfactorily.

As a silane coupling agent mix | blended at the process 2, the thing similar to the silane coupling agent mix | blended with the process 1 is mentioned. Of these, bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide, and mercapto-based silane coupling agents are preferred because of good processability and high silica dispersibility. Is preferred.

In the present invention, it is preferable to use a different silane coupling agent from the viewpoint of kneading processability. For example, the mercapto-based silane coupling agent is blended in Step 1 and bis (3-triethoxy in Step 2 is used. It is preferable to incorporate a sulfide-based silane coupling agent such as silylpropyl) tetrasulfide or bis (3-triethoxysilylpropyl) disulfide.

The compounding amount of the silane coupling agent in the step 2 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 silica compounded in the step 2. If it is less than 3 parts by mass, rolling resistance characteristics and rubber strength may be deteriorated. Moreover, this compounding quantity becomes like this. Preferably it is 15 mass parts or less, More preferably, it is 12 mass parts or less, More preferably, it is 10 mass parts or less. If it exceeds 15 parts by mass, unreacted silane coupling agent remains, and the kneading processability may be deteriorated.

In step 2, carbon black is preferably blended. The carbon black has a nitrogen adsorption specific surface area (N ₂ SA) of preferably 30 m ² / g or more, more preferably 60 m ² / g or more. If it is less than 30 m ² / g, sufficient reinforcing performance cannot be obtained, and the rubber strength tends to decrease. The N ₂ SA of the carbon black is preferably 150 m ² / g or less, more preferably 100 m ² / g or less. If it exceeds 150 m ² / g, the dispersibility tends to be inferior, and the rolling resistance characteristics tend to deteriorate.
Incidentally, _N 2 SA of carbon black, JIS K 6217-2: determined by 2001.

As the kneading method in step 2, the same method as in step 1 is preferable, and the same conditions as in step 1 are preferable as the kneading temperature and kneading time.

In Step 2, other than the above components, zinc oxide, stearic acid, various anti-aging agents, oil, and the like can be appropriately blended.

(Process 3)
In step 3, the kneaded product 2 and the vulcanization accelerator obtained in step 2 are kneaded. Examples of the vulcanization accelerator include 2-mercaptobenzothiazole, dibenzothiazyl disulfide, and thiazole vulcanization accelerators such as N-cyclohexyl-2-benzothiazylsulfenamide; tetramethylthiuram monosulfide, tetramethylthiuram disulfide Thiuram vulcanization accelerators such as: N-cyclohexyl-2-benzothiazole sulfenamide, Nt-butyl-2-benzothiazole sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, N- Sulfenamide vulcanization accelerators such as oxyethylene-2-benzothiazole sulfenamide and N, N′-diisopropyl-2-benzothiazole sulfenamide; such as diphenylguanidine, diortolylguanidine, orthotolylbiguanidine Guanidine-based vulcanization accelerators can be mentioned, and the blending amount thereof is preferably 0.1 to 5 parts by weight, more preferably 0.2 to 0.2 parts by weight with respect to 100 parts by weight of the rubber component in the rubber composition to be prepared. 3 parts by mass.

In step 3, sulfur is usually blended. The compounding quantity of sulfur can be selected suitably.

Examples of the kneading method in step 3 include known finishing kneading methods. The kneading temperature and kneading time can be appropriately selected.

(Process 4)
Next, a step 4 of vulcanizing the kneaded product 3 obtained in the step 3 is usually performed. Thereby, a vulcanized rubber composition is obtained.

In the rubber composition obtained by the above production method, the content of NR in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 30% by mass or more, and further preferably 50% by mass or more. . If it is less than 10% by mass, rolling resistance characteristics, rubber strength and kneading workability tend to deteriorate. The content is preferably 90% by mass or less, more preferably 80% by mass or less. If it exceeds 90 mass%, the rubber strength tends to deteriorate.

In the rubber composition, the BR content in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 20% by mass or more. If it is less than 10% by mass, sufficient bending fatigue resistance may not be obtained. The content is preferably 90% by mass or less, more preferably 70% by mass or less. When it exceeds 90% by mass, kneading workability tends to deteriorate.

In the rubber composition, 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 it is less than 15% by mass, the effect of blending the modified diene rubber tends to be small. The content is preferably 90% by mass or less, more preferably 70% by mass or less. If it exceeds 90% by mass, the rubber strength and kneading processability tend to decrease.

In the rubber composition, 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 rubber composition, 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 50 parts by mass or less. If it exceeds 100 parts by mass, kneading workability tends to deteriorate.

In the rubber composition, the total content of rod-like silica and silica is preferably 10 parts by mass or more, and more preferably 40 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. If it exceeds 150 parts by mass, the kneadability tends to deteriorate.

In the rubber composition, the content of the silane coupling agent is preferably 3 parts by mass or more and 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 the amount is less than 3 parts by mass, the coupling effect is insufficient and good filler dispersibility tends to be not obtained. Moreover, 15 mass parts or less are preferable, and, as for content of this silane coupling agent, 10 mass parts or less are more preferable. If it exceeds 15 parts by mass, unreacted silane coupling agent remains, which may cause deterioration in processability and fracture characteristics of the resulting rubber composition.

In the rubber composition, 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, a good reinforcing effect tends not to be exhibited. 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 decrease.

The rubber composition can be used for each member of a tire, and particularly, can be suitably used as a rubber composition for covering a tire cord of a member including 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 two-wheeled vehicles, a tire for competitions, and the like, and particularly 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.
Cyclohexane: cyclohexane 1,3-butadiene manufactured by Kanto Chemical Co., Ltd .: 1,3-butadiene tetramethylethylenediamine manufactured by Tokyo Chemical Industry Co., Ltd .: tetramethylethylenediamine n-butyllithium manufactured by Kanto Chemical Co., Ltd .: Kanto Chemical 1.6M n-butyllithium hexane solution modifier manufactured by Co., Ltd .: 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 Corp., detector: differential refractometer, column: TSKGELSUPERMALTPORE HZ-M manufactured by Tosoh Corp.). Measured.

(Production Example 1)
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, 1 g of 2,6-tert-butyl-p-cresol was added to the reaction solution, and then a polymer (modified BR) was obtained by reprecipitation purification. The Mw of the polymer 1 was 460000.

Hereinafter, various chemicals used in Examples and Comparative Examples will be described together.
NR: TSR20
BR: BR150B manufactured by Ube Industries, Ltd.
Polymer (modified BR): Production Example 1 above
Silica: ULTRASIL VN3 manufactured by Degussa (nitrogen adsorption specific surface area: 175 m ² / g)
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)
Silane coupling agent 1: Si75 (bis (3-triethoxysilylpropyl) disulfide) manufactured by Degussa
Silane coupling agent 2: NXT-Z45 manufactured by Momentive Performance Materials (copolymer of bonding unit A and bonding unit B, bonding unit A: 55 mol%, bonding unit B: 45 mol%)
Carbon black: Show Black N330 manufactured by Cabot Japan Co., Ltd. (nitrogen adsorption specific surface area: 75 m ² / g)
Aroma oil: Process X-140 manufactured by Japan Energy Co., Ltd.
Anti-aging agent: Santoflex 13 manufactured by Flexis
Zinc oxide: Two types of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Stearic acid “Kashiwa” manufactured by NOF Corporation
Sulfur: Powder sulfur vulcanization accelerator manufactured by Tsurumi Chemical Industry Co., Ltd .: Noxera-NS (N-tert-butyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

Examples and Comparative Examples (Production of Rubber Composition)
Process 1: The component shown in the process 1 of Table 1 was mix | blended, and it knead | mixed for 4 minutes at 150 degreeC using the Banbury mixer made from Kobe Steel Co., Ltd., and obtained the kneaded material 1.
Step 2: The components shown in Step 2 were further added to the kneaded product 1, and kneaded at 150 ° C. for 4 minutes to obtain a kneaded product 2.
Step 3: The components shown in Step 3 were further added to the kneaded product 2 and kneaded for 4 minutes at 90 ° C. to obtain an unvulcanized rubber composition.
Step 4: The obtained unvulcanized rubber composition was press vulcanized for 12 minutes at 170 ° C. to prepare a vulcanized rubber sheet.

The following evaluation was performed using the unvulcanized rubber composition and the vulcanized rubber sheet. The results are shown in Table 1.

(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.
(Kneading workability index) = (Mooney viscosity of Comparative Example 1) / (Mooney viscosity of each formulation) × 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.
(Low heat generation performance index) = (tan δ of Comparative Example 1) / (tan δ 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.
(Rubber strength index) = (breaking elongation of each compound) / (breaking elongation of Comparative Example 1) × 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.
(Bending fatigue resistance index) = (Number of times of each blending) / (Number of times of Comparative Example 1) × 100

From Table 1, compared with the comparative example which knead | mixed the whole quantity of rod-shaped silica, a silica, and a rubber component simultaneously at the process 1, the Example which produced and prepared the masterbatch of a rubber component, specific rod-shaped silica, and a silane coupling agent previously. Then, good performance was obtained. For example, from the results of Comparative Example 3 and Example 4, it has been clarified that the masterbatch production improves all the kneading processability, rolling resistance characteristics, rubber strength, and bending fatigue resistance. Particularly when BR or modified BR was blended, the bending fatigue resistance was remarkably improved.

Claims (9)

Kneading a rubber component, rod-like silica having an average width of 3 to 35 nm and an average length of 50 nm to 5 μm and a silane coupling agent;
The kneaded product 1 obtained in the step 1, the step 2 of kneading the silica and the silane coupling agent, and
A method for producing a rubber composition for a tire, comprising the kneaded product 2 obtained in the step 2 and the step 3 of kneading the vulcanization accelerator. The blending amount of the silane coupling agent in step 1 is 3 to 15 parts by mass with respect to 100 parts by mass of the rod-like silica blended in step 1.
The method for producing a rubber composition for a tire according to claim 1, wherein the compounding amount of the silane coupling agent in Step 2 is 3 to 15 parts by mass with respect to 100 parts by mass of silica compounded in Step 2. The manufacturing method of the rubber composition for tires of Claim 1 or 2 with which the said rubber component contains natural rubber and / or diene type synthetic rubber. In step 1, silica is further kneaded,
The rubber composition for tires according to any one of claims 1 to 3, wherein the compounding ratio of silica in Step 1 is 1 to 30% by mass with respect to 100% by mass of total silica used for production of the rubber composition. Method. The rubber component is

(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 tire rubber composition according to any one of claims 1 to 4, comprising a diene rubber modified with a compound represented by the same or different formula: a hydrogen atom or an alkyl group, and n represents an integer. Manufacturing method. The method for producing a rubber composition for a tire according to any one of claims 1 to 5, wherein the rod-like silica is obtained by defibrating a sepiolite mineral. The rubber composition for tires obtained by the manufacturing method in any one of Claims 1-6. The rubber composition for a tire according to claim 7, wherein the content of the rod-like silica is 2 to 50 parts by mass and the content of the silica is 5 to 100 parts by mass with respect to 100 parts by mass of the rubber component. A pneumatic tire produced using the rubber composition according to claim 7 or 8.

Images