JP7615715B2 - Rubber composition and composite - Google Patents

Description

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

Technologies have been proposed for compounding fillers such as carbon black and silica into rubber compositions to reinforce the rubber composition and improve its modulus (complex elastic modulus). For example, various techniques for dispersing fillers have been disclosed, such as a method for producing a silica-natural rubber composite from a compounded latex obtained by mixing natural rubber latex with a dispersion of fine silica particles with an average particle size of 1 μm or less in the presence of a nonionic or cationic surfactant (see Patent Document 1, etc.).

JP 2012-107211 A

However, in recent years, as long-distance driving on expressways has become common, further improvements in handling stability during high-speed driving are desired.
An object of the present invention is to provide a rubber composition, a composite, and a tire that can solve the above problems and improve the steering stability during high-speed driving.

The present invention relates to a rubber composition having a Mooney viscosity V and a complex modulus E ^* [MPa] that satisfy the following formula (1).
(1) V/E ^* ≦3.0
(In the formula, V represents the Mooney viscosity ML ₁₊₄ at a temperature of 130° C., and E ^* represents the complex modulus of elasticity under the conditions of a temperature of 30° C., an initial strain of 5%, a dynamic strain of ±1%, and a frequency of 10 Hz.)

The rubber composition preferably contains silica having a nitrogen adsorption specific surface area of 190 m ² /g or more.

The rubber composition preferably contains a nonionic surfactant and an anionic surfactant.

The rubber composition preferably contains a complex obtained by mixing isoprene-based rubber, silica, a nonionic surfactant, and an anionic surfactant.

It is preferable that the Mooney viscosity V and the complex modulus E ^* [MPa] of the rubber composition satisfy the following formulas.
V/E ^* ≦2.2

The rubber composition according to any one of claims 1 to 5, wherein the Mooney viscosity V satisfies the following formula:
V≦40.0

It is preferable that the complex elastic modulus E ^* [MPa] satisfies the following formula.
E ^* ≧8.0 MPa

The rubber composition preferably contains at least one selected from the group consisting of ether-type nonionic surfactants, ester-type nonionic surfactants, and ether-ester-type nonionic surfactants.

The rubber composition preferably contains at least one selected from the group consisting of carboxylic acid-based anionic surfactants, sulfonic acid-based anionic surfactants, sulfate ester-based anionic surfactants, and phosphate ester-based anionic surfactants.

The present invention relates to a composite obtained by a manufacturing method including a step of mixing a surfactant and a filler dispersion to prepare a mixed liquid, and a step of mixing the prepared mixed liquid with rubber latex, in which the surfactant includes a nonionic surfactant and an anionic surfactant, the filler includes silica, and the rubber latex includes an isoprene-based rubber.

The composite preferably contains silica having a nitrogen adsorption specific surface area of 190 m ² /g or more.

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

According to the present invention, the rubber composition has the Mooney viscosity V and the complex modulus E ^* [MPa] that satisfy the above formula (1), and therefore the steering stability during high-speed driving can be improved.
(1) V/E ^* ≦3.0
(In the formula, V represents the Mooney viscosity ML ₁₊₄ at a temperature of 130° C., and E ^* represents the complex modulus of elasticity under the conditions of a temperature of 30° C., an initial strain of 5%, a dynamic strain of ±1%, and a frequency of 10 Hz.)

The present invention is a rubber composition having a Mooney viscosity V and a complex modulus E ^* that satisfy the above formula (1). The rubber composition can impart good steering stability during high-speed driving.

The reason why the above-mentioned effects are obtained is not entirely clear, but it is presumed that they are due to the following mechanism.
In order to improve the steering stability, it is necessary to increase the rigidity of the rubber composition, but if the gauge varies around the tire, the stress generation will be different between the thick and thin parts. Therefore, during high-speed driving where the rubber composition frequently comes into contact with the road surface repeatedly, the effect of this difference will be significant, and it is considered that the steering stability during high-speed driving cannot be improved by simply improving the rigidity. The present invention satisfies the formula (1) by lowering the Mooney viscosity at 130°C of the rubber composition and increasing the complex modulus E ^* under the conditions of initial strain 5%, dynamic strain ±1%, and frequency 10 Hz. This makes it possible to increase the rigidity of the rubber while making the rubber flow (gauge) during vulcanization uniform around the tire. Therefore, during high-speed driving where the rubber frequently comes into contact with the road surface repeatedly, the rubber gauge around the tire becomes uniform, and the stress around the tire becomes uniform and high, so that high steering stability can be imparted. Therefore, it is presumed that the steering stability during high-speed driving will be significantly improved by satisfying the formula (1).

In this way, the problem (objective) of improving steering stability during high-speed driving is solved by configuring the rubber composition so that the Mooney viscosity V and the complex modulus E ^* satisfy the above formula (1). That is, the parameter of formula (1) "V/E ^* ≦3.0" does not define the problem (objective), but the object of the present application is to improve steering stability during high-speed driving, and a configuration that satisfies the parameter is used as a means to achieve this.

The rubber composition has a Mooney viscosity V (Mooney viscosity V of an unvulcanized rubber composition) and a complex modulus E ^* [MPa] (complex modulus E ^* of a vulcanized rubber composition) that satisfy the following formula (1).
(1) V/E ^* ≦3.0
(In the formula, V represents the Mooney viscosity ML ₁₊₄ at a temperature of 130° C., and E ^* represents the complex modulus of elasticity under the conditions of a temperature of 30° C., an initial strain of 5%, a dynamic strain of ±1%, and a frequency of 10 Hz.)

From the viewpoint of handling stability during high-speed driving, V/E ^* is preferably 2.7 or less, more preferably 2.4 or less, even more preferably 2.2 or less, particularly preferably 2.0 or less, and most preferably 1.8 or less. There is no particular restriction on the lower limit of V/E ^* , but it is preferably 0.3 or more, more preferably 0.5 or more, even more preferably 0.7 or more, and particularly preferably 0.9 or more.

From the viewpoint of steering stability during high-speed driving, it is preferable that the Mooney viscosity V of the rubber composition (Mooney viscosity V of an unvulcanized rubber composition) satisfies the following formula:
V≦40.0
V is preferably 35.0 or less, more preferably 30.0 or less, even more preferably 28.0 or less, particularly preferably 26.0 or less, and most preferably 24.0 or less. The lower limit of V is not particularly limited, but is preferably 10.0 or more, more preferably 15.0 or more, even more preferably 18.0 or more, and particularly preferably 20.0 or more.

From the viewpoint of steering stability during high-speed driving, the rubber composition preferably has a complex modulus E ^* [MPa] (complex modulus E ^* of the rubber composition after vulcanization) satisfying the following formula:
E ^* ≧8.0 MPa
E ^* is preferably 9.0 MPa or more, more preferably 10.0 MPa or more, even more preferably 10.5 MPa or more, particularly preferably 11.0 MPa or more, and most preferably 12.0 MPa or more. The upper limit of E ^* is not particularly limited, but is preferably 20.0 MPa or less, more preferably 18.0 MPa or less, and even more preferably 16.0 MPa or less.

The Mooney viscosity V ( _ML1+4 (130°C)) of a rubber composition (unvulcanized rubber composition) can be adjusted by the types and amounts of chemicals (particularly rubber components, fillers, softeners, sulfur, vulcanization accelerators, silane coupling agents, and surfactants) blended into the rubber composition. For example, V tends to become smaller when a surfactant is used, when a rubber with a low Mooney viscosity is used, or when the amount of filler is reduced.

The complex modulus E ^* of the rubber composition (rubber composition after vulcanization) can be adjusted by the type and amount of chemicals (particularly rubber components, fillers, softeners, sulfur, vulcanization accelerators, and silane coupling agents) blended in the rubber composition. For example, E ^* tends to increase with a decrease in the amount of softener, an increase in the amount of filler, an increase in the amount of sulfur, or an increase in the amount of vulcanization accelerator.

The V/E ^* of a rubber composition can be adjusted by the type and amount of chemicals (particularly rubber components, fillers, softeners, sulfur, vulcanization accelerators, silane coupling agents, and surfactants) compounded in the rubber composition. For example, the V/E* tends to be smaller when a surfactant (particularly a nonionic surfactant or an anionic surfactant) is used, when a rubber with a low Mooney viscosity is used, when silica with a large nitrogen adsorption specific surface area is used, or when the ^silica is combined with a surfactant.

The Mooney viscosity V is the Mooney viscosity ML1 ₊₄ (130°C) of an unvulcanized rubber composition, and the complex modulus E ^* is the complex modulus of a vulcanized rubber composition (under conditions of temperature 30°C, initial strain 5%, dynamic strain ±1%, and frequency 10 Hz). Specifically, they can be measured by the method described in the Examples below.

(Rubber component)
As the rubber component usable in the rubber composition, for example, diene rubber can be used. As the diene rubber, isoprene rubber, butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), etc. can be mentioned. In addition, butyl rubber, fluororubber, etc. can be mentioned. These may be used alone or in combination of two or more. Among them, from the viewpoint of steering stability during high-speed driving, isoprene rubber, BR, SBR are preferable, and isoprene rubber is more preferable.

The diene rubber may be a non-modified diene rubber or a modified diene rubber.
The modified diene rubber may be any diene rubber having a functional group that interacts with a filler such as silica. Examples of the modified diene rubber include terminal-modified diene rubber (terminal-modified diene rubber having the functional group at the terminal) in which at least one terminal of the diene rubber has been modified with a compound (modifier) having the functional group, main-chain modified diene rubber having the functional group in the main chain, main-chain terminal-modified diene rubber having the functional group in the main chain and at least one terminal (for example, main-chain terminal-modified diene rubber having the functional group in the main chain and at least one terminal modified with the modifier), and terminal-modified diene rubber modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule and having a hydroxyl group or epoxy group introduced therein.

The above-mentioned functional groups include, for example, amino groups, amide groups, silyl groups, alkoxysilyl groups, isocyanate groups, imino groups, imidazole groups, urea groups, ether groups, carbonyl groups, oxycarbonyl groups, mercapto groups, sulfide groups, disulfide groups, sulfonyl groups, sulfinyl groups, thiocarbonyl groups, ammonium groups, imide groups, hydrazo groups, azo groups, diazo groups, carboxyl groups, nitrile groups, pyridyl groups, alkoxy groups, hydroxyl groups, oxy groups, and epoxy groups. These functional groups may have a substituent. Among them, amino groups (preferably amino groups in which the hydrogen atoms of the amino groups are substituted with alkyl groups having 1 to 6 carbon atoms), alkoxy groups (preferably alkoxy groups having 1 to 6 carbon atoms), and alkoxysilyl groups (preferably alkoxysilyl groups having 1 to 6 carbon atoms) are preferred.

Isoprene-based rubbers include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, modified IR, etc. NR can be, for example, SIR20, RSS#3, TSR20, etc., which are common in the rubber industry. IR is not particularly limited, and can be, for example, IR2200, etc., which are common in the rubber industry. Modified NR can be, for example, deproteinized natural rubber (DPNR), high-purity natural rubber (UPNR), etc. Modified NR can be, for example, epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, etc. Modified IR can be, for example, epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber, etc. These can be used alone or in combination of two or more.

In the rubber composition, the content of isoprene-based rubber in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 50% by mass or more, even more preferably 75% by mass or more, particularly preferably 85% by mass or more, and may be 100% by mass. By keeping it within the above range, handling stability during high-speed driving tends to be improved.

The BR is not particularly limited, and examples of the BR that can be used include high cis BR with a high cis content, BR containing syndiotactic polybutadiene crystals, and BR synthesized using a rare earth catalyst (rare earth BR). These may be used alone or in combination of two or more. In particular, the BR preferably contains high cis BR with a cis content of 90% by mass or more. The cis content is more preferably 95% by mass or more. The cis content can be measured by infrared absorption spectroscopy.

Both unmodified and modified BR can be used. Modified BR includes modified BR with the same functional groups as modified diene rubber. Hydrogenated butadiene polymer (hydrogenated BR) can also be used.

For example, products from Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, Zeon Corporation, etc. can be used as BR.

When the rubber composition contains BR, the content of BR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more. The upper limit is preferably 50% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less. By keeping it within the above range, the handling stability during high-speed driving tends to be improved.

The SBR is not particularly limited, and for example, emulsion-polymerized styrene-butadiene rubber (E-SBR), solution-polymerized styrene-butadiene rubber (S-SBR), etc. can be used. These may be used alone or in combination of two or more types.

The styrene content of the SBR is preferably 5% by mass or more, more preferably 20% by mass or more, and even more preferably 25% by mass or more. The styrene content is preferably 45% by mass or less, more preferably 40% by mass or less, and even more preferably 35% by mass or less. By keeping the styrene content within the above range, the handling stability during high-speed driving tends to be improved.
In this specification, the styrene content can be measured by ¹ H-NMR measurement.

The vinyl bond content of SBR is preferably 3% by mass or more, more preferably 5% by mass or more, and even more preferably 7% by mass or more. The vinyl bond content is preferably 25% by mass or less, more preferably 15% by mass or less, and even more preferably 13% by mass or less. By keeping it within the above range, the handling stability during high-speed driving tends to be improved.
In this specification, the vinyl bond amount (1,2-bonded butadiene unit amount) can be measured by infrared absorption spectroscopy.

As SBR, either unmodified SBR or modified SBR can be used. Modified SBR includes modified SBR into which functional groups similar to those in modified diene rubbers have been introduced. Hydrogenated styrene-butadiene copolymer (hydrogenated SBR) can also be used as SBR.

As SBR, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., etc. can be used.

When the rubber composition contains SBR, the content of SBR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more. The upper limit is preferably 50% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less. By keeping it within the above range, the handling stability during high-speed driving tends to be improved.

(Filler)
From the viewpoint of steering stability during high-speed driving, the rubber composition desirably contains a filler.

The filler (filling material) is not particularly limited, and materials known in the rubber field can be used, such as inorganic fillers such as silica, carbon black, calcium carbonate, talc, alumina, clay, aluminum hydroxide, aluminum oxide, and mica; and poorly dispersible fillers. Among these, from the viewpoint of handling stability during high-speed driving, silica; carbon-derived fillers (carbon-containing fillers) such as carbon black are preferred, and silica is more preferred.

In the rubber composition, the filler content (total amount of filler) is preferably 5 parts by mass or more, more preferably 30 parts by mass or more, even more preferably 40 parts by mass or more, and particularly preferably 50 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit of the content is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, even more preferably 130 parts by mass or less, and particularly preferably 120 parts by mass or less. By keeping the content within the above range, handling stability during high-speed driving tends to be improved.

Examples of silica that can be used include dry process silica (anhydrous silica) and wet process silica (hydrated silica). Of these, wet process silica is preferred because it has a large number of silanol groups. Commercially available products include those from Degussa, Rhodia, Tosoh Silica, Solvay Japan, and Tokuyama. These 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 100 m ² /g or more, even more preferably 150 m ² /g or more, particularly preferably 180 m ² /g or more, and most preferably 190 m ² /g or more. The upper limit of the N ₂ SA of silica is not particularly limited, but is preferably 350 m ² /g or less, more preferably 300 m ² /g or less, and even more preferably 250 m ² /g or less. By keeping it within the above range, the steering stability during high-speed driving tends to be improved. In particular, by using fine particle silica such as N ₂ SA 190 m ² /g or more, sufficient reinforcing properties can be obtained, so that the specific parameters of the present application are easily satisfied, and the effect of improving the steering stability during high-speed driving also tends to be large.
The N ₂ SA of silica is a value measured by the BET method in accordance with ASTM D3037-93.

In the rubber composition, the content of silica is preferably 5 parts by mass or more, more preferably 30 parts by mass or more, even more preferably 40 parts by mass or more, and particularly preferably 50 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit of the content is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, even more preferably 130 parts by mass or less, and particularly preferably 120 parts by mass or less. By keeping the content within the above range, handling stability during high-speed driving tends to be improved.

When the rubber composition contains silica, it is preferable that the rubber composition further contains a silane coupling agent.
The silane coupling agent is not particularly limited, and those known in the rubber field can be used. For example, bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl)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, bis(3-trimethoxysilylpropyl)disulfide, bis(2-trimethoxysilylethyl)disulfide, bis(4-trimethoxysilylbutyl)disulfide, 3-trimethoxysilylpropyl-N, Examples of such silylsilanes include sulfide-based silylsilanes such as N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, and 3-triethoxysilylpropyl methacrylate monosulfide; mercapto-based silylsilanes such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and Momentive's NXT and NXT-Z; vinyl-based silylsilanes such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based silylsilanes such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy-based silylsilanes such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based silylsilanes such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based silylsilanes such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. As commercially available products, products of Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., Dow Corning Toray Co., Ltd., etc. can be used. These may be used alone or in combination of two or more kinds.

In the rubber composition, the content of the silane coupling agent is preferably 0.1 parts by mass or more, more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, and particularly preferably 7 parts by mass or more, per 100 parts by mass of silica. The upper limit of the content is preferably 50 parts by mass, more preferably 20 parts by mass or less, even more preferably 15 parts by mass or less, and particularly preferably 10 parts by mass or less. By keeping it within the above range, handling stability during high-speed driving tends to be improved.

The carbon black that can be used in the rubber composition is not particularly limited, but examples include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. Commercially available products include those from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Co., Ltd., Lion Co., Ltd., Shin-Nichika Carbon Co., Ltd., Columbia Carbon Co., Ltd., and the like. These may be used alone or in combination of two or more types.

The nitrogen adsorption specific surface area ( _N2SA ) of the carbon black is preferably 30 ^m2 /g or more, more preferably 50 ^m2 /g or more, and even more preferably 70 ^m2 /g or more. The _N2SA is preferably 200 ^m2 /g or less, more preferably 150 ^m2 /g or less, even more preferably 130 ^m2 /g or less, and even more preferably 120 ^m2 /g or less. By keeping the N2SA within the above range, the steering stability during high-speed driving tends to be improved.

In the rubber composition, the carbon black content is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit of the content is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 20 parts by mass or less, and particularly preferably 10 parts by mass or less. By keeping the carbon black content within the above range, handling stability during high-speed driving tends to be improved.

Examples of poorly dispersible fillers include microfibrillated plant fibers, short fiber cellulose, gel compounds, etc. Among these, microfibrillated plant fibers are preferred.

As the microfibrillated plant fiber, cellulose microfibrils are preferred because they provide good reinforcing properties. The cellulose microfibrils are not particularly limited as long as they are derived from natural products, and examples include those derived from resource biomass such as fruits, grains, and root vegetables, wood, bamboo, hemp, jute, and kenaf, as well as pulp, paper, cloth, agricultural waste, waste biomass such as food waste and sewage sludge obtained using these as raw materials, unused biomass such as rice straw, wheat straw, and thinned wood, as well as cellulose produced by sea squirts, acetic acid bacteria, and the like. These microfibrillated plant fibers may be used alone or in combination of two or more types.

In this specification, cellulose microfibrils typically refer to cellulose fibers having an average fiber diameter of 10 μm or less, and more typically refer to cellulose fibers having a microstructure formed by an assembly of cellulose molecules and an average fiber diameter of 500 nm or less. A typical cellulose microfibril is formed, for example, as an assembly of cellulose fibers having the above-mentioned average fiber diameter.

In the rubber composition, the content of the poorly dispersible filler is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit of the content is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 20 parts by mass or less, and particularly preferably 10 parts by mass or less. By keeping the content within the above range, handling stability during high-speed driving tends to be improved.

(Surfactant)
From the viewpoint of steering stability during high-speed driving, the rubber composition desirably contains a surfactant.

The surfactant is a compound having a hydrophobic group and a hydrophilic group, and examples thereof include nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants. The surfactants may be used alone or in combination of two or more types, but it is preferable to use two or more types in combination. Among them, from the viewpoint of handling stability during high-speed driving, nonionic surfactants and anionic surfactants are preferred, and it is more preferable to use a combination of nonionic surfactants and anionic surfactants.

The reason why the above-mentioned effects are obtained is not entirely clear, but it is presumed that they are due to the following mechanism.
For example, when silica is used as a filler, first, the aggregates of silica are loosened by the nonionic surfactant, and strong adsorption occurs due to hydrogen bonds between the SiOH ⁺ on the surface of the loosened silica and the anionic groups such as COO ^- of the anionic surfactant, making it possible to stably disperse silica in a silica dispersion or the like. Next, when such a dispersion in which silica is stabilized is mixed with a rubber component such as a rubber latex, an interaction occurs between the hydrophobic groups of the anionic surfactant and the rubber, and the silica is adsorbed around the rubber particles via the surfactant. Then, by further mixing the mixture of rubber, silica, etc. produced with a roll or the like, the loosely aggregated silica is dispersed, and a silica-rubber composite (master batch) in which the silica is dispersed throughout the rubber is obtained. Therefore, it is presumed that by using such a composite in a rubber composition, excellent steering stability during high-speed driving can be obtained.

The nonionic surfactant is not particularly limited, and known surfactants can be used. For example, ether-type nonionic surfactants, ester-type nonionic surfactants, and ether-ester-type nonionic surfactants can be preferably used.

The ether-type nonionic surfactant is not particularly limited, and conventionally known surfactants can be used, such as polyoxyalkylene alkyl ethers such as polyoxyethylene alkyl ethers, polyoxyethylene polypropylene alkyl ethers, and polyoxyethylene polybutylene alkyl ethers; polyoxyalkylene alkenyl ethers such as polyoxyethylene alkenyl ethers; polyoxyethylene alkyl phenyl ethers; and higher fatty acid alkanolamides.

Specific examples of suitable ether-type nonionic surfactants include polyoxyethylene alkyl ethers and polyoxyethylene alkenyl ethers, such as polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene behenyl ether, and polyoxyethylene 2-octyldodecyl ether.

As the ether-type nonionic surfactant, the compounds represented by the following formulas (I-1) to (I-3) can be preferably used. Among them, the compound represented by the following formula (I-1) is particularly preferably used.

R ¹¹ -O-(EO) _x1 -H (I-1)
(In the formula, R ¹¹ represents an alkyl group having 3 to 50 carbon atoms or an alkenyl group having 3 to 50 carbon atoms. EO represents an oxyethylene group. The average number of moles added x1 is 3 to 100.)

The number of carbon atoms in R ¹¹ is preferably 5 to 30, and more preferably 8 to 20. The above x1 is preferably 5 to 50, and more preferably 8 to 30.

R ¹² -O-(AO) _y1 (EO) _z1 -H (I-2)
(In the formula, R ¹² represents an alkyl group having 3 to 50 carbon atoms or an alkenyl group having 3 to 50 carbon atoms. AO represents an oxypropylene group or an oxybutylene group, and EO represents an oxyethylene group. The average number of moles added, y1 is 3 to 100, and the average number of added moles z1 is 3 to 100.

The number of carbon atoms in ^R12 is preferably 5 to 30, more preferably 8 to 20. The above y1 is preferably 5 to 50, more preferably 8 to 30. The above z1 is preferably 5 to 50, more preferably 8 to 30. The arrangement of EO and AO may be block or random.

In the above formula (I-3), R ¹³ to R ¹⁵ are the same or different and represent a hydrogen atom, an alkyl group having 1 to 30 carbon atoms, an alkenyl group having 1 to 30 carbon atoms, or an alkoxy group having 1 to 30 carbon atoms. ^{R 16} represents an alkylene group having 1 to 30 carbon atoms. EO represents an oxyethylene group. The average number of moles added a is 0 to 50, the average number of moles added b is 0 to 50, and the average number of moles added c is 1 to 50.

The carbon number of R ¹³ and R ¹⁴ is preferably 1 to 25, and R ¹⁵ is preferably a hydrogen atom or an alkyl group having 1 to 25 carbon atoms. The carbon number of R ¹⁶ is preferably 3 to 8. The above a and b are preferably 0 to 30, more preferably 5 to 30, and the above c is preferably 1 to 30, more preferably 1 to 10.

The ester-type nonionic surfactant is not particularly limited, and examples thereof include alkylene oxide adducts of fatty acids, alkylene oxide adducts of polyhydric alcohol fatty acid esters, and fatty acid adducts (esterified products) of polyhydric alcohols. Among these, alkylene oxide adducts of fatty acids are preferred.

The fatty acids constituting these ester-type nonionic surfactants are preferably fatty acids having 10 or more carbon atoms, more preferably 12 or more carbon atoms. There is no particular upper limit, but the number of carbon atoms is preferably 30 or less, more preferably 24 or less. Specific examples of fatty acids include saturated fatty acids such as capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, nonadecylic acid, arachidic acid, henicosylic acid, behenic acid, tricosylic acid, and lignoceric acid; and unsaturated fatty acids such as α-linolenic acid, stearidonic acid, eicosapentaenoic acid, docosapentaenoic acid, docosahexaenoic acid, linoleic acid, γ-linolenic acid, dihomo-γ-linolenic acid, arachidonic acid, docosapentaenoic acid, palmitoleic acid, vaccenic acid, paulic acid, oleic acid, elaidic acid, erucic acid, and nervonic acid.

The alkylene oxides constituting these ester-type nonionic surfactants include ethylene oxide, propylene oxide, butylene oxide, etc. Among these, ethylene oxide and propylene oxide are preferred, and ethylene oxide is more preferred.

Examples of polyhydric alcohols constituting these ester-type nonionic surfactants include polyhydric alcohols represented by CH ₂ OH-(CHOH) _n -CH ₂ OH (n is an integer of 1 to 20). The compound represented by this formula may be cyclized by dehydration. Specific examples of compounds represented by this formula include glycerin, sorbitol, and sorbitan. Another example of the polyhydric alcohol is polyglycerin.

Specific examples of suitable ester-type nonionic surfactants include fatty acid ethylene oxide adducts such as polyethylene glycol monolaurate and polyethylene glycol monooleate; fatty acid esters of glycerol such as glycerol monostearate; fatty acid esters of pentaerythritol such as pentaerythritol di-tallow fatty acid ester; fatty acid esters of sorbitol and sorbitan such as polyoxyethylene sorbitan monolaurate and polyoxyethylene sorbitan monostearate; fatty acid esters of sucrose, etc.

As an ester-type nonionic surfactant, a compound represented by the following formula (II) can be preferably used.

R ²¹ -C(O)-O-(EO) _x2 -H (II)
(In the formula, R ²¹ represents an alkyl group having 3 to 50 carbon atoms or an alkenyl group having 3 to 50 carbon atoms. EO represents an oxyethylene group. The average number of moles added x2 is 3 to 100.)

The number of carbon atoms in R ²¹ is preferably 5 to 30, and more preferably 8 to 20. The above x2 is preferably 5 to 50, and more preferably 8 to 30.

The ether ester type nonionic surfactant may be a compound in which a polyalkyleneoxy group (preferably an ethyleneoxy group, a propyleneoxy group, or a butyleneoxy group, more preferably an ethyleneoxy group or a propyleneoxy group, and even more preferably an ethyleneoxy group) is added to a portion of the hydroxyl groups to which no fatty acid is added in the fatty acid adduct of the polyhydric alcohol. Specific examples include polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate, polyoxyethylene sorbitan tetraoleate, and polyoxyethylene sorbitol tetraoleate. Other examples include polyoxyethylene castor oil and polyoxyethylene hydrogenated castor oil.

The HLB value of the nonionic surfactant (calculated by the Griffin method) is preferably 8.0 or more, more preferably 10.0 or more, even more preferably 11.0 or more, and particularly preferably 11.5 or more. The HLB value is preferably below 19.0, more preferably below 17.0, even more preferably below 15.0, and particularly preferably below 14.0. By keeping the HLB value within the above range, handling stability during high-speed driving tends to be improved.

Commercially available nonionic surfactants include those from Elementis, Kao Corporation, Daiichi Kogyo Seiyaku Co., Ltd., Sanyo Chemical Industries, Ltd., etc.

The anionic surfactant is not particularly limited, and any known surfactant having a hydrophobic group and a hydrophilic group can be used.

The hydrophobic group may be any hydrophobic functional group, but is preferably a hydrocarbon group. The hydrocarbon group may be linear, branched, or cyclic, and examples of the hydrocarbon group include an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, and an aromatic hydrocarbon group. Of these, an aliphatic hydrocarbon group and an aromatic hydrocarbon group are preferred. The number of carbon atoms in the hydrocarbon group is preferably 4 to 20, more preferably 4 to 15, and even more preferably 4 to 12.

The aliphatic hydrocarbon group preferably has 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, and even more preferably 1 to 6 carbon atoms. Preferred examples include alkyl groups having the above carbon numbers, specifically, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, 2-ethylhexyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, and octadecyl groups. In addition, alkenyl and alkynyl groups having the above carbon numbers are also included, examples of which include alkenyl groups such as vinyl, allyl, 1-propenyl, 1-methylethenyl, and isobutylene groups, and alkynyl groups such as ethynyl and propargyl groups. Of these, the isobutylene group is preferred. The above aliphatic hydrocarbon group may be a group further having a substituent in addition to the exemplified aliphatic hydrocarbon groups.

The alicyclic hydrocarbon group preferably has 3 to 8 carbon atoms, and specific examples thereof include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclopropenyl group, a cyclobutenyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, and a cyclooctenyl group. The alicyclic hydrocarbon group may be a group further having a substituent in addition to the alicyclic hydrocarbon group exemplified above.

The aromatic hydrocarbon group preferably has 6 to 12 carbon atoms, and specific examples thereof include a phenyl group, a benzyl group, a phenethyl group, a tolyl group, a xylyl group, and a naphthyl group. Among these, a phenyl group, a benzyl group, and a phenethyl group are preferred, a phenyl group and a benzyl group are more preferred, and a phenyl group is particularly preferred. The substitution position of the methyl group on the benzene ring in the tolyl group and the xylyl group may be any of the ortho, meta, and para positions. The aromatic hydrocarbon group may be a group further having a substituent in the exemplified aromatic hydrocarbon group, etc.

The hydrophilic group is preferably at least one selected from the group consisting of a carboxyl group, a sulfonic acid group, a sulfate group, and a phosphate group. Of these, a carboxyl group is particularly preferred.

The above anionic surfactants can be specifically classified into surfactants such as carboxylic acid-based, sulfonic acid-based, sulfate-based, and phosphate-based surfactants.

Examples of the carboxylic acid surfactant include fatty acid salts having 6 to 30 carbon atoms, polycarboxylic acid salts, rosin acid salts, dimer acid salts, polymer acid salts, tall oil fatty acid salts, polycarboxylic acid type polymer surfactants, etc., and preferably carboxylic acid salts, polycarboxylic acid salts, and polycarboxylic acid type polymer surfactants having 10 to 20 carbon atoms, and particularly preferably polycarboxylic acid type polymer surfactants. Examples of the sulfonic acid surfactant include alkylbenzene sulfonate, alkyl sulfonate, alkylnaphthalene sulfonate, naphthalene sulfonate, diphenyl ether sulfonate, etc. Examples of the sulfate ester surfactant include alkyl sulfate ester, polyoxyalkylene alkyl sulfate ester, polyoxyalkylene alkylphenyl ether sulfate, tristyrenated phenol sulfate ester, distyrenated phenol sulfate ester, α-olefin sulfate ester, alkylsuccinic acid sulfate ester, polyoxyalkylene tristyrenated phenol sulfate ester, polyoxyalkylene distyrenated phenol sulfate ester, etc. Examples of the phosphate ester surfactants include alkyl phosphate ester salts and polyoxyalkylene phosphate ester salts. Examples of salts of these compounds include metal salts (Na, K, Ca, Mg, Zn, etc.), ammonium salts, and amine salts (triethanolamine salts, etc.). The alkyl groups in these surfactants include alkyl groups having 4 to 30 carbon atoms. The polyoxyalkylene groups include those having alkylene groups having 2 to 4 carbon atoms, and for example, those having an added mole number of ethylene oxide of about 1 to 50 moles can be used.

The anionic surfactant preferably has a weight average molecular weight (Mw) of 500 or more, more preferably 1000 or more, and even more preferably 1500 or more. In addition, Mw is preferably 50,000 or less, more preferably 30,000 or less, and even more preferably 20,000 or less.

Commercially available anionic surfactants include those from Elementis, Kao Corporation, Daiichi Kogyo Seiyaku Co., Ltd., Sanyo Chemical Industries, Ltd., EVONIK-DEGUSSA Co., Ltd., Huntsman Co., Ltd., etc.

In the rubber composition, the surfactant content (total amount of surfactants such as nonionic surfactants and anionic surfactants) is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and even more preferably 9 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit of the content is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 25 parts by mass or less, and particularly preferably 20 parts by mass or less. By keeping it within the above range, the handling stability during high-speed driving tends to be improved. It is also preferable that the nonionic surfactant content and the anionic surfactant content are in the same range.

(Plasticizer)
The rubber composition may contain a plasticizer. A plasticizer is a material that imparts plasticity to a rubber component, and examples of the plasticizer include liquid plasticizers (plasticizers that are in a liquid state at room temperature (25° C.)) and resins (resins that are in a solid state at room temperature (25° C.)).

In the rubber composition, the content of the plasticizer (total amount of plasticizer) is preferably 100 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 10 parts by mass or less, particularly preferably 5 parts by mass or less, and may be 0 parts by mass, per 100 parts by mass of the rubber component, from the viewpoint of handling stability during high-speed driving.

Liquid plasticizers (plasticizers that are liquid at room temperature (25°C)) that can be used in rubber compositions are not particularly limited, and examples include oils and liquid polymers (liquid resins, liquid diene-based polymers, etc.). These may be used alone or in combination of two or more types.

In the rubber composition, the content of the liquid plasticizer is preferably 100 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 10 parts by mass or less, particularly preferably 5 parts by mass or less, and may be 0 parts by mass, per 100 parts by mass of the rubber component, from the viewpoint of handling stability during high-speed driving. The oil content is also preferably in a similar range. In this case, the oil content includes the oil contained in the extension oil.

Examples of the oil include process oil, vegetable oil, or a mixture thereof. Examples of the process oil include paraffin-based process oil, aromatic process oil, and naphthenic process oil. Examples of the vegetable oil include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, and tung oil. Examples of commercially available products include those from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Japan Energy Co., Ltd., Orisoi Co., Ltd., H&R Co., Ltd., Toyokuni Seiyu Co., Ltd., Showa Shell Sekiyu K.K., Fuji Kosan Co., Ltd., and Nisshin Oillio Group Co., Ltd. Among these, process oils (paraffin-based process oils, aromatic process oils, naphthenic process oils, etc.) and vegetable oils are preferred.

Liquid resins include terpene resins (including terpene phenol resins and aromatic modified terpene resins), rosin resins, styrene resins, C5 resins, C9 resins, C5/C9 resins, dicyclopentadiene (DCPD) resins, coumarone-indene resins (including coumarone and indene simple resins), phenol resins, olefin resins, polyurethane resins, acrylic resins, etc. Hydrogenated versions of these resins can also be used.

Liquid diene polymers include liquid styrene butadiene copolymers (liquid SBR), liquid butadiene polymers (liquid BR), liquid isoprene polymers (liquid IR), liquid styrene isoprene copolymers (liquid SIR), liquid styrene butadiene styrene block copolymers (liquid SBS block polymers), liquid styrene isoprene styrene block copolymers (liquid SIS block polymers), liquid farnesene polymers, liquid farnesene butadiene copolymers, etc. that are liquid at 25°C. The ends or main chains of these may be modified with polar groups. Hydrogenated versions of these may also be used.

The above resins (resins in a solid state at room temperature (25°C)) that can be used in the rubber composition include, for example, aromatic vinyl polymers in a solid state at room temperature (25°C), coumarone-indene resins, coumarone resins, indene resins, phenolic resins, rosin resins, petroleum resins, terpene resins, and acrylic resins. The resins may also be hydrogenated. These may be used alone or in combination of two or more. Of these, aromatic vinyl polymers, petroleum resins, and terpene resins are preferred.

When the rubber composition contains the above resin, the content of the above resin is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit of the content is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less. By keeping the content within the above range, handling stability during high-speed driving tends to be improved.

The softening point of the resin is preferably 60° C. or higher, more preferably 70° C. or higher, and even more preferably 80° C. or higher. The upper limit is preferably 160° C. or lower, more preferably 130° C. or lower, and even more preferably 115° C. or lower. By keeping the softening point within the above range, the handling stability during high-speed driving tends to be improved.
The softening point of the resin is the temperature at which the ball drops when the softening point specified in JIS K6220-1:2001 is measured using a ring and ball softening point tester.

The aromatic vinyl polymer is a polymer containing an aromatic vinyl monomer as a constituent unit. For example, it can be a resin obtained by polymerizing α-methylstyrene and/or styrene, and specifically, it can be a homopolymer of styrene (styrene resin), a homopolymer of α-methylstyrene (α-methylstyrene resin), a copolymer of α-methylstyrene and styrene, a copolymer of styrene and another monomer, etc.

The above-mentioned coumarone-indene resin is a resin containing coumarone and indene as the main monomer components that make up the resin skeleton (main chain). Other monomer components contained in the skeleton besides coumarone and indene include styrene, α-methylstyrene, methylindene, vinyltoluene, etc.

The above coumarone resin is a resin that contains coumarone as the main monomer component that constitutes the resin skeleton (main chain).

The above-mentioned indene resin is a resin that contains indene as the main monomer component that constitutes the resin skeleton (main chain).

The phenolic resin may be, for example, a known polymer obtained by reacting phenol with an aldehyde such as formaldehyde, acetaldehyde, or furfural using an acid or alkali catalyst. Among these, those obtained by reacting with an acid catalyst (such as novolac-type phenolic resin) are preferred.

The above-mentioned rosin resins include rosin-based resins such as natural rosin, polymerized rosin, modified rosin, ester compounds thereof, and hydrogenated products thereof.

The petroleum resins include C5 resins, C9 resins, C5/C9 resins, dicyclopentadiene (DCPD) resins, and hydrogenated versions of these resins. Of these, DCPD resins and hydrogenated DCPD resins are preferred.

The terpene resin is a polymer that contains terpene as a structural unit. Examples include polyterpene resins obtained by polymerizing terpene compounds, and aromatic modified terpene resins obtained by polymerizing terpene compounds and aromatic compounds. Hydrogenated products of these resins can also be used.

The polyterpene resin is a resin obtained by polymerizing a terpene compound. The terpene compound is a hydrocarbon represented by the composition (C ₅ H ₈ ) _n and its oxygen-containing derivatives, and is a compound having a basic skeleton of a terpene classified into monoterpene (C ₁₀ H ₁₆ ), sesquiterpene (C ₁₅ H ₂₄ ), diterpene (C ₂₀ H ₃₂ ), etc., and examples thereof include α-pinene, β-pinene, dipentene, limonene, myrcene, alloocimene, ocimene, α-phellandrene, α-terpinene, γ-terpinene, terpinolene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, and γ-terpineol.

The polyterpene resins mentioned above include pinene resin, limonene resin, dipentene resin, pinene/limonene resin, etc., which are made from the above-mentioned terpene compounds. Of these, pinene resin is preferred. Pinene resins usually contain both α-pinene and β-pinene, which are isomers, but depending on the components they contain, they are classified into β-pinene resins, which are mainly made of β-pinene, and α-pinene resins, which are mainly made of α-pinene.

The aromatic modified terpene resin may be a terpene phenol resin made from the above terpene compound and a phenolic compound, or a terpene styrene resin made from the above terpene compound and a styrene compound. Terpene phenol styrene resin made from the above terpene compound, a phenolic compound, and a styrene compound may also be used. Examples of phenolic compounds include phenol, bisphenol A, cresol, and xylenol. Examples of styrene compounds include styrene and α-methylstyrene.

The acrylic resin is a polymer containing an acrylic monomer as a constituent unit. For example, there is a styrene-acrylic resin such as a styrene-acrylic resin that has a carboxyl group and is obtained by copolymerizing an aromatic vinyl monomer component and an acrylic monomer component. Among them, a solvent-free carboxyl group-containing styrene-acrylic resin can be preferably used.

The above-mentioned solvent-free carboxyl group-containing styrene acrylic resin is a (meth)acrylic resin (polymer) synthesized by a high-temperature continuous polymerization method (high-temperature continuous bulk polymerization method) (methods described in U.S. Pat. No. 4,414,370, JP-A-59-6207, JP-B-5-58005, JP-A-1-313522, U.S. Pat. No. 5,010,166, Toa Gosei Kenkyuu Nenpo TREND 2000 Vol. 3, pp. 42-45, etc.) with minimal use of auxiliary raw materials such as polymerization initiators, chain transfer agents, and organic solvents. In this specification, (meth)acrylic means methacryl and acrylic.

Examples of the acrylic monomer components constituting the acrylic resin include (meth)acrylic acid, (meth)acrylic acid esters (alkyl esters such as 2-ethylhexyl acrylate, aryl esters, aralkyl esters, etc.), (meth)acrylamide, and (meth)acrylic acid derivatives such as (meth)acrylamide derivatives. Note that (meth)acrylic acid is a general term for acrylic acid and methacrylic acid.

Examples of the aromatic vinyl monomer components constituting the acrylic resin include aromatic vinyls such as styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, and divinylnaphthalene.

In addition, other monomer components may be used in addition to (meth)acrylic acid, (meth)acrylic acid derivatives, and aromatic vinyl as monomer components constituting the acrylic resin.

Examples of the plasticizer that can be used include products from Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical Company, Nitto Chemical Co., Ltd., Nippon Shokubai Co., Ltd., ENEOS Corporation, Arakawa Chemical Industries Co., Ltd., and Taoka Chemical Co., Ltd.

(Other materials)
From the viewpoints of crack resistance, ozone resistance, and the like, the rubber composition preferably contains an antioxidant.

The anti-aging agent is not particularly limited, but may be naphthylamine-based anti-aging agents such as phenyl-α-naphthylamine; diphenylamine-based anti-aging agents such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylene Examples of such antioxidants include p-phenylenediamine antioxidants such as diamines; quinoline antioxidants such as polymerized 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol antioxidants such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; and bis, tris, and polyphenol antioxidants such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. Among these, p-phenylenediamine antioxidants and quinoline antioxidants are preferred, and N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and polymerized 2,2,4-trimethyl-1,2-dihydroquinoline are more preferred. Commercially available products include those from Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Co., Ltd., and Flexis.

In the rubber composition, the content of the antioxidant is preferably 0.2 parts by mass or more, and more preferably 0.5 parts by mass or more, per 100 parts by mass of the rubber component. The content is preferably 7.0 parts by mass or less, and more preferably 4.0 parts by mass or less.

The rubber composition preferably contains stearic acid. The content of stearic acid in the rubber composition is preferably 0.5 to 10 parts by mass, more preferably 0.5 to 5 parts by mass, per 100 parts by mass of the rubber component.

The stearic acid used may be any known product, such as products from NOF Corp., NOF Corporation, Kao Corp., Fujifilm Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., etc.

The rubber composition preferably contains zinc oxide. The content of zinc oxide in the rubber composition is preferably 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass, per 100 parts by mass of the rubber component.

As zinc oxide, any conventionally known product can be used, for example, products from Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. can be used.

Wax may be compounded in the rubber composition. The wax content in the rubber composition is preferably 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass, per 100 parts by mass of the rubber component.

The wax is not particularly limited, and examples include petroleum-based waxes and natural waxes. Synthetic waxes obtained by refining or chemically processing multiple waxes can also be used. These waxes may be used alone or in combination of two or more types.

Petroleum-based waxes include paraffin wax, microcrystalline wax, etc. Natural waxes are not particularly limited as long as they are derived from resources other than petroleum, and examples include vegetable waxes such as candelilla wax, carnauba wax, Japan wax, rice wax, and jojoba wax; animal waxes such as beeswax, lanolin, and spermaceti; mineral waxes such as ozokerite, ceresin, and petrolactam; and refined products thereof. Commercially available products include those from Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Seiko Chemical Co., Ltd., etc.

The rubber composition may contain a processing aid.
Examples of processing aids include fatty acid metal salts, fatty acid amides, amide esters, silica surfactants, fatty acid esters, mixtures of fatty acid metal salts and amide esters, mixtures of fatty acid metal salts and fatty acid amides, etc. Commercially available products include those from Rhein Chemie and Struktol. These may be used alone or in combination of two or more. Among these, fatty acid metal salts are preferred.

The fatty acids constituting the fatty acid metal salt include saturated or unsaturated fatty acids (preferably saturated or unsaturated fatty acids having 6 to 28 carbon atoms (more preferably 10 to 25 carbon atoms, and even more preferably 14 to 20 carbon atoms)), such as lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, arachidic acid, behenic acid, and nervonic acid. These can be used alone or in combination of two or more. Of these, saturated fatty acids are preferred, and saturated fatty acids having 14 to 20 carbon atoms are more preferred.

Examples of metals constituting fatty acid metal salts include alkali metals such as potassium and sodium, alkaline earth metals such as magnesium, calcium and barium, zinc, nickel, molybdenum, etc. These may be used alone or in combination of two or more. Of these, zinc is preferred.

The content of the processing aid is preferably 1 part by mass or more, more preferably 1.5 parts by mass or more, and even more preferably 2 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 8 parts by mass or less, more preferably 6 parts by mass or less, and even more preferably 4 parts by mass or less.

It is preferable to add sulfur to the rubber composition, as this forms appropriate cross-linked chains in the polymer chains and provides good performance.

In the rubber composition, the sulfur content is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and even more preferably 0.5 parts by mass or more, per 100 parts by mass of the rubber component. The content is preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less, and even more preferably 2.0 parts by mass or less.

Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and soluble sulfur, which are commonly used in the rubber industry. Commercially available products include those from Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexis Corporation, Nippon Kanzuri Kogyo Co., Ltd., and Hosoi Chemical Industry Co., Ltd. These may be used alone or in combination of two or more types.

The rubber composition preferably contains a vulcanization accelerator.
In the rubber composition, the content of the vulcanization accelerator is not particularly limited and may be freely determined according to the desired vulcanization speed and crosslink density, but is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, and even more preferably 1.5 parts by mass or more, relative to 100 parts by mass of the rubber component. The upper limit is preferably 8.0 parts by mass or less, more preferably 6.0 parts by mass or less, and even more preferably 5.0 parts by mass or less.

There are no particular restrictions on the type of vulcanization accelerator, and any commonly used accelerator can be used. Examples of the vulcanization accelerator include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiazyl sulfenamide; thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazole sulfenamide, N-t-butyl-2-benzothiazolyl sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine-based vulcanization accelerators such as diphenyl guanidine, di-orthotolyl guanidine, and orthotolyl biguanidine. These may be used alone or in combination of two or more. Among them, sulfenamide-based, guanidine-based, and benzothiazole-based vulcanization accelerators are preferred.

In addition to the above components, the rubber composition may contain compounding agents that are commonly used in the tire industry, such as release agents, as appropriate.

The rubber composition can be produced by a known method, for example, by kneading the components using a rubber kneading device such as an open roll or a Banbury mixer, and then vulcanizing the mixture.

In particular, from the viewpoint of steering stability during high-speed driving, the rubber composition is preferably produced by a production method including a step of mixing a rubber component, a filler, and a surfactant to produce a rubber-filler composite. In the above step, the rubber component preferably contains isoprene-based rubber, and the filler preferably contains silica. The surfactant preferably contains a nonionic surfactant, and more preferably contains a nonionic surfactant and an anionic surfactant. In particular, when isoprene-based rubber, silica, a nonionic surfactant, and an anionic surfactant are used, a composite with high silica dispersibility is obtained.

The rubber-filler composite can be suitably produced, for example, by a method including a step of mixing rubber latex, a filler dispersion, and a surfactant. Among these, a production method including a step of mixing a surfactant and a filler dispersion to produce a mixed liquid (step (1)), and a step of mixing the mixed liquid with rubber latex (step (2)) is preferred.

(Step (1))
The filler dispersion is a dispersion (slurry) in which the filler is dispersed in a solvent. The solvent is not particularly limited, and examples thereof include water and organic solvents such as alcohol, among which water is preferred.

The filler content (solid content) in the filler dispersion is not particularly limited, but is preferably 0.2 to 20% by mass, more preferably 0.5 to 10% by mass, and even more preferably 0.5 to 7% by mass.

In the above step (1), the method of mixing the surfactant and the filler dispersion to prepare a mixture can be, for example, a method of mixing the surfactant and the filler dispersion using a known stirring device such as a high-speed homogenizer, an ultrasonic homogenizer, a colloid mill, or a blender mill, and the mixture can be obtained by stirring thoroughly until the surfactant and the filler dispersion are sufficiently dispersed. The temperature and time when preparing the mixture can be appropriately set within the range normally used until the surfactant and the filler dispersion are sufficiently dispersed, and for example, 10 to 40°C for 3 to 120 minutes are preferable, and 15 to 30°C for 5 to 90 minutes are more preferable.

The amount of surfactant added is preferably 1 to 50 parts by mass per 100 parts by mass of rubber latex (rubber solids) used in the rubber-filler composite. The amount added is more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more. Also, it is more preferably 25 parts by mass or less, even more preferably 20 parts by mass or less, and particularly preferably 15 parts by mass or less.

The amount of filler is preferably 1 to 100 parts by mass per 100 parts by mass of rubber latex (rubber solids) used in the rubber-filler composite. The amount is more preferably 10 parts by mass or more, even more preferably 20 parts by mass or more, and particularly preferably 30 parts by mass or more. Also, it is more preferably 90 parts by mass or less, even more preferably 80 parts by mass or less, and particularly preferably 70 parts by mass or less. When silica is used as the filler, the amount of silica is also preferably in the same range.

(Step (2))
In the present invention, the next step (step (2)) is to mix the mixture obtained in the step (1) with rubber latex.

As the rubber latex, for example, diene-based rubber latex such as natural rubber latex, modified natural rubber latex (saponified natural rubber latex, epoxidized natural rubber latex, etc.), synthetic diene-based rubber latex (latex such as butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), isoprene rubber, acrylonitrile butadiene rubber, ethylene vinyl acetate rubber, chloroprene rubber, vinylpyridine rubber, and butyl rubber) can be suitably used. These rubber latexes may be used alone or in combination of two or more. Among them, natural rubber latex, isoprene-based rubber latex such as isoprene rubber latex, SBR latex, and BR latex are preferred, and isoprene-based rubber latex is more preferred.

Natural rubber latex is collected as sap from natural rubber trees such as Hevea trees, and contains water, proteins, lipids, inorganic salts, etc. in addition to rubber components, and the gel content in the rubber is thought to be due to the presence of a complex of various impurities. In the present invention, the natural rubber latex that can be used includes raw latex (field latex) that comes out by tapping Hevea trees, concentrated latex concentrated by centrifugation or creaming methods (refined latex, high ammonia latex to which ammonia has been added by the usual method, LATZ latex stabilized with zinc oxide, TMTD, and ammonia, etc.), etc.

The pH of the rubber latex is preferably 8.5 or higher, more preferably 9.5 or higher. When the pH is 8.5 or higher, the rubber latex tends not to become unstable and not to coagulate. The pH of the rubber latex is preferably 12.0 or lower, more preferably 11.0 or lower. When the pH is 12.0 or lower, the rubber latex tends not to deteriorate.

Rubber latex can be prepared by a conventional method, and various commercially available products can also be used. It is preferable to use rubber latex with a rubber solids content of 10 to 80% by mass. More preferably, it is 20% by mass or more and 60% by mass or less.

In the above step (2), the mixed liquid obtained in step (1) and the rubber latex can be mixed, for example, in a known stirring device such as a high-speed homogenizer, ultrasonic homogenizer, colloid mill, or blender mill, by placing the rubber in the device and dropping the mixed liquid obtained in step (1) while stirring, or dropping the rubber latex into the mixed liquid obtained in step (1) while stirring. By stirring thoroughly until the rubber is sufficiently dispersed, a mixture of the mixed liquid obtained in step (1) and the rubber (compounded latex) can be obtained. The temperature and time for preparing the mixture can be appropriately set within the ranges normally used until the mixed liquid obtained in step (1) and the rubber are sufficiently dispersed, but for example, 10 to 40°C for 3 to 120 minutes are preferable, and 15 to 30°C for 5 to 90 minutes are more preferable.

The pH of the mixture (compounded latex) obtained in step (2) above is preferably 9.0 or more, and more preferably 9.5 or more. Also, it is preferably 12.0 or less, and more preferably 11.5 or less. When the pH of the mixture (compounded latex) of the mixed liquid obtained in step (1) above and the rubber latex is in this range, deterioration can be suppressed and the mixture can be stabilized.

The mixture (compounded latex) obtained in step (2) above is coagulated as necessary, and the coagulated material (coagulated material containing coagulated rubber and filler) is filtered and dried by a known method. After further drying, rubber kneading is performed using a two-screw roll or Banbury roll to obtain a composite (rubber-filler composite) in which the filler is sufficiently dispersed in the rubber matrix. The rubber-filler composite may contain other components as long as they do not impair the effect.

The coagulation is usually carried out by adding an acid to the mixture (compounded latex) obtained in step (2) above. Examples of acids for coagulation include sulfuric acid, hydrochloric acid, formic acid, and acetic acid. The temperature during coagulation is preferably 10 to 40°C.

During the coagulation, it is preferable to adjust the pH of the mixture (compounded latex) obtained in step (2) to 3 to 5, and more preferably to 3 to 4.

Flocculants may also be added to control the state of coagulation (the size of the coagulated aggregated particles). Cationic polymers and the like can be used as flocculants.

A rubber-filler composite is produced by the above-mentioned manufacturing method, and the rubber composition can be produced by, for example, kneading the rubber-filler composite and other components using a rubber kneading device such as an open roll or Banbury mixer, and then vulcanizing the mixture.

As for the kneading conditions, in the base kneading process where additives other than the vulcanizing agent and vulcanization accelerator are kneaded, the kneading temperature is usually 50 to 200°C, preferably 80 to 190°C, and the kneading time is usually 30 seconds to 30 minutes, preferably 1 minute to 30 minutes. In the finish kneading process where the vulcanizing agent and vulcanization accelerator are kneaded, the kneading temperature is usually 100°C or less, preferably room temperature to 80°C. Furthermore, the composition kneaded with the vulcanizing agent and vulcanization accelerator is usually subjected to a vulcanization treatment such as press vulcanization. The vulcanization temperature is usually 120 to 200°C, preferably 140 to 180°C.

The rubber composition can be used in various pneumatic tire components such as cap tread, base tread, sidewall, bead apex, clinch apex, inner liner, undertread, breaker topping, ply topping, and insert (sidewall reinforcing layer). In particular, it can be used in cap tread and base tread.

Tires are manufactured by the usual method using a rubber composition. That is, the rubber composition containing the above components is extruded while still unvulcanized to fit the shape of the cap tread, base tread, etc., and molded together with other tire components in a tire building machine by the usual method to form an unvulcanized tire. The unvulcanized tire is then heated and pressurized in the vulcanizer to obtain a tire.

The tires include pneumatic tires and non-pneumatic tires. Of these, pneumatic tires are preferred. The tires can be used for passenger car tires, large passenger car tires, large SUV tires, heavy load tires such as trucks and buses, light truck tires, motorcycle tires, racing tires (high performance tires), run-flat tires, etc. Of these, the tires are particularly suitable for use as passenger car tires.

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

Various chemicals used in the examples and comparative examples will be collectively described below.
NR: TSR20
Natural rubber latex: Field latex obtained from Muhibbah LATEKS was used ^{. Silica 1: 9100Gr (N2SA235m2} _/ g) manufactured by Degussa
Silica 2: Ultrasil VN3 (N ₂ SA 175 m ² /g) manufactured by Evonik Degussa
Surfactant 1: Emanon 4110 manufactured by Kao Corporation (nonionic surfactant (ester type), polyethylene glycol monooleate, HLB 11.6, EO number 10)
Surfactant 2: Emulgen 409P manufactured by Kao Corporation (non-ionic surfactant (ether type), polyoxyethylene oleyl ether, HLB 12, EO number 9, Mw 2000)
Surfactant 3: NUOSPERSE FX 600 manufactured by Elementis (anionic surfactant, polycarboxylate amine salt (containing a phenyl group as a hydrophobic group and a carboxyl group as a hydrophilic group), Mw 2000)
Carbon black: N220 ( _N2SA114m2 /g) manufactured ^by Mitsubishi Chemical
Wax: Ozoace 0355 manufactured by Nippon Seiro Co., Ltd.
Antioxidant 6C: Nocrac 6C (N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine) (6PPD) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
Antioxidant RD: Nocrac RD (poly(2,2,4-trimethyl-1,2-dihydroquinoline)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
Stearic acid: Camellia, manufactured by NOF Corp. Zinc oxide: Zinc oxide type 2, manufactured by Mitsui Mining & Smelting Co., Ltd. Processing aid: EF44 (saturated fatty acid zinc salt), manufactured by Struktol Co., Ltd.
Silane coupling agent: Si266 (bis(3-triethoxysilylpropyl)disulfide) manufactured by Evonik Degussa
Oil: Diana Process NH-70S (aromatic process oil) manufactured by Idemitsu Kosan Co., Ltd.
Sulfur: HK-200-5 (powdered sulfur containing 5% by mass of oil) manufactured by Hosoi Chemical Industry Co., Ltd.
Vulcanization accelerator 1: Sancerer NS-G (N-tert-butyl-2-benzothiazole sulfenamide) manufactured by Sanshin Chemical Industry Co., Ltd.
Vulcanization accelerator 2: Sancerer D (diphenyl guanidine) manufactured by Sanshin Chemical Industry Co., Ltd.

(Preparation of Silica Dispersion)
190 g of pure water was added to 10 g of silica to prepare a 5% by mass (solid content) silica suspension, which was stirred and subjected to ultrasonic treatment for 10 minutes to obtain a silica dispersion.

(Preparation of Mixture (Silica/Surfactant))
According to the formulation in Table 1, each mixed liquid (silica/surfactant) was prepared.
Specifically, a surfactant was added to the prepared silica dispersion, and the mixture was stirred at room temperature (20 to 30° C.) for 5 minutes using a high-speed homogenizer to obtain a mixture (mixture) of the silica dispersion and the surfactant.

(Preparation of Rubber-Filler Composite)
According to the compounding recipe in Table 2, each rubber-filler composite (MB-1 to MB-4) was produced.
Specifically, the prepared mixture was added to natural rubber latex and stirred at room temperature for 5 minutes using a high-speed homogenizer to obtain a compounded latex with a pH of 10.2. Next, a 2% by mass aqueous solution of formic acid was added at room temperature to adjust the pH to 3 to 4 to obtain a coagulum. The obtained coagulum was filtered and dried to obtain a rubber-filler composite.

<Preparation of compounded rubber (unvulcanized rubber composition, vulcanized rubber composition)>
Chemicals other than sulfur and the vulcanization accelerator were kneaded using a 1.7 L Banbury mixer according to the compounding recipe in Table 3. Next, sulfur and the vulcanization accelerator were added to the kneaded mixture using a roll and kneaded to obtain an unvulcanized rubber composition.
The unvulcanized rubber composition thus obtained was then press-vulcanized at 170° C. for 15 minutes to obtain a vulcanized rubber composition.

The properties of the unvulcanized and vulcanized rubber compositions prepared were measured as follows, and the results are shown in Table 3.

(Mooney Viscosity V)
For the unvulcanized rubber composition obtained, in accordance with JIS K 6300-1 "Unvulcanized rubber-Physical properties-Part 1: Determination of viscosity and scorch time using a Mooney viscometer", a small rotor was rotated at a temperature condition of 130°C, which was heated by preheating for 1 minute, and the Mooney viscosity V (ML ₁₊₄ /130°C) after 4 minutes had elapsed was measured using a Mooney viscosity tester.

(Viscoelasticity measurement (E ^* (30°C))
The complex modulus E ^* of the obtained vulcanized rubber composition was measured using an Iplexer manufactured by GABO Corporation under the conditions of a temperature of 30° C., an initial strain of 5%, a dynamic strain of ±1%, and a frequency of 10 Hz.

<Tire manufacturing>
According to the compounding recipe in Table 3, chemicals other than sulfur and vulcanization accelerator were kneaded for 4 minutes at 150°C using a 1.7L Banbury mixer manufactured by Kobe Steel, Ltd., and then sulfur and vulcanization accelerator were added, and the mixture was kneaded for 5 minutes at 80°C using an open roll to prepare an unvulcanized rubber composition. Thereafter, the unvulcanized rubber composition was molded into a cap tread shape, laminated together with other tire components on a tire building machine, and press-vulcanized for 20 minutes at 170°C to prepare a test tire (195/65R15).

The test tires were evaluated as follows, and the results are shown in Table 3.

(Handling stability at high speeds)
The test tires were fitted to all wheels of a domestically produced FF 2000cc vehicle, which was driven on a test course at a speed of 100 km/h, and the handling stability was evaluated by the driver's sensory evaluation while the vehicle was meandering. Based on the feelings of 10 drivers, each was evaluated on a 10-point scale. The total score was calculated as a rating, and the standard comparative example was assigned a score of 100, which was then indexed. The higher the index, the better the handling stability during high-speed driving.

From Tables 1 to 3, it can be seen that the tires of the examples which satisfied the above formula (1) "(1) V/E ^* ≦3.0" had excellent steering stability during high-speed running.

Claims (15)

A rubber composition having a Mooney viscosity V and a complex modulus E ^* [MPa] that satisfy the following formula (1):
(1) V/E ^* ≦ 2.7
(In the formula, V represents the Mooney viscosity ML ₁₊₄ at a temperature of 130° C., and E ^* represents the complex modulus of elasticity under the conditions of a temperature of 30° C., an initial strain of 5%, a dynamic strain of ±1%, and a frequency of 10 Hz.)
Contains a rubber component and a filler,
The rubber composition has a filler content of 5 parts by mass or more and 200 parts by mass or less based on 100 parts by mass of the rubber component . A rubber composition having a Mooney viscosity V and a complex modulus E ^* [MPa] that satisfy the following formula (1):
(1) V/E ^* ≦3.0
(In the formula, V represents the Mooney viscosity ML ₁₊₄ at a temperature of 130° C., and E ^* represents the complex modulus of elasticity under the conditions of a temperature of 30° C., an initial strain of 5%, a dynamic strain of ±1%, and a frequency of 10 Hz.)
Contains a rubber component and a filler,
an amount of the filler relative to 100 parts by mass of the rubber component is 5 parts by mass or more and 200 parts by mass or less;
A rubber composition comprising silica having a nitrogen adsorption specific surface area of 190 m ² /g or more. A rubber composition having a Mooney viscosity V and a complex modulus E ^* [MPa] that satisfy the following formula (1):
(1) V/E ^* ≦3.0
(In the formula, V represents the Mooney viscosity ML ₁₊₄ at a temperature of 130° C., and E ^* represents the complex modulus of elasticity under the conditions of a temperature of 30° C., an initial strain of 5%, a dynamic strain of ±1%, and a frequency of 10 Hz.)
Contains a rubber component and a filler,
an amount of the filler relative to 100 parts by mass of the rubber component is 5 parts by mass or more and 200 parts by mass or less;
A rubber composition comprising a nonionic surfactant and an anionic surfactant. Mooney viscosity V, complex modulus E ^* A rubber composition in which [MPa] satisfies the following formula (1):
(1) V/E ^* ≦3.0
(Wherein, V is the Mooney viscosity ML at a temperature of 130° C. ₁₊₄ Represents E. ^* represents the complex modulus of elasticity under the conditions of a temperature of 30°C, an initial strain of 5%, a dynamic strain of ±1%, and a frequency of 10 Hz.
The Mooney viscosity V satisfies the following formula:
V≦40.0
Contains a rubber component and a filler,
The rubber composition has a filler content of 5 parts by mass or more and 200 parts by mass or less based on 100 parts by mass of the rubber component. 5. The rubber composition according to claim 1, further comprising at least one surfactant selected from the group consisting of nonionic surfactants and anionic surfactants. The rubber composition according to claim 1, 2 or 4, which contains a nonionic surfactant and an anionic surfactant. The rubber composition according to any one of claims 1 to 6 , comprising a composite obtained by mixing an isoprene-based rubber, silica, a nonionic surfactant, and an anionic surfactant. The rubber composition according to any one of claims 1 to 7 , wherein the Mooney viscosity V and the complex modulus E ^* [MPa] satisfy the following formula:
V/E ^* ≦2.2 The rubber composition according to any one of claims 1 to 3 , wherein the Mooney viscosity V satisfies the following formula:
V≦40.0 The rubber composition according to any one of claims 1 to 9 , wherein the complex elastic modulus E ^* [MPa] satisfies the following formula:
E ^* ≧8.0 MPa The rubber composition according to any one of claims 1 to 10 , comprising at least one selected from the group consisting of ether-type nonionic surfactants, ester-type nonionic surfactants, and ether-ester-type nonionic surfactants. The rubber composition according to any one of claims 1 to 10, comprising at least one selected from the group consisting of a carboxylic acid-based anionic surfactant, a sulfonic acid-based anionic surfactant, a sulfate ester -based anionic surfactant, and a phosphate ester-based anionic surfactant. A composite obtained by a production method including a step of mixing a surfactant and a filler dispersion to prepare a mixed liquid, and a step of mixing the prepared mixed liquid with a rubber latex,
The surfactant includes a nonionic surfactant and an anionic surfactant.
The filler comprises silica,
The rubber latex is a composite containing an isoprene-based rubber. The composite according to claim 13 , comprising silica having a nitrogen adsorption specific surface area of 190 m ² /g or more. A tire using the rubber composition according to any one of claims 1 to 12 or the composite according to any one of claims 13 to 14 .