JP2020139112A - Tire rubber composition and pneumatic tire - Google Patents

Abstract

To provide a tire rubber composition that has notably improved general performance such as on-ice brake performance, fracture strength, and a pneumatic tire prepared using the rubber composition.SOLUTION: A tire rubber composition contains a rubber component, an inorganic filler with a Mohs hardness of 1.0-4.0, and a farnesene polymer.SELECTED DRAWING: None

Description

The present invention relates to a rubber composition for a tire and a pneumatic tire.

One of the important performances of studless tires is braking performance on ice. Conventionally, a method of softening low-temperature hardness by focusing on adhesive friction, and a method of increasing the hysteresis loss of rubber by focusing on hysteresis friction. Focusing on scratch friction, a method of blending a material with a higher molar hardness than ice to improve the frictional force of the rubber itself, and in order to improve the frictional force on ice, it occurs between the rubber and ice during braking. Improvement of the performance is being studied by a method of constructing a pattern or a method of constructing a water channel for allowing water to escape from the friction surface in the rubber in order to eliminate the water.

On the other hand, unlike a dry road surface, on ice, there are various friction coefficients due to differences in temperature, etc., and the contribution of each friction differs depending on the mode, so tires that can express a wide range of high frictional forces in as many scenes as possible are available. It has been demanded. To solve such a problem, for example, when a method of adding a material having a Mohs hardness higher than that of ice is applied to a compound having a softened low-temperature hardness, the fracture strength of the soft compound is lower than that of a normal summer tire. Further, since such a scratching material has a small reinforcing property, there is a problem that the breaking strength is further lowered and the durability is lowered by the combined use.

An object of the present invention is to solve the above problems and to provide a rubber composition for a tire in which the braking performance on ice and the total performance of fracture strength are remarkably improved, and a pneumatic tire produced by using the rubber composition. And.

The present invention relates to a rubber composition for a tire containing a rubber component, an inorganic filler having a Mohs hardness of 1.0 to 4.0, and a farnesene-based polymer.

The average particle size of the inorganic filler is preferably 0.2 to 2.0 μm.

The present invention also relates to pneumatic tires made using the rubber composition.
The pneumatic tire is preferably a studless tire.

According to the present invention, since it is a rubber composition for a tire containing a rubber component, an inorganic filler having a Mohs hardness of 1.0 to 4.0, and a farnesene-based polymer, the total performance of braking performance on ice and breaking strength is remarkable. Will be improved.

The rubber composition for a tire of the present invention contains a rubber component, an inorganic filler having a predetermined Mohs hardness, and a farnesene-based polymer.

The reason why the rubber composition can obtain the above-mentioned effects is not always clear, but it is presumed that the rubber composition exerts the following effects.
When a farnesene-based polymer is added to the soft formulation, for example, both the isoprene-based rubber and the farnesene-based polymer have isoprene and isoprenoid in their partial structures, so that they are compatible with each other and have good compatibility. Further, during vulcanization, the farnesene-based polymer is crosslinked with the polymer component to lengthen the molecular chain of the rubber and increase the apparent molecular weight, so that the breaking strength TB is improved. Therefore, sufficient durability can be obtained even when an inorganic filler having a predetermined Mohs hardness is added as a scratching material. It is presumed that the above-mentioned working functions will significantly improve the overall performance of braking performance on ice and fracture strength.

The rubber components include isoprene rubber, butadiene rubber (BR), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), and styrene-isoprene-butadiene copolymer rubber (SIBR). ) And other diene rubbers. These diene rubbers may be used alone or in combination of two or more. Of these, isoprene-based rubber and BR are preferable from the viewpoint of braking performance on ice.

When the rubber composition contains isoprene-based rubber, the content (total content) of isoprene-based rubber in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 25% by mass or more, still more preferably 35. It is mass% or more. By setting it above the lower limit, good fracture strength tends to be obtained. The upper limit of the content is not particularly limited, but is preferably 80% by mass or less, more preferably 60% by mass or less, and further preferably 50% by mass or less. By setting the value below the upper limit, the amount of BR is secured, and the overall performance of braking performance on ice and fracture strength tends to be significantly improved.

Examples of the isoprene rubber include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, modified IR and the like. As the NR, for example, SIR20, RSS # 3, TSR20 and the like, which are common in the tire industry, can be used. The IR is not particularly limited, and for example, an IR 2200 or the like that is common in the tire industry can be used. Modified NR includes deproteinized natural rubber (DPNR), high-purity natural rubber (UPNR), etc., and modified NR includes epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, etc. Examples of the modified IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber, and the like. These may be used alone or in combination of two or more.

When the rubber composition contains BR, the content (total content) of BR in 100% by mass of the rubber component is preferably 20% by mass or more, preferably 40% by mass or more, and more preferably 50% by mass or more. is there. By setting it above the lower limit, good braking performance on ice tends to be obtained. The upper limit of the content is not particularly limited, but is preferably 90% by mass or less, more preferably 80% by mass or less, and further preferably 70% by mass or less. By setting it below the upper limit, the overall performance of braking performance on ice and fracture strength tends to be significantly improved.

The BR is not particularly limited, and a BR having a high cis content, a BR containing syndiotactic polybutadiene crystals, a rare earth BR, and the like can be used. As commercially available products, for example, products such as Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, and Zeon Corporation can be used. The BR may be either a non-modified BR or a modified BR, and examples of the modified BR include a modified BR into which the above-mentioned functional group has been introduced. These may be used alone or in combination of two or more. Of these, BRs with a high cis content and rare earth-based BRs are preferable.

The cis content (cis-1,4-bonding amount) of the high cis content BR is preferably 80% by mass or more, more preferably 90% by mass or more, and further preferably 95% by mass or more from the viewpoint of braking performance on ice. ..

Rare earth-based BR is a butadiene rubber synthesized by using a rare earth element-based catalyst, and has a feature of high cis content and low vinyl content. As the rare earth BR, for example, a general-purpose product in the tire field can be used.

As the rare earth element catalyst used for the synthesis of the rare earth BR, a known catalyst can be used, for example, a catalyst containing a lanthanum series rare earth element compound, an organoaluminum compound, an aluminoxane, a halogen-containing compound, and a Lewis base if necessary. Can be mentioned. Of these, a rare earth element catalyst using a lanthanum series rare earth element compound is preferable.

Examples of the lanthanum series rare earth element compound include halides, carboxylates, alcoholates, thioalcolates, and amides of rare earth metals having atomic numbers 57 to 71. Of these, the use of an Nd-based catalyst is preferable in that BR having a high cis content and a low vinyl content can be obtained.

As the organoaluminum compound, it is represented by AlR ^a R ^b R ^c (in the formula, ^Ra , R ^b , R ^c are the same or different and represent hydrogen or a hydrocarbon group having 1 to 8 carbon atoms). You can use things. Examples of the aluminoxane include chain aluminoxane and cyclic aluminoxane. Examples of the halogen-containing compound include AlX _k R ^d _3-k (in the formula, X is halogen, R ^d is an alkyl group having 1 to 20 carbon atoms, an aryl group or an aralkyl group, and k is 1, 1.5, 2 or 3). Aluminum halide represented by); strontium halides such as Me ₃ SrCl, Me ₂ SrCl ₂ , MeSr HCl ₂ , and MeSrCl ₃ ; metal halides such as silicon tetrachloride, tin tetrachloride, and titanium tetrachloride. .. The Lewis base is used to complex a lanthanum series rare earth element compound, and acetylacetone, a ketone, an alcohol and the like are preferably used.

Rare earth element-based catalysts can be used in the state of being dissolved in an organic solvent (n-hexane, cyclohexane, n-heptane, toluene, xylene, benzene, etc.) during the polymerization of butadiene, or silica, magnesia, magnesium chloride, etc. It may be used by supporting it on a suitable carrier. The polymerization conditions may be either solution polymerization or bulk polymerization, the preferred polymerization temperature is -30 to 150 ° C., and the polymerization pressure may be arbitrarily selected depending on other conditions.

The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the rare earth BR is preferably 1.2 or more, more preferably 1.5 or more. When it is 1.2 or more, good workability tends to be obtained. The Mw / Mn is preferably 5.0 or less, more preferably 4.0 or less. When it is 5.0 or less, good breaking strength tends to be obtained.

The Mw of the rare earth BR is preferably 300,000 or more, more preferably 500,000 or more, and preferably 1.5 million or less, more preferably 1.2 million or less. Further, the Mn of the rare earth BR is preferably 100,000 or more, more preferably 150,000 or more, and preferably 1 million or less, more preferably 800,000 or less. When Mw or Mn is at least the lower limit, good fracture strength tends to be obtained. When it is less than the upper limit, good workability tends to be obtained.

In the present specification, the weight average molecular weight (Mw) and the number average molecular weight (Mn) are gel permeation chromatographs (GPC) (GPC-8000 series manufactured by Toso Co., Ltd., detector: differential refractometer, column: It can be obtained by standard polystyrene conversion based on the measured value by TSKGEL SUPERMULTIPORE HZ-M manufactured by Toso Co., Ltd.

From the viewpoint of fracture strength, the cis content of the rare earth BR is preferably 90% by mass or more, more preferably 93% by mass or more, and further preferably 95% by mass or more. When it is 90% by mass or more, good breaking strength tends to be obtained.

The vinyl content of the rare earth BR is preferably 1.8% by mass or less, more preferably 1.0% by mass or less, still more preferably 0.5% by mass or less, and particularly preferably 0.3% by mass or less. When it is 1.8% by mass or less, good fracture strength tends to be obtained.
In the present specification, the cis content (cis-1,4-bonding amount) and vinyl content can be calculated from the signal intensity measured by NMR analysis.

The modified BR may be a BR having a functional group that interacts with a filler such as silica. For example, at least one end of the BR is modified with a compound having the above functional group (modifying agent). BR (terminal modified BR having the above functional group at the end), main chain modified BR having the above functional group in the main chain, and main chain terminal modified BR having the above functional group in the main chain and the end (for example, in the main chain) Main chain terminal modified BR having the above functional group and at least one end modified with the above modifying agent) or a polyfunctional compound having two or more epoxy groups in the molecule, which is modified (coupling) with a hydroxyl group. And terminally modified BR into which an epoxy group has been introduced.

Examples of the functional group include an amino group, an amide group, a silyl group, an alkoxysilyl group, an isocyanate group, an imino group, an imidazole group, a urea group, an ether group, a carbonyl group, an oxycarbonyl group, a mercapto group, a sulfide group and a disulfide. Examples thereof include a group, a sulfonyl group, a sulfinyl group, a thiocarbonyl group, an ammonium group, an imide group, a hydrazo group, an azo group, a diazo group, a carboxyl group, a nitrile group, a pyridyl group, an alkoxy group, a hydroxyl group, an oxy group and an epoxy group. .. In addition, these functional groups may have a substituent. Among them, an amino group (preferably an amino group in which the hydrogen atom of the amino group is replaced with an alkyl group having 1 to 6 carbon atoms), an alkoxy group (preferably an alkoxy group having 1 to 6 carbon atoms), and an alkoxysilyl group (preferably an alkoxy group having 1 to 6 carbon atoms). An alkoxysilyl group having 1 to 6 carbon atoms) is preferable.

（式中、Ｒ^１、Ｒ^２及びＲ^３は、同一又は異なって、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、同一又は異なって、水素原子又はアルキル基を表す。Ｒ^４及びＲ^５は結合して窒素原子と共に環構造を形成してもよい。ｎは整数を表す。） As the modified BR, a BR modified with a compound (modifying agent) represented by the following formula is particularly preferable.

(In the formula, R ¹ , R ² and R ³ represent the same or different alkyl group, alkoxy group, silyloxy group, acetal group, carboxyl group (-COOH), mercapto group (-SH) or derivatives thereof. R ⁴ and R ⁵ represent the same or different hydrogen atoms or alkyl groups. R ⁴ and R ⁵ may combine to form a ring structure with a nitrogen atom. N represents an integer.)

Alkoxy groups are preferable as R ¹ , R ² and R ³ (preferably alkoxy groups having 1 to 8 carbon atoms, and more preferably alkoxy groups having 1 to 4 carbon atoms). Alkyl groups (preferably alkyl groups having 1 to 3 carbon atoms) are suitable as R ⁴ and R ⁵ . n is preferably 1 to 5, more preferably 2 to 4, and even more preferably 3. Further, when R ⁴ and R ⁵ are bonded to form a ring structure together with a nitrogen atom, a 4- to 8-membered ring is preferable. The alkoxy group also includes a cycloalkoxy group (cyclohexyloxy group, etc.) and an aryloxy group (phenoxy group, benzyloxy group, etc.).

Specific examples of the above modifier include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, and 2-diethylaminoethyltri. Examples thereof include methoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, and 3-diethylaminopropyltriethoxysilane. Of these, 3-dimethylaminopropyltrimethoxysilane, 3-dimethylaminopropyltriethoxysilane, and 3-diethylaminopropyltrimethoxysilane are preferable. These may be used alone or in combination of two or more.

As the modified BR, a modified BR modified with the following compound (modifying agent) can also be preferably used. Examples of the modifier include polyglycidyl ethers of polyhydric alcohols such as ethylene glycol diglycidyl ether, glycerin triglycidyl ether, trimethylolethanetriglycidyl ether, and trimethylolpropane triglycidyl ether; and two or more diglycidylated bisphenol A and the like. Polyepoxy compounds of aromatic compounds having a phenol group of; 1,4-diglycidylbenzene, 1,3,5-triglycidylbenzene, polyepoxidized liquid polybutadiene and other polyepoxy compounds; 4,4'-diglycidyl-diphenyl Epoxy group-containing tertiary amines such as methylamine, 4,4'-diglycidyl-dibenzylmethylamine; diglycidylaniline, N, N'-diglycidyl-4-glycidyloxyaniline, diglycidyl orthotoluidine, tetraglycidyl metaxylene diamine , Tetraglycidylaminodiphenylmethane, tetraglycidyl-p-phenylenediamine, diglycidylaminomethylcyclohexane, tetraglycidyl-1,3-bisaminomethylcyclohexane and other diglycidylamino compounds;

Amino group-containing acid chlorides such as bis- (1-methylpropyl) carbamic acid chloride, 4-morpholincarbonyl chloride, 1-pyrrolidincarbonyl chloride, N, N-dimethylcarbamic acid chloride, N, N-diethylcarbamic acid chloride; 1 , 3-Bis- (glycidyloxypropyl) -tetramethyldisiloxane, (3-glycidyloxypropyl) -pentamethyldisiloxane and other epoxy group-containing silane compounds;

(Trimethylsilyl) [3- (trimethoxysilyl) propyl] sulfide, (trimethylsilyl) [3- (triethoxysilyl) propyl] sulfide, (trimethylsilyl) [3- (tripropoxysilyl) propyl] sulfide, (trimethylsilyl) [3 -(Tributoxysilyl) propyl] sulfide, (trimethylsilyl) [3- (methyldimethoxysilyl) propyl] sulfide, (trimethylsilyl) [3- (methyldiethoxysilyl) propyl] sulfide, (trimethylsilyl) [3- (methyldimethoxysilyl) propyl] Sulfide group-containing silane compounds such as propoxysilyl) propyl] sulfide and (trimethylsilyl) [3- (methyldibutoxysilyl) propyl] sulfide;

N-substituted aziridine compounds such as ethyleneimine and propyleneimine; alkoxysilanes such as methyltriethoxysilane; 4-N, N-dimethylaminobenzophenone, 4-N, N-di-t-butylaminobenzophenone, 4-N, N-diphenylaminobenzophenone, 4,4'-bis (dimethylamino) benzophenone, 4,4'-bis (diethylamino) benzophenone, 4,4'-bis (diphenylamino) benzophenone, N, N, N', N' A (thio) benzophenone compound having an amino group such as −bis- (tetraethylamino) benzophenone and / or a substituted amino group; 4-N, N-dimethylaminobenzaldehyde, 4-N, N-diphenylaminobenzaldehyde, 4-N, Benzaldehyde compounds having an amino group and / or a substituted amino group such as N-divinylaminobenzaldehyde; N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N-phenyl-2-pyrrolidone, N-t-butyl- N-substituted pyrrolidone such as 2-pyrrolidone and N-methyl-5-methyl-2-pyrrolidone N-substituted piperidone such as N-methyl-2-piperidone, N-vinyl-2-piperidone and N-phenyl-2-piperidone N-methyl-ε-caprolactam, N-phenyl-ε-caprolactam, N-methyl-ω-laurilolactam, N-vinyl-ω-laurilolactam, N-methyl-β-propiolactam, N-phenyl N-substituted lactams such as −β-propiolactam;

N, N-bis- (2,3-epoxypropoxy) -aniline, 4,4-methylene-bis- (N, N-glycidylaniline), tris- (2,3-epoxypropyl) -1,3,5 -Triazine-2,4,6-triones, N, N-diethylacetamide, N-methylmaleimide, N, N-diethylurea, 1,3-dimethylethyleneurea, 1,3-divinylethyleneurea, 1,3 -Diethyl-2-imidazolidinone, 1-methyl-3-ethyl-2-imidazolidinone, 4-N, N-dimethylaminoacetophen, 4-N, N-diethylaminoacetophenone, 1,3-bis (diphenyl) Amino) -2-propanone, 1,7-bis (methylethylamino) -4-heptanone and the like can be mentioned. Of these, modified BR modified with alkoxysilane is preferable.
The modification with the above compound (denaturing agent) can be carried out by a known method.

In the rubber composition, the total content of the isoprene-based rubber and BR in 100% by mass of the rubber component is preferably 50% by mass or more, preferably 80% by mass or more, and more preferably 90% by mass or more. The upper limit of the content is not particularly limited, and is preferably 100% by mass. Within the above range, the overall performance of braking performance on ice and fracture strength tends to be significantly improved.

The rubber composition contains an inorganic filler having a Mohs hardness of 1.0 to 4.0. The Mohs hardness is preferably 1.0 to 3.0, more preferably 1.0 to 2.0, from the viewpoint of scratching effect, preventing polymer cutting, and ensuring good fracture strength. Mohs hardness is one of the mechanical properties of materials and has been widely used in minerals for a long time. The substance whose hardness is to be measured is rubbed with a standard substance, and the Mohs hardness is measured by the presence or absence of scratches. To do.

The average particle size of the inorganic filler is preferably 0.2 μm or more, more preferably 0.3 μm or more, still more preferably 0.5 μm or more, from the viewpoint of braking performance on ice. The average particle size of the clay is preferably 2.0 μm or less, more preferably 1.7 μm or less, and further preferably 1.5 μm or less from the viewpoint of fracture strength.
The average particle size of the inorganic filler is a number average particle size, which is measured by a transmission electron microscope.

The content of the inorganic filler is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and further preferably 5 parts by mass or more with respect to 100 parts by mass of the rubber component. By setting it above the lower limit, the scratching effect is exhibited and good braking performance on ice tends to be obtained. The content is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, still more preferably 20 parts by mass or less. By setting it below the upper limit, good fracture strength tends to be maintained.

Examples of the inorganic filler include alumina having the moth hardness, alumina hydrate, aluminum hydroxide, magnesium hydroxide, magnesium oxide, talc, titanium white, titanium black, calcium oxide, calcium hydroxide, aluminum oxide magnesium, clay, and the like. Pyrophyllite, bentonite, aluminum silicate, magnesium silicate, calcium silicate, aluminum calcium silicate, magnesium silicate, zirconium, zirconium oxide and the like can be mentioned. Of these, clay is preferable. These inorganic compounds may be used alone or in combination of two or more.

As the clay, for example, hard clay (crown clay manufactured by South Eastern Clay, Union Clay RC1 manufactured by Takehara Chemical Co., Ltd., Glomax LL, etc.), which is a clay containing kaolinite as a main component, was fired at 600 ° C. Examples thereof include a calcined clay (such as Ice Cap K manufactured by Burgess) and a silane modified clay (such as Burgess KE manufactured by Burgess) which is fired at 600 ° C. and then treated with a silane coupling agent. Of these, hard clay is preferable.

The rubber composition preferably contains carbon black. Here, the content of carbon black is preferably 1 part by mass or more, and more preferably 3 parts by mass or more with respect to 100 parts by mass of the rubber component. The content is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, still more preferably 8 parts by mass or less. Within the above range, good braking performance on ice and breaking strength tend to be obtained.

The carbon black is not particularly limited, and furnace black (furness carbon black) such as SAF, ISAF, HAF, MAF, FEF, SRF, GPF, APF, FF, CF, SCF and ECF; acetylene black (acetylene carbon black). Thermal black (thermal carbon black) such as FT and MT; channel black (channel carbon black) such as EPC, MPC and CC; graphite and the like. These may be used alone or in combination of two or more.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 50 m ² / g or more, more preferably 80 m ² / g or more, and more preferably 80 m ² / g or more, because good braking performance on ice and breaking strength can be obtained. It is preferably 200 m ² / g or less, more preferably 150 m ² / g or less. For the same reason, the amount of dibutyl phthalate (DBP) absorbed by carbon black is preferably 50 ml / 100 g or more, more preferably 80 ml / 100 g or more, and preferably 200 ml / 100 g or less, more preferably 150 ml / 100 g or less. Is.
The nitrogen adsorption specific surface area of carbon black is measured according to ASTM D4820-93, and the amount of DBP absorbed is measured according to ASTM D2414-93.

The carbon black is not particularly limited, and examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. These may be used alone or in combination of two or more.

Examples of carbon black products include Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin Nikka Carbon Co., Ltd., and Columbia Carbon Co., Ltd. Can be used.

The rubber composition preferably contains silica. Examples of silica include dry silica (anhydrous silica) and wet silica (hydrous silica). Of these, wet silica is preferable because it has many silanol groups.

The content of silica is preferably 5 parts by mass or more, more preferably 30 parts by mass or more, and further preferably 50 parts by mass or more with respect to 100 parts by mass of the rubber component. By setting it above the lower limit, good braking performance on ice and breaking strength tend to be obtained. The content is preferably 150 parts by mass or less, more preferably 100 parts by mass or less, still more preferably 80 parts by mass or less. By setting it below the upper limit, good dispersibility tends to be obtained.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 40 m ² / g or more, more preferably 70 m ² / g or more, and further preferably 110 m ² / g or more. By setting it above the lower limit, good braking performance on ice and breaking strength tend to be obtained. The N ₂ SA of silica is preferably 220 m ² / g or less, more preferably 200 m ² / g or less. By setting it below the upper limit, good dispersibility tends to be obtained.
The N ₂ SA of silica is a value measured by the BET method according to ASTM D3037-93.

As the silica, for example, products such as Degussa, Rhodia, Tosoh Silica Co., Ltd., Solvay Japan Co., Ltd., Tokuyama Corporation can be used.

The rubber composition preferably contains a silane coupling agent together with silica.
The silane coupling agent is not particularly limited, and 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, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyltetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyltetrasulfide, 3- Sulfide type such as triethoxysilylpropyl methacrylate monosulfide, 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, mercapto type such as NXT and NXT-Z manufactured by Momentive, vinyl triethoxysilane, vinyl tri Vinyl type such as methoxysilane, amino type such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane, glycidoxy such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane. Examples thereof include nitro systems such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane, and chloro systems such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. These may be used alone or in combination of two or more. Of these, sulfide-based and mercapto-based are preferable because the effects of the present invention can be obtained more satisfactorily.

As the silane coupling agent, for example, products such as Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., Toray Dow Corning Co., Ltd. can be used.

The content of the silane coupling agent is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, based on 100 parts by mass of silica. When it is 3 parts by mass or more, the effect of the addition tends to be obtained. The content is preferably 25 parts by mass or less, more preferably 20 parts by mass or less. When it is 25 parts by mass or less, an effect commensurate with the blending amount can be obtained, and good processability at the time of kneading tends to be obtained.

The total content of the filler (inorganic filler having the predetermined Mohs hardness, carbon black, silica, etc.) is based on 100 parts by mass of the rubber component from the viewpoint that the overall performance of braking performance on ice and breaking strength is remarkably improved. It is preferably 30 to 120 parts by mass, more preferably 40 to 100 parts by mass, and further preferably 50 to 80 parts by mass.

The rubber composition preferably contains a farnesene-based polymer.
The content of the farnesene polymer is preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, and preferably 50 parts by mass or less with respect to 100 parts by mass of the rubber component. , More preferably 30 parts by mass or less, still more preferably 20 parts by mass or less. Within the above range, good braking performance on ice and breaking strength tend to be obtained.

The farnesene-based polymer is a polymer obtained by polymerizing farnesene, and has a structural unit based on farnesene. Farnesene includes α-farnesene ((3E, 7E) -3,7,11-trimethyl-1,3,6,10-dodecatetraene) and β-farnesene (7,11-dimethyl-3-methylene-1). , 6,10-dodecatorien) and other isomers are present, but (E) -β-farnesene having the following structure is preferable.

The farnesene-based polymer may be a farnesene homopolymer (farnesene homopolymer) or a copolymer of farnesene and a vinyl monomer (farnesene-vinyl monomer copolymer).

Examples of vinyl monomers include styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, α-methylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, 4-tert-butylstyrene, 5- t-Butyl-2-methylstyrene, vinylethylbenzene, divinylbenzene, trivinylbenzene, divinylnaphthalene, tert-butoxystyrene, vinylbenzyldimethylamine, (4-vinylbenzyl) dimethylaminoethyl ether, N, N-dimethylaminoethyl Styrene, N, N-dimethylaminomethylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethylstyrene, 2-t-butylstyrene, 3-t-butylstyrene, 4-t-butylstyrene, vinylxylene, Examples thereof include aromatic vinyl compounds such as vinylnaphthalene, vinyltoluene, vinylpyridine, diphenylethylene and tertiary amino group-containing diphenylethylene, and conjugated diene compounds such as butadiene and isoprene. These may be used alone or in combination of two or more. Of these, butadiene is preferable. That is, as the farnesene-vinyl monomer copolymer, a copolymer of farnesene and butadiene (farnesene-butadiene copolymer) is preferable.

As the farnesene-based polymer, a liquid farnesene-based polymer can be preferably used. The liquid farnesene polymer is a farnesene polymer that is liquid at room temperature (25 ° C.), and a polymer having a weight average molecular weight (Mw) of 3000 to 300,000 can be preferably used. The Mw of the liquid farnesene polymer is preferably 8,000 or more, more preferably 10,000 or more, and preferably 100,000 or less, more preferably 60,000 or less, still more preferably 50,000 or less.

The glass transition temperature (Tg) of the farnesene polymer is preferably −100 ° C. or higher, more preferably −78 ° C. or higher, and preferably −10 ° C. or lower, more preferably −30 ° C. or lower, still more preferably −. It is 54 ° C. or lower. Within the above range, the effect of the present invention tends to be obtained better.
Tg is a value measured under the condition of a heating rate of 10 ° C./min using a differential scanning calorimeter (Q200) manufactured by TA Instruments Japan, Inc. in accordance with JIS-K7121: 1987. ..

The melt viscosity of the farnesene polymer is preferably 0.1 Pa · s or more, more preferably 0.7 Pa · s or more, and preferably 500 Pa · s or less, more preferably 100 Pa · s or less, still more preferably 13 Pa · s. It is less than or equal to s. Within the above range, the effect of the present invention tends to be obtained better.
The melt viscosity is a value measured at 38 ° C. using a Brookfield type viscometer (manufactured by BROOKFIELD ENGINEERING LABS. INC.).

In the farnesene-vinyl monomer copolymer, the mass-based copolymerization ratio (farnesene / vinyl monomer) of farnesene and vinyl monomer is preferably 40/60 to 90/10.

As the farnesene polymer, for example, a product such as Kuraray Co., Ltd. can be used.

The rubber composition preferably contains oil.
The oil content is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and further preferably 12 parts by mass or more with respect to 100 parts by mass of the rubber component from the viewpoint of braking performance on ice. From the viewpoint of breaking strength, the upper limit is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and further preferably 20 parts by mass or less.
The oil content also includes the amount of oil contained in rubber (oil spread rubber).

Examples of the oil include process oils, vegetable oils and fats, or mixtures thereof. As the process oil, for example, a paraffin-based process oil, an aroma-based process oil, a naphthen-based process oil, or the like can be used. Vegetable oils and fats include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, palm oil, peanut oil, rosin, pine oil, pineapple, tall oil, corn oil, rice oil, beni flower oil, sesame oil, Examples thereof include olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, and tung oil. These may be used alone or in combination of two or more. Of these, naphthenic process oils are preferable because the effects of the present invention can be obtained better.

Examples of oils include 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 Co., Ltd., Fuji Kosan Co., Ltd. And other products can be used.

A liquid diene polymer may be blended in the rubber composition.
The liquid diene polymer is a diene polymer in a liquid state at room temperature (25 ° C.). Liquid diene polymer preferably has a weight average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC) (Mw) is a ^{1.0 × 10 3 ~2.0 × 10 5} , 3.0 More preferably, it is × 10 ^{3 to} 1.5 × 10 ⁴ . Examples of the liquid diene polymer include a liquid styrene-butadiene copolymer (liquid SBR), a liquid butadiene polymer (liquid BR), a liquid isoprene polymer (liquid IR), and a liquid styrene isoprene copolymer (liquid SIR). Be done.

The total content of the softening agent (hydrocarbon, resin, etc. in a liquid state at room temperature (25 ° C) such as liquid farnesene polymer, oil, liquid diene polymer, etc.) in the rubber composition is the braking performance on ice and the breaking strength. From the viewpoint of overall performance, the amount is preferably 1 to 50 parts by mass, more preferably 5 to 40 parts by mass, and further preferably 10 to 35 parts by mass with respect to 100 parts by mass of the rubber component.

The rubber composition may contain a resin in a solid state at room temperature (25 ° C.).
In the rubber composition, the total content of the solid resin (the resin in the solid state at room temperature (25 ° C.)) is preferably 1 to 10 parts by mass and 3 to 5 parts by mass with respect to 100 parts by mass of the rubber component. Is more preferable.

The resin (resin in a solid state at room temperature) is not particularly limited as long as it is widely used in the tire industry, and is styrene resin, kumaron inden resin, terpene resin, pt-butylphenol acetylene resin, acrylic. Examples include based resins. Of these, styrene-based resins are preferable from the viewpoint of braking performance on ice and overall performance of fracture strength.

The styrene-based resin is a polymer using a styrene-based monomer as a constituent monomer, and examples thereof include a polymer obtained by polymerizing a styrene-based monomer as a main component (50% by mass or more). Specifically, styrene-based monomers (styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, A homopolymer obtained by independently polymerizing o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, etc.), a copolymer obtained by copolymerizing two or more styrene-based monomers, and a styrene-based monomer. And other monomer copolymers that can be copolymerized with this.

Examples of the other monomer include acrylonitrile such as acrylonitrile and methacrylonitrile, unsaturated carboxylic acids such as acrylics and methacrylic acid, unsaturated carboxylic acid esters such as methyl acrylate and methyl methacrylate, chloroprene and butadiene. Examples thereof include dienes such as isoprene, olefins such as 1-butane and 1-pentene; α, β-unsaturated carboxylic acids such as maleic anhydride or acid anhydrides thereof;

Among them, α-methylstyrene resin (α-methylstyrene homopolymer, copolymer of α-methylstyrene and styrene, etc.) is preferable from the viewpoint of braking performance on ice and comprehensive performance of fracture strength.

The softening point of the styrene resin is preferably 30 ° C. or higher, more preferably 60 ° C. or higher, and even more preferably 80 ° C. or higher. At 30 ° C. or higher, the desired wet grip performance tends to be obtained. The softening point is preferably 160 ° C. or lower, more preferably 130 ° C. or lower, and even more preferably 100 ° C. or lower. When the temperature is 160 ° C. or lower, the dispersibility of the resin is good, and the wet grip performance and fuel efficiency tend to be improved.
In the present invention, the softening point of the resin is the temperature at which the ball drops when the softening point defined in JIS K 6220-1: 2001 is measured by a ring-ball type softening point measuring device.

The kumaron indene resin is a resin containing kumaron and indene as monomer components constituting the skeleton (main chain) of the resin. Examples of the monomer component contained in the skeleton other than kumaron and indene include styrene, α-methylstyrene, methylindene, vinyltoluene and the like.

Examples of the terpene resin include polyterpenes, terpene phenols, and aromatic-modified terpene resins.
Polyterpenes are resins obtained by polymerizing terpene compounds and their hydrogenated products. The terpene compound is a hydrocarbon having a composition of (C ₅ H ₈ ) _n and an oxygen-containing derivative thereof, and is a mono terpene (C ₁₀ H ₁₆ ), a sesqui terpene (C ₁₅ H ₂₄ ), and a diterpen (C ₂₀ H _32). ) Etc., and are compounds having a terpene as a basic skeleton. , 1,8-Cineol, 1,4-Cineol, α-terpineol, β-terpineol, γ-terpineol and the like.

Examples of the polyterpene include terpene resins such as α-pinene resin, β-pinene resin, limonene resin, dipentene resin, and β-pinene / limonene resin made from the above-mentioned terpene compound, and hydrogen obtained by hydrogenating the terpene resin. Additive terpene resin can also be mentioned.
Examples of the terpene phenol include a resin obtained by copolymerizing the above-mentioned terpene compound and a phenol-based compound, and a resin obtained by hydrogenating the resin. Specifically, the above-mentioned terpene compound, the phenolic compound and the formalin are condensed. Resin is mentioned. Examples of the phenolic compound include phenol, bisphenol A, cresol, xylenol and the like.
Examples of the aromatic-modified terpene resin include a resin obtained by modifying the terpene resin with an aromatic compound, and a resin obtained by hydrogenating the resin. The aromatic compound is not particularly limited as long as it is a compound having an aromatic ring, and for example, a phenol compound such as phenol, alkylphenol, styrenephenol, and unsaturated hydrocarbon group-containing phenol; naphthol, alkylnaphthol, alkoxynaphthol, etc. Naftor compounds such as unsaturated hydrocarbon group-containing naphthol; styrene derivatives such as styrene, alkylstyrene, alkoxystyrene, and unsaturated hydrocarbon group-containing styrene; kumaron, inden and the like can be mentioned.

Examples of the pt-butylphenol acetylene resin include a resin obtained by subjecting pt-butylphenol and acetylene to a condensation reaction.

The acrylic resin is not particularly limited, but a solvent-free acrylic resin can be preferably used from the viewpoint that a resin having few impurities and a sharp molecular weight distribution can be obtained.

The solvent-free acrylic resin is a high-temperature continuous polymerization method (high-temperature continuous lump polymerization method) (US Pat. No. 4,414,370) without using polymerization initiators, chain transfer agents, organic solvents, etc. as auxiliary raw materials as much as possible. Japanese Patent Application Laid-Open No. 59-6207, Japanese Patent Application Laid-Open No. 5-58805, Japanese Patent Application Laid-Open No. 1-313522, US Pat. No. 5,010,166, Toa Synthetic Research Annual Report, TREND2000, No. 3, p42 Examples thereof include a (meth) acrylic resin (polymer) synthesized by the method described in −45 and the like). In the present invention, (meth) acrylic means methacrylic and acrylic.

It is preferable that the acrylic resin does not substantially contain a polymerization initiator, a chain transfer agent, an organic solvent, etc., which are auxiliary raw materials. Further, the acrylic resin preferably has a relatively narrow composition distribution and molecular weight distribution obtained by continuous polymerization.

As described above, the acrylic resin preferably contains substantially no polymerization initiator, chain transfer agent, organic solvent, etc., which are auxiliary raw materials, that is, one having high purity. The purity of the acrylic resin (ratio of the resin contained in the resin) is preferably 95% by mass or more, more preferably 97% by mass or more.

Examples of the monomer component constituting the acrylic resin include (meth) acrylic acid, (meth) acrylic acid ester (alkyl ester, aryl ester, aralkyl ester, etc.), (meth) acrylamide, and (meth) acrylamide derivative. (Meta) acrylic acid derivatives such as.

In addition, as the monomer component constituting the acrylic resin, styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, divinylnaphthalene, etc., together with (meth) acrylic acid and (meth) acrylic acid derivative, etc. Aromatic vinyl may be used.

The acrylic resin may be a resin composed of only a (meth) acrylic component or a resin having a component other than the (meth) acrylic component as a component.
Further, the acrylic resin may have a hydroxyl group, a carboxyl group, a silanol group and the like.

Examples of resins such as styrene resin and Kumaron inden resin include Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Toso Co., Ltd., Rutgers Chemicals Co., Ltd., BASF Co., Ltd. Products such as Nikko Chemical Co., Ltd., Nippon Catalyst Co., Ltd., JXTG Energy Co., Ltd., Arakawa Chemical Industry Co., Ltd., and Taoka Chemical Industry Co., Ltd. can be used.

The rubber composition preferably contains an amide compound.
The content of the amide compound with respect to 100 parts by mass of the rubber component is preferably 0.1 part by mass or more, more preferably 1 part by mass or more, further preferably 2 parts by mass or more, and preferably 10 parts by mass or less. It is preferably 7 parts by mass or less. Within the above range, the overall performance of braking performance on ice and fracture strength tends to be significantly improved. In the present specification, when a mixture containing a fatty acid metal salt other than the amide compound is used as the amide compound, the content of the amide compound means the amount including the fatty acid metal salt.

The amide compound is not particularly limited, and examples thereof include fatty acid amides and fatty acid amide esters. The amide compound may be used alone or in combination of two or more. Of these, fatty acid amides are preferable, and a mixture of fatty acid amides and fatty acid amide esters is more preferable.

The fatty acid amide may be a saturated fatty acid amide or an unsaturated fatty acid amide. Examples of the saturated fatty acid amide include stearic acid amide and behenic acid amide, and examples of the unsaturated fatty acid amide include oleic acid amide and erucic acid amide. Of these, unsaturated fatty acid amides are preferable, and oleic acid amides are more preferable.

The fatty acid amide ester may be a saturated fatty acid amide ester or an unsaturated fatty acid amide ester. Examples of the saturated fatty acid amide ester include stearic acid amide ester and behenic acid amide ester, and examples of the unsaturated fatty acid amide ester include oleic acid amide ester and erucic acid amide ester. These may be used alone or in combination of two or more. Of these, unsaturated fatty acid amide esters are preferable, and oleic acid amide esters are more preferable.

As the amide compound, a mixture of the amide compound and the fatty acid metal salt can also be preferably used.
Examples of the metal constituting the fatty acid metal salt include potassium, sodium, magnesium, calcium, barium, zinc, nickel and molybdenum. Of these, alkaline earth metals such as calcium and zinc are preferable, and calcium is more preferable.

The fatty acid constituting the fatty acid metal salt may be a saturated fatty acid or an unsaturated fatty acid. Examples of saturated fatty acids include decanoic acid, dodecanoic acid, stearic acid and the like, and examples of unsaturated fatty acids include oleic acid and elaidic acid. Of these, saturated fatty acids are preferable, and stearic acid is more preferable. Moreover, oleic acid is preferable as an unsaturated fatty acid.

As the amide compound, for example, products such as NOF CORPORATION, Stractol, and Lanxess can be used.

The rubber composition preferably contains wax.
The wax content is preferably 0.5 to 20 parts by mass, and more preferably 1.0 to 10 parts by mass with respect to 100 parts by mass of the rubber component from the viewpoint of braking performance on ice and comprehensive performance of fracture strength. ..

The wax is not particularly limited, and examples thereof include petroleum wax such as paraffin wax and microcrystalline wax; natural wax such as plant wax and animal wax; and synthetic wax such as a polymer such as ethylene and propylene. These may be used alone or in combination of two or more. Of these, petroleum wax is preferable, and paraffin wax is more preferable.

As the wax, for example, products of Ouchi Shinko Kagaku Kogyo Co., Ltd., Nippon Seiro Co., Ltd., Seiko Kagaku Co., Ltd. and the like can be used.

The rubber composition preferably contains an anti-aging agent.
The content of the anti-aging agent is preferably 1 to 10 parts by mass or more, more preferably 2 to 7 parts by mass or more, based on 100 parts by mass of the rubber component, from the viewpoint of braking performance on ice and comprehensive performance of fracture strength. ..

Examples of the anti-aging agent include 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-phenylenediamine, etc. P-Phenylenediamine-based anti-aging agent; quinoline-based anti-aging agent such as a polymer of 2,2,4-trimethyl-1,2-dihydroquinolin; 2,6-di-t-butyl-4-methylphenol, Monophenolic anti-aging agents such as styrenated phenol; tetrax- [methylene-3- (3', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] bis, tris, polyphenolic aging such as methane Examples include preventive agents. These may be used alone or in combination of two or more. Of these, p-phenylenediamine-based anti-aging agents and quinoline-based anti-aging agents are preferable, and N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine, 2,2,4-trimethyl-1 , 2-Dihydroquinoline polymers are more preferred.

As the anti-aging agent, for example, products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., Flexis Co., Ltd. and the like can be used.

The rubber composition preferably contains stearic acid. The content of stearic acid is preferably 0.5 to 10.0 parts by mass or more, more preferably 1.0 to 5 parts by mass with respect to 100 parts by mass of the rubber component, from the viewpoint of braking performance on ice and comprehensive performance of fracture strength. It is 0.0 parts by mass or more.

As the stearic acid, conventionally known ones can be used. For example, products such as NOF Corporation, NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries, Ltd., and Chiba Fatty Acid Co., Ltd. are used. it can.

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

As the zinc oxide, conventionally known zinc oxide can be used, for example, Mitsui Metal Mining Co., Ltd., Toho Zinc Co., Ltd., HakusuiTech Co., Ltd., Shodo Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. Products can be used.

The rubber composition preferably contains sulfur.
The sulfur content is preferably 0.1 to 10.0 parts by mass, more preferably 0.5 to 5.0 parts by mass with respect to 100 parts by mass of the rubber component, from the viewpoint of braking performance on ice and comprehensive performance of breaking strength. It is by mass, more preferably 0.7 to 3.0 parts by mass.

Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and soluble sulfur, which are generally used in the rubber industry. These may be used alone or in combination of two or more.

As the sulfur, for example, products such as Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Kasei Industry Co., Ltd., Flexis Co., Ltd., Nippon Inui Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd. can be used. ..

The rubber composition preferably contains a vulcanization accelerator.
The content of the vulcanization accelerator is preferably 0.3 to 7.0 parts by mass, more preferably 1.0 to 1.0 parts by mass with respect to 100 parts by mass of the rubber component, from the viewpoint of braking performance on ice and comprehensive performance of fracture strength. It is 5.0, more preferably 1.5 to 4.0 parts by mass.

Examples of the sulfide accelerator include thiazole-based sulfide-based sulfide accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiadylsulfenamide; ), Tetrabenzyl thiuram disulfide (TBzTD), tetrakis (2-ethylhexyl) thiuram disulfide (TOT-N) and other thiuram-based sulfide accelerators; N-cyclohexyl-2-benzothiazolesulfenamide, N-t-butyl- 2-benzothiazolyl sulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N, N'-diisopropyl-2-benzothiazolesulfenamide, etc. Sulfenamide-based sulfide accelerator; guanidine-based sulfide accelerators such as diphenylguanidine, dioltotrilguanidine, orthotrilbiguanidine can be mentioned. These may be used alone or in combination of two or more. Of these, sulfenamide-based vulcanization accelerators and guanidine-based vulcanization accelerators are preferable from the viewpoint of overall performance of braking performance on ice and fracture strength.

An organic cross-linking agent may be added to the rubber composition.
The organic cross-linking agent is not particularly limited, and examples thereof include maleimide compounds, alkylphenol / sulfur chloride condensates, organic peroxides, amine organic sulfides, and the like. These may be used alone, in combination of two or more, or in combination with sulfur. The organic cross-linking agent is blended in an amount of 0.5 to 10 parts by mass with respect to 100 parts by mass of the rubber component, for example.

The rubber composition is produced by a general method. That is, it can be produced by a method of kneading each of the above components with a Banbury mixer, a kneader, an open roll, or the like, and then vulcanizing.

As the kneading conditions, in the base kneading step of kneading additives other than the vulcanizing agent and the vulcanization accelerator, 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 final kneading step of kneading the vulcanizing agent and the vulcanization accelerator, the kneading temperature is usually 100 ° C. or lower, preferably room temperature to 80 ° C. Further, the composition obtained by kneading the vulcanizing agent and the 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 of the present invention is preferably used for treads (cap treads), but other members such as sidewalls, base treads, under treads, clinch apex, bead apex, breaker cushion rubber, carcass cord coating. It may be used for rubber, insulation, chafer, inner liner, etc., and as a side reinforcing layer for run-flat tires.

The pneumatic tire of the present invention is produced by a usual method using the above rubber composition.
That is, the rubber composition containing the above components is extruded according to the shape of each tire member such as a tread at the unvulcanized stage, and molded together with other tire members by a normal method on a tire molding machine. By doing so, an unvulcanized tire is formed. A tire is obtained by heating and pressurizing this unvulcanized tire in a vulcanizer.

The pneumatic tire is preferably used as a studless tire (winter tire), a passenger car tire, a heavy load tire such as a truck / bus, a two-wheeled vehicle tire, a competition tire, and the like, and is particularly preferably used as a studless tire.

Although the present invention will be specifically described based on Examples, the present invention is not limited to these.

<Synthesis Example 1 (Synthesis of Conjugated Diene Polymer)>
In advance, a cyclohexane solution containing 0.18 mmol of neodymium versaticate, a toluene solution containing 3.6 mmol of methylarmoxane, a toluene solution containing 6.7 mmol of diisobutylaluminum hydride, and 0.36. A catalyst composition (iodine atom / lanthanoid-containing compound (molar ratio) = 2.0) obtained by reacting and aging a toluene solution containing mmol of trimethylsilyliodide and 0.90 mmol of 1,3-butadiene at 30 ° C. for 60 minutes. ) Was obtained. Subsequently, 2.4 kg of cyclohexane and 300 g of 1,3-butadiene were charged into a nitrogen-substituted 5 L autoclave. Then, the catalyst composition was put into the autoclave and polymerized at 30 ° C. for 2 hours to obtain a polymer solution. The reaction conversion rate of the added 1,3-butadiene was almost 100%.

<Production Example 1 (Synthesis of Modified Conjugated Diene Polymer)>
In order to obtain a modified conjugated diene-based polymer (hereinafter, also referred to as “modified polymer”), the following treatment was performed on the polymer solution of the conjugated diene-based polymer of Synthesis Example 1. A toluene solution containing 1.71 mmol of 3-glycidoxypropyltrimethoxysilane was added to the polymer solution kept at a temperature of 30 ° C., and the mixture was reacted for 30 minutes to obtain a reaction solution. Then, a toluene solution containing 1.71 mmol of 3-aminopropyltriethoxysilane was added to this reaction solution, and the mixture was stirred for 30 minutes. Subsequently, a toluene solution containing 1.28 mmol of tetraisopropyl titanate was added to this reaction solution, and the mixture was stirred for 30 minutes. Then, in order to stop the polymerization reaction, a methanol solution containing 1.5 g of 2,4-di-tert-butyl-p-cresol was added to prepare this solution as a modified polymer solution. The yield was 2.5 kg. Subsequently, 20 L of an aqueous solution adjusted to pH 10 with sodium hydroxide was added to this modified polymer solution, and a condensation reaction was carried out at 110 ° C. for 2 hours with desolvation. Then, it was dried with a roll of 110 degreeC, and the obtained dried product was used as a modified polymer (modified BR).

Regarding the obtained modified polymer (modified BR), the cis-1,4-bonding amount was 99.2% by mass, the 1,2-vinyl bonding amount was 0.21% by mass, and the Mooney viscosity (ML _{1 + 4} , 125 ° C.). The molecular weight distribution (Mw / Mn) was 2.4, the cold flow value was 0.3 mg / min, the stability over time was 2, and the glass transition temperature was −106 ° C.

In addition, various physical property values of the polymer were measured by the measuring method shown below.
[Sith-1,4-bonding amount, 1,2-vinyl binding amount]
The content of cis-1,4-bond and the content of 1,2-vinyl bond were measured by ^{1 1} H-NMR analysis and ¹³ C-NMR analysis. The trade name "EX-270" manufactured by JEOL Ltd. was used for the NMR analysis. Specifically, as ¹ H-NMR analysis, the polymer was obtained from the signal intensities at 5.30 to 5.50 ppm (1,4-bond) and 4.80-5.01 ppm (1,2-bond). The ratio of 1,4-bond and 1,2-bond in the above was calculated. Furthermore, as for ¹³ C-NMR analysis, the signal intensities at 27.5 ppm (cis-1,4-bond) and 32.8 ppm (trans-1,4-bond) show that cis-1,4 in the polymer. The ratio of −-bond to trans-1,4-bond was calculated. The ratio of these calculated values was calculated and used as the cis-1,4-bonding amount (mass%) and the 1,2-vinyl binding amount (mass%).

[Moony Viscosity (ML _{1 + 4} , 125 ° C)]
According to JIS K 6300, the measurement was performed using an L rotor under the conditions of preheating 1 minute, rotor operating time 4 minutes, and temperature 125 ° C.

[Mw, molecular weight distribution (Mw / Mn)]
A gel permeation chromatograph (trade name: HLC-8120GPC, manufactured by Tosoh Corporation) was used, and a differential refractometer was used as a detector to measure under the following conditions and calculated as a standard polystyrene conversion value.
Column; Product name "GMHHXL", 2 (manufactured by Tosoh),
Column temperature; 40 ° C,
Mobile phase; tetrahydrofuran, flow velocity; 1.0 ml / min,
Sample concentration; 10 mg / 20 ml

[Cold flow value]
The measurement was carried out by extruding the polymer through a 1/4 inch orifice at a pressure of 3.5 lb / in ² and a temperature of 50 ° C. After leaving for 10 minutes to bring it into a steady state, the extrusion speed was measured and the measured value was displayed in milligrams per minute (mg / min).

[Stability over time]
The Mooney viscosity (ML _{1 + 4} , 125 ° C.) after storage in a constant temperature bath at 90 ° C. for 2 days was measured, and is a value calculated by the following formula. The smaller the value, the better the stability over time.
Formula: [Moony viscosity after storage in a constant temperature bath at 90 ° C for 2 days (ML _{1 + 4} , 125 ° C)]-[Moony viscosity measured immediately after synthesis (ML _{1 + 4} , 125 ° C)]

[Glass-transition temperature]
The glass transition temperature is measured according to JIS K 7121 by using a differential scanning calorimeter (Q200) manufactured by TA Instruments Japan Co., Ltd. while raising the temperature at a heating rate of 10 ° C./min. , Was determined as the glass transition start temperature.

The various chemicals used in Examples and Comparative Examples will be described below.
NR: TSR20
BR: BR730 manufactured by JSR Corporation (BR synthesized using a high cis BR, Nd catalyst, cis content 97% by mass, Mw / Mn2.51, vinyl content 0.9% by mass)
Modified BR: Nd-based modified BR synthesized in Production Example 1
Carbon black: Mitsubishi Chemical Corporation Seest N220 (N ₂ SA: 111m ² / g, DBP absorption amount: 115ml / 100g)
Silica: Evonik Degussa Uratosyl VN3 (N ₂ SA172m ² / g)
Inorganic filler: Hard clay (crown clay manufactured by South Eastern Cray, Mohs hardness 1.5, average particle size 0.6 μm)
Silane coupling agent: Si266 manufactured by Evonik Degussa
Oil: Diana Process NH-70S (aroma process oil) manufactured by Idemitsu Kosan Co., Ltd.
Styrene-based resin: Sylvatraxx4401 manufactured by Arizona Chemical Co., Ltd. (copolymer of α-methylstyrene and styrene, softening point 85 ° C.)
Farnesene-based polymer: L-FBR-742 (liquid farnesene butadiene copolymer) manufactured by Kuraray
Wax: Ozo Ace 0355 manufactured by Nippon Seiro Co., Ltd.
Anti-aging agent 6C: Nocrack 6C (N-phenyl-N'-(1,3-dimethylbutyl) -p-phenylenediamine) (6PPD) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Anti-aging agent RD: Antage RD manufactured by Kawaguchi Chemical Industry Co., Ltd. (polymer of 2,2,4-trimethyl-1,2-dihydroquinoline)
Stearic acid: Tung amide compound manufactured by Nichiyu Co., Ltd .: WB16 manufactured by Stractol (mixture of fatty acid calcium, fatty acid amide and fatty acid amide ester, ash content 4.5%)
Zinc oxide: Zinc oxide type 2 sulfur manufactured by Mitsui Metal Mining Co., Ltd .: HK200-5 (powdered sulfur containing 5% oil) manufactured by Hosoi Chemical Industry Co., Ltd.
Vulcanization accelerator CZ: Noxeller CZ (N-cyclohexyl-2-benzothiazolysulfeneamide) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Vulcanization accelerator M: Noxeller M (2-mercaptobenzothiazole) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Vulcanization accelerator DPG: Noxeller D (diphenylguanidine) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.

(Examples and comparative examples)
According to the formulation shown in each table, materials other than sulfur and vulcanization accelerator are kneaded for 5 minutes under the condition of about 150 ° C. using a 1.7L Banbury mixer manufactured by Kobe Steel, Ltd., and the kneaded product is kneaded. Got Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and the mixture was kneaded for 3 minutes under the condition of about 80 ° C. using an open roll to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition is molded into a tread shape, bonded together with other tire members on a tire molding machine to form an unvulcanized tire, vulcanized at 170 ° C. for 15 minutes, and tested studless. Tires (size: 195 / 65R15, DSX-2 pattern passenger car tires) were manufactured.

The obtained test studless tires were evaluated as follows, and the overall performance of braking performance on ice (-10 ° C), braking performance on ice (0 ° C), wet grip performance, and fracture strength resistance was shown. The results are shown in each table. The criteria in Tables 1 and 2 are Comparative Examples 1-3 and 2-2, respectively.

(Brake performance on ice (-10 ° C, 0 ° C))
A test studless tire was attached to a domestically produced 2000cc FR vehicle, and the actual vehicle was driven on ice under the following conditions to evaluate the braking performance on ice. Specifically, as an evaluation of braking performance on ice, the stopping distance (stopping distance on ice) required for traveling on ice using the above vehicle, stepping on the lock brake at a speed of 30 km / h, and stopping is measured. It is displayed as an index when the standard comparison example is set to 100 (on-ice braking performance index). The larger the index, the better the braking performance on ice (grip performance on ice).
(On ice)
Test location: Test course Temperature: -10 ° C or 0 ° C

(Wet grip performance)
The test studless tires were mounted on all wheels of the vehicle (domestic FF2000cc), the braking distance from the initial speed of 100km / h was calculated on a wet asphalt road surface, and the index was displayed as an index when the standard comparison example was set to 100 (wet). Grip performance index). The larger the index, the shorter the braking distance and the better the wet grip performance.

(destruction strength)
Using a No. 3 dumbbell type test piece made of rubber cut out from the tread of a test studless tire, perform a tensile test at room temperature according to JIS K 6251 "Vulcanized rubber and thermoplastic rubber-How to determine tensile properties". It was carried out, the breaking strength TB (MPa) was measured, and it was displayed as an index when the reference comparative example was set to 100. The larger the index, the larger the breaking strength TB and the better the durability.

From Tables 1 and 2, examples containing an inorganic filler having a predetermined Mohs hardness and a farnesene-based polymer have excellent on-ice braking performance and breaking strength as compared with a formulation not containing the inorganic filler and a comparative example not containing the farnesene-based polymer. The overall performance of was obtained. Further, from the comparison between Examples 1-1 and Comparative Examples 1-4 in Table 1 and Comparative Examples 1-3 and 1-1, it is better to add the farnesene polymer to the inorganic filler compound having a predetermined Mohs hardness. It was clarified that the overall performance was remarkably improved and synergistically improved as compared with the case where it was added to the formulation containing no inorganic filler.

Claims (4)

A rubber composition for a tire containing a rubber component, an inorganic filler having a Mohs hardness of 1.0 to 4.0, and a farnesene-based polymer. The rubber composition for a tire according to claim 1, wherein the average particle size of the inorganic filler is 0.2 to 2.0 μm. A pneumatic tire produced by using the rubber composition according to claim 1 or 2. The pneumatic tire according to claim 3, which is a studless tire.