JP6733873B2 - Rubber composition and tire - Google Patents

Description

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

Tires have various steering stability (dry grip performance) on dry road surface and steering stability on wet road surface (wet grip performance), as well as steering stability at low temperature and on snowy and snowy road surface (ice grip performance). Braking performance is required. In particular, winter tires are required to have a high level of braking performance under a wide range of conditions such as ice grip performance.
In order to improve the ice grip performance, it is effective to increase the contact area between the rubber constituting the tire and the ice and snow, so that the rubber for the tire is required to have high flexibility. As a method of imparting flexibility, a softening agent such as oil is used.
For example, in Patent Document 1, a solution-polymerized styrene-butadiene rubber and a natural rubber are contained as rubber components in a specific ratio, and a naphthenic natural oil, a MES (Mild Extracted Solvates), a TDAE (Treated Distilled Aromatic Extracts), etc. It is described that a rubber composition containing the above is improved, and friction and resistance on wet road surfaces and road surfaces in winter are improved.
However, in such a rubber composition, the addition of oil causes bleed-out, and when cured, there is a problem of deterioration over time in which the ice grip performance deteriorates. Therefore, it has been attempted to add a farnesene resin as a softening agent in place of oil to improve the flexibility at low temperatures and on snowy and snowy roads.
Patent Document 2 describes a rubber composition containing a rubber component and a farnesene resin in a specific ratio, and it is described that the performance on ice and snow, the wear resistance, and the like are good, and the hardness change is small.
Patent Document 3 discloses a rubber composition containing styrene-butadiene rubber, high-cis polybutadiene, and polyisoprene rubber in specific proportions in a rubber component, silica having a specific nitrogen adsorption specific surface area, and farnesene resin. It is described that the abrasion resistance and the steering stability are improved.
Patent Document 4 discloses a rubber composition containing a farnesene-derived monomer unit in a specific ratio, a copolymer having a specific weight average molecular weight, a rubber component, and carbon black or silica in a specific ratio. It is described that the article has a high level of abrasion resistance, wet grip performance, ice grip performance and the like.

European Patent Application Publication No. 1270657 JP, 2014-218631, A JP, 2005-54875, A JP, 2005-74699, A

However, although the rubber compositions described in Patent Documents 1 to 4 have improved wear resistance and various braking performances as compared with conventional rubber compositions, they are not yet sufficient in ice grip performance, and further improvement is desired. ing.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a rubber composition capable of providing a tire having a high level of ice grip performance, and a tire using the rubber composition. ..

The present inventors have conducted intensive studies to solve the above problems, a solid rubber component containing styrene-butadiene rubber and natural rubber, a liquid polymer containing a farnesene-derived monomer unit, and a filler. A rubber composition containing, the content of the liquid polymer and the filler in the rubber composition, and the content of styrene-butadiene rubber in the solid rubber component are within a specific range, styrene-butadiene rubber, natural rubber The present invention has been completed by finding that the above problems can be solved by satisfying a specific relationship between the solubility parameters of the liquid polymer and the liquid polymer.

That is, the present invention relates to the following [1] and [2].
[1] A solid rubber component containing a styrene-butadiene rubber (A) and a natural rubber (B), a liquid polymer (C) containing a monomer unit (a) derived from farnesene, and a filler (D). A rubber composition,
The content of the liquid polymer (C) is 1 to 50 parts by mass with respect to 100 parts by mass of the solid rubber component,
The content of the filler (D) is 20 to 150 parts by mass with respect to 100 parts by mass of the solid rubber component,
The content of styrene-butadiene rubber (A) in the solid rubber component is more than 50% by mass and less than 100% by mass,
Solubility parameter [delta] _A styrene-butadiene rubber (A), the solubility parameter [delta] _B of the natural rubber (B), and the solubility parameter [delta] _C of the liquid polymer (C) satisfies the following formula (1), the rubber composition.
│δ _A −δ _C │<｜δ _A −δ _B ｜ (1)
[2] A tire using at least a part of the rubber composition described in [1] above.

According to the present invention, it is possible to provide a rubber composition capable of providing a tire having a high level of ice grip performance, and a tire using the rubber composition.

[Rubber composition]
The rubber composition of the present invention comprises a solid rubber component (hereinafter also simply referred to as “solid rubber component”) containing styrene-butadiene rubber (hereinafter simply referred to as “SBR”) (A) and natural rubber (B), and farnesene. A rubber composition comprising a liquid polymer (C) (hereinafter, also simply referred to as "polymer (C)") containing a derived monomer unit (a) and a filler (D), the polymer comprising: The content of (C) is 1 to 50 parts by mass with respect to 100 parts by mass of the solid rubber component, and the content of the filler (D) is 20 to 150 parts by mass with respect to 100 parts by mass of the solid rubber component. And
The content of SBR (A) in said solid rubber component is less than 50 wt percent 100 wt%, the solubility parameter [delta] _A of the SBR (A), the solubility parameter [delta] _B of the natural rubber (B), and polymer (C The solubility parameter δ _{C in} () satisfies the following formula (1).
│δ _A −δ _C │<｜δ _A −δ _B ｜ (1)

In the present invention, the “solubility parameter δ” is calculated based on the Hoy's estimation method, and the estimation method is estimated from the molecular structure based on the cohesive energy density and the molar molecular volume (DW Van Krevelen, K. te Nijenhuis, “Properties of Polymers, Fourth Edition”, Elsevier Science, 2009, pp.216-221).
In the above estimation method, all the structures occupying 10 mol% or more in each of SBR (A), natural rubber (B) or polymer (C) are considered. Also, for structures with less than 10 mol%, those with a clear structure and molar fraction are included in the calculation.
When the calculation method cannot be performed, the solubility parameter can be calculated by an experimental method by determining whether or not the solubility parameter is dissolved in a known solvent, and the solubility parameter can be used as a substitute (“Polymer Handbook 4th Edition (Polymer Handbook Fourth Edition)" by J. Brand, published by Wiley in 1998). In this case, as the solubility parameter of SBR (A), natural rubber (B) and polymer (C) used for calculating the solubility parameter, values obtained by the same experimental method are used.

[Solid rubber component]
In the present invention, the solid rubber component contains SBR (A) and natural rubber (B), and the content of SBR (A) in the solid rubber component is more than 50% by mass and less than 100% by mass.
In the present invention, the “solid rubber” means a solid rubber that is not in a liquid state and usually has a Mooney viscosity (ML1+4) of 20 to 200 at 100°C.

<Styrene butadiene rubber (A)>
As the SBR (A) used as the solid rubber component, those commonly used for tires can be used, but specifically, those having a styrene content of 0.1 to 70% by mass are preferable, and 5 to 50% by mass. Are more preferred. The vinyl content is preferably 0.1 to 60% by mass, more preferably 0.1 to 55% by mass.
The weight average molecular weight (Mw) of SBR is preferably 100,000 to 2,500,000, more preferably 150,000 to 2,000,000, and further preferably 200,000 to 1,500,000. Within the above range, it is possible to achieve both moldability and mechanical strength of the tire obtained.
The glass transition temperature (Tg) of SBR (A) determined by the differential thermal analysis method is preferably in the range of -95 to 0°C, more preferably -95 to -5°C. When the Tg is within the above range, it is possible to suppress the increase in viscosity of the rubber composition and facilitate handling.

The SBR that can be used in the present invention is obtained by copolymerizing styrene and butadiene. The method for producing SBR is not particularly limited, and any of an emulsion polymerization method, a solution polymerization method, a gas phase polymerization method, and a bulk polymerization method can be used, and the emulsion polymerization method and the solution polymerization method are preferable.
Emulsion-polymerized styrene-butadiene rubber (hereinafter, also referred to as “E-SBR”) can be produced by a usual emulsion-polymerization method, for example, a predetermined amount of styrene and butadiene monomer is emulsified and dispersed in the presence of an emulsifier to perform radical polymerization. It is obtained by emulsion polymerization with an initiator. Further, a chain transfer agent can be used to adjust the molecular weight of the obtained E-SBR. After termination of the polymerization reaction, unreacted monomers are removed from the obtained latex as needed, and then salts such as sodium chloride, calcium chloride, potassium chloride are used as a coagulant, and nitric acid, sulfuric acid, etc. are added as necessary. The acid can be added to adjust the pH of the coagulation system to a predetermined value to coagulate the copolymer, and then the dispersion solvent can be separated to recover the copolymer as crumbs. E-SBR can be obtained by washing the crumb with water, dehydration, and drying with a band dryer or the like.

Solution-polymerized styrene-butadiene rubber (hereinafter, also referred to as “S-SBR”) can be produced by a conventional solution-polymerization method, for example, using an anion-polymerizable active metal in a solvent and optionally in the presence of a polar compound. It can be produced by polymerizing styrene, styrene and butadiene. The anion-polymerizable active metal is preferably an alkali metal or an alkaline earth metal, more preferably an alkali metal, and even more preferably an organic alkali metal compound.
Examples of the organic alkali metal compound include organic monolithium compounds such as n-butyllithium, sec-butyllithium, t-butyllithium, hexyllithium, phenyllithium, and stilbenelithium; dilithiomethane, 1,4-dilithiobutane, 1,4- Examples thereof include polyfunctional organolithium compounds such as dilithio-2-ethylcyclohexane and 1,3,5-trilithiobenzene; sodium naphthalene, potassium naphthalene and the like. Among these, organolithium compounds are preferred, and organomonolithium compounds are more preferred. The amount of the organic alkali metal compound used is appropriately determined according to the required molecular weight of S-SBR.
Examples of the solvent include aliphatic hydrocarbons such as n-butane, n-pentane, isopentane, n-hexane, n-heptane and isooctane; cycloaliphatic hydrocarbons such as cyclopentane, cyclohexane and methylcyclopentane; benzene and toluene. And the like. It is generally preferable to use these solvents in a range where the monomer concentration is 1 to 50% by mass.

The polar compound is not particularly limited as long as it does not deactivate the reaction in anionic polymerization and is usually used for adjusting the microstructure of the butadiene site and the distribution in the copolymer chain of styrene. Examples thereof include ether compounds such as dibutyl ether, tetrahydrofuran and ethylene glycol diethyl ether; tertiary amines such as tetramethylethylenediamine and trimethylamine; alkali metal alkoxides and phosphine compounds.
The temperature of the polymerization reaction is usually -80 to 150°C, preferably 0 to 100°C, more preferably 30 to 90°C. The polymerization mode may be either batchwise or continuous. The polymerization reaction can be stopped by adding an alcohol such as methanol or isopropanol as a polymerization terminator. A polymerization end modifier may be added before adding the polymerization terminator. After the termination of the polymerization reaction, the solvent of the polymerization solution can be separated by direct drying, steam stripping or the like to recover the desired S-SBR. Before removing the solvent, the polymerization solution and the extending oil may be mixed in advance and recovered as an oil-extended rubber.

In the present invention, a modified SBR in which a functional group is introduced into SBR may be used as long as the effects of the present invention are not impaired. Examples of the functional group include an amino group, an alkoxysilyl group, a hydroxyl group, an epoxy group, and a carboxyl group. In this modified SBR, the position where the functional group in the polymer is introduced may be at the polymer terminal or at the side chain of the polymer.
These SBRs may be used alone or in combination of two or more. When two or more types of SBR are mixed and used, the combination can be arbitrarily selected within a range that does not impair the effects of the present invention, and the physical properties can be adjusted by the combination.
The content of SBR (A) in the solid rubber component is more than 50% by mass and less than 100% by mass, preferably 60 to 90% by mass, more preferably 65 to 80% by mass.

Further, as the solid rubber component, a synthetic rubber other than SBR(A) may be contained as long as the effect of the present invention is not impaired.
Examples of other synthetic rubber components include butadiene rubber, isoprene rubber, butyl rubber, halogenated butyl rubber, ethylene propylene diene rubber, butadiene acrylonitrile copolymer rubber, and chloroprene rubber. Among these, at least one selected from butadiene rubber and isoprene rubber is preferable, and butadiene rubber is more preferable. Further, the manufacturing method of these is not particularly limited, and commercially available ones can be used.

(Butadiene rubber)
As the butadiene rubber, for example, a commercially available butadiene rubber obtained by polymerization using a Ziegler-based catalyst, a lanthanoid-based rare earth metal catalyst, an organic alkali metal compound, or the like can be used. Among these, butadiene rubber obtained by polymerization using a Ziegler type catalyst is preferable from the viewpoint of high cis content. Also, a butadiene rubber having an ultrahigh cis content obtained by using a lanthanoid rare earth metal catalyst may be used.
The vinyl content of the butadiene rubber is preferably 50% by mass or less, more preferably 40% by mass or less, still more preferably 30% by mass or less. When the vinyl content is 50% by mass or less, the mechanical strength becomes good. The lower limit of the vinyl content is not particularly limited.

The glass transition temperature (Tg) of the butadiene rubber determined by the differential thermal analysis method varies depending on the vinyl content, but is preferably -40°C or lower, more preferably -50°C or lower.
The weight average molecular weight (Mw) of the butadiene rubber is preferably 90,000 to 2,000,000, more preferably 150,000 to 1,500,000, and further preferably 250,000 to 800,000. When the weight average molecular weight is in the above range, the moldability and the mechanical strength of the obtained tire are good.
The butadiene rubber is partially branched by using a polyfunctional modifier such as tin tetrachloride, silicon tetrachloride, an alkoxysilane having an epoxy group in the molecule, or an amino group-containing alkoxysilane. It may have a structure or a polar functional group.

(Isoprene rubber)
As the isoprene rubber, for example, a commercially available isoprene rubber obtained by polymerization using a Ziegler type catalyst, a lanthanoid type rare earth metal catalyst, an organic alkali metal compound or the like can be used. Among these, isoprene rubber obtained by polymerization using a Ziegler type catalyst is preferable from the viewpoint of high cis content. In addition, an isoprene rubber having an ultrahigh cis content obtained by using a lanthanoid rare earth metal catalyst may be used.
The vinyl content of the isoprene rubber is preferably 50% by mass or less, more preferably 40% by mass or less, still more preferably 30% by mass or less. When the vinyl content is 50% by mass or less, the mechanical strength becomes good. The lower limit of the vinyl content is not particularly limited.

The glass transition temperature (Tg) of the isoprene rubber determined by the differential thermal analysis method varies depending on the vinyl content, but it is preferably -20°C or lower, more preferably -30°C or lower.
The weight average molecular weight (Mw) of the isoprene rubber is preferably in the range of 90,000 to 2,000,000, more preferably 150,000 to 1,500,000, still more preferably 500,000 to 1,500,000, and even more preferably 800,000 to 1,500,000. .. When the weight average molecular weight is within the above range, the moldability and the mechanical strength of the obtained tire are good.
The isoprene rubber is partially branched by using a polyfunctional modifier such as tin tetrachloride, silicon tetrachloride, an alkoxysilane having an epoxy group in the molecule, or an amino group-containing alkoxysilane. It may have a structure or a polar functional group.
When the solid rubber component contains a synthetic rubber other than SBR (A), the content of the other synthetic rubber in the solid rubber component is preferably 20% by mass or less, more preferably 10% by mass or less, further preferably 5% by mass or less. It is less than 1% by mass, more preferably less than 1% by mass, and it is even more preferred that the solid rubber component consists only of SBR (A) and natural rubber (B).

<Natural rubber (B)>
The natural rubber (B) used as the solid rubber component is, for example, TSR such as SMR, SIR, STR, natural rubber generally used in the tire industry such as RSS, high-purity natural rubber, epoxidized natural rubber, hydroxylated natural rubber. , Modified natural rubber such as hydrogenated natural rubber and grafted natural rubber. Among these, SMR20, STR20, and RSS#3 are preferable from the viewpoint of little variation in quality and easy availability.
The glass transition temperature (Tg) of the natural rubber (B) determined by the differential thermal analysis method is preferably in the range of -95 to 0°C, more preferably -95 to -5°C. When the Tg is within the above range, it is possible to suppress the increase in viscosity of the rubber composition and facilitate handling.
These natural rubbers may be used alone or in combination of two or more. When two or more kinds of natural rubbers are mixed and used, the combination can be arbitrarily selected within a range that does not impair the effects of the present invention, and the physical properties can be adjusted by the combination.
The content of the natural rubber (B) in the solid rubber component is more than 0% by mass and less than 50% by mass, preferably 10 to 40% by mass, and more preferably 20 to 35% by mass.

<Liquid polymer (C)>
The polymer (C) used in the present invention is a liquid polymer containing a farnesene-derived monomer unit (a) (hereinafter, also simply referred to as “monomer unit (a)”).
In the present invention, the "liquid polymer" is a polymer which is liquid at room temperature, and usually refers to a polymer having a Mooney viscosity (ML1+4) of less than 20 at 100°C.

[Monomer unit (a)]
The monomer unit (a) may be a monomer unit derived from α-farnesene, or may be a monomer unit derived from β-farnesene represented by the following formula (I), Although it may contain a monomer unit derived from α-farnesene and a monomer unit derived from β-farnesene, it is preferable to contain the monomer unit derived from β-farnesene from the viewpoint of ease of production.
The content of the β-farnesene-derived monomer unit is preferably 80 mol% or more, more preferably 90 mol% or more, still more preferably 100 mol, in the monomer unit (a) from the viewpoint of ease of production. %, that is, all the monomer units (a) are β-farnesene-derived monomer units.
The content of the monomer unit (a) in the polymer (C) is preferably 1 to 75% by mass, more preferably 10 to 70% by mass, further preferably from the viewpoint of improving ice grip performance and bleeding resistance. Is in the range of 15 to 65% by mass, more preferably 20 to 55% by mass.

[Monomer unit (b)]
The polymer (C) may be a copolymer further containing a monomer unit (b) derived from a monomer other than farnesene (hereinafter, simply referred to as “monomer unit (b)”). Good.
When the polymer (C) is a copolymer of the monomer unit (a) and the monomer unit (b),
The content of the monomer unit (b) in the polymer (C) is preferably 25 to 99% by mass, more preferably 30 to 90% by mass, still more preferably 35 to 85% by mass, still more preferably 45 to 90% by mass. It is in the range of 80% by mass.
The monomer other than farnesene capable of forming the monomer unit (b) is not particularly limited as long as it is copolymerizable with farnesene, and examples thereof include an aromatic vinyl compound and a conjugated diene compound other than farnesene, Examples thereof include acrylic acid and its derivatives, methacrylic acid and its derivatives, acrylamide and its derivatives, methacrylamide and its derivatives, and acrylonitrile.

Examples of the aromatic vinyl compound include styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-propylstyrene, 4-t-butylstyrene, 4-cyclohexylstyrene and 4-methylstyrene. Dodecylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, 2,4,6-trimethylstyrene, 2-ethyl-4-benzylstyrene, 4-(phenylbutyl)styrene, N,N-diethyl-4. -Styrene derivatives such as aminoethylstyrene, 4-methoxystyrene, monochlorostyrene and dichlorostyrene; 1-vinylnaphthalene, 2-vinylnaphthalene, vinylanthracene, vinylpyridine and the like. Among these, styrene and its derivatives are preferable, and styrene is more preferable. These aromatic vinyl compounds may be used alone or in combination of two or more.

Examples of the conjugated diene compound include butadiene, isoprene, 2,3-dimethylbutadiene, 2-phenylbutadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene and 1,3-octadiene. , 1,3-cyclohexadiene, 2-methyl-1,3-octadiene, 1,3,7-octatriene, myrcene, chloroprene and the like. Among these, butadiene, isoprene and myrcene are preferable, and butadiene is more preferable. These conjugated dienes may be used alone or in combination of two or more.

As the acrylic acid derivative, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, isononyl acrylate, lauryl acrylate, Stearyl acrylate, cyclohexyl acrylate, isobornyl acrylate, dicyclopentenyl oxyethyl acrylate, tetraethylene glycol acrylate, tripropylene glycol acrylate, 4-hydroxybutyl acrylate, 3-hydroxy-1-adamantyl acrylate, acrylic Examples thereof include tetrahydrofurfuryl acid, methoxyethyl acrylate, and N,N-dimethylaminoethyl acrylate.

Examples of the methacrylic acid derivatives include methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, tridecyl methacrylate, stearyl methacrylate, Cyclohexyl methacrylate, isobornyl methacrylate, dicyclopentanyl methacrylate, benzyl methacrylate, dicyclopentenyloxyethyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxy-1-adamantyl methacrylate. , Tetrahydrofurfuryl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, glycidyl methacrylate, and the like.

Examples of the acrylamide derivative include dimethylacrylamide, acryloylmorpholine, isopropylacrylamide, diethylacrylamide, dimethylaminopropylacrylamide, dimethylaminopropylacrylamide methyl chloride quaternary salt, hydroxyethylacrylamide, and 2-acrylamido-2-methylpropanesulfonic acid. Can be mentioned.

Examples of the methacrylamide derivative include dimethylmethacrylamide, methacryloylmorpholine, isopropylmethacrylamide, diethylmethacrylamide, dimethylaminopropylmethacrylamide, and hydroxyethylmethacrylamide.
These other monomers may be used alone or in combination of two or more.

The polymer (C) further contains at least one selected from a monomer unit (b-1) derived from an aromatic vinyl compound and a monomer unit (b-2) derived from a conjugated diene compound other than farnesene. Is preferred, and it is more preferred that the monomer unit (b-1) derived from an aromatic vinyl compound (hereinafter, also simply referred to as “monomer unit (b-1)”) is included. This makes it possible to maintain good wet grip performance while improving ice grip performance and bleed resistance.
The content of the monomer unit (b-1) in the polymer (C) is preferably 1 to 40 mass from the viewpoint of improving ice grip performance and bleeding resistance and maintaining good wet grip performance. %, more preferably 5 to 35% by mass, and further preferably 10 to 30% by mass.
The polymer (C) is a monomer unit (b-2) of a conjugated diene compound other than farnesene (hereinafter referred to as “from the viewpoint of improving ice grip performance and bleeding resistance” and maintaining good wet grip performance). , And also simply referred to as “monomer unit (b-2)”). The content of the monomer unit (b-2) in the polymer (C) is preferably 15 to 60% by mass, more preferably 20 to 55% by mass, and further preferably 25 to 50% by mass.

The polymer (C) is a monomer unit (b) derived from an aromatic vinyl compound as a monomer unit (b) from the viewpoint of improving ice grip performance and bleeding resistance and maintaining good wet grip performance. It is preferable to use b-1) together with a monomer unit (b-2) derived from a conjugated diene compound other than farnesene.
The mass ratio [(b-1)/(b-2)] of the content of the monomer unit (b-1) to the content of the monomer unit (b-2) in the polymer (C) is preferably Is 10/90 to 50/50, more preferably 15/85 to 45/55, and further preferably 20/80 to 40/60.
When the monomer unit (b-1) and the monomer unit (b-2) are used in combination, the combination of the monomer unit (b-1) and the monomer unit (b-2) is styrene. A combination of a monomer unit derived from the monomer unit and a monomer unit derived from at least one compound selected from butadiene, isoprene and myrcene is preferable, and a monomer unit derived from the styrene and at least 1 selected from butadiene and isoprene. A combination with a monomer unit derived from a certain compound is more preferable, and a combination of a monomer unit derived from styrene and a monomer unit derived from butadiene is further preferable.

The glass transition temperature (Tg) of the polymer (C) obtained by the differential thermal analysis is different from that of other than the farnesene-derived monomer unit (a) and the binding mode (microstructure). Although it varies depending on the content of the monomer unit (b), it is preferably −100 to −36° C., more preferably −80 to −40° C., further preferably −75 to −45° C., and even more preferably − It is in the range of 70 to -50°C. Within the above range, a flexible polymer is obtained, and moldability, wet grip performance and ice grip performance are improved.
The glass transition temperature in the present invention is based on the method described in Examples below.

The weight average molecular weight (Mw) of the polymer (C) is preferably 2,000 to 500,000, more preferably 4,000 to 300,000, still more preferably 6,000 to 100,000, still more preferably 8,000. The range is up to 50,000. When the weight average molecular weight (Mw) is within the above range, excellent mechanical strength, fluidity and molding processability can be obtained.
The molecular weight distribution (Mw/Mn) of the polymer (C) is preferably 1.0 to 4.0, more preferably 1.0 to 3.0, still more preferably 1.0 to 2.0, even more preferably. Is in the range of 1.0 to 1.5. When Mw/Mn is within the above range, the variation in the viscosity of the polymer (C) becomes small.
The weight average molecular weight and the molecular weight distribution in the present invention are based on polystyrene conversion determined by gel permeation chromatography (GPC) by the method described in the examples below.

The vinyl content of the monomer unit (a) of the polymer (C) is preferably 3 to 50 mol%, more preferably 5 to 40 mol%, further preferably from the viewpoint of improving ice grip performance and bleeding resistance. Is in the range of 10 to 30 mol %.
When the polymer (C) is a copolymer and the monomer unit (b) contains a butadiene-derived monomer unit, the vinyl content of the butadiene-derived monomer unit of the polymer (C) Is preferably 3 to 30 mol%, more preferably 5 to 25 mol%, and further preferably 7 to 20 mol% from the viewpoint of improving ice grip performance and bleeding resistance.
In the present invention, the “vinyl content of the monomer unit (a)” refers to the content of the mode of bonding in the monomer units derived from farnesene, excluding the 1,4 bond as represented by the following formula (II). Yes, it can be measured by the method using ¹ H-NMR described in Examples below.
The "vinyl content of the butadiene-derived monomer unit" is the content of the butadiene-derived monomer units in the bonding mode excluding the 1,4 bond, and is described in Examples described later. ^It can be measured by a method using ¹ H-NMR.

The content of the polymer (C) in the rubber composition is 1 to 50 parts by mass, preferably 3 to 40 parts by mass, with respect to 100 parts by mass of the solid rubber component, from the viewpoint of improving ice grip performance and bleeding resistance. Parts, more preferably 5 to 30 parts by mass.

(Method for producing liquid polymer (C))
As the polymer (C), a farnesene-containing monomer is described in an emulsion polymerization method, a solution polymerization method, a bulk polymerization method, a suspension polymerization method or International Publication No. 2010/027463 and International Publication No. 2010/027464. It can be manufactured by the method described above. Among these, the emulsion polymerization method or the solution polymerization method is preferable, and the solution polymerization method is more preferable.

The farnesene contained in the monomer used in the method for producing the polymer (C) may be α-farnesene, or β-farnesene represented by the formula (I), and α-farnesene Farnesene and β-farnesene may be mixed and used. Farnesene used in the production method of the present invention, from the viewpoint of ease of production, preferably contains β-farnesene, the content of β-farnesene in the total amount of farnesene is preferably 80 mol% or more, more preferably It is 90 mol% or more, more preferably 100 mol %.
The content of farnesene in the monomer used in the method for producing the polymer (C) is preferably 1 to 75% by mass, more preferably 10 to 70% by mass, still more preferably 15 to 65% by mass, still more preferably Is in the range of 20 to 55 mass %.
The monomer may further contain a monomer other than farnesene. Examples of such other monomer include a monomer capable of forming the above-mentioned monomer unit (b).
The content of other monomers in the monomers used in the method for producing the polymer (C) is preferably 25 to 99% by mass, more preferably 30 to 90% by mass, and further preferably 35 to 85% by mass. , And more preferably 45 to 80% by mass.

(Solution polymerization method)
A known method can be applied to the solution polymerization method used as the production method of the present invention. For example, in a solvent, a Ziegler-based catalyst, a metallocene-based catalyst, and an anion-polymerizable active metal are used to polymerize a monomer containing farnesene, optionally in the presence of a polar compound.
Examples of the anion-polymerizable active metal include alkali metals such as lithium, sodium and potassium; alkaline earth metals such as beryllium, magnesium, calcium, strontium and barium; lanthanide rare earth metals such as lanthanum and neodymium. .. Among these, alkali metals and alkaline earth metals are preferable, and alkali metals are more preferable. Among the alkali metals, organic alkali metal compounds are more preferable.

Examples of the organic alkali metal compound include organic lithium compounds such as methyllithium, ethyllithium, n-butyllithium, sec-butyllithium, t-butyllithium, hexyllithium, phenyllithium and stilbenelithium; dilithiomethane, dilithionaphthalene. 1,4-dilithiobutane, 1,4-dilithio-2-ethylcyclohexane, 1,3,5-trilithiobenzene, and other polyfunctional organolithium compounds; sodium naphthalene, potassium naphthalene, and the like. Among these, organolithium compounds are preferred, and organomonolithium compounds are more preferred. The amount of the organic alkali metal compound used is appropriately determined according to the required molecular weight of the liquid polymer, but is preferably 0.01 to 3 parts by mass with respect to 100 parts by mass of the monomer.
The organic alkali metal compound can also be used as an organic alkali metal amide by reacting with a secondary amine such as dibutylamine, dihexylamine or dibenzylamine.

Examples of the solvent include aliphatic hydrocarbons such as n-butane, n-pentane, isopentane, n-hexane, n-heptane and isooctane; alicyclic hydrocarbons such as cyclopentane, cyclohexane and methylcyclopentane; benzene, Examples thereof include aromatic hydrocarbons such as toluene and xylene.

The polar compound is used for controlling the microstructure or random structure of the farnesene-derived portion or the conjugated diene compound-derived portion other than farnesene without deactivating the reaction in anionic polymerization. Examples of polar compounds include ether compounds such as dibutyl ether, diethyl ether, tetrahydrofuran, dioxane, and ethylene glycol diethyl ether; pyridine; tertiary amines such as tetramethylethylenediamine and trimethylamine; alkali metal alkoxides such as potassium t-butoxide. A phosphine compound and the like. The polar compound is preferably used in the range of 0.01 to 1,000 molar equivalents with respect to the organic alkali metal compound.

The polymerization temperature of the solution polymerization is usually -80 to 150°C, preferably 0 to 100°C, more preferably 10 to 90°C. The polymerization mode may be either batch type or continuous type.
When the polymer (C) is a copolymer, farnesene and a compound other than farnesene are added to the reaction solution so that the composition ratio of farnesene and a monomer other than farnesene in the polymerization system falls within a specific range. The other monomer may be continuously or intermittently supplied. In addition, a random copolymer can be produced by supplying a mixture of farnesene and a monomer other than farnesene adjusted to a specific composition ratio in advance. Further, the block copolymer can be produced by sequentially polymerizing farnesene and a monomer other than farnesene in the reaction solution so as to have a specific composition ratio.
The polymerization reaction can be stopped by adding an alcohol such as methanol or isopropanol as a polymerization terminator. The copolymer can be isolated by pouring the obtained polymerization reaction solution into a poor solvent such as methanol to precipitate the copolymer, or washing the polymerization reaction solution with water, separating and drying it.

(Emulsion polymerization method)
A known method can be applied to the emulsion polymerization method used as the method for producing the polymer (C). For example, a monomer containing a predetermined amount of farnesene is emulsified and dispersed in the presence of an emulsifier, and emulsion-polymerized with a radical polymerization initiator.
As the emulsifier, for example, a long-chain fatty acid salt having 10 or more carbon atoms or a rosin acid salt is used. Specific examples thereof include potassium or sodium salts of fatty acids such as capric acid, lauric acid, myristic acid, palmitic acid, oleic acid, stearic acid.
Water is usually used as the dispersant, and may contain a water-soluble organic solvent such as methanol or ethanol as long as the stability during polymerization is not impaired.
Examples of the radical polymerization initiator include persulfates such as ammonium persulfate and potassium persulfate, organic peroxides, hydrogen peroxide and the like.

A chain transfer agent may be used to adjust the molecular weight of the resulting polymer (C). Examples of the chain transfer agent include mercaptans such as t-dodecyl mercaptan and n-dodecyl mercaptan; carbon tetrachloride, thioglycolic acid, diterpenes, terpinolene, γ-terpinene, α-methylstyrene dimer and the like.
The polymerization temperature of the emulsion polymerization can be appropriately selected depending on the type of radical polymerization initiator used, but is usually 0 to 100°C, preferably 0 to 60°C. The polymerization mode may be either continuous or batch.
The polymerization reaction can be stopped by adding a polymerization terminator. Examples of the polymerization terminator include amine compounds such as isopropylhydroxylamine, diethylhydroxylamine and hydroxylamine, quinone compounds such as hydroquinone and benzoquinone, and sodium nitrite.
After stopping the polymerization reaction, an antioxidant may be added if necessary. After termination of the polymerization reaction, unreacted monomers are removed from the obtained latex as needed, and then salts such as sodium chloride, calcium chloride, potassium chloride are used as a coagulant, and nitric acid, sulfuric acid, etc. are added as necessary. The polymer (C) is coagulated while the pH of the coagulation system is adjusted to a predetermined value by adding an acid, and then the dispersion solvent is separated to recover the polymer (C). Next, the polymer (C) is obtained by washing with water, dehydration and drying. In addition, at the time of coagulation, if necessary, the latex and the extending oil made into an emulsion dispersion may be mixed in advance and recovered as an oil-extended polymer.

(Solubility parameter)
In the present invention, the solid rubber component is preferably an incompatible polymer blend. As a result, the rubber obtained by vulcanizing the rubber composition forms a sea-island phase-separated structure, and when the content of SBR (A) in the solid rubber component is within the above range, the SBR (A) The phase (hereinafter, also simply referred to as “(A) phase”) is a sea phase, and the phase made of natural rubber (B) (hereinafter, also simply referred to as “(B) phase”) is an island phase.

Then, in the present invention, the solubility parameter [delta] _A of the SBR (A), the solubility parameter [delta] _B of the natural rubber (B), and the solubility parameter [delta] _C of the polymer (C) satisfies the following formula (1).
│δ _A −δ _C │<｜δ _A −δ _B ｜ (1)
As a result, the polymer (C) is compatible with the (A) phase, more polymer (C) is distributed to the (A) phase, and the plasticizing effect of the polymer (C) improves flexibility. , The ice grip performance can be improved.
The order of the solubility parameters δ _A , δ _B , and δ _C may be in the order of δ _A >δ _C >δ _B or δ _C >δ _A >δ _B , and preferably δ _A >δ _C >δ _B.
The upper limit of δ _C is not particularly limited as long as the effect of the present invention is not impaired. For example, when δ _C >δ _A , it is preferable that δ _C <δ _B +2.0, and δ _C <δ _B +1. It is more preferably 0.6.
The unit of the solubility parameter is (J/cm ³ ) ^1/2 .

The absolute value |δ _A −δ _C | of the difference between the solubility parameters of SBR (A) and polymer (C) is preferably 0 to 0.60 (from the viewpoint of improving flexibility and improving ice grip performance. J / cm ^{3) 1/2,} more preferably ^{0~0.50 (J / cm 3) 1/2} , more preferably ^{0~0.40 (J / cm 3) 1/2} , more preferably more 0 Is about 0.30 (J/cm ³ ) ^1/2 .
The absolute value |δ _A −δ _B | of the difference in solubility parameter between SBR (A) and natural rubber (B) is preferably 0.65 to 0 from the viewpoint of forming a sea-island phase-separated structure. .90 (J/cm ³ ) ^1/2 , more preferably 0.70 to 0.85 (J/cm ³ ) ^1/2 , still more preferably 0.75 to 0.80 (J/cm ³ ) ^{1/ Is 2} .

Further, the absolute value |δ _B −δ _C | of the difference in solubility parameter between the natural rubber (B) and the polymer (C) is preferably more than 0.20 (J/cm ³ ) ^1/2 . Thereby, the polymer (C) is more distributed to the (A) phase than the (B) phase, the flexibility is improved, and the ice grip performance can be improved.
From such a viewpoint, the difference in solubility parameter |δ _B −δ _C | between the natural rubber (B) and the polymer (C) is preferably more than 0.20 (J/cm ³ ) ^1/2 , It is more preferably 0.30 (J/cm ³ ) ^1/2 or more, ^still more preferably 0.50 (J/cm ³ ) ^1/2 or more. The upper limit of the absolute value |δ _B −δ _C | of the difference in solubility parameter between the natural rubber (B) and the polymer (C) is not particularly limited, but preferably less than 2.0 (J/cm ³ ) ^1/2. , And more preferably less than 1.6 (J/cm ³ ) ^1/2 .

Although the solubility parameter δ _A of SBR(A) changes depending on the styrene content, the butadiene content, and the vinylation degree of butadiene, it is preferably 18.20 to 19 from the viewpoint of improving flexibility and improving ice grip performance. .50 (J/cm ³ ) ^1/2 , more preferably 18.40 to 19.10 (J/cm ³ ) ^1/2 , still more preferably 18.60 to 18.90 (J/cm ³ ) ^{1/ Is 2} . As a specific solubility parameter δ _A , for example, when the vinylation degree is 20%, the SBR having a styrene content of 20% by mass and a butadiene content of 80% by mass is 18.70 (J/cm ³ ) ^1/2 , and the styrene content is SBR with 40 mass% and butadiene content of 60 mass% is 18.95 (J/cm ³ ) ^1/2 , SBR with styrene content of 60 mass% and butadiene content of 40 mass% is 19.20 (J/cm ³ ) ^{1/ Is 2} . When the degree of vinylation is 60%, the SBR having a styrene content of 20 mass% and a butadiene content of 80 mass% is 18.21 (J/cm ³ ) ^1/2 , a styrene content of 40 mass% and a butadiene content of 60 mass%. Has an SBR of 18.57 (J/cm ³ ) ^1/2 , a styrene content of 60 mass% and a butadiene content of 40 mass% of SBR is 18.95 (J/cm ³ ) ^1/2 .
When two or more rubbers are used together as SBR(A), the solubility parameter δ _A of SBR(A) is the solubility of polymer (C) in the rubber contained in SBR(A) in an amount of 20% by mass or more. The value closest to the parameter is taken as the solubility parameter δ _A of SBR(A). When there is no rubber occupying 20% by mass or more in the SBR(A), the solubility parameter of the most abundant rubber in the SBR(A) is the solubility parameter δ _A of the SBR(A). ..

The solubility parameter δ _B of the natural rubber (B) is preferably 17.60 to 18.50 (J/cm ³ ) ^1/2 , more preferably 17 from the viewpoint of improving flexibility and improving ice grip performance. It is 0.80 to 18.30 (J/cm ³ ) ^1/2 , and more preferably 18.0 to 18.10 (J/cm ³ ) ^1/2 . As a specific solubility parameter δ _B , for example, natural rubber is 18.02 (J/cm ³ ) ^1/2 .
When two or more kinds of rubbers are used together as the natural rubber (B), the solubility parameter of the natural rubber (B) is the same as that of the polymer (C) among the rubbers contained in the natural rubber (B) in an amount of 20% by mass or more. The value closest to the solubility parameter is taken as the solubility parameter of the natural rubber (B). When there is no rubber occupying 20% by mass or more of the natural rubber (B), the solubility parameter of the most abundant rubber in the natural rubber (B) is regarded as the solubility parameter of the natural rubber (B). To do.

The solubility parameter δ _C of the polymer (C) is preferably 18.0 to 19.50 (J/cm ³ ) ^1/2 , more preferably 18 from the viewpoint of improving flexibility and improving ice grip performance. The range is from 0.10 to 19.00 (J/cm ³ ) ^1/2 , more preferably from 18.30 to 18.80 (J/cm ³ ) ^1/2 .
When two or more polymers (C) are used together as the polymer (C), the solubility parameter of the polymer (C) is the solubility parameter calculated by the weighted average from the molar ratio of each polymer (C). Used as the solubility parameter of the combined (C).

In the present invention, from the viewpoint of improving flexibility, improving ice grip performance, and maintaining good wet grip performance, SBR relative to the absolute value of the difference in solubility parameter between SBR (A) and natural rubber (B). The ratio of absolute values of the difference in solubility parameter between (A) and the polymer (C) {|δ _A −δ _C |/|δ _A −δ _B |} (hereinafter, simply referred to as “ratio {|δ _A −δ _C | /|δ _A −δ _B |}”) further preferably satisfies the following formula (2).
{|δ _A −δ _C |/|δ _A −δ _B |}<0.80 (2)
The ratio {|δ _A −δ _C |/|δ _A −δ _B |} is preferably 0 from the viewpoint of improving flexibility and improving ice grip performance, and maintaining good wet grip performance. It is 0.75, more preferably 0 to 0.60, still more preferably 0 to 0.50, still more preferably 0 to 0.40, still more preferably 0 to 0.30.

(Distribution ratio)
In the present invention, the distribution ratio of the polymer (C) to the SBR (A) and the natural rubber (B) [(A)/(B)] (hereinafter, also simply referred to as “distribution ratio [(A)/(B)]” (Referred to) is preferably 55/45 or more.
In the present invention, the “distribution ratio” refers to the distribution ratio of the polymer (C) to each phase in the solid rubber component having the (A) phase and the (B) phase.
When the distribution ratio [(A)/(B)] is 55/45 or more, more polymer (C) is distributed from (B) phase to (A) phase, and due to the plasticizing effect of polymer (C). The flexibility can be improved and the ice grip performance can be improved. From such a viewpoint, the distribution ratio [(A)/(B)] is preferably 55/45 to 100/0, more preferably 60/40 to 100/0, and further preferably 70/30 to 100/0. , And more preferably 80/20 to 100/0.
The distribution ratio is measured by differential scanning calorimetry (DSC) using a measuring rubber mixture containing SBR (A), natural rubber (B) and polymer (C) to obtain a base rubber having a Tg of the rubber mixture. When the amount of change from Tg ₁ is 0.5° C. or more, it is calculated by DSC, and when the amount of change is less than 0.5° C., the area ratio of the AFM image is determined by using an atomic force microscope (AFM). It is calculated.

In the present invention, the method for calculating the distribution ratio of the polymer (C) using DSC is based on the report by Naito et al. (Naito (1996), Journal of Applied Polymer Science, 61, 5, 755-762). is there.
Naito et al. reported that in incompatible polymer blends such as natural rubber/butadiene rubber and natural rubber/SBR, additives such as oil exhibit a partitioning phenomenon in each phase, and a plurality of incompatible polymers And a method of qualitatively estimating the distribution of oil from the change of the glass transition temperature (Tg) of the polymer using oil.
Therefore, in the present invention, SBR (A), from Tg ₁ of natural rubber (B) and Tg based rubber polymer (C) a rubber mixture comprising (i.e. SBR (A) or natural rubber (B)) When the amount of change is 0.5° C. or higher, it is calculated from the change in Tg measured by differential calorimetry (DSC) based on the method by Naito et al.
The method of calculating the distribution ratio by DSC will be described below.
Generally, when the base rubber and the liquid rubber are compatible with each other, the Tg of these rubber mixtures is represented by the Fox equation of the following equation (3).

(In the formula (3), Tg is the glass transition temperature of the rubber mixture, Tg ₁ is the glass transition temperature of the base rubber, Tg ₂ is the glass transition temperature of the liquid rubber, and X is the weight fraction of the liquid rubber.)

When the above formula (3) is arranged for the weight fraction X of the liquid rubber, it is represented by the following formula (4).
In addition, each code|symbol in following formula (4) is synonymous with said formula (3).

Therefore, in the present invention, first, SBR (A) as the base rubber and the polymer (C) as the liquid rubber are used in advance to measure Tg when they are compatible with each other at the weight fraction X, and 1/Tg and the polymer ( A calibration curve with the weight fraction X of C) is prepared to obtain the slope and intercept of the formula (4) relating to the rubber mixture containing SBR (A), the polymer (C) and the crosslinking agent.
Similarly, the natural rubber (B) as the base rubber and the polymer (C) as the liquid rubber are used to measure the Tg when they are compatible with each other in the weight fraction X, and the natural rubber (B), the polymer (C) and Obtain the slope and intercept of equation (4) for the rubber mixture containing the crosslinker.
Then, the Tg of a rubber mixture (mass ratio [(A)/(B)/(C)]=50/50/20) containing SBR(A), natural rubber (B), polymer (C) and a crosslinking agent. And using the two calibration curves obtained, the weight fraction X _A of the polymer (C) compatible with the phase ( _A ) and the weight of the polymer (C) compatible with the phase (B). Calculate the fraction X _B. Then, the ratio (X _A /X _B ) of the weight fractions X _A and X _B calculated in this way is calculated by dividing the distribution ratio [(A) of the polymer (C) to the SBR (A) and the natural rubber (B). /(B)].
The rubber mixture is prepared by kneading SBR (A), natural rubber (B) and polymer (C) together with a crosslinking agent and other additives in a prescribed formulation to prepare a rubber mixture. The rubber mixture is prepared, for example, by adding SBR (A), natural rubber (B) and polymer (C) to a Brabender in a predetermined formulation, kneading the mixture at a starting temperature of 130° C. and a rotation speed of 100 rpm for 5 minutes, and then blending it. Take out to the outside of lavender and cool to room temperature, put them and the cross-linking agent and other additives into the brabender, knead for 2 minutes at a starting temperature of 80°C and a rotation speed of 80 rpm, then take out of the brabender and cool to room temperature. , Rubber mixtures can be prepared.

Next, a method of calculating the distribution ratio of the polymer (C) using AFM will be described.
The distribution ratio of the polymer (C) using AFM was calculated by observing the cross section of the vulcanized sheet using AFM, and the obtained AFM image was subjected to image analysis to determine the area ratio of the (A) phase and the (B) phase. It is calculated from [(A)/(B)].
Specifically, first, after producing a vulcanized sheet of a crosslinked product (vulcanized rubber) composed of a rubber mixture of SBR (A) and natural rubber (B) containing no polymer (C), an ultramicrotome or the like is prepared. A vulcanized sheet is used to make a smooth observation cross section. An AFM image showing the phase-separated structure of the (A) phase and the (B) phase is obtained from the phase difference image that reflects the viscoelasticity of the surface of the vulcanized sheet, which is obtained by the method called the phase mode of AFM. By performing image analysis on the obtained AFM image, the area ratio [(A)/(B) of the (A) phase and the (B) phase can be obtained from the phase difference between the (A) phase and the (B) phase. ] Can be calculated.
When an AFM image of a vulcanized sheet of a crosslinked product (vulcanized rubber) composed of a rubber mixture of SBR (A), natural rubber (B) and polymer (C) is observed, a phase in which the polymer (C) is compatible Area ratio increases. Therefore, in the present invention, the area ratio [(A)/(B)] of the (A) phase and the (B) phase in the vulcanized sheet containing the polymer (C) whose distribution ratio is known is calculated by DSC, and The difference between the area ratio [(A)/(B)] of the (A) phase and the (B) phase in the vulcanized sheet not containing the coalescence (C) is obtained, and the difference in the area ratio obtained from the AFM image is taken as the x-axis. , A distribution curve [(A)/(B)] obtained from DSC is used as a y-axis to prepare a calibration curve.
Next, by observing the AFM image of the vulcanized sheet to be evaluated, measuring the area ratio, and using the calibration curve, the distribution ratio of the polymer (C) using AFM can be calculated. Details of the method of calculating the distribution ratio will be described in Examples described later.
Note that, depending on the composition of the rubber mixture, the vulcanized sheet contains an oligomer component, so that the oligomer bleeds out on the surface after cross-section preparation, which may make the surface unstable and not suitable for observation. In this case, as a pretreatment, the vulcanized sheet before the observation cross-section preparation may be subjected to an extraction treatment of the oligomer component by immersing it in a solvent in which both the solid rubber component and the polymer (C) are insoluble. Further, regarding the preparation of the observed cross section of the vulcanized sheet, the cross section may be prepared by freezing the vulcanized sheet with liquid nitrogen and breaking it.

<Filler (D)>
The rubber composition of the present invention contains the filler (D) in an amount of 20 to 150 parts by mass based on 100 parts by mass of the solid rubber component.
By using the filler (D), physical properties such as mechanical strength, heat resistance, and weather resistance are improved, hardness can be adjusted, and the amount of the rubber composition can be increased.
Examples of the filler (D) used in the present invention include oxides such as silica and titanium oxide; silicates such as clay, talc, mica, glass fiber and glass balloons; carbonates such as calcium carbonate and magnesium carbonate; magnesium hydroxide. , Hydroxides such as aluminum hydroxide; sulfates such as calcium sulfate and barium sulfate; inorganic fillers such as carbons such as carbon black and carbon fiber; organic fillers such as resin particles, wood powder and cork powder. .. These may be used alone or in combination of two or more.
The content of the filler (D) in the rubber composition is 20 to 150 parts by mass, preferably 25 to 130 parts by mass, and more preferably 30 to 110 parts by mass with respect to 100 parts by mass of the solid rubber component. is there. When the content of the filler (D) is in the above range, moldability, braking performance, mechanical strength, and wear resistance are improved.

The filler (D) is preferably an inorganic filler, more preferably at least one selected from silica and carbon black, from the viewpoint of improving moldability, braking performance, mechanical strength, and wear resistance, and silica and carbon black Is more preferably used in combination.

〔silica〕
Examples of the silica include dry process silica (silicic acid anhydride), wet process silica (silicic acid anhydride), calcium silicate, aluminum silicate, and the like. Moldability, braking performance, mechanical strength, and abrasion resistance are included. From the viewpoint of improving the properties, wet process silica is preferable. These may be used alone or in combination of two or more.
The average particle diameter of silica is preferably 0.5 to 200 nm, more preferably 5 to 150 nm, further preferably 10 to 100 nm, from the viewpoint of improving moldability, braking performance, mechanical strength, and wear resistance. More preferably, it is 10 to 60 nm.
The average particle diameter of silica can be determined by measuring the diameter of the particles with a transmission electron microscope and calculating the average value.

〔Carbon black〕
As the carbon black, for example, carbon black such as furnace black, channel black, thermal black, acetylene black, and Ketjen black can be used. Of these, furnace black is preferable from the viewpoint of improving the vulcanization rate of the rubber composition and the mechanical strength of the vulcanized product. These may be used alone or in combination of two or more.
Examples of commercially available furnace blacks include Mitsubishi Chemical Co., Ltd. "Dia Black", Tokai Carbon Co., Ltd. "Ceast", and the like. Examples of commercially available acetylene black include “Denka Black” manufactured by Denki Kagaku Kogyo Co., Ltd. Examples of commercially available Ketjen Black include “ECP600JD” manufactured by Lion Corporation.

The carbon black may be subjected to an acid treatment with nitric acid, sulfuric acid, hydrochloric acid or a mixed acid thereof, or a surface oxidation treatment by a heat treatment in the presence of air, from the viewpoint of improving the wettability and dispersibility in the rubber component. .. From the viewpoint of improving mechanical strength, heat treatment may be performed at 2,000 to 3,000°C in the presence of a graphitization catalyst. As the graphitization catalyst, boron, boron oxide (for example, B ₂ O ₂ , B ₂ O ₃ , B ₄ O ₃ , B ₄ O ₅ etc.), boron oxo acid (for example, orthoboric acid, metaboric acid, Tetraboric acid and the like) and salts thereof, boron carbide (for example, B ₄ C, B ₆ C and the like), boron nitride (BN) and other boron compounds are preferably used.

The average particle size of carbon black can be adjusted by pulverization or the like. For crushing carbon black, high speed rotary crusher (hammer mill, pin mill, cage mill), various ball mills (rolling mill, vibration mill, planetary mill), stirring mill (bead mill, attritor, flow tube mill, annular mill) Etc. can be used.
The average particle size of carbon black is preferably 5 to 100 nm, more preferably 5 to 80 nm, and still more preferably 10 to 70 nm from the viewpoint of improving the dispersibility of carbon black, the wear resistance of the tire, and the mechanical strength.
The average particle diameter of carbon black can be determined by measuring the diameter of the particles with a transmission electron microscope and calculating the average value.

When carbon black and silica are used in combination in the rubber composition of the present invention, the compounding ratio of each component is not particularly limited and can be appropriately selected according to the desired performance.

<Arbitrary ingredients>
The rubber composition of the present invention may contain optional components other than the components (A) to (D) within a range that does not impair the effects of the present invention. The content of the optional component in the rubber composition is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, and further preferably 20 parts by mass or less with respect to 100 parts by mass of the solid rubber component.

(Silane coupling agent)
The rubber composition of the present invention preferably contains a silane coupling agent. Examples of the silane coupling agent include sulfide compounds, mercapto compounds, vinyl compounds, amino compounds, glycidoxy compounds, nitro compounds and chloro compounds.
Examples of the sulfide compound include bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilyl). Ethyl) tetrasulfide, bis(3-triethoxysilylpropyl) trisulfide, bis(3-trimethoxysilylpropyl) trisulfide, bis(3-triethoxysilylpropyl) disulfide, bis(3-trimethoxysilylpropyl) disulfide , 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, 3-triethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, 2-trimethoxysilylethyl-N,N-dimethylthiocarbamoyltetrasulfide Examples thereof include sulfide, 3-trimethoxysilylpropyl benzothiazole tetrasulfide, 3-triethoxysilylpropyl benzothiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide and 3-trimethoxysilylpropyl methacrylate monosulfide.
Examples of the mercapto-based compound include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, and 2-mercaptoethyltriethoxysilane.

Examples of vinyl compounds include vinyltriethoxysilane and vinyltrimethoxysilane.
Examples of amino compounds include 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-(2-aminoethyl)aminopropyltriethoxysilane, and 3-(2-aminoethyl)aminopropyltrimethoxysilane. Examples thereof include silane.
Examples of the glycidoxy compound include γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, and γ-glycidoxypropylmethyldimethoxysilane. Can be mentioned.
Examples of the nitro compound include 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane.
Examples of the chloro-based compound include 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane, and 2-chloroethyltriethoxysilane.
These may be used alone or in combination of two or more. Among these, bis(3-triethoxysilylpropyl)disulfide, bis(3-triethoxysilylpropyl)tetrasulfide, and 3-mercaptopropyltrimethoxysilane are preferable from the viewpoint of large addition effect and cost.

When the silane coupling agent is contained, the content of the silane coupling agent is preferably 0.1 to 30 parts by mass, more preferably 0.5 to 20 parts by mass, and 1 to 15 parts by mass with respect to 100 parts by mass of silica. Part by mass is more preferred. When the content of the silane coupling agent is within the above range, the dispersibility, the coupling effect, the reinforcing property, and the wear resistance of the tire are improved.

(Filler other than silica and carbon black)
The rubber composition of the present invention contains, if necessary, silica and carbon for the purpose of improving mechanical strength, improving physical properties such as heat resistance and weather resistance, adjusting hardness, and improving economy by including an extender. It may further contain a filler other than black.
When the rubber composition of the present invention contains a filler other than silica and carbon black, the content thereof is preferably 0.1 to 120 parts by mass, more preferably 5 to 90 parts by mass with respect to 100 parts by mass of the solid rubber component. Preferably, it is 10 to 80 parts by mass, and more preferably. When the content of the filler is within the above range, the mechanical strength of the vulcanized product is further improved.

(Crosslinking agent)
The rubber composition of the present invention is preferably used after being crosslinked (vulcanized) by adding a crosslinking agent. Examples of the cross-linking agent include sulfur and sulfur compounds, oxygen, organic peroxides, phenol resins and amino resins, quinone and quinone dioxime derivatives, halogen compounds, aldehyde compounds, alcohol compounds, epoxy compounds, metal halides and organometallic halogens. Compounds, silane compounds other than silane coupling agents, and the like. Among these, sulfur and sulfur compounds are preferable. These may be used alone or in combination of two or more. The content of the cross-linking agent is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 8 parts by mass, and even more preferably 0.8 to 5 parts by mass with respect to 100 parts by mass of the solid rubber component.

When sulfur and a sulfur compound are used among the crosslinking agents, the rubber composition of the present invention can be vulcanized and used as a vulcanized rubber. The vulcanization conditions and method are not particularly limited, but it is preferable to perform the vulcanization using a vulcanization mold under a pressure and heating condition of a vulcanization temperature of 120 to 200° C. and a vulcanization pressure of 0.5 to 2.0 MPa.

The rubber composition of the present invention may contain a vulcanization accelerator. Examples of the vulcanization accelerator include guanidine compounds, sulfenamide compounds, thiazole compounds, thiuram compounds, thiourea compounds, dithiocarbamic acid compounds, aldehyde-amine compounds or aldehyde-ammonia compounds, imidazoline compounds. Examples thereof include compounds and xanthate compounds. These may be used alone or in combination of two or more. When the vulcanization accelerator is contained, the content thereof is preferably 0.1 to 15 parts by mass, more preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the solid rubber component.

The rubber composition of the present invention may further contain a vulcanization aid. Examples of the vulcanization aid include fatty acids such as stearic acid; metal oxides such as zinc oxide; and fatty acid metal salts such as zinc stearate. These may be used alone or in combination of two or more. When the vulcanization aid is contained, its content is preferably 0.1 to 15 parts by mass, and more preferably 1 to 10 parts by mass, relative to 100 parts by mass of the solid rubber component.

The rubber composition of the present invention is intended to improve molding processability, fluidity, etc. within a range that does not impair the effects of the invention, and if necessary, silicone oil, aroma oil, TDAE (Treated Distilled Aromatic Extracts), MES ( Mild Extracted Solvates), RAE (Residual Aromatic Extracts), process oils such as paraffin oil and naphthene oil, aliphatic hydrocarbon resins, alicyclic hydrocarbon resins, C9 resins, rosin resins, coumarone-indene resins, A liquid component other than the polymer (C) such as a resin component such as a phenol resin, a low molecular weight polybutadiene, a low molecular weight polyisoprene, a low molecular weight styrene-butadiene copolymer, and a low molecular weight styrene isoprene copolymer is appropriately used as a softening agent. Can be used. The copolymer may be in any polymerization form such as block or random. The weight average molecular weight of the liquid polymer other than the polymer (C) is preferably 500 to 100,000 from the viewpoint of moldability.

The rubber composition of the present invention, as long as it does not impair the effects of the invention, for the purpose of improving weather resistance, heat resistance, oxidation resistance and the like, if necessary, an antioxidant, an antioxidant, a wax, a lubricant, and a light agent. Stabilizers, anti-scorch agents, processing aids, colorants such as pigments and dyes, flame retardants, antistatic agents, matting agents, antiblocking agents, UV absorbers, mold release agents, foaming agents, antibacterial agents, antifungal agents. One or two or more kinds of additives such as agents and fragrances may be contained.
Examples of antioxidants include hindered phenol compounds, phosphorus compounds, lactone compounds, and hydroxyl compounds.
Examples of the antiaging agent include amine-ketone compounds, imidazole compounds, amine compounds, phenol compounds, sulfur compounds and phosphorus compounds.

(Method for producing rubber composition)
The method for producing the rubber composition of the present invention is not particularly limited, and the above components may be uniformly mixed. As a method for uniformly mixing, for example, a tangential or meshing closed type kneader such as a kneader ruder, a Brabender, a Banbury mixer, an internal mixer, a single-screw extruder, a twin-screw extruder, a mixing roll, a roller, etc. For example, it can be carried out usually in the temperature range of 70 to 270°C.

[tire]
The tire of the present invention is a tire using at least a part of the rubber composition of the present invention.
The rubber composition of the present invention can be used for various members of tires, and can be particularly preferably used as a tire tread for passenger cars, truck buses, motorcycles, and industrial vehicles.
Particularly, since the braking performance such as ice grip performance is good, it is preferable to use the rubber composition of the present invention as a winter tire at least partially.
A crosslinked product obtained by crosslinking the rubber composition of the present invention may be used for the tire of the present invention. The tire using the rubber composition of the present invention or the crosslinked product of the rubber composition of the present invention can maintain characteristics such as braking performance such as ice grip performance.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to these Examples.
The components used in the examples and comparative examples are as follows.
[SBR (A)]
Styrene butadiene rubber: SBR1500 (JSR Corporation, Tg-53° C., solubility parameter 18.79 (J/cm ³ ) ^1/2 ).
[Natural rubber (B)]
STR20 (made in Thailand): VON BUNDIT, Tg-63° C., solubility parameter 18.02 (J/cm ³ ) ^1/2
[Filler (D)]
Silica: ULTRASIL 7000GR (Evonik Japan KK, wet silica, average particle size 14 nm)
Carbon black: Diamond black I (N220) (manufactured by Mitsubishi Chemical Corporation, average particle size 20 nm)

[Arbitrary ingredients]
(Silane coupling agent)
SI75 (Evonik Japan Co., Ltd.)
(Crosslinking agent)
Sulfur: Fine powder sulfur 200 mesh (made by Tsurumi Chemical Industry Co., Ltd.)
(Vulcanization aid)
Stearic acid: LUNAC S-20 (manufactured by Kao Corporation)
Zinc flower: Zinc oxide (made by Sakai Chemical Industry Co., Ltd.)
(Vulcanization accelerator)
Vulcanization accelerator (1): NOXCELLER CZ (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)
Vulcanization accelerator (2): NOXCELLER D (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)
Vulcanization accelerator (3): NOXCELLER TBT-N (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)
Vulcanization accelerator (4): Sunceller NS (manufactured by Sanshin Chemical Industry Co., Ltd.)
(Other ingredients)
Wax: Suntite S (manufactured by Seiko Chemical Co., Ltd.)
Anti-aging agent: Nocrac 6C (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)
TDAE: VivaTec500 (manufactured by H&R)
The glass transition temperatures (Tg) of SBR (A) and natural rubber (B) are based on the measuring method described later.

Production Example 1 (Production of Polymer C-1)
In a pressure-resistant container that had been purged with nitrogen and dried, 1750 g of cyclohexane as a solvent and 75 g of sec-butyllithium (10.5 mass% cyclohexane solution) as a polymerization initiator were charged, and the temperature was raised to 50° C., after which 1.6 g of tetrahydrofuran was added. A mixed solution of 225 g of β-farnesene, 176 g of styrene and 349 g of butadiene prepared in advance was added at 5 ml/min and polymerization was carried out for 4 hours. After 5 g of methanol was added to the obtained polymerization reaction liquid to terminate the polymerization, the polymerization reaction liquid was washed with 2 L of water. The polymerization reaction liquid after washing and water were separated and dried under reduced pressure at 70° C. for 12 hours to produce a polymer C-1.

Production Example 2 (Production of Polymer C-2)
In a pressure-resistant container that had been purged with nitrogen and dried, 1750 g of cyclohexane as a solvent and 65.9 g of sec-butyllithium (10.5 mass% cyclohexane solution) as a polymerization initiator were charged, and the temperature was raised to 50° C., after which 1.5 g of Tetrahydrofuran was charged, and a previously prepared mixture liquid of 375 g of β-farnesene, 176 g of styrene and 199 g of butadiene was added at 5 ml/min, and polymerization was carried out for 4 hours. After 5 g of methanol was added to the obtained polymerization reaction liquid to terminate the polymerization, the polymerization reaction liquid was washed with 2 L of water. Polymer C-2 was produced by separating the washed polymerization reaction liquid and water and drying under reduced pressure at 70° C. for 12 hours.

Production Example 3 (Production of Polymer C-3)
Into a pressure-resistant container which had been purged with nitrogen and dried, 1140 g of cyclohexane as a solvent and 56.2 g of sec-butyllithium (10.5 mass% cyclohexane solution) as a polymerization initiator were charged, and the temperature was raised to 50° C., and then 1080 g prepared in advance. A mixed solution of β-farnesene and 720 g of butadiene was added at 10 ml/min and polymerization was carried out for 1 hour. After 5 g of methanol was added to the obtained polymerization reaction liquid to terminate the polymerization, the polymerization reaction liquid was washed with 2 L of water. The polymer C-3 was produced by separating the washed polymerization reaction liquid from water and drying under reduced pressure at 70° C. for 12 hours.

Production Example 4 (Production of Polymer C-4)
In a pressure-resistant container which had been purged with nitrogen and dried, 1201 g of cyclohexane as a solvent and 54.2 g of sec-butyllithium (10.5 mass% cyclohexane solution) as a polymerization initiator were charged, and the temperature was raised to 60° C., after which 1.7 g of Tetrahydrofuran was charged, and when prepared in advance, a mixed solution of 206 g of styrene and 309 g of butadiene was added at 5 ml/min and polymerization was carried out for 4 hours. After 5 g of methanol was added to the obtained polymerization reaction liquid to terminate the polymerization, the polymerization reaction liquid was washed with 2 L of water. The polymerization reaction liquid after washing and water were separated and dried under reduced pressure at 70° C. for 12 hours to produce a polymer C-4.

Production Example 5 (Production of Polymer C-5)
2211 g of hexane and 80.7 g of n-butyllithium (17% by mass hexane solution) were charged into a pressure-resistant container which had been purged with nitrogen and dried, and the temperature was raised to 70° C., and then 1000 g of isoprene was added and polymerization was carried out for 1 hour. After 10 g of methanol was added to the obtained polymerization reaction liquid, the polymerization reaction liquid was washed with 2 L of water. Water was separated, and the polymerization reaction liquid was dried at 70° C. for 12 hours to obtain a polymer C-5.

Production Example 6 (Production of Polymer C-6)
241 g of cyclohexane as a solvent and 28.3 g of sec-butyllithium (10.5 mass% cyclohexane solution) as a polymerization initiator were charged in a pressure-resistant container which had been purged with nitrogen and dried, and the temperature was raised to 50° C., and then 342 g prepared in advance. Was added at 10 ml/min and polymerization was carried out for 1 hour. After 2 g of methanol was added to the obtained polymerization reaction solution to terminate the polymerization, the polymerization reaction solution was washed with 2 L of water. Polymer C-6 was produced by separating the washed polymerization reaction liquid and water and drying under reduced pressure at 70° C. for 12 hours.

Using the polymers C-1 to C-6 obtained in Production Examples 1 to 6 as samples, liquid polymers were evaluated according to the methods described below. The results are shown in Table 1.

(Weight average molecular weight and molecular weight distribution)
"HLC-8320" manufactured by Tosoh Corporation was used, and it was measured by adjusting the concentration of sample/tetrahydrofuran = 5 mg/10 mL. Tetrahydrofuran manufactured by Wako Pure Chemical Industries, Ltd. was used as the developing solution.
The weight average molecular weight (Mw) and the molecular weight distribution (Mw/Mn) were determined by GPC (gel permeation chromatography) in terms of standard polystyrene. The measuring device and conditions are as follows.
[Measuring device and measuring conditions]
-Device: GPC device "HLC-8320" manufactured by Tosoh Corporation
-Separation column: Tosoh Corporation column "TSKgelSuperHZM-M"
・Eluent: Tetrahydrofuran ・Eluent flow rate: 0.7 ml/min
・Sample concentration: 5mg/10ml
・Column temperature: 40℃

(Glass transition temperature (Tg))
10 mg of a sample was placed in an aluminum open pan, an aluminum lid was placed on the sample, and the sample was sealed with a sample sealer. A thermogram was measured by a differential scanning calorimetry (DSC) under a temperature rising rate condition of 10° C./minute, and the peak top value of DSC was defined as the glass transition temperature (Tg). The measuring device and conditions are as follows.
[Measuring device and measuring conditions]
・Device: Differential scanning calorimeter "DSC6200" manufactured by Seiko Instruments Inc.
-Cooling device: Seiko Instruments Inc. cooling controller-Detection unit: Heat flow rate type-Sample weight: 10 mg
・Rate of heating: 10°C/min
-Cooling conditions: After cooling at 10°C/min, the temperature was kept constant at -130°C for 3 minutes to start the temperature rise.
・Reference container: Aluminum ・Reference weight: 0mg

(Vinyl content)
A solution prepared by dissolving 50 mg of the polymer (C) in 1 ml of deuterated chloroform (CDCl ₃ ) was measured by ¹ H-NMR at 400 MHz with 512 integrations.
Regarding the vinyl content derived from farnesene, the 4.94 to 5.22 ppm portion of the chart obtained by the measurement is the spectrum derived from the vinyl structure, and the portion of 4.45 to 4.85 ppm is the synthetic spectrum of the vinyl structure and the 1,4 bond. The vinyl content was calculated based on the following formula.
{Vinyl content (from farnesene)}=integral value of 4.94 to 5.22 ppm/2/{integral value of 4.94 to 5.22 ppm/2+(integral value of 4.45 to 4.85 ppm-4.94) Up to 5.22 ppm integrated value)/3}
Regarding the vinyl content derived from butadiene, the 4.85 to 4.94 ppm part of the chart obtained by the measurement is the spectrum derived from the vinyl structure, and the part of 5.22 to 5.65 ppm is the synthetic spectrum of the vinyl structure and the 1,4 bond. The vinyl content was calculated based on the following formula.
{Vinyl content (from butadiene)}=Integral value of 4.85 to 4.94 ppm/2/{Integral value of 4.85 to 4.94 ppm/2+[Integral value of 5.22 to 5.65 ppm-(4. 85 to 4.94 ppm integrated value/2)]/2}

(Solubility parameter)
The solubility parameter of the polymer (C) was calculated by the Hoy's estimation method described in paragraph [0009] of the present specification.

(Distribution ratio)
The distribution ratio of the polymer (C) in the solid rubber component was calculated by using a measuring rubber mixture containing SBR (A), natural rubber (B) and the polymer (C), and differential scanning calorimetry (DSC). variation from Tg ₁ of the base rubber Tg of the rubber mixture to be measured (i.e. SBR (a) or natural rubber (B)) is calculated by DSC in the case of more than 0.5 ℃, the variation amount When is less than 0.5° C., the area ratio of the AFM image was calculated using an atomic force microscope (AFM).
As the rubber mixture used for calculating the distribution ratio, each of the polymers C-1 to C-6 obtained in Production Examples 1 to 6 is the same as each component used in the rubber composition described below except for the vulcanization accelerator. 6 kinds of rubber mixtures having different compounding recipes shown in Table 2 were prepared using the above. In the rubber mixture of Comparative Example 4, TDAE was used instead of the polymer (C).

[Preparation of rubber mixture for measurement]
SBR (A), natural rubber (B) and polymer (C) were added to a Brabender with the compounding recipe shown in Table 2 and kneaded at a starting temperature of 130° C. and a rotation speed of 100 rpm for 5 minutes. After taking out and cooling to room temperature, the components other than the components (A) to (C) described in Table 2 were added to a Brabender with the formulation shown in Table 2, and the starting temperature was 80° C. and the rotation speed was 80 rpm. After kneading for a minute, the mixture was taken out of the Brabender and cooled to room temperature to prepare a rubber mixture.

[Calculation of distribution ratio by DSC]
(1) Preparation of calibration curve A rubber mixture in which SBR (A) and polymer (C) were mixed at an arbitrary weight fraction X of compounding formulations 1 and 2 shown in Table 2 was press molded (press condition: 160 C., 20 to 40 minutes) to prepare a vulcanized sheet (2 mm thick) of a crosslinked product (vulcanized rubber). Using the obtained vulcanized sheet, Tg was measured by DSC measurement, 1/Tg was plotted on the y-axis and the weight fraction X was plotted on the x-axis to obtain a rubber mixture of SBR (A) and polymer (C). The calibration curve represented by the formula (4) was obtained, and the slope and intercept numerical values of the calibration curve were calculated. Similarly, a vulcanized sheet was similarly prepared for a rubber mixture in which the natural rubber (B) and the polymer (C) were mixed at an arbitrary weight fraction X of the compounding formulations 3 and 4 shown in Table 2. Tg was measured to obtain a calibration curve represented by the above formula (4) for the mixture consisting of the natural rubber (B) and the polymer (C), and the slope and intercept of the calibration curve were obtained.

(2) Evaluation Vulcanized sheet (2 mm) of a crosslinked product (vulcanized rubber) was obtained by press molding (press condition: 160° C., 20 to 40 minutes) the rubber mixture of compounding recipe 5 shown in Table 2 obtained above. (Thickness) was prepared and the DSC was measured.
Then, using the two calibration curves obtained in (1) above, the weight fractions X _A and X _B of the polymer (C) compatible with the (A) phase and the (B) phase were calculated. The ratio [X _A /X _B ] was defined as the distribution ratio (calculated value). Table 3 shows the distribution ratio (calculated value).
In addition, in Table 3, together with the above calculated value, the polymer (C) in the rubber composition (mass ratio [(A)/(B)/(C)]=70/30/20) converted from the calculated value is shown. The distribution ratio (converted value) of is also shown.

[Calculation of distribution ratio by AFM]
(1) Preparation of calibration curve A rubber mixture (mass ratio [(A)/(B)]=50/50) of compounding formulation 6 containing no polymer (C) was press-molded (press conditions: 160° C., 20 to 20). After 40 minutes, a vulcanized sheet (2 mm thick) of a crosslinked product (vulcanized rubber) was produced. A 1 cm×5 cm×2 mm test piece was cut out from the obtained vulcanized sheet, and the sample was cooled in liquid nitrogen and fractured to prepare an observation cross section. The AFM image is observed according to the following conditions, and the area ratio [(A)/(B)] of the (A) phase and the (B) phase is calculated using the image analysis software “Imagepro plus” (manufactured by Nippon Roper Co., Ltd.). did.
Similarly, using a vulcanized sheet containing the polymer (C) used in the measurement of DSC (compounding formulation 5, specifying the distribution ratio [X _A /X _B ] by DSC), observation of the AFM image (A ) Phase and (B) phase area ratio [(A)/(B)] is calculated, and the above-mentioned area ratio [(A)/(B)] in the vulcanized sheet not containing the polymer (C) is calculated. Was calculated.
_A calibration curve was prepared with the obtained area ratio difference as the x-axis and the distribution ratio [X _A /X _B ] calculated by DSC as the y-axis.
[Measuring device and measuring conditions]
・Device: Shimadzu Corporation Scanning probe microscope "SPM-9700"
・Cantilever: "OMCL-AC240TS-C3" manufactured by Olympus Corporation
・Measurement mode ：Phase mode ・Measurement range ：5μm×5μm
・Measurement frequency: 1 Hz

(2) Evaluation Vulcanized sheet (2 mm) of a crosslinked product (vulcanized rubber) was obtained by press molding (press condition: 160° C., 20 to 40 minutes) the rubber mixture of compounding recipe 5 shown in Table 2 obtained above. (Thickness) was prepared and the AFM image was observed in the same manner as above to calculate the area ratio [(A)/(B)] of the (A) phase and the (B) phase.
Then, using the calibration curve obtained in (1) above, the distribution ratio (calculated value) was calculated from the area ratio [(A)/(B)]. Table 3 shows the distribution ratio (calculated value).
In addition, in Table 3, together with the above calculated value, the polymer (C) in the rubber composition (mass ratio [(A)/(B)/(C)]=70/30/20) converted from the calculated value is shown. The distribution ratio (converted value) of is also shown.

Examples 1-2, Reference Example 1 and Comparative Examples 1-4
According to the blending ratio (parts by mass) shown in Table 3, SBR (A), natural rubber (B), polymer (C), filler (D), vulcanization aid, silane coupling agent and other components were added. Then, each was put into a closed Banbury mixer, kneaded for 6 minutes so that the starting temperature was 60° C. and the resin temperature was 140° C., then taken out of the mixer and cooled to room temperature. Next, this mixture was again charged into a closed Banbury mixer, a crosslinking agent and a vulcanization accelerator were added, and the mixture was kneaded for 75 seconds so that the starting temperature was 50° C. and the ultimate temperature was 100° C. to obtain a rubber composition.
The obtained rubber composition is press-molded (press condition: 160° C., 60 minutes) and vulcanized to prepare a tire-shaped vulcanized rubber sample having a diameter of 80 mm and a width of 16 mm, and rubbed on ice based on the following method. The coefficient (μ) was evaluated.
Further, the rubber composition obtained in the same manner as above was press molded (press conditions: 160° C., 20 to 25 minutes) to prepare a vulcanized sheet (2 mm thick) of a crosslinked product (vulcanized rubber). Based on the above method, tan δ was measured to evaluate the wet grip performance.
Further, the rubber composition obtained in the same manner as above is press molded (press conditions: 160° C., 30 minutes) to prepare a vulcanized sheet (2 mm thick) of a crosslinked product (vulcanized rubber), and the following method is used. Based on the above, the weight reduction rate was measured and the bleeding resistance was evaluated.
The results are shown in Table 3.

(Frictional coefficient on ice (μ))
The friction coefficient on ice (μ) was evaluated as an index of the ice grip performance of the rubber composition.
It measured using the friction coefficient on ice of the vulcanized rubber sample obtained in Examples 1-2, the reference example 1, and the comparative examples 1-4. The measuring device and conditions are as follows.
The friction coefficient of the tire and the road surface was measured in the range of 0 to 40%, and the maximum value of the obtained friction coefficient was defined as the friction coefficient on ice (μ). The higher the friction coefficient on ice (μ), the better the ice grip performance.
In addition, Table 3 also shows the relative value when the numerical value of Comparative Example 4 is set to 100 together with the actually measured value.
[Measuring device and measuring conditions]
・Apparatus: Ueshima Seisakusho RTM friction tester ・Measuring temperature: -3.0°C
・Road surface: Ice・Speed: 30km/hrs
・Load: 50N
・Slip ratio: 0-40%

(Wet grip performance)
A test piece measuring 40 mm in length and 7 mm in width was cut out from the vulcanized sheets prepared in Examples 1 and 2, Reference Example 1 and Comparative Examples 1 to 4, and the measurement temperature was 0° C. using a dynamic viscoelasticity measuring device manufactured by GABO. , Tan δ was measured under the conditions of a frequency of 10 Hz, a static strain of 10%, and a dynamic strain of 2%, and used as an index of wet grip performance. The larger the value, the better the wet grip performance of the rubber composition.
In addition, Table 3 also shows the relative value when the numerical value of Comparative Example 4 is set to 100 together with the actually measured value.

(Bleed resistance)
One test piece having a length of 75 mm and a width of 45 mm was cut out from each of the vulcanized sheets having a thickness of 2 mm prepared in Examples 1 and 2, Reference Example 1 and Comparative Examples 1 to 4. Two test pieces measuring 75 mm in length and 45 mm in width are cut out from a 5 mm thick vulcanized sheet containing no plasticizer described below, and the 2 mm thick vulcanized sheet is sandwiched between the 5 mm thick vulcanized sheets and a load of 250 g is applied. And left in an oven at 70° C. for 20 days. By comparing the weight of a vulcanized sheet having a thickness of 2 mm containing the polymer (C) before and after standing, and calculating the weight reduction rate according to the following formula, the migration property of the polymer (C) was evaluated, and the bleeding resistance was evaluated. Was used as an index.
Weight reduction rate (% by weight)={(weight of 2 mm thick vulcanized sheet before standing)-(weight of 2 mm thick vulcanized sheet after standing for 20 days)}/(2 mm thick vulcanized sheet before standing) Weight) x 100
The smaller the value of the weight reduction rate, the lower the migration property, that is, the higher the bleeding resistance, and the smaller the change in the physical properties of the rubber composition over time. The weight loss rate is preferably less than 3% by weight.
The vulcanized sheet having a thickness of 5 mm and containing no plasticizer was 100 parts by mass of natural rubber (“STR20” manufactured by VON BUNDIT), 40 parts by mass of carbon black (“Diablack I” manufactured by Mitsubishi Chemical Corporation), 3.5 parts by mass of zinc white, 2 parts by mass of stearic acid, 1 part by mass of anti-aging agent ("Nocrac 6C" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.), anti-aging agent ("Antage RD" manufactured by Kawaguchi Chemical Co., Ltd.) 1 part by mass, 1.5 parts by mass of sulfur, and 1.2 parts by mass of a vulcanization accelerator (“SANCELLER NS-G” manufactured by Sanshin Chemical Industry Co., Ltd.) were mixed under a press condition of 145° C. for 20 minutes. Other than the above, it was produced under the same conditions as the vulcanized sheet (2 mm thick) of the above example.

From Table 3, in the rubber compositions of Examples 1 and 2 and Reference Example 1 , the polymer (C) was compatible with the (A) phase, and a large amount of the polymer (C) was distributed into the (A) phase. Therefore, since the friction coefficient on ice is higher than in Comparative Examples 1 to 4, it is clear that the ice grip performance is excellent and the bleeding resistance is good.
Moreover, since the polymer (C) contains the monomer unit derived from styrene, since the rubber composition of Examples 1-2 maintains favorable wet grip performance, it has ice grip performance and wet grip. It can be seen that the balance between performance and bleed resistance is excellent.

The rubber composition of the present invention has a high level of ice grip performance, and a tire using at least a part of the rubber composition can be particularly preferably used as a winter tire.

Claims (9)

A solid rubber component containing styrene-butadiene rubber (A) and natural rubber (B), a monomer unit (a) derived from farnesene, a monomer unit (b-1) derived from an aromatic vinyl compound, and a conjugate other than farnesene A rubber composition containing a liquid polymer (C) containing a monomer unit (b-2) derived from a diene compound and a filler (D),
The content of the monomer unit (b-1) in the liquid polymer (C) is 10 to 30% by mass,
The content of the liquid polymer (C) is 1 to 50 parts by mass with respect to 100 parts by mass of the solid rubber component,
The content of the filler (D) is 20 to 150 parts by mass with respect to 100 parts by mass of the solid rubber component,
The content of styrene-butadiene rubber (A) in the solid rubber component is more than 50% by mass and less than 100% by mass,
Solubility parameter [delta] _A styrene-butadiene rubber (A), the solubility parameter [delta] _B of the natural rubber (B), and the solubility parameter [delta] _C of the liquid polymer (C) satisfies the following formula (1), the rubber composition.
│δ _A −δ _C │<｜δ _A −δ _B ｜ (1) The rubber composition according to claim 1, wherein the distribution ratio [(A)/(B)] of the liquid polymer (C) to the styrene-butadiene rubber (A) and the natural rubber (B) is 55/45 or more. The rubber composition according to claim 1 or 2, wherein the content of the farnesene-derived monomer unit (a) in the liquid polymer (C) is 1 to 75% by mass. Liquid glass transition temperature of the polymer (C) (Tg) is -100 to-36 ° C., the rubber composition according to any one of claims 1-3. Liquid polymers the weight average molecular weight in terms of polystyrene determined by gel permeation chromatography (C) (Mw) is 2,000～50 ten thousand, rubber composition according to any one of claims 1-4. Liquid molecular weight distribution of the polymer (C) (Mw / Mn) is 1.0 to 4.0, the rubber composition according to any one of claims 1-5. Solubility parameter [delta] _A styrene-butadiene rubber (A), the solubility parameter [delta] _B of the natural rubber (B), and the solubility parameter [delta] _C of the liquid polymer (C) is satisfied further following formula (2), according to claim 1 7. The rubber composition according to any one of 6 .
{|δ _A −δ _C |/|δ _A −δ _B |}<0.80 (2) Tire using at least a portion of the rubber composition according to any one of claims 1-7. Winter tire using at least a portion of the rubber composition according to any one of claims 1-7.