JP7163620B2 - Rubber composition and pneumatic tire - Google Patents

Description

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

For vulcanization of diene-based polymers, vulcanization accelerators, zinc oxide, fatty acids, etc., as well as powdered sulfur, insoluble sulfur, and other hybrid cross-linking agents capable of reducing the amount of sulfur components are generally used. A method of using a sulfur-containing powder or liquid compound instead of powdered sulfur has also been proposed.

Furthermore, a method is known in which the amount of sulfur is reduced and resorcinols or phenolic resins and formalin are used to reinforce crosslinks, but these resins are highly polar and cannot penetrate into the interior of the polymer. It is difficult to obtain time elongation, abrasion resistance, and the like.

As described above, the conventional method still has low affinity with diene polymers such as styrene-butadiene rubber, butadiene rubber, and natural rubber, and it is difficult to uniformly distribute the sulfur element in the rubber. As a result, more uniform sulfur crosslinks cannot be sufficiently formed inside the polymer, and good tensile properties cannot be obtained. Furthermore, tire performance such as durability of grip during running and running performance is not sufficiently satisfactory, and improvement is desired.

An object of the present invention is to solve the above problems and to provide a rubber composition having improved initial dry grip performance, durability of dry grip performance and chipping resistance (elongation at break).

TECHNICAL FIELD The present invention relates to a rubber composition containing a diene polymer, carbon black and/or silica, and a sulfur-containing oligomer having a polystyrene-equivalent weight average molecular weight of 4000 or more by GPC using a chloroform solvent.

（式中、Ｒは、ヘテロ原子を含んでもよい置換又は非置換の２価炭化水素基である。ｘ（平均値）は、１．０～１０．０である。） The sulfur-containing oligomer preferably has a sulfur element content of 10 to 95% by mass.
The sulfur-containing oligomer preferably has a repeating unit represented by the following formula (I).

(Wherein, R is a substituted or unsubstituted divalent hydrocarbon group that may contain a heteroatom. x (average value) is 1.0 to 10.0.)

（式中、Ｈは、同一又は異なってハロゲン原子である。Ｒは、ヘテロ原子を含んでもよい置換又は非置換の２価炭化水素基である。）

（式中、Ｍは、アルカリ金属である。ｘ（平均値）は、１．０～１０．０である。） The sulfur-containing oligomer preferably has a polarity parameter SP value of 12.5 or less.
The sulfur-containing oligomer is preferably obtained by reacting a dihalogen compound represented by the following formula (I-1) and an alkali metal polysulfide represented by the following formula (I-2).

(Wherein, H is the same or different and is a halogen atom. R is a substituted or unsubstituted divalent hydrocarbon group which may contain a heteroatom.)

(In the formula, M is an alkali metal. x (average value) is 1.0 to 10.0.)

The dihalogen compound is preferably 2,2'-dichloroethyl ether.
It is preferable that the content of the sulfur-containing oligomer is 1.0 parts by mass or more relative to 100 parts by mass of the diene polymer.

It preferably contains one or more vulcanization accelerators.
The present invention also relates to a pneumatic tire produced using the rubber composition.

According to the present invention, since it is a rubber composition containing a diene polymer, carbon black and / or silica, and a specific sulfur-containing oligomer, initial dry grip performance, durability of dry grip performance and chipping resistance performance ( elongation at break) can be improved.

The rubber composition of the present invention contains a diene polymer, carbon black and/or silica, and a sulfur-containing oligomer having a weight average molecular weight of 4000 or more in terms of polystyrene by GPC using chloroform solvent. The rubber composition is excellent in initial dry grip performance, durability of dry grip performance and chipping resistance (elongation at break). The present invention is a novel invention in that such a sulfur-containing oligomer (rubber-like, etc.) having a predetermined molecular weight is used as a sulfur donor for sulfur cross-linking of a diene rubber compound. Performance balance between durability of dry grip performance and chipping resistance performance (elongation at break) is improved.

Although the reason (mechanism) that such effects are obtained is not clear, it is speculated as follows.
The sulfur-containing oligomer used in the rubber composition is a polymer (oligomer) and is well compatible with diene-based polymers such as styrene butadiene. , the sulfur dispersion in the rubber is good. In addition, the sulfur-containing oligomer has a characteristic of intercalating between diene-based polymers (between polymers of diene-based rubber) with less occurrence of cleavage of the oligomer chain. Then, when the sulfur-containing oligomer reaches a normal vulcanization temperature, elemental sulfur is released (released), and the released sulfur, vulcanization accelerator, zinc oxide, fatty acid, etc. form a crosslinked composite (crosslinked intermediate body) is uniformly produced in the diene-based polymer to form uniform inter-polymer crosslinks. This crosslinked complex forms crosslinks not only at the polymer ends of the diene-based polymer, but also at the diene portion in the center of the polymer chain.

Therefore, when applied to tires, even if the sulfur crosslinks at the ends of the polymer break during running, the next supporting crosslink point exists nearby, so the entanglement of the diene polymer chains and the relative position with the filler/other compounding agent is retained. Therefore, the liquid styrene-butadiene copolymer, resin, carbon black, etc. are also difficult to separate from the diene polymer, and the grip performance is maintained. In addition, excellent elongation at break and chipping resistance are also obtained. Therefore, in the rubber composition using the specific sulfur-containing oligomer of the present application, the initial dry grip performance, the durability of the dry grip performance, and the chipping resistance are superior to those using conventional cross-linking agents such as powdered sulfur and hybrid cross-linking agents. Excellent performance (elongation at break). In particular, it is speculated that the dry grip performance in the latter period will be remarkably improved.

[Crosslinking agent]
The rubber composition contains a sulfur-containing oligomer having a polystyrene equivalent weight average molecular weight (Mw) of 4000 or more by GPC using a chloroform solvent. Since sulfur-containing oligomers with Mw of 4000 or more have rubbery properties, they have extremely good affinity and mixing with diene-based polymers such as SBR and NR, and have very good dispersibility in diene-based polymers. . Therefore, initial dry grip performance, durability of dry grip performance, and chipping resistance (elongation at break) tend to be improved. The lower limit of Mw is preferably 8,000 or more, more preferably 10,000 or more. The upper limit of Mw is not particularly limited, and correct molecular weight measurement is difficult due to molecular cleavage by the solvent, but molecular weight comparable to SBR and NR, that is, preferably 2 million or less, more preferably 1.6 million or less, and still more preferably 1.4 million or less. Moreover, the upper limit of Mw may be 100,000 or less, 80,000 or less, or 50,000 or less.
Mw is polystyrene-equivalent Mw when GPC (gel permeation chromatography) is measured using chloroform as a solvent, and specifically, it is a value measured by the method described later in Examples.

From the viewpoint of the performance balance, the sulfur-containing oligomer preferably has a sulfur element content of 10 to 95% by mass. The lower limit is more preferably 30% by mass or more, still more preferably 40% by mass or more, and particularly preferably 45% by mass or more. The upper limit is more preferably 90% by mass or less, and even more preferably 75% by mass or less.

（式中、Ｒは、ヘテロ原子を含んでもよい置換又は非置換の２価炭化水素基である。ｘ（平均値）は、１．０～１０．０である。） The sulfur-containing oligomer preferably has a repeating unit represented by the following formula (I). This improves the performance balance.

(Wherein, R is a substituted or unsubstituted divalent hydrocarbon group that may contain a heteroatom. x (average value) is 1.0 to 10.0.)

The substituted or unsubstituted divalent hydrocarbon group of R which may contain a heteroatom may be a straight-chain, cyclic or branched group, with a straight-chain group being particularly preferred. The heteroatom is not particularly limited and includes oxygen, nitrogen and the like. The number of carbon atoms in the divalent hydrocarbon group is preferably 1 or more, more preferably 2 or more, preferably 20 or less, more preferably 18 or less, even more preferably 12 or less, and particularly preferably 8 or less.

Specific examples of the divalent hydrocarbon group include a substituted or unsubstituted alkylene group having 1 to 18 carbon atoms, a cycloalkylene group having 5 to 18 carbon atoms, and an alkylene group including an oxyalkylene group having 1 to 18 carbon atoms. etc. Among them, a substituted or unsubstituted alkylene group having 1 to 18 carbon atoms and an alkylene group including a substituted or unsubstituted oxyalkylene group having 1 to 18 carbon atoms are preferable. The substituent of the divalent hydrocarbon group of R is not particularly limited, and functional groups such as hydroxyl, phenyl, and benzyl may be mentioned.

Specific examples of substituted or unsubstituted alkylene groups having 1 to 18 carbon atoms include substituted or unsubstituted methylene, ethylene, trimethylene, tetramethylene, pentamethylene, hexamethylene, octylene and nonylene groups. , a decylene group, a 1,2-propylene group, and the like.

Examples of the alkylene group containing a substituted or unsubstituted oxyalkylene group having 1 to 18 carbon atoms include a group represented by (CH ₂ CH ₂ O) _p , a group represented by (CH ₂ ) _q and (CH ₂ O) _r (p is an integer of 1 to 5, q is an integer of 0 to 2, r is an integer of 0 to 2) optionally bonded to an alkylene group including an oxyalkylene group. Preferred groups include -CH ₂ CH ₂ OCH ₂ CH ₂ -, -(CH ₂ CH ₂ O) ₂ CH ₂ CH ₂ -, -(CH ₂ CH ₂ O) ₃ CH ₂ CH ₂ -, -(CH _{2 CH2O} ) _{4CH2CH2 -} , _{- ( CH2CH2O ) 5CH2CH2 -} , _{- ( CH2CH2O ) 2CH2 - , - CH2CH2OCH2OCH2CH2} - and the like.

x is an average of 1.0 to 10.0, preferably 2.0 or more, more preferably 3.0 or more, still more preferably 3.5 or more, preferably 6.0 or less, more preferably It is 5.0 or less, more preferably 4.5 or less. The number n (average value) of repeating units represented by the formula (I) is preferably 10 or more, more preferably 20 or more, still more preferably 35 or more, preferably 1000 or less, more preferably 400 or less, and further Preferably it is 110 or less.

The sulfur-containing oligomer preferably has a polarity parameter SP value of 12.5 or less. In this case, the dispersibility in the diene polymer is enhanced, and the performance balance is improved. The upper limit of the SP value is preferably 12.0 or less, more preferably 11.5 or less. Although the lower limit is not particularly limited, it is preferably 7.0 or higher, more preferably 8.0 or higher, still more preferably 9.0 or higher, particularly preferably 10.0 or higher, and most preferably 10.5 or higher.
In this specification, the polarity parameter SP value means a solubility parameter calculated by the Hoy method based on the structure of the compound. The Hoy method is, for example, K.K. L. Hoy "Table of Solubility Parameters", Solvent and Coatings Materials Research and Development Department, Union Carbites Corp.; (1985).

（式中、Ｈは、同一又は異なってハロゲン原子である。Ｒは、ヘテロ原子を含んでもよい置換又は非置換の２価炭化水素基である。）

（式中、Ｍは、アルカリ金属である。ｘ（平均値）は、１．０～１０．０である。） The sulfur-containing oligomer is preferably obtained by reacting a dihalogen compound represented by the following formula (I-1) and an alkali metal polysulfide represented by the following formula (I-2).

(Wherein, H is the same or different and is a halogen atom. R is a substituted or unsubstituted divalent hydrocarbon group which may contain a heteroatom.)

(In the formula, M is an alkali metal. x (average value) is 1.0 to 10.0.)

In the above formula (I-1), the halogen atom for H includes fluorine, chlorine, bromine and iodine, with chlorine and bromine being preferred. The substituted or unsubstituted divalent hydrocarbon group optionally containing a heteroatom for R is the same as described above. The dihalogen compound is preferably 2,2'-dichloroethyl ether (bis(2-chloroethyl) ether).

In the above formula (I-2), examples of alkali metals for M include sodium, potassium, and lithium. x (average value) is the same as described above.

For example, the sulfur-containing oligomer is obtained by (1) dihalogen compound of formula (I-1) and alkali metal polysulfide of formula (I-2) in an immiscible mixed solvent of hydrophilic solvent and hydrophobic solvent. (2) a dihalogen compound of formula (I-1) is added to a solution of an alkali metal polysulfide of formula (I-2), the dihalogen compound and the alkali metal polysulfide; It can be prepared by a method of adding and reacting at a rate that causes reaction at the interface, or the like.

In the production methods (1), (2), etc., the reaction of the dihalogen compound and the alkali metal polysulfide is an equivalent reaction, and the ratio of the dihalogen compound: the alkali metal polysulfide is 0.95:1.0 to It is preferable to react at 1.0:0.95 (equivalent ratio). The reaction temperature is preferably 50-120°C, more preferably 70-100°C.

A hydrophilic solvent and a hydrophobic solvent (lipophilic solvent) are not particularly limited, and any solvent that is immiscible and forms two phases in the reaction system can be used. Hydrophilic solvents include water; alcohols such as methanol, ethanol, ethylene glycol and diethylene glycol; and the like. Examples of hydrophobic solvents include aromatic hydrocarbons such as toluene, xylene and benzene; aliphatic hydrocarbons such as pentane and hexane; ethers such as dioxane and dibutyl ether; esters such as ethyl acetate; . The hydrophilic solvent and the hydrophobic solvent may be used alone or in combination of two or more.

In the case of the production method (1), it is preferable to use a solvent containing water, ethanol and toluene. In the case of the production method (2), a mixture of the alkali metal polysulfide represented by the formula (I-2) and a solvent containing water and/or ethanol is added to the mixture represented by the formula (I-1). A mixture of the dihalogen compound and toluene is preferably added dropwise at an appropriate rate, and the solvent may be appropriately changed according to the dihalogen compound.

A catalyst is not particularly necessary during the reaction of the dihalogen compound and the alkali metal polysulfide, but may be added as necessary. Quaternary ammonium salts, phosphonium salts, crown ethers and the like can be used as catalysts. Specifically, (CH ₃ ) ₄ N ⁺ Cl ⁻ , (CH ₃ ) ₄ N ⁺ Br ⁻ , (C ₄ H ₉ ) ₄ N ⁺ Cl ⁻ , (C ₄ H ₉ ) ₄ N ⁺ Br ⁻ , C _12H25N ⁺ _{( CH3} ) _3Br- ^, ( _C4H9 ) _4P ⁺ _{Br- , CH3P} ⁺ _{( C6H5} ⁾ _3I- ^, _C16H33P ⁺ _{( C4H9} ) ₃ Br ⁻ , 15-crown-5, 18-crown-6, Benzo-18-crown-6 and the like.

(1) a sulfur-containing oligomer having a polystyrene equivalent weight average molecular weight of 4000 or more by GPC using a chloroform solvent, (2) a sulfur-containing oligomer having a sulfur element content of 10 to 95% by mass, and (3) Further, a sulfur-containing oligomer having a repeating unit represented by the above formula (I) and (4) a sulfur-containing oligomer having an SP value of 12.5 or less can also be prepared by the above-described method.

In the rubber composition, the content of the sulfur-containing oligomer with respect to 100 parts by mass of the diene polymer is preferably 0.2 parts by mass or more, more preferably 0.5 parts by mass or more, from the viewpoint of the performance balance. Although the upper limit is not particularly limited, it is preferably 10.0 parts by mass or less, more preferably 8.0 parts by mass or less, and even more preferably 6.0 parts by mass or less.

When used in a cap tread, the content of the sulfur-containing oligomer with respect to 100 parts by mass of the diene polymer is preferably 0.2 mass from the viewpoint of the performance balance of initial dry grip performance, durability of dry grip performance and chipping resistance performance. parts or more, more preferably 0.5 parts by mass or more. Although the upper limit is not particularly limited, it is preferably 10.0 parts by mass or less, more preferably 5.0 parts by mass or less, and still more preferably 4.5 parts by mass or less from the viewpoint of chipping resistance after aging.

When used in the base tread, the content of the sulfur-containing oligomer with respect to 100 parts by mass of the diene polymer is preferably 1.0 parts by mass or more, more preferably 2.0 parts by mass or more, and still more preferably from the viewpoint of elongation at break. is 3.0 parts by mass or more, particularly preferably 3.5 parts by mass or more. Although the upper limit is not particularly limited, it is preferably 10.0 parts by mass or less, more preferably 7.0 parts by mass or less, and even more preferably 6.0 parts by mass or less from the viewpoint of elongation at break after aging.

In this application, examples of the base tread are described in addition to the tread formulation, but the point that the elongation at break can be improved is other members such as sidewalls, wings, clinch apex, breaker cushions, tie gums, inner liners. etc. can also be applied.

In addition to the sulfur-containing oligomer, the rubber composition may further contain other cross-linking agents such as ordinary powdered sulfur, insoluble sulfur, and hybrid cross-linking agents.

Sulfur includes powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur and the like commonly used in the rubber industry. As commercially available products, products of Tsurumi Chemical Industry Co., Ltd., Karuizawa Io Co., Ltd., Shikoku Kasei Kogyo Co., Ltd., Flexis Co., Ltd., Nippon Kantan Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. can be used. These may be used alone or in combination of two or more.

（式中、Ａは炭素数２～１０のアルキレン基、Ｒ^１１及びＲ^１２は、同一若しくは異なって、チッ素原子を含む１価の有機基を表す。） The hybrid cross-linking agent is not particularly limited, and includes 1,3-bis(citraconimidomethyl)benzene, compounds represented by the following formula, and the like.

(In the formula, A is an alkylene group having 2 to 10 carbon atoms, and R ¹¹ and R ¹² are the same or different and represent a monovalent organic group containing a nitrogen atom.)

The alkylene group (having 2 to 10 carbon atoms) of A is not particularly limited, and may be linear, branched or cyclic. Among them, a linear alkylene group is preferred. The number of carbon atoms is preferably 4-8. Specific alkylene groups include ethylene, trimethylene, tetramethylene, pentamethylene, hexamethylene, heptamethylene, octamethylene and decamethylene groups. Among them, a hexamethylene group is preferred.

R ¹¹ and R ¹² are not particularly limited as long as they are monovalent organic groups containing a nitrogen atom, but those containing at least one aromatic ring are preferred, and NC (= Those containing a bonding group represented by S)- are more preferred. R ¹¹ and R ¹² may be the same or different, but are preferably the same.

Examples of compounds represented by the above formula include 1,2-bis(N,N'-dibenzylthiocarbamoyldithio)ethane, 1,3-bis(N,N'-dibenzylthiocarbamoyldithio)propane, 1,4-bis(N,N'-dibenzylthiocarbamoyldithio)butane, 1,5-bis(N,N'-dibenzylthiocarbamoyldithio)pentane, 1,6-bis(N,N'-di benzylthiocarbamoyldithio)hexane, 1,7-bis(N,N'-dibenzylthiocarbamoyldithio)heptane, 1,8-bis(N,N'-dibenzylthiocarbamoyldithio)octane, 1,9-bis (N,N'-dibenzylthiocarbamoyldithio)nonane, 1,10-bis(N,N'-dibenzylthiocarbamoyldithio)decane and the like. Among them, 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane is preferred.

In addition to the sulfur-containing oligomer, when other cross-linking agents such as ordinary powdered sulfur, insoluble sulfur, and hybrid cross-linking agents are further contained, the total content of the cross-linking agents is appropriately adjusted to the content of the sulfur-containing oligomer. is preferred.

[Vulcanization accelerator]
The rubber composition preferably contains a vulcanization accelerator from the viewpoint of a balance between initial dry grip performance, durability of dry grip performance, and chipping resistance performance (elongation at break).

The type of the vulcanization accelerator is not particularly limited because the sulfur-containing oligomer facilitates uniform dispersion of sulfur. For example, thiazole additives such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide (DM (2,2'-dibenzothiazolyl disulfide)), N-cyclohexyl-2-benzothiazylsulfenamide, etc. Thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); N-cyclohexyl-2-benzothiazole Sulfenamide, Nt-butyl-2-benzothiazolylsulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N,N'- Sulfenamide-based vulcanization accelerators such as diisopropyl-2-benzothiazolesulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, dioltolylguanidine and orthotolylbiguanidine. These may be used alone or in combination of two or more. Among these, sulfenamide-based vulcanization accelerators are preferable from the viewpoint of the aforementioned performance balance. In the case of cap tread, combined use of sulfenamide-based and guanidine-based vulcanization accelerators is preferred.

In the rubber composition, the content of the vulcanization accelerator is preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, relative to 100 parts by mass of the diene polymer. Moreover, the content is preferably 10 parts by mass or less, more preferably 7 parts by mass or less. Within the above numerical range, there is a tendency to obtain a good performance balance.

When used for a cap tread, the content of the vulcanization accelerator is preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, relative to 100 parts by mass of the diene polymer. Moreover, the content is preferably 10 parts by mass or less, more preferably 7 parts by mass or less. Within the above numerical range, there is a tendency that the performance balance among the initial dry grip performance, the durability of the dry grip performance and the chipping resistance performance is improved.

When used in the base tread, the content of the vulcanization accelerator is preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, relative to 100 parts by mass of the diene polymer. Moreover, the content is preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less. Within the above numerical range, the elongation at break tends to be improved.

[Diene polymer]
The type of the diene-based polymer used in the rubber composition is not particularly limited because the sulfur-containing oligomer contributes to uniform dispersion of sulfur. For example, isoprene rubber (isoprene rubber (IR), epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber, natural rubber (NR), deproteinized natural rubber (DPNR), high-purity natural rubber (UPNR), epoxy hydrogenated natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber), styrene-butadiene rubber (SBR), butadiene rubber (BR), styrene isoprene-butadiene rubber (SIBR), chloroprene rubber (CR), acrylonitrile butadiene Rubber (NBR) etc. are mentioned. These may be used alone or in combination of two or more. Among them, SBR, BR, and isoprene-based rubbers are preferable from the viewpoint of the above-described performance balance. For the cap tread, BR and SBR are preferably used in combination, and for the base tread, BR and isoprene rubber are preferably used in combination.

The BR is not particularly limited, and includes BR with a high cis content, BR containing 1,2-syndiotactic polybutadiene crystals (SPB), butadiene rubber synthesized using a rare earth catalyst (rare earth BR), etc. Anything common in the tire industry can be used. Tin-modified butadiene rubber modified with a tin compound (tin-modified BR) can also be used. Commercially available products include, for example, those manufactured by Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, Zeon Corporation, Lanxess Corporation, and the like. These may be used alone or in combination of two or more.

BR may be non-modified BR, silica-modified or carbon black-modified BR.
Modified BR is preferable from the viewpoint of fuel efficiency, and the modified BR may be any BR having a functional group that interacts with a filler such as silica. For example, at least one end of BR has the following functional group Terminal-modified BR modified with a compound (modifier) (terminal-modified BR having the following functional group at the terminal), main chain-modified BR having the following functional group in the main chain, and main chain and terminal having the following functional group Main chain end-modified BR (e.g., main chain end-modified BR having the following functional group in the main chain, at least one end of which is modified with a compound (modifier) having the following functional group), or two in the molecule Terminal-modified BR, etc., which are modified (coupled) with the polyfunctional compound having an epoxy group as described above and into which a hydroxyl group or an epoxy group is introduced, may be mentioned.

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

From the viewpoint of breaking performance and wear resistance, it is preferable to use rare earth BR as the BR.
As the rare earth-based BR, conventionally known ones can be used, for example, rare earth-based catalysts (lanthanum-based rare earth element compounds, organoaluminum compounds, aluminoxanes, halogen-containing compounds, and optionally Lewis base-containing catalysts) are used. Synthesized by Among them, butadiene rubber (Nd-based BR) synthesized using a neodymium-based catalyst using a neodymium (Nd)-containing compound as the lanthanide-based rare earth element compound is preferable.

The glass transition temperature (Tg) of BR is preferably −160° C. or higher, more preferably −130° C. or higher, from the viewpoint of the aforementioned performance balance. Further, it is preferably -60°C or lower, more preferably -90°C or lower.
In this specification, the glass transition temperature is measured according to JIS-K7121 using a differential scanning calorimeter (Q200) manufactured by TA Instruments Japan under the condition of a temperature increase rate of 10° C./min. It is a measured value.

The cis content of BR is preferably 95% by mass or more.
In this specification, the cis content (cis 1,4 bond content) of BR can be measured by infrared absorption spectrometry.

When BR is contained, the content of BR in 100% by mass of the diene polymer is preferably 5% by mass or more, more preferably 10% by mass or more, and still more preferably 15% by mass or more. The content is preferably 80% by mass or less, more preferably 60% by mass or less. By setting it within the above range, the performance balance tends to be improved.

When used for a cap tread, the content of BR in 100% by mass of the diene polymer is preferably 5% by mass or more, more preferably 10% by mass or more, and still more preferably 15% by mass or more. The content is preferably 80% by mass or less, more preferably 60% by mass or less. Within the above range, there is a tendency to improve the performance balance among initial dry grip performance, durability of dry grip performance, and chipping resistance performance.

When used for the base tread, the content of BR in 100% by mass of the diene polymer is preferably 5% by mass or more, more preferably 10% by mass or more, and still more preferably 15% by mass or more. The content is preferably 60% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less. Elongation at break tends to be improved by setting it within the above range.

The SBR is not particularly limited, and those commonly used in the tire industry, such as emulsion polymerization SBR (E-SBR) and solution polymerization SBR (S-SBR), can be used. As commercially available products, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Co., Ltd., Asahi Kasei Co., Ltd., Nippon Zeon Co., etc. can be used. These may be used alone or in combination of two or more.

SBR may be unmodified SBR or modified SBR. Examples of modified SBR include modified SBR into which functional groups similar to those of the modified BR are introduced.

The styrene content of SBR is preferably 5% by mass or more, more preferably 10% by mass or more, and still more preferably 15% by mass or more. The styrene content is preferably 60% by mass or less, more preferably 50% by mass or less, even more preferably 45% by mass or less, and particularly preferably 40% by mass or less. When the styrene content is within the above range, the performance balance tends to be improved.
In this specification, the styrene content of SBR is calculated by H ¹ -NMR measurement.

The vinyl content of SBR is preferably 10 mol % or more, more preferably 20 mol % or more, still more preferably 30 mol % or more, from the viewpoint of improving the performance balance. The vinyl content is preferably 75 mol % or less, more preferably 70 mol % or less.
In this specification, the vinyl content of SBR indicates the vinyl content of the butadiene portion (unit quantity of vinyl groups in the butadiene structure), and is calculated by H ¹ -NMR measurement.

The glass transition temperature (Tg) of SBR is preferably −90° C. or higher, more preferably −50° C. or higher, from the viewpoint of improving the performance balance. Also, it is preferably 0° C. or lower, more preferably -10° C. or lower.

The weight average molecular weight (Mw) of SBR is preferably 150,000 or more, more preferably 200,000 or more, and even more preferably 220,000 or more, from the viewpoint of improving the performance balance. The Mw is preferably 2,000,000 or less, more preferably 1,000,000 or less, and still more preferably 500,000 or less.
In this specification, the weight average molecular weight (Mw) of SBR is measured by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: manufactured by Tosoh Corporation. TSKGEL SUPERMALTPORE HZ-M) can be obtained by standard polystyrene conversion.

When SBR is contained, the content of SBR in 100% by mass of the diene polymer is preferably 20% by mass or more, more preferably 30% by mass or more. The content is preferably 95% by mass or less, more preferably 90% by mass or less. By setting it within the above range, the performance balance tends to be improved.

When used for a cap tread, the SBR content in 100% by mass of the diene polymer is preferably 20% by mass or more, more preferably 40% by mass or more. The content is preferably 95% by mass or less, more preferably 90% by mass or less. Within the above range, there is a tendency to improve the performance balance among initial dry grip performance, durability of dry grip performance, and chipping resistance performance.

When used for the base tread, the SBR content in 100% by mass of the diene polymer is preferably 20% by mass or less, more preferably 10% by mass or less, and may be 0% by mass. By setting it within the above range, there is a tendency that the performance balance between crack growth resistance and elongation at break is improved.

〔filler〕
The rubber composition preferably contains carbon black. The performance balance is remarkably improved by the reinforcing effect of carbon black. Examples of usable carbon black include, but are not limited to, N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762, and the like. Commercially available products include Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Co., Ltd., Lion Corporation, Shin Nikka Carbon Co., Ltd., and Columbia Carbon Co., Ltd. can. These may be used alone or in combination of two or more.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 5 m ² /g or more, more preferably 30 m ² /g or more, and even more preferably 50 m ² /g or more. By making it more than the lower limit, there is a tendency that good reinforcing properties can be obtained. Also, it is preferably 300 m ² /g or less, more preferably 130 m ² /g or less. By making it below the upper limit, there is a tendency for good dispersion of carbon black to be obtained.

When used for a cap tread, the nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 50 m ² /g or more, more preferably 80 m ² /g or more, and even more preferably 100 m ² /g or more. By making it more than the lower limit, there is a tendency that good grip performance can be obtained. Also, it is preferably 300 m ² /g or less, more preferably 150 m ² /g or less, and even more preferably 130 m ² /g or less. By making it below the upper limit, there is a tendency for good dispersion of carbon black to be obtained.

When used for the base tread, the nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 5 m ² /g or more, more preferably 30 m ² /g or more, and even more preferably 50 m ² /g or more. By making it more than the lower limit, there is a tendency that good elongation at break can be obtained. Also, it is preferably 100 m ² /g or less, more preferably 80 m ² /g or less. By making it below the upper limit, there is a tendency for good dispersion of carbon black to be obtained.
In this specification, the nitrogen adsorption specific surface area of carbon black is determined according to JIS K 6217-2:2001.

In the rubber composition, the content of carbon black is preferably 1 part by mass or more, more preferably 3 parts by mass or more with respect to 100 parts by mass of the diene polymer. By making it more than the lower limit, there is a tendency that sufficient reinforcing properties can be obtained. Also, it is preferably 80 parts by mass or less, more preferably 50 parts by mass or less. By making it below the upper limit, there is a tendency that good carbon black dispersibility can be obtained.

When used for a cap tread, the content of carbon black is preferably 1 part by mass or more, more preferably 3 parts by mass or more, relative to 100 parts by mass of the diene polymer. By making it more than the lower limit, there is a tendency that sufficient reinforcement can be obtained and good grip performance can be obtained. Also, it is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less. By making it below the upper limit, there is a tendency that good carbon black dispersibility can be obtained.

When used in the base tread, the content of carbon black is preferably 5 parts by mass or more, more preferably 15 parts by mass or more, and even more preferably 20 parts by mass or more with respect to 100 parts by mass of the diene polymer. By making it more than the lower limit, there is a tendency that sufficient reinforcing properties can be obtained and good elongation at break can be obtained. Also, it is preferably 80 parts by mass or less, more preferably 50 parts by mass or less, and even more preferably 35 parts by mass or less. By making it below the upper limit, there is a tendency that good carbon black dispersibility can be obtained.

From the viewpoint of fuel efficiency and elongation at break, the rubber composition preferably contains silica. Silica is not particularly limited, and for example, dry process silica (anhydrous silica), wet process silica (hydrous silica), etc. can be used, but wet process silica (hydrous silica) is preferable because it has many silanol groups. . Commercially available products of Degussa, Rhodia, Tosoh Silica, Solvay Japan, Tokuyama, etc. can be used. These may be used alone or in combination of two or more.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 80 m ² /g or more, more preferably 115 m ² /g or more, still more preferably 150 m ² /g or more. By making it more than the lower limit, there is a tendency that good grip performance can be obtained. Also, it is preferably 400 m ² /g or less, more preferably 200 m ² /g or less, still more preferably 180 m ² /g or less. By making it below the upper limit, there is a tendency that good silica dispersibility can be obtained.
The N ₂ SA of silica is a value measured by the BET method according to ASTM D3037-93.

In the rubber composition, the content of silica is preferably 30 parts by mass or more, more preferably 50 parts by mass or more, and still more preferably 70 parts by mass or more with respect to 100 parts by mass of the diene polymer. By making it more than the lower limit, there is a tendency that sufficient reinforcement can be obtained and good grip performance can be obtained. Also, it is preferably 150 parts by mass or less, more preferably 100 parts by mass or less, and even more preferably 85 parts by mass or less. By making it below the upper limit, there is a tendency that good dispersion of silica is likely to be obtained.

〔Silane coupling agent〕
When the rubber composition contains silica, it preferably contains a silane coupling agent together with silica.
As the silane coupling agent, any silane coupling agent conventionally used in combination with silica in the rubber industry can be used without particular limitation. (2-triethoxysilylethyl) tetrasulfide, bis(4-triethoxysilylbutyl) tetrasulfide, bis(3-trimethoxysilylpropyl) tetrasulfide, bis(2-trimethoxysilylethyl) tetrasulfide, bis(2 -triethoxysilylethyl)trisulfide, bis(4-trimethoxysilylbutyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)disulfide, bis(4-triethoxysilyl) butyl) disulfide, bis(3-trimethoxysilylpropyl) disulfide, bis(2-trimethoxysilylethyl) disulfide, bis(4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N,N-dimethylthio Sulfides such as carbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxy mercapto-based silanes such as NXT and NXT-Z manufactured by Momentive; vinyl-based products such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based products such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; Glycidoxy-based compounds such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based compounds such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; Chloro compounds such as methoxysilane and 3-chloropropyltriethoxysilane are included. As commercially available products, products of Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., Dow Corning Toray Co., Ltd., etc. can be used. These may be used alone or in combination of two or more. Among them, sulfide-based and mercapto-based are preferable from the viewpoint of the above-mentioned performance balance.

When the rubber composition contains a silane coupling agent, the content thereof is preferably 2 parts by mass or more, more preferably 5 parts by mass or more, relative to 100 parts by mass of silica. By making it more than the lower limit, there is a tendency that the effect of blending the silane coupling agent can be obtained. Also, it is preferably 20 parts by mass or less, more preferably 15 parts by mass or less. By setting the content to the upper limit or less, there is a tendency that an effect commensurate with the blending amount can be obtained, and good workability during kneading can be obtained.

[Resin]
A resin may be blended into the rubber composition, and good grip performance can be obtained particularly when used for a cap tread.

The softening point of the resin is preferably -10 to 170°C. Within the above range, the compatibility with the diene-based polymer is sufficiently good, and the effects of the present invention tend to be obtained favorably. The softening point is more preferably 0°C or higher, and still more preferably 10°C or higher. Also, it is more preferably 160° C. or lower, still more preferably 150° C. or lower, and even more preferably 140° C. or lower.
In this specification, the softening point is the temperature at which a ball descends when the softening point specified in JIS K6220:2001 is measured with a ring and ball type softening point measuring device.

The glass transition temperature (Tg) of the resin is preferably -40 to 100°C. Within the above range, the compatibility with the diene-based polymer is sufficiently good, and the effects of the present invention tend to be obtained favorably. The glass transition temperature is more preferably -30°C or higher.

Examples of resins include aromatic vinyl polymers, coumarone-indene resins, indene resins, rosin resins, terpene-based resins, and acrylic resins. Commercially available products include Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical, Nichinuri Chemical Co., Ltd., Japan. Catalysts, products of JX Nippon Oil & Energy Corporation, Arakawa Chemical Industries, Ltd., Taoka Chemical Industries, Ltd., Toagosei Co., Ltd., etc. can be used. These may be used alone or in combination of two or more. Among them, aromatic vinyl polymers, coumarone-indene resins, terpene-based resins, and rosin resins are preferred.

The above-mentioned aromatic vinyl polymer is a resin obtained by polymerizing α-methylstyrene and/or styrene. A copolymer etc. are mentioned. Among them, a copolymer of α-methylstyrene and styrene is preferred.

The above-mentioned coumarone-indene resin is a resin containing coumarone and indene as main monomer components constituting the skeleton (main chain) of the resin. - methylstyrene, methylindene, vinyltoluene, and the like.

The indene resin is a resin containing indene as a main monomer component constituting the skeleton (main chain) of the resin.

Examples of the rosin resin include natural rosin, polymerized rosin, modified rosin, ester compounds thereof, and rosin-based resins represented by hydrogenated products thereof.

As the terpene-based resin, a polyterpene resin obtained by polymerizing a terpene compound, an aromatic modified terpene resin obtained by polymerizing a terpene compound and an aromatic compound, or the like can be used. Hydrogenated products of these can also be used.

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

Examples of the polyterpene resins include pinene resins, limonene resins, dipentene resins, pinene/limonene resins and the like made from the terpene compounds described above. Among them, pinene resin is preferable because it is easy to undergo a polymerization reaction and because natural pine resin is used as a raw material, it is inexpensive. Pinene resins usually contain both α-pinene and β-pinene, which are in an isomer relationship. It is classified as α-pinene resin, which is mainly composed of pinene.

Examples of the aromatic modified terpene resins include terpene phenol resins made from the above terpene compounds and phenol compounds, and terpene styrene resins made from the above terpene compounds and styrene compounds. Terpene phenol styrene resins made from the above terpene compounds, phenolic compounds and styrene compounds can also be used. Examples of phenolic compounds include phenol, bisphenol A, cresol, and xylenol. Styrene-based compounds include styrene and α-methylstyrene.

As the acrylic resin, a styrene-acrylic resin such as a styrene-acrylic resin having a carboxyl group and obtained by copolymerizing an aromatic vinyl monomer component and an acrylic monomer component can be used. Among them, solvent-free carboxyl group-containing styrene-acrylic resins can be preferably used.

The above solvent-free carboxyl group-containing styrene-acrylic resin is a high-temperature continuous polymerization method (high-temperature continuous bulk polymerization method) (U.S. patent No. 4,414,370, JP-A-59-6207, JP-B-5-58005, JP-A-1-313522, US Pat. No. 5,010,166, Toagosei Research It is a (meth)acrylic resin (polymer) synthesized by the method described in Annual Report TREND 2000, No. 3, pp. 42-45). In addition, in this specification, (meth)acryl means methacryl and acryl.

Examples of the acrylic monomer component constituting the acrylic resin include (meth)acrylic acid, (meth)acrylic acid ester (alkyl ester such as 2-ethylhexyl acrylate, aryl ester, aralkyl ester, etc.), (meth)acrylamide , (meth)acrylamide derivatives and other (meth)acrylic acid derivatives. (Meth)acrylic acid is a generic term for acrylic acid and methacrylic acid.

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

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

In the rubber composition, the resin content is preferably 30 parts by mass or less with respect to 100 parts by mass of the diene polymer. Within the above range, the effects of the present invention tend to be favorably obtained. The content is more preferably 25 parts by mass or less, still more preferably 22 parts by mass or less, and particularly preferably 20 parts by mass or less. The lower limit is not particularly limited, but when blended, it is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and still more preferably 10 parts by mass or more.

〔oil〕
Oil may be blended in the rubber composition. By blending the oil, workability is improved, flexibility can be imparted to the tire, and the effects of the present invention can be obtained satisfactorily.

Oils include, for example, process oils, vegetable oils, or mixtures thereof. As the process oil, for example, paraffinic process oil, aromatic process oil, naphthenic process oil, etc. can be used. Vegetable oils include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice bran oil, safflower oil, sesame oil, Olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, tung oil and the like. Commercial products include Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Japan Energy Co., Ltd., Orisoi Co., Ltd., H&R Co., Ltd., Toyokuni Oil Co., Ltd., Showa Shell Sekiyu K.K., Fuji Kosan Co., Ltd., etc. products can be used. These may be used alone or in combination of two or more. Among them, aromatic process oils are preferable because the effects of the present invention can be suitably obtained.

In the rubber composition, the content of the oil is preferably 1 part by mass or more, more preferably 3 parts by mass or more, relative to 100 parts by mass of the diene polymer. Also, it is preferably 50 parts by mass or less, more preferably 30 parts by mass or less. The effect of the present invention can be suitably obtained by setting it within the above range.
In this specification, the content of oil also includes the amount of oil contained in the oil-extended rubber.

When used for a cap tread, the content of the oil is preferably 1 part by mass or more, more preferably 3 parts by mass or more, relative to 100 parts by mass of the diene polymer. Also, it is preferably 50 parts by mass or less, more preferably 30 parts by mass or less. Within the above range, the workability, initial dry grip performance, durability of dry grip performance, and chipping resistance tend to be improved in performance balance.

When used for the base tread, the content of the oil is preferably 1 part by mass or more, more preferably 3 parts by mass or more, relative to 100 parts by mass of the diene polymer. Also, it is preferably 20 parts by mass or less, more preferably 10 parts by mass or less. Within the above range, workability and elongation at break tend to be improved.

In the rubber composition, the total content of the resin and oil is preferably 1 part by mass or more, more preferably 3 parts by mass or more, relative to 100 parts by mass of the diene polymer. Also, it is preferably 50 parts by mass or less, more preferably 30 parts by mass or less. The effect of the present invention can be suitably obtained by setting it within the above range.

When used for a cap tread, the total content of the resin and oil is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, relative to 100 parts by mass of the diene polymer. Also, it is preferably 50 parts by mass or less, more preferably 30 parts by mass or less. Within the above range, there is a tendency to improve the performance balance among initial dry grip performance, durability of dry grip performance, and chipping resistance performance.

When used for the base tread, the total content of the resin and oil is preferably 1 part by mass or more, more preferably 3 parts by mass or more, relative to 100 parts by mass of the diene polymer. Also, it is preferably 15 parts by mass or less, more preferably 10 parts by mass or less. Within the above range, the elongation at break tends to be improved.

〔wax〕
A wax may be blended in the rubber composition, and for example, paraffin wax can be preferably used. Here, paraffin wax can be defined as an alkane having 20 or more carbon atoms. Those mainly containing alkanes (straight-chain alkanes) are used (in this specification, normal alkanes having 20 or more carbon atoms are also simply referred to as "normal alkanes"). That is, in the present invention, paraffin waxes containing mainly normal alkanes can be preferably used. As commercially available products, products of Ouchi Shinko Kagaku Kogyo Co., Ltd., Nippon Seiro Co., Ltd., Seiko Kagaku Co., Ltd., etc. can be used. The paraffin wax may be used alone, or two or more of them may be used in combination with other types of waxes having different carbon number distributions and normal ratios (ratio of normal alkanes in all alkanes).

The paraffin wax containing normal alkane is not particularly limited, and for example, paraffin wax containing each normal alkane having 20 to 55 carbon atoms can be used. Among them, the content of normal alkane in the paraffin wax is preferably 70% by mass or more, more preferably 80% by mass or more.

In the rubber composition, the content of the paraffin wax is preferably 0.3 to 5.0 parts by mass, more preferably 0.8 to 3.0 parts by mass, with respect to 100 parts by mass of the diene polymer. 0 to 2.0 parts by mass is more preferable.

[Anti-aging agent]
The rubber composition preferably contains an antioxidant.
Antiaging agents are not particularly limited, and examples include naphthylamine antiaging agents such as phenyl-α-naphthylamine; diphenylamine antiaging agents such as octylated diphenylamine and 4,4′-bis(α,α′-dimethylbenzyl)diphenylamine. Inhibitor; N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p - p-phenylenediamine antioxidants such as phenylenediamine; quinoline antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; 2,6-di-t-butyl-4 -monophenol antioxidants such as methylphenol and styrenated phenol; , polyphenol-based antioxidants, and the like. As commercially available products, products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Kagaku Kogyo Co., Ltd., Flexis, etc. can be used. These may be used alone or in combination of two or more. Among them, p-phenylenediamine antioxidant (more preferably N-(1,3- dimethylbutyl)-N'-phenyl-p-phenylenediamine) is preferred.

In the rubber composition, the content of the antioxidant is preferably 0.3 parts by mass or more, more preferably 1 part by mass or more, and still more preferably 2 parts by mass or more with respect to 100 parts by mass of the diene polymer. . Also, it is preferably 7 parts by mass or less, more preferably 6 parts by mass or less, and even more preferably 5 parts by mass or less. Within the above range, the effects of the present invention can be sufficiently exhibited.

〔fatty acid〕
The rubber composition preferably contains fatty acids such as stearic acid, palmitic acid and oleic acid.
Conventional stearic acid can be used, for example, NOF Corporation, NOF Corporation, Kao Corporation, Wako Pure Chemical Industries, Ltd., Chiba Fatty Acids Co., Ltd. products can be used.

In the rubber composition, the content of the fatty acid is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, relative to 100 parts by mass of the diene polymer. Moreover, the content is preferably 10 parts by mass or less, more preferably 5 parts by mass or less. Within the above numerical range, the effects of the present invention tend to be favorably obtained.

[Zinc oxide]
The rubber composition preferably contains zinc oxide.
As the zinc oxide, conventionally known ones can be used, for example, products of Mitsui Kinzoku Mining Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. can be used.

In the rubber composition, the content of zinc oxide is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, relative to 100 parts by mass of the diene polymer. Also, the content is preferably 5 parts by mass or less, more preferably 4 parts by mass or less. Within the above numerical range, the effects of the present invention tend to be favorably obtained.

In addition to the above components, the rubber composition may contain additives commonly used in the tire industry, such as calcium carbonate, talc, alumina, clay, aluminum hydroxide, aluminum oxide, mica, and magnesium sulfate. Fillers; processing aids such as plasticizers and lubricants; surfactants; other softening agents;

As a method for producing the rubber composition, a known method can be used. For example, the above components are kneaded using a rubber kneading device such as an open roll, a Banbury mixer, or a kneader, and then vulcanized. can be manufactured.

As for the kneading conditions, the kneading temperature is usually 120 to 180°C, preferably 130 to 170°C in the base kneading step for kneading additives other than the cross-linking agent (vulcanizing agent) and the vulcanization accelerator. In the finishing kneading step of kneading the vulcanizing agent and the vulcanization accelerator, the kneading temperature is usually 120°C or lower, preferably 85 to 110°C. A composition obtained by kneading a vulcanizing agent and a vulcanization accelerator is usually subjected to vulcanization treatment such as press vulcanization. The vulcanization temperature is generally 140-190°C, preferably 150-185°C.

The rubber composition is suitably used for treads (cap tread, base tread), and is used for members other than treads, such as sidewalls, undertreads, clinch apex, bead apex, breaker cushion rubber, and carcass cord coating. It may be used for rubber, insulation, chafer, inner liner, etc., and for side reinforcing layers of run-flat tires.

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

The pneumatic tire can be used for passenger car tires, large passenger car tires, large SUV tires, heavy load tires for trucks and buses, light truck tires, motorcycle tires, racing tires (high performance tires), etc. is. In particular, it is suitable for racing tires.

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

(Production Example 1: Synthesis of sulfur-containing oligomer 1 (rubber-like))
104.4 g (0.180 mol) of 30% sodium polysulfide aqueous solution, 150 g of ion-exchanged water, and 150 g of ethanol are placed in a flask completely purged with an inert gas such as nitrogen gas or argon gas, stirred, and heated to 90°C. , 25.0 g (0.175 mol) of bis(2-chloroethyl) ether diluted with 100 g of toluene was added dropwise over 2 hours. Vacuum concentration and drying yielded 27.3 g of the desired oligomer.
The resulting sulfur-containing oligomer 1 (rubber-like) had a Mw of 21,000, a sulfur element content of 55% by mass, and a repeating unit of the above formula (I) (R=(CH ₂ ) ₂ O(CH ₂ ) ₂ , x (average value) = 4.0, SP value 11.1).

(Production Example 2: Synthesis of sulfur-containing oligomer 2 (rubber-like))
104.4 g (0.180 mol) of 30% aqueous sodium polysulfide solution, 150 g of ion-exchanged water, 150 g of ethanol, 100 g of toluene, and bis(2-chloroethyl ) 25.0 g (0.175 mol) of ether was taken, stirred, heated and reacted at 90°C for 5 hours to separate the organic layer, then vacuum concentrated and dried at 90°C to obtain 26.0 g of the target oligomer. Obtained.
The resulting sulfur-containing oligomer 2 (rubber-like) had a Mw of 17,000, a sulfur element content of 55% by mass, and a repeating unit of the above formula (I) (R=(CH ₂ ) ₂ O(CH ₂ ) ₂ , x (average value) = 4.0, SP value 11.1).

(Production Example 3: Synthesis of sulfur-containing oligomer 3 (rubber-like))
A flask completely purged with an inert gas such as nitrogen gas or argon gas was charged with 104.4 g (0.180 mol) of a 30% aqueous solution of sodium polysulfide, 150 g of ion-exchanged water, 150 g of ethanol, and tetrabutylammonium chloride ( TBAB) 1.25 g was taken and stirred, and after heating to 90° C., 25.0 g (0.175 mol) of bis(2-chloroethyl) ether diluted with 100 g of toluene was added dropwise over 2 hours. After reacting for some time and separating the organic layer, it was vacuum-concentrated and dried at 90° C. to obtain 28.5 g of the desired oligomer.
The resulting sulfur-containing oligomer 3 (rubber-like) had a Mw of 42,000, a sulfur element content of 55% by mass, and a repeating unit of the above formula (I) (R=(CH ₂ ) ₂ O(CH ₂ ) ₂ , x (average value) = 4.0, SP value 11.1).

(Production Example 4: Synthesis of sulfur-containing oligomer 4 (liquid))
104.4 g (0.180 mol) of a 30% sodium polysulfide aqueous solution, 150 g of ion-exchanged water, and 1 part of tetrabutylammonium chloride (TBAB) as a reaction catalyst were placed in a flask completely purged with an inert gas such as nitrogen gas or argon gas. 25 g of the mixture was stirred, heated to 90° C., 25.0 g (0.175 mol) of bis(2-chloroethyl)ether diluted with 100 g of toluene was added dropwise over 2 hours, and the mixture was further reacted at the same temperature for 3 hours. After separating the organic layer with , it was vacuum-concentrated and dried at 90° C. to obtain 25.5 g of the target oligomer.
The resulting sulfur-containing oligomer 4 (liquid) had a Mw of 2670, a sulfur element content of 55% by mass, and the repeating unit of formula (I) (R=(CH ₂ ) ₂ O(CH ₂ ) ₂ , x (average value )=4.0, SP value 11.1).

(Production Example 5: Synthesis of sulfur-containing oligomer 5 (liquid))
104.4 g (0.180 mol) of a 30% sodium polysulfide aqueous solution and 150 g of ion-exchanged water are placed in a flask that has been completely purged with an inert gas such as nitrogen gas or argon gas. 25.0 g (0.175 mol) of bis(2-chloroethyl) ether diluted with is added dropwise over 2 hours, and the mixture is further reacted at the same temperature for 3 hours to separate the organic layer. After drying, 25.0 g of the desired oligomer was obtained.
The resulting sulfur-containing oligomer 5 (liquid) had an Mw of 1250, a sulfur element content of 55% by mass, and the repeating unit of formula (I) (R=(CH ₂ ) ₂ O(CH ₂ ) ₂ , x (average value )=4.0, SP value 11.1).

(Production Example 6: Synthesis of sulfur-containing oligomer 6 (liquid))
28.1 g (0.15 mol) of 1,2-bis(2-chloroethoxy)ethane and 89.76 g (0.155 mol) of 30% sodium polysulfide (Na ₂ S ₄ ) aqueous solution were mixed with 150 g of water and 100 g of toluene in a non-phase The mixture was reacted at 90° C. for 5 hours in a mixed solvent. After completion of the reaction, the organic phase was separated and concentrated at 90° C. under reduced pressure to obtain 34.3 g of cyclic polysulfide (sulfur-containing oligomer 6 (liquid)) (yield 94%).
The obtained sulfur-containing oligomer 6 (liquid) had an Mw of 500, a sulfur element content of 55% by mass, and a repeating unit of the above formula (I) (R=(CH ₂ ) ₂ O(CH ₂ ) ₂ O(CH ₂ ) ₂ , x (average value) = 4, n (average value) = 1 to 5, SP value 11.1).

(Production Example 7: Synthesis of sulfur-containing oligomer 7 (rubber-like))
104.4 g (0.180 mol) of a 30% sodium polysulfide aqueous solution and 150 g of ion-exchanged water are placed in a flask that has been completely purged with an inert gas such as nitrogen gas or argon gas. 27.13 g (0.175 mol) of 1,6-dichlorohexane diluted with , was added dropwise over 2 hours, followed by reaction at the same temperature for 3 hours to separate the organic layer, followed by vacuum concentration and drying at 90°C. 28.0 g of the desired oligomer was obtained.
The resulting sulfur-containing oligomer 7 (rubber-like) had an Mw of 16,000, a sulfur element content of 58% by mass, and a repeating unit of the above formula (I) (R = -(CH ₂ ) ₅ -, x (average value )=4.0, SP value 11.1).

The structures of the sulfur-containing oligomers 1 to 3 used in the examples are presumed to be compounds having repeating units represented by the following formula (Chem. 8).

The structure of the sulfur-containing oligomers 4 and 5 is presumed to be a mixture of compounds represented by the above formula (8) and the following formula (9) (a mixture of formulas 8 and/or 9).

The structure of the sulfur-containing oligomer 6 is presumed to be a mixture of the following formula (Formula 10) and/or a ring-opened oligomer (straight chain).

The structure of sulfur-containing oligomer 7 is presumed to be a compound having repeating units represented by the following formula (Chem. 11).

Various chemicals used in Examples and Comparative Examples are collectively described below.
NR: TSR20
SBR: Non-oil-extended SBR (styrene content 20% by mass, vinyl content 66 mol%, Tg -23°C, Mw 240,000)
BR: BUNA-CB25 manufactured by LANXESS (rare earth-based BR synthesized using Nd-based catalyst, cis content 97% by mass, Tg-110°C)
Carbon black 1: Show Black N220 (N ₂ SA114 m ² /g) manufactured by Cabot Japan
Carbon black 2: Show Black N351H (N ₂ SA69 m ² /g) manufactured by Cabot Japan Co., Ltd.
Silica: Ultrasil VN3 from Degussa (N ₂ SA 175 m ² /g)
Silane coupling agent: Si75 bis(3-triethoxysilylpropyl) disulfide resin manufactured by Evonik Co., Ltd. 1: YS resin TO-125 manufactured by Yasuhara Chemical Co., Ltd. (aromatic modified terpene resin, softening point 125° C., Tg 64° C.)
Resin 2: Harima Kasei Haristar TF (rosin ester fat, softening point 80°C, Tg 40°C)
Resin 3: Sylvatraxx 4401 manufactured by Arizona Chemical Co. (a copolymer of α-methylstyrene and styrene, softening point: 85°C, Tg: 43°C)
Resin 4: NOVARES C10 manufactured by Rutgers Chemicals (liquid coumarone-indene resin, softening point 10°C, Tg -30°C)
Wax: Ozoace 0355 manufactured by Nippon Seiro Co., Ltd. (paraffin wax, melting point 70° C., normal alkane content 85% by mass)
Stearic acid: stearic acid "Tsubaki" manufactured by NOF Corporation (melting point: 53°C)
Oil: Aroma-based process oil Anti-aging agent: N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (melting point 45°C)
Zinc oxide: Type 2 zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur-containing oligomer 1 (rubber-like): Production Example 1 above
Sulfur-containing oligomer 2 (rubber-like): Production Example 2 above
Sulfur-containing oligomer 3 (rubber-like): Production Example 3 above
Sulfur-containing oligomer 4 (liquid): Production Example 4 above
Sulfur-containing oligomer 5 (liquid): Production Example 5 above
Sulfur-containing oligomer 6 (liquid): Production Example 6 above
Sulfur-containing oligomer 7 (rubber-like): Production Example 7 above
Hybrid cross-linking agent 1: 1,3-bis(citraconimidomethyl)benzene hybrid cross-linking agent 2: 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane Sulfur: 5 manufactured by Hosoi Chemical Industry Co., Ltd. % oil-containing powdered sulfur vulcanization accelerator 1: N-tert-butyl-2-benzothiazolylsulfenamide (melting point 103°C)
Vulcanization accelerator 2: diphenylguanidine (melting point 145°C)

The styrene content, vinyl content and Mw analysis of SBR were performed by the following methods.
(Structure identification)
Structural identification of SBR (styrene content, vinyl content) was performed using a JNM-ECA series device manufactured by JEOL Ltd. For the measurement, 0.1 g of polymer was dissolved in 15 ml of toluene, slowly poured into 30 ml of methanol to reprecipitate, and then dried under reduced pressure.

Further, Mw and structural identification of sulfur-containing oligomers were performed by the following methods.
(Weight average molecular weight (Mw), structure identification)
Mw was obtained by standard polystyrene conversion based on the measured value measured by gel permeation chromatography (GPC) under the following apparatus and conditions.
In addition, by fractionating each peak portion in the chromatogram obtained by GPC measurement and analyzing each fraction by gas chromatography mass spectrometry (GC/MS), the molecular weight of each peak portion was determined. asked.
Furthermore, the sulfur-containing oligomer was analyzed by ¹³ CNMR.
Then, the structure of the sulfur-containing oligomer was identified based on the analysis results by ¹³ CNMR, the weight average molecular weight measured by GPC, and the molecular weight of each peak portion measured by GC/MS.
(1) Pretreatment method After dissolving the sample in a solvent, the sample was filtered through a 0.45 μm membrane filter to obtain a measurement solution.
(2) Apparatus and measurement conditions Apparatus: GPC-8000 series manufactured by Tosoh Corporation Column: TSKGel SuperAWM-H x 2 + SuperAW2500 x 1 (6.0 mm ID x 150 mm x 3) manufactured by Tosoh Corporation
Solvent: chloroform Flow rate: 0.6 mL/min.
Detector: RI detector Column temperature: 40°C
Injection volume: 20 μL
Molecular weight standard: standard polystyrene

(Examples and Comparative Examples)
According to the formulations shown in Tables 1 and 2, using a 1.7 L Banbury mixer manufactured by Kobe Steel, Ltd., chemicals other than sulfur and vulcanization accelerators were kneaded at 150°C for 5 minutes, A kneaded product was obtained. Next, sulfur and a vulcanization accelerator were added to the resulting kneaded product, and the mixture was kneaded for 5 minutes with an open roll under the conditions of a roll temperature control of 70° C. to obtain an unvulcanized rubber composition. The resulting unvulcanized rubber composition is molded into the shape of a cap tread or base tread, laminated together with other tire members to produce an unvulcanized tire, and press-vulcanized at 170° C. for 10 minutes. A test tire (size: 215/45R17) was obtained. For evaluation of test pieces, rubber was cut out from the cap tread portion or base tread portion of the test tire.

The obtained test tires were evaluated as follows. The results are shown in Tables 1 and 2 (reference in Table 1: Comparative Example 1, reference in Table 2: Comparative Example 14).

(early and late dry grip performance)
The test tire was mounted on a domestic FR vehicle with a displacement of 2000 cc, and the actual vehicle was driven on a dry asphalt test course for 15 laps. The initial dry grip performance was evaluated based on the average time of 1st to 5th laps, and the late dry grip performance was evaluated based on the average time of 10th to 15th laps, and indexed. The larger the numerical value, the better the initial dry grip performance and the late dry grip performance. In Table 1, if it exceeds 105, it is good.

(Chipping resistance performance)
The above test tire was mounted on a 2000 cc domestically produced FR vehicle, ran 10 times on a rough road test course simulating a rocky place, and the degree of chipping of the tread rubber was evaluated by appearance and indexed. A larger value indicates better chipping resistance. In Table 1, a value of 110 or more is good.

(Tensile test)
According to JIS K6251 "Determination of tensile properties of vulcanized rubber and thermoplastic rubber", a tensile test was performed using a No. 3 dumbbell-shaped test piece made of a vulcanized rubber composition, and when the vulcanized rubber composition was broken Elongation (tensile elongation; EB [%]) was measured (room temperature). In Table 1, over 500% is good. In Table 2, it is indexed, and when it exceeds 110, it is good.

(Comprehensive performance)
In Table 1, the average of the initial dry grip performance index, late dry grip performance index, and chipping resistance index was evaluated as comprehensive performance. If the total performance is 107 or more, it is good.

From Table 1, it is clear that in the examples using the specific sulfur-containing oligomer of the present application, the initial dry grip performance, the durability of the dry grip performance, and the chipping resistance performance (elongation at break) are remarkably improved.

From Table 2, in Examples, the elongation at break could be improved by 10% or more while maintaining fuel efficiency.

Claims (8)

A diene-based polymer, carbon black and silica, and a sulfur-containing oligomer having a polystyrene-equivalent weight-average molecular weight of 4000 or more by GPC using a chloroform solvent,
The diene-based polymer includes styrene-butadiene rubber and butadiene rubber,
The content of the carbon black is 1 to 30 parts by mass with respect to 100 parts by mass of the diene polymer,
The sulfur-containing oligomer is obtained by reacting a dihalogen compound represented by the following formula (I-1) and an alkali metal polysulfide represented by the following formula (I-2),
The rubber composition, wherein the dihalogen compound is 2,2'-dichloroethyl ether.

(Wherein, H is the same or different and is a halogen atom. R is a substituted or unsubstituted divalent hydrocarbon group which may contain a heteroatom.)

(In the formula, M is an alkali metal. x (average value) is 1.0 to 10.0.) The rubber composition according to claim 1, wherein the sulfur-containing oligomer has a sulfur element content of 10 to 95% by mass. 3. The rubber composition according to claim 1, wherein said sulfur-containing oligomer has a repeating unit represented by the following formula (I).

(Wherein, R is a substituted or unsubstituted divalent hydrocarbon group that may contain a heteroatom. x (average value) is 1.0 to 10.0.) The rubber composition according to any one of claims 1 to 3, wherein the sulfur-containing oligomer has a polarity parameter SP value of 12.5 or less. The rubber composition according to any one of claims 1 to 4, wherein the content of the sulfur-containing oligomer is 1.0 parts by mass or more relative to 100 parts by mass of the diene polymer. The rubber composition according to any one of claims 1 to 5, comprising one or more vulcanization accelerators. The rubber composition according to any one of claims 1 to 6, comprising a sulfenamide vulcanization accelerator and a guanidine vulcanization accelerator. A pneumatic tire produced using the rubber composition according to any one of claims 1 to 7.