JP2010126656A - Rubber composition for run-flat tire, and crosslinked molded article for run-flat tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for run-flat tire having a rubber layer for reinforcing a part of sidewall having a high elastic modulus and excellent in low heat build-up property, and to provide a crosslinked molded article of the same. <P>SOLUTION: The rubber composition for run-flat tire includes a 100 pts.wt. rubber component whose essential component is a functional group-modified conjugated diene-based rubber having at least one functional group selected from the group consisting of an amino, hydroxyl, epoxy, carbonyl, alkoxysilyl, silanol, and a siloxane group represented by general formula (1):-SiR<SP>A</SP>R<SP>B</SP>-O-, wherein R<SP>A</SP>and R<SP>B</SP>are each -CH<SB>3</SB>or -CH<SB>2</SB>V, and V is an organic group, a 30-80 pts.wt. reinforcing agent whose essential component is silica, and a crosslinking agent. The crosslinked molded article is made from the rubber composition, and the run-flat tire comprises the crosslinked molded article for run-flat tire. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a rubber composition for a run-flat tire, a crosslinked molded article, and a run-flat tire. More specifically, it has a rubber composition for run-flat tires, a cross-linked molded product obtained by cross-linking the rubber composition, and a rubber layer for reinforcing a side wall portion having a high elastic modulus and low heat build-up consisting of the cross-linked molded product. Regarding run-flat tires.

Run-flat tires have been developed that can safely travel a certain distance even if the tire is punctured. One of them is a core type system. In the core type system, an annular core is attached to the rim bottom, and a tire punctured by the core is supported from the inside to prevent tire deformation.
Another is a side-reinforced system. The side-reinforcing system maintains the rigidity of the tire when the tire punctures by arranging a thick elastic rubber layer with a high modulus of elasticity on the side wall, and even when subjected to repeated bending deformation, the rubber breaks. By mitigating, long-distance travel is possible.
However, if it is intended to ensure run-flat running performance using rubber having a low elastic modulus, it is necessary to increase the volume of the reinforcing rubber layer, which is not preferable from the viewpoint of tire weight and low heat build-up.
Therefore, as a method for improving the run-flat running performance, a highly elastic rubber layer and a crack-resistant rubber layer each having a specific Shore A hardness and a 100% elongation modulus are arranged at specific ratios in the sidewall reinforcing layer. It has been proposed to increase the elastic modulus of the rubber of the side reinforcing layer (Patent Document 1).
Further, as a method for increasing the elastic modulus of rubber, a method of blending a specific resorcin / formalin resin (Patent Document 2), or a polybutadiene rubber containing syndiotactic crystals in natural rubber and / or isoprene rubber as a rubber component is used. It is proposed to blend (Patent Document 3).
However, these methods improve the rigidity of the run-flat tire as a reinforcing rubber layer, but have insufficient low heat build-up, resulting in a problem of poor run-flat durability.
As a method for improving run flat durability, a tire rubber composition containing a star-type polybutadiene rubber having a specific structure obtained by coupling with tin tetrachloride has been proposed (Patent Document 4).
However, this rubber composition has an insufficient balance between the elastic modulus of rubber and low heat build-up.

Japanese Patent Laid-Open No. 62-279107 JP 2006-124602 A JP 2005-75952 A JP 2005-263893 A

  Accordingly, an object of the present invention is to provide a run-flat tire having a rubber layer for reinforcing a sidewall portion that has a high elastic modulus and excellent low heat build-up, a rubber composition for a run-flat tire for obtaining the run-flat tire, and its An object is to provide a crosslinked molded article.

  As a result of diligent research to achieve the above-mentioned problems, the present inventors have blended a specific amount of a specific reinforcing agent with a polybutadiene rubber having a specific structure, and further blended with a crosslinking agent to achieve a high elastic modulus and The present inventors have found that a rubber composition excellent in low heat build-up can be obtained, and have further advanced research based on this finding to complete the present invention.

Thus, according to the present invention, an amino group, a hydroxyl group, an epoxy group, a carbonyl group, an alkoxysilyl group, a silanol group, and the general formula (1): —SiR ^A R ^B —O— (wherein R ^A and R ^B are , Each of which is —CH ₃ or —CH ₂ V. V is an organic group.) A functional group-modified conjugated diene rubber having one or more functional groups selected from the group consisting of siloxane groups A rubber composition for a run-flat tire comprising 100 parts by weight of a rubber component having an essential component, 30 to 80 parts by weight of a reinforcing agent having silica as an essential component, and a crosslinking agent is provided.

Moreover, according to this invention, the crosslinked molded object for run flat tires formed by bridge | crosslinking the said rubber composition for run flat tires is provided.
The cross-linked molded product for run-flat tire is preferably a rubber layer for reinforcing the sidewall portion of the run-flat tire.
Furthermore, according to the present invention, there is provided a run flat tire comprising the above-mentioned crosslinked molded product for run flat tires.

  Since the crosslinked molded product obtained from the rubber composition for run-flat tires of the present invention has a high elastic modulus and excellent low heat build-up, it can be suitably used as a sidewall reinforcing rubber layer for run-flat tires.

  The rubber composition for a run-flat tire of the present invention contains 100 parts by weight of a rubber component containing a functional group-modified conjugated diene rubber as an essential component, 30 to 80 parts by weight of a reinforcing agent containing silica as an essential component, and a crosslinking agent. Become.

The functional group-modified conjugated diene rubber used in the present invention includes an amino group, a hydroxyl group, an epoxy group, a carbonyl group, an alkoxysilyl group, a silanol group, and a general formula: —SiR ^A R ^B —O— (wherein R ^A and R ^B is each —CH ₃ or —CH ₂ V. V is an organic group.) The functional group-modified conjugate having one or more functional groups selected from the group consisting of siloxane groups represented by: Diene rubber.

The functional group-modified conjugated diene rubber used in the present invention can be produced by using a known method. For example, the monomer having the specific functional group is used as a monomer for obtaining a conjugated diene rubber. A method used as at least a part, a method of polymerizing a conjugated diene monomer using the polymerization initiator having the specific functional group, or a reaction of the compound having the specific functional group with a conjugated diene rubber It can be produced by a method of introducing the specific functional group into a conjugated diene rubber.
More specific examples of the method using the monomer having the specific functional group include a method of copolymerizing the monomer having the specific functional group in the molecule with a conjugated diene monomer or the like. Can do.
Further, as a more specific example of the method using the polymerization initiator having the specific functional group described above, an organic alkali metal amide compound is used as a polymerization initiator as described later, and an amino group-containing conjugated diene rubber is used. A method for introducing a structure can be mentioned.
As a more specific example of the method of reacting the compound having the specific functional group with a conjugated diene rubber, a conjugated diene rubber having an active end obtained by using an organic active metal as a polymerization initiator, Examples thereof include a method of reacting a compound having the specific functional group in the molecule (sometimes referred to as “functional group-modifying compound”).

The conjugated diene monomer that can be used to obtain the functional group-modified conjugated diene rubber used in the present invention is not particularly limited, and specific examples thereof include 1,3-butadiene, 2-methyl-1,3. -Butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene (piperylene) and the like. Among these, 1,3-butadiene and 2-methyl-1,3-butadiene are preferable, and 1,3-butadiene is more preferable.
In order to obtain the functional group-modified conjugated diene rubber used in the present invention, the conjugated diene monomer having the specific functional group in the molecule can be used as at least a part of the monomer to be used.
A conjugated diene monomer may be used individually by 1 type, and may be used in combination of 2 or more type.

The functional group-modified conjugated diene rubber used in the present invention may be a copolymer of a conjugated diene monomer and a monomer copolymerizable with the conjugated diene monomer. The monomer copolymerizable with the conjugated diene monomer is not particularly limited, but an aromatic vinyl monomer is preferably used.
Specific examples of the aromatic vinyl monomer having no specific functional group in the molecule include styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, and 2,4-diisopropyl. Examples thereof include styrene, 2,4-dimethylstyrene, 4-t-butylstyrene, 5-t-butyl-2-methylstyrene, divinylbenzene, diisopropenylbenzene, and the like.
Further, in order to introduce a functional group into the functional group-modified conjugated diene rubber used in the present invention, an aromatic vinyl monomer having the specific functional group in the molecule may be used. Aromatic vinyl unit having an amino group such as dimethylaminomethylstyrene, dimethylaminoethylstyrene, 1- (4-N, N-dimethylaminophenyl) -1-phenylethylene, 1- (morpholinophenyl) -1-phenylethylene Mer, o-hydroxystyrene, m-hydroxystyrene, p-hydroxystyrene, o-hydroxy-α-methylstyrene, m-hydroxy-α-methylstyrene, p-hydroxy-α-methylstyrene, p-vinylbenzyl Examples thereof include aromatic vinyl monomers having a hydroxyl group such as alcohol.
An aromatic vinyl monomer may be used individually by 1 type, and may be used in combination of 2 or more type. As the aromatic vinyl monomer, styrene is particularly preferable.

Furthermore, in order to introduce a functional group into the functional group-modified conjugated diene rubber used in the present invention, a monomer having the specific functional group in the molecule and using a monomer other than those described above Can do. Specific examples thereof include amino group (pyridyl group) -containing vinyl compounds such as 4-vinylpyridine; hydroxyl group-containing vinyl ether compounds such as hydroxymethyl vinyl ether, 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, and 4-hydroxybutyl vinyl ether. Hydroxyl group-containing vinyl compounds such as hydroxyl group-containing vinyl ketone compounds such as hydroxymethyl vinyl ketone, 2-hydroxyethyl vinyl ketone, 3-hydroxypropyl vinyl ketone, 4-hydroxybutyl vinyl ketone; and oxirane compounds such as ethylene oxide and propylene oxide Glycidyl such as glycidyl methyl ether, glycidyl ethyl ether, glycidyl isopropyl ether, glycidyl phenyl ether, glycidyl butyl ether Epoxy group-containing compounds that generate hydroxyl groups by ring-opening polymerization such as ether compounds; vinyl group-containing unsaturated carboxylic acid compounds such as (meth) acrylic acid and itaconic acid, methyl (meth) acrylate, ethyl (meth) acrylate, propyl Unsaturated carboxylic acid ester compounds such as (meth) acrylate and butyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxy Hydroxyl-containing unsaturated carboxylic acid ester compounds such as butyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, glycidyl (meth) acrylate, 4-oxycyclohexyl (meth) acrylic Epoxy group-containing unsaturated carboxylic acid ester compounds such as N-hydroxymethyl (meth) acrylamide, N- (2-hydroxyethyl) (meth) acrylamide, N, N-bis (2-hydroxymethyl) (meta ) Carbonyl group-containing compounds such as hydroxyl group-containing unsaturated amide compounds such as acrylamide, and amino group-containing unsaturated amide compounds such as N, N-dimethylaminopropyl (meth) acrylamide; γ- (meth) acryloxypropyltriethoxy Examples include alkoxysilyl group-containing compounds such as alkoxysilyl group-containing (meth) acrylic acid ester compounds such as silane.
Monomers having these specific functional groups in the molecule may be used alone or in combination of two or more.

  In the case where the functional group-modified conjugated diene rubber used in the present invention is obtained using the monomer having the specific functional group in the molecule, the total monomer units in the functional group-modified conjugated diene rubber are The proportion of the unit composed of the monomer having a specific functional group in the molecule is preferably 0.01 to 5% by weight.

  Other specific examples of the monomer copolymerizable with the conjugated diene monomer include cyano group-containing vinyl compounds such as acrylonitrile, (meth) acrylonitrile, and vinylacetonitrile.

A polymer unit derived from a conjugated diene monomer in the functional group-modified conjugated diene rubber used in the present invention (referred to as “conjugated diene monomer unit”) and a monomer copolymerizable with the conjugated diene monomer. The ratio of polymerized units (referred to as “copolymerizable monomer units”) is such that the ratio of conjugated diene monomer units / copolymerizable monomer units is 50/50 to 100 / A range of 0 is preferable, a range of 65/35 to 100/0 is more preferable, and a range of 75/25 to 100/0 is particularly preferable.
If the amount of polymerized units derived from monomers other than the conjugated diene monomer is too large, the low exothermic property and low temperature brittleness of the crosslinked molded article may be deteriorated.

  The method for polymerizing the functional group-modified conjugated diene rubber used in the present invention is not particularly limited, and specific examples thereof include emulsifying and dispersing the monomer in an aqueous medium in the presence of an emulsifier, and using a radical polymerization initiator. Examples thereof include a method of emulsion polymerization and a solution polymerization method of polymerizing the monomer using an organic active metal as an initiator in an inert solvent. Among these, the solution polymerization method is preferable because various structures of the polymer can be easily controlled.

In the case of obtaining a functional group-modified conjugated diene rubber by a solution polymerization method, the inert solvent used for the polymerization reaction medium is not particularly limited as long as it is usually used in solution polymerization and does not inhibit the polymerization reaction.
Specific examples thereof include aliphatic hydrocarbons such as butane, pentane, hexane and 2-butene; alicyclic hydrocarbons such as cyclopentane, cyclohexane and cyclohexene; and aromatic hydrocarbons such as benzene, toluene and xylene. And the like. The amount of the inert solvent used is such that the monomer concentration is usually 1 to 50% by weight, preferably 10 to 40% by weight.

Specific examples of the organic active metal include an organic alkali metal compound, an organic alkaline earth metal compound, and an organic transition metal compound. Of these, organic transition metal compounds of lanthanum series metals that are used in combination with organic aluminum compounds and organic alkali metal compounds are preferably used. These organic active metals can be used alone or in combination of two or more. Of these organic active metals, organic alkali metal compounds are preferably used.
The amount of the organic active metal used is usually in the range of 1 to 50 mmol, preferably 2 to 20 mmol, per 1,000 g of the monomer mixture.
Specific 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, Organic polyvalent lithium compounds such as 4-dilithio-2-ethylcyclohexane and 1,3,5-trilithiobenzene; organic sodium compounds such as sodium naphthalene; and organic potassium compounds such as potassium naphthalene; Among these, an organic lithium compound, particularly an organic monolithium compound is preferable.
The organic alkali metal compound may be used as an organic alkali metal amide compound by reacting with a secondary amine such as dibutylamine, dihexylamine, and dibenzylamine in advance. When an organic alkali metal amide compound is used, an amino group-containing structure can be introduced into the conjugated diene rubber.

When polymerizing monomers using organic active metals, polar compounds are added to the polymerization reaction system for the purpose of adjusting the amount of vinyl bonds in the conjugated diene monomer unit or to prevent deactivation of the catalyst. can do.
Examples of the polar compound include ether compounds such as dibutyl ether, tetrahydrofuran and 2,2-di (tetrahydrofuryl) propane; tertiary amines such as tetramethylethylenediamine; alkali metal alkoxides; phosphine compounds; Among these, ether compounds and tertiary amines are preferable, tertiary amines are more preferable, and tetramethylethylenediamine is particularly preferable.
The usage-amount of a polar compound is 0.01-100 mol normally with respect to 1 mol of organic active metals, Preferably it is the range of 0.3-30 mol.

The temperature of the polymerization reaction is usually -78 ° C to + 150 ° C, preferably 0 to 100 ° C, more preferably 30 to 90 ° C.
As the polymerization mode, any of batch mode and continuous mode can be adopted.

  As described above, when a monomer containing a conjugated diene monomer is polymerized using an organic active metal, a conjugated diene polymer having an active terminal can be obtained. By reacting the conjugated diene polymer having an active terminal with a compound having in its molecule a specific functional group or a group that can be converted to the specific functional group (referred to as “modification reaction”), Even when only a monomer having no group in the molecule is used as a monomer, a functional group-modified conjugated diene rubber can be obtained.

The functional group-modifying compound to be reacted with the conjugated diene polymer having an active end can react with the active end of the conjugated diene polymer with the specific functional group or the group that can be converted into the specific functional group to form a bond. If it is a compound which has group in a molecule | numerator, it will not specifically limit. The group that can react with the active terminal to form a bond may be a group corresponding to the specific functional group. That is, the functional group modifying compound may be a compound having a plurality of the specific functional groups. In addition, since the epoxy group reacts with the conjugated diene polymer having an active end to form a bond and gives a hydroxyl group as a reaction residue, the functional group modifying compound may be a compound having only one epoxy group. good.
Specific examples of the group that can react with the active terminal to form a bond and do not correspond to the specific functional group include a group containing an ethylenically unsaturated bond such as a vinyl group or an allyl group. .

Specific examples of the functional group-modifying compound that can be used to obtain a functional group-modified conjugated diene rubber having an amino group include N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N-phenyl- N-substituted cyclic amide compounds such as 2-pyrrolidone and N-methyl-ε-caprolactam; N-substituted cyclic urea compounds such as 1,3-dimethylethyleneurea and 1,3-diethyl-2-imidazolidinone; Linear amine compounds such as 1,1-dimethoxytrimethylamine and 1,1-diethoxytrimethylamine; N-substituted carbodiimide compounds such as dicyclohexylcarbodiimide; Schiff base compounds such as N-ethylethylideneimine and N-methylbenzylideneimine 4,4′-bis (dimethylamino) benzophenone, 4,4′-bis (diethyla) Mino) N-substituted aminoketone compounds such as benzophenone; aromatic isocyanate compounds such as diphenylmethane diisocyanate and 2,4-tolylene diisocyanate; dimethylaminomethylstyrene, dimethylaminoethylstyrene, 1- (4-N, N-dimethyl) Amino group-containing vinyl aromatic compounds such as aminophenyl) -1-phenylethylene and 1- (morpholinophenyl) -1-phenylethylene; amino group-containing unsaturated amides such as N, N-dimethylaminopropyl (meth) acrylamide Compounds; pyridyl group-containing vinyl compounds such as 4-vinylpyridine; and the like. The functional group-modified conjugated diene rubber may be a conjugated diene rubber containing a quaternary amino group. Examples of a method for obtaining a conjugated diene rubber containing a quaternary amino group include a method of treating a conjugated diene rubber having a tertiary amino group with a quaternizing agent in a state where it is dissolved in an organic solvent. it can. Examples of the quaternizing agent used in this manner include alkyl nitrate, potassium alkyl sulfate, dialkyl sulfuric acid, arylsulfonic acid alkyl ester, alkyl halide, metal halide and the like.

  Examples of the functional group-modifying compound that can be used to obtain a functional group-modified conjugated diene rubber having a hydroxyl group include epoxy compounds. Specific examples of epoxy compounds that can be used as the functional group modifying compound include oxirane compounds such as ethylene oxide and propylene oxide, and glycidyl such as glycidyl methyl ether, glycidyl ethyl ether, glycidyl isopropyl ether, glycidyl phenyl ether, and glycidyl butyl ether. Examples include ether compounds.

  Examples of functional group-modifying compounds that can be used to obtain a functional group-modified conjugated diene rubber having an epoxy group include tetraglycidyl-1,3-bisaminomethylcyclohexane, tetraglycidyldiaminodiphenylmethane, and tetraglycidyl-p-phenylene. Examples include diamines and amino group-containing glycidyl compounds such as triglycidyl isocyanurate. The epoxy group of the functional group-modified conjugated diene rubber having an epoxy group can be converted to a hydroxyl group by hydrolysis.

  Examples of functional group-modifying compounds that can be used to obtain a functional group-modified conjugated diene rubber having a carbonyl group include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, and butyl (meth) acrylate. Unsaturated carboxylic acid ester compounds such as glycidyl (meth) acrylate and the like, and epoxy group-containing unsaturated carboxylic acid ester compounds such as glycidyl (meth) acrylate.

Examples of the functional group-modifying compound that can be used to obtain a functional group-modified conjugated diene rubber having an alkoxysilyl group include bis (trimethoxysilylpropyl) ethane, bis (triethoxysilylpropyl) ethane, and bis (triethoxy Silylpropyl) tetrasulfide, bis (tributoxysilylpropyl) tetrasulfide, tetramethoxysilane, tetraethoxysilane, trimethoxymethylsilane, dimethoxydimethylsilane, triphenoxymethylsilane, diphenoxydichlorosilane, dimethoxydichlorosilane, diethoxydi Alkoxysilane compounds such as chlorosilane, methoxytrichlorosilane, ethoxytrichlorosilane, and phenoxytrichlorosilane; N, N-bis (trismethylsilyl) -3-aminopropy Amino group-containing alkoxysilane compounds such as triethoxysilane, {3- (diethylamino) propyl} triethoxysilane, {3- (diethylamino) propyl} methylethoxysilane, 2-cyanoethyltriethoxysilane; 3-glycidoxyethyl Trimethoxysilane, 3-glycidoxybutylpropyltrimethoxysilane, 3-glycidoxybutyltrimethoxysilane, 3-glycidoxypropyltripropoxysilane, 3-glycidoxypropyltriphenoxysilane, 3-glycidoxy Epoxy group-containing alkoxysilane compounds such as propylmethyldimethoxysilane; 1,3,5-tris (3-trimethoxysilylpropyl) isocyanurate, 1,3,5-tris (3-triethoxysilylpropyl) isocyanurate, 1 Alkoxysilyl group-containing isocyanurate compounds such as alkoxysilyl isocyanurate such as 3,5-tris (3-tripropoxysilylpropyl) isocyanurate, 1,3,5-tris (3-tributoxysilylpropyl) isocyanurate; and alkoxysilyl group-containing (meth) acrylic acid ester compounds such as γ-acryloxypropyltriethoxysilane and γ-methacryloxypropyltriethoxysilane;
Among these compounds, it is preferable to use a compound having two or more alkoxysilyl groups.
The alkoxysilyl group of the functional group-modified conjugated diene rubber having an alkoxysilyl group can be converted to a silanol group by hydrolysis.

In order to obtain a functional group-modified conjugated diene rubber having a silanol group, a compound having a group such as a halosilyl group that can be converted into a silanol group by the action of a proton donor is usually used as the functional group-modifying compound. It is preferable to employ a method in which a proton donor is allowed to act on the polymer obtained thereby.
Specific examples of the compound having a halosilyl group that can be used in this method include dichlorodimethylsilane, dichlorodiethylsilane, dichlorodiphenylsilane, dichlorophenylmethylsilane, dichlorovinylmethylsilane, hexachlorodisilane, bis (trichlorosilyl) methane, bis (Trichlorosilyl) ethane, bis (trichlorosilyl) propane, bis (trichlorosilyl) hexane, bis (trichlorosilyl) nonane and the like can be mentioned.

General formula (1): -SiR ^A R ^B —O— (wherein R ^A and R ^B are each —CH ₃ or —CH ₂ V. V is an organic group). As a functional group-modifying compound that can be used to obtain a functional group-modified conjugated diene rubber having a siloxane group, a polyorganosiloxane represented by the following general formula (2), (3), or (4) is used. Can be mentioned.

（一般式（２）中、Ｒ^１〜Ｒ^８は、炭素数１〜６のアルキル基又は炭素数６〜１２のアリール基であり、これらは互いに同一であっても相違してもよい。Ｘ^１及びＸ^４は、（ｉ）重合体の活性末端と反応しうる官能基であるか、又は、（ｉｉ）炭素数１〜６のアルキル基又は炭素数６〜１２のアリール基であり、Ｘ^１及びＸ^４は同一であっても相違してもよい。Ｘ^２は、重合体の活性末端と反応しうる官能基である。Ｘ^３は、２〜２０のアルキレングリコールの繰返し単位を含有する基であり、Ｘ^３の一部は２〜２０のアルキレングリコールの繰返し単位を含有する基から導かれる基であってもよい。ｍは３〜２００の整数であり、ｎ及びｋは、それぞれ、０〜２００の整数である。）

(In General Formula (2), R ^{1 to} R ⁸ are each an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, and these may be the same as or different from each other. ¹ and X ⁴ are (i) a functional group capable of reacting with the active terminal of the polymer, or (ii) an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, ¹ and X ⁴ may be the same or different, X ² is a functional group capable of reacting with the active end of the polymer, and X ³ contains 2 to 20 alkylene glycol repeating units. And a part of X ³ may be a group derived from a group containing an alkylene glycol repeating unit of 2 to 20. m is an integer of 3 to 200, and n and k are respectively It is an integer from 0 to 200.)

Examples of the alkyl group having 1 to 6 carbon atoms constituting R ^{1 to} R ⁸ and X ¹ and X ⁴ include methyl group, ethyl group, n-propyl group, isopropyl group, butyl group, pentyl group, hexyl group, A cyclohexyl group etc. are mentioned. Examples of the aryl group having 6 to 12 carbon atoms include a phenyl group and a methylphenyl group. Among these alkyl groups and aryl groups, a methyl group is particularly preferable.

The functional group capable of reacting with the active terminal of the polymer constituting X ¹ , X ² and X ⁴ includes an alkoxy group having 1 to 5 carbon atoms, a hydrocarbon group containing 2-pyrrolidonyl group, and an epoxy group Preferred is a group having 4 to 12 carbon atoms.

  Specific examples of the alkoxy group having 1 to 5 carbon atoms include methoxy group, ethoxy group, propoxy group, isopropoxy group, butoxy group and the like. Of these, a methoxy group is preferable.

  Preferred examples of the hydrocarbon group containing a 2-pyrrolidonyl group include a group represented by the following general formula (5).

一般式（５）中、ｊは２〜１０の整数である。特に、ｊが２であることが好ましい。

In general formula (5), j is an integer of 2-10. In particular, j is preferably 2.

The group having 4 to 12 carbon atoms and having an epoxy group is represented by the following general formula (6): -ZTE.
In General Formula (6), Z is an alkylene group having 1 to 10 carbon atoms or an alkylarylene group, T is a methylene group, a sulfur atom or an oxygen atom, and E is a carbon atom having 2 to 10 carbon atoms having an epoxy group. It is a hydrogen group. Among these, those in which T is an oxygen atom are preferable, those in which T is an oxygen atom and E is a glycidyl group are more preferable, Z is an alkylene group having 3 carbon atoms, T is an oxygen atom, and E is Those that are glycidyl groups are particularly preferred.

In the general formula (2), a part of X ¹ and / or X ⁴ is an alkoxy group having 1 to 5 carbon atoms, a hydrocarbon group containing 2-pyrrolidonyl group, and a group having 4 to 12 carbon atoms containing an epoxy group. And the remainder is a group derived from the functional group or a single bond. X ² is a group partially selected from an alkoxy group having 1 to 5 carbon atoms, a hydrocarbon group containing a 2-pyrrolidonyl group, and a group having 4 to 12 carbon atoms containing an epoxy group, and the remainder is , A group derived from the functional group or a single bond.

In the polyorganosiloxane represented by the general formula (2), when at least part of X ¹ , X ² and X ⁴ is a hydrocarbon group containing a 2-pyrrolidonyl group, the polyorganosiloxane is added to the active terminal of the polymer. When reacted, the carbon-oxygen bond of the carbonyl group constituting the 2-pyrrolidonyl group is cleaved to form a structure in which the polymer chain is directly bonded to the carbon atom.
Further, when at least part of X ¹ , X ² and X ⁴ is a group having 4 to 12 carbon atoms containing an epoxy group, an epoxy ring is formed by reacting an active conjugated diene polymer chain with a polyorganosiloxane. The oxygen-carbon bond to be cleaved forms a structure in which the polymer chain is bonded to the carbon atom.

In the polyorganosiloxane represented by the general formula (2), as X ¹ and X ⁴ , among the above, a group having 4 to 12 carbon atoms containing an epoxy group and a group derived therefrom or 1 to 6 carbon atoms And X ² is preferably a group having 4 to 12 carbon atoms containing an epoxy group and a group derived therefrom.

In the polyorganosiloxane represented by the general formula (2), X ³ , that is, a group containing 2 to 20 alkylene glycol repeating units is preferably a group represented by the following general formula (7).

（式中、ｔは２〜２０の整数であり、Ｐは炭素数２〜１０のアルキレン基又はアルキルアリーレン基であり、Ｒは水素原子又はメチル基であり、Ｑは炭素数１〜１０のアルコキシル基又はアリーロキシ基である。Ｑの一部は単結合であってもよい。これらの中でもｔが２〜８の範囲であり、Ｐが炭素数３のアルキレン基であり、Ｒが水素原子であり、かつＱがメトキシ基であるものが好ましい。）

(In the formula, t is an integer of 2 to 20, P is an alkylene group or alkylarylene group having 2 to 10 carbon atoms, R is a hydrogen atom or a methyl group, and Q is an alkoxyl having 1 to 10 carbon atoms. A part of Q may be a single bond, in which t is in the range of 2 to 8, P is an alkylene group having 3 carbon atoms, and R is a hydrogen atom. And Q is preferably a methoxy group.)

In the general formula (2), m is preferably an integer of 20 to 150, more preferably an integer of 30 to 120. When this number is small, the processability of an uncrosslinked rubber compound in which a filler is blended with a conjugated diene rubber is lowered, or low heat build-up is inferior. When this number is large, the production of the corresponding polyorganosiloxane becomes difficult, and the viscosity of the polyorganosiloxane becomes too high, making it difficult to handle.
In the general formula (2), n is preferably an integer of 0 to 150, more preferably an integer of 0 to 120. k is an integer of 0 to 200, preferably an integer of 0 to 150, more preferably an integer of 0 to 120.
The total number of m, n and k is preferably 400 or less, more preferably 300 or less, and particularly preferably 250 or less. When the total number is too large, it becomes difficult to produce the polyorganosiloxane, and the viscosity of the polyorganosiloxane becomes too high, making it difficult to handle.

（一般式（３）中、Ｒ^９〜Ｒ^１６は、炭素数１〜６のアルキル基又は炭素数６〜１２のアリール基であり、これらは互いに同一であっても相違してもよい。Ｘ^５〜Ｘ^８は、重合体の活性末端と反応しうる官能基である。）

(In the general formula ^{(3), R} 9 ~R ¹⁶ is an alkyl group or an aryl group having 6 to 12 carbon atoms having 1 to 6 carbon atoms, which may be different even they are identical to each other .X ^{5 to} X ⁸ are functional groups capable of reacting with the active terminal of the polymer.)

（一般式（４）中、Ｒ^１７〜Ｒ^１９は、炭素数１〜６のアルキル基又は炭素数６〜１２のアリール基であり、これらは互いに同一であっても相違してもよい。Ｘ^９〜Ｘ^１１は、重合体の活性末端と反応しうる官能基である。ｓは１〜１８の整数である。）

(In the general formula (4), R ^{17 to} R ¹⁹ are an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, and these may be the same as or different from each other. ^{9 to} X ¹¹ are functional groups capable of reacting with the active terminal of the polymer, and s is an integer of 1 to 18.)

In the general formulas (3) and (4), the alkyl group having 1 to 6 carbon atoms, the aryl group having 6 to 12 carbon atoms, and the functional group capable of reacting with the active terminal of the polymer are represented by the general formula (2). This is the same as described above.
In addition, all the functional groups which can react with the active terminal of the polymer which the polyorganosiloxane represented by the general formula (2), (3) or (4) has may react with the active terminal, Moreover, a part may remain unreacted.

Among the specific functional group, from the viewpoint of remarkably improving the dispersibility of the filler, the introduction of a general formula [-SiR ^A R ^B -O- structure represented by, and, 1,3-diethyl-2-imidazolidine Lydinone, 4,4′-bis (diethylamino) benzophenone, dimethylaminomethylstyrene, tetraglycidyl-1,3-bisaminomethylcyclohexane, γ-glycidoxypropyltrimethoxysilane, methyltriphenoxysilane, 1- (4 It is more preferable to react —N, N-dimethylaminophenyl) -1-phenylethylene with a conjugated diene polymer having an active end as a functional group-modifying compound, and the general formula (2), (3) or It is particularly preferable to react the polyorganosiloxane (4). When the conjugated diene polymer obtained by reacting the compound has a polymerization activity with respect to the conjugated diene monomer, the polymerization may be continued by adding the monomer.

  In the case of using the functional group-modified compound, the ratio of the polymer chain having the functional group-modified structure introduced into the entire polymer chain of the conjugated diene polymer is preferably 20 to 100% by weight. 50 to 100% by weight is more preferable, and 70 to 100% by weight is most preferable.

When a functional group-modified compound is used, a functional group-modified compound having two or more groups capable of reacting with the active end of the conjugated diene polymer having an active end is used to couple the conjugated diene polymer having an active end. It is preferable to obtain a functional group-modified conjugated diene rubber obtained by ringing.
In this case, the coupling rate of the functional group-modified conjugated diene rubber is 25% or more, preferably 30% or more. When the coupling rate is less than 25%, not only the effect of low exothermicity is lowered, but also the storage stability performance of the functional group-modified conjugated diene rubber is lowered and the flow becomes easy.
The coupling rate can be adjusted by the amount of the functional group-modifying compound used in the modification reaction, and the specific amount can be determined by a preliminary experiment.

The reaction temperature of the conjugated diene polymer having an active end and the functional group-modified compound is usually in the range of 0 to 100 ° C, preferably 30 to 90 ° C, more preferably 50 to 80 ° C, and the reaction time is usually It is in the range of 1 second to 120 minutes, preferably 1 to 60 minutes, more preferably 2 to 30 minutes.

  When the modification reaction is performed, after the modification reaction, and when the modification reaction is not performed, after the polymerization reaction, an alcohol such as methanol or isopropanol; water; acid; Then, if desired, after adding an anti-aging agent such as a phenol-based stabilizer, a phosphorus-based stabilizer, a sulfur-based stabilizer or the like, it is directly dried or dried through coagulation to obtain a target functional group-modified conjugated diene system. Collect the rubber. Further, an extension oil can be added and recovered as an oil-extended rubber.

  As the extending oil for obtaining the oil-extended rubber, those usually used in the rubber industry can be used, and examples thereof include paraffinic, aromatic and naphthenic petroleum softeners; plant softeners; fatty acids; . In the case of petroleum softeners, those having a polycyclic aromatic content of less than 3% are preferred. This content is measured by the method of IP346 (the testing method of THE INSTITUTE PETROLEUM, UK). The amount used is usually 5 to 100 parts by weight, preferably 10 to 60 parts by weight, and more preferably 20 to 50 parts by weight with respect to 100 parts by weight of the functional group-modified conjugated diene rubber.

  In the functional group-modified conjugated diene rubber used in the present invention, the vinyl bond content in the conjugated diene monomer unit portion is not particularly limited, but is usually 0 to 95% by weight, preferably 0 to 75% by weight, more preferably. 0 to 40% by weight. Further, the cis-1,4 bond content in the conjugated diene monomer unit portion is not particularly limited, but is usually 100 to 5% by weight or more, preferably 100 to 10% by weight, more preferably 40 to 20% by weight. is there.

  The glass transition temperature of the functional group-modified conjugated diene rubber used in the present invention is not particularly limited, but is usually -120 ° C to -10 ° C, preferably -120 ° C to -30 ° C, more preferably -120 ° C to -50 ° C. Especially preferably, it is -100 degreeC--70 degreeC. If the glass transition temperature is too high, the low exothermic property and low temperature brittleness of the crosslinked molded article may be deteriorated.

The weight average molecular weight (Mw) of the functional group-modified conjugated diene rubber used in the present invention is usually 1,000 to 3,000,000, preferably 10,000 to 2,000,000, more preferably 200,000. It is suitably selected within a range of ˜1,200,000. When the weight average molecular weight is too high, kneading tends to be difficult, and the processability of the uncrosslinked rubber composition containing the filler tends to be lowered. On the other hand, if the weight average molecular weight is too low, the low heat build-up tends to decrease, or the cost for producing the functional group-modified conjugated diene rubber tends to increase.
The molecular weight distribution of the functional group-modified conjugated diene rubber is such that the ratio Mw / Mn of Mw, which is a molecular weight distribution index, and the number average molecular weight (Mn) is usually 1.1 to 6.0, preferably 1.2. It is -4.0, More preferably, it is the range used as 1.4-2.5. If Mw / Mn is too small, the workability may be inferior. Conversely, if Mw / Mn is too large, the heat build-up and the elastic modulus may be inferior.

  The Mooney viscosity of the functional group-modified conjugated diene rubber used in the present invention is appropriately selected in the range of usually 10 to 200, preferably 30 to 150. If the Mooney viscosity is too high, blending of the filler tends to be difficult, or the processability of the uncrosslinked rubber composition blended with the filler tends to decrease. On the other hand, if the Mooney viscosity is too low, the low heat build-up tends to decrease, or the cost for producing the functional group-modified conjugated diene rubber tends to increase.

The rubber composition for a run-flat tire of the present invention contains the functional group-modified conjugated diene rubber obtained as described above as at least a part of the rubber component.
The ratio of the functional group-modified conjugated diene rubber in the rubber component in the rubber composition of the present invention is preferably 10 to 100% by weight, more preferably 20 to 100% by weight of the total rubber component, 30 It is especially preferable to set it as -100 weight%. If this ratio is too low, the low heat build-up will deteriorate.

Specific examples of rubber components other than the functional group-modified conjugated diene rubber used in the rubber composition of the present invention include natural rubber, polyisoprene rubber, styrene-butadiene copolymer rubber, polybutadiene rubber, styrene-isoprene. Copolymer rubber, butadiene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, styrene-acrylonitrile-butadiene copolymer rubber, acrylonitrile-butadiene copolymer rubber, styrene-butadiene-styrene block copolymer, etc. Conjugated diene rubbers other than the functional group-modified conjugated diene rubbers used in the present invention; acrylic rubber; epichlorohydrin rubber; fluorine rubber; silicon rubber; ethylene-propylene rubber; These rubbers may be used alone or in combination of two or more.
Among these, natural rubber, polyisoprene rubber, polybutadiene rubber and styrene-butadiene copolymer rubber are preferably used.
The polybutadiene rubber may contain a syndiotactic crystal. Examples of the polybutadiene rubber containing such a syndiotactic crystal include VCR-412 and 617 manufactured by Ube Industries.

The rubber composition of the present invention contains a reinforcing agent containing silica as an essential component.
The silica is not particularly limited, and specific examples thereof include dry method white carbon, wet method white carbon, colloidal silica, and precipitated silica. Among these, wet method white carbon mainly containing hydrous silicic acid is preferable. Alternatively, a carbon-silica dual phase filler in which silica is supported on the carbon black surface may be used. These silicas may be used alone or in combination of two or more.

The nitrogen adsorption specific surface area of the silica (measured by the BET method according to ASTM D3037-81) is not particularly limited, and a plurality of silicas having different nitrogen adsorption specific surface areas may be used. The average value of the surface area is preferably 40 to 140 m ² / g, more preferably 60 to 130 m ² / g, and most preferably 80 to 120 m ² / g. If the nitrogen adsorption specific surface area of silica is too low, there is a tendency that the reinforcing effect of silica cannot be obtained. Conversely, if it is too high, hysteresis loss increases and low exothermicity tends to deteriorate.

  The compounding amount of the reinforcing agent is required to be 30 to 80 parts by weight, preferably 35 to 70 parts by weight, and more preferably 40 to 60 parts by weight with respect to 100 parts by weight of the rubber component. If the blending amount of the filler is too small, the rigidity of the rubber is insufficient and the effect of improving the run-flat running performance is lowered. On the other hand, if the amount is too large, hysteresis loss increases and low heat build-up tends to deteriorate.

  The amount of silica in the reinforcing agent is preferably 20% by weight or more, more preferably 30% by weight or more, still more preferably 50% by weight, and most preferably 80% by weight or more. If the proportion of silica is low, the balance between the reinforcement effect and hysteresis loss cannot be achieved, and the balance between run-flat running performance and low heat build-up will deteriorate.

  In order to introduce the reinforcing agent into the rubber composition, the solid rubber may be filled by a dry kneading method, or a wet kneading method, that is, by blending each filler in a polymer emulsion or a polymer solution, It may be directly dried or coagulated / dried.

The rubber composition of the present invention can be further made into a rubber composition having a better balance between elastic modulus and low exothermicity by blending an appropriate amount of a silane coupling agent.
Specific examples of the silane coupling agent include vinyltriethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane, and 3-octylthio. -1-propyltriethoxysilane, γ-mercaptopropyl-di (tridecyl-oligooxyalkylene) ethoxysilane, bis (3- (triethoxysilyl) propyl) tetrasulfide, bis (3- (triethoxysilyl) propyl) disulfide , Γ-trimethoxysilylpropyldimethylthiocarbamyl tetrasulfide, γ-trimethoxysilylpropylbenzothiazyl tetrasulfide, and the like. These silane coupling agents may be used alone or in combination of two or more.
Among these silane coupling agents, those containing 4 or less sulfur in one molecule are preferable. By using such a silane coupling agent, scorch during kneading can be avoided.
The amount of the silane coupling agent is preferably 0.1 to 20 parts by weight, more preferably 0.5 to 15 parts by weight, and most preferably 1 to 10 parts by weight with respect to 100 parts by weight of silica.

As the reinforcing agent, carbon black can be used in addition to silica.
Specific examples of carbon black include furnace black, acetylene black, thermal black, channel black, fullerene and the like. Among these, furnace black is preferable, and specific examples thereof include SAF-HS, SAF, ISAF-HS, ISAF, ISAF-LS, IISAF-HS, HAF, HAF-HS, HAF-LS, MAF-HS, MAF. MAF-LS, FEF-HS, FEF, GPF, SRF-HS, SRF, SRF-LS and the like. These carbon blacks may be used alone or in combination of two or more.

  You may mix | blend fillers other than a reinforcing agent with the rubber composition of this invention. Specific examples thereof include corn starch, calcium carbonate, clay, talc, diatomaceous earth, alumina, aluminum sulfate, barium sulfate, calcium sulfate, basic magnesium carbonate, and aluminum hydroxide.

In the rubber composition of the present invention, a crosslinking agent is blended in order to make this a crosslinked molded article.
A crosslinking agent will not be specifically limited if it is normally used for bridge | crosslinking of conjugated diene type rubber | gum. Specific examples include sulfur such as powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur; sulfur halides such as sulfur monochloride and sulfur dichloride; dicumyl peroxide and ditertiary butyl peroxide. Organic peroxides; quinone dioximes such as p-quinone dioxime and p, p'-dibenzoylquinone dioxime; triethylene tetramine, hexamethylene diamine carbamate, 4,4'-methylene bis-o-chloroaniline, etc. Organic polyamine compounds; alkylphenol resins having a methylol group; and the like. Among these, sulfur is preferable.
These crosslinking agents may be used alone or in combination of two or more.
The amount of the crosslinking agent is preferably 2 to 15 parts by weight, more preferably 3 to 10 parts by weight, and most preferably 3.5 to 6 parts by weight with respect to 100 parts by weight of the rubber component. If the amount of the cross-linking agent is too small, the rigidity of the rubber is insufficient and the run-flat running performance is deteriorated. On the other hand, if the amount of the crosslinking agent is too large, the crosslinking speed becomes too fast and the moldability may be deteriorated.

Moreover, a crosslinking accelerator or a crosslinking activator can be used in combination with the crosslinking agent.
Specific examples of the crosslinking accelerator include N-cyclohexyl-2-benzothiazole sulfenamide, Nt-butyl-2-benzothiazole sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, N- Sulfenamide-based crosslinking accelerators such as oxyethylene-2-benzothiazole sulfenamide and N, N′-diisopropyl-2-benzothiazole sulfenamide; guanidines such as diphenylguanidine, diortolylguanidine, orthotolylbiguanidine Thiourea crosslinking accelerators such as diethylthiourea; thiazole crosslinking accelerators such as 2-mercaptobenzothiazole, dibenzothiazyl disulfide, 2-mercaptobenzothiazole zinc salt; tetramethylthiuram monosulfide, tetrame Thiuram-based cross-linking accelerators such as tilthiuram disulfide; Dithiocarbamic acid-based cross-linking accelerators such as sodium dimethyldithiocarbamate and zinc diethyldithiocarbamate; And the like, and the like. These crosslinking accelerators may be used alone or in combination of two or more.
Among these crosslinking accelerators, those containing a sulfenamide-based crosslinking accelerator are preferable.
The blending amount of the crosslinking accelerator is preferably 0.3 to 15 parts by weight, more preferably 0.5 to 5 parts by weight with respect to 100 parts by weight of the rubber component.

As the crosslinking activator, for example, higher fatty acids such as stearic acid, zinc oxide and the like can be used.
As the zinc oxide, it is preferable to use one having a particle size of 5 μm or less with high surface activity, and specific examples thereof include activated zinc white having a particle size of 0.05 to 0.2 μm and zinc white having a particle size of 0.3 to 1 μm. Can be mentioned. Zinc oxide may be surface-treated with an amine-based dispersant or wetting agent.
These crosslinking activators may be used individually by 1 type, and may be used in combination of 2 or more types.
The blending ratio of the crosslinking activator is appropriately selected depending on the type of the crosslinking activator. The compounding amount of the higher fatty acid is preferably 0.3 to 10 parts by weight, more preferably 0.5 to 5 parts by weight with respect to 100 parts of rubber. The compounding amount of zinc oxide is preferably 0.1 to 5 parts by weight, more preferably 0.5 to 3 parts by weight with respect to 100 parts by weight of the rubber component.

Examples of other compounding agents that can be incorporated into the rubber composition of the present invention include process oils, activators such as diethylene glycol, polyethylene glycol, and silicone oil, and waxes.
As the process oil, the same oil as the above-described extension oil can be used.

The rubber composition of the present invention can be obtained by kneading each component according to a conventional method.
For example, a rubber composition can be obtained by mixing a compounding agent excluding a crosslinking agent and a crosslinking accelerator and a rubber component and then mixing the obtained kneaded material with a crosslinking agent and a crosslinking accelerator.
The kneading temperature of the compounding agent excluding the crosslinking agent and the crosslinking accelerator and the rubber component is preferably 80 to 200 ° C, more preferably 120 to 180 ° C, and the kneading time is preferably 30 seconds to 30 minutes. . The obtained kneaded product is mixed with the crosslinking agent and the crosslinking accelerator after cooling the kneaded product to 100 ° C. or lower, preferably 80 ° C. or lower.

The rubber composition of the present invention can be crosslinked to form a crosslinked molded product.
The crosslinking method is not particularly limited, and may be selected according to the properties and size of the crosslinked molded body. A rubber composition containing a crosslinking agent may be filled in a mold and heated to be crosslinked simultaneously with the molding. A rubber composition containing a crosslinking agent may be pre-molded and then heated to be crosslinked. May be. The crosslinking temperature is preferably 120 to 200 ° C, more preferably 100 to 190 ° C, and most preferably 120 to 180 ° C. The crosslinking time is usually about 1 to 120 minutes.

The crosslinked molded body obtained by crosslinking the rubber composition of the present invention can be suitably used as a rubber layer for reinforcing a sidewall portion of a run flat tire.
The reinforcing rubber layer is disposed on the sidewall portion and is used to increase the rigidity of the tire.
Specifically, the reinforcing rubber layer is arranged from the bead portion to the shoulder portion in contact with the inside of the tire carcass ply, and a crescent-shaped reinforcing rubber layer, carcass ply that gradually decreases in thickness in both end directions. Examples thereof include a reinforcing rubber layer disposed between the bead portion and the tread portion end between the main body portion and the folded portion, and two reinforcing rubber layers disposed between the plurality of carcass plies or the reinforcing plies.
The thickness of the reinforcing rubber layer is preferably 5 to 30 mm, more preferably 8 to 20 mm. If the thickness of the reinforcing rubber layer is less than 5 mm, the rigidity of the reinforcing rubber layer is insufficient and the run-flat performance tends to be inferior. If it exceeds 30 mm, the reinforcing rubber layer tends to be thick and the tire weight tends to be too heavy. .

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. In addition, the part and% in an Example and a comparative example are a basis of weight unless there is particular notice.

Various physical properties were measured according to the following methods.
(1) Content of cis-1,4 bond unit and content of vinyl bond unit in 1,3-butadiene unit of conjugated diene rubber
^It was measured by ¹ H-NMR.
(2) Molecular weight (Mw), molecular weight distribution (Mw / Mn) and coupling rate of conjugated diene polymer Conjugated diene polymer before reaction with functional group-modified compound and finally obtained conjugated diene rubber Were measured by gel permeation chromatography under the following conditions.
Measuring instrument: HLC-8020 (manufactured by Tosoh Corporation)
Column: A column in which two GMH-HR-H (manufactured by Tosoh Corporation) were connected in series was used.
Detector: Differential refractometer RI-8020 (manufactured by Tosoh Corporation)
Eluent: Tetrahydrofuran
Column temperature: 40 ° C
From the obtained analysis chart, the weight average molecular weight (Mw), the molecular weight distribution (Mw / Mn), and the coupling rate were determined. (Mw and Mn are standard polystyrene equivalent values.)

(3) Mooney viscosity Measured according to JIS K6300 using a Mooney viscometer (manufactured by Shimadzu Corporation).
(4) Glass transition temperature Using a differential scanning calorimeter (DSC manufactured by Perkinelmer), the differential scanning calorific value was measured by raising the temperature from −150 ° C. to + 150 ° C. at a heating rate of 10 ° C./min in a nitrogen atmosphere. The inflection point was obtained by differentiating the obtained endothermic curve. This inflection point was taken as the glass transition temperature.
(5) Hardness According to JIS K6253, the hardness at 23 ° C. was measured using a Duro-A hardness meter (manufactured by Kobunshi Keiki Co., Ltd.). A higher value indicates a higher elastic modulus.
(6) Viscoelasticity (tan δ)
Using a viscoelasticity measuring device, tan δ at 60 ° C. was measured under conditions of dynamic strain of 0.5% and 10 Hz. The measurement results were each expressed as an index with the measured value of Comparative Example 1 as 100. It shows that it is excellent in low exothermic property, so that the index | expansion of tan-delta is small.
(7) Heat generation characteristics Using a flexometer FT-1260 (manufactured by Ueshima Seisakusho Co., Ltd.), a test was conducted for 15 minutes under the conditions of a test temperature of 40 ° C., a static load of 30 kgf, a dynamic strain of 3.5 mm, and 10 Hz. The difference between the temperature inside the test piece and the temperature inside the test piece before the test was calculated. It shows that it is excellent in low exothermic property, so that this temperature is low.

[Production Example 1 of Functional Group-Modified Conjugated Diene Rubber]
Into an autoclave equipped with a stirrer, 4000 g of cyclohexane and 600 g of 1,3-butadiene were charged, 11.0 mmol of n-butyllithium was added, and polymerization was started at 50 ° C. After 20 minutes from the start of polymerization, 400 g of 1,3-butadiene was continuously added over 30 minutes. The maximum temperature during the polymerization reaction was 80 ° C.
After completion of the continuous addition, the polymerization reaction was continued for another 15 minutes, and after confirming that the polymerization conversion was 100%, a small amount of the polymerization solution was sampled. A small amount of the sampled polymerization solution was added with excess methanol to stop the reaction, and then air-dried to obtain a polymer, which was used as a sample for gel permeation chromatography analysis.
Immediately after sampling a small amount of the polymerization solution, 20 parts of polyorganosiloxane A having an average structure satisfying the following conditions in the general formula (2) in an amount corresponding to 0.004 times mol of n-butyllithium used was obtained. Polymerization containing a functional group-modified polybutadiene rubber by adding methanol in an amount corresponding to 2 moles of n-butyllithium used as a polymerization terminator after adding it in the form of a% xylene solution and reacting for 30 minutes. A solution was obtained.
0.15 parts of 4,6-bis (octylthiomethyl) -o-cresol (trade name “Irganox 1520L”, manufactured by Ciba Specialty Chemicals) as an anti-aging agent with respect to 100 parts of functional group-modified polybutadiene rubber Was added to the polymerization solution, and then the polymerization solvent was removed by steam stripping, followed by vacuum drying at 60 ° C. for 24 hours to obtain a solid functional group-modified polybutadiene rubber R1.
The cis-1,4 bond unit content in the 1,3-butadiene unit in the 1,3-butadiene unit of the obtained functional group-modified polybutadiene rubber R1 is 35%, the vinyl bond unit content is 9.1%, The weight average molecular weight was 410,000, the coupling rate was 57%, the molecular weight distribution was 1.4, the Mooney viscosity was 44, and the glass transition temperature was -95 ° C.

[Production Example 2 of Functional Group-Modified Conjugated Diene Rubber]
Other than using the compound (polyorganosiloxane B) having an average structure satisfying the following conditions in the above general formula (2) as the polyorganosiloxane with the amount of n-butyllithium used for polymerization being 9.7 mmol Produced a functional group-modified polybutadiene rubber R2 in the same manner as in Production Example 1 of the functional group-modified conjugated diene rubber.
The functional group-modified polybutadiene rubber R2 has a cis-1,4 bond unit content of 35%, a vinyl bond unit content of 9.1%, a weight average molecular weight of 450,000, a coupling rate of 57%, and a molecular weight distribution of 1. 5. The Mooney viscosity was 60 and the glass transition temperature was -95 ° C.

[Production Example 3 of Functional Group-Modified Conjugated Diene Rubber]
Polymerization of butadiene was carried out in the same manner as in Production Example 2 of the functional group-modified conjugated diene rubber. After reaching a polymerization conversion rate of 100%, a 20% xylene solution of 0.87 mmol of N, N-bis (trismethylsilyl) -3-aminopropyltriethoxysilane was added and reacted for 30 minutes. , N-bis (trismethylsilyl) -3-aminopropyltriethoxysilane (4.0 mmol) was added as a 20% xylene solution and reacted for 30 minutes. Thereafter, the same operation as in Production Example 1 was carried out to obtain a functional group-modified polybutadiene rubber R3.
The obtained functional group-modified polybutadiene rubber R3 has a cis-1,4 bond unit content of 35%, a vinyl bond unit content of 9.1%, a weight average molecular weight of 380,000, a coupling rate of 32%, and a molecular weight distribution. Was 1.5, Mooney viscosity was 44, and glass transition temperature was -95 ° C.

[Production Example 4 of Functional Group-Modified Conjugated Diene Rubber]
Except for using 20% xylene solution of 1,3,5-tris (3-trimethoxysilylpropyl) isocyanurate 0.45 mmol instead of polyorganosiloxane B, the same operation as in Production Example 2 was carried out, A functional group-modified polybutadiene rubber R4 was obtained.
The resulting functional group-modified conjugated diene rubber R4 has a cis-1,4 bond unit content of 35%, a vinyl bond unit content of 9.1%, a weight average molecular weight of 530,000, a coupling rate of 55%, The molecular weight distribution was 1.6, the Mooney viscosity was 66, and the glass transition temperature was -95 ° C.

[Reference production example 1 of functional group-modified conjugated diene rubber]
A polybutadiene rubber RC1 was obtained in the same manner as in Production Example 2, except that a 20% cyclohexane solution of 1.2 mmol of tin tetrachloride was used in place of the polyorganosiloxane B.
The polybutadiene rubber RC1 does not have a specific functional group defined in the present invention.
The resulting polybutadiene rubber RC1 has a cis-1,4 bond unit content of 35%, a vinyl bond unit content of 9.1%, a weight average molecular weight of 620,000, a coupling rate of 70%, and a molecular weight distribution of 1. 4. Mooney viscosity was 73 and glass transition temperature was -95 ° C.

The polybutadiene rubbers RC2 and RC3, natural rubber RN (both are commercially available rubbers) and compounding agents shown in Table 1 are as follows.
(Commercially available rubber)
Polybutadiene rubber RC2: Polybutadiene rubber (manufactured by Zeon Corporation, trade name “Nipol BR1220”)
Cis-1,4 bond unit content in 1,3-butadiene units: 97%, Mooney viscosity: 43
Polybutadiene rubber RC3: Polybutadiene rubber containing syndiotactic crystals (trade name “UBEPOL VCR-412” manufactured by Ube Industries, Ltd.) Syndiotactic crystal content: 12.0%, cis-1 in 1,3-butadiene units , 4-bond unit content: 98%, glass transition temperature -110 ° C., Mooney viscosity: 45
Natural rubber RN: Natural rubber: SMR-CV60

(Combination agent)
Silica I: BET specific surface area = 112 m ² / g (trade name “Zeosil 1115MP” manufactured by Rhodia)
Silica II: BET specific surface area = 165 m ² / g (manufactured by Degussa, trade name “Ultrasil VN-3”)
Carbon black: BET specific surface area = 42 m ² / g (trade name “SEAST SO” manufactured by Tokai Carbon Co., Ltd.)
Process oil: (British Petroleum, trade name “Etherthene 1849A”)
Stearic acid Zinc oxide: Zinc flower No. 1 Anti-aging agent: N-phenyl-N ′-(1,3-dimethylbutyl) -p-phenylenediamine (trade name “NOCRACK 6C” manufactured by Ouchi Shinsei Chemical Co., Ltd.)
Cross-linking agent: Sulfur (Sulfur # 325)
Silane coupling agent: bis (3- (triethoxysilyl) propyl) tetrasulfide (manufactured by Degussa, trade name “Si69”)
Cross-linking accelerator CZ: N-cyclohexyl-2-benzothiazolylsulfenamide (manufactured by Ouchi Shinsei Chemical Co., Ltd., trade name “Noxeller CZ”)
Cross-linking accelerator D: 1,3-diphenylguanidine (made by Ouchi Shinsei Chemical Co., Ltd., trade name “Noxeller D”)

Example 1
In a Banbury mixer with a volume of 250 ml, 70 parts of functional group-modified polybutadiene rubber R1 and 30 parts of natural rubber RN were masticated for 30 seconds, then 49 parts of silica I, 2.94 parts of silane coupling agent, 6 parts of Carbon black, 5 parts of process oil, 3 parts of zinc oxide, 2 parts of stearic acid and 1 part of anti-aging agent were added, kneaded for 4 minutes and 30 seconds, and the rubber kneaded material was discharged from the Banbury mixer.
After the rubber kneaded product was cooled to room temperature, it was kneaded again in a Banbury mixer for 3 minutes, and then the rubber kneaded product was discharged from the Banbury mixer.
Subsequently, after kneading 4.5 parts of a crosslinking agent, 2.5 parts of a crosslinking accelerator CZ and 1.3 parts of a crosslinking accelerator D as a crosslinking agent in an open roll at 50 ° C., a sheet form A crosslinker-containing rubber composition was obtained. This crosslinking agent-containing rubber composition was press-crosslinked at 160 ° C. for 15 minutes to obtain a crosslinked molded body S1. Various physical properties of the obtained crosslinked molded body S1 were measured. The results are shown in Table 1.

(Examples 2 to 4)
Instead of the functional group-modified polybutadiene rubber R1, cross-linked molded bodies S2 to S4 were obtained in the same manner as in Example 1, except that the functional group-modified polybutadiene rubbers R2 to R4 were used. Various physical properties of the obtained crosslinked molded bodies S2 to S4 were measured. The results are shown in Table 1.

(Example 5)
Of the functional group-modified polybutadiene rubber R1, 30 parts were changed to polybutadiene rubber RC3. (In correspondence with this, the amounts of silica, silane coupling agent, crosslinking agent and crosslinking accelerator are as shown in Table 1. Other than that, a crosslinked molded body S5 was obtained in the same manner as in Example 1. Various physical properties of the obtained crosslinked molded body S5 were measured. The results are shown in Table 1.

(Example 6)
A crosslinked molded body S6 was obtained in the same manner as in Example 5 except that the functional group-modified polybutadiene rubber R3 was used in place of the functional group-modified polybutadiene rubber R1. Various physical properties of the obtained crosslinked molded body S6 were measured. The results are shown in Table 1.

(Example 7)
The amount of silica II shown in Table 1 was used as the silica (note that the amount of the silane coupling agent and crosslinking accelerator was changed as shown in Table 1). In the same manner as in Example 5, a crosslinked molded product S7 was obtained. Various physical properties of the obtained crosslinked molded body S7 were measured. The results are shown in Table 1.

(Example 8)
The amount of the cross-linking agent was reduced as shown in Table 1 (in response, the amounts of silica, silane coupling agent and cross-linking accelerator were also changed, and process oil was also changed). In the same manner as in Example 1, a crosslinked molded body S8 was obtained. Various physical properties of the obtained crosslinked molded body S8 were measured. The results are shown in Table 1.

(Comparative Example 1)
Instead of the functional group-modified polybutadiene rubber R1, a crosslinked molded body SC1 was obtained in the same manner as in Example 1 except that polybutadiene rubber RC1 coupled with tin tetrachloride but not modified with a functional group was used. Various physical properties of the obtained crosslinked molded body SC1 were measured. The results are shown in Table 1.

(Comparative Example 2)
Except that polybutadiene rubber RC2 was used in place of the functional group-modified polybutadiene rubber R1, the amounts of silica and silane coupling agent were changed correspondingly, as shown in Table 1. In the same manner as in Example 1, a cross-linked molded body SC2 was obtained. Various physical properties of the obtained crosslinked molded body SC2 were measured. The results are shown in Table 1.

(Comparative Example 3)
Instead of the functional group-modified polybutadiene rubber R1, a crosslinked molded body SC3 was obtained in the same manner as in Example 5 except that polybutadiene rubber RC1 coupled with tin tetrachloride but not modified with a functional group was used. Various physical properties of the obtained crosslinked molded body SC3 were measured. The results are shown in Table 1.

(Comparative Example 4)
A polybutadiene rubber RC2 was used in place of the functional group-modified polybutadiene rubber R3 (note that the amounts of silica and silane coupling agent were changed correspondingly as shown in Table 1). In the same manner as in Example 6, a crosslinked molded body SC4 was obtained. Various physical properties of the obtained crosslinked molded body SC4 were measured. The results are shown in Table 1.

(Comparative Example 5)
In the same manner as in Example 5 except that the amount of silica I was changed (the amount of the silane coupling agent and the cross-linking agent was changed as shown in Table 1 correspondingly). A molded body SC5 was obtained. Various physical properties of the obtained crosslinked molded body SC5 were measured. The results are shown in Table 1. Note that the heat generation characteristics could not be measured because the hardness at 23 ° C. was 80 or more.

(Comparative Example 6)
As in Example 1, except that silica was not used and the amount of carbon black was increased as shown in Table 1 (correspondingly, no silane coupling agent and crosslinking accelerator were used). In this manner, a cross-linked molded body SC6 was obtained. Various physical properties of the obtained crosslinked molded body SC6 were measured. The results are shown in Table 1.

From the results in Table 1, the following can be understood.
The crosslinked molded product obtained from the rubber composition for run-flat tires using the conjugated diene rubber having no specific functional group defined in the present invention is inferior in low heat generation (Comparative Examples 1 to 4).
Comparing Example 5 and Comparative Example 5, it can be seen that when the amount of silica exceeds the upper limit specified in the present invention, the resulting crosslinked molded article is inferior in elastic modulus and low heat build-up.
When Example 1 and Comparative Example 6 are compared, it can be seen that even when a conjugated diene rubber having a specific functional group is used, the resulting crosslinked molded article is inferior in low exothermicity when silica is not used.
On the other hand, the crosslinked molded body obtained from the rubber composition for run-flat tires that satisfies the requirements defined in the present invention has a high elastic modulus and excellent low heat build-up (Examples 1 to 8). From comparison between Example 5 and Example 7, it can be seen that when the BET specific surface area of silica is in the range of 40 to 140 m ² / g, the low heat build-up is more excellent. From a comparison between Example 1 and Example 8, it can be seen that when the crosslinking agent is in the range of 2 to 15 parts by weight with respect to 100 parts by weight of the total rubber component, the elastic modulus and the low heat build-up are more excellent.

Claims (4)

Amino group, hydroxyl group, epoxy group, carbonyl group, alkoxysilyl group, silanol group, and general formula (1): —SiR ^A R ^B —O— (wherein R ^A and R ^B are each —CH ₃ or —CH ₂ V. V is an organic group.) A rubber component containing a functional group-modified conjugated diene rubber having one or more functional groups selected from the group consisting of siloxane groups represented by A rubber composition for a run-flat tire comprising 100 parts by weight, 30 to 80 parts by weight of a reinforcing agent containing silica as an essential component, and a crosslinking agent.   A cross-linked molded article for a run flat tire obtained by cross-linking the rubber composition for a run flat tire according to claim 1.   The cross-linked molded article for run-flat tire according to claim 2, which is a rubber layer for reinforcing a sidewall portion of the run-flat tire.   A run flat tire comprising the cross-linked molded product for a run flat tire according to claim 2 or 3.