JP7222193B2 - Tire rubber composition and tire - Google Patents

Description

TECHNICAL FIELD The present invention relates to a tire rubber composition and a tire.

Conventionally, a composition containing a diene rubber, silica, a foaming agent and a silane coupling agent is known as a rubber composition used for tires (in particular, tire tread portions of studless tires) (practice of Patent Document 1 (see example).

JP-A-2005-320374

In recent years, with the demand for higher levels of safety, tires, especially studless tires, have been required to have further improvements in ice performance and wet performance.
The inventor prepared a rubber composition with reference to the examples of Patent Document 1 and evaluated its performance. was found to be desirable.

Accordingly, an object of the present invention is to provide a tire rubber composition that exhibits excellent performance on ice and wet performance when made into a tire, and a tire manufactured using the rubber composition for tire.
Hereinafter, "excellent on-ice performance when made into a tire" is also simply referred to as "excellent on-ice performance", and "excellent wet performance when made into a tire" is also simply called "excellent wet performance".

As a result of intensive studies, the inventors have found that the above object can be achieved by adopting the following configuration.
That is, the present invention provides the following [1] to [3].

[1] 100 parts by mass of a diene rubber, 30 to 150 parts by mass of silica, 0.5 to 20 parts by mass of a foaming agent, and 1 to 25% by mass of a silane coupling agent relative to the silica content , wherein the diene rubber contains 30% by mass or more of butadiene rubber and natural rubber or isoprene rubber, and the silane coupling agent is a silane cup represented by the following formula (1) A tire comprising at least one selected from the group consisting of a ring agent 1 and a silane coupling agent 2 represented by the following formula (2), wherein the silica and the silane coupling agent satisfy the following formula (3): rubber composition for

(In formula (1) above, R ¹ is R ⁶ O-, R ⁶ C(=O)O-, R ⁶ R ⁷ C=NO-, R ⁶ R ⁷ CNO-, R ⁶ R ⁷ N- or - (OSiR ⁶ R ⁷ ) _m (OSiR ⁵ R ⁶ R ⁷ ) (provided that R ⁶ and R ⁷ are each independently a hydrogen atom or a monovalent hydrocarbon group having 1 to 18 carbon atoms), R ² is R ¹ , a hydrogen atom or a monovalent hydrocarbon group having 1 to 18 carbon atoms; R ³ is R ¹ , R ² or —[O(R ⁸ O) _a H] group (where R ⁸ ~18 alkylene group, a is an integer of 1 to 4), R ⁴ is a divalent hydrocarbon group having 1 to 18 carbon atoms, and R ⁵ is a monovalent hydrocarbon group having 1 to 18 carbon atoms. and x, y and z are numbers that satisfy the relationships of x + y + z = 3, 0 ≤ x ≤ 3, 0 ≤ y ≤ 2, 0 ≤ z ≤ 1.)

(In the above formula (2), R ¹¹ may be the same or different when there is more than one, and each is a linear, branched or cyclic alkyl group having 1 to 8 carbon atoms, and a substituent selected from 2 to 8 straight-chain or branched-chain alkoxyalkyl groups, and R ¹² may be the same or different when there are more than one, and each is a straight chain having 1 to 8 carbon atoms; is a linear, branched or cyclic alkyl group, and when there are a plurality of R ¹³ , they may be the same or different, and each is a linear or branched alkylene group having 1 to 8 carbon atoms. Yes, k has an average value of 3 or less, p and r may be the same or different, and each has an average value of 0 to 3, but both p and r cannot be 3.)

I=(A×B/C)/(D×E)≧9.5×10 ⁻⁴ (3)
(In the above formula (3),
A: Content of the silane coupling agent B: Total atomic weight of sulfur atoms in the silane coupling agent C: Molecular weight of the silane coupling agent D: Content of silica E: Silicon in the silane coupling agent Indicates the number of alkoxy groups bonded to an atom. )

[2] The rubber composition for tires according to [1] or [2] above, wherein the value of I is 7.5×10 ⁻³ or less.
[3] A tire produced using the tire rubber composition described in [1] or [2] above.

ADVANTAGE OF THE INVENTION According to this invention, the rubber composition for tires which is excellent in ice performance and wet performance, and the tire manufactured using the said rubber composition for tires when it is made into a tire can be provided.

1 is a schematic partial cross-sectional view of an example embodiment of a tire of the present invention; FIG.

The rubber composition for tires of the present invention and the tire manufactured using the rubber composition for tires of the present invention are described below.
In this specification, a numerical range represented by "to" means a range including the numerical values before and after "to" as lower and upper limits.
Each component contained in the rubber composition for tires of the present invention may be used singly or in combination of two or more. When two or more of each component are used in combination, the content of that component refers to the total content unless otherwise specified.

[Rubber composition for tires]
The rubber composition for tires of the present invention (hereinafter also referred to as "the composition of the present invention") comprises 100 parts by mass of a diene rubber, 30 to 150 parts by mass of silica, 0.5 to 20 parts by mass of a foaming agent, 1 to 25% by mass of a silane coupling agent relative to the silica content, and the diene rubber contains 30% by mass or more of butadiene rubber, and natural rubber or isoprene rubber and the silane coupling agent is at least one selected from the group consisting of a silane coupling agent 1 represented by the following formula (1) and a silane coupling agent 2 represented by the following formula (2), A rubber composition for tires in which the silica and the silane coupling agent satisfy the following formula (3).

(In formula (1) above, R ¹ is R ⁶ O-, R ⁶ C(=O)O-, R ⁶ R ⁷ C=NO-, R ⁶ R ⁷ CNO-, R ⁶ R ⁷ N- or - (OSiR ⁶ R ⁷ ) _m (OSiR ⁵ R ⁶ R ⁷ ) (provided that R ⁶ and R ⁷ are each independently a hydrogen atom or a monovalent hydrocarbon group having 1 to 18 carbon atoms), R ² is R ¹ , a hydrogen atom or a monovalent hydrocarbon group having 1 to 18 carbon atoms; R ³ is R ¹ , R ² or —[O(R ⁸ O) _a H] group (where R ⁸ ~18 alkylene group, a is an integer of 1 to 4), R ⁴ is a divalent hydrocarbon group having 1 to 18 carbon atoms, and R ⁵ is a monovalent hydrocarbon group having 1 to 18 carbon atoms. and x, y and z are numbers that satisfy the relationships of x + y + z = 3, 0 ≤ x ≤ 3, 0 ≤ y ≤ 2, 0 ≤ z ≤ 1.)

(In the above formula (2), R ¹¹ may be the same or different when there is more than one, and each is a linear, branched or cyclic alkyl group having 1 to 8 carbon atoms, and a substituent selected from 2 to 8 straight-chain or branched-chain alkoxyalkyl groups, and R ¹² may be the same or different when there are more than one, and each is a straight chain having 1 to 8 carbon atoms; is a linear, branched or cyclic alkyl group, and when there are a plurality of R ¹³ , they may be the same or different, and each is a linear or branched alkylene group having 1 to 8 carbon atoms. Yes, k has an average value of 3 or less, p and r may be the same or different, and each has an average value of 0 to 3, but both p and r cannot be 3.)

I=(A×B/C)/(D×E)≧9.5×10 ⁻⁴ (3)
(In the above formula (3),
A: Content of the silane coupling agent B: Total atomic weight of sulfur atoms in the silane coupling agent C: Molecular weight of the silane coupling agent D: Content of silica E: Silicon in the silane coupling agent Indicates the number of alkoxy groups bonded to an atom. )

Such a composition of the present invention is excellent in performance on ice and wet performance. Although the reason is not clear, it is presumed as follows.
That is, in a rubber composition with a relatively high silica content, for example, if the content of silica or a silane coupling agent becomes excessive, the reaction between the two proceeds too much, the gaps in the rubber composition decrease, and the foaming agent causes Foaming may be inhibited, and performance on ice may not be fully exhibited.
Therefore, if an attempt is made to moderately suppress the above reaction by, for example, reducing the content of the silane coupling agent, the wet performance may become insufficient.
However, when the value of I (I value), which is a parameter based on the content of silica and the silane coupling agent, is a predetermined value or more, the silica and the silane coupling agent secure a gap in the rubber composition. It is thought that both ice performance and wet performance are excellent because it responds appropriately while maintaining

<Diene rubber>
The diene rubber contains butadiene rubber (BR) and natural rubber (NR) or isoprene rubber (IR).
The content of butadiene rubber (BR) in the diene rubber is 30% by mass or more.

The diene rubber may contain other diene rubbers, specific examples of which include acrylonitrile-butadiene rubber (NBR), styrene-butadiene rubber (SBR), styrene-isoprene rubber (SIR), styrene -isoprene-butadiene rubber (SIBR), butyl rubber (IIR), halogenated butyl rubber (Br-IIR, Cl-IIR), chloroprene rubber (CR) and derivatives of these rubbers.

The diene rubber has excellent performance on ice and wet, excellent processability, wear performance, fuel efficiency, heat resistance, cold resistance, deterioration resistance, stain resistance, light resistance, and steering stability when made into a tire. It preferably contains butadiene rubber (BR) and natural rubber (NR) because of their superior properties.
Hereafter, "Excellent performance on ice and wet, excellent workability, excellent wear performance, fuel efficiency performance, heat resistance, cold resistance, deterioration resistance, stain resistance, light resistance, and steering stability when made into a tire. is also referred to as "the effects of the present invention are more excellent."

The content of butadiene rubber (BR) in the diene rubber is preferably 30 to 70% by mass, more preferably 30 to 50% by mass, because the effects of the present invention are more excellent.
The content of natural rubber (NR) or isoprene rubber (IR) in the diene rubber is preferably 30 to 70% by mass, more preferably 50 to 70% by mass, because the effects of the present invention are more excellent. .

The weight molecular weight (Mw) of the diene rubber is not particularly limited, but is preferably 100,000 to 10,000,000, more preferably 200,000 to 1,500,000, because the effects of the present invention are more excellent. is more preferred, and 300,000 to 3,000,000 is even more preferred.
The number average molecular weight (Mn) of the diene rubber is not particularly limited, but is preferably 50,000 to 5,000,000, more preferably 100,000 to 750,000, because the effects of the present invention are more excellent. More preferably, 150,000 to 1,500,000 is even more preferable.
The Mw and/or Mn of at least one diene rubber contained in the diene rubber is preferably included in the above range, and the Mw and/or Mn of all the diene rubbers contained in the diene rubber are the above More preferably included in the range.
In the present specification, Mw and Mn are standard polystyrene conversion values obtained by gel permeation chromatography (GPC) measurement under the following conditions.
・Solvent: Tetrahydrofuran ・Detector: RI detector

<silica>
The silica is not particularly limited, and any conventionally known silica compounded in rubber compositions for use in tires and the like can be used.
Specific examples of silica include wet silica, dry silica, fumed silica, and diatomaceous earth. Among them, wet silica is preferable because the effects of the present invention are more excellent. As for the silica, one type of silica may be used alone, or two or more types of silica may be used in combination.
The CTAB (cetyltrimethylammonium bromide) adsorption specific surface area of silica is not particularly limited, but is preferably 80 to 300 m ² /g, more preferably 90 to 250 m ² /g, because the effects of the present invention are more excellent.
As used herein, the CTAB adsorption specific surface area is a value obtained by measuring the amount of CTAB adsorbed on the silica surface according to JIS K6217-3:2001 "Part 3: Determination of specific surface area - CTAB adsorption method".

"Content"
The content of the silica is 30 to 150 parts by mass with respect to 100 parts by mass of the diene rubber, and is preferably 40 to 150 parts by mass, and more than 45 parts by mass, because the effects of the present invention are more excellent. 150 parts by mass or less is more preferable.

<Blowing agent>
The foaming agent is not particularly limited, and examples thereof include thermally expandable microcapsules, chemical foaming agents, physical foaming agents, supercritical fluids, and the like. Among them, thermally expandable microcapsules and/or chemical foaming agents are preferred because the effects of the present invention are more excellent.

《Thermal expansion microcapsules》
A thermally expandable microcapsule is composed of thermoplastic resin particles encapsulating a substance that is vaporized or expanded by heat to generate gas. The thermally expandable microcapsules become microcapsules in which a gas is enclosed in an outer shell made of a thermoplastic resin by heating at a temperature (for example, 130 to 190 ° C.) above the vaporization or expansion start temperature of the above substance. .
The particle size of the thermally expandable microcapsules before expansion is preferably 5 to 300 μm, more preferably 10 to 200 μm.
As the thermoplastic resin, for example, a (meth)acrylonitrile polymer and/or a copolymer having a high (meth)acrylonitrile content is preferably used. Other monomers (comonomers) in the case of a copolymer include vinyl halides, vinylidene halides, styrene-based monomers, (meth)acrylate-based monomers, vinyl acetate, butadiene, vinylpyridine, chloroprene, and other monomers. .
The thermoplastic resins include divinylbenzene, ethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, allyl (meth) ) cross-linkable with a cross-linking agent such as acrylate, triacrylformal, triallyl isocyanurate; As for the form of cross-linking, it is preferably not cross-linked, but may be partially cross-linked to the extent that the properties as a thermoplastic resin are not impaired.
Specific examples of the substance contained in the thermally expandable microcapsules that vaporize or expand by heat to generate gas include, for example, n-pentane, isopentane, neopentane, butane, isobutane, hexane, petroleum ether, and the like. Hydrocarbons; chlorinated hydrocarbons such as methyl chloride, methylene chloride, dichloroethylene, trichloroethane, trichlorethylene; Solids such as hydrazide derivatives, aromatic succinylhydrazide derivatives and the like can be mentioned.
As such thermally expandable microcapsules, commercially available products may be used. It is available under the trade names "Matsumoto Microsphere F-85", "Matsumoto Microsphere F-100", "Matsumoto Microsphere F-100D", etc.
The thermally expandable microcapsules may be used singly or in combination of two or more.

《Chemical blowing agent》
When the composition of the present invention contains a chemical foaming agent, when the composition of the present invention is vulcanized to produce a vulcanized rubber, air bubbles derived from the chemical foaming agent are formed in the vulcanized rubber. .
The chemical blowing agents include azodicarbonamide (ADCA), dinitrosopentamethylenetetramine (DNPT), dinitrosopentastyrenetetramine, benzenesulfonylhydrazide derivatives, p,p'-oxybisbenzenesulfonylhydrazide (OBSH), bicarbonate ammonium, sodium bicarbonate, ammonium carbonate, nitrosulfonylazo compound, N,N'-dimethyl-N,N'-dinitrosophthalamide, toluenesulfonyl hydrazide, p-toluenesulfonyl semicarbazide, p,p'-oxybisbenzenesulfonyl semicarbazide and the like, and among them, dinitrosopentamethylenetetramine (DNPT) is preferred.
The above chemical foaming agents may be used singly or in combination of two or more.
In addition, it is preferable to use together the chemical foaming agent with, for example, urea, zinc stearate, zinc benzenesulfinate, zinc white, etc. as a foaming aid. The foaming aid may be used singly or in combination of two or more. The content of the foaming assistant is preferably 1 to 30 parts by mass with respect to 100 parts by mass of the diene rubber because the effects of the present invention are more excellent.

"Content"
The content of the foaming agent is 0.5 to 20 parts by mass with respect to 100 parts by mass of the diene rubber.

<Silane coupling agent>
The silane coupling agent is at least one selected from the group consisting of a silane coupling agent 1 described later and a silane coupling agent 2 described later.

<<Silane coupling agent 1>>
The silane coupling agent 1 is represented by the following formula (1).

In the above formula (1), R ¹ is R ⁶ O-, R ⁶ C(=O)O-, R ⁶ R ⁷ C=NO-, R ⁶ R ⁷ CNO-, R ⁶ R ⁷ N- or -( OSiR ⁶ R ⁷ ) _m (OSiR ⁵ R ⁶ R ⁷ ) (provided that R ⁶ and R ⁷ are each independently a hydrogen atom or a monovalent hydrocarbon group having 1 to 18 carbon atoms), R ² is R ¹ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 18 carbon atoms; R ³ is R ¹ , R ² or —[O(R ⁸ O) _a H] group (where R ⁸ is a 18 alkylene groups, a is an integer of 1 to 4), R ⁴ is a divalent hydrocarbon group having 1 to 18 carbon atoms, and R ⁵ is a monovalent hydrocarbon group having 1 to 18 carbon atoms. , x, y, and z are numbers that satisfy the relationships x+y+z=3, 0≦x≦3, 0≦y≦2, and 0≦z≦1.

In the above formula (1), the monovalent hydrocarbon group having 1 to 18 carbon atoms includes, for example, an alkyl group having 1 to 18 carbon atoms, an alkenyl group having 2 to 18 carbon atoms, and an aryl group having 6 to 18 carbon atoms. , and aralkyl groups having 7 to 18 carbon atoms. Here, the alkyl group and alkenyl group may be linear, branched or cyclic, and the aryl group and aralkyl group have a substituent such as a lower alkyl group on the aromatic ring. good too.
Specific examples of monovalent hydrocarbon groups having 1 to 18 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, octyl group, decyl group, dodecyl group, cyclopentyl group, cyclohexyl group, vinyl group, propenyl group, allyl group, hexenyl group, octenyl group, cyclopentenyl group, cyclohexenyl group, phenyl group, tolyl group, xylyl group, naphthyl group, benzyl group, phenethyl group, naphthylmethyl group and the like.

In the above formula (1), the alkylene group having 1 to 18 carbon atoms represented by R ⁸ may be linear, branched or cyclic, preferably linear. Specific examples of linear alkylene groups include methylene, ethylene, trimethylene, tetramethylene, pentamethylene, hexamethylene, octamethylene, decamethylene and dodecamethylene groups.

In the above formula (1), the divalent hydrocarbon group having 1 to 18 carbon atoms represented by R ⁴ includes, for example, an alkylene group having 1 to 18 carbon atoms, an alkenylene group having 2 to 18 carbon atoms, and an alkenylene group having 2 to 18 carbon atoms. 18 to 18 cycloalkylene groups, 6 to 18 carbon atom cycloalkylalkylene groups, 6 to 18 carbon atom arylene groups, 7 to 18 carbon atom aralkylene groups, and the like. Alkylene groups and alkenylene groups may be linear or branched, and cycloalkylene groups, cycloalkylalkylene groups, arylene groups and aralkylene groups have a substituent such as a lower alkyl group on the ring. You may have
R ⁴ is preferably an alkylene group having 1 to 6 carbon atoms, and particularly preferably a linear alkylene group such as methylene, ethylene, trimethylene, tetramethylene, pentamethylene, and hexamethylene. .

Specific examples of the silane coupling agent 1 include 3-hexanoylthiopropyltriethoxysilane, 3-octanoylthiopropyltriethoxysilane, 3-decanoylthiopropyltriethoxysilane, and 3-lauroylthiopropyltriethoxysilane. , 2-hexanoylthioethyltriethoxysilane, 2-octanoylthioethyltriethoxysilane, 2-decanoylthioethyltriethoxysilane, 2-lauroylthioethyltriethoxysilane, 3-hexanoylthiopropyltrimethoxysilane, 3-octanoylthiopropyltrimethoxysilane, 3-decanoylthiopropyltrimethoxysilane, 3-lauroylthiopropyltrimethoxysilane, 2-hexanoylthioethyltrimethoxysilane, 2-octanoylthioethyltrimethoxysilane, 2 -decanoylthioethyltrimethoxysilane, 2-lauroylthioethyltrimethoxysilane, and the like.
Among these, 3-octanoylthiopropyltriethoxysilane is preferred because the effects of the present invention are superior.

<<Silane coupling agent 2>>
The silane coupling agent 2 is represented by the following formula (2).

In the above formula (2), R ¹¹ may be the same or different when there are more than one, and each is a linear, branched or cyclic alkyl group having 1 to 8 carbon atoms, and is a substituent selected from linear or branched alkoxyalkyl groups of 1 to 8, and R ¹² may be the same or different when there are more than one, and each is a linear C 1-8 linear , a branched or cyclic alkyl group, and when there are a plurality of R ¹³ , they may be the same or different, and each is a linear or branched alkylene group having 1 to 8 carbon atoms. , k have an average value of 3 or less, p and r may be the same or different, and each have an average value of 0 to 3, but p and r cannot both be 3.

In the above formula (2), examples of linear, branched or cyclic alkyl groups having 1 to 8 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, cyclobutyl group, n-pentyl group, isopentyl group, neopentyl group, tert-pentyl group, cyclopentyl group, n-hexyl group, isohexyl group, 4-methyl-2-pentyl group, cyclohexyl group, n-heptyl group, 4-heptyl group, n-octyl group, isooctyl group, 2-ethylhexyl group and the like.
Linear or branched alkoxyalkyl groups having 2 to 8 carbon atoms include, for example, methoxymethyl group, methoxyethyl group, methoxypropyl group, methoxybutyl group, methoxypentyl group, 1-ethoxypropyl group, 2 - ethoxypropyl group, 1-ethoxy-1-methylethyl group, 1-methyl-2-ethoxyethyl group, 1-(1-methylethoxy) propyl group, 2-(1-methylethoxy) propyl group, 1-( 1-methylethoxy)-1-methylethyl group, 2-(1-methylethoxy)-1-methylethyl group, 3-ethoxypropyl group and the like.
Linear or branched alkylene groups having 1 to 8 carbon atoms include, for example, methylene group, ethylene group, propylene group, butylene group, pentamethylene group, hexamethylene group, octamethylene group, 2,2- A dimethyl-1,3-propylene group and the like can be mentioned.
k is preferably 2 to 3 as an average value.

Specific examples of the silane coupling agent 2 include bis(3-triethoxysilylpropyl) disulfide, bis(3-trimethoxysilylpropyl) disulfide, bis(3-methyldimethoxysilylpropyl) disulfide, bis(2 -triethoxysilylethyl)disulfide, bis(3-triethoxysilylpropyl)trisulfide, bis(3-trimethoxysilylpropyl)trisulfide, bis(3-methyldimethoxysilylpropyl)trisulfide, bis(2-triethoxy silylethyl)trisulfide, bis(3-monoethoxydimethylsilylpropyl)trisulfide, bis(3-monoethoxydimethylsilylpropyl)disulfide, bis(3-monomethoxydimethylsilylpropyl)trisulfide, bis(3-monomethoxy dimethylsilylpropyl)disulfide, bis(2-monoethoxydimethylsilylethyl)trisulfide, bis(2-monoethoxydimethylsilylethyl)disulfide and the like.
Among these, bis(3-triethoxysilylpropyl)disulfide is preferred because the effects of the present invention are superior.

"Content"
The silane coupling agents may be used alone or in combination of two or more.
In the composition of the present invention, the content of the silane coupling agent is 1 to 25% by mass with respect to the content of the silica. %, more preferably 5 to 15% by mass.

<I value>
In the composition of the present invention, the silica and the silane coupling agent satisfy the following formula (3).
I=(A×B/C)/(D×E)≧9.5×10 ⁻⁴ (3)

In the above formula (3),
A: Content of the silane coupling agent B: Total atomic weight of sulfur atoms in the silane coupling agent C: Molecular weight of the silane coupling agent D: Content of silica E: Silicon in the silane coupling agent Indicates the number of alkoxy groups bonded to an atom.

In the above formula (3), the “alkoxy group bonded to the silicon atom in the silane coupling agent” in E is specifically, “Si—OR ⁶ ” in the above formula (1), or the above formula It is “Si—OR ¹¹ ” in (2).
Therefore, the "alkoxy group" in E is a concept broader than general alkoxy groups (may include phenoxy groups and the like).

Specifically calculating the I value, for example, in Example 1 described later, the silica content is 60 parts by mass, and "3-octanoylthiopropyltriethoxysilane" as the silane coupling agent 1 is 4.8. Since it contains parts by mass,
A: Content of silane coupling agent = 4.8 (parts by mass)
B: total atomic weight of sulfur atoms in the silane coupling agent = 32.1 × 1 = 32.1
C: Molecular weight of silane coupling agent = 364.62
D: Content of silica = 60 (parts by mass)
E: Number of alkoxy groups bonded to silicon atoms in the silane coupling agent = 3
and therefore
I=(4.8×32.1/364.62)/(60×3)=2.35×10 ⁻³
is calculated.

When two or more of the silane coupling agents are used in combination, the sum of the I values of the two or more silane coupling agents is used.
That is, for example, when the silane coupling agent 1 and the silane coupling agent 2 are used together, specifically, the following formula (4) must be satisfied.
I=(A1×B1/C1)/(D1×E1)+(A2×B2/C2)/(D2×E2)≧9.5×10 ⁻⁴ (4)
In the above formula (4),
A1: content of silane coupling agent 1 B1: total atomic weight of sulfur atoms in silane coupling agent 1 C1: molecular weight of silane coupling agent 1 D1: content of silica E1: silane coupling agent Number of alkoxy groups bonded to silicon atoms in 1 A2: Content of silane coupling agent 2 B2: Total atomic weight of sulfur atoms in silane coupling agent 2 C2: Molecular weight of silane coupling agent 2 D2: Content of Silica E2: The number of alkoxy groups bonded to silicon atoms in the silane coupling agent 2 is shown.
In the above formula (4), D1 and D2 have the same value.

The value of I (I value) is preferably 1.0 × 10 ^-3 or more, more preferably 1.2 × 10 ^-3 or more, more preferably 2.0 × 10 ^-3 or more is more preferable.
On the other hand, the I value is preferably 7.5×10 ⁻³ or less, more preferably 6.5×10 ⁻³ or less, because the effects of the present invention are more excellent.

<Optional component>
The composition of the present invention can contain components (optional components) other than the components described above, if necessary.
Examples of such components include inorganic fillers other than silica, carbon black, zinc oxide (zinc white), stearic acid, antioxidants, waxes, processing aids, oils, liquid polymers, plasticizers, thermosetting various additives commonly used in rubber compositions for tires, such as curable resins, vulcanizing agents (eg, sulfur), and vulcanization accelerators.

《Inorganic filler》
The inorganic filler is not particularly limited as long as it is an inorganic filler other than silica, and examples thereof include calcium carbonate, magnesium carbonate, layered clay minerals, platy clay minerals, alumina, aluminum hydroxide, titanium oxide, and calcium sulfate. and inorganic fillers, of which one may be used alone or two or more may be used in combination. In this specification, carbon black shall not correspond to an inorganic filler.

"Carbon black"
The carbon black is not particularly limited, for example, various grades such as SAF-HS, SAF, ISAF-HS, ISAF, ISAF-LS, IISAF-HS, HAF-HS, HAF, HAF-LS, FEF, GPF, and SRF of carbon black can be used.
The nitrogen adsorption specific surface area (N ₂ SA) of the carbon black is not particularly limited, but is preferably 50 to 200 m ² /g, more preferably 70 to 150 m ² /g, because the effects of the present invention are more excellent. .
Nitrogen adsorption specific surface area (N ₂ SA) is a value obtained by measuring the amount of nitrogen adsorption on the surface of carbon black according to JIS K6217-2:2001 "Part 2: Determination of specific surface area-Nitrogen adsorption method-Single point method". is.
The composition of the present invention preferably contains carbon black because the effects of the present invention are more excellent.
When the composition of the present invention contains carbon black, the content thereof is preferably 1 to 50 parts by mass with respect to 100 parts by mass of the diene rubber because the effects of the present invention are more excellent. ~30 parts by mass is more preferable.

<Method for preparing rubber composition>
The method for producing the composition of the present invention is not particularly limited, and specific examples include, for example, kneading the components described above using known methods and devices (e.g., Banbury mixer, kneader, rolls, etc.). methods and the like. When the composition of the present invention contains sulfur or a vulcanization accelerator, the components other than sulfur and the vulcanization accelerator are first mixed at a high temperature (preferably 100 to 155 ° C.), cooled, and then sulfur or It is preferred to mix a vulcanization accelerator.
The compositions of the present invention can be vulcanized or crosslinked under conventionally known vulcanization or crosslinking conditions.

<Application>
As described above, the composition of the present invention is suitable for tires, particularly studless tires, because it has excellent performance on ice and wet performance.

[tire]
The tire of the present invention is a tire manufactured using the composition of the present invention described above, and is preferably a studless tire manufactured using the composition of the present invention described above.
Among them, it is more preferable to be a tire comprising a tire tread portion manufactured using the composition of the present invention, and more preferably a studless tire comprising a tire tread portion manufactured using the composition of the present invention. preferable.
FIG. 1 shows a schematic partial cross-sectional view of a tire representing an example of an embodiment of the tire of the present invention. However, the tire of the present invention is not limited to the embodiment shown in FIG.

In FIG. 1, reference numeral 1 denotes a bead portion, reference numeral 2 denotes a sidewall portion, and reference numeral 3 denotes a tire tread portion.
A carcass layer 4 in which fiber cords are embedded is mounted between the pair of left and right bead portions 1 . The end portion of the carcass layer 4 is folded back from the inside of the tire to the outside around the bead core 5 and the bead filler 6 and rolled up.
In the tire tread portion 3 , a belt layer 7 is arranged outside the carcass layer 4 over one circumference of the tire.
A rim cushion 8 is arranged at a portion of the bead portion 1 that contacts the rim.
The tire tread portion 3 is formed from the composition of the present invention described above.

The tire of the present invention can be manufactured, for example, according to a conventionally known method. As the gas to be filled in the tire of the present invention, in addition to normal air or air with adjusted oxygen partial pressure, inert gas such as nitrogen, argon, and helium can be used.

The present invention will be described in detail below with reference to examples. However, the present invention is not limited to the following examples.

<Preparation of rubber composition>
The components shown in Table 1 below were blended in proportions (parts by mass) shown in the same table. Specifically, first, the components shown in Table 1 below are mixed in a 1.7-liter closed Banbury mixer at a temperature of about 150°C, mixed for 5 minutes, then discharged, and cooled to room temperature. Cooling gave a masterbatch. Furthermore, sulfur and a vulcanization accelerator were mixed with the obtained masterbatch using the Banbury mixer to obtain a rubber composition.

<evaluation>
The obtained rubber composition was press-vulcanized in a predetermined mold at 170° C. for 10 minutes to prepare a vulcanized rubber test piece. Then, the vulcanized rubber test pieces thus obtained were evaluated as follows.

《Expansion ratio》
Regarding the obtained vulcanized rubber test piece, the foaming rate (unit: %) was obtained from the following formula, with the specific gravity before vulcanization being d ₁ and the specific gravity after vulcanization being d ₂ .
Foaming ratio = (d ₁ - d ₂ )/d ₁ × 100
The results are shown in Table 1 below. The results were expressed as an index with the foaming ratio of Standard Example 1 being 100.

《Performance on ice》
A vulcanized rubber test piece was attached to a flat cylindrical base rubber, and measured with an inside drum type friction tester on ice at a temperature of -1.5°C, a load of 5.5 kg/cm ³ , and a drum rotation speed of 25 km/hour. The coefficient of friction on ice was measured under the conditions of
The results are shown in Table 1 below. The results were expressed as an index with the coefficient of friction on ice of Standard Example 1 being 100. The larger the index, the greater the frictional force between rubber and ice, and the better the performance on ice when the tire is made. From the viewpoint of performance on ice, the index is preferably greater than 100.

《Wet Performance》
For vulcanized rubber test pieces, according to JIS K6394: 2007, using a viscoelastic spectrometer (manufactured by Toyo Seiki Seisakusho Co., Ltd.), under the conditions of extensional deformation strain rate of 10% ± 2%, frequency of 20 Hz, and temperature of 0 ° C. , tan δ (0° C.) were measured.
The results are shown in Table 1 below. The results were expressed as an index with the tan δ (0° C.) measurement value of Standard Example 1 set to 100. The larger the index, the larger the tan δ (0°C), and the better the wet performance when made into a tire. From the viewpoint of wet performance, an index of 95 or more is acceptable.

<<Description of each component>>
Details of each component in Table 1 are as follows.
・NR: TSR20 (natural rubber, glass transition temperature (Tg): -62°C)
・ BR: NIPOL BR1220 (butadiene rubber) manufactured by Nippon Zeon Co., Ltd.
・ Silica 1: Zeosil 1165MP (CTAB adsorption specific surface area: 159 m ² /g, manufactured by Solvay)
・ Silica 2: Zeosil 1115MP (CTAB adsorption specific surface area: 110 m ² /g, manufactured by Solvay)
- Silane coupling agent X: "Si69", manufactured by Evonik, bis (3-triethoxysilylpropyl) tetrasulfide, number of S atoms = 4
- Silane coupling agent 1: "NXT Silane", manufactured by Momentive, 3-octanoylthiopropyltriethoxysilane, number of S atoms = 1
・Silane coupling agent 2: “Si75”, manufactured by Evonik, bis(3-triethoxysilylpropyl) disulfide, number of S atoms = 2
・Carbon black: Show Black N339 manufactured by Cabot Japan
・ Zinc white: 3 types of zinc oxide (manufactured by Seido Chemical Industry Co., Ltd.)
・Stearic acid: Stearic acid manufactured by NOF Co., Ltd. ・Antiaging agent: Santoflex 6PPD (manufactured by Solusia Europe)
・Sulfur: Oil treated sulfur (manufactured by Karuizawa Refinery Co., Ltd.)
・ Vulcanization accelerator 1: Noccellar CZ-G (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)
・ Vulcanization accelerator 2: Noccellar D (manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.)
・ Plasticizer: BM-4 (manufactured by Daihachi Chemical Industry Co., Ltd.)
・ Thermally expandable microcapsules: Matsumoto Microsphere F-100 manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.
・Chemical foaming agent: dinitrosopentamethylenetetramine (DNPT)

《Summary of Table 1》
As is clear from the results shown in Table 1 above, 30 to 150 parts by mass of silica is contained with respect to 100 parts by mass of diene rubber, and 1 to 25% by mass of a silane coupling agent is contained with respect to the content of silica. Moreover, Examples 1 to 9 having an I value of 9.5×10 ⁻⁴ or more exhibited good performance on ice and wet performance.
On the other hand, Comparative Example 1 in which the content of the silane coupling agent exceeds 25% by mass of the silica content, and Comparative Example 2 in which the silica content exceeds 150 parts by mass with respect to 100 parts by mass of the diene rubber , had poor performance on ice.
Comparative Example 3, in which the I value was not 9.5×10 ⁻⁴ or more, had insufficient wet performance.

1: bead portion 2: sidewall portion 3: tire tread portion 4: carcass layer 5: bead core 6: bead filler 7: belt layer 8: rim cushion

Claims (3)

100 parts by mass of diene rubber;
silica ;
0.5 to 20 parts by mass of a foaming agent;
1 to 25% by mass of a silane coupling agent with respect to the content of silica,
The diene rubber contains 30% by mass or more of butadiene rubber and contains natural rubber or isoprene rubber,
The silane coupling agent is a silane coupling agent 1 represented by the following formula (1) or a silane coupling agent 2 represented by the following formula (2),
When the silane coupling agent is the silane coupling agent 1, the content of the silica is 50 to 150 parts by mass with respect to 100 parts by mass of the diene rubber, and the silica and the silane coupling agent 1 are or ^_ _
When the silane coupling agent is the silane coupling agent 2, the content of the silica is 60 to 150 parts by mass with respect to 100 parts by mass of the diene rubber, and the silica and the silane coupling agent 2 are is a rubber composition for tires that satisfies that the value of I determined by the following formula (3) is from 1.61×10 ⁻³ to 1.80×10 ⁻³ .

(In formula (1) above, R ¹ is R ⁶ O-, R ⁶ C(=O)O-, R ⁶ R ⁷ C=NO-, R ⁶ R ⁷ CNO-, R ⁶ R ⁷ N- or - (OSiR ⁶ R ⁷ ) _m (OSiR ⁵ R ⁶ R ⁷ ) (provided that R ⁶ and R ⁷ are each independently a hydrogen atom or a monovalent hydrocarbon group having 1 to 18 carbon atoms), R ² is R ¹ , a hydrogen atom or a monovalent hydrocarbon group having 1 to 18 carbon atoms; R ³ is R ¹ , R ² or —[O(R ⁸ O) _a H] group (where R ⁸ ~18 alkylene group, a is an integer of 1 to 4), R ⁴ is a divalent hydrocarbon group having 1 to 18 carbon atoms, and R ⁵ is a monovalent hydrocarbon group having 1 to 18 carbon atoms. and x, y and z are numbers that satisfy the relationships of x + y + z = 3, 0 ≤ x ≤ 3, 0 ≤ y ≤ 2, 0 ≤ z ≤ 1.)

(In the above formula (2), R ¹¹ may be the same or different when there are more than one, and each is a linear, branched or cyclic alkyl group having 1 to 8 carbon atoms, and a substituent selected from 2 to 8 straight-chain or branched-chain alkoxyalkyl groups, and R ¹² may be the same or different when there are more than one, and each is a straight chain having 1 to 8 carbon atoms; is a linear, branched or cyclic alkyl group, and when there are a plurality of R ¹³ , they may be the same or different, and each is a linear or branched alkylene group having 1 to 8 carbon atoms. Yes, k has an average value of 3 or less, p and r may be the same or different, and each has an average value of 0 to 3, but both p and r cannot be 3.)
I=(A×B/C)/(D×E ) (3)
(In the above formula (3),
A: content of the silane coupling agent 1 or 2 B: total atomic weight of sulfur atoms in the silane coupling agent 1 or 2 C: molecular weight of the silane coupling agent 1 or 2 D: content of silica E : Indicates the number of silicon-bonded alkoxy groups in the silane coupling agent 1 or 2 . ) 2. The rubber composition for a tire according to claim 1 , wherein when the silane coupling agent is the silane coupling agent 1, the value of I is 7.5×10 ⁻³ or less. A tire manufactured using the tire rubber composition according to claim 1 or 2.

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