JP2018150505A - Rubber composition for tire, and pneumatic tire - Google Patents

Abstract

An object of the present invention is to provide a rubber composition for a tire which is excellent in wet grip properties and on-ice performance when formed into a tire, and a pneumatic tire using the rubber composition for a tire. SOLUTION: The diene rubber (A), the ester compound (B), and the white filler (C) are contained, and the diene rubber (A) is 30 mass% or more and 90 mass% or more of isoprene rubber. Less than the above, the ester compound (B) is at least one ester compound selected from polyoxyethylene alkyl ether phosphates, and the content of the ester compound (B) is the white filler ( C) A rubber composition for a tire, which has a content of 0.5 to 20 parts by mass relative to 100 parts by mass and has a rubber hardness of JIS type A of less than 55 at a temperature of 0° C. after curing. [Selection diagram] None

Description

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

  Conventionally, as a rubber composition (rubber composition for a studless tire) used for a tire tread portion of a studless tire, a rubber composition in which silica and a thermally expandable microcapsule are blended with a diene rubber containing natural rubber and butadiene rubber is used. It is known (see, for example, Patent Document 1).

JP 2012-007068 A

On the other hand, with the improvement in the required safety level, further improvements in wet grip properties and on-ice performance are required.
Then, this invention makes it a subject to provide the rubber composition for tires which is excellent in wet-grip property and on-ice performance, and a pneumatic tire using the said rubber composition for tires when it is set as a tire.

As a result of intensive studies to solve the above-mentioned problems, the present inventors found that a specific ester compound was assigned to a rubber composition containing a diene rubber containing isoprene-based rubber at a predetermined ratio and a white filler. It has been found that the wet grip properties and the performance on ice are improved when the tire is formed by quantitative blending, and the present invention has been completed.
That is, the present inventors have found that the above problem can be solved by the following configuration.

[1] A diene rubber (A), an ester compound (B), and a white filler (C),
The diene rubber (A) contains 30% by mass or more and less than 90% by mass of isoprene-based rubber,
The ester compound (B) is a polyoxyethylene alkyl ether sulfate, polyoxyethylene alkyl ether phosphate, polyoxyethylene alkyl ether acetate, polyoxyethylene alkyl sulfosuccinate, and polyoxyethylene fatty acid amide ether sulfate. At least one ester compound selected from the group consisting of esters,
Content of the said ester compound (B) is 0.5-20 mass parts with respect to 100 mass parts of said white fillers (C),
A rubber composition for tires, wherein the rubber hardness of type A specified by JIS at a temperature of 0 ° C. after curing is less than 55.

[2] The rubber composition for tires according to [1], wherein the ester compound (B) is a polyoxyethylene alkyl ether phosphate represented by the following formula (1).
Here, the equation (1), ^{R 1} represents an alkyl group having 3 to 21 carbon atoms, n represents an integer of 1 to 10, m represents 1 or 2, ^{R 2} is a hydrogen atom or a carbon atoms 1 to 10 alkyl groups, and when m is 1, the plurality of R ² may be the same or different, and when m is 2, the plurality of R ¹ are respectively the same May be different.

[3] The tire rubber composition according to [1] or [2], wherein the content of the white filler (C) is 30 to 80 parts by mass with respect to 100 parts by mass of the diene rubber (A). object.
[4] The tire rubber composition according to any one of [1] to [3], wherein the white filler (C) has a CTAB adsorption specific surface area of 140 to 300 m ² / g.

[5] Furthermore, the modified butadiene polymer which has the functional group containing a nitrogen atom and a silicon atom at the terminal is contained,
The modified butadiene polymer is a polymer having a weight average molecular weight of 1,000 to 15,000 and a molecular weight distribution of 2.0 or less,
The rubber composition for tires according to any one of [1] to [4], wherein the content of the modified butadiene polymer is 1 to 25% by mass with respect to the content of the white filler (C).

[6] Further, a piperazine compound represented by the following formula (2) is contained,
The rubber composition for tires according to any one of [1] to [5], wherein the content of the piperazine compound is 5.5 to 60 parts by mass with respect to 100 parts by mass of the ester compound (B).
Here, in the above formula (2), X ¹ , X ² , X ³ and X ⁴ each independently represent a hydrogen atom or a substituent, and A ¹ and A ² each independently represent a single bond or 2 Represents a valent linking group, and R ¹¹ and R ¹² each independently represents a hydrogen atom or a substituent. However, at least one of R ¹¹ and R ¹² represents a monovalent hydrocarbon group having 3 to 30 carbon atoms.

[7] A pneumatic tire using the tire rubber composition according to any one of [1] to [6] for a tire tread.
[8] The pneumatic tire according to [7], which is used for a studless tire.

  As described below, according to the present invention, it is possible to provide a tire rubber composition having excellent wet grip properties and on-ice performance when formed into a tire, and a pneumatic tire using the tire rubber composition. it can.

It is a typical fragmentary sectional view of the tire showing an example of the embodiment of the pneumatic tire of the present invention.

Below, the rubber composition for tires of this invention and the pneumatic tire using the rubber composition for tires of this invention are demonstrated.
In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

[Rubber composition for tire]
The rubber composition for tires of the present invention (hereinafter simply referred to as “the rubber composition of the present invention”) contains a diene rubber (A), an ester compound (B), and a white filler (C). To do.
The diene rubber (A) contains 30% by mass or more and less than 90% by mass of isoprene-based rubber.
The ester compound (B) is composed of polyoxyethylene alkyl ether sulfate, polyoxyethylene alkyl ether phosphate, polyoxyethylene alkyl ether acetate, polyoxyethylene alkyl sulfosuccinate, and polyoxyethylene fatty acid amide. It is at least one ester compound selected from the group consisting of ether sulfates.
Moreover, content of the said ester compound (B) is 0.5-20 mass parts with respect to 100 mass parts of said white fillers (C).
Further, the rubber composition of the present invention is a rubber composition in which the rubber hardness of type A specified by JIS at a temperature of 0 ° C. after curing is less than 55.

In the present invention, as described above, by blending a predetermined amount of a specific ester compound (B) with a rubber composition containing a diene rubber containing a predetermined proportion of isoprene-based rubber and a white filler, When used as a tire, wet grip performance and on-ice performance are good.
This is not clear in detail, but is estimated to be as follows.
That is, the specific ester compound (B) such as polyoxyethylene alkyl ether phosphate contained in the rubber composition of the present invention is considered to be easily hydrolyzed. Alkyl ether phosphoric acid is considered to be generated.
And it is thought that polyoxyethylene alkyl ether phosphoric acid produced | generated by hydrolysis and the hydroxyl group which may exist on the surface of a white filler (especially silica) are interacting by the condensation by a dehydration reaction, or a hydrogen bond. .
Therefore, in the present invention, the hydrolysis product of the specific ester compound (B) is chemically bonded to the surface of the white filler, thereby increasing the white filler in the rubber composition containing the diene rubber. It becomes possible to disperse at a level, and as a result, it is considered that the rubber was given flexibility and the wet grip performance and on-ice performance were improved.
Below, the rubber hardness of the rubber composition of this invention and each component which the rubber composition of this invention contains are demonstrated in detail.

[Rubber hardness]
The rubber hardness of Type A specified by JIS at a temperature of 0 ° C. after curing of the rubber composition of the present invention is less than 55.
Here, “JIS-specified type A rubber hardness at a temperature of 0 ° C.” is JIS K 6253-3: 2012 “Vulcanized rubber and thermoplastic rubber-Determination of hardness-Part 3: Durometer hardness” Conforms to the hardness of rubber measured by durometer type A at a temperature of 0 ° C.
In the present invention, the rubber hardness is measured by using the rubber composition after being cured by heating the rubber composition at 170 ° C. for 10 minutes.

The rubber hardness is preferably 40 or more and less than 55, and more preferably 42 or more and less than 55, because the performance on ice when tires are improved.
Moreover, the said rubber hardness can be adjusted by changing the compounding quantity of the white filler (C) mix | blended with a rubber composition or arbitrary plasticizers (for example, oil etc.).

[Diene rubber (A)]
The diene rubber (A) contained in the rubber composition of the present invention is not particularly limited as long as it contains 30% by mass or more and less than 90% by mass of isoprene-based rubber.

Examples of the isoprene rubber contained in the diene rubber (A) include isoprene rubber (IR), natural rubber (NR), and modified natural rubber. The NR includes deproteinized natural rubber (DPNR) and high-purity natural rubber (HPNR).
Specifically, as NR, for example, SIR20, RSS # 3, TSR20 and the like that are common in the tire industry can be used.
Specific examples of the modified natural rubber include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber.
Among these isoprene-based rubbers, NR and IR are preferable, and NR is more preferable for the reason that local share tends to be applied during kneading.

The content of the isoprene-based rubber in the diene rubber (A) is not particularly limited as long as it is 30% by mass or more and less than 90% by mass. However, from the reason that the performance on ice when the tire is made is 35 to 35%. It is preferable that it is 80 mass%.
The "content of isoprene-based rubber in the diene rubber (A)" refers to the content (% by mass) of the isoprene-based rubber with respect to the entire diene rubber (A).

The diene rubber (A) may contain a rubber component other than the isoprene rubber.
Specific examples of such rubber components include butadiene rubber (BR), aromatic vinyl-conjugated diene copolymer rubber, acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR), and halogenated butyl rubber. (Br-IIR, Cl-IIR), chloroprene rubber (CR) and the like. These may be used alone or in combination of two or more.
Here, examples of the aromatic vinyl-conjugated diene copolymer rubber include styrene-butadiene copolymer rubber (SBR) and styrene isoprene copolymer rubber.
Of these rubber components, BR or SBR is preferably used in combination with isoprene-based rubber, and BR is more preferably used in combination with isoprene-based rubber because the performance on ice when tires are improved.

  In the present invention, the diene rubber (A) is modified (modified) with the end or side chain of each rubber described above being an amino group, an amide group, a silyl group, an alkoxy group, a carboxy group, a hydroxy group, an epoxy group, or the like. Or a derivative thereof.

In the present invention, the average glass transition temperature (Tg) of the diene rubber (A) is preferably less than −60 ° C., more preferably −100 ° C. or more and less than −60 ° C., More preferably, it is 85 ° C to -70 ° C.
Here, the average Tg of the diene rubber (A) is obtained by multiplying the Tg of each rubber component by the mass% of each rubber component. The Tg of each rubber was measured by a differential scanning calorimeter (DSC) at a rate of temperature increase of 20 ° C./min, and calculated by the midpoint method.

[Ester compound (B)]
The ester compound (B) contained in the rubber composition of the present invention includes polyoxyethylene alkyl ether sulfate, polyoxyethylene alkyl ether phosphate, polyoxyethylene alkyl ether acetate, polyoxyethylene alkyl sulfosuccinate, and And at least one ester compound selected from the group consisting of polyoxyethylene fatty acid amide ether sulfates.

In the present invention, it is preferable that the ester compound (B) is a polyoxyethylene alkyl ether phosphate ester represented by the following formula (1) because the wet grip property becomes better when the tire is formed. preferable.
Here, the equation (1), ^{R 1} represents an alkyl group having 3 to 21 carbon atoms, n represents an integer of 1 to 10, m represents 1 or 2, ^{R 2} is a hydrogen atom or a carbon atoms 1 to 10 alkyl groups, and when m is 1, the plurality of R ² may be the same or different, and when m is 2, the plurality of R ¹ are respectively the same May be different.

The alkyl group having 3 to 21 carbon atoms represented by R ¹ may be a linear alkyl group or a branched alkyl group. Moreover, it is preferable that it is 5-15, as for carbon number of an alkyl group, it is more preferable that it is 7-13, and it is still more preferable that it is 9-13.
Specific examples of such an alkyl group include, for example, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group. Pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, eicosyl group, heneicosyl group and the like.

n represents an integer of 1 to 10, is preferably an integer of 2 to 8, and is preferably an integer of 3 to 6. In addition, since it can be said that n is the addition mole number of ethyleneoxy group (O—CH ₂ —CH ₂ ), it is preferably a number of about 3 to 10 in terms of an average value (average addition mole number).

The alkyl group having 1 to 10 carbon atoms represented by R ² may be a linear alkyl group or a branched alkyl group.
Specific examples of such an alkyl group include, for example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a butyl group, a pentyl group, and a hexyl group.

  Specific examples of the polyoxyethylene alkyl ether phosphate represented by the above formula (1) include, for example, polyoxyethylene decyl ether phosphoric acid monoester, polyoxyethylene decyl ether phosphoric acid diester, and polyoxyethylene Phosphoric acid monoester of ethylene isodecyl ether, phosphoric acid diester of polyoxyethylene isodecyl ether, phosphoric acid monoester of polyoxyethylene lauryl ether, phosphoric acid diester of polyoxyethylene lauryl ether, phosphorus of polyoxyethylene tridecyl ether Examples thereof include acid monoesters and phosphoric acid diesters of polyoxyethylene tridecyl ether, and these may be used alone or in combination of two or more.

  Content of the said ester compound (B) is 0.5-20 mass parts with respect to 100 mass parts of white fillers (C) mentioned later, and it is preferable that it is 1-15 mass parts, and 2-12 masses. More preferably, it is part.

[White filler (C)]
The white filler (C) contained in the rubber composition of the present invention is not particularly limited, and specific examples thereof include silica, calcium carbonate, magnesium carbonate, talc, clay, alumina, aluminum hydroxide, titanium oxide, calcium sulfate. These may be used, and these may be used alone or in combination of two or more.
Of these, silica is preferable from the viewpoint of reinforcing properties.

Specific examples of silica include wet silica (hydrous silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, and the like, and these may be used alone. Two or more kinds may be used in combination.
Among these, wet silica is preferable from the viewpoint of improving wet grip performance and balancing the rolling resistance, wear resistance, and the like.

In the present invention, the reason why the kneading property becomes good, the white filler (C) is preferably CTAB adsorption specific surface area of 140~300m ² / g, it is 150 to 250 ² / g More preferred.
Here, the CTAB adsorption specific surface area was determined by measuring the adsorption amount of n-hexadecyltrimethylammonium bromide on the silica surface according to JIS K6217-3: 2001 “Part 3: Determination of specific surface area—CTAB adsorption method”. Value.

  Moreover, in this invention, it is preferable that content of the said white filler (C) is 30-80 mass parts with respect to 100 mass parts of said diene rubber (A), and is 40-75 mass parts. It is more preferable, and it is still more preferable that it is 50-70 mass parts.

[Modified butadiene polymer]
The rubber composition of the present invention has a functional group containing a nitrogen atom and a silicon atom (hereinafter also abbreviated as “specific functional group”) at the end for the reason that the wet grip performance becomes better when a tire is formed. It is preferable to contain a modified butadiene polymer (hereinafter also referred to as “specifically modified BR”) having a weight average molecular weight of 1,000 or more and 15,000 or less and a molecular weight distribution of 2.0 or less.

Hereinafter, the specific modified BR will be described in detail.
As described above, the specific modified BR has a functional group (specific functional group) containing a nitrogen atom and a silicon atom at the end, has a weight average molecular weight of 1,000 to 15,000, and a molecular weight distribution of 2.0. The following is a butadiene polymer (modified butadiene polymer).

<Specific functional group>
As described above, the specific modified BR has a functional group containing a nitrogen atom and a silicon atom (specific functional group) at the terminal. The specific functional group may be at least at one end.

(Preferred embodiment)
The specific functional group is not particularly limited as long as it is a functional group containing a nitrogen atom and a silicon atom, but for the reason that wet grip performance is further improved when it is made into a tire, the nitrogen atom is converted into an amino group (—NR ₂ : R is hydrogen). Atom or hydrocarbon group), and preferably a silicon atom as a hydrocarbyloxysilyl group (≡SiOR: R is a hydrocarbon group).

  The specific functional group is preferably a group represented by the following formula (M) because the wet grip performance is further improved when the tire is made into a tire.

In the formula (M), R ₁ and R ₂ each independently represent a hydrogen atom or a substituent.
In the above formula (M), L represents a divalent organic group.

The substituent is not particularly limited as long as it is a monovalent substituent. For example, a halogen atom, a hydroxy group, a nitro group, a carboxy group, an alkoxy group, an amino group, a mercapto group, an acyl group, an imide group, a phosphino group, and a phosphinyl group. Group, a silyl group, a hydrocarbon group which may have a hetero atom, and the like.
As said halogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom etc. are mentioned, for example.
Examples of the hetero atom of the hydrocarbon group that may have a hetero atom include an oxygen atom, a nitrogen atom, a sulfur atom, and a phosphorus atom.
Examples of the hydrocarbon group that may have a hetero atom include an aliphatic hydrocarbon group, an aromatic hydrocarbon group, or a group obtained by combining these.
The aliphatic hydrocarbon group may be linear, branched or cyclic. Specific examples of the aliphatic hydrocarbon group include a linear or branched alkyl group (particularly having 1 to 30 carbon atoms), a linear or branched alkenyl group (particularly having 2 to 30 carbon atoms), Examples thereof include a linear or branched alkynyl group (particularly having 2 to 30 carbon atoms).
As said aromatic hydrocarbon group, C6-C18 aromatic hydrocarbon groups, such as a phenyl group, a tolyl group, a xylyl group, a naphthyl group, etc. are mentioned, for example.

In the above formula (M), R ₁ represents a hydrogen atom, an alkyl group (preferably having 1 to 10 carbon atoms), an alkylsilyl group (preferably C1-C10) and an aromatic hydrocarbon group (preferably C6-C18) are preferable, and a hydrogen atom is more preferable.
A plurality of R ₁ may be the same or different.

R ₂ is preferably a hydrocarbyloxy group (—OR group: R is a hydrocarbon group), and an alkoxy group (preferably having a carbon number of 1 to 2) because wet grip performance is further improved when the tire is formed. 10) is more preferable.

As described above, in the above formula (M), L represents a single bond or a divalent organic group.
Examples of the divalent organic group include an aliphatic hydrocarbon group (for example, an alkylene group, preferably 1 to 10 carbon atoms), an aromatic hydrocarbon group (for example, an arylene group, preferably 6 to 18 carbon atoms), —O—, —S—, —SO ₂ —, —N (R) — (R: alkyl group), —CO—, —NH—, —COO—, —CONH—, or a combination thereof (for example, , alkyleneoxy radical _{(-C m} H 2m O-: _m is a positive integer), alkyleneoxy carbonyl group, an alkylene carbonyl group) and the like.
L is preferably an alkylene group (preferably having a carbon number of 1 to 10) because the wet grip performance is further improved when the tire is formed.

In said formula (M), n represents the integer of 0-2.
n is preferably 2 because the wet grip performance is further improved when the tire is formed.

In the above formula (M), m represents an integer of 1 to 3.
m is preferably 1 because the wet grip performance is further improved when the tire is formed.

  In the above formula (M), n and m satisfy the relational expression of n + m = 3.

  In the above formula (M), * represents a bonding position.

<Weight average molecular weight>
As described above, the weight average molecular weight (Mw) of the specific modified BR is 1,000 or more and 15,000 or less. Especially, it is preferable that it is 5,000 or more and less than 10,000 from the reason that wet grip performance is further improved when a tire is formed.

<Number average molecular weight>
The number average molecular weight (Mn) of the specific modified BR is not particularly limited as long as the weight average molecular weight and the molecular weight distribution of the specific modified BR are within a specific range, but because the wet grip performance is further improved when made into a tire, It is preferably 1,000 or more and 15,000 or less, and more preferably 5,000 or more and less than 10,000.

<Molecular weight distribution>
As described above, the molecular weight distribution (Mw / Mn) of the specific modified BR is 2.0 or less. Among them, it is preferably 1.7 or less, more preferably 1.5 or less, and even more preferably 1.3 or less, because the wet grip performance is further improved when the tire is used. .
Although a minimum in particular is not restrict | limited, Usually, it is 1.0 or more.

In this specification, the weight average molecular weight (Mw) and the number average molecular weight (Mn) are standard polystyrene conversion values obtained by gel permeation chromatography (GPC) measurement under the following conditions.
・ Solvent: Tetrahydrofuran ・ Detector: RI detector

<Microstructure>
(Vinyl structure)
In the specific modified BR, the ratio of the vinyl structure is not particularly limited, but is preferably 10 to 50 mol%, preferably 20 to 40 mol%, because the wet grip performance is further improved when the tire is formed. Is more preferable.
Here, the ratio of the vinyl structure refers to the ratio (mol%) occupied by the repeating unit having a vinyl structure among the repeating units derived from butadiene.

(1,4-trans structure)
In the specific modified BR, the ratio of the 1,4-trans structure is not particularly limited, but it is preferably 10 to 70 mol%, and preferably 30 to 50 mol, because the wet grip performance is further improved when the tire is formed. % Is more preferable.
Here, the ratio of the 1,4-trans structure refers to the ratio (mol%) occupied by the repeating unit having a 1,4-trans structure among all repeating units derived from butadiene.

(1,4-cis structure)
In the specific modified BR, the ratio of the 1,4-cis structure is not particularly limited, but it is preferably 10 to 50 mol% for the reason that the wet grip performance is further improved when the tire is formed, and preferably 20 to 40 mol. % Is more preferable.
Here, the ratio of the 1,4-cis structure refers to the ratio (mol%) occupied by the repeating units having a 1,4-cis structure out of all repeating units derived from butadiene.

  Hereinafter, “ratio of vinyl structure (mol%), ratio of 1,4-trans structure (mol%), ratio of 1,4-cis structure (mol%)” is also expressed as “vinyl / trans / cis”. .

<Glass transition temperature>
The glass transition temperature (Tg) of the specific modified BR is not particularly limited, but is preferably −100 to −60 ° C., and −90 to −70 ° C., because the wet grip performance is further improved when the tire is made. It is more preferable that it is -85-75 degreeC.
In this specification, the glass transition temperature (Tg) is measured at a rate of temperature increase of 10 ° C./min using a differential scanning calorimeter (DSC) and calculated by the midpoint method.

<Viscosity>
The viscosity of the specific modified BR is not particularly limited, but is preferably 1,000 to 10,000 mPa · s, and preferably 3,000 to 6,000 mPa · s, because the wet grip performance is further improved when the tire is made. More preferably, it is s.
Further, the viscosity of the butadiene polymer before modifying the specific modified BR is not particularly limited, but is preferably 500 to 5,000 mPa · s for the reason that the wet grip performance is further improved when the tire is formed. 500 to 3,000 mPa · s is more preferable.
Further, the viscosity of the specific modified BR is preferably 150 to 240% with respect to the viscosity of the butadiene polymer before modification, because the wet grip performance is further improved when the tire is formed. Hereinafter, the viscosity of the property-modified BR after modification with respect to the specific modification BR before modification is also referred to as “viscosity (after modification / before modification)”.
In the present specification, the viscosity is measured using a cone plate viscometer according to JIS K5600-2-3.

In the present invention, the content of the specific modified BR is preferably 1 to 25% by mass, and 2.0 to 10.0% by mass with respect to the content of the white filler (C). More preferred.
In addition, the content of the specific modified BR is 1 part by mass or more and less than 10 parts by mass with respect to 100 parts by mass of the diene rubber (A) because the wet grip performance is further improved when the tire is formed. It is preferable.

<Method for producing specific modified BR>
The method for producing the specific modified BR is not particularly limited, and a conventionally known method can be used. A method for specifically limiting the molecular weight and the molecular weight distribution is not particularly limited, and examples thereof include a method of adjusting an amount ratio of an initiator, a monomer and a terminator, a reaction temperature, a rate of adding the initiator, and the like.

(Preferred embodiment)
As a preferred embodiment of the method for producing the specific modified BR, for example, butadiene is polymerized using an organolithium compound, and then the polymerization is stopped using an electrophile containing a nitrogen atom and a silicon atom (hereinafter, referred to as “a butadiene polymer”). Also referred to as “the method of the present invention”). When the method of the present invention is used, the specific modified BR obtained has better dispersibility, workability, toughness, low heat build-up and wear resistance when used in a rubber composition containing a white filler. Show.

<Organic lithium compounds>
The organolithium compound is not particularly limited, and specific examples thereof include monoorganolithium compounds such as n-butyllithium, sec-butyllithium, tert-butyllithium, n-propyllithium, iso-propyllithium, and benzyllithium; 1,4-dilithiobutane, 1,5-dilithiopentane, 1,6-dilithiohexane, 1,10-dilithiodecane, 1,1-dilithiodiphenylene, dilithiopolybutadiene, dilithiopolyisoprene, 1,4-dilithio Benzene, 1,2-dilithio-1,2-diphenylethane, 1,4-dilithio-2-ethylcyclohexane, 1,3,5-trilithiobenzene, 1,3,5-trilithio-2,4,6- Polyfunctional organolithium compounds such as triethylbenzene can be mentioned. Of these, mono-organic lithium compounds such as n-butyllithium, sec-butyllithium, and tert-butyllithium are preferable because the wet grip performance is further improved when the tire is formed.

  The amount of the organolithium compound used is not particularly limited, but is preferably 0.001 to 10 mol% with respect to butadiene because the wet grip performance is further improved when the tire is formed.

<Copolymerization of butadiene>
The method for polymerizing butadiene using an organolithium compound is not particularly limited, but the above-described organolithium compound is added to an organic solvent solution containing butadiene, and the temperature range is 0 to 120 ° C. (preferably 30 to 100 ° C.). Examples include a stirring method.

<Specific electrophile>
In the method of the present invention, polymerization of butadiene is stopped using an electrophile containing nitrogen atoms and silicon atoms (hereinafter also referred to as “specific electrophile”). By stopping the polymerization using a specific electrophile, a modified butadiene polymer having the above-mentioned specific functional group at the terminal can be obtained.
The specific electrophile is not particularly limited as long as it is a compound containing a nitrogen atom and a silicon atom. However, for the reason that wet grip performance is further improved when a tire is formed, the nitrogen atom is replaced with an amino group (—NR ₂ : R is hydrogen). Atoms or hydrocarbon groups), and silicon atoms are preferably included as hydrocarbyloxysilyl groups (≡SiOR: R is a hydrocarbon group).

  The specific electrophile is preferably silazane, and more preferably cyclic silazane, because wet grip performance is further improved when the tire is made into a tire. Here, silazane intends a compound having a structure in which a silicon atom and a nitrogen atom are directly bonded (compound having a Si—N bond).

  The cyclic silazane is preferably a compound represented by the following formula (S) because wet grip performance is further improved when the tire is made into a tire.

In the above formula (S), R _{1 to} R ₃ each independently represents a hydrogen atom or a substituent. Specific examples and preferred embodiments of the substituent are the same as R ₁ and R _{2 in the} above formula (M).
In the above formula (S), L represents a divalent organic group. Specific examples and preferred embodiments of the divalent organic group are the same as L in the above-described formula (M).

In the above formula (S), R ₁ represents an alkyl group (preferably having a carbon number of 1 to 10), an alkylsilyl group (preferably having a carbon number of 1) because the wet grip performance is further improved when a tire is formed. To 10), an aromatic hydrocarbon group (preferably having 6 to 18 carbon atoms), and more preferably an alkylsilyl group.

In the above formula (S), R ₂ and R ₃ are each independently a hydrocarbyloxy group (—OR group: R is a hydrocarbon group) because wet grip performance is further improved when the tire is formed. It is preferably an alkoxy group (preferably having 1 to 10 carbon atoms).

  In the above formula (S), L is an alkylene group (preferably having a carbon number of 1 to 10, more preferably 2 to 8, more preferably 3 to 5) because the wet grip performance is further improved when a tire is formed. ) Is preferable.

Examples of the compound represented by the formula (S) include Nn-butyl-1,1-dimethoxy-2-azasilacyclopentane and N-phenyl-1,1-dimethoxy-2-azasilacyclopentane. N-trimethylsilyl-1,1-dimethoxy-2-azasilacyclopentane, N-trimethylsilyl-1,1-diethoxy-2-azasilacyclopentane, and the like.
In addition, it is thought that the silicon atom of cyclic silazane shows electrophilicity.

  Although the amount of the specific electrophile with respect to the organolithium compound is not particularly limited, it is preferably 0.1 to 10 in terms of molar ratio because the wet grip performance is further improved when the tire is formed. It is more preferable that

[Piperazine compound]
The rubber composition of the present invention preferably contains a piperazine compound represented by the following formula (2) from the reason that wet grip performance and on-ice performance are better when formed into a tire.
Here, in the above formula (2), X ¹ , X ² , X ³ and X ⁴ each independently represent a hydrogen atom or a substituent, and A ¹ and A ² each independently represent a single bond or 2 Represents a valent linking group, and R ¹¹ and R ¹² each independently represents a hydrogen atom or a substituent. However, at least one of R ¹¹ and R ¹² represents a monovalent hydrocarbon group having 3 to 30 carbon atoms.

The above formula (2), X ¹ , X ² , X ³ and X ⁴ each independently represent a hydrogen atom or a substituent, and preferably a hydrogen atom.
The substituent is not particularly limited as long as it is a monovalent substituent. For example, a halogen atom, hydroxy group, nitro group, carboxy group, alkoxy group, amino group, mercapto group, acyl group, imide group, phosphino group , A phosphinyl group, a silyl group, a hydrocarbon group optionally having a hetero atom, and the like.
As said halogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom etc. are mentioned, for example.
Examples of the hetero atom of the hydrocarbon group that may have a hetero atom include an oxygen atom, a nitrogen atom, a sulfur atom, and a phosphorus atom.
Examples of the hydrocarbon group that may have a hetero atom include an aliphatic hydrocarbon group, an aromatic hydrocarbon group, or a group obtained by combining these.
The aliphatic hydrocarbon group may be linear, branched or cyclic. Specific examples of the aliphatic hydrocarbon group include a linear or branched alkyl group (particularly having 1 to 30 carbon atoms), a linear or branched alkenyl group (particularly having 2 to 30 carbon atoms), Examples thereof include a linear or branched alkynyl group (particularly having 2 to 30 carbon atoms).
Examples of the aromatic hydrocarbon group include an aryl group and a naphthyl group. As said aryl group, C6-C18 aryl groups, such as a phenyl group, a tolyl group, a xylyl group, etc. are mentioned, for example.

The above formula (2), A ¹ and A ² each independently represent a single bond or a divalent linking group.
Examples of the divalent linking group include a divalent hydrocarbon group which may have a substituent; a divalent oxygen atom-containing linking group containing an oxygen atom; and 2 which may have a substituent. A combination of a valent hydrocarbon group and a divalent oxygen atom-containing linking group; and the like.
Here, as the divalent hydrocarbon group, for example, a divalent aliphatic hydrocarbon group such as an alkylene group, a cycloalkylene group, and an alkenylene group; a divalent aromatic hydrocarbon group such as an arylene group and an aralkylene group; Is mentioned. Among these, a divalent aliphatic hydrocarbon group is preferable, an alkylene group is more preferable, and an alkylene group having 1 to 6 carbon atoms is more preferable.
In addition, the divalent oxygen atom-containing linking group may have a hetero atom other than an oxygen atom (for example, a carbon atom, a hydrogen atom, a sulfur atom, a nitrogen atom, etc.). Bond (—O—), ester bond (—C (═O) —O—), amide bond (—C (═O) —NH—), carbonyl group (—C (═O) —), carbonate bond ( -O-C (= O) -O-), an imide bond (-C (= O) -N (Q) -C (= O)-) and the like. Note that Q in the imide bond represents a monovalent hydrocarbon group, for example, a monovalent aliphatic hydrocarbon group such as an alkyl group, a cycloalkyl group, or an alkenyl group; a monovalent aliphatic group such as an aryl group or an aralkyl group. Aromatic hydrocarbon group; and the like.
The divalent hydrocarbon group substituents which may be possessed by, for example, include the same as those described in X ^1, X ^2, X ³ and X ⁴ in the formula (1) . Of these, a hydroxy group is preferable.

The above formula (2), R ¹¹ and R ¹² each independently represent a hydrogen atom or a substituent. However, at least one of R ¹¹ and R ¹² represents a monovalent hydrocarbon group having 3 to 30 carbon atoms.
As said substituent, the thing similar to what was demonstrated in X < ¹ >, X < ² >, X < ³ > and X < ⁴ > of the said Formula (1) is mentioned, for example. Of these, a hydroxy group is preferable.
Moreover, as a C3-C30 monovalent hydrocarbon group, an alkyl group, a cycloalkyl group, an alkenyl group etc. are mentioned, for example.
Examples of the alkyl group include n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, isopentyl group, neopentyl group, tert-pentyl group, 1 -Methylbutyl group, 2-methylbutyl group, 1,2-dimethylpropyl group, n-hexyl group, n-heptyl group, n-octyl group and the like can be mentioned. Among them, an alkyl group having 3 to 18 carbon atoms is preferable.
Examples of the cycloalkyl group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, and among them, a cycloalkyl group having 3 to 10 carbon atoms is preferable.
Examples of the alkenyl group include a 1-propenyl group, an allyl group, an isopropenyl group, a 1-butenyl group, and a 2-butenyl group. Among them, an alkenyl group having 3 to 18 carbon atoms is preferable.

Specific examples of the piperazine compound represented by the above formula (2) include compounds represented by the following formulas (2-1) to (2-6). In addition, in following formula (2-5), r represents the integer of 1-10, and it is preferable that it is an integer of 1-5.

  In this invention, it is preferable that content in the case of containing the said piperazine compound is 5.5-60 mass parts with respect to 100 mass parts of said ester compounds (B), and is 10-55 mass parts. Is more preferable.

〔Silane coupling agent〕
The rubber composition of the present invention preferably contains a silane coupling agent for the purpose of improving the reinforcing performance of the tire.
The content when the silane coupling agent is blended is preferably 0.1 to 20 parts by mass, and 4 to 12 parts by mass with respect to 100 parts by mass of the white filler (C). More preferred.

  Specific examples of the silane coupling agent include bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, Bis (2-triethoxysilylethyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxy Silane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N, N- Methylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropyl Methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis (3-diethoxymethylsilylpropyl) tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, Dimethoxymethylsilylpropylbenzothiazole tetrasulfide and the like, and these may be used alone, It may be used in combination with more species.

  Of these, bis- (3-triethoxysilylpropyl) tetrasulfide and / or bis- (3-triethoxysilylpropyl) disulfide is preferably used from the viewpoint of reinforcing effect. Specifically, Examples thereof include Si69 [bis- (3-triethoxysilylpropyl) tetrasulfide; manufactured by Evonik Degussa], Si75 [bis- (3-triethoxysilylpropyl) disulfide; manufactured by Evonik Degussa).

[Incompatible organic substances]
The rubber composition of the present invention preferably further contains an organic material incompatible with the diene rubber (A) for the reason that the performance on ice becomes better when the tire is formed.
Here, “incompatible with the diene rubber (A)” does not mean that it is incompatible with all the rubber components included in the diene rubber (A), and the organic substance used is the above. It means that it is incompatible with the diene rubber (A).

Examples of the organic material include thermally expandable microcapsules; a cured product obtained by curing a crosslinkable oligomer or polymer that is incompatible with the diene rubber (A).
Here, the “cured cured product” refers to a cured product obtained by curing a crosslinkable oligomer or polymer in advance before mixing and preparing the rubber composition of the present invention.

<Thermal expandable microcapsules>
The thermally expandable microcapsule is a thermally expandable thermoplastic resin particle in which a liquid that can be vaporized by heat is encapsulated in a thermoplastic resin. When the thermally expandable microcapsule is heated at a temperature equal to or higher than the expansion start temperature (usually 130 to 190 ° C.), the thermally expandable microcapsule expands, and the gas-sealed heat in which gas is sealed in the outer shell made of a thermoplastic resin. It becomes plastic resin particles.

In the thermally expandable microcapsule, the expansion start temperature is preferably 100 ° C. or higher, and more preferably 120 ° C. or higher. The maximum expansion temperature is preferably 150 ° C. or higher, and more preferably 160 ° C. or higher.
As the thermoplastic resin constituting the thermally expandable microcapsule, for example, a polymer of (meth) acrylonitrile and a copolymer having a high (meth) acrylonitrile content are preferably used. In the case of the above copolymer, examples of other monomers (comonomer) other than (meth) acrylonitrile include vinyl halide, vinylidene halide, styrene monomer, (meth) acrylate monomer, vinyl acetate, butadiene, and vinylpyridine. Monomers such as chloroprene are used.
Examples of the thermoplastic resin include divinylbenzene, ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, allyl It may be crosslinked with a crosslinking agent such as (meth) acrylate, triacryl formal, triallyl isocyanurate or the like. The crosslinked form is preferably uncrosslinked, but may be partially crosslinked so as not to impair the properties as a thermoplastic resin.

  Examples of the liquid constituting the thermally expandable microcapsule include hydrocarbons such as n-pentane, isopentane, neopentane, butane, isobutane, hexane, and petroleum ether; methyl chloride, methylene chloride, dichloroethylene, trichloroethane, trichloroethylene, and the like. Of chlorinated hydrocarbons.

The said thermally expansible microcapsule may be used individually by 1 type, and may use 2 or more types together.
The particle size of the thermally expandable microcapsule before expansion is preferably 5 to 300 μm, more preferably 10 to 200 μm.

  As such thermally expandable microcapsules, commercially available products can be used. Specifically, for example, EXPANCEL 091DU-80, EXPANCEL 092DU-120 manufactured by EXPANCEL; Sphere F-85, Microsphere F-100;

<Hardened product>
Examples of a cured product obtained by curing a crosslinkable oligomer or polymer that is not compatible with the diene rubber include, for example, “a crosslinkable oligomer that is not compatible with the diene rubber (A)” described in JP-A-2015-066763. Examples thereof include the same as “cured product (C) obtained by curing polymer (c1)”.

The cured product preferably has a JIS A hardness of 3 to 45, more preferably 3 to 30, and still more preferably 3 to 20.
Here, the JIS A hardness of the cured product is a durometer hardness defined in JIS K6253-3: 2012, and means a hardness measured at a temperature of 25 ° C. with a type A durometer.

Moreover, the said hardened | cured material is a granular material with an average particle diameter of 5-250 micrometers from the reason that the dispersibility to the said diene-type rubber (A) becomes favorable and the performance on ice becomes further favorable when it is set as a tire. Is preferred.
Here, the average particle diameter of the cured product is obtained by analyzing the image of the cross-section of the vulcanized specimen of the rubber composition for a tire with an electron microscope (magnification: about 500 to 2000 times) and observing the particles of the cured product observed. The maximum length is measured with an arbitrary 10 or more particles, and is an averaged value.

  In this invention, content in the case of containing the organic substance incompatible with the said diene rubber (A) is 0.5-30 mass parts with respect to 100 mass parts of the said diene rubber (A). It is preferably 1 to 20 parts by mass.

〔Carbon black〕
The rubber composition of the present invention preferably contains carbon black for the purpose of improving the reinforcing performance of the tire.
Specific examples of the carbon black include furnace carbon blacks such as SAF, ISAF, HAF, FEF, GPE, and SRF. These may be used alone or in combination of two or more. May be.
In addition, the carbon black preferably has a nitrogen adsorption specific surface area (N ₂ SA) of 10 to 300 m ² / g from the viewpoint of processability at the time of mixing the rubber composition, reinforcement of the pneumatic tire, and the like. More preferably, it is 20-200 m < ² > / g.
Here, N ₂ SA is a value obtained by measuring the amount of nitrogen adsorbed on the carbon black surface in accordance with JIS K 6217-2: 2001 “Part 2: Determination of specific surface area—nitrogen adsorption method—single point method”. .

  In the present invention, the content in the case of containing the carbon black is preferably 40 to 130 parts by mass, more preferably 50 to 100 parts by mass with respect to 100 parts by mass of the diene rubber (A). Is preferred.

[Other ingredients]
In addition to the components described above, the rubber composition of the present invention comprises a filler such as calcium carbonate; dinitrosopentamethylenetetraamine (DPT), azodicarbonamide (ADCA), dinitrosopentastyrenetetramine, oxybisbenzenesulfonylhydrazide (OBSH). ), Benzenesulfonyl hydrazide derivatives, ammonium bicarbonate generating carbon dioxide, ammonium carbonate, sodium bicarbonate, toluenesulfonyl hydrazide generating nitrogen, P-toluenesulfonyl semicarbazide, nitrososulfonylazo compound, N, N'-dimethyl-N , N′-dinitrosophthalamide, P, P′-oxy-bis (benzenesulfonyl semicarbazide), etc .; sulfur and other vulcanizing agents; sulfenamide, guanidine, thiazole, Generally used in rubber compositions for tires such as urea and thiuram vulcanization accelerators; vulcanization accelerators such as zinc oxide and stearic acid; waxes; aroma oils; anti-aging agents; Various other additives can be blended.
As long as the amount of these additives is not contrary to the object of the present invention, a conventional general amount can be used. For example, for 100 parts by mass of the diene rubber (A), 0.5 to 5 parts by mass of sulfur, 0.1 to 5 parts by mass of the vulcanization accelerator, and 0.1 to 10 parts by mass of the vulcanization accelerator aid. Parts, anti-aging agent 0.5-5 parts by mass, wax 1-10 parts by mass, aroma oil 5-30 parts by mass, respectively.

[Method for producing rubber composition for tire]
The method for producing the tire rubber composition of the present invention is not particularly limited. For example, the above-described components are kneaded using a known method or apparatus (for example, a Banbury mixer, a kneader, a roll, or the like). Is mentioned.
The tire rubber composition of the present invention can be vulcanized or crosslinked under conventionally known vulcanization or crosslinking conditions.

[Pneumatic tire]
The pneumatic tire of the present invention is a pneumatic tire using the above-described tire rubber composition of the present invention for a tire tread.
FIG. 1 shows a schematic partial sectional view of a tire representing an example of an embodiment of the pneumatic tire of the present invention, but the tire of the present invention is not limited to the embodiment shown in FIG.

In FIG. 1, the code | symbol 1 represents a bead part, the code | symbol 2 represents a sidewall part, and the code | symbol 3 represents the tread part comprised from the rubber composition for tires of this invention.
Further, a carcass layer 4 in which fiber cords are embedded is mounted between the pair of left and right bead portions 1, and the end of the carcass layer 4 extends from the inside of the tire to the outside around the bead core 5 and the bead filler 6. Wrapped and rolled up.
In the tire tread 3, a belt layer 7 is disposed over the circumference of the tire on the outside of the carcass layer 4.
Moreover, in the bead part 1, the rim cushion 8 is arrange | positioned in the part which touches a rim | limb.

  The pneumatic tire of the present invention can be manufactured, for example, according to a conventionally known method. Moreover, as gas with which a tire is filled, inert gas, such as nitrogen, argon, helium other than the air which adjusted normal or oxygen partial pressure, can be used.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these.

<Synthesis of Piperazine Compound 1>
13.3 g of 1-bromooctadecane (produced by Tokyo Chemical Industry Co., Ltd.) and 13.0 g of 1- (2-hydroxyethyl) piperazine (hydroxyethylpiperazine produced by Nippon Emulsifier Co., Ltd.) in tetrahydrofuran and dichloromethane at room temperature The reaction was carried out at (23 ° C.) for 1 hour.
Next, the reaction solution was washed with an aqueous potassium carbonate solution, extracted with dichloromethane, and dehydrated with anhydrous magnesium sulfate.
Subsequently, anhydrous magnesium sulfate was filtered off and concentrated to obtain a piperazine compound 1 represented by the following formula.

<Synthesis of specific modified BR1>
n-BuLi (manufactured by Kanto Chemical Co., Ltd .: 1.60 mol / L (hexane solution), 50 mL, 80 mmol), 1,3-butadiene (198 g, 3667 mmol) and 2,2-di (2-tetrahydrofuryl) propane (Tokyo Kasei) (Manufactured, 0.1 mL, 0.55 mmol) in cyclohexane (2.96 kg) mixed solution and stirred at room temperature for 6 hours. After the reaction, N-trimethylsilyl-1,1-dimethoxy-2-azasilacyclopentane (30 g, 137 mmol) was added to terminate the polymerization. The resulting solution was removed and concentrated under reduced pressure. The concentrated solution was poured into methanol (5.0 L) to separate methanol-insoluble components. As a result, modified BR having a functional group represented by the above formula (m1) at the terminal (specifically modified BR1) (182 g, Mn = 4,100, Mw = 4,400, Mw / Mn = 1.1) was 92. % Yield. In addition, it was estimated by IR analysis that cis / trans / vinyl = 31/45/24. Moreover, Tg was -83 degreeC. The viscosity (after modification / before modification) was 196%.

[Standard Example 1, Examples 1 to 7 and Comparative Examples 1 to 4]
The components shown in Table 1 below were blended in the proportions (parts by mass) shown in Table 1 below.
Specifically, first, the components excluding sulfur and the vulcanization accelerator in the components shown in Table 1 below were raised to around 150 ° C. using a 1.7 liter closed Banbury mixer, and then for 5 minutes. After mixing, the mixture was discharged and cooled to room temperature to obtain a master batch.
Next, using the above Banbury mixer, sulfur and a vulcanization accelerator were mixed into the obtained master batch to obtain a tire rubber composition.

<Rubber hardness after curing>
The prepared tire rubber composition (unvulcanized) was heated in a cylindrical mold (15 cm × 15 cm × 0.2 cm) at 170 ° C. for 10 minutes to be cured (vulcanized).
Based on JIS K 6253-3: 2012 "vulcanized rubber and thermoplastic rubber-Determination of hardness-Part 3: Durometer hardness", the hardness of the obtained rubber after curing (rubber hardness) Measured at a temperature of 0 ° C. The results are shown in Table 1 below.

<Wet grip>
The prepared tire rubber composition (unvulcanized) was press vulcanized for 10 minutes at 170 ° C. in a cylindrical mold (15 cm × 15 cm × 0.2 cm) to obtain a vulcanized rubber test piece. Was made.
About the produced vulcanized rubber test piece, in accordance with JIS K6394: 2007, using a viscoelastic spectrometer (manufactured by Iwamoto Seisakusho Co., Ltd.), conditions of 10% ± 2% elongation deformation strain, frequency 20 Hz, temperature 0 ° C. Tan δ (0 ° C.) was measured.
The results are shown in Table 1 below. The results were expressed as an index with tan δ (0 ° C.) of Standard Example 1 as 100. The larger the index, the larger the tan δ (0 ° C.), and the better the wet grip property when made into a tire.

<Performance on ice>
The vulcanized rubber test piece prepared as described above was attached to a flat cylindrical base rubber, and measured with an inside drum type on-ice friction tester: measurement temperature: −1.5 ° C., load: 5.5 kg / cm ³ , drum rotation The friction coefficient on ice was measured under the condition of speed: 25 km / hour. And the friction coefficient index on ice was computed from the following formula.
Friction coefficient on ice index = (Friction coefficient on ice of sample / Friction coefficient on ice of standard example 1) × 100
The results are shown in Table 1 below. The higher the friction coefficient index on ice, the greater the frictional force between rubber and ice, and the better the performance on ice when used as a tire.

The following were used for each component in Table 1 above.
NR: TSR20 (Tg: -62 ° C)
-BR1: Nipol BR1220 (made by Nippon Zeon)
Silica 1: Zeosil 1165MP (CTAB adsorption specific surface area = 160 m ² / g, manufactured by Rhodia)
Silica 2: Zeosil Premium 200MP (CTAB adsorption specific surface area = 200 m ² / g, manufactured by Rhodia)
Silica 3: Zeosil 1115MP (CTAB adsorption specific surface area = 110 m ² / g, manufactured by Rhodia)

Polyoxyethylene alkyl ether phosphate ester 1: Polyoxyethylene tridecyl ether phosphate ester (Pricesurf A215C, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
Comparative phosphate ester: bis (2-ethylhexyl) phosphate (LB-58, manufactured by Johoku Chemical Industry Co., Ltd.)
Piperazine compound 1: Synthetic product described above Specific modified BR1: Synthetic product described above Unmodified liquid rubber: Liquid butadiene homopolymer (RICON 142, manufactured by CRAY VALLEY)

Silane coupling agent: Si69 (manufactured by Evonik Degussa)
・ Stearic acid: Bead stearic acid YR (manufactured by NOF Corporation)
・ Zinc flower: 3 types of zinc oxide
・ Anti-aging agent: Amine-based anti-aging agent (Santflex 6PPD, manufactured by Flexsys)
・ Process oil: Extract No. 4 S (made by Showa Shell Sekiyu KK)
・ Sulfur: Fine sulfur with Jinhua stamp oil (manufactured by Tsurumi Chemical Co., Ltd.)
・ Vulcanization accelerator 1: Vulcanization accelerator CBS (Noxeller CZ-G, manufactured by Ouchi Shinsei Chemical Co., Ltd.)
・ Vulcanization accelerator 2: Vulcanization accelerator DPG (Noxeller D, manufactured by Ouchi Shinsei Chemical Co., Ltd.)

From the results shown in Table 1, it was found that when a phosphoric acid ester not corresponding to the ester compound (B) was used, the wet grip property when used as a tire was inferior (Comparative Example 1).
In addition, for the diene rubber (A), when the content of isoprene rubber is 90% by mass or more, the wet grip property when the tire is made is good, but the performance on ice is inferior (Comparative Example). 2).
Further, when the content of the ester compound (B) is less than 0.5 parts by mass with respect to 100 parts by mass of the white filler (C), the wet grip property when made into a tire is not improved, and the performance on ice is also improved. It was found to be inferior (Comparative Example 3).
Moreover, when content of ester compound (B) is more than 20 mass parts with respect to 100 mass parts of white fillers (C), it turns out that both wet grip property and on-ice performance when using a tire are inferior. (Comparative Example 4).

On the other hand, when the content of the ester compound (B) is in the range of 0.5 to 20 parts by mass with respect to 100 parts by mass of the white filler (C), It was found that the performance on ice was good (Examples 1 to 7).
In particular, it was found from the comparison between Example 1 and Example 2 that the wet grip property and the on-ice performance of the tire were improved by blending the piperazine compound.
Further, from the results of Examples 3 and 6, it was found that the wet grip property when the tire was made further improved by blending the specific modified BR.

1 Bead part 2 Side wall part 3 Tire tread part 4 Carcass layer 5 Bead core 6 Bead filler 7 Belt layer 8 Rim cushion

Claims (8)

Containing a diene rubber (A), an ester compound (B), and a white filler (C);
The diene rubber (A) contains 30% by mass or more and less than 90% by mass of isoprene-based rubber,
The ester compound (B) is a polyoxyethylene alkyl ether sulfate, polyoxyethylene alkyl ether phosphate, polyoxyethylene alkyl ether acetate, polyoxyethylene alkyl sulfosuccinate, and polyoxyethylene fatty acid amide ether sulfate. At least one ester compound selected from the group consisting of esters,
Content of the said ester compound (B) is 0.5-20 mass parts with respect to 100 mass parts of said white fillers (C),
A rubber composition for tires, wherein the rubber hardness of type A specified by JIS at a temperature of 0 ° C. after curing is less than 55. The tire rubber composition according to claim 1, wherein the ester compound (B) is a polyoxyethylene alkyl ether phosphate represented by the following formula (1).
Here, the formula (1), ^{R 1} represents an alkyl group having 3 to 21 carbon atoms, n represents an integer of 1 to 10, m represents 1 or 2, ^{R 2} is a hydrogen atom or a carbon atoms 1 to 10 alkyl groups, and when m is 1, the plurality of R ² may be the same or different, and when m is 2, the plurality of R ¹ are respectively the same May be different.   The tire rubber composition according to claim 1 or 2, wherein a content of the white filler (C) is 30 to 80 parts by mass with respect to 100 parts by mass of the diene rubber (A). The rubber composition for tires in any one of Claims 1-3 whose CTAB adsorption | suction specific surface area of the said white filler (C) is 140-300 m < ² > / g. Furthermore, it contains a modified butadiene polymer having a functional group containing a nitrogen atom and a silicon atom at its end,
The modified butadiene polymer is a polymer having a weight average molecular weight of 1,000 to 15,000 and a molecular weight distribution of 2.0 or less,
The tire rubber composition according to any one of claims 1 to 4, wherein a content of the modified butadiene polymer is 1 to 25 mass% with respect to a content of the white filler (C). Furthermore, it contains a piperazine compound represented by the following formula (2),
The tire rubber composition according to any one of claims 1 to 5, wherein a content of the piperazine compound is 5.5 to 60 parts by mass with respect to 100 parts by mass of the ester compound (B).
Here, in the formula (2), X ¹ , X ² , X ³ and X ⁴ each independently represent a hydrogen atom or a substituent, and A ¹ and A ² each independently represent a single bond or 2 Represents a valent linking group, and R ¹¹ and R ¹² each independently represents a hydrogen atom or a substituent. However, at least one of R ¹¹ and R ¹² represents a monovalent hydrocarbon group having 3 to 30 carbon atoms.   The pneumatic tire which uses the rubber composition for tires in any one of Claims 1-6 for a tire tread.   The pneumatic tire according to claim 7, which is used for a studless tire.