JP2019052219A - Rubber composition for studless tires, and studless tire - Google Patents

Abstract

To provide a rubber composition for studless tires which is excellent in processability and is excellent in on-ice performance when formed into a studless tire, and to provide a studless tire using the rubber composition for studless tires.SOLUTION: The rubber composition for studless tires contains: a diene rubber; silica; a heterocyclic compound having a C3-30 hydrocarbon group and at least one heterocyclic ring selected from the group consisting of a piperazine ring, a morpholine ring, and a thiomorpholine ring (provided that the heterocyclic compound has no silicon atom); and a sulfur-containing silane coupling agent. The diene rubber has an average glass transition temperature lower than -60°C. The content of the silica is 30-150 pts.mass based on 100 pts.mass of the diene rubber. The content of the heterocyclic compound is 0.5-20 mass% based on the silica. The content of the sulfur-containing silane coupling agent is 1-25 mass% based on the silica. The rubber composition for studless tires has a type A rubber hardness specified by JIS at a temperature of 0°C of 55 or less after curing.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a rubber composition for studless tires and a studless tire.

Conventionally, a rubber composition in which silica and a thermally expandable microcapsule are blended with a diene rubber containing natural rubber and butadiene rubber has been known as a rubber composition (studless tire rubber composition) used for a studless tire. (For example, see Patent Document 1).
Further, a method is known in which a hydrolyzable silane that functions as a coupling agent between a filler and a diene elastomer is added to a rubber composition.
For example, Patent Document 2 discloses a diene elastomer composition containing a diene elastomer, a hydrolyzable silane, and a curing agent for the diene elastomer, wherein the hydrolyzable silane has a specific structure. A diene elastomer composition is described which is a silane.

JP 2012-007068 A Special table 2015-502357 gazette

On the other hand, with the improvement of the safety level required for studless tires, further improvement in performance on ice (the frictional force between rubber and ice is large) is required.
The inventors prepared a rubber composition for a studless tire with reference to Patent Documents 1 and 2, and evaluated the rubber composition. As a result, such a rubber composition has a high Mooney viscosity and a low workability. It has become clear that, in some cases, the level of on-ice performance currently required may not be satisfied.
Therefore, the present invention provides a rubber composition having excellent processability (for example, Mooney viscosity is in an appropriate range) and having excellent performance on ice when it is made into a studless tire, and a studless tire using the rubber composition. The purpose is to do.

As a result of diligent research to solve the above-mentioned problems, the present inventors include a diene rubber, silica, a predetermined heterocyclic compound and a sulfur-containing silane coupling agent, and an average glass transition temperature of the diene rubber, rubber hardness. And it discovered that the said subject could be solved by content of a silica, a heterocyclic compound, and a sulfur containing silane coupling agent being a specific range, respectively, and came to this invention.
That is, the present invention can solve the above problems by the following configuration.

1. Diene rubber,
Silica,
A heterocyclic compound having a hydrocarbon group having 3 to 30 carbon atoms and at least one heterocyclic ring selected from the group consisting of a piperazine ring, a morpholine ring and a thiomorpholine ring (provided that the heterocyclic compound has a silicon atom). Not)
Containing a sulfur-containing silane coupling agent,
The diene rubber has an average glass transition temperature of less than −60 ° C.,
The content of the silica is 30 to 150 parts by mass with respect to 100 parts by mass of the diene rubber.
The content of the heterocyclic compound is 0.5 to 20% by mass with respect to the silica,
Content of the said sulfur containing silane coupling agent is 1-25 mass% with respect to the said silica,
A rubber composition for studless tires, wherein the rubber hardness of JIS-regulated Type A at a temperature of 0 ° C. after curing is 55 or less.
2. 2. The rubber composition for studless tires according to 1 above, wherein the heterocyclic compound is a compound represented by the following formula (I).

In the formula (I), X ₇ represents at least one selected from the group consisting of a nitrogen atom, an oxygen atom and a sulfur atom,
X ₃ , X ₄ , X ₅ and X ₆ each independently represent a hydrogen atom or a hydrocarbon group.
If X ₇ is a nitrogen atom, n3 is 1, one or both of X ₁ and X ₂ are, each independently, formula _{(I-1) :-( A 1} ) n1-1 -R 1 _-1 for
When only one of X ₁ and X ₂ represents formula (I-1), the remaining groups are a hydrogen atom, a sulfone protecting group, a carbamate protecting group, and formula (I-3): — (R ₂ -O) represents at least one selected from the group consisting of _n2 -H,
In formula (I-3), each R ₂ independently represents a divalent hydrocarbon group,
n2 represents 1-10.
When X ₇ is at least one selected from the group consisting of an oxygen atom and a sulfur atom, n3 represents 0, and X ₁ represents the formula (I-1):-(A ₁ ) _n1-1 -R _1- Represents ₁ .
In Formula (I-1), A ₁ represents at least one selected from the group consisting of a carbonyl group and Formula (I-2): —R _1-2 (OH) —O—,
n1-1 represents 0 or 1,
R _1-1 represents a hydrocarbon group having 3 to 30 carbon atoms,
In formula (I-2), R _1-2 represents a trivalent hydrocarbon group.
3. The heterocyclic compound is a compound represented by the above formula (I), X ₇ is a nitrogen atom, n3 is 1,
The rubber composition for studless tires according to 2 above, wherein both X ₁ and X ₂ independently represent the above formula (I-1).
4). The heterocyclic compound is a compound represented by the above formula (I), X ₇ is a nitrogen atom, n3 is 1,
Only one of X ₁ and X ₂ represents the above formula (I-1),
In the above 2, wherein the remaining group represents at least one selected from the group consisting of a hydrogen atom, a sulfone-based protective group, a carbamate-based protective group, and formula (I-3): — (R ₂ —O) _n2 —H The rubber composition for studless tires as described. In formula (I-3), R ₂ independently represents a divalent hydrocarbon group, and n2 represents 1 to 10.
5. Furthermore, the rubber composition for studless tires in any one of said 1-4 containing a thermally expansible microcapsule.
6). 5. The mass ratio of the content of the heterocyclic compound to the content of the thermally expandable microcapsule (the content of the heterocyclic compound / the content of the thermally expandable microcapsule) is 0.0025 to 48, The rubber composition for studless tires as described.
7). The rubber composition for studless tires according to 5 or 6 above, wherein the content of the thermally expandable microcapsule is 0.5 to 20 parts by mass with respect to 100 parts by mass of the diene rubber.
8). The studless tire which has arrange | positioned the rubber composition for studless tires in any one of said 1-7 in the cap tread.

The rubber composition for studless tires of the present invention is excellent in processability and excellent in ice performance when made into a studless tire.
Moreover, according to the present invention, a studless tire can be provided.

1 is a schematic partial cross-sectional view of a tire that represents an example of an embodiment of a studless tire of the present invention.

The present invention will be described in detail below.
In the present specification, (meth) acrylate represents acrylate or methacrylate, (meth) acryloyl represents acryloyl or methacryloyl, and (meth) acryl represents acryl or methacryl.
In the present specification, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.
In the present specification, unless otherwise specified, each component is not particularly limited with respect to its production method. For example, a conventionally well-known thing is mentioned.
In the present specification, unless otherwise specified, each component can be used alone or in combination of two or more of the substances corresponding to the component. When a component contains two or more types of substances, the content of the component means the total content of the two or more types of substances.
In the present specification, the fact that at least one of workability and performance on ice is more excellent may mean that the effect of the present invention is more excellent.

[Rubber composition for studless tire]
The rubber composition for a studless tire of the present invention (the composition of the present invention)
Diene rubber,
Silica,
A heterocyclic compound having a hydrocarbon group having 3 to 30 carbon atoms and at least one heterocyclic ring selected from the group consisting of a piperazine ring, a morpholine ring and a thiomorpholine ring (provided that the heterocyclic compound has a silicon atom). Not)
Containing a sulfur-containing silane coupling agent,
The diene rubber has an average glass transition temperature of less than −60 ° C.,
The content of the silica is 30 to 150 parts by mass with respect to 100 parts by mass of the diene rubber.
The content of the heterocyclic compound is 0.5 to 20% by mass with respect to the silica,
Content of the said sulfur containing silane coupling agent is 1-25 mass% with respect to the said silica,
It is a rubber composition for studless tires having a JIS stipulated type A rubber hardness of 55 or less after curing at a temperature of 0 ° C.

Since the composition of this invention takes such a structure, it is thought that a desired effect is acquired. The reason is not clear, but it is presumed that it is as follows.
The heterocyclic compound contained in the composition of the present invention has a hydrocarbon group having 3 to 30 carbon atoms and at least one heterocyclic ring selected from the group consisting of a piperazine ring, a morpholine ring and a thiomorpholine ring.
Since the hydrocarbon group has hydrophobicity, it easily interacts with the diene rubber, and the heterocycle has hydrophilicity, so it is considered that it easily interacts with silica.
Thus, the heterocyclic compound having the hydrocarbon group as a hydrophobic portion and the heterocyclic ring as a hydrophilic portion functions as a surfactant in a composition containing a diene rubber and silica, The inventors speculate that the dispersibility of the silica in the diene rubber is increased, which lowers the Mooney viscosity in the unvulcanized rubber.
The heterocyclic compound interacts with the diene rubber in the hydrocarbon group, but does not form a chemical bond. The heterocyclic compound interacts with silica in the heterocyclic ring, but the heterocyclic compound contains a silicon atom. Since it does not have, it is thought that the said heterocyclic compound does not form a chemical bond with a silica. For this reason, since the said heterocyclic compound is not too high in curing (vulcanization) acceleration effect, scorch (discoloration) can be suppressed and / or the curing rate (vulcanization rate) is not excessively increased. The inventors speculate.
As described above, the presence of the heterocyclic compound lowers the Mooney viscosity, suppresses scorch, or makes the curing rate (vulcanization rate) suitable, so that the composition of the present invention is workable. It is considered excellent.
In addition, as described above, the heterocyclic compound increases the dispersibility of silica in the diene rubber, thereby reducing the hardness of the rubber after curing the rubber composition (cured rubber) under low temperature conditions, Since it is excellent in flexibility at low temperatures, it is presumed that when the composition of the present invention is made into a studless tire, it is excellent in performance on ice.
Hereinafter, each component contained in the composition of this invention is explained in full detail.

<< Diene rubber >>
The composition of the present invention contains a diene rubber. In the present invention, the average glass transition temperature of the diene rubber is less than -60 ° C.
The diene rubber is not particularly limited as long as it has a double bond in the main chain. For example, natural rubber (NR); aromatic vinyl-conjugated diene copolymer such as isoprene rubber (IR), butadiene rubber, styrene butadiene rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR) ), Halogenated butyl rubber (Br-IIR, Cl-IIR), chloroprene rubber (CR) and the like.
Among these, at least one selected from the group consisting of natural rubber and butadiene rubber is preferable.

The diene rubber may be modified. The modified diene rubber (modified diene rubber) can have a modifying group. The modifying group is preferably a group capable of interacting with or binding to silica. For example, hydroxy group, carboxy group, amino group, imino group, thiol group, epoxy group, polysiloxane group such as polyorganosiloxane group, hydrocarbyloxysilane group such as alkoxysilyl group, silanol group, and combinations thereof And a modifying group.
Examples of the main chain of the modified diene rubber include those similar to the diene rubber.
The modifying group may be bonded to either the side chain or the terminal of the main chain.
The modifying group and the main chain (the diene rubber) can be bonded directly or via an organic group. The organic group is not particularly limited.
The modified diene rubber is preferably a modified butadiene rubber.
Examples of the combination of the diene rubber include a combination of natural rubber and unmodified butadiene, and a combination of natural rubber and / or butadiene rubber and modified butadiene rubber as the unmodified diene rubber.

  When the diene rubber contains a modified diene rubber, the content of the modified diene rubber is preferably an amount exceeding 10% by mass in the total amount of the diene rubber, from the viewpoint of being excellent due to the effects of the present invention. 20-60 mass% is more preferable, and 35-45 mass% is still more preferable.

In the present invention, the weight average molecular weight of the diene rubber can be 30,000 or more. The upper limit of the weight average molecular weight of the diene rubber excluding natural rubber can be 2 million or less.
The weight average molecular weight of the diene rubber is a standard polystyrene equivalent value based on a measured value by gel permeation chromatography (GPC) using tetrahydrofuran as a solvent.

<< Average glass transition temperature >>
In the present invention, the average glass transition temperature (average Tg) of the diene rubber is less than −60 ° C.
The average glass transition temperature is preferably −65 ° C. to −90 ° C., more preferably −70 ° C. to −90 ° C., and −70 ° C. to −78 ° C. from the viewpoint that the effect of the present invention (particularly performance on ice) is superior. Is more preferable.
The average Tg of the diene rubber is obtained by multiplying the glass transition temperature (Tg) of each diene rubber by the mass% of each diene rubber with respect to the entire diene rubber, and adding them.
When one kind of diene rubber is used as the diene rubber, the average glass transition temperature of the diene rubber is the glass transition temperature of the one kind of diene rubber.
The glass transition temperature of each diene rubber is measured by a differential scanning calorimeter (DSC) at a heating rate of 20 ° C./min and calculated by the midpoint method.

<< Silica >>
The silica contained in the composition of the present invention is not particularly limited. For example, conventionally known silica blended in a rubber composition for applications such as tires can be used.
Examples of the silica include wet silica, dry silica, fumed silica, diatomaceous earth, and the like.

(CTAB adsorption specific surface area of silica)
The CTAB adsorption specific surface area of the silica is preferably 100 to 300 m ² / g, more preferably 110 to 250 m ² / g, from the viewpoint that the effect of the present invention (particularly performance on ice) is excellent and wet performance (wet grip performance) is excellent. More preferred.
In the present invention, the CTAB adsorption specific surface area of the silica can be less than 210 m ² / g.
Here, the CTAB adsorption specific surface area is a surrogate property of the surface area that silica can use for adsorption with the silane coupling agent, and the amount of CTAB (cetyltrimethylammonium bromide) adsorbed on the silica surface is JIS K6217-3: 2001 “No. It is a value measured according to “3 parts: determination of specific surface area—CTAB adsorption method”.

<< Content of silica >>
In the present invention, the content of the silica is 30 to 150 parts by mass with respect to 100 parts by mass of the diene rubber.
The content of the silica is 30 to 120 parts by mass with respect to 100 parts by mass of the diene rubber from the viewpoint that the effect of the present invention (particularly on-ice performance) is excellent and the balance between the on-ice performance and the wet performance is excellent. It is preferably 35 to 100 parts by mass.

<< Heterocyclic Compound >>
The heterocyclic compound contained in the composition of the present invention is a compound having a hydrocarbon group having 3 to 30 carbon atoms and at least one heterocyclic ring selected from the group consisting of a piperazine ring, a morpholine ring and a thiomorpholine ring. It is. In the present invention, the heterocyclic compound does not have a silicon atom.
The said C3-C30 hydrocarbon group can function as a hydrophobic part.
In addition, the said heterocyclic compound can be made into what does not have an enamine structure (N-C = C).

<C3-C30 hydrocarbon group>
Examples of the hydrocarbon group having 3 to 30 carbon atoms include aliphatic hydrocarbon groups (including linear, branched and cyclic), aromatic hydrocarbon groups, and combinations thereof.
Of these, an aliphatic hydrocarbon group is preferable and a saturated aliphatic hydrocarbon group is more preferable from the viewpoint of superior processability.

  The number of carbon atoms of the hydrocarbon group having 3 to 30 carbon atoms is preferably 8 to 22 and more preferably 8 to 18 from the viewpoint of superior workability.

One preferred embodiment of the hydrocarbon group having 3 to 30 carbon atoms is composed of only carbon atoms and hydrogen atoms.
One preferred embodiment of the hydrocarbon group having 3 to 30 carbon atoms is monovalent.
One molecule of the heterocyclic compound can have one or a plurality of the hydrocarbon groups having 3 to 30 carbon atoms, and one or two of them are preferable.

<Heterocycle>
In the present invention, the heterocyclic compound has at least one heterocyclic ring selected from the group consisting of a piperazine ring, a morpholine ring, and a thiomorpholine ring.
One molecule of the heterocyclic compound can have one or a plurality of the heterocyclic rings, and one preferable embodiment is one.
The heterocyclic ring is preferably a piperazine ring or a morpholine ring, more preferably a piperazine ring, from the viewpoint of superior processability.

(Piperazine ring)
The piperazine ring means the skeleton of piperazine. A heterocyclic compound having a piperazine ring as a heterocyclic ring may be hereinafter referred to as a “piperazine compound”. In the present invention, the piperazine ring does not contain a triethylenediamine skeleton (diazabicyclooctane skeleton).
(Morpholine ring)
A morpholine ring means a morpholine skeleton. A heterocyclic compound having a morpholine ring as a heterocyclic ring may be hereinafter referred to as a “morpholine compound”.
(Thiomorpholine ring)
A thiomorpholine ring means the skeleton of thiomorpholine. A heterocyclic compound having a thiomorpholine ring as a heterocycle may be hereinafter referred to as a “thiomorpholine compound”.

(Coupling of C3-C30 hydrocarbon group and heterocycle)
The hydrocarbon group having 3 to 30 carbon atoms can be bonded directly or via an organic group to the nitrogen or carbon atom of the heterocyclic ring that the heterocyclic compound has.
One preferred embodiment of the hydrocarbon group having 3 to 30 carbon atoms is bonded directly or via an organic group to the heterocyclic nitrogen atom of the heterocyclic compound.
In the heterocyclic compound, when the heterocyclic ring is a morpholine ring, the hydrocarbon group having 3 to 30 carbon atoms can be bonded directly or through an organic group to the nitrogen atom or carbon atom in the morpholine ring. . The same applies when the heterocycle is a thiomorpholine ring.

The organic group is not particularly limited. For example, the hydrocarbon group which has an oxygen atom is mentioned. Examples of the hydrocarbon group are the same as those described above.
The oxygen atom may form, for example, a carbonyl group or a hydroxy group.
When the organic group is a hydrocarbon group having an oxygen atom at the terminal, the oxygen atom may be bonded to a hydrocarbon group having 3 to 30 carbon atoms to form an ether bond. The hydrocarbon group having an oxygen atom may further have a hydroxy group.

The said piperazine compound can have further substituents other than a C3-C30 hydrocarbon group and a piperazine ring. Examples of the substituent include at least one selected from the group consisting of a sulfone-based protecting group, a carbamate-based protecting group, and formula (I-3): — (R ₂ —O) _n2 —H.
When the piperazine compound further has the above substituent, the above substituent can be bonded to the nitrogen atom of the piperazine ring of the piperazine compound.

  In the piperazine compound, one hydrocarbon group having 3 to 30 carbon atoms is bonded to one of two nitrogen atoms of the piperazine ring, and the remaining nitrogen atom of the piperazine ring is substituted with a hydrogen atom or the above-described substitution. A group can be attached.

(Sulfone protecting group)
Examples of the sulfone protecting group include a methanesulfonyl group, a tosyl group, and a nosyl group.

(Carbamate protecting group)
Examples of the carbamate protecting group include a tert-butoxycarbonyl group, an allyloxycarbonyl group, a benzyloxycarbonyl group, and a 9-fluorenylmethyloxycarbonyl group.

(Formula (I-3))
In formula (I-3): — (R ₂ —O) _n2 —H, each R ₂ independently represents a divalent hydrocarbon group.
In the formula (I-3), the divalent hydrocarbon group preferably has 2 to 3 carbon atoms.
The divalent hydrocarbon group is preferably an aliphatic hydrocarbon group. The aliphatic hydrocarbon group may be linear, branched, cyclic, or a combination thereof.
n2 represents 1 to 10, and preferably 1 to 5.

The heterocyclic compound is preferably a compound represented by the following formula (I) from the viewpoint of excellent processability and excellent dispersibility of silica.

In the formula (I), X ₇ represents at least one selected from the group consisting of a nitrogen atom, an oxygen atom and a sulfur atom,
X ₃ , X ₄ , X ₅ and X ₆ each independently represent a hydrogen atom or a hydrocarbon group.
If X ₇ is a nitrogen atom, n3 is 1, one or both of X ₁ and X ₂ are, each independently, formula _{(I-1) :-( A 1} ) n1-1 -R 1 _-1 for
When only one of X ₁ and X ₂ represents formula (I-1), the remaining groups are a hydrogen atom, a sulfone protecting group, a carbamate protecting group, and formula (I-3): — (R ₂ -O) represents at least one selected from the group consisting of _n2 -H,
In formula (I-3), each R ₂ independently represents a divalent hydrocarbon group,
n2 represents 1-10.
When X ₇ is at least one selected from the group consisting of an oxygen atom and a sulfur atom, n3 represents 0, and X ₁ represents the formula (I-1):-(A ₁ ) _n1-1 -R _1- Represents ₁ .
In Formula (I-1), A ₁ represents at least one selected from the group consisting of a carbonyl group and Formula (I-2): —R _1-2 (OH) —O—,
n1-1 represents 0 or 1,
R _1-1 represents a hydrocarbon group having 3 to 30 carbon atoms,
In formula (I-2), R _1-2 represents a trivalent hydrocarbon group.

In formula (I), one or both of X ₁ and X ₂ each independently represents formula (I-1): — (A ₁ ) _n1-1 —R _1-1 .

(Formula (I-1))
In formula (I-1): — (A ₁ ) _n1-1 —R _1-1 , A ₁ is a group _consisting of a carbonyl group and formula (I-2): —R _1-2 (OH) —O—. Represents at least one selected from
n1-1 represents 0 or 1.
R _1-1 represents a hydrocarbon group having 3 to 30 carbon atoms. The hydrocarbon group having 3 to 30 carbon atoms is the same as described above.

(Formula (I-2))
In Formula (I-2): —R _1-2 (OH) —O—, R _1-2 represents a trivalent hydrocarbon group.
As for carbon number of a trivalent hydrocarbon group, 3-30 are preferable.
The trivalent hydrocarbon group is preferably an aliphatic hydrocarbon group. The aliphatic hydrocarbon group may be linear, branched, cyclic, or a combination thereof.

In the formula (I-2), the hydroxy group may be bonded to any carbon atom constituting R _1-2 .
In formula (I-1):-(A ₁ ) _n1-1 -R _1-1 , n1-1 is 1, and A ₁ is represented by formula (I-2): -R _1-2 (OH) -O In the case _of- , R _1-2 in the formula (I-2) is bonded to a heterocyclic nitrogen atom, the oxygen atom (-O-) in the formula (I-2) is bonded to R _1-1 , R _1-2 (3 divalent hydrocarbon group) is 3 to 30 carbon atoms, between the oxygen atom (-O-) and the nitrogen atom of the heterocycle, R _1-2 (3 divalent hydrocarbon One preferred embodiment is that three or more carbon atoms of the carbon atoms of the group) are arranged side by side.

(X ₃ , X ₄ , X ₅ and X ₆ )
In the formula (I), X ₃ , X ₄ , X ₅ and X ₆ each independently represent a hydrogen atom or a hydrocarbon group.
The hydrocarbon group is not particularly limited. The hydrocarbon group may be the hydrocarbon group having 3 to 30 carbon atoms, or may be another hydrocarbon group.
X ₃ , X ₄ , X _5, and X ₆ are listed as one preferred embodiment that is a hydrogen atom.

In the formula (I), when X ₇ is a nitrogen atom, n3 is 1, and only one of X ₁ and X ₂ represents the above formula (I-1), the remaining group is a hydrogen atom, It can represent at least one selected from the group consisting of a sulfone-based protecting group, a carbamate-based protecting group, and formula (I-3): — (R ₂ —O) _n2 —H.
That is, when X ₁ represents the above formula (I-1), X ₂ is a hydrogen atom, a sulfonic-based protective group, carbamate protecting groups and formula _{(I-3) :-( R 2} -O) n2 -H And at least one selected from the group consisting of:
Also, if X ₂ represents the above formula _(I-1), X 1 is a hydrogen atom, a sulfonic-based protective group, carbamate protecting groups and formula _{(I-3) :-( R 2} -O) n2 -H And at least one selected from the group consisting of: The sulfone-based protecting group, carbamate-based protecting group, and formula (I-3) are the same as described above.

(When the heterocyclic compound is a compound represented by formula (I), X ₇ is a nitrogen atom, and n3 is 1)
The heterocyclic compound represented by the formula (I), X ₇ is a nitrogen atom, and n3 is 1 is represented by the following formula (II).

In formula (II), one or both of X ₁ and X ₂ each independently represents formula (I-1): — (A ₁ ) _n1-1 —R _1-1 .

(Formula (I-1))
In formula (I-1): — (A ₁ ) _n1-1 —R _1-1 , A ₁ is a group _consisting of a carbonyl group and formula (I-2): —R _1-2 (OH) —O—. Represents at least one selected from
n1-1 represents 0 or 1.
R _1-1 represents a hydrocarbon group having 3 to 30 carbon atoms. The hydrocarbon group having 3 to 30 carbon atoms is the same as described above.

(Formula (I-2))
In Formula (I-2): —R _1-2 (OH) —O—, R _1-2 represents a trivalent hydrocarbon group.
As for carbon number of a trivalent hydrocarbon group, 3-30 are preferable.
The trivalent hydrocarbon group is preferably an aliphatic hydrocarbon group. The aliphatic hydrocarbon group may be linear, branched, cyclic, or a combination thereof.

In the formula (I-2), the hydroxy group may be bonded to any carbon atom constituting R _1-2 .
In formula (I-1):-(A ₁ ) _n1-1 -R _1-1 , n1-1 is 1, and A ₁ is represented by formula (I-2): -R _1-2 (OH) -O In the case of-, R _1-2 in the formula (I-2) is bonded to the nitrogen atom of the piperazine ring, the oxygen atom (-O-) in the formula (I-2) is bonded to R _1-1 , R _1-2 (3 divalent hydrocarbon group) is 3 to 30 carbon atoms, between the nitrogen atoms of the oxygen atom (-O-) and piperazine ring, R _1-2 (3 divalent hydrocarbon One preferred embodiment is that three or more carbon atoms of the carbon atoms of the group) are arranged side by side.

(X ₃ , X ₄ , X ₅ and X ₆ )
In the formula (II), X ₃ , X ₄ , X ₅ and X ₆ each independently represent a hydrogen atom or a hydrocarbon group.
The hydrocarbon group is not particularly limited. The hydrocarbon group may be the hydrocarbon group having 3 to 30 carbon atoms, or may be another hydrocarbon group.
X ₃ , X ₄ , X _5, and X ₆ are listed as one preferred embodiment that is a hydrogen atom.

In the formula (II), when only one of X ₁ and X ₂ represents the above formula (I-1), the remaining groups are a hydrogen atom, a sulfone protecting group, a carbamate protecting group and the formula (I- 3) :-( R ₂ -O) may represent at least one selected from the group consisting of _n2 -H.
That is, when X ₁ represents the above formula (I-1), X ₂ is a hydrogen atom, a sulfonic-based protective group, carbamate protecting groups and formula _{(I-3) :-( R 2} -O) n2 -H And at least one selected from the group consisting of:
Also, if X ₂ represents the above formula _(I-1), X 1 is a hydrogen atom, a sulfonic-based protective group, carbamate protecting groups and formula _{(I-3) :-( R 2} -O) n2 -H And at least one selected from the group consisting of: The sulfone-based protecting group, carbamate-based protecting group, and formula (I-3) are the same as described above.

As a specific aspect of a piperazine compound, the following aspect 1 or 2 is mentioned, for example.
(Aspect 1 of piperazine compound)
Embodiment 1 of the piperazine compound is represented by the formula (II),
Both of X ₁ and X ₂ are compounds independently representing the above formula (I-1).
In the above embodiment 1, X ₃ , X ₄ , X ₅ and X ₆ are preferably hydrogen atoms.

  Specific examples of the aspect 1 include piperazine compounds 3, 5 and 8 represented by the following formula.

Piperazine compound 3

Piperazine compound 5

Piperazine compounds 8 (-C ₁₂ H ₂₅ R each independently or represents -C ₁₃ H _27.)

The piperazine compound 8 is a compound in which both R are —C ₁₂ H ₂₅ , a compound in which both R are —C ₁₃ H ₂₇ , and one R is —C ₁₂ H ₂₅ and the remaining R is —C _It may be a mixture of at least two selected from the group consisting of compounds that are ₁₃ H ₂₇ .

(Aspect 2 of piperazine compound)
Embodiment 2 of the piperazine compound is represented by the formula (II),
Only one of X ₁ and X ₂ represents formula (I-1)
The remaining groups, being a compound represents at least one selected from a hydrogen atom, a sulfonic-based protective group, carbamate protecting group and the formula _{(I-3) :-( R 2} -O) group consisting of _n2 -H .
In the above embodiment 2, X ₃ , X ₄ , X ₅ and X ₆ are preferably hydrogen atoms.

  Specific examples of the aspect 2 include piperazine compounds 1, 2, 4, 6 and 7 represented by the following formula.

Piperazine compound 1

Piperazine compound 2 (in the following structural formula, n is 1 to 10, preferably 1 to 5)

Piperazine compound 4

Piperazine compound 6

Piperazine compounds 7 (R is -C ₁₂ H _25, or, -C ₁₃ represents a H _27. Piperazine compound 7, piperazine compounds piperazine compounds wherein R is -C ₁₂ H ₂₅ and R is -C ₁₃ H ₂₇ It may be a mixture with

(When the heterocyclic compound is a compound represented by the formula (I), X ₇ is an oxygen atom or a sulfur atom, and n3 is 0)
The heterocyclic compound represented by the formula (I), wherein X ₇ is an oxygen atom or a sulfur atom, and n3 is 0 is represented by the following formula (III).

In formula (III), X ₁ is the same as formula (I-1):-(A ₁ ) _n1-1 -R _{1-1 in} formula (I), and X ₃ , X ₄ , X ₅ and X ₆ is the same respectively X _3, X _4, X ₅ and X ₆ in the formula (I), X ₈ is at least one selected from the group consisting of oxygen and sulfur atoms.

  Examples of the compound represented by the formula (III) include morpholine compounds 1 to 4 represented by the following formula.

(Morpholine Compound 1)

(Morpholine compound 2)

(Morpholine compound 3)

(Morpholine compound 4)

In morpholine compound 4 R is -C ₁₂ H _25, or represents -C ₁₃ H _27. The morpholine compound 4 may be a mixture of a morpholine compound in which R is —C ₁₂ H ₂₅ and a morpholine compound in which R is —C ₁₃ H ₂₇ .

The method for producing the heterocyclic compound is not particularly limited. For example, a conventionally well-known thing is mentioned.
Specifically, for example, at least one selected from the group consisting of piperazine, morpholine and thiomorpholine which may have a substituent, a halogen atom (chlorine, bromine, iodine, etc.), an acid halogen group (acid chloride group) , An acid bromide group, an acid iodide group, etc.) and a hydrocarbon compound having 3 to 30 carbon atoms and having at least one selected from the group consisting of glycidyloxy groups, in a solvent as necessary. Can be obtained. The substituent is the same as described above. The hydrocarbon group having 3 to 30 carbon atoms contained in the hydrocarbon compound is the same as described above.
Further, as described above piperazine compound 2, as a method for producing a piperazine compound where further having the above formula _{(I-3) :-( R 2} -O) n2 -H, for example, hydroxy as piperazine compounds 1 Examples include a method in which a piperazine compound having a group and an alkylene oxide are reacted in the presence of a metal alkoxide.

<< Content of heterocyclic compound >>
In this invention, content of the said heterocyclic compound is 0.5-20 mass% with respect to content of the said silica. When content of the said heterocyclic compound is said range, it is excellent in workability and on-ice performance. Moreover, when the content of the heterocyclic compound is within the above range, when the composition of the present invention further contains a thermally expandable microcapsule, the curing rate (vulcanization rate) of the composition is set during curing. The thermally expandable microcapsules can be sufficiently expanded by adjusting to an appropriate speed.
The content of the heterocyclic compound is excellent due to the effects of the present invention, and is excellent in silica dispersibility, or when the composition of the present invention further contains a thermally expandable microcapsule, From the viewpoint that the capsule can be sufficiently expanded, 1 to 15% by mass is preferable, and 1 to 10% by mass is more preferable.
In addition, the content of the heterocyclic compound is preferably 5% by mass or more with respect to the content of silica from the viewpoint that the performance on ice is more excellent.

<< Sulfur-containing silane coupling agent >>
The composition of the present invention contains a sulfur-containing silane coupling agent.
The sulfur-containing silane coupling agent is not particularly limited as long as it is a silane coupling agent containing a sulfur atom. The sulfur-containing silane coupling agent has a hydrolyzable group in addition to the sulfur atom.
The hydrolyzable group is not particularly limited, and examples thereof include an alkoxy group, a phenoxy group, a carboxyl group, and an alkenyloxy group. Of these, an alkoxy group is preferable. When the hydrolyzable group is an alkoxy group, the alkoxy group preferably has 1 to 16 carbon atoms, more preferably 1 to 4 carbon atoms. As a C1-C4 alkoxy group, a methoxy group, an ethoxy group, a propoxy group etc. are mentioned, for example.

The sulfur atom which a sulfur containing silane coupling agent has may comprise the group which has a sulfur atom. The sulfur atom can constitute, for example, a sulfide group (including a monosulfide group and a polysulfide group), a mercapto group, and a carbonylthio group.
The sulfur-containing silane coupling agent may further have a polysiloxane skeleton.
The polysiloxane skeleton means a polymer having a plurality of repeating units of-(Si-O)-. The polysiloxane skeleton can be linear, branched, or three-dimensional, or a combination thereof.
The sulfur-containing silane coupling agent may further have a polysiloxane skeleton, or may not have a polysiloxane skeleton.

Examples of the sulfur-containing silane coupling agent include bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, and bis (2- Trimethoxysilylethyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (3-trimethoxysilylpropyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, bis (3-trimethoxysilyl) Polysulfide silanes such as propyl) disulfide;
A silane coupling agent represented by the following formula (a);
A silane coupling agent represented by the following formula (b);
It is represented by the following formula (2) such as 3- [ethoxybis (3,6,9,12,15-pentaoxaoctacosan-1-yloxy) silyl] -1-propanethiol (Si363 manufactured by Evonik Degussa). And silane coupling agents containing mercapto groups such as γ-mercaptopropylmethyldimethoxysilane and γ-mercaptopropyltrimethoxysilane.

  Among these, from the viewpoint that the effects of the present invention (particularly on-ice performance) are excellent and wet performance is excellent, a silane coupling agent represented by the following formula (a) and a silane coupling agent represented by the following formula (b) And at least one selected from the group consisting of mercapto group-containing silane coupling agents.

-Silane coupling agent represented by Formula (a) Formula (a) is (C _L H _{2L + 1} O) ₃ —Si— (CH ₂ ) _m —S—C (═O) — (C _n H _{2n + 1} ).
In formula (a), L is 1 to 3, m is 1 to 3, and n is 1 to 15.
C _L H _{2L + 1} may be linear or branched.
(C _n H _{2n + 1} ) may be linear, branched or cyclic, or a combination thereof.

  Examples of the silane coupling agent represented by the formula (a) include 3-octanoylthio-1-propyltriethoxysilane.

_-Silane coupling agent represented by Formula (b) Formula (b) is (A) _a (B) _b (C) _c (D) _d (R ¹ ) _e SiO _{(4-2a-bcde) / 2} It is.
Formula (b) is an average composition formula.

In formula (b), A represents a divalent organic group containing a sulfide group. B represents a monovalent hydrocarbon group having 5 to 10 carbon atoms. C represents a hydrolyzable group. D represents an organic group containing a mercapto group. R ¹ represents a monovalent hydrocarbon group having 1 to 4 carbon atoms. a to e are 0 ≦ a <1, 0 <b <1, 0 <c <3, 0 ≦ d <1, and 0 ≦ e <2, and satisfy the relational expression of 0 <2a + b + c + d + e <4.
However, the case where a and d are 0 at the same time is excluded.

  One preferred embodiment of the silane coupling agent represented by the formula (b) is to have a polysiloxane skeleton.

(A)
In the above formula (b), A represents a divalent organic group containing a sulfide group (hereinafter also referred to as a sulfide group-containing organic group). The organic group can be, for example, a hydrocarbon group that may have a hetero atom such as an oxygen atom, a nitrogen atom, or a sulfur atom.
Especially, it is preferable that it is group represented by following formula (4).
^{_{* - (CH 2) n -S}} x - (CH 2) n - * (4)
In said formula (4), n represents the integer of 1-10, and it is preferable that it is an integer of 2-4 especially.
In said formula (4), x represents the integer of 1-6, and it is preferable that it is an integer of 2-4 especially.
In the above formula (4), * indicates a bonding position.
Specific examples of the group represented by the formula (4), for ^{_{example, * -CH 2 -S 2 -CH 2}} - *, * -C 2 H 4 -S 2 -C 2 H 4 - *, * - _{C 3 H 6 -S 2 -C 3} H 6 - *, * -C 4 H 8 -S 2 -C 4 H 8 - *, * -CH 2 -S 4 -CH 2 - *, * -C 2 H _{4 -S 4 -C 2 H 4 -} *, * -C 3 H 6 -S 4 -C 3 H 6 - *, * -C 4 H 8 -S 4 -C 4 H 8 - * , and the like.

(B)
In said formula (b), B represents a C1-C10 monovalent hydrocarbon group, As a specific example, a hexyl group, an octyl group, a decyl group etc. are mentioned, for example. B can protect the mercapto group.
B is preferably a monovalent hydrocarbon group having 8 to 10 carbon atoms from the viewpoint of being excellent in the effects (particularly processability) of the present invention and excellent in dispersion of silica.

(C)
In the above formula (b), C represents a hydrolyzable group, and specific examples thereof include an alkoxy group, a phenoxy group, a carboxyl group, an alkenyloxy group, and the like. Especially, it is preferable that it is group represented by following formula (5).
^* -OR ² (5)

In the above formula (5), R ² is an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aralkyl group (aryl alkyl group) or an alkenyl group having 2 to 10 carbon atoms having 7 to 10 carbon atoms Represents. In particular, R ² is preferably an alkyl group having 1 to 5 carbon atoms.

Specific examples of the alkyl group having 1 to 20 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, an octyl group, a decyl group, and an octadecyl group.
Specific examples of the aryl group having 6 to 10 carbon atoms include a phenyl group and a tolyl group.
Specific examples of the aralkyl group having 7 to 10 carbon atoms include a benzyl group and a phenylethyl group.
Specific examples of the alkenyl group having 2 to 10 carbon atoms include a vinyl group, a propenyl group, and a pentenyl group.
In the above formula (5), * indicates a bonding position.

(D)
In the above formula (b), D represents an organic group containing a mercapto group. Especially, it is preferable that it is group represented by following formula (6).
^{_{* - (CH 2) m -SH}} (6)

In said formula (6), m represents the integer of 1-10. In particular, m is preferably an integer of 1 to 5.
In the above formula (6), * indicates a bonding position.

Specific examples of the group represented by the formula _{^{(6), * -CH 2 SH}} , * -C 2 H 4 SH, * -C 3 H 6 SH, * -C 4 H 8 SH, * -C 5 ^{_{H 10 SH, * -C 6 H}} 12 SH, * -C 7 H 14 SH, * -C 8 H 16 SH, * -C 9 H 18 SH, include * -C ₁₀ H ₂₀ SH.

(R ¹ )
In the above formula (b), R ¹ represents a monovalent hydrocarbon group having 1 to 4 carbon atoms. For example, a methyl group, an ethyl group, a propyl group, and a butyl group are mentioned.

(Ae)
In the above formula (b), a to e are 0 ≦ a <1, 0 <b <1, 0 <c <3, 0 ≦ d <1, 0 ≦ e <2, 0 <2a + b + c + d + e <. 4 is satisfied.

  The silane coupling agent represented by the formula (b) is excellent due to the effects of the present invention, and is preferably greater than 0 (0 <a) from the viewpoint of excellent wet performance or low rolling resistance. It is more preferable that <a ≦ 0.50.

  In the above formula (b), b is preferably 0.10 ≦ b ≦ 0.89 from the viewpoint of being excellent in the effects (particularly workability) of the present invention and excellent in silica dispersion.

  In the above formula (b), c is preferably 1.2 ≦ c ≦ 2.0 from the viewpoint that it is excellent due to the effects of the present invention and is excellent in silica dispersion.

  In the above formula (b), d is preferably 0.1 ≦ d ≦ 0.8 from the viewpoint that it is excellent due to the effects of the present invention and is excellent in silica dispersion.

  In the above formula (b), 0 <2a + b + c + d + e ≦ 3 is preferable from the viewpoint that the effect of the present invention (especially on-ice performance) is excellent and the balance between wet performance and low rolling resistance is excellent.

  The silane coupling agent represented by the formula (b) has good dispersibility of silica, is superior in the effects of the present invention (particularly performance on ice), and is excellent in wet performance and low rolling resistance. In (b), A is a group represented by the above formula (4), C is a group represented by the above formula (5), and D is a group represented by the above formula (6). A is a group represented by the above formula (4), C is a group represented by the above formula (5), D is a group represented by the above formula (6), and B is It is more preferably a monovalent hydrocarbon group having 8 to 10 carbon atoms.

  The weight average molecular weight of the silane coupling agent represented by the formula (b) is preferably 500 to 2300, more preferably 600 to 1500 from the viewpoint that it is excellent in the effects (particularly processability) of the present invention and is excellent in silica dispersion. It is more preferable that The molecular weight of the silane coupling agent represented by the formula (b) is a weight average molecular weight determined in terms of polystyrene by gel permeation chromatography (GPC) using toluene as a solvent.

  Mercapto equivalent of silane coupling agent represented by formula (b) by acetic acid / potassium iodide / potassium iodate addition-sodium thiosulfate solution titration method is 550 to 1900 g / mol from the viewpoint of excellent vulcanization reactivity. It is preferable that it is 600-1800 g / mol.

-Silane coupling agent represented by Formula (2) Formula (2) is as follows.

In formula (2), R ²¹ represents an alkoxy group having 1 to 8 carbon atoms. R ²² represents a polyether group having a hydrocarbon group at the terminal. R ²³ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. R ²⁴ represents an alkylene group having 1 to 30 carbon atoms. l represents an integer of 1 to 2, m represents an integer of 1 to 2, n represents an integer of 0 to 1, and l, m, and n satisfy the relational expression of l + m + n = 3. A plurality of R ²¹ when l is 2 may be the same or different, and a plurality of R ²² when m is 2 may be the same or different.

(R ²¹⁾
In the above formula (2), R ²¹ represents an alkoxy group having 1 to 8 carbon atoms, and among these, an alkoxy group having 1 to 3 carbon atoms is preferable because a tire excellent in low rolling resistance can be obtained. Examples of the alkoxy group having 1 to 3 carbon atoms include a methoxy group and an ethoxy group.
(R ²² )
In the above formula (2), R ²² represents a polyether group having a terminal hydrocarbon group. The polyether group is a group having two or more ether bonds.
As a suitable aspect of the polyether group which has a hydrocarbon group at the terminal, group represented by following formula (5) is mentioned.

(R ⁵¹ )
In the above formula (5), R ⁵¹ represents a linear alkyl group, a linear alkenyl group, or a linear alkynyl group, and among them, a linear alkyl group is preferable. As the linear alkyl group, a linear alkyl group having 1 to 20 carbon atoms is preferable, and a linear alkyl group having 8 to 15 carbon atoms is more preferable. Specific examples of the linear alkyl group having 8 to 15 carbon atoms include octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group and the like, and tridecyl group is particularly preferable.
(R ⁵² )
In the above formula (5), R ⁵² represents a linear alkylene group, a linear alkenylene group or a linear alkynylene group, and among them, a linear alkylene group is preferable. As said linear alkylene group, a C1-C2 linear alkylene group is preferable and an ethylene group is more preferable.
(P)
In said formula (5), p represents the integer of 1-10 and it is preferable that it is 3-7.
In the above formula (5), * indicates a bonding position.

(R ²³⁾
In the formula (2), R ²³ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.
(R ²⁴⁾
In the above formula (2), R ²⁴ represents an alkylene group having 1 to 30 carbon atoms, among them preferably an alkylene group having 1 to 12 carbon atoms, more preferably an alkylene group having 1 to 5 carbon atoms. Specific examples of the alkylene group having 1 to 5 carbon atoms include a methylene group, an ethylene group, a trimethylene group, and a propylene group.
(L, m, n)
In said formula (2), l represents the integer of 1-2 and it is preferable that it is 1. In said formula (2), m represents the integer of 1-2 and it is preferable that it is 2. n represents an integer of 0 to 1, and is preferably 0. l, m, and n satisfy the relationship of l + m + n = 3.

  Specific examples of the silane coupling agent represented by the formula (2) include 3- [ethoxybis (3,6,9,12,15-pentaoxaoctacosan-1-yloxy) silyl] -1- Examples include propanethiol (Si363 manufactured by Evonik Degussa).

  The method for producing the sulfur-containing silane coupling agent is not particularly limited. For example, a conventionally well-known thing is mentioned.

In this invention, content of the said sulfur containing silane coupling agent is 1-25 mass% with respect to the said silica.
The content of the sulfur-containing silane coupling agent is superior to the effect of the present invention (particularly on-ice performance), and from the viewpoint of excellent balance between on-ice performance, wet performance, and low rolling resistance, 3% relative to the silica. -20 mass% is preferable and 4-15 mass% is more preferable.

(Organic material incompatible with diene rubber)
The composition of the present invention preferably further contains an organic material that is incompatible with the diene rubber from the viewpoint of being superior in performance on ice.
In the present invention, the organic substance is not compatible with the diene rubber.

  The organic substance can be in the form of particles.

Examples of the organic substance include particles having high hardness; thermally expandable microcapsules; and a cured product obtained by curing a crosslinkable oligomer or polymer that is incompatible with the diene rubber. When particles having a high hardness are further contained, a scratching effect is produced and the performance on ice is more excellent. When the thermally expandable microcapsule is further contained, a water film removing performance is generated, and the performance on ice is more excellent. When a cured product obtained by curing a crosslinkable oligomer or polymer that is incompatible with the diene rubber is further contained, an incompatible island structure is generated in the diene rubber, and the performance on ice is more excellent.
One example of a preferable embodiment of the organic material includes at least a thermally expandable microcapsule.

-Thermally expansible microcapsule The said thermally expansible microcapsule is the thermally expansible thermoplastic resin particle which included the liquid which can be vaporized with a heat | fever 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;

Cured product obtained by curing a cross-linkable oligomer or polymer that is not compatible with the diene rubber The cured product obtained by curing the cross-linkable oligomer or polymer that is not compatible with the diene rubber is, for example, Japanese Patent Application Laid-Open No. 2015-066766. Examples thereof include those similar to the cured product (C) obtained by curing a crosslinkable oligomer or polymer (c1) that is incompatible with the diene rubber (A).

  From the viewpoint that the content of the organic material incompatible with the diene rubber (for example, thermally expandable microcapsules) is superior due to the effect of the present invention (particularly performance on ice), the content of the diene rubber is 100 parts by mass. 0.5-30 mass parts is preferable, and 1-20 mass parts is more preferable.

The mass ratio of the content of the heterocyclic compound to the content of the organic material incompatible with the diene rubber (the content of the heterocyclic compound / the content of the organic material incompatible with the diene rubber) is the present invention. 0.0025 to 48 is preferable, and 0.003 to 45 is more preferable from the viewpoint of being more excellent in the effect (particularly on-ice performance).
The mass ratio is preferably 0.4 to 2 from the viewpoint that the effect of the present invention (particularly performance on ice) is superior.

When the organic material incompatible with the diene rubber is the thermally expandable microcapsule, the mass ratio of the heterocyclic compound content to the thermally expandable microcapsule content (the heterocyclic compound content / The content of the thermally expandable microcapsule) is superior to the effect of the present invention (especially on-ice performance), and when the composition of the present invention is cured, the curing speed (vulcanization speed) of the composition is adjusted to an appropriate speed. And from a viewpoint that the said thermally expansible microcapsule can fully be expanded, 0.0025-48 are preferable and 0.003-45 are more preferable.
The mass ratio is preferably 0.4 to 2 from the viewpoint that the effect of the present invention (particularly performance on ice) is superior.

(Additive)
The composition of this invention can contain an additive further in the range which does not impair the effect and objective as needed. Examples of additives include rubbers other than diene rubbers; fillers other than silica (for example, carbon black); silane coupling agents other than sulfur-containing silane coupling agents; vulcanization accelerators; zinc oxide; stearic acid; Anti-aging agents; processing aids; plasticizers; vulcanizing agents such as sulfur; peroxides and the like commonly used in tire rubber compositions. The content of the additive can be appropriately selected.

(Carbon black)
The composition of the present invention may further contain carbon black.
The carbon black is not particularly limited. As carbon black, for example, SAF (Super Abbreviation Furnace. The same applies hereinafter) -HS (High Structure. Same applies hereinafter), SAF, ISAF (Intermediate Super Absorption Furnace. Same applies hereinafter) -HS, ISAF, ISAF-LrSurLS. The same can be used, and various grades such as IISAF (Intermediate ISAF) -HS, HAF (High Abbreviation Furnace, and so on) -HS, HAF, HAF-LS, FEF (Fast Extracting Furnace), and the like can be used.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 50 to 200 m ² / g from the viewpoint of being excellent in workability. The nitrogen adsorption specific surface area of carbon black shall be measured according to JIS K6217-2.

  1-50 mass parts is preferable with respect to 100 mass parts of diene rubbers, and, as for content of carbon black, 1-20 mass parts is more preferable.

(Plasticizer)
Examples of the plasticizer include carboxylic ester plasticizers; phosphate ester plasticizers; sulfonate ester plasticizers; oils such as paraffinic process oils, naphthenic process oils, and aromatic process oils. Is mentioned.

(Method for producing rubber composition for studless tire)
The method for producing the composition of the present invention is not particularly limited. Specific examples thereof include, for example, a method of mixing each component described above under a condition of 100 to 200 ° C. using a known method and apparatus (for example, a Banbury mixer, a kneader, a roll, etc.).

(Curing of rubber composition for studless tire of the present invention)
Moreover, the composition of this invention can be hardened by vulcanizing or bridge | crosslinking the composition of this invention, for example.
Conditions for curing (vulcanizing or crosslinking) the composition of the present invention are not particularly limited. For example, the temperature condition during curing can be set to 130 to 200 ° C.

<< Rubber hardness >>
In the present invention, after curing of the composition of the present invention, the rubber hardness of JIS standard type A at a temperature of 0 ° C. is 55 or less. When the rubber hardness is in a predetermined range, the rubber after curing under low temperature conditions can be excellent in flexibility, and the performance on ice is excellent.
In the present invention, for example, the rubber hardness can be set within a predetermined range by controlling the blending amount of a plasticizer such as silica or oil or the dispersion state of silica.
The above-mentioned “JIS A-type rubber hardness at 0 ° C.” conforms to JIS K 6253-3: 2012 “Vulcanized rubber and thermoplastic rubber-Determination of hardness-Part 3: Durometer hardness”. This means the hardness of rubber measured under the condition of a temperature of 0 ° C. by durometer type A.
In the present invention, the rubber hardness is measured by using a rubber after the composition of the present invention is heated and cured for 10 minutes at 170 ° C.

  The rubber hardness is preferably 40 to 55, more preferably 42 to 55, from the viewpoint that the effect of the present invention (particularly performance on ice) is superior.

For example, a pneumatic tire can be produced using the composition of the present invention, and more specifically, a studless tire can be produced.
The constituent member of a pneumatic tire (for example, a studless tire) that can be produced with the composition of the present invention is not particularly limited. Examples of the member include a tire tread such as a cap tread; a sidewall; and a bead filler.
It is preferable to form a tire tread of a pneumatic tire (for example, a studless tire) using the composition of the present invention, and it is more preferable to form a cap tread.

[studless tire]
The studless tire of this invention is a studless tire which has arrange | positioned the rubber composition for tires of this invention in the cap tread.
The rubber composition used for the cap tread is not particularly limited as long as it is a rubber composition for tires of the present invention (composition of the present invention).
The cap tread is a portion that is in direct contact with the road surface in the studless tire.
The studless tire of the present invention is not particularly limited except that the composition of the present invention is disposed on the cap tread (the cap tread is formed of the composition of the present invention).
FIG. 1 is a schematic partial sectional view of a tire representing an example of an embodiment of the studless tire of the present invention. The present invention is not limited to the attached drawings.

In FIG. 1, the studless tire has a bead portion 1, a sidewall portion 2, and a tire tread portion 3. 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 portion of the carcass layer 4 is folded from the inside of the tire to the outside around the bead core 5 and the bead filler 6. It is rolled up. In the tire tread portion 3, a belt layer 7 is disposed over the circumference of the tire outside the carcass layer 4. In the bead portion 1, a rim cushion 8 is disposed at a portion in contact with the rim.
The tire tread portion 3 has a cap tread on the belt layer 7.
The above-described composition of the present invention is disposed on the cap tread in the tire tread portion 3.

  The studless tire of the present invention can be manufactured, for example, according to a conventionally known method.

The studless tire of the present invention can be produced, for example, by curing (vulcanizing or cross-linking) the composition of the present invention under the above-described temperature conditions during curing to form a cap tread, for example.
The studless tire of the present invention can be used in winter.
The studless tire of the present invention can be used on roads that are dry or wet, snow or non-snow, or frozen or non-frozen.
As a gas filled in the studless tire of the present invention, for example, an inert gas such as nitrogen, argon, helium, etc. can be used in addition to air having a normal or oxygen partial pressure adjusted.

The present invention will be specifically described below with reference to examples. However, the present invention is not limited to these.
<< Production of Piperazine Compound >>
<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 For 1 hour. The reaction solution was washed with aqueous potassium carbonate solution, extracted with dichloromethane, and dehydrated with anhydrous magnesium sulfate. Anhydrous magnesium sulfate was filtered off and concentrated to obtain piperazine compound 1 represented by the following formula.
(Piperazine Compound 1)

<Synthesis of Piperazine Compound 2>
39.6 g of the piperazine compound 1 obtained as described above, 13.2 g of ethylene oxide, and 0.004 g of sodium methoxide were reacted. The reaction solution was neutralized with phosphoric acid and filtered to obtain a piperazine compound 2 represented by the following formula. N in the following formula is 3.
(Piperazine Compound 2)

<Synthesis of Piperazine Compound 3>
66.6 g of 1-bromooctadecane (produced by Tokyo Chemical Industry Co., Ltd.) and 19.04 g of piperazine hexahydrate (piperazine hexahydrate produced by Nippon Emulsifier Co., Ltd.) in tetrahydrofuran and dichloromethane at room temperature for 1 hour. Reacted. The reaction solution was washed with aqueous potassium carbonate solution, extracted with dichloromethane, and dehydrated with anhydrous magnesium sulfate. Anhydrous magnesium sulfate was filtered off and concentrated to obtain a piperazine compound 3 represented by the following formula.
(Piperazine Compound 3)

<Synthesis of Piperazine Compound 4>
Stearoyl chloride (manufactured by Tokyo Chemical Industry Co., Ltd.) 30.3 g, 1- (2-hydroxyethyl) piperazine (Japanese emulsifier Co., Ltd. hydroxyethylpiperazine) 13.0 g, and triethylamine 15.2 g in toluene The mixture was reacted for 1 hour at 0 ° C. The reaction solution was washed with an aqueous sodium carbonate solution, extracted with toluene, and dehydrated with anhydrous magnesium sulfate. Anhydrous magnesium sulfate was filtered off and concentrated to obtain piperazine compound 4 represented by the following formula.
(Piperazine Compound 4)

<Synthesis of Piperazine Compound 5>
Stearoyl chloride (manufactured by Tokyo Chemical Industry Co., Ltd.) 60.6 g, piperazine hexahydrate (Japanese emulsifier Co., Ltd. piperazine hexahydrate) 19.04 g, and triethylamine 30.4 g in toluene at 0 ° C. The reaction was carried out for 1 hour under the following conditions. The reaction solution was washed with an aqueous sodium carbonate solution, extracted with toluene, and dehydrated with anhydrous magnesium sulfate. The anhydrous magnesium sulfate was filtered off and concentrated to obtain a piperazine compound 5 represented by the following formula.
(Piperazine Compound 5)

<Synthesis of Piperazine Compound 6>
18.5 g of 2-ethylhexyl glycidyl ether (Epogosei (registered trademark) 2EH manufactured by Yokkaichi Synthesis Co., Ltd.) and 13.0 g of 1- (2-hydroxyethyl) piperazine (hydroxyethylpiperazine manufactured by Nippon Emulsifier Co., Ltd.) By reacting at 60 ° C. for 4 hours, piperazine compound 6 represented by the following formula was obtained.

The results of ¹ H-NMR of piperazine compound 6 are as follows.
¹ H-NMR (400 MHz, CDCl ₃ ): δ 3.85 (m, 1H), 3.60 (t, 2H), 3.30-3.47 (m, 4H), 2.65 (m, 2H) ), 2.54 (t, 4H), 2.46 (t, 2H), 2.38 (dd, 2H), 1.52 (q, 1H), 1.26-1.41 (m, 8H) , 0.89 (t, 5H), 0.85 (s, 1H)
(Piperazine Compound 6)

<Synthesis of Piperazine Compound 7>
28.4 g of C12-13 mixed alcohol glycidyl ether (Epogosei (registered trademark) EN manufactured by Yokkaichi Synthesis Co., Ltd., a mixture of C12 alcohol glycidyl ether and C13 alcohol glycidyl ether) and 1- (2-hydroxyethyl) piperazine ( Piperazine compound 7 represented by the following formula (R is -C ₁₂ H ₂₅ , or-by reacting 13.0 g of Nippon Emulsifier Co., Ltd. (hydroxyethylpiperazine) under the condition of 60 ° C for 4 hours. Represents C ₁₃ H _27. Piperazine compound 7 was a mixture of a piperazine compound in which R is —C ₁₂ H ₂₅ and a piperazine compound in which R is —C ₁₃ H ₂₇ .
(Piperazine Compound 7)

<Synthesis of Piperazine Compound 8>
C12-13 mixed alcohol glycidyl ether (Epogosei (registered trademark) EN manufactured by Yokkaichi Synthesis Co., Ltd.) 56.8 g, piperazine hexahydrate (piperazine hexahydrate manufactured by Nippon Emulsifier Co., Ltd.) 19.04 g, ethanol The reaction was allowed to proceed for 6 hours at 60 ° C. The reaction solution was washed with saturated brine, extracted with ethyl acetate, and dried over anhydrous magnesium sulfate. By filtering off anhydrous magnesium sulfate and concentrating, piperazine compound 8 represented by the following formula (R each independently represents —C ₁₂ H ₂₅ or —C ₁₃ H ₂₇ ) was obtained.
(Piperazine Compound 8)

<Synthesis of Morpholine Compound 4>
Reaction of 28.4 g of C12-13 mixed alcohol glycidyl ether (Epogosei registered trademark EN manufactured by Yokkaichi Synthesis Co., Ltd.) and 8.7 g of morpholine (manufactured by Tokyo Chemical Industry Co., Ltd.) for 4 hours at 60 ° C. be to, morpholine represented by the following compound 4 (R is -C ₁₂ H _25, or represents. a -C ₁₃ H ₂₇₎ was obtained. The morpholine compound 4 is a mixture of a morpholine compound in which R is —C ₁₂ H ₂₅ and a morpholine compound in which R is —C ₁₃ H ₂₇ .
(Morpholine compound 4)

<< Manufacture of a composition for studless tires >>
Each component of the following Table 1 was blended with the composition (parts by mass) shown in the same table.
Specifically, first, the components excluding sulfur and the vulcanization accelerator among the components shown in Table 1 below were raised to around 150 ° C. using a 1.7 liter closed Banbury mixer, and then 5 After mixing for a minute, it was discharged and cooled to room temperature to obtain a masterbatch. Furthermore, using the Banbury mixer, sulfur and a vulcanization accelerator were mixed with the obtained master batch to obtain a rubber composition for a studless tire (hereinafter sometimes referred to as “composition”).

  The rubber compositions for studless tires were produced in the same manner as in Table 1 for each of Tables 2 to 4.

<Hardness of cured product (rubber hardness after curing)>
The composition produced as described above was cured (vulcanized) by heating for 10 minutes in a mold having a cylindrical shape at 170 ° C.
The hardness (rubber hardness) of the cured rubber obtained as described above is JIS K 6253-3: 2012 “Vulcanized rubber and thermoplastic rubber-Determination of hardness-Part 3: Durometer hardness”. In accordance with a durometer type A, the measurement was performed at a temperature of 0 ° C.

<Evaluation>
The following evaluation was performed using the composition manufactured as described above. The results are shown in Tables 1 to 4, respectively. In each table, for each evaluation item, the evaluation result of each example was expressed as an index with respect to the evaluation result (100) of the reference example.

(Mooney viscosity)
The Mooney viscosity (ML _{1 + 4} ) at 100 ° C. was measured according to the method of JIS K6300-1: 2013. The smaller the Mooney viscosity index, the better the processability.
In the present invention, when the index is less than 100, the processability is excellent. The index is preferably 90 or more.

(Pain effect)
The rubber composition for studless tires produced as described above was vulcanized for 20 minutes at 160 ° C., and the resulting vulcanized rubber was used in accordance with ASTM D6204 and at 100 ° C. under the conditions of RPA2000 ( The strain shear stress G ′ (0.56%) with a strain of 0.56% and the strain shear stress G ′ (100%) with a strain of 100% are measured with an α-Technology strain shear stress measuring machine. '= G' (0.56%)-G '(100%) was calculated.
-Evaluation criterion of the Payne effect The smaller the index of ΔG ', the better the reduction or suppression of the Payne effect (the better the dispersibility of the silane).

(Performance on ice)
The composition obtained as described above was press vulcanized at 170 ° C. for 10 minutes in a predetermined mold to prepare a vulcanized rubber test piece.
A vulcanized rubber test piece was attached to a flat cylindrical base rubber and measured with an inside drum type on-ice friction tester, measuring temperature: −1.5 ° C., load: 5.5 kg / cm ³ , drum rotation speed: 25 km / hour Under the conditions, the friction coefficient on ice was measured. 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 reference example in same table) × 100
The coefficient of friction coefficient on ice obtained as described above is shown in the column of “performance on ice” in each table. The larger 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.
In the present invention, when the index exceeds 100, it is assumed that the performance on ice when the tire is made is excellent.

Details of each component shown in the above tables are as follows.
NR: natural rubber, TSR20 (Tg: -67 ° C)

  BR1: Unmodified butadiene rubber, Nipol 1220 (manufactured by Zeon Corporation), Tg-105 ° C., weight average molecular weight 470,000

  BR2: glycidylamine-modified butadiene rubber, Asaprene E40 (Asahi Kasei Co., Ltd.), Tg-89 ° C., weight average molecular weight 370,000

SBR1: unmodified styrene butadiene rubber (non-oil extended), trade name Nipol 1502 (manufactured by Nippon Zeon Co., Ltd.), Tg-55 ° C., weight average molecular weight 4.5 × 10 ⁵

SBR2: unmodified styrene butadiene rubber (Oil Exhibition), trade name Nipol 1739 (manufactured by Nippon Zeon Co., Ltd.), Tg-39 ° C., weight average molecular weight 7.5 × 10 ⁵ . SBR2 contains 37.5 parts by mass of oil-extended oil with respect to 100 parts by mass of net SBR. The net SBR in SBR2 is 72.7% by weight. In the column of SBR2 in the table, the upper value is the amount of SBR2 used, and the lower value is the amount of net SBR in SBR2.

Silica 1: Zeosil 1165MP (CTAB adsorption specific surface area = 159 m ² / g, manufactured by Rhodia)
Silica 2: Silica, Rhodia Zeosil PREMIUM 200MP, CTAB adsorption specific surface area 200 m ² / g
Silica 3: silica, Rhodia Zeosil 1115MP, CTAB adsorption specific surface area 110 m ² / g

  ・ Sulfur-containing silane coupling agent: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide, manufactured by Evonik Degussa)

Carbon black: Seast 6 (N ₂ SA = 116 m ² / g, manufactured by Tokai Carbon Co., Ltd.)

・ Zinc oxide: 3 types of zinc oxide (manufactured by Shodo Chemical Industry Co., Ltd.)
・ Stearic acid: Bead stearic acid YR (manufactured by NOF Corporation)
・ Anti-aging agent: 6PPD (manufactured by Flexis)

・ Sulfur: Fine sulfur with Jinhua stamp oil (manufactured by Tsurumi Chemical Co., Ltd.)
・ Vulcanization accelerator 1: CBS, Noxeller CZ-G (Vulcanization accelerator CBS, manufactured by Ouchi Shinsei Chemical Co., Ltd.)
・ Vulcanization accelerator 2: DPG, Noxeller D (Vulcanization accelerator DPG, manufactured by Ouchi Shinsei Chemical Co., Ltd.)

  ・ Plasticizer: Oil, Extract No. 4 S (manufactured by Showa Shell Sekiyu KK)

  -Thermally expandable microcapsules: Microsphere F100 (manufactured by Matsumoto Yushi Co., Ltd.)

Piperazine compound 7: Piperazine compound 7 synthesized as described above
Morpholine compound 4: Morpholine compound 4 synthesized as described above

Comparative piperazine compound 1: Hydroxyethylpiperazine, 1- (2-hydroxyethyl) piperazine manufactured by Nippon Emulsifier Co., Ltd. Comparative piperazine compound 2: Reagent [3- (1-piperazinyl) propyl] triethoxysilane) Comparative piperazine compound 2 is silicon Has atoms.

As is apparent from the results shown in Table 1, Comparative Example 1 in which the content of the predetermined heterocyclic compound exceeds the predetermined range was inferior in performance on ice to Reference Example 1.
In Comparative Example 2 in which the content of the predetermined heterocyclic compound is less than the predetermined range, the processability is comparable to that of Reference Example 1, and the performance on ice is inferior to that of Reference Example 1.
Comparative Example 3, which did not contain a predetermined heterocyclic compound and instead contained a piperazine compound having a hydroxyethyl group, was inferior to the performance on ice than that of Reference Example 1.
The comparative example 4 which does not contain a predetermined heterocyclic compound and instead contains a piperazine compound having a silicon atom was inferior to the performance on ice than the reference example 1.
Comparative Example 5 in which the rubber hardness exceeded a predetermined range was inferior in workability and on-ice performance to Reference Example 1.

  In contrast, the composition of the present invention was excellent in processability and performance on ice.

As is clear from the results shown in Table 2, Comparative Example 6 in which the content of the predetermined heterocyclic compound exceeds the predetermined range was inferior in performance on ice to Reference Example 2.
In Comparative Example 7 in which the content of the predetermined heterocyclic compound was less than the predetermined range, the processability was comparable to that of Reference Example 2, and the performance on ice was inferior to that of Reference Example 2.

  In contrast, the composition of the present invention was excellent in processability and performance on ice.

As is apparent from the results shown in Table 3, Comparative Example 8 in which the content of the predetermined heterocyclic compound exceeds the predetermined range was inferior in performance on ice to Reference Example 3.
In Comparative Example 9 in which the content of the predetermined heterocyclic compound was less than the predetermined range, the processability was comparable to that of Reference Example 3, and the performance on ice was inferior to that of Reference Example 3.

  In contrast, the composition of the present invention was excellent in processability and performance on ice.

As is clear from the results shown in Table 4, the comparative example 10 in which the average glass transition temperature of the diene rubber exceeds the predetermined range is inferior to the reference example 1 in workability and performance on ice.
In Comparative Example 11 in which the silica content exceeds the predetermined range, the sulfur-containing silane coupling agent is not included, and the rubber hardness exceeds the predetermined range, the workability and the performance on ice are inferior to those of Reference Example 1.

  In contrast, the composition of the present invention was excellent in processability and performance on ice.

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)

Diene rubber,
Silica,
A heterocyclic compound having a hydrocarbon group having 3 to 30 carbon atoms and at least one heterocyclic ring selected from the group consisting of a piperazine ring, a morpholine ring and a thiomorpholine ring (provided that the heterocyclic compound has a silicon atom). Not)
Containing a sulfur-containing silane coupling agent,
The diene rubber has an average glass transition temperature of less than −60 ° C .;
The silica content is 30 to 150 parts by mass with respect to 100 parts by mass of the diene rubber.
The content of the heterocyclic compound is 0.5 to 20% by mass with respect to the silica,
Content of the said sulfur containing silane coupling agent is 1-25 mass% with respect to the said silica,
A rubber composition for studless tires, wherein the rubber hardness of JIS-regulated Type A at a temperature of 0 ° C. after curing is 55 or less. The rubber composition for studless tires according to claim 1, wherein the heterocyclic compound is a compound represented by the following formula (I).

In the formula (I), X ₇ represents at least one selected from the group consisting of a nitrogen atom, an oxygen atom and a sulfur atom,
X ₃ , X ₄ , X ₅ and X ₆ each independently represent a hydrogen atom or a hydrocarbon group.
If X ₇ is a nitrogen atom, n3 is 1, one or both of X ₁ and X ₂ are, each independently, formula _{(I-1) :-( A 1} ) n1-1 -R 1 _-1 for
When only one of X ₁ and X ₂ represents formula (I-1), the remaining groups are a hydrogen atom, a sulfone protecting group, a carbamate protecting group, and formula (I-3): — (R ₂ -O) represents at least one selected from the group consisting of _n2 -H,
In formula (I-3), each R ₂ independently represents a divalent hydrocarbon group,
n2 represents 1-10.
When X ₇ is at least one selected from the group consisting of an oxygen atom and a sulfur atom, n3 represents 0, and X ₁ represents the formula (I-1):-(A ₁ ) _n1-1 -R _1- Represents ₁ .
In Formula (I-1), A ₁ represents at least one selected from the group consisting of a carbonyl group and Formula (I-2): —R _1-2 (OH) —O—,
n1-1 represents 0 or 1,
R _1-1 represents a hydrocarbon group having 3 to 30 carbon atoms,
In formula (I-2), R _1-2 represents a trivalent hydrocarbon group. The heterocyclic compound is a compound represented by the formula (I), X ₇ is a nitrogen atom, n3 is 1,
The rubber composition for studless tires according to claim 2, wherein both X ₁ and X ₂ independently represent the formula (I-1). The heterocyclic compound is a compound represented by the formula (I), X ₇ is a nitrogen atom, n3 is 1,
Only one of X ₁ and X ₂ represents the formula (I-1),
The remaining groups, represents at least one hydrogen atom, sulfone protecting groups, carbamate protecting groups and formula (I-3) is selected from :-( R ₂ -O) group consisting of _n2 -H, claim 2 The rubber composition for studless tires described in 1. In formula (I-3), R ₂ independently represents a divalent hydrocarbon group, and n2 represents 1 to 10.   Furthermore, the rubber composition for studless tires of any one of Claims 1-4 containing a thermally expansible microcapsule.   The mass ratio (content of heterocyclic compound / content of thermally expandable microcapsule) of the content of the heterocyclic compound with respect to the content of the thermally expandable microcapsule is 0.0025 to 48. The rubber composition for studless tires described in 1.   The rubber composition for a studless tire according to claim 5 or 6, wherein a content of the thermally expandable microcapsule is 0.5 to 20 parts by mass with respect to 100 parts by mass of the diene rubber.   The studless tire which has arrange | positioned the rubber composition for studless tires of any one of Claims 1-7 in the cap tread.