JP2012102255A - Rubber composition and pneumatic tire using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition capable of certainly performing scraping effect on an icy or snowy road and capable of improving fuel consumption of a tire by restraining excessive gripping while performing a studless effect, and a pneumatic tire using the same.SOLUTION: The rubber composition includes (A) a rubber component made of a natural rubber and/or a diene-based synthetic rubber, (B) an inorganic filler, (C) an organic silicon compound having a cyclic structure including a nitrogen atom and a silicon atom, one or more sulfur atoms in the molecule, and a portion with one or more groups with a small steric hindrance bonded with the silicon atom, (D) a fine particle-containing fiber including fine particles of at least one selected from the group consisting of a metal oxide, a metal carbonate and a clay mineral containing a metal, and a hydrophilic resin, and (E) a foaming agent. Also provided is a pneumatic tire using the rubber composition for a tire tread part.

Description

  The present invention relates to a rubber composition and a pneumatic tire using the rubber composition, and more particularly, suitable for a pneumatic tire capable of improving tire fuel efficiency by suppressing excessive grip while exhibiting a studless effect. The present invention relates to a rubber composition and a pneumatic tire using the same.

Since the regulation of spike tires, various studies have been made particularly on the tread portion of the tire in order to improve the braking performance and driving performance (on-ice performance) of the tire on an icy and snowy road surface.
For example, by mixing hollow fibers in a tread rubber of a tire, water on an icy and snowy road surface is eliminated at the hollow portion of the hollow fibers, and the performance on ice of the tire is improved. However, in this case, there is a problem that the hollow fiber cannot maintain a hollow shape due to pressure, rubber flow, temperature, and the like at the time of molding the tread rubber, and the on-ice performance of the tire cannot be obtained sufficiently.

  In response to this problem, 1) In a tire using a rubber composition containing a foaming agent-containing fiber in a tread portion, by forming a micro drainage groove in the tread portion, the drainage performance of the tire is improved and the performance on ice is improved. Technology to improve (for example, see Patent Documents 1 and 2) 2) In a tire using a rubber composition containing fine particle-containing organic fibers in the tread portion, by increasing the content of fine particles contained in the organic fibers, In addition to the ability to remove the water film of the tread, a technique (for example, see Patent Document 3) that improves the scratching effect and further improves the performance on ice is known.

However, in each of the technologies described in Patent Documents 1 to 3, if the on-ice performance of the tire is further improved, the wear resistance deteriorates as the grip is improved, and excessive grip is generated. Since it becomes difficult to carry forward, there are problems such as poor fuel economy, and further improvements are required.
As another approach for improving the performance on ice, a method of incorporating fine particles into the fiber is known. However, increasing the amount of fine particles increases the performance on ice, but the content of fine particles is limited. For example, in the fine particle-containing organic fiber described in Patent Document 3, the fine particles mixed in the resin may induce fiber cutting at the spinning / stretching stage in which the resin is stretched at a high temperature in the fiber production process. When the fine particles are increased, there is a problem that the production of fibers becomes extremely difficult.

On the other hand, as an inorganic filler component serving as a reinforcing filler used in pneumatic tires, carbon black and silica are mainly used, and silica is used as a filler capable of improving on-ice performance and low fuel consumption. Yes. When this silica is used, it is usually used in combination with a silane coupling agent in order to ensure reinforcement as a filler and dispersibility in the rubber component.
However, it is conceivable to increase the amount of reinforcing filler in order to improve on-ice performance and wear resistance, but simply increasing the blending amount causes problems such as a decrease in performance on ice and a decrease in workability. is the current situation.

Japanese Patent Laid-Open No. 11-60770 (Claims, Examples, etc.) JP 2001-2832 A (Claims, Examples, etc.) JP 2001-233993 A (Claims, Examples, etc.)

  The present invention is to solve the above-mentioned problems of the prior art, and in a rubber composition containing fine particles-containing fibers and inorganic fillers such as silica, the scratching effect on ice and snow road surfaces is achieved. An object is to provide a rubber composition and a pneumatic tire using the rubber composition that can be reliably exhibited and exhibit a studless effect while suppressing excessive grip and improving tire fuel efficiency.

  As a result of intensive investigations in view of the above-described problems of the prior art, the present inventor has a cyclic structure containing a nitrogen atom (N) and a silicon atom (Si) in the molecule, and one or more sulfur atoms ( S) and an organosilicon compound having a site in which one or more groups having small steric hindrance are bonded to a silicon atom (Si) has a high reaction rate with an inorganic filler such as silica. By blending the organosilicon compound with the rubber component together with the inorganic filler, the efficiency of the coupling reaction is improved, the hysteresis loss of the rubber composition is greatly reduced, and the wear resistance is improved. A rubber composition for the above-mentioned purpose that can surely exert drainage effect and scratching effect on ice and snow road surfaces by combining specific fine particles with a hydrophilic resin having a functional group and containing fine particles-containing fibers, and pneumatic using the same T Found that Ya is obtained, it was accomplished the present invention.

〔式（Ｉ）中、Ａは硫黄原子を含み且つゴム成分と反応する基であり、Ｗは−ＮＲ^４−、
−Ｏ−又は−ＣＲ^４Ｒ^５−（ここで、Ｒ^５は−Ｒ^６又は−Ｃ_ｍＨ_２ｍ−Ｒ^７であり、但し、Ｒ^７は−ＮＲ^４Ｒ^６、−ＮＲ^４−ＮＲ^４Ｒ^６又は−Ｎ＝ＮＲ^４であり、Ｒ^４は−Ｃ_ｎＨ_２ｎ＋１で、Ｒ^６は−Ｃ_ｑＨ_２ｑ＋１で、ｍ、ｎ及びｑはそれぞれ独立して０〜１０である）で表わされ、
Ｒ^１及びＲ^２は、それぞれ独立して−Ｍ−Ｃ_ｌＨ_２ｌ−（ここで、Ｍは−Ｏ−又は−ＣＨ_２−で、ｌは０〜１０である）で表わされ、但し、Ｒ^１及びＲ^２の一つ以上は、Ｍが−Ｏ−であり、Ｒ^３は水素原子、メチル基又はヒドロキシル基である。〕
（４） 前記一般式（Ｉ）中におけるＡが、ポリサルファイド基、チオエステル基、チオール基、ジチオカーボネート基、ジチオアセタール基、ヘミチオアセタール基、ビニルチオ基、α−チオカルボニル基、β−チオカルボニル基、Ｓ−ＣＯ−ＣＨ_２−Ｏ部分、Ｓ−ＣＯ−ＣＯ部分、及びＳ−ＣＨ_２−Ｓｉ部分からなる群から選択される少なくとも一種を含むことを特徴とする上記（３）に記載のゴム組成物。
（５） 前記一般式（Ｉ）中のＡが、下記一般式（ＩＩ）又は式（ＩＩＩ）で表わされることを特徴とする上記（３）に記載のゴム組成物。

〔式（ＩＩ）中のＷ、Ｒ^１、Ｒ^２及びＲ^３は上記と同義であり、式（ＩＩ）及び式（ＩＩＩ）中のＲ^８は、下記一般式（ＩＶ）又は式（Ｖ）：

（式中、Ｍ、ｌ及びｍは上記と同義であり、Ｘ及びＹはそれぞれ独立して−Ｏ−、−ＮＲ^４−又は−ＣＨ_２−で、Ｒ^１０は−ＯＲ^４、−ＮＲ^４Ｒ^６又は−Ｒ^４で、Ｒ^１１は−ＮＲ^４−、−Ｎ
Ｒ^４−ＮＲ^４−又は−Ｎ＝Ｎ−であり、但し、Ｒ^４及びＲ^６は上記と同義である）或いは−Ｍ−Ｃ_ｌＨ_２ｌ−（ここで、Ｍ及びｌは上記と同義である）で表わされ、
式（ＩＩＩ）中のＲ^９は下記一般式（ＶＩ）又は式（ＶＩＩ）：

（式中、Ｍ、Ｘ、Ｙ、Ｒ^１０、Ｒ^７、ｌ及びｍは上記と同義である）或いは−Ｃ_ｌＨ_２ｌ−Ｒ^１２（ここで、Ｒ^１２は−ＮＲ^４Ｒ^６、−ＮＲ^４−ＮＲ^４Ｒ^６、−Ｎ＝ＮＲ^４又は−Ｍ−Ｃ_ｍＨ_２ｍ＋１或いは炭素数６〜２０の芳香族炭化水素基であり、但し、Ｒ^４、Ｒ^６、Ｍ、ｌ及びｍは上記と同義である）で表わされ、式（ＩＩ）及び式（ＩＩＩ）中のｘは１〜１０である。〕
（６） 前記微粒子含有繊維（Ｄ）の親水性樹脂が、カルボキシル基、水酸基、エステル基、エーテル基及びカルボニル基よりなる群から選択される少なくとも一種の官能基を含む樹脂であること特徴とする上記（１）に記載のゴム組成物。
（７） 前記微粒子含有繊維（Ｄ）の金属酸化物が、酸化チタン、酸化アルミニウム、セラミックス及びゼオライト（アルミノケイ酸塩）から選ばれる少なくとも一つであることを特徴とする上記（１）又は（６）に記載のゴム組成物。
（８） 前記微粒子含有繊維（Ｄ）の金属炭酸塩が炭酸カルシウムであることを特徴とする上記（１）に記載のゴム組成物。
（９） 前記微粒子含有繊維（Ｄ）の金属を含有する粘土鉱物がモンモリロナイトであることを特徴とする上記（１）に記載のゴム組成物。
（１０） 前記微粒子含有繊維（Ｄ）は、平均径が１〜１００μｍであり、平均長さが０．１〜２０ｍｍであることを特徴とする上記（１）に記載のゴム組成物。
（１１） 前記微粒子含有繊維（Ｄ）が、親水性樹脂１００質量部に対し、微粒子を０．５〜２００質量部含有することを特徴とする上記（１）に記載のゴム組成物。
（１２） 前記無機充填剤（Ｂ）がシリカ又は水酸化アルミニウムであることを特徴とする上記（１）に記載のゴム組成物。
（１３） 前記シリカのＢＥＴ表面積が４０〜３５０ｍ^２／ｇであることを特徴とする上記（１２）に記載のゴム組成物。
（１４） ゴム成分（Ａ）１００質量部に対して、前記無機充填剤（Ｂ）５〜１４０質量部、前記有機ケイ素化合物（Ｃ）を、前記無機充填剤（Ｂ）の含有量の１〜２０質量％含み、前記微粒子含有繊維（Ｄ）が０．５〜３０質量部であることを特徴とする上記（１）〜（１２）の何れか一つに記載のゴム組成物。
（１５） 上記（１）〜（１４）の何れか一つに記載のゴム組成物をタイヤトレッド部に用いたことを特徴とする空気入りタイヤ。 That is, the present invention resides in the following (1) to (15).
(1) For the rubber component (A) composed of natural rubber and / or diene-based synthetic rubber, an inorganic filler (B), a cyclic structure containing nitrogen and silicon atoms in the molecule, and one or more An organosilicon compound (C) having a sulfur atom and having one or more groups with small steric hindrance bonded to a silicon atom, and a clay mineral containing a metal oxide, a metal carbonate, and a metal A rubber composition comprising a fine particle-containing fiber (D) and a foaming agent (E) comprising at least one kind of fine particles selected from the group consisting of and a hydrophilic resin.
(2) The organosilicon compound according to (1) above, wherein the group having a small steric hindrance in the organosilicon compound (C) is at least one selected from the group consisting of a hydrogen atom, a methyl group and a hydroxyl group. Compound.
(3) The rubber composition as described in (1) above, wherein the organosilicon compound (C) is represented by the following general formula (I).

Wherein (I), A is a group which reacts with and the rubber component comprises a sulfur atom, W is -NR 4 ^-,
—O— or —CR ⁴ R ⁵ — (where R ⁵ is —R ⁶ or —C _m H _2m —R ⁷ , provided that R ⁷ is —NR ⁴ R ⁶ , —NR ⁴ —NR ⁴ R ⁶ or a -N = NR ^{4, R 4} is ^{_{-C n H 2n + 1, R}} 6 is _{-C q H 2q + 1, m} , n and q are represented by each independently a 0-10) ,
R ¹ and R ² are each independently represented by —M—C ₁ H _{2 1} — (wherein M is —O— or —CH ₂ —, and 1 is 0 to 10), provided that In one or more of R ¹ and R ² , M is —O—, and R ³ is a hydrogen atom, a methyl group or a hydroxyl group. ]
(4) A in the general formula (I) is a polysulfide group, thioester group, thiol group, dithiocarbonate group, dithioacetal group, hemithioacetal group, vinylthio group, α-thiocarbonyl group, β-thiocarbonyl group The rubber as described in (3) above, comprising at least one selected from the group consisting of: S—CO—CH ₂ —O moiety, S—CO—CO moiety, and S—CH ₂ —Si moiety. Composition.
(5) The rubber composition according to the above (3), wherein A in the general formula (I) is represented by the following general formula (II) or formula (III).

[W, R ¹ , R ² and R ³ in the formula (II) are as defined above, and R ⁸ in the formula (II) and the formula (III) is represented by the following general formula (IV) or formula (V) :

(Wherein M, l and m are as defined above, X and Y are each independently —O—, —NR ⁴ — or —CH ₂ —, and R ¹⁰ is —OR ⁴ , —NR ⁴ R). in ⁶ or -R ^{4, R 11} is ^-NR 4 -, - N
R ⁴ —NR ⁴ — or —N═N—, wherein R ⁴ and R ⁶ are as defined above, or —M—C ₁ H _2l — (where M and l are as defined above). Is)
R ⁹ in formula (III) is the following general formula (VI) or formula (VII):

(Wherein, M, X, Y, R ¹⁰ , R ⁷ , l and m are as defined above) or —C ₁ H _2l —R ¹² (where R ¹² represents —NR ⁴ R ⁶ , —NR ^4- NR ⁴ R ⁶ , —N═NR ⁴ or —M—C _m H _{2m + 1} or an aromatic hydrocarbon group having 6 to 20 carbon atoms, provided that R ⁴ , R ⁶ , M, l and m are the above X in formula (II) and formula (III) is 1-10. ]
(6) The hydrophilic resin of the fine particle-containing fiber (D) is a resin containing at least one functional group selected from the group consisting of a carboxyl group, a hydroxyl group, an ester group, an ether group, and a carbonyl group. The rubber composition as described in (1) above.
(7) The metal oxide of the fine particle-containing fiber (D) is at least one selected from titanium oxide, aluminum oxide, ceramics, and zeolite (aluminosilicate), (1) or (6) ) Rubber composition.
(8) The rubber composition as described in (1) above, wherein the metal carbonate of the fine particle-containing fiber (D) is calcium carbonate.
(9) The rubber composition as described in (1) above, wherein the clay mineral containing metal of the fine particle-containing fiber (D) is montmorillonite.
(10) The rubber composition according to (1), wherein the fine particle-containing fiber (D) has an average diameter of 1 to 100 μm and an average length of 0.1 to 20 mm.
(11) The rubber composition as described in (1) above, wherein the fine particle-containing fiber (D) contains 0.5 to 200 parts by mass of fine particles with respect to 100 parts by mass of the hydrophilic resin.
(12) The rubber composition as described in (1) above, wherein the inorganic filler (B) is silica or aluminum hydroxide.
(13) The rubber composition as described in (12) above, wherein the silica has a BET surface area of 40 to 350 m ² / g.
(14) With respect to 100 parts by mass of the rubber component (A), 5 to 140 parts by mass of the inorganic filler (B), and 1 to 1 of the content of the inorganic filler (B), the organosilicon compound (C). The rubber composition as described in any one of (1) to (12) above, wherein the rubber composition contains 20% by mass and the fine particle-containing fiber (D) is 0.5 to 30 parts by mass.
(15) A pneumatic tire using the rubber composition according to any one of (1) to (14) above in a tire tread portion.

  According to the present invention, a rubber composition capable of reliably exhibiting drainage effect and scratching effect on icy and snowy road surfaces, suppressing excessive grip and improving tire fuel efficiency while exhibiting a studless effect, and a rubber composition thereof A used pneumatic tire is provided.

It is sectional drawing which shows an example of the vulcanized rubber obtained by the rubber composition of this invention. It is sectional drawing which shows an example of the pneumatic tire of this invention.

Hereinafter, embodiments of the present invention will be described in detail for each invention.
The rubber composition of the present invention comprises an inorganic filler (B) and a cyclic structure containing a nitrogen atom and a silicon atom in the molecule with respect to a rubber component (A) comprising a natural rubber and / or a diene synthetic rubber. An organosilicon compound (C) having one or more sulfur atoms and having one or more small steric hindrance groups bonded to silicon atoms, a metal oxide, a metal carbonate, and a metal. It contains at least one kind of fine particles selected from the group consisting of clay minerals and fine particles-containing fibers (D) and a foaming agent (E) made of a hydrophilic resin.

  The rubber component (A) used in the rubber composition of the present invention comprises natural rubber and / or a diene synthetic rubber. Here, examples of the diene synthetic rubber include styrene-butadiene copolymer rubber (SBR), polybutadiene rubber (BR), polyisoprene rubber (IR), butyl rubber (IIR), and ethylene-propylene copolymer. The rubber component (A) preferably has a carbon-carbon double bond in the molecule in order to react with the organosilicon compound (C). These rubber components (A) may be used alone or in a blend of two or more.

Examples of the inorganic filler (B) used in the rubber composition of the present invention include silica, aluminum hydroxide, alumina, clay, calcium carbonate, etc. Among these, silica and aluminum hydroxide are preferable from the viewpoint of reinforcement. Silica is preferred and particularly preferred.
When the inorganic filler (B) to be used is silica, the organosilicon compound (C) described later is a functional group having a high affinity with a silanol group on the silica surface and / or a functional group having a high affinity with a silicon atom (Si). Since it has a group, the coupling efficiency is greatly improved, the hysteresis loss of the rubber composition is reduced, and the effect of improving the wear resistance becomes more remarkable. The silica that can be used is not particularly limited, and wet silica (hydrous silicic acid), dry silica (anhydrous silicic acid), and the like can be used. (Trademark, Showa Denko) is preferably used.

The silica that can be used preferably has a BET surface area of 40 to 350 m ² / g. When the BET surface area of silica is less than 40 m ² / g, the particle size of the silica is too large and wear resistance is greatly reduced. When the BET surface area of silica exceeds 350 m ² / g, the silica Since the particle diameter is too small, the hysteresis loss is greatly increased.

The content of these inorganic fillers (B) is desirably in the range of 5 to 140 parts by mass with respect to 100 parts by mass of the rubber component (A).
When the content of the inorganic filler (B) is less than 5 parts by mass with respect to 100 parts by mass of the rubber component (A), the effect of reducing the hysteresis is insufficient, and when it exceeds 140 parts by mass, the workability is increased. This is because of the remarkable deterioration.

<Organic silicon compound>
The organosilicon compound (C) used in the rubber composition of the present invention has in its molecule a cyclic structure containing a nitrogen atom (N) and a silicon atom (Si), and one or more sulfur atoms (S). And having at least one site having a small steric hindrance bonded to a silicon atom (Si).
The organosilicon compound (C) to be used has a cyclic structure including a nitrogen atom (N) and a silicon atom (Si), and the cyclic structure includes a silicon-oxygen bond (Si-O). Is stable. Therefore, the silicon-oxygen bond (Si—O) is not hydrolyzed to generate an alcohol component, and the volatile organic compound (VOC) gas in use can be reduced.

  In addition, since the organosilicon compound (C) to be used contains a nitrogen-containing functional group such as an amino group, an imino group, a substituted amino group, or a substituted imino group that has high affinity with the surface of an inorganic filler such as silica, a nitrogen atom These unshared electron pairs can participate in the reaction between the organosilicon compound and the inorganic filler, have a high coupling reaction rate, and function as a silane coupling agent. However, when the cyclic structure containing a nitrogen atom (N) and a silicon atom (Si) is a bicyclic structure, since the steric hindrance around the silicon atom (Si) is large, the reactivity with the inorganic filler is low, Coupling efficiency is greatly reduced. On the other hand, since the organosilicon compound (C) used in the present invention has a site where one or more groups having small steric hindrance are bonded to a silicon atom, the reactivity with an inorganic filler such as silica is high. . Therefore, instead of the conventional silane coupling agent, by adding the organosilicon compound (C) used in the present invention to the inorganic filler (B) compounded rubber composition, the coupling efficiency is improved, and as a result, It is possible to greatly improve the wear resistance while greatly reducing the hysteresis loss of the rubber composition. Moreover, since the organosilicon compound (C) used for this invention has high addition efficiency, a high effect is acquired even if it is a small amount, and it contributes also to reduction of a compounding cost.

In the organosilicon compound (C) to be used, the group having a small steric hindrance is preferably a hydrogen atom (—H), a methyl group (—CH ₃ ) and a hydroxyl group (—OH). When a hydrogen atom, a methyl group or a hydroxyl group is bonded to a silicon atom (Si), the reactivity between the organosilicon compound and the inorganic filler is particularly high, and the coupling efficiency can be greatly improved. Moreover, it is preferable that the organosilicon compound of this invention has 1-6 silicon-oxygen bonds (Si-O). When the organosilicon compound has 1 to 6 silicon-oxygen bonds (Si—O), the reactivity with an inorganic filler such as silica is high, and the coupling efficiency is further improved.

More specifically, the organic silicon compound (C) to be used is preferably a compound represented by the following general formula (I). These organosilicon compounds may be used alone or in combination of two or more.

<Compound of Formula (I)>
In the above general formula (I), A is a group containing a sulfur atom (S) and reacting with the rubber component. In the organosilicon compound represented by the above formula (I), since the cyclic structure portion reacts with an inorganic filler such as silica, the rubber component and the inorganic filler The coupling ability is as follows. Here, the group containing a sulfur atom (S) and reacting with the rubber component is a polysulfide group, a thioester group, a thiol group, a dithiocarbonate group, a dithioacetal group, a hemithioacetal group, a vinylthio group, an α-thiocarbonyl group, It preferably contains at least one selected from the group consisting of β-thiocarbonyl group, S—CO—CH ₂ —O moiety, S—CO—CO moiety (thiodiketone group), and S—CH ₂ —Si moiety, It is particularly preferable that at least one of a polysulfide group and a thioester group is included.

In the above general formula (I), W is represented by —NR ⁴ —, —O— or —CR ⁴ R ⁵ —, wherein R ⁵ is —R ⁶ or —C _m H _2m —R ⁷ . Provided that R ⁷ is —NR ⁴ R ⁶ , —NR ⁴ —NR ⁴ R ⁶ or —N═NR ⁴ , R ⁴ is —C _n H _{2n + 1} , and R ⁶ is —C _q H _{2q. +1} , m, n, and q are each independently 0-10. Incidentally, -C _m H _2m -, since m is 0-10, a single bond or an alkylene group having 1 to 10 carbon atoms. Here, examples of the alkylene group having 1 to 10 carbon atoms include a methylene group, an ethylene group, a trimethylene group, and a propylene group, and the alkylene group may be linear or branched. Moreover, -C _n H _{2n + 1} and -C _q H _{2q + 1,} since n and q are 0, is hydrogen or an alkyl group having 1 to 10 carbon atoms. Here, examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, and a decyl group. It may be linear or branched.

In the above general formula (I), R ¹ and R ² are each independently represented by —M—C ₁ H _{2 1} —, where M is —O— or —CH ₂ —, and 1 is 0 -10. However, in one or more of R ¹ and R ² , M is —O—. In addition, since l is 0 to 10, —C ₁ H _2l — is a single bond or an alkylene group having 1 to 10 carbon atoms. Here, the alkylene group having 1 to 10 carbon atoms includes a methylene group, Examples thereof include an ethylene group, a trimethylene group, and a propylene group. The alkylene group may be linear or branched.

In the above general formula (I), R ³ is a hydrogen atom, a methyl group or a hydroxyl group. Since R ³ has small steric hindrance, it greatly contributes to the improvement of the coupling reaction between the rubber component and the inorganic filler.

ここで、式(II)中のＷ、Ｒ¹、Ｒ²及びＲ³は上記と同義であり、式(II)及び式(III)中のＲ⁸は、下記一般式(IV)又は式(V)或いは−Ｍ−Ｃ_lＨ_2l−で表わされ、式(III)中のＲ⁹は、下記一般式(VI)又は式(VII)或いは−Ｃ_lＨ_2l−Ｒ¹²で表わされ、式(II)及び式(III)中のｘは１〜１０であり、好ましくは２〜４である。ここで、Ｍは−Ｏ−又は−ＣＨ₂−であり、ｌは０〜１０である。なお、−Ｃ_lＨ_2l−については、上述のとおりである。

A in the general formula (I) is preferably represented by the following general formula (II) or formula (III).

Here, W, R ¹ , R ² and R ³ in the formula (II) are as defined above, and R ⁸ in the formula (II) and the formula (III) is represented by the following general formula (IV) or formula ( V) or -M-C ₁ H _2l- , and R ⁹ in formula (III) is represented by the following general formula (VI) or formula (VII) or -C ₁ H _2l -R ¹² In the formulas (II) and (III), x is 1 to 10, preferably 2 to 4. Here, M is -O- or -CH ₂ -, l is 0. In addition, -C _l H _2l- is as described above.

In the above formulas (IV) and (V), M is —O— or —CH ₂ —, and l and m are 0 to 10. In the formula (IV), X and Y are each independently —O—, —NR ⁴ — or —CH ₂ —, and R ¹⁰ is —OR ⁴ , —NR ⁴ R ⁶ or —R ⁴ . Yes, where R ⁴ is —C _n H _{2n + 1} and R ⁶ is —C _q H _{2q + 1} . Further, in the above formula (V), R ¹¹ is —NR ⁴ —, —NR ⁴ —NR ⁴ —, or —N═N—, where R ⁴ is —C _n H _{2n + 1} . Note that the -C _n H _{2n + 1} and -C _q H _{2q + 1,} as described above.

R ⁹ in the above formula (III) is represented by the above general formula (VI) or (VII), or —C ₁ H _2l —R ¹² , particularly represented by —C ₁ H _{2l + 1} . However, M, X, Y, R ¹⁰ , R ⁷ , l and m are as defined above. Here, R ¹² is —NR ⁴ R ⁶ , —NR ⁴ —NR ⁴ R ⁶ , —N═NR ⁴ or —M—C _m H _{2m + 1,} or an aromatic hydrocarbon group having 6 to 20 carbon atoms. Provided that R ⁴ , R ⁶ , M, l and m are as defined above. Incidentally, -C _l H _2l - For are as described above, also, -C _m H _{2m + 1,} since m is 0-10, is hydrogen or an alkyl group having 1 to 10 carbon atoms, Here, examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, and a decyl group. It may be linear or branched. Examples of the aromatic hydrocarbon group having 6 to 20 carbon atoms include aryl groups such as phenyl group, tolyl group, xylyl group, cumenyl group, naphthylene group and tolylene group, and aralkyl groups such as benzyl group and phenethyl group. .

In the compound of the above formula (I), M is preferably —O— (oxygen). In this case, M is -CH ₂ - are highly reactive with an inorganic filler such as silica as compared to compounds wherein.

When the W is represented by —NR ⁴ —, the R ¹ and R ² are preferably each independently represented by —O—C ₁ H _2l —, and the R ³ is a hydrogen atom, methyl group or It is a hydroxyl group, and R ⁸ is preferably represented by —C ₁ H _2l —, and R ⁹ is a linear or branched alkyl group represented by —C ₁ H _{2l + 1} , or a carbon number It is preferably a 6-20 aromatic hydrocarbon group.

On the other hand, when the W is represented by —O— or —CR ⁴ R ⁶ —, the R ¹ and R ² are preferably independently represented by —O—C ₁ H _2l —, and the R ³ is It is a hydrogen atom, a methyl group or a hydroxyl group, and R ⁸ is preferably represented by —C ₁ H _2l —, and R ⁹ is preferably represented by —C ₁ H _{2l + 1} .

<Synthesis Method of Organosilicon Compound (C)>
The organosilicon compound (C) used is, for example, (C _l H _{2l + 1} O) ₂ R ³ Si-A [wherein l, R ³ and A are as defined above] An amine compound such as N-methyldiethanolamine or N-ethyldiethanolamine is added. Further, an acid such as p-toluenesulfonic acid or hydrochloric acid, or a titanium alkoxide such as titanium tetra n-butoxide is added as a catalyst, followed by heating. _l H _{2l + 1} O— can be synthesized by substituting with a divalent group represented by —R ¹ —W—R ² —.

<Specific examples of organosilicon compound (C)>
Specifically, as the organosilicon compound (C) used in the present invention, 3-octanoylthio-propyl (methyl) 1,3-dioxa-6-methylaza-2-silacyclooctane, bis (3- (methyl) 1, 3-dioxa-6-methylaza-2-silacyclooctyl-propyl) disulfide, 3-octanoylthio-propyl (hydroxy) 1,3-dioxa-6-methylaza-2-silacyclooctane, bis (3- (hydroxy) 1 , 3-Dioxa-6-methylaza-2-silacyclooctyl-propyl) disulfide, 3-octanoylthio-propyl (hydro) 1,3-dioxa-6-methylaza-2-silacyclooctane, bis (3- (hydro) 1,3-dioxa-6-methylaza-2-silacyclooctyl-propyl) disulfide, 3-octanoylthio-propyl (methyl) 1,3-dioxa-6-butylaza-2 -Silacyclooctane, bis (3- (methyl) 1,3-dioxa-6-butylaza-2-silacyclooctyl-propyl) disulfide and the like.
The rubber composition of the present invention comprises an inorganic filler (B), the above-described organosilicon compound (C), and fine particle-containing fiber (D) with respect to a rubber component (A) comprising natural rubber and / or a diene synthetic rubber. And a foaming agent (D). Preferably, the inorganic filler (B) 5 is used with respect to 100 parts by mass of the rubber component (A) made of natural rubber and / or diene synthetic rubber. It is desirable to contain -140 mass parts, and to make the above-mentioned organosilicon compound (C) into 1-20 mass% of content of the above-mentioned inorganic filler (B).

  Here, if the content of the organosilicon compound (C) is less than 1% by mass of the content of the inorganic filler (B), the effect of reducing the hysteresis loss of the rubber composition and the effect of improving the wear resistance are ineffective. On the other hand, if it exceeds 20% by mass, the effect will be saturated.

The fine particle-containing fiber (D) used in the rubber composition of the present invention is composed of at least one fine particle selected from the group consisting of a metal oxide, a metal carbonate, and a clay mineral containing a metal, and a hydrophilic resin. Is.
By containing the fine particle-containing fiber (D) in the rubber composition of the present invention, it is possible to coat the elongated bubbles with a hydrophilic resin. In addition, when the fiber is contained in the rubber composition, a long bubble functioning as a micro drainage groove is formed, and it is not formed only by directly containing the resin.

Examples of the hydrophilic resin constituting the fine particle-containing fiber (D) include a resin containing a functional group such as a carboxyl group, a hydroxyl group, an ester group, an ether group, or a carbonyl group.
Examples of hydrophilic resins that can be used include ionomer resins (functional group: carboxyl group). As the hydrophilic resin, a resin containing a hydroxyl group or a carboxyl group is particularly preferable.

The hydrophilic resin constituting the fine particle-containing fiber (D) has a melting point or a softening point that is the highest temperature reached by the rubber composition during vulcanization of the rubber composition, specifically, less than the highest vulcanization temperature. It is preferable.
When the fine particle-containing fiber (D) is contained in a rubber composition containing the foaming agent (E) described later, the hydrophilic resin constituting the fine particle-containing fiber (D) is melted or softened during vulcanization. On the other hand, the gas generated from the foaming agent (E) during vulcanization in the rubber matrix remains in the melted or softened hydrophilic resin constituting the fiber, compared to the rubber matrix in which the vulcanization reaction has proceeded. Tend. Here, if the melting point or softening point of the hydrophilic resin is less than the maximum vulcanization temperature, the resin quickly melts or softens during the vulcanization of the rubber composition, and long cells are efficiently formed. Can do. On the other hand, if the melting point or softening point of the hydrophilic resin is too close to the maximum vulcanization temperature, the hydrophilic resin does not melt immediately (including softening) at the initial stage of vulcanization, and the hydrophilic resin melts at the end of vulcanization. To do. At the end of vulcanization, the gas generated from the foaming agent (E) is dispersed or taken into the vulcanized rubber matrix, and a sufficient amount of gas is not retained in the molten resin.

  The upper limit of the melting point or softening point of the hydrophilic resin is preferably selected in consideration of the above points, and is generally preferably 10 ° C. or lower than the maximum vulcanization temperature of the rubber composition, More preferably, it is 20 ° C. or lower. The industrial vulcanization temperature of the rubber composition is generally about 190 ° C. at the maximum. For example, when the maximum vulcanization temperature is set to 190 ° C., the melting point of the hydrophilic resin or The softening point is usually selected within a range of 190 ° C. or less, preferably 180 ° C. or less, and more preferably 170 ° C. or less.

  The fine particles constituting the fine particle-containing fiber (D) exhibit an adhesive action with the hydrophilic resin. Examples of the fine particles include fine particles of metal oxides such as titanium oxide (titania) and aluminum oxide (alumina), fine particles of metal carbonates such as calcium carbonate, fine particles of clay minerals such as montmorillonite, and the like. Among these, fine particles of clay mineral are particularly preferable because of the presence of metal ions. These fine particles may be used individually by 1 type, and may use 2 or more types together. The metal oxide may be used as ceramics or zeolite (aluminosilicate).

  In the present invention, the fine particles constituting the fine particle-containing fiber (D) preferably have a particle size of 0.1 to 500 μm from the viewpoint of ease of production. When the particle size is less than 0.1 μm, the scratching effect on the snowy and snowy road surface cannot be sufficiently obtained. On the other hand, when the particle size exceeds 500 μm, the yarn is cut at the time of fiber production (melt spinning). It becomes difficult.

  In the fine particle-containing fiber (D) to be used, it is desirable to contain 0.5 to 200 parts by mass, more preferably 1 to 100 parts by mass with respect to 100 parts by mass of the hydrophilic resin. When the content of the fine particles is less than 0.5 parts by mass, the scratching effect on the snowy and snowy road surface cannot be sufficiently obtained. On the other hand, when the content exceeds 200 parts by mass, the spinning operability is inferior and thread breakage may occur.

  In the rubber composition of the present invention, the content of the fine particle-containing fiber (D) is preferably 0.5 to 30 parts by mass with respect to 100 parts by mass of the rubber component. If the content of the fine particle-containing fiber is less than 0.5 parts by mass, the volume ratio of the elongated voids in the vulcanized rubber is small, so that there is a risk that sufficient performance on ice may not be obtained. If it exceeds 1, the dispersibility of the fine particle-containing fibers in the rubber composition is lowered, and the processability of the rubber composition may be lowered.

  The fine particle-containing fiber (D) to be used preferably has an average diameter of 1 to 100 μm, and more preferably 10 to 100 μm. In this case, the long air bubbles covered with the hydrophilic resin constituting the fiber can function efficiently as a micro drainage groove. If the average diameter of the fine particle-containing fibers is less than 1 μm, spinning from the hydrophilic resin and the fine particles may not be possible. On the other hand, if the average diameter exceeds 100 μm, the weight of the fine particle-containing fibers increases, and the blending in the rubber composition The number of copies may be too high.

  The fine particle-containing fiber to be used preferably has an average length of 0.1 to 20 mm, more preferably 0.5 to 20 mm, and still more preferably 1 to 10 mm. In this case, the long air bubbles covered with the hydrophilic resin constituting the fiber can function efficiently as a micro drainage groove. In addition, when the average length of the fine particle-containing fibers is less than 0.1 mm, long bubbles are hardly formed. On the other hand, if the average length of the fine particle-containing fibers exceeds 20 mm, the hardness of the fibers becomes too high to be sufficiently kneaded, and the sipe of the tread is usually about 20 mm, and the average length of the fibers Even if it exceeds 20 mm, it is difficult to obtain the effect of performance on ice.

  The fine particle-containing fiber (D) to be used can be produced by a conventional method, and examples of the method for producing the fiber include a melt spinning method, a gel spinning method, and a solution spinning method. For example, in the melt spinning method, after the raw material resin is heated and melted in an extruder, fine particles are dispersed, and then a bundle of fibers extruded from a spinning nozzle is stretched in a spinning cylinder and cooled by an air stream to be solidified. Then, fine particle-containing fibers can be produced by applying an oil agent, collecting them into one, and winding them up. On the other hand, in the solution spinning method, fine particles are dispersed in a polymer solution in which a raw material resin is dissolved, and this is extruded from a spinning nozzle, and fiber removal is performed to remove the solvent, thereby producing a fiber.

  Examples of the foaming agent (E) used in the rubber composition of the present invention include azodicarbonamide (ADCA), dinitrosopentamethylenetetramine (DPT), dinitrosopentastyrenetetramine, benzenesulfonylhydrazide derivatives, p, p'- Oxybisbenzenesulfonyl hydrazide (OBSH), ammonium bicarbonate generating carbon dioxide, sodium bicarbonate, ammonium carbonate, nitrososulfonylazo compound generating nitrogen, N, N'-dimethyl-N, N'-dinitrosophthalamide , Toluenesulfonyl hydrazide, p-toluenesulfonyl semicarbazide, p, p′-oxybisbenzenesulfonyl semicarbazide and the like. Among these foaming agents, azodicarbonamide (ADCA) and dinitrosopentamethylenetetramine (DPT) are preferable from the viewpoint of production processability, and azodicarbonamide (ADCA) is particularly preferable. These foaming agents may be used individually by 1 type, and may use 2 or more types together. Moreover, the compounding quantity of this foaming agent is although it does not specifically limit, The range of 0.1-10 mass parts is preferable with respect to 100 mass parts of rubber components.

  The foaming agent (E) is preferably used in combination with urea, zinc stearate, zinc benzenesulfinate, zinc white or the like as a foaming aid. These may be used individually by 1 type and may use 2 or more types together. By using an appropriate amount of a foaming aid, the foaming reaction can be promoted to increase the degree of completion of the reaction, and unnecessary deterioration can be suppressed over time.

  The rubber composition of the present invention comprises an inorganic filler (B), an organosilicon compound (C), a fine particle-containing fiber (D), a foaming agent (E), and a foaming aid as necessary. In addition, compounding agents commonly used in the rubber industry, for example, fillers such as carbon black, softeners, stearic acid, anti-aging agents, zinc white, vulcanization accelerators, vulcanizing agents, etc. In the range which does not injure, it can select and contain, and it can manufacture by kneading | mixing, heating, extrusion, etc.

  Next, the vulcanized rubber obtained by the rubber composition of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing an example of a vulcanized rubber obtained from the rubber composition of the present invention. This vulcanized rubber is obtained by vulcanizing the above rubber composition. As shown in FIG. 1, the vulcanized rubber 1 has long bubbles 2, and the long bubbles 2 are coated. 3, the coating 3 surrounding the elongated bubbles 2 is composed of the hydrophilic resin 3 a and the fine particles 3 b constituting the fine particle-containing fiber. Here, while the scratching effect on the snowy and snowy road surface is enhanced by the fine particles 3b constituting the coating 3, the long bubble 2 that efficiently collects water on the snowy and snowy road surface by the hydrophilic resin 3a and acts as a micro drainage groove. By draining, the on-ice performance of the tire can be greatly improved.

  The elongated bubbles 2 shown in FIG. 1 are oriented in a certain direction, but as a method for aligning the orientation of the elongated bubbles, fine particle-containing fibers dispersed in the unvulcanized rubber composition are fixed. What is necessary is just to arrange in a direction, for example, the method of extruding the rubber composition containing microparticles | fine-particles containing fiber (D) using the extruder whose flow-path cross-sectional area reduces toward an exit is mentioned.

In the present invention (including examples), the foaming rate (Vs) of the vulcanized rubber obtained from the rubber composition is preferably 3 to 50%, more preferably 3 to 40%, and particularly preferably 5 to 35%. Is more desirable.
If the foaming rate is less than 3%, the volume of long bubbles that can remove water on the snowy and snowy road surface is too small, and the drainage performance may be deteriorated. The number of bubbles is too large, and the durability of the tire decreases. In addition, the said foaming rate (Vs) is a total foaming rate of a long bubble and the bubble formed without staying inside the hydrophilic resin which comprised the microparticle containing fiber.

The foaming rate (Vs) (%) is expressed by the following formula:
Vs = (ρ ₀ / ρ ₁ −1) × 100
[Wherein, ρ ₁ is the density (g / cm ³ ) of the vulcanized rubber, and ρ ₀ is the density of the solid phase part (g / cm ³ ) in the vulcanized rubber].

The pneumatic tire of the present invention is characterized by using the rubber composition in a tire tread portion. The pneumatic tire of the present invention will be described in more detail with reference to the drawings.
FIG. 2 is a cross-sectional view of an example of the pneumatic tire of the present invention. The pneumatic tire shown in FIG. 2 has a pair of left and right bead portions 4 and a pair of sidewall portions 5, and a tire tread portion 6 connected to both sidewall portions 5, and a toroidal shape between the pair of bead portions 4. A carcass 7 that reinforces the respective parts 4, 5, and 6 and a belt 8 that is disposed on the outer side in the tire radial direction of the crown portion of the carcass 7.

Here, the pneumatic tire of the present invention is characterized in that the above-described rubber composition (vulcanized rubber) is applied to the tire tread portion 6 serving as a tire member.
The pneumatic tire of the present invention is provided with a vulcanized rubber obtained from the above rubber composition in the tread portion, so that long air bubbles are formed at least in the ground contact portion, and can exhibit excellent performance on ice. In addition, the molecule has a cyclic structure containing a nitrogen atom (N) and a silicon atom (Si), one or more sulfur atoms (S), and one small steric hindrance group. Since the organosilicon compound (C) having a site bonded to the silicon atom (Si) is contained, the reaction rate with the inorganic filler (B) such as silica contained is high, so the organosilicon compound (C ) In the rubber component together with the inorganic filler (B), the efficiency of the coupling reaction is improved, the hysteresis loss of the rubber composition is greatly reduced, and the wear resistance is improved. Contains contained fiber (D) By improving the scratching effect on the snowy and snowy road surface by fine particles, the water on the snowy and snowy road surface can be efficiently collected by the hydrophilic resin and drained by the long air bubbles that act as micro drainage grooves. Since the performance can be greatly improved, the tireless fuel consumption can be improved by suppressing the excessive grip while exhibiting the studless effect, and the wear life by the low grip is also improved.

The carcass 7 of the pneumatic tire shown in FIG. 2 is composed of a single carcass ply, and a main body portion extending in a toroid shape between a pair of bead cores 9 embedded in the bead portion 4, respectively. Each of the bead cores 9 includes a folded portion that is wound radially outward from the inside in the tire width direction toward the outside. In the pneumatic tire of the present invention, the number of plies and the structure of the carcass 7 are limited to this. Is not something
Also, the pneumatic tire belt 8 shown in FIG. 2 is composed of two belt layers, and each belt layer is usually a rubberized layer of cord, preferably extending obliquely with respect to the tire equatorial plane, preferably The belt 8 is composed of a rubberized layer of a steel cord, and two belt layers are laminated so that the cords constituting the belt layer intersect with each other across the tire equatorial plane. The belt 8 in the figure is composed of two belt layers. However, in the pneumatic tire of the present invention, the number of belt layers constituting the belt 8 is not limited to this.

  Further, in the pneumatic tire of the present invention, an unvulcanized tread rubber is formed using the rubber composition, and a raw tire including the unvulcanized tread rubber in a tread portion is formed according to a conventional method. By vulcanizing the tire, long air bubbles covered with the hydrophilic resin constituting the fine particle-containing fiber can be formed in the tread portion.

  Furthermore, in the pneumatic tire of the present invention, it is preferable that the long bubbles are oriented in the tire circumferential direction from the viewpoint of improving drainage. In this case, an unvulcanized tread rubber is formed by using the rubber composition obtained by the above-described method in which fibers are arranged in a certain direction, and the orientation direction of the fibers in the rubber composition coincides with the tire circumferential direction. Thus, the unvulcanized tread rubber may be disposed. In the pneumatic tire of the present invention, as the gas filled in the tire, normal or air with a changed oxygen partial pressure, or an inert gas such as nitrogen can be used.

  EXAMPLES Next, although an Example and a comparative example are given and this invention is demonstrated in more detail, this invention is not limited to the following Example at all.

As the organosilicon compound (C) and the fine particle-containing fiber (D) to be used, those obtained by the following production methods were used.
<Production Example 1 of Organosilicon Compound (C)>
In a 500 mL four-necked flask, 60 g of 3-octanoylthio-propyldiethoxymethylsilane, 20 g (1.02 eq) of N-methyldiethanolamine, 0.8 g of titanium tetra-n-butoxide, and 220 mL of toluene are weighed. While stirring with a mechanical stirrer, while flowing dry nitrogen (0.2 L / min), the flask was heated in an oil bath, a Dimroth condenser was attached, and reflux was performed for 11 hours. Thereafter, the solvent is removed by a rotary evaporator at 20 hPa / 40 ° C., and then the remaining volatile components are removed by a rotary pump (10 Pa) and a cold trap (dry ice + ethanol), and 70 g of a yellow transparent liquid [organic Silicon compound (C-1)] was obtained. It was confirmed that the liquid obtained as a result of analysis by gas chromatography (GC) was composed of 10% raw material and 90% target product. Furthermore, it was analyzed resulting liquid with _{^{1 H-NMR, 1 H-}} NMR (CDCl 3, 700MHz, δ; ppm) = 3.8 (m; 4H), 2.8 (t; 2H), 2 .5 (m; 6H), 2.4 (m; 3H), 1.6 (m; 4H), 1.3 (m; 8H), 0.8 (t; 3H), 0.7 (t; 2H), 0.1 (s; 3H), represented by formula (I), A is formula (III), W is —N (CH ₃ ) —, and R ¹ is —O—CH. ₂ CH ₂ — (where the O side is linked to Si), R ² is —O—CH ₂ CH ₂ — (where the O side is linked to Si), R ³ is —CH ₃ , and R ⁸ is —CH ₂ CH ₂ CH ₂ - and, ^{R 9} is is _-C 7 _{H 15,} x is 1 compound [i.e., 3-octanoylthio - propyl (methyl) 1,3-dioxa-6-Mechiruaza - - it was found to be silacyclooctane.

<Production Example 2 of organosilicon compound (C)>
In a 500 mL four-necked flask, 40 g of bis (3-diethoxymethylsilylpropyl) disulfide, 20 g (1.02 eq) of N-methyldiethanolamine, 0.8 g of titanium tetra-n-butoxide, and 220 mL of toluene are weighed. While stirring with a mechanical stirrer, while flowing dry nitrogen (0.2 L / min), the flask was heated in an oil bath, a Dimroth condenser was attached, and reflux was performed for 11 hours. Thereafter, the solvent is removed by a rotary evaporator at 20 hPa / 40 ° C., and then the remaining volatile components are removed by a rotary pump (10 Pa) and a cold trap (dry ice + ethanol), and 50 g of a yellow transparent liquid [organic Silicon compound (C-2)] was obtained. It was confirmed that the liquid obtained as a result of analysis by gas chromatography (GC) was composed of 10% raw material and 90% target product. Furthermore, it was analyzed resulting liquid with _{^{1 H-NMR, 1 H-}} NMR (CDCl 3, 700MHz, δ; ppm) = 3.8 (m; 8H), 2.7 (t; 4H), 2 0.5 (m; 8H), 2.4 (m; 6H), 1.8 (m; 4H), 0.7 (t; 4H), 0.1 (s; 6H), and the formula (I) A is the formula (II), W is —N (CH ₃ ) —, R ¹ is —O—CH ₂ CH ₂ — (where the O side is linked to Si), and R ² is —O—CH ₂ CH ₂ — (provided that the O side is linked to Si), R ³ is —CH ₃ , R ⁸ is —CH ₂ CH ₂ CH ₂ —, and x is 2 [ie, bis (3- (methyl) 1,3-dioxa-6-methylaza-2-silacyclooctyl-propyl) disulfide].

<Production Example of Fine Particle-Containing Fiber (D), Fibers A to F>
Using a hydrophilic resin and fine particles having the formulation shown in Table 1 below, fine particle-containing fibers were produced according to a normal melt spinning method. In addition, the average diameter and average length of this fiber were measured by the following method. These results are shown in Table 1 below.

(1) Average diameter and average length The obtained fine particle-containing fibers were randomly selected at 20 locations, the diameter (μm) and length (mm) were measured using an optical microscope, and the average value was obtained.

(Examples 1-11 and Comparative Examples 1-15)
According to the blending formulation shown in Table 2 below, a rubber composition in which blended fine particle-containing fibers (D) [fibers A to F] are arranged in a certain direction was prepared. A tread rubber was produced using each of the obtained rubber compositions, and a raw tire was produced by arranging the tread rubber so that the fine particle-containing fibers (D) in the rubber composition were oriented in the tire circumferential direction. .
Next, the obtained raw tire was vulcanized to produce a radial tire for passenger cars of size 185 / 70R13. The maximum vulcanization temperature during vulcanization of each rubber composition was 200 ° C.

About the obtained tire, foaming rate (Vs) was computed by the above-mentioned formula, and dynamic viscoelasticity (rolling resistance), abrasion resistance, and performance on ice were evaluated by the following method.
These results are shown in Table 2.

(Measuring method of dynamic viscoelasticity)
Using a spectrometer (dynamic viscoelasticity measuring tester) manufactured by Ueshima Seisakusho, tan δ of the vulcanized rubber was measured at a frequency of 52 Hz, an initial strain of 10%, a measurement temperature of 60 ° C., and a dynamic strain of 1%. The value was expressed as an index with the value of tan δ being 100. The smaller the index value, the lower the tan δ, indicating that the rubber composition is less exothermic.
(Abrasion resistance test)
In accordance with JIS K 6264-2: 2005, a test was performed using a Lambone-type wear tester under the conditions of room temperature and a slip rate of 25%, and the reciprocal of the amount of wear in Comparative Example 1 was represented as an index. The larger the index value, the smaller the wear amount and the better the wear resistance.

(Performance on ice)
Drive on a flat road on ice on a passenger car fitted with tires with a 20% wear rate on the tread, apply the brakes at a speed of 20 km / h to lock the tires, and measure the braking distance until the vehicle is stopped. did. The reciprocal of the braking distance of the tire of Comparative Example 1 is shown as an index with 100 as the inverse. The larger the index value, the better the braking performance on ice. In addition, the wear rate of the tread part was calculated by the following formula.
Wear rate (%) = (1−groove depth after wear / groove depth when new) × 100

  As is apparent from Table 2 above, the pneumatic tires of Examples 1 to 11 that fall within the scope of the present invention are more resistant to wear, rolling resistance, and tires than Comparative Examples 1 to 15 that fall outside the scope of the present invention. It has been found that the performance on ice can be greatly improved.

DESCRIPTION OF SYMBOLS 1 Vulcanized rubber 2 Elongated bubble 3 Coating 3a Hydrophilic resin 3b Fine particle 4 Bead part 5 Side wall part 6 Tread part 7 Carcass 8 Belt 9 Bead core

  While exhibiting the studless effect, it can be suitably used for a pneumatic tire that can suppress excessive grip and improve the fuel efficiency of the tire.

Claims (15)

  For the rubber component (A) made of natural rubber and / or diene-based synthetic rubber, an inorganic filler (B), a cyclic structure containing nitrogen and silicon atoms in the molecule, and one or more sulfur atoms And a group consisting of an organosilicon compound (C) having a site in which one or more groups having a small steric hindrance are bonded to a silicon atom, and a clay mineral containing a metal oxide, a metal carbonate, and a metal A rubber composition comprising fine-particle-containing fibers (D) and a foaming agent (E) comprising at least one selected fine particle and a hydrophilic resin.   The organosilicon compound according to claim 1, wherein the group having a small steric hindrance in the organosilicon compound (C) is at least one selected from the group consisting of a hydrogen atom, a methyl group and a hydroxyl group. The rubber composition according to claim 1, wherein the organosilicon compound (C) is represented by the following general formula (I).

Wherein (I), A is a group which reacts with and the rubber component comprises a sulfur atom, W is -NR 4 ^-,
—O— or —CR ⁴ R ⁵ — (where R ⁵ is —R ⁶ or —C _m H _2m —R ⁷ , provided that R ⁷ is —NR ⁴ R ⁶ , —NR ⁴ —NR ⁴ R ⁶ or a -N = NR ^{4, R 4} is ^{_{-C n H 2n + 1, R}} 6 is _{-C q H 2q + 1, m} , n and q are represented by each independently a 0-10) ,
R ¹ and R ² are each independently represented by —M—C ₁ H _{2 1} — (wherein M is —O— or —CH ₂ —, and 1 is 0 to 10), provided that In one or more of R ¹ and R ² , M is —O—, and R ³ is a hydrogen atom, a methyl group or a hydroxyl group. ] A in the general formula (I) is a polysulfide group, thioester group, thiol group, dithiocarbonate group, dithioacetal group, hemithioacetal group, vinylthio group, α-thiocarbonyl group, β-thiocarbonyl group, S— The rubber composition according to claim 3, comprising at least one selected from the group consisting of a CO—CH ₂ —O moiety, an S—CO—CO moiety, and an S—CH ₂ —Si moiety. The rubber composition according to claim 3, wherein A in the general formula (I) is represented by the following general formula (II) or formula (III).

[W, R ¹ , R ² and R ³ in the formula (II) are as defined above, and R ⁸ in the formula (II) and the formula (III) is represented by the following general formula (IV) or formula (V) :

(Wherein M, l and m are as defined above, X and Y are each independently —O—, —NR ⁴ — or —CH ₂ —, and R ¹⁰ is —OR ⁴ , —NR ⁴ R). in ⁶ or -R ^{4, R 11} is ^-NR 4 -, - N
R ⁴ —NR ⁴ — or —N═N—, wherein R ⁴ and R ⁶ are as defined above, or —M—C ₁ H _2l — (where M and l are as defined above). Is)
R ⁹ in formula (III) is the following general formula (VI) or formula (VII):

(Wherein, M, X, Y, R ¹⁰ , R ⁷ , l and m are as defined above) or —C ₁ H _2l —R ¹² (where R ¹² represents —NR ⁴ R ⁶ , —NR ^4- NR ⁴ R ⁶ , —N═NR ⁴ or —M—C _m H _{2m + 1} or an aromatic hydrocarbon group having 6 to 20 carbon atoms, provided that R ⁴ , R ⁶ , M, l and m are the above X in formula (II) and formula (III) is 1-10. ]   The hydrophilic resin of the fine particle-containing fiber (D) is a resin containing at least one functional group selected from the group consisting of a carboxyl group, a hydroxyl group, an ester group, an ether group, and a carbonyl group. The rubber composition as described in 2.   The rubber composition according to claim 1 or 6, wherein the metal oxide of the fine particle-containing fiber (D) is at least one selected from titanium oxide, aluminum oxide, ceramics, and zeolite (aluminosilicate). object.   The rubber composition according to claim 1, wherein the metal carbonate of the fine particle-containing fiber (D) is calcium carbonate.   The rubber composition according to claim 1, wherein the clay mineral containing metal of the fine particle-containing fiber (D) is montmorillonite.   The rubber composition according to claim 1, wherein the fine particle-containing fiber (D) has an average diameter of 1 to 100 μm and an average length of 0.1 to 20 mm.   The rubber composition according to claim 1, wherein the fine particle-containing fiber (D) contains 0.5 to 200 parts by mass of fine particles with respect to 100 parts by mass of the hydrophilic resin.   The rubber composition according to claim 1, wherein the inorganic filler (B) is silica or aluminum hydroxide. The rubber composition according to claim 12, wherein the silica has a BET surface area of 40 to 350 m ² / g.   5 to 140 parts by mass of the inorganic filler (B) and 1 to 20% by mass of the content of the inorganic filler (B) with respect to 100 parts by mass of the rubber component (A). The rubber composition according to claim 1, wherein the fine particle-containing fiber (D) is 0.5 to 30 parts by mass.   A pneumatic tire using the rubber composition according to any one of claims 1 to 11 in a tire tread portion.

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