JP6310186B2 - Rubber composition for tire and pneumatic tire - Google Patents

Description

The present invention relates to a rubber composition for a tire and a pneumatic tire produced using the same.

In recent years, due to increasing interest in environmental issues, there has been a strong demand for lower fuel consumption for automobiles, and rubber compositions used for automobile tires are also required to have excellent fuel efficiency. .

As a method for improving fuel efficiency, a method of reducing the filler such as carbon black or silica is known. However, if the filler is reduced, there is room for improvement in that wet grip performance and wear resistance are reduced. There is. As described above, usually, low fuel consumption is in contradiction with wet grip performance and wear resistance, and it has been difficult to prepare a rubber composition having these performances.

As a method for improving fuel economy, wet grip performance and wear resistance in a well-balanced manner, Patent Document 1 discloses a method of blending a diene rubber modified with an organosilicon compound containing an amino group and an alkoxy group. Patent Document 2 discloses a method in which anhydrous silica and hydrous silica are used in combination. However, in recent years, further improvements have been demanded for low fuel consumption, wet grip performance, and wear resistance.

JP 2000-344955 A JP 2003-192842 A

An object of the present invention is to solve the above-mentioned problems and to provide a rubber composition for a tire that can improve wet grip performance while maintaining good wear resistance and low fuel consumption, and a pneumatic tire using the same. To do.

The present invention contains a rubber component, silica, and an inorganic compound whose crystal system is a hexagonal crystal, the content of the silica with respect to 100 parts by mass of the rubber component is 5 to 150 parts by mass, and the silica has a mass of 100 parts by mass. It is related with the rubber composition for tires whose content of the said inorganic compound with respect to a part is 2-10 mass parts.

The tire rubber composition preferably contains 0.2 parts by mass or more of a silane coupling agent having a mercapto group with respect to 100 parts by mass of the silica.

The inorganic compound is preferably a compound represented by the composition formula of the following formula (1).
A _α (B) _β (C) _γ (1)
(In the formula (1), A is at least one monovalent or divalent atom selected from the group consisting of H, Na, Mg, Sr, K and Ca, and B is PO ₄ ^3- and / or CO ₃ ^2- and C is OH ⁻ , F ⁻ or Cl ⁻ , α is 0 to 5, β is 0 to 3, and γ is a number represented by 0 to 1.)

The present invention also relates to a pneumatic tire produced using the rubber composition.

According to the present invention, since it is a rubber composition for a tire in which a predetermined amount of silica and an inorganic compound having a crystal system of hexagonal crystal are blended with a rubber component, low fuel consumption, wet grip performance and wear resistance are obtained. A pneumatic tire improved in a well-balanced manner can be provided.

The rubber composition of the present invention contains a rubber component, silica, and an inorganic compound whose crystal system is hexagonal (hereinafter also referred to as hexagonal inorganic compound). When the hexagonal inorganic compound interacts with silica, the dispersibility of silica can be improved, and wet grip performance can be improved while maintaining good wear resistance and low fuel consumption.

As the rubber component, natural rubber (NR), styrene butadiene rubber (SBR), polybutadiene rubber (BR), polyisoprene rubber (IR) and the like can be used in the tire industry. These may be used individually by 1 type and may use 2 or more types together. Among these, SBR and BR are preferably used from the viewpoint that low fuel consumption, wet grip performance, and wear resistance can be obtained in a well-balanced manner.

The content of SBR in 100% by mass of the rubber component is preferably 40% by mass or more, more preferably 60% by mass or more. If it is less than 40% by mass, good wet grip performance may not be ensured. The content of SBR in 100% by mass of the rubber component is preferably 90% by mass or less, more preferably 80% by mass or less. If it exceeds 90% by mass, good fuel efficiency may not be ensured.

The content of BR in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 20% by mass or more. If it is less than 10% by mass, good abrasion resistance may not be ensured. The content of BR in 100% by mass of the rubber component is preferably 60% by mass or less, more preferably 40% by mass or less. If it exceeds 60% by mass, good fuel efficiency may not be secured.

Examples of hexagonal inorganic compounds include silicate minerals and phosphate minerals containing beryllium. From the viewpoint that low fuel consumption, wet grip performance and wear resistance can be obtained in a well-balanced manner, it is preferable to use a compound represented by the following formula (1) as the hexagonal inorganic compound.
A _α (B) _β (C) _γ (1)
(In the formula (1), A is at least one monovalent or divalent atom selected from the group consisting of H, Na, Mg, Sr, K and Ca, and B is PO ₄ ^3- and / or CO ₃ ^2- , C is OH ⁻ , F ⁻ or Cl ⁻ , α is 0 to 5, β is 0 to 3, and γ is a number represented by 0 to 1.)

In the above formula (1), the atom represented by A is any one of Ca, Na, Mg, Sr, K, and H from the viewpoint that fuel economy, wet grip performance, and wear resistance can be obtained in a balanced manner. One is preferred, and Ca is more preferred. B is preferably PO ₄ ^3- . C is OH ^- is preferable. α is preferably 1 to 5, and more preferably 3 to 5. β is preferably 1 to 3, and more preferably 2 to 3. γ is preferably 1.

Examples of hexagonal inorganic compounds represented by the formula (1) include fluorapatite (Ca ₅ (PO ₄ ) ₃ F), chlorapatite (Ca ₅ (PO ₄ ) ₃ Cl), hydroxyapatite (Ca ₅ (PO ₄ ) ₃ (OH)), fluorinated apatite (Ca ₅ (PO ₄ , CO ₃ ) ₃ F), carbonated hydroxyapatite (Ca ₅ (PO ₄ , CO ₃ ) ₃ (OH)) and the like. . These may be used individually by 1 type and may use 2 or more types together. Of these, hydroxyapatite (Ca ₅ (PO ₄ ) ₃ (OH)) can be preferably used.

The average particle size of the hexagonal inorganic compound is preferably 500 μm or less, more preferably 50 μm or less, and even more preferably 25 μm or less from the viewpoint of wear resistance. The lower limit of the average particle diameter is not particularly limited, and a smaller particle diameter is more preferable from the viewpoint of wear resistance.
In addition, in this specification, an average particle diameter is the value measured by transmission electron microscope (TEM) observation. Specifically, a photograph is taken with a transmission electron microscope. When the shape of the fine particles is spherical, the diameter of the sphere, when the needle or bar is a short diameter, when it is irregular, the average particle diameter from the center is measured. The average value of 100 particles is the average particle size.

The content of the hexagonal inorganic compound is 2 parts by mass or more, preferably 3 parts by mass or more with respect to 100 parts by mass of silica. If it is less than 2 parts by mass, the wet grip performance may not be sufficiently exhibited. The content of the hexagonal inorganic compound is 10 parts by mass or less, preferably 8 parts by mass or less. If it exceeds 10 parts by mass, good wear resistance may not be ensured.

Examples of the silica include, but are not limited to, dry process silica (anhydrous silicic acid), wet process silica (hydrous silicic acid), and wet process silica is preferable because of its large number of silanol groups.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 30 m ² / g or more, more preferably 100 m ² / g or more, and further preferably 150 m ² / g or more. If it is less than 30 m < ² > / g, there exists a tendency for a reinforcement effect to be small and for abrasion resistance to fall. Further, N ₂ SA of silica is preferably 300 m ² / g or less, more preferably 250 m ² / g or less. When it exceeds 300 m ² / g, the dispersibility of silica is lowered, and there is a possibility that sufficient fuel economy and wear resistance cannot be obtained.
The nitrogen adsorption specific surface area of silica is a value measured by the BET method according to ASTM D3037-81.

The content of silica is 5 parts by mass or more, preferably 30 parts by mass or more, more preferably 50 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 5 parts by mass, sufficient fuel economy, wet grip performance and wear resistance tend not to be obtained. The content of silica is 150 parts by mass or less, preferably 100 parts by mass or less. When it exceeds 150 parts by mass, silica is difficult to disperse and wear resistance tends to deteriorate.

（式（２）中、Ｒ^１０１〜Ｒ^１０３は、分岐若しくは非分岐の炭素数１〜１２のアルキル基、分岐若しくは非分岐の炭素数１〜１２のアルコキシ基、又は−Ｏ−（Ｒ^１１１−Ｏ）_ｚ−Ｒ^１１２（ｚ個のＲ^１１１は、分岐若しくは非分岐の炭素数１〜３０の２価の炭化水素基を表す。ｚ個のＲ^１１１はそれぞれ同一でも異なっていてもよい。Ｒ^１１２は、分岐若しくは非分岐の炭素数１〜３０のアルキル基、分岐若しくは非分岐の炭素数２〜３０のアルケニル基、炭素数６〜３０のアリール基、又は炭素数７〜３０のアラルキル基を表す。ｚは１〜３０の整数を表す。）で表される基を表す。Ｒ^１０１〜Ｒ^１０３はそれぞれ同一でも異なっていてもよい。Ｒ^１０４は、分岐若しくは非分岐の炭素数１〜６のアルキレン基を表す。）

（式（３）及び（４）中、Ｒ^２０１は水素、ハロゲン、分岐若しくは非分岐の炭素数１〜３０のアルキル基、分岐若しくは非分岐の炭素数２〜３０のアルケニル基、分岐若しくは非分岐の炭素数２〜３０のアルキニル基、又は前記アルキル基の末端の水素が水酸基若しくはカルボキシル基で置換されたものを表す。Ｒ^２０２は分岐若しくは非分岐の炭素数１〜３０のアルキレン基、分岐若しくは非分岐の炭素数２〜３０のアルケニレン基、又は分岐若しくは非分岐の炭素数２〜３０のアルキニレン基を表す。Ｒ^２０１とＲ^２０２とで環構造を形成してもよい。） The rubber composition of the present invention preferably contains a silane coupling agent having a mercapto group (hereinafter also referred to as a mercapto silane coupling agent). By further blending a mercapto silane coupling agent, the highly reactive mercapto silane coupling agent interacts with the hexagonal inorganic compound, so that the dispersibility of silica can be synergistically improved. Thereby, the improvement effect of each performance can be improved notably. The mercapto-based silane coupling agent is not particularly limited as long as it is a silane coupling agent having a mercapto group, and those commonly used in the tire industry can be used, but there is a balance between fuel efficiency, wet grip performance and wear resistance. From the viewpoint of being obtained well, a compound comprising a compound represented by the following formula (2) and / or a binding unit A represented by the following formula (3) and a binding unit B represented by the following formula (4). It can be used suitably.

(In the formula (2), R ^{101 to} R ¹⁰³ are each a branched or unbranched C 1-12 alkyl group, a branched or unbranched C 1-12 alkoxy group, or —O— (R ¹¹¹ — O) _z- R ¹¹² (z R ¹¹¹ represents a branched or unbranched divalent hydrocarbon group having 1 to 30 carbon atoms. The z R ^{111 s} may be the same as or different from each other. ¹¹² represents a branched or unbranched alkyl group having 1 to 30 carbon atoms, a branched or unbranched alkenyl group having 2 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, or an aralkyl group having 7 to 30 carbon atoms. Z represents an integer of 1 to 30.) R ^{101 to} R ¹⁰³ may be the same as or different from each other, and R ¹⁰⁴ has 1 to 6 carbon atoms which are branched or unbranched. Represents an alkylene group of

(In the formulas (3) and (4), R ²⁰¹ is hydrogen, halogen, branched or unbranched alkyl group having 1 to 30 carbon atoms, branched or unbranched alkenyl group having 2 to 30 carbon atoms, branched or unbranched. Or an alkyl group substituted with a hydroxyl group or a carboxyl group, and R ²⁰² represents a branched or unbranched C 1-30 alkylene group, branched or It represents an unbranched C2-C30 alkenylene group or a branched or unbranched C2-C30 alkynylene group, and R ²⁰¹ and R ²⁰² may form a ring structure.)

Hereinafter, the compound represented by Formula (2) is demonstrated. By using the compound represented by the formula (2), the filler is well dispersed, and the fuel economy and wear resistance can be remarkably improved.

R ^{101 to} R ¹⁰³ are each a branched or unbranched alkyl group having 1 to 12 carbon atoms, a branched or unbranched alkoxy group having 1 to 12 carbon atoms, or —O— (R ¹¹¹ —O) _z —R ¹¹² . Represents the group represented. Among these, at least one of R ^{101 to} R ¹⁰³ is preferably a group represented by —O— (R ¹¹¹ —O) _z —R ¹¹² , and two of them are —O— (R ¹¹¹ —O) _z —. a group represented by R ^112, and it is more preferred one is a branched or unbranched alkoxy group having 1 to 12 carbon atoms.

Examples of the branched or unbranched alkyl group having 1 to 12 carbon atoms (preferably 1 to 5 carbon atoms) represented by R ^{101 to} R ¹⁰³ include, for example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, and n-butyl. Group, iso-butyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, 2-ethylhexyl group, octyl group, nonyl group and the like.

Examples of the branched or unbranched alkoxy group having 1 to 12 carbon atoms (preferably 1 to 5 carbon atoms) of R ^{101 to} R ¹⁰³ include, for example, a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, n- Examples include butoxy, iso-butoxy, sec-butoxy, tert-butoxy, pentyloxy, hexyloxy, heptyloxy, 2-ethylhexyloxy, octyloxy, nonyloxy and the like.

In —O— (R ¹¹¹ —O) _z —R ¹¹² of R ^{101 to} R ¹⁰³ , R ¹¹¹ represents a branched or unbranched carbon number of 1 to 30 (preferably having 1 to 15 carbon atoms, more preferably 1 carbon number). To 3) a divalent hydrocarbon group. Examples of the hydrocarbon group include a branched or unbranched alkylene group having 1 to 30 carbon atoms, a branched or unbranched alkenylene group having 2 to 30 carbon atoms, and a branched or unbranched alkynylene group having 2 to 30 carbon atoms. And an arylene group having 6 to 30 carbon atoms. Of these, a branched or unbranched alkylene group having 1 to 30 carbon atoms is preferable.

Examples of the branched or unbranched alkylene group having 1 to 30 carbon atoms (preferably 1 to 15 carbon atoms, more preferably 1 to 3 carbon atoms) of R ¹¹¹ include, for example, a methylene group, an ethylene group, a propylene group, and a butylene group. Pentylene group, hexylene group, heptylene group, octylene group, nonylene group, decylene group, undecylene group, dodecylene group, tridecylene group, tetradecylene group, pentadecylene group, hexadecylene group, heptadecylene group, octadecylene group and the like.

Examples of the branched or unbranched carbon atoms 2-30 alkenylene group (preferably 2 to 15 carbon atoms, more preferably 2 to 3 carbon atoms) of R ^111, for example, vinylene group, propenylene group, 2-propenylene Group, 1-butenylene group, 2-butenylene group, 1-pentenylene group, 2-pentenylene group, 1-hexenylene group, 2-hexenylene group, 1-octenylene group and the like.

Examples of the branched or unbranched carbon atoms 2-30 alkynylene group (preferably 2 to 15 carbon atoms, more preferably 2 to 3 carbon atoms) of R ^111, for example, ethynylene group, propynylene group, butynylene group, pentynylene group Hexynylene group, heptynylene group, octynylene group, noninylene group, decynylene group, undecynylene group, dodecynylene group and the like.

Examples of the arylene group having 6 to 30 carbon atoms (preferably 6 to 15 carbon atoms) of R ¹¹¹ include a phenylene group, a tolylene group, a xylylene group, and a naphthylene group.

z represents an integer of 1 to 30 (preferably 2 to 20, more preferably 3 to 7, further preferably 5 to 6).

R ¹¹² represents a branched or unbranched alkyl group having 1 to 30 carbon atoms, a branched or unbranched alkenyl group having 2 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, or an aralkyl group having 7 to 30 carbon atoms. Represent. Of these, a branched or unbranched alkyl group having 1 to 30 carbon atoms is preferable.

Examples of the branched or unbranched alkyl group having 1 to 30 carbon atoms (preferably 3 to 25 carbon atoms, more preferably 10 to 15 carbon atoms) of R ¹¹² include, for example, a methyl group, an ethyl group, an n-propyl group, Isopropyl, n-butyl, iso-butyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, 2-ethylhexyl, octyl, nonyl, decyl, undecyl , Dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, octadecyl group and the like.

Examples of the branched or unbranched alkenyl group having 2 to 30 carbon atoms (preferably 3 to 25 carbon atoms, more preferably 10 to 15 carbon atoms) for R ¹¹² include, for example, a vinyl group, a 1-propenyl group, and 2-propenyl. Group, 1-butenyl group, 2-butenyl group, 1-pentenyl group, 2-pentenyl group, 1-hexenyl group, 2-hexenyl group, 1-octenyl group, decenyl group, undecenyl group, dodecenyl group, tridecenyl group, tetradecenyl group Group, pentadecenyl group, octadecenyl group and the like.

Examples of the aryl group having 6 to 30 carbon atoms (preferably 10 to 20 carbon atoms) of R ¹¹² include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and a biphenyl group.

Examples of the aralkyl group having 7 to 30 carbon atoms (preferably 10 to 20 carbon atoms) of R ¹¹² include a benzyl group and a phenethyl group.

Specific examples of the group represented by —O— (R ¹¹¹ —O) _z —R ¹¹² include, for example, —O— (C ₂ H ₄ —O) ₅ —C ₁₁ H ₂₃ , —O— (C _{2 H 4 -O) 5 -C 12 H} 25, -O- (C 2 H 4 -O) 5 -C 13 H 27, -O- (C 2 H 4 -O) 5 -C 14 H 29, -O _{- (C 2 H 4 -O)} 5 -C 15 H 31, -O- (C 2 H 4 -O) 3 -C 13 H 27, -O- (C 2 H 4 -O) 4 -C 13 H _{27, -O- (C 2 H 4} -O) 6 -C 13 H 27, such as _{-O- (C 2 H 4 -O)} 7 -C 13 H 27 and the like. Among _{these, -O- (C 2 H 4 -O} ) 5 -C 11 H 23, -O- (C 2 H 4 -O) 5 -C 13 H 27, -O- (C 2 H 4 -O) 5 _{-C 15 H 31, -O- (C} 2 H 4 -O) 6 -C 13 H 27 are preferable.

Examples of the branched or unbranched alkylene group having 1 to 6 carbon atoms (preferably 1 to 5 carbon atoms) of R ¹⁰⁴ include the same groups as the branched or unbranched alkylene group having 1 to 30 carbon atoms of R ^111. Can give.

Examples of the compound represented by the above formula (2) include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and the following formula: Examples include compounds represented by (5) (Si363 manufactured by EVONIK-DEGUSSA), and the compounds represented by the following formula can be preferably used. These may be used alone or in combination of two or more.

Next, the compound containing the coupling unit A represented by the formula (3) and the coupling unit B represented by the formula (4) will be described. The compound containing the bond unit A represented by the formula (3) and the bond unit B represented by the formula (4) is more viscous during processing than a polysulfide silane such as bis- (3-triethoxysilylpropyl) tetrasulfide. The rise is suppressed. This is presumably because the increase in Mooney viscosity is small because the sulfide portion of the bond unit A is a C—S—C bond and is thermally stable compared to tetrasulfide and disulfide.

Moreover, the shortening of the scorch time is suppressed as compared with mercaptosilane such as 3-mercaptopropyltrimethoxysilane. This is because the bonding unit B has a structure of mercaptosilane, but the —C ₇ H ₁₅ part of the bonding unit A covers the —SH group of the bonding unit B, so that it does not easily react with the polymer and scorch is less likely to occur. This is probably because of this.

In the silane coupling agent having the above structure, the content of the bond unit A is preferably 30 from the viewpoint that the effect of suppressing the increase in viscosity during processing and the effect of suppressing the shortening of the scorch time can be enhanced. It is at least mol%, more preferably at least 50 mol%, preferably at most 99 mol%, more preferably at most 90 mol%. The content of the binding unit B is preferably 1 mol% or more, more preferably 5 mol% or more, further preferably 10 mol% or more, and preferably 70 mol% or less, more preferably 65 mol% or less, More preferably, it is 55 mol% or less.

Further, the total content of the binding units A and B is preferably 95 mol% or more, more preferably 98 mol% or more, and particularly preferably 100 mol%. The content of the bond units A and B is an amount including the case where the bond units A and B are located at the terminal of the silane coupling agent. The form in which the bonding units A and B are located at the end of the silane coupling agent is not particularly limited, as long as the units corresponding to the formulas (3) and (4) indicating the bonding units A and B are formed. .

Examples of the halogen for R ²⁰¹ include chlorine, bromine, and fluorine.

^Examples of the branched or unbranched alkyl group having 1 to 30 carbon atoms of R ²⁰¹ include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, iso-butyl group, sec-butyl group, tert- Examples thereof include a butyl group, a pentyl group, a hexyl group, a heptyl group, a 2-ethylhexyl group, an octyl group, a nonyl group, and a decyl group. Carbon number of the alkyl group is preferably 1-12.

^Examples of the branched or unbranched C 2-30 alkenyl group of R ²⁰¹ include a vinyl group, 1-propenyl group, 2-propenyl group, 1-butenyl group, 2-butenyl group, 1-pentenyl group, and 2-pentenyl. Group, 1-hexenyl group, 2-hexenyl group, 1-octenyl group and the like. The alkenyl group preferably has 2 to 12 carbon atoms.

^Examples of the branched or unbranched alkynyl group having 2 to 30 carbon atoms of R ²⁰¹ include ethynyl group, propynyl group, butynyl group, pentynyl group, hexynyl group, heptynyl group, octynyl group, nonynyl group, decynyl group, undecynyl group, And dodecynyl group. The alkynyl group preferably has 2 to 12 carbon atoms.

Examples of the branched or unbranched alkylene group having 1 to 30 carbon atoms of R ²⁰² include an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, a nonylene group, a decylene group, an undecylene group, Examples include dodecylene group, tridecylene group, tetradecylene group, pentadecylene group, hexadecylene group, heptadecylene group, octadecylene group and the like. The alkylene group preferably has 1 to 12 carbon atoms.

^Examples of the branched or unbranched C2-C30 alkenylene group of R202 include vinylene group, 1-propenylene group, 2-propenylene group, 1-butenylene group, 2-butenylene group, 1-pentenylene group and 2-pentenylene. Group, 1-hexenylene group, 2-hexenylene group, 1-octenylene group and the like. The alkenylene group preferably has 2 to 12 carbon atoms.

Examples of the branched or unbranched alkynylene group having 2 to 30 carbon atoms of R ²⁰² include ethynylene group, propynylene group, butynylene group, pentynylene group, hexynylene group, heptynylene group, octynylene group, noninylene group, decynylene group, undecynylene group, And dodecynylene group. The alkynylene group preferably has 2 to 12 carbon atoms.

In the compound containing the bonding unit A represented by the formula (3) and the coupling unit B represented by the formula (4), the repetition of the total of the repeating number (x) of the bonding unit A and the repeating number (y) of the bonding unit B The number (x + y) is preferably in the range of 3 to 300. Within this range, since the mercaptosilane of the bond unit B is covered by —C ₇ H ₁₅ of the bond unit A, it is possible to suppress the scorch time from being shortened and to have good reactivity with silica and rubber components. Can be secured.

Examples of the compound containing the bond unit A represented by the formula (3) and the bond unit B represented by the formula (4) include NXT-Z30 and NXT-Z45 manufactured by Momentive Performance Materials Japan GK, NXT-Z60 or the like can be used. These may be used alone or in combination of two or more.

The rubber composition of the present invention may be used in combination with other silane coupling agents in addition to the mercapto silane coupling agent. Examples of other silane coupling agents include sulfide, vinyl, amino, glycidoxy, nitro, and chloro silane coupling agents.

The content of the mercapto-based silane coupling agent is preferably 0.2 parts by mass or more, more preferably 5 parts by mass or more with respect to 100 parts by mass of silica. If it is less than 0.2 parts by mass, the wear resistance tends to decrease. Further, the content of the mercapto-based silane coupling agent is preferably 12 parts by mass or less, more preferably 11 parts by mass or less, and still more preferably 10 parts by mass or less. When the amount exceeds 12 parts by mass, effects such as improvement in wear resistance and reduction in rolling resistance due to addition of a mercapto-based silane coupling agent tend to be insufficient.
In addition, also when using other silane coupling agents, such as a sulfide type, it is preferable that the total content of the silane coupling agent to mix | blend is in the said range.

In addition to the above components, the rubber composition of the present invention includes compounding agents generally used in the production of rubber compositions, for example, reinforcing fillers such as carbon black, clay and talc, silane coupling agents, and zinc oxide. , Stearic acid, processing aids, various anti-aging agents, softeners such as oil, vulcanizing agents such as wax and sulfur, vulcanization accelerators, and the like can be appropriately blended.

Carbon black is not particularly limited, and carbon black commonly used in the tire industry can be used.

From the viewpoint of wet grip performance, wear resistance, rubber reinforcement, etc., the nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 40 m ² / g or more, more preferably 50 m ² / g or more, and 250 m. ² / g or less is preferable, and 200 m ² / g or less is more preferable. From the same viewpoint, the carbon black dibutyl phthalate oil absorption (DBP) is preferably 50 ml / 100 g or more, more preferably 60 ml / 100 g or more, and preferably 200 ml / 100 g or less, more preferably 180 ml / 100 g or less.
Incidentally, _N 2 SA of carbon black, JIS K 6217-2: determined by 2001. The DBP of carbon black is measured according to JIS K 6217-4: 2001.

The content of carbon black is preferably 1 part by mass or more, more preferably 5 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 1 part by mass, sufficient reinforcement may not be obtained. The content of carbon black is preferably 150 parts by mass or less, more preferably 130 parts by mass or less, and still more preferably 10 parts by mass or less. If it exceeds 150 parts by mass, the workability may be reduced.

As a method for producing the rubber composition for a tire of the present invention, a known method can be used, for example, the above components are kneaded using a rubber kneader such as an open roll, a Banbury mixer, a closed kneader, Thereafter, it can be produced by a vulcanization method. The rubber composition can be suitably used for a tire tread (cap tread).

The pneumatic tire of the present invention is produced by a usual method using the rubber composition. That is, a rubber composition containing various additives as necessary is extruded in accordance with the shape of the tire member at an unvulcanized stage, molded by a normal method on a tire molding machine, After bonding together with the tire member to form an unvulcanized tire, the tire can be manufactured by heating and pressing in a vulcanizer.

The pneumatic tire of the present invention can be applied to any tire, and in particular, can be suitably used as a tire for passenger cars.

The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

Below, various chemical | medical agents used by the Example and the comparative example are demonstrated.
SBR: SBR1502 manufactured by JSR Corporation (styrene unit amount: 23.5% by mass)
BR: Ubepol BR150B manufactured by Ube Industries, Ltd.
Inorganic compound A: HAP200 (Ca ₅ (PO ₄ ) ₃ (OH) manufactured by Taihei Chemical Industry Co., Ltd., average particle size: _{5 to} 20 μm, crystal system: hexagonal crystal)
Inorganic compound B: Spherical HAP (Ca ₅ (PO ₄ ) ₃ (OH), average particle size: 15 to 20 μm, crystal system: hexagonal crystal) manufactured by Taihei Chemical Industry Co., Ltd.
Inorganic compound C: Whiten SB (calcium carbonate, average particle size: 2.2 μm, crystal system: trigonal or orthorhombic) manufactured by Shiroishi Calcium Co., Ltd.
Inorganic compound D: PTX-25 (boron nitride, average particle size: 25 μm, crystal system: hexagonal crystal) manufactured by Momentive Performance Materials Japan GK
Silica: ULTRASIL VN3 manufactured by Degussa (N ₂ SA: 175 m ² / g)
Silane coupling agent A: Si266 (bis- (3-triethoxysilylpropyl) disulfide) manufactured by Degussa
Silane coupling agent B: NXT-Z45 manufactured by Momentive Performance Materials Japan GK (copolymer of bond unit A and bond unit B (bond unit A: 55 mol%, bond unit B: 45 mol%) ))
Carbon black: Diamond Black I manufactured by Mitsubishi Chemical Corporation (N ₂ SA: 98 m ² / g, DBP: 124 ml / 100 g)
Oil: Process X-140 manufactured by Japan Energy Co., Ltd.
Zinc oxide: Zinc Hua No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Anti-aging agent manufactured by NOF Corporation: NOCRACK 6C (N- (1,3-3-) manufactured by Ouchi Shinsei Chemical Co., Ltd. Dimethylbutyl) -N′-phenyl-p-phenylenediamine)
Sulfur: Powder sulfur vulcanization accelerator manufactured by Tsurumi Chemical Industry Co., Ltd .: Noxera-NS (N-tert-butyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

<Examples and Comparative Examples>
In accordance with the formulation shown in Tables 1 to 3, materials other than sulfur and a vulcanization accelerator were kneaded for 3 minutes at 160 ° C. using a Banbury mixer to obtain a kneaded product. Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded for 5 minutes at 80 ° C. using a biaxial open roll to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press vulcanized at 170 ° C. for 15 minutes to obtain a vulcanized rubber composition.
Further, the obtained unvulcanized rubber composition was molded into a tread shape and bonded together with other tire members on a tire molding machine to form an unvulcanized tire, and then vulcanized at 170 ° C. for 12 minutes, Test tires were manufactured.

The following evaluation was performed using the obtained vulcanized rubber composition and the test tire. Each result is shown to Tables 1-3.

<Evaluation items and test methods>
(Wet grip performance)
Wear test tires on all wheels of the vehicle, measure the braking distance from the initial speed of 40, 60, and 80 km / h on wet asphalt road surface, and set Comparative Example 1 to 100 at each speed. Calculated the index by the following formula. In Tables 1-3, the average value of three indexes is displayed. It shows that wet grip performance is excellent, so that a numerical value is large.
(Wet grip performance index) = (Brake distance of Comparative Example 1) / (Brake distance of each formulation) × 100

(Abrasion resistance)
Wear test tires on all wheels of the vehicle, measure the remaining grooves after traveling 10,000 km on the paved road surface, calculate the mileage required for the tread to wear 1 mm, and set Comparative Example 1 to 100. About compounding, the index was displayed with the following formula. It shows that abrasion resistance is so favorable that an index | exponent is large.
(Abrasion resistance index) = (travel distance of each formulation) / (travel distance of Comparative Example 1) × 100

(Low fuel consumption)
Using a viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho Co., Ltd.), the loss tangent (tan δ) of the vulcanized rubber composition was measured at a temperature of 50 ° C., an initial strain of 10%, and a dynamic strain of 2%. With the tan δ of Example 1 being 100, other blends were indicated by an index using the following formula. The larger the index, the better the rolling resistance characteristics (low fuel consumption).
(Low fuel consumption index) = (tan δ of Comparative Example 1) / (tan δ of each formulation) × 100

(Total performance)
It is a value obtained by averaging the wet grip performance index, the wear resistance index, and the low fuel consumption index. The larger the index, the better the overall performance.

As shown in Tables 1 to 3, Examples containing a predetermined amount of the inorganic compound A, B or D, which is a hexagonal inorganic compound, have improved silica dispersibility and good wear resistance compared to the Comparative Example. The wet grip performance was improved while maintaining the performance and fuel efficiency, and these performances were obtained in a well-balanced manner. In particular, in the example in which a predetermined amount of silane coupling agent B, which is a mercapto silane coupling agent, was added in addition to the hexagonal inorganic compound, an excellent improvement effect was obtained.

Claims (4)

Containing a rubber component, silica, and an inorganic compound whose crystal system is hexagonal;
The inorganic compound is a compound represented by the following formula (1),
The silica content with respect to 100 parts by mass of the rubber component is 5 to 150 parts by mass,
The rubber composition for tires whose content of the said inorganic compound with respect to 100 mass parts of said silicas is 2-10 mass parts.
A _α (B) _β (C) _γ (1)
(In the formula (1), A is Ca , B is PO ₄ ³⁻ and / or CO ₃ ²⁻ , C is OH ⁻ , F ⁻ or Cl ⁻ . Α is 1 to 5, β is 0 to 3 and γ are numbers represented by 0 to 1 (except when β = γ = 0) . The rubber composition for a tire according to claim 1, comprising 0.2 parts by mass or more of a silane coupling agent having a mercapto group with respect to 100 parts by mass of the silica. The tire rubber composition according to claim 1 or 2, wherein a content of styrene-butadiene rubber in 100% by mass of the rubber component is 40 to 90% by mass and a content of butadiene rubber is 10 to 60% by mass. The pneumatic tire produced using the rubber composition in any one of Claims 1-3.