JP5615737B2 - Rubber composition for tire and pneumatic tire - Google Patents

Description

  The present invention relates to a tire rubber composition containing surface-treated silica and a pneumatic tire using the same.

  In recent years, automobile tires have various characteristics such as low fuel consumption, steering stability, wear resistance, and riding comfort, and various measures have been taken to improve these performances. For example, in order to reduce fuel consumption, that is, to reduce rolling resistance, a method of reducing the amount of filler (filler) is used. However, any method cannot avoid a decrease in wear resistance due to a decrease in reinforcement and a decrease in wet grip performance (grip performance on a wet road surface).

  In order to improve fuel efficiency, it is effective to reduce the hysteresis loss of the rubber composition constituting the tire so as to reduce heat generation, and silica is used as a filler. However, since silica has a silanol group (Si—OH) on the particle surface and is hydrophilic, there is a problem that the particles are likely to aggregate and inferior in dispersibility. Therefore, a silane coupling agent is blended to improve the dispersibility of silica, but further reduction in fuel consumption is required.

  Therefore, in order to improve the dispersibility of silica in the rubber composition, it has been proposed that the silica be surface-treated with a silane coupling agent in advance.

  For example, Patent Documents 1 and 2 below disclose that surface-treated silica obtained by treating silica with a sulfide silane coupling agent is blended in a tire rubber composition. However, silica surface-treated only with a sulfide silane coupling agent is not sufficiently dispersed in the rubber component.

  Patent Documents 3 and 4 below disclose that a surface-treated silica treated with a sulfide silane coupling agent, an organic silane compound, and a hydrophobizing agent is blended in a tire rubber composition. Patent Document 5 listed below discloses blending a surface-treated silica treated with a mercaptosilane coupling agent, an aminosilane coupling agent, and a fatty acid. Further, Patent Document 6 below discloses that a surface-treated silica treated with a sulfur-containing silane coupling agent and a hydrophobizing agent such as a fatty acid, a polyether, a higher alcohol, and a surfactant is blended. Although the surface-treated silica disclosed in these documents can improve the balance between low fuel consumption and wear resistance, the balance between low fuel consumption, wear resistance and wet grip is insufficient. Further improvement is required.

JP 2007-169559 A JP 2010-189647 A JP 2010-059269 A JP 2010-059270 A JP 2010-059271 A JP 2010-059272 A

  In view of the above points, the present invention has an object to provide a rubber composition for a tire that can improve the balance between fuel efficiency, wear resistance, and wet grip, and a pneumatic tire using the same. To do.

The tire rubber composition according to the present invention, the silica of the following general for 100 parts by mass of the diene rubber component, BET specific surface area of 220~400m ² / g and CTAB adsorption specific surface area of 180~400m ² / g Ri Na by blending the surface-treated silica 10 to 200 parts by mass surface-treated with a sulfur-containing silane coupling agent and a hydrophobing agent of formula (1), wherein the hydrophobizing agent is, (a). 10 to the number of carbon atoms 20 fatty acids, (b) a diene liquid polymer having at least one functional group selected from the group consisting of an amino group, a carboxyl group, an acid anhydride group, an epoxy group and a hydroxyl group, and (c) 12 carbon atoms It is at least one selected from the group consisting of -30 saturated or unsaturated alcohols or glycidyl ethers thereof . Moreover, the pneumatic tire according to the present invention is formed using such a rubber composition.
(R ¹ ) _m (R ² ) _n Si-A (1)
(In the formula, R ¹ is a methoxy group or an ethoxy group, R ² is —O— (R ^a —O) _k —R ^b, where R ^a is an alkylene group having 1 to 4 carbon atoms, and R ^b is the number of carbon atoms. 1 to 16 alkyl groups, k = 1 to 20.), m = 1 to 3, m + n = 3, and A is the following general formula (2) or (3).
_{^{-R 3 -S x -R 4 -Si (}} R 1) m (R 2) n ... (2)
-R ⁵ -SH ... (3)
(Wherein R ³ and R ⁴ are each independently an alkylene group having 2 to 4 carbon atoms , R ⁵ is an alkylene group having 2 to 4 carbon atoms, and x is 2 to 4).

  When the rubber composition according to the present invention is used, the silica having the predetermined BET specific surface area and the CTAB adsorption specific surface area is surface-treated in advance with a sulfur-containing silane coupling agent and a hydrophobizing agent, and the obtained surface-treated silica is obtained. By blending with the diene rubber component, it is possible to remarkably improve the balance between fuel efficiency, wear resistance and wet grip.

  Hereinafter, matters related to the implementation of the present invention will be described in detail.

  In the rubber composition according to this embodiment, a diene rubber having an unsaturated bond that can react with a functional group containing a sulfur atom of a sulfur-containing silane coupling agent is used as the rubber component. The diene rubber is not particularly limited, but natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), styrene-isoprene rubber, butadiene-isoprene rubber, styrene-butadiene. -Isoprene rubber, nitrile rubber (NBR), ethylene-propylene-diene terpolymer and the like can be mentioned, and these can be used alone or in admixture of two or more. More preferred is NR, SBR, BR, or a blend rubber thereof.

  Surface-treated silica is blended in the rubber composition according to this embodiment. The surface-treated silica includes (a) silica surface-treated with a sulfur-containing silane coupling agent and a hydrophobizing agent, and (b) a sulfur-containing silane coupling agent, an aminosilane coupling agent, and a hydrophobizing agent. Surface-treated silica can be used, and these surface-treated silicas may be used alone or in combination.

Examples of the silica to be treated in producing the surface-treated silica include various hydrophilic silicas having a hydroxyl group (silanol group) on the particle surface. For example, wet precipitation silica, wet gelation silica, Examples thereof include dry silica. In the present embodiment, silica having a BET specific surface area of 220 to 400 m ² / g and a CTAB adsorption specific surface area of 180 to 400 m ² / g is used. By using silica having such a high BET specific surface area and CTAB adsorption specific surface area as an object to be processed, it is possible to improve wear resistance and wet grip properties and improve the balance between these and low fuel consumption. If the BET specific surface area or CTAB adsorption specific surface area is less than the above lower limit, the wear resistance and wet grip properties, particularly wet grip properties, are inferior, and the effect of improving the balance between fuel efficiency, wear resistance and wet grip properties is insufficient. It becomes.

The BET specific surface area is a nitrogen adsorption specific surface area according to the BET method, and is measured according to the BET method described in ISO 5794. The BET specific surface area is preferably 220 to 300 m ² / g.

The CTAB adsorption specific surface area is obtained by adsorbing CTAB (cetyltrimethylammonium bromide) and measuring the amount of adsorption based on the method of ASTM D3765-80. CTAB adsorption specific surface area is preferably 180~300m ² / g, more preferably 200 to 300 m ² / g.

  The surface-treated silica can be obtained by surface-treating silica having such specific BET specific surface area and CTAB adsorption specific surface area with a sulfur-containing silane coupling agent and a hydrophobizing agent. The surface-treated silica is more excellent in dispersibility in rubber than untreated silica that has not been surface-treated or silica that has been treated with a sulfur-containing silane coupling agent alone. Specifically, the sulfur-containing silane coupling agent surface-treated on silica can bind silica and a diene rubber polymer, and gives a reinforcing effect to silica and improves dispersibility. Moreover, the hydrophobizing agent surface-treated on silica improves the dispersibility of silica in rubber by making the silica surface hydrophobic.

  As the sulfur-containing silane coupling agent, it is preferable to use a compound represented by the following general formula (1). The compound has an alkoxy group capable of reacting with a silanol group of silica and a functional group A containing a sulfur atom capable of reacting with a rubber polymer.

(R ¹ ) _m (R ² ) _n Si-A (1)
(Wherein R ¹ is an alkoxy group having 1 to 3 carbon atoms, R ² is an alkyl group, alkenyl group or alkyl polyether group having 1 to 40 carbon atoms, m = 1 to 3, m + n = 3, and A is (It is one of the following general formulas (2) to (4).)
_{^{-R 3 -S x -R 4 -Si (}} R 1) m (R 2) n ... (2)
-R ⁵ -SH ... (3)
-R < ⁶ > -S-CO-R < ⁷ > (4)
(Wherein R ³ and R ⁴ are each independently an alkylene group having 1 to 8 carbon atoms, R ⁵ is an alkylene group having 1 to 16 carbon atoms, R ⁶ is an alkylene group having 1 to 5 carbon atoms, and R ⁷ is carbon. (The number 1-18 alkyl group, x is 2-8.)

In the above formula (1), R ¹ is more preferably a methoxy group or an ethoxy group. R ² is preferably an alkyl group having 1 to 4 carbon atoms or an alkenyl group, and more preferably an alkyl group having 1 to 4 carbon atoms. For R ² , the alkyl polyether group is —O— (R ^a —O) _k —R ^b (where R ^a is an alkylene group having 1 to 4 carbon atoms, and R ^b is an alkyl group having 1 to 16 carbon atoms). It is preferable that it is an alkyl group and k = 1-20. In addition, when there are two or more R ¹ and R ² in one molecule, they may be the same or different. For m and n, it is preferable that m = 3 and n = 0.

R ³ and R ⁴ are more preferably each independently an alkylene group having 2 to 4 carbon atoms. R ⁵ is more preferably an alkylene group having 2 to 4 carbon atoms. R ⁶ is more preferably an alkylene group having 2 to 4 carbon atoms. R ⁷ is more preferably an alkyl group having 5 to 9 carbon atoms. x is 2 to 8, more preferably 2 to 4. In addition, x has a normal distribution, that is, it is generally marketed as a mixture having different numbers of sulfur chain bonds, and x represents an average value thereof. Note that R ¹ , R ² , m, and n in the above formula (2) are the same as in the above formula (1).

  Examples of the sulfide silane coupling agent in which the functional group A is represented by the above formula (2) include bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide, and bis (2 Preferred examples include -triethoxysilylethyl) tetrasulfide, bis (4-triethoxysilylbutyl) disulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) disulfide and the like.

Examples of the mercaptosilane coupling agent in which the functional group A is represented by the above formula (3) include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3- Mercaptopropyldimethylmethoxysilane, mercaptoethyltriethoxysilane, and “VP Si363” manufactured by Evonik Degussa (R ¹ : OC ₂ H ₅ , R ² : O (C ₂ H ₄ O) _k —C ₁₃ H ₂₇ , R ⁵ : — (CH ₂ ) ₃ —, m = average 1, n = average 2, k = average 5) and the like.

  Preferred examples of the protected mercaptosilane coupling agent in which the functional group A is represented by the above formula (4) include 3-octanoylthio-1-propyltriethoxysilane and 3-propionylthiopropyltrimethoxysilane. Can be mentioned.

  Each of the sulfur-containing silane coupling agents listed above can be used alone or in combination of two or more.

  The hydrophobizing agent is bonded or adsorbed to the silanol group of silica by an interaction such as hydrogen bond, and the various types of silica that can reduce the polarity of the silica surface by surface treatment, that is, reduce the hydrophilicity. A compound is used. Examples of the hydrophobizing agent include fatty acids having 5 to 30 carbon atoms and derivatives thereof, modified liquid polymers, higher alcohols and glycidyl ethers thereof, and polyethers. These are used alone or in combination of two or more. be able to.

  The fatty acid acts as a hydrophobizing agent because it binds to a silanol group on the silica surface with a hydrophilic carboxyl group and exhibits hydrophobicity with a hydrocarbon group. It is preferable that carbon number of a fatty acid is 10-30, More preferably, it is 10-20. The fatty acid may be a saturated fatty acid or an unsaturated fatty acid, and may have a linear structure or a branched structure. Specific examples include hexanoic acid, decanoic acid, dodecanoic acid, myristic acid, isomyristic acid, palmitic acid, isopalmitic acid, stearic acid, isostearic acid, oleic acid, and behenylic acid. It can be used alone or in combination of two or more.

  Examples of the fatty acid derivatives include fatty acid metal salts, fatty acid halides, fatty acid esters, and fatty acid amides. Examples of the fatty acid metal salt include zinc salts, sodium salts, potassium salts and the like of the above-mentioned various fatty acids. Examples of fatty acid halides include acid chlorides and acid bromides of the above-mentioned various fatty acids. Examples of fatty acid esters include ester compounds of the above various fatty acids with alcohols, polyalkylene glycols, and the like. Examples of fatty acid amides include fatty acid alkanolamides such as lauric acid diethanolamide and myristic acid diethanolamide.

  As the modified liquid polymer, various modified liquid polymers having a functional group that interacts with a silanol group of silica can be used. The modified liquid polymer is a polymer that is liquid at normal temperature, and those having a number average molecular weight of 1000 to 50000 are preferably used. The number average molecular weight is more preferably 2000 to 10000, still more preferably 3000 to 5000. Here, the number average molecular weight (Mn) is a value measured at 40 ° C. by GPC (gel permeation chromatography), solvent: THF (tetrohydrofuran).

The functional group of the modified liquid polymer is preferably at least one selected from the group consisting of an amino group, a carboxyl group (—COOH), an acid anhydride group, an epoxy group, and a hydroxyl group (—OH). The amino group may be any of a primary amino group, a secondary amino group, and a tertiary amino group. Examples of the carboxyl group include maleic acid, phthalic acid, acrylic acid, and methacrylic acid. The acid anhydride group consists of an anhydride of a dicarboxylic acid such as maleic acid or phthalic acid. The hydroxyl group includes a phenol group as well as a methylol group (—CH ₂ OH) and an ethylol group. These functional groups may be at least one in the molecule of the modified liquid polymer, but in order to facilitate interaction with silica, the functional group is preferably introduced at the polymer end, that is, the terminal end. It is preferable to use a modified liquid polymer.

  The modified liquid polymer is preferably a diene liquid polymer. That is, a diene liquid polymer as a base polymer and a functional group introduced therein is preferably used. Examples of the diene liquid polymer include liquid polybutadiene, liquid polyisoprene, liquid styrene-butadiene rubber, and liquid nitrile rubber. Such a modified liquid polymer can be obtained, for example, by introducing the functional group by reacting a compound having the functional group with an unmodified liquid polymer synthesized by anionic polymerization or the like. Alternatively, a liquid polymer having a functional group can be obtained by polymerization using a polymerizable monomer having the functional group. Such a polymerization method and modification method of the polymer itself can be a conventionally known method.

  The higher alcohol functions as a hydrophobizing agent because it is hydrogen bonded to the silanol group on the silica surface at the terminal hydroxyl group and exhibits hydrophobicity at the hydrocarbon group. Examples of the higher alcohol include saturated or unsaturated aliphatic alcohols having 12 or more carbon atoms (more preferably 12 to 30 carbon atoms) such as lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, and oleyl alcohol. These may be used alone or in combination of two or more. Examples of the glycidyl ether of higher alcohol include glycidyl ethers of these saturated or unsaturated aliphatic alcohols.

  The above polyether is hydrogen bonded to the silanol group on the silica surface with an ether bond or a terminal hydroxyl group, and the entire structure including the alkylene group is less hydrophilic than the silanol group before the surface treatment. Works. As the polyether, for example, polyalkylene glycols such as polyethylene glycol and polypropylene glycol are preferably used. Although the number average molecular weight of polyalkylene glycol is not specifically limited, It is preferable that it is 500-20000, More preferably, it is 1000-10000.

  As the aminosilane coupling agent, a compound represented by the following general formula (5) is preferably used. The compound has an alkoxy group capable of reacting with a silanol group of silica and an amino group capable of reacting with the carboxyl group when the hydrophobizing agent has a carboxyl group.

^{_{(R 8) p (R 9}} ) q Si-R 10 - (NH-R 11) r -NH 2 ... (5)
In formula (5), R ⁸ is an alkoxy group having 1 to 3 carbon atoms, R ⁹ is an alkyl group having 1 to 40 carbon atoms, an alkenyl group or an alkyl polyether group, R ¹⁰ is an alkylene group having 1 to 16 carbon atoms, R ¹¹ is an alkylene group having 1 to 4 carbon atoms, and p = 1 to 3, p + q = 3, and r = 0 to 5. Specifically, R ⁸ is more preferably a methoxy group or an ethoxy group. R ⁹ is more preferably an alkyl group or an alkenyl group having 1 to 10 carbon atoms, more preferably 1 to 4 carbon atoms. As for R ⁹ , the alkyl polyether group means —O— (R ^a —O) _k —R ^b (where R ^a is an alkylene group having 1 to 4 carbon atoms, and R ^b is the same as R ² above). It is preferable that it is a C1-C16 alkyl group and k = 1-20. Incidentally, R ^8, R ^9, when each of a plurality in one molecule, they may be the same or different. R ¹⁰ is preferably an alkylene group having 1 to 4 carbon atoms, and examples thereof include a methylene group, an ethylene group, a propylene group, an isopropylene group, a butylene group, and an isobutylene group. Examples of R ¹¹ include a methylene group, an ethylene group, a propylene group, and an isopropylene group. p is more preferably 2 to 3. R is more preferably 0 or 1.

  Specific examples of such aminosilane coupling agents include 2-aminoethyltrimethoxysilane, 2-aminoethyltriethoxysilane, 2-aminoethylethyldiethoxysilane, 3-aminopropyltrimethoxysilane, and 3-aminopropyl. Triethoxysilane, 3- (2-aminoethyl) aminopropylmethyldimethoxysilane, 3- (2-aminoethyl) aminopropyltrimethoxysilane, 3- (2-aminoethyl) aminopropyltriethoxysilane, 3- (2 -Aminoethyl) aminopropylethyldiethoxysilane and the like can be mentioned, and these can be used alone or in combination of two or more.

  The surface-treated silica (a) is obtained by surface-treating silica with a sulfur-containing silane coupling agent and a hydrophobizing agent. Preferably, the surface treatment is first performed with a sulfur-containing silane coupling agent, and then the surface treatment is performed with a hydrophobizing agent. By treating in this order, it is easy to ensure the amount of the sulfur-containing silane coupling agent to be bonded to the silanol groups on the particle surface by reaction. The surface treatment method is not particularly limited, and can be performed according to a normal hydrophobized surface treatment method. For example, a sulfur-containing silane coupling agent may be added while stirring silica in a mixer or blender, and then a hydrophobizing agent may be added and stirred. These surface treatments can also be performed in a state where silica is dispersed in a solvent such as water, isopropyl alcohol, or toluene.

  The surface-treated silica (b) can be obtained by surface-treating silica with a sulfur-containing silane coupling agent, an aminosilane coupling agent, and a hydrophobizing agent. Preferably, the surface treatment is first performed with a sulfur-containing silane coupling agent and an aminosilane coupling agent, and then the surface treatment is performed with a hydrophobizing agent. The surface treatment method is not particularly limited, and can be performed according to a normal hydrophobized surface treatment method. For example, a sulfur-containing silane coupling agent and an aminosilane coupling agent may be added while stirring silica in a mixer or blender, and then a hydrophobizing agent may be added and stirred. Either one of the sulfur-containing silane coupling agent and the aminosilane coupling agent may be reacted first, or may be reacted at the same time. Preferably, the sulfur-containing silane coupling agent is first treated with the sulfur-containing silane coupling agent. These surface treatments can also be performed in a state where silica is dispersed in a solvent such as water, isopropyl alcohol, or toluene.

  By producing in this way, the sulfur-containing silane coupling agent and the aminosilane coupling agent are each bonded to the silanol group on the silica surface. As for the hydrophobizing agent, it is chemically or physically bonded or adsorbed to the silanol group remaining on the silica surface, or the functional group that can be bonded to the amino group of the aminosilane coupling agent. In the case of having a carboxyl group (for example, a carboxyl group), the hydrophobizing agent may be bonded to an aminosilane coupling agent.

  Therefore, the surface-treated silica of (b) has a sulfur-containing silane coupling agent bonded to a silanol group on the silica surface and a hydrophobizing agent bonded to the silanol group on the silica surface via an aminosilane coupling agent and / or It is thought to have a hydrophobizing agent that is directly bonded to or adsorbed to the silanol group on the silica surface. Therefore, similar to the above (a), excellent dispersibility by the hydrophobizing agent and reinforcing effect and dispersibility by the sulfur-containing silane coupling agent can be obtained, and the same or better than the above (a). An effect is obtained.

  In the surface-treated silica, the amount of the sulfur-containing silane coupling agent used is not particularly limited, but is preferably 2 to 20 parts by mass, more preferably 4 to 100 parts by mass with respect to 100 parts by mass of silica (hydrophilic silica). 15 parts by mass. When there is too little usage-amount of a sulfur containing silane coupling agent, it is inferior to the reinforcement improvement effect when mix | blending with a rubber composition.

  Although the usage-amount of a hydrophobizing agent is not specifically limited, It is preferable that it is 0.5-20 mass parts with respect to 100 mass parts of silica (hydrophilic silica), More preferably, it is 1-10 mass parts. When the amount of the hydrophobizing agent used is too small, the effect of improving the dispersibility of the surface-treated silica is poor.

  In the surface-treated silica of (b) using an aminosilane coupling agent, the amount of the aminosilane coupling agent is not particularly limited, but is 0.5 to 10 parts by mass with respect to 100 parts by mass of silica (hydrophilic silica). It is preferable that it is 0.8-5 mass parts.

  About the compounding quantity in the rubber composition of the said surface treatment silica, it is preferable that it is 10-200 mass parts with respect to 100 mass parts of diene type rubber components, More preferably, it is 20-120 mass parts, More preferably. 40 to 100 parts by mass.

  You may mix | blend the untreated silica which is not surface-treated with the said surface-treated silica with the rubber composition which concerns on this invention. In that case, it is preferable that the surface-treated silica and untreated silica are added in a total amount of 20 to 200 parts by mass with respect to 100 parts by mass of the rubber component. In addition, when mix | blending untreated silica, it is preferable to add a sulfur containing silane coupling agent separately to a rubber composition. In that case, it is preferable that the compounding quantity of the post-added sulfur containing silane coupling agent is 2-20 mass parts with respect to 100 mass parts of untreated silica. As the sulfur-containing silane coupling agent, various sulfur-containing silane coupling agents represented by the general formula (1) can be used.

  In addition to the above components, the rubber composition according to the present invention includes a vulcanizing agent, a vulcanization accelerator, an anti-aging agent, zinc white, a softening agent, a plasticizer, an activator, carbon black and other fillers and lubricants. Various additives such as can be added as necessary.

  Examples of the vulcanizing agent include sulfur and sulfur-containing compounds, and are not particularly limited. However, the blending amount is preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the rubber component. More preferably, it is 0.5-5 mass parts. Moreover, as a compounding quantity of a vulcanization accelerator, it is preferable that it is 0.1-7 mass parts with respect to 100 mass parts of said rubber components, More preferably, it is 0.5-5 mass parts.

  The rubber composition of the present invention can be prepared by kneading according to a conventional method using a commonly used mixer such as a Banbury mixer or a kneader. That is, it is obtained by adding the above-mentioned surface-treated silica and, if necessary, the above-mentioned other additives to the rubber component and mixing (kneading) them. The rubber composition thus obtained can be used for a tread rubber, a sidewall rubber or the like of a pneumatic tire. Preferably, it is used for the tread rubber which comprises the contact surface of a pneumatic tire, and this tread part can be formed by vulcanization-molding at 140-180 degreeC, for example according to a conventional method.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

[Details of ingredients used]
Sulfur-containing silane coupling agent A: “Si75” manufactured by Evonik Degussa, bis (3-triethoxysilylpropyl) disulfide ・ Sulfur-containing silane coupling agent B: “Z-6062” manufactured by Toray Dow Corning Co., Ltd. 3-mercaptopropyltrimethoxysilane / sulfur-containing silane coupling agent C: “VP Si363” manufactured by Evonik Degussa
Hydrophobizing agent A: stearic acid, “Lunac S-20” manufactured by Kao Corporation
Hydrophobizing agent B: stearyl alcohol, “Calcoal” manufactured by Kao Corporation
Hydrophobizing agent C: Modified liquid polymer (carboxyl group-terminal modified liquid BR), “HYPRO CTB2000X162” manufactured by PTI Japan, number average molecular weight = 4800
Hydrophobizing agent D: Stearyl glycidyl ether, “Epiol SK” manufactured by NOF Corporation
Hydrophobizing agent E: Modified liquid polymer (OH group terminal modified liquid BR), “Krasol LBH5000” manufactured by Sartomer, number average molecular weight = 5000
Aminosilane coupling agent A: “Z-6020” manufactured by Toray Dow Corning Co., Ltd., 3- (2-aminoethyl) aminopropyltrimethoxysilane, silica A: “Ultrasil 7000GR” manufactured by Evonik Degussa (BET = 170 m ² / g, CTAB = 160 m ² / g)
・ Silica B: “Nip seal AQ” manufactured by Tosoh Silica Co., Ltd. (BET = 200 m ² / g, CTAB = 155 m ² / g)
Silica C: “Zeosil Premium 200MP” manufactured by Rhodia (BET = 220 m ² / g, CTAB = 200 m ² / g)
Silica D: “Ultrasil 9000GR” manufactured by Evonik Degussa (BET = 240 m ² / g, CTAB = 200 m ² / g)
-SBR: "VSL5025-0HM" manufactured by LANXESS Co., Ltd., styrene-butadiene rubber. BR: "BR150B" manufactured by Ube Industries, Ltd., polybutadiene rubber.

[Surface Treatment Silica 1] (Comparative Example)
In a Henschel mixer preheated to 100 ° C., 1000 g of silica A was added and stirred, and 80 g of sulfur-containing silane coupling agent A was sprayed. Stirring was continued for 20 minutes and the temperature was raised to 120 ° C. Stirring was further continued for 30 minutes to obtain surface-treated silica 1.

[Surface Treatment Silica 2] (Comparative Example)
In a Henschel mixer preheated to 100 ° C., 1000 g of silica A was added and stirred, and 80 g of sulfur-containing silane coupling agent A was sprayed. Subsequently, 30 g of hydrophobizing agent A was added, stirring was continued for 20 minutes, and the temperature was raised to 120 ° C. Stirring was further continued for 30 minutes to obtain surface-treated silica 2.

[Surface Treatment Silica 3] (Comparative Example)
In a Henschel mixer preheated to 100 ° C., 1000 g of silica B was added and stirred, and 80 g of sulfur-containing silane coupling agent A was sprayed. Subsequently, 30 g of hydrophobizing agent A was added, stirring was continued for 20 minutes, and the temperature was raised to 120 ° C. Stirring was further continued for 30 minutes to obtain surface-treated silica 3.

[Surface Treatment Silica 4] (Comparative Example)
In a Henschel mixer preheated to 100 ° C., 1000 g of silica C was added and stirred, and 80 g of sulfur-containing silane coupling agent A was sprayed. Stirring was continued for 20 minutes and the temperature was raised to 120 ° C. Stirring was further continued for 30 minutes to obtain surface-treated silica 4.

[Surface-treated silica 5] (Example)
In a Henschel mixer preheated to 100 ° C., 1000 g of silica C was added and stirred, and 80 g of sulfur-containing silane coupling agent A was sprayed. Subsequently, 30 g of hydrophobizing agent A was added, stirring was continued for 20 minutes, and the temperature was raised to 120 ° C. Stirring was further continued for 30 minutes to obtain surface-treated silica 5.

[Surface-treated silica 6] (Example)
In a Henschel mixer preheated to 100 ° C., 1000 g of silica D was added and stirred, and 80 g of sulfur-containing silane coupling agent A was sprayed. Subsequently, 30 g of hydrophobizing agent A was added, stirring was continued for 20 minutes, and the temperature was raised to 120 ° C. Stirring was further continued for 30 minutes to obtain surface-treated silica 6.

[Surface treatment silica 7] (Example)
In a Henschel mixer preheated to 100 ° C., 1000 g of silica C was added and stirred, and 80 g of sulfur-containing silane coupling agent A and 20 g of aminosilane coupling agent A were sprayed. Subsequently, 30 g of hydrophobizing agent A was added, stirring was continued for 20 minutes, and the temperature was raised to 120 ° C. Stirring was further continued for 30 minutes to obtain surface-treated silica 7.

[Surface treatment silica 8] (Example)
In a Henschel mixer preheated to 100 ° C., 1000 g of silica C was added and stirred, and 80 g of sulfur-containing silane coupling agent A was sprayed. Subsequently, 30 g of hydrophobizing agent B was added, stirring was continued for 20 minutes, and the temperature was raised to 120 ° C. Stirring was further continued for 30 minutes to obtain surface-treated silica 8.

[Surface Treatment Silica 9] (Example)
In a Henschel mixer preheated to 100 ° C., 1000 g of silica C was added and stirred, and 80 g of sulfur-containing silane coupling agent A was sprayed. Subsequently, 30 g of hydrophobizing agent C was added, stirring was continued for 20 minutes, and the temperature was raised to 120 ° C. Stirring was further continued for 30 minutes to obtain surface-treated silica 9.

[Surface treatment silica 10] (Example)
In a Henschel mixer preheated to 100 ° C., 1000 g of silica D was added and stirred, and 100 g of sulfur-containing silane coupling agent A was sprayed. Subsequently, 30 g of hydrophobizing agent A was added, stirring was continued for 20 minutes, and the temperature was raised to 120 ° C. Stirring was further continued for 30 minutes to obtain surface-treated silica 10.

[Surface treatment silica 11] (Example)
In a Henschel mixer preheated to 100 ° C., 1000 g of silica C was added and stirred, and 80 g of sulfur-containing silane coupling agent B was sprayed. Subsequently, 30 g of hydrophobizing agent A was added, stirring was continued for 20 minutes, and the temperature was raised to 120 ° C. Stirring was further continued for 30 minutes to obtain surface-treated silica 11.

[Surface Treatment Silica 12] (Example)
In a Henschel mixer preheated to 100 ° C., 1000 g of silica C was added and stirred, and 80 g of sulfur-containing silane coupling agent C was sprayed. Subsequently, 30 g of hydrophobizing agent A was added, stirring was continued for 20 minutes, and the temperature was raised to 120 ° C. Stirring was further continued for 30 minutes to obtain surface-treated silica 12.

[Surface Treatment Silica 13] (Example)
In a Henschel mixer preheated to 100 ° C., 1000 g of silica D was added and stirred, and 80 g of sulfur-containing silane coupling agent C was sprayed. Subsequently, 30 g of hydrophobizing agent A was added, stirring was continued for 20 minutes, and the temperature was raised to 120 ° C. Stirring was further continued for 30 minutes to obtain surface-treated silica 13.

[Surface treatment silica 14] (Example)
In a Henschel mixer preheated to 100 ° C., 1000 g of silica C was added and stirred, and 80 g of sulfur-containing silane coupling agent A was sprayed. Subsequently, 30 g of hydrophobizing agent D was added, stirring was continued for 20 minutes, and the temperature was raised to 120 ° C. Stirring was further continued for 30 minutes to obtain surface-treated silica 14.

[Surface treatment silica 15] (Example)
In a Henschel mixer preheated to 100 ° C., 1000 g of silica C was added and stirred, and 80 g of sulfur-containing silane coupling agent A was sprayed. Subsequently, 30 g of hydrophobizing agent E was added, stirring was continued for 20 minutes, and the temperature was raised to 120 ° C. Stirring was further continued for 30 minutes to obtain surface-treated silica 15.

[Evaluation of rubber composition]
Using a Banbury mixer, according to the formulation (parts by mass) shown in Tables 1 and 2 below, first, in the first mixing stage, components other than sulfur and vulcanization accelerator are added and mixed, and then the resulting mixture is In the final mixing stage, sulfur and a vulcanization accelerator were added and mixed to prepare a tire tread rubber composition. The common formulation is as follows. In addition, in each compounding of the example and the comparative example, the compounding amount was set so that the total mass of the silica component excluding the surface treating agent was constant at 80 parts by mass.

  The common formulation is 40 parts by weight of process oil ("Extract 4 S" manufactured by Showa Shell Sekiyu KK) and 100 parts by weight of diene rubber component, carbon black ("Dia Black N339 manufactured by Mitsubishi Chemical Corporation)". ”) 10 parts by mass, 3 parts by mass of zinc white (“ Zinc Flower No. 1 ”manufactured by Mitsui Mining & Smelting Co., Ltd.), 2 parts by mass of anti-aging agent (“ Antigen 6C ”manufactured by Sumitomo Chemical Co., Ltd.) 2 parts by mass of “Lunac S-20” manufactured by Co., Ltd., 2 parts by mass of wax (“OZOACE0355” manufactured by Nippon Seiki Co., Ltd.), sulfur (“5% oil-filled fine powder sulfur” manufactured by Tsurumi Chemical Co., Ltd.) 1.5 parts by mass, vulcanization accelerator 1 (“Soxinol CZ” manufactured by Sumitomo Chemical Co., Ltd.) 1.8 parts by mass, vulcanization accelerator 2 (“Noxeller D” manufactured by Ouchi Shinsei Chemical Co., Ltd.) 2 0.0 part by mass.

  Using each rubber composition obtained as a tread rubber, a pneumatic radial tire of 185 / 70R14 is manufactured in accordance with a conventional method. The fuel efficiency (rolling resistance), wet grip property, wear resistance, and these three performances The balance was evaluated. Each evaluation method is as follows.

Low fuel consumption: The rolling resistance was measured when running at 80 Km / h with a single-axis drum tester for measuring rolling resistance at a room temperature of 23 ° C. with an air pressure of 230 kPa and a load of 4.4 kPa. The results were expressed as an index with the value of Comparative Example 1 as 100. The smaller the index is, the smaller the rolling resistance is, and thus the better the fuel efficiency.

-Wet grip property: The tire was mounted on a 2000 cc FF vehicle and ran on a wet road surface (road surface with water at a depth of 2 to 3 mm). The grip property was evaluated by measuring the friction coefficient at a speed of 100 km / h. The value of Comparative Example 1 is expressed as an index, and the larger the index, the greater the coefficient of friction and the better the wet grip properties.

Abrasion resistance: Each tire was mounted on a 2000 cc FF vehicle, and the remaining groove depth after running 10,000 km was measured while rotating back and forth every 2500 km. The remaining groove was expressed as an index with an average value of four tires and the value of Comparative Example 1 as 100. It shows that it is excellent in abrasion resistance, so that an index | exponent is large.

-Balance of three performances: An index of a balance between low fuel consumption, wet grip and wear resistance, and was calculated by (wet grip x wear resistance) / low fuel consumption. The higher this value, the better.

  The results are as shown in Tables 1 and 2. As in Comparative Examples 2 to 10, when rubber was mixed with silica added with a sulfur-containing silane coupling agent or a hydrophobizing agent, the comparison was a control. Compared to Example 1, the improvement effect of low fuel consumption was small or hardly obtained, and the wear resistance was insufficient. In Comparative Example 10, although the fuel efficiency was excellent, the wet grip property was inferior and the balance of the three performances was inferior. In Comparative Example 11, the silica was surface-treated in advance, but the silica whose surface area deviated from the specified value was surface-treated only with the sulfur-containing silane coupling agent, and thus improved fuel economy and wear resistance. Was insufficient and the wet grip property was inferior. In Comparative Examples 12 and 13, the silica was surface-treated in advance with a sulfur-containing silane coupling agent and a hydrophobizing agent, but the specific surface area of the silica to be treated deviated from the specified value. The improvement effect was small and the wet grip property was deteriorated, and the effect of improving the balance of the three performances was insufficient. In Comparative Example 14, the silica having a specific surface area within the specified value was previously surface-treated, but since it was treated only with the sulfur-containing silane coupling agent, the effect of improving the wear resistance was small, The wet grip property was deteriorated, and the effect of improving the balance of the three performances was insufficient.

  On the other hand, in Examples 1 to 11, a silica having a high BET specific surface area and a CTAB adsorption specific surface area, which was previously surface-treated with a sulfur-containing silane coupling agent and a hydrophobizing agent, was used as a comparative example. On the other hand, the balance of fuel efficiency, wear resistance and wet grip was significantly improved. Moreover, compared with the comparative examples 11-14 using the surface treatment silica, it was excellent in wet grip property and abrasion resistance. In particular, Examples 5 and 11 using a modified liquid polymer as a hydrophobizing agent were excellent in improving wet grip properties.

Claims (3)

A sulfur-containing silane represented by the following general formula (1) is used for silica having a BET specific surface area of 220 to 400 m ² / g and a CTAB adsorption specific surface area of 180 to 400 m ² / g with respect to 100 parts by mass of the diene rubber component. Ri Na by blending the surface-treated silica 10 to 200 parts by mass surface-treated with a coupling agent and a hydrophobic agent,
The hydrophobizing agent comprises (a) a fatty acid having 10 to 20 carbon atoms, (b) at least one functional group selected from the group consisting of an amino group, a carboxyl group, an acid anhydride group, an epoxy group, and a hydroxyl group. A diene-based liquid polymer, and (c) at least one selected from the group consisting of a saturated or unsaturated alcohol having 12 to 30 carbon atoms or a glycidyl ether thereof.
Rubber composition for tires.
(R ¹ ) _m (R ² ) _n Si-A (1)
(In the formula, R ¹ is a methoxy group or an ethoxy group, R ² is —O— (R ^a —O) _k —R ^b, where R ^a is an alkylene group having 1 to 4 carbon atoms, and R ^b is the number of carbon atoms. 1 to 16 alkyl groups, k = 1 to 20.), m = 1 to 3, m + n = 3, and A is the following general formula (2) or (3).
_{^{-R 3 -S x -R 4 -Si (}} R 1) m (R 2) n ... (2)
-R ⁵ -SH ... (3)
(Wherein R ³ and R ⁴ are each independently an alkylene group having 2 to 4 carbon atoms , R ⁵ is an alkylene group having 2 to 4 carbon atoms, and x is 2 to 4). The surface-treated silica is a surface-treated silica surface-treated with an aminosilane coupling agent represented by the following general formula (5) together with the sulfur-containing silane coupling agent and the hydrophobizing agent. Item 2. A rubber composition for tires according to Item 1 .
_{^{(R 8) p (R 9}} ) q Si-R 10 - (NH-R 11) r -NH 2 ... (5)
(Wherein R ⁸ is an alkoxy group having 1 to 3 carbon atoms, R ⁹ is an alkyl group, alkenyl group or alkyl polyether group having 1 to 40 carbon atoms, R ¹⁰ is an alkylene group having 1 to 16 carbon atoms, R ¹¹ Is an alkylene group having 1 to 4 carbon atoms, and p = 1 to 3, p + q = 3, and r = 0 to 5.) A pneumatic tire comprising the rubber composition according to claim 1 or 2.