JP2011174011A - Rubber composition for tire and pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition and a pneumatic tire, excellent in low fuel consumption. <P>SOLUTION: This rubber composition for the tire is obtained by blending, with a rubber component, at least one kind of a surface-treated silica selected from (a) the silica surface-treated with a sulfur-containing silane coupling agent and a fatty acid and (b) the silica surface-treated with the sulfur-containing silane coupling agent, an aminosilane coupling agent and the fatty acid, a non-treated hydrophilic silica and the sulfur-containing silane coupling agent. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

  In order to improve the fuel efficiency of a pneumatic tire, it is effective to reduce the hysteresis loss of the rubber composition constituting the tire so as to reduce heat generation. Accordingly, silica as a filler is blended in a tire rubber composition. 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, the dispersibility of silica is improved by blending a silane coupling agent.

  The demand level of pneumatic tires has recently been increasing, and in order to improve the dispersibility of silica, silica is preliminarily surface-treated with a silane coupling agent. For example, Patent Document 1 below proposes a method for producing silica surface-treated with an alkoxysilane compound having a thiocyanate group or a sulfide bond, and its blending into a rubber composition.

  Patent Document 2 below discloses that silica treated with a protected mercaptosilane such as 3-octanoylthio-propyltriethoxysilane is added to a rubber composition for a tread in order to improve the dispersibility of the silica. Has been.

  On the other hand, Patent Document 3 below discloses blending blended hydrophilic precipitated silica and preliminarily hydrophobized precipitated silica in order to improve the braking performance on the wet road surface of the tire. However, this document does not disclose that a fatty acid is used as a hydrophobizing agent for silica. In particular, this document is characterized in that when the hydrophilic silica and the hydrophobized silica are mixed with the rubber composition, a silane coupling agent or an alkoxysilane is not blended, that is, the hydrophilic silica remains as it is. It is required to be present in the rubber composition in a hydrophilic state (see page 2, [0033]), and does not suggest the present invention.

Japanese Patent Laid-Open No. 05-017705 JP 2005-320374 A US Patent Application Publication No. 2009 / 0151831A1

  An object of the present invention is to provide a rubber composition for a tire excellent in low heat build-up and a pneumatic tire that can improve fuel economy by using the rubber composition.

  The present inventor blended untreated hydrophilic silica with a surface-treated silica in advance with respect to the rubber component, and further blended with a silane coupling agent, whereby untreated hydrophilic silica and silane coupling agent. It has been found that there is a synergistic effect on low exothermicity in comparison with the case of using together with the surface treatment silica alone. In addition, the use of surface-treated silica alone has a short scorch time and is difficult to process, but the use of a blend with untreated hydrophilic silica suppresses the scorch time from becoming too short, resulting in scorch resistance. It has been found that the balance of low heat generation can be improved.

The tire rubber composition according to the present invention comprises:
For rubber component,
Silica surface-treated with a sulfur-containing silane coupling agent and a fatty acid, and at least one surface-treated silica selected from silica surface-treated with a sulfur-containing silane coupling agent, an aminosilane coupling agent, and a fatty acid; ,
Hydrophilic silica,
A sulfur-containing silane coupling agent;
Are blended.

  The present invention also provides a pneumatic tire having a rubber portion using the rubber composition.

  According to the present invention, a pneumatic tire that is excellent in the effect of improving low heat buildup of the rubber composition and excellent in fuel efficiency by blending hydrophilic silica and a sulfur-containing silane coupling agent together with the surface-treated silica. Can be provided.

It is a graph which shows the relationship between the amount of surface treatment silica substitution which concerns on 1st Example, and a fuel-efficient index. It is a graph which shows the relationship between the surface treatment silica substitution amount which concerns on 2nd Example, and a fuel-efficient index. It is a graph which shows the relationship between the surface treatment silica substitution amount which concerns on 3rd Example, and a fuel-efficient index. It is a graph which shows the relationship between the surface treatment silica substitution amount which concerns on 4th Example, and a fuel-efficient index.

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

  The rubber composition according to the present invention contains a rubber component, surface-treated silica, hydrophilic silica, and a sulfur-containing silane coupling agent.

  As the rubber component, a diene rubber having an unsaturated bond capable of reacting with a functional group containing a sulfur atom of a sulfur-containing silane coupling agent is suitable. The diene rubber is not particularly limited, but natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, styrene-isoprene rubber, butadiene-isoprene rubber, styrene-butadiene-isoprene rubber, nitrile rubber, ethylene-propylene-diethylene. An enter polymer etc. are mentioned, These can be used individually or in mixture of 2 or more types, respectively.

  The surface-treated silica was (a) silica surface-treated with a sulfur-containing silane coupling agent and a fatty acid, and (b) surface-treated with a sulfur-containing silane coupling agent, an aminosilane coupling agent, and a fatty acid. Silica can be used, and these surface-treated hydrophobic silicas may be used alone or in combination. By using such surface-treated silica, dispersibility in rubber can be improved and low heat build-up can be improved as compared to when untreated silica and a silane coupling agent are used.

  More specifically, the surface-treated silica (a) is previously surface-treated with a sulfur-containing silane coupling agent having a reactive site for the rubber component and a fatty acid as a hydrophobizing agent. This is because silica with only a surface treatment with a sulfur-containing silane coupling agent has poor dispersibility in rubber, and silica with a surface treatment with only fatty acids has poor reinforcement with rubber. By surface-treating in advance with both fatty acid and fatty acid, it is possible to obtain a surface-treated silica having both dispersibility in rubber and reinforcement. Here, the sulfur-containing silane coupling agent is bonded to the silanol group on the silica surface, and the functional group containing a sulfur atom reacts when mixed with the rubber component, thereby binding the silica and the rubber component. It is done. Fatty acids are considered to be bonded to the silanol groups on the silica surface by hydrophilic carboxyl groups or by dehydration condensation, etc., and in a state mixed with the rubber component, the hydrocarbon groups It acts as a hydrophobizing agent by exhibiting hydrophobicity.

  The surface-treated silica (b) is previously surface treated with a sulfur-containing silane coupling agent, an aminosilane coupling agent, and a fatty acid. Thereby, the silica which has the sulfur containing silane coupling agent couple | bonded with the silanol group on the silica surface and the fatty acid couple | bonded via the aminosilane coupling agent with the silanol group on the silica surface can be obtained. Therefore, similar to the above (a), the excellent dispersibility by the fatty acid and the reinforcing and dispersibility effects by the sulfur-containing silane coupling agent are obtained, and the excellent effect equal to or more than the above (a) is obtained. can get.

  Examples of the silica to be treated for obtaining these surface-treated silicas include various hydrophilic silicas having a hydroxyl group (silanol group) on the particle surface, such as wet precipitation silica, wet gelation silica, Examples thereof include dry silica.

  As said sulfur containing silane coupling agent, what is shown to following General formula (1) is used preferably.

(R ¹ ) _m (R ² ) _n Si-A (1)
In formula (1), 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, and m + n = 3. A is any 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)
In formulas (2) to (4), 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, and R ⁶ is an alkylene group having 1 to 5 carbon atoms. Group R ⁷ is an alkyl group having 1 to 18 carbon atoms, and x is 2 to 8.

  As described above, the sulfur-containing silane coupling agent 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 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.

R ³ and R ⁴ are each independently an alkylene group having 1 to 8 carbon atoms, and more preferably an alkylene group having 2 to 4 carbon atoms. R ⁵ is an alkylene group having 1 to 16 carbon atoms, more preferably an alkylene group having 2 to 4 carbon atoms. R ⁶ is an alkylene group having 1 to 5 carbon atoms, more preferably an alkylene group having 2 to 4 carbon atoms. R ⁷ is an alkyl group having 1 to 18 carbon atoms, and 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. In the formula (2), R ¹ , R ² , m, and n are the same as those 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- Triethoxysilylethyl) tetrasulfide, bis (4-triethoxysilylbutyl) disulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) disulfide and the like are preferable.

Examples of the mercaptosilane coupling agent in which the functional group A is represented by the above formula (3) include γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, mercaptopropylmethyldimethoxysilane, and 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 are preferable.

  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. It is done.

  As said fatty acid, a C5-C30 thing is used preferably. When the fatty acid has 4 or less carbon atoms, the effect of hydrophobizing silica may be insufficient. More preferably, the lower limit of the number of carbon atoms in the fatty acid is 10 or more, further 14 or more, and the upper limit is 20 or less.

  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.

  As said aminosilane coupling agent, what is shown by following General formula (5) is used preferably.

^{_{(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.

  Thus, the aminosilane coupling agent is a silane coupling agent having an alkoxy group capable of reacting with a silanol group of silica and an amino group capable of reacting with a fatty acid which is a hydrophobizing agent.

R ⁸ is more preferably a methoxy group or an ethoxy group. R ⁹ 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 ⁹ , 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. When there are a plurality of R ⁸ and R ⁹ in one molecule, they may be the same or different.

R ¹⁰ is more 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. R ¹¹ is an alkylene group having 1 to 4 carbon atoms, and examples thereof 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 2-aminoethyltriethoxysilane, 3-aminopropyltriethoxysilane, and 3- (2-aminoethyl) aminopropyltrimethoxysilane are preferable. These can be used alone or in combination of two or more.

  The surface-treated silica (a) is obtained by surface-treating hydrophilic silica with the above-described sulfur-containing silane coupling agent and a fatty acid. Preferably, the surface treatment is first performed with a sulfur-containing silane coupling agent, and then the surface treatment is performed with a fatty acid. 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 hydrophilic silica in a mixer or blender, and then a fatty acid 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 or isopropyl alcohol.

  The surface-treated silica (b) is obtained by surface-treating hydrophilic silica with the sulfur-containing silane coupling agent, aminosilane coupling agent, and fatty acid. Preferably, first, a surface treatment is performed in advance with a sulfur-containing silane coupling agent and an aminosilane coupling agent, and a fatty acid is reacted with an amino group of the aminosilane coupling 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 hydrophilic silica in a mixer or blender, and then a fatty acid may be added and stirred. Either one of the sulfur-containing silane coupling agent and the aminosilane coupling agent may be reacted first or simultaneously. These surface treatments can also be performed in a state where silica is dispersed in a solvent such as water or isopropyl alcohol. By producing in this way, the sulfur-containing silane coupling agent and the aminosilane coupling agent are each bonded to silanol groups on the surface of the hydrophilic silica particles, and the fatty acid is bonded to the aminosilane coupling agent.

  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 15 parts by mass with respect to 100 parts by mass of the hydrophilic silica. Part. 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. Moreover, when there are too many the usage-amounts, while it is expensive and uneconomical, the coupling | bonding amount with respect to the silica surface of a fatty acid or an aminosilane coupling agent will decrease.

  Although the usage-amount of a fatty acid is not specifically limited, It is preferable that it is 1-20 mass parts with respect to 100 mass parts of hydrophilic silica, More preferably, it is 2-10 mass parts. When there is too little usage-amount of a fatty acid, it is inferior to the dispersibility improvement effect with respect to a rubber composition. Moreover, when there is too much the usage-amount, it will be expensive and uneconomical.

  In the surface-treated silica (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 the hydrophilic silica. Is more preferable, and 0.8 to 4 parts by mass is more preferable. When there is too little usage-amount of an aminosilane coupling agent, it is inferior to the dispersibility improvement effect with respect to a rubber composition. Moreover, when there are too many the usage-amounts, while it is expensive and uneconomical, the coupling | bonding amount with respect to the silica surface of a sulfur containing silane coupling agent will decrease.

  As the hydrophilic silica used in combination with the surface-treated silica described above, untreated silica that has not been subjected to such surface treatment can be used. Therefore, various types of silica having silanol groups on the particle surface, for example, wet Precipitated silica, wet gelation silica, dry silica and the like can be used as they are.

  The ratio between the surface-treated silica and the hydrophilic silica is not particularly limited. By blending the two (although addition of a sulfur-containing silane coupling agent described later is essential), the ratio is low and the heat generation is synergistic. An effect is obtained. However, the ratio of the surface-treated silica to the total amount of the surface-treated silica and the hydrophilic silica is 30% by mass or more and 100% by mass in terms of the mass of silica (hereinafter, this ratio may be referred to as the surface-treated silica substitution amount (%)) It is preferable that it is less than mass%. That is, the surface treatment silica substitution amount (%) is represented by {X / (X + Y)} × 100 (%), where X is the mass of silica in the surface treatment silica and Y is the mass of hydrophilic silica. The surface treatment silica substitution amount (%) is preferably 30% or more and less than 100%. The surface treatment silica substitution amount (%) is preferably 30 to 90% (that is, X: Y = 30: 70 to 90:10), more preferably 40 to 90% (that is, X: Y). = 40: 60 to 90:10). The reason why the combined use of the surface-treated silica and the hydrophilic silica provides a superior synergistic effect compared to the case of the surface-treated silica alone is that the interaction between the surface-treated silica and the hydrophilic silica results in the respective silicas. It is thought that this is because the dispersibility of the toner is further improved.

  In the rubber composition of the present invention, the amount of silica is not particularly limited, but the total amount of the surface-treated silica and the hydrophilic silica is 10 to 200 parts by mass with respect to 100 parts by mass of the rubber component. It is preferable that it is 20 to 150 parts by mass.

  In the rubber composition of the present invention, a sulfur-containing silane coupling agent is added to the rubber component together with the surface-treated silica and the hydrophilic silica. The sulfur-containing silane coupling agent is necessary for the dispersibility and reinforcement of the untreated hydrophilic silica. By adding the sulfur-containing silane coupling agent even in the post-addition as described above, the surface-treated silica and the hydrophilic silica are hydrophilic. Combined with the use of the conductive silica, an excellent synergistic effect of low exothermic property can be exhibited.

  The amount of such post-added sulfur-containing silane coupling agent is preferably 2 to 20 parts by mass, more preferably 4 to 15 parts by mass with respect to 100 parts by mass of the untreated hydrophilic silica. is there. As a sulfur containing silane coupling agent, the various silane coupling agents represented by General formula (1) used for manufacture of the said surface treatment silica 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.

  The rubber composition can be prepared by kneading using a usual mixer such as a Banbury mixer or a kneader. That is, the rubber component is obtained by adding the above-mentioned surface-treated silica, hydrophilic silica, sulfur-containing silane coupling agent, and, if necessary, the above-mentioned other additives, and mixing (kneading) them. .

  The rubber composition can be used for tires, and constitutes rubber parts (tread rubber, sidewall rubber, etc.) of various pneumatic tires by vulcanization molding at 140 to 180 ° C., for example, according to a conventional method. Can do. In particular, it is preferably used for a tread rubber of a pneumatic tire, and a tire excellent in fuel efficiency can be manufactured. In addition, when the rubber composition is a surface-treated hydrophobic silica alone, it is possible to suppress the problem that the scorch time is too short, and to improve the balance between scorch resistance and low heat build-up. The fuel efficiency of the pneumatic tire can be improved while ensuring the workability.

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

[Details of ingredients used]
The detail of each component used for preparation of surface treatment silica is as follows.

・ Silica: “Nip Seal AQ” manufactured by Tosoh Silica Corporation
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 / aminosilane coupling agent A: “Z-6020” manufactured by Toray Dow Corning Co., Ltd., 3- (2-aminoethyl) aminopropyltrimethoxysilane / aminosilane coupling agent B: Toray -"Z-6011" manufactured by Dow Corning Co., Ltd., 3-aminopropyltriethoxysilane, stearic acid: "Lunac S-20" manufactured by Kao Corporation

[Production of surface-treated silica]
-Preparation of surface-treated silica 1 80 g of a sulfur-containing silane coupling agent A, 50 g of distilled water, and 50 g of ethanol were placed in a beaker and stirred to prepare a sulfur-containing silane coupling agent treatment solution. 20 g of aminosilane coupling agent A, 20 g of distilled water, and 20 g of ethanol were placed in a beaker and stirred to prepare an aminosilane coupling agent treatment solution. 50 g of stearic acid and 150 g of ethanol were placed in a beaker and stirred to prepare a stearic acid treatment solution.

  1000 g of silica was dried in an oven at 120 ° C. for 2 hours, and the above-mentioned dried silica was put into a 20 L Henschel mixer preheated to 110 ° C. and stirred, and the sulfur-containing silane coupling agent treatment liquid, aminosilane cup The ring agent treatment liquid and the stearic acid treatment liquid were sprayed in this order. Stirring was further continued for 15 minutes, and the treated silica was taken out. The obtained treated silica was heat-treated in an oven at 120 ° C. for 2 hours to obtain surface-treated silica 1.

-Preparation of surface-treated silica 2 80 g of a sulfur-containing silane coupling agent A, 50 g of distilled water, and 50 g of ethanol were placed in a beaker and stirred to prepare a sulfur-containing silane coupling agent treatment solution.

  1000 g of silica was dried in an oven at 120 ° C. for 2 hours, and the dried silica was put in a 20 L Henschel mixer preheated to 110 ° C. and stirred, and the sulfur-containing silane coupling agent treatment solution was sprayed. . Stirring was further continued for 15 minutes, and the treated silica was taken out. The obtained treated silica was heat-treated in an oven at 120 ° C. for 2 hours to obtain surface-treated silica 2.

-Preparation of surface-treated silica 3 80 g of sulfur-containing silane coupling agent A, 50 g of distilled water, and 50 g of ethanol were placed in a beaker and stirred to prepare a sulfur-containing silane coupling agent treatment solution. 50 g of stearic acid and 150 g of ethanol were placed in a beaker and stirred to prepare a stearic acid treatment solution.

  1000 g of silica was dried in an oven at 120 ° C. for 2 hours, and the dried silica was put in a 20 L Henschel mixer preheated to 110 ° C. and stirred, and the sulfur-containing silane coupling agent treatment solution, stearic acid It sprayed in order of the process liquid. Stirring was further continued for 15 minutes, and the treated silica was taken out. The obtained treated silica was heat-treated in an oven at 120 ° C. for 2 hours to obtain surface-treated silica 3.

-Preparation of surface-treated silica 4 5000 mL of isopropyl alcohol was added to a mixer, and 1000 g of silica was further added and stirred. Subsequently, 80 g of a sulfur-containing silane coupling agent A was added, and after stirring for 20 minutes, 20 g of aminosilane coupling agent A was added and further stirred for 20 minutes. The solvent was removed under reduced pressure until the solvent was about 1/3 of the slurry. Then, 50 g of stearic acid was melted at 50 ° C. in 500 mL of toluene, mixed with the previous slurry, and stirred for 120 minutes. It dried under reduced pressure with the evaporator and heat-processed at 120 degreeC for 2 hours in oven, and obtained the surface treatment silica 4. FIG.

-Preparation of surface-treated silica 5 80 g of a sulfur-containing silane coupling agent B, 50 g of distilled water, and 50 g of ethanol were placed in a beaker and stirred to prepare a sulfur-containing silane coupling agent treatment solution. 20 g of aminosilane coupling agent B, 20 g of distilled water, and 20 g of ethanol were placed in a beaker and stirred to prepare an aminosilane coupling agent treatment solution. 50 g of stearic acid and 150 g of ethanol were placed in a beaker and stirred to prepare a stearic acid treatment solution.

  1000 g of silica was dried in an oven at 120 ° C. for 2 hours, and the above-mentioned dried silica was put into a 20 L Henschel mixer preheated to 110 ° C. and stirred, and the sulfur-containing silane coupling agent treatment liquid, aminosilane cup The ring agent treatment liquid and the stearic acid treatment liquid were sprayed in this order. Stirring was further continued for 15 minutes, and the treated silica was taken out. The obtained treated silica was heat-treated in an oven at 120 ° C. for 2 hours to obtain surface-treated silica 5.

[First embodiment]
Using a Banbury mixer, according to the composition (parts by mass) shown in Table 1 below, first, in the first mixing stage, components other than sulfur and vulcanization accelerator are added and mixed, and then the resulting mixture is finally mixed. A rubber composition for a tire tread was prepared by adding and mixing sulfur and a vulcanization accelerator in the stage. The detail of each component of Table 1 is as follows. In each formulation of Examples and Comparative Examples, the blending amount of the surface-treated silica and the untreated hydrophilic silica was set so that the total mass of the silica content was constant at 80 parts by mass.

SSBR: Styrene-butadiene rubber, LANXESS "VSL5025-0HM"
・ Process oil: "Extract 4S" manufactured by Showa Shell Sekiyu KK
Carbon black: “Diamond Black N339” manufactured by Mitsubishi Chemical Corporation
・ Hydrophilic silica: Untreated silica, “Nip Seal AQ” manufactured by Tosoh Silica Co., Ltd.
・ Sulfur-containing silane coupling agent A: “Si75” manufactured by Evonik Degussa Co., Ltd., bis (3-triethoxysilylpropyl) disulfide ・ Zinc flower: “Zinc Flower No. 1” manufactured by Mitsui Metal Mining Co., Ltd.
Anti-aging agent: “Antigen 6C” manufactured by Sumitomo Chemical Co., Ltd.
・ Stearic acid: “Lunac S-20” manufactured by Kao Corporation
・ Wax: Nippon Seiki Co., Ltd. “OZOACE0355”
・ Sulfur: “5% oil-filled fine powder sulfur” manufactured by Tsurumi Chemical Co., Ltd.
・ Vulcanization accelerator 1: “Sokushinol CZ” manufactured by Sumitomo Chemical Co., Ltd.
・ Vulcanization accelerator 2: “Noxeller D” manufactured by Ouchi Shinsei Chemical Co., Ltd.

  Each rubber composition obtained was evaluated for low fuel consumption (low fuel consumption index) and scorch (scorch time index), and the balance (scorch / low fuel consumption). Each evaluation method is as follows.

-Low fuel consumption: For test pieces vulcanized at 160 ° C x 30 minutes, according to JIS K6394, using a viscoelasticity tester manufactured by Toyo Seiki, temperature 60 ° C, frequency 10Hz, initial strain 10%, dynamic strain 1 The loss factor tan δ was measured under the condition of%, and it was expressed as an index with the value of Comparative Example 1 being 100. The smaller the index, the smaller the tan δ, and the less the heat is generated, that is, the low heat build-up property and the low fuel consumption.

Scorch property: Mooney scorch test in accordance with JIS K6300 was performed using a rheometer (L-shaped rotor), and the t5 value at the time of measurement at a temperature of 125 ° C. for 1 minute was obtained. Expressed as an index. As the index is larger, burns are less likely to occur and the scorch property is better.

Scorch property / low fuel consumption property: An index of a balance between low fuel consumption property and scorch property, and was calculated by (Scorch time index / low fuel efficiency index) × 100. The higher this value, the better.

  The results are as shown in Table 1. In Comparative Example 2 in which the surface-treated silica was used alone, although the fuel efficiency was improved, the scorch property was greatly deteriorated. In Comparative Example 3, the surface-treated silica and the hydrophilic silica were used in combination, but since the sulfur-containing silane coupling agent was not added, the effect of improving the fuel efficiency was not obtained. In Comparative Example 4, the surface-treated silica 2 to be blended with hydrophilic silica was a single treatment containing a sulfur-containing silane coupling agent and was not treated with a fatty acid. Therefore, a sulfur-containing silane coupling agent was added at the time of rubber compounding. In spite of this, the improvement effect of low fuel consumption was small.

  On the other hand, since it is Examples 1-3, it uses together predetermined surface-treated silica and hydrophilic silica, and also added a sulfur containing silane coupling agent at the time of rubber compounding, so it suppresses deterioration of scorch property. However, it was possible to improve fuel efficiency. As shown in FIG. 1, in the case of an example in which surface-treated silica and hydrophilic silica were blended, the surface-treated silica was not blended (Comparative Example 1: surface treatment silica substitution amount 0%), and surface-treated silica. The low fuel consumption index was below the straight line connecting the one with the replacement amount of 100% (Comparative Example 2), and the synergistic effect of low fuel consumption by the blend was shown.

[Second Embodiment]
Using a Banbury mixer, according to the composition (parts by mass) shown in Table 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 finally mixed A rubber composition for a tire tread was prepared by adding and mixing sulfur and a vulcanization accelerator in the stage. Details of each component are the same as in the first embodiment.

  Using each of the obtained rubber compositions, as in the first example, the fuel economy and scorch properties and the balance between them were evaluated. The results are as shown in Table 2 and FIG. 2. In the case of surface-treated silica 3 surface-treated with a sulfur-containing silane coupling agent and a fatty acid, the surface treatment was performed with a sulfur-containing silane coupling agent, an aminosilane coupling agent, and a fatty acid. The same effect as in the case of the first example using the surface-treated silica 1 was observed.

[Third embodiment]
Using a Banbury mixer, according to the composition (parts by mass) shown in Table 3 below, first, in the first mixing stage, components other than sulfur and a vulcanization accelerator are added and mixed, and then the resulting mixture is finally mixed. A rubber composition for a tire tread was prepared by adding and mixing sulfur and a vulcanization accelerator in the stage. Details of each component are the same as in the first embodiment.

  Using each of the obtained rubber compositions, as in the first example, the fuel economy and scorch properties and the balance between them were evaluated. The results are as shown in Table 3 and FIG. 3. Even when the surface-treated silica 4 by wet treatment was used, the same effect as in the first example using the surface-treated silica 1 was recognized.

[Fourth embodiment]
Using a Banbury mixer, according to the composition (parts by mass) shown in Table 4 below, first, in the first mixing stage, components other than sulfur and vulcanization accelerator are added and mixed, and then the resulting mixture is finally mixed. A rubber composition for a tire tread was prepared by adding and mixing sulfur and a vulcanization accelerator in the stage. About the component of Table 4, sulfur containing silane coupling agent B is Toray Dow Corning Co., Ltd. product "Z-6062" (3-mercaptopropyltrimethoxysilane), and other components are the same as 1st Example. It is.

  Using each of the obtained rubber compositions, as in the first example, the fuel economy and scorch properties and the balance between them were evaluated. Evaluation is an index with the value of Comparative Example 7 as 100. The results are as shown in Table 4 and FIG. 4. Even when mercaptosilane was used as the sulfur-containing silane coupling agent, the same effect as in the first example was observed.

Claims (7)

For rubber component,
Silica surface-treated with a sulfur-containing silane coupling agent and a fatty acid, and at least one surface-treated silica selected from silica surface-treated with a sulfur-containing silane coupling agent, an aminosilane coupling agent, and a fatty acid; ,
Hydrophilic silica,
A sulfur-containing silane coupling agent;
The rubber composition for tires which mix | blends. The tire rubber composition according to claim 1, wherein the sulfur-containing silane coupling agent is represented by the following general formula (1).
(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.) The tire rubber composition according to claim 1 or 2, wherein the aminosilane coupling agent is represented by the following general formula (5).
_{^{(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.)   The rubber composition for tire according to any one of claims 1 to 3, wherein the fatty acid is a fatty acid having 5 to 30 carbon atoms.   The tire according to any one of claims 1 to 4, wherein a ratio of the surface-treated silica to a total amount of the surface-treated silica and the hydrophilic silica is 30% by mass or more and less than 100% by mass in terms of a silica mass ratio. Rubber composition.   The surface-treated silica and the hydrophilic silica are blended in a total amount of 10 to 200 parts by mass with respect to 100 parts by mass of the rubber component, and the sulfur-containing silane coupling agent is added to 2 parts by mass of 100 parts by mass of the hydrophilic silica. The rubber composition for tires according to any one of claims 1 to 5, which is formulated by blending ~ 20 parts by mass.   The pneumatic tire which has a rubber part which uses the rubber composition of any one of Claims 1-6.

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