JP6790726B2 - Manufacturing method of rubber composition for tires - Google Patents

Description

The present invention relates to a method for producing a rubber composition for a tire.

In recent years, in response to increasing environmental awareness, it has been required to reduce the rolling resistance of tires in order to improve the fuel efficiency of automobiles.

Generally, in order to reduce rolling resistance, a method of blending silica with tread rubber is used, but when silica is blended, there is a problem that the Mooney viscosity after kneading becomes high and the workability is lowered. .. Silica is a hydrophilic material whose surface is covered with silanol groups, and is difficult to mix with the diene rubber used in rubber compositions for tires. However, by using it in combination with a silane coupling agent, silica and silane cups can be used. Since the ring agent is bonded by polycondensation and the surface of silica is made hydrophobic, it can be easily dispersed in diene rubber (see, for example, Patent Document 1).

Recently, with the enforcement of tire labeling systems in each country, tread rubber is required to have not only low fuel consumption but also high-level compatibility with fracture characteristics, which is a performance that contradicts low fuel consumption. , Current technology is not sufficient to meet this requirement.

JP-A-2002-363346

An object of the present invention is to solve the above problems and to provide a method for producing a rubber composition for a tire, which has improved fuel efficiency, fracture characteristics and workability in a well-balanced manner.

In the present invention, a rubber component, silica and a silane coupling agent are added and kneaded to obtain a first kneaded product, and the first kneaded product is further kneaded to obtain a second kneaded product. And the third step of adding the second kneaded product and the vulcanizing chemicals and kneading them to obtain an unvulcanized rubber composition, which was set in the range of 150 to 170 ° C. in the first step. The present invention relates to a method for producing a rubber composition for a tire, in which a reaction process of kneading the rubber component, the silica and the silane coupling agent is carried out until the following formulas (1) and (2) are satisfied while maintaining the reaction temperature.
Equation (1) ΔG * t / ΔG * 0 × 100 <80
(In the formula, ΔG * 0 is G * of 100 ° C. and 0.5% strain and G of 100 ° C. and 64% strain of the unreacted kneaded product obtained by completing kneading when the reaction temperature is reached. The difference from * is that ΔG * t is G * and 100 of the first kneaded product obtained by kneading for a predetermined time after reaching the same reaction temperature as ΔG * 0 at 100 ° C. and 0.5% strain. The difference from G * at ° C and 64% strain.)
Equation (2) Vt / V0 × 100 <80
(In the formula, V0 is the Mooney viscosity at 130 ° C. of the unreacted kneaded product obtained by terminating the kneading when the reaction temperature is reached, and Vt is a predetermined value after reaching the same reaction temperature as V0. The Mooney viscosity of the first kneaded product obtained by time kneading at 130 ° C.).

（式中、Ｒ^１００１は−Ｃｌ、−Ｂｒ、−ＯＲ^１００６、−Ｏ（Ｏ＝）ＣＲ^１００６、−ＯＮ＝ＣＲ^１００６Ｒ^１００７、−ＯＮ＝ＣＲ^１００６Ｒ^１００７、−ＮＲ^１００６Ｒ^１００７及び−（ＯＳｉＲ^１００６Ｒ^１００７）_ｈ（ＯＳｉＲ^１００６Ｒ^１００７Ｒ^１００８）から選択される一価の基（Ｒ^１００６、Ｒ^１００７及びＲ^１００８は同一でも異なっていても良く、各々水素原子又は炭素数１〜１８の一価の炭化水素基であり、ｈは平均値が１〜４である。）であり、Ｒ^１００２はＲ^１００１、水素原子又は炭素数１〜１８の一価の炭化水素基、Ｒ^１００３はＲ^１００１、Ｒ^１００２、水素原子又は−［Ｏ（Ｒ^１００９Ｏ）_ｊ］_０．５−基（Ｒ^１００９は炭素数１〜１８のアルキレン基、ｊは１〜４の整数である。）、Ｒ^１００４は炭素数１〜１８の二価の炭化水素基、Ｒ^１００５は炭素数１〜１８の一価の炭化水素基を示し、ｘ、ｙ及びｚは、ｘ＋ｙ＋２ｚ＝３、０≦ｘ≦３、０≦ｙ≦２、０≦ｚ≦１の関係を満たす数である。） The silane coupling agent is preferably a thioester-based silane coupling agent represented by the following formula (S1).

(In the formula, R ¹⁰⁰¹ is -Cl, -Br, -OR ¹⁰⁰⁶ , -O (O =) CR ¹⁰⁰⁶ , -ON = CR ¹⁰⁰⁶ R ¹⁰⁰⁷ , -ON = CR ¹⁰⁰⁶ R ¹⁰⁰⁷ , -NR ¹⁰⁰⁶ R ^{1007 and-} ( The monovalent groups (R ¹⁰⁰⁶ , R ¹⁰⁰⁷ and R ¹⁰⁰⁸ ) selected from the OSiR ¹⁰⁰⁶ R ¹⁰⁰⁷ ) _h (OSiR ¹⁰⁰⁶ R ¹⁰⁰⁷ R ¹⁰⁰⁸ ) may be the same or different, each having a hydrogen atom or 1-18 carbon atoms. It is a monovalent hydrocarbon group, h has an average value of 1 to 4), R ¹⁰⁰² is R ¹⁰⁰¹ , a hydrogen atom or a monovalent hydrocarbon group having 1 to 18 carbon atoms, and R ¹⁰⁰³ is R. ¹⁰⁰¹ , R ¹⁰⁰² , hydrogen atom ^or- [O (R ¹⁰⁰⁹ O) _j ] _0.5 -group (R ¹⁰⁰⁹ is an alkylene group having 1 to 18 carbon atoms, j is an integer of 1 to 4), R ¹⁰⁰⁴ Is a divalent hydrocarbon group having 1 to 18 carbon atoms, R ¹⁰⁰⁵ is a monovalent hydrocarbon group having 1 to 18 carbon atoms, and x, y and z are x + y + 2z = 3, 0 ≦ x ≦ 3,0. It is a number that satisfies the relationship of ≦ y ≦ 2 and 0 ≦ z ≦ 1.)

The method for producing a rubber composition for a tire is preferably to produce a rubber composition for a cap tread.

According to the present invention, the reaction treatment of kneading the rubber component, silica and the silane coupling agent at a predetermined temperature is carried out until the formulas (1) and (2) are satisfied, thereby resulting in low fuel consumption, fracture characteristics and processing. A rubber composition for a tire having improved properties in a well-balanced manner can be produced.

In the present invention, a rubber component, silica and a silane coupling agent are added and kneaded to obtain a first kneaded product, and the first kneaded product is further kneaded to obtain a second kneaded product. And the third step of adding the second kneaded product and the vulcanizing chemicals and kneading them to obtain an unvulcanized rubber composition, which was set in the range of 150 to 170 ° C. in the first step. The present invention relates to a method for producing a rubber composition for a tire, in which a reaction process of kneading the rubber component, the silica and the silane coupling agent is carried out until the following formulas (1) and (2) are satisfied while maintaining the reaction temperature.
Equation (1) ΔG * t / ΔG * 0 × 100 <80
(In the formula, ΔG * 0 is G * of 100 ° C. and 0.5% strain and G of 100 ° C. and 64% strain of the unreacted kneaded product obtained by completing kneading when the reaction temperature is reached. The difference from * is that ΔG * t is G * and 100 of the first kneaded product obtained by kneading for a predetermined time after reaching the same reaction temperature as ΔG * 0 at 100 ° C. and 0.5% strain. The difference from G * at ° C and 64% strain.)
Equation (2) Vt / V0 × 100 <80
(In the formula, V0 is the Mooney viscosity at 130 ° C. of the unreacted kneaded product obtained by terminating the kneading when the reaction temperature is reached, and Vt is a predetermined value after reaching the same reaction temperature as V0. The Mooney viscosity of the first kneaded product obtained by time kneading at 130 ° C.).

When the polycondensation reaction between silica and the silane coupling agent is promoted and the dispersibility of silica is improved, ΔG * (Pain effect) defined by the difference between G * in the low strain region and G * in the high strain region and , Mooney viscosity decreases. ΔG * t / ΔG * 0 × 100 in the formula (1) is an index showing how much ΔG * in the example in which the reaction treatment was performed decreased with reference to ΔG * in the example in which the reaction treatment was not performed. Yes, Vt / V0 × 100 in the formula (2) is an index showing how much the Mooney viscosity of the example in which the reaction treatment was carried out decreased based on the Mooney viscosity of the example in which the reaction treatment was not carried out. Therefore, the degree of dispersion of silica can be determined from these indexes. Utilizing this, in the present invention, in the first step, the reaction treatment of kneading the rubber component, silica and the silane coupling agent is carried out until the formulas (1) and (2) are satisfied, so that the silica is good. It is possible to produce a rubber composition for tires, which is dispersed in a balanced manner and has improved fuel efficiency, fracture characteristics and workability in a well-balanced manner.

Further, the measurement of G * (complex elastic modulus in shear mode) is usually carried out in a state where the rubber is vulcanized, but in the present invention, it is carried out in a state where the rubber is not vulcanized. As a result, the effect of dispersion of pure silica can be extracted, and the dispersibility of silica can be estimated accurately.

First, each component used in the present invention will be described.

(Rubber component)
As the rubber component, it is preferable to use a diene-based rubber. Natural rubber (NR) and diene synthetic rubber can be used as the diene rubber, and examples of the diene synthetic rubber include isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), and acrylonitrile butadiene rubber. (NBR), chloroprene rubber (CR), butyl rubber (IIR) and the like. These may be used alone or in combination of two or more. Among them, NR, BR, and SBR are preferable, and BR and SBR are more preferable, because they show fuel efficiency, fracture characteristics, and workability in a well-balanced manner.

In the rubber composition obtained by the production method of the present invention, the content of BR in 100% by mass of the rubber component is preferably 5% by mass or more because fuel efficiency, fracture characteristics and workability can be obtained in a well-balanced manner. , More preferably 15% by mass or more, and preferably 70% by mass or less, more preferably 50% by mass or less.

In the rubber composition obtained by the production method of the present invention, the content of SBR in 100% by mass of the rubber component is preferably 30% by mass or more because low fuel consumption, fracture characteristics and workability can be obtained in a well-balanced manner. , More preferably 50% by mass or more, and preferably 95% by mass or less, more preferably 85% by mass or less.

(silica)
Examples of silica include, but are not limited to, silica prepared by a dry method (anhydrous silica) and silica prepared by a wet method (hydrous silica), which have many silanol groups on the surface and are silane cups. Silica prepared by a wet method is preferable because it has many reaction points with the ring agent. Only one type of silica may be used, or two or more types may be used in combination. Examples of commercially available silica products include Ultrasil VN3 manufactured by Evonik Industries, Inc.

Nitrogen adsorption specific surface area _(N 2 SA) of silica is preferably ^90m 2 / g or more, more preferably ^{95 m} 2 / g or more, further preferably 100 m ² / g or more. If it is less than 90 m ² / g, sufficient fracture characteristics may not be obtained. The N ₂ SA of silica is preferably 300 m ² / g or less, more preferably 240 m ² / g or less. If it exceeds 300 m ² / g, it becomes difficult to disperse it in rubber, which may cause poor dispersion.
The nitrogen adsorption specific surface area of silica is a value measured by the BET method according to ASTM D3037-81.

In the rubber composition obtained by the production method of the present invention, the silica content is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, still more preferably 50 parts by mass or more with respect to 100 parts by mass of the rubber component. Is. If it is less than 5 parts by mass, it may not be possible to obtain the reinforcing property required for the tire. The silica content is preferably 200 parts by mass or less, more preferably 180 parts by mass or less, and further preferably 150 parts by mass or less. If it exceeds 200 parts by mass, the workability deteriorates and the processing may become difficult.

（式中、Ｒ^１００１は−Ｃｌ、−Ｂｒ、−ＯＲ^１００６、−Ｏ（Ｏ＝）ＣＲ^１００６、−ＯＮ＝ＣＲ^１００６Ｒ^１００７、−ＯＮ＝ＣＲ^１００６Ｒ^１００７、−ＮＲ^１００６Ｒ^１００７及び−（ＯＳｉＲ^１００６Ｒ^１００７）_ｈ（ＯＳｉＲ^１００６Ｒ^１００７Ｒ^１００８）から選択される一価の基（Ｒ^１００６、Ｒ^１００７及びＲ^１００８は同一でも異なっていても良く、各々水素原子又は炭素数１〜１８の一価の炭化水素基であり、ｈは平均値が１〜４である。）であり、Ｒ^１００２はＲ^１００１、水素原子又は炭素数１〜１８の一価の炭化水素基、Ｒ^１００３はＲ^１００１、Ｒ^１００２、水素原子又は−［Ｏ（Ｒ^１００９Ｏ）_ｊ］_０．５−基（Ｒ^１００９は炭素数１〜１８のアルキレン基、ｊは１〜４の整数である。）、Ｒ^１００４は炭素数１〜１８の二価の炭化水素基、Ｒ^１００５は炭素数１〜１８の一価の炭化水素基を示し、ｘ、ｙ及びｚは、ｘ＋ｙ＋２ｚ＝３、０≦ｘ≦３、０≦ｙ≦２、０≦ｚ≦１の関係を満たす数である。） (Silane coupling agent)
As the silane coupling agent, the thioester-based silane represented by the following formula (S1) is easy to control the temperature during the reaction treatment in the first step and is excellent in the effect of improving the reinforcing property of the rubber composition. A coupling agent can be preferably used.

(In the formula, R ¹⁰⁰¹ is -Cl, -Br, -OR ¹⁰⁰⁶ , -O (O =) CR ¹⁰⁰⁶ , -ON = CR ¹⁰⁰⁶ R ¹⁰⁰⁷ , -ON = CR ¹⁰⁰⁶ R ¹⁰⁰⁷ , -NR ¹⁰⁰⁶ R ^{1007 and-} ( The monovalent groups (R ¹⁰⁰⁶ , R ¹⁰⁰⁷ and R ¹⁰⁰⁸ ) selected from the OSiR ¹⁰⁰⁶ R ¹⁰⁰⁷ ) _h (OSiR ¹⁰⁰⁶ R ¹⁰⁰⁷ R ¹⁰⁰⁸ ) may be the same or different, each having a hydrogen atom or 1-18 carbon atoms. It is a monovalent hydrocarbon group, h has an average value of 1 to 4), R ¹⁰⁰² is R ¹⁰⁰¹ , a hydrogen atom or a monovalent hydrocarbon group having 1 to 18 carbon atoms, and R ¹⁰⁰³ is R. ¹⁰⁰¹ , R ¹⁰⁰² , hydrogen atom ^or- [O (R ¹⁰⁰⁹ O) _j ] _0.5 -group (R ¹⁰⁰⁹ is an alkylene group having 1 to 18 carbon atoms, j is an integer of 1 to 4), R ¹⁰⁰⁴ Is a divalent hydrocarbon group having 1 to 18 carbon atoms, R ¹⁰⁰⁵ is a monovalent hydrocarbon group having 1 to 18 carbon atoms, and x, y and z are x + y + 2z = 3, 0 ≦ x ≦ 3,0. It is a number that satisfies the relationship of ≦ y ≦ 2 and 0 ≦ z ≦ 1.)

In the above formula (S1), R ¹⁰⁰⁵ , R ¹⁰⁰⁶ , R ¹⁰⁰⁷ and R ¹⁰⁰⁸ each independently consist of a linear, cyclic or branched alkyl group having 1 to 18 carbon atoms, an alkenyl group, an aryl group and an aralkyl group. It is preferably a group selected from the group. When R ¹⁰⁰² is a monovalent hydrocarbon group having 1 to 18 carbon atoms, it is a group selected from the group consisting of a linear, cyclic or branched alkyl group, an alkenyl group, an aryl group and an aralkyl group. It is preferable to have. R ¹⁰⁰⁹ is preferably a linear, cyclic or branched alkylene group, particularly of which is linear. ^R1004 is, for example, an alkylene group having 1 to 18 carbon atoms, an alkenylene group having 2 to 18 carbon atoms, a cycloalkylene group having 5 to 18 carbon atoms, a cycloalkylalkylene group having 6 to 18 carbon atoms, and an arylene having 6 to 18 carbon atoms. Examples include a group and an aralkylene group having 7 to 18 carbon atoms. The alkylene group and the alkenylene group may be linear or branched, and the cycloalkylene group, the cycloalkylalkylene group, the arylene group and the aralkylene group have a functional group such as a lower alkyl group on the ring. You may have. As the R ¹⁰⁰⁴ , an alkylene group having 1 to 6 carbon atoms is preferable, and a linear alkylene group such as a methylene group, an ethylene group, a trimethylene group, a tetramethylene group, a pentamethylene group and a hexamethylene group are particularly preferable.

Specific examples of R ¹⁰⁰² , R ¹⁰⁰⁵ , R ¹⁰⁰⁶ , R ¹⁰⁰⁷ and R ^{1008 in} the above formula (S1) include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group and sec-. Butyl group, tert-butyl group, pentyl group, hexyl group, octyl group, decyl group, dodecyl group, cyclopentyl group, cyclohexyl group, vinyl group, propenyl group, allyl group, hexenyl group, octenyl group, cyclopentenyl group, Cyclohexenyl group, phenyl group, tolyl group, xsilyl group, naphthyl group, benzyl group, phenethyl group, naphthylmethyl group and the like can be mentioned.
Examples of R ¹⁰⁰⁹ in the above formula (S1) include methylene group, ethylene group, n-propylene group, n-butylene group, hexylene group and the like as the linear alkylene group, and the branched alkylene group includes the branched alkylene group. , Isopropylene group, isobutylene group, 2-methylpropylene group and the like.

Specific examples of the thioester-based silane coupling agent represented by the above formula (S1) include 3-hexanoylthiopropyltriethoxysilane, 3-octanoylthiopropyltriethoxysilane, and 3-decanoylthiopropyltriethoxysilane. , 3-Lauroylthiopropyltriethoxysilane, 2-hexanoylthioethyltriethoxysilane, 2-octanoylthioethyltriethoxysilane, 2-decanoylthioethyltriethoxysilane, 2-lauroylthioethyltriethoxysilane, 3 -Hexanoylthiopropyltrimethoxysilane, 3-octanoylthiopropyltrimethoxysilane, 3-decanoylthiopropyltrimethoxysilane, 3-lauroylthiopropyltrimethoxysilane, 2-hexanoylthioethyltrimethoxysilane, 2- Examples thereof include octanoylthioethyltrimethoxysilane, 2-decanoylthioethyltrimethoxysilane, and 2-lauroylthioethyltrimethoxysilane. These may be used alone or in combination of two or more. Of these, 3-octanoylthiopropyltriethoxysilane (NXTsilane manufactured by Momentive Performance Materials) is particularly preferable. Since 3-octanoylthiopropyltriethoxysilane does not have a plurality of alkoxysilyl groups in the molecule, there is little aggregation between the coupling agents, and the mercapto group having high reactivity with the polymer part becomes a fatty acid thioester. As a result, non-uniformity due to a rapid reaction is prevented, so that the chemical bond between the silica and the polymer can be uniformly formed.

In the rubber composition obtained by the production method of the present invention, the content of the silane coupling agent is preferably 1 part by mass or more, more preferably 2 parts by mass or more, based on 100 parts by mass of silica. If it is less than 1 part by mass, good workability may not be obtained. The content of the silane coupling agent is preferably 20 parts by mass or less, more preferably 15 parts by mass or less. If it exceeds 20 parts by mass, the effect commensurate with the increase in cost tends not to be obtained.

(Vulcanization chemicals)
Examples of the vulcanization chemical include a vulcanizing agent and a vulcanization accelerator, and it is preferable to use a vulcanizing agent and a vulcanization accelerator in combination.

As the vulcanizing agent, an organic peroxide, a sulfur-based vulcanizing agent, or the like can be used. Examples of the organic peroxide include benzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, t-butyl cumyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide, 2,5-dimethyl-2, 5-Di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, 2,5-dimethyl-2,5-di (t-butylperoxy) hexin- Examples thereof include 3,1,3-bis (t-butylperoxypropyl) benzene. Examples of the sulfur-based vulcanizing agent include sulfur and morpholine disulfide. These may be used alone or in combination of two or more. Among them, a sulfur-based vulcanizing agent is preferable, and sulfur is more preferable, because the effect of the present invention can be obtained satisfactorily.

In the rubber composition obtained by the production method of the present invention, the content of the vulcanizing agent is preferably the content of the vulcanizing agent with respect to 100 parts by mass of the rubber component, because low fuel consumption, fracture characteristics and processability can be obtained in a well-balanced manner. It is 0.1 part by mass or more, more preferably 0.5 part by mass or more, and preferably 8 parts by mass or less, more preferably 5 parts by mass or less.

Examples of the vulcanization accelerator include sulfenamide-based, thiazole-based, thiuram-based, thiourea-based, guanidine-based, dithiocarbamic acid-based, aldehyde-amine-based, aldehyde-ammonia-based, imidazoline-based, and xanthate-based vulcanization accelerator. Can be mentioned. These may be used alone or in combination of two or more. Of these, sulfenamide-based and guanidine-based are preferable, and sulfenamide-based and guanidine-based are more preferable in combination because the effects of the present invention can be obtained satisfactorily.

In the rubber composition obtained by the production method of the present invention, the content of the vulcanization accelerator is preferably based on 100 parts by mass of the rubber component, because low fuel consumption, fracture characteristics and processability can be obtained in a well-balanced manner. Is 0.5 parts by mass or more, more preferably 1.5 parts by mass or more, and preferably 10 parts by mass or less, more preferably 8 parts by mass or less.

(Other ingredients)
In addition to the above-mentioned components, the rubber composition obtained by the production method of the present invention includes a compounding agent generally used for producing the rubber composition, for example, carbon black; antiaging agent; softening agent such as oil; stearic acid. , Vulcanization aids such as zinc oxide; etc. can be blended.

Next, each kneading step in the production method of the present invention will be described.

(First step)
The first step is a step of adding a rubber component, silica and a silane coupling agent and kneading them to obtain a first kneaded product.

In this step, the reaction process of kneading the rubber component, silica and the silane coupling agent while maintaining the reaction temperature set in the range of 150 to 170 ° C. is carried out until the following formulas (1) and (2) are satisfied. carry out. Thereby, the reaction between silica and the silane coupling agent can be sufficiently promoted.
Equation (1) ΔG * t / ΔG * 0 × 100 <80
(In the formula, ΔG * 0 is G * of 100 ° C. and 0.5% strain and G of 100 ° C. and 64% strain of the unreacted kneaded product obtained by completing kneading when the reaction temperature is reached. The difference from * is that ΔG * t is G * and 100 of the first kneaded product obtained by kneading for a predetermined time after reaching the same reaction temperature as ΔG * 0 at 100 ° C. and 0.5% strain. The difference from G * at ° C and 64% strain.)
Equation (2) Vt / V0 × 100 <80
(In the formula, V0 is the Mooney viscosity at 130 ° C. of the unreacted kneaded product obtained by terminating the kneading when the reaction temperature is reached, and Vt is a predetermined value after reaching the same reaction temperature as V0. The Mooney viscosity of the first kneaded product obtained by time kneading at 130 ° C.).

When the reaction temperature is less than 150 ° C., the reaction rate of the silica and the silane coupling agent is slow, and the silica cannot be sufficiently hydrophobic, so that the necessary dispersion of silica and the bond between the silica and the polymer cannot be ensured, resulting in low fuel consumption. And the breaking strength may not be improved or deteriorated. Further, when the reaction temperature exceeds 170 ° C., the reaction rate of silica and the silane coupling agent becomes too fast, and the reaction between the coupling agent and the polymer occurs during kneading, so that the dispersibility of silica is rather deteriorated. , Fuel efficiency and breaking strength may not be improved or deteriorated.

The procedure of the first step will be described below. For example, when the reaction temperature is set to 150 ° C, when the rubber temperature reaches 150 ° C during kneading, the rotation speed of the mixer, the falling pressure of the ram, the temperature inside the chamber, etc. are adjusted so as to maintain 150 ° C. Kneading while doing (reaction processing). This reaction treatment is carried out for a predetermined time until the first kneaded product satisfies the formulas (1) and (2). Then, when the time required for the first kneaded product to satisfy the formulas (1) and (2) elapses, the kneading is completed and the first kneaded product is discharged from the kneader. The G * and Mooney viscosities of the first kneaded product thus obtained are measured, and ΔG * t and Vt are calculated.
In this example, ΔG * 0 and V0 are unreacted kneaded products obtained by completing the kneading when the rubber temperature reaches 150 ° C. (the first step is completed without performing the reaction treatment). It is determined based on the measurement result of the kneaded product obtained above. Since ΔG * 0 and V0 are different for each reaction temperature, it is necessary to determine ΔG * 0 and V0 at the changed reaction temperature when the reaction temperature is changed.

The reaction processing time required for the first kneaded product to satisfy the formulas (1) and (2) depends on the type of kneading machine used for kneading, the content of the first kneaded product, the set reaction temperature, and the like. Although different, 80-800 seconds is usually preferred.

The rubber temperature (temperature of the kneaded product) during the reaction treatment affects the reaction between silica and the silane coupling agent and the reaction between the silane coupling agent and the rubber component. Therefore, from the viewpoint of stabilizing the quality of the obtained rubber composition, the rubber temperature during the reaction treatment is preferably as constant as possible, and specifically, it is in the range of ± 3 ° C. of the set reaction temperature. Is preferable.

As the kneader used in the first step, a closed type Banbury mixer is preferable. The shape of the rotor of the Banbury mixer may be either a tangential type or a meshing type.

The rubber component, silica, and silane coupling agent to be added in the first step may be the total amount or a part, but the total amount is preferable.

In the first step, in addition to the rubber component, silica and the silane coupling agent, other components may be added and kneaded. The other components are not particularly limited as long as they are components other than vulcanizing chemicals, and examples thereof include carbon black, oil, antiaging agents, waxes, stearic acid, zinc oxide and the like.

(Second step)
The second step is a step of further kneading the first kneaded product obtained in the first step to obtain a second kneaded product. By providing the second step, the dispersion of silica is further promoted.
In the second step, only the first kneaded product may be kneaded, or other components may be added and kneaded together with the first kneaded product.

The kneading in the second step is preferably carried out under the same conditions as in the first step. That is, it is preferable to carry out the same reaction treatment as in the first step in the second step. Further, as the kneader to be used, a closed type Banbury mixer is preferable as in the first step.

(Third step)
The third step is a step of adding the second kneaded product and the vulcanizing chemical obtained in the second step and kneading them to obtain an unvulcanized rubber composition.

In the third step, in order to prevent scorch from being generated due to an increase in the rubber temperature during kneading, kneading is terminated when the rubber temperature reaches a predetermined temperature (preferably 60 to 120 ° C.), and unvulcanized. It is preferable to discharge the rubber composition from the kneader. The kneading time of the third step is not particularly limited, but is preferably about 1 to 15 minutes.

The kneader used in the third step may be a closed type Banbury mixer or an open roll as in the first step.

(Other processes)
The unvulcanized rubber composition obtained in the third step is extruded according to the shape of the tire member (preferably cap tread), molded by a normal method on a tire molding machine, and another tire member. After forming an unvulcanized tire by laminating the tire together with the tire, the tire can be manufactured by heating and pressurizing in a vulcanizer.

The present invention will be specifically described based on Examples, but the present invention is not limited thereto.

Hereinafter, various chemicals used in Examples and Comparative Examples will be collectively described.
SBR: NS616 manufactured by Zeon Corporation
BR: BR1220 manufactured by Nippon Zeon Corporation (cis 1, 4 content: 96% by mass)
Carbon Black: Seest N220 manufactured by Mitsubishi Chemical Corporation
Silica: Ultrasil VN3 manufactured by Evonik (average primary particle size: 15 nm, N ₂ SA: 175 m ² / g)
Oil: Process X-140 manufactured by Japan Energy Co., Ltd.
Silane coupling agent: NXTsilane (3-octanoylthiopropyltriethoxysilane) manufactured by Momentive Performance Materials.
Anti-aging agent: Antigen 6C (N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd.
Wax: Sunknock N manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Stearic acid: Stearic acid "Camellia" manufactured by NOF CORPORATION
Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Metal Mining Co., Ltd. Sulfur: Powdered sulfur vulcanization accelerator manufactured by Karuizawa Sulfur Co., Ltd. (1): Noxeller CZ (N-cyclohexyl) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd. -2-benzothiazolyl vulcan amide)
Vulcanization accelerator (2): Noxeller D (N, N'-diphenylguanidine) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.

(Examples and comparative examples)
(First step)
In accordance with the formulation shown in Table 1, materials other than sulfur and the vulcanization accelerator were put into a Banbury mixer and kneaded to obtain a first kneaded product or an unreacted kneaded product. The kneading was carried out while adjusting the rubber temperature to be ± 3 ° C. of the reaction temperature after the rubber temperature reached the set reaction temperature, and ended when a predetermined time (reaction time) had elapsed. .. The reaction temperature and reaction time of each example are as shown in Tables 2 to 6.
(Second step)
The obtained first kneaded product or unreacted kneaded product was put into a Bunbury mixer and further kneaded to obtain a second kneaded product. The kneading conditions are the same as in the first step.
(Third step)
The obtained second kneaded product, sulfur and a vulcanization accelerator were put into an open roll and kneaded to obtain an unvulcanized rubber composition. The kneading was completed when the rubber temperature reached 110 ° C. The kneading time was 5 minutes.
(Vulcanization process)
The obtained unvulcanized rubber composition was vulcanized at 170 ° C. for 12 minutes to obtain a vulcanized rubber composition.

The first kneaded product, the unreacted kneaded product, the unvulcanized rubber composition, and the vulcanized rubber composition obtained above were evaluated as follows. The results are shown in Tables 2-6.

(Moony viscosity)
According to JIS K6300, the Mooney viscosity of the first kneaded product or the unreacted kneaded product was measured at 130 ° C. The results are expressed exponentially with Comparative Example 1 as 100 (VIS index after the first step). The smaller the index, the better the workability.
In addition, Vt / V0 × 100 of the formula (2) was calculated for each set reaction temperature (VIS reduction rate).

(Pain effect)
Using RPA2000 (manufactured by Alpha Technologies), G * of 100 ° C. and 0.5% strain and G * of 100 ° C. and 64% strain of the first kneaded product or unreacted kneaded product were measured and ΔG. * Was calculated. The results were exponentially displayed with Comparative Example 1 as 100 (ΔG * index after the first step).
Further, ΔG * t / ΔG * 0 × 100 of the formula (1) was calculated for each set reaction temperature (ΔG * reduction rate).

(Tanδ)
Using a spectrometer manufactured by Ueshima Seisakusho Co., Ltd., the tan δ of the vulcanized rubber composition was measured at a dynamic strain amplitude of 1%, a frequency of 10 Hz, and a temperature of 50 ° C. The results were exponentially displayed with Comparative Example 1 as 100 (tan δ index). The smaller the index, the lower the rolling resistance and the better the fuel efficiency.

(Destructive energy)
In accordance with JIS K 6251 "Vulcanized rubber and thermoplastic rubber-How to determine tensile properties", a tensile test was carried out using a 2 mm thick No. 3 dumbbell formed from the above vulcanized rubber composition, and the breaking strength (TB) was obtained. And elongation at break (EB) were measured, respectively. Then, the destructive energy defined by the product of TB and EB is exponentially displayed with Comparative Example 1 as 100 (destructive energy index). The larger the index, the better the fracture characteristics.

(Performance index)
In order to comprehensively evaluate the performance of each example, the performance index was calculated by the following formula.
Performance index = ((100 / VIS index after the first process) x 100 + (100 / tan δ index) x 100 + fracture energy index) / 3

As shown in Tables 2 to 6, in the first step, the reaction temperature was set in the range of 150 to 170 ° C., and the reaction treatment was carried out until the formulas (1) and (2) were satisfied. Nos. 12 have the same reaction temperature, but have lower fuel consumption, fracture characteristics, and workability as compared with Comparative Examples 1 to 6 in which the reaction treatment was not performed until the formulas (1) and (2) were satisfied. It was significantly improved.
In Comparative Examples 7 to 18 in which the reaction temperature was set outside the range of 150 to 170 ° C., the equations (1) and (2) could not be satisfied even if the reaction time was lengthened, and sufficient performance improvement was observed. There wasn't.
From these results, it was clarified that the dispersibility of silica can be improved by a simple method of adjusting the kneading method using the formulas (1) and (2) as indexes without changing the type of the compounded chemicals. ..

Claims (2)

The first step of adding the rubber component, silica and silane coupling agent and kneading to obtain the first kneaded product, and
The second step of further kneading the first kneaded product to obtain the second kneaded product, and
Including the third step of adding the second kneaded product and the vulcanized chemicals and kneading them to obtain an unvulcanized rubber composition.
In the first step, the reaction treatment of kneading the rubber component, the silica and the silane coupling agent while maintaining the reaction temperature set in the range of 150 to 170 ° C. is carried out by the following formulas (1) and (1). Carry out until 2) is satisfied ,
A method for producing a rubber composition for a tire, wherein the silane coupling agent is a thioester-based silane coupling agent represented by the following formula (S1) .
Equation (1) ΔG * t / ΔG * 0 × 100 <80
(In the formula, ΔG * 0 is G * of 100 ° C. and 0.5% strain and G of 100 ° C. and 64% strain of the unreacted kneaded product obtained by completing kneading when the reaction temperature is reached. The difference from * is that ΔG * t is G * and 100 of the first kneaded product obtained by kneading for a predetermined time after reaching the same reaction temperature as ΔG * 0 at 100 ° C. and 0.5% strain. The difference from G * at ° C and 64% strain.)
Equation (2) Vt / V0 × 100 <80
(In the formula, V0 is the Mooney viscosity at 130 ° C. of the unreacted kneaded product obtained by terminating the kneading when the reaction temperature is reached, and Vt is a predetermined value after reaching the same reaction temperature as V0. The Mooney viscosity of the first kneaded product obtained by time kneading at 130 ° C.).

(In the formula, R ¹⁰⁰¹ is -Cl, -Br, -OR ¹⁰⁰⁶ , -O (O =) CR ¹⁰⁰⁶ , -ON = CR ¹⁰⁰⁶ R ¹⁰⁰⁷ , -ON = CR ¹⁰⁰⁶ R ¹⁰⁰⁷ , -NR ¹⁰⁰⁶ R ^{1007 and-} ( The monovalent groups (R ¹⁰⁰⁶ , R ¹⁰⁰⁷ and R ¹⁰⁰⁸ ) selected from the OSiR ¹⁰⁰⁶ R ¹⁰⁰⁷ ) _h (OSiR ¹⁰⁰⁶ R ¹⁰⁰⁷ R ¹⁰⁰⁸ ) may be the same or different, each having a hydrogen atom or 1-18 carbon atoms. It is a monovalent hydrocarbon group, h has an average value of 1 to 4), R ¹⁰⁰² is R ¹⁰⁰¹ , a hydrogen atom or a monovalent hydrocarbon group having 1 to 18 carbon atoms, and R ¹⁰⁰³ is R. ¹⁰⁰¹ , R ¹⁰⁰² , hydrogen atom ^or- [O (R ¹⁰⁰⁹ O) _j ] _0.5 -group (R ¹⁰⁰⁹ is an alkylene group having 1 to 18 carbon atoms, j is an integer of 1 to 4), R ¹⁰⁰⁴ Is a divalent hydrocarbon group having 1 to 18 carbon atoms , R ¹⁰⁰⁵ is a monovalent hydrocarbon group having 1 to 18 carbon atoms, and x, y and z are x + y + 2z = 3, 0 ≦ x ≦ 3,0. It is a number that satisfies the relationship of ≦ y ≦ 2 and 0 ≦ z ≦ 1.) The process according to claim 1 Symbol placement tire rubber composition to produce a cap tread rubber composition.