JP5957210B2 - Rubber composition and method for producing the same - Google Patents

Description

  The present invention relates to a rubber composition capable of improving low heat build-up and a method for producing the rubber composition.

In recent years, there has been an increasing demand for fuel efficiency reduction of automobiles in connection with the global movement of regulation of carbon dioxide emissions due to increasing interest in environmental problems. In order to meet such demands, tires are required to reduce rolling resistance. As a technique for reducing the rolling resistance of the tire, a technique of applying a low heat-generating rubber composition to the tire can be mentioned.
As a method for obtaining a rubber composition having low exothermicity, in the case of a synthetic diene rubber, a method of using a polymer having enhanced affinity for carbon black and silica as the rubber composition (see, for example, Patent Document 1) ). Further, (i) a diene elastomer, (ii) an inorganic filler as a reinforcing filler, (iii) a polysulfated alkoxysilane, (iv) 1,2-dihydropyridine and (v) a guanidine derivative (for example, Patent Document 2) Reference).
According to Patent Documents 1 and 2, the exothermic property of the rubber composition can be lowered by increasing the affinity between the rubber component and a filler such as an inorganic filler. Thereby, a tire with low hysteresis loss can be obtained.
However, there is a need for further improvements in tires with low heat build-up, and there is also a need for improved wear resistance.

JP 2003-514079 A Special table 2003-523472 gazette

  This invention makes it a subject to provide the manufacturing method of the rubber composition which can improve the low heat buildup and abrasion resistance of a tire.

As a result of various experimental analyzes, the present inventors have been able to further improve the dispersibility of inorganic fillers, particularly silica, by using specific thioglycolic acids (B). As a result, the present invention has been completed.
That is, the present invention
[1] A method for producing a rubber composition comprising a rubber component (A), a thioglycolic acid (B) represented by the following general formula (I), and a filler containing an inorganic filler (C). The rubber composition is kneaded in a plurality of stages, and in the first stage of kneading, all or part of the rubber component (A), the thioglycolic acid (B), and the inorganic filler (C) Is a method for producing a rubber composition.

[Wherein, X ¹ and X ² are each independently a hydrogen atom or a carboxy group, at least one of X ¹ and X ² is a carboxy group, and the carboxy group may form a salt. R ^a and R ^b are each independently a single bond or a hydrocarbon group having 1 to 6 carbon atoms, and R ^a and R ^b may be bonded to each other to form a ring structure. ]

  ADVANTAGE OF THE INVENTION According to this invention, provision of the manufacturing method of the rubber composition which can improve the low heat buildup and abrasion resistance of a tire can be provided.

The present invention is described in detail below.
The method for producing a rubber composition of the present invention includes a rubber component (A), a thioglycolic acid (B) represented by the following general formula (I), and a filler containing an inorganic filler (C). A method for producing a rubber composition, wherein the rubber composition is kneaded in a plurality of stages, and in the first stage of kneading, the rubber component (A), the thioglycolic acid (B), and the inorganic filler ( All or part of C) is kneaded.

In the general formula (I), X ¹ and X ² are each independently a hydrogen atom or a carboxy group, at least one of X ¹ and X ² is a carboxy group, and the carboxy group forms a salt. Also good. R ^a and R ^b are each independently a single bond or a hydrocarbon group having 1 to 6 carbon atoms, and R ^a and R ^b may be bonded to each other to form a ring structure. Here, the single bond means that a carbon atom bonded to —SH and X ¹ or X ² are directly bonded by a single bond.

In the production method of the present invention, the rubber composition is kneaded in a plurality of stages, and in the first stage of kneading, the rubber component (A), the thioglycolic acid (B) and the inorganic filler (C) are kneaded. At the final stage of kneading, a vulcanizing agent and a vulcanization accelerator are blended to produce a vulcanizable rubber composition.
If desired, an intermediate kneading stage may be provided between the first stage and the final stage of kneading.
The first stage of kneading in the present invention refers to the first stage of kneading the rubber component (A) and the inorganic filler (C). In the first stage, the rubber component (A) and the inorganic filler (C Steps in the case of kneading with a filler other than) or in the case of preliminarily kneading only the rubber component (A) are not included.

  In the production method of the present invention, the maximum temperature of the rubber composition in the first stage of kneading is preferably 120 to 190 ° C, more preferably 130 to 175 ° C, and 140 to 170 ° C. Is more preferable. The kneading time is preferably 10 seconds to 20 minutes, more preferably 10 seconds to 10 minutes, and further preferably 30 seconds to 5 minutes.

[Thioglycolic acids (B)]
The thioglycolic acids (B) according to the present invention include thioglycolic acid and thioglycolic acid derivatives.
The salt formed by the carboxy group in the general formula (I) is not limited, and examples thereof include metal salts such as sodium salt, potassium salt, calcium salt, magnesium salt, and ammonium salt.
In the above general formula (I), R ^a and R ^b are preferably each independently an alkylene group having 1 to 20 carbon atoms, when R ^a and R ^b form a ring structure. When it does, a C6-C20 aromatic or C3-C20 alicyclic ring structure is preferable.
The rubber composition obtained by the production method of the present invention may be referred to as the thioglycolic acid (B) represented by the general formula (I) {hereinafter referred to as “thioglycolic acid (B)”. }, The dispersibility of the inorganic filler (C), particularly silica, is greatly improved, and the low heat buildup and wear resistance of the rubber composition are remarkably improved.

  Preferred examples of the thioglycolic acids (B) according to the present invention include thioglycolic acid, 2-mercaptobenzoic acid, 4-mercaptobenzoic acid, calcium thioglycolate trihydrate, 2-mercaptobenzoic acid sodium, thioglycol Examples thereof include compounds selected from sodium acid, 3-mercaptoisobutyric acid, ammonium thioglycolate, 3-mercaptopropionic acid, and thiomalic acid.

  The thioglycolic acid (B) contained in the rubber composition according to the production method of the present invention is preferably blended in an amount of 0.1 to 5 parts by mass with respect to 100 parts by mass of the rubber component (A). This is because if the amount is 0.1 parts by mass or more, the effect of improving the dispersibility of a sufficient filler is exhibited, and if the amount is 5 parts by mass or less, the vulcanization speed is not greatly affected. More preferably, the compounding quantity of thioglycolic acid (B) is 0.25-2 mass parts with respect to 100 mass parts of rubber components (A).

[Rubber component (A)]
The rubber component (A) used in the rubber composition according to the production method of the present invention is preferably composed of at least one selected from natural rubber and synthetic diene rubber. Synthetic diene rubbers include styrene-butadiene copolymer rubber (SBR), polybutadiene rubber (BR), polyisoprene rubber (IR), butyl rubber (IIR), ethylene-propylene-diene terpolymer rubber (EPDM). Etc. can be used. Natural rubber and synthetic diene rubber may be used singly or in a combination of two or more.

[Filler]
The filler that can be added to the conventional rubber composition can be used as the filler of the present invention, and includes the inorganic filler (C).
As the filler according to the present invention, the inorganic filler (C) and other fillers may be used in combination, or the inorganic filler (C) alone may be used.
The reason why the filler needs to contain the inorganic filler (C) is to improve the low heat generation property.

<Inorganic filler (C)>
In the present invention, among the inorganic fillers (C) described above, silica is preferable from the viewpoint of achieving both low rolling properties and wear resistance. Any commercially available silica can be used, among which wet silica, dry silica, and colloidal silica are preferably used, and wet silica is particularly preferably used. The BET specific surface area (measured in accordance with ISO 5794/1) of silica is preferably 40 to 350 m ² / g. Silica having a BET specific surface area within this range has an advantage that both rubber reinforcement and dispersibility in a rubber component can be achieved. From this point of view, the BET specific surface area is more preferably silica in the range of 80~350m ² / g, BET specific surface area of greater than 130m ² / g, more preferably silica or less 350 meters ² / g, a BET specific surface area Silica in the range of 135 to 350 m ² / g is particularly preferred. Examples of such silica include Tosoh Silica Co., Ltd., trade name “Nip Seal AQ” (BET specific surface area = 205 m ² / g), “Nip Seal KQ” (BET specific surface area = 240 m ² / g), trade name manufactured by Degussa. Commercial products such as “Ultrazil VN3” (BET specific surface area = 175 m ² / g) can be used.

In the rubber composition containing inorganic filler (C), particularly silica, the dispersibility of inorganic filler (C), particularly silica, is greatly improved by adding thioglycolic acid (B), and the rubber composition The low heat buildup can be remarkably improved.
In a rubber composition in which an inorganic filler (C) such as silica is blended, in order to enhance the reinforcing property of the rubber composition with silica, or to improve the wear resistance as well as the low heat generation property of the rubber composition, It is preferable that a ring agent (D) is blended.
In the rubber composition in which the inorganic filler (C), particularly silica, and the silane coupling agent (D) are blended, the thioglycolic acid (B) includes the inorganic filler (C) and the silane coupling agent (D). It is also considered that this reaction is favorably promoted. As described above, according to the rubber composition according to the present invention, the dispersibility of silica is greatly improved, and the low heat generation property of the rubber composition can be remarkably improved.
Details of the silane coupling agent (D) will be described later.

<Blending amount>
The filler is preferably used in an amount of 20 to 150 parts by mass with respect to 100 parts by mass of the rubber component (A). If it is 20 mass parts or more, it is preferable from a viewpoint of the reinforcement property improvement of a rubber composition, and if it is 150 mass parts or less, it is preferable from a viewpoint of rolling resistance reduction.
The inorganic filler (C) is preferably used in an amount of 20 to 120 parts by mass with respect to 100 parts by mass of the rubber component (A). If it is 20 mass parts or more, it is preferable from a viewpoint of ensuring wet performance, and if it is 120 mass parts or less, it is preferable from a viewpoint of rolling resistance reduction. Furthermore, it is more preferable to use 30-100 mass parts.
From the viewpoint of achieving both wet performance and rolling resistance, the inorganic filler (C) in the filler is preferably 30% by mass or more, more preferably 40% by mass or more, and 70% by mass or more. Is more preferable.
In addition, when using a silica as an inorganic filler (B), it is preferable that the silica in the said filler is 30 mass% or more.

<Other inorganic fillers>
In addition to silica, an inorganic compound represented by the following general formula (1) can be used for the rubber composition of the present invention.
dM ¹ · xSiO _y · zH ₂ O (1)
Here, in the general formula (1), M ¹ is a metal selected from the group consisting of aluminum, magnesium, titanium, calcium, and zirconium, an oxide or hydroxide of these metals, and a hydrate thereof. Or at least one selected from carbonates of these metals, and d, x, y and z are each an integer of 1 to 5, an integer of 0 to 10, an integer of 2 to 5, and an integer of 0 to 10 is there.
In addition, when both x and z in the general formula (1) are 0, the inorganic compound is at least one metal, metal oxide or metal hydroxide selected from aluminum, magnesium, titanium, calcium and zirconium. It becomes.

As the inorganic compound represented by the general formula (1), .gamma.-alumina, alpha-alumina, such as alumina (Al ₂ O _3), boehmite, alumina monohydrate such as diaspore _{(Al 2 O 3 · H 2} O ), Aluminum hydroxide such as gibbsite, bayerite [Al (OH) ₃ ], aluminum carbonate [Al ₂ (CO ₃ ) ₂ ], magnesium hydroxide [Mg (OH) ₂ ], magnesium oxide (MgO), magnesium carbonate (MgCO _3), talc _{(3MgO · 4SiO 2 · H 2} O), attapulgite _{(5MgO · 8SiO 2 · 9H 2} O), titanium white (TiO _2), titanium black (TiO _2n-1), calcium oxide (CaO) , calcium hydroxide [Ca (OH) _2], magnesium aluminum oxide _{(MgO · Al 2 O 3)} , clay _{(Al 2 O 3 · 2SiO 2} ), kaolin (Al _{2 3 · 2SiO 2 · 2H 2 O} ), pyrophyllite _{(Al 2 O 3 · 4SiO 2} · H 2 O), bentonite _{(Al 2 O 3 · 4SiO 2} · 2H 2 O), aluminum silicate (Al ₂ SiO ₅ Al ₄ · 3SiO ₄ · 5H ₂ O, etc.), magnesium silicate (Mg ₂ SiO ₄ , MgSiO ₃ etc.), calcium silicate (Ca ₂ · SiO ₄ etc.), aluminum calcium silicate (Al ₂ O ₃ · CaO) 2SiO ₂ ), magnesium calcium silicate (CaMgSiO ₄ ), calcium carbonate (CaCO ₃ ), zirconium oxide (ZrO ₂ ), zirconium hydroxide [ZrO (OH) ₂ .nH ₂ O], zirconium carbonate [Zr (CO _{3) 2],} hydrogen to correct electric charge as various zeolites, such as crystalline aluminosilicates including alkali metal or alkaline earth metal can be used .
Further, it is preferable that M ¹ in the general formula (1) is at least one selected from aluminum metal, aluminum oxide or hydroxide, hydrates thereof, and aluminum carbonate.

The inorganic compound represented by the general formula (1) may be used alone or in combination of two or more. The average particle size of these inorganic compounds is preferably in the range of 0.01 to 10 μm, more preferably in the range of 0.05 to 5 μm, from the viewpoints of kneading workability, wear resistance, and wet grip performance balance.
As the inorganic filler (C) in the present invention, silica alone may be used, or silica and one or more inorganic compounds represented by the general formula (1) may be used in combination.

<Carbon black>
The filler according to the present invention may contain carbon black if desired. A commercially available carbon black can be used. By containing carbon black, it is possible to enjoy the effect of reducing electrical resistance and suppressing charging.
The carbon black is not particularly limited. For example, high, medium or low structure SAF, ISAF, IISAF, N339, HAF, FEF, GPF, SRF grade carbon black can be used. In particular, SAF, ISAF, IISAF, N339, HAF, and FEF grade carbon black are preferably used.
DBP absorption of carbon black is preferably 80 cm ^3/100 g or more, more preferably 100 cm ^3/100 g or more, particularly preferably 110 cm ^3/100 g or more. Moreover, the nitrogen adsorption specific surface area (measured in accordance with N ₂ SA, JIS K 6217-2: 2001) of carbon black is preferably 85 m ² / g or more, more preferably 100 m ² / g or more, particularly preferably. 110 m ² / g or more.

[Silane coupling agent (D)]
The rubber composition according to the production method of the present invention further contains a silane coupling agent (D), and it is preferable to knead all or part of the silane coupling agent (D) in the first stage of kneading.
As the silane coupling agent (D) that can be used in combination with the inorganic filler (C), a compound selected from one or more compounds selected from the group consisting of compounds represented by the following general formulas (II) to (V) may be used. it can. Hereinafter, the following general formulas (II) to (V) will be described in order.

In the formula, when there are a plurality of R ^{1 s} , they may be the same or different, and each of them may be a linear, cyclic or branched alkyl group having 1 to 8 carbon atoms, or a linear or branched alkoxy group having 2 to 8 carbon atoms. A substituent selected from an alkyl group and a silanol group, and when there are a plurality of R ^{2 s} , they may be the same or different and each is a linear, cyclic or branched alkyl group having 1 to 8 carbon atoms; ³ may be the same or different when there are a plurality, and each is a linear or branched alkylene group having 1 to 8 carbon atoms. a is an average value of 2 to 6, and p and r may be the same or different, and are each an average value of 0 to 3. However, both p and r are not 3.

  Specific examples of the silane coupling agent (D) represented by the general formula (II) include bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, and bis (3-methyl). Dimethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide, bis (3-trimethoxysilylpropyl) disulfide, bis (3-methyldimethoxysilylpropyl) Disulfide, bis (2-triethoxysilylethyl) disulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (3-trimethoxysilylpropyl) trisulfide, bis (3-methyldimethoxysilylpropyl) trisulfide Bis (2-triethoxysilylethyl) trisulfide, bis (3-monoethoxydimethylsilylpropyl) tetrasulfide, bis (3-monoethoxydimethylsilylpropyl) trisulfide, bis (3-monoethoxydimethylsilylpropyl) disulfide, Bis (3-monomethoxydimethylsilylpropyl) tetrasulfide, bis (3-monomethoxydimethylsilylpropyl) trisulfide, bis (3-monomethoxydimethylsilylpropyl) disulfide, bis (2-monoethoxydimethylsilylethyl) tetrasulfide Bis (2-monoethoxydimethylsilylethyl) trisulfide, bis (2-monoethoxydimethylsilylethyl) disulfide, and the like.

Wherein, R ⁴ is ^{-Cl, -Br, R 9 O-,} R 9 C (= O) O-, R 9 R 10 C = NO-, R 9 R 10 CNO-, R 9 R 10 N-, And-(OSiR ⁹ R ¹⁰ ) _h (OSiR ⁹ R ¹⁰ R ¹¹ ) are each a monovalent group (R ⁹ , R ¹⁰ and R ¹¹ are each a hydrogen atom or a monovalent hydrocarbon having 1 to 18 carbon atoms. H is an average value of 1 to 4, and R ⁵ is R ⁴ , a hydrogen atom or a monovalent hydrocarbon group having 1 to 18 carbon atoms, and R ⁶ is R ⁴ , R ⁵ , a hydrogen atom or a — [O (R ¹² O) _j ] _0.5 — group (R ¹² is an alkylene group having 1 to 18 carbon atoms, j is an integer of 1 to 4), and R ⁷ is a carbon number. A divalent hydrocarbon group having 1 to 18 carbon atoms, and R ⁸ is a monovalent hydrocarbon group having 1 to 18 carbon atoms. x, y, and z are numbers satisfying the relationship of x + y + 2z = 3, 0 ≦ x ≦ 3, 0 ≦ y ≦ 2, and 0 ≦ z ≦ 1.

In the general formula (III), R ⁸ , R ⁹ , R ¹⁰ and R ¹¹ are each independently a linear, cyclic or branched alkyl group, alkenyl group, aryl group and aralkyl group having 1 to 18 carbon atoms. A group selected from the group is preferred. When R ⁵ 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, alkenyl group, aryl group and aralkyl group. Preferably there is. R ¹² is preferably a linear, cyclic or branched alkylene group, particularly preferably a linear one. R ⁷ 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, or an arylene having 6 to 18 carbon atoms. And aralkylene groups having 7 to 18 carbon atoms. The alkylene group and alkenylene group may be either linear or branched, and the cycloalkylene group, cycloalkylalkylene group, arylene group and aralkylene group have a substituent such as a lower alkyl group on the ring. You may have. R ⁷ is preferably an alkylene group having 1 to 6 carbon atoms, particularly a linear alkylene group such as a methylene group, an ethylene group, a trimethylene group, a tetramethylene group, a pentamethylene group, or a hexamethylene group.

Specific examples of the monovalent hydrocarbon group having 1 to 18 carbon atoms of R ⁵ , R ⁸ , R ⁹ , R ¹⁰ and R ^{11 in} the general formula (III) include a methyl group, an ethyl group, an n-propyl group, Isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, octyl group, decyl group, dodecyl group, cyclopentyl group, cyclohexyl group, vinyl group, propenyl group, Examples include allyl group, hexenyl group, octenyl group, cyclopentenyl group, cyclohexenyl group, phenyl group, tolyl group, xylyl group, naphthyl group, benzyl group, phenethyl group, and naphthylmethyl group.
Examples of R ¹² in the general formula (III) include methylene group, ethylene group, trimethylene group, tetramethylene group, pentamethylene group, hexamethylene group, octamethylene group, decamethylene group, dodecamethylene group and the like.

  Specific examples of the silane coupling agent (D) represented by the general formula (III) include 3-hexanoylthiopropyltriethoxysilane, 3-octanoylthiopropyltriethoxysilane, and 3-decanoylthiopropyltriethoxy. Silane, 3-lauroylthiopropyltriethoxysilane, 2-hexanoylthioethyltriethoxysilane, 2-octanoylthioethyltriethoxysilane, 2-decanoylthioethyltriethoxysilane, 2-lauroylthioethyltriethoxysilane, 3-hexanoylthiopropyltrimethoxysilane, 3-octanoylthiopropyltrimethoxysilane, 3-decanoylthiopropyltrimethoxysilane, 3-lauroylthiopropyltrimethoxysilane, 2-hexanoylthioethyltrimethoxysilane Down, 2-octanoylthiopropyl ethyltrimethoxysilane, 2- deca Neu thio ethyltrimethoxysilane, and 2-lauroyl thio ethyl trimethoxysilane. Of these, 3-octanoylthiopropyltriethoxysilane (Momentive Performance Materials, trade name: NXT silane) is particularly preferable.

In the formula, when there are a plurality of R ^{13 s} , they may be the same or different, and each of them may be a linear, cyclic or branched alkyl group having 1 to 8 carbon atoms, or a linear or branched alkoxy group having 2 to 8 carbon atoms. A substituent selected from an alkyl group and a silanol group, and when there are a plurality of R ^{14 s} , they may be the same or different and each is a linear, cyclic or branched alkyl group having 1 to 8 carbon atoms; ^When there are a plurality of ^15s , they may be the same or different and each is a linear or branched alkylene group having 1 to 8 carbon atoms. R ¹⁶ is selected from the general formulas (—S—R ¹⁷ —S—), (—R ¹⁸ —S _m1 —R ¹⁹ —) and (—R ²⁰ —S _m2 —R ²¹ —S _m3 —R ²² —). Divalent groups (R ^{17 to} R ²² are each selected from a divalent hydrocarbon group having 1 to 20 carbon atoms, a divalent aromatic group, and a divalent organic group containing a hetero element other than sulfur and oxygen. Each of m1, m2 and m3 is an average value of 1 or more and less than 4, and a plurality of k's may be the same or different, and each of the average values is 1 to 6 , S, and t are 0 to 3 as average values. However, both s and t are not 3.

As a specific example of the silane coupling agent (D) represented by the general formula (IV),
Average composition formula _{(CH 3 CH 2 O) 3} Si- (CH 2) 3 -S 2 - (CH 2) 6 -S 2 - (CH 2) 3 -Si (OCH 2 CH 3) 3,
Average composition formula _{(CH 3 CH 2 O) 3} Si- (CH 2) 3 -S 2 - (CH 2) 10 -S 2 - (CH 2) 3 -Si (OCH 2 CH 3) 3,
Average composition formula _{(CH 3 CH 2 O) 3} Si- (CH 2) 3 -S 3 - (CH 2) 6 -S 3 - (CH 2) 3 -Si (OCH 2 CH 3) 3,
Average composition formula (CH ₃ CH ₂ O) ₃ Si— (CH ₂ ) ₃ —S ₄ — (CH ₂ ) ₆ —S ₄ — (CH ₂ ) ₃ —Si (OCH ₂ CH ₃ ) ₃ ,
Average composition formula _{(CH 3 CH 2 O) 3} Si- (CH 2) 3 -S- (CH 2) 6 -S 2 - (CH 2) 6 -S- (CH 2) 3 -Si (OCH 2 CH 3 ₃
Average composition formula _{(CH 3 CH 2 O) 3} Si- (CH 2) 3 -S- (CH 2) 6 -S 2.5 - (CH 2) 6 -S- (CH 2) 3 -Si (OCH 2 CH 3 ₃
Average composition formula _{(CH 3 CH 2 O) 3} Si- (CH 2) 3 -S- (CH 2) 6 -S 3 - (CH 2) 6 -S- (CH 2) 3 -Si (OCH 2 CH 3 ₃
Average composition formula _{(CH 3 CH 2 O) 3} Si- (CH 2) 3 -S- (CH 2) 6 -S 4 - (CH 2) 6 -S- (CH 2) 3 -Si (OCH 2 CH 3 ₃
Average composition formula _{(CH 3 CH 2 O) 3} Si- (CH 2) 3 -S- (CH 2) 10 -S 2 - (CH 2) 10 -S- (CH 2) 3 -Si (OCH 2 CH 3 ₃
Average composition formula _{(CH 3 CH 2 O) 3} Si- (CH 2) 3 -S 4 - (CH 2) 6 -S 4 - (CH 2) 6 -S 4 - (CH 2) 3 -Si (OCH 2 CH _{3) 3,}
Average composition formula _{(CH 3 CH 2 O) 3} Si- (CH 2) 3 -S 2 - (CH 2) 6 -S 2 - (CH 2) 6 -S 2 - (CH 2) 3 -Si (OCH 2 CH _{3) 3,}
Average composition formula _{(CH 3 CH 2 O) 3} Si- (CH 2) 3 -S- (CH 2) 6 -S 2 - (CH 2) 6 -S 2 - (CH 2) 6 -S- (CH 2 ) ₃ -Si (OCH ₂ CH ₃ ) _{3 and the} like are preferred.

In the formula, R ²³ is a linear, branched or cyclic alkyl group having 1 to 20 carbon atoms, and a plurality of Gs may be the same or different, and each is an alkanediyl group or alkenediyl group having 1 to 9 carbon atoms. There, the plurality of Z ^a may be the same or different, is a functional group capable of binding with each of two silicon atoms, and _{[-0-] 0.5, [- 0} -G-] 0.5 and [- O—G—O—] is a functional group selected from _0.5 , and a plurality of Z ^b may be the same or different, each being a functional group capable of bonding to two silicon atoms, and [—O— G-O-] _0.5 is a functional group, and a plurality of Z ^c may be the same or different, and each represents —Cl, —Br, —OR ^e , R ^e C (═O) O—, R ^{e R f C = NO-, R} e R f N-, R e - and HO-G-O- (G coincides with the notation.) selected from Is a functional group, R ^e and R ^f are each linear having 1 to 20 carbon atoms, branched or cyclic alkyl group. m, n, u, v and w are 1 ≦ m ≦ 20, 0 ≦ n ≦ 20, 0 ≦ u ≦ 3, 0 ≦ v ≦ 2, 0 ≦ w ≦ 1, and (u / 2) + v + 2w. = 2 or 3. When there are a plurality of A parts, each of Z ^a _u , Z ^b _v and Z ^c _w in the plurality of A parts may be the same or different. When there are a plurality of B parts, Z ^a in the plurality of B parts Each of _u , Z ^b _v and Z ^c _w may be the same or different.

  Specific examples of the silane coupling agent (D) represented by general formula (V) include general formula (VI), general formula (VII), and general formula (VIII).

In the formula, each L is independently an alkanediyl group or alkenediyl group having 1 to 9 carbon atoms, and x = m and y = n.

Examples of the silane coupling agent that can be obtained as a commercial product represented by the general formula (VI) include “NXT Low-V Silane” manufactured by Momentive Performance Materials.
Moreover, as a silane coupling agent which can be obtained as a commercial item represented by general formula (VII), the product name "NXT Ultra Low-V Silane" by Momentive Performance Materials is mentioned.
Furthermore, examples of the silane coupling agent that can be obtained as a commercial product represented by the general formula (VIII) include “NXT-Z” manufactured by Momentive Performance Materials.

The silane coupling agent (D) according to the present invention is particularly preferably a compound represented by the general formula (II) among the compounds represented by the general formulas (II) to (V). This is because the thioglycolic acids (B) are likely to activate polysulfide bond sites that react with the rubber component (A).
In this invention, a silane coupling agent (D) may be used individually by 1 type, and may be used in combination of 2 or more type.

  The compounding amount of the silane coupling agent (D) in the rubber composition of the present invention is such that the mass ratio {silane coupling agent (D) / inorganic filler (C)} is (1/100) to (20/100). Preferably there is. If it is (1/100) or more, the effect of improving the low heat build-up of the rubber composition will be more suitably exhibited. If it is (20/100) or less, the cost of the rubber composition will be reduced, and the economic efficiency will be reduced. This is because it improves. Furthermore, a mass ratio (3/100) to (20/100) is more preferable, and a mass ratio (4/100) to (10/100) is particularly preferable.

In a rubber composition in which an inorganic filler (C) such as silica is blended, in order to enhance the reinforcing property of the rubber composition with silica, or to improve the wear resistance as well as the low heat generation property of the rubber composition, It is preferable to mix a ring agent (D). However, if the reaction between the inorganic filler (C) and the silane coupling agent (D) is insufficient, the effect of enhancing the reinforcement of the rubber composition by the inorganic filler (C) cannot be sufficiently obtained. Wear resistance may be reduced. Further, when the unreacted silane coupling agent in the kneading step of the rubber composition reacts during the extrusion step performed after the kneading step, the rubber composition extrudate is porous (multiple bubbles or holes). Occurs, causing a decrease in the size and weight accuracy of the extruded product.
On the other hand, when the number of kneading steps in the kneading step is increased, the reaction between the inorganic filler (C) and the silane coupling agent (D) can be completed in the kneading step, and the generation of porosity can be suppressed. Is possible. However, there is a problem that the productivity of the kneading process is significantly reduced.
Since the thioglycolic acid (B) according to the present invention favorably promotes the reaction between the inorganic filler (C) and the silane coupling agent (D), it is possible to obtain a rubber composition excellent in low heat build-up. . As described above, according to the rubber composition of the present invention, it is possible to obtain a pneumatic tire that is further excellent in workability at the time of rubber processing and has lower heat generation.
In particular, the thioglycolic acid (B) improves the dispersibility of the inorganic filler (C), particularly silica and improves the wear resistance, and the carboxy group of the thioglycolic acid (B) interacts with the silica to produce a mercapto group. Interacts with the rubber component, so that the reaction of the silica, the silane coupling agent and the rubber component can be enhanced to obtain a high low heat build-up.

  In the first stage of the kneading according to the present invention, the thioglycolic acid (B) is added as (2/100) to (200/100) as a mass ratio {thioglycolic acid (B) / silane coupling agent (D)}. It is preferred that If it is (2/100) or more, the silane coupling agent (D) is sufficiently activated, and if it is (200/100) or less, the vulcanization rate is not greatly affected. More preferably, the thioglycolic acid (B) is added as a mass ratio {thioglycolic acid (B) / silane coupling agent (D)} (5/100) to (100/100).

[Vulcanizing agent, Vulcanization accelerator]
A vulcanizing agent and a vulcanization accelerator are blended in the rubber composition according to the present invention. Examples of the vulcanizing agent include sulfur. Although it does not specifically limit as a vulcanization accelerator, For example, thiazole, such as M (2-mercaptobenzothiazole), DM (dibenzothiazolyl disulfide), CZ (N-cyclohexyl-2-benzothiazolylsulfenamide) And guanidine vulcanization accelerators such as DPG (diphenylguanidine).

[Organic acid compound]
The rubber composition according to the present invention usually contains an organic acid compound as a vulcanization acceleration aid. Organic acid compounds include stearic acid, palmitic acid, myristic acid, lauric acid, arachidic acid, behenic acid, lignoceric acid, capric acid, pelargonic acid, caprylic acid, enanthic acid, caproic acid, oleic acid, vaccenic acid, linoleic acid And saturated fatty acids and unsaturated fatty acids such as linolenic acid and nervonic acid, and organic acids such as resin acids such as rosin acid and modified rosin acid, and esters of the saturated fatty acids and unsaturated fatty acids and resin acids.
In the present invention, 50 mol% or more in the organic acid compound is preferably stearic acid because it is necessary to sufficiently exhibit the function as a vulcanization acceleration aid.

  In the first step of kneading, the method for producing a rubber composition of the present invention comprises at least the rubber component (A), the thioglycolic acids (B), and all or part of the inorganic filler (C), Alcohol such as ethanol and other volatile organic components produced by reaction of the inorganic filler (C) and the silane coupling agent (D) by kneading all or part of the silane coupling agent (D) Can be volatilized during kneading. Thereby, volatilization of alcohol etc. in an extrusion process performed after a kneading process can be controlled, and it can prevent generating porous in an extrusion molding.

  As a method of adding thioglycolic acid (B) in the first stage of kneading according to the present invention, thioglycolic acid (B) is added after kneading all or part of rubber component (A) and inorganic filler (C). It is preferable to further knead. This is because the dispersibility of the inorganic filler (C) is further improved by this charging method.

  In the case of a rubber composition containing an inorganic filler (C) and a silane coupling agent (D) as a method for charging the thioglycolic acid (B) according to the present invention, in the first stage of kneading, the rubber component (A) After kneading all or part of the inorganic filler (C) and all or part of the silane coupling agent (D), it is preferable to add the thioglycolic acid (B) and further knead. This is because, by this charging method, the reaction between the silane coupling agent (D) and the rubber component (A) can be advanced after the reaction between the silane coupling agent (D) and the silica has sufficiently progressed.

If it is difficult to produce a masterbatch only by the first stage of kneading, or if desired, an intermediate stage of kneading may be provided after the first stage of kneading.
When the intermediate stage after the first stage and before the final stage is included, the maximum temperature of the rubber composition in the intermediate stage of kneading is preferably 120 to 190 ° C, and preferably 130 to 175 ° C. More preferably, it is 140-170 degreeC. The kneading time is preferably 10 seconds to 20 minutes, more preferably 10 seconds to 10 minutes, and further preferably 30 seconds to 5 minutes. In addition, when including an intermediate | middle stage, it is preferable to advance to the next stage, after lowering | hanging 10 degreeC or more from the temperature after completion | finish of the kneading | mixing of the previous stage.
The final stage of kneading refers to a process of blending and kneading vulcanizing chemicals (vulcanizing agent, vulcanization accelerator). The maximum temperature of the rubber composition in this final stage is preferably 60 to 140 ° C, more preferably 80 to 120 ° C, and further preferably 100 to 120 ° C. The kneading time is preferably 10 seconds to 20 minutes, more preferably 10 seconds to 10 minutes, and further preferably 20 seconds to 5 minutes.
When proceeding from the first stage and the intermediate stage to the final stage, it is preferable to proceed to the next stage after lowering the temperature by 10 ° C. or more from the temperature after completion of the previous stage of kneading.
For example, in the first stage of kneading, as the first masterbatch kneading stage, all or part of the rubber component (A), the inorganic filler (C), and all or part of the silane coupling agent (D) are kneaded. Then, after natural cooling and curing, as an intermediate stage, thioglycolic acid (B) may be added and further kneaded.

  The rubber composition in the present invention is kneaded using a Banbury mixer, roll, intensive mixer, kneader, twin screw extruder or the like. Then, it is extruded in an extrusion process and formed as a tread member. Subsequently, it is pasted and molded by a normal method on a tire molding machine to form a raw tire. The green tire is heated and pressed in a vulcanizer to obtain a tire. The tread in the present invention refers to a cap tread constituting a ground contact portion of a tire and / or a base tread disposed inside the cap tread.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.
[Evaluation method]
<Low exothermic property (tan δ index)>
Using a viscoelasticity measuring apparatus (Rheometrics), tan δ was measured at a temperature of 60 ° C., a dynamic strain of 5%, and a frequency of 15 Hz. The reciprocal of tan δ in Comparative Example 1 was taken as 100, and indexed by the following formula. A larger index value indicates a lower exothermic property and a smaller hysteresis loss.
Low exothermic index = {(tan δ of vulcanized rubber composition of Comparative Example 1) / (tan δ of test vulcanized rubber composition)} × 100
<Abrasion resistance (index)>
In accordance with JIS K 6264-2: 2005, a test was performed at room temperature (23 ° C.) with a slip rate of 25% using a Lambone-type wear tester. As an index by the following formula. The larger the value, the better the wear resistance.
Abrasion resistance index = {(Abrasion amount of vulcanized rubber composition of Comparative Example 1) / (Abrasion amount of test vulcanized rubber composition)} × 100

Production Example 1 Average composition formula
(CH ₃ CH ₂ O) ₃ Si- (CH ₂ ) ₃ -S- (CH ₂ ) ₆ -S _2.5- (CH ₂ ) ₆ -S- (CH ₂ ) ₃ -Si (OCH ₂ CH ₃ ) ₃ Production of represented silane coupling agent 119 g (0.5 mol) of 3-mercaptopropyltriethoxysilane was charged into a 2 liter separable flask equipped with a nitrogen gas inlet tube, a thermometer, a Dimroth condenser and a dropping funnel. While stirring, 151.2 g (0.45 mol) of an ethanol solution of sodium ethoxide containing 20% by mass of the active ingredient was added. Thereafter, the temperature was raised to 80 ° C., and stirring was continued for 3 hours. Thereafter, the mixture was cooled and transferred to a dropping funnel.
Next, 69.75 g (0.45 mol) of 1,6-dichlorohexane was charged into a separable flask similar to the above, heated to 80 ° C., and then the above 3-mercaptopropyltriethoxysilane and sodium ethoxide were added. The reaction was slowly added dropwise. After completion of dropping, stirring was continued at 80 ° C. for 5 hours. Thereafter, the mixture was cooled, and the salt was filtered off from the resulting solution, and ethanol and excess 1,6-dichlorohexane were distilled off under reduced pressure. The resulting solution was distilled under reduced pressure to obtain 137.7 g of a colorless transparent liquid having a boiling point of 148 to 150 ° C./0.005 torr (0.67 Pa). As a result of IR analysis, ¹ H-NMR analysis and mass spectrum analysis (MS analysis), a compound represented by (CH ₃ CH ₂ O) ₃ Si— (CH ₂ ) ₃ S— (CH ₂ ) ₆ —Cl Met. The purity by gas chromatographic analysis (GC analysis) was 97.5%.
Next, 80 g of ethanol, 5.46 g (0.07 mol) of anhydrous sodium sulfide and 3.36 g (0.105 mol) of sulfur were charged into a 0.5 liter separable flask similar to the above, and the temperature was raised to 80 ° C. did. While stirring this solution, 49.91 g (0.14 mol) of the above (CH ₃ CH ₂ O) ₃ Si— (CH ₂ ) ₃ —S— (CH ₂ ) ₆ —Cl was slowly added dropwise. After completion of dropping, stirring was continued at 80 ° C. for 10 hours. After completion of the stirring, the mixture was cooled and the formed salt was filtered off, and then ethanol as a solvent was distilled under reduced pressure.
The obtained reddish-brown transparent solution was subjected to IR analysis, ¹ H-NMR analysis and supercritical chromatography analysis.
(CH ₃ CH ₂ O) ₃ Si- (CH ₂ ) ₃ -S- (CH ₂ ) ₆ -S _2.5- (CH ₂ ) ₆ -S- (CH ₂ ) ₃ -Si (OCH ₂ CH ₃ ) ₃ It was confirmed that the compound was represented. The purity of this product by GPC analysis was 85.2%.

Examples 1-12
In the first stage of kneading, the rubber component (A), thioglycolic acid (B), carbon black, inorganic filler (C), silane coupling agent (D), aromatic oil, stearic acid and Anti-aging agent 6PPD was kneaded and adjusted so that the maximum temperature of the rubber composition in the first stage of kneading was 150 ° C.
Next, in the final stage of kneading, the remaining compounding agents listed in Table 1 were added and kneaded, and the maximum temperature of the rubber composition in the final stage of kneading was adjusted to 110 ° C.
The low heat build-up (tan δ index) and wear resistance of the vulcanized rubber compositions obtained from these rubber compositions were evaluated by the above methods. The results are shown in Table 1.

Example 13
In the first stage of kneading, after adding rubber component (A), carbon black, inorganic filler (C), silane coupling agent (D), aromatic oil, stearic acid and anti-aging agent 6PPD, kneading for 60 seconds The thioglycolic acid (B) was added and further kneaded. The maximum temperature of the rubber composition in the first stage of kneading was adjusted to 150 ° C.
Next, in the final kneading stage, the remaining compounding agents shown in Table 1 were added and kneaded, and the maximum temperature of the rubber composition in the final kneading stage was adjusted to 110 ° C.
The low exothermic property (tan δ index) and wear resistance of the vulcanized rubber composition obtained from this rubber composition were evaluated by the above methods. The results are shown in Table 1.

Comparative Examples 1-8
Kneading was carried out in the same manner as in Examples 1 to 12 except that the thioglycolic acid (B) was not added in the first stage of kneading. The obtained vulcanized rubber composition was evaluated for low heat build-up (tan δ index) and wear resistance by the above methods. The results are shown in Table 1.

Comparative Examples 9-11
Kneading was carried out in the same manner as in Examples 1 to 12 except that the thioglycolic acid (B) was not added in the first stage of kneading but was added in the final stage. The obtained vulcanized rubber composition was evaluated for low heat build-up (tan δ index) and wear resistance by the above methods. The results are shown in Table 1.

[note]
* 1: Solution polymerized styrene-butadiene copolymer rubber (SBR) manufactured by Asahi Kasei Co., Ltd., trade name “Toughden 2000”
* 2: RSS # 3
* 3: N220 (ISAF), manufactured by Asahi Carbon Co., Ltd., trade name “# 80”
* 4: Product name “Nip Seal AQ” manufactured by Tosoh Silica Co., Ltd., BET specific surface area 205 m ² / g
* 5: Bis (3-triethoxysilylpropyl) disulfide (average sulfur chain length: 2.35), Evonik silane coupling agent, trade name “Si75” (registered trademark)
* 6: 3-octanoylthiopropyltriethoxysilane, manufactured by Momentive Performance Materials, trade name “NXT silane” (registered trademark)
* 7: Silane coupling agent represented by the above chemical formula (VIII), manufactured by Momentive Performance Materials, trade name “NXT-Z” (registered trademark)
* 8: Silane coupling agent obtained in Production Example 1
(CH ₃ CH ₂ O) ₃ Si- (CH ₂ ) ₃ -S- (CH ₂ ) ₆ -S _2.5- (CH ₂ ) ₆ -S- (CH ₂ ) ₃ -Si (OCH ₂ CH ₃ ) ₃
* 9: Thioglycolic acid, manufactured by Daicel Chemical Industries, Ltd. * 10: 2-mercaptobenzoic acid, manufactured by Tokyo Chemical Industry Co., Ltd. * 11: Calcium thioglycolate trihydrate, manufactured by Tokyo Chemical Industry Co., Ltd. * 12: N -(1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine, manufactured by Ouchi Shinsei Chemical Co., Ltd., trade name "NOCRACK 6C"
* 13: 1,3-diphenylguanidine, manufactured by Sanshin Chemical Industry Co., Ltd., trade name “Sunseller D”
* 14: 2,2,4-trimethyl-1,2-dihydroquinoline polymer, manufactured by Ouchi Shinsei Chemical Co., Ltd., trade name “NOCRACK 224”
* 15: Di-2-benzothiazolyl disulfide, manufactured by Sanshin Chemical Industry Co., Ltd., trade name “Sunseller DM”
* 16: N-tert-butyl-2-benzothiazolylsulfenamide, manufactured by Sanshin Chemical Industry Co., Ltd., trade name “Sunseller NS”

  As is clear from Table 1, the rubber compositions of Examples 1 to 13 all have low heat build-up (tan δ index) and wear resistance compared to the rubber compositions to be compared with Comparative Examples 1 to 11. Was good.

  The rubber composition of the present invention improves the dispersibility of the filler, is excellent in low heat buildup and wear resistance, and further suppresses the activity reduction of the coupling function of the silane coupling agent, and has a coupling function. Since the activity is further enhanced and low heat generation is particularly excellent, various pneumatic tires for passenger cars, light trucks, light passenger cars, light trucks and heavy vehicles (for trucks, buses, construction vehicles, etc.) Each member is suitably used as a tread member of a pneumatic radial tire.

Claims (8)

A rubber component (A) which is a diene rubber, a thioglycolic acid (B) represented by the following general formula (I) , an inorganic filler (C) which is silica, a silane coupling agent (D), And a filler containing the rubber composition, wherein the rubber composition is kneaded in a plurality of stages, and in the first stage of kneading, the rubber component (A) and the inorganic filler (C) are mixed. A method for producing a rubber composition, comprising kneading all or part of the silane coupling agent (D) or all or part of the silane coupling agent (D), adding the thioglycolic acid (B), and further kneading.


[Wherein, X ¹ and X ² are each independently a hydrogen atom or a carboxy group, at least one of X ¹ and X ² is a carboxy group, and the carboxy group may form a salt. R ^a and R ^b are each independently a single bond or a hydrocarbon group having 1 to 6 carbon atoms, and R ^a and R ^b may be bonded to each other to form a ring structure. ]   The thioglycolic acids (B) are thioglycolic acid, 2-mercaptobenzoic acid, 4-mercaptobenzoic acid, calcium thioglycolate trihydrate, sodium 2-mercaptobenzoate, sodium thioglycolate, 3-mercaptoiso The method for producing a rubber composition according to claim 1, which is at least one compound selected from butyric acid, ammonium thioglycolate, 3-mercaptopropionic acid, and thiomalic acid. The rubber composition according to claim 1 or 2, wherein the silane coupling agent (D) is a compound selected from the group consisting of compounds represented by the following general formulas (II) to (V). Production method.

[In the formula, when there are a plurality of R ^{1 s} , they may be the same or different, and each of them may be a linear, cyclic or branched alkyl group having 1 to 8 carbon atoms, a linear or branched alkyl group having 2 to 8 carbon atoms. A substituent selected from an alkoxyalkyl group and a silanol group, and when there are a plurality of R ^{2 s} , they may be the same or different and each is a linear, cyclic or branched alkyl group having 1 to 8 carbon atoms, When there are a plurality of R ^{3 s} , they may be the same or different and each is a linear or branched alkylene group having 1 to 8 carbon atoms. a is an average value of 2 to 6, and p and r may be the same or different, and are each an average value of 0 to 3. However, both p and r are not 3. ]

{Wherein, ^{R 4} is ^{-Cl, -Br, R 9 O-,} R 9 C (= O) O-, R 9 R 10 C = NO-, R 9 R 10 CNO-, R 9 R 10 N- , And-(OSiR ⁹ R ¹⁰ ) _h (OSiR ⁹ R ¹⁰ R ¹¹ ) are each a monovalent group (R ⁹ , R ¹⁰ and R ¹¹ are each a hydrogen atom or a monovalent carbon atom having 1 to 18 carbon atoms. H is an average value of 1 to 4), R ⁵ is R ⁴ , a hydrogen atom or a monovalent hydrocarbon group having 1 to 18 carbon atoms, R ⁶ is R ⁴ , R ⁵ , a hydrogen atom, or — [O (R ¹² O) _j ] _0.5 — group (R ¹² is an alkylene group having 1 to 18 carbon atoms, j is an integer of 1 to 4), and R ^7. is a divalent hydrocarbon group having 1 to 18 carbon atoms, R ⁸ is a monovalent hydrocarbon group having 1 to 18 carbon atoms. x, y, and z are numbers satisfying the relationship of x + y + 2z = 3, 0 ≦ x ≦ 3, 0 ≦ y ≦ 2, and 0 ≦ z ≦ 1. }

[In the formula, when there are a plurality of R ^{13 s} , they may be the same or different, and each of them may be a linear, cyclic or branched alkyl group having 1 to 8 carbon atoms, a linear or branched alkyl group having 2 to 8 carbon atoms. A substituent selected from an alkoxyalkyl group and a silanol group, and when there are a plurality of R ^{14 s} , they may be the same or different and each is a linear, cyclic or branched alkyl group having 1 to 8 carbon atoms, When there are a plurality of R ^{15 s} , they may be the same or different and each is a linear or branched alkylene group having 1 to 8 carbon atoms. R ¹⁶ is selected from general formulas (—S—R ¹⁷ —S—), (—R ¹⁸ —S _m1 —R ¹⁹ —) and (—R ²⁰ —S _m2 —R ²¹ —S _m3 —R ²² —). Divalent groups (R ^{17 to} R ²² are each selected from a divalent hydrocarbon group having 1 to 20 carbon atoms, a divalent aromatic group, and a divalent organic group containing a hetero element other than sulfur and oxygen. Each of m1, m2 and m3 is an average value of 1 or more and less than 4, and a plurality of k's may be the same or different, and each of the average values is 1 to 6 , S, and t are 0 to 3 as average values. However, both s and t are not 3. ]

{In the formula, R ²³ is a linear, branched or cyclic alkyl group having 1 to 20 carbon atoms, and a plurality of Gs may be the same or different, and each is an alkanediyl group or alkenediyl group having 1 to 9 carbon atoms. , and the the plurality of Z ^a may be the same or different, is a functional group capable of binding with each of two silicon atoms, and _{[-0-] 0.5, [- 0} -G-] 0 _.5 and [—O—G—O—] _0.5 is a functional group selected from _0.5 , and a plurality of Z ^b may be the same or different and each is a functional group capable of bonding to two silicon atoms. And a functional group represented by [—O—G—O—] _0.5 , and a plurality of Z ^c may be the same or different, and each represents —Cl, —Br, —OR ^e , R ^{e. C (= O) O-, R} e R f C = NO-, R e R f N-, R e - and HO-G-O- G is a functional group selected from.) Matching the above notation, R ^e and R ^f are each linear having 1 to 20 carbon atoms, branched or cyclic alkyl group. m, n, u, v and w are 1 ≦ m ≦ 20, 0 ≦ n ≦ 20, 0 ≦ u ≦ 3, 0 ≦ v ≦ 2, 0 ≦ w ≦ 1, and (u / 2) + v + 2w. = 2 or 3. When there are a plurality of A parts, each of Z ^a _u , Z ^b _v and Z ^c _w in the plurality of A parts may be the same or different, and when there are a plurality of B parts, Z ^a in ^a plurality of B parts Each of _u , Z ^b _v and Z ^c _w may be the same or different. }   The method for producing a rubber composition according to claim 3, wherein the silane coupling agent (D) is a compound represented by the general formula (II). The method for producing a rubber composition according to any one of claims 1 to 4 , wherein the inorganic filler (C) is 30% by mass or more in the filler. The method for producing a rubber composition according to any one of claims 1 to 5 , wherein the maximum temperature of the rubber composition in the first stage of the kneading is 120 to 190 ° C. The rubber composition according to any one of claims 1 to 6 , wherein the rubber composition contains 0.1 to 5 parts by mass of the thioglycolic acid (B) with respect to 100 parts by mass of the rubber component (A). Method. The blending amount of the thioglycolic acid (B) in the first stage of the kneading is (2/100) to (200/100) in a mass ratio {thioglycolic acid (B) / silane coupling agent (D)}. the method for producing a rubber composition according to one any one of claims 1-7.