JP2014091777A - Production method of rubber composition for tire tread - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of a rubber composition for a tire tread that highly combines low heat build-up and abrasion resistance.SOLUTION: Provided is a production method of a rubber composition for a tire tread that includes: based on a rubber constituent (A) that comprises at least one selected from a natural rubber and a synthetic diene rubber; a filler (B) including silica in which a cetyltrimethylammonium bromide (CTAB) adsorption specific surface is 60-135 (m/g); a silane coupling agent (C); a vulcanization accelerator that is at least one selected from thiurams, dithiocarbamates, thioureas, xanthogenates and guanidines, or a salt compound (D) formed by a secondary amine or a secondary amine and a weak acid component. The production of a rubber composition for a tire tread is characterized in that the rubber composition is kneaded by two or more stages, in a first step of the kneading, the all or one part of the rubber constituent (A), and the filler (B) including silica, and the all or one part of the silane coupling agent (C), and the vulcanization accelerator or the salt compound (D) formed by secondary amine or secondary amine and a weak acid component are kneaded.

Description

  The present invention relates to a method for producing a rubber composition for a tire tread having sufficient wear resistance without impairing low heat build-up.

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, reduction of rolling resistance is also demanded for tire performance. Conventionally, as a method of reducing the rolling resistance of the tire, a method of optimizing the tire structure has been studied, but a rubber composition having lower heat generation is currently used as a rubber composition applied to a tire tread. It is the most common method.
As a method for obtaining such a rubber composition for a tire tread having a low exothermic property, a method using an inorganic filler such as silica as a filler is known.

  For example, a rubber composition that can be used in the manufacture of tires, comprising at least: (i) a diene elastomer, (ii) a silica-based or alumina-based filler as a reinforcing filler, preferably an inorganic filler that is highly dispersible silica, iii) A rubber composition based on polysulfated alkoxysilane (PSAS) as a coupling agent and (iv) 1,2-dihydropyridine (1,2-DHP) and (v) a guanidine derivative (see, for example, Patent Document 1) )It has been known.

JP 2003-523472 A (Claims, Examples, etc.)

  The present invention provides a method for producing a rubber composition for a tire tread that is highly compatible with low heat buildup and wear resistance even when silica having a large particle diameter is used in consideration of the above-described conventional technology. For the purpose.

  As a result of intensive studies on the above-described conventional techniques and the like, the present inventor has found that the rubber component (A) composed of at least one selected from natural rubber and synthetic diene rubber contains a filler containing silica having specific physical properties (A). B), a silane coupling agent (C), at least one vulcanization accelerator selected from thiurams, dithiocarbamates, thioureas, xanthates and guanidines, or secondary amines, or 2 A method for producing a tire tread rubber composition comprising a salt compound (D) formed from a secondary amine and a weak acid component, wherein the rubber composition is kneaded in a plurality of stages, and in the first stage of kneading, To knead the specific components in (A) to (D), find that the above-described method for producing a rubber composition for a tire tread is obtained, and to complete the present invention. Than it was Tsu.

  According to the present invention, there is provided a method for producing a rubber composition for a tire tread that achieves both low heat buildup and wear resistance at a high level, and low heat buildup and wear resistance even when silica having a large particle size is used. A tire having a highly compatible tread rubber is provided.

The present invention is described in detail below.
The method for producing a rubber composition for a tire tread of the present invention comprises (B) cetyltrimethylammonium bromide (CTAB) adsorption ratio with respect to a rubber component (A) composed of at least one selected from natural rubber and synthetic diene rubber. Selected from a filler (B) containing silica having a surface area of 60 to 135 (m ² / g), a silane coupling agent (C), thiurams, dithiocarbamates, thioureas, xanthates and guanidines A method for producing a rubber composition for a tire tread, comprising at least one vulcanization accelerator, or a secondary amine, or a salt compound (D) formed from a secondary amine and a weak acid component,
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 filler (B) containing silica, and the silane coupling agent (C) It is characterized by kneading all or part of the vulcanization accelerator, or a secondary amine, or a salt compound (D) formed from a secondary amine and a weak acid component.

The kneading step of the rubber composition for a tire tread in the present invention includes a vulcanization accelerator, a secondary amine, or another vulcanizing agent other than the salt compound (D) formed from the secondary amine and a weak acid component. Including a first stage of kneading that does not contain a vulcanizing agent, etc., and a final stage of kneading that contains a vulcanizing agent, etc., and if necessary, a vulcanization accelerator, a secondary amine, or 2 An intermediate stage of kneading that does not contain other vulcanizing agents other than the salt compound (D) formed from the secondary amine and the weak acid component may be included. Here, vulcanizing agents and the like refer to vulcanizing agents and vulcanization accelerators.
The first stage of kneading in the present invention refers to the first stage of kneading the rubber component (A), the filler (B) containing silica and the silane coupling agent (C). The stage in the case of kneading (A) and a filler other than the filler (B) containing silica or the case of preliminarily kneading only the rubber component (A) is not included.

[Rubber component (A)]
As the synthetic diene rubber of the rubber component (A) used in the production method of the present invention, styrene-butadiene copolymer rubber (SBR), polybutadiene rubber (BR), polyisoprene rubber (IR), butyl rubber (IIR), Ethylene-propylene-diene terpolymer rubber (EPDM) or the like can be used, and natural rubber and synthetic diene rubber may be used singly or as a blend of two or more.

[Filler containing silica (B)]
The silica used in the production method of the present invention needs to have a cetyltrimethylammonium bromide (CTAB) adsorption specific surface area of 60 to 135 (m ² / g).
Silica with CATB in the above range is greatly improved in dispersibility in the rubber component in combination with the kneading method of the present invention, so that both low heat buildup and wear resistance are highly compatible as will be described later. can do.

In the present invention, the cetyltrimethylammonium bromide adsorption specific surface area (CTAB) is the specific surface area (m ² / g) of hydrous silicic acid calculated from the amount of cetyltrimethylammonium bromide adsorbed on the hydrous silicic acid surface. Moreover, the measurement of CTAB can be performed in accordance with the method described in ASTM D3765-92. Since the method described in ASTM D3765-92 is a method for measuring CTAB of carbon black, it is slightly modified. That is, a standard solution of cetyltrimethylammonium bromide (hereinafter abbreviated as CE-TRAB) is prepared without using a carbon black standard product, and thereby a hydrous silicate OT (sodium di-2-ethylhexylsulfosuccinate) solution is prepared. The specific surface area is calculated from the adsorption amount of CE-TRAB, assuming that the adsorption cross-sectional area per molecule of CE-TRAB on the hydrous silicate surface is 0.35 nm ² .

Silica (hydrous silicic acid) used in the present invention has a CTAB of 60 to 135 (m ² / g), preferably 80 to 135 (m ² / g). When the CTAB is less than 60 (m ² / g), the storage elastic modulus of the rubber composition is remarkably lowered. On the other hand, when the CTAB is larger than 135 (m ² / g), the wear resistance is not improved.

Silica (hydrous silicic acid) having the above characteristics is produced in accordance with a method for producing hydrous silicic acid by precipitation. For example, sodium silicate and sulfuric acid are placed in a reaction vessel in which a certain amount of warm water is previously filled while controlling pH and temperature, and a hydrous silicate slurry is obtained after a certain period of time.
Subsequently, the hydrated silicate slurry is filtered and washed by a filter capable of cake washing such as a filter press to remove the by-product electrolyte, and then the obtained hydrated silicate cake is slurried, and a spray dryer or the like It is dried and manufactured using a dryer.
Further, commercially available products having the above characteristics [CTAB: 60 to 135 (m ² / g)], for example, silica of “Zeosil 1115MP” manufactured by Rhodia Co., Ltd. [CTAB: 112 (m ² / g)] Can do. These silicas may be used alone or in combination of two or more.

  In addition to the silica used in the present invention, the filler may further contain other fillers such as carbon black. By containing carbon black as a filler, it is possible to enjoy the effect of reducing electrical resistance and suppressing charging.

The silica used in the present invention is preferably used in an amount of 20 to 200 parts by mass with respect to 100 parts by mass of the rubber component (A). If the compounding amount of silica is 20 parts by mass or more, it is preferable from the viewpoint of securing the WET performance, and if it is 200 parts by mass or less, it is preferable from the viewpoint of reducing rolling resistance. Furthermore, it is more preferable to use 50 to 90 parts by mass. Moreover, when using carbon black etc. as a filler in this invention, it is preferable to use 20-200 mass parts of total filler content with a silica with respect to 100 mass parts of rubber components (A). More preferably, the amount is 50 to 200 parts by mass. If content of all the fillers 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 200 mass parts or less, it is preferable from a viewpoint of rolling resistance reduction.
In all the fillers, the silica content is preferably 50% by mass or more from the viewpoint of both wet performance and rolling resistance, and more preferably 70% by mass to 100% by mass.

[Silane coupling agent (C)]
The silane coupling agent (C) used in the production method of the present invention is not particularly limited, and examples thereof include bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, and bis (3 -Triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, 3-mercaptopropyltrimethoxy Silane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-nitropropyltrimethoxylane, 3-nitropropyltriethoxysilane, 3-chloropropylmeth Sisilane, 3-chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane, 2-chloroethyltriethoxysilane, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl- N, N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, 3 -Triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis (3-diethoxymethylsilylpropyl) tetrasulfide 3-mercaptopropyldimethoxymethylsilane, 3-nitropropyldimethoxymethylsilane, 3-chloropropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, dimethoxymethylsilylpropylbenzothiazole tetrasulfide And at least one of them.
By using these silane coupling agents (C), it is possible to provide a tire tread that is further excellent in workability at the time of rubber processing and has better wear resistance.

  It is preferable that the compounding quantity of the silane coupling agent (C) used for this invention is 1-20 mass% of the silica to be used. If the amount is less than 1% by mass, the effect of improving the low heat buildup of the tire tread rubber composition will be difficult to achieve. is there. Furthermore, it is more preferable that it is 2-20 mass% of the silica to be used, and it is especially preferable that it is 2-14 mass% of a silica.

[Vulcanization accelerator, secondary amine, or salt compound (D) formed from secondary amine and weak acid component]
Examples of the vulcanization accelerator used in the present invention include at least one selected from thiurams, dithiocarbamates, thioureas, xanthates and guanidines.
Examples of thiurams that can be used in the present invention include tetramethyl thiuram disulfide, tetraethyl thiuram disulfide, tetrapropyl thiuram disulfide, tetraisopropyl thiuram disulfide, tetrabutyl thiuram disulfide, tetrapentyl thiuram disulfide, tetrahexyl thiuram disulfide, tetraheptyl. Thiuram disulfide, tetraoctyl thiuram disulfide, tetranonyl thiuram disulfide, tetradecyl thiuram disulfide, tetradodecyl thiuram disulfide, tetrastearyl thiuram disulfide, tetrabenzyl thiuram disulfide, tetrakis (2-ethylhexyl) thiuram disulfide, tetramethyl thiuram monosulfide, tetraethyl thiuram Mo Sulfide, tetrapropyl thiuram monosulfide, tetraisopropyl thiuram monosulfide, tetrabutyl thiuram monosulfide, tetrapentyl thiuram monosulfide, tetrahexyl thiuram monosulfide, tetraheptyl thiuram monosulfide, tetraoctyl thiuram monosulfide, tetranonyl thiuram monosulfide, Examples include tetradecyl thiuram monosulfide, tetradodecyl thiuram monosulfide, tetrastearyl thiuram monosulfide, tetrabenzyl thiuram monosulfide, dipentamethylene thiuram tetrasulfide and the like. Of these, tetrakis (2-ethylhexyl) thiuram disulfide and tetrabenzylthiuram disulfide are preferred because of their high reactivity.

  Examples of dithiocarbamates that can be used in the present invention include zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dipropyldithiocarbamate, zinc diisopropyldithiocarbamate, zinc dibutyldithiocarbamate, zinc dipentyldithiocarbamate, and zinc dihexyldithiocarbamate. , Zinc diheptyldithiocarbamate, zinc dioctyldithiocarbamate, zinc di (2-ethylhexyl) dithiocarbamate, zinc didecyldithiocarbamate, zinc didodecyldithiocarbamate, zinc N-pentamethylenedithiocarbamate, N-ethyl-N-phenyldithiocarbamine Zinc oxide, zinc dibenzyldithiocarbamate, copper dimethyldithiocarbamate, copper diethyldithiocarbamate Copper dipropyldithiocarbamate, copper diisopropyldithiocarbamate, copper dibutyldithiocarbamate, copper dipentyldithiocarbamate, copper dihexyldithiocarbamate, copper diheptyldithiocarbamate, copper dioctyldithiocarbamate, copper di (2-ethylhexyl) dithiocarbamate, didecyldithiocarbamate Acid copper, copper dododecyl dithiocarbamate, copper N-pentamethylenedithiocarbamate, copper dibenzyldithiocarbamate, sodium dimethyldithiocarbamate, sodium diethyldithiocarbamate, sodium dipropyldithiocarbamate, sodium diisopropyldithiocarbamate, sodium dibutyldithiocarbamate, dipentyl Sodium dithiocarbamate, dihexyl dithiocar Sodium minate, sodium diheptyldithiocarbamate, sodium dioctyldithiocarbamate, sodium di (2-ethylhexyl) dithiocarbamate, sodium didecyldithiocarbamate, sodium didodecyldithiocarbamate, sodium N-pentamethylenedithiocarbamate, sodium dibenzyldithiocarbamate , Ferric dimethyldithiocarbamate, ferric diethyldithiocarbamate, ferric dipropyldithiocarbamate, ferric diisopropyldithiocarbamate, ferric dibutyldithiocarbamate, ferric dipentyldithiocarbamate, ferric dihexyldithiocarbamate , Ferric diheptyldithiocarbamate, ferric dioctyldithiocarbamate, di (2-ethylhexyl) di Examples thereof include ferric thiocarbamate, ferric didecyldithiocarbamate, ferric didodecyldithiocarbamate, ferric N-pentamethylenedithiocarbamate, ferric dibenzyldithiocarbamate and the like. Of these, zinc dibenzyldithiocarbamate, zinc N-ethyl-N-phenyldithiocarbamate, zinc dimethyldithiocarbamate and copper dimethyldithiocarbamate are preferred because of their high reactivity.

  Examples of thioureas that can be used in the present invention include N, N′-diphenylthiourea, trimethylthiourea, N, N′-diethylthiourea, N, N′-dimethylthiourea, and N, N′-dibutylthiourea. , Ethylenethiourea, N, N′-diisopropylthiourea, N, N′-dicyclohexylthiourea, 1,3-di (o-tolyl) thiourea, 1,3-di (p-tolyl) thiourea, 1, 1-diphenyl-2-thiourea, 2,5-dithiobiurea, guanylthiourea, 1- (1-naphthyl) -2-thiourea, 1-phenyl-2-thiourea, p-tolylthiourea, o-tolylthiourea Etc. Of these, N, N'-diethylthiourea, trimethylthiourea, N, N'-diphenylthiourea and N, N'-dimethylthiourea are preferred because of their high reactivity.

  Examples of xanthates that can be used in the present invention include, for example, zinc methylxanthate, zinc ethylxanthate, zinc propylxanthate, zinc isopropylxanthate, zinc butylxanthate, zinc pentylxanthate, zinc hexylxanthate, Zinc heptylxanthate, zinc octylxanthate, zinc 2-ethylhexylxanthate, zinc decylxanthate, zinc dodecylxanthate, potassium methylxanthate, potassium ethylxanthate, potassium propylxanthate, potassium isopropylxanthate, butylxanthate Potassium, potassium pentylxanthate, potassium hexylxanthate, potassium heptylxanthate, octyl Potassium santhate, potassium 2-ethylhexylxanthate, potassium decylxanthate, potassium dodecylxanthate, sodium methylxanthate, sodium ethylxanthate, sodium propylxanthate, sodium butylxanthate, sodium butylxanthate, sodium pentylxanthate Sodium hexyl xanthate, sodium heptyl xanthate, sodium octyl xanthate, sodium 2-ethylhexyl xanthate, sodium decyl xanthate, sodium dodecyl xanthate, and the like. Of these, zinc isopropylxanthate is preferable because of its high reactivity.

  Examples of guanidines that can be used in the present invention include 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, and di-o-tolylguanidine salt of dicatechol borate. 1,3-di-o-cumenyl guanidine, 1,3-di-o-biphenyl guanidine, 1,3-di-o-cumenyl-2-propionyl guanidine, and the like may be mentioned, 1,3-diphenyl guanidine, 1,3-di-o-tolylguanidine and 1-o-tolylbiguanide are preferred because of their high reactivity, and 1,3-diphenylguanidine is particularly preferred because of their higher reactivity.

  In the secondary amine used in the present invention or a salt compound formed from a secondary amine and a weak acid component (hereinafter sometimes abbreviated as “secondary amine salt”), the secondary amine is secondary. Any compound having an amino group may be used without particular limitation, and any of aliphatic amines and aromatic amines can be used.

  As the aliphatic amine, those having an aliphatic group having 5 to 20 carbon atoms are preferable. For example, dihexylamine, di- (2-ethylhexyl) amine, didecylamine, didodecylamine, ditetradecylamine, dihexaamine. Examples include decylamine, dioctadecylamine, dicyclopentylamine, dicyclohexylamine, dicyclooctylamine, dibenzylamine and diphenethylamine. Of these aliphatic amines, dicyclohexylamine, dibenzylamine, di (2-ethylexyl) amine and dioctadecylamine are preferred.

  On the other hand, as the aromatic amine, an amine having or not having a substituent such as a lower alkyl group on the aromatic ring, or an amine having an aromatic group and an aliphatic group can be used. Examples of such amines include diphenylamine, ditolylamine, dixylylamine, dinaphthylamine, dipyridylamine, dithienylamine, N-phenyl-N-methylamine, N-butyl-N-phenylamine, N-naphthyl-N-methylamine. , N-butyl-N-naphthylamine, N- (2-ethylhexyl) -N-phenylamine, and the like. Of these aromatic amines, diphenylamine, ditolylamine, dinaphthylamine, dipyridylamine, dithienylamine, N-phenyl-N-methylamine and N-butyl-N-naphthylamine are preferred.

  The above aliphatic amines and aromatic amines may be used alone or in combination of two or more thereof. Among these, dicyclohexylamine is preferable from the viewpoint of performance and effects. It is.

The secondary amine salt used is a salt compound formed from at least one secondary amine selected from the aliphatic secondary amines and aromatic secondary amines described above and a weak acid, and the weak acid As, for example, monohydric alcohols such as ethanol, propanol, isopropanol, butanol, isobutanol, pentanol, cyclohexanol, 2-ethylhexanol, decanol and dodecanol, or ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, neo Mention may be made of polyhydric alcohols such as pentyl glycol, trimethylolpropane, glycerol and pentaerythritol.
As the monohydric alcohol, ethanol, butanol and dodecanol are preferable, and as the polyhydric alcohol, ethylene glycol and trimethylolpropane are preferable.

  In the present invention, the weak acid used for forming the secondary amine salt may be used alone or in combination of two or more. Among the weak acids, performance and availability are obtained. Ethylene glycol is preferred from the viewpoints of properties and economy. That is, the secondary amine salt is preferably a dicyclohexylamine salt of ethylene glycol. A mixture of 80% by mass of a dicyclohexylamine salt of ethylene glycol and 20% by mass of a higher alkyl alcohol is commercially available from Ouchi Shinsei Chemical Co., Ltd. as a registered trademark “Knockmaster EGS” (vulcanization activator). Has been.

In the present invention, in the first stage of kneading, the vulcanization accelerator, the secondary amine, or the salt compound (D) formed from the secondary amine and the weak acid component is added and kneaded as described above. As described above, this is to increase the activity of the coupling function of the silane coupling agent (C).
In the present invention, the vulcanization accelerator, or the secondary amine, or the salt compound (D) formed from the secondary amine and the weak acid component may be used alone or in combination. A combination of the above may also be used.

Number of molecules of vulcanization accelerator, secondary amine, or salt compound (D) formed from secondary amine and weak acid component in the tire tread rubber composition in the first stage of kneading according to the present invention It is preferable that (number of moles) is 0.1 to 1.0 times the number of molecules (number of moles) of the silane coupling agent (C). This is because the activation of the silane coupling agent (C) occurs sufficiently when the ratio is 0.1 times or more, and the vulcanization speed is not greatly affected when the ratio is 1.0 times or less. More preferably, the number of molecules (number of moles) of the vulcanization accelerator, or the secondary amine, or the salt compound (D) formed from the secondary amine and the weak acid component is the molecule of the silane coupling agent (C). It is 0.2 to 0.6 times the number (number of moles).
The vulcanization accelerator, or the secondary amine, or the salt compound (E) formed from the secondary amine and the weak acid component is also used as a sulfur vulcanization accelerator. Also, an appropriate amount may be blended if desired.

In the present invention, the vulcanization accelerator, secondary amine, or a salt compound (D) formed from a secondary amine and a weak acid component is preferably suppressed from reducing the activity improvement effect of the coupling function. Therefore, it is preferable to mix an organic acid compound in the rubber composition in the first stage of kneading.
Examples of organic acid compounds that can be used 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, and oleic acid. , Organic acids such as saturated fatty acids and unsaturated fatty acids such as vaccenic acid, linoleic acid, linolenic acid and nervonic acid, and resin acids such as rosin acid and modified rosin acid, alkali metals of the saturated fatty acids and unsaturated fatty acids and resin acids Examples thereof include salts and esters. As the alkali metal, sodium, potassium and the like are preferable.
More preferably, 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.
Further, when an emulsion-polymerized styrene-butadiene copolymer is used as a part or all of the rubber component (A), rosin acid (50 mol% or more in the organic acid compound is contained in the emulsion-polymerized styrene-butadiene copolymer ( Modified rosin acid is also included) and / or a fatty acid is preferable from the viewpoint of an emulsifier necessary for polymerizing an emulsion-polymerized styrene-butadiene copolymer.

In the present invention, zinc oxide (zinc white) is preferably added after the second stage of kneading from the viewpoint of unvulcanized viscosity and rolling resistance.
The blending amount of zinc oxide to be used is preferably 0.1 to 5 parts by mass, more preferably 0.1 to 100 parts by mass of the rubber component (A) from the viewpoint of unvulcanized viscosity and rolling resistance. It is desirable to set it as ~ mass part.

In the method for producing a rubber composition for tires of the present invention, various compounding agents such as vulcanization activators such as zinc white and anti-aging agents, which are usually compounded in the rubber composition, are the first stage of kneading as necessary. Alternatively, they are kneaded in the final stage or in an intermediate stage between the first stage and the final stage.
As a kneading apparatus in the production method of the present invention, a Banbury mixer, a roll, an intensive mixer or the like is used.

  In the present invention, in order to more suitably increase the activity of the coupling function of the silane coupling agent (C), the maximum temperature of the rubber composition in the first stage of kneading is 120 to 190 ° C. Preferably, it is 130-175 degreeC, More preferably, it is 140-170 degreeC.

  In the present invention, in the first stage of kneading, after adding all or part of the rubber component (A), the filler (B) containing silica, or all or part of the silane coupling agent (C), The time until the vulcanization accelerator, secondary amine, or the salt compound (D) formed from the secondary amine and the weak acid component is added during the first stage is 10 to 180 seconds. Is preferred. The lower limit of this time is more preferably 30 seconds or more, the upper limit is more preferably 150 seconds or less, and even more preferably 120 seconds or less. If this time is 10 seconds or more, the reaction of (B) and (C) can be sufficiently advanced. Even if this time exceeds 180 seconds, the reaction of (B) and (C) has already proceeded sufficiently, so that it is difficult to enjoy further effects, and the upper limit is preferably set to 180 seconds.

  Further, as a method for charging the vulcanization accelerator in the first stage, or a secondary amine, or a salt compound (D) formed from the secondary amine and a weak acid component, a rubber component (A) and a packing containing silica are used. After kneading all or part of the material (B) and all or part of the silane coupling agent (C), it is formed from a vulcanization accelerator, or a secondary amine, or a secondary amine and a weak acid component. It is preferable to add the salt compound (D) and further knead. This is because, by this charging method, the reaction between the silane coupling agent (C) and the rubber component (A) can be advanced after the reaction between the silane coupling agent (C) and the silica has sufficiently progressed.

In the method for producing a rubber composition for a tire tread of the present invention configured as described above, (B) cetyltrimethylammonium is used for the rubber component (A) composed of at least one selected from natural rubber and synthetic diene rubber. Bromide (CTAB) Adsorption specific surface area of silica (B) containing 60 to 135 (m ² / g), silane coupling agent (C), thiurams, dithiocarbamates, thioureas, xanthates And at least one vulcanization accelerator selected from guanidines, or secondary rubber, or a salt compound (D) formed from a secondary amine and a weak acid component. A method,
By kneading the rubber composition in a plurality of stages, and kneading all or part of (A) and (B) and all or part of (C) and (D) in the first stage of kneading. , Which promotes the efficient formation of bound rubber and, as a result, further improves the dispersibility of silica with the above characteristics, so that even with the use of silica with a large particle diameter, a tire that is highly compatible with low heat buildup and wear resistance A rubber composition for a tread is obtained.
In addition, since the tire of the present invention has the tread rubber produced by the above production method, a tire having a high degree of compatibility between low heat buildup and wear resistance can be obtained. In particular, it can be suitably used as various tires for passenger cars, small trucks, light passenger cars, light trucks and large vehicles (for trucks, buses, construction vehicles, etc.).

  EXAMPLES Next, although an Example and a comparative example are given and this invention is demonstrated in more detail, this invention is not limited to the following Example at all.

  As silica used in Examples and the like, five types of silica 1 to 5 having different CTAB properties were used. Silica 1, 3, and 5 used each commercial item, and silica 2 and 4 used each physical property silica manufactured by the following manufacturing examples A and B. Moreover, the measurement of CTAB of silica 1-5 was performed by the following method.

(Measurement method of CTAB)
This was carried out in accordance with the method described in ASTM D3765-92. Since the method described in ASTM D3765-92 is a method for measuring CTAB of carbon black, some modifications were made. That is, a standard solution of cetyltrimethylammonium bromide (hereinafter abbreviated as CE-TRAB) was prepared without using IRB # 3 (83.0 m 2 / g), which is a standard product of carbon black, and thereby hydrous silica. The acid OT (sodium di-2-ethylhexylsulfosuccinate) solution was standardized, and the adsorption cross-section per CE-TRAB molecule on the hydrous silicic acid surface was 0.35 nm ² from the adsorption amount of CE-TRAB, and the specific surface area (m ² / g) was calculated. This is because carbon black and hydrous silicic acid have different surfaces, and it is considered that there is a difference in the amount of CE-TRAB adsorbed even with the same surface area.

[Production of Silica 2 (Production Example A)]
In a 180 L jacketed stainless steel reaction vessel equipped with a stirrer, 86 L of water and 0.5 L of an aqueous sodium silicate solution were placed and heated to 96 ° C. The Na ₂ O concentration in the obtained solution was 0.005 mol / L.
While maintaining the temperature of this solution at 96 ° C., the same aqueous sodium silicate solution as described above was simultaneously added dropwise at a flow rate of 615 ml / min and sulfuric acid (18 mol / L) at a flow rate of 27 ml / min. While adjusting the flow rate, the neutralization reaction was performed while maintaining the Na ₂ O concentration in the reaction solution in the range of 0.00 to 0.01 mol / L. From the middle of the reaction, the reaction solution started to become cloudy, and the viscosity increased to a gel solution at 40 minutes. Further addition was continued and the reaction was stopped in 90 minutes. After stopping the reaction, the reaction solution temperature was maintained at 96 ° C. for 30 minutes. The silica concentration in the resulting solution was 62 g / L. Subsequently, sulfuric acid having the above-mentioned concentration was added until the pH of the solution reached 3, to obtain a silicic acid slurry. The obtained silicic acid slurry was filtered with a filter press and washed with water to obtain a wet cake. Next, the wet cake was made into a slurry using an emulsifier and dried with a spray dryer to obtain a wet method hydrous silicic acid (silica 2).
CTAB: 80 (m ² / g)

[Production of Silica 4 (Production Example B)]
Using the same container and raw materials as in Production Example A, 93 L of water and 0.6 L of an aqueous sodium silicate solution were added and heated to 90 ° C. The Na ₂ O concentration in the obtained solution was 0.005 mol / L.
While maintaining the temperature of this solution at 90 ° C., the same sodium silicate aqueous solution as described above was simultaneously added dropwise at a flow rate of 540 ml / min and sulfuric acid (18 mol / L) at a flow rate of 24 ml / min. While adjusting the flow rate, the neutralization reaction was performed while maintaining the Na ₂ O concentration in the reaction solution in the range of 0.00 to 0.01 mol / L. From the middle of the reaction, white turbidity started, and the viscosity increased at 47 minutes to form a gel solution. Further addition was continued and the reaction was stopped in 90 minutes. After stopping the reaction, the reaction solution temperature was maintained at 90 ° C. for 30 minutes. The silica concentration in the resulting solution was 55 g / L. Subsequently, sulfuric acid having the above-mentioned concentration was added until the pH of the solution reached 3, to obtain a silicic acid slurry. Thereafter, wet method hydrous silicic acid (silica 4) was obtained in the same manner as in Production Example A.
CTAB: 134 (m ² / g)

(Examples 1-5 and Comparative Examples 1-7)
A rubber composition for a tire tread was prepared by the blending formulation shown in Table 1 below and two kneading methods.
In Examples 1 to 5, the components in column A of Table 1 were adjusted and kneaded with a Banbury mixer so that the maximum temperature of the rubber composition in the first stage of kneading was 150 ° C., and for each tire tread A rubber composition was prepared. 1,3-diphenylguanidine which is a guanidine as a rubber component (A), all of silica, silane coupling agent (C), and vulcanization accelerator (D) in the first stage of kneading the rubber composition for tire tread (DPG) was added simultaneously and kneaded.
In Comparative Examples 1 to 7, a rubber composition for each tire tread was prepared by adding an ordinary kneading method, that is, 1,3-diphenylguanidine (DPG), which is a guanidine, simultaneously with the crosslinking agent.
The tan δ and wear resistance of each of the obtained tire tread rubber compositions were calculated and evaluated by the following methods. In addition, tire performance evaluation (rolling resistance, wear resistance) was calculated and evaluated by the following methods using the obtained rubber composition for tire tread in a tread having a tire size of 195 / 65R15.
These results are shown in Table 1 below.

(Evaluation method of tan δ)
The value of tan δ at 60 ° C. was measured at a frequency of 52 Hz, an initial strain rate of 2%, and a dynamic strain rate of 1% using a spectrometer (dynamic viscoelasticity tester) manufactured by Ueshima Seisakusho Co., Ltd. As an index.

(Abrasion resistance evaluation method)
The amount of wear with a slip rate of 25% at room temperature was measured using a Lambourn type wear tester, and the index was displayed with the reciprocal of the amount of wear in Comparative Example 5 (control) as 100.

(Rolling resistance evaluation method)
When a tire was rotated at a speed of 80 km under the action of a load of 4500 N (460 kg) using a rotating drum having a steel smooth surface with an outer diameter of 1707.6 mm and a width of 350 mm, the measurement was performed by the coasting method. The tire of Comparative Example 5 was displayed as an index with 100 as the index. The larger the index, the lower the heat generation.

(Abrasion resistance evaluation method)
After traveling 10,000 km on a paved road surface with an actual vehicle, the remaining groove is measured, and the distance traveled to wear the tread by 1 mm is relatively compared. The tire of Comparative Example 5 is displayed as an index as 100 (equivalent to 8000 km / mm). did. The larger the index, the better the wear resistance.

* 1 to * 10 in Table 1 are as follows.
* 1: Solution polymerization SBR manufactured by Asahi Kasei Co., Ltd., trade name “Toughden 2000”
* 2: Product name “# 80” manufactured by Asahi Carbon Co., Ltd.
* 3: Silica, “Ultrazil 360” manufactured by Degussa CTAB: 45 m ² / g
* 4: Silica, “Zeosil 1115MP” CTAB manufactured by Rhodia Co., Ltd .: 112 m ² / g
* 5: Silica, “Nipseal AQ” manufactured by Tosoh Silica Co., Ltd. CTAB: 158 m ² / g
* 6: Bis (3-triethoxysilylpropyl) disulfide (average sulfur chain length: 2.35), silane coupling agent manufactured by Evonik, trade name “Si75” (registered trademark)
* 7: N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine, manufactured by Ouchi Shinsei Chemical Industry Co., Ltd., trade name “NOCRACK 6C”
* 8: 1,3-diphenylguanidine, manufactured by Sanshin Chemical Industry Co., Ltd., trade name “Sunseller D”
* 9: Noxeller CZ, manufactured by Ouchi Shinsei Chemical Co., Ltd., N-cyclohexyl-2-benzothiazolylsulfenamide * 10: Noxeller DM, manufactured by Ouchi Shinsei Chemical Co., Ltd., dibenzothiazolyl sulfide

  As is clear from the results of Table 1 above, Examples 1 to 5, which are within the scope of the present invention, have higher exothermic properties and abrasion resistance than Comparative Examples 1 to 7, which are outside the scope of the present invention. It was found that a rubber composition for a tire tread and a tire that are compatible with each other can be obtained.

  The method for producing a tire tread rubber composition according to the present invention can provide a tire tread rubber composition that has both a low heat buildup and a high wear resistance, and is therefore suitable for passenger cars, light trucks, and light passenger cars. It is suitably used as a method for producing various members of pneumatic tires for light trucks and large vehicles (for trucks and buses, construction vehicles, etc.), particularly tread members for pneumatic radial tires.

Claims (6)

Silica having (B) cetyltrimethylammonium bromide (CTAB) adsorption specific surface area of 60 to 135 (m ² / g) with respect to rubber component (A) composed of at least one selected from natural rubber and synthetic diene rubber And a silane coupling agent (C) and at least one vulcanization accelerator selected from thiurams, dithiocarbamates, thioureas, xanthates and guanidines, or secondary A method for producing a rubber composition for a tire tread comprising an amine or a salt compound (D) formed from a secondary amine and a weak acid component,
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 filler (B) containing silica, and the silane coupling agent (C) A rubber composition for a tire tread characterized by kneading all or part of the vulcanization accelerator, or a secondary amine, or a salt compound (D) formed from a secondary amine and a weak acid component. Manufacturing method.   The method for producing a rubber composition for a tire tread according to claim 1, wherein the maximum temperature of the rubber composition in the rubber composition in the first stage is 120 to 190 ° C.   The filler (B) contains silica and carbon black, and the amount of the filler (B) is 20 to 200 parts by mass with respect to 100 parts by mass of the rubber component (A). Or the manufacturing method of the rubber composition for tire treads of 2.   The method for producing a rubber composition for a tire tread according to claim 3, wherein the content of the silica is 50 to 100% by mass in the entire filler (B).   The method for producing a rubber composition for a tire according to any one of claims 1 to 4, wherein zinc oxide is added after the second stage of kneading.   A tire having a tread rubber manufactured by the manufacturing method according to claim 1.