JP2014221863A - Tire rubber composition and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire rubber composition which can improve wet grip performance while keeping excellent wear resistance and fuel economy, and a pneumatic tire prepared using the same.SOLUTION: This invention relates to a tire rubber composition comprising a rubber component, carbon black, an amphoteric compound having acidic and basic functional groups, and an inorganic compound whose crystal system is monoclinic crystal.

Description

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

In recent years, there has been an increasing demand for low fuel consumption for automobiles, and it is known that the rubber physical properties of tires have an important effect on low fuel consumption. Therefore, it is possible to provide a tire rubber composition with excellent fuel efficiency. It is desired.

As a method for improving fuel economy, a method of reducing the filler such as carbon black is known, but there is room for improvement in that the wet grip and wear resistance are reduced when the filler is reduced. . As described above, usually, low fuel consumption is in contradiction with wet grip properties and wear resistance, and it has been difficult to prepare a rubber composition having these properties.

As a method for improving fuel economy, wet grip and wear resistance in a well-balanced manner, Patent Document 1 discloses a method of blending a diene rubber modified with an organosilicon compound containing an amino group and an alkoxy group. ing. However, in recent years, further improvements have been demanded for low fuel consumption, wet grip performance, and wear resistance.

JP 2000-344955 A

An object of the present invention is to solve the above problems and provide a rubber composition for a tire that can improve wet grip properties while maintaining good wear resistance and low fuel consumption, and a pneumatic tire using the same. And

The present invention relates to a rubber composition for a tire containing a rubber component, carbon black, an amphoteric compound having acidic and basic functional groups, and an inorganic compound having a monoclinic crystal system.

（式（Ｉ）中、Ｒ^１は炭素数２〜３０のアルキレン基、アルケニレン基又はアルキニレン基を表す。Ａは酸性官能基を表す。Ｒ^２及びＲ^３は、同一又は異なって、水素原子、炭素数１〜２０のアルキル基、アルケニル基若しくはアルキニル基、又は炭素数１〜２０のアルコキシシリル基を表す。式（Ｉ）で表される化合物は、該化合物の金属塩でもよい。） The amphoteric compound is preferably a compound represented by the following formula (I).

(In the formula (I), R ¹ represents an alkylene group having 2 to 30 carbon atoms, an alkenylene group or an alkynylene group. A represents an acidic functional group. R ² and R ³ are the same or different and each represents a hydrogen atom, Represents an alkyl group having 1 to 20 carbon atoms, an alkenyl group or an alkynyl group, or an alkoxysilyl group having 1 to 20 carbon atoms, and the compound represented by the formula (I) may be a metal salt of the compound.

（式（Ｉ−１）中、ｐは２〜８の整数を表す。式（Ｉ−２）中、ｑは２〜８の整数を表す。Ｍ^ｒ＋は金属イオンを表し、ｒはその価数を表す。） The amphoteric compound is preferably a compound represented by the following formula (I-1) and / or a compound represented by the following formula (I-2).

(In formula (I-1), p represents an integer of 2 to 8. In formula (I-2), q represents an integer of 2 to 8. Mr ⁺ represents a metal ion, and r represents a valence thereof. Represents.)

The metal ion represented by ^{Mr +} in the above formula (I-2) is preferably a lithium ion, a sodium ion, a potassium ion, a cesium ion, a cobalt ion, a copper ion, or a zinc ion.

It is preferable that the content of the amphoteric compound is 0.01 to 30 parts by mass with respect to 100 parts by mass of the carbon black.

（式（ＩＩ）中、Ｍは、アルミニウム、マグネシウム、チタン、カルシウム、鉄及びジルコニウムからなる群より選択される少なくとも１種の金属、該金属の酸化物若しくは水酸化物、該酸化物若しくは該水酸化物の水和物、該金属の炭酸塩、又はこれらの混合物を表す。ｎは１〜５の整数、ｘは０〜１０の整数、ｙは２〜５の整数、ｚは０〜１０の整数を表す。） The inorganic compound is preferably a compound represented by the composition formula of the following formula (II).

(In the formula (II), M is at least one metal selected from the group consisting of aluminum, magnesium, titanium, calcium, iron and zirconium, an oxide or hydroxide of the metal, the oxide or water. Represents an oxide hydrate, a carbonate of the metal, or a mixture thereof, n is an integer of 1 to 5, x is an integer of 0 to 10, y is an integer of 2 to 5, and z is 0 to 10. Represents an integer.)

The present invention also relates to a pneumatic tire produced using the rubber composition.

According to the present invention, a tire rubber composition containing a rubber component, carbon black, an amphoteric compound having acidic and basic functional groups, and an inorganic compound having a monoclinic crystal system is preferable. The wet grip can be improved while maintaining excellent wear resistance and low fuel consumption.

The rubber composition for tires of the present invention includes a rubber component, carbon black, an amphoteric compound having acidic and basic functional groups, and an inorganic compound having a monoclinic crystal system (crystal lattice) (hereinafter referred to as monoclinic crystal). Also referred to as an inorganic compound).

By compounding carbon black and an amphoteric compound having both an acidic functional group and a basic functional group into the rubber component, the acidic functional group of the amphoteric compound is rubber and the basic functional group is the surface of the carbon black. As the carbon black and polymer are restrained, heat generation is suppressed and good wear resistance and fuel efficiency are maintained. While improving wet grip. Furthermore, by adding a monoclinic inorganic compound in addition to the above components, the dispersibility of the carbon black can be further improved by the interaction of the inorganic compound with the carbon black, resulting in good wear resistance and low fuel consumption. The wet grip properties can be further improved while maintaining the properties, and the balance between these performances is synergistically improved.

Rubber components include NR, diene-based synthetic rubber (isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR). ), Ethylene propylene diene rubber (EPDM), butyl rubber (IIR), halogenated butyl rubber (X-IIR), etc.). Among them, NR is preferable from the viewpoint of fuel economy and mechanical strength, BR is preferable from the viewpoint of wear resistance and bending crack resistance, and the effects of the present invention can be obtained more suitably. It is more preferable to use NR and BR together. A rubber component may be used independently and may use 2 or more types together.

The NR is not particularly limited, and for example, those commonly used in the tire industry such as SIR20, RSS # 3, TSR20, and the like can be used.

The content of NR in 100% by mass of the rubber component is preferably 20% by mass or more, more preferably 30% by mass or more, and further preferably 40% by mass or more. If it is less than 20% by mass, sufficient rubber strength and low fuel consumption tend not to be obtained. The upper limit of the content of NR is not particularly limited, and may be 100% by mass. However, when other rubber components are used together with NR, 70% by mass or less is preferable.

It is not particularly limited as BR, for example, BR1220 manufactured by Nippon Zeon Co., Ltd., BR with high cis content such as BR150B manufactured by Ube Industries, Ltd., 1, VCR412, VCR617 manufactured by Ube Industries, etc. Commonly used in the tire industry such as BR containing 2-syndiotactic polybutadiene crystal (SPB) can be used. Of these, BR having a cis content of 95% by mass or more is preferred because of its high effect of improving wear resistance. The cis content can be measured by infrared absorption spectrum analysis.

The content of BR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, and still more preferably 20% by mass or more. When it is less than 5% by mass, sufficient wear resistance tends to be not obtained. Further, the BR content is preferably 70% by mass or less, more preferably 60% by mass or less.

The total content of NR and BR is preferably 80% by mass or more, more preferably 90% by mass or more, and may be 100% by mass in 100% by mass of the rubber component. If it is less than 80% by mass, a good performance balance may not be obtained with respect to wear resistance and fuel efficiency.

（式（ＩＩ）中、Ｍは、アルミニウム、マグネシウム、チタン、カルシウム、鉄及びジルコニウムからなる群より選択される少なくとも１種の金属、該金属の酸化物若しくは水酸化物、該酸化物若しくは該水酸化物の水和物、該金属の炭酸塩、又はこれらの混合物を表す。ｎは１〜５の整数、ｘは０〜１０の整数、ｙは２〜５の整数、ｚは０〜１０の整数を表す。） Examples of monoclinic inorganic compounds include talc, feldspar, gypsum (calcium sulfate), chlorite (epidote), rhyolite (clinozoite), gibbsite (aluminum hydroxide), etc. It is done. From the viewpoint that low fuel consumption, wet grip properties and wear resistance can be obtained in a well-balanced manner, it is preferable to use a compound represented by the following formula (II) as the monoclinic inorganic compound.

(In the formula (II), M is at least one metal selected from the group consisting of aluminum, magnesium, titanium, calcium, iron and zirconium, an oxide or hydroxide of the metal, the oxide or water. Represents an oxide hydrate, a carbonate of the metal, or a mixture thereof, n is an integer of 1 to 5, x is an integer of 0 to 10, y is an integer of 2 to 5, and z is 0 to 10. Represents an integer.)

In the above formula (II), as M, magnesium and aluminum are preferable, magnesium is more preferable, and magnesium oxide is more preferable because low fuel consumption, wet grip properties, and wear resistance can be obtained in a balanced manner. n is preferably from 2 to 4, and more preferably from 3 to 4. x is preferably from 1 to 8, and more preferably from 2 to 6. y is preferably 2-4. z is preferably 1 to 5, and more preferably 1 to 3.

Examples of monoclinic inorganic compounds represented by the formula (II) include talc (3MgO.4SiO ₂ .H ₂ O), gibbsite (Al (OH) ₃ ), clinozoite (Ca ₂ Al ₃ (OH) · 3SiO _4), epidote _{(Ca 2 (Al, Fe)} 3 OH · 3SiO 4) , and the like. Of these, talc is preferable. These may be used individually by 1 type and may use 2 or more types together.

The average particle size of the monoclinic inorganic compound is preferably 500 μm or less, more preferably 50 μm or less, still more preferably 25 μm or less, and particularly preferably 15 μm or less from the viewpoint of wear resistance. The lower limit of the average particle diameter is not particularly limited, and a smaller particle diameter is more preferable from the viewpoint of wear resistance.
In addition, in this specification, an average particle diameter is the value measured by transmission electron microscope (TEM) observation. Specifically, a photograph is taken with a transmission electron microscope. When the shape of the fine particles is spherical, the diameter of the sphere, when the needle or bar is a short diameter, when it is irregular, the average particle diameter from the center is measured. The average value of 100 particles is the average particle size.

The content of the monoclinic inorganic compound is preferably 2 parts by mass or more, more preferably 3 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 2 parts by mass, the wet grip property may not be sufficiently exhibited. The content of the monoclinic inorganic compound is preferably 10 parts by mass or less, more preferably 8 parts by mass or less. If it exceeds 10 parts by mass, good wear resistance may not be ensured.

In the present invention, an amphoteric compound having an acidic functional group and a basic functional group is used. Examples of acidic functional groups include carboxylic acid groups, sulfonic acid groups, phosphoric acid groups, thiosulfonic acid groups (—SSO ₃ H), dithiocarboxylic acid groups (—CSSH), and thioalkylcarboxylic acids having an alkyl group having 1 to 20 carbon atoms. Examples include an acid group (-SRCOOH: R is a linear or branched alkyl group), a phenolic hydroxyl group, and the like, and among them, a thiosulfonic acid group is preferable. Examples of basic functional groups include primary amino groups, secondary amino groups, and tertiary amino groups. The amphoteric compound may be a metal salt of the compound.

The basic functional group portion of the amphoteric compound reacts with a functional group such as a carboxy group present on the surface of the carbon black to bond with carbon black, and the acidic functional group portion reacts with a double bond of the polymer. Therefore, the dispersibility of carbon black is improved and the dispersion state can be maintained. Moreover, since carbon black and a polymer are restrained by reaction, it becomes possible to suppress exothermic property. Therefore, wear resistance and fuel efficiency can be improved in a well-balanced manner.

（式（Ｉ）中、Ｒ^１は炭素数２〜３０のアルキレン基、アルケニレン基又はアルキニレン基を表す。Ａは酸性官能基を表す。Ｒ^２及びＲ^３は、同一又は異なって、水素原子、炭素数１〜２０のアルキル基、アルケニル基若しくはアルキニル基、又は炭素数１〜２０のアルコキシシリル基を表す。式（Ｉ）で表される化合物は、該化合物の金属塩でもよい。） The amphoteric compound is preferably a compound represented by the following formula (I).

(In the formula (I), R ¹ represents an alkylene group having 2 to 30 carbon atoms, an alkenylene group or an alkynylene group. A represents an acidic functional group. R ² and R ³ are the same or different and each represents a hydrogen atom, Represents an alkyl group having 1 to 20 carbon atoms, an alkenyl group or an alkynyl group, or an alkoxysilyl group having 1 to 20 carbon atoms, and the compound represented by the formula (I) may be a metal salt of the compound.

The carbon number of the alkylene group, alkenylene group, and alkynylene group of R ¹ is preferably 2 to 18, more preferably 2 to 12. R ¹ may be linear or branched, and specific examples of the alkylene group include ethylene group, propylene group, butylene group, and specific examples of the alkenylene group include vinylene group, propenylene group, butenylene group, etc. Specific examples of the alkynylene group include an ethynylene group, a propynylene group, and a butynylene group. R ¹ is preferably an alkylene group.

Examples of the acidic functional group for A include those described above.

Examples of the alkyl group having 1 to 20 carbon atoms of R ² and R ³ include a methyl group, an ethyl group, a propyl group, and a butyl group. Examples of the alkenyl group include a vinyl group, a propenyl group, and a butenyl group. An ethynyl group, a propynyl group, a butynyl group, etc. are mentioned, As a C1-C20 alkoxysilyl group, a triethoxysilyl group, a trimethoxysilyl group, etc. are mentioned. R ² and R ³ are preferably a hydrogen atom.

（式（Ｉ−１）中、ｐは２〜８の整数を表す。式（Ｉ−２）中、ｑは２〜８の整数を表す。Ｍ^ｒ＋は金属イオンを表し、ｒはその価数を表す。） The amphoteric compound is preferably a compound represented by the following formula (I-1) and / or a compound represented by the following formula (I-2).

(In formula (I-1), p represents an integer of 2 to 8. In formula (I-2), q represents an integer of 2 to 8. Mr ⁺ represents a metal ion, and r represents a valence thereof. Represents.)

The compound represented by the above formula (I-2) can be produced by any known method. For example, a method of reacting a haloalkylamine with sodium thiosulfate, a method of reacting a potassium salt of phthalimide and a dihaloalkane with a sodium thiosulfate, and hydrolyzing the resulting compound. Can be mentioned.

Specifically, when q is a compound of 6, a method of reacting 6-halohexylamine with sodium thiosulfate, a compound obtained by reacting a potassium salt of phthalimide and 1,6-dihalohexane, and thiosulfuric acid Examples include a method of reacting with sodium and hydrolyzing the obtained compound.

Further, when q is a compound of 3, a method of reacting 3-halopropylamine and sodium thiosulfate, a compound obtained by reacting a potassium salt of phthalimide and 1,3-dihalopropane, and sodium thiosulfate And a method of hydrolyzing the resulting compound.

The compound represented by the above formula (I-1) can be produced, for example, by reacting the compound represented by the above formula (I-2) with a protonic acid.

In the present invention, a mixture of compounds represented by the above formulas (I-1) and (I-2) can also be used. The mixture includes a method of mixing a compound represented by the formula (I-1) and a compound represented by the formula (I-2), a hydroxide containing a metal represented by the M, and a carbonate. And a method in which a part of the compound represented by the formula (I-1) is metallated using a hydrogen carbonate and the like, and a part of the compound represented by the formula (I-2) by using a protonic acid. It can be produced by a neutralizing method. The compounds represented by the above formulas (I-1) and (I-2) thus produced can be taken out of the reaction mixture by operations such as concentration and crystallization, and the taken out formula (I) -1) The compound represented by (I-2) usually contains about 0.1 to 5% of water. In the present invention, only the compound represented by the above formula (I-1) or only the compound represented by the above formula (I-2) can be used. Further, a plurality of types of compounds represented by the above formula (I-1) and compounds represented by the above formula (I-2) may be used in combination.

In said formula (I-1), p represents the integer of 2-8 and 2-6 are preferable. In said formula (I-2), q represents the integer of 2-8 and 2-6 are preferable.

As the metal ion represented by ^{Mr +} , lithium ion, sodium ion, potassium ion, cesium ion, cobalt ion, copper ion and zinc ion are preferable, lithium ion, sodium ion and potassium ion are more preferable, and sodium ion is more preferable. . r represents the valence of the metal ion, and is not limited as long as it is a possible range for the metal. In general, r is 1 when the metal ion is an alkali metal ion, 2 or 3 when the metal ion is cobalt ion, an integer of 1 to 3 when the metal ion is copper ion, and 2 when the metal ion is zinc ion. According to the said manufacturing method, although the sodium salt of the compound represented by the said formula (I-1) is obtained normally, it can convert into another metal salt by performing a cation exchange reaction.

The median diameter of the compounds represented by the above formulas (I-1) and (I-2) is preferably in the range of 0.05 to 100 μm, more preferably in the range of 1 to 100 μm. The median diameter can be measured by a laser diffraction method.

The compounds represented by the above formulas (I-1) and (I-2) may be used after being previously mixed with a carrier. Examples of the support agent include “inorganic fillers and reinforcing agents” described on pages 510 to 513 of “Rubber Industry Handbook <Fourth Edition>” edited by the Japan Rubber Association. Among them, carbon black, silica, calcined, etc. Clay and aluminum hydroxide are preferred. Although the usage-amount of a support agent is not specifically limited, 10-1000 with respect to 100 mass parts of total amounts of the compound represented by the said formula (I-1) and / or the compound represented by (I-2). A range of parts by mass is preferred.

In the rubber composition of the present invention, the content of the amphoteric compound is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, and still more preferably 0.5 parts by mass with respect to 100 parts by mass of carbon black. More than part by mass. If the amount is less than 0.01 parts by mass, the effect of improving fuel economy is low, and the wear resistance may not be sufficiently improved. The content is preferably 30 parts by mass or less, more preferably 15 parts by mass or less, still more preferably 10 parts by mass or less, and particularly preferably 5 parts by mass or less. Even if it exceeds 30 mass parts, the further improvement effect of fuel-consumption property is not acquired, but there exists a tendency for workability and abrasion resistance to fall.

No particular limitation is imposed on the carbon black used in the present invention, the wet grip performance of the tread rubber composition, in view of abrasion resistance and rubber reinforcing property, the nitrogen adsorption specific surface area (N 2 _SA) of carbon black is 40 m ² / G or more is preferable, 60 m ² / g or more is more preferable, and 80 m ² / g or more is more preferable. Further, the _N 2 SA is preferably 250 meters ² / g or less, more preferably 200 meters ² / g or less, more preferably 150 meters ² / g or less, particularly preferably 120 m ² / g. If it is less than 40 m ² / g, the wear resistance tends to decrease, and if it exceeds 250 m ² / g, the fuel efficiency tends to deteriorate. Incidentally, _N 2 SA of carbon black, JIS K 6217-2: determined by 2001.

Carbon black has a dibutyl phthalate oil absorption (DBP) of preferably 50 ml / 100 g or more, more preferably 60 ml / 100 g or more, and still more preferably 80 ml / 100 g or more. The DBP is preferably 200 ml / 100 g or less, more preferably 180 ml / 100 g or less, and still more preferably 150 ml / 100 g or less. If it is less than 50 ml / 100 g, the wear resistance tends to be reduced, and if it exceeds 200 ml / 100 g, the fracture performance and durability tend to deteriorate. The DBP of carbon black is measured according to JIS K 6217-4: 2001.

The content of carbon black in the rubber composition is preferably 10 parts by mass or more, more preferably 35 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 10 parts by mass, sufficient reinforcement may not be obtained. Moreover, this content becomes like this. Preferably it is 100 mass parts or less, More preferably, it is 95 mass parts or less, More preferably, it is 70 mass parts or less. When it exceeds 100 parts by mass, the workability is lowered, and there is a possibility that the performance balance of low fuel consumption, wet grip properties and wear resistance may be lowered.

In the rubber composition of the present invention, in addition to the above components, compounding agents generally used in the production of rubber compositions, for example, reinforcing fillers such as silica and clay, silane coupling agents, zinc oxide, Stearic acid, processing aids, various anti-aging agents, softeners such as oil, aromatic petroleum resins, waxes, vulcanizing agents such as sulfur, vulcanization accelerators, and the like can be appropriately blended.

Examples of the vulcanization accelerator include sulfenamide, thiazole, thiuram, thiourea, guanidine, dithiocarbamic acid, aldehyde-amine or aldehyde-ammonia, imidazoline, or xanthate vulcanization accelerators. Is mentioned. Of these, sulfenamide vulcanization accelerators are preferred.

Examples of the sulfenamide vulcanization accelerator include N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N, N And '-dicyclohexyl-2-benzothiazolylsulfenamide (DZ). Of these, TBBS is preferable.

The content of the vulcanization accelerator is preferably 0.2 parts by mass or more, more preferably 0.6 parts by mass or more with respect to 100 parts by mass of the rubber component. Moreover, Preferably it is 3 mass parts or less, More preferably, it is 2 mass parts or less. By adjusting within the above range, it is possible to prepare a rubber excellent in performance balance between low fuel consumption and wear resistance.

The oil content is preferably 2 parts by mass or more, more preferably 8 parts by mass or more, with respect to 100 parts by mass of the rubber component. If it is less than 2 parts by mass, the processability is inferior, and the fuel economy and wear resistance tend to decrease. Moreover, Preferably it is 20 mass parts or less, More preferably, it is 12 mass parts or less. If it exceeds 20 parts by mass, wet grip properties and wear resistance may be deteriorated.

The rubber composition of the present invention can be suitably used for treads (cap treads), base treads, undertreads, and the like, and can be particularly suitably used for treads.

As a method for producing the rubber composition for tires of the present invention, known methods can be used, for example, the above components are kneaded using a rubber kneader such as an open roll, a Banbury mixer, a closed kneader, Thereafter, it can be produced by a vulcanization method.

The pneumatic tire of the present invention is produced by a usual method using the rubber composition. That is, a rubber composition containing various additives as necessary is extruded in accordance with the shape of the tire member at an unvulcanized stage, molded by a normal method on a tire molding machine, After bonding together with the tire member to form an unvulcanized tire, the tire can be manufactured by heating and pressing in a vulcanizer.

The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

(Production Example 1: S- (3-aminopropyl) thiosulfuric acid (amphoteric compound A))
To a reaction vessel substituted with nitrogen gas, 75 g of 3-bromopropylamine hydrobromide, 85.26 g of sodium thiosulfate pentahydrate, 375 ml of methanol and 375 ml of water were added, and the mixture was refluxed at 70 ° C. for 5 hours. did. After allowing to cool, methanol was removed under reduced pressure. To the residue was added 13.68 g of sodium hydroxide, and the mixture was stirred at room temperature for 1 hour, and then the solvent was removed under reduced pressure. 600 ml of ethanol was added to the obtained residue and refluxed for 1.5 hours. Hot filtration was performed, and the filtrate was concentrated under reduced pressure to obtain crystals. The crystals were taken out by filtration, washed with ethanol, and further washed with hexane. The obtained crystals were vacuum-dried to obtain sodium S- (3-aminopropyl) thiosulfate. 52 g of sodium S- (3-aminopropyl) thiosulfate, 90 ml of water and 5 mol / l hydrochloric acid were added to the reaction vessel substituted with nitrogen gas, and the resulting solution was concentrated under reduced pressure, and the crystals were taken out by filtration. The obtained crystals were vacuum-dried to obtain S- (3-aminopropyl) thiosulfuric acid.

(Production Example 2: S- (6-aminohexyl) thiosulfuric acid (amphoteric compound B))
To the reaction vessel, 99.2 g of potassium phthalimide and 480 ml of dimethylformamide were added. To this mixture, a mixture of 200 g of 1,6-dibromohexane and 200 ml of dimethylformamide was added dropwise at room temperature. After completion of the dropwise addition, the resulting mixture was heated to 120 ° C. and refluxed for 5 hours. After standing to cool, the solvent was distilled off from the reaction mixture. Ethyl acetate and water were added for liquid separation, and then the organic layer was concentrated. Hexane and ethyl acetate were added to the resulting residue to precipitate crystals. The crystals were taken out and dried under vacuum to obtain N- (6-bromohexyl) phthalimide. To the reaction vessel, 40 g of N- (6-bromohexyl) phthalimide, 32.0 g of sodium thiosulfate pentahydrate, 200 ml of methanol and 200 ml of water were added, and the mixture was refluxed for 5 hours, allowed to cool and then the reaction mixture. The solvent was distilled off. To the obtained residue, 200 ml of ethanol was added and refluxed for 1.5 hours. Hot filtration was performed, and the filtrate was concentrated under reduced pressure to obtain crystals, and then allowed to stand. The crystals were taken out by filtration, washed with ethanol, and further washed with hexane. The obtained crystals were vacuum-dried to obtain 6-phthalimidohexyl thiosulfate sodium salt. A reaction vessel purged with nitrogen was charged with 20.0 g (54.7 mmol) of sodium salt of 6-phthalimidohexylthiosulfate and 200 ml of ethanol, and 4.25 g (84.8 mmol) of hydrazine monohydrate was added to the resulting mixture. It was dripped. After completion of the dropwise addition, the resulting mixture was stirred at 70 ° C. for 5 hours, and then ethanol was distilled off under reduced pressure. 100 ml of methanol was added to the residue and refluxed for 1 hour. Crystals were obtained by hot filtration, washed with methanol, and vacuum-dried to obtain S- (6-aminohexyl) thiosulfate sodium salt. 26 g of sodium S- (6-aminohexyl) thiosulfate, 45 ml of water and 5 mol / l hydrochloric acid were added to the reaction vessel substituted with nitrogen gas, the resulting solution was concentrated under reduced pressure, and the crystals were taken out by filtration. The obtained crystals were vacuum-dried to obtain S- (6-aminohexyl) thiosulfuric acid.

The median diameter (50% D) of the amphoteric compounds A and B obtained in the above Production Examples 1 and 2 was measured by a laser diffraction method (measurement procedure is as follows) using SALD-2000J type manufactured by Shimadzu Corporation. When measured, the median diameter (50% D) was 66.7 μm. The obtained amphoteric compounds A and B were pulverized, their median diameter (50% D) was adjusted to 14.6 μm, and used in the following examples.
<Measurement operation>
Amphoteric compounds A and B are dispersed at room temperature in a mixed solution of a dispersion solvent (toluene) and a dispersant (10% by mass sodium di-2-ethylhexyl sulfosuccinate / toluene solution), and ultrasonic waves are applied to the resulting dispersion. While irradiating, the dispersion was stirred for 5 minutes to obtain a test solution. The test solution was transferred to a batch cell and measured after 1 minute. (Refractive index: 1.70-0.20i)

Below, various chemical | medical agents used by the Example and the comparative example are demonstrated.
NR: TSR20
BR: Ubepol BR150B manufactured by Ube Industries, Ltd. (cis content: 97% by mass)
Amphoteric Compound A: S- (3-Aminopropyl) thiosulfate Amphoteric Compound B Prepared in Production Example 1 S- (6-Aminohexyl) thiosulfate Inorganic Compound A Prepared in Production Example 2 Nippon Mistron Mistrone Vapor (Talc, average particle size: 5.7 to 7.0 μm, crystal system: monoclinic crystal)
Inorganic compound B: calcium sulfate dihydrate produced by Yoshino Gypsum Co., Ltd. (average particle size: 17 μm, crystal system: monoclinic)
Inorganic compound C: Whiten SB (calcium carbonate, average particle size: 2.2 μm, crystal system: trigonal or orthorhombic) manufactured by Shiroishi Calcium Co., Ltd.
Carbon black: Diamond Black I manufactured by Mitsubishi Chemical Corporation (N ₂ SA: 98 m ² / g, DBP: 124 ml / 100 g)
Oil: Process X-140 manufactured by Japan Energy Co., Ltd.
Zinc oxide: Zinc Hua No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Anti-aging agent manufactured by NOF Corporation: NOCRACK 6C (N- (1, 3- Dimethylbutyl) -N′-phenyl-p-phenylenediamine)
Sulfur: Powder sulfur vulcanization accelerator manufactured by Tsurumi Chemical Industry Co., Ltd .: Noxera-NS (N-tert-butyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

<Examples and Comparative Examples>
In accordance with the formulation shown in Table 1, materials other than sulfur and a vulcanization accelerator were kneaded for 3 minutes at 160 ° C. using a Banbury mixer to obtain a kneaded product. Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded for 5 minutes at 80 ° C. using a biaxial open roll to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press vulcanized at 170 ° C. for 15 minutes to obtain a vulcanized rubber composition.
Further, the obtained unvulcanized rubber composition was molded into a tread shape and bonded together with other tire members on a tire molding machine to form an unvulcanized tire, and then vulcanized at 170 ° C. for 12 minutes, Test tires were manufactured.

<Evaluation items and test methods>
(Wet grip)
Test tires were mounted on all wheels of the vehicle, and braking distances from initial speeds of 40, 60, and 80 km / h were measured on wet asphalt road surfaces. The braking distance of Comparative Example 1 was set to 100, and indexed by the following calculation formula. Table 1 shows the average value of the three indices. It shows that wet grip property is excellent, so that a numerical value is large.
(Wet grip property index) = (Brake distance of Comparative Example 1) / (Brake distance of each formulation) × 100

(Abrasion resistance)
The test tires were mounted on all the wheels of the vehicle, the remaining grooves after traveling 10,000 km on the paved road surface were measured, and the travel distance required for the tread to wear 1 mm was calculated. The traveling distance of Comparative Example 1 was set to 100, and the index was expressed by the following calculation formula. It shows that it is excellent in abrasion resistance, so that an index | exponent is large. When the index was 95 or more, it was judged to be good.
(Abrasion resistance index) = (travel distance of each formulation) / (travel distance of Comparative Example 1) × 100

(Low fuel consumption)
Using a viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho Co., Ltd.), the loss tangent (tan δ) of the vulcanized rubber composition was measured at a temperature of 50 ° C., an initial strain of 10%, and a dynamic strain of 2%. With the tan δ of Example 1 being 100, other blends were indicated by an index using the following formula. The larger the index, the better the rolling resistance characteristics (low fuel consumption).
(Low fuel consumption index) = (tan δ of Comparative Example 1) / (tan δ of each formulation) × 100

As shown in Table 1, examples containing amphoteric compounds A or B which are amphoteric compounds having acidic and basic functional groups and inorganic compounds A or B which are monoclinic inorganic compounds are comparative examples. In comparison, the dispersibility of carbon black was improved, wet grip properties were improved while maintaining good wear resistance and low fuel consumption, and these performances were well-balanced.

Claims (7)

A tire rubber composition comprising a rubber component, carbon black, an amphoteric compound having acidic and basic functional groups, and an inorganic compound having a monoclinic crystal system. The tire rubber composition according to claim 1, wherein the amphoteric compound is a compound represented by the following formula (I).

(In the formula (I), R ¹ represents an alkylene group having 2 to 30 carbon atoms, an alkenylene group or an alkynylene group. A represents an acidic functional group. R ² and R ³ are the same or different and each represents a hydrogen atom, Represents an alkyl group having 1 to 20 carbon atoms, an alkenyl group or an alkynyl group, or an alkoxysilyl group having 1 to 20 carbon atoms, and the compound represented by the formula (I) may be a metal salt of the compound. The tire rubber composition according to claim 1, wherein the amphoteric compound is a compound represented by the following formula (I-1) and / or a compound represented by the following formula (I-2).

(In formula (I-1), p represents an integer of 2 to 8. In formula (I-2), q represents an integer of 2 to 8. Mr ⁺ represents a metal ion, and r represents a valence thereof. Represents.) The rubber composition for a tire according to claim 3, wherein the metal ion represented by ^{Mr +} in the formula (I-2) is a lithium ion, a sodium ion, a potassium ion, a cesium ion, a cobalt ion, a copper ion, or a zinc ion. object. The tire rubber composition according to any one of claims 1 to 4, wherein a content of the amphoteric compound is 0.01 to 30 parts by mass with respect to 100 parts by mass of the carbon black. The tire rubber composition according to claim 1, wherein the inorganic compound is a compound represented by a composition formula of the following formula (II).

(In the formula (II), M is at least one metal selected from the group consisting of aluminum, magnesium, titanium, calcium, iron and zirconium, an oxide or hydroxide of the metal, the oxide or water. Represents an oxide hydrate, a carbonate of the metal, or a mixture thereof, n is an integer of 1 to 5, x is an integer of 0 to 10, y is an integer of 2 to 5, and z is 0 to 10. Represents an integer.) The pneumatic tire produced using the rubber composition in any one of Claims 1-6.