JP2013241482A - Rubber composition for tire and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for a tire, which can have improved low-fuel consumption performance and wear resistance while achieving excellent processability; and to provide a pneumatic tire produced using the rubber composition.SOLUTION: A rubber composition for a tire comprises: at least one selected from a group composed of natural rubbers and diene-based synthetic rubbers; an amphoteric compound having acidic and basic functional groups; and a self-dispersible carbon black.

Description

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

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 the performance thereof. Therefore, it is hoped to provide a rubber composition for tires with excellent fuel efficiency. It is rare. Carbon black has been widely used as a filler for rubber compositions for tires in terms of reinforcement and wear resistance. Generally, in order to make a fuel-efficient tire, the hysteresis loss of the rubber composition is reduced. It is effective.

For this reason, in order to reduce fuel consumption with carbon black, methods such as increasing the carbon black particle size and reducing the amount of carbon black are conceivable, but a decrease in performance such as reinforcement and wear resistance is inevitable. . On the other hand, it is also known to reduce fuel consumption by using silica as a filler, but wear resistance is inferior to carbon black and it is difficult to obtain sufficient performance.

Patent Document 1 proposes a technique for improving the dispersibility of carbon black by adding a diamine compound to improve low heat buildup. However, there is still room for improvement in terms of improving fuel efficiency while maintaining good wear resistance. Furthermore, there is a problem that the scorch time is short and the processability is poor.

Japanese Patent No. 2912845

The present invention provides a rubber composition for a tire that can solve the above-mentioned problems and improve fuel economy and wear resistance while obtaining good processability, and a pneumatic tire using the rubber composition. Objective.

The present invention relates to a tire rubber composition containing at least one selected from the group consisting of natural rubber and diene-based synthetic rubber, an amphoteric compound having acidic and basic functional groups, and self-dispersing carbon black. .

（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 represent hydrogen. An atom, 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.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 (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 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.

The self-dispersing carbon black is preferably obtained by oxidizing carbon black having a nitrogen adsorption specific surface area of 80 to 280 m ² / g.
The self-dispersing carbon black preferably has an oxygen-containing hydrophilic functional group. Here, the oxygen-containing hydrophilic functional group is preferably a carboxyl group and / or an alkali metal salt thereof.

The content of the self-dispersing carbon black is preferably 10 to 100 parts by mass with respect to 100 parts by mass of the rubber component, and the content of the amphoteric compound is based on 100 parts by mass of the self-dispersing carbon black. It is preferable that it is 0.01-30 mass parts.
The present invention also relates to a pneumatic tire produced using the rubber composition.

According to the present invention, a tire rubber composition containing at least one selected from the group consisting of natural rubber and diene-based synthetic rubber, an amphoteric compound having acidic and basic functional groups, and self-dispersing carbon black. Since it is a thing, low fuel consumption and abrasion resistance can be improved, obtaining favorable workability.

The tire rubber composition of the present invention contains at least one selected from the group consisting of natural rubber and diene-based synthetic rubber, an amphoteric compound having acidic and basic functional groups, and self-dispersing carbon black. .

By blending natural rubber or diene-based synthetic rubber with amphoteric compounds having acidic functional groups and basic functional groups and self-dispersing carbon black, the acidic functional groups of the amphoteric compounds are converted into rubber components and basic functional groups. Since it reacts with an oxygen-containing hydrophilic functional group such as a carboxyl group formed on the surface of the self-dispersing carbon black, the dispersibility of the carbon black is improved, and excessive heat generation can be suppressed by restraining the carbon black. Therefore, while obtaining good processability, the fuel economy and wear resistance can be improved in a well-balanced manner, and these performance balances can be synergistically improved.

In the present invention, natural rubber (NR), diene synthetic rubber (isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), chloroprene rubber (CR) are used as rubber components. ), Acrylonitrile butadiene rubber (NBR), ethylene propylene diene rubber (EPDM), butyl rubber (IIR), halogenated butyl rubber (X-IIR), etc.). Among these, NR is preferable from the viewpoint of low fuel consumption, and BR is preferable from the viewpoint of wear resistance. In addition, the combined use of NR and BR is preferable from the viewpoint of efficiently improving the balance between fuel efficiency and wear resistance. 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.

The BR is not particularly limited. For example, BR1220 manufactured by Nippon Zeon Co., Ltd., BR150B manufactured by Ube Industries, Ltd., high cis content BR, 1, VCR412, VCR617 manufactured by Ube Industries, etc. Commonly used in the tire industry such as BR containing 2-syndiotactic polybutadiene crystals (SPB) can be used. Among these, BR having a cis content of 95% or more is preferable because good wear resistance can be obtained. 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. If it is less than 5% by mass, sufficient wear resistance may not be obtained. Moreover, this content becomes like this. Preferably it is 70 mass% or less, More preferably, it is 60 mass% or less. When it exceeds 70% by mass, there is a tendency that sufficient processability cannot be obtained.

The total content of NR and BR in 100% by mass of the rubber component is preferably 80% by mass or more, more preferably 90% by mass or more, and may be 100% by mass. By blending a self-dispersing carbon black and an amphoteric compound with a rubber component containing a large amount of NR and BR, processability, fuel efficiency and wear resistance can be improved in a balanced manner.

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, secondary, and tertiary amino groups. The amphoteric compound may be a metal salt of the compound. In addition, an amphoteric compound may be used independently or may use 2 or more types together.

（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。） As the amphoteric compound, a compound represented by the following formula (I) can be preferably used.

(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 represent hydrogen. An atom, 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.The compound represented by the formula (I) may be a metal salt of the compound.)

The nitrogen-containing basic functional group moiety of formula (I) reacts with the oxygen-containing hydrophilic functional group such as a carboxyl group present on the surface to bind to the self-dispersing carbon black, and the acidic functional group moiety is a polymer. Reacts with the double bond. Therefore, the dispersibility of carbon black is improved and the dispersion state can be maintained. Moreover, since carbon black is restrained by reaction, it becomes possible to suppress exothermic property. Therefore, the above-described performance can be improved with a good balance.

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。） In the present invention, as the amphoteric compound, it is preferable to use 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.

When q is a compound of 3, a method of reacting 3-halopropylamine and sodium thiosulfate, a compound obtained by reacting 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 formula (I-1) and / or (I-2) can also be used. The mixture is obtained by mixing a compound represented by the formula (I-1) and a compound represented by the formula (I-2), a metal-containing hydroxide, carbonate, and carbonic acid represented by the above M. A method of metallizing a part of the compound represented by the formula (I-1) using a hydrogen salt or the like, a method of neutralizing a part of the compound represented by the formula (I-2) using a proton acid Can be manufactured. The compounds represented by the formulas (I-1) and (I-2) thus produced can be removed from the reaction mixture by operations such as concentration and crystallization, and the extracted 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 formula (I-1) or only the compound represented by the formula (I-2) can be used. Furthermore, the compound represented by multiple types of compound represented by Formula (I-1) and the compound represented by Formula (I-2) can also be used together.

In formula (I-1), p represents an integer of 2 to 8, preferably 2 to 5. In formula (I-2), q represents an integer of 2 to 8, and preferably 2 to 5.

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 a 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, The range of 10-1000 mass parts is with respect to 100 mass parts of total amounts of the compound represented by the said formula (I-1) and / or (I-2). preferable.

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, further preferably 100 parts by mass of the self-dispersing carbon black. 1 part by mass or more. Moreover, this content becomes like this. Preferably it is 30 mass parts or less, More preferably, it is 20 mass parts or less, More preferably, it is 10 mass parts or less. If the content is out of the range, the wear resistance, fuel efficiency and processability may not be improved in a well-balanced manner.

The self-dispersing carbon black used in the present invention is one that can be easily dispersed in a solvent without using a dispersant. Specific examples include those obtained by adding oxygen-containing hydrophilic functional groups to ordinary carbon black, and generally obtained by subjecting carbon black to oxidation treatment.

Examples of the oxygen-containing hydrophilic functional group include a carboxyl group, an alkali metal salt of a carboxyl group, and a hydroxyl group. Especially, a carboxyl group and / or its alkali metal salt are preferable, and a carboxyl group is more preferable.

As a method for imparting an oxygen-containing hydrophilic functional group to carbon black, a conventionally known method such as gas phase oxidation treatment or wet oxidation treatment can be employed. For example, as a gas phase oxidation treatment, an oxidation method by contact with air, a dry oxidation treatment by reaction with nitrogen oxide or ozone, and carbon black described in JP-A-57-159856 is oxidized by low-temperature oxygen plasma. Treatment method: wet oxidation treatment includes nitric acid, potassium permanganate, potassium dichromate, perchloric acid, hypochlorous acid, hypohalite, hydrogen peroxide, bromine aqueous solution, ozone aqueous solution, etc. And wet oxidation treatment using phosphine, and a method of oxidizing carbon black described in JP-A-48-18186 with an aqueous solution of hypohalite. A liquid phase oxidation method (wet oxidation treatment) using an acid salt is preferred.

Specifically, carbon black is added to an oxidizing agent such as an aqueous solution of hypohalite, and a wet oxidation treatment is performed by stirring. Self-dispersible carbon black can be prepared.

When preparing the self-dispersing carbon black, the nitrogen adsorption specific surface area of the raw material carbon black _(N 2 SA) is preferably more than ^{80 m} 2 / g, more preferably at least 100 m ² / g, more preferably more than 120 m ² / g . If it is less than 80 m < ² > / g, there exists a possibility that reaction with sufficient basic functional group may not be obtained. The N ₂ SA is preferably 280 m ² / g or less, more preferably 220 m ² / g or less, and even more preferably 170 m ² / g or less. When it exceeds 280 m ² / g, the dispersibility of the self-dispersing carbon black tends to be lowered, and the wear resistance tends to be lowered.
In this specification, _N 2 SA of carbon black, JIS K 6217-2: measured according to 2001.

The total concentration of the surface carboxyl group of the self-dispersing carbon black and its alkali metal salt is preferably 70 μmol / g or more, more preferably 200 μmol / g or more, still more preferably 300 μmol / g or more, and particularly preferably 500 μmol / g or more. If it is less than 70 μmol / g, there is a possibility that a reaction with a sufficient basic functional group cannot be obtained. The total concentration is preferably 1400 μmol / g or less, more preferably 1200 μmol / g or less, and still more preferably 1000 μmol / g or less. When it exceeds 1400 μmol / g, the reinforcing property is deteriorated and the wear resistance may be lowered.
Note that the total concentration of the surface carboxyl group of the self-dispersing carbon black and its alkali metal salt can be measured by X-ray photoelectron spectroscopy.

As the self-dispersing carbon black, commercially available products can also be used. For example, Regal 400R and Regal 330R manufactured by Cabot, Raven 7000 and Raven 5750 manufactured by Colombian Carbon, Color Black FW1, Color Black FW2, manufactured by Degussa, Mitsubishi Chemical ( No. manufactured by Co., Ltd. 25, no. 33, Bonjet Black CW-2 manufactured by Orient Chemical Industry Co., Ltd., SMP and the like.

In the rubber composition of the present invention, the content of the self-dispersing carbon black 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. The content is preferably 100 parts by mass or less, more preferably 95 parts by mass or less, and still more preferably 75 parts by mass or less. If it exceeds 100 parts by mass, the workability may be reduced, and the performance balance between low fuel consumption and wear resistance may be reduced.

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

The oil content is preferably 1 part 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 1 part by mass, the processability is inferior, and the fuel efficiency and wear resistance tend to decrease. The oil content is preferably 15 parts by mass or less, more preferably 8 parts by mass or less. If it exceeds 15 parts by mass, the wear resistance and wet grip performance may be deteriorated.

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, and preferably 3 parts by mass or less, more preferably 100 parts by mass of the rubber component. Is 2 parts by mass 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 rubber composition of the present invention can be suitably used for tread, cap tread, base tread, under tread, clinch apex and the like. In particular, it is desirable to apply to treads, cap treads, and clinch apex from the viewpoint of not only low fuel consumption but also excellent wear resistance.

As a method for producing the rubber composition for a tire of the present invention, a known method 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.

Hereinafter, various chemicals used in the production examples will be described together.
3-bromopropylamine hydrobromide: manufactured by Kanto Chemical Co., Ltd. Sodium thiosulfate pentahydrate: manufactured by Kanto Chemical Co., Ltd. phthalimide potassium: manufactured by Kanto Chemical Co., Ltd. dimethylformamide: manufactured by Kanto Chemical Co., Ltd. 1,6-dibromohexane: Kanto Chemical Co., Ltd. hydrazine monohydrate: Kanto Chemical Co., Ltd. carbon black: Cabot Japan manufactured by KK SHOWBLACK ^{_{N110 (N 2 SA: 145m 2}} / g)
Sodium hypochlorite solution: Wako Pure Chemical Industries

(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 to B obtained in the above Production Examples 1 and 2 was measured by a laser diffraction method (measurement operation is as follows) using a SALD-2000J type manufactured by Shimadzu Corporation. When measured, the median diameter (50% D) was 66.7 μm. The obtained amphoteric compounds A to B were pulverized and their median diameter (50% D) was adjusted to 14.6 μm and used in the following examples.
<Measurement operation>
Amphoteric compounds A to B were dispersed in a mixed solution of a dispersion solvent (toluene) and a dispersant (10% by mass sodium di-2-ethylhexyl sulfosuccinate / toluene solution) at room temperature, and ultrasonic waves were 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)

(Production Example 3 Self-Dispersing Carbon Black (Carbon Black B)
Carbon black was suspended in a potassium hypochlorite solution, stirred at 25 ° C. for 24 hours, and subjected to wet oxidation treatment of carbon black to generate carboxyl groups in carbon black. Thereafter, 6N hydrochloric acid was added for neutralization, followed by washing with water and drying to obtain carbon black (B).

Hereinafter, various chemicals used in Examples and Comparative Examples will be described together.
NR: TSR20
BR: Ubepol BR150B manufactured by Ube Industries, Ltd.
Carbon Black (A): Carbon Black: Show Black N110 (N ₂ SA: 145 m ² / g) manufactured by Cabot Japan
Carbon black (B): self-dispersing carbon black prepared in Production Example 3 (total concentration of surface carboxyl groups and alkali metal salts thereof: 630 μmol / g)
Carbon black (C): SMP (total concentration of surface carboxyl groups and alkali metal salts thereof: 900 μmol / g, oxidized carbon surface having a nitrogen adsorption specific surface area of 200 m ² / g, manufactured by Orient Chemical Industry Co., Ltd. Obtained by
Amphoteric compound (A): S- (3-aminopropyl) thiosulfuric acid (prepared in Production Example 1)
Amphoteric compound (B): S- (6-aminohexyl) thiosulfuric acid (prepared in Production Example 2)
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: Powdered sulfur vulcanization accelerator manufactured by Tsurumi Chemical Industry Co., Ltd .: Noxeller NS (N-tert-butyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

(Examples and Comparative Examples)
According to the formulation shown in Table 1, materials other than sulfur and a vulcanization accelerator were kneaded for 3 minutes at 160 ° C. using a 1.7 L 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.
The following evaluation was performed about the obtained unvulcanized rubber composition and vulcanized rubber composition. The results are shown in Table 1.

(1) Measurement of Mooney Viscosity The unvulcanized rubber composition was measured at 130 ° C. according to the Mooney viscosity measurement method based on JIS K 6300. The Mooney viscosity (ML _{1 + 4} ) of Comparative Example 1 was set to 100, and each formulation was displayed as an index (Mooney viscosity index). The larger the index, the lower the Mooney viscosity and the better the processability.

(2) Viscoelasticity test Viscoelasticity spectrometer VES (manufactured by Iwamoto Seisakusho Co., Ltd.) was used for each compounding (vulcanized rubber composition) under the conditions of a temperature of 50 ° C, an initial strain of 10%, and a dynamic strain of 2%. Loss tangent (tan δ) was measured. The tan δ of Comparative Example 1 was set to 100, and the index was expressed by the following formula (rolling resistance index). The larger the index, the better the rolling resistance characteristics (low fuel consumption).
(Rolling resistance index) = (tan δ of Comparative Example 1) / (tan δ of each formulation) × 100

(3) Abrasion resistance test The vulcanized rubber composition was measured for the amount of Lambourn wear under the conditions of a temperature of 20 ° C, a slip rate of 20% and a test time of 2 minutes using a Lambourn abrasion tester. Further, the volume loss amount was calculated from the measured Lambourne wear amount, the volume loss amount of Comparative Example 1 was set to 100, and the volume loss amount of each formulation was displayed as an index by the following formula (Lambourn wear index). It shows that it is excellent in abrasion resistance, so that a Lambourn abrasion index is large.
(Lambourn wear index) = (volume loss amount of Comparative Example 1) / (volume loss amount of each formulation) × 100

In the example in which both components of self-dispersing carbon black and amphoteric compound were blended with NR and BR, processability, fuel efficiency and wear resistance were improved in a well-balanced manner. Further, compared to Comparative Example 6 in which neither component is blended, Comparative Example 3 in which untreated carbon black is replaced with self-dispersing carbon black and Comparative Example 1 in which amphoteric compound is blended show no improvement in performance. Nevertheless, in Example 1 in which both components were blended, it became clear that the fuel economy and wear resistance were improved while maintaining good processability, and that these performance balances could be improved synergistically. .

Claims (9)

A rubber composition for tires comprising at least one selected from the group consisting of natural rubber and diene-based synthetic rubber, an amphoteric compound having acidic and basic functional groups, and self-dispersing carbon black. 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 represent hydrogen. An atom, 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.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 (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 tire rubber 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. Composition. The tire rubber composition according to any one of claims 1 to 4, wherein the self-dispersing carbon black is obtained by oxidizing carbon black having a nitrogen adsorption specific surface area of 80 to 280 m ² / g. object. The tire rubber composition according to any one of claims 1 to 5, wherein the self-dispersing carbon black has an oxygen-containing hydrophilic functional group. The tire rubber composition according to claim 6, wherein the oxygen-containing hydrophilic functional group is a carboxyl group and / or an alkali metal salt thereof. The content of the self-dispersing carbon black is 10 to 100 parts by mass with respect to 100 parts by mass of the rubber component, and the content of the amphoteric compound is 0.01 to 30 with respect to 100 parts by mass of the self-dispersing carbon black. It is a mass part, The rubber composition for tires in any one of Claims 1-7. The pneumatic tire produced using the rubber composition in any one of Claims 1-8.