JP5529520B2 - Rubber composition for tread and studless tire - Google Patents

Description

The present invention relates to a rubber composition for a tread and a studless tire using the same.

Conventionally, spike tires have been used for running on snowy and snowy roads, and chains have been attached to tires. However, environmental problems such as dust problems have occurred, and studless tires have been developed as alternatives to snowy and snowy road running tires. . In studless tires, various efforts have been made to improve the coefficient of friction on slippery ice-burn road surfaces.

It is considered that the friction on the ice burn road surface is reduced by the water film on the surface, and a device for gripping the ice below the water film is devised. For example, in a studless tire having a tread rubber containing foamed rubber, the water film is removed by the foamed holes, the sticking friction is increased, and the friction caused by digging into the ice below the water film can be increased by the edge portions of the foamed holes. Similarly, Patent Document 1 discloses that adhesion friction and digging friction can be increased by blending ebonite. Further, Patent Document 2 discloses that adhesion friction and digging friction can be increased by embedding a high-hardness rubber perpendicular to the ground contact surface in the base tread rubber.

However, these technologies have room for improvement in terms of the balance of wear resistance, performance on ice (grip performance on ice), fuel efficiency, and wet grip performance.

JP-A-8-225682 JP-A-7-32817

The present invention solves the above-mentioned problems, and provides a rubber composition for a tread excellent in the balance of wear resistance, on-ice performance (grip performance on ice), low fuel consumption, and wet grip performance, and used for a tire tread. The object is to provide a studless tire.

The present invention relates to a rubber composition for a tread containing 3 to 30 parts by mass of ebonite with respect to 100 parts by mass of the rubber component, and having a sulfur content of 10 to 25 parts by mass with respect to 100 parts by mass of the rubber component in the ebonite. .

The glass transition temperature of the ebonite is preferably 5 ° C. or lower.

The ebonite preferably has a hardness of 30-60.

It is preferable that the average particle diameter of the ebonite is 500 μm or less.

The present invention also relates to a studless tire having a tread produced using the rubber composition.

According to the present invention, since it is a rubber composition for a tread that contains a specific amount of ebonite and the sulfur content in the ebonite is a predetermined amount, wear resistance, performance on ice (grip performance on ice), low Excellent balance between fuel efficiency and wet grip performance.

The rubber composition for a tread of the present invention contains a specific amount of ebonite, and the content of sulfur in the ebonite is a predetermined amount.
Ebonite having a sulfur content greater than a predetermined amount has few double bonds remaining in the ebonite and cannot sufficiently form a chemical bond with the rubber component contained in the rubber composition by vulcanization. Since the adhesiveness of the rubber becomes low and the rubber composition easily falls off, the wear resistance is poor. Moreover, since the glass transition temperature is also increased, tan δ in the vicinity of 30 to 70 ° C. is large, leading to deterioration in fuel economy. In the present invention, wear resistance, on-ice performance, low fuel consumption, and wet grip performance can be obtained in a well-balanced manner by using ebonite having a predetermined sulfur content.

In the present invention, a specific ebonite is used. Thereby, wear resistance, performance on ice, fuel efficiency, and wet grip performance can be improved in a well-balanced manner. In the present invention, ebonite is a hard rubber obtained by adding sulfur (a vulcanization accelerator if necessary) to a rubber component and vulcanizing.

In the present specification, the rubber component contained in the rubber composition for a tread of the present invention is described as a rubber component (base rubber) or base rubber, and the rubber component contained in the ebonite is described as a rubber component (ebonite). And Further, when it is described as a rubber component without particular mention, it means the rubber component contained in the rubber composition for a tread of the present invention. The rubber component contained in the tread rubber composition of the present invention does not contain the rubber component contained in ebonite.

(ebonite)
As rubber components (rubber component (ebonite)) used for ebonite, natural rubber (NR), epoxidized natural rubber (ENR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), Examples thereof include diene rubbers such as styrene isoprene butadiene rubber (SIBR), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), and butyl rubber (IIR). Diene rubbers may be used alone or in combination of two or more. Among these, NR, IR, and BR are preferable because of excellent abrasion resistance and a glass transition temperature (Tg) in a suitable range. Moreover, it is preferable that one of the rubber components of the ebonite and one of the rubber components contained in the rubber composition of the present invention are the same because of excellent adhesion between the base rubber and ebonite. Furthermore, it is more preferable that all of the rubber components of ebonite are the same as the rubber components contained in the rubber composition of the present invention.

The NR is not particularly limited, and for example, SIR20, RSS # 3, TSR20, deproteinized natural rubber (DPNR), high-purity natural rubber (HPNR), etc., which are common in the tire industry can be used. IR is not particularly limited, and conventionally known IR can be used. The ENR is not particularly limited, and may be a commercially available epoxidized natural rubber or an epoxidized natural rubber (NR).

The total content of NR and IR in 100% by mass of the rubber component (ebonite) is preferably 10% by mass or more, more preferably 20% by mass or more. If it is less than 10% by mass, sufficient wear resistance may not be obtained. The total content is preferably 90% by mass or less, more preferably 80% by mass or less.

The BR is not particularly limited. For example, BR1220 manufactured by Nippon Zeon Co., Ltd., BR130B manufactured by Ube Industries, Ltd., BR150B and other high cis content BR, BR1250H manufactured by Nippon Zeon Co., Ltd., Asahi Kasei Chemicals ( BR having a low cis content such as diene NF35R manufactured by Co., Ltd., BR containing syndiotactic polybutadiene crystals such as VCR 412 and VCR 617 manufactured by Ube Industries, Ltd. can be used. Among these, BR having a cis content of 90% by mass or more is preferable because of its low glass transition temperature.

The content of BR in 100% by mass of the rubber component (ebonite) is preferably 10% by mass or more, more preferably 20% by mass or more. If it is less than 10% by mass, sufficient wear resistance may not be obtained, and rolling resistance may be deteriorated. The BR content is preferably 90% by mass or less, more preferably 80% by mass or less. If it exceeds 90% by mass, sufficient wear resistance may not be obtained.

As the sulfur, powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur and the like can be used.

The content of sulfur in the ebonite is 10 parts by mass or more, preferably 12 parts by mass or more with respect to 100 parts by mass of the rubber component (ebonite). If it is less than 10 parts by mass, the glass transition temperature (Tg) becomes low, and the wet grip performance tends to be lowered. The sulfur content is 25 parts by mass or less, preferably 20 parts by mass or less. When it exceeds 25 parts by mass, the glass transition temperature (Tg) becomes too high, and the wear resistance tends to be lowered. When the sulfur content is within the above range, the adhesion between ebonite and the base rubber is improved.

You may mix | blend a vulcanization accelerator with sulfur. Examples of the vulcanization accelerator include sulfenamide, thiazole, thiuram, thiourea, guanidine, dithiocarbamic acid, aldehyde-amine or aldehyde-ammonia, imidazoline, or xanthate vulcanization accelerator. It is possible to use an agent or the like.

Examples of the sulfenamide system include CBS (N-cyclohexyl-2-benzothiazolylsulfenamide), TBBS (N-tert-butyl-2-benzothiazolylsulfenamide), N, N-dicyclohexyl-2- Sulfenamide compounds such as benzothiazolylsulfenamide, N-oxydiethylene-2-benzothiazolylsulfenamide, and N, N-diisopropyl-2-benzothiazole sulfenamide can be used. Of these, TBBS and CBS are preferred because of their high vulcanization rate.

The content of the vulcanization accelerator in the ebonite is preferably 0.2 parts by mass or more, more preferably 0.8 parts by mass or more with respect to 100 parts by mass of the rubber component (ebonite). If it is less than 0.2 parts by mass, the vulcanization time may be prolonged. The content of the vulcanization accelerator is preferably 8 parts by mass or less, more preferably 6 parts by mass or less. If the amount exceeds 8 parts by mass, the bloom increases and the effect of shortening the vulcanization time may be reduced.

In addition to the rubber component (ebonite), sulfur, and vulcanization accelerator, other components (for example, carbon black) can be appropriately mixed with ebonite.

Examples of carbon black include GPF, FEF, HAF, ISAF, and SAF, but are not particularly limited. Carbon black may be used alone or in combination of two or more.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 80 m ² / g or more, and more preferably 100 m ² / g or more. If it is less than 80 m < ² > / g, there exists a possibility that sufficient abrasion resistance may not be obtained. Further, the nitrogen adsorption specific surface area of the carbon black is preferably 280 meters ² / g or less, more preferably 250 meters ² / g, more preferably from 200 meters ² / g or less, and particularly preferably 150m ² / g. When it exceeds 280 m ² / g, dispersion becomes difficult, and there is a possibility that sufficient wear resistance may not be obtained.
In addition, the nitrogen adsorption specific surface area of carbon black is calculated | required by A method of JISK6217.

The carbon black content in the ebonite is preferably 10 parts by mass or more, more preferably 20 parts by mass or more with respect to 100 parts by mass of the rubber component (ebonite). If it is less than 10 parts by mass, the effect of improving wear resistance may not be sufficiently obtained. The carbon black content is preferably 80 parts by mass or less, more preferably 60 parts by mass or less. If it exceeds 80 parts by mass, fuel efficiency may be deteriorated.

The ebonite of the present invention is produced by a general method. That is, it can be produced by a method of kneading the above components with a Banbury mixer, a kneader, an open roll or the like and then vulcanizing.

The vulcanization temperature is preferably 140 ° C. or higher, more preferably 150 ° C. or higher.
If it is lower than 140 ° C., the vulcanization time becomes longer and sufficient hardness may not be obtained. The vulcanization temperature is preferably 190 ° C. or lower, more preferably 180 ° C. or lower. If the temperature exceeds 190 ° C., the rubber itself will decompose, and the ebonite may become weak (brittle).

The vulcanization time in the production of ebonite is measured using a vibration type vulcanization tester defined in JIS K 6300. The vulcanization time is preferably T95 (95% vulcanization time) or less, more preferably T40 to T60. By adjusting the vulcanization time within the above range and stopping the vulcanization in the middle, vulcanization proceeds even between the ebonite and the base rubber during the vulcanization of the unvulcanized rubber composition containing ebonite. It can be expected that the adhesion between the rubber and the base rubber will be improved. When T95 is exceeded, the vulcanization of ebonite proceeds too much, and the double bonds remaining in the ebonite are reduced, so that the adhesiveness with the base rubber (tread rubber) is lowered and the wear resistance tends to be lowered. When it is less than T40, the hardness is not sufficient, and pulverization of ebonite tends to be difficult, and it tends to be difficult to reduce the average particle size.

The hardness of ebonite is preferably 30 or more, more preferably 35 or more, and still more preferably 40 or more. If it is less than 30, the performance on ice tends to decrease. The hardness is preferably 60 or less, more preferably 58 or less, and still more preferably 55 or less. When it exceeds 60, adhesiveness with a rubber composition will become low, it will become easy to fall out from a rubber composition, and there exists a tendency for abrasion resistance to fall.
In addition, in this specification, hardness is a value obtained by the measuring method as described in the Example mentioned later.

The glass transition temperature (Tg) of ebonite is preferably 5 ° C. or lower, more preferably 0 ° C. or lower, and still more preferably −5 ° C. or lower. When it exceeds 5 ° C., fuel economy, wear resistance, and wet grip performance tend to decrease. The Tg is preferably −30 ° C. or higher, more preferably −25 ° C. or higher, and still more preferably −20 ° C. or higher. If it is less than -30 ° C, the wet grip performance tends to decrease.
In addition, in this specification, a glass transition temperature is a value obtained by the measuring method as described in the Example mentioned later.

Ebonite is preferably pulverized as necessary. The method for crushing ebonite is not particularly limited, and examples thereof include roll crushing, low-temperature crushing, and screen type fine crushing.

The average particle diameter of ebonite is preferably 500 μm or less, more preferably 300 μm or less, still more preferably 250 μm or less, and particularly preferably 100 μm or less. When it exceeds 500 μm, the fracture characteristics are lowered and the wear resistance tends to be lowered. The lower limit of the average particle size is not particularly limited.
In addition, in this specification, an average particle diameter is a value obtained by the measuring method as described in the Example mentioned later.

(Rubber composition for tread)
Examples of the rubber component used in the tread rubber composition of the present invention include the diene rubbers and ethylene propylene diene rubber (EPDM). A rubber component may be used independently and may use 2 or more types together. Of these, diene rubbers are preferred because of their excellent low-temperature characteristics, and NR, IR, and BR are more preferred.

As NR and IR, the above NR and IR can be preferably used.

The total content of NR and IR in 100% by mass of the rubber component is preferably 30% by mass or more, more preferably 40% by mass or more. If it is less than 30% by mass, the wear resistance tends to decrease. The total content is preferably 80% by mass or less, more preferably 70% by mass or less. If it exceeds 80% by mass, the on-ice performance tends to decrease.

The BR is not particularly limited, and BR similar to ebonite can be used. Among these, BR having a cis content of 90% by mass or more is preferable because of excellent wear resistance and low temperature characteristics.

The content of BR in 100% by mass of the rubber component is preferably 20% by mass or more, more preferably 30% by mass or more. If it is less than 20% by mass, the wear resistance and the performance on ice tend to decrease. The BR content is preferably 70% by mass or less, more preferably 60% by mass or less. If it exceeds 70% by mass, rubber chipping tends to occur, and the wear resistance tends to decrease.

The content of the ebonite is 3 parts by mass or more, preferably 5 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 3 parts by mass, there is a tendency that the effect of improving fuel economy, performance on ice, and wet grip performance cannot be obtained sufficiently. The ebonite content is 30 parts by mass or less, preferably 25 parts by mass or less, more preferably 20 parts by mass or less. When it exceeds 30 parts by mass, the wear resistance tends to decrease.

In addition to the components described above, the rubber composition of the present invention includes compounding agents conventionally used in the rubber industry, such as inorganic and organic fillers such as silica and carbon black, silane coupling agents, anti-aging agents, oils, etc. Softeners, vulcanizing agents such as zinc oxide, stearic acid, wax, sulfur, vulcanization accelerators, processing aids and the like can be appropriately blended.

The rubber composition of the present invention preferably contains silica. Thereby, wet performance and on-ice performance are improved.

The silica is not particularly limited, and examples thereof include dry process silica (anhydrous silicic acid), wet process silica (hydrous silicic acid), and the like, but wet process silica is preferable because of its large number of silanol groups. Silica may be used alone or in combination of two or more.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 30 m ² / g or more, more preferably 50 m ² / g or more, still more preferably 80 m ² / g or more, and particularly preferably 120 m ² / g or more. If it is less than 30 m ² / g, wear resistance and grip performance (wet grip performance) tend to decrease. The N ₂ SA of silica is preferably 250 m ² / g or less, more preferably 220 m ² / g or less. If it exceeds 250 m ² / g, the workability deteriorates and the dispersibility of silica decreases, and there is a tendency that the wear resistance, performance on ice, fuel efficiency, and wet grip performance cannot be improved in a well-balanced manner.
The nitrogen adsorption specific surface area of silica is a value measured by the BET method according to ASTM D3037-81.

The content of silica is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, and still more preferably 20 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 10 parts by mass, the effects of improving wet performance and on-ice performance may not be sufficiently obtained. Content of this silica becomes like this. Preferably it is 120 mass parts or less, More preferably, it is 100 mass parts or less, More preferably, it is 80 mass parts or less. When the amount exceeds 120 parts by mass, kneading becomes difficult, productivity may be lowered, and fuel efficiency may be deteriorated.

In the present invention, it is preferable to use a silane coupling agent in combination with silica.
Examples of the silane coupling agent include bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, and bis (2-triethoxy). Silylethyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyl Trimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N, N-dimethylthiocarb Moyl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilyl Propyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis (3-diethoxymethylsilylpropyl) tetrasulfide, 3-mercaptopropyl dimethoxymethylsilane, dimethoxymethylsilylpropyl-N, N-dimethylthiocarbamoyltetra Examples thereof include sulfide and dimethoxymethylsilylpropylbenzothiazole tetrasulfide. Of these, bis (3-triethoxysilylpropyl) disulfide, bis (3-triethoxysilylpropyl) tetrasulfide, and 3-trimethoxysilylbromylbenzothiazolyl tetrasulfide are preferable from the viewpoint of reinforcing effect. . These silane coupling agents may be used alone or in combination of two or more. Moreover, you may use as an oligomer which condensed these beforehand.

1 mass part or more is preferable with respect to 100 mass parts of silica, as for content of a silane coupling agent, 2 mass parts or more are more preferable, and 4 mass parts or more are still more preferable. If it is less than 1 part by mass, the viscosity of the unvulcanized rubber composition tends to be high and the processability tends to deteriorate. Moreover, 20 mass parts or less are preferable with respect to 100 mass parts of silica, and, as for content of this silane coupling agent, 15 mass parts or less are more preferable. If it exceeds 20 parts by mass, effects such as improvement in fracture strength and reduction in rolling resistance corresponding to the amount of silane coupling agent added cannot be obtained, and the cost tends to increase unnecessarily.

The carbon black is not particularly limited, and the same carbon black as ebonite can be used. Carbon black may be used alone or in combination of two or more.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 80 m ² / g or more, and more preferably 100 m ² / g or more. If it is less than 80 m < ² > / g, sufficient wet grip performance will not be acquired and there exists a tendency for abrasion resistance to fall. Further, the nitrogen adsorption specific surface area of the carbon black is preferably at most 280 meters ² / g, more preferably not more than ^{250m 2 / g, 200m 2 /} g or less is more preferable. When it exceeds 280 m ² / g, the dispersibility is inferior and the wear resistance tends to be lowered.
In addition, the nitrogen adsorption specific surface area of carbon black is calculated | required by A method of JISK6217.

When the rubber composition of the present invention contains carbon black, the content of carbon black is preferably 5 parts by mass or more, more preferably 10 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 5 parts by mass, the wear resistance tends to decrease. The carbon black content is preferably 150 parts by mass or less, more preferably 100 parts by mass or less, and still more preferably 50 parts by mass or less. If it exceeds 150 parts by mass, the workability tends to deteriorate.

When the rubber composition of the present invention contains carbon black and silica, the total content of carbon black and silica is preferably 40 parts by mass or more, more preferably 50 parts by mass or more with respect to 100 parts by mass of the rubber component. is there. If it is less than 40 parts by mass, sufficient reinforcing properties cannot be obtained and the wear resistance may be inferior. The total content is preferably 180 parts by mass or less, more preferably 150 parts by mass or less, and still more preferably 100 parts by mass or less. If it exceeds 180 parts by mass, the workability may be deteriorated and it may be difficult to disperse the filler.

Examples of the vulcanizing agent include organic peroxides or sulfur-based vulcanizing agents. Examples of the organic peroxide include benzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, and t-butyl cumyl peroxide. Examples of the sulfur vulcanizing agent include sulfur and morpholine disulfide. Of these, sulfur-based vulcanizing agents such as sulfur are preferable from the viewpoints of blending effects and strength characteristics.

The content of the vulcanizing agent is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 0.5 part by mass, the strength is not sufficient and the wear resistance may be lowered. Further, the content of the vulcanizing agent is preferably 5 parts by mass or less, more preferably 3 parts by mass or less. If it exceeds 5 parts by mass, the elongation of the rubber becomes small and the wear resistance may be reduced.

As a vulcanization accelerator, the same vulcanization accelerator as the above ebonite can be used. Of these, sulfenamide-based and guanidine-based vulcanization accelerators are preferable from the viewpoint of excellent vulcanization characteristics. Among the sulfenamide vulcanization accelerators, the above CBS is preferable, and among the guanidine vulcanization accelerators, N, N′-diphenylguanidine (DPG) is preferable. More preferably, CBS and DPG are used in combination.

The rubber composition of the present invention is produced by a general method. That is, it can be produced by a method of kneading the above components with a Banbury mixer, a kneader, an open roll or the like and then vulcanizing.

(studless tire)
The rubber composition of the present invention is used as a tread for a studless tire.

The studless tire of the present invention can be produced by a normal method using the rubber composition. That is, the rubber composition is extruded to match the shape of the tread at the unvulcanized stage, molded by a normal method on a tire molding machine, and bonded together with other tire members to form an unvulcanized tire To do. This unvulcanized tire can be heated and pressed in a vulcanizer to produce a studless tire.

The studless tire of the present invention is suitably used as a studless tire for passenger cars and trucks / buses.

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.
NR: Natural rubber (TSR20)
BR: BR150B manufactured by Ube Industries, Ltd. (cis content 97% by mass)
Carbon black: N220 (N ₂ SA: 125 m ² / g) manufactured by Cabot Japan
Sulfur: powder sulfur vulcanization accelerator NS manufactured by Tsurumi Chemical Co., Ltd. NS: Noxeller NS (N-tert-butyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Co., Ltd.

Production Examples 1-5
(Preparation of ebonite)
According to the composition shown in Table 1, using an open roll, the mixture was kneaded for 3 minutes at 80 ° C. to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press vulcanized at 160 ° C. for a predetermined time to produce a 2 mm slab. The obtained slab was pulverized with a roll, and particles of 100 μm or more were removed with a sieve having an opening of 100 μm to prepare an ebonite powder.

The following evaluation was performed about the obtained ebonite powder. The results are shown in Table 1. The hardness and glass transition temperature were measured using ebonite before pulverization.

(hardness)
The hardness (Shore A) at 23 ° C. was measured with a type A durometer in accordance with JIS K6253 “vulcanized rubber and thermoplastic rubber—how to obtain hardness”.

(Glass transition temperature (Tg))
When the temperature is raised to a dynamic strain amplitude of 0.5%, a frequency of 10 Hz, and a temperature of -40 to 70 ° C. at a rate of temperature rise of 2 ° C./min using a spectrometer (VR-7110) manufactured by Ueshima Seisakusho Co., Ltd. Tan δ was measured, and the peak temperature of tan δ was defined as Tg.

(Average particle size)
The average particle size was measured using a particle size distribution measuring apparatus LA-910 manufactured by Horiba, Ltd.

Hereinafter, various chemicals used in Examples and Comparative Examples will be described together.
NR: Natural rubber (TSR20)
BR: BR150B manufactured by Ube Industries, Ltd. (cis content 97% by mass)
Ebonite powder (1): Ebonite powder prepared in Preparation Example 1 Ebonite powder (2): Ebonite powder prepared in Preparation Example 2 Ebonite powder (3): Ebonite powder prepared in Preparation Example 3 Ebonite powder (4): Ebonite powder prepared in Production Example 4 Ebonite powder (5): Ebonite powder carbon black prepared in Production Example 5: N220 (N ₂ SA manufactured by Cabot Japan Co., Ltd.) : 125m ² / g)
Silica: Ultrazil VN3 manufactured by Degussa (N ₂ SA: 175 m ² / g)
Silane coupling agent: Si75 (bis (3-triethoxysilylpropyl) disulfide) manufactured by Degussa
Oil: Mineral oil PW-380 manufactured by Idemitsu Kosan Co., Ltd.
Stearic acid: Zinc stearate manufactured by NOF Corporation: Zinc Hua 1 anti-aging agent manufactured by Mitsui Mining & Smelting Co., Ltd .: NOCRACK 6C (N- (1, 3) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd. -Dimethylbutyl) -N'-phenyl-p-phenylenediamine)
Wax: Sunnock wax manufactured by Ouchi Shinsei Chemical Co., Ltd. Sulfur: Sulfur powder vulcanization accelerator CZ manufactured by Tsurumi Chemical Co., Ltd. CZ: Noxeller CZ (N-cyclohexyl- manufactured by Ouchi New Chemical Co., Ltd.) 2-benzothiazolylsulfenamide)
Vulcanization accelerator D: Noxeller D (N, N′-diphenylguanidine) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

Examples 1-4 and Comparative Examples 1-4
According to the contents shown in Table 2, materials other than sulfur and a vulcanization accelerator were kneaded for 4 minutes at 150 ° 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 3 minutes at 80 ° C. using an open roll to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press vulcanized with a 0.5 mm thick mold at 170 ° C. for 15 minutes to obtain a vulcanized rubber composition.

The following evaluation was performed using the obtained vulcanized rubber composition. Each test result is shown in Table 2.

(hardness)
The hardness of the vulcanized rubber composition was measured. In addition, the measurement of hardness was performed similarly to the case of the above ebonite.

(Abrasion resistance)
Using a LAT tester (Laboratory Abbreviation and Skid Tester), the volume loss amount of each vulcanized rubber composition was measured under the conditions of a load of 50 N, a speed of 20 km / h, and a slip angle of 5 °. The volume loss of Comparative Example 1 is shown as an index with the amount being 100. The higher the index, the better the wear resistance.

(Performance on ice (μ on ice))
The grip performance was evaluated using an inside drum type friction tester (FR6010 type) manufactured by Ueshima Seisakusho. Using a cylindrical rubber test piece having a width of 20 mm and a diameter of 100 mm, changing the slip ratio of the sample to the road surface from 0 to 30% under the conditions of speed 10 km / h, load 4 kg, road surface temperature -5 ° C, The maximum value of the detected coefficient of friction was read. The value of Comparative Example 1 was taken as 100 and displayed as an index. A large index indicates that the grip performance (ice performance) on ice is high.

(Low fuel consumption, wet grip performance)
Using a viscoelasticity measuring tester manufactured by TS Instruments Co., Ltd., tan δ at a temperature of 50 ° C., a frequency of 10 Hz, and an amplitude of 1% was shown as an index with Comparative Example 1 as 100. The larger the index, the lower the tan δ and the lower the cost.
Similarly, the elastic modulus (G *) at a temperature of 0 ° C., a frequency of 1 Hz, and an amplitude of 0.1% is shown as an index with Comparative Example 1 as 100. The larger the index, the lower the G * and the better the wet grip performance.

According to Table 2, in an example including a specific amount of ebonite and the content of sulfur in the ebonite is a predetermined amount, wear resistance, performance on ice (grip performance on ice), low fuel consumption, wet grip performance Excellent balance. Comparative Example 1 containing no ebonite was inferior to Examples in terms of performance on ice, fuel efficiency, and wet grip performance. The comparative example 2 which mix | blended more than 40 mass parts and specific amounts of ebonite was inferior to the Example in abrasion resistance. In Comparative Examples 3 and 4 in which ebonite having a sulfur content in ebonite of 30 parts by mass and more than a predetermined amount was blended, the wear resistance and fuel efficiency were inferior to those of the examples.

Claims (9)

Per 100 parts by mass of the rubber component includes 3 to 30 parts by weight of ebonite produced between T40~ T9 5 of vulcanization,
The rubber composition for treads whose sulfur content is 10 to 25 parts by mass with respect to 100 parts by mass of the rubber component in the ebonite. The rubber composition for treads according to claim 1 whose glass transition temperature of said ebonite is 5 ° C or less. The rubber composition for a tread according to claim 1 or 2, wherein the ebonite has a hardness of 30 to 60. The rubber composition for a tread according to any one of claims 1 to 3, wherein the ebonite has an average particle size of 500 µm or less. The rubber composition for a tread according to any one of claims 1 to 4, wherein the ebonite contains a vulcanization accelerator and / or carbon black. The rubber composition for a tread according to any one of claims 1 to 5, wherein the rubber composition for a tread contains silica and / or carbon black and a vulcanizing agent. The rubber composition for tread according to any one of claims 1 to 6, wherein the base rubber in the rubber composition for tread and the rubber component in the ebonite both contain natural rubber and / or isoprene rubber and butadiene rubber. object. The manufacturing method of the rubber composition for treads in any one of Claims 1-7 including the process of knead | mixing the said ebonite, base rubber | gum, and carbon black and / or a silica. Studless tire having a tread produced from the rubber composition according to any one of claims 1-7.