JP2008031244A - Tire tread rubber composition and pneumatic tire using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire tread rubber composition which can give a tire with wet performance improved without detriment to rolling resistance and abrasion resistance and to provide a pneumatic tire using the same. <P>SOLUTION: The tire tread rubber composition is a composition consisting of at least either a natural rubber or a synthetic rubber and a filler component consisting entirely of silica or consisting of silica and carbon black, wherein the silica consists of at least amorphous spherical silica microparticles having an average particle diameter in the range of 0.05 to 1.00 μm. It is desirable that the tire tread rubber composition contains 2-40 pts.mass amorphous spherical silica particles per 100 pts.mass rubber component. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rubber composition for a tire tread capable of improving wet performance while maintaining the rolling resistance and wear resistance of a pneumatic tire, and a pneumatic tire using the same.

  In recent years, with the pursuit of automobile safety, it has been demanded to provide a pneumatic tire with improved wet performance while ensuring good fuel efficiency. Conventionally, wet silica, that is, hydrous silicic acid, has been proposed as a tread rubber filler to improve rolling resistance, wear resistance, and wet performance, but this technology provides grip performance on dry road surfaces. There is a problem that it tends to decrease. Further, a technique for improving the wet performance by increasing the glass transition temperature (Tg) of the tread rubber has been proposed, but in this case, there is a problem that the rolling resistance is increased and the wear resistance is easily deteriorated. On the other hand, there has also been proposed a technique that makes it possible to achieve both rolling resistance and wet performance by blending aluminum hydroxide into tread rubber. However, in this case, there is a problem that the wear resistance tends to deteriorate.

Patent Document 1 discloses that 100 parts by weight of a polymer is used for the purpose of obtaining a rubber composition that is excellent in silica dispersibility, can provide a tire tread having a good balance in rolling friction resistance characteristics, wet and dry grip characteristics, and wear resistance. 10 to 200 parts by weight of hydrous silica, and formula (1): Z—R—S _n —R—Z, formula (2): Z—R—SH, formula (3): Z—R—NH ₂ Formula (4): Z—CH═CH ₂ or Formula (5): Z—R—Cl
(In the formula, R is a hydrocarbon group having 1 to 18 carbon atoms, n is an integer of 2 to 8, Z is —Si (R ¹ ) ₂ R ² , —SiR ¹ (R ² ) ₂ , or —Si (R ² ) ₃ (where R ¹ is an alkyl group having 1 to 4 carbon atoms, a cyclohexyl group or a phenyl group, and R ² is an alkoxy group having 1 to 8 carbon atoms or a cycloalkoxy group having 5 to 8 carbon atoms). ), And a weight of the water-containing silica at 400 ° C. with respect to the weight at 100 ° C. when the water-containing silica is heated from 20 ° C. to 500 ° C. at a rate of 5 ° C./min. A rubber composition has been proposed in which the proportion of weight loss is 0.70% by weight or less and the amount of the silane compound is equivalent to 1 to 10% by weight of the amount of hydrous silica. The purpose of this technology is to improve dispersibility and improve the reaction efficiency between the silane coupling agent and the polymer and silica by blending a silane compound with less bound water. There is still room for improvement.

Patent Document 2 provides a rubber composition having improved silica dispersibility and excellent flexibility, that is, a rubber composition having a low elastic modulus, and a tire having excellent wet grip performance. The purpose of the present invention is to provide a rubber composition comprising a mixture obtained by previously blending silica having a bulk specific gravity of 160 g / l or less with an aroma oil in advance, wherein the silica content is 50% by weight or more of the reinforcing agent in the rubber composition. Certain rubber compositions have been proposed. However, the techniques of Patent Documents 1 and 2 have a problem in that sufficient wear resistance may not be obtained.
Japanese Patent Laid-Open No. 11-172050 JP 2005-41926 A

  The present invention solves the above-mentioned problems, and provides a rubber composition for a tire tread capable of improving wet performance without deteriorating rolling resistance and wear resistance, and a pneumatic tire using the same. With the goal.

  The present invention contains at least a rubber component composed of at least one of natural rubber and synthetic rubber and a filler component composed of only silica or silica and carbon black, and the silica has an average particle size of 0.05 to 0.05. The present invention relates to a tire tread rubber composition containing at least amorphous silica spherical fine particles in a range of 1.00 μm.

  The rubber composition for a tire tread of the present invention preferably contains amorphous silica spherical fine particles in a range of 2 to 40 parts by mass with respect to 100 parts by mass of the rubber component.

  In the rubber composition for a tire tread of the present invention, the content of the filler component is preferably in the range of 5 to 200 parts by mass with respect to 100 parts by mass of the rubber component.

  In the tire tread rubber composition of the present invention, the content of the amorphous silica spherical fine particles is preferably in the range of 5 to 50% by mass of silica.

  The present invention also relates to a pneumatic tire using the above-described tire tread rubber composition in a tread portion.

  According to the present invention, a pneumatic tire with improved wet performance can be obtained without reducing rolling resistance and wear resistance by using a rubber composition for tire treads containing amorphous silica spherical fine particles. .

  The rubber composition for a tire tread of the present invention contains at least a rubber component composed of at least one of natural rubber and synthetic rubber and a filler component composed of only silica or silica and carbon black. By blending silica, or silica and carbon black, it is possible to maintain the rolling resistance as low as desired while ensuring the wear resistance of the rubber composition for a tire tread.

Further, the silica includes at least amorphous silica spherical fine particles having an average particle diameter in the range of 0.05 to 1.00 μm. The amorphous silica spherical fine particles used in the present invention are mainly composed of silicic acid (SiO ₂ ) and are also referred to as silica fume, and typically are obtained by melting and reducing silica, iron, and carbon. It is obtained as a by-product when ferrosilicon (FeSi) is produced.

The content of silicic acid (SiO ₂ ) in the amorphous silica spherical fine particles is preferably 70% by mass or more, more preferably 75% by mass or more, and further preferably 85% by mass or more. When content of silicic acid is 70 mass% or more, the reinforcement effect and the improvement effect of wet performance are favorable. The content of silicic acid (SiO ₂ ) in the amorphous silica spherical fine particles is ideally 100% by mass. For example, the content is 97% by mass or less, and further 95% by mass or less. In this case, the amorphous silica spherical fine particles are more inexpensive and are preferable in terms of the manufacturing cost of the pneumatic tire. The content of silicic acid (SiO ₂ ) in the amorphous silica spherical fine particles can be evaluated by, for example, a method of detecting fluorescent X-rays by irradiating a sample with an electron beam or X-ray.

  In the present invention, by containing amorphous silica spherical fine particles having an average particle size of 0.05 to 1.00 μm and a very small particle size as a filler component, The dispersibility in the tire tread rubber composition is good, and the reinforcing effect on the tire tread rubber composition is good. Further, since the amorphous silica spherical fine particles have a remarkably small particle size, the contact area with the road surface of the amorphous silica spherical fine particles can be increased without adding a large amount of the amorphous silica spherical fine particles. Thereby, the grip property to the wet road surface of the rubber composition for tire treads can be improved, without reducing rolling resistance and abrasion resistance. In addition, the wet performance in the present invention particularly means the grip property to the wet road surface.

  The average particle diameter of the amorphous silica spherical fine particles is set to 0.05 μm or more. In this case, a desired effect of reinforcing the tire tread rubber composition is obtained, and processability at the time of preparing the tire tread rubber composition is ensured. The average particle size is set to 1.00 μm or less. In this case, the fracture resistance of the pneumatic tire, particularly the wear resistance, is ensured. The average particle size is preferably 0.10 μm or more, more preferably 0.80 μm or less, and further preferably 0.50 μm or less. In addition, the average particle diameter of the amorphous silica spherical fine particles is obtained by, for example, morphological observation using an electron microscope, measuring the particle diameter of the amorphous silica spherical fine particles in the observation field by image analysis, and the number average of the measured values. Can be obtained by calculating.

  In the amorphous silica spherical fine particles used in the present invention, the water content is preferably set to 5% by mass or less, and in this case, the reinforcing effect on the tire tread rubber composition is good. The moisture content is preferably 3% by mass or less, and more preferably 1% by mass or less. Although the moisture content of the amorphous silica spherical fine particles is preferably as low as possible, for example, 0.2 mass% or more, and further 0.5 mass% or more can increase the manufacturing cost of the rubber composition for a tire tread excessively. Can be prevented.

  The ignition loss of the amorphous silica spherical fine particles is 5% by mass or less, further 2% by mass or less, and further 1% by mass or less in that the reinforcing effect and the wet performance improving effect can be obtained satisfactorily. It is preferable. The ignition loss can be considered as an index of the content of the organic component in the amorphous silica spherical fine particles, and the smaller the ignition loss, the more advantageous the content of the organic matter. The ignition loss is preferably as small as possible. However, for example, when the content is 0.5% by mass or more, and further 1% by mass or more, it is preferable in terms of preventing an excessive increase in the cost of amorphous silica spherical fine particles.

The nitrogen adsorption specific surface area (BET specific surface area) of the amorphous silica spherical fine particles is preferably in the range of 5 to 35 m ² / g. When the nitrogen adsorption specific surface area is 5 m ² / g or more, the reinforcing effect and the wet performance improvement effect are good, and when it is 35 m ² / g or less, the pneumatic tire has an increased cost due to amorphous silica spherical fine particles. An excessive increase in manufacturing cost can be prevented. The nitrogen adsorption specific surface area is further preferably 10 m ² / g or more, further preferably 15 m ² / g or more, more preferably 30 m ² / g or less, and further preferably 25 m ² / g or less.

  The rubber composition for a tire tread of the present invention preferably contains amorphous silica spherical fine particles in a range of 2 to 40 parts by mass with respect to 100 parts by mass of the rubber component. When the content of the amorphous spherical silica fine particles is 2 parts by mass or more with respect to 100 parts by mass of the rubber component, the effect of improving the wet performance is good, and when the content is 40 parts by mass or less, the abrasion resistance of the pneumatic tire. Good properties. The content is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and further preferably 30 parts by mass or less, and further preferably 25 parts by mass or less.

  In the rubber composition for a tire tread of the present invention, the content of the filler component is preferably in the range of 5 to 200 parts by mass with respect to 100 parts by mass of the rubber component. When the content of the filler component is 5 parts by mass or more with respect to 100 parts by mass of the rubber component, the tire tread rubber composition has good wear resistance. When the content is 200 parts by mass or less, the tire tread rubber The processability during preparation of the composition is not impaired. The content of the filler component is preferably 30 parts by mass or more, more preferably 50 parts by mass or more, and 150 parts by mass or less, and further preferably 120 parts by mass or less.

  In the tire tread rubber composition of the present invention, the content of the amorphous silica spherical fine particles is preferably in the range of 5 to 50% by mass of silica. When the content is 5% by mass or more, the effect of improving the wet performance can be obtained satisfactorily. In the present invention, all of the silica compounded as the filler component may be amorphous silica spherical fine particles, but the average particle diameter is larger than the amorphous silica spherical fine particles and the amorphous silica spherical fine particles. It is also preferred to use in combination with silica. When the content of the amorphous silica spherical fine particles in the silica is 50% by mass or less, it is possible to ensure good wear resistance by using, for example, silica having a particle size larger than that of the amorphous silica spherical fine particles. It is. The content of the amorphous silica spherical fine particles is further preferably 10% by mass or more, more preferably 15% by mass or more, and further preferably 45% by mass or less, and further preferably 40% by mass or less.

In the present invention, when amorphous silica spherical fine particles and other silica having an average particle size larger than the amorphous silica spherical fine particles are used in combination, the other silica is used as a reinforcing material. Dry method white carbon, wet method white carbon, colloidal silica and the like can be combined. Among these, wet method white carbon mainly containing hydrous silicic acid is preferable. The above other nitrogen adsorption specific surface area of the silica (BET method specific surface area) is preferably in the range of e.g. 50 to 300 m ² / g, further 100 to 200 m ² / g. When the nitrogen adsorption specific surface area of the other silica is 50 m ² / g or more, the durability of the tire is improved by sufficiently obtaining a reinforcing effect for the rubber composition for a tire tread. On the other hand, when the nitrogen adsorption specific surface area is 300 m ² / g or less, the processability of the rubber composition for a tire tread is good. Here, the nitrogen adsorption specific surface area is a value measured by the BET method according to ASTM D3037-81.

  When carbon black is used as the filler component of the present invention, the carbon black content is preferably in the range of 5 to 150 parts by mass with respect to 100 parts by mass of the rubber component. When the content is 5 parts by mass or more, the wear resistance of the tire tread rubber composition is good. When the content is 150 parts by mass or less, the tire tread rubber composition does not become too hard and the pneumatic tire Good durability. The content is preferably 7 parts by mass or more, more preferably 15 parts by mass or more, and further preferably 100 parts by mass or less, further 70 parts by mass or less, and further preferably 50 parts by mass or less.

  As a particularly preferred combination, a combination in which silica is blended within a range of 15 to 100 parts by mass and carbon black is blended within a range of 10 to 50 parts by mass with respect to 100 parts by mass of the rubber component can be exemplified.

As the carbon black, for example, those having a nitrogen adsorption specific surface area of 100 m ² / g or more and 1500 m ² / g or less are preferably used. When the nitrogen adsorption specific surface area is 100 m ² / g or more, the reinforcing effect is good, and when the nitrogen adsorption specific surface area is 1500 m ² / g or less, it is preferable in terms of securing workability at the time of production.

  The rubber composition for a tire tread of the present invention includes, in addition to a filler component consisting of silica alone or silica and carbon black, clay, alumina, talc, calcium carbonate, magnesium carbonate, aluminum hydroxide, magnesium hydroxide, magnesium oxide. In addition, fillers such as titanium oxide can be blended alone or in admixture of two or more.

  As the rubber component used in the rubber composition for tire tread in the present invention, natural rubber and / or synthetic rubber can be used, natural rubber (NR), polyisoprene synthetic rubber (IR), butadiene rubber (BR), styrene. -Butadiene rubber (SBR), butyl rubber (IIR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), ethylene-propylene rubber, ethylene-propylene-diene rubber, styrene-isoprene rubber, styrene-isoprene-butadiene copolymer rubber (SIBR), isoprene-butadiene rubber, chlorosulfonated polyethylene, acrylic rubber, epichlorohydrin rubber, polysulfide rubber, silicone rubber, fluorine rubber, urethane rubber, brominated product of isobutylene-p-methylstyrene copolymer, etc. May be used alone or two or more.

  Examples of rubber components include natural rubber (NR), polyisoprene synthetic rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), butyl rubber (IIR), acrylonitrile-butadiene rubber (NBR), and chloroprene rubber. Diene rubbers such as (CR) and styrene-isoprene-butadiene copolymer rubber (SIBR) can be preferably used alone or in combination of two or more.

  It is preferable to mix | blend a silane coupling agent with the rubber composition for tire treads of this invention. In this case, the wear resistance and wet performance of the pneumatic tire become better. It is preferable that the compounding quantity of a silane coupling agent shall be in the range of 1-20 mass% of the quantity of a silica, for example. When the compounding amount of the silane coupling agent is 1% by mass or more of the amount of silica, the effect of improving wear resistance and wet performance is good, and when it is 20% by mass or less of the amount of silica, the rubber composition for tire treads In the kneading and extruding steps during the production of the product, it is preferable in that the scorch is less likely to occur. The compounding amount of the silane coupling agent is preferably 5% by mass or more, more preferably 6% by mass or more, and further preferably 8% by mass or more, more preferably 18% by mass or less, and further 15% by mass or less of the amount of silica. More preferably.

  As a preferable silane coupling agent, as a sulfur-containing silane coupling agent, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl-tetrasulfide, trimethoxysilylpropyl-mercaptobenzothiazole tetrasulfide, triethoxysilylpropyl- Examples include methacrylate-monosulfide, dimethoxymethylsilylpropyl-N, N-dimethylthiocarbamoyl-tetrasulfide, bis- [3- (triethoxysilyl) -propyl] tetrasulfide, 3-mercaptopropyltrimethoxysilane, and the like.

  Other silane coupling agents include vinyltrichlorosilane, vinyltris (2-methoxyethoxy) silane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ- (2-aminoethyl) Aminopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and the like can be used.

  In the present invention, other coupling agents such as aluminate coupling agents and titanium coupling agents can be used alone or in combination with a silane coupling agent depending on the application.

  In the rubber composition for a tire tread used in the present invention, other various components described below that are blended in a normal tire rubber composition can be appropriately blended.

  As the crosslinking agent, an organic peroxide, a sulfur-based vulcanizing agent, or the like is preferably used, and can be blended within a range of, for example, 3 to 8 parts by mass with respect to 100 parts by mass of the rubber component in the tire tread rubber composition. Examples of the organic peroxide include benzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, t-butyl cumyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide, 2,5-dimethyl-2,5- One or more of di (t-butylperoxy) hexane and the like can be used. Moreover, as a sulfur type vulcanizing agent, 1 type (s) or 2 or more types can be used among sulfur, a morpholine disulfide, etc., for example.

  Vulcanization accelerators include sulfenamide, thiazole, thiuram, thiourea, guanidine, dithiocarbamic acid, aldehyde-amine, aldehyde-ammonia, imidazoline, or xanthate vulcanization accelerators. Of these, one or more can be blended.

  As an anti-aging agent, 1 type (s) or 2 or more types can be mix | blended among amine type, a phenol type, an imidazole type, a carbamic acid metal salt, a wax, etc., for example.

  Softeners include process oil, lubricant, paraffin, liquid paraffin, petroleum asphalt, petroleum softener such as petroleum jelly, fatty oil softener such as castor oil, linseed oil, rapeseed oil, coconut oil, beeswax, carnauba wax In addition to waxes such as lanolin, tall oil, sub, linoleic acid, palmitic acid, stearic acid, lauric acid and the like can be blended.

  Examples of plasticizers include DMP (dimethyl phthalate), DEP (diethyl phthalate), DBP (dibutyl phthalate), DHP (diheptyl phthalate), DOP (dioctyl phthalate), DINP (diisononyl phthalate), DIDP. (Diisodecyl phthalate), BBP (butyl benzyl phthalate), DLP (dilauryl phthalate), DCHP (dicyclohexyl phthalate) and the like may be blended.

  Furthermore, in order to prevent or delay scorch, for example, organic acids such as phthalic anhydride, salicylic acid and benzoic acid, nitroso compounds such as N-nitrosodiphenylamine, N-cyclohexylthiophthalimide and the like can be blended as scorch preventing agents.

  A tread using the tire tread rubber composition according to the present invention is prepared by kneading the components of the tire tread rubber composition at 130 ° C. or higher and 160 ° C. or lower with a Banbury mixer or a kneader, for example. It can be formed by preparing an uncrosslinked product of the composition, applying the uncrosslinked product to a tread portion of a pneumatic tire, and performing vulcanization molding.

  The amorphous silica spherical fine particles when blended as a blending component of the tire tread rubber composition preferably have a pH in the range of 8.0 to 9.5, more preferably 8.0 to 9.0. Can be set within range. In this case, it is possible to obtain a pneumatic tire having a low risk of deteriorating other components of the rubber composition for a tire tread and having excellent durability.

  The present invention can be applied to various tires for passenger cars, trucks / buses, heavy machinery and the like. FIG. 1 is a cross-sectional view showing a right half of a tire according to the present invention. The tire T has a bead portion 1, a sidewall portion 2, and a tread portion 3. Further, a bead core 4 is embedded in the bead portion 1. In addition, a carcass 5 provided from one bead portion 1 to the other bead portion, folded back at both ends to lock the bead core 4, and a belt layer 6 composed of two or more plies outside the crown portion of the carcass 5. Has been placed. The belt layer 6 is arranged such that a ply made of a cord such as a steel cord or an aramid fiber intersects with each other so that the cord is usually at an angle of 5 to 30 ° with respect to the tire circumferential direction. In the carcass, organic fiber cords such as polyester, nylon, and aramid are arranged at approximately 90 ° in the tire circumferential direction. An apex 7 is arranged.

[Example]
EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

<Examples 1 and 2 and Comparative Example 1>
Of the blending components shown in Table 1, the components excluding sulfur and the vulcanization accelerator were kneaded at about 120 ° C. for 10 minutes using a banbury. Thereafter, sulfur and a vulcanization accelerator were added, and kneaded at about 80 ° C. for 2 minutes using a biaxial open roll. A rubber sheet having a thickness of 10 mm is prepared using the obtained unvulcanized material, applied to the tread portion of the pneumatic tire, vulcanized at 160 ° C. for 30 minutes, and a test pneumatic tire of 185 / 70R14 size is obtained. Obtained.

  Further, a rubber sheet having a thickness of 5 mm was prepared using the above unvulcanized material, and vulcanized at 160 ° C. for 30 minutes to obtain a test rubber composition.

<JIS A hardness>
Measure the JIS-A hardness of the test rubber composition,
JIS-A hardness index = (JIS-A hardness of test rubber composition according to each example and comparative example) / (JIS-A hardness of test rubber composition according to comparative example 1)
According to the above, the JIS-A hardness index was calculated. The results are shown in Table 1.

<Complex modulus E *, loss tangent tan δ>
The complex elastic modulus E * and loss tangent tan δ of the above rubber composition for test were measured at 60 ° C. at a frequency of 10 Hz, an initial strain of 10%, and a dynamic strain of 2% using a viscoelasticity measuring device.
Complex elastic modulus E * index = (complex elastic modulus E * of test rubber composition according to each example and comparative example) / (complex elastic modulus E * of test rubber composition according to comparative example 1) × 100
Loss tangent tan δ index = (loss tangent tan δ of test rubber composition according to each example and comparative example) / (loss tangent tan δ of test rubber composition according to comparative example 1) × 100
Thus, the complex elastic modulus E * index and loss tangent tan δ index were calculated. The results are shown in Table 1.

<Wet performance>
At the test course on the asphalt road surface where the above-mentioned test pneumatic tire is mounted on a normal passenger car and water is sprinkled, run while making a circular turn while increasing the speed, and measure the speed when the slip occurs as the limit speed. , The following formula,
Wet performance index = (limit speed of pneumatic tire according to each example and comparative example) / (limit speed of pneumatic tire according to comparative example 1) × 100
The wet performance index was calculated according to The larger the value, the better the wet performance. The results are shown in Table 1.

<Rolling resistance>
With respect to the test rubber composition, loss tangent (tan δ) at 60 ° C. was measured at a frequency of 10 Hz, an initial strain of 10%, and a dynamic strain of 2% using VES-F-3 manufactured by Iwamoto Seisakusho Co., Ltd. . For the reciprocal of the value of tan δ,
Rolling resistance index = (Reciprocal number of tan δ of rubber composition according to each Example and Comparative Example) / (Reciprocal number of tan δ of rubber composition according to Comparative Example 1) × 100. The larger the value, the smaller the rolling resistance and the more advantageous. The results are shown in Table 1.

<Abrasion resistance>
With respect to the above rubber composition for test, the wear coefficient was measured at a load of 3.0 kg and a slip ratio of 30% using a measuring device manufactured by Iwamoto Seisakusho Co., Ltd. The following formula,
Abrasion resistance index = (Abrasion coefficient of rubber composition according to Comparative Example 1) / (Abrasion coefficient of rubber composition according to each Example and Comparative Example) × 100
The wear resistance index was calculated according to The higher the value, the better the wear resistance. The results are shown in Table 1.

Note 1: Natural rubber is “RSS3” made in Thailand.
Note 2: SBR is “Nippol N9520” manufactured by Nippon Zeon Co., Ltd.
Note 3: Carbon Black N339 is “Show Black N339” manufactured by Showa Cabonet Co., Ltd.
Note 4: Silica is “Ultra Seal VN3” (average particle diameter: 5 to 15 μm, N ₂ SA: 210 m ² / g) manufactured by Degussa.
Note 5: Silane coupling agent is “Si69” manufactured by Degussa.
Note 6: Aroma oil is “JOMO Process X140” manufactured by Japan Energy.
Note 7: Stearic acid is “stearic acid” manufactured by NOF Corporation.
Note 8: Zinc Hana is “Zinc Hana 1” manufactured by Mitsui Kinzoku Kogyo.
Note 9: Anti-aging agent 6C is “Nockluck 6C” manufactured by Ouchi Shinsei Chemical Co., Ltd.
Note 10: Sulfur is “powder sulfur” manufactured by Tsurumi Chemical.
Note 11: Vulcanization accelerator NS is “Noxeller NS” manufactured by Ouchi Shinsei Chemical Co., Ltd.
Note 12: The vulcanization accelerator DPG is “Soccinol D” manufactured by Sumitomo Chemical Co., Ltd.
Note 13: Amorphous silica spherical fine particles are silica fume “SF-R” (average particle size: 0.1 to 1.0 μm, SiO ₂ content: 91.4% by mass, manufactured by Kuzuneki Alloy Iron Co., Ltd. (made in Russia). Loss on ignition: 1.94% by mass, water content: 0.51% by mass, BET specific surface area: 20.1 m ^{2 /} g, pH: 8.0 to 9.5).

  From the results shown in Table 1, in Examples 1 and 2, compared with Comparative Example 1, while the rolling resistance and the wear resistance were substantially equal, the wet performance was remarkably improved. Therefore, it can be seen that the wet performance can be improved while maintaining the rolling resistance and the wear resistance by using the rubber composition for a tire tread of the present invention containing amorphous silica spherical fine particles.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  In the pneumatic tire using the rubber composition for a tire tread of the present invention, the wet performance is improved without lowering rolling resistance and wear resistance. Therefore, the pneumatic tire is used for passenger cars, trucks and buses. It can be suitably applied to various uses such as for industrial use and heavy machinery.

It is sectional drawing which shows the right half of the tire which concerns on this invention.

Explanation of symbols

  T tire, 1 bead part, 2 sidewall part, 3 tread part, 4 bead core, 5 carcass, 5a folded part, 6 belt layer, 7 bead apex.

Claims (5)

Containing at least a rubber component composed of at least one of natural rubber and synthetic rubber, and a filler component composed of silica alone or silica and carbon black,
The rubber composition for a tire tread, wherein the silica includes at least amorphous silica spherical fine particles having an average particle diameter in the range of 0.05 to 1.00 μm.   The rubber composition for a tire tread according to claim 1, wherein the amorphous silica spherical fine particles are contained within a range of 2 to 40 parts by mass with respect to 100 parts by mass of the rubber component.   The rubber composition for a tire tread according to claim 1, wherein a content of the filler component is in a range of 5 to 200 parts by mass with respect to 100 parts by mass of the rubber component.   The rubber composition for a tire tread according to claim 1, wherein the content of the amorphous silica spherical fine particles is in the range of 5 to 50% by mass of the silica.   The pneumatic tire which used the rubber composition for tire treads in any one of Claims 1-4 for the tread part.

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