JP2010143963A - 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 having improved gripping performance from medium to high temperature and a pneumatic tire using the same. <P>SOLUTION: The tire tread rubber composition contains, based on 100 pts.mass rubber component, 1-30 pts.mass magnetic powder, and 1-30 pts.mass MR fluid. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a rubber composition for a tire tread containing a magnetic powder and an MR fluid, and a pneumatic tire using the same.

  In recent years, while the performance of automobiles has increased and the horsepower has increased, awareness of safety has increased, and the demand for grip performance on tires has increased. For example, various performances during high-speed traveling are listed as one of them. The tread portion of the pneumatic tire generates heat as the vehicle travels, and grip performance deteriorates due to high temperatures.

  Conventionally, as a technique for improving grip performance, for example, a rubber composition for a tire tread can be prepared by blending a basic anti-aging agent such as imidazoles and lactams and an organometallic compound as disclosed in Patent Document 1. Among them, a basic anti-aging agent having an ionic bond could be imparted, and as a result, the grip performance could be improved. However, the organometallic compound used for imparting an ionic bond to the basic anti-aging agent has a problem that carboxylic acid is generated and crosslinking is inhibited.

Further, as a method for improving grip performance, Patent Document 2 discloses a rubber composition for tires containing a granular material coated with a resin composition in which inorganic porous particles are used as a core material in a rubber component and a metal magnetic powder is mixed. Things are listed. The rubber composition is obtained by dispersing a granular material in a rubber component and then melting the surface of the granular material by electromagnetic induction heating to release and diffuse inorganic porous particles as a core material. When the porous particles are used as a filler of the rubber composition, there is a problem that the tensile strength is lowered.
JP 2006-124423 A JP 2001-261894 A

  An object of this invention is to provide the rubber composition for tire treads which improved the grip performance over medium-high temperature, and a pneumatic tire using the same.

  The present invention is a tire tread rubber composition containing 1 to 30 parts by mass of a magnetic powder and 1 to 30 parts by mass of an MR fluid with respect to 100 parts by mass of a rubber component.

  The tire tread rubber composition preferably further contains 1 to 30 parts by mass of a piezoelectric element with respect to 100 parts by mass of the rubber component.

  The tire tread rubber composition preferably further contains 0.1 to 20 parts by mass of a compound containing hydrogen bonds and / or a compound containing ionic bonds with respect to 100 parts by mass of the rubber component.

  The present invention is a pneumatic tire having a tread using the rubber composition for a tire tread.

  ADVANTAGE OF THE INVENTION According to this invention, the rubber composition for tire tread which improved the grip performance of a wide temperature range, and a pneumatic tire using the same can be provided.

  The rubber composition for a tire tread of the present invention contains a rubber component, a magnetic powder and an MR fluid.

<Rubber component>
The rubber component is not particularly limited, but natural rubber (NR), styrene-butadiene rubber (SBR), butadiene rubber (BR), butyl rubber (IIR), acrylonitrile butadiene rubber (NBR), isoprene rubber (IR) ), Ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR) and the like. These rubber components may be used alone or in combination of two or more. Especially, since it has sufficient intensity | strength as rubber | gum for tire treads and shows outstanding abrasion resistance, it is preferable to use NR, SBR, or BR, and it is more preferable to use SBR.

  Examples of SBR include those obtained by emulsion polymerization and those obtained by solution polymerization, but are not particularly limited.

  The bound styrene content of SBR is preferably 10% by mass or more, more preferably 20% by mass or more, further preferably 30% by mass or more, and particularly preferably 35% by mass or more. When the amount of bound styrene of SBR is less than 10% by mass, there is a tendency that a sufficient improvement effect of grip performance cannot be obtained under medium temperature (30 to 50 ° C.) and high temperature (around 100 ° C.) conditions. The amount of bound styrene in SBR is preferably 60% by mass or less, more preferably 50% by mass or less, and further preferably 45% by mass or less. When the amount of bound styrene of SBR exceeds 60% by mass, the rubber becomes hard, the contact area with the road surface decreases, and high grip performance tends to be not obtained.

  When SBR is contained in the rubber component, a sufficient grip performance can be obtained, and therefore the SBR content is preferably 100% by mass.

<Magnetic powder>
In the present invention, the magnetic powder is a general powder having magnetism.

  Examples of the magnetic powder include ferrite magnets, rare earth magnets, γ iron oxide, chromium dioxide, and cobalt-chromium alloys. Examples of ferrite magnets include ferrite, barium ferrite, strontium ferrite, manganese zinc ferrite, nickel zinc ferrite, and copper zinc ferrite. Specific examples of rare earth elements used in rare earth magnets include samarium and neodymium. Among them, it is preferable to use ferrite because it is easily available.

  The average particle size of the magnetic powder is preferably 0.5 μm or more, and more preferably 1.0 μm or more, because it has excellent wear performance. Further, the average particle size of the magnetic powder is preferably 50 μm or less, and more preferably 40 μm or less, because it is excellent in high filling.

  The content of the magnetic powder is preferably 1 part by mass or more and more preferably 3 parts by mass or more with respect to 100 parts by mass of the rubber component because sufficient magnetic force can be obtained. Moreover, it is preferable that it is 30 mass parts or less with respect to 100 mass parts of rubber components, and, as for content of a magnetic body powder, it is more preferable that it is 25 mass parts or less from the reason that it is excellent in abrasion resistance performance.

The magnetic flux density of the magnetic powder is preferably 5 to 1000 mT.
<MR fluid>
In the present invention, the MR fluid is a slurry in which ferromagnetic metal fine particles are dispersed at a high concentration in a liquid as a medium, and the magnetized ferromagnetic metal fine particles attract each other strongly due to the influence of an external magnetic field. The viscosity of is increased.

  When the magnetic powder was blended and the rubber composition was made magnetized, it was difficult to disperse and the wearability was also deteriorated due to the foreign matter. By combining a small amount of Rheological Fluid) into the rubber composition, the high temperature grip can be improved and the wear resistance can be suppressed.

As the ferromagnetic metal fine particles contained in the MR fluid, iron is preferable.
The average particle diameter of the ferromagnetic metal fine particles contained in the MR fluid is preferably 0.5 μm or more, and more preferably 1.0 μm or more, because of excellent wear performance. Further, the average particle diameter of the ferromagnetic metal fine particles contained in the MR fluid is preferably 50 μm or less, and more preferably 40 μm or less, because it is excellent in high filling.

  The content of the ferromagnetic metal fine particles contained in the MR fluid is preferably 1% by mass or more, and more preferably 3% by mass or more, because sufficient magnetic force can be obtained. In addition, for the reason of excellent dispersibility, the ferromagnetic fluid fine particles are preferably contained in the MR fluid in an amount of 30% by mass or less, and more preferably 25% by mass or less.

  As the liquid used as the medium for the MR fluid, it is preferable to use poly-α-olefin for the reason that it can be easily mixed with oil which is a plasticizer for rubber.

  The content of the MR fluid is preferably 1 part by mass or more and more preferably 3 parts by mass or more with respect to 100 parts by mass of the rubber component because a sufficient magnetic force can be obtained. Moreover, it is preferable that it is 30 mass parts or less with respect to 100 mass parts of rubber components from the reason that it is excellent in abrasion resistance performance, and it is more preferable that it is 25 mass parts or less.

<Piezoelectric element>
The piezoelectric element used in the present invention has a function of converting vibration energy into electric energy. As such a piezoelectric element, piezoelectric ceramic or piezoelectric polymer is used. Specifically, BaTiO ₃ , (Ba, Pb) TiO ₃ , (Ba, Ca) TiO ₃ , (K, Na) NbO ₃ , (K, Li) NbO ₃ , Pb (Zr, Ti) O ₃ (that is, PZT), PZT blended with composite perovskite, PLZT (La doped PZT), Bi ₄ Ti ₃ O ₁₂ , LiNbO ₃ , LiTiO _3, etc., as well as piezoelectric ceramics such as ZnO, AlN, PbTiO ₃ , polyvinylidene fluoride, In addition to copolymers of vinylidene fluoride and trifluoroethylene, copolymers of vinylidene cyanide and vinyl acetate, polytetrafluoroethylene, iodinated polyvinyl acetate, etc., there are polymer piezoelectric materials such as polyurea.

  The compounding quantity of a piezoelectric element is 1-30 mass parts with respect to 100 mass parts of rubber components, Preferably it is 3-15 mass parts, More preferably, it is 5-10 mass parts. If the blending amount is less than 1 part by mass, the effect of improving the grip performance of the tire is insufficient. Moreover, when it exceeds 30 mass parts, abrasion resistance will fall.

  The average particle size of the piezoelectric element is preferably 0.01 to 50 μm, and more preferably 0.01 to 10 μm. If the average particle size is less than 0.01 μm, the effect of improving the grip performance of the tire tends to be insufficient. Further, when the average particle size exceeds 50 μm, the wear resistance tends to be lowered. The shape of the piezoelectric element does not need to be spherical, and may be a plate shape, a thin film shape, or an irregular shape, but in any case, the maximum diameter is the average particle size by grinding or cutting. It is preferable to be within the diameter range.

  The Curie temperature of the piezoelectric element is preferably 100 ° C. or higher. When the Curie temperature is less than 100 ° C., there is a tendency that the effect of improving the grip performance cannot be obtained due to the disappearance of piezoelectricity.

The piezoelectric constant (g33) of the piezoelectric element is preferably 5 × 10 ⁻³ Vm / N or more. If it is less than 5 × 10 ⁻³ Vm / N, the effect of improving the grip performance tends not to be obtained.

  The piezoelectric element can be aligned in polarization by a poling process such as an operation of applying high piezoelectricity in heated silicon oil.

<Compound containing hydrogen bond and / or compound containing ionic bond>
The present invention preferably further contains a compound containing a hydrogen bond and / or a compound containing an ionic bond. A compound containing a hydrogen bond and / or a compound containing an ionic bond is a compound that can replace external stimuli such as strain and heat with binding energy loss. By blending a compound having a hydrogen bond with a rubber composition, grip performance under an intermediate temperature condition (30 to 50 ° C.) can be improved, and by blending a compound having an ionic bond with a rubber composition, The grip performance under high temperature conditions (around 100 ° C.) can be improved.

  Examples of the compound containing a hydrogen bond include piperidine derivatives, imidazoles and caprolactams. Of these, imidazoles and caprolactams are preferable because they are easily available.

  Examples of the compound containing an ionic bond include organometallic compounds such as organic carboxylic acid metal salts, thiocarboxylic acids, and phosphates. Of these, calcium propionate and magnesium acetate are preferred because they are easily available.

  A compound containing a hydrogen bond and / or a compound containing an ionic bond may be used alone or in combination of two or more. For reasons of excellent grip performance, it is preferable to use a combination of two or more compounds containing hydrogen bonds and compounds containing ionic bonds.

  The content of the compound containing a hydrogen bond and / or the compound containing an ionic bond is preferably 0.1 parts by mass or more with respect to 100 parts by mass of the rubber component because the grip performance is excellent. Further, the content of the compound containing a hydrogen bond and / or the compound containing an ionic bond is preferably 20 parts by mass or less with respect to 100 parts by mass of the rubber component because of excellent wear performance and workability.

<Carbon black>
The rubber composition for a tire tread of the present invention can further contain a reinforcing filler. The reinforcing fillers may be used alone or in combination of two or more. Examples of the reinforcing filler include carbon black, silica, calcium carbonate, magnesium oxide and the like, and carbon black is preferable because of its large reinforcing effect.

  The content of carbon black is preferably 10 to 200 parts by mass and more preferably 20 to 150 parts by mass with respect to 100 parts by mass of the rubber component. When the content of carbon black is less than 10 parts by mass, the wear resistance tends to decrease. Moreover, when it exceeds 200 mass parts, there exists a tendency for workability to deteriorate.

Nitrogen adsorption specific surface area of carbon black is preferably 80~280m ² / g, more preferably 100 to 200 m ² / g. When the nitrogen adsorption specific surface area is less than 80 m ² / g, grip performance and wear resistance tend to be lowered. On the other hand, if the nitrogen adsorption specific surface area exceeds 280 m ² / g, good dispersion is difficult to obtain, and the workability tends to decrease.

<Anti-aging agent>
The rubber composition for a tire tread of the present invention preferably further contains an anti-aging agent.

  As the anti-aging agent, amine-based, phenol-based, and imidazole-based compounds, carbamic acid metal salts, waxes, and the like can be appropriately selected and used.

  The content of the anti-aging agent is preferably 0.1 to 20 parts by mass and more preferably 1 to 10 parts by mass with respect to 100 parts by mass of the rubber component. When the content of the anti-aging agent is less than 0.1 parts by mass, the anti-aging effect tends to be small. Moreover, when it exceeds 20 mass parts, there exists a tendency for tire performance to deteriorate.

<Softener>
The rubber composition for a tire tread of the present invention preferably further contains a softening agent.

  Examples of the softening agent include oils such as aroma oil, naphthene oil, paraffin oil, and vegetable oil, and resins such as coumarone resin, petroleum resin, phenol resin, terpene resin, and xylene resin.

  When oil is contained, the oil content is preferably 10 to 200 parts by mass, more preferably 20 to 150 parts by mass, including oil-extended oil, with respect to 100 parts by mass of the rubber component. . If the oil content is less than 10 parts by mass, the wet grip performance tends to be insufficient. Moreover, when it exceeds 200 mass parts, there exists a tendency for abrasion resistance to fall remarkably.

  The softening point of the resin is preferably 40 to 200 ° C, and more preferably 60 to 180 ° C. If the softening point of the resin is less than 40 ° C., the grip performance under high temperature conditions tends to decrease. When the temperature exceeds 200 ° C., the dispersibility during kneading tends to decrease.

  When the resin is blended, the content of the resin is preferably 1 to 50 parts by mass, and more preferably 5 to 30 parts by mass with respect to 100 parts by mass of the rubber component. If the resin content is less than 1 part by mass, grip performance tends to be insufficient. Moreover, when it exceeds 50 mass parts, since it shows excessive adhesiveness, there exists a tendency for a process to become difficult.

  For reasons of excellent grip performance, it is preferable to use an oil and a resin in combination.

<Vulcanizing agent>
As the vulcanizing agent, an organic peroxide or a sulfur vulcanizing agent can be used. 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-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne- 3 or 1,3-bis (t-butylperoxypropyl) benzene or the like can be used. Moreover, as a sulfur type vulcanizing agent, sulfur, morpholine disulfide, etc. can be used, for example. Of these, sulfur is preferred.

<Vulcanization accelerator>
Vulcanization accelerators include sulfenamide, thiazole, thiuram, thiourea, guanidine, dithiocarbamic acid, aldehyde-amine or aldehyde-ammonia, imidazoline, or xanthate vulcanization accelerators. Those containing at least one of them can be used.

<Vulcanization aid>
As the vulcanization aid, stearic acid, zinc oxide (zinc white) or the like can be used.

<Other additives>
In addition to the above components, additives such as an ozone deterioration inhibitor can be blended with the rubber composition for tire treads of the present invention.

<Method for producing rubber composition for tire tread>
The rubber composition for a tire tread of the present invention can be obtained by first mixing an MR fluid in a step of mixing a rubber component and a magnetic powder and blending oil as a plasticizer. By producing in such a process, the magnetic material can be dispersed in both the rubber component and the oil.

<Tire manufacturing method>
The tire of the present invention is produced by a usual method using the rubber composition for a tire tread of the present invention. That is, the rubber composition for a tire tread of the present invention, which is blended with the additives as necessary, is extruded in accordance with the shape of the tread of the tire at an unvulcanized stage and is processed on a tire molding machine by a usual method. An unvulcanized tire is formed by molding. This unvulcanized tire can be heated and pressurized in a vulcanizer to obtain a pneumatic tire.

<Examples 1-4, Comparative Examples 1-11>
(Preparation of rubber composition for tire tread)
According to the formulation shown in Tables 1 and 2, using a Banbury mixer, chemicals other than sulfur and a vulcanization accelerator were kneaded for 3 minutes at 150 ° C. to obtain a kneaded product. Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded for 5 minutes at 100 ° C. using an open roll to obtain an unvulcanized rubber composition.

  Furthermore, the unvulcanized rubber composition was press-vulcanized for 12 minutes at 170 ° C., and vulcanized rubber sheets of Examples 1 to 4 and Comparative Examples 1 to 11 were produced. The following items were measured for the vulcanized rubber sheet.

(Degree of crosslinking (SWELL))
The vulcanized rubber sheet was immersed in toluene at 25 ° C. for 24 hours, and the volume change rate (SWELL) before and after immersion was measured. The larger the measured value, the smaller the degree of crosslinking and the greater the variation, which is not preferable.

(Viscoelasticity test)
Using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd., physical properties (complex elastic modulus E ′) of a vulcanized rubber sheet at 40 ° C. and 100 ° C. under conditions of initial strain of 10%, dynamic strain of 2% and frequency of 10 Hz. (Unit: MPa) and loss tan δ) were measured. In addition, it shows that it is excellent in rigidity, so that E 'is large, and it shows that grip property is so high that tan-delta is large, and it is excellent in grip performance.

(Tensile test)
In accordance with JIS K 6251 “Vulcanized Rubber and Thermoplastic Rubber—How to Obtain Tensile Properties”, evaluation was performed using a No. 3 dumbbell type rubber test piece made of the vulcanized rubber sheet. By this test, 300% elongation stress (M300) was measured for each vulcanized rubber sheet. In Example 1 and Comparative Examples 1 to 6, M300 of Comparative Example 1 was set to 100, and in Examples 2 to 4 and Comparative Examples 7 to 11, M300 of Comparative Example 7 was set to 100, and indexed according to the following calculation formulas. The larger the tensile strength index, the better the abrasion wear resistance.

(Tensile strength index) = (M300 of each formulation) / (M300 of Comparative Example 1 or Comparative Example 7) × 100
(Actual vehicle evaluation)
An unvulcanized rubber sheet is formed into a tread shape, bonded to other tire members, and press vulcanized at 170 ° C for 12 minutes to produce an 11 x 7.10-5 size cart tire. did.

  The tire prepared in the cart was mounted, and the test course of 1 lap 2 km was run 8 laps. Example 1 and Comparative Examples 1 to 6 had three grip performances of the tire of Comparative Example 1, and Examples 2 to 4 In Comparative Examples 7 to 11, the grip performance of the tire of Comparative Example 7 was set to 3 points, and the test driver made a sensory evaluation with a maximum score of 5 points. The higher the score, the higher the grip performance. The initial grip performance indicates the grip performance of the first to fourth laps, and the second half grip performance indicates the grip performance of the fifth to eighth laps. Further, Example 1 and Comparative Examples 1 to 6 have three appearances of the tire of Comparative Example 1 after traveling, and Examples 2 to 4 and Comparative Examples 7 to 11 have three points of appearance of the tire of Comparative Example 7. The wear appearance of each formulation was evaluated relative to a maximum of 5 points. The higher the score, the less the amount of tire wear and the better the wear resistance.

  The results are shown in Tables 1 and 2.

(Note 1) SBR: Toughden 4350 manufactured by Asahi Kasei Co., Ltd. (39% by mass of bound styrene, 50 parts by mass of oil per 100 parts by mass of rubber component)
Carbon black: Diamond Black A (N110, nitrogen adsorption specific surface area: 130 m ² / g) manufactured by Mitsubishi Chemical Corporation
Anti-aging agent 6C: Santoflex 13 manufactured by Flexis Co., Ltd.
Anti-aging agent 224: NOCRACK 224 manufactured by Flexis Co., Ltd.
Stearic acid: Zinc stearate manufactured by Nippon Oil & Fats Co., Ltd .: Zinc oxide 2 types aroma oil manufactured by Mitsui Mining & Smelting Co., Ltd. Aroma oil: Process X-260 manufactured by Japan Energy Co., Ltd.
Resin: Neopolymer 140 manufactured by Nippon Petrochemical Co., Ltd.
Nitrogen compound: Curesol 2MZ (2-methylimidazole) manufactured by Shikoku Kasei Kogyo Co., Ltd.
Acid: 4,4′-butylidenebis- (3-methyl-6-tert-butylphenol)
Magnesium acetate: Magnesium acetate magnetic powder manufactured by Kishida Chemical Co., Ltd .: Ferrite powder FH-800 manufactured by Toda Kogyo Co., Ltd. (average particle size: 1.2 μm, N ₂ SA: 2.2 m ² / g, compression density) : 3.1 g / m ³ , magnetic flux density: 1680 G)
MR fluid: E-600 manufactured by Sigma High Chemical (ferromagnetic metal fine particles: iron (average particle diameter: 10 μm, content: 85 mass%), medium: poly-α-olefin)
Piezoelectric element: polyvinylidene fluoride manufactured by Kureha Chemical Co., Ltd. (average particle size: 5 μm, Curie temperature: 120 ° C., piezoelectric constant: 7.0 × 10 ⁻² Vm / N)
Sulfur: Powder sulfur vulcanization accelerator manufactured by Tsurumi Chemical Co., Ltd .: Noxeller NS manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
(Evaluation results)
[Example 1, Comparative Examples 1 to 6]
Example 1 is a rubber composition containing a magnetic powder, an MR fluid, a compound containing a hydrogen bond (nitrogen compound and acid) and a compound containing an ionic bond (magnesium acetate), and a tire using the rubber composition. Compared to Comparative Example 1 which does not contain any of magnetic powder, MR fluid, a compound containing hydrogen bonds and a compound containing ionic bonds, it is excellent in rigidity and grip at both medium temperature (40 ° C.) and high temperature (100 ° C.). Yes. Furthermore, as for tires, the latter half grip performance is very good.

  Comparative Example 2 is a rubber composition containing a compound containing hydrogen bonds but not containing magnetic powder and MR fluid, and a tire using the rubber composition. Compared to Comparative Example 1, the rigidity and grip properties were improved both at medium temperature (40 ° C.) and at high temperatures (100 ° C.), and the latter half grip performance was improved for the tire, but inferior to Example 1.

  Comparative Example 3 is a rubber composition containing a compound containing a hydrogen bond and a compound containing an ionic bond, but not containing magnetic powder and MR fluid, and a tire using the rubber composition. Compared to Comparative Example 1, the rigidity and grip properties were improved both at medium temperature (40 ° C.) and at high temperatures (100 ° C.), and the latter half grip performance was improved for the tire, but inferior to Example 1.

  Comparative Example 4 is a rubber composition containing a compound containing a hydrogen bond, a compound containing an ionic bond, and a magnetic powder, but no MR fluid, and a tire using the rubber composition. Compared to Comparative Example 1, the rigidity and grip properties were improved both at medium temperature (40 ° C.) and at high temperatures (100 ° C.), and the latter half grip performance was improved for the tire, but inferior to Example 1. In addition, abrasion resistance and wear appearance were greatly deteriorated.

  Comparative Example 5 is a rubber composition containing a magnetic powder, MR fluid, a compound containing hydrogen bonds and a compound containing ionic bonds, and a tire using the rubber composition. Compared to Comparative Example 1, the rigidity and grip performance were improved both at medium temperature (40 ° C.) and at high temperature (100 ° C.), and the latter half grip performance of the tire was improved. Each performance is inferior to Example 1 because the amount is as small as 0.5 parts by mass with respect to 150 parts by mass of SBR (100 parts by mass of rubber component).

  Comparative Example 6 is a rubber composition containing a magnetic powder, MR fluid, a compound containing hydrogen bonds and a compound containing ionic bonds, and a tire using the rubber composition. The contents of the magnetic powder and the MR fluid were as large as 40 parts by mass with respect to 150 parts by mass of SBR (rubber component 100 parts by mass), respectively, and the wear resistance performance was extremely deteriorated.

[Examples 2 to 4, Comparative Examples 7 to 11]
Example 2 is a rubber composition containing a magnetic powder, MR fluid, a compound containing a hydrogen bond (nitrogen compound and acid) and a compound containing an ionic bond (magnesium acetate), and a tire using the rubber composition. Compared to Comparative Example 7, both the intermediate temperature (40 ° C.) and the high temperature (100 ° C.) are excellent in rigidity and grip. Furthermore, as for tires, the latter half grip performance is excellent. The wear appearance is equivalent.

  Example 3 is a rubber composition containing a magnetic powder, MR fluid, a compound containing hydrogen bonds and a compound containing ionic bonds, and a tire using the rubber composition. Compared to Comparative Example 7, both rigidity and grip properties are excellent at medium temperature (40 ° C.) and high temperature (100 ° C.), but abrasion wear resistance is inferior. Furthermore, the tires have excellent second half grip performance, but the wear appearance is inferior.

  Example 4 is a rubber composition containing a magnetic powder, an MR fluid, a piezoelectric element, a compound containing hydrogen bonds and a compound containing ionic bonds, and a tire using the rubber composition. Compared to Comparative Example 7, both the intermediate temperature (40 ° C.) and the high temperature (100 ° C.) are excellent in rigidity and grip properties, and abrasion resistance is equivalent. Furthermore, the tires have excellent second-half grip performance and the same wear appearance.

  Comparative Example 8 is a rubber composition containing a magnetic powder, a compound containing a hydrogen bond and a compound containing an ionic bond, but not containing an MR fluid and a piezoelectric element, and a tire using the rubber composition. Compared to Comparative Example 7, the grip performance is equivalent, but the abrasion resistance and abrasion appearance are inferior. Furthermore, with regard to tires, the initial grip performance and the latter half grip performance were improved.

  Comparative Example 9 is a rubber composition containing a magnetic powder, MR fluid, a compound containing hydrogen bonds, a compound containing ionic bonds (magnesium acetate), and a piezoelectric element, and a tire using the rubber composition. Although the contents of the magnetic substance powder and the MR fluid are less than 0.5 parts by mass with respect to 150 parts by mass of SBR (100 parts by mass of rubber component), respectively, the abrasion resistance and abrasion appearance are improved compared to Comparative Example 7. The mid-temperature (40 ° C.) and high-temperature (100 ° C.) rigidity and grip properties were equivalent, and the tires had the same second-half grip performance.

  Comparative Example 10 is a rubber composition containing an MR fluid, a compound containing hydrogen bonds and a compound containing ionic bonds, but not containing magnetic powder and piezoelectric elements, and a tire using the rubber composition. Compared to Comparative Example 7, the grip performance is equivalent, but the abrasion resistance and abrasion appearance are inferior.

  Comparative Example 11 is a rubber composition containing a piezoelectric element, a compound containing hydrogen bonds, and a compound containing ionic bonds, but not containing magnetic powder and MR fluid, and a tire using the rubber composition. Compared to Comparative Example 7, the grip performance is equivalent, but the abrasion resistance and abrasion appearance are inferior.

  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.

Claims (4)

  A rubber composition for a tire tread containing 1 to 30 parts by mass of a magnetic powder and 1 to 30 parts by mass of an MR fluid with respect to 100 parts by mass of a rubber component.   Furthermore, 1-30 mass parts of piezoelectric elements are contained with respect to 100 mass parts of said rubber components, The rubber composition for tire treads of Claim 1.   Furthermore, the rubber composition for tire treads of Claim 1 or 2 containing 0.1-20 mass parts of compounds containing a hydrogen bond and / or a compound containing an ionic bond with respect to 100 mass parts of said rubber components.   The pneumatic tire which has a tread using the rubber composition for tire treads of any one of Claims 1-3.