JP2007284536A - Tire tread rubber composition and tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition and a tire which inhibit the occurrence of a radio noise, maintain high wet skid performance, and can maintain low rolling resistance. <P>SOLUTION: This rubber composition comprises 100 pts.mass rubber component, 0.1-20 pts.mass potassium titanate, and 30-150 pts.mass silica and has an electrostatic capacity at 100 Hz, when a voltage of 5 V is initially applied to a 2 mm-thick rubber plate and thereafter an alternating current of 100 Hz is applied, of not more than 100 μF and a volume resistivity of not more than 1×10<SP>11</SP>Ω cm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rubber composition for a tire tread and a tire.

  In recent years, demand for low fuel consumption for automobiles has been increasing. Therefore, since the rolling resistance of the rubber material constituting the tread portion having a large tire area greatly affects the fuel efficiency, development of a rubber composition for a tread having a low rolling resistance has been promoted. As a method for reducing rolling resistance, it is a common practice to use silica instead of carbon as a reinforcing agent. Carbon has the property of flowing electricity when blended in large quantities, but silica does not conduct electricity. For this reason, if silica is used as a reinforcing agent, static electricity generated between the tread part of the tire and the ground may cause interference with radio wave reception (radio noise), or generate static electricity when getting on and off the car. This may cause problems such as discomfort caused by fire or cause a fire when refueling.

  Silica has the property of being excellent in rolling resistance and wet skid performance. Therefore, when silica is not used to prevent radio noise and the like, there is a problem that rolling resistance and wet skid performance are poor.

In order to solve such problems, a pneumatic tire is disclosed in Japanese Patent Application Laid-Open No. 8-244409 (Patent Document 1) for the purpose of reducing rolling resistance of a tread portion and improving electrostatic discharge characteristics. The pneumatic tire disclosed in Patent Document 1 is a pneumatic tire in which a conductive thin film having a thickness of 0.5 mm or less is continuously disposed on the tread surface in the circumferential direction of the tire. The resistance is 10 ⁵ Ω · cm or less.

Further, for the purpose of exhibiting excellent fuel efficiency and exhibiting antistatic properties, a rubber composition for tire tread disclosed in Japanese Patent Application Laid-Open No. 2005-171095 (Patent Document 2) is disclosed. The rubber composition for a tire tread disclosed in Patent Document 2 is a rubber composition for a tire tread formed by blending 5 to 100 parts by weight of silica with respect to 100 parts by weight of a crosslinkable polymer, and an applied voltage of 1000 V, The volume resistivity at a temperature of 10 ° C. and a relative humidity of 15% is 10 ^11.0 Ω · cm or less.

However, in the methods of Patent Documents 1 and 2, there is still room for improvement in terms of preventing radio noise from occurring and achieving both high wet skid performance and low rolling resistance at a sufficiently satisfactory level. is there.
JP-A-8-244409 JP 2005-171095 A

  The present invention has been made to solve the above-described problems, and an object of the present invention is to prevent generation of radio noise when used in a tire, maintain high wet skid performance, and maintain low rolling resistance. It is to provide a rubber composition for a tire tread and a tire.

The rubber composition for a tire tread of the present invention is blended with 0.1 to 20 parts by mass of potassium titanate and 30 to 150 parts by mass of silica with respect to 100 parts by mass of the rubber component. The electrostatic capacity is 100 μF or less and the volume resistivity is 1 × 10 ¹¹ Ω · cm or less when an AC voltage of 100 Hz is applied after applying an initial voltage of 5 V to a rubber plate having a thickness of 2 mm. is there.

According to the rubber composition for a tire tread of the present invention, by setting the blending amount of potassium titanate to 0.1 parts by mass or more, a capacitance of 100 μF or less and a volume resistivity of 1 × 10 ¹¹ Ω · cm or less. Can be expressed. When it exceeds 20 mass parts, it will become hard and wet skid performance will fall. In addition, when the capacitance is 100 μF or less and the volume resistivity is 1 × 10 ¹¹ Ω · cm or less, generation of radio noise can be prevented when used for a tire. Further, since radio noise can be reduced, silica can be blended in an amount of 30 to 150 parts by mass. By blending silica in this range, wet skid performance is improved while reducing radio noise when used in a tire. At the same time, low rolling resistance can be maintained. Therefore, when used for a tire, generation of radio noise can be prevented, high wet skid performance can be maintained, and low rolling resistance can be maintained.

  In the tire tread rubber composition, preferably, 30 parts by mass or more and 50 parts by mass or less of silica is blended with respect to 100 parts by mass of the rubber component. When 50 parts by mass of silica is blended, the electrical characteristics are not further affected.

  In the tire tread rubber composition, preferably, carbon black of more than 0 and 25 parts by mass or less is further blended with respect to 100 parts by mass of the rubber component. By incorporating carbon black, processability is improved. By setting the blending amount of carbon black to 25 parts by mass or less, radio noise can be further prevented through reduction of electric resistance.

  In the tire tread rubber composition, the potassium titanate preferably has a tin oxide conductive layer on the surface. Thereby, while being able to make an electrostatic capacitance smaller, volume resistivity can be reduced more.

  The tire according to the present invention is formed by using the rubber composition for a tire tread in a tread portion. By using the tire tread rubber composition in the tread portion where the tire occupies a large area, it is possible to prevent the occurrence of radio noise, maintain high wet skid performance, and maintain a low rolling resistance.

  According to the rubber composition for a tire tread of the present invention, when used for a tire, generation of radio noise can be prevented, high wet skid performance can be maintained, and low rolling resistance can be maintained.

The rubber composition for a tire tread of the present invention is blended with 0.1 to 20 parts by mass of potassium titanate and 30 to 150 parts by mass of silica with respect to 100 parts by mass of the rubber component. The electrostatic capacity is 100 μF or less and the volume resistivity is 1 × 10 ¹¹ Ω · cm or less when an AC voltage of 100 Hz is applied after applying an initial voltage of 5 V to a rubber plate having a thickness of 2 mm. is there.

  Specifically, the electrostatic capacity when an alternating current of 100 Hz is applied after applying an initial voltage of 5 V to a rubber plate having a thickness of 2 mm of the rubber composition for a tire tread is 100 μF or less, preferably 10 μF or more. 90 μF or less, more preferably 30 μF or more and 70 μF or less. When the capacitance exceeds 100 μF, radio noise is generated. Generation of radio noise can be further prevented by setting the capacitance to 90 μF or less. Generation of radio noise can be further prevented by setting the capacitance to 70 μF or less. The smaller the capacitance, the better in terms of preventing the occurrence of radio noise. However, since other compounding agents such as silica are appropriately blended, the capacitance is preferably 10 μF or more.

The volume resistivity of the rubber composition for tire tread is 1 × 10 ¹¹ Ω · cm or less, preferably 1 × 10 ¹ Ω · cm or more and 1 × 10 ^10.5 Ω · cm or less, and more preferably 1 × 10 10 ¹ Ω · cm or more and 1 × 10 ⁷ Ω · cm or less. If the volume resistivity is greater than 1 × 10 ¹¹ Ω · cm, it becomes difficult for current to flow, and radio noise is generated. By setting the volume resistivity to 1 × 10 ^10.5 Ω · cm or less, since it is not easy to conserve electricity, radio noise can be further prevented. By setting the volume resistivity to 1 × 10 ⁷ Ω · cm or less, radio noise can be further prevented. On the other hand, a lower volume resistivity is preferable in that generation of radio noise can be prevented.

  The rubber component used in the rubber composition of the present invention is not particularly limited, but a diene rubber is preferably used from the viewpoint of excellent strength. Examples of the diene rubber include natural rubber (NR), polyisoprene rubber (IR), polybutadiene rubber (BR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber ( IIR), styrene-isoprene-butadiene copolymer rubber (SIBR), ethylene-propylene-diene rubber (EPDM) and the like, and rubber components containing one or more of these are preferred. From the viewpoint of a balance between low rolling resistance and high wet skid performance, it is particularly preferable to use styrene-butadiene rubber (SBR). The ethylene-propylene-diene rubber (EPDM) is an ethylene-propylene rubber (EPM) containing a third diene component. Examples of the third diene component include non-conjugated dienes having 5 to 20 carbon atoms such as 1,4-pentadiene, 1,4-hexadiene, 1,5-hexadiene, and 2,5-dimethyl-1,5. -Hexadiene and 1,4-octadiene, cyclic dienes such as 1,4-cyclohexadiene, cyclooctadiene, dicyclopentadiene, 5-ethylidene-2-norbornene, 5-butylidene-2-norbornene, 2-methallyl-5 Preferred examples include alkenyl norbornene such as -norbornene and 2-isopropenyl-5-norbornene. In particular, dicyclopentadiene, 5-ethylidene-2-norbornene and the like can be preferably used.

Potassium titanate is blended in an amount of 0.1 to 20 parts by mass, preferably 1 to 10 parts by mass, and preferably 2 to 8 parts by mass with respect to 100 parts by mass of the rubber component. More preferably, it is blended. When the blending amount of potassium titanate is less than 0.1 parts by mass, a capacitance of 100 μF or less and a volume resistivity of 1 × 10 ¹¹ Ω · cm or less cannot be expressed, and processability and dispersibility deteriorate. By setting the amount of potassium titanate to 1 part by mass or more, the capacitance and volume resistivity can be further reduced, and the workability and dispersibility can be further improved. By setting the blending amount of potassium titanate to 2 parts by mass or more, capacitance and volume resistivity can be further reduced. On the other hand, when the compounding quantity of potassium titanate exceeds 20 parts by mass, it becomes hard and the wet skid performance deteriorates. Moreover, since radio noise can be reduced by setting the blending amount of potassium titanate to 20 parts by mass or less, a reinforcing agent such as silica capable of improving wet skid performance and maintaining low rolling resistance can be blended. By setting the blending amount of potassium titanate to 10 parts by mass or less, it becomes easy to blend a reinforcing agent capable of improving wet skid performance and maintaining low rolling resistance. By setting the amount of potassium titanate to 8 parts by mass or less, it becomes easier to mix a reinforcing agent that improves wet skid performance and can maintain low rolling resistance. As such a reinforcing agent, for example, silica or the like can be used.

Potassium titanate is represented by the general formula K ₂ O · nTiO ₂ . n is preferably 1, 2, 4, 6, or 8. For example, potassium dititanate (K ₂ Ti ₂ O ₅ ) and potassium tetratitanate (K ₂ Ti ₄ O ₉ ) having a layered structure in which n is 2, 4 or potassium 6 titanate (K ₂ having a tunnel structure). Ti ₆ O ₁₃ ) and potassium potassium titanate (K ₂ Ti ₈ O ₁₇ ) can be used. As the potassium titanate, a white needle crystal having a fiber length of 1 to 30 μm, preferably 1 to 20 μm can be used. When the fiber length is 1 μm or more, it is easy to obtain, and when the fiber length is 30 μm or less, the dispersibility is good.

  In view of availability, potassium titanate preferably has a tin oxide conductive layer on the surface. Such potassium titanate is available, for example, under the trade name “Dentor WK” manufactured by Otsuka Chemical Co., Ltd.

  Silica is blended in an amount of 30 to 150 parts by weight, preferably 30 to 60 parts by weight, and preferably 40 to 50 parts by weight with respect to 100 parts by weight of the rubber component. Is more preferable. When the amount of silica is less than 30 parts by mass, the waist skid performance is poor. The wet skid performance can be improved by blending 30 parts by mass or more of silica. The wet skid performance can be further improved by blending 40 parts by mass or more of silica. On the other hand, when silica exceeding 150 parts by mass is blended, the dispersibility in the rubber component is deteriorated, the processability cannot be improved, and the electrical characteristics are affected. By blending 60 parts by mass or less of silica, the dispersibility into the rubber component is not deteriorated, the processability can be improved, and the electrical characteristics are not affected. By setting it to 50 parts by mass or less, workability can be further improved.

  Silica is not particularly limited, and those generally used for general-purpose rubber can be used. For example, it can be appropriately selected from dry silica, wet silica, etc., but wet silica such as wet white carbon containing hydrous silicic acid as a main component is preferably used. By using wet process silica, silica having a high specific surface area, a primary particle condensation structure, and a high pore volume and adsorption amount can be blended in the rubber composition.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is 20 to 400 m ² / g. Preferably, the nitrogen adsorption specific surface area of silica is 30 to 250 m ² / g. More preferably, the nitrogen adsorption specific surface area of silica is 40 to 120 m ² / g. The silica reinforcing effect can be further obtained by k with N ₂ SA of silica being 20 m ² / g or more. By making N ₂ SA 30 m ² / g or more, a reinforcing effect can be further obtained. By setting N ₂ SA to 40 m ² / g or more, a reinforcing effect can be further obtained. On the other hand, when N ₂ SA is 400 m ² / g or less, the dispersibility of silica is not lowered and the processability is improved. By making N ₂ SA 250 m ² / g or less, workability can be further improved. By making N ₂ SA 120 m ² / g or less, workability can be further improved. The nitrogen adsorption specific surface area is a value measured by the BET method according to ASTM D3037-81.

The rubber composition of the present invention preferably further contains more than 0 and 25 parts by mass or less of carbon black with respect to 100 parts by mass of the rubber component. More preferably, it is blended. When carbon black is blended, conductivity is generally expressed, but the capacitance increases, and wet skid performance and rolling resistance deteriorate. However, when carbon black is blended in the above proportion by blending potassium titanate as in the present invention, the electrostatic capacity can be reduced and the electrical resistance can be lowered. Furthermore, carbon black has the advantage of good workability. The amount of carbon black by 10 weight parts on more than can be improved more workability. On the other hand, when the blending amount of carbon black is 25 parts by mass or less, the deterioration of wet skid performance and rolling resistance can be reduced. By making it 20 parts by mass or less, it is possible to further reduce the deterioration of wet skid and rolling resistance.

The physical properties of carbon black are such that the nitrogen adsorption specific surface area (BET method) is in the range of 70 to 300 m ² / g, the DBP oil absorption is in the range of 5 to 300 ml / 100 g, and the iodine adsorption is in the range of 146 to 152 mg / g. A thing is suitable at the point of the reinforcement effect with respect to a rubber composition.

  In the tire rubber composition of the present invention, the following components generally blended in other rubber products can be blended as appropriate.

  When silica is blended in the rubber composition of the present invention, a silane coupling agent, preferably a sulfur-containing silane coupling agent, may be blended in an amount of 1% by mass or more and 20% by mass or less based on the mass of silica. preferable. By adding a silane coupling agent, the wear resistance and steering stability of the tire can be improved. When the amount of the silane coupling agent is 1% by mass or more, the effect of improving the wear resistance and steering stability is good. Is obtained. Moreover, when the compounding quantity of a silane coupling agent is 20 mass% or less, there is little danger that the rubber | gum kneading | mixing and the burning (scorch) in an extrusion process will arise. As sulfur-containing silane coupling agents, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl-tetrasulfide, trimethoxysilylpropyl-mercaptobenzothiazole tetrasulfide, triethoxysilylpropyl-methacrylate-monosulfide, dimethoxymethyl Examples include silylpropyl-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 addition, for the rubber composition, other fillers such as clay, alumina, talc, calcium carbonate, magnesium carbonate, aluminum hydroxide, magnesium hydroxide, magnesium oxide, and titanium oxide may be used alone or in combination of two or more. Can do.

  In addition to the above, the rubber composition is used in the normal rubber industry such as a vulcanizing agent, a vulcanization accelerator, a softening agent, a plasticizer, an anti-aging agent, a foaming agent, an anti-scorch agent, and a processing aid. The compounding agent to be added can be appropriately blended.

  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, di-t-butylperoxy-diisopropylbenzene, t-butylperoxybenzene, 2,4-dichlorobenzoyl peroxide, 1,1-di- t-butylperoxy-3,3,5-trimethylsiloxane, n-butyl-4,4 And the like can be used di -t- butyl peroxy valerate. Of these, dicumyl peroxide, t-butylperoxybenzene and di-t-butylperoxy-diisopropylbenzene are preferred. Moreover, as a sulfur type vulcanizing agent, sulfur, morpholine disulfide, etc. can be used, for example. Of these, sulfur is preferred.

  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.

  Examples of the sulfenamide system include CBS (N-cyclohexyl-2-benzothiazylsulfenamide), TBBS (Nt-butyl-2-benzothiazylsulfenamide), N, N-dicyclohexyl-2- Examples thereof include sulfenamide compounds such as benzothiazylsulfenamide, N-oxydiethylene-2-benzothiazylsulfenamide, and N, N-diisopropyl-2-benzothiazolesulfenamide.

  Examples of the thiazole type include MBT (2-mercaptobenzothiazole), MBTS (dibenzothiazyl disulfide), sodium salt of 2-mercaptobenzothiazole, zinc salt, copper salt, cyclohexylamine salt, 2- (2,4-dinitro). Phenyl) mercaptobenzothiazole, 2- (2,6-diethyl-4-morpholinothio) benzothiazole and the like.

  Examples of thiurams include TMTD (tetramethyl thiuram disulfide), tetraethyl thiuram disulfide, tetramethyl thiuram monosulfide, dipentamethylene thiuram disulfide, dipentamethylene thiuram monosulfide, dipentamethylene thiuram tetrasulfide, dipentamethylene thiuram hexasulfide. , Tetrabutyl thiuram disulfide, pentamethylene thiuram tetrasulfide and the like.

  Examples of thiourea compounds include thiourea compounds such as thiacarbamide, diethyl thiourea, dibutyl thiourea, trimethyl thiourea, and diortolyl thiourea.

  Examples of guanidine compounds include guanidine compounds such as diphenyl guanidine, diortolyl guanidine, triphenyl guanidine, orthotolyl biguanide, and diphenyl guanidine phthalate.

  Examples of dithiocarbamate include zinc ethylphenyldithiocarbamate, zinc butylphenyldithiocarbamate, sodium dimethyldithiocarbamate, zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, zinc diamyldithiocarbamate, zinc dipropyldithiocarbamate , Complex salt of zinc pentamethylenedithiocarbamate and piperidine, zinc hexadecyl (or octadecyl) isopropyldithiocarbamate, zinc dibenzyldithiocarbamate, sodium diethyldithiocarbamate, piperidine pentamethylenedithiocarbamate, selenium dimethyldithiocarbamate, tellurium diethyldithiocarbamate, diamyl Di, such as cadmium dithiocarbamate Such Okarubamin acid compounds.

  Examples of the aldehyde-amine system or aldehyde-ammonia system include acetaldehyde-aniline reaction product, butyraldehyde-aniline condensate, hexamethylenetetramine, acetaldehyde-ammonia reaction product, and the like.

  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.

  In the present invention, a softener may be used in combination in order to further improve kneading processability. Softeners include process oil, lubricating oil, paraffin, liquid paraffin, petroleum asphalt, petroleum jelly such as petroleum jelly, fatty oil softener such as castor oil, linseed oil, rapeseed oil, coconut oil, tall oil, , Waxes such as beeswax, carnauba wax and lanolin, and fatty acids such as linoleic acid, palmitic acid, stearic acid and lauric acid.

  As plasticizers, DMP (dimethyl phthalate), DEP (diethyl phthalate), DBP (dibutyl phthalate), DHP (diheptyl phthalate), DOP (dioctyl phthalate), DINP (diisononyl phthalate), DIDP (phthalate) Acid diisodecyl), BBP (butyl benzyl phthalate), DLP (dilauryl phthalate), DCHP (dicyclohexyl phthalate), hydrophthalic anhydride, DOZ (di-2-ethylhexyl azelate), DBS (dibutyl sebacate), DOS (Dioctyl sebacate), acetyl triethyl citrate, acetyl tributyl citrate, DBM (dibutyl maleate), DOM (2-ethylhexyl maleate), DBF (dibutyl fumarate) and the like.

  As the scorch preventing agent for preventing or delaying 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 used.

  The rubber composition of the present invention can be produced by a commonly used known method, and is kneaded using a rubber kneading apparatus such as a Banbury mixer or an open roll, and is heated at 140 to 150 ° C. for 25 to 35 minutes, for example. A method of sulfurating can be used.

  Further, when the rubber composition of the present invention is used for the tread portion, for example, the rubber composition is processed into a sheet shape and pasted into a predetermined shape or charged into two or more extruders. It can be produced by a method of forming two layers at the head outlet of the extruder.

  The rubber composition of the present invention can be suitably used for pneumatic tires for passenger cars, buses, trucks, and the like. FIG. 1 is a cross-sectional view showing the right half of a pneumatic tire to which the present invention is applied. In FIG. 1, a tire T includes a pair of bead portions 1, a pair of sidewall portions 2, and a tread portion 3 connected to both sidewall portions, and the bead cores 4 embedded between the pair of bead portions 1. And a belt 6 that reinforces the tread portion 3 on the outer periphery of the carcass 5. The carcass 5 has a carcass main body portion extending between the pair of bead cores 4 and a turn-up portion 5a wound around the bead core 4 from the inner side to the outer side in the tire radial direction. A bead apex 7 extending in the sidewall direction from the upper end of the bead core 4 is disposed in a region surrounded by the carcass 5 and the folded portion 5a. The carcass 5 is made of a ply in which a radial arrangement cord such as a steel cord or an ultrahigh strength organic fiber cord such as aramid is coated with rubber. The rubber composition of the present invention is suitably used for the tread portion 3 of the pneumatic tire having the basic structure as described above.

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

Of the blending components shown in Tables 1 and 2, the components excluding sulfur and the vulcanization accelerator were kneaded at about 150 ° C. for 3 minutes using a 1.7 L Banbury, and further added with sulfur and a vulcanization accelerator. The rubber composition for tire treads of Examples 1 to 7 and Comparative Examples 1 to 4 was obtained by kneading at about 80 ° C. for 4 minutes using an axial roller. Further, the rubber composition for tire tread was formed into a sheet shape, charged into a mold, and press vulcanized at 170 ° C. for an optimum time. The vulcanization time was measured with a curast meter or the like, and was appropriately adjusted with a 95% torque rise time t ₉₅ [minute] as a guide, to obtain a vulcanized rubber slab sheet having a thickness of about 2 mm and a side of 130 mm.

  Below, the various compounding agents used in Examples 1-7 and Comparative Examples 1-4 are demonstrated. In addition, the unit of the compounding quantity in Table 1 is a mass part.

(Note 1) E10 manufactured by Asahi Kasei Co., Ltd. was used as the styrene butadiene rubber.
(Note 2) As potassium titanate, WK300R manufactured by Otsuka Chemical Co., Ltd. was used.
(Note 3) Ultrasil VN3 (N ₂ SA 170 m ² / g) manufactured by Degussa Co. was used as the silica.
(Note 4) Diablack I manufactured by Mitsubishi Chemical Corporation was used as carbon black.
(Note 5) Si75 manufactured by Degussa Co. was used as the silane coupling agent.
(Note 6) As process oil, Diana Process AH-24 manufactured by Idemitsu Kosan Co., Ltd. was used.
(Note 7) As zinc oxide, zinc oxide manufactured by Mitsui Kinzoku Mining Co., Ltd. was used.
(Note 8) As stearic acid, a koji made by Nippon Oil & Fats Co., Ltd. was used.
(Note 9) Antigen 6C manufactured by Sumitomo Chemical Co., Ltd. was used as an anti-aging agent.
(Note 10) As a wax, Sunnock N manufactured by Ouchi Shinsei Chemical Co., Ltd. was used.
(Note 11) As sulfur, powder sulfur manufactured by Karuizawa Sulfur Co., Ltd. was used.
(Note 12) As the vulcanization accelerator CZ, Noxeller CZ manufactured by Ouchi Shinsei Chemical Co., Ltd. was used.
(Note 13) As the vulcanization accelerator DPG, Noxeller D manufactured by Ouchi Shinsei Chemical Co., Ltd. was used.

(Measurement of capacitance)
Using an LCR meter (manufactured by Ando Electric Co., Ltd.), the electrostatic capacity of the vulcanized rubber scrub sheets of Examples 1 to 7 and Comparative Examples 1 to 4 was applied to a rubber plate having a thickness of 2 mm with an initial voltage of 5V. Was measured under the conditions when 100 Hz alternating current was applied. The results are shown in Table 1.

(Measurement of volume resistance)
Vulcanization of Examples 1 to 7 and Comparative Examples 1 to 4 under conditions of normal temperature and normal humidity (23 ° C., relative humidity 55%) using a digital ultrahigh resistance microammeter R-8340A manufactured by Advantest Corporation The volume specific resistance value of the rubber slab sheet was measured. The applied voltage was set to 1000 V, and before measurement, the sample was measured after being acclimated to the measurement atmosphere for 5 hours or more. For other items, the volume resistivity measurement method described in JIS K6911 was followed. The results are shown in Tables 1 and 2.

  Next, a rubber sheet was produced using the rubber composition for tire treads of Examples 1 to 7 and Comparative Examples 1 to 4, and molded as a tread portion of a tire, and 150 ° C., 35 minutes, 25 kgf (245.16625N). Vulcanization was performed under the conditions described above to produce a pneumatic tire having the following specifications with the basic structure shown in FIG.

Carcass: 1670 dtex / 2 polyester (50 ends)
1 piece Cord angle with respect to the circumferential direction 90 °
Belt layer: 2 steel cords (40 ends)
Cord angle with respect to circumferential direction + 20 °, -20 °
Tire size 195 / 65R15
Ends means the number of embedded codes per 5 cm of ply.

(Measurement of rolling resistance)
The test tires of Examples 1 to 7 and Comparative Examples 1 to 4 are mounted on a regular rim (15 × 6JJ), and rolled at an internal pressure of 230 kPa, an speed of 80 kmh, and a load of 3.43 kN using a rolling resistance tester manufactured by STL. Resistance was measured. Tables 1 and 2 show the measured rolling resistance expressed as an index using Comparative Example 1 as 100 (reference). In addition, it is so favorable that an index | exponent is large.

(Measurement of radio noise)
The test tires of Examples 1 to 7 and Comparative Examples 1 to 4 were mounted, and the presence or absence of radio wave interference (radio noise) was confirmed. Tables 1 and 2 show the results regarding the presence or absence of radio noise.

(Measurement of wet skid performance)
The test tires of Examples 1 to 7 and Comparative Examples 1 to 4 were mounted on the front wheels of a passenger car with a standard rim defined by JATMA standard and the maximum air pressure, and the braking distance from a wet asphalt road surface from 100 km / h was measured. The measured braking distance is
(Braking distance of comparative example 1 / braking distance of each example or comparative example) × 100
Table 1 and Table 2 show the results obtained as an index. In addition, it is so favorable that an index | exponent is large.

  As shown in Tables 1 and 2, tires using the tire tread rubber compositions of Examples 1 to 7 are free from radio noise, maintain low rolling resistance, and improve wet skid performance. It was. On the other hand, in the tire using the rubber composition for tire tread of Comparative Example 1 in which potassium titanate was not blended and the capacitance and volume resistance could not be lowered, radio noise was generated. The tire using the rubber composition for a tire tread of Comparative Example 2 in which the compounding amount of potassium titanate was large has deteriorated wet skid performance. The tire using the rubber composition for tire treads of Comparative Example 3 which did not contain potassium titanate and had a high capacitance generated radio noise, had high rolling resistance, and reduced wet skid performance. The tire using the rubber composition for tire treads of Comparative Example 4 in which potassium titanate and silica were not blended had very high rolling resistance and very poor wet skid performance.

As described above, according to the embodiment, 0.1 to 20 parts by mass of potassium titanate and 30 to 150 parts by mass of silica are blended with respect to 100 parts by mass of the rubber component. The electrostatic capacity is 100 μF or less and the volume resistivity is 1 × 10 ¹¹ Ω · cm or less when an AC voltage of 100 Hz is applied after applying an initial voltage of 5 V to a rubber plate having a thickness of 2 mm. It was confirmed that a tire using a rubber composition for a tire tread can prevent generation of radio noise, maintain high wet skid performance, and maintain low rolling resistance.

  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.

It is sectional drawing which shows the right half of the pneumatic tire with which this invention is applied.

Explanation of symbols

  1 bead part, 2 side wall part, 3 tread part, 4 bead core, 5 carcass, 6 belt, 7 bead apex, T tire.

Claims (5)

0.1 to 20 parts by mass of potassium titanate and 30 to 150 parts by mass of silica are blended with respect to 100 parts by mass of the rubber component,
A tire having a capacitance of 100 μF or less and a volume resistivity of 1 × 10 ¹¹ Ω · cm or less when an AC voltage of 100 Hz is applied after applying an initial voltage of 5 V to a rubber plate having a thickness of 2 mm. Tread rubber composition.   The rubber composition for a tire tread according to claim 1, wherein the silica is blended in an amount of 30 to 50 parts by mass with respect to 100 parts by mass of the rubber component.   The rubber composition for tire treads according to claim 1 or 2, wherein carbon black of more than 0 and 25 parts by mass or less is further blended with respect to 100 parts by mass of the rubber component.   The rubber composition for a tire tread according to any one of claims 1 to 3, wherein the potassium titanate has a tin oxide conductive layer on a surface thereof.   The tire which uses the rubber composition for tire treads in any one of Claims 1-4 for a tread part.

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