JP7151243B2 - Rubber composition, pneumatic tire and vulcanized bladder - Google Patents

Description

The present invention relates to rubber compositions, pneumatic tires and vulcanized bladders.

Rubber products such as tires are usually manufactured by kneading materials in a kneader, molding each member with an extruder, and then vulcanizing with a vulcanization mold. Excessive adhesion to the machine or vulcanization mold increases the frequency of product defects and mold contamination.

Various release agents have been studied to suppress the occurrence of excessive adhesion. For example, Patent Document 1 discloses a molten mixture of ω-9 fatty acid amide and calcium stearate.

JP 2017-206583 A

However, as a result of investigation by the present inventors, calcium stearate maintains a granular, spherical or plate-like shape even at high temperatures, but when kneaded in a rubber composition containing oil or resin, the melting point is lowered and the viscosity becomes viscous. As a result, the physical releasability could not be sufficiently improved in some cases.

An object of the present invention is to solve the above problems and to provide a rubber composition excellent in releasability, and a pneumatic tire and a vulcanized bladder produced using the rubber composition.

A first aspect of the present invention contains a rubber component containing a diene rubber, and magnesium oxide having an apparent specific gravity of less than 0.4 g/ml and a particle size of less than 10 µm at 50% of the integrated value in the mass-based particle size distribution curve. and a rubber composition in which the content of the diene rubber is 70% by mass or more in 100% by mass of the rubber component.

The content of the magnesium oxide in the rubber composition is preferably 1 part by mass or less with respect to 100 parts by mass of the rubber component.

The rubber composition preferably contains a filler containing aluminum hydroxide, and the content of the aluminum hydroxide is preferably 8 parts by mass or less with respect to 100 parts by mass of the rubber component.

The rubber composition is more effective when the content of the filler with respect to 100 parts by mass of the rubber component is 100 parts by mass or more.

Preferably, the rubber composition contains paraffin wax, and the content of the paraffin wax is 2.4 parts by mass or less with respect to 100 parts by mass of the rubber component.

The rubber composition is preferably a tire outer layer rubber composition.

The first present invention also relates to a pneumatic tire having a tire outer layer member produced using the tire outer layer rubber composition.

A second aspect of the present invention contains a rubber component containing a butyl-based rubber, and magnesium oxide having an apparent specific gravity of less than 0.3 g/ml and a particle size of less than 3 µm at an integrated value of 50% in a mass-based particle size distribution curve. and a rubber composition in which the content of the butyl-based rubber is 70% by mass or more in 100% by mass of the rubber component.

The rubber composition preferably contains a copolymer of an aromatic hydrocarbon and an aliphatic hydrocarbon.

The rubber composition is preferably a vulcanized bladder rubber composition or an inner liner rubber composition.

The second invention also relates to a vulcanized bladder produced using the rubber composition for a vulcanized bladder.

A second aspect of the present invention also relates to a pneumatic tire having an innerliner produced using the rubber composition for an innerliner.

According to the first aspect of the present invention, a predetermined amount of diene rubber and magnesium oxide having an apparent specific gravity of less than 0.4 g/ml and a particle size of less than 10 μm at an integrated value of 50% in a mass-based particle size distribution curve are contained. Since it is a rubber composition that has a good releasability, it is possible to obtain good releasability.

According to the second aspect of the present invention, a predetermined amount of butyl rubber and magnesium oxide having an apparent specific gravity of less than 0.3 g/ml and a particle size of less than 3 μm at an integrated value of 50% in a mass-based particle size distribution curve are contained. Since it is a rubber composition that has a good releasability, it is possible to obtain good releasability.

A first aspect of the present invention is a rubber containing a predetermined amount of diene rubber and magnesium oxide having an apparent specific gravity of less than 0.4 g/ml and a particle size of less than 10 µm at 50% of the integrated value in the mass-based particle size distribution curve. A composition comprising a predetermined amount of butyl rubber, magnesium oxide having an apparent specific gravity of less than 0.3 g/ml and a particle diameter of less than 3 μm at 50% of the integrated value in a mass-based particle size distribution curve. It is a rubber composition containing

Magnesium oxide is also used as a medicine such as laxatives and antiflatulents, and in the field of rubber, it is used as a vulcanization retarder to suppress scorch. It is considered that this effect is exhibited by keeping the water content in the rubber composition constant due to the water absorption of magnesium oxide, and by keeping the decomposition rate of the vulcanization accelerator constant.

When a vulcanization retarder is added, the initial vulcanization speed (t10) is slowed down, which prolongs the time during which the kneaded product remains in a free-flowing state and increases the outflow of liquid components from the inside of the kneaded product. As a result, the wettability and contact area of the metal micro-roughness increase, and it is usually expected that excessive adhesion to equipment tends to occur, resulting in deterioration of releasability.

However, in the rubber compositions of the first and second aspects of the present invention, the particle size (d50) at the cumulative value of 50% in the particle size distribution curve based on apparent specific gravity and mass is within a specific range. It creates a physical separation between the equipment metal surface and the rubber surface, resulting in better release properties than conventional release agents. This is presumably because the magnesium oxide has water resistance and organic solvent resistance, so that it does not melt and retains its shape even when kneaded in a rubber composition containing oil or resin. .

<First invention>
The rubber composition and the pneumatic tire according to the first invention are described below.

The rubber composition contains a diene rubber. The content of the diene rubber in 100% by mass of the rubber component may be 70% by mass or more, preferably 90% by mass or more, more preferably 95% by mass or more, and may be 100% by mass. .

Examples of diene rubber include styrene butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (natural rubber (NR), isoprene rubber (IR), etc.), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), Butyl rubber (IIR), styrene-isoprene-butadiene copolymer rubber (SIBR) and the like can be mentioned. These may be used individually by 1 type, and may use 2 or more types together. Among them, SBR, BR, NR and IR are preferred, and SBR and BR are more preferred.

The SBR is not particularly limited, and for example, emulsion-polymerized styrene-butadiene rubber (E-SBR), solution-polymerized styrene-butadiene rubber (S-SBR), etc. can be used. As commercially available products, products of Sumitomo Chemical Co., Ltd., JSR Co., Ltd., Asahi Kasei Co., Ltd., Nippon Zeon Co., Ltd., etc. can be used. These may be used individually by 1 type, and may use 2 or more types together.

SBR may be either unmodified SBR or modified SBR.
The modified SBR may be an SBR having a functional group that interacts with a filler such as silica. SBR (end-modified SBR having the above functional group at the end), main chain-modified SBR having the above-mentioned functional group in the main chain, main chain end-modified SBR having the above-mentioned functional group in the main chain and end (for example, the main chain Main chain end-modified SBR having the above functional group and at least one end modified with the above modifier), or modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule, hydroxyl group and terminal-modified SBR into which an epoxy group is introduced.

Examples of the functional groups include amino group, amido group, silyl group, alkoxysilyl group, isocyanate group, imino group, imidazole group, urea group, ether group, carbonyl group, oxycarbonyl group, mercapto group, sulfide group, disulfide group, sulfonyl group, sulfinyl group, thiocarbonyl group, ammonium group, imide group, hydrazo group, azo group, diazo group, carboxyl group, nitrile group, pyridyl group, alkoxy group, hydroxyl group, oxy group, epoxy group and the like. . In addition, these functional groups may have a substituent. Among them, an amino group (preferably an amino group in which the hydrogen atom of the amino group is substituted with an alkyl group having 1 to 6 carbon atoms), an alkoxy group (preferably an alkoxy group having 1 to 6 carbon atoms), an alkoxysilyl group ( An alkoxysilyl group having 1 to 6 carbon atoms is preferred.

（式中、Ｒ^１、Ｒ^２及びＲ^３は、同一又は異なって、アルキル基、アルコキシ基、シリルオキシ基、アセタール基、カルボキシル基（－ＣＯＯＨ）、メルカプト基（－ＳＨ）又はこれらの誘導体を表す。Ｒ^４及びＲ^５は、同一又は異なって、水素原子又はアルキル基を表す。Ｒ^４及びＲ^５は結合して窒素原子と共に環構造を形成してもよい。ｎは整数を表す。） As the modified SBR, an SBR modified with a compound (modifying agent) represented by the following formula is particularly suitable.

(wherein R ¹ , R ² and R ³ are the same or different and represent an alkyl group, alkoxy group, silyloxy group, acetal group, carboxyl group (--COOH), mercapto group (--SH) or derivatives thereof (R ⁴ and R ⁵ are the same or different and represent a hydrogen atom or an alkyl group. R ⁴ and R ⁵ may combine to form a ring structure together with a nitrogen atom. n represents an integer.)

As the modified SBR modified with the compound (modifier) represented by the above formula, among others, the polymerization terminal (active terminal) of solution-polymerized styrene-butadiene rubber (S-SBR) is modified with the compound represented by the above formula. Modified SBR (such as the modified SBR described in JP-A-2010-111753) is preferably used.

R ¹ , R ² and R ³ are preferably alkoxy groups (preferably C 1-8 alkoxy groups, more preferably C 1-4 alkoxy groups). An alkyl group (preferably an alkyl group having 1 to 3 carbon atoms) is suitable for R ⁴ and R ⁵ . n is preferably 1-5, more preferably 2-4, even more preferably 3. Also, when R ⁴ and R ⁵ combine to form a ring structure with a nitrogen atom, it is preferably a 4- to 8-membered ring. The alkoxy group also includes a cycloalkoxy group (cyclohexyloxy group, etc.) and an aryloxy group (phenoxy group, benzyloxy group, etc.).

Specific examples of the modifier include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, methoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, 3-diethylaminopropyltriethoxysilane and the like. Among them, 3-dimethylaminopropyltrimethoxysilane, 3-dimethylaminopropyltriethoxysilane, and 3-diethylaminopropyltrimethoxysilane are preferred. These may be used alone or in combination of two or more.

As modified SBR, modified SBR modified with the following compounds (modifying agents) can also be suitably used. Modifiers include, for example, polyglycidyl ethers of polyhydric alcohols such as ethylene glycol diglycidyl ether, glycerin triglycidyl ether, trimethylolethane triglycidyl ether, trimethylolpropane triglycidyl ether; polyglycidyl ethers of aromatic compounds having a phenol group of; 1,4-diglycidylbenzene, 1,3,5-triglycidylbenzene, polyepoxy compounds such as polyepoxidized liquid polybutadiene; 4,4'-diglycidyl-diphenyl epoxy group-containing tertiary amines such as methylamine and 4,4'-diglycidyl-dibenzylmethylamine; diglycidylaniline, N,N'-diglycidyl-4-glycidyloxyaniline, diglycidylorthotoluidine, tetraglycidylmetaxylenediamine , tetraglycidylaminodiphenylmethane, tetraglycidyl-p-phenylenediamine, diglycidylaminomethylcyclohexane, tetraglycidyl-1,3-bisaminomethylcyclohexane and other diglycidylamino compounds;

amino group-containing acid chlorides such as bis-(1-methylpropyl)carbamic acid chloride, 4-morpholinecarbonyl chloride, 1-pyrrolidinecarbonyl chloride, N,N-dimethylcarbamic acid chloride and N,N-diethylcarbamic acid chloride;1 , 3-bis-(glycidyloxypropyl)-tetramethyldisiloxane, (3-glycidyloxypropyl)-pentamethyldisiloxane and other epoxy group-containing silane compounds;

(trimethylsilyl)[3-(trimethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(triethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(tripropoxysilyl)propyl]sulfide, (trimethylsilyl)[3 -(tributoxysilyl) propyl] sulfide, (trimethylsilyl) [3-(methyldimethoxysilyl) propyl] sulfide, (trimethylsilyl) [3-(methyldiethoxysilyl) propyl] sulfide, (trimethylsilyl) [3-(methyldi sulfide group-containing silane compounds such as propoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldibutoxysilyl)propyl]sulfide;

N-substituted aziridine compounds such as ethyleneimine and propyleneimine; methyltriethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltriethoxy Alkoxysilanes such as silane, N,N-bis(trimethylsilyl)aminoethyltrimethoxysilane, N,N-bis(trimethylsilyl)aminoethyltriethoxysilane; 4-N,N-dimethylaminobenzophenone, 4-N,N- Di-t-butylaminobenzophenone, 4-N,N-diphenylaminobenzophenone, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, 4,4'-bis(diphenylamino ) benzophenone, N,N,N',N'-bis-(tetraethylamino)benzophenone and other (thio)benzophenone compounds having amino groups and/or substituted amino groups; 4-N,N-dimethylaminobenzaldehyde, 4- N,N-diphenylaminobenzaldehyde, 4-N,N-divinylaminobenzaldehyde and other benzaldehyde compounds having amino groups and/or substituted amino groups; N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N- N-substituted pyrrolidones such as phenyl-2-pyrrolidone, Nt-butyl-2-pyrrolidone, N-methyl-5-methyl-2-pyrrolidone, N-methyl-2-piperidone, N-vinyl-2-piperidone, N - N-substituted piperidones such as phenyl-2-piperidone; - N-substituted lactams such as methyl-β-propiolactam and N-phenyl-β-propiolactam;

N,N-bis-(2,3-epoxypropoxy)-aniline, 4,4-methylene-bis-(N,N-glycidylaniline), tris-(2,3-epoxypropyl)-1,3,5 -triazine-2,4,6-triones, N,N-diethylacetamide, N-methylmaleimide, N,N-diethylurea, 1,3-dimethylethyleneurea, 1,3-divinylethyleneurea, 1,3 -diethyl-2-imidazolidinone, 1-methyl-3-ethyl-2-imidazolidinone, 4-N,N-dimethylaminoacetophenone, 4-N,N-diethylaminoacetophenone, 1,3-bis(diphenyl amino)-2-propanone, 1,7-bis(methylethylamino)-4-heptanone and the like.
Modification with the above compound (modifying agent) can be carried out by a known method.

The styrene content of SBR is preferably 5% by mass or more, more preferably 15% by mass or more, and is preferably 60% by mass or less, more preferably 50% by mass or less. Within the above range, the effect tends to be obtained more favorably.
The styrene content of SBR can be measured by ¹ H-NMR measurement.

The vinyl content of SBR is preferably 5% by mass or more, more preferably 15% by mass or more, and is preferably 60% by mass or less, more preferably 45% by mass or less. Within the above range, the effect tends to be obtained more favorably.
The vinyl content (1,2-bonded butadiene unit content) of SBR can be measured by infrared absorption spectrometry.

The glass transition temperature (Tg) of SBR is preferably −100° C. or higher, more preferably −80° C. or higher, and is preferably −20° C. or lower, more preferably −40° C. or lower. Within the above range, the effect tends to be obtained more favorably.
The Tg is a value measured according to JIS-K7121 using a differential scanning calorimeter (Q200) manufactured by TA Instruments Japan under conditions of a temperature increase rate of 10° C./min.

The weight average molecular weight (Mw) of SBR is preferably 400,000 or more, more preferably 600,000 or more, still more preferably 750,000 or more, and preferably 1,500,000 or less, more preferably 1,200,000 or less. Within the above range, the effect tends to be obtained more favorably.
Note that Mw is based on the value measured by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation). can be obtained by standard polystyrene conversion.

When SBR is contained, the content of SBR in 100% by mass of the rubber component is preferably 40% by mass or more, more preferably 60% by mass or more, and still more preferably 80% by mass or more. The upper limit is not particularly limited, and may be 100% by mass when used for high-performance tires (competition tires). Within the above range, the effect tends to be obtained more favorably.

BR is not particularly limited, and examples thereof include BR with a high cis content (high-cis BR), BR containing 1,2-syndiotactic polybutadiene crystals (SPB-containing BR), and butadiene synthesized using a rare earth catalyst. Rubber (rare earth-based BR), tin-modified butadiene rubber modified with a tin compound (tin-modified BR), and other rubbers commonly used in the tire industry can be used. Tin-modified BR is usually BR with low cis content (low-cis BR). BR may be either non-modified BR or modified BR, and modified BR includes modified BR into which the aforementioned functional groups have been introduced. Modified BR may be either low-cis BR or high-cis BR. As commercially available products, products of Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., etc. can be used. These may be used alone or in combination of two or more. From the viewpoint of wear resistance, rare earth BR is preferable.

As the rare earth-based BR, conventionally known ones can be used, for example, rare earth-based catalysts (lanthanum-based rare earth element compounds, organoaluminum compounds, aluminoxanes, halogen-containing compounds, and optionally Lewis base-containing catalysts) are used. Synthesized by Among them, butadiene rubber (Nd-based BR) synthesized using a neodymium-based catalyst using a neodymium (Nd)-containing compound as the lanthanide-based rare earth element compound is preferable.

The cis content of BR is preferably 90% by mass or more, more preferably 95% by mass or more, still more preferably 97% by mass or more, and the upper limit is not particularly limited. Within the above range, the effect tends to be obtained more favorably.
The cis content of BR can be measured by infrared absorption spectroscopy.

The vinyl content of BR is preferably 10% by mass or less, more preferably 5% by mass or less, still more preferably 1% by mass or less, and the lower limit is not particularly limited. Within the above range, the effect tends to be obtained more favorably.
The vinyl content of BR (1,2-bonded butadiene unit content) can be measured by infrared absorption spectrometry.

The glass transition temperature (Tg) of BR is preferably −160° C. or higher, more preferably −130° C. or higher, and is preferably −60° C. or lower, more preferably −90° C. or lower. Within the above range, the effect tends to be obtained more favorably.

When BR is contained, the content of BR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, and is preferably 60% by mass or less, more preferably 40% by mass. % or less, more preferably 20 mass % or less. Within the above range, the effect tends to be obtained more favorably.

The rubber composition contains magnesium oxide having an apparent specific gravity of less than 0.4 g/ml and a particle diameter (d50) of less than 10 μm at 50% integrated value in a mass-based particle size distribution curve.
Commercially available products of the above magnesium oxide include Kyowa Chemical Industry Co., Ltd., Fuji Film Wako Pure Chemical Industries, Ltd., Kishida Chemical Co., Ltd., and the like. These may be used individually by 1 type, and may use 2 or more types together.

The apparent specific gravity of the magnesium oxide may be less than 0.4 g/ml, preferably 0.3 g/ml or less, more preferably 0.25 g/ml or less, and preferably 0.05 g/ml. ml or more, more preferably 0.15 g/ml or more. Within the above range, the effect tends to be obtained more favorably.
The apparent specific gravity of the magnesium oxide is a value obtained by weighing 30 ml of apparent volume into a 50 ml graduated cylinder and calculating from the mass.

The d50 of the magnesium oxide may be less than 10 μm, preferably 4.5 μm or less, more preferably 1.5 μm or less, still more preferably less than 0.75 μm, and preferably 0.05 μm or more, more preferably It is preferably 0.45 μm or more. Within the above range, the effect tends to be obtained more favorably.
The d50 of the magnesium oxide is the particle diameter at 50% of the integrated value in the mass-based particle size distribution curve obtained by the laser diffraction scattering method.

The nitrogen adsorption specific surface area (N ₂ SA) of the magnesium oxide is preferably 100 m ² /g or more, more preferably 115 m ² /g or more, and is preferably 250 m ² /g or less, more preferably 225 m ² / g or less, more preferably 200 m ² /g or less. Within the above range, the effect tends to be obtained more favorably.
The N ₂ SA of magnesium oxide is a value measured by the BET method according to JIS Z8830:2013.

The content of the magnesium oxide is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, still more preferably 0.2 parts by mass or more, and particularly preferably 0 parts by mass with respect to 100 parts by mass of the rubber component. .3 parts by mass or more, preferably 4 parts by mass or less, more preferably 2 parts by mass or less, and even more preferably 1 part by mass or less. Within the above range, the effect tends to be obtained more favorably.

The rubber composition preferably contains a filler. This tends to result in better effects.

Examples of fillers include aluminum hydroxide, magnesium sulfate, carbon black, silica, talc, alumina, clay and mica. These may be used individually by 1 type, and may use 2 or more types together. Among them, aluminum hydroxide, magnesium sulfate, carbon black and silica are preferred, and aluminum hydroxide, carbon black and silica are more preferred.
In addition, in this specification, magnesium oxide is not included in the filler.

The filler content (for example, when using three types of fillers, aluminum hydroxide, carbon black, and silica, the total amount of these) is preferably 80 parts by mass or more, more preferably 80 parts by mass or more, relative to 100 parts by mass of the rubber component. is 85 parts by mass or more, more preferably 90 parts by mass or more, particularly preferably 100 parts by mass or more, and preferably 150 parts by mass or less, more preferably 140 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

Wet grip performance can be improved by including aluminum hydroxide in the rubber composition. In addition, when aluminum hydroxide is used, due to its flatness and orientation, the raw rubber fabric (unvulcanized rubber composition) has a higher smoothness and wettability to the metal surface is improved. Although there is a tendency for the releasability to deteriorate, good releasability can be ensured by using it in combination with the magnesium oxide.
_In addition, in this specification, aluminum hydroxide means Al ₍ OH) ₃ or _Al2O3.3H2O . As commercially available products, products of Sumitomo Chemical Co., Ltd., Showa Denko Co., Ltd., Nabaltec, etc. can be used. These may be used individually by 1 type, and may use 2 or more types together.

The nitrogen adsorption specific surface area (N ₂ SA) of aluminum hydroxide is preferably 5 m ² /g or more, more preferably 7 m ² /g or more, and is preferably 50 m ² /g or less, more preferably 30 m ² / g or less. Within the above range, the effect tends to be obtained more favorably.
The N ₂ SA of aluminum hydroxide is a value measured by the BET method according to JIS Z8830:2013.

When aluminum hydroxide is contained, the content of aluminum hydroxide with respect to 100 parts by mass of the rubber component is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and preferably 20 parts by mass or less, more preferably is 12 parts by mass or less, more preferably 8 parts by mass or less. Within the above range, releasability as well as wet grip performance and abrasion resistance can be obtained in a well-balanced manner.

When the rubber composition contains carbon black, the effect tends to be obtained more favorably.
Examples of carbon black include, but are not limited to, N134, N110, N220, N234, N219, N339, N330, N326, N351, N550 and N762. Commercially available products include Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Co., Ltd., Lion Corporation, Shin Nikka Carbon Co., Ltd., and Columbia Carbon Co., Ltd. can. These may be used alone or in combination of two or more.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 80 m ² /g or more, more preferably 110 m ² /g or more, and is preferably 200 m ² /g or less, more preferably 150 m ² /g. It is below. Within the above range, the effect tends to be obtained more favorably.
The N ₂ SA of carbon black is a value measured according to JIS K6217-2:2001.

When carbon black is contained, the content of carbon black is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and preferably 30 parts by mass or less, or more, relative to 100 parts by mass of the rubber component. Preferably, it is 10 parts by mass or less. Within the above range, the effects of the present invention can be obtained more favorably.

When the rubber composition contains silica, the effect tends to be obtained more favorably.
Examples of silica include dry silica (anhydrous silicic acid) and wet silica (hydrated silicic acid), but wet silica is preferred because it contains many silanol groups. Commercially available products of Evonik Degussa, Rhodia, Tosoh Silica, Solvay Japan, Tokuyama, etc. can be used. These may be used individually by 1 type, and may use 2 or more types together.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 110 m ² /g or more, more preferably 150 m ² /g or more, still more preferably 170 m ² /g or more, and preferably 300 m ² /g or less. , more preferably 280 m ² /g or less. Within the above range, the effect tends to be obtained more favorably.
The nitrogen adsorption specific surface area of silica is a value measured by the BET method according to ASTM D3037-81.

When silica is contained, the content of silica is preferably 50 parts by mass or more, more preferably 80 parts by mass or more, still more preferably 90 parts by mass or more, relative to 100 parts by mass of the rubber component. It is 150 parts by mass or less, more preferably 130 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

When the rubber composition contains silica, it preferably further contains a silane coupling agent. This tends to result in better effects.
The silane coupling agent is not particularly limited, and examples thereof include bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, Bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (2-triethoxysilylethyl) trisulfide, bis (4-trimethoxysilylbutyl) trisulfide, bis ( 3-triethoxysilylpropyl) disulfide, bis(2-triethoxysilylethyl) disulfide, bis(4-triethoxysilylbutyl) disulfide, bis(3-trimethoxysilylpropyl) disulfide, bis(2-trimethoxysilylethyl) ) disulfide, bis(4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3- sulfides such as triethoxysilylpropyl methacrylate monosulfide; 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane; vinyl-based such as methoxysilane; amino-based such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy-based such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. As commercially available products, products of Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., Dow Corning Toray Co., Ltd., etc. can be used. These may be used alone or in combination of two or more.

When a silane coupling agent is contained, the content of the silane coupling agent is preferably 3 parts by mass or more, more preferably 6 parts by mass or more, and preferably 15 parts by mass with respect to 100 parts by mass of silica. Below, more preferably 10 mass parts or less. Within the above range, the effect tends to be obtained more favorably.

The rubber composition preferably contains an adhesive resin. This tends to result in better effects.
Examples of adhesive resins include phenol-based resins, alkylphenol-based resins, terpene-based resins, coumarone-based resins, indene-based resins, coumarone-indene-based resins, styrene-based resins, acrylic-based resins, rosin-based resins, which are commonly used in the tire industry. Aromatic hydrocarbon-based resins such as dicyclopentadiene-based resins (DCPD-based resins), aliphatic hydrocarbon-based resins such as C5-based resins, C8-based resins, C9-based resins, C5/C9-based resins, and hydrogenation of these things, etc. Commercially available products include Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical, Nichinuri Chemical Co., Ltd., Japan. Catalysts, products of JX Nippon Oil & Energy Corporation, Zeon Corporation, Harima Kasei Co., Ltd., Toagosei Co., Ltd., Arakawa Chemical Industry Co., Ltd., Taoka Chemical Industry Co., etc. can be used. These may be used alone or in combination of two or more. Among these, styrene-based resins and terpene-based resins are preferred.

Styrene-based resins are polymers containing styrene-based monomers (styrene-based compounds) as constituent monomers, and include polymers obtained by polymerizing styrene-based monomers as main components (50% by mass or more). Specifically, styrene monomers (styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, etc.), copolymers obtained by copolymerizing two or more styrenic monomers, styrenic monomers and these Copolymers with other monomers that can be copolymerized with, hydrogenated products thereof, and the like can be used. These may be used individually by 1 type, and may use 2 or more types together.

Other monomers include acrylonitriles such as acrylonitrile and methacrylonitrile, acrylics, unsaturated carboxylic acids such as methacrylic acid, unsaturated carboxylic acid esters such as methyl acrylate and methyl methacrylate, terpenes, chloroprene, Conjugated dienes such as butadiene isoprene; olefins such as 1-butene and 1-pentene; α,β-unsaturated carboxylic acids such as maleic anhydride and acid anhydrides thereof; These may be used individually by 1 type, and may use 2 or more types together.

The styrene resin is preferably an α-methylstyrene resin (α-methylstyrene homopolymer, copolymer of α-methylstyrene and styrene, etc.) because it tends to provide better effects. A copolymer of α-methylstyrene and styrene is more preferred.

The softening point of the styrene-based resin is preferably 50°C or higher, more preferably 80°C or higher, and preferably 120°C or lower, more preferably 100°C or lower. Within the above range, the effect tends to be obtained more favorably.
In the present invention, the softening point is the temperature at which a ball descends when the softening point specified in JIS K 6220-1:2001 is measured with a ring and ball type softening point measuring device.

A terpene-based resin is a polymer containing a terpene-based compound (terpene-based monomer) as a constituent monomer, and examples thereof include a polymer obtained by polymerizing a terpene-based compound as a main component (50% by mass or more). Specifically, a polyterpene resin obtained by polymerizing a terpene-based compound, an aromatic-modified terpene resin obtained by polymerizing a terpene-based compound and an aromatic compound, and hydrogenated products thereof can be used. These may be used individually by 1 type, and may use 2 or more types together.

The terpene compounds are hydrocarbons represented by the composition _{( C5H8} ) _n and oxygen-containing derivatives thereof, such as monoterpene _{( C10H16} ), sesquiterpene ( _C15H24 ), diterpene _{( C20H} ), ₃₂ ), etc., which are compounds having a terpene as a basic skeleton, such as α-pinene, β-pinene, dipentene, limonene, myrcene, alloocimene, ocimene, α-phellandrene, α-terpinene, γ-terpinene, terpinolene, 1,8-cineol, 1,4-cineole, α-terpineol, β-terpineol, γ-terpineol and the like. These may be used individually by 1 type, and may use 2 or more types together.

Examples of aromatic compounds used in the aromatic modified terpene resin include phenolic compounds and styrene compounds. These may be used individually by 1 type, and may use 2 or more types together.

Polyterpene resins and aromatic modified terpene resins (especially copolymers of terpene compounds and styrene compounds) are preferred as terpene resins because they tend to provide better effects.

The softening point of the terpene resin is preferably 90° C. or higher, more preferably 120° C. or higher, and preferably 160° C. or lower, more preferably 140° C. or lower. Within the above range, the effect tends to be obtained more favorably.

When containing a styrene resin and/or a terpene resin, the content thereof is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and preferably 30 parts by mass with respect to 100 parts by mass of the rubber component. It is not more than 20 parts by mass, more preferably not more than 20 parts by mass. Within the above range, the effect tends to be obtained more favorably.

The rubber composition preferably contains wax.
The wax is not particularly limited, and includes petroleum waxes such as paraffin wax and microcrystalline wax; natural waxes such as plant waxes and animal waxes; synthetic waxes such as polymers of ethylene and propylene. As commercially available products, products of Ouchi Shinko Kagaku Kogyo Co., Ltd., Nippon Seiro Co., Ltd., Seiko Kagaku Co., Ltd., etc. can be used. These may be used individually by 1 type, and may use 2 or more types together. Among them, paraffin wax is preferable from the viewpoint of the ozone resistance of the rubber composition. When paraffin wax is used, it forms a physical film, which tends to improve ozone resistance, but tends to reduce mold releasability and wet grip performance. By blending aluminum hydroxide according to , it is possible to ensure good releasability and wet grip performance even when paraffin wax is used.
In addition, microcrystalline wax is preferable because it has a small effect of improving ozone resistance, but is excellent in the effect of improving releasability.

When wax is contained, the wax content is preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, and preferably 2.6 parts by mass with respect to 100 parts by mass of the rubber component. parts or less, more preferably 2.4 parts by mass or less, and even more preferably 1.2 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

The rubber composition may contain oil.
Oils include, for example, process oils, vegetable oils, or mixtures thereof. As the process oil, for example, paraffinic process oil, aromatic process oil, naphthenic process oil, or the like can be used. Vegetable oils include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice bran oil, safflower oil, sesame oil, Olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, tung oil and the like. These may be used alone or in combination of two or more.

When oil is contained, the content of the oil is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and preferably 60 parts by mass or less, more preferably 100 parts by mass of the rubber component. It is 50 parts by mass or less.

The rubber composition may contain an antioxidant.
Examples of anti-aging agents include naphthylamine-based anti-aging agents such as phenyl-α-naphthylamine; diphenylamine-based anti-aging agents such as octylated diphenylamine and 4,4′-bis(α,α′-dimethylbenzyl)diphenylamine; -Isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, etc. p-phenylenediamine-based antioxidants; quinoline-based antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; 2,6-di-t-butyl-4-methylphenol, monophenolic anti-aging agents such as styrenated phenol; inhibitors and the like. As commercially available products, products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Kagaku Kogyo Co., Ltd., Flexis, etc. can be used. These may be used individually by 1 type, and may use 2 or more types together. Among them, p-phenylenediamine antioxidants and quinoline antioxidants are preferred.

When an anti-aging agent is contained, the content of the anti-aging agent is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and preferably 10 parts by mass or less with respect to 100 parts by mass of the rubber component. , more preferably 8 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

The rubber composition may contain fatty acids, especially stearic acid.
As the stearic acid, conventionally known ones can be used, and commercially available products include NOF Corporation, NOF Corporation, Kao Corporation, Fuji Film Wako Pure Chemical Industries, Ltd., Chiba Fatty Acids Co., Ltd., and the like. Available. These may be used individually by 1 type, and may use 2 or more types together.

When stearic acid is contained, the content of stearic acid is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and preferably 10 parts by mass or less, or more, relative to 100 parts by mass of the rubber component. It is preferably 5 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

The rubber composition may contain zinc oxide.
As zinc oxide, conventionally known ones can be used, and commercially available products are available from Mitsui Kinzoku Mining Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd. etc. products can be used. These may be used individually by 1 type, and may use 2 or more types together.

When zinc oxide is contained, the content of zinc oxide is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and preferably 10 parts by mass or less, or more, relative to 100 parts by mass of the rubber component. It is preferably 5 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

The rubber composition may contain sulfur.
Sulfur includes powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur and the like commonly used in the rubber industry. As commercially available products, products of Tsurumi Chemical Industry Co., Ltd., Karuizawa Io Co., Ltd., Shikoku Kasei Kogyo Co., Ltd., Flexis Co., Ltd., Nippon Kantan Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. can be used. These may be used alone or in combination of two or more.

When sulfur is contained, the content of sulfur is preferably 0.6 parts by mass or more, more preferably 1 part by mass or more, and preferably 5 parts by mass or less, or more, relative to 100 parts by mass of the rubber component. Preferably, it is 3 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

The rubber composition may contain a vulcanization accelerator.
Vulcanization accelerators include thiazole vulcanization accelerators such as 2-mercaptobenzothiazole and di-2-benzothiazolyl disulfide; tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), tetrakis (2 -ethylhexyl) thiuram-based vulcanization accelerators such as thiuram disulfide (TOT-N); N-cyclohexyl-2-benzothiazolylsulfenamide, Nt-butyl-2-benzothiazolylsulfenamide, N-oxy Sulfenamide-based vulcanization accelerators such as ethylene-2-benzothiazolesulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N,N'-diisopropyl-2-benzothiazolesulfenamide; diphenylguanidine , diototolylguanidine and orthotolylbiguanidine. As commercially available products, products of Sumitomo Chemical Co., Ltd., Ouchi Shinko Kagaku Kogyo Co., Ltd., etc. can be used. These may be used alone or in combination of two or more. Among them, sulfenamide-based vulcanization accelerators and guanidine-based vulcanization accelerators are preferred.

When a vulcanization accelerator is contained, the content of the vulcanization accelerator is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and preferably 10 parts by mass with respect to 100 parts by mass of the rubber component. parts or less, more preferably 8 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

In addition to the above components, the rubber composition may further contain additives commonly used in the tire industry, such as organic peroxides. The content of the additive is preferably 0.1 to 200 parts by mass with respect to 100 parts by mass of the rubber component.

The above rubber composition can be produced, for example, by kneading each of the above components using a rubber kneading apparatus such as an open roll mixer or a Banbury mixer, followed by vulcanization.

As for the kneading conditions, the kneading temperature is usually 100 to 180°C, preferably 120 to 170°C in the base kneading step in which additives other than the vulcanizing agent and the vulcanization accelerator are kneaded. In the finishing kneading step of kneading the vulcanizing agent and the vulcanization accelerator, the kneading temperature is usually 120°C or lower, preferably 85 to 110°C. A composition obtained by kneading a vulcanizing agent and a vulcanization accelerator is usually subjected to vulcanization treatment such as press vulcanization. The vulcanization temperature is generally 140-200°C, preferably 150-195°C. Vulcanization time is usually 5 to 15 minutes.

The rubber composition can be suitably used for tire outer layer members such as treads, sidewalls, clinches and wings, and is particularly suitable for treads (cap treads).

A pneumatic tire according to the first aspect of the present invention is manufactured by a conventional method using the above rubber composition.
That is, the rubber composition is extruded according to the shape of the tread or the like in an unvulcanized stage, and molded together with other tire members on a tire molding machine by a conventional method to obtain an unvulcanized tire. to form A tire is obtained by heating and pressurizing this unvulcanized tire in a vulcanizer.

The pneumatic tire can be used for passenger car tires, truck and bus tires, motorcycle tires, high-performance tires, etc., and is particularly suitable for passenger car tires and high-performance tires (racing tires).

<Second invention>
The rubber composition, vulcanized bladder and pneumatic tire according to the second aspect of the present invention are described below.

The rubber composition includes butyl rubber. The content of the butyl rubber in 100% by mass of the rubber component may be 70% by mass or more, preferably 90% by mass or more, more preferably 95% by mass or more, and may be 100% by mass. .

The butyl rubber includes halogenated butyl rubber (X-IIR) such as brominated butyl rubber (BR-IIR), chlorinated butyl rubber (Cl-IIR), butyl rubber (IIR), and copolymers of isobutylene and p-alkylstyrene. , halides of the copolymer, and the like. As commercially available products, products of ExxonMobil, JSR Corporation, Japan Butyl Co., etc. can be used. These may be used alone or in combination of two or more. Among them, for inner liners, halogenated butyl rubber is preferable, and brominated butyl rubber is more preferable. In the rubber composition for vulcanized bladders, a combined use of butyl rubber and chloroprene rubber, which is a diene rubber, or a copolymer of isobutylene and p-alkylstyrene is preferred.

The rubber composition contains magnesium oxide having an apparent specific gravity of less than 0.3 g/ml and a particle diameter (d50) of less than 3 μm at 50% integrated value in a mass-based particle size distribution curve.
Commercially available products of the above magnesium oxide include Kyowa Chemical Industry Co., Ltd., Fuji Film Wako Pure Chemical Industries, Ltd., Kishida Chemical Co., Ltd., and the like. These may be used individually by 1 type, and may use 2 or more types together.

The apparent specific gravity of the magnesium oxide may be less than 0.3 g/ml, preferably less than 0.25 g/ml, more preferably 0.05 g/ml or more, more preferably 0.15 g/ml. That's it. Within the above range, the effect tends to be obtained more favorably.
The apparent specific gravity of the magnesium oxide is a value obtained by weighing 30 ml of apparent volume into a 50 ml graduated cylinder and calculating from the mass.

The d50 of the magnesium oxide may be less than 3 μm, preferably less than 1.5 μm, more preferably less than 0.75 μm, and preferably 0.05 μm or more, more preferably 0.45 μm or more. . Within the above range, the effect tends to be obtained more favorably.
The d50 of the magnesium oxide is the particle diameter at 50% of the integrated value in the mass-based particle size distribution curve obtained by the laser diffraction scattering method.

The nitrogen adsorption specific surface area (N ₂ SA) of the magnesium oxide is preferably 100 m ² /g or more, more preferably 115 m ² /g or more, and is preferably 250 m ² /g or less, more preferably 225 m ² / g or less, more preferably 200 m ² /g or less. Within the above range, the effect tends to be obtained more favorably.
The N ₂ SA of magnesium oxide is a value measured by the BET method according to JIS Z8830:2013.

The content of the magnesium oxide is preferably 0.01 parts by mass or more, more preferably 0.2 parts by mass or more, and still more preferably 0.3 parts by mass or more with respect to 100 parts by mass of the rubber component, and It is preferably 4 parts by mass or less, more preferably 2 parts by mass or less, and even more preferably 1 part by mass or less. Within the above range, the effect tends to be obtained more favorably.

The rubber composition preferably contains a copolymer of an aromatic hydrocarbon and an aliphatic hydrocarbon. As a result, good air barrier properties (pneumatic pressure retention properties) can be obtained.
The above copolymer is a polymer (resin) containing aromatic hydrocarbons such as styrene and aliphatic hydrocarbons such as ethylene and propylene as constituent monomers. products can be used. These may be used individually by 1 type, and may use 2 or more types together. Among them, a resin containing ethylene, propylene and styrene as constituent monomers (ethylene-propylene-styrene copolymer) is preferable.

The softening point of the copolymer is preferably 20° C. or higher, more preferably 40° C. or higher, still more preferably 60° C. or higher, and preferably 140° C. or lower, more preferably 100° C. or lower. Within the above range, the effect tends to be obtained more favorably.

When the copolymer is an ethylene-propylene-styrene copolymer, the ethylene-propylene content (EP content) in 100% by mass of the ethylene-propylene-styrene copolymer is preferably 70% by mass or more, more preferably 80% by mass. % or more, preferably 98 mass % or less, more preferably 95 mass % or less. Within the above range, the effect tends to be obtained more favorably.

When the above copolymer is contained, the content of the ethylene propylene styrene copolymer is preferably 1 part by mass or more, more preferably 5 parts by mass or more, relative to 100 parts by mass of the rubber component. 20 parts by mass or less, more preferably 10 parts by mass or less. Within the above range, the effects of the present invention can be obtained more favorably.

The rubber composition may contain carbon black.
As the carbon black, the same carbon black as in the first invention can be used.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 15 m ² /g or more, more preferably 30 m ² /g or more, and preferably 100 m ² /g or less, more preferably 50 m ² /g. It is below. Within the above range, the effect tends to be obtained more favorably.

When carbon black is contained, the content of carbon black is preferably 30 parts by mass or more, more preferably 50 parts by mass or more, and preferably 100 parts by mass or less, with respect to 100 parts by mass of the rubber component. Preferably, it is 80 parts by mass or less. Within the above range, the effects of the present invention can be obtained more favorably.

The rubber composition may contain oil.
As the oil, the same oil as in the first invention can be used.

When oil is contained, the content of oil is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and preferably 30 parts by mass or less, more preferably 100 parts by mass of the rubber component. It is 15 parts by mass or less.

The rubber composition may contain an antioxidant.
As the anti-aging agent, the same anti-aging agent as in the first aspect of the present invention can be used, but a quinoline-based anti-aging agent is preferred.

When an anti-aging agent is contained, the content of the anti-aging agent is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and preferably 10 parts by mass with respect to 100 parts by mass of the rubber component. parts or less, more preferably 5 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

The rubber composition may contain fatty acids, especially stearic acid.
As the stearic acid, the same stearic acid as used in the first aspect of the present invention can be used.

When stearic acid is contained, the content of stearic acid is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and preferably 10 parts by mass or less with respect to 100 parts by mass of the rubber component. , more preferably 5 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

The rubber composition may contain zinc oxide.
As zinc oxide, the same one as in the first invention can be used.

When zinc oxide is contained, the content of zinc oxide is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and preferably 10 parts by mass or less with respect to 100 parts by mass of the rubber component. , more preferably 5 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

The rubber composition may contain sulfur.
As sulfur, the same sulfur as in the first invention can be used.

When sulfur is contained, the content of sulfur is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and preferably 5 parts by mass or less with respect to 100 parts by mass of the rubber component. , more preferably 3 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

The rubber composition may contain a vulcanization accelerator.
As the vulcanization accelerator, the same one as in the first invention can be used, but a thiazole-based vulcanization accelerator is preferred.

When a vulcanization accelerator is contained, the content of the vulcanization accelerator is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, relative to 100 parts by mass of the rubber component. It is 10 parts by mass or less, more preferably 5 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

In addition to the above components, the rubber composition contains additives commonly used in the tire industry, such as organic peroxides, silica, carbon black, graphite, calcium carbonate, aluminum hydroxide, alumina, zirconium, Zirconium oxide, magnesium sulfate, etc. may be further blended. The content of the additive is preferably 0.1 to 200 parts by mass with respect to 100 parts by mass of the rubber component. The content of the filler is preferably 30 to 100 parts by mass with respect to 100 parts by mass of the rubber component.

The above rubber composition can be produced, for example, by kneading each of the above components using a rubber kneading apparatus such as an open roll mixer or a Banbury mixer, followed by vulcanization.

As for the kneading conditions, the kneading temperature is usually 100 to 180°C, preferably 120 to 170°C in the base kneading step in which additives other than the vulcanizing agent and the vulcanization accelerator are kneaded. In the finishing kneading step of kneading the vulcanizing agent and the vulcanization accelerator, the kneading temperature is usually 120°C or lower, preferably 85 to 110°C. A composition obtained by kneading a vulcanizing agent and a vulcanization accelerator is usually subjected to vulcanization treatment such as press vulcanization. The vulcanization temperature is generally 140-200°C, preferably 150-195°C. Vulcanization time is usually 5 to 15 minutes.

The rubber composition can be suitably used for vulcanized bladders or innerliners.

A vulcanized bladder according to the second aspect of the present invention is produced by a conventional method using the above rubber composition. That is, the above rubber composition is molded into a rod shape in an unvulcanized stage, then jointed at both ends to form a ring shape in a vulcanizer, and heated and pressurized to obtain a vulcanized bladder.

A pneumatic tire according to the second aspect of the present invention is manufactured by a conventional method using the above rubber composition.
That is, the rubber composition is processed into a sheet for use as an inner liner in an unvulcanized stage, and is molded together with other tire members on a tire molding machine by a conventional method to obtain an unvulcanized tire. Form. A tire is obtained by heating and pressurizing this unvulcanized tire in a vulcanizer.

The pneumatic tire can be used for passenger car tires, truck and bus tires, motorcycle tires, high-performance tires, etc., and is particularly suitable for passenger car tires.

EXAMPLES The present invention will be specifically described based on Examples, but the present invention is not limited to these.

Various chemicals used in the examples and comparative examples according to the first invention will be collectively described below.
<SBR1>
Nippon Zeon Co., Ltd. N9548 (E-SBR, oil extended (containing 37.5 parts by mass of oil content per 100 parts by mass of rubber solids), styrene content: 35 mass%, vinyl content: 18 mass%, Tg : -40°C, Mw: 1,090,000)
<SBR2>
Nippon Zeon Co., Ltd. NS612 (S-SBR, non-oil extended, styrene content: 15% by mass, vinyl content: 30% by mass, Tg: -65 ° C., Mw: 780,000)
<BR>
CB25 manufactured by Lanxess Corporation (BR synthesized using an Nd-based catalyst (Nd-based BR), cis content: 97% by mass, vinyl content: 0.7% by mass, Tg: -110 ° C.)
<Carbon Black N220>
Show Black N220 (N ₂ SA: 114 m ² /g) manufactured by Cabot Japan Co., Ltd.
<Silica 1>
Ultrasil VN3 (N ₂ SA: 175 m ² /g) manufactured by Evonik Degussa
<Silica 2>
Rhodia Z115Gr (N ₂ SA: 115 m ² /g)
<Aluminum hydroxide>
Apyral 200SM (N ₂ SA: 15 m ² /g) manufactured by Nabaltec
<Silane coupling agent>
Si75 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Evonik Degussa
<α-methylstyrene resin>
Arizona Chemical Co. Sylvatraxx 4401 (a copolymer of α-methylstyrene and styrene, softening point: 85 ° C.)
<Aromatic modified terpene resin>
Yasuhara Chemical Co., Ltd. YS resin TO125 (a copolymer of styrene and a terpene compound, softening point: 125 ° C.)
<Oil 1>
Diana Process AH-24 (aromatic process oil) manufactured by Idemitsu Kosan Co., Ltd.
<MgO release agent 1>
Kyowamag 150 (magnesium oxide, apparent specific gravity 0.36 g/ml, d50: 4.46 μm, N ₂ SA: 145 m ² /g) manufactured by Kyowa Chemical Industry Co., Ltd.
<MgO release agent 2>
Kyowamag 150MF (magnesium oxide, apparent specific gravity 0.23 g/ml, d50: 0.72 μm, N ₂ SA: 119 m ² /g) manufactured by Kyowa Chemical Industry Co., Ltd.
<MgO release agent 3>
Kyowa Chemical Industry Co., Ltd. prototype (magnesium oxide, apparent specific gravity 0.33 g / ml, d50: 10 μm)
<MgO release agent 4>
Prototype manufactured by Kyowa Chemical Industry Co., Ltd. (magnesium oxide, apparent specific gravity 2.4 g / ml, d50: 4 μm)
<Comparison release agent 1>
Prototype manufactured by NOF Corporation (calcium stearate)
<Comparative release agent 2>
Prototype manufactured by NOF Corporation (zinc stearate)
<Comparative release agent 3>
EF44 (fatty acid zinc) manufactured by Structol
<Comparative release agent 4>
Structol WB16 (mixture of fatty acid calcium, fatty acid amide and fatty acid amide ester)
<Stearic acid>
NOF Co., Ltd. stearic acid "Tsubaki"
<Anti-aging agent 6PPD>
Antigen 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd.
<Anti-aging agent TMQ>
Nocrac 224 (2,2,4-trimethyl-1,2-dihydroquinoline polymer) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
<Paraffin wax>
Ozoace0355 manufactured by Nippon Seiro Co., Ltd.
<Zinc oxide>
Two types of zinc oxide <sulfur> manufactured by Mitsui Mining & Smelting Co., Ltd.
Hosoi Chemical Co., Ltd. HK-200-5 (powder sulfur containing 5% oil)
<Vulcanization accelerator TBBS>
Noccellar CZ (N-cyclohexyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
<Vulcanization accelerator DPG>
Noccellar D (diphenylguanidine) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.

<Examples and Comparative Examples>
According to the compounding recipe shown in Table 1, using a 1.7 L Banbury mixer manufactured by Kobe Steel, Ltd., chemicals other than sulfur, vulcanization accelerators and release agents were kneaded at 150°C for 5 minutes. , to obtain a kneaded product. Next, sulfur, a vulcanization accelerator and a release agent were added to the resulting kneaded material, and kneaded for 5 minutes at 80°C using an open roll to obtain an unvulcanized rubber composition.
The obtained unvulcanized rubber composition was rolled into a sheet having a thickness of 2 mm with a roll and press vulcanized at 170° C. for 10 minutes to obtain a vulcanized rubber composition.
In addition, the obtained unvulcanized rubber composition was molded into the shape of a cap tread, laminated together with other tire members to prepare an unvulcanized tire, and vulcanized for 10 minutes under conditions of 170 ° C. for testing. A tire (size: 205/65R15) was obtained.

The obtained vulcanized rubber compositions and test tires were evaluated as follows. Table 1 shows the results.

<Minor defect rate>
Vulcanized rubber composition is visually inspected for visual appearance, and those with rubber chipping, blisters (foaming), bare (keloids), gauge unevenness, or extreme dents are considered minor defects, and those without any of these are considered good. Then, the occurrence rate of minor defects (minor defect rate) was calculated. The results were indexed according to the following evaluation criteria. The larger the index, the more suppressed the occurrence of slight defect rate due to excessive adhesion to the mold, indicating that the releasability is excellent. An index of 105 or more was judged to be good.
[Evaluation criteria (index)]
120: Minor defect rate 0.5%
100: Minor defect rate 1.0%
80: Minor defect rate 2.0%

<Abrasion resistance>
The test tire was mounted on a 2000 cc domestically produced FR vehicle, and the actual vehicle was run on a dry asphalt test course. The vehicle mounting positions of the control tire and the test tire were exchanged every 1000 km, and the vehicle running factors to wear were averaged. After running 30,000 km, the remaining groove amount of the tire tread rubber of the test tire was measured (8.0 mm when new), and indicated as an index with Comparative Example 1-1 being 100. The larger the index, the smaller the amount of worn rubber and the better the wear resistance. An index of 100 or more was judged to be good.

<Wet grip performance>
The test tires were mounted on a 2000 cc domestically produced FR vehicle, and the actual vehicle was driven 10 laps on a wet asphalt test course. At that time, the stability of control during steering was sensory evaluated by a test driver, and was indexed with Comparative Example 1-1 being 100. A larger index indicates better wet grip performance.

From Table 1, examples containing a predetermined amount of diene rubber and magnesium oxide having an apparent specific gravity of less than 0.4 g/ml and a d50 of less than 10 μm (MgO release agents 1 and 2) are conventional release agents. Compared to Comparative Examples 1-1, 1-4, 1-5, and 1-6 using agents (comparative release agents 1 to 4), the release property is improved, and the wear resistance and wet grip performance are also good. Met.

Comparative Example 1-2 using magnesium oxide (MgO release agent 3) with a d50 of 10 μm and Comparative Example 1-3 using magnesium oxide (MgO release agent 4) with an apparent specific gravity of 2.4 g/ml , the releasability index was less than the target value.

Various chemicals used in Examples and Comparative Examples according to the second aspect of the present invention will be collectively described below.
<Brominated butyl rubber>
Bromobutyl 2255 from ExxonMobil
<Carbon Black N660>
Show Black N660 (N ₂ SA: 35 m ² /g) manufactured by Cabot Japan Co., Ltd.
<Anti-aging agent TMQ>
Nocrac 224 (2,2,4-trimethyl-1,2-dihydroquinoline polymer) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
<Stearic acid>
NOF Co., Ltd. stearic acid "Tsubaki"
<Oil 2>
Diana Process PA32 (paraffin-based process oil) manufactured by Idemitsu Kosan Co., Ltd.
<Ethylene Propylene Styrene Copolymer>
Structol 40MS manufactured by Structol (softening point 78 ° C., EP content: 82% by mass)
<Sulfur>
Hosoi Chemical Co., Ltd. HK-200-5 (powder sulfur containing 5% oil)
<Vulcanization accelerator MBTS>
Noxceler DM (di-2-benzothiazolyl disulfide) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
<Zinc oxide>
Two types of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. <Comparative release agent 4>
Structol WB16 (mixture of fatty acid metal salt (fatty acid calcium, constituent fatty acid: saturated fatty acid having 14 to 20 carbon atoms) and fatty acid amide)
<MgO release agent 1>
Kyowamag 150 (magnesium oxide, apparent specific gravity 0.36 g/ml, d50: 4.46 μm, N ₂ SA: 145 m ² /g) manufactured by Kyowa Chemical Industry Co., Ltd.
<MgO release agent 2>
Kyowamag 150MF (magnesium oxide, apparent specific gravity 0.23 g/ml, d50: 0.72 μm, N ₂ SA: 119 m ² /g) manufactured by Kyowa Chemical Industry Co., Ltd.

<Examples and Comparative Examples>
According to the compounding recipe shown in Table 2, using a 1.7 L Banbury mixer manufactured by Kobe Steel, Ltd., chemicals other than sulfur, vulcanization accelerator, zinc oxide and release agent were mixed at 150° C. for 5 minutes. The mixture was kneaded to obtain a kneaded product. Next, sulfur, a vulcanization accelerator, zinc oxide and a release agent are added to the resulting kneaded product, and kneaded for 5 minutes at 80° C. using an open roll to obtain an unvulcanized rubber composition. Obtained.
The obtained unvulcanized rubber composition was rolled into a sheet having a thickness of 2 mm with a roll and press vulcanized at 170° C. for 10 minutes to obtain a vulcanized rubber composition.

The obtained vulcanized rubber composition was evaluated as follows. Table 2 shows the results.

<Minor defect rate>
Vulcanized rubber composition is visually inspected for visual appearance, and those with rubber chipping, blisters (foaming), bare (keloids), gauge unevenness, or extreme dents are considered minor defects, and those without any of these are considered good. Then, the occurrence rate of minor defects (minor defect rate) was calculated. The results were indexed according to the following evaluation criteria. The larger the index, the more suppressed the occurrence of slight defect rate due to excessive adhesion to the mold, indicating that the releasability is excellent. When the index was 110 or more, it was judged to be good.
[Evaluation criteria (index)]
120: Minor defect rate 0.5%
100: Minor defect rate 1.0%
80: Minor defect rate 2.0%

<Air barrier property>
The amount of air permeation of the vulcanized rubber composition was measured according to the ASTM D-1434-75M method, and expressed as an index with Comparative Example 2-1 as 100 according to the following formula. The larger the index, the smaller the amount of air permeation and the better the air barrier property (air pressure retention property). When the index was 103 or more, it was judged to be good.
(Air barrier index) = (air permeation amount of Comparative Example 2-1) / (air permeation amount of each formulation) x 100

From Table 2, examples containing a predetermined amount of butyl rubber and magnesium oxide (MgO release agent 2) having an apparent specific gravity of less than 0.3 g/ml and a d50 of less than 3 μm are similar to conventional release agents ( Comparative Example 2-1 using comparative release agent 4) and Comparative Examples 2-2 and 2 using magnesium oxide (MgO release agent 1) having an apparent specific gravity of 0.36 g/ml and a d50 of 4.46 μm As compared with -3, the releasability was improved, and the air barrier property was also good.

Claims (7)

A rubber component containing a diene rubber and magnesium oxide having an apparent specific gravity of less than 0.4 g/ml and a particle size of less than 10 μm at an integrated value of 50% in a mass-based particle size distribution curve,
The diene rubber includes styrene-butadiene rubber and butadiene rubber,
A rubber composition in which the content of the diene rubber is 70% by mass or more in 100% by mass of the rubber component. 2. The rubber composition according to claim 1, wherein the content of said magnesium oxide relative to 100 parts by mass of said rubber component is 1 part by mass or less. containing a filler containing aluminum hydroxide,
3. The rubber composition according to claim 1, wherein the content of said aluminum hydroxide is 8 parts by mass or less per 100 parts by mass of said rubber component. 4. The rubber composition according to claim 3, wherein the content of said filler relative to 100 parts by mass of said rubber component is 100 parts by mass or more. Contains paraffin wax,
The rubber composition according to any one of claims 1 to 4, wherein the content of said paraffin wax is 2.4 parts by mass or less with respect to 100 parts by mass of said rubber component. The rubber composition according to any one of claims 1 to 5, which is a rubber composition for a tire outer layer. A pneumatic tire comprising a tire outer layer member produced using the tire outer layer rubber composition according to claim 6 .