JP7222273B2 - Tire rubber composition and pneumatic tire - Google Patents

Description

TECHNICAL FIELD The present invention relates to a rubber composition for tires and a pneumatic tire.

Tires have various components. For example, rubber compositions for covering cords used in carcasses and belts include rubber components such as natural rubber, isoprene rubber, and styrene-butadiene rubber, and reinforcing fillers such as carbon black. , and the like are commonly used.

Rubber compositions for tires, such as rubber compositions for covering cords, are required to have various properties such as elongation at break, strength at break, modulus, etc., in addition to adhesion to cords, and further improvements are required. Desired.

An object of the present invention is to solve the above-mentioned problems and to provide a rubber composition for tires having excellent physical properties such as breaking strength, elongation at break and modulus, and a pneumatic tire using the same.

The present invention contains a rubber component and soft particles, the content of the soft particles is 0.5 to 30 parts by mass with respect to 100 parts by mass of the rubber component, and the average particle size of the soft particles is 0.08 to 2.0 parts by mass. It relates to a rubber composition for tires having a particle size of 0 μm.

The soft particles preferably have a hardness lower than that of the rubber component.
The flexible particles are preferably at least one selected from the group consisting of resin beads and foamed particles that are foamed to form a cavity inside.

It is preferably a rubber composition for cord coating.
The present invention also relates to a pneumatic tire using the rubber composition for tires.

According to the present invention, a rubber component and soft particles are included, the content of the soft particles is 0.5 to 30 parts by mass with respect to 100 parts by mass of the rubber component, and the average particle size of the soft particles is 0.08 to 0.08. Since the tire rubber composition has a particle size of 2.0 μm, physical properties such as breaking strength, elongation at break and modulus can be improved.

The rubber composition for tires contains a rubber component and soft particles having a predetermined average particle size in a predetermined blend. Thereby, good physical properties such as strength at break, elongation at break and modulus can be obtained.

The reason why such an effect is obtained is not necessarily clear, but in a single rubber component such as styrene-butadiene rubber (SBR), stress concentration occurs at the tips of cracks that occur in the rubber component, but the addition of soft particles is effective. Therefore, it is presumed that the following two mechanisms are produced separately or simultaneously by dispersing the soft particles in the rubber component (matrix).
1. When the soft particles are softer than the rubber component (matrix), the particles in the matrix are moderately deformed to dissipate the stress concentration at the tip of the crack, thereby improving physical properties such as breaking strength, breaking elongation and modulus.
2. When the flexible particles are harder than the rubber component (matrix), the particles in the matrix act as a reinforcing material, and in the vicinity of the fracture where the deformation is sufficiently large, the above-mentioned 1. As in , the particles are deformed moderately and the stress concentration at the tip of the crack is dissipated, so physical properties such as breaking strength, breaking elongation, and modulus are improved.

For example, when soft particles that are softer than the matrix of SBR are added to and dispersed in SBR, the stress concentration dissipation effect described above is exhibited, and the strength is improved compared to the SBR carrier. % modulus, 200% modulus), etc., the strength at break and elongation at break are greatly improved, and physical properties such as strength at break, elongation at break and modulus are improved in a well-balanced manner. As a result, it is presumed that there is an effect such as retardation of crack propagation in the rubber composition.

The rubber composition for tires contains soft particles having an average particle size of 0.08 to 2.0 μm.
The lower limit is preferably 0.01 µm or more, more preferably 0.05 µm or more, and even more preferably 0.08 µm or more. The upper limit is preferably 100 µm or less, more preferably 50 µm or less, and even more preferably 20 µm or less. By adjusting the content within the above range, good physical properties such as strength at break, elongation at break and modulus can be obtained. Here, when the flexible particles are "expanded particles that have been expanded so as to form a cavity inside", which will be described later, the average particle size is the value before expansion.

In this specification, the method for measuring the average particle size of the soft particles is a value obtained by a light scattering method or a light diffraction method using a laser or the like. Note that the examples are measured values by a light scattering method using a laser. As a measuring device to be used, Shimadzu Corporation laser diffraction particle size distribution measuring device SALD-2300 and the like can be mentioned.

The content of the soft particles is 0.5 parts by mass or more, preferably 1 part by mass or more, more preferably 2 parts by mass or more with respect to 100 parts by mass of the rubber component. The content is 30 parts by mass or less, preferably 15 parts by mass or less, more preferably 10 parts by mass or less. Within the above range, good physical properties such as strength at break, elongation at break and modulus can be obtained.

The hardness of the soft particles may be less than or greater than the hardness of the rubber component for the reasons described in [0010]. As a result, the strength is improved as compared with the single rubber component of the matrix, and good rubber physical properties can be obtained. Among them, it is preferable to use SBR as the rubber component and to add and disperse the soft particles.

The hardness H _R of the rubber component and the hardness H _P of the flexible particles preferably satisfy the following formulas from the viewpoint of obtaining good physical properties such as good breaking strength and elongation modulus.
H _P /H _R ≧0.40
More preferably H _P /H _R ≧0.80, still more preferably H _P /H _R ≧0.90.
On the other hand, the upper limit of _HP / _HR is not particularly limited, but _HP / _HR≤4.00 , more preferably _HP / _HR≤1.80 .

The hardness H _R of the rubber component, the hardness H _P of the flexible particles, and the hardness H _sample of the rubber composition (sample) containing the flexible particles are values measured by the following methods.
(1) First, H _R and H _samples are measured with a type A durometer according to JIS K6253 "Testing method for hardness of vulcanized rubber and thermoplastic rubber".
(2) _HP is calculated by the following formula.
H _p =[H _samples ×(100+P(phr) _−HR ×100]/P(phr)
_HR : Hardness of rubber component measured by type A durometer H _sample : Hardness of rubber composition (sample) measured by type A durometer P (phr): Amount (parts by mass) of flexible particles per 100 parts by mass of rubber component

(∵H _samples = [ _HR x 100 + _Hp x P (phr)]/[100 + P (phr)])

As the flexible particles, for example, resin beads (resin particles) such as melamine beads, acrylic beads, acrylic-styrene beads, polycarbonate beads, polyethylene beads, polystyrene beads, vinyl chloride beads, urethane crosslinked fine particles, silicone beads, etc. can be suitably used. .

As the flexible particles, foamed particles that are foamed to form a cavity inside can also be preferably used. The expanded particles are preferably expanded particles obtained by expanding particles having thermal expandability, and more preferably expanded particles obtained by thermally expanding and expanding thermally expandable microcapsules. Here, the thermally expandable microcapsules are those in which a volatile substance such as a low boiling point solvent is encapsulated inside a shell resin. Since it expands, the pressure causes the outer shell to expand and the particle size to increase, resulting in expanded particles. The temperature at which the thermally expandable microcapsules are foamed is not particularly limited, but it is preferably higher than the foaming start temperature described later and less than the maximum foaming temperature.

The outer shell of the thermally expandable microcapsules is preferably made of a thermoplastic resin. Examples of thermoplastic resins include vinyl polymers such as ethylene, styrene, vinyl acetate, vinyl chloride, vinylidene chloride, acrylonitrile, butadiene and chloroprene, and copolymers thereof; polyamides such as nylon 6 and nylon 66; polyesters such as polyethylene terephthalate. ; and the like. Among them, acrylonitrile copolymers are preferred.

Volatile substances contained inside the thermally expandable microcapsules include, for example, propane, propylene, butene, normal butane, isobutane, isopentane, neopentane, normal pentane, hexane, heptane, and other hydrocarbons having 3 to 7 carbon atoms. ; petroleum ether; methane halides such as methyl chloride and methylene chloride; chlorofluorocarbons such as CCl ₃ F and CCl ₂ F ₂ ; tetraalkylsilanes such as tetramethylsilane and trimethylethylsilane; mentioned.

Preferred examples of thermally expandable microcapsules include microcapsules in which a copolymer of acrylonitrile and vinylidene chloride is used as an outer shell resin and a hydrocarbon having 3 to 7 carbon atoms such as isobutane is encapsulated.

The thermally expandable microcapsules are preferably expanded to have an average particle size of 2 to 10 times to become the expanded particles. Moreover, the foaming start temperature of the thermally expandable microcapsules is preferably 95 to 150°C, more preferably 105 to 140°C. Also, the maximum foaming temperature is preferably 120 to 200°C, more preferably 135 to 180°C.

Soft particles include “Hyper” manufactured by Nemoto Kogyo Co., Ltd.; “EXPANCEL” manufactured by Nippon Philite Co., Ltd.; “Advancel” manufactured by Sekisui Chemical Co., Ltd.; , thermally expandable microcapsules such as "Microsphere" manufactured by Kureha Co., Ltd.;

The rubber composition for tires contains one or more rubber components.
From the viewpoint of good physical properties, the hardness _HR of the rubber component (rubber component contained in the rubber composition) preferably satisfies the following formula.
H _R ≤ 48
More preferably, H _R ≤43.
On the other hand, the lower limit of H _R is preferably H _R ≧36, more preferably H _R ≧40.

As the rubber component, for example, diene rubber can be used.
Diene rubbers include isoprene rubber, butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR). ) and the like. In addition, rubber components other than those described above include butyl-based rubbers, fluororubbers, and the like. These may be used alone or in combination of two or more. As the rubber component, SBR, BR, and isoprene-based rubber are preferable, and SBR is more preferable.

Here, the rubber component preferably has a weight average molecular weight (Mw) of 200,000 or more, more preferably 350,000 or more. Although the upper limit of Mw is not particularly limited, it is preferably 4,000,000 or less, more preferably 3,000,000 or less.
In the present specification, Mw and number average molecular weight (Mn) are measured by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: manufactured by Tosoh Corporation. TSKGEL SUPERMULTIPORE HZ-M) can be obtained by standard polystyrene conversion.

The rubber component may be non-modified diene rubber or modified diene rubber.
The modified diene rubber may be any diene rubber having a functional group that interacts with a filler such as silica. Terminal modified diene rubber modified with (terminal modified diene rubber having the above functional group at the end), main chain modified diene rubber having the above functional group on the main chain, and the above functional group on the main chain and terminal main chain end-modified diene rubber (for example, main chain end-modified diene rubber having the above functional group in the main chain and at least one end modified with the above modifier), or two or more in the molecule A terminal-modified diene rubber modified (coupled) with a polyfunctional compound having an epoxy group and introduced with a hydroxyl group or an epoxy group is exemplified.

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.

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. These may be used alone or in combination of two or more.

When SBR is contained, the content of SBR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 15% by mass or more, and still more preferably 20% by mass or more. The content is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less. Within the above range, there is a tendency to obtain good physical properties such as strength at break, elongation at break, and modulus.

The styrene content of SBR is preferably 5% by mass or more, more preferably 10% by mass or more, and still more preferably 15% by mass or more. Also, the styrene content is preferably 60% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less. Within the above range, the above effects can be obtained more favorably.
In this specification, the styrene content of SBR is calculated by H ¹ -NMR measurement.

SBR may be unmodified SBR or modified SBR. Examples of modified SBR include modified SBR into which functional groups similar to those of modified diene rubber have been introduced.

As SBR, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Co., Ltd., Asahi Kasei Co., Ltd., Nippon Zeon Co., Ltd., etc. can be used.

The isoprene rubber includes natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, modified IR, and the like. As NR, for example, those commonly used in the tire industry, such as SIR20, RSS#3, and TSR20, can be used. The IR is not particularly limited, and for example IR2200 or the like commonly used in the tire industry can be used. Modified NR includes deproteinized natural rubber (DPNR), high-purity natural rubber (UPNR), etc. Modified NR includes epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, etc. Examples of modified IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber, and the like. These may be used alone or in combination of two or more.

When isoprene-based rubber is contained, the content of isoprene-based rubber in 100% by mass of the rubber component is preferably 20% by mass or more, more preferably 50% by mass or more, and still more preferably 60% by mass or more. The content is preferably 90% by mass or less, more preferably 80% by mass or less. Within the above range, there is a tendency to obtain good physical properties such as strength at break, elongation at break, and modulus.

The total content of SBR and isoprene rubber is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and may be 100% by mass in 100% by mass of the rubber component. Within the above range, there is a tendency to obtain good physical properties such as strength at break, elongation at break, and modulus.

BR is not particularly limited, and for example, high cis BR having a high cis content, BR containing syndiotactic polybutadiene crystals, BR synthesized using a rare earth catalyst (rare earth BR), and the like can be used. These may be used alone or in combination of two or more. Among them, high-cis BR having a cis content of 90% by mass or more is preferable because it improves wear resistance performance.

BR may be non-denatured BR or denatured BR. Examples of modified BR include modified BR into which functional groups similar to those of modified diene rubber have been introduced.

As BR, for example, products of Ube Industries, Ltd., JSR Corporation, Asahi Kasei Co., Ltd., Nippon Zeon Co., Ltd., etc. can be used.

The rubber composition may further contain a filler (reinforcing filler).
Other fillers include, but are not limited to, carbon black, silica, calcium carbonate, talc, alumina, clay, aluminum hydroxide, aluminum oxide, mica, and the like. Among them, carbon black and silica are preferable from the viewpoint of the above effects.

Examples of carbon black include, but are not limited to, GPF, FEF, HAF, ISAF, and SAF.

The content of carbon black is preferably 2 parts by mass or more, more preferably 4 parts by mass or more with respect to 100 parts by mass of the rubber component. When the amount is 2 parts by mass or more, the adhesiveness and strength between the rubber composition and the tire cord tend to be improved. Also, the content of the carbon black is preferably 80 parts by mass or less, more preferably 65 parts by mass or less. By setting the content to 80 parts by mass or less, there is a tendency that good workability and the like can be obtained.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 50 m ² /g or more, more preferably 65 m ² /g or more. By making it 50 m ² /g or more, there is a tendency that the adhesiveness and strength between the rubber composition and the tire cord are improved. Further, the N ₂ SA of carbon black is preferably 150 m ² /g or less, more preferably 130 m ² /g or less. Good workability and the like tend to be obtained by making it 150 m ² /g or less.
Incidentally, the N ₂ SA of carbon black is determined by the A method of Section 7 of JIS K6217.

As carbon black, for example, products of Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Co., Ltd., Lion Corporation, Shin Nikka Carbon Co., Ltd., Columbia Carbon Co., Ltd. can be used.

The rubber composition preferably contains silica. Good strength and the like can be obtained by using silica.

The amount of silica compounded with respect to 100 parts by mass of the rubber component is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, and still more preferably 40 parts by mass or more. The blending amount is preferably 150 parts by mass or less, more preferably 100 parts by mass or less, and even more preferably 80 parts by mass or less. Within the above range, there is a tendency to obtain good physical properties such as strength at break, elongation at break, and modulus.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 40 m ² /g or more, more preferably 80 m ² /g or more, still more preferably 100 m ² /g or more. The N ₂ SA is preferably 300 m ² /g or less, more preferably 180 m ² /g or less, still more preferably 130 m ² /g or less. Within the above range, there is a tendency to obtain good physical properties such as strength at break, elongation at break, and modulus.
The nitrogen adsorption specific surface area of silica is a value measured by the BET method according to ASTM D3037-81.

Examples of silica include dry-process silica (anhydrous silica) and wet-process silica (hydrous silica), but wet-process silica is preferable because it contains many silanol groups.

As silica, for example, products of Degussa, Rhodia, Tosoh Silica, Solvay Japan, Tokuyama, etc. can be used.

The rubber composition preferably contains a silane coupling agent together with silica. Thereby, there is a tendency that good strength and the like can be obtained.

The content of the silane coupling agent is preferably 0.1 parts by mass or more, more preferably 2 parts by mass or more, and still more preferably 3 parts by mass or more with respect to 100 parts by mass of silica. Also, the content is preferably 20 parts by mass or less, more preferably 16 parts by mass or less, and even more preferably 12 parts by mass or less. By setting it within the above range, there is a tendency that good strength and the like can be obtained.

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. These may be used alone or in combination of two or more. Among them, sulfide-based and mercapto-based are preferable because the above effects can be obtained satisfactorily.

The rubber composition may contain a plasticizer. The plasticizer is not particularly limited, but examples thereof include oils, liquid polymers (liquid diene-based polymers), and liquid resins. One type of these plasticizers may be used, or two or more types may be used in combination.

When a plasticizer is contained, its content is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, relative to 100 parts by mass of the rubber component. In addition, the content is preferably 30 parts by mass or less, more preferably 25 parts by mass or less. When the content of the plasticizer is in this range, there is a tendency that good rubber physical properties are obtained.

Among the plasticizers, oils, liquid polymers, and liquid resins are preferred, and oils are particularly preferred from the viewpoint of workability and the like.

From the environmental point of view, the plasticizer preferably has a polycyclic aromatic content (PCA) of less than 3% by mass, more preferably less than 1% by mass. The polycyclic aromatic content (PCA) is measured according to the British Petroleum Institute method 346/92.

The above oils are not particularly limited, and process oils such as paraffinic process oils, aromatic process oils, and naphthenic process oils, low PCA (polycyclic aromatic) process oils such as TDAE and MES, vegetable oils and fats, and Conventionally known oils such as mixtures thereof can be used. Of these, aromatic process oils are preferred from the standpoint of rubber physical properties. Specific examples of the aromatic process oil include the Diana process oil AH series manufactured by Idemitsu Kosan Co., Ltd., and the like.

The liquid polymer (liquid diene-based polymer) is a diene-based polymer that is liquid at room temperature (25° C.).
3. The liquid diene polymer preferably has a polystyrene equivalent weight average molecular weight (Mw) of 1.0×10 ³ to 2.0×10 ⁵ as measured by gel permeation chromatography (GPC). It is more preferably 0×10 ³ to 1.5×10 ⁴ .
In addition, in this specification, Mw of a liquid diene polymer is a polystyrene conversion value measured by gel permeation chromatography (GPC).

Liquid diene-based polymers include liquid styrene-butadiene copolymer (liquid SBR), liquid butadiene polymer (liquid BR), liquid isoprene polymer (liquid IR), liquid styrene-isoprene copolymer (liquid SIR), and the like. be done.

Examples of the liquid resin include, but are not limited to, liquid aromatic vinyl polymers, coumarone-indene resins, indene resins, terpene resins, rosin resins, and hydrogenated products thereof.

A liquid aromatic vinyl polymer is a resin obtained by polymerizing α-methylstyrene and/or styrene. Examples include liquid resins such as copolymers.

A liquid coumarone-indene resin is a resin containing coumarone and indene as main monomer components constituting the skeleton (main chain) of the resin. , styrene, α-methylstyrene, methylindene, and vinyltoluene.

A liquid indene resin is a liquid resin containing indene as a main monomer component that constitutes the skeleton (main chain) of the resin.

Liquid terpene resins are resins obtained by polymerizing terpene compounds such as α-pinene, β-pinene, camphor, and dipetene, and liquids represented by terpene phenol, which is a resin obtained from a terpene compound and a phenolic compound as raw materials. It is a terpene resin.

The liquid rosin resin is a liquid rosin resin represented by natural rosin, polymerized rosin, modified rosin, ester compounds thereof, or hydrogenated products thereof.

The rubber composition may contain a solid resin (a polymer that is solid at room temperature (25° C.)).

When a solid resin is contained, the content thereof is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and still more preferably 5 parts by mass or more with respect to 100 parts by mass of the rubber component. Also, the content is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less. Within the above range, good wet grip performance tends to be obtained.

The solid resin is not particularly limited, but for example, solid styrene-based resin, coumarone-indene resin, terpene-based resin, pt-butylphenolacetylene resin, acrylic resin, dicyclopentadiene-based resin (DCPD-based resin). , C5 petroleum resin, C9 petroleum resin, C5C9 petroleum resin, and the like. These may be used alone or in combination of two or more.

The solid styrenic resin is a solid polymer using a styrenic monomer as a constituent monomer, and examples thereof include polymers polymerized with a styrenic monomer as a main component (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.), homopolymers obtained by polymerizing each alone, copolymers obtained by copolymerizing two or more styrene monomers, and styrene monomers and copolymers of other monomers copolymerizable therewith.

Examples of the other monomers include acrylonitrile and methacrylonitrile, acrylics, unsaturated carboxylic acids such as methacrylic acid, unsaturated carboxylic acid esters such as methyl acrylate and methyl methacrylate, chloroprene, and butadiene. dienes such as isoprene; olefins such as 1-butene and 1-pentene; α,β-unsaturated carboxylic acids such as maleic anhydride and acid anhydrides thereof;

Among them, solid α-methylstyrene resins (α-methylstyrene homopolymers, copolymers of α-methylstyrene and styrene, etc.) are preferred.

Examples of the solid coumarone-indene resin include solid resins having the same structural units as those of the liquid coumarone-indene resin described above.

Solid terpene-based resins include polyterpene, terpenephenol, and aromatic modified terpene resins.
Polyterpenes are resins obtained by polymerizing terpene compounds and hydrogenated products thereof. Terpene compounds are hydrocarbons represented by the composition (C ₅ H ₈ ) _n and their oxygen-containing derivatives, such as monoterpene (C ₁₀ H ₁₆ ), sesquiterpene (C ₁₅ H ₂₄ ), diterpene (C ₂₀ H ₃₂ ) and the like, 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-cineole, 1,4-cineole, α-terpineol, β-terpineol, γ-terpineol and the like.

As the solid polyterpene, terpene resin such as α-pinene resin, β-pinene resin, limonene resin, dipentene resin, β-pinene/limonene resin made from the above-mentioned terpene compound as a raw material, and hydrogenation of the terpene resin Also included are solid resins such as treated hydrogenated terpene resins.

Examples of the solid terpene phenol include a solid resin obtained by copolymerizing the terpene compound and a phenolic compound, and a solid resin obtained by hydrogenating the resin. Specifically, the terpene compound, the phenolic compound and A solid resin obtained by condensing formalin can be mentioned. Examples of phenolic compounds include phenol, bisphenol A, cresol, and xylenol.

Examples of solid aromatic-modified terpene resins include solid resins obtained by modifying terpene resins with aromatic compounds, and solid resins obtained by hydrogenating the resins. The aromatic compound is not particularly limited as long as it is a compound having an aromatic ring. Examples include phenol compounds such as phenol, alkylphenol, alkoxyphenol, unsaturated hydrocarbon group-containing phenol; naphthol compounds such as unsaturated hydrocarbon group-containing naphthol; styrene derivatives such as styrene, alkylstyrene, alkoxystyrene, unsaturated hydrocarbon group-containing styrene; coumarone, indene, and the like.

Examples of solid pt-butylphenol acetylene resins include solid resins obtained by condensation reaction of pt-butylphenol and acetylene.

Although the solid acrylic resin is not particularly limited, a solvent-free acrylic solid resin can be preferably used because it contains few impurities and provides a resin with a sharp molecular weight distribution.

A solid solvent-free acrylic resin is produced by a high-temperature continuous polymerization method (high-temperature continuous bulk polymerization method) (U.S. Pat. No. 4,414) without using polymerization initiators, chain transfer agents, organic solvents, etc. , 370, JP-A-59-6207, JP-B-5-58005, JP-A-1-313522, US Pat. (meth)acrylic resins (polymers) synthesized by the method described in No. pp. 42-45, etc.). In addition, in this specification, (meth)acryl means methacryl and acryl.

The solid acrylic resin preferably does not substantially contain auxiliary materials such as a polymerization initiator, a chain transfer agent, and an organic solvent. Further, the acrylic resin preferably has a relatively narrow composition distribution and molecular weight distribution obtained by continuous polymerization.

As described above, the solid acrylic resin preferably does not substantially contain auxiliary materials such as a polymerization initiator, a chain transfer agent, an organic solvent, etc., that is, has a high purity. The purity of the solid acrylic resin (percentage of resin contained in the resin) is preferably 95% by mass or more, more preferably 97% by mass or more.

Examples of monomer components constituting solid acrylic resins include (meth)acrylic acid, (meth)acrylic acid esters (alkyl esters, aryl esters, aralkyl esters, etc.), (meth)acrylamide, and (meth) Examples include (meth)acrylic acid derivatives such as acrylamide derivatives.

In addition to (meth)acrylic acid and (meth)acrylic acid derivatives, styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, and divinyl are also used as monomer components constituting solid acrylic resins. Aromatic vinyls such as naphthalene may also be used.

The solid acrylic resin may be a resin composed only of a (meth)acrylic component, or a resin containing components other than the (meth)acrylic component as constituent elements.
Moreover, the solid acrylic resin may have a hydroxyl group, a carboxyl group, a silanol group, or the like.

Plasticizers and solid resins, for example, Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF Corporation, Arizona Chemical Co., Nichinuri Chemical Co., Ltd. , Nippon Shokubai Co., Ltd., JXTG Energy Co., Ltd., Arakawa Chemical Industry Co., Ltd., Taoka Chemical Industry Co., Ltd., etc. can be used.

The rubber composition preferably contains stearic acid.
Conventionally known stearic acid can be used, for example, products of NOF Corporation, NOF, Kao Corporation, Fuji Film Wako Pure Chemical Industries, Ltd., Chiba Fatty Acids Co., Ltd. can be used.

When stearic acid is contained, the content of stearic acid is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, relative to 100 parts by mass of the rubber component. The above content is preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less, and even more preferably 2.5 parts by mass or less.

The rubber composition preferably contains 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. These may be used alone or in combination of two or more. Among them, p-phenylenediamine-based antioxidants and quinoline-based antioxidants are preferable, and N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, 2,2,4-trimethyl-1 , 2-dihydroquinoline polymers are more preferred.

As the anti-aging agent, products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Kagaku Kogyo Co., Ltd., Flexis, etc. can be used, for example.

When an antioxidant is contained, the content of the antioxidant is preferably 0.5 parts by mass or more, more preferably 0.7 parts by mass or more, relative to 100 parts by mass of the rubber component. Moreover, the content is preferably 10 parts by mass or less, more preferably 7 parts by mass or less.

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. These may be used alone or in combination of two or more.

As the wax, for example, products of Ouchi Shinko Kagaku Kogyo Co., Ltd., Nippon Seiro Co., Ltd., Seiko Kagaku Co., Ltd., etc. can be used.

When wax is contained, the wax content 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. Moreover, the content is preferably 10 parts by mass or less, more preferably 7 parts by mass or less.

The rubber composition preferably contains 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. These may be used alone or in combination of two or more.

As sulfur, for example, 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.

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, relative to 100 parts by mass of the rubber component. Moreover, the content is preferably 10 parts by mass or less, more preferably 7 parts by mass or less. Within the above numerical range, the above effects tend to be obtained favorably.

The rubber composition preferably contains a vulcanization accelerator.
Vulcanization accelerators include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiazylsulfenamide; tetramethylthiuram disulfide (TMTD ), tetrabenzyl thiuram disulfide (TBzTD), tetrakis (2-ethylhexyl) thiuram disulfide (TOT-N) and other thiuram vulcanization accelerators; N-cyclohexyl-2-benzothiazolesulfenamide, Nt-butyl- 2-benzothiazolylsulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N,N'-diisopropyl-2-benzothiazolesulfenamide, etc. and guanidine-based vulcanization accelerators such as diphenylguanidine, diorthotolylguanidine and orthotolylbiguanidine. 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 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, relative to 100 parts by mass of the rubber component. Moreover, the content is preferably 10 parts by mass or less, more preferably 7 parts by mass or less. Within the above numerical range, the above effects tend to be obtained favorably.

In addition to the above components, the rubber composition may contain additives commonly used in the tire industry, vulcanizing agents other than sulfur (e.g., organic cross-linking agents, organic peroxides); etc. can be exemplified.

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

From the viewpoint of good physical properties, the hardness H _sample of the rubber composition (sample) preferably satisfies the following formula.
H _samples ≤ 48
More preferably, H _samples ≤ 43.
On the other hand, the lower limit of H _samples is preferably H _samples ≧36, more preferably H _samples ≧40.

The rubber composition includes tread (cap tread), sidewall, base tread, undertread, clinch apex, bead apex, breaker cushion rubber, carcass cord covering rubber, insulation, chafer, inner liner, runflat. It can be used for various tire members such as tire side reinforcing layers. Among others, it is suitable as a rubber composition for covering tire cords such as carcass cords and band cords (rubber composition for covering cords). Specifically, it is used for the carcass shown in the drawings of Japanese Patent Application Laid-Open No. 2009-13220 and the band shown in the drawings of Japanese Patent Application Laid-Open No. 6-270606.

When the rubber composition is used as a rubber composition for covering a cord, for example, a plurality of cords are stretched and arranged in parallel, and the unvulcanized rubber composition for covering a cord is topped on the upper and lower sides of the cord to obtain a carcass. etc. can be produced. As the cord, conventionally known cords can be used, including textile cords (fiber cords) made of organic fibers such as polyester, steel cords made of steel, and the like.

The pneumatic tire can be produced by a normal method using the rubber composition.
For example, in the case of a cord covering rubber composition, a cord is first covered with the cord covering rubber composition and then molded into a member such as a carcass. Next, an unvulcanized tire is prepared by laminating the molded member to another tire member. After that, a pneumatic tire can be obtained by vulcanizing the unvulcanized tire.

The pneumatic tire can be suitably used for passenger car tires, large passenger car tires, large SUV tires, heavy load tires for trucks and buses, light truck tires, motorcycle tires, run-flat tires, and competition tires. is. In particular, it can be used more preferably as a passenger car tire.

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

Various chemicals used in Examples and Comparative Examples are collectively described below.
Natural rubber (NR): TSR
SBR: Emulsion polymerized styrene-butadiene rubber (E-SBR): Nipol 1502 manufactured by Nippon Zeon Co., Ltd. (bound styrene content: 23.5%)
Soft particles 1: MM101 (urethane beads, average particle size 0.08 μm) manufactured by Nemoto Kogyo Co., Ltd.
Flexible particles 2: Nipol 502 manufactured by Nippon Zeon (latex beads, average particle size 0.3 μm)
Soft particles 3: MM120 (urethane beads, average particle size 2.0 μm) manufactured by Nemoto Kogyo Co., Ltd.
Soft particles 4: urethane beads (average particle size 0.01 μm)
Soft particles 5: urethane beads (average particle size 5.0 μm)
Silica: ZEOSIL 115GR from Rhodia (N ₂ SA: 115 m ² /g)
Silane coupling agent: Si266 (bis (3-triethoxysilylpropyl) disulfide) manufactured by Degussa
Carbon black: N220 (N ₂ SA: 120 m ² /g, DBP: 114 cm ³ /100 g) manufactured by Showa Cabot Co., Ltd.
Aroma oil: Process X-140 manufactured by Japan Energy Co., Ltd.
Zinc oxide: Zinc white No. 1 manufactured by Mitsui Kinzoku Mining Co., Ltd. Stearic acid: Camellia sulfur manufactured by NOF Corporation: Powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. Vulcanization accelerator 1: Ouchi Shinko Kagaku Kogyo ( Noxceler NS (N-tert-butyl-2-benzothiazolylsulfenamide) manufactured by Co., Ltd.
Vulcanization accelerator 2: Noxceler D (N,N'-diphenylguanidine) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.

(Examples and Comparative Examples)
<Preparation of rubber test piece and test tire>
Chemicals other than sulfur and a vulcanization accelerator were kneaded according to the formulation shown in Table 1 using a 1.7 L Banbury. Next, using a roll, sulfur and a vulcanization accelerator were added to the resulting kneaded material and kneaded to obtain an unvulcanized rubber composition.
A textile cord was coated with the obtained unvulcanized rubber composition, molded into a carcass shape, and laminated with other tire members to produce an unvulcanized tire. A test tire was produced by vulcanizing it at 150° C. for 30 minutes.

The vulcanized rubber (sample) collected from the carcass of the test tire, the rubber component (70 parts by mass of NR + 30 parts by mass of SBR), and the soft particles were evaluated as follows. Table 1 shows the results.

[Measurement of H _R , H _P , H _sample ]
(1) First, H _R and H _samples were measured with a type A durometer according to JIS K6253 "Testing method for hardness of vulcanized rubber and thermoplastic rubber".
(2) _HP was calculated by the following formula.
H _p =[H _samples ×(100+P(phr) _−HR ×100]/P(phr)
_HR : Hardness of rubber component measured by type A durometer H _sample : Hardness of rubber composition (sample) measured by type A durometer P (phr): Amount (parts by mass) of flexible particles per 100 parts by mass of rubber component

[Tensile test]
Based on JIS K6251: 2010, a dumbbell-shaped No. 3 test piece was prepared from the obtained vulcanized rubber, and a tensile test was performed at normal temperature (25 ° C.) to measure breaking strength TB (MPa) and elongation at break EB. (%) was measured. TB, EB, and TB×EB/2 of Comparative Example 1 are expressed as 1.00. A larger index indicates better rubber physical properties such as strength.

[M100, M200]
Based on JIS K6251: 2010, a dumbbell-shaped No. 6 test piece was prepared from the obtained vulcanized rubber, and a tensile test was performed at normal temperature (25 ° C.) to obtain a stress at 100% elongation (M100) (MPa ), and the stress (M200) (MPa) at 200% elongation was measured. M100 and M200 of Comparative Example 1 were indexed as 100. A larger index indicates better rubber physical properties such as strength.

From the results of Comparative Example 1 and each example in Table 1, the example containing soft particles was excellent in overall performance (rubber strength) combining TB, EB, M100, and M200. A good TB×EB/2 was also obtained. Therefore, it has been clarified that performance such as good crack growth resistance can be obtained.

Further, from the comparative examples and the examples, it was clarified that physical properties such as rubber strength and crack growth resistance were significantly improved when a predetermined amount of soft particles having a predetermined average particle size were blended. .

Claims (4)

including a rubber component and flexible particles,
The content of the soft particles is 0.5 to 30 parts by mass with respect to 100 parts by mass of the rubber component,
The soft particles have an average particle size of 0.08 to 2.0 μm,
The rubber composition for a tire , wherein the flexible particles are urethane beads . 2. The rubber composition for tires according to claim 1, wherein the soft particles have a hardness lower than that of the rubber component. The rubber composition for tires according to claim 1 or 2, which is a rubber composition for covering cords. A pneumatic tire using the tire rubber composition according to any one of claims 1 to 3 .