JP6897397B2 - Pneumatic tires - Google Patents

Description

The present invention relates to a pneumatic tire.

In recent years, from the standpoint of resource saving, energy saving, and environmental protection, social demands for reduction of carbon dioxide emissions have been increasing, and various countermeasures such as weight reduction and use of electric energy are being considered for automobiles. ing. Therefore, it is required to reduce the rolling resistance of automobile tires and improve fuel efficiency, and it is also desired to improve performance such as wear resistance.

As a method for improving fuel efficiency, methods such as adoption of silica compounding, reduction of filler, and use of filler having low reinforcing property are known, but wear resistance and the like tend to be deteriorated.

As another method for improving the fuel efficiency, for example, Patent Document 1 proposes a method using a diene-based rubber (modified rubber) modified with an organosilicon compound containing an amino group and an alkoxy group. Although the fuel efficiency performance is improved by such a conventional technique, it is also an important issue to sufficiently secure the wear resistance performance from the viewpoint of economy and safety. In response to the above problems, the conventional technology does not have sufficient wear resistance, which is a trade-off performance with respect to fuel efficiency, and there is room for improvement.

Japanese Unexamined Patent Publication No. 2000-344955

An object of the present invention is to solve the above-mentioned problems and to provide a pneumatic tire having improved fuel efficiency, wear resistance and the like in a well-balanced manner.

The present invention relates to a pneumatic tire having a tread prepared by using a rubber composition containing a rubber component containing styrene-butadiene rubber, isoprene-based rubber and liquid isoprene rubber, and an aromatic resin.

The rubber composition preferably contains 70 parts by mass or more of silica with respect to 100 parts by mass of the rubber component.

The average amount of styrene in the styrene-butadiene rubber is preferably 30% by mass or more.

It is preferable that the aromatic resin contains a styrene resin and an aromatic petroleum resin.

It is preferable that the rubber composition contains 1 part by mass or more of a processing aid with respect to 100 parts by mass of the rubber component.

According to the present invention, it is a pneumatic tire having a tread prepared by using a rubber composition containing a rubber component containing styrene-butadiene rubber, isoprene-based rubber and liquid isoprene rubber, and an aromatic resin. Fuel performance and wear resistance are improved in a well-balanced manner.

The pneumatic tire has a tread prepared by using a rubber composition containing a rubber component containing styrene-butadiene rubber (SBR), isoprene-based rubber and liquid isoprene rubber (liquid IR), and an aromatic resin. As a result, the fuel efficiency performance and the wear resistance performance are remarkably (synergistically) improved in a well-balanced manner. In addition, wet grip performance, dry grip performance and processing performance (productivity) are remarkably (synergistically) improved in a well-balanced manner.
The reason why such an action effect is obtained is not always clear, but it is presumed as follows.

In the above rubber composition, the isoprene-based rubber and the liquid IR are compatible with each other, and the SBR and the aromatic resin are compatible with each other to form a more uniform compound, so that a fracture starting point is less likely to occur, and thus wear resistance. It is believed that performance will be improved. Furthermore, it is thought that isoprene-based rubber and liquid IR will improve fuel efficiency because the molecular chains will be cross-linked after vulcanization and the molecular motion will be suppressed, which will reduce the heat generated by the molecular motion. Be done. Therefore, it is expected that fuel efficiency and wear resistance will be improved in a well-balanced manner.

(Rubber composition)
The rubber composition contains SBR, isoprene-based rubber, and liquid IR as rubber components.
In the present specification, SBR and isoprene-based rubber are rubbers in a solid state having no fluidity at room temperature (25 ° C.), and usually mean high molecular weight rubbers having a weight average molecular weight (Mw) of 100,000 or more. Further, the liquid IR is a rubber in a liquid state having fluidity at room temperature (25 ° C.), and usually means a low molecular weight rubber having a Mw of less than 100,000.
In the present specification, Mw is gel permeation chromatography (GPC) (GPC-8000 series manufactured by Toso Co., Ltd., detector: differential refractometer, column: TSKGEL SUPERMALTPORE HZ-M manufactured by Toso Co., Ltd.). It can be obtained by standard polystyrene conversion based on the measured value according to.

The SBR is not particularly limited, and for example, an emulsion-polymerized styrene-butadiene rubber (E-SBR), a solution-polymerized styrene-butadiene rubber (S-SBR), or the like can be used. These may be used alone or in combination of two or more.

The average molecular weight of SBR contained in the rubber composition is preferably 250,000 or more, more preferably 300,000 or more, still more preferably 320,000 or more. The upper limit is not particularly limited, but is preferably 450,000 or less, more preferably 400,000 or less, and further preferably 350,000 or less. Within the above range, the effect of the present invention tends to be obtained better.

Here, the average molecular weight of SBR (average molecular weight of all SBR) is Σ (content ratio of each SBR in all SBR × Mw of each SBR), and the content ratio of each SBR is each SBR in all SBR. In the case of a rubber component consisting of 70% by mass of SBR (A), 10% by mass of SBR (B), 10% by mass of NR, and 10% by mass of BR, the content of SBR (A) and (B) is contained. The ratios are 0.875 (= 70 / (70 + 10)) and 0.125 (= 10 / (70 + 10)), respectively. Therefore, for example, the rubber component is SBR (A) (styrene amount 35% by mass, Mw 650,000). When it is composed of 70% by mass, SBR (B) (40% by mass of styrene, 950,000 Mw), 10% by mass of NR, and 10% by mass of BR, the average molecular weight of SBR is 678,500 (678,500 = 0. 875 x 650,000 + 0.125 x 950,000)).

The average amount of styrene of SBR contained in the rubber composition is preferably 25% by mass or more, more preferably 30% by mass or more. The upper limit is not particularly limited, but is preferably 45% by mass or less, more preferably 40% by mass or less, and further preferably 35% by mass or less. Within the above range, the effect of the present invention tends to be obtained better.

Here, the average amount of styrene of SBR is {Σ (content ratio of each SBR in all SBR × amount of styrene of each SBR × Mw of each SBR)} / average molecular weight of all SBR. For example, when SBR (A) (styrene amount 35% by mass, Mw 650,000) 70% by mass, SBR (B) (styrene amount 40% by mass, Mw 950,000) 10% by mass, NR 10% by mass, BR 10% by mass, the average The amount of styrene is 35.86% by mass (= {70 / (70 + 10) × 35 × 650,000 + 10 / (70 + 10) × 40 × 950,000} / 68.75 million).

The amount of styrene in each SBR is preferably 5% by mass or more, more preferably 15% by mass or more, and further preferably 20% by mass or more. The amount of styrene is preferably 60% by mass or less, more preferably 50% by mass or less, still more preferably 45% by mass or less. Within the above range, the effect of the present invention tends to be obtained better.
In the present specification, styrene content of SBR ^is calculated by H 1 -NMR measurement.

The amount of vinyl in each SBR is preferably 10% by mass or more, more preferably 20% by mass or more. The amount of vinyl is preferably 80% by mass or less, more preferably 70% by mass or less. Within the above range, the effect of the present invention tends to be obtained better.
In the present specification, the amount of vinyl (1,2-bonded butadiene unit amount) can be measured by infrared absorption spectrum analysis.

The Mw of each SBR is preferably 150,000 or more, more preferably 200,000 or more. The Mw is preferably 1 million or less, more preferably 700,000 or less, still more preferably 500,000 or less. Within the above range, the effect of the present invention tends to be obtained better.

Further, the SBR may be a non-modified SBR or a modified SBR. These may be used alone or in combination of two or more.
The modified SBR may be any SBR having a functional group that interacts with a filler such as silica. For example, at least one end of the SBR is modified with a compound having the above functional group (modifying agent). SBR (terminal modified SBR having the above functional group at the end), main chain modified SBR having the above functional group in the main chain, and main chain terminal modified SBR having the above functional group in the main chain and the end (for example, in the main chain) Main chain terminal modified SBR having the above functional group and having at least one end modified with the above modifying agent) or a polyfunctional compound having two or more epoxy groups in the molecule, which is modified (coupling) with a hydroxyl group. And terminally modified SBR into which an epoxy group has been introduced. These may be used alone or in combination of two or more.

Examples of the functional group include an amino group, an amide group, a silyl group, an alkoxysilyl group, an isocyanate group, an imino group, an imidazole group, a urea group, an ether group, a carbonyl group, an oxycarbonyl group, a mercapto group, a sulfide group and a disulfide. Examples thereof include a group, a sulfonyl group, a sulfinyl group, a thiocarbonyl group, an ammonium group, an imide group, a hydrazo group, an azo group, a diazo group, a carboxyl group, a nitrile group, a pyridyl group, an alkoxy group, a hydroxyl group, an oxy group and an epoxy group. .. 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 replaced with an alkyl group having 1 to 6 carbon atoms) and an alkoxy group (preferably) because the effect of the present invention can be obtained more preferably. An alkoxy group having 1 to 6 carbon atoms) and an alkoxysilyl group (preferably an alkoxysilyl group having 1 to 6 carbon atoms) are preferable.

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

The content of SBR in 100% by mass of the rubber component is preferably 20% by mass or more, more preferably 40% by mass or more, and further preferably 50% by mass or more. The content is preferably 90% by mass or less, more preferably 80% by mass or less. Within the above range, the effect of the present invention tends to be obtained better.

Examples of the isoprene-based rubber include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, modified IR and the like. As the NR, for example, SIR20, RSS # 3, TSR20 and the like, which are common in the tire industry, can be used. The IR is not particularly limited, and for example, an IR 2200 or the like that is common in the tire industry can be used. Modified NR includes deproteinized natural rubber (DPNR), high-purity natural rubber (UPNR), etc., and modified NR includes epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, etc. Examples of the 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.

The content of the isoprene-based rubber in 100% by mass of the rubber component is preferably 0.5% by mass or more, more preferably 2% by mass or more. The content is preferably 20% by mass or less, more preferably 10% by mass or less, still more preferably 6% by mass or less. Within the above range, the effect of the present invention tends to be obtained better.

The liquid IR is a polyisoprene polymer having isoprene as a constituent unit, and as described above, is a rubber in a liquid state having fluidity at room temperature (25 ° C.), and is usually a low molecular weight rubber having a Mw of less than 100,000.

The liquid IR may be a non-modified liquid IR or a modified liquid IR. These may be used alone or in combination of two or more.
Examples of the modified liquid IR include a modified liquid IR in which a functional group similar to that of the above-mentioned modified SBR is introduced.

The Mw of the liquid IR is preferably 1000 or more, more preferably 10,000 or more, and further preferably 30,000 or more. The Mw is preferably 80,000 or less, more preferably 60,000 or less. Within the above range, the effect of the present invention tends to be obtained better.

The content of the liquid IR in 100% by mass of the rubber component is preferably 0.1% by mass or more, more preferably 0.5% by mass or more. The content is preferably 10% by mass or less, more preferably 6% by mass or less, still more preferably 4% by mass or less. Within the above range, the effect of the present invention tends to be obtained better.

The total content of the isoprene-based rubber and the liquid IR in 100% by mass of the rubber component is preferably 1% by mass or more, more preferably 3% by mass or more. The total content is preferably 20% by mass or less, more preferably 10% by mass or less, and further preferably 8% by mass or less. Within the above range, the effect of the present invention tends to be obtained better.

The ratio (A / B) of the isoprene-based rubber content (A) to the liquid IR content (B) in 100% by mass of the rubber component is preferably 0.1 or more, more preferably 0.5 or more. More preferably, it is 1 or more. The ratio is preferably 10 or less, more preferably 6 or less, still more preferably 4 or less. Within the above range, the effect of the present invention tends to be obtained better.

Examples of other rubber components include butadiene rubber (BR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), styrene-isoprene-butadiene copolymer rubber (SIBR), and the like. In the present specification, these are rubbers in a solid state having no fluidity at room temperature (25 ° C.), and usually mean high molecular weight rubbers having a weight average molecular weight (Mw) of 100,000 or more. Examples of other rubber components include these liquid rubbers, SBR, and isoprene-based rubber liquid rubbers (excluding the above liquid IR) (the description of the liquid rubber is the same as that of the above liquid IR). These may be used alone or in combination of two or more. Of these, BR is preferable because the effects of the present invention tend to be obtained better.

The BR is not particularly limited, and for example, BR having a high cis content, BR containing syndiotactic polybutadiene crystals, and the like can be used. These may be used alone or in combination of two or more.

The BR may be a non-modified BR or a modified BR. These may be used alone or in combination of two or more.
Examples of the modified BR include modified BR into which a functional group similar to that of the above-mentioned modified SBR has been introduced.

The content of BR in 100% by mass of the rubber component is preferably 1% by mass or more, more preferably 5% by mass or more, and further preferably 10% by mass or more. The content is preferably 50% by mass or less, more preferably 40% by mass or less, and further preferably 30% by mass or less. Within the above range, the effect of the present invention tends to be obtained better.

The content of the high molecular weight rubber having a Mw of 100,000 or more in 100% by mass of the rubber component is preferably 70% by mass or more, more preferably 80% by mass or more, and particularly preferably 90% by mass or more. The content is preferably 95% by mass or less. Within the above range, the effect of the present invention tends to be obtained better.

The rubber composition contains an aromatic resin.

The aromatic resin is a polymer containing an aromatic compound as a constituent component. The aromatic compound is not particularly limited as long as it is a compound having an aromatic ring, and is, for example, a phenol compound such as phenol, alkylphenol, alkoxyphenol, and unsaturated hydrocarbon group-containing phenol; naphthol, alkylnaphthol, alkoxynaphthol, and non-aromatic compound. Naftor compounds such as saturated hydrocarbon group-containing naphthol; styrene derivatives such as styrene, alkylstyrene, alkoxystyrene, unsaturated hydrocarbon group-containing styrene; kumaron, inden and the like can be mentioned.

Examples of the aromatic resin include styrene resin, aromatic petroleum resin, Kumaron inden resin, aromatic-modified terpene resin, terpene aromatic resin, and the like, and each resin also contains these hydrogenated resins. Is done. These may be used alone or in combination of two or more. Among them, a styrene resin and an aromatic petroleum resin are preferable, and a styrene resin and an aromatic petroleum resin are more preferable in combination because the effects of the present invention tend to be obtained more satisfactorily.

The styrene-based resin is a polymer using a styrene-based monomer as a constituent monomer, and examples thereof include a polymer obtained by polymerizing a styrene-based monomer as a main component (50% by mass or more). Specifically, styrene-based monomers (styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, A homopolymer obtained by independently polymerizing o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, etc.), a copolymer obtained by copolymerizing two or more types of styrene-based monomers, and a styrene-based monomer. And other monomer copolymers that can be copolymerized with this. These may be used alone or in combination of two or more.
Examples of the other monomer include acrylonitrile such as acrylonitrile and methacrylonitrile, unsaturated carboxylic acids such as acrylics and methacrylic acid, unsaturated carboxylic acid esters such as methyl acrylate and methyl methacrylate, chloroprene and butadiene. Examples thereof include dienes such as isoprene, olefins such as 1-butane and 1-pentene; α, β-unsaturated carboxylic acids such as maleic anhydride or acid anhydrides thereof; and the like.
As the styrene-based resin, α-methylstyrene-based resin (α-methylstyrene homopolymer, copolymer of α-methylstyrene and styrene, etc.) is particularly preferable.

Aromatic petroleum resin is a C9 petroleum resin obtained by polymerizing a C9 fraction having vinyl toluene, inden, and methyl inden as main monomers obtained by naphtha decomposition, and a naphtha decomposition in addition to the C9 fraction. Examples thereof include C5C9-based petroleum resins obtained by polymerizing a C5 fraction having olefins and diolefins as main monomers obtained by the above. These may be used alone or in combination of two or more.
As the aromatic petroleum resin, C5C9 petroleum resin is particularly preferable.

The softening point of the aromatic resin is preferably 30 ° C. or higher, more preferably 60 ° C. or higher, and even more preferably 80 ° C. or higher. At 30 ° C. or higher, the desired wet grip performance tends to be obtained. The softening point is preferably 160 ° C. or lower, more preferably 130 ° C. or lower, and even more preferably 100 ° C. or lower. When the temperature is 160 ° C. or lower, the dispersibility of the resin becomes good, and the wet grip performance and the fuel consumption performance tend to be improved.
In the present specification, the softening point of the resin is the temperature at which the sphere has fallen when the softening point defined in JIS K 6220-1: 2001 is measured by a ring-ball type softening point measuring device.

The content of the aromatic resin is preferably 1 part by mass or more, and more preferably 5 parts by mass or more with respect to 100 parts by mass of the rubber component. The content is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and further preferably 15 parts by mass or less. Within the above range, the effect of the present invention tends to be obtained better.

The rubber composition preferably contains carbon black.
The carbon black is not particularly limited, and examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. These may be used alone or in combination of two or more.

Nitrogen adsorption specific surface area _(N 2 SA) of carbon black is preferably at least ^{5 m} 2 / g, more preferably not less than ^{50m 2 / g, 100m 2 /} g or more is particularly preferable. When it is 5 m ² / g or more, the reinforcing property is improved and sufficient wear resistance tends to be obtained. Further, the _N 2 SA is preferably 200 meters ² / g or less, more preferably 150 meters ² / g, more preferably not more than 130m ² / g. When it is 200 m ² / g or less, good dispersion of carbon black is likely to be obtained, and good wear resistance performance and low fuel consumption performance tend to be obtained.
The nitrogen adsorption specific surface area of carbon black is determined by JIS K6217-2: 2001.

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

The content of carbon black is preferably 1 part by mass or more, and more preferably 5 parts by mass or more with respect to 100 parts by mass of the rubber component. When it is 1 part by mass or more, sufficient reinforcing property can be obtained, and there is a tendency that better wear resistance performance can be obtained. The content is preferably 30 parts by mass or less, preferably 15 parts by mass or less. When it is 30 parts by mass or less, better rolling resistance tends to be obtained.

The rubber composition preferably contains silica.
Examples of silica include dry silica (silicic anhydride) and wet silica (hydrous silicic acid), but wet silica is preferable because it contains a large amount of silanol groups. These may be used alone or in combination of two or more.

The nitrogen adsorption specific surface area (N ₂ SA) of ^{silica is preferably 70 m 2} / g or more, and more preferably 150 m ² / g or more. By setting it to 70 m ² / g or more, the wear resistance performance and the like tend to be further improved. _N 2 SA of the silica is preferably 500 meters ² / g or less, more preferably 200m ² / g. By setting the content to 500 m ² / g or less, the processing performance tends to be further improved.
The nitrogen adsorption specific surface area of silica is a value measured by the BET method according to ASTM D3037-81.

As the silica, for example, products such as Degussa, Rhodia, Tosoh Silica Co., Ltd., Solvay Japan Co., Ltd., Tokuyama Corporation can be used.

The content of silica is preferably 30 parts by mass or more, more preferably 50 parts by mass or more, and further preferably 70 parts by mass or more with respect to 100 parts by mass of the rubber component. When it is 30 parts by mass or more, the fuel efficiency performance tends to be further improved. The content is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, still more preferably 110 parts by mass or less, and particularly preferably 100 parts by mass or less. When it is 200 parts by mass or less, the balance between processing performance and fuel efficiency performance tends to be further improved.

When the rubber composition contains silica, it is preferable to further contain a silane coupling agent.
The silane coupling agent is not particularly limited, and for example, 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-dimethylthiocarbamoyltetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyltetrasulfide, 3- Sulfates such as triethoxysilylpropyl methacrylate monosulfide, 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, mercaptos such as Momentive's NXT and NXT-Z, vinyltriethoxysilane, vinyltri Vinyl type such as methoxysilane, amino type such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane, glycidoxy such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane. Examples thereof include nitro systems such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane, and chlorosystems such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. These may be used alone or in combination of two or more. Of these, a mercapto-based silane coupling agent is preferable because the effects of the present invention tend to be obtained better.

（式（１）中、ｐは１〜３の整数、ｑは１〜５の整数、ｋは５〜１２の整数である。） As the silane coupling agent, it is preferable to use the silane coupling agent represented by the formula (1). As a result, better fuel efficiency performance, wear resistance performance and the like can be obtained.

(In equation (1), p is an integer of 1 to 3, q is an integer of 1 to 5, and k is an integer of 5 to 12.)

In the formula (1), p is an integer of 1 to 3, but 2 is preferable. When p is 3 or less, the coupling reaction tends to be fast.
Although q is an integer of 1 to 5, 2 to 4 is preferable, and 3 is more preferable. When q is 1 to 5, synthesis tends to be easy.
k is an integer of 5 to 12, but 5 to 10 is preferable, 6 to 8 is more preferable, and 7 is even more preferable.

Examples of the silane coupling agent represented by the formula (1) include 3-octanoylthio-1-propyltriethoxysilane.

As the silane coupling agent, for example, products such as Degussa, Momentive, Shinetsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., Toray Dow Corning Co., Ltd. can be used.

The content of the silane coupling agent is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, based on 100 parts by mass of silica. When it is 3 parts by mass or more, the effect of the addition tends to be obtained. The content is preferably 20 parts by mass or less, more preferably 15 parts by mass or less. When it is 20 parts by mass or less, an effect commensurate with the blending amount can be obtained, and good processability at the time of kneading tends to be obtained.

The rubber composition preferably contains oil.
Examples of the oil include process oils, vegetable oils and fats, or mixtures thereof. As the process oil, for example, a paraffin-based process oil, an aroma-based process oil, a naphthen-based process oil, or the like can be used. Vegetable oils and fats include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, palm oil, peanut oil, rosin, pine oil, pineapple, tall oil, corn oil, rice oil, beni flower oil, sesame oil, Examples thereof include olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, and tung oil. These may be used alone or in combination of two or more. Of these, process oils are preferable, and aroma-based process oils are more preferable, because the effects of the present invention can be obtained satisfactorily.

The oil content is preferably 1 part by mass or more, more preferably 5 parts by mass or more, based on 100 parts by mass of the rubber component. The content is preferably 30 parts by mass or less, more preferably 20 parts by mass or less. Within the above numerical range, the effect of the present invention tends to be obtained better.

The rubber composition preferably contains wax.
The wax is not particularly limited, and examples thereof include petroleum wax such as paraffin wax and microcrystalline wax; natural wax such as plant wax and animal wax; and synthetic wax such as a polymer such as ethylene and propylene. These may be used alone or in combination of two or more. Of these, petroleum-based wax is preferable, and paraffin wax is more preferable.

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

From the viewpoint of the performance balance, the wax content is preferably 0.3 to 20 parts by mass, and more preferably 0.5 to 10 parts by mass with respect to 100 parts by mass of the rubber component.

The rubber composition preferably contains an anti-aging agent.
Examples of the anti-aging agent 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; N. -Isopropyl-N'-phenyl-p-phenylenediamine, N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine, N, N'-di-2-naphthyl-p-phenylenediamine, etc. P-Phenylenediamine-based anti-aging agents; quinoline-based anti-aging agents such as polymers of 2,2,4-trimethyl-1,2-dihydroquinolin; 2,6-di-t-butyl-4-methylphenol, Monophenolic anti-aging agents such as styrenated phenol; tetrakis- [methylene-3- (3', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] bis, tris, polyphenolic aging such as methane Preventive agents and the like can be mentioned. These may be used alone or in combination of two or more. Of these, p-phenylenediamine-based anti-aging agents and quinoline-based anti-aging agents are preferable.

As the anti-aging agent, for example, products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., Flexis Co., Ltd. and the like can be used.

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

The rubber composition preferably contains a processing aid.
By blending a processing aid in addition to SBR, isoprene rubber, liquid IR, and aromatic resin, grip performance such as wet grip performance and dry grip performance, and processing performance can be significantly (synergistically) improved. ..
The reason why such an action effect is obtained is not always clear, but it is presumed as follows.
Aromatic resins and processing aids are deposited on the surface of the formulation regardless of the temperature range, but since liquid IR has a relatively higher molecular weight than these, it is entangled with the molecular chains of SBR and isoprene rubber, and at low temperatures. It is considered that it does not precipitate on the surface but precipitates on the surface in a high temperature range of 80 ° C. or higher. Therefore, it is considered that by combining these, the hardness of the rubber surface is lowered in the entire temperature range and the road surface followability is improved, so that the grip performance is improved. Further, it is considered that the processing performance is improved because the viscosity is reduced in the temperature range of rubber processing. Therefore, grip performance and processing performance are improved.

The processing aid is not particularly limited, and those commonly used in the tire industry can be used. For example, fatty acid metal salt, fatty acid amide, amide ester, silica surface active agent, fatty acid ester, fatty acid metal salt and amide ester. Mixtures, mixtures of fatty acid metal salts and fatty acid amides, etc. can be used. These may be used alone or in combination of two or more. Of these, a mixture of a fatty acid metal salt, an amide ester, a fatty acid metal salt and an amide ester or a fatty acid amide is preferable, and a mixture of a fatty acid metal salt and a fatty acid amide is particularly preferable.

The fatty acid constituting the fatty acid metal salt is not particularly limited, but is saturated or saturated with saturated or unsaturated fatty acids (preferably 6 to 28 carbon atoms (more preferably 10 to 25 carbon atoms, still more preferably 14 to 20 carbon atoms)). (Unsaturated fatty acids), for example, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, arachidic acid, behenic acid, nervonic acid and the like. These can be used alone or in admixture of two or more. Of these, saturated fatty acids are preferable, and saturated fatty acids having 14 to 20 carbon atoms are more preferable.

Examples of the metal constituting the fatty acid metal salt include alkali metals such as potassium and sodium, alkaline earth metals such as magnesium, calcium and barium, zinc, nickel and molybdenum. Of these, zinc and calcium are preferable, and zinc is more preferable.

The fatty acid amide may be a saturated fatty acid amide or an unsaturated fatty acid amide. Examples of the saturated fatty acid amide include N- (1-oxooctadecyl) sarcosin, stearic acid amide, and behenic acid amide. Examples of the unsaturated fatty acid amide include oleic acid amide and erucic acid amide.

Specific examples of the mixture of the fatty acid metal salt and the fatty acid amide include WB16 manufactured by Structor Co., Ltd., which is a mixture of fatty acid calcium and the fatty acid amide.

The content of the processing aid is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, and further preferably 1 part by mass or more with respect to 100 parts by mass of the rubber component. The content is preferably 10 parts by mass or less, more preferably 5 parts by mass or less. Within the above range, the above-mentioned effects tend to be obtained more.

The rubber composition preferably contains stearic acid.
As the stearic acid, conventionally known ones can be used, and for example, products such as NOF Corporation, NOF Corporation, Kao Corporation, Wako Pure Chemical Industries, Ltd., and Chiba Fatty Acid Co., Ltd. can be used.

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

The rubber composition preferably contains zinc oxide.
Conventionally known zinc oxide can be used. For example, products of Mitsui Metal Mining Co., Ltd., Toho Zinc Co., Ltd., HakusuiTech Co., Ltd., Shodo Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. Can be used.

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

The rubber composition preferably contains sulfur.
Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and soluble sulfur, which are generally used in the rubber industry. These may be used alone or in combination of two or more.

As the sulfur, for example, products of Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemicals Corporation, Flexis Co., Ltd., Nippon Inui Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd. and the like can be used.

The sulfur content is preferably 0.1 part by mass or more, and more preferably 0.5 part by mass or more with respect to 100 parts by mass of the rubber component. The content is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and further preferably 3 parts by mass or less. Within the above numerical range, the effect of the present invention tends to be obtained better.

The rubber composition preferably contains a vulcanization accelerator.
Examples of the vulcanization accelerator include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiadylsulfenamide; tetramethylthiuram disulfide (TMTD). ), Tetrabenzyl thiuram disulfide (TBzTD), tetrakis (2-ethylhexyl) thiuram disulfide (TOT-N) and other thiuram-based vulcanization accelerators; N-cyclohexyl-2-benzothiazolesulfenamide, N-t-butyl- 2-benzothiazolyl sulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N, N'-diisopropyl-2-benzothiazolesulfenamide, etc. Sulfenamide-based vulcanization accelerator; guanidine-based vulcanization accelerators such as diphenylguanidine, dioltotrilguanidine, orthotrilbiguanidine can be mentioned. These may be used alone or in combination of two or more. Of these, sulfenamide-based vulcanization accelerators and guanidine-based vulcanization accelerators are preferable because the effects of the present invention can be obtained more preferably.

The content of the vulcanization accelerator is preferably 1 part by mass or more, and more preferably 3 parts by mass or more with respect to 100 parts by mass of the rubber component. The content is preferably 10 parts by mass or less, more preferably 7 parts by mass or less. Within the above numerical range, the effect of the present invention tends to be obtained better.

In addition to the above components, additives generally used in the tire industry can be added to the rubber composition, and organic peroxides; calcium carbonate, talc, alumina, clay, aluminum hydroxide, mica. Fillers such as; etc. can be exemplified.

The rubber composition can be produced, for example, by kneading each of the components using a rubber kneading device such as an open roll or a Banbury mixer, and then vulcanizing.

(Pneumatic tire)
The pneumatic tire is manufactured by a usual method using the rubber composition. That is, the rubber composition containing the above components is extruded according to the tread shape at the unvulcanized stage, and is molded together with other tire members by a normal method on a tire molding machine. Form vulcanized tires. A tire is obtained by heating and pressurizing this unvulcanized tire in a vulcanizer.

The pneumatic tire can be suitably used for passenger car tires, large passenger car tires, large SUV tires, heavy-duty tires for trucks, buses, and light truck tires.

The present invention will be specifically described with reference to Examples, but the present invention is not limited thereto.

Various chemicals used in Examples and Comparative Examples will be described together.
NR: TSR20 (Mw: 1 million)
SBR1: Modified SBR produced in Production Example 1 below (styrene amount: 25% by mass, vinyl amount: 60% by mass, Mw: 300,000)
SBR2: Modified SBR produced in Production Example 2 below (styrene amount: 40% by mass, vinyl amount: 30% by mass, Mw: 400,000)
BR: BR150B (Mw: 400,000) manufactured by Ube Industries, Ltd.
Liquid IR: LIR-50 (Mw: 54000) manufactured by Kuraray Co., Ltd.
Aromatic petroleum resin: Petrotac 90V manufactured by Tosoh Corporation (C5C9 petroleum resin, softening point: 87 ° C)
Styrene-based resin: SYLVATRAX 4401 manufactured by Arizona Chemical Co., Ltd. (α-methylstyrene-based resin (copolymer of α-methylstyrene and styrene), softening point: 85 ° C.)
Carbon black: Diamond black N220 (N ₂ SA: ^{114m 2} / g) manufactured by Mitsubishi Chemical Corporation
Silica: Ultrasil VN3 manufactured by Degussa (N ₂ SA: 175m ² / g)
Silane coupling agent: NXT (3-octanoylthio-1-propyltriethoxysilane) manufactured by Momentive.
Process oil: X140 (aroma oil) manufactured by Japan Energy Co., Ltd.
Wax: Sunknock N manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Anti-aging agent 1: Nocrack 6C (N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Anti-aging agent 2: Nocrack 224 (2,2,4-trimethyl-1,2-dihydroquinoline polymer) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Processing aid: WB16 manufactured by Straktor (a 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)
Stearic acid: Beads made by NOF Corporation Tsubaki stearic acid Zinc oxide: Zinc oxide type 2 made by Mitsui Metal Mining Co., Ltd. Sulfur: Powdered sulfur made by Tsurumi Chemical Industry Co., Ltd. (containing 5% oil)
Vulcanization Accelerator 1: Noxeller NS (N-tert-butyl-2-benzothiazolyl sulfeneamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
Vulcanization accelerator 2: Noxeller D (diphenylguanidine) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.

(Manufacturing Example 1)
Hexane, 1,3-butadiene, styrene, tetrahydrofuran, and ethylene glycol diethyl ether were charged into a nitrogen-substituted autoclave reactor. Next, bis (diethylamino) methylvinylsilane and n-butyllithium were added as cyclohexane solution and n-hexane solution, respectively, and polymerization was started.
The stirring speed was 130 rpm, the temperature inside the reactor was 65 ° C., and copolymerization of 1,3-butadiene and styrene was carried out for 3 hours while continuously supplying the monomers into the reactor. Next, the obtained polymer solution was stirred at a stirring speed of 130 rpm, 3-diethylaminopropyltriethoxysilane was added, and the reaction was carried out for 15 minutes. After completion of the polymerization reaction, 2,6-di-tert-butyl-p-cresol was added. Then, the solvent was removed by steam stripping and dried by a heat roll adjusted to 110 ° C. to obtain a modified styrene-butadiene rubber (SBR1).

(Manufacturing Example 2)
Hexane, 1,3-butadiene, styrene, tetrahydrofuran, and ethylene glycol diethyl ether were charged into a nitrogen-substituted autoclave reactor. Next, bis (diethylamino) methylvinylsilane and n-butyllithium were added as cyclohexane solution and n-hexane solution, respectively, and polymerization was started.
The stirring speed was 130 rpm, the temperature inside the reactor was 65 ° C., and copolymerization of 1,3-butadiene and styrene was carried out for 3 hours while continuously supplying the monomers into the reactor. Next, the obtained polymer solution was stirred at a stirring speed of 130 rpm, 3-diethylaminopropyltriethoxysilane was added, and the reaction was carried out for 15 minutes. After completion of the polymerization reaction, 2,6-di-tert-butyl-p-cresol was added. Then, the solvent was removed by steam stripping and dried by a heat roll adjusted to 110 ° C. to obtain a modified styrene-butadiene rubber (SBR2).

(Examples and comparative examples)
In accordance with the formulation shown in Table 1, materials other than sulfur and the vulcanization accelerator were kneaded under the condition of 150 ° C. for 5 minutes using a Banbury mixer manufactured by Kobe Steel, Ltd. to obtain a kneaded product. Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and the mixture was kneaded for 5 minutes under the condition of 80 ° C. using an open roll to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition is formed into a tread shape and bonded together with other tire members to form an unvulcanized tire, which is press-vulcanized for 10 minutes under the condition of 170 ° C. to obtain a test tire (test tire). Size: 195 / 65R15) was manufactured. The evaluations shown below were performed using the obtained test tires, and the results are shown in Table 1.

(Wet grip performance)
Each test tire was attached to all wheels of the vehicle (domestic FF2000cc), the braking distance from the initial speed of 100km / h was obtained on a wet asphalt road surface, and it was displayed as an index when Comparative Example 1 was set to 100 (wet). Grip performance index). The larger the index, the shorter the braking distance and the better the wet grip performance.

(Dry grip performance)
Each test tire was attached to the vehicle, and the actual vehicle ran 10 laps on the test course on the dry asphalt road surface. The test site was the Okayama test course of Sumitomo Rubber Industries, Ltd., and the temperature was 20 to 25 ° C.
Then, the test driver evaluated the stability of the control at the time of steering at that time, and the comparative example 1 was set as 100 and displayed as an index (dry grip performance index). The larger the index, the better the dry grip performance.

(Abrasion resistance)
Each test tire was mounted on a domestic FF vehicle, the groove depth of the tire tread portion after a mileage of 8000 km was measured, the mileage when the tire groove depth was reduced by 1 mm was calculated, and Comparative Example 1 was set to 100. Expressed as an index of time (wear resistance performance index). The larger the index, the longer the mileage when the tire groove depth is reduced by 1 mm, and the better the wear resistance performance is.

(Fuel efficiency performance)
Using a rolling resistance tester, measure and compare the rolling resistance when the test tire is run at a rim (15 x 6JJ), internal pressure (230 kPa), load (3.43 kN), and speed (80 km / h). It is displayed as an index when Example 1 is set to 100 (fuel efficiency performance index). The larger the index, the better the fuel efficiency performance.

(Processing performance)
For each unvulcanized rubber composition, follow the method for measuring Mooney viscosity according to JIS K 630-1 "Unvulcanized rubber-Physical characteristics-Part 1: How to determine viscosity and scorch time with Mooney viscometer". Mooney viscosity (ML1 + 4) was measured under a temperature condition of 130 ° C. The result was expressed exponentially with the Mooney viscosity of Comparative Example 1 as 100 (processing performance index). The smaller the index, the lower the Mooney viscosity and the better the workability.

Claims (7)

Pneumatic tire with tread made using a rubber composition containing a rubber component containing styrene-butadiene rubber, isoprene-based rubber and liquid isoprene rubber (excluding hydrogenated liquid isoprene rubber) and an aromatic resin. .. It has a tread prepared by using a rubber composition containing a rubber component containing styrene-butadiene rubber, isoprene-based rubber and liquid isoprene rubber, an aromatic resin, and carbon black.
A pneumatic tire in which the content of the carbon black is 1 to 8 parts by mass with respect to 100 parts by mass of the rubber component. It has a tread prepared by using a rubber composition containing a rubber component containing styrene-butadiene rubber, isoprene-based rubber and liquid isoprene rubber, an aromatic resin, and silica.
A pneumatic tire having a silica content of 120 to 200 parts by mass with respect to 100 parts by mass of the rubber component. The pneumatic tire according to claim 1 or 2 , wherein the rubber composition contains 70 parts by mass or more of silica with respect to 100 parts by mass of the rubber component. The pneumatic tire according to any one of claims 1 to 4, wherein the average amount of styrene of the styrene-butadiene rubber is 30% by mass or more. The pneumatic tire according to any one of claims 1 to 5 , wherein the aromatic resin contains a styrene resin and an aromatic petroleum resin. The pneumatic tire according to any one of claims 1 to 6 , wherein the rubber composition contains 1 part by mass or more of a processing aid with respect to 100 parts by mass of the rubber component.