JP2011057922A - Tire rubber composition and pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for a tire capable of achieving wet grip performance, low fuel consumption performance, and abrasion resistance together in a high level, and a pneumatic tire using the rubber composition for a tread of the tire. <P>SOLUTION: The rubber composition for a tire comprises 20-150 pts.mass of silica based on 100 pts.mass of a rubber component, and a content of an acrylonitrile-butadiene rubber containing 30-50 mass% of a bound acrylonitrile is 10-30 mass% in 100 mass% of the rubber component. Preferably, a carboxyl group is introduced to the acrylonitrile-butadiene rubber. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a rubber composition for tires and a pneumatic tire using the same.

Conventionally, the fuel efficiency of a vehicle has been reduced by reducing the rolling resistance of the tire (improving the fuel efficiency). In recent years, there has been an increasing demand for low fuel consumption of vehicles, and excellent low fuel consumption performance has been demanded for rubber compositions for producing treads that have a high occupation ratio among tire components. ing.

In general, in order to improve the wet grip performance (grip performance on a wet road surface or braking distance) as well as low fuel consumption performance of a pneumatic tire, silica is used as a filler in the tread rubber composition, and a rubber composition at a low temperature. There are known methods for increasing the hysteresis. As a method for increasing the hysteresis at a low temperature, there is a method using a rubber composition having a high glass transition temperature. However, a rubber composition having a high glass transition temperature can improve wet grip performance, but at the same time, there is a problem in that hysteresis at high temperatures also increases and rolling resistance increases (low fuel consumption performance deteriorates). Wear performance also tends to decrease. As a method for improving the low fuel consumption performance of the rubber composition, a method for reducing the content of the reinforcing filler is known. However, in this case, since the hardness of the rubber composition is lowered, the tire is softened, and there is a problem that the handling performance (steering stability) and the wet grip performance of the car are lowered and the wear resistance is lowered. .

Patent Document 1 discloses a rubber composition that can achieve both wet grip performance, low fuel consumption performance, and wear resistance by blending ultrafine powder rubber as a filler. However, cross-linked acrylonitrile-butadiene rubber is used as the ultrafine powder rubber, but the use of acrylonitrile-butadiene rubber as a rubber component and the amount of acrylonitrile-butadiene rubber bound acrylonitrile have been studied in detail. However, there is still room for improvement in terms of both wet grip performance, low fuel consumption performance, and wear resistance.

JP 2006-89552 A

An object of the present invention is to solve the above-described problems and provide a rubber composition for a tire that can achieve high compatibility between wet grip performance, low fuel consumption performance, and wear resistance, and a pneumatic tire using the same for a tire tread. And

The present invention includes 20 to 150 parts by mass of silica with respect to 100 parts by mass of the rubber component, and the content of acrylonitrile-butadiene rubber having a combined acrylonitrile amount of 30 to 50% by mass is 10 to 30% by mass in 100% by mass of the rubber component. % Of the tire rubber composition.

It is preferable that a carboxyl group is introduced into the acrylonitrile-butadiene rubber.

The rubber component preferably contains a low-polar diene rubber having a glass transition temperature of −40 ° C. or lower.

The present invention also relates to a pneumatic tire having a tread produced using the rubber composition.

According to the present invention, since a specific amount of silica is blended with a rubber component containing a specific amount of a specific acrylonitrile-butadiene rubber, air that can achieve both high wet grip performance, low fuel consumption performance, and high wear resistance. Provided tires.

The rubber composition for tires of the present invention contains a specific amount of silica with respect to a rubber component containing a specific amount of a specific acrylonitrile-butadiene rubber (NBR).

In the present invention, a specific NBR is used. By using specific NBR as a rubber component, wet grip performance, low fuel consumption performance, and wear resistance can be improved. In addition, when NBR of powder rubber (NBR after vulcanization (crosslinking)) is blended, the NBR after vulcanization does not disperse finely, so the interaction at the interface between the unvulcanized rubber and the NBR after vulcanization is Get smaller. On the other hand, in the present invention, since unvulcanized NBR is used, NBR is easy to finely disperse, interaction at the interface increases, and vulcanization at the interface may occur, which is preferable.

The amount of bound acrylonitrile of NBR is 30% by mass or more, preferably 35% by mass or more, and more preferably 40% by mass or more. If it is less than 30% by mass, the wet grip performance may not be sufficiently improved. Moreover, there is a risk that the strength of the rubber is lowered without improving the dispersibility of the silica.
The amount of bound acrylonitrile of NBR is 50% by mass or less, preferably 45% by mass or less, more preferably 40% by mass or less. If it exceeds 50% by mass, the strength (particularly elongation) of the rubber is lowered, so that the wear performance may be lowered.
The amount of bound acrylonitrile of NBR was determined by measuring the amount of generated nitrogen according to JIS K6364 mil oven method, converting the amount of bound acrylonitrile from the molecular weight of acrylonitrile.

In the present invention, it is preferable that a carboxyl group is introduced into NBR because silica can be finely dispersed in rubber, which can sufficiently improve wet grip performance, low fuel consumption performance, and wear resistance. NBR introduced with a carboxyl group (carboxyl-modified NBR (XNBR)) is not particularly limited, and carboxyl group-containing polymerizable monomers such as carboxylated NBR end groups, methacrylic acid, acrylic acid, maleic acid and the like. And a terpolymer rubber of mer, acrylonitrile, and butadiene. Examples of commercially available XNBR products include Nipol DN631 manufactured by Nippon Zeon Co., Ltd., Nipol LX1571 manufactured by Nippon Zeon Co., Ltd., and the like.

The content of NBR in 100% by mass of the rubber component is 10% by mass or more, preferably 15% by mass or more. If it is less than 10% by mass, the wet grip performance may not be sufficiently improved. The NBR content is 30% by mass or less, more preferably 25% by mass or less. If it exceeds 30% by mass, the wear performance may be reduced (the tensile properties of the rubber may be reduced).

Examples of rubber components that can be used other than NBR in the present invention include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), epoxidized natural rubber (ENR), and chloroprene rubber. And diene rubbers such as (CR), butyl rubber (IIR), styrene-isoprene-butadiene copolymer rubber (SIBR), and ethylene-propylene-diene rubber (EPDM). These diene rubbers may be used alone or in combination of two or more. Among these, low polar diene rubbers such as SBR and NR are preferably included because of a good balance between rubber processability, wet grip performance and low fuel consumption performance.
In addition, the low polar diene rubber in the present invention means a diene rubber having a glass transition temperature (Tg) of −40 ° C. or lower.

The glass transition temperature (Tg) of the low-polar diene rubber is −40 ° C. or lower, preferably −45 ° C. or lower. If it exceeds −40 ° C., the balance between the wet grip performance and the low fuel consumption performance may be deteriorated. The lower limit of Tg is not particularly limited. In addition, Tg in this invention is the value measured on the temperature increase rate of 10 degree-C / min conditions using the differential scanning calorimeter (Q200) by a TA instrument Japan company according to JIS-K7121. is there.

The content of the low-polar diene rubber having Tg in the above temperature range in 100% by mass of the rubber component is preferably 70% by mass or more, more preferably 75% by mass or more. If it is less than 70% by mass, the tensile strength of the rubber may be lowered.
The content of the low-polar diene rubber is preferably 90% by mass or less, more preferably 85% by mass or less. If it exceeds 90% by mass, the amount of NBR will decrease, and there is a risk that wet grip performance, fuel efficiency and wear resistance cannot be improved.

Among the low-polar diene rubbers having Tg in the above temperature range, SBR and NR are preferable because the balance between rubber processability and strength is good.

The SBR is not particularly limited as long as it has a Tg in the above temperature range, and is an emulsion polymerization SBR (E-SBR), a solution polymerization SBR (S-SBR), a modified SBR modified by a primary amino group or the like. Etc. Among these, modified SBR is preferable because it can improve the dispersibility of silica and reduce heat generation.

As the modified SBR, those coupled with tin or silicon are preferably used. As a coupling method of the modified SBR, for example, an alkali metal (such as Li) or an alkaline earth metal (such as Mg) at the molecular chain terminal of the modified SBR is reacted with tin halide or silicon halide according to a conventional method. The method etc. are mentioned.

The modified SBR is a copolymer of styrene and butadiene and preferably has a primary amino group or an alkoxysilyl group. The primary amino group may be bonded to any of the polymerization initiation terminal, the polymerization termination terminal, the polymer main chain, and the side chain, but it can suppress the energy loss from the polymer terminal and improve the hysteresis loss characteristics. From the viewpoint, it is preferably introduced at the polymerization initiation terminal or the polymerization termination terminal.

Among the modified SBRs, those obtained by modifying solution-polymerized styrene butadiene rubber (SBR) with a compound represented by the following formula (1) (modified S-SBR) are preferably used. Thereby, it is easy to control the molecular weight of the polymer, the low molecular weight component that increases tan δ can be reduced, the bond between silica and the polymer chain is further strengthened, and the heat generation and strength of the rubber can be improved.

（式中、Ｒ^１、Ｒ^２及びＲ^３は、同一若しくは異なって、アルキル基、アルコキシ基、シリルオキシ基、アセタール基、カルボキシル基、メルカプト基又はこれらの誘導体を表す。Ｒ^４及びＲ^５は、同一若しくは異なって、水素原子又はアルキル基を表す。ｎは整数を表す。）

(Wherein R ¹ , R ² and R ³ are the same or different and each represents an alkyl group, an alkoxy group, a silyloxy group, an acetal group, a carboxyl group, a mercapto group or a derivative thereof. R ⁴ and R ⁵ are (The same or different, and represents a hydrogen atom or an alkyl group. N represents an integer.)

In the compound represented by the above formula (1), R ¹ , R ² and R ³ are the same or different and are an alkyl group, an alkoxy group, a silyloxy group, an acetal group, a carboxyl group (—COOH), a mercapto group (— SH) or derivatives thereof. As said alkyl group, C1-C4 alkyl groups, such as a methyl group, an ethyl group, n-propyl group, isopropyl group, n-butyl group, t-butyl group, etc. are mentioned, for example. Examples of the alkoxy group include alkoxy groups having 1 to 8 carbon atoms such as methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group and t-butoxy group (preferably having 1 to 6 carbon atoms). More preferably, C1-C4) etc. are mentioned. The alkoxy group includes a cycloalkoxy group (cycloalkoxy group having 5 to 8 carbon atoms such as cyclohexyloxy group) and an aryloxy group (aryloxy group having 6 to 8 carbon atoms such as phenoxy group and benzyloxy group). ) Is also included.

Examples of the silyloxy group include a silyloxy group substituted with an aliphatic group having 1 to 20 carbon atoms and an aromatic group (trimethylsilyloxy group, triethylsilyloxy group, triisopropylsilyloxy group, diethylisopropylsilyloxy group, t- Butyldimethylsilyloxy group, t-butyldiphenylsilyloxy group, tribenzylsilyloxy group, triphenylsilyloxy group, tri-p-xylylsilyloxy group, etc.).

Examples of the acetal group include groups represented by -C (RR ')-OR "and -O-C (RR')-OR". Examples of the former include a methoxymethyl group, an ethoxymethyl group, a propoxymethyl group, a butoxymethyl group, an isopropoxymethyl group, a t-butoxymethyl group, and a neopentyloxymethyl group. The latter includes a methoxymethoxy group, an ethoxy group, and the like. Methoxy group, propoxymethoxy group, i-propoxymethoxy group, n-butoxymethoxy group, t-butoxymethoxy group, n-pentyloxymethoxy group, n-hexyloxymethoxy group, cyclopentyloxymethoxy group, cyclohexyloxymethoxy group, etc. Can be mentioned. R ¹ , R ² and R ³ are preferably alkoxy groups. Thereby, excellent wet grip performance, low fuel consumption performance, and wear resistance can be obtained.

Examples of the alkyl group for R ⁴ and R ⁵ include the same groups as the above alkyl group.

As n (integer), 1-5 are preferable. Thereby, excellent wet grip performance, low fuel consumption performance, and wear resistance can be obtained. Furthermore, n is more preferably 2 to 4, and most preferably 3. When n is 0, it is difficult to bond a silicon atom and a nitrogen atom, and when n is 6 or more, the effect as a modifier is reduced.

Specific examples of the compound represented by the above formula (1) include 3-aminopropyldimethylmethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylethyldimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, Aminopropyldimethylethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyldimethylbutoxysilane, 3-aminopropylmethyldibutoxysilane, dimethylaminomethyltrimethoxysilane, 2-dimethyl Aminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 4-dimethylaminobutyltrimethoxysilane, dimethylaminomethyldimethoxymethylsilane, 2-dimethylaminoethyldimethoxy Methylsilane, 3-dimethylaminopropyldimethoxymethylsilane, 4-dimethylaminobutyldimethoxymethylsilane, dimethylaminomethyltriethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 4-dimethylaminobutyl Triethoxysilane, dimethylaminomethyldiethoxymethylsilane, 2-dimethylaminoethyldiethoxymethylsilane, 3-dimethylaminopropyldiethoxymethylsilane, 4-dimethylaminobutyldiethoxymethylsilane, diethylaminomethyltrimethoxysilane, 2- Diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 4-diethylaminobutyltrimethoxysilane, diethylamino Tildimethoxymethylsilane, 2-diethylaminoethyldimethoxymethylsilane, 3-diethylaminopropyldimethoxymethylsilane, 4-diethylaminobutyldimethoxymethylsilane, diethylaminomethyltriethoxysilane, 2-diethylaminoethyltriethoxysilane, 3-diethylaminopropyltriethoxysilane 4-diethylaminobutyltriethoxysilane, diethylaminomethyldiethoxymethylsilane, 2-diethylaminoethyldiethoxymethylsilane, 3-diethylaminopropyldiethoxymethylsilane, 4-diethylaminobutyldiethoxymethylsilane, and the like. These may be used alone or in combination of two or more.

As a method for modifying a styrene butadiene rubber with the compound represented by the above formula (1) (modifier), conventionally known methods such as those described in JP-B-6-53768 and JP-B-6-57767 are known. Can be used. For example, a styrene butadiene rubber and a modifier may be brought into contact with each other. A method of polymerizing styrene butadiene rubber and adding a predetermined amount of the modifier to the polymer rubber solution, or adding a modifier to the styrene butadiene rubber solution. The method of making it react is mentioned.

The amount of bound styrene in SBR is preferably 23% by mass or less, more preferably 15% by mass or less, and still more preferably 12% by mass or less. When it exceeds 23 mass%, there exists a possibility that tensile strength may fall. Moreover, the lower limit of the amount of bound styrene of SBR is not particularly limited.
The amount of styrene is calculated by H ¹ -NMR measurement.

The content of SBR in 100% by mass of the rubber component is preferably 30% by mass or more, more preferably 50% by mass or more, and further preferably 60% by mass or more. If it is less than 30% by mass, the balance between the exothermic property of rubber and the strength of rubber may be deteriorated. The SBR content is preferably 90% by mass or less, more preferably 85% by mass or less. If it exceeds 90% by mass, the amount of NBR will be reduced, and sufficient wet grip performance will not be improved, or NR will not be able to be added, and workability may be deteriorated.

The NR is not particularly limited as long as the NR has a Tg in the above temperature range. For example, those commonly used in the tire industry such as SIR20, RSS # 3, and TSR20 can be used. When the rubber composition of the present invention contains NR, processability during rubber kneading is improved.

The total content of SBR and NR in 100% by mass of the rubber component is preferably 70% by mass or more, more preferably 75% by mass or more. If it is less than 70% by mass, the processability of the rubber is deteriorated, and it may be difficult to form the sheet. Moreover, there exists a possibility that the tensile strength of rubber | gum may fall.
The total content is preferably 90% by mass or less, more preferably 85% by mass or less. If it exceeds 90% by mass, the amount of NBR will decrease, and there is a risk that wet grip performance, fuel efficiency and wear resistance cannot be improved.

In the present invention, silica is used. Thereby, wet grip performance, low fuel consumption performance, and wear resistance can be improved. The silica is not particularly limited, and examples thereof include dry process silica (anhydrous silicic acid), wet process silica (hydrous silicic acid), and the like, but wet process silica is preferable because of its large number of silanol groups. Examples of the wet process silica include Ultrasil VN3 manufactured by Degussa and Nip Seal VN3 AQ manufactured by Nippon Silica Industry Co., Ltd. Silica may be used alone or in combination of two or more.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 50 m ² / g or more, more preferably 55 m ² / g or more. If it is less than 50 m ² / g, the dispersibility improving effect and the reinforcing effect tend to decrease. Further, N ₂ SA of silica is preferably 300 m ² / g or less, more preferably 200 m ² / g or less. If it exceeds 300 m ² / g, the dispersibility is poor and the heat generation of the tire tends to increase.
The nitrogen adsorption specific surface area of silica is a value measured by the BET method according to ASTM D3037-81.

The content of silica is 20 parts by mass or more, preferably 30 parts by mass or more, more preferably 45 parts by mass or more, particularly preferably 60 parts by mass or more, and most preferably 80 parts by mass or more with respect to 100 parts by mass of the rubber component. It is. If the amount is less than 10 parts by mass, the wet grip performance, low fuel consumption performance, and wear resistance tend to be insufficiently improved. Content of this silica is 150 mass parts or less, Preferably it is 120 mass parts or less, More preferably, it is 100 mass parts or less. If it exceeds 150 parts by mass, the dispersibility of silica in the rubber composition will deteriorate, and the wear resistance, strength and the like will tend to decrease.

The rubber composition of the present invention preferably contains a silane coupling agent together with silica. As the silane coupling agent, any silane coupling agent conventionally used in combination with silica can be used in the rubber industry. For example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-tri Ethoxysilylethyl) tetrasulfide, bis (4-triethoxysilylbutyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (4-trimethoxysilyl) Butyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (2-triethoxysilylethyl) trisulfide, bis (4-triethoxysilylbutyl) trisulfide, bis (3-trimethoxysilylpropyl) Trisulfi Bis (2-trimethoxysilylethyl) 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, 3-triethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-trime Xylylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3- Sulfide type such as trimethoxysilylpropyl methacrylate monosulfide, mercapto type such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, vinyltri Vinyl series such as ethoxysilane and vinyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysila , Glycidoxy type such as γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, nitro type such as 3-nitropropyltrimethoxysilane, 3-nitropropyltriethoxysilane, 3-chloropropyl Examples include chloro-based compounds such as trimethoxysilane, 3-chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane, and 2-chloroethyltriethoxysilane. Product names include Si69, Si75, Si363 (Degussa), NXT, NXT-LV, NXT-ULV, NXT-Z (GE). Of these, bis (3-triethoxysilylpropyl) tetrasulfide, 3-mercaptopropyltriethoxysilane, and bis (3-triethoxysilylpropyl) disulfide are preferable from the viewpoint of the reinforcing effect and processability of the silane coupling agent. Furthermore, from the viewpoint of processability, bis (3-triethoxysilylpropyl) tetrasulfide and bis (3-triethoxysilylpropyl) disulfide are more preferable. These silane coupling agents may be used alone or in combination of two or more.

3 mass parts or more are preferable with respect to 100 mass parts of silica, and, as for content of a silane coupling agent, 5 mass parts or more are more preferable. If the amount is less than 3 parts by mass, the reaction with silica is not sufficient, and physical properties may not be improved. Moreover, 15 mass parts or less are preferable, as for content of this silane coupling agent, 10 mass parts or less are more preferable, and 8 mass parts or less are still more preferable. If it exceeds 15 parts by mass, the tensile strength of the rubber may be reduced. Moreover, it becomes extremely soft and may cause a problem.

You may mix | blend carbon black with the rubber composition of this invention. By blending carbon black, it is possible to enhance the reinforcement. Examples of carbon black that can be used include GPF, FEF, HAF, ISAF, and SAF, but are not particularly limited.

In addition to the above-mentioned components, the rubber composition includes a compounding agent conventionally used in the rubber industry, for example, fillers such as clay, softeners (oils such as paraffinic, aromatic, naphthenic process oils, plastics, etc. Agent), tackifier (coumarone indene resin, rosin resin, cyclopentadiene resin, etc.), wax, antioxidant, anti-aging agent, vulcanization accelerator (stearic acid, zinc oxide, etc.), sulfur, You may contain vulcanizing agents, such as a sulfur-containing compound, a vulcanization accelerator, etc.

When sulfur is used as the vulcanizing agent, the sulfur content is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more with respect to 100 parts by mass of the rubber component. Moreover, this content becomes like this. Preferably it is 3.0 mass parts or less, More preferably, it is 2.5 mass parts or less. If the amount is less than 0.5 parts by mass, the vulcanization rate tends to be slow and tends to be insufficiently vulcanized. If the amount exceeds 3.0 parts by mass, the vulcanization rate tends to be high and scorching tends to occur.

Examples of the vulcanization accelerator include guanidine, aldehyde-amine, aldehyde-ammonia, thiazole, sulfenamide, thiourea, thiuram, dithiocarbamate, and zanddate compounds. These vulcanization accelerators may be used alone or in combination of two or more. Among these, from the viewpoint of dispersibility in rubber and stability of vulcanization properties, sulfenamide vulcanization accelerators [N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl -2-benzothiazolylsulfenamide (CBS), N, N-dicyclohexyl-2-benzothiazolylsulfenamide (DCBS), N, N-diisopropyl-2-benzothiazole sulfenamide, etc.], guanidine series Sulfur accelerators (diphenylguanidine (DPG), diortotriguanidine, triphenylguanidine, orthotolylbiguanide, diphenylguanidine phthalate, etc.) are preferable, and it is particularly preferable to use CBS and DPG in combination.

The blending amount of the vulcanization accelerator is preferably 1.0 part by mass or more, more preferably 1.5 parts by mass or more with respect to 100 parts by mass of the rubber component. Moreover, this compounding quantity becomes like this. Preferably it is 4.0 mass parts or less, More preferably, it is 3.0 mass parts or less. If the amount is less than 1.0 part by mass, the vulcanization rate tends to be slow and vulcanization tends to be insufficient, and if the amount exceeds 4.0 parts by mass, the vulcanization rate becomes high and scorching tends to occur.

The rubber composition of the present invention is produced by a general method. That is, it can be produced by a method of kneading the above components with a Banbury mixer, a kneader, an open roll or the like and then vulcanizing. For example, in the first step, a rubber component, a vulcanizing agent such as silica and a silane coupling agent, and a compounding agent other than a vulcanization accelerator are kneaded at a kneading temperature of 130 to 160 ° C. using a Banbury mixer. . Next, for example, using an open roll, the kneaded material, sulfur and vulcanization accelerator kneaded by a Banbury mixer are kneaded at a kneading temperature of 80 to 120 ° C. When the kneading temperature is less than 80 ° C., the dispersion of each component is poor and tends to be insufficiently vulcanized, and when it exceeds 120 ° C., vulcanization starts and tends to scorch. The obtained unvulcanized rubber is usually vulcanized at a temperature of 150 to 190 ° C., more preferably 160 to 180 ° C., to obtain a vulcanized tire.

The rubber composition of the present invention can be used for tire treads. The tread can be produced by pasting a sheet into a predetermined shape, or by inserting it into two or more extruders and forming it in two layers at the head outlet of the extruder.

The pneumatic tire of the present invention can be produced by a usual method using the rubber composition. That is, the rubber composition is extruded to match the shape of the tread at the unvulcanized stage, molded by a normal method on a tire molding machine, and bonded together with other tire members to form an unvulcanized tire To do. This unvulcanized tire can be heated and pressurized in a vulcanizer to produce a tire.

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

Hereinafter, various chemicals used in Examples and Comparative Examples will be described together.
SBR: HPR340 manufactured by JSR Corporation (modified S-SBR, amount of bound styrene: 10% by mass, Tg: -60 ° C., coupled with alkoxysilane, introduced at the terminal, modified by the compound represented by formula (1) (R ¹ , R ² , R ³ = methyl group, R ⁴ , R ⁵ = hydrogen atom in formula (1), n = 3))
NBR (1): LX550 manufactured by Nippon Zeon Co., Ltd. (bound acrylonitrile content: 28% by mass, carboxyl group-containing NBR)
NBR (2): LX1571 manufactured by Nippon Zeon Co., Ltd. (bound acrylonitrile content: 45% by mass, carboxyl group-containing NBR)
NBR (3): LX513 manufactured by Nippon Zeon Co., Ltd. (bound acrylonitrile content: 35% by mass, carboxyl group-free NBR)
NR: RSS # 3 (Tg: -74 ° C)
Carbon black: Seast NH manufactured by Tokai Carbon Co., Ltd. (N ₂ SA74m ² / g)
Silica: ULTRASIL VN3 manufactured by Degussa (N ₂ SA: 175 m ² / g)
Silane coupling agent: Si75 (bis (3-triethoxysilylpropyl) disulfide) manufactured by Degussa
Zinc oxide: Zinc Hua 1 manufactured by Mitsui Mining & Smelting Co., Ltd.
Aroma oil: Process X-140 manufactured by Japan Energy Co., Ltd.
Anti-aging agent: Antigen 6C (N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd.
Wax: Sunnock N manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Sulfur: Powder sulfur vulcanization accelerator manufactured by Karuizawa Sulfur Co., Ltd. (1): Noxeller CZ (N-cyclohexyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Co., Ltd.
Vulcanization accelerator (2): Noxeller D (N, N'-diphenylguanidine) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

Examples 1-8 and Comparative Examples 1-6
According to the contents shown in Table 1, materials other than sulfur and a vulcanization accelerator were kneaded for 5 minutes at 150 ° C. using a Banbury mixer to obtain a kneaded product. Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded for 3 minutes at 80 ° C. using an open roll to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was molded into a tread shape, bonded to another tire member, and vulcanized at 160 ° C. for 30 minutes to produce a test tire (195 / 65R15).

The following evaluation was performed using the obtained test tire. Each test result is shown in Table 1.

(Low fuel consumption performance)
Using a rolling resistance tester, the rolling resistance when a test tire was run at a rim (15 × 6JJ), internal pressure (230 kPa), load (3.43 kN), speed (80 km / h) was measured and compared. The value was expressed as an index (rolling resistance index) when Example 1 was 100. A larger index indicates better fuel efficiency. 100 or more was considered acceptable.

(Wet grip performance)
The test tire was mounted on a 2000 cc domestic FR vehicle, and the braking distance from the initial speed of 100 km / h was determined on a wet asphalt road surface. The result is expressed as an index. The larger the index, the better the wet grip performance. The index was calculated by the following formula. 110 or higher was accepted.
Wet grip index = (braking distance of comparative example 1) / (braking distance of each example or comparative example) × 100

(Abrasion resistance)
On a test course on an asphalt road surface, the test tire was mounted on a 2000 cc domestic FR vehicle and traveled 30000 km. After the travel, the depth of the tire groove was measured. Larger values indicate better wear resistance. More than 95 was accepted.

(Tensile test)
Tensile test using No. 3 dumbbell type rubber test piece made of vulcanized rubber composition cut out from tread part of test tire according to JIS K 6251 “Vulcanized rubber and thermoplastic rubber-Determination of tensile properties” And the breaking strength (TB) and the elongation at break EB (%) were measured. The result was expressed as an index with the result of Comparative Example 1 being 100. The larger the index of TB and EB, the better the rubber strength.

According to Table 1, with respect to a rubber component containing a specific amount of a specific acrylonitrile-butadiene rubber (NBR), in an example including a specific amount of silica, wet grip performance, low fuel consumption performance, wear resistance, and rubber strength are highly enhanced. I was able to achieve both. On the other hand, the comparative example 1 which did not mix | blend NBR was not able to make wet grip performance, low fuel consumption performance, abrasion resistance, and rubber strength highly compatible. The comparative example 2 which mix | blended NBR with few amounts of bond acrylonitrile was inferior in wet grip performance and the intensity | strength of rubber | gum.

Comparative Example 3 in which the specific NBR content was as small as 5 parts by mass was inferior in wet grip performance and rubber strength. Comparative Example 6 in which the specific NBR content was as large as 50 parts by mass was inferior in fuel efficiency, wear resistance, and rubber strength.

In Comparative Example 4 where the amount of silica was as small as 5 parts by mass, wet grip performance, wear resistance, and rubber strength were inferior. Comparative Example 5 in which the amount of silica was as large as 155 parts by mass was inferior in fuel efficiency and rubber strength.

Claims (4)

20 to 150 parts by mass of silica with respect to 100 parts by mass of the rubber component,
A rubber composition for tires, wherein the content of acrylonitrile-butadiene rubber having an amount of bound acrylonitrile of 30 to 50% by mass is 10 to 30% by mass in 100% by mass of the rubber component. The tire rubber composition according to claim 1, wherein a carboxyl group is introduced into the acrylonitrile-butadiene rubber. The rubber composition for tires according to claim 1 or 2 in which said rubber ingredient contains low polar diene system rubber whose glass transition temperature is -40 ° C or less. A pneumatic tire having a tread produced using the rubber composition according to claim 1.