JP2015013924A - Rubber composition for tire, and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition that gives excellent ozone resistance while suppressing discoloration (browning or whitening), and a pneumatic tire using the composition.SOLUTION: The rubber composition for a tire is obtained through a base kneading step of kneading a rubber component, a filler and an anti-ageing agent comprising a compound having an ozone resistant effect and reactivity with a polymer. The content of the above compound is 0.5 to 7.0 parts by mass with respect to 100 parts by mass of the rubber component.

Description

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

In addition to flex crack growth resistance and chip cut resistance, tire sidewalls and tread rubber are required to have performance such as oxidation resistance, ozone resistance, and ultraviolet resistance, while maintaining these performances. N-phenyl-N ′-(1,3-dimethylbutyl) -p-phenylenediamine (6C) and 2,2,4-trimethyl for the purpose of minimizing tea discoloration derived from the blended chemicals Anti-aging agents such as -1,2-dihydroquinoline polymer (RD) are blended.

Anti-aging agent 6C is excellent in ozone resistance and flex crack growth resistance, but has a problem that it tends to precipitate on the tire surface, is inferior in thermal stability such as volatility, and easily changes its color to brown derived from chemicals. Such discoloration becomes a serious problem in appearance on a tire mounted on a vehicle with low traveling frequency and a tread groove bottom portion that does not wear. In addition, when blended with a two-layer structure tread composed of a cap tread and a base tread, the anti-aging agent 6C may be transferred from the base tread to the cap tread and discoloration of the cap tread surface may occur.

On the other hand, if an anti-aging agent RD that is difficult to discolor is used, sufficient ozone resistance cannot be secured, and there is a risk that rubber breakage such as cracks or rubber chipping is likely to occur. Moreover, although the anti-aging agent 3C is excellent in ozone resistance, it has low solubility in rubber, is easily volatilized, and cannot exist in the rubber for a long time. Thus, it is generally difficult to improve ozone resistance while suppressing discoloration.

Patent Documents 1 to 3 propose a method for improving discoloration resistance and ozone resistance by using N-phenyl-N ′-(1,3-dimethylbutyl) -p-phenylenediamine as an anti-aging agent. However, further improvement is desired in terms of achieving both of these performances.

JP 2012-180387 A JP 2013-95836 A JP 2013-95837 A

An object of the present invention is to solve the above-mentioned problems and to provide a rubber composition capable of obtaining excellent ozone resistance while suppressing discoloration (browning, whitening), and a pneumatic tire using the rubber composition. To do.

The present invention is obtained through a base kneading step of kneading a rubber component, a filler, and an anti-aging agent containing a compound having ozone resistance and reactivity with a polymer, and the content of the compound with respect to 100 parts by mass of the rubber component The present invention relates to a tire rubber composition having an amount of 0.5 to 7.0 parts by mass.

The base kneading step includes a first base kneading step of kneading only the rubber component, the filler, and the anti-aging agent containing a compound having ozone resistance and reactivity with a polymer. And a second base kneading step for kneading the kneaded product and zinc oxide.
The base kneading step is preferably performed at a discharge temperature of 150 ° C. or higher.

Further, the base kneading step was obtained as a first base kneading step of kneading only the rubber component, the filler, and the anti-aging agent containing a compound having ozone resistance and reactivity with the polymer. And a second base kneading step for kneading the first kneaded product and zinc oxide, and it is particularly preferable that the first base kneading step is discharged at a discharge temperature of 150 ° C. or higher.

（式中、Ｒ^１、Ｒ^３、Ｒ^４及びＲ^５は、同一若しくは異なって、水素原子、又は置換若しくは非置換の１価炭化水素基を表す。Ｒ^２は、同一若しくは異なって、置換若しくは非置換の２価炭化水素基を表す。） The compound having ozone resistance and reactivity with the polymer is preferably a compound represented by the following formula (1).

(Wherein R ¹ , R ³ , R ⁴ and R ⁵ are the same or different and each represents a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group. R ² is the same or different and is substituted or substituted. Represents an unsubstituted divalent hydrocarbon group.)

The rubber composition is preferably a rubber composition for sidewalls, treads or base treads.
The present invention also relates to a pneumatic tire produced using the rubber composition.

Since the present invention is a rubber composition for tires obtained through a base kneading step of kneading a rubber component, a filler, and an anti-aging agent containing a predetermined amount of a compound having ozone resistance and reactivity with a polymer, While suppressing discoloration (browning, whitening), excellent ozone resistance can be obtained.

The rubber composition for tires of the present invention is obtained through a base kneading step of kneading a rubber component, a filler, and an anti-aging agent containing a predetermined amount of a compound having ozone resistance and reactivity with a polymer. .

By performing a base kneading process for kneading a rubber component, a filler, and an anti-aging agent containing a predetermined amount of a compound having ozone resistance and polymer reactivity, the rubber component, ozone resistance and polymer reactivity A modified rubber is prepared by the reaction of a compound having an acid, and the modified rubber is bonded to the chain or the terminal of the polymer, so that it is difficult to deposit on the tire surface and suppresses unnecessary surface deposition. it can. Therefore, by using the rubber composition produced through the base kneading step, the compound prevents the discoloration by preventing the compound from being excessively deposited on the tire surface, and at the same time, has excellent ozone resistance due to the action of the compound. Is also demonstrated. Therefore, excellent ozone resistance is obtained while obtaining good discoloration resistance, and can be suitably applied to each member of a tire such as a tread, a sidewall, and a base tread.

In particular, the base kneading step includes a first base kneading step of kneading only the rubber component, filler, and anti-aging agent, and a second base kneading step of kneading the obtained first kneaded material and zinc oxide. By carrying out the process and making the base kneading step a step of discharging at a discharge temperature of 150 ° C. or higher (particularly preferably, setting the discharge temperature of the first base kneading step to 150 ° C. or higher), The performance balance between discoloration and ozone resistance can be remarkably improved.

The rubber composition of the present invention is obtained by performing a base kneading step for kneading a rubber component, a filler, and an anti-aging agent containing a predetermined amount of a compound having ozone resistance and reactivity with a polymer. However, for example, a first base kneading step for kneading only a rubber component, a filler, and an anti-aging agent containing a compound having ozone resistance and reactivity with a polymer, and the obtained first kneaded product and oxidation Aging process comprising a base process including a second base kneading process for kneading zinc, followed by a normal finishing kneading process, a rubber component, a filler, and a compound having ozone resistance and reactivity with a polymer The inhibitor can be manufactured by a production method in which a base kneading process is performed in which the inhibitor is kneaded at a discharge temperature of 150 ° C. or higher, and then a normal finishing kneading process is performed.

Among them, the first base kneading that kneads only the rubber component, the filler, and an anti-aging agent containing a predetermined amount of a compound having ozone resistance and reactivity with the polymer, and discharging at a first discharge temperature of 150 ° C. or higher. A production process including a step, a second base kneading step of kneading the obtained first kneaded material and zinc oxide, and a final kneading step of kneading the obtained second kneaded material, vulcanizing agent and vulcanization accelerator A rubber composition having a remarkably excellent performance balance is produced. Hereinafter, although this manufacturing method is demonstrated in detail, the manufacturing method of the rubber composition of this invention is not limited to this.

(First base kneading process)
In the first base kneading step, only the rubber component, the filler, and an anti-aging agent containing a predetermined amount of a compound having ozone resistance and reactivity with the polymer are kneaded.

As rubber components, natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), etc. And diene rubber. Of these, NR and BR are preferable for the sidewall and base tread, and a combination thereof is more preferable. Moreover, NR and SBR are preferable for the tread, and a combination of these is more preferable.

As the NR, for example, those commonly used in the tire industry such as SIR20, RSS # 3, TSR20 can be used. As BR, what is common in tire industry, such as BR150B made from Ube Industries, Ltd., can be used, for example.

Although it does not specifically limit as SBR, The thing modified | denatured by the compound represented by the following formula (I) described in Unexamined-Japanese-Patent No. 2010-111753 can be used conveniently from the point which is excellent in wet grip performance.

（式中、Ｒ^１１、Ｒ^１２及びＲ^１３は、同一若しくは異なって、アルキル基、アルコキシ基（好ましくは炭素数１〜８、より好ましくは炭素数１〜４のアルコキシ基）、シリルオキシ基、アセタール基、カルボキシル基（−ＣＯＯＨ）、メルカプト基（−ＳＨ）又はこれらの誘導体を表す。Ｒ^１４及びＲ^１５は、同一若しくは異なって、水素原子又はアルキル基（好ましくは炭素数１〜４のアルキル基）を表す。ｎは整数（好ましくは１〜５、より好ましくは２〜４、更に好ましくは３）を表す。）

(Wherein R ¹¹ , R ¹² and R ¹³ are the same or different and are an alkyl group, an alkoxy group (preferably an alkoxy group having 1 to 8 carbon atoms, more preferably an alkoxy group having 1 to 4 carbon atoms), a silyloxy group, and an acetal. Represents a group, a carboxyl group (—COOH), a mercapto group (—SH) or a derivative thereof, R ¹⁴ and R ¹⁵ are the same or different and each represents a hydrogen atom or an alkyl group (preferably an alkyl group having 1 to 4 carbon atoms). N represents an integer (preferably 1-5, more preferably 2-4, still more preferably 3).

As R ¹¹ , R ¹² and R ¹³ , an alkoxy group is desirable, and as R ¹⁴ and R ¹⁵ , a hydrogen atom is desirable. Thereby, the outstanding wet grip performance is obtained.

Specific examples of the compound represented by the above formula (I) include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyldimethylmethoxysilane, 3-aminopropylmethyldimethoxysilane, 2- Examples include dimethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, and 3-dimethylaminopropyltrimethoxysilane. These may be used alone or in combination of two or more.

Examples of the method for modifying styrene butadiene rubber with the compound represented by the above formula (I) (modifier) are described in JP-B-6-53768, JP-B-6-57767, JP-T2003-514078, and the like. A conventionally known method such as a known method can be used. For example, it can be modified by bringing a styrene butadiene rubber into contact with a modifier. Specifically, after a styrene butadiene rubber is prepared by anionic polymerization, a predetermined amount of the modifier is added to the rubber solution to polymerize the styrene butadiene rubber. Examples thereof include a method of reacting a terminal (active terminal) with a modifier.

The amount of bound styrene of SBR is preferably 5% by mass or more, more preferably 20% by mass or more, preferably 50% by mass or less, more preferably 35% by mass or less. Within the above range, good wet grip performance can be obtained.
In the present invention, the styrene content of SBR is calculated by H ¹ -NMR measurement.

The filler is not particularly limited, and fillers known in the rubber field can be used. Among them, carbon black and silica are preferable. In particular, it is preferable to mix carbon black in the sidewall and base tread, and it is preferable to mix silica in the tread.

In the sidewall, the lower limit of the nitrogen adsorption specific surface area (N ₂ SA) of the carbon black is preferably 25 m ² / g or more, more preferably 35 m ² / g or more, and the upper limit is preferably 120 m ² / g or less, 50 m ² / g. The following is more preferable. If it is less than the lower limit, sufficient bending crack resistance and chip-cut performance may not be obtained, and if it exceeds the upper limit, workability tends to deteriorate.

In the base tread, the nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 40 m ² / g or more, more preferably 60 m ² / g or more. If it is less than 40 m < ² > / g, there exists a tendency for sufficient reinforcement property not to be acquired. Also, _N 2 SA of carbon black is preferably 100 m ² / g, more preferably at most ^{80 m} 2 / g. When it exceeds 100 m < ² > / g, there exists a tendency for rolling resistance to deteriorate.
Incidentally, _N 2 SA of carbon black, JIS K 6217-2: determined by 2001.

In the tread, the nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 80 m ² / g or more, more preferably 100 m ² / g or more. If it is less than 80 m ² / g, sufficient fracture strength may not be obtained. Further, N ₂ SA of silica is preferably 240 m ² / g or less, more preferably 130 m ² / g or less. If it exceeds 240 m ² / g, the rolling resistance characteristics tend to deteriorate.
The _N 2 SA of silica is a value measured by the BET method in accordance with ASTM D3037-81.

As a compound having ozone resistance and reactivity with a polymer (hereinafter also referred to as “ozone resistant modifier”), the rubber composition is given ozone resistance and is reactive to a polymer such as a diene polymer. If it is a compound which has this, it will not specifically limit.

Examples of the ozone-denaturing agent include amine-based antioxidants having reactivity with polymers (such as aromatic amine-based or amine-ketone-based amine antioxidants having reactivity). Especially, the compound shown by following formula (1) can be conveniently used as an ozone-resistant modifier from the point that the performance balance of ozone resistance and discoloration resistance can be improved.

（式中、Ｒ^１、Ｒ^３、Ｒ^４及びＲ^５は、同一若しくは異なって、水素原子、又は置換若しくは非置換の１価炭化水素基を表す。Ｒ^２は、同一若しくは異なって、置換若しくは非置換の２価炭化水素基を表す。）

(Wherein R ¹ , R ³ , R ⁴ and R ⁵ are the same or different and each represents a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group. R ² is the same or different and is substituted or substituted. Represents an unsubstituted divalent hydrocarbon group.)

Examples of the substituted or unsubstituted monovalent hydrocarbon group for R ¹ , R ³ , R ⁴ and R ⁵ include a substituted or unsubstituted C 1-18 linear, cyclic or branched alkyl group, alkenyl group, An aryl group, an aralkyl group and the like are preferable. The substituted or unsubstituted divalent hydrocarbon group for R ² may be any of linear, cyclic or branched groups, and is particularly preferably a linear group. Specifically, a substituted or unsubstituted C1-C18 alkylene group, a C2-C18 alkenylene group, a C5-C18 cycloalkylene group, a C6-C18 cycloalkylalkylene group, carbon A C6-C18 arylene group, a C7-C18 aralkylene group, etc. are mentioned, Among these, a substituted or unsubstituted C1-C18 alkylene group is preferable. Incidentally, the substituent of the hydrocarbon group R ¹ to R ⁵ is not particularly limited, include a functional group such as a hydroxyl group, among them, it is preferred that R ³ has a substituent.

Specific examples of the substituted or unsubstituted monovalent hydrocarbon group for R ¹ , R ³ , R ⁴ and R ⁵ include a substituted or unsubstituted methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl. Group, isobutyl group, sec-butyl group, tert-butyl group and the like. Specific examples of the substituted or unsubstituted divalent hydrocarbon group for R ² include a substituted or unsubstituted methylene group, ethylene group, trimethylene group, tetramethylene group, pentamethylene group, hexamethylene group and the like. In the above formula, it is particularly preferred that R ¹ , R ⁴ and R ⁵ are hydrogen atoms, R ² is a substituted or unsubstituted linear alkylene group, and R ³ is an alkyl group such as a methyl group.

Specific examples of the ozone-modifying agent include N-phenyl-N ′-(3-methacryloyloxy-2-hydroxypropyl) -p-phenylenediamine.

In the present invention, anti-aging agents that can be used in addition to the ozone-modifying agent include those known in the rubber field. For example, an amine-based anti-aging agent is preferably used from the viewpoint of excellent fracture characteristics. Examples of amine-based antioxidants include diphenylamine-based and p-phenylenediamine-based amine derivatives. Examples of the diphenylamine derivative include p- (p-toluenesulfonylamide) -diphenylamine, octylated diphenylamine, and the like. Examples of p-phenylenediamine derivatives include N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine (6PPD), N-phenyl-N′-isopropyl-p-phenylenediamine (IPPD). ), N, N′-di-2-naphthyl-p-phenylenediamine, and the like.

In the first base kneading step, the total amount of each of the rubber component, filler, ozone-modifying agent, and anti-aging agent used in the rubber composition production step is preferably 80% by mass or more, more preferably. Is preferably 100% by mass. If it is less than 80 mass%, there is a possibility that both discoloration resistance and ozone resistance cannot be achieved.

The kneading method in the first base kneading step is not particularly limited, and a kneader used in a general rubber industry such as a Banbury mixer and an open roll can be used.

The discharge temperature of the first base kneading step is 150 ° C. or higher, preferably 150 to 180 ° C., more preferably 150 to 170 ° C. If it is lower than 150 ° C., the reaction between the rubber component and the ozone-resistant modifier does not proceed, and the desired modified rubber may not be sufficiently prepared during kneading. The kneading time may be appropriately adjusted so that the discharge temperature is 150 ° C. or higher, but is preferably 1 to 15 minutes, more preferably 2 to 8 minutes.

(Second base kneading process)
In the second base kneading step, at least the first kneaded material discharged at the discharge temperature of 150 ° C. or higher in the first base kneading step and zinc oxide are kneaded. Zinc oxide is not particularly limited, and those used in the rubber field can be used. A silane coupling agent, oil, wax, stearic acid, etc. may be appropriately kneaded in the second base kneading step.

As the silane coupling agent, any silane coupling agent conventionally used in combination with silica can be used in the rubber industry, and examples thereof include sulfide systems such as bis (3-triethoxysilylpropyl) disulfide, 3- Mercapto type such as mercaptopropyltrimethoxysilane, vinyl type such as vinyltriethoxysilane, amino type such as 3-aminopropyltriethoxysilane, glycidoxy type of γ-glycidoxypropyltriethoxysilane, 3-nitropropyltrimethoxy Examples thereof include nitro compounds such as silane and chloro compounds such as 3-chloropropyltrimethoxysilane. Among these, sulfide type is preferable, and bis (3-triethoxysilylpropyl) disulfide is more preferable.

As the oil, for example, process oil, vegetable oil, or a mixture thereof can be used. As the process oil, for example, a paraffin process oil, an aroma process oil, a naphthenic process oil, or the like can be used. Of these, an aroma-based process oil is preferably used. Although it does not specifically limit as wax, Paraffin wax is preferable from the point that discoloration can be suppressed and the outstanding ozone resistance and wet grip performance are obtained.

The kneading method in the second base kneading step is not particularly limited, and the same method as in the first base kneading step can be used.

The discharge temperature of the second base kneading step is preferably 150 to 180 ° C, more preferably 150 to 170 ° C. The kneading time is preferably 1 to 15 minutes, more preferably 2 to 8 minutes. If each is less than the lower limit, the rubber composition having the desired performance may not be obtained due to insufficient kneading, and if it exceeds the upper limit, the compounding material may be deteriorated.

(Finish kneading process)
In the finish kneading step, at least the second kneaded product obtained in the second base kneading step, the vulcanizing agent, and the vulcanization accelerator are kneaded. In the final kneading step, for example, a step of kneading the second kneaded product obtained in the second base kneading step, a vulcanizing agent such as sulfur, and a vulcanization accelerator using an open roll is performed. A vulcanized rubber composition is obtained. Then, a vulcanized rubber composition is obtained by performing a vulcanization step.

In the rubber composition obtained by the above-described production method or the like, in the case of a sidewall, excellent bending crack growth resistance is obtained, and the effect of the present invention can be obtained favorably. The lower limit of the NR content is preferably 20% by mass or more, more preferably 30% by mass or more, and the upper limit is preferably 80% by mass or less, more preferably 60% by mass or less.

In the case of a sidewall, the lower limit of the content of BR in 100% by mass of the rubber component is preferably 20% by mass or more because excellent bending crack growth resistance is obtained and the effect of the present invention is obtained satisfactorily. The upper limit is preferably 80% by mass or less, and more preferably 60% by mass or less.

In the case of a sidewall, the content of carbon black is preferably 10 parts by mass or more, more preferably 40 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 10 parts by mass, there is a possibility that sufficient bending cracking resistance and chip-cutting performance cannot be obtained. The content is preferably 90 parts by mass or less, more preferably 60 parts by mass or less. When it exceeds 90 mass parts, workability may be deteriorated.

In the rubber composition obtained by the above-described production method or the like, in the case of a tread, the content of SBR in 100% by mass of the rubber component is preferably 50% by mass or more, more preferably 60% by mass or more. If it is less than 50% by mass, sufficient wet grip performance may not be obtained, which is not desirable as a tread for a passenger car tire or the like. The content may be 100% by mass, but is preferably 80% by mass or less.

In the case of a tread containing NR, the content of NR in 100% by mass of the rubber component is preferably 20 to 50% by mass. Within the above range, the effects of the present invention can be obtained satisfactorily.

In the case of a tread, the content of silica is preferably 40 parts by mass or more, more preferably 50 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 40 parts by mass, the effect of improving wet grip performance by adding silica may not be sufficiently obtained. Moreover, there exists a tendency for the improvement effect of ozone resistance to fall, and the tendency which cannot suppress discoloration effectively. The content is preferably 120 parts by mass or less, more preferably 70 parts by mass or less. When it exceeds 120 parts by mass, silica is difficult to disperse, and workability may be deteriorated.

Although it is preferable that a silane coupling agent is included with silica, in this case, the content of the silane coupling agent is preferably 1 to 15 parts by mass with respect to 100 parts by mass of silica. Within the above range, good wet grip performance can be obtained.

In the case of a tread, carbon black may be used from the viewpoint of reinforcement, but it is preferable to keep the carbon black content as small as possible from the viewpoint of securing sufficient wet grip performance. The content is preferably 20 parts by mass or less, more preferably 5 parts by mass or less with respect to 100 parts by mass of the rubber component.

In the rubber composition obtained by the above-described production method or the like, in the case of a base tread, the content of NR in 100% by mass of the rubber component is preferably 55% by mass or more, more preferably 70% by mass or more. If it is less than 55% by mass, sufficient rubber strength may not be obtained. The content is preferably 95% by mass or less, more preferably 85% by mass or less. If it exceeds 95% by mass, ozone resistance tends to deteriorate.

In the case of a base tread, the content of BR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 15% by mass or more. If it is less than 5% by mass, ozone resistance tends to deteriorate. The content is preferably 45% by mass or less, more preferably 30% by mass or less. If it exceeds 45 mass%, sufficient rubber strength may not be obtained.

In the case of a base tread, the content of carbon black is preferably 10 parts by mass or more, more preferably 30 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 10 parts by mass, sufficient rubber strength may not be obtained. The content is preferably 60 parts by mass or less, more preferably 45 parts by mass or less. When it exceeds 60 mass parts, there exists a tendency for rolling resistance to deteriorate.

In the rubber composition of the present invention obtained by the above-described production method and the like, the content of the ozone-resistant modifier is 0.5 parts by mass or more, preferably 1.0 part by mass or more with respect to 100 parts by mass of the rubber component. More preferably, it is 1.5 parts by mass or more. If it is less than 0.5 part by mass, the effects of the present invention tend not to be sufficiently obtained. The content is 7.0 parts by mass or less, preferably 6.0 parts by mass or less, more preferably 5.0 parts by mass or less. Even if it exceeds 7.0 parts by mass, further improvement in ozone resistance cannot be expected, and there is a possibility that a problem of discoloration of the rubber surface may occur.

In the rubber composition, the oil content is preferably 2 parts by mass or more, more preferably 4 parts by mass or more, and the upper limit is preferably 10 parts by mass or less, with respect to 100 parts by mass of the rubber component. Preferably it is 6 mass parts or less. If it is within the above range, the bending crack resistance and workability can be obtained satisfactorily.

The content of the wax is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 0.5 parts by mass, the effect of blending the wax tends to be insufficient. The content of the wax is preferably 3.5 parts by mass or less, more preferably 2 parts by mass or less. If it exceeds 3.5 parts by mass, the tire surface may be discolored by the precipitation of wax.

The lower limit of the blending amount of the anti-aging agent to be added in addition to the ozone-resistant modifier is not particularly limited, and if the desired anti-aging performance is obtained, addition is not necessary, but when blending, the lower limit is the rubber component. Preferably it is 0.1 mass part or more with respect to 100 mass parts, More preferably, it is 0.2 mass part or more. If it is less than 0.1 parts by mass, the desired ozone resistance may not be obtained. Moreover, this compounding quantity becomes like this. Preferably it is 1.5 mass parts or less, More preferably, it is 1.0 mass part or less, More preferably, it is 0.5 mass part or less. If it exceeds 1.5 parts by mass, bloom may be generated on the surface.

The rubber composition of the present invention can be suitably used for tire sidewalls, treads, base treads, and the like.

The pneumatic tire of the present invention can be produced by a usual method using the rubber composition. That is, the rubber composition containing the above components is extruded in accordance with the shape of sidewalls, treads, base treads, etc. at an unvulcanized stage, and is used in a normal method on a tire molding machine together with other tire members. An unvulcanized tire can be formed by molding with. A tire is obtained by heating and pressurizing the unvulcanized tire in a vulcanizer.

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.
NR1: TSR20
NR2: RSS # 3
BR: BR150B manufactured by Ube Industries, Ltd. (cis content: 97% by mass)
SBR1: HPR355 manufactured by JSR Co., Ltd. (modified S-SBR (coupled with alkoxysilane and introduced at the terminal, R ¹¹ , R ¹² and R ¹³ = —OCH ₃ , R ¹⁴ and R ¹⁵ = H, n = 3) Styrene content: 28% by mass, vinyl content: 56% by mass)
SBR2: HPR355 (modified with 3-aminopropyltrimethoxysilane)
Reactive anti-aging agent: N-phenyl-N ′-(3-methacryloyloxy-2-hydroxypropyl) -p-phenylenediamine (NOCRACK G-1 (Ouchi Shinsei Chemical Co., Ltd.))
Anti-aging agent 6PPD: Antigen 6C manufactured by Sumitomo Chemical Co., Ltd.
Silica: ZEOSIL 115GR manufactured by Rhodia (N ₂ SA: 115 m ² / g, average primary particle size: 20 nm)
Silane coupling agent: Si266 (bis (3-triethoxysilylpropyl) disulfide) manufactured by Degussa
Carbon Black 1: Dia Black E (N550) manufactured by Mitsubishi Chemical Corporation (N ₂ SA: 41 m ² / g)
Carbon Black 2: Show Black N351 (N ₂ SA: 69 m ² / g) manufactured by Cabot Japan
Carbon Black 3: Show Black N220 (N ₂ SA: 111 m ² / g) manufactured by Cabot Japan
Aroma oil: Process X-140 manufactured by Japan Energy Co., Ltd.
Zinc oxide: Zinc oxide stearic acid manufactured by Mitsui Mining & Smelting Co., Ltd .: Agate wax manufactured by NOF Co., Ltd. 1: Sunnock wax (paraffin wax) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Wax 2: Ozoace 0355 (paraffin wax) manufactured by Nippon Seiki Co., Ltd.
Sulfur 1: Seimisulfur manufactured by Nippon Kiboshi Kogyo Co., Ltd. (60% insoluble matter due to carbon disulfide, 10% oil content)
Sulfur 2: Powder sulfur vulcanization accelerator manufactured by Karuizawa Sulfur Co., Ltd. 1: Noxeller NS (N-tert-butyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Vulcanization accelerator 2: Noxeller D (N, N'-diphenylguanidine) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

(Examples and Comparative Examples)
<Sidewall and tread>
In accordance with the formulation shown in Tables 1-2, each chemical was filled in a 1.7 L Banbury manufactured by Kobe Steel Co., Ltd. and kneaded at 80 rpm until the discharge temperature shown in the table was reached (first base kneading step). The obtained first kneaded product was filled with each chemical according to the formulation shown in the table, and kneaded at 80 rpm until reaching 140 ° C. (second base kneading step). The resulting second kneaded product was kneaded with sulfur and a vulcanization accelerator using an open roll to obtain an unvulcanized rubber composition for sidewalls and treads (finish kneading step). In addition, as described in the table, in Comparative Examples 1, 4 and Examples 3 and 6, the second base kneading step was not performed.

The obtained unvulcanized rubber composition (compound for sidewall) was vulcanized at 160 ° C. for 20 minutes to obtain a vulcanized rubber composition for sidewall. Moreover, the vulcanized rubber composition for treads was obtained by vulcanizing the obtained unvulcanized rubber composition (compound for tread) at 170 ° C. for 15 minutes.

The following evaluation was performed about the obtained vulcanized rubber composition (vulcanized rubber piece) for side walls and treads. The results are shown in Tables 1-2.

(Ozone resistance)
In accordance with JIS K6259, a static ozone deterioration test is performed in which a vulcanized rubber piece (length 60 mm x width 10 mm x thickness 2.0 mm) is stretched 30% and left to stand at an ozone concentration of 50 pphm and an ambient temperature of 40 ° C for 24 hours. It was. Further, in accordance with the same standard, a dynamic ozone deterioration test was performed in which the ozone concentration was 50 pphm, the ambient temperature was 40 ° C., and the reciprocating motion was extended at 0 to 20% for 24 hours. The state of occurrence of cracks after the test was visually observed, and the ozone resistance performance was evaluated according to the following criteria.
1: No cracks generated 2: Fine cracks present 3: Cracks less than 1 mm: 4: Cracks greater than 1 mm 5: Large cracks present

(discoloration)
A vulcanized rubber piece (length 150 mm × width 150 mm × thickness 2.0 mm) was placed in a gear oven whose temperature was adjusted to 60 ° C. and left for 30 days, and then the surface of the vulcanized rubber piece was visually observed, Discoloration was evaluated in 5 stages of 1-5. 1 indicates a black (no discoloration) state, 5 indicates a brown (large discoloration) state, and the smaller the numerical value, the smaller the discoloration and the better.

(Flexible crack growth resistance)
A rubber slab sheet of 1 mm x 50 mm x 20 mm is produced using the vulcanized rubber composition, cut with a razor to a sample width of 2 mm, and an initial crack is formed, in the long side direction (direction perpendicular to the cutting direction). Repeated distortion was added. The distortion rate was 5%, the frequency was 5 Hz, and the sample temperature was 70 ° C.
The initial crack growth rate dc / dn (m / cycle) from the time when repeated strain was applied until the crack growth length reached about 1 mm was measured. Since the crack growth rate dc / dn is the crack growth length per repeated extension, the smaller the crack growth rate dc / dn, the better the crack growth resistance. In addition, the crack growth rate dc / dn of Comparative Example 1 was set to 100, and the crack growth rate dc / dn of each formulation was displayed as an index. The smaller the flex crack growth resistance evaluation index, the better the flex crack growth resistance. The data was an average of N = 4.

(Wet grip performance)
Using a viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho Co., Ltd.), the loss tangent (tan δ) of each compound was measured under the conditions of a temperature of 0 ° C., an initial strain of 10%, and a dynamic strain of 0.5%. The tan δ of 4 was taken as 100, and the index was expressed by the following formula (wet grip performance index). The larger the index, the better the wet grip performance.
(Wet grip performance index) = (tan δ of each formulation) / (tan δ of Comparative Example 4) × 100

<Base tread>
In accordance with the formulation shown in Table 3, each chemical was filled into a 1.7 L Banbury manufactured by Kobe Steel Co., Ltd., and kneaded at 80 rpm until the discharge temperature shown in the table was reached (first base kneading step). The obtained first kneaded product was filled with each chemical according to the formulation shown in the table, and kneaded at 80 rpm until reaching 140 ° C. (second base kneading step). To the obtained second kneaded product, sulfur and a vulcanization accelerator were kneaded using an open roll to obtain an unvulcanized rubber composition for base tread (finish kneading step). In addition, as described in the table, in Comparative Example 7 and Example 9, the second base kneading step was not performed.
Further, according to the formulation shown in Table 4, ordinary base kneading and finishing kneading were carried out to knead each component to obtain an unvulcanized rubber composition for cap treads.

The obtained unvulcanized rubber composition was processed into a base tread shape and a cap tread shape, bonded to another tire member, and vulcanized at 170 ° C. for 15 minutes to obtain a test tire.
The following evaluation was performed about the obtained tire for a test. The results are shown in Table 3.

(Ozone resistance)
Based on JIS K6259: 2004 “Vulcanized rubber and thermoplastic rubber-How to obtain ozone resistance” for a test sample (cap tread and base tread bonded together) cut out from the tread portion of the test tire. Cap tread after 48 hours test under dynamic ozone deterioration test, reciprocating frequency 0.5 ± 0.025Hz, ozone concentration 50 ± 5 pphm, test temperature 40 ° C., tensile strain 20 ± 2% The ozone resistance was evaluated by visually observing the state of cracks on the surface. The evaluation criteria are as follows.
1: No cracks generated 2: Fine cracks present 3: Cracks less than 1 mm: 4: Cracks greater than 1 mm 5: Large cracks present

(discoloration)
The test tire was allowed to stand for 1 week at ozone at 50 pphm and 40 ° C., and the color change (white discoloration and brown discoloration) was evaluated by measuring the blackness of the cap tread surface of the test tire thereafter using a color difference meter. . Evaluation is made in 5 stages of 1 to 5, 1 indicates a black (no discoloration) state, 5 indicates a brown (large discoloration) state, and the smaller the numerical value, the smaller the discoloration and the better.

From Tables 1 to 3, the performance balance of discoloration resistance and ozone resistance can be improved by preparing a vulcanized rubber composition through a process of kneading a rubber component, a filler, and a predetermined amount of reactive anti-aging agent. It was. In particular, the discharge temperature of the base kneading step is a divided base kneading step consisting of the first base kneading and the second base kneading, and the step of kneading the rubber component, the filler and a predetermined amount of the reactive anti-aging agent is 150 ° C. It has been clarified that the performance balance can be remarkably improved by the above. Furthermore, the effect of improving the crack growth resistance in the sidewall and the wet grip performance in the tread were exhibited.

Claims (7)

Obtained through a base kneading step of kneading a rubber component, a filler, and an anti-aging agent containing a compound having ozone resistance and reactivity with a polymer,
The rubber composition for tires whose content of the said compound with respect to 100 mass parts of said rubber components is 0.5-7.0 mass parts. The base kneading step includes a first base kneading step in which only the anti-aging agent containing the rubber component, the filler, and the compound having ozone resistance and reactivity with the polymer is kneaded, and the first obtained The tire rubber composition according to claim 1, comprising a kneaded product and a second base kneading step of kneading zinc oxide. The tire rubber composition according to claim 1, wherein the base kneading step is performed at a discharge temperature of 150 ° C. or higher. The base kneading step includes a first base kneading step in which only the anti-aging agent containing the rubber component, the filler, and the compound having ozone resistance and reactivity with the polymer is kneaded, and the first obtained A second base kneading step of kneading the kneaded product and zinc oxide,
The tire rubber composition according to claim 1, wherein the first base kneading step is discharged at a discharge temperature of 150 ° C. or higher. The tire rubber composition according to any one of claims 1 to 4, wherein the compound having ozone resistance and reactivity with a polymer is a compound represented by the following formula (1).

(Wherein R ¹ , R ³ , R ⁴ and R ⁵ are the same or different and each represents a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group. R ² is the same or different and is substituted or substituted. Represents an unsubstituted divalent hydrocarbon group.) The tire rubber composition according to any one of claims 1 to 5, which is a rubber composition for a sidewall, a tread or a base tread. The pneumatic tire produced using the rubber composition in any one of Claims 1-6.