JP6448973B2 - Pneumatic tires for winter - Google Patents

Description

The present invention relates to a winter pneumatic tire.

In order to prevent dust pollution caused by spiked tires, the prohibition of spiked tires was legislated, and in cold regions, winter pneumatic tires such as studless tires were used instead of spiked tires.
In such winter pneumatic tires, particularly studless tires, in order to improve the grip performance on ice or snow, a method of improving the adhesive friction by lowering the elastic modulus (modulus) at low temperature by reducing the hardness of the rubber There is. In particular, since the braking force on ice is greatly affected by the effective contact area of rubber with ice, it is required to make the rubber flexible in order to increase the braking force. For these reasons, natural rubber and high-cis polybutadiene rubber are generally used as the main component of the tread rubber for studless tires not only for trucks / buses and light trucks but also for passenger cars. However, when natural rubber and butadiene rubber are used in combination, grip performance on ice and snow, rolling resistance and wear resistance can be compatible, but there is a problem that wet grip performance cannot be achieved.

On the other hand, if the hardness of the rubber is simply lowered by a method such as increasing the amount of oil, there is a problem that the rigidity is insufficient when used on ice or snow, and the steering stability is deteriorated.
Furthermore, with recent improvements in road maintenance, not only grip performance on ice and snow but also fuel efficiency has been strongly demanded.

Although low fuel consumption can be achieved by applying polysulfide-based silane coupling agents as a way to reduce fuel consumption, it has been found that softness at low temperatures, which is important for workability and performance on snow and ice, deteriorates. Yes. Further, a technique of reducing the amount of filler in order to realize softness at a low temperature is known, but in such a case, wet grip performance is deteriorated in exchange.

On the other hand, as a method for improving fuel economy, wet grip performance and the like in a well-balanced manner, a rubber composition containing a molten mixture of a solid resin having a specific softening point and a specific softening agent is disclosed (for example, a patent Reference 1). Further, a rubber composition in which a specific amount of a specific conjugated diene polymer and silica are blended is disclosed (see, for example, Patent Documents 2 and 3).

JP 2012-36370 A International Publication No. 2013/018424 International Publication No. 2013/077018

Thus, various methods for improving fuel economy, wet grip performance and the like in a well-balanced manner have been studied. However, for example, Patent Document 1 proposes that low fuel consumption, grip performance (particularly wet grip performance), and wear resistance can be improved by combining a solid resin and a liquid resin. The diene rubber that has been used is a modified SBR using a conventional modifying group, and such a rubber composition tends to have a low fuel consumption and is a method with room for improvement. Patent Document 2 proposes that fuel efficiency, wet grip performance, wear resistance and processability are improved in a well-balanced manner by blending a diene rubber modified with a specific modifying group. Patent Document 3 satisfies low fuel consumption, wet grip performance, wear resistance and workability by combining a specific modifier and a specific silane coupling agent in a solid resin compounding system having a low glass transition temperature. Propose to let you. However, in the methods described in Patent Documents 2 and 3, the grip performance on ice or snow is not sufficient for winter pneumatic tires, particularly studless tires.
As described above, there is room for improvement in achieving both low fuel consumption and grip performance on ice and snow in winter pneumatic tires, particularly studless tires.

The present invention solves the above problems and maintains or improves wet grip performance while improving rolling resistance (low fuel consumption), braking power on snow and ice (performance on snow and ice), and wear resistance in a well-balanced manner. An object is to provide a pneumatic tire with high productivity.

The present invention is a winter pneumatic tire having a tread produced using a rubber composition, wherein the rubber composition includes a rubber component, silica, a silane coupling agent having a mercapto group, and the following formula (I ) And / or (II), and a winter pneumatic tire characterized by being obtained by kneading the polysulfide compound in a step prior to the vulcanizing chemical kneading step.

In the above formula (I), R ¹ is, same or different, represent a monovalent hydrocarbon group which may having 3 to 15 carbon atoms have a substituent. n represents an integer of 2 to 6.

In the formula (II), R ² is the same or different and each represents a divalent hydrocarbon group which may having 3 to 15 carbon atoms have a substituent. m represents an integer of 2 to 6.

In 100% by mass of the rubber component, the content of diene rubber is preferably 40 to 80% by mass, and the content of polyisoprene rubber is preferably 20 to 60% by mass.

It is preferable that content of the said silica with respect to 100 mass parts of said rubber components is 10-80 mass parts.

It is preferable that content of the said polysulfide compound with respect to 100 mass parts of said silica is 0.5-20 mass parts.

It is preferable that content of the said silane coupling agent which has the said mercapto group with respect to 100 mass parts of said silicas is 0.5-20 mass parts.

The silane coupling agent having the mercapto group is a compound represented by the following formula (1) and / or a binding unit A represented by the following formula (2) and a binding unit B represented by the following formula (3): It is preferable that it is a compound containing.

In the above formula (1), R ^{101 to} R ¹⁰³ are each a branched or unbranched alkyl group having 1 to 12 carbon atoms, a branched or unbranched alkoxy group having 1 to 12 carbon atoms, or —O— (R ¹¹¹ _-O) z ^{-R 112} (z pieces ^{by R 111,} the .z pieces ^{by R 111} representing a divalent hydrocarbon group of branched or unbranched C1-30 may respectively be the same or different. R ¹¹² is a branched or unbranched alkyl group having 1 to 30 carbon atoms, a branched or unbranched alkenyl group having 2 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, or an aralkyl having 7 to 30 carbon atoms. Represents a group, and z represents an integer of 1 to 30). R ^{101 to} R ¹⁰³ may be the same or different from each other. R ¹⁰⁴ represents a branched or unbranched alkylene group having 1 to 6 carbon atoms.

In the above formulas (2) and (3), x is an integer of 0 or more, and y is an integer of 1 or more. R ²⁰¹ represents a hydrogen atom, a halogen atom, a branched or unbranched C 1-30 alkyl group, a branched or unbranched C 2-30 alkenyl group, a branched or unbranched C 2-30 alkynyl group. Or a group in which the hydrogen atom at the terminal of the alkyl group is substituted with a hydroxyl group or a carboxyl group. R ²⁰² represents a branched or unbranched alkylene group having 1 to 30 carbon atoms, a branched or unbranched alkenylene group having 2 to 30 carbon atoms, or a branched or unbranched alkynylene group having 2 to 30 carbon atoms. R ²⁰¹ and R ²⁰² may form a ring structure.

The silica preferably contains silica (1) having a nitrogen adsorption specific surface area of 125 m ² / g or less and silica (2) having a nitrogen adsorption specific surface area of 155 m ² / g or more.

The rubber composition preferably further contains 1 to 30 parts by mass of a resin having a glass transition temperature of −40 to 45 ° C. with respect to 100 parts by mass of the rubber component.

The winter pneumatic tire is preferably a studless tire.

According to the present invention, a rubber composition comprising a rubber component, silica, a silane coupling agent having a mercapto group, and a specific polysulfide compound, the specific polysulfide compound before the vulcanizing chemical kneading step. Since it is a winter pneumatic tire having a tread produced using a rubber composition obtained by kneading in the process, while maintaining or improving wet grip performance, rolling resistance (low fuel consumption), on snow and ice It is possible to provide winter pneumatic tires with improved productivity in a balanced manner in terms of braking power (performance on snow and ice) and wear resistance.

The rubber composition in the present invention contains a rubber component, silica, a silane coupling agent having a mercapto group, and a specific polysulfide compound. In a compound containing a rubber component and silica, a silane coupling agent having a mercapto group, which is expected to have an effect of improving the performance such as low fuel consumption, but has a concern about a decrease in processability, and a specific polysulfide compound Thus, the workability is improved, and at the same time, the fuel economy, the performance on snow and ice, and the wear resistance are improved, and the performance balance can be improved synergistically. That is, when a specific polysulfide compound is blended alone, the processability, performance on snow and ice, and abrasion resistance deteriorate, and the fuel efficiency can hardly be improved. By combining with a silane coupling agent having a mercapto group that causes deterioration of the wettability, it is possible to improve processability while maintaining or improving wet grip performance, and in addition to snow and ice performance, wear resistance, and low fuel consumption. The effect is obtained.

The rubber composition in the present invention is usually obtained by a base kneading step of kneading chemicals other than vulcanizing chemicals (vulcanizing agent and vulcanizing accelerator) such as sulfur and vulcanization accelerator, and the step. The kneaded product is manufactured by performing a finishing kneading step in which kneaded chemicals are added and kneaded in this order. In the present invention, the polysulfide compound is kneaded in the base kneading step performed before the finishing kneading step. To do. Thereby, the workability is dramatically improved and the performance balance can be improved more remarkably.

Since the pneumatic tire for winter of the present invention has a tread produced using the rubber composition thus obtained, the rolling resistance (low fuel consumption), while maintaining or improving the wet grip performance, The braking power on snow and ice (performance on snow and ice) and wear resistance are improved in a well-balanced manner. Moreover, since the processability of unvulcanized rubber is improved, the tire can be produced with high productivity.

The rubber component preferably contains 40 to 80% by mass of diene rubber and 20 to 60% by mass of polyisoprene rubber in 100% by mass of the rubber component. Furthermore, other rubber components other than the diene rubber and the polyisoprene rubber may be included.
In the present specification, the diene rubber means a diene rubber other than the polyisoprene rubber. The above-described synergistic improvement effect is particularly exhibited when polyisoprene rubber is blended as a rubber component.

The content of the diene rubber is preferably 40% by mass or more, more preferably 45% by mass or more, and still more preferably 50% by mass or more, in 100% by mass of the rubber component. If it is less than 40% by mass, the performance on snow and ice and the wear resistance tend to decrease. Moreover, 80 mass% or less is preferable, 75 mass% or less is more preferable, and 70 mass% or less is still more preferable. When it exceeds 80% by mass, there is a tendency that processability cannot be secured.

The content of the polyisoprene-based rubber is preferably 20% by mass or more, more preferably 25% by mass or more, in 100% by mass of the rubber component. Moreover, 60 mass% or less is preferable, 55 mass% or less is more preferable, and 50 mass% or less is still more preferable. If it is less than 20% by mass, the effects of the present invention may not be sufficiently obtained. On the other hand, when it exceeds 60 mass%, workability tends to deteriorate, wear resistance tends to deteriorate, and sufficient performance on snow and ice tends not to be obtained.

In the present invention, the total content of the diene rubber and the polyisoprene rubber in 100% by mass of the rubber component is preferably 70% by mass or more, and 90% by mass from the viewpoint that the above effects can be sufficiently obtained. More preferably, it may be 100% by mass.

Examples of the diene rubber include styrene butadiene rubber (SBR), butadiene rubber (BR), butadiene-isoprene rubber, styrene isoprene rubber (SIR), styrene isoprene butadiene rubber (SIBR), chloroprene rubber (CR), acrylonitrile butadiene rubber ( NBR). Among these, BR and SBR are preferable, and BR is more preferable from the viewpoints of wear resistance, performance on snow and ice, fuel efficiency, handling stability, and wet grip performance.

The BR is not particularly limited, and for example, BR1220 manufactured by Nippon Zeon Co., Ltd., BR130B, BR150B manufactured by Ube Industries, Ltd., BR51, T700, BR730 manufactured by JSR Co., Ltd. (High cis BR), BR containing a syndiotactic polybutadiene crystal such as VCR 412 and VCR 617 manufactured by Ube Industries, Ltd. can be used. Among them, high cis BR is preferable from the viewpoints of reduction in hysteresis loss and improvement in fuel efficiency, and dynamic strength and handling stability. Here, the cis content of the high cis BR is preferably 95% by mass or more. Moreover, as said SBR, what is common in the tire industry, such as emulsion polymerization SBR (E-SBR), solution polymerization SBR (S-SBR), and these modified SBR, can be used.

Examples of the polyisoprene rubber include natural rubber (NR) and polyisoprene rubber (IR). NR is not particularly limited. For example, SIR20, RSS # 3, TSR20, deproteinized natural rubber (DPNR), high purity natural rubber (HPNR), epoxidized natural rubber (ENR), etc., which are common in the tire industry Can be used. Similarly, IR that is common in the tire industry can be used. By blending the polyisoprene-based rubber, the hardness and strength of the rubber are improved, and the rubber is better packed at the time of kneading, so that the workability can be improved. Among these polyisoprene rubbers, NR is preferable.

Examples of the other rubber components include butyl rubber (IIR), ethylene propylene diene rubber (EPDM), ethylene-propylene copolymer, and ethylene-octene copolymer.

As the rubber component in the present invention, among those described above, a form containing NR and BR is preferable from the viewpoint that the performance on snow and ice, fuel efficiency, wet grip performance, wear resistance and workability can be improved in a balanced manner. A form composed of NR and BR and a form composed of NR, BR and SBR are more preferred. In particular, it is one of the preferred embodiments of the present invention that the rubber component is in the form of NR and BR. When the rubber component contains NR and BR, the above-described synergistic improvement effect can be more suitably obtained.

The rubber composition in the present invention contains silica. The silica is not particularly limited, and examples thereof include dry method silica (anhydrous silica), wet method silica (hydrous silica) and the like, and wet method silica is preferable because of its large number of silanol groups. As silica which can be used, what is illustrated as silica (1) or (2) mentioned later can be mentioned, for example. 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 20 m ² / g or more, more preferably 30 m ² / g or more, still more preferably 50 m ² / g or more, and particularly preferably 100 m ² / g or more. If it is less than 20 m ² / g, the reinforcing effect is small, and the wear resistance and fracture strength tend to be lowered. In addition, steering stability and wet grip performance tend to decrease. The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 400 m ² / g or less, more preferably 360 m ² / g or less, still more preferably 300 m ² / g or less, and particularly preferably 240 m ² / g or less. When it exceeds 400 m < ² > / g, it will become difficult to disperse | distribute a silica and there exists a tendency for low-fuel-consumption property and workability to deteriorate. On the other hand, if the nitrogen adsorption specific surface area of silica is within the above range, low fuel consumption and workability can be obtained in a well-balanced manner.
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 preferably 10 parts by mass or more, more preferably 15 parts by mass or more, still more preferably 20 parts by mass or more, still more preferably 30 parts by mass or more, relative to 100 parts by mass of the rubber component. 45 parts by mass or more is particularly preferable. Most preferably, it is 60 mass parts or more. When the amount is less than 10 parts by mass, the effect of blending silica cannot be sufficiently obtained, and the fuel economy, wear resistance, steering stability, and wet grip performance tend to deteriorate. Moreover, it is preferable that content of a silica is 150 mass parts or less, 100 mass parts or less are more preferable, and 80 mass parts or less are still more preferable. Especially preferably, it is 75 mass parts or less, Most preferably, it is 70 mass parts or less. If it exceeds 150 parts by mass, it will be difficult to uniformly disperse silica in the rubber composition, the processability of the rubber composition may be deteriorated, and the fuel economy and wear resistance tend to be deteriorated. is there.

In the present invention, silica (1) and silica (2) satisfying the following conditions may be used in combination as silica. By using both silica (1) and silica (2), it is possible to achieve both reduction of rolling resistance and improvement of breaking strength, and further remarkably improve workability, low fuel consumption, on snow and ice. The performance will be even better.

Silica (1) a nitrogen adsorption specific surface area _(N 2 SA) is preferably 125m ² / g or less, more preferably 100 m ² / g or less, more preferably ^{80 m} 2 / g or less, particularly preferably ^{60 m} 2 / g or less is there. If it exceeds 125 m ² / g, the effect of blending with silica (2) is small. Further, N ₂ SA of silica (1) is preferably 20 m ² / g or more, more preferably 30 m ² / g or more. If it is less than 20 m < ² > / g, there exists a tendency for the hardness and fracture strength of the rubber | gum of the rubber composition obtained to fall.

Silica (1) is not particularly limited and can be obtained, for example, as Ultrazil 360 manufactured by Degussa, Z40 manufactured by Rhodia, RP80 manufactured by Rhodia, or the like.

As silica (1), only 1 type may be used and it may be used in combination of 2 or more type.

5 mass parts or more are preferable with respect to 100 mass parts of rubber components, as for content of a silica (1), 10 mass parts or more are more preferable, and 20 mass parts or more are still more preferable. If the amount is less than 5 parts by mass, the rolling resistance tends not to be sufficiently reduced. Moreover, 70 mass parts or less are preferable, as for content of a silica (1), 65 mass parts or less are more preferable, and 50 mass parts or less are still more preferable. If it exceeds 70 parts by mass, the rolling resistance can be reduced, but the workability, the hardness of the rubber and the fracture strength tend to be reduced.

The nitrogen adsorption specific surface area (N ₂ SA) of silica (2) is preferably 155 m ² / g or more, more preferably 170 m ² / g or more, still more preferably 180 m ² / g or more, particularly preferably 190 m ² / g or more. is there. If it is less than 155 m < ² > / g, there exists a possibility that coexistence with the reduction | decrease of rolling resistance by blending with a silica (1) and the improvement of wet grip performance may not become enough. Further, N ₂ SA of silica (2) is preferably 400 m ² / g or less, more preferably 360 m ² / g or less, further preferably 300 m ² / g or less, particularly preferably 240 m ² / g or less, and most preferably 210 m. ² / g or less. When it exceeds 400 m ² / g, not only the workability is deteriorated, but also the rolling resistance tends not to be sufficiently reduced.

Silica (2) is not particularly limited, and for example, it can be obtained as Rhosil Zeosyl 1205MP, Degussa Ultrasil VN3-G, or the like.

As silica (2), only 1 type may be used and it may be used in combination of 2 or more type.

5 mass parts or more are preferable with respect to 100 mass parts of rubber components, as for content of a silica (2), 10 mass parts or more are more preferable, and 20 mass parts or more are still more preferable. If it is less than 5 parts by mass, there is a tendency that sufficient fracture strength cannot be obtained. Moreover, 70 mass parts or less are preferable, as for content of a silica (2), 65 mass parts or less are more preferable, and 55 mass parts or less are still more preferable. If it exceeds 70 parts by mass, the workability tends to deteriorate even if the fracture strength is improved.

The total content of silica (1) and silica (2) is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, still more preferably 20 parts by mass or more, particularly preferably 100 parts by mass of the rubber component. 30 parts by mass or more, most preferably 45 parts by mass or more. If it is less than 10 mass parts, there exists a possibility that the sufficient reinforcement effect by blending a silica (1) and a silica (2) may not be acquired. The total content of silica (1) and silica (2) is preferably 150 parts by mass or less, more preferably 100 parts by mass or less, still more preferably 80 parts by mass or less, and particularly preferably 70 parts by mass or less. If it exceeds 150 parts by mass, it will be difficult for silica to be uniformly dispersed in the rubber composition, and not only the processability of the rubber composition will deteriorate, but also the rolling resistance may increase.

The content of silica (1) and the content of silica (2) preferably satisfy the following formula. In addition, content of a silica means content (mass part) with respect to 100 mass parts of rubber components here.
[Content of silica (1)] × 0.2 ≦ [Content of silica (2)] ≦ [Content of silica (1)] × 6.5
The content of silica (2) is preferably 0.2 times or more, more preferably 0.5 times or more of the content of silica (1). If it is less than 0.2 times, the fracture strength may decrease. Further, the content of silica (2) is preferably 6.5 times or less, more preferably 4 times or less, and still more preferably 2 times or less of the content of silica (1). If it exceeds 6.5 times, rolling resistance may increase.

The rubber composition in the present invention contains a silane coupling agent having a mercapto group (—SH). As a silane coupling agent having a mercapto group, a compound represented by the following formula (1) and / or a binding unit A represented by the following formula (2) and a binding unit B represented by the following formula (3) A compound containing can be preferably used.

In the above formula (1), R ^{101 to} R ¹⁰³ are each a branched or unbranched alkyl group having 1 to 12 carbon atoms, a branched or unbranched alkoxy group having 1 to 12 carbon atoms, or —O— (R ¹¹¹ _-O) z ^{-R 112} (z pieces ^{by R 111,} the .z pieces ^{by R 111} representing a divalent hydrocarbon group of branched or unbranched C1-30 may respectively be the same or different. R ¹¹² is a branched or unbranched alkyl group having 1 to 30 carbon atoms, a branched or unbranched alkenyl group having 2 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, or an aralkyl having 7 to 30 carbon atoms. Represents a group, and z represents an integer of 1 to 30). R ^{101 to} R ¹⁰³ may be the same or different from each other. R ¹⁰⁴ represents a branched or unbranched alkylene group having 1 to 6 carbon atoms.

In the above formulas (2) and (3), x is an integer of 0 or more, and y is an integer of 1 or more. R ²⁰¹ represents a hydrogen atom, a halogen atom, a branched or unbranched C 1-30 alkyl group, a branched or unbranched C 2-30 alkenyl group, a branched or unbranched C 2-30 alkynyl group. Or a group in which the hydrogen atom at the terminal of the alkyl group is substituted with a hydroxyl group or a carboxyl group. R ²⁰² represents a branched or unbranched alkylene group having 1 to 30 carbon atoms, a branched or unbranched alkenylene group having 2 to 30 carbon atoms, or a branched or unbranched alkynylene group having 2 to 30 carbon atoms. R ²⁰¹ and R ²⁰² may form a ring structure.

Hereinafter, the compound represented by the formula (1) will be described.

By using the compound represented by the above formula (1), silica is well dispersed and the effects of the present invention can be obtained satisfactorily. Particularly, the performance on snow and ice and the fuel efficiency can be remarkably improved.

R ^{101 to} R ¹⁰³ are each a branched or unbranched alkyl group having 1 to 12 carbon atoms, a branched or unbranched alkoxy group having 1 to 12 carbon atoms, or —O— (R ¹¹¹ —O) _z —R ^112. Represents a group represented by From the viewpoint that the effect of the present invention can be obtained satisfactorily, at least one of R ^{101 to} R ¹⁰³ is preferably a group represented by —O— (R ¹¹¹ —O) _z —R ¹¹² , and two of them are — More preferably, it is a group represented by O— (R ¹¹¹ —O) _z —R ¹¹² , and one is a branched or unbranched C 1-12 alkoxy group.

Examples of the branched or unbranched alkyl group having 1 to 12 carbon atoms (preferably 1 to 5 carbon atoms) represented by R ^{101 to} R ¹⁰³ include, for example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, and n-butyl. Group, iso-butyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, 2-ethylhexyl group, octyl group, nonyl group and the like.

Examples of the branched or unbranched alkoxy group having 1 to 12 carbon atoms (preferably 1 to 5 carbon atoms) of R ^{101 to} R ¹⁰³ include, for example, methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n- Examples include butoxy, iso-butoxy, sec-butoxy, tert-butoxy, pentyloxy, hexyloxy, heptyloxy, 2-ethylhexyloxy, octyloxy, nonyloxy and the like.

In —O— (R ¹¹¹ —O) _z —R ¹¹² of R ^{101 to} R ¹⁰³ , R ¹¹¹ represents a branched or unbranched carbon number of 1 to 30 (preferably having 1 to 15 carbon atoms, more preferably 1 carbon number). To 3) a divalent hydrocarbon group.
Examples of the hydrocarbon group include a branched or unbranched alkylene group having 1 to 30 carbon atoms, a branched or unbranched alkenylene group having 2 to 30 carbon atoms, and a branched or unbranched alkynylene group having 2 to 30 carbon atoms. And an arylene group having 6 to 30 carbon atoms. Of these, a branched or unbranched alkylene group having 1 to 30 carbon atoms is preferable.

Examples of the branched or unbranched alkylene group having 1 to 30 carbon atoms (preferably 1 to 15 carbon atoms, more preferably 1 to 3 carbon atoms) of R ¹¹¹ include, for example, a methylene group, an ethylene group, a propylene group, and a butylene group. Pentylene group, hexylene group, heptylene group, octylene group, nonylene group, decylene group, undecylene group, dodecylene group, tridecylene group, tetradecylene group, pentadecylene group, hexadecylene group, heptadecylene group, octadecylene group and the like.

Examples of the branched or unbranched carbon atoms 2-30 alkenylene group (preferably 2 to 15 carbon atoms, more preferably 2 to 3 carbon atoms) of R ^111, for example, vinylene group, propenylene group, 2-propenylene Group, 1-butenylene group, 2-butenylene group, 1-pentenylene group, 2-pentenylene group, 1-hexenylene group, 2-hexenylene group, 1-octenylene group and the like.

Examples of the branched or unbranched carbon atoms 2-30 alkynylene group (preferably 2 to 15 carbon atoms, more preferably 2 to 3 carbon atoms) of R ^111, for example, ethynylene group, propynylene group, butynylene group, pentynylene group Hexynylene group, heptynylene group, octynylene group, noninylene group, decynylene group, undecynylene group, dodecynylene group and the like.

Examples of the arylene group having 6 to 30 carbon atoms (preferably 6 to 15 carbon atoms) of R ¹¹¹ include a phenylene group, a tolylene group, a xylylene group, and a naphthylene group.

z represents an integer of 1 to 30 (preferably 2 to 20, more preferably 3 to 7, further preferably 5 to 6).

R ¹¹² represents a branched or unbranched alkyl group having 1 to 30 carbon atoms, a branched or unbranched alkenyl group having 2 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, or an aralkyl group having 7 to 30 carbon atoms. Represent. Of these, a branched or unbranched alkyl group having 1 to 30 carbon atoms is preferable.

Examples of the branched or unbranched alkyl group having 1 to 30 carbon atoms (preferably 3 to 25 carbon atoms, more preferably 10 to 15 carbon atoms) of R ¹¹² include, for example, a methyl group, an ethyl group, an n-propyl group, Isopropyl, n-butyl, iso-butyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, 2-ethylhexyl, octyl, nonyl, decyl, undecyl , Dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, octadecyl group and the like.

Examples of the branched or unbranched alkenyl group having 2 to 30 carbon atoms (preferably 3 to 25 carbon atoms, more preferably 10 to 15 carbon atoms) for R ¹¹² include, for example, a vinyl group, a 1-propenyl group, and 2-propenyl. Group, 1-butenyl group, 2-butenyl group, 1-pentenyl group, 2-pentenyl group, 1-hexenyl group, 2-hexenyl group, 1-octenyl group, decenyl group, undecenyl group, dodecenyl group, tridecenyl group, tetradecenyl group Group, pentadecenyl group, octadecenyl group and the like.

Examples of the aryl group having 6 to 30 carbon atoms (preferably 10 to 20 carbon atoms) of R ¹¹² include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and a biphenyl group.

Examples of the aralkyl group having 7 to 30 carbon atoms (preferably 10 to 20 carbon atoms) of R ¹¹² include a benzyl group and a phenethyl group.

Specific examples of the group represented by —O— (R ¹¹¹ —O) _z —R ¹¹² include, for example, —O— (C ₂ H ₄ —O) ₅ —C ₁₁ H ₂₃ , —O— (C _{2 H 4 -O) 5 -C 12 H} 25, -O- (C 2 H 4 -O) 5 -C 13 H 27, -O- (C 2 H 4 -O) 5 -C 14 H 29, -O _{- (C 2 H 4 -O)} 5 -C 15 H 31, -O- (C 2 H 4 -O) 3 -C 13 H 27, -O- (C 2 H 4 -O) 4 -C 13 H _{27, -O- (C 2 H 4} -O) 6 -C 13 H 27, such as _{-O- (C 2 H 4 -O)} 7 -C 13 H 27 and the like. Among _{these, -O- (C 2 H 4 -O} ) 5 -C 11 H 23, -O- (C 2 H 4 -O) 5 -C 13 H 27, -O- (C 2 H 4 -O) 5 _{-C 15 H 31, -O- (C} 2 H 4 -O) 6 -C 13 H 27 are preferable.

Examples of the branched or unbranched alkylene group having 1 to 6 carbon atoms (preferably 1 to 5 carbon atoms) of R ¹⁰⁴ include the same groups as the branched or unbranched alkylene group having 1 to 30 carbon atoms of R ^111. Can give.

Examples of the compound represented by the formula (1) include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and the following formula: The compound represented by the following formula (Si363 manufactured by EVONIK-DEGUSSA) and the like can be used, and a compound represented by the following formula can be preferably used. These may be used alone or in combination of two or more.

Next, the compound containing the bond unit A represented by the above formula (2) and the bond unit B represented by the above formula (3) will be described.

The compound containing the bond unit A represented by the above formula (2) and the bond unit B represented by the above formula (3) is being processed compared to polysulfide silanes such as bis- (3-triethoxysilylpropyl) tetrasulfide. An increase in the viscosity of the resin is suppressed. This is presumably because the increase in Mooney viscosity is small because the sulfide portion of the bond unit A is a C—S—C bond and is thermally stable compared to tetrasulfide and disulfide.

Moreover, the shortening of the scorch time is suppressed as compared with mercaptosilane such as 3-mercaptopropyltrimethoxysilane. This is because the bonding unit B has a structure of mercaptosilane, but the —C ₇ H ₁₅ part of the bonding unit A covers the —SH group of the bonding unit B, so that it does not easily react with the polymer and scorch is less likely to occur. This is probably because of this.

In the silane coupling agent having the above structure, the content of the bond unit A is preferably 30 from the viewpoint that the effect of suppressing the increase in viscosity during processing and the effect of suppressing the shortening of the scorch time can be enhanced. It is at least mol%, more preferably at least 50 mol%, preferably at most 99 mol%, more preferably at most 90 mol%. Further, the content of the bond unit B is preferably 1 mol% or more, more preferably 5 mol% or more, further preferably 10 mol% or more, preferably 70 mol% or less, more preferably 65 mol% or less, More preferably, it is 55 mol% or less. Further, the total content of the binding units A and B is preferably 95 mol% or more, more preferably 98 mol% or more, and particularly preferably 100 mol%.
The content of the bond units A and B is an amount including the case where the bond units A and B are located at the terminal of the silane coupling agent. The form in which the bonding units A and B are located at the end of the silane coupling agent is not particularly limited, as long as the units corresponding to the formulas (2) and (3) indicating the bonding units A and B are formed. .

Examples of the halogen atom for R ²⁰¹ include a chlorine atom, a bromine atom, and a fluorine atom.

^Examples of the branched or unbranched alkyl group having 1 to 30 carbon atoms of R ²⁰¹ include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, iso-butyl group, sec-butyl group, tert- Examples thereof include a butyl group, a pentyl group, a hexyl group, a heptyl group, a 2-ethylhexyl group, an octyl group, a nonyl group, and a decyl group. The number of carbon atoms of the alkyl group is preferably 1-12.

^Examples of the branched or unbranched C 2-30 alkenyl group of R ²⁰¹ include a vinyl group, 1-propenyl group, 2-propenyl group, 1-butenyl group, 2-butenyl group, 1-pentenyl group, and 2-pentenyl. Group, 1-hexenyl group, 2-hexenyl group, 1-octenyl group and the like. The alkenyl group preferably has 2 to 12 carbon atoms.

^Examples of the branched or unbranched alkynyl group having 2 to 30 carbon atoms of R ²⁰¹ include ethynyl group, propynyl group, butynyl group, pentynyl group, hexynyl group, heptynyl group, octynyl group, nonynyl group, decynyl group, undecynyl group, And dodecynyl group. The alkynyl group preferably has 2 to 12 carbon atoms.

Examples of the branched or unbranched alkylene group having 1 to 30 carbon atoms of R ²⁰² include an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, a nonylene group, a decylene group, an undecylene group, Examples include dodecylene group, tridecylene group, tetradecylene group, pentadecylene group, hexadecylene group, heptadecylene group, octadecylene group and the like. The alkylene group preferably has 1 to 12 carbon atoms.

^Examples of the branched or unbranched C2-C30 alkenylene group of R202 include vinylene group, 1-propenylene group, 2-propenylene group, 1-butenylene group, 2-butenylene group, 1-pentenylene group and 2-pentenylene. Group, 1-hexenylene group, 2-hexenylene group, 1-octenylene group and the like. The alkenylene group preferably has 2 to 12 carbon atoms.

Examples of branched or unbranched alkynylene group having 2 to 30 carbon atoms R ^202, ethynylene group, propynylene group, butynylene group, pentynylene group, hexynylene group, heptynylene group, octynylene group, nonynylene group, decynylene group, undecynylene group, And dodecynylene group. The alkynylene group preferably has 2 to 12 carbon atoms.

In the compound containing the bond unit A represented by the above formula (2) and the bond unit B represented by the above formula (3), the total of the repeating number (x) of the bonding unit A and the repeating number (y) of the bonding unit B Is preferably in the range of 3 to 300. Within this range, since the mercaptosilane of the bond unit B is covered by —C ₇ H ₁₅ of the bond unit A, it is possible to suppress the scorch time from being shortened and to have good reactivity with silica and rubber components. Can be secured.

As the compound containing the binding unit A represented by the above formula (2) and the coupling unit B represented by the above formula (3), for example, NXT-Z30, NXT-Z45, NXT-Z60 manufactured by Momentive, etc. are used. can do. These may be used alone or in combination of two or more.

The content of the silane coupling agent having a mercapto group is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, still more preferably 2 parts by mass or more, particularly preferably 100 parts by mass of silica. It is 4 parts by mass or more. If it is less than 0.5 parts by mass, there is a possibility that an improvement effect such as low fuel consumption cannot be obtained sufficiently. The content is preferably 20 parts by mass or less, more preferably 12 parts by mass or less, still more preferably 10 parts by mass or less, and particularly preferably 9 parts by mass or less. If it exceeds 20 parts by mass, the rubber strength and wear resistance tend to decrease.

In the present invention, the rubber composition may further contain another silane coupling agent in addition to the silane coupling agent having a mercapto group.
Examples of the other silane coupling agents include 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, and 2-triethoxy. Silylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-triethoxy Methoxysilylpropyl methacrylate monosulfide, bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (3-tri Toxisilylpropyl) disulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (3-diethoxymethylsilyl) Propyl) tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, dimethoxymethylsilylpropylbenzothiazole tetrasulfide and the like.

The rubber composition in the present invention contains a polysulfide compound represented by the following formula (I) and / or (II).

In the above formula (I), R ¹ is, same or different, represent a monovalent hydrocarbon group which may having 3 to 15 carbon atoms have a substituent. n represents an integer of 2 to 6.

In the formula (II), R ² is the same or different and each represents a divalent hydrocarbon group which may having 3 to 15 carbon atoms have a substituent. m represents an integer of 2 to 6.

In the above formula (I), R ¹ is a monovalent hydrocarbon group having 3 to 15 carbon atoms which may have a substituent, and the carbon number is preferably 5 to 12, more preferably 6 -10. The monovalent hydrocarbon group for R ¹ may be linear, branched or cyclic, and any of saturated and unsaturated hydrocarbon groups (aliphatic, alicyclic, aromatic hydrocarbon groups, etc.) But you can. Of these, an aromatic hydrocarbon group which may have a substituent is preferable.

Examples of R ¹ include an alkyl group having 3 to 15 carbon atoms, a substituted alkyl group, a cycloalkyl group, a substituted cycloalkyl group, an aralkyl group, and a substituted aralkyl group. Among these, an aralkyl group and a substituted aralkyl group are exemplified. preferable. Here, examples of the alkyl group include a butyl group and an octyl group; examples of the cycloalkyl group include a cyclohexyl group; examples of the aralkyl group include a benzyl group and a phenethyl group; and examples of the substituent include an oxo group (═O). And polar groups such as hydroxy group, carboxyl group, carbonyl group, amino group, acetyl group, amide group and imide group.

In the above formula (I), n is an integer of 2 to 6, preferably 2 to 3, and more preferably 2.

In the formula (II), R ² is a divalent hydrocarbon group having 3 to 15 carbon atoms which may have a substituent, and the carbon number is preferably 3 to 10, more preferably 4 ~ 8. The divalent hydrocarbon group for R ² may be linear, branched, or cyclic, and any of saturated and unsaturated hydrocarbon groups (aliphatic, alicyclic, aromatic hydrocarbon groups, etc.) But you can. Especially, the aliphatic hydrocarbon group which may have a substituent is preferable, and a linear aliphatic hydrocarbon group is more preferable.

Examples of R ² include an alkylene group having 3 to 15 carbon atoms and a substituted alkylene group. Here, examples of the alkylene group include a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, and a nonylene group, and examples of the substituent include those similar to the substituent for R ¹ .

In said formula (II), m is an integer of 2-6, Preferably it is 2-3, More preferably, it is 2.

Specific examples of the polysulfide compound represented by the above formulas (I) and (II) include N, N′-di (γ-butyrolactam) disulfide, N, N′-di (5-methyl-γ-butyrolactam) disulfide, N, N′-di (5-ethyl-γ-butyrolactam) disulfide, N, N′-di (5-isopropyl-γ-butyrolactam) disulfide, N, N′-di (5-methoxy-γ-butyrolactam) disulfide N, N′-di (5-ethoxy-γ-butyrolactam) disulfide, N, N′-di (5-chloro-γ-butyrolactam) disulfide, N, N′-di (5-nitro-γ-butyrolactam) Disulfide, N, N'-di (5-amino-γ-butyrolactam) disulfide, N, N'-di (δ-valerolactam) disulfide, N, N'-di (δ- Caprolactam) disulfide, N, N'-di (ε-caprolactam) disulfide, N, N'-di (3-methyl-δ-caprolactam) disulfide, N, N'-di (3-ethyl-ε-caprolactam) disulfide N, N′-di (3-isopropyl-ε-caprolactam) disulfide, N, N′-di (δ-methoxy-ε-caprolactam) disulfide, N, N′-di (3-ethoxy-ε-caprolactam) Disulfide, N, N′-di (3-chloro-ε-caprolactam) disulfide, N, N′-di (δ-nitro-ε-caprolactam) disulfide, N, N′-di (3-amino-ε-caprolactam ) Disulfide, N, N′-di (ω-heptalactam) disulfide, N, N′-di (ω-octalactam) disulfide, dithiodica Rorakutamu, morpholine disulfide, N-benzyl-N - [(dibenzylamino) disulfanyl] phenylmethanamine (N, N'- dithiobis (dibenzyl amine)), and the like. Among these, dithiodicaprolactam and N-benzyl-N-[(dibenzolamino) disulfuryl] phenylmethanamine are particularly preferable.
These polysulfide compounds may be used alone or in combination of two or more.

The content of the polysulfide compound is preferably 0.5 parts by mass or more, more preferably 1.5 parts by mass or more with respect to 100 parts by mass of the silica. If it is less than 0.5 parts by mass, good workability cannot be ensured, and the performance balance may not be sufficiently improved. Moreover, this content becomes like this. Preferably it is 20 mass parts or less, More preferably, it is 13 mass parts or less, More preferably, it is 10 mass parts or less. If it exceeds 20 parts by mass, the rubber strength and processability tend to be reduced, which may lead to undesirable results in terms of cost.

Further, the content of the polysulfide compound 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 silane coupling agent having a mercapto group. Moreover, this content becomes like this. Preferably it is 250 mass parts or less, More preferably, it is 150 mass parts or less. When it is less than the lower limit, when it exceeds the upper limit, there is a tendency similar to the above.

The rubber composition in the present invention preferably contains carbon black as a reinforcing filler in addition to silica. The effect of the present invention can be more suitably obtained by further blending carbon black with silica, a silane coupling agent having a mercapto group, and a specific polysulfide compound. The carbon black that can be used is not particularly limited, and those that are common in the tire industry can be used. For example, SAF, ISAF, HAF, MAF, FEF, SRF, GPF, APF, FF, CF, SCF, and ECF are used. Furnace black (furness carbon black); Acetylene black (acetylene carbon black); Thermal black (thermal carbon black) like FT, MT; Channel black (channel carbon black) like EPC, MPC, CC; Can be mentioned. These may be used alone or in combination of two or more.

Carbon black nitrogen adsorption specific surface area _(N 2 SA) is usually 5 to 200 m ² / g, the lower limit is preferably ^{50 m} 2 / g, more preferably ^{80 m} 2 / g, more preferably ^{85 m} 2 / g. On the other hand, the upper limit is preferably 150 meters ² / g, more preferably 120 m ² / g, more preferably 105m ² / g. Carbon black has a dibutyl phthalate (DBP) absorption amount of usually 5 to 300 ml / 100 g, preferably 80 ml / 100 g, more preferably 100 ml / 100 g, and still more preferably 110 ml / 100 g. On the other hand, the upper limit is preferably 180 ml / 100 g, more preferably 140 ml / 100 g. If the amount of N ₂ SA or DBP absorbed by the carbon black is less than the lower limit of the above range, the reinforcing effect tends to be small and the wear resistance tends to decrease, and sufficient steering stability may not be obtained. On the other hand, if the upper limit of the above range is exceeded, dispersibility is poor, hysteresis loss tends to increase, and fuel efficiency tends to decrease, and workability may deteriorate.
The nitrogen adsorption specific surface area of carbon black is measured according to JIS K 6217-2: 2001, and the DBP absorption is measured according to JIS K 6217-4: 2001.
As commercially available products of carbon black, there can be used Seast 6, Seast 7HM, Seast KH, Degussa CK3, Special Black 4A, Mitsubishi Chemical Dia Black N339, and the like.

The content of carbon black is preferably 1 part by mass or more, more preferably 3 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 1 part by mass, sufficient reinforcement may not be obtained. In addition, sufficient steering stability may not be obtained. The carbon black content is preferably 90 parts by mass or less, more preferably 85 parts by mass or less, still more preferably 60 parts by mass or less, still more preferably 30 parts by mass or less, and particularly preferably 15 parts by mass or less. If it exceeds 90 parts by mass, the fuel efficiency tends to deteriorate.

The rubber composition in the present invention preferably has a carbon ratio of 40 or more. If it is less than 40, the wear resistance at high loads tends to deteriorate. Further, the carbon ratio is preferably 90 or less, and more preferably 80 or less. If it exceeds 90, there is a possibility that sufficient fuel efficiency cannot be obtained.
The carbon ratio is calculated according to the following formula, where A is the carbon black mass fraction determined by JIS K 6226-1: 2003 and B is the ash mass fraction.
(Carbon ratio) = A / (A + B) × 100

In the rubber composition of the present invention, the total content of silica and carbon black is preferably 40 parts by mass or more, and more preferably 55 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, sufficient reinforcement may not be obtained. The total content is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, still more preferably 100 parts by mass or less, and particularly preferably 80 parts by mass or less. If the amount exceeds 200 parts by mass, sufficient fuel economy and processability may not be obtained.

When the rubber composition in the present invention contains silica and carbon black, from the viewpoint of the above performance balance, the silica content in the total content of silica and carbon black of 100% by mass is preferably 50% by mass or more, and 70% by mass. % Or more is more preferable, and 80 mass% or more is still more preferable. Moreover, 95 mass% or less is preferable.

The rubber composition in the present invention preferably further contains 30 parts by mass or less of a solid resin having a softening point of 60 to 120 ° C. with respect to 100 parts by mass of the rubber component. By blending a predetermined amount of such a solid resin, the wet grip performance can be further improved. Thereby, even if it is a case where the amount of fillers is reduced, favorable wet grip performance is obtained, and favorable snow and ice performance and wet grip performance can be achieved at a high level. In addition, steering stability and wear resistance can be improved. When the rubber composition in the present invention contains the solid resin, the content is preferably 3 parts 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 the rubber composition in the present invention does not contain the solid resin, sufficient wet grip performance, steering stability, and wear resistance (particularly wet grip performance) may not be obtained. Further, the content is preferably 30 parts by mass or less, and more preferably 15 parts by mass or less with respect to 100 parts by mass of the rubber component. When it exceeds 30 parts by mass, the elastic modulus of the rubber composition in the low temperature region is significantly increased, and the grip performance on the snowy road surface and the wet grip performance in the cold region tend to be deteriorated.

As a softening point of the said solid resin, 60 degreeC or more is preferable and 75 degreeC or more is more preferable. If it is less than 60 degreeC, the sufficient wet grip performance improvement effect may not be acquired. The softening point of the solid resin is preferably 120 ° C. or lower, and more preferably 100 ° C. or lower. When the temperature exceeds 120 ° C., the loss elastic modulus in the high temperature region significantly increases, and the fuel efficiency tends to deteriorate.
The softening point of the solid resin is a temperature at which the sphere descends when the softening point specified in JIS K 6220-1: 2001 is measured with a ring and ball softening point measuring device.

The solid resin is not particularly limited as long as the softening point is in the range of 60 to 120 ° C., for example, aromatic vinyl such as α-methylstyrene and / or α-methylstyrene resin obtained by polymerizing styrene. Polymer: Coumarone-based resin such as coumarone indene resin, which is a resin containing coumarone and indene as a monomer component constituting the main chain skeleton of the resin; Inden, a resin containing indene as the monomer component constituting the main chain skeleton of the resin Indene resins such as resins; polyterpene resins obtained by polymerizing terpene compounds; terpene resins such as aromatic modified terpene resins obtained by polymerizing terpene compounds and aromatic compounds; rosin resins and the like. As the above-mentioned solid resin, among others, the adhesiveness at the time of unvulcanization and the low fuel consumption performance are good, so the aromatic vinyl polymer, the coumarone indene resin, the terpene resin, the rosin resin, and these It is preferably at least one selected from the group consisting of resin derivatives, and aromatic vinyl polymers are more preferred.

In the aromatic vinyl polymer, styrene and α-methylstyrene are used as the aromatic vinyl monomer (unit), and either a homopolymer of each monomer or a copolymer of both monomers is used. Good. The aromatic vinyl polymer is economical, easy to process, and excellent in wet grip performance. Therefore, α-methylstyrene or a homopolymer of styrene or a copolymer of α-methylstyrene and styrene is used. A copolymer of α-methylstyrene and styrene is more preferable.

As the aromatic vinyl polymer, for example, commercially available products such as SYLVARES SA85, SA100, SA120, SA140 manufactured by Arizona Chemical Co., and R2336 manufactured by Eastman Chemical Co. can be suitably used.

The rubber composition in the present invention preferably further contains 1 to 30 parts by mass of a resin having a glass transition temperature of −40 to 45 ° C. with respect to 100 parts by mass of the rubber component. By blending a predetermined amount of such resin, the wet grip performance can be further improved. In addition, grip performance in a wide temperature range, especially on snow and ice, can be improved, and rubber breaking strength and wear resistance can be improved while maintaining low fuel consumption performance. When the rubber composition in the present invention contains the resin, the content 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. If it is less than 1 part by mass, sufficient improvement effects of wet grip performance and rubber breaking strength may not be obtained. The content is preferably 30 parts by mass or less and more preferably 20 parts by mass or less with respect to 100 parts by mass of the rubber component. When the amount exceeds 30 parts by mass, plasticity of the rubber composition proceeds, and steering stability and wet grip performance tend to deteriorate.

The glass transition temperature of the resin is preferably −40 ° C. or higher, and more preferably −20 ° C. or higher. If it is less than -40 degreeC, the effect as a plasticizer will become conspicuous and it exists in the tendency for abrasion resistance to deteriorate. Alternatively, there may be a case where sufficient wet grip performance improvement effect cannot be obtained. The glass transition temperature of the resin is preferably 45 ° C. or lower. When it exceeds 45 degreeC, a loss elastic modulus will deteriorate and it exists in the tendency for low-fuel-consumption performance to deteriorate.
The glass transition temperature of the resin is a value measured by performing differential scanning calorimetry (DSC) according to JIS K 7121 under the condition of a heating rate of 10 ° C./min.

The resin is not particularly limited as long as the glass transition temperature is in the range of −40 to 45 ° C., for example, α-methylstyrene and / or aromatic such as α-methylstyrene resin obtained by polymerizing styrene. Vinyl polymer; coumarone-based resin such as coumarone indene resin, which is a resin containing coumarone and indene as a monomer component constituting the main chain skeleton of the resin; a resin containing indene as the monomer component constituting the main chain skeleton of the resin Indene resins such as indene resins; polyterpene resins obtained by polymerizing terpene compounds, terpene resins such as aromatic modified terpene resins obtained by polymerizing terpene compounds and aromatic compounds; rosin resins, etc. . Among the above resins, aromatic vinyl polymers, coumarone indene resins, terpene resins, rosin resins, and these resins, among others, are excellent in non-vulcanized tackiness and low fuel consumption performance. It is preferable that it is at least 1 sort (s) selected from the group which consists of these derivatives, and an aromatic vinyl polymer is more preferable.

In the aromatic vinyl polymer, styrene and α-methylstyrene are used as the aromatic vinyl monomer (unit), and either a homopolymer of each monomer or a copolymer of both monomers is used. Good. The aromatic vinyl polymer is economical, easy to process, and excellent in wet grip performance. Therefore, α-methylstyrene or a homopolymer of styrene or a copolymer of α-methylstyrene and styrene is used. A copolymer of α-methylstyrene and styrene is more preferable.

As the aromatic vinyl polymer, for example, commercially available products such as SYLVARES SA85, SA100, SA120, SA140 manufactured by Arizona Chemical Co., and R2336 manufactured by Eastman Chemical Co. can be suitably used.

The rubber composition in the present invention usually contains a vulcanized chemical that is added and kneaded in the final kneading step. Examples of vulcanizing chemicals include vulcanizing agents and vulcanization accelerators.

Examples of the vulcanizing agent include sulfur such as powdered sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur, and insoluble sulfur.

When the rubber composition in the present invention contains sulfur, the content thereof is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, further preferably 1 with respect to 100 parts by mass of the rubber component. .5 parts by mass or more. If it is less than 0.5 mass part, there is little bridge | crosslinking and there exists a possibility that various rubber physical properties may deteriorate. Further, the content is preferably 6.0 parts by mass or less, more preferably 4.5 parts by mass or less, still more preferably 4.0 parts by mass or less, and particularly preferably 2.3 parts by mass or less. If it exceeds 6.0 parts by mass, the rubber strength tends to decrease.

Examples of the vulcanization accelerator include sulfenamide, thiazole, thiuram, thiourea, guanidine, dithiocarbamic acid, aldehyde-amine or aldehyde-ammonia, imidazoline, and xanthate vulcanization accelerators. Among them, sulfenamide-based and guanidine-based vulcanization accelerators are preferable from the viewpoint of excellent vulcanization characteristics.

Examples of the sulfenamide vulcanization accelerator include CBS (N-cyclohexyl-2-benzothiazylsulfenamide), TBBS (Nt-butyl-2-benzothiazylsulfenamide), N-oxyethylene- Examples include 2-benzothiazylsulfenamide, N, N′-diisopropyl-2-benzothiazylsulfenamide, N, N-dicyclohexyl-2-benzothiazylsulfenamide, and the like. Examples of thiazole vulcanization accelerators include 2-mercaptobenzothiazole, dibenzothiazolyl disulfide and the like. Examples of thiuram vulcanization accelerators include tetramethylthiuram monosulfide and tetramethylthiuram disulfide. Examples of the guanidine vulcanization accelerator include diphenyl guanidine (DPG), diortolyl guanidine, orthotolyl biguanidine and the like. Among these, CBS is preferable, and it is more preferable to use CBS and DPG in combination.

When the rubber composition of the present invention contains a vulcanization accelerator, the content thereof is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, further with respect to 100 parts by mass of the rubber component. Preferably it is 0.7 mass part or more, Most preferably, it is 1.2 mass part or more. If it is less than 0.1 parts by mass, the vulcanization start time tends to be delayed. The content is preferably 5.0 parts by mass or less, more preferably 4.0 parts by mass or less, and still more preferably 3.5 parts by mass or less. If it exceeds 5.0 parts by mass, the vulcanization speed is high, and there is a possibility that scorch occurs during processing.

In addition to the above components, the rubber composition according to the present invention can contain additives generally used in the tire industry. Examples of such additives include vulcanized products such as stearic acid and zinc oxide. Activators; organic peroxides; fillers such as calcium carbonate, talc, alumina, clay, aluminum hydroxide, mica; processing aids such as extender oils, plasticizers, lubricants, waxes; anti-aging agents It can be illustrated.

Examples of the extending oil include aromatic mineral oil (viscosity specific gravity constant (VGC value) 0.900 to 1.049), naphthenic mineral oil (VGC value 0.850 to 0.899), paraffinic mineral oil (VGC value 0.790 to 0.849), and the like. The polycyclic aromatic content of the extender oil is preferably less than 3% by mass, more preferably less than 1% by mass. The polycyclic aromatic content is measured according to the British Petroleum Institute 346/92 method. Moreover, the aromatic compound content (CA) of the extending oil is preferably 20% by mass or more. These extending oils may be used in combination of two or more.

As a method for producing the rubber composition in the present invention, a production method that is usually employed can be used. For example, the respective components are kneaded using a rubber kneading apparatus such as an open roll or a Banbury mixer, and then vulcanized ( It can be produced by a method of crosslinking). However, in the present invention, the polysulfide compound is kneaded in a step before the vulcanizing chemical kneading step. By doing this, while improving workability, good snow and ice performance, low fuel consumption, and wear resistance can be obtained, but when the polysulfide compound is kneaded during the vulcanizing chemical kneading process, the above performance also decreases. In particular, sufficient hardness cannot be obtained. The rubber composition in the present invention, for example, kneads the rubber component, silica, a silane coupling agent having a mercapto group and the above polysulfide compound, and the kneaded product and vulcanized chemical obtained in the step 1 are kneaded. It can manufacture suitably with the manufacturing method including the process 2. In this case, the workability is dramatically improved, and the performance such as fuel efficiency is remarkably improved.

(Process 1 (base kneading process))
In step 1, the rubber component, silica, a silane coupling agent having a mercapto group and the polysulfide compound are kneaded. The kneading method is not particularly limited, and a kneader used in a general rubber industry such as a Banbury mixer or an open roll can be used. The base kneading step may be performed once, but the number of kneading is not particularly limited, such as dividing the additive or increasing the kneading.

The kneading temperature in step 1 is preferably 50 ° C. or higher, more preferably 80 ° C. or higher, still more preferably 120 ° C. or higher, and preferably 200 ° C. or lower, more preferably 190 ° C. or lower. The kneading time is not particularly limited, but is usually 30 seconds to 30 minutes, preferably 1 to 30 minutes. If it is less than the lower limit, the reaction between the silane coupling agent and silica does not proceed sufficiently, silica cannot be dispersed well, and the effect of improving rubber properties tends to be reduced. On the other hand, when the upper limit is exceeded, the Mooney viscosity increases and the processability tends to deteriorate.

The rubber component kneaded in step 1 is preferably 60% by mass or more, more preferably 80% by mass or more, and still more preferably 100% when the total amount is 100% by mass from the viewpoint that the effects of the present invention can be obtained satisfactorily. % By mass.

(Process 2 (finishing process))
After performing Step 1, the kneaded product obtained in Step 1 is cooled as necessary, and further vulcanized chemicals such as a vulcanizing agent and a vulcanization accelerator are added and kneaded, and an unvulcanized rubber composition Get.

The kneading temperature in step 2 is usually 100 ° C. or lower, and preferably room temperature (20 ° C.) to 80 ° C. If the temperature exceeds 100 ° C., rubber scorch may occur. The kneading time in step 2 is not particularly limited, but is usually 30 seconds or longer, preferably 1 to 30 minutes.

(Process 3 (vulcanization process))
A vulcanized rubber composition is obtained by vulcanizing the unvulcanized rubber composition obtained in step 2 by a known method such as press vulcanization. The vulcanization temperature in step 3 is preferably 120 ° C. or higher, more preferably 140 ° C. or higher, and preferably 200 ° C. or lower, more preferably 180 ° C. or lower, from the viewpoint that the effects of the present invention can be obtained satisfactorily. It is.

The timing of kneading the appropriately added compounding materials (carbon black, stearic acid, zinc oxide, extender oil, plasticizer, lubricant, wax, anti-aging agent, etc.) is not particularly limited. preferable.

The vulcanized rubber composition is excellent in wet grip performance, performance on snow and ice, fuel efficiency, wear resistance, and processability when not vulcanized, and can obtain a remarkable improvement effect of these performances. .

The rubber composition in the present invention can be suitably used for each member of a tire, and can be particularly suitably used for a tread.

The winter pneumatic tire of the present invention is produced by a usual method using the rubber composition. That is, a rubber composition containing various additives as necessary is extruded in accordance with the shape of a tire tread (including a tread of a base tread and a cap tread) at an unvulcanized stage, Molded by a normal method on a tire molding machine and bonded together with other tire members to form an unvulcanized tire. The unvulcanized tire can be heated and pressurized in a vulcanizer to produce the winter pneumatic tire of the present invention. Thereby, the winter pneumatic tire which has the tread produced using the above-mentioned rubber composition is obtained.

The winter pneumatic tire of the present invention can be suitably used as a studless tire (particularly for passenger cars).

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

Below, various chemical | medical agents used by the Example and the comparative example are demonstrated.
NR: Natural rubber TSR20
BR: Ubepol BR150B manufactured by Ube Industries, Ltd. (high cis BR, cis content: 97% by mass)
Silica 1: Ultrazil VN3-G (N ₂ SA: 175 m ² / g) manufactured by Degussa
Silica 2: Ultrazil 360 manufactured by Degussa (N ₂ SA: 50 m ² / g)
Silica 3: Zeosyl 1205MP (N ₂ SA: 200 m ² / g) manufactured by Rhodia
Silane coupling agent 1: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by EVONIK-DEGUSSA
Silane coupling agent 2: NXT-Z45 manufactured by Momentive (a copolymer having a bond unit A and a bond unit B, in the above formulas (2) to (3), bond unit A: 55 mol%, bond unit B: 45 mol%)
Silane coupling agent 3: Si363 (compound represented by the following formula) manufactured by EVONIK-DEGUSSA

Carbon black: Dia Black N339 manufactured by Mitsubishi Chemical Corporation (N ₂ SA: 96 m ² / g, DBP absorption: 124 ml / 100 g)
Oil: X-140 manufactured by Japan Energy Co., Ltd.
α-methylstyrene resin: SYLVARES SA85 manufactured by Arizona Chemical Co., Ltd. (copolymer of α-methylstyrene and styrene, softening point: 90 ° C., glass transition temperature: 43 ° C.)
Anti-aging agent: Antigen 3C (N-phenyl-N′-isopropyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd.
Stearic acid: Stearic acid “椿” manufactured by NOF Corporation
Zinc oxide: Zinc Hua 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Wax: Sunnock N manufactured by Ouchi Shinsei Chemical
Polysulfide compound 1: dithiodicaprolactam (manufactured by Sanshin Chemical Co., Ltd., a compound represented by the following formula)

Polysulfide compound 2: N-benzyl-N-[(dibenzylamino) disulfanyl] phenylmethanamine (a compound represented by the following formula, manufactured by Aldrich)

Polysulfide compound 3: Noxeller DM (dibenzothiazolyl disulfide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Sulfur: Powder sulfur vulcanization accelerator manufactured by Tsurumi Chemical Co., Ltd. 1: Soxinol CZ (N-cyclohexyl-2-benzothiazole sulfenamide) manufactured by Sumitomo Chemical Co., Ltd.
Vulcanization accelerator 2: Soxinol D (diphenylguanidine) manufactured by Sumitomo Chemical Co., Ltd.

(Examples and Comparative Examples)
Using a 1.7 L Banbury mixer manufactured by Kobe Steel Co., Ltd., the materials described in the item of base kneading in Table 1 were kneaded for 5 minutes at 150 ° C. to obtain a kneaded product (base kneading Process). Next, the materials described in the item of finish kneading in Table 1 are added to the kneaded material obtained, and kneaded for 3 minutes under the condition of 80 ° C. using an open roll to obtain an unvulcanized rubber composition. Obtained (finishing and kneading step). The obtained unvulcanized rubber composition was press vulcanized at 170 ° C. for 20 minutes to obtain a vulcanized rubber composition.

Further, the obtained unvulcanized rubber composition was molded into a tread shape and bonded together with other tire members on a tire molding machine to form an unvulcanized tire, and then press vulcanized at 170 ° C. for 12 minutes. A winter pneumatic tire for test (size: 195 / 65R15, DS-2 pattern, studless tire) was manufactured.

The following evaluation was performed using the obtained unvulcanized rubber composition, vulcanized rubber composition, and a test winter pneumatic tire. The evaluation results are shown in Table 1.

(Processability (Mooney viscosity))
About the obtained unvulcanized rubber composition, the Mooney viscosity based on JISK6300 was measured at 130 degreeC. The Mooney viscosity (ML _{1 + 4} ) of Comparative Example 1 was set to 100, and indexed by the following formula (workability index). The larger the index, the lower the Mooney viscosity, the better the processability, and the better the productivity when manufacturing tires. In addition, if the index is 100 or more, it can be said that the workability has no practical problem.
(Workability index) = (ML _{1 + 4} of Comparative Example 1) / (ML _{1 + 4 of} each formulation) × 100

(Low fuel consumption)
The loss tangent (tan δ) of the vulcanized rubber composition was measured using a spectrometer manufactured by Ueshima Seisakusho at a dynamic strain amplitude of 1%, a frequency of 10 Hz, and a temperature of 50 ° C. The reciprocal value of tan δ was displayed as an index with Comparative Example 1 being 100 (low fuel consumption index). The larger the value, the lower the rolling resistance and the better the fuel efficiency of the tire.
Note that if the fuel efficiency index is 120 or more, it can be said that the fuel efficiency is particularly excellent.

(Performance on snow and ice)
The test winter pneumatic tire was mounted on a domestic 2000cc FF vehicle, and the vehicle was run on snow and ice under the following conditions to evaluate the performance on snow and ice.
(On ice) (on snow)
Test place: Hokkaido Nayoro Test Course Hokkaido Nayoro Test Course Temperature: -1 to -6 ° C -2 ° C to -10 ° C

For the performance evaluation on snow and ice, the vehicle traveled on snow and ice, and the stop distance on the snow and ice (braking stop distance) required to stop the vehicle by stepping on the lock brake at a speed of 30 km / h was measured. Then, using Comparative Example 1 as a reference, calculation was performed from the following formula and displayed as an index (performance index on snow and ice). The larger the index, the better the grip performance on snow and ice. If the performance index on snow and ice is larger than 105, it can be said that the performance on snow and ice is particularly excellent.
(Performance index on snow and ice) = (braking stop distance of Comparative Example 1) / (braking stop distance of each formulation) × 100

(Wet braking performance)
The test winter pneumatic tire was mounted on all wheels of a domestic 2000cc FF vehicle, and the braking distance from the initial speed of 100 km / h was obtained on the wet asphalt road surface. The result is expressed as an index. Wet braking performance (wet grip performance) is good. The index was calculated by the following formula.
(Wet braking performance index) = (braking stop distance of Comparative Example 1) / (braking stop distance of each formulation) × 100

(Abrasion resistance)
Mount the above test winter pneumatic tire on a domestic FF vehicle, measure the groove depth of the tire tread after running 8000 km, calculate the running distance when the tire groove depth decreases by 1 mm, and use the following formula Indexed (wear resistance index). The higher the index, the better the wear resistance. In addition, if the abrasion resistance index is 105 or more, it can be said that the abrasion resistance is particularly excellent.
(Abrasion resistance index) = (travel distance when 1 mm groove depth decreases) / (travel distance when tire groove of Comparative Example 1 decreases by 1 mm) × 100

From the results in Table 1, a rubber composition containing a rubber component, silica, a silane coupling agent having a mercapto group, and a specific polysulfide compound, the specific polysulfide compound before the vulcanizing chemical kneading step. In the examples using the rubber composition produced by kneading in the process, the wet grip performance is maintained or improved while improving the rubber processability, rolling resistance (low fuel consumption), braking force on snow and ice. (Snow and ice performance) and wear resistance can be improved synergistically in a well-balanced manner.
In comparison with Comparative Examples 1, 2, 5 and Example 1, in the silica compounding system, the mercapto group was compared with the case of using a silane coupling agent having a mercapto group or a specific polysulfide compound alone. It has been found that when the silane coupling agent and the specific polysulfide compound are used in combination, an improvement effect more than the addition can be obtained in improving workability, fuel efficiency, performance on snow and ice, and wear resistance.
A rubber composition comprising a rubber component, silica, a silane coupling agent having a mercapto group, and a polysulfide compound (polysulfide compound 3) not corresponding to the polysulfide compound represented by the above formula (I) and / or (II). Compared to Examples 1 and 2, the used Comparative Example 8 has poor workability, and particularly inferior performance on snow and ice and wear resistance. Therefore, the effect of the present invention described above has a mercapto group. It turns out that it is the specific synergistic effect obtained by using a silane coupling agent and a specific polysulfide compound together.

Claims (8)

A winter pneumatic tire having a tread produced using a rubber composition,
The rubber composition, a rubber component, silica, silane coupling agent having a mercapto group, a polysulfide compound represented by the following following formula (I) and / or (II), as well as the glass transition temperature is: -40 to 45 ° C. 1 to 30 parts by mass of resin with respect to 100 parts by mass of the rubber component ,
A winter pneumatic tire obtained by kneading the polysulfide compound in a step prior to a kneading step of a vulcanizing chemical.

(In Formula (I), R ¹ is the same or different and represents a monovalent aromatic hydrocarbon group having 3 to 15 carbon atoms which may have a substituent. N is an integer of 2 to 6) Represents.)

(In Formula (II), R ² is the same or different and represents a C 3-15 divalent linear aliphatic hydrocarbon group which may have a substituent. M is 2-6. Represents an integer.) The winter according to claim 1, wherein in 100% by mass of the rubber component, the content of diene rubber other than polyisoprene rubber is 40 to 80% by mass, and the content of polyisoprene rubber is 20 to 60% by mass. Pneumatic tires. The winter pneumatic tire according to claim 1 or 2, wherein a content of the silica with respect to 100 parts by mass of the rubber component is 10 to 80 parts by mass. The winter pneumatic tire according to any one of claims 1 to 3, wherein a content of the polysulfide compound with respect to 100 parts by mass of the silica is 0.5 to 20 parts by mass. The winter pneumatic tire according to any one of claims 1 to 4, wherein a content of the silane coupling agent having a mercapto group with respect to 100 parts by mass of the silica is 0.5 to 20 parts by mass. The silane coupling agent having a mercapto group is a compound represented by the following formula (1) and / or a binding unit A represented by the following formula (2) and a binding unit B represented by the following formula (3): The winter pneumatic tire according to claim 1, which is a compound containing

(In the formula (1), R ^{101 to} R ¹⁰³ are each a branched or unbranched C 1-12 alkyl group, a branched or unbranched C 1-12 alkoxy group, or —O— (R ¹¹¹ _-O) z ^{-R 112} (z pieces ^{by R 111,} the .z pieces ^{by R 111} representing a divalent hydrocarbon group of branched or unbranched C1-30 may respectively be the same or different. R ¹¹² is a branched or unbranched alkyl group having 1 to 30 carbon atoms, a branched or unbranched alkenyl group having 2 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, or an aralkyl having 7 to 30 carbon atoms. Z represents an integer of 1 to 30.) R ^{101 to} R ¹⁰³ may be the same or different, and R ¹⁰⁴ represents a branched or unbranched carbon number. Represents 1 to 6 alkylene groups .)

(In Formula (2) and Formula (3), x is an integer of 0 or more, y is an integer of 1 or more. R ²⁰¹ is a hydrogen atom, a halogen atom, a branched or unbranched alkyl having 1 to 30 carbon atoms. Group, branched or unbranched alkenyl group having 2 to 30 carbon atoms, branched or unbranched alkynyl group having 2 to 30 carbon atoms, or a hydrogen atom at the terminal of the alkyl group substituted with a hydroxyl group or a carboxyl group R ²⁰² represents a branched or unbranched alkylene group having 1 to 30 carbon atoms, a branched or unbranched C 2-30 alkenylene group, or a branched or unbranched C 2-30 alkynylene group. (R ²⁰¹ and R ²⁰² may form a ring structure.) The said silica contains the silica (1) whose nitrogen adsorption specific surface area is 125 m < ² > / g or less, and the silica (2) whose nitrogen adsorption specific surface area is 155 m < ² > / g or more. Pneumatic tire for winter. Winter pneumatic tire according to any one of claims 1 to 7 which is a studless tire.