JP5524659B2 - Rubber composition for tread and pneumatic tire - Google Patents

Description

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

As a technique for improving the wet grip performance of a tire, it is generally known to add silica as a filler to a rubber composition. In order to achieve both wet grip performance and dry grip performance, it is necessary to increase the amount of silica. However, increasing the amount of silica makes it difficult for silica to disperse and tends to deteriorate crack resistance, workability, and the like. Therefore, a method for improving these performances in a well-balanced manner is desired.

Patent Document 1 proposes a rubber composition that achieves both low heat buildup and breaking strength by using a specific alkylphenol / sulfur chloride condensate in combination with a modified styrene butadiene rubber or the like. However, there is still room for improvement in terms of improving the wet grip performance, dry grip performance, crack resistance and workability in a well-balanced manner.

JP 2009-114427 A

The present invention solves the above problems and provides a rubber composition for a tread that can improve wet grip performance, dry grip performance, crack resistance and workability in a well-balanced manner, and a pneumatic tire having a tread produced using the rubber composition. The purpose is to do.

（式中、Ｒ^１、Ｒ^２及びＲ^３は、同一若しくは異なって、炭素数５〜１２のアルキル基を示す。ｘ及びｙは、同一若しくは異なって、２〜４の整数を示す。ｍは０〜１０の整数を示す。） The present invention includes a rubber component, silica (1) having a nitrogen adsorption specific surface area of 130 m ² / g or less, silica (2) having a nitrogen adsorption specific surface area of 150 m ² / g or more, and the following formula (1): The total content of the silica (1) and (2) is 50 to 110 parts by mass with respect to 100 parts by mass of the rubber component, and is represented by the following formula (1). It is related with the rubber composition for treads whose content of the alkylphenol and sulfur chloride condensate is 1-10 mass parts.

(Wherein R ¹ , R ² and R ³ are the same or different and represent an alkyl group having 5 to 12 carbon atoms. X and y are the same or different and represent an integer of 2 to 4. m is Represents an integer of 0 to 10.)

The rubber composition preferably contains 2 to 15 parts by mass of a silane coupling agent with respect to 100 parts by mass of the total content of the silicas (1) and (2).

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

According to the present invention, since the rubber composition contains a predetermined amount of two types of silica having different nitrogen adsorption specific surface areas and a specific alkylphenol / sulfur chloride condensate with respect to the rubber component, the rubber composition is By using it as a tread, it is possible to provide a pneumatic tire that has a well-balanced wet grip performance, dry grip performance and crack resistance and is easy to manufacture.

The rubber composition of the present invention comprises a rubber component, silica (1) having a nitrogen adsorption specific surface area of 130 m ² / g or less, silica (2) having a nitrogen adsorption specific surface area of 150 m ² / g or more, and the above formula The alkylphenol / sulfur chloride condensate represented by (1) is contained.

When silica (1) and (2) are used in combination and the amount of silica is increased, both wet grip performance and dry grip performance can be achieved, and good workability can be maintained despite high silica loading. . However, when silica having a large nitrogen adsorption specific surface area (small particle diameter) such as silica (2) is blended or the amount of silica is increased, crack resistance tends to deteriorate. On the other hand, in the present invention, by using the alkylphenol-sulfur chloride condensate represented by the above formula (1) and silica (1) and (2) in combination, even if the amount of silica is increased, good crack resistance Sex can be maintained. Therefore, the combined use of these components can increase the amount of silica, achieve both wet grip performance and dry grip performance, and obtain good crack resistance and workability. As a result, wet grip performance, dry grip performance, crack resistance and workability can be improved in a well-balanced manner.

Examples of the rubber component include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), Examples thereof include diene rubbers such as halogenated butyl rubber (X-IIR) and styrene isoprene butadiene rubber (SIBR). These may be used alone or in combination of two or more. Especially, it is preferable to use NR and SBR, and it is more preferable to use NR and SBR together from the point that wet grip performance, dry grip performance, and crack resistance can be obtained in a balanced manner. NR and SBR are not particularly limited, and materials common in the tire industry can be used.

The content of NR in 100% by mass of the rubber component is preferably 25% by mass or more, more preferably 35% by mass or more, and further preferably 45% by mass or more. If it is less than 25% by mass, the crack resistance tends to deteriorate. The NR content is preferably 75% by mass or less, more preferably 65% by mass or less, and still more preferably 55% by mass or less. If it exceeds 75 mass%, wet grip performance and dry grip performance tend to deteriorate.

The content of SBR in 100% by mass of the rubber component is preferably 25% by mass or more, more preferably 35% by mass or more, and further preferably 45% by mass or more. If it is less than 25% by mass, wet grip performance and dry grip performance tend to deteriorate. The SBR content is preferably 75% by mass or less, more preferably 65% by mass or less, and still more preferably 55% by mass or less. If it exceeds 75% by mass, the crack resistance tends to deteriorate.

Examples of silica (1) and (2) include silica (anhydrous silicic acid) prepared by a dry method, silica (hydrous silicic acid) prepared by a wet method, and the like. Of these, silica prepared by a wet method is preferred because of the large number of silanol groups on the surface and many reactive sites with the silane coupling agent.

The nitrogen adsorption specific surface area (N ₂ SA) of silica (1) is 130 m ² / g or less, preferably 100 m ² / g or less, more preferably 70 m ² / g or less. When it exceeds 130 m ² / g, there is a possibility that the effect (compatibility of wet grip performance and dry grip performance, ensuring good workability) by the combined use of two types of silica cannot be obtained sufficiently. Further, N ₂ SA of silica (1) is preferably 20 m ² / g or more, more preferably 30 m ² / g or more, and further preferably 40 m ² / g or more. If it is less than 20 m < ² > / g, silica (1) becomes a fracture nucleus and there exists a tendency for crack resistance to deteriorate.
The nitrogen adsorption specific surface area (N ₂ SA) of silica is a value measured by the BET method according to ASTM D3037-81.

The nitrogen adsorption specific surface area ^{_{(N 2 SA) 130m 2 /}} g or less of silica, for example, from Degussa ^{_{ULTRASIL360 (N 2 SA: 50m 2}} / g), produced by Rhodia of ^{_{ZEOSIL115GR (N 2 SA: 115m 2}} / g), ZEOSIL1115MP (N ₂ SA: 115 m ² / g) manufactured by Rhodia, and the like.

N ₂ SA of silica (2) is 150 m ² / g or more, preferably 160 m ² / g or more, more preferably 170 m ² / g or more. If it is less than 150 m < ² > / g, there exists a possibility that the effect by combined use of two types of silica may not fully be acquired. Further, N ₂ SA of silica (2) is preferably 300 m ² / g or less, more preferably 240 m ² / g or less, and further preferably 220 m ² / g or less. When it exceeds 300 m < ² > / g, dispersion | distribution of a silica (2) will become difficult and there exists a tendency for workability to deteriorate.

The nitrogen adsorption specific surface area ^{_{(N 2 SA) 150m 2 /}} g or more silica, for example, from Degussa ^{_{ULTRASILVN3 (N 2 SA: 175m 2}} / g), produced by Rhodia of ^{_{ZEOSIL1165MP (N 2 SA: 160m 2}} / g), Rhodia's ZEOSIL 1205MP (N ₂ SA: 200 m ² / g) and the like.

The content of silica (1) is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and further preferably 15 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 5 parts by mass, improvement in wet grip performance may not be expected. Further, the content of silica (1) is preferably 35 parts by mass or less, more preferably 30 parts by mass or less, and still more preferably 25 parts by mass or less. If it exceeds 35 parts by mass, the dry grip performance tends to deteriorate.

The content of silica (2) is preferably 45 parts by mass or more, more preferably 50 parts by mass or more, and further preferably 55 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 45 parts by mass, the dry grip performance tends to deteriorate. Further, the content of silica (2) is preferably 75 parts by mass or less, more preferably 70 parts by mass or less, and still more preferably 65 parts by mass or less. If it exceeds 75 parts by mass, the workability tends to deteriorate.

The total content of silica (1) and (2) is 50 parts by mass or more, preferably 60 parts by mass or more, more preferably 70 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 50 mass parts, there exists a tendency for the reinforcement effect by addition of silica (1) and (2) not to be fully acquired. The total content is 110 parts by mass or less, preferably 100 parts by mass or less, more preferably 90 parts by mass or less. When it exceeds 110 mass parts, it will become difficult to disperse | distribute silica (1) and (2) uniformly, and there exists a tendency for workability to deteriorate.

The content of silica (2) is preferably 0.2 times or more of the content of silica (1), more preferably 1.5 times or more, and further preferably 2.0 times or more. preferable. If it is less than 0.2 times, the dry grip performance tends to deteriorate. Moreover, it is preferable that content of a silica (2) is 6.5 times or less of content of a silica (1), It is more preferable that it is 4.5 times or less, It is 3.5 times or less. Is more preferable. When it exceeds 6.5 times, workability may deteriorate and processing may become difficult.

Silica (1) and (2) are preferably used in combination with a silane coupling agent. As the silane coupling agent, any silane coupling agent conventionally used in combination with silica can be used in the rubber industry. For example, sulfide systems such as bis (3-triethoxysilylpropyl) tetrasulfide, 3 -Mercapto type such as mercaptopropyltrimethoxysilane, vinyl type such as vinyltriethoxysilane, amino type such as 3-aminopropyltriethoxysilane, glycidoxy type of γ-glycidoxypropyltriethoxysilane, 3-nitropropyltri Examples thereof include nitro compounds such as methoxysilane and chloro compounds such as 3-chloropropyltrimethoxysilane. These may be used alone or in combination of two or more. Among these, sulfide type is preferable, and bis (3-triethoxysilylpropyl) tetrasulfide is more preferable.

The content of the silane coupling agent is preferably 2 parts by mass or more, more preferably 4 parts by mass or more, and further preferably 6 parts by mass or more with respect to 100 parts by mass of the total content of silica (1) and (2). It is. If it is less than 2 parts by mass, the crack resistance tends to deteriorate. The content of the silane coupling agent is preferably 15 parts by mass or less, more preferably 12 parts by mass or less, and still more preferably 10 parts by mass or less. When it exceeds 15 parts by mass, there is a tendency that an effect commensurate with the increase in cost cannot be obtained.

The rubber composition of the present invention contains an alkylphenol / sulfur chloride condensate represented by the above formula (1). By using the alkylphenol / sulfur chloride condensate as a cross-linking agent, a thermally stable cross-linked structure can be formed compared to ordinary sulfur cross-linking, and crack resistance can be improved.

m is an integer of 0 to 10 and preferably an integer of 1 to 9 from the viewpoint of good dispersibility of the alkylphenol / sulfur chloride condensate in the rubber component. x and y are integers of 2 to 4 from the viewpoint that reversion can be suppressed, and both are preferably 2. R ^{1 to} R ³ are alkyl groups having 5 to 12 carbon atoms, preferably alkyl groups having 6 to 9 carbon atoms, from the viewpoint of good dispersibility of the alkylphenol / sulfur chloride condensate in the rubber component.

The alkylphenol / sulfur chloride condensate can be prepared by a known method and is not particularly limited. For example, a method of reacting alkylphenol and sulfur chloride at a molar ratio of 1: 0.9 to 1.25, etc. Is mentioned.

Specific examples of the alkylphenol / sulfur chloride condensate include Takkol V200 (following formula (2)) manufactured by Taoka Chemical Co., Ltd.

（式中、ｍは０〜１０の整数を表す。）

(In the formula, m represents an integer of 0 to 10.)

The sulfur content of the alkylphenol / sulfur chloride condensate is a ratio obtained by heating to 800 to 1000 ° C. in a combustion furnace and converting it into SO ₂ gas or SO ₃ gas, optically quantifying it from the amount of gas generated. Say.

The content of the alkylphenol / sulfur chloride condensate is 1 part by mass or more, preferably 2 parts by mass or more, more preferably 3 parts by mass or more, and still more preferably 4 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, the crack resistance may not be sufficiently improved. Moreover, this content is 10 mass parts or less, Preferably it is 8 mass parts or less, More preferably, it is 6 mass parts or less. When it exceeds 10 parts by mass, the crosslinking density becomes too high, and the crack resistance tends to deteriorate.

In the rubber composition of the present invention, in addition to the above components, compounding agents generally used in the production of rubber compositions, for example, reinforcing fillers such as carbon black, zinc oxide, stearic acid, various anti-aging agents, Vulcanizing agents such as oil, wax and sulfur, vulcanization accelerators and the like can be appropriately blended.

The rubber composition of the present invention may contain carbon black. Conventionally, in applications where excellent crack resistance is required, it is common to add a large amount of carbon black to increase mechanical strength. On the other hand, in the rubber composition of the present invention, the combination of silica (1) and (2) and the alkylphenol-sulfur chloride condensate represented by the above formula (1) is good even if the amount of carbon black is reduced. High crack resistance can be ensured.

The content of carbon black is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, still more preferably 8 parts by mass or less, and particularly preferably 6 parts by mass or less with respect to 100 parts by mass of the rubber component. The lower limit of the carbon black content is not particularly limited, but is preferably 2 parts by mass or more, more preferably 3 parts by mass or more.

The rubber composition of the present invention preferably contains oil. Thereby, favorable wet grip performance and dry grip performance are obtained. As the oil, for example, process oil, vegetable oil and fat, a mixture thereof and the like can be used.

Examples of the process oil include paraffinic process oil, naphthenic process oil, aromatic process oil (aromatic oil) and the like. As vegetable oils and fats, castor oil, cottonseed oil, sesame oil, rapeseed oil, soybean oil, palm oil, palm oil, peanut hot water, rosin, pine oil, pineapple, tall oil, corn oil, rice bran oil, beet flower oil, sesame oil, Examples include olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, and tung oil.

The oil content is preferably 5 parts by mass or more, more preferably 15 parts by mass or more, and still more preferably 20 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 5 parts by mass, the wet grip performance and the dry grip performance may not be sufficiently improved. The oil content is preferably 50 parts by mass or less, more preferably 35 parts by mass or less, and still more preferably 30 parts by mass or less. If it exceeds 50 parts by mass, the crack resistance tends to deteriorate.
The oil content includes the amount of oil contained in rubber (oil-extended rubber).

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

The rubber composition of the present invention is used for a tread of a pneumatic tire, and is preferably used for a tread of a motorcycle tire or a motocross tire.

The pneumatic tire of the present invention is 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 the tread at an unvulcanized stage and molded together with other tire members on a tire molding machine by a normal method. Form a vulcanized tire. The pneumatic tire of the present invention can be manufactured by heating and pressurizing this unvulcanized tire in a vulcanizer.

The pneumatic tire of the present invention is preferably used as a tire for passenger cars, a tire for trucks and buses, a tire for motorcycles, a tire for motocross, and the like, and particularly preferably used as a tire for motorcycles and a tire for motocross.

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.
SBR: SBR1502 manufactured by JSR Corporation (styrene content: 23.5% by mass)
NR: TSR-20
Silica (1): ULTRASIL 360 manufactured by Degussa (N ₂ SA: 50 m ² / g)
Silica (2): ZEOSIL 1205MP (N ₂ SA: 200 m ² / g) manufactured by Rhodia
Carbon Black: Show Black N220 (N ₂ SA: 111 m ² / g) manufactured by Cabot Japan
Silane coupling agent: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by Degussa
Zinc oxide: Zinc oxide stearic acid manufactured by Mitsui Mining & Smelting Co., Ltd .: Stearic acid “Kashiwa” manufactured by NOF Corporation
Process oil: Diana Process AH-24 manufactured by Idemitsu Kosan Co., Ltd.
Anti-aging agent: Antigen 6C manufactured by Sumitomo Chemical Co., Ltd.
Wax: Sunnock N manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Sulfur: Powder sulfur vulcanization accelerator CZ manufactured by Karuizawa Sulfur Co., Ltd .: Noxeller CZ manufactured by Ouchi Shinsei Chemical Co., Ltd.
Vulcanization accelerator DPG: NOCELLER D manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Heat-resistant cross-linking agent: Tacakiol V200 manufactured by Taoka Chemical Industry Co., Ltd. (alkylphenol / sulfur chloride condensate represented by formula (2), m: 0 to 10, x and y: 2, R ^{1 to} R ³ : C ₈ H ₁₇ (octyl group), sulfur content: 24% by mass)

Examples 1-3 and Comparative Examples 1-3
According to the formulation shown in Table 1, materials other than sulfur and a vulcanization accelerator were kneaded for 3 minutes at a discharge temperature of 150 ° C. using a Banbury mixer to obtain a kneaded product. Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded for 5 minutes at 80 ° C. using a biaxial open roll to obtain an unvulcanized rubber composition. Further, the obtained unvulcanized rubber composition was molded into a tread shape, bonded together with other tire members on a tire molding machine, and vulcanized at 170 ° C. for 12 minutes, so that a test tire (motocross tire) was obtained. ) Was manufactured.

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

(Wet grip performance)
The test driver evaluated the stability of the steering control during the running of the motocross bike equipped with the above test tire on the test course (wet road surface) of 2 km per lap for 8 laps. The evaluation results were displayed with a maximum of 5 points, with Comparative Example 1 as 3 points. It shows that wet grip performance is so favorable that a numerical value is large.

(Dry grip performance)
The test driver evaluated the stability of the steering control during the run on the motocross bike equipped with the above test tire for 8 laps on the 2 km test course (dry road surface). The evaluation results were displayed with a maximum of 5 points, with Comparative Example 1 as 3 points. It shows that dry grip performance is so favorable that a numerical value is large.

(Crack resistance)
The test tire was left in an oven at 80 ° C. for 2 weeks, and then left in a greenhouse with an ozone concentration of 50 ppm for 2 weeks. And the number and magnitude | size of the crack which generate | occur | produced in the said tire for a test were observed visually, and crack resistance was evaluated. The evaluation results were displayed with a score of 10 on a scale of 5 for Comparative Example 1. It shows that crack resistance is so favorable that a numerical value is large. Ten points are in a state where no cracks are generated.

(Processability)
The shape and ease of processing (viscosity) of the unvulcanized rubber composition were observed to evaluate the processability. The evaluation results are shown as Comparative Example 1 with 5 points. It shows that workability is so favorable that a numerical value is large. Three or more points are levels that can be processed without problems.

From Table 1, the examples using two types of silica with different N ₂ SA and V200 (heat-resistant cross-linking agent) improved wet grip performance, dry grip performance and crack resistance in a balanced manner compared to the comparative example. did. In addition, the workability was at a level with no problem. On the other hand, the comparative example which did not use the said component together could not improve these performances with sufficient balance.

Claims (5)

A rubber component containing styrene-butadiene rubber and natural rubber, silica (1) having a nitrogen adsorption specific surface area of 130 m ² / g or less, silica (2) having a nitrogen adsorption specific surface area of 150 m ² / g or more, and the following formula Containing the alkylphenol-sulfur chloride condensate represented by (1),
The total content of the silica (1) and (2) is 60 to 110 parts by mass with respect to 100 parts by mass of the rubber component, and the alkylphenol / sulfur chloride condensate content represented by the following formula (1) is 1 to 1 parts. The rubber composition for treads which is 10 mass parts.

(Wherein R ¹ , R ² and R ³ are the same or different and represent an alkyl group having 5 to 12 carbon atoms. X and y are the same or different and represent an integer of 2 to 4. m is Represents an integer of 0 to 10.) The rubber composition for treads of Claim 1 containing 2-15 mass parts silane coupling agent with respect to 100 mass parts of total content of the said silica (1) and (2). The rubber composition for a tread according to claim 1 or 2, wherein the content of the silica (2) is 2.0 times or more of the content of the silica (1). R ¹ , R ² And R ³ The rubber composition for treads in any one of Claims 1-3 which shows a C6-C9 alkyl group. The pneumatic tire which has a tread produced using the rubber composition in any one of Claims 1-4 .