JP5466415B2 - Rubber composition and tire for base tread - Google Patents

Description

The present invention relates to a rubber composition for a base tread and a tire.

Conventionally, as a technology to reduce rolling resistance of tires (car fuel efficiency reduction), a method of blending silica as a filler in a rubber composition is known. When silica is blended with tread rubber, rolling resistance is reduced. In addition, the WET traction performance can be improved at the same time. For example, Patent Documents 1 to 3 disclose that rolling resistance performance, steering stability, wet skid performance, and the like can be improved in a balanced manner by blending two types of silica having different nitrogen adsorption specific surface areas into tread rubber. Yes.

However, the improvement of only tread rubber has a limit in the effect of reducing rolling resistance, and tire components other than tread rubber are required to have excellent low heat generation. For example, base tread rubber is also required to improve rolling resistance performance. Yes. In addition, the base tread rubber is required to improve not only the rolling resistance performance, but also the performance such as fracture resistance, in a well-balanced manner, and also to be excellent in workability in an unvulcanized state.

As another technique that can reduce the rolling resistance, a method of reducing the content of the reinforcing filler is known. However, since the hardness of the rubber composition is lowered, the tire is softened and the steering stability is inferior. is there.

In the base tread rubber composition, unlike the tread rubber, carbon black having a large particle diameter is conventionally used to reduce fuel consumption. Therefore, even if part or all of the carbon black is replaced with silica, the effect of reducing rolling resistance is not so great. Moreover, when it substitutes for a silica, there also exists a problem that fracture strength and steering stability fall. Furthermore, when silica is used for the rubber composition for a base tread, there are disadvantages in processability, such as an increase in unvulcanized rubber viscosity (Mooney viscosity).

As described above, in the rubber composition for a base tread, a rubber composition that satisfies all of the rolling resistance performance, fracture resistance strength, unvulcanized processability, and handling stability at the same time has not been obtained. Currently.

JP 2006-233177 A JP 2008-50570 A JP 2008-101127 A

The present invention provides a rubber composition for a base tread that solves the above-mentioned problems and can obtain all the performances of rolling resistance performance, fracture resistance, unvulcanized processability, and steering stability in a well-balanced manner, and It aims at providing the used tire.

In the present invention, 10 parts by mass of (1) silica having a nitrogen adsorption specific surface area of 130 m ² / g or less and (2) silica having a nitrogen adsorption specific surface area of 150 m ² / g or more per 100 parts by mass of the diene rubber component. 100 parts by mass, and 2-100 parts by mass of a silane coupling agent with respect to 100 parts by mass of the total content of the silica (1) and (2), and the silicas (1) and (2) The content relates to a rubber composition for a base tread that satisfies the following formula.
[Content of silica (1)] × 0.2 ≦ [Content of silica (2)] ≦ [Content of silica (1)] × 6.5

The diene rubber preferably contains at least one rubber component selected from natural rubber, isoprene rubber, epoxidized natural rubber, styrene butadiene rubber, and butadiene rubber.

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

According to the present invention, rolling resistance performance is obtained by blending silica having a low specific surface area, silica having a high specific surface area and a silane coupling agent and setting the mixing ratio of the contents of the two types of silica within a predetermined range. Further, it is possible to provide a rubber composition for base tread in which fracture resistance, workability in an unvulcanized state, and vehicle handling stability can be obtained in a well-balanced manner, and a tire having a base tread produced using the rubber composition.

The rubber composition for a base tread of the present invention comprises a diene rubber component, (1) silica having a nitrogen adsorption specific surface area of 130 m ² / g or less (hereinafter referred to as silica (1)), and (2) a nitrogen adsorption specific surface area. Contains 150 m ² / g or more of silica (hereinafter referred to as silica (2)) and a silane coupling agent.

Examples of the diene rubber component include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), epoxidized natural rubber (ENR), acrylonitrile butadiene rubber (NBR), chloroprene. Examples include rubber (CR), butyl rubber (IIR), and styrene-isoprene-butadiene copolymer rubber (SIBR). These diene rubbers may be used alone or in combination of two or more. Of these, NR, IR, ENR, and BR are preferable, and NR and BR are more preferably used in combination from the viewpoint of achieving both rolling resistance performance and durability.

In the rubber composition of the present invention, NR that can be used is not particularly limited. For example, SIR20, RSS # 3, TSR20, and the like that are common in the tire industry can be used. Also, the BR is not particularly limited. For example, BR1220 manufactured by Nippon Zeon Co., Ltd., BR130B manufactured by Ube Industries, Ltd., BR150B and other high cis content BR, VCR412 manufactured by Ube Industries, Ltd., VCR617, etc. BR containing a syndiotactic polybutadiene crystal can be used. From the viewpoint of improving mechanical strength, BR having a high cis content is preferable, and the cis content of BR is preferably 95% by mass or more.

The total content of NR, IR and ENR in 100% by mass of the diene rubber is preferably 35% by mass or more, more preferably 40% by mass or more. When it is less than 35% by mass, it is difficult to obtain sufficient tensile strength and cut resistance. The total content is preferably 59% by mass or less, more preferably 55% by mass or less.

The content of BR in 100% by mass of the diene rubber is preferably 41% by mass or more, more preferably 45% by mass or more. The BR content is preferably 65% by mass or less, more preferably 55% by mass or less. When it exceeds 65% by mass, it is difficult to obtain sufficient tensile strength and cut resistance.

Examples of silica (1) and (2) include silica prepared by a dry method (silicic anhydride), silica prepared by a wet method (hydrous silicic acid), and the like, and there are many silanol groups on the surface, Silica prepared by a wet method is preferred because it has many reactive sites with the silane coupling agent.

The nitrogen adsorption specific surface area (hereinafter referred to as N ₂ SA) of silica (1) is 130 m ² / g or less, preferably 125 m ² / g or less, more preferably 120 m ² / g or less. When N ₂ SA of silica (1) exceeds 130 m ² / g, the effect obtained by mixing with silica (2) is small. Further, N ₂ SA of silica (1) is preferably 20 m ² / g or more, and more preferably 30 m ² / g or more. When N ₂ SA of silica (1) is less than 20 m ² / g, the fracture resistance of the rubber composition tends to decrease.
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 SA50m 2 / g}} ), produced by Rhodia of ^{_{ZEOSIL115GR (N 2 SA115m 2 / g}} ), Rhodia ZEOSIL1115MP (N ₂ SA115m ² / g) manufactured by KK

The content of silica (1) is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and still more preferably 20 parts by mass or more with respect to 100 parts by mass of the diene rubber component. When the content of silica (1) is less than 5 parts by mass, the rolling resistance tends not to be sufficiently reduced. Moreover, 80 mass parts or less are preferable and, as for content of a silica (1), 60 mass parts or less are more preferable. When the content of silica (1) exceeds 80 parts by mass, the rolling resistance tends not to be sufficiently reduced.

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. When N ₂ SA of silica (2) is less than 150 m ² / g, the effect obtained by mixing with silica (1) is small. Also, _N 2 SA of the silica (2) is preferably from 300 meters ² / g or less, more preferably 240 m ² / g. When N ₂ SA of silica (2) exceeds 300 m ² / g, processability tends to deteriorate.

The nitrogen adsorption specific surface area ^{_{(N 2 SA) 150m 2 /}} g or more silica, for example, from Degussa ^{_{ULTRASILVN3 (N 2 SA175m 2 / g}} ), produced by Rhodia of ^{_{ZEOSIL1165MP (N 2 SA160m 2 / g}} ), Rhodia ZEOSIL 1205MP (N ₂ SA ₂₀₀ m ² / g) manufactured by KK

The content of silica (2) is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and further preferably 20 parts by mass or more with respect to 100 parts by mass of the diene rubber component. When the content of silica (2) is less than 5 parts by mass, there is a tendency that sufficient steering stability cannot be obtained. Moreover, 60 mass parts or less are preferable and, as for content of a silica (2), 50 mass parts or less are more preferable. When the content of silica (2) exceeds 60 parts by mass, processability tends to deteriorate.

The total content of silica (1) and (2) is 10 parts by mass or more, preferably 15 parts by mass or more, more preferably 20 parts by mass or more with respect to 100 parts by mass of the diene rubber component. When the total content of silica (1) and (2) is less than 10 parts by mass, the rolling resistance reduction effect tends not to be sufficiently obtained. The total content of silica (1) and (2) is 100 parts by mass or less, preferably 70 parts by mass or less, more preferably 60 parts by mass or less. When the total content of silica (1) and (2) exceeds 100 parts by mass, it becomes difficult for silica to be uniformly dispersed in the rubber composition, and the processability of the rubber composition tends to deteriorate.

The content of silica (1) and the content of (2) satisfy the following formula.
[Content of silica (1)] × 0.2 ≦ [Content of silica (2)] ≦ [Content of silica (1)] × 6.5

The content of silica (2) is 0.2 or more times, preferably 0.3 or more times the content of silica (1). If the content of silica (2) is less than the amount obtained by multiplying the content of silica (1) by 0.2, the fracture resistance tends to decrease. The content of silica (2) is not more than 6.5 times, preferably not more than 5.5 times, more preferably not more than 4.0 times the content of silica (1). When the content of silica (2) is larger than the amount obtained by multiplying the content of silica (1) by 6.5, workability tends to deteriorate and the rolling resistance reduction effect tends not to be sufficiently obtained.

In the present invention, by incorporating a silane coupling agent, excellent rolling resistance performance and unvulcanized processability can be obtained in a well-balanced manner. As the silane coupling agent used in the present invention, any silane coupling agent conventionally used in combination with silica can be used. For example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2- Triethoxysilylethyl) tetrasulfide, bis (4-triethoxysilylbutyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (4-trimethoxy) Silylbutyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (2-triethoxysilylethyl) trisulfide, bis (4-triethoxysilylbutyl) trisulfide, bis (3-trimethoxysilylpropyl) ) Trisulfide Bis (2-trimethoxysilylethyl) trisulfide, bis (4-trimethoxysilylbutyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) disulfide, bis (4- Triethoxysilylbutyl) disulfide, bis (3-trimethoxysilylpropyl) disulfide, bis (2-trimethoxysilylethyl) disulfide, bis (4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N, N -Dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-trimeth Sisilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxy Sulfide series such as silylpropyl methacrylate monosulfide, mercapto series such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, vinyltriethoxysilane , Vinyl type such as vinyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3- (2- Amino-ethyl) aminopropyltriethoxysilane, 3- (2-aminoethyl) aminopropyltrimethoxysilane and other amino compounds, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycine Glycidoxy series such as sidoxypropylmethyldiethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, nitro series such as 3-nitropropyltrimethoxysilane, 3-nitropropyltriethoxysilane, 3-chloropropyltrimethoxysilane, Examples include chloro-based compounds such as 3-chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane, and 2-chloroethyltriethoxysilane. Of these, bis (3-triethoxysilylpropyl) tetrasulfide and bis (3-triethoxysilylpropyl) disulfide are preferable from the viewpoint of excellent processability.

Content of a silane coupling agent is 2 mass parts or more with respect to 100 mass parts of total content of silica (1) and (2), Preferably it is 4 mass parts or more, More preferably, it is 6 mass parts or more. When the content of the silane coupling agent is less than 2 parts by mass, there is a tendency that the rolling resistance reduction effect is not sufficiently obtained. Moreover, content of a silane coupling agent is 15 mass parts or less, Preferably it is 12 mass parts or less, More preferably, it is 10 mass parts or less. When the content of the silane coupling agent exceeds 15 parts by mass, there is a tendency that the rolling resistance reducing effect corresponding to the amount of the expensive silane coupling agent added cannot be obtained.

The rubber composition according to the present invention includes, in addition to the rubber component, silica (1) and (2), and a silane coupling agent, an additive generally used in the production of a rubber composition, a silica such as carbon black and clay. Other reinforcing fillers, anti-aging agents, softening agents such as oil, vulcanizing agents such as zinc oxide, stearic acid, wax and sulfur, vulcanization accelerators, processing aids and the like can be appropriately blended.

The rubber composition of the present invention preferably contains carbon black. Thereby, fracture strength and workability (workability in an unvulcanized state) can be improved. As carbon black, GPF, HAF, FF, ISAF, SAF, etc. can be used, for example.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 40 m ² / g or more, and more preferably 45 m ² / g or more. If it is less than 40 m < ² > / g, there exists a tendency for reinforcement property and abrasion resistance to deteriorate remarkably. Further, the nitrogen adsorption specific surface area of carbon black is preferably 120 m ² / g or less, and more preferably 90 m ² / g or less. When it exceeds 120 m ² / g, the dispersibility is poor, and on the contrary, the reinforcing property and the wear resistance tend to be lowered.
In addition, the nitrogen adsorption specific surface area of carbon black is calculated | required by A method of JISK6217.

When the rubber composition contains carbon black, the total content of silica and carbon black is preferably 40 parts by mass or more, more preferably 50 parts by mass or more with respect to 100 parts by mass of the diene rubber component. If it is less than 40 parts by mass, the rubber hardness tends to be low and the breaking strength tends to be insufficient. The total content is preferably 130 parts by mass or less, more preferably 90 parts by mass or less, and still more preferably 70 parts by mass or less with respect to 100 parts by mass of the rubber component. If it exceeds 130 parts by mass, the heat build-up becomes high and the durability tends to decrease.

As the oil used in the rubber composition of the present invention, for example, process oil, vegetable oil or a mixture thereof may be used. Examples of the process oil include paraffinic process oil, naphthenic process oil, and aromatic process oil. Vegetable oils include castor oil, cottonseed oil, sesame oil, rapeseed oil, soybean oil, palm oil, palm oil, peanut oil, 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, cocoon oil, jojoba oil, macadamia nut oil, safflower oil, and tung oil. Of these, aromatic process oils (such as Diana Process Oil AH24 manufactured by Idemitsu Kosan Co., Ltd.) are preferable from the viewpoint of cost and processability.

The blending amount of the oil 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 diene rubber component. If the amount of oil is less than 3 parts by mass, the viscosity of the unvulcanized rubber may be too high. The blending amount of oil is preferably 20 parts by mass or less, and more preferably 10 parts by mass or less. When the blending amount of oil exceeds 20 parts by mass, the hardness of the vulcanized rubber becomes soft and the steering stability may be deteriorated.

Examples of the vulcanization accelerator include N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N, N′-dicyclohexyl-2- Examples include benzothiazolylsulfenamide (DZ), mercaptobenzothiazole (MBT), dibenzothiazolyl disulfide (MBTS), and diphenylguanidine (DPG). Of these, TBBS and CBS are preferable from the viewpoint that the scorch and the vulcanization speed can be controlled in a balanced manner.

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. Moreover, in this invention, since the workability of an unvulcanized state improves (Mooney viscosity falls), the workability of a kneading | mixing process or an extrusion process can be improved.

The rubber composition of the present invention is used as a tire base tread. The base tread is an inner layer portion of a tread having a multilayer structure, and is an inner surface layer in a tread having a two-layer structure [a surface layer (cap tread) and an inner surface layer (base tread)]. Specifically, the base tread is a member shown in FIG. 1 of Japanese Patent Laid-Open No. 2008-285628, FIG. 1 of Japanese Patent Laid-Open No. 2008-303360, or the like.

A tread having a multilayer structure is produced by pasting a sheet into a predetermined shape, or by inserting it into two or more extruders and forming it into two or more layers at the head outlet of the extruder. Can do.

The pneumatic tire of the present invention is produced by a usual method using the rubber composition. That is, a rubber composition blended with various additives as necessary is extruded according to the shape of the base tread of the tire at an unvulcanized stage, and molded by a normal method on a tire molding machine, Bonding together with other tire members forms an unvulcanized tire. This unvulcanized tire can be heated and pressurized in a vulcanizer to produce a tire. The obtained pneumatic tire has low heat build-up (excellent rolling resistance performance), and excellent handling stability and fracture strength.

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

Hereinafter, various chemicals used in Examples and Comparative Examples will be described together.
NR: RSS # 3
BR: BR130B manufactured by Ube Industries, Ltd. (cis content 96% by mass)
Carbon Black: Show Black N351 (N ₂ SA71m ² / g) manufactured by Cabot Japan
Silica (1): ULTRASIL 360 (N ₂ SA 50 m ² / g) manufactured by Degussa
Silica (2): ZEOSIL 1205MP (N ₂ SA ²⁰⁰ m ² / g) manufactured by Rhodia Japan
Silane coupling agent: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by Degussa
Zinc oxide: Zinc Hua No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Sakai Process Oil manufactured by NOF Corporation: Diana Process Oil AH24 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 manufactured by Karuizawa Sulfur Co., Ltd. CZ: Noxeller CZ (N-cyclohexyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Co., Ltd.

Examples 1-4 and Comparative Examples 1-6
In accordance with the formulation shown in Table 1, a Banbury mixer was used to knead chemicals other than sulfur and vulcanization accelerator for 3 minutes, and further kneaded sulfur and vulcanization accelerator with an open roll to obtain an unvulcanized rubber composition I got a thing.
Further, the obtained unvulcanized rubber composition was rolled into a sheet and then press vulcanized for 30 minutes with a mold at 150 ° C. to obtain a vulcanized rubber sheet.

Further, after molding the obtained unvulcanized rubber composition into a base tread shape (processing into a sheet having a thickness of about 2 mm), it is bonded to another tire member and vulcanized to obtain a test tire (tire Size: 195 / 65R15).

The following evaluation was performed using the obtained unvulcanized rubber composition, vulcanized rubber sheet, and test tire. Each test result is shown in Table 1.

(Mooney viscosity)
In accordance with JIS K 6300-1 “Unvulcanized rubber—physical properties—Part 1: Determination of viscosity and scorch time using Mooney viscometer”, it was heated by preheating for 1 minute using a Mooney viscosity tester. Under the temperature condition of 130 ° C., the small rotor was rotated, and the Mooney viscosity (ML _{1 +} 4/130 ° C.) of the unvulcanized rubber composition after 4 minutes was measured. The measurement results are shown as an index with the result of Comparative Example 1 as 100. The larger the index, the lower the viscosity and the easier the processing.

(Rolling resistance index)
Using a viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho Co., Ltd.), tan δ of each compound (vulcanized rubber sheet) was measured and compared at a temperature of 70 ° C., an initial strain of 10%, and a dynamic strain of 2%. The tan δ in Example 1 was set to 100, and the index was displayed by the following calculation formula. The larger the index, the better the rolling resistance performance.
(Rolling resistance index) = (tan δ of Comparative Example 1) / (tan δ of each formulation) × 100

(Destructive strength)
The vulcanized rubber sheet was subjected to a tensile test using a No. 3 dumbbell according to JIS K6251, and the breaking strength (TB) was measured as the elongation at break EB (%). The numerical value of TB × EB / 2 was used as the fracture resistance, and the index was expressed as an index with the fracture resistance of Comparative Example 1 as 100. The larger the index, the better the fracture strength.

(Maneuvering stability)
The test tires were mounted on all wheels of a vehicle (domestic FF2000cc) and the vehicle was run on the test course, and the steering stability was evaluated by sensory evaluation of the driver. Relative evaluation was performed with 10 points being a perfect score and Comparative Example 1 being 6 points. The larger the value, the better the steering stability and the better.

As shown in Table 1, examples in which silica having a low specific surface area and silica having a high specific surface area were simultaneously used as fillers are all about rolling resistance performance, fracture strength, workability in an unvulcanized state, and handling stability. We were able to get a good balance of performance. On the other hand, in Comparative Example 1 using carbon black having a large particle diameter that has been used in the past, the overall performance was inferior compared to the Examples. Moreover, the comparative example 2 which reduced carbon black was inferior to fracture strength and steering stability. In Comparative Examples 3 to 6 in which two types of silica were not used at the same time, it was not possible to obtain all the performances of rolling resistance performance, fracture resistance, unvulcanized processability, and steering stability in a well-balanced manner. It was.

Claims (4)

For 100 parts by weight of diene rubber component including natural rubber and butadiene rubber,
(1) A nitrogen adsorption specific surface area of 130 m ² / g or less of silica and (2) a nitrogen adsorption specific surface area of 150 m ² / g or more of silica are contained in a total of 10 to 100 parts by mass,
Furthermore, 2 to 15 parts by mass of a silane coupling agent is contained with respect to 100 parts by mass of the total content of silica (1) and (2),
The rubber composition for base treads in which the contents of the silicas (1) and (2) satisfy the following formula ,
[Content of silica (1)] × 0.2 ≦ [Content of silica (2)] ≦ [Content of silica (1)] × 6.5
Furthermore, a rubber composition for base treads containing oil . The rubber composition for a base tread according to claim 1, comprising carbon black having a nitrogen adsorption specific surface area of 40 to 120 m ² / g. The rubber composition for a base tread according to claim 1 or 2, comprising N -cyclohexyl-2-benzothiazolylsulfenamide. The tire which has a base tread produced using the rubber composition for base treads in any one of Claims 1-3.