JP2002020542A - Rubber composition and pneumatic tire using the composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition which is suitable for the tread of a tire, and in which the gripping power against a road surface (gripping performance) is compatible with abrasion resistance during running when it is used as the tread. SOLUTION: The rubber composition contains 100 pts.wt. of a rubber component containing >=75 wt.% of a styrene-butadiene copolymer, 80-150 pts.wt. of carbon black having a nitrogen absorption specific area of >=85 mm2/g, 50-150 pts.wt. of a softening agent containing at least 50-150 pts.wt. of aroma oil and 0.1-3.0 pts.wt. of isostearic acid. Preferable examples of the softening agent include a composition containing 0-50 pts.wt. of a thermoplastic resin or that containing 0.5-3.0 pts.wt. of the isostearic acid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition which is suitable for a tire tread and which, when used in a tire tread, can achieve both a grasping force (grip performance) on a road surface during running and abrasion resistance. Further, the present invention relates to a pneumatic tire having high performance and suitable as a racing tire.

[0002]

2. Description of the Related Art A tire tread, particularly a racing tire tread, is required to have excellent gripping ability (grip performance) and abrasion resistance of a road surface during running. Traditionally,
For the purpose of improving the wear resistance, carbon black,
Incorporation of an inorganic filler, zinc white and the like into a rubber composition has been performed. At this time, in order to uniformly disperse the carbon black and the like in the rubber composition, a low molecular weight organic compound such as stearic acid is added to the rubber composition. However, since the low molecular weight organic compound such as stearic acid is easily leached on the surface of the rubber composition, when the rubber composition is used for a tire tread,
There is a problem that the grip performance is significantly reduced. For this reason, the grip performance and the wear resistance are completely trade-off performances, and it is difficult to satisfy both at the same time.

[0003] Japanese Patent Application Laid-Open No. 3-29256 discloses a technique disclosed in
JP-A-4-261443, JP-A-9-32857
No. 5, JP-A-3-29256, JP-A-4-2
Japanese Patent No. 61443 and Japanese Patent Application Laid-Open No. 9-328574 disclose rubber compositions containing isostearic acid, and these rubber compositions are used for competition tires having extremely high input and severe wear. Cannot be applied. At present, a technique that achieves both the grip performance and the wear resistance has not yet been provided.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and achieve the following objects. That is, the present invention is suitable for a tire tread, and when used in the tire tread, a rubber composition that achieves both a gripping force (grip performance) of a road surface during traveling and abrasion resistance, and An object of the present invention is to provide a pneumatic tire having performance and suitable as a competition tire.

[0005]

Means for solving the above problems are as follows. That is, <1> 100 parts by weight of a rubber component containing 75% by weight or more of a styrene-butadiene copolymer, and a nitrogen adsorption specific surface area of 8%.
Carbon black 80 to 150 of 5 mm ² / g or more
A rubber composition characterized by comprising 50 parts by weight of a softening agent containing at least 50 to 150 parts by weight of aroma oil, and 0.1 to 3.0 parts by weight of isostearic acid. . <2> The rubber composition according to <1>, wherein the softener contains 0 to 50 parts by weight of a thermoplastic resin. <3> The rubber composition according to <1> or <2>, containing 0.5 to 3.0 parts by weight of isostearic acid. <4> A pneumatic tire using the rubber composition according to any one of <1> to <3>. <5> The pneumatic tire according to <4>, which is used as a competition tire.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION (Rubber Composition) The rubber composition of the present invention comprises a rubber component, carbon black, a softener, and isostearic acid. It contains the component of.

-Rubber component- The rubber component must contain the styrene-butadiene copolymer in an amount of 75% by weight or more, and preferably 85% by weight or more. Examples of the rubber component other than the styrene-butadiene copolymer include natural rubber (NR) and butadiene rubber (BR).

[0008] The styrene-butadiene copolymer preferably has a Mooney viscosity at 100 ° C of 30 or more, more preferably 40 or more. If the Mooney viscosity is less than 30, the wear resistance may deteriorate. The Mooney viscosity can be obtained, for example, by measuring ML1 + 4 at 100 ° C. using a Mooney clay tester, for example, a rotorless Mooney tester manufactured by Toyo Seiki.

The styrene content in the styrene-butadiene copolymer is preferably from 10 to 70% by weight, more preferably from 20 to 50% by weight. The content is
If it is less than 10% by weight, the grip performance at high temperatures may be insufficient, and if it exceeds 70% by weight, the grip performance at low temperatures may be insufficient. As the styrene-butadiene copolymer, a commercially available product can be used and may be oil-extended.

-Carbon Black- The carbon black is used as a reinforcing filler in the rubber composition. The carbon black is not particularly limited and can be appropriately selected depending on the purpose. The carbon black may be used alone or in combination of two or more.
In addition, commercially available products can be used.

The nitrogen adsorption specific surface area (N ₂ SA) of the carbon black is preferably at least 85 m ² / g,
20-180 m < ² > / g is more preferable. When the nitrogen adsorption specific surface area (N ₂ SA) is less than 85 m ² / g, the abrasion resistance of the rubber composition may not be sufficient. Incidentally, the nitrogen adsorption specific surface area (N ₂ SA) was determined according to ASTM D303.
It is defined in 7-88 and means the nitrogen adsorption specific surface area per unit weight (m ² / g).

The carbon black preferably has a dibutyl phthalate oil absorption (hereinafter sometimes referred to as “DBP oil absorption”) of preferably 100 to 150 cm ³ / g, and more preferably 120 to 150 cm ³ / g.
１４０140 cm ³ / g is more preferred. The dibutyl phthalate oil absorption is less than 100 cm ³ / g, sometimes the abrasion resistance can not be sufficiently secured, 150 cm ³ /
If it exceeds g, processability and elongation properties are inferior, and general properties as a rubber may be deteriorated. In addition, the said DBP oil absorption is JIS K6221 (1982) 6.1.2.
A value measured according to Method A,
The amount of dibutyl phthalate absorbed per 0 g (m
l).

The content of the carbon black in the rubber composition must be 80 to 150 parts by weight, preferably 90 to 130 parts by weight, based on 100 parts by weight of the styrene-butadiene copolymer. When the content of the carbon black is less than 80 parts by weight, the abrasion resistance of the rubber composition cannot be sufficiently secured, general properties such as strength are not sufficient, and the grounding property is deteriorated, and the lap time is also deteriorated. When the amount exceeds 150 parts by weight, the rubber composition becomes too hard, and on the contrary, the abrasion resistance is reduced, and the workability may be extremely deteriorated.

-Softener- The softener is not particularly limited as long as it contains at least an aroma oil, and can be appropriately selected according to the purpose. It may contain a thermoplastic resin.
The softener may be composed of a single substance, or may be composed of two or more substances. The latter case is preferred in that the temperature dependence of the hardness of the rubber composition can be widened.

The thermoplastic resin is not particularly limited and may be appropriately selected depending on the intended purpose. C5 petroleum resin, C9 petroleum resin and the like are preferred.

The C5 petroleum resin is a C5 cut resin obtained by pyrolysis of naphtha. Examples of the C5 fraction include olefin-based hydrocarbons and diolefin-based hydrocarbons. Examples of the olefinic hydrocarbon include pentene, 2-methylbutene,
3-methylbutene, 2-methylbutene, and the like. As the C5 petroleum resin, a commercially available product can be suitably used. Examples of the commercially available product include Struktol TS30 (manufactured by Struktol) and TX-500.
(Manufactured by Mitsui Chemicals, Inc.).

The C9 petroleum resin is a C9 cut resin obtained by pyrolysis of naphtha. Examples of the C9 fraction include diolefin-based hydrocarbons. As the diolefin-based hydrocarbon, benzene,
Toluene, xylene, styrene, α-methylstyrene,
1,2-pentadiene, and the like. As the C9 petroleum resin, commercially available products can be suitably used. Examples of the commercially available products include Quinton (manufactured by Zeon Corporation), Neopolymer (manufactured by Nippon Oil Co., Ltd.), and Cholecin ( BASF).

The melting point of the thermoplastic resin is from 80 to
160 ° C is preferred, and 100 to 140 ° C is more preferred. When the melting point of the thermoplastic resin is less than 80 ° C,
In some cases, the rigidity of the rubber at a high temperature is insufficient, and when it exceeds 160 ° C., the flexibility of the rubber at a low temperature may be insufficient.

The content of the softener in the rubber composition is such that the content of the aroma oil contained in the softener is 50 to 150 parts by weight based on 100 parts by weight of the styrene-butadiene copolymer. And 80 to 120 parts by weight is preferred. If the content of the aroma oil is less than 50 parts by weight, workability and elongation properties may be inferior. If it exceeds 150 parts by weight, abrasion resistance may not be sufficiently secured.

[0020] The content of the thermoplastic resin contained in the softening agent may be the styrene-butadiene copolymer 1
0 to 50 parts by weight, preferably 10 to 50 parts by weight,
30 parts by weight are preferred. When the thermoplastic resin is contained, it is preferable in that tan δ can be improved, and when the content of the thermoplastic resin exceeds 50 parts by weight,
Temperature dependence may be worsened.

The ratio of the thermoplastic resin to the aroma oil (thermoplastic resin (weight) / aroma oil (weight)) in the softener is preferably 0.7 or less, and 0.5 or less. More preferably, there is. The ratio is
If it exceeds 0.7, the temperature dependency of the hardness of the rubber composition may increase.

-Isostearic acid-The isostearic acid is not particularly limited and may be appropriately selected depending on the intended purpose. One type may be used alone, or two or more types may be used in combination. Moreover, you may use a commercial item.

The content of the isostearic acid in the rubber composition is preferably from 0.1 to 3.0 parts by weight, more preferably from 0.5 to 3.0 parts by weight. When the content of the vulcanization accelerator is less than 0.1 part by weight, the function as a dispersant may not be sufficient, and when the content exceeds 3.0 parts by weight, leaching on the surface of the rubber composition may occur. And the grip performance may be degraded.

-Other components- The other components can be appropriately selected and used within a range not to impair the object of the present invention, and include, for example, inorganic fillers, softeners, and vulcanizing agents such as sulfur. Accelerators such as dibenzothiazyl disulfide, vulcanization aids, anti-aging agents such as N-cyclohexyl-2-benzothiazyl-sulfenamide, N-oxydiethylene-benzothiazyl-sulfenamide, zinc oxide, stearic acid , Ozone deterioration inhibitor, coloring agent, antistatic agent, lubricant, antioxidant, softener, coupling agent, foaming agent, foaming aid and other additives, as well as various compounding agents usually used in the rubber industry. No. These can use a commercial item suitably.

-Production of Rubber Composition- The rubber composition of the present invention comprises the styrene-butadiene copolymer, the carbon black, the softening agent, the isostearic acid, It can be manufactured by kneading, heating, extruding, vulcanizing and the like with other components.

The conditions for the kneading are not particularly limited, and various conditions such as the volume to be charged into the kneading apparatus, the rotation speed of the rotor, the ram pressure, the kneading temperature, the kneading time, and the type of the kneading apparatus are used. Can be appropriately selected according to the purpose. Examples of the kneading device include a Banbury mixer, an intermix, and a kneader that are usually used for kneading a rubber composition.

The heating conditions are not particularly limited, and various conditions such as a heating temperature, a heating time, and a heating device can be appropriately selected according to the purpose. Examples of the warming device include, for example, a roll machine usually used for warming a rubber composition.

The conditions for the extrusion are not particularly limited, and various conditions such as an extrusion time, an extrusion speed, an extrusion apparatus, and an extrusion temperature can be appropriately selected depending on the purpose. As the extruder, for example, an extruder or the like usually used for extruding a rubber composition for a tire is exemplified. The extrusion temperature can be appropriately determined.

At the time of the extrusion, for the purpose of controlling the fluidity of the rubber composition, plasticizers such as aroma oils, naphthene oils, paraffin oils, ester oils, liquid polyisoprene rubber, liquid polybutadiene rubber, etc. A processability improver such as a liquid polymer can be appropriately added to the rubber composition. In this case, the viscosity of the rubber composition before vulcanization can be reduced, the fluidity thereof can be increased, and extrusion can be performed very well.

The vulcanizing apparatus, system, conditions and the like are not particularly limited and can be appropriately selected according to the purpose. As an apparatus for performing the vulcanization, for example, a molding vulcanizer using a mold usually used for vulcanizing a rubber composition for a tire may be mentioned. The temperature of the vulcanization is usually about 100 to 190 ° C.

-Applications- Although the rubber composition of the present invention can be suitably used in various fields, it can be particularly preferably used for treads of competition tires and the like, and is suitable for the pneumatic tire of the present invention. Can be used for

(Pneumatic Tire) The pneumatic tire of the present invention comprises at least the rubber composition of the present invention, preferably at least a tread. The pneumatic tire of the present invention is not particularly limited except that the rubber composition of the present invention is used, and the configuration of a known pneumatic tire can be employed as it is.

An example of the pneumatic tire is a pneumatic tire having a pair of bead portions, a carcass connected to the bead portions in a toroidal shape, a belt for tightening a crown portion of the carcass, and a tread. Preferable examples include tires. The pneumatic tire of the present invention may have a radial structure or may have a bias structure.

The structure of the tread is not particularly limited and may be a one-layer structure or a multi-layer structure. An upper-layer cap portion directly grounded to a road surface and an air-filled portion of the cap portion are provided. A so-called cap comprising a lower base portion arranged adjacent to the inside of the tire.
It may have a base structure. In the present invention, it is preferable that at least the cap portion is formed of the rubber composition of the present invention.

The pneumatic tire of the present invention is not particularly limited with respect to the method for producing it, and can be produced, for example, as follows. That is, first, the rubber composition of the present invention is prepared, and the rubber composition is pasted on an unvulcanized base portion previously pasted on a crown portion of a fresh pneumatic tire case. And it can be manufactured by vulcanization molding under a predetermined temperature and a predetermined pressure in a predetermined mold.

The pneumatic tire of the present invention can be particularly suitably used not only for so-called passenger cars but also for racing cars and other racing cars.

[0037]

Embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

(Examples 1 to 8 and Comparative Examples 1 to 6) Rubber compositions having the compositions shown in Table 1 were prepared, and each rubber composition was used for a tread to obtain a competition tire (size: 215 / 40R1).
8) was prototyped. The competition tires were mounted on a competition vehicle and run on a test course, and the grip feeling and wear resistance of the actual vehicle were evaluated as follows. The results are shown in Table 1.

<Evaluation of actual vehicle grip feeling (rating)
> The best lap time during circuit running was compared with that of Comparative Example 1, and the evaluation of Comparative Example 1 was set to 100 and indicated by an index.
The larger the value, the better the actual vehicle grip feeling and the faster the lap time.

<Wear Resistance (Wear Skin Rating)> After running a certain distance on the circuit, the size of the ablation of the tire was visually evaluated. The score of Comparative Example 1 was set to 3, and the smaller the value, the smaller the value. It means that it has excellent wear resistance.

[0041]

[Table 1]

In Table 1, "SBR1" is a styrene-butadiene rubber (manufactured by JSR Co., Ltd .;
SR0120: Mooney viscosity at 100 ° C. = 51,
35% by weight of styrene, 37.5 parts by weight of aroma oil). “SBR2” is a styrene-butadiene rubber (manufactured by Asahi Kasei Corporation, Tuffden 4350: Mooney viscosity at 100 ° C. = 43, containing styrene 39% by weight,
Aroma oil 50 parts by weight). "Carbon black 1", Tokai Carbon Co., Ltd., is a N234 (nitrogen adsorption specific surface area ^{_{(N 2 SA) = 126m 2}} / g, a dibutyl phthalate oil absorption = 125cm ³ / g). “Carbon black 2” is manufactured by Asahi Carbon Co., Ltd. and has N110 (nitrogen adsorption specific surface area (N ₂ SA) = 141 m ² / g, dibutyl phthalate oil absorption = 122 cm ³ / g). “Thermoplastic resin” is Neopolymer 140 manufactured by Nisseki Chemical Co., Ltd. "Antioxidant 6C" represents an antioxidant (manufactured by Sumitomo Chemical Co., Ltd.). "Accelerator DPG" is a vulcanization accelerator (Diphenylguanidine manufactured by Sumitomo Chemical Co., Ltd.)
Represents "Accelerator DM" represents a vulcanization accelerator (dibenzothiazyl disulfide, manufactured by Ouchi Shinko Chemical Co., Ltd.). “Accelerator NS” represents a vulcanization accelerator (N-tert-butyl-2-benzothiazolylsulfenamide, manufactured by BAYER).

From the results in Table 1, it can be seen that when the rubber compositions of Comparative Examples 1 to 6 containing stearic acid were used for the tread of a tire, both the grip performance during running and the wear resistance were compatible. In contrast, when each of the rubber compositions of Examples 1 to 8 in which isostearic acid was blended in a predetermined amount was used for a tread of a tire, both grip performance and abrasion resistance during running could be achieved. It is clear that.

[0044]

According to the present invention, the above-mentioned problems in the prior art can be solved, which is suitable for a tire tread. It is possible to provide a rubber composition capable of achieving both abrasion resistance and a pneumatic tire having high performance and suitable as a competition tire.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // (C08L 9/06 (C08L 9/06 57:02) 57:02)

Claims (5)

[Claims] 1. A rubber component containing 75% by weight or more of a styrene-butadiene copolymer, 100 parts by weight of a rubber component, and a carbon black having a nitrogen adsorption specific surface area of 85 mm ² / g or more.
150 parts by weight and at least 50 to 15 aroma oils
A rubber composition comprising 50 to 150 parts by weight of a softening agent containing 0 parts by weight and 0.1 to 3.0 parts by weight of isostearic acid. 2. The rubber composition according to claim 1, wherein the softener contains 0 to 50 parts by weight of a thermoplastic resin. 3. The rubber composition according to claim 1, which contains 0.5 to 3.0 parts by weight of isostearic acid. 4. A pneumatic tire using the rubber composition according to any one of claims 1 to 3. 5. Use as a racing tire.
A pneumatic tire according to claim 1.