JP3224627B2 - Rubber composition and pneumatic tire using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rubber composition and a racing tire using the same in a tread rubber.

[0002]

2. Description of the Related Art Since tread rubber of a racing tire is required to have a high gripping force, carbon black and a softening agent are highly blended. Therefore, heat generation becomes large, and blowout often occurs during running. Blowout is closely related to the structure of the crosslinked chain of rubber, and the higher the crosslink density, the better the blowout resistance. However, as the crosslink density increases, grip performance decreases, and high-speed steering stability decreases. Therefore, conventionally, in a rubber composition, the following formula

Embedded image TMTD (tetramethylthiuram disulfide) represented by
It is known to incorporate a thiuram-based compound such as

[0003]

However, such a conventional rubber compound does not sufficiently satisfy the blowout resistance. In view of the above disadvantages, an object of the present invention is to provide a rubber composition capable of sufficiently satisfying blowout resistance and a pneumatic tire using the same in a tread and having excellent high-speed steering stability. .

[0004]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that a compound selected from the group consisting of a specific thiuram compound and a specific dithiocarbamate compound is combined with a benzothiazole vulcanization accelerator. It has been found that the use can achieve the above object. The configuration of the present invention is as follows. That is, the rubber composition of the present invention comprises 100 to 180 parts by weight of a rubber component containing 80 parts by weight or more of a styrene butadiene rubber, and 100 to 180 parts by weight of a softening agent.
Parts by weight, following formula

Embedded image (Wherein, R ₁ , R ₂ , R ₃ , and R ₄ each independently represent a straight-chain or branched-chain alkyl group having 7 to 12 carbon atoms, preferably 8 carbon atoms), and , The following equation

[0005]

Embedded image (Wherein, R ₅ and R ₆ each independently represent a carbon number of 7 to 12,
Preferably a straight or branched alkyl group of 8;
Is a divalent or higher valent metal, and n is a number equal to the valency of the metal of M) at least one of the compounds selected from the group consisting of dithiocarbamate compounds
~ 15 parts by weight, benzothiazole vulcanization accelerator 1.5 to 1
0 parts by weight are blended. Further, the ratio of the benzothiazole-based vulcanization accelerator to a compound selected from the group consisting of the thiuram compound and the dithiocarbamate compound (benzothiazole-based vulcanization accelerator / (thiuram compound and.
Or dithiocarbamate compound) is preferably 0.5 to 5.0.

It is preferable that R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are each a 2-ethylhexyl group, M is antimony, and n is 3. Furthermore, it is preferable to use each of the above rubber compositions for a tread rubber of a tire,
For example, racing tires for passenger cars, motorcycles, carts and the like can be mentioned.

The above rubber composition can be produced by kneading with a conventional mixer or kneader. At this time, if necessary, fillers such as carbon black, anti-aging agents, resins, vulcanization accelerators such as stearic acid and zinc oxide, vulcanizing agents such as sulfur, processing aids such as an adhesion inhibitor, etc. Can be blended.

[0008] When used as a tread rubber for a tire, it can be carried out by a usual tire manufacturing method. Here, the reason that the styrene-butadiene rubber in the rubber component is 80 parts by weight or more is to impart steering stability to the rubber composition composed of these rubbers, and if it is at the end of 80 parts by weight, the steering stability is inferior. This is inconvenient.

[0009] Examples of the softener include aromatic oil, spindle oil, naphthenic oil, paraffinic oil, vegetable oil, and sub oil. When the softener is less than 100 parts by weight, when used as a racing tire tread. When the softening agent exceeds 180 parts by weight, the abrasion resistance is significantly impaired, which is inconvenient. If the carbon number of R ₁ , R ₂ , R ₃ and R ₄ is 6 or less, the dispersion in the rubber becomes poor, and the blowout resistance and the like are inferior. Is inconvenient because it is very late.

Similarly, when the carbon number of R ₅ and R ₆ is 6 or less, the dispersion in the rubber becomes poor, and the blowout resistance and the like are inferior. Is inconvenient because it is very late. Examples of the metal of M include antimony, iron, copper, zinc, nickel, lead, tellurium, and the like. However, when M is monovalent, it is inconvenient because the effect of promoting vulcanization is insufficient. The compounding amount is 2 parts by weight or more and 15 parts by weight or less, but if it is less than 2 parts by weight, the blowout resistance is inferior. This is inconvenient. Preferably, it is at least 3 parts by weight and at most 8 parts by weight.

The thiuram compound or dithiocarbamate compound is preferably a compound having 8 carbon atoms among the carbon atoms having 7 to 12 carbon atoms of R _{1 to} R ₆ , and the thiuram compound is, for example, tetrakis (2-ethylhexyl) Thiuram disulfide (TEHT), tetrakis (1-isopropylpentyl) thiuram disulfide, tetrakis (1-ethyl-3-methylpentyl) thiuram disulfide, tetrakis (1-ethylhexyl) thiuram disulfide, tetranormal octylthiuram disulfide (TOTD) and the like. Can be

The benzothiazole vulcanization accelerators include mercaptobenzothiazole (MBT), dibenzothiazyl disulfide (MBTS), Nt-butyl-2-benzothiazolylsulfenamide (TBBS), N- Cyclohexyl-2-benzothiazolylsulfenamide (CBS),
N-oxydiethylene-2-benzothiazolylsulfenamide (MBS), N, N-dicyclohexyl-2-benzothiazolylsulfenamide (DCBS), zinc salt of mercaptobenzothiazole, 2- (4-morpholinodithio ) Benzothiazole, 2- (2,4-dinitro-phenyl) -mercaptobenzothiazole, salts of mercaptobenzothiazole and cyclohexylamine, N, N-diethylthiocarbamoyl-2-benzothiazolyl sulfide, and the like, If it is less than 1.5 parts by weight, sufficient vulcanization density cannot be obtained, and if it exceeds 10 parts by weight, not only does the vulcanization density not increase any more, but also when it is used for a tire tread, the adjacent rubber composition may be damaged. It is inconvenient because it shifts and has an adverse effect. Preferably, it is 2 parts by weight or more and 7 parts by weight or less.

Further, if the ratio of the benzothiazole vulcanization accelerator to the compound selected from the group consisting of the thiuram compound and the dithiocarbamate compound is less than 0.1, the effect of the addition on the vulcanization density is reduced, which is desirable. In order to obtain a vulcanized density, a larger amount is required.
As a result, the advantage of processing stability is reduced, which is inconvenient. On the other hand, if it exceeds 5.0, the surplus effect on the vulcanization density is similarly reduced, so that more compounding amount is required to obtain the desired vulcanization density. is there.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments. Example A (Examples 1 to 6, Comparative Examples 1 to 3) Table 1 shows the compounding ratio (unit: parts by weight) of the rubber composition, the physical properties of the rubber composition, and a tire using the rubber composition for a tread rubber. The characteristics of In Examples 1 to 6, the ratio of the benzothiazole vulcanization accelerator to the thiuram compound or dithiocarbamate compound was kept constant (1), TEHT and TOTD were used as thiuram compounds, and EH-Sb and EH-Zn were used as dithiocarbamate compounds. Shows an example in which TBBS, CBBS, and MBTS are blended as a bezothiazole compound. Comparative Examples 1 to 3 show that TEH was used as an accelerator.
Only T (Comparative Example 1), only TBBS (Comparative Example 2), and an example in which TMTD was blended as a thiuram compound (Comparative Example 3) are shown. In addition, TMTD of Comparative Example 3 had the same molar amount as TEHT of Example 1.

The respective test methods are as follows. Vulcanization density Measured according to the tensile test method of JIS K6301. Using a ring-shaped sample, the vulcanization density was defined as the male ratio at 300% elongation. This value is preferably 60 or less when used as a tread rubber for a racing tire. Blowout resistance (heat resistance) ASTM-D using Goodrich flexometer
The temperature (unit: ° C.) when the sample was blown out was measured according to the method of -623-58. The larger the value, the better the blowout resistance and the better. High-speed steering stability Tires (tire size: front 4.5 / 10.5) using the rubber composition of each example and each comparative example for the tread
-6, rear 7.0 / 11.5-6), and drive at high speed on the circuit, and its driving / braking properties, handling responsiveness,
Comparative Examples 3, 4, 5, 6, 7 (4 to 7)
A tire using the rubber composition having the composition described later) in a tread was used as a ke control tire, and the tire was compared with the tire and comprehensively evaluated by feeling.

The comparison criteria are as follows.

[Expression 1] +1 → Protest driver feels better than control tires +2 → General driver feels good enough for skilled driver +3 → General driver feels good -1 → If you feel that the protest driver is bad enough to change compared to the control tires -2 → If you feel that the experienced driver among the general drivers is bad enough to know -3 → If you feel that the general driver is bad enough to know

[0017]

[Table 1]

Explanation of abbreviations TO120 TEHT manufactured by SBR JSR Corporation tetrakis-2-ethylhexyl thiuram disulfid
e) TOTD tetra n-octhylthiuram disulfide (TMTD) TMTD tetramethyl thiuram disulfide (tetra)
methyl thiuram disulfide) EH-Sb Anti-2-ethylhexyl dithiocarbamate Antimony (Antimony di 2-ethyl hexyl dithiocar
bamate) EH-Zn di 2-ethylhexyl dithiocarbamate zinc TBBS Nt-butyl-2-benzothiazolyl sulfenamide (Nt-buthyl-2-benzothiazolyl sulfenamide) CBBS N-cyclohexyl benzothia Zolyl sulfenamide (N-cyclohexyl benzothiazolyl sulfenamid
e) MBTS dibenzothiadisulfide
zyl disulfide)

As described above, the rubber compositions of Examples 1 to 6 are excellent in both the blowout resistance and the vulcanization density, and the high-speed steering stability when this rubber composition is used for a tread rubber of a racing tire. It turns out that it is very excellent. On the other hand, Comparative Examples 1 to 3 are not only inferior in blowout resistance than each Example, but also very poor in high-speed steering stability,
It turns out that it is not suitable for the tread rubber of a racing car.

Example B (Examples 7 and 8 Comparative Examples 4 and 5) Similarly, Table 2 shows the mixing ratio (unit: parts by weight) of the rubber composition, the physical properties of the rubber composition, and the rubber composition. The following shows the characteristics of the tire used for the tread rubber. Example B is
Keeping the ratio of TBBS / TEHT constant, TBBS, TEHT
The amounts of HT and softener were varied.

[0021]

[Table 2]

As described above, it can be seen that rubbers having better blowout resistance can be obtained as compared with Comparative Examples 4 and 5 using TMTD for both Examples 7 and 8. Further, it can be seen that the tire using this as a tread rubber of a racing tire has excellent high-speed steering stability.

Example C (Examples 9 to 15, Comparative Example 6) Similarly, Table 3 shows the mixing ratio (unit: parts by weight) of the rubber composition, the physical properties of the rubber composition, and the tread of the rubber composition. Shows the characteristics of the tire used for rubber. Example C is
The ratio of TBBS / TEHT and TBBS / EH-Sb was changed.

[0024]

[Table 3] The ratio of TBBS / TEHT and TBBS / EH-Sb is
It is understood that a rubber having particularly good blowout resistance can be obtained when it is in the range of 0.1 to 5. However, if this ratio exceeds 5, the improvement in blowout resistance is not so large. Moreover, compared to Comparative Example 6 using TMTD,
It can be seen that high-speed steering stability when this rubber composition is used for a tread rubber of a racing tire is excellent.

Example D (Examples 16 and 17 and Comparative Example 7) Similarly, Table 4 shows the compounding ratio of the rubber composition, the physical properties of the rubber composition, and a tire using the rubber composition for a tread rubber. The characteristics of Example D comprises SB as a component.
20 parts by weight of NR were added in addition to 80 parts by weight of R. MBTS was used as a benzothiazole vulcanization accelerator.

[0026]

[Table 4]

Also in this case, it can be seen that a rubber composition having good blowout resistance can be obtained when two kinds of the thiuram compound or the dithiocarbamate accelerator and the benzothiazole accelerator according to the present invention are blended. Comparative Example 7 using TMTD as the thiuram-based accelerator may have poor blowout resistance. Further, this rubber composition,
It can be seen that the high-speed steering stability when used for the tread rubber of the racing tire is superior to the comparative example.
As can be seen from the above examples, the rubber composition of the present invention has improved vulcanizability and the like, and a tire using this as a tread rubber has improved high-speed steering stability.

[0028]

As described above, according to the present invention,
By using a specific thiuram compound or a specific dithiocarbamate compound in combination with a benzothiazole vulcanization accelerator in a specific compounding ratio, a rubber composition capable of sufficiently satisfying blow-out resistance and the like is provided. When used for a tread, a tire excellent in steering stability and the like can be realized.

Continuation of the front page (56) References JP-A-5-262916 (JP, A) JP-A-59-213745 (JP, A) JP-A-1-165636 (JP, A) JP-A-56-11933 (JP) JP-A-5-271476 (JP, A) JP-A-5-279528 (JP, A) JP-A-5-279525 (JP, A) JP-A-5-279514 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C08L 9/06 B60C 1/00 C08K 5/39 C08K 5/47

Claims (4)

(57) [Claims] 1. A softening agent of 100 to 18 parts per 100 parts by weight of a rubber component containing 80 parts by weight or more of styrene butadiene rubber.
0 parts by weight, the following formula (Wherein R ₁ , R ₂ , R ₃ and R ₄ each independently represent a straight-chain or branched-chain alkyl group having 7 to 12 carbon atoms), and the following formula: 2] (Wherein, R ₅ and R ₆ each independently represent a straight-chain or branched-chain alkyl group having 7 to 12 carbon atoms, M is a divalent or higher-valent metal, and n is a valence of the metal of M. At least one compound selected from the group consisting of dithiocarbamate compounds represented by the following formulas: 2 to 15 parts by weight, and 1.5 to 10 parts by weight of a benzothiazole vulcanization accelerator. A rubber composition characterized by the following: 2. The benzothiazole vulcanization accelerator,
The rubber composition according to claim 1, wherein the ratio of the compound selected from the group consisting of the thiuram compound and the dithiocarbamate compound is 0.1 to 5. 3. The method according to claim ₂ , wherein R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are each a 2-ethylhexyl group, M is antimony, and n is 3. Item 1 or 2
The rubber composition as described in the above. 4. A pneumatic tire using the rubber composition according to claim 1 for a tread rubber.