JP2001240704A - Rubber composition for tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition which gives a tire which, while retaining excellent abrasion resistance and driving stability attainable by a sulfur vulcanization system, exhibits an improvement in excellent thermal stability attainable by an organic peroxide vulcanization system and has improved initial grip properties and especially the degradation of the grip properties of which with an increase in running distance is reduced. SOLUTION: Based on 100 pts.wt. diene rubber, this rubber composition contains 0.2-3.0 pts.wt. sulfur, an organic peroxide in an amount of 0.02-0.20 pt.wt. in terms of active oxygen, and 2-5 pts.wt. tackifier.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-performance rubber composition for tires, particularly a tread rubber for tires, which has reduced initial grip performance and reduced grip performance with running distance while maintaining abrasion resistance and steering stability. Composition.

[0002]

2. Description of the Related Art Conventionally, in order to obtain high grip properties in a tread rubber composition for a high-performance tire, a styrene-butadiene rubber having a high styrene content has been used or a large amount of fine carbon particles and a softener have been blended. Has been attempted to increase the hysteresis loss. In such a rubber composition, internal heat generation occurs with high-speed running of the tire, and grip properties tend to decrease with the running distance. Therefore, in order to maintain grip properties, it is necessary to increase the thermal stability of the rubber composition, but such thermal stability is affected by the crosslinked form of the vulcanized rubber.

[0003] The most common vulcanized rubber composition based on a sulfur vulcanization system composed of sulfur and a vulcanization accelerator generally has a polysulfide bond as a main component, and therefore has excellent abrasion resistance but low thermal stability. There is a problem of inferiority. That is, the cross-linked form of the polysulfide bond changes to the cross-linked form of monosulfide due to internal heat generation during running of the tire, so that the grip property is lowered.

On the other hand, EV vulcanization systems have long been known for the purpose of improving the thermal stability of sulfur vulcanization rubber compositions. The EV vulcanization system is a vulcanization method in which the amount of sulfur as a vulcanizing agent is reduced as much as possible and the number of sulfur per unit crosslink is reduced as much as possible. Small, short fatigue life, poor adhesion to metals and the like.

On the other hand, organic peroxides that do not use sulfur have a heat-resistant cross-linking of carbon-carbon bonds, and have little change in the cross-linked structure of the rubber composition during running, resulting in a change in grip properties.
That is, it is possible to reduce a decrease in grip performance. However, since the crosslinked structure becomes strong and the degree of freedom inside the rubber molecule is restricted, the loss tangent (tan δ) of the vulcanized rubber composition itself is reduced, and the initial gripping property is reduced.

[0006]

SUMMARY OF THE INVENTION The present invention improves the thermal stability of an organic peroxide vulcanization system while maintaining excellent abrasion resistance and steering stability in a sulfur vulcanization system. Provided is a rubber composition for a tire, in particular, a tread rubber composition for a tire, which has improved gripping properties, and in particular, reduces the reduction in gripping properties with running distance.

[0007]

The present invention relates to a diene rubber 1
0.2 to 3.0 parts by weight of sulfur, 0.02 to 0.20 parts by weight of active oxygen in organic peroxide and 2 to 5 parts by weight of a tackifier with respect to 00 parts by weight. It is a rubber composition for tires.

The rubber component used in the present invention may be a styrene-butadiene rubber, a butadiene rubber, a natural rubber, a synthetic isoprene rubber alone or any combination thereof, for example, a blend of a styrene-butadiene rubber and a natural rubber, a styrene-butadiene rubber, In addition to blends mainly composed of styrene-butadiene rubber, such as blends of synthetic isoprene rubber, styrene-butadiene rubber, natural rubber and synthetic isoprene rubber, blends of butadiene rubber and natural rubber, blends of butadiene rubber and synthetic isoprene rubber, A blend of butadiene rubber, natural rubber, and synthetic isoprene rubber may be employed. 40% by weight of rubber component
The following other rubber components can be blended.

In the rubber composition of the present invention, a sulfur vulcanizing system and a crosslinking system with an organic peroxide are used in combination as a vulcanizing agent. The sulfur vulcanization system refers to a combination of sulfur and a vulcanization accelerator. The amount of sulfur is 0.2 to 100 parts by weight of the rubber component.
3.0 parts by weight. If the amount is less than 0.2 part by weight, the crosslink density is small and the tensile strength and abrasion resistance of the rubber composition are not sufficient. If the amount exceeds 3.0 parts by weight, the rubber composition becomes too hard and the gripping property is reduced.

As the vulcanization accelerator, general vulcanization accelerators can be used, for example, mercaptobenzothiazole, dibenzothiazyldisulfide, N-cyclohexylbenzothiazylsulfenamide, N-tert-butyl-2-yl- Benzothiazolylsulfenamide may be used. The compounding amount of the vulcanization accelerator is generally 0.2 to 0.4 parts by weight per 100 parts by weight of the rubber component.

The organic peroxides used in the present invention are those used for ordinary rubber vulcanization, such as dicumyl peroxide, 2,2-bis (tert-butylperoxy) octane, 2,5-dimethyl-2. , 5-di (tert-butylperoxy) hexane, α, α'-bis (tert-butylperoxy) diisopropylbenzene, 1,3-bis (tert-butylperoxyisopropyl) benzene and the like.

The amount of the organic peroxide is 0.02 to 0.20 per 100 parts by weight of the rubber component.
It is blended so as to be parts by weight. Active oxygen refers to free radicals generated from the organic peroxide. If the amount of active oxygen is less than 0.02 parts by weight, it is not possible to suppress a decrease in grip properties, while if it exceeds 0.20 parts by weight, energy loss (tan δ) becomes too small and grip properties are reduced.

Here, the theoretical active oxygen content (Aw) is obtained by dividing the product of the number of active oxygen atoms (N) in the organic peroxide and the atomic weight of the active oxygen (16) by the molecular weight (W) of the organic peroxide. Expressed as a percentage. The active oxygen amount (C) is defined as the product of the value and the compounding amount (P) of the organic peroxide with respect to 100 parts by weight of the diene rubber. That is, Aw = (16 N / W) × 100 C = Aw × P.

The tackifier used in the rubber composition of the present invention may be a coumarone / indene resin, a terpene resin, a rosin derivative, a phenol / formaldehyde resin, an alkylphenol resin, a petroleum resin, or a xylene / formaldehyde resin. And oligomers such as polybutene, and liquid rubber such as liquid polyisoprene. Particularly, coumarone-indene resin, terpene resin, alkylphenol resin and rosin derivative are preferable.

The terpene resin is a polymer of a terpene monomer and a polymer containing the second component in a polymer chain. In addition to the terpene resin represented by the formula (1), a styrene terpene resin, Phenol-modified terpene resins and hydrogenated terpene resins obtained by hydrogenating these resins are also included.

[0016]

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In the expression (1), m represents an integer. When such a tackifier is exemplified by a trade name, a process resin A8 of Kobe Oil Chemical Co., Ltd. is used as a coumarone resin.
1. Process resin AC5, process resin TX, Okuma Shinko Co., Ltd. Coumalon CL, Nippon Steel Chemical Co., Ltd. Coumarone resin NG4. Also, as a terpene / phenol resin, Tackroll 101, Tackroll 160, Tackroll EP20, Tackroll EP of Sumitomo Chemical Co., Ltd.
30, Sumitomo Durez Sumilite Resin PR19
There are 900.

As petroleum-based resins, hydrogenated terpene resin Clearon P105 of Yashara Chemical Co., Ltd., Alcon P90 and Ester Gum H of Arakawa Hayashi Sansui Co., Ltd., Petrozine # 80 of Mitsui Petrochemical Co., Ltd., Heylets G100X
There is.

Further, as rosin derivatives, Nikanol A70 of Mitsubishi Gas Chemical Co., Ltd.
And rosin ester resin of Arakawa Chemical Co., Ltd.

The compounding amount of the tackifier is 2 to 5 parts by weight based on 100 parts by weight of the rubber component. The tackifier compensates for a decrease in loss tangent (tan δ) due to peroxide crosslinking, that is, a decrease in grip properties. When the amount is less than 2 parts by weight, improvement in grip properties cannot be expected. On the other hand, when the amount exceeds 5 parts by weight, internal heat generation during tire running becomes large, leading to a decrease in grip performance and a decrease in steering stability.

Further, the rubber composition of the present invention contains a reinforcing agent.
It is desirable to mix carbon black. Mosquito
The carbon black has a nitrogen adsorption specific surface area of 60 to 25.
0m ^Two/ G, DBP oil absorption of 70-150ml / g
Are preferred. Nitrogen adsorption specific surface area is 60m^Two/ G
If the DBP oil absorption is less than 70 ml / g, the abrasion resistance
Inferior, nitrogen adsorption specific surface area is 250m^Two/ G
Dispersion of carbon black in the rubber composition becomes worse. Also
When DBP oil absorption exceeds 150ml / g, viscosity increases.
Therefore, the processability tends to deteriorate.

The rubber composition of the present invention may further contain, if necessary, a softener, an antioxidant and the like. The rubber composition for a tire of the present invention can be used for various parts of a tire, and is particularly preferably used for a tread for a tire.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments.

A rubber composition having the compounding composition shown in Table 1 was prepared, and a passenger car tire having a tire size of TL195 / 55R15 was manufactured. The contents of the composition shown in Table 1 are as follows.

[0025]

[Table 1]

Note 1) SBR: solution-polymerized styrene-butadiene rubber having a styrene content of 35% by weight.

Note 2) Aroma oil: Aromax No
5 (Fujikosan Co., Ltd.) Note 3) Tackifier: Rosin ester resin (Harima Kasei Co., Ltd.) Note 4) Vulcanization accelerator: Accelerator CZ (Sanshin Chemical Industry Co., Ltd.) Note 5) Organic resin Oxide: α, α'-bis (tert-butylperoxy) diisopropylbenzene (Nippon Oil & Fats Co., Ltd.) Note 6) The active oxygen content is calculated by adding a coefficient of 0 to the amount of organic peroxide.
0386 can be obtained.

The physical properties of the vulcanized rubber composition and the tire were evaluated by the following methods. (1) Viscoelastic properties (tan δ) A test piece of a vulcanized rubber composition was prepared, and an initial strain of 10%, a dynamic strain of 2%, and a frequency of 10H were measured with an Iwamoto-type viscoelastic spectrometer.
The loss tangent (tan δ) was measured at z and a temperature of 70 ° C. The value of Comparative Example 1 was set to 100 and indicated by an index. The larger the value, the better the grip.

(2) Grip Property (Evaluation of Actual Car Driving) The tire was mounted on a passenger car, and continuous running was performed on a circuit. Average lap time of 5 to 10 laps / 1 lap and 2
The average lap time / one lap of 0 to 30 laps was measured, and the difference between the lap times was determined. The smaller the difference between the lap times, the less the grip performance is reduced by the running distance.

From Table 1, it can be seen that Examples of the present invention have a larger loss tangent (tan δ) than Comparative Example 1 containing no tackifier, and no reduction in grip properties is observed. Further, it is clear that the initial gripping property is most excellent when the tackifier is in the range of 2 to 4 parts by weight, and the reduction in gripping property is small.

The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[0032]

As described above, in the present invention, the sulfur vulcanization system and the organic peroxide vulcanization system are used in combination, and a predetermined amount of tackifier is blended, so that the grip performance with traveling distance is maintained while maintaining the initial grip performance. Can be reduced.

Claims (2)

[Claims] 1. Sulfur 0.2 to 3.0 parts by weight, organic peroxide active oxygen content of 0.02 to 0.20 parts by weight and tackifier 2 parts by weight per 100 parts by weight of diene rubber. A rubber composition for a tire, wherein the rubber composition comprises from 5 to 5 parts by weight. 2. A tackifier comprising a coumarone-indene resin,
The rubber composition for a tire according to claim 1, which is a terpene resin, an alkylphenol resin, and a rosin derivative.