JPH05247267A - Rubber composition - Google Patents

Abstract

PURPOSE:To provide a new rubber composition improved in the prevention of wet skid and heat buildup. CONSTITUTION:The title composition comprises 10-90wt.% random styrene/ butadiene copolymer rubber having a combined styrene content of 3.0-30wt.% and a content of 1, 2 bonds in the butadiene part of 60-95% and is prepared by polymerization in the presence of an organoalkali metal catalyst and 90-10wt.% butadiene rubber of a glass transition temperature of -40 deg.C or below. This composition can give a vulcanizate having excellent wet skid resistance and low heat buildup, and can be desirably used for tires as well as tread rubbers.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel rubber composition, particularly to a rubber composition suitable for a tire tread.

[0002]

2. Description of the Related Art As the performance of rubber for automobile tire treads, wet skid characteristics related to running stability, heat generation characteristics, durability, etc. are good, and rolling frictional resistance related to fuel consumption is small. It became important.

Conventionally, there is no single rubber to satisfy these various characteristics, and a blend composition of different kinds of rubber has been used in order to balance various characteristics. For example, as a tread rubber for passenger cars, a composition comprising styrene-butadiene copolymer rubber / polybutadiene rubber has been widely used. However, these compositions are not always sufficient in terms of wet skid characteristics, and their improvement has been desired. Conventionally, it has been known that a resin having a high glass transition temperature is used as a means for improving the wet skid characteristics, but there is a problem that the dynamic characteristics, particularly the heat generation characteristics are remarkably reduced. Was difficult.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a novel rubber composition having improved wet skid characteristics and heat generation characteristics.

[0005]

SUMMARY OF THE INVENTION Random styrene butadiene copolymers polymerized in accordance with the present invention under an organoalkali metal catalyst with 3 to 30% by weight bound styrene and 60% to 95% 1,2 bonds in the butadiene moiety. Rubber 10
There is provided a rubber composition comprising from 90% to 90% by weight and from 90% to 10% by weight of a polybutadiene rubber having a glass transition temperature of -40 ° C or lower.

The random styrene-butadiene copolymer rubber of the present invention is prepared by IM Kolthoff et al. J. Polymer Sci. Vol. 1 p429 (1
946) and the like, means a styrene-butadiene copolymer rubber in which the bound styrene content in the bound styrene is 10% by weight or less.

The rubber composition according to the present invention has substantially the same exothermic property as compared with the conventional tire tread rubber composition, but is significantly improved in the wet skid property. Further, as compared with a rubber composition having the same wet skid characteristics by adding a polymer having a high glass transition temperature such as resin or high styrene rubber, the heat generation property is remarkably improved. It is also excellent in compatibility and workability between blended rubbers. These features of the present invention are characterized in that the bound styrene is 3 to 30% by weight, preferably 5 to 20% by weight, and the 1,2 bond of the butadiene portion is 60 to 95%, preferably 70 to 95%, more preferably 80 to 95%. Mooney viscosity polymerized with alkali metal catalyst (ML _{1 + 4} 100 ℃) 20
This is accomplished by using ~ 150 random styrene butadiene copolymer rubbers as part of the rubber component.

3% by weight of bound styrene of the copolymer rubber
If it is less, the tensile strength will be low, while if it is more than 30% by weight, the heat generation characteristics will be deteriorated. In addition, 1, of the butadiene part
If the two-bond is less than 60%, the wet skid property is deteriorated. If the Mooney viscosity is less than 20, it is not preferable in terms of tensile strength and heat generation characteristics, and if the Mooney viscosity exceeds 150, it is not preferable in terms of workability.

The organic alkali metal catalyst used in the present invention is an organic compound of an alkali metal such as Li, Na and K, and an organic lithium compound is preferably used. The random styrene-butadiene copolymer rubber polymerized with the organolithium compound catalyst is, for example, JP-B-36-15386, JP-B-48-4.
As described in 1038, it is obtained by polymerizing a styrene or butadiene monomer in a hydrocarbon solvent with an organolithium compound as an initiator in the presence of an additive such as an ether or a tertiary amine.

Further, the styrene-butadiene copolymer rubber which is the object of the present invention can be obtained, for example, by the method described in JP-A-52-101287.

In the composition of the present invention, the random styrene butadiene copolymer rubber is used in a proportion of 10 to 90% by weight, preferably 20 to 80% by weight, and the proportion is less than 10% by weight. Wet skid characteristics are not improved, and when it is more than 90% by weight, breaking characteristics are deteriorated, which is not preferable.

The rubber compounded with the above-mentioned random styrene-butadiene copolymer rubber is a polybutadiene rubber having a glass transition temperature of -40 ° C or lower, preferably -50 ° C or lower and having a high cis 1, polymerized by a Ziegler type catalyst. 4 polybutadiene, low-cis polybutadiene polymerized with an organolithium catalyst, etc. are used. By using a rubber having Tg of −40 ° C. or less, a rubber composition having excellent wear resistance and durability can be obtained. On the other hand, if a rubber having a high Tg is combined, the wet skid resistance is improved, but the heat generation temperature becomes high, which is not preferable. This rubber is used in the composition in a proportion of 10% to 90% by weight.

The rubber composition of the present invention is used by blending process oil, carbon black, other filler, antioxidant, antiozonant, zinc white, stearic acid, vulcanization accelerator, vulcanizing agent and the like. ..

[0014]

The present invention will be described below with reference to examples, but the scope of the present invention is not limited by the examples.

Example 1 Styrene as a monomer in 8 liters of cyclohexane,
1,3-Butadiene was charged, and potassium dodecylbenzene sulfonate and diethylene glycol dimethyl ether were used as a randomizing agent and a 1,2 bond amount controlling agent for the butadiene portion, and n-butyllithium was used as a polymerization initiator for polymerization. Polymer is polymer 1 in polymer solution
After adding 1.0 part by weight of 2,6-ditert-butyl p-cresol to 00 parts by weight, the solvent was removed by steam stripping, and the product was obtained by drying at 100 ° C. on a roll.

The polymerization conditions and the main properties of the polymer are shown in Table 1.

Of the rubbers listed in Table 1, styrene-butadiene copolymer rubbers (1) to (3) are specific random styrene-butadiene copolymer rubbers used in the present invention.

[0018]

[Table 1] Examples 2 to 4 and Comparative Examples 1 to 2 Using the random styrene-butadiene copolymer rubber (1) obtained in Example 1, vulcanization physical properties were evaluated by changing the compounding ratio with cis 1,4 polybutadiene. did. The compounding recipe and vulcanization conditions are shown in Table 2. The properties of the vulcanizates are shown in Table 3.

Examples 2 to 4 have a large wet skid resistance and are excellent in terms of modulus, tensile strength, tear strength and flex crack growth resistance, and are well balanced.

[0020]

[Table 2]

[0021]

[Table 3] Example 5, Comparative Examples 3-4 Styrene-butadiene copolymer rubbers obtained in Example 1
(1), styrene-butadiene copolymer rubber (3), styrene-butadiene copolymer rubber (4), polybutadiene rubber
Using (1), the vulcanization physical properties were evaluated with the rubber proportions shown in Table 4 and with the same compounding formulation as in Table 2.

The results are shown in Table 4.

[0023]

[Table 4]

[0024]

EFFECTS OF THE INVENTION The vulcanized product of the rubber composition of the present invention has excellent wet skid characteristics and has low heat build-up, and is therefore suitable for use in tires such as tread rubber.

Further, in addition to tire applications, it can be used as an industrial rubber which takes advantage of the characteristics of the rubber composition of the present invention, for example, an industrial belt having good heat resistance and traction.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsuhiko Sakakibara 1 Morikayama-cho, Yokkaichi-shi, Mie Prefecture

Claims (2)

[Claims] 1. A random styrene butadiene copolymer rubber polymerized under an organoalkali metal catalyst having (A) 3.0 to 30% by weight of bound styrene and 60 to 95% of 1,2 bonds in the butadiene moiety. % To 90% by weight, and (B) a butadiene rubber having a glass transition temperature of −40 ° C. or less 9
A rubber composition comprising 0% to 10% by weight. 2. The composition according to claim 1, wherein the bonded styrene of the random styrene-butadiene copolymer rubber is 5 to 20% by weight, and the 1,2 bond of the butadiene portion is 70 to 95%.