KR100722206B1 - Rubber composition for tire tread - Google Patents

Abstract

The present invention relates to a rubber tread rubber composition, using 50 to 80 parts by weight of epoxidized styrene butadiene rubber and 20 to 50 parts by weight of butadiene rubber as a raw material rubber to reduce the wear performance and cold resistance performance There is an effect to improve the rotational resistance and electrical conductivity without making.

Rolling resistance * conductivity * tread * rubber

Description

Tire composition for tire tread

The present invention relates to a tread rubber composition, and more particularly, by using epoxidized styrene butadiene rubber and butadiene rubber in which an epoxy group is introduced into an unsaturated group of styrene butadiene rubber as raw material rubber, rotation resistance and electrical resistance are not reduced. A tread rubber composition for improving conductivity.

The performance required for a tire generally varies greatly depending on the intended use and site, and particularly, the tread rubber composition in contact with the road surface requires characteristics such as wear resistance, braking force, and rolling resistance.

Abrasion resistance is economically related to tire durability, braking power is closely related to safety, and rolling resistance is a major concern for consumers due to its fuel economy and environmental impact.

Conventionally, in order to improve rotational resistance, a mixture of butadiene rubber and terminally modified styrene-butadiene polymer is used as a raw material rubber to lower the hysteresis of the compounded rubber, thereby lowering the rotational resistance. It also has a disadvantage of low workability. In addition, the wear resistance is reduced when using the reinforcing filler silica used to lower the rolling resistance, there was a problem that must include a separate structure or additives for the electrostatic performance basically required for the tire tread.

In order to solve this problem, in the present invention, by using styrene butadiene rubber containing epoxy as well as butadiene rubber as raw material rubber, at the same time lowering the rotational resistance and increasing the bonding strength with silica as a reinforcing filler to improve wear resistance and static electricity. It is an object to provide a tread rubber composition to prevent.

Tire tread rubber composition of the present invention for achieving the above object is characterized in that the raw material made of 50 to 80% by weight of epoxidized styrene butadiene rubber and 20 to 50% by weight of butadiene rubber as the epoxidation rate of 30 to 50 mol%. .

Hereinafter, the present invention will be described in more detail.

The raw material rubber of the present invention is composed of two kinds of epoxidized styrene butadiene rubber and butadiene rubber.

Epoxidized styrene butadiene rubber (ESBR) is an epoxy group introduced into styrene butadiene rubber, and an epoxy group is added to the main chain of styrene butadiene rubber.

The glass transition temperature (Tg) increases by about 0.8 ° C / mol% depending on the epoxidation rate (%) in the ESBR. When the epoxy group is used less than 30 mol%, the increase in the glass transition temperature is low, so the braking performance is less improved. When the epoxy group is used more than 50 mol%, the glass transition temperature is too high.

In addition, when using less than 50% by weight of ESBR, the effect of the rotational resistance is not great, the use of more than 80% by weight is a problem of deterioration of rubber tensile properties.

Therefore, the ESBR of the present invention is 30 to 50 mol% epoxidation rate and 50 to 80% by weight of the total raw rubber.

ESBR used in the present invention is characterized by a number average molecular weight of 100,000 to 250,000, molecular weight distribution of 1.2 to 2.0.

The reinforcing filler of the present invention uses silica alone, and a silica coupling agent is used to improve the dispersibility of the silica. The filler serves to have low heat generation and high hardness characteristics using silica, and is used in an amount of 10 to 100 parts by weight based on 100 parts by weight of the raw material rubber.

In addition, the silica coupling agent is not easy to bond with the rubber due to the nature of the silica is used to enable the bond with the rubber powder. Although the specific compound of a silica coupling agent is not limited, TESPT (bis (3-triethoxy silyl propyl tetrasulfane, Degussa), MPTES (Mercaptopropyl triethoxy silane), etc. can be used. It is preferable that a silica coupling agent is included in 5-30 weight part with respect to 100 weight part of raw material rubbers.

In addition to the above-mentioned composition, the present invention can of course be used to select various additives such as active agents, anti-aging agents, processing oils, vulcanizing agents and vulcanization accelerators used in conventional tire tread compositions.

Although the present invention will be described in more detail with reference to the following examples, the following examples are merely illustrative of the present invention and the present invention is not limited by the following examples.

<Examples and Comparative Examples>

Next, a tire rubber composition was prepared according to Examples and Comparative Examples using the composition shown in Table 1. The manufacture of the tire rubber composition was in accordance with a conventional tire production method, and is not particularly limited.

Table 1

Item (parts by weight) Comparative Example 1 Comparative Example 2 Comparative Example 3 Example 1 Butadiene rubber 30 30 30 30 Terminally Modified Styrene Butadiene Rubber 70 - - - ESBR-A ⁽¹⁾ - 70 - - ESBR-B ⁽²⁾ - - 70 - ESBR-C ⁽³⁾ - - - 70 Silica (parts by weight) 70 70 70 70 Silica Coupling Agent (parts by weight) 8 8 8 8

Specific contents of the raw material rubber and silica used in Table 1 are as follows.

⁽¹⁾ ESBR-A : Epoxidized styrene butadiene rubber with 10 mol% epoxidation rate, number average molecular weight 100,000-250,000, molecular weight distribution 1.2-2.0

⁽²⁾ ESBR-B : Epoxidized styrene butadiene rubber with 60 mol% epoxidation rate, number average molecular weight 100,000-250,000, molecular weight distribution 1.2-2.0

⁽³⁾ ESBR-C : Epoxidized styrene butadiene rubber with 40 mol% epoxidation rate, number average molecular weight 100,000-250,000, molecular weight distribution 1.2-2.0

Experimental Example

The rubber composition blended according to the above Examples and Comparative Examples was subjected to physical property tests with vulcanized rubber which was vulcanized at 150 ° C. for 30 minutes, and the results are shown in Table 2 below.

Tensile properties were measured by ASTM D638 test with a conventional Intron machine.

-tan δ was evaluated using DMTS, temperature sweep was performed. The test conditions were tension and torsion type under 0.5% strain and 10Hz.

Abrasion resistance was measured by a slip ratio of 15% and 25% with a Lambourn wear tester.

Electrical conductivity was measured by ASTM D257.

Cold resistance was cooled by using dry ice to evaluate the low temperature fracture test.

Table 2

    * The higher the number, the better the wear resistance, electrical conductivity, and cold resistance performance.

As can be seen from the results in Table 2, the physical properties are largely changed according to the epoxidation rate of molten ESBR, which is attributable to the result of changing the glass transition temperature due to the difference in the mutual pullover in the rubber molecules. When using less than 30mol% epoxidation rate as in Comparative Example 2 has a disadvantage of low rotational resistance, when using an excessively high epoxidation rate as in Comparative Example 3, the electrical conductivity and rotational resistance is good, but the glass transition temperature is too high, which is disadvantageous to cold resistance performance.

It can be seen that the rubber of the example prepared by the tread rubber composition of the present invention has improved rotational resistance and electrical conductivity without degrading abrasion performance and cold resistance performance compared to the rubber specimen of the comparative example.

The tread rubber composition according to the present invention has an effect of improving rotational resistance and electrical conductivity without lowering abrasion performance and cold resistance performance compared to conventional terminal modified SBR with low hysteresis. This property is advantageous for heat generation upon repeated fatigue under high load conditions, and has an antistatic effect in the formulation using silica as a filler.

Claims (2)

In the rubber composition for tire tread, The raw material rubber is a tire tread rubber composition composed of 50 to 80 parts by weight of epoxidized styrene butadiene rubber having an epoxidation rate of 30 to 50 mol% and 20 to 50 parts by weight of butadiene rubber. The method of claim 1, The epoxidized styrene butadiene rubber has a number average molecular weight of 100,000 to 250,000, molecular weight distribution of 1.2 to 2.0, the rubber composition for tire treads.