KR100426006B1 - Silica reinforced rubber composition for tire tread - Google Patents

Abstract

The present invention relates to a rubber composition for tire treads, comprising 40 to 80 parts by weight of silica and 6 to 10% by weight of coupling agent based on 100 parts by weight of a diene rubber single component or a blend rubber thereof as a raw material rubber. And the raw rubber is chlorinated rubber. According to the invention, while the viscosity of the blend is reduced, the physical properties of the vulcanizate are improved, improving silica dispersion and improving the reaction between silica and rubber.

Description

Rubber composition for tire treads reinforced with silica {SILICA REINFORCED RUBBER COMPOSITION FOR TIRE TREAD}

The present invention relates to a rubber composition for tire treads, comprising 40 to 80 parts by weight of silica and 6 to 10% by weight of coupling agent based on 100 parts by weight of a diene rubber single component or a blend rubber thereof as a raw material rubber. And the raw rubber is chlorinated rubber.

In order to reduce the rolling resistance of the tire as part of the low fuel consumption of the conventional vehicle, technologies that use silica instead of carbon black, which occupies a large proportion in the tire tread rubber composition, have been continuously developed.

However, since silica is composed of polar silanol groups, silica is mainly used for tire treads such as acrylonitrile butadiene rubber (NBR), styrene butadiene rubber (SBR) or butadiene rubber (BR). There is a problem that the reaction with the polymer is weak. In addition, since the silanol groups are strongly bonded by hydrogen bonds, and are not easily dispersed in the blending process, there is a problem in that a stronger shear force or a blending process should be added.

To solve this problem, a silane coupling agent was developed, and its function was to bridge the silica surface with the polymer. However, the silane coupling agent is expensive, and there is a problem in that ethanol or the like is volatilized in the process, and also a problem in that a large amount of compounding time is required in order to sufficiently react the coupling agent with the silica.

In order to improve the inefficiency in the compounding process of the conventional silica rubber composition as described above, the rubber composition is reinforced with silica including a rubber obtained by chlorination of a diene rubber molecule, which is a nonpolar polymer, as a raw material rubber. To provide that purpose.

The silica-reinforced rubber composition of the present invention contains 40 to 80 parts by weight of silica and 6 to 10% by weight of coupling agent based on 100 parts by weight of a common diene rubber single component or a blend rubber thereof as a raw material rubber. The raw rubber is characterized in that the rubber is chlorinated.

The rubber component used in the present invention may include, for example, a single diene-based rubber single component such as acrylonitrile butadiene rubber (NBR), styrene butadiene rubber (SBR) or butadiene rubber (BR) or blends thereof.

In the present invention, the raw rubber component as described above is finely divided and pelletized, and then used by chlorination treatment in a chlorine solution. The treatment method in the chlorine solution may include, for example, a treatment method including the following steps.

(a) preparing a 1-20% chlorine solution using distilled water, NaOCl and HCl;

(b) leaving the raw rubber pelletized in the chlorine solution;

(c) removing the rubber from the chlorine solution and neutralizing it in 1-5% ammonia solution;

(d) removing the rubber from the ammonia solution, washing with distilled water, drying in vacuo and then leaving it at room temperature.

The concentration or content of distilled water, NaOCl, and HCl used to make the chlorine solution of 1 to 20% in the step (a) may be any one that can be mixed to form the chlorine solution. Preferably, 100 parts by weight of distilled water, 6 parts by weight of 5.25% NaOCl and 1 part by weight of 37% HCl are mixed to prepare a 3% chlorine solution. When the concentration of the chlorine solution is less than 1%, the concentration is so low that the chlorination of the raw material rubber is not good, and if the concentration of the chlorine solution exceeds 20%, the chlorination effect of the raw material rubber does not increase significantly compared to the concentration, it is economically desirable Not.

The time left for pelletization in step (b) may be appropriately adjusted according to the concentration of the chlorine solution used.

When the concentration of the ammonia solution used in the step (c) is less than 1%, the concentration is too low to take a long time to neutralize, if it exceeds 5%, the shortening of the neutralization time is not significant compared to the concentration. Not desirable

In addition, the silica used in the present invention is a precipitated silica having a specific surface area of 100 to 200 m ² / g measured using BET and a dibutyl phthalate (DBP) adsorption value of 150 to 300 ml / 100 g. It is preferable that it is 40-80 weight part with respect to a weight part.

Coupling agents used in the present invention, for example, a silane coupling agent such as tetraethoxysilyl propyl tetrasulfide (TESPT) may be used, the content of which is 6 to 10% by weight of the silica desirable. If the content is less than 6% by weight, the physical properties are deteriorated. If the content is more than 10%, no coupling effect occurs.

Hereinafter, the present invention will be described in detail through embodiments. However, these examples are for illustrative purposes only, and the present invention is not limited to these examples.

Example

To prepare a rubber composition according to a conventional method with the composition shown in Table 1, after preparing a specimen for measuring the physical properties and vulcanization was measured by physical properties according to the ASTM standard method, the results are shown in Table 2.

The raw rubbers used in Examples 1 and 2 below were pelleted rubbers that were chopped to increase the surface area and chlorinated by a chlorine solution treatment method comprising the following steps.

(a) preparing a 3% chlorine solution using 100 parts by weight of distilled water, 6 parts by weight of 5.25% NaOCl and 1 part by weight of 37% HCl;

(b) leaving the pelletized raw rubber in the chlorine solution for 10 minutes;

(c) removing the rubber from the chlorine solution and neutralizing in 2% ammonia solution for 1 minute;

(d) removing the rubber from the ammonia solution, washing in distilled water for about 30 seconds, drying in vacuum for 1 hour, and then leaving it at room temperature for 1 hour.

The rubbers thus treated were mixed alone or in a blend in an internal mixer, and the vulcanization of the specimens was heated at a hot press at the hot press with an optimum cure time using the rheometer results analyzed at 160 ° C. It was vulcanized at high pressure.

Comparative example

In this Comparative Example, 50 parts by weight of SMR60CV and 50 parts by weight of SBR-1502 which were not treated with a chlorine solution were used as raw materials rubber, and the silane coupling agent was mixed using 6.4% by weight based on the silica used to prepare a rubber composition. .

Example 1

In this example, 50 parts by weight of SMR60CV treated with chlorine solution and 50 parts by weight of SBR-1502 treated with chlorine solution were used as raw material rubber, except that the silane coupling agent used 4.8% by weight based on the silica used. Same as Example 1.

Example 2

This example is the same as Example 1 except that 50 parts by weight of SMR60CV treated with chlorine solution and 50 parts by weight of SBR-1502 treated with chlorine solution are used as the raw rubber.

Table 1. Rubber composition

Composition (part by weight) Comparative example Example 1 Example 2 SMR 60CV 50 (not treated with chlorine solution) 50 (treated with chlorine solution) 50 (treated with chlorine solution) SBR-1502 50 (not treated with chlorine solution) 50 (treated with chlorine solution) 50 (treated with chlorine solution) Silica 80 80 80 TESPT * 6.4 4.8 6.4 Zinc (ZNO-S) 3 3 3 Stearic acid 2 2 2 sulfur 1.5 1.5 1.5 CZ ** 1.5 1.5 1.5 DPG *** 1.5 1.5 1.5

* TESPT: Tetraethoxysilyl propyl tetrasulfide (silane coupling agent)

** CZ: cyclohexyl benzothiazol sulfenamide (primary accelerator)

*** DPG: Diphenyl guanidine (secondary promoter)

Table 2. Properties of Rubber Composition

Properties Comparative example Example 1 Example 2 1. Mooney test @ 125 ℃ viscosity Scoring time T5 (minutes) Leotest @ 160 ℃ T40 (minutes) T90 (minutes) MAXE.C 89631014.23815.6 836010.115.73817.3 78557.511.34112.5 2. Tensile strength 300% Modulus (kg / cm ² ) Tensile strength (kg / cm ² ) EB (%) 6689220580 66100250600 68110250560 3. Dynamic Test Glass Transition Temperature (Tg) (℃) TAN δ0 ℃ TAN δ70 ℃ -290.2330.102 -320,2210,091 -320.2230.085 4. Wear characteristics pico loss (g) 0.031 0.028 0.025

As shown in Table 2, the rubber composition of the present invention improved the dispersibility of the rubber and silica, while maintaining a low viscosity compared to the rubber composition of the comparative example, the other physical properties showed the same level or more improved results.

According to the present invention, the diene rubber, which is a nonpolar polymer, is chlorinated to introduce polarity to the surface, thereby enhancing affinity with silica, increasing the polymer-silica reaction, and reducing the amount of the silane coupling agent to reduce costs. Silica-reinforced rubber compositions can be obtained that can improve environmental problems, reduce energy required for the process, and simplify the blending process steps.

In addition, the physical properties of the vulcanizate is improved while the viscosity of the blend is reduced, thereby obtaining a silica-reinforced rubber composition having improved silica dispersion and improved reaction between silica and rubber.

Claims (3)

Silica-reinforced rubber composition comprising 40 to 80 parts by weight of silica and 6 to 10% by weight of coupling agent based on 100 parts by weight of chlorinated diene rubber single component or 100 parts by weight of blended rubber thereof. . 2. The silica reinforced rubber composition according to claim 1, wherein the chlorinated rubber is prepared by a process comprising the following steps: (a) preparing a 1-20% chlorine solution using distilled water, NaOCl and HCl; (b) leaving the raw rubber pelletized in the chlorine solution; (c) removing the rubber from the chlorine solution and neutralizing it in 1-5% ammonia solution; (d) removing the rubber from the ammonia solution, washing with distilled water, drying in vacuo and then leaving it at room temperature. The silica-reinforced rubber composition according to claim 1, wherein the silica is a precipitated silica having a specific surface area measured by BET of 100 to 200 m ² / g and a dibutyl phthalate (DBP) adsorption value of 150 to 300 ml / 100 g. .