KR20020037595A - Tire tread rubber composition - Google Patents

Abstract

PURPOSE: A rubber composition for a tire tread is provided, to improve the strength and abrasion resistance of rubber and the productivity by using fatty acid metal salt derivatives for lowering the polarity of the silica surface. CONSTITUTION: The rubber composition comprises 100 parts by weight of rubber; 0.1-10 parts by weight of a mixture of two or more kinds of fatty acid metal salt derivatives represented by the formula 1; silica; and a silane coupling agent. In the formula 1, R is an alkyl group of C13-C22; and M is Zn, Ca, Na or K.

Description

Tire tread rubber composition

The present invention relates to a tire tread rubber composition, and more particularly, to a tire tread rubber composition in which silica is used as a filler and a fatty acid metal salt derivative is added to a conventional rubber containing a silane coupling agent to improve dispersibility. .

Compound rubbers used in the tire industry consist of a mixture of materials with different physical properties.

The basic condition that determines the success or failure of compound rubber design in tire products is how well the basic intention of the compound designer is reflected in the performance of the product.

In practice, however, there are many cases where there is a substantial difference between the rationale, experimental values, rubber properties and product performance. This is because each component in the compounding rubber, for example, raw rubber, filler, vulcanizing agent, anti-aging agent, etc., does not meet the designer's intention during processing. That is, the components having different shapes and physical properties are not ideally mixed and do not be sufficiently dispersed in the compounding rubber due to their independent behavior. In particular, rubber and fillers such as carbon black, silica, etc. are often difficult to mix due to the different polarity of the surface.

On the other hand, in recent years, with regard to preventing pollution, countries are increasing interest in low-fuel tires due to tightening regulations on emissions of automobiles, and many technologies for applying silica, a new concept filler, have been announced. Unlike carbon black, silica is distributed evenly with polar groups, so it does not mix well with rubber and has a strong tendency to agglomerate with each other. Therefore, a silane-coupling agent is used to increase even dispersion and rubber interaction in the rubber. However, the application of such silane-coupling agents requires several mixing processes, and it is quite difficult to obtain a satisfactory dispersion. As mentioned above, rubber with poor dispersion does not achieve the rubber properties intended by the compounding designer, and thus, tire performance cannot be improved.

Thus, the present inventors have been trying to solve the problem of dispersion, which is difficult to solve only by the coupling agent in the rubber composition in which silica is added as a filler, and as a result of adding the fatty acid-metal salt derivative, the dispersibility of the filler in the rubber is improved Simultaneously, it was found that the processing efficiency can be increased during the mixing and extruding of the compound rubber, thereby completing the present invention.

Accordingly, an object of the present invention is to add a fatty acid-metal salt derivative to silica compounding rubber to improve dispersibility of fillers in rubber, and to increase processing efficiency during mixing and extruding compounding rubber to improve tire performance and energy of production process. The present invention provides a rubber composition for tire treads to reduce consumption.

The rubber composition for tire treads of the present invention for achieving the above object is made by adding silica and a silane coupling agent to the raw material rubber, wherein a mixture of two or more fatty acid-metal salt derivatives represented by the following Formula 1 is 0.1 to 10 It is characterized by that it is made so as to be added by weight.

Wherein R is an alkyl group having 13 to 22 carbon atoms,

M is Zn, Ca, Na or K.

The present invention will be described in more detail as follows.

The rubber composition for tire treads according to the present invention is identical and similar in composition to rubber for tire treads, and is particularly effective for rubber compositions containing silica as a filler and a silane coupling agent.

The rubber composition of the present invention includes a derivative of a fatty acid metal salt as represented by Formula 1, which can be obtained through the reaction of a fatty acid and a metal.

These fatty acid-metal salt derivatives react with the polar groups on the silica surface to lower the polarity of the silica surface, thereby reducing the properties of agglomeration between the silica and increasing the compatibility with the rubber.

In addition, since the fatty acid metal salt derivative acts as a kind of lubricant in the process of mixing in the rubber, the energy required when mixing can be significantly reduced. However, when the silane coupling agent is added together to increase the degree of interaction between rubber and silica, the silane coupling agent and the silica are competing with each other. Therefore, the mixture should be added after the silane coupling agent and the silica have completely reacted. It can be maximized.

By increasing the dispersibility of silica in this way, it is possible to improve the strength and abrasion performance of the rubber, etc., which can achieve a significant side effect.

The content of the fatty acid metal salt derivative represented by Chemical Formula 1, which plays such a role, is preferably 0.1 to 10 parts by weight based on 100 parts by weight of the raw material rubber.

If the amount is more than 10 parts by weight, a sliding phenomenon occurs in the mixing process, rather, the Mooney viscosity of the rubber is slightly higher and the dispersibility of the silica is also lowered.

In addition, the rubber composition of the present invention can be added to the softener, zinc oxide, stearic acid, antioxidant, sulfur, vulcanization accelerator and the like.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited by the Examples.

Examples 1-3 and Comparative Examples 1-3

Based on the mixing conditions as shown in Table 1, and compared in the Banbury mixer under the mixing conditions as shown in the mixing conditions and the energy input during the mixing process and the dispersion degree of silica after mixing, the physical properties of each of these rubber Shown in

(Unit: parts by weight) Example Comparative example One 2 3 One 2 3 s-SBR 70 70 70 70 70 70 BR 30 30 30 30 30 30 Silica 75 75 75 75 75 75 Coupling agent 7 7 7 - 10 - Fatty acid metal salts 3 5 10 - - 10 Softener 10 10 10 10 10 10 Zinc oxide 3 3 3 3 3 3 Stearic acid 2 2 2 2 2 2 Anti-aging 3 3 3 3 3 3 brimstone 2 2 2 2 2 2 accelerant One One One One One One DPG One One One One One One S-SBR: Solution-polymerized styrene-butadiene rubber (Nippon Zeon, NS116) BR: Butadiene rubber (Kumho Petrochemical, BR01), Silica: Zeosil 175 coupling agent: Si69, Softener: Aromatic oil DPG: Diphenylguanidine

(Mixed condition)

① Stage 1

Dosing compound: Rubber, 55 parts by weight of silica, 7 parts by weight of coupling agent, other compounding agents, fatty acid metal salt, if added, add the coupling agent.

Mixing condition: Mixing is maintained at below 150 ℃ for 3 minutes 40 seconds at 60rpm

②Step 2

Dosing compound; Mixing rubber of the first step, 20 parts by weight of silica, 3 parts by weight of coupling agent

Mixing condition: Mixing is maintained at below 150 ℃ for 3 minutes 40 seconds at 60rpm

③Step 3

Remilling

Mixing condition: Mixing at 60 rpm for 2 minutes and 30 seconds while maintaining the mixing temperature below 150 ℃

④ Final step

Input compounding agent: mixed rubber, sulfur, accelerator, DPG of the three steps

Open mill mixing: 10 minutes mixing time

Example Comparative example One 2 3 One 2 3 Stage 1 Energy input (index) 92 85 82 100 95 90 Mooney viscosity 145 141 140 165 152 156 Tier 2 Energy input (index) 91 85 82 100 93 93 Mooney viscosity 120 108 118 135 121 125 Tier 3 Energy input (index) 90 87 82 100 93 90 Mooney viscosity 92 82 105 118 92 92 Final steps Mooney viscosity (M _{1 + 4} ) 62 59 70 92 63 64 % Dispersion 96 99 94 45 88 84

In Table 2, the input energy is the power used in the Banbury mixer mixing process as Comparative Example 1 to 100 to represent the power consumption of each rubber in an index. In addition, the dispersion degree of silica is measured by counting the number of silica particles of a predetermined size or more in the same region by using a microscope and an image analyzer, the larger the value, the better the dispersibility.

From the results of Table 1, from Comparative Examples 1 and 2 it can be seen that the effect of the coupling agent, when using a combination of silica and the coupling agent is reduced energy input during mixing and significantly improve the dispersibility of the silica. . Therefore, in the case of general silica compound rubber, it is preferable to use a coupling agent together rather than to use silica alone.

However, compared to using only the coupling agent as in Comparative Example 1, the addition of fatty acid metal salt derivatives as shown in Example 1 can significantly reduce the energy input during rubber mixing, and also significantly improve the dispersibility of silica. .

On the other hand, when combining the results of Examples 1 to 3, when the fatty acid metal salt derivative is added, the energy input during rubber mixing decreases as the input amount increases, but when the input amount is excessive, slippage occurs in the mixing process. Rather, the pattern viscosity of the rubber is slightly higher, and silica dispersibility is slightly lower. Therefore, the usage-amount of a preferable fatty acid metal salt derivative is 1-7 weight part.

On the other hand, Comparative Example 4 is a case in which only a fatty acid metal salt derivative is used without using any coupling agent, compared to the case of using only the coupling agent of Comparative Example 2, the energy input during rubber mixing is almost similar, but the degree of processing of rubber can be compared. It was concluded that the Mooney viscosity reduction rate was less than that of Comparative Example 2, and the dispersibility of silica was less than that of using only the coupling agent, and when the fatty acid metal salt derivative was used alone, the performance was lower than that of the rubber using the coupling agent alone.

As described in detail above, when the fatty acid metal salt derivative is added to a rubber tread rubber composition comprising silica and a silane coupling agent according to the present invention, energy of mixing the silica compounding rubber can be reduced, and at the same time, By improving dispersibility, rubber strength, abrasion performance and fatigue resistance can be improved.

Claims (1)

In the rubber composition for tire treads made by adding silica and a silane coupling agent to 100 parts by weight of raw rubber, Rubber composition for a tire tread, characterized in that made by adding 0.1 to 10 parts by weight of a mixture of two or more fatty acid-metal salt derivatives represented by the following formula (1) with respect to 100 parts by weight of the raw rubber. Formula 1 Wherein R is an alkyl group having 13 to 22 carbon atoms, M is Zn, Ca, Na or K.