KR20030030592A - Tread Rubber composition improved wet traction - Google Patents

Abstract

PURPOSE: Provided is a tread rubber composition which uses, as raw rubber, a mixture of liquid butadiene rubber having carboxyl group and natural rubber and improves a braking capability of tire. CONSTITUTION: The tread rubber composition uses a mixture of 70-98 phr of epoxidized natural rubber(ENR) and 2-30 phr of carboxyl terminated reactive liquid polybutadiene(CT-RLP) as a raw rubber. The content of epoxy group of the epoxidized natural rubber(ENR) is 10-60 mol%. The number of carboxyl group of carboxyl terminated reactive liquid polybutadiene is 3-10. The tread rubber composition can retain an anti-wear at least equivalent to existing tread rubber composition.

Description

Tread Rubber composition improved wet traction

The present invention relates to a tread rubber composition with improved braking properties. More specifically, in a known tread rubber composition, 70 to 98 phr of epoxidized natural rubber (ENR) in which an epoxy group is introduced into an unsaturated group of a natural rubber, and a carboxyl group are introduced. It is characterized by using a mixture of carboxylated liquid butadiene rubber (CT-RLP) 2 to 30 phr as raw material rubber.

The required performance of automobile tires varies greatly depending on the use and parts of the tire. In particular, the tread rubber that is in direct contact with the road surface has many demanding characteristics such as wear resistance, braking force on a wet road surface, and crack resistance.

Among these required characteristics, abrasion resistance is directly related to tire durability, and the economical relationship of tire use is large, and thus the consumer's required characteristic is large, and the braking performance of tires related to safety is closely related to vehicle braking. One of the required characteristics.

Conventionally, in order to improve the braking property of the tread rubber, a mixture of natural rubber and styrene-butadiene emulsion (E-SBR) is used as the raw material rubber to improve the braking property, but the styrene-butadiene emulsion is less elastic than the natural rubber. When repeated loads are applied, the heat generation is large and may be used for the tire tread rubber, which may cause separation of the tread and the belt part while driving, and also has the disadvantage of reducing the wear resistance.

Recently, in order to solve the problems described above, carbon black, which is a reinforcing filler, is used to improve braking property on wet roads and improve wear resistance by using epoxidized natural rubber containing epoxy instead of general natural rubber. In order to solve the disadvantage that the extrusion process is poor due to the increase in the viscosity of the carbon black, the use of low-viscosity liquid isoprene rubber is used to improve the processability, but the physical properties of the rubber compound are deteriorated. There is.

The present invention is a conventional tread rubber composition when using a mixture of epoxidized natural rubber and a liquid butadiene rubber incorporating a carboxyl group to improve the processability and physical properties to improve the braking properties while trying to solve the problems as described above In comparison, it has been found that they have more than equivalent physical properties and can improve braking properties.

Accordingly, an object of the present invention is to provide a tread rubber composition which improves braking property by using a mixture of epoxidized natural rubber and liquid butadiene rubber having a carboxyl group as a raw material rubber.

The tread rubber composition of which the braking property of the present invention is improved is 70-98 phr of epoxidized natural rubber (ENR) in which an epoxy group is introduced into an unsaturated group of natural rubber, and a carboxyl group having a carboxyl group. Carboxyl terminated reactive liquid polybutadiene (CT-RLP) is characterized in that a mixture of 2 to 30 phr is used as a raw material rubber.

The epoxidized natural rubber is characterized in that the glass transition temperature (Tg) is increased by adding an epoxy group to the main chain of the natural rubber. In the present invention, the epoxy group content of the epoxidized natural rubber is 10 to 60 mol%, but when the epoxy group is used below 10 mol%, the glass transition temperature is lowered and the braking performance is insignificant. It has a disadvantage in that the cold resistance performance is lowered and the physical properties are also lowered, so the epoxy group content of the epoxidized natural rubber is preferably maintained at 10 to 60 mol%.

In addition, if the epoxidized natural rubber is less than 70 phr, the braking performance is reduced. If it is more than 98 phr, the braking performance is improved, but the physical properties of the rubber compound are deteriorated. It is recommended to keep 70-98 phr.

In order to improve the abrasion resistance of epoxidized natural rubber, carbon black, a reinforcing filler, is used a lot, but there is a problem that the processability decreases due to the increase in viscosity. Therefore, liquid isoprene (LIR) is used to improve the processability. But there is a problem that the physical properties fall. In the present invention, while making various efforts to solve the disadvantages of the liquid isoprene rubber, when the liquid carboxylated butadiene rubber in which the carboxyl group (-COOH) is introduced is mixed with the epoxidized natural rubber and used as the raw material rubber, the carboxyl group is improved. It was found that the elasticity is increased and the physical properties are improved by the reaction of the epoxy group.

In the present invention, when the carboxylated liquid butadiene rubber in the raw material rubber is less than 2 phr, there is a problem that the physical properties are deteriorated. Keep 70 phr.

In addition, the carboxyl group content of the carboxylated liquid butadiene rubber has a functional group number of 3 to 10. If the number of carboxyl groups is less than 3, there is a problem in that the braking performance of the present invention is reduced. There is a problem that the carboxyl group content of the carboxylated liquid butadiene rubber in the raw material rubber is maintained at 3 to 10.

Hereinafter, the present invention will be described by the following comparative examples, examples and test examples. However, these do not limit the scope of the present invention.

Comparative Example

100 phr of natural rubber is used as a raw material, and 60 phr of carbon black which is a commonly used tire additive, 5 phr of galvanized, 2 phr of stearic acid, 2 phr of antioxidant, 3 phr of process oil, 2 phr of sulfur and 1 phr of accelerator After vulcanization at a temperature of 155 ℃ for 30 minutes to release to prepare a rubber specimen. Table 1 below shows the mixing ratio of the rubber composition.

<Example 1>

100 phr of epoxidized natural rubber (ENR) having an epoxy group content of 25 mol% is used as a raw material, 60 phr of carbon black which is a commonly used tire additive, 5 phr of zinc, 5 phr of stearic acid, 2 phr of an antioxidant, process oil 3 phr, sulfur 2 phr, and accelerator 1 phr were mixed and vulcanized at a temperature of 155 ° C. for 30 minutes before release to prepare a rubber specimen. Table 1 below shows the mixing ratio of the rubber composition.

<Example 2>

Rubber was prepared using the same blending ratio and method as in Example 1, except that a mixture of 90 phr of epoxidized natural rubber (ENR) and 10 phr of liquid isoprene rubber (LIR) having an epoxy group content of 25 mol% was used. Specimen was prepared.

<Example 3>

The above procedure was carried out except that a mixture of 90 phr of epoxidized natural rubber (ENR) having an epoxy group content of 25 mol% and 10 phr of a liquid carboxylated butadiene rubber (CT-RLP) in which a carboxyl group was introduced was used. Rubber specimens were prepared using the same mixing ratio and method as in Example 1.

Table 1. Mixing ratio of rubber composition of Comparative Example and Example (unit: phr)

Item Comparative example Example 1 Example 2 Example 3 Raw material rubber Natural rubber 100 - - - ENR - 100 90 90 LIR - - 10 - CT-RLP - - - 10 Carbon black 60 60 60 60 Zincification 5 5 5 5 Stearic acid 2 2 2 2 Anti-aging One One One One Process oil 3 3 3 3 sulfur 2 2 2 2 accelerant One One One One

<Test Example>

The rubber, rubber, and abrasion resistance of the rubber specimens prepared from Comparative Examples and Examples were measured by a standard method, and the results are shown in Table 2 below.

Table 2. Measurement results of the rubber specimens of Comparative Examples and Examples

Item Comparative example Example 1 Example 2 Example 3 Viscosity 100 93 112 110 Braking performance 100 140 138 145 Wear resistance 100 90 80 99

At this time, the numerical value of each Example is a value converted on the basis of the comparative example 100 means that the higher the value.

As shown in Table 2, the tread rubber composition using the epoxidized natural rubber and carboxylated butadiene rubber of the present invention as the raw material rubber is a conventional tread rubber composition using only natural rubber or a mixture of natural rubber and liquid isoprene rubber as the raw material rubber. In comparison, abrasion resistance can be maintained at an equivalent level or higher, and the braking performance related to safety can be improved to improve braking performance even on wet roads.

Claims (3)

In a known tread rubber composition, a tread rubber composition using a mixture of 70 to 98 phr of epoxidized natural rubber (ENR) and 2 to 30 phr of carboxylated liquid butadiene rubber (CT-RLP) as a raw material rubber The tread rubber composition according to claim 1, wherein the epoxy group content of the epoxidized natural rubber is 10 to 60 mol%. The tread rubber composition according to claim 1, wherein the carboxyl group content of the carboxylated liquid butadiene rubber is 3 to 10 functional groups.