KR20090072845A - Rubber composition for tire undertread - Google Patents

Abstract

A rubber composition for tire undertread is provided to improve conductivity while not degrading tensile strength and modulus by comprising electroconductive carbon black. A rubber composition for tire undertread comprises 1-4 parts by weight of electroconductive carbon black based on the base rubber 100.0 parts by weight. The electroconductive carbon black has a I2 surface area of 500~900 mg/g and DBP adsorption value of 300~500 ml/100g. The base rubber is usable as a natural rubber, a synthetic rubber or a rubber mixture of natural rubber and synthetic rubber. The rubber composition comprises carbon black, softening agent, zinc oxide, stearic acid vulcanizate and vulcanization accelerator.

Description

Rubber composition for tire undertread

The present invention relates to a tire undertread rubber composition, and more particularly, to a tire tread rubber composition having improved electrical conductivity of a tire to effectively discharge static electricity generated from a vehicle to the ground.

In recent years, in the rubber composition for tire treads, the application rate of silica instead of carbon black is rapidly increasing as a reinforcing filler in consideration of stability and environmentally friendly aspects such as low fuel efficiency and traction on wet roads.

However, in the case of tires applied with silica, the low fuel efficiency and traction can be gradually improved on wet and ice roads.

That is, in the case of silica, unlike carbon black, in which electrons are movable in the plate-like structure, the electrons are not movable, and thus the conductivity of the silica is significantly decreased as the amount of silica is increased.

In order to solve such a problem of static electricity generation, conventionally, the carbon black is used alone or more than 100 parts by weight of the raw rubber in the tread rubber composition, or the conductive carbon black having an I ₂ surface area of 1000 mg / g or more is added. How to improve has been introduced.

However, in the former case, the price of the conductive carbon black is very high, which makes it difficult to solve the cost problem. In the latter case, when the conductive carbon black having a very large surface area is used, the tensile properties such as hardness and modulus are changed. Problems arise that are difficult to control.

On the other hand, there is also a method of improving the electrical conductivity of the tread rubber composition in the above manner or by structurally designing the under tread to contact the ground in the center portion to discharge static electricity to the ground through the ground, but the electrical conductivity of the under tread first It is necessary to improve.

The present invention was created to solve the above problems, more specifically I ₂ surface area of 500 ~ 900 mg / g and DBP adsorption value of 300 ~ 500 ml / 100g using the conductive carbon black tensile strength, It is to provide a rubber composition for tire under tread, which does not deteriorate various physical properties such as modulus and at the same time significantly improves electrical conductivity.

Other objects and advantages of the invention will be described below and will be appreciated by the embodiments of the invention. Furthermore, the objects and advantages of the present invention can be realized by means and combinations indicated in the claims.

The rubber composition for tire treads according to the present invention contains 1 to 4 parts by weight of electroconductive carbon black based on 100 parts by weight of the raw material rubber.

As the raw material rubber used in the present invention, any compound rubber made of synthetic rubber, a mixture of natural rubber and synthetic rubber can be used.

In addition, the rubber composition of the present invention may include a carbon black, a softener, zinc oxide, stearic acid, a vulcanizing agent and a vulcanization accelerator as a reinforcing agent in the raw rubber.

Hereinafter, the conductive carbon black will be described in detail.

The conductive carbon black used as an example of the present invention preferably has an I ₂ surface area of 500 to 900 mg / g and a DBP adsorption value of 300 to 500 ml / 100 g. If the I ₂ surface area is less than 500 mg / g, the distance between the particles is too long, and electricity is more than 900 mg / g.

In addition, if the DBP adsorption value is less than 300ml / 100g, the cohesion is weak, and if it exceeds 500ml / 100g, there is a problem of cost increase.

On the other hand, the amount of the electrically conductive carbon black used in the present invention is preferably 1 to 4 parts by weight. If the conductive carbon black of the conductive carbon black is less than 1 part by weight, the electrical conductivity is not improved. If the conductive carbon black is used in an amount greater than 4 parts by weight, the electrical conductivity and the reinforcement are improved, but the fatigue performance is lowered.

The terms or words used in this specification and claims are not to be construed as being limited to their ordinary or dictionary meanings, and the inventors may appropriately define the concept of terms in order to best describe their invention. It should be interpreted as meaning and concept corresponding to the technical idea of the present invention based on the principle that the present invention.

Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiment of the present invention and do not represent all of the technical idea of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

The rubber composition for tire treads according to the present invention as described above provides the following effects.

By incorporating the conductive carbon black into the rubber composition, an undertread rubber composition can be obtained in which the tensile strength and modulus are equivalent to or higher than those of the conventional undertread rubber composition, and the electrical conductivity is improved.

Hereinafter, the rubber composition for tire treads according to the present invention will be described in more detail with reference to Examples and Comparative Examples. It should be noted, however, that the present invention is not limited by this embodiment.

The rubber composition was prepared after mix | blending the composition as shown in following [Table 1] in the half-barrier mixer.

Furtherance Unit: parts by weight Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Example 1 Example 2 Example 3 Raw Material Rubber ⁽¹⁾ 100 100 100 100 100 100 100 Carbon Black ⁽²⁾ 55 54.5 50 50 54 53 51 Conductive Carbon Black ⁽³⁾ - 0.5 5 One 2 4 Conductive Carbon Black ⁽⁴⁾ 5 Process oil 8 8 8 8 8 8 8 Zinc oxide 3 3 3 3 3 3 3 Stearic acid One One One One One One One brimstone 2.8 2.8 2.8 2.8 2.8 2.8 2.8 Vulcanization accelerator One One One One One One One

Corporation

(1) Raw material rubber: styrene-butadiene rubber

(2) Carbon Black: GPF N660

(3) Conductive Carbon Black: I ₂ Surface Area 500 ~ 900mg / g

(4) Conductive carbon black: I ₂ surface area over 1000mg / g

Comparative Example 1

As with the compounding ratio disclosed in Table 1, 55 parts by weight of carbon black, 8 parts by weight of process oil, 3 parts by weight of zinc oxide, 1 part by weight of stearic acid, 2.8 parts by weight of sulfur, and 1 part by weight of vulcanization accelerator based on 100 parts by weight of the raw material rubber The rubber composition was prepared by adding and blending in a half-barrier mixer.

Comparative Example 2

A rubber composition was prepared under the same conditions as in Comparative Example 1 except that 54.5 parts by weight of carbon black and 0.5 part by weight of conductive carbon black having an I ₂ surface area of 500 to 900 mg / g were used based on 100 parts by weight of the raw material rubber.

Comparative Example 3

A rubber composition was prepared under the same conditions as in Comparative Example 1 except that 50 parts by weight of carbon black and 5 parts by weight of conductive carbon black having an I ₂ surface area of 500 to 900 mg / g were used.

Comparative Example 4

A rubber composition was prepared under the same conditions as in Comparative Example 1 except that 50 parts by weight of carbon black and 5 parts by weight of conductive carbon black having an I ₂ surface area of 1000 mg / g or more were used for 100 parts by weight of the raw material rubber.

Example 1

A rubber composition was prepared under the same conditions as in Comparative Example 1 except that 54 parts by weight of carbon black and 1 part by weight of conductive carbon black having an I ₂ surface area of 500 to 900 mg / g were used based on 100 parts by weight of the raw material rubber.

Example 2

A rubber composition was prepared under the same conditions as in Comparative Example 1 except that 53 parts by weight of carbon black and 2 parts by weight of conductive carbon black having an I ₂ surface area of 500 to 900 mg / g were used based on 100 parts by weight of the raw material rubber.

Example 3

A rubber composition was prepared under the same conditions as in Comparative Example 1 except that 51 parts by weight of carbon black and 4 parts by weight of conductive carbon black having an I ₂ surface area of 500 to 900 mg / g were used.

The evaluation results of the rubber specimens prepared in Comparative Examples and Examples are as shown in Table 2 and measured according to the following method.

(1) Tensile Properties: It was measured according to ASTM D412 test method using an Instron tester.

(2) Resistance: Measured according to Korean Industrial Standard ISO 2878.

(3) Fatigue Properties: The fatigue properties were confirmed by measuring the crack growth length at 50000 cycles after aging at 100 ° C. for 24 hours using a Demattia tester.

Property measurement result division Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Example 1 Example 2 Example 3 Tensile Properties Hardness 54 55 61 55 57 58 60 100% Modulus (kgf / cm ² ) 18 20 25 22 21 23 24 300% modulus (kgf / cm ² ) 95 97 107 100 102 107 106 % Elongation 498 492 464 485 484 477 468 Tensile strength (kgf / cm ² ) 204 203 191 205 200 197 195 Resistance (kΩ) Voltage (1KV) 270 259 3.2 5.2 97 5.4 3.4 Fatigue Properties Crack growth length (mm) 3.82 4.13 6.98 7.02 4.28 4.65 5.13

As can be seen from the measurement results of the physical properties shown in Table 2, in the case of Comparative Example 2 which does not use the conductive carbon black or 0.5 parts by weight of the conductive carbon black, the electrical conductivity is not improved, but the conductive carbon black is 1 part by weight. In the case of Example 1 to Example 3 and Comparative Example 3 to Comparative Example 4 used above, it was confirmed that the electrical conductivity is improved.

In addition, Examples 1 to 3 and Comparative Example 3 using more than 1 parts by weight of conductive carbon black was confirmed that the hardness and modulus increased. However, in the case of Comparative Example 3, in which 5 parts by weight of conductive carbon black was applied, it was confirmed that a problem of lowering tensile strength and fatigue performance occurred. In addition, in the case of Comparative Example 4 using a conductive carbon black having an I ₂ surface area of 1000 mg / g or more, the same amount of conductive carbon black was used in comparison with Comparative Example 3 using an I ₂ surface area of 500 to 900 mg / g due to the problem of dispersibility. Nevertheless, it can be confirmed that hardness and physical properties are low. In the tread rubber composition containing carbon black, it was found that the use of conductive carbon black is preferably used in an amount of 1 to 4 parts by weight based on 100 parts by weight of the rubber material.

Claims (3)

A rubber composition for tire under tread comprising 1 to 4 parts by weight of electroconductive carbon black based on 100 parts by weight of raw rubber. The method of claim 1, The electrically conductive carbon black has a I ₂ surface area of 500 ~ 900 mg / g and a DBP adsorption value of 300 ~ 500 ml / 100g, the rubber composition for tire under tread. The method according to claim 1 or 2, The raw material rubber is a rubber composition for tire under tread, characterized in that selected from natural rubber, synthetic rubber or mixed rubber made of a mixture of natural rubber and synthetic rubber.