KR101398712B1 - Rubber composition for tire-tread - Google Patents

Abstract

The present invention discloses rubber compositions for tire treads.
The rubber composition for a tire tread according to the present invention is a rubber composition for a tire tread comprising silica as a raw material rubber and silica as a reinforcing agent, wherein an unsaturated fatty acid derivative having a dropping point of 90 to 120 占 폚 And the silica is used in an amount of 1 to 10 parts by weight, and the silica is contained in an amount of 50 to 90 parts by weight. In this case, an excessive amount of a silica reinforcing agent is used to reduce the rotational resistance of the tire, , Thereby solving the problem that the viscosity of the rubber composition increases.

Description

[0001] Rubber composition for tire tread [0002]

The present invention relates to a rubber composition for a tire tread, and more particularly to a rubber composition for a tire tread, in which an excessive amount of a silica reinforcing agent is used in order to reduce the rolling resistance of a tire to solve the problem of difficulty in dispersion, To a rubber composition for a tire tread.

Currently, efforts are being made to develop fuel-efficient tires by reducing the rolling resistance of tires as part of the fuel cost reduction of automobiles. As a result, technologies that use silica as a substitute for carbon black, which has been used in rubber compositions for tire treads, .

However, unlike carbon black, the silica developed for the substitution of carbon black has a problem that the workability and mixing property with nonpolar rubber is reduced because the surface chemistry is polarity.

In addition, since the silanol groups of the silica are bonded by hydrogen bonding, they are not easily dispersed in the compounding process of the rubber composition, and therefore, there is a problem that a separate compounding process such as dropping a higher shearing force is added to disperse the silica.

In addition, recent efforts have been made to maximize rolling resistance and traction performance by using a silica content of 80 parts by weight or more based on 100 parts by weight of rubber of a rubber composition for tread of environmentally friendly products, As the content is increased, the workability is greatly reduced, and there is also a need to complement the equipment aspect.

In order to solve these problems, a silane coupling agent has been developed. This silane coupling agent reacts with the silanol group of the silica to change the polar nature of the silica to nonpolar, However, such a silane coupling agent is expensive, and by-products such as ethanol due to the reaction with silica in the process are generated and volatilized during the process. In order to sufficiently react with the silane coupling agent and silica, And time control over time.

Therefore, in order to solve the problem of the silane coupling agent, attempts have been made to add or replace the silane coupling agent with a dispersant in order to improve the dispersibility and fairness of the silica in the rubber composition. However, I can see. And another problem of lowering the physical properties of the silica rubber due to the addition of the dispersant is caused.

An object of the present invention is to solve the problem that an excessive amount of a silica reinforcing agent is used in order to reduce the rolling resistance of a tire, thereby solving the problem of difficulty in dispersing and thus raising the viscosity of the rubber composition.

Disclosure of the Invention In order to solve the above technical problems, the present invention provides a rubber composition for tire tread comprising silica as a raw material rubber and a reinforcing agent, wherein a dropping point of 90 to 120 占 폚 1 to 10 parts by weight of a zinc salt of an unsaturated fatty acid derivative, and 50 to 90 parts by weight of the silica.

According to one embodiment of the present invention, the unsaturated fatty acid derivative may be oleic acid, linoleic acid or linolenic acid.

According to another embodiment of the present invention, the silica may have a BET of 100 to 400 m 2 / g and a hydrogen ion index of 4 to 12.

According to another embodiment of the present invention, the content of zinc in the unsaturated fatty acid derivative zinc salt may be 7 to 9 mol%.

According to the rubber composition for a tire tread according to the present invention, an excessive amount of a silica reinforcing agent is used in order to reduce the rotational resistance of the tire, thereby solving the problem of difficulty in dispersing, and thereby solving the problem of increasing the viscosity of the rubber composition.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. However, those skilled in the art will appreciate that various modifications and equivalent embodiments are possible without departing from the scope of the present invention. I will understand that. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

The rubber composition for a tire tread according to the present invention is a rubber composition for a tire tread containing silica as a raw material rubber and a reinforcing agent, wherein the unsaturated fatty acid having a dropping point of 90 to 120 占 폚 1 to 10 parts by weight of the zinc salt of the derivative, and 50 to 90 parts by weight of the silica.

Styrene-butadiene rubber, natural rubber, or butadiene rubber may be used in combination as a raw material rubber in order to ensure the use of the tire and necessary properties.

In addition, the unsaturated fatty acid derivative is used as a fatty acid zinc salt having 16 to 18 carbon atoms, and may be oleic acid, linoleic acid, or linolenic acid in particular.

If the number of carbon atoms is 16 to 18, the dropping point can be maintained at 90 to 120 캜, and it is easy to manage in a solid state and physical properties are reduced as a result of rubber compounding .

If the dropping point of the zinc salt of the unsaturated fatty acid derivative is less than 90 ° C, the dispersibility is not improved when an excessive amount of silica is used, for example, 50 parts by weight or more, so that the scorch stability of the extrusion process The effect of improving the rolling resistance may be insignificant. On the other hand, if the temperature is higher than 120 ° C., it may be difficult to mix the rubber with sufficient rubber during the rubber compounding process, and problems such as poor dispersibility, scorch instability and rotational resistance may also occur.

The zinc salt of the unsaturated fatty acid derivative is preferably used in an amount of 1 to 10 parts by weight per 100 parts by weight of the raw material rubber. If less than 1 part by weight, the effect of improving the dispersibility may be insignificant. On the other hand, The physical properties of the rubber composition may be deteriorated.

In addition, the content of the zinc salt of the unsaturated fatty acid derivative may be 7 to 9 mol% in the unsaturated fatty acid derivative. If the amount of the unsaturated fatty acid derivative is less than 7 mol%, it may be difficult to improve dispersibility in the case of mixing excess silica with rubber, If it is more than 9 mol%, there may be a problem that the vulcanization rate changes and the physical properties of the compounded rubber increase.

On the other hand, the silica has a specific surface area of 100 to 400 m < 2 > / g and a hydrogen ion index of 4 to 12 as measured using BET. If it is less than 100 m2 / g, On the other hand, if the concentration exceeds 400 m < 2 > / g, dispersion may be difficult, and if the hydrogen ion index is less than 4, the reaction with the coupling agent may be difficult. There may be an unreacted residual amount or excessive by-products such as ethanol may be generated.

The silica used in the present invention is particularly high in the specific surface area of the silica to be applied to the tire, and it is important to solve the dispersibility.

The silica is used in an amount of 50 to 90 parts by weight based on 100 parts by weight of the raw material rubber. If the amount is less than 50 parts by weight, it is difficult to improve the rolling resistance and the traction performance. On the other hand, There may be problems in effect and dispersion.

On the other hand, the rubber composition according to the present invention is generally used as a compounding agent to be added, such as N-cyclohexyl-2-benzothiazyl sulfenamide as a vulcanization accelerator, sulfur vulcanizing agent, stearic acid, zinc oxide, - dihydroquinoline or waxy hydrocarbon may be used as needed.

Examples 1-5

The rubber composition for a tire tread according to the present invention was prepared in accordance with the contents shown in Table 1 below, which is represented by styrene-butadiene rubber, butadiene rubber, silica, carbon black, antioxidant, vulcanization accelerator, sulfur or dispersant 2.

Comparative Examples 1 to 4

The rubber composition for tire tread was prepared as a comparative example by mixing according to the contents shown in Table 1 below, styrene-butadiene rubber, butadiene rubber, silica, carbon black, antioxidant, vulcanization accelerator, sulfur or dispersant 1.

division Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Example 1 Example 2 Example 3 Example 4 Example 5 SBR 70 70 70 70 70 70 70 70 70 BR 30 30 30 30 30 30 30 30 30 Silica 50 50 90 90 50 90 90 90 90 Carbon black 10 10 10 10 10 10 10 10 10 Silane coupling agent 4.0 4.0 7.2 7.2 4.0 7.2 7.2 7.2 7.2 Dispersant 1 0 5 5 10 0 0 0 0 0 Dispersant 2 0 0 0 0 5 One 5 10 15 Zinc oxide 3 3 3 3 3 3 3 3 3 Stearic acid 2 2 2 2 2 2 2 2 2 Antioxidants 1 One One One One One One One One One Antioxidants 2 One One One One One One One One One Vulcanization accelerator 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 brimstone 1.7 1.7 1.7 1.7 1.7 1.7 1.7 1.7 1.7

(1) Styrene-butadiene rubber (SBR): SBR 1739 (Kumho Petrochemical)

(2) Butadiene rubber (BR): BR-01 (Kumho Petrochemical)

(3) Silica: silica having a BET of 200 m < 2 > / g and a hydrogen ion index of 6.0

(4) Carbon black: Carbon black having a DBP adsorption value of 70 to 130 mg / 100 g, an iodine adsorption value of 60 to 150 mg / g, and a TINT (% of IRB # 3)

(5) Dispersant 1: Fatty acid esters with a DP (Dropping point) of 60 to 65 ° C.

(6) Dispersant 2: An unsaturated fatty acid derivative mixture containing 8 mol% of zinc (Zn) and having a carbon chain length of 16 to 18 and having a DP (Dropping point) of 90 to 120 ° C.

(7) Anti-aging agent 1: 1,2-dihydroquinoline

(8) Anti-Aging Agent 2: Waxy Hydrocarbon

(9) Varying agent: N-tert-butyl-2-benzothiazylsulfenamide

(10) Sulfur: Ground sulfur

Experimental Example

The Mooney viscosity and the scorch stability of the rubber specimens prepared in Examples 1 to 3 and Comparative Examples were measured at MV2000. The hardness of the rubber specimens was measured by ASTM shore-A hardness meter Stress-strain curves were measured from the curve of strain-stress when a specimen with a length of 20 mm and a width of 5 mm was stretched by using a dumbbell having a length of 100 mm, an outer width of 25 mm and an inner width of 5 mm and a 300% % Of the elongation at break, and the elongation at break was measured by the method of ASTM D 790, in which the value of the strain was expressed in% in the tensile tester until the test piece was broken. The dispersion is measured by the Image Analyzer analysis method, and the dispersion of the stiffener in a certain area of the vulcanized rubber is measured based on the 100% dispersion. The result is expressed as an index, and the larger the value, the better . Table 2 shows the results of the above experimental method.

division Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Example 1 Example 2 Example 3 Example 4 Example 5 Micheal Pattern viscosity (100 degree seed) 70 67 80 75 67 79 77 73 70 Scorch stability (minutes) 10 11 8 9 12 7 12 15 17 Tensile properties Hardness 60 58 68 65 58 70 68 67 65 300% modulus (kgf / cm2) 120 110 115 95 115 125 123 120 105 Tensile strength (kgf / cm ² ) 190 180 180 170 185 190 190 187 178 Dispersivity (%) 80 90 70 60 98 75 90 93 80

(1) Scorch stability (minutes): 10 minutes or longer is preferable.

(2) 300% modulus: 105 or more is preferable.

(3) Tensile strength: 180 or more is preferable

(4) Dispersibility (%): 85% or more is preferable, and larger is more advantageous.

From the results shown in Table 2, it can be seen that, in the case of Comparative Example, when the amount of silica is used in an excess amount of 90 parts by weight, the scorch stability drop, tensile property drop and dispersibility are extremely reduced.

However, in the case of the embodiment according to the present invention, it can be seen that even when 90 parts by weight of silica is used, the viscosity is improved, the scorch stability is improved, the tensile property is secured, and the dispersibility is improved.

In addition, the rubber composition for tire tread according to Examples and Comparative Examples was extruded and processed to produce a tire, and the extrusion stability and rotational resistance were measured. The results are shown in Table 3 below.

division Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Example 1 Example 2 Example 3 Example 4 Example 5 Extrusion stability (%) 60% 85% 50% 55% 88 & 65% 86% 90% 80% Rotation resistance (%) 70% 85% 70% 68% 85% 90% 95% 100% 95%

(1) Stability of extrusion (%): The higher the extrusion speed (RPM), the better.

(2) Rotational resistance (%): Rolling Resistance Coefficient (RRc, kgf / ton)

(3) Evaluation of rotational resistance Product specification: 195/65 R15

From the results of Table 3, it can be seen that the extrusion stability and the rotational resistance performance of the finished product are somewhat improved in the case of the comparative example, but it is not effective when the silica is used excessively.

However, in the case of Examples, it can be seen that the extrusion stability and the rotation resistance performance are excellent even when an excessive amount of silica is used.

Claims (4)

A rubber composition for a tire tread comprising silica as a raw material rubber and a reinforcing agent,
1 to 10 parts by weight of a zinc salt of an unsaturated fatty acid derivative having a dropping point of 90 to 120 ° C relative to 100 parts by weight of the raw material rubber, and 50 to 90 parts by weight of the silica,
Wherein said unsaturated fatty acid derivative is oleic acid, linoleic acid or linolenic acid,
Wherein the content of zinc in the unsaturated fatty acid derivative zinc salt is 7 to 9 mol%.
delete The method according to claim 1,
Wherein the silica has a BET of 100 to 400 m < 2 > / g and a hydrogen ion index of 4 to 12. The rubber composition for a tire tread according to claim 1,
delete