KR100553996B1 - Rubber composition for tire tread - Google Patents

Abstract

The present invention relates to a rubber tread rubber composition comprising butadiene rubber and solution-polymerized styrene-butadiene rubber alone or mixed rubber thereof as a raw material rubber, including silica as a reinforcing agent, and including a processing aid, wherein the acid value is 90 to 120 mgKOH as a processing aid. 1 to 10 parts by weight of a saturated or unsaturated fatty acid having 10 to 20 carbon atoms having a softening point of 70 to 90 ° C. and a double bond substituted with an OH group, based on 100 parts by weight of the rubber of the raw material, The present invention provides a rubber composition for tire treads, which increases productivity by improving workability during extrusion and increases productivity, minimizes energy costs, and minimizes mechanical properties of rubber such as tensile strength, elongation and hardness.

Description

Rubber composition for tire treads

The present invention relates to a rubber composition for tire treads, and more particularly, to a rubber tread composition for a tire tread containing a processing aid for improving silica dispersibility of rubber and improving workability without deteriorating rubber properties.

As the tire industry develops, we are expanding our technology to produce low fuel consumption, low rolling resistance and environmentally friendly products. The first concern was to improve the interaction between carbon black and polymers, the most widely used reinforcing agent.

However, due to the characteristics of carbon black, there is a problem in that the heat generation of the rubber while driving the vehicle not only decreases the durability of the tire but also generates high heat during processing, thereby lowering the physical properties of the rubber.

As a solution to this, silica has been proposed.Since silica has a high polarity, it is not easily miscible with a nonpolar rubber, so that a coupling agent (coupling agent), which is sometimes referred to as a silane coupler, is introduced. The working force could be improved, and from then on, tire technology using silica began to develop remarkably.

The use of silica in tire treads improves low fuel consumption, low rolling resistance and braking performance on wet roads compared to carbon black.However, compared to conventional carbon black, silica is more difficult to disperse. Development was needed.

By the way, the processing aid used to improve the dispersibility of the silica compound improved the dispersibility to improve the processability, but seriously deteriorated the physical properties of the rubber caused a decrease in product quality.

Conventionally used processing aids include fatty acid esters, saturated and unsaturated fatty acid ester complexes, including metal salts.

Accordingly, the present inventors can improve the dispersibility of the reinforcing agent in the mixing of the rubber and improve the workability during extrusion, thereby increasing the productivity, minimizing the energy cost, and seeking a method for minimizing the deterioration of the mechanical properties of the rubber. While the acid value of 90 to 120mgKOH / g, the softening point of 70 to 90 ℃, a saturated or unsaturated fatty acid having 10 to 20 carbon atoms substituted with an OH group in a double bond as a processing aid, it was found that this can be satisfied, the present invention To complete.

Accordingly, an object of the present invention is to increase the dispersibility of the reinforcing agent when mixing the rubber, to improve the workability during extrusion, to increase the productivity, to minimize the energy cost and to minimize the degradation of the mechanical properties of the rubber, such as tensile strength, elongation and hardness The present invention provides a rubber composition for tire treads.

The rubber composition for tire treads of the present invention for achieving the above object comprises butadiene rubber and solution-polymerized styrene-butadiene rubber as a raw material rubber, silica as a reinforcing agent and a processing aid, wherein the processing aid is acid value 90 Saturated or unsaturated fatty acids having 10 to 20 mgKOH / g and a softening point of 70 to 90 ℃ and a double bond is substituted with an OH group, characterized in that it comprises 1 to 10 parts by weight based on 100 parts by weight of the raw material rubber.

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

The rubber composition for tire treads of the present invention includes silica as a reinforcing agent, and as a processing aid, an acid value of 90 to 120 mgKOH / g, a softening point of 70 to 90 ° C, and a saturated or unsaturated fatty acid having 10 to 20 carbon atoms in which a double bond is substituted with an OH group. Use

Such processing aids are obtained by substituting OH groups for double bonds of saturated, unsaturated fatty acids having 10 to 20 carbon atoms, such as oleic acid, linolenic acid, etc., which in turn result in -COOH and -OH functional groups. By hydrogen bonding to the silanol groups on the silica surface to improve the dispersion of silica in the rubber compound and to lower the viscosity serves to improve the processability.

The amount of the processing aid that plays such a role is 1 to 10 parts by weight based on 100 parts by weight of the raw material rubber. If the content of the processing aid is less than 1 part by weight based on 100 parts by weight of the raw material rubber, the effect of silica dispersion and viscosity drop is exerted. It is hard to find, and if it exceeds 10 parts by weight, modulus and hardness are lowered, which adversely affects mechanical properties.

In the rubber tread rubber composition of the present invention, the raw material rubber is butadiene rubber or styrene-butadiene rubber, and in particular, a solution-polymerized styrene-butadiene rubber having a glass transition temperature of -50 to -10 ° C to improve braking performance on wet road surfaces is used. It is preferable to include in rubber | gum. Solution-polymerized styrene-butadiene rubber having a glass transition temperature of -50 to -10 ° C can be used in 30 to 100% by weight of raw rubber. If the content is less than 30% by weight of all raw rubber, braking performance on wet road surface The improvement is minimal.

Silica used as a reinforcing agent has a nitrogen adsorption specific surface area of 100 to 400 mm 2 / g and a hydrogen ion index of 4 to 12, wherein the nitrogen adsorption specific surface area is used in the Brunauer-Emmett-Teller method using nitrogen as an adsorbent. Refers to the value of the specific surface area of the precipitated silica (hereinafter referred to as "BET specific surface area").

The content of silica is preferably 10 to 120 parts by weight based on 100 parts by weight of the raw material rubber. When the silica content is less than 10 parts by weight based on 100 parts by weight of the raw material rubber, the amount of silica is small, and thus the effect of the processing aid for silica is not seen. If more than 120 parts by weight there is a problem that is difficult to process the silica compound for tread.

In addition, the rubber composition for tire treads of the present invention may include additives such as a vulcanizing agent, a vulcanizing agent, a softening agent, a vulcanization accelerator, and a coupling agent, as in a conventional rubber composition, and the coupling agent has two functional groups and is polar silica. It facilitates the mixing of rubber and non-polar rubber and serves to improve the reinforcement of silica. Coupling agents used in rubber treads for tire treads typically include sulfur in the area capable of bonding rubber, where the reaction with rubber is monosulfide, disulfide, and poly It is classified as a case of polysulfide. Examples of the use of sulfur-containing coupling agents include U.S. Pat. .

Hereinafter, the present invention will be described in more detail with reference to the following Examples, which are not intended to limit the present invention.

Examples 1 to 3 and Comparative Examples 1 to 4

As shown in Table 2, KBR 31 and solution-polymerized styrene-butadiene rubber (S-SBR), coupling agent Si-69, softener aromatic oil (A # 2 Oil), zinc oxide, stearic acid, sulfur, vulcanization accelerator Phosphorus CA and 1,3-diphenylguanidine were added and blended in a Banbury mixer, followed by release at 155 ° C. to prepare a rubber composition.

Specifically, first, silica, Si-69, A # 2 Oil, zinc oxide, and stearic acid were added to the raw material rubber, mixed in a Banbury mixer, and then discharged at 155 ° C. Then, sulfur and zinc oxide were added to the resultant compound rubber, mixed in a Banbury mixer, and then discharged after 1 minute and 30 seconds.

Processing aids used in each of the examples are shown in Table 1 below.

Kinds Characteristic Processing aid A Fatty acid esters containing Zn salts (A series. Strukto) Processing aid B Fatty acid esters containing Zn, K salts (EF series, manufactured by Strukto) Processing aid C Saturated, unsaturated fatty acid ester complexes (Ultralube series, manufactured by PA) Processing aid D Saturated or unsaturated fatty acids having 10 to 20 carbon atoms in which the acid value is 90 to 120 mgKOH / g, the softening point is 70 to 90 ° C., and the forgetful bond is substituted with an OH group.

Here, the processing aid D was added 500 g of saturated or unsaturated fatty acid having 10 to 20 carbon atoms, 50 ml of 40% NaHCO ₃ solution and 30 ml of 30% hydrochloric acid in 500 ml of normal heptane, and heated at 90 ° C. for about 2 hours, followed by 50 ml of distilled water. It was obtained by refluxing at about 2 hours at reflux and cooling and drying.

Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Example 1 Example 2 Example 3 BR (rubber solids content) 33 (24) 33 (24) 33 (24) 33 (24) 33 (24) 33 (24) 33 (24) S-SBR 76 76 76 76 76 76 76 Silica 80 80 80 80 80 80 80 Coupling Agent (Si-69) 6.4 6.4 6.4 6.4 6.4 6.4 6.4 Softener (A # 2 Oil) 31 31 31 31 31 31 31 Zinc oxide 3 3 3 3 3 3 3 Stearic acid 2 2 2 2 2 2 2 Processing aid A - 4 - - - - - Processing aid B - - 4 - - - - Processing aid C - - - 4 - - - Processing aid D - - - - 2 4 10 brimstone 1.4 1.4 1.4 1.4 1.4 1.4 1.4 CZ 1.7 1.7 1.7 1.7 1.7 1.7 1.7 1,3-diphenyl guanidine 2 2 2 2 2 2 2 Unit: parts by weight BR: KBR31 (butadiene rubber in which A # 2 Oil is 37.5 phr inherited for rubber solids) S-SBR: solution polymerized styrene-butadiene rubber with glass transition temperature -20 ° C

The Mooney viscosity, hardness, 300% modulus, elongation, and spiral flow length of the rubber products obtained according to the above Examples and Comparative Examples were measured and the results are shown in Table 3 below.

The specific measuring method is as follows.

(1) Mooney viscosity: measured on MV2000.

(2) Hardness: Measured after leaving for 1 hour in a temperature-controlled combustion chamber by the ASTM Shore-A durometer method.

(3) 300% modulus and elongation: using 100mm in length, 25mm in outer width and 5mm in width, and using 300mm in length and 20mm in length and 5mm in width while holding the test piece with the specimen and stretching the strain-stress curve from the initial 300% As a method of stress on elongation, the elongation at break indicates the strain value in% until the test piece breaks in the tensile tester.

(4) Spiral Flow Length Measurement Condition:

Test Rubber-23g (4.5 × 4.5 × 1cm)

Vulcanization Condition-170 ℃ × 10min

Test Method-Insert the rubber of the specified amount into the spiral mold and measure the amount of rubber that flows out during the vulcanization under the above vulcanization conditions.

Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Example 1 Example 2 Example 3 Mooney viscosity (@ 125 ℃) 80 73 72 76 72 68 62 Shore A 60 57 56 59 59 59 58 300% modulus (Mpa) 110 99 98 106 111 110 105 Elongation (%) 446 511 511 476 440 472 493 Spiral Flow length (cm) 13 14 13.4 13.5 15 17 19

From the results in Table 3, as in Examples 1 to 3, a double bond is substituted with an OH group as a processing aid, and an acid value of 90 to 120 mgKOH / g and a C10 to 20 fatty acid having a softening point of 70 to 90 ° C. is used. It can be seen that it exhibits favorable workability in Mooney viscosity and Spiral Flow Length compared to Comparative Example 4, and has an advantageous value in Mooney viscosity and Spiral Flow Length without modulus degradation and hardness compared to Comparative Example 2 and Comparative Example 4 And it can be seen that the degradation of the mechanical properties of the rubber, such as hardness is minimized.

As described in detail above, in the case of using a fatty acid having 10 to 20 carbon atoms having a double bond substituted with an OH group and having an acid value of 90 to 120 mgKOH / g and a softening point of 70 to 90 ° C in a rubber composition including silica as a reinforcing agent according to the present invention. It is possible to increase productivity by increasing silica dispersibility and improve processability during extrusion, minimizing energy cost, and minimizing mechanical properties of rubber such as tensile strength, elongation and hardness. .

Claims (3)

In the rubber composition for tire treads comprising butadiene rubber and solution-polymerized styrene-butadiene rubber alone or mixed rubber thereof as raw material rubber, silica as a reinforcing agent, and a processing aid, The processing aid is an acid value of 90 to 120mgKOH / g, a softening point of 70 to 90 ℃ and a double bond is a saturated or unsaturated fatty acid having 10 to 20 carbon atoms substituted with OH group, it comprises 1 to 10 parts by weight based on 100 parts by weight of the raw material rubber Rubber composition for tire treads, characterized in that. The rubber composition for tire treads according to claim 1, wherein the raw material rubber comprises 30 to 100 wt% of the solution-polymerized styrene-butadiene rubber having a glass transition temperature of -50 to -10 ° C. (Correction) The method according to claim 1, characterized in that the silica contains 10 to 120 parts by weight based on 100 parts by weight of the raw material rubber with a nitrogen adsorption specific surface area of 100 to 400 mm 2 / g and a hydrogen ion index of 4 to 12. Rubber composition for tire tread.