KR100582470B1 - Rubber composition for tire tread - Google Patents

Abstract

The present invention relates to a rubber tread rubber composition comprising silica as a reinforcing agent, and by adding a low molecular weight butadiene polymer having an OH group introduced at the end thereof, the OH group at the butadiene polymer terminal reacts with the OH group on the silica surface to form a hydrogen bond. By converting the surface chemical properties of silica into non-polar like rubber, it improves dispersibility when mixing silica and rubber, and also improves the physical properties of compounded rubber by adding butadiene rubber. It provides a rubber composition for a tire tread that can prevent the degradation of physical properties due to the addition of a dispersant.

Description

Rubber composition for tire treads

The present invention relates to a rubber tread rubber composition containing silica, and more particularly, to a conventional silica-containing tread rubber composition by adding a polymer having a functional group for improving the dispersibility of silica, dispersibility and processability of the silica tread rubber The present invention relates to a silica-containing tread rubber composition having improved.

As part of the low fuel consumption of automobiles, the company is trying to develop low-fuel tires by reducing the rolling resistance of tires. As a result, technologies using silica instead of carbon black used in tire tread rubber compositions have been continuously made. Is being developed.

However, silica developed as a substitute for carbon black has a polarity in surface chemical properties unlike carbon black, and thus, poor workability and mixing property with nonpolar rubber. In addition, since these silanol groups of silica are strongly bonded by hydrogen bonds and are not easily dispersed during the compounding process, more shear force and the addition of the compounding process are required for dispersion of the silica in the rubber during the compounding process. have.

In order to solve this problem, a silane coupling agent has been developed, and the silane coupling agent reacts with the silanol group of the silica to change the polar property of the silica into nonpolar, so that it is easy to mix with the nonpolar rubber. It will play a role. However, such a silane coupling agent is an expensive material, and ethanol or the like is generated by reaction with silica in the process, and these have a problem of volatilization during the process, and in order to sufficiently react the silane coupling agent with silica, a compounding process There is a problem in that it is necessary to adjust the temperature and time at.

Therefore, in order to make up for the disadvantages of such silane coupling agents, attempts have been made to introduce dispersants to improve the dispersibility and fairness of silica in rubber. However, the addition of such a dispersant can be seen the effect of the dispersion. Another problem of lowering the physical properties of the silica rubber due to the addition of the dispersant has a possibility of occurrence.

Accordingly, the present inventors have solved the problem of dispersion by using silica in the silica rubber composition for tire treads, and in the search for another method that does not bring about physical property deterioration due to the use of a dispersant, a hydroxyl group is applied to a low molecular weight butadiene polymer. As a result of the addition of a polymer having an OH group at the end, the OH group at the end of the butadiene polymer reacts with the OH group on the surface of the silica, converting the surface chemical properties of the silica into a non-polar like rubber through hydrogen bonding, The present invention has been completed by improving the dispersibility when mixing the rubber and improving the physical properties of the compounded rubber through the addition of butadiene rubber.

Accordingly, an object of the present invention is to solve the degradation of dispersibility caused by the different polarity of silica and rubber, by adding a low molecular weight butadiene polymer having an OH group at the end, and the physical properties of the tire through the addition of butadiene rubber It is to provide a rubber composition for tire tread containing silica improved.

Rubber composition for tire treads of the present invention for achieving the above object as containing a silica as a reinforcing agent, further comprises a low molecular weight butadiene polymer having an OH group at the end, characterized in that it does not contain a separate dispersant It is done.

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

The present invention relates to a rubber composition for silica-containing tire treads, further comprising a low molecular weight butadiene polymer having an OH group at its terminal.

In the low molecular weight butadiene polymer having an OH group at the terminal, it is preferable that the butadiene polymer having a molecular weight of about 1,000 to 30,000 is used as the molecular weight of the low molecular weight butadiene polymer to introduce the OH group at the terminal. If the molecular weight of the low molecular weight butadiene polymer is less than 1,000, it will not show any effect in terms of physical properties upon addition to the rubber, and if it has a molecular weight of more than 30,000, it will exhibit an adverse tendency in mixing with rubber.

The method of introducing an OH group into the terminal of the low molecular weight butadiene polymer is not particularly limited, but after dissolving the low molecular weight butadiene polymer in cyclohexane, the solution is added with NaHCO ₃ , stirred uniformly, and then mixed with hydrochloric acid. do. After mixing is completed, a certain amount of distilled water is added to the reaction with stirring. After the reaction, the mixture is cooled, washed and dried to obtain a low molecular weight butadiene polymer having an OH group introduced at the terminal.

When a low molecular weight butadiene polymer having an OH group introduced at the end is added to a rubber composition containing silica as a reinforcing agent, the OH group at the terminal of the glutadiene polymer reacts with the OH group on the surface of the silica, thereby improving the surface chemical properties of the silica through hydrogen bonding. By converting to non-polar like rubber, it improves dispersibility when mixing silica and rubber, and improves physical properties of compounded rubber through addition of butadiene rubber.

The low molecular weight butadiene polymer in which OH is introduced at the terminal which plays such a role is preferably used in an amount of 5 to 30 parts by weight based on 100 parts by weight of the raw material rubber.

If the content is less than 5 parts by weight based on 100 parts by weight of the raw material rubber, the effect using the properties of the added butadiene polymer is not sufficiently obtained. If the content is more than 30 parts by weight, the dispersibility and physical properties of the excessive addition of the butadiene polymer are reduced. There is a concern.

In the rubber composition of the present invention, the raw material rubber may be a mixed rubber of styrene-butadiene rubber and butadiene rubber.

Silica used in the present invention has a specific surface area of 100 to 400 m 2 / g measured using BET and has a hydrogen ion index of 4 to 12, the content of which is 40 to 100 parts by weight based on 100 parts by weight of the raw material rubber desirable. If the content of silica is less than 40 parts by weight based on 100 parts by weight of the raw rubber, it may not play a role as a filler, but if it exceeds 100 parts by weight, there may be problems in reinforcing effect and dispersion.

On the other hand, the rubber composition used in the present invention is conventionally added compounding agents, for example, 2.0 parts by weight of N-cyclohexyl-2-benzothiazyl sulfenamide as a vulcanization accelerator, 1.7 parts by weight of sulfur as a vulcanizing agent, 2 parts by weight of stearic acid, 3 parts by weight of zinc oxide, 1 part by weight of 1,2-dihydro quinoline, 1 part by weight of waxy hydrocarbon as an anti-aging agent of rubber, but is not limited thereto.

In the following, the effects obtained by carrying out the present invention are described by comparing the properties of the rubber compositions prepared in Examples and Comparative Examples to explain the effects, but the present invention is not limited thereto.

Preparation Example: Preparation of low molecular weight butadiene polymer having OH group introduced at the terminal

300 g of a low molecular weight butadiene polymer (Krasol LB-series (manufactured by Sartomer)) having a molecular weight of 10,000 was dissolved in 500 ml of cyclohexane, and then added to 100 ml of NaHCO ₃ 30% solution. Mix for 1 h.

After the mixing was completed, 50 ml of distilled water was added, followed by stirring. After the reaction for 2 hours, the mixture was cooled, washed, and dried to prepare a low molecular weight butadiene polymer having OH groups introduced at the terminals.

Examples 1-4 and Comparative Examples 1-2

Next, rubber specimens were prepared according to the composition of Table 1.

Example Comparative example One 2 3 4 One 2 SBR ⁽¹⁾ 70 70 70 70 70 70 BR ⁽²⁾ 30 30 30 30 30 30 Low Molecular Weight Polybudadiene ⁽³⁾ 5 10 15 20 - - Silica ⁽⁴⁾ 80 80 80 80 80 80 Silane Coupling Agents ⁽⁵⁾ 12.8 12.8 12.8 12.8 12.8 12.8 Dispersants ⁽⁶⁾ - - - - - 5 Zinc oxide 3 3 3 3 3 3 Stearic acid 2 2 2 2 2 2 Antioxidant ⁽⁷⁾ One One One One One One Antioxidant ⁽⁸⁾ One One One One One One Accelerators ⁽⁹⁾ 2.0 2.0 2.0 2.0 2.0 2.0 Sulfur ⁽¹⁰⁾ 1.7 1.7 1.7 1.7 1.7 1.7

(1) SBR: SBR 1712 (Hyundai Petrochemical)

(2) BR: KBR-31 (37.5% Oil-Extanded BR)

(3) Low molecular weight polybutadiene having OH group introduced at the terminal obtained according to Production Example

(4) silica having a BET of 175 m 2 / g and having a hydrogen ion index of 6.0;

(5) TESPT: tetraethoxy silyl propyl tetra sulfide

(6) dispersants of hydrophilic fatty acid esters

(7) 1,2-dihydroquinoline

(8) waxy hydrocarbon

(9) N-tert-butyl-2-benzothiazyl sulfenamide

(10) Sulfur: Ground sulfur

The Mooney viscosity and scorch stability of the rubber specimens prepared in Examples 1 to 4 and the rubber compounded in the comparative example were measured in MV2000, and the hardness of the prepared rubber specimens was controlled in a temperature-controlled combustion chamber using the ASTM shore-A durometer method. Measured after 1 hour, 300% modulus is 300mm from the beginning of the strain-stress curve when using a dumbbell-shaped 100mm in length, 25mm in width, 5mm in width, holding the test specimen with a length of 20mm, 5mm width As a method of stress for% elongation, the elongation at break indicates the strain value in% until the test piece breaks in the tensile tester, the tensile strength is according to ASTM D 790, and the wear resistance is slippery at room temperature. %, The loss of rubber worn by rotating at 1.5Kg load was estimated. When the index is expressed, the higher the index, the better the wear resistance.

Example Comparative example One 2 3 4 One 2 Miga   Pattern viscosity (125 ℃) 80 75 72 70 95 90 Scotch Stability (min) 29 31 33 35 18 20 Tensile Properties Hardness 70 70 69 68 70 67 300% modulus (kgf / ㎠) 120 118 108 106 125 105 Elongation at Break (%) 448 468 472 479 410 440 Tensile strength (kgf / ㎠) 160 168 170 158 150 140 Abrasion Resistance Index 106 110 115 102 100 85 Dispersion% 92 95 97 91 85 88

From the results of Table 2, in the case of the rubber viscosity, when a low molecular weight butadiene polymer having an OH group introduced therein is used (Examples 1 to 4), the result is lower than that of Comparative Example 1, which is not added, and the addition amount thereof is increased. The rubber viscosity decreases as the result decreases, and it can be seen that the rubber viscosity is lower than that of Comparative Example 2 using a hydrophilic fatty acid ester-based dispersant. This results in a decrease in rubber viscosity as the dispersion of silica is improved.

Even in the tensile physical properties, in Comparative Example 1, since the silica is not dispersed, the hardness is high, and the value of 300% modulus is high while the elongation is low. In the case of tensile strength, the case of Example shows a higher value than the case of Comparative Examples 1 and 2. In addition, in the case of the wear resistance index, all of the examples showed good wear resistance, and especially when the low molecular weight butadiene polymer containing 15 parts by weight of OH introduced at the end, as shown in Example 3, showed the best wear resistance. The results also show the best results.

As described in detail above, when a low molecular weight butadiene polymer having an OH group introduced at the terminal is added to a tire tread rubber composition including silica as a reinforcing agent, the OH group at the butadiene polymer terminal reacts with the OH group at the silica surface. In addition, it converts the surface chemical properties of silica into non-polar like rubber through hydrogen bonding and improves dispersibility when mixing silica and rubber, and also improves physical properties of compound rubber by adding butadiene rubber. Since it is not necessary to add the addition, it is possible to prevent the degradation of physical properties due to the addition of the dispersant.

Claims (4)

In the rubber composition for tire tread containing silica as a raw material rubber and a reinforcing agent, and including a silane coupling agent therein , A rubber composition for tire treads, further comprising a low molecular weight butadiene polymer having an OH group introduced at the end thereof, and containing no separate dispersant. The rubber composition for a tire tread according to claim 1, wherein the low molecular weight butadiene polymer having an OH group introduced into the terminal is included in an amount of 5 to 30 parts by weight based on 100 parts by weight of the raw material rubber. The rubber composition for a tire tread according to claim 1 or 2, wherein the silica is contained in an amount of 40 to 100 parts by weight based on 100 parts by weight of the raw material rubber. The rubber composition for tire treads according to claim 1, wherein the low molecular weight butadiene polymer has a molecular weight of 1,000 to 30,000.