KR20050120027A - Rubber composition for tire tread - Google Patents

Abstract

The present invention includes silica as a reinforcing agent, and includes a solution-polymerized styrene-butadiene rubber having a polyrotaxane form in which the cyclodextrin or its derivative represented by Chemical Formula 1 is sewn on the rubber chain of the butadiene moiety. -Butadiene moiety inserted into the hollow interior of the cyclodextrin or derivative thereof by strongly bonding to the silica to which -OH group or -OR group (herein, R = alkyl group or hydroxyalkyl group) possessed by the cyclodextrin or derivative thereof is added as a reinforcing agent The rubber chain may have fluidity due to external deformation, and thus may exhibit characteristics of the rubber itself. Thus, a rubber composition for tire treads may be used to improve rolling resistance and wear resistance while maintaining braking performance on wet road surfaces. to provide.

Description

Rubber composition for tire treads

The present invention relates to a rubber composition for tire treads, and more particularly, to a raw material rubber, a solution-polymerized styrene-butadiene rubber in the form of polyrotaxane in which a cyclodextrin or a derivative thereof is sewn on the rubber chain of the butadiene portion. By using silica as a reinforcing agent, the interaction force between the rubber and the reinforcing agent is improved, thereby reducing the rolling resistance and improving the wear resistance of the tire tread.

Recently, the development direction of the tire industry uses silica as a reinforcing agent for the purpose of securing low fuel consumption due to low rolling resistance and stability during braking after driving, and rubber containing binder to increase the interaction force between polar silica and nonpolar rubber. There has been a focus on compositions.

However, in the case of the silica rubber composition, there is a problem in that the wear resistance of the tire is lowered as compared with the rubber composition including carbon black having high interaction force with rubber.

On the other hand, styrene-butadiene rubbers used in silica rubber compositions so far are emulsion-polymerized rubbers or solution-polymerized rubbers obtained by using an organolithium initiator, and a polar group is introduced at the end of the rubber chain to improve the interaction force with silica. Although one study has been conducted, there is a limit in improving the interaction force with rubber due to the nature of the polar silica.

In view of this, in the present invention, a cyclodextrin or a derivative thereof which is covalently bonded to silica is used as a polyrotaxane-type rubber in which a styrene-butadiene rubber chain is sewn, resulting in cyclodextrin or a derivative thereof. The present invention has been completed by knowing that an OH group or an -OR group (here, R = alkyl group or hydroxyalkyl group) can be strongly combined with silica added as a reinforcing agent to reduce the rolling resistance and improve the wear resistance.

Accordingly, it is an object of the present invention to provide a rubber composition for tire treads with reduced rolling resistance and improved wear resistance.

The rubber composition for tire treads of the present invention for achieving the above object comprises a solution-polymerized styrene-butadiene rubber in the raw rubber and silica as a reinforcing agent, wherein the solution-polymerized styrene-butadiene rubber is represented by the following formula (1) The cyclodextrin or derivative thereof is characterized in that it has a polyrotaxane form sewn on the rubber chain of the butadiene moiety.

Formula 1

Looking at the present invention in detail as follows.

The rubber composition for tire treads of the present invention includes a solution-polymerized styrene-butadiene rubber as a raw material rubber, specifically, a cyclodextrin or a derivative thereof represented by Formula 1 on the rubber chain of the butadiene part, so-called polyrotaxane It has a form of phosphorus.

The cyclodextrin added in preparing the solution-polymerized styrene-butadiene rubber in the form of such polyrotaxane is a cyclic oligosaccharide including 6 to 8 glucose units, and the repeating glucose unit is represented by the following Chemical Formula 2. By α-1,4 binding and arrangement of glucose units, cyclodextrins have a conical molecular structure with a hollow interior. The hollow interior is relatively hydrophobic because it contains a hydrogen atom connecting a hydrogen atom and a glucose unit, and the outside is surrounded by an -OH group to exhibit hydrophilicity.

Therefore, the hydrocarbon chain formed during the solution polymerization of styrene-butadiene is inserted into the hollow interior of the cyclodextrin or its derivatives to have a polyrotaxane form, and -OH or -OR group of the cyclodextrin or its derivatives. (Where R = alkyl group or hydroxyalkyl group) can form a strong bond with the silica added as a reinforcing agent.

Specifically, cyclodextrins used in the preparation of solution-polymerized styrene-butadiene rubber in the form of polyrotaxane may include α-cyclodextrin or derivatives thereof, β-cyclodextrin or derivatives thereof, or γ-cyclodextrin or derivatives thereof. And, mainly, some -OH groups may be substituted with -OR groups, where R = alkyl group or hydroxyalkyl group. In the present invention, dimethyl-β-cyclodextrin is preferably used, but is not limited thereto.

The method for preparing a solution-polymerized styrene-butadiene rubber in the form of polyrotaxane using such cyclodextrin is in accordance with a conventional method for preparing a solution-polymerized styrene-butadiene rubber, for example, styrene and butadiene monomers in a polymerization solvent and After injecting the polar additive, the organolithium initiator is injected at a temperature of 40 to 50 ° C. and polymerization is performed for about 2 hours. Then, cyclodextrin or a derivative solution thereof is injected to proceed the polymerization for about 1 hour, and then the reaction is terminated with a polymerization terminator.

The solution-polymerized styrene-butadiene rubber prepared as described above is preferably about 10 to 45% by weight of styrene and 25 to 70% by weight of vinyl in the butadiene portion.

If the styrene content and the vinyl content of the butadiene portion are less than the above ranges, the wear resistance and the braking performance of the wet road surface cannot be expected to increase, and if the styrene content and the vinyl content of the butadiene portion exceed the above ranges, the wear resistance is improved and A decrease in rolling resistance cannot be expected.

The polymerization solvent that can be used in solution polymerization may include at least one hydrocarbon solvent, aromatic, paraffinic or cycloparaffinic compound, and of these, cyclohexane is preferable.

The polar additives that can be used for solution polymerization include tetrahydrofuran, N, N, N, N-tetra methylethylenediamine, trimethylamine, triethylamine, di-normalpropyl ether, di-isopropyl ether, di-normal butyl Ether, ethylbutyl ether, triethylene glycol and the like are used, of which tetrahydrofuran is preferred.

As an organolithium initiator, what is normally used at the time of solution polymerization styrene-butadiene rubber superposition | polymerization is represented by R'-Li (where R is an alkyl group containing 1-10 carbon atoms), Especially normal butyllithium is preferable. .

Dimethyl sulfoxide is used as the solvent used for the cyclodextrin or a derivative thereof.

The solution-polymerized styrene-butadiene rubber prepared as described above may be included in the rubber tread rubber composition using alone or in combination with a conventional raw rubber, and may be used in 10 to 100% by weight of the raw rubber.

If using the solution-polymerized styrene-butadiene rubber according to the present invention in less than 10% by weight of the raw material rubber, the addition effect is insignificant.

In the rubber composition for tire treads of the present invention, the silica used as the reinforcing agent is preferably used within 100 parts by weight based on 100 parts by weight of the raw material rubber.

The rubber composition for tire treads prepared by using a solution-polymerized styrene-butadiene rubber in the form of polyrotaxane and a reinforcing agent in which cyclodextrin or a derivative thereof is sewn on the rubber chain of the butadiene portion is cyclodextrin or The butadiene moiety rubber chain in which the -OH group or -OR group (here, R = alkyl group or hydroxyalkyl group) possessed by the derivative is strongly bonded to silica added as a reinforcing agent and inserted into the hollow interior of the cyclodextrin or a derivative thereof is As it can have the fluidity according to the characteristics of the rubber itself can be improved while reducing the rolling resistance and wear resistance while maintaining the braking performance on the wet road surface.

In addition to the above components, a compounding agent usually used in a tire tread rubber composition may be added, for example, silica binder, zinc oxide, stearic acid, oil, antioxidant, wax, resin, sulfur, vulcanization accelerator, and the like. can do.

Hereinafter, the content of the present invention will be described in detail through examples. However, the present invention is not limited by the examples.

Comparative Production Example

200 g of styrene, 800 g of butadiene, 100 g of tetrahydrofuran and 5000 g of cyclohexane were injected into a 10 L reactor, and 0.32 g (5 mmol) of normal butyllithium was injected for 2 hours while maintaining the reactor internal temperature at 50 ° C. When the reaction temperature reached the highest temperature, a small amount of butadiene was injected, followed by an additional 1 hour, and the reaction was terminated with methyl alcohol. The polymer obtained in the reaction was put in hot water heated with steam, stirred to remove the solvent, and dried.

Production Example

A solution-polymerized styrene-butadiene rubber was prepared in the same manner as in Comparative Example, except that 5.83 g (15 mmol) of dimethyl-β-cyclodextrin was added before the injection of a small amount of butadiene, and cyclodextrin or a derivative thereof was stitched onto the rubber chain of butadiene. A solution-polymerized styrene-butadiene rubber in the form of polyrotaxane was prepared.

Physical properties of the solution-polymerized styrene-butadiene rubber obtained through the Comparative Preparation Example and Preparation Example are shown in Table 1 below.

Comparative Production Example Production Example Polymerization condition Dimethyl-β-cyclodextrin (g) - 5.83 Rubber property Styrene Content (%) 19 20 Vinyl content of butadiene part (%) 62 59 Number average molecular weight (Mn) 190000 202000 Weight average molecular weight (Mw) 210000 243000 Coupling Efficiency (%) 12 9

Examples and Comparative Examples

Each solution-polymerized styrene-butadiene rubber, silica and other compounding agents obtained through the Comparative Preparation Examples and Preparation Examples were mixed by conventional mixing methods in the mixing ratios shown in Table 2 below, and the mixed rubber was mixed at 160 ° C. for 20 minutes. After quenching, the test specimen was prepared. The physical properties of the rubber composition thus prepared are shown in Table 3 below.

Compounding agent Parts by weight Solution Polymerized Styrene-Butadiene Rubber 100 Silica 70 Zinc oxide 3 Stearic acid 2 Aromatic oils 35 Anti-aging 3 X50-S 12 sulfur 1.2 CZ 1.7 DPG 1.6 Silica: N2SA value of 175 m2 / g, DBP oil absorption 240 mL / 100 gX50-S: 50:50 mixture of N330 carbon black and Si-69 (binder) CZ: N-cyclohexyl-2-benzothiazyl sulfenamide DPG: Diphenylguanidine

Comparative example Example Hardness 73 74 300% modulus 125 130 Tensile Strength (kg / ㎠) 190 205 0 ℃ tanδ 0.363 0.360 60 ℃ tanδ 0.137 0.130 Rambon Wear Index 100 108

It can be seen from the results of Table 3 that the rubber composition according to the present invention has a reduction in rotational resistance and improved abrasion resistance by 60 ° C. tanδ and arambon wear test.

As described in detail above, according to the present invention, a silica rubber composition comprising a solution-polymerized styrene-butadiene rubber in the form of polyrotaxane, in which a cyclodextrin or a derivative thereof is sewn on the rubber chain of the butadiene portion, has a rotational resistance. It is useful as a tire tread rubber by reducing and improving wear resistance.

Claims (3)

In the rubber composition for tire tread containing solution-polymerized styrene-butadiene rubber in the raw material rubber and silica as a reinforcing agent, The solution-polymerized styrene-butadiene rubber is a rubber composition for tire treads, characterized in that the cyclodextrin represented by the following formula (1) or a derivative thereof has a polyrotaxane form sewn on the rubber chain of the butadiene portion. Formula 1 The cyclodextrin of claim 1, wherein the cyclodextrin is α-cyclodextrin or a derivative thereof, β-cyclodextrin or a derivative thereof, or γ-cyclodextrin or a derivative thereof, wherein some -OH groups are -OR groups, wherein R = alkyl group or hydride. A rubber composition for tire treads, which is substituted or unsubstituted with an oxyalkyl group). The rubber composition for tire treads according to claim 1, wherein the solution-polymerized styrene-butadiene rubber is contained in 10 to 100% by weight of the raw material rubber.