KR20050046851A - Rubber composition for tire tread - Google Patents

Abstract

The present invention relates to a rubber tread rubber composition, wherein in the rubber tread rubber composition comprising a raw material rubber, a reinforcing material, a coupling agent, a vulcanizing agent and a vulcanization accelerator, the reinforcing material is 10 to 120 weight of silica based on 100 parts by weight of the raw material rubber Rubber prepared from a composition containing 5 to 20 parts by weight of lipophilic nanoclay modified with a polymer and a polymer is added to the silica as a reinforcing agent by adding a small amount of lipophilic nanoclay to include silica and nanoclay reinforcing agent. In addition to improving the dispersibility and wear performance by solving the problem of deterioration in dispersibility and wear, the braking performance on the wet road surface, which is basically required as a rubber for tire tread, is improved to the same level or higher. Reduction of mass due to small amount of clay replacement also improves rolling resistance performance. Effects can be obtained.

Description

Rubber composition for tire treads

The present invention relates to a rubber tread rubber composition, and more particularly, to a small amount of lipophilic nanoclay surface-modified with silica and polymer as a reinforcing agent to a conventional rubber tread rubber composition to improve dispersibility and abrasion performance. It relates to an improved rubber tread rubber composition.

With the recent development of the tire industry, we are concentrating our technology to produce low fuel consumption, low rolling resistance, and environmentally friendly products. The first interest was to improve the interaction between carbon black and polymers, which are widely used as reinforcing agents.

However, silica has been proposed as a solution to the carbon black because of its limitations. Silica was also not easily miscible with nonpolar rubber due to its strong polarity. By introducing a coupling agent, it was possible to improve the interaction force between silica and polymer, and the tire technology using silica began to develop remarkably.

Coupling agents having two functional groups (also called 'silane couplers') have been known to enhance the reinforcement of inorganic fillers by acting to chemically bond the interaction with inorganic fillers used as polymer reinforcements. In the early days, it was used to improve the reinforcement of glass fiber, which is a reinforcing agent of resin, but in recent years, its use has been expanded to include surface treatment of inorganic materials, solidification of active materials, and manufacture of tires using silica as a reinforcing agent. to be.

Meanwhile, in order to improve wet road surface braking performance and rolling resistance performance, a conventional rubber tread portion uses a carbon black having a large surface area and a large structure or a rubber composition using a large amount of silica.

However, such a rubber composition has a problem in that the silanol groups on the silica surface have strong reactivity and cohesiveness, and thus dispersibility is poor, and rotation resistance and braking performance on wet roads are improved, but wear performance is reduced. In order to improve this, silica may be developed and used with high dispersibility, or amines may be added to improve dispersibility to improve wear performance.

Recently, many attempts have been made to study the effects of new reinforcing agents that can replace small amounts of silica, such as the addition of nanoclays. Research is conducted to improve dispersibility, abrasion performance, and braking performance by partially replacing silica reinforcement with lipophilic nanoclay, which has a layered nanoclay modified by polymer to increase the layer spacing and improve affinity with rubber. It is becoming.

However, in order to evenly disperse the nanoclay in the rubber composition, an effective peeling process is necessary when mixing with the rubber composition, otherwise it has a disadvantage in that it is disadvantageous in terms of dispersibility.

Accordingly, the present inventors, while solving the above dispersion problem in using nanoclay as a rubber reinforcing agent, while trying to manufacture a rubber composition to play a role as a reinforcing agent, using only conventional silica as a rubber reinforcing agent Part of the silica was added to replace the lipophilic nanoclay surface-modified with a side chain ammonium salt having 15 to 30 carbon atoms, the dispersion and wear performance, braking performance and other physical properties were observed to complete the present invention.

Accordingly, it is an object of the present invention to use other types of lipophilic nanoclays which are more advantageous in terms of physical properties than conventional lipophilic nanoclays in rubber compositions containing silica / nanoclay double adjuvant partially substituted for nanoclays. Therefore, to improve the tread area wear performance, wet road surface braking performance and rolling resistance performance of the passenger radial tire, and to provide a rubber composition for a tire tread with improved silica dispersibility.

In order to achieve the above object, the rubber composition for tire treads of the present invention comprises a raw material rubber, a reinforcing agent, a coupling agent, a vulcanizing agent, and a vulcanization accelerator, wherein the reinforcing agent is silica based on 100 parts by weight of the raw material rubber. It is characterized in that it comprises 10 to 120 parts by weight and 5 to 20 parts by weight of lipophilic nanoclays surface-modified with a polymer.

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

The rubber composition of the present invention is a rubber compound for a tire tread in which a reinforcing agent, a coupling agent, a vulcanizing agent, and a vulcanization accelerator are added to the raw material rubber, together with a silica-modified lipophilic nanoclay as a reinforcing agent. .

Specifically, since the raw material rubber includes styrene-butadiene rubber having a glass transition temperature of -50 to -10 ° C, braking performance on wet road surfaces by using raw rubber for styrene-butadiene rubber having a glass transition temperature in the above range. To increase. The styrene-butadiene rubber which can be used in the present invention can be used as long as it has a glass transition temperature in the above range. In addition, it is preferable that the raw material rubber except the styrene-butadiene rubber is butadiene rubber.

The silica used as the reinforcing agent includes a precipitated silica having a CTAB value of 100 to 400 m 2 / g, a BET value of 100 to 400 m 2 / g and a DOP value of 150 to 400 ml / 100 g.

It is preferable to contain the addition amount of a silica in 10-120 weight part with respect to 100 weight part of raw material rubbers. When the content of silica is less than 10 parts by weight based on 100 parts by weight of the raw material rubber, the reinforcing performance is lowered, and when it exceeds 120 parts by weight, there is a problem that the dispersibility and wear resistance decreases.

In addition, the present invention uses a lipophilic nanoclay surface-modified with a polymer together with the silica as a reinforcing agent. The lipophilic nanoclay surface-modified with a polymer is based on the structure shown in Fig. 1, and then the existing clay is finely divided into a plate-like structure and then treated with a polymer to reduce the bonding strength between particles, and when compounding as shown in Fig. 2. It is broken on the rubber to facilitate dispersion.

       The nanoclay used in the present invention is Southern Clay's MMT25A product, modified with a branched ammonium salt having 15 to 30 carbon atoms, and reinforcement, abrasion resistance, and dispersibility of a rubber composition as compared to a nanoclay surface-modified with a conventional polymer. There is an advantage to improve the back.

The nanoclay is preferably added in 2 to 20 parts by weight of the total rubber composition. If the added amount is less than 2 parts by weight, the wear performance of the desired rubber composition does not improve. If the amount exceeds 20 parts by weight, the workability is deteriorated, the rotation resistance is degraded, and the elongation may be deteriorated.

In addition, the rubber composition of the present invention can be added to the coupling agent, softener, vulcanizing agent zinc oxide and stearic acid, vulcanizing agent, vulcanization accelerator and other additives which are added in the conventional tire tread rubber composition as described above. .

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited by the Examples.

Examples 1-3 and Comparative Examples 1-4

As shown in the following Table 1, the raw material rubber, silica, softener, and zinc oxide, stearic acid, nanoclay, vulcanizing agent, vulcanization accelerator, and coupling agent were added at the Banbury mixer after releasing at a constant temperature. .

Specifically, reinforcing agents and coupling agents, nanoclays, zinc oxide, stearic acid, and softeners corresponding to raw rubber 2/3 were added, mixed in a Banbury mixer, and then discharged at 160 ° C. To the blended rubber was added the reinforcing agent, coupling agent and softener corresponding to the remaining amount of 1/3, mixed in a Banbury mixer and then released at 160 ° C.

A vulcanizing agent and a vulcanization accelerator were added to the blended rubber and released after 1 minute and 30 seconds of mixing in a Banbury mixer.

The physical properties of the rubber product thus obtained were evaluated, and the results are shown in Table 2 below.

(Unit: parts by weight) Example Comparative example One 2 3 One 2 3 4 Raw material rubber KBR31 ⁽¹⁾ 33 s-SBR ⁽²⁾ 76 Silica ⁽³⁾ 70 70 60 80 70 70 60 Nanoclay I.44PA ⁽⁴⁾ - - - - 10 5 15 MMT25A ⁽⁵⁾ 10 5 15 - - - - Coupling Agent (Si69) 5.6 5.6 4.8 6.4 5.6 5.6 4.8 Softener (A # 2 Oil) 31 Zinc oxide 3 Stearic acid 2 Antioxidant 1.5 brimstone 1.4 accelerant 1.7 Accelerator (DPG) 2 (1) KBR31: A # 2 oil 37.5 phr extended BR, pattern viscosity 30-40. (2) s-SBR: Tg -50 to -10 degreeC solution-polymerized styrene-butadiene rubber. (3) Silica: Precipitated silica with a CTAB value of 165, a BET value of 175, and a DOP value of 280. (4) Nanoclay I.44PA is a product of Nanocor, surface modified with a polyolefin-based polymer. (5) Nanoclay MMT25A is Southern Clay. Moving product.

Example Comparative example One 2 3 One 2 3 4 300% modulus (MPa) 14.1 12.7 14.8 12.0 13.6 12.5 14.2 Elongation (%) 410 435 400 412 400 430 390 Wear (g) 0.078 0.081 0.077 0.089 0.080 0.082 0.079 Dispersion 92 93 90 89 90 91 89 tan δ (0 ° C) 0.650 0.644 0.655 0.616 0.647 0.639 0.651

In Table 2, the wear degree is PICO abrasion, and 0 ° C tanδ indicates braking characteristics, and the higher the value, the better the braking performance, and 60 ° C tanδ indicates the rotational resistance characteristic. This is excellent.

From the results in Table 2, in the case of the rubber composition according to the present invention, the tensile properties, wear performance, braking performance, and rotational resistance performance of the lipophilic nanoclays surface-modified with silica and polymer than the rubber composition using silica alone as a reinforcing agent It can be seen that it is more advantageous in the case of a rubber composition in which a small amount is substituted. The physical properties of the rubber composition are affected by the type of nanoclay used, which appears to be due to differences in the type of polymer used in the hydrophilization process of the nanoclay.

As described in detail above, in the conventional rubber tread rubber composition comprising silica as a reinforcing agent according to the present invention, in the case of partially adding a lipophilic nanoclay surface-modified with silica and a polymer as a reinforcing agent, problems of silica compounding It can solve the problem of deterioration of phosphorus wear performance, and it improves the braking performance on wet road surface, which is basically required as a rubber for tire tread, and improves the performance of rolling resistance due to the weight reduction by replacing the performance by a small amount. You can get it.

1 shows a lipophilic nanoclay surface modified with a polymer,

Figure 2 shows the process of dispersion during compounding of the surface-modified lipophilic nanoclay with polymer.

Claims (4)

In the rubber composition for tire treads comprising raw rubber, reinforcing material, coupling agent, vulcanizing agent and vulcanization accelerator, The reinforcing material is a rubber composition for tire treads, characterized in that it comprises 10 to 100 parts by weight of silica and 5 to 20 parts by weight of lipophilic nanoclays modified with a polymer. The rubber composition for tire treads according to claim 1, wherein the raw material rubber is styrene-butadiene rubber having a glass transition temperature of -50 to -10 ° C. The tire tread according to claim 1, wherein the silica is a precipitated silica having a CTAB value of 100 to 400 m 2 / g, a BET value of 100 to 400 m 2 / g, and a DOP value of 150 to 400 ml / 100 g. Rubber composition. The rubber composition for tire treads according to claim 1, wherein the polymer used for modifying the nanoclay is a branched ammonium salt having 15 to 30 carbon atoms.