KR100606190B1 - Rubber composition for studless snow tire tread - Google Patents

Abstract

The present invention provides a rubber composition for studless snow tire treads to which poly paraphenylene terephthalamide fiber (poly aramid fiber) is added in the rubber composition, which is due to the high Young's Modulus and tensile strength of the poly aramid fiber. It is not easily detached by impact and plays a role of reinforcing the compounded rubber, and in general, it is possible to prevent abnormal wear and uneven wear, which is a problem in improving the driving and braking performance of ice sheets by applying short fibers or natural fibers as foreign substances. In addition, the ice braking characteristics are improved, which is useful as a studless snow tire tread rubber.

Description

Rubber composition for studless snow tire tread {Rubber composition for studless snow tire tread}             

1 is an SEM photograph of a rubber specimen obtained according to Comparative Example 2,

2 is a SEM photograph of a rubber specimen obtained according to Example 2.

The present invention relates to a rubber composition for studless snow tire tread, and more particularly, to a poly aramid using natural rubber, styrene-butadiene rubber and butadiene rubber, which are used in a conventional rubber composition for studless tire tread. The present invention relates to a rubber composition for a studless snow tire tread having a suitable blend of system fibers and excellent driving force and braking force on a winter snow road.

Conventional winter tires are roughly divided into spike tires and studless tires, and double spike tires have spike pins mounted on the treads for the purpose of increasing friction in ice and snow areas. All. However, in the case of tires with spike pins, driving on general roads other than ice and snow roads will not only result in poor riding comfort, but also cause environmental pollution such as noise, dust, and road damage. In the case of a tire with a rubber spike, the wear of the pin is faster than that of the tread rubber, and the tire is easily broken during use. In addition, attempts have been made to improve the braking performance on the ice surface by using an auxiliary device or a new polymer in addition to the spikes, and efforts to improve the new patterns and structures have shown significant effects, but these require further improvement. It is true. In addition, products that use rubber spike pins that control the glass transition temperature and harden at room temperature to act as micro spikes are commercially available, and some products employ silica that improves braking power on wet roads and reduces fuel consumption.

On the other hand, the studless tire includes a general studless tire, a studless tire using an organic blowing agent, and a studless tire using other foreign substances. The studless tire using the double organic blowing agent is manufactured by mixing and vulcanizing the organic blowing agent in the tread rubber of the tire, and the ground area between the ground and the tread is wide due to the micro-cell effect caused by the pores generated during the vulcanization. It has been introduced under the concept of reducing the braking distance and preventing slippage on the snow surface by increasing friction and improving ice grip. However, even if the foaming itself is effective in improving the performance on the snow surface, the tread block stiffness is weakened and wear resistance is lowered. In addition, at the end of the tire use, there is a problem in that the driving and braking performance on the ice snow road deteriorates due to an increase in block stiffness and hardness due to aging. In addition, when the foreign matter is applied to the product, because the foreign matter dispersed in the tread rubber composition is not chemically bonded to the base rubber, but physically bonded, the separation phenomenon is serious, resulting in irregular wear. For example, when foreign tires such as short fibers and natural fibers were applied to tread rubber, tires with improved winter performance appeared, noise was reduced, and environmental problems such as road damage were somewhat resolved. Since the shape is spherical, it is easily separated by an external impact while driving, causing irregular abnormal wear and partial wear. Such a problem shortens the life of the tire and causes performance deterioration, leading to consumer complaints.

Therefore, the inventor of the present invention, while trying to solve the problems of the prior art as described above, even when using a short fiber or natural fiber by applying a foreign matter to the rubber composition for the tire tread can improve the ice sheet driving and braking performance Wear, rotational resistance, and adjustment stability, which are other major performance demands of tires, are difficult to satisfy, and the use of Poly-Aramid fibers instead prevents abnormal wear and wear of the tires. The polyaramid fiber has been found to improve the ice sheet braking properties to complete the present invention.

When the poly aramid fiber is used in the tire tread rubber composition, the driving and braking force on the ice snow surface can be basically improved as compared to the non-use. In the case of fibers, they are oriented linearly as they are due to high Young's Modulus and tensile strength, so they are not easily released by external impact, and also reinforce the compounded rubber due to high Young's Modulus and tensile strength. Done.

The rubber composition for studless snow tire tread of the present invention for achieving the above object is made of natural rubber, styrene-butadiene rubber and butadiene rubber, which are used in the conventional rubber composition for studless tire tread, and made of poly aramid. It is characterized by including para-Aramid fiber which is a system fiber within 10 weight part with respect to 100 weight part of rubber powder.

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

The raw material rubber of the rubber composition for tire treads according to the present invention is natural rubber, styrene-butadiene rubber and butadiene rubber. More specifically, natural rubber literally refers to rubber obtained in nature.

Styrene-butadiene rubber is produced by the emulsion polymerization method, the styrene content in the microstructure composition of 20 to 25%, 100 ℃ Mooney viscosity of 55 to 65, the stress relaxation time slope is -0.30 to-0.38. If the Mooney viscosity of styrene-butadiene rubber is high, processing is difficult. In addition, when the styrene content or the stress relaxation time slope in the microstructure composition is out of the above range, the workability is poor. Styrene-butadiene rubber that satisfies these characteristics can improve ice-braking performance and rolling resistance while maintaining wear resistance.

In addition, butadiene rubber constituting the raw material rubber is a diene rubber prepared by a solution polymerization method, butadiene rubber having a 1,4-cis butadiene content in the fine composition of 96% or more.

The raw material rubber thus prepared contains carbon black or silica as a process oil and a reinforcing agent, and a general additive, wherein the process oil has an aromatic content of 5 to 25% in oil and 25 to 45% by weight of naphthenic material. It is preferable that the paraffin content is 35 to 65% by weight. If the composition of the process oil is outside the above range and the aromatic content is increased, the ice sheet braking performance is poor.

In addition, carbon black and silica added as a reinforcing agent are not specifically limited, The content is 40-90 weight part with respect to 100 weight part of raw material rubber. If the content is less than 40 parts by weight based on 100 parts by weight of the raw material rubber, the rolling resistance is improved, but the ice sheet braking performance is poor. If the content is more than 100 parts by weight, the workability is poor due to poor dispersion of carbon black and silica and the heat generation is increased. The adverse effect of poor wear resistance occurs.

In the present invention, the poly aramid fiber is para aramid, para aramid is poly paraphenylene terephthalamide (poly parapheylene terephthalamide), Young's modulus has a mechanical property of 24 ~ 30GPa, tensile strength 2400 ~ 3000MPa.

This para-aramid fiber acts as a stud used in stud tires in rubber, which improves braking and driving power on ice-covered roads. Unlike traditional short or natural fibers, Young's Modulus and tensile strength It is strong and is arranged in a linear rather than spherical shape in the compounding rubber so that it does not lead to a decrease in wear performance.

The content is within 10 parts by weight based on 100 parts by weight of the raw material rubber, preferably 2 to 10 parts by weight. If the content of para aramid exceeds 10 parts by weight with respect to 100 parts by weight of the raw material rubber, the workability is poor, and due to excessive use, the dispersibility is poor in rubber, so that the wear resistance is adversely affected.

On the other hand, in the present invention, the "normal additive" usually means zinc oxide, stearic acid, sulfur, anti-aging agent or the like added to the rubber for tire tread.

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

Examples 1-2 and Comparative Examples 1-3

A rubber composition was prepared by combining natural rubber with styrene-butadiene rubber, butadiene rubber, carbon black, and conventional additives in the component ratios shown in Table 1 below. This was vulcanized to prepare a rubber specimen. In Table 1, a unit is PHR.

Low temperature hardness test, ice friction coefficient, viscoelasticity, etc. were measured for the obtained specimens, and the results are shown in Table 1 below. In addition, the surface of the rubber was observed using SEM, and photographs of the rubber surfaces of Comparative Example 2 and Example 2 are shown in FIGS. 1 and 2, respectively.

In the evaluation, the low temperature hardness was measured after standing for 1 hour in a chamber capable of temperature control with an ASTM Shore A durometer (hardness at -20 ° C).

The ice friction coefficient was measured at a speed of 30 km / hr on an ice road surface frozen by a dynamic friction tester (manufactured by sunny Koken) for 24 hours.

The abrasion test was measured using a rambon abrasion tester, and the higher the index, the better the wear performance.

The braking performance index is a value obtained by converting tires manufactured according to the 195 / 65R 15T standard using a rubber composition on various road surfaces and converting the results into indices. The larger the index, the shorter the braking distance.

Comparative Example 1 Comparative Example 2 Comparative Example 3 Example 1 Example 2 NR / BR / SBR Carbon Black / Silica Process Oil * Zinc Oxide Stearic Acid Antioxidant Short or Natural Fiber Para Aramid ** 50/30/20 40/20 25 3 2 2-- 50/30/20 40/20 25 3 2 2 4- 50/30/20 40/20 25 3 2 2-12 50/30/20 40/20 25 3 2 2-4 50/30/20 40/20 25 3 2 2-8 -20 ℃ Hardness Ice Friction Coefficient Rambon Wear Index 50 0.35 100 51 0.41 93 55 0.42 92 51 0.40 101 52 0.45 99 Actual vehicle test result Snow / ice braking dry road braking wear resistance 100 100 100 105 95 93 106 95 92 105 100 105 110 99 98 Process oil: Process oil consisting of 5-25% aromatics, 25-45 wt% naphthenic, 35-65 wt% paraffinic ** Para aramid: poly paraphenylene terephthal Amide, Young's modulus 24GPa, tensile strength 2400 to 3000Mpa, trade name Twaron

From the results of Table 1, comparing Comparative Example 1 and Comparative Example 2 shows that the braking on the snow ice road surface is much improved compared to not using them when short fibers or natural fibers are used, while wear resistance is deteriorated. Characteristic

On the other hand, when using the poly aramid fiber as in Examples 1 and 2, the snow ice performance is improved as existing short fibers or natural fibers and at the same time has the characteristics of maintaining the wear resistance.

This is because the short shear or natural fibers do not preserve the shape of the fiber due to the high shear force required for rubber compounding, while the polyaramid fiber is oriented in the original shape due to the high Young's modulus and tensile strength. This is because it is not easily released by external impact and also serves to reinforce the compounded rubber due to high Young's modulus and tensile strength.

In the case of Comparative Example 3, an excessive amount of poly aramid fiber is used. In this case, the hardness at low temperature is excessively increased and the enveloping performance with the road surface is reduced, so that the braking performance is reduced on the snow ice road surface. As a result, it can be seen that poor dispersion occurs in the compounded rubber and the wear performance is lowered.

As described in detail above, the rubber composition comprising para-aramid fibers, which are poly aramid fibers according to the present invention, is not easily separated by external impact due to high Young's Modulus and tensile strength of the poly aramid fibers, It is possible to prevent abnormal wear and uneven wear, which is a problem in improving ice driving and braking performance by applying short fibers or natural fibers as foreign materials, and also improves ice braking characteristics. It is useful as a tire tread rubber.

Claims (4)

(Correction) In a tread rubber composition of a studless tire comprising natural rubber, styrene-butadiene rubber and butadiene rubber as raw material rubber, A rubber composition for studless snow tire treads, comprising 20 to 30 GPa of Young's Modulus and 2 to 10 parts by weight of linear poly paraphenylene terephthalamide having a tensile strength of 2400 to 3000 MPa based on 100 parts by weight of the raw material rubber. (delete) A stud according to claim 1, comprising a process oil comprising an aromatic content in the oil of 5 to 25%, a naphthenic content of 25 to 45% by weight, and a paraffinic content of 35 to 65% by weight. Rubber composition for lease snow tire tread. The rubber composition for a studless snow tire tread according to claim 1 or 3, wherein the reinforcing agent is included in an amount of 40 to 90 parts by weight based on 100 parts by weight of the raw material rubber.

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