KR20030043361A - Tire tread rubber composition - Google Patents

Abstract

PURPOSE: A rubber composition for a studless tire tread is provided, to maximize the braking property on an icy or snowy road without deterioration of the braking property and the abrasion resistance on a dry road. CONSTITUTION: The rubber composition comprises 100 parts by weight of a diene-based rubber containing a polybutadiene rubber and a natural rubber; silica and carbon black as a reinforcing agent; 1-15 parts by weight of a water-soluble polymer resin; and 1-10 parts by weight of a metal salt. Preferably the water-soluble polymer resin is selected from the group consisting of hydrophilic acryl-based polymer, poly(vinyl alcohol) and polyoxyethylene, and has a diameter of 1-200 micrometers in the rubber composition, a glass transition temperature of 50-90 deg.C and a melting point of 150-250 deg.C; and the metal salt is Al2(OH)3 or Fe2(OH)3, and has a diameter of 0.01-1 micrometers in the rubber composition.

Description

Rubber tread rubber composition for studless tire treads

The present invention relates to a rubber composition for studless tire treads, and more particularly, to a rubber composition for studless tire treads that maximizes braking performance on ice / snow while maintaining braking and wear resistance on dry road surfaces. .

Snow tires are usually divided into stud tires with spike pins embedded in them and studless tires without spike pins. Recently, as the social necessity of the stud tire is raised in accordance with the regulation of the stud tire due to environmental problems, a wide examination of the tread rubber composition having excellent ice / snow braking property has been made.

The conventional snow studless tire tread rubber composition uses micro-spikes at room temperature by adjusting the glass transition temperature of the tread to improve ice / snow braking, and foamed rubber on the tread surface, and natural rubber or poly There were foam rubber tires used in a rubber composition mainly comprising butadiene rubber, emulsion polymerization styrene-butadiene rubber and carbon black.

However, when foamed rubber is used, there is a problem in that braking and steering stability on dry roads are reduced, and wear resistance is also reduced. In order to improve such degraded wear performance, polybutadiene rubber is usually increased, and in this case, it has a property of reducing braking property on dry or wet road surfaces.

In order to solve this problem, a method of using silica instead of carbon black as a filler has been widely used in recent years.

However, when silica is used as a filler, the particles do not disperse well due to hydrogen bonding of silanol groups, which are functional groups on the surface of silica, and tend to aggregate with each other. The problem of this deterioration remains. In addition, insufficient dispersion of silica into rubber increases the Mooney viscosity of the rubber composition, greatly reducing extrusion processability, and decreases the total length of the extrudate as time passes after extrusion, which leads to problems in tire molding and less dispersed silica. This causes a problem that the wear performance is lowered.

In order to solve this problem, a water-soluble polymer may be added. As an example of this, Japanese Patent Application Laid-Open No. 2000-80206 discloses a tire obtained by including 50 to 150 parts by weight of silica, 4 to 15 parts by weight of a silane coupling agent, and 5 to 20 parts by weight of a water-soluble absorbent resin, based on 100 parts by weight of a rubber component. Tread rubber compositions have been disclosed. Further, Japanese Laid-Open Patent Publication No. 2000-191832 discloses a rubber composition comprising a matrix rubber containing at least one rubber component selected from natural rubber and diene-based synthetic rubber, and a water-soluble resin having a melting point of 120 to 200 ° C. have. Japanese Laid-Open Patent Publication No. 2000-191830 discloses a matrix rubber having at least one rubber component selected from natural rubber and diene-based synthetic rubber, at least 95 mole% being a vinyl alcohol unit and a vinyl acetate unit. A rubber composition comprising a water-soluble polyvinyl alcohol-based resin in the range of 5 to 30 mol% is disclosed, wherein the polyvinyl alcohol-based resin is short fibers having a length of 1 to 10 mm and a diameter of 10 to 100 μm.

Thus, when the water-soluble polymer resin is added, it is possible to maximize the ice / snow braking performance and at the same time improve the braking performance and wear performance on the dry road surface. Specifically, the water-soluble polymer resin may be expected to have an effect such as forming a micro cell on the rubber surface by dissolving the water-soluble resin connected with natural rubber or polybutadiene rubber with water on the ice / snow road surface. In addition, since the entire rubber does not have a microcell like foam rubber, that is, only water-soluble molecules on the rubber surface react with water to dissolve, thereby improving braking property and wear reduction on the dry road surface of conventional foam rubber. do.

The present invention is to improve the composition that improved the braking on the ice / snow surface and the braking property on the dry road surface and the wear reduction by using a water-soluble polymer resin as described above, by adding a metal salt to form irregularities on the rubber surface The purpose is to improve the roughness of the rubber surface.

That is, the present invention forms a microcell using a water-soluble polymer resin and simultaneously forms a micro spike by adding a metal salt, thereby maintaining braking and abrasion resistance on a dry road surface, and at the same time ice / snow road surface when using the water-soluble polymer resin alone. It is an object to provide a rubber composition for tire treads that can further maximize the braking properties in the.

The rubber composition for tire treads of the present invention for achieving the above object comprises a diene rubber containing polybutadiene rubber and natural rubber as the main component rubber, and includes silica and carbon black as a reinforcing agent, wherein the water-soluble polymer resin To 1 to 15 parts by weight based on 100 parts by weight of the diene rubber, and a metal salt is added to 1 to 10 parts by weight based on 100 parts by weight of the diene rubber.

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

As the main component rubber in the rubber composition of the present invention, a diene rubber used in a conventional snow studless tire tread rubber composition is used. Specifically, natural rubber and polybutadiene rubber are used.

Since silica and carbon black are used here as a reinforcing agent, silica is used in an amount of 5 to 80 parts by weight based on 100 parts by weight of the diene rubber, and specifically, silica prepared by the sedimentation method is used. Although silica is not specifically limited, It is preferable that BET surface area is 130-250 m <2> / g, CTAB surface area is 130-190 m <2> / g, and DBP oil absorption amount is 180-280 ml / 100g. Carbon black is used in an amount of 5 to 80 parts by weight based on 100 parts by weight of the diene rubber, which preferably has a DBP oil absorption of 10 to 150 ml / 100 g and a nitrogen adsorption specific surface area of 110 to 140 m 2 / g.

On the other hand, the water-soluble resin used in the present invention is used in 1 to 15 parts by weight with respect to 100 parts by weight of the diene rubber, hydrophilic acrylic polymer, polyvinyl alcohol, polyoxyethylene and the like are used as possible water-soluble resin material. The water-soluble resin is present in the form of a white or pink powder, and is easily dissolved by water. Such water-soluble resins are commonly used in the rubber composition having a diameter of 1 to 200 µm, a glass transition temperature of 50 to 90 ° C, and a melting point of 150 to 250 ° C.

In general, the addition of a water-soluble resin to the tire tread composition is intended to apply the water-soluble property of such a water-soluble resin. In other words, the water-soluble resin connected to the diene-based rubber reacts with the moisture present on the snow / ice road surface to dissolve and fall off, thus creating a kind of microcell on the surface of the rubber, thereby producing the same performance as the snow / ice road surface. Will be shown in. On the other hand, the water-soluble resin present in the rubber composition to which such a water-soluble resin is added does not exist in the form of foamed rubber because it cannot react with water, and because it exists as a kind of filler in ordinary rubber, foamed rubber In use, the block strength of the rubber is weakened by the microcell, so that the braking performance and the wear performance are not reduced on the dry road surface.

If the water-soluble resin that plays such a role is used in less than 1 part by weight based on 100 parts by weight of the diene rubber, the effect of addition is insignificant, and when used in excess of 15 parts by weight, too much microcells are formed on the rubber surface. Due to melting) may cause a problem of deterioration of braking performance and abrasion resistance on dry road surfaces.

On the other hand, in the present invention, the metal salt is added to maximize the effect of the water-soluble polymer resin as described above.

Al ₂ (OH) ₃ or Fe ₂ (OH) ₃ or the like may be used as the metal salt, and the content thereof is preferably 1 to 10 parts by weight based on 100 parts by weight of the diene rubber.

When metal salts are added, the metal salts connected to the diene rubber form microscopic spike pins on the rubber surface. The metal salts protruding above the surface of the rubber form fine uneven portions to scrape the surface of the ice like spike pins, thereby improving the ice performance of the tire.

If the added amount of the metal salt that plays such a role is less than 1 part by weight, the addition effect is insignificant. If it is added more than 10 parts by weight, too many spike pins are formed, thereby reducing the braking performance on the dry road surface (lack of enveloping between road surface and rubber) Or wear resistance may be degraded.

As a result, in the present invention, a microcell is formed by applying a water-soluble resin, and a metal spike is added thereto to form a micro spike pin to maximize ice / snow performance.

Meanwhile, in the present invention, compounding agents usually added to the rubber tread composition, for example, processing oil, coupling agent, zinc oxide, stearic acid, anti-aging agent, sulfur, vulcanization accelerator, etc. can be used.

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 1-3 and Comparative Examples 1-7

Next, a studless tire was manufactured using a tread rubber composition blended using the compounding ingredients shown in Table 1, and various specimens were prepared using the rubber composition to measure main physical properties. Specific measurement methods are as follows, and the results are shown in Table 2 below.

1) Low Temperature Hardness: Measured after 1 hour in a chamber with temperature control by ASTM Shore-A hardness tester

2) Ice friction coefficient: Friction coefficient measured at a speed of 30 km / hr on an ice road surface frozen for 24 hours using a dynamic friction tester (manufactured by Sunny Koken)

3) Rambon Abrasion Index: A measure of wear resistance, which indicates the amount of rubber in worn rubber.The larger the index, the better the wear resistance.

4) Braking Performance Index: The tires manufactured in 195 / 65R 15T standard using the rubber composition were subjected to braking tests on various road surfaces, and the results were converted into indices. The larger the index, the shorter the braking distance.

5) Abrasion performance index: The tire is made of 195 / 65R 15T standard using a rubber composition after converting the wear after a certain distance in terms of the index, the larger the index, the better the wear performance.

(Unit: parts by weight) Example Comparative Example One 2 3 One 2 3 4 5 6 7 NR / BR 60/40 60/40 60/40 60/40 60/40 50/50 60/40 60/40 60/40 60/40 Carbon / silica 40/15 40/15 40/15 40/15 25/30 40/15 55 /- 40/15 40/15 40/15 Processing oil 28 28 28 28 28 28 28 28 28 28 Coupling agent 2.4 2.4 2.4 2.4 4.8 2.4 - 2.4 2.4 2.4 Zinc oxide 4 4 4 4 4 4 4 4 4 4 Stearic acid 2 2 2 4 2 2 2 2 2 2 Anti-aging 4 4 4 4 4 4 4 4 4 4 Water soluble resin 5 15 7 - - - - 5 17 - Metal salt 5 3 10 - - - - - - 12 blowing agent - - - - - - 5 - - - sulfur 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 Accelerator 1 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 Accelerator 2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 NR: Natural rubber with the brand name SIR20 BR: Polybutadiene rubber, Kumho Petrochemical Carbon: Brand name N234, Korea Carbon Zesilica: Trade name Zoesil 175GR, Coplanage Co., Ltd. Ring agent: bis (triethoxy silyl propyl) tetra sulfide, degussa anti-aging agent: 6-C (N-phenyl-N '-(1,3-dimethyl butyl) -p-phenylene diamine foaming agent: oxy bissulfonyl Hydrazide (OBSH) water-soluble resin: polyvinyl alcohol having a diameter of 10 μm in a rubber composition, Tg 58 ° C., melting point 170 ° C., trade name P24S, a metal salt made by Tong Yang Chemical Co., Ltd .: A1 having a diameter of 0.1 μm in a rubber composition ₂ (OH) ₃ Promoter 1: CBS, Promoter 2: DPG

(Unit: parts by weight) Example Comparative Example One 2 3 One 2 3 4 5 6 7 Hardness (-20 ℃) 54 52 56 59 62 60 54 57 52 55 Ice friction coefficient 0.41 0.49 0.46 0.26 0.33 0.32 0.38 0.37 0.49 0.47 Rambon Wear Index 101 99 98 100 90 106 82 103 82 89 195 / 65R 15T Standard Vehicle Evaluation Snow / Ice Braking 130 137 133 100 105 106 116 120 135 132 Dry road 105 100 101 100 102 92 86 106 87 90 Wear resistance 103 99 102 100 91 105 88 104 85 87

From the results in Table 2, it can be seen that the physical properties and performance of the embodiments of the present invention are superior to those of the comparative example. Specifically, when silica is increased (Comparative Example 2) compared to Comparative Example 1, it can be seen that the ice / snow performance is improved, but the abrasion performance is lowered because the dispersibility of silica is poor. In addition, when the polybutadiene rubber is increased as in Comparative Example 3, the snow / ice braking and abrasion resistance may be improved, but the braking performance on the dry road surface may be lower than that of Comparative Example 1. And, in the case of using the foam rubber as in Comparative Example 4, it can be seen that the snow / ice performance is excellent, but the result is that the braking resistance and wear resistance on the dry road surface is reduced.

When using a water-soluble resin as in Comparative Example 5 it can be seen that compared to Comparative Example 1 can maximize the snow / ice performance without deterioration of braking performance and wear performance on the dry road surface. However, when using a metal salt at the same time as the water-soluble resin as in the embodiments of the present invention it can be seen that the snow / ice performance is much improved than when using the water-soluble resin alone.

As described in detail above, according to the present invention, when a metal salt is added together with a water-soluble resin to a tire tread composition including a common diene-based rubber as a main raw material and carbon black and silica as a reinforcing agent, the water-soluble polymer resin may form a microcell. By forming micro spikes at the same time due to the metal salt, it is possible to maintain the braking resistance and the wear resistance on the dry road surface and at the same time maximize the braking performance on the ice / snow road surface than using the water-soluble polymer resin alone.

Claims (3)

In a studless tire tread rubber composition comprising a diene-based rubber containing polybutadiene rubber and natural rubber as a main component rubber and containing silica and carbon black as reinforcing agents, A water-soluble polymer resin is added to the composition so as to add 1 to 15 parts by weight with respect to 100 parts by weight of the diene rubber, and a metal salt is added so as to add 1 to 10 parts by weight with respect to 100 parts by weight of the diene rubber. Tread rubber composition. The water-soluble polymer resin according to claim 1, wherein the water-soluble polymer resin is selected from the group consisting of hydrophilic acrylic polymer, polyvinyl alcohol and polyoxyethylene, and has a diameter of 1 to 200 µm and a glass transition temperature of 50 to 90 in the rubber composition. And a melting point of 150 to 250 ° C. 2. The studless tire tread rubber composition according to claim 1, wherein the metal salt is composed of A1 ₂ (OH) ₃ or Fe ₂ (OH) ₃ as a main raw material, and has a diameter of 0.01 to 1 m in the rubber composition.