KR100464730B1 - Tire tread rubber composition - Google Patents

Abstract

The present invention relates to a rubber tread rubber composition with a maximum improvement in braking performance while minimizing sacrifice of abrasion resistance and rolling resistance performance, which has a styrene content of 38-42% by weight and an emulsion in which aromatic oils are inherited. A rubber composition comprising styrene-butadiene rubber prepared by polymerization in a base rubber and containing carbon black and silica as a reinforcing agent.

Description

Tire tread rubber composition

The present invention relates to a rubber composition for tire treads, and more particularly, to a rubber composition for tire treads that maximizes braking performance while minimizing sacrifice of wear resistance and rolling resistance performance.

Most of the development of tires can be concentrated on the structural aspects and the development of application technology of materials used for tires. In particular, most researches have been made on the development of tires that focus on energy saving aspects and environmental problems.

In recent years, the tire development direction that has been made in terms of materials includes low fuel cost tires, high wear resistance tires, high braking tire development, chip cut resistance, and tire development combining these characteristics.

However, quality problems that appear directly to consumers in the tire market can be classified into three or four types, and the most problematic quality problems are braking performance and wear resistance performance.

These two performances are the trade-off performance of the tread rubber composition for passenger cars as well as the rolling resistance performance of the tire. In general, when the abrasion resistance of the tread rubber is improved, the rolling resistance performance and the braking performance are essentially deteriorated. Many studies have been made to overcome this problem, and the main development directions are the development of polymers used as base rubbers and fillers used as reinforcing agents.

In particular, the recent tire rubber compounding technology is concentrated on a combination technology between these characteristics, and for this purpose, research and development applying many new materials recently developed have been attempted.

For example, Japanese Patent Laid-Open Nos. 55-12133 and 56-127650 disclose rubber compounding compositions in which high vinyl butadiene (hereinafter referred to as V-BR) is particularly applied, and 57-55204 and 57. -73030 discloses a rubber compounding composition applying high vinyl styrene-butadiene (hereinafter referred to as V-SBR), but these exhibit high moisture damping and low heat generation properties, but exhibit inferior wear resistance.

The development of polymers was mainly made by Japanese companies, and the solution polymerization SBR rubber was developed, which was a chance to rapidly improve braking performance and rolling resistance. In addition, coupled polymers have been developed to improve rotational resistance performance. A representative polymer thereof is a polymer such as NS116 developed by Nippon Zeon of Japan.

On the other hand, the low affinity of the solution-polymerized rubber, that is, the low affinity with the reinforcing agent carbon black, shows a very low processability in the mixing process. It began to develop polymers substituted with hydroxyl or carboxyl groups in the side chain.

Of course, polymers substituted with hydroxyl or carboxyl groups add to the need for development by using silica as a reinforcing agent, and representative polymers are modified polymers developed at Bayer, Germany, Ameripol Synpol, and Asahi Chem, Japan.

In addition, Japanese Patent Laid-Open Nos. 61-141741 and 61-42552 also use V-SBR, but it is known that they do not solve inferior abrasion resistance performance. Therefore, when it is difficult to expect the improvement of physical properties through the polymer, the problem was solved through the application of new carbon black. For example, in Patent Publication No. 59-2451, the minimum unit in which carbon black exhibits a reinforcing effect in the formulation is not only a conventional method of using carbon black having a small particle size or reducing the amount of carbon black used. By applying the results of the research, the aggregate size level, the inventors invented a compound composition that mainly maintained other characteristics (high wear resistance and high braking resistance) and improved low fuel efficiency and in situ mixing processability, but also did not significantly increase wear resistance.

In another aspect, the developed material uses silica instead of carbon black as a filler.

Wear resistance decreased to some extent by using silica instead of carbon black, but rotational resistance and braking performance in tires, especially braking performance on wet roads, were dramatically improved.

Of course, some advanced carbon blacks have been developed to overcome the main advantages of silica, such as rotational resistance and braking performance on wet roads, but they do not overcome the advantages of using silica and coupling agents.

The present invention is applied to the diene rubber which can improve the braking force by changing the content of the existing microstructure to solve the problems as described above, and the difficulty of field processability, molecular structure characteristics, molecular weight distribution control and dielectric oil By overcoming and improving the wear resistance through this, the present invention has been found to minimize heat generation characteristics and rotational resistance deterioration and to improve braking performance on wet roads.

Accordingly, an object of the present invention is to provide a rubber tread composition for tire tread that maximizes the braking performance on wet road surface while minimizing the sacrifice of wear resistance and rolling resistance performance.

The rubber composition for tire treads of the present invention for achieving the above object is made by adding a reinforcing agent and a conventional additive to 100 parts by weight of the base rubber, wherein the base rubber is a glass transition to the diene rubber prepared by the emulsion polymerization method Temperature is -40 ~ -20 ℃, styrene content is 38 ~ 43% by weight, stress relaxation time slope (logT / log time) is 0.30 ~ 0.34, Mooney viscosity is 55 ~ 65, aromatic oil is rubber Styrene-butadiene rubber inherited at 48 to 52 parts by weight with respect to 100 parts by weight of solid content, and 20 to 40 parts by weight of silica and 40 to 70 parts by weight of carbon black are used as the reinforcing agent based on 100 parts by weight of the base rubber rubber solid content. It is characterized by.

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

The present invention relates to a rubber tread composition for tire treads to maximize the braking performance while minimizing the sacrifice of wear resistance and rolling resistance performance.

The most problematic quality problem for passenger car tires is rolling resistance, braking performance and wear resistance. Some measures to improve these performances at the same time can be solved by improving the raw material properties, but some can be solved by using the technology of using and blending some improved raw materials.

The present invention relates to a tread rubber composition for tires using some improved polymers and high-strength agents and applying a blending technique to minimize rotational resistance performance and wear resistance and to maximize braking performance.

As the base rubber, SBR manufactured by the emulsion polymerization method is used as the base rubber.

Here, the SBR prepared by the emulsion polymerization method has a glass transition temperature of -40 to -20 ° C, a styrene content of 38 to 42% by weight in the microstructure, and 48 to 52% by weight of an aromatic oil, and thus, stress relaxation time. It is a diene rubber produced by 70-100% by weight of styrene-butadiene rubber having a slope of 0.30 to 0.34 and a Mooney viscosity of 55 to 65 and a solution polymerization method.

As the reinforcing agent, the CTAB value was 180 to 190 m 2 / g, the surface area of iodine adsorbed particles was 194 to 210 m 2 / g, the DBP oil absorption was 129 to 139 ml / 100 g, and the C-DBP oil absorption was 110 ml / 100 g or more. It has a coloring power of 143 to 153, a nitrogen adsorption particle surface area (N2SA) of 210 m 2 / g or more, an STSA (particle surface area using a statistical method) of 185 to 195 m 2 / g, and a STSA-N2SA (surface activity) of 25 Carbon black having the following characteristics is used in an amount of 40 to 70 parts by weight based on 100 parts by weight of the base rubber, and silica is used in commercially available Z-175 (produced by Rodia) to improve braking performance and rolling resistance. It is preferable that it is 20-40 weight part with respect to 100 weight part of rubber-rubber solid content.

Of course, it is also possible to use additives commonly used in tire rubber. Examples of additives include anti-aging and vulcanizing agents, accelerators and the like.

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

Example 1 and Comparative Examples 1-10

Styrene-butadiene rubber, butadiene rubber, carbon black and conventional additives were formulated in the component ratios shown in Table 1 below to prepare a rubber composition. This was vulcanized to prepare a rubber specimen.

The component ratio unit of the composition of Table 1 is PHR. For the blending method, the method used in ASTM 3185-99 was used for convenience.

In addition, the characteristics of the styrene-butadiene rubber used in the composition of Table 1 are shown in Table 2 below.

Example 1 Comparative Example One 2 3 4 5 6 7 8 9 10 Butadiene rubber - - - - - - 20 30 30 30 30 Styrene-butadiene rubber A - 137.5 - - - - - - - - - B - - 137.5 - - - - - - - - C - - - 150 - - - - - - - D 150 - - - - - 120 105 105 105 105 E - - - - 150 - - - - - - F - - - - - 137.5 - - - - - Carbon black 70 70 70 70 70 70 70 60 50 30 90 Silica (Z-175) 20 20 20 20 20 20 20 30 40 40 40 Aromatic oils - 12.5 12.5 - - 12.5 10 15 15 15 15 Zinc oxide 3 3 3 3 3 3 3 3 3 3 3 Stearic acid One One One One One One One One One One One brimstone 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Vulcanization accelerator (TBBS) 1.7 1.7 1.7 1.7 1.7 1.7 1.7 1.7 1.7 1.7 1.7 Carbon black: CTAB value is 180-190 m 2 / g, iodine adsorption particle surface area is 194-210 m 2 / g, DBP oil absorption is 129-139 ml / 100 g, C-DBP oil absorption is 110 ml / 100 g or more, Colored power of 143 to 153, nitrogen adsorption particle surface area (N2SA) of 210 m 2 / g or more, STSA (particle surface area using statistical method) of 185 to 195 m 2 / g and STSA-N2SA (surface activity) of 25 or less To have.

Mooney viscosity (ML _{1 + 4} , 100 ℃) Slope of stress relaxation time, 100 ℃ Aromatic oil content (parts by weight based on 100 parts by weight of rubber solids) Styrene Content (%) Glass transition temperature (-℃) Styrene-butadiene rubber A 52 0.36 to 0.38 27.3 23.5 56 B 43 0.36 to 0.38 27.3 40.0 38 C 52 0.35 to 0.37 50.0 40.0 39 D 61 0.30 to 0.34 50.0 42.0 31 E 70 0.29-0.31 48.0 42.0 30 F 70 0.27 to 0.29 27.3 23.5 57 Butadiene rubber 44 - 1,4-cis butadiene content 95% or more Mooney viscosity and stress relaxation time slope were measured using MV-2000E manufactured by Monsanto.

Example 1 Comparative Example One 2 3 4 5 6 7 8 9 10 Rheometer + 5 min. 21.6 24.2 26.1 22.4 17.5 19.2 25.7 22.4 24.4 22.1 20.4 Rhemeter + 90min. 12.7 14.2 14.3 13.6 12.5 11.5 12.4 13.1 12.5 12.4 12.6 Compound Mooney Viscosity, 125 ℃ 70 56 56 66 74 73 64 75 74 64 77 Tensile Properties (Room Temperature) Hardness (Shore A) 76 68 69 74 72 75 76 77 78 78 78 300% Modulus Index (kg / ㎠) 108 100 99 121 117 135 127 135 128 96 134 Cutting strength index 113 100 118 112 120 115 112 113 114 98 118 Elongation at break index 99 100 87 109 78 85 99 96 77 120 90 Tear Index 121 100 94 110 112 89 121 145 121 96 104 Breaking energy index 126 100 86 120 98 94 118 138 112 98 111 Tensile Properties (Aging) Hardness (Shore A) 72 60 60 68 77 77 66 77 76 68 80 300% Modulus Index (kg / ㎠) 134 100 92 130 145 118 108 144 168 77 132 Cutting strength index 124 100 92 119 114 105 98 161 152 80 128 Elongation at break index 105 100 86 110 75 78 89 94 81 121 109 Tear Index 118 100 93 105 86 89 86 122 83 87 109 Breaking energy index 124 100 87 103 89 85 88 132 79 76 131 Rambon Wear Index 101 100 84 92 97 91 111 112 111 115 93 Fever index 111 100 98 105 101 98 101 98 99 94 108 Surface roughness 5 4 5 5 One One 3 4 One 5 One 0 ℃ tanδ 0.25 0.24 0.27 0.25 0.26 0.26 0.26 0.27 0.27 0.29 0.30 60 ℃ tanδ 0.16 0.14 0.18 0.15 0.19 0.19 0.16 0.16 0.15 0.14 0.15 Braking performance Dry road surface 126 100 112 115 124 102 112 114 111 94 136 Wet road surface 125 100 106 106 121 99 108 105 107 96 124 (1) Rheometer +5: measured at 125 ° C, (2) Rheometer +90: measured at 150 ° C (3) Tensile test conditions: equipment used, Instron, Cross head speed: 500mm / min (4) Surface roughness (5) Heat generation characteristics: Using BF Goodrich Flexometer (higher index indicates better heat generation) (6) Braking performance was evaluated at 100km / hr based on NCAP. P195 / 70R14H.

From the results of Table 3, the diene rubber prepared by the emulsion polymerization as in Example 1, the glass transition temperature is -40 ~ -20 ℃, the styrene content in the microstructure composition is 38 to 42% by weight, aromatic oil The use of 100 parts by weight of styrene-butadiene rubber having a content of 48 to 52 parts by weight based on 100 parts by weight of rubber solid content and a 55 to 65 degree of Mooney viscosity at 100 ° C. minimizes abrasion resistance and rotational resistance, while braking on wet road surfaces. It is desirable to improve performance.

However, when the Mooney viscosity of the styrene-butadiene rubber is less than 54 as in Comparative Examples 1 to 3 or when the Mooney viscosity is more than 66 as in Comparative Examples 4 to 5, the effect of increasing the wear resistance according to the addition of styrene-butadiene rubber was not large. . When the Mooney viscosity was less than 54, the workability was excellent, but the abrasion resistance was low. When the Mooney viscosity was above 66, there were many problems in the on-site workability due to the increase in the mixing of butadiene rubber and the carbon black content.

In addition, when the aromatic oil content inherited in the styrene-butadiene rubber is less than 48% by weight as in Comparative Examples 1 and 2, carbon black mixing and processing are poor, and when the aromatic oil content is more than 52 parts by weight, the wear resistance is lowered and the molecular weight is reduced. The increase in wear resistance is not expected to increase as well.

When the styrene-butadiene Mooney viscosity is as high as 55 to 65 as in Comparative Examples 6 to 10, butadiene rubber weight ratio of 32 PHR or more may improve abrasion resistance and rotational resistance performance, but is not preferable for improving braking performance. .

When the amount of carbon black used is too low (less than 30 PHR) as in Comparative Example 9, a low heat generation composition can be obtained, but the reinforcing effect is not improved, and the wear resistance is not improved. Due to the poor workability is poor, the heat generation is increased and the wear resistance is adversely affected.

As a result, Example 1 satisfies both the carbon black content and the silica content while satisfying both the styrene content and the glass transition temperature in the styrene-butadiene rubber, the inherent aromatic oil content, the dielectric aromatic oil content, and the microstructure composition. It can be seen that there are even improvements in wear resistance, rotational resistance performance, and braking performance.

As described in detail above, according to the present invention, styrene-butadiene rubber obtained in the emulsion polymerization in which the styrene content is 38 to 42% by weight in the microstructure composition and the aromatic oil is inherited is applied as the base rubber, and the braking force is improved and the wear resistance is improved. By using carbon black and silica as reinforcing agents, it is possible to minimize heat generation characteristics and rotational resistance deterioration by using a large amount of reinforcing agents and improve braking performance on wet roads.

Claims (2)

In the rubber composition for tire treads formed by adding a reinforcing agent and an ordinary additive to a base rubber, The base rubber is a diene rubber prepared by the emulsion polymerization method, the glass transition temperature is -40 ~ -20 ℃, the styrene content of the microstructure composition 38 ~ 43% by weight, the stress relaxation time slope (logT / log time) is 0.30 to 0.34, Mooney viscosity of 55 to 65, aromatic oils are styrene-butadiene rubbers inherited at 48 to 52 parts by weight based on 100 parts by weight of the rubber solids content , The reinforcing agent is a rubber composition for tire treads, characterized in that 20 to 40 parts by weight of silica and 40 to 70 parts by weight of carbon black based on 100 parts by weight of the base rubber solid content . The carbon black has a CTAB value of 180 to 190 m 2 / g, an iodine adsorption particle surface area of 194 to 210 m 2 / g, a DBP oil absorption of 129 to 139 ml / 100 g, and a C-DBP oil absorption of 110. Ml / 100g or more, coloring power of 143-153, nitrogen adsorption particle surface area (N2SA) of 210 m 2 / g or more, STSA (particle surface area using statistical method) of 185-195 m 2 / g, and STSA-N2SA (surface Rubber composition for a tire tread, characterized in that it has a characteristic (activity) of 25 or less.