KR100445829B1 - Tire tread rubber composition - Google Patents

Abstract

The present invention is a diene-based synthetic rubber prepared by solution polymerization in a random arrangement of styrene and butadiene in a microstructure attached to 37.5 parts by weight of aromatic oil, glass transition to a synthetic rubber having a Mooney viscosity of 70 ℃ to 80 ℃ level 90 to 110 parts by weight of rubber having a temperature of -30 to -10 ° C and a diene rubber prepared by solution polymerization method, having a glass transition temperature of -100 to -110 ° C and a content of 1,4-cis butadiene in the microstructure composition of 96 It is prepared by solution polymerization on a blend rubber composed of 10 to 14 parts by weight of butadiene rubber having a Mooney viscosity of 55% to 65% or more, and has a 1,4 cis structure, a molecular weight of 80,000 to 100,000, and a terminal substituted with a hydroxyl group. 100 parts by weight of rubber made by adding 10 to 20 parts by weight of isoprene liquid rubber; 80-100 parts by weight of silica having a CTAB value of 160 to 170 m 2 / g; And it relates to a rubber tread rubber composition made of a conventional additive, which is substituted with silica by adding a polyisoprene liquid rubber having excellent molecular weight and end-substituted by a hydroxyl group having a high affinity with a silica and a reinforcing agent and It is possible to provide a tire tread rubber that facilitates dispersion processing and improves the braking performance of the tire while not losing abrasion performance and rolling resistance.

Description

Tire tread rubber composition with improved braking performance

The present invention relates to a rubber tread rubber composition with improved braking performance, and more particularly, a solution having a high glass transition temperature for a liquid synthetic rubber having excellent processability by replacing an end group having a high affinity with a specific reinforcing agent and having an appropriate molecular weight. In addition to the blended polymer styrene-butadiene rubber and butadiene rubber blend, it facilitates mixing and dispersing with silica, a useful reinforcing agent, and improves the braking performance of the tire, but without the loss of wear performance and rolling resistance. It is about.

Most of the development of tires can be concentrated on the structural aspects and the development of application technology of materials used in the 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 direction of tire development in terms of materials has been focused on developing tires that combine high braking tires, low fuel cost tires, high wear resistant tires, chip cut resistance, and characteristics thereof. In particular, the recent tire rubber compounding technology is concentrated on the combination technology between these characteristics, for this purpose, many research and development to apply a variety of new materials recently developed.

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

Currently, low-fuel tire performance is often required due to energy-saving aspects and environmental issues, and tire companies competitively high-fill silica in blends of solution-polymerized styrene-butadiene rubber and solution-polymerized butadiene rubber with high glass transition temperature. It was possible to satisfy satisfactory low-rotation resistance compounding composition and wear performance by applying the application. However, in this case, productivity was extremely reduced due to the difficulty of in situ mixing processability.

In order to solve this problem, a method of lowering the Mooney viscosity of the compounded rubber by introducing a solution-polymerized styrene-butadiene rubber having a low Mooney viscosity was introduced, thereby obtaining a rubber composition having improved braking performance with appropriate processability. However, in this case, it is inevitably disadvantageous in other wear performance and exothermic performance except braking performance.

Another traditional method is to solve the processability problem by adding a small amount of natural rubber, which is not a fundamental solution because the mixing time needs to be extended.

Accordingly, the inventors of the present invention, while trying to develop a rubber tread rubber composition that can improve the workability while combining the high braking resistance, low fuel consumption, high wear resistance, chip cut resistance and characteristics of the conventional tire, the specific end group As a result of the addition of molecular weight-controlled liquid synthetic rubber to the blend of solution-polymerized styrene-butadiene rubber and butadiene rubber with high glass transition temperature, it is easy to process using silica as a reinforcing agent and improves the braking performance of the tire. It has been found that there is no loss of wear performance and rotational resistance to complete the present invention.

Accordingly, an object of the present invention is to provide a tire tread rubber composition having excellent workability and low heat generation, low fuel consumption (low rotational resistance) and abrasion resistance while high braking performance is realized.

The tire tread rubber composition of the present invention for achieving the above object is a diene-based synthetic rubber prepared by solution polymerization in a random arrangement of styrene and butadiene in the microstructure and aromatic oil is 37.5 parts by weight based on the solid content of rubber Synthetic rubber having a Mooney viscosity of 70-80 at 100 ° C and 90-110 parts by weight of rubber having a glass transition temperature of -30 ° C to 10 ° C, and a diene rubber prepared by solution polymerization method. The blend rubber is composed of 10-14 parts by weight of butadiene rubber having a 1,4-cis butadiene content of 96% or more and a Mooney viscosity of 55-65 in a microstructure composition, prepared by solution polymerization. 100 parts by weight of rubber having a 1,4 cis structure and having a molecular weight of 80,000 to 100,000 and a terminal of which is substituted with a hydroxyl group of 10 to 20 parts by weight of polyisoprene liquid rubber Based on solids content); 80-100 parts by weight of silica having a CTAB value of 160 to 170 m 2 / g; And it is characterized by consisting of the usual additives.

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

The rubber of the tire tread rubber composition of the present invention is obtained by adding a liquid synthetic rubber having a specific end group substituted with a controlled molecular weight to a solution-polymerized styrene-butadiene rubber and a butadiene blend rubber having a high glass transition temperature.

Specifically, the solution-polymerized styrene-butadiene rubber is a structure in which styrene and butadiene are randomly arranged in the microstructure, and 37.5 parts by weight of the aromatic oil is added to the rubber solid content, and the viscosity of the honeycomb is 100 to 70 ° C. The rubber has a glass transition temperature of -30 to -10 ° C. The usage-amount is 90-110 weight part in rubber | gum.

If the rubber content having such characteristics is less than 90 parts by weight, the wear resistance can be sufficiently realized, but the rubber component of the high glass transition temperature is reduced, so that the braking performance of the tire is sharply worsened, so the amount used is 90 parts by weight. It is preferable to maintain at least 110 weight part.

The solution-polymerized styrene-butadiene rubber and the butadiene rubber blended with the above characteristics, butadiene rubber is prepared by the solution polymerization method, the glass transition temperature is -100 ~ -110 ℃ and 1,4-cis in the microstructure composition The butadiene content is 96% or more and the Mooney viscosity is 55 to 65 level, the content is preferably 10 to 15 parts by weight of the rubber.

If butadiene rubber having such characteristics is not used, wear resistance is poor.

In addition to the blend of the above-described solution polymerization styrene-butadiene rubber and butadiene rubber, a diene-based liquid rubber prepared by solution polymerization is added.

The diene liquid rubber prepared by solution polymerization is a polyisoprene synthetic rubber having a fine structure of 1,4 cis structure, its molecular weight is 80,000 to 100,000, and its terminal is substituted with a hydroxyl group.

When such liquid polyisoprene synthetic rubber is added to the styrene-butadiene rubber and butadiene rubber blends, it can facilitate the incorporation and dispersion processing with silica added as a reinforcing agent. In addition, it improves the braking performance of the tire and there is no loss of wear performance and rolling resistance.

The polyisoprene synthetic rubber which plays such a role should use the one whose molecular weight is properly adjusted, because if the molecular weight is high, the processability improvement effect by the injection of liquid rubber is halved.

Therefore, in the present invention, the liquid polyisoprene rubber having a molecular weight of 80,000 to 100,000 is used. When the molecular weight of the liquid polyisoprene rubber is less than 80,000, it is more advantageous in processability, but the crosslinking density of the whole vulcanizate is reduced due to the low molecular weight. It is very important that the molecular weight of the added liquid rubber is used at the same level as above without deteriorating the physical properties since the effect of deterioration is clearly shown but the wear resistance and other basic physical properties are deteriorated.

As a useful reinforcing agent for the rubber component, a CTAB value of 160 m 2 / g and a silica containing N 2 SA of 170 m 2 / g are mixed, and the content thereof is 80 to 100 based on 100 parts by weight of the rubber component (based on the rubber solid content). It is preferable that it is a weight part.

If the amount of silica is less than 80 parts by weight, the processing surface is excellent and the characteristics of the styrene-butadiene rubber prepared by solution polymerization having a high glass transition temperature are well realized, and the braking performance can be dramatically improved, but the reinforcing effect is improved. Abrasion resistance falls off sharply. On the other hand, when more than 100 parts by weight of silica is used, it is difficult to process without adding aromatic oil or the like, or using a master batch rubber compound, and the aromatic oil used for facilitating processing has a sharp decrease in physical properties. Adverse effects. In addition, manufacturing of masterbatch rubber blends requires additional processing and is therefore generally not preferred by the tire industry.

On the other hand, additives used in conventional tire tread rubber compositions, i.e., zincated, stearic acid, aromatic processing oil, sulfur, accelerators, silica coupling agents and the like can be used as a matter of course.

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 1-9

Solution-polymerized styrene-butadiene rubber, butadiene rubber, natural rubber and liquid polyisoprene rubber, silica and conventional additives were formulated in the component ratios shown in Table 1 below to prepare a rubber composition, followed by optimum vulcanization to prepare rubber specimens.

The unit of the component ratio of the composition of the following Table 1 is PHR (based on rubber solids content), and an aromatic oil was further added to make the content of the total aromatic oil the same.

The rubber specimens thus obtained were subjected to physical property tests and the results are shown in Table 2 below.

Example 1 Comparative Example One 2 3 4 5 6 7 8 9 S-SBR (Rubber Solid Content) 96 (70) 110 (80) 96 (70) 96 (70) 96 (70) 110 (80) 110 (80) 110 (80) 83 (60) 96 (70) BR 15 10 15 20 15 10 - 15 10 25 SMR-CV - 10 - - - - - - - - a - - 15 - - - - - - - b - - - 10 - - - - - - c - - - - 15 - - - - - a * - - - - - 10 - - - - b * 15 - - - - - 20 5 30 5 Process oil 18.4 15.7 18.4 18.4 18.4 15.7 15.7 15.7 21.1 18.4 Silica 80 80 85 90 100 85 85 95 85 70 Coupling agent 6.4 6.4 6.8 7.2 8.0 6.8 6.8 7.2 6.8 5.6 ZnO 3 3 3 3 3 3 3 3 3 3 Stearic acid 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 Accelerator CBBS 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 Accelerator D 2 2 2 2 2 2 2 2 2 2 1) S-SBR: Styrene and butadiene randomly arranged in the microstructure, 37.5 parts by weight of aromatic oil is attached to the rubber solid content, 100 ℃ Mooney viscosity 76, glass transition temperature is -20 ℃ Phosphorus solid rubber 2) BR: Solid rubber with 1,4-cis butadiene content of microstructure composition 97%, Mooney viscosity 61 and glass transition temperature of -106 ° C 3) SMR-CV: Standard Malaysian Rubber (Mooney Viscosity 63) 4) a: Polyisoprene synthetic rubber with 1,4 sheath structure, liquid rubber with molecular weight 51,000 b) Microstructure is polyisoprene synthetic rubber with 1,4 sheath structure, Liquid rubber having molecular weight of 83,000 6) c: Polyisoprene rubber having a microstructure of 1,4 cis structure, Liquid rubber having a molecular weight of 138,000 7) a *: Polyisoprene synthetic rubber having a 1,4 sheath structure, Liquid rubber with molecular weight 47,000 and end group substituted by hydroxyl group 8) b *: Structure is cis-1,4 structure of polyisoprene rubber, molecular weight 87,000, and terminal groups of the liquid rubber substituted with a hydroxy group

Example 1 Comparative Example One 2 3 4 5 6 7 8 9 Rheometer t ₅ min. 27.1 29.5 28.4 27.5 29.9 27.4 26.4 28.9 25.4 30.5 Rheometer t ₉₀ min. 25.4 19.6 31.4 28.8 26.8 24.8 20.4 21.6 33.5 22.7 Mooney viscosity (125 ℃) 76 94 66 78 83 67 71 88 54 84 Tensile Properties (Room Temperature) Hardness (Shore A) 72 75 54 58 72 68 68 74 52 77 M300 Index (kg / ㎠) 97 100 84 92 97 96 92 105 99 92 Cutting strength index 104 100 89 92 91 97 111 88 100 94 Elongation at break index 118 100 110 104 102 111 121 72 128 99 Tear Index 99 100 958 94 91 97 104 101 99 108 Breaking energy index 117 100 87 95 91 101 111 78 101 104 Tensile Properties (Aging) Hardness (Shore A) 81 89 66 71 89 78 79 85 61 89 M300 Index (kg / ㎠) 98 100 87 94 92 96 96 108 99 90 Cutting strength index 103 100 86 95 96 99 110 89 104 96 Elongation at break index 124 100 106 101 103 121 123 70 121 94 Tear Index 101 100 94 96 96 98 105 94 94 103 Breaking energy index 128 100 84 92 94 119 127 76 103 101 Pico Wear Index 110 100 91 91 92 100 91 104 101 94 Rambon Wear Index 109 100 88 94 100 91 85 116 99 91 Dean wear index 118 100 96 95 96 92 87 108 96 101 Exothermic characteristics 104 100 108 106 102 104 98 92 104 114 Surface roughness 2 5 2 2 3 One 2 4 One 3 0 ℃ tanδ 0.56 0.44 0.41 0.40 0.41 0.47 0.51 0.49 0.34 0.51 60 ℃ tanδ 0.11 0.10 0.11 0.10 0.14 0.14 0.13 0.16 0.10 0.17 1) Mooney viscometer (t ₅ measurement temperature): 125 ° C 2) Rheometer t ₉₀ measurement temperature: 160 ° C 3) Tensile test conditions: Equipment used (Instron), Cross Head Speed: 500 mm / min. Vulcanization conditions: 160 ° C × (t ₉₅ × 1.2) min. Aging condition: 100 ℃ × 12hr.4) Surface roughness: 1-5 (The larger the number, the smoother the surface, the better the processing)

Looking at the results of Table 2, the conventional methods using liquid polyisoprene rubber as in Comparative Examples 2 to 4 in place of the natural rubber in Comparative Example 1 which is a conventional rubber composition may be advantageous in processability, but wear resistance performance And most of the disadvantageous properties in the breakdown energy index, because the low molecular weight material is advantageous for processing but has a very bad effect on the final physical properties. In addition, when the high molecular weight of the liquid polyisoprene rubber used in Comparative Examples 2-4 was used, it turns out that the processability improvement effect is halved by the addition of liquid rubber.

From the results of Comparative Example 5, if the molecular weight of the added liquid polyisoprene rubber is too small, it is more advantageous in workability, but the low molecular weight clearly shows the effect of lowering the crosslinking density of the whole vulcanizate, which has a high wear resistance and other It can be seen that the degradation of the basic physical properties.

From the results of Comparative Example 6, it can be seen that the use of the liquid polyisoprene according to the present invention instead of butadiene rubber in the blend composition of the existing styrene-butadiene rubber and butadiene rubber is poor wear resistance performance.

From the results of Comparative Example 7, it can be seen that even if the addition amount of the liquid polyisoprene according to the present invention is too small, the improvement in processing performance due to the addition of the liquid rubber cannot be expected sufficiently.

From the results of Comparative Example 8, it can be seen that the braking performance of the tire deteriorates rapidly when the content of the solution-polymerized styrene-butadiene rubber is small.

From the results of Comparative Example 9, when the amount of silica used is small, the processing surface is excellent, and the characteristics of the styrene-butadiene rubber prepared by solution polymerization having a high glass transition temperature can be well implemented, and the braking performance can be significantly improved. In addition, it can be seen that the wear resistance is drastically reduced due to the poor reinforcing effect.

As described in detail above, a solution-polymerized styrene having a high glass transition temperature for a liquid polyisoprene rubber having a high molecular weight and having an appropriate molecular weight, the terminal of which is substituted by a hydroxyl group having high affinity with silica used as a reinforcing agent according to the present invention. The rubber composition obtained by further mixing butadiene rubber and butadiene rubber blends facilitates mixing and dispersing with silica, improves braking performance of the tire, and has no loss of wear performance and rolling resistance. Is suitable as.

Claims (1)

(Correction) A diene-based synthetic rubber prepared by solution polymerization, in which the styrene and butadiene are randomly arranged in a microstructure, and the aromatic oil is attached to 37.5 parts by weight with respect to the rubber solid content, and the Mooney viscosity of 100 ° C. is 70-80. 90 to 110 parts by weight of rubber having a glass transition temperature of -30 to -10 ° C and a diene-based rubber prepared by solution polymerization method, having a glass transition temperature of -100 to -110 ° C and having a fine structure It is a blend rubber composed of 10-14 parts by weight of butadiene rubber having a cis butadiene content of 96% or more and a Mooney viscosity of 55-65, and has a fine structure of 1,4 sheath structure and its molecular weight is 80,000-100,000. 100 parts by weight of rubber (based on rubber solids content) made by adding 10 to 20 parts by weight of polyisoprene liquid rubber whose terminal is substituted with a hydroxyl group; 80-100 parts by weight of silica having a CTAB value of 160 to 170 m 2 / g; And tire tread rubber composition with improved braking performance consisting of conventional additives.