KR19990031480A - Rubber composition for tire tread - Google Patents

Abstract

The present invention relates to a rubber composition for tire treads with improved wet braking performance and fuel efficiency.

The present invention is 5 to 20 parts by weight of natural rubber, 20 to 40 parts by weight of emulsion-polymerized styrene-butadiene rubber, 40 to 60 parts by weight of solution-polymerized styrene-butadiene rubber having a glass transition temperature of -40 ° C. or more and 5 to 10 parts by weight of halogenated butyl rubber For tire treads composed of 30 to 60 parts by weight of carbon black as a reinforcing agent and 10 to 40 parts by weight of silica in powder or granule form, 3 to 30 parts by weight of aromatic oil as a softener, and a conventional additive, based on 100 parts by weight of a rubber base composed of parts. It is a rubber composition.

Thus, the rubber composition of the present invention using two or more kinds of rubbers having different glass transition temperatures and using silica as a reinforcing agent in addition to carbon black has a high 0 ° C tanδ / 60 ° C tanδ ratio to maintain wear resistance at the same level. It improves wet braking performance and fuel efficiency.

Description

Rubber composition for tire tread

The present invention is a rubber composition for tire treads with improved wet braking performance and fuel efficiency. More specifically, it is a rubber composition in which two or more rubbers having a large difference in glass transition temperature are mixed and silica is used as a reinforcing agent to improve wet braking performance and fuel efficiency.

In general, the wet braking performance and the fuel economy performance move at the same time, so if the wet braking performance is improved, the fuel efficiency is worse, and the lower the fuel efficiency, the wet braking performance is worse, so it is very difficult to satisfy both performances at once.

Among the viscoelastic properties of rubber, the dynamic loss factor (tanδ) is highly correlated with wet braking performance, and the dynamic loss factor (tanδ) at 60 ° C is closely related to the rolling resistance. . Here, the rotational resistance is related to the fuel efficiency, and the fuel efficiency decreases as the value of the rotational resistance increases.

Therefore, in order to simultaneously improve wet braking performance and fuel efficiency, the ratio 0 ° C tanδ / 60 ° C tanδ should be large.

Rubber compositions used for general tire treads should not only consider wet braking performance and fuel economy performance (rotational resistance) but also wear performance. Therefore, carbon black or silica must be added to some extent as a reinforcing agent. Reducing the amount of reinforcing agent can improve the wet braking performance and fuel efficiency by increasing the 0 ° C tanδ / 60 ° C tanδ ratio, but there is a problem that the 0 ° C tanδ / 60 ° C tanδ ratio is not large because the reinforcing agent should be used to some extent.

In addition, when the amount of the halogenated butyl rubber is increased in the rubber composition, the 0 ° C. tanδ / 60 ° C. tanδ ratio may be advantageously increased. However, when used a lot, there is a problem in that the wear resistance and toughness value are very low.

Accordingly, the present invention solves the above problems by using two or more kinds of rubber having a large difference in glass transition temperature, and using a silica in addition to carbon black as a reinforcing agent to improve the wet braking performance and fuel efficiency performance at the same time the tire tread rubber composition To provide.

The present invention is 5 to 20 parts by weight of natural rubber, 20 to 40 parts by weight of emulsion-polymerized styrene-butadiene rubber having a styrene bond of 20 to 40 mol%, a glass transition temperature of -40 ℃ or more, styrene bond of 15 to 25 mol% DBP oil absorption as a reinforcing agent with respect to 100 parts by weight of a rubber base consisting of 40 to 60 parts by weight of a solution-polymerized styrene-butadiene rubber having a vinyl group content of butadiene portion of 50 to 70 mol% and 5 to 10 parts by weight of a halogenated butyl rubber. 30 to 60 parts by weight of carbon black having a nitrogen adsorption specific surface area of 120 to 140 m ₂ / g, 150 to 190 m ₂ / g of N ₂ SA, and 150 to 190 m ₂ / g CTAB 10 to 40 parts by weight of silica in the form, 3 to 30 parts by weight of aromatic oil as a softener, and a rubber composition for tire treads with improved wet braking performance and fuel efficiency.

Hereinafter, the present invention will be described in more detail.

As the rubber used in the present invention, two or more rubbers having a glass transition temperature difference of 30 ° C. or more are used to increase the 0 ° C. tanδ / 60 ° C. tanδ ratio to 1.5 or more.

In the above, a solution-polymerized styrene-butadiene rubber is used as the rubber having a high glass transition temperature, and the glass transition temperature of the rubber is -40 ° C or higher. In addition, the content thereof should be 40 to 60 parts by weight to increase the 0 ℃ tan δ / 60 ℃ tan δ ratio. Therefore, when the solution-polymerized styrene-butadiene rubber is used less than 40 parts by weight there is a problem that the required 0 ℃ tanδ / 60 ℃ tanδ ratio is not obtained.

As the rubber having a low glass transition temperature, natural rubber, emulsion-polymerized styrene-butadiene rubber, and butyl halide rubber are used. For reference, the glass transition temperature of natural rubber is -100 ° C.

In addition, in the present invention, 5 to 20 parts by weight of natural rubber is used, which is used to prevent steaming during separation after vulcanization in the mold.

In the above, other diene rubbers such as isoprene rubber or butadiene rubber may be used instead of the emulsion polymerization styrene-butadiene rubber having 20 to 40 mol% of styrene bond.

In the present invention, 5 to 10 parts by weight of halogenated butyl rubber is used. Here, when using less than 5 parts by weight of halogenated butyl rubber, the effect of increasing the ratio of 0 ° C tanδ / 60 ° C tanδ is inadequate, whereas when it is used more than 10 parts by weight, the wear resistance and toughness values are lowered. Not desirable

In the case of the carbon black used as a reinforcing agent, a small particle size and a large DBP oil absorption should be used to increase the 0 ° C tanδ / 60 ° C tanδ ratio and maintain wear resistance at the same time.

Silica, which is another reinforcing agent, tends to increase 0 ° C tanδ and lower 60 ° C tanδ, which uses 10 to 40 parts by weight in the present invention.

In the above, as a conventional additive, a vulcanizing agent, a vulcanization accelerator, a coupling agent, etc. are used.

Hereinafter, the present invention will be described in more detail with reference to Examples.

The following abbreviations have the following meanings.

SBR 1502: Emulsion-polymerized styrene-butadiene rubber having a styrene bond amount of 23.5 mol%.

S-SBR: styrene bond amount is 20 mol%, butadiene portion vinyl bond amount is 60 mol%

Phosphorus solution polymerized styrene-butadiene rubber.

Carbon black (1): nitrogen adsorption specific surface area of 96 m 2 / g, DBP oil absorption 120ml / 100g.

Carbon black ②: Nitrogen adsorption specific surface area 120-135㎡ / g, DBP oil absorption 125-145ml

/ 100g.

Silica: N ₂ SA is 150 to 190 m ₂ / g and CTAB is 150 to 190 m 2 / g.

Process oil: Aromatic oils commonly used in rubber compounding

Halogenated Butyl Rubber: Br-IIR or Cl-IIR

Example 1

100 parts by weight of a rubber base composed of 10 parts by weight of natural rubber, 40 parts by weight of SBR1502, 40 parts by weight of S-SBR and 10 parts by weight of halogen butyl rubber, 40 parts by weight of carbon black ②, 20 parts by weight of silica, 16 parts by weight of processing oil, and activator 3 A rubber composition was prepared by combining parts by weight, 2 parts by weight of stearic acid, 5 parts by weight of antioxidant, 2 parts by weight of sulfur, and 1.3 parts by weight of vulcanization accelerator.

Example 2

In the same manner as in Example 1 to prepare a rubber composition by combining each component in the composition ratio shown in Table 1.

Comparative Examples 1 to 5

In the same manner as in Example 1 to prepare a rubber composition by combining each component in the composition ratio shown in Table 1.

ingredient Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Natural rubber 10 10 - 40 - 10 10 SBR 1502 40 30 100 60 100 40 20 S-SBR 40 50 - - - 40 40 Halogenated Butyl Rubber 10 10 - - - 10 30 Carbon black① / ② -/ 40 -/ 35 73 /- 50 /- 90 /- -/ 60 -/ 40 Silica 20 20 - - - - 20 Processing oil (oil) 16 13 42.5 3 49 16 16 Active agent 3 3 3 3 3 3 3 Stearic acid 2 2 2 2 2 2 2 Anti-aging 5 5 5 5 5 5 5 brimstone 2.0 2.0 2.0 2.0 2.0 2.0 2.0 Vulcanization accelerator 1.3 1.3 1.5 0.8 2.0 1.3 1.3

Test Example

With the rubber composition specimens obtained in Examples 1 to 2 and Comparative Examples 1 to 5, the following physical properties were measured and the results are shown in Table 4.

0 ℃ tanδ, 60 ℃ tanδ

As a method of measuring the dynamic loss coefficient, a temperature sweep is used to measure a 0.5% strain at a frequency of 10 Hz using a tortion type viscoelastic tester. The relationship between 0 ° tanδ and wet braking performance and 60 ° C. tanδ and rotational resistance (fuel efficiency) can be confirmed through the following vehicle tests, and is shown in Tables 2 and 3 below.

Tread Rubber Composition A B C D 60 ℃ tanδ 0.151 0.090 0.135 0.123 R.R. (unit: N) 40.1 31.4 34.4 33.9 Actual fuel efficiency (km / ℓ) 15.7 16.6 - 16.2

Tire specifications are P175 / 70R13T.

R.R. (rotational resistance): Measure the tire rotational resistance (speed: 80km / ℓ, air pressure: 1.8㎏ / ㎠) on the drum by laboratory test.

Tread Rubber Composition E F G H 0 ℃ tanδ 0.208 0.204 0.240 0.266 Wet Braking Distance (Unit: m) 24.3 26.0 22.1 21.2 60 ℃ tanδ 0.175 0.092 0.209 0.233 R.R. (unit: N) 49.8 38.5 57.7 62.1

Tire specifications are P195 / 70R14T.

Wet Braking Distance: The braking distance measured when braking at wet speed of 60km / h.

As shown in Table 2, the larger the value of 60 [deg.] C. tanδ, the greater the rotational resistance, and thus the lower the fuel efficiency. In addition, as shown in Table 2, the wet braking distance increases as the value of 0 ° C tanδ decreases, while the value of rotational resistance increases as the value of 60 ° C tanδ increases.

Properties Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 0 ℃ tanδ 0.277 0.289 0.224 0.173 0.235 0.236 0.285 60 ℃ tanδ 0.159 0.157 0.186 0.146 0.203 0.175 0.151 0 ℃ / 60 ℃ tanδ ratio 1.74 1.84 1.20 1.18 1.16 1.35 1.89 Tensile HD300% ElongT.S. 66114495208 66113505207 6197557211 63102547223 67125480215 67133478217 66121424181 Lambourn Index 98 96 100 91 95 99 84

As shown in Table 4, in Examples 1 and 2, the 0 ° C tanδ / 60 ° C tanδ ratio was 1.5 or more, and both wet braking performance and fuel efficiency were excellent, and at the same time, abrasion resistance was not lowered.

On the other hand, Comparative Example 1 is a rubber composition used in a general tire, Comparative Example 2 is a rubber composition used when manufacturing a low fuel economy tire, Comparative Example 3 is a general rubber composition used for a tire with improved wet braking performance to be. As shown in Table 4, Comparative Examples 1 to 3 may increase 0 ° C tanδ related to wet braking performance or lower 60 ° C tanδ related to rolling resistance, but did not improve both performances. In Comparative Example 4, the ratio of 0 ° C tanδ / 60 ° C tanδ was not large when silica was not used, and in Comparative Example 5 in which halogenated butyl rubber was excessively used, the ratio of 0 ° C tanδ / 60 ° C tanδ was large, but the wear resistance was high. This fell significantly.

As can be seen from these results, the rubber composition of the present invention using a rubber having a large difference in glass transition temperature and additionally using silica as a reinforcing agent increases the 0 ° C tanδ / 60 ° C tanδ ratio to maintain abrasion resistance at the same level. It improves wet braking performance and fuel efficiency.

Claims (2)

5 to 20 parts by weight of natural rubber, 20 to 40 parts by weight of an emulsion-polymerized styrene-butadiene rubber having a styrene bond of 20 to 40 mol%, a glass transition temperature of at least -40 ° C, a styrene bond of 15 to 25 mol%, and butadiene DBP oil absorption as a reinforcing agent with respect to 100 parts by weight of a rubber base composed of 40 to 60 parts by weight of a solution-polymerized styrene-butadiene rubber having a vinyl group content of 50 to 70 mol% and 5 to 10 parts by weight of a halogenated butyl rubber. 30 to 60 parts by weight of carbon black having a nitrogen adsorption specific surface area of 120 to 140 m 2 / g, and 150 to 190 m 2 / g of N ₂ SA and 150 to 190 m ₂ / g CTAB A rubber composition for tire treads, consisting of 10 to 40 parts by weight, 3 to 30 parts by weight of aromatic oil as a softener, and a conventional additive. The rubber composition for tire treads according to claim 1, wherein isoprene rubber or butadiene rubber, which is a diene rubber, is used instead of the emulsion-polymerized styrene-butadiene rubber having 20 to 40 mol% of styrene bond.