KR100237254B1 - A rubber composition for sidewall of tire - Google Patents

Abstract

The present invention relates to a rubber composition for a white sidewall and a black cover strip of a tire.

The present invention relates to a low molecular weight liquid ethylene propylene diene based on 100 parts by weight of a total rubber component consisting of 30 to 70 parts by weight of diene rubber, 15 to 35 parts by weight of conventional polymer ethylene propylene diene terpolymer rubber and 15 to 35 parts by weight of halogenated butyl rubber. To provide a rubber composition for a white sidewall and a black cover strip of a tire consisting of 2 to 20 parts by weight of terpolymer rubber and conventional additives.

Such a rubber composition maintains weather resistance, ozone resistance, oxidation crack resistance as well as fatigue resistance, tensile strength, and tear strength without discoloration or deterioration of white sidewalls and black cover strips.

Description

Rubber composition for white sidewalls and black cover strips on tires

The present invention relates to a rubber composition for a white sidewall and a black cover strip of a tire. More specifically, the low molecular liquid ethylene propylene diene rubber is used to maintain fatigue resistance, tensile strength and tear strength as well as weather resistance, ozone resistance and oxidation crack resistance without deterioration without the use of amine antioxidants or waxes. A rubber composition for white sidewalls and black cover strips.

Generally, since the sidewall part of a tire is a part which requires weather resistance, ozone resistance, and oxidation cracking resistance, the rubber composition which mix | blended a large amount of an amine antioxidant and wax with diene rubber is used.

However, the anti-aging agent has a disadvantage in that it precipitates or discolors the rubber surface over time. In particular, in the case of the black cover strip rubber covering the white sidewalls and the white sidewalls of the sidewalls, discoloration by the amine antioxidant is noticeable.

Therefore, in order to prevent such deterioration of the appearance of the rubber, a very small amount of an anti-aging agent is used or no formulation is carried out, but instead a large amount of wax is blended. Thus, the rubber composition using a large amount of wax can prevent the deterioration of appearance by the amine antioxidant to some extent while maintaining weather resistance, ozone resistance, and oxidation cracking resistance. However, as the wax precipitates on the black cover strip surface, another deterioration occurs that turns white.

This problem can be solved only when no amine anti-aging agent or wax is blended at all. However, when no amine anti-aging agent or wax is used at all, there is a problem in that weather resistance, ozone resistance, and oxidation cracking resistance, which are main requirements of the sidewall rubber, are greatly decreased.

In order to maintain the required physical properties, a rubber composition composed of ethylene propylene diene terpolymer copolymer rubber, halogenated butyl rubber and diene rubber is used for the white sidewall portion and the black cover strip, and the ratio of diene rubber is reduced and ethylene propylene diene is used. The amount of terpolymer rubber or halogenated butyl rubber should be greatly increased. However, in this case, the durability, such as fatigue resistance, tensile strength, tear strength is significantly weakened.

The present invention provides a rubber composition for white sidewalls and black cover strips to maintain weather resistance, ozone resistance, oxidation cracking resistance as well as fatigue resistance, tensile strength, tear strength without discoloration or appearance deterioration to solve the above problems For the purpose of

The present invention relates to a low molecular weight liquid ethylene propylene diene based on 100 parts by weight of a total rubber component consisting of 30 to 70 parts by weight of diene rubber, 15 to 35 parts by weight of conventional polymer ethylene propylene diene terpolymer rubber and 15 to 35 parts by weight of halogenated butyl rubber. A rubber composition for a white sidewall and a black cover strip of a tire composed of 2 to 20 parts by weight of terpolymer rubber and conventional additives.

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

In general, ozone cracks occur in natural rubber and continue to grow until the ends of the cracks meet ethylene propylene diene terpolymer rubber regions that are dispersed and present as particles or regions on the natural rubber.

There is also a critical crack length in this region where the growth of ozone cracks stops in contact with the ethylene propylene diene terpolymer rubber region.

Ozone cracks below this critical crack length will stop growth in contact with the ethylene propylene diene terpolymer rubber region, while ozone cracks grown beyond the critical length will bypass ethylene propylene diene rubber particles when they are in contact with the ethylene propylene diene terpolymer rubber region. You will continue to grow.

Therefore, even if the concentration of ethylene propylene diene rubber is well dispersed on the natural rubber matrix, the growth of the ozone crack is in contact with the grain or area of ethylene propylene diene rubber before the ozone crack grows above the critical length, so Can be stopped below a threshold length.

In the present invention, by using the low molecular liquid ethylene propylene diene terpolymer rubber as described above, the dispersibility of high molecular weight ethylene propylene diene rubber and other unsaturated rubbers (particularly, halogenated butyl rubber) and additives such as a crosslinking agent or accelerator, By adding liquid ethylene propylene diene terpolymer rubber, the effect of increasing the unsaturated rubber is the ozone resistance, weather resistance, oxidation cracking resistance as well as fatigue resistance, tensile strength and tear strength without the addition of amine antioxidant or wax. Keep it.

In addition, the low molecular weight liquid ethylene propylene diene terpolymer rubber acts as a reactive compatibilizer to lower the processing viscosity of the rubber composition and improve the compatibility of the rubber polymer as well as the compounding agent contributes greatly to the voids.

In the present invention, the low molecular liquid ethylene propylene diene terpolymer rubber has a molecular weight of 3,000 to 9,000, a molar ratio of ethylene and propylene of 30/70 to 70/30, and the diene terpolymer is dicyclopentadiene or ethyldiene norbornene. And ethylene propylene diene terpolymer rubber having an unsaturated ratio of 3 to 15%.

In addition, these low molecular weight liquid ethylene propylene diene terpolymer rubber is preferably used 2 to 20 parts by weight, when using less than 2 parts by weight does not exhibit a sufficient role as a compatibilizer, and exceeds 20 parts by weight In the case of using, the problem occurs that the physical properties due to excessive use of low molecular weight material is greatly reduced.

Typical additives in the present invention include carbon black, zinc oxide, stearic acid, sulfur, sulfur donors, accelerators and the like except for waxes and antioxidants.

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

Examples 1-4

Next, the rubber sheet composition before vulcanization was blended in the usual manner using the composition shown in Table 1, and the rubber sheet thus blended was vulcanized at 170 ° C. for 20 minutes to prepare a test sample. Table 1 shows examples of rubber compositions for cover strips.

Comparative Example 1

Next, the rubber sheet composition was blended using the composition shown in Table 1, and the same procedure as in Example was performed.

(Unit: parts by weight) Comparative example Example One One 2 3 4 Natural rubber 40 40 40 45 45 Polybutadiene rubber 20 20 20 15 15 EPDM 20 20 20 20 20 Br-IIR 20 20 20 20 20 Liquid-EPDM - 5 10 5 10 Carbon black 40 40 40 40 40 Zinc oxide 3 3 3 3 3 Stearic acid 2 2 2 2 2 Wax 4 - - - - brimstone 3.2 3.2 3.2 3.2 3.2 Sulfur donor 0.8 0.8 0.8 0.8 0.8 accelerant 0.5 0.5 0.5 0.5 0.5

EPDM: Ethylene Propylene Diene Terpolymer Rubber

Br-IIR: Halogenated Butyl Rubber

Accelerator: NS, N-t-butyl-2-benzodiazyl-sulfenamide

Sulfur donor: Alkylphenol disulfide

Test Example 1

The physical properties of the test samples obtained in Examples 1 to 4 and Comparative Example 1 were measured as follows, and the results are shown in Table 2.

Positive fatigue

The results were performed at a strain rate of 125% and a frequency of 2 Hz.

Ozone resistance

During the ozone resistance evaluation, static is the time of crack initiation at 50 PPHM and dynamic is the time at which the specimen begins to break.

Outdoor weather resistance

The test results were shown in the outdoor while giving a 2 cm × 10 cm specimen a strain of 100% and a strain rate of 60 rpm.

Comparative example Example One One 2 3 4 Tensile Strength [kg / ㎠] 110 120 120 120 115 Tear strength [kg / ㎠] 42 42 39 42 40 Constant strain fatigue [kcycle] 330 330 330 330 330 Crack Growth Rate [㎛ / cycle] 0.03 0.03 0.03 0.10 0.03 Ozone Resistance [Sun] dynamic 30 30 More than 30 More than 30 More than 30 silence More than 100 More than 100 More than 100 More than 100 More than 100 Outdoor weatherability [kcycle] More than 7000 More than 7000 More than 7000 More than 7000 More than 7000 Discoloration White discoloration No discoloration No discoloration No discoloration No discoloration

When comparing Examples 1 to 4 and Comparative Example 1 according to the present invention as shown in Table 2, in the case of Examples 1 to 4 using a low-molecular liquid ethylene propylene diene terpolymer rubber, discoloration does not occur without using wax Tensile strength was slightly superior, tear strength, static strain, crack growth rate, ozone resistance and outdoor weather resistance were maintained at the same level as in Comparative Example 1.

Examples 5-8

Next, the rubber sheet composition before vulcanization was blended in the usual manner using the composition shown in Table 3, and the rubber sheet thus blended was vulcanized at 170 ° C. for 20 minutes to prepare a test sample. Table 3 shows examples of rubber compositions for white sidewalls.

Comparative Example 2

Next, the rubber sheet composition was blended using the composition shown in Table 3, and the same procedure as in Example was performed.

(Unit: parts by weight) Comparative example Example 2 5 6 7 8 Natural rubber 55 55 55 50 50 EPDM 20 20 20 20 20 Cl-IIR 25 25 25 30 30 Liquid-EPDM - 5 10 5 10 White filler 45 45 45 45 45 Zinc oxide 4 4 4 4 4 Stearic acid 2 2 2 2 2 Wax 2.5 - - - - brimstone 1.3 1.3 1.3 1.3 1.3 Sulfur donor 1.3 1.3 1.3 1.3 1.3 accelerant 1.0 1.0 1.0 1.0 1.0

EPDM: Ethylene Propylene Diene Terpolymer Rubber

Cl-IIR: Halogenated Butyl Rubber

Accelerator: NS, N-t-butyl-2-benzodiazyl-sulfenamide

Sulfur donor: Alkylphenol disulfide

Test Example 2

The physical properties of the test samples obtained in Examples 5 to 8 and Comparative Example 2 were measured in the same manner as in Test Example 1, and the results are shown in Table 4.

Comparative example Example 2 5 6 7 8 Tensile Strength [kg / ㎠] 140 137 130 130 124 Tear strength [kg / ㎠] 40 40 39 40 37 Constant strain fatigue [kcycle] 12 13 15 15 17 Crack Growth Rate [㎛ / cycle] 0.13 0.03 0.03 0.10 0.03 Ozone Resistance [Sun] dynamic 30 30 More than 30 More than 30 More than 30 silence More than 100 More than 100 More than 100 More than 100 More than 100 Outdoor weatherability [kcycle] 2250 2240 2850 2850 3460

Table 4 shows the rubber composition of Examples 5 to 8 using low molecular liquid ethylene propylene diene terpolymer rubber without using wax, and compared with Comparative Example 2, tensile strength, tear strength, strain strain, crack growth rate, Ozone resistance and outdoor weather resistance were maintained or improved to a similar level.

The rubber composition invented by the above method maintains weather resistance, ozone resistance, oxidation crack resistance as well as fatigue resistance, tensile strength and tear strength without discoloration or deterioration.

Claims (5)

30 to 70 parts by weight of a diene rubber composed of 20 to 40 parts by weight of natural rubber and 10 to 30 parts by weight of polybutadiene rubber, 15 to 35 parts by weight of a common polymer ethylene propylene diene terpolymer rubber and 15 to 35 parts by weight of a butyl rubber A rubber composition for a white sidewall and a black cover strip of a tire composed of 2 to 20 parts by weight of a low molecular liquid ethylene propylene diene terpolymer rubber and a conventional additive, based on 100 parts by weight of the total rubber component. The rubber composition according to claim 1, wherein the low molecular liquid ethylene propylene diene terpolymer rubber has a molecular weight of 3,000 to 9,000. The rubber composition according to claim 1, wherein the low molecular liquid ethylene propylene diene terpolymer rubber has a molar ratio of ethylene and propylene of 30/70 to 70/30. The rubber composition according to claim 1, wherein the low molecular liquid ethylene propylene diene terpolymer rubber is a diene terpolymer of dicyclopentadiene or ethyldiene norbornene. The rubber composition according to claim 1, wherein the low molecular liquid ethylene propylene diene terpolymer rubber has an unsaturated ratio of 3 to 15%.