KR20000046695A - Rubber composition for use in tire sidewall - Google Patents

Abstract

PURPOSE: A rubber composition for use in tire sidewall having good tensile strength, tear resistance, anti-cracking and anti-exhaustion while retaining weather resistance, anti-ozone property and anti-oxidation property without decoloration and degradation of appearance is provided. CONSTITUTION: A rubber composition for use in tire sidewalls according to the present invention comprises: a) 100 parts by weight of rubber containing 20 to 80 parts by weight of diene rubber, 10 to 40 parts by weight of high molecular weight ethylene-propylene-diene terpolymer rubber and 10 to 40 parts by weight of halogenated butyl rubber; and b) 2 to 20 parts by weight of low molecular weight liquid isobutylene rubber.

Description

Rubber composition for tire sidewall

The present invention relates to a rubber composition for a sidewall of a tire. More specifically, it is to provide a rubber composition in which the sidewalls have weathering properties, ozone resistance, and oxidation resistance without discoloration or appearance deterioration, and have physical properties such as tensile strength, tear strength, crack growth resistance, fatigue resistance, and the like. .

The sidewall of the tire is exposed to oxygen, ozone and ultraviolet rays because it is always in contact with the outside, so weather resistance, ozone resistance, and oxidation resistance are required to increase the durability of the tire. Therefore, an amine antioxidant or wax is applied to the diene rubber. It is used extensively and is used extensively as a rubber composition for sidewalls.

The amine-based antioxidant or wax is moved to the surface layer of the sidewall over time to perform a function, which results in discoloration of the sidewall to deteriorate the appearance. Therefore, in order to reduce the appearance deterioration of the surface discolored by the amine antioxidant, the amount of the amine antioxidant is increased, the amount of wax is increased, and the unsaturated ethylene polymer ethylene propylene diene terpolymer rubber or halogenated butyl rubber is reduced. It has been used as a rubber composition of sidewalls with rubbers to improve weather resistance, ozone resistance, and oxidation resistance.However, when the amount of diene rubber used decreases, physical properties such as tensile strength, tear strength, crack growth resistance and fatigue resistance decrease. In addition, the surface was discolored by a wax result. To solve this problem, it is necessary to reduce the use of wax and aging weak diene-based rubber and to increase the use of low unsaturated unsaturated polymer ethylene propylene diene terpolymer rubber or halogenated butyl rubber. It can result in falling.

Therefore, in order to reduce discoloration and reduce property degradation, the sidewall is divided into two layers, and the diene rubber composition is used to maintain the physical properties in the interior which is less affected by oxygen or ozone, and the outside which comes into contact with the outside. The layer is used to reduce the amount of amine antioxidants or waxes and diene-based rubbers as much as possible and to increase the amount of low-unsaturated polymer ethylene propylene diene terpolymer rubber or halogenated butyl rubber to reduce discoloration to the maximum while reducing weather resistance and weather resistance. Measures to improve ozone resistance and oxidation resistance and maintain properties such as tensile strength have been studied, but until now, methods to maintain physical properties such as tensile strength, tear strength, crack growth resistance and fatigue resistance while completely preventing discoloration This state is not presented.

Therefore, the present invention maintains weather resistance, ozone resistance, oxidation resistance, and the like without discoloration or appearance deterioration by not using an amine anti-aging agent or wax in the sidewall rubber composition, and tensile strength, tear strength, crack growth resistance, fatigue resistance An object of the present invention is to provide a rubber composition for a tire sidewall having both physical properties such as the like.

The present invention relates to low molecular liquid isobutylene rubber 2 to 80 parts by weight of a rubber consisting of 20 to 80 parts by weight of diene rubber, 10 to 40 parts by weight of polymer ethylene propylene diene terpolymer rubber, and 10 to 40 parts by weight of halogenated butyl rubber. It is a rubber composition for tire sidewalls consisting of 20 parts by weight.

Hereinafter, the present invention will be described in detail.

The rubber composition for the sidewall of the tire of the present invention reduces the amount of diene-based rubber that is susceptible to aging, and uses high ethylene propylene diene terpolymer rubber and halogenated butyl rubber with less unsaturation.

Therefore, in the present invention, 20 to 80 parts by weight of diene rubber, 10 to 40 parts by weight of polymer ethylene propylene diene terpolymer rubber, and 10 to 40 parts by weight of rubber of halogenated butyl rubber are low molecular weights that serve as a compatibilizer thereto. 2-20 weight part of liquid isobutylene rubbers are mix | blended.

When the polymer ethylene propylene diene terpolymer copolymer and the halogenated butyl rubber are used in the range of 100 parts by weight or more, the use of the polymer in the above range is preferable, since the tensile properties are deteriorated, thereby reducing the durability of the tire. .

The low molecular liquid isobutylene rubber is used having a molecular weight of 20,000 to 120,000. The low molecular liquid isobutylene rubber acts as a processing aid due to its low molecular weight, thereby reducing the processing viscosity even if the amount of oil, etc., which has an adverse effect on physical properties, is reduced, and the halogenated butyl rubber and diene rubber of the polymer is used. It improves the compatibility with (natural rubber or polybutadiene rubber) to improve the dispersion of the halogenated butyl rubber of the polymer in the diene rubber in the continuous phase. In this case, when the crack caused by ozone or oxygen continues to grow and encounters the halogenated butyl rubber of the polymer, growth stops. At this point, the crack length is below a certain length, and there is a critical crack length at which the growth stops. Above the length, the halogenated butyl rubber particles are bypassed and grown continuously. At this time, the low molecular liquid isobutylene rubber improves the dispersion of the halogenated butyl rubber particles in the diene rubber in the continuous phase, so that the number of cracks in which the growth proceeds meets the halogenated butyl rubber particles is increased to suppress the growth of such cracks. can do. In addition, if the compatibility is increased, it may advantageously work to improve physical properties such as tensile strength, thereby improving durability.

When the low molecular weight liquid isobutylene rubber is blended in an amount of 2 parts by weight or less, it is not effective, and when it is blended in an amount of 20 parts by weight or more, it is preferable to use 2 to 20 parts by weight since other mechanical properties such as tensile strength are inferior. .

Therefore, by combining the low molecular liquid isobutylene rubber can play a role that can reduce the compatibility and unsaturation without using any amine-based antioxidants or waxes.

Carbon black, a filler, a vulcanizing agent, a vulcanization accelerator, and the like are suitably blended in the rubber composition as a conventional compounding agent.

The rubber composition may also be applied to the white rubber and cover strip rubber composition of the white sidewalls.

The white sidewall consists of white rubber and a cover strip attached to the white rubber. Due to the nature of white rubber, carbon black, the most powerful reinforcing agent of rubber, cannot be used, resulting in deterioration of physical properties. Therefore, the black rubber layer called the cover strip is placed on the outside to remove only the white rubber exposed areas so that white rubber appears. By manufacturing a tire, it serves to prevent white contamination of white rubber during the tire manufacturing process and to improve durability during use.

The white rubber composition of the white sidewall is used by appropriately blending a white filler, a white pigment, a vulcanizing agent, a vulcanization accelerator, and the like to the rubber composition.

Moreover, the rubber composition of the cover strip of a white sidewall uses carbon black, a filler, a vulcanizing agent, a vulcanization accelerator, etc. as an appropriate compounding agent to the rubber composition of this invention, and mix | blends them suitably.

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

Example 1

40 parts by weight of natural rubber, 20 parts by weight of polybutadiene rubber, 20 parts by weight of EPDM (polymer ethylene propylene diene terpolymer rubber), 20 parts by weight of Br-IIR (halogenated butyl rubber), 5 parts by weight of low molecular liquid isobutylene rubber, A rubber composition for a tire sidewall was prepared by combining 42 parts by weight of carbon black, 3 parts by weight of zinc oxide, 2 parts by weight of stearic acid, 3 parts by weight of sulfur, 0.9 parts by weight of sulfur donor, and 0.5 parts by weight of accelerator. This is shown in Table 1 below.

Example 2

It was prepared in the same manner as in Example 1 except that 10 parts by weight of the low molecular liquid isobutylene rubber was used. This is shown in Table 1 below.

Example 3

Except for using 45 parts by weight of natural rubber and 15 parts by weight of polybutadiene rubber was prepared in the same manner as in Example 1. This is shown in Table 1 below.

Example 4

Except for using 10 parts by weight of low molecular weight liquid isobutylene rubber was prepared in the same manner as in Example 3. This is shown in Table 1 below.

Comparative Example 1

It was prepared in the same manner as in Example 1 except that 3 parts by weight of oil and 4 parts by weight of wax were used without using a low molecular liquid isobutylene rubber. This is shown in Table 1 below.

(Unit: parts by weight) Example Comparative example One 2 3 4 One Natural rubber 40 40 45 45 40 Polybutadiene rubber 20 20 15 15 20 EPDM 20 20 20 20 20 Br-IIR 20 20 20 20 20 Low Molecular Liquid Isobutylene Rubber 5 10 5 10 0 Carbon black 42 42 42 42 42 zinc oxide 3 3 3 3 3 Stearic acid 2 2 2 2 2 oil 0 0 0 0 3 Wax 0 0 0 0 4 brimstone 3 3 3 3 3 Sulfur donor 0.9 0.9 0.9 0.9 0.9 accelerant 0.5 0.5 0.5 0.5 0.5

Sulfur donor: Alkylphenol disulfide

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

Example 5

50 parts by weight of natural rubber, 25 parts by weight of EPDM, 25 parts by weight of Cl-IIR (halogenated butyl rubber), 5 parts by weight of low molecular liquid isobutylene rubber, 30 parts by weight of titanium oxide, 25 parts by weight of clay, 5 parts by weight of zinc oxide, 2 parts by weight of stearic acid, 25 parts by weight of calcium carbonate, 2 parts by weight of sulfur, 1.3 parts by weight of a sulfur donor and 1 part by weight of an accelerator were prepared to prepare a white rubber composition of a white sidewall. This is shown in Table 2 below.

Example 6

It was prepared in the same manner as in Example 5 except that 10 parts by weight of the low molecular liquid isobutylene rubber was used. This is shown in Table 2 below.

Example 7

45 parts by weight of natural rubber, except that 30 parts by weight of Cl-IIR was prepared in the same manner as in Example 5. This is shown in Table 2 below.

Example 8

Except for using 10 parts by weight of low molecular weight liquid isobutylene rubber was prepared in the same manner as in Example 7. This is shown in Table 2 below.

Comparative Example 2

It was prepared in the same manner as in Example 5 except that the low molecular weight liquid isobutylene rubber was used and 2 parts by weight of the wax was used. This is shown in Table 2 below.

(Unit: parts by weight) Example Comparative example 5 6 7 8 2 Natural rubber 50 50 45 45 50 EPDM 25 25 25 25 25 Cl-IIR 25 25 30 30 25 Low Molecular Liquid Isobutylene Rubber 5 10 5 10 0 Titanium oxide 30 30 30 30 30 Clay 25 25 25 25 25 zinc oxide 5 5 5 5 5 Stearic acid 2 2 2 2 2 Calcium carbonate 25 25 25 25 25 Wax 0 0 0 0 2 brimstone 2 2 2 2 2 Sulfur donor 1.3 1.3 1.3 1.3 1.3 accelerant One One One One One

Example 9

42 parts by weight of natural rubber, 18 parts by weight of polybutadiene rubber, 20 parts by weight of EPDM, 20 parts by weight of Br-IIR, 5 parts by weight of low molecular liquid isobutylene rubber, 38 parts by weight of carbon black, 3 parts by weight of zinc oxide, 2 parts by weight of stearic acid Parts, 7 parts by weight of oil, 3 parts by weight of sulfur, 0.9 parts by weight of sulfur donor and 0.5 parts by weight of accelerator to prepare a cover strip rubber composition of a white sidewall. This is shown in Table 3 below.

Example 10

Except for using 10 parts by weight of low molecular weight liquid isobutylene rubber and 5 parts by weight of oil was prepared in the same manner as in Example 9. This is shown in Table 3 below.

Example 11

Except for using 15 parts by weight of polybutadiene rubber, 23 parts by weight of Br-IIR was prepared in the same manner as in Example 9. This is shown in Table 3 below.

Example 12

Except for using 10 parts by weight of low molecular weight liquid isobutylene rubber and 5 parts by weight of oil was prepared in the same manner as in Example 11. This is shown in Table 3 below.

Comparative Example 3

It was prepared in the same manner as in Example 9, except that 4 parts by weight of wax and 9 parts by weight of oil were used without using a low molecular liquid isobutylene rubber. This is shown in Table 3 below.

(Unit: parts by weight) Example Comparative example 9 10 11 12 3 Natural rubber 42 42 42 42 42 Polybutadiene rubber 18 18 15 15 18 EPDM 20 20 20 20 20 Br-IIR 20 20 23 23 20 Low Molecular Liquid Isobutylene Rubber 5 10 5 10 0 Carbon black 38 38 38 38 38 zinc oxide 3 3 3 3 3 Stearic acid 2 2 2 2 2 oil 7 5 7 5 9 Wax 0 0 0 0 4 brimstone 3 3 3 3 3 Sulfur donor 0.9 0.9 0.9 0.9 0.9 accelerant 0.5 0.5 0.5 0.5 0.5

Test Example 1

The rubber compositions of Examples 1 to 4 and Comparative Example 1 were vulcanized at 168 ° C. for 20 minutes and then subjected to the following test.

Tensile Strength: Dumbbell No. 3 specimens of 2-3 mm thickness were tested at a clamping speed of 500 ± 25 mm / min.

Tear strength: 2.3 mm to 2.8 mm thick, type B specimens were tested at a clamping speed of 500 ± 25 mm / min.

Positive fatigue: Dumbbell-type specimens were repeatedly stretched at 100 rpm and elongation at 120% to measure the number of cycles until the specimens were cut.

Crack growth rate: Using a Demattia tester, giving an initial crack of 2mm and repeated bending at 300 cpm conditions to measure the grip distance from 65mm to 19mm was measured crack length in a certain cycle.

Ozone resistance: 2mm in thickness and 10mm in width under ozone concentration of 50 pphm and temperature of 40 ℃, it is fixed to 100mm long specimen with 20% elongation and fixed at the time of crack occurrence and dynamic to 60mm length specimen. Cracks were recorded at repeated elongation at 25% elongation.

Outdoor weatherability: Crack initiation was measured by repeatedly stretching specimens of length 100mm, thickness 2mm, and width 10mm at 20% elongation and 1Hz in outdoor.

Appearance discoloration: The degree of discoloration of the specimen was visually measured after the outdoor weathering test.

The results of the test are shown in Table 4 below.

Example Comparative example One 2 3 4 One Tensile Strength (㎏ / ㎠) 125 118 128 125 110 Tear strength (㎏ / ㎠) 40 38 40 39 38 Positive fatigue (kcycle) 75 72 70 68 70 Crack Growth Rate (㎛ / cycle) 0.02 0.02 0.02 0.02 0.02 Ozone Resistance (Sun) dynamic 15 15 15 15 15 silence 80 or more 80 or more 80 or more 80 or more 80 or more Outdoor kcycle More than 6000 More than 6000 More than 6000 More than 6000 More than 6000 Discoloration appearance No discoloration No discoloration No discoloration No discoloration Feces

In the above test examples, when comparing the rubber composition of Examples 1 to 4 with the rubber composition of Comparative Example 1, Examples 1 to 4 in tensile strength, tear strength, static strain, crack growth rate, ozone resistance and outdoor weather resistance The rubber composition of Comparative Example 1 and the rubber composition of Comparative Example 1 exhibited almost similar values, and whether or not appearance discoloration occurred in the rubber composition of Comparative Example 1, but discoloration of the rubber compositions of Examples 1 to 4 did not occur.

Test Example 2

After the rubber compositions of Examples 5 to 8 and Comparative Example 2 were vulcanized at 168 ° C. for 15 minutes, the tensile strength, tear strength, strain strain, crack growth rate, ozone resistance, and outdoor weather resistance were obtained as in Test Example 1. And the appearance color change is measured and shown in Table 5 below.

Example Comparative example 5 6 7 8 2 Tensile Strength (㎏ / ㎠) 125 120 120 120 120 Tear strength (㎏ / ㎠) 31 31 31 32 32 Positive fatigue (kcycle) 11 13 10 10 10 Crack Growth Rate (㎛ / cycle) 0.10 0.11 0.10 0.11 0.09 Ozone Resistance (Sun) dynamic 5 7 5 8 5 silence 14 24 10 28 10 Outdoor kcycle 5000 5500 5500 5500 4500 Discoloration appearance No discoloration No discoloration No discoloration No discoloration Feces

In the above test examples, when the rubber composition of Experimental Examples 5 to 8 compared with the rubber composition of Comparative Example 2, the rubber composition of Examples 5 to 8 in tensile strength, tear strength, static strain fatigue, ozone resistance and outdoor weather resistance And the rubber composition of Comparative Example 2 showed almost similar values, and whether or not the appearance of discoloration in the rubber composition of Comparative Example 2, but the whitening occurred in the rubber composition of Examples 5 to 8 did not occur.

Test Example 3

After vulcanizing the rubber compositions of Examples 9 to 12 and Comparative Example 3 at 170 ° C. for 20 minutes, the tensile strength, tear strength, strain strain, crack growth rate, ozone resistance, and outdoor weather resistance were obtained as in Test Example 1. And the appearance color change was measured and described in the following Table 6.

Example Comparative example 9 10 11 12 3 Tensile Strength (㎏ / ㎠) 115 115 120 120 105 Tear strength (㎏ / ㎠) 38 36 38 37 35 Positive fatigue (kcycle) 115 110 105 105 110 Crack Growth Rate (㎛ / cycle) 0.02 0.02 0.02 0.02 0.02 Ozone Resistance (Sun) dynamic 15 15 15 15 15 silence 80 or more 80 or more 80 or more 80 or more 80 or more Outdoor kcycle More than 7000 More than 7000 More than 7000 More than 7000 More than 7000 Discoloration appearance No discoloration No discoloration No discoloration No discoloration Feces

In the above test examples, when the rubber composition of Experimental Examples 9 to 12 compared with the rubber composition of Comparative Example 3, Examples 9 to 10 in tensile strength, tear strength, strain fatigue, crack growth rate, ozone resistance, and outdoor weather resistance. The rubber compositions of Example 12 and Comparative Example 3 exhibited almost similar values, and whether or not the appearance of discoloration occurred in the rubber composition of Comparative Example 3, but the discoloration of the rubber compositions of Examples 9 to 12 did not occur.

As mentioned above, the rubber composition of the present invention has no ozone resistance, weather resistance, oxidation resistance, etc., as well as tensile strength, tear strength, fatigue resistance, etc., without discoloration, as compared with the comparative example. Does not have a rubber composition.

The rubber composition according to the present invention can be used in the sidewall of the tire to increase the durability of the tire because it maintains physical properties such as tensile strength, tear strength, crack growth resistance, fatigue resistance while completely preventing discoloration.

Claims (2)

2 to 20 parts by weight of a low molecular weight liquid isobutylene rubber based on 100 parts by weight of a rubber consisting of 20 to 80 parts by weight of diene rubber, 10 to 40 parts by weight of polymer ethylene propylene diene terpolymer rubber, and 10 to 40 parts by weight of halogenated butyl rubber. A rubber composition for tire sidewalls. The rubber composition for tire sidewalls according to claim 1, wherein the molecular weight of the low molecular liquid isobutylene rubber is 20,000 to 120,000.