JPH05156085A - Rubber composition for tire sidewall - Google Patents

Abstract

PURPOSE:To obtain the subject composition having excellent ozone-degradation resistance, adhesiveness, co-vulcanizability, breaking strength and flexural fatigue resistance by compounding a specific compound to a specific diene rubber component. CONSTITUTION:The objective composition is produced by compounding (A) 100 pts.wt. of a diene rubber component containing >=30 pts.wt. of an ethylene- propylene-diene polymer rubber having a Mooney viscosity of >=110 at l00 deg.C and an iodine value of 24-35 with (B) preferably 0.1-5.0 pts.wt. of a compound of formula [Z is RNH (R is 1-18C aliphatic or cycloaliphatic group); R1 and R2 are H or 1-12C alkyl; R1 and R2 may together form a ring].

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition for tire sidewall, which is excellent in ozone deterioration resistance and improved in breaking strength and flex fatigue resistance.

[0002]

2. Description of the Related Art Conventionally, a rubber composition for a sidewall of a pneumatic tire is a rubber composition which has good ozone deterioration resistance to light, ozone, etc. and also has good adhesion to other kinds of rubber. As a component, there is a rubber composition using a blend rubber of an ethylene-propylene-diene copolymer rubber (hereinafter abbreviated as EPDM) and a diene rubber. However, this rubber composition has a drawback that the breaking strength and flex fatigue resistance are poor, and it cannot be said that the physical properties required as a rubber for sidewalls are sufficiently satisfied. In particular, when the proportion of the diene component of EPDM is reduced to improve the ozone deterioration resistance, the reactivity of EPDM itself is significantly lowered, and the covulcanizability with the diene rubber is impaired, and uniform vulcanization is difficult. Therefore, there is a problem that the breaking strength and the flex fatigue resistance are significantly reduced.

[0003]

It is an object of the present invention to improve the breaking strength and the co-vulcanizability of EPDM and diene rubber without impairing the ozone deterioration resistance and the adhesion to other rubbers. It is intended to provide a rubber composition for a sidewall which is excellent in flex fatigue resistance.

[0004]

DISCLOSURE OF THE INVENTION The present invention which achieves such an object is a diene rubber containing 30 parts by weight or more of EPDM having a Mooney viscosity of 110 or more at 100 ° C. and an iodine value of 24 to 35. A compound represented by the following chemical formula 1 is mixed with 100 parts by weight of the component.

Chemical formula 1

In the chemical formula 1, Z is an amino group represented by RNH- (R is a chain aliphatic group having 1 to 18 carbon atoms or a cycloaliphatic group, and an oxygen atom or a nitrogen atom is May or may not be included), R ₁ and R ₂ are
Hydrogen atom or the same or different number of carbon atoms 1 to 1 respectively
2 is an alkyl group, and R ₁ and R ₂ may be bonded to each other to form a ring.

As described above, by compounding the compound represented by the chemical formula 1, the co-vulcanization property of EPDM and diene rubber is improved, and the breaking strength and flexing resistance are maintained without impairing ozone deterioration resistance and adhesiveness. A rubber composition for sidewalls having excellent fatigue resistance can be obtained. In the present invention, the Mooney viscosity is a value measured according to the measuring method defined in JIS K6300, and it indicates the scale of the molecular weight of rubber. The larger this value, the larger the molecular weight.

The iodine value is a value measured by the following method and represents a measure of the reactivity of rubber. The larger this value is, the higher the reactivity is. Method for measuring iodine value: 0.5 g of purified EPDM was added with 100 ml of carbon tetrachloride and dissolved by heating. After cooling, 5 ml of 20% trichloroacetic acid solution, N / 10
25 ml of iodine solution and 25 ml of mercuric acetate solution were added in the above order, stirred well, and allowed to stand for 1 hour to react with iodine.

Next, 75 ml of a 7.5% potassium iodide aqueous solution was added and the mixture was vigorously shaken to transfer iodine to the aqueous layer, and then titrated with N / 10 sodium thiosulfate. When the iodine color becomes light, 1 ml of a starch solution is added to continue the titration, and when the color disappears, the titration is performed by shaking vigorously again and the point obtained when the color no longer returns to brown is the end point.

In the present invention, the diene rubber as the rubber component is not particularly limited as long as it satisfies the physical properties for sidewalls. For example, natural rubber, styrene-butadiene copolymer rubber (SB
R), polyisobutylene rubber (IR), polybutadiene rubber (BR), or a mixture of two or more of these can be used.

EPDM used in combination with the above-mentioned diene rubber
Needs to have a Mooney viscosity of 110 or more at 100 ° C. When the Mooney viscosity is less than 110, the molecular weight is small, and thus the breaking strength and flex fatigue resistance cannot be improved without impairing good ozone deterioration resistance. Further, its iodine value must be in the range of 24-35. When the iodine value is less than 24, the reactivity with the compound represented by the chemical formula 1 becomes small, and the covulcanizability with the diene rubber cannot be improved. On the other hand, when it exceeds 35, ozone resistance is deteriorated, which is not preferable.

Examples of the compound represented by the chemical formula 1 include a nitroamine derivative compound in which R ₁ and R ₂ are both methyl groups and Z is a group described below. Z: a group represented by the following chemical formula 2,

Chemical formula 2

CH ₃ NH-, CH ₃ CH ₂ NH-, CH
₃ (CH ₂ ) ₂ NH-, (CH ₃ ) ₂ CHNH, (CH
_{3) 3 CNH-, CH 3 CH} 2 CH (CH 3) NH-,
_{CH 3 (CH 2) 5 NH} -, (CH 3) 2 CHCH 2 C
_{H (CH 3) NH -,} (CH 3) 3 CCH 2 CH 2 NH
_{-, CH 3 (CH 2)} 7 NH-, CH 3 (CH 2) 9 N
_{H-, CH 3 (CH 2)} 11 NH-, CH 3 (CH 2) 17
NH-, and as the compounds represented by the above chemical formula 1 other than the compounds represented by the chemical formula 1 having these groups,
_{CH 3 (CH 2) 3 NH} -CH 2 CH 2 NO 2, CH 3
_{(CH 2) 7 NH-CH} 2 CH 2 NO 2, CH 3 (CH
₂ ) ₃ NH-CH ₂ CH (NO ₂ ) CH ₃ , CH ₃ (C
_{H 2) 7 NH-CH 2} CH (NO 2) may be mentioned nitramine derivative compound of the CH ₃ and the like.

The compounding amount of the compound represented by the chemical formula 1 is preferably in the range of 0.1 to 5.0 parts by weight with respect to 100 parts by weight of the rubber component. If it is less than 0.1 part by weight, the compounding effect cannot be sufficiently obtained, and EPD for diene rubber is not obtained.
The co-vulcanizability of M cannot be sufficiently improved,
If it exceeds 5.0 parts by weight, the scorch is accelerated and the workability is deteriorated.

Further, the rubber composition of the present invention contains carbon black, zinc white (zinc oxide), stearic acid, antioxidant, wax, aromatic oil, sulfur, vulcanization compounded in a usual rubber for sidewalls. A rubber chemical such as an accelerator can be appropriately mixed.

[0017]

EXAMPLES Rubber components 1 to 6 having the compounding compositions shown in Table 1 were prepared by introducing the rubber components and compounding chemicals into a B type Banbury mixer having a side wall temperature of 50 ° C. rotating at a rotor speed of 400 rpm and kneading for 5 minutes. Were prepared respectively.

[0018]

Further, EPDM-1 has a Mooney viscosity of 126 at 100 ° C., a rubber having an iodine value of 33, and ethylene /
Propylene blend ratio = 74/26 (wt%). Mooney viscosity at 100 ° C. of EPDM-2 = 1
50, iodine value = 33, ethylene / propylene blend ratio = 75/25 (wt%). The compound of Chemical Formula 1 is 1,6-bis (2-nitro, 2-methylpropylamino) hexane represented by Chemical Formula 3 below.

Chemical formula 3 The rubber compositions 1 to 6 in Table 1 were evaluated for vulcanization degree tensile rupture strength, high temperature tensile rupture strength, flexural fatigue resistance and crack growth by the following methods. The results are shown in Table 2. Vulcanization degree Tensile breaking strength: Measured according to the method specified in JIS-K6301. High temperature tensile breaking strength: A value obtained by carrying out a tensile test prescribed in JIS-K6301 under the condition of an atmospheric temperature of 100 ° C. Bending fatigue resistance (constant strain fatigue test): ASTM D-4, except that a Fatigue Tester manufactured by Monsanto Co., Ltd. was used and the condition of strain rate = 100% was applied.
It measured until it fractured according to the method prescribed in 482. The measurement result is based on the measurement value of Comparative Example 1 (100)
It is displayed with the index. The larger this index value, the better the constant strain fatigue resistance (flexing fatigue resistance). Crack growth: Using a Demacha-type tester specified in JIS K6301, the measurement was performed with a stroke number of 40 mm, and when the required number of bendings was reached, the operation was stopped and the crack length was measured.

[0021] As shown in Table 1, each of Comparative Example 1 and Example 1, Comparative Example 2 and Example 2, and Comparative Example 3 and Example 3 may or may not contain the compound represented by Chemical Formula 3 above. The only difference is that the composition and amount of the other rubber components and compounded chemicals are the same. As shown in Table 2, the corresponding Comparative Example 1
It can be seen that the rubber compositions of Examples 1 to 3 have higher rupture strength when stretched at high temperature, excellent constant strain fatigue resistance, and less crack growth than Comparative Examples 1 to 3.

[0022]

As described above, according to the present invention,
By mixing 100 parts by weight of a diene rubber component containing 100 parts by weight of EPDM having a Mooney viscosity of 110 or more and an iodine value of 24 to 35 at 100 ° C. with a compound represented by the chemical formula 1, diene rubber and EPDM can be obtained. It is possible to obtain a rubber composition for a sidewall of a pneumatic tire that has improved co-vulcanizability with, and has excellent breaking strength and flex fatigue resistance without impairing ozone deterioration resistance and adhesion to other rubbers. ..

Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display area C08L 23:16)

Claims (1)

[Claims] 1. The Mooney viscosity at 100 ° C. is 110.
As described above, a tire side in which 100 parts by weight of a diene rubber component containing 30 parts by weight or more of an ethylene-propylene-diene copolymer rubber having an iodine value of 24 to 35 are compounded with a compound represented by the following chemical formula 1 Rubber composition for walls. Chemical formula 1 However, in Chemical Formula 1, Z is an amino group represented by RNH- (R is a chain aliphatic group having 1 to 18 carbon atoms or a cyclic aliphatic group, and contains an oxygen atom or a nitrogen atom. R ₁ and R ₂ are each a hydrogen atom or the same or different alkyl group having 1 to 12 carbon atoms, and R ₁ and R ₂ are bonded to each other to form a ring. May be.