JPH0762156A - Rubber composition - Google Patents

Abstract

PURPOSE:To obtain a rubber composition excellent in ozone resistance and appearance. CONSTITUTION:The composition comprises 100 pts.wt. rubber component, 0.5-6 pts.wt. aromatic secondary amine antioxidant, and 0.2-2.2 pts.wt. thiourea antioxidant. This composition is excellent in both ozone resistance and appearance and hence less tends to develop cracks. Therefore, a tire excellent in durability and appearance can be produced from the composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition suitable for use in tire sidewalls, and more particularly to a rubber composition having excellent ozone resistance and appearance.

[0002]

2. Description of the Related Art Tire sidewalls tend to crack under the influence of ozone in the atmosphere during long-term use.

Therefore, in order to improve ozone resistance, it has been conventionally practiced to blend an aromatic secondary amine-based antioxidant with a rubber composition for a sidewall. However, the aromatic secondary amine anti-aging agent is contaminated with the compounded rubber, and there is a problem that the oxide generated by the reaction of the amine anti-aging agent with ozone causes the rubber surface to turn brown. .

Further, a thiourea antiaging agent has been blended in order to improve the ozone resistance, but the effect of improving the ozone resistance was low although the problem of discoloration did not occur.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to provide a rubber composition having improved ozone resistance and appearance.

[0006]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that the use of a specific amount of an aromatic secondary amine anti-aging agent and a thiourea anti-aging agent has made it difficult to achieve the conventional resistance. The present invention has been completed by discovering that both the ozone property and the appearance property can be improved.

That is, in the present invention, 0.5 to 6 parts of an aromatic secondary amine anti-aging agent and 0.2 parts of a thiourea anti-aging agent are used with respect to 100 parts (parts by weight; hereinafter the same) of a rubber component.
To 2.2 parts by weight of the rubber composition.

[0008]

According to the present invention, by combining both antiaging agents, a synergistic effect which cannot be predicted from the results of using each of them alone can be obtained. Ie aromatic 2
By replacing a part of the primary amine anti-aging agent with a thiourea anti-aging agent, not only the appearance but also the ozone resistance is improved, and the conventional anti-diffusion property is improved.

In the rubber composition of the present invention, the rubber component is not particularly limited, but the effect of the present invention can be obtained by using a diene rubber having a problem of ozone resistance, such as NR, IR, BR or SBR, as a main component. Effectively demonstrated.

As the aromatic secondary amine anti-aging agent,
Nocrac 6C (N-phenyl-N '-(1,3-dimethylbutyl) -p-phenylenediamine) manufactured by Ouchi Shinko Chemical Co., Ltd., Nocrac 810-NA (manufactured by Ouchi Shinko Chemical Co., Ltd.) N-phenyl-N'-isopropyl-
p-phenylenediamine), Nocrac DP (N, N'-diphenyl-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Co., Ltd., Ozonone 35 (octylated diphenylamine) manufactured by Seiko Chemical Co., Ltd., Seiko Chemical ( Nonflex F (N, N'-di-2-naphthyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd., Sumilizer MXA (mixture of diallyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd., and the like.

As the thiourea antiaging agent, Nocrac NS-10-N (1, Ouchi Shinko Chemical Co., Ltd.)
3-bis (dimethylaminopropyl) -2-thiourea), Nocrac TBTU manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
(Tributylthiourea) and the like.

The aromatic secondary amine anti-aging agent is 0.5 to 6 parts, preferably 1.5 to 6 parts, based on 100 parts of the rubber component.
6 parts are blended. If it is less than 0.5 part, the effect of improving the ozone resistance tends to be poor, and if it is more than 6 parts, discoloration to an unacceptable degree tends to occur.

The thiourea-based antioxidant is a rubber component 10
0.2 to 2.2 parts, preferably 0.3 to 0 parts
1.5 parts, more preferably 0.3 to 1.0 parts are blended. If it is less than 0.2 parts, the effect of improving the appearance and the effect of improving the ozone resistance may not be obtained so much.
If it is more than 2.2 parts, the thiourea anti-aging agent tends to bleed to the rubber surface and the appearance tends to be poor. In the present invention, the effect of improving discoloration resistance and ozone resistance can be obtained even if the amount of the thiourea antiaging agent is less than 1 part.

Aromatic 2 to 100 parts of the rubber component
When the blending amount of the primary amine-based antioxidant is x (part) and the blending amount of the thiourea-based antioxidant is y (part)

[0015]

[Equation 1]

It is more preferable that the relationship

[0017]

[Equation 2]

This is because, if ozone cracks occur, there may be deep and large cracks although the number is small.

The carbon black blended in the rubber composition of the present invention has a nitrogen adsorption specific surface area of 35 m ² / g to
The range of 125 m ² / g is preferable from the viewpoint of mechanical properties. When it is less than 35 m ² / g, the reinforcing effect is poor,
If it exceeds 125 m ² / g, it becomes too hard. Preferred examples of such carbon black include ISAF, HAF and FEF.

The carbon black is preferably blended in an amount of 20 to 100 parts, particularly 30 to 70 parts, based on 100 parts of the rubber component. If it is less than 20 parts, the reinforcing effect tends to be poor, and if it is more than 100 parts, it tends to be too hard.

The rubber composition of the present invention is appropriately compounded with a compounding agent which is usually used, for example, a softening agent, a reinforcing agent, zinc white, stearic acid, a vulcanization accelerator, a vulcanizing agent, sulfur and the like depending on the use. be able to.

The rubber composition of the present invention can be produced by a usual method using a rubber component, an aromatic secondary amine anti-aging agent, a thiourea anti-aging agent, carbon black and the above compounding agent.

The rubber composition of the present invention is preferably used for a portion where ozone resistance and discoloration resistance are required, for example, a sidewall of a tire, a tread industrial hose, and a fender.

The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

Example 1 Experimental Example 1-1 Using the following formulation, a compounding agent excluding sulfur and an accelerator was kneaded with a small Banbury mixer, and after mixing the sulfur and the accelerator with a two-roll mill, 150 ° C. A rubber composition for a sidewall of a tire was prepared by vulcanizing for 30 minutes.

Natural rubber 50 parts Butadiene rubber ⁽¹⁾ 50 parts Carbon black ⁽²⁾ 40 parts Softener ⁽³⁾ 5 parts Wax 1 part Zinc white 5 parts Stearic acid 1 part Aromatic secondary amine anti-aging agent ^{(4 )} 2 parts Thiourea type anti-aging agent ⁽⁵⁾ 1 part Sulfur 2 parts Accelerator ⁽⁶⁾ 1 part As the butadiene rubber (1), BR150B manufactured by Ube Industries, Ltd., as carbon black (2), Mitsubishi As a softening agent (3) manufactured by Kasei Co., Ltd., Diablack H (HAF) (nitrogen adsorption specific surface area 79 m ² / g), an aromatic oil, and as an aromatic secondary amine antiaging agent (4), Ouchi Nocrac 6C manufactured by Shinko Chemical Industry Co., Ltd.
(N-phenyl-N '-(1,3-dimethylbutyl)-
p-phenylenediamine) and thiourea anti-aging agent (5) include Nocrac NS-10-N (1,3-bis (dimethylaminopropyl) -2-thiourea) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. As the accelerator (6), Nocceller CZ (N-cyclohexyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. was used.

The ozone resistance and discoloration resistance of the obtained rubber composition were tested by the following methods. The results and the formulation of the antioxidant are shown in Table 1.

[Ozone resistance] After being left for 72 hours under the conditions of JIS K6301 elongation ratio of 20%, ozone concentration of 50 pphm and 40 ° C., the ozone deterioration test was carried out by the method of ozone degradation test specified in JIS K6301. The result is J
It is shown by the crack state display method defined in IS K6301. Although it cannot be generally stated, it is desirable that the result is A-2 or higher.

After being left for 72 hours under the conditions of a visual elongation ratio of 20%, an ozone concentration of 50 pphm, and a temperature of 40 ° C., the state of cracking was visually judged 1
It was evaluated by the 0-point method. The larger the value, the smaller the degree of deterioration. Strongly speaking, 7 or more is desirable.

[Discoloration resistance] b value Elongation ratio of 20%, ozone concentration of 50 pphm, left for 72 hours under conditions of 40 ° C., and then using a color difference meter (MINOLTA CR-310) manufactured by Minolta Camera Co., Ltd. It is the obtained measurement value. It is desirable that it be smaller than 0 if it is forced.

After being left for 72 hours under the conditions of a visual elongation ratio of 20%, an ozone concentration of 50 pphm, and a temperature of 40 ° C., the blackness was visually judged 1
It was evaluated by the 0-point method. The larger the value is, the darker the black color is. Speaking strongly, 6 or more is desirable.

Experimental Examples 1-2 to 1-5 A rubber composition was prepared in the same manner as in Experimental Example 1-1, except that the composition of the antioxidant was changed as shown in Table 1. These rubber compositions were tested for ozone resistance and discoloration resistance in the same manner as in Experimental Example 1-1. The results and the formulation of the antioxidant are shown in Table 1.

Experimental Examples 1-6 to 1-8 A rubber composition was prepared in the same manner as in Experimental Example 1-1, except that the composition of the antioxidant was changed as shown in Table 1. These rubber compositions were tested for ozone resistance and discoloration resistance in the same manner as in Experimental Example 1-1. The results and the formulation of the antioxidant are shown in Table 1. In Experimental Example 1-6, the thiourea-based antioxidant was replaced with Nocrac TBTU (tributylthiourea) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
In Experimental Example 1-7, an aromatic secondary amine anti-aging agent was used as Nocrac 810-NA manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
Instead of (N-phenyl-N′-isopropyl-p-phenylenediamine), in Experimental Example 1-8, an aromatic secondary amine-based antioxidant was used as Sumilizer MXA (diallyl-p-) manufactured by Sumitomo Chemical Co., Ltd. It was used instead of the phenylenediamine mixture).

[0034]

[Table 1]

In the above experimental example, experimental examples 1-1 and 1-
It can be said that 2, 1-6, 1-7 and 1-8 are excellent in both ozone resistance and discoloration resistance, since they are a well-balanced blend of an aromatic secondary amine anti-aging agent and a thiourea anti-aging agent. In Experimental Example 1-3, the degree of cracking is small, but the discoloration is large. In Experimental Examples 1-4, the degree of cracking was large and the discoloration was very small, but the thiourea-based antioxidant bleeded on the surface of the rubber and the overall appearance was poor.
In addition, Experimental Examples 1-5 did not use any aromatic secondary amine anti-aging agent or thiourea anti-aging agent and were inferior in ozone resistance.

Since the ozone resistance by visual observation was 6 in Experimental Example 1-3 using only the amine anti-aging agent and 3 in Experimental Example 1-4 using only the thiourea anti-aging agent, both aging were observed. In Experimental Examples 1-1 and 1-2 using the inhibitor, it is expected that the ozone resistance by visual observation will be a value of 3 to 6, but in reality, the values are 10 and 7, which are higher than expected. That is, the synergistic effect of using two kinds of antiaging agents in the present invention together is shown. Also,
Regarding the discoloration (brown discoloration), in Experimental Examples 1-1 and 1-2, the values deviated from the results of Experimental Examples 1-3 and 1-4 in a direction better than the value expected assuming the additive effect, This is also considered to be a synergistic effect.

[0037]

The rubber composition of the present invention is excellent in both ozone resistance and appearance, and when a tire is produced by using this rubber composition for a sidewall, cracks are less likely to occur, resulting in durability. A tire with excellent appearance can be obtained.

Claims (2)

[Claims] 1. To 100 parts by weight of a rubber component, 0.5 to 6 parts by weight of an aromatic secondary amine-based antioxidant and 0.2 to 2.2 parts by weight of a thiourea-based antioxidant are blended. Rubber composition. 2. The rubber composition according to claim 1, wherein the rubber component contains at least a diene rubber.