JPH0625471A - Rubber composition and its use - Google Patents

Abstract

PURPOSE:To obtain a rubber compsn. resistant to fatigue due to repeated flexing and elongation by compounding a rubber with a specific 3,3',5,5'-tetrasubstd. 4,4'-dihydroxybiphenyl and a specific N,N'-disubstd. p-phenylenediamine. CONSTITUTION:100 pts.wt. at least one rubber selected from the group consisting of natural and synthetic diene rubbers is compounded with 0.1-5 pts.wt. 3,3',5,5'-tetrasubstd. 4,4'-dihydroxybiphenyl of formula I (wherein R and R' are each independently 1-12C linear or branched alkyl, phenyl, cycloalkyl, amino, aryl, naphthyl, aralkyl, methoxyphenyl, or alkenyl) and 0-5 pts.wt. N,N'-disubstd. p-phenylenediamine of formula II (wherein R and R' are each independently 3-8C linear or branched alkyl or phenyl).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a rubber composition. More specifically, the present invention relates to a rubber composition and an antiaging agent, which prevent aging of rubber, particularly repeated bending and extension fatigue.

[0002]

2. Description of the Related Art Rubber compositions exhibiting viscoelastic behavior are widely used in various rubber products such as tires, conveyor belts, and other industrial rubber products that are subject to repeated bending and extension strains by utilizing this unique property. Has been done. When used under such conditions for a long time, fatigue caused by oxidation by oxygen, ozone, or heat generation causes a crack, which grows and finally breaks. If the fatigue due to such repeated bending and extension can be improved, not only the failure caused by the fatigue can be reduced but also the weight can be reduced, and in the case of the tire, the fuel efficiency can be promoted as an effect.

Conventionally, N, N'-di-substituted-p-phenylenediamine has been widely used as a method for improving repeated flexion-extension fatigue. However, even if a large amount of these is blended, the effect is limited, and if blended in a relatively large amount, blooming occurs in a short period of time, causing the phenomenon that the surface of the rubber product is discolored to brown, which deteriorates the appearance. There is a drawback that. Even when such N, N′-di-substituted-p-phenylenediamine is used, its effect cannot be sufficiently achieved. In addition, as a non-colored and non-staining antioxidant, there is a phenol derivative, and for example, a monophenol derivative, a polyphenol derivative, or a bisphenol derivative in which a phenol derivative is bonded directly to each other or through an alkylene group and a sulfide as an intermediate. Can be given.

This is because these phenol derivatives are generally less effective than the aforementioned N, N'-di-substituted-p-phenylenediamine. Against this background, at present, there is a demand for development of a technique for a rubber composition having improved repeated flexural extension fatigue. Regarding biphenol derivatives directly bonded to each other, for example, 3,3 ', 5,5'-tetra-substituted-5,5'-dihydroxybiphenyl is described in Dutch Patent No. 66,055 as stability of cracked gasoline. US Pat. No. 3,095,287 is described to improve the thermal stability of jet fuels, and British Patent No. 1,073.
No. 0,960 describes improving the prevention of oxidation of polymers of α-olefins such as polypropylene. However, there is no example of using a biphenol derivative in rubber.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a rubber composition which is resistant to repeated bending and elongation fatigue, which cannot be obtained with conventional antioxidants.

[0006]

The present inventor has conducted extensive studies in view of the above-mentioned circumstances, and as a result, the following chemical formula 3 (in the formula, R,
R'independently represents a linear or branched alkyl group having 1 to 12 carbon atoms, phenyl group, cycloalkyl group, amino group, aryl group, naphthyl group, aralkyl group, methoxyphenyl group, alkenyl group) By blending 3,3′5,5′-tetra-substituted-4,4′-dihydroxybiphenyl represented by
And a compound represented by Chemical formula 4 (in the formula, R and R'independently represent a linear or branched alkyl group having 3 to 8 carbon atoms or a phenyl group), N, N'-di- By a synergistic action with a substituted-p-phenylenediamine, a rubber composition which resists repeated flexural extension fatigue resistance has been found, and the present invention has been completed.

[0007]

[Chemical 3]

[Chemical 4]

3,3 'represented by the chemical formula 3 in the present invention,
Specific examples of 5,5′-tetra-substituted-4,4′-dihydroxybiphenyl include those shown below. 3,3 ', 5,5'-tetramethyl-4,4'
-Dihydroxybiphenyl, 3,3'-diethyl-5,
5'-dimethyl-4,4'-dihydroxybiphenyl,
3,3'-di-secondary butyl-5,5'-dimethyl-
4,4'-dihydroxybiphenyl, 3,3'-di-tertiary butyl-5,5'-methyl-4,4'-dihydroxybiphenyl, 3,3 ', 5,5'-tetraethyl-
4,4'-Dihydroxybiphenyl, 3,3'-dimethyl-5,5'-dioctyl-4,4'-dihydroxybiphenyl, 3,3 ', 5,5'-tetra-tertiary butyl-4,4 '-Hydroxybiphenyl, 3,3'-di (diisobutyl) -5,5'-didodecyl-4,4'-dihydroxybiphenyl.

Specific examples of the N, N'-di-substituted-p-phenylenediamine represented by the formula 4 are N-isopropyl-N'-phenyl-p-phenylenediamine and N- (1,3- Dimethylbutyl) -N'-phenyl-p-phenylenediamine, N- (1-methylheptyl) -N'-phenyl-p-phenylenediamine, N,
N'-diphenyl-p-phenylenediamine etc. are mentioned.

[0010]

The rubber composition of the present invention has the above 3,3 ', 5,
A rubber composition obtained by adding 5'-tetra-substituted-dihydroxybiphenyl or N, N'-di-substituted-p-phenylenediamine to unvulcanized rubber.
A rubber anti-aging agent, particularly a rubber composition which prevents repeated bending fatigue, and a rubber anti-aging method. The rubber may be natural rubber or diene-based synthetic rubber, and the diene-based synthetic rubber may be of any type.

The compounding amount of 3,3 ', 5,5'-tetra-substituted-4,4'-dihydroxybiphenyl according to the present invention is about 0.1 to 5 parts by weight based on 100 parts by weight of the rubber component. And preferably 0.3 to 1 part by weight. Also N,
The ratio when N'-di-substituted-p-phenylenediamine is used in combination is 5 parts by weight or less, preferably 0.5 to
It is 1.0 part by weight. As a concrete operation method of the method of the present invention, for example, a vulcanizing agent, a vulcanization accelerator,
Appropriate auxiliary agents such as activators, fillers, reinforcing agents, anti-aging agents, extenders, coloring agents, etc. are added as necessary, and the above 3,3 ', 5,5'-tetra-substituted-4 is added. , 4'-dihydroxybiphenyl or N, N'-di-substituted-
Add and mix with p-phenylenediamine. The rubber mixture of this unvulcanized rubber may be vulcanized by an appropriate means according to the purpose from the conventionally used conventional methods such as thermal vulcanization and high frequency vulcanization.

As described above, according to the present invention, there are various advantages as shown below, which is extremely significant industrially. The first feature is that the 3,3 ′, 5,5′-tetra-substituted-4,4′-dihydroxybiphenyl according to the present invention has a low volatility and therefore does not volatilize and scatter during vulcanization. Secondly, 3,3 ′, 5,5′-tetra-substituted-4,4 ′ according to the present invention.
-Dihydroxybiphenyl has little effect on early vulcanization (scorch) and vulcanization. Thirdly, according to the present invention 3,
3 ', 5,5'-Tetra-substituted-4,4'-dihydroxybiphenyl has less coloring and contamination on the vulcanized rubber. Fourth, 3,3 ′, 5,5′-tetra-substituted-according to the present invention
4,4'-Dihydroxybiphenyl has little decrease in tensile strength, tensile stress and hardness of the vulcanized rubber.

[0013]

EXAMPLES Next, the present invention will be described with reference to examples, but the present invention is not limited to these examples. Example 1 5 g of a sample was precisely weighed in a glass weighing bottle having a diameter of 3.5 mm and a depth of 40 mm, and left in a thermostat at 180 ° C. for a predetermined time,
Precisely weigh each sample after standing, and from the following formula,
The weight loss% after heat treatment of each sample was determined. Weight loss% = (A−B) / A × 100 where A = sample weight before heat treatment, B = sample weight after heat treatment This weight loss% was taken as the volatile scale of each sample. The results are shown in Table 1.

[0014]

[Table 1]

Example 2 The formulations in Table 2 were kneaded in the usual manner at a roll temperature of 70 ± 5 ° C. using 8 ″ φ × 20 ″ L test rolls. Then, the effect of preventing repeated bending and elongation fatigue of the product of the present invention and the scorch by the method shown below, the vulcanization rate,
The effect of the vulcanized rubber on the tensile properties, hardness or colorability was tested. The results are shown in Table 3. The repeated flexion elongation fatigue test is performed by repeating the repeated elongation and flexion of a JIS No. 3 dumbbell-shaped sample having a thickness of 2 mm at a rate of 300% at a cycle rate of 300 cycles / min using a de-marcher type flexural cracking tester until it breaks. The number of repeated cycles (fatigue life) was measured.

The Mooney Scorch test is JIS K 63
It was carried out at 125 ° C. according to 00. The curastometer test was performed at 160 ° C. under the following test conditions. Testing machine: JSR curast meter, die: 2m
m, amplitude: ± 3 °, induction time: t ₁₀ (minutes, seconds), vulcanization time: t ₉₀ (minutes, seconds), rising speed: t ₉₀ −t
₁₀ was adopted. Vulcanized rubber tensile and hardness tests are JI
It was carried out according to SK 6301. In the coloring test of the vulcanized rubber, a tandem sample having a thickness of 2 mm, a width of 70 mm and a length of 215 mm was exposed outdoors for 2 weeks, and then the colored state was visually observed. The vulcanized rubber had a press vulcanization time of 16
Estimated proper vulcanization time of Curastometer at 0 ℃ 2
It was adopted t ₉₀ -t _10.

[0017]

[Table 2]

[0018]

[Table 3]

Example 3 According to Example 2, the formulations shown in Table 4 were tested below.
Table 5 shows the results of testing the effect of preventing repeated bending and elongation fatigue of the product of the present invention and the effects on the scorch, the vulcanization rate, and the tensile properties and hardness of the vulcanized rubber.

[0020]

[Table 4]

[0021]

[Table 5]

Example 4 In accordance with Example 2, the formulations shown in Table 6 were tested below.
Table 7 shows the results of testing the effect of preventing repeated bending and elongation fatigue of the product of the present invention and the effects on the scorch, the vulcanization rate, and the tensile properties and hardness of the vulcanized rubber.

[0023]

[Table 6]

[0024]

[Table 7]

Example 5 According to Example 2, the formulations shown in Table 8 were tested below.
Table 9 shows the results of testing the effect of preventing repeated bending and elongation fatigue of the product of the present invention and the effects on scorch, vulcanization rate, tensile properties and hardness of vulcanized rubber.

[0026]

[Table 8]

[0027]

[Table 9]

[0028]

As is apparent from the above-mentioned embodiments, 3,3 ', 5,5'-tetra-substituted-4,4' according to the present invention.
-Dihydroxybiphenyls, and optionally N, N '
By blending the -di-substituted-p-phenylenediamines, a rubber composition that resists aging of rubber, particularly repeated bending and extension fatigue that cannot be obtained by conventional antioxidants can be provided.

Claims (8)

[Claims] 1. With respect to 100 parts by weight of at least one rubber selected from the group consisting of natural rubber and / or diene-based synthetic rubber, Chemical Formula 1 (wherein R and R ′ are each independently, 3,3 ', 5 represented by a linear or branched alkyl group having 1 to 12 carbon atoms, phenyl group, cycloalkyl group, amino group, aryl group, naphthyl group, aralkyl group, methoxyphenyl group, alkenyl group) , 5'-
Tetra-substituted-4,4'-dihydroxybiphenyl
0.1 to 5 parts by weight, N, N'- represented by Chemical formula 2 (in the formula, R and R'independently represent a linear or branched alkyl group having 3 to 8 carbon atoms or a phenyl group) Di-substituted-p
-Phenylenediamine A rubber composition containing 0 to 5 parts by weight. [Chemical 2] 2. The rubber composition according to claim 1, wherein the compound of Chemical formula 1 is 3,3′-di-tertiary butyl-5,5′-dimethyl-4,4′-dihydroxybiphenyl. 3. The compound of Chemical formula 2 is N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine and / or N-isopropyl-N'-phenyl-p-phenylenediamine. The rubber composition according to 1. 4. A method for preventing aging of the rubber by the rubber composition according to claim 1. 5. A method for preventing repeated bending and extension fatigue of the rubber by the rubber composition according to claim 1. 6. Chemical formula 1 0.1-5 parts by weight, chemical formula 2
A rubber anti-aging agent consisting of 0 to 5 parts by weight. 7. An agent for preventing repeated bending and elongation fatigue of rubber, which comprises the compound according to claim 6. 8. 3,3'-Di-tertiary butyl-5,5'-
Dimethyl-4,4'-dihydroxybiphenyl 0,1
An agent for preventing repeated bending and extension fatigue of rubber by 5 parts by weight.