JPH01163228A - Rubber composition - Google Patents

Abstract

PURPOSE:To obtain a rubber composition, containing an antioxidant containing an oil gelling agent added thereto, having improved resistance to ozone, crack and flex cracking and useful as tires, etc. CONSTITUTION:The aimed rubber composition containing an antioxidant [e.g., N-phenyl-N'-isopropyl-p-phenylenediamine expressed by formula II, N-phenyl-N '-(1,3-dimethylbutyl)-p-phenylenediamine expressed by formula III or N-(1- methylheptyl)-N'-phenyl-p-phenylenediamine expressed by formula IV] containing an oil gelling agent (e.g., N-lauroyl-L-glutamic acid-alpha,gamma-di-n-butyramide expressed by formula I) added thereto.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rubber composition with improved ozone crack resistance and flex crack resistance.

[Prior art]

-II, rubbery polymeric materials, especially materials having unsaturated bonds in their molecular chains, undergo aging when exposed to the effects of ozone, oxygen, light, heat, etc., resulting in a significant decline in various properties;
In many cases, it becomes impractical. In order to prevent such aging, various anti-aging agents such as phenolic and amine-based anti-aging agents have traditionally been added to rubber. It's demonstrating itself. However, for rubber products used in harsh environments such as tires, these anti-aging agents alone are insufficient. For example, in the case of a practical pneumatic tire, when it is filled with internal pressure and exposed to ozone, an ozone crank is generated at the groove bottom of the side part or trend part, and especially in the side rubber, the crank grows from the crank as a starting point due to transfer strain. There is.

Conventionally, in order to prevent the occurrence of such ozone cracks, in addition to anti-aging agents, wax (
WAX) has been used in combination. However, wax easily peels off from the surface of the molded product, has low mechanical strength and is prone to cracks, and the cracks cause ozone deterioration of the rubber composition. The blooming of wax on the rubber composition is unavoidable, and this significantly reduces the adhesion of the unvulcanized rubber composition, which hinders the bonding of the rubber composition during molding, resulting in problems such as reduced workability. .

In addition, the abrasion resistance, crank growth resistance, heat generation resistance, etc. of the rubber composition are also reduced.

In view of the above-mentioned circumstances, the present inventors conducted intensive research to develop an ozone crack prevention agent to replace wax, and found that by adding an oil gelling agent to the anti-aging agent, it was possible to eliminate the need for a single anti-aging agent. It was discovered that excellent ozone crank resistance and flex crack resistance, which had not previously been obtained, were exhibited. The present invention has been made based on this knowledge.

[Purpose of the invention]

Therefore, an object of the present invention is to provide a rubber composition with improved ozone crack resistance and flex crack resistance.

[Structure of the invention]

Therefore, the gist of the present invention is a rubber composition containing an anti-aging agent to which an oil gelling agent is added.

Hereinafter, the configuration of the present invention will be explained in detail.

(al　oil gelling agent.

Any ordinary oil gelling agent may be used, and there are no particular limitations.

To solidify an organic medium such as oil, for example, a method of adding metal soap and a small amount of water to a hydrocarbon fuel, a method of using a condensate of polyhydric alcohol and benzaldehyde, a method of using O/W
A method of adding a type (oil-in-water type) surfactant and a small amount of water, a method of adding a grease prepared by adding metal soap to mineral oil to machine oil, and a method of adding N-acylamino acid ester, N-acylamino acid amide, or A method of adding an amino acid-based gelling agent such as an N-acylamino acid amine salt is known (Japanese Patent Publication No. 13434/1983), but the gelling agent used in the present invention is not suitable for use as an anti-aging agent. What we are doing,
Furthermore, from the viewpoint of ease of handling and hygiene, an amino acid-based oil gelling agent is preferable. In other words, amino acid-based oil gelling agents (1) can gel a wide range of liquid organic media such as aliphatic hydrocarbons, aromatic hydrocarbons, ester lubricating oils, animal and vegetable oils, and (2) can heat gelled oils. It has so-called thermoreversible properties, returning to a liquid state and gelling again when cooled. (3) Has the effect of suppressing oil volatilization. (4) Only requires a small amount to be added. It has the following characteristics: it does not require the addition of auxiliary additives, the processing method is simple, and (6) it is highly safe and has good biodegradability.

(b) Anti-aging agents. Next, the anti-aging agent to be used may be either an amine-based or a phenol-based anti-aging agent, but the lower the melting point and the less damaging the property, the better. Particularly effective is a liquid anti-aging agent containing a large number of alkyl groups, which is gelatinized to improve storage stability and processing workability.

(C) To add an oil gelling agent to an anti-aging agent, no special method is required and the anti-aging agent and gelling agent may be simply mixed together, but it is preferable to add oil to the anti-aging agent. It is preferable to perform a heat dissolution process in which a gelling agent is added, heated above the dissolution temperature, and cooled. The amount of the gelling agent added is 0.01% by weight or more, preferably 0.1 to 50% by weight, based on 100 parts by weight of the anti-aging agent. especially,
As for the anti-aging agent which is liquid at room temperature, by controlling the amount added, it is possible to adjust the hardness to be convenient for processing operations.

In the present invention, as described above, an anti-aging agent added with an oil gelling agent is blended into rubber, but there is no particular limitation on the type of rubber to be blended. Although it can be applied to natural rubber and various synthetic rubbers, it is effective for rubbers that have unsaturated bonds and are susceptible to aging, such as natural rubber or diene-based synthetic rubber. Furthermore, the method of adding it to rubber is no different from the conventional method of adding anti-aging agents.

Examples and comparative examples are shown below.

Examples, comparative examples (1) Oil gelling agent.

The oil gelling agent used was Ajinomoto (JL Coagulan G).
P-1 (chemical name; N-lauroyl-L-glutamic acid-
α,γ-di-n-butyramide) and has the structural formula shown in (I) below.

CH3(CH2) r. C0NII ClIC0NH(
CHz) 3C1+3CHzCHgCONH(CHz)
*CHi The gelling mechanism of this oil gelling agent is based on the formation of a three-dimensional network structure due to hydrogen bonds between amide groups within the molecule, and gelation occurs when oil is entrapped within this network.

(2) Anti-aging agent.

The anti-aging agent is N-phenyl-N having the following formula (n)
'-Isopropyl-p-phenylenediamine (Iriuchi Shinko Kagaku Kogyo ■; Tsukrak 810-NA), the following formula (l
N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (Irunai Shinko Kagaku Kogyo ■; Tsukrak 6C) having I[) and N, a liquid anti-aging agent having the following formula (IV) -(1-methylhebutyl)-N
'-Phenyl-p-phenylenediamine (Seiko Chemical ■;
Osinon 35) was used.

H)I m, p, 70℃ or more m, p, 44℃ or more m, p, 10℃ or more (3) Addition of oil gelling agent to anti-aging agent.

A predetermined amount of an oil gelling agent was added to each of the above anti-aging agents, maintained at about 120° C. in an oil bath to completely dissolve these components, and then left to cool.

N-phenyl-N-isopropyl-p-phenylenediamine (n) and N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (III) are
Since it is solid at room temperature, it solidifies completely even after cooling, but N-(1-methylheptyl)-N-phenyl-p-phenylenediamine (IV), which is liquid at room temperature, lost fluidity and gelled.

(4) Compounding and mixing.

The blending contents (parts by weight) are shown in Tables 1 and 2.

Table 1 shows SBR (styrene-butadiene copolymer rubber)
System formulation (ASTM 03191-75), Table 2 is NR
(natural rubber) based formulation.

(Margins below this page) In the SBR formulation, the sulfur and accelerator (vulcanization system) were removed and kneaded using a Banbury mixer, and then the vulcanization system was mixed using an oven roll. The amount of anti-aging agent added is 2
parts by weight, and the amount of gelling agent added was 0.1% by weight (
(5% by weight when converted to 100 parts by weight of anti-aging agent).

In the NR system formulation, natural rubber, zinc white, stearic acid, carbon black and process oil were kneaded in a Banbury mixer, and the anti-aging agent and oil gelling agent were mixed together with the vulcanization system in an oven roll. The amount of anti-aging agent added is generally 3 parts by weight, and the amount of gelling agent added is 0.6 parts by weight for Tsukrak 6C and 0.3 parts by weight for Osinon 35.
Parts by weight (20% by weight each when converted to anti-aging agent)
, 10 times percent). In addition, evaluations were also conducted in the case where a gelling agent alone was blended, and in the case where the gelling agent and anti-aging agent were blended together without being heated and dissolved (Tane 9, N11IO).

The samples were prepared by vulcanizing the SBR formulation at 150°C for 30 minutes and the NR formulation at 140°C for 40 minutes. Static ozone and flex crack tests were conducted using this sample.

(5) Experiments and results.

The static ozone test was conducted in accordance with JIS 6301.
Ozone concentration 1100pph, elongation rate 20%, temperature 0℃
The measurement was carried out under the conditions of 50°C and 50°C.

In addition, the flex crack test was conducted with reference to BS 903.
The degree of occurrence of cracks and cracks was evaluated by grading the specified number of bends.

The results of the static ozone test are shown in Tables 3 and 4, and the results of the flex crack initiation test are shown in Tables 5 and 6.

(Margins below the wooden page) note) A: Few cracks.

B: Few cracks.

C: Numerous cracks.

1: Something that cannot be seen with the naked eye, but can be confirmed with a 10x magnifying glass.

2: Something that can be confirmed with the naked eye.

3: The crack is deep and relatively large (less than 1 crane).

4: Deep and large cracks (1 crane or more and less than 3n+).

5: Items that are likely to cause cracks or cuts of 3mm or more.

In particular, the symbol e was used to indicate cracks occurring at the edges.

(Leave space below next summer) Note) A: Several (10 or less) small racks have appeared here and there on the surface.

B: The number of cracks is increased compared to A. However, it is small and appears to have little depth.

C: The crack appears to have depth, and the width and length appear to be equal.

D = Cracks are concentrated along the group center line, some of them cluster together and stick together.

E: Many cracks are grouped together to form a large rack, and the length to width ratio is 2 to 3 degrees. The shape of the group is slightly deformed to relieve the tension on the central surface.

G: The large rack begins to tear towards the edge of the group.

H: The fissure moves closer and closer to the edge and absorbs a small orifice.

J: The fissure almost reaches the end.

K: The croup is completely torn.

As is clear from Tables 3 and 4, it can be seen that the rubber compositions of the present invention shown in Examples have improved ozone crack resistance compared to the rubber compositions containing a single antioxidant. Furthermore, it can be seen from Tables 5 and 6 that the flex cracking resistance was also improved.

In addition, from Nl19, it can be seen that the oil gelling agent alone has almost no effect. Ozone crack resistance and flex crack resistance are improved only when used in combination with an anti-aging agent. In addition, the preparation of the oil gelling agent and anti-aging agent is easier than mixing the gelling agent and anti-aging agent together.
It can be seen that the effect is slightly higher if the heating and dissolving treatment is performed in advance (comparison between Nos. 10 and 11).

Looking at the skeleton of the anti-aging agents of formulas (If) to (1) above, the larger the alkyl group and the more susceptible to gelling action, the greater the effect of improving ozone crack resistance and flex crack resistance. be.

〔Effect of the invention〕

As explained above, according to the present invention, the ozone resistance and flex crack resistance of the rubber composition can be improved by adding an oil gelling agent to the antiaging agent. Compared to the conventional method of improving ozone resistance using a combination of anti-aging agent and wax, only a small amount of gelling agent is required (1710 to 1/2 that of wax), and processing using wax-like plumes is possible. There is no need to worry about reduction in work efficiency. Moreover, it also has the effect of exhibiting flex cracking resistance that cannot be seen with wax. In addition, liquid anti-aging agents have the advantage of being solidified due to their gelling effect, making them easier to process, and having better storage stability because of their reduced volatility.

Agent: Patent Attorney Nobuo Kogawa -

Claims (1)

[Claims] A rubber composition containing an anti-aging agent to which an oil gelling agent is added.