JPH0593104A - Radiation-resistant elastomer composition - Google Patents

Abstract

PURPOSE:To prepare the title compsn. excellent in radiation resistance while preventing blooming and degradation in finish by mixing a specific ethylene- acrylic elastomer with 4,4'-thio-bis(6-t-butyl-3-methylphenol). CONSTITUTION:The title comps. is prepd. by mixing 100 pts.wt. ethylene-acrylic elastomer comprising repeating units of formulae I and II and having crosslinking sites (e.g. Vamac B 124) with 3-50 pts.wt. 4,4'-thiobis(6-t-butyl-3- methylphenol). The elastomer is first mixed with ingredients other than the cross-linker at about 120 deg.C for about 20min on a mixing roll of about 150mm diameter. Then the roll temp. is lowered to about 50 deg.C, and the cross-linker is added to the elastomer with mixing for about 10min. The resulting compsn. is crosslinked by pressing in a metal frame, etc., and cooled under pressure to give a sheet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation resistant elastomer composition which is used as a jacket for electric wires and cables (hereinafter simply referred to as "cable").

[0002]

2. Description of the Related Art A cable used in a radiation environment such as a nuclear power plant is required to have radiation resistance.
In particular, the control cables for manipulator operations for handling nuclear fuel and maintaining the core are exposed to extremely high radiation, and therefore higher radiation resistance is required.

This radiation resistance is mainly borne by an outer sheath (sheath), and as a polymer material for the outer sheath of this type of cable, conventionally, polyetheretherketone has been disclosed in Japanese Utility Model Publication No. 60-84024. (Hereinafter referred to as PEEK) is well known. However, this PEEK is expensive and has a problem of poor workability. In addition,
Elasticity is also required as a cable material.

Therefore, it is an object of the present invention to provide a radiation resistant elastomer composition which has high radiation resistance, is inexpensive, and has excellent processability and elasticity.

[0005]

In order to solve the above problems, in the present invention, ethylene comprising a repeating unit represented by the following formula (I), a repeating unit represented by the formula (II) and a crosslinking site is used.・ Acrylic elastomer 1
That is, 3 to 50 parts by weight of 4,4′-thio-bis (6-t-butyl-3-methylphenol) was added to 00 parts by weight.

[0006]

[Chemical 3]

[0007]

[Chemical 4]

When the content of 4,4'-thio-bis (6-t-butyl-3-methylphenol) is less than the above range, the elongation is lowered and the resin is cured by receiving radiation. On the other hand, if it exceeds the above range, bloom (deposition on the surface) occurs, which is not preferable in appearance.

The above ethylene-acrylic elastomer is
Baymac B whose cross-linking site structure is shown below
124 (trade name, manufactured by DuPont) and 4,4′-thio-bis (6-t-butyl-3) represented by the formula:
Examples of -methylphenol) include Sumilizer WXR (trade name, manufactured by Sumitomo Chemical Co., Ltd.).

[0010]

[Chemical 5]

[0011]

[Chemical 6]

[0012]

The elastomer composition according to the present invention thus constructed has the required elasticity and,
Radiation resistance is improved by the addition of the required amount of 4′-thio-bis (6-t-butyl-3-methylphenol).

[0013]

[Examples] Examples 1 to 1 with the compounding ratio (parts by weight) shown in Table 1
3 and the elastomer compositions of Comparative Examples 1 to 3 were kneaded and prepared. The kneading preparation is as follows:
Test roll of 120 ° C, 20
After kneading for 10 minutes, the temperature was lowered to 50 ° C. as a second kneading, and a crosslinking agent was added and kneading was performed for 10 minutes.

The resin composition thus obtained has a thickness of 1 mm,
Inner dimensions: 15mm x 150mm, put in a metal frame, 15
After press-crosslinking at 0 kgf / cm ² × 170 ° C. × 15 minutes,
By pressure cooling, a test sheet having a thickness of 1 mm × a length of 150 mm × a width of 150 mm was obtained.

Looking at the finished appearance of this sheet (presence or absence of bloom), the elongation (El) at each γ-ray irradiation dose (using ⁶⁰ Co as a radiation source and a dose rate of 0.8 MR / hr. In the atmosphere at room temperature) and The results of measuring the tensile strength (Ts) are shown in the lower column of Table 1. In the table, the units of El and Ts are% and kg /
a mm ^2, circle and double circle good, × is bad, the blank represents the unmeasurable, "original" is of γ-ray-free illumination. Tensile speed is 20 according to JISK6301
It was performed at 0 mm / min.

[0016]

[Table 1]

From the results of this test, it can be understood that the elastomer composition according to the present invention is excellent in finishability and radiation resistance without generation of bloom at the specific blending ratio. Therefore, it can be sufficiently satisfied as an insulation coating for radiation-resistant electric wires and cables.

[0018]

Since the present invention is configured as described above, the radiation resistance is improved without suppressing the generation of bloom and causing the deterioration of the finishability.

Claims (1)

[Claims] 1. 100 parts by weight of an ethylene / acrylic elastomer consisting of a repeating unit represented by the following formula (I), a repeating unit represented by the formula (II) and a crosslinking site, and 4,4′-thio-bis (6- A radiation resistant elastomer composition obtained by adding 3 to 50 parts by weight of (t-butyl-3-methylphenol). [Chemical 1] [Chemical 2]