JP2517876B2 - Non-halogen flame-retardant resin molding for radiation exposure environment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-halogen flame-retardant resin molding for a radiation exposure environment, which exhibits excellent radiation resistance in a radiation exposure environment.

[0002]

2. Description of the Related Art Conventionally, electric wires and cables used in a radiation exposure environment such as a nuclear power plant have been required to have excellent radiation resistance in their electrical insulators. At the same time, in order to maintain high safety, it is required to have excellent fire spread resistance even in the event of a fire. In order to meet these requirements, currently used materials use a flame-retardant resin composition in which a halogen-based flame retardant is mixed with a polyolefin resin such as polyethylene. However, the molded product made of such a composition containing a halogen-based flame retardant has a problem that it generates a metal corrosive gas or a large amount of smoke during combustion. On the other hand, recently, a halogen-free flame-retardant resin composition obtained by blending a large amount of a metal hydrate with a polyolefin resin has been developed and put into practical use. A molded article using such a non-halogen flame-retardant resin composition has a high safety because it has a small amount of smoke when burned and does not generate a halogen-based gas that exhibits metal corrosiveness. It is also expected to be applied to applications such as nuclear power plants that require

[0003]

However, such a conventional non-halogen flame-retardant resin molded article becomes very brittle when exposed to a large amount of radiation, and particularly its elongation property is deteriorated, and its practicality is impaired. There was a drawback that it was significantly reduced. The present invention focuses on the radiation-degrading property found in conventional non-halogen flame-retardant resin moldings, and exhibits excellent radiation resistance in a radiation-exposed environment. It is intended to provide a flammable resin molded body.

[0004]

Means for Solving the Problems In the present invention, as a result of extensive studies aimed at achieving the above object, it was noted that the π-electrons of the benzene ring have a stabilizing effect on radiation, and a crosslinking reaction By introducing this monomer having a benzene ring into the halogen-based flame-retardant resin composition, the radiation resistance of the molded product can be improved. That is, the non-halogen flame-retardant resin molding for use in a radiation-exposed environment of the present invention contains 80 to 200 parts by weight of magnesium hydroxide and 2,4-diphenyl-based resin based on 100 parts by weight of polyolefin resin.
It is characterized in that a resin composition containing 0.5 to 10 parts by weight of 4-methyl-1-pentene and a desired amount of a crosslinking agent is molded and subjected to a crosslinking treatment by heating.

Another halogen-free flame-retardant resin molding for use in a radiation-exposed environment of the present invention is 80 to 2 parts magnesium hydroxide per 100 parts by weight of polyolefin resin.
00 parts by weight and 2,4-diphenyl-4-methyl-1
A resin composition containing 0.5 to 10 parts by weight of pentene is molded and subjected to a crosslinking treatment by electron beam irradiation.

The polyolefin resin in the present invention is not particularly limited as long as it is capable of containing magnesium hydroxide in a high proportion, but preferred are very low density polyethylene (VLDPE) and ethylene-
Examples thereof include ethyl acrylate copolymer (EEA), ethylene-vinyl acetate copolymer (EVA), ethylene-methyl acrylate copolymer (EMA). The reason for incorporating magnesium hydroxide as the flame retardant-imparting agent is that the electrical characteristics of the obtained molded article deteriorate with a metal hydrate other than magnesium hydroxide. Further, the compounding amount of magnesium hydroxide is preferably 80 to 200 parts by weight with respect to 100 parts by weight of the polyolefin-based resin, and if it is less than 80 parts by weight, the flame retardancy of the obtained molded article is insufficient.
If the amount exceeds 0 parts by weight, there is a problem that the mechanical properties of the obtained molded product are significantly deteriorated. The average particle size of magnesium hydroxide is preferably about 0.8 to 5 μm.

Further, 2,4-diphenyl-4-methyl-
The compounding amount of 1-pentene is 100
0.5 parts by weight to 10 parts by weight is preferable, and if less than 0.5 parts by weight, the effect of imparting radiation resistance to the obtained flame-retardant resin molded article is small, and 10 parts by weight is added. Even if compounded in a large amount exceeding the above range, further improvement of the radiation resistance imparting effect was not recognized, but on the other hand, the degree of crosslinking of the composition came to be greatly reduced, and a molded product having practical mechanical strength was obtained. I will not be able to.

The resin molding of the present invention is subjected to a crosslinking treatment by a chemical crosslinking method using a crosslinking agent or a radiation irradiation crosslinking method of irradiating an electron beam or the like. In the case of a chemical cross-linking method using a cross-linking agent, for example, dicumyl peroxide (DC
P), t-butylcumyl peroxide, α, α ^, -bis (t-butylperoxy-m-isopropyl) benzene, m- (t-butylperoxyisopropyl) isopropylbenzene and other organic peroxides as cross-linking agents Used as
The blending amount may be about 0.5 to 10 parts by weight with respect to 100 parts by weight of the polyolefin resin. In addition,
When the cross-linking treatment is performed by the chemical cross-linking method or the radiation cross-linking method, not only the cross-linking reaction but also the polymer chain-breaking reaction may occur and the cross-linking reaction may be inhibited. However, it is preferable to use a crosslinking aid having an effect of promoting the crosslinking reaction in combination. Preferred crosslinking aids used for such purpose include triallyl isocyanate (TAIC), triallyl cyanurate (TAC), trimethylolpropane trimethacrylate (TMPT) and the like.

[0009]

In the non-halogen flame-retardant resin molding for use in the radiation exposure environment of the present invention, the compounded 2,4-diphenyl-4 is used.
-Methyl-1-pentene is grafted to a polyolefin resin through a double bond portion in the molecule during the cross-linking treatment, and 2,4-diphenyl-4-methyl-1-pentene having a benzene ring is present in the resin. And acts as a cross-linking auxiliary agent involved in the cross-linking reaction and improves the radiation resistance of the cross-linked molded article.

[0010]

EXAMPLES The present invention will be described below with reference to examples. (Examples 1 to 5 and Comparative Examples 1 to 5) The compositions obtained by mixing the components shown in Table 1 were uniformly kneaded with a roll, and then press-molded at a temperature of 160 ° C. for 30 minutes to obtain a test crosslinked product sheet. Each was produced. The test cross-linked product sheet thus prepared was measured and evaluated for mechanical properties, flame retardancy, radiation resistance and the like. The obtained results are also shown in Table 1. In addition,
Generally, the tensile strength of cable insulators and sheaths is
10MP for polyethylene and polyvinyl chloride according to S standard
A or more is required. As for the elongation, the flexibility after bending is required. Therefore, the higher the elongation rate after γ-ray irradiation, the better.

[0011]

[Table 1]

As is clear from Table 1, an example in which ethylene-vinyl acetate copolymer was used as a polyolefin resin, and 2,4-diphenyl-4-methyl-1-pentene was added thereto and chemically crosslinked was used. Molded bodies 1 to 3 are γ
The total radiation dose is 1.0 × 10 ⁶ Gy, the tensile strength is 11.0 to 11.6 MPa, and the elongation is 320 to 3
It retained a high elongation of 93% (56 to 62% before gamma ray irradiation). In addition, the total irradiation dose of γ rays is 225 × 10 ⁶
Even Gy has a tensile strength of 7.8 to 8.8 MPa and an elongation of 178 to 250% (30 to 3 before γ-ray irradiation).
9%) was maintained. On the other hand, 2,4-
The molded articles of Comparative Examples 1 to 3 containing no diphenyl-4-methyl-1-pentene had a total γ-ray irradiation dose of 1.0 × 10.
The tensile strength was ⁶ Gy and the tensile strength was 10.7 to 12.3 MPa, which was equivalent to that of the example product of the present invention.
Elongation is 195-243% (36-48 before gamma irradiation
%). And the total γ-ray irradiation dose is 2,
At 25 × 10 ⁶ Gy, the tensile strength is 10.5-11.
Although it did not decrease so much as 4 MPa, the elongation was 132-
It was 153% (24 to 30% before gamma ray irradiation), which was a large decrease. In addition, the molded product of Comparative Example 4 in which the content of 2,4-diphenyl-4-methyl-1-pentene was greater than the specified amount in the present invention, the tensile strength before γ-ray irradiation due to crosslinking inhibition. The initial value of was already much lower at 8.7 MPa.

In Examples 4 to 5 and Comparative Example 5 in which extremely low density polyethylene was used as the polyolefin resin, the molded articles of Examples 4 to 5 had a total gamma ray irradiation dose of 1.0.
× 10 ⁶ Gy, with tensile strength of 10.7 to 11.3M
It possessed Pa and had a high elongation of 204 to 252% (39 to 43% before gamma ray irradiation). On the other hand, the molded body of Comparative Example 5 containing no 2,4-diphenyl-4-methyl-1-pentene had a total γ-ray irradiation dose of 1,
At 0 × 10 ⁶ Gy, the tensile strength was significantly reduced to 9.3 MPa, and the elongation was also significantly reduced to 65% (19% before γ-ray irradiation). And the total γ-ray irradiation dose is 2, 25 × 1
In 0 ⁶ Gy, the tensile strength did not decrease so much as 11.2 MPa, but the elongation was 50% or less (9
% Or less).

(Examples 6 to 7 and Comparative Examples 6 to 7) The compositions obtained by mixing the respective components shown in Table 2 were uniformly kneaded with a roll and then taken out in a band shape, which was then granulated (square pellets).
Turned into Next, the granular pellets were extrusion-coated on a conductor having a thickness of 2 mm ^{2 with} an extruder so that the outer diameter was 3.4 mm, to produce an insulated electric wire. Next, the produced insulated wire was irradiated with an electron beam under the conditions of an irradiation amount of 15 Mrad and an accelerating voltage of 750 kev to perform a crosslinking treatment. Mechanical properties, flame retardancy, radiation resistance, etc. were measured for the crosslinked insulated wire manufactured as described above. The obtained results are also shown in Table 2.

[0015]

[Table 2]

As is apparent from Table 2, the insulators of the crosslinked insulated wires of Examples 6 to 7 had a total γ ray irradiation dose of 1.0 × 1.
The tensile strength is 0. ⁶ Gy, and the tensile strength is 11.3 to 13.6 MPa.
Is almost the same as before the γ-ray irradiation treatment, and the elongation is 3
It held 68 to 385% (61 to 73% before γ-ray irradiation treatment). And the total γ-ray irradiation dose is 225 × 10
^{At 6} Gy, the tensile strength is 10.8 to 11.5 MPa.
And has an elongation of 88-105% (16-
17%). On the other hand, in the insulator of Comparative Example 6 in which 2,4-diphenyl-4-methyl-1-pentene was not mixed, the total γ-ray irradiation dose was 1,0 × 10 ⁶ Gy.
So, its tensile strength was 10.7 MPa,
The elongation was significantly reduced to 180% (41% before the γ-ray irradiation treatment). Then, the total irradiation dose of γ-rays is 225 × 10 ⁶ G
In y, the tensile strength was as high as 12.9 MPa, and the elongation was 50% or less (11% or less before the γ-ray irradiation treatment), which was significantly reduced. In addition, 2,4-diphenyl-
In the insulator of Comparative Example 7 in which the content of 4-methyl-1-pentene was larger than the specified amount in the present invention, the initial value of the tensile strength before γ-ray irradiation was already 6. 6M
It was much lower than Pa.

[0017]

As is apparent from the above examples, the non-halogen flame-retardant resin molding for use in a radiation exposure environment of the present invention does not impair flame retardancy under a radiation exposure environment. It has excellent radiation resistance, and its practical value is extremely large.

Claims (2)

(57) [Claims] 1. 80 to 200 parts by weight of magnesium hydroxide and 0.5 to 2,4-diphenyl-4-methyl-1-pentene based on 100 parts by weight of a polyolefin resin.
A halogen-free flame-retardant resin molded article for use in a radiation-exposed environment, which is obtained by molding a resin composition containing 10 parts by weight and a desired amount of a cross-linking agent and subjecting the resin composition to cross-linking by heating. 2. 80 to 200 parts by weight of magnesium hydroxide and 0.5 to 2,4-diphenyl-4-methyl-1-pentene based on 100 parts by weight of the polyolefin resin.
A non-halogen flame-retardant resin molded article for use in a radiation exposure environment, which is obtained by molding a resin composition containing 10 parts by weight of the resin composition and subjecting the resin composition to crosslinking treatment by electron beam irradiation.