JP2001164057A - Radiation-resistant flame-retardant resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a radiation-resistant nonhalogen-based flame-retardant resin composition having not only excellent flame retardance even after radiation exposure but also sufficiently controlling deterioration of mechanical characteristics such as tensile strength, elongation, etc., having excellent mechanical characteristics. SOLUTION: This radiation-resistant flame-retardant resin composition is characterized in that a base resin comprising a polyethylene produced by using a single-site catalyst and an ethylene-ethyl acrylate copolymer as main components is compounded with a metal hydroxide, an ultraviolet light absorber and an antioxidant as essential components and the compounding ratio of the total of the ultraviolet light absorber and the antioxidant is 2-4 pts.wt. of based on 100 pts.wt. of the base resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation-resistant non-halogen flame-retardant resin composition used for covering electric wires and cables used in nuclear facilities and facilities.

[0002]

2. Description of the Related Art Conventionally, electric wires and cables coated with a halogen-free flame-retardant coating material have been used in nuclear-related facilities and facilities such as nuclear power plants. The flame-retardant coating materials for wires and cables for nuclear applications include:
In addition to the mechanical properties such as tensile strength and elongation required for flame-retardant coating materials used for wires and cables for general use and flame retardancy, radiation resistance, that is, their properties due to radiation exposure (irradiation), especially There is a demand for a property that the mechanical properties do not deteriorate.

When a halogen-free flame-retardant coating material used for wires and cables for general use is used for a flame-retardant coating material for wires and cables for nuclear power applications, its properties, particularly mechanical properties, after radiation exposure are reduced. Will deteriorate. Therefore, various types of radiation-resistant non-halogen flame-retardant resin compositions have been conventionally proposed. For example, a resin composition comprising a base resin such as low-density polyethylene mixed with a metal hydroxide and an ultraviolet absorber. (Japanese Unexamined Patent Publication (Kokai) No. 3-115339) or a resin composition in which a certain metal hydroxide, a certain metal powder and an ultraviolet absorber are blended with a base resin such as ultra-low density polyethylene (Japanese Unexamined Patent Publication (Kokai) No. 3-17333).
No. 4) has been proposed. However, none of the conventionally proposed radiation-resistant non-halogen flame-retardant resin compositions still has a problem that the effect of suppressing deterioration of mechanical properties after radiation exposure is not sufficient.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention, in view of the above-mentioned conventional circumstances, that even after being exposed to radiation,
Radiation-resistant non-halogen flame-retardant resin compositions that have excellent mechanical properties, as well as having excellent flame retardancy, as well as having sufficiently suppressed deterioration of mechanical properties such as tensile strength and elongation. To provide.

[0005]

In order to achieve the above-mentioned object, the present invention relates to a polyethylene produced using a single-site catalyst (hereinafter abbreviated as a single-site catalytic polyethylene) and ethylene-ethyl acrylate. A metal hydroxide, an ultraviolet absorber and an antioxidant are compounded as essential components in a base resin containing a polymer as a main component, and the total compounding ratio of the ultraviolet absorber and the antioxidant is 100%. Provided is a radiation-resistant flame-retardant resin composition, which is 2 to 4 parts by weight based on parts by weight.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. In the present invention, one main component of the base resin is a single-site catalytic polyethylene. The single-site catalyst used in the production of polyethylene has a high polymerization activity with respect to ethylene and has a uniform active site (single-site), and examples thereof include cyclopentadienyl-titanium complex salts. , A metallocene catalyst or a Kaminski catalyst from the inventor's name. The single-site catalyst includes various improved catalysts and, if necessary, a cationic activator is used in combination as a cocatalyst. Polyethylene produced using this single-site catalyst generally has a narrower molecular weight distribution and homogenous structure than polyethylene produced using, for example, a titanium-based catalyst (multi-site catalyst) other than the single-site catalyst. It has the characteristic of. In the present invention, the type of the single-site catalytic polyethylene is not particularly limited, and various commercially available single-site catalytic polyethylenes can be appropriately selected and used, and if necessary, a plurality of types can be mixed. It can also be used.

The other main component of the base resin is an ethylene-ethyl acrylate copolymer (EEA). The ratio of ethylene to ethyl acrylate in the copolymer can be appropriately set as required, but preferably contains 10 to 30 mol% of ethyl acrylate.

[0008] The mixing ratio of the single-site catalytic polyethylene to the ethylene-ethyl acrylate copolymer in the base resin is determined in consideration of elongation and tensile strength after exposure to radiation, etc., to the single-site catalytic polyethylene 1 relative to the single-site catalytic polyethylene 1. 1.25-ethyl acetate copolymer
The ratio is preferably 2.3.

Further, the above-mentioned base resin may be blended with another resin as required. For example, low density polyethylene (LDPE) produced using a catalyst other than a single site catalyst, linear low density polyethylene (LLDP)
E), polyethylene such as very low honey polyethylene (VLDPE), or ethylene-vinyl acetate copolymer (EV
A) and copolymers such as ethylene-propylene copolymer (EPM). In addition, these resins can be used as a mixture of two or more, if necessary.

In the present invention, the metal hydroxide, which is one of the essential components to be added to the base resin, may be any of known various types of flame retardants conventionally used in non-halogen flame-retardant resin compositions. A metal hydroxide can be appropriately selected and used. Examples include magnesium hydroxide, aluminum hydroxide, zirconium hydroxide, and the like. Among them, magnesium hydroxide is preferably used. These metal hydroxides can be used as a mixture of two or more as necessary. Further, the compounding amount of the metal hydroxide can be appropriately set in consideration of desired flame retardancy, mechanical properties, and the like, but is preferably 50 to 250 parts by weight based on 100 parts by weight of the base resin. preferable. When this blending amount is less than 50 parts by weight, the flame retardant effect is reduced,
When the amount exceeds 250 parts by weight, the flame retardancy is excellent, but the mechanical properties deteriorate.

As the UV absorber as another essential component to be added to the base resin, various known UV absorbers conventionally used in various resin compositions can be appropriately selected and used. As an example, for example, 2- (2′-
(Hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-5'-t-octylphenyl) benzotriazole, 2- (2'-hydroxy-
3 ', 5'-di-t-amylphenyl) benzotriazole, 2- (2'-hydroxy-3'-t-butyl-5
Benzotriazole-based ultraviolet absorbers such as' -methylphenyl) -5-chlorobenzotriazole and benzophenone-based ultraviolet absorbers such as 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone and 4-dodecyloxy-2-hydroxybenzophenone , 2
Acrylate UV absorbers such as -ethylhexyl-2-cyano-3,3'-diphenylacrylate, 2-ethyl-2-cyano-3,3'-diphenylacrylate, and 2,4-di-t-butylphenyl-3 And benzoate-based ultraviolet absorbers such as', 5'-di-t-butyl-4'-hydroxybenzoate. In addition, these ultraviolet absorbers can be used as a mixture of two or more as necessary.

As the antioxidant, which is another essential component to be added to the base resin, various known antioxidants conventionally used in various resin compositions can be appropriately selected and used. Examples thereof are 1,1,3-tris- (2-methyl-4-hydroxy-5-tert-butylphenyl) butane and 4,4'-butylidenebis- (3-methyl-6-tert-butylphenol). , Tetrakis [methylene-3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] methane, octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate and the like Hindered phenolic antioxidants, pentaerythritol tetrakis (β-laurylthiopropionate), 2,2-thio [diethyl-bis-3 (3,5-di-tert-butyl-4-hydroxyphenol) propionate], 4, 4'-thiobis (3-
Sulfur-based antioxidants such as methyl-6-t-butylphenol), and amine-based oxidations such as N, N'-diβ-naphthyl-p-phenylenediamine and 2,2,4-trimethyl-1,2-di-hydroquinone polymer. Inhibitor, tetrakis (2,4-di-t-butylphenyl) -4,4'-biphenylenediphosphonite tris- (2,4-di-t-
And a phosphorus-based antioxidant such as (butylphenyl) phosphite. These antioxidants can be used as a mixture of two or more, if necessary.

The total amount of the above ultraviolet absorber and antioxidant is 2 to 100 parts by weight of the above base resin.
It is blended with the base resin so as to be 4 parts by weight. When this compounding ratio is less than 2 parts by weight, the effect of suppressing the deterioration of mechanical properties after the radiation exposure intended by the present invention is not obtained, and when this compounding ratio exceeds 4 parts by weight, Grooming that precipitates on the surface of the covering material when it is made into an electric wire or cable will occur. The ratio between the ultraviolet absorber and the antioxidant can be appropriately set as needed.
It is preferably a ratio of 0.

In the present invention, if necessary,
Various additives, such as an inorganic filler, a lubricant, and a coloring agent, which are generally blended in a covering material for electric wires and cables, can be added to the base resin in an appropriate amount.

The radiation-resistant resin composition of the present invention is prepared by adding a predetermined amount of each of the essential components and optional additives to a base resin, using a Henschel mixer, an open roll mixer, a Banbury mixer, It can be performed using a known kneading means such as a kneader. Moreover, when coating | covering an electric wire and a cable using the radiation-resistant resin composition of this invention, it can carry out according to a usual method using well-known molding means, such as an extrusion molding machine.

In the present invention, if necessary,
The base resin may be appropriately cross-linked within a range that does not impair the intended purpose of the present invention. This cross-linking can be carried out by a conventional method by appropriately selecting a known chemical cross-linking method, silane cross-linking method, radiation cross-linking method or the like conventionally used for cross-linking of polyethylene or an ethylene copolymer.
When the chemical crosslinking method is adopted, dicumyl peroxide, benzoyl peroxide, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexyne-3 are added to the radiation-resistant resin composition of the present invention in advance. A free radical generator such as an organic peroxide such as 1,3-bis (tert-butylperoxyisopropyl) benzene or the like is blended, and a cross-linking treatment is performed by heating or the like when or after coating the electric wire / cable. When the silane cross-linking method is employed, the radiation-resistant resin composition of the present invention may be added in advance with vinyltrimethoxysilane, vinyltriethoxysilane, vinyltributoxysilane,
A silane crosslinking agent such as vinylmethyldiethoxysilane, vinylphenyldimethoxysilane, or vinyltriacetoxysilane may be used together with the above-described free radical generator, or the free radical generator and dibutyltin dilaurate, dibutyltin dimaleate, dibutyltin. It is blended with both silanol condensation catalysts such as diacetate and dibutyltin dioctate, and after coating the wires and cables, silane crosslinking treatment such as immersion in warm or hot water is performed.
When the radiation crosslinking method is employed, the radiation-resistant resin composition of the present invention is subjected to a crosslinking treatment of irradiating with ionizing radiation after coating the wires and cables.

[0017]

The present invention will be described more specifically with reference to the following examples and comparative examples, but the present invention is not limited to the following examples.

Examples 1 to 4 and Comparative Examples 1 to 16 Each component was mixed as shown in Table 1 and kneaded with a pressure kneader to prepare a test resin composition. The obtained test resin composition was formed into a sheet to form a test piece, and the tensile strength and the elongation were measured in accordance with JIS C 3005. In addition, using the test resin composition, a wire-core
Performed in accordance with CEA S61-402. Table 1 shows the test results. In addition, as for the one-core test of the wire core, those that passed were indicated by ○, and those that failed were indicated by x. Further, in the judgment column, those having a tensile strength of 10 MPa or more, elongation of 350% or more, and having passed the single-core test were indicated by a circle, and those not having the same were indicated by a cross.

[0019]

[Table 1]

* 1: single-site catalyzed polyethylene;
"Engag" manufactured by DuPont Dow Elastomers, Inc.
e8540 "(density 0.908) * 2: Ethylene-ethyl acrylate copolymer; Nippon Unicar Co., Ltd." DPDJ-6182 "(ethyl acrylate content 15%, MFR 1.5) * 3: Hydroxide Magnesium; "Kisuma 5A" manufactured by Kyowa Chemical Co., Ltd. * 5: Phenolic antioxidant; "Antage RC" manufactured by Ciba Specialty Chemicals, Inc. * 5: Benzotriazole-based ultraviolet absorber; Shiraishi Calcium Co., Ltd. "Seesorb 709"

Further, in order to examine the resistance to radiation, ⁶⁰ Co-γ-rays were applied to the above-mentioned test pieces at room temperature in the atmosphere for 0.1 min.
Irradiated with 5MGy. This γ-ray irradiation dose of 0.5 MGy is based on the assumption of a radiation dose in the life of a nuclear power plant of 40 years.
Then, the elongation of the test piece after γ-ray irradiation was measured by the same method as described above. The results are shown in Table 2. In addition, in the final judgment column, it passed the judgment criteria (tensile strength of 10 MPa or more, elongation of 350% or more, and wire core single-pass test) shown in Table 1, and the elongation after γ-ray irradiation of 250%
Those described above were marked with a circle as the final judgment, and those not matched were marked with a cross.

[0022]

[Table 2]

Tables 1 and 2 show that the test resin compositions of the examples according to the present invention show good mechanical properties even after exposure to radiation. On the other hand, even though the test resin composition of the comparative example shows good mechanical properties before exposure to radiation, the mechanical strength is significantly reduced after exposure to radiation.

[0024]

As described above, according to the present invention,
Radiation-resistant non-halogen-based material that has excellent mechanical properties such as excellent tensile strength and elongation as well as excellent flame retardancy even after being exposed to radiation. A flame retardant resin composition is provided.

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Claims (4)

[Claims] 1. A metal hydroxide, an ultraviolet absorber and an antioxidant are essential components in a base resin mainly composed of polyethylene and ethylene-ethyl acrylate copolymer produced using a single-site catalyst. A radiation-resistant flame-retardant resin composition, wherein the total amount of the ultraviolet absorber and the antioxidant is 2 to 4 parts by weight based on 100 parts by weight of the base resin. 2. The base resin according to claim 1, wherein the ethylene-ethyl acrylate copolymer has a ratio of 1.25 to 2.3 with respect to polyethylene 1 produced using a single-site catalyst. 2. The radiation-resistant flame-retardant resin composition according to 1. 3. The ultraviolet absorber 1, wherein the ratio of the antioxidant to the ultraviolet absorber 1 is 0.5 to 2.0.
Or the radiation-resistant flame-retardant resin composition according to 2. 4. The radiation-resistant flame-retardant flame according to claim 1, wherein the metal hydroxide is mixed in an amount of 50 to 250 parts by weight based on 100 parts by weight of the base resin. Resin composition.