JP3409466B2 - Polyolefin composition and insulated wire coated therewith - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyolefin composition having excellent heat resistance and an insulated wire having excellent heat resistance using the polyolefin composition as an insulating coating.

[0002]

2. Description of the Related Art Polyethylene and ethylene-vinyl acetate copolymers are used for coating electric wires because they have excellent electric insulation and are flexible. However, since this alone is inferior in heat aging resistance, various antioxidants have been developed for polyolefins and used for preventing heat aging of polyolefins. Recently, a phenol-based primary antioxidant is often used as an antioxidant that does not color the resin. Further, it is known that a combination of a sulfur-based or phosphorus-based secondary antioxidant and a phenol-based antioxidant further improves the heat aging resistance.

[0003]

[Prior Art] [Prior Art 1]
When a secondary antioxidant and a sulfur-based or phosphorus-based secondary antioxidant are combined, the heat aging resistance is improved. Further, the larger the amount added, the greater the antioxidant effect. However, if the amount of the antioxidant added is too large, the antioxidant may deposit (bloom) on the resin surface and impair the appearance of the product.
Therefore, the amount of antioxidant added should be as low as possible,
Moreover, development of a polyolefin composition having excellent heat aging resistance is desired.

[0004]

Means for Solving the Problems As a result of various studies on the above problems, the present inventor has selected a metal deactivator consisting of a specific compound represented by the structural formula (1) or (2), an antioxidant and a zinc compound. Crosslinking possible by adding in a specific range
Such a polyolefin composition and to Rukoto, of 180 ° C.
In the oven test, they found that they exhibited an excellent heat aging resistance effect and that no bloom occurred, and they completed the present invention.

That is, the present invention is:   Polyolefin
Structural formula (1) or (2) per 100 parts by weight
Compounds from 0.05 to 10 parts by weight and antioxidant
Agent 0.05 parts by weight or more and 20 parts by weight or less and zinc compound 1
More than 50 parts by weight added,CrosslinkablePolio
A reffin composition is also provided. Also,

[Chemical 2]   Indicated inCrosslinkableLed polyolefin composition
Insulated electric wire coated on the body and cross-linked to a gel fraction of 40% or more
Will also be provided.

The polyolefins used in the present invention include, for example, polyethylene, polypropylene, ethylene-
Vinyl acetate copolymer, ethylene-1-butene copolymer,
Examples thereof include ethylene-ethyl acrylate copolymers and ethylene-methyl acrylate copolymers, and homopolymers of ethylene and propylene, and copolymers of ethylene and propylene and α-olefins.

As the antioxidant, 4,4'-dioctyl-diphenylamine, N, N'-diphenyl-p-phenylenediamine, 2,2,4-trimethyl-1,2-
Amine-based antioxidants such as dihydroquinoline polymers;
Tetrakis- [methylene-3- (3'5'-di-tert-butyl-4'-hydroxyphenyl) propionate] methane, triethyleneglycol-bis [3- (3-tert-butyl-5-methyl-4-) Hydroxyphenyl) propionate], 6- (4-hydroxy-3,5-di-tert-butylanilino) -2,4-bisoctyl-thio-1,3,5-triazine and other phenolic antioxidants Agent: 1,1'-thiobis (2-naphthol), 2-mercaptobenzimidazole, 2-mercaptomethylbenzimidazole, zinc salt of 2-mercaptobenzimidazole; 1,3-bis (dimethylaminopropyl)
Examples thereof include sulfur-based antioxidants such as 2-thiourea, β-alkylthioester-propionate, and pentaerythritol-tetrakis- (β-lauryl-thiopropionate). Examples of the zinc compound include zinc oxide and zinc borate.

The amount of the compound having the structural formula (1) or (2) added is 100 parts by weight of polyolefins,
0.05 parts by weight or more than 10 parts by weight, preferably 0.1
It is necessary to be 3 parts by weight or more by weight. If the addition amount of the above compound is less than 0.05 parts by weight, the antioxidant effect is not sufficient, and even if the addition amount is more than 10 parts by weight, the antioxidant effect remains almost unchanged and there is no point in increasing the amount. Further, if the addition amount is too large, blooming may occur and the appearance may be impaired. Further, the amount of the antioxidant added needs to be 0.05 parts by weight or more and 20 parts by weight or less, preferably 0.1 parts by weight or more and 10 parts by weight or less . If the added amount is less than 0.05 parts by weight, the antioxidant effect is small, and if the added amount exceeds 20 parts by weight, blooming occurs.

The amount of the zinc compound added should be 1 part by weight or more and 50 parts by weight or less, preferably 5 parts by weight or more and 20 parts by weight or less . If the addition amount is less than 1 part by weight, the antioxidant effect is not sufficient, and if the addition amount exceeds 50 parts by weight and the addition amount is too large, initial mechanical properties such as elongation and tensile strength deteriorate. The composition of the present invention may optionally contain various additives such as a lubricant, a light stabilizer, a filler, a flame retardant, a coloring agent and an ultraviolet absorber, and other resins and a small amount of rubber. Since the polyolefin composition of the present invention has excellent heat aging resistance, it is particularly useful as a covering material for insulated electric wires.

When the crosslinkable polyolefin composition of the present invention is used as an insulated wire coating, it may be carried out by a known coating means such as extrusion coating. The obtained coated electric wire needs to be crosslinked by irradiation with ionizing radiation or by blending a peroxide-based crosslinking agent , and electron beam irradiation is good from the viewpoint of adjusting the degree of crosslinking, which further improves heat resistance. . At that time, it is necessary that the polyolefin composition is cross-linked to a gel fraction of 40% or more, preferably 50% or more. If the degree of crosslinking is less than 40% gel fraction, the heat resistance becomes insufficient. Here, the gel fraction is measured by immersing the composition in xylene at 120 ° C. for 12 hours, drying the insoluble component, and measuring the weight.

In particular, when ionizing radiation is used, examples include electron beams, γ rays, X rays, ion beams, neutron rays, and the like, and the use of electron beams and γ rays is preferable. The dose of ionizing radiation is generally preferably about 1 to 50 Mrad. For the production of the composition of the present invention, a single-screw extruder, a multi-screw extruder, a Banbury mixer, a roll, a kneader, a heatable Henschel mixer type high-speed fluid mixer or the like can be used. It can be manufactured by melt-kneading at a temperature higher than the melting point of the resin. Applications of the composition of the present invention include insulating wire coating materials, heat-shrinkable tubes, injection-molded products, extrusion-molded products, stretched and foam-molded products, and the like. In particular, use for insulated wire coating materials is preferred.

[0012]

The present invention is illustrated by the following examples, which do not limit the scope of the invention. A resin was roll-mixed in the formulation shown in Table 1 and a 1 mm thick sheet was formed by press molding. This sheet was irradiated with an electron beam having an acceleration voltage of 2 MeV at 200 kGy to crosslink the sheet. Sheet JI
The sample was punched into a No. S3 dumbbell and a tensile test was performed at a speed of 500 mm / min to measure elongation and tensile strength. For heat aging, use JIS No. 3 dumbbell in a 180 ° C gear oven.
After being left for a week, a tensile test was performed and evaluated. After the electron beam cross-linking sheet is left at room temperature for 1 month,
The presence or absence of precipitates on the surface of the sheet was visually determined.

Examples 1 to 4 As shown in Examples 1 to 4 in Table 1, the structural formula (1) or
The polyolefin composition obtained by combining the compound (2) with the antioxidant and the zinc compound has an elongation of 300% or more even after heat aging at 180 ° C. for 7 days, and has excellent heat aging resistance. Moreover, the composition has no bloom and does not impair the sheet appearance.

Example 5 A resin composition having the same composition as in Example 4 in Table 1 was roll-mixed, pelletized, and then 0.81 mm with a 50 mm extruder.
This composition was extruded on a φ conductor with a wall thickness of 0.4 mm. An electron beam with an accelerating voltage of 2 MeV was applied to this at 200 kGy.
Irradiation was carried out to produce a crosslinked insulated electric wire. The coating of this electric wire was immersed in xylene heated to 120 ° C. for 12 hours, insoluble components were dried and weighed, and the gel fraction was measured to be 67.
%Met. Remove the conductor of this wire,
When the elongation after the heat aging test for a day was measured, the elongation was 35
It was 0% and was excellent in heat aging resistance. Even after one month, there was no precipitate on the surface of the insulator, and the appearance was good.

(Comparative Examples 1 to 4) Even if only 1 part of the antioxidant is added as in Comparative Example 1 in Table 1, the compound of the structural formula (1) and the antioxidant are added as in Comparative Examples 2 and 3. Even with only the combination of agents, the elongation becomes 100% or less after the heat aging test at 180 ° C. for 7 days. When a primary antioxidant and a secondary antioxidant are combined as in Comparative Example 4, the heat aging resistance is improved, but the bloom is impaired in appearance due to the large amount of the antioxidant added.

[0016]

[Table 1]

Note) 1) Tetrakis- [methylene-3- (3 ', 5'-di-
tert-Butyl-4-hydroxyphenyl) propionate] methane 2) Dilauryl-thiodipropionate 3) After the sheet was prepared, it was left at room temperature for 1 month, and the presence or absence of a precipitate on the surface was visually determined. ○: no bloom ×: bloom

[0018]

As described above, the crosslinking of the present invention is possible.
No bloom with an excellent antioxidant effect in polyolefin compositions and <br/> small amount in combination of a particular additive, in which excellent in heat aging resistance without impairing the product appearance .

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Claims (2)

(57) [Claims] 1. A compound represented by the structural formula (1) or (2) in an amount of 0.05 parts by weight or more and 10 parts by weight or less and an antioxidant of 0.05 parts by weight or more 2 per 100 parts by weight of polyolefins.
A crosslinkable polyolefin composition, characterized in that 0 part by weight or less and 1 part by weight or more and 50 parts by weight or less of a zinc compound are added. [Chemical 1] 2. An insulated electric wire obtained by coating the crosslinkable polyolefin composition according to claim 1 on a conductor and crosslinking the gel fraction to 40% or more.