JPH0892425A - Polyolefin composition and insulated electric wire coated with the same - Google Patents

Abstract

(57) [Summary] [Structure] The following structural formula (1) for polyolefins
Alternatively, a polyolefin composition containing the compound (2), an antioxidant and a zinc compound. An insulated electric wire obtained by coating the polyolefin composition on a conductor and crosslinking the gel fraction to 40% or more. [Chemical 1] [Effect] Since a small amount of addition has an excellent antioxidation effect, it has very good heat aging resistance without bloom and without impairing the appearance of the product.

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 same 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 achieved outstanding results by combining a specific compound represented by the structural formula (1) or (2) with an antioxidant and a zinc compound. They have found that they exert an antioxidant effect and do not cause bloom, and have completed the present invention.

That is, the present invention is: The following structural formula (1) or (2) for polyolefins:
There is provided a polyolefin composition to which a compound represented by, an antioxidant and a zinc compound are added. Also,

[Chemical 3] 0.05 parts by weight or more and 10 parts by weight or less of the compound represented by the structural formula (1) or (2), and 0.05 parts by weight or more and 20 parts by weight or less of an antioxidant and 1 part by weight of a zinc compound, relative to 100 parts by weight of polyolefins. The present invention also provides a polyolefin composition containing 50 parts by weight or less. Also,

[Chemical 4] Also provided is an insulated electric wire obtained by coating the polyolefin composition shown in 1 above on a conductor and cross-linking it to a gel fraction of 40% or more.

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 antioxidants, 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, triethylene glycol-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) -2-thiourea, β-alkylthioester-
Propionate, pentaerythritol-tetrakis-
Examples include sulfur-based antioxidants such as (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) to be added is 100 parts by weight of the polyolefins,
It is desirable that the amount is 0.05 parts by weight or more and 5 parts by weight or less, preferably 0.1 parts by weight or more and 3 parts by weight or less. 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. Also,
The amount of the antioxidant added is 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 more. 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 is preferably 1 part by weight or more and 50 parts by weight or less, more preferably 5 parts by weight or more and 20 parts by weight or more. 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 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 coated electric wire thus obtained is preferably cross-linked by irradiation with ionizing radiation or by blending a peroxide-based cross-linking agent, and electron beam irradiation is good from the viewpoint of adjusting the degree of cross-linking, whereby the heat resistance is further improved. 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 means that the composition is added to xylene at 120 ° C.
It is measured by dipping for 2 hours, drying insoluble components, and weighing.

[0012] In particular, when ionizing radiation is used, examples include electron beams, γ rays, X rays, ion beams, and neutron rays, but the use of electron beams and γ rays is preferable. The dose of ionizing radiation is generally preferably about 1 to 50 Mrad. In 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.

[0013]

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, a polyolefin composition obtained by combining the compound of the structural formula (1) or (2) with an antioxidant and a zinc compound is 180 ° C. Even after heat aging for 7 days, the elongation is 300% or more, and it 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 that of Example 4 in Table 1 was roll-mixed and then pelletized to obtain 50.
This composition was extruded with a thickness of 0.4 mm on a conductor having a diameter of 0.81 mm using an mm extruder. 2M acceleration voltage
An electron beam of eV was irradiated with 200 kGy to produce a crosslinked insulated electric wire. The coating of this electric wire was dipped in xylene heated to 120 ° C. for 12 hours, the insoluble component was dried and weighed, and the gel fraction was measured and found to be 67%. The conductor of this electric wire was taken out and the elongation after the heat aging test at 180 ° C. for 7 days was measured. As a result, the elongation was 350%, which 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 of Table 1, the compound of the structural formula (1) and the antioxidant are also added as in Comparative Examples 2 and 3. Even with a combination of agents alone, the elongation is 100 after a heat aging test at 180 ° C for 7 days.
% Or less. 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.

[0017]

[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 precipitates on the surface was visually determined. ○: Without bloom ×: With bloom

[0019]

As described above, the composition of the present invention has an excellent antioxidation effect even when added in a small amount, and therefore has excellent heat aging resistance without blooming and without damaging the appearance of the product. .

Claims (3)

[Claims] 1. The following structural formula (1) for polyolefins:
Alternatively, a polyolefin composition comprising the compound represented by (2), an antioxidant, and a zinc compound added. [Chemical 1] 2. 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 0.05 parts by weight or more 2 with respect to 100 parts by weight of polyolefins.
A polyolefin composition comprising 0 part by weight or less and 1 part by weight or more and 50 parts by weight or less of a zinc compound. [Chemical 2] 3. An insulated electric wire obtained by coating the polyolefin composition according to claim 1 on a conductor and crosslinking the gel fraction to a gel fraction of 40% or more.