JP3409467B2 - 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. In addition, antioxidants and structural formulas (1) and (2)
It is a commonly practiced method to combine with a copper damage inhibitor such as the compound shown in (Japanese Patent Publication No. 43-186).
No. 07 publication). However, in this system, heat aging resistance is insufficient, and bloom tends to occur.

[0004]

As a result of various studies on the above problems, the present inventor has the structural formula (1) or (2) known to be an excellent copper damage inhibitor as described above. by be Rukoto paired engagement <br/> Align was crosslinkable polyolefin composition specific consisting of compounds of copper deactivator and a phenolic antioxidant and further zinc compound in the addition amount of the specific range, copper damage preventing effect In addition to exhibiting an excellent antioxidation effect, it has been found that bloom does not occur, and the present invention has been completed.

That is, the present invention is:   Structural formula (1) or 100 parts by weight of polyolefins
Or a compound represented by (2) 0.05 parts by weight or more and 10 parts by weight
Below the section andPhenolicAntioxidant 0.05 parts by weight or more
20 parts by weight or less and zinc compound 1 part by weight or more and 50 parts by weight
Added below,CrosslinkableProvide polyolefin composition
To do. 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
I will provide a.

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.

The phenolic antioxidant used in the present invention is 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 the like can be mentioned.
I can . 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 required 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. The amount of phenolic antioxidant to be added is 20 parts by weight or less than 0.05 parts by weight, preferably have at least 10 parts by weight or more 0.1 part by weight. If the added amount is less than 0.05 parts by weight, the antioxidant effect is small,
Blooming occurs when the amount added is too much over the parts by weight.

[0009] The amount of the added zinc compound is 1 part by weight to 50 parts by weight or less, preferably requires less than 20 parts by weight or more 5 parts by weight. 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, if necessary, a lubricant,
You may mix | blend various additives, such as a light stabilizer, a filler, a flame retardant, a coloring agent, and a ultraviolet absorber, and other resin and a small amount of rubber. Since the crosslinkable polyolefin composition of the present invention is excellent in heat aging resistance, it is particularly useful as a covering material for insulated 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 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 is measured by immersing the composition in xylene at 120 ° C., drying insoluble components, 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 in which the compound (2) is combined with the phenolic 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 phenolic antioxidant is added as in Comparative Example 1 in Table 1, the structural formula (1) is obtained as in Comparative Examples 2 and 3.
Even if only the combination of the compound and the phenolic antioxidant is used, the elongation becomes 100% or less after the heat aging test at 180 ° C. for 7 days. When a phenol-based primary antioxidant and a sulfur-based 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.
Since the polyolefin composition has excellent antioxidant effect and <br/> small amount in combination of a particular additive, in which excellent in heat aging resistance without impairing the product appearance without bloom .

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI H01B 7/29 H01B 7/34 A (56) References JP-A 63-89517 (JP, A) JP-A 57-67640 ( JP, A) JP 54-48863 (JP, A) JP 43-18607 (JP, B1) (58) Fields investigated (Int.Cl. ⁷ , DB name) C08L 23 / 00-23 / 36 C08K 3/00-13/08 H01B 7/36

Claims (2)

(57) [Claims] 1. A compound represented by the structural formula (1) or (2) in an amount of 0.05 part by weight or more and 10 parts by weight or less and a phenolic antioxidant 0.05 parts by weight based on 100 parts by weight of a polyolefin.
A crosslinkable polyolefin composition, characterized in that 1 part by weight or more and 20 parts 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.