JPH0824015B2 - Method for manufacturing foam insulated wire - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a foam-insulated electric wire, which is capable of high foaming and which prevents adhesion between a conductor and a foam insulator.

[Background Art] In high-speed information circuits such as computers and telephone communications, low dielectric constant electric wires are required, and foamed polyolefin insulated electric wires are frequently used. As a method for producing a foamed polyolefin insulated wire, a method is generally known in which a polyolefin containing a chemical foaming agent is supplied to an extruder, melt-kneaded at a temperature equal to or higher than the decomposition temperature of the foaming agent, and extruded around the conductor. However, in this method, the decomposition gas of the foaming agent is liable to be scattered, and it is difficult to obtain a high foam of 50% or more.

As a measure to prevent the decomposition gas of the foaming agent from scattering, in JP-B-53-4909, a plastic mixture containing a foaming agent is extrusion-coated on a conductor and then continuously crosslinked by radiation and electron beams, There has been proposed a manufacturing method in which foaming is performed by heating in a pressurized fluid atmosphere.

[Problems to be Solved by the Invention] However, this method lacks versatility due to the necessity of a fluid pressurizing facility, and has non-uniform outer diameter due to pressure fluctuation, and contamination of insulated wires due to fluid. There is such a problem.

For this reason, various studies were conducted on heat foaming under normal pressure. When the most suitable azodicarbonamide was used as a foaming agent, the conductor and foamed insulation adhered and the foamed insulation was peeled off using a wire stripper. At this time, it has been pointed out that the foam insulation remains around the conductor and the workability of the terminal treatment is extremely deteriorated.

The present invention has been made on the basis of the above, and is a method for manufacturing a foam insulated wire, which is capable of high foaming, and which suppresses adhesion between a conductor and a foam insulating material and facilitates peeling of the foam insulating material. It is intended to be provided.

[Means for Solving the Problems] The method for producing a foamed insulated wire according to the present invention comprises a polyolefin
Azodicarboxylic resin composition containing 0.5 to 15 parts by weight of azodicarbonamide and 0.05 to 5 parts by weight of zinc soap (R is an alkyl group having 7 or more carbon atoms) represented by the formula Zn (OOCR) ₂ with respect to 100 parts by weight. Characterized by extrusion coating the outer circumference of a conductor at a temperature not higher than the decomposition temperature of amide and then crosslinking by irradiation with ionizing radiation, and then heating to a temperature not lower than the decomposition temperature of azodicarbonamide to form a foamed insulator. Is.

Examples of the polyolefin in the present invention include, but are not limited to, low density polyethylene, medium and high density polyethylene, linear low density polyethylene, ultra low density polyethylene, polypropylene and the like.

Azodicarbonamide is a powder substance having a decomposition temperature of 200 to 210 ° C., and a gas generated by the decomposition forms a foam. The addition amount of azodicarbonamide must be in the range of 0.5 to 15 parts by weight per 100 parts by weight of polyolefin, and if it is less than 0.5 part by weight, foaming is insufficient, and if it exceeds 15 parts by weight, the foaming state is controlled. Becomes difficult.

The zinc soap represented by the formula Zn (OOCR) ₂ (R is an alkyl group having 7 or more carbon atoms) is added to suppress the adhesion between the conductor and the foamed insulator. That is, the adhesion between the conductor and the foamed insulator is due to the decomposition residue of azodicarbonamide, and the zinc soap suppresses the generation of this decomposition residue. The amount of zinc soap added is in the range of 0.05 to 5 parts by weight with respect to 100 parts by weight of the polyolefin. Since the decomposition temperature of dicarbonamide is remarkably lowered, foaming occurs during extrusion molding.

As the zinc soap, zinc salts such as stearic acid, lauric acid, ricinoleic acid, naphthenic acid, 2-ethylhexoic acid, octylic acid, hydroxystearic acid, and phthalic acid are preferable, and further, linderic acid, elaidic acid, and tunic acid. Duzic acid, cadrenic acid, ficetrain acid, gondoic acid, myristoleic acid, whale oil acid, zomarinic acid, erucic acid, petroselinic acid, prandic acid, oleic acid, ceracoilenic acid, linoleic acid, linoelaidic acid, linolenic acid, eleo Stearic acid, moloctic acid, valinaric acid,
Examples include zinc salts such as arachidonic acid, sardine acid, hiragashicholic acid and nisinic acid.

The resin composition containing polyolefin, azodicarbonamide and zinc soap as essential components is melt-kneaded at a temperature not higher than the decomposition temperature of azodicarbonamide, for example at a temperature not higher than 160 ° C., and extrusion-coated on the outer circumference of the conductor. Subsequently, ionizing radiation such as an electron beam is irradiated in the range of 0.5 to 5 Mrad to crosslink, and the foamed insulator is formed by heating at a temperature not lower than the decomposition temperature of azodicarbonamide under normal pressure. This heating
It is preferable to carry out continuously using an electric furnace or the like, and the set temperature is preferably higher than the decomposition temperature of azodicarbonamide by several tens of degrees. Of course, high temperatures at which the polyolefin decomposes should be avoided.

[Examples of the Invention] Example 1 To 100 parts by weight of low-density polyethylene (UBEC-400 manufactured by Ube Industries, Ltd.), 3 parts by weight of azodicarbonamide was added, and 135 parts of this was added.
The mixture was kneaded with an 8-inch roll set at 0 ° C., and then 0.5 part by weight of zinc stearate was added to obtain a compound. This compound was introduced into a 28 mm extruder (set temperature 130 ° C.), melt-kneaded, and extrusion-coated to a thickness of 1.0 mm on the outer circumference of a tin-plated copper wire having an outer diameter of 0.45 mm. Subsequently, 1.5 Mrad was irradiated by an electron beam irradiation device to perform cross-linking, and the foamed insulated wire was manufactured by passing through a cylindrical electric furnace having an inner diameter of 70 mmφ and a furnace length of 2.5 m set at 300 ° C. under normal pressure.

The degree of foaming of this insulated wire was about 68%, and the foamed insulator was extremely easily peeled off by the wire stripper.

Example 2 A foam insulated wire was produced in the same manner as in Example 1 except that 3 parts by weight of azodicarbonamide and 0.5 part by weight of zinc ricinoleate were added to 100 parts by weight of low-density polyethylene (UBEC-400 manufactured by Ube Industries).

The degree of foaming of this insulated wire was about 71%, and it was extremely easy to peel off the foamed insulation with a wire stripper.

Example 3 Low-density polyethylene (Mitsui Petrochemical Mirason 3530) 10
A foam insulated wire was produced in the same manner as in Example 1 except that 4 parts by weight of azodicarbonamide and 0.3 part by weight of zinc stearate were added to 0 parts by weight.

The degree of foaming of this insulated wire was about 73%, and it was extremely easy to peel off the foamed insulation with a wire stripper.

Example 4 Low-density polyethylene (Mitsui Petrochemical Mirason 3530) 10
A foam insulated wire was produced in the same manner as in Example 1 except that 4 parts by weight of azodicarbonamide and 0.7 parts by weight of zinc laurate were added to 0 parts by weight.

The foamed degree of this insulated wire was about 74%, and the foamed insulator was extremely easily peeled off by the wire stripper.

Example 5 Low-density polyethylene (Mitsui Petrochemical Mirason 3530) 10
A foam insulated wire was produced in the same manner as in Example 1 except that 4 parts by weight of azodicarbonamide and 0.5 part by weight of zinc naphthenate were added to 0 parts by weight.

The foamed degree of this insulated wire was about 70%, and the foamed insulator was extremely easily peeled off by the wire stripper.

Example 6 A foam insulated wire was produced in the same manner as in Example 1 except that 3 parts by weight of azodicarbonamide and 0.5 part by weight of zinc hydroxystearate were added to 100 parts by weight of low-density polyethylene (UBEC-400 manufactured by Ube Industries).

The foamed degree of this insulated wire was about 96%, and the foamed insulator was extremely easily peeled off by the wire stripper.

Comparative Example 1 A foam insulated wire was produced in the same manner as in Example 1 except that a composition obtained by adding 3 parts by weight of azodicarbonamide to 100 parts by weight of low-density polyethylene (UBEC-400 manufactured by Ube Industries) was used.

Although the degree of foaming of this insulated wire was about 70%, the conductor and the foamed insulator adhered to each other. When the foamed insulator was peeled off with a wire stripper, the foamed insulator remained on the conductor.

Comparative Example 2 Low Density Polyethylene (Mitsui Petrochemical Mirason 3530) 10
A foam insulated wire was produced in the same manner as in Example 1 except that the composition in which 4 parts by weight of azodicarbonamide was added to 0 parts by weight.

Although the foaming degree of this insulated wire was about 76%, the conductor and the foamed insulator adhered to each other. When the foamed insulator was peeled off with a wire stripper, the foamed insulator remained on the conductor.

Comparative Example 3 A foam insulated wire was produced in the same manner as in Example 1 except that the amount of zinc stearate added was 8 parts by weight.

It was impossible to manufacture an insulated wire because foaming occurred in the step of extrusion-coating the outer circumference of the conductor.

Comparative Example 4 A foam insulated wire was produced in the same manner as in Example 1 except that the amount of zinc ricinoleate added was 8 parts by weight.

It was impossible to manufacture an insulated wire because foaming occurred in the step of extrusion-coating the outer circumference of the conductor.

Comparative Example 5 Low-density polyethylene (Mitsui Petrochemical Mirason 3530) 10
A foam insulated wire was produced in the same manner as in Example 1 except that a compound obtained by adding 3 parts by weight of azodicarbonamide and 0.5 part by weight of citearic acid to 0 part by weight was used.

The degree of foaming of this insulated wire was about 75%, but the conductor and the foamed insulation adhered to each other, and when the foamed insulation was stripped off with a wire stripper, the foamed insulation remained on the conductor.

[Effects of the Invention] As described above, according to the present invention, it is possible to realize a foamed insulated wire that can be highly foamed and that can prevent sticking between a conductor and a foamed insulator to improve workability of terminal treatment. become.

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Hirotoshi Okubo 5-1-1 Hidaka-cho, Hitachi-shi, Ibaraki Electric Cable Research Laboratory, Hitachi Cable, Ltd. (72) Inventor Takayasu Asai 5 Hidaka-cho, Hitachi-shi, Ibaraki 1-1-1 Hitachi Cable Co., Ltd. Hidaka Plant (72) Inventor Norimoto Abe 5-1-1 Hidakacho, Hitachi City, Ibaraki Hitachi Cable Co., Ltd. Hidaka Plant (56) References 48-22559 (JP, A) JP-A-61-44933 (JP, A)

Claims (1)

[Claims] 1. 0.5 to 15 parts by weight of azodicarbonamide and 100 parts by weight of polyolefin and zinc soap represented by the formula Sn (OOCR) ₂ (R is an alkyl group having 7 or more carbon atoms).
The resin composition containing 05 to 5 parts by weight is extrusion-coated on the outer circumference of the conductor at a temperature not higher than the decomposition temperature of azodicarbonamide, and then crosslinked by irradiation of ionizing radiation, and then heated to a temperature not lower than the decomposition temperature of azodicarbonamide. A method for producing a foam insulated wire, comprising forming a foam insulator.