JPH0743971B2 - Method for manufacturing foam insulated wire - Google Patents

Description

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

[Prior Art] In a high-speed information circuit such as a computer and a telephone communication, an electric wire having a low dielectric constant is required, and a foamed polyolefin insulated electric wire is often 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 extrusion-coated on the outer circumference of the conductor. However, in this method, the decomposition gas of the foaming agent is easily scattered, and it is difficult to obtain a high-foamed product of 50% or more.

As a measure to prevent the decomposition gas of the foaming agent from scattering,
For 53-4909, a manufacturing method is proposed in which a plastic mixture containing a foaming agent is extrusion-coated on a conductor, continuously crosslinked by radiation and electron beams, and subsequently heated in a pressurized fluid atmosphere to foam. Has been done.

[Problems to be Solved by the Invention] However, this method lacks versatility because a fluid pressurizing facility is required, and the outer diameter is not uniform due to pressure fluctuation, and the insulated wire is contaminated by fluid. There are problems such as.

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 the foamed insulation adhered to each other, and the foamed insulation was peeled off using a wire stripper. In this case, there is a problem that the foamed insulator remains around the conductor and the workability of the terminal treatment is extremely deteriorated.

As a method of suppressing the adhesion between the conductor and the foamed insulator to improve the workability of the terminal treatment, zinc soap such as zinc stearate,
It has been confirmed that adding a small amount of lead soap such as lead stearate is effective. However, the addition of such a compound lowers the decomposition temperature of azodicarbonamide and makes it easier to decompose, so the extrusion conditions of the compound become strict, and it is possible to produce a uniform foam insulated wire over a long length. The problem of becoming difficult has come to the fore.

Since the present invention is made based on the above, it is possible to achieve high foaming, suppress the adhesion between the conductor and the foamed insulating material, and easily peel off the foamed insulating material. Moreover, the foamed insulating material is uniform over a long length. It is an object of the present invention to provide a method for producing a foam insulated wire from which a body is obtained.

[Means for Solving Problems] The method for producing a foam insulated wire according to the present invention is a polyolefin 10
0.5 to 15 parts by weight of azodicarbonamide to 0 parts by weight,
Zinc compound 0.1 to 10 parts by weight and fatty acid amide 0.05 to 5
Parts of the compound contained by weight are extrusion-coated on the outer circumference of the conductor at a temperature below the decomposition temperature of azodicarbonamide and then crosslinked by irradiation with ionizing radiation, and then heated above the decomposition temperature of azodicarbonamide to form a foamed insulator. It is characterized by forming.

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 amount of azodicarbonamide added should be in the range of 0.5 to 15 parts by weight with respect to 100 parts by weight of the polyolefin.If it is less than 0.5 parts by weight, the foaming is insufficient. Becomes difficult.

In the present invention, the combined use of the zinc compound and the fatty acid amide makes it possible to suppress the adhesion between the conductor and the foamed insulation, and to form a foamed insulation which is uniform over a long length. That is,
During the extrusion of the compound, the zinc compound and the fatty acid amide are hardly in a dispersed state, so that the decomposition temperature of the azodicarbonamide is hardly lowered. It is considered that this suppresses the generation of decomposition residues of azodicarbonamide that contributes to the adhesion between the conductor and the foamed insulator.

The zinc compound and the fatty acid amide are added in amounts of 0.1 to 10 parts by weight and 0.
It is in the range of 05 to 5 parts by weight. If the zinc compound is less than 0.1 part by weight or the fatty acid amide is less than 0.05 part by weight, the effect of preventing the adhesion between the conductor and the foamed insulator is not obtained. In addition, the zinc compound is 10
If the weight part or the fatty acid amide exceeds 5 parts by weight, the decomposition temperature of the azodicarbonamide is remarkably lowered.
It becomes difficult to obtain a foamed insulator that is foamed during extrusion molding and uniform over a long length, and it is difficult to obtain a foamed insulator having a low dielectric constant.

Examples of the zinc compound include zinc oxide (zinc white), inorganic zinc compounds such as zinc silicate, zinc carbonate, zinc sulfide, zinc aluminate, zinc salt of 2-mercaptobenzothiazole, zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, Zinc N-ethyl-N-phenyldithiocarbamate, Zinc butylxanthogenate, Zinc salt of 2-mercaptobenzimidazole, Zinc salt of 2-benzamidothiophenol, Zinc di-n-butyldithiocarbamate, Zinc dibenzyldithiocarbamate, N -Organominc compounds such as zinc pentamethylene / dithiocarbamate, zinc acetate, and basic zinc acetate.

Examples of the fatty acid amides include caproic acid amide, caprylic acid amide, capric acid amide, lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, arachidic acid amide, behenic acid amide, palmitoleic acid amide, oleic acid amide, and eicosene amide. Acid amide, erucic acid amide, elaidic acid amide, trans-11-eicosenoic acid amide, trans-13-docosenoic acid amide, linoleic acid amide, linolenic acid amide, ridinoleic acid amide, ethylenebisstearoamide, methylenebisstearoamide , Behenamide, methylolamide, methylenebis stearobehenamide, oxystearoamide, erucyl anide and the like.

The compound containing polyolefin, azodicarbonamide, zinc compound and fatty acid amide as essential components is melt-kneaded at a temperature not higher than the decomposition temperature of azodicarbonamide, for example, not higher than 160 ° C., and extrusion-coated on the outer periphery of the conductor. Then, ionizing radiation such as an electron beam is applied to 0.5
Irradiation is carried out in the range of up to 5 Mrad to crosslink, and the foamed insulation is formed by heating under atmospheric pressure above the decomposition temperature of azodicarbonamide. This heating is preferably performed continuously using an electric furnace or the like, and the set temperature is preferably several tens of degrees higher than the decomposition temperature of azodicarbonamide. Of course, the high temperatures at which the polyolefin decomposes should be avoided.

Polyolefin, azodicarbonamide, zinc compound and a compound containing a fatty acid amide can be obtained by adding azodicarbonamide, a zinc compound and a fatty acid amide to the polyolefin and mixing them respectively, or a azodicarbonamide and a zinc compound to the polyolefin. A method of mixing a mixture obtained by adding and mixing, and a mixture obtained by adding azodicarbonamide and a fatty acid amide to polyolefin, a mixture obtained by adding either a zinc compound or a fatty acid amide to polyolefin, and a polyolefin Examples of the method include, but are not limited to, a method of mixing azodicarbonamide with a mixture of the remaining zinc compound or fatty acid amide and mixing them.

[Examples of the Invention] Example 1 3 parts by weight of azodicarbonamide and 2 parts by weight of zinc white were added to 100 parts by weight of low-density polyethylene (UBEC-400 manufactured by Ube Industries, Ltd.), and the resulting mixture was placed on an 8-inch roll set at 135 ° C. After kneading, 0.5 part by weight of erucylamide was added to obtain a compound. Use this compound with a 28 mm extruder (set temperature 14
(0 ° C.), melt kneading was performed, and the outer circumference of a tin-plated copper wire having an outer diameter of 0.45 mm was extrusion-coated to a thickness of 0.2 mm. Then, 1.5Mrad is irradiated by an electron beam irradiation device to crosslink and 300 ° C.
The foamed insulated wire was manufactured by passing it through a cylindrical electric furnace having an inner diameter of 70 mmφ and a furnace length of 2.5 m set at 1.

The foamed degree of this insulated wire was about 70%, and the foamed insulator was extremely easily peeled off by the wire stripper. Further, since the foaming was performed uniformly in the length direction, there was almost no fluctuation in the outer diameter in the length direction.

Example 2 Low-density polyethylene (Mitsui Petrochemical Mirason 3530) 100
4 parts by weight of azodicarbonamide and 1.52 parts by weight of zinc dimethyldithiocarbamate were kneaded with 8 parts by weight of an 8-inch roll set at 130 ° C.
The compound was added by weight. Subsequently, using a 28 mm extruder (set temperature 135 ° C.), a foam insulated wire was manufactured in the same manner as in Example 1.

The degree of foaming of this insulated wire was about 78%, and the foamed insulator was extremely easily peeled off by the wire stripper. Further, since the foaming was performed uniformly in the length direction, there was almost no fluctuation in the outer diameter in the length direction.

Example 3 A foam insulated wire was produced in the same manner as in Example 1 except that ethylene bisstearoid was used instead of erucylamide.

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. Further, since the foaming was performed uniformly in the length direction, there was almost no fluctuation in the outer diameter in the length direction.

Example 4 Low-density polyethylene (Mitsui Petrochemical Mirason 3530) 100
3 parts by weight of azodicarbonamide and 2 parts by weight of zinc salt of 2 mercaptobenzothiazole were added to 135 parts by weight,
The composition was obtained by kneading with an 8-inch roll set at 0 ° C.
In addition, low-density polyethylene (Mitsui Petrochemical Mirason 353
0) 3 parts by weight of azodicarbonamide and 0.8 parts by weight of erucylamide were added to 100 parts by weight and kneaded with an 8-inch roll set at 135 ° C. to obtain a composition. The above two compositions were each pelletized, dry-blended at a ratio of 50:50 and introduced into a 28 mm extruder (set temperature 140 ° C.), and a foam insulated wire was manufactured in the same manner as in Example 1.

The degree of foaming of this insulated wire was about 76%, and the stripping of the foamed insulation by the wire stripper was extremely easy. Further, since the foaming was performed uniformly in the length direction, there was almost no fluctuation in the outer diameter in the length direction.

Comparative Example 1 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 to 100 parts by weight of low-density polyethylene (UBEC-400 manufactured by Ube Industries) was used.

The degree of foaming of this insulated wire was about 70%, but the conductor and the foamed insulator adhered to each other, and when the foamed insulation was stripped with a wire stripper, the foamed insulation remained on the conductor.

Comparative Example 2 Low-density polyethylene (Mitsui Petrochemical Mirason 3530) 100
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 stearate were added to the compound.

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. However, the foaming was non-uniform, and the variation of the outer diameter in the length direction was large.

Comparative Example 3 Low-density polyethylene (Mitsui Petrochemical Mirason 3530) 100
3 parts by weight of azodicarbonamide and 2 parts by weight of zinc white
Example 1 except that a compound added with parts by weight was used.
A foam insulated wire was produced in the same manner as in.

The degree of foaming of this insulated wire was about 76%, 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.

Comparative Example 4 Low-density polyethylene (Mitsui Petrochemical Mirason 3530) 100
A foam insulated wire was produced in the same manner as in Example 1 except that a compound in which 3 parts by weight of azodicarbonamide and 0.5 part by weight of stearic acid amide were added to parts by weight was used.

The degree of foaming of this insulated wire was about 75%, but when the conductor and the foamed insulation adhered and 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 achieve high foaming, prevent the adhesion between the conductor and the foamed insulating material, and improve the workability of the terminal treatment, and moreover, it is uniform over a long length. It becomes possible to realize a foam insulated wire having an outer diameter.

Front page continuation (72) Hideo Takano 5-1-1 Hidaka-cho, Hitachi, Hitachi, Ibaraki Prefecture Hidaka Plant, Hitachi Cable, Ltd. (72) Norimoto Abe 5-1-1 Hidaka-cho, Hitachi, Ibaraki No. 1 Inside the Hidaka Plant of Hitachi Cable, Ltd. (72) Inventor Toshiaki Ichimo 5-1-1 Hidaka-cho, Hitachi City, Ibaraki Prefecture Inside the Hidaka Plant of Hitachi Cable Ltd. (56) Reference JP-A-58- 201825 (JP, A) JP 59-225156 (JP, A) JP 61-148242 (JP, A) JP 43-24525 (JP, B1)

Claims (1)

[Claims] 1. A compound containing 0.5 to 15 parts by weight of azodicarbonamide, 0.1 to 10 parts by weight of a zinc compound and 0.05 to 5 parts by weight of fatty acid amide per 100 parts by weight of polyolefin at a temperature not higher than the decomposition temperature of azodicarbonamide. A method for producing a foam-insulated electric wire, which comprises extrusion-coating the outer circumference of a conductor, crosslinking the same by irradiation with ionizing radiation, and then heating it to a temperature not lower than the decomposition temperature of azodicarbonamide to form a foam-insulated body.