JPH0668939B2 - Method for manufacturing foam insulated wire - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a conductor and a foam insulated wire.

[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,
53-4909 proposes a manufacturing method in which a plastic mixture containing a foaming agent is extrusion-coated on a conductor, continuously cross-linked by radiation and electron beams, and then 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.

The present invention has been 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. An object of the present invention is to provide a method for producing a foam insulated wire from which an insulator can be 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,
A compound containing 0.1 to 10 parts by weight of an inorganic lead compound and 0.05 to 5 parts by weight of a fatty acid is extrusion-coated on the outer circumference of a conductor at a temperature not higher than the decomposition temperature of azodicarbonamide, and then crosslinked by irradiation with ionizing radiation, and then azodicarbonate. It is characterized in that the foamed insulator is formed by heating at a temperature not lower than the decomposition temperature of the amide.

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, by using the inorganic lead compound and the fatty acid in combination, it is possible to suppress the adhesion between the conductor and the foamed insulator, and to form a foamed insulator that is uniform over a long length. That is, when the compound is extruded, the inorganic lead compound and the fatty acid rarely lower the decomposition temperature of the azodicarbonamide because they are simply in a dispersed state, and the inorganic lead compound and the fatty acid react during the heat foaming, It is considered that this suppresses the generation of decomposition residues of azodicarbonamide, which contributes to the adhesion between the conductor and the foamed insulator.

The amount of the inorganic lead compound and fatty acid added is 0.1 to 10 parts by weight and 0.05 to 100 parts by weight of the polyolefin, respectively.
It is in the range of 5 parts by weight. If the inorganic lead compound content is less than 0.1 parts by weight or the fatty acid content is less than 0.05 parts by weight, the effect of preventing the adhesion between the conductor and the foamed insulation is ineffective. Further, when the content of the inorganic lead compound exceeds 10 parts by weight or the fatty acid exceeds 5 parts by weight, the decomposition temperature of azodicarbonamide is remarkably lowered, which makes it difficult to obtain a foamed insulator which is foamed during extrusion molding and long. In addition, it becomes difficult to obtain a foamed insulator having a low dielectric constant.

Inorganic lead compounds include lead orthosilicate, tribasic lead sulfate, basic lead sulfite, dibasic lead phosphite, basic lead carbonate, lead oxide, dilead trioxide, trilead tetraoxide, lead sulfide. , Lead chloride, tribasic phosphorus trilead.

As the fatty acid, stearic acid, lauric acid, ricinoleic acid, naphthenic acid, 2-ethylhexoic acid, octylic acid, hydroxystearic acid, phthalic acid, lindelic acid,
Elaidic acid, tudzuic acid, gadrenic acid, ficetrain acid, gondoic acid, myristoleic acid, whale oil acid, zomarinic acid, erucic acid, petroselinic acid, planzic acid, oleic acid, serracoylenic acid, linoleic acid, linoelaidic acid, linolenic acid Acid, eleostearic acid, moloctic acid, vinalinaric acid, arachidonic acid, sardine acid, hiragashilaic acid,
Examples include nisinic acid.

A compound containing polyolefin, azodicarbonamide, an inorganic lead compound and a fatty acid 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. Next, 0.5 to 0.5
Irradiation is performed in the range of 5 Mrad to crosslink, and the foamed insulator is formed by heating under normal pressure to a temperature 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, as a method of obtaining a compound containing an inorganic lead compound and a fatty acid, azodicarbonamide, a method of adding an inorganic lead compound and a fatty acid to the polyolefin, respectively,
A method of mixing a mixture of azodicarbonamide and an inorganic lead compound added to polyolefin, and a method of mixing a mixture of azodicarbonamide and a fatty acid added to polyolefin, either the inorganic lead compound or the fatty acid added to polyolefin. Examples of the method include, but are not limited to, a method of mixing a mixture obtained by adding and mixing, and a mixture obtained by adding either azodicarbonamide and the remaining inorganic lead compound or fatty acid to a polyolefin, and the like. is not.

[Examples of the Invention] Examples 1 and 2 and Comparative Example 1 3 parts by weight of azodicarbonamide and 100 parts by weight of low-density polyethylene (UBEC-400, Ube Industries Ltd.) and a predetermined amount of the additives shown in Table 1 were added, and 6 inches A compound was prepared by uniformly kneading with a test roll (130 ° C.). The compound was placed in a glass tube, and the glass tube was placed in silicone oil heated to 200 ° C. to measure the foaming start time of the compound of each example.

The results are shown in Table 1, and the compounds of Examples 1 and 2 had a longer foaming start time than Comparative Example 1, which means that the extrusion conditions have a margin. It is a thing.

Example 3 To 100 parts by weight of low density polyethylene (UBEC-400 manufactured by Ube Industries, Ltd.), 3 parts by weight of azodicarbonamide and 1 part by weight of tribasic lead sulfate were added, and the mixture was kneaded with an 8-inch roll set at 135 ° C. Then, 0.5 part by weight of stearic acid was added to obtain a compound. This compound was introduced into a 28 mm extruder (set temperature 135 ° C.), melt-kneaded, and extrusion-coated to a thickness of 0.2 mm on the outer circumference of a tin-plated copper wire having an outer diameter of 0.45 mm. Then, 1.5 Mrad was irradiated by an electron beam irradiation device to perform cross-linking, and the product was passed through a tubular electric furnace having an inner diameter of 70 mmφ and a furnace length of 2.5 m set at 300 ° C. under normal pressure to manufacture a foam insulated wire.

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 4 100 parts by weight of low-density polyethylene (Mitsui Petrochemical Mirason 3530) was kneaded with 4 parts by weight of azodicarbonamide and 2 parts by weight of lead oxide by an 8-inch roll set at 130 ° C., and then 0.5 part by weight of lauric acid was added. And made it a compound. Subsequently, a foam insulated wire was manufactured in the same manner as in Example 1.

The foamed degree of this insulated wire was about 74%, 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 5 A foam insulated wire was produced in the same manner as in Example 1 except that lead carbonate was used instead of tribasic lead sulfate.

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 6 A composition was prepared by adding 3 parts by weight of azodicarbonamide and 2 parts by weight of tribasic lead sulfate to 100 parts by weight of low density polyethylene (Mitsui Petrochemical Mirason 3530) and kneading with an 8-inch roll set at 135 ° C. Got Further, 3 parts by weight of azodicarbonamide and 0.8 parts by weight of stearic acid were added to 100 parts by weight of low-density polyethylene (Mitsui Petrochemical Mirason 3530), and the mixture was kneaded with an 8-inch roll set at 135 ° C. to obtain a composition. The above two compositions were each pelletized, then 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 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.

Comparative Example 2 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 3 A foamed insulated electric wire was prepared in the same manner as in Example 1 except that 4 parts by weight of azodicarbonamide and 0.5 parts by weight of zinc stearate were added to 100 parts by weight of low-density polyethylene (Mitsui Petrochemical Mirason 3530). Manufactured.

The degree of foaming of this insulated wire was about 73%, and it was extremely easy to peel it off with a foamed insulation wire stripper. However, the foaming was non-uniform, and the variation of the outer diameter in the length direction was large.

Comparative Example 4 Foam insulation in the same manner as in Example 1 except that 100 parts by weight of low-density polyethylene (Mitsui Petrochemical Mirason 3530), 3 parts by weight of azodicarbonamide and 2 parts by weight of tribasic lead sulfate were used. Manufactured an electric wire.

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 5 A foam insulated wire was produced in the same manner as in Example 1 except that a compound prepared by adding 3 parts by weight of azodicarbonamide and 0.5 part by weight of stearic acid to 100 parts by weight of low-density polyethylene (Mitsui Petrochemical Mirason 3530) was used. did.

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.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masami Maeda 5-1-1 Hidaka-cho, Hitachi-shi, Ibaraki Hitachi Cable Co., Ltd. Hidaka factory (72) Inventor Hideo Takano 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 63-304533 (JP, A)

Claims (1)

[Claims] 1. A compound containing 0.5 to 15 parts by weight of azodicarbonamide, 0.1 to 10 parts by weight of an inorganic lead compound, and 0.05 to 5 parts by weight of fatty acid to 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 an outer periphery of a conductor, cross-linking it by irradiation with ionizing radiation, and then heating it to a temperature not lower than a decomposition temperature of azodicarbonamide to form a foamed insulator.