JPH05217439A - Manufacture of foam insulated electric wire - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a novel method for producing a foam insulated wire, which has a high foaming rate, is excellent in dimensional accuracy, and can achieve both thin and thin wall thickness and thick and thick wall thickness. [Structure] Insulated wire with insulation around the conductor,
The composition constituting the insulator is a polymer obtained by adding a heat-expandable hollow sphere to the polymer, and a polymer having a molding temperature lower than the foaming temperature of the heat-expandable hollow sphere is foam-molded. Method for manufacturing foam insulated wire.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foam insulated wire, and more particularly to a method for producing a foam insulated wire using a thermally expandable hollow sphere.

[0002]

2. Description of the Related Art With the remarkable progress of electronics technology, various electric wires and cables with higher signal transmission speed are required.

In order to meet these requirements, foam insulators are used as insulators for electric wires and cables.

That is, by foaming the insulator, the relative permittivity is lowered and the desired high performance such as high-speed transmission, low electrostatic capacity, and low attenuation is achieved.

By the way, various conventional foaming methods for insulators have been proposed and put into practical use.
Alumina, shirasu, a method of adding inorganic hollow spheres that are already foam such as glass to the polymer, or adding organic already hollow spheres or heat-expandable hollow spheres to the UV curable coating. And heat it to form a foam, etc.
Foamed insulators using so-called hollow spheres have been proposed.

However, the method of adding inorganic hollow spheres to a polymer has a limit in the amount to be added from the viewpoint of the bulk density of the foam, the foaming degree is limited, and the mechanical share during kneading or extrusion molding. Due to this, the hollow sphere will be destroyed, and since it is a hollow sphere that has already been foamed, it is not possible to make an insulation thickness less than this diameter.Inorganic hollow spheres have an inherently large dielectric constant. Since it was inferior, there were drawbacks such as poor mechanical properties. In addition, the method of adding the organic heat-expandable hollow spheres to the ultraviolet curable material is curing and foaming, that is, the ultraviolet curable material is crosslinked and cured and then heat-foamed, or conversely, foamed and then crosslinked and cured by ultraviolet rays. In addition to the degree of foaming, it affects not only the degree of foaming but also the size, etc., and it is difficult to balance them.Because a low-viscosity liquid is applied to the conductor, it is greatly affected by the conductor structure and the structure and dimensions become uneven. There are drawbacks such that it is difficult to form a thick insulator, and the material forming the shell of the hollow sphere is softened or swelled depending on the oligomer or monomer used, thereby significantly deteriorating the foamability.

Further, since the ultraviolet curable material is expensive, there have been problems such as economic problems and safety and hygiene.

[0008]

An object of the present invention is to solve the above-mentioned drawbacks of the prior art, to provide a new foamed insulated wire which has a high foaming rate, is excellent in dimensional accuracy, and can achieve both thin and thin wall thickness and large diameter and thick wall thickness. It is to provide a manufacturing method.

[0009]

That is, the gist of the present invention is that in an insulated wire in which an insulating material is applied to the outer circumference of a conductor, the composition of the insulating material is obtained by adding a thermally expandable hollow sphere to a polymer. Further, there is provided a method for producing a foam insulated wire, characterized in that a polymer having a molding temperature lower than the foaming temperature of the heat-expandable hollow sphere is foam-molded.

[0010]

The polymer used in the present invention is preferably a polymer having a small dielectric constant such as polyolefin, but is not particularly limited thereto, and if necessary, a polyvinyl chloride composition or a rubber composition. Can also be used.

The thermally expandable hollow sphere is made up of Shel.
As the l composition, acrylic acid ester, methacrylic acid ester, acrylonitrile, vinylidene chloride-acrylonitrile, methyl methacrylate-acrylonitrile, etc. are used.

Representative examples of the encapsulating agent involved in foaming are low-boiling hydrocarbons such as isobutane, pentane, hexane and heptane, and halogenated hydrocarbons.

As a matter of course, the Shell polymer and the encapsulating agent can be changed according to the purpose and are not limited to the above examples. The thermally expandable hollow spheres are those which, when the Shell polymer is heated, soften and at the same time, the vapor pressure of the expander contained therein starts to rise and the Shell is pushed and expanded to expand and expand.

In this example, Matsumoto Yushi-Seiyaku Co., Ltd. Matsumoto Microsphere F series, especially high temperature type was examined.

It is important to limit the molding temperature of the polymer and the softening and foaming temperature of the heat-expandable hollow spheres. In the present invention, the softening and foaming temperature of the heat-expandable hollow spheres is always higher than the polymer processing temperature.

The conductor is not particularly limited and may be a single wire, a twisted wire, a bundled metal coated twisted wire, or the like.

Typical examples of energy beam irradiation include ultraviolet rays and electron beams.

Example 1 100 parts by weight of an ethylene-vinyl acetate copolymer having a melting point of 65 ° C., a Shell polymer of methyl methacrylate acrylonitrile, an encapsulating agent of isobutane, a softening and foaming starting temperature of 100 ° C., and a particle diameter of 32 Insulation after foaming on a core wire with an outer diameter of 0.38 mm (28 AWG) made by twisting seven strands with a conductor diameter of 0.102 into a compound with 20 parts by weight of 62 μm thermally expandable hollow spheres added It was extruded to a body thickness of 200 μm.

The foamed insulated wire had a foaming degree of 72% and a dielectric constant of 1.52 and had a good appearance. When the electric wire was applied with a load of 300 g at a temperature of 50 ° C., the deformation rate was 8%, and the deformation after 5 minutes from removal of the load was 2% or less.

Example 2 The same compound as in Example 1 was extruded on a single wire having a conductor diameter of 1.05 so that the thickness of the insulator after foaming was 4 mm.

The foamed insulated wire had a foaming degree of 80% and had a smooth appearance and good appearance. This dielectric constant is 1.40.

When this wire was applied with a load of 500 g at a temperature of 50 ° C., the deformation rate was 12%, and the deformation after 5 minutes from removal of the load was 2% or less.

Example 3 100 parts by weight of an ethylene-ethyl acrylate copolymer having a melting point of 85 ° C., Shell polymer was methyl methacrylate-acrylonitrile, and an encapsulating agent was isobutane.
Softening decomposition temperature 100 ℃, particle size 32 to 62 μm
20 parts by weight of the heat-expandable hollow sphere as a compound is used as a compound, and seven strands of a conductor having a diameter of 0.102 are twisted together to form an insulator after foaming on a core wire having an outer diameter of 0.38 mm (28 AWG). It was extruded to a thickness of 200 μm. 2 to this
A crosslinking treatment was performed by irradiating with an electron beam of 0 Mrad.

The foamed insulated wire had a foaming degree of 70% and a dielectric constant of 1.51 and had a good appearance. 8 this wire
Deformation rate is 6 when a load of 300g is applied at a temperature of 0 ° C.
The deformation after 5 minutes after removing the load was 2% or less. Further, even when this foamed electric wire was immersed in solder at 380 ° C. for 3 seconds, the insulator did not melt.

Comparative Example 1 100 parts by weight of polyethylene having a melting point of 108 ° C. was added with Shel.
A compound was prepared by adding 20 parts by weight of thermally expandable hollow spheres having a softening and foaming initiation temperature of 100 ° C. and a particle size of 32 to 62 μm, in which the polymer is methyl methacrylate-acrylonitrile and the encapsulating agent is isobutane, and the compound is used as a conductor. Outer diameter 0.3 with 7 strands of diameter 0.102 twisted together
The thickness of the insulator after foaming was planned to be 200 μm on the core wire of 8 mm (28 AWG).

When this compound was kneaded with an open roll at 120 ° C. to make it, the compound remarkably foamed at this stage and the extrusion molding was abandoned.

[0027]

As is apparent from the above description, the present invention provides an insulator having a low dielectric constant, which has both a small diameter and a thin wall and a large diameter and a thick wall, has a good appearance, and has an extremely high degree of foaming. Moreover, this hollow sphere exists as a closed cell and has a strong Sh.
Due to the effect of the ell polymer, it is possible to form a foamed insulator that is extremely resistant to deformation under pressure and compression.

These characteristics can be expected to exert excellent effects in high-speed transmission, low capacitance, and low attenuation of various electric wires and cables in the field of electronics.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical display location B29K 105: 08 B29L 23:00 4F (72) Inventor Toshiaki Ichige 5 Hidakacho, Hitachi City, Ibaraki Prefecture 1-1-1 Hitachi Cable Co., Ltd. Hidaka Factory

Claims (4)

[Claims] 1. An insulated wire in which an insulating material is applied to the outer circumference of a conductor, wherein the composition of the insulating material is obtained by adding thermally expandable hollow spheres to a polymer, and the molding temperature of the polymer is thermally expanded. A method for producing a foam insulated wire, characterized in that a foamed hollow sphere having a temperature lower than the foaming temperature is foam-molded. 2. The method for producing a foam insulated wire according to claim 1, wherein when the insulator is processed on the conductor, foam molding is performed. 3. The method for producing a foam-insulated electric wire according to claim 1, wherein an insulator is molded on the conductor and then heat-foamed. 4. The method for producing a foam insulated wire according to claim 1, wherein the insulated wire is irradiated with energy rays to be crosslinked.