JPH0547247A - Method for manufacturing foam insulated wire - Google Patents

Abstract

PURPOSE:To easily manufacture a thin highly foamed insulated cable having an outer diameter less than 1mm and a foaming ratio of 70% or more with good appearance and good adhesion. CONSTITUTION:When a foamed insulating material having an outer diameter less than 1.0mm and a foaming ratio of 70% or more is molded on a conductor by extrusion, a polyolefin in which swelling ratio is 65% or more, melt tension is 2-5g, and maximum drawing speed in melting is 50-200m/min is used as the material for the foamed insulating material to provide an insulated cable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a method of manufacturing an insulated electric wire having a small diameter and high foaming, which is used, for example, in wiring of computer peripherals.

[0002]

2. Description of the Related Art As a cable for wiring a computer peripheral device, a small-diameter high-foam insulated wire which is effective for speeding up signal propagation, lowering the dielectric constant, reducing the weight and saving space is used. Conventionally, various studies have been conducted in order to manufacture this type of highly foamed insulated electric wire. For example, a method of manufacturing by adding a blowing agent of hydrocarbon or fluorocarbon to an insulating material having a swelling ratio of 40% to 75% (see Japanese Patent Publication No. 57-30253), and a swelling ratio of 55.
% Or more insulating material with a chemical foaming agent and / or an inert gas foaming agent (Japanese Patent Publication No. 61-1141)
(See Japanese Patent Publication No. 58-11047). A method of producing a resin by using a double die to extrude foamed plastic in an inner die and extruded non-foamed plastic in an outer die to simultaneously perform double extrusion (see Japanese Patent Publication No. 58-11047). Are known. With these methods, CAT with an outer diameter of 10 mm or more
A V cable or an OA cable having an outer diameter of about 2 mm can be obtained.

[0003]

As shown in FIG. 1, a high-speed coaxial multi-flat cable 10 having a pitch between signal lines 12 of 1.27 mm is used for wiring a computer peripheral device. In order to manufacture a cable in which the pitch between the signal lines 12 is 1.27 mm, the flat cable 10 has an outer diameter formed by using the signal lines 12 as a conductor and extruding and covering the foamed insulation 14 thereon. 1.0 m
An insulated electric wire 16 having a length of m or less, particularly 0.6 to 0.8 mm is used. In FIG. 1, reference numeral 18 is a drain wire,
Reference numeral 20 is an electromagnetic shielding layer, and reference numeral 22 is a sheath. In such a small-diameter, thin-wall system, it is difficult to obtain a high-foam insulated wire with a foaming ratio of 70% or more, and it is possible to achieve a foaming with a foaming ratio of 70% or more by using any of the above-mentioned conventional techniques. could not. Further, when an attempt was made to manufacture an insulated electric wire having a small diameter and high foaming by using any of the above-mentioned conventional methods, it was not possible to obtain a highly foamed insulated electric wire having a rough surface and a good appearance.

An object of the present invention is to provide a method capable of avoiding the above-mentioned drawbacks and manufacturing a thin, thin-walled high-foam insulated wire with a good appearance.

[0005]

In order to solve the above-mentioned problems, the present invention provides a method for forming a foamed insulating material having an outer diameter of 1.0 mm or less and a foaming degree of 70% or more on a conductor by extrusion. In addition, as a material for the foamed insulation, a polyolefin having a swelling ratio of 65% or more, a melt tension of 2 to 5 g, and a maximum take-up speed during melting of 50 to 200 m / min is used. To provide a method.

[0006]

When the swelling ratio of polyolefin, which is the material of the foamed insulation, is 65% or more, a highly foamed insulation can be obtained, and when the melt tension is 2 to 5 g, the melt elasticity of the material is appropriate. Therefore, it is possible to obtain a preferable foaming by appropriately dispersing bubbles with a proper size.
Furthermore, the maximum take-up speed when the polyolefin is melted is 50 to 2
When it is 00 m / min, the foam insulated wire can be taken while maintaining a sufficient melt tension without impairing the extrusion appearance.

[0007]

EXAMPLES The present invention will be described in detail. A foam insulated wire to be manufactured according to the present invention has a conductor, an outer diameter of 1.0 mm or less formed on the conductor, and a foam degree of 7 or less.
It is composed of 0% or more of foamed insulation, and this foamed insulated wire is manufactured by molding a material of foamed insulation on a conductor by extrusion.

According to the method of the present invention, the material for the foamed insulating material has a swelling ratio of 65% or more and a melt tension of 2 or more.
~ 5g, the maximum take-up speed during melting is 50-200m /
Min is used. As the polyolefin used in the present invention, low density polyethylene (LDP)
E), high density polyethylene (HDPE), ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer (EEA) and other ethylene-based copolymers, polypropylene (PP) and the like alone or two of these Mixtures of more than one can be used.

It is known that the swelling ratio is related to foaming characteristics, and as a result of experiments, the swelling ratio is 65.
It was found that if it is less than%, high foaming cannot be obtained. However, when the outer diameter of the foam insulation is 1.0 mm or less,
It has been found that a swelling ratio of 65% or more is not sufficient, and in addition, the melt tension and the maximum take-up speed during melting are related to the foaming property.

That is, the melt tension of the insulating material is 2 g.
If it is smaller than the above range, the melt elasticity of the material is too low, so that large bubbles or continuous bubbles are generated, which is not suitable for a system having an outer diameter of 1 mm or less. If it exceeds 5 g, the melt elasticity of the material is too high, and the material cannot overcome the pressure of the foaming gas to obtain high foaming, and the cells of the bubbles cannot grow sufficiently, so that the foaming gas is near the conductor. There is a drawback that the adhesive force between the conductor and the insulator is reduced due to concentration.

On the other hand, when the insulating material is melted, the maximum take-up speed is 5
If it is less than 0 m / min, the insulating material has poor moldability,
It is not suitable because the appearance of extrusion of the insulating material is rough and unsuitable, and when it exceeds 200 m / min, the melt tension is lowered and the bubbles become large, which is not suitable.

As the foaming agent used in the method of the present invention, either a chemical foaming agent or an inert gas foaming agent can be used alone or in combination of two or more kinds. As the chemical foaming agent, azodicarbonamide, nitrogen at a decomposition temperature of 4.4'-oxybisbenzenesulfonylhydrazide or the like or higher,
A compound that generates a gas such as carbon dioxide can be used, and as the inert gas foaming agent, nitrogen, argon,
Hydrocarbon gas such as carbon dioxide gas, methane, propane or chlorofluorocarbon gas can be used. The blending amount of these foaming agents and the heating temperature are appropriately selected so that the foaming degree of the foamed insulating material is 70% or more.

In molding a foamed insulation, a reinforcing agent such as talc, 2.6-di-t-butyl-paracresol, and 2.2'-methylenebis-4-methyl-, in addition to the foaming agent, are used.
An antioxidant such as 6-t-butylphenol and an appropriate auxiliary agent such as a colorant can be added.

Next, some specific embodiments of the present invention,
Some comparative examples will be described together with the results, and in these examples and comparative examples, the swelling ratio, melt tension, maximum take-up speed during melting, foaming degree of foamed insulation and appearance and foamed insulation and conductor The adhesive force was measured by the following method.

(Swelling ratio) As described later, J
When measuring the melt index using the melt indexer specified in IS K6067, where the outer diameter of the extrudate is D ₀ and the outer diameter of the orifice is D _i , the swelling ratio is represented by the following equation. Swelling ratio (%) = 100 (D ₀ −D _i ) / D _i The temperature at the time of this measurement was 190 ° C., the orifice inner diameter was 2.095 mm, and the orifice length was 8 mm.

(Melt tension and maximum take-up speed during melting) A molten resin extruded at a constant speed from a nozzle of a melt indexer specified in JIS K6067 is drawn in a filament shape and guided to a roll through a load detector. The filament take-up speed is gradually increased and the take-up speed at the moment when the filament is cut is taken as the maximum take-up speed during melting. On the other hand, the melt tension is a value recorded in the load detector, and is an average value of the values from the start of filament taking up to the cutting. Under these measurement conditions, the resin temperature was 190 ° C., the piston descending speed was 10 mm / min, the orifice was tapered with an inner diameter of 1.0 mm and a length of 4 mm, and the measurement atmosphere temperature was 23 ° C.

(Expansion degree) The expansion degree is expressed by the following formula when measured by the specific gravity method. Foaming degree (%) = 100 (d ₀ −d) / d ₀ where d ₀ is the density of the resin before foaming, and d is
The density of the foam is shown.

(Appearance) The foamed insulated wire obtained was cut into a length of 5 cm, and the average surface roughness of the foamed insulation was measured by a surface roughness measuring instrument. In this case, the surface roughness is 3.0μ
Those having a thickness of m or less were regarded as good, and those exceeding 3.0 μm were regarded as defective.

(Adhesion) 10 m of the obtained foam insulated wire
It was cut to a length of m, and the adhesion between the conductor and the foamed insulation was measured by a tensile tester. Adhesion of 100 g or more was rated as good and less than 100 g was rated as poor.

Table 1 shows an extruded material obtained by adding 1 part of azizocarbonamide as a foaming agent and 1 part of talc as a reinforcing agent to low-density polyethylene which is an insulating material by an extruder and having an outer diameter of 0.18 mm. When extruding upward, CFC gas was further injected as a foaming agent from the middle of the extruder so that the outer diameter was 0.7.
The results of the characteristics are shown in Examples 1 and 2 of the present invention and Comparative Examples 1 to 3 in which the melt index, the melt tension and the maximum take-up speed during melting were variously changed in the production of a 0 mm foam insulated wire.

[0021]

[Table 1]

As is clear from Table 1, Examples 1 and 2
The foaming degree, the extruded appearance and the adhesion were all good, but in Comparative Examples 1 to 3, the foamed degree was lower than the predetermined foaming degree of 70%, and in Comparative Example 1, the extruded appearance was And the adhesion was poor.

Further, Table 2 shows an extruded material obtained by adding 1 part of azozocarbonamide which is a foaming agent and 1 part of talc which is a reinforcing agent to polyolefin blends of various combinations which are insulating materials by using an extruder, When extruding onto a conductor of 0.18 mm, when a fluorocarbon gas is further injected as a foaming agent from the middle of the extruder to produce a foam insulated wire with an outer diameter of 0.70 mm, the melt index, melt tension, and the maximum during melting Examples 3 to 5 of the present invention and Comparative Examples 4 to 6 in which the take-up speed is variously changed are shown together with the results of their characteristics.

[0024]

[Table 2]

The individual characteristics of the materials A to D shown in Table 2 were as shown in Table 3 below.

[Table 3]

As is clear from Table 2, Examples 3 to 5
The foaming degree, the extrusion appearance, and the adhesion were all good, but in Comparative Examples 4 to 6, the foaming degree is lower than the predetermined foaming degree of 70%, and in Comparative Examples 4 and 5, The extrusion appearance and adhesion were both poor.

[0027]

According to the present invention, as described above, a thin and highly foamed insulated wire having an outer diameter of 1 mm or less and a foaming degree of 70% or more can be easily manufactured with a good appearance and a good adhesion. There are real benefits you can do.

[Brief description of drawings]

FIG. 1 is a perspective view showing a cut end of a coaxial multi-flat cable suitable for being manufactured using a foam insulated wire manufactured according to the present invention.

[Explanation of symbols]

 10 Coaxial Multi-Flat Cable 12 Conductor 14 Foam Insulator 16 Foam Insulated Wire 18 Drain Wire 20 Electromagnetic Shielding Layer 22 Sheath

Front page continuation (51) Int.Cl. ⁵ Identification code Office reference number FI Technical display location B29K 105: 04 4F 105: 20 4F B29L 9:00 4F 23:00 4F (72) Inventor Makoto Kato Chiba Prefecture 8-1 Goi Minamikaigan, Ichihara-shi Ube Industries Ltd. Chiba Petrochemical Factory

Claims (1)

[Claims] 1. When a foamed insulation having an outer diameter of 1.0 mm or less and a foaming degree of 70% or more is formed on a conductor by extrusion, the material of the foamed insulation has a swelling ratio of 65.
% Or more, the melt tension is 2 to 5 g, and the polyolefin having a maximum take-up speed during melting of 50 to 200 m / min is used.