JPS63184214A - Manufacture of foam insulated wire - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method for manufacturing a foam insulated wire in which a conductor is coated with a foam insulator by extrusion.

[Prior art]

In recent years, with the increasing capacity and integration of computers, there has been a demand for cables that can transmit signals at higher speeds and require smaller storage space.

Various foam insulated wires have been proposed as electric wires meeting this purpose, each of which is coated with a foamed insulator made of thermoplastic fluororesin by extrusion.

As shown in FIG. 2, for example, a foamed insulated wire 3 in which a conductor 1 is coated with an insulating material made of thermoplastic fluororesin by foaming a liquefied gas such as hydrocarbon or fluorocarbon as a foaming agent. There is. Here code 4
indicates bubbles.

By the way, when foam insulated wire 3 is manufactured by foaming thermoplastic fluororesin with liquefied gas, the resin pressure in the crosshead provided at the tip of the extrusion coating machine increases the pressure of the foam insulator 2, as shown in FIG. It was found that it has a close and large influence on the foaming rate.

This means that, unlike conventional insulating materials such as polyethylene, in the case of thermoplastic or fluororesin, the viscosity thereof is more easily influenced by the resin pressure in the crosshead and changes easily. As a result, as shown in FIG. 3, it is estimated that there is a large correlation between the resin pressure in the crosshead and the foaming rate.

Therefore, in extrusion coating, it is important to maintain the resin pressure in the crosshead at a predetermined value, but when using liquefied gas as a blowing agent, the resin pressure in the crosshead can be adjusted by changing the screw rotation speed of the extrusion coating machine. The conventional general method of controlling by controlling the temperature cannot be applied. The reason for this is that when liquefied gas is used as a blowing agent, the liquefied gas is injected from the middle of the screw barrel of the extrusion coating machine, so changing the screw rotation speed also changes the pressure at the liquefied gas injection part, resulting in liquefied gas. There is a problem that a constant foaming rate cannot be obtained in the longitudinal direction of the electric wire because the amount of gas injected changes.

[Purpose of the invention]

In view of the above-mentioned problems, an object of the present invention is to maintain the resin pressure in the crosshead at a predetermined value without changing the screw rotation speed, thereby producing a foamed insulated wire made of thermoplastic fluororesin that has a uniform expansion rate in the longitudinal direction. The object of the present invention is to provide a method for easily and stably obtaining the same.

[Structure of the invention]

In order to achieve the above object, the present invention provides a method for manufacturing a foam insulated wire in which a conductor is coated with a foamed insulation made by foaming a thermoplastic fluororesin using liquefied gas using a crosshead of an extrusion coating machine. The present invention is characterized in that the traveling speed of the foam insulated wire is changed in accordance with the amount of change in the resin pressure, thereby maintaining the resin pressure in the crosshead constant.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail below with reference to the drawings.

The present inventor has studied various ways to maintain the resin pressure in the crosshead 6 at a constant value without affecting the amount of liquefied gas injected into the screw barrel of the extrusion coating machine 5 as much as possible. As a result, we discovered the following method. That is, the present invention
As shown in Figure 1, on the running conductor l, for example, a tetrafluoroethylene-hexafluoropropylene copolymer resin, a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin, or a 47-fluoroethylene-ethylene copolymer resin. A foamed insulator 2 made by foaming a thermoplastic fluororesin such as, for example, using a liquefied gas (a gas that is liquefied at normal temperature and pressure or under normal temperature and pressure) such as hydrocarbon or fluorocarbon as a foaming agent,
When manufacturing the foamed insulated wire 3 by extrusion coating using the crosshead 6 of the extrusion coating machine 5, the running speed of the foamed insulated wire 30 is controlled in accordance with changes in the resin pressure in the crosshead 6. By changing the temperature of the head 6, the resin pressure inside the cross head 6 is maintained at a predetermined value.

That is, when the resin pressure in the crosshead 6 increases, the traveling speed of the foam insulated wire 3 is increased, and conversely, when the resin pressure decreases, the traveling speed is decreased.

By controlling the traveling speed of the foamed VA electric wire and maintaining the resin pressure in the crosshead 6 within a predetermined pressure range during manufacturing, the viscosity of the resin within the crosshead 6 can be maintained within a predetermined range. As a result, a foamed insulated wire 3 having a uniform foaming rate in the longitudinal direction of the wire can be manufactured.

〔Concrete example〕

Conductor: 7 strands of silver-mebuki copper wire with an outer diameter of 0.08 mm.

Absolute a Material n--Tetrafluoroethylene-perfluoroalkoxy copolymer foaming agent--Nucleating agent Boron nitride 0.5-
% Foaming agent Freon 22 (trade name of DuPont) Foamed insulated wire --- Outer diameter 1.0 mII + Foaming rate approx. 70% Extrusion coating wire speed --- 6 ± 2 m/win Resin pressure in crosshead under the above conditions By controlling the traveling speed of the foam insulated wire and maintaining it at 100±10 kg/cm, it was possible to obtain an extremely stable foam insulated wire with a longitudinal foaming rate of 70±5%.

〔Effect of the invention〕

As described above, according to the method for manufacturing a foam insulated wire of the present invention,
It is possible to easily obtain a stable foamed insulated wire by improving the foaming rate in the longitudinal direction.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of the manufacturing equipment of the foam insulated wire according to the present invention, Fig. 2 is a cross-sectional view of an example of the foam insulated wire, and Fig. 3 shows the relationship between the resin pressure in the crosshead and the foaming rate. This is a graph showing. - Thick conductor 2 ~ Foamed insulator 3 ~ Foamed insulated wire 6 ~ Crosshead Patent applicant Furukawa Electric Co., Ltd. Figure 1 Figure 2

Claims (3)

[Claims] (1) In a method of manufacturing a foamed insulated wire in which a foamed insulator made by foaming a thermoplastic fluororesin with liquefied gas is extruded and coated on a conductor using a crosshead of an extrusion coating machine, the amount of change in the resin pressure in the crosshead is A method for manufacturing a foam insulated wire, characterized in that the traveling speed of the foam insulated wire is changed accordingly to keep the resin pressure in the crosshead constant. (2) The method for manufacturing a foam insulated wire according to claim 1, wherein the liquefied gas is a hydrocarbon or a fluorocarbon. (3) The foamed insulator is made by foaming a tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin or a tetrafluoroethylene-hexafluoropropylene copolymer resin containing boron nitride as a nucleating agent. A method for manufacturing a foam insulated wire according to claim 1, characterized in that: