JPS63216218A - Manufacture of high foam resin 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 [Industrial Field of Application] The present invention relates to a method for producing a highly foamed plastic insulated wire having uniform foaming characteristics.

[Prior Art] Cables insulated with foamed plastic are already widely used in the field of communication cables.

Methods for manufacturing this type of cable include (1) a method in which a plastic premixed with a foaming agent such as azodicarbonamide is heated in an extruder to a temperature higher than the decomposition temperature of the foaming agent, and then extruded and coated on the conductor; (2) A common method is to inject a gas, such as monochlorotrichloromethane, which becomes a gas at room temperature and pressure into the plastic in an extruder, and then extrude and coat the plastic.

[Problems to be Solved by the Invention] However, in the conventional manufacturing method in which plastic is extruded and coated at the same time as foaming, the gas for foaming fills between the plastic and the conductor, creating a large gap. The adhesion between the plastic and the conductor is often lost. This tendency becomes more pronounced as the degree of foaming is increased, and has become a major problem especially when attempting to obtain a degree of foaming of 50% or more.

The present invention has been made in view of the above circumstances, and its purpose is to eliminate the drawbacks of the prior art described above and to provide a method for manufacturing a highly foamed plastic insulated wire having uniform foaming properties. be.

[Means for Solving the Problems] The gist of the present invention is to extrude and coat the outer periphery of a conductor with a plastic mixture mixed with a foaming agent in an unfoamed state at a temperature below the decomposition temperature of the foaming agent, and to apply ionizing radiation to the plastic mixture. The purpose is to foam the foaming agent by irradiating the wire to achieve appropriate crosslinking, and then extrusion coating the electric wire with a foaming agent-free plastic heated above the decomposition temperature of the foaming agent. here,
Low-density polyethylene is preferable as the plastic, and azodicarbonamide is preferable as the blowing agent.

[Function] Due to the pressure of the heated outer layer plastic (4), even if the inner layer plastic (insulator) foams to a high degree, it is prevented from rising on the conductor.

[Example] An embodiment of the present invention will be described with reference to the accompanying drawings.

Fig. 1 is an explanatory diagram schematically showing an example of a vertical extrusion line according to the present invention, Fig. 2 is a horizontal cross-sectional view of an insulated wire during extrusion, and Fig. 3 is a noodle-edge electric wire manufactured according to the present invention. FIG.

1 is a conductor made of copper with a diameter of 0.20 m+n, and 2 is an insulator extruded and coated on the outer periphery of the conductor 1 to a thickness of 0.15 mm. The insulator 2 has a melt index of 0,
25 low density polyethylene mixed with 2 to 4 phr azodicarbonamide blowing agent was used and was applied in the unfoamed state. After this, insulator 2 has 1 to 5 M
rad radiation was applied to obtain a gel fraction of 25-35%. Thereafter, in the vertical extrusion line shown in FIG. At the same time, as external wave 3, low density polyethylene with a melt index of 5.0 is
It is extruded and coated to a thickness of 5 to 0.10 au, and then passed through a cooling device 8 where it is cooled with water or the like, taken up by a capstan 9, and wound onto a bobbin (not shown) by a winding machine 10. Ta. At this time, the speed accuracy of capstan 9 is ±0
．． 05m or less, the preheating furnace is a homogeneous gas (e.g. air)
The temperature was controlled to be within ±0.5°C.

In this way, a highly foamed plastic insulated wire was obtained in which the degree of foaming of the insulator 2 was 70% or more, the surface was smooth, and the insulator 2 and the conductor 1 had good adhesion.

[Effects of the Invention] As explained above, according to the present invention, it is possible to provide a highly foamed plastic insulated electric wire in which the rising of the insulator on the conductor is prevented by the pressure of external waves, and therefore has uniform foaming characteristics with a clean appearance. is possible.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram schematically showing an example of a vertical extrusion line according to the present invention, FIG. 2 is a cross-sectional view of an insulated wire during extrusion, and FIG. 3 is a cross-sectional view of an insulated wire manufactured according to the present invention. It is a front view. 1: Conductor, 2: Insulator, 3: Sheath, 4: Delivery device, 5: Preheating furnace, 6: Extruder, 7: Crosshead, 8: Cooling tank, 9: Capstan, 10 : Winding machine. -Edge size separation aOg-

Claims (1)

[Claims] A plastic mixture mixed with a foaming agent is extruded and coated on the outer periphery of the conductor in an unfoamed state at a temperature below the decomposition temperature of the foaming agent, and this is irradiated with ionizing radiation to perform appropriate crosslinking, and then foamed onto the wire. 1. A method for producing a highly foamed plastic insulated wire, which comprises foaming the foaming agent by extrusion coating the foaming agent-free plastic heated above the decomposition temperature of the foaming agent.