JPH0361290B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing a foam insulated wire having uniform and high foaming characteristics.

[Prior art] Insulated wires used for internal wiring of electronic devices are
Recently, wires have become thinner and thinner, and because they are used for high-density packaging, they are required to have high heat resistance as well as insulation properties.

In addition to improving the above-mentioned characteristics, especially for insulated wires used in large computers, etc., in order to speed up signal transmission speed, the equivalent dielectric constant of the insulation material of the insulated wire is lowered, and the dielectric constant is made as close to 1 as possible. That is required.

Fluororesin compounds are currently used as coating materials for insulated wires, as they are the best in terms of properties such as heat resistance, insulation, mechanical strength, and workability.In order to reduce the dielectric constant, Continuous coating production is carried out while foaming in the extrusion coating process.

As an example, the degree of foaming of this insulated wire is required to be 60% or more of its covering volume, the outer diameter of the conductor is 0.56 mm, the thickness of the covering is 150 μm, and the size of the foamed particles is about 80 to 150 μm.

Therefore, it is most delicate that foamed particles of 80 to 150 microns are lined up in a line within the coating thickness of 150 microns.

[Problems to be Solved by the Invention] Incidentally, the insulated wire that comes out of the covering part (generally the crosshead) in the extrusion process needs to be cooled and formed, but in the case of ordinary wires, the insulated wire runs in a cooling water tank and is cooled. However, immediately after exiting the crosshead for extrusion coating, the foamed insulated wire is run in the atmosphere to be cooled and taken up by a take-off machine so as not to adversely affect the state of the foamed particles.

In this case, with the water cooling method, the shape of the foamed particles changes due to water entering between the foamed particles, the viscous resistance of the cooling water during running, etc., and rapid thermal contraction.
The drawback was that only an insufficient product could be produced due to the slight pressure in the water.

On the other hand, when cooling by running in the atmosphere, the work is done in an air-conditioned room, but even within the air-conditioned room there are local changes in temperature and humidity, so the product is more stable than water cooling methods. There was a drawback that it was not possible to manufacture sufficient products.

[Means for Solving the Problems] An object of the present invention is to eliminate the drawbacks of the prior art described above and to provide a method for manufacturing a foam insulated wire having a uniform and high degree of foaming.

That is, the gist of the present invention is to provide a method for manufacturing a foam insulated wire in which a highly foamed insulator is extruded and coated on the outer periphery of a conductor and then immediately cooled, and the cooling device includes a mirror-surfaced cylindrical air-cooled cooling tank. A method of manufacturing a foam insulated wire is characterized in that:

[Example] Next, an example of the manufacturing method of the present invention will be further described with reference to the accompanying drawings.

Reference numeral 1 denotes a foam insulated wire, which is coated with a foam insulator at the crosshead 7 of the extruder, passes through the cooling gas outlet 4 of the cooling tank, and passes through the cooling tank main body 2.
Furthermore, it travels as shown by the arrow to a take-up machine (not shown) via the cooling gas blow-off section 3.

Reference numeral 5 denotes a constant temperature and constant humidity cooling gas generator, in which cooling gas is sent to the cooling gas blowing section 3 through an introduction pipe 6.

The cooling gas blowing part 3 has uniform slits machined on the circumference in order to send the cooling gas as a uniform laminar flow to the inner cylinder of the cylindrical cooling tank 2, and the cooling gas flows from the entire circumference of the slit. It's getting old.

On the other hand, the cooling gas outlet section 4 is also machined with pores having the same diameter at an even pitch around the entire circumference so that the cooling gas can exit uniformly from the cooling tank 2.

Therefore, the cooling gas flows in a laminar flow, and uniform temperature and humidity distributions are obtained around the outer periphery of the insulated wire, resulting in a highly foamed insulated wire with a uniform foam structure.

The cooling tank body 2 is composed of a cylindrical inner tube and an outer tube, and the space between them is thermally insulated by a heat insulating material or vacuum, and the inner surface of the inner tube, through which the foam insulated wire 1 passes, is heated to make the temperature uniform. It has a mirror surface.

In other words, since the inner cylinder of the cooling tank body has a mirror surface, the reflection of heat is constant, and a uniform temperature and humidity distribution can be obtained around the outer circumference of the insulated wire, resulting in highly foamed insulation with a uniform foam structure. Electric wire is obtained.

A temperature detection sensor 8 and a humidity detection sensor 9 are attached to a part of the mirror surface, and the detected values are sent to the constant temperature constant humidity cooling gas generator 5 so as to keep the temperature and humidity inside the cylinder of the cooling tank 2 constant. We are providing feedback to

Here, the cooling gas introduced from the cylindrical cooling gas blowing part 3 flows through the slits around the entire circumference of the blowing part 3 in a uniform laminar flow in the direction opposite to the foam insulated wire, and a part of the cooling gas flows through the foam insulated wire. The laminar flow flows to the outside from the outlet of the blow-off section 3, but the gap between the inlet and outlet of the foam-insulated wire is very narrow so that most of it flows in the direction of the cooling gas outlet section 4 of the foam-insulated wire.

As the cooling gas, nitrogen gas, which is an inert gas, is preferable because the humidity can be easily controlled.

[Effects of the Invention] According to the manufacturing method of the present invention as described above, since the temperature and humidity of the cooling gas are constant, it is possible to provide a uniform highly foamed insulated wire.

Further, it is possible to manufacture uniform foam insulated wires even in an air-conditioned room that does not require an air-conditioned room or has very low precision.Furthermore, there is an advantage that the manufacturing work is easy because the cooling work conditions can be easily changed.

[Brief explanation of drawings]

The accompanying drawings are explanatory drawings showing one embodiment of the manufacturing method of the present invention. 1: Foam insulated wire, 2: Air-cooled cooling tank body, 3:
Cooling gas blowing section, 4: Cooling gas outlet section, 5: Constant temperature and constant humidity cooling gas generator, 6: Cooling gas introduction piping, 7: Extruder crosshead, 8: Temperature detection sensor, 9: Humidity detection sensor.

Claims (1)

[Claims] 1. A foam insulated wire manufacturing method in which a highly foamed insulator is extruded around the outer periphery of a conductor and immediately cooled, the cooling device being a mirror-surfaced cylindrical air-cooled cooling tank. manufacturing method.