JPH0193012A - Manufacture of foam fluorine resin insulating coverage - Google Patents

Abstract

PURPOSE:To form a thin and highly foamed insulating coverage by using two sorts or more of fluorocarbons with different vapor pressures as a foaming agent, and injecting such a foaming agent on the way of an extruding machine. CONSTITUTION:As a foaming agent, two or more fluorocarbons with different vapor pressures are used, and such a foaming agent is injected in a fused fluorine resin on the way of an extruding machine. As the fluorocarbons used as the foaming agent, dichlorodifluoromethane, dichloromonofluoromethane, monochlorodifluoromethane, trichloromonofluoromethane, monochloropentafluoroethane, trichlorotrifluoroethane, and the like are used.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to a method for forming a foamed fluororesin insulation coating that can be applied to insulated wires, coaxial cables, and the like.

[Prior Art] With the development of electronic devices such as computers and their peripheral devices, there is a strong demand for higher performance and higher reliability for the signal transmission wires and cables used in the devices. It is becoming. Among these, there are particularly strong requirements for thin insulation coatings, high signal transmission speeds, no crosstalk noise, and flame retardance.

To satisfy these requirements, fluororesin is suitable because it is inherently flame retardant and has good electrical properties, and foaming this resin leads to improvements in electrical properties such as dielectric constant. .

Conventionally, various methods for forming a foamed fluororesin insulation coating have been proposed, for example, Japanese Patent Application Laid-Open No. 59-1134.
No. 0 discloses a method of impregnating a fluororesin with Freon gas as a foaming agent, and the use of a specific boron nitride as a foaming aid.

[Problems to be Solved by the Invention] However, in the method of impregnating a fluororesin with a blowing agent as disclosed in JP-A-59-11340, the degree of foaming is 60.
It is difficult to obtain a highly foamed material exceeding %.

Furthermore, in the method of foaming fluororesin, various factors influence each other, and it is difficult to obtain an excellent foam simply by selecting the foaming agent and foaming aid.

Particularly, when obtaining an insulation coating of 1M or less and a foaming degree of 60% or more, it is necessary that a large number of microbubbles be uniformly distributed, but this cannot be achieved using conventional techniques.

The present invention has been made to solve the above problems, and aims to provide a method for forming a fluororesin foam insulation coating that can realize a thin, highly foamed insulation coating by uniformly distributing a large number of microbubbles. This is the purpose.

[Means and effects for solving the problems] The above object of the present invention is to introduce a hot melt extrudable fluororesin and a gas or liquid blowing agent into an extruder, and uniformly distribute the blowing agent into the molten fluororesin. In the method of forming a foamed fluorocarbon resin insulation coating by extrusion coating on the outer periphery of the conductor after being dispersed, two or more types of fluorocarbons with different vapor pressures are used as the foaming agent, and these are injected midway through the extruder. This is achieved by a method for forming a foamed fluororesin insulation coating characterized by the following.

In the present invention, examples of fluororesins that can be hot melt extruded include tetrafluoroethylene-hexafluoropropylene copolymer and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (hereinafter referred to as IPFAJ).
, tetrafluoroethylene-perfluoropropylene copolymer (hereinafter referred to as rFEPJ), ethylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, vinylidene fluoride polymer, and the like.

- Fluorocarbons used as blowing agents in the present invention include dichlorodifluoromethane, dichloromonofluoromethane, monochlorodifluoro[comethane, trichloromonofluoromethane, monochloropentafluoroethane, trichlorotrifluoroethane, etc.].

In the present invention, a method is adopted in which the foaming agent is injected into the molten fluororesin during extrusion '/a, thereby making it possible to achieve high foaming.

In addition, two or more different types of fluorocarbons have different vapor pressures and their vapor components are different, so they form different bubbles, so even if the injection pressure is low, the bubbles will have a small diameter. It is thought that the degree of foaming increases.

In the present invention, it is also possible to use a foaming adhesive in order to facilitate the adjustment of the cell diameter and the formation of uniform cells, and boron nitride is a typical example thereof.

[Example] An example of the method for forming a foamed fluororesin insulation coating of the present invention will be described.

PFA (manufacturer: Daikin Industries, product name: NEOFLON PF△, AP-2) is used as a hot melt extrudable fluororesin.
10) was used. 0.5 parts by weight of boron nitride was blended with 100 parts by weight of this boria, and this was supplied from the hopper of the extruder. In Example 1, two types of blowing agents, chlorodifluoromethane and monoclopentafluoroethane, were used. ,
The weight ratio was 1:1. Further, as Example 2, two types of chlorodifluoromethane and dichlorodifluoromethane were used, and the weight ratio was set to 3:1. In both cases, the blowing agent was injected at a pressure of 5 kg/ciG in the middle of the extruder, and after uniformly dispersing the blowing agent in the molten fluororesin, the outer diameter was 0.2 s.
The outer periphery of the ψ conductor was extruded and coated to form a foam insulation coating with a thickness of 0.3 m.

The extrusion conditions were as follows: using a 20s extruder, L/D=25,
Compression ratio = 2.5, depth of supply section = 2.5s, total M
groove depth = 1.0m, screw rotation speed = 4rom,
The set temperature of each part of the cylinder was -400°C, the crosshead set temperature was 370°C, and the die set temperature was 320°C.

Also, as Comparative Example-1, chlorodifluoromethane, Comparative Example-
Monochloropentafluoroethane as 2, Comparative Example-3
The blowing agent was 5 K'j/ci in the extrusion mode.
It was injected at a pressure of G to form a foam insulation coating.

The foamed electric wire thus produced was evaluated for its foaming degree and foaming state.

The degree of foaming was determined as follows. First, the specific gravity of the foam was measured, and then the volume fraction of the air bubbles was expressed as a percentage using the following formula.

(Degree of foaming) = (1--) X 100 [%] where 9: specific gravity of foamed body 90: specific gravity of non-foamed body The foamed state was evaluated by observing the cross section of the electric wire cut into rings using a microscope.

The results are shown in Table 1.

As is clear from Table 1, in Examples 1 and 2 in which two types of blowing agents were used as a mixture, highly foamed products with a degree of foaming of 60% or more were obtained, and the foamed state was also fine and uniform, which was good. .

On the other hand, in Comparative Example 1°2.3 in which one type of foaming agent was used, the degree of foaming was low and the cell diameter was large.

[Effect of the invention]

Claims (1)

[Claims] (1) Introduce a hot-melt extrudable fluororesin and a gas or liquid foaming agent into an extruder, and after uniformly dispersing the foaming agent in the molten fluororesin, extrusion coat the outer periphery of the conductor to insulate the foamed fluororesin. In the method of forming a coating, as a blowing agent,
A method for forming a foamed fluororesin insulation coating, which comprises using two or more types of fluorocarbons having different vapor pressures and injecting them into an extruder.