JPH0195421A - Molding method for foamed fluorinated resin insulation coat - Google Patents

Abstract

PURPOSE:To improve adhesion with a conductor in thin low density foam by filling a gas or liquid foaming agent from the intermediate part of an extruder and applying an extrusion coat to the internal surface of the conductor having a preliminarily foamed thin film adhesion layer of fluorinated resin. CONSTITUTION:A conductor 1 is coated, for example, with the fine particle of tetrafluoroalkylvinyl ether copolymer (PFA) and heated, thereby melting and adhering PFA particles, and forming a thin film fusion layer. PFA is used as fluorinated resin allowing thermal fusion extrusion and 0.5wt part of boron nitride is blended with 100 wt. parts of PFA. This PFA is fed from the hopper of an extruder and Freon 115 (trade name) is filled thereto at the intermediate part of the extruder. After a foaming agent is uniformly dispersed in fused fluorinated resin, this resin is extruded to coat the external surface of the con ductor 1 having an adhesion layer, thereby forming a foamed insulation coat layer 2. As a result, good adhesion is available between the conductor 1 and the insulation coat layer 2, and excellent quality can be thereby ensured for a product having a thin low density foam insulation coat.

Description

DETAILED DESCRIPTION OF THE INVENTION 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.

[Conventional technology]

With the development of electronic devices such as computers and their peripherals, there is a strong demand for higher performance and higher reliability for the signal transmission wires and cables used in these devices. .

Among them, the insulation coating is particularly thin, and the signal transmission speed is fast (
There are strong requirements for such things as being noise-free, crosstalk-free, and flame-retardant.

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. .

[Problem that the invention seeks to solve]

However, in recent years, it has been desired to further increase the foaming degree to improve performance, and although the higher the foaming degree is, the more desirable the foaming degree is. The problem was that the conductor and the insulating coating layer separated, resulting in unsatisfactory adhesion.

Conventionally, with respect to extruded foamed fluororesin, it has been difficult to achieve high foaming, so no proposals have been made regarding the accompanying improvement in conductor adhesion.

Therefore, conventionally it has not been a problem to bring a thin, highly foamed fluororesin into close contact with a conductor.

The present invention was made in order to solve the steam problem, and aims to provide a method for forming a highly foamed fluororesin insulation coating that can improve adhesion to a conductor in thin-walled and highly foamed products. be.

[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 highly foamed fluororesin insulation coating by extrusion coating the outer periphery of the conductor after being dispersed, the gas or liquid foaming agent is injected midway through the extruder, and a thin fused layer of fluororesin is formed on the conductor in advance. This is achieved by a method for forming a foamed fluororesin insulation coating, which is characterized by extrusion coating on the outer periphery of the foamed fluororesin insulation coating.

In the present invention, examples of fluororesins that can be extruded by hot melting include tetrafluoroethylene-hexafluoropropylene copolymer and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (hereinafter referred to as rPFAJ).
, tetrafluoroethylene-perfluoropropylene copolymer (hereinafter referred to as rFEPJ), ethylene-tetrafluoroethylene copolymer 5, ethylene-chlorotrifluoroethylene copolymer, and vinylidene fluoride polymer. As the fluororesin used for the thin film adhesive layer, any of the above-mentioned fluororesins that can be extruded by hot melting can be used.

The blowing agent used in the present invention is normally gaseous or liquid, and includes inert gases such as nitrogen, helium, neon, and argon, hydrocarbons such as propane, butanehexane, and pentane, and dichlorodifluoromethane and dichloromonofluoromethane. Examples include halogenated fluorinated hydrocarbons such as methane, monochlorodifluoromethane, trichloromonofluoromethane, and trichlorotrifluoroethane.

In the present invention, it is also possible to use a foaming nucleating agent to facilitate adjustment of the bubble diameter and formation of uniform bubbles, and boron nitride is a typical example of this agent.

In the present invention, a method is adopted in which the foaming agent is injected into the melted fluororesin midway through the extruder, thereby making it possible to achieve high foaming.

As a method of forming a thin film adhesive layer of fluororesin on the conductor in advance, a method of embedding the fluororesin in a Cr plating layer is used.

Since the i-film adhesive layer of the present invention does not contain a foaming agent, it plays the role of adhesion to the conductor and the foam layer.

〔Example〕

One embodiment of the method for forming a highly foamed fluororesin insulation coating of the present invention will be described.

Fine particles of fluororesin PFA or FEP were coated on the conductor, and then heated for 5 minutes at a temperature 100° C. higher than the melting point to melt and adhere the fine particles of PFA or FEP. This operation was repeated twice to form a thin fusion layer having a thickness of 0.02 mm.

Next, PFA (manufacturer: Daikin Industries ■, product name: NEOFLON PFA,
AP-210), 0.5 parts by weight of boron nitride is mixed with 100 parts by weight of PFA, this is fed from the hopper of the extruder, and Freon 1) 5 (DuPont product name) is added to the middle part of the extruder. is injected with a pressure of 7 to 8 kg/c+dG to uniformly disperse the foaming agent in the molten fluororesin, and then extrusion coating the outer periphery of the conductor with an outer diameter of 0.2 φ provided with the fusion layer, A foam insulation coating with a thickness of 9.3 mm was formed.

In addition, the extrusion conditions are L/D-25 using a 20-cm extruder.
, compression ratio = 2.5, groove depth of supply section = 2.5fl, groove depth of measuring section -1, Qmm, screw rotation speed 4rpI1
), the set temperature of each part of the cylinder = 400°C, the set crosshead temperature = 370°C, and the set temperature of the die = 320°C.

The foamed electric wire thus produced was evaluated for foaming degree and conductor adhesion. Regarding the degree of foaming, the specific gravity of the foam was measured, and then the volume fraction of the bubbles was expressed as a percentage using the following formula.

Here, P: Specific gravity of the foam Po: Specific gravity of the non-foamed material Regarding the foaming degree, as shown in Table 1, the same excellent foaming degree was obtained in all formulations, but Table 1 shows that the same excellent foaming degree was obtained. As for the PF, as shown in Figure 1, we evaluated the cross section of the electric wire by observing it with a microscope.
A. In the case where FEP was used as the fusion layer, the conductor layer l and the insulating liquid riN2 were in close contact with each other and exhibited excellent insulation performance, but the case without the fusion layer is shown in Figure 2. As such, a space 3 was formed between the conductor 1 and the insulating liquid 1iii2 and the conductor was separated, resulting in a rejected product.

〔Effect of the invention〕

The present invention introduces a hot-melt extrudable fluororesin and a gas or liquid foaming agent into an extruder, disperses the foaming agent uniformly in the molten fluororesin, and then extrudes and coats the outer periphery of the conductor to insulate the conductor with highly foamed fluororesin. In the method of forming the coating, the gas or liquid foaming agent is injected into the middle of an extruder, and the foamed fluororesin insulation is extruded and coated on the outer periphery of a conductor on which a thin film fusion layer of fluororesin has been previously formed. The coating formation method improves the adhesion between the conductor and the insulation coating layer, making it possible to ensure excellent quality of the thin, highly foamed insulation coating product.

[Brief explanation of the drawing]

Fig. 1 shows a cross-sectional view of an electric wire cable manufactured according to the present invention, and Fig. 2 shows a cross-sectional view of a comparative example. 1...Conductor 2...Insulating coating layer 3...Space% 1 Figure

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, extrude and coat the outer periphery of the conductor with highly foamed fluororesin. A method for forming an insulating coating, characterized in that the gas or liquid foaming agent is injected into the middle of an extruder, and extrusion coating is carried out on the outer periphery of a conductor on which a thin film fusion layer of fluororesin has been formed in advance. Method of forming insulation coating.