JPH0448509A - Foaming plastic insulated wire - Google Patents

Abstract

PURPOSE:To suppress a volume increase of an inside part of a foaming amorphous fluororesin layer being extruded to outside the periphery of a conductor core wire at a high temperature near a prescribed degree to be coated and cooled to a room temperature to become a solid state, and to generate no gap between the conductor core wire and itself by using a foaming substance of amorphous fluororesin having viscosity at a temperature 300 deg.C within the range of a specific value Pa.s in order to cover the periphery of a core wire. CONSTITUTION:In order to realize a foamed plastic insulated wire generating no gap between a foamed plastic insulated layer having a high foaming degree accordingly, being excellent in a mechanical and electric characteristic even in the case of an extremely thin outer diameter, the periphery of a conductor core wire is covered with a foamed body of amorphous fluororesin having viscosity in the range of 10<3> to 10<5>Pa.s(Pascal sec) at a temperature 300 deg.C. Fluororesin expressed by the following formula is desirable as the amorphous resin having viscosity 10<3> to 10<5>Pa.s(Pascal sec).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a foamed plastic insulated wire, particularly a foamed fluororesin insulated wire suitable for high-speed signal transmission.

[Conventional technology]

Signal transmission wires and cables used in electronic devices such as computers are required to have thin insulation coatings and to be able to transmit signals at high speed. In response to this request,
2. Description of the Related Art Insulated wires are known in which the outer periphery of a conductor is coated with a highly foamed insulator made by foaming a low dielectric constant plastic such as polyethylene, polypropylene, polystyrene, or fluororesin to a degree of foaming exceeding 70%. According to this highly foamed insulated wire, the dielectric constant of the insulator can be approximated to that of air, so not only high-speed signal transmission can be expected, but also signal transmission loss can be reduced.

[Problem to be solved by the invention]

However, in the above-mentioned plastic foam insulator-covered electric wire with a foaming degree exceeding 70%, when the outer diameter is small, especially when the outer diameter is 1.
In the case of an extremely small diameter smaller than OB, the inner diameter of the foamed insulating layer becomes larger than the outer diameter of the conductor, creating a phenomenon in which a void is created between the two. This phenomenon becomes more remarkable as the degree of foaming of the insulating layer increases. When a gap occurs between the conductor core wire and the insulating layer, not only the mechanical properties of the wire deteriorate, but also the capacitance changes, which adversely affects electrical properties such as propagation delay time and impedance.

Therefore, the object of the present invention is to
An object of the present invention is to realize a foamed plastic insulated wire that does not create a gap between a foamed plastic insulating layer having a high degree of foaming and a conductor core wire, and therefore has excellent mechanical and electrical properties.

[Means to solve the problem]

In the present invention, even when the outer diameter is extremely small, no void is created between the highly foamed plastic insulating layer and the conductor core wire, and therefore a foamed plastic insulated wire with excellent mechanical and electrical properties is realized. Therefore, the outer periphery of the conductor core wire was coated with an amorphous fluororesin foam having a viscosity in the range of 10'' to 10'Pa-5 (Pascal seconds) at a temperature of 300°C.

The viscosity defined in the present invention is at a shear rate of 100 sec.
-' and can be measured, for example, by flow tests adjusted in this way. Note that the shear rate (sec-
) is calculated by the following formula (1).

For example, a flow tester die has a radius of 0.2511.
A land length of 1.0 am is used.

The viscosity of the amorphous fluororesin must be 103 Pa-s or more in order to prevent the formation of voids between the foamed insulating layer and the conductor core, but if it exceeds 10'Pa-5, extrusion coating becomes difficult.

The viscosity at a temperature of 300°C is 10' to 10'Pa-5 (
A preferable amorphous fluororesin having a temperature in the range of (Pascal seconds) is a fluororesin represented by the following general formula (2).

(In the formula, m and n are positive integers.) In general formula (2), m/n is 80/20 to 10/90 (the numbers mean mol% and do not mean the absolute values of m and n)
It is more preferable if the glass transition point is in the range of 80 to 300°C. Instead of just one type of amorphous fluororesin, two or more types of resins with different viscosities may be used. A foaming agent is added to the amorphous fluororesin that forms the foamed plastic insulation layer before it is coated on the conductor core wire. Blowing agents include inert gases such as nitrogen, helium, neon, argon, and carbon dioxide, hydrocarbons such as methane, propane, butane, pentane, and hexane, fluorotrichloromethane, difluorodichloromethane, trifluorochloromethane, tetrafluoromethane, It is selected from low molecular weight fluorocarbons such as difluorochloromethane, trifluoromethane, trifluorotrichloroethane, and tetrafluorodichloroethane. Two or more types of blowing agents may be used. The blowing agent is uniformly kneaded into the amorphous fluororesin, or in the case of a gaseous blowing agent, it is blown into the resin using a pipe or the like. If necessary, inorganic fine powder such as boron nitride, silicon dioxide, titanium dioxide, alumina, zirconium oxide, etc. is added as a foaming nucleating agent to adjust and make the cell diameter uniform.

In the case of extrusion coating, foaming of the blowing agent in the fluororesin is mainly performed by pressure changes when the resin containing the blowing agent is press-fitted from an extruder into a crosshead or the like and extruded from a die to the outside. When the extruded molten resin is cooled and solidified, a foamed fluororesin insulation layer is formed.

A non-foamed reinforcing layer of fluororesin, vinyl chloride resin, or the like may be further provided on the outer periphery of the expanded fluororesin insulation layer.

The present invention can be applied to various conductor core wires.

That is, it can be applied to any commonly used metal conductor such as copper, aluminum, and alloys thereof. The outer periphery of the conductor core wire may be made of a different material than the inside (for example, silver-plated copper wire).

[Effect]

In the present invention, the temperature of 30
By using an amorphous fluororesin foam with a viscosity in the range of 10' to 10' Pa-s (Pascal seconds) at 0°C, it is extruded and coated on the outer periphery of the conductor core wire at a high temperature of around 300°C, and then cooled to room temperature. The increase in volume of the inner portion of the foamed amorphous fluororesin layer, which becomes a solid state after being heated, is suppressed, and no voids are generated between the foamed amorphous fluororesin layer and the conductor core wire.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

[Example 1] An example of a foamed plastic insulated wire according to the present invention includes a conductor having a silver-plated copper wire with an outer diameter of 0.254 mm, and a foamed plastic insulation layer having a temperature of 300 inches and a C1 shear rate of 100 seconds.
An amorphous fluororesin (TEFLON AF-manufactured by DuPont) whose viscosity at
1600) is foamed with Freon 22 (difluorochloromethane) using 0.5% by weight of boron nitride as a nucleating agent, and has a foaming degree of 85.5% and a thickness of about 0.25 am. The outer diameter is 0.75 mm.

This insulated wire is manufactured as follows.

Amorphous fluororesin containing 0.5% by weight of boron nitride was supplied from the hopper of the extruder and melted in a cylinder set at a temperature of 300°C, and Freon 22 was installed in the center of the cylinder using a plunger pump. The gas is continuously injected from the gas inlet at a pressure of 5 to 6 kg and 7 cm2G to uniformly disperse it in the molten resin, and then introduced to a crosshead at a set temperature of 220°C.

Pass the silver-plated copper wire through the hole in the nipple and into the hole in the die.
It is coated with amorphous fluororesin that is extruded from between the nipple and the die while being taken off at a predetermined speed. The fluororesin containing a foaming agent is foamed during extrusion to form a foamed insulating layer.

Details of the extrusion conditions are as follows. Using an extruder with a screw diameter of 20M, the L/D of the extruder is 25, the compression ratio is 2.5, the depth of the groove in the feeding section is 2.50,
The depth of the groove in the measuring section is 1.0 mm, the rotation speed of the screw is 4 rp.
m, the die inner diameter is 0.4M, and the die set temperature is 160°C (the cylinder set temperature and crosshand set temperature are as above).

When the adhesion between the conductor and the foamed insulating layer was evaluated by a wire pulling test, good results were shown ranging from 400 g weight/170 mm to 800 g weight/170 nun. In addition, the propagation delay time was measured using the TD method by attaching an electrode to the outside of the foam insulating layer, and the result was T d ~3.6 ns 7 m
Met.

Furthermore, using another extruder, a vinyl chloride resin jacket was extruded and coated around the outer periphery of the foamed insulating layer, and then the variation in the propagation delay time in the length direction was examined. the result,
Out of 200 samples, 95% were within the range of ±25 ps/m. This indicates that the degree of foaming and the adhesion between the conductor and the insulating layer are uniform in the length direction.

[Example 2] A second example of the foamed plastic insulated wire according to the present invention is as follows:
The conductor is a silver-plated copper wire with an outer diameter of 0.254 mrrr, and the foamed plastic insulation layer is heated at a temperature of 300°C and a shear rate of 100.
The viscosity at sec-' is 6 X 10' Pa-s,
- Amorphous fluororesin (TEFLON manufactured by DuPont), represented by the formula [1], where m is 15 and n is 85.
AI'-2400) with 0.5 boron nitride as a nucleating agent.
Added weight% and foamed with Freon 22, foaming degree 82.3
%, a thickness of about 0.25111 ffl, and an outer diameter of 0.75 mm.

To manufacture this insulated wire, the cylinder set temperature must be set at 35
The procedure was the same as in Example 1 except that the temperature was 0°C, the crosshead temperature was 300'C, and the die temperature was 240°C.

The results of the pull-out test were the same as in Example 1.

As a result of measuring the propagation delay time, Td is 3.65ns/m
Met. The variation in propagation delay time was the same as in Example 1.

[Comparative Example] For comparison, the conductor was a silver-plated copper wire with an outer diameter of 0.254 mm, and the foamed plastic insulation layer had a viscosity of 2 x 103 Pa·S at a temperature of 340°C and a shear rate of 100 sec-'.
0.5% by weight of boron nitride was added as a nucleating agent to the tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer and foamed with Freon 114 (tetrafluorodichloroethane), with a foaming degree of 80% and a thickness of about 0.24 am.
A pullout test and propagation delay time were evaluated for a foamed fluororesin insulated wire with an outer diameter of 0.74 11 m, which is a foamed fluororesin layer. To manufacture this insulated wire, the cylinder temperature should be set at 400℃, the crosshead temperature should be set at 370℃,
The same procedure as in Example 1 was carried out except that the die setting temperature was 280°C.

When the inner diameter of the foamed fluororesin insulation layer was measured, it was found to be 0.50.
mm, which is significantly larger than the outer diameter of the conductor, which is 0.254 mm, and there is a gap of approximately 0.12 M around the conductor (assuming that it is located coaxially), and there is a gap between the conductor and the foam insulation layer. were not in close contact at all. Further, an electrode was attached to the outside of the foamed insulating layer, and the propagation delay time was measured by the TD method, and as a result, T d = 3.75 ns/m.

〔Effect of the invention〕

According to the present invention, even when the outer diameter of the foamed plastic insulated wire is extremely small, no void is created between the highly foamed plastic insulation layer and the conductor core wire, resulting in excellent mechanical and electrical properties. An ultra-thin diameter foamed plastic insulated wire is provided.

Claims (2)

[Claims] (1) Foamed plastic insulation characterized by extrusion covering the outer periphery of the conductor core wire with an amorphous fluororesin foam having a viscosity in the range of 10^3 to 10^5 Pa·s (Pascal seconds) at a temperature of 300°C. Electrical wire. (2) Claim 1, wherein the amorphous fluororesin is represented by a mathematical formula, a chemical formula, a table, etc. (in the formula, m and n are positive integers), and the foam has a foaming degree of more than 70%. Foamed plastic insulated wire.