JPH05144325A - Foaming plastic insulated wire - Google Patents

Abstract

PURPOSE:To provide a foaming plastic insulated wire such that the uniformity of the mechanical and electrical characteristics in its longitudinal direction is excellent when its outer diameter is small or when the degree of foaming in its foaming plastic insulating layer is enhanced. CONSTITUTION:The outer periphery of a conductor core wire 1 is coated with the mixture 2 of an amorphous fluorocarbon resin having a glass-transition temperature of 80 to 300 deg.C and a copolymer made from a tetrafluoroethylene and a perfluoroalkylvinyl ethel or a hexafluoropropylene (i.e., PFA or FEP), and subsequently a foaming insulating layer 3 made of the PFA or the FEP is provided outside it.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foamed plastic insulated wire, and more particularly to a foamed fluororesin insulated wire suitable for high-speed signal transmission.

[0002]

2. Description of the Related Art Signal transmission wires and cables used in electronic equipment such as computers are required to have a thin insulating coating, capable of high-speed signal transmission, and flame-retardant. In order to meet this requirement, a low dielectric constant fluororesin such as tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) or tetrafluoroethylene-hexafluoropropylene copolymer (FEP) is foamed in an amount of more than 70%. An insulated wire in which the outer circumference of the conductor is covered with a highly foamed insulator that is foamed at a certain degree is useful. According to this high-foam insulated wire, the dielectric constant of the insulator can be approximated to that of air, so that not only high-speed signal transmission can be expected, but also signal transmission loss can be reduced.

In such a high-foam plastic insulated wire, especially in the case of an extra fine wire having an outer diameter of 1 mm or less, there is a phenomenon that a void is generated between the conductor core wire and the insulating layer as described later. In order to prevent this, a method of coating the surface of the conductor core wire with a plastic layer having a melting point lower than that of the foamed insulator and further coating the outer surface with the foamed insulation layer is proposed in Japanese Patent Publication No. 55-6969. ..

[0004]

However, the electric wire having the low dielectric constant foam insulation coating having a foaming degree of more than 70% is capable of high-speed signal transmission, but especially when the outer diameter is small, the outer diameter is particularly low. In the case of an ultra-fine diameter electric wire of 1.0 mm or less, the phenomenon that the inner diameter of the covered foam insulation layer becomes larger than the outer diameter of the conductor and a void is generated between them is observed. This phenomenon becomes more remarkable as the foaming degree of the insulating layer is increased. When a gap is formed between the conductor core wire and the insulating layer, not only the mechanical characteristics of the electric wire deteriorate, but also the capacitance changes, which adversely affects the electric characteristics such as propagation delay time and impedance.

Further, the surface of the conductor core wire described in JP-B-55-6969 is covered with a plastic layer (hereinafter referred to as an inner layer) having a melting point lower than that of the foam insulating layer, and further covered with the foam insulating layer. In the case of an ultra-fine wire with an outer diameter of 1 mm or less, the inner layer is considerably thin, that is, usually 60 μm.
The thickness is required to be m or less, but it is practically difficult to uniformly form such a thin inner layer on the outer circumference of the conductor. Especially when using a fluorine resin having a high melting point,
It is extremely difficult to form a uniform layer.

Furthermore, when the conductor core wire is coated with the inner layer as described above and then the foamed plastic is further extrusion-coated, the inner layer comes into contact with the nipple during the process to peel off in some places, and the conductor and foam are formed in this portion. The adhesion defect of the insulating layer occurs. As the degree of foaming increases, the foamed insulating layer is more likely to have large voids inside thereof, so that the influence of nonuniformity and defects in the inner layer increases.

The object of the present invention is to provide excellent uniformity of mechanical and electrical properties in the longitudinal direction even when the outer diameter is extremely small and when the foaming degree of the foamed plastic insulating layer is increased. , To realize foamed plastic insulated wire.

[0008]

According to the present invention, even when the outer diameter is extremely small and the foaming degree of the foamed plastic insulating layer is increased, the mechanical and electrical characteristics are uniform in the longitudinal direction. Amorphous fluorine resin having a glass transition point of 80 to 300 ° C and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) for realizing a foamed plastic insulated wire with excellent properties
And a mixture (blend polymer) of at least one of tetrafluoroethylene-hexafluoropropylene copolymer (FEP) to cover the outer periphery of the conductor core wire, and to provide a foamed fluororesin insulating layer on the outside thereof.

As the amorphous fluororesin having a glass transition point of 80 to 300 ° C., a fluororesin represented by the following general formula [1] is preferable. (Where m and n are positive integers)

The glass transition point (Tg) of the amorphous fluororesin represented by the general formula [1] depends on the ratio of m and n.
The smaller / n is, the higher it is. m / n is 80/20 to 10 /
When it is in the range of 90 (the number means mol% of m and n, not the absolute value), the resin of the general formula [1] has a glass transition point in the range of 80 to 300 ° C. Those having a glass transition point in the range of 150 to 250 ° C. are preferable in terms of heat resistance and adhesion to a conductor. The amorphous fluorine resin is not limited to one type, and two or more types of resins having different glass transition points may be used.

PFA or FEP in blend polymer
The content of (or both) is preferably 60 to 90% by weight.

Tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) or tetrafluoroethylene-hexafluoropropylene copolymer (FEP) is used as the fluorine resin constituting the foamed plastic insulating layer. You may use both together. PFA and FEP have a small dielectric constant and are excellent in electrical characteristics.

A foaming agent is added to the fluororesin forming the outer layer of the insulator before coating the conductor. Blowing agents include nitrogen, helium, neon, argon, inert gases such as carbon dioxide, hydrocarbons such as methane, propane, butane, pentane, fluorotrichloromethane, difluorodichloromethane, trifluorochloromethane, tetrafluoromethane, difluorochloro. It is selected from low molecular weight fluorocarbons such as methane, trifluoromethane, trifluorotrichloroethane, and tetrafluorodichloroethane. You may use 2 or more types of foaming agents. The blowing agent is uniformly kneaded with the fluororesin, or in the case of a gaseous blowing agent, it is blown into the resin using a pipe or the like. Inorganic fine powder such as boron nitride, silicon dioxide, titanium dioxide, alumina, zirconium oxide, etc. is added as a foam nucleating agent, if necessary, in order to adjust and make uniform the bubble diameter. A known method can be used for foaming with these foaming agents.

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

When the foamed plastic insulated wire of the present invention is manufactured, the outer circumference of the conductor core wire is covered with a fluororesin mixture and the outside thereof is covered with a fluororesin containing a foaming agent. The method used can be used. However, in order to prevent damage to the inner layer when the outer circumference of the layer containing the amorphous fluororesin (hereinafter referred to as the inner layer) is covered with the foamed fluororesin layer, the amorphous fluororesin and the foamed fluororesin are respectively provided in one crosshead. A method is preferred in which the conductor core wires passing through the nipples and the center hole of the die are simultaneously extruded by extruding from between the nipples provided in double and between the nipple and the die.

Foaming of the foaming agent in the fluororesin is mainly performed when the fluororesin layer containing the foaming agent is extrusion-coated and when the resin pressed into the crosshead from the extruder is extruded from the die of the crosshead to the outside. It is performed by the pressure change of. When the extruded molten resin is cooled and solidified, a foamed fluororesin insulating layer is formed.

The inner layer made of amorphous fluororesin which is in contact with the surface of the conductor core does not need to be foamed, but when the inner layer and the foamed fluororesin layer are simultaneously extruded and covered, the foaming agent or the like diffuses from the foamed fluororesin layer to the inner layer. Therefore, it slightly foams even if no foaming agent is added. The inner layer may be foamed by adding a foaming agent or a nucleating agent as long as the effect of the present invention is not impaired.

The present invention can be applied to various conductor core wires. That is, it can be applied to various commonly used metal conductors such as copper, aluminum and alloys thereof. The conductor may have a coating layer such as a plating layer of a different conductor material on the outer periphery (for example, a silver-plated copper wire).

[0019]

The foamed plastic insulated wire of the present invention comprises an amorphous fluororesin having a glass transition point of 80 to 300 ° C., PFA and FEP between the conductor and the foamed fluororesin layer.
And a layer of a mixture with at least one of them, the intermediate layer adheres well to the conductor and the foamed fluororesin layer, and even if the thickness is extremely thin (for example, 60 μm or less), it is formed uniformly , Uniform adhesion in the length direction is obtained, and thereby uniform mechanical and electrical characteristics are obtained in the length direction.

[0020]

The present invention will be described in more detail with reference to the following examples. Example 1 An example of a foamed plastic insulated wire according to the present invention is shown in FIG. The insulated wire includes a conductor core wire 1, an in-insulator layer 2, and an insulator outer layer 3. Conductor 1 has an outer diameter of 0.
The 254 mm silver-plated copper wire and the in-insulator layer 2 are made of amorphous fluorine resin (TEFLON AF-16 manufactured by DuPont).
00) and FEP (copolymer of tetrafluoroethylene-hexafluoropropylene) at a weight ratio of 1: 5, the layer having a thickness of 30 μm, and the outer insulator layer 3 are PFA (copolymer of tetrafluoroethylene-perfluoroalkyl vinyl ether). A foamed fluororesin layer having a thickness of about 0.22 mm, which is composed of a copolymer having a polymerization ratio of 95: 5). The amorphous fluororesin has a m of 35 and an n of 65 in the general formula [1].
The glass transition point is 160 ° C. The outer diameter of the insulated wire is 0.75 mm.

This insulated wire is manufactured as follows using the coating apparatus shown in FIG. The coating apparatus shown in FIG. 2 includes a crosshead 21, an extruder 22 disposed below the crosshead 21, and an extruder 23 disposed above, and the crosshead 21 includes a die 26, an inner nipple 24, and an outer nipple 25. A gas inlet 27 is provided at the center of the cylinder of the extruder 23. One extruder 2
2, a fluororesin mixture containing an amorphous fluororesin is supplied from a hopper (not shown), melted at 300 ° C., and guided to the crosshead 21. Boron nitride was added to PFA as a nucleating agent.
Add 5% and put into the other extruder 23
While melting at 0 ° C., while using a plunger pump (not shown), CFC 114 is continuously injected from the gas inlet 27, and the cross head 2 is uniformly melt-kneaded at 400 ° C.
Send to 1. As the conductor 1, a silver-plated copper wire with an outer diameter of 0.254 mm is passed from the left side of the drawing through the hole at the center of the inner nipple 24,
It is passed through the center hole of the die 26 and moved to the right. Conductor 1
Is covered with the fluororesin mixture 2a extruded from between the inner nipple 24 and the outer nipple 25 and the foamed fluororesin 3a extruded along the outer surface of the outer nipple 25 while moving to the right. Foamed fluororesin 3a containing a foaming agent
Is foamed immediately after extrusion, and the outer insulator layer 3 contains bubbles.
(FIG. 1). The degree of foaming was 81.0%.

When the adhesion between the conductor and the insulating layer was evaluated by a pull-out test of the electric wire, the weight was 400 g / 170 mm to 80 g.
Good results up to 0 g weight / 170 mm were shown. Also,
An electrode was attached to the outside of the insulator outer layer 3 and the propagation delay time was measured by the TD method. The result was Td = 3.6 ns / m.

Using another extrusion machine (not shown), the outer periphery of the insulator outer layer 3 was extrusion-coated with a vinyl chloride resin jacket, and the variation in the propagation delay time in the longitudinal direction was examined. As a result, about 9 per 200 samples
5% was in 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 Instead of the amorphous fluororesin having a glass transition point of 160 ° C. in Example 1, an amorphous fluororesin having a glass transition point of 240 ° C. (DuPo) was used.
TEFLON AF-2400 manufactured by nt Co., Ltd. was used, and PFA was used instead of FEP to melt at 350 ° C.
For the outer layer, FEP was used instead of PFA. A foamed fluororesin insulated wire was obtained in the same manner as in Example 1 except for the above. The amorphous fluororesin used is m in the general formula [1].
15 and n is 85, PFA has a copolymerization ratio of tetrafluoroethylene and perfluoroalkyl vinyl ether of :, and FEP has a copolymerization ratio of tetrafluoroethylene and hexafluoropropylene of 95: 5.
belongs to.

The results of the pull-out test and the propagation delay time measurement were the same as in Example 1.

COMPARATIVE EXAMPLE In Example 1, the extruder 22 was closed, the introduction of the fluororesin mixture was omitted, and only the extruder 23 and the crosshead 21 were used.
Only the extrusion coating of A was performed to obtain a foamed fluororesin insulated electric wire having an outer diameter of 0.74 mm and a foamed insulation layer having a foaming degree of 72%.

The foamed insulating layer had an inner diameter of about 0.40 mm, and a gap of about 73 μm was formed between the foamed insulating layer and the conductor having an outer diameter of 0.254 mm. The result of measuring the propagation delay time by the TD method is Td = 3.
It was 87 ns / m.

[0028]

The foamed plastic insulated wire of the present invention is
Even when the outer diameter is extremely small, or when the foamed insulation layer has a high degree of foaming, the conductor and the foamed insulation layer are evenly adhered to each other in the length direction through the inner layer containing the amorphous fluororesin, and the voids are locally formed. Since it does not occur, not only the mechanical characteristics are uniform in the length direction, but also the electrical characteristics such as the signal propagation speed are uniform. Having a uniform mechanical strength in the length direction means that there is no portion having a small mechanical strength, so that the tensile strength as a whole is large.

According to the present invention, the foaming degree of the foamed insulating layer can be increased without impairing the uniformity of mechanical and electrical characteristics in the longitudinal direction, so that the signal propagation speed of the insulated wire is increased. be able to.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of a foamed plastic insulated wire according to the present invention.

FIG. 2 is an explanatory view of an apparatus used in an example of a method for producing a foamed plastic insulated wire according to the present invention.

[Explanation of symbols]

 1 Conductor Core Wire 2 Insulator Inner Layer 2a Fluorine Resin Mixture 3 Insulator Outer Layer 3a Foamed Fluororesin 21 Crosshead 22 Extruder 23 Extruder 24 Inner Nipple 25 Outer Nipple 26 Die 27 Gas Inlet

Claims (2)

[Claims] 1. A conductor core wire, a first insulating layer made of a first resin covering the conductor core wire, and a second insulating layer made of a second resin covering the first insulating layer. In the foamed plastic insulated wire having bubbles in the second insulating layer, the first resin is an amorphous fluororesin having a glass transition point of 80 to 300 ° C. and a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer. And a mixture of at least one of tetrafluoroethylene-hexafluoropropylene copolymer, wherein the second resin comprises a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer and a tetrafluoroethylene-hexafluoropropylene copolymer. Characterized by being at least one resin selected,
Foam plastic insulated wire. 2. The foamed plastic insulated wire according to claim 1, wherein the amorphous fluororesin has a glass transition point of 150 to 250 ° C.