JPH0528839A - Insulated electric wire - Google Patents

Abstract

PURPOSE:To enhance resistance to thermal deformation and resistance against chemicals by covering a conductor with a foaming substance chiefly containing denatured polyphenylene oxide either directly or with other insulation interposed, thus forming an inner insulative layer, and covering it with an outer insulative layer chiefly containing aromatic polymers. CONSTITUTION:A conductor 1 is covered with an inner insulative layer 2 chiefly containing non-foaming denatured polyphenylene oxide (PPO), which is further covered with an outer insulative layer 3 chiefly containing aromatic polymers. The denatured PPO used here is a one which was denatured for giving PPO particular characteristics about elongation, etc., and its elongation at the ruptural point shall be 50% or more. The aromatic polymers shall be of substantially linear type having an aromatic ring as main chain and contain chiefly a mixture of one or more of the polyethylene terephthalate, polyacetal, etc. Thereby the specific dielectricity factor can be lessened, and the anti- thermodeformativeness and resistance against chemicals can be enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication wire, and more particularly to an insulated wire used as a core of a coaxial cable.

[0002]

2. Description of the Related Art A coaxial cable has a structure in which a conductor is covered with an insulating layer and an outer conductor is externally mounted on the insulating layer.
As the insulating layer coated on the conductor, one using low density polyethylene (LDPE) or high density polyethylene (HDPE) foamed or non-foamed is known.
Moreover, the thing using modified polyphenylene oxide (PPO) is also known.

[0003]

LDPE as an insulating layer
The one using the resin and the one using HDPE are poor in heat resistance, particularly in heat softening resistance. Heat distortion temperature is LDPE = 70
-90 degreeC and HDPE = 90-110 degreeC. Modified PP
O has a heat distortion temperature of 140 to 180 ° C. and is excellent in heat distortion resistance as compared with LDPE and HDPE, but has a drawback that chemical resistance, particularly oil resistance is poor.

Therefore, an object of the present invention is to provide an insulated electric wire which has improved heat resistance and heat distortion resistance and is also excellent in chemical resistance.

[0005]

In order to achieve the above object, the present invention provides a method of coating an inner insulating layer containing a modified polyphenylene oxide as a main component on a conductor directly or through another insulator to form an inner insulating layer. The outer side of the layer is covered with an outer insulating layer containing an aromatic polymer as a main component.

[0006]

In the present invention, the modified PPO layer has excellent heat distortion resistance, and the presence of the aromatic polymer layer improves the chemical resistance. As an insulated wire, particularly as a core of a coaxial cable, the heat distortion resistance and chemical resistance are improved. It has excellent properties and the usage environment is not limited.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention shown in FIG. 1 is that a conductor 1 is coated with an inner insulating layer 2 containing modified polyphenylene oxide (PPO, non-foamed) as a main component, and the inner insulating layer 2 is One is coated with the outer insulating layer 3 containing an aromatic polymer as a main component. As the modified PPO used here, PPO is modified to impart properties such as elongation, and for example, the trade name "Noryl" (manufactured by Engineering Plastics Co., Ltd.) can be preferably used. Modified P
The elongation at break of PO is preferably 50% or more. The aromatic polymer is a substantially linear polymer having an aromatic ring in the main chain and mainly contains one kind or a mixture of two or more kinds selected from the polymer group listed in Table 1 below. Is.

[0008]

[Table 1]

The chemical resistance of aromatic polymers is shown in Table 2.
As shown in. In Table 2, PE = polyethylene, PC = polycarbonate, PEI = polyetherimide, PAr = polyarylate, PBT = polybutylene terephthalate, PEEK = polyetheretherketone, each in room temperature at room temperature for 2 days. The results of the immersion are shown, and the mark "○" indicates "no change".

[0010]

[Table 2]

FIG. 2 shows a structure in which the inner insulating layer 2 is formed of a foam, and a gas foaming method, a chemical foaming method or the like can be adopted as a foaming method. The outer insulating layer 3 may be coated after foaming the inner insulating layer 2, or the unfoamed inner insulating layer 2 may be coated with the outer insulating layer 3 and then heated to modify P.
The chemical foaming agent in PO may be foamed.

The modified PPO of the inner insulating layer 2 and the aromatic polymer of the outer insulating layer 3 may be those in which the main components of each layer belong to their respective concepts (modified PPO, aromatic polymer). That is, even if it is a blend of other components such as polyolefin, the modified PPO and the aromatic polymer may be the main components. In addition, modified PPO is used for aromatic polymers.
Is also included. For example, the main components of the inner and outer insulating layers 2 and 3 are both modified PPO, and both are not melt-integrated,
What is recognized as two layers by some means such as etching when the cross section is cut is within the scope of the present invention. The reason for this is that if two layers can be confirmed by etching or the like, cracks may occur in the inner insulating layer 2 even if crazing or the like occurs in the outer insulating layer due to treatment with chemicals or even if cracking does not occur. This is because the object of the present invention can be achieved with almost no crazing. Here, crazing refers to a defect that is optically visible in the local stress relaxation portion of the molecular extension portion.

Table 3 shows the results of comparison between Examples 1 to 8 and Comparative Examples 1 and 2 in terms of chemical resistance.

[0014]

[Table 3]

[0015]

As described above, the inner insulating layer has the modified P
The main component is PO, and the modified PPO has a small relative permittivity (ε
= 2.6) and excellent in heat deformation resistance, and is useful as an insulator for communication cables, particularly coaxial cables, and an outer insulating layer containing an aromatic polymer as a main component outside the inner insulating layer. As a result, the insulated wire is excellent not only in heat resistance but also in chemical resistance. Foaming the inner insulating layer is suitable as an insulator of a coaxial cable. In such an insulator, electrical loss is reduced as the air occupies more area.

[Brief description of drawings]

FIG. 1 is a sectional view showing a preferred embodiment of the present invention.

FIG. 2 is a cross-sectional view of a foamed inner insulating layer.

[Explanation of symbols]

1 conductor 2 Inner insulation layer 3 Outer insulation layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical indication location H01B 11/18 C 6969-5G (72) Inventor Hideo Sunazuka 1-5-1 Kiba, Koto-ku, Tokyo Fujikura Electric Line Co., Ltd.

Claims (2)

[Claims] 1. A conductor (1) is coated with an inner insulating layer (2) containing a modified polyphenylene oxide as a main component, directly or through another insulator, and an aromatic compound is provided outside the inner insulating layer (2). An insulated wire coated with an outer insulating layer (3) containing a polymer as a main component. 2. Insulated wire according to claim 1, characterized in that the inner insulating layer (2) is a foam.