JPH05101711A - Low electrostatic capacity type insulated wire - Google Patents

Abstract

PURPOSE:To provide a low electrostatic capacity type insulated wire principally related to a TE cord (terminal cord) corresponding to an ISDN(integrated service digital network), having a characteristic value that electrostatic capacity at 10m cable length is 350 PF/10m or less, not only conforming to a recommended value of the CCITT but also because of high foaming making an insulative body hard to be crushed, excellent in electric/mechanical characteristics and inexpensive. CONSTITUTION:In an insulated wire in which a plurality of paired stranded wires of foaming insulative core wires 4, wherein center conductors are covered with foaming insulative bodies, are provided and a sheathing 6 is applied thereto, high density polyethylene is of 100%, or blending ratio thereof with respect to low density polyethylene is 70%, or more in a base resin of the foaming insulative body and foaming degree is determined 35% or higher. The foaming insulative core wire 4 is cross-linked by radiation of electron beams of 15-25 Mrad.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is mainly used for ISDN (Service Integrated Digital Network) compatible TE code (terminal code).
Related to 10m cable length and capacitance of 350
A low capacitance modular plug that has a characteristic value of PF / 10m or less, not only conforms to the CCITT recommended value, but also is highly foamed, the insulator does not easily collapse, has excellent electrical and mechanical characteristics, and is inexpensive. Related insulated wire.

[0002]

2. Description of the Related Art In recent years, ISDN, which is rapidly becoming popular, uses a TE cord with an 8-pin modular plug conforming to the FCC (Federal Communications Commission) standard for connecting a rosette and a terminal device. .. The specifications of this TE code are defined as follows by the recommendation of CCITT (International Telegraph and Telephone Consultative Committee). Regarding the capacitance of the cable, (1). For cords up to 7 m long, the maximum capacitance of the transceiver pair should be less than 300 PF. (2). For cords greater than 7 m and up to 10 m, the maximum capacitance of the transceiver pair must be less than 350 PF. In response to such a recommendation, conventionally, a cable structure as shown in FIG. 5 has been adopted. In these cables, an insulating material having a low dielectric constant must be used in order to reduce the capacitance value. Among materials having a low dielectric constant, polypropylene and polyethylene are widely used because they are inexpensive and easy to process. However, this cable has manufacturing restrictions that it is necessary to attach modular plugs to both ends, and the outer diameter of the insulator must be manufactured within a range of 0.90 to 0.95 mmφ. Therefore, the capacitance when cables are manufactured with these structures has a limit of about 37 PF / m, and the capacitance cannot be further reduced, and the capacitance exceeds 7 m and 10 m.
In the case of the cords up to this point, it was very difficult to manufacture a cable that complies with the recommended value of CCITT.

[0003]

DISCLOSURE OF THE INVENTION As a result of intensive studies in order to solve these problems, the present invention has a characteristic value of a capacitance of 350 PF / 10 m or less at a cable length of 10 m, and CCIT
In addition to conforming to the recommended value of T, it is made for the purpose of providing a low capacitance type insulated electric wire 1 which is highly foamed, the insulator is hard to be crushed, has excellent electrical and mechanical characteristics, and is inexpensive. The gist of the invention is, firstly, an insulated electric wire in which a plurality of twisted pairs of foamed insulation core wires, each of which has a center conductor covered with a foamed insulation material, is provided with a sheath to provide a base resin of the foamed insulation material. 1 high density polyethylene
It is a low capacitance type insulated wire characterized by having a blending ratio of 00% or high density polyethylene to low density polyethylene of 70% or more and a foaming degree of 35% or more. Secondly, the foam insulation core wire
It is a low capacitance type insulated electric wire characterized by being crosslinked by electron beam irradiation of 5 to 25 Mrad.

[0004]

Embodiments of the low capacitance insulated wire 1 of the present invention will now be described in detail with reference to the accompanying drawings. Figure 4 (a)
Shows a side view of a finished product in which modular plugs 2 are attached to both ends of a low capacitance type insulated electric wire 1 of the present invention. Figure 4 (b)
FIG. 3 is a plan view of the modular plug 2 . FIG. 1 is a cross-sectional view of a low capacitance type insulated electric wire 1 of the present invention, which is a side view of a completed product, which is a cross-sectional view taken along the line AA ′ of FIG. As is clear from the figure, the low capacitance type insulated electric wire 1 of the present invention is
This is a structure in which the center conductor 3 is formed by twisting two foam insulating core wires 4 each covered with a foam insulating material 5 to provide a plurality of twisted pair wires, on which a sheath 6 such as PVC is applied. There are LDPE (low density polyethylene) and HDPE (high density polyethylene) in foamed polyethylene, but when LDPE is used with an insulation core diameter of about 0.95 mm, the foaming degree is 65%.
Although it is technically possible to raise it to a certain degree, conversely, the mechanical strength of the insulator is significantly reduced, the insulator is crushed when it is made into a cable, and the distance between the conductors of the twisted pair is reduced. It becomes impossible to obtain the target value. However, if the ratio of HDPE is increased in the base resin of the foamed insulating material, the decrease in mechanical strength can be suppressed.
If the ratio of HDPE is 70% or more, the degree of foaming is 45 to 5
Even if it is 0%, the crushing of the insulator can be suppressed to a small level. FIG. 2 is an enlarged view of the foam insulating core wire 4 of FIG. 1 according to the first embodiment of the present invention. In the figure, a foam insulating core wire 4 coated with a foam insulator 5 covered with a central conductor 3
Is molded by an extrusion method. FIG. 3 shows the second aspect of the present invention.
It is an enlarged view of the foam insulation core wire 4 of FIG. 1 in an Example. In the figure, the non-foamed skin layer 7 is covered by 5 to 50 μm on the outer peripheral surface of the foamed insulating core wire 4 which is covered with the foamed insulator 5 which is covered by the central conductor 3. The foamed insulation core wire 4 of the present invention may have the structure shown in FIG. 2, but in the case of multiple cores, if coloring is required to identify the core wire, as shown in FIG. When the skin layer 7 is provided on the outer periphery of the foamed insulator 5 and the skin layer 7 is colored and identified, the uniformity of the foamed cells is maintained and the electrical characteristics are better.

(Embodiment) In the structure of FIG.
Table 1 shows the result of the characteristic test of the capacitance of the present invention in which the outer diameter of the insulation is 0.08 TA and the outer diameter of the insulation is 0.95.

[Table 1] As is clear from the above-mentioned capacitance characteristic test results, it is understood that the foamed polyethylene has a foaming degree of 35% or more, preferably 45% or more, in order to reduce the capacitance to 350 PF / 10 m or less. In addition, when the mixing ratio of HDPE is small, the insulator is crushed, so that the capacitance does not become so low. Therefore, it is desirable that HDPE is 100%,
It is also possible to set the blending ratio of HDPE to LDPE to 70% or more. From the above, the base resin of the foamed insulator of the low capacitance type insulated electric wire 1 of the present invention has a high density polyethylene of 100% or a blending ratio of the high density polyethylene to the low density polyethylene of 70% or more. It is characterized in that the degree of foaming is 35% or more.
With the above structure, the capacitance between the pair of core wires is small, and it is possible to meet the allowable value of 350 PF / 10 m even with a cable length of 10 m.

Up to now, the ratio of high-density polyethylene to low-density polyethylene has been described, but polyethylene is generally subjected to a crosslinking treatment in order to improve its mechanical strength and heat resistance. The foam insulation core wire 4 of the present invention is 1
Crosslinking by electron beam irradiation of 5 to 25 Mrad improved the mechanical strength and obtained good results. Further, although the number of cores and the shape have been described as representative examples, it goes without saying that various modifications are included within the scope of the present invention in terms of design.

[0007]

As described above, according to the low capacitance type insulated electric wire 1 of the present invention, the capacitance is 350 PF / 10 m or less at the cable length of 10 m, and the CCIT
Not only does it comply with the recommended value of T, but it also has the excellent effects that it is highly foamed, the insulator does not easily collapse, it has excellent electrical and mechanical properties, and it is inexpensive, so its industrial value is I believe that it is very large.

[Brief description of drawings]

FIG. 1 is a sectional view of a low capacitance type insulated electric wire 1 of the present invention.

FIG. 2 is an enlarged view of the insulating core wire 4 of FIG. 1 according to the first embodiment of the present invention.

3 is an enlarged view of the insulating core wire 4 of FIG. 1 according to the second embodiment of the present invention.

FIG. 4A is a side view of a completed product in which the modular plugs 2 are attached to both ends of the low capacitance type insulated electric wire 1 of the present invention.
(B) is a plan view of the modular plug 2 .

FIG. 5 is a sectional view of a conventional cable 1 ′.

[EXPLANATION OF SYMBOLS] 1 low capacitance type insulated wire 2 modular plug 3 central conductor 4 foam insulated wire 5 foamed insulation 6 sheath 7 skin layer 1 'cable 3' central conductor 4 'foam insulated wires 5' foam insulation Body 6'sheath

Claims (2)

[Claims] 1. An insulated electric wire in which a plurality of twisted pairs of a foamed insulating core wire having a center conductor coated with a foamed insulating material is provided with a sheath to provide a sheath, and the base resin of the foamed insulating material is 100% high-density polyethylene. Alternatively, the low capacitance type insulated wire is characterized in that the blending ratio of the high density polyethylene to the low density polyethylene is 70% or more and the foaming degree is 35% or more. 2. The foam insulating core wire according to claim 1,
A low capacitance type insulated electric wire, which is cross-linked by Mrad electron beam irradiation.