JPS6210804A - Highly foaming crosslinked polyolefin covered cable - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a cable having a highly foamed insulating layer, and more particularly to a cable having a coating made of highly foamable crosslinked polyolefin with a foaming rate of 90% or more. The target is cables that are used as coaxial cables with an outer conductor placed on a highly foamed layer.

(Prior Art) In recent years, with the explosive increase in the amount of information, the demand for even lower 11 loss and 16 loss for high frequency couples has become extremely high. Through this method, the insulation layer of the coaxial cable could be highly foamed. However, the foam layer of the cable is around 80%, and at present there are no cables with a foaming ratio of 90% or more.

(Problems solved by the invention) However, in the conventional structure, the foam layer has a low cell ratio of about 80%, making it difficult to provide sufficient insulation performance to the foam layer.

Furthermore, in the conventional structure, the foam layer is a single plastic layer that is not subjected to treatments such as crosslinking, so the heat resistance of the foam layer,
The mechanical strength, abrasion resistance, and adhesion strength of the foam layer to the conductor are low, and in these respects as well, there are problems with its function as an insulating layer.

(Means for Solving the Problems) In order to solve the above problems, the present invention forms the cable covering with a foam layer of highly foamable crosslinked polyolefin, and provides a solid layer of polyolefin between the conductor and the foam layer. It was something that
Next J: It is composed of sea urchins.

However, in the present invention, a solid layer of Bore A resin is provided around a metal conductor, and a foaming rate of 90% or more is provided on the solid layer.
It is characterized by having a foam layer of highly foamable crosslinked polyurethane.

The highly foamable crosslinked polyolefin of the foam layer is low density polyethylene or high density polyethylene 100% fi1.
Add 1 part to 1 part of azodicarbonamide or P,P'-oxybeth (penzelsulfonyl hydrazide) as a blowing agent and 1 part of 50Tl as a blowing agent, and 0.1 to 2.0 parts of dicumyl peroxide as a crosslinking agent. It can be constituted by blending part B>.

Further, additives such as flame retardants, antioxidants, copper damage inhibitors, etc. may be added as necessary.

The adhesive layer composition may include a crosslinking agent so that simultaneous crosslinking occurs during crosslinking of the highly foamable polyolefin.

In addition, the solid layer is used to increase the adhesion strength m between the foam layer and the conductor, and it grips the conductor and is in close contact with the inner surface of the foam H to some extent, allowing gas from the foam layer to flow between this layer and the conductor. J: Does not accumulate.Specifically, the solid layer is made of the same polyethylene secondary resin as the foam layer, such as polypropylene, polybutene, polybentene, especially low-density polyethylene, or the polyolefin of the foam layer J: has a low melting point. It can be formed from vinyl acetate, acrylic esters, and copolymers of methacrylic acid and ethylene.

Further, the solid layer material can be constructed by blending the same crosslinking agent as the foam layer.

(Example) According to the example of the present invention, in the extrusion coated culm, the second
As shown in the figure, conductor 1 made of metal wire such as annealed copper wire is filled with M2.
A cable W (material) is formed which is triple-coated with foamed I+ layer 3 (unfoamed) and solid layer 4. The solid layer 2 is in close contact with the entire outer peripheral surface of the conductor 1. The foamed solid layer 3 and the solid layer 1 are also in close contact with the entire outer peripheral surfaces of the solid layer 2 and the foamed material layer 3, respectively.

The solid layer 2 is in close contact with the conductor 1 and the foam material layer 3 (of course, it may be fused), and the foam material layer 3 is peeled off from the conductor 1.
The solid layer 2 is a part for preventing the foaming from occurring, and for this purpose, a material with excellent adhesion to the conductor 1 and the foamed material layer 3 is used for the solid layer 2.

Specifically, the solid layer 2 is composed of a polyolefin-based material, for example, Ll) PE (low-density polyethylene) and DCP (crosslinking agent) are mixed at a weight ratio of about 100:1.0. Specifically, it is composed of vinyl acetate, acrylic acid ester, and a copolymer of methacrylic acid and ethylene.

If necessary, it is also possible to add a compounding agent for coloring, anti-aging, anti-copper, etc. to the solid layer 2.

The foaming layer 3 is also made of polyolefin-based materials, such as LDI"E (low-density polyethylene) and DC.
P (crosslinking agent) and ADCA (foaming agent) at a ratio of approximately 100:0.
Chichino etc. are used mixed in a weight ratio of 5:10.

Also, HDPE (high density polyethylene) can be used instead of low density polyethylene, and more specifically,
As the foamed material layer 3, 1 to 50 parts by weight of azodicarbonamide as a foaming agent and 1.0 parts of dicumyl peroxide as a crosslinking agent are added to 100 parts by weight of low-density polyethylene or high-density polyethylene. It is possible to use a blend of 2.0 to 2.0 wheel stones.

The composition of solid layer 4 is similar to that of solid layer 2.

The extrusion coating step is carried out at a temperature at which the blowing agent does not decompose.

The above-mentioned cable W is then sent to a crosslinking process to form a solid layer 2,
The foam material layer 3 and the solid layer 4 are crosslinked. Specific methods for this crosslinking include adding an organic peroxide to polyolefin and heating it with Nagland dice, molten salt, gas, infrared rays, or steam, and crosslinking water-crosslinked polyolefin. , a method of crosslinking polyolefin by irradiating it with an electron beam, etc. can be adopted.

In addition, the heating temperature and heating time in the crosslinking step are, for example, about 18
The temperature was set at 0° C. for 10 minutes, and the blowing agent was kept from decomposing.

Kashi +! ]] After completing the process, the material is then sent to the foaming process, and the foam material 11 layer 3 is foamed to form the foam vJ5 and 4 shown in Figure 1.
[ru. In this foaming process, bubbles are generated from the foamed material ()'3i'vJa itself, but as mentioned above, the foamed material layer 3 has already been crosslinked and has high elasticity and viscosity, so a large number of independent bubbles are formed in the foamed layer 5. This greatly prevents foaming gas from escaping from the surface of the cable W to the outside. Therefore, the foaming rate of foaming P/J5 is high, reaching a value of 90% or more. Moreover, the density of the bubbles inside the foam layer 5 is made uniform.

Specifically, the foaming is carried out by heating foaming using a long land die 10 (FIG. 3), heating foaming using molten salt, gas heating foaming, infrared heating foaming, steam heating foaming, etc., which will be described next. Also, the heating temperature and heating time are, for example, about 2
The temperature is set at 20°C for 5-10 minutes.

In FIG. 3, the long land die 10 has a long straight part 11 extending with a generally constant inner diameter, and a constricted part 12 which is continuously tapered and reduced in diameter at its downstream end. Further, a lubricating oil supply passage 14 is opened on the inner surface of the throttle part 12. The couple W passes through the long land die 10 while being in pressure contact with the inner surface 13 of the long land die 10, and is heated by the long land die 10 during this time. Further, while the cable W passes through the long land die 10, it is formed into a predetermined shape, and the surface of the solid layer 4 is smoothed. Furthermore, since the foam layer 5 is compressed from the periphery by the long land die 10, the density of the cells inside the foam layer 5 is made more uniform.

In place of the long land die 10 shown in FIG. 3, the sizing plays 1 to 15 shown in FIG. 4 can also be used. The sizing plate device 15 is used when heating with gas or infrared rays, and has a structure in which a plurality of sizing plates 17 are arranged at intervals on the right side of a hole 16 through which the cable W passes. In this structure, a plurality of sizing plates 17 are used instead of the long large die shown in FIG. 3, so the structure is simple. In addition, the cable W can be heated with gas or infrared rays through the gap 18 between the holes 16 and 16, so that the long wire die 1 of the doll can be heated as shown in FIG.
The structure of the heating device can also be simplified compared to the case where the entire 0 is heated. Furthermore, since the sizing plate 17 has a structure that can be divided into upper and lower parts, the cable W is inserted into the hole 16 when starting work.
Guide work and maintenance/inspection work are easy.

The cable W that has been foamed and sized in this way is cooled in the cooling process, and the foam layer 5 is solidified.
It becomes a prescribed product. This cooling is performed by showering, and although not shown, specifically, it is performed by passing the cable W through the center of the cooling chamber and spouting cooling water toward the cable W from around the cable W.

By adopting showering cooling in this way, the cable W can be sufficiently cooled, and the problem of the conventional method in which the cable passes through cooling water, that is, the problem of the cable floating and insufficient cooling, has been solved. This can be reliably prevented.

(Effects of the Invention) As explained above, according to the method of the present invention, the cable covering is formed with the foam layer 5 made of highly foamable crosslinked polyolefin with a foaming degree of 90% or more, so that the insulation performance of the foam layer 5 can be improved. can. Moreover, since the foam layer 5 is cross-linked,
It also has high heat resistance, mechanical strength, and abrasion resistance, and can enhance the function of the foam layer 5 as an insulating layer in these respects as well. Furthermore, since the solid layer 2 is provided between the conductor 1 and the foam layer 5, peeling of the foam layer 5 can be reliably prevented.

[Brief explanation of the drawing]

Figure 1 is a schematic cross-sectional diagram of the cable after the foaming process, Figure 2 is a schematic cross-sectional diagram of the cable before the foaming process, Figure 3 is a schematic cross-sectional diagram of the long land die, and Figure 1 is a schematic cross-sectional diagram of the 1-noising plate. be. 1... Metal conductor, 2... Solid layer, 3
...Foam material F! 1 layer, 5... foam layer, W... cable patent applicant Dai [1 Nippon Cable Co., Ltd. No. 11/4

Claims (5)

[Claims] (1) A highly foamable crosslinked polyolefin characterized in that a polyolefin-based solid layer is provided around a metal conductor, and a foamed layer of highly foamable crosslinked polyolefin with a foaming rate of 90% or more is provided on the solid layer. coated cable. (2) As the composition of the highly foamable crosslinked polyolefin of the foam layer, azodicarbonamide or P,P'-oxybeth (benzelsulfonyl hydrazide) is added as a foaming agent to 100 parts by weight of low-density polyethylene or high-density polyethylene. 1 to 50 parts by weight of the highly foamable crosslinked polyolefin according to claim 1, which is formed by blending 0.1 to 2.0 parts by weight of dicumyl peroxide as a crosslinking agent. coated cable. (3) The highly foamable crosslinked polyolefin coating according to claim 1 or 2, wherein the solid layer composition contains a crosslinking agent, and simultaneous crosslinking occurs during crosslinking of the highly foamable polyolefin. cable. (4) The highly foamable crosslinked polyolefin coated cable according to any one of claims 1 to 3, wherein the solid layer is made of polyolefin. (5) The solid layer is formed of any one of vinyl acetate, acrylic acid ester, and a copolymer of methacrylic acid and ethylene, which have a lower melting point than the polyolefin of the foam layer. The highly foamable crosslinked polyolefin coated cable according to any one of items 1 to 3.