JPS6210810A - Manufacture of crosslinked foaming 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 Field of Application) The present invention relates to a method for manufacturing a foamed cable, and more particularly to a method for manufacturing a cable with a coating made of highly foamable crosslinked polyolefin. Foamed cables are generally used as the core wire of coaxial cables, and the polyolefin foam layer covering the conductor acts as an insulator.

(Conventional technology) However, in the conventional structure, the foam layer is not crosslinked.
Since the foaming rate is only about 80%, it is difficult to provide sufficient insulation performance to the foam layer.

Furthermore, in the conventional structure, the heat resistance, mechanical strength, and abrasion resistance of the foam layer as well as the adhesion strength of the foam layer to the conductor are low, and there are also problems in the function as an insulating layer in these respects.

On the other hand, as a means for improving the mechanical strength of the foam layer, a method of crosslinking the foam layer has also been proposed. This manufacturing method using crosslinking and foaming involves first foaming, and then crosslinking the foamed layer.

(Problems to be Solved by the Invention) However, according to this conventional method, the foaming rate can be reduced to 90%.
% or more, there was a problem that the foam layer and the conductor would peel off, resulting in poor pull.

(Means for solving the problem) The above problem can be solved by first crosslinking the foamed layer and then foaming it, and forming the Lieple coating with a highly foamable crosslinked foam layer. This problem can be solved by providing a solid polyolefin layer that functions as an adhesion layer between the cables.
6I is intended to provide information on how to proceed with the following J:

1. That is, the present invention covers a conductor by extrusion with a crosslinkable polyolefin-based solid layer and a foamed polyolefin layer made of foamed 1 riboliolenoin, and after crosslinking the solid layer and the foamed solid layer, It is characterized by foaming the material layer.

11 Foam material 1PIFi is good land tltlI lI
! Foaming can be carried out using a one-person heated Ising die, or it is possible to heat with gas or infrared rays and simultaneously perform sizing with a sizing plate to stop foaming.

After the above foaming, the boreolefin foam layer is cooled when showering.
1 to J: It can be solidified to form a coating layer.

(Example) According to the example of the present invention, in the extruded II culm, the second
As shown in the figure, a conductor 1 made of a metal wire such as an annealed copper wire is connected to a solid layer 2.
, the foamed material layer 3, and the solid layer 4 form a 3@ coated cable W (cumulus).

The solid layer 2 is in close contact with the entire outer peripheral surface of the conductor 1.

The foam material layer 3 and the solid layer 4 are also fully filled) liIj2,
The foam material layer 3 is closely adhered (fused; including b) to the entire outer circumferential surface of the foam material layer 3.

The solid layer 2 is a part that is in close contact with the conductor 1 and the foamed metal layer 3 to prevent the foamed metal layer 3 from peeling off from the conductor 1. A material with excellent adhesion to the layer 3 is used.

Specifically, the solid layer 2 is made of a polyolefin material, such as polyethylene, polypropylene,
Poly1tene, polypentene, especially LDPE (low density polyethylene) mixed with DCP (crosslinking agent) in a ratio of about 100:1.0, or vinyl acetate, acrylic ester, and methacrylic acid It is composed of a co-minor combination of and Brene, etc., and DCP. If necessary, compounded chemicals such as coloring, anti-aging, anti-copper, etc. may be added to the solid layer 2.

The foamed layer 3 is also composed of polyolenoin-based U)Ql, for example, Ll)PE (low density polyethylene), DCP (crosslinking agent), and ADCA (foaming agent) in a ratio of about 100:0.5: A mixture of 10 °b and the like has been used for heavy oil. Also, instead of low density polyethylene, HDP
E(^density polyethylene) can also be used. More specifically, as the foam layer li1□3, 100 parts by weight of low-density polyethylene or high-density polyethylene and azodicarbomide or P, as a foaming agent are used. P”:
4xybeth (penzelsul small nyl hydrazide) 1-b
O wheel stone part and dicumyl par J-=t ”J as a bridging material
A mixture containing 0.1 to 2.0 parts by weight of id can be used.

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

Extrusion temperature is below the decomposition temperature of the crosslinking agent.

The above-mentioned cable W is then sent to the bridging ■culm, and the solid layer 2,
The foamed material Fi1 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 a long land die, molten salt, gas, infrared rays, or steam, and crosslinking water-crosslinkable polyolefin with steam. , a method of crosslinking polyolefin by irradiating it with an electron beam, etc. can be adopted.

The heating temperature and heating time in the first stage of crosslinking are, for example, about 1
The temperature was set at 80'C for 110 minutes, and care was taken to prevent foaming from proceeding.

After completing the crosslinking process, the material No. 1 is sent to the next step of foaming, and the foamed material layer 3 is foamed to form the foamed layer F) in FIG. During this foaming step, bubbles are generated from the foam layer 3 itself, but as mentioned above, the foam material layer 3 is cross-linked and has high elasticity and viscosity, so a large number of independent bubbles are formed in the foam layer 5. This greatly prevents foaming gas from escaping from the surface of the cable W to the outside. Therefore, the foam layer 5 has a high cell ratio, for example, about 90% or more.

Furthermore, the density of the bubbles inside the foam layer 5 is made uniform.

Specifically, the foaming described in h is carried out by heat foaming, heat foaming with molten salt, gas heat foaming, infrared heat foaming, steam heat foaming, etc. J, will be held. Further, the heating temperature and heating time are set to, for example, about 220° C. and 5 to 10 minutes.

In FIG. 3, the above-mentioned land die 1 ( ) is equipped with a part 11 of a good straight line extending with an approximately constant inner diameter, and a constriction part 12 that is continuously tapered in diameter at its downstream end. . Also, on the inner surface of the throttle part 12, there is a 1rlI lubricant supply passage 14.
is open. The couple W passes through the long land die 10 while being pressed against the inner surface 13 of the long land die 10,
It is heated by a land die 10 between the slots. 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 bIt is compressed from the periphery by the long land die 10, the density of the bubbles inside the foam layer 5 is made more uniform.

Sizing plate 4 in Figure 4 instead of long land die 10 in Figure 3! It is also possible to use position 15. 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 having holes 16 through which the couple W passes are arranged at intervals. . In this structure, instead of the long large die shown in Fig. 3, a plurality of sizing plates 1
Since 7゛ is used, the structure is simple. Also hole 16.
Since the cable W can be heated with gas or infrared rays through the gap 18 between the holes 16 and 16, the structure of the heating device can be Can be simplified to q1. Furthermore, since the 1J Ising plate 17 has a structure that can be divided into upper and lower parts, it is easy to guide the cable W into the hole 16 at the start of work and to perform maintenance and inspection work.

Couple W finished foaming and sizing in this way
The foamed layer 5 is cooled to about a cold fJII temperature, and the foamed layer 5 is solidified to form a predetermined product. This cooling is carried out by cooling (not shown), but specifically, the cooling chamber W is passed through the center of the cooling chamber, and the cable W is passed around it.
This is done by jetting cooling water towards the

By adopting shirt ring cooling in this way, the cable W can be sufficiently cooled, which solves the problem of the conventional method in which the cable passes through cooling water, that is, the cable floats up, resulting in insufficient cooling. It is possible to reliably cover the 1st floor.

[Comparative Example 1 A copper conductor with a diameter of 4III and a high foaming polyethylene (density aO, 9F), melt index 0.5
) was extruded and foamed using dichlorotetrafluoroethane as a foaming agent and -C azodicarbonamide as a nucleating agent to obtain a foamed polyethylene electric wire with a molding speed of 10 m/1n and an outer diameter of 17 contraction. . The obtained insulator had a dielectric constant of 1.31 (expansion degree of about 75%) and a dielectric loss tangent of 0.023%.

E Example 1] On a copper conductor with a diameter of 4#, a solid layer made of low density polyethylene with a density of 0.92 and a melt index of 1.0 mixed with 2.0 parts of Dycumyl peroxide as a crosslinking agent, Dycumyl Peroxy 9 as a crosslinking agent in similar resins
0.5 parts of azodicarbonamide as a blowing agent, 20 parts of azodicarbonamide as a blowing agent.
A foam adhesion layer containing 1.5 parts of the same resin as No. 1 and 0.5 parts of the first side of Dyke Milpar as a crosslinking agent was added at a molding speed of 50 m/min and a molding temperature of 1120 m/min.
'C was extrusion coated to obtain an uncrosslinked and unfoamed electric wire with an outer diameter of 5.8M. The obtained uncrosslinked and unfoamed electric wire was crosslinked and heated in nitrogen gas by infrared rays, and then foamed while being plate sized to obtain a crosslinked foamed electric wire with an outer diameter of 17 am. The dielectric constant of the obtained insulator was 1.゜08 (foam nails approx. 91!1%
), invitation city 11 - contact is 0. (') 0/15%, which was very good compared to the comparative example.') The foam insulated wire had an electrical rating of 11 at 7<'.

[Example 2] A low-density poly T-'f-len filled layer with a density of 0.92 and a melt index of 1.0 was deposited on a copper conductor with a diameter of 4#.
Azodicarbonamide 2 as a blowing agent in similar resins
Two foamed bamboo layers were prepared by extruding and coating the same resin on Fumihizo No. 1 at a molding speed of 100 m/min and a molding temperature of 150° C. to form an outer diameter of 5. Bttrm uncrosslinked and unfoamed electric wire 1; also. (1) The uncrosslinked and unfoamed electric wire was exposed to an electron beam, and an unfoamed electric wire was obtained. The foamed wire was foamed in nitrogen gas with infrared heating and plate sizing to obtain a cross-linked foamed wire with an outer diameter of 17mm. )
The dielectric loss tangent was 0.0037%, which was very good compared to the comparative example./The foam insulated wire had electrical properties of 41.

[Example 31: A solid layer containing 2.0 parts of Dyckmilver oxide as a crosslinking agent and a low-density polycorene with a density of 0.92 and a melt index of 1.0 on a copper conductor with a diameter of 4 tnm] A foamable layer is prepared by mixing the same resin with 0.5 parts of Daiku Milpar A-11 night as a crosslinking agent and 20 parts of azodicarbonamide as a foaming agent. id 0.
1. :B was extruded and coated with an outer diameter of 5.8M at a conductivity rate of 3 m/min and a molding temperature of 120°C, while poly-I-chill synthetic oil (Product name: I-Nyl, Butyl) was applied as a lubricant to the inside of the die. 75 old-2620, l-1 oil and fat) was poured into a heated Nagarand die for 10 minutes at 180°C for cross-linking, and then heated to 220℃.
G. Foam for 5 minutes to obtain a cross-linked foamed wire with an outer diameter of 17#.

The dielectric constant of the obtained insulator is 1.06 (degree of foaming approximately 95%)
The dielectric loss tangent was 0.0035%, and the foamed insulated wire had very good electrical properties compared to the comparative example.

Of course, the present invention is also useful as a method for producing a foamed cable with low foaming, for example, a foaming ratio of 50% or more.

(Effects of the Invention) As described above, according to the present invention, the foam material layer 3 is crosslinked and then the foam layer 5 is formed. It can make the cell density uniform and improve the insulation performance of the foam layer. In addition, the foam layer 5 has good heat resistance, mechanical strength, and abrasion resistance, and in these respects, the function of the foam layer 5 as an insulating layer can be enhanced. Furthermore, since the adhesive layer made of the solid layer 2 is provided between the shelf 1 and the foam layer 50, peeling of the foam layer 5 can be reliably prevented.

[Brief explanation of drawings]

Figure 1 is a schematic cross-sectional view of the couple after foaming II, Figure 2 is a cross-sectional view of the cable of the foamed weighing section, Figure 3 is a cross-sectional view of the 1F11 cross-section of the Utsuland die, and Figure 4 is the cross-section of the 1J Ising plate. im schematic diagram. 1... Gold B conductor, 2...
Solid layer, 5... Foam layer, W... Couple patent applicant Dai ``[Nippon Electric Cable Co., Ltd.; de → :] J et al.: Yumishi X

Claims (4)

[Claims] (1) A conductor is coated with a crosslinkable polyolefin solid layer and a foam material layer of foamable polyolefin by extrusion, and after crosslinking the solid layer and the foam material layer, the foam material layer is foamed. A method for manufacturing a cross-linked foam cable. (2) The method for manufacturing a cross-linked foamed cable according to claim 1, characterized in that the foamed material layer is foamed using a long land lubricating oil injected heated sizing die. (3) The method for producing a cross-linked foam cable according to claim 1, characterized in that the foam material layer is foamed while being heated with gas or infrared rays and simultaneously sizing using a plurality of sizing plates. (4) Production of a crosslinked foamed cable according to any one of claims 1 to 3, characterized in that the foamed polyolefin foam layer is solidified by showering and cooling to form a coating layer. Method.