JPH01272012A - Manufacture of high foaming polyethylene insulated wire - Google Patents

Abstract

PURPOSE:To produce a small-sized ultra-high foaming insulated wire by adding azodicarbonamide to high density polyethylene, and, after extruding the mixture to cover the circumference of a conductor, heating it over the decomposing temperature of azodicarbonamide for foaming. CONSTITUTION:A compound that contains 0.5 to 20 weight part of azodicarbonamide, in relation 100 weight part of a high-pressure method polyethylene with its density over 0.924 also contained therein is mixed and kneaded to be homogenous. Then, the compound, after being heated under the decomposing temperature of azodicarbonamide, is extruded to cover the circumference of a conductor, exposed to ionizing radiation to undergo bridge formation, and then heated over the decomposing temperature of azodicarbonamide to develop a foam insulator, thereby resulting in production of a small-sized, highly foaming polyethylene insulated wire. As a result it is possible to reduce significantly the fraction of the total volume for wires in an electronic device or the like, thereby bringing about great benefits such as compact size the device and accelerated transmission of signal information.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing a highly foamed polyethylene insulated wire.

[Conventional technology In high-speed information circuits such as cocomputers and telephone communications,
There is a need for electric wires with a low visit rate for the insulator, and foamed polyolefin insulated wires are increasingly being used.

A generally known method for producing foamed polyethylene insulated wires is to supply polyethylene containing a chemical foaming agent to an extruder, melt and knead it at a temperature equal to or higher than the decomposition temperature of the foaming agent, and extrude and coat the outer periphery of the conductor. In this method, the decomposed gas of the blowing agent tends to scatter, and various measures are required to obtain a high degree of foaming of 50% or more. For example, a plastic mixture containing a blowing agent is crosslinked, followed by heat foaming [
In recent years, in order to reduce the diameter of TL wires and to transmit information at high speed, there has been a demand for thin highly foamed insulated wires with an outer diameter of 0.9 mm or less and a foaming degree of 70% or more. It's here.

However, there are the following problems in realizing such a small diameter highly foamed insulated wire.

First, because the foaming ratio is extremely high, minute deformations, scratches, uneven thickness, outside diameter fluctuations, etc. of the insulator before foaming are magnified after foaming, resulting in a significant loss of uniformity. Next, since it becomes a highly foamed material, its mechanical strength decreases, and its outer diameter changes due to compression during the Tt, wire twisting, and jacket covering steps. This change in outer diameter is directly related to the impedance of the wire and is therefore a fatal drawback.

It is an object of the present invention to overcome the drawbacks of the prior art and to provide an ultra-fine ultra-high foam insulated wire and a method for manufacturing the same.

[Means for Solving the Problems] In the present invention, 0.0 parts of azodicarbonamide is added to 100 parts of high-pressure polyethylene having a density of 0.924 or more.
A compound containing 5 to 20 parts by weight is extrusion coated on the outer periphery of the conductor at a temperature below the decomposition temperature of azodicarbonamide, and then 'i! A method for producing a small-diameter, highly foamed polyethylene insulated wire that is crosslinked by irradiation with dissociative radiation and then heated to a temperature higher than the decomposition temperature of azodicarbonamide to form a foamed insulator, and an insulated wire made by this method. .

[Example] If the density of the insulator is 0.924 or more, the mechanical strength of the foam is high and it can withstand the compression applied during the twisting of 'rtt wires and the jacket covering process. It is also less susceptible to scratches and deformation before foaming. The higher the density, the better.

If the density is less than 0.924, it will be difficult to finally obtain a uniform highly foamed wire. For this reason, high-pressure polyethylene is a necessary condition for obtaining a high degree of foaming.

Polyethylene is classified by polymerization method into low-pressure polyethylene, medium-pressure polyethylene, and high-pressure polyethylene. As a result of various studies on these polyethylenes, only high-pressure polyethylene was found to have a high degree of foaming. The reasons for this are not clear, but include the excellent dispersibility of the blowing agent (azodicarbonamide), the uniform distribution of the crosslinked structure, and the excellent appearance during extrusion molding.
It is thought that the fact that there is little change in the outer diameter during extrusion molding results in an electric wire with a high degree of foaming.

If the azodicarbonamide is less than 0.5 parts by weight, sufficient foaming cannot be obtained, and if it is more than 20 parts by weight, it becomes difficult to control the degree of foaming. Hereinafter, specific examples will be described together with comparative examples.

Example 1 4 parts by weight of azodicarbonamide was added to high-pressure polyethylene L-XLON M-14 (manufactured by Nippon Petrochemical Co., Ltd., ct=o, 925.MI=0.25), and the mixture was mixed with a Panbali mixer (
The mixture was kneaded for 6 minutes at a temperature of 150°C (Kobe Steel, Ltd.) to form a uniform compound. This was applied using a 28mm extruder at a temperature of 150°C onto a 0.2mmφ tinned copper wire with an insulation pressure of 0.
．． Extrusion coated to 0.06 mmt. The extrusion appearance was good. Next, the insulator was crosslinked by irradiation of 2 M rad with an electron beam accelerator, and then the wire was passed through a cylindrical electric furnace (furnace length: 3 m) at a temperature of 300°C to obtain a foamed insulated wire.

Although the outer diameter of this foamed electric wire was extremely thin, 0.65 mmφ, the degree of foaming was extremely high at 83.7%. Also,
This electric wire is twisted in pairs and made into a 40mm extruder with a wall thickness of 0.5mm.
mmt polyvinyl chloride jacket. There was almost no change in the diameter of the foam insulated wire, and manufacturing was possible without any problems.

Example 2 High-pressure polyethylene Betrocene 219 (manufactured by Toyo Soda Co., Ltd., d=0.932.MI=3) was added with 5 parts by weight of azodicarbonamide, and the irradiation dose by the electron beam accelerator was set to 4 Mrad. A foam insulated wire was produced in the same manner as in Example 1. The extrusion appearance was good, and the twisting and polyvinyl chloride jacket coating processes were carried out without any problems. Although the outer diameter of the foamed insulator was extremely thin at 0.75 mmφ, it achieved an amazing foaming degree of 88%.

Example 3 A foam insulated wire was prepared in the same manner as in Example 1 by adding 5 parts by weight of azodicarbonamide to high-pressure polyethylene UBEC-180 (manufactured by Ube Industries, Ltd., d=0.924.MI=0.25). Manufactured.

The extruded appearance was good, and the twisting and polyvinyl chloride jacket coating processes were carried out without any problems. The outer diameter of the foamed insulator was 0.63 mmφ9, and the degree of foaming was 82.5%.

Example 4 High-pressure polyethylene Miralin C-260-4P (manufactured by Mitsui Petrochemical Co., Ltd. d=0.932°MI=2.5')
A foamed insulated wire was produced in the same manner as in Example 1, except that 4 parts by weight of azodicarbonamide was added to the mixture and the irradiation amount by the electron beam accelerator was set to 4 Mrad. The outer diameter of this foamed insulator was extremely fine, 0.7 mmφ, and a high foaming degree of 86% could be obtained.

Comparative example 1 Medium/low pressure polyethylene Shorex 54002
(Showa Denko Co., Ltd. d=0.934゜MI=0.30
Example 1 by adding 4 parts by weight of azodicarbonamide to )
An attempt was made to manufacture foam insulated wire in the same manner. However, the appearance became rough during the extrusion stage, making it difficult to manufacture uniformly foamed electric wires.

The maximum foaming degree is 68%, which is too low for practical use.
Mechanical strength was sufficient.

Comparative example 2 Medium/low pressure polyethylene Shorex C-4309
(Showa Denko Co., Ltd. d=0.942°MI=0.9)
A foam insulated wire was produced in the same manner as in Example 1 by adding 4 parts by weight of azodicarbonamide to the resulting mixture. However, comparative example 1
Similarly, a uniform foam insulated wire could not be obtained. The degree of foaming was also 70%.

Comparative example 3 Medium/low pressure polyethylene Linrex AF-3720
(manufactured by Nippon Petrochemical Co., Ltd. d=0.935, MI=2.
A foamed insulated wire was produced in the same manner as in Example 1 by adding 4 parts by weight of azodicarbonamide to 0). A relatively uniform extrusion appearance was obtained. In addition, the degree of foaming was low at 71%, which was far short of the target, perhaps because the mechanical strength was sufficient.

Comparative Example 4 A foam insulated wire was produced in the same manner as in Example 1 using high-pressure polyethylene UBEC-150 (manufactured by Ube Industries, Ltd., d=0.919.MI=0.25). Foaming degree 78
However, due to twisting and jacket coating, the outer diameter was reduced by 7%, making it impossible to put it into practical use.

Comparative Example 5 Medium/low pressure polyethylene Linrex AMO710 (
d=0.935. MI=0.3) Linrex AF-3
310 (d = 0.922. MI = 2.0) and Ultzex 3520L manufactured by Mitsui Petrochemicals Co., Ltd. (d = 0.9
35. AF- for each polyethylene with MI=2゜6)
Regarding 3310 and 352OL, foamed insulated wires were manufactured in the same manner as in Example 1 except that 4 Mrad of electron beam was applied. However, only the TL line with a degree of foaming of 65 to 72% and a large variation in outer diameter was obtained.

[Effects of the Invention] As explained above, according to the present invention, it is possible to manufacture a small-diameter, ultra-highly foamed insulated wire. Therefore, the volume occupied by electric wires in electronic devices and the like is significantly reduced, allowing the devices to be made more compact. It also brings about great benefits such as increasing the transmission speed of information signals.

Claims (2)

[Claims] 1. High pressure polyethylene 100 with a density of 0.924 or more
A compound containing 0.5 to 20 parts by weight of azodicarbonamide based on the weight part is extruded and coated on the outer periphery of the conductor at a temperature below the decomposition temperature of the azodicarbonamide, and then crosslinked by irradiation with ionizing radiation. A method for producing a highly foamed polyethylene insulated wire, the method comprising forming a foamed insulator by heating above the decomposition temperature of azodicarbonamide. 2. A method for manufacturing a highly foamed polyethylene insulated wire, which comprises forming a foamed insulator on the outer periphery of the conductor while decomposing the azodicarbonamide using the compound according to claim 1 using an extruder.