JPH01283715A - Manufacture of foam plastic insulated cable - Google Patents

Abstract

PURPOSE:To improve attachment degree between a conductor and an insulating body under a high foaming degree by providing a foaming tube obtained by scattering foaming agent in molten plastic uniformly and then extruding it in the form of a tube around a conductor. CONSTITUTION:Plastic which can be melted by heat and extruded and foaming agent are put into an extruder, the foaming agent is scattered uniformly in the plastic, which is then extruded in the form of a tube to be foamed, and the foaming tube is provided around a conductor 1. That is, after forming the foaming tube, the conductor 1 of a similar outer diameter to the inner diameter of the tube is inserted by forming a slit 3 along its length, for example, so attachment degree between the conductor 1 and the foam insulation body 2 is improved. A reinforcement layer 4 is then extruded to coat the circumference of the tube. A thin and high foam rate plastic insulated cable of a good attachment degree of a conductor 1 and a high foam insulation body 2 can thus be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing a foamed plastic insulated wire, particularly a small diameter foamed plastic insulated wire used for signal transmission lines of various electronic devices including computers. The present invention relates to a manufacturing method suitable for obtaining.

[Background Art] With the development of electronic devices such as computers and their peripheral devices, the electric wires and wires used for signal transmission in the devices have increased.
There is also a strong demand for higher performance and higher reliability for cables. In particular, there has been a strong demand for wires and cables with thin insulation coatings that can transmit signals at high speeds close to the speed of light in a vacuum.

Foamed plastic insulation that satisfies this type of requirement is made by forming a foamed insulator with a foaming degree of over 70% around the outer periphery of the conductor using a low dielectric constant plastic such as polyethylene, polypropylene, polystyrene, or fluororesin. Electric wire is proposed.

[Problems to be Solved by the Invention] However, when attempting to obtain a highly foamed insulator with a degree of foaming exceeding, for example, 70%, the entire foamed insulator expands in the outer circumferential direction, causing the conductor and the foamed insulator to become loose. There is a problem in that the adhesion between the two is thick (decreased).This tendency is particularly noticeable when the foamed insulator is thin, such as 1 mm or less.

The present invention has been made based on the above, and aims to provide a method for manufacturing a foamed plastic insulated wire that can improve the adhesion between a conductor and an insulator even when the insulator is highly foamed. It is.

[Means for Solving the Problems] The method for manufacturing a foamed plastic insulated wire of the present invention includes introducing hot-melt extrudable plastic and a foaming agent into an extruder,
This method is characterized in that a foaming agent is uniformly dispersed in molten plastic and then extruded into a tube shape to foam it, and then this foamed tube is provided around the outer periphery of the conductor.

That is, in the present invention, after forming a foam tube, slits are made along the length of the tube to insert a conductor having an outer diameter that almost matches the inner diameter of the tube, thereby improving the adhesion between the conductor and the foam insulator. It is.

Note that the outer diameter of the tip of the nipple in the crosshead of the extruder when manufacturing the foam tube is between 0 and 1 of the outer diameter of the conductor.
x ~ 0.8
It is preferable to set it as the range of o, 6y.

In the present invention, plastics that can be hot melt extruded include low-density polyethylene, medium-density polyethylene, high-density polyethylene, polypropylene, ethylene-α-olefin copolymer, ethylene-vinyl acetate copolymer, and copolymer of ethylene and acrylic monomer. Examples include polymers and polybutin. In addition, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), ethylene-tetrafluoroethylene copolymer (ETFE),
chlorotrifluoroethylene copolymer (ECTFE),
Fluorine thread resins such as vinylidene fluoride (PVdF) can also be mentioned.

As blowing agents, chemical blowing agents such as azodicarbonamide and 4,4'-oxybisbenzenesulfonyl hydrazide, inert gases such as nitrogen, argon, and carbon dioxide gas,
hydrocarbons such as methane, propane, butane, and pentane;
Examples include fluorocarbons such as monofluorotrichloromethane, difluorodichloromethane, trifluorotrichloroethane, and tetrafluorodichloroethane.
It may be impregnated or dissolved in the resin in advance (or it may be injected midway through the extruder).

Further, a foaming nucleating agent may be used to facilitate adjustment of the cell diameter and formation of uniform cells. As a foaming nucleating agent,
Examples include boron nitride, silicon oxide, titanium oxide, alumina oxide, and zirconium oxide.

[Examples of the invention] Example 1 PFA (manufactured by Daikin Industries, product name: NEOFLON PF
A AP-210) A mixture containing 0.5 parts by weight of boron nitride per 100 parts by weight was supplied from the hopper of the extruder, and 7 to 8 kg/kg of Freon 115 (trade name of DuPont) was added in the middle of the extruder. After injecting with a pressure of cm'G and uniformly dispersing it in the molten resin, it was extruded using an extrusion nipple with a tip outer diameter of 0.2 mmφ and an extrusion die with an exit inner diameter of 0.5 mmφ, and the inner diameter was 0.3 mmφ. Outer diameter 0.9m
A foamed tube with a diameter of mφ and a degree of foaming of 75% was obtained.

The extrusion conditions for the foamed tube were as follows: using a 20 mm extruder, L/D = 25, compression ratio = 2.5, groove depth of the feeding section = 2.5 mm, and groove depth of the measuring section ~1. Omm, screw rotation speed = 4 rpm, set temperature of each part of the cylinder = 40
The crosshead temperature setting was 370°C, and the die setting temperature was 320°C.

Next, slits were made continuously in the longitudinal direction of the foam tube, an annealed copper wire with an outer diameter of 0.3 mm was inserted, and PFA with a thickness of 0.03 mm was extruded and coated as a reinforcing layer on the outer periphery of the tube to form a foam insulated wire. Manufactured.

The attached drawing shows a cross section of the foam insulated wire produced in this manner, where 1 is a conductor, 2 is a foam insulator, 3 is a slit, and 4 is a reinforcing layer.

Comparative Example 1 A foamed insulated wire was manufactured by extrusion coating PFA on the outer periphery of an annealed copper wire having an outer diameter of 0.3 mmφ under the same conditions as in Example 1. The foam insulation has a foaming ratio of 75% and an outer diameter of 1.1
It was mmφ.

Example 2 Polyethylene (density 0.943, melt index 0
．． 9 g/10 minutes, 1.0 part by weight of azodicarbonamide was added to 100 parts by weight of Showa Denko (manufactured by Kiki, trade name Niziyolex C4309), and the mixture was fed from the hopper of the extruder, and After injecting Freon 114 (trade name of DuPont) and uniformly dispersing them in the molten resin, extrusion was performed using an extrusion nipple with a tip outer diameter of 0.2 mmφ and an extrusion die with an exit inner diameter of 0.5 mmφ. , inner diameter 0.4 mmφ, outer diameter 1. A foamed tube with a diameter of 0 mm and a degree of foaming of 85% was obtained.

Note that the extrusion conditions for the foam tube are as follows: using a 30 mm extruder, L/D = 30, compression ratio = 2.5, and groove depth of the feeding section =
2.5mm, groove depth of measuring part = 1. Omm, screw rotation speed = 5 rpm, set temperature of each part of the cylinder = 200°C
The crosshead set temperature was 150°C and the die set temperature was -130°C.

Next, slits were made continuously in the longitudinal direction of the foam tube, and an annealed copper wire with an outer diameter of 0.4 mm was inserted, and a reinforcing layer of polyethylene with a thickness of 0.03 mm was extruded and coated on the outer periphery of the tube to form a foam insulated wire. Manufactured.

Comparative Example 2 A foamed insulated wire was manufactured by extrusion coating polyethylene on the outer periphery of an annealed copper wire having an outer diameter of 0.4 mmφ under the same conditions as in Example 2. The foaming ratio of the foamed insulator was 85%, and the outer diameter was 1.4 mmφ.

Table 1 shows the results of evaluating the conductor pull-out force of the highly foamed insulated wires of Examples and Comparative Examples. In addition, the conductor pulling force is
Evaluation was carried out by measuring the pulling force when a 100 mm insulated wire was held vertically and the conductor was pulled out at a speed of 100 mm Z.

Table 1 As is clear from Table 1, the insulated wire of the example had a large pulling force of 20 g/100 mm and 50 g/7100 mm, whereas the insulated wire of the comparative example had a gap between the conductor and the insulation coating. Since both were completely separated, the pulling force was O.

"Effects of the Invention" As explained above, according to the present invention, it is possible to realize a thin, highly foamed plastic insulated wire with excellent adhesion between a conductor and a highly foamed insulator.

[Brief explanation of the drawing]

The accompanying drawing is an explanatory cross-sectional view of an example of a highly foamed insulated wire manufactured according to the present invention. l: Conductor 2: Foamed insulator 3 Nislit
4: Reinforcement layer

Claims (1)

[Claims] 1) Introducing hot melt extrudable plastic and a foaming agent into an extruder, uniformly dispersing the foaming agent in the molten plastic, extruding it into a tube shape and foaming it, and then providing this foamed tube around the outer periphery of the conductor. A method of manufacturing a foamed plastic insulated wire characterized by: