JPS6358709A - Conductor insulated with multi-layer high temperature resistant insulating body - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an insulated conductor having a dielectric layer that can withstand relatively high temperatures and mechanical abuse, and its production.

Insulated conductors that can be used satisfactorily at relatively high temperatures, ie, temperatures above 200° C., are desired for many applications, particularly for aircraft and missile equipment. One such insulated conductor is described in Military Subsification Sheet MIL-W-81381/7E, which consists of two screw threads of silver or nickel plated fluorocarbon/polyimide tape. It has a plurality of twisted wires arranged in wire layers. The outer layer of the tape is coated with an aromatic polyimide resin. This tape appears to be the type of film sold under the trademark KAPTON by E.I. DuPont de Nemoret Cambany of Wilmington, P.O.; A combination of fluorinated ethylene-propylene copolymer films for sealing. Polyimide resin coatings are also used for color coding and to provide lubricity and protection from the environment after wrapping the tape.

Although the insulated conductors described above meet the requirements of a temperature rating of 200°C, they have several drawbacks. Their biggest drawback is that the coatings are susceptible to hydrolysis and therefore have problems adhering properly to the tape. Other drawbacks are the need to wrap the two layers on both sides with proper overlap and the problem of maintaining dimensions at the splice points of the tape.

Another insulated conductor is ethylene-tetrafluoroethylene copolymer (ETFE) cross-linked by radiation.
It has two extruded layers. However, such insulators do not fully meet flammability requirements;
Moreover, even the temperature rating of 150° C. is only barely satisfied.

Polyimides, both thermoplastic and thermosetting, have good high temperature properties, but are difficult to apply directly to conductors because of the air present in the interstices of the conductors. Moreover, it is difficult to remove this insulating material because it strongly adheres to the conductor. Polyimide layers that are not nearly completely crosslinked are susceptible to cracking and hydrolysis, while complete crosslinking is difficult under normal manufacturing conditions.

One object of the present invention is to provide an insulated conductor that can have a temperature rating of 200° C. or higher.

Another object of the invention is to solve the above-mentioned problems with insulated conductors.

According to a preferred embodiment of the invention, a first layer of a perfluoroalkoxy resin (PFA) compound or a polytetrafluoroethylene resin (PTFE) compound is extruded over and in contact with the conductor(s). This results in an insulating layer that can withstand temperatures of at least 250° C., and also allows the multilayer insulator to be easily peeled off from the conductor. The outer surface of this first layer is etched by conventional methods, and then a layer of relatively highly concentrated polyimide in a solvent is extruded over the first layer and heated to remove the solvent and form a solidified polyimide. Get the second layer. A third layer of PFA compound, ethylene-tetrafluoroethylene copolymer (ETFE) compound, or polyvinylidene fluoride (I'VDF) compound is then extruded over the second layer. Such a third layer protects the polyimide second layer from the environment.

While in the preferred embodiments described above a ball of insulation layer is extruded onto the conductor or conductor coated with two or more insulation layers, alternative embodiments may extrude a ball of insulation layer onto the conductor or conductor coated with two or more insulation layers, but in other embodiments one or more layers or all layers may be extruded onto the conductor or conductor coated with two or more insulation layers, respectively. It may be applied by the following coating method.

Other objects and advantages of the invention will become apparent from the presently preferred embodiments detailed below. The following description should be understood in conjunction with the accompanying drawings.

FIG. 1 illustrates an insulated conductor of the present invention having a center conductor, in this case consisting of a plurality of copper wires. However, the conductor may also be a single wire. The wires are plated with a metal such as tin, silver, or nickel. If the temperature rating of the insulated conductor is 150°C then tin, if the temperature rating is 200°C then silver higher than 200°C e.g.
50"C, nickel can be used. Of course, nickel can be used for all of the above temperature ratings, and silver can be used for all temperature ratings up to 200"C. The temperature rating of the conductor is Military Svesifice, R John MIL-W-8.
1381A, as determined by the tests described or cited in 1381A. The insulated conductor of the present invention can be heated to temperatures higher than 200°C, for example 2°C, if the wire or wire group is coated with nickel.
Has a temperature rating of 50°C. Of course, in some cases, metal plating can be omitted, especially when it is not necessary to comply with military regulations.

The conductor 1 is covered by a first layer 2 extruded or applied onto it. Layer 2 for easy peeling
is a thermoplastic PFAO layer extruded or applied onto the conductor 1 by conventional wire coating equipment and methods. Alternatively, PTF applied in the form of a paste or extruded around the conductor 1 using conventional wire coating equipment and methods.
covered by a layer of E. PFA extruded layer 2
layer, it is simply cooled after application to the conductor 1. layer 2
If it is a layer made of extruded PTFE, it will be sintered and thermoset by heating.

After the first layer 2 has solidified, it is covered with a second layer 3 which is extruded or applied onto it. More preferably layer 2
To improve the adhesion between layer 3 and layer 3, the outer surface of layer 2 is etched by conventional methods such as using acid or plasma before extruding or coating layer 3.

When the second layer 3 is formed by applying it to the first layer 2, this is done in a conventional manner using a lacquer of thermosetting polyimide in a known solvent. The lacquer may contain other known ingredients to prevent settling of the polyimide or for other purposes.

When the polyimide is a thermoplastic, it can be extruded onto the first layer 2 in the usual manner.

However, in a preferred embodiment, the lacquer contains 20% polyimide solids to have a relatively high viscosity.
]] is extruded onto layer 2. This method allows a relatively thick layer of polyimide, e.g. 1-2 mils, to be formed over layer 2 without passing the layer 2 coated conductor through polyimide lacquer baths multiple times.

2 and 3 illustrate the novel method and apparatus of the present invention for extruding a polyimide-containing lacquer onto an elongated article, such as a conductor l coated with layer 2. FIG. However, the method and apparatus of the present invention does not apply to tubes, rods,
It can also be used to coat other objects such as wire and the like.

As shown in FIG. 2, a conductor coated with layer 2 (6a
) is supplied from a reel 7 through an etching bath 8. In this bath the outer surface of layer 2 is etched and etched. The insulated conductor 6a is then passed through a bath 9 to remove the etching agent and then dried. The conductor 6a further passes around the pulley 10 and changes its direction into a vertical path.

The vertical path is used to prevent the applied lacquer from drooping to one side of the conductor and causing layer 3 to be out of concentricity with respect to the axis of the conductor.

From the pulley 10, the conductor 6a has an extension 12 7,
It passes through the hole of the die insertion part 11 held by the die body 13. The insert 11 has a groove 14 and the body 13 has a groove 15 for receiving a clip (not shown) that holds the insert 11 therein.

As the insulated conductor 6a exits the extension 12, a layer of viscous polyimide lacquer is extruded onto it, replacing the insulated conductor (1-, denoted -q6b) with layers 2 and 3. This insulated conductor 6b is passed through a series of ovens 16 where the lacquer solvent is driven off and the layer 3 is thermally cured. The temperature of the furnace 16 is selected based on the boiling point of the solvent and the temperature required for crosslinking of the polyimide, and the temperature typically increases from the outlet of the furnace 16 to the outlet. For example, the inlet temperature is 250-30
The temperature at the outlet is 600°C. Insulated conductor 6b
The time that the polyimide passes through the oven 16 is selected to remove the solvent and allow crosslinking or heat curing of the polyimide.

The die consists of a body 13 and an insert F$11, but has a cavity 17 around the extension 12. This receives the carrier 23 forming the layer 3 into the body 13 via the opening 18 (see FIGS. 2 and 3). The lacquer 23 is extruded in a tubular manner around the insulated conductor for the extension 12 and shrinks around the layer 2. In addition, since there is an extension part 12, layer 3
has a uniform thickness around the entire circumference and is concentric with the axis of the conductor.

The lacquer containing polyimide is supplied from the metering pump 19;
It is supplied under pressure via a pipe 21, and the pump 19 is fed via a pipe 22 from a normal supply source. To accelerate the crosslinking reaction, the lacquer applied to the openings 18 can contain conventional crosslinking agents such as acetic anhydride or β-picoline. The crosslinking agent was added using a separate metering pump (
The pressure at which the lacquer is fed into the opening 18, preferably by a pump 19 as shown in FIG. depends on several factors, including the viscosity of the insulated conductor and the speed at which the insulated conductor passes through the die. For the types of lacquers mentioned below, this pressure is between 150 and 200 psi (
10.5 to 14 Kgf/cm2).

Polyimide lacquers containing 15% by weight or more of thermosetting polyimide solids are commercially available and are commonly used for coating purposes. Such lacquers also usually contain small amounts of suspending agents, antioxidants and other ingredients. The solvent used depends on various factors, but the solvent content of the polyimide solid
and the solvent used are chosen such that the lacquer has a relatively high viscosity.

Preferably, the content of polyimide solids is greater than or equal to 25% and the viscosity of the lacquer is at least 200,000 centipoise. One suitable solvent is common methylpyrrolidone. A lacquer containing 25 times the thermosetting polyimide solid in such a solvent and having a viscosity of about 240,000 centipoise has been found to be satisfactory. Using such a lacquer and the method and apparatus of the present invention, a thermoset layer 3 of 1 to 2 mils in thickness can be coated in a single pass through the die shown in FIG.

FIG. 4 shows the die insertion section 1 shown in FIGS. 2 and 3.
One variation of 1 is shown. Although the dies of FIGS. 2 and 3 are preferred as they allow better control of the thickness and concentricity of the layer 3, it can be seen that a die with the insert 11a shown in FIG. 4 may also be satisfactory. Will.

In one embodiment shown in FIG. 4, the die body 13 is the same as that in FIGS. 2 and 3, and the insert portion 11a is the extension portion 1.
It is substantially the same as the insertion section 11, except that the extension section 2a is shorter than the extension section 12 or is omitted altogether. Insertion part 11a
In this case, the anchor 23 is angled directly into the insulated conductor 6a within the cavity 17. Due to the disturbance in the flow of the lacquer 23, the insulated conductor 6
It may be moved radially by the lacquer 23 and thus become non-concentric with the axis of the conductor at points in the axial direction of the conductor. However, this can be used depending on the end use of the insulated conductor.

It is preferable to thermally cure the polyimide by heating it together with a crosslinking agent, since the layer 3 is first heated in an oven to remove the solvent, and this heating thermally cures the polyimide along with the removal of the solvent. Needless to say, this can also be achieved using conventional methods. In this way, it is not necessary to use a crosslinking agent, and the polyimide can be cured by heating or by irradiating the layer 3.

After a layer 3 of polyimide lacquer is formed by extrusion or coating onto layer 2, layer 3 is heated in a known manner to drive off the solvent and heat cure the material of layer 3.

After curing layer 3, a third layer 4 is extruded or applied on top of layer 3. The third layer 4 can be a plastic material that withstands the temperatures to which the insulated conductor is exposed and protects the layer 3 from the environment. Preferably the third layer 4 consists of PFA, ETFE or PVDF, but for temperature ratings above 200°C the third layer 4 preferably consists of PFA, which is added to the L of layer 3 in a conventional manner. Extruded or painted. E.T.
When using FE or PVDF, it is extruded or coated on top of layer 3 in conventional manner; optionally, when layer 4 is made of PVDF, layer 4 may be crosslinked by radiation.

The radial thicknesses of layers 2, 3 and 4 are chosen such that the overall radial thickness of the insulation is the desired value. For example, if the desired overall thickness is 7 mils, layers 2 and 4 may each be 3 mils thick, and layer 3 may be 1 mils thick. The thickness of layer 2 and M4 do not have to be the same, but usually layer 3
be larger than the thickness of For example, less than 3 times the thickness of layer 3,
Or more.

The insulated conductor manufactured as described above has at least 1
If it has a temperature rating of 50°C and layer 4 is made of PFA,
Has a temperature rating of 200℃ or higher.

It will be appreciated that in a preferred embodiment, the dimensions and concentricity of each insulating layer can be precisely controlled, and either layer is extruded without multiple passes of the conductor through the liquid. Furthermore, there is no need for tape wrapping or splicing. Also, applying the polyimide resin directly to the conductor and the problems associated therewith are eliminated, and problems such as cracking, peeling, and hydrolysis of the polyimide layer are also avoided or overcome.

The various insulation layers are applied while advancing the conductor in the lengthwise direction.
It can be formed using conventional extrusion equipment used to extrude insulating layers onto conductors. That is, the first layer is extruded around the conductor as it is advanced longitudinally. Once the first layer has solidified, the second layer is extruded onto it while advancing the conductor coated with the first layer longitudinally. Once the second layer has solidified, the conductor coated with the first and second layers is advanced longitudinally and the third layer is extruded thereon. Each layer may be formed individually, i.e., after each layer is formed, the conductor is wound onto a reel and stored, and then fed from the reel to the equipment that forms the next layer, or the appropriate By properly selecting the spacing and processing conditions between the extruders, the insulated conductors of the invention are produced in a continuous operation, feeding the conductor to one end of the production line and removing the finished insulated conductor from the other end. You can also do that.

The insulated conductors of the present invention can be used as is or further surrounded by an insulating layer or conductive copper. A plurality of such conductors may be twisted together in pairs or bundled and covered with a protective sheath. Alternatively, several insulated conductors may be lined up so that their side surfaces touch each other and joined at the contact surfaces.

FIG. 5 shows three insulated conductors 6 of the present invention twisted together,
A sheath 20 of plastic material is shown. The plastic material for the sheath is selected to provide the desired temperature rating, as previously discussed. For example, PFA can be used as the plastic material for temperature ratings of 200°C or higher.

In various embodiments, the plastic material may include conventional fillers that do not substantially adversely affect the desired properties of the cable insulation.

While the preferred embodiments of the invention have been described and illustrated, it will be obvious to those skilled in the art that various modifications can be made without departing from the spirit of the invention.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an insulated conductor of the present invention. FIG. 2 is a partially schematic, partially sectional view showing the method of extruding a polyimide-containing lacquer onto a first layer of conductor. FIG. 3 is an end view of the die shown in FIG. 2. FIG. 4 is a partial cross-sectional view of a variation of the die shown in FIG. FIG. 5 is a cross-sectional view of three twisted insulated conductors of the present invention surrounded by a plastic sheath. 1--1 conductor, 2-111 first layer (extruded PF8 or PTFE resin), 3-111 second layer (extruded polyimide resin),
6---M! , edged conductor FIG, l.

Claims (1)

[Claims] 1. A first layer made of a plastic insulating material selected from perfluoroalkoxy resin and polytetrafluoroethylene resin is in contact with the periphery thereof, and a second layer made of polyimide resin is attached to the first layer. a third layer of a plastic insulating material selected from perfluoroalkoxy resins, ethylene-tetrafluoroethylene copolymer resins and polyvinylidene fluoride resins around the second layer; An insulated conductor with a temperature rating of 150°C or more that is insulated with a plastic insulator. 2. The insulated conductor according to claim 1, wherein the plastic insulating material of the first and third layers is a perfluoroalkoxy resin and has a temperature rating of 200° C. or higher. 3. The insulated conductor of claim 1, wherein the second layer is in contact with the first layer and the third layer is in contact with the second layer. 4. Claim 1, wherein the radial thickness of the first layer and the third layer is greater than the radial thickness of the second layer.
Insulated conductors as described in Section. 5. The insulated conductor according to claim 1, wherein the polyimide resin of the second layer is thermosetting. 6. The insulated conductor of claim 1, wherein at least one of said layers is thermoplastic. 7. The insulated conductor of claim 1, wherein said second layer is an extruded layer. 8. The insulated conductor of claim 1, wherein at least one said layer is an extruded layer. 9. The insulated conductor of claim 1, wherein each of said first, second and third layers is an extruded layer. 10. The insulated conductor of claim 1, wherein at least one said layer is a coated layer. 11. While advancing the conductor longitudinally, forming a first layer of plastic insulation material selected from perfluoroalkoxy compounds and polytetrafluoroethylene compounds around and in contact with the conductor; forming a second layer of insulating material comprising a polyimide compound around the first layer while advancing the conductor having the first and second layers around it; forming a third layer of insulating material around the second layer with longitudinal advancement, selected from compounds of perfluoroalkoxy resins, ethylene-tetrafluoroethylene copolymer resins, and polyvinylidene fluoride resins; A method for manufacturing an insulated conductor with a temperature rating of 150°C or more. 12. The method of claim 11, wherein the outer surface of the first layer is etched before extruding the second layer around the first layer. 13. Forming the second layer around the first layer by extruding a viscous lacquer containing a solvent and polyimide and having a content of polyimide solids of 20% by weight or more, and removing the solvent from the second layer by heating. Claim 1 removing from the two layers
The method described in Section 1. 14. The method of claim 13, wherein the polyimide in the lacquer is heat cured while heating the second layer to remove the solvent. 15. The plastic material of the first layer is a polytetrafluoroethylene resin compound, which is extruded around the conductor in the form of a glue, and before extruding the second layer around the first layer, the first layer is 14. The method as set forth in claim 13, wherein the polytetrafluoroethylene resin compound is thermally cured by heating. 16. The method of claim 15, wherein heating the lacquer at a temperature and time at which the polyimide is thermally cured when heating the second layer to remove the solvent. 17. The method of claim 13, wherein the plastic material of the third layer is a perfluoroalkoxy compound. 18. The method of claim 13, wherein the plastic material of the first and third layers is a perfluoroalkoxy compound. 19. Elongating the elongated article through a die having a passageway having an inlet and an outlet for passing the stretched article and having a cavity around the passageway adjacent to the outlet for receiving a polyimide-containing lacquer under pressure. advancing the article laterally; while advancing the article through the passageway, a viscous lacquer consisting of a solvent and a thermosetting polyimide solid, the content of which is greater than or equal to 15% by weight, is applied from the cavity to the around an elongated article; applying pressure sufficient to cause the lacquer-coated article to flow around the article; while the lacquer-coated article is being advanced, the solvent is removed from it and the polyimide is heat-cured; How to form a layer of polyimide on. 20. The method of claim 19, wherein the lacquered article is advanced along a vertical path. 21, wherein the die has a section between the cavity and the passageway extending to the outlet of the passageway, and around this section another passageway extending from the cavity to an adjacent passageway exit, and the lacquer is 20. A method as claimed in claim 19, in which the flow passes through the further passage around the article as it exits the outlet of the first passage. 22, said passageway having its exit within said cavity, said cavity having an opening facing outwardly of said die at a distance in the direction of article advancement from said passageway exit; 20. The method of claim 19, wherein the flow is carried around the article. 23, the content of polyimide solids in the lacquer is 25
% or more and the viscosity of the lacquer is 200.000 centipoise or more. 24. The method of claim 19, wherein the lacquer coated article is heated for a time and at a temperature sufficient to remove the solvent and heat cure the polyimide. 25. The method of claim 24, wherein the lacquer contains a crosslinking agent.