EP3441986A1 - Insulated electrical conductor - Google Patents

Abstract

In order to increase the adhesion of an insulating coating (2) to an electrical conductor (1), preferably made of copper or aluminum, according to the invention an insulated electrical conductor comprising an electrical conductor (1), preferably made of copper or aluminum, with an insulating coating (2) proposed
wherein the insulating coating (2) either
comprises at least one insulating layer (3) of thermoplastic material,
or
the insulating layer (3) and a plastic-containing intermediate layer (4, 5),
wherein an oxide layer formed on a surface of the electrical conductor (1) is removed
and subsequently either
the at least one insulation layer (3) is applied directly to the oxide layer-free surface of the electrical conductor (1)
or, in the case that the coating (2) comprises the plastic-containing intermediate layer (4, 5),
at least the plastic-containing intermediate layer (4,5) is applied directly to the oxide layer-free surface of the electrical conductor (1).

Description

FIELD OF THE INVENTION

The invention relates to an insulated electrical conductor comprising an electrical conductor, preferably of copper or aluminum, with an insulating coating, wherein the insulating coating comprises at least one outer insulating layer made of thermoplastic material, and to a method for producing such an insulated electrical conductor.

STATE OF THE ART

Insulated electrical conductors are installed in almost any electrical device to conduct electrical current without causing short circuits that may be caused by the contact of non-electrically insulated conductors. Such insulated electrical conductors comprise a copper electrical conductor and a coating electrically insulating the electrical conductor, which usually comprises one or more layers. To insure the insulation of the electrical conductor, the insulating coating comprises an insulating layer of thermoplastic material.

While it is advantageous in many applications, when the adhesion of the insulating coating to the electrical conductor is weak to allow easy stripping of the electrical conductor, it is desirable in other applications to ensure the greatest possible adhesion. Such applications are found for example in electrical engineering and in particular in electric motors or transformers, where the insulated electrical conductors are also exposed to an elevated temperature. The processability of the insulated electrical conductors often requires increased adhesion of the insulating coating to the electrical conductor, in some cases even at high operating temperatures.

In order to check the adhesion, a round cut is usually carried out on the insulated electrical conductor perpendicular to a conductor axis, the electrical conductor is stretched by 20% and then the detachment of the insulating coating from the electrical conductor is measured. The lower the detachment of the insulating coating from the electrical conductor, the better the adhesion.

In conventional insulated electrical conductors having an insulating coating with a, preferably high temperature resistant, insulating layer, the adhesion between the electrical conductor, in particular of copper, and the insulating coating, in particular the insulating layer, rather low, since the adhesion of a plastic to the electrical conductor is low due to the surface properties.

OBJECT OF THE INVENTION

It is therefore an object of the invention to propose an insulated electrical conductor which overcomes the disadvantages of the prior art and ensures good adhesion between the insulating coating and the electrical conductor.

PRESENTATION OF THE INVENTION

The electrical conductor of generic insulated electrical conductors consists of copper or an alloy with a high copper content or aluminum or other electrically conductive materials. Under the electrical conductor is understood to mean both a single conductor and a strand containing several individual conductors. The cross-sectional geometry of the electrical conductor, which is normal to a conductor axis, can have any geometric shape: square, rectangular, circular or elliptical, where it Usually, any edges should be rounded off or profiled. The insulation of the electrical conductor is ensured by the provided at least one insulating layer of thermoplastic material, wherein the at least one insulating layer can advantageously form the outermost layer of the insulating coating. However, it is also conceivable that one or more further insulation layers are applied to the at least one insulation layer.

By contact with oxygen, which is unavoidable if the electrical conductor is exposed to the atmosphere, an oxide layer, for example of copper oxide or aluminum oxide, forms on the surface of the electrical conductor. Extensive series of experiments have shown that the oxide layer has a negative effect on the adhesion properties of a layer of the insulating coating applied to the surface of the electrical conductor.

However, when the oxide layer is removed, the adhesion of the layer of the insulating coating applied to the surface of the electrical conductor removed from the oxide layer is significantly improved. It has been found that the oxide layer can be completely removed by a plasma treatment under an oxygen-free protective gas atmosphere, wherein other impurities can be removed by the plasma treatment. It is even possible that the top atomic layers of the electrical conductor are removed by the plasma treatment.

In the plasma treatment, a gas plasma is generated in the protective gas atmosphere and the electrical conductor in the plasma is bombarded with ions of the protective gas in order to remove at least the oxide layer by the ion bombardment. Suitable protective gas or process gas are, for example, nitrogen, argon or hydrogen. The plasma treatment has, in addition to the removal of the oxide layer, further positive effects on the insulated electrical conductor: on the one hand, the electrical conductor is heated by the impact energy of the ions on the surface and can be annealed during the plasma treatment to On the other hand, the surface energy of the electrical conductor can be increased by the ion bombardment, which additionally improves the adhesion of the insulating coating to the surface of the electrical conductor. One speaks in this context of an activation of the surface of the electrical conductor. Another effect of the plasma treatment is to increase the micro-roughness of the surface of the electrical conductor, which also has a positive effect on the adhesion of the insulating coating.

In order to prevent the reformation of an oxide layer on the surface of the electrical conductor, at least part of the insulating coating is applied to the surface of the electrical conductor under a protective gas atmosphere, preferably under the same protective gas atmosphere under which the plasma treatment is carried out.

In order to solve the problem set out above, in an insulated electrical conductor comprising an electrical conductor, preferably made of copper or aluminum, with an insulating coating
the insulating coating either
comprises at least one insulating layer of thermoplastic material
or
at least one insulating layer of thermoplastic material and a plastic-containing intermediate layer, preferably a plasma polymer layer or at least
a fluoropolymer layer comprising
Therefore, the invention provides that an oxide layer formed on a surface of the electrical conductor, preferably by bombardment of the electrical conductor with ions of a protective gas of a protective gas atmosphere in a gas plasma, is removed
and subsequently either
the at least one insulating layer is applied directly to the oxide layer-free surface of the electrical conductor
or, in the case that the coating comprises the plastic-containing intermediate layer,
at least the plastic-containing intermediate layer of the insulating coating is applied directly to the oxide layer-free surface of the electrical conductor.

An inventive insulated electrical conductor has by the direct application of a plastic-containing intermediate layer of the insulating coating or by the direct application of the insulating layer of thermoplastic material on the plasma-treated and thus oxide layer-free surface of the electrical conductor particularly good adhesion properties: Is a wrap around the insulated electrical conductor vertically carried out to a conductor axis and the conductor stretched by 20% so the detachment of the insulating coating from the electrical conductor measured in the direction of the conductor axis is only a maximum of 3 mm, preferably a maximum of 2 mm, in particular a maximum of 1 mm.

The adhesion effect is thus achieved in both variants in that a plastic layer, which preferably consists of plastic, is applied under protective gas atmosphere directly on the, preferably plasma-cleaned and thereby, oxide layer-free surface of the electrical conductor. On the one hand, the plastic layer may directly be the at least one insulating layer of thermoplastic material if no intermediate layer is provided. On the other hand, the plastic layer may also be a plastic-containing intermediate layer, preferably a plasma polymer layer or at least one fluoropolymer layer. If the insulating coating has a plastic-containing intermediate layer, the at least one insulating layer is preferably applied directly to the plastic-containing intermediate layer. However, it is also conceivable that one or more further intermediate layers are provided between the plastic-containing intermediate layer and the at least one insulating layer.

Although a plurality of different plastics is conceivable which are suitable as material for the plastic-containing intermediate layer of the insulating coating, the plastic-containing intermediate layer of the insulating coating is preferably the plasma polymer layer or the at least one fluoropolymer layer.

If no plastic-containing intermediate layer is provided and the insulating layer is applied directly to the surface of the electrical conductor, it is particularly preferred if the insulating coating consists of the at least one insulating layer, ie has no further intermediate layers.

Surprisingly, it has been found in the context of test series that the detachment of the insulating coating from the electrical conductor usually remains well below 1 mm, in particular at most 0.2 mm, preferably at most 0.1 mm, preferably at most 0.05 mm, particularly preferably at maximum 0.01 mm, is when the at least one insulating layer is applied directly to the surface of the electrical conductor. Particularly advantageous effects can be achieved in that the at least one insulating layer comprises a polyaryletherketone [PAEK], in particular polyetheretherketone [PEEK], or consists of polyaryletherketone [PAEK], in particular polyetheretherketone [PEEK].

A variant of the invention provides that the electrical conductor is arranged continuously until the application of the insulating coating under a protective gas atmosphere in order to prevent the formation of a new oxide layer on the surface of the electrical conductor. It is also possible to pass through several inert gas atmospheres in succession, as long as the plasma-treated electrical conductor is arranged uninterruptedly under one of the inert gas atmospheres.

In a further embodiment variant of the invention, it is provided that the gas plasma for bombarding the electrical conductor is a low-pressure plasma, preferably with a pressure below 80 mbar, which can be produced in a manner known per se. For example, pressures below 50 mbar or even below 20 mbar are conceivable.

In order to enable the use of the insulated electrical conductor in an environment with elevated temperature, for example in electrical machines with increased operating temperature, is provided in a further embodiment of the invention that the insulating coating, in particular the at least one insulating layer, a temperature resistance of at least 180 ° C, preferably of at least 200 ° C, in particular of at least 220 ° C.

Particularly good properties in terms of temperature resistance and resistance to a variety of organic and chemical solvents, in particular against hydrolysis, are achieved in a preferred embodiment of the insulated electrical conductor and the method according to the invention characterized in that the thermoplastic of the at least one insulating layer is selected from the group consisting of polyaryletherketone [PAEK], polyimide [PI], polyamideimide [PAI], polyetherimide [PEI], polyphenylene sulfide [PPS], and combinations thereof. It goes without saying that the thermoplastic material may comprise one or more of the above-mentioned plastics and optionally further constituents, such as fiber material, fillers or other plastics.

Polyaryl ether ketones are composed of oxygen bridges, ie ether or ketone groups, linked phenyl groups, the number and sequence of the ether or ketone groups within the polyaryl ether ketones being variable. Polyimides are plastics whose most important structural feature is the imide group. These include polysuccinimide (PSI), Polybismaleimide (PBMI) and polyoxadiazobenzimidazole (PBO), polyimide sulfone (PISO) and polymethacrylimide (PMI).

Accordingly, in a particularly preferred embodiment of the insulated electrical conductor according to the invention and the method according to the invention, it is provided that the thermoplastic of the at least one insulation layer is a polyaryletherketone [PAEK] selected from the group consisting of polyetherketone [PEK], polyetheretherketone [PEEK], polyetherketone ketone [PEKK ], Polyether ether ketone ketone [PEEKK], polyether ketone ether ketone ketone [PEKEKK], and combinations thereof. Polyetheretherketone [PEEK] has proven particularly suitable for the at least one insulating layer.

In a further embodiment variant of the invention, it is provided that the at least one insulating layer has a thickness between 10 and 1000 μm, preferably between 25 μm and 750 μm, particularly preferably between 30 μm and 500 μm, in particular between 50 μm and 250 μm. It goes without saying that other layer thicknesses are conceivable, for example 40 .mu.m, 60 .mu.m, 80 .mu.m, 100 .mu.m or 200 .mu.m, to name a few possibilities. It goes without saying that the stated values can relate both to the thickness of a single layer of the insulating layer and to the total thickness of the insulating layer if the insulating layer comprises more than one layer.

The at least one insulating layer can be produced cheaply and quickly if it is applied by an extrusion process, that is, it is extruded. Therefore, in a further preferred embodiment variant of the invention, it is provided that the, preferably outer, insulating layer can be produced by means of an extrusion method.

If the insulating coating consists of the at least one insulating layer and the at least one insulating layer is applied directly to the surface of the electrical conductor, a particular simple and inexpensive production of an insulated electrical conductor according to the invention allows, since the adhesion of the at least one insulating layer on the surface of the electrical conductor by the plasma treatment is already so good that no intermediate layers are necessary.

Therefore, in a further particularly preferred embodiment variant of the invention, it is provided that the insulating coating consists of the at least one insulating layer and that the intermediate layer containing the plastic, which is applied directly to the surface of the electrical conductor, is the at least one insulating layer.

Thus, the particularly preferred embodiment relates to an insulated electrical conductor comprising an electrical conductor, preferably made of copper or aluminum, with an insulating coating, wherein the insulating coating consists of at least one insulating layer of thermoplastic material, obtainable by a method in which the electrical conductor below an inert gas atmosphere in a gas plasma is bombarded with ions of the protective gas to remove an oxide layer formed on a surface of the electrical conductor and / or to increase the surface energy of the electrical conductor, and the at least one insulating layer applied directly to the surface of the electrical conductor is applied, the at least one insulating layer under a protective gas atmosphere on the electrical conductor.

In the same way, the particularly preferred embodiment also relates to an insulated electrical conductor comprising an electrical conductor, preferably of copper or aluminum, with an insulating coating, wherein the insulating coating consists of at least one insulating layer of thermoplastic material, wherein according to the invention it is provided that a formed on a surface of the electrical conductor oxide layer by bombardment of the electrical conductor with ions of a Protective gas of a protective gas atmosphere is removed in a gas plasma and subsequently the at least one insulating layer is applied directly to the oxide layer-free surface of the electrical conductor.

The insulating coating may, for example, consist only of a single insulating layer, which is applied directly on the surface of the electrical conductor, in order to allow a particularly simple production.

However, in order to drastically reduce the likelihood of a defect in the insulating coating, for example a portion of the electrical conductor not provided with the insulating coating due to an error in the manufacturing process of an insulating layer, in a further particularly preferred embodiment of the invention, it is provided that the insulating Coating consists of exactly two or more than two, for example, three or four, insulating layers. In any case, a lowermost insulating layer is applied directly on the surface of the electrical conductor, wherein the further insulating layers are respectively applied to one of the preceding insulating layers. If an error has occurred in the lowermost insulation layer, that is to say that a section of the electrical conductor is not covered by the lowermost insulation layer, then the probability that exactly the defective section of the lowermost insulation layer will not be covered by the subsequent insulation layers will not be covered by the subsequent insulation layers. reduced following an exponential function. The higher the number of insulating layers, the lower the probability that a section of the electrical conductor has no insulating coating. In order to achieve the improved adhesion of the subsequent insulation layers to the electrical conductor, all the insulation layers are applied under a protective gas atmosphere, so that the adhesion of subsequent insulation layers in the region of defective sections of the preceding insulation layers is improved.

In principle, at least one, for example one, two, three or four, further insulating layer of thermoplastic material can be applied to the insulating coating or to the insulating coating consisting of the at least one insulating layer. The at least one further insulating layer is preferably constructed analogously to the at least one insulating layer, so that the thermoplastic of the at least one further insulating layer is selected from the group consisting of polyaryletherketone [PAEK], in particular polyetheretherketone [PEEK], polyimide [PI], polyamide-imide [PAI ], Polyetherimide [PEI], polyphenylene sulfide [PPS], and combinations thereof.

Since the defective sections of the at least one insulating layer are generally relatively small areas, it is also conceivable for at least one further insulating layer outside the protective gas atmosphere to be applied to the insulating coating in order to cover any defective sections of the insulating coating in the region of the defective portions of the insulating coating, the adhesion of the further insulating layer is not improved. Of course, other insulation layers can be applied if a greater thickness of the insulation is required. Therefore, in a further embodiment of the invention, it is provided that at least one, preferably one, two or three, further insulating layer is applied to the insulating coating, wherein the at least one further insulating layer is not applied under a protective gas atmosphere.

In a first alternative embodiment variant of the invention, in order to improve the adhesion of the insulating coating to the surface of the electrical conductor, it is provided that the insulating coating has a plasma polymer layer of crosslinked macromolecules of non-uniform chain length applied directly to the surface of the electrical conductor, which plasma polymer layer by polymerization of a gaseous monomer in a gas plasma, preferably in the gas plasma for bombarding the electrical conductor, can be produced. In other words, the intermediate layer of the insulating coating, which is applied directly to the surface of the electrical conductor, is the plasma polymer layer in this exemplary embodiment. The plasma polymer layer serves as an intermediate layer and, on the one hand, adheres excellently to the surface of the electrical conductor and, on the other hand, enables increased adhesion of the layer of the insulating coating applied to the plasma polymer layer, for example the at least one insulation layer.

A further embodiment variant of the first alternative embodiment provides that the plasma polymer layer has a thickness of 1 μm or less. It is conceivable thicknesses up to one hundredth of a micrometer as the lower limit. Due to the small layer thickness, the plasma polymer layer affects only insignificantly on the entire thickness of the insulated electrical conductor.

According to a further embodiment variant of the first alternative embodiment variant, the monomer for producing the plasma polymer layer is ethylene, buthenol, acetone or tetrafluoromethane [CF ₄ ]. The plasma polymer layers formed by these monomers in the plasma are distinguished by particularly good adhesion properties. In particular, if the plasma polymer layer should have similar properties as polytetrafluoroethylene [PTFE] or perfluoroethylene propylene [FEP], CF ₄ is suitable as a monomer.

In a second alternative embodiment, it is provided that the insulating coating has at least one, applied directly to the surface of the electrical conductor, preferably polytetrafluoroethylene [PTFE] or perfluoroethylene propylene [FEP] comprising fluoropolymer layer. The fluoropolymer layer is characterized by excellent adhesion properties, both on the electrical conductor and on the layer applied to the fluoropolymer layer, and serves as an intermediate layer of the insulating coating. It is also conceivable that several fluoropolymer layers, for example two three or four, are applied one above the other to the electrical conductor. Particularly advantageous adhesion properties are achieved in that the thickness of the at least one fluoropolymer layer is between 1 μm and 120 μm, preferably between 5 μm and 100 μm, more preferably between 10 μm and 80 μm, in particular between 20 μm and 50 μm ,

In order to achieve the above-described improved adhesion properties for layers of the insulating coating applied to the plasma polymer layer or the at least one fluoropolymer layer, in particular for the at least one insulating layer, on the electrical conductor, so that the adhesion of subsequent layers in the region of defective sections of the preceding is increased on the electrical conductor applied layers, the entire insulating coating is applied in a preferred embodiment of the invention under a protective gas atmosphere.

In order to reduce the number of different layers in the insulating coating and to keep the associated production costs low, it is provided in a further embodiment of the invention that the at least one insulating layer is applied directly to the plasma polymer layer or the at least one fluoropolymer layer. In other words, the insulating coating consists of at least two layers: the first lower, directly applied to the electrical conductor layer according to the first or second alternative embodiment and the second upper layer in the form of at least one insulating layer of thermoplastic material. The outermost layer of the insulating coating can be formed either by the at least one insulation layer itself or by one or more further layers.

• Beschießen eines unter einer Schutzgasatmosphäre angeordneten elektrischen Leiters, vorzugsweise aus Kupfer oder Aluminium, mit Ionen des Schutzgases in einem Gas-Plasma, vorzugsweise einem Niederdruckplasma, um eine auf der Oberfläche des elektrischen Leiters ausgebildete Oxidschicht zu entfernen und/oder die Oberflächenenergie des elektrischen Leiters zu erhöhen;
• Aufbringen einer isolierenden Beschichtung auf die Oberfläche des elektrischen Leiters, wobei die isolierende Beschichtung entweder
  zumindest eine Isolationsschicht aus thermoplastischem Kunststoff umfasst,
  oder
  zumindest eine Isolationsschicht aus thermoplastischem Kunststoff und
  eine Kunststoff enthaltende Zwischenschicht, vorzugsweise eine Plasmapolymer-Schicht oder zumindest eine Fluoropolymer-Schicht, umfasst
  wobei entweder
  die zumindest eine Isolationsschicht unter Schutzgasatmosphäre unmittelbar auf die Oberfläche des elektrischen Leiters aufgebracht wird
  oder, im dem Fall, dass die Beschichtung die Kunststoff enthaltende Zwischenschicht umfasst,
  zumindest die Kunststoff enthaltende Zwischenschicht der isolierenden Beschichtung unter Schutzgasatmosphäre unmittelbar auf die Oberfläche des elektrischen Leiters aufgebracht wird.

An insulated electrical conductor according to the invention can be produced by a method for producing an insulated electrical conductor, which comprises the following method steps having:

• Shooting an under an inert gas arranged electrical conductor, preferably made of copper or aluminum, with ions of the protective gas in a gas plasma, preferably a low-pressure plasma to remove an oxide layer formed on the surface of the electrical conductor and / or the surface energy of the electrical conductor increase;
• Applying an insulating coating to the surface of the electrical conductor, wherein the insulating coating is either
  comprises at least one insulating layer of thermoplastic material,
  or
  at least one insulating layer of thermoplastic material and
  a plastic-containing intermediate layer, preferably a plasma polymer layer or at least one fluoropolymer layer
  either
  the at least one insulating layer is applied directly to the surface of the electrical conductor under a protective gas atmosphere
  or, in the case that the coating comprises the plastic-containing intermediate layer,
  at least the plastic-containing intermediate layer of the insulating coating is applied directly to the surface of the electrical conductor under a protective gas atmosphere.

The electrical conductor, preferably made of copper or aluminum, is subjected to the process in the form of a band or a wire. In this case, the electrical conductor is either "inline", ie directly after the preparation of the electrical conductor (such as by cold forming or extrusion), treated according to the inventive method or the electrical conductor is provided in a wound-up form via a coil sequence available. In general, the electrical conductor before the plasma treatment is still one subjected to mechanical and / or chemical pre-cleaning. The plasma treatment is carried out analogously to the previous embodiments, wherein the electrical conductor is continuously conveyed through the plasma treatment unit performing the plasma treatment. By suitable choice of the process parameters, the thickness of the layer removed by the plasma treatment from the electrical conductor can be adjusted precisely. In addition, it is also possible to define the temperature for the soft annealing and the associated recrystallization of the structure of the electrical conductor.

After the plasma treatment, ie the removal of the oxide layer and any impurities from the surface of the electrical conductor, wherein even thin layers of the surface of the electrical conductor itself (less than 1 .mu.m, preferably less than 0.1 microns) can be removed by bombardment with ions in the gas plasma or the activation of the surface of the electrical conductor, the insulating coating is applied to the treated surface of the electrical conductor. The insulating coating adheres particularly well on the surface of the electrical conductor due to the removal of the oxide layer or by the activation of the surface by increasing the surface energy of the electrical conductor. In order to prevent the formation of a new oxide layer on the surface of the electrical conductor, which would prevent or at least decisively attenuate the effect according to the invention, either the at least one insulating layer or at least the plastic-containing intermediate layer of the insulating coating, ie in particular the plasma polymer layer or at least one fluoropolymer layer, applied under protective gas atmosphere directly on the oxide layer-free surface of the electrical conductor. In particular, it is advantageous if the electrical conductor is arranged continuously until the application of the insulating coating under a protective gas atmosphere. It goes without saying that, provided that two, three or more insulating layers of thermoplastic material are provided, at least the first of the insulating layers is applied directly to the surface of the electrical conductor and the following Insulation layers are at least partially applied to the underlying insulating layers.

Such isolated electrical conductors produced by the immediate application of a plastic-containing intermediate layer of the insulating coating or by the immediate application of at least one insulating layer of thermoplastic material on the plasma-treated, oxide-free surface of the electrical conductor particularly good adhesion properties: Is a wrap around the insulated electrical conductor performed perpendicular to a conductor axis and the conductor stretched by 20% so the detachment of the insulating coating from the electrical conductor measured in the direction of the conductor axis is only a maximum of 3 mm, preferably a maximum of 2 mm, in particular a maximum of 1 mm.

If the at least one insulating layer of thermoplastic material is applied directly to the surface of the electrical conductor, it has been found that the detachment of the insulating coating from the electrical conductor usually remains well below 1 mm, in particular not more than 0.2 mm, preferably not more than 0.1 mm, preferably not more than 0.05 mm, particularly preferably not more than 0.01 mm. Particularly advantageous effects are achieved when the thermoplastic of the at least one insulating layer is selected from the group consisting of polyaryletherketone [PAEK], in particular polyetheretherketone [PEEK], polyimide [PI], polyamideimide [PAI], polyetherimide [PEI], polyphenylene sulfide [ PPS] and combinations thereof.

A variant of the method provides that the at least one insulating layer is extruded. Extrusion is a cost-effective method for applying the insulation layer and is particularly suitable for PAEK, in particular PEEK, and PPS. The at least one insulating layer can thus also be applied in a simple manner as the outermost layer of the insulating coating.

By preheating the electrical conductor, which is particularly advantageous when the at least one insulating layer or the insulating coating is extruded directly onto the surface of the electrical conductor, a sudden cooling of the plastic-containing intermediate layer is reduced in contact with the electrical conductor and thus negative influences on the adhesion minimized. Likewise, it can be provided that the electrical conductor is cooled before applying the insulating coating in order to prevent excessive heating, such as a melt, the plastic-containing intermediate layer in contact with the electrical conductor. Therefore, in a further preferred embodiment of the method is provided that the electrical conductor is brought to a temperature of at least 200 ° C, preferably at least 400 ° C before applying the insulating coating.

In a further embodiment variant of the method, it is provided that the insulated electrical conductor is cooled after the at least one insulation layer has been extruded, depending on the strength of the at least one insulation layer to be achieved. The adjustment of the mechanical properties of the at least one insulating layer, in particular the mechanical strength, takes place, inter alia, by the defined cooling of the insulated electrical conductor and the consequent adjustment of the degree of crystallization and is particularly important if the at least one insulating layer is the outermost layer the insulating coating is. If, for example, the insulated electrical conductor is cooled slowly, for example by cooling in the air, the crystallinity of the at least one insulation layer is high. It is also conceivable quenching in a water bath, so an abrupt cooling, or a combination of abrupt and slow cooling.

In order to further improve the adhesion of the insulating coating on the electrical conductor, in particular if the at least one insulating layer directly onto the surface of the electrical conductor is applied, is provided in a preferred embodiment of the method, that the insulated electrical conductor after extruding the at least one insulating layer on rollers, preferably pressure rollers, is performed. It is particularly advantageous if the at least one insulating layer forms the outermost layer of the insulating coating. A tight guiding of the insulated electrical conductor via the pressure rollers under pressure of the insulated electrical conductor leads to a particularly good adhesion of the insulating coating or in particular the at least one insulating layer on the surface of the electrical conductor. In this case, the boundary surfaces of the insulating coating between the individual layers, if several are present, and / or the interface of the lowermost layer of the insulating coating and the surface of the electrical conductor are pressed together, thus enhancing the adhesion effects.

In a particularly preferred embodiment of the invention, which is characterized by particularly good adhesion properties, it is provided that the insulating coating consists of the at least one insulating layer and that the at least one insulating layer as a plastic-containing intermediate layer of the insulating coating under a protective gas atmosphere directly on the surface of the electrical Ladder is applied. The following process step is carried out accordingly:
Applying an insulating coating on the surface of the electrical conductor, wherein the insulating coating consists of at least one insulating layer of thermoplastic material and wherein the at least one insulating layer is applied directly under inert gas atmosphere on the surface of the electrical conductor.

As a result, the aforementioned particularly small detachment of less than 1 mm is also achieved.

In order to drastically reduce the probability of a defect in the insulating coating, as already mentioned above, it is provided in another embodiment that the insulating coating consists of at least two, preferably exactly two, insulating layers and the insulating coating is produced by tandem extrusion under a protective gas atmosphere. As a result of the tandem extrusion, the at least two insulation layers are produced independently of one another, so that blockage of an extrusion tool only causes an error in one of the insulation layers. As a result, the defective section is covered by the subsequent extrusion steps with high probability.

If, as stated above, due to the relatively small area of the defect, can be dispensed with improved adhesion or a thicker insulating coating is required, provides a further embodiment of the invention that at least one further insulating layer of thermoplastic material by tandem extrusion on the insulating Coating is extruded, wherein the extrusion of the further insulating layer does not take place under a protective gas atmosphere.

The thermoplastic of the at least one further insulating layer is preferably selected from the group consisting of polyaryletherketone [PAEK], in particular polyetheretherketone [PEEK], polyimide [PI], polyamideimide [PAI], polyetherimide [PEI], polyphenylene sulfide [PPS] and combinations thereof.

If the insulating coating comprises at least one fluoropolymer layer which is applied directly to the surface of the electrical conductor as a plastic-containing intermediate layer, the steps required for producing the insulating coating can be reduced by the fact that the at least one insulating layer and the at least one fluoropolymer Layer can be prepared by co-or tandem extrusion. So both layers in only a single manufacturing step and with an extrusion unit can be produced.

In order to improve the adhesion of the insulating coating to the electrical conductor, it is provided in another embodiment that directly on the surface of the electrical conductor by polymerization of a gaseous monomer in a gas plasma, a plasma polymer layer is applied as a plastic-containing intermediate layer.

Since a high temperature resistance and high adhesion of the insulating coating on the electrical conductor, in particular in electrical engineering is important, it is provided that an inventive insulated electrical conductor is used as a winding wire for electrical machines, preferably electric motors or transformers.

BRIEF DESCRIPTION OF THE FIGURES

The invention will now be explained in more detail with reference to exemplary embodiments. The drawings are exemplary and are intended to illustrate the inventive idea, but in no way restrict it or even reproduce it.

Fig. 1

eine schematische Darstellung eines erfindungsgemäßen Verfahrens;

Fig. 2a

eine erste Ausführungsvariante eines isolierten elektrischen Leiters mit rechteckigem Querschnitt;

Fig. 2b

eine zweite Ausführungsvariante eines isolierten elektrischen Leiters mit rechteckigem Querschnitt;

Fig. 2c

eine dritte Ausführungsvariante eines isolierten elektrischen Leiters mit rechteckigem Querschnitt;

Fig. 3a-3c

die erste bis dritte Ausführungsvariante mit rundem Querschnitt.

Showing:

Fig. 1

a schematic representation of a method according to the invention;

Fig. 2a

a first embodiment of an insulated electrical conductor with a rectangular cross-section;

Fig. 2b

a second embodiment of an insulated electrical conductor with a rectangular cross-section;

Fig. 2c

a third embodiment of an insulated electrical conductor with a rectangular cross-section;

Fig. 3a-3c

the first to third embodiment with round cross-section.

WAYS FOR CARRYING OUT THE INVENTION

Fig. 1 shows a schematic representation of a method for producing an insulated electrical conductor, as shown in the FIGS. 2a to 2d or. 3a to 3d is shown. The insulated electrical conductor comprises an electrical conductor 1 made of copper, wherein other materials such as aluminum are conceivable, and an insulating coating 2, which has at least one insulating layer 3 of thermoplastic, preferably high temperature resistant, plastic. In the following exemplary embodiments, the at least one insulation layer 3 is formed as an outer insulation layer 3 and thus forms the outermost layer of the insulating coating 2. However, it is self-evident that in alternative embodiments on the insulation layer 3, one or more further layers, preferably Insulation layers may be applied, which can then form the outermost layer of the insulating coating 2.

The electrical conductor 1 is continuously supplied in the illustrated embodiment as a belt or wire via a coil outlet 7 to the process and can be prepared for example by means of cold forming process, such as drawing or rolling, or extrusion, for example by means of Conform® technology. It goes without saying that the method according to the invention can also be carried out "in-line", that is, directly connected to the production process. In a first step, the electrical conductor 1 is prepurified in a pre-cleaning unit 8 mechanically, for instance by means of a grinding process, or chemically, for instance by means of suitable solvents or acids, in order to remove coarse dirt from the electrical conductor 1.

In the next process step, the pre-cleaned electrical conductor 1 enters a plasma treatment unit 9 in which a protective gas atmosphere of nitrogen, argon or hydrogen prevails and a gas plasma in the form of a low-pressure plasma with less than 20 mbar pressure is produced. However, a low pressure plasma can already at a pressure of less than 80 mbar are produced. In this low-pressure plasma, the surface of the electrical conductor 1 is bombarded with ions of the protective gas in order to remove or remove an oxide layer formed on a surface of the electrical conductor 1. At the same time, the electrical conductor 1 is soft-annealed by the plasma treatment and the surface energy of the electrical conductor 1 therefore increases, activating the surface.

By removing the oxide layer and any impurities from the surface of the electrical conductor 1, it may even be provided that very thin layers of the electrical conductor 1 itself are removed from the surface, and the increase of the surface energy, the adhesion between the electrical conductor. 1 made of copper and the applied on the electrical conductor 1 insulating coating 2 are decisively improved.

In the first embodiment of the insulated electrical conductor according to the invention, shown in FIG FIG. 2a as flat conductor with rectangular cross section and in Fig. 3a With a round cross-section, the insulating coating 2 consists only of an insulating layer 3. The insulating layer 3 has a temperature resistance of over 180 ° C, preferably of over 220 ° C, so that the insulated electrical conductor can be used even at high operating temperatures. The outer insulation layer 3 consists of polyetheretherketone [PEEK], which has both high temperature resistance and high resistance to a large number of organic and inorganic substances. Alternatively, the outer insulation layer 3 may also consist of polyphenylene sulfide [PPS] or comprise PEEK and / or PPS.

In order to achieve the increased adhesion between the electrical conductor 1 and the outer insulation layer 3, after passing through the plasma treatment unit 9, the electrical conductor 1 passes into the extrusion unit 11 in which the outer insulation layer 3 extrudes onto the electrical conductor 1 becomes. In this case, the electrical conductor 1 is preheated to a temperature of at least 200 ° C, preferably at least 300 ° C. In order to prevent the re-formation of an oxide layer, both the extrusion and the transport of the conductor 1 in the extrusion unit 11 takes place under a protective gas atmosphere. An insulated electrical conductor produced in this way can be used, for example, as a winding wire, which is also known in English as "magnet wire", in an electric machine, such as an electric motor or a transformer. The thickness of the outer insulating layer 3 is about 30 microns in the present embodiment.

In particular, when the insulating layer 3 consists of a polyaryletherketone [PAEK] such as polyetheretherketone [PEEK], particularly good adhesion properties are achieved. Thus, the detachment of the insulating layer 3 from the electrical conductor 1 usually remains well below 1 mm, and in particular is at most 0.2 mm, preferably at most 0.1 mm, preferably at most 0.05 mm, particularly preferably at most 0.01 mm. Even if the thermoplastic material of the insulation layer 3 is polyimide [PI], polyamide-imide [PAI], polyetherimide [PEI], polyphenylene sulfide [PPS], increased adhesion properties can be achieved.

In general, the at least one insulation layer 3 may also comprise two, three, four or more individual insulation layers 3, all of which are produced under a protective gas atmosphere in the extrusion unit 11. As a result, the probability of errors in the insulating coating 2 can be drastically reduced, since errors in the lowermost of the insulation layers 3 are compensated by subsequent insulation layers 3. Tandem extrusion processes are particularly suitable for such a preparation.

In addition or instead, it may also be provided that further insulation layers, which are preferably constructed analogously to the at least one insulation layer 3, ie in particular of a polyaryletherketone [PAEK] such as Polyetheretherketone [PEEK] or another of the aforementioned plastics, are applied to the insulating coating 2 outside the inert gas atmosphere in a further extrusion unit 12.

In order to increase the adhesion between the insulating coating 2 and the electrical conductor 1 as an alternative to the first embodiment, the insulating coating 2 in the in Figures 2b and 3b illustrated second embodiment in addition to the outer insulation layer 3 made of PEEK or PPS a plastic-containing intermediate layer in the form of a plasma polymer layer 4. This plasma polymer layer 4 is prepared in the process according to the invention in a plasma polymerization unit 10, after the plasma treatment unit 9 and the extrusion unit 11 is arranged. It is also conceivable that the plasma treatment and the plasma polymerization are carried out in a combined device. In the plasma polymerization unit 10, after the oxide layer is removed and the surface energy increased, as above, the plasma polymer layer 4 is formed on the surface of the electrical conductor 1 by reacting a gaseous monomer such as ethylene, butenol, acetone or tetrafluoromethane [CF ₄ ] is activated by the plasma and thereby highly crosslinked macromolecules of different chain length and a proportion of free radicals form, which deposit as a plasma polymer layer 4 on the surface of the electrical conductor 1. In the present exemplary embodiment, the resulting plasma polymer layer 4 is less than 1 μm thick and adheres particularly well to the activated and oxide-free surface of the electrical conductor 1.

The outer insulation layer 3 is in turn extruded onto the plasma polymer layer 4 in the extrusion unit 11 as described above, whereby the adhesion between the plasma polymer layer 4 and the outer insulation layer 3 is also high.

In the third embodiment, shown in the Figures 2c and 3c 1, the insulating coating 2 includes, besides the outer insulating layer 3 of PEEK, a fluoropolymer layer 5 formed from polytetrafluoroethylene [PTFE] or perfluoroethylene propylene [FEP] plastic containing intermediate layer which is applied directly to the surface of the electrical conductor 1 and the adhesion between the electrical conductor 1 and the outer insulating layer 3 further improved. The fluoropolymer layer 5 is produced together with the outer insulation layer 3 in the extrusion unit 11 by means of a co-or tandem extrusion process. The thickness of the fluoropolymer layer 5 is in the present embodiment about 30 microns.

After extruding the outer insulation layer 3, the insulated electrical conductor is cooled in a controlled manner, for example by air cooling, and passed over a series of pressure rollers which further improve adhesion by applying pressure to the insulated electrical conductor. Finally, the insulated electrical conductor is wound on a Spulenaufwickler 13.

In the illustrated devices in Fig. 1 it is an overview, in which all the facilities are shown, which are necessary for the production of the individual variants. While the order, from right to left, of the devices passed through are independent of the embodiment and in any case, the plasma treatment unit 9 and the extrusion unit 11 have to be traversed, the plasma polymerization unit 9 and the further extrusion unit 12 optional equipment that is used only in the production of specific design variants. It goes without saying that instead of a co-or tandem extrusion process, several individual extrusions can be carried out sequentially.

LIST OF REFERENCE NUMBERS

1

electrical conductor

2

insulating coating

3

insulation layer

4

Plasma polymer layer

5

Fluoropolymer layer

6

metal layer

7

package unwinding

8th

Pre-cleaning unit

9

Plasma treatment unit

10

Plasma polymerization unit

11

Extrusion unit

12

further extrusion unit

13

Spulenaufwickler

Claims (16)

Includes insulated electrical conductor
an electrical conductor (1), preferably made of copper or aluminum, with an insulating coating (2),
wherein the insulating coating (2) either
at least one insulating layer (3) made of thermoplastic material
or
at least one insulating layer (3) made of thermoplastic material and a plastic-containing intermediate layer (4, 5), preferably a plasma polymer layer (4) or at least one fluoropolymer layer (5),
characterized in that on a surface of the electrical conductor (1) formed oxide layer, preferably by bombardment of the electrical conductor (1) with ions of a protective gas of a protective gas atmosphere in a gas plasma, is removed
and subsequently either
the at least one insulating layer (3) directly on
the oxide layer-free surface of the electrical conductor (1) is applied
or, in the case that the coating (2) comprises the plastic-containing intermediate layer (4, 5),
at least the plastic-containing intermediate layer (4,5) is applied directly to the oxide layer-free surface of the electrical conductor (1). Insulated electrical conductor according to claim 1, characterized in that on the surface of the electrical conductor (1) formed oxide layer by bombardment of the electrical conductor is removed with ions of a protective gas of a protective gas atmosphere in a gas plasma. Insulated electrical conductor according to claim 1 or 2, characterized in that the insulating coating (2), in particular the at least one insulating layer (3), a temperature resistance of at least 180 ° C, preferably of at least 200 ° C, in particular of at least 220 ° C. , having. Insulated electrical conductor according to one of claims 1 to 3, characterized in that the thermoplastic of the at least one insulating layer (3) is selected from the group consisting of polyaryletherketone [PAEK], polyimide [PI], polyamide-imide [PAI], polyetherimide [PEI ], Polyphenylene sulfide [PPS] and combinations thereof. Insulated electrical conductor according to one of Claims 1 to 4, characterized in that the thermoplastic of the at least one insulating layer (3) is a polyaryletherketone [PAEK] selected from the group consisting of polyetherketone [PEK], polyetheretherketone [PEEK], polyetherketone ketone [PEKK] , Polyether ether ketone ketone [PEEKK], polyether ketone ether ketone ketone [PEKEKK], and combinations thereof. Insulated electrical conductor according to one of Claims 1 to 5, characterized in that the at least one insulation layer (3) has a thickness between 10 and 1000 μm, preferably between 25 μm and 750 μm, particularly preferably between 30 μm and 500 μm, in particular between 50 μm and 250 μm. Insulated electrical conductor according to one of claims 1 to 6, characterized in that the at least one insulating layer (3) can be produced by means of an extrusion method. Insulated electrical conductor according to one of Claims 1 to 7, characterized in that the insulating coating (2) consists of the at least one insulating layer (3). Insulated electrical conductor according to claim 8, characterized in that the insulating coating (2) consists of an insulating layer (3). Insulated electrical conductor according to claim 8, characterized in that the insulating coating (2) consists of at least two, preferably exactly two, insulating layers (3). Insulated electrical conductor according to one of claims 1 to 10, characterized in that at least one further insulating layer of thermoplastic material is applied to the insulating coating (2), wherein the at least one further insulating layer is not applied under a protective gas atmosphere. Insulated electrical conductor according to claim 11, characterized in that the thermoplastic of the at least one further insulating layer is selected from the group consisting of polyaryletherketone [PAEK], preferably polyetheretherketone [PEEK], polyimide [PI], polyamide-imide [PAI], polyetherimide [PEI ], Polyphenylene sulfide [PPS] and combinations thereof. Insulated electrical conductor according to one of Claims 1 to 7, characterized in that the insulating coating (2) has at least one fluoropolymer layer (5)
and that the intermediate layer applied to the plastic directly on the surface of the electrical conductor (1) is the fluoropolymer layer (5). An insulated electrical conductor according to claim 13, characterized in that the fluoropolymer layer (5) comprises polytetrafluoroethylene [PTFE] or perfluoroethylene propylene [FEP]. Insulated electrical conductor according to one of claims 13 to 14, characterized in that the thickness of the at least one fluoropolymer layer (5) between 1 .mu.m and 120 .mu.m, preferably between 5 .mu.m and 100 .mu.m, more preferably between 10 .mu.m and 80 .mu.m, in particular between 20 microns and 50 microns, is. Insulated electrical conductor according to one of Claims 13 to 15, characterized in that the entire insulating coating (2) is applied to the electrical conductor (1) under a protective gas atmosphere.

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