U.S. patent application number 16/089270 was filed with the patent office on 2019-05-02 for insulated electric conductor.
The applicant listed for this patent is Gebauer & Griller Metallwerk GmbH. Invention is credited to Jurgen Hochstoger, Ewald Koppensteiner, Rudolf Schrayvogel.
Application Number | 20190131037 16/089270 |
Document ID | / |
Family ID | 55697019 |
Filed Date | 2019-05-02 |
![](/patent/app/20190131037/US20190131037A1-20190502-D00000.png)
![](/patent/app/20190131037/US20190131037A1-20190502-D00001.png)
![](/patent/app/20190131037/US20190131037A1-20190502-D00002.png)
United States Patent
Application |
20190131037 |
Kind Code |
A1 |
Hochstoger; Jurgen ; et
al. |
May 2, 2019 |
INSULATED ELECTRIC CONDUCTOR
Abstract
In order to increase the adhesion of an insulating coating (2)
to an electric conductor (1), preferably of copper or aluminum, an
insulated electric conductor comprising an electric conductor (1),
preferably made of copper or aluminum, with an insulating coating
(2) is proposed according to the invention, wherein the insulating
coating (2) either comprises at least one insulating layer (3) made
of thermoplastic material, or the insulating layer (3) and a
plastic-containing intermediate layer (4, 5), obtainable by a
method in which the electric conductor (1) is placed under a
protective gas atmosphere and is bombarded with ions of the
protective gas in a gas plasma in order to remove an oxide layer
formed on a surface of the electric conductor (1) and/or to
increase the surface energy of the electric conductor (1), and
subsequently either the at least one insulating layer (3) 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 surface of the
electric conductor (1) under a protective gas atmosphere.
Inventors: |
Hochstoger; Jurgen; (St.
Valentin, AT) ; Schrayvogel; Rudolf; (St. Leonhard am
Forst, AT) ; Koppensteiner; Ewald; (St. Florian,
AT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Gebauer & Griller Metallwerk GmbH |
Wien |
|
AT |
|
|
Family ID: |
55697019 |
Appl. No.: |
16/089270 |
Filed: |
March 20, 2017 |
PCT Filed: |
March 20, 2017 |
PCT NO: |
PCT/EP2017/056489 |
371 Date: |
September 27, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01B 13/145 20130101;
H01B 13/141 20130101; H01B 13/003 20130101; H01B 3/427 20130101;
H01B 7/0216 20130101; H01B 3/441 20130101; H01B 7/0275 20130101;
H01B 3/301 20130101; H01B 3/307 20130101; H01B 3/306 20130101; H01B
3/305 20130101 |
International
Class: |
H01B 13/14 20060101
H01B013/14; H01B 13/00 20060101 H01B013/00; H01B 7/02 20060101
H01B007/02 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 1, 2016 |
EP |
16163536.2 |
Claims
1. An insulated electric conductor, comprising an electric
conductor having an insulating coating, wherein the insulating
coating either comprises at least one insulating layer made of
thermoplastic material, or at least one insulating layer made of
thermoplastic material and a plastic-containing intermediate layer,
obtainable by a method in which the electric conductor is placed
under a protective gas atmosphere and is bombarded with ions of the
protective gas in a gas plasma in order to remove an oxide layer
formed on a surface of the electric conductor and/or to increase
the surface energy of the electric conductor, and subsequently
either the at least one insulating layer is applied directly to the
surface of the electric conductor under protective gas atmosphere
or, in case the coating comprises the plastic-containing
intermediate layer, at least the plastic-containing intermediate
layer is applied directly under protective gas atmosphere to the
surface of the electric conductor.
2. The insulated electric conductor according to claim 1, wherein
the electric conductor is placed continuously under protective gas
atmosphere until the application of the insulating coating in order
to prevent the formation of a new oxide layer on the surface of the
electric conductor.
3. The insulated electric conductor according to claim 1, wherein
the gas plasma for bombarding the electric conductor is a
low-pressure plasma.
4. The insulated electric conductor according to claim 1, wherein
the insulating coating has a temperature resistance of at least
180.degree. C.
5. The insulated electric conductor according to claim 1, wherein
the thermoplastic material 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.
6. The insulated electric conductor according to claim 1, wherein
the thermoplastic material of the at least one insulating layer is
a polyaryletherketone [PAEK] selected from the group consisting of
polyetherketone [PEK], polyetheretherketone [PEEK],
polyetherketoneketone [PEKK], polyetheretherketoneketone [PEEKK],
polyetherketoneetherketoneketone [PEKEKK] and combinations
thereof.
7. The insulated electric conductor according to claim 1, wherein
the at least one insulating layer has a thickness between 10 and
1000 .mu.m.
8. The insulated electric conductor according to claim 1, wherein
the at least one insulating layer can be produced by means of an
extrusion method.
9. The insulated electric conductor according to claim 1, wherein
the insulating coating consists of the at least one insulating
layer.
10. The insulated electric conductor according to claim 9, wherein
the insulating coating consists of one insulating layer or two
insulating layers or at least two insulating layers.
11. (canceled)
12. The insulated electric conductor according to claim 1, wherein
at least one further insulating layer made of thermoplastic
material is applied to the insulating coating, wherein the at least
one further insulating layer is not applied under a protective gas
atmosphere.
13. The insulated electric conductor according to claim 12, wherein
the thermoplastic material of the at least one further insulating
layer is selected from the group consisting of polyaryletherketone
[PAEK], polyetheretherketone [PEEK], polyimide [PI], polyamideimide
[PAI], polyetherimide [PEI], polyphenylene sulfide [PPS] and
combinations thereof.
14. (canceled)
15. (canceled)
16. (canceled)
17. The insulated electric conductor according to claim 1, wherein
the insulating coating has at least one fluoropolymer layer, and
the plastic-containing intermediate layer which is applied directly
to the surface of the electric conductor consists of the
fluoropolymer layer.
18. The insulated electric conductor according to claim 17, wherein
the fluoropolymer layer comprises polytetrafluoroethylene [PTFE] or
perfluoroethylene propylene [FEP].
19. The insulated electric conductor according to claim 17, wherein
the thickness of the at least one fluoropolymer layer is between 1
.mu.m and 120 .mu.m.
20. The insulated electric conductor according to claim 17, wherein
the entire insulating coating is applied to the electric conductor
under-protective gas atmosphere.
21. An insulated electric conductor, comprising an electric
conductor having an insulating coating, wherein the insulating
coating either comprises at least one insulating layer made of
thermoplastic material, or at least one insulating layer made of
thermoplastic material and a plastic-containing intermediate layer,
further comprising that an oxide layer formed on a surface of the
electric conductor is removed by bombardment of the electric
conductor with ions of a protective gas of a protective gas
atmosphere in a gas plasma, and subsequently either the at least
one insulating layer is applied directly to the oxide-layer-free
surface of the electric conductor or, in case the coating comprises
the plastic-containing intermediate layer, at least the
plastic-containing intermediate layer is applied directly to the
oxide-layer-free surface of the electric conductor.
22. (canceled)
23. The insulated electric conductor according to claim 21, wherein
the thermoplastic material 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.
24. The insulated electric conductor according to claim 21, wherein
the thermoplastic material of the at least one insulating layer is
a polyaryletherketone [PAEK] selected from the group consisting of
polyetherketone [PEK], polyetheretherketone [PEEK],
polyetherketoneketone [PEKK], polyetheretherketoneketone [PEEKK],
polyetherketoneetherketoneketone [PEKEKK], and combinations
thereof.
25. (canceled)
26. (canceled)
27. The insulated electric conductor according to claim 21, wherein
the insulating coating consists of the at least one insulating
layer.
28. The insulated electric conductor according to claim 27, wherein
the insulating coating consists of one insulating layer or two
insulating layers or at least two insulating layers.
29. (canceled)
30. The insulated electric conductor according to claim 21, wherein
at least one further insulating layer of thermoplastic material is
applied to the insulating coating, wherein the at least one further
insulating layer is not applied under protective gas
atmosphere.
31. The insulated electric conductor according to claim 30, wherein
the thermoplastic material of the at least one further insulating
layer is selected from the group consisting of polyaryletherketone
[PAEK], polyetheretherketone [PEEK], polyimide [PI], polyamideimide
[PAI], polyetherimide [PEI], polyphenylene sulfide [PPS] and
combinations thereof.
32. (canceled)
33. (canceled)
34. (canceled)
35. (canceled)
36. (canceled)
37. (canceled)
38. (canceled)
39. A method for producing an insulated electric conductor, which
comprises the following method steps: bombarding an electric
conductor which is arranged under a protective gas, with ions of
the protective gas in a gas plasma in order to remove an oxide
layer formed on the surface of the electric conductor and/or to
increase the surface energy of the electric conductor; applying an
insulating coating to the surface of the electric conductor,
wherein the insulating coating comprises either at least one
insulating layer made of thermoplastic material, or at least one
insulating layer made of thermoplastic material and a
plastic-containing intermediate layer, wherein either the at least
one insulating layer is applied directly to the surface of the
electric conductor under protective gas atmosphere or, in case the
coating comprises the plastic-containing intermediate layer, at
least the plastic-containing intermediate layer is applied directly
under protective gas atmosphere to the surface of the electric
conductor.
40. The method according to claim 39, wherein the thermoplastic
material 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.
41. The method according to claim 39, wherein the thermoplastic
material of the at least one insulating layer (3) is a
polyaryletherketone [PAEK] selected from the group consisting of
polyetherketone [PEK], polyetheretherketone [PEEK],
polyetherketoneketone [PEKK], polyetheretherketoneketone [PEEKK],
polyetherketoneetherketoneketone [PEKEKK] and combinations
thereof.
42. The method according to claim 39, wherein the at least one
insulating layer is extrusion-coated.
43. The method according to claim 39, wherein the electric
conductor is brought to a temperature of at least 200.degree. C.
before the application of the insulating coating.
44. The method according to claim 42, wherein the insulated
electric conductor is cooled after the extrusion-coating of the at
least one insulating layer depending on the achievable strength of
the at least one insulating layer.
45. The method according to claim 42, wherein the insulated
electric conductor is guided via rollers after the
extrusion-coating of the at least one insulating layer.
46. The method according to claim 42, wherein the insulating
coating consists of the at least one insulating layer.
47. The method according to claim 46, wherein the insulating
coating consists of at least two insulating layers and the
insulating coating is produced by tandem extrusion under a
protective gas atmosphere.
48. The method according to one claim 46, wherein at least one
further insulating layer of thermoplastic material is
extrusion-coated onto the insulating coating by means of tandem
extrusion, wherein the extrusion of the at least one further
insulating layer does not take place under protective gas
atmosphere.
49. The method according to claim 48, wherein the thermoplastic
material of the at least one further 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.
50. (canceled)
51. The method according to claim 42, wherein the insulating
coating comprises at least one at least one fluoropolymer layer and
the fluoropolymer layer is applied as a plastic-containing
intermediate layer of the insulating coating under protective gas
atmosphere directly to the surface of the electric conductor.
52. The method according to claim 51, wherein at least one
fluoropolymer layer and the at least one insulating layer are
produced by co-extrusion or tandem extrusion.
53. (canceled)
54. The insulated electric conductor according to claim 5, wherein
the at least one insulating layer has a thickness between 10 and
1000 .mu.m.
55. The insulated electric conductor according to claim 6, wherein
the at least one insulating layer has a thickness between 10 and
1000 .mu.m.
56. The insulated electric conductor according to claim 5, wherein
the at least one insulating layer can be produced by means of an
extrusion method.
57. The insulated electric conductor according to claim 6, wherein
the at least one insulating layer can be produced by means of an
extrusion method.
58. The insulated electric conductor according to claim 5, wherein
the insulating coating consists of the at least one insulating
layer.
59. The insulated electric conductor according to claim 6, wherein
the insulating coating consists of the at least one insulating
layer.
60. The insulated electric conductor according to claim 23, wherein
the insulating coating consists of the at least one insulating
layer.
61. The insulated electric conductor according to claim 24, wherein
the insulating coating consists of the at least one insulating
layer.
62. The method according to claim 40, wherein the at least one
insulating layer is extrusion-coated.
63. The method according to claim 41, wherein the at least one
insulating layer is extrusion-coated.
64. The method according to claim 40, wherein the electric
conductor is brought to a temperature of at least 200.degree. C.
before the application of the insulating coating.
65. The method according to claim 41, wherein the electric
conductor is brought to a temperature of at least 200.degree. C.
before the application of the insulating coating.
66. The insulated electric conductor according to claim 1 wherein
the electric conductor is made of aluminum or copper.
67. The insulated electric conductor according to claim 5 wherein
the electric conductor is made of aluminum or copper.
68. The insulated electric conductor according to claim 6 wherein
the electric conductor is made of aluminum or copper.
69. The insulated electric conductor according to claim 21 wherein
the electric conductor is made of aluminum or copper.
70. The insulated electric conductor according to claim 23 wherein
the electric conductor is made of aluminum or copper.
71. The insulated electric conductor according to claim 24 wherein
the electric conductor is made of aluminum or copper.
72. The method according to claim 39 wherein the electric conductor
is made of aluminum or copper.
73. The method according to claim 40 wherein the electric conductor
is made of aluminum or copper.
74. The method according to claim 41 wherein the electric conductor
is made of aluminum or copper.
Description
FIELD OF THE INVENTION
[0001] The invention relates to an insulated electric conductor
comprising an electric conductor, preferably of copper or aluminum,
having 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 electric
conductor.
DESCRIPTION OF THE PRIOR ART
[0002] Insulated electric 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 electric
conductors comprise a copper electric conductor and a coating
electrically insulating the electric conductor, which usually
comprises one or more layers. In order to ensure the insulation of
the electric conductor, the insulating coating comprises an
insulating layer of thermoplastic material (also called
thermoplastic resin, thermoplastic synthetic material or
thermoplastic polymer).
[0003] While it is advantageous in many applications that the
adhesion of the insulating coating to the electric conductor is
weak to allow easy stripping of the electric conductor, it is
desirable in other applications to ensure the greatest possible
adhesion. Such applications can be found for example in electrical
engineering and in particular in electric motors or transformers,
where the insulated electric conductors are also exposed to an
elevated temperature. The processability of the insulated electric
conductors often requires increased adhesion of the insulating
coating to the electric conductor, in some cases even at high
operating temperatures.
[0004] In order to check the adhesion, a round cut is usually
carried out on the insulated electric conductor perpendicular to a
conductor axis, the electric conductor is stretched by 20% and then
the detachment of the insulating coating from the electric
conductor is measured. The lower the detachment of the insulating
coating from the electric conductor, the better the adhesion.
[0005] In conventional insulated electric conductors having an
insulating coating with an insulating layer which is preferably
highly temperature-resistant, the adhesion between the electric
conductor, in particular made of copper, and the insulating
coating, in particular the insulating layer, is rather low, since
the adhesion of a plastic to the electric conductor is low due to
the surface properties.
OBJECT OF THE INVENTION
[0006] It is therefore an object of the invention to propose an
insulated electric conductor which overcomes the disadvantages of
the prior art and ensures good adhesion between the insulating
coating and the electric conductor.
SUMMARY OF TEE INVENTION
[0007] The electric conductor of generic insulated electric
conductors consists of copper or an alloy with a high copper
content or aluminum or other electrically conductive materials. The
electric conductor is understood to mean both a single conductor
and a strand containing several individual conductors. The
cross-sectional geometry of the electric conductor, which is normal
to a conductor axis, can have any geometric shape: square,
rectangular, circular or elliptical, wherein it is customary to
round off any edges, or they are profiled. The insulation of the
electric conductor is ensured by the at least one provided
insulating layer of thermoplastic material (also called
thermoplastic resin, thermoplastic synthetic material or
thermoplastic polymer), wherein the at least one insulating layer
can advantageously form the outermost layer of the insulating
coating. However, it is also conceivable for one or more additional
insulating layers to be applied to the at least one insulating
layer.
[0008] By contact with oxygen which is unavoidable if the electric
conductor is exposed to the atmosphere, an oxide layer, e.g. copper
oxide or aluminum oxide, forms on the surface of the electric
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
electric conductor.
[0009] However, when the oxide layer is removed, the adhesion of
the layer of the insulating coating applied to the surface of the
electric conductor removed from the oxide layer is significantly
improved. It has been shown 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
electric conductor are removed by the plasma treatment.
[0010] In the plasma treatment, a gas plasma is generated in the
protective gas atmosphere and the electric 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. For example,
nitrogen, argon or hydrogen is suitable as a protective gas or
process gas. The plasma treatment has in addition to the removal of
the oxide layer further positive effects on the insulated electric
conductor: on the one hand, the electric conductor is heated by the
impact energy of the ions on the surface and can be annealed during
the plasma treatment to recrystallize the structure of the electric
conductor; on the other hand, the ion bombardment increases the
surface energy of the electric conductor, which additionally
improves the adhesion of the insulating coating to the surface of
the electric conductor. In this context, this is also referred to
as an activation of the surface of the electric conductor. Another
effect of the plasma treatment is to increase the micro-roughness
of the surface of the electric conductor, which also has a positive
effect on the adhesion of the insulating coating.
[0011] In order to prevent the reformation of an oxide layer on the
surface of the electric conductor, at least part of the insulating
coating is applied to the surface of the electric conductor under a
protective gas atmosphere, preferably under the same protective gas
atmosphere under which the plasma treatment is carried out.
[0012] In order to achieve the object set out above, it is
therefore provided according to the invention that the insulated
electric conductor comprises an electric conductor, preferably of
copper or aluminum, with an insulating coating,
wherein the insulating coating either comprises [0013] at least one
insulating layer made of thermoplastic material, or [0014] at least
one insulating layer made of thermoplastic material and [0015] a
plastic-containing intermediate layer, preferably a plasma polymer
layer or at least one fluoropolymer layer, obtainable by a method
in which the electric conductor is placed under a protective gas
atmosphere and is bombarded with ions of s the protective gas in a
gas plasma in order to remove an oxide layer formed on a surface of
the electric conductor and/or to increase the surface energy of the
electric conductor, and subsequently either [0016] the at least one
insulating layer is applied directly to the surface of the electric
conductor under protective gas atmosphere or, in the case that the
coating comprises the plastic-containing intermediate layer, [0017]
at least the plastic-containing intermediate layer of the
insulating coating is applied directly under protective gas
atmosphere to the surface of the electric conductor.
[0018] An insulated electric conductor according to the invention
has particularly good adhesion properties 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 electric conductor: If a circular
cut is performed around the insulated electric conductor
perpendicular to a conductor axis and the conductor is stretched by
20%, the detachment of the insulating coating from the electric
conductor measured in the direction of the conductor axis is only
at most 3 mm, preferably at most 2 mm, in particular at most 1
mm.
[0019] The adhesion effect is thus achieved in both variants in
that a plastic layer, which preferably consists of plastic, is
applied directly under protective gas atmosphere on the
plasma-cleaned and thus oxide layer-free surface of the electric
conductor. On the one hand, the plastic layer may directly be the
at least one insulating layer made of thermoplastic material if no
intermediate layer is provided. On the other hand, the plastic
layer can 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.
[0020] 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.
[0021] If no plastic-containing intermediate layer is provided and
the insulating layer is applied directly to the surface of the
electric conductor, it is particularly preferred if the insulating
coating consists of the at least one insulating layer, i.e. it has
no further intermediate layers.
[0022] Surprisingly, it has been found in the context of test
series that the detachment of the insulating coating from the
electric conductor usually remains far below 1 mm, in particular at
most 0.2 mm, preferably at most 0.1 mm, more preferably at most
0.05 mm, particularly preferably at most 0.01 mm, when the at least
one insulating layer is applied directly to the surface of the
electric 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].
[0023] The same effects of the invention can be achieved in an
insulated electric conductor comprising an electric conductor,
preferably made of copper or aluminum, having an insulating
coating,
wherein the insulating coating either comprises [0024] at least one
insulating layer made of thermoplastic material, or [0025] at least
one insulating layer made of thermoplastic material and [0026] a
plastic-containing intermediate layer, preferably a plasma polymer
layer or at least one fluoropolymer layer, in such a way that an
oxide layer formed on a surface of the electric conductor is
removed, preferably by bombardment of the electric conductor with
ions of a protective gas of a protective gas atmosphere in a gas
plasma, and subsequently either [0027] the at least one insulating
layer is applied directly to the oxide-layer-free surface of the
electric conductor or, in the case that the coating comprises the
plastic-containing intermediate layer, [0028] at least the
plastic-containing intermediate layer of the insulating coating is
applied directly to the oxide-free surface of the electric
conductor.
[0029] An embodiment variant of the invention provides that the
electric conductor is arranged continuously under a protective gas
atmosphere until the application of the insulating coating in order
to prevent the formation of a new oxide layer on the surface of the
electric conductor. It is also possible to pass through several
protective gas atmospheres in succession, as long as the
plasma-treated electric conductor is arranged uninterruptedly under
one of the inert gas atmospheres.
[0030] In a further embodiment variant of the invention, it is
provided that the gas plasma for bombarding the electric conductor
concerns a low-pressure plasma, preferably having 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.
[0031] In order to enable the use of the insulated electric
conductor in an environment with elevated temperature, for example
in electrical machines with increased operating temperature, it is
provided in a further embodiment variant of the invention that the
insulating coating, in particular the at least one insulating
layer, has a temperature resistance of at least 180.degree. C.,
preferably of at least 200.degree. C., in particular of at least
220.degree. C.
[0032] Particularly good properties in terms of temperature
resistance and resistance to a variety of organic and chemical
solvents, in particular also against hydrolysis, are achieved in a
preferred embodiment of the insulated electric conductor according
to the invention and the method according to the invention in that
the thermoplastic material 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 is
understood 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.
Polyaryletherketones are composed phenyl groups linked by means of
oxygen bridges, i.e. ether or ketone groups, wherein the number and
sequence of ether or ketone groups within the polyaryletherketones
is 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).
[0033] Accordingly, in a particularly preferred embodiment variant
of the insulated electric conductor according to the invention and
the method according to the invention, it is provided that the
thermoplastic material of the at least one insulating layer is a
polyaryletherketone [PAEK] selected from the group consisting of
polyetherketone [PEK], polyetheretherketone [PEEK],
polyetherketoneketone [PEKK], polyetheretherketoneketone [PEEKK],
polyetherketoneetherketoneketone [PEKEKK], and combinations
thereof. Polyetheretherketone [PEEK] has proven to be particularly
suitable for the at least one insulating layer.
[0034] 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 .mu.m, preferably between 25 .mu.m and 750
.mu.m, particularly preferably between 30 .mu.m and 500 .mu.m, in
particular between 50 .mu.m and 250 .mu.m. It is understood 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 is understood that the stated values can relate
both to the thickness of a single layer of the insulating layer and
also to the total thickness of the insulating layer if the
insulating layer comprises more than one layer.
[0035] The at least one insulating layer can be produced cheaply
and quickly if it is applied by an extrusion process, i.e. it is
extrusion-coated. 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.
[0036] 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 electric conductor, a particularly
simple and cost-effective production of an insulated electric
conductor according to the invention is made possible because the
adhesion of the at least one insulating layer to the surface of the
electric conductor by the plasma treatment is already so good that
no intermediate layers are necessary.
[0037] 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 which is directly applied to the surface of the
electric conductor and contains the plastic is the at least one
insulating layer.
[0038] Thus, the particularly preferred embodiment relates to an
insulated electric conductor comprising an electric conductor,
preferably made of copper or aluminum, having an insulating
coating, wherein the insulating coating consists of at least one
insulating layer of thermoplastic material, obtainable by a method
in which the electric conductor is placed under a protective gas
atmosphere and is bombarded with ions of the protective gas in a
gas plasma to remove an oxide layer formed on a surface of the
electric conductor and/or to increase the surface energy of the
electric conductor, and the at least one insulating layer is
applied directly to the surface of the electric conductor, the at
least one insulating layer is applied to the electric conductor
under protective gas atmosphere.
[0039] In the same way, the particularly preferred embodiment also
relates to an insulated electric conductor comprising an electric
conductor, preferably made of copper or aluminum, having 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 an oxide layer
formed on a surface of the electric conductor is removed by
bombardment of the electric conductor with ions of a protective gas
of a protective gas atmosphere in a gas plasma and subsequently the
at least one insulating layer is applied directly to the
oxide-layer-free surface of the electric conductor.
[0040] The insulating coating may, for example, only consist of a
single insulating layer, which is applied directly to the surface
of the electric conductor in order to allow a particularly simple
production.
[0041] However, in order to drastically reduce the likelihood of a
defect in the insulating coating, for example a section of the
electric conductor not provided with the insulating coating due to
an error in the production process of an insulating layer, it is
provided in a further particularly preferred embodiment of the
invention that the insulating coating consists of exactly two or
more than two, for example, three or four, insulating layers. In
this case, a lowermost insulating layer is applied directly to the
surface of the electric conductor, wherein the further insulating
layers are respectively applied to one of the preceding insulating
layers. If a defect has occurred in the lowermost insulating layer,
i.e. if a section of the electric conductor is not covered by the
lowermost insulating layer, then the probability that precisely the
defective section of the lowermost insulating layer will not be
covered by the subsequent insulating layers will be reduced
following an exponential function. The higher the number of
insulating layers, the lower the probability that a portion of the
electric conductor has no insulating coating. In order to achieve
the improved adhesion of the subsequent insulating layers to the
electric conductor, all insulating layers are applied under a
protective gas atmosphere, so that the adhesion of subsequent
insulating layers is ensured in the region of defective sections of
the preceding insulating layers.
[0042] 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
material of the at least one further 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.
[0043] 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 to be applied outside the
protective gas atmosphere 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, so that
the adhesion of the further insulating layer is not improved in the
region of the defective portions of the insulating coating. It is
understood that other insulating layers can be applied, if a
greater thickness of the insulation is required. Therefore, in a
further embodiment variant of the invention, it is provided that at
least one further insulating layer, preferably one, two or three
thereof, is applied to the insulating coating, wherein the at least
one further insulating layer is not applied under a protective gas
atmosphere.
[0044] In a first alternative embodiment variant of the invention,
in order to improve the adhesion of the insulating coating to the
surface of the electric conductor, it is provided that the
insulating coating has a plasma polymer layer of cross-linked
macromolecules of non-uniform chain length applied directly to the
surface of the electric conductor, which plasma polymer layer can
be produced by polymerization of a gaseous monomer in a gas plasma,
preferably in the gas plasma for bombarding the electric conductor.
In other words, the intermediate layer of the insulating coating
which is applied directly to the surface of the electric conductor
and contains plastic 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 electric conductor and, on the other hand, enables increased
adhesion of the layer of the insulating coating, for example the at
least one insulating layer, that is applied to the plasma polymer
layer.
[0045] A further embodiment variant of the first alternative
embodiment provides that the plasma polymer layer has a thickness
of 1 .mu.m or less. Thicknesses of up to one hundredth of a
micrometer are conceivable as the lower limit. Due to the small
layer thickness, the plasma polymer layer has an insignificant
effect on the entire thickness of the insulated electric
conductor.
[0046] 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.sub.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.sub.4 is suitable as a
monomer.
[0047] In a second alternative embodiment, it is provided that the
insulating coating has at least one fluoropolymer layer, applied
directly to the surface of the electric conductor, preferably
comprising polytetrafluoroethylene [PTFE] or perfluoroethylene
propylene [FEP]. The fluoropolymer layer is also distinguished by
excellent adhesion properties, both on the electric 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 electric
conductor. Particularly advantageous adhesion properties are
achieved in that the thickness of the at least one fluoropolymer
layer is between 1 .mu.m and 120 .mu.m, preferably between 5 .mu.m
and 100 .mu.m, particularly preferably between 10 .mu.m and 80
.mu.m, in particular between 20 .mu.m and 50 .mu.m.
[0048] 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 electric
conductor, so that the adhesion of subsequent layers in the region
of defective sections of the preceding layers applied to the
electric conductor is increased, the entire insulating coating is
applied in a preferred embodiment of the invention under a
protective gas atmosphere.
[0049] 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 layer applied directly to the electric conductor
according to the first or second alternative embodiment variant 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 insulating layer
itself or by one or more further layers.
[0050] The invention further relates to a method for producing an
insulated electric conductor, which has the following method steps:
[0051] bombarding an electric conductor placed under a protective
gas, 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 electric
conductor and/or to increase the surface energy of the electric
conductor; [0052] applying an insulating coating to the surface of
the electric conductor, wherein the insulating coating either
comprises [0053] at least one insulating layer made of
thermoplastic material, or [0054] at least one insulating layer
made of thermoplastic material and [0055] a plastic-containing
intermediate layer, preferably a plasma polymer layer or at least
one fluoropolymer layer, wherein either [0056] the at least one
insulating layer is applied directly to [0057] the surface of the
electric conductor under protective gas atmosphere or, in the case
that the coating comprises the plastic-containing intermediate
layer, [0058] at least the plastic-containing intermediate layer of
the insulating coating is applied directly under protective gas
atmosphere to the surface of the electric conductor.
[0059] The electric conductor, preferably made of copper or
aluminum, is subjected to the method in the form of a band or a
wire. In this case, the electric conductor is treated either
"in-line", i.e. directly after the production of the electric
conductor (such as by cold forming or extrusion), according to the
method according to the invention, or the electric conductor is
provided in a wound-up form via a coil outlet. As a rule, the
electric conductor is subjected to a mechanical and/or chemical
pre-cleaning before the plasma treatment. The plasma treatment is
carried out analogously to the previous embodiments, wherein the
electric 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 electric 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 microstructure of the electric
conductor.
[0060] After the plasma treatment, i.e. the removal of the oxide
layer and any impurities from the surface of the electric
conductor, wherein even thin layers (less than 1 .mu.m, preferably
less than 0.1 .mu.m) of the surface of the electric conductor
itself can be removed by bombardment with ions in the gas plasma or
the activation of the surface of the electric conductor, the
insulating coating is applied to the treated surface of the
electric conductor. The insulating coating adheres particularly
well to the surface of the electric conductor due to the removal of
the oxide layer or by the activation of the surface by increasing
the surface energy of the electric conductor. In order to prevent
the formation of a new oxide layer on the surface of the electric
conductor, which would prevent or at least significantly weaken 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, i.e. in particular the plasma
polymer layer or at least one fluoropolymer layer, is applied under
protective gas atmosphere directly to the oxide layer-free surface
of the electric conductor. In particular, it is advantageous if the
electric conductor is arranged continuously under a protective gas
atmosphere until the application of the insulating coating. 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
electric conductor and the subsequent insulating layers are at
least partially applied to the underlying insulating layers.
[0061] Insulated electric conductors produced in this manner show
particularly good adhesion properties as a result of the direct
application of a plastic-containing intermediate layer of the
insulating coating or by the direct application of at least one
insulating layer of thermoplastic material on the plasma-treated,
oxide-free surface of the electric conductor: If a circular cut is
carried out perpendicular to a conductor axis on the insulated
electric conductor and the conductor is stretched by 20%, the
detachment of the insulating coating from the electric conductor
measured in the direction of the conductor axis is only at most 3
mm, preferably at most 2 mm, in particular at most 1 mm.
[0062] If the at least one insulating layer of thermoplastic
material is applied directly to the surface of the electric
conductor, it has been found that the detachment of the insulating
coating from the electric conductor usually remains far below 1 mm,
in particular not more than 0.2 mm, preferably not more than 0.1
mm, more preferably not more than 0.05 mm, particularly preferably
not more than 0.01 mm. Particularly advantageous effects are
achieved when the thermoplastic material 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.
[0063] A variant of the method provides that the at least one
insulating layer is extrusion-coated. Extrusion is a cost-effective
method for applying the insulating layer and is particularly also
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.
[0064] By preheating the electric conductor, which is particularly
advantageous when the at least one insulating layer or the
insulating coating is extruded directly onto the surface of the
electric conductor, a sudden cooling of the plastic-containing
intermediate layer is reduced in contact with the electric
conductor and thus negative influences on the adhesion minimized.
Likewise, it can be provided that the electric conductor is cooled
before applying the insulating coating in order to prevent
excessive heating, such as a melt, of the plastic-containing
intermediate layer in contact with the electric conductor.
Therefore, it is provided in a further preferred embodiment variant
of the method according to the invention that the electric
conductor is brought to a temperature of at least 200.degree. C.,
preferably at least 400.degree. C., prior to the application of the
insulating coating.
[0065] In a further embodiment variant of the invention, it is
provided that after the at least one insulating layer has been
extrusion-coated, the insulated electric conductor is cooled
depending on the strength of the at least one insulating 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
electric 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. If,
for example, the insulated electric conductor is cooled slowly, for
example by cooling in the air, a high degree of crystallinity of
the at least one insulating layer is achieved. It is also
conceivable to provide quenching in a water bath, therefore an
abrupt cooling, or a combination of abrupt and slow cooling.
[0066] In order to further improve the adhesion of the insulating
coating to the electric conductor, in particular if the at least
one insulating layer is applied directly to the surface of the
electric conductor, it is provided in a preferred embodiment of the
method according to the invention that the insulated electric
conductor, after extruding the at least one insulating layer onto
the surface, is guided via rollers, preferably pressure rollers. It
is particularly advantageous in this case if the at least one
insulating layer forms the outermost layer of the insulating
coating. Tight guiding of the insulated electric conductor via the
pressure rollers under pressure of the insulated electric conductor
leads to a particularly good adhesion of the insulating coating or
in particular of the at least one insulating layer on the surface
of the electric conductor. In this case, the boundary surfaces of
the insulating coating between the individual layers, if several
are present, and/or the boundary surfaces of the lowermost layer of
the insulating coating and the surface of the electric conductor
are pressed together, thus enhancing the adhesion effects.
[0067] In a particularly preferred embodiment variant of the
invention, which is characterized by particularly good adhesion
properties, it is provided that the insulating coating consists of
at least one insulating layer and that the at least one insulating
layer is applied directly to the surface of the electrical
conductor as a plastic-containing intermediate layer of the
insulating coating under a protective gas atmosphere. Accordingly,
the following method step is carried out:
[0068] Applying an insulating coating to the surface of the
electric 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 under protective gas
atmosphere directly to the surface of the electric conductor.
[0069] This also achieves the previously mentioned particularly low
detachment of less than 1 mm.
[0070] In order, as mentioned above, to drastically reduce the
probability of a defect in the insulating coating, it is provided
in another embodiment variant 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. Due to the tandem extrusion, the at
least two insulating layers are produced independently of one
another, so that an obstruction of an extrusion tool only causes a
defect in one of the insulating layers. As a result, the defective
section is covered by the subsequent extrusion steps with high
probability.
[0071] If, as stated above, due to the relatively small area of the
defects, improved adhesion can be dispensed with or a thicker
insulating coating is required, a further embodiment variant of the
invention provides that at least one further insulating layer of
thermoplastic material is extruded by tandem extrusion onto the
insulating coating, wherein the extrusion of the further insulating
layer does not take place under a protective gas atmosphere.
[0072] Preferably, the thermoplastic material of the at least one
further 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.
[0073] If the insulating coating comprises at least one
fluoropolymer layer, which is applied as a plastic-containing
intermediate layer directly to the surface of the electric
conductor, the steps required for the production of 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-extrusion or tandem extrusion. Thus, both layers can be produced
in a single manufacturing step and with an extrusion unit.
[0074] In order to improve the adhesion of the insulating coating
to the electric conductor, it is provided in a further embodiment
that a plasma polymer layer is applied directly to the surface of
the electric conductor by polymerization of a gaseous monomer in a
gas plasma as a plastic-containing intermediate layer.
[0075] Since high temperature resistance and high adhesion of the
insulating coating on the electric conductor is important, in
particular in electrical engineering, it is provided according to
the invention that an insulated electric conductor according to the
invention is used as a winding wire for electrical machines,
preferably electric motors or transformers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0076] The invention will now be explained in more detail below
with reference to exemplary embodiments. The drawings are provided
by way of example and are intended to explain the concept of the
invention, but shall in no way restrict it or even render it
conclusively, wherein:
[0077] FIG. 1 shows a schematic representation of a method
according to the invention;
[0078] FIG. 2a shows a first embodiment variant of an insulated
electric conductor with a rectangular cross-section;
[0079] FIG. 2b shows a second embodiment variant of an insulated
electric conductor with a rectangular cross-section.
[0080] FIG. 2c shows a third embodiment variant of an insulated
electric conductor with a rectangular cross-section;
[0081] FIGS. 3a-3c show the first to third embodiment variant with
a round cross-section.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0082] FIG. 1 shows a schematic representation of a method for
producing an insulated electric conductor, as shown in FIGS. 2a to
2d and 3a to 3d. The insulated electric conductor comprises an
electric 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 made of thermoplastic material
(also called thermoplastic resin, thermoplastic synthetic material
or thermoplastic polymer), preferably a high-temperature-resistant
plastic. In the following exemplary embodiments, the at least one
insulating layer 3 is formed as an outer insulating layer 3 and
thus forms the outermost layer of the insulating coating 2. It is
understood, however, that in alternative embodiment variants still
one or more further layers, preferably insulating layers, may be
applied to the insulating layer 3, which can then form the
outermost layer of the insulating coating 2.
[0083] The electric conductor 1 is continuously supplied in the
illustrated embodiment as a band or wire via a coil outlet 7 to the
process and can be prepared for example by means of cold forming
processes, such as drawing or rolling, or extrusion, for example by
means of Conform.RTM. technology. It goes without saying that the
method according to the invention can also be carried out
"in-line", i.e. directly connected to the production process. In a
first step, the electric conductor 1 is pre-cleaned mechanically in
a pre-cleaning unit 8, for example by means of a grinding process,
or chemically, for example by means of suitable solvents or acids,
in order to remove coarse soiling from the electric conductor
1.
[0084] In the next method step, the pre-cleaned electric conductor
1 enters a plasma treatment unit 9 in which a protective gas
atmosphere of nitrogen, argon or hydrogen is present and a gas
plasma in the form of a low-pressure plasma is produced with less
than 20 mbar pressure. However, a low-pressure plasma can already
be produced even at a pressure of less than 80 mbar. In this
low-pressure plasma, the surface of the electric conductor 1 is
bombarded with ions of the protective gas in order to carry off or
remove an oxide layer formed on a surface of the electric conductor
1. At the same time, the electric conductor 1 is soft-annealed by
the plasma treatment and the surface energy of the electric
conductor 1 therefore increases, thus activating the surface.
[0085] By removing the oxide layer and any contaminants from the
surface of the electric conductor 1, wherein it may even be
provided that very thin layers of the electric conductor 1 itself
are removed from the surface, and by the increase of the surface
energy, the adhesion between the electric conductor 1 made of
copper and the insulating coating 2 applied to the electric
conductor 1 can be improved decisively.
[0086] In the first embodiment variant of the insulated electric
conductor according to the invention, shown in FIG. 2a as a flat
conductor with a 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 more than 180.degree. C., preferably above
220.degree. C., so that the insulated electric conductor can be
used even at high operating temperatures. The outer insulating
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
insulating layer 3 may also consist of polyphenylene sulfide [PPS]
or comprise PEEK and/or PPS.
[0087] In order to achieve the increased adhesion between the
electric conductor 1 and the outer insulating layer 3, the electric
conductor 1 reaches the extrusion unit 11 after passing through the
plasma treatment unit 9, in which the outer insulating layer 3 is
extrusion-coated onto the electric conductor 1. In this case, the
electric conductor 1 is preheated to a temperature of at least
200.degree. C., preferably at least 300.degree. C. In order to
prevent the re-formation of an oxide layer, both the extrusion and
the transport of the conductor 1 into the extrusion unit 11 takes
place under a protective gas atmosphere. An insulated electric
conductor produced in this way can be used, for example, as a
winding wire, which is also known in English as a "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 .mu.m in
the present exemplary embodiment.
[0088] 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 electric conductor 1
usually remains well below 1 mm, and is in particular at most 0.2
mm, preferably at most 0.1 mm, more preferably at most 0.05 mm,
particularly preferably at most 0.01 mm. Even if the thermoplastic
material of the insulating layer 3 is polyimide [PI],
polyamideimide [PAI], polyetherimide [PEI], polyphenylene sulfide
[PPS], increased adhesion properties can be achieved.
[0089] In general, the at least one insulating layer 3 may also
comprise two, three, four or more individual insulating layers 3,
all of which are produced under a protective gas atmosphere in the
extrusion unit 11. As a result, the probability of defects in the
insulating coating 2 can be drastically reduced, since defects in
the lowermost of the insulating layers 3 are compensated by
subsequent insulating layers 3. Tandem extrusion processes are
particularly suitable for such a preparation.
[0090] Additionally or instead, it may also be provided that
further insulating layers, which are preferably constructed
analogously to the at least one insulating layer 3, i.e. 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
protective gas atmosphere in a further extrusion unit 12.
[0091] In order to increase the adhesion between the insulating
coating 2 and the electric conductor 1 as an alternative to the
first embodiment variant, the insulating coating 2 comprises in the
second embodiment shown in FIGS. 2b and 3b, in addition to the
outer insulating layer 3 made of PEEK or PPS, a plastic-containing
intermediate layer in form of a plasma polymer layer 4. This plasma
polymer layer 4 is produced in the method according to the
invention in a plasma polymerization unit 10, which is arranged
after the plasma treatment unit 9 and before the extrusion unit 11.
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
surface energy increased, as above, the plasma polymer layer 4 is
formed on the surface of the electric conductor 1 by activating a
gaseous monomer such as ethylene, butenol, acetone or
tetrafluoromethane [CF.sub.4] by the plasma and thereby forming
highly cross-linked macromolecules of different chain length and a
proportion of free radicals, which deposit as a plasma polymer
layer 4 on the surface of the electric conductor 1. In the present
exemplary embodiment, the resulting plasma polymer layer 4 is less
than 1 .mu.m thick and adheres particularly well to the activated
and oxide-free surface of the electric conductor 1.
[0092] The outer insulating layer 3 is in turn extruded in the
extrusion unit 11 onto the plasma polymer layer 4 as described
above, wherein the adhesion between the plasma polymer layer 4 and
the outer insulating layer 3 is also high.
[0093] In the third embodiment variant, illustrated in FIGS. 2c and
3c, the insulating coating 2 comprises, in addition to the outer
insulating layer 3 made of PEEK, a plastic-containing intermediate
layer formed as a fluoropolymer layer 5 of polytetrafluoroethylene
[PTFE] or perfluoroethylene propylene [FEP], which is applied
directly to the surface of the electric conductor 1 and further
improves the adhesion between the electric conductor 1 and the
outer insulating layer 3. The fluoropolymer layer 5 is produced
together with the outer insulating layer 3 in the extrusion unit 11
by means of a co-extrusion or tandem extrusion process. The
thickness of the fluoropolymer layer 5 is about 30 .mu.m in the
present embodiment.
[0094] After extrusion-coating the outer insulating layer 3, the
insulated electric 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 electric conductor. Finally, the insulated electric
conductor is wound on a coil winder 13.
[0095] The illustrated devices in FIG. 1 concern an overview in
which all devices are shown, which are necessary for the production
of the individual embodiment variants. While the sequence, from
right to left, of the devices passed through are independent of the
embodiment variant and in any case the plasma treatment unit 9 and
the extrusion unit 11 have to be passed, the plasma polymerization
unit 9 and the further extrusion unit 12 are optional devices which
are used only in the production of specific design variants. It is
understood that instead of a co-extrusion or tandem extrusion
process, several individual extrusions can be carried out
sequentially.
LIST OF REFERENCE NUMERALS
[0096] 1 Electric conductor [0097] 2 Insulating coating [0098] 3
Insulating layer [0099] 4 Plasma polymer layer [0100] Fluoropolymer
layer [0101] 6 Metal layer [0102] 7 Coil outlet [0103] 8
Precleaning unit [0104] 9 Plasma treatment unit [0105] 10 Plasma
polymerization unit [0106] 11 Extrusion unit [0107] 12 Further
extrusion unit [0108] 13 Coil winder
* * * * *