Method for manufacturing an electrical insulating wire

Abstract

Method for the manufacture of an electrical insulating wire (200) comprising the steps: - Providing a copper wire (201, 301, 601) coated with a primary coating (202, 602), wherein the primary coating (202, 602) comprises at least one thermoset selected from the group consisting of polyesterimides, THEIC-modified polyesterimides, polyamideimides, polybenzimidazoles, polyesters, polyurethanes, polyimides and combinations thereof, - thermal processing (203, 203a, 603a, 603b, 603c, 603d, 603e) of the primary coating (202, 602) to obtain a surface-textured primary coating (202a, 302a), - Coating the surface-treated primary coating (202a, 302a) with a secondary coating (204, 304), wherein the secondary coating (204, 304) comprises at least one thermoplastic material selected from the group consisting of thermoplastic polyimides, thermoplastic polyamide-imides, polyetherimides, polysulfones, polyphenylsulfones, polyethersulfones, polyphenylene sulfides, polybenzimidazoles, syndiotactic and isotactic polystyrenes, polyacetals, polyphenylene ethers, liquid-crystalline polymers, polyarylates, polyamides (PA), polyaryletherketones, fluoropolymers and combinations thereof, and - Encasing the copper wire (201, 301, 601) coated with a primary coating (202, 602) with a sleeve-like casing (206) that is at least partially permeable for thermal processing (203, 203a, 603a, 603b, 603c, 603d, 603e) prior to thermal processing (203, 203a, 603a, 603b, 603c, 603d, 603e), wherein the thermal processing (203, 203a, 603a, 603b, 603c, 603d, 603e) is processing by means of a UV, IR, SHG / green light or excimer laser (607).

Description

[0001] The invention relates to a method for manufacturing an electrical insulating wire.

[0002] Insulated wires are used in almost every electrical device and appliance. Insulation serves two purposes: firstly, to protect against external influences such as moisture or weathering, and secondly, to protect the environment from electrical currents. Polyesterimides and polyamideimides are very commonly used for wire insulation (as the primary layer). However, a frequent problem is that these materials tend to crack above a certain thickness, which has disastrous consequences for their electrical insulation performance.

[0003] Alternatively, polyetheretherketone (PEEK) coatings can be used for wire insulation, but these are considerably more expensive.

[0004] A good compromise is therefore represented by wire insulations made of polyesterimide or polyamideimide primary layer and PEEK secondary layer, as described in part in the prior art.

[0005] EP 3 193 339 B1 describes an electrical insulating wire, a coil, an electrical / electronic device, and a method for manufacturing an electrical insulating wire. A polyetheretherketone (PEEK) layer is applied to a polyester-based primary layer.

[0006] EP 3 089 170 B1 discloses a multilayer insulated wire, a coil, and electrical / electronic equipment. The multilayer insulated wire comprises a polyester-based resin layer formed from a polyester-based resin containing at least one trivalent or higher-valent alcohol component, on a conductor, and a PEEK resin layer formed from polyetheretherketone or modified polyetheretherketone, either directly on or by applying an intermediate layer to the polyester-based resin layer. Further examples of insulated wires are disclosed in WO 2020 / 205 428 A1, CN 1 02 969 051 A, US 2016 / 0 307 663 A1, US 2017 / 0 004 900 A1, EP 3 093 854 A1, and EP 4 080 525 A1.

[0007] A sulfone polymer composition, which can be used for cables, for example, is disclosed, inter alia, in EP 3 189 092 B1.

[0008] Surface treatment of polymeric materials is described, for example, in WO 2009 / 003 856 A1, in DE 689 18 300 T2, in US 4 803 021 A, in EP 0 245 320 B1, in DE 36 36 395 A1, in EP 3 630 769 A1, in T. Bahners, Optical and Quantum Electronics 1995, 27, 1337-1348, in Kunststoffe 1 / 2010, Carl Hanser Verlag, Munich, and in Praschak et al., Appl. Phys. A 2000, 71, 577-581.

[0009] Occasionally, thermoset layers (e.g., polyesterimides, polyamideimides) and thermoplastic materials (e.g., PEEK) do not adhere sufficiently to each other. Particularly when bending wires, this can lead to delamination, a phenomenon known as tubing, where the thermoplastic secondary layer separates from the thermoset primary layer. Such phenomena can result in production rejects, among other things.

[0010] The object of the present invention was therefore to provide electrical insulating wires and methods for their manufacture which at least partially overcome the disadvantages of the prior art.

[0011] This problem is solved by the method according to claim 1.

[0012] A method according to the invention for producing an electrical insulating wire comprises the following steps: - Providing a copper wire coated with a primary coating, wherein the primary coating comprises at least one thermoset selected from the group consisting of polyesterimides, trishydroxyethyl isocyanurate (THEIC)-modified polyesterimides, polyamideimides, polybenzimidazoles, polyesters, polyurethanes, polyimides and combinations thereof, - thermal processing of the primary coating to obtain a surface-structured primary coating, - Coating the surface-treated primary coating with a secondary coating, wherein the secondary coating comprises at least one thermoplastic material selected from the group consisting of thermoplastic polyimides, thermoplastic polyamide-imides, polyetherimides, polysulfones, polyphenylsulfones, polyethersulfones, polyphenylene sulfides, polybenzimidazoles, syndiotactic and isotactic polystyrenes, polyacetals, polyphenylene ethers, liquid-crystalline polymers, polyarylates, polyamides (PA), polyaryletherketones, fluoropolymers, and combinations thereof, and - Encasing the copper wire coated with a primary coating with a sleeve-like casing that is at least partially permeable to thermal processing prior to thermal processing, wherein the thermal processing is processing using UV, IR, SHG / green light or excimer lasers.

[0013] The copper wire can be a commercially available flat copper wire (e.g. SHTherm® 210 Flat from Synflex) or round copper wire (e.g. SHTherm® V180 from Synflex) or aluminum flat wire (e.g. SHTherm® 210 Flat Alu from Synflex) or aluminum round wire (e.g. SHTherm® 210 Alu from Synflex) for electric machines.

[0014] A typical dimension for a copper or aluminium flat wire in the field of applications for electric machines would be 1.8 x 3.8 mm, for round wires typically 0.75 mm in diameter.

[0015] A method according to the invention comprises the step of providing a copper wire coated with a primary coating, wherein the primary coating comprises at least one thermoset selected from the group consisting of polyesterimides, trishydroxyethyl isocyanurate (THEIC)-modified polyesterimides, polyamideimides, polybenzimidazoles, polyesters, polyurethanes, polyimides, and combinations thereof. The coating material is preferably applied in liquid form as a solution, dispersion, suspension, or melt.

[0016] Thermosets are plastics that cannot be reshaped after curing. The primary coating can consist of a polyesterimide.

[0017] Alternatively, the primary coating can consist of a polyamide-imide.

[0018] Alternatively, the primary coating can also be a combination of at least two of the aforementioned thermosets.

[0019] The primary coating may also contain further additives. These could include thermally conductive additives such as hexagonal boron nitride or magnesium oxide.

[0020] The additives in the primary coating, if present, can be in a quantity ranging from 0.1 to 35 wt.%.

[0021] A method according to the invention further comprises the step of thermally processing the primary coating to obtain a surface-structured primary coating, wherein the thermal processing is processing using UV, IR, SHG / green light or excimer lasers.

[0022] During the thermal processing of the primary coating, preferably at least a portion of the surface of the primary coating facing away from the copper wire is processed. The thermal processing of the surface is preferably always performed in the same way, i.e., there is no treated top and untreated bottom.

[0023] The surface structure of the primary coating after thermal treatment can be either a defined or an arbitrary surface structure. Preferably, it is a defined surface structure that increases the adhesion of a further layer, such as the secondary layer.

[0024] Thermal processing involves processing with UV, IR, SHG / green light, or excimer lasers. Preferably, processing is carried out using a UV laser. Pulsed lasers can also be used. In particular, the laser is a UV laser with a wavelength of 355 nm, a power output of 3 W, and a Q-switching frequency of 40 to 400 kHz. A typical UV laser of this type would be the MD-U1000C from Keyence. Processing speeds can be varied from 1 to 12,000 mm / s. The laser can create rectangular recesses with dimensions of 10 x 10 µm or holes with a diameter of approximately 10 µm and a depth of approximately 3 µm. The depth in the material is primarily determined by the exposure time. Values ​​from the single-digit µm range up to 0.2–0.3 mm are possible.

[0025] UV lasers typically produce sharp contours, which in turn are due to the low heat input (= small heat-affected zone).

[0026] Thermal processing can also involve processing with an IR laser with a wavelength of 1064 nm, a power output of 13-25 W, and pulse operation from 1 to 400 kHz. A typical IR laser of this type would be the MD-X2050A from Keyence.

[0027] Furthermore, the use of green lasers (SHG: second harmonic generation; 532 nm wavelength) is also possible. Technically, IR lasers (1064 nm wavelength) can now be converted into green light (Second harmonic generation = SHG = frequency doubling, resulting in 532 nm) and this in turn into UV light (355 nm).

[0028] Furthermore, excimer lasers with different wavelengths (e.g. 157, 193, 222, 249, 308 and 350 nm) can be used.

[0029] By using UV lasers to treat the surface of the primary layer, such as roughening the polyesterimide or polyamideimide (wire enamel) surface, improved adhesion for the secondary coating (e.g., PEEK) can be achieved. Furthermore, peeling of the secondary coating can be reduced and potentially even prevented, while simultaneously providing good wire insulation. The improved adhesion can be created by undercutting (or slitting) with the pulsed UV laser. Undercutting (or slitting) means that, ideally, the laser creates cavities in the primary wire enamel layer, which are then filled by the secondary layer material, resulting in a strong bond between the primary and secondary layers.

[0030] Laser ablation speeds can range from 1 to 12,000 mm / s.

[0031] In a method according to the invention, the resilience of the wire coating can be improved, which also facilitates the production of electrical components with electrical insulating wires according to the invention, such as in electric motors, for example by reducing the sensitivity of the insulated wires to bending processes. Ultimately, this would also extend the service life of the electrical components, e.g., the electric motors, since insulation damage due to delamination phenomena between the primary and secondary coatings becomes less likely.

[0032] In a further step of a process according to the invention, the surface-treated primary coating is coated with a secondary coating, wherein the secondary coating comprises at least one thermoplastic material selected from the group consisting of thermoplastic polyimides, thermoplastic polyamide imimides, polyetherimides, polysulfones, polyphenylsulfones, polyethersulfones, polyphenylene sulfides, polybenzimidazoles, syndiotactic and isotactic polystyrenes, polyacetals, polyphenylene ethers, liquid crystalline polymers, polyarylates such as polycarbonates, polyester carbonates, polyethylene terephthalates, polybutylene terephthalates, polyamides (PA), etc. B. Polyamide-6 or polyamide-6.6, PA 6.9 (hexamethylenediamine / azelaic acid), PA 6.12 (hexamethylenediamine / dodecanedioic acid), PA 11 (11-aminoundecanoic acid), PA 12 (laurinlactam or ω-aminododecanoic acid), PA 4.6 (tetramethylenediamine / adipic acid), PA 12.12 (dodecanediamine / dodecanedioic acid), PA 6.12 (caprolactam / laurinlactam), PA 10.10 (1,10-Decamethylenediamine / 1,10-Decanedioic acid), polyaryletherketones, in particular polyetheretherketones and polyetherketoneketones, fluoropolymers such as polyvinyl fluorides, polyvinylidene fluorides, polytetrafluoroethylenes, polychlorotrifluoroethylenes, perfluoroalkoxy polymers, ethylene-tetrafluoroethylene copolymers, perfluoro(ethylene-propylene) copolymers and combinations thereof.

[0033] A thermoplastic material is a plastic that can reversibly deform under the influence of heat.

[0034] Preferably, the thermoplastic material is polyetheretherketone (PEEK).

[0035] Alternatively, it can also be a combination of different thermoplastic materials, e.g. polyetheretherketone and polyetherimide, polyetheretherketone and polycarbonate (e.g. according to EP 3 193 339 B1) or polyphenylsulfone and polyetherimide (e.g. according to EP 3 189 092 B1).

[0036] The secondary coating may also contain further additives. These could include thermally conductive additives such as hexagonal boron nitride or magnesium oxide, e.g., in concentrations of 0.1–35 wt.%.

[0037] The secondary coating can be applied by extrusion, hot-dip coating or other suitable methods.

[0038] A method according to the invention further comprises the step of encasing the copper wire coated with a primary coating with a sleeve-like covering that is at least partially permeable to thermal processing prior to thermal processing.

[0039] By using a sleeve-like casing, e.g. a rounded, sleeve-like casing with hole-like recesses, for the coated copper wire, the thermal effect can be reduced.

[0040] The casing can be a template, e.g. made from a sheet of steel.

[0041] The presence of a shell allows the thermal treatment to be limited to very specific areas of the primary coating. For example, this can ensure that, for instance, at most 80%, preferably at most 60%, and more preferably at most 50% of the primary coating is surface-textured.

[0042] The presence of the encapsulation also ensures that the primary coating has a surface structure (e.g., a specific pattern). An encapsulation, used to partially "protect" the wire coating, is frequently employed in high-energy excimer lasers.

[0043] The outer shell is preferably removed before the secondary coating is applied.

[0044] In addition to a casing, a marking laser can also be used for surface structuring of the primary layer. Using a marking laser allows for the creation of a specific surface structure pattern. A marking laser can be a UV laser operating at a wavelength of 355 nm.

[0045] In one embodiment, the primary coating is cured before the thermal treatment.

[0046] The primary coating can have a thickness in the range of 15 µm to 45 µm before thermal treatment. Preferably, the primary coating can have a thickness in the range of 20 µm to 40 µm, more preferably in the range of 25 µm to 30 µm.

[0047] Preferably, the thickness of the wire and the wire coating - along a wire - (primary and secondary coating) are always the same.

[0048] In one embodiment, the secondary coating has a thickness in the range of 120 µm to 200 µm. Preferably, the secondary coating can have a thickness in the range of 140 µm to 180 µm, more preferably in the range of 160 µm to 170 µm.

[0049] The primary coating can be fully or partially surface-treated by thermal treatment. In one embodiment, at least 50% of the primary coating is surface-treated.

[0050] Furthermore, an electrical insulating wire produced according to a method according to the invention is described.

[0051] Furthermore, the use of a method according to the invention for the production of an electrical insulating wire is described.

[0052] The description also includes an electrical insulating wire: - a copper wire, - a surface-structured primary coating for sheathing the copper wire, wherein the primary coating comprises at least one thermoset selected from the group consisting of polyesterimides, THEIC-modified polyesterimides, polyamideimides, polybenzimidazoles, polyesters, polyurethanes, polyimides and combinations thereof, and - a secondary coating in direct contact with the primary coating, wherein the secondary coating comprises at least one thermoplastic material selected from the group consisting of thermoplastic polyimides, thermoplastic polyamide-imides, polyetherimides, polysulfones, polyphenylsulfones, polyethersulfones, polyphenylene sulfides, polybenzimidazoles, syndiotactic and isotactic polystyrenes, polyacetals, polyphenylene ethers, liquid crystalline polymers, polyarylates, polyamides (PA), polyaryletherketones, fluoropolymers and combinations thereof.

[0053] The copper wire, the surface-structured primary coating and the secondary coating can be the respective items as described herein.

[0054] The surface structure is preferably produced by a laser (e.g. a UV, IR, SHG / green light or excimer laser).

[0055] In one embodiment, the surface-structured primary coating has recesses that are filled with the secondary coating. Preferably, the surface is smoothed by the secondary coating, and the recesses can help to increase the adhesion between the primary and secondary coatings.

[0056] Furthermore, the use of an electrical insulating wire according to the invention in an electric machine is described. These electric machines can be used, for example, in motor vehicles, rail vehicles, watercraft, aircraft, in the mining industry, in chemical plant construction, or in robotics.

[0057] Exemplary embodiments of the invention are now described by way of example and with reference to the accompanying drawing, in which: Fig. 1 schematically an embodiment of a method for the production of an electrical insulating wire, Fig. 2 schematically an embodiment of a method according to the invention, Fig. 3 schematically an embodiment of an electrical insulating wire according to the invention. Fig. 4a-4g schematically show different surface structures on primary coatings, Fig. 5a-5e schematically show different elliptical laser ablations of the primary coatings, and Fig. Figures 6a-6e schematically show different thermal treatments.

[0058] An embodiment of a method for producing an electrical insulating wire 100 is described in Fig. Figure 1 shows a copper wire 101 encased in a primary coating 102 made of a thermoset. The primary coating 102 can be polyamide-imide or polyester-imide with a layer thickness of 6 x 5 µm = 30 µm, i.e., six 5 µm thick layers are applied to minimize the probability of layer defects (compared to a single application). The primary coating is thermally treated by a laser (103, 103a) (see, e.g., Figure 1). Fig. 4a-4g, Fig. 5a-5e and Fig. 6a-6e). After thermal treatment, a surface-treated primary coating 102a with recesses is obtained. In a further step, a secondary coating 104 is applied to the surface-treated primary coating 102a. The secondary coating 104 can be a combination of different thermoplastics. For example, the secondary layer can consist of 90 wt.% polyetheretherketone and 10 wt.% polycarbonate. The secondary layer can have a thickness of 170 µm. Preferably, the wire thickness is the same over its entire length. The secondary coating 104 can fill the recesses of the surface-treated primary coating 102a. The secondary coating 104 can be applied to the surface-treated primary coating 102a by extrusion, thus obtaining the electrical insulating wire 105.

[0059] Another embodiment of a method according to the invention for producing an electrical insulating wire 200 is described in Fig. Figure 2 shows a copper wire 201 encased in a primary coating 202 made of a thermoset. The primary coating 202 can be polyamide-imide or polyester-imide with a layer thickness of 6 x 5 µm = 30 µm, i.e., six 5 µm thick layers are applied to minimize the probability of layer defects (compared to a single application). The copper wire 201 coated with the primary coating 202 is encased in a shell with perforations 206. The perforations in the shell 206 serve as a mask for partial laser shielding. The primary coating is thermally treated by a laser (203, 203a) (see, e.g., Figure 203). Fig. 4a-4g, Fig. 5a-5e and Fig. 6a-6e). After thermal treatment, a surface-treated primary coating 202a with recesses is obtained. By using the sleeve-like casing 206, it can be ensured that only certain portions of the primary coating 202 are subjected to thermal treatment by the laser. For example, 50% of the total surface area of ​​the primary coating 202 can be treated in this way. In a further step, a secondary coating 204 is applied to the surface-treated primary coating 202a. The secondary coating 204 can be a combination of different thermoplastics. For example, the secondary coating can consist of 90 wt.% polyetheretherketone and 10 wt.% polycarbonate. The secondary coating can have a thickness of 170 µm. Preferably, the wire thickness is the same over its entire length.The secondary coating 204 can fill the voids in the surface-treated primary coating 202a. In this case, the secondary coating 204 can be applied to the surface-treated primary coating 202a by extrusion, thus obtaining the electrical insulating wire 205.

[0060] Fig. Figure 3 schematically shows an embodiment of an electrical insulating wire 305. The electrical insulating wire 205 has a copper wire 301, a surface-treated primary coating 302a and a secondary coating 304.

[0061] Fig. 4a-4g show different surface structures on primary coatings. Fig. 4a and Fig. Figure 4b shows examples of raster-like laser ablation of the primary coatings. Fig. Figure 4c shows an example of elliptical laser ablation of the primary coating (ellipses transverse, oblique and longitudinal possible), Fig. Figure 4d shows an example of slit-like laser ablation of the primary coating (slits can be transverse, oblique and longitudinal). Fig. Figure 4e shows an example of spot-like laser ablation of the primary coating. Fig. Figure 4f shows an example of laser ablation in a hexagonal structure. Fig. Figure 4g shows an example of laser ablation in a wave-like structure.

[0062] Fig. Figures 5a-5e show various elliptical laser ablations of the primary coatings (possible transversely and longitudinally). Fig. Figure 5a shows an example of laser ablation in a wave-like / sinusoidal structure (possible transversely and longitudinally). Fig. Figure 5b shows an example of laser ablation in a rectangular wave-like structure (possible transversely and longitudinally). Fig. Figure 5c shows an example of laser ablation in a sawtooth wave-like structure (possible transversely and longitudinally). Fig. Figure 5d shows an example of laser ablation in a triangular wave-like structure (possible transversely and longitudinally). Fig. Figure 5e shows a schematic example of laser ablation in a circumferential, spiral-like structure. Mixed forms of laser ablation, such as spot and sinusoidal structures, are also possible. Continuous lines, dotted lines, and combinations thereof are also achievable with laser ablation.

[0063] Fig.Figures 6a-6e show different embodiments of thermal treatments 603a, 603b, 603c, 603d, and 603e. Figure 603a shows a flat wire, such as a copper wire 601 with a primary coating 602, running horizontally and being treated by a laser 607 at two different locations. Figure 603b shows a flat wire, such as a copper wire 601 with a primary coating 602, running horizontally and being treated by a laser 607 at two different locations. The laser 607 acts directly on the surface of the primary coating 602. Part of the radiation from the laser 607 is reflected by a laser mirror 608. The reflected radiation also acts on the surface of the primary coating 602. Fig. 603c shows a round wire, such as a copper wire 601 with primary coating 602, which is subjected to treatment by laser 607 at two different locations.Figure 603d shows a round wire, such as a copper wire 601 with a primary coating 602, which is subjected to thermal treatment at two different locations. Laser 607 acts directly on the surface of the primary coating 602. Part of the radiation from laser 607 is reflected by a laser mirror 608. The reflected radiation also acts on the surface of the primary coating 602. Figure 603e shows a rotating round wire, such as a copper wire 601 with a primary coating 602, which is subjected to treatment by laser 607. Reference symbol list 100, 200 Methods for the production of an electrical insulating wire 101, 201, 301, 601 copper wire 102,202,602 Primary coating 102a, 202a, 302a surface-treated primary coating 103, 103a, 203, 203a, thermal treatment 603a, 603b, 603c, 603d, 603e thermal treatment 104, 204, 304 Secondary coating 105, 205, 305 Electrical insulating wire 206 husk-like casing 607 Laser 608 laser mirrors

Claims

[1] Method for the manufacture of an electrical insulating wire (200) comprising the steps: - Providing a copper wire (201, 301, 601) coated with a primary coating (202, 602), wherein the primary coating (202, 602) comprises at least one thermoset selected from the group consisting of polyesterimides, THEIC-modified polyesterimides, polyamideimides, polybenzimidazoles, polyesters, polyurethanes, polyimides and combinations thereof, - thermal processing (203, 203a, 603a, 603b, 603c, 603d, 603e) of the primary coating (202, 602) to obtain a surface-textured primary coating (202a, 302a), - Coating the surface-treated primary coating (202a, 302a) with a secondary coating (204, 304), wherein the secondary coating (204, 304) comprises at least one thermoplastic material selected from the group consisting of thermoplastic polyimides, thermoplastic polyamide-imides, polyetherimides, polysulfones, polyphenylsulfones, polyethersulfones, polyphenylene sulfides, polybenzimidazoles, syndiotactic and isotactic polystyrenes, polyacetals, polyphenylene ethers, liquid-crystalline polymers, polyarylates, polyamides (PA), polyaryletherketones, fluoropolymers and combinations thereof, and - Encasing the copper wire (201, 301, 601) coated with a primary coating (202, 602) with a sleeve-like casing (206) that is at least partially permeable for thermal processing (203, 203a, 603a, 603b, 603c, 603d, 603e) prior to thermal processing (203, 203a, 603a, 603b, 603c, 603d, 603e), wherein the thermal processing (203, 203a, 603a, 603b, 603c, 603d, 603e) is processing by means of a UV, IR, SHG / green light or excimer laser (607). [2] Method according to claim 1, wherein the thermal treatment (203, 203a, 603a, 603b, 603c, 603d, 603e) is carried out using a UV laser (607). [3] Method according to one of claims 1 or 2, wherein the primary coating (202, 602) is cured before the thermal treatment (203, 203a, 603a, 603b, 603c, 603d, 603e). [4] Method according to any one of claims 1 to 3, wherein the primary coating (202, 602) has a thickness in the range of 15 µm to 45 µm before the thermal treatment (203, 203a, 603a, 603b, 603c, 603d, 603e). [5] Method according to any one of claims 1 to 4, wherein the secondary coating (204, 304) has a thickness in the range of 120 µm to 200 µm. [6] Method according to any one of claims 1 to 5, wherein at least 50% of the surface-treated primary coating (202a, 302a) is laser-treated.

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