DE10163797A1 - Coating metal conductors, especially wire, comprises applying a coating of a wire lacquer comprising a heat-curable binder and curing the coating with near infrared radiation - Google Patents

Abstract

Process for coating metal conductors comprises applying a coating of a wire lacquer comprising a heat-curable binder and curing the coating with near infrared radiation. An Independent claim is also included for a metal conductor coated and cured as above.

Description

The invention relates to a method for painting metallic conductors for production an electrically insulating coating with improved color stability.

Electrical conductors, e.g. B. Wires are usually covered with an insulating coating provided, which are based on conventional wire coating agents, for example Basis of polyester, polyester imides and hydroxyl-containing polyesters. Furthermore, it is known to use compositions for electrical insulating coatings, which, for example, titanium acid esters or complexes of organic titanium compounds (Titanium chelates) and / or the corresponding vanadium or zirconium Connections included. Such compounds serve as a catalyst or Crosslinker in the film formation reaction. The electrical insulating varnishes have a improved hardness, adhesive strength, permanent temperature and heat shock resistance as well also has improved partial discharge resistance.

Wire enamels can usually be applied to the metallic after nozzle or felt application Applied ladder and using conventional methods such. B. convection and / or IR heat to be burned in. The painting speed and the temperature are matched to one another in such a way that optimal branding is possible of the wire enamel results. The serves as a measure of the degree of burn-in of the wire enamel Determination of the tangent δ of the paint film (DIN EN 60851). In addition, the color of the baked paint film a first indication of the degree of baking and a essential criterion to be able to make a decision in advance, whether the stoving process is close to the optimum.

Through various undesirable thermal decomposition processes, the Lacquer film, however, appear dark. A conclusion on the degree of stoving is therefore hardly recognizable from the coloring of the burned-on lacquer film.

The object of the present invention is a method for coating to provide metallic conductor, which makes it possible, after the Hardening the wire enamel to achieve significantly lighter enamel film layers and thus to enable the degree of burn-in to be recognized. In addition, the Properties such as surface quality and flexibility of the coating are guaranteed his.

• a) Auftrag mindestens einer Überzugsschicht aus einer Drahtlack-Zusammensetzung, welche ein thermisch härtbares Bindemittelsystem enthält, auf die Oberfläche eines metallischen Leiters, insbesondere eines Drahtes und
• b) thermische Härtung der Überzugsschicht(en) durch Bestrahlung mit Nahinfrarot- Strahlung.

It has been shown that this object can be achieved by a process for coating metallic conductors, in particular wires, which is composed of the successive process steps:

• a) application of at least one coating layer of a wire enamel composition, which contains a thermally curable binder system, to the surface of a metallic conductor, in particular a wire and
• b) thermal curing of the coating layer (s) by irradiation with near infrared radiation.

The wire enamel composition can be applied directly to the uncoated the wire or on the pre-coated wire. The coating is then hardened with near infrared radiation. In general, irradiation with near infrared radiation leads to a complete one Hardening of the wire enamel composition.

A combination of curing by irradiation with near infrared Radiation and thermal curing by conventional methods of Heat supply without near-infrared radiation are used, e.g. Burning in an oven or by IR heat radiation.

If, for example, an additional oven hardening is used, the hardening can be carried out by Near infrared radiation at any time in the method according to the invention after the wire enamel composition has been applied, for example before or after thermal curing in the oven. For example. can follow the Near infrared radiation thermal curing by means of convection and / or IR Connect heat, or thermal curing using convection and / or IR Heat can precede curing by near-infrared radiation.

The coating and thermal hardening according to the invention can, if necessary, several Times in succession. The inventive method is suitable for one Single-layer application and its hardening as well as for a multi-layer application appropriate hardening between the individual layers or the hardening according to the invention after completion of the order.

The expression used in the description and in the claims "Hardening" means hardening in the sense of chemical crosslinking of the wire enamel Composition by forming chemical bonds between the Components of the thermally curable binder system and the application of non-reactive, dissolved polymers on the conductor by evaporating the in the Composition contained solvents.

Known wire enamels can be used for the process according to the invention. Compositions are used. The wire enamels can be used as primers, Basecoat and / or top coat as well as in combination. The usual wire enamel compositions can be coatings, for example. Insulation coatings, which as a top coat, the improved mechanical Protection as well as the creation of the desired surface property and the Serve smoothing. The topcoat compositions are then particularly suitable For example, compositions based on polyamides, poyamidimides, Polyimides and epoxides.

The wire enamel compositions are based, for example, on binders such as polyester, Polyesterimides, polyurethanes, polyamides, polyamideimides, THEIC polyesterimides, Polyimides, polyvinyl acetals, epoxies, acrylate resins.

Polyester and / or polyester imides, in particular THEIC Polyester imides, as well as polyamides and polyamide imides are used.

As polyester, for example, those used for wire coating can be used are known. This can also polyester with heterocyclic, nitrogen-containing Rings, for example polyester with condensed imide and hydantoin and Benzimidatol structures.

The polyesters are in particular condensation products made from polyvalent ones aliphatic, aromatic and / or cycloaliphatic carboxylic acids or their Anhydrides, polyhydric alcohols, in the case of imide-containing compounds containing polyesteramino groups, optionally with a proportion of monofunctional compounds, for example monohydric alcohols. Unsaturated polyester resins and / or polyesterimides can also be used. The saturated polyesterimides are preferably based on Therephthalic acid polyesters, which in addition to diols and also polyols and as additional Dicarboxylic acid component is a reaction product of diaminodiphenylmethane and Trimellitic anhydride may contain. Saturated polyesters and / or polyester imides are preferably used.

As polyamides, for example, thermoplastic polyamides as well Polyamide imides are used, as they are known for. B. are made from Trimellitic anhydride and the isocyanato-diphenylmethane. usable Phenolic resins and / or polyvinyl formals are available, for example, novolaks by polycondensation of phenols and aldehydes or polyvinyl formals, available from polyvinyl alcohols and aldehydes and / or ketones. Furthermore are usable masked isocyanates such. B. adducts of polyols, amines, CH- acidic compounds (e.g. acetoacetic esters, malonic esters, etc.) and diisocyanates, cresols and phenols are customarily used as capping agents can.

The wire enamel compositions can optionally be monomers and / or polymers contain element-organic compounds, for example. ortho-titanium acid esters and / or ortho-zirconic acid ester, titanium tetralactate, hafnium and silicon compounds and / or various silicone resins.

Furthermore, reactive particles on the wire enamel compositions Basis of an element-oxygen network with elements from the series Aluminum, tin, boron, germanium, gallium, lead, the transition metals and the Contain lanthanides and actinides, the reactive particle being based on the Element-oxygen network, on the surface of which reactive functions and possibly. non-reactive and / or partially reactive reactions via the oxygen of the network are bound. The inorganic network can preferably comprise the elements from the series titanium, Contain silicon, aluminum and / or zirconium. Examples of these reactive particles are mentioned in WO / 0054286 (99P006).

The polymeric and / or monomeric element-organic compounds mentioned or reactive particles can, for example, with a content of 0 to 70% by weight in the Wire enamel compositions may be included.

The wire enamel compositions can be conventional additives such as pigments and / or Contain fillers as well as conventional paint additives, such as extenders, plasticizers Components, accelerators, initiators, stabilizers, defoamers and Leveling agents.

To increase solubility, the compositions can be organic Solvents, such as aromatic hydrocarbons, N-methylpyrrolidone, cresols, Phenols, styrenes, for example in amounts of 30 to 95% by weight, contain.

With the method according to the invention, metallic conductors, in particular Wires, regardless of the type and diameter of the wire, coated and be hardened.

The application according to the method according to the invention can be applied both to Round wire as well as on flat wire. All can the specialist known types of conductors, e.g. B. made of copper, aluminum, zinc, iron, gold, silver or Alloys thereof are used. For example. can coat wires with a diameter of 5 µm to 12 mm become.

Before the metallic conductor is coated according to the method according to the invention pretreatment of the metallic conductor is generally carried out a so-called annealing process. This means the strong heating of the Metal conductor to prevent this from contamination from previous To free production steps that can significantly disrupt the painting process. Furthermore, the drawing and bending ability of the Metal wires, especially copper wires, improved. The glow takes place in the generally before coating at temperatures between 500 and 800 ° C, for example by means of an annealing furnace.

This annealing process can also be carried out using near infrared radiation, and is preferably carried out with near infrared radiation. This will reduce itself Significant energy and space requirements.

According to the invention, the wires can be made with or without existing coatings coated and hardened. Existing coatings can be, for example Insulation and flame retardant coatings. In such cases the total layer thickness of the coating layer (s) can differ greatly.

According to the invention, the composition can be in customary layer thicknesses be applied. This can e.g. B. be thin layers without Partial discharge resistance as well as adhesion, strength and elasticity of the Coatings is adversely affected. But thicker layers can also be used applied and hardened, which also have the desired properties correspond to a wire enamel coating.

The near infrared radiation (NIR- Radiation) is a short-wave infrared radiation in the wavelength range of about 750 to about 1500 nm, preferably 750 to 1200 nm.

Radiation sources for NIR radiation are, for example, customary NIR emitters which can emit focussed areas, lines or points. Such NIR radiators are commercially available (for example from Adphos). These are, for example, high-performance halogen emitters with an intensity (radiation power per area) of generally more than 10 kW / m ² to, for example, 10 MW / m ² , preferably between 100 kW / m ² and 800 kW / m ² . The emitters reach, for example, an emitter surface temperature (filament temperature) of more than 2000 ° K, preferably more than 2900 ° K, z. B. a temperature between 2000 and 3500 ° K. Suitable emitters, for example, have an emission spectrum with a maximum between 750 and 1200 nm.

The arrangement of the NIR emitters can reflect the circumstances of the coated Wire to be adjusted.

The NIR radiation can, for example, in one with one or more NIR Equipped equipment or with one or more NIR emitters in front the wire to be irradiated are positioned, performed, or the wire to be irradiated and / or the NIR radiator or radiators are during the Irradiation moved relative to each other. For example, the one to be irradiated Wire through one equipped with one or more NIR emitters Irradiation tunnel moved and / or one with one or more NIR emitters equipped robot can the or the NIR emitter over the to be irradiated Lead surface, for example in the sense of a silhouette-like guidance of the NIR Radiator.

In principle, radiation duration, object distance, Radiation power and / or radiator surface temperature of the NIR radiator can be varied. The distance between the wire and the NIR emitter can be 2, for example up to 60 cm. The NIR radiation can be continuous or discontinuous (clocked). The radiation duration can be, for example, 1 to 100, preferably not more than 60 seconds. The irradiation time refers either for the duration of continuous radiation or for the total the duration of different radiation cycles. By carefully selecting the different parameters can have different surface temperatures can be set, for example surface temperatures from 100 to 300 ° C.

The various radiation parameters, such as speed or Irradiation time, object distance, radiation power of the NIR used Spotlights can be designed by a specialist according to the needs of each Painting task to be adjusted.

When combining near infrared radiation with thermal hardening conventional methods e.g. B. an oven, the arrangement of the ovens can be horizontal or be done vertically, with coating conditions such as duration and number of the coatings, baking temperature, coating speed in Depending on the type of wire to be coated can be designed. For example. can use the coating temperatures when combined ovens range from room temperature to 400 ° C. Furthermore can also paint at ambient temperatures above 400 ° C, e.g. 800 ° C and be possible without affecting the quality of the Coats can be found.

The method according to the invention surprisingly enables one Improvement of the color stability of the baked wire enamel composition. Clearly lighter paint films can be produced using the process according to the invention produce, which make it possible to the degree of burn-in of the respective paint film close without darkening due to signs of decomposition the paint films are coming. In addition, the desired paint properties such as partial discharge resistance as well as adhesion, strength and elasticity of the Guaranteed coatings of the coated metallic conductor.

The following examples show the superiority of near infrared radiation hardened wire enamel compositions for lighter shades in Comparison to oven drying based on the yellowing values.

Examples exams

Solids content 1 g / 1 h / 180 ° C [%] DIN EN ISO 3251

Viscosity at 25 ° C [mPa.s] or [Pa.s] DIN 53015

Example wire enamel 1

In a 2 liter three-necked flask with stirrer, thermometer and distillation unit (Column and distillation bridge) are 261.2 g of tris (2-hydroxyethyl) isocyanurate (THEIC), 93.2 g ethylene glycol, 194.2 g dimethyl terephthalate (DMT) and 0.5 g Zinc acetate heated to 210 ° C in 4 hours. 60 g of methanol are distilled off. After cooling to 150 ° C., 192.1 g of trimellitic anhydride (TMA) are added and 99.0 g methylenedianiline (DADM). The mixture is stirred at 220 ° C. within 3 hours heated and kept at this temperature for a further 3 hours. Distilled 33 g of water are removed. It is then cooled to 180 ° C. and 500 g are added Cresol.

With further stirring, the present resin solution with 882.0 g of cresol, 273.0 g Solvesso 100, 100.0 g xylene, 50 g of a commercially available phenolic resin and 18.0 g ready-made ortho-titanium acid tetra-butyl ester.

The resulting wire enamel has a solids content of 31.3% and a viscosity of 410 mPa.s.

Example wire enamel 2

545 g of N-methylpyrrolidone, 190 g of trimellitic anhydride, 4.9 g of benzyl alcohol and 260 g of 4,4'-methylene-bis- (phenyl isocyanate) are placed at 123 ° for 6 hours in a 2-liter three-necked flask equipped with a stirrer, thermometer, reflux condenser and gas volume counter C. heated. 46.8 l of CO _{2 are} developed. If 2 parts of the resulting solution are mixed with 1 part of N-methylpyrrolidone, a solution with a viscosity of 5800 mPa.s / 25 ° C. is obtained. The product is ready-made by adding 350 g of N-methylpyrrolidone and 300 g of xylene.

The resulting wire enamel has a solids content of 27.8% and Viscosity of 1850 mPa.s / 25 ° C.

Example 3 Measurement of yellowing after application and hardening of the wire enamels from example 1 and Example 2

In order to carry out the yellowing measurement, the wire enamels are made Examples 1 and 2 applied to a substrate with a gray coil coating lacquer coated sheets are (thickness 0.7 mm).

Wire enamel according to example 1

There is a three times a 15 micron wet film of the wire enamel, which one Dry layer thickness of 5 microns corresponds, and each for 40 min. at 240 ° C Cured oven temperature.

After heat pretreatment of the sheet (3 × for 40 min. At 240 ° C.), a 15 μm wet film is knife-coated three times, which corresponds to a dry layer thickness of 5 μm. In each case at a distance of 10 cm, curing takes place using near-infrared radiation with the following output: 8 s-100%; 60 s-25%; 6 s-100%. For this purpose, a high-burn lamp from Adphos is used with a max. Area performance of 400 kW / m ² .

Wire enamel according to example 2

A 50 µm wet film is doctored, which has a dry film thickness of 14 µm corresponds, and for 30 min. cured at 240 ° C oven temperature.

After heat pretreatment of the sheet by annealing at 240 ° C for 30 min. a 50 micron wet film is knife-coated, which corresponds to a dry layer thickness of 14 microns, and then hardened by near-infrared radiation at a distance of 10 cm with the following power: 5 s-100%, 60 s-25%, 5 s-100%. For this purpose, a high-burn lamp from Adphos is used with a max. Area performance of 400 kW / m ² .

The heat pretreatment in the case of near infrared radiation is done in both Cases from the same initial state of the color situation.

The yellowing measurement is measured in accordance with DIN 6174 using the b * values (CIELAB system) with a spectrophotometer. Results

The smaller the b * value, the less yellowing. This makes it clear that by means of the method according to the invention by irradiation with near infrared Radiation the yellowing can be reduced and thus significantly lighter shades result.

Claims (10)

1. A method for coating metallic conductors, in particular wires, characterized by a) application of at least one coating layer of a wire enamel composition, which contains a thermally curable binder system, to the surface of a metallic conductor, in particular a wire and b) thermal curing of the coating layer (s) by irradiation with near infrared radiation. 2. The method according to claim 1, characterized in that the thermal Hardening by combining near infrared radiation and conventional thermal curing takes place. 3. The method according to claim 1 and 2, characterized in that wire enamel Compositions based on polyesters and / or polyesterimides be used. 4. The method according to any one of the preceding claims, characterized in that the near-infrared radiation is infrared radiation from the Wavelength range from 750 to 1500 nm. 5. The method according to any one of the preceding claims, wherein near-infrared emitters with an intensity of 10 kW / m ² to 10 MW / m ^{2 are used} as a source for the near-infrared radiation. 6. The method according to any one of the preceding claims, characterized in that after hardening the wire enamel coating layers at least one more Coating layer is applied. 7. The method according to any one of the preceding claims, wherein as a metallic Conductor an electrically conductive wire is used. 8. The method according to any one of the preceding claims, characterized in that a metallic conductor is used, which is pretreated by a Annealing process using near infrared radiation. 9. The method according to any one of the preceding claims, characterized in that a pre-coated electrical conductor is used. 10. Metallic conductor, characterized in that it according to the method Claim 1 to 9 is coated and cured.