Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Patent
1997-11-21
1998-12-29
Niland, Patrick D.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
528271, 528289, 528298, 528308, C08J 300, C08K 320, C08L 5100, C08L 6700
Patent
active
058543341
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a wire-coating composition comprising polyester resins or polyesterimide resins or hydroxyl-containing polyesters with an isocyanate component whose free isocyanate groups are completely blocked.
The wire-coating compositions which are customarily employed today are in general solutions of the typical binders, for example polyesters, polyesterimides and hydroxyl-containing polyesters, with blocked isocyanates in solvents, in combination if desired with commercial hydrocarbon diluents.
Wire-coating compositions based on polyester resins are known, for example, from U.S. Pat. No. 3,342,780, U.S. Pat. No. 3,249,578, EP-B-144281 and PCT/EP 92/02776. The hydroxyl component employed in the documents mentioned is tris(2-hydroxyethyl) isocyanurate (THEIC).
The wires coated with wire-coating compositions based on polyester resins are notable for the fact that the enamel film possesses good adhesion to copper wires. Furthermore, the coated wires exhibit a high thermal pressure if the polyester resins used are modified with THEIC.
From PCT/EP92/02776 it is also known that it is possible, by admixing bismaleimide resins, to obtain significant increases in the level of properties of THEIC-modified polyester coating compositions, especially the thermal shock resistance and the thermal pressure.
The disadvantage of the wire-coating compositions based on polyester resins is that the wires coated with polyester resin enamels exhibit a low thermal shock. The THEIC-modified polyester resin enamels are therefore used in the form of two-coat enamels for wires in such a way that the polyester resin coatings form the basecoat on which, for example, polyamideimide wire enamel is applied as topcoat.
Polyesterimide resins are known, for example, from DE-A 1445263 and 1495100 and from WO 91/07469 (PCT/EP 90/01911). Owing to their good mechanical, thermal and chemical properties they have found broad use in mechanical engineering. The polyesterimides cannot match the two-coat enamel with a polyamideimide as topcoat in terms of their thermal and chemical properties.
Electrically insulating coating compositions based on polyurethanes are described, for example, in DE-144749 and DE-1957157. Electrically insulating coating compositions of this kind, when used as wire-coating compositions, are distinguished in particular by their good insulating properties. They have the additional advantage that they can be soldered. Solderable insulated wires, when immersed in a solder bath which has been heated to elevated temperatures, undergo destruction of the insulating layer to expose the bare metal of the conductor, which is therefore directly accessible for electrically conductive connections. The important factor here is that the time for removal of the insulating coat should be as short as possible. The requirement of great thermal lability under soldering conditions stands in opposition to the high thermal stability required of coated wires for use in electrical components. This requirement for improved thermal stability of solderable enamelled wires stands, in principle, in contradiction to the short flux time which is required for rapid processing of the wires.
The object of the present invention is therefore to provide wire-coating compositions, comprising polyester resins or polyesterimide resins or hydroxyl-containing polyesters together with an isocyanate component whose free isocyanate groups are completely blocked, which avoid the disadvantages of the coating compositions known to date and are therefore significantly improved in their profile of properties. The wire-coating compositions according to the invention are in particular to be stable on storage, to have good adhesion, especially to copper wires, to have maximum thermal pressure and high thermal shock. Furthermore, the wire-coating compositions should have a maximum solids content at a viscosity which is favourable for processing. Where polyurethane wire-coating compositions are employed, the intention is at the same time to achieve a shortene
REFERENCES:
patent: 3374114 (1968-03-01), Wiener
Database WPI week 9140 derwent Publications Ltd., London, GB An 91-291110 XP002005637 & Jp, A, 03192739 (Tanaka Denshi Kogyo) 8/22/91.
Kirwin John
Rix Geoff
Schink Michael
BASF Lacke & Farben, AC
Niland Patrick D.
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