Coating processes – Electrical product produced – Wire conductor
Patent
1995-09-05
1998-04-07
Beck, Shrive
Coating processes
Electrical product produced
Wire conductor
427120, 525124, 2521822, 25218221, 528 44, 528 60, 524108, 524386, B05D 512, C08F 830, C08G 1810
Patent
active
057361932
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to solderable wire-coating compositions based on hydroxyl group-containing polyesters, blocked polyisocyanates, organic solvents and catalysts. The present invention also relates to a process for the continuous coating of wires using these solderable wire-coating compositions.
It is known to produce insulating, solderable coatings on electrical conductors. This term is understood to refer to coatings which, when the insulated electrical conductors are immersed in a solder bath heated to elevated temperature, are destroyed or detached to the extent that the conductor has been immersed in the bath, so that on these areas the bare metal is exposed and can be used directly for electrically conducting connections. For this purpose it is necessary for the insulating coating to be removed, on immersion in the solder bath, in as short a time as possible, in other words within a few seconds. The shorter this time, the easier it is to achieve final insulation and thus an industrially advantageous procedure.
Electrically insulating coatings based on hydroxyl group-containing polyesters and blocked isocyanates are known in large numbers and are described, for example, in DE-A-16 44 794 and DE-A-19 57 157. Electrically insulating coatings of this kind are notable in particular, when used as wire enamels, for their good insulating properties and for the fact that they are solderable (IEC 851-4, IEC 317-4). When immersed in a solder bath heated to elevated temperatures, solderable insulated wires undergo destruction of the insulating layer to expose the bare metal of the conductor, which is thus directly accessible for electrically conducting connections. A technical advantage can be obtained by the time for removing the insulating coat being as short as possible. The requirement of great thermal lability under the conditions of the solder bath is countered by the high thermal stability required of coated wires for use in electrical components, for example electrical transistors or transformers. Whereas the solderability is to be attributed to the presence of urethane groups in the coating film, the heat resistance is decisively influenced by the choice of polyester. In this context, polyesters of aromatic dicarboxylic acids result in a particularly good temperature index and a good resistance of the resulting coatings to thermal shock (IEC 851-6).
The organic solvents which are predominantly used for solderable wire enamels based on hydroxyl group-containing polyesters and blocked polyisocyanates are phenols, in particular cresols and xylenols. However, the use of these cresolic or phenolic solvents is associated with numerous problems, for example odor nuisance and environmental hazard because of the toxicity of these solvents when such wire enamels are applied. Indeed, attempts are being made to replace these cresolic and phenolic solvents by other suitable organic solvents.
Moreover, the efforts are aimed at providing wire enamels having as high as possible a solids content.
Japanese Laid-Open Application No. 58-101162 discloses solderable wire-coating compositions based on blocked polyisocyanates, hydroxyl group-containing polyesters, organic solvents and acetylacetonate-metal complex catalysts. The solvent content of the wire-coating compositions described is below 40% by weight, based on the sum of blocked polyisocyanate, hydroxyl group-containing polyester and organic solvent. In the examples of JP-A-58-101162 the solvent used is exclusively cresol. However, the use of cresols is associated with numerous problems, such as odor nuisance and environmental hazards because of the toxicity of the cresol when cresolic wire enamels are applied. It emerges from the Japanese Laid-Open Application that wire enamels based on hydroxyl group-containing polyesters, blocked polyisocyanates, cresol and heavy metal naphthenates instead of acetyl-acetonate-metal complex catalysts lead to turbid coating compositions which, after application to wires, result in coatings with poor properties.
The present
REFERENCES:
patent: 3988283 (1976-10-01), Shelby et al.
patent: 4104235 (1978-08-01), Ohm
patent: 4239814 (1980-12-01), Nagel
patent: 4369301 (1983-01-01), Knoig et al.
Hentschel Silvia
Lienert Klaus Wilhelm
Runge Joachim
Schink Michael
BASF Lacke & Farben AG
Beck Shrive
Talbot Brian K.
LandOfFree
Solderable wire-coating compositions and process for the continu does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Solderable wire-coating compositions and process for the continu, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Solderable wire-coating compositions and process for the continu will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-10676