Wire enamel formulation with internal lubricant

Details Wire enamel formulation with internal lubricant Wire enamel formulation with internal lubricant

1998-01-13

2000-02-08

Seidleck, James J.

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...

106 10, 524276, 524277, 524310, 524313, 524378, C08J 510, C08L 9106

Patent

active

060229187

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to a wire enamel formulation obtaining components known per se with an internal lubricant.
Enamelled copper wires are coated with a lubricant in order to improve their processing properties. Conventional lubricants consist of a 0.5 to 2% strength solution of paraffins or waxes in a readily volatile solvent. On application to the wire, the solvent evaporates to leave the paraffin or was film. A disadvantage of this procedure is that the solvents customarily used may give rise to cracks in the surface of the enamel film.
These and other disadvantages disappear if internal lubricants are used. Such lubricants are added to the enamelling material. After the wire enamel has cured, they are incompatible with it. They migrate to the surface where they form a layer which possesses improved lubricity.
The problem is that many of these internal lubricants are incompatible with the liquid enamelling material and lead to phase separation or instances of precipitation.
DE 32 37 022A describes a lubricant comprising an aliphatic hydrocarbon mixture as solvent and 1% paraffin wax and also 1% hydrogenated triglyceride. The paraffin wax has a melting point of 50-52.degree. C. The hydrogenated triglyceride is a commercial product with a melting point of from 47.degree. C. to 50.degree. C. this solution is applied to a wire coated with a polyamideimide. In addition, it is also possible for an internal lubricant to be used. The latter is added to the polyamideimide in a concentration of 1%. The internal lubricant consists of tall oil fatty acid esters. No information is given on the coefficients of friction which are achieved.
EP 00 72 178A describes the modification of wire enamel binders, in the course of which a C21 hydrocarbon chain is incorporated into the polymer. This chain leads to an improved coefficient of friction in the enamelled wires. The document gives no information on the thermal properties. It is suspected that the softening of the enamel film and the dielectric loss factor are adversely affected by the introduction of the hydrocarbon chain.
EP 0 103 307A describes conventionally applied lubricants which, on the wires in relays, show a reduced gas-escape tendency. This is achieved by the substitution of the terminal hydrogen in a polypropylene glycol by an organic radical.
EP 0 267 736 describes comparisons between paraffinic and polymeric lubricants. In the relay reliability test, the polymeric lubricants perform considerably better. No information is given on the stability of the processed polymer/wire enamel mixtures.
Another document (JP 0 524 7374A) describes how the use of dispersions of fluorinated waxes in conventional wire enamels leads to an improvement in the lubricity of the wires produced therewith. Such systems have a tendency, however, to undergo phase separation.
JP 0 521 7427A describes the use of a polyethylene wax dispersion in a polyamideimide wire enamel. Experience indicates that these systems are not stable on storage.
From the examples given it is evident that an optimum lubricant must be an internal lubricant. Moreover, the lubricity-improving additive should be a polymeric material, and the formulation should be stable on storage.
The object of the present invention, accordingly, was to provide a wire enamel formulation obtaining components known per se and an internal lubricant, which formulation meets the requirements set cut above.
This object is surprisingly achieved in that the internal lubricant obtains a polyethylene wax, preferably having a molecular means [M.sub.W ] of from 3000 to 6000 [g/mol], and a wetting agent, preferably fatty alcohol ethoxylate.
In accordance with the invention it is possible to use wire enamels containing a polyesterimide as binder. Such polyesterimide resins are known and are described, for example, in DE-A 14 45 263 and DE-A 14 95 100.
The polyesterimides are prepared in a known manner by esterification of polybasic carboxylic acids with polyhydric alcohols, with or without the addition of hydroxycarboxylic acids, and

REFERENCES:
patent: 4146499 (1979-03-01), Rosano
patent: 4450258 (1984-05-01), Pauze
patent: 5746812 (1998-05-01), Muller et al.

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