Dr. Beck & Co Ag

Basf Aktiengesellschaft

Ferdinand Hansch

Karl Schmidt

Hans-Malte Rombrecht

Harald Janssen

Hans-Joachim Beck

Hans-Uwe Schenck

Udo Reiter

Helmut Lehmann

Knut Von Loh

Harald JanBen

Aqueous thermosetting electrical insulating varnishes are prepared by a process wherein hydroxyl-containing polyester-imides which have kinematic viscosities of from 16 to 30 mm.sup.2 .multidot. s.sup.-1 and acid numbers of &lt;10, and which have been obtained by condensing aromatic tricarboxylic acid monoanhydrides, aromatic dicarboxylic acids or their esterifiable or transesterifiable derivatives, diamines, diols, and triols containing an isocyanurate ring, are treated, at from 80.degree. to 130.degree. C., in the presence or absence of up to 5% by weight, based on polyester-imide, of an organic solvent, with from 5 to 15% by weight, based on polyester-imide, of ammonia in the form of an aqueous solution, thereby producing aminolysis and hydrolysis so that a neutral or slightly acidic solution results, which is diluted to a viscosity of from 100 to 10,000 mPa.s by adding demineralized water, from 0.1 to 5% by weight, based on polyester-imide, of a water-soluble curing catalyst being added, if desired, after the treatment with ammonia. The electrical insulating varnishes are used as wire enamels or as impregnating varnishes.

Preparation of aqueous thermosetting electrical insulating varnishes

A method of insulating an electrical conductor by applying thereto a coating of a polyesterimide resin which can be hardened through its free OH groups from a resin melt at above 100.degree. C., wherein the resin used is solvent-free and has been prepared by esterification or ester-exchange of starting materials for the polyesterimide in the presence of an excess of one or more short-chain diols and subsequent removal of the diol or diols in such a way that the condensation is only effected to an extent such that the Durrans softening point of the unhardened resin is not above 150.degree. C. (preferably not above 100.degree. C.) and the viscosity of the molten resin at 180.degree. C. is not above 5000 (preferably not above 1000) mPa s (cP). This process avoids the disadvantages encountered when a solvent is present in the insulating bath.

Polyester-amide resin

Method of insulating an electrical conductor

Polyester imide resins containing 5-membered imide rings between the ester groups. The resins are soluble in cresol, and cresol solutions are useful as enameling lacquers for wire conductors.

Conductors having insulation of polyester imide resin

An aqueous electrically insulating varnish is provided along with a process for producing the varnish; the process comprises the steps of reacting cyclopentane tetracarboxylic acid with dicyclic, diprimary aromatic diamine in the presence of water and neutralizing the condensation product to form a varnish.

Aqueous electrically insulating varnish and a process for its production

Diimidodicarboxylic acids for the preparation of polyester resins which in addition to ester groups, contain imide groups between functional groups of the molecule. The imide groups are in the form of 5-membered imide rings resulting from the condensation of, for example, an aromatic carboxylic acid anhydride and a primary amine. The resins can be used in lacquers for production of insulated electrical conductors, with the resin being the film forming component of the lacquers.

Diimidodicarboxylic acids

Polyester imide resin having ester groups of acid and alcohol moieties in the chain, and also in the chain a content of 5-membered imide rings of the general formula: ##STR1## The resin is soluble in cresol solvent and can be combined with such solvents to form a lacquer suitable for enameling of wire.

Polyester imide resins

Water dilutable electroinsulation enamels are made by reacting a hydroxyl group containing polyesteramide of low acid number with at least one amine in an amount of 5 to 30% by weight relative to the weight of the ester imide whereupon the reaction product is diluted with water until it has the desired viscosity for lacquering purposes.

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Wedel, Germany

Ferdinand Hansch