Insulation system for winding of electric rotating machines and process of production thereof

A process for producing an insulated winding for electric rotating machines which comprises wrapping a plurality of layers of a sheet-form insulating material having thermal resistance of at least class H around a winding conductor, impregnating the thus treated winding conductor with a varnish consisting essentially of (a) 1 equivalent of a polyepoxide compound containing at least two vicinal epoxy groups, and (b) more than one equivalent of an organic polyisocyanate, and then heating the impregnated winding conductor at a first temperature such that isocyanurate rings are formed by the trimerization of the polyisocyanate and then a second temperature such that oxazolidone rings are formed and cross-linking and curing occur to form and cure a resin having recurring units represented by the formula:

• ##STR5## wherein R is a residue of the polyisocyanate, R' is a residue of the polyepoxide, p is an integer of at least 2, and m and r are integers of at least 1, at least two isocyanurate rings directly bonded to one another through the residue of the polyisocyanate and two oxazolidone rings directly bonded to each other through the residue of the polyepoxide in the insulating layers, in the presence of 0.01-10% by weight of a catalyst which forms an isocyanurate ring and an oxazolidone ring and is selected from the group consisting of imidazole and morpholine derivatives based on the total amount of the polyepoxide and the polyisocyanate.

A process for producing an insulated winding for electric rotating machines which comprises wrapping a plurality of layers of a sheet-form insulating material having thermal resistance of at least class H around a winding conductor, impregnating the thus treated winding conductor with a solution of a catalyst, for forming isocyanurate rings and oxazolidone rings and selected from the group consisting of imidazole and morpholine derivatives, dissolved in an organic solvent, until 0.01 to 10% by weight of the catalyst is held in the layers based on the total amount of a polyepoxide and an organic polyisocyanate as described below, removing the solvent, impregnating the treated winding with a varnish consisting essentially of (a) one equivalent of a polyepoxide containing at least two vicinal epoxy groups and (b) more than one equivalent of the organic polyisocyanate, and then heating the impregnated winding conductor at a first temperature such that isocyanurate rings formed by the trimerization of the polyisocyanate and then at a second temperature such that oxazolidone rings are formed and cross-linking and curing occur to form and cure a resin having recurring units represented by the formula:

• ##STR6## wherein R is a residue of the polyisocyanate, R' is a residue of the polyepoxide, p is an integer of at least 2, and m and r are integers of at least 1, at least two isocyanurate rings directly bonded to one another through the residue of the polyisocyanate and two oxazolidone rings directly bonded to each other through the residue of the polyepoxide.