Abstract: A process for the production of polycondensates linked by cyclic imide groups, wherein at least one organic polyisocyanate or masked isocyanate, formic acid and at least one cyclic dicarboxylic acid anhydride compound which, in addition to the cyclic anhydride group, is substituted at least once by another cyclic anhydride, carboxyl, carbalkoxy, carbaroxy or SO.sub.3 H group, are polycondensed at temperatures in the range from 0.degree. to 450.degree. C.

Abstract: A process for the production of polycondensates linked by nitrogen containing five membered rings, wherein a unsaturated cyclic anhydride compound is polycondensed with alcohols and organic polyisocyanates.

Abstract: This invention relates to a new process for the preparation of oligourethanes having isocyanate end groups blocked with alkanol and/or cycloalkanol groups, the compounds which can be obtained by this process and their use for the production of polyurethane resins by the isocyanate polyaddition process.

Abstract: A process for the low solvent or solvent free coating of heat resistant substrates by using a coating substance which has a melting point or range below about 200.degree. C and which is heat crosslinkable. The substrate is coated at temperatures between about 20.degree. and 250.degree. C and the coating is subsequently heated to more elevated temperatures to effect crosslinking. The coating substance contains active hydrogen, preferably hydroxyl bearing compounds and blocked polyisocyanates which become reactive when the coating substance is heated to effect cross-linking. In a preferred embodiment, the blocked polyisocyanates consist of at least 40 equivalent percent alkanol or cycloalkanol blocked polyisocyanates. Also a coating substance containing at least 50 wt.% of a combination of active hydrogen, preferably hydroxyl bearing compounds and blocked isocyanates. The combination has a melting point of less than 200.degree. C and a blocked isocyanate group to active hydrogen ratio of about 1:2 to 1:9.

Abstract: A process for the production of polyimides by the condensation of cyclic polycarboxylic acid anhydrides with polyisocyanates and isocyanurates substituted with masked isocyanate groups in the presence of lactams or polyols, and the production of coatings on metals, in particular of lacquers on wires, and of films thereof.

Abstract: Process for the preparation of polyhydantoins or polyparabanic acids, characterized in that bis- or polyglycine derivatives or bis- or poly-monoamidooxalic acid derivatives are heated to temperatures of 20.degree. to 250.degree. C with di- or polyiso(thio)cyanate derivatives without solvents and the highly fluid melt which has a melt viscosity of at the most 40,000 m.Pa.s. is optionally subjected to a shaping process and is polycondensed by adjustment to the reaction of 80.degree. to 700.degree. C.