Abstract: The present invention relates to a solvent-free, low viscosity binder composition which contains, in amounts sufficient to provide an NCO:OH equivalent ratio of 0.5:1 to 2.0:1,A) a polyisocyanate component containing one or more organic polyisocyanates andB) a solvent-free polyhydroxy component having a hydroxyl group content of 3.0 to 18 wt. % and a viscosity at 23.degree. C. of 200 to 10,000 mPa.s, which containsB.sub.1) a hydroxy-functional polyacrylate component which is prepared by polymerizing a mixture of olefinically unsaturated monomers in which at least one monomer is hydroxy-functional in the presence ofB.sub.2) a compound containing ether groups and having one or more hydroxy groups.The invention also relates to the use of this binder composition in solvent-free two-component polyurethane coating compositions for coating metallic or mineral substrates.

Abstract: The invention relates to a process for the preparation of carbonates having a six-membered ring, of the formula ##STR1## by transesterification of 1,3-propanediol compounds with carbonic acid esters and subsequent distillative depolymerization of the oligo- or polycarbonate initially formed, one or more catalysts from the group consisting of compounds of Sn, Ti or Zr being employed both for the transesterification and for the depolymerization and, if appropriate, the distillation residue is at least partly recycled into the transesterification. Such carbonates having a six-membered ring can furthermore be stabilized against undesirable polymerization by addition of small amounts of acids of sulfur or phosphorus or esters or salts thereof.