Abstract: The present invention relates to a process for the production of trimerized polyisocyanates containing at least 30 mole % of iminooxadiazinedione groups (asymmetric trimers) in the trimer mixture by catalytically trimerizing a starting isocyanate selected from organic di- or polyisocyanates having a number average molecular weight of 140 to 600 and containing aliphatically, cycloaliphatically and/or araliphatically bound isocyanate groups in the presence of quaternary ammonium and phosphonium fluoride trimerization catalysts corresponding to the formulaR.sub.4 E.sup.+ F.sup.- (I),whereinE represents N or P andR represents identical or different, optionally branched, aliphatic, aromatic and/or araliphatic C.sub.1 -C.sub.

Abstract: The present invention relates to a process for the preparation of trimerized polyisocyanates that contain at least 30 mole % of iminooxadiazinedione groups (asymmetric trimers) in the trimer mixture, by catalytically trimerizing a starting isocyanate selected from organic di- or polyisocyanates having a number average molecular weight of 140 to 600 and containing aliphatically, cycloaliphatically and/or araliphatically bound isocyanate groups in the presence of a quaternary phosphonium polyfluoride trimerization catalyst corresponding to the formulaR.sub.4 P.sup.+ F.sup.- n(HF)whereinR represents identical or different, optionally branched aliphatic, aromatic and/or araliphatic C.sub.1 -C.sub.20 groups, or two or more R groups may also form, with one another and with the phosphorus atom, saturated or unsaturated rings andn has a value of 0.1 to 20.

Abstract: This present invention relates to a process for thermally cracking carbamic acid esters into the corresponding isocyanate and hydroxyl compounds in the liquid phase, wherein the reaction proceeds as a reactive rectification in the stripping zone of a column and in an inert, high-boiling solvent, which acts as a buffer to keep the reaction away from the evaporator region of the column.

Abstract: The invention relates to a process and an apparatus for determining the heat output rate in a reactor. This is achieved by determining the heat output rate in a sensor connected to the chemical reactor and taking into account the volume or mass ratio between the reactor and sensor contents. The apparatus allows balancing of the sensor, on the one hand, and continuous adjustment of the material composition and temperature of the reactor and sensor contents, on the other hand.