| abstract |
Isocyanurate polymers of organic isocyanates contaminated with unpolymerized isocyanates are purified by volatilizing the unpolymerized isocyanate from a thin film of the mixture of isocyanate polymer and unpolymerized isocyanate. The process is preferably carried out under reduced pressure or with a stream of inert gas being passed over the thin film while the latter is agitated. The thin film may be arranged to flow down the inner walls of a heated cylindrical tube supported at an angle to the horizontal, while being constantly swept and agitated by rotating blades or sweeps mounted on a rotatable shaft centrally mounted along the longitudinal axis of said cylindrical tubes. The isocyanates may be derived from isocyanates containing two or more isocyanate groups and optional halogen atoms, if desired in admixture with monoisocyanates. Specifications 809,809, 920,080 and 952,932 are referred to. |