Process for preparing polycarbonates

Claim 1

A process of preparing linear polycarbonates containing terminal hydroxyl groups, said process comprising, reacting an alkylene carbonate composed of a 5 to 7 membered ring with a hydroxy compound selected from the group consisting of cycloaliphatic diols and aliphatic diols containing from 4 to 40 carbon atoms, and polyoxyalkylene glycols containing from 2 to 20 alkoxy groups er molecule with each alkoxy group containing from 2 to 4 carbon atoms, said hydroxy compound having a boiling point greater than 4.9° C over the by-product formed in ester interchange reaction with said alkylene carbonate, said hydroxy compound and alkylene carbonate being admixed in a molar ratio of 10 to 1, to 1 to 10, said reaction being carried out at temperatures between 100° C and 300° C and pressures between 0.1 and 300 Hg in a first and second stage wherein low molecular polycarabonate is formed in a first stage at a molecular chain length of from 2 to 10 units while distilling off by-product glycol from the reaction mixture, and then removing unreacted hydroxyl compound and alkylene carbonate and beginning a second stage which comprises condensing the low molecular weight polycarbonate by distilling off all glycol formed at temperatures of from 100 to 300° C to form high molecular weight polycarbonate.