Prepn. of solvent-free polycarbonate - by preparing oligo-carbonate from aromatic di-hydroxy cpd. and carbonic acid di-ester, grinding and solid phase polycondensing

摘要

The three-stage prepn. of aromatic solvent-free polycarbonate comprises (a) preparing an oligocarbonate from an aromatic dihydroxy cpd. and a carbonic acid diester; (b) grinding the cooled oligocarbonate melt and crystallising in a short time; and (c) polycondensing in solid phase. The ground oligocarbonate has an apparent density of 0.8-0.5(0.75-0.55)g/ml and a core size distribution such that 50% are of size 2000-0.1, esp. 700-100 microns. The Mw of the oligomer carbonate is 1000-17000. 0.05 ppm-0.1 wt% catalyst is used and the diphenol is at least 50 mol% bisphenol-A. The solid phase polycondensation occurs at a temp. below the Tm of the oligomer and above the Tg. The size of the obtd. polycarbonate is 15,000-200,000. USE/ADVANTAGE -The grinding of the oligocarbonate results in the sepn. of side-reaction. The required crystallinity degree is reached within 30 mins. due to the grinding of the oligocarbonate. The polycarbonate can be used to make moulded articles, sheets, etc. and used in electrotechnology and in the prodn. of automobiles