Phase behavior of semicrystalline polyester resin in supercritical fluid solvents and solvent mixtures: Implications for supercritical fluid processing

Abstract

Cloud-point data between 40 and 240 degreesC and pressures to 2750 bar are presented for a low molecular weight, semicrystalline polyester resin of 53.4 mol % adipic acid and 46.6 mol % 1,4-cyclohexanedimethanol in supercritical CO2, dimethyl ether (DME), and chlorodifluoromethane (CDFM), and in mixtures of CO2 with DME, CDFM, methanol, ethanol, butanol, octanol, hexafluoroisopropanol, acetone, and cyclohexane. Carbon dioxide, by itself, is an extremely weak supercritical fluid (SCF) solvent because this polyester only dissolves at pressures in excess of 2000 bar and at temperatures over 180 degreesC. However, DME and CDFM are excellent solvents for this polyester, which dissolves at 16 bar and 40 degreesC in CDFM and at 167 bar and 55 degreesC in DME. The melting point of this polyester is reduced from 105 to 40 degreesC in CDFM and to 55 degreesC in DME, which makes the polyester amenable to high intensity mixing for the efficient dispersion of inorganics or crosslinking agents and other hard to deposit materials. (C) 2001 John Wiley & Sons, Inc.