Supercritical fluid fractionation of copolymers based on chemical composition and molecular weight

摘要

AbstractPoly(ethylene‐co‐methyl acrylate) copolymers of 30, 40, 60, and 70 wt acrylate in the backbone have been fractionated with supercritical (SCF) propane, propylene, butane, 1‐butene, and chlorodifluoromethane. The fractionations were performed isothermally using an increasing pressure profile that provided gram‐sized fractions with molecular weight distributions of ∼ 1.2 to 2.2 as compared to those of the parent copolymers, which were ∼ 2.6 to 3.5. If the chemical composition distribution of the copolymer is greater than ±2, it is possible to fractionate with respect to chemical composition by chosing solvents that preferentially dissolve the nonpolar ethylene‐rich or the polar acylate‐rich oligomers. Cloud‐point curves were determined for each copolymer in the SCF solvents to provide an indication of whether the solvent would dissolve the copolymer at temperatures and pressures within the range of the fractionation apparatus. © 1993 J