PURPOSE: To obtain a useful coating material which can improve the yield of a rolled product, e.g. a plastic sheet, by dissolving a specified polymer in a chlorine-free fluorocarbon solvent.

CONSTITUTION: A polymer having a principal chain comprising perfluoropolyether is purified, e.g. by using an organic solvent serving as a good solvent for this compound and an organic solvent serving as a poor solvent for it to give a polymer having such a purity that no impurity is recognized by gel chromatography in the average molecular weight region of below 1000. The obtained polymer is dissolved in a chlorine-free fluorocarbon solvent to give the title composition.