a composition comprising 10 - 80 % by weight of a cellulose ether and a solvent selected from a water - soluble polyhydric alcohol , polyhydric alcohol ether , polyhydric alcohol ester , and ethanolamine is effective for purging extrusion and injection molding machines . the purging composition exerts a satisfactory purging or cleaning effect , but little abrasion effect , thus avoiding any abrasion of machine internal components by purging . even if part of the purging composition is left within the machine after the composition is discharged out , the residue can be readily removed .