The present invention is directed to a process for separating polyester, and particularly polyethylene terephthalate, from various contaminants and impurities. In general, the process includes the steps of mixing materials containing polyester with an alkaline composition in a mixer. The mixer imparts sufficient energy to the slurry to provide substantially complete, even coating of the polyester containing materials with the alkaline composition and cause saponification of the outer surface of the polyester with the alkaline composition. After reaction in the mixer, the mixture is heated causing some of the impurities to be chemically modified into a more separable form. After heating, the mixture can be washed with water and the polyester can be easily separated from the remaining impurities. Through the process of the present invention, polyester can be separated and recovered from waste materials such as those containing polyvinyl chloride and aluminum. The process is also effective at removing coatings adhered to the polyester and at removing entrained organic and inorganic compounds contained within the polyester.