The manufacturing method of multilayer APET sheet

摘要

PURPOSE: Provided is a low cost preparation method of polyester back layer sheet with excellent transparency. It is produced by co-polymerizing high purity isophthalic acid (PIA), 1,4-cyclohexanedimethanol (CHDM), terephthalic acid (TPA) and ethylene glycol (EG). The copolymer resins with more than 1 mole % modifier differences are co-extruded so that polyester resins with less modifiers are arranged to the outer layers. The arranged 3 to 7 layers of sheet are produced and used as substitutes for windows of building, vinyl sheets for agricultural use, as well as clear soundproofing walls, coating materials and advertizing boards. CONSTITUTION: The clear polyester sheet of 3-10mm thickness is prepared by the steps of copolymerizing and making copolymer chips of 0.5-1 intrinsic viscosity, with pure PIA, CHDM, TPA, EG together with non-linear copolymer modifier of 0-20 mole % to the phthalic acid, selected from isophthalic acid, naphthalenedicarboxylic acid, phthalic acid, 1,4-cyclohexanediol, bisphenols and their alkyl ester and co-extruding in a way that surface layer has less modifier content than the inner layer.