Patent ID: 6797225
Filing Date: 2004-09-28
Classification: B29C,B29K,B29L

Abstract:
A process for producing a polyester sheet by dropping a molten polyester sheet extruded from an orifice-form nozzle on a cooling roll having the grooves of a large number of micro-cracks formed on the surface, closely adhering it to the cooling roll and solidifying it on the cooling roll, whereinthe surface temperature (T, Â° C.) of the molten polyester sheet 10 mm below the orifice-form nozzle is maintained at a temperature which satisfies the following expression (1): (Tc+20)Â° C.&lE;T&lE;(Tm+40)Â° C.â€ƒâ€ƒ(1) wherein Tc and Tm are the falling temperature crystallization temperature (Â° C.) and melting point (Â° C.) of the polyester, respectively and T is as defined hereinabove, and the surface temperature of the cooling roll when it contacts the molten polyester sheet is controlled to a range of 5 to (Tgâˆ’20)Â° C. to continuously form the polyester sheet while preventing the adhesion of a sublimate from the molten polyester to the inside of the groove of each micro-crack of the cooling roll.