Current Development Stage of Flat Film Extrusion.

This paper reviews the current development stage of standard equipment for the production of normal, thermoforming and stretch grade films which should be considered as fairly positive. This is essentially due to the fact that biaxially oriented film of extremely high quality is produced on large extrusion lines by the casting process. The experience gained in this production has contributed to many modifications and improvements. Special-purpose screws for particularly good melt homogeneity, large-sized filters with extreme filter units, casting dies for very close thickness tolerances as well as chill rolls for optimal film cooling and temperature control that have been developed for computer-controlled large lines with outputs of several tons per hour are now also used in the production of fine film and thermoforming film. This has led to a particularly high quality standard in conjunction with high efficiency. The author describes all these modifications which now form part of the current technological standard.