RINGFORMET DYSEMUNDSTYKKE TIL STRENGPRESSER

1396164 Tubular film die BADISCHE ANILIN- & SODA-FABRIK AG 10 Aug 1972 [11 Aug 1971] 37336/72 Heading B5A A die for the extrusion of blown thermoplastics film comprises an annular outlet 7 defined between a mandrel 8, and a surrounding die ring 1 having an outer heating means 5 within which is located 16 to 192 circumferentially spaced chambers 2 for the passage of a fluid heating or cooling medium. The chambers are preferably arranged as 4 to 12 individually temperature controlled segments 9, each comprising 4 to 16 and preferably 6 to 10 of the chambers 2. The means 5 may be continuous, but preferably comprises a separately controlled segment for each chamber segment 9. The fluid medium may comprise air or oil, either circulating in the opposite direction to that of extrusion or, as shown, in the same direction from an inlet 3, including an insulating baffle 6, to an outlet 4 of adjustable size. The individually controlled sectors enable control of the temperature around the outlet to control film thickness, micro melt fracture, and transparency. The thermoplastic may comprise homo- and copolymers of ethylene and of propylene, or copolymers of styrene and of vinyl chloride, or may comprise polyamide.