Process for the manufacture of polyolefin film

Details Process for the manufacture of polyolefin film Process for the manufacture of polyolefin film

1975-04-23

1976-12-28

Thurlow, Jeffery R.

Plastic and nonmetallic article shaping or treating: processes

Pore forming in situ

Composite article making

264210R, 264237, 264290R, 425326R, B29C 1702

Patent

active

040002349

ABSTRACT:
A process for the manufacture of polyolefin film, especially high density polyethylene film, is disclosed. In the process molten polyolefin is extruded through an annular die and the tubular molten polyolefin film so formed is withdrawn from the die, expanded, cooled and flattened. The process is controlled so that (a) the ratio of the diameter of the expanded tubular film to the diameter of the annular die is in the range 1.8:1 to 5:1, (b) the frost line formed as the polyolefin cools is at least four feet from the annular die, (c) the completion of the expansion of the tubular film is juxtaposed to, and prior to, the formation of the frost line. The ratio of diameters and the frost line are co-operatively adjusted with the rate at which the film is withdrawn from the annular die and the temperature at which the molten polymer is extruded through the die so that the Elmendorf tear in the machine direction is at least 15 gms./mil. In an embodiment the Elmendorf tear in the machine direction is at least 30 gms./mil. In another embodiment the ratio of the Elmendorf tear in the machine direction to that in the transverse direction is at least 0.3. The film is especially useful in the manufacture of bags, e.g., notion and millinery bags.

REFERENCES:
patent: 2461975 (1949-02-01), Fuller
patent: 3061876 (1962-11-01), Lloyd et al.
patent: 3304352 (1967-02-01), Gerow
patent: 3551540 (1970-12-01), Pellicciari et al.
patent: 3577488 (1971-05-01), Bigland
patent: 3888609 (1975-06-01), Saint Eve et al.
Clegg et al., The Effect of Extrusion Variables on the Prop. of Tubular Polythene Film- Part I & II - Plastics - vol. 26, Apr.-May 1961, pp. 119-120 & 107-110.

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