Treatment of films of plastics material

Abstract

Abstract There is disclosed an improved machine suitable for treating films of plastics material, such as polypropylene, so that the film, after its initial production and before stretching, is on passing through the machine, modified so as to make it, on stretching, readily reducible to strand form of a required crosssection. Basically the improved machine includes a pair of co-operating rollers, means for bringing the rollers together to form a nip through which such a film of plastics material may pass, means for adjusting the nip pressure, means for rotating each of the rollers at selected speeds, means for controlling the temperature of the rollers, and peripheral formations on at least one of the rollers whereby the film on passing through the nip may have its cross-sectional shape modified to provide alternately across its width enlarged portions from which strand forms will be produced, and portions of reduced thickness which serve to preserve the transverse continuity of the film for the time being. Also disclosed are various roller constructions. In one construction there is a stationary cylindrical support, a closefitting annular rotor carried thereby, generally axial cavities being provided between the two, and means for circulating cooling or heating liquid through certain cavities in one direction and through other cavities in the other direction. The rotor may be supported on the support for rotation by a hydrostatic bearing arrangement. One feature of this can consist in the use of axial cavities to carry bearing liquid and thereby give radial support. For axial bearing support there may be provided, on the support, an annular portion of enlarged diameter which fits in a groove in the rotor, passages being provided to supply bearing liquid between the sides of the annular member and the groove.

Inventors

• 👤 F Aspin

Bibliographic Details