GB909149A - A method and apparatus for continuously passing flat-films through treating baths - Google Patents

Abstract

<PICT:0909149/IV(a)/1> In processes for making or treating flat films and ribbons by continuously passing them through coagulating or treating baths, the film leaving the liquid in an upward direction through the free surface of the bath, the film is passed at a high velocity, preferably a velocity of more than 100 metres a minute, through the bath and in leaving the bath is passed freely between two plates, one at either side of the film extending over the whole width of the film, and connected by side plates, which plates partly extend into the bath liquid and form, at least at their lower edges, a narrow slitshaped passage for the film, the passage of the film between the plates being effected in a way by which direct contact between the film and the plates is avoided. As shown in the drawing, a film 1 of regenerated cellulose is formed by extruding viscose through a slot die 2 which is submerged below the surface 3 of a spinning bath liquid in a container 4. The film 1 is drawn over a guide rod 7 obliquely upwards between two blade-shaped plates 9 and 10 arranged across the whole width of the film and closed at each side by a side wall (not shown). The plates 9 and 10 curve gradually upwards into a horizontal plane and taper downwards to a slit 0,9 mm. wide, the thickness of the regenerated cellulose film 1 at the plates being 0,15 mm. and the path of travel of the film from the guide rod 7 to a guide roll 8 being such that the film does not touch the edges of the slit. If the width of the slit S between the plates is below an upper limit C1, then on increasing the rate of travel V of the film, a point will be reached at which the bath liquid between the plates suddenly disappears and the plates wipe almost the entire adherent liquid coating from the film. This effect is obtained if V is greater than the expression C2/(C1-S) wherein C1 and C2 represent constants which are functions of the thickness of the film, the nature of the surface of the film and the plates, the shape of the plates, and the specific gravity and viscosity of the liquid. The invention enables adhering bath liquid to be efficiently removed from the film leaving the spinning or treatment bath without risk of damage to the film such as may be caused by wipers or squeege rollers.