GB492370A - Process of and apparatus for the manufacture of films, foils, bands and the like from cellulose solutions - Google Patents

Abstract

<PICT:0492370/IV/1> Films, foils, membranes, bands, and the like are obtained from a cuprammonium solution of cellulose by pouring the solution on to a support moving through a coagulating bath, subjecting the layer of solution to partial coagulation, detaching it entirely from the support and completing the coagulation in a second bath containing a coagulating fluid of similar nature to, but preferably of lower concentration than, that in the first bath. Cuprammonium solutions having a high ammonia content may be used, and removal of the bulk of the ammonia may be effected after the film is detached from the forming surface. In an example, a cuprammonium cellulose solution is spread by a slot nozzle or other spreading device a, on to a drum or belt b, and the layer of solution passes into a solution of caustic soda. The film, superficially coagulated, is removed from the support b and passed to a belt d. It is then led into a bath f containing a more dilute caustic soda solution where coagulation is completed. The film then passes into a bath g of dilute sulphuric acid. During the travel of the film on the belt d and from thence to the bath f considerable quantities of ammonia are removed. The film may be subjected to stretching when it is detached from the support b. A take-up drum may be used instead of belt d. The Specification as open to inspection under Sect. 91 comprises also the production of films wherein coagulation, consolidation, and finishing treatments are carried out while the film is still on the support. The treatment liquids may be applied by spraying or sprinkling, or by means of laying-on rollers. The support may be a belt having more than two guide drums and some of these may be mounted in and some above the precipitating and treating baths. The support may be of non-corrosive material. The drives for the drums or belts may be provided with differential gearing enabling compensation to be made for changes in the shrinkage of the film during the various treatments. The cellulosic films may be dried by first heating in an atmosphere saturated with vapour, and then while keeping the temperature constant, allowing the vapour content of the drying air to fall. In this manner, drying of the film proceeds from inside to outside. This subject-matter does not appear in the Specification as accepted.