Patent GB-414394-A (GB)
Title: Improvements in the production or treatment of shaped articles of cellulose derivatives or other film-forming bases
IPC: C08L1/08
Filed: 1933-02-02
Abstract: Shaped articles of cellulose derivatives or other film-forming base soluble in organic solvents, for example, films, sheets, tubes, containers or other hollow articles, and even solids, but not filaments and the like, or fabrics containing them, are subjected to the action of a shrinking medium containing a latent solvent for the film-forming base, and allowed to shrink.  A tube or other covering or sheath of the desired film-forming material may be applied to a metal or other tube, rod, or other article, after which the shrinking medium is applied to shrink the covering or sheath into position. The shrinking medium may be applied to the tube or other covering before the latter is applied to the article to be covered.  Latent solvents which are suitable are methylene chloride, ethylene chloride, chloroform, tetrachlorethane, and ethyl acetate, and these may be employed with diluents such as water, glycol, glycerol, benzene, toluene, xylene, benzine, petrol ether, kerosene, carbon tetrachloride, trichlorethylene, perchlorethylene, and tetra- and deca-hydronaphthalene.  In the case of a film or other article of commercial cellulose acetate, good results are obtained with a 50--75 per cent solution of methylene chloride in benzene or carbon tetrachlorde.  Films and sheets may be allowed to shrink longitudinally, or transversely, or both, and by amounts which may be from 5--10 up to 15--20 per cent of the original dimensions. The restriction of the shrinkage may be effected by suitably diluting the shrinking agent, and/or by effecting the treatment under a sufficient tension.  Alternatively, the articles may be allowed to shrink and be subsequently stretched.  When covering an article with a tube, sheath, or other covering, the amount of shrinkage allowed is about 5--7 per cent.  Films or other articles may be treated with the shrinking agent in a bath treatment or in the form of vapour or by spraying methods, and shrinkage may take place continuously with the production of the films or other articles by dry or wet processes. The process may be applied with advantage to films which have been subjected to a stretching process, for example, according to the processes of Specifications 400,589 and 400,597.  The films or other articles may consist of organic derivatives of cellulose, polymerized vinyl acetate or other polymerized vinyl compound, and may contain additional substances such as synthetic or natural resins, pigments, colouring matters, and plasticizers.  The following examples are given: (1) a cellulose acetate film containing about 8 per cent of tricresyl phosphate is passed through a bath containing 70 per cent of methylene chloride and 30 per cent of benzene, a longitudinal shrinkage of 10 per cent being allowed, lateral shrinkage being prevented; (2) a cellulose acetate film is immersed in a bath consisting of 76--80 per cent of ethylene chloride and 24--20 per cent of benzine so that about 10 per cent shrinkage is obtained; (3) a similar film is immersed in a bath consisting of 80 per cent of ethyl acetate and 20 per cent of toluene, 5 per cent shrinkage being obtained; (4) a tube or rod is wrapped with a film of cellulose acetate and immersed in a shrinking medium consisting of 80 per cent of ethyl acetate and 20 per cent of toluene; (5) a rod or tube is slipped into a preformed hollow cylinder of cellulose acetate film, and immersed in a medium consisting of 80 per cent ethyl acetate and 20 per cent of toluene.  Specifications 380,504, 380,505, and 389,823 also are referred to.