Patent GB-450936-A (GB)
Title: Improvements relating to the manufacture or treatment of artificial filaments, threads, films and like materials
IPC: D01F2/28
Filed: 1935-01-23
Abstract: A process for improving the properties of cellulose acetate or like filament forming bases in the form of filaments, threads, ribbons or films comprises shrinking the materials by treatment with a mixture having a swelling action on the filament-forming base and consisting substantially of two or more volatile non-aqueous liquids of different solvent powers for said base but of substantially the same volatility at the operating temperature which is in general from 25 DEG  C. to 35 DEG  C.  Preferably the mixture consists of a swelling agent or latent solvent with a liquid of very low solvent power, e.g. ethyl acetate and benzene; methyl ethyl ketone and benzene or cyclohexane; or methylene ethylene ether with n-butyl chloride. Preferably the liquid employed is such that in the absence of tension shrinkage is small, e.g. 5--10 per cent, but shrinkages of 15--20 per cent are not excluded.  The liquid may be applied by padding or spraying but is preferably applied in a bath and shrinkage may take place in the bath or at least in part during a subsequent batching operation.  The threads are preferably drawn through the bath by rollers, advantageously in warp formation and the process is preferably continuous.  The materials may be treated in the form of hanks or cakes, or on bobbins or swifts.  Resilient bobbins or swifts permit shrinkage in package form.  Filaments proceeding from a spinning or stretching process may be treated according to the invention, the softening-agent being preferably the same in both the stretching and shrinking processes.  The materials may be pretreated, e.g. with one or more constituents of the shrinking medium in such concentration as to exert little or no shrinking action, or they may be treated to remove water or other liquid capable of reducing the rate of shrinkage.  The pretreating agents should advantageously fulfil the same condition as to volatility as the shrinking medium. In an example, cellulose acetate yarn in warp formation is passed through a number of successive sets of spaced rollers through a bath containing ethyl acetate mixed with 25--30 per cent of its volume of benzene, and driven at progressively diminishing speed so that the yarn shrinks by 5--10 per cent of its original length.  The bath temperature is between 25 and 35 DEG  C.  In a further example a hank of cellulose acetate yarn of high tenacity is suspended by one end from a rotating mandrel in the above mentioned bath for \ba1/2\be--3 minutes, or the same yarn wound on a perforated bobbin may be immersed in the bath for 1--3 minutes.  Specification 423,168 is referred to.  The Provisional Specification is concerned with the treatment of artificial materials generally, particularly filaments, threads, ribbons, films, and like materials and also states that the treatment may take place under just sufficient tension to prevent shrinkage without causing stretching.  Specifications 277,089, 323,790, [both in Class 2 (ii)], 336,217, and 389,823 also are referred to.