Patent GB-319378-A (GB)
Title: Manufacture of viscose and of artificial products therefrom
IPC: D01F2/08
Filed: 1928-03-22
Abstract: 319,378. Lilienfeld, L. March 22, 1928. Alkali cellulose to be used in the manufacture of viscose is prepared in such a manner that the temperature exceeds 80‹ C. or even 100‹ C. during at least, part of the preparation, for example the cellulose may be impregnated with or steeped in a solution of alkali of the required temperature or the mixture of cellulose and alkali solution after impregnation or steeping may be heated to the desired temperature whilst an excess of the alkali solution is still present or after the removal of such excess alkali by pressing, centrifuging, or the like. The raised temperature may be maintained in two of more stages of the preparation and it may be maintained throughout the stage or stages of the preparation or for any suitable proportion thereof. The alkali cellulose is made into viscose according to any known method and then worked up into any desired form such as a fibre, film, ribbon, or plate or into coatings, dressing layers on fabrics, or pointed layers, coagulation being effected by any known precipitation agent, such as an acid or a mixture of an acid and a salt or an acid salt, or by heating or steaming. Miiller baths, for example, as described in Specification 10094/06, or baths containing or consisting of a strong mineral acid as described in Specification 264,161, 274,521, and 274,690, and particularly those containing not less than 55 per cent and preferably not less than 65 per cent of sulphuric acid monohydrate may be employed. In one example wood cellulose having a water content of 7.5-9 per cent is immersed in an 18 per cent caustic soda solution at 106‹ C. and as soon as the, whole of the cellulose has been introduced, the containing vessel is placed in ice and the contents further stirred until the temperature has fallen to 15‹ C. The reaction mixture is then allowed to stand and finally pressed, comminuted, and converted into a viscose solution containing 5.5-6.5 per cent of cellulose and 8 per cent of caustic soda. The viscose may be coagulated in a bath of the kind described in Specification 274,521, containing 60-70 per cent of sulphuric acid. In a second example the procedure is substantially the same except that the parent material is linters having a water content of 6.5-7 per cent. In a third example the procedure is the same as in either of the first two examples with the exception that the mixture of cellulose and alkali solution is maintained at the raised temperature for half an hour after the introduction of the cellulose before being cooled. In a further example the procedure is the same as in any of the above examples except that the caustic soda solution i, initially at 15‹ C. and the mixture of caustic soda and cellulose is heated quickly to 100‹ C. In other examples the procedure is the same as in the first example except that the caustic soda solution is initially at 15‹ C. and no heat is applied until after comminution of the mass, which is then raised quickly to 100-106‹ C. in a well closed vessel, maintained for 1 to 5 minutes at this temperature and then cooled or as soon as the introduction of the cellulose into the alkali solution at 106‹ C. is complete, the mixture is introduced into a preheated rotary autoclave, which is further heated so that. the mixture attains a temperature of 125-130‹ C. in 2-3 minutes, whereupon the mixture is removed and cooled quickly. In a further example the procedure is the same as that in any of the previous examples except that the soda cellulose is allowed to mature for 36 hours at room temperature before it is converted into viscose and in a final example the procedure, is substantially the same as that in the first three and the last examples except that a caustic soda. solution of 30 per cent strength at a temperature of 120‹ C. is used for making the alkali cellulose.