US1915072A - Processing of viscose rayon - Google Patents

Description

Patented June 20, 1933 was ATES

GEORGE A. RICHTER AND PHILIP G. SCHERER, JR., OF BERLIN, NEW HAMPSHIRE,

ASSIGNORS TO BROWN COMPANY, OF BERLIN, NEW HAMPSHIRE, A CORPORATION OF MAINE No Drawing.

This invention relates to the processing of viscose-rayon, and deals more particularly with the treating operations to which crude viscose-rayon yarn (i. e.,,yarn coming from 5 the spinning bath) is subjected before being used as a raw material in the manufacture of rayon goods. I

Crude rayon yarn contains considerable sulphur and an appreciable amount of organic coloring matter, even after it has been Washed and dried. In order to produce yarn of the desired luster and whiteness, it has been found necessaryto subject the crudeyarn to desulphuriz'ing and decolorizing treatments. Desulphurization isusually accomplished by treating the yarn with dilute solutions of sodium sulphide at about 80 to 100 C., whereupon after washing and souring to remove traces of sodium sulphide, the desulphurized yarn isdecolorized by bleaching as with dilute chlorine water. The decolorized yarn is then washed, treated with antichlor solution, e. g., sulphurous acid, N again washed, and finally dried. This sequence of treating operations heretofore commonly practised in the industry involves considerable handling of wet rayon yarn, and accordingly is time-consuming and expenslve.

We have discovered that it is possible to desulphurize and decolorize crude viscoserayon yarn to the desired condition, if such yarn is immersed in an alkaline bath and oxygen in suitable form is supplied to the bath. Thus, -we have found that the yarn may be desulphurized and decolorized in a single step, if it is immersed in a hot, dilute alkaline solution and a current of oxygencontaining gas, e. g., air or oxygen, passed into the solution. We have further'found that similar results may be obtained by dis- PROCESSING OF VISGOSE RAYON Application filed December 2'7, 1928. Serial No. 328,852.

resulting from the processes heretofore employed. The process of the present inven tion thus makes possible the removal of sulphur and coloring mater from crude ViSCOSB-r rayon yarn by a simpler, less expensive process, comprising fewer steps, consuming much less time, and yielding a product of excellent characteristics.

While we do not know precisely the action r of the ferric or manganese salts on the yarn, in view of the fact that organic coloring mat ter is removed therefrom, it is highly probable that these salts slowly furnish nascent oxygen, which exerts a bleaching effect. The

.E'zvample 1 Crude rayon yarn, say in skein form or wound on a reel, is immersed in a hot, dilute solution of sodium hydroxide, preferably a 0.2% solution, at to 100 C. -A current ofair or oxygen is passed into the solution until the yarn is thoroughly desulphurized; (about 30 minutes), at which time it is also bleached to snow-whiteness. The yarn is then removed from the solution, thoroughly washed with water, anddried.

Example 2 v Crude rayon yarn is immersed in a hot, dilute solution of sodium hydroxide containing ferric or manganese salts, preferably in a 0.2% solution containing about 0.2% ferric nitrate or manganese sulphate and at 80 to 100 C. The solution. is maintained at this temperature and is stirred until desulphurization is complete (about 30 minutes) whereupon the yarn is removed from the bath. The colored ferric or manganese salts deposited subsequently washed and dried, a pure white product is obtained.

E wample 5 Crude rayon yarn is immersed in a hot, dilute solution of sodium hydroxide contammg ferric or manganese salts, preferably 1n a 12% solution containing about 0.2% ferric nitrate-or manganese sulphate-and at 80 to 100C. Into the solution is passed a current of air or oxygen, until desulphurization is complete (about 30 minutes). The yarn is .then removed from the solution, treated as described in Example 2 for the removal of the colored iron or manganesesaltsdeposited thereon, and then washed and dried.

The foregoing examples are merely illustrative, as there are various other alkaline compounds and catalytic oxidizing agents which may be used in the treating bath. ,F or instance, in lieu-of caustic soda, we may use such alkaline salts as sodium carbonate, sodium phosphate, borax, or the like, andin lieu of ferric or manganese salts, we may useothersalts, such as those of cobalt, nickel, chromium, and vanadium, which in the presence of organic reducing agents tendeto change valence from higher to lower form, the concentration .of solution and the tem perature and time of treatment being such as will best suit the yarn being treated.

Having thus described the process of the present invention and certain modes of practising the same, it should be evident to those skilled inthe art that various changes and modifications might be made therein without departing from the spirit orscope of invention as defined by the appended claims.

We claim:

1. A process which comprises treating crude viscose-rayon yarn with an alkaline solution whileprogressively furnishing the solution with oxygen from an outside source until the yarn has been desulphurized.

2. A process which comprises maintaining crude viscose-rayon yarn in contact with an alkaline solution while progressively .furnishing the solution with oxygen from an outside source until the yarn has been desulphurized, and washing the product.

3. A process which comprises maintaining crude viscose-rayon yarn in contact with a hot, dilute alkaline solution while progressively furnishingthe solution with oxygen from an outside source until the yarn has been desulphurized.

4-. A process which comprises immersing crude viscose-rayon yarn in an alkaline solution containing a catalytic oxidizing agent, and passing an oxygen-containing gas into the solution.

5. A process which comprises immersing crude viscose-rayon yarn in an alkaline solution, and passing an oxygen-containing gas into the solution.

v6. A process which comprises maintaining crude viscose-rayon yarn in contact with an alkaline solution containing a catalytic oxidizing agent until the yarn has been desulphurized, said agent being selected from a group consisting of iron, manganese, cobalt,

nickel, chromium, and vanadium salts.

7. A process which comprises maintaining crude viscose-rayon yarn in contact with an alkaline solution containing a colored catalytic oxidizing agent selected from agroup consistingof iron, manganese, cobalt, nickel, chromium and vanadium salts, until .the yarn has been desulphurized, and removing the colored agentdeposited on the yarn.

8. A process which comprises maintaining crude viscose-.rayon yarn incontact with an alkaline solution containing a ferric salt until the yarn has been desulphurized,.and removing the salt deposited on the yarn.

, 9. A process which comprises maintaining crude viscose-rayon yarnin contact with an alkaline solution containing a ,ferr1c salt until the yarn has been desulphurized, treating with oxalicacid solution to remove the salt deposited on the yarn, and washing.

10. A process which comprises maintaining crude viscose-rayon yarn in contact with an alkaline solution containing ferric nitrate untilthe yarn has been desulphurized,,treating with oxalic acid solution to remove the salt deposited on the yarn, and washing.

.11. A process which comprises maintaining crude viscose-rayon yarn in contact with an alkaline solution containing a manganese salt unitl theyarn has been desulphurized, and removing the salt deposited on the yarn.

12. A process which comprises maintaining crude viscose-rayon yarn in contact with an alkaline solution containing a manganese salt until the yarn has been desulphurized, treating with sulphurous acid solution to remove the salt deposited on the yarn, and washing. 13. A process which comprises maintaining crude viscose-rayonyarn in contact with an alkaline solution containing manganese sulphate until the yarnhas been desulphur 'ized, treating with sulphurous acid solution an alkaline solution containing the compound of an element having more than one valence and tending to change from higher GEORGE A. RICHTER. PHILIP C. SCHERER, JR.