US2194470A - Process and apparatus for the manufacture of artificial silk - Google Patents

Description

March 26, 1940. HARTMANN ET AL 2,194,470

PROCESS AND APPARATUS FOR THE MANUFACTURE OF ARTIFICIAL SILK Filed March 19, 1957 Patented Mar. 26, 1940 PROCESS AND APPARATUS FOR THE MANU- FACTURE OF ARTIFICIAL SILK August Hartmann and Johannes Uytenbogaart, Berlin-Lichterlelde, Germany, assignors to North American Rayon Corporation, New York, N. Y., a corporation of Delaware Application March 19, 1937, Serial No. 131,942 In Germany February 6, 1934 12 Claims.

The present invention relates to the manufacture of filaments of artificial origin but more particularly has for its object to devise a process of and apparatus for the desulphurization of viscose rayon in a continuous process.

In the usual methods used in the manufacture of viscose rayon with acid spinning baths, a thread is obtained after coagulation, washing, drying, etc., which contains a considerable amount of sulphur. A special after-treatment is required to remove this sulphur during which more or less alkaline compounds such as sodium hydroxide, sodium sulphite, soda, sodium sulphide, etc., are applied to the threads. Since the aforementioned sulphur occurs in the freshly spun thread precipitated in the usual spinning bath in a chemically combined form as well as in physical or mechanical suspension, a relatively strong treatment must be applied with the chemical compounds mentioned above.

Now it has been found possible to remove, under certain conditions, a large portion of the sulphur from the threads and to convert the remainder of the sulphur to such a chemical and mechanical state that it may be removed by simple soaping. In addition, it has been found that favorable results can be achieved with this method if the removal and conversion of the sulphur takes place immediately after the coagulation of the threads in a precipitating bath which is low in acid concentration and high in salt content, whereby the threads are not fully regenerated and the after-treatment solutions have access to and throughout the entire thread.

The continuously progressing thread should be treated within a few seconds, or fraction thereof, after leaving the spinning bath or while the sulphur is in a colloidal state.

The so-called continuous spinning process followed by an immediate wet-treatment of the thread may be adapted advantageously to this novel process.

The novel process is especially adaptable to the so-called continuous spinning process in which rollers, described for example in French Patent No. 745,254, or the United States equivalent Patent 2,002,995 may be used. I

It is therefore an object of the present invention to provide a novel process and apparatus for the desulphurization of viscose rayon.

Another object of the present invention is to provide a precipitatory bath for viscose rayon which precipitates the sulphur in the filaments in a state which allows ready removal of the sulphur.

Still another object of the present invention is to provide an after-treatment process for viscose rayon which removes the greater part of the sulphur therefrom.

Other objects will become apparent.

In describing the, invention reference will be made to the drawing in which is illustrated diagrammatically a vertical cross-section of a spinning machine.

In describing the invention reference will be made to a single unit of the machine. Such single units may be operated individually, or as herein illustrated, may be combined in a long row of units using common precipitatory tanks, coni veyor pipes, drive shafts, etc.

In the drawing the numeral l indicates a spinning nozzle from which is drawn the thread 3.

The nozzle I is immersed in the spinning or precipitating bath 2 through which the threads 3 are drawn and coagulated.

A driven roller 4 delivers the thread to the inclined treating cylinders 5 and 6 over which the thread is passed in an approximately helical path. These rollers 5 and 6 which are inclined for a purpose to be later explained, are also in- 26 clined with respect to each other whereby the thread which is looped a plurality of times around the rollers is fed from one end of the said rollers to the other end thereof. The thread 3 is then carried from the lower roller to a stationary 30 guide 1 and from there passes to any suitable collecting device (not shown). The said thread 3 may first becarried from the rollers 5 and 6 to other treating steps such as washing and drying before being passed to a collecting device.

A sulphuric acid solution is sprayed from the nozzle 8 which is mounted on the end of a supply pipe 9.

The sulphuric acid is sprayed onto the top roller 5 in a regulated amount whereby it spreads in a film down over the surface of the cylinder and the loops of thread conveyed thereon. The acid flows in a film evenly down the cylinder 5 and drips oil the lower edge thereof and is caught by a drip pan III. From the drip pan ill the spent acid is. carried off by a drain pipe II.

A supply pipe l2 carries water to a nozzle 13 which sprays the lower roller or cylinder 6 in a regulated quantity so that no spraying of the water results. The water flows down in an even film over the roller 6 and across the thread winding to the lower edge of the roller from where it drips into a drip pan l4. A drain pipe l5 carries off the waste water.

By using a pair of rollers for conveying the thread through the desulphurizing steps and treating with one liquid on one inclined roller and with a second liquid on the second inclined roller practically perfect separation of the different treating fluids is obtained. Also recovery of the separate liquids is simple due to the inclination of the treating rollers.

Another feature in the treating of the threads in the manner hereinbefore described is that only small quantities of treating liquids are necessary.

The spent sulphuric acid which is carried away bythe drain pipe ll may be recovered by carrying it to storage tanks in which the colloidal sulphur carried by the acid may be allowed to settle. After removal of this sulphur, which is done by allowing it to settle out and filtering, the acid may again be used.

As an example of the process to be used in desulphurizing the viscose filaments, the following example is given.

The viscose spinning solution is extruded 'through the spinning nozzle I into a precipitating bath which is preferably maintained at a temperature of about -'70 C. (preferably -60) and which consists of an aqueous solution containing about 80 to 200 gr. sulphuric acid (1.84 specific gravity) (preferably about 119-121 gr.), about 240-300 gr. of sodium sulphate, (preferably about 280-285 gr.), and about 5-25 gr. of zinc sulphate, (preferably about 16.0-16.5 gr.), per liter. This bath, which is low in acid concentration and high in salt concentration, is used because it is necessary to keep the viscose from becoming fully regenerated so that in the immediate after-treatment with sulphuric acid on the rollers the said acid may have full access throughout the thread to more readily wash out the collodial sulphur precipitated therein. This type of bath also produces a thread which minimizes shrinkage particularly longitudinally and imparts a definite elastic tension whereby it may more readily feed along the rollers.

A further advantage to be gained by the use of such a bath is that a thread is produced which is in a low hydrated state, making it an easy matter to wash out the residual acid.

Other salts which might be used in place of sodium sulphate are aluminum sulphate, magnesium sulphate, ammonium sulphate, zinc sulphate, or potassium sulphate.

The high zinc sulphate concentration in the bath is used because the hydrated zinc groups are more slowly decomposed than the sodium groups. This has the effect of acting as a buffer against the action of the sulphuric acid on the threads. A further advantage of the high zinc concentration is that the threads which are treated thereby have deeper dyeing qualities.

The somewhat high temperature of the bath compensates somewhat for the slowness of coagulation of the viscose and at the same time results on keeping the volume of the spin bath as near constant as possible due to evaporation.

The threads after passing through the spinm'ng bath, described above, are drawn therefrom by the drawing roller 4 and passed to the rollers 5 and 6 for treatment with acid and water.

The sulphuric acid which is applied to the roller 5 is an aqueous solution containing about to 170 gr. of sulphuric acid (preferably to gr.), per liter. This sulphuric acid solution is applied to the roller at a temperature of about 20 to 60 C. although it is preferably about 40 to 45 C. and the water which is applied to the other roller 6 is at a temperature above 80 C.

In using this arrangement and sequence of baths the sulphur may be removed from the filaments by the action of the sulphuric acid solution which contacts it very shortly after the initial regeneration of the cellulose and before the regeneration of the cellulose is completed, and also before the sulphur fiocculates or while it is .in a collodial state. This treatment with acid may continue for a considerable distance, i. e., 5, 15, or 20 meters.

The threads passing from the precipitating bath to the spaced roller may be and preferably are stretched therebetween. Due to the fact that the threads have been only partially coagulated or regenerated a more satisfactory stretching may be given or imparted to the filament.

The sulphur while in a colloidal or semi-colloidal state and before flocculation thereof is easily removed physically by the acid on the roller and retained and carried away thereby. The removal of the sulphur in this state is differentiated from a chemical separation which takes place after complete regeneration of the cellulose and flocculation of the sulphur. The result is a golden-yellow, dilute sulphuric acid solution in which the sulphur is present in a collodial or semi-collodial form, which, when the said acid solution is carried to a settling tank and allowed to stand, will settlefto the bottom of the tank. The acid may then be carried off from the top of the tank and filtered. This acid may then be re-used.

The invention as disclosed comprises extruding a viscose solution into a setting bath which partially coagulates them and precipitates the sulphur in a form whereby the sulphur may be readily removed by immediate treatment of the thread with a pure substantially salt-free sulphuric acid while the sulphur is still in a colloidal state, and also serves to further regenerate the cellulosic filaments. As the filaments proceed under the nozzle l3 they are subjected to a washing action, whereby the acid solution and sulphur, zinc, etc., carried by it are removed.

The application of the acid and water (preferably hot) causes the thread to shrink longitudinally and maintain the necessary tension in order to cause the filaments to be fed upwardly by the rotating rollers.

The operations are preferably conducted so as to keep the degree of hydration of the filaments as low as possible in order that lateral shrinkage of the filaments will be minimized.

Also by maintaining the hydration at a low point a greater amount of water is eliminated, resulting in a more sponge-like structure andv one which has a higher aflinity for dye-stuffs. Thus it will absorb dyes more readily and hold them more tenaciously.

Furthermore, the threads made as described herein will have uniform properties, such as, uniform dyeing properties, uniform shrinkage properties and uniform denier, strength and elongation thoughout every length.

This application is a continuation in part of a co-pending application to August Hartmann et al. for Manufacture of artificial silk, Serial No. 3,413, filed January 25, 1935.

It is obvious that many variations may be made in the method and apparatus described herein while utilizing the invention of the present application and it is not intended to restrict the invention to the particular descriptions or examples given herein. The terms used in describing the invention have been used in their descriptive sense and not as terms of limitation and it is intended that all equivalents thereof be included within the scope of the appended claims.

What is claimed is:

1. An apparatus for continuously spinning and treating filaments of artificial origin, comprising, a spinning nozzle, a precipitating bath, a plurality of spaced rotors over which said filaments are conveyed alternately from one to the other of said rotors in a plurality of loops after leaving said precipitating bath, and means to supply a different treating liquid to each of said rotors.

2. An apparatus for continuously spinning and treating filaments of artificial origin, comprising, a spinning nozzle, a precipitating bath, a plurality of spaced rotors over which said filaments are conveyed in plurality of loops after leaving said precipitating bath, said rotors having their axes at an angle to the horizontal, and means to supply a different treating liquid to each of said rotors.

3. An apparatus for continuously spinning and treating filaments of artificial origin, comprising, a spinning nozzle, a precipitating bath, a plurality of spaced rotors over which said filaments are conveyed in plurality of loops after leaving said precipitating bath, said rotors having their axes at an angle to the horizontal, and means to supply a different treating liquid to each of said rotors in such quantities that they will substantially vertically drip from the lower ends of said rollers.

4. An apparatus for continuously spinning and treating filaments of artificial origin, comprising, a spinning nozzle, a precipitating bath, a pair of spaced rollers about which the filaments are looped a plurality of times after leaving said precipitating bath, said rollers having their axes at an angle to the horizontal, and means to supply a diiferent treating liquid to each of said rollers in such regulated amounts that they will substantially vertically drip from the lower ends of said rollers.

5. The process of desulphurizing viscose rayon comprising treating a freshly spun viscose thread immediately after coagulation in successive lengths of a plurality of meters with a dilute and substantially salt-free sulphuric acid, and subsequently washing said thread with water, said acid containing about 80 to 170 grams of H2804 per liter of H20.

6. The process of desulphurizing viscose rayon comprising helically winding a freshly spun viscose thread around a pair of spaced rollers, treating said thread with a dilute and substantially salt-free sulphuric acid, and subsequently washing said thread with water, said acid containing about 80 to 170 grams of H2804 per liter of water.

'7. The process of desulphurizing viscose rayon comprising helically winding a freshly spun viscose thread around a pair of spaced rollers, applying a dilute and substantially salt-free sulphuric acid to one of said rollers and applying water to the other one of said rollers, said acid containing about 80 to 170 grams of H2304 per liter of water.

8. The process of desulphurizing viscose rayon comprising helically winding a freshly spun viscose thread around a pair of spaced rollers whose axes are at an angle to the horizontal, applying a dilute and substantially salt-free sulphuric acid to one of said rollers, and applying water to the other one of said rollers, said sulphuric acid and water being applied in such amounts that they will substantially vertically drip from the lower ends of said rollers, said acid containing about 80 to 170 grams of H2804 per liter of water.

9. In a continuous process of spinning viscose rayon, the steps which comprise extruding a viscose solution into a buffered precipitating bath at a temperature of about 45 to 70 0. whereby a partial retarded decomposition of said viscose solution into regenerated cellulose containing colloidal sulphur is effected, substantially removing said sulphur from said cellulose by applying thereto a substantially salt-free sulphuric acid solution at a temperature of about 20 to 60 C.

- and subsequently washing said regenerated cellulose with water having a temperature of at least 80 C., said precipitating bath containing about 80 to 200 g. of H2804 and about 245 to-325 g. of soluble salts per liter of water, and said salt-free sulphuric acid solution containing about 80 to 170 g. of H2804 per liter of water.

10. In a continuous process of spinning viscose rayon, the steps which comprise extruding a viscose solution into a buffered precipitating bath at a temperature of about 45 to 70 C. whereby a partial retarded decomposition of said viscose solution into regenerated cellulose containing colloidal sulphur is eifected, substantially removing said sulphur from said cellulose by applying thereto a substantially salt-free sulphuric acid solution at a temperature of about 20 to 60 C. and subsequently washing said regenerated cellulose with water having a temperature of at leastv 80 C., said precipitating bath containing about 80 to 200 g. of H2804, about 5 to g. of zinc sulphate and about 240 to 300 .g. of sodium sulphate per liter of water, and said salt-free sulphuric acid solution containing about 80 to 170 g. of H2804 per liter of water.

11. In a continuous process of spinning viscose rayon, the steps which comprise extruding a viscose solution into a buffered precipitating bath at a temperature of about 45 to 70 0. whereby a partial retarded decomposition of said viscose solution into regenerated cellulose containing colloidal sulphur is effected, substantially removing said sulphur from said cellulose by applying thereto a substantially salt-free sulphuric acid solution at a temperature of about 20 to 60 C. and subsequently washing said regenerated cellulose with water having a temperature of at least 80 0., said precipitating bath containing about 119 to 121 g. of H2804 and about 296 to 301.5 g. of dissolved salts per liter of water, and said salt-free sulphuric acid solution containing about 80 to 170 g. of H2504 per liter of water.

12. In a continuous process of spinning viscose rayon, the steps which comprise extruding a viscose solution into a bufi'ered precipitating bath at a temperature of about 45 to- 70 C. whereby a partial retarded decomposition of said viscose solution into regenerated cellulose containing colloidal sulphur is effected, substantially removing said sulphur from said cellulose by applying thereto' a substantially salt-free sulphuric acid solution at a temperature of about 20 to 60 C. and subsequently washing said regenerated cellulose with water having a temperature of at least 80 0., said precipitating bath containing about 119 to 121 g. of H2304, about 16.5 g. of zinc sulphate and about 280 to 285 g of sodium sulphate per liter of water, and said salt-free sulphuric acid solution containing about 80 to 1'70 g. of H2304 per liter of water.

AUGUST HAR'I'MANN. JOHANNES UY'IENBOGAART.

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