US2015201A - Precipitating bath for viscose filaments - Google Patents

Description

Patented Sept. 24, 1935 PRECIPITATING BATH FOR VISCOSE FILAMENTS Johann Joseph Stiickly and August Briitz, Teltow- Seehof,

Germany, assignors to North American Rayon Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application July 15, 1930, Serial No. 468,197. In Germany July 15, 1929 3 Claims.

In the use of sulphuric acid-sodium sulphate baths as precipitating means for extruded filamerits, it is well known that particularly desirable products are obtained if the sodium sulphate is 5 present in a sufiicient quantity to overcome the bi-sulphate reaction from the sulphuric acid present. In order to prevent loss of lustre and softness and shrinking of the filaments, the use of the processes now known necessitate the application of tension to the filaments during the washing and first drying step. This is indicated by the usual method of washing and drying the filaments while they are on the fixed take-up de- 'vices, in the spool spinning, and glass-roller spinning machines. When the so called centrifuged spinning process is used, installations of stretching trucks, or the addition of other elements, is necessary.

According to the present invention, the use for any of these spools, glass-rollers, stretching or stiffening devices, etc., is done away with, and are not necessary in and treating (especially drying) the newly spun filaments. When the well known Mueller bath discussed in paragraph one, is used,

together with the abridged treatment later described the two bath ingredients above do not prevent shrinkage, loss of lustre and softness, etc. The use of a higher concentration of the salt solution will improve matters to a slight degree,

but crystallization of the salts with consequent damage to the filaments, may result.

The present invention contemplates the addition of certain quantities of zinc sulphate to the bath, this addition producing good results in obviating the defects above mentioned. Experience, however, has shown that despite the addition of zinc sulphate, the sulphate concentration of the bath must not sink below a certain minimum percentage of sulphuric acid present, if

good results are to be obtained. Further, it has been discovered that the sodium sulphate concentration must not be allowed to drop to less than about 230 gr. NazSOr per liter. Although the concentration of sodium sulphate may be increased, the best results are obtained when about 250 gr. Na2SO4 per liter are used.

The addition of the zinc sulphate, and the quantity of this salt to be added, is important. For the best results, at least 5 gr./litre of ZnSO4 should be present, although the exact percentage present is dependent upon the concentration of sulphuric acid used.

As a general rule, higher concentrations of sulphuric acid necessitate the use of larger percentages of zinc sulphate. For example, it has been found that when grs. H2804 per liter and 250 gr. NazSOr per liter are used, 10 gr. of ZIlSOa must be added to give the best results. Similarly, for gr. H2804 per liter, 15 gr. ZnSOr per liter are necessary. When still higher concentration 5 of sulphuric acid is used, for instance, 135 gr. H2804 per liter, 25 gr. ZnSO4 per liter are necessary.

The addition of too great a percentage of ZnSO4 makes it necessary that the filaments contact 10 with the bath for a longer period of time. Otherwise, incomplete coagulation of the filaments results in their agglutination. This latter difiiculty may be overcome or prevented by acidifying the newly spun thread before washing and dry- 15 mg.

This new process may be advantageously used with the centrifugal spinning method. The newly spun cakes are reeled in a wet and acidic condition, and then washed in suitable washing machines, 20 treated, and hung up freely to dry. In this manner it is possible by eliminating the first washing and first drying, to obtain the skeins in one stroke.

In spite of this shortened process the yarn is not unduly shrunk, and possesses the desired lustre 5 and softness.

Another advantage may arise from using this new process in the centrifugal spinning method. The newly spun cakes may be washed, desulphurized, bleached, soaped, scoured, etc., without the 30 use of any stiffening bodies, and these cakes may then be dried and. used for various purposes without the necessity of using any stiiiening bodies, or stretching.

35 Example Normal viscose containing 7% cellulose and 7% alkali, aged from 9-l0 I-Iottenroth, is spun into artificial silk of denier, 5 denier to the single 40 filament, by use of the usual metallic or nonmetallic spinnerettes. The following spinning bath is used;

110 gr. H2804 per liter,

250 gr. Na2SO4 per liter, 45

15 gr. ZnSO4 per liter,

dipping distance 20 cm.

If themachine used is the well known centrifugal spinning machine, the spun cakes are at once reeled in their wet and acidic condition, then 50 thoroughly washed and dried without stretching. This method produces a lustrous, soft, and not unduly shrunk yarn, especially when the desulphurization step is completed,

We claim: 55

1. In a process for the manufacture of artificial filaments, yarns, threads, etc., from a viscose solution, the steps of preparing a normal viscose solution, and spinning it into a bath containing:

Gr/litre Sulphuric acid 110 Sodium sulphate 250 Zinc sulphate 15 and then washing, after-treating and. drying the filaments, yarn, etc., in an unstretched condition. 2. In a process for the manufacture of artificial filaments, yarns, threads, etc., from a viscose solution, the steps of preparing a normal viscose solution, and spinning it into a bath containing:

Per cent Sulphuric acid 8.25 to 10.71 Sodium sulphate 18.75 to 19.82

Zinc sulphate 0.825 to 1.98

Grams/liter Sulphuric acid 100 Sodium sulphate 230 Zinc sulphate 10 and then treating the freshly extruded product and drying it Without the application of such tension as would cause stretching.

JOHANN JOSEPH s'rijcKLY. AUGUST BROTZ.