US1970384A - Cell for use in spinning cellulose acetate in the dry process - Google Patents

Description

Aug. 14, 1934. MANClNl 1,970,384

CELL FOR USE IN SPINNING CELLULOSE ACETATE IN THE DRY PROCESS Filed April 21, 1928 Patented Aug. 14, 1934 (JELL FUR USE IN SPINNING CELLULOSE ACETATE IN THE DRY PRQCESS Ugo Mancini, Milan, Italy, assignor to Ruth- Aldo Company Inc, New York, N. Y., a corporation of New York Application April 21, 1928, Serial No. 271,91

In Italy March 23, 1928 23 Claims.

assistance of an accurately adjustable regulator.

The spinning nozzle is disposed in the interior of a cell which maybe of circular or rectangular section; it may be located 'in the top or the bottom of the cell. The liquid filaments issuing fromthe various orifices of the nozzle traverse the entire length of the cell and are encountered,

, or accompanied, by a suitably heated current of air which evaporates the solvent so that at the end cf their passage through the cell, the filaments are transformed into solid filaments which, when brought together form a silkenthread.

It has been found that, in addition to the intrinsic qualities of the colloidal solution, the

elastic characteristics of the thread produced in this manner depend on the following physical factors:- a

v (1) Rate of evaporation of the solventaand therefore the temperatures and the amounts of the vaporized solvents present in the atmosphere enveloping the thread during its passage through the cell and the rate at which the air in the cell.

is renewed:

(2) Also the ratio between the rate at which the thread is wound and the rate at which the liquid filaments issue from the spinning nozzle; that is to say, the amount of stretching to which the thread is subjected in theinterior oi the cell.

More particularly with regard to this ratio, it has been found that:-

(a) The rate of winding the thread should always be the higher, and therefore it is necessary that the filament should be maintained in a plastic condition for a considerable time, in order that the stretching to which it is subjected may be distributed over a considerable length and effected in a gradual manner. dition is not fulfilled, the entire tension acts on the filament in the immediate vicinity of the spinning nozzle, and the whole of the stretching takes place suddenly as soon as the jet issues from the nozzle and causes rupture of the filament if the tension is high.

The conditions for satisfactory spinning are therefore highly favourable if the atmosphere surrounding the filament has a very high content of vaporized solvent in the neighborhood of the spinning nozzle; and the concentration of the vapors should diminish gradually in the direction of the orifice-through which the thread is dis- When this constagnant to prevent any deformation of the filainents under the action of atmospheric eddies, such deformation being afterwards irremediable and becoming manifest in the finished thread as broken filaments, or filaments of greater length than the others composing the same thread.

The high concentration of vaporized solvent, which is necessary for the production of the optimum characteristics of the thread, is attended with the great inconvenience of loss of solvent through leakage into the atmosphere at the openings in the cell. In fact, it is known that the rate of diffusion of vapors or gases between atmospheres' having adirferent degree of saturation depends on the difference in saturation and the gradation with which the passage from the greatest saturation to the lowest proceeds. As the change between the concentration on the inside and that on the outside is generally very rapid in the vicinity of the openings, and is almost instantaneous, the rate of dii fusion becomes very high.

On the other hand, it is not advantageous to admit the air into the cell at an excessive velocity,

' strength and:

(II) Friction between the filaments and the incoming dry air, which friction electrifies the filaments, increases their tendency to fly apart and results in irregular windingof the thread, and causes breakage.

The object of the present invention is to establish the most satisfactory conditions for spinning and, by avoiding the causes of loss of solvent, provide the best conditions for the formation of the thread constituted by the filaments.

To the attainment of this object I have, after numerous experiments, devised a novel spinning cell, one constructional form of which is illustrated in the accompanying drawing.

Figjl represents a sectional elevation of this embodiment; Fig. 2 is a plan view of one of the cell ports; Fig. 3 represents a diagram of the air velocities in the cell; Fig. 4 is a sectional view of a cell port and on line l-% of Fig. 2; Fig. 5 is a detail of one form of variable iris or exit opening for the passage of the filaments from the cell.

A spinning cell according to the invention may be regarded as consisting of three parts:-

(a) An upper chamber or head, for the spinning nozzle, in which there is no movement of the air, and therefore the formation of the filament is not disturbed by eddies. The stagnant air in this chamber has a maximum content of the vapors of the solvent:

(b) An intermediate chamber, or cell body, in which there is an upward movement of air.

This movement displays the following characteristics:

Dry air, or air relatively low in vapors, enters the bottom of the chamber through a small annular mouth formed by the outer wall of the cell and the cylindrical wall of a concentric tube, the air being thus guided in such a way that it flows parallel with the wall of the cell, and therefore does not come in contact with the filaments. Consequently, it may be endowed with a high velocity without the filaments being affected thereby.

It is natural that the air zones in theinterior of this flow should be involved by the movement of the latter, as is the case in injectors, but their velocity diminishes progressively towards the centre through which the filaments pass and where there is a movement of air, due to the adhesion of the threads, flowing in the opposite Y direction to that of the outer flow of air.

I have ascertained that the air velocities vary;

vents takes place, which vapors, in moving away from the filament, enrich the-air zone of higher velocity and are therefore carried off more readily.

The air circulating in said chamber is collected, at the upper part of same and by way of a circular gap, into a circular collector, whence it is aspirated into an apparatus for recovering. the solvent:

(c) A lower chamber or base in the bottom of which is the orifice through which the filament issues.

filament.

I have found that, by increasing the length of this chamber, the amount of the vaporized solvent evaporated may be raised to a value closely approximating completion. 1 Ports situated in the upper and lower chambers afford access for the assembling and upkeep of the spinning nozzle and for cleaning out the cell and starting the spinning. The opening of these ports would entail a loss of the vaporized solvent, to an extent increasing with the frequency and duration of their being opened. On this account there is disposed, round each opening, an aspirating gap which is normally closed by the port itself, but which communicates with the interior of the cell when the port is opened, in order to prevent the vapors escaping from the cell.

Referring now to the drawing, the collodion to be spun issues through the orifices of the spinning nozzle A located in the head E of the cell and, after passing right through the cell, the filaments are collected in the guide B, situated at the bottom of the base T of the cell, whence they are led to a winding device. The cell body'C is composed of a metal tube of circular section, provided with flanges D and D at the top and bottom.

On the upper flange D rests the head E supporting the spinning nozzle A and provided with two ports F and G, the former being fixed, whilst the other opens on a hinge and affords access to the spinning nozzle for assembling and replacement. In the lower part of said head is an annular passageI-I, communicating with the cell by way of a circular'slot K. Communication between the annular passage and the slot is controlled by a perforated plate I which efiects uniform distribution of the air drawn into said passages, through the mouth L of which the air passes to the device for recovering the solvent.

At the bottom of the intermediate cell portion C, heated air passes from a pipe M into an annular passage N and then through a perforated distributing plate 0 into an annular space P in the flange D whence it enters the body of the cell at a high velocity and in a direction parallel with the walls.

The base T of the cell is provided with two ports R and S, adapted to open on hinges; andin the bottom is an iris diaphragm U permitting the variation at will of the area of the orifice through which the thread issues to the outside and passes to the guide B.

The air admitted into the cell is heated outside.

In order to maintain the temperature, a chamber V is provided, which is traversed by water or other liquid heated to the desired temperature.

' The ports G R. S may be opened for changing the spinning nozzle or for removing waste, their construction being shown in Figs. 2 and 4.

The port (denoted as a in Fig. 4) is preferably surrounded by a frame I) in which is formed an annular passage 0 which is kept under constant negative pressure or suction by means of an aspirator communicating with the device for recovering the solvent. Passage 0 has an annular slit d in its inner side which slit is adapted to be closed by the door e which is preferably provided with a double glass closure f. The door e may be held tightly closed by means of retaining screws g and nuts h as indicated in the drawing. When the door e is closed the slit (1 is closed thereby. If for any reason the port is to be opened, the door e is opened thereby uncovering the slit d and the aspirated air which is present in the interior of the cell and would tend to diffuse into the surrounding atmosphere, is aspirated, in association with a certain amount of outside air, and passed to the device for recovering the solvent. By this means the recovery of nearly the whole of the solvent is assured.

Having now fully described my said invention and the manner in which the same is to be performed, I declare that what I claim as my invention and desire to secure by Letters Patent is:

1. Apparatus for use in spinning cellulose esters dissolved in volatile solvents, comprising a spinning cell providing at least three superposed chambers to be successively traversed by the spun filaments, a spinning nozzle in the upper chamber, means for admitting air at a point between the lower and intermediate chambers, means for drawing ofi air and solvent vapors at a point between the intermediate and upper chambers, and which lower chamber carries ports which on opening thereby open a suction line which pre vents escape'of solvent vapors to the outside at- I mosphere.

2. Apparatus for use in spinning cellulose esters filaments, a spinning nozzle in the upper chamber, means for admitting air at a point between the lower and intermediate chambers so that said air rises as an annular zone, means for drawing off air and solvent vapors at a point between the intermediate and upper chambers, and which lower chamber carries ports which on opening thereby open a suction line which prevents escape of solvent vapors to the outside atmosphere.

3. Apparatus for use in spinning cellulose esters dissolved in volatile solvents, comprising a spinning cell providing at least three superposed chambers to be successively traversed by the spun filaments, a spinning nozzle in the upper chamber, means providing an annular air inlet at the bottom of the intermediate chamber, means providing an annular air and solvent vapor outlet at the top of said intermediate chamber, and which lower chamber carries ports which on opening thereby open a suction line which prevents escape of solvent vapors to the outside atmosphere.

4:. Apparatus for use in spinning cellulose esters dissolved in volatile solvents, comprising a spinning cell providing at least three superposed chambers to be successively traversed by the spun filaments; a spinning nozzle in the upper chamber, means for admitting air at a point between the lower and intermediate chambers, means for drawing off air and solvent vapors at a point between the intermediate and upper chambers, an exit orifice of variable area by which the filaments leave the cell, and which lower chamber carries ports which on opening thereby open a suction line which prevents escape of solvent vapors to the outside atmosphere.

5. Apparatus for use in spinning cellulose esters dissolved in volatile solvents, comprising-a spinning cell providing at least three superposed chambers to be successively traver ed by the spun filaments, a spinning nozzle in the upper chamber, means for admitting air at' a point between the lower and intermediate chambers so that said air rises as an annular zone, means for drawing off air and solvent vapors at a point between the inter-.

mediate and upper chambers, an exit orifice of variable area by which the filaments leave the cell, and which lower chambers carries ports which on opening thereby open a suction line which prevents escape of solvent vapors to the outside atmosphere.

6. Apparatus for use in spinning cellulose esters dissolved in volatile solvents, comprising a spinning cell providing at least three superposed chambers to be successively traversed by the spun filament, a spinning nozzle in the upper chamber, means providing an annular air inlet at the bottom of the intermediate chamber, means providing an annular air and solvent vapor outlet at the top of said intermediate chamber, an exit orifice of variable area by which the filaments leave the cell, and which lower chamber carries ports which on opening thereby open asuction line which prevents escape of solvent vapors to the outside atmosphere.

7. Apparatus for use in spinning cellulose esters dissolved in volatile solvents, comprising a spinning cell providing at least three superposed chambers to be successively traversed by the spun filaments, a spinning nozzle in the upper chamber, means for admitting air at a point between the lower and intermediate chambers, means for drawing off air and solvent vapors at a point between the intermediate and upper chambers, and an exit orifice of variable area by which the filaments leave the bottom of the cell, and which lower chamber carries ports which on opening thereby open a suction line which prevents escape of solvent vapors to the outside atmosphere.

8. Apparatus for use in spinning cellulose esters dissolved in volatile solvents, comprising a spinning cell providing at least three superposed chambers to be successively traversed by the spun filaments, a spinning nozzle in the upper chamber, means for admitting air at a point between the lower and intermediate chambers so that said air rises as an annular zone, means for drawing off air and solvent vapors at a point between the intermediate and upper chamber, and an exit orifice of variable area by which the filaments leave the bottom of the cell, and which lower chamber carries ports which on opening thereby open a suction line which prevents escape of solvent vapors to the outside atmosphere.

9. Apparatus for use in spinning cellulose esters dissolved in volatile solvents, comprising a spinning cell providing at least three superposed chambers to be successively traversed by the spun filaments, a spinning nozzle in the upper chamber, means providing an annular air inlet at the bottom of the intermediate chamber, means providing an annular air and solvent vapor outlet at the top of said intermediate chamber, and an exit orifice of variable area by which the filaments leave the cell, and which lower chamber carries ports which on opening thereby open a suction line which prevents escape of solvent vapors to the outside atmosphere.

10. A cell for use in spinning cellulose esters dissolved in volatile solvents, comprising upper, intermediate and lower chambers to be successively traversed by the spun filaments; a spinning nozzle in the upper chamber; which chamber contains only a single opening exposed on its downward side to moving currents of the gaseous medium; means for directing a flowing medium through the intermediate chamber longitudinally thereof so that its vapor contents diminishes to approximately nothing along the course taken by the filaments and so that its velocity increases outward from the axis of the intermediate chamber, and a lower chamber with its innermost opening in free contact with the moving currents of the gaseous medium.

11. A cell for use in spinning cellulose esters dissolved in volatile solvents, comprising upper, intermediate and lower chambers to be successively traversed by the spun filaments; a spinning nozzle in the upper chamber, which chamber contains only a single opening exposed on its downward side to moving currents of the gaseous medium; a flowing medium in the intermediate chamber whose vapor content diminishes to approximately nothing along the course taken by the filaments and whose velocity increases outwards from the axis of the intermediate chamber, a lower chamber with only a single opening in free contact with the moving currents of the gaseous medium, and an exit orifice of variable area.

12. A cell for use in spinning cellulose esters dissolved in volatile solvents, comprising upper, intermediate and lower chambers to be successively traversed by the spun filaments; a spinning wards from the axis of theintermediatechamber,

a lower chamber with only a single opening in' free contact with the moving currents of the gaseous medium, and an exit orifice'of variable area by which the filaments leave the bottom of the cell. I

13. A cell for main spinning cellulose esters dissolved in volatile solvents, comprising upper, intermediate and lower chambers to be successively traversed by the spun filaments; a spinning nozzle in the upper chamber, which chamber contains only a single opening exposed on its downward side to moving currents of the gaseous medium; a flowing medium in the intermediate chamber whose vapor content diminishes along the course taken by the filaments and whose velocity increases outwards from the axis of the intermediate chamber, a lower chamber with only a single opening in free contact with the .moving currents of the gaseous medium, and

contains only a single opening exposed on its "dissolved in volatile solvents, comprising upper,

which lower chamber carries ports which on opening thereby open a suction line which prevents escape of solvent vapors to the outside atmosphere. i

II 14. A cell for use in spinning cellulose esters dissolved in volatile solvents, comprising upper, intermediate and lower chambers to be successively traversed by the spun filaments; a spinning nozzle in the upper chamber; which chamber downward side to moving currents of the gaseous medium; a flowing medium in the intermediate chamber whose vapor content diminishes along the course taken by the filaments and whose jjvielocity increases outwards from the axis of the intermediate chamber, and a lower chamber with only a single opening in free contact with the moving currents of the gaseous medium, an exit rifice of variable area by which the filaments leave the cell; and which lower chamber carries portswhich on opening thereby open a suction line which prevents escape of solvent vapors to the outside atmosphere.

15. A cell for use in spinning cellulose esters intermediate and lower chambers to be successively traversed by the spun filaments; a spinning nozzle in the upper chamber, which chamber contains only a single opening exposed on its downward side to moving currents of the gaseous medium, a flowing medium in the intermediate chamber whose vapor content diminishes along the course taken by the filaments and whose velocity increases outwards from the axis'ot the intermediate chamber, and a-lower chamber with fthe port having an aspirating chamber adapted to communicate with the port when the latter is opened; and a door fitted to said frame for closing the port, said door when closed preventing communication of the port with said chamber {but permitting communication therebetween when open.

17; A closure for the port of a cellulose ester spinning cell; comprising a frame surrounding an opening in the cell and having an annular chamber: connected with a suction line, said chamber having an internal slit adapted to communicate with said opening; and a door having a glass inset and adapted to close said opening and said slot when closed, and when opened to uncover said slit and permit aspiration of air into said chamber.

18. A process of spinning cellulose esters consisting of passing the ester dissolved in a volatile solvent through a spinneret into a stagnant atmosphere approximately saturated with vapor of the solvent, then into a counter-current flowing atmosphere all cross sections of which are moving at substantially the same velocity and finally again'into an approximately stagnant atmosphere containing only a slight concentration of the vapor of the solvent, the said flowing atmosphere having its minimum velocity in the vicinity of the filaments.

19. A process of spinning cellulose esters consisting of passing the ester dissolved in a volatile solvent through a spinneret into a stagnant atmosphere approximately saturated with vapor of the solvent, then into a counter-current fiowing atmosphere, all cross sections of which are moving at substantially the same velocity and finally again into an approximately stagnant atmosphere containing only a slight concentration of the vapor of the solvent, and passing in exit through an opening whose area is regulatable.

20. Apparatus for use in spinning cellulose esters dissolved in volatile solvents; comprising a spinning. cell containing at least three superposed zones to besuccessively traversed by the spun filaments; a spinning nozzle in the upper zone, means for admitting an annular column of air free from solvent vapors at a point between the lower and intermediate zones and causing said column to travel substantially parallel to the spun filaments with its velocity increasing outwardly from the axis of the intermediate chamber; and means for drawing off all the air and a solvent vapors to be removed from the cell at a point between the intermediate zone and the upper zone, while the atmosphere in the upper and lower zones remains substantially stagnant.

21. Apparatus as set forth in claim 20, having an orifice of variable area in its lower end for the withdrawal of filaments therefrom.

22. Apparatus as set forth in claim 20 having means for heating the intermediate zone.

23. Apparatus for use in spinning cellulose esters dissolved in volatile solvents, comprising a spinning cell containing at least three superposed zonesto be successively traversed by the spun filaments, aspinning nozzle in the upper zone, means for admitting air free from solvent vapors at a point between the lower and intermediate zones, and meansfor withdrawing air mixed with solvent vapors at a point between the intermediate and upper zones while maintaining the atmosphere in the upper and lower zones substantially stagnant, said cell having an orifice of variable area in its lower end for the withdrawal of filaments therefrom.

UGO MANCINI.

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