US2917775A - Apparatus for the closed circuit dry spinning of artificial or synthetic macromolecular substances - Google Patents

Description

Dec. 22, 1959 p c L zz o 2,917,775

APPARATUS FOR THE CLOSED CIRCUIT DRY SPINNING 0F ARTIFICIAL OR SYNTHETIC -MACROMOLECULAR SUBSTANCES Filed April 21, 1958 p Q, L.

APPARATUS FOR THE CLOSED CIRCUIT DRY SPINNING F ARTIFICIAL 0R SYNTHETIC MACROMOLECULAR SUBSTANCES Pierre Calizzano, Ligny-en-Barrois, France, assignor to Societe Rhovyl, Paris, France, a Frenchcorporation Application April 21, 1958, Serial No. 729,891

(Ilaims priority, application France April 30, 1957 ll Claim. (Cl. 18-8) It is known that it is possible to effect the dry spinning of artificial or synthetic macromolecular substances in a closed circuit, the atmosphere of which is moved by any driving force, for example simplyby the movement of the yarns. By dry spinning is meant the operation consisting in passing a solution of a macromolecular substance through the holes in a spinneret and evaporating solvent from the extruded filaments so as to set them.

A closed circuit dry spinning process is described in United States Patent No. 2,472,842. In this process the evaporating atmosphere is set in motion by the yarn and consequently circulates in the direction of travel of the latter; and after leaving the setting zone it is freed from solvent vapour by passing it through a condenser, and after being heated is returned to the setting Zone in the neighbourhood of the spinneret.

The apparatus employed for carrying out this process generally consists of two juxtaposed tubes, each provided with a heating device, and connected at the top by a tube of like diameter and at the bottom through a condenser. This apparatus, although operating satisfactorily, is bulky and relatively costly to construct.

It is also known, especially from French Patent No. 658,700 to effect the spinning in a cell consisting of a single closed tube, of which the upper part is heated and the lower part cooled. Spinning with such an apparatus is very difficult by reason of the fact that as the filaments pass through the cooled Zone they carry with them appreciable quantities of solvent; when the number of filaments is large this renders spinning practically impossible. Moreover since the atmosphere cannot circulate in a single direction, turbulence is produced which considerably impairs the stability of spinning.

The present invention concerns an improved apparatus for closed circuit dry spinning having numerous advantages over the type heretofore known, especially reduced overall dimensions, very simple construction, more economic operation and very high spinning stability.

Apparatus for dry spinning in accordance with the invention comprises a substantially vertical outer shell having a lateral opening at a level well spaced from both ends for the passage of a yarn having a drain at its lower end, a downwardly facing spinneret in the said shell adjacent to its upper end, upper and lower tubes within and substantially coaxial with the said shell, the upper end of the one and the lower end of the other being spaced from the upper and lower ends of the shell respectively and the tubes being separated by a space at least suflicient for the free passage of a yarn, means for heating a gas passing down the said upper tube, means for cooling a gas passing down the said lower tube, and yarn guide means so positioned that filament formed in the apparatus may be drawn round it and out through the said lateral opening after they have passed through the upper tube.

Preferably the means for heating the upper tube serves also to heat the annular space between it and the shell.

The upper tube may be heated and the lower tube nited States Patent r 2,917,775 Patented 12c 1 9 cooled by means of heat-exchange fluids flowing through jackets surrounding the tubes. Other methods may how ever be used, for example cooling coils or (for heating the upper tube) electrical resistance heaters. The cooling means for the lower tube may be inside and/ or outside the tube. l i

In operation, filaments coming from the spinneret at the top of the apparatus pass through the heated zone within the upper tube, in which they become set by the evaporation of solvent and then pass round the yarn guide and leave the cell through the lateral outlet. While passing through the tube they draw with them a current of the air or other evaporation medium which becomes charged with solvent vapour and which continues its travel through the lower tube. This lower tube, which performs the function of a condenser, is cooled to a temperature such that the solven'tvapours are at least partly, preferably practically completely, condensed. The condensate is discharged threu'ghthe drain at the bottom of the apparatus, and maybe directly reused forthe preparation of further spinning solution. The cold solvent-free air rises again in the annular space between. the two tubes and the shell, and while passing between the upper tube and the shell is heated. The current 0t gas therefore very regularly flows downwards through the two tubes and upwards through the annular space between them and the shell, alternately passing through heated and cooled zones, it being unable to follow any other circuit by reason of the arrangement of the heating and cooling means.

It is also to be noted that, in an apparatus of the type described, the heat and cold losses due to radiation are minimised by virtue of the fact that the heating and cooling are both within the spinning cell. Thus spinning apparatus according to the present invention may consume about half as much heat for the evaporation of a given weight of solvent as an apparatus of the type described in United States Patent No. 2,472,842.

The best temperatures to be maintained in the various parts of the apparatus depend on the material to be spun, the solvent employed and the spinning conditions, and may readily be determined by simple tests.

A form of apparatus in accordance with this invention is illustrated in the accompanying drawing.

Referring now to the drawing, the apparatus comprises a vertical cylindrical shell or outer tube 1 closed at its upper end, and provided at its lower end with a conical extension 2 terminating in a condensate drain 3. A spinneret mounting 4 carrying a spinneret 5 provided with feed means (not shown) for spinning solution is positioned centrally at the upper end of the shell. About halfway down the shell a guide pin 6 extends diametrically across it, opposite an opening 7 for the passage of yarn from the shell.

Inside and coaxial with the shell are mounted an upper tube 8 and lower tube 9 provided with jackets 10, 11 respectively through which heat-exchange fluids can be caused to flow. Between the ends of the tubes and the top and bottom of the shell respectively there is suflicient space to enable evaporative medium to pass freely, and between the two tubes is sufficient space to allow the apparatus to be threaded up. The filaments formed are indicated by the reference numeral 12.

In operation a heating fluid is passed through the jacket 10 and a cooling fluid through the jacket 11, the temperatures of these fluids being appropriate to the boiling point of the spinning solvent, the concentration and initial temperature of the spinning solution, the rate of spinning, and other relevant variables as will be apparent to any one skilled in the art. A spinning solution comprising a volatile solvent is extruded through the spinneret 5, the filaments produced are drawn round the guide pin 6 and out of the device by the opening 7. The

air in the device is drawn down through the tube 8 by the drag of the filaments 12, and during its passage through the tube 8 takes up solvent vapour from the filaments. At the guide pin 6 the filaments as already stated are drawn aside, but the air travels on under its own momentum through the lower tube 9 in which it is cooled sufiiciently to condense at least part of its content of solvent vapour. The condensate leaves the device by the drain 3. The air flows from the lower end of the tube 9 into the annular space between the tubes and the shell, up which it passes until it again reaches the vicinity of the spinneret. Between the upper tube 8 and the shell 1 it is heated by the fluid in the jacket 10.

7 represents the outlet for the condensed solvent.

It has been found that the apparatus according to the invention makes possible very high spinning stability by reason of the fact that the atmosphere freed from solvent and returning towards the spinneret is regularly distributed around the latter.

Apparatus according to the invention may be used for spinning solutions of macromolecular substances such as cellulose acetate and other cellulose esters, polyvinyl chloride, polyacrylonitrile, copolymers of vinyl chloride and vinyl acetate, and in general all substances which can be converted into yarns from solutions in volatile solvent.

I claim:

A dry spinning apparatus suitable for spinning solutions of synthetic polymeric substances by a closed circuit method, comprising two concentric tubes spaced apart, the inner tube being open at both ends and its upper part being provided with heating means and its lower part with cooling means, and the outer tube completely surrounding the inner and being provided at its lower end with an outlet for condensed solvent, a coaxially mounted downwardly facing spinneret inside the outer tube and above the open upper end of the inner tube, and means for guiding a yarn formed in the upper part of the spinning tube laterally out of the inner tube between the heated and cooled parts thereof and thence out of the apparatus.

References Cited in the file of this patent UNITED STATES PATENTS 2,007,389 Taylor et a1. July 9, 1935 2,022,260 Viviani Nov. 26, 1935 2,472,842 Mouchiroud et al. June 14, 1949

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