US2732585A

US2732585A - Spinner head

Info

Publication number: US2732585A
Authority: US
Publication date: 1956-01-31
Anticipated expiration: 1973-01-31

Description

Jan. 31., .1956 W|KER 2,732,585

SPINNER HEAD Filed Feb. 12, 1952 5 Sheets-Sheet l INVENTOR ATTORNEY Jan. 31, 1956 c. B. WICKER 2,732,585

SPINNER HEAD FiledFeb. 12, 1952 3 SheetS -Sheet 2 INVENTOR 0,4 5. W/CKf/P film KM ATTORNEY D. B. WICKER SPINNER HEAD Jan. 31, 1956 3 Sheets-Sheet 3 Filed Feb. 12, 1952 INVENTOR flflA/B. W/CKF/P BY )p z E I ATTORNEY United States Patent O SPINNER" HEAD Dan B- Wicken. Stamford, Cun-.,,assignor to American Cyaua id Company, New Yorlt N, 12;, a. corporation This invention relates to a spinner headfbr the extrusion of a coagulable material" in themanufacture' of. artificial fibers. g

In producing artificial filaments'b t-lie spinning Qfsolutions of a fiber-forming material, it frequently ha pens that the solution at: normal temperature, or when warmed only slightly, is so viscous that it cannot be extruded or spun satisfactorily because of. low'pullaway'speed from the face of'the spinneret' with a. resulting. low production rate per spinning. unit andexcessive power: consumption in extruding the thick dope through small orifices. The solution of this problem in some: instances resides in merelyheating a large bulk of the; spinning solution or dope prior to pumping this'dopeto'thespinner head. This technique is unsuitable forthewetspinning ofsolutions: of polymeric and. copolymeric acrylonitril'c in concentrated aqueous solutionsiof certainsalts asidescribedin Cresswell Patent No. 2,558,730 becauseiofobjectionable alterations in theproperti'es'ofsuch solutions upon heating. for a relatively prolonged period of time. In addition the viscosity of these solutions is such, that;there is relatively little mixing of the viscousdope while beingpumped through, a. relatively' long pipe to a spinneret; hence the'heat lbsti by. the peripheral portion of the dope stream in. its flow through the pipe resultsin lack ofuniformityin the temperatures of various portionsor strataiof." the spinning solution. Such. lack of'uniform temperature becomes seriouswhen a hot spinning dope must flow through conduits submerged in a cold spinning bath as used in the C'resswell" process: This etfectis intensified in the production oftow or staple fibers as. a correspondingly larger amount of the dope passes through larger pipe lines in spinning 5'00 to 5000 or more filaments per spinning header'ih contrast to. the

30 to 240 filaments per unit typical of continuous filament yarn production. Withother; conditions constantiinthe Cresswell process, the size; of fibers. extrudingfrom the orifices of a spinneret varies asan inverse function of'tlie viscosity of the spinning dope, and such. viscosity is,. of course, an inverse function of the ambient temperature of each particular orifice; therefore a uniform temperature at the numerous orifices. is essentialto theproduction of a strand or tow of fibers of. uniform. diameten. Various heated spinning heads are known in the.- art. hut these, without exception, have been found inadequate tor. the production of tow by the Cresswell process. since. none were able to deliver. the Spinning done with. suflicient thermal. uniformity to eachofamultiplicity ohorifices. for the production of uniformly sized fibers and. none were capable of supplying the necessary. large quantity oi heat at a point close to thevspinneretfacer The. failure to. meet the latter requirementmeant a considerablyv greater; num: ber of spinning units wouldbe requiredfor any given: production rate thereby lowering. the manufacturing @lfi'r ciency. I 1 H 5 An object of the invention is; to provide an; improved. de vice for the extrusion of artificial; fibers;

Another object of the invention is to; ptcuide anz' have proved device for the spinning of an artificial fiber tow from: a viscous coagulable material.

A further object of the invention is to provide an improved" device for heating a reiatively large amount of a viscous dope to a uniform temperature immediately prior to extrusion;

Other objects and advantages of the invention will be apparent to those skilledin the art from the description hereinbelow;

The present invention concerns a spinning headhaving a multiconduit indirectheat exchanger and a spinneret locatedadjacent" to the outlet thereof. Other features of the invention include a projecting flange which transfers heat to the spinning dope immediately prior to its extrusion, means for insulating the heat exchanger, upper and lower'condensatetrapsand'meansfor positioning the device in various positions; The invention accordingly comprisesthe features"ofconstruction, combinations of elements and' arrangernent of parts, which will be exemplified in'the construction hereinafter set'forth, and the scope of the invention willbeindicated in the claims.

A better understanding of the nature and objects of the prcsent'inventionwill be had by reference to the accompanying drawings in which:

Fig. 1 is a longitudinal sectional view through the centerof the spinningheadwith certain parts removed;

Fig; 2 is a fragmentary enlarged sectional view of the extrusion end of the apparatus taken-on the same plane as Fig: l;

Figs. 3; 4 and'5 aresomewhat diagrammatic elevation views of'the spi'nni'ngh-ead in various positions.

Referring now to Fig. 1 thespinner unit is mounted in the casing It) which i'sfastened to a shaft 12 by a cap screw 14 or other suitable means. Within this casing is an indirect heat exchanger 1'6 of" the multitubul'ar type known asa-shell and tube-heat exchanger. This heat exchanger consists ofshell" 18 and the inlet and outlet tube sheetsZOia-nd 22irespectivel'y; which are rigidly'secured to theshell 1S by'brazing, welding or other suitable means. Suitable-access doors (not shown) are provided in casing 10 for the installation and' maintenance of'the equipment contained therein.

Theshell is 7%r inches'long and 3 inches in diameter. There-are 3T tubes: 24- with inside and outside diameters of% inch and- 7 inch, respectively, mounted in the tube sheets. A heater of this size has been found to be very satisfactory in the Cresswell" process in extruding up to about 5000 filaments of acrylbnitriie copolymer tow through orifices having a diameter of 65 microns. The size, number and length of'tubes'may, of course, be varied to accommodate greater or smaller numbers or sizes of A fluid medium is used for heating this multitubulan heaterand it may be either a liquid, vapor or gaseous'substance. Steam isgenerally preferred for the purpose, especially for spinning fibers from acrylonitrile polymers and copolymers at about to C.

The short shaft 12 extends through the casing 10 and projects outside into bearings (not shown) mounted in suitable supports on both sides of" the casing. The in: coming heating medium is' introduced through suitable channels in one of these hearings which communicate withthe longitudinalpassage 26in the'center of shaft 12. Thispassage leads to the channel 28 and tube or pipe 39" which carries the steam to. the inlet 32 located near the exittube' sheet 22". From this point the heating medium flows. over: the exterior surfaces of the tubes throughout the shell and passes to the left; it leaves the heat ex-' changer: through oneor both of the outlets 34 which arelocated at' the top and bottom. of shell 18 in close proximity to inlet tube sheet; 20.: When: steam is: employed for heating,. the thermostatic steeurrv traps 36' and 38. are Rrovidethfor; separating. condensate.

fromthesteama Lines

40 and 42 respectively connect these traps with the exhaust line 44 which communicates with passage 46 and longitudinal hole 48 in shaft 12. Channel 48 is in communication with a suitable annular passage in the bearing or bearing cap (not shown) thus providing for removal of the cold heating medium or condensate at any angular position of the spinner head. The coagulable polymeric material or spinning dope from which the fibers are formed is pumped into the spinning head through a central channel in the opposite bearing or bearing cap (not shown) and passages (not shown) similar to

intake channels

26 and 28. These dope feed passages communicate with the tube 50 and inlet header 52 which is bolted or otherwise secured to the inlet tube sheet 20. Under the influence of the uniform pressure in header 52, the spinning dope flows at uniform velocities through the tubes 24 of uniform length and diameter to the outlet tube sheet 22. The tubes are of relatively small diameter and are heated evenly by the steam, hence all'portions of all of the streams flowing through the exit tube sheet are at substantially the same temperature even in the case of a viscous polyacrylonitrile dope which is prone to form strata of different temperatures. It will be noted that the flow is countercurrent to the flow of the heating medium for maximum heat transfer efliciency with noncondensing heating media. The heat exchanger 16 and its accessories are fastened to the casing with an appropriate number of cap screws 54 and the joint is sealed with a moisture-proof rubber gasket 56 which also serves to reduce the loss of heat by conduction from the heat exchanger to the casing.

Turning now to Fig. 2 the heated dope leaving the tubes 24 enters a chamber 58 bounded by the tube sheet 22 with its integral cylindrical flange or fin 60 and the spinneret 62 which is provided with a large number of tiny orifices 64 which are shown only schematically. Within the chamber 58 is a filtering device which is made up of a fabric filter 66 consisting of about four layers of woven nylon or other textile materials which are relatively unatfected by the solvent and ambient thermal conditions. The number of layers of filter cloth depends on the coarseness of the weave and size of the interstices. If a tightly woven or finely woven fabric is available, one layer may provide a satisfactory filter. The cloth is held in place by a stainless steel wire screen 68 to which is attached an annular or ring separator 70 made of nylon or other suitable corrosion-resistant material and provided with a series of deep serrations or notches 72 on both sides of the ring in order to permit the free flow of the spinning dope between the interior and the exterior of the ring on both sides thereof. The function of ring 70 is to keep the filter spaced from the spinning orifices 64 to avoid blocking any of the holes. In mounting the spinneret assembly on the spinner header a rubber gasket 74 is placed on the projecting flange 60. This is followed by the layers of nylon cloth 66 and another rubber gasket 76. Next the screen 68 with' its attached spacer 70 are held against the cloth 66 while the spinneret 62 is pushed into place on the flange 60. The spinneret is fastened in place by the clamp ring 78 which is desirably fashioned out of cloth laminated with a plastic, such as a phenolformaldehyde condensation product. For extra strength it is desirable to mold a flat metallic plate insert 80 into the clamp ring. The clamoring issecured by the circular row of cap screws 82 which engage threads in the annular boss 84 in casing 10. In order to seal the casing, which is particularly necessary when the assembly is to be operated in a submerged position, the seals 86 around the spinneret as well as 88 and 90 around the boss 84 are provided. Each of these consists of a deformable rubber ring placed in an annular groove of suitable size. It will be noted that this construction provides a sizable annular pocket or air space 92 between casing 10 and clamp ring 78. This as well as the low thermal conductivity of the plastic used in the ring serve to effectively insulate the heat exchanger 16 against heat losses except for the amount of heat which is necessarily lost through contact of the face of spinneret 62 with the coagulating medium. In this connection it should be observed that the projecting fin 60 serves to conduct a substantial amount of heat to the spinning solution in the spinneret 62 in order to maintain the dope at spinning temperature until it is in actual contact with the coagulating medium.

The various positions of the spinner header are illustrated in Figs. 3, 4 and 5. In Fig. 3 the header is locked back out of the coagulating bath 94 by means of the double hook 96 which is pivotally attached to the casing 10 by means of the pivot 98. The hook 96 is provided with two slots 100 and one of these engages the crossbar 102 which is fastened to the frame member 104. This frame member 104 is riveted or otherwise securely attached to the tank 106. Other fastening or holding means, such as latches, hooks on chains or ropes, gear arrangements, etc. are contemplated as substitutes for the rigid hooks 96.

In preparing the header for extrusion operations, it is moved to the position shown in Fig. 4 by engaging the hook 96 with the crossbar 108 which is also attached to the frame 104. This unit is brought to the optimum operating temperature and the entire spinning dope feed system is purged free of air in this position; inasmuch as the spinneret face is tilted slightly downward, the extruded dope falls free of the operating face of the spinner head instead of flooding over it. The dope extruded at this time, while purging the spinner head, may be caught in any suitable container in order to avoid having random bits of coagulated polymer circulating through the bath 94. After being thoroughly purged and heated, the header is swung into the operating position shown in Fig. 5 and fixed in the position by the engagement of hook 96 with a crossbar 110 which extends through the bath and is fastened to the tank in any suitable manner.

When the spinning unit is in the inverted or starting-up position of Fig. 4 the condensate from the steam drains out through the trap 36 which is in the lower position while the upper trap 38 performs the extremely useful function of bleeding air out of the heating system. However, in the normal operating positions shown in Figs. 1 and 5, the condensed liquid drains out through the lower trap 38 andtrap 36 does not function unless some air has gotten into the system.

In the aforementioned Cresswell process polymers and copolymers of acrylonitrile dissolved in a suitable solvent, such as a concentrated aqueous solution of sodium thiocyanate, is extruded at a temperature of about 60 to 100 C. into a liquid coagulating bath of a relatively dilute aqueous sodium thiocyanate solution maintained below 10 C. and preferably within a few degrees above or below 0 C.- In the production of tow the extrusion temperature may run as high as about 110 C.; however it is preferred to extrude the filaments of tow at 95 C. into a liquid coagulant maintained at 0 C. The tempera- .tures of that process are critical therefore insulation of the multitubular heat exchanger is unusually important in minimizing the transfer of heat to the low temperature coagulating bath and in reducing both the heating and the refrigeration loads. From the construction described herein it is apparent that the spinneret has been completely shielded'o'r insulated from the cold coagulant except for the spinneret face which must necessarily be exposed. The construction described also reduces the heat lost through the side and flange of the spinneret to the chilled coagulating solution as these members are shielded by the ring 78 made of a plastic material of low thermal conductivity. Minimizing this heat loss results in the outermost-or peripheral orifices 64 being maintained at substantially the same temperature as the inner orifices. Becauseof this, fibers of substantially uniform size are formed in all of the orifices rather than undersized filaments-at somewhat cooler outer orifices.

A number of advantages accrue from the pivotal mounting of the spinner head. In the inverted position the device is readily accessible for adjustment or maintenance, and the passages and tubes carrying the spinning solution may be purged free of air and brought up to temperature without interfering with the adjacent units in a battery of these spinning heads. At this time all of the extruded dope may be readily collected in any suitable container; then the unit may be readily and quickly swung into operating position by releasing the hook from crossbar 108 and fastening it on crossbar 110. In approaching the operating position it will be noted that the spinning head is swinging in the direction of extrusion of the filaments; in other words, the head is approaching its operating position from the rear. This has been found highly desirable in avoiding interference with the adjacent spinning units in the battery as the likelihood of dribbling dope into fibers being taken off of the adjacent spinning positions is negligible.

Although the device of the present invention is particularly useful in the wet spinning of high-viscosity solutions of polymers and copolymers of acrylonitrile, its utility is not limited either to polyacrylonitrile or to wet spinning. It can be employed in the wet spinning of other artificial fiber dopes and also in dry spinning operations wherein a hot solution of polyacrylonitrile or other fiber forming material in an organic or other suitable solvent is extruded into a heated atmosphere to evaporate the solvent and to coagulate the filamentary material.

While there are above disclosed but a limited number of embodiments of the structure of the invention herein presented, it is possible to produce still other embodiments without departing from the inventive concept herein disclosed, and it is desired therefore that only such limitation be imposed on the appended claims as are stated therein or required by the prior art.

Having disclosed my invention in detail, what I claim as new and desire to secure by Letters Patent is:

1. A device for the extrusion of filaments of a coagulable material which comprises an indirect heat exchanger having a shell provided with walls supporting a plurality of conduits in which the coagulable material is heated while passing therethrough by heat transferred through the conduits from a heating medium circulating through the shell on the outside of the conduits, a cup-shaped spinneret provided with orifices through which the heated coagulable material is extruded in the form of filaments and a projecting flange of high thermal conductivity attached to a conduit outlet wall and extending into the spinneret in order to supply heat from the heating medium to the coagulable material immediately adjacent to the spinneret orifices.

2. A device according to claim 1 in which the heat exchanger is substantially enclosed in a casing separated therefrom in such manner as to provide heat-insulating space surrounding a major portion of the exterior of the heat exchanger.

3. A device according to claim 1 in which said device is swingably mounted and provided with means for fixing said device in a predetermined position.

4. A device according to claim 1 in which the heating medium is introduced from a supply means through an inlet near the conduit outlet wall and circulated through the shell to an outlet near the conduit inlet wall countercurrently to the flow of coagulable material.

5. A device according to claim 1 in which condensate traps are provided adjacent the opposite sides of the shell for the removal of the condensate of a condensable heating medium.

6. A device accordingto claim 1 in which a condensable heating medium is circulated through the shell countercurrently to the flow of coagulable material by means including a heating medium inlet near the conduit outlet wall and condensate traps adjacent opposite sides of the shell near the conduit inlet wall for the removal of the condensate of the heating medium.

7. A device for the extrusion of filaments of coagulable material which comprises a shell and tube indirect heat exchanger provided with tube sheets supporting a plurality of substantially parallel tubes in which the coagulable material is heated While passing therethrough by heat transferred through the walls of the tubes from a condensable heating medium circulated countercurrently through the shell on the outside of the tubes by means including a heating medium inlet near an outlet tube sheet and condensate traps near an inlet tube sheet for the removal of condensate of the heating medium, the condensate traps being located adjacent the top and bottom of the shell when the tubes are in horizontal alignment, a cup-shaped spinneret provided with orifices through which the heated coagulable material is extruded in the form of filaments, a projecting flange of high thermal conductivity attached to the outlet tube sheet and extending into the spinneret in order to supply heat from the heating medium to the coagulable material immediately adjacent to the spinneret orifices, a swingably-mounted casing substantially enclosing the heat exchanger and separated therefrom in such manner as to provide heat-insulating space surrounding a major portion of the exterior of the heat exchanger, and means for fixing the casing in a predetermined position.

References Cited in the file of this patent UNITED STATES PATENTS 1,176,612 Snider Mar. 21, 1916 1,450,131 Borzykowski Mar. 27, 1923 1,918,816 Lecomte July 18, 1933 2,272,880 Greenup Feb. 10, 1942 2,369,553 Fields Feb. 13, 1945 2,425,782 Bludworth et al. Aug. 19, 1947 2,514,189 Spencer et al July 4, 1950 2,586,970 McDermott Feb. 26, 1952