US2983571A - Process for wet spinning and washing synthetic fibers - Google Patents

Description

y 9, 1961 G. w. STANTQN 2,983,571

PROCESS FOR WET SPINNING AND WASHING SYNTHETIC FIBERS Filed April 23, 1958 2 Sheets-Sheet 1i Fresh wo/er in /e a (1/ I I 14 .1 5 45, 75

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George 11/ 8/0/7/0/7 May 9, 1961 G. w. STANTON PROCESS FOR WET SPINNING AND WASHING SYNTHETIC FIBERS Filed April 25, 1958 2 Sheets-Sheet 2 INVENTOR. Geo/9E 14 S/an/ofl HTTORNfY United States Patent Of ice The Dow Chemical Company, Midland, Mich, a corporation of Delaware Fae-a Apr. 23, 1958, Ser. No. 730,315 7 Claims. (31. 18-54) The present invention resides in the field of synthetic textile fibersand contributes tothe art of their manufacture. ,More precisely, it relates to a useful and advantageous process for the simultaneous and continuous wet spinning and washing of man-made fibers that are prepared by being coagulated from suitable spinning solutions or equivalent compositions (such as spinnable dispersions inaqueous coagulating spin baths and subsequently washed with water to remove residual spinning solution solvent from the freshly wet spun fiber. The in,- ventionhas particular reference to the manufactured acrylonitrile polymer fibers which are fabricated from fiber-forming acrylonitn'le polymers that contain in the polymers molecule at least about 80 Weight percent of acrylonitrile, especially polyacrylonitrile, which are wet spun in and with systems that are adapted to utilize aqueous coagulating liquids for the spinning operation, such as systems wherein ethylene glycol, dimethyl formarnide, dimethyl sulfoxide, butyrolacetone and the like or the various aqueous saline polyacrylonitrile-dissolving solvents are employed as spinning solution solvents forthe polymer and are also present in non-polymer-dissolving quantities in the aqueous coagulating liquid used in the spin bath. The utile, known aqueous saline solvents for the various fiber-forming acrylonitrile polymers and polyacrylonitrile, include zinc chloride, the various thiocyanates such as calcium, lithium bromide, salt mixtures of the, so-called flyotropic series, and others recognized by the art, as has been disclosed, among other places, in United States Letters Patents Nos. 2,140,921; 2,425,192; 2,648,592; 2,648,593; 2,648,646; 2,648,648; and 2,648,649. Advantageously, aqueous zincchloride solutions are used forthe purpose. I I It isthe major object of the present invention to providean improved process for the continuous wet spinning and simultaneous washing of various synthetic polymer fibers, particularly acrylonitrile polymer fibers, wherein the spinning, coagulation and complete water washing of the fibers is advantageously accomplished in continuous se'quencein the same unitary processing operation in and with the same, unitary, integral manufacturing apparatus. A particular object of the invention is to provide a process of' the indicated type and nature that would be peculiar'ly well adapted for utilization for and in the preparation of acrylonitrile polymer fibers, yarn, threads, tow bundles and the like and related filamentary products using the highly advantageous salt spinning techniques with aqueous systems, such as those that employ aqueous solutions of zinc chloride or its saline equivalents for dissolution of the polymer into a spinning solution and for constitution, in ,non-polymer-dissolving quantities, of the coagulating spin bath. i i These objects and cognate benefits and advantages ma be achieved readily in the practice of the present invention whose process, in continuous and uninterpretedsequence,,comprises and entails extruding or spinning into filamentaryor- (the like form a spinning solution of a syniiber-formingpolymer dissolved in a watermiscible Patented May 9, 1961 solvent for said polymer, said spinning solutionibeing adapted to be coagulated in an aqueous solution of said solvent of non-polymer-dissolving concentration, said spinning solution being extruded through a suitable spinnerette or other extruding device into the spinning end or zone of a chamber that is comprised of a spinning end or zone and a withdrawing end or zone and having a plurality of separate, intercommunicating liquid recirculating zones between said spinning end and said withdrawing end; said chamber being filled with an aqueous liquid of gradient increasing concentration from that of substantially pure water in said withdrawing end of said chamber to that, in said spinning end of said chamber, of a non-polymer-dissolving aqueous coagulating solution of said solvent constituent with respect to its dissolved concentration of said solvent constituent from said spinning solution; coagulating said freshly wet spun filaments of said spinning solution in said non-polymer-dissolving or coagulating solution portion of saidliquid in said spinning zone insaid chamber; passing said freshly wet spun and coagulated filaments through aqueous liquid in sequence from said spinning zone through said intercommunicat ing, liquid recirculating zones in said chamber to said withdrawing end or zone of said chamber; admitting substantially pure water in said withdrawingend or zone of said chamber and passing it countercu'rrent to said fila-' ments in said chamber at such a rate and in such quanti} ties with respect to such extrusion of spinning solution that theconcentration of polymer solventin said non polymer-dissolving aqueous solution of said solvent in said portion of said liquid in said spinning zone of said chamber is maintained at an efiicient and effective coagulating concentration for said spinning solution; withdrawing liquid from said withdrawing zone of said chamber at about the same volumetric rate as it is applied to said chamber in the form of said water admitted to said withdrawing zone and the liquid extruded with said spinning solution less the quantity of liquid removed from said chamber with said filaments; recirculating said aqueous liquid in each of said recirculating zones substantially transversely through and about said freshly Wet spun filaments passing therethrough so as to extract and remove residual spinning solution solvent therefrom; and withdrawing said freshly wet spun and washed filaments from said withdrawing zone in said chamber. i

Further features and advantages of the invention will be manifest in the following description and specification, taken in connection with the accompanying drawing, which schematically illustrates the invention in several views, wherein:

Figure 1 is a simplified cross-sectional elevation which represents an apparatus that is adapted to perform the present process and wherein said process is being-conducted;

Figure 2 is a fragmentary, schematic,cross-sectional elevation of part of another suitable apparatus for practice of the invention which illustrates a modified arrange ment of the liquid recirculating means in oneof the re:

circulating zones; and

Figures 3 and 4 are schematic cross-sectional plan views that depict suitable structural configurations of the chamber and further respectively illustrate theliquid recirculating means in Figures 1 and 2.

In order to successfully practice the invention, a unitary, integral container or chamber is required having a spinning end or zone at one of its extremitiesand a withdrawing end or zone at its opposite extremity, said spinning and withdrawing zones being separated in said chamber by a plurality of liquid recirculating zones or sections which are so formed and disposed as to permit liquid communication between .said spinning and withdrawing zonesand to allow travel or progression of filamentary material through the chamber. Such an installation is indicated generally by the reference letter C in the several figures of the accompanying drawing. With predominant reference to Figure l, the chamber C has'a spinning zone or end A at one of its extremities and a withdrawing end' or zone Z at the opposite extremity. A plurality of recirculating zones O are dis posed between the spinning zone A and the withdrawing zone Z of said chamber. Each of the recirculating zones are bounded and defined by spaced baflie plates B. Each of the bafiles B'has a uniform and respectively similar central opening H therein to permit communication through the plurality of installed bafiles from the spinning zone to the withdrawing zone of said chamber and to provide for uninterrupted passage of filaments through the apparatus. V

The chamber C may have any desired configuration and be of any suitable'physical dimensions so as to be adapted for the intended manufacturing purpose. The baffles B are of such construction as to fit within the chamber and to provide the central aligned openings H. Thus as shown in Figure 3, the chamber C may have a cylindrical configuration with theinterfitting bafiles B being of annular design. Or, as shown in Figure 4, a generally rectangular chamber may be utilized with suitable, centrally open, accommodating bafiies. Of course, as will be appreciated by those with the skill of their calling, many other equivalent and satisfactory designs are possible. The central openings H in the bafile B must, of course, be sufficiently large to permit ready passage of the freshly wet spun filaments through the length of the chamber and the generally countercurrent movement of the liquid through the chamber against the path of travel of the filaments from the withdrawing zone to the spinning zone of said chamber. The openings H themselves may be'shaped in any manner to best accommodate with suitably close spacing the filamentary bundle being handled. Thus, generally round or rope like tow bundles are ordinarily better handled through round openings H, as illustrated in Figure 3. Tow bundles having a relatively fiat and wide, ribbon-like assembly are usually better passed through matching rectangular openings H, as in Figure 4. As will be readily apparent, the openings H in the baflies B should not be so large asto interfere with efiicient internal recirculation ofthe liquid in each of the recircling zones in said chamber or to prevent a thorough flushing and treating action of the counter-current flowing liquid on the freshly wet spun filaments during their passage through the chamber. Suitable dimensions .in particular instances can be readily designed by elementary investigation and application of known principles.

A spinning solution or other spinnable dispersion of fiber-forming material of the indicated variety is provided under an extrusion pressure (developed by any suitable means not shown) in a conduit or mass tube M, upon which is mounted the spin head S. The spin head S may be comprised of a conventional spinnerette (or a plural bank of same). for the extrusion of filamentary materials or any other desired extrusion device, such as multiple orifice die or the like, adapted for the spinning of liquid coagulable fiber-forming compositions into desired filamentary products. If desired, of course, the

invention may be practiced so as to prepare monofilamerits in each apparatus installation by utilizing a single orifice spinnerette or die for the spin head. It is ordinarily, a decided advantage, however, for the spinning solution to be directly. spun through multiple orifice spinnerettes or the like extrusion devices which are adapted to simultaneously prepare a plurality of filaments so as to directly form multiple filament strands to tow bundles. of considerable magnitude, such as those comprised of at least about 3,000 individual filaments of the desired size. Oftentimes, large tow bundles may comprise as many as 10,000 or 50,000 to 200,000 or more individual filaments. As'indicated, the tow bundle 4 a, can be assembled and handled so as to haveranydesired cross-sectional patterns.

Upon its extrusion, the spinning solution is coagulated into the filaments F by the action and effect of the nonpolymer-dissolving aqueous coagulating solution of the portion of the liquid L in said spin zone which contains the maximum concentration in said liquid of the solvent constituent from said spinning solution. The freshly wet spun filaments are passed in tow bundle or other desired form from the spinning zone A of the chamber C through the recirculating zones 0 of-the chamber to the withdrawing zone Z, from which they are withdrawn by means of a suitable pair of towbighting nip or withdrawing rolls R or other equivalent tow withdrawing or forwarding means (including various thread advancing devices) that may be desired. During their travel through the chamber (which maybe heatedor cooled, or both, along its length in any desired or necessary manner), the freshly wet spun filaments are passed through the countercurrent flow of aqueous liquid L in' the chamber until they are subjected to substantially pure water in the withdrawing zone Z. The water is admitted to zone Z through the fresh water inlet-I by; any suitable means, such as ametering pump, not shown; This accomplishes a thorough and final washing and extraction of residual solvent from the spinning-sol d tion that obtains in the freshly wet spun fibers. I-f 'cool fresh water isdesired in the process it may also be ad vantageous to employ a suitablecooling means (likewise not shown) in operative association with theinlet I to permit satisfactory regulation and control of theeteme perature of the water being admitted. v a

The liquid L in each of the recirculating zones O'be tween the spinning zone A and the withdrawing zone Z of the chamber is recirculated during its generally countercurrent passage through the length of the chamber within each of the zones 0 by any suitable means adapted to locally pass the portion of liquid in the individual're' circulating zone substantially transversely through and between the freshly wet spun filaments which are passing through each of the recirculating zones 0 in their travel through the chamber. Advantageously, the recir culating means for the liquid in each of the recirculating zones 0 may be a pump means P which withdraws' liquid from each of the recirculating zones through the recirculating tube outlet W and readmits it in a path generally-transverse to the filaments through the recirculating tube'inlet X. Of course, more than one liquid 'r'ecirculating' means or pump maybe utilized ineach recirculating "zone oand the recirculating tube outlets and inlets W and X, respectively, can be disposed at opposite sides from one another in the chamber or in other arrangements. They-need not be in communication with the recirculating zone'at substantially the same point therein, despite the fact that they are so shown in Figure 1 of the drawing. Figures 2 and 4 of the drawing illustrate one of the indicated suitable variations in which the recirculating tube outletsand inlets are on opposite sides of a rectangular chamber. Frequently, such an arrangement may be beneficial to accomplish 'a more positive through-flushing action on the'filamerits. In addition, the recirculating tube inlets X may be arranged and adapted toexpel therecirculated liquid at a point immediately adjacent to the filaments'bein'g it is withdrawn through the outlet tube Valong with additional liquid introduced in said spinning solution and not carried out with the filaments withdrawn from the withdrawing zone. A pump or other liquid withdrawing means (not shown in the drawing) may be employed in aces-n conjunction with the outlet tube V. During its counter.- current passage through the chamber, the concentration of spinning solution solvent in the liquid L gradually increases. This, as is apparent, is by virtue of the extracting and washing efiect of the aqueous liquid on the watermiscible spinning solvent being removed'from the freshly wet spun filaments. Such action, of course, results in the final washing of the filaments prior to their withdrawal from the withdrawal zone Z of the chamber and provides the non-polymer-dissolving, aqueous coagulating solution of said solvent constituent of the portion of the liquid L whichoccurs in the spinning zone Z of the chamber.

As will be appreciated by those who are skilled in the art, the volume of substantially pure water to be admitted in the withdrawing zone I of the chamber must be correlated to the requirements of the wet spinning solvent desired for coagulation in the portion of the liquid in the spinning zone A of the chamber. Of course, the volumetric requirement of substantially pure water for efiicient washing of the freshly wet spun filaments must also be met. In the usual case, however, the quantity of water required to continuously dilute the solvent from the spinning solution to a dissolving coagulated concentration is at least ample for purposes of thoroughly washing the freshly wet spun filaments, particularly when the chamber C is provided with an adequate length and has a satisfactory and eificacious number of recirculating zones 0 interdisposed between the spinning zone A and the withdrawing zone Z. 1

. In many cases, it is most desirable, as implied in the drawing, to practice the invention with the apparatus in vertical disposition withthe spinning and filament progression being in a generally upward direction. This simplifies handling of the liquid through the zones by taking advantage of gravity flow. Of course, the spinning may also be downward using pumps to effect progress of the liquid through the zones. Horizontally and otherwise disposed units may also be employed. fAfter their extrusion, coagulation, washing and-withdrawal from the liquid in the chamber, the freshly vwet spun filaments may be subsequently handled and treated in any desired or necessarymanner for purposes of converting them to a finished fiber product. Thus, they may be stretched or otherwise treated for purpose. of heat treating or relaxing the fibers in any desired way or they may be subjected to additional treatments of any appropriate nature, including application of finishes, lubricants and the like. or imposition of crimp prior to being dried and finally collected as completely manufactured products.

I As has been indicated, when acrylonitrile polymer, particularly polyacrylonitrile, fibers are being manufactured, zinc chloride may most advantageously be utilized as the sole, or at least the principal, saline solute in the spinning solvent employed for the polymer. In such instances, the aqueous solution of zinc chloride in the spinning solution may advantageouslybe in a concentration of from 55. to 65, preferably about 60 percent by weight, based on the weight of the aqueous solution. The quantity of sub.- stantially pure water passed countercurrent tothe filaments in the chamber should be sufficient, when such aqueous zinc chloride solvent spinning solutions are em ployed, so as to maintain the concentration of zinc chloride in the portion of the liquid in the spinning zone at a non-polymer-dissolving coagulating concentration of at least about percent-by weight; advantageously frorn about to 50 percent by weight, and preferably between about and percent by Weight. In such aqueous zinc chloride systems for acrylonitrile polymers, wherein the freshly wet spun polymer is generally obtained in an aquagel form, it is generally desirable for the spinning solution that is extruded to contain between about 4 and 20 percent by weight of dissolved polymer; more advantageously from about 6 to 15 percent by weight of dissolved polymer; and preferably,particularly when. polyacrylonitrile fibers are being manufactured, from about 8.5 to 11.5 percent by weight of fiber-formingpolymeric solids in the spinning solution. I 1

Aqueous zince chloride spinning solutions of fiberforming acrylonitrile polymers are beneficially extruded at a spinning temperature of from O to 50 C.; preferably from about l0to 30C., into an aqueous zinc chloride coagulating liquid that is maintained at a coagulating temperature of from 0 to 30 C.; preferably from about 10 to 20 C. Under the indicated conditions, the amount of fresh water that is required to effect a suit able coagulating atmosphere in the portion of. .the liquid in the spinning zone A can be determined by simple material balance, taking into account the quantity per unit time of spinning solution being extruded and the amount of water being withdrawn from the liquid. by entrapment and entrainment in the freshly wet spun and washed aquagel fibers. Thoroughly washed acrylonitrile polymer aquagel fibers, incidentally, are usually found to contain not more than 5 /2 parts by weight of water (including residual extrinsic or exterior water associated therewith) for each part by weight of dry polymer there in. More frequently, washed acrylonitrile polymer aquagel fibers are found to contain from about 2 and usually from about 3 to 4 parts by weight of water for each part by weight of polymer. I

When practicing the present invention, it is usually advantageous to employ an apparatus having at least about four to six or even at least eight recirculating zones between the spinning and withdrawing zones in thechamher and for each of the recirculating zones to be about of equal physical proportions. In general, as will be appreciated by artisans versed in the premises, the 'total number of recirculating zones necessary will be in inverse-proportion to the fiber flushing or washing efficiency ineach zone. Better and more thorough circulation .(within the limits imposed by safe handling of the freshly extruded and characteristically physically tender and sus? ceptible to damage fibers) of the liquid in each zone diminishes requirements for total numbers of individual zones. In such apparatus it is desirable for the spinning zone to comprise not more than about 20 percent of the total length of the chamber and for the withdrawing zone to have about the same dimensions as each ofthe recirculating zones employed. It is generally advantageous for the chamber. that is utilized to have a length of at least about ,15 and preferably at least about 30 feet. In the operation of the process, it is beneficial and most practical to recirculate the liquid in each of the recirculating zones at such a rate that at least about 15 parts by volume of liquid are recirculated through and between the filaments or fibers being passed through the zone for each part by volume of liquid progressing through the zone inits generally countercurrent passage through the chamber. More advantageously, at least about 20 parts by volume, and preferably at least about .30 parts by volume, of the liquid in each zone is recirculated'for eachpartby volume of liquid passing countercurrently through the chamber.

The invention is further manifest in and by the following docent examples.

' Example I A process and apparatus similar to that represented in Figure 1 (and 3) of the accompanying drawing is utilized for the manufacture of synthetic polyacrylonitrile fibers. The vertically disposed chamber C iscylindrical in, configuration. and has an internal diameterof about /2 foot with a liquid-containing internal length of about 34 feet. It is separated into 15 recirculating zones by a total'of 16 annular bafiies, each having round, central openings of about inch in diameter. The baffies are provided atuniformly spaced intervals in the chamber of about 2 feet, with the length of the spinning zone A being about 3 feet. A single multiple orifice spinnerette 7 having. a total of about three thousand individual round jet hoIesofIS rnil diameterieach is utilized asa spin head. and is situate in the spinning zone at the bottom of thechamber.

' The spinning solution extrude is comprised of polyacrylonitrile having an average molecular weight between about'SO and 35 thousand dissolved in an aqueous 60 percent" by weight solution of zinc chloride. The spinningsolution has a total polymer solids content of about 10 percent by weight,based on the weight of the solution. All of the spinning solution is continuously extruded upwardly through the spin head at a temperature of about 25 C. and under a rate, of extrusion of about 60 pounds per'hour so as to be coagulated in the form of aquagel filaments at a continuous linear rate of about 12.5 feet per minute by the action of the aqueous, nonpolymer-dissolving solution ofzinc chloride in the liquid in the lowermost spinning zone portion of the chamber. The freshly wet spun filaments are formed and handled in the" form of a generally round, relatively rope-like tow bundle.

The zinc chloride concentration of the coagulating liquid in the spinning zone portion is maintained at about 44 percent by weight, and is held at an average temperature'of'about 15 C." during the spinning operation. A cooling jacket is employed about the spinning zone to assist in" temperature regulation. About 43 pounds per hour of fresh water,at a temperature of about 20 C., is introduced through the inlet I in the withdrawing zone of the chamber and is continuously passed countercurrentto the filaments therein In each of the recircu lating zones the liquid is recirculated substantially transversely through the filaments at a rate of about 30 parts by volume of recirculating liquid for each part by volume of liquid being introduced as fresh water in the withdrawing zone of the chamber. The recirculation of liquid in each of'the recirculating zones is accompaniedby means of recirculating pumps of sufiicient capacity for the purpose and connected (as shown in Figures 1 and 3 of the drawing) through inlet and outlet tubes forhandling the recirculatedliquid. About 73 p'oun'dsper hour of a 44 percent by weight aqueous solution of zinc chloride is withdrawn from the coagulating liquid outlet V from the spinning zone A of the chamber. The aquagel filaments are withdrawn from the uppermostzone Z of the chamber in a thoroughly'washed condition in which they contain only about 0.1 percent by weight of salt (including the salt in the residual liquid adhering thereto), based on the weight of the polyacrylonitrile therein, and about 4 parts by weight of water for each part by weight of dry polymer therein. After being withdrawn from the chamber, the fibers are oriented by stretching in hot water to a total of 12 times their wet spun, unstretched length. They are then dried for 20 minutes in hot air at 150 C.

By the foregoing procedure, there is continuously produced premimur'nquality, 3 denier per filament polyacrylonitrile fibers having a tensile strength in the neighborhood of 4 grams per denier, an elongation in the neighborhood of 30 percent and a wet yield strength of about 1 gram per denier, The product fibers are colorless and, upon immersion in boiling water, experience less than 1 percent shrinkage.

Example II gular openings of about A x 2 /2 inches to pass the flat tow' bundle through the zones. The liquid is recirculated through the filaments in each zone using a single pump for each'zone with the inlet and outlet tubes in opposite sides of the zone across the tow, as depicted in Figure 4 of the drawing; Commensurate excellent results are obtained. 7

Excellent results are also realized when the forgoing procedure is followed to wet spin acrylonitrile and other fiber-forming polymers using other solvent and aqueous coagulating systems therefor; The present invention is intended to be gauged in its interpretation in the light of the hereto appended claims without unnecessary limitation to or by the foregoing demonstrative specification and description. i What is claimed is: 1. Method for continuously wet spinning and washing synthetic textile fibers which comprises forming a watercoagulable spinning solution of a synthetic fiber-forming polymer in a water miscible solvent for said'polyme'r extruding said spinning solution through a filament shaping device into the spinning zone of an elongate chamber having a spinning zone and a withdrawing zone and a plurality of separate, intercommunicating liquid recit culating zones therebetween; maintaining said chamber full of an aqueous liquid of gradient increasing 00116611? tration from that of substantially pure water in said withdrawing zone to that, in said spinning zone, of an aqueous coagulating solution of said solvent for said spinning solu tion; coagulating said freshly wet spun filaments of said spinning solution in filamentary form in said coagulating solution portion of said liquid in said spinning zone; pass ing said freshly wet spun and coagulated filaments from said spinning zone through said intercommu'nic'ating, liquid recirculating zones'in said chamber to said with drawing zone; admitting substantially pure water in said withdrawing zone of said chamber and passing it countercurrent to said filaments in said chamber at a rate that is adapted to maintain the water concentration in said aqueous coagulating solution in said spinning zone at a coagulating concentration for said spinning solution; passing aqueous liquid from said withdrawing zone of said chamber internally to said spinning zone of the chamber at about the same volumetric rate as it is supplied thereto; recirculating said aqueous liquid being passed internally in said chamber in each of saidrecirculating zones substantially transversely through and about said freshly wet spun filaments passing therethrough; and withdrawing said freshly wet spun and washed filaments from said withdrawing zone in said chamber.

2. The method of claim 1, wherein said filamentary material is passed through at least about 8 recirculating zones between said spinning zone and said withdrawing zone.

3. The method of claim 1, wherein at least about 15 parts by volume of liquid are continuously recirculated within each of the recirculating zone through and between the filaments being passed through each zone for each part by volume of liquid progressing in a generally countercurrent manner to said filaments through each of said zones.

4. The method of claim 1, wherein said spinningsolution is comprised of a fiber-forming acrylonitrile polymer containing in the polymer molecule at least about percent by weight of acrylonitrile dissolved in a water miscible solvent therefor.

5. A method in accordance with the method set forth in claim 4, wherein said solvent is an aqueous polyacrylonitrile-dissolving saline solution. a

6. A method in accordance with the method set forth in claim 5, wherein said aqueous saline solution is a solution of zinc chloride in water that contains from 55 to 65 percent by weight of dissolved zinc chloride, based on the weight of the solution. 1 a i 7. The method of claim 1, wherein said spinning solution is extruded and said freshly wet spun filaments are handled and passed through said chamber in a generally vertically upward direction.

References Cited in the file of this patent UNITED STATES PATENTS 2,094,099 Dreyfus Sept. 28, 1937 Roberts Jan. 2, 1951 Hoxie Sept. 30, 1952 Stanton Apr. 30, 1957 FOREIGN PATENTS Germany Sept. 15, 1932 Great Britain July 1, 1928

Claims (1)

1. METHOD FOR CONTINUOUSLY WET SPINNING AND WASHING SYNTHETIC TEXTILE FIBERS WHICH COMPRISES FORMING A WATERCOAGULABLE SPINNING SOLUTION OF A SYNTHETIC FIBER-FORMING POLYMER IN A WATER MISCIBLE SOLVENT FOR SAID POLYMER EXTRUDING SAID SPINNING SOLUTION THROUGH A FILAMENT SHAPING DEVICE INTO THE SPINNING ZONE OF AN ELONGATE CHAMBER HAVING A SPINNING ZONE AND A WITHDRAWING ZONE AND A PLURALITY OF SEPARATE, INTERCOMMUNICATING LIQUID RECIRCULATING ZONES THEREBETWEEN, MAINTAINING SAID CHAMBER FULL OF AN AQUEOUS LIQUID OF GRADIENT INCREASING CONCENTRATION FROM THAT OF SUBSTANTIALLY PURE WATER IN SAID WITHDRAWING ZONE TO THAT, IN SAID, SPINNING ZONE, OF AN AQUEOUS COAGULATING SOLUTION OF SAID SOLVENT FOR SAID SPINNING SOLUTION, COAGULATING SAID FRESHLY WET SPUN FILAMENTS OF SAID SPINNING SOLUTION IN FILAMENTARY FORM IN SAID COAGULATING SOLUTION PORTION OF SAID LIQUID IN SAID SPINNING ZONE, PASSING SAID FRESHLY WET SPUN AND COAGULATED FILAMENTS FROM SAID SPINNING ZONE THROUGH SAID INTERCOMMUNICATING, LIQUID RECIRCULATING ZONES IN SAID CHAMBER TO SAID WITHDRAWING ZONE, ADMITTING SUBSTANTIALLY PURE WATER IN SAID WITHDRAWING ZONE OF SAID CHAMBER AND PASSING IT COUNTERCURRENT TO SAID FILAMENTS IN SAID CHAMBER AT A RATE THAT IS ADAPTED TO MAINTAIN THE WATER CONCENTRATION IN SAID AQUEOUS COAGULATING SOLUTION IN SAID SPINNING ZONE AT A COAGULATING CONCENTRATION FOR SAID SPINNING SOLUTION, PASSING AQUEOUS LIQUID FROM SAID WITHDRAWING ZONE OF SAID CHAMBER INTERNALLY TO SAID SPINNING ZONE OF THE CHAMBER AT ABOUT THE SAME VOLUMETRIC RATE AS IT IS SUPPLIED THERETO, RECIRCULATING SAID AQUEOUS LIQUID BEING PASSED INTERNALLY IN SAID CHAMBER IN EACH OF SAID RECIRCULATING ZONES SUBSTANTIALLY TRANSVERSELY THROUGH AND ABOUT SAID FRESHLY WET SPUN FILAMENTS PASSING THERETHROUGH, AND WITHDRAWING ZONE IN SAID WASHED FILAMENTS FROM SAID WITHDRAWING ZONE IN SAID CHAMBER.

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