US2919465A - Method and apparatus for filament spinning - Google Patents

Description

Jan. 5, 1960 c; E. HIESERMAN' ETAL METHOD AND APPARATUS FOR FILAMENT SPINNING Filed Nov. 14, 1957 INVENTORS CLARENCE E. H/ESERMAN C24RRE TT LEW/ BY ATTORNE VS Unite rates Patent Office 2,919,465 Patented Jan. 5, 1960 minor) AND APPARATUS FOR FILAMENT SPINNING Clarence Hieserman and Lewis C. Garrett, Decatur, Ala., assignors to The Chemstrand Corporation, De-

catur, Ala., a corporation of Delaware Application November 14, 1957, Serial No. 696,37? '4 Claims. (31. 18-8 This invention relates to a method and apparatus for filament spinning and more particularly to a method and apparatus for circulating the coagulating liquid in a spin bath employed in the wet-spinning of continuous filaments of a synthetic material such as that formed from acrylonitrilc polymers and the like.

In one type of spinning operation known generally as Wet spinning for producing synthetic filaments, a spinning material or dope is supplied to a spinning device or 'spinnere'tte, the face of which is provided with a plurality of spinning orifices. During spinning, the spinnerette is immersed in a coagulating liquid or bath so thatthe spinning material extruded from the orifices reacts with the liquid and solidifies to form a bundle of continuous filaments. The orifices in the spinnerette face may be of any desired number, spacing and diameter in accordance with the filamentary end product to be produced, v

As is well kown,in such spinning operations the hot spinning material (generally 75 to 90 C.) adds considerable heat to the relatively cool spin bath.

Furthermore, during the process of filament coagulation, not only is bath concentrating liquid transferred from the filaments to the bath during coagulation, but reaction products from the coagulation process are added to'the liquid which are contaminating in nature. In such spin bath arrangements, therefore, a circulation of the bath is highly desirable to maintain the normally critical bath teniperature at its predetermined level and to present relatively uncontaminated and uniformly concentrated coagulating liquid to the spinning material and to the coagulated filaments prior to emergence from the bath. This circulation becomes increasingly important adjacent the face of the spinnerette in the zone where the spinning material initially solidifies to form the individual filamerits.

Ina spinning operation where the number of filaments arerelatively large in number, in size, or both, or Where the orifices are closely spaced, the denseness or compactness of the bundle or end of filaments obstructs or reduces the circulation of the coagulating liquid in the bath throughout the face of the spinnerette as well as the central "area of the filament bundle. In addition, the location of the spinnerette in some spinning arrangements produces *an interruption of the flow pattern throughout the spin 'bath and gives a relatively static condition adjacent the faceo'fthe spinneret'te.

It has been found that when improper heat transfer conditionsexist at the spinnerette face and the bath temperature is not maintained constant as a result of poor bath circulation, filaments of erratic and non-uniform properties are formed. This irregular filament formation :presents a serious problem during the subsequent filament washing operation and renders the complete removal of solverit from the filaments difiicult, if not impossible, Furthermore, non-uniform filaments mean that thephysical characteristics of the yarn and fabric formed ffoin these filaments do not measure up 'to specific 'rei iifr'fnefifs. In addition t'othe lack of bath temperature control, further difficulty is experienced in filament quality control as the concentration of the bath varies where it contacts the filaments and as a result of the presence of excessive contaminating material in the bath which has not been removed. It has been proposed to increase the circulation of the bath liquid to maintain bath uniformity. However, this approach has resulted in the creation of turbulence in the bath which produces a deleterious effect during filament formation and coagulation.

Accordingly, a primary object of this invention is to provide a new and novel filament spinning method and apparatus.

Another object of this invention is to provide a new and improved wet-spinning apparatus for spinning continuous synthetic filaments which provides a highly efficient circulation of coagulating liquid throughout the spin bath.

A further object of this invention is to provide a new and novel arrangement for a wet-spinning operation which enables the presentation of coagulating liquid at the proper concentration and temperature to the spinning material emerging from the orifices of a spinnerette at all times throughout the spinning operation.

Still another object of this invention is to provide a new and improved filament spinning apparatus which enables the spinning of continuous filaments of synthetic material formed from acrylonitrile polymers and the like from which the coagulating liquid may be easily removed in a thorough manner during a subsequent Washing operation and which produces filaments having physical characteristics which are substantially uniform throughout.

This invention further contemplates the provision of a new and improved filament spinning apparatus which includes an arrangement for circulating the spin bath coagulating liquid in a positive and predetermined manner Without the need for a high rate of circulation within the bath tank and which insures that all portions of the formed filaments, particularly those portions directly adjacent the spinning orifices, are reacted with properly concentrated, coagulating liquid which is substantially free of contaminating decomposition products, and which is maintained with a high degree of accuracy at a predetermined temperature level.

Other objects and advantages of the invention will become apparent from the following description taken in in connection with the accompanying drawings.

The specific objects of the invention are accomplished by providing a container or tank for a spin bath in which is positioned in any conventional manner a spinnerette having a plurality of orifices within its face. The container is filled to theproper level with coagulating liquid so that the spinnerette is immersed therein and spinning material extruded through the spinnerette orifices is coagulated into filamentary form upon contact with the liquid. Nozzle means are positioned adjacent the face of the spinnerette and are arranged to inject a secondary flow of coagulating liquid outwardly from the face of the spinnerette to induce a liquid fiow or current throughout the space or-zone defined by the spinnerette face and the nozzle means and to circulate bath liquid within the central area of the spun filament bundle.

The novel features which are believed to be characteristic of the invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, maybe bestunder'stood by reference to the following description taken in conjunction with the accompanying drawing in which:

Figure 1 is 'a'side view showingfilament spinning app'ar'atusconstructed in accordancewith the invention;

Figure 2 is an enlarged perspective view of a portion of the apparatus of Figure 1 illustrating the invention; and

Figure 3 is an enlarged view taken substantially along line 33 of Figure 1.

As generally illustrative of the invention there is shown in Figure l a tank or container 11 in which is suspended in any suitable manner a spinnerette 12 of the type for extruding or ejecting a synthetic filamentary material or dope such as material formed of acrylonitrile polymers or the like. The spinning material is supplied to the spinnerette 12 by a conduit or supply line 13 suitably connected to the spinnerette as shown and which is connected at its other end to a suitable source of spinning material designated generally by the numeral 14. As shown, the conduit 13 may be pivoted at 16 so as to permit the spinnerette 12 to be moved from an elevated position above the tank 11 to the supported spinning position shown in Figure 1 wherein the spinnerette is rigidly held in a generally inclined plane in the well known manner.

The tank 11 is filled with a coagulating liquid 17 which is continuously supplied to the tank 11 by means such as an inlet18 so that the spinnerette 12 is immersed in the coagulating liquid 17 during the spinning operation. The liquid level in the tank may be maintained by means of an outlet 19 through which liquid moving across the tank flows continuously.

As is well known, spinning material or dope preferably in a viscous fluid form is fed to the spinnerette 12 through the conduit 13 and discharged through a plurality of orifices 21 in the spinnerette face 22 (Figure 2). As is well known, the viscous dope emerging from the ori fices 21 solidifies upon contact with the coagulating liquid 17 and forms a plurality of filaments 23 which are subsequently directed around snubber bars 24 and removed from the tank 11 in the form of a filamentary tow 26.

In spinning operations where the spinnerette face 22 contains a high number of orifices relative to the area of the face or where the orifices are relatively closely spaced, a dense or compact bundle of filaments is formed so that it is relatively difficult to obtain adequate circulation of the spinning solution 17 throughout each of the filaments 23 in the tow 26. This circulation problem is considerably magnified in the portion of the bundle of filaments directly adjacent the spinnerette face 22. It has been found in such spinning arrangements that the circulation of the liquid bath 17 is greatly reduced adjacent the spinnerette face 22 not only as a result of the denseness of the filamentary bundle, but additionally by the liquid currents set up by the moving filaments 23. It has been found that the moving filaments actually set up current spaced aroundtne bundle which move in the opposite direction from the filaments and which tend to create a somewhat static condition at the spinnerette face. Furthermore, in spinning apparatus as shown in Figure l, the position of the spinnerette tends to obstruct the flow of liquid in its laminar flow across the tank 11 from the inlet 18 to the outlet 19.

As is understood, the filaments 23 are initially formed as the dope emerges from the spinnerettes orifices 21 and the physical and chemical state of the coagulating liquid 17 is, therefore, very critical at this point. It is well known that the temperature of the coagulating liquid 17 is very critical in the proper formation of filaments 23 particularly in the spinning of filaments formed from acrylonitrile polymers and the like. The relatively hot dope emerging from the orifices 21 transfers relatively large quantities of heat to the bath as a result of the relatively low temperature liquid in the bath. Unless the liquid is constantly replaced with fresh solution at this point in particular this heat is not removed, and the bath temperature at the spinnerette face rises appreciably causing severe limitations in the filament forming operation such as inadequate solvent removal in subsequent washing steps and highly erratic and non-uniform physical properties in the spun filaments. Furthermore, poor circulation of the bath at the spinnerette causes a material change in the concentration of the bath further contributing materially to the improper formation of the filaments. As is Well known, the filament coagulating process is one of solvent removal. Improper bath circulation, therefore, not only produces poor results adjacent the spinnerette face, but as the bundle of formed filaments move within the bath, the coagulating liquid throughout the central portion of the filament bundle increases in concentration with the continuous transfer of solvent to the bath from the filaments. Thus, for proper results, bath circulation must be effectively carried out adjacent all portions of the filaments immersed in the bath 17. Previous attempts to increase bath circulation by high bath liquid feed rates or by moving bath liquid across the tank in a direction opposite to the direction of filament movement only created turbulence in the filament bundle which produced improper filament formation.

Means, therefore, have been provided to increase the circulation of the coagulating liquid 17 adjacent the face 22 of the spinnerette 12 and accurately control the formation of the filaments 23. More specifically, there is provided nozzle means as shown in Figures 2, 3 designated generally by the numeral 27 for injecting a secondary flow of coagulating liquid into the tank 17 and for inducing a radially inward liquid flow across the face 22 of the spinnerette 12 and within the area defined by the spinnerette face and the nozzle means. In the specific embodiment shown, the nozzle means 27 comprises a tubular ring 28 which is positioned forward of the spinnerette face 22 as shown in Figure 2 and preferably within a plane substantially parallel to the spinnerette face.

The ring 28 may be supported in any suitable manner. For instance, the ring 28 may be supported on the spinnerette 12 by means such as a bracket 29 suitably secured at opposite ends to the spinnerette 12 and ring 28 as shown best in Figure 2.

The ring 28 contains a central opening 31 which encompasses or encircles the bundle of filaments 23 moving outwardly from the spinnerette face 22 and toward the snubber bar 24. On the side of the ring 28 opposite from that of the spinnerette 12, port means are provided for injecting a secondary flow of liquid preferably coagulating liquid as in the container 11 outwardly from the spinnerette face 22. In the specific embodiment illustrated the port means comprise a plurality of circumferentially spaced openings or ports 32 which preferably extend completely around the side of the ring opposite from that of the spinnerette 12.

In order to supply liquid to the interior of the ring 28, a conduit 30 is connected to the ring in any suitable manner as shown in Figure 3. The conduit 30 is connected at its other end to a suitable source of liquid so that liquid may be fed continuously to the interior of ring 28 and discharged outwardly through the ports 32 in a plurality of secondary streams 33. Although the streams 33 may be directed in any generally outward direction from the spinnerette face 22, the ports 32 are so located that the streams flow in a slightly converging manner as shown in Figure 2. However, if desired, any flow direction may be selected in accordance with the desired flow pattern such as in a direction substantially perpendicular to the spinnerette face 22.

During the spinning operation, the coagulating liquid 17 is supplied continuously with fresh liquid from the inlet 18 and flows outwardly through outlet 19 as previously described. Spinning material is supplied to the conduit 13 and thence through spinnerette 12 to form filaments 23 which pass coaxially through the opening 31 in the ring 28 as shown, and which are directed subsequently over snubber bars 24 in the form of tow 26. In accordance with the invention, coagulating liquid is supplied through conduit 30 to the ring 28 and a plurality of liquid stream:

33 emerge from ports 32 outwardly from the face of the spinnerette 12.

In the space or zone defined by the spinnerette face 22 and the ring 23 a secondary flow of coagulating liquid 17 is induced by the reaction to the secondary streams 33 and the liquid flows across and throughout the space as indicated by the multiple arrows H in Figure 2. Thus fresh coagulating liquid which is properly concentrated, uncontaminated, and of the proper temperature is continuously supplied to the spinning material emerging from the orifices 21 and filaments 23 of the proper physical and chemical characteristics are formed. With this arrangement the denseness or compactness of a filamentary bundle does little to inhibit circulation of the coagulating liquid. As the secondary streams 33 are directed so as to converge slightly the streams will move into the bundle of filaments 23 to prevent the build-up of highly contaminated bath liquid within the central portion of the bundle.

It has been found in practice that this induced flow of bath liquid adjacent the spinnerette face 22 is best obtained when the ring 28 is located at a distance between /2 to 2 /2 inches forwardly of the spinnerette face 22. For example, satisfactory performance has been obtained When the ring 28 is located approximately 2 inches forwardly of the spinnerette face 22.

It can be seen that there has been provided a novel arrangement for presenting coagulating liquid or solution to spinning material emerging from a spinnerette in a filament spin bath in which the bath is constantly maintained at the proper temperature and concentration to enable a uniform filamentary tow to be produced having the desired physical and chemical properties. Circulation of the bath is accomplished in a simple and easy manner and the flow of coagulating liquid through the main bath may be maintained at a relatively low level to avoid any turbulence within the filaments. Furthermore, it can be seen that the induced current flow produced by the invention is capable of wide variation which may be brought about by changing the configuration of the ring 28 and the size, shape, and position of the ports 32 within the ring. For instance, both the direction and the quantity of secondary flow may be varied to induce current flow of greater variety.

While there has been described what at present has been considered to be the preferred embodiment of the invention, it will be understood by those skilled in the art that various changes and modifications may be made therein without departing from the invention and therefore it is the aim of the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

Having thus described the invention, what is claimed is:

1. Apparatus for wet spinning synthetic filaments comprising, in combination, a container for filament coagulating liquid, inlet means for supplying fresh coagulating liquid to said container, outlet means for removing coagulating liquid from said container, a spinnerette supported in said container for immersion in said filament coagulating liquid, a tubular ring positioned concentrically with said spinnerette in close encompassing relationship with the bundle of filaments normally advancing from said spinnerette, and port means in said ring adapted to inject a secondary flow of fresh coagulating liquid into said filament coagulating liquid in said container in a generally outward direction from the face of said spinnerette, said ring being entirely spaced forward with respect to the face of said spinnerette so as to define an annular zone therebetween and concentric therewith, whereby a radially inward current flow of coagulating liquid in said container into said annular Zone will be induced when the coagulating liquid issues from said port means.

2. Filament spinning apparatus in accordance with claim 1 wherein said tubular ring is provided with a plurality of circumferentially spaced openings in the side of said ring opposite said spinnerette face, said openings in said tubular ring being arranged to emit a plurality of streams outwardly from the face of said spinnerette in a converging relationship.

3. In the manufacture of synthetic filaments by the wet spinning process wherein a coagulable spinning material is extruded through the orifices of a spinnerette immersed in a filament coagulating liquid in a container therefor to form a bundle of densely packed synthetic filaments, said filament bundle being continuously withdrawn from said filament bath, and wherein the filament coagulating liquid is continuously flowed radially toward the extrusion axis in a zone normal to and adjacent the spinnerette, the improvement comprising the step of establishing a radially inward current flow of filament coagulating liquid into said zone and into said filament bundle by introducing into said filament coagulating liquid at a point entirely and slightly forward with respect to the face of said spinnerette a plurality of streams of fresh coagulating liquid arranged in an annular pattern and closely encompassing said filament bundle, the direction of said streams being generally outward from the face of said spinnerette.

4. The method as defined in claim 3 wherein the directional flow of the streams of fresh coagulating liquid is in a converging direction.

References Cited in the file of this patent UNITED STATES PATENTS 2,642,333 Tomonari et a1. June 16, 1953 FOREIGN PATENTS 501,476 Belgium Mar. 15, 1951

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