US2697251A - Method and apparatus for manufacturing artificial filaments - Google Patents

Description

Dec. 21, 1954 E. K. BAUER 2,697,251

METHOD AND APPARATUS FOR MANUFACTURING ARTIFICIAL FILAMENTS Filed Feb. 7. 1951 INVENTOR. ERNEST A. BAUER ATTORNEY.

United States Patent 2,697,251 Patented Dec. 21, 1954 tice METHOD AND APPARATUS FOR MANUFAC- TURING ARTIFICIAL FILAMENTS Ernest K. Bauer, Meadville, Pa., assignor to American Viscose Corporation, Wilmington, Del., a corporation of Delaware Application February 7, 1951, Serial No. 209,881 7 Claims. (Cl. 18-8) This invention relates to a method and apparatus for manufacturing artificial filaments, fibers, strands, and the like. More particularly, a method and apparatus for dry spinning cellulose derivatives, vinyl resins, or other materials that can be melted or dissolved in a volatile solvent and extruded in fine streams into a cooling or an evaporative gaseous or vaporous medium, such as cold, warm or hot air, to form continuous filaments. The term dry spinning, as used throughout the specification and claims, is intended in a generic sense to cover both melt-spinning and dry-spinning of a solution in a volatile solvent.

Generally, in dry spinning, the spinning solution or dope or melt is passed through a spinneret into a cell or tube which contains a gaseous medium, such as air. In dry spinning proper, the volatile solvent of the spinning solution evaporates in the cell or tube and the hardened artificial filaments are withdrawn, treated and/ or wound in the usual manner. In melt spinning, the molten mass is'cooled, and filaments withdrawn may be subsequently treated. The spinning speed in the cell or tube is governed by the temperature of the gaseous medium therein, the rate of evaporation of the volatile solvent into the gaseous medium when a solvent is used, the length of the tube or cell and the temperature of the spinning solution or melt.

In dry spinning proper, it is customary to circulate air in the cell in order to remove the volatile solvent therefrom. In dry spinning proper, the temperature of the dope or spinning solution is limited to a temperature just below that at'which the filaments will explode because of sudden solvent evaporation. The cell or tube temperature cannot be raised too high since the filaments will get brittle. Then again, making a longer tube or cell is costly and requires a taller building. Therefore,

increased rate of spinning is not practical by varying these factors. By increasing the rate of evaporation of the volatile solvent through higher air velocities in the tube or cell, it is possible to increase the spinning speed. However, when employing conventional systems, the velocity of the air is limited because when the air flows in a direction opposite to that in which the filaments are spun, too high a velocity will lift the yarn or filaments upward, when spinning in a downward direction, making lacing of the tube or cell difficult. When the air flows codirectionally with the travel of the filaments, there is the danger of unduly stretching and possibly rupturing the filaments at the spinneret before they have had sufiicient time to harden.

It is an object of the present invention to overcome the aforementioned difiiculties and provide a method and apparatus for dry spinning artificial filaments, and the like, at higher speeds than heretofore attainable, without raising the temperature of the spinning solution or employing a larger tube or cell.

It is another object to provide a method and apparatus for dry spinning artificial filaments at higher speeds than is now practical by increasing the rate of evaporation of the volatile solvent through higher air velocities in the tube or cell.

It is a specific object to provide a method and means for circulating and recirculating air in different parts of the tube until the air has absorbed a sufiicient amount of solvent and the mixture of air and solvent is below the explosive limit.

It is another specific object of the invention to employ :a minimum amount .of fresh air in .order to reduce the the invention is concerned with V is reintroduced to the other volume of air and volatile solvent which passes through the recovery system thus reducing the size and cost of the recovery system.

Other objects and advantages of the present invention will be obvious from the description thereof hereinafter.

Generally, the objects of the present invention are ac complished by extruding a spinning material into a closed chamber, tube, or cell, conveying the extruded filaments or yarn through the chamber and then withdrawing them therefrom and winding or further treating them in the usual manner. A gaseous medium is continuously passed into the chamber at a point intermediate the ends thereof. The gaseous medium in the chamber is divided into two streams flowing toward the opposite ends of the chamber, the streams being withdrawn from the chamber near each end thereof. At least one of the withdrawn streams is recirculated to the chamber while continuously introducing fresh gaseous medium to the circulating stream in advance of the point of introduction to the chamber and continuously changing the temperature of the circulating stream between the point of introduction thereto of fresh gaseous medium and the point of introduction of the gaseous medium into the chamber.

In the case of dry spinning proper, the system is operated by introducing heated air into the spinning tube or chamber at a point intermediate the entrance or spinning end and the exit end in such a manner as not to disturb the filaments passing therethrough. The solventladen air is withdrawn at a point adjacent the exit end, reheated and recirculated through the tube. A portion of the solvent-laden air is withdrawn from the tube at the entrance end and sent to a solvent recovery system while at the same time a portion of fresh air, equal to the portion of solvent-laden air withdrawn from the tube, is introduced into the circulatory system, and so on continuously during operation. Alternatively, a portion of the solvent-laden air may be withdrawn from the tube at a point adjacent the entrance end and recirculated through the heating system and tube, in addition to that withdrawn and recirculated from the exit end. The air is introduced and withdrawn from the tube without creating undue turbulence. The solvent-laden air is withdrawn from, and fresh air admitted to the system at such a rate as to keep the mixture of air and solvent in the system below the explosive limit while at the same time utilizing a minimum amount of additional or fresh air. Hot air may be recirculated in the whole tube or only a portion thereof. In the main the direction of flow of air m the tube is downward or with the direction of travel of the filaments, but in portions of the tube, the direction of flow is upward (countercurrent to the filaments). The air may be circulated in both directions in the tube, i. e. different directions in different portions of the tube, thus substantially reducing or equalizing any drag on the filaments or yarn.

In the case of melt spinning, the system is operated by introducing a cooled gaseous medium into the chamber, tube, or cell at a point intermediate the ends thereof. In this instance, the withdrawn stream is recirculated through a cooling means before again entering the chamber. In those instances where an inert gaseous medium is employed, a closed system is used, i. e., one stream is recirculated to the cooling means and back to the chamber while the other passes through a purifying means and then circulating stream in advance of the point of introduction to the cooling means. other factors may remain the same in both dry-spinning and melt-spinning.

In order to better understand the following detailed description of the invention, reference should be had to the accompanying drawing in which Figure I is a side elevation view, partly in section, of one embodiment of the invention,

Figure 2 is a side elevation view of another embodiment of the invention, and

Figure 3 is an enlarged fragmentary longitudinal sectional detail showing one of the air manifolds used in the construction of Figures 1 and 2.

Referring to the embodiment shown is employed a vertical spinning tube chamber 4, jacketed tubular portions in Figure 1, there which comprises a 5 having circular or annular manifolds 6 inserted therebetween and an exit chamber 7. The tubular portions comprise an inner casing 8 and an outer casing 9 with a space It) therebetween for receiving a suitable heat-transfer medium, such as steam, hot water, and the like, or cold water and the like when spinning a melt. Mounted in the casing 9 is a pipe or conduit 11 for the introduction of steam or the like, to the space It the exhaust steam or the like leaving through the pipe or conduit 12, also mounted on casing 9. If desired, the tube .or cell may be covered with an insulating material, such as magnesia, asbestos, cork, or the like, (as shown by the dotted line 13.

Positioned centrally within the entrance chamber 4 is a spinneret 14. The spinning melt or solution is introduced to the spinneret 14 through the conduit or pipe 15, and then through a candle filter 16 to which the spinneret is connected. In the wait of the chamber 4, there are inserted one or two ports, windows, or hand- holes 17 and 18, provided with hinged door frames containing panes of glass or other suitable transparent material so that the formation of the filaments 19 may be observed by the operator without opening the spinning tube to the outside atmosphere or may be tended merely by opening the door to the port.

The filaments 19 are spun downwardly and pass centrally through the spinning tube or cell to the exit chamber 7. If desired, the filaments may be spun in an upward direction with necessary rearrangement of parts. The spinning tube has a portion 3a extending down into the exit chamber 7 for reasons hereinafter explained. The exit chamber 7 has a sloped bottom wall 20 which is provided with an opening 21. The walls of the exit or end chamber 7 are made of materials which are poor conductors of heat so that an operator will not be burned upon touching the walls of the chamber when employing hot evaporative media. The opening 21 is'preferably of ample size to permit the insertion 'of the hand so that an operator can reach into the exit chamber 7 to seize the material falling into the chamber. A door 22 hinged at 23 is arranged to cover the opening '21 except for a small portion 21:: thereof in registry with the upper end of a slot 24 in door 22 thereby constituting an effective small-sized discharge orifice through which the filaments 19 may pass during normal operation of the unit. When the operator has grabbed the filament mass 19 in chamber 7 through the open door, he can lace up the delivery roll or godet 25 and the take-up device 26 and then close the door 22 without interfering with the continuous dis charge of filaments 19 from chamber 7. Preferably, the

door has a bossed portion 2211 which in a closed position fills the opening 21 and has an inside surface flush with the inside surface of wall 21). A coating device comprising a grooved roll 27 may be disposed in advance of the godet 25 as shown or beyond it, if desired. It may be used to apply a lubricating or a conditioning liquid medium to the filaments.

The lateral wall 28 of chamber 7 is provided with an opening at the bottom which is normally covered by door 29 which may be hinged at 30. Any waste material from the spinning tube that is not drawn through the orifice 21a slides down to the corner of the chamber 7 behind the associated door 29. This permits the material to be gathered out of the way of the line of spinning in a portion of chamber 7 offset from the tube from which it may at any convenient subsequent time be removed by the operator merely by opening door 29. Such removal does not interfere with the spinning operation 'since it does not involve transfer past the line of spinning. ,Suitable clamps or hooks 31 and 32 may be provided to hold doors 22 and 2 respectively in closed positions.

All of the manifolds 6 may be provided with a valve, shutter, or damper 33 connected by conduit 34 thereto, said conduit opening into the annular chamber 35 (see Figure 3) in the manifold. The detailed construction of the manifolds will be described hereinafter. Connected to the opening :-2 in the lateral wall 28, of exit chamber 7, is a conduit 36 which is connected at its other end to the intake port in the side of a blower 37. Connected to the intake port and conduit 36 is a conduit 38 which acts as a fresh air inlet. There is a valve or damper 39 in conduit 38 to regulate the fiow of air therethrough, and a valve or damper 36a in conduit 36 to regulate the flow of solvent laden air to the heat interchanger 4B.

The exhaust port of blower 37 is connected to the bottom of an air heater 40 which may be of any conventional type. Connected to the top of the heater 40 is a conduit 41 which is connected at its other end to the valve on the next to the uppermost manifold 6 in the tube.

In the top of the chamber 4, there is a circular series of openings 43 cut therein encircling the pipe 15. Fastened to the top of chamber 4, over the openings, is a conduit 4-4. The pipe 15 enters the side of conduit 44 and passes downward centrallythereof. The conduit 44 is connected to the intake port in the side of blower 45, the exhaust port of which is connected by conduit 46 tpfi a solvent recovery system shown diagrammatically at a a.

The operation of the embodiment shown in Figure l is as follows: heated air from heater 4i) passes through conduit 41 and manifold 6 into the spinning tube where it divides into two streams, part going up the tube and part going down, as indicated by the arrows. The air passing down the tube picks up solvent from the filaments then passes into chamber 7 and up between the walls of tube extension 3:! and chamber 7 to the opening 42. The advantage of having the tube extend into chamber 7 b..- low the opening therein is to prevent the filaments or filament mass from being drawn out of its normal path by the rush of solvent-laden air to opening 42. The solvent laden air passes through conduit 36 to the blower 37 and then through heater 4t) and back through the spinning tube. The valve 39 is adjusted to admit a predetermined amount of fresh air into the system to replace the solvent-laden air which is withdrawn and sent to the solvent recovery system 46a. The withdrawn solventladen air passes up the tube past the spinneret through the openings 43, conduit 4-4 to blower 45 and then to the recovery system 46a. The air, with solvent vapors removed, is exhausted from the recovery system, which may be of any conventional type, through conduit 8t) which has a valve or damper 81 therein. Alternatively, the air, with solvent vapors removed, may be readmitted to the system via conduit 46?), connected to fresh air conduit 33, in which case the valve or damper 460 in conduit 46b would be opened and the dampers 39 and 81, in the fresh air conduit 38 and the conduit St) respectively, would be closed. In the case of melt spinning when employing an inert gaseous medium, such as nitrogen, and the like, the system will be entirely closed, i. e.,

the nitrogen, which may have picked up decomposition materials in the tube, is sent to the recovery or purifying system 4641 and then readmitted, in pure condition, to the system via conduit 45b and conduit By placing the conduit 44 around pipe 15, it serves also as a heat exchanger, the heated solvent-laden air heating the spinhing solution passing down through pipe 15.

The speed of spinning is increased because of faster evaporation of solvent from the filaments. The faster evaporation is brought about by increased velocity of air in the tube. For example: assuming the blower 45 is regulated to remove 50 cu. ft. of solvent-laden air per minute from the tube, the blower 37 to deliver cu. ft. of air per minute to the tube and valve 39 is set to allow 50 cu. ft. :of fresh air per minute to enter the system, then velocity V1 is equal to velocity V2. By having part of the air pass in an upward direction in the tube, particularly in the portion adjacent the spinneret, the danger of unduly stretching or possibly rupturing the filaments at the spinneret, by passing air in a downward direction in the tube, is alleviated. 1f the blower .37 delivers cu. ft. of air per .minute .to the tube, all other factors being the same, then V2 is equal to 2 times V1, which permits far better solvent evaporation. .Here again, even with increased velocity of air in a downward direction in approximately of the tube, the danger of unduly stretching or possibly rupturing the filaments at the spinneret is alleviated. While the velocity in a downward direction is greater than, such as twice, that in an upward direction, the downward velocity has no appreciable efiect on the filaments until they reach the manifold through which the air is entering, which manifold is spaced down the tube so that the filaments have had a chance to harden sufficiently so as not to be affected by the increased air velocity in .a concurrent direction. The fresh air intake .and solvent-laden air withdrawal will always be equal for best results, being varied only to prevent the solvent-air mixture, circulating through the tube, from reaching the explosive point.

Referring to Figure 3, there is shown a cross-section of a manifold 6. The manifold comprises a collar 47 having an annular tongue 48 0:1 the upper surface thereof which acts as a separating means for casings 8 and 9 which rest on shoulders 49 and 50 respectively at the base of tongue 48 and on either side thereof. Collar 47 is connected by bolts 51 to collar 52, there being a gasket 53 therebetween. Collar 52 encircles the casing 54 which has a flanged top 55 which rests on the shoulder 56 of collar 52. The collar 52 and casing 54 form the annular chambers 35 and 57. The chambers 35 and 57 are joined by the annular opening 58. A series of circular openings 59 are drilled in the casing 54 which communicate with the chamber 57. A third collar 60, similar to collar 47, is fastened to the bottom of collar 52 by means of bolts 61, there being a gasket 62 therebetween. The next lower casings 8 and 9 abut against shoulders 63 and 64 respectively of collar 60 with the tongue 65 therebetween. Each manifold is similarly constructed with the exception of the uppermost manifold in which case it is attached to the chamber 4 directly and collar 47 may be eliminated. As previously pointed out, conduit 34 is connected to collar 52 communicating with openin 35.

3A manifold constructed in the manner just described has many advantages, chief among which is that it prevents the incoming air from hitting the filaments from one direction only and distributes the air around the tube evenly so that the air enters the tube from all directions with equal force, the air following the course shown by the arrows.

Referring to Figure 2, there is shown another embodiment of the present invention which differs from the embodiment shown in Figure 1 only in the manner in which the air is circulated and recirculated through the spinning chamber, tube or cell. In this embodiment, a conduit 66 is connected to the valve or damper 33 on the lowermost manifold 6. Conduit 66 is joined with conduit 68 and their juncture is connected to conduit 69 which in turn is attached to the intake port of blower 70. Conduit 68 has a valve or damper 71 therein and is connected to the second manifold in the tube when counting down. Connected to conduit 69 is a fresh air conduit 72 having a valve or damper 73 therein. The exhaust port of blower 70 is connected to the heater 74 and the top of the heater is connected by pipe 75 to the third manifold down the tower.

In this embodiment, the evaporative medium is delivered to the spinning cell through conduit 75 approximately centrally thereof and the evaporative medium divides into two streams, one going up the tube and the other down the tube, as indicated by the arrows. A portion of the solvent-laden air is withdrawn from the top of the tube in the same manner as indicated in the embodiment shown in Figure 1. The remainder of the evaporative or gaseous medium is recirculated through conduits 66 and 68 to heater 74 then back to the tube. In addition, fresh air is continually added to the system through conduit 72 in the same manner as indicated in the embodiment in Figure 1. It is, of course, to be understood that when employing the embodiment of Figure 2 there would be no opening 42 in the exit chamber 7 or the opening would be closed by means of a damper, shutter, valve, or the like.

When using either of the embodiments shown in Figures l and 2, all manifolds not connected to a conduit are blocked off by closing the valves or dampers 33 connected thereto. It is also to be noted that all of the conduits carrying the solvent-laden air, fresh air and recirculated air, etc. may be lagged with a suitable insulating material, if desired.

With reference to both embodiments of the invention, shown in Figures 1 and 2, the solvent-laden air can be withdrawn from the system or cell through the uppermost manifold and conduit 76 attached thereto, rather than through the entrance chamber 4 and conduit 44. in this way, the atmosphere in the chamber 4 around the jet can be kept substantially stagnant with the advantages attendant thereto. If desired, the solvent-laden air may be withdrawn from the cell through both of the conduits 44 and 76 at the same time. In this event conduit 76 is connected to conduit 46b by means of blower 45a and conduit 76a.

When employing either of the embodiments shown in Figures 1 and 2 for melt spinning, cold water or the like would be circulated through the spaces or jackets 10surrounding the tube and the heaters 40 and 74 would be replaced by coolers in order to cool the gaseous medium being circulated through the tube or cell. 1

By means of the present invention, hot air can be circulated in the whole tube or only a portion thereof. The system permits considerably higher spinning speeds and in addition increases the capacity of the tube or cell without increasing the diameter of the tube or lengthening it. That is, by means of the present invention, it is possible to produce filament bundles or yarn having a greater total denier or bundles of filaments composed of many more filaments than heretofore possible.

Numerous other advantages will be obvious to those skilled in the art.

It should be noted that changes and variations may be made in the present invention without departing from the spirit and scope thereof and therefore, the invention should not be limited to the illustrative embodiments shown and described herein only insofar as the same is defined in the appended claims.

I claim:

1. A method for spinning artificial filaments, and the like, comprising extruding a spinning solution in a volatile solvent into a heated vertical closed chamber, drawing the extruded filaments through the chamber and with drawing them therefrom, continuously passing heated air into the chamber at a point intermediate the ends thereof, dividing the heated air introduced into two streams flowing toward the opposite ends of the chamber, withdrawing the downwardly flowing stream from the chamber near the bottom end thereof and recirculating it to the chamber, withdrawing a portion of the upwardly flowing stream from the chamber near the top end thereof and recirculating it with the first withdrawn stream to the chamber, continuously introducing fresh air to the combined circulating streams in advance of the point of introduction to the chamber, reheating the circulating stream between the point of introduction thereto of fresh air and the point of introduction into the chamber, and conveying the remaining portion of the upwardly flowing stream past the point of filament extrusion while withdrawing it from the chamber.

2. A method for spinning artificial filaments and the like, comprising extruding a spinning material into a closed chamber adjacent one end thereof, drawing the extruded filaments through the chamber and withdrawing them therefrom, continuously passing a gaseous medium into the chamber at a point intermediate the ends thereof, dividing the medium introduced into two streams flowing toward the opposite ends of the chamber, withdrawing one of the streams from the chamber near one end thereof and recirculating it to the chamber, withdrawing the other stream from the chamber adjacent the filament extrusion point and removing undesirable gaseous material therefrom, conveying the purified stream to the first circulating stream in advance of the point of introduction to the chamber, and changing the temperature of the circulating stream between the point of introduction thereto of the purified stream and the point of introduction into the chamber.

3. A method for spinning artificial filaments and the like comprising extruding a spinning solution of a filament-forming material in a volatile solvent into the upper end of a vertical closed elongated chamber, drawing the extruded filaments downwardly through the chamber and withdrawing them from the bottom end thereof, continuously passing heated air into the chamber at a point intermediate the ends thereof and spaced from the point of extrusion, dividing the heated air introduced into two streams flowing toward the opposite ends of the chamber, withdrawing the downwardly flowing stream from the chamber near the bottom end thereof and recirculating it to the chamber, dividing the upwardly flowing stream near the top of the chamber, withdrawing a divided upwardly flowing stream from the chamber below the point of filament extrusion, withdrawing another divided upwardly flowing stream from the top of the chamber past the point of filament extrusion, recovering volatile solvent from at least one of said upwardly flowing streams, and recirculating it with the first withdrawn stream to the chamber, continuously introducing fresh air to the combined circulating streams in advance of the point of introduetion to the chamber, and reheating the circulating thereof and an entrance chamber attached to one end stream between the point of introduction thereto of fresh air and the point of introduction into the chamber.

4. An apparatus for spinning artificial filaments and the like comprising an elongated vertical spinning tube hava baffle in said manifold displaced axially from said conduit means, walls defining an annular passage around the tube on the opposite side of the baflie, walls defining a plurality of orifices spaced around the periphery of the ing a plurality of manifolds inserted along the length tube and communicating with said annular passage wherethereof and an exit chamber attached to the other end, filament extrusion means positioned in the entrance chamber, first conduit means connected to a manifold at a by gaseous me conduit with periphery of the tube.

dium is introduced into the tube from the substantially equal velocity around the 6. Apparatus in accordance with claim having a point intermediate the entrance chamber and the exit chamber adjacent the filament-removing means through chamber for conveying a gaseous medium to the tube, second conduit means connected to the exit chamber for conducting a gaseous medium therefrom, a heat exchanger connected to both of said conduit means, re-circulating which gaseous medium is withdrawn from the tube, a heat exchanger connected between said chamber and one of the manifolds for re-circulating gaseous medium with drawn through said chamber, and means for introducing means connected to said heat exchanger, third conduit additional gaseous medium to the intake of Said heat means connected to the entrance chamber adjacent the exchangerfilament extrusion means for removing a portion of the gaseous medium from the tube, gaseous medium purifying means connected to said third conduit means, and

fourth conduit means connecting the purifying means and ducing 3560 means into th the heat exchanger for conveying purified gaseous medium back to the tube through the heat exchanger.

5. In apparatus for spinning artificial filaments and the like, the improvement which comprises an elongated com posite tube assembly having a filament extrusion spinneret positioned at one end thereof, means for withdraw- Number ing a filament at the opposite end thereof, a plurality 1,592,006 of filament-treating tube sections between the ends of the 1,962,605 tube, each section comprising a jacket surrounding the 2,060,048 tube, means for circulating heating fluid through said 2,252,684 jacket, a manifold surrounding the tube and forming 21 2,341,615 terminus for said jacket, conduit means for introducing 2,463,676 a gaseous medium to said manifold in a radial direction, 2515393 7. Apparatus in accordance with claim 6 having conduit means for withdrawing gaseous medium from the filament extrusion end of the tube and means for introus medium withdrawn through last said e intake of the heat exchanger.

References Cited in the file of this patent UNITED STATES PATENTS Name Date Roy July 13, 1926 Mancini June 12, 1934 Dreyfus Nov. 10, 1936 Babcock Aug. 19, 1941 Hoifman Feb. 15, 1944 Bludworth et a1. Mar. 8, 1949 Burke July 18, 1950

Images