US3398429A - Spinneret enclosure - Google Patents

Description

1968 F. s. DICKSON m SPINNERET ENCLOSURE 2 Sheets-Sheet 1 Filed Oct. 10. 1966 a Wa t In Aug. 27, 1968 F. s. DICKSON m SPINNERET ENCLOSURE 2 Sheets-Sheet 2 Filed Oct. 10, 1966 W J J lllll {will}!!! 1 United States Patent 3,398,429 SPINNERET ENCLOSURE Frederick Stoever Dickson III, Martinsville, Va., assignor to E. l. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Filed Oct. 10, 1966, Ser. N0.'585,641

6 Claims. (Cl. 18-8) ABSTRACT OF THE DISCLOSURE An array of spinnerets equipped with swingably mounted enclosure flaps for confining a blanketing medium to zones adjacent the spinnerets.

The present invention relates generally to the production of synthetic filaments and, more particularly, to apparatus in which the exposed face of a spinneret is blanketed with an inert gas. I

In a melt-spinning operation, there is a tendency for some of the fiber-forming material to build up around each extrusion orifice. The degrading etfect of free oxygen on such material manifests itself in the form of bent filaments or drips. Although these effects can be avoided to a large extent by blanketing the spinneret with an inert medium, the costs cannot be justified in a process where the spinning speed is slow and can instead be stopped periodically for removal of buildups by wiping.

v At higher spinning speeds, known routes for blanketing become more practical but are nevertheless ineflicient and costly. Although it is relatively easy to blanket a single spinneret with inert gas, a certain amount of air still contaminates the gas, the amount depending on equipment design, quench-air turbulence and filament pattern. In the newer high-speed, high-production, spinning machines, a number of spinnerets may be so closely spaced together as to require a single blanketer. Under these circumstances, it is even more difi'icult to make the blanketing gas cover critical areas of all the spinneret faces equally and to avoid air intrusion. For effective blanketing, it is essential that the inert gas be so guided and directed that it will cover the orificed area of each spinneret without mixing with air and then exit from the blanketed zones with sufficient velocity that it will prevent strayair currents from coming up and entering those zones. Also, it is advantageous to prevent cross currents between adjacent spinnerets.

' The various goals and objectives disclosed herein have been accomplished by providing an enclosure assembly for a spinning block, which block houses an aligned array of closely spaced spinnerets and also carries equipment for blanketing all of the spinnerets with an inert gas. Basically, the enclosure assembly is comprised of a pair of elongated, streamlined flaps pivotally mounted on opposite sides of the array for swinging movement toward and away from a closed position adjacent the spinnerets. When in the closed position, longitudinal edges of the flaps are spaced apart, leaving openings through which groups of filaments emerge from the several spinnerets.

In the drawings, FIGURE 1 is a fragmentary transverse sectional view through a preferred apparatus embodiment, on lines corresponding to II in FIG. 2; and FIG. 2 is a fragmentary longitudinal sectional view taken on line 1III in FIG. 1.

With reference to FIG. 1, the spinning apparatus includes a hollow spinning block 10 adapted to contain a suitable heat exchange fluid such as Dowtherm. The lower surface of block 10 has four wells 12 extending inwardly from a bottom wall 14. Each well 12 houses a pack assembly 16, which contains the normal filtering and distribution elements in a casing 17 and also includes a spin- 3,398,429 Patented Aug. 27, 1 968 ice neret 18. Each pack 16 is held in its well -12 by apack nut 20. Molten polymer is supplied under pressure through polymer supply lines 23 to the tops of the pack assemblies 16. Filaments 22 issue from the bottom face of each spinneret 18. A cross-current flow of quenching air has been indicated at 24.

In order to prevent free oxygen from reaching the exposed faces of spinnerets .18, a blanketing device 26 and an enclosure assembly 28 are placed below the spinneret. As shown in FIG. 2, the blanketing equipment or device 26 includes a rectangular shaped metal plate 30 having an elongated opening 31 in registry with the aligned array of closely spaced spinnerets 18. Each spinneret 18 has a rectangular pattern of orifices fromwhich a group of filaments 22 issues and passes downwardlythrough opening 31. At both ends and on its left orfront side (FIG. 1), metal plate 30 is of one thickness. On its back side, plate 30 is recessed to receive cover plate 32. Under the metal parts, there is a supporting block 34 which isrnade from rigid heat insulation material. The blanketing equipment 26 is mounted in heat exchange relationship with the block bottom 14 so that the metal parts, namely the metal plate 30 and the cover plate 32, are maintained at substantially the same temperature as heated block 10. In the back side of metal plate 30, there is a relatively large primary plenum 36 and a secondary plenum 38. As shown in FIG. 2, plenums 36, 38 evtend substantially through the length of device 26 and primary plenum 36 extends on to the edge of plate 30. By further recessing the back side of plate 30, a shallow passage 40 is provided between plates 30, 32, in communication with secondary plenum 38. Mounted at the inner edge of plate 32, there is an elongated weir plate 42 over which an inert gas flows from the delivery slot presented by shallow passage 40. The blanketing medium is supplied to the open end of primary plenum 36 by pipe 44. In order to achieve good distribution across the four spinnerets, there are two sonic nozzles 46 located between primary plenum 36 and secondary plenum 38.

In operation, an inert gas, preferably steam, is supplied to primary plenum 36 by pipe 44 and flows through sonic nozzles 46 to the secondary plenum 38. It then flows inwardly through shallow passage 40. With the metal plate 30 and the cover plate 32 at or near block temperature and because of the high area-to-volume ratio of heat exchange surface to steam in passage 40, steam is discharged from the delivery slot at nearly the temperature of heated block 10. Upon leaving passage 40, the remaining kinetic velocity is reduced as the steam flows up and over weir plate 42.

If the steam were just permitted to flow over weir plate 42, it would blanket the face of spinneret 18 and provide some improvement in spinning. However, it has been found that, because of stray currents and circulation due to the pumping action of filaments 22 and from the thermal currents set up between the faces of the spinnerets, the cooling filaments and the quenching air, free oxygen will circulate close to the spinnerets. Such contamination of the blanketed zonesis avoided by confining the steam during its travel to and across the spinneret faces. This is accomplished with the enclosure assembly 28.

The enclosure assembly of this invention comprises a pair of elongated, contoured doors or flaps, a back flap 48 and a front flap 50. As illustrated, flaps 48, 50 are relatively thick and have streamlined inner edges. They are mounted on opposite sides of the spinneret array by hinges 52 and 54, respectively. Front flap 50 has a series of fingers 56 so shaped and arranged that, when the back flap and front flap are in position, there are four rectangular openings 58 (FIG. 2) defined by the spaced longitudinal edges of flaps 48, '50 and by fingers 56. It is through restricted openings 58 that filaments 22 leave the enclosure defined by assembly 28. There are suitable seals at the edges,

hinges and other joints to prevent air leakage inward. In the lattei' connection, itshould be noted that outermost fingers 560 are halved.

The streamlined shapes and angular dispositions of flaps 48, 50 around each opening 58 are such'as to give a venturi effect in the direction of the exiting steam, as indicated by the arrows in FIG. 1. In the latter connection, flap 50 has an upper surface substantially parallel'to the faces of spinnerets 18 and the operable length of flap 48 is angularly disposed with respect to and terminates at a lower level than flap 50. Steam leaving weir plate 42 with low kinetic velocity is directed upward and across the faces of spinnerets 18. The supply rate is such that the steam as it" leaves through the venturi-shaped openings 58 achieves sufiicient velocity to preclude turbulence and to prevent any stray air currents from coming upward toward the spinnerets. In'this way, the free oxygen level inside the enclosure is greatly reduced. Since there are no other openings, free oxygen cannot get into the enclosure. In addition, fingers '56 function to prevent cross currents between the four spinnerets.

The front flap 50 is held in its closed position adjacent spinnerets' 18 by the engagement of spaced fingers 56 its heating capabilities usually has suflicient capacity to heat the ste'am. If additional heat transfer capacity is' de achieved by controlling and monitoring piess'ure.

with the upper surface of flap 48 which, in turn, is held in position by a releasable pin 60. When it is desired to change a pack assembly, releasable supporting pin 60, being mounted on a slide bar arrangement, is moved backward until it is beneath support block 34. This permits back flap 48 to fall to a vertical position. Removal of the support of back flap 48 permits the front flap 50 to fall into a vertical position. If desired, the operator can rotate the front flap another 90 so that it is now 180 out of its operating position and thereby gain free access to packs 16 The following example illustrates that the equipment described above radically reduces the oxygen level at the face of the spinneret.

EXAMPLE Nylon 6-6 filaments were spun using the equipment described above, but without the blanketing equipment 26 or the enclosure assembly 28. Dowtherm temperature in block 10 was 293 C. The face of the spinneret had to be wiped every three hours to insure continued spinning of good product.

In a second run, blanketer 26 was attached, the enclosure 28 was left off, and no steam was used. The oxygen level was measured at various locations inside the blanketer and ranged from 2 to 15%. Then, steam at 100 C. and 4 p.s.i.g. was supplied to primary plenum 36 and r flowed through the blanketer 26 at the rate of 1.0 lb./ hour (454 g./hour). The oxygen level ranged from 3 to 6%. At this level, the time between wipes was increased to over six hours.

Finally, enclosure assembly 28 was added with the steam flow rate remaining at 1.0 lb./hour. The oxygen level was dramatically reduced to less than 1% at all loca tions. The time between wipes was increased to more than 24 hours.

The use of a large area-to-volume passage 40 has eliminated the need for a heat exchanger in block 10 or for a separate superheater in the inert gas supply line. It has been found that steam, since it is normally so readily available, is the preferred inert gas. The heated block with The number and location of the sonic nozzles or flow controlling orifices is not critical and depends upon the blanketer design. The essential feature is to assure good distribution of the inert gas across the spinnerets'in each blanketer. When more than one blanketer is used, for example on a large spinning machine, it isimportant to control the flow of inert gas to each blanketer. A single nozzle for each blanketer, external of the blan'keting device, will be satisfactory in many installations. Variations and modifications of a similar nature will occur to those skilled in the art without departing from'the spirit of the present invention which is, therefore, intended to be limited only by the scope of the appended claims.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. In combination witha spinning block housing an aligned array of closely spaced spinnerets and carrying equipment for blanketing all of the spinnerets with an inert gas, an enclosure assembly comprising a pair of elongated flaps extending through the length of said array and means mounting the flaps on opposite sides of said array for swinging movement toward and away from a closed position closely adjacent the spinnerets, said flaps having spaced longitudinal edges when in said position.

2. The combination of claim 1 wherein one of said flaps is provided with spaced fingers extending outwardly from its longitudinal edge into an overlapping relationship with the other flap when in said position, thereby presenting a restricted opening beneath each spinneret.

3. The combination of claim 2 wherein said flaps are relatively angularly disposed, said one flap being closer to and substantially parallel with said spinnerets, the other flap being in engagement with said fingers. I

4. The combination of claim 3 wherein is provided a releasable support for holding the flaps in said position.

5. The combination of claim 1 wherein said flaps are relatively thick and said edges have streamlined contours.

6. The combination of claim 3 wherein said flaps are relatively thick and said edges have streamlined contours.

References Cited Musser 188 WILLIAM J; STEPHENSON, Primary Examiner.

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