US 2820985 A
Description (OCR text may contain errors)
Jan. 28, 1958. I v CRESSWELL 2,820,985
SPINNERETTE INSERT AND ASSEMBLY Filed July 11, 1955 l & 1
I It: FA, 0'66 26 I I INVENTOR.
United States Patent SPINNERE'ITE INSERT AND ASSEMBLY Arthur Cresswell, Stamford, Conn., assignor to American Cyanamid Company, New York, N. Y., a corporation of Maine Application July 11, 1955, Serial No. 521,199
3 Claims. (Cl. 18-8) This invention relates broadly to a spinning device (that is, a device used in the spinning or forming of synthetic filaments or threads), and more particularly to a novel spinnerette insert and assembly. The apparatus of the present invention is especially adapted for use in the production of artificial or synthetic filaments, especially those made from a viscous spinning solution, e. g., a viscous solution of an acrylonitrile polymerization product. Such solutions generally must be heated immediately prior to extrusion of the solution through the holes or openings in the face of the spinnerette, thereby reducing the viscosity so that it can be extruded or spun satisfactorily.
The problem of spinning or extruding hot spinning solutions to obtain a high pullaway speed from the face of the spinnerette (and, consequently, a high production rate per spinning unit) is intensified in certain wet-spinning processes, for examples processes such as are disclosed and claimed in Cresswell U. S. Patents 2,558,730, -1, and 2, and Cresswell and Wizon U. S. Patent 2,558,733, all of which are dated July 3, 1951. In these processes a solution of a polymer or copolymer of acrylonitrile, dissolved in a concentrated aqueous solution of a water-soluble salt which yields highly hydrated ions in an aqueous solution (e. g., sodium thiocyanate) is extruded into a liquid coagulant comprising water. This coagulant is at a temperature not exceeding |l0 C., e. g., from 15 C. to +5 C. When the outer face, or both the outer face and outer sides, of the spinnerette are in contact with such a low-temperature coagulating bath, there is a tendency for the spinning solution or dope to be cooled, especially the portion thereof which is close to the inner surface of the spinnerette. The cooling effect of the cold coagulant upon the side walls of the spinnerette can be lessened by pro viding a suitably insulated header, but this does not entirely solve the problem.
Cooling of the spinning solution within the cup of the spinnerette has been found to be greater, when the solution is extruded into a cold coagulating bath, the larger the free volume within the spinnerette. As a result, an uneven temperature exists within the spinnerette; and, consequently, extrusion through the numerous holes or openings in the face of the spinnerette also is uneven. The latter, in turn, is accentuated the larger spinnerette that is used, e. g., spinnerettes of the size employed for extruding tow that is to be cut into staple.
Prior methods of trying to solve this problem have involved the use of spinnerettes wherein the holes in the face of the spinnerette have been drilled to a special pattern in an effort to obtain uniformity (or minimum lack of uniformity) of filament size when extruding warm or hot spinning solution into a cold coagulating bath.
The present invention provides a different solution to the problem described briefly above, namely the use of a par- 2,820,985 Patented Jan. 28, 1958 prises superimposed laminae of porous fabric woven from a relatively hard filamentary material (e. g., wire screening and more particularly stainless steel wire cloth), which is resistant to attack by hot spinning solution passing through the spinnerette when it is in use. The laminae of the aforesaid fabric are suitably held or united together to form a porous structure, and preferably to form a rigid, porous, unitary structure. The laminae may be removably or fixedly held or joined together, e. g., by means of clamps, screws, pins, tie rods, sintering or fusing, spot welding or bonding, cementing (for instance, at the edge or outer periphery), etc., but preferably are fixedly fastened or united together so that a unitary structure results. Each lamina of the insert is positioned with respect to adjoining lamina so that in use there is a tortuous flow of spinning solution through the insert. A preferred method of obtaining this tortuous flow is by positioning each lamina so that filaments of alternate laminae are disposed at difierent angles in the plane of lamination.
The novel features which are characteristic of my invention are set forth in the appended claims. The invention itself, however, will best be understood by reference to the following more detailed description when considered in connection with the accompanying drawing in which Fig. 1 is a perspective view, partly broken away to show the lamina beneath and adjacent to the top or surface lamina, of a spinnerette insert embodying my invention;
Fig. 2 is an elevational view of two of the lamina of the insert shown in Fig. 1, the lower lamina of the figure being shown as having been rotated 45, in the plane of lamination, with respect to the lamina shown in the upper part of the figure;
Fig. 3 is a sectional view of a spinnerette assembly embodying the invention and illustrating somewhat schematically the tortuous flow of spinning solution through the spinnerette and spinnerette insert; and
Fig. 4 is a side view showing somewhat schematically a spinnerette assembly of the invention provided with a header, and the use of the same in the formation of filaments.
It will be understood by those skilled in the art that the various figures of the drawing are merely illustrative of structures or apparatus embodying my invention, and that many modifications thereof are possible without in any way departing from the spirit and scope of the invention.
Referring to the drawing and more particularly to Fig. 1 thereof, there is shown a spinnerette insert 10 comprising superimposed laminae of porous fabric woven from relatively hard filamentary material which is resistant to attack by hot spinning solution passing through said spinnerette when it is in use. Depending upon the composition of the particular spinning solution employed, the fabric may be woven from filaments of wire, more particularly stainless steel wire, or from filaments of nylon, glass, polyethylene, polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene chloride, polymerized ethylene terephthalate or other available filamentary material having the aforementioned physical properties. Preferably the chosen material is one which also is a good heat condoctor, and hence fabric made of copper wire advantageously can be used if it is unattached by, and has no harmful elfect upon, the particular spinning solution employed. By using laminae of fabric which is a good heat conductor in the construction of the insert, the insert facilitates better heat conductivity within the spinning solution or dope that is in the cup of the spinnerette during use of the device and assists in equalizing the temperature of the aforesaid dope, with obvious advantages.
In Fig. l are shown the top or surface lamina 12 and the next lower layer or lamina 14 which is in contact with 12, followed by a plurality of other superimposed, contacting laminae. lamina 14 is rotated (the rotation having been effected before the laminae are united), in the plane of lamination, about 45 with respect to the contacting superimposed lamina 12. This rotation (clockwise or counterclockwise) can be varied as desired or as conditions may require, e. g., from to 80", but it may be even'more or less provided that the desired tortuous flow thereby is obtained. Alternate laminae, which may be in the form of disks (e. g., disks of wire screening), are similarly rotated in the plane of lamination with respect to the contacting superimposed lamina. The alternate laminae, specifically disks (that is, laminae or disks after the first lamina or disk of the insert), need not each be rotated to the same degree, but it is generally desirable to follow a definite predetermined pattern of rotation in order to assure uniformity of results from the use of the inserts.
The laminae can be united together to form the insert by various means such as have been mentioned hereinbefore. One suitable method of forming an insert from Type 316 stainless steel wire cloth is described below. This cloth was 12 x 12 mesh, and was formed of wire which was 0.033 inch in diameten'with 0.051 inch openings.
Seven disks of the above-described cloth or screening were clamped together between two steel plates by drawing them together with four bolts and nuts. The disks were assembled, prior to clamping, so that alternate laminae were rotated, in the plane of lamination, about 45 with respect to the contacting superimposed lamina. The surfaces of the steel end plates which contacted the top and bottom lamina were coated with an aqueous paste of a refractory cement, prior to assembling and clamping the disks together, in order to prevent sintering of the outside screens to the end plates. Any refractory cement or refractory bonding mortar which is unaffected at the sintering temperature can be used, e. g., silica, alumina, ground refractory fire brick, etc., in paste or other suitable form. The clamped assembly was heated in a small furnace in a hydrogen atmosphere at 2200 F. for 30 minutes, after which the assembly was removed from the furnace and quenched in cold mineral oil. After unclamping, it was noted that a rigid, porous, unitary structure of disks, sintered together, had been formed.
Another suitable method of forming a spinnerette insert of this invention is as follows:
An assembly of eight screen disks of the same type described above, and similarly assembled and clamped together, was placed in a molten salt bath at 2408 F. for 35 minutes, after which the assembly was quenched in two cool baths. After cooling, the draw bolts were sawed to free the steel end plates from the assembled disks. The assembly was then washed with water to remove the salts. The disks were well sintered together to form a' rigid, porous, unitary structure, which was ground down to a cylindrical, porous plug slightly less than 1.5 inches in diameter.
Spinnerette inserts produced as described above can be used with a spinnerette. to form a spinnerette assembly, and the latter then employed in producing filaments from a spinning solution as herein described.
In selecting the material of which the insert is formed it will be understood, of course, by those skilled in the art that the diameter of the wire or other filamentary material, and the mesh size (that is, the porosity or openings between the Woven threads or filaments) are such as will permit relatively good flow of the spinning solution through the insert with minimum back pressure.
In the embodiment of the invention illustrated in Figs. 1 and 2, the laminae are positioned so that filaments of alternate laminae are disposed at different angles in the plane of lamination. This is one method, and my preferred method, of positioning each lamina of the insert, with respect to adjoining lamina, so that there is obtained the aforementioned tortuous flow of spinning solution As shown in Fig. 1, and also in Fig. 2, A
through the insert when it is in use. Another method is to use lamina of wire screening or other woven fabric which has been cut, prior to making the assembly, so that when the laminae are superimposed the horizontal axes of filaments of alternate laminae will be in different vertical planes. In other words, corresponding threads of alternate laminae are parallelbut are displaced an appreciable distance (for instance /4 to the distance, say, /2 the distance) between threads.
Referring now to Fig. 3, the spinnerette assembly there shown comprises a spinnerette 16 having a plurality of holes or openings 18 in the face of the spinnerette; and a spinnerette 10 fitting within the cup of the spinnerette. The thickness of the insert is preferably slightly less than the interior depth of the spinnerette, that is, slightly less than the inside depth of the spinnerette cup, so as to provide a good seating of the spinnerette flanges. When this is done it also will permit the placement, if desired, of a layer of filter fabric as a guard filter inside the spinnerette. Preferably a filter fabric 20 .is positioned, as shown in Fig. 3, so that the outer portion thereof rests upon the lip 22 of the spinnerette and is then held firmly in place when the spinnerette is fixed in its support. When such a filter cloth or fabric is employed (and its use is optional), it is preferably one having a porosity which is less than that of the individual lamina of which theinsert is formed.
Such a filter cloth may comprise, for instance, a cloth woven from 15 denier nylon thread and having about 400 threads per inch. Or the cloth may be woven from threads of polymeric ethylene terephthalate, polyvinylidene chloride and others which are resistant to attack by and will not harmfully affect the spinning solution passing therethrough.
The arrows 24 indicate the direction of flow of spinning solution from a supply source (not shown) into the spinnerette, while the tortuous fiow of the solution through the insert is indicated by the arrows 26, thence passing through openings 18 in the faceof the spinnerette. Upon being extruded through the openings 18 the solution is.
coagulated in the coagulating bath 28 (Fig. 4) to form a plurality of filaments 30 (Fig. 4), which likewise are indicated in Fig. 3. V
The spinnerette assembly of the invention, an embodiment of which is illustrated in Fig. 3, is fitted into a header 32 (Fig. 4), and is used in the production of filamentary material as schematically illustrated in that figure. The present invention permits the use of spinnerettes having conventional circles of holes and thus minimizes adhesion between individual filaments of freshly extruded material. Such adhesion is often a considerable problem when spinnerettes utilizing a special pattern of hole drilling are employed as a means of solving the problem described earlier in this specification. With spinnerettes having conventional circles of holes, rapid diffusion of the solvent into the coagulating bath also is provided.
What I claim is: 1. A spinnerette assembly comprising, in combination, a spinnerette having a cup and a lip; an insert ofsuch size and shape as to permit it to fit snugly within the cup of the said spinnerette, the thickness of the said insert being slightly less than the inside depth of the spinnerette cup, said insert comprising superimposed disks of stainless steel wire cloth sintered together to form a rigid, porous unitary structure, the disks of said'insert, after the first disk, having been rotated in the plane of lamination from 10 to with respect to contacting superimposed disks, before being united together, and the openings between the woven filaments comprising the said wire cloth being such that, when the assembly is in use, there will be relatively good flow of the spinning solution through the insert with minimum back pressure; and a filter fabric positioned adjacent the said insert so that the outer portion thereof rests upon the lip of the spinnerette and is then held firmly in place when the 5 spinnerette is fixed in its support, said fabric having a porosity which is less than that of the individual disks of stainless steel wire cloth of which the said insert is formed.
2. A spinnerette assembly as in claim 1 wherein the filter fabric positioned adjacent the insert comprises a cloth woven from thread of synthetic polymeric material selected from the class consisting of nylon, polymeric ethylene terephthalate and polyvinylidene chloride.
3. A spinnerette assembly as in claim 1 wherein the disks of the insert, after the first disk, have been rotated in the plane of lamination about 45 with respect to the contacting suprimposed laminae.
References Cited in the file of this patent UNITED STATES PATENTS Re. 24,081 Webb Oct. 25, 1955 2,266,368 Hull Dec. 16, 1941 2,278,875 Graves Apr. 7, 1942 2,589,870 Sale Mar. 18, 1952 2,617,147 McDermott Nov. 11, 1952 U. S. DEPARTMENT OF COMMERCE PATENT OFFICE CERTIFICATE OF CGRRECTION Patent Noa 2,820,985 January 28, 1958 Arthur Gresswell It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Let uers Patent should read as corrected below.
after the Word "larger" insert w the column 4,
Column 1, line 57,
insert a comma; column 6, line 2, for "suprimposed" line 65, after "porous" read superimposed em Signed and sealed this let day of April 1958.)
KARL Ha AXLINE ROBERT C. WATSON Attesting Officer Commissioner of Patents