US2891278A - Spinneret - Google Patents

Description

H. M. cooK SPINNERET June 23, 1959 2 SheetsSh.eet 1 Filed May 14, 1956 ATTORNEY June 23. 1959 H. cooK SPINNERET 2 Sheetsheet 2 Filed May 14. 1956 INVENTOR v HARRY M. COOK United States Patent fifice SPINNERET Harry M. Cook, Staunton, Va., assignor to E. I. du Pont de Nemours andCompany, Wilmington, DeL, a corporation of Delaware Application May 14, 1956, Serial No. 584,770 5 Claims. (Cl. 18-8) This invention relates to a new and novel spinneret and more particularly to a spinneret having a large number of extrusion orifices especially designed for the evaporative spinning of a large bundle of synthetic textile filaments. Heretofore, one disadvantage of spinning acrylonitrile polymers and copolymersfrom a solution such as a N,N-dimethylformamide solution was that when the polymer was extruded through a large number of closely spaced orifices some of the adjoining filaments would touch and stick together. Even when using specially designed spinnerets and observing great care with respect to uniform spacing of orifices, many such stuck or twinned filaments were formed.

A common spinneret design arranges the extrusion orifices equally spaced both radially and circumferentially in a series of concentric circles. Such a design does not effectively overcome the twinning problem.

An object of the present invention is to provide an improved arrangement of orifices in a spinneret which prevents or greatly eliminates the formation of twinned or stuck filaments. Another object is to provide an improved mounting for the new spinneret to insure uniform filamentation and evenly divided flow to all the orifices in the spinneret. A still further object is to provide means for preventing leakage around the filter elements and to give dependable initial solution flow through the spinneret. Other objects will become apparent as the description of the invention proceeds.

These and other objects are accomplished by providing a spinneret having a large number, preferably not less than 400, of extrusion capillaries arranged in a plurality of concentric circles, preferably at least 4. The extrusion orifices or capillaries are arranged in the face of the spinneret so that the center of each capillary falls on a separate radial line. In other words, if radii are drawn to each capillary they will differ by a constant central angle, and there will be as many separate radii as there are capillaries.

There may be as many as 2000 extrusion capillaries arranged in as many as concentric circles, but in commercial practice there will be preferably about 700 to 1400 extrusion capillaries arranged in from 5 to 8 concentric circles. It will be apparent that the capillary orifices must be very precisely located since for example with 1414 capillaries the central angles between adjacent radii will be about /4 In one preferred arrangement, all the capillaries are located in an outwardly cupped annular protrusion and in each concentric circle the same number of holes are provided uniformly spaced one from the other, which means that the holes in the outer circles will be spaced somewhat farther apart than those in the inner circles.

In the drawing, Figure 1 represents a sectional view of a spinneret head assembly incorporating the present invention. Figure l-a is an enlarged view of area A clearly the arrangement of which the invention particularly relates.

of Figure l to show more the parts to Patented June 23, 1959 Figures l-b and 1-c are perspective views not drawn to scale of adapter 2 and ring nut 6. Figure 2 is a front view of the spinneret face. Figure 3 is an enlarged broken diagrammatic plan view showing :a radius drawn from the center of the spinneret to each of the extrusion capillaries. This view clearly illustrates that each capillary is at the terminus of a separate radius.

In all the figures, 1 represents a conventional spinneret body to which an adapter 2 is firmly secured by threads 16. The spinneret plate 17 is provided with a back support 3 and a front support 4 between which the spinneret plate is held by cap screw 5. The back support 3 is provided with several (feed orifices 14 and a plurality of filter screens 12 and a clamp 13 for holding the filter screens firmly against the back support 3. This assembly is held tightly against the adapter 2 by means of a ring nut 6. The adapter isprovided with internal threads 16a to receive the spinneret body 1. It also is provided with external lugs 18 having a beveled portion 19. The ring nut 6 has aninterrupted flange forming protrusions 20 spaced to receive lugs 18. A twist of about 30 forces the lugs beneath the protrusions 20 with a cam action which assures a tight fit. Escape of fluid between the various parts is prevented by suitable gaskets shown as 7. The spinneret plate 17 is provided with counterbored extrusion orifices 10 which terminate in extrusion capillaries 11 as shown particularly in Figgure l-A.

In operation the liquid polymer either as a melt or in the form of a solution is delivered through the body of the spinneret into feed chamber 15 where it is then filtered through screens 12 and passes through the feed orifices 14 through a second filter 8 and finally into the counterbored orifice 10 and through extrusion capillaries 11. After the polymer emerges from these capillaries it is contacted with a suitable fluid for cooling the filaments in the case of melt extrusion or evaporating the solvent in the case of evaporative spinning.

The following example illustrates the ing out the invention, but no limitation is placed thereon since the number of holes and spacing may be varied within the limits given above.

Example I A 29% solution of acrylonitrile polymer in N,N-dimethylformamide was prepared and delivered to a spinneret having 1344 extrusion capillaries arranged in 7 concentric circles of 192 capillaries each. Each capillary had a diameter of 0.12 mm. Each circle was separated from an adjacent circle by a distance of 2 mm. The outer circle had a diameter of 146 mm. and the hole spacing was 2.39 mm. The innermost circle hada diameter of 122 mm. and the hole spacing was 2.00 mm. In order that the center of each extrusion capillary fall on a different radial line, the center line for the first row of holes in the 7 concentric rings was tilted 8 /2 from the diameter of the spinneret with the apex of this angle at the center of the hole in the outermost circle as shown in Figure 3. Subsequent rows of holes were similarly located until all 1344 holes were arranged in the outwardly cupped annular space. The central angle between adjacent radial lines to each orifice was slightly more than and was substantiallyconstant for each adjacent radii.

The acrylonitrile in solution was spun at the rate of 200 y.p.-m. to produce a 5260 denier bundle of 1344 filaments or 3.9 denier per filament. After drawing 5.6x and relaxing, the final filament denier was below 1. The quality of the yarn was excellent and was free of stuck or twinned filaments. The rate of spinning production was over 14 lbs. per hour per spinneret.

manner of carry- Example 11 Example I was repeated using a 1080 hole spinneret which was made with 180 holes in each of the 6 concentric circles. The spacing between the holes on the outer circle. were 2.53 mm. and 2.13 mm. on the inner ring. The diameter of the outer circle was 145' mm; and the inner circle 122 Each ring ,was spaced from the adjacent ring by a distance of 213 The holes in each successive circle were located on a line 8 from the center line of the spinneret which gave a centrah angular spacing of adjacent radial lines to the holes of about /3", The spinning performance of this spinneret was excellent and produced about 11.3 lbs. per hour of undrawnxfilaments. These were drawn and. relaxed as in Example I to give a denier of about 1' per filament. The yarn so. produced was free, of stuck or twinned filaments and the uniformity of filament size and physical properties were very satisfactory.

In previous tests with spinnerets having orifices uniformly spaced in the severalgconcentric rings and containing a total of only about 800 holes, stuck or twinned filaments were found in every run.

While the invention is especially adapted to spinning a large bundle of low denier filaments it may also be used to advantage in the production of relatively larger or smaller filaments which after drawing from 2x to 10X may range in the size of from /2 denier up to 12 or 15 denier.

The invention is not limited to spinning acryl onitrile' polymers but may be used with cellulose acetate or any synthetic filament which may be spun by evaporative, meltor wet-spinning methods. The spinneret herein described also has the advantage that it provides easy changing of spinneret plates and quick effective" sealing.

The position of the gaskets and filter screens shownpermit no bypassing of solution around the filter means and further provides a uniform supply of material to each orifice. This arrangement likewise produces better initial production when spinning is started.

It will be apparent that many widely different ernbodiments of this invention may be made without departing from the spirit and scope thereof, and therefore it is not intended to be limited except as indicated in the appended claims.

I claim: a

1. A spinneret having an annular perforated area containing at least about 400 symmetrically disposed p'erfo rations, the perforations being extrusion orifices located on the circumference of at least four closely spaced concentric circles, each such orifice being located. terminally on a separate radius andeach such radius forming an equal central angle with its adjacent radius and each perforation being substantially equi-distant from adjacent perforations on the same circle.

The. spinneret of claim 1 in which there are from 400t9 2000 extrusion capillaries located on from 4 to 10 concentric circles, r p

vfinj lhe, spinneret of claim 1 inwhich there are from 700to1400 extrusion capillaries arranged in from 5 to 8 concentric. circles.

4-. The spinneret of claim 1 in which the central angles between adjacent radii. are from to /3. Q

5. The spinneret of claim 1 in which the annular perforated area is outwardly cupped.

References Cited the file of this patent FOREIGN PATENTS o enna y Nev. 15, 1951 Germany Nov. 19, 1953

Images