US 2954271 A
Description (OCR text may contain errors)
L. CENZATO PROCESS FOR PRODUCING SHAPED ARTICLES USING SONIC Sept.- 27, 1960 VIBRATIONS TO ENHANCE SOLIDIFICATION 2 Sheets-Sheet 1 Filed March 10, 1958 FUN?! ATTORNEY Sept. 27, 1960 CENZATO 2,954,271
PROCESS FOR PRQDUCING SHAPED ARTICLES USING SONIC VIBRATIONS To ENHANCE SOLIDIFICATION Filed March 10, 1958 2 Sheets-Sheet 2 INVENTOR LORENZO CENZATO BY 2 m ATTORNEY Unite States Patent F PROCESS FOR PRODUCNG SHAPED ARTICLES USING SONIC VIBRATIONS TO ENHANCE SOLIDIFIC'ATION Lorenzo Cenzato, Wilmington, Del., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Filed Mar. 10, 1958, Ser. No. 720,136
8 Claims. (Cl. 1854) This invention relatm to the use of low frequency sound waves in a process for preparing shaped articles. More particularly, this invention relates to the use of sound waves of a frequency from about 10 to 1000 cycles per second in a process of meltand dry-spinning organic polymers.
The use of high frequency sonic treatments in the production of shaped structures is, of course, known. However, I have now found that surprising and unexpected results are obtained using low frequency sound waves in the production of such structures. By directing sound waves in the range from about 10 to 1000 cycles per second into a spinning tube in meltand dry-spinning apparatus, the productivity or throughput can be increased over 200%. Surprisingly, this increased productivity is achieved without complicated process control and without deleterious effects or changes in the structures produced. Even more surprising, I have found that by using low frequency sound waves that are resonant with the spinning cell, substantial reductions in power requirements as well as case of control of the process is achieved.
Many attempts have been made to achieve the increase in productivity of shaped articles made possible by the present invention. In the preparation of fibres, filaments and films by the extrusion of a solution of a polymer into an evaporative medium, that is by dry-spinning, the removal of the solvent to a sufliciently low level to permit collecting the product has been one limiting factor. Attempts have been made to increase production by raising the temperature of the medium and thereby raise its evaporative capacity; however, this procedure has not proved to be satisfactory since the upper level of temperature, dictated primarily by the thermal discoloration of the product, is .quickly reached. Other attempts have been directed to replenishing the evaporative medium at a greater rate through the spinning or casting cell, but again such attempts have not been satisfactory because an upper limit, where the increased flow of gas results in excessive threadline movement and other bad spinning or casting behavior, particularly when a number of shaped articles are being extruded side by side, is quickly reached. Similarly, the attempts to solve the problem of productivity in melt-spinning, that is when a melt of 'a polymer is extruded into fibers or films, have not met with success. In this case, a gaseous medium is used to coagulate or set the shaped articles. The amount of molten polymer that can be extruded through a single orifice or slit in a definite time, i.e., the through-put, is limited by the quenching ability of the medium. Therefore, only a limited amount of polymer can be extruded through each orifice. When attempts are made to extrude a greater amount of polymer, insufficient quenching results, and when the orifices in the system are placed too closely together the threads coalesce.
As previously stated, the use of sonic treatments in the production of shaped structures is known. However, most prior art applications have been limited to the use of frequencies suificiently high to cause physical rear- Patented Sept. 27, 1960 rangement of the molecular structure of the material being treated. Such frequencies do not produce the results of this invention. In these high frequency applications the power requirements are quite high which, of course, adds greatly to operating cost of the process. Furthermore high frequency sound waves in the audible range are annoying and sometimes painful to operators working in adjacent areas.
The objects of this invention are apparent from the foregoing discussion. Obviously, the primary object is to provide a process which permits a substantial increase in productivity in the extrusion of shaped articles.
Another more specific object of this invention is to provide a process which permits an improved removal of solvent from an object extruded from a solution of a polymer without changing the polymer structure and without deleterious effects to the shaped article.
Another object of this invention is to provide a process which permits the extrusion of melts from slits or orifices having much closer spacing than has heretofore been possible.
A further object is to provide greater productivity per orifice or slit for the extrusion of a melted polymer than has been possible.
A still further object of this invention is to provide more uniform melt-spun multifilament yarn.
Still other objects will be apparent from the following discussion.
The objects of this invention are achieved by a process which comprises extruding a film-forming composition through a spin-neret or extruder, subsequently passing the extruded shaped articles while in a plastic state, i.e., before solidification, through a chamber containing a gaseous medium while continuously directing low frequency sound waves in the range from about 10 to 1000 cycles per second into said gaseous medium and thereafter passing said shaped articles to a collecting device. Preferred embodiments of the process include the use of a cylindrical chamber and \a frequency within the aforementioned range which is resonant with the chamber. Frequencies in the range from about 20 to 400 cycles per second are preferred.
The invention will be more readily understood by reference to the following detailed description and the accompanying drawings. In the description, the term filmforming composition is meant to include solutions, melts, plasticized melts, and dispersions of both natural and synthetic filmor fiber-forming organic polymers which are capable of being formed into shaped articles by the meltand dry-spinning or extrusion processes. The term shaped article is meant to include fibers, filaments and films shaped from natural and synthetic polymers. The term gaseous medium is meant to include all gaseous compositions to which the film-forming material being extruded is inert, e.g., air, nitrogen, carbon dioxide, mixtures of nitrogen and carbon dioxide, and the like. By the expression power input is meant the power de livered to the loud speaker or diaphragm of any suitable sound generating apparatus. The power is conveniently measured by inserting an ammeter and voltmeter between the amplifier and speaker. It will be apparent from the following discussion that the power input is not a limitative feature for all embodiments of the present invention since various mechanical sound generating means capable of producing sound waves within the range specified may be used. Of course, the relatively small amount of power required to generate the low frequency sound waves, whether it be mechanical or electrical, particularly when frequencies resonant with the spinning chamber are used, is a highly desirable feature of the present invention.
"Figure 1 is a schematic drawing of a suitable form of apparatus for carrying out dry-spinning by the process of this invention;
Figure 2 is a schematic drawing showing suitable apparatus for melt-spinning a film-forming composition by the present invention;
Figure 3 is a schematic drawing showing an alternate embodiment of suitable apparatus for melt-spinning; and
Figure 4 shows an alternate form of apparatus for dryspinning by the process of this invention.
Referring to Figure 1 of the drawings, reference numeral 1 designates a spinneret containing a plurality of orifices through which a solution'of polymeric film-forming material fed from a source not shown is extruded under pressure to form filaments 2. The filaments are extruded into the spinning cell or chamber 3 which contains a gaseous medium. After leaving the spinning cell, the filaments pass around guide roller 4 and to a suitable collecting device not shown. It will be noted that the filaments are not restrained as they pass through chamber 3.
Sound-generating unit 5 is positioned at opening 6- in wall 7 of chamber 3. The temperature of the spinning cell is controlled by jacket 8. A gaseous medium is forced into the spinning cell through an annular opening 9 around spinneret 1. Extension ltlmay be attached to wall 7 of the spinning tube to receive the speaker of sound-generating unit 5.
Referring to Figure 2 of the drawings, reference numeral 11 designates a spinneret. A viscous polymer is fed from a source not shown through orifices in the spinneret where it is formed into filaments 12. Reference numeral 13 designates a quenching tube having an opening 14 which may be open or partially closed through which filaments 12 pass to a guide roller 15 and then to a suitable collecting device not shown. Sound-generating unit 16 is positioned at extension 18 to direct sound waves through opening 17 into the quenching tube. A natural flow of a gaseous medium may occur in the quenching tube, or co-current or counter-current flows may be established by forcing the gaseous medium through annular opening 19 or opening 14, respectively. The filaments are not restrained as they pass through quenching tube 13.
As shown in Figure 3, the apparatus for melt-spinning has been modified to include a perforated liner'20 which is placed inside quenching tube 23. The polymeric material is formed into filaments 22 as it is fed through spinneret 21. As the filaments pass through tube 23 and liner to opening 24 and guide roller 25, soundgenerating unit 26 is operated to set up the low frequency vibrations. A supplementary flow of a gaseous medium may be introduced into the tube at any selected point, e.g., through orifices 27 and 28. Suitable bafliing, not shown, may be used to distribute the air evenly through perforated liner 20.
In the dry-spinning of some materials it has been found desirable to localize the quenching action of the resonating medium. An elbow-shaped spinning cell, as shown in Figure 4, may be used. Filaments 30, formed by spinneret 29, pass through the vertical arm of the tube through orifice 31 and to guide roller 32. The soundgenerating unit 33 is preferably located at opening 34 in the end of the horizontal arm of the elbow but may be located at any point along the spinning cell. A gaseous medium may be forced into the cell through annular opening 36. The temperature may be controlled by jacket 35. By using an elbow-shaped spinning cell it is possible to localize the quenching action and at the same time obtain the improved results through the use of the low frequency sonic treatment.
It will be obvious that other types of apparatus similar to those just described may be uitlized in carrying out the process of the present invention.
The invention will be further illustrated but is not intended to be limited by the following examples.
4 Example I A copolymer of acrylonitrile and methyl acrylate (94/6 percent by weight) of intrinsic viscosity 1.5 was made into a 27% solution with dimethylformamide (DMF). This solution was extruded using apparatus similar to that shown in Figure 1 at 125 C. through a spinneret having orifices 0.005 inch in diameter (located in concentric circles) into a spinning cell 6 inches in diameter and 13 feet long, and the filaments Wound up at 340 yards per minute below the spinning cell. Nitrogen gas heated to 200 C. was forced into the spinning cell at about 3 cubic feet per minute around the spinneret and flowed down with the threadline. The spinning cell itself was heated to 275 C. by an oil-heated jacket in the cell wall. At a point about 20 inches below the location of the spinneret, a 2 /2 inch diameter hole was cut in the spinning cell. A metal cylinder 6 inches long connected the spinning cell and a 15-watt loud-speaker (magnetic type) which in turn was connected to a variable audiooscillator with a range of 10 to 100,000 cycles per second, Model GE 850D, made by the General Electric Company, with an audio-amplifier. A sheet of poly(ethylene terephthalate) film 0.002 inch thick was located in front of the loud-speaker to protect it from DMF. Voltmeters and ammeters were connected between the amplifier and speaker to obtain data for computing the power input to the loud-speaker.
When the spinning was conducted with the loudspeaker off, good spinning was obtained, and the yarn (5 denier per filament) as wound up contained 14.5% residual DMF based on the dry weight of the yarn. When the audio-oscillator was adjusted to a frequency that was resonant with the spinning chamber, 110, 165, 220, and 440 cycles per second, at a power consumption of 0.3 watt or lower, it was observed in all cases that the yarn had a greatly reduced residual solvent level of 7%.
The values of the resonant frequencies were readily determined by listening to the sound level of the equipment and measuring the power consumption. At the resonant frequencies a reduction in power consumption of the loud-speaker at the same sound level was observed. The yarn produced by spinning at resonant frequencies was of excellent quality and color, and could be drawn to yield strong fibers.
The use of frequencies in the range of -460 cycles per second that were non-resonant with the spinning cell at a power input of 4 to 10 watts also afforded an improved solvent removal as compared to the use of no sound, but the effect was much lower than shown above with resonant frequencies.
A similar improvement in solvent removal at resonant frequencies was obtained in the dry-spinning of a 30% solution of the polyurethane from piperazine and ethylene-bis-chloroformate in chloroform/formic acid 85/15. Like results were also obtained in the dry-spinning of cellulose triacetate from a methyl acetate/ acetone (60/40 by weight) solution.
Example II Poly(ethylene terephthalate) of relative viscosity 31.6 was extruded at 270 C. through a spinneret having a total of 187 orifices, 0.005 inch in diameter, spaced 0.05 inch apart on centers from adjacent orifices and located in three concentric circles. The filaments'were extruded into a spinning column 3 inches in diameter and 5 feet in length located approximately 1 inch below the face of the spinneret. Ten (10) inches below thetop of the tube, a 3-inch diameter hole ,was cut in the spinning column, and to this was attached ametal. cone and a loudspeaker connected to an oscillator and amplifier of the type described in Example I. The bottom of the column had metal slides for adjusting the size of the opening through which the threadline passed. The apparatus was similar to that shown in Figure 2 of the drawings. The polymer was spun at various frequencies. A power input of 4 to 5 watts, no cross-flow quench of air other than that provided by the moving threadline itself, a throughput of 0.42 gram of polymer per orifice per minute, and a windup speed of 1000 yards per minute were used.
The results obtained were as follows: I
(1) At the resonant frequencies which were determined by the reduced power consumption at the given level of sound used, 100, 150, 200, and 250 cycles per second, excellent spinning was obtained with no coalescence of adjacent filaments. As the power was increased to about 7 to 8 watts at the higher resonant frequencies, spinning performance deteriorated.
(2) At resonant frequencies of 300 cycles per second and higher and a power input of from 4 to 5 watts, the spinning performance deteriorated with an increase in coalesced filaments resulting. It is believed that this is due to the reduced amplitude of the waves at the higher frequencies at a constant power level.
(3) At non-resonant frequencies below 300 cycles per second, 106-144, 156-194, and 206-244 cycles per second, the spinning was noticeably improved over that experienced with the loud-speaker off but still inferior to that at resonant frequencies within this range.
The yarn produced by spinning at the resonant frequencies above was of excellent quality and could be drawn 2.2 to 3.5 times its original length to yield strong fibers having a tenacity of 4.0 grams per denier and percent elongation of 39.
Using the same polymer, spinneret, and through-put rate as described above and the best known conditions of cross-air quenching as taught in U.S. Patent 2,273,105, good spinning without the use of low frequency sound waves could not be obtained. The filaments coalesced with no satisfactory product being obtained. Spacing of the orifices at least 0.l25.inch from center to center of adjacent orifices was necessary in order to permit good spinning with the prior art process. Using the process of this invention, a 250% increase in productivity was obtained.
Example III Poly(hexamethylene adipamide) of relative viscosity 41 was extruded at 280 C. through a spinneret having 15 orifices of 0.020 inch in diameter spaced 0.175 inch apart on their centers into the spinning cell as described in Example II and the yarn wound upv at 1,344 yards per minute. The spinning cell was located one inch below the spinneret. The fundamental frequency of the system was observed to be 28 to 30 cycles per second.
The process as described above was inoperable at throughaput levels about 1.5 grams of polymer/orifice/ minute when the loud-speaker was ofi due to coalescence of adjacent filaments in the threadline. Excellent spinning was possible when the loud-speaker was operating at about 4 watts input with a resonant frequency of 30 cycles per second. At about 150 cycles per second, a maximum throughput of 3.9 grams of polymer per orifice per minute was: possible with good spinning. In the region of 240-260 cycles per second a maximum through-put of 3.1 grams per orifice per minute was possible with good spinning. The use of non-resonant frequencies at 4 watts input gave improved performance over the system with no sound, but inferior to that obtained with the resonant frequencies at the same power input.
The maximum through-put for the above spinneret and polymer by prior art processes is about 1.5 grams per orifice per minute. An increase in productivity of about 150% was possible using the process of this invention.
Example IV The spinning column of Example II was modified by the addition of a 2 /2 inch long quenching ring consisting of a 4 inch (outer diameter) outer wall of steel with an wire gauze with suitable bafliing so that air is distributed pertinent references.
evenly through the wire gauze towards the center of the spinning column. The assembly is positioned with its top /2 inch below the base of the spinneret which has 44 orifices of 0.009 inch in diameter spaced 0.175 inch apart on their centers.
Poly(hexamethylene adipamide) of relative viscosity 46 was extruded at 285 C. through the above-described spinneret at a through-put rate of 1.1 grams/minute/ orifice and the yarn wound down through the spinning column at 340 yards per minute.
When the above conditions were used with 125 cubic feet per minute of air at a temperature from 10 C. to 15 C. being supplied to the quenching section and the sound turned off, the asaspun yarn obtained had an average birefringence of 0.0030 with a range over the entire bundle of 44 filaments of 0.0013. Birefringence was determined by observing filaments between cross planepolarizing elements (e.g., Nicol prisms). This method is treated in detail by I-Ieyn in The Textile Research Journal 22: 513 (1952).
Using the same spinning conditions as described above with the exception of 20 cubic feet per minute of air at a temperature of 25 C. being supplied to the quenching section and the audio-oscillator operating at a frequency resonant with the spinning column, 45 cycles per second, at a power consumption of 2 watts, the as-spun yarn obtained had an average birefringence of 0.0010 with a range over the bundle of 0.0008. This yarn with its greatly improved filament-tofilament uniformity could be drawn to a greater maximum draw ratio than the first yarn and thus afforded significantly stronger yarns after drawing. 7
When no sound was used at the low quench level in the second spinning, the spinning was very poor, and the filaments could not be collected.
The foregoing examples illustrate the practice of this invention but, as previously indicated, are not intended to be limitative since any variations in materials and apparatus given herein may be substituted directly for those used in the examples.
This invention can be used to great advantage in all processes wherein shaped articles are made by the extrusion of a film-forming composition into a coagulative or an evaporative gaseous medium. Such compositions include solutions, melts, plasticized melts, or dispersions of all types of polymeric materials, natural and synthetic. Suitable synthetic polymeric materials include those linear polymers of a suflioient molecular weight to be filmforming made by addition or condensation polymerization methods of low molecular weight monomers. Such polymers include polyamides, polysulfonamides, polyesters, polyurethanes, and polyureas as described in U.S. 2,071,250, U.S. 2,130,948, U.S. 2,667,468, U.S. 2,465,319, U.S. 2,511,544, French Patent No. 895,395, U.S. 2,660,575, and U.S. 2,708,617 to mention a few of the Shaped structures of addition polymers, such as polyacrylonitrile, polyhydrocarbons such as polyethylene and polypropylene, polyvinyl chloride, polyvinylidene chloride, and copolymers of the monomers of these polymers with each other and other monomers may also be advantageously prepared by the process of this invention. copolymers containing or more acrylonitrile with numerous monomers, such as ethylenically unsaturated sulfonic acids as described in U.S. 2,527,300 and U.S. 2,601,256, and others such as those disclosed in U.S. 2,436,926 and U.S. 2,456,360 may be treated by the process of this invention. Polymers such as cellulose esters, cellulose ethers, and the like, can also be used where the melts or solutions are extruded into a gaseous medium.
The foregoing description has been related to the spinning of multifilament yarns; however, it will be obvious that these teachings can be applied to the use of the present invention in a wide variety of processes concerned 7-. with the extrusion of shaped articles, and particularly those in which multiple streams of polymer are extruded.
The spinning cell in which the gaseous medium is vibrated can be of any convenient size or shape but is preferably cylindrical. Cylinders of variable length may be used to facilitate tuning to a resonant frequency within the range heretofore described for practicing this invention. The spinning cell can be located contiguous with the spinneret, or it can be separated some distance from it. However, it is preferable that it be placed near enough to the spinneret to insure that the threadline is in a plastic state when submitted to the vibrating gas. The filaments can be spun upward, downward, or in a horizontal position, whichever is most practical, with the spinning cell being located to accommodate spinning in the desired direction.
When extruding solutions of a film-forming polymer, the gaseous medium is conveniently heated as previously indicated to increase evaporation of the solvent from the threadline. If the flow of gas is cocurrent with the threadline, the spinning cell conveniently surrounds the spinneret as shown in Figure l of the drawings. When extruding polymeric melts, the gas used to quench the threadline may be conveniently drawn from the surrounding working area. In this case, in the event that co -current gas flow is to be used, the spinning cell may be separated from the extruding head as shown in Figure 2 to permit entrance of the gas between the spinning cell and the spinneret. The spinning chamber can be cooled by using suitable refrigerants or cooling devices in order to increase the quenching efiiciency of the gas within the chamber. The use of a normal quenching chamber can also be used in conjunction with this invention and may be a part of the spinning cell or precede it. Useful modifications of the principles of this invention will be obvious to those skilled in the art.
The gaseous medium within the spinning cell can be vibrated in any convenient manner. It is preferable, for the greatest freedom of operation, that the frequency and the power input to the vibrator be variable. A loud-speaker or diaphragm of the electromagnetic, electrostatic, piezoelectric crystal or magnetostrictive type in combination with a sonic generator and an amplifier may be used. Various types of simple mechanical sound-generating devices can be used including tuning forks and other mechanically operated sound generators, such as a diaphragm struck by a revolving cam, etc., the primary requirement being the ability to produce sound waves within the frequencies specified for practicing this invention. The force of the gaseous medium itself can be used to cause sound with a proper design of spinning cell.
It will also be obvious to those skilled in the art that the low frequency sound waves used in this invention can be induced in the gaseous medium at any desired point along the spinning cell and that the source of the sound waves can be positioned apart from the spinning cell itself as long as there is a proper coupling for transmitting the waves from the source to the cell.
Although the use of low frequency sound waves that are non-resonant with the spinning cell is within the scope of this invention and afiords improved spinning performance in a given system as compared to spinning without the sound, in using such frequencies from 10 to 100 times more power is required to produce the same results as with a frequency resonant with the spinning cell. Therefore, the use of resonant frequencies is greatly preferred for reasons of economy as Well as for ease of control which will be apparent from later discussion.
Although the power used is preferably kept at a low level, it is obvious that various factors such as the frequency being used, the size of the spinning column, and the size and number of filaments being processed will influence the selection of an optimum power level for practicing this invention. However, the optimum level can be readily determined. It is believed that optimum 8 conditions exist when the gaseous medium vibrates at an amplitude which creates an average gas velocity necessary to give adequate mixing of adjacent layers of the gas which do not cause an excessive movement of the extruded article. Increasing the amplitude of the vibrating waves beyond the optimum level will induce more and more vibration in the threadline and lead to unsatisfactory spinning. Therefore, the power input to the sound generator,-and hence the amplitude of the vibrating waves at a given frequency, can readily be selected by observing the threadline.
In a preferred embodiment of this invention, a frequency resonant with the spinning cell is used. A frequency that is resonant with the spinning cell or chamher is readily detected by a decreased power consumption at a given sound level at resonance or with the occurrence of the greatly improved spinning performance. Of course, the fundamental frequency of the resonating chamber can be calculated by well-known methods using the dimensions of the chamber and the composition and temperature of the gas being vibrated.
Although the optimum operating frequencies are readily determined, the following discussion will aid in selecting the frequency. The minimum frequency used should be higher than the fundamental frequency of the threadline in order to avoid excessive movement of the threadline. This frequency can be calculated by classical methods and is directly proportional to the tension on the threadline, which for a given composition is related to the ratio between the speed at which the polymer solution or melt is extruded from the spinneret and the speed at which the yarn is wound up. The minimum operable resonant frequency is also inversely proportional to the denier of the extruded filament (or the through-put of the solution or melt through the spinneret). The mum operable resonant frequency is, of course, inversely proportional to the length of the threadline. In order to conserve power, the lowest operable frequency is preferred, since the power requirements to produce a constant amplitude of vibration increase in proportion to the square of the frequency. 7
In general, resonant frequencies of 10 to 1000 cycles per second are useful in this invention at power levels of 0.1 to St) watts. Non-resonant frequencies within the same range may be used, but in order to approach the desired results power levels of 10 to times as much power is required as has previously been indicated.
This invention is of great utility in that by means of very simple apparatus and extremely low power consumption greatly improved spinning is obtained. In the case of dry-spinning it is possible to spin either drier yarn under a given set of conditions or it is possible to spin higher denier yarns than has previously been possible due to the difiiculty of removing the solvent from them. In the realm of melt-spinning, the superior performance of this invention makes possible the spinning of filaments closer together, i.e., with closer orifice spacing, than has heretofore been possible, or, alternatively, it makes practicable spinning at a much greater polymer through-put per orifice than has heretofore been possible.
The invention is also of great advantage in that remarkably improved inter-filament uniformity is obtained when spinning multifilament yarns. This improved uniformity permits the use of a higher maximum draw ratio and hence greater tenacities and more uniform dyeing of the filaments is possible.
Throughout the specification and claims, any reference to parts, proportions and percentages refers to parts, proportions and percentages by weight unless otherwise specified.
It will be apparent that many Widely different embodiments of this invention may be made without departing from. the spirit and scope thereof and, therefore, his not intended to be limited except as indicated in the appended claims.
9 I claim: 1. A process for preparing a shaped article from an organic film-forming material which comprises extruding a film-forming composition through an extruder to form the shaped article, passing the said article While in a plastic state through a chamber containing a gaseous medium, simultaneously generating low frequency sound waves in the range from about 10 to 1000 cycles per second at a point remote from said shaped article and directing said sound waves into said gaseous medium, thereafter passing said shaped article to a collecting device.
2. The process of claim 1 wherein a solvent is present in said filrn forming composition.
3. The process of claim 1 wherein said film-forming composition is a melt of an organic polymer.
4. The process of claim 1 wherein said shaped article is in the form of a filament.
5. The process of claim 4 wherein a plurality of filaments are prepared by extruding said polymer through a spinneret.
6. The process of claim 1 wherein the frequency of the sound waves is resonant with the chamber.
7. The process of claim 1 wherein the sound waves are in the range from about 20 to 400 cycles per second.
8. The process of claim 6 wherein said chamber is cylindrical.
References Cited in the file of this patent UNITED STATES PATENTS 1,952,877 Mancini Mar. 27, 1934 2,121,802 Kleist et al. June 28, 1938 2,273,105 Heckert Feb. 17, 1942 2,542,301 Barrington Feb. 20, 1951 2,645,031 Edwards July 14, 1953 FOREIGN PATENTS 806,030 France Dec. 5, 1936 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent N0. 2,954,271 September 27 1960 LorenzoCe-nzato It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.
Column 5, line 51; for "about" read above Signed and sealed this 25th day of April 1961.
ERNEST W. SWIDER DAVID L LADD Atteating Oflicer Commissioner of Patents