US 2474885 A
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Description (OCR text may contain errors)
July 5, 1949.
J. H. BLOMQUIST METHOD AND MEANS FOR THE STARTING OF SYNTHETIC YARN SPINNING Filed May 15, 1948 INVENTOR. John Howard B/omquisf A T TORNE Y Patented July 5, 1949 so STAT ES or 2,474,885 METHOUAND MEANS Ffoitriiii sTAifiiN" OF'SYNTHETIC YARN'SPINNING' John Howard Blomquist, wiliriiiigtoni'Del'i, as"-' signor to E. I. du Pont de'fNemou'i's ac CompamnI Wilmington, Del., a corporation of Delaware ApplicationMay 15, isisiseriaint; 27,194"
7 Claims. 1.
This invention-relates to themanufacture of artificial textile filaments',- yarns and threads, and more particularly,- to improvements in the dryand melt-spi'nningof synthetic filament-forming materials.
In the past, in the meltand dry-spinning of synthetic filament-forming materials, e. g. nylon, cellulose acetate, etc., considerable difficulty has been experienced, when starting up a spinning -position,in obtaining uniform and equal extrusion through the orifices of the many-holed spinneretsused in'the production of continuous filament yarns. Conventionally,l the material to be spun is pumped from-a melt pool or manifold supply system through a series offilteis orsand packs, and then extruded; through a 'spinneret into an evaporative and/or cooling atmosphere. The evapotative or cooling atmosphere is commonly contained in a tubular structure referred toas a spinning cell. solidify by evaporation ofthesolvent, or in the case of melt-spunfilaments, by cooling, to form the continuous filaments commonly usedin the textile trade.
Each of these spinning positions must from time to-time be shut down temporarily; This is frequently done for the purpose of cleaning the spinnerets, the various apertures of which may become clogged. Again, some part Of the'packing-may-fail and leakages occur. Also, the filters orspinning packs must be replaced at'frequent intervals. Therefore, a typeof preventative maintenance is usually 'followed whereby the various spinnerets are changed at regular intervals, each change, of course, necessitating-a cessation of spinning from that particular position.
When the various parts have been cleaned or renewed and theposit'i'onreassembled, pumping to the position to resume production of the continuous filaments is again'started; A very considerable 'difiiculty encountered in the start-up resides inthe-fact that as the pumping'starts, the spinning solution or melt is notdistributed evenly over'the back face of the spinneret before extrusion starts. In other words, holes in one portion of the spinneret face startspinning before-holes in the other portions and the'last holes to 1 spin quite frequently drip,-'i. e. do not-pass a continuous stream of' material, or "are slow holes, 1. e. an insufficientamoufltofmaterial is extruded to form asuitable-filament.
This difficulty is experienced with most spinnercts. Howeveiz it is especially troublesomein the "case ofvery"large-spinnerets, i. e. 200-ho1e pinnerets and larger-'(3 to 5 inches in diameter),
In this cell, the filaments of the type generally used to spin a tow ioroon version into staple. It can be readily seen that when certain hol'e'sin a spinneret f ace either drip 01"do-n0tf. spin 'atl *the' same rate asvthe others, corrective steps must be immediately taken or: else a non-uniform yarn-bundle will "result. The procedure usuallyfollowedxis. that of wiping. In other words,- the" spinneret." face is wiped. clean in the hope that all the holes will. commence spinning uniformly." ,F quean this, must, be done several"times 'bfore spin 'ingxprooeeds in the' proper v manner; and]: con u'e'nny 'er'itail'sfa considerable loss: of production as wellflas" adding another operation} j. T
A principal ob J'ect 'cijth'is invention", therefore, is'to 'seciireffrom'theistartfof a dry or'meltr s inning operation simultaneous and uniform extrusionsiiromall holes'l f multi hole' spinner'ets'. Another-obj ec't. is to providesimme, inexpensive means for securing'fa satisfactory start-up ofIa conventional 'dryjor' melt-spinning operation. other objects j will more clearly a pear" herein.- after.
Theseobje'ct's are, realized by the pr'e'sent inl- "verition 'ivl iicli, briefly stated, comprises. provid-v ing the multi-liqlespinneret, before th e S inning operationisinitiated, with a rupturable barrier plajc'edin contact with the inner or outer face of the spinneret and sized to cover or close all of the'fholes of thespinnerti whereby to permitb'a'ck pressuifeto piat 'the' inner face ofthe. spin neiet'" and hence cause the,'spinning imaterialto be distributed uniformly overthejback face of the spinnere'tQ Gradually, the back pressurereaches a point'where the barrier ruptures" at all. spine neretfholes, simultaneouslmfthus insuring suffe 'fi'cie'nt pressure iortheimmediate and uniform extrusipnfof 'spinningiinaterial' through all, of said'h oles. I g I A n The rupturable'barrie'r utilizedfin accordance with the principles of thisinvention'may be of any convenient fi1m Ql"fOl1-WhlCh will withstand the operating temperatures encountered in the spinning head; Asi suitable 1 "examples of metals from which" these "rupturabie barriers" m be prepared, "the 'foll'oWing"-"'ma'y be mentioned? ammimim; beryllium, chromium, copper; gold; iron} magnesiumf nickelj'platinum z'ir'icfjetci, and various alloy'sj th reofi'; n th' c' ecrmateriai that are spun at -re anve1y 1ow temperatures, suitalile barriers may be pre ared from'yarious film-forming polymeric materials? As fsuitable examples; are films repared'rmm poly-amides and fpolyesteis aswell a's --'various vinyl polymers suclras polyacrylonitrile; vinylidene chloride, etc;
3 In addition, films prepared from cellulose esters and regenerated cellulose may be used for many such applications. However, for high temperature applications, e. g. such as those encountered in the melt spinning of polyamides, metallic barriers will normally be preferred.
The main requirement with regard to operativeness is that the foil should be thin enough so that it will rupture when the back pressure has reached that which is normally encountered in the spinning operation, thus insuring that abnormal back pressures are not built up. Suitable thicknesses for such foils may vary from 0.0001 inch to 0.01 inch, depending upon the material used in making the film. As a method for determining the correct thickness of the film to be used, the following equation serves to givea useful approximation:
t=thickness of film or foil (inches) P=operating back pressure (pounds per square inch) R=radius of spinneret aperture (inches) a=teI1Si1e strength of film or foil at operating temperature (pounds per square inch) Although the rupturable barrier may be placed at either the front or back face of the spinneret, in most instances, and particularly where a metal foil is to used, it will be found most convenient to position the rupturable barrier over the back (inner) face of the spinneret. Alternatively a suitable barrier may be formed by coating the outerface of the spinneret with an appropriate filmformer of the type hereinabove mentioned, or a. barrier of film or foil may be cemented to the front face of the spinneret or secured thereon by any one of a number of conventional clamping expedients, e. g. a contractible band fitted around the outer side wall of the spinneret. In the case of the recessed type spinneret wherein a filter pack is placed directly against the back face of the spinneret, e. g. dry-spinning of cellulose acetate, the film or foil may be conveniently used across the polymer supply side of the filter pack. Here again, the primary purpose is served. 1. e. the spinning material is distributed evenly over the area of the pack and spinneret, causing pack compression before the film bursts, thus insuring uniform extrusion.
The principles and practice of the invention are further illustrated by the following examplesof preferred embodiments, reference being had to the accompanying drawing wherein is shown, diagrammatically, a typical system involving the use of the novel rupturable barrier of this invention. Legends in the description refer to like parts in the drawing.
Example I A melt pool I containing molten polyhexa-- methylene adipamide is maintained in the vicinityof 280 C. The molten polymer is forced by a suitable pump 2 through a sand pack filter 3 to the spinneret 4. Across the back face of the spinneret, there is a rupturable barrier 5 comprising an aluminum foil 0.001 inch in thickness. The spinneret itself is a 70-hole spinneret 3 inches in diameter, each hole being 0.00? inch in diameter. The aluminum foil barrier causes the back pressure within the pack and polymer supply line to build up until it is suflicient to rupture 4 the aluminum foil at each point of non-support, i. e. the individual spinneret holes. When the pressure is sufiicient to do this, holes are burst in the foil by the back pressure and uniform extrusion through all the holes of the spinneret occurs. Using the process of this invention with this type spinneret in the spinning of 3 denier per filament staple, fifteen out of twenty successful starts were achieved. For comparison, when the start-up procedure was tried without using a rupturable barrier, it was only possible to achieve twenty successful starts out of fortythree tries.
Example II In a procedure, as in Example I, a 0.001 inch thick aluminum foil is used in the starting up of a spinneret 4% inches in diameter containing 200 holes, each 0.007 inch in diameter, for the spinning of 1 A, denier per filament staple. Using the same procedure as outlined in Example I, three successful starts out of four tries are achieved using the aluminum foil. For comparative purposes, without the use of aluminum foil, only one successful start out of five tries is obtained.
Emample III This same procedure is repeated using the apparatus described in Example II, but substituting in the place of the aluminum foil 0.00025 inch thick nickel foil. Here again, a considerable improvement in start-up performance is achieved. Out of ten tries, seven successful start-ups are obtained. For comparison, without the use of the foil, in ten tries only five successful start-ups are realized.
As many apparently widely different embodiments can be made without departing from the spirit and scope of my invention, it is to be understood that said invention is not limited in any Way except as set forth in the appended claims.
1. In the process of spinning filaments, yarns and threads of synthetic filament-forming materials wherein a spinning composition comprising synthetic filament-forming material is extruded through a multi-hole spinneret into a gaseous atmosphere, the improvement which comprises covering the holes of the spinneret, prior to spinning, with a rupturable barrier of sufficient thickness to prevent the extrusion of spinning composition through the holes of said spinneret only until the pressure of spinning composition over the inner face of the spinneret has reached the level customarily encountered in the spinning operation, at which point the barrier ruptures at substantially all holes of the spinneret simultaneously to permit extrusion of spinning composition therethrough, and thereafter forcing spinning composition into said spinneret whereby to rupture said barrier and initiate spinning.
2. In the process of spinning filaments, yarns and threads of synthetic filament-forming materials wherein a spinning composition comprising synthetic filament-forming material is extruded through a multi-hole spinneret into a gaseous atmosphere, the improvement which comprises covering the inner face of the spinneret, prior to spinning, with a rupturable barrier of suflicient thickness to prevent the extrusion of spinning composition through the holes of the spinneret only until the pressure of spinning composition over the inner face of the spinneret has reached the level ordinarily encountered in the 5 spinning operation, at which point the barrier ruptures at substantially all the holes of the spinneret to permit extrusion of spinning composition therethrough, and thereafter forcing spinning composition into said spinneret whereby to rupture said barrier and initiate spinning.
3. A multi-hole spinneret, the holes of which are covered by a rupturable barrier of a thickness to prevent spinning solution from passing through said holes only until the back pressure in said spinneret reaches the level ordinarily encountered in the normal operation of said spinneret.
4. A multi-hole spinneret, the inner face of which is substantially covered with an impervious barrier whereby to close the holes of said spinneret, said barrier being of a thickness to prevent No references cited.