US2508462A

US2508462A - Method and apparatus for the manufacture of synthetic staple fibers

Info

Publication number: US2508462A
Application number: US583258A
Authority: US
Inventors: Walter R Marshall
Original assignee: Union Carbide and Carbon Corp
Current assignee: Union Carbide Corp
Priority date: 1945-03-17
Filing date: 1945-03-17
Publication date: 1950-05-23
Anticipated expiration: 1967-05-23
Also published as: GB609167A

Description

May 23, 1950 w. R. MARSHALL 2,5431%,462

METHOD AND APPARATUS FOR THE MANUFACTURE OF SYNTHETIC STAPLE FIBERS Filed March 17, 1945 ix, I

b'upg zelieigied INVENTOR WALTER R. MARSHALL ATTORN Patented May 23 195 UNITED ATENT OFFICE METHOD AND ARPARATUSTFOR" THE'MANU-.. FAQTUBE 0F" SYNTHETIG STAPLE FIBERS Application March 17, 1945, Serial No. 583,258

12 Claims.

.This. invention. relatesv to. .a. method and apparatus for the. manufacture. of fibrous products made-from fibers-forming thermoplastic organic polymers, more particularly elongated or orientedstaple. fibers.

Heretofore synthetic organic fibers have usu-. ally been made in the formof continuous fila-. ments by the extrusion and drawing. of liquefied fiber-forming polymer through minute. orifices. By'subsequent treating operations; the continuous fiber can be stretched to improve-its strength by molecular orientation, mechanically or otherwise treated to: impart a kink .or curl to the fibers. to. improve felting and spinning characteristics, and then cut into desired staple lengths.

The present invention is directed to a method and apparatus for rapidly and economically. producing feltable oriented staple fibers-from fiberforming organic polymers in a single. operation. The invention is based upon the discovery that momentarily heating such a polymer to decomposition temperatures under non-oxidizing conditions whereby the polymer is brought into a highly fluid condition, and then immediately sub jecting a film of the. fluid-polymer to a velocity and temperature controlled blast of inert hot vapor or gas discharging as a jet into the atmosphere causes filaments tc :be pulled off the film surface whichare at once attenuated by the blast until they. break into staple length fibers and. at the same time are sorapidly cooled to a nonplastic state-while suspended in the blast that elastic deformation or cold drawing occurs under conditions promoting a rand0m-angu1ar curl, twist or kink in each fiber.

The invention is more fullydisc'losed in the fol-' lowing description taken in conjunction with the drawing in which:

Fig. 1 is a sectional elevation view, partly diagrammatic, of an apparatus for making and collecting syntheticstaple fibers;

Fig. 2 is a longitudinal sectional elevation view (along the line 2-2 of Fig. 3) of acombined heating and blowing means for forming the staple fibers;

Fig. 3 is a, cross-sectional elevation view along the line. 3.3 of Fig. 2;

' Eis- 4 is a c os -s ct na eleva ion ie al n the l l-' ,-ofli i 2..

Referring to Fig. I there is shown a cylindrical vessel 5 enclosed by a heating jacket .6 and qu pped with a combina ion agitatorand pump: i-ng screw means i driven by an electric motor 8 through a gear reducer 9. Heating fluid or vapor, such as hot oil or diphenyl oxide, is, sup: plied to the jacket 6 of the. .cylindricalivessel 5 at an inlet connection llland is exhausted at an outlet connection ll. Viscous or granular fiberrforming polymer is introduced. into. the cylindrical vessel 5. through a loading opening I=2 .to. be heated until it is, fluid enough to be pumped. The polymer is then forced out of the cylindrical e l-. y the a itator screw means I andis picked. up by a constant delivery. gear pump. 1.3., also enclosed in a heatin jacket 14 fitted with an inlet; connection 15 tor hot vapor or fluid and an exhaust connection I6 for removal of the. used heatin fluid. The gear pump. l3..delivers molten polymer to. a fiber-forming metal nozzle assembly. ll which in turn is also connectedto a supply line. ill of superheated steam or other inert hot vapor. or as whose pressure is. regulated by .a valve t9, prefer-ably of. .a type capab1e..of-. main: tam-ingaoonstant.desiredpressure. superheated steam. is preferably used as: the. inertyaporsince it has fayorable temperature-pressure relations. and. furthermore. aids. in dissipating electrostatic charges that may form-on the. fibers. .Encirclingi the. fiber-forming. nozzleassembly- I! about mid, point in its lengthis an electric induction heater wand another induction heater 2| is positioned close to the-exit end of nozzle assembly ll. :'Ex-. panding steamer other inert. vapor or gas and synthetic fibers emerge. from the nozzleassembly l'l. through a nozzle tip; 22. and strikea rotating drum- 23; having a foraminous-collecting surface 24. such-as cotton cloth. to-which the fiber; adheres. The fiber collectingdrum 23 is mounted within a partly enclosed. chamber 25. having a venturi type diverging throat opening 26 large. enough to permit tree induction of atmospheric gases. by the jet action of the expanding steam comingout of the nozzle tip-22. The synthetic fibers collect and felt together on-the foraminous surfacefi i of the rotating drum 28 while theexpa-nded steam and atmospheric gases are removed from the enclosedchamber 25 through a vent 211 connected to a ventilating fan 25.

Referr n t the i tere li n trusti n of the fiber-forming 'nozzle assembly I! shows that the molten polymer and the superheated steam are separately ported through the major part of the nozzle assembly I! until mutual contact is finally made within the nozzle tip 22. The individual porting is obtained by means of a cylindrical metal member internally positioned within an outer tubular metal casing 45 by its attachment to a plug bushing 32 at one end and by a spider bushing 39 at the other end. Longitudinally-extending through cylindrical member 30 in a circumferentially arranged pattern tending to taper together in a direction towards the nozzle tip 22 are eight passageways 3| for the polymer. A tapered metal rod 34 (the degree of taper being too small to satisfactorily illustrate in the drawing) is positioned in each passageway 3| by means of protruding pins33 to provide a decreasing annular clearance space within each passageway 3|, in a direction towards the nozzle tip 22. The plug bushing 32 is centrally tapped for connection with the polymer inlet pipe 29 and by means of internal threads is engaged to a threaded end portion of cylindrical member 30. A relieved area in the internal face'of the plug bushing 32 forms a manifold space 33 for fluid polymer to flow at substantially equal pressure into the annular spaces 35 of each passageway 3|. At the opposite end of cylindrical member 30, the fiuid polymer flows out of the annular spaces 35 into another manifold area 31 formed by an annular depression at this end of the cylindrical member 30. Directly communicating with this manifold area 31 and registering with passageways 3| are eight circumferentially arranged counterbored orifices 38 in the nozzle tip 22. These orifices 38 converge together within the nozzle tip 22 and enter at an angle of about 15 degrees a reduced common orifice 40 centrally located in the nozzle tip 32. 'The spider bushing 39 connects the rear face of the nozzle tip 22 to the end of cylindrical member 30 in fiuidtight relationship.

A central pasageway 4| and an annular passageway 42 are provided for the steam that enters the nozzle assembly H from supply pipe l8. The central steam passageway 4| is a longitudinally bored hole in the center of the cylindrical member 30 and extends from the common orifice 4|! in the nozzle tip 22 to almost the opposite terminus of the cylindrical member 30. At right angles to the central steam passage 4| and in communicationtherewith as more particularly shown in Fig. 3, are several inlet ports 43 which extend to the exterior surface of cylindrical member 30, but which are so spaced in radial extension as not to communicate with the fluid polymer passageways 3|. The annular steam passageway 42 is created by the enclosure of cylindrical member 30 by the casing 45 which is connected'at' one end by means of a coupling 44 to inlet cap 32 and partly plugged at the other end by the spider ring bushing 39 and a nozzle cap 41. Steam supplied by pipe l8 enters an enlarged annular chamber formed by the unengaged internal threads of coupling 44 and then flows along annular passageway 42, but with a considerable part being diverted into the ports 43 and thence through the central steam passageway 4|. Flow of steam along annular steam passageway 42 is to the spider bushing 39, where the steam escapes through the relieved sections of the spider bushing 39 to enter into an auxiliary nozzle chamber 46 formed by auxiliary nozzle bushing 41 that is threaded into the end of casing 45 in such manner as to have the orifice of the auxiliary nozzle bushing 41 concentrically superimposed on the exterior surface of nozzle tip 22. An annular jet space 48 is thereby provided through which steam escapes to the atmosphere to continually blow into fibers any accumulation of excess molten polymer at the external end 49 of the nozzle tip 22 which excess would otherwise tend to break loose periodically in the form of shot or pellets.

The phenomenon of directly forming feltable oriented staple fibers from organic fiber-forming polymers is dependent uponseveral factors, which unless mutually coordinated result in the polymer being atomized into small beads, pellets or shot rather than formed into filaments. Foremost among these factors is the fluidity of the polymer as it emerges from the nozzle orifices 38 a and comes into violent contact with the steam jet in the main orifice 40. The desirable fluidity value cannot be stated with numerical precision since reliable rheological data on fiber-forming polymers at extremely elevated temperatures are not readily obtainable, but by extrapolation of known viscosity-temperature curves on these polymers, the viscosity component of these polymers at such decomposing temperatures can be estimated as being less than poises but prob ably more than 10 poises, since with lower viscosities it is extremely doubtful that the polymers are sufiiciently viscous to overcome surface tension forces tending to form drops rather than threads. It is generally agreed, however, that all fiber-forming polymers when heated above their softening temperature exhibit both plastic flow and viscous flow and with increasing temperature viscous flow becomes the predominant component and in the practice of the present invention it has been found necessary to heat the fiber-forming polymers to temperatures favoring maximum fiber-forming fluidity and minimum plastic flow. Fiber-forming fluidity as herein defined is approximately comparable with the stringytackiness that is observed when such substances as bodied drying oils, varnishes and rubber solutions are spread out as a film and then momentarily contacted by a finger which in withnecessary fiber-forming fluidity it has been found that the heating'rate must be extremely rapid and the polymer exposed to such decomposing temperatures for the least possible time. To accomplish this rapid heating with minimum exposure of the polymer to decomposing temperature, the polymer is heated in two stages; the first stage comprising a melting operation conducted in the tank 5 or alternatively in a jacketed extruder where the polymer is heated only to a temperature imparting sufiicient fluidity to enable it to be delivered at predetermined flow rates by the gear pump L3 or other constant delivery means to the fiber-forming nozzle I1; and the second stage comprising a rapid heating to a decomposing temperature of only the relatively small quantity of polymer required to fill the thin tapered annular spaces provided by the filler pins 34 in the cylindrical member ltll. The

e tin Q h m me! e. seco d stage e efiepted n m lr bxcementum o hea w e nz he fi er -od' 3. and q l'ndrigalm her 311 y eddr entsrand h teens-l sse (tiemo e i g- 1mm eel trical a, ma et c aoteristics of the metalsusedimthe construction ofthenozzle) induced by, induction coils 20 and 24. Preferably these coils; are. of. apmulti-turn type n in fl i 10Wv fr uen altern t n current, e. g. 6Q. cycles, to obtainacqnsiderable. depthv and uniformity of; heating, throughout the metallic mass comprising the fiber-forming nozzle I1. Uniform'heating ofTthe entire metalmassof the, nozzle assem loly -I-l is alsopromoted by. suite able: choice .of metals used inits construction, As for, example'by using. stainless steel or other none magnetic metal for thetcasing 45.. and. a highly magnetic material such ascast. iron orv carbon steelfor the, cylindrical member. 3|} and the filler rods 34, the casing 45 is then primarily heatedby eddy currents, and the cylindrical member wand its filler rods 34 both byeddycurrents and magnetic hysteresis effects. Control of. the. heating energy developed by each. induction coil. is obtainedby. varying the. voltage. of the alternating current supplyv by means of transformers (not. shown in, the drawing) in. accordance with the heat requirements of theparticular fiber-form-,v ing polymer bein processed. The first induction coil Zdmay be controlled to produce asomewhat lower temperature in the, mass, of metal immediately within, its efiectiyerange than the second induction. coil 2]. superimposed immediately aroundthe orifices of theno'z zle 22,i n order to reduce the exposure time of the-polymer to. decomposing, temperatures.

Alternatively. the. nozzle. assembly. 11. may be, heated. by other means thanby, induction coils; as for example by electric resistance heaters. in.

bayonet form to substitute for the filler rod s 35',

or by suitable-channelingwithin the nozzle as-. sem 'oly, and filler. rods aseparate supply. of hot gas; or. vapor (other thantha't employed to. pick, up; the fiber) may be, supplied to thenozz1eassembly. solely for heating. purposes. Such alterna.-.. tive heating, means involve. a. more: complicated. construction andrequireadditional control means. for precisely regulating. their heat input.

In additionto the factor ofbringing the polymer. to: a. fiber-forming temperature there i an r additional factor comprising thecoordinated effect of the temperature, pressure. and; velocity. ofthe. inert gas or vapor in the picking. up of the polymer and. forming it intora fiber. In.explana-v tion of this coordinated effect, attention is di-. rected to the f-act'that the polymer as it emerges from the; polymer. orifices 38. into. the central nozzle orifice 40-,flows as a continuous liquid film alongthe Walls of the nozzle orifice lfl to the outer edgeof. the nozzle tipYZZ, being propelled in this direction by the frictionalcontactiof the-escaping steam in the central passageway 41, {fibers are picked. up. by. the escaping steam all; along the moving. film of polymer beginning; ,atthejunction pointor the polymer orifices 38; and the central nozzle orifice 32; and continuing out tot-he extrerne end 490i nozzleitipilwhererany remaining excess polymer collects'iirv an annular shapedmound to bealso drawn into fibers by; the. joint. action, of steam escaping through the. annular nozzle orifice 48 and. through the central orifice. 40.

Depending upon the velocity and temperature he wearin tre m: he. undle: or. nd v d al ratha -mve be n..formingeellielonz;the-cane 9w veloe t h te ta nt r neeq 101 1 .miqrqns ndshoweely; ight. c t ct n h neent d ei ce we ing' temperature. Theyn ust; e b a. col dr eevp mt qm m lecularorientationand then a cr'mpo our Ivemp e to. h ir be rethe.y-e-..c t. tm ple lengths.

hen t t m eleeitx is. substant ally cr s d eppr ecl w 21. .spe Orde of. a t 0 000 O- IQQQ ice; 9

r mned. a d are utometic lly' sa e (10m Staple lengths qfrkto hes-. results accomplishedunder thee c ,are Pr u bl o e ac .t atleashx h r romem n ins he iQ mefilz lt zit el qc ui tfi in e n zle i ce ndeiefied t. into theatmosphereistravel g-atanaoce ra 1 ngspeed, b t t th a a e t me-t efibe -isbeine: -e i y q d; the; ediahati all'r expand n Steam; nd he mQSRhQ iQ. ase drawn and: mix d nto e eera- Qu side t e, no zlet p .5 ha hefiber 0. ed. o,-acqldz rawine tempera turezwithi -a few waytf omrtheinozzleltint xtr me y .an lqq l ne. fiect-withinzth mendin et. am. an ber is o. pror nounped that on e hen enbe eld th rein wi hout li QQmi l at; di$t.a ce: as close: as...15; h s; t h zzlei i irom. which super-l heated steam at; 15 to., 0 p siandtfibersjissuelatt w me ret re of. 3 .0 10. 00 cQompanyin he 12 1. Q i i g:Off hifibfilfi; oz zcqldidrawin mper ure; is heir. elented motion; in; acre. rection generally parallel; to the jet. so; that. the; art o the e urthest. away from the nozzle. exerts a suifi nt' pulling force. on; that; part; l ee to he ZlQi.timtozcausexold drawingor n a i n I: h e l l hzinte imt-z'diate between 1. Since the jetof steam -expandsin. a :mannerthe-fiberslare evidently caught. in, crosscurrentssubj ectingt them to: twisting and: curling motions while they are.-still in =a fluld plastic .state and these; twists ands curls are prace: 7i, icallso instantaneously; frozenr into.- tlierflbere' r v Probably to a minor extent some of the total crimping'efiect is due to differential orientation between the surface and the inner core of the fiber sincecooling of the core would tend to lag behind the cooling of the surface and therefore it {can be presumed that with the surface havin a greater amount of frozen elastic strain than the interior, the fiber by curling or twisting on itself partially equalizes the unequal strains. Severance of the fiber'into staple lengths probably occurs within or just at the nozzle tip 22 due to the fiber 'being formed and drawn out from its originating point in the film at a faster rate than the film is replenished at this point by polymer issuing out of the nozzle orifices 38. It is the irregular curliness or kinkiness of these staple fii bers that makes them eminently suitable for pinning into yarns for textile purposes, or for forming highly integrated felted masses suitable for thermal and acoustic insulation purposes, or as coherent preforms for molding articles of almost any desired final molded density between the apparent density of the felt up to the full molded densityof the solid polymer.

'In continuance of the efiect of steam velocity on the fiber production, it was observed that as the steam velocity is further increased to theoretical speeds of the order of 80,000 feet per minute, but being maintained substantially at the same temperature as the polymer as it emerges from the orifices 38, the total fiber production is increased slightly but is accompanied by the formation ofincreasingly shorter staple length fibers and a lower amount of orientation. Under these circumstances the fiber is picked up from the film so rapidly that only short lengths can be formed and the cooling of the fibers being less rapid due'to the proportionally higher total heat content in the higher velocity steam, the propulsive forces exerted on the fibers by the steam are" almost completely expended at about the moment the fibers have been cooled to a cold drawing temperature and therefore only a minimum of cold'dr awing is accomplished.

Temperature regulation of the steam or other inertgas or vapor is the additional important factor to be taken into consideration with the velocity of the gas as it escapes from the nozzle, since if the temperature of the steam is substantially lower than the polymer at fiber-forming fluidity only atomization of the polymer into beads occurs. -As the temperature of the steam approaches that of the polymer more fibers and lessbeads intermixed therewith are formed. In some instances a small proportion of beads in admixture with the fibers is of advantage when the fibers as they are formed are to be collected as a felted mass, the beads increasing the density of the felted mass and by their retention of heat for a longer period than the fibers are sufliciently plastic to weld together fibers intersecting in their vicinity. As the temperature of the steam or inert vapor exceeds the temperature of the polymer at fiber-forming fluidity, fibers of decreasing orientation and staple lengths are formed and with still higher temperatures the polymer is depolymerized or decomposed.

Where emphasis is on the production of highly oriented and crimped staple fibers of an average staple length suitable for twisting or felting purposes, e. g. to inches, the elastic fluid is supplied to the nozzle assembly. ll at a high enough temperature such that despite temperature losses caused; byadiabatic expansions within the nozzle. passageways and conductionof heat to the metal surfaces of the nozzle body, the elastic fluid arrives at the junction of the polymer feed orifices 38 with the central orifice 40 at substantially the same temperature as the fiber-forming fluidity temperature of the polymer. superheated steam, is a desirable inert gas for forming fibersfrom most polymers since together with its inertness to most polymers, adequate high temperatures are available when it is supplied atmoderate pressures such as;5 to 60 p. s. i. to a fiber-forming nozzle as illustrated in the drawing having a central common orifice 40 with a bore of about inch diameter andan auxiliary annular nozzle port 68 of about 0.015 inch radial width.

In the following examples operational details are given with respect to various fiber forming organic polymers for the purpose of further illustrating the invention, but not in limitation of theinvention except as defined in the appended claims.

Example 1.-Polystyrene of about 50,000 aver- I age molecular weight was heated to 200-260 C.

in a closed container and then pumped into a fiber-forming nozzle as depicted in the drawing. The annular film of molten styrene in each passageway 3| of the fiber-forming nozzle was about 0.010 inch radial thickness at the exit end of the passageway 3|. Two multi-turn induction coils producing about 15,000 ampere turns of 60 cycle alternating electric current with about 160 to 200 volts imposed on the coils produced a nozzle tip22 temperature of about 380 C. as determined by a pyrometer. Saturated steam at p. s. i. was superheated in a gas fired superheater to between 315 to 400 C. and then fed into the steam passages ll and 42 of the fiber forming nozzle at about 35 p. s. i. 'The combined heating effect of the steam and induction heaters caused the polystyrene to attain a'maximum temperature of about 370 C. as it left the nozzle. Adjusting the pumping means to feed molten polystyrene at a 5 lb. per hour rate to the nozzle polymer orifices 38 of about 0.040 inch diameter and a common central orifice 40 of about 0.1875 inch diameter resulted in a continuous production of a stream or tow of kinky oriented staple fibers having an average diameter of about 4 microns and a length estimated at about 4 to 10 inches and which were elastically deformed or cold drawn to the extent of 300 to 400 percent as evidencedby contraction of the fibers when subsequently reheated,

to their softening temperature. When superheated steam at 50 p. s. i; was supplied to the nozzle, the mass of fibers ejecting from the nozzle tended to fuse together when collected due to the excess heat contained in the steam at higher pressure, and the fibers were oriented or cold drawnfto lesser degree, although attenuatedinto finer and shorter filaments. When the nozzle tip temperature was reduced to about 300 C. and lower by reducing'or completely cutting off the current to the induction coils and de-.

pendingsolely upon the superheated steam for heating of the polymer mostly beads or atomized particles of polystyrene were obtained out of the .versely with styreneepolymers of lower average o e u ar wei ht. lower: ozzle. t n tempe atures normal operating; conditions, as herein described? less than to leper cent of-the-polymer isilostqby decomposition into' monomeric or other; Volatile;-

products, although inmostlinstances the; fibers are characterized; by. a. lower. average molecular; weight than the original holymer.

It issurprising, however, that the presence of minor amounts, per cent. and.less,-. 0i. plastie cizer: or up to IQ-per centof unreacted. monomer, high boiling solventsinthe fiber-fermingpolymer as supplied to the nozzle assemblydoes. not. ap-- preciably lowerthe, nozzle tip temperatures, otherwise required. for substantially pure poly mer of thesame average molecular weight. or appreciably affect theproperties. of, the fiber. Apparently these volatile substances; are almost instantly vaporized as soonas they contact. the hot vapor. or gas jet in the central com-monorifice Even-the. high.bciling. and substan tially-nonevolatile compatible,- plasticizers are to a considerable extent remo-yed from the polymer at these high temperatures. Accordinglyalthough. pure polymersare generally; desirable, polymers contaminated with solvent or monomer may also-be satisfactorily-usedin the-production of fibers.

Example 2.Polydichl,orostyrenehaving an average molecular weightcf about 90,000 was f ormed-into kinky. oriented-staple-fibers using, the same apparatus and technie as described in Example 1. A somewhat. lower nozzle tip 22 temperature than that required for the poly-. styrene was found to be feasible; for fibers of an estimated average staple length, of; about 1.- to 20 inches were readily obtainedwhen thepoly dichlorostyrene came out of thenozzletip at, a. temperature between, 330 to 350 C.

Example 3.Highly polymerized. polyvinyl. carbazole containing 10 per-cent of a plasticizer to reduce its melting.- point to less than 200 C. was formed into. kinky oriented; staple fibers in the same manner asdescribedinthe previous examplealthough it was.- found necessary tov heatthe polyvinyl carbazole in. the nozzle to issue: therefrom at a considerably higher temperature such as between 400 to 430 C.

Example 4.Polyethylene of about 20,000. average molecular weight formed short kinky oriented staple fibers when. heated to abQ l l4Q0 C. and ejected from the same fiber-forming nozzle by superheated, steam at p.,s. i. and, similarly a polyethylene polymer'of about 28,000 average molecular weight was processed into short kinky oriented staple fibers when heated to about 430 C. Although polyethylene is ordinarily" sensitive to oxidation at elevated temperatures, no' perceptible oxidation occurred during the fiber-forming operation. the steam employed" in forming and ejecting the fiber being itself.- inert to the polymer together with the; rapid: cooling sufficiently protected the; fiber against oxidation.

The staple fibers: produced in,- accordance withv the present invention find many'uses; They may be employed as textile fibers in the; production of,v water and chemicallyresistant fabrics. When Presumably softening point of the polymers. The density of the bats can be variedaccording to the methods employed for collecting thefibersand-anygsubsequentpressing operation. Thefiberswhen decollected in. the format atsby depo i ion; of: r

the; fibers on a suitable foraminous suriace. hey can be employed s extremely li ht weight posited in a randomand heterogeneousinanner yield bats having in many instances apparent specific gravities lessthan 0.0.5 especially when .;precautions are taken to, form fibers. having a minimum quantity of. attached beads.

The fibers can also; be used as moldin materials and' by varying the molding pressure, and temperature molded articles of any desired low density and up to the full molded density of the solidpolymer can. be readily.- obtained. In practically all instances. considerably. lower moldings temperatures and pressures than is. normally; necessary for the polymer,in:.a.,grami1arcondie.

tion. can be employed thus; permitting. the use. of such low temperature and pressure. moldin procedures as the various bag;moldinscoperations.

Molding operations. can also be facilitated: by; the. use of, preforms torwhich technic the present;

invention contributes advantagesthatwerelacke. ing in fibers formed by spinneret. extrusion. of:-

synthetic fiber-forming polymers... The, spinneret fibers; lack sufiicientv twist: or curl. for forming.

interfelted bats andwhile preforrrr bats. can be formed from them, the fibers are normally.-.de-.. posited in parallel laminar fashion. within the bats. Accordingly these bats are limited. to planar shapes and must be, carefully: handledto. avoid injury or self-destruction before insertion in, the mold.

In contrast thereto self-coherent preform bats.

ofv any desired configuration can be readilyformed from fibers produced: according to. the: present invention. Byejecting the fibersasthey: areformed against rotating foraminous..collect-.-. ing surfaces, having a surface configurationv C0111 formingv to the preform shape, acoherent felted:- bat of anydesired thickness can be efficientlyprepared, thereonv and stripped therefrom. when: of the desired size and shape. oscillatory-an dior other changes in rotative movements. imparted to the foraminous collecting surfaces can beeme. ployed; to suitably regulate the thickness; of-ithe bat at variousparts as. for instance: in dome.- shaped preforms where a rim portion. of: con, siderable thickness is required and thin walls in. the remainder of the shell; Interfelting of: the. fibers deposited on collecting surfaces. can: be. promoted by maintaining the interior ofthe fiber collecting surface at lower atmospheriepressures than; normal, thereby drawing the fibers together. Alternatively the fiber-forming. nozzle. may be controlled in the manner previously do; scribed so that a certain proportion ofbeads. are. formed together with the fibers. The beads be! cause of their greater mass cool at a. slower rate than the. fibers and therefore act as. local? hot spots: to cause welding of intersecting fibers. in; their-proximity. Bats. containing beads arersomea what higher in apparent density, but are more. resistant to fiber segregation, and: can. be elon-. gated by applied tension to-asmuch; as, 30%. bee. fore disintegrating.

In illustration of the molding properties of thek fibers; reference is particularly made to the polystyrene fiber prepared in accordance with Example 1 These. fibers. were collected as a baton therotating. drum 23: and were compression molded; at various. temperatures and; pressures intobars.

nd other flatshanes suitable for physical test.

11 ing byconventional methods. The test results are given in the table.

Table Mold Molding Curing Density of Tempera- Pressure, Cycle in of Molded ture, F p. s. i. Minutes Piece Tensile and flexural strength of the molded articles increases as the density increases; tensile strength being from'600. to 2000 p. s. i. for test bars having densities in the range between 0.630 and 0.910 and similarly the fiexural strengths range from 1700 to 3200 p. s. i.

The power factor for the above molded samples as measured at 15 megacycles ranges from 0.00010 l to 0.0003; dielectric constant is generally a direct function of the density of the molded article ran ing from 1.6 to 2.3.

Softening temperatures of the molded articles are'practically identical with molded articles of full molded density prepared from conventional polymer in granular form, since panels molded frointhe fibers withstood a temperature of l90i F. for two hours without any measurable distortion'due to unmolding. I i

In the appended claims, the expression fiberforming organic polymer is intended to define those fusible organic polymers which in the absence of oxygen or air can be heated rapidly to a fiber-forming fluidity without being substantially decomposed or depolymerized. These polymers,

in addition to the polymers described in the examples include the polymers resulting from the polymerization of ethylenically unsaturated monomers'such as the vinyl polymers and copoly- 1 mers', acrylates, and acrylonitrile polymers and' 1.'Method for forming fibers from a fusible fiber-formingorganic polymer which comprises liquefying the polymer by rapidly heating it to its decomposition temperature under non-oxidizing conditions, forming a liquid film of the heated polymer on a solid surface from which oxygen is excluded and which is substantially at the same temperature as the heated polymer, acting upon the film of the liquid polymer by a stream of inert elastic fluid substantially at the sametemperature as'the liquid polymer to draw outfibers from the film, and ejecting'the elastic fiuidand the' fibers into the atmosphere to cool and solidify the fibers; V

2; Method for forming staple fibers from a fusible fiber-forming organic polymer which comprises liquefying the polymer by rapidly heating;

it to its decomposition temperature undernonoxidizing conditions, forming a liquid film of the heated polymer on a solid surface from which oxygen is excluded and which is substantially at:

of inert elastic fluid substantially at the same term perature as the liquid polymer and moving at a velocity sufiicient to draw out fibers from the film and to sever the fibers into staple lengths,

and ejecting the elastic fluid and the fibers into the atmosphere to cool and solidify the fibers.

3. Method for forming feltable oriented staplefibers from a fusible fiber-forming organic polymer liquefying the polymer byrapidly heating it to its decomposition temperature under non-oxidizing conditions, forming a, liquid film of the heated polymer on a solid surface from which oxygen is excluded and which is substantially at the same temperature as the heated polymer,

acting upon the film of the liquid polymer by a blast of inert elastic fluid substantially at the same temperature as the liquid polymer and moving at a velocity sufficient to draw out fibers from the film and to sever the fibers into staple lengths,

discharging the elastic fluid and the fibers into the atmosphere, cooling the fibers to a cold-drawing temperature while being propelled by the elastic fluid, and cold-drawing the cooled fibers by action thereon of the propellingelastic fluid.

4. Method of forming an integral felted bat from a fusible fiber-forming organic polymer which comprises liquefying the polymer by rapidly heating it to its decomposition temperature under non-oxidizing conditions, forming a liquid film of the heated polymer on a solid surface from which oxygen is excluded and which is substantially at the same temperature as the heated polymer, acting upon the film of the liquid polymer by a blast of inert elastic fluid substantially at the same temperature as the liquid polymer and moving at a velocity sufficient to draw out fibers from the film and to sever the fibers into staple lengths, discharging the elastic fluid and the fibers into the atmosphere to cool and solidify the fibers and collecting the cooled fibers on a foraminous surface. 7

5. Method of forming an integral felted bat from a fusible fiber-forming organic polymer which comprises liquefying the polymer by rapidly heating it to its decomposition temperature under non-oxidizing conditions, forming. a liquid film of the heated polymer on a solid surface from which oxygen is excluded and which is substantially at the same temperature as the heated polymer, acting upon the film of the liquid polymer by a blast of inert elastic fluid at a lower temperature than the liquid polymer to cause fibers and a small proportion of beads to be withdrawn from 17118 polymer by rapidly heating it to its decomposition temperature under non-oxidizing condi tions, forming a liquid film of the heated polymer on a solid surface from'which oxygen is excluded andwhich is substantially at the same temperature as the heated polymer, acting upon the film of the polymer by a blast of superheated steam substantially at the sametemperature as the liquid polymer and moving at avelocity sufiicient to draw out fibers from the film' and to sever the drawn fibers into staple lengths, and discharging the fibers and the steam into the atmosphere to cool and solidify the fibers.

'7. Apparatus for forming fibers under non-oxidizing conditions from a fusible organic polymer comprising a container having two entrance ports and a tubular nozzle having an interior lateral Wall, a passageway for said polymer extending through the container from one of said ports and terminating in an opening through said lateral wall enabling liquid polymer to flow from said passageway onto the lateral wall as a continuous film, a filler-rod positioned in said passageway ahead of said opening to form therewith a narrow annular passage, means associated with the container for heating to fiber-forming fluidity the polymer being forced through the annular passage on its way to the tubular nozzle and another passageway through the container from the second port to the tubular nozzle for conducting elastic fluid from said port to the nozzle for drawing the fluid polymer into fibers.

8. Apparatus for forming fibers under non-oxidizing conditions from a fusible organic polymer comprising a metal container having two entrance ports and a tubular nozzle having an interior lateral wall, passageways for liquefied polymer extending through the container from one of said ports and terminating in openings through the lateral wall enabling liquefied polymer to flow out of said passageways and directly onto said lateral wall as a continuous film, a metal filler-rod positioned in each passageway to form therewith a narrow annular passage, electric induction heating means associated with the container for heating to fiber-forming fluidity the polymer being forced through the annular passages to the tubular nozzle, and other passageways through the container from the second port to the tubular nozzle for conducting elastic fluid from said port to the nozzle for drawing the fluid polymer into fibers.

9. Apparatus for forming fibers under non-oxidizing conditions from a fusible organic polymer comprising a metal container having two entrance ports, a tubular nozzle having an interior lateral surface, an annular nozzle encircling the end of the tubular nozzle, passageways for liquefied polymer extending through the container from one of said ports and terminating in openings in said interior lateral surface enabling liquid polymer to be discharged from said passageway and directly flow onto said surface as a liquid film, a metal filler-rod positioned in each passageway to form therewith a narrow annular passage, heating means associated with the container for heating to fiber-forming fluidity polymer being forced through the annular passages to the tubular nozzle, other passageways through the container from the second port to the tubular nozzle for conducting elastic fluid from said port to the nozzle for drawing the fluid polymer into fibers, and still other passageways through the container from the second port to the annular nozzle for conducting elastic fiuid to draw fluid polymer collecting at the end. of the tubular nozzle into fibers.

10. Apparatus for forming fibers under nonoxidizing conditions from a fusible organic polymer comprising a metal container having two entrance ports, a tubular nozzle having a perforated lateral wall, an annular nozzle encircling the end of the tubular nozzle, passageways for liquefied polymer extending through the container from one of said ports and terminating in the perfora- 14 tions of the tubular nozzle at an acute angle thereto enabling liquid polymer to discharge from said passageways directly onto said perforated lateral wall as a film thereon, a metal filler-rod in each of the passageways to form a narrow annular passage, a low-frequency electric induction heating means encircling the container for heating to fiber-forming fluidity polymer forced through the annular passages to the tubular nozzle, other passageways through the container from the second port to the tubular nozzle for conducting elastic fluid from said port to the tubular nozzle for drawing said film of fluid polymer into fibers, and still other passageways through the container from the second port to the annular nozzle for conducting elastic fluid to draw fluid polymer collecting at the end of the tubular nozzle into fibers.

11. A method for preparing fibers from a fiberforming polymer by the action thereon of an inert elastic fluid in a structure having an annular passage for the polymer, a, tubular nozzle and an opening from the passage into the interior lateral wall of the nozzle which comprises imparting fiber-forming fluidity to the polymer by heating the polymer in the passage and in the absence of oxygen to its decomposition temperature under non-oxidizing conditions, continuously forcing the heated polymer through the opening and depositing it as a liquid film on the interior wall of the tubular nozzle, forming fibers by acting upon the film with inert elastic fiuid substantially at the same temperature as the liquid film and moving through the nozzle at a velocity suificient to draw fibers off said film, ejecting the fibers from the nozzle and cooling the ejected fibers below their softening temperature.

12. A method for preparing fibers from a fiberforming polymer by the action thereon of an inert elastic fluid which comprises imparting fiberforming fluidity to the polymer by rapidly heating a thin layer of the polymer in the absence of oxygen to its decomposition temperature under non-oxidizing conditions, forming a liquid film of the heated polymer on a solid surface from which oxygen is excluded and which is substantially at the same temperature as the heated polymer, forming fibers by acting upon the liquid polymer film with an inert elastic fiuid substantially at the same temperature as the film and moving at a velocity sufficient to draw fibers from the liquid film and cooling the fibers below their softening temperature.

WALTER R. MARSHALL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re.21,814 Albertson June 3, 1941 Re. 22,494 Ferguson June 13, 1944 1,769,181 Jackson July 1, 1930 1,916,402 Allen July 4, 1933 2,126,411 Powell Aug. 9, 1938 2,130,948 Carothers Sept. 20, 1938 2,133,235 Slayter Oct. 11, 1938 2,156,316 Slayter et al May 2, 1939 2,190,153 Holmes Feb. 13, 1940 2,219,346 Thomas et al Oct. 29, 1940 2,226,447 Smith et a1. Dec. 24, 1940 2,338,473 Von Pozsiczky Jan. 4, 1944 2,411,660 Manning Nov. 26, 1946 "the-same may conform to the record of the case in the Patent Ofiice.

Certificate of Correction Patent No. 2,508,462 May 23, 1950 WALTER-RQMARSHALL It is hereby certified that error appearsinithe printed specification of themabove numbered patent requiring correction as follows: i

Column 12, line 12, before the word liquefying insert which comprises;

andthat the said Letters Patent should be read with this correction therein that Signed and sealed this 26th day of September, A. D. 1950.

THOMAS F. MURPHY,

Assistant C'ommz'ssioner of Patents.

Claims

7. APPARATUS FOR FORMING FIBERS UNDER NON-OXIDIZING CONDITIONS FROM A FUSIBLE ORGAIC POLYMER COMPRISING A CONTAINER HAVING TWO ENTRANCE PORTS AND A TUBULAR NOZZLE HAVING AN INTERIOR LATERAL WALL, A PASSAGEWAY FOR SAID POLYMER EXTENDING THROUGH THE CONTAINER FROM ONE OF SAID PORTS AND TERMINATING IN AN OPENING THROUGH SAID LATERAL WALL ENABLING LIQUID POLYMER TO FLOW FROM SAID PASSAGEWAY ONTO THE LATERAL WALL AS A CONTINUOUS FILM, A FILLER-ROD POSITIONED IN SAID PASSAGEWAY AHEAD OF SAID OPENING TO FORM THEREWITH A NARROW ANNULAR PASSAGE, MEANS ASSOCIATED WITH THE CONTAINER FOR HEATING TO FIBER-FORMING FLUIDITY THE POLYMER BEING FORCED THROUGH THE ANNULAR PASSAGE ON ITS WAY TO THE TUBULAR NOZZLE AND ANOTHER