US 3219739 A
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Nov. 23, 1965 A L. BREEN ETAL 3,219,739
PROCESS FOR PREPARING GONVOLUTED FIBERS Filed May 27, 1963 6 Sheets-Sheet 1 INVENTORS ALVIN L. BREEN RALPH J. COVELL BY @MZZW ATTORNEY NOV. 23, 1965 A BREEN ETAL 3,219,739
PROCESS FOR PREPARING CONVOLUTED FIBERS Filed May 27, 1963 6 Sheets-Sheet 2 Eig 4 Eig. 5
INVENTOR5 ALVIN L. BREEN RALPH J. COVELL BY hp, w L. VH1 w ATTORNEY Nov. 23, 1965 A. BREEN ETAL 3,219,739
PROCESS FOR PREPARING GONVOLUTED FIBERS Filed May 27, 1963 6 Sheets-Sheet 5 INVENTORS ALVIN L BREEN RALPH J. COVELL ATTORNEY Nov. 23, 1965 A, BREEN ETAL ,2
PROCESS FOR PREPARING CQNVOLUTED FIBERS Filed May 27, 1963 6 Sheets-Sheet 4 Z EL'QJT E k- Q' E yits- 5 5- INVENTORS ALVIN L. BREEN RALPH J. COVELL BY q maezi ATTORNEY NOV. 23, 1965 L BREEN ETAL 3,219,739
PROCESS FOR PREPARING CONVOLUTED FIBERS Filed May 27, 1963 6 Sheets-Sheet 5 AR E A PREFERRED WORKING ZONE AR EA B AREA A 2; 455m 2:: Em
WIDTH THICKNESS (W T) 0F FILAHENT FINS Nov. 23, 1965 B ETAL 3,219,739
PROCESS FOR PREPARING CONVOLUTED FIBERS Filed May 27, 1963 6 Sheets-Sheet 6 Eig.26
SHRlNKAGE-- ORIENTATION INVENTORS ALVIN L. BREEN RALPH J. COVELL BY i n ATTORNEY United States Patent 3,219,739 PROCESS FOR PREPARING CONVOLUTED FXBERS Alvin Leonard Breen, Wilmington, Del., and Ralph Joseph Covell, West Chester, Pa., assignors to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Deiaware Filed May 27, 1963, Ser. No. 285,192 6 Claims. (Cl. 264-177) This application is a continuation-in-part of our copending application Serial No. 675,728, filed August 1, 1957 and now abandoned.
This invention relates to a process for preparing synthetic fibers having a convoluted structure which imparts high bulk to yarns composed of such fibers.
Investigators in the textile field have long been concerned with obtaining voluminous strands of continuous laments with properties similar to those yarns obtained from natural staple fibers. Production of staple fiber yarn (also called spun yarn) is quite expensive and requires a complex series of operations involving aligning the fibers, combining them into an elongated band and drawing the bundle to smaller diameter while twisting to prevent excessive slippage of adjacent fibers past each other, together with still further operations required to produce a yarn or thread useful for textile purposes.
Synthetic fibers are produced directly as continuous filaments by an extrusion-spinning process. Strands or yarn can be made merely by combining the continuous filaments and without the time-consuming and expensive processing steps required for the making of spun yarn from staple fibers. The continuous filament yarn can be made very strong because of the absence of loose ends found in staple yarn that are unable to transmit imposed stresses. However, due to their lack of loose ends and their cross-sectional and longitudinal uniformity, conventional continuous filament yarns are more compact and dense than their staple counterparts since the continuous filaments lie close together in the yarn. This compactness, when the yarns are made into fabric, e.g., Woven or knitted fabric, limits the amount of insulating air space present, reduces the visual covering power of a given weight of fabric and imparts to the fabric a hard slick hand typical of synthetic continuous filaments.
Bulky continuous filament yarns have been made by heat setting a highly twisted yarn of, for example, nylon, at least partially untwisting the yarn with, if necessary, further twist in the opposite direction and then plying two ends of opposite twists. Such a process is very expensive and, while affording a voluminous yarn, is too elastic for many textile applications.
It has also been proposed to make a voluminous continuous filament yarn by mechanically crimping the yarn, for example, by a hot stufiing box process. Such a product, while more voluminous than uncrimped continuous filament yarn, has the disadvantage that it must be fabricated in the bulky form and the further drawback that it loses an appreciable amount of its bulk due to the crimp being pulled out by the tensions encountered in fabric formation.
Self-crimping filaments have also been proposed. It has been suggested, for example, to spin two different fiber-forming materials in a side-by-side arrangement followed by drawing of the composite fiber to impart a ditference in shrinkability between the components when relaxed under shrinking conditions. Upon shrinking, such filaments become crimped with from about 1 to 30 helical crimps per inch. Yarns made or such filaments have the disadvantage for many applications of being elastic. Also, they do not develop the desired bulk because adjacent filaments will crimp together in a follow-the-leader 'ice manner such as may be observed, for example, in crimped staple chips and thus each filament will not exist as a separate and distinct crimped structure. Furthermore, the relatively coarse crimp permits the filaments to pack together readily in processing.
Other procedures for imparting crimp have been proposed, but have resulted likewise in products having a relatively coarse crimp and subject to the disadvantages recited above.
It is an object of this invention to provide a process for preparing bulky, continuous filament yarns.
A more specific object comprises a melt-spinning process for the production of bulky polyester yarns.
Other objects will appear hereinafter.
The objects of this invention are accomplished by a process comprising the steps of extruding a molten synthetic linear polyester through an orifice to form a filament having at least one fin extending from a stem portion, quenching the filament by directing a controlled flow of quenching gas across it near the orifice, and forwarding the filament through the quenching zone at a high rate of speed. The quenched filament is then drawn from 1 to 4 times its original length under amorphous retaining conditions, i.e., under conditions which induce a minimum of crystallinity.
In carrying out the process, the molten polymer is extruded through an orifice having at least one elongated slot having a width to thickness ratio of at least three, preferably 3 to 16, projecting from an aperture having a width significantly greater than the width of the slot. If the orifice has three or more slots, the aperture need not be of increased width but may be formed by the intersection of the slots at a central location. In quenching the filament, the minimum velocity of the gas is controlled in accordance with the expression 1200 150 (forwarding speed with the forwarding or spinning speed being expressed in yards per minute. Preferably, the flow rate is at least 250 feet per minute with speeds up to 2500 feet per minute being operable. The quenching medium should be held at a temperature between about and 40 C. The filament is forwarded through the quench zone at a speed between about 1000 and 3400 yards per minute and then drawing 1 to 4 and preferably 1.5 to 3 times its original length. The drawn filament may then be shrunk 15 to to provide a convoluted filamentary structure which will be described in detail later herein. The filament may be shrunk prior to or after being incorporated into a multifilament yarn or fabric.
The filaments provided by the process of thisinvention comprise a stem and at least one fin having a Width at least 1.4 times its thickness, the fin or fins of which have an average angular displacement (in the form of a ruflle or helix around the stem) of at least 0.3/,u. (03 per micron); a displacement of O.3/,u is equal, for example to about 20 complete turns per inch in the case of a helical convolution of the fin around a stem. The filaments are preferably of textile denier and may be termed unitary filaments since they are single-component filaments as distinct from multi-component filaments (which comprise more than one polymer). It will be understood that in a given length of filament, the distance measured along the outermost edge of a convoluted fin is at least 1% longer than the distance measured through the cross-sectional center-of-gravity.
The term textile filament denier, as used herein, signifies a denier of from 1 to 10 per filament.
The term rufiie," as used herein, signifies (unless other wise indicated) a sinuous conformation of the fin, analogous to the ruflle on a window curtain.
The term convolution, as used herein, (unless otherwise indicated) comprehends not only rufiles but also spiral or helical turns of the fins about the filament stem. By the practice of the invention either rufiles or spiral convolutions or both together are imparted to filaments.
The expression convolutions per inch or ruffles per inch, as used herein, represents the number of complete (360) cycles of a projection of a fin, whether in the form of ruffies or helices, as viewed longitudinally per inch of length of the filament.
The term fin, as used herein, (unless otherwise indicated) signifies, with respect to cross-sectional area (although the fin will proceed lengthwise of the filament), that part of a non-round filament enscribed by (1) a line (termed fin base line) drawn through the cross-sectional center of gravity (which may also be termed the center of area) of the filament normal to the line that determines the width of the fin (i.e., cross-sectional length as described below) and (2) the periphery of the filament intercepting said fin base line. Thus, although the term fin would normally be considered as comprising only the web or extension to the filament, it also includes a portion of the filament stem or root for the purpose of description.
By the term width of the fin, is meant the length of the longest straight line (termed width line) that can be drawn within the periphery of the fin cross section from the center of area to the tip of the fin, assuming the fin to be straightened out normal to its base line. Many fins are not straight and the line for determining width would not be straight if drawn within many actual fins.
By the term thickness of the fin, is meant the average distance across the fin periphery as measured normal to said width line.
By the term stem of the filament, is meant the root or body of the filament from which the fin webs protrude. The stem will, of course, include a portion of the fin as defined above, although, from a practical standpoint, the physically protruding fin (as distinct from the fin as defined above) is distinct from the stem.
By angular displacement is meant the total angle (in degrees) swept out, without regard to direction, by width lines between two spaced points along the filament axis, said angle being measured by projecting the width lines, between the two points, on the plane of a width line perpendicular to the filament axis at one of said points. The angular displacements referred to herein are determined from measurements on cross-sectional and longitudinal photomicrographs of the filaments. The longitudinal photomicrographs are used to measure the angle i at which a fin crosses over the stem. It will be understood that angular displacement data and ruffies per inch will not be absolutely equivalent for all sampes due to differences in sampling.
In refering herein to the cross section of a filament, it will be understood that the cross sections are perpendicular to the filament axis.
filament, greatly magnified, having a difierent form of convolution, i.e., spirals or helices, characteristic of the filaments of this invention;
FIGURES 4-13, inclusive, represent spinning orifices of various sizes and shapes, together with dimensions,
used in the production of filaments of the present invention;
FIGURE 14 is a diagrammatic view of an air chimney, used for the quenching and solidification of filaments, in accordance with this invention, with a diagramatic showingot a spinneret and of the filaments as they pass from the spinneret through the chimney;
FIGURES 15-24, inclusive, are views of cross sections of filaments greatly magnified (1000 times) which are produced in accordance with this invention;
FIGURE 25 is a graph showing the preferred working zone area for spinning speeds in yards per minute (as ordinates) plotted against the ratio of width to thickness of filament fins;
FIGURE 26 is a graph of shrinkage percentages (as ordinates) against degrees of orientation (as abscissae) for a filament of a characteristic polymer; and
FIGURE 27 is a view of a jet used for the elongation and shrinking of filaments of this invention.
An understanding of angular displacement and its measurement can readily be obtained by reference to FIGURE 1 of the drawings. This figure is drawn in perspective in which the lines are approximately 30 to the horizontal so as to show the development of the fin convolution, i.e., a rufile in this case. The filament is of keyhole cross-sectional shape such as may be obtained by use of a keyhole spinning orifice shown in FIGURES 4, 5, and 6 and has the general appearance of the filament shown in FIGURE 2 of the drawings. For convenience, in this figure, the cross-sectional end of this filament shows the fin in vertical position.
FIGURE 1 is a greatly magnified view of a short length of filament having one-half a complete convolution or ruflle of the fin (in this case one-half a complete sine wave). In this figure, the center of gravity or center of area of the filament cross section is designated as 1 and a line 2, 3 (the fin base line) is drawn, as shown, through 1. A line 4, 5 is drawn from the center of the fin tip through 1, this line being the longest line that can be drawn through the fin, and lines 2, 3 and 4, 5 are drawn perpendicular to each other. The fin 6 is shown as onehalf a complete convolution, the other half (not shown) being in reverse in this case to that shown. (Where the convolution is a helix, the other half of the helix obviously proceeds in the same direction rather than in the opposite direction.) Vertical plane 7, 8, 9, 10 is drawn through line 4, 5 and through the filament center of gravity axis 1, 11. Midway of the one-half fin convolution shown in FIGURE 1, a line 12, 13 (fin width line) is drawn from line 1, 11 to the tip of fin 6, the angle 14 subtended by plane '7, 8, 0, 10 and this line being the angular displacement. In FIGURE 1, the length of filament ,from the left-hand side of the figure to the center point (where a value of for angle 14 was measured) is 20 microns (0.02 mm.), giving an angular displacement of 4/n (280 complete convolutions per inch). The angular displacement per micron of length that is referred to herein indicates the degree and intensity of convoluting characteristics of the filaments of this invention. It will be understood that if lines were drawn from the line of origin 1, 11 to the tip of fin 6 between the beginning of the filament section shown in FIGURE 1 and point 11, the angular displacement would be /40,u. or, in other words, 4/,u.
Reference has been made in the above descriptions, in connection with FIGURE 1 of the drawing, to ruffles as one form of convolution characteristic of the filaments of this invention. A filament showing rufiles along a continuous length is illustrated in FIGURE 2 of the drawings.
In addition to the ruffles just referred to, the filaments of this invention may, as stated, alternatively assume a spiral or helical convolution along the axis of the filament as shown in FIGURE 3 of the drawings, which, like FIGURE 2, represents a greatly magnified view of the filament.
Both the rufile referred to in FIGURES 1 and 2 and the spiral convolution shown in FIGURE 3 are to be distinguished from the crimps of the prior art which merely represent either the approximate folding back of filaments upon themselves or upon adjacent filaments, as in the stutter-box type of crimping or in mechanical gear crimping, or the helical type of crimp (which may reverse itself) in which the filaments spiral in helical or coiled spring-like fashion around a core of air.
The convolutions which characterize the filaments of this invention reverse themselves at random intervals, not only in the sense of reversal to complete a 360 path for one rufile or convolution as described with respect to FIGURE 1, but by actual change in direction along the filament at intervals. The reversal points may be from .02 to .001 inch apart. Nevertheless, the total number of rutfies or convolutions, as designated herein in the examples, will include all regardless of direction of fin distortion. The number of rufiles per inch (i.e., the angular displacement) is a measure of the volume or space effectively swept by a filament. The reversal of the convolutions prevents intermeshing of adjacent filaments.
In the examples, the relative viscosity (1 i.e., the viscosity of a solution of polymer relative to that of the solvent, is used as a measure of the molecular weight. The polyester solution used for determining the relative viscosity referred to herein contained 2.15 grams of the polymer and ml. of a 7/ 10 mixture of trichlorophenol/ phenol, and the viscosity was measured at C.
By the expression draw ratio is meant the ratio between the initial undrawn (as-spun) length of yarn or filament and the final permanently drawn length or filament. It will be understood that reference to permanently drawn length means the length of the filament assumed after release of the drawing force.
The volume of water retained by a standard weight of yarn is used as a measure of the bulk of the yarn. In this test a 10 gram skein of yarn is immersed in 90 mls. (milliliters) of distilled water at room temperature (75 F.) contained in a 100 ml. graduate and allowed to remain there for 15 minutes. The yarn is then removed and allowed to drain back into the graduate for 15 minutes. The water retention value is the amount of water (in mls.) retained by the skein after the 15 minutes drain. A skein of thirty-four, 2 d.p.f. (denier per filament) round cross section, uncrimped filaments of poly (ethylene terephthalate) retains 11 ml. of water by this test.
In the evaluation of fabrics the specific volume in cubic centimeters per gram (cm. gram) is used. This volume is calculated from the weight of the given piece of fabric usually in ounces per square yard and the average thickness of the fabric as measured by a plunger-type of instrument that exerts a pressure of 5 grams/sq. cm. during the measurement.
Birefringence values are determined according to standard methods by measuring (with a microscope fitted with a quartz wedge), the retardation of light transmitted through longitudinal regions of both stem and fin and dividing the measured retardation values by the thickness of the measured regions.
With further reference to the drawings, FIGURE 14 shows a form of cross-flow air chamber and spinning cell applicable to use in the practice of this invention, in which the air chamber 15 is provided with an air inlet 17 and perforated rear wall 16 to permit some incoming air to escape so as to avoid turbulence. A perforated front Wall 18 (the opening referred to in the examples with reference to flow of air against the filaments) permits the flow of air to be distributed across the filaments 19 (shown in dotted lines within spinning cell 33) and outwardly through opening 20, which is formed above baffle 21, removable as described in Example VII (below). Spinneret 22 is shown disposed at the top of the spinning cell.
Referring to FIGURE 27, this figure illustrates a form of air jet similar to that used in the examples, which may forward the undrawn yarn at high speed and can be used in a shrinking of the drawn yarn. This jet and its mode of operation are discribed in the patent of John N. Hall, US. 2,958,112, the substance of which. insofar as it is necessary to understand this jet structure and operation is incorporated herein by reference. Briefly, this jet comprises jet housing 23 having cylindrical bore 24 with fitting 25 screwed into housing 23 and being provided with a longitudinal passage comprising counterbore 26 and venturi-shaped passage 27, together with bore 28 which angles upwardly towards and is constricted in the direction of bore 24 as shown. Bore 28 accommodates yarn tube 29 carried by casing 30. The upper and inner end of yarn tube 29 is received in blind extension 31 of bore 28. Yarn tube 29 is partly cut away at 32 to a half cylindrical form which is open on the upper side, in the region of the constricted portion of venturi-shaped passage 27 to permit ejection of the yarn therefrom. The threaded end of housing 23 is connected to a source of compressed air. Yarn tube 29 is supplied with yarn inserted at the outer end through the tube, the yarn tube 29 is carefully turned to position its cut away portion 32 to face upwardly so that the yarn will be ejected upwardly, the compressed air is turned on, and the upward flow of air through the main bore 26 and venturi 27 will stringnp and impel the yarn at high speed through venturishaped passage 27.
The following examples in which parts, proportions, and percentages are by weight, and elongations and tenacities are on a dry basis, unless otherwise indicated, illustrate the invention.
EXAMPLE I Poly(ethylene terephthalate) of 1 34 is extruded at 288 C. through a spinneret containing 13 regularly spaced keyhole-shapedorifices of the design and dimensions shown in FIGURE 5 into air at room temperature. The threadline is advanced by means of an air jet at a rate of about 3,000 y.p.m. (yards per minute) and cut into short lengths by a revolving cutter knife. The threadline is quenched at right angles to the direction of travel starting at a point about 1.5 inches below the spinneret with room temperature (25 C) air coming from a 2.5 x 35 inch opening in the apparatus of FIGURE 14 at a rate of about 150 c.f.m. (cubic feet per minute) and a velocity of 250 f.p.m. (feet per minute) across the filaments. The as-spun yarn resembles normal uncrimped staple fiber with no curl and has a tenacity of 1.3 g.p.d. (grams per denier), an elongation of an initial modulus of 24, and a d.p.f. (denier per filament) of 3.15. A typical filament criss section (magnified) is shown in FIGURE 15. When the staple fiber is exposed free of tension to atmospheric steam for about 5 seconds, it shrinks about 68% in length and the staple fiber becomes very bulky. About 90l00% of the filaments have ruflled fins with to ruflies per inch and the angular displacement of the fins is about 4.5 a as estimated from photomicrographs of the filaments. A 10 gram bundle of the staple retains 52 ml. of water in the standard water retention test.
EXAMPLE II Poly(ethylene terephthalate) of 1;, 34 is spun at 288 C. through a spinneret containing 13 slots, each 3 x 78 mils in size, into air at room temperature and the yarn wound up at 1200 y.p.rn. The extruded ribbons are quenched (i.e., rapidly chilled) with the maximum flow of air (25 C.) across the filaments that would permit spinning, estimated to be about 100 c.f.m. (a velocity of f.p.m. across the filaments) from an opening 2.5 inches x 35 inches located behind the vertically moving threadline. The resulting yarn is drawn in a dry state 2.7 (l70% increase in length over yarn prior to this drawing) over a pin heated to 48 C. to yield a yarn with a tenacity of 3.0
g.p.d., and dry elongation at break of 32% and a denier per filament of 3.5. A typical magnified cross section of these drawn filaments is shown in FIGURE 16. The yarn shrinks about 53 in boiling water to yield a highly 8 truded at 298 C. through a 3-inch diameter spinneret having 34 propeller-shaped orifices as shown in FIGURE 8 but having a 9 mil center hole and the yarn wound up at 1500 y.p.m. The threadline is quenched with air bulky product in which each edge of the filaments has- (24 C.) at right angles to the motion of the threadline about 100 to 150 convolutions per inch and shows an with a chimney similar to that shown in FIGURE 14 angular displacement of about 1.8" per micron. The conwhere the opening 20 is 2 inches high and 5.25 inches volutions are reversed at frequent (1 to 100 per inch) wide. The total input of air at the point 17 is 400 irregular intervals. About 90-95% of the ribbons disc.f.m. which aifords 54 c.f.m. across the threadline (veplay this alternating twisting. A gram skein of the 10 locity across the filaments 740 f.p.m.) and out the openyarn retains 52 ml. (milliliters) of water with the standing 20. The yarn is drawn dry over a pin heated to 85 ard water retention test. The birefringence at the center to a draw ratio of 2.04 to yield a straight uncrimped of the drawn but unshrunk ribbon is +0.t113 and +0.138 yarn with a denier per filament of 2.9, and an ultimate near the edge of the ribbon. While these ribbon-like elongation of 17%. A typical cross section is shown in products represent an embodiment of the invention which 15 FIGURE 19. is less desirable than ruffle filaments of irregular cross Item B.--The same polymer as above is extruded section (illustrated in the remaining examples) they are through a spinneret containing 17 round holes of 9 mil superior to prior art two-component self-crimping filadiameter and 17 Y-shaped orifices, as shown in FIGURE rnents. 12, with other conditions as above. The yarn is drawn The above procedure is repeated at 700 y.p.m. with no 20 dry 2.31 over a pin heated to 78 C. to yield a straight cross-air quench. The yarn is drawn wet over a pin at uncrimped yarn with a total denier of 89 and an ultiroom temperature to afford the best opportunity for bulkmate elongation of 13.5%. A typical cross section of a ing. It shrinks 60% in boiling water and does not ruifie Y-shaped fil nt i ho i FIGURE 21, but has 3 a Slight P- The wn but un hr Item C.-The above spin is repeated with a spinneret filament has a uniform birefringence of +0160 from the having 34 Y-shaped orifices, as shown in FIGURE 11. center of the ribbon to the edges. The yarn is drawn 2.01 over a pin heated to 85 C. This example illustrates a fume filament in Which the to yield a straight uncrimped yarn with a total denier of ribbon filament is Composed entirely of 1W0 The 99.8 and an ultimate elongation of 18.8%. A typical Y- filament stem in this case should be considered, from a h d fil t i Shown i FIGURE 2() practical standpoint, as the median portion of the ribbon The above three it are shrunk 32, 49, and 38%, Cress Seetien eVeI 1 g from the standpoiflt of defini' respectively, by exposure under low tension to 100 C. tion, the r1bbon 1s all fin, 1.e., composed entirely of two Steam at atmospheric pressure for 1 minute The Chap acteristics of the shunk yarns are given in Table I. For EXAMPLE HI purposes of comparison, an uncrimped, continuous 34 A poly(ethylene terepht-halate) of q 36 is extruded 3D filament, 70 denier yarn of round cross section made at 288 C. through a spinneret having 34 propeller-shaped from poly(ethylene terephthalate) is included as item D.
Table I g Rufiie Elonga- Initial Item Shrinkage, Tenacity, tion, modulus Yarn Water percent g.p.d. percent (Ml) denier Filaments Frequency, Angular disretention having, per- 1b./inch placement,
A =3: shape.-- 30,32,52 1.9 27.6 31 117 20-25 325-550 1.3 38/22 B Y& 0 shape 38 1.6 37.9 11.1 117 a 200 1.9 39/30 0 AllYshape.-. 49 1.2 88.5 8.0 171 (O 15 300-500 1.3 37/18 D A110 about7 3.09 23.3 23.1 70/34 none 0 0 11/11 orifices as shown in FIGURE 9. The threadline is trans- Under the heading water retention, the values to versely quenched by about 150 c.f.m. of air (25 C.) (a the left and right of the virgule represent the bulked and velocity of 250 f.p.m. across the filaments) from a unbulked yarns, respectively. The advantage of the con- 2' /2 x inch opening whose longer dimension parallels volutions afforded by as few as 15% of the fins over the threadline and the top of which is located 1% inches and above the cross section modification alone is apbelow the spinneret. The yarn is wound up at 1000 parent.
y.p.m. The resulting straight yarn is drawn 2.1x in a The above yarns are woven into fabrics with a basket wet state over a pin heated to 77 C. to yield a straight, weave under such conditions that all the finished fabrics uncrimped yarn having a tenacity of 1.8 g.p.d., an elonhave essentially the same construction after shrinking gation of 13% and a total denier of 76.5. A typical and finishing. The specific volumes (cm. gram) are magnified cross section is shown in FIGURE 18. The 4.2, 3.6, and 1.9 for fabrics containing 100% of item C, yarn shrinks 70% in boiling water and became highly B, and D, respectively. The fabrics from the filaments bulked. Microscope examination of the yarn shows with ruflied fins have the appearance and handle of fabric that the fins of the filaments are highly convoluted so from spun staple yarns and have a low luster, whereas that each fin forms about 400-500 rufiles per inch. The the fabric of item D has the typical lustrous appearance average angular displacement is about 5/micron. Apand slippery slick handle of continuous filament fibers. proximately 100% of the filaments display this extent Items A, B, and C are also used as a filling with a warp f fuming. of item D to make fabrics, and the specific volumes are Birefringence of the drawn but unshrink filaments is 2.5, 2.7, and 3.3, respectively, as compared with the 1.9 +0.094 and +0.174 as measured in the center of the for the all-round filament fabric. The use of these new filament and near the tip of the fins respectively and filaments in the fill alone change the appearance and gradually increases from the center outward. bangle of the fabric so that 1t resembles a spun staple ro uct. EXAMPLE IV D The covering power and the specific volumes of all Item A.Poly(ethylene terephthalate) of 33 is exthe fabrics of the convoluted filaments are significantly superior to similar fabrics made of non-convoluted finned filaments having a Y or cruciform cross section so that the advantages of the convolutions are plainly evident.
10 A skein of each of the above items is boiled in water for minutes. The properties of the resulting bulked yarns are given below in Table II.
EXAMPLE V 5 Table II Poly(ethylene terephthalate) of 1 33 is extruded R All through a spinneret having 17 cruciform-shaped orifices Filaments gum as shown in FIGURE 13, and 17 round holes of 9 mil Item WIT 235 53? count/m 615p i diameter at 298 C. and the yarn wound up at 1500 y.p.m. The yarn is quenched by 400 c.f.m. of air (24 A 1.6 1-5 225 2.6 C.) entering at 17 and 70 c.f.m. leaving the 3 x 5.25 inch 3 g8 g-g opening 20, as shown in FIGURE 14. The velocity n across the filaments was 640 f.p.m. The spun yarn is drawn 231x in a dry condition over a pin heated to It is apparent that as the wldth to thlcknessftlo C. to give a Straight, uncn'mped yam with a total (W/ of the fins of filaments processed under similar denier of 59 having an ultimate elongation of 183% conditions is increased, the amount of convolution and and a tenacity of 2.2 g.p.d. A typical cross section of a hence the bull? of ms Yam ls mcreasedif h d filament made above is Shown in The following examples illustrate process variables n URE the forming of ruffled filaments from polyesters.
The yarn shrinlcs 34% in boiling water to give a bulky 2O EXAMPLE VII yarn. Microscopic examination 1n the bulked form reveals that 80% of the fins of the cruciform filaments polflethylene tefephthalate) of m is fiXtl'llded at are highly convoluted having 400 rufiies per inch and an through a sPmIleret With 17 P holes, as average angular displacement f 4 9= A temgl-am shown in FIGURE 11, and 17 round orifices 9 mils in skein of the bulked yarn retains 57 ml. of water with diameter- Tht? baflle 21 (FIGURE is removed fI'Om h Standard test the 39-inch long spinning chimney and difierent inputs of In a Similar manna, a hi bulked yarn is made by 24 C. air (at 17 in FIGURE 14) used. A number of extruding the above polymer through a spinneret whose yarns are Wound "P at Various Speeds and drawn in a orifices consist of three 2 x 40 mil slots arranged crossdry State Over a P heated at 75 at Such draw ratios wise to form a 6-pointed star, drawing and shrinking as as would afiord a drawn y with about 20% Ultimate b elongation. The yarns (except that indicated as spun at 2500 y.p.m.) are shrunk by passing them through an air EXAMPLE VI jet, as shown in FIGURE 27, located between two pairs Item A.-Poly(ethylene terephthalate) of n, 33.3 is of driving rolls. The windup rolls are operated at 90 extruded at 298 C. through a spinneret having 17 round y.p.m. and the input rolls are adjusted to a speed sufiiholes 9 mils in diameter and 17 Y-shaped orifices, as ciently higher to permit the desired shrinkage. Air at shown in FIGURE 10. The spinning chimney is sup- 210 C. and under 3 p.s.i. (pounds per square inch gauge) Table III Drawn yarn properties Filaments Spinning Conditions Velocity Draw ratio with rufi1e* Ruflles speed quench (f.p.m.) Dry percent Shrinkage, Dry tenacity (percent) per inch (y.p.m.) (c.f.ru.) elongation percent (g.p.d.)
iii 3:? it 12 3:1 58 58 125 13 2.9 21 is 3.3 o 0 1,400 3-25 114 2. r 20 23 2. s so so s s 1,600 i 352 114 2 a 19 33 21s 170 1,s00 325 114 2. a 22 40 2. 1 75 250 *Non-round cross section.
plied with 400 c.t.m. of air (24 C.) at 17 (FIGURE 14) pressure is delivered to the jet. The results are sumso that about 70 c.f.m. of air quenches the threadline marized in Table III. and leaves through the 3 x 5.25 inch opening 20. The The results in Table III show the inverse relationship velocity across the filaments was 640 f.p.m. The yarn is of the spinning speed and intensity of the quench, i.e., wound up at 1500 y.p.m. The dry yarn is drawn 2.43 X a higher quench must be used at lower speed to produce over a pin heated to 75 C. to give a straight, uncrimped rufiiing than is required to produce rufiling at a higher yarn having an ultimate elongation of 21% and a total speed. In addition to the spins illustrated in Table III, denier of 100. A typical cross section of the drawn G0 the same spinning conditions are used at speeds from Y-shaped filaments is shown in FIGURE 20. 2,000 to 3,750 y.p.m. with a constant quench of 400 cirn. Item B.T he above procedure is repeated with a spin- As the spinning speed increases from 2,000 up to and neret having 17 round holes 9 mils in diameter and 17 including 3,400 followed by similar draw ratios (which Y-shaped orifices, as shown in FIGURE 11. The dry are lower than required at the lower speeds) and shrinkyarn is drawn 2.3x over a pin heated to 75 C. to give a s5 ing, yarns having approximately 90% of the filaments straight, uncrimped yarn having an elongation of 21.8% with ruffled fins are obtained. The frequency of the and a total denier of 102. A typical cross section of the ruflles increases as the spinning speed is increased. How drawn Y-shaped filaments is shown in FIGURE 20. ever, at 3,600 and 3,750 ruflles are no longer produced Item C.-The above procedure is repeated with a spindespite lower draw ratios. neret having 17 round holes 9 mils in diameter and 17 Y-shaped orifices, as shown in FIGURE 12. The dry EXAMPLE VH1 yarn is drawn 2.35 X over a pin heated to C. to give a Poly(ethylene terephthalate) of 1 34 is used in the straight, uncrimped yarn having an elongation of 25.4% following items. and a. total denier of 102. A typical cross section of the A spinneret with 15 propeller-shaped orifices as shown drawn Y-shaped filaments is shown in FIGURE 20. 75 in FIGURE 8 but having a 9 mil center hole is used to and temperature.
1 1 extrude the yarn of item A of the following table, at 1200 y.p.m. with the quenching conditions of 400 c.f.m. of 24 C. air at 17 of- FIGURE 14 with a 4-inch bafiie opening 20 of FIGURE 14. The velocity across the filaments was 1360 f.p.m. The yarn is then drawn at various conditions and shrinks in boiling water. The same spinneret is used to produce item B of following Table IV at 1206 y.p.m. with 500 c.f.m. of 24 C. air input to the quenching chimney and no baffle 21 of FIGURE 14. The velocity across the filaments was 173 f.p.m. The yarn is 12 with ruflied fins are as follows: tenacity, 0.7 to 1.7 g.p.d.; elongation at the break, 98 to 390%; initial modulus, 2.7 to 11 g.p.d.; and yarn denier, 62 to 138 denier for the 34 filaments.
At draw roll temperatures of 92 C., 89 C., and 86 C. it is found that the maximum amount of convolutions (after shrinking) are produced at draw ratios of 1.8, 1.8, and 1.9, respectively. In these yarns 80% of the filaments have ruflied fins at a frequency of 330 to 500 ruffles per inch.
Table V Drawing conditions Drawn yarn properties Non-round cross section Rufifie filaments frequency Ratio Tempera- Elongation, Shrinkage, ruflied, percent ture, 0. percent percent By 190 air. drawn over 90 and 100 pins at such a draw ratio (a 25 In the preparation of a poly(ethylene terephthalate) and b in the table) as to obtain approximately 20% elongation. The drawn yarn is shrunk in boiling water.
To obtain the yarn in item C of following Table IV, the spinneret and polymer of Example VII is used to spin filaments at 1500 y.p.m. with 325 c.f.m. 24 C. air quench. The yarns are drawn under different conditions over a pin and then shrunk in a 190 air jet.
The effect of drawing conditions upon rufiiing and physical properties are given in Table IV. It is to be noted that, if the yarn is drawn in a water-wet condition, higher temperatures can be used to obtain a product that will rufiie than if the yarn is drawn dry. Also, as the temperature of the drawing pin is increased from room temperature, the shrinkage and extent of rufile decreases with a given filament.
Those yarns with ruffled fins have the following physical properties: tenacity, 0.4 to 1.2 g.p.d.; break elongation,
filament that will bulk due to the convoluting of its fins, the first process requirement is the extrusion of a filament with the proper cross section. Filaments, with one or more fins whose width/thickness ratio varies from about 1.4 to 6.0, have been illustrated.
The cross section of the extruded filament is :a function of the melt viscosity of the polymer and the shape of the extrusion orifice. The melt viscosity of the polymer is a function of the extrusion temperature (inversely related) and the relative viscosity (directly relate-d) of the polymer. The ruffled products of this invention have been made of poly(ethylene terephthalate) with 1 from 23 to 43. Extrusion temperatures of 282298 C. have been employed with these polymers. Since an extruded filament tends to contract in volume upon solidifying, it is necessary to use an extrusion orifice that has a fin width/thickness ratio of 2 to 6 times larger than that deto 512%; initial modulus, 4 to 19. sired in the solidified filament. With poly-ethylene Table IV Drawing conditions Drawn yarn properties Shrunk yarn properties Item Yarn Tempera- Non-round Rufl-le Draw ratio ture, C. Elongation Shrinkage filaments frequency ruflied 2. 7 105 wet 22 71 5 250 2. 7 105 dry 19 10 none 0 a 100 Wet. 25 52 100 2, 000 a 100 dry 28 18 none 0 b 90 Wet 21 100 2, 000 b 90 dry 20 15 5-10 50-100 2.1 82 dry 22 50 80 200 2.1 81 Wet 0. 15 44 70 1, 000 2. 1 66 wet 18 59 80 1, 000 2.1 60 dry 26 48 80 350 EXAMPLE IX terephthalate) of 1 of 23 to 43 extruded at 282298 C.,
- Example VIII (items 4 and 6), it is seen that hot roll drawing permits greater shrinkage and a higher degree of convolutions than pin drawing at the same draw ratio The physical properties of the yarns spinnerets having width/thickness fin ratios of 3 to 16 have been used to make filaments that could be convoluted.
It is postulated that the convoluted filaments of this invention are caused by a difference in shrinkage between the stem and fins of a filament. This differential shrinkage is considered to be caused by a greater orientation of the fins than the stem.
The relationships between orientation, crystallinity, and physical properties of the filament are quite complex. The orientation of filaments can occur in the spinning process due to the fact that the solidified filaments are usually accelerated to :a greater linear velocity than the polymer is extruded. Filaments can be oriented in a step subsequent to spinning by cold drawing (stretching), i.e., below about 120 C. along the fiber axis. At speeds of 100 to 2500 y.p.m. with an air quench, most of the orientation in a final yarn of round filaments is ordinarily introduced by a separate drawing step. The higher the spinning speed at a given rate of quenching, the higher the orientation as evidenced by birefringence measurements.
Filaments with no orientation have little or no tendency to shrink. As the degree of orientation is increased, the tendency for the molecules to relax from the strained condition and hence shrinkage in a hot media increases. This process would proceed indefinitely, but for the fact that increasing the extent of orientation also increases the tendency for the polymer to crystallize. Crystallization restricts shrinkage. As further orientation takes place, additional crystallization sets in and further retricts shrinkage. A schematic diagram of this relationship is shown in FIGURE 26. If filaments are drawn under conditions that aid crystallization (use of elevated temperatures in the absence of water) or exposed to crystallizing conditions (e.g., heat or latent solvents) in a taut state before relaxing (shrinking) after drawing, the shrinkage is relatively intensitive to the degree of orientation.
Other physical properties that are of importance are tenacity, initial modulus (Mi) and the ultimate elongation. In general, it can be stated that the tenacity and Mi increase with increasing orientation and that elongation decreases with increasing orientation. Elongation can be used as a rough measure of orientation if the orientating conditions are kept constant. Since a filament may be oriented by cold drawing, it is obvious that the elongation of a given filament generally decreases with an increasing draw ratio.
It is postulated that for a fin of a filament to convolute upon shrinking, it must have a greater orientation than the stern and this orientation must be greater than that shown at point A of FIGURE 26. A difference in birefringence between the stern and fins of products that can rufie has been observed (before the filaments were shrunk). Also, no difierential birefringence has been observed on unshrunk filaments that could not be rulfied although they have the proper cross section section and potential shrinkage required for ruffling. It is also believed that the tips of the fins are preferentially cooled by the cross-air quench so that the fins solidify preferentially and are thus preferentially oriented in the spinning process. It is apparent that the larger the width/thickness ratio of the fins, the more pronounced will be this effect.
FIGURE 25 defines the preferred working zone, spe cifically drawn for poly(ethylene terephthalate) but also applicable to fialrnents composed of other polyesters and other types of synthetic linear polymers, for spinning speed at various fin width/thickness ratios, that, in conjunction with sufiicient quenching or cooling, will provide filaments that will ruffie when processed under conditions giving a high shrinkage. The proper quenching conditions to use with a given spinning speed and filament cross section within the working zone of FIGURE 25 can be readily determined. Quenching should be accomplished Within 2 to 4 feet below the spinneret. At the highest velocities of quenching gas, the quench zone may be an inch or less below the spinneret. Increasing the intensity of the quench from a given set of conditions will increase the difference in birefringence between the stem and fin; decrease the ultimate elongation of the asspun yarn; and increase the amount of ruffle when drawn to give the desired shrinkage. Opposite effects will be obtained by lowering the amount of quenching. In general, the most intensive quenching conditions are required in the working zone adjacent to area A of FIGURE 25. As one proceeds from area A through area B at an angle of 45 in FIGURE 26, the quenching requirements will be reduced. Area C represents a zone which, although 14 possibly affording the required differential orientation between stem and fin, yields a filament having too low an :as-spun elongation and too low a potential shrinkage, regardless of drawing conditions to afford a rufiled product.
The use of more intense quenching conditions, such as spinning into a liquid, permits the use of a lower spinning speed to give a rufiieable filament than can be obtained with the maximum air quench alone.
In order for the filaments of this invention to develop the proper bulk, from 15-75% or higher shrinkage is required with 4565% being preferred. It is known to pin-draw a polyester filament 4X to 6X at temperatures of C. to C. in conjunction with a plate heated to 180 C. in order to produce a yarn that has a shrinkage of the order of 8% or less. It is believed that the higher temperatures induce crystallization which stabilizes the oriented filaments against shrinkage. It is also known that the higher the draw ratio, the more the yarn is oriented and the easier it is for it to crystallize. To prepare the filaments of this invention, particularly polyester filaments, drawing conditions are used that are termed amorphous retaining, i.e., they tend to induce a minimum of crystallinity. These conditions are represented by a maximum draw ratio for a filament spun under certain conditions and for a maximum temperature of drawing, as discussed below. Drawing may be carried out by passing over a heated pin approximately 1.5 inches in diameter. Since a yarn has such a short contact time with the pin, much of the internal heat generated by the drawing cannot be dissipated through the pin, and the high yarn temperature helps to crystallize the yarn. In general, the lower the pin temperature, the more amorphous will be the drawn filament. A pin temperature of 90 C. is about the maximum that can be used with dry polyester yarn to obtain a yarn with an elongation as low as 20% with filaments prepared in accordance with this invention that will ruflie. Filaments. having an elongation of 2030% are commercially preferred because of their yield point and initial modulus. Somewhat higher temperatures can be used with a smaller draw ratio (to obtain an elongation greater than 20%).
By running the yarn through a water bath or over a water wick prior to pin drawing, higher temperatures (e.g., as high as C.) can be used to obtain a yarn with the required high shrinkage and an elongation of 20% or more. It is believed that the water helps to dissipate the heat of drawing.
Another method of drawing is by means of 2 or more rolls, around each of which the yarn is wrapped and which revolve at different peripheral speeds. The yarn may be wrapped any desired number of times around the heated feed roll. Thus, depending on the draw ratio, the size of the roll, the number of wraps and the contact time, temperatures as high as 105 C. may be used to draw dry yarn to obtain a high shrinking yarn with an elongation of 20% or more.
The maximum draw ratio to be used will depend upon the orientation of the fins which is dependent upon spinning speed, quenching conditions and the width/thickness (W/ T) ratio of the fin as previously discussed. Sufficient elongation must be present in the fiin so that a useable textile product can be made. Draw ratios. of 1x to 4X can be used With 1X to 3X being preferred. The exact draw ratio and drawing conditions for any as-spun filament that will give a shrinkage in boiling water greater than 15% can readily be determined by experiment.
In general, lowering the temperature of the pin at a given draw ratio increases the amount of shrinkage, and a higher draw ratio can therefore be used to obtain the same shrinkage. Also, drawing the yarn wet gives a greater shrinkage at a given draw ratio than dry drawing, and thus a higher draw ratio can be used with wet drawing to obtain the desired high shrinkage.
Shrinkage of the yarn to cause convoluting of the fins may take place in any convenient manner. A boil-off in water, exposure to steam, or a blast of hot air or other suitable relaxing media will sufiice.
It is preferred that the filaments of this invention have an average angular displacement for each convoluted fin of at least 2.0/p. and at least 100 convolutions per inch; a Width to thickness ratio of from 2 to 4 is also preferred. In carrying out the invention, spinning speeds of at least 1000 yards per minute are preferred.
Polymers crystallizing less readily than poly(ethylene terephthalate) are also quite useful in the practice of this invention. A copolymer, poly(ethylene terephthalate/ sodium sulfoisophthalate) 98/ 2% by weight (described in the copending application of Grifiing and Remington, Serial No. 519,269, filed June 30, 1955), now abandoned, when spun under the conditions of Example VII developed a moderate bulk when shrunk in a 210 C. air jet even though the yarn was drawn on a 93 pin to 20% elongation.
In a preferred embodiment of the invention, the polyester polymer is a synthetic linear condensation polyester of bifunctional ester-forming compounds wherein at least about 75% of the repeating structural units of the polymer chain include at least one divalent carbocyclic ring containing at least six carbon atoms present as an integral part of the polymer chain and having a minimum of four carbon atoms between the points of attachment of the ring in the polymer chain (para-relationship in the case of a single 6-membered ring). The polyesters may be derived from any suitable combination of bifunctional ester-forming compounds. Such compounds include hydroxy acids such as 4-(2-hydroxyethyl)benzoic acid and 4-(2-hydroxyethoxy)benzoic acid, or mixtures. of the various suitable bifunctional acids or derivatives thereof and the various suitable dihydroxy compounds and derivatives thereof. The repeating structural units of the polymer chain comprise recurring divalent ester radicals as in-chain linking units which are separated by predominantly carbon atom chains or rings comprising hydrocarbon radicals, halogen-substituted hydrocarbon radicals, and chalcogen-containing hydrocarbon radicals wherein each chalcogen atom is bonded to carbon or a different chalcogen atom, and no carbon is bonded to more than one chalcogen atom. Thus, the repeating units may contain ether, sulfonyl, sulfide, or carbonyl radicals. Sulfonate salt substituents may also be present in minor amount, up to about mol percent total sulfonate salt substituents in the polyester based on the number of ester linkages present in the polyester. See, for example, US. 3,018,272. Other suitable substituents may also be present.
Among the various suitable dicarboxylic acids are terephthalic acid, bromoterephthalic acid, hexahydroterephthalic acid, 4,4'-sulfonyldibenzoic acid, 4,4'-diphenic acid, 4,4'-benzophenonedicarboxylic acid, 1,2-bis (4-car boxyphenyl)ethane, 1,2 bis(p carboxyphenoxy)ethane bis-4-carboxyphenyl ether and various of the naphthalenedicarboxylic acids, especially the 1,4-, 1,5-, 2,6-, and 2,7- isomers. Isophthalic acid is also suitable, especially when used in combination with a 1,4-dihydroxyaromatic compound. Carbonic acid is similarly suitable.
Among the various suitable dihydroxy compounds are the glycols, such as ethylene glycol and other glycols taken from the series HO(CH OH, where n is 2 to 10; cisor trans-p-hexahydroxylylene glycol; diethylene glycol; quinitol; neopentylene glycol; 1,4-bis(hydroxyethyl)benzene; and 1,4--bis(hydroxyethoxy)benzene. Other suitable compounds include dihydroxyaromatic compounds such as 2,2-bis (4-hydroxy-3,S-dichlorophenyl) propane, hydroquinone, and 2,5- or 2,6-dihydroxynaphthalene. Other suitable glycols can be selected from the class having the general formula: HOCH Q(R) Q--CH OH wherein Q and Q are saturated hydrocarbon radicals of the group consisting of 1,3-cyclohexylene, 1,4-cyclohexylene, and lower alkyl derivatives thereof; In is 0 or 1; and R is a saturated divalent hydrocarbon radical of 1 to 8 carbon atoms. Bis(4-hydroxymethylcyclohexyl) and 1,2- bis (4-hydroxymethylcyclohexyl)ethane are especially useful. This general class of glycols is made by a twostage reduction of the corresponding bibenzoic acids or bis(carboxyphenyl) alkanes or ethers, involving reduction of the aromatic nuclei to alicyclic nuclei (e.g., hydrogenation of an ester of the acid using platinum oxide as a catalyst) followed by reduction of the carboxy groups to hydroxymethyl groups (e.g., reaction with lithium aluminum hydride).
Suitable polyesters are described, e.g., in U.S. Patents 2,465,319, 2,658,055 (DMe3E) and 2,676,945 (Poly OH acetic acid).
Although the filaments of this invention having two or more fins have been illustrated only by cross sections with fins of substantially equal length disposed in a symmetrical manner, the invention is not limited thereto. The fins on a filament can vary in length and in cross section disposition within the limits of this invention.
The advantages of the highly bulked product of this invention are obtained when only one fin is present on a filament. However, filaments having two or more fins are preferred because of the greater bulk obtained for a given weight of filament.
An especially advantageous product is a combination of Y and 0 cross section filaments in the same yarn bundle because of better fiber mobility in the yarn bundle and softer handle of the fabrics made therefrom.
It is preferred that both the potentially convolutable and also the convoluted filaments of this invention have a denier of 1 to 10 and that either continuous or staple yarns composed of these filaments have a denier of 30 to 8000. These denier ranges are particularly adaptable to the textile industry.
The filaments of this invention will have 20 or more complete convolutions per inch. It is preferred, however, that they have at least complete convolutions per inch. The relatively high frequency of the ruffles on the fins of these products confer bulk and resistance to packing that is not attained by the crimped filaments of the prior art. The filaments prepared by the process of this invention may be fabricated before shrinking in the form of continuous filament yarn or cut to staple fiber, formed into yarn and bulk developed in the fabric with the finishing step. Alternatively, the fibers may be shrunk to give a prebulked filament, yarn or staple before fabrication.
The products of this invention are of great utility, either as continuous filaments or staple fibers, in the production of yarns and in the formation of bulky fabrics, whether knitted, woven or felted.
The filaments and yarns made by the process of this invention prior to convoluting, may be woven into fabric and the convolutions developed in the fabric; alternatively, they may first be convoluted and then woven into fabric. We claim:
1. The process which comprises (1) extruding a molten synthetic linear polyester through an orifice having at least one elongated slot having a width to thickness ratio of at least three projecting from an aperture having a width greater than the width of said slot to form a filament having at least one fin extending from a stem portion,
(2) quenching said filament by directing a flow of quenching gas across said filament near said orifice at a velocity of at least 1200 2 X (forwarding speed where the forwarding speed is expressed in yards per minute,
(3) forwarding said filament at a speed between about 1,000 and 3,400 yards per minute and (4) drawing said filament from 1 to 4 times its original length under amorphous retaining conditions, said quenching, forwarding and drawing steps imparting to the fin and stem portions of said filaments a difierential shrinkability, and shrinking the drawn filament between about 15 to 75% thereby providing a convoluted filamentary structure.
2. The process of claim 1 wherein the velocity of said quenching gas is between 250 and 2500 feet per minute.
3. The process of claim 2 wherein said filament is forwarded at a speed between 1300 and 3400 yards per minute.
4. The process which comprises (1) extruding a molten synthetic linear polyester through an orifice having at least three elongated slots having a width to thickness ratio of at least three projecting from a central aperture to form a filament having at least three fins extending from a stern portion,
(2) quenching said filament by directing a flow of quenching gas across said filament near said orifice at a velocity of at least 1200 2 150 X (forwarding speed Where the forwarding speed is expressed in yards per minute,
(3) forwarding said filament at a speed between about 1,000 and 3,400 yards per minute and (4) drawing said filament from 1 to 4 times its original length under amorphous retaining conditions, said quenching, forwarding and drawing steps imparting to the fin and stem portions of said filament a differential shrinkability, and shrinking the drawn filament between about 15 to 75% thereby providing a convoluted filamentary structure. 5. The process of claim 4 wherein the velocity of said quenching gas is between 250 and 2500 feet per minute. 6. The process of claim 5 wherein said filament is forwarded at a speed between 1300 and 3400 yards per minute.
References Cited by the Examiner UNITED STATES PATENTS 2,002,153 5/1935 Mendel 161-177 2,831,748 4/ 1958 Finlayson et al 264-177 2,945,739 7/1960 Lehmicke 264-177 FOREIGN PATENTS 712,950 6/ 1952 Great Britain.
ALEXANDER H. BRODMERKEL, Primary Examiner. ROBERT F. WHITE, Examiner.