US3734993A

US3734993A - Method for extruding t-shaped filaments

Info

Publication number: US3734993A
Application number: US00167524A
Authority: US
Inventors: P Paliyenko; W Beier
Original assignee: Individual
Current assignee: Celanese Corp
Priority date: 1968-06-20
Filing date: 1971-07-29
Publication date: 1973-05-22
Anticipated expiration: 1990-05-22

Abstract

Method for extruding filament-forming material through a spinnerette having plurality of T-shaped orifices wherein the orifices are arranged annually with respect to the center of the spinnerette. each of the T-shaped orifices comprises a crossbar and a stem extending perpendicularly from the crossbar at its midpoint with the stem facing away from the center of the spinnerette. Further embodiments of the spinnerette include a split T-configuration.

Description

May 22, 1973 p, PALIYENKO ET AL 3,734,993

METHOD FOR EXTRUDING T-SHAPED FILAMENTS Original Filed June 20, 1968 2 Sheets-Sheet 1 MOLTEN POLYMER & I6 1 FIG I (PRIOR ART) FIG 2 (PRIOR ART) I I9 MOLTEN POLYMER i4- 4i O r Us 3 FIG 4 HL ---u- 24 WC 1 2 M L5 Ll 46 FIG 5 May 22,1973 P, PALIYENKO E 3,734,993

' METHOD FOR EX'I'RUDING T-SHAPED FILAMENTS Original Filed June 20, 1968 2 Sheets-Sheet 2 FIG 7 FIGS 9 United States Patent 3,734,993 METHOD FOR EXTRUDING T-SHAPED FILAMENTS Paul Paliyenko, 6350 Gaywind Drive, Charlotte, N.C.

28211, and Werner E. Beier, Sardis View Lane, Matthews, N.C. 28105 Original application June 20, 1968, Ser. No. 745,652, now Patent No. 3,640,670. Divided and this application July 29, 1971, Ser. No. 167,524

Int. Cl. B2811 21/54; B29f 3/00 US. Cl. 264-177 F 9 Claims ABSTRACT OF THE DISCLOSURE This is a division of application Ser. No. 745,652, file'd June 20, 1968, now US. Pat. No. 3,640,670.

BACKGROUND OF THE INVENTION This invention generally relates to man-made filaments having a non-circular cross-section. It particularly relates to a process of and apparatus for extruding such filaments. Even more specifically, it relates to novel spinnerettes for extruding filaments having a generally T- shaped cross-section.

The spinning of organic materials into filaments by extrusion of the material through an orifice is a generally accepted and well known practice in textile manufacture. Such practice in the past has been to a large degree concerned with the production of filaments which possess a round or nearly round transverse cross-section, which cross-sectional shape is produced most easily under the cooling or coagulating conditions used generally in fiber production. However, filaments having round, or as is commonly referred to, regular cross-sections, have certain disadvantages for particular end uses. Fabrics woven or knitted from yarns of filaments or fibers having such cross-sections often do not possess the desired aesthetic properties such as bulk or cover, stiffness, etc. Moreover, the fabrics often have a shiny, smooth appearance and for this reason and others, in some instances are undesirable in the manufacture of wearing apparel and the like.

It is to avoid the above-mentioned disadvantages and others that non-circular filaments, i.e., filaments having other than a round cross-section, have come into importance in relatively recent years. By altering the crosssectional shape of the filaments it is possible to produce yarns with a mixture of the properties normally associated with two distinct fibers. One example of this is a nylon yarn with filaments of triangular cross-section which has high abrasion resistance and tensile strength normally associated with nylon, combined with appearance and handle similar to natural silk. A wide variety of non-circular cross-sectional filaments have been provided. Such filament shapes as ribbons, cruciform, trilobal and other multilobal shapes are known to exist and possess certain desirable properties. It has been discovered that by modifying the fiber cross-section, it is possible to advantageously alter the yarn properties with respect to, e.g., the covering power, handle, stiffness, luster, such as the provision of a sparkling luster and the elimination of a gloss or sheen, among other desirable physical and/ or aesthetic properties.

The simplest way of producing non-circular filaments is to use non-circular holes for extrusion. However, in melt-spinning the newly formed filaments remain in a mobile liquid form for an appreciable period after extrusion. During this time the surface tension tends to draw the filament perimeter into a ciricle, but the flow necessary for this change in shape is restricted by the viscosity of the molten filament forming material. It has been discovered, as hereinafter more fully described, that a non-circular hole generally results in a filament having a cross-sectional configuration intermediate between the hole shape and a circle. It has also been discovered that the cross-section of the filament can be made closer to the hole shape by increasing the viscosity of the polymer (by using a polymer of higher molecular weight or by spinning at a lower temperature) i.e., setting the extruded filamentary material more rapidly. The best results in the production of non-circular filaments with non-circular holes are obtained therefore with high viscosity polymer and high cooling rates. There are practical limits, however, to both of these in the normal extrusion apparatus. Filaments produced from very high viscosity polymer have lower dye-uptake than those produced from standard viscosity polymers. Excessive cooling tends to introduce variability into the product due to difliculty in controlling such conditions.

Another method known in the art for producing yarns having filaments of non-circular cross-section is to fuse or coalesce together a number of circular or, other shaped filaments such as, for example, ribbon or fiat shaped filaments, to give composite filaments of various shapes.

In addition to the above specifically mentioned noncircular or irregular shaped cross-sectioned filaments, it is known also to extrude bell, pear or generally T-shaped filaments as is disclosed, for example, in US. Pat. Nos. 2,945,739; 3,038,237; 3,097,414; 3,121,040 and 3,135,646. While the T-shaped filament as described in US. Pats. 3,038,237 and 3,097,414 is the result of a conjugate extrusion process through a circular hole, T-shaped filaments formed in the remaining patents result from the extrusion of a polymeric material through a T-shaped orifice. However, it is often difficult to extrude a filament approaching a well-defined T-shape even from a spinnerette having such shaped orifices. As alluded to above, the filament cross-section often looks more like an inverted hell or pear rather than a sharply defined T.

Moreover, with the extrusion of T-shaped cross-sectioned filaments the extrusion heretofore was further complicated because the filaments would knee toward the center of the spinnerette resulting in some instances with coalescence of adjacent filaments and in other instances with licking-back of the filament-forming material onto the spinnerette face, thus forming drips or blobs of polymer thereon. In time, the blobs of filament-forming material became degraded and blocked off the spinnerette orifices wholly or at least in part thereby resulting in some instances with no filaments at all being extruded from some holes or filaments of less than the desired filament denier being extruded thereby resulting subsequently in undesirable broken filaments.

As used herein, a filament is said to knee when the line of flow of the filament is bent out of the vertical at an angle back toward the spinnerette face. When the filament is bent to such an extent that the filament touches the spinnerette face and ceases to flow as a filament, it is said to lick-back and forms what is known as a drip or blob of filament-forming material.

It is an object of this invention to eliminate kneeing and drips or blobs in extruding filament-forming material through T-shaped spinnerete holes.

It is a further object of this invention to provide an improved process for extruding filament-forming material for the formation of filaments having a relatively welldefined T-shaped cross-section.

It is another object of this invention to provide an improved process for extruding filaments having a T-shaped cross-section from orifices having a T-shaped crosssection.

It is still a further object of this invention to provide T-shaped cross-section filaments having certain desirable physical and aesthetic characteristics compared with regular cross-section filaments such as better drapability, greater resistance to matting in carpets, better dye uniformity, better resiliency, better bulking properties, better filaments for texturing, better cover, sparkly luster, crisper hand and the like.

It is an additional object of this invention to provide novel spinnerettes having a unique arrangement of T- shaped orifices for extruding filaments having a generally T-shaped cross-section whereby kneeing of the filaments is eliminated.

It is yet a further object to provide novel spinnerettes for extruding filaments having a relatively well-defined T-shaped cross-section over a relatively wide range of spinning conditions.

These and other objects will become more apparent to those skilled in the art from the following detailed description.

THE INVENTION In accordance with the invention, a spinnerette is provided for extruding filament-forming polymeric material having a plurality of T-shaped orifices, said orifices being arranged annularly with respect to the center of the spinnerette, each of said T-shaped orifices comprising a crossbar and a stem extending perpendicularly from the crossbar at its midpoint, at least half of said stems facing away from the center of the spinnerette, said orifice having a hole aspect ratio (HAR) of about 2.6 to 86 as expressed by the equation:

y x EAR- wherein y=the distance from the center of the crossbar to the end of the stem, x=the distance from the center of the crossbar to the end of said crossbar and Z is the distance from the center of the crossbar to the intersection or projected intersection of the crossbar and stem. In a preferred embodiment of the present invention a spinnerette is provided having a split T orifice wherein the crossbar and stem are separated by a gap of up to about 0.008 inch. The split T orifice not only eliminates kneeing independent of the placement of the orifice in the spinnerette but also results in the production of a novel T cross-section of an unusually high filament aspect ratio in the range of 2.5 to 5.0. The present invention provides a spinnerette particularly useful for producing T crosssection filaments while eliminating difiiculties with kneeing filament coalescence, drops and consequent deformities in the spun filaments by (1) utilizing a novel split T orifice and/or (2) positioning the T orifices in annular arrangement with the stern of the T facing away from the center of the spinnerette plate. Particular novel yarn effects can be achieved by the present spinnerette and method while eliminating the problem of filament coalescence by alternating the position of the T orifices wherein at least half of the stems of the T orifice face away from the center of the spinnerette plate. The use of the split T eliminates kneeing and the consequent spinning diificulties independent of the placement thereof in the spinnerette plate.

DETAILS OF THE INVENTION The invention will be described more fully with reference to the drawings in which:

FIG. 1 is a plan view of a spinnerette plate used heretofore for the spinning of T-shaped filaments;

FIG. 2 is a partial schematic sectional view with enlarged detail of a spinnerette assembly including crosssection of the spinnerette plate shown in FIG. 1 taken on lines 22 thereof showing the filaments kneeing toward the center of the spinnerette;

FIG. 3 is a plan view of a spinnerette plate having T- shaped orifices arranged annularly and in accordance with the present invention;

FIG. 4 is a partial schematic sectional view with enlarged detail of a spinnerette assembly including a crosssection of the spinnerette plate shown in FIG. 3, taken on line 4-4 thereof, showing extrusion of the T-shaped filaments without kneeing;

FIG. 5 is a greatly enlarged plan view of one of the T-shaped orifices in the spinnerette plate shown in FIG. 3;

FIG. 6 is a sectional view of a filament extruded from the T-shaped orifice shown in FIG. 5;

FIG. 7 is a plan view of a spinnerette plate having a plurality of pairs of slots arranged annularly to form split T orifices according to the invention wherein the stem of the T is faced inwardly as can be conveniently used with the split T;

FIG. 8 is a greatly enlarged view of one of the split T orifices in the spinnerette plate shown in FIG. 7; and

FIG. 9 is a sectional view of a. well-defined T-shaped filament extruded from a split T orifice constructed in accordance with FIG. 8.

According to one aspect of the invention, a filament having a generally T-shaped cross-section is formed from filament-forming material without kneeing or the formation of drips or blobs by extruding such material through T-shaped orifices arranged annularly in a spinnerette plate with the stern of the T pointed away from the center of the spinnerette.

Referring now more particularly to the drawings, there is shown in FIG. 1, a spinnerette plate, designated generally by reference numeral 10, used prior to the invention herein for the spinning of filaments having a generally T-shaped cross-section.

Spinnerette plate 10 has an annular body portion 12 by which the spinnerette plate is fastened to a spinnerette assembly 13, diagrammatically shown in FIG. 2, for the extrusion of filament-forming material. The spinnerette plate 10 has a plurality of T-shaped orifices 14 having cross bars 15 and stems 16. The orifices 14 are arranged annularly in the spinnerette 10 with stems 16 of the T- shaped orifices 14 directed toward the center of the spinnerette. Generally, in the melt extrusion of made-made organic polymeric filaments, the thermoplastic filament-,

forming material, as is diagrammatically shown in FIG. 2, is subjected to heat and pressure in feed zone next to spinnerette plate 10. The temperature in this zone is sufficient to maintain the fiber-forming material in a molten condition whereby the molten material is forced through the orifices 14 to form a plurality of filamentary structures 17. The extruded filamentary material is subjected to controlled cooling conditions such as is provided by a spinning cabinet or the like (not shown). A flow of inert gas is conventionally employed in a zone directly adjacent to and in front of the face of spinnerette which brings the molten material to the desired solidified condition in the form of solid filaments 17.

Heretofore, the extrusion of T-shaped filaments 17 has been accomplised by kneeing, as is illustrated in FIG. 2 of the drawing. Filaments 17 are bent out of the vertical flow line inwardly toward the center of spinnerette plate 10 forming an angle with respect to the face 18 of the spinnerette plate. Under some otherwise desirable spinning conditions, the filamentary material is bent to such an angle as to cause licking-back, i.e., contact with the spinnerette plate face 18 thereby resulting in a drip or blob of filament-forming material on the fiber. Often the blob increases in size and runs back into the orifice opening, causing the opening to be either wholly or partially blocked-off. Such blocked orifices result in either no filament being formed at all, or alternatively, filaments of lesser diameter, and/or deformed cross-sections being formed which, with subsequent drawing, results in numerous broken filaments and nonuniformity in the yarn produced.

Quite unexpectedly, it has been discovered that the particular arrangement of the T-shaped orifices 14 in the spinnerette plate influences the kneeing of the filaments and the formation of drips or blobs. It has been found that kneeing can be substantially eliminated by reversing the direction of the stem of the T, that is, so that the stem of the T points away from the center of the spinnerette rather than toward the center of the spinnerette. To the extent that kneeing is not completely eliminated, as may be encountered under certain spinning conditions, the spun filaments are directed away [from each other thereby preventing coalescence of the various filaments. Such an arrangement of T-shaped orifices 14 is shown in spinnerette plate 19 disclosed in FIG. 3 of the drawing.

Spinnerette plate 19 is provided with an annular rim which aids in the fastening of the plate into spinnerette assembly 13 as is disclosed diagrammatically in FIG. 4 of the drawing. Spinnerette plate 19 is provided with a plurality of T-shaped orifices 14 which are arranged annularly in a circle that is preferably concentric with annular rim 20. Stems 16 of the orifices 14 lie on an imaginary radius of the spinnerette plate 19 and, contrary to the arrangement shown in FIG. 1, all face away from the center of the spinnerette.

The extrusion of molten material through the orifices in spinnerette plate 19 results in the formation of generally T-shaped filaments 22 without kneeing and without the formation of drips or blobs. Filaments 22 have a rather distorted T-shape, \as is shown in FIG. '6, such being described more fully h'ereinafter. The cross-sectional shape is also referred to by some as an inverted bell or pear shape.

While the drawings illustrate a rather limited number of orifices 14 in spinnerette plate 19, it is realized, that the actual number used is merely a matter of choice. Quite obviously, the number of orifices 14 in any spinnerette plate depends upon the size thereof and number of filaments desired to be extruded. Merely by way of example, however, in a inch thick spinnerette plate, manufactured of stainless steel 430 metal, there may be provided from as few as about 7 to as many as 640 or more orifices having a T-shape. Thus, the size of the T also can be varied to provide different denier per filament, changes in filament aspect ratio and the like. Moreover, the orifices may, if desired, be arranged in a plurality of concentric circles.

It has also been discovered in accordance with the invention, that the production of T-shaped filaments having a wide range of modification ratios is possible. The modification ratio (M), hereinafter called the filament aspect ratio (FAR), as defined in US. Pat. 2,939,201, is the ratio of the radius a to the radius b of a circle having a center c inscribed within the filament cross-section. With the filaments extruded according to the invention hereindescribed, the FAR may vary from as little as about 1.2 to as much as 5.0 or more. More preferably, however the FAR is in the range of about 1.8 to 2.6 for a conventional T-shape and about 2.5 to 5.0 for a split T, exact number depending on denier per filament and specific fabric properties such as cover, luster, crisp handle and mechanical quality of the yarn and the like.

The cross-sectional configuration of a non-circular filament, i.e., the noncircularity or filament aspect ratio (FAR) as defined more fully hereinafter, has been found to be controlled or varied according to the hole aspect ratio (HAR), polymer type, polymer intrinsic-viscosity, throughput per hole for a given hole size or actually eX- trusion velocity, spinning temperature, and the rate of quench and the like, which factors are preferably described for polyester by the following relationship:

The above expression applies to the range of condition as follows for polyester filament-forming polymer:

T=275 C. to 310 C. V=10 to 200 feet per minute 'I.V.=0.40 to 0.94 (as measured at 25 C. with 8 grams of polymer in cubic centimeters of O-chlorophenol) HAR=2.6 to 64 Q=0 to 20 standard cubic feet per minute Similar relationships can also be derived experimentally for polyamides, acrylics, polyethylene, polypropylene and the like filament-forming polymers.

While filaments 22 extruded from spinnerette plate 19 desirably have a generally T-shaped cross-section as shown in FIG. 6, it has been discovered that under extreme conditions even circular filaments can, if desired, be extruded from such non-circular holes. Conditions such as low [.V. and high spinning temperatures would produce circular filaments as can be determined from the above equation.

The relationship between the filament cross-section and the hole shape will now be described in greater detail with reference to FIGS. 5 and 6. In FIG. 5 there is shown in a greatly enlarged view one of orifices 14 in spinnerette plate 19. The T-shaped orifice 14 has a crossbar 15 and a tail or stem 16. Crossbar 15 has a width (W,,) which may vary from about 0.002 to 0.020 inch and a length (L which may vary from about 0.008 to 0.060 inch. More preferably, the Width W is in the range of about 0.003 to 0.012 inch and the length L 0.010 to 0.040 inch. Stem 16 likewise has a lengthwise dimension (L which may vary from about 0.007 to 0.060 inch and a widthwise dimension (W which may vary from about 0.002 to 0.020 inch. More preferably, the L is about 0.010 to 0.040 inch and the W is 0.003 to 0.012 inch. A most preferred orifice had a crossbar measuring 0018x0004 inch and a stem measuring 0016x0004 inch.

The orifice or hole noncircularity or aspect ratio (HAR) is determined from the following formula:

where y as disclosed in FIG. is the distance in inches from the center of crossbar 15 to the end 23 of stem 16 and x is the distance in inches from the center of crossbar 15 to the end 24 of crossbar 15. The dimension z is the distance in inches from the center of crossbar 15 to point 25, the intersection between crossbar 15 and stem 16. The range of each y/z and x/z varies from 1.3 to 43.0. Quite desirably, the ratio of each is greater than 1.3 thus resulting in an HAR ranging from about 2.6 to 86.0. More preferably, the range of HAR is between about 5.0 and 25.0.

Contrary to the trilobal filaments described in US. Pat. Nos. 2,939,201 and 2,939,202 wherein the filaments have essentially a symmetrical trilobal cross-section, the trilobal cross-section of filaments produced in accordance with the description herein, as shown in FIG. 6, are asymmetrical. Moreover, in contrast to having the sides either all convex or all concave, as disclosed in the noted patents, the filaments herein disclosed have a unique combination of convex and concave sides which contribute to the attainment of certain desired specialty effects.

As shown in FIG. 6, filament 22 has three

lobate tip portions

33, 34 and 35 joining together two

concave sides

36, 37 and one convex side 38. The lobe 34 opposite the convex side is longer than the other two lobes 33 and 35. The FAR, i.e., the ratio of radius a over radius b extending from center 0, e.g. a/b, radius a always being the larger radius, can be varied by varying the hole aspect ratio (HAR), as seen more clearly from the above formula. As above-mentioned, filament 22 is asymmetrical; however, it does have one plane of symmetry. The filament 32 is symmetrical with respect to a line 30-30 which bisects convex side 38 and lobe 34.

According to another aspect of the invention, as is shown more clearly in FIGS. 7 and 8, it has also been discovered that a T-shaped cross-section filament can be extruded without kneeing and the formation of drips by extruding filament-forming material through a split T orifice 39 illustrated in FIG. 7 independent of the positioning of the T orifice with respect to the center of the spinnerette. Moreover, it has been discovered that with extrusion of filament-forming material through a split T orifice, it is possible to form T-shaped filaments having a much improved definition of T cross-section and having a much higher FAR than heretofore deemed possible. Such higher FAR values are partticularly useful in carpet applications wherein higher denier per filament yarns are used. 7

Furthermore, in contrast to the regular T-shaped orifice, the split T orifice allows spinning of filaments having a relatively well defined T cross-section over a wide range of spinning conditions thereby allowing for better control of yarn properties, such as tenacity and elongation, and better process economies.

The split T orifice 39 in spinnerette plate 40 is more clearly illustrated in FIG. 8. The orifice has a slot forming crossbar 41 having a length L and width W and a slot forming tail or stem 42 having a length L" and width W". Stem 42 depends perpendicularly from crossbar 41 at substantially the midpoint of crossbar 41. The dimensions of crossbar 41 and stem 42 of the split T correspond to those given for the regular T-shaped orifice wherein the stem is preferably greater than one-half the length of the crossbar. However, stem 42 is spaced from the crossbar 41 so as to form a gap s therebetween by a distance which may be from about 0.0001 inch to about 0.008 inch, more preferably about 0.002 inch.

The filament-forming material streams extruding from the split T orifices 39 in spinnerette plate 40 as pairs of ribbons (not shown) coalesce in a zone about to /2.

inch from the face of the spinnerette plate to form a relatively well defined T-shaped filament 43 as shown in FIG. 9. As shown by the drawing, filament 43 has three

asymmetrical lobes

44, 45, 46 integrally joined together and forming one convex side 47 and two concave sides 48 and 49. The filament is seen to be asymmetrical with respect to line 50-50 which bisects convex side 47 and the longer of the three lobes 45.

While the invention has been described more specifically above with respect to melt spinning fiber forming material, it is deemed applicable broadly to all types of fiber forming materials Whether such materials are melt spun, dry spun or wet spun although melt spinning is most preferred to obtain the definition of filament cross-section more specifically described herein. Illustrative of those melt spinnable polymers which may be used in the practice of this invention are the polyamides, such as polyhexamethylene adipamide, and polyepsiloncaprolactam, polyesters such as polyethylene terephthalate or copolymers derived from ethylene glycol, terephthalate acid and up to 15 mol percent of some other dibasic acid, polyethylene, polypropylene and meltable cellulose derivatives. In addition, plasticized melt spinnable fibers such as acrylonitrile may be utilized.

In preparing the filaments of the present invention, various additives may be included in the filament-forming composition, e.g. delustrants, oxidation inhibitors, dye additives and the like. The denier of the filaments may vary within wide limits. Denier in the range of from 1.0 to 20.0 are usually preferred, however, deniers of 40 or higher may be utilized, depending on the end use of the textile material being prepared.

The invention will be more fully described in the following examples which are deemed illustrative and not intended to be limiting.

Example 1 A A inch stainless steel spinnerette plate was prepared according to conventional techniques having 24 T-shaped orifices therein, such being annularly arranged as is shown in FIG. 1 of the drawing. The crossbar of the T-shaped orifices had a length of about 0.020 inch and a width of about .006 inch, and the stem, which as is shown in FIG. 1, is directed toward the center of the spinnerette, had a length of about 0.020 inch (not including the crossbar width), and a width of about 0.004 inch.

Polyethylene terephthalate, having an intrinsic viscosity of 0.60 deciliters per gram (as measured at 25 degrees centigrade using 8 grams of polymer in cubic centimeters of O-chlorophenol), and containing 0.4 percent titanium idoxide, was spun at 3.5 pounds per hour throughput at a spinning temperature of about 285 degrees centigrade from the spinnerette described above using a standard metering pump. The filaments extruding from the spinnerette were quenched with an 8 cubic feet per minute air inflow and were collected in a single filament bundle. The filament bundle was wound up at a speed of about 3500 feet per minute (f.p.m.). The filament bundle had a spun denier of about 230. The FAR was determined by measurement (as described in column 5) and was found to be 2.0. Photographs of the crosssection of the spun filaments were taken at 400x magnification and the cross-section was generally that as is shown in FIG. 6. The cross-sectional shape, as one can determine from examining FIG. 6 was a distorted T with a bulging crossbar and a relatively small tail-like stem.

Example 2 Polyethylene terephthalate polymer as in Example 1 was extruded through the same spinnerette as described therein at a spinning temperature of about 300 degrees centigrade at a throughput of 1.75 pounds per hour. The extruded filaments were collected and wound up at 3500 feet per minute. The spun denier was 120. The resulting filament aspect ratio was determined to be 1.2.

In both Examples 1 and 2 the stern of the T was directed toward the center of the spinnerette and all filaments during their extrusion tended to knee inwards. Frequent thread line breaks were experienced at a rate which generally would not be commercially acceptable. Attempts at equalizing the areas of both the stem and the crossbar did not eliminate the kneeing problem.

Example 3 A spinnerette having 36 T-shaped orifices arranged annularly, with respect to the center of the spinnerette plate, wherein the crossbar dimension was 0.018 inch by 0.004 inch and the stem dimension was 0.018 inch by 0.004 inch was prepared according to conventional techniques. However, in contrast to the spinnerette described in Example 1, the stem of the T-shaped orifice was pointed away from the center of the spinnerette as is shown in FIG. 3 of the drawing.

Polyethylene terephthalate polymer having an intrinsic viscosity of 0.60 was extruded through the T-shaped holes at a throughput of about 4.3 pounds per hour at a spinning temperature of about 290 degrees centigrade to provide a bundle of filaments having a total denier of 230. A controlled quench of standard cubic feet per minute air was employed. The filament bundle was wound up at 4000 feet per minute. The filaments were determined to have a filament aspect ratio of 2.1.

Quite unexpectedly, the filaments did not knee during extrusion and no breaks or coalescence of filaments were experienced during the spinning run. In the same manner, a similar spinnerette having a 0.018 by 0.004 inch crossbar and a 0.016 by 0.004 inch stem was used to spin lower denier per filament yarn with correspondingly good results.

Example 4 A spinnerette having a plurality of pairs of slots, seven in number,-was manufactured according to usual techniques with the pair of slots arranged annularly, as shown in FIG. 7, to form a circle of split T orifices. The slot forming the crossbar of the T was 0.025 by 0.004 inches and the slot forming the stem of the T was 0.020 by 0.004. The bridge or spacing separating the crossbar slot and stem slot was about 0.002 inch.

Polyethylene terephthalate polymer having an intrinsic viscosity (I.V.) of about 0.60 was extruded at a rate of about 3 pounds per hour throughput through the described spinnerette at a spinning temperature of about 290 degrees centigrade thereby producing a bundle of filaments having a spun denier of about 70. The filament bundle was wound up at about 1750 feet per minute.

The polymeric material extruding from the cross-bar and stem slots was quenched with an air inflow of about 8 standard cubic feet per minute and coalesced at about one-fourth inch from the spinnerette face to form a filament having a T cross-section.

In contrast to the T-shaped filament shape formed by extruding filament-forming material through a regular T-shaped orifice, the filament as shown in FIG. 9 of the drawing had a well defined T cross-sectional shape. The filament aspect ratio was determined to be 3.28.

Yarn comprising filaments with the cross-sectional configuration specified in this invention are useful in a wide variety of textile products. They may be used to advantage in all sorts of woven materials including hosiery, lingerie and other light weight knit structures. They are useful as feed yarns in a large number of bulking processes such as the well known stufier box crimping process, the jet bulking process and the various false twist crimping techniques. The crimped product prepared by any of these processes may be used in sweaters, upholstery, carpets, underwear, Shirting materials and the like. The crimped product may also be cut up into staple and recombined in the form of a staple yarn. These yarns, of course, are useful for preparing suiting materials, sweaters and a wide variety of bulky textile materials.

While the invention of the split T spinnerette has been described more particularly with respect to a rectangular end on the stem extension next to the crossbar, particularly good results are also obtained when the stem end is brought into extremely close proximity to the crossbar with the shape of the end of the stem modified to a tapered or pointed configuration. In particular, an angled point or curved end produces particularly good results when the projecting end is positioned from just touching the crossbar up to about 0.008 inch away from the crossbar. The polymer flow characteristics from such orifice configurations produce results corresponding to the more fuly described split T orifice.

It will be apparent that modification of this invention will occur to persons skilled in the art and all such are considered to fall within the spirit and scope of the invention as defined in the following claims.

What is claimed is:

1. A method of forming filaments having a T-shaped cross section comprising melt extruding a filament forming polymeric material through a spinnerette having a plurality of T-shaped orifices, said orifices being arranged annularly with respect to the center of the spinnerette, each of said T-shaped orifices comprising a cross bar and a stem extending perpendicularly from the cross bar at its mid point, at least half of said stems facing away from the center of the spinnerette, said orifice having a hole aspect ratio (HAR) of about 2.6 to 86 as expressed by the equation: HAR=Y/Z+X/Z wherein Y is the distance from the center of the cross bar to the end of the stem, X is the distance from the center of the cross bar to the end of said cross bar and Z is the distance from the center of the cross bar to the intersection or projected intersection of the cross bar stem.

2. The method of claim 1 wherein the filament forming material is a polyamide.

3. The method according to claim 1 wherein the filament forming material is a polyester.

4. The method according to claim 3 wherein the polyester is polyethylene terephthalate.

5. The method acording to claim 3 wherein the filaments are defined by a filament aspect ratio (FAR) of from about 1.2 to 5.0 in accordance with the expression:

A'I-=melt spinning temperature in degrees centigrade minus 290 C.

AV=extrusion velocity in feet per minute minus 31 AI.V.=polymer intrinsic viscosity minus 0.64

EARL-spinnerette hole aspect ratio minus 6.70

Q=inflow quench in standard cubic feet per minute minus 5 and wherein the HAR is between from about 2.6 to about 86.

6. Method of forming filaments having a pronounced T-shaped cross-section comprising melt extruding a filament forming material through a split T orifice comprising a crossbar and a stem which is substantially perpendicular to the crossbar at its midpoint, said stern and crossbar being positioned from each other so as to form a coalesceable bridge therebetween, extruding said filament-forming material from the crossbar and stem and coalescing the extrudant material to form a filament having a T-shaped cross-section.

7. The method of extruding a filament according to claim 6 wherein the bridge is produced by close proxim ity of the stem to the crossbar in a distance of up to about 0.008 inch.

1 1 1 2 8. The method according to claim 7 wherein the fila- 3,156,085 11/1964 Jamieson 264177 F ment forming material is polyester. 3,156,607 11/1964 Strachan 264177 F 9. The method according to claim 7 wherein the fila- 3,340,571 9/1967 Bishop et a1. 264177 F ment forming material is polyamide. 3,493,459 2/1970 McIntosh et a1. 264177 F 5 3,499,958 3/1970 Stuchlik 264177 F References Cited 3,652,753 3/1972 Shemdin 264177 F UNITED STATES PATENTS JAY H. WOO, Primary Examiner 3,078,544 2/1963 Shealy 264171 3,121,040 2/1964 Shaw et a1. 264--177 F U.S. Cl. X.R.

3,135,646 6/1964 Hayden 264177 F 10 264176 F