This invention concerns improvements in and relating to polyester (continuous) mixed-filament yarns of differing filament denier and/or cross- section, including fine filaments, and preferably to such yarns with a capability of providing from the same feed stock polyester mixed-filament yarns of various differing properties; including improved processes and new products therefrom.

Historically, synthetic fibers for use in apparel, including polyester fibers, have generally been supplied to the textile industry for use in fabrics and garments with the object of more or less duplicating and/or improving on natural fibers. For many years, commercial synthetic textile filaments, such as were made and used for apparel, were mostly of deniers per filament (dpf) in a similar range to those of the commoner natural fibers; i.e., cotton and wool. More recently, however, polyester filaments have been available commercially in a range of dpf similar to that of natural silk, i.e. of the order of 1 dpf, and even in sub deniers, i.e., less than about 1 dpf, despite the increased cost. Various reasons have been given for the recent commercial interest in such lower dpfs, such as about 1 dpf, or even sub deniers.

Our so-called "parent application" WO 92/13 19, the disclosure of which is hereby incorporated herein by reference, was concerned with the preparation of fine filaments by a novel direct melt spinning/ winding process, in contrast with prior processes of first spinning larger filaments which then needed to be further processed, in a coupled or a separate (split) process involving drawing, to obtain the desired filaments of reduced denier with properties suitable for use in textiles. The filaments of the "parent application" are "spin-oriented"; that is, produced as "undrawn" filaments. The significance of this is discussed in the art and hereinafter.

We have found that consumer reaction to fine filament textile (flat or textured) yarns (all filaments being of the same cross-section and ^" the same denier, and especially wherein the filaments are of denier less than aoout 1), has tended to limit their use to selected textile fabrics where fabric "body" and "drape" has not been important or where providing such fabric "body" and "drape" through twisting of the multi-filament yarns and/or change in fabric

construction is too expensive for the particular end-use and/or where such changes adversely affect other properties (such as visual and tactile aesthetics) that make such fabrics undesirable. It would be desirable to make fine textile fabrics with desired "body" and "drape" from fine filament ya s without twisting of the fine filament yams and/or change in fabric construction. It would also be desirable to provide spin-oriented undrawn fine filament yams that, depending on their combination of properties, can be used as direct-use yams or as draw feed yams (e.g., to provide drawn flat yams or textured "bulky" yams) that can provide fabric "body" and "drape" without having to incur costly yam twisting, for example, and without having to change fabric construction and compromise visual and tactile fabric aesthetics.

It is important to maintain uniformity, both along-end and between the various spin-oriented filaments and drawn filaments therefrom. Lack of uniformity often shows up in the eventual dyed fabrics as dyeing defects, so is undesirable.

For textile purposes, a "textile yam" must have certain properties, such as sufficiently high modulus and yield point, and sufficiently low shrinkage, which have distinguished conventional textile yams from conventional "feed yams" that have require further processing to provide the minimum properties required for making textiles and subsequent use. Generally, herein, we refer to untextured filament yams as "flat yams" and to undrawn flat filament yams by terms such as "feed" or "draw-feed" ya s. Filament yams which can be used as a textile yam without need for further drawing and/or heat treatment are referred herein as "direct-use yams".

It is important to recognize that what is important for any particular end-use is the combination of all the properties of the specific yam (or filament), sometimes in the yam itself during processing, but also in the eventual fabric or garment of which it is a component. It is easy, for instance, to reduce shrinkage by a processing treatment, but this modification is generally accompanied by other changes, so it is the combination or balance of properties of any filament (or staple fiber) that is important. It is also understood that the filaments may be supplied and/or processed according to the invention in the form of a yam or as a bundle of filaments that does not necessarily have the coherency of a true "yarn", but for convenience herein a plurality of filaments

may often be referred to as a "yam" or "bundle", without intending specific limitation by such term. It will be recognized that, where appropriate, the technology may apply also to polyester filaments in other forms, such as tows, which may then be converted into staple fiber, and used as such in accordance with the balance of properties that is desirable and may be achieved as taught hereinafter.

The polyester polymer used for preparing spin-oriented undrawn fine mixed-filament yams of the invention may be the same as for the "parent application".

The spin-orientation process for preparing polyester undrawn fine mixed-filament feed yams comprised of two or more types of filaments that differ, by cross-section and/or denier wherein at least one of the filament components has denier less than about 1; preferably wherein the average yam filament denier when drawn to 30% elongation is less than about 1; and especially wherein the average yam filament denier of the fine mixed-filament yam is less than about 1, is essentially the same process as the "spin-orientation" process of the "parent application" (described herein in the "Background of the Parent Application" and in the discussion of Figures 4A, B, and C), except for the selection of spinneret capillary dimensions (L and D) and exit orifice shape, to co-spin two or more different filament components; and spinning hardware configuration modifications, if needed, to quench and converge the different filament components into a mixed-filament bundle prior to interlacing and winding into packages.

It was very surprising to us that such mixtures of deniers and cross-sections could be cospun from a single spinneret with uniformity, as desired, in view of previous attempts to cospin mixtures of polyester filaments at higher dpfs, and to cospin mixtures of polyester filaments at prior art low speeds to provide undrawn filaments of low orientation. There is something unique about the process technique of the parent application that makes possible such a surprising result.

As will be understood, particularly useful mixed-filament draw feed yams have two types of filaments, one of which has a dpf less than about 1, and is referred to as "(dpf)i" while the dpf of the other is not only greater

than 1 as regards the draw feed yam but also such that the resulting dpf is greater than 1 even after drawing to the desired extent, such as to the desired residual draw ratio (RDR).

It is generally desirable that the RDRs of both types of drawn filaments be in the approximate range 1.2X to 1.4X. It is also desirable that the draw feed yams be drawable without incurring broken filaments or "neck-drawn" defects. It is desirable, accordingly, for the RDRs of both types of filaments to differ by less than about 40%, so that the RDRs of the types of the drawn filaments differ by about 20% or less. Providing a higher dpf filament of odd (non-round) cross-section can be a very effective technique for achieving the desired objective(s).

Mixed-filament yams of differing dpfs (one type more than 1 and the other less than one) of different cross-sections and that are "flat" are expected to be desirable for tactile and aesthetic reasons. Similar mixed-filament yams that are direct-use yams in which all filaments are of low shrinkage are also expected to be useful. In this regard, non-round cross-sections for the higher dpf filaments are expected to provide a useful way to obtain the desired objective.

The yams prepared by the process of the invention may be used as: 1) draw feed yams (such as drawing in split or coupled processes, warp- draw processes, draw air-jet texturing, draw false-twist texturing, draw gear- crimping and draw stuffer-box crimping); 2) undrawn fine mixed-filament ya s capable of being used as direct-use "textile" mixed-filament yams without need for further drawing and/or heating; 3) undrawn direct-use "textile" yams that may be used as feed yams without drawing as in air-jet texturing, stuffer-box and gear-crimping to provide bulky textile filament yams; 4) undrawn direct-use "textile" fine mixed-filament yams that are capable of being partially or fully drawn with or without heat and with or without post heat-treatment to uniform fine mixed-filament yams.

The spin-orientation process of the process, described herein before, provides a spin-oriented polyester undrawn fine mixed-filament ya , wherein the polyester polymer is characterized by a relative viscosity (LRV) in the range of about 13 to about 23, a zero-shear melting point (T^ ⁰ ) in the range

of about 240 C to about 265 C, and a glass-transition temperature (Tg) in the range of about 40 C to about 80 C; and wherein the mixed-filament yam, comprised of two or more filament components that differ in cross-section and/or denier such that at least one filament component has a filament denier less than about 1 (preferably having an average yam filament denier (dpf) _s such that the average drawn yam filament denier (dpf)D is less than about 1, where (dpf)o is defined by {(dpf) _s x[(1.3)/(l + Eb/100) _s }; and especially where the undrawn yam average filament denier (dpf) _s is less than about 1) such that for mixed-denier ya s the filament denier ratio of the high denier filaments (2) to the low denier filaments (1) is about 2 to about 6; and further characterized by: a maximum dry heat shrinkage tension STmax less than about 0.2 g/d at a dry heat peak shrinkage tension temperature T(ST _max ) about 5 C to about 30 C greater than about the polymer glass-transition temperature Tg; a (1-S/Sm) value at least about 0.1 (and preferably at least about 0.25) to provide age stability shrinkage; an elongation-to-break (Eg) about 40% to about 160% (preferably about 90% to about 120% for draw feed yams, and especially about 40% to about 90% with a (1-S/Sm) value of at least about 0.85 for use as an undrawn direct-use yam); a tenacity-at-7% elongation (T7) in the range of about 0.5 and about 1.75 g/d (preferably in the range of about 0.5 to about 1 g/d (and especially such that the tenacity-at-7% elongation T7 is less than the tenacity-at- 20% elongation T20 for improved draw stability) for a draw feed yam and especially in the range of about 1 to about 1.75 g/d for use as a direct-use yam); and a break tenacity (Tβ) _n , normalized to 20.8 polymer LRN, at least about 5 g/d (preferably at least about 6 g/d); and preferably having a Shrinkage Differential (DHS-S) of less than +2 % .

The undrawn mixed filament yams of the invention provide for drawn flat or air-jet textured mixed-filament yams, having a filament Shrinkage Differential of at least 5%, prepared by drawing the undrawn mixed-filament ya s at a temperature in the range of about the polymer glass-transition temperature (Tg) and about the onset temperature of major crystallization (T _c °) and further characterized by a residual elongation-to-break (Eg) about 15% to about 45%, and a tenacity-at-7% elongation (T7) at least about 1 g/d; and especially drawn mixed-filament flat and air-jet textured yams having a Shrinkage Differential of at least 5 % by cold drawing without post heat setting the undrawn direct-use mixed-filament yams, described herein above and

wherein the cold drawn differential mixed-filament yams are further characterized by a residual elongation-to-break (Eg) about 15% to about 55 % , and a tenacity-at-7% elongation (T7) at least about 1 g/d.

The invention provides uniform drawn polyester flat and textured fine mixed-filament yams, prepared from the undrawn fine mixed-filament feed yams of the invention as described herein before, of an elongation-to-break (Eg) about 15 to about 45%, a (1-S/Sm) value at least about 0.85, a tenacity-at-7% elongation (T7) at least about 1 g/d, preferably a post-yield modulus (Mpy) about 5 to about 25 g/d; and preferably wherein the drawn flat fine-mixed filament yams are further characterized by an along-end uniformity as measured by an along-end denier spread (DS) of less than about 3% (especially less than about 2%).

Further aspects and embodiments of the invention will appear hereinafter.

Figure 1A is a representative enlarged photograph of cross-sections of filaments for which post-coalescence was incomplete (herein called "opens") and which are believed novel and useful and inventive; Figure IB is a representative enlarged photograph of cross-sections of round filaments according to the invention (claimed herein) with a concentric longitudinal void (hole); and Figure IC is a representative enlarged photograph of filaments of a textured hollow filament yam, also according to the invention, showing that the void is almost completely collapsed on draw false-twist texturing.

Figure IB plots the ratio (dpf)2/( ^r )l for co-spun round filaments 1 and 2 vs (LiD2/L2Di) ⁿ (D2/Di) ³ , which is a simplified expression of [(L/D) ⁿ /D ³ ] !/[(L/D) ⁿ /D ]2 for spinneret capillaries (1) and (2) of length (L) and diameter (D), (the value of "n" is 1 for Newtonian fluids; for the range of polymer LRV and process conditions used herein, the value of "n" is experimentally found to be about 1.1, in other words, n = 1 is a useful practical approximation herein).

Figure 2A is a representative plot of boil-off shrinkage (S) versus elongation-to-break (Eg) wherein Lines 1, 2, 3, 4, 5, and 6 represent (1-S/S _m )- values of 0.85, 0.7, 0.5, 0.25, 0.1 and 0, respectively; and curved line 7 represents a typical shrinkage versus elongation-to-break relationship for a series

of yams formed, for example, by increasing spinning speed, but keeping all other process variable unchanged. Changing other process variables (such as dpf or polymer viscosity) produces a "family" of similar curves, essentially parallel to each other. The vertical dashed lines denote ranges of approximate EB- values for preferred filaments of the invention, i.e., 40% to 90% for direct-use, and 90% to 120% for draw feed yams, with 160% as an approximate upper limit, based on age stability. The preferred filaments of the invention suitable as a draw feed yam, are denoted by the "widely-spaced" W W W -area, having Eβ-values of about 90% to 120% and a (1-S/S _m ) ratio of at least about 0.25 (below line 4). The preferred filaments of the invention suitable as direct use textile yams are denoted by "densely-spaced" W W W -area, having Eg-values of about 40% to 90%, and a (1-S/S _m ) ratio of at least about 0.85 (below line

1).

Figure 2B is a representative plot of boil-off shrinkage (S) of spin-oriented "solid" filaments (not according to the invention) having a wide range of elongations-to-break Eg from about 160% to about 40% , spun using a wide range of process conditions (e.g., filament denier and cross- section, spin speed, polymer LRN, quenching, capillary dimensions (LxD), and polymer temperature Tp) versus volume percent crystallinity (Xv), measured by flotation density, and corrected for % pigment. The single relationship between S and density (i.e., a measure of the extent of stress-induced crystallization of the amorphous regions during melt-spinning, SIC) obtained for yams of such differing Eg-values supports the view that the degree of SIC is the primary structural event and that the degree of stress-induced orientation of the amorphous regions during melt-spinning (SIO) is a secondary structural event in this range of Eg-values for determining the degree of S. The range of S from about 50% to about 10% corresponding to a range of Xv of about 10 to 20% (a- b) is the preferred level of SIC for draw feed ya s and the range of less than about 10% shrinkage corresponding to Xv greater than about 20% is preferred level of SIC for direct-use tensile yams (b-c).

Figure 3 A is a representative plot of T _cc (the peak temperature of "cold crystallization" (T _cc ), as measured by Differential Scanning Calorimetry (DSC) at a heating rate of 20 C per minute), versus amorphous birefringence, a measure of amorphous orientation (as expressed by Frankfort and Knox). For filaments for which measurement of birefringence is difficult, the value of T _cc

is a useful measure of the amorphous orientation. The filaments of the invention have T _cc values between about 90 C and 110 C.

Figure 3B is a representative plot of the post-yield secant modulus (Tan beta) (i.e., "Mpy") versus birefringence. The Mpy herein is calculated from the expression (1.20 T20-1.07 T7)/0.13, where T20 is the tenacity at 20% elongation, T7 being the tenacity at 7% elongation. As may be seen, above about 2 g/d, the post-yield modulus (Mpy) provides a useful measure of birefringence of spin-oriented, drawn, and textured filaments. Preferred drawn filaments of the invention have Mpy values of about 5 to 25 g/d.

Figure 4A is a graphical representation of spinline velocity (V) plotted versus distance (x) from the face of the spinneret, where the spin speed increases from the velocity at extrusion (V ₀ ) to the final (withdrawal) velocity after having completed attenuation (typically measured downstream at the point of convergence, V _c ); wherein, the apparent internal spinline stress is taken as being proportional to the product of the spinline viscosity at the neck point (i.e. , herein found to be approximately proportional to about the ratio LRV(T _m °/Tp)6, where the temperatures are in Degrees C),and the velocity gradient at the neck point (dV/dx) (herein found to be approximately proportional to about V^/dpf , especially over the spin speed range of about 2 to 4 km/min, and proportional to about V^^/ pf at higher spin speeds, e.g., in the range of about 4 to 6 km/min). The spin line temperature is also plotted versus spinline distance (x) and is observed to decrease uniformly with distance as compared to the sharp rise in spinline velocity at the neck point. Process conditions are selected to provide during attenuation the development of an apparent internal spinline stress in the range of about 0.045 to about 0.105 g/d for preparing spin-oriented filaments, especially suitable for draw feed yams (DFY), characterized with tenacity-at-7% -elongation (T7) values in the range of about 0.5 to about 1 g/d, and an apparent internal spinline stress in the range of about 0.105 to about 0.195 g/d for preparing spin-oriented filaments especially suitable for direct-use yams (DUY), characterized by tenacity-at-7% -elongation (T7) in the range of about 1 to about 1.75 g/d; wherein, the apparent internal spinline stress is expressed herein by an empirical analytical expression: k(LRV/LRV20.8)(TR/Tp)6(V ² /dpf)(A _o /# _c ) ⁰ - ⁷ , wherein k has an approximate value of (0.01/SOC) for spin-oriented filaments of density in the range of about

1.345 to about 1.385 g/cm ³ , that is about 1.36 g/cm ³ and SOC is the "stress- optical coefficient" for the polyester polymer (e.g., about 0.7 in recipro al g/d for 2GT homopolymer); TR is the polymer reference temperature defined by (TM ^{0 + 4} 0 C) where T^j ⁰ is the zero-shear (DSC) polymer melting point; Tp is the polymer melt spin temperature, C; V is the withdrawal speed expressed in km/min; # _c is the number of filaments (i.e., capillaries) for a given extrusion surface, A ₀ , expressed as # _c /cn-2; LRV is the measured polymer (lab) viscosity and LRV20.8 is ^me corresponding reference LRV-value (where LRV is defined herein after) of the polyester polymer having the same zero-shear "Newtonian" melt viscosity at 295 C as that of 2GT homopolymer having an LRV-value of 20.8 (e.g., cationic-dyeable polyester of 15 LRV is found to have a melt viscosity as indicated by capillary pressure drop in the range of 2GT homopolymer of about 20 LRV and thereby a preferred reference LRV for such modified polymers is about 15.5 and is determined experimentally from standard capillary pressure drox measurements).

Figure 4B is a graphical representation of the birefringence of the spin-oriented filaments versus the apparent internal spinline stress, the slope of which is referred to as the "stress-optical coefficient, (SOC), Lines 1, 2, and 3 have SOC values of 0.75, 0.71, and 0.645 (g/d)"*, respectively, and are typical relationships found in literature for 2GT polyester. Thus, an average SOC is about 0.7.

Figure 4C is a graphical representation of the tenacity-at-7% - elongation (T7) of the spin-oriented filaments versus the apparent internal spinline stress. The near linear relationships of birefringence and T7 (each versus the apparent internal spinline stress) permits the use of T7 as a practical measure of the filament average molecular orientation. Birefringence is a very difficult structural parameter to measure for fine filaments with deniers less than 1 and especially of odd-cross-section (including hollow filaments).

Figure 5 is a representative plot of the elongations-to-break (Eg) of spin-oriented undrawn nylon (I) and polyester (II) versus spinning speed. Between about 3.5 Km/min and 6.5 Km/min (denoted by region ABCD) and especially between about 4 and 6 Km/min, the elongations of undrawn polyester and nylon filaments are of the same order. The elongation of the undrawn nylon filaments may be increased by increasing polymer RV (Chamberlin U.S. Patent

4,583,357 and 4,646,514), by use of chain branching agents (Nunning U.S. Patent 4,721,650), or by use of selected copolyamides and higher RV (Knox EP Al 0411774). The elongation of the undrawn polyester may be increased by lower intrinsic viscosity and use of copolyesters (Knox U.S. Patent 4, 156,071 and Frankfort and Knox U.S. Patents 4, 134,882 and 4, 195,051), and by incorporating minor amounts of chain branching agents (MacLean U.S. Patent 4,092,229, Knox U.S. Patent 4,156,051 and Reese U. S. Patents 4,883,032, 4,996,740, and 5,034, 174). The elongation of polyester filaments is especially responsive to changes in filament denier and shape, with elongation decreasing with increasing filament surface-to-volume (i.e., with either or both decreasing filament denier and non-round shapes).

Figure 6 shows the relationship between the relaxation/heat setting temperature TR, (in degrees C) and the residual draw ratio of the drawn yams (RDR)D for nylon 66 graphically by a plot of [1000/(TR, +273)] VS. (RDR)D as described by Boles et al in U. S. Patent No. 5,219,503. Drawn filaments, suitable for critically dyed end-uses are obtained by selecting conditions met by the regions I (ABCD) and II (ADEF). Acceptable along-end dye uniformity is achieved if the extent of drawing and heat setting are balanced as described by the relationship: 1000/(T _R , + 273) > /= [4.95 - 1.75(RDR) _D j. This relaxation temperature vs. (RDR)D relation is also applied when co- drawing and heat-relaxing mixed-filament ya s, or heat- relaxing previously drawn and co-mingled mixed-filament yams, such as co-drawn mixed-filament yams, such as nylon/polyester filament yams.

The undrawn fine mixed-filament yams of the invention are formed, essentially, according to the process of the "parent application" except for modifications to permit two or more different type filaments to be co-spun, quenched, and converged into a fine mixed-filament bundle. For example, mixed-denier filament ya s may be provided by combining filament bundles of different filament deniers and or cross-sections spun from the same or from different spin packs prior to interlacing and winding, but preferably prior to convergence and finish application. Advantageously, if desired, yams may be prepared according to the invention from undrawn feed yams that have been treated with caustic in the spin finish (as taught by Grindstaff and Reese in U.S. Patent No. 5,069,844) to enhance their hydrophilicity and provide improved moisture-wicking and comfort.

The degree of stress-induced (amorphous) orientation (SIO) imparted to these m-j'-awn filaments during melt attenuation lowers the peak temperature of cole ^• " ^tallization (T _cc ), where the T _cc is typically about 135 C for amorphous unor 1 filaments and which ?s decreased to less than 100 C with increased stress-i. ι. ed orien u on (SIC ^' the non crystalline

(amorphous) polymer chains. This is _fe raphica .lustrated in Figure 3A by a plot of the peak temperature of cold crystallization T _cc versus amorphous birefringence [as defined by Frankfort and Knox]. The amorphous birefringence is known to increase with increasing spinning speed, and thereby with decreasing elongation-to-break (Eg) of the undrawn filaments. For the preferred undrawn spin-oriented filaments with elongations (Eg) in the range of 40 to about 120%, the measured T _cc - values in the range of about 90 C to about 110 C which is believed to permit the onset of further crystallization even under mild drawing conditions and is believed, in part, to be important in providing uniform drawn polyester fine mixed-filament yams even when drawn cold.

The degree of stress-induced crystallization (SIC), a consequence of the extent of the SIO of the amorphous regions, is conventionally defined by the density of the polymeric material which is experimentally difficult to measure for fine filament ya s because of air entrapment between the fine filaments and onto the large surface area of the fine filaments; hence, a relative measure of stress-induced crystallization (SIC) is used herein based on the extent of boil-off shrinkage (S) for a given yam elongation-to-break (Eg). For a given fiber polymer crystallinity the boil-off shrinkage (S) is expected to increase with molecular extension (i.e., with decreasing elongation-to-break, Eg); and therefore a relative degree of stress-induced crystallization (SIC) is defined, herein, by the expression: (1-S/S _m ), where S _m is the expected maximum shrinkage for filaments of a given degree of molecular extension (Eg) in the absence of crystallinity; and S _m is defined herein by the expression: S _m (%) =

([(EB)max-EB)]/[( ^E B)max+ 100])100% » wherein (E _B ) _max is the expected maximum elongation-to-break (Eg) of totally amorphous "isotropic" filaments.

For polyester filaments spun from polymer of typical textile intrinsic viscosities in the range of about 0.56 to about 0.68 (corresponding to LRV in the range of about 16 to about 23), the nominal value of (Eg) _max is experimentally found to be about 550% providing for a maximum residual draw ratio of 6.5 (High Speed Fiber Spinning, ed. A. Ziabicki and H. Kawai, Wiley Interscience

(1985), page 409) and thus, S _m (%) may in turn be defined, herein, by the simplified expression: S _m , % = [(550-Eg)/650] xl00% (graphically represented in Figure 2A). The filaments of the invention are described by having a (1-S/S _m ) value of greater than about 0.1 (and preferably greater than about 0.25) to provide sufficient SIC for age stability) and an elongation (Eg) between about 40 and about 160%.

The spin-oriented mixed-filament yams of the invention are characterized by a maximum shrinkage tension (ST _max ) of less than about 0.2 g/d occurring at a shrinkage tension peak temperature T(ST _max ) in the range 5 C to about 30 C greater than about the polymer Tg (e.g., 70 - 100 C for homopolymer 2GT with polymer Tg about 65 C; where preferred undrawn fine mixed-filament feed yams are further characterized by an elongation-to- break (Eg) in the range of about 90% to about 120%, a tenacity-at-7% elongation (T7) in the range of about 0.5 to about 1 g/d; and a (1-S/S _max )- value of at least about 0.25; and especially preferred undrawn filament ya s suitable for use as direct-use ya s are further characterized by an elongation-to- break (Eg) in the range of about 40% to about 90%, a tenacity-at-7% elongation (T7) in the range of about 1 and 1.75 g/d, and a (l-S/S _m )-value of at least about 0.85.

Denier per filament of a mixed-filament yarn spun from the same spinneret is determined by capillary mass flow rates, w = (Vs x dpf)/9000, through the spinneret capillary which is inversely proportional to the capillary pressure drop (herein taken as being approximately proportional (L/D) ⁿ /D ³ ) where n has a value of 1 for Newtonian fluids, and L is the capillary length and D is capillary diameter. For non round cross-section capillaries of conventional short lengths, the value of (L/D) ⁿ /D ³ is taken from that of the metering capillary that feeds the polymer into the shape determining exit orifice; such that, (dp l x [(L/D) ⁿ /D ] ₁ = (dpf>2 x [(L/D) ⁿ /D ]2 and therefore the ratio (dpf)2/(dpf)l] = [(L/D) ⁿ /D ³ ]l/[(L/D) ⁿ /D ³ - ² . For example, co-spinning using spinnerets with metering capillaries of 15x72 mils and 8x32 mils, will provide filaments of mixed dpf in the ratio (dpf)2/(dpf)i) of about 476.7mm ³ /86.5mm ² (= 5.5) for a value of n about 1.1 for the range of process conditions used herein. If spinning filaments of different cross-section, but of the same dpf, it may be required that the metering capillaries be of slightly different dimensions (i.e. , of different [(L/D) ⁿ /D ³ ]-values so to overcome any small, but

meaningful, differences in the pressure drop of the shape forming exit orifices. However, if spinning the different filament components from separate spin packs and combining them into a single mixed-filament bundle, for example; then the dpf of the filaments from a given spin pack is independent of pack pressure and spinneret dimensions and is simply given by: dpf =

9000W/(V _s #p), where W is the total spin pack mass flow rate (g/min), #p is the number (#) of filaments (F) per spin pack, and V _s is the withdrawal speed expressed as m/min.

In particular the invention includes, but not limited to, the following processes (and products therefrom):

(1) A spin-orientation process of the invention provides spin- oriented polyester undrawn fine mixed-filament yams, wherein the polyester polymer is characterized by a relative viscosity (LRV) in the range of about 13 to about 23, a zero-shear melting point (TJ^J ⁰ ) in the range of about 240 C to about 265 C, and a glass-transition temperature (Tg) in the range of about 40 C to about 80 C; and wherein the mixed-filament yam, comprised of two or more filament components that differ in cross-section and/or denier such that at least one filament component has a filament denier less than about 1 (preferably having an average yam spun filament denier (dpf) _s such that the average drawn yam filament denier (dpf)τj> is less than about 1, where (dpf)D is defined by

{(dpf) _s x[(1.3)/(l + Eb/100) _s }; and especially where the undrawn yam average filament denier (dpf) _s is less than about 1, such that for mixed-denier yams the filament denier ratio of the high denier filaments (2) to the low denier filaments (1) is about 2 to about 6; and further characterized by: a maximum dry heat shrinkage tension STmax less than about 0.2 g/d at a dry heat shrinkage tension peak temperature T(ST _max ) about 5 C to about 30 C greater than about the polymer glass-transition temperature Tg; a (1-S/Smax) value at least about 0.1 (and preferably at least about 0.25) to provide age stability shrinkage; an elongation-to-break (Eg) about 40% to about 160% (preferably about 90% to about 120% for draw feed yams wherein there is essentially no loss of void content on drawing, and especially about 40% to about 90% with a (1-S/Sm) value of at least about 0.85 for use as draw feed yam or as an undrawn direct-use yam); a tenacity-at-7% elongation (T7) in the range of about 0.5 and about 1.75 g/d (preferably in the range of about 0.5 to about 1 g/d for a draw feed yam and especially in the range of about 1 to about 1.75 for use as a direct-use yam);

and a break tenacity (Tg) _n , normalized to 20.8 LRV, at least about 5 g/d (preferably at least about 6 g/d); and preferably having a difference (DHS-S) of less than +2%.

The spin-orientation process is characterized by:

(i) the polyester polymer is selected to have a relative viscosity

(LRV) in the range of about 13 to about 23, a zero-shear melting point (T^ ⁰ ) in the range about 240 C to about 265 C, and a glass-transition temperature (Tg) in the range of about 40 C to about 80 C; said polymer is melted and heated to a temperature (Tp) in the range about 25 C to about 55 C above the- apparent polymer melting point and filtered sufficiently rapidly to minimize degradation; and then extruded through spinneret capillaries selected to have a cross-sectional area (A _c ) in the range about 125x10"^ cm ² to about 1250x10 ^" ^ cm ² , and a length (L) and diameter (DRND) such that the (L/DRjsτj))-ratio is at least about 1.25 and less than about 6 (preferably less than about 4) and wherein the exit orifice shapes and/or capillary L and D values are selected to provide filaments of differing cross-section and/or denier (as described herein before);

(ii) the extruded melt is protected from direct cooling as it emerges from the spinneret capillary over a distance (LT>Q) of at least about 2 cm and less than about [12(dpf)ι ^ ² ] cm; cooled to below the polymer glass- transition temperature (Tg) and attenuating the finer filaments to an apparent spinline strain in the range of about 5.7 to about 7.6, where (dpf)ι is that of the finer filament of the mixed-filament yam;

(iii) the mixed-filaments are then converged into a mixed-filament bundle by use of a low friction surface at a distance (L _c ) in the range about 50 cm to about [90(dpf)ι ^ ² ] cm; interlaced to provide filament bundle integrity and then winding up the mixed-filament ya at a withdrawal speed (V _s ) in the range of about 2 to about 6 km/min;

(2) Coupled spin/draw processes or split spin/draw processes, such as described by Knox and Noe in U.S. Patent No. 5,066,447; including draw texturing process (e.g. , draw false-twist texturing and draw air-jet texturing) for preparing:

(i) drawn flat or air-jet textured mixed-filament yams, having a differential filament shrinkage of at least 5 % , prepared by drawing the undrawn mixed-filament yams at a temperature in the range of about the glass-transition temperature (Tg) and about the onset temperature of major crystallization (T _c °) of the polyester polymer and further characterized by a residual elongation-to- break (Eg) about 15% to about 45%, and a tenacity-at-7% elongation (T7) at least about 1 g/d; and especially drawn mixed-filament flat and air-jet textured yams having a differential shrinkage of at least 5 % by cold drawing without post heat setting the undrawn direct-use mixed-filament yams, described herein above and wherein the cold drawn differential mixed-filament yams are further characterized by a residual elongation-to-break (Eg) about 15% to about 55%, and a tenacity-at-7% elongation (T7) at least about 1 g/d.

(ii) drawn polyester flat and textured fine mixed-filament yams, prepared from the undrawn fine mixed-filament feed yams of the invention as described hereinbefore, are characterized by an elongation-to-break (Eg) about 15 to about 45%, a (1-S/Sm) value at least about 0.85, a tenacity-at-7% elongation (T7) at least about 1 g/d, preferably a post-yield modulus (Mp _y ) about 5 to about 25 g/d; and preferably wherein the drawn flat fine-mixed filament yams are further characterized by an along-end uniformity as measured by an along-end denier spread (DS) of less than about 3% (especially less than about 2%).

(iii) preferred polyester mixed-filament yams of an average yam filament denier less than about 1 and of a residual elongation-to-break (Eg) about 15% to about 55%, (1-S/Sm) value at least about 0.85, tenacity-at-7% elongation (T7) at least about 1 g/d, and preferably a post-yield modulus (M _py ) about 5 to about 25 g/d, prepared by cold or hot drawing with or without post heat treatment in single-end split or coupled processes or in a form of a weftless warp sheet, and the undrawn mixed-filament yams especially having a residual elongation of about 40% to about 90% with a (1-S/Sm) value of at least about 0.85 for use as a ^* undrawn direct-use yam); a tenacity-at-7% elongation (T7) in the range of about 1 and about 1.75 g/d by selecting a spin-oriented mixed- filament feed yam of the invention wherein all the filaments are characterized by the undrawn direct-use mixed-filament yams of the invention, as described herein before; and preferably wherein the drawn flat fine-mixed filament yams

are further characterized by an along-end uniformity as measured by an along- end denier spread (DS) of less than about 3% (especially less than about 2%).

(iv) uniform drawn air-jet textured fine mixed-filament ya s and uniform drawn textured fine mixed-filament yams; wherein the process is comprised of uniformly draw air-jet texturing or draw false-twist texturing the undrawn mixed-filament feed yams, formed by the spin-orientation process described hereinabove, to provide uniform drawn bulky mixed-filament yams characterized by a residual elongation-to-break (Eg) about 15 % to about 45 % , a (1-S/Sm) value of at least about 0.85, a tenacity-at-7% elongation (T7) at least about 1 g/d, and preferably a post-yield modulus (Mpy) about 5 to about 25 g/d.

(v) drawn bulky mixed-filament yams having differential filament shrinkage of at least 5 % on heat relaxing drawn flat mixed-filament yams or drawn air-jet textured mixed-filament yams of the invention prepared by cold drawing without post heat treatment the undrawn mixed-filament direct-use yarns of the invention, as described herein before, so to provide uniform drawn bulky mixed-filament yams characterized by a residual elongation-to-break (Eg) about 15% to about 55%, a (1-S/Sm) value of at least about 0.85, a tenacity-at- 7% elongation (T7) at least about 1 g/d, and a preferably post-yield modulus (Mpy) about 5 to about 25 g/d.

(vi) drawn bulky mixed-filament yams having differential filament shrinkage of at least 5% on heat relaxing drawn flat mixed-filament ya s or drawn air-jet textured mixed-filament yams of the invention prepared by drawing without post heat treatment the undrawn mixed-filament yams of the invention at a draw ratio in the range of about Tg and about T _c °, as described herein before, so to provide uniform drawn bulky mixed-filament yams characterized by a residual elongation-to-break (Eg) about 15% to about 45% , a (1-S/Sm) value of at least about 0.85, a tenacity-at-7% elongation (T7) at least about 1 g/d, and a post-yield modulus (Mpy) about 5 to about 25 g/d.

(vii) drawn yams with shrinkage tensions (ST _max ) greater than about 0.25 g/d for use in tightly constructed fabrics so to permit the yams to overcome yam-to-yam restraints within the fabric during dyeing and finishing by drawing the undrawn mixed-filament yams above the invention at temperatures of the glass transition temperature Tg and less than about the onset

temperature of major crystallization (T _c °), wnerein post heat treatment is adjusted to provide desired balance of Shrinkage S and Shrinkage Tension ST..

The fine ό ^~ τ flat filaments of the invention are further characterized by an the along-end yam denier variation [herein called Denier Spread, DS] is less than about 4% (preferably less than about 3%, especially less than 2%); making the uniform denier fine mixed-filament yams suitable in textile fabrics requiring critical dye (configurational) uniformity; and nonround filaments (incorporated for enhanced tactile and visual aesthetics, and comfort) have a shape factor (SF) at leist about 1.25, wherein the shape factor (SF) is defined by the ratio of the measured filament perimeter (PM) and ^tne calculated perimeter (PRND) ° ^{r a τoun} - filament of equivalent cross-sectional area. The filaments of the invention are further characterized by being of good mechanical quality with a tenacity-at-break (Tg) _n normalized to 20.8 LRV.

TEST METHODS

Many of the polyester parameters and measurements mentioned herein are fully discussed and described by Knox in USP 4, 156,071, Knox and Noe in USP 5,066,447, and Frankfort and Knox in USP 4,434,882, all of which are hereby specifically incorporated herein by reference, so further detailed discussion, herein would, therefore be redundant. For clarification, herein, boil-off shrinkage is given by "S" (sometimes by Sj, or by SI in the

Tables); the Differential Shrinkage (DHS - S) of the as-spun yarns in all the Examples is always less than +2; Tg (sometimes T5 in Tables) is the tenacity base"- ⁴ on denier at break (i.e., based on the drawn denier, as is Mpy) T being defin l by the product of conventional textile tenacity and the residual draw ratio RDR (= 1 + Eg/100) and the normalized (Tg) _n is defined by

[(Tg)(20.8/LRV)°- ⁷⁵ (l-% delusterant/lOO)" ⁴ ]. The mixed filament yams of the invention are characterized by Tg-values, normalized to 20.8 polymer LRV, at least about 5 g/d, and preferably at least about 6 g/d.

The values of a polymer's glass-transition temperature Tg, temperature at the onset of major crystallization T _c °, and temperature at the maximum rate of crystallization T _{c max} may be determined by conventional DSC analytical procedures; but the values may also be estimated from the polymer's zero-shear melting point Tj^ ⁰ (expressed in degrees Kelvin) for a

given class of chemistry, such as polyesters using the approach taken by R. F. Boyer [Order in the Amorphous State of Polymers, ed. S. E. Keinath, R. L. Miller, and J. K. Riecke, Plenum Press (New York), 1987]; wherein, Tg = 0.65 T _M °; T _c ° = 0.75 T _M °; and T _Cjmax = 0.85 T _M o _; wherein all temperatures are expressed in degrees Kelvin.

Various embodiments of the processes and products of the invention are illustrated by, but not limited to, the following Examples with details summarized in the Tables.

EXAMPLE A

In Example A Mixed filament ya s were prepared by co- spinning low denier filaments with higher denier filaments (such as low shrinkage (crystalline) spin-oriented filaments of, e.g., Knox U. S. Patent No. 4,156,071, and/or high shrinkage (amorphous) spin-oriented POY filaments of Piazza and Reese U. S. Patent No. 3,772,872 to provide potential for mixed- shrinkage (e.g., post-bulking in fabric) such as when low shrinkage filaments are combined with high shrinkage filaments).

Such high and low dpf filaments may be spun from separate pack cavities and then combined to form a single mixed-dpf filament bundle, but are preferably spun from a single pack cavity, wherein the capillary dimensions (L and D) and the number of capillaries # _c are selected to provide for differential mass flow rates; e.g., by selecting capillaries such that the ratio of spun filament deniers, [(dpf)2/(dpf)i is approximately equal to [(L1D2/L2D1 x [(D2/D1) ³ ], where 1 and 2 denote filaments of differing deniers; n = 1 for Newtonian polymer melts (and herein "n" is experimentally found to have an average value of 1.1 for the polymer and process conditions used herein; and; wherein the measured average yam filament denier is defined by: (dpf)avg. ⁼⁼ [(#ldpfι + #2dpf2)/(#ι + #2)]-

Examples 1-6 Yams were spun from 2GT homopolymer of nominal 21.2 LRV at a polymer temperature (Tp) of about 290 C; quenched using a radial quench fitted with a 1.2 inch (2.75 cm) delay tube and using room temperature air at a velocity of about 40-50 mpm; then converged at a distance about 109 cm from the face of the spinneret using a metered finish applicator guide and then withdrawn at speeds as indicated in Tables I and III to form 200-

filament yams of nominal denier varying from about 127 to about 239 as indicated. The "Spun DPF Avg" is such nominal denier divded by 200. The "DPF Ratio" is the ratio of measured high dpf to measured low dpf (and was fairly close to the nominal dpf ratio of 3.54, mentioned hereinafter). The 200-filament as spun yams comprised 24 high dpf filaments (2) and 176 low dpf filaments (1). The nominal (dpf)2/(dpf)l -ratio was about 3.54, for Examples 1-3 respectively, as a consequence of using spinneret capillaries of different dimensions; that is 24 capillaries of length (L) 12.5 mils (0.318 mm) and diameter (D) 39 mils (0.975 mm) and 176 capillaries of length (L) 36 mils (0.914 mm) and diameter (D) 9 mils (0.229 mm) such to provide a pressure drop-ratio ratio of 3.54; that is, (dpf)2/(dpf)ι = [(L1D2/L2D1 x [D2/D1) ³ ], where "n" is 1 for Newtonian fluids and found experimentally to have a value of 1.1 for polymer LRV and process conditions used herein. The measured average yam denier = #ι(dpf)ι + #2(dpf)2 = ^# l( ^d Pf)l + #2{K<W(dp0l](dpf)2} ⁼ #ι(dpf)i + 3.54[# ₂ (dpf)i] = [#ι + 3.54(# ₂ )](dpf)l = t ²⁴ + 3.54(176)(dpf)i, where (dpf)i = measured average ya denier/[24 + 3.54(176)] and (dpf)2 = 3.54 (dpf)!].

In Example 1. the high dpf filaments (2) were spun from capillaries positioned on the outer rings of a multi-ring capillary array (because of an earlier expectation that the high dpf filaments would benefit from more quenching than the smaller dpf filaments). In Example 2 the capillaries for the high dpf filaments (2) were positioned in the middle of the array, where such spin filaments (2) would naturally tend to "migrate" during quenching and convergence. In Example 3. the capillaries for the high dpf filaments (2) were arranged symmetrically throughout the capillaries of the multi-ring array. The data for Examples 1 to 3 are in Tables I to III, and include a column "Drawn DPF Avg" calculated from values on drawn yams referred to in Example 4-6 and given in Tables IV to VI as "Drawn Den", divided by 200.

Surprisingly we found in practice that the symmetric array of Example 3 provided the best denier uniformity, generally, and the outer array of

Example 1 the worst. The break tenacities (Tg) for the symmetric (3) and outer ring (1) arrays were essentially equal, while the inner array (2) was significantly worse.

In Examples 4-6 the spun yams of Examples 1-3, respectively, were carefully warp drawn at 400 mpm, using draw and set temperatures of 180 C, to residual elongations between 25% and 45% having a nominal average yam filament (dpf) j less than 1 dpf. The same relative order of uniformity and break tenacity was observed for the drawn yams as for the spun feed ya s of Examples 1 to 3. The optimum filament array will depend on number of filaments, the dpf-ratio, and the desired balance of along-end denier uniformity (DS) and tensile strength (as measured here by Tg). The properties are summarized in Tables V through VI, respectively, for yams from Examples 4-6.

In the next series, instead of mixing the filaments, separate yam bundles of high dpf and low dpf were made and drawn separately to provide data on the filament properties and behavior, it being understood that the filament could have been mixed together.

EXAMPLE 7

Individual bundles of 50 high dpf and of 200 low dpf filaments were spun from separate spin packs using 15x60 and 9x36 mil capillaries, respectively; and wound up separately (data summarized in Table VII). The resulting low dpf filaments had higher tensiles (Modulus, T7, Tg) and lower break elongations (Eg) than the high dpf filaments. Based on warp-drawing and draw-texturing experience, we selected a dpf-ratio of a 4 to 1 to provide the higher dpf filaments with a drawn dpf of about 2 for fine fabrics to avoid "glitter" from differential reflections off the different size filament surfaces of different curvature; a 4-to-l dpf-ratio provided a difference in Eg-values of about 20% to about 40%, but a lower difference in Eg-values would generally be preferred to provide optimum drawn yarn mechanical properties and uniformity.

EXAMPLE 8

The ya s of Example 7 were drawn at 400 m/min for draw ratio series of 1.4X, 1.5X, and 1.6X at a draw temperature of about 180 C and a set temperature of about 180 C. The drawn elongations generally differed about 10-

20%, the higher dpf filaments having the higher elongations. The drawn yam is summarized in Table VIII.

EXAMPLE 9

The 172 denier 200-filament and the 172 denier 50-filament bundles from Example 7 were drawn at 400 mpm and a constant draw-ratio of 1.64 with the set plate initially at room temperature (25 C, items 1 and 2). The draw temperature was increased from room temperature (cold draw) to 180 C (i.e., about the temperature of maximum rate of crystallization T _{c max} for 2GT polyester), and as indicated in Table IX. The shrinkages decreased with increasing draw temperature, especially above about 120 C onset of major crystallization T _c °, and so the differential shrinkage decreased to about 2% at 130 C. This showed it was possible to provide at higher draw temperatures drawn mixed-denier filament yams that were flat (i.e., not bulked, because the mixed dpf filaments had similar shrinkage) from the same mixed-denier feed stock, we used to produce mixed shrinkage drawn yams, capable of self-buling when drawn at lower draw temperatures.

EXAMPLE 10

In Example 10, for items 1 to 11, a nominal 200-200 spun yam comprised of 24 filaments of an average dpf of 2.45 and 176 filaments of an average dpf of 0.78 was warp drawn at 1.64X draw-ratio at 400 mpm with the set plate at room temperature (25 C), and the draw temperature was increased from 25 C to 180 C. As the draw temperature increased, the shrinkage S\ decrease i from 47.2% to 5.8%. The decrease in shrinkage Sj after a draw temperature of about 114 C was minimal, which supports the results of Example 9. In Items 12 and 13 a 127 denier feed yam comprised of 24 filaments of 1.65 dpf and 176 filaments of 0.5 dpf was drawn 1.4X. Item 12 was drawn cold and without post heat treatment (i.e., set plate remained at room temperature of about 25 C). In Item 13 the 127 denier yam was drawn at 180 C and set at 180 C giving a shrinkage Si of 5.9 versus 28.4 for Item 12. This illustrates the degree to which the shrinkage may be controlled by selection of drawn set temperatures. Data for Example 10 is summarized in Table X.

EXAMPLE 11

127-200 and 159-200 (denier-filament) yams of Example 3 (24 high dpf and 174 low dpf) were draw air-jet textured at 200 m/min using 1.4X and 1.6X draw-ratios and the draw and set temperatures were varied from room

temperature (i.e., heater switched off) to.180 C. It was possible to prepare draw air-jet textured ya s with shrinkages less than 2% and as high as about 40% which provides the potential for preparing mixed-shrinkage yams from the same feed stock. Data is summarized in Table XL

EXAMPLE 12

Nominal 200 denier-200 filament as spun yams (items 5-8 from Table HI) were draw false-twist textured at 180 C on a Barmag FK6-900L at 450 m/min with a 1.506 draw ratio and a 1.707 D/Y-ratio using a 1/7/1BB disk stack (PU disk type). The drawn ya denier was 136.7 (0.68 dpf) at a 40.6% elongation with a 3.66 g/d tenacity and a 20.7 g/d modulus. The boil-off shrinkage was 5.6% and the Leesona skein shrinkage (a measure of textured yam bulk) was 23.7%. The mixed dpf filament yams provided higher bulk than the 100% micro-denier filament yams and depending on final elongation-to- break, a pleasing heather yam could be made.

EXAMPLE 13

A spun feed ya as for Example 12 was warp drawn at 400 m/min using a pre-draw temperature of 75 C and drawing 1.64X at a draw temperature of 115 C (about the cold crystallization temperature T _cc ) providing a 10% boil-off shrinkage. The drawn yam denier at a 37.5 % elongation was 124.8 (average filament (dpfjrj of 0.62) and a tenacity of 3.98 g/d with a modulus of 66.8 g/d and a T7 of 2.47 g/d. The fine denier yams had a denier spread of 2.2% and slow Uster of 0.6% making these yams suitable for critically dyed end-uses.

EXAMPLE 14

A mixed filament yam was prepared by cospinning 50 1.83 denier filaments of shrinkage S of 21 %, giving a (l-Sι/S _m )-ratio of 0.67, and 200 filaments of 0.46 denier having a shrinkage S^ of 5.2%, giving a (l-Sι/Sm)-ratio of 0.92, at 2743 mpm to provide a post-bulkable mixed-shrinkage yam (refer to Items 17 and 19 of Table VII). A similar post-bulkable yam with shrinkages of 7.8 % and 39.4 % was prepared by co-spinning at 2743 mpm 50 filaments of 2.28 dpf and 200 filaments of 0.57 dpf (Items 13 and 14 of Table VII). At lower spin speeds the shrinkage of the

lower dpf filaments increased to reduce the difference in shrinkages between the low and high dpf filaments and to give excessive fabric loss. It is preferred that the low shrinkage filaments have shrinkages less than about 10%, that is, having (l-Sι/S _m )-values of at least about 0.85, as illustrated in Items 13 and 17 of Table VII, to provide for mixed-shrinkage and to minimize fabric loss which is, at most, equal to the shrinkage of the high shrinkage component if the high shrinkage component has sufficient shrinkage tension to overcome the restraints in the fabric. To minimize fabric loss on post-bulking in fabric form, the bulking can take place during warping by overfeeding at the temperatures sufficient to develop shrinkage and bulk; but preferably leaving some residual shrinkage for development of bulk in fabric form which helps to randomize differences in stitch tightness and improves configurational uniformity. About 3-4% residual shrinkage is sufficient for warp knits and light weight wovens.

Example 15

200 (mixed-) filament yams were spun from 2GT homopolymer of nominal 21.2 LRV at a polymer temperature (Tp) of about 290 C and quenched using a radial quench fitted with a 1.7 inch (4.32 cm) delay tube and using room temperature air at a velocity of about 30-50 mpm, then converged at a distance about 109 cm from the face of the spinneret using a metered finish applicator guide and then withdrawn to form 200-filament yams of nominal denier varying from about 124 denier to about 220 denier, wherein the 200- filament yarris are comprised of 24 high dpf filaments having non-round cross section and 176 low dpf filaments of round cross-section. The spinneret capillaries used for producing the 176 low dpf filaments have a capillary length (L) of 36 mils (0.914 mm) and diameter (D) of 9 mils (0.229 mm). Spinneret capillaries for forming the 24 high dpf filaments were selected for shaping the fiber cross-section as desired; yams were produced where the high dpf component had the following cross-sections: 1) trilobal, 2) octalobal, 3) multilobal ribbon, 4) hollow. A dpf ratio of about 3.5: 1 was obtained by use of a metering plate having 24 capillaries with capillary length (L) of 56 mils (1.42 mm) and diameter (D) of 14 mils (0.356 mm) to control polymer delivery to the non-round forming capillaries; a low pressure drop metering plate capillary of length (L) of 90 mils (2.29 mm) and diameter (D) of 40 mils (1.02 mm) was used for the low dpf component, such that the low dpf polymer flow rate was essentially controlled by the spinneret capillary.

This process was used to provide yams comprised of filaments of mixed-denier and of mixed cross-sectional shape, thus reducing the differential between the elongations of the low and high denier filaments, and therefore improving the co-drawing (i.e. , providing both components being capable of being co-drawn to elongations between about 20% and about 40% for improved mechanical properties and denier uniformity) and producing high denier filaments of low shrinkage, thus making the mixed-filament yarn suitable for a direct-use flat yam.

The invention lends itself to many variations and further modifications will be apparent, especially as these and other technologies advance. For example, any type of draw winding machine may be used; post heat treatment of the feed and/or drawn yams, if desired, may be applied by any type of heating device (such as heated godets, hot air and/or steam jet, passage through a heated tube, microwave heating, etc.); finish application may be applied by convention roll application, herein metered finish tip applicators are preferred and finish may be applied in several steps, for example during spinning prior to drawing and after drawing prior to winding; interlace may be developed by using heated or unheated entanglement air-jets and may be developed in several steps, such as during spinning and during drawing and other devices may be used, such by use of tangle- reeds on a weftless sheet of yams. Furthermore, if desired, hollow filaments spun via post-coalescence from segmented spinneret capillary orifices may be incorporated as one (or more) of the filament components in the mixed-filament yams of the invention to provide lighter weight fabrics with greater bulk for improved fabric drape, and to provide a difference in cross-section, at least, as disclosed in copending application No. (DP-4555-H) filed by Aneja et al simultaneously herewith, and the disclosure of which is hereby incorporated herein by reference.

TABLE IV

036

TABLE X