CA1122370A - Poly(ethylene terephthalate) staple fibre with improved dyeing characteristics - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Poly(ethylene terephthalate) filaments of enhanced dyeability, low boil-off shrinkage (even in as-spun condition), good thermal stability over a large temperature range, and useful as texturing feed yarns and/or as hard yarns requiring no further drawing are prepared by spinning at a withdrawal speed (V in yards/minute) of at least about 5500 yards/minute and with a polymer temperature (Tp) measured (in °C) in the filter pack at a point 50-100 mils above the center of the spinneret plate of wherein (L) and (D) are the length and diameter (in mils) of the spinneret capillary and (w) is the throughput (in pounds/
hour) per capillary. The filaments are characterized by a long period spacing above 300 .ANG. in their as-spun condition, and, whether in as-spun condition or after heat-treatment, by a low skin-core value as measured by a differential birefrin-gence in relation to their stress measured at 20% extension (which correlates approximately with the spinning speed), a large crystal size, and low amorphous orientation. The continuous filament yarns may be draw-textured to provide textured yarns which also show enhanced dyeability. The staple fiber yarns also have very useful properties as compared with conventional staple yarns. A preferred process of spinning at these extremely high speeds is characterized by the use of a spinneret with capillary-dimensions that produce high shear as the polyester is extruded and is applicable also to copoly-esters, whose filaments show a similar low skin-core in relation to their stress at 20% extension, the precise values for copoly-mers being different from the relationship for poly(ethylene terephthalate).

Description

BACKGROUND OF THE INVENTION
This invention concerns improvements in and re-lating to synthetic linear polyester filaments, and more particularly to the dyeability, thermal stability and texturability of such filaments, and to processes for the production of such filaments.
Polyester filaments have been prepared commer-cially for more than 25 years, and are now manufactured in large quantities amounting to billions of pounds annually.
Most of this commercial manufacture has been of poly (ethylene terephthalate). These commercial polyester fila-ments have been difficult to dye, e.g. as mentioned by H. Ludewig in Section 11.4 "Dyeing Properties" of his book "Polyester Fibers, Chemistry and Technology", German Edition 1964 by Akademie-Verlag and English translation 1971 by John Wiley and Sons Limited. Special dyeing techniques have therefore been used commercially, e.g. dye bath additives called "carriers" have been used to dye the homopolymer, usually at higher pressures and temperatures, or the chemi-cal nature of the polyester has been modified to increase the rate of dyeing or to introduce dye-receptive groups, e.g. as discussed in Griffing & ~emington U.S. Patent No.
3,018,272. These special techniques involve considerable expense, and it has long been desired to provide poly-ester filaments having useful physical properties, e.g. for apparel and home furnishing applications, but having a dye-ability morè like that of natural fibers, such as cotton, or cellulosic fibers, such as viscose rayon, which can be dyed at the boil within a reasonable period of time without the need for special techniques of the type referred to.

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Any reduction in the amount of carrier used is desirable for ecologic as well as economic reasons. Although there have been many suggestions for solving this long-standing problem, it has still been necessary, in commercial practice, to use special dyeing techniques or to introduce chemical modification, as indicated above.
For most consumer purposes, polyester filaments should have good thermal stability, i.e. relatively low shrinkage and preferably over a large temperature range.
The maximum permissible shrinkage may vary depending on the intended use, but a boil-off shrinkage of less than about 2~ in the final fabric has become generally accepted as necessary for consumer applications. Hitherto, commercial polyester yarns have been pre~ared with considerably higher boil-off shrinkage, e.g. 8 to 10%, so it has been customary to prepare fabrics with these yarns and then reduce the boil-off shrinkage by heat-setting the fabric. Any new polyester yarns should have a boil-off shrinkage no higher - than is customary. It would also be advantageous to be able to prepare continuous filaments having the desired low boil-off shrinkage directly, i.e. by spinning such filaments without any need for further treatment such as heat-setting. A low shrinkage at higher temperatures (120-200C), such as are usually encountered during textile finishing and pressing operations! i.e. a low dry heat shrinkage, would also be desirable. Hitherto, most commer-cial polyester filaments have had a dry heat shrinkage sig-nificantly more than their boil-off shrinkage. It has long been desired to provide a polyester yarn with good thermal stability when subjected to either boil-off or such dry ll;~Z3 ~0 heat at higher temperatures.
Thus, it would have been vlery desirable to provide poly(ethylene terephthalate) filaments with a combination of good thermal stability and good dyeing properties. Such a combination has not been commercially available heretofore.
A large amount of polyester yarn is subjected to a texturing process to increase its bulk. False-twist texturing has generally been the preferred process. Textur-ability of a polyester yarn is an important requirement,therefore, in the sense that it is required that the polyester yarn be texturable on a commercial false-twist texturing machine without producing a large number of yarn defects, such as broken filaments,or lack of dye uniformity, which may become manifest only in the final fabric.
For many years polyester filaments were melt spun and wound onto a package without drawing at speeds of up to about 1000 meters/minute, e.g. as described in Chapter 5 of Ludewig. This process (which can now be termed "low speed spinning") provided filaments of relatively low orientation (as ~easured by a low birefringence), relatively low tenacity, low yield-point and relatively high break-elongation. These filaments were not useful as textile yarns until they had been subjected to a drawing process.
Thus it was originally standard procedure first to make a package of spun polyester filament and then to subject the filament to a drawing and annealing process which increased tenacity, yield point, orientation (birefringence) and crystallinity, and reduced break-elongation, thus producing "hard" filaments which could be used commercially.

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This procedure was referrecl to as the "split process" and was expensive, primarily because of the need to operate the stages of the process at different speeds, and therefore, to wind up filaments at each intermediate stage. It has long been desirable to produce hard fila-- ments continuously, i.e. to reduce the number of separate stages involved in hard filament production and thus avoid the need for winding up after any intermediate processes.
For instance, the processes of melt spinning and drawing have been combined into a coupled spin-drawing process without intermediate windup, e.g. as disclosed in Example IV of Chantry & Molini U.S. Patent No. 3,216,187, wherein the polyethylene terephthalate was melt spun at a (low) withdrawal speed of 500 yards/minute (450 meters/
minute), and drawn immediately (i.e. without intermediate windup) 6X and annealed before windup at 3000 yards/minute (2700 meters/minute). Coupled spin-drawing produces a drawn yarn of high tenacity, crystallinity, orientation,yield point and reduced break-elongation, i.e. a hard yarn, comparable to drawn yarn produced by low speed spinning and drawing in separate process-stages, i.e. the split process.
In recent years, polyester filaments have been manufactured by a process of "high speed spinning". This typically involves the use of windups operating at speeds, e.g., of 3000 to 4000 meters/minute, similar to those in the coupled spin-drawing process, but is a one-step process in which the polyester filamentsare spun and wound directly at` a high withdrawal speed, without any drawing step.
High speed spinning has been used to produce partially oriented yarns that are particularly useful for draw-11;~23`~0 texturing, as disclosed by Petrille in U.S. Patent No.3,771,307, and this process is now operated commercially on a large scale. The partially oriented yarn that has been produced by high speed spinning has higher orientation (birefringence) and tenacity, with reduced break-elongation, compared to undrawn yarn produced by low speed spinning. The partially oriented yarn produced by high speed spinning has a lower crystallinity than drawn yarn produced theretofore by either a coupled or a split process. Although high speed spinning of polyester filaments had been patented in July 1952 by Hebeler in U.S. Patent No. 2,604,689, and received further technical attention, e.g. in Section 5.4.1 in Ludewig, and by Griehl in U.S. Patent No. 3,053,611, it has only been within the present decade that high speed spinning has been commercially practiced.
Hebeler also described, in U.S. Patent No. 2,604,667, using still higher withdrawal speeds, in excess of 5200 yards/
minute (4700 meters/minute), to produce polyester filaments having tenacities of at least 3 grams/denier and boil-off shrinkages of about 4% or less in the as-spun state. Although this disclosure has been available for more than 20 years, and has been extensively investigated by experts such as Ludewig, it has not been suggested by such experts that the need for poly(ethylene terephthalate) filaments having the aforesaid combination of properties (enhanced dyeability accompanied by thermal stability over a large temperature range) could have been satisfied by spinning the filaments at extremely high withdrawal speeds.

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THE INVENTI02~
It has now been found that poly(ethylene terephthalate) filaments spun using extremely high with-drawal speeds (e.g. over about 5000 meters/minute) show excellent "dye at the boil capability", i.e. it is possible r to dye such filaments at the boil within a reasonable period of time without the need for conventional "carriers"
or chemical modifiers mentioned above. Prior commercial poly(ethylene terephthalate) textile yarns, having similar physical properties, e.g. tensile properties and boil-off shrinkage, have not shown this capability. ~hen these dyeable yarns are textured, they may lose some of this capability, to an extent depending on the speed of with-drawal during spinning, but such textured yarns can be dyed with a reduced need for carriers. It has also now been found that polyester filaments that have been spun at these extremely high withdrawal speeds have good thermal stability, i.e. relatively low shrinkage over a large temperature range. Prior commercial polyester textile filaments have not shown such stability. It has also been found that most filaments spun at these extremely high withdrawal speeds are characterized by a high long-period spacing (LPS) of over 300 A. These properties seem to be largely inherent in filaments spun at withdrawal speeds taught by Hebeler in ~.S. Patent ~o. 2,604,667. Ot-her useful characteristics have also now been discovered in yarns produced at ex-tremely high speeds, especially above 6000 meters/minute.
Increasingly difficult problems with broken fila-ments have, however, been encountered as the withdrawal speed has been increased, to the extent that sometimes it li;~Z370 has not even ~een possible to achieve continuity of winding at these extremely high speeds. Broken filaments and other yarn defects have also presented problems during subsequent textile operations, such as texturing, when using filaments spun at these extremely high withdrawal speeds.
It has now been found that many of these problems during spinning at these extremely high speeds, or during subsequent textile operations on the resulting filaments, can be associated with a significant difference between the birefringence of the surface and the birefringence of the core of the filament, and that better filaments can, there-fore, be obtained more reliably and consistently by con-trolling the spinning and cooling conditions so as to mini-mize such difference in the as-spun filament. We refer to this difference herein as differential birefringence (~95 5 being the difference in birefringence between points along the radius of the filament at the indicated 95 and 5 per-`` centage distances from the axis, or more simply as "skin-core". The skin-core values generally increase with the spinning speed, i.e. the speed of withdrawal from the spin-neret, which correlates approximately with the stress required to extend the as-spun yarn by 20% (~20) As the spinning speed increases from about 5500 yards/minute (about 5000 meters/minute), it becomes increasingly more difficult to ensure that the skin-core value is low enough to reduce the likelihood of problems, such as broken fila-ments, to an acceptable level. If the filaments are spun at about 5500 yards/minute ~about 5000 meters/minute), problems resulting from high skin-core values may become manifest only during subsequent textile operations, e.g.

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broken filaments during texturing, or breaks and other defects in, e.g. woven fabrics. As the spinning speed in-creases, however, high skin-core values in the solidified filaments are more likely to cause continuity problems in the actual spinning process. Problems with continuity in spinning or with yarn and fabric defects can also be caused by other factors, so that it is not a complete solution to such problems merely to arrange for the filaments to be spun with a low skin-core, and to ignore the effect of other factors, but it has now been found that the spinning of filaments having high skin-core values at these ex-tremely high withdrawal speeds will generally cause such problems, despite care in controlling other factors.
There are provided, therefore, according to the invention, low shrinkage poly(ethylene terephthalate) filaments having enhanced dyeability, a long-period spacing (LPS) of more than 300 ~ and a differential birefringence (~95_5) as herein defined according to the relationship ~95_5 ~ O.0055 + O0014 C~20 where or20 is the stress measured in grams per denier (gpd) at 20~ extension and is at least 1.6 gpd. When cr20 is between 3 and 4 gpd, however, ag5 5 may be~0.0065 ~20-0.0100.
Qg5_5 is preferably less than 0.008.
When these filaments are annealed, the long-period spacing (LPS) decreases significantly. The filaments are, however, characterized by an amorphous birefringence (~am) less than 0.07, and crystal size (CS) of at least (1250 p - 1670)~ where p is the density, which is preferably at least 1.37 g/cm3, whether such filaments are as-spun or annealed. Preferred features of these filaments are that the _ g _ ll;~Z3`~0 dyeability be such that the relative disperse dye rate (RDDR
defined hereinafter) be at least 0.050, the thermal stabil-ity be such that the dry heat shrinkage (DHS) be not more than 1~ more than the boil-off shrinkage (BOS), and that' the mean birefringence ~5 be between 0.09 and 0.14.
The filaments are especially useful in the form of continuous filamentary yarns and continuous filamentary tows. Wound packages comprising at least 60,000 meters, and preferably at least 250,030 meters of such poly(ethylene terephthalate) continuous filamentary yarn having the above properties are provided.
"Hard" as-spun poly(ethylene terephthalate) con-tinuous filament yarns of ~20 ~ 2.6 gpd having dye-at-the-boil capability, thermal stability and other properties as mentioned herein,and wound packages of such yarns are provided.
Staple fiber having useful properties are also provided, and processes therefor.
There is also provided, in a process for melt-spinning ethylene terephthalate polyester filaments with alow differential birefringence between the surface and the core of such filaments, the improvement, when withdrawing the filaments at a speed (V in yards/minute) of at least about 5200 yards/minute (4700 meters/minute), preferably at least about 5500 yards/minute, wherein the polymer temperature (Tp), measured (in C) in the filter pack at a point 50-100 mils above the center of the spinneret plate, is maintained above a minimum value dependin~ on an ex-ponential of the speed V and a function of the length (L) and diameter (D) (in mils) of the spinneret capillary 3'7~1 and the throughput (w) per capillary (in pounds per hour, pph), i.e.
r t v \l /Lw\0.685 Tp ~ 284-5 lexp ~85,000JJ - 660 ~D4J

The dimensions of the capillary are generally:
diameter 9 to 15 mils; D4 20 X 10-4 to 100 X 10-4, prefer-- ably 20 X 10-4 to 70 X 10-4, mils 3, when spinning such throughput as to obtain ~ilamentc of 4 to 7 denier per filament.
For copolyesters, e.g. a 90/10, by weight, co-polymer of ethylene terephthalate and 2,2-dimethyl propylene terephthalate, the numerical values of skin-core may be different from those for poly(ethylene terephthalate), but it has been found possible to reduce skin-core by practicing the same process technique as for homopolymer, and thus produce useful filaments by spinning this copolymer at these extremely high speeds. Copolymer filaments can be used in the form of continuous filamentary yarns or tows, and as staple fiber, either alone or in admixture with poly(ethylene terephthalate) filaments and/or other fila-mentary materials.
There is also provided a process for draw-texturing poly(ethylene terephthalate) continuous filamentary yarns having the above properties.
Draw-textured yarns of poly(ethylene terephthalate) continuous filaments having a dye-at-the-boil capability, a loss modulus peak temperature (TEIlMax) of 115C or less, and a temperature at the maximum shrinkage tension (TmaXST) of at least 258C are also provided.

BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic representation of a 3`70 typical process for high speed spinning for use in prepar-ing filaments according to the invention.
Figure 2 shows in partial cross-section a view through one form of spinneret that may be used in a pre-ferred process according to the invention.
Figures 1 and 2 are discussed hereinafter in relation to process aspects of the invention.
Figure 3 is a graph plotting the skin-core value (~9S-S) against the stress at 20% extension (cr2o) for poly(ethylene terephthalate) filaments spun at high with-drawal speeds, i.e. havingcr20 values above 1.6 gpd, and is discussed after Example 44.
YARN CHARACTERISTICS AND MEASVREMENTS
Since this invention concerns novel filaments, characterized by special measurements, it may be helpful at this point to describe and define various character-istics and measurements that are used throughout this ap-plication. These characteristics and measurements are grouped together here for convenience, although some are standard. The novel filaments will generally be used in the form of yarns or tows, the tows may be processed into staple fiber and yarns, or be used as such, the yarns will generally be processed into fabrics, and the fabrics may be processed into garments, or used for other purposes, e.g. upholstery, or the filaments may be processed into non-woven webs, e.g. in the form of spun-bonded or spun-laced webs. The following measurements, however, are, for con-venience, described in relation to a multifilament yarn of continuous filaments, unless otherwise indicated.
The tenacity, elongation, initial modulus and 3 ~'0 stress at 20~ extension (~ ) are measured on an INSTRON*

Tester TTB (Instron Engineering Corporation) with a Twister Head made by the Alfred Suter Company and using l-inch x l-inch flat-faced jaw clamps (Instron ~ngineering Corpora-tion) with a 10-inch sample length, 2 turns of twist per lnch at a 60% per minute rate of extension at 65% Relative Humidity and 70F; tenacity and ~20 values are calculated on the unstrained denier of the yarn. The tenacity and initial modulus increase with the spinning speed, while the elongation decreases, as a general rule, and so the yarns (as-spun) are distinguished from partially-oriented yarn (POY), e.g. prepared by spinning at about 3000 meters/minute, by having a higher tenacity and a lower elongation. Preferred values are a tenacity of at least 3.2 grams per denler (gpd), especially at least 4 gpd, and an elongation of less than 75~, especially 45~ or less. The stress at 20% extension (a2o) also increases with spinning speed, as a general rule, for the as-spun yarns, and is at least about 1.6 gpd, corre-sponding to a spinning speed of about 5000 meters/minute.
The advantage of as-spun filaments according to the invention generally increases as the ~20 value increases, especially at ~20 values over about 2 gpd, corresponding to about 6000 yards/minute (about 5500 meters/minute), and more particu-larly at ~20 values over about 2.6 gpd since yarns of such filaments are generally "hard".
A yarn can be considered "hard" if its modulus decreases continuously after its maximum, when plotted against the extension. The modulus at any given extension d tstress) is given by d (extension) , i.e. the slope of the curve of stress plotted against extension. When the modulus is * denotes trade mark 11~23;70 plotted against the extension, the modulus rises rapidly to its maximum and then decreases, eventually reaching a limiting value before the sample breaks.
Hard yarns are, therefore, hereby defined as those whose modulus at an extension between 3~ and 8~
(ModulusE 3-8) is greater than the limiting modulus that is observed as the extension increases from 8~ to 20%.
By spinning at a sufficiently high speed and by maintaining a low skin-core value, it is possible to pre-pare hard continuous filaments according to the inventiondirectly, i.e. merely by spinning without arranging for a separate drawing step after cooling below the second-order transition temperature.
Hitherto, as-spun commercial polyester yarns (pre-pared by low speed spinning ( split process) and partially-oriented yarns) have had a modulus which has decreased below the limiting value and has then increased to its limiting value. Such yarns yield under ordinary stresses, and have not been useful as such, e.g. for textile applica-tions, but have to be drawn. Drawing (e.g. in a split pro-cess, a coupled process or as part of a draw-texturing operation) changes the slope of the modulus plotted against extension, so that the modulus does not dip below its limit-ing value significantly, i.e. ignoring minor oscillations as the limiting value is approached. Such drawn yarns are hard yarns, like those now discussed according to the present invention, but have been made commercially by first spinning and then drawing in a separate operation after cooling below the second-order transition temperature of the solidified polyester.
Thus, yarns whose ~20 values are at least 2~70 2.6 gpd (corresponding to about 7000 yards/minute about 6400 meters/minute) are especially useful. Wound packages containing at least 60,000 meters, and preferably more than 250,000 meters of such hard continuous filament polyester yarn having ~20 at least 2.6 gpd, can be prepared _- directly by spinning such filaments with low skin-core values according to the present invention.
As the spinning speed and Cr20 value bothincrease, it becomes increasingly difficult to collect useful filaments because ofapparatus limitations, e.g. the windups that are available now. With increasing spinning speed and Cr20, it also becomes more difficult, in practice, to avoid making filaments with high skin-core values. Thus, with present limitations, e.g. of ~pparatus, it has not been practical to windup filaments of o-2G much greater than about 3.7 gpd, corresponding to about 8000 yards/
minute (about 7300 meters/minute). Other filament collec-tion methods, however, already exist, e.g. piddlers, and as spinning speeds increase beyond 8000 ypm, it will still 20 be desirable to maintain a low skin-core value even at such increased spinning speeds, i.e. in filaments having higher c~20 values. As indicated hereinafter in more detail in relation to Figure 3, the relationship between C~20 and a desirable maximum practical skin-core value is not linear over the whole range of cr20, but curves upward. In practice, at or20 values over about 3 gpd, corresponding ` to a s?inning speed of about 7000 meters/minute, e.g. over a range of cr~0 of about 3 to abolt 4 gpd, the skin-core values may be lower than a maximum given by the relationship ~95_5 ~ O.0065 cr20 - O.01~0.

3`~

The skin-core value of any yarn is generally reduced by drawing, but drawing increases amorphous orienta-tion, which reduces dyeability, and also reduces the long-period spacing.
A high long-period spacing (LPS, above 300~) is a characteristic of most of the as-spun filaments of the in-vention. This long-period spacing is obtained from small-angle x-ray scattering (SAXS) patterns made by known photographic procedures. X-radiation of a known wave-length, e.g., CuK~ radiation having a wavelength of 1.5418 A, is passed through a parallel bundle of filaments in a di-rection perpendicular to the filament axis,ar.d the diffrac-tion pattern is recorded on photographic film. Pinhole collimation must be used in order to observe the four-point or quadrant diagram characteristic of these samples. An evacuated small-angle camera of moderately high resolution is required to resolve the quadrant spots. Matched pinh~les of 0.25 mm diameter spaced 15 cm apart and a sample-to-film distance of 32 cm with a 2.5 mm diameter beam stop near the film are sufficient to resolve the diagram. Slit-smearing small-angle diffractometers and cameras cannot be used be-cause the smeared continuous scatter near the main beam obscures the quadrant spots. The repeat distance ('d') is calculated from a measurement of the separation of the quadrant spots in a direction parallel to the fiber axis by application of the Polanyi equation n~ = d sin ~
;; where n is the constant 1 (first order 'layer line'), ~ is the wavelength and ~ is half the angular separation of the quadrant spots measured parallel to the fiber axis. For a ( '`
3`7~

sample to film distance, f, and a spot separation, Q, since = sin ~ = tan ~ at small angles:

d - 2~f _ 986.75 Q Q(mm) for f = 320 mm and ~ = 1.5418 A. A more detailed description of the methods of obtaining and interpreting small-angle x-ray data may be found in the book 'X-ray Diffraction Methods in Polymer Science' by L. E. Alexander, published by John Wiley and Sons, New York, N.Y. (1969). The camera is described in Chapter 2, section 3.5 and the interpretation in Chapter 5, section 5.2. The measurement of long-period spacing is time-consuming. The measurement has not been carried out on every single Example, since the correlation between spinning speed and long-period spacing became apparent from many measurements.
The long-period spacing of prior art commercial yarns, and of other filaments spun at lower withdrawal speeds typically have values less than 300 A and usually are char-acterized by the more usual two-point meridional scattering pattern. For prior art yarns having such scattering patterns the Bragg equation is used as described in Chantry & Molini U.S. Patent No. 3,216,187 (Column 3). As the spinning speed increases, the long-period spacing of the filaments of the invention increases to a maximum and then decreases below 300 A again. The precise speed at which the long-period spacing decreases below 300 A will depend on various factors, especially polymer temperature (Tp), but is generally over 7000 yards/minute, and usually over 7500 yards/minute.

Annealing as-spun filaments of the invention significantly reduces their long-period spacing below 300 A. Such fila-ll'~Z3`7() ments still have useful dyeability and thermal stability.
The density (P) is me~sured as disclosed inPiazza ~ Reese V.S. Patent No. 3,772,872 (Column 3) or in ASTM D1505-63T. Density of the polymer is a convenient measure of crystallinity. The densities given in the Examples are of the polymer and have been corrected for TiO2 content. Yarns according to this invention are generally of (polymer) density at least 1.365, preferably at least 1.37 g/cm3, and generally less than 1.425, pre-ferably less than 1.4 g/cm3. These densities are higherthan for as-spun yarns prepared by low speed spinning or for co~mercial partially-oriented yarns. The crystallinity of such prior commercial yarns has been raised to desirahle values by drawing and annealing, which reduces dyeability.
The crystal size (CS) is estimated from the Scherrer formula CS = K~/3cos~ where K is taken to be unity; ~ is 1.5418 A, the wavelength of CuX~ X-rays; ~ is the ~ragg angle of diffraction; ~ is line broadening cor-rected for instrumental broadening by ~2 = B2-b2 where B is ~;20 the observed broadening and b is the instrumental broadening `as measured on a ZnO pattern assuming infinitely large crystallites (all measurements in radians). The crystal size (CS) is measured using the diffraction at a diffraction arc 2~ = 17.5 for the 010 diffraction arc, and is measured radially along the equator, i.e. at its maximum intensity, by the techniques described by H. P. Klug and L. E. Alexander in "X-ray Diffraction Procedures", John ~iley and Sons, Inc.
New York (195~), Chapter 9.
The filaments of this invention preferably have crystal sizes that are greater than about 55 ~, especially (~
Z3`70 greater than 70 ~, and that are preEerably related to the fiber denslty by the relation CS ~ (1250p - 1670) A.
Prior art yarns that are crystallized in other textile processes, e.g., spin/draw and draw-set-texturing are considered to have crystal sizes that are less than those formed by spinning at these extremely high speeds, at any given value of density according to the above expression.
The large crystal size is a characteristic of filaments of the invention, whether as-spun or annealed, unlike the long-period spacing.
Birefringence (~) is a measure of the orientation of the polymer chain segments. It is measured as in British Patent ~o. 1,406,810 (pages 5 and 6). The value reported (~5) is the mean for 10 filaments measured near the center of each filament (+5% away from the filament axis). Pre-ferred values are at least 0.09, which distinguishes from partially-oriented yarns, to not more than 0.14, which distinguishes from conventionally drawn yarns.
As stated already, it is important to have a low differential birefringence (~95_5) when spinning poly (ethylene terephthalate) filaments as the spinning speed increases to extremely high values from about 5000 meters/
minute. This desideratum is referred to herein as low "skin-core" in the sense that it is important to minimize any skin on the surface of the filament, such skin being detectable by a large difference between the birefringence near the surface and that near the center of the filament, i.e. it is important to minimize this difference. It be-comes more difficult, in practice,to achieve this as the Cr20 value increases because of any increase in spinning (-- --11 ;~Z3 70 speed. Differential birefringence (Q95_5) is defined here-in as the difference between the chord average birefringence near the surface of a filament (~95) and the chord average birefringence within the filament near its center (~5).
A double-beam interference microscope, such as is manufactured by E. Leitz, Wetzlar, A.G., is used. The filament to be tested is immersed in an inert liquid of refractive index nL differing from that of the filament by an amount which produces a maximum displacement of the interference fringes of 0.2 to 0.5 of the distance between adjacent undisplaced fringes. The value of nL is determined with an Abbe refractometer calibrated for sodium D light (for measurements herein it is not corrected for the mercury green light used in the interferometer). The filament is placed in the liquid so that only one of the double beams passes through the filament. The filament is arranged with its axis perpendicular to the undisplaced fringes and to the optical axis of the microscope. The pattern of interference fringes is recorded on T-410 .
Polaroid film at a magnification of lOOOX. Fringe displace-ments are related to refractive indices and to filament thicknesses, according to the equation:

d (n - nL)t D
where n is the refractive index of the filament, ~ is the wavelength of the light used (0.546 micron), d is the fringe displacement, D is the distance between undisplaced adjacent fringes, and 1~ 2'3 ~0 t is the path length of light (i.e., filament thickness) at the point where d is measured.
For each fringe displacement, d, measured on the film, a single n and t set applies. In order to solve for the two unknowns, the measurements are made in two liquids, pre-ferably one with higher than one with lower refractive index than the filament according to criteria given above. Thus, for every point across the width of the filament, two sets of data are obtained from which n and t are then calculated.
This procedure is carried out first usinsQolarized lighthaving the electric vector perpendicular to the filament axis, at measuring points .05, .15, ... .85, .95 of the distance from the center of the filament image to the edge of the filament image. This procedure yields the chord average nl refractive index distribution. The n ¦¦ re-fractive index distribution is obtained from one additional interference micrograph with the light electric vector polarized parallel to the filament axis (using an appropriate immersion liquid preferably having a refractive indexslightly higher than that of the filament). The t (path length) distribution determined in the n' measurerlent is uced ~or vhe n ¦¦ determination.
Birefringence (~) , by definition is the differ-ence (n ¦¦ - nl). Differential birefringence ~95_5 is then the difference between ~ at the 0.95 point and the .05 point on the same side of the filament image. The value of ~95 5 for a filament is the mean of the two ~95_5 values obtained on opposite sides of the filament image.
In all of the above calculations, all linear dimensions are in the same units and are converted, where 2~70 necessary, either to the magnified units of the photograph or to the absolute units of the filament.
This procedure is intended to be applied to filaments having round cross sections. It can also be applied to filaments having other cross sections by chang-ing only the definition of the averaging procedure to ob~ain ~ ~95_5. The "skin" as defined above amounts to about 10% of the fiber volume. In applying this to a non-round fiber the portion defined as skin should also include the outer 10~ of the fiber, but there must be sufficient averaging with respect to different positions in the fiber skin, effected by rotating the fiber about its axis to various angles, to ensure that the skin birefringence value is truly representative.
~ c and ~am are the birefringence values for the crystalline and amorphous phases, respectively, and ~ is the crystalline orientation anqle. For partly oriented semi-crystalline polymer filaments, the contribution of the crystalline and amorphous polymer segments to the bire-fringence (~) may be expressed as ~ = X~c + (l-X)~am~ where X is the fraction of crystalline material and may be cal-culated from the measured polymer density (p) and the densities of the crystalline phase (Pc = 1.455 gm/cm3) and ` of the amorphous phase (Pam = 1.335 gm/cm3) since X = P Pam PC- Pam The crystalline birefringence (~c) is defined as the product of the Hermans' orientation function (fc) and the intrinsic birefringence (~c) of a perfectly oriented crystalline phase. The approximate value of 0.220 given ~ Z370 by J. H. Dumbleton, Journal of Polymer Science, A-2, 6 (1968) page 795 has been used herein for ~c For typical fila-ments of the invention with reasonablywell-oriented crystals, fc can be calculated from fc ~ 180 The crystal orientation angle ~ is the azimuthal angle in degrees at half-maximum intensity of the 100 re-flection of the yarn sample (20 = 25.64), corrected by subtracting the angular equlvalent of the radial breadth of the arc. ~ is preferably not more than 18, which is smaller than for many prior co~nercial textile yarns.
The amorphous birefringence (~am) may, therefore be calculated from the relation ~am = ~ ~ X~c or from - O. 220fCX
am ~ 1 - X

The yarns of this invention are characterized by highly oriented crystalline regions with values of fc typically greater than0.9 (where a value of 1.0 indicates perfect orientation with respect to the fiber axis) and highly disoriented amorphous regions with birefringence ~am less than 0.07 and typically less than 0.06. The amorphous birefringence is considerably less than that observed for conventionally drawn yarns.
The boil-off shrinkage (30S) is me sured as in Piazza ~ Reese V.S. Patent No. 3,772,872. A yarn having a low boil-off shrinkage of 2-2.5% can be package-dyed without the use of special packages or heat-setting.
The dry heat shrinkage (DHS, 16GC) is unusually low, generàlly being less than 1% more than the BOS, and is measured in the same manner as the BOS except that the sample is heated in air in a 160C oven.

The HRV is the relative viscosity measured as in ll;~Z3`70 British Patent No. 1,406,810. Preferred textile values are 20 to 24 for poly(ethylene terephthalate).
The melting_point (T melt) is measured by a Du Pont DTA Thermal Analyzer 900, calibrated with oxanilide (m.p.
251C), the sample being heated 20C/minute under a nitrogen atmosphere. Preferred poly(ethylene terephthalate) yarns have melting points above 258C, which is higher than usually encountered with prior art yarns.
The sonic modulus (Es) is defined by the relation Es = pVs2 where ~ is the polymer density and V~ is the sonic velocity in km/sec as measured with a Morgan dynamic modulus tester according to ASTM procedures [ASTM F89-68, Annual Standards, Part 15, 866-873 (1968)] at a frequency of 10,000 cycles per second and under a tensile load cor-responding to about 0.7 gpd at 65~ Relative Humidity and 70F. The filaments of this invention preferably have sonic moduli greater than about 10 x 101 dynes/cm2, whereas commercial yarns spun at lower speeds have values less than 10 x 101 dynes/cm2. Commercial spin/drawn yarns have values of about 15 x 101 dynes/cm2 or more, as do filaments of the invention spun at higher speeds such as 8000 yards/
minute.
The torsional modulus (G) and Poisson's ratio (v) are useful indicators of filament structure in the trans-verse direction (e.g. skin-core structure differences), since torsion involves filament deformations perpendicular to the filament axis. The torsional modulus is measured by a Toray Fiber Torsional Rigidity Analyzer, which measures the torque (M) for different twist angles (~), where ~ is defined as the rotation in radians of two filament cross-Z3`70 sections relative to each other divided by the distance between them. The filament specimen to be tested is carefully mounted to two sample tabs with an adhesive cement available from E.I. du Pont de Nemours and Company under the trade mark D~CO. The specimen is then clamped into position using the tabs. This procedure reduces handling of the specimen and the possibility of filament slippage in the clamps. Tension on the specimen is held constant at 0.5 gram and all measure-ments are made at 60% relative humidity (R.H.) and 70F.
Initially torque (M) and twist angle (~) are linearly related with a proportionality constant ST, the measure of torsional rigidity as given by M = ST~ where the value of ST is described by ST = KTA G, in which KT is a shape factor (0.159 for round fibers); A is the cross-sectional area; and G is the shear modulus. Values of KT and a discus-sion of the relationships are given in S. Timoshenko and T. N. Goodier, "Theory of Elasticity", McGraw ~ill, N.Y.
(1951). The average value of G is defined by the expression:
~r4Gdr/~r4dr, where G is a function of the radius r. It is therefore readily seen that the average shear modulus (G) is sensitive to the "skin" structure. A measure of the anisotropy (e.g., uniaxial prientation) of a filament may be given by the ratio of the elongational modulus (E) and the shear modulus (G), E/G = 2(1+v), where v is the Poisson's ratio. For perfectly isotropic incompressible materials the Poisson's ratio is 0.5 and the ratio of the elongational and shear moduli is exactly 3. In the calculation of v the elongational modulus is determined from the sonic velocity, i.e., the so~ic modulus (Es)~

1:;1 ;~Z3 7~

The yarns of this invention preferably have values of G of about 1.0 to 1.6 x 10+1 dynes/cm2 and values of v of about 2 to 5 (see Table XIII). The values of v and G
increase, in general, with increasing spinning speed and with decreasing dpf. At any given spinning speed, yarns - with high G95_5 values are observed to have higher values of G giving rise to lower values of v. Filaments charac-terized by larger values of G are more rigid than expected for a given level of bulk molecular orientation, are found to have a larger skin-core structure, and are more brittle on torsional strain. Lower skin-core structures (as defined by differential birefringence Q95_5) apparently correlate with lower torsional moduli.
Flex resistance is measured as described in ~.S.
Patent No. 3,415,782, col. 8, line 51 to col. 9, line 6, and is a measure of the brittleness of filaments to blend-ing (flexing) deformations. For staple filaments this property is important and the staple filaments of this invention are found to have 2-3X the flex resistance of commercial staple filaments.
The dyeability of various yarns is compared herein by measuring their disperse dye rate, DDR, which is defined hereby as the initial slope of a plot of per-cent dye in filament by weight versus the square root of dyeing time which is a measure of a dye diffusi~n co-efficient (if corrected for difference in surface to vol-ume ratioj. -The values of the disperse dye rate are nor-malized to a "round filament" of 4.7 denier per filament (dpf) having a density of 1.335 gms/cm3, i.e. of an "amorphous" 160-34 round filament yarn, as a relative disperse dye rate, RDDR, defined by the relation:

(~
Z37~

RDDR = DDR(measured) X [dpf/4.7)(1.:335/p)(100/(100-BOS)]~
where p is the polymer density; dpf :is the filament denier;
and BOS is the yarn boil-off shrinkage. The RDDR value is approximately lnde~endent of the surface-to-volume ratio of the dyed filaments and reflects differences in filamentary structure affecting dye diffusion.
The disperse dye rates are measured using "Latyl"
Yellow 3G (CI 47020) at 212DF for 9, 16 and 25 minutes using a 1000 to 1 bath to fiber ratio and 4% owf (on weight of fiber) of pure dyestuff. The dyestuff is dispersed in distilled water using 1 gram of "Avitone T" (a sodium hydrocarbon sulfonate) per liter of dye solution. Approxi-mately 0.1 gram yarn sample is dyed for each interval of time; quenched in cold distilled water at the end of the dyeing cycle; rinsed in cold acetone to remove surface held dye; air dried and then weighed to four decimal places. The dyestuff is extracted repeatedly with hot monochlorobenzene. The dyestuff is extracted repeatedly with hot monochlorobenzene. The dye extract solution is then cooled to room temperature (~ 70DF) and diluted to 100 ml with monochlorobenzene. The absorbance of the diluted dye extract solution is measured spectrophotometrically using a Beckmann model DU spectrophotometer and 1 cm corex cells at 449~. The ~ dye (by weight) is calculated by the relation:
% dye (wt.) = absorbance X dye molecular wt.
sample wt. (gms) extinction coefficient X volume of diluted dye extract solution (ml) X 100 The ratio of the dye molecular weight and molar extinction coefficient is 0.00693 gm. And the measured Z3~) value of DDR is the slope of the plot of % dye (by weight) versus dyeing time (min) /2 .
Commercial coupled spin/draw yarns are found to have RDDR values of~0.025 and may require up to 5g/~ of carriers to dye-at-the-boil. The as-spun yarns of this invention have RDDR values greater than O.050 and typically > 0.060. Aithough it may be desirable to use levelling agents and/or small amounts of carrier in practice when dyeing yarns of thls invention, especially to deep shades, such yarns do have a capability of being dyed by disperse dyes without a carrier.
The dyeability of filaments of the invention depends to some extent on the process conditions used to prepare the filaments. The advantage of enhanced dye-ability, as co~pared with prior con,mercial hard yarns, is first that the yarns of the invention can be dyed at the boil without a carrier, whereas prior commercial hard yarns needed higher temperatures and pressures and/or the presence of a carrier, and second that the yarns of the invention can be dyed more rapidly, i.e. the time required for dyeing can be significantly reduced without sacrificing depth of dyeing.
In some cases, depending on the dyestuff, it may be possible to increase the depth of dyeing, provided that the preferred high shear spinneret is used to prepare the filaments of the invention.
K/S is a measure of apparent dye depth (visual : color intensity) according to the equation (100 - R)2 /S =

; 30 wherein R is the percent light (of wavelength corresponding ~ 28 -Z3`7'0 to that of maximum absorption) reflected from the sample compared to that reflected from a barium sulfate plate (Color in Business, Science, and Industry, Deane B. Judd, Gunter Wyszecki, 2nd Edition, John Wiley & Sons, 1963, at page 289). A Diano Colorlmeter (available from Diano Corporation, Mansfield, Mass.) is used for the measurement.
The draw-textured yarns of the invention are dif-ferent from prior commercial textured poly(ethylene terephthalate) yarns in that they can be dyed at the boil (i.e. with a dispersed dyestuff without a carrier). The dyeability of the draw-textured yarns increases, in general, with the spinning speed of the feed yarns (whereas the dye-ability of the feed yarns, i.e. before draw-texturing, decreases, in general, with the spinning speed). Prior feed yarns for draw-texturing (i.e. partially-oriented yarns) have had a dye-at-the-boil capability, but the draw-textured yarns have lost this capability because of the drawing operation, which has reduced the dyeability. For feed yarns for draw-texturing purposes it is desirable that the dyeability (of the textured yarns) not be significantly affected by the spinning speed, since small changes in spinning speed (when making the feed yarn) would cause dyeing defects in the final fabrics containing the textured yarns. It is preferred, therefore to use draw-textured yarns prepared from feed yarns of ~20 at least about 2.0 gpd, i.e. spun at more than about 5500 meters/minute, since the increase in the differential dyeability of the draw-textured yarns becomes less significant as the spinning speed of the feed yarns is increased, e.g., to 6400 meters/minute, cor-responding to an cr20 of about 2.6 gpd.

~l~z3~l The draw-textured yarns of the invention preferably have a RDDR value > O.045; especially > O.055, and can be characterized by a loss modulus ~eak temperature (TE,,maX) of 115C or less and by a temperature at the maximum shrinkage tension (TmaXsT) of at least 258C.
The shrinkage tension (Sh. Tens.) is measured using a shrinkage tension-temperature spectrometer (The Industrial Electronics Co.) equipped with a Stratham Load Cell (Model UL4-0.5) and a Stratham Universal Transducing CEU Model UC3 (Gold Cell) on a 10 cm loop held a constant length under an initial load of 0.005 gpd and heated in an oven at 30C per minute and the temperature at the maximum shrinkage tension (TmaXsT) is noted. The maximum shrinkage tension of the as-spun filaments of the invention are typically less than 0.2 gpd which distinguishes these filaments from commercial spin/draw filaments and from "space-drawn" filaments as described in French Patent No. 74.32295 (Davis et al.) published April 19, 1975. The TmaXsT for the draw-textured yarns is found to increase with spinning speed (of the feed yarn) and is preferably over 260C, especially about 265C or more, in contrast to 245-250C for textured drawn yarns and 255C for draw-textured partially-oriented feed yarns.
The relation between the dyeability of poly(ethylene terephthalate) and the loss modulus peak temperature (TE,,maX) has been noted by Dumbleton et al., J. Applied Polymer Science, Vol. 12 (1968) pp 2491-2508, see also Kolloid-Z, Vol. 228 (1968) pp 54-58. A TE"maX of 115C or less, preferably 110-112C, distinguishes-draw-textured yarns of ~he invention from prior commercial textured yarns, namely 131C for textured drawn yarns and 118C for draw-textured partially-oriented yarns.

3`7C~

E" max The test instrument is a modified RHEOVIBRON*
model DDV II oven; the original oven has been modified for rapid heating maintaining the same geometry; (a standard RHEOVIBRON oven could be used); the amplitude factor step attenuator is replaced with a 10-turn, 1500 Q HELIPOT*
potentiometer and the original, spring loaded clamps are replaced with screw fastening magnesium alloy clamps having grooved gripping surfaces and weighing 3.5 g each, including the support rod.
The sample of textured yarn of about 160 denier (determined by weighing a sample of length 9.0 cm measured under a tension of 100 g) of sample gauge length (i.e.
distance between clamp jaws) set at 2.00 + 0.1 cm at room temperature and at zero tension.
Measurements are performed at a constant static stress of 0.5 gpd based on the initial denier. This static stress is applied when the sample is cold and is not relaxed during the test. This stress is maintained manually using the "stress" measuring position and the sample-length adjust-ment knob. There is some creep, so that frequent rechecking of the static stress component is necessary. The static stress is not allowed to fall below 0.45 gpd nor to rise above 0.55 gpd when the sample is heated above 30C. The sample is equilibrated at each measuring temperature for 25 minutes (includes heat up time), 15 minutes under static load only, and 10 minutes under combined static and dynamic loads, before the loss tangent and dynamic modulus are measured.
The sample length in this test is set to 2.00 +
0.1 cm at room temperature. A higher temperatures the * denotes trade mark ( 23;~0 sample length necessary to maintain 0.5 gpd static tension is greater and the modulus measurements are corrected for this length change. Modulus measurernents are also corrected for the compliance of the stress (T-l) gauge. No corrections for gauge compliance or mass of the clamps are applied to the loss tangent measurement. In this test the dynamic stress amplitude is maintained constant at 0.25 gpd at test temperatures equal to or less tnan 120C.
In the event that at higher temperatures (above 120C) the instrument's maximum dynamic displacement ampli-tude will not produce a dynamic stress of 0.25 gpd, the displacement amplitude is set at this maximum value and tne test is continued at whatever lower dynamic stress amplitude obtains. The static stress is maintained con-stant as described above. The measurement temperatures are 80, 90, 95, 100, 105, 110, 115, 120, 130 and 140C
+ 1C. Throughout a test of one specimen the test tempera-ture intervals are 5 + 1C, the measuring frequency is 35 Hz.
Loss modulus peak temperatures are interpolated from the data by fitting the highest measured loss modulus value, the two values at 5 and 10C higher temperature and the two values at 5 and 10C lower temperature and the respective test temperatures to a parabola using the method of least squares. To assure temperature calibration, a calibrated thermocouple in contact with a test specimen clamped in the specimen clamps is used to measure the temperature difference between a process temperature thermocouple which is fixed in position close to the sample and the true sample temperature. In subsequent 3 ;~() tests the specimen temperature is defined as the "process"
temperature plus (or minus as appropriate) the measured temperature difference.
The crimp contraction values after heating (herein termed CCA5) are measured as the crimp development (CDW) described in Piazza & Reese U.S. Patent No. 3,772,872 in col.
4, where w = 5 mg/denier.
Work Recovery, W , from x = 1, 3, and 5% elongation x is a measure of the freedom from permanent realignment of the polymer molecules following stretching of the fiber or yarn.
The ratio of the work done by the polymer molecules in attempting to return to their original alignment followins stretching to a predetermined elongation to the work done on the sample during stretching is termed the work recovery.
An INSTRON tester, Model TT-B or TM (Instron Engineering Crp) fitted with a tensile load cell, Model B and pneumatic air clamps with l-inch X l-inch jaw faces were used. The samples were conditioned at 130~F for 2 hours and then at 70F and 65% RH for 16 hours. In this test the conditioned sample is stretched at the rate of 10% of its test length per minute until it has reached 1% elongation, after which it is held at this elongation for 30 sec. and then allowed to retract at a controlled rate of 10% per minute, based on its original length. Wl% is calculated as the percentage ratio of the area under the controlled load-relaxation curve to the area under the stretching load-extension curve. The above cycle is repeated for 3% and 5% elongations based on the original sample length (i.e. correcting for any developed slack in the sample from the previous cycle).

Z3~0 Yarns according to the invention are characterized by unique properties in the sense that they have not hitherto been founc in commercial poly(ethylene terephthalate) yarns, namely: (1) hard yarn-like tensile properties for as-spun yarns of high ~20 (preferably ~ 2.6 gpd); (2) low boil-off shrinkage in the as-spun condition; (3) good thermal stabil-ity at elevated temperatures, e.g., up to 200C; and (4) dye-at-the-boil capability without carrier. The textured yarns have similar properties with slightly reduced dye-ability, as compared with the feed yarns from which theywere prepared. Although the invention is not intended to be limited to any theory, the following general comments may be helpful in relation to polyester filaments that have been prepared by spinning at these extremely high speeds that overlap the speed range taught by Hebeler in U.S. Patent 2,604,667.
; The low shrinkage and good thermal stability at elevated temperatures are attributed to the large crystals.
On annealing the as-spun filaments, the long-period spacing, as measured by SAXS, precipitously decreases in value from over 300 A to about 150 A.
The annealed structure now resembles that of con-ventional polyester structures giving the familiar two-point SAXS pattern, wnile the as-spun yarns give the four-point pattern. The interpretation of the crystal "structures" as represented by the change in SAXS patterns is schematically represented by A. Peterlin in Textile Research Journal, January, 1972, p. 21 and is also discussed by L. E. Alexander in "X-ray Diffraction Methods in Polymer Science", John hliley and Sons, Inc., New York (1969), pp. 24-26, 332-342. Other polyester yarns are found to have four-point diagrams, such as yarns drawn sufficiently to induce fibrillation (H. Berq, Chemiefasern/Textilindustrie, March, 1972, pp. 215-222); but these yarns are found to have LPS values less than 200 A.
The new annealed yarns differ from conventional annealed yarns in that the crystal size is larger for any given density.
The improved dyeability of the filaments is partially attributed to their large crystals and low amorphous orientation. An increase in crystallinity and/
or a decrease in crystal size will reduce potential dye-ability. Increasins the orientation of the amorphous chains decreases the segmental chain mobility as indicated by a larger T(E~max) and reduced dyeability. The above structural features appear characteristic of yarns spun at extremely high speeds, but to make a useful yarn with these desirable properties at these speeds, it is necessary to avoid forming a skin on the filaments. The absence of any significant skin is indicated by low ~95_5 values and by low torsional moduli G. The "concave" upward de-pendence of ~95_5 versus spinning speed (i.e.,cr20) is expected to be similar to that of the bulk birefringence and should therefore be an increasing function of ~20 which is consistent with the "shape" of the plot of ~95_5 versus ~20 in Figure 3, where the increase in ~95_5 is simplified and represented by two linear relations.

~l~Z~ ~O

D~TAILED DESCRIPTION OF PROCESS ASPECTS
A process by which round filaments may be prepared in its various aspects will be further described with refer-ence to the accompanying drawings.
Referring to Figure 1 showing a typical high speed spinning apparatus, for use in preparing filaments according to the invention, molten polyester is melt spun through - orlfices in a heated spinneret block 2 and cooled in the atmosphere to solidify as filaments 1. As the molten poly-ester emerges from block 2, it is preferably protected fromthe atmosphere by a metal tube 3 (insulated from the face of the spinneret and block by a gasket) surrounding the filaments as they pass between the orifices and a zone 10 in which cooling air is introduced, preferably symmetrically around the filaments through the holes in a foraminous metal tube 11, essentially as described in Dauchert U.S.
Patent No. 3,067,458. The filaments pass between conver-gence guides 21, which are arranged so as to confine the filaments, and then in contact with rolls 20 which rotate in a bath of spin-finish and thus apply the desired amount of finisn to the solid filaments, and then pass another set of guides 22 which hold the filaments in contact with the finish roll 20 and direct the filaments to the next set of guides 25, and on to the windup system, which comprises a first driven roll 31, a second driven roll 32, a traversing guide 35 and a driven take up roll 33, the yarn being inter-laced by an interlacing jet 34.
Figure 2 shows part of a spinning plate with an orifice capillary that is of generally conventional shape, except for the dimensions, as will be mentioned in greater - 36 - :

detail hereinafter. Molten polyester is pumped through a passage 4 in spinneret plate 5, which is located at the base of block 2 in Figure 1. The lower portion of passage 4 is a capillary 7 that is of diameter smaller than that of the upper portion, and ends in orifice 6, through which the molten polyester emerges. The diameter (D) and length (L) of caplllary 7 are indicated in Figure 2.
Many factors are important when spinning polyester filaments at extremely high speeds. It is possible to control the skin-core value, and thus improve the quality of the filaments and/or the continuity of the spinning process by proper attention to these factors, as will be explained hereinafter. An important factor is the type of spinneret that is chosen. It has also been found preferable to con-trol the temperature of the polymer after it passes through most of the filter pack and before it passes through the spinneret orifices, since control of the temperature of the spinneret block alone was not adequate for controlling skin-core value.
The polymer is passed into the spinneret block in molten form, and its temperature can be measured, e.g., by a calibrated thermocouple, before it is further heated by friction as it passes the metering pump, the filter pack and through the orifices in the spinneret plate. This measured temperature can be considered the initial tempera-ture (Ti), in contrast to the block temperature (T~ rhe temperature can also be measured before the polymer passes through the spinneret plate. This is an important tempera-ture, and is referred to hereinafter in the Examples as the polymer temperature (Tp), being the average (bulk) temperature ~l~Z3`;10 measured in the filter pack at a point 50-100 mils above the center of the spinneret plate. The polymer is further heated, as it passes through the orifice in the spinneret plate, to an average polymer temperature at extrusion (TeX).
If a high shear spinneret is used, there is a significant difference (~T) between the temperature at the surface of the polymer (Ts) as it is extruded at the wall of the ca?illary and that in the center of the emerging filament. This difference (~T) and the difference between TeX and T are considered to depend mainly on the pressure drop in the spinneret capillary, and are both approximately power-law functions of ~ pph mils 3, where L, D and w are, respect-ively, the length and diameter of the capillary in mils and the capillary throughput in pounds per hour (pph). Thus, the surface temperature (Ts) can be expressed as an approxi-mation:
Ts = Tp + b (~) where b and _ are constants.
The minimum desired surface temperature as the spinning speed (V) increases can be expressed by:

Ts ~ T ' ~exp (~)~

where T' is a constant, being a temperature, and _ is a constant.

One can express the (simplified) requirement for a high (i.e., minimum desired) temperature (Ts) at the surface of the filament being extruded in terms of the polymer tempera-ture (Tp), being required to be above a minimum value which varies according to the following relationship with the spinning speed (V), the length (L) and diameter (D) of the ,0 capillary and the throughput ~w) per capillary, as:

(~ 3 7~

Tp ~ T' [exp (~ b (L4) where a, b, m and T' are constants. This relationship indi-cates practical ways to maintain a low skin-core value as the spinning speed V increases. Thus, if Tp is to be kept con-stant, as V increases, then Lw should be increased, i.e. a _ higher shear spinneret (increased _~ is a preferred way of maintaining low skin-core values with increasing V. If the same spinneret 'L4) is retained, as V increases, Tp should be increased. If a lower denier filament is desired (lower w) at the same speed V, then a higher shear spinneret (increased L4) or higher Tp should be used.
It will be understood that if additional heat is introduced to the polymer at the spinneret plate, e.g., by a separate heater, then the polymer temperature (Tp) should be lower to get the same surface temperature (Ts)~ but this method is not preferred because of the cost of such addi-tional heat.
Thus, improvements in polyester filaments, that have been wound up at very high speeds, have been achieved according to the invention by using a special spinneret with orifice capillaries providing high shear by reason of the dimensions, specifically the diameter (D) and the quotient (L ) obtained by dividing the length (L) by the fourth power of the diameter (D).
The lower limit for the diameter (D) of about 9 mils (0.23 mm) is important for good yarn quality when spinning such filaments of about 5 dpf; capillaries of diameter 8 mils (0.2 mm) are not recommended because particles tend to plug the capillaries. Spinnerets of lower diameter, such as 8 mils (0.2 mm), may be used for filaments of lower ~ ~ 3g -ll;~Z3`;~0 dpf if so~dparticles are prevented from reaching the capillaries. One will generally prefer to use a low dia-meter within the practical range, e.g., a diameter of 9 to 11 mils (0.23-0.23 mm~ for filaments of about 5 dpf, for practical reasons, since a larger diameter will require making a longer capillary, in order to keep the 4 within the desired range. Thus the upper limit of diameter is chosen mainly for practical reasons, since a capillary of diameter 15 mils (0.38 mm) would require a length (L) of the order of a tenth of an inch (2.5 mm) or more.
The L/D4 ratio is very important. Filaments of about 5 dpf were spun and wound with continuity and having only few broken filaments using a capillary of diameter 10 mils (0.25 mm) and L/D4 20 x 10-4 mils~3 (120 mm~3) at 6700 yards per minute (~ 6100 meters/minute). These results were not as good as when a preferred capillary of L/D4 40 x 10-4 mils~3 (250 mm~3) was used. When a capillary of diameter 9 mils (0.23 mm) and of L/D4 18 x 10 4 mils 3 (110 mm 3) was used to spin at about 7000 ypm (~6400 mpm), yarn quality was poorer than that obtained with the above 10 mils (0.25 mm) capillaries of L/D4 ratios 20 x 10 4 mils 3 (120 mm 3) and 40 x 10-4 mils~3 (250 mm 3). A higher range of L/D4 is pre-ferred for filaments of smaller dpf, because of the lower throughput, at the same speed. Although, as already indi-cated, several other conditions can affect continuity and yarn quality when spinning at these extremely high speeds, an L/D4 ratio of at least 20 x 10 4 mils~3 (120 mm 3) is preferred when spinning filaments of about 5 dpf. An upper L/D4 limit of about 100 x 10 4 mils~3 (600 mm 3), preferably about 70 x 10 4 mils 3 (425 mm 3), is based on a desire to (` l~;~Z3'70 avoid excessive pack pressures. Lower values of L/D within this range are generally preferred for practical reasons, i.e., to avoid making excessively long capillaries.
As will be seen hereinafter, a spinneret with an orifice capillary of 10 mils (D) x 40 mils (L) 0.25 mm x l mm is preferred for spinning filaments of about 5 dpf. Such capillary has an L:D ratio of 4:1. Preferably the L:D ratio is at least about 4:1. As this L:D ratio is reduced, the filaments may tend to be less uniform, because the melt has less time to achieve a steady state as it passes through the capillary.
It is surprising that continuity is improved and/
or other advantages are obtained, by using a capillary of relatively small diameter and relatively large length at these very high speeds. One might have expected instead that the spinning of filaments of the same denier at higher spinning speeds would have been achieved more easily with orifices of larger diameter because of the need to increase the throughput of the extremely viscous polymer to an extent corresponding to the higher speed, and to avoid a problem referred to as "melt fracture" or "capillary break-up", whereby the polymer flow through the capillary lacks uni-formity and eventually forms droplets instead of a continu-ous filament. Although the invention is not limited to any particular theory, it is considered that the value L4 is significant because it is related to the pressure drop through the capillary, and the pressure drop is related to the work done by the viscous polymer melt as it passes through the capillary (causing a temperature rise near the wall of the capillary). A significant difference in 1~23`70 temperature (~T) between the exterior and the interior of the emerging melt is desirable to make the filaments of the invention.
This temperature difference ~T may be estimated from theoretical considerations. It is found that the approximate temperature difference is 2C for a 20 mil (0.5 mm) diameter capillary with an L/D4 ratio 5 x 10 mils 3 (c. 30 mm 3) while a preferred spinneret with a 10 mil (0.25 mm) diameter and an L/D4 ratio of 40 x 10 mils 3 (c. 250 mm ) has an approximate temperature difference of 9C. At extremely high spinning speeds, a temperature difference of at least 5C is preferred when spinning with block temperatures less than about 310C. For block tempera-tures more than about 310C it is observed that the spinning continuity and yarn quality become less sensitive to the capillary dimensions. To reduce the possibility of polymer degradation, however, block temperatures less than 310C are generally preferred, and so the use of a high shear (heat-generating) spinneret is preferred to obtain the surface temperature of about 305C to 330C that is believed to be desirable for continuity in spinning and better filament quality when spinning at extremely high speeds. Also it has been found that increasing the temperature (Ts) of the polymer at the wall of the capillary has a greater beneficial effect on skin-core at lower values of Ts up to a preferred minimum Ts,-and thereafter any further decrease in skin-core is generally less proportionately for a further increase in Ts. Thls preferred minimum TS increases with spinning speed.
The values herein have been obtained by working with filaments of 1 to 7 dpf. As indicated already, a change in dpf is important since this changes the throughput w. By using an average throughput value w, equivalent to that preferred for 4-7 dpf, namely 0.44 pounds of polymer/
hour/capillary (ppH) (0.2 kg/hr/capillary), at block tempera-tures of less than about 310C, the preferred L/D4 limits of 20 x 10-4 to 70 x 10-4, generally up to 100 x 10-4 mils 3 (120 mm~3 to 925 mm~3, generally up to 600 mm~3) convert to Lw values of 9 x 10-4 to 30 x 10-4, generally up to 45 x 10-4 ppH mils~3 (25 to 85, generally up to 125 x mm~3 kg/hr) the lower limiting value of which may depend to some extent on spinning speed, i.e., 8-9 x 10 4 ppH mils 3 (25 mm~3 kg/hr) giving satisfactory continuity and/or yarn quality at speeds such as 6000 yards per minute (about 5500 meters/
minute), while being only borderline at greater speeds, where as 4 values of 5 x 10 4 ppH mils 3 (15 mm~3 kq/hr) give unsatisfactory results even at 6000 yards/minute (about 5500 meters/minute).
At block temperatures more than about 310~C, as indicated above, the need for shear heating is not as stringent so the preferred lower limits of L/D4 may be 5 x 10 4 mils 3 (30 mm 3) and of Lw/D4 2.5 x 10-4 ppH mils 3 (7 x mm~3 kg/hr).
Spinnerets having orifice capillaries with small diameter, e.g., less than 15 mils (0.38mm), have been suggested but it was not expected that use of such spinnerets within certain limits of L/D4 could be advantageous under the condi-tions (especially of temperature and throughput w) indicated because these conditions are close to those that might have been expected to give melt fracture. Previously it was pre-ferred to avoid operating near melt fracture conditions.
~o Another important feature is the treatment of the 3`~0 filaments as they emerge from the orifices. The prior art contains many suggestions for special devices to cool and solidify the freshly-extruded filament bundle or strand.

As the speed of withdrawal has increased, the throughput of hot polymer has increased, and it has been thought important to increase the flow of cooling air, in order to obtain adequate cooling of this larger throughput. The most effective forced cooling device has been a forced flow of cross-flow air, i.e.
a unidirectional stream of air passed across and through the filament strand. We have found, however, that at very high spinning speeds the amount of forced air should be reduced.
When there is no flow of air the threadline is very unstable and the filaments frequently strike adjacent moving filaments and fuse and break. A slight flow of air causes a significant improvement in yarn quality. Increasing air flow rate further appears to make the threadline brittle since the frequency of broken filaments first increases sharply and then begins to level off and eventually decreases slightly at very high quench air flow rates. Thus, when spinning at extremely high speeds, as the quench air flow rate is increased, the number of broken filaments passes through a minimum (optimum) value, which is not usually observed at conventional spinning speeds, especially if the temperature has been properly chosen. At these extremely high speeds, it is preferred to delay cool-ing of the emerging filaments immediately below the spinneret.
It is preferred to provide a zone in which protection is provided for the filaments and for the spinneret face from turbulent eddies. This can be achieved by a hollow tube surrounding the emerging filament strand in a known manner.
Introduction of some gas, e.g. air, as a coolant below the 3`7~

spinneret is desirable to avoid turbulent conditions that would otherwise result from air being drawn up towards the face of the spinneret by the pumping action of the fast-moving filaments. Thus, it is advantageous to introduce gaseous coolant symmetrically, i.e. radially, around the filament strand below the protective tube, e.g., by using ~ a foraminous tube and outer plenum chamber, preferably with a lower impervious tube also surrounding the filament strand, as suggested in Dauchert U.S. Patent No. 3,067,458, and it is preferred to introduce sufficient gaseous coolant as to prevent such a significant amount of air from being pumped up into this tube zone as would cause turbulence. The amount of gaseous coolant that is introduced is much less than in prior art suggestions for forced cooling, being less than 4, preferably less ihan 3 scfm/pound of polymer through-put per hour (less than about 250, preferably less than about 190 liters/min/kg/hr); these amounts contrast with a flow OL
about 6 scfm/pound/hour (about 375 liters/min/kg/hr) for cooling commercial 150 denier equivalent polyester feed yarn for draw-texturing. The amount of gaseous coolant for forced cooling of low dpf yarns (e.g. less than about 4 dpf) is found to be less than 7 scfm/pound/hour (440 liters/min/kg/hr), preferably less than 6 scfm/pound/hour (375 liters/min/kg/hr);
these amounts are greater than those used for high dpf yarns (>4 dpf) as described above; but contrast with a flow of about 8 to 10 scfm/pound/hour (500 to 625 liters/min/kg/hr) for cooling of commercial polyester draw-texturing feed yarns of equivalent dpf. Air is the preferred coolant because of its - low cost, but inert coolants, such as nitrogen or inert gases may be preferred for some purposes. The coolant will generally Z3`~1D

be at ambient temperature, but it may sometimes be preferre~
to control tne conditions, e.g. of temperature and humidity, and to introduce heated gas into this zone to further delay the cooling and solidification of the filaments as suggested in Chantry ~ Molini U.S. Patent No. 3,216,187 and Cenzato U.S. Patent No. 3,361,859. It will be understood that heat-ing of cross-flow air is one way of improving the results of this system.
It is noted that at spinning speeds according to this invention threadline stability (absence of sideways motion) must be maintained to prevent the freshly extruded filaments from sticking together. Factors which reduce spinning stresses such as high polymer temperature and quench environment temperature tend to decrease threadline stability. At high polymer temperatures it may be necessary to decrease the length of the hollow metal tube and/or to allow for greater heat exchange through the tube. ~nder low-spinning-stress conditions it may even be necessary to use a greater flow (even more than 4 scfm/pph (250 liters/
min/kg/hr) of quench gas to insure threadline stability.
After solidifying the filaments and combining them into a strand, and preferably after applying finish, we have sometimes found it helpful to deflect the strand around a guide 25, in its passage to the first driven roll 31. It is considered that such guide may control possible surges in tension that would otherwise be applied to the solidifying filaments as they are withdrawn from the spinneret.
The polymer should preferably be at a temperatur below iis glass transition temperature as it passes any tension-controlling device. Any tension-controlling device is preferably downstream from finish roll 20, whereby the finisn helps to prevent filament abrasion and significant increase in temperature of the filaments from frictional causes at this location. In practice, the precise arranse-ment is achieved empirically according to the precise condi-~- tions of spinning. Although conventional pin guides have been used, other conventional guides could be used to act as a tension-controlling device, or alternative means can be used to control surges of tension on the filaments as they are withdrawn from the spinneret.
The terms spinning speed and withdrawal speed have been used herein to refer to the speed of the first driven roll wrapped (at least partially) b~ the filaments, i.e. feed roll 31 in Figure 1 tnot finish roll 20, which is merely kissed). The term spinning speed is used more fre~uently in the art, and is essentially similar to the winding speed (i.e. the speed at which the filaments are wound on a package) in the spinning stage of a split pro-cess or in a hign-speed spinning process. In a coupled process, the winding speed is faster than the spinning speed, and so the term withdrawal speed has sometimes been referred to herein, so as to avoid confusion with the winding spe`ed.
It will also be understood that additives such as pigments and delusterants may be incorporated in the fila-ments of the invention, and conventional aspects of polyester filament production, such as additives, have not been dis-cussed herein.
The invention is further illustrated in the folloh-ing Examples, which are for convenience presented mainly in the form of Tables showing the conditions of preparation and the properties of the yarns produced, Examples with a letter C (e.g., Example 2C) concern yarns with skin-core values above the line XYZ in Figure 3, which is d:iscussed after Example 44.
All the finishes are aqueous emulsions containing 8 to 10% by weight of non-aqueous ingredients, and are applied so as to pro~ide 0.3 to 0.5% by weight of such ingredients on the weight of the yarn.
Finish 1 is as described in Example 1 of U.S. Patent No. 3,859,122.
Finish 2 is based on PLURONIC* L-64 (BASF Wyandotte) (a polyoxyalkylene block copolymer of ethylene oxide and propylene oxide) with minor amounts of sodium dioctyl sulfo-succinate, buffering agents and antioxidants.
Finish 3 comprises:
27 parts ditridecyl adipate 12.3 parts polyoxyethylene(30)sorbitol tetrastearate 4.9 parts polyoxyethylene(20)sorbitan tristearate

5.0 parts isostearic acid 1.6 parts potassium hydroxide (45~) 50 parts of a block copolymer of ethylene oxide and propylene oxide (1:10 mole ratio) having a number average molecular weight of 1100 0.25 part tris(nonylphenyl)phosphite 0.25 part 4,4'-butylidene bis(6-t-metacresol) 0.3 part of a random copolymer of ethylene oxide and propylene oxide hàving a viscosity of 9150 SUS at 100F.
EXA~LES 1-29C
These Examples are presented in Table I. Molten * denotes trade mark ll~Z3';1C~

poly(ethylene terephthalate), having an HRV of 22, and con-taining 0.3% by weight of TiO2, is fed to a spinning machine, forced through a filter pack under the pressure shown in psig and extruded to form 34 filaments by usinq two adjacent spinnerets, each having 17 orifices,which filaments are cooled and wound up as a yarn of the indicated denier at the indicated speed using an apparatus essentially as shown in Figure 1.
The orifices in each spinneret are located on two concentric circles with an orifice spacing of at least 1/8 inch. The capillary dimensions and throughput of polymer per capillary are as shown, D for diameter and L for length in mils, and w (flow) in pph (pounds per hour). The L4and 4 values are shown in 10-4 x mils~3, and 10-4 x pph mils 3, respectively. All temperatures are given in C. The polymer temperatures (Tp), in the filter pack at a point 50-100 mils above the center of the spinneret plate are calculated, except for Example 27, which was measured.
Each bundle of filaments is subjected to a trans-verse flow of air at room temperature (20C) and at the rate shown in standard cubic feet/minute for every pound per hour of bundle throughput (scfm/pph) before passing into the atmosphere. In Examples 1 to 15C and 19-24C the bundle is treated with cross-flow air through a foraminous screen extend-ing over a length of 30 inches; in Examples 17-18 and 28-29C
a similar cross-flow screen extends for 54 inches; in Examples 25 and 27 a similar 54 inch screen is used, but with a metal protective tube around the freshly-emerging filaments for a distance extending for the first 4 inches below the spin-neret; and in ~xamples 16 and 26, radial systems 3~

are used as described and illustrated in Figure 1, with a metal protective tube 3 of internal diameter 2-3/4 inches (and of length 3 inches in Example 16, but of length 3-7/8 inches in Example 26)~ below which is a further tube of diameter 2-7/8 inches and of length 12-1/2 inches, the upper 6 inch portion of which is foraminous and the lo~er

6-1/2 inch portion of which is impervious.
The filaments in each bundle converge at guide 21 and pass over roll 20 applying the finish shown. The two bundles pass further guides and are converged to a 34 filament yarn, which is wound up at the speed shown.
As-spun yarn characteristics are given in Table l;
the measurements have already been discussed. The long-period spacing (LPS) is over 300 A for the as-spun filaments of the invention spun at speeds of 5500 to 7000 YPM, but has not always been measured. The SAXS pattern was not suffi-ciently discrete to permit a measurement of long-period spacing for Example 28, spun at 8000 yards/minute. It is doubted that the yarns of Examples 27-29C have long-period spacings over 300 A. Preferred as-spun filaments have skin-core values that are significantly below line XYZ in Figure 3, e.g., Example 12, whereas as-spun yarns having skin-core values that are above the line XYZ in Figure 3 are for convenience marked with a C in the Table, e.g.
Examples 14C and 15C. Figure 3 is discussed in more detail after Example 44. All the filaments have large average crystal size (at least 55 A) and low amorphous birefringence (less than 0.070) whether in as-spun or annealed condition.

The process described in Example 26 was essentiall~

Z3`~D

followed, except that the rate of flow of air was varied when spinning at 6000 yards/minute (30-32) and 7000 yards/
minute (33-35C). The actual process conditions and yarn characteristics are given in Table II. It will be noted that the skin-core values increase with an increasing rate of flow of air when spinning at 7000 yards/minute, whereas the skin-core values are essentially similar at 6000 yards/
minute, regardless of a variation in the air flow over a range of 0.8 to 3.8 scfm/pph. The long-period spacing of the yarnof Example 34 is 320 A; although the other long-period spacing measurements were not made for these Examples, enough other values have been measured to establish that filaments spun at these high speeds (6000 and 7000 yards/
minute) do have long-period spacing of over 300 A.

The process described in Examples 17-18 was essentially followed (at 7000 yards/minute) while varying the block temperature, the capillary dimensions and the flow of air, the values being given in Table III; the polymer temperatures (Tp) were measured in Examples 36 and 37. It will be noted that preferred low skin-core values are obtained in Example 37 with a high shear spinneret, a low block temperature and low air flow, and in Example 39 with a low shear spinneret, high block temperature and high air flow, the c-20 values being somewhat different. By increas-ing the air flow with the high shear spinneret in Example 36 (to the same rate as in Example 39) or by using a slightly lower block temperature (305C, which is still high) with the low shear spinneret in Example 38C, the skin-core values were raised significantly.

All these Examples were run at 7000 yards/minute, the conditions and yarn characteristics being given in Table IV, and show the effect on skin-core value of s?inning filaments of lower denier per filament (dpf), i.e., of lowering the capillary throughput (w). Example 41 is the same as Example 34 and should be contrasted with Exam?le 40C, run under similar conditions, includins the same volume flow of air, but lower polymer throughput, consequently lower denier and lower polymer temperature, and the skin-core value is higher. It is preferred, therefore, to raise the polymer temperature and use a higher shear capillary spinneret (10 x 80 mil) as in Examples 42-44, which were otherwise run essentially as in Example 25, with varying pack pressures, and so formed filaments of even lower dpf and of low skin-core value. The polymer temperatures (Tp) were measured in Examples 42 and 44.
As indicated above, a general correlation has been noted between high skin-core values and continuity problems in spinning, especially as the speed is increased to about 7000 yards/minute. Thus it was not possible to wind yarn in Examples 22C, 23C or 24C, and only feed roll wraps were ob-tained, in contrast to Examples 20C and 21, where good con-tinuity was achieved for several minutes, but the objective of winding a package for a full 40 minutes was not relia~ly obtained, Example 19 where the continuity in spinning was better and averaged 15 minutes, and Example 16, where ex-cellènt continuity in winding yarn packages was achieved.
As indicated hereinafter, although spinning continuity was obtained to some extent in Example 20C, the resulting yarns presented problems in draw-texturing. Some continuity problems have, however, been traced to other factors, e.g., apparatus features.

5, _ Th~L~ 3 70 Example 1 2C 3 SE~in. Sp-ed, YP,~ 5500 5500 5500 Orlflc~ (D~;L), I~ils 10X40 20X80 15}:~0 L 10-4 miLs 3 40 12 D
Flow (w) pph/cap 365 .377 .393 wL 10-4 pph mils 14.60 1.89 4.62 -Block Temp. TB C 297 298 297 Pack Press. psig 5250 3150 3700 Poly. Temp. Tp (C) 299 299 293 Air, scfm/pph 3.2 3.2 3.2 Finish Type 1 2 2 Denier 158 174 180 ~it. ~d. gpd 60.8 65.1 63.0 ~20~ 9pd 1.61 1.64 1.60 Tenacity, gpd 3 - 47 3- 34 3.52 Elang. 96 62.1 59.1 6r- 3 BOS, ~ 3-3 3. 3.2 DHS, 160CC, % 3-7 3- 3.2 Max. Sh. Tens. gpd .101 .095 .oa3 Denslty (p), g/cc V~;; icm~sec 2.72 3.06 2.66 T~nelt~ C 258 257 25 o 61 65 55 CS~ A

LPS, A
~,5 .0958 .0965 .059 95--5 .0077 .0082 . OOD9 .201 .206 .198 ~am .038 . o46 RDDP~ , ~ aye/min ~ . r,65 .077 .070 ( TABL~ I (Con't.) 3 g~O
Example 4 5 6 7 Spill. Sp~, YPi-~6000 6000 6000 ~000 Orifice (D.~L), inils 10X40 10X40 9X36 10l:20 4 , 10 4 mils 3 40 40 55 2G
Flow (w) pph/cap .462 .400 391 .'~04 wL 10-4 pph mils 3 18.48 16. oo 21.47 8.û8 Block Temp. TB C 294 297 296 293 Pack Press. psig 4500 4900 5100 3700 Poly. Temp. Tp (C) 297 299 299 29c Air, scfm/pph 2.9 2.9 2.9 2.1 Finish Type 1 2 2 Denier 194 169 165 17i }nit. M~d. gpd 79 4 71.6 69.2 c7.8 20~ gpd 1.89 2.01 1.9 1.,^9 Tenacity, gpd 3.76 3.c1 3.72 3.75 Elang. ~ 57.6 52.9 53.1 53.5 BOS, ~ 3-6 3.7 2.
D~S, 160C, % 3.6 3.6 3.4 Max. Sh. Tens. gpd .109 .116 .114 .lû9 De~sity (p), g/cc 1.3810 1.3770 1.3781 i.~`C~l ~,~m/sec 2.70 2.91 2.86 2.51 Tmelt' C 258 259 259 257 ~~ 11 16 14 11 LPS, A 37 329 .1078 .1082 .1077 .10c'' _5 .0080 .0û66 .û07. .0074 ~c .206 .201 .203 .'~
.047 .057 .055 04,~
.û13 .o60 .~5 .~ic8 RDDR, ~ dye/mln ~

~ T~BL~ I (Con't.) 3 ~0 Example 8C 9C 10C 11 Spin. Spee~, Yr~ 6000 6000 6000 6000 Orifice (D.~L), ~ 20X80 20X80 15X60 1,~.60 L4 , 10 4 mils 3 5 5 12 12 Flow (w) pph/cap 407 405 .406 .429 wL 10-4 pph mils~3 2.03 4.81 ,.o8 Block Temp. TB C 296 300 23 300 Pack Press. psig 3200 3350 4300 3800 Poly. Temp. Tp (C) 298 301 296 301 Air, scfm/pph 2.9 2.1 2.C 2.1 Finish Type 2 2 2 2 D~nier 171 170 172 182 ~nit M~d. gpd 82.3 76.0 56.6 75.4 - 20~ gpd 1.91 1.97 1.89 1.34 Tenacity, gpd 3-48 3.57 3-67 3.S7 Elong. ~ 53.8 53.6 54.0 5S.7 BOSf ~ 3.9 2.8 3.3 3.1 DHS, 160C, ~ 4.2 2.8 3.3 2.8 Max. Sh. Tens. gpd .180 .122 .122 .109 ~ensity (p), g/cc 1.3829 1.3789 1.3So2 1-3,C~
,~m/sec 2.86 3.02 2.86 2.51 Tmelt~ C 258 261 261 261 ' '3 16 12 15 CS,A 74 67 75 65 LPS, A - 43 .1021 .1065 .1044 .1089 a95-5 .0106 .oo83 . oo8s . ooSo ac ~05 .201 .~05 .^02 aam 034 045 .053 .053 .r~7~ .0l2 .0c~ .06S
RDDR, % dye~m~n ~

"
~ABLE I (Con't.)

7~
Example 12 13 14C 15C
Spin. Speed, YPM 6500 6500 6500 6500 Orifice (DxL), mils 10X40 9X36 20x80 15;:60 L4 , 10 4 mils 3 40 55 5 12 Flow (w) pph/cap .419 .412 .417 ~ r wL 10-4 pph mils 16.76 22.62 2.09 ~ 5.15 Block Temp. TB C 29& 299 302 302 Pack Press. psig 4850 5200 3725 4000 Poly. Temp. Tp (C) 300 301 303 303 Air, scfm/pph 2.8 2.8 ~1.3 2.1 Finish Type 2 2 2 2 Denier 165 161 163 170 ~nit. Mca. gpd 76.1 75.4 92.5 l.0 - 20~ gpd 2.41 2.31 2.29 2.17 Tenacity, gpd 3.88 3.95 3.72 3.82 Elong. % 47.2 48.2 47.6 48.o BOS, % 3.1 2.5 2.4 2.D
D~S, 160QC, % 3~3 3.2 2.4 2.6 Max. Sh. Tens. gpd .129 .149 .128 .132 Density (p), g/cc 1.3887 1.3844 1.3852 1.3 Vs,~m/sec 2.98 3.07 3.05 3.02 Tmelt' C 263 263 264 26 ~,c o 14 14 15 14 CS,A 72 72 64 66 LPS, A 325 390 - 440 .1153 .1147 .1109 .1115 ~95-5 .oo64 .0079 .0095 .0-)99 ~c .203 .203 .20~ .2Q3 ~am 5 RDDR, % dye/min ~ .060 .065 .070 .062 T~. L~ I (C~n ' t . ) Exam?le 16 17 18 19 Spin. Sp-e~, Y~;~ 7000 7000 7000 7000 Orifice (D~L), lilils 10X40 10X40 10X20 10X40 L 10-4 milS 3 40 20 40 D

Flot~ ( w) pph/cap 439 449 .442 .471 wL 10 4 pph mils 17.56 17.96 8.84 18.84 Block Temp. TB C 300 315 314 300 Pack Press. psig 5300 5600 4700 5300 Poly. Te~p. ~p (C) 302 313 312 302 Air, scfmJpph 2.5 2.7 2.8 2.0 Finish Type 2 3 3 2 Denier 163 162 160 163 Init. M~d. gpd 78.9 90.9 90.8 87.3 20~ gpd 2.88 2.96 2.99 2.74 Tenacity, gpd 4.32 4.33 4.48 4.02 Elong. % 45.0 42.7 45.9 43.5 BOS, ~ 1.8 2.4 2.5 2.5 ~S, 160C, % 2.9 3.1 3.0 3.7 Mbx. Sh. Tens. gpd .123 .120 .144 .128 1 3875 1 3868 1.3870 1.3860 Dens~ty ( p), g/cc ~s; ~m/sec 3.34 3.22 3.15 3.12 Tmelt' C 263 261 259 261 ~ 14 12 11 11 LPS, A
.1233 .1241 .1229 .1174 _5 0073 .0074 .0084 .0072 ~c .203 .205 . ~7 .207 ~am .061 .063 .059 .051 RDDR, ~ dye/min ~ 053 049 055 057 TABLE I (Con't.) Example 20C 21 22C 2 Spin. Speed, YPM 7000 7000 7000 7000 Orifice (DxL), mils 10X40 9X36 20X80 15X60 L4 , 10 4 mils 3 40 55 5 12 Flow (w) pph/cap .447 .455 .394 .437 wL , 10 4 pph mils 17.88 24.98 1.97 5.18 D

Block Temp. TB C 295 300 - 302 296 Pack Press. psig 4900 5900 3800 4100 Poly. Temp. Tp (C) 298 302 303 298 Air, scfm/pph 2.0 2.0 <1.3 2.7 Finish Type 2 2 2 2 Denier 171 162 143 159 Init. Mod. gpd 84.7 90.0 85.3 81.4 ~20' gpd 2.68 2.77 2.33 2.51 Tenacity, gpd 3.97 3.92 3.53 3.75 Elong. % 43.3 39.7 45.4 40.7 BOS, % 2.4 2.5 2.2 2.8 DHS, 160C, % 3.0 3.0 2.8 3.0 Max. Sh. Tens. gpd .137 .130 .112 .145 Density (p), g/cc 1.3859 1.3873 1.3871 1.3844 Vsl km/sec 3.23 3.23 3.18 3.20 melt' 263 264 265 267 ~, 15 22 13 10 CS, A 69 72 74 77 LPS, A 355 450 390 449 .1111 .1168 .1098 .1064 .0108 .0092 .0110 .0163 ~c .202 .193 .204 .208 .043 .060 037 ~035 am RDDR, % dye/min ~ .062 .053 - .067 TABLE I (Con ' t. ) 3~
Example 24C 25 26 Spln. Spe~, YP;1 7000 7000 7000 Orifice (D.~L), milS 15X60 15X60 10X;O
L4, lO 4 mils 3 12 12 40 Flow ( ~) pph/cap , 4 37 . 4 38 . 4 4 0 wL 10-4 pph mils 3 5.18 5.19 17.60 Block Temp. TB C 302 315 302 Pack Press. psig 4200 5800 4800 Poly. Temp. Tp (C) 303 314 303 ~ir, scfm/pph ~1. 3 2.8 1.2 Finish Type 2 3 3 Denier 160 158 159 ~ t. ~d. gpd 94.4 92.0 126.4 o - 20' gpd 2.77 3.02 2.71 Tenacity, g!pd 3.72 4 . 41 4 .27 Elong. ~ 40.6 44.1 47.9 BOS, ~ 2.8 2.6 2.5 D~S, 160C, % 2.5 3.0 3.0 Max. Sh. Ten gpd .134 .148 .138 D2nsity ~p), g/cc 1.3845 1.3871 1.3857 Vs, ~m~sec 3. ~0 3.16 3.15 Tme1t~ C 265 260 257 ~O 18 13 13 CS, A 68 71 _ 350 LPS, A
.1149 .1241 .1237 .0174 .0074 .0070 ~C .198 . 204 . .05 aam .056 .063 .056 RDDR, ~ dye/min ~ . 050 .053 TABLE I (Con~ 3~

E x amp l e _ 7 28 29C
SLlin. Speed, Yril 7500 8000 ~;8000 Orifice (D~L), mils 10,'60 10X60 10X20 L 10-4 mils 3 60 60 20 D
Flow (~) pph/cap .471 .513 .511 wL 10-4 pph mils 28.26 30.78 10.22 D

Block Temp. TB ~C 315 315 315 Pack Press. psig 6500 7100 7100 Poly. Temp. Tp (C) 313 311 316 Air, scfm/pph 2.6 2.4 2.4 Finish Type 3 3 3 Denie~ 159 162 161 ~it M~d. gpd 93.8 106.6 101.0 ~20' gpd 3.32 3.49 3.46 Tenacity, gpd 4-33 4.12 4.01 Elong. ~ 35.2 31.8 30.2 BOS, ~ 2.1 2.0 2.0 D~S, 160C, % 2.7 2.5 2.6 Max. Sh. Tens. gpd .155 .186 .173 . 1.3901 1.3870 1.3898 Dens ty ( p), g/cc V5, ~m/seC 3.24 3.56 3.50 Tmelt' C 269 265 264 ~ 12.5 12 11 CS, A 70 72 71 LPS, A - N
a5 .1253 .1227 .1210 0095 .0115 .0139 ag5_5 .205 .205 .207 .058 .060 .049 ~am . 052 .057 .056 RDDR, % dye/mln Z3~0 TABLE I I

Example 3l 32 Spi n . Spee~, YP~

Ori~lce (D,~L), Inils 10X40 10X40 10X40 L 10-4 mils 3 40 40 Flo~ (t~) pph/cap 0 390 0.391 0.392 D4 ' 10 pph mils 3 15.64 15.68 Block Temp. TB C 300 300 300 Pack Press. psig 4 300 4300 4300 Poly. Temp. Tp (C) 301 301 301 Air, scfm/pph 0 .8 2.7 3.8 Finish Type 3 3 3 Denier 165 165 165 I~ t. Mod. gpd 104.9 100.0 104. 4 ~-20' gpd 2.09 2.04 1.98 Tenacity, gpd 3.99 4.02 4.00 ~long. % 55.2 57.9 58.9 BOS, ~ 3.2 3.2 3.2 D~S, 160C, ~ 3.9 3.9 3.7 Max. Sh. Tens. gpd .104 .109 .101 Density (p), g/cc 1.3766 1.3735 1.3747 Vs;~m/sec 2.84 2.77 2.77 Tmelt' C 253 258 254 ~, 12.5 12 14 CS, A 72 72 60 LPS, A
.1099 .1075 .1075 .0068 .0069 .0064 ~95-5 .205 .205 .203 059 .061 .060 ~am 057 .055 .057 RDD~, ~ dye/mln ~ -li2Z3'70 TA~LE I I ( Co~ t ' d ) ~ample 33 34 35C
Spin. Speecl, YP~I 7000 7000 7000 ~rifice ~D.~L), mil~ 10X40 10X40 10x40 L4 , 10 4 mils 3 40 40 40 Flow ( w) pph/cap 0.441 0.438 0.442 wL 10-4 pph mils 3 17.64 17.52 17.68 Block Temp. TB C 302 302 302 Pack Press. psig 4800 4900 5100 Poly. Temp. Tp (C) 303 303 303 Air, scfm/pph 0.7 2.4 3.3 Finish Type 3 3 3 Denier 159 158 160 ~nit. Mod. gpd 137.9 120.4 124.1 ~-20~ gpa 2.78 2.72 2.59 Tenacity, gp~ 4.36 4.46 4.06 Elang. % 47.3 51.7 46.5 BOS, ~ 2.6 2.5 2.4 D~S, 160C, % 3- 3 3.0 2.8 Max . Sh . Tens . gpd .146 .137 .135 Density ( p), g/cc 1.3844 1.3851 1.3841 Vs, ~m/sec 3.14 3.10 3.05 Tmelt~ C 257 257 258 ~D 13.5 12.5 11 CS, A 66 72 74 LPS, A
~ .1230 .1191 .1170 .0070 .0087 .0098 ~95-5 .203 .205 .207 .056 .056 .057 ~am .053 .053 .060 RDD~, ~ dye/min ~

TABLE III
Example S~in. Spet'~, YP~ 70007000 7000 7000 ~rifice (D.~L), mi1s i0X8010X80 9X12 9X12 L 10-4 mi15 3 80 8018.3 18.3 D

Flow (~) pph/cap .423 .442 .442 .434 wL 10-4 pph mils 33 84 35.39 8.09 7.94 E31Ock Temp. T C

Pack Press. psig 5300 7150 4500 3500 Poly. Temp. Tp (C) 315 295 306 314 ~ir, sc~m/pph 7 0 2.8 4.8 7.0 Finish Type 3 3 3 3 Denier 153 166 160 157 Init. Mod. gpd 92.1 94.3 99.0 95.1 o-20' gPd 2.99 2.89 3.03 3.01 Tenacity, gpd 4.41 3.91 4.44 4.37 Elang. % 44.1 36.8 43.4 42.3 BOS, ~ 2.7 2.5 2.4 2.4 D~S, 160C, % 3.1 2.8 3.0 2.8 Max. Sh. Tens. gpd .157 .157 .168 .171 Density (p), g~cc 1.3835 l.3872 1.3851 1.3855 Us;~mJsec 3.15 3.10 3.26 3.10 Tme1t' C 258 260 259 259 ~ 18 13 15 15 CS,A 64 72 66 72 LPS, A
a5 .1236 .1237 .1217 .1243 .0093 .0075 .0100 .0076 ag5_5 .198 .204 .202 .202 .073 .062 .064 .068 ~am RDDR, % dye/min ~ 049 057 054 050 ~ABLE IV 11~23 70 Example 40C 41 42 43 44 Spin. Speed, YPM 7000 7ooo 7000 7000 7000 Orlfice (D~L), mils 10~;40 10X40 10X80 10~:80 10~80 L4 , 10 4 mils 3 40 40 80 80 80 Flow (~) pph/cap .331 .43~ .276 .35, .443 wL 10-4 pph mils 13 24 17.52 22.08 2.4 35.44 Block Temp. TB C 302 302 315 315 315 Pack Press. psig 3600 4900 5500 520C 7000 Poly. Temp. Tp (~C) 301 303- 310 312 317 Air, sc~m/pph 3.2 2.4 2.9 2.2 2.8 Finish Type 3 3 3 3 3 Denier 120 158 100 128 160 ~nit. M~d. gpd 89.1 120.4 88.1 90.7 &6.7 ~-2~' gpd 2.80 2.72 2.90 2.93 3.G, Tenacity, gpd 4 03 4.46 4.1& 4.3~ 4.57 Elong. % 41.2 51.7 42.2 45.1 45.2 BOS, ~ 2.8 2.5 2.3 2.4 2.5 D~S, 160C, % 3-3 3 3 3.1 M~x. Sh. Ten-~. gpd .203 .137 157 .l4g .149 Density ( p), g/cc 1.3867 1.3851 1.3867 1.3~5 1.3~15 ;~mJsec 3.12 3.10 3.07 3.37 3.73 Tmelt~ C 261 257 260 262 261 c 12 13 12 13 13 lr .

LPS, A
~ .1174 .1191 .1182 .1218 .1231 a . 0104 .0087 .oo78 .0075 .0070 ~c .205 .205 .205 .205 .2n-l .051 .056 .052 .059 .059 ~am .oj6 .053 .o46 .051 .n54 RDDR, ~ dye/min ~

~iL;~3`,~

Figure 3 has been prepared to illustrate the relationship of the skin-core (~95_5) to the o20 values for the as-spun filaments prepared in the foregoing Examples, except for the following, which have been omitted from Figure 3 because the points would have been so close to other points; Examples 7, 31 and 32, in the region of Examples 5 and 6; Example 26, close to Example 19;
Examples 37 and 43, in the region of Examples 16, 17 and 42; Example 41, in the region of Examples 21 and 34; and Examples 39 and 44, close to Example 25. The line XP is defined by the equation used herein:

~95-5 0 0055 + O.0014 C20 Examples with a "C", e.g., 2C, have skin-core values above this line. For as-spun filaments of 20 above about 3, the line YZ is defined by the equation used herein:

~95_5 0.0065 Cr20 ~ .0100 The skin-core values of Examples 38C and 29C that were spun at 7000 and 8000 ypm, respectively, are also above the line XYZ, which is a mathematical approximation of a concave (upward) curve, i.e., the upward slope increases more rapidly when C20 rises above about 3 gpd. These "C
Examples" produce significantly more broken filaments or other defects during spinning (especially those at higher C~20 values) and/or during subsequent textile processing than the preferred filaments of the invention that have skln-core values significantly below line XYZ, and generally ,Z;3~0 have poorer tensile properties than such preferred fila-ments. Filaments having skin-core values in the neighbor-hood of line XYZ are borderline and do not generally per-form so well as the preferred filaments, especially during draw-texturing. It is considered, however, that, even in the borderline area, over a prolonged period of time, as ~ occurs when spinning millions of pounds of polymer commer-cially, less filament breaks will occur during spinning and/or subsequent processing with filaments having l~wer skin-core values than with filaments having higher skin-core values although no significant difference may be appar-ent from their filament properties, such as tensile proper-ties and shrinkage properties.

The line XYZ has been selected empirically from a study of many samples, based on sensitivity of skin-core value to processing variables, in particular capillary dimensions and polymer temperature.
From a filament-processing standpoint, it is pre-ferred to keep the skin-core value low in absolute terms, preferably below about 0.008, regardless of spinning speed and or20. From a practical standpoint, however, it becomes increasingly difficult to control the spinning conditions as the spinning speed increases, so it may be more practical to compromise with a higher skin-core value as the C~20 value increases.

Various areas below the line XYZ have been roughly apportioned according to their approximate cr20 value. Thus any prior art filaments in Area A would have ~20 <1.6 gpd and would have been spun at lower withdrawal speeds, e.g. 3500 ypm for spinning partially oriented ;

., ~ '~ 3J~

draw-texturing feed yarn. The filaments in Area B have 1.6 < ~20 ~ 2 gpd and were spun at relativelv low speeds within the range of extremely high speeds that are used to get filaments of the invention. The filaments in Area C
have 2 < a20 < 2.6 gpd and the advantage of a low skin-core value is more pronounced than in Area B. The filaments in Area D have 2.6 < a20 < 3 and are "hard" as defined herein, i.e. can be subjected (without deformation) to much greater stress than is desirable for filaments in Area C or especially in Area B, although it should be understood that all these filaments of the invention are suitable for some end uses without further drawing. The filaments in Area E
may be under line YZ, rather than YP, it beinc understood that the line XYZ is actually a mathematical ap~roximation of a concave (upward) curve and that it is preferred to have skin-core values that are significantly below the curve, and not in the borderline area.
~ .s the a20 and spinning speed increase, the dye-ability of the as-spun filaments generally decreases and of any draw-textured filaments generally increases, although the conditions of preparation of the feed yarns can have a significant effect on dyeability. Thus, as the a20 and spinning speed increase, the difference in dveability between a draw-textured varn and its as-spun feed yarn decreases, and this is advantageous, since it is easier to avoid introducing dyeing defects when draw-texturing such yarns (of higher a20 and spinning speed). Thus filaments in Area C are preferred over those in Area B because of this dyeability phenomenon and similarly filaments in Areas D and E are, respectively, even more desirable, if economic .

i ~9~Z370 considerations are ignored.
Generally, the use of a higher polymer temperature Tp at these extremely high spinning speeds yields low skin-core filaments of dyeability inferior to that of similar filaments prepared at lower polymer temperatures, e.g. by use of high shear capillaries to obtain a high temperature difference (~T) between the polymer at the wall and in the center of the capillary, although filaments of Example 28 (in Area E) showed surprisingly good dyeability despite the use of a high Tp, and so this effect seems to be more notable for filaments in Areas B, C and D, than in Area E, whose filaments were prepared at higher spinning speeds. A higher Tp generally, however, provides as-spun filaments having improved tensile properties than as-spun filaments of similar low skin-core value prepared by a high shear capillary tech-nique, provided the Tp is not so excessive as to cause polymer degradation which causes broken filaments.
It is noted generally that the dyeability of filaments of lower denier per filament according to the invention is greater than that of otherwise similar filaments of higher denier per filament.
To lower skin-core value even further below line XYZ than is shown in Figure 3 becomes increasingly expensive, and requires more extreme process conditions such as may introduce other problems of process control, which may be-come manifest in product quality, e.g. use of higher polymer temperatures may detract from the attractive dyeing character-istics of filaments having low skin-core values, and having been prepared using lower polymer temperatures, so it is Z,3`70 generall~ preferred to prepare filaments of skin-core value such that ~95 5 > 0.0014 ~20 where about 1.6 ~ ~20 ~ about 3 gpd, i.e. above line ST in Figure 3, and ~95 5 > 0.0065 ~20 ~
0.0155 where G20 > about 3 gpd, i.e. above line RS in Figure 3, using present process techniques and under present economic conditions although these may change.

EXA~lPLES 45-47 These Examples concern production of filaments of non-round cross-section following a procedure essentially similar to that of Example 17, except that for Examples 46 and 47 all 34 filaments were spun in a single bundle from a single spinneret. The conditions and yarn characteristics are given in Table V. In Example 45, the filaments have a trilobal cross-section, in Example 46, a scalloped oval cross-section and in Example 47, an octalobal cross-section.
To spin filaments of scalloped oval and of octalobal cross-section, a two-plate spinneret is used, as described in Gorrefa, U.S. Patent No. 3,914,888 and McKay, U.S. Patent No.
3,846,969, respectively. The top plate, referred to as a metering plate, is similar to that pictured in Figure 2 with capillaries of dimensions D and L, whereas the bottom plate contains orifices of the appropriate design. Trilobal fila-ments are spun as described in Holland, U.S. Patent No.
2,939,201 and to increase the pressure drop ~Ps in the spin-; neret and the capillary shear as given by the L/D4 ratio, the capillary dimensions are altered by inserting a meterplug in the counterbore of the spinneret and/or meterplate as described by Hawkins in U.S. Patent No. 3,859,031.

3~

EXAMPLES 48 and 49 A 90/10 percent by weight copolymer of ethylene terephthalate and 2,2-dimethyl propylene terephthalate of 26 HRV is spun into filaments having low skin-core values at 6000 yards/minute (Example 48) and 7000 yards/minute - (Example 49) essentially as in Example 1. The con-ditions and yarn characteristics are shown in Table VI.

~ 70 -J~ 3~
TABLE V
Example 45 46 47 Spin. Speed, YPM 7000 6000 6000 Capillary (DxL), mils 9X50 15X72 15X72 L 10 4 milS 76.2 14.2 14.2 Flow (w) pph/cap .442 .410 .395 wL 10-4 pph mils 33.68 5.82 5.61 Block Temp. TB C 315 305 308 Pack Press. psig 6000 6000 4600 Poly. Temp. Tp (C) 314 307 308 Air, scfm/pph 5.6 ~1.5 ~1.5 Finish Type 3 3 2 Denier 160 171 167 Init. Mod. gpd 92.4 71.5 74.6 ~20' gpd 2.89 2.03 2.24 Tenacity, gpd 3.73 3.63 3.88 Elong. ~ 34.2 49.3 49.6 BOS, % 2.5 3.2 2.9 DHS, 160C, % 3.0 4.3 3.7 Max. Sh. Tens. gpd .132 .124 .115 Density (p), g/cc 1.3845 1.3771 1.3773 Vs, km/sec 3.12 2.86 2.86 Tmelt~ C 262 252 256 ~, 12.5 12 13 CS, A 72 71 72 LPS, A 320 - _ _ 95-5 ~ - _ ~c .205 .205 .204 am RDDR, % dye/min ~ .063 .064 .048 23`7~
(~ TABLE VI

E~a~21e 48 49 Spin. Speed, YP~ 6000 7~
Orifice (D.~L), mils 10X20 10X20 L 10-4 milS 3 20 20 Flow (~) pph/cap .398 .430 wL 10-4 pph mils 7.96 8.60 D

Block Temp. TB ~C 293 296 Pack Press . ps ig 5000 5600 Poly. Temp. Tp (C) 295 298 Air, sc~m/pph 3.0 2.0 Finish Type 2 2 Denier 168 156 ~nit, MDd. gpd 56.2 70.3 - 20~ gpd 1.62 2.28 Tenacity, gpd 3.21 3.51 58.1 49.8 Elong. ~
BOS, ~ 10.8 6.6 11.6 8.0 DHS, 160CC, %
139 .167 ~ax. Sh. Tens. gpd 1.3429 1.3512 Density ~p), g~cc 2.46 2.74 ~s' ~m~sec Tmelt~ C
~,~ 12 13 " 68 64 CS, A
o 320 LPS, A
.0750 .0089 ~95-5 c aam RD~R, ~ dye~min ~ .120 23`-~

Draw-Texturing Examples 50--63D
Some of the yarns of the foregoing Examples are used as feed yarns in a draw-texturing process on an ARCT
480 machine using a sapphire spindle under the conditions shown in Table VII to give draw-textured yarns having ~ properties that are also shown in Table VII, for comparison with the properties of other draw-textured yarns shown in Table VIII, Examples 57D and 61D of which represent commer-cial yarns.
Both feed yarns for Examples 50 and 51 were pre-pared by spinning at 6000 yards/minute, but the as-spun yarn properties are different as can be seen from Examples 4 and 31 in TableI. Thus the feed yarn for Example 50 (Example4) has better dyeability (RDDR of 0.073 v. 0.055) which is associated with a lower amorphous birefringence (~am of 0 047 v. 0.061), while the feed yarn for Example ;1 (Example 31) has better tensile properties as a flat (i.e. untextured) yarn. The RDDR values of the draw-textured yarns are reduced (to 0.060 for Example 50 v. 0.042 for Example 51) and are considered to be related inversely to the loss modulus peak temperature (TE~maX of 109.3 v. 114.4) of these textured yarns. Thus it will be noted that the dye-ability of the draw-textured yarn of Example 50 is signifi-~ ;23`70 cantly superior to that of Example 51 and to those of the commercial yarns (57D and 61D) in Table VIII, and that this superior dyeability is accompanied by useful tensile properties and a satisfactory crimp level. This superior dyeability (Example 50 v. 51) is considered to result from . the use of a slightly lower polymer temperature (Tp of about 297 v. 301) and the use of cross-flow air without any protective tube in F.xample 4 in contrast with the use of a protective tube of length 3-7/8 inches and radial air-flow in Example 31. Thus, to obtain as-spun and textured yarns of better dyeability, it is preferred to use as low a poly-mer temperature as possible and to avoid delay in cooling the freshly-extruded filaments so far as is consistent with maintaining the skin-core value sufficiently low to avoid problems with broken filaments.
The feed yarns for Examples 52X, 53 and 54 were prepared by spinning at 7000 yards/minute, and again the RDDR values of the draw-textured yarns differ (0.057, 0.052 and 0.047, respectively) and can be related inversely to the 20 respective loss modulus peak temperatures (110.7, 112.7 and 113.3) of the textured yarns and to the RDDR values . (0.062, 0.059 and 0.054) and polymer temperatures (Tp) of the respective feed yarns (298, 302 and 317) and the use of a protective tube of length 3 inches and radial air-flow in Example 16 (53) in contrast to cross-flow air without any protective tube in Examples 20C and 44 (52X and 54 respect-ively), confirmin.g the desirability of using a low polymer tempèrature (Tp) and/or avoiding delay in cooling the fr_shly-extruded filaments so as to obtain filaments of superior dyeability. The draw-textured yarn of Example 52X, 37~

however, had an excessive number of broken filaments, and would not be satisfactory commercially, despite its superior dyeability. It will be noted that the feed yarn for Example 52X (Example 20C) had a high skin-core value above line XYZ in Figure 3. Thus, although in Example 20C con-tinuity was achieved in spinning a yarn with superior dye-ability, the yarn is not a suitable draw-texturing feed yarn because of the high skin-core value.
The feed yarn for Example 55 was prepared by 10 spinning at 8000 yards/minute (Example 28) with a polymer temperature (Tp) of about 311C and cross-flow air without any protective tube. The feed yarn shows good dyeability (RDDR of 0.057, amorphous birefringence of 0.060) as does the draw-textured yarn (RDDR also of 0.057, TE~maX of 111.3), despite the use of a high polymer temperature (Tp), so the effect on dyeability of using high polymer temperatures may be less at these extremely high speeds, above 7000 yards/minute. It will be noted that the TmaXsT is slightly lower (at 257~C) than is preferred when the feed yarns have been spun at lower speeds.
It will be noted that, as the spinning speed in-creases, from 6000 yards/minute, the difference between the RDDR values of the feed yarn and of the draw-textured yarn decreases and then disappears.
The feed yarn for Example 56 is the copolymer .:.
yarn of Example 4~. The draw-textured yarn has very good dyeability (RDDR of 0.095), which correlates with its low TE~maX of 102.6, which is much lower than the value for the draw-textured homopolymer yarn of Example 50. Thus, the draw-textured copolymer filaments preferably have a TE~maX

less than about 107C, and a TmaXsT greater than about 215~C, which values are different from those preferred for homo-polymer draw-textured yarns.
Table VIII shows the properties of various other draw-textured yarns for comparison with the yarn properties in Table VII, and the ~xamples in Table VIII are labelled with a "D" to show that they are draw-textured comparison yarns. The dyeability of the draw-textured yarns can be compared by referring to the RDDR values at the bottom of Tables VII and VIII, and also to the K/S values of some of these yarns shown in Tables IX and X, whereas the K/S
values of some feed yarns are compared in Table XI, in which the feed yarns of Table VIII are referred to with a "F".
Example 57D is prepared from 57F, a commercially-available partially oriented feed yarn prepared by spinning at 3500 yards/minute, as described by Piazza & Reese in ~.S.
Patent No. 3,772,872. The feed yarn for Examples 59D and 60D is 59F and is prepared by a simi'ar process, except that 'he spinning speed is 5000 yards/minute, and the feed yarn for Example 58D is similar except that radial air-flow is used to cool the freshly-extruded filaments. Example 61D
is prepared from 61F, a commercially-available flat yarn used also as a texturing feed yarn, prepared by coupled spin-drawing, i.e. spinning at about 1000 yards/minute and drawing 3.5X before winding up as a fully drawn yarn.
Example 62D is prepared from 62F, which is prepared by drawing 59F 1.2X on a commercially-available draw-winder.
The feed yarn for Example 63D is prepared from a spin-drawn yarn, similar to 61F, by relaxing about 20~ and then redraw-ing by a similar amount in separate (split)steps.

It will be noted tha' the RDDR values of the onlytwo commercial samples (57D and 61D) are less than 0.045, and thus inferior to the preferred draw-textured yarns of the invention prepared with a low polymer temperature (Tp).
If, however, as-spun yarns of the invention are draw-textured ~using higher draw-texturing tensions than are used on the pin-texturing machines in the Examples, e.g. 50-70 grams, such as are customary with high speed friction-twist draw-texturing machines, the dyeability of the draw-textured yarns -is reduced, as occurs when draw-friction-twisting co~mercic1 prior art feed yarn that has been spun at about 3500 ypm, and the difference in dyeability over such prior art draw-textured yarns is not so large.
If, however, as-spun yarns of the invention are draw-textured using higher draw-texturing tensions than are used on the pin-texturing machines in the Examples, e.g.
50-70 grams, such as are customary with high speed friction-twist draw-texturing machines, the dyeability of the draw-textured yarns is reduced, as occurs when draw-friction-twisting commercial prior art feed yarn that has been spunat about 3500 ypm, and the difference in dyeability over such prior art draw-textured yarns is not so large.

The apparent dye depths (K/S values) of some of the yarns in the Examples are shown also in Table IX after dyeing with a 40 to 1 dye bath to fiber ratio, using two levels of the disperse dyestuff with and without a carrier (Liquid JET JT, a biphenyl base) under atmospheric pressure;
it will be noted that the K/S values are similar when a carrier is used, but that a significant advantage is show without currier for the yarn of Example 50.

,237~

Tables X and XI show the results of competitive dyeing (i.e. in the same dye bath) various draw-textured yarns and feed yarns, respectively. As shown by the RDDR
values in Tables VII and VIII and the ~/S values in Table IX (comparative) and in Table X (competitive), the draw-textured yarns of the invention have dyeability superior to that of commercially-available draw-textured yarns.
It will be noted also from Tables VII and VIII
that the high TmaXsT (at least 258C) and low TE.~max (115~C or less) distinguishes the textured yarns of the invention from the comparative samples. Although ~xample 63D shows good dyeability, the textured yarns are not suffi-ciently bulky (low CCA5).

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3`70 TABLE X

COMPETITIVE DYE-AT-THE-BOIL
OF VARIOUS DRAW SET-TEXTURED YARNS
(2~ ~ Disperse Blue 27) TEXTURED TEXTURED YARN K/
YARN TYPE DESIGNATION S-VALUES
(speed in ypm) Draw-Relax- 63D 9.15 Redraw 1000 ypm 3.5X Draw 613 2.35 5000 ypm 1.2X Draw 623 7.14 3500 ypm Cross flow 573 5.21 5000 ypm Cross flow 593 6,93 6000 ypm Cross flow 50 10.18 6000 ypm Copolymer 56 23.76 7000 ypm Radlal 53 7.59 7000 ypm Cross flow 52~: 11.49 7000 ypm Cross flow 54 8.86 8000 ypm Cross flow 55 11.22 Z;3~0 TABLE XI

COMPETITIVE DYE-AT-THE BOIL
OF VARIOUS POLYESTER FEED YARNS
(2~ owf Disperse Blue 27) FEED YARN FEED YARN /S-VA UES
TYPE DESIGNATION L
-(speed ln ypm) -1000 ypm 3.5X Draw 61F 2.50 5000 ypm 62F 4.85 3500 ypm 57F 14.50 5000 ypm 9 75 ; Cross flow 5gF
6000 ypm 9 71 Cross flow 4 6000 ypm 48 16.56 Cross flow 19 8.31 7000 ypm 16 7.31 Cross f~ow 36 6.96 7000 ypm 8 81 Cross flow 37 Cross flow 28 8.45 Z3~C~

EXAMPLES 64-71P (Table XII) STAPLE ~IBERS
Examples 65 to 70 relate to 1.5 inch (38 mm) staple fibers that were prepared with different treatment conditions (indicated in the headings of Table XII) from the same feed yarn (similar to the as-spun yarn of Exam?le 12). All the feed yarns were cut with a knife; some measurements, however, were made on the uncut filaments, rather than on the staple fibers, for convenience. The feed yarns of Examples 67 and 70 were drawn, using a draw ratio of about 1.37X, at about 100 feet min, using feed and draw baths at temperatures, respectively, of 75 and 95C. The feed yarns of Examples 65, 66, 68 and 70 were steam-crimped in a stuffer box with steam at 4 psig. The feed yarns of Examples 66, 69 and 70 were relaxed in an oven at 135 for about 6 minutes. The properties of these staple fibers are compared in the Table with those of the feed yarn (Example 64) and with those of a commercial control staple yarn (Example 71C).
Both undrawn and drawn staple fibers of this in-vention have adequate tensiles, (c07 is stress at 7extension), work recovery properties (Wx) and crimp properties (cpi), and significantly better R3DR and sig-nificantly higher single filament flex resistance than the control (71P), which are important improvements. The fact that staple fibers of the invention have the indicated properties equivalent to and better than those of commer-cially-available staple, even without drawing and without rela~ing after crimping such new filaments, is a significant economic advantage since such steps may be omitted.
Furthermore, a tow of filaments of the invention may be con-verted into staple by stretch-breaking without prior drawing, if desired.

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EXAMPLES 72C-83 (TABLE XIII) The torsional moduli G and Poisson's ratios v of various yarns are compared in Table XIII. The yarns of Examples 74C, 75, 76 and 77C are as-spun yarns as prepared in Examples lOC, 5, 18 and 29C, respectively. The yarns of Examples 72P, 73P and 78P are similar to the feed yarns 57F, 59F and 61F, respectively, discussed in relation to Tables VIII and XI. The yarn of Example 79P is similar to the draw-set-textured yarn of Exampie 57D.
It is noted that the torsional modulus G generally increases with spinning speed, i.e. with increasing uniaxial molecular orientation, given here by the sonic modulus Es, provided the skin-core value is low. Thus, although the sonic modulus E5 for Example 74C is less than that for Example 75, the torsional modulus is significantly higher, and the skin-core value is larger. The sensitivity of the torsional modulus G to skin-core value is also represented by a decrease in the Poisson's ratio v for a given level of sonic modulus. Thus, the feed yarns of this invention, being characterized by low skin-core values, have correspond-ingly lower torsional moduli G and larger Poisson's ratios v than yarns having higher skin-core values and having similar sonic moduli Es.

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f~ 3'70 ~lany variations are possible. For instance, in Examples 48 and 49, a 90.10 bv weight copolymer of 90 ethylene terephthalate and 10~ 2,2-dimethyl proPylene terephthalate of 26 HRV has been spun to give polyester yarns whose properties are essentia:Lly similar in many respects to those for the homopolymer but the boil-off and dry heat shrinkages are higher for the copolymer. This difference in properties, resulting from spinnina polymers of different chemical composition at the same speed, makes possible the pr~duction of multifilament yarns having filaments of differing (2 or more different) properties in the same yarn bundle. Thus, the following variations are possible, for example:-A. A low shrinkage post-bulkable mixed shrinkage cospun yarn obtained by cospinning homopolymer filaments and copolymer filaments as described immediately above; hard yarns re-sult from spinning at, e.g. 6300 meters/minute, or drawable yarns from spinning at suitable lower speeds.

B. Heather yarns made directly by selecting one or more of the filaments in A to have a different inherent coloration, as described in Reese U.S. Patent No. 3,593,513, without the need for the drawing step described therein.

C. Control of ~uench conditions, e.g.
asymmetrical passage of hot air below the spin-neret, to lead to a differential shrinkage and crimp potential.

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D. Spun-like multifilament yarns obtained by breaking only some of the filaments. Selec-tion, e.g. of capillary dimensions, some being inside the preferred limits, while others are of e.g. larger diameter and/or lower - 4 ratio, would give multifilament varns, some filaments of which would have higher skin-core and tend to break, especially during texturing. The pill resistance of the broken filaments would be expected to be greater because of their lower strength.

E. Jet screen bulking, if desired in combination with or instead of other types of texturing.

F. Bicomponent filaments of polymers of - differing viscosity levels.

G. Fiberfill products.

The application is a division of copending Canadian Serial No. 280 331, filed 1977 June 10.

Claims (4)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Poly(ethylene terephthalate) staple fiber having a relative disperse dye rate, RDDR, greater than 0.050 and a differential birefringence (.DELTA.95-5) between the surface and the core of the fiber of less than 0.0055 + 0.0014 o20, where o20 is the stress measured at 20% extension and is at least 1.6 gpd.

2. Staple fiber according to Claim 1, wherein the staple fiber has a loss modulus peak temperature of 115°C or less and a temperature at the maximum shrinkage tension of at least 258°C.

3. Staple fiber according to Claim 1, wherein the staple fiber has an average crystal size of at least 55 .ANG., and of at least (1250 p - 1670) .ANG., where p is the density of the polymer in g/cm3, and an amorphous birefringence of less than 0.07.

4. Staple fiber according to Claim 1, wherein the RDDR is greater than 0.060.