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Publication numberUS3452130 A
Publication typeGrant
Publication dateJun 24, 1969
Filing dateFeb 2, 1967
Priority dateFeb 2, 1967
Publication numberUS 3452130 A, US 3452130A, US-A-3452130, US3452130 A, US3452130A
InventorsGilbert Pitzl
Original AssigneeDu Pont
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Jet initiated drawing process
US 3452130 A
Abstract  available in
Previous page
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Claims  available in
Description  (OCR text may contain errors)

June 24, 1969 G. mm $452,130

JET INITIATED DRAWING rnocsss Filed Feb. 2, 1967 Sheet of 2 June 24, 1969 G. PITZL 3,452,130

JET INITIATED DRAWING PROCESS Filed Feb. 2, 1967 Sheet 3 of 2 United States Patent U.S. Cl. 264-2 5 Claims ABSTRACT OF THE DISCLOSURE Filaments are orientation drawn by replacement of the usual snubbing device with a jet device through which the yarn advances toward a draw roll. In the jet device, drawing is initiated by exposure to an intersecting jet of a heated gaseous fluid such as air or superheated steam. Fluid temperature and pressure must be such as to heat the yarn to the drawn initiation point in less than ten milliseconds.

This is a continuation-in-part directed to subject matter divided from my copending application Ser. No. 167,083, filed Jan. 18, 1962, now U.S. Patent No. 3,303,169. The invention relates generally to the production of filamentary structures from synthetic linear polymers and more particularly to the processes by which such structures are drawn and oriented.

"It is well known that synthetic linear polyamide filaments are usually drawn to increased length in order to produce an oriented structure having high tensile strength. When nylon was first introduced, this step was accomplished merely by tensioning filamentary yarn between feed and draw rolls operated at differential speeds. Although product quality was acceptable, various difficulties such as differential dyeability were encountered as a result of nonuniform tensile properties and variable orientation along the length of the drawn yarn. Subsequently, the use of a snubbing pin in the drawn zone and localization of the drawn point on the surface of the pin were disclosed by Babcock in U.S. Patent No. 2,289,232. With this modification, yarn properties and uniformity are improved substantially but additional process considerations such as the application of finish to the yarn for the purpose of reducing friction are involved. To avoid variations in yarn properties, the amount, distribution and composition of the finish must be controlled carefully. For a given set of process conditions, there is an upper limit on the speed with which yarn can be drawn in order to insure that adequate time is available for the uniform application of finish to each filament of a bundle. Similarly, where a heated pin is employed, there is a limit imposed on drawing speed by the minimum contact time required to heat the running yarn sufficiently.

An additional problem which has been encountered in pin-drawing nylon yarn is that the drawn yarn undergoes a gradual lengthwise retraction with time. These effects are accelerated by heat and moisture. For example, representative nylon yarns have a boil-off shrinkage of or more. Where that degree of shrinkage is excessive, a separate shrinking step prior to utilization of the yarn is required. In addition to the extra processing and handling involved in such preshrinking procedures, the yarn usually suffers a reduction in initial modulus due to a diminution of yarn orientation and is therefore more sensitive to tension variations encountered in subsequent processing stages.

The various improvements and advantages disclosed herein are accomplished in a single-stage drawing process which includes the steps of advancing a filamentary yarn 3,452,130 Patented June 24, 1969 ice over feed and draw rolls and substantially instantaneously heating the filaments in the draw zone to a temperature of at least C. as they pass through an enclosure. In the enclosure, a heated, single-phase gaseous fluid is jetted on the filaments in intersecting relationship therewith, thereby initiating drawing, reducing the drawing tension substantially and localizing a significant fraction of the draw in the enclosure.

As noted, the desired effects are attained when a yarn temperature of at least 115 C. and preferably C. or more is reached. With a substantially instantaneous increase in filament temperature to about C. much more stable operation and improved product uniformity are achieved. The maximum operable filament temperature corresponds to the fiber stick temperature which is generally about 2035 C. below the polymer melting point. When this temperature is reached, it is believed that individual filaments break and stick to the body of the jet enclosure, thereby fouling the yarn passages and rapidly breaking down the thread line. Broken filaments observed under these conditions show evidence of fusing.

Where reference is made herein to a substantially instantaneous increase in filament temperature, the relationship between fluid conditions and yarn speed is such that the yarn is raised to the desired temperature in less than ten milliseconds, preferably in less than about one millisecond. Under these circumstances, fluid temperatures above the polyamide melting point are usually required but have no adverse effect on the yarn because of the high rate of speed at which it travels through the fluid jet.

Although a substantially instantaneous increase in filament temperature within the jet enclosure is essential to initiation of drawing, it is apparent that such temperature measurements oftentimes can only be made with great difliculty. Furthermore, in the lower range of operable filament temperatures, small variations can have a large effect on the degree of fiber orientation and, for that reason, the close control of process variables is important. In this respect, it has been found that the reduction in tension resulting from the transfer of heat to the filamentary structures is an accurate reflection of the yarn temperature in the jet enclosure. Since the reduction in tension can be measured readily, it is also useful as a control parameter and has been reported herein as a process characterization. When the temperature and pressure conditions are sufficiently intense to raise the yarn to a temperature of about 115 C., there is a corresponding reduction in tension in the draw zone to about 75% of the tension observed when no heating fluid is supplied. Much greater improvements are obtained when the drawing tension is reduced to the 65% level and below.

In addition to yarn temperature in the jet and tension level in the draw zone, the extent to which the yarn is drawn is another process variable on which the degree of orientation is dependent. However, since as-spun yarn is partially oriented, reference to the draw ratio alone does not give an accurate or reliable indication of the total orientation observed in the drawn yarn. Where the phrase total draw ratio X is used herein, the various types of orientation introduced into the yarn have been considered. Thus, the factor X includes the conventional machine draw ratio X which is the ratio of feed and draw roll surface speeds if no slippage occurs. Since the yarn entering the drawing stage may be under slight tension, an added predrawing stretch ratio X may have been imposed; usually this orientation factor is insignificant and can be ignored. The as-spun yarn also has a degree of orientation, produced in the spinning process and measured by filament birefringence, which can be expressed as a draw ratio X With this information available, a reasonably accurate indication of the degree of orientation can be obtained by computing the total draw ratio X which is the product of the machine draw ratio X and the as-spun orientation factor X In the following specification and examples, reference is made to the accompanying drawings wherein:

FIGURE 1 is a schematic illustration of an installation useful in the practice of a split process;

FIG. 2 is an enlarged, longitudinal, sectional view of the single orifice jet shown schematically in FIG. 1;

FIG. 3 is a schematic illustration of an installation useful in the practice of a coupled process;

FIG. 4 is a longitudinal, sectional view of a two orifice jet suitable for use as a replacement in the arrangements of FIGS. 1 and 3;

FIG. 5 is a perspective view, partially sectioned of another jet embodiment; and

FIG. 6 is a schematic illustration of an apparatus arrangement which has been included for purposes of comparison.

In the process installation of FIG. 1 (Example I), undrawn nylon filamentary yarn 10 is unwound from a package 12, moistened in its travel over finish roll 14, passed between guide pins 16 and tensioned between driven feed roll 18 and draw roll 20. In order that the filamentary structure will be drawn to several times its extruded length, rolls 18, 20 are operated at differential surface speeds, i.e., roll 20 has a peripheral speed considerably higher than that of roll 18. From roll 20, the drawn filamentary structure passes between pins 22 to a suitable windup '24.

In the draw zone between rolls 18, 20, a jet device 26 of the type shown in FIG. 2. is positioned. Device 26 is provided with a longitudinal passage or enclosure 27 through which the tensioned yarn travels. Intermediate its ends, passage 27 communicates with the orifice of a jet conduit 28, which is disposed at an angle of about 30 with the axis of passage 27. Device 26 is adapted for connection at 29 to a suitable high pressure fitting which functions to deliver a controlled supply of a single-phase heated gaseous fluid to conduit 28 for discharge into passage 27 in intersecting relationship with yarn passing therethrough in the direction indicated.

The process installation of FIG. 3 (Examples II, V) is similar to that shown in FIG. 1 except that yarn 10 is spun from a spinneret 12' and a tandem arrangement of two jet devices 26 is provided in the draw zone between rolls 18', 20'.

In other process installations (Examples III, IV and VII-IX), the jet devices of FIGS. 4 and 5 are substituted for the device 26 of FIG. 1 or for the devices 26' of FIG. 3. The device 40 of FIG. 4 is similar to that shown in FIG. 2, except for the provision of two angularly disposed jet conduits 41, 42 discharging into the longitudinal passage 43 at an angle of 45. The jet device of FIG. 5 has an initial passage 51 through which yarn travels to expansion chamber '52, passage 53 and tail pipe 54. In chamber 52, heated fluid from four symmetrically disposed jet conduits 55 is jetted onto the yarn in intersecting relationship therewith.

The apparatus arrangement of FIG. 6 includes a plurality of pins 61 which support yarn 62 in the draw zone as heated fluid is discharged thereon from a plurality of jet conduits '63, each in communication with a manitold 64. This arrangement has been disclosed herein for purposes of comparison (Example V1) with operable embodiments wherein the yarn is in a passage or enclosure when exposed to the fluid jet. In this respect, it should be noted that the embodiments of FIGS. 4 and 5 have a passage or enclosure equivalent to that shown at 27 in FIG. 2, i.e., a passage which is completely enclosed except for the yarn inlet and outlet. and the jet orifice(s) Other constructions are feasible. For example, a device comprised of a pair of opopsed flat plates between which the yarn travels as fluid is jetted thereon from an orifice in one of the plates is operable under certain conditions. The principal requirement is that the heated fluid must impinge on the yarn in an at least partially restricted zone. Fluid expansion in that zone of contact or impingement contributes to a separation of the yarn bundle and to the substantially instantaneous increase in filament temperature which is essential to the instant process. When these conditions are achieved, heat transfer from the gas to the yarn is optimum, due at least in part to separation of the filaments in the yarn bundle during such treatment (Example III). The separation of the filaments also helps to avoid fusing at high gas temperatures.

Any gas reasonably inert to the yarn may he employed as the jet medium, hot air or superheated steam being preferred in most applications. Other possibilities include nitrogen, carbon dioxide and mixtures thereof. Saturated steam is believed to adversely affect the yarn modulus at temperatures required to obtain minimum yarn shrinkage. In addition, the presence of condensate on the drawn yarn is though to contribute to product nonuniformity.

The temperature and pressure of the heated, single phase gaseous fluid must be carefully controlled to maintain a product with uniform properties. At constant pres sure, the temperature of the fluid determines the amount of tension in the yarn during drawing as well as the shrinkage and retraction of the product. Any increase in fluid temperature at constant pressure results in a substantial decrease in all three values, the upper limit usually being set by temperatures at which filaments fuse or break in a given jet. Conversely, at constant temperature, an increase in fluid pressure not only results in a decrease in the yarn tension during drawing but also leads to a further reduction in the residual shrinkage and retraction of the drawn yarn. The temperature and pressure selected will also depend on yarn speed because of its relationship to the period of yarn exposure to the jet medium. A comparison (Table I, runs AF and AK) of the relative efficiency of superheated steam and hot air at the same pressure, using the same fluid jet, shows a distinct temperature advantage in favor of steam, as reflected by the level of tension during drawing and by the shrinkage and retraction of the product.

In the examples which follow, the use of different combinations of the illustrated apparatus under various drawing conditions has been described. When polyamide filaments are drawn in accordance with the minimum process requirements, the drawn yarn is characterized by high modulus and tenacity as well as by low shrinkage and retraction. It also has good mechanical quality and excellent property uniformity. Since snubbing elements are not employed, the problems previously encountered with friction and finish uniformity are avoided.

Under the more severe process conditions reported in some of the examples, an unusual and hitherto unobtainable combination of properties is achieved in that the drawn yarn has a break elongation of at least 25%, an initial modulus of at least 38 grams/ denier and a boiloff shrinkage of not over 6.5%. X-ray analysis shows that the crystalline structure is highly oriented and has a large transverse area. The average X-ray orientation angle is preferably less than about 14, and the crystal cross sectional area is at least 1250 square angstroms, preferably at least 1500 A measured prior to boil-off, relaxation or anneal-ing treatments. This product is so stable that, even after boil-ofi, its high modulus is largely retained, and fabrics woven therefrom are characterized by an unusually high crease recovery, indicating superior wrinkle resistance and resilience.

The yarn samples employed in the exemplified tests and comparisons were obtained by stripping representative -150 cm. lengths from the extremities and from the longitudinal center of a package, throughout the entire package and yarn length.

Where retraction is reported, sample length was determined immediately after removal from the package by tying the ends of the sample together, hanging a weight equivalent to about 0.1 g.p.d. in the loop and measurlng loop length. After exposure for 24 hours at 75 F.

described by C. W. Bunn and E. V. Garner, Proc. Royal Soc., 1898A, 39 (1947), for example. Crystal orientation is actually calculated from the half widths of the equatorial reflections, determined from an azimuthal photometer trace, following the methods described by H. G. In-

(24 C.), 72% relative humidity, loop length Was m 5 gersol in Journ. Appl. Phys, 17, 924 (1946). Crystal diured again and percent retraction was calculated. mensions are estimated from the breadth of these dltfrac- For shrinkage values, yarn samples were taken from tion spots, measured from equatorial photometer traces, p g which had been conditioned for one y at according to the method of H. P. Klug and L. F. Alex- F. (24 C.), 72% relative humidity. After determination l0 ander, X-Ray Diffraction Procedures, John Wiley and of the initial length, -a loop of conditioned yarn was sub- Sons, Inc., New York, 1954, Ch. 9. Warrens correction merged i b ni t r for about 20 minutes and then for line broadening due to instrumental effects was used as dried for about 25 minutes under 0.1 g.p.d. tension. After a correction for Scherrers line broadening equation. Zinc measuring the length of the rboiled-oif loop, percent oxide was the reference material. A value of 0.9 was emshrinkage was calculated. ployed for the shape factor K is Scherrers equation.

The initial modu s, rep e n e y the Symbol 1 Where reference is made to the relative viscoslty of is defined as the ratio of change in stress to strain in the polymer o ya it w d t rmin d as d ib d i US, first reasonably linear portion of a stress-strain curve. The Patent No. 2,385,890. units employed herein make the initial modulus numer- Example I ically equ1valent to 100 times the force In grams per denier required to stretch the specimen the first 1%. In the ex- A 34 filament yarn was spun from molteri polyhexaamples, the modulus is obtained from yarn stress-strain methylene adipamide havmga relativevlscosity of about curves recorded on an Instron Tensile Tester of the type 33.5 and contarnln'g 0. t tanl m d oXlde as de which stretches the yarn at a constant rate of elongation. trant, packaged and subsequently drawn 4.0X 1n the From the stress-strain curve, the slope of the initial straight apparatus of FIGS. 1 and 2 to a nominal as-drawn den er line portion is determined graphically. Tenacity and break of 70 at a speed of 1000 yards/minute (915 meters/mmelongation are also read from the curve. All yarn tested ute). The undrawn yarn had a ablrefrlngence of 0.005 corwas conditioned on the package for one day at 75 F., responding to a spmnmg drawn ratlo X of 1.12. The total 72% relative humidity, prior to testing. draw ratio X was therefore 4.48. After drawlng, the yarn It is believed that the maximum benefits of the proc Wohnh at tension of P grams on of this invention are attained when the yarn is heated in drlVeIl reclpfocatlng traverse f p- The results Obtamed the jet enclosure to a sufficiently high temperature to under various conditions of fluid temperature and pressure achieve a pseudo-hexagonal crystal structure, as deterare reported (runs AC-AO) in Table I. In each of runs mined by X-ray diffraction. The yarn is observed immethe heated fiuld Was at a pressure of pa -gdiately after leaving the jet enclosure. Temperatures ap- 35 (4.4 atm.). In runs AN and A0, the pressures were 25 proximating the force-to-draw transition are usually and p.s.1.g. (2.7 and 5.4 'atmQ, respect1vely, required to produce this structure, Runs AA and AB have been lncluded for purposes Of The force-to-draw transition temperature is the tem- Ih ah hhheated Shhhhlhg plh of the type perature at which a discontinuity is observed in the ratio (hsclosed by Babcock was p oyed. In AB, the yarn was of the logarithm of the tension required to draw an 40 uncontrolled 1n the draw zone, 1.e., ne1ther a pm nor a drawn filament versus the reciprocal of the drawing temfluld Jet was employed perature, as expressed in degrees on an absolute temper- A referehc? to the drawlhg tehslohs and yam Proper ature scale. The force-to-draw transition temperature is hes reported In Tahle I Shows that the h h fh conveniently determined by forwarding filamentary yarn present process begin to h f when fiuld Jet Commons from the Spinning Windmp packaue at 21/2 yards per 45 are such that drawlng tension 1s less than about of O D 9 I a me (23 meters per minute), to and about a hot steel that measured for the delocallzed control 1n run AB, 1.e., when the yarn temperature 1n the et enclosure exceeds snubbmg pm one 1nch (2.5 cm.) in dlameter and prov1ded h 1 t d u fi h th b d C. In thls respect, much better yarn properties are m a c rome'p 6 ma f ms e yarn f fawn obtained with tensions less than about 65% of AB (filam; Thehrawlhg force 15 measured the h temper 50 ment temperatures above 119 C.). Under corresponding athhe 1S vaned; From a f' of the se h h h the Q conditions of temperature and jet pressure, superheated ordinates prev1ously specified, the d1scont1nu1ty is readily Steam (AK) is a more effective heat transfer fluid than 1dent1fied and evaluated. hot air (AE). Equivalent yarn properties are obtained at Crystal onefltatlon and average lateral Crystal l a given tension level, regardless of the identity of the jet sions of the h1gh modulus product of this invention are 55 gas. determined from the principal equatorial X-ray diffraction In addition to initiation of drawing, the tabulation maxrma. Polyamlde dlifraction patterns of this type are shows that more than 25% of the draw must occur (AF TABLE I Heat transfer- Draw zone Yarn properties Tension, Percent Fluid temp., Yarn Tension, percent draw in en- Shrinkage, Retraction, Initial mod- C. temp., C g.p.d. control closure percent percent ulus, g.p.d. Draw pin 2.38 98. 0 9, 8 2. 2 31. 6 Delocalized 2.43 100.0 9. 9 2. 3 31. 8

control and A] in the yarn passage of the jet device in order to achieve the desired combination of properties. Preferably (AG and AK), at least 50% of the draw is localized in that passage. By comparison with the accepted view that 100% of the draw should be localized at a snubbing pin 8 Example III Under the conditions shown in Table III, additional runs are made, using the same prepackaged yarn as in Example I and the tandem jet arrangement of Example i or its equivalent 1n order to obtain controlled drawing, J2 iomparabl? ig g ig g zgz ig it is interesting to note that good yarn properties are obg gfi g A additional Su tained at much lower percentages of localization in the a e P Pmsent rocess port for the conclusion that an equivalent combmation p Exam 1e H of properties can be achieved at a somewhat higher tenp 10 sion level with prepackaged as against freshly spun yarn. In an apparatus arrangement of the type shown in A similar comparison with runs AI-AL (Table I) shows 3, 34 filament y was p from molten P Y- that more effective heating is accomplished with the tanhexamethylene adiparnide of 33.5 relative viscosity and dem jet arrangement .and that incremental property imdrawn continuously to a total draw ratio of 4.5X. The l provements are obtained as the treatment conditions beyarn was drawn to a final denier of and wound at a 5 come more severe. speed of 2000 yards/ min. (1830 meters/min), at a ten- The test is then repeated using the jet embodiment of sion of 7-10 grams. The two jet devices were spaced FIG. 5 in which superheated steam is jetted onto the yarn apart 1.5 inches (3.7 cm.) along the yarn line. With this from four orifices disposed in planes at right angles. Yarn tandem arrangement, effective heating of the yarn at the properties and test conditions for runs CE-CI are also higher winding speed was achieved. Results obtained in reported in Table III. The results show that, with no a series of tests using superheated steam at diiterent temincrease in steam temperature, drawing conditions and peratures and pressures are reported in Table II. yarn properties improve with each increase in steam pres- The percent crystallinity was determined by the density sure. On the basis of these improvements, it is believed method of Starkweather and Moynihan, Journal of Polythat an important factor in obtaining the advantages of rner Science, 22, 363 (1956). The determinations are a the process of this invention is to provide gas to the jet based on an estimated density of 1.069 for amorphous conduit at a sufficient pressure so that the yarn bundle nylon and a density of 1.220 for the crystalline regions. will be separated or splayed by vibration or otherwise into The density of yarn samples was determined by the methits individual filaments as a result of the impingement of TABLE 11 Heat transfer Draw zone Yarn properties Steam pressure Steam temp, C. Yarn Tension, Shrink- Retrac- Initial Crystalternp., Tension, percent, ag tion, modulus, linity, P.s.i.g. (Atm.) Jet #1 Jets #2 C. g.p.d. control percent percent g.p.d percent None 1. 81 100. 0 3. 0

50 4. 4) 250 260 86 1. 79 99. 0 50 4. 4) 270 290 1. 64 90. 5 70 (5. s) 250 250 114 1. 50 82. 9 50 (4. 4 280 280 114 1. 43 79. 0 5o (4. 4) 295 295 115 1. 3e 75. 2 50 (4. 4) 290 310 116 1. 29 71. 3 70 5. s) 280 280 117 1. 21 es. s 10 (5.8) 265 285 120 1. 14 e3. 0 70 (5. s) 270 290 1. 07 59. 1 7o (5. s) 280 290 125 1. 07 59. 1

0d of Boyer, Spencer and Wiley, J. Poly. Sci., 1, 249 the jet or jets thereon. As evidence to support this (1946). hypothesis, drawn 70 denier 34 filament yarn was at- From a review of the data in Table II, it is apparent tached to a fixed support, passed through the jet of FIG. that the desirable combination of properties is not 5 and thence over a pulley. A weight was attached to the achieved, with freshly spun fila ments, until drawing tenyarn. The jet for this experiment was equipped with a sions are reduced to a somewhat lower level than was re- 50 glass tail pipe so that the yarn could be more easily o'bquired with the prepackaged yarn of Example I. It is served. Room temperature air was passed through the also apparent that the yarn properties improve as the jet. At an air pressure of 50 p.s.i.g. (4.4 atm.) and at a treatment becomes more severe. Although good results dead load corresponding to the yarn tension in run CF, are achieved when tension is reduced to from 65-70% W the yarn was observed to vibrate. It was observed that of the control run BA, a greater incremental improvethe air pressure must exceed 25 p.s.i.g. (2.7 atm.) in ment is observed when the drawing tension is less than order to maintain stable vibration. It was concluded that 60% of control. It is observed that the increased stability the air pressure in runs CF-CI is in the range required of the yarn (to retraction and shrinkage) is obtained with to initiate and maintain stable vibration or splaying of some increase in modulus, which is contrary to expecta- 60 the yarn bundle, at the drawing tension observed. tions.

TABLE III Heat transfer Draw zone Yarn properties Steam pressure Steam temp, C. Yarn Tension, Shrink- Retrac- Initial temp. Tension, percent age, tion, modulus, Tenacity, Run 1 P.s.i.g. (atm.) Jet #1 Jet #2 g.p.d. control percent percent gpd. g.p.d

i jets: 2. 43 100. o s. s 2. 3 31. s 1.22 52.3 4.8 1.2 32.6 1. 22 52.3 4.8 1.2 34.8 1.14 48.8 3.5 0.8 3&1

Elongation, percent.

After replacing the illustrated jet device with that shown in FIG. 4, the apparatus arrangement of FIG. 1 was used to draw prepackaged 34 filament 6-6 nylon 10 Example VI Prepacka-ged 34 filament 6-6 nylon yarn having a birefringence of 0.005 and a relative viscosity of 38.5 was drawn to a machine draw ratio X of 4.0 in an apparatus yarn (birefringence 0.005) of 36.5 relative viscosity at arrangement of the type shown in FIG. 1. The results a machine draw ratio X of 4.0. The yarn was drawn obtained under various jet conditions and with different to a final denier of about 70 and wound at a speed of jet devices have been reported in the 'following table in 500 yards/min. (450 meters/min). For purposes of comorder to illustrate the advantage of having the heated fluid parison, delocalized control run EA and pin drawn run impinge on the yarn in an at least partially restricted EB have been included in Table IV. zone. IA is a delocalized control run. In J B, an enclosed The increased crystallinity of the test yarns (runs two-orifice jet device of the type shown in FIG. 4 was EC-EG) compared with the pin-drawn control yarn used in place of that shown in FIG. 1. For runs JC-JF, (run EB) is readily apparent. The surprising tensile propthe jet device Was replaced with the arrangement of FIG. erties of the yarns of this invention are also demonstrated. 6. For run JG, conduits 63 were located opposite pins 61 For example, in the series of runs EC to EG, the yarn rather than between them. In JC-IG, temperatures were tenacity is seen to increase appreciably while the yarn measured at the orifice of a jet conduit 63. The yarn was elongation (break elongation) remains substantially drawn and wound at a speed of 500 yards/minute (450 constant. meters/ min.

TABLE IV Heat transfer Draw zone Yarn properties Steam pressure Steam Yarn Tension, Elonga- Crystaltemp., temp, Tension, percent Tenacity, tion, linity, P.s.i.g. (Atm.) 0 C. g.p.d. control g.p.d. percent percent None 2. 86 100. 0 35. 5 None, draw pin 2. 50 87. 5 5.1 27. 5 34. 1 50 (4. 4) 260 116 2. 07 72. 4 5. s 27. 2 35. 1 50 (4. 4) 270 119 1. 86 65.0 5. 9 27. 0 35. 5 50 (4. 4) 295 121 1. 79 62. 6 6. 0 27. 2 36. s 60 (5.1) 260 123 1. 72 60. 2 6. 1 27. 7 36. 3 60 (5. 1) 290 126 1. 65 57. 7 6. 3 28.2 36. 1

Because of the numerous filament breaks at the sup- Example V porting pins, runs IF and JG were deemed lnoperable. nd t COIldltlOIlS forth freshly In JE, drawing tension was reduced to 68% of control ep nylon Y of e Y VlSeOsltY drawn JA. However, yarn shrinkage and retraction percentages In an apparatus g h h slmllaf t0 were considerably in excess of those obtained in test run 3 eXCePt for the Othlssloh of one Of the J devlees JB, i.e., with the enclosed jet device of FIG. 4. In run I D, and e t e Q the Y P e enclosure III the drawing tension was reduced to 71.5% of control IA, Iemahllhg J devlee- The heated fiuld Was superheated but shrinkage remained at the relatively high level of steam and the windup speed was 2000 yards/min. (1830 40 9 a l I. nie iformit of meters/mm) as in Ex mpe I De r un y Example VII TABLE V Thirty-four filament, 33.5 relatlve v1scos1ty poly(hexa- Heat transfer Draw zone Product methylene adipamide) yarn of 0.005 birefringence was st st T delflier spun at 500 y.p.m. (450 meters/min.) and packaged. e121,? 3% Tension, 535 23,} 2,3 The packaged yarn was drawn in the apparatus arrange- Run 0. si-g- (A an control ment of FIG. 1, using the two-orifice jet of FIG. 4, at a FAN" None, pimdmwn control 21 draw ratio X of 4.0. The yarn was drawn to a denier of control 28-? H about 70 under the conditions and at the speeds indicated in Table VII. KA is a delocalized (no pin, no jet, room Percent coefficient of variation. temperature) t l runthis yarn and of two control yarns, as reported in the X-ray examination of the drawn yarn according to the above table, was determined automatically by capaprocedures described previously shows that they have TABLE VI Heat transfer Draw zone Yarn properties Steam pressure Steam Steam Yarn Tension, Shrink- Retractemp., flow, temp Tension, percent age, tion Run P.s.i.g. (Atm.) C. c f.m. g.p. control percent percent;

N one-control 3. 15 100. O 10. 5 2. 5 35 (3. 4) 1. 22 38.7 4. 0. 9 70 (5.8) 3. 15 100. 0 10. 6 2. 4 70 (5. s) 2. 25 71. 5 9. o 2. 1 70 (5.8) 2.15 68.3 8.3 1. 9 70 5. s) 2.07 65. 7 7. 5 1. 7 70 (5.8) 2. 07 65. 7 7. 6 1. 8

itance variation measurements using a Model C Uster Tester.

Drawing tension for run PC is within the scope of the invention. The data in Table V show that the test yarn (run PC) is more uniform than the pin-drawn control (run FA) or the cold-drawn control (run FB). As in the preceding examples, the mechanical uniformity of the product and the operability level of the process are generally superior to those of the comparable operations involving a draw pin or other snubbing element.

exceptionally large transverse crystal cross sections, combined with a high degree of orientation, as indicated by the low orientation angles. The results are given in Table VIII along with corresponding values for shrinkage and modulus. Also included, for purposes of comparison, is a pin-drawn control KF prepared from similar yarn spun at 1500 y.p.m. (1370 meters/min), packaged, then drawn 2.90X at a tension of 2.5 g.p.d. KF has a spun yarn birefringence of 0.020, corresponding to a drawn ratio X of 1.56. The total draw ratio is, therefore, 4.5X.

The novel product obtained under the process conditions of run KD has a conditioned modulus (on the drawing package) of at least 38 and. and a boil-off shrinkage of not over 6.5%. This product is characterized by a crystallite cross section of at least 1250 A? and an From the tabulated results, it is apparent that jet drawn yarn (LA) has a higher initial modulus than conventionally drawn yarn (LB) and also retains a somewhat greater fraction of the initial modulus after boil-01f. The latter improvement correlates well with the improved crease orientation angle of less than 145. Even more desirable recovery of the scoured fabric. products, characterized by a crystallite cross section of Exam 16 IX at least 1500 A? and an orientation angle of less than p 14.0", are obtained under the process conditions of Ten f i polflhexamethylfine adlPamlde) y f run KB 35.5 relative vlscosity was spun and drawn at the maxib1 d Exam 1e VH1 mum opera e machine raw rat1o and to a denier of 60 p 1n an apparatus arrangement of the type shown in FIG. Prepackaged 34 filament 6-6 nylon yarn having abire- 3, using the jet device of FIG. 4. As a treating fluid, fringence of 0.005 was drawn (LA) in a FIG. 1 apparatus steam was delivered to the jet at a pressure of 30 p.s.i.g. arrangement, using the jet device of FIG. 4. Draw con- (3.0 atm.) and a temperaure of 315 C. The drawn yarn ditions were as follows: steam pressure p.s.i.g. (3.0 was wound at a speed of 2000 yards/min. (1830 meters/ atm.), steam temperature 275" C., machine draw ratio min). Various drawing conditions and yarn properties X 4.0, windup speed 500 y.p.m. (450 meters/min). A for test run MA are reported in the following table for control (LB) was prepared from the same prepackaged purposes of comparison with the corresponding values yarn under the same draw conditions except that an un- 29 obtained in run MB in which the jet device was replaced heated pin was used. In both runs, modulus with an unheated draw pin.

TABLE V11 Windnp speed Heat transfer Draw zone Steam pressure Steam Steam flow Yarn Tension, Tension, Y.p.m. (Meters/min.) temp., mp., g.p.d. percent p.s.i.g. (Atm.) C. C.t.m (Liters/min.) C. control 1, 000 (910) Delocalized Control None 2. 64 100. 0 1,000 (910) 30 (3. 0) 280 2. 9 (52) 116 2. 0o 75. 7 1, 000 (910) (3. 7 285 3. 6 (102) 117 1. 79 67. s 750 (640) 40 (3. 7) 285 3. 6 (102) 124 1. 57 59. 4 500 (450) 40 (3. 7) 285 3.6 (102) 139 1. 3e 51. 5

TABLE VIII Yarn properties Crystallite dimensions Shrinkage, Tenacity, Elongation, Width, Breadth, Orientation angle Mi, g.p.d. percent g.p.d. percent A., D A., D Area, A?

IA IO Average 34. 1 10.7 5. 0 27. 3 34 23 780 15. 7 14. 7 15. 2 37. 5 9. 5 5. 4 2s. 2 as 25 900 14. 2 14. 0 14. 1 37. 6 7. 8 5. 5 25. 2 39 25 975 14. 2 13. 6 13. 0 3s. 2 6. 5 5. 4 25. 2 43 29 250 12.4 12. 4 12. 4 3s. 2 5. 5 5.0 30. 3 52 33 1, 720 12. 3 12. 0 12. 2 33. 5 10. 0 37 23 850 15. 0 15. 0 15. 5

was determined on as drawn yarn samples and also TABLE X after boil-ofi. Thereafter, fabric samples were prepared R from the yarns of runs LA and LB by weaving 104 x 75 MA MB count taffeta and scoured in the conventional manner. grawrati mxm 5.60 4. so The crease recovery is determined by means of a modified 532352? ;}g 5: 572 Monsanto crease recovery test which provides an accurate fi pg c nt-n 18.? 20. 3 measurement of fabric resilience. All result are reported j g i l fg gggi t 33: "15 rys a mi y, ercen .3 33.0 m Table 1X Coeificieni; of d enier variation, percent 1. 4 2. 0

T E 1X ABL From Table X, it is apparent that the process of the Run LA LB invention (run MA) permits drawing at higher draw As drawn, M1 40.4 27.8 ratios to obtain yarn of higher tenacity, modulus, crystal- After boibofi, i -P' linity and denier uniformity, at constant drawing tension, Percent crease recovery war 55.1 43.3 as compared to conventional pm drawing (run MB). Fllllng..- When the test was repeated, using yarn spun from Average 7Z3 high viscosity vacuum-finished poly(caproam1de), similar result were obtained. The generally accepted method for measuring crease Example X recovery is the Monsanto test which has been described as the Vertical Strip Crease Recovery Test in the A polymer mixture consisting of 80 parts polyhexa- American Society for Testing Materials Manual. For methylen? ad}Pam1d@ and 20 Parts polyhexamethyleneiso' the purposes of this example, the test was modified by Phthalamldfi 1S p to a 14 fi1ament y at Yards P placing a plate 0.070 inch (1.8 mm.) thick within the mlf'llfie meiers P m1nute) and lmmedlately drawn fold of the fabric being creased, thus producing a much (wlthoutpackagmgi at the maximum p a ma less sharp crease in the fabric than obtained by the standdraw Iat10- test P p a l slmllflf t0 ard method. Recovery from this crease (in two minutes) that shown in FIG. 2 15 used in the draw zone. This jet,

was determined according to the specified test procedure.

however, has a constricted yarn inlet, slightly larger than the yarn bundle. The outlet, for yarn and steam, is rectangular in cross section. There is a narrow slot parallel with and connected to the yarn passage, permitting easy stringup. The jet is fed with 250 C. superheated steam at 50 p.s.i.g. For comparison, a control NB is also run at maximum operable draw ratio, using identical yarn and an unheated snubbing pin in the draw zone. Yarn properties are given in the following table.

Example XI A composite filament yarn is prepared substantially as described in British Patent 950,429. The filaments consist of a sheath of 6-6 nylon (polyhexamethylene adipamide) of 40 relative viscosity and an eccentrically disposed core of a random copolymer which is 50 weight percent 6-6 and 50 percent 6-10 nylon (polyhexamethylene sebacamide) of 48 relative viscosity. Technical grade sebacic acid is used. Substantially equal amounts of each component are used in each composite filament. The polymers are melted and extruded to a 7 filament yarn using a spinneret arrangement substantially as in FIG. 2 of the British patent. The spinning speed is 1000 yd./min. (915 meters/ min.). The birefringence of the component of spun yarn having the higher birefringence is 0.016. After quenching by a transversely directed current of air, the filaments are forwarded to the draw zone by means of a feed roll and associated separator roll and pass in multiple wraps around a pair of driven draw rolls, thence to a tension letdown roll followed by a reciprocating traverse, surface driven windup. The final yarn denier is about 41. Spinning speed is kept constant at 1000 yd./min. (915 meters/ min.), and the draw ratio is varied by changing the speed of the draw rolls. For most of the tests, a jet similar to FIG. 2 is placed in the draw zone. The yarn passage 27 is rectangular in cross section, inch wide by 4 inch deep (2.4 mm. x 6.3 mm.), and it is about 5 inches (12.7 cm.) long. Air inlet 28 is 0.08 inch (2.0 mm.) in diameter. An inverted U-shaped warn guide is placed in the yarn passage 27, just before the point where hot air contacts the yarn. The air pressure is 80 p.s.i.g. (6.45 atmospheres). Yarn temperatures in the jet enclosure are estimated from low draw, yarn uniformity is poor. When hot air is introduced into the jet, the draw initiation point moves into the jet enclosure, even at higher draw ratios. In Run 4, it is noted that an air temperature of 150 C. is insuflicient to raise the filaments to the required temperature. Under these conditions, the draw initiation point moves out of the jet enclosure and numerous yarn defects (broken filaments) are observed. It is further observed that increasing air temperatures permit the use of higher drawn ratios to provide increased yarn tenacity, along with improved uniformity of sonic modulus and interfilament denier, and also fewer defects such as broken filaments.

Example XII In order to develop the maximum crimp potential in the composite filament yarn of Example XI, the drawn yarn is subjected to a precrimping heat treatment. In this case, the precrimping step is carried out by passing the yarn through another jet supplied with heated air at 90 p.s.i.g. (7.1 atm. absolute), after it leaves the draw rolls. The precrimping jet is like the draw jet, except that the yarn path channel is expanded in a funnel-like cross section to give an exit air velocity of about 60 ft. (20 meters) per minute. The unheated tension let-down rolls are operated at a lower surface speed than the draw rolls, to permit the drawn yarn to retract (relax) and crimp in the jet. It is then cooled and stretched enough to remove the crimp prior to windup. The development of final crimp occurs after this yarn is converted to fabric (e.g., knitted or woven), as it is boiled off. The crimp retraction of the yarn against restraint is a measure of the crimp obtainable when the fabric is boiled off, and is measured as described on page 5, lines 1646 of British 950,429. In preparation for these tests, the effect of different draw ratios was studied. The air temperature in the draw jet was increased until the draw initiation point was observed to enter and remain within the jet enclosure. It was observed that this occurred at a drawing tension of 35 to 40 grams, independent of draw ratio. A draw ratio of 3.7 and an air supply temperature of 210 C., 80 p.s.i.g., were selected as giving good tenacity, yarn uniformity and operability.

Under the above drawing conditions, air temperatures in the precrimping jet are varied in order to obtain the greatest crimp retraction. The extent of yarn relaxation between draw rolls and windup is 16%. The results are listed in Table XIII.

measurements of yarn temperatures outside the jet en- TABLE XIII closure.

Precrimplng Crimp Properties of the yarns produced under varlous operat- Run jet air retraction, ing conditions are reported in Table XII, along with umtemp-Y Percent formity of sonic modulus, denier uniformity and yarn 1 220 27.1 2 230 27.1 qua a 240 26.7 It is observed that when the et 1s not used (Run 1), a 4 250 23.8 draw of 3.04 is the maximum that can be used; when this TABLE XII Yarn quality Draw jet; Yarn properties Defects Percent Percent Machine Air Yarn E1ong., sonic mod. denier Pe Run No draw ratio temp., C. temp., 0. Ten., g.p.d. percent variation uniformity 10 yd 10 meters 3. 04 Unheated Unheatecl 3. s 54 20. 0 2. 5 1. 1 1. 2 3.1 275 143 3.6 42 9.0 1.4 0.13 0.14 3. 3 300 148 3. 8 32 9. 0 1. 9 2. 1 3. 5 150 81 4. 7 38 15. 7 42. 3 44. a 3. 5 300 144 4. 4 29 8.8 1. 5 0. 20 0. 22

ratio is exceeded, the draw initiation point moves to the Best results are observed when the precrimping jet is feed roll and broken filaments are produced. Even at this operated at 10 to 30 C. above the draw jet.

When superheated steam is used in the draw jet in place of heated air, similar results are obtained, but at somewhat lower steam temperatures, due to its greater efliciency as a heat transfer fluid.

The process of thi invention is useful in the drawing of most synthetic linear polycarbonamides or nylons, such as those disclosed in US. Patents Nos. 2,071,250 and 2,071,253. The preparation and spinning of these compounds is described in US. Patents Nos. 2,130,948, 2,163,- 636 and 2,477,156. Particular example of such polyamides are those prepared from suitable diamines and dibasic acids, e.g., from hexamethylene diamine and adipic acid and their amide-forming derivatives, and also from terminalamino carboxylic acids, e.g., from omega amino caproic acid, omega amino undecanoic acid and their amide-forming derivatives, such as caprolactam. Yarns spun from copolyamides, grafted polyamides, blends of polyamides with other compatible polymers and differentially shrinkable polyamide component may also be drawn to good advantage in the process of this invention.

The process is particularly useful in drawing polyamide yarns at high speeds, requiring substantially instantaneous yarn heating. Although marked improvements are obtained at 500 y.p.rn., the higher velocity jets disclosed herein, which effectively heat the filaments to the required temperature at exposure times (in the jet enclosure) in the order of from 0.01 to 0.001 second, permit drawing speeds of 2,000 y.p.m. or more, a level unattainable by prior art processes.

As disclosed in detail in my copending application Ser. No. 591,850, filed Nov. 3, 1966, the process is also useful in the drawing of filamentary yarns spun from polyesters. Particular examples are polyethylene terephthalate and the copolyester prepared from ethylene glycol and a 98/2 mixture of the dimethyl esters of terephthalic/S-(sodium sulfo)-isophthalic acid. Other examples of crystallizable, linear condensation polyesters are polyethylene terephthalate/isophthalate (85/ 15), poly-p-hexahydroxylene terephthalate, polydiphenylolopropane isophthalate, polydiphenylolpropane carbonate, the polyethylene naphthalene dicarboxylates and poly-m-phenylene isophthalate.

The instant process permits very effective single stage drawing, and may be followed by such important operations as setting, relaxing, twisting, crimping, alternate twisting, false twisting, and the like. The instant process is also useful in drawing filaments of modified cross section, e.g., Y, propellor-shaped, triolbal, etc., since substantially no distortion of the desired cross. section is involved.

Advantages of the instant invention over prior art procedures include reduced drawing tensions, leading to improved process operability and product mechanical 11111- formity; elmination of snubbing elements, thereby avoiding frictional problems and the necessity for uniform finish application; and the provision of yarn having reduced shrinkage and retraction values, such yarn being provided in a single step and characterized by both a high retention of initial modulus and improved crystallinity. The drawn yarn can be packaged at reduced tension, owing to its dimensional stability. Furthermore, this yarn can be prepared over a. wide range of tenacities at a given elongation. The process can be carried out in a rapid, continuous and economic fashion using either freshly-spun or packaged yarn.

Use of freshly-formed or as-spun yarn, prior to initial packaging, in the practice of thi invention is particularly advantageous. Since the as-spun yarn is relatively amorphous, maximum reductions in drawing tension plus added flexibility in drawing and associated operations are facilitated. The necessity of a separate drawing stage or step is eliminated, thereby leading to better mechanical quality due to reduced handling, uniformity of lag time (between spinning and drawing) and elimination of an intervening packaging step. Over-all process economy results. However, freshly-formed yarn is substantially amorphous and more stringent control of fluid temperature and pressure during drawing is required in order to insure uniform levels of shrinkage and retraction. When yarn of minimum shrinkage is desired, it has been found that more uniform property levels are obtained when the spin-draw operation is followed immediately by a coupled, controlled relaxation stage. The additional reductions in shrinkage and retraction are not accompanied by an unacceptable reduction in initial modulus when the process of this invention is employed in the drawing stage.

After drawing with extremely hot air or superheated steam, it may be desirable to treat the yarn with moisture, preferably prior to packaging, in order to permit the yarn to regain its normal or equilibrium moisture content. Such moisture may be supplied during a subsequent relaxation stage merely by using steam as the relaxing medium. This combined procedure usually leads to further improvements in yarn properties.

The filamentary structures of this invention may contain the usual textile additives such as delustrants, antioxidants and the like. In this respect, the presence of an antioxidant may be desirable when gas at very high temperature is employed. Suitable antioxidants are disclosed in US. Patents Nos. 2,705,227, 2,640,004, and 2,630,421. Other useful additives are disclosed in US. Patents Nos. 2,510,777 and 2,345,700. In addition, finish may be applied to the structures, though the uniformity of finish application is not as critical as it is in drawing over or about snubbing elements.

The products of this invention are useful in all conventional textile and industrial applications, especially those which require yarn of improved dimensional stability. Because of their reduced retraction values, the drawn yarn can be packaged on inexpensive disposable shipping cores. The high modulus makes them especially suitable for use in fabrics requiring improved resilience and wrinkle resistance.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. In a high speed process, the steps of drawing nylon filamentary yarn and, in the draw zone, separating the yarn and heating the filaments substantially instantaneously to the draw initiation point by passing the yarn through an enclosure and, in said enclosure, impinging a jet of a single-phase heated gaseous fluid thereon in intersecting relationship therewith, the time-temperature-pressure relationship of yarn exposure being such as to heat the yarn to a temperature of at least C. in the enclosure.

2. The process of claim 1 wherein the fluid is superheated steam.

3. The process of claim 1 wherein the fluid is air.

4. In a high speed process, the steps of: drawing nylon filamentary yarn in a single stage and, in that stage separating the yarn and heating the filaments substantially instantaneously to the draw initiation point by passing the yarn through an at least partially restricted zone and, in that zone, impinging a jet of a single-phase high temperature gaseous fluid thereon in intersecting relationship therewith, the time-temperature-pressure relationship of yarn exposure in said zone being such as to reduce the drawing tension to no more than 75% of the tension on the yarn in the absence of said fluid.

5. In a high speed process, the steps of: drawing filamentary yarn spun from a composition consisting essentially of polyhexamethylene adipamide and, in the draw zone, separating the warn and heating the filaments substantially instantaneously to the draw initiation point by passing the yarn through an at least partially restricted zone and, in that zone, impinging a jet of a single-phase heated gaseous fluid thereon in intersecting relationship therewith, the time-temperature-pressure relationship of yarn exposure ture of at least 115 C.

in said zone being such as to heat the yarn to a tempera- References Cited UNITED STATES PATENTS Lodge 264-210 Griehl 264210 Claussen et a1 264210 Oberly.

FOREIGN PATENTS 10/ 1956 Great Britain.

DONALD J. ARNOLD, Primary Examiner.

US. Cl. X.R.

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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3549740 *Dec 14, 1966Dec 22, 1970Du PontTreatment of polyester fibers to improve adhesion of rubber
US3630824 *May 19, 1969Dec 28, 1971Barmag Barmer MaschfHollow monofilament of high-loading capacity and method of making same
US3748844 *Aug 4, 1971Jul 31, 1973Du PontPolyester yarn
US3966865 *Apr 22, 1974Jun 29, 1976Kanebo, Ltd.Method for producing fibril fibrous structures
US4035464 *Jul 11, 1975Jul 12, 1977Bayer AktiengesellschaftProcess for the production of polyamide-6 filament yarns
US4476079 *Oct 7, 1983Oct 9, 1984Eastman Kodak CompanyProcess for manufacture of textile yarns
US5136763 *Dec 18, 1990Aug 11, 1992E. I. Du Pont De Nemours And CompanyProcess for the production of uniform yarns via reduced tension-induced slippage
US5259098 *Mar 12, 1992Nov 9, 1993E. I. Du Pont De Nemours And CompanySteam-drawing process for yarns
US5284612 *Nov 23, 1992Feb 8, 1994E. I. Du Pont De Nemours And CompanySteam draw-jet process for making partially-oriented polyamide yarns
U.S. Classification264/555, 264/172.17, 264/172.15, 264/172.18, 264/288.8
International ClassificationD02J1/22, D01D10/04
Cooperative ClassificationD02J1/222, D01D10/0481
European ClassificationD01D10/04H5, D02J1/22C