CA1152273A - Process for forming a continuous filament yarn from a melt spinnable synthetic polymer and novel polyester yarns produced by the process - Google Patents

Abstract

ABSTRACT
PROCESS FOR FORMING A CONTINUOUS FILAMENT YARN FROM A
MELT SPINNABLE SYNTHETIC POLYMER AND NOVEL POLYESTER YARNS
PRODUCED BY THE PROCESS
A process for forming a continuous filament yarn from a melt-spinnable synthetic linear polymer and novel yarns of polyethylene terephthalate and yarns of polyhexamethylene adipamide produced by the process, the process comprising extruding the molten polymer through a shaped orifice to form a molten filamentary material, passing the molten filament-ary material through a solidification zone, passing the solidified filamentary material through a conditioning zone provided with a gaseous atmosphere at a temperature above the glass transition temperature of the material and below its melting temperature, withdrawing the resulting filamentary yarn from the conditioning zone and winding up such yarn, characterised in that the gaseous atmosphere in the conditioning zone is compressed steam at an absolute pressure in excess of 136 kN/m2 and preferably, in the case of a yarn of poly-ethylene terephthalate, between 446 and 1176 kN/m2 and preferably, in the case of a yarn of polyhexamethylene adipamide, between 200 and 580 kN/m2.

Description

PROCESS ~OR FOR~G A CO~I~IJOUS FILAMEe~T YARN ~OM A M~T SPI~ABLE
5YN~l~TIC POLY~ A~ID ~OVhl, POLYES~E~ YAR~S PRODIJCED :~f ~ EIOCESS
This invention relates to a process for forming continuous filament ya~ns from molten melt-spinnable synthetic linear polymers9 such yarns not requiring to be dræ~n subsequent to winding up after spinning. It also relates to novel polyester yarns which may be produced by the process. It further relates to polyamide yarns producea by the process.
Polymeric filamenta~y yarns have been produced under ~ wide variety of melt extrusion conditions.
~ ~ærman Patent O~S 2 117 659 there is describea a melt e~trusion process co~prising extruding a polymeric melt through a multiorifice spinneret to form a plurality of fil~ments, passing the filaments through a transverse current of a cooling gas -in order to solidify the filaments, passing the solidified filaments through a heating zone and winding up the fil~ments. In one embodiment of the process, the heating zone comprises an air-filled heated shaft through which the solidified filaments are passed.
In ~ritish Patent Specification ~o 1 487 843 there is described a somewhat s;~;lar process for forming a polyester filamentary material comprising extruding a melt-spinnable polyester material through a shaped orifice, passing the resulting molten filamentary material through a solidification zone consisting of a gaseous atmosphere at a temperature below the glass transition temperature of the material, passing the resulting solidified filamentary material through a conditioning zone provided with a gas-eous atmosphere at a temperature above its glass transition temperature and below its melting temperature, and withdrawing the resulting crystallised filamentary material from the conditioning zone. The gaseous atmosphere used in the conditioning zone of the process described in Specification No 1 487 843, may, amongst other gases, be static air or steam Also in ~ritish Patent Specification 1~o.1574305 there i8 described another process for producing filamentary materi~1 ~3 ' '~

1~L5;~Z73 based on either polyamides or polyesters comprising extruding the molten polymeric material to form filaments, advancing the molten filaments through a solidification zone, advancing the solidified filaments through a tensioning zone without inducing substantial drawing thereof within the zone, advancing the solidified filaments through a treatment zone comprising a fluid atmosphere heated to a temperature above the glass transition temperature of the filaments and withdrawing the filaments from the treatment zone at a velocity of from 1000 1Q metres/minute. ~h~ flllid is preferably air but may be nitrogen or steam.
,:
A further process is described in ~ritish Patent Specification No 1 478 787 in which immediately after being quenched, a spun yarn composed of polyhexamethylene adipamide (Nylon-6,6) is subjected to a steam atmosphere in an open tube preferably supplied with steam. m e steam at atmospheric pressure serves to provide the yarn with a positive dry thexmal shrinkage between 90 and 140C.
We have now found that considerable advantages can be achieved by passing a melt-spun filamentary yarn through a conditioning zone comprising a steam atmosphere at pressures much higher than those used previously.
Aocording to the invention, therefore, we provide a process for forming a continuous filament yaxn from a melt-spinnable synthetio linear polymer comprising extruding themolten polymer through a shaped orifice to form a lten filamentary material, passing the molten filamentary material in the direction of its length through a solidification zone wherein the molten filamentary material is ~olidified, passing the solidified filamentary material in the direotion of its length bhrough a oonditioning zone provided with a gaseous atmosphere at a temperature above the glass transition temperature of the material and below its melting temperature, withdrawing the resulting filamentary yarn from the conditioning zone and ~5 winding up such yarn, characterised in that the gaseous atmosphere in the conditioning zone is compressed steam at an absolute ~S~'73 pressure in excess of 136 kW/m and more preferably in excess of 170 kN/m2.
~he term "yarn" as used herein means a monofilament ya~n, a multifilament yarn or a multifilament staple tow.
~he process of the invention can be used to produce filament yarns from any of the usual synthetic linear polymers which can be melt-spun into individual filaments such as polyesters, polyamides or polyolefines,in particular, for example, polyethylene terephthalate and its copolyesters, -10 polyepsilon - caproamide, polyhexamethylene adipamide, polypropy_ lene and t~e like. ~hese polymers may be spun into very fine individual filaments which may then be combined, according to - end use, into yarns or tows which may then be processed in the usual way.
qlhe process is particularly suitable for producing filamentary fibres from melt-spinnable polyesters based on polyethylene terephthalate and oontaining at least 85 mol percent ethylene terephthalate and preferably at least 90 mol percent ethylene terephthalate. In a particularly preferred 20 embodiment of the process the melt-spinnable polyester is substantially all polyethylene terephthalate. Alternatively during preparation of the polyester, minor amounts of one or more ester-forming ingredients other than ethylene glycol or terephthalic acid or its derivatives may be copolymerised. For 25 instance, the melt spinnable polyester may contain 85 to 100 mol percent (preferably 90 to 100 mol percent) ethylene terephthalate structural units and 0 to 15 mol percent (pre~erably O to 10 mol percent) copolymerised esber units other than ethylene terephthalate. Illustrative examples of other ester-forming ingredients which may be copolymerised with ethylene terephthalate units include glycols such as diethylene glycol, tetramethylene glycol, hexamethylene glycol, and dicarborylic acids Puch as hexahydro terephthalic acid, diben~oic acid9 adipic acid, sebacic acid, acelaic acid.
~he melt-spinnable polyethylene terephthalate selected _ 4 1~ 5~ 27 3 for use in the process preferably exhibits an intrinsic viscosity, i.e. IV, of 0.45 to 1.0 dl/gm, and more preferably an IV of between 0.60 and 0.95 dl/gm. The IV of the melt spinnable polyester may be conveniently determined by the formula:
IV - limit ln~
C
as C approaches zero, where ~r is the "relative viscosity~ obtained by dividing the viscosity of a dilute solution of thepolymer by the viscosity of the solvent employed (measured at the same temperature) and C
is the polymer conce~tration in the solution expressed in grams/
100 ml.
The polyethylene terephthalate additionally commonly exhibits a glass transition temperature of 75-80C and a meltlng . point of 250 to 265C e.~g. about 260C.
The extrusion orifice may be selected from those spinnerets commonly used to extrude fibres. The spinneret wlll be provided with a plurality of extrusion orifices - in the case of a filament yarn up to about 40 orifices will be used and in the case of a tow, several thousand orifices will be used.
For instance, a standard spinneret containing a multiplicity of orlfices, such as commonly used in the melt spinning of polyethylene terephthalate, each orifice having a diameter of 125-500 ~um may be utilised in the process. The :" orifices may be circular or non-circular in cross-section.
The polyester material is supplied to the extrusion orifice at a temperature above its melting point, more preferably at a temperature of 270 to 310C and most preferably at a temperature o~ 285 to 305C.
:~ Subsequent to extrusion through the shaped orifice the resulting molten filamentary material is passed in the dlrection of its length through a solidi~ication zone, often referred to as a "quench" zone, provided with a gaseous atmosphere at a temperature below the glass transition temperature thereof ?5 wherein the molten filamentary material is converted into a solid filamentary material. Within the solidification zone the ;r ~ .

, 1152Z~3 molten material passes from the molten to a semi-solid consistency and then from a semi-solid consiætency to a solid consistency. While present as a semi-solid the filamentary material undergoes substantial orientation.
Preferably the gaseous atmosphere of the solidification zone is provided at a temperature of 10 to 40 C and most preferably at ambient temperature. ~he chemical composition of the gaseous atmosphere is not critical provided it iæ
not unduly reactive with the polyester material. In practice air is usually used.
The gaseous atmosphere in the solidification zone preferably impinges upon the molten filamentar~ material so as to provide a uniform quench so that no substantial radial non-homogenity exists in the solidified product.
~he solidification zone is preferably disposed immediately below the shaped extrusion orifice. If desired, however, a hot shroud may be positioned intermediate the shaped orifice and the solidification zone.
It is preferred that the extruded filamentary material resides in the solidification zone, while axially suspended therein, for a period of between 10 and 250 milliseconds and m~re preferably between 30 and 150 milliseconds. Commonly the solidification zone has a length of between 0.5 metre and 4 metres and preferably a length of between 1 and 3 metres.
~he solidified filamenta~y material is converged into a yarn which is passed in the direction of its length through a oonditioning tube containing an atmosphere of compre~ed eteam having~ preferably~ an ab~olute pre~sure of be~ween 239 and 1548 k~/m2 and more preferably between 446 and 1176 kN/m2.
A suitable conditioning tube consists of a metal tube fitted with valves at each end. ~he valves, when open~ permit the yarn to be fed through the tube. ~he valves, when closed, still allow free movement of the yarn. Inevitably, however, there is a continuous, but small, loss of steam from the conditioning tube.
.

~15Z273 The tube i5 fitted with appropriate means for facilitating stea~pressure control at the required levels.
~ he tube may be lagged. Preferably, however, it is provided with an insulation jacket into which is fed steam from the same source of supply as that used in the conditioning tube ~tself.
Preferably the tube is of circular section and has a length in the range 10 cm to 1.5 metres and an internal diameter in the range 3 mm to 40 mm.
The yarn is withdrawn from the conditioning zone at ~ a velocity in excess of 3000 metres/min and more preferably in excesC of 3500 metres/min and is finally wound-up on a suitable rotating bobbin winder, optionally after the application of a suitable spin finish to the yarn.
Under the influence of the hot pressurised steam within the conditioning zone and the tension applied to the yarn by winding it up at a high wind-up speea, crystallisation and orientation of the filaments within the yarn occurs, a process which can be compared with a drawing process commonly carried out on the yarn as a post wind-up stage in the processing of yarn. ~hus in the process of the invention the filament yarn is drawn while it is in, and immediately after leaving, the conditioning zone so that there is a difference in speed and thickness of the filaments before and after the conditioning zone.
The distance of the conditioning zone from the spinneret oan be selected within wide limits depending on the polymerio material. When the polymerio material is polyethylene terephthalate then we have found th~t an optimum distance between the outlet of the spinneret and the commencement of the oonditioning zone may be seleoted in the range 0.5 to 4.0 metres.
Furthermore the length of the oonditioning zone will depend on the temperature of the steam atmosphere within the oonditioning zone. However the length of the oonditioning zone must in an~ case be such that the desired crystallisation and orientation of the filament yarn can be achieved.

~152273 Using the process of the invention for processing a polyester the following advantages are achievea.
1. Rapid and uniform heating of the filaments occurs due to very good heat transfer and becau~e of this the filaments can be converged and treated in the conditioning zone as a yarn or tow so reducing filament to filament variability.

2. ~ecause a considerable number of filaments are heated at the same time at a uniform temperature we ensure that there is more uniformity of properties between spinning positions in addition to the increased uniformity between filaments within a yarn gained by treating the filaments as a yarn instead of individually.
.. .
A further advantage, however, is that the process allows the production of novel fibres based on polyethylene terephthalate.
According, therefore, to a further aspect of the invention we provide a continuous filament yarn formed from a melt spinnable polyethylene terephthalate characterised in that the filaments have a birefringence ( ~ n) greater than Os105 and 5/0 modulus greater than 290 centi ~ewtons/tex and an initial modulus (IM) defined by the function:
IM >, 260 cosh ~ ~ n ~irefringence, as will be known to those skilled in the art, is a function of the orientation of a filamentary fibre and expressed as the difference in the refractive index of a filamentary fibre parallel to and perpendicular to its axis.
~ irefringence is measured using a polarisln~ microscope and a ~erek compensator as de~cribed for example by R C Faust in "Physical Methods of Investigating Textiles't, Edited by R Meredith and J W S ~earle and published by ~extile ~ook Publishers Inc.
Modulus is defined as the ratio of load to extension.
However~ for polymers, since the load-extension curve is not a straight line the modulus must be referred to in relation to a ~1~2273 portion of the curve. Modulus may be measured on an Instron testing machine.
Tn;tial Modulus is defined as the maximum slope of the load-extension curve within the region 0-2~ extension.
~he ~/o Modulus is the slope of the line joining the origon of the load-extension curve to the point on the curve corresponding to a 5/0 extension.
~oth modulii are measures of the resistance of the filamentary material under test to extension and bending.
A long-period spacing (IPS) of less than 200 ~ is a characteristic of most and probably all of the filament yarns of the invention produced from polyethylene terephthalate.
The long-period spacing is obtained from small angle -=~Y~ Ga~eriII~ patterns made by known photographic proce~ures.
x-radiation of wavelength 1.54 ~ is passed through a parallel bundle of filaments mounted in a Kratky low-a~gle camera in a direction perpendicular to the filament axis and the diffraction pattern is recorded on photographic film mounted 29~5 cm from the filaments. Discrete meridional scattering is obtained at angles of less than about 1. ~he intensity pattern is de~
smeared by known mathematical procedures, and from a knowledge of the geomet~y of the apparatus and the measured diffraction ~ygles~ the long period spacing is calculated as described~
for example, in the book "X-ray Diffraction Methods in Polymer Science" by ~ E Alexander, published by J Wiley and Sons, ~ew York (1969).
~he process of the invention, as stated previously, is also eminen-tly suited to the processing of filament yarn of polyhexamethylene adip~mide (~ylon-6~6) and polyepsilon-~0 caproa~ide (~ylon-6).
Ihe extruded and solidified filamentary material prepared in a manner similar to that already described for polyethylene terephthalate is next passed through the conditioning zone provided by an atmosphere of compressed steam having ~5 preferably an absolute pressure of between 170 and 618 kN/m and more preferably between 200 and 580 k~/m2.

l~SZ273 The filament yarn is withdrawn and wound-up as for poly-ethylene terephthalate.
The invention will now be described with reference to the accompanying drawings wherein Figure 1 shows diagrammatically an apparatus for use in the prepaxation of filamentary fibres according to the invention, and Figure 2 is a graphical representation of the results obtained in the Examples described hereinafter.
In Figure 1, filaments 1 are extruded from a spinneret assembly 2 into a solidification (quench) zone comprising a chimney

3 in which the filaments are quenched by air, at room temperature, flowing (not shown) from one side of the chimney to the other side of the chimney.
The filaments are solidified and converged into a yarn by a guide 4 and the pass into a conditioning zone 5.
The conditioning zone is a metal tube fitted with valves (not shown) at each end. The valves, when open, permit the yarn to be fed through the tube. The valves, when closed, still allow free movement of the yarn. Inevitably, however, there is a continuous, but small, loss of steam from the conditioning tube. Means (not shown) are provided for feeding steam from an appropriate source (not shown) into the tube at various required pressures.
The tube may be lagged. Alternatively, however, it is provided with a jacket into which pressurised steam can be fed from the same steam source as is used for the conditioning tube itself.
In this way uniform temperatures may be maintained in the condition-ing tube.
After leaving the conditioning zone the yarn optionally passes through a guide 6, over a finish roller 7, partially im~sed in a finishing bath 8, through a guide 9, wrapped around high-speed puller rollers 10 and 11 and then is wound up as a package 12 on a bobbin 13.
The invention will now be described with reference to the following Examples:-In a process for melt spinning a filament yarn from molten polyethylene terephthalate through a spinneret at 291C

'~',~3 ~52273 employing an ambient air quench zone immediately below the spinneret to effect solidification of the filaments, the solidified filaments were passed through a conditioning zone. ~he zone consisted of a vertically disposed tube, about 0.5 metre in length and 0.5 cm in diameter, located (entry point) 2.2 metres below the exit from the spinneret.
~he yarn entered and exited from the tube through suitable valves located at each end of the tube. Within the tube was an atmosphere of pressurised steam which was continuously fed into the tube from a suitable source. A continuous leakage of steam occurred through the valves.
After the application of a spin finish, the yarns produced were finally wound-up on a bobbin at velocities of 4,000 to 6,000 metres/minute.
qhe process conditions were varied considerably and the resultæ obtained tabulated in ~able 1.

l~ SZZ73 ~ABIE 1 _ _ ~ S~EAM __ _ ~ ~ ~ ~ ~ ~ æ ~ ~ ~ ~ ~ ~ ~ ~ ~ _ _ . ~ _ _ 1 4489 4.75 0.64 92.1 20 446 147 112 3o4 615 -2 4493 4-75 o.64 92.0 20 79o 166 131 418 835135 3 4497 4-75 o.64 91.7 20 962 177 125 419 791 -

4 4611 5.o 0.62 93.o 20 652 162 110 295 632 _ 4620 5.o 0.62 49.6 20 652 162 115 351 648 _ 1 o - 6 465 - o- ~ 0.62 91.o 20 1101 184 123 315 652 -7 4671 5-o 0.60 88.7 20~ 1272 189 110 33 695 ~
8 4684 5.o 0.62 63.7 3o 1203 186 116 292 639 -9 4687 5.0 0.62 63.3 3o 1203 186 119 3oo 65p -4690 5- o.63 63.7 3o 928 173 119 295 658 -11 4691 5.o 0.62 63.2 3o 928 173 120 293 649 _ 12 4700 5.0 0.62 51.2 20 1203 186 121 368 745 -13 4702 5.o 0.62 51.4 20 1203 186 113 297 643 _ 14 474 5.o 0.62 51.6 20 1410 195 116 342 651 _ 475 5.o 0.62 51.4 20 1410 195 119 381 767155 16 4706 5.5 0.62 51.1 20 1410 195 116 372 745 _ _ .. . . ~ _ . _ _ Polyethylene terephthalate was melt spun into a yarn using the process described in ~xa-mples 1 to 16, but with a steam pressure in the conditionin~ tube of only 239 kN/m2. The properties 25 of the yarn were as follows.
.

_ ~ -- ~ b ~

..... .. .
3o 4 75 o .64 91.5 20 239 126 95 53 , :1~52Z73 Polyethylene terephthalate was melt spun into a yarn using the process described in Examples 1 to 16 but replacing the steam conditioning tube by an open-ended tube 1 metre long

5 and 20 mm diameter. Hot air at a temperature of 200c was introduced into the bottom of the tube so that i~ flowed up the tube at a flow rate of 90 litres/min. lhe yarn properties produced were as follows.
~ _ u.~ ~- , ~ .
10 ~ ~ 1~ h ~ ~ i~ !~ ~
. ~
3.5 o.63 56 20 133 668 Polyethylene te~ephthalate was melt spun into yarns using a conventional ~I~inning process without a conditioner tube.
These yaxns were then drawn on a conventional draw frame using a hot roll ,~nd hot plate. The properties of the resultant ,varns are sho-~n in ~able 2.
~LE 2 ¦ ~! R I I r 192.0 5.31 88 ~ 204140j24 1250 183 205.2 4.63 81 220* 138/36 840 174 218.1 3.22 83 170 84/15 799 160 223-5 2.5 9o _ 85/17 447 105 233.5 3.o 9o _ B7/17 631 140 3o 243 - 5 3.o 9o170 84/17 669 145 253.5 3.5 9o 170 84/17 861 164 263-5 3.5 90 _ 85/17 892 169 273-5 4.o 9o 170 86/17 1079 181 283.5 4. o go _ B8/17 969 187 35 *~ot roll followed by 5.6% relax.
.

S~2~3 It should be noted that Examples 22, 23, 26 and 28 were prepared without the use of a hot plate.
A graph was produced (Eig 2) by plotting Initial Modulus against ~irefringenoe for all the samples prepared in aocordance with Examples 1 to 28. On the graph is also shown lines A'and ~'which'together serve to define the boundary limits of the novel polyethylene terephthalate fibres of the invention ie line A corresponds to the minimum birefringence of 0.105 and line B co~responds to 260 cosh ~0~07n84 3.
It ca,n be seen that examples 1-16 fall within the scope -of the invention but tEat Examples 17-28 are all outside -- -the scope of the invention.

In a process for melt spinning a filament yarn from molten nylon 6,6 polyamide through a spinneret at 288C employing am ambient air quench zone immediately below the spinneret to effect solidification of the filaments, the solidified filaments were passed through a oonditioning tube as described in Examples 1 to 16.
After application'of a spin finish, the yarrsproduced were finally wound up on a bobbin at velocities of 4.0-5.0 ~ min.
The prooess oonditions were varied oonsiderably and the results obtained tabulated in ~able 3. These results show that both the tenaoity and the modulus are increased with increased steam pressure/temperature in the conditioning zone.

~ Z~7 3 AslE ~ 14 _ ~ li, S~F ~AM ~ H MODUI~ ~ ~ . .
~o REF ~ ~ DTEX ~ ~ ~_ ~ ~ æ/0 50/o 1~/o . i~ _ _ . ~ _ 29 1551 5. o 44.2 13 352 137 39 03 52.0 333 244 162 3o 1552 5.o 44.o 13 239 124 37.87 45.o 334 298 185 31 1553 5.o 44.4 13 204 119 38.41 43.o 353 3o9 199 32 1556 5. o 46.5 13 101 100 37.52 55.0 327 232 156 33 1657 4.5 68.6 20 445 147 39.86 54.1 329 226 157 34 1659 4.5 68.6 20 342 137 38.58 53.7 364 226 156 1661 4.5 68.6 20 239 124 37.89 53.7 363 z8 151 - - - -- 36 1665 4.5 68.7 20 171 114 37.09 59.7 357 217 143 3~ -f6Gg- -~- 568.2 20 101 100 36.64 64.3 338 201 129 38 1566 4.o 4o.5 13 239 124 39.20 45.2 315 237 162 39 1567 4.o 45.2 13 342 137 40.33 54.2 331 212 147 4o 1569 4.o 44.8 13 171 114 43.75 50 7 350 263 171 41 1572 4.o 45.2 13 101 100 38.16 54.1 ~25 217 139 In the above Table 3 it should be noted that Examples - 32, 37, 41 are outside the scope of the present invention.
EX~MæLES 42-4~
Ex2mples 1-16 were repeated using slightly different processing conditions. ~he results obtained are tabulated in Table 4.
~~,ABLE 4 25 ¦ ~ ~ ~ H ~ H ~ _ _ ~b ~N~ ~ô ~ _ ~ ~ ~ _ _ _ _ _~ __ __ _ _ 42 1955 5.o 0.63 49.5 20 79o 166 146 460 892 140 43 1946 5oo o.63 49.7 20 79o 166 126 402 826 160 3o 44 1950 5.o 0.63 48.8 20 823 171 131 386 879 160 1949 5.o o.63 49.7 20 790 166 117 351 820 135 _ _ _ _ __ _ ..

Claims (8)

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

1. A process for forming a continuous filament yarn from a melt-spinnable synthetic linear polymer selected from the group of polyethylene terephthalate and polyhexamethylene adipamide comprising extruding the molten polymer through a shaped orifice to form a molten filamentary material, passing the molten fila-mentary material in the direction of its length through a solidification zone wherein the molten filamentary material is solidified, passing the solidified filamentary material in the direction of its length through a conditioning zone provided with a gaseous atmosphere at a temperature above the glass transition temperature of the material and below its melting temperature, withdrawing the resulting filamentary yarn from the conditioning zone and winding up such yarn, in which the gaseous atmosphere in the conditioning zone is compressed steam at an absolute pressure in excess of 136 kN/m2.

2. A process as claimed in Claim 1 in which the compressed steam is at an absolute pressure in excess of 170 kN/m2.

3. A process for forming a continuous filament yarn as claimed in Claim 1 wherein the melt-spinnable synthetic linear polymer is polyethylene terephthalate containing at least 85 mol percent of ethylene terephthalate in which the compressed steam is at an absolute pressure of between 239 and 1548 kN/m2.

4. A process as claimed in Claim 3 in which the compressed steam is at an absolute pressure of between 446 and 1176 kN/m2.

5. A continuous filament yarn formed from a melt spinnable polyethylene terephthalate in which the filaments have a birefringence (?n) greater than 0.105 and 5% modulus greater than 290 centi Newtons/tex and an initial modulus (IM) defined by the function:
IM > 260 cosh

6. A continuous filament yarn as claimed in Claim 5 which has a long-period spacing of less than 200 .ANG..

7. A process for forming a continuous filament yarn as claimed in Claim 1 wherein the melt-spinnable synthetic linear polymer is polyhexamethylene adipamide in which the compressed steam has an absolute pressure of between 170 and 618 kN/m2.

8. A process as claimed in Claim 7 in which the steam has an absolute pressure of between 200 and 580 kN/m2.