False-twist texturing yarn of polyester filaments having multilobal cross sections

Abstract

multifilament polyester yarn, of multilobal filaments having specified cross-sectional characteristics, is false-twist textured into yarn which provides fabrics having improved visual aesthetics. The examples illustrate that freedom from objectionable glitter is obtained with 6 to 10-lobed filaments, having essentially symmetric lobes of equal length equispaced around a central axis of the filament, when the modification ratio is from 1.17 to 1.85, and the denier per filament is between 3.8 and a maximum value which is a function of the modification ratio and the number of lobes.

Description

REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part of application Ser. No. 243,795, filed Apr. 13, 1972 (now abandoned), which is in turn a continuation-in-part of application Ser. No. 99,446, filed Dec. 18, 1970, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to false-twist textured yarns made from continuous filaments having modified cross-sections, and is more particularly concerned with polyester yarns which can be false-twist textured for use in fabrics having improved visual aesthetics.

2. Description of the Prior Art

Apparel fabrics knitted or woven from false-twist textured, continuous filament synthetic yarns are finding increasing acceptance in the trade. The texturing is needed to eliminate the undesirable slickness of fabrics made from synthetic filaments. The fabric aesthetics can be further improved by using fibers having a modified (i.e., non-round) cross-section which lead to higher bulk, a crisper and drier hand, better cover, and a pleasing subdued luster. Unfortunately, fabrics produced from false-twist textured yarns often have an undesirable glitter or sparkle, i.e., reflection of light in intense beams from tiny areas of the fabrics. Except for certain novelty applications, this glitter is highly objectionable and detracts from the appearance of the fabric, particularly when the fabric is dyed in dark shades.

A variety of methods are used to texture filaments depending on the use of the yarn. One which has met with considerable Friction coefficient is determined against an AlSiMag® 513 pin 3/16 inch in diameter (Moh hardness 9, surface roughness 24 ± 2 micro inches). The wrap angle θ is about 495° and the yarn speed is 700 yards per minute. The yarn is fed to the pin at a tension (T₁) of 10 grams by pretension means and is pulled away from the pin by driven rolls under a measured output tension (T₂). The yarn tension is measured adjacent to the pin with strain gauges. Between the pretension means and the first strain gauge, the yarn travels for a distance of 39 inches in contact with a heater maintained at the usual texturing temperature for such yarn. The friction coefficient (f) is calculated from the belt equation, T₂ /T₁ = e ^fθ, wherein e is 2.718, the base of natural logarithms, and the other symbols are as indicated above.

The number of filament cross-sections with a flattened periphery greater than 10 microns in length is determined by microscopic examination of the yarn cross-section. The yarn is embedded in a suitable material and is cut transversely to expose a clear view of the fialment filament ends. The length of the flattened periphery of the filament cross-sections may be determined by use of a calibrated eyepiece. Preferably, however, a thin transverse slice of the embedded yarn is prepared on a microtome and this is placed on a microscope stage in an immersion oil. Photomicrographs are prepared showing the cross-section at a known magnification. The length of the flattened portions are then measured along a straight line with a ruler on the photomicrograph. The measured values are then converted to actual filament values using the magnification factor. To determine the percent of filaments having cross-sections with a flattened periphery greater than 10 microns, the number of flattened filaments greater than 10 microns is divided by the total number examined and multiplied by 100 to get percent.

Intrinsic viscosities of polymers given in the examples are measured in a solvent consisting of 25 parts by volume of trifluoracetic acid and 75 parts by volume of methylene chloride at 25°C

Finishes used in Examples I-VII VI to provide suitable frictional characteristics for acceptable texturing performance are given below. These finishes are diluted with water before application and generally applied in amounts of about 0.8 to 1.4 percent by weight of the yarn (based on the non-aqueous components).

______________________________________
Finish A                Parts by Weight
______________________________________
Isocetyl stearate       49
Sodium di-(2-ethylhexyl)-sulfosuccinate
24.5
Condensation product of 1 mole stearyl
24.5
alcohol with 3 moles of ethylene oxide
Triethanolamine         1
Oleic acid              1
______________________________________

______________________________________
Finish B                Parts by Weight
______________________________________
Coconut oil             65
Sulfated glyceryl trioleate
15
Glyceryl mono-oleate    10
Condensation product of 1 mole nonyl
10
phenol with 5-6 moles of ethylene oxide
Oleic acid              1
Triethanolamine         1
______________________________________

The number of lobes for the filaments of the invention is in the range 6 to 10. It is difficult to fabricate spinneret orifices to produce filaments having more than 10 lobes, and the differences in glitter and non-glitter filaments are modest and hard to differentiate in filaments with 5 lobes or less. Of course, by reducing the filament denier sufficiently, it is possible to produce glitter-free yarns after texturing regardless of the starting cross-section. However, low-denier multilobal filaments are difficult to produce and are less desirable because they provide fabrics which are too soft and lack crispness. In accordance with the present invention, a soft (uncrisp) hand is avoided by use of yarns in which the denier per filament is greater than 3.8. In addition, as previously disclosed, the filaments must have the proper combination of modification ratio, denier per filament, and number of lobes. The importance of these requirements will become apparent from the examples.

Filaments of the proper denier are prepared by melt-spinning filaments of higher denier and then drawing by known methods to produce filaments with denier in the required range. Since the denier of the original melt-spun filament is equal to the denier of the drawn filament times the draw ratio, one can calculate the denier to be spun once one has determined the optimum draw ratio and the final denier per filament. The drawing operation may occur after melt-spinning as a separate step or may be part of a coupled spinning and drawing operation as in Example 1. On the other hand, the drawing may be done as part of a unitary draw-texturing process as in Example IX. If one elects a "simultaneous" draw-texturing process, partially oriented yarn is passed over a hot plate where it is both drawn and false-twisted. The filaments in this yarn pass from the hot plate to the twist trap. After passing the twist trap, the filaments are untwisted and the tension is partially reduced as the yarn is wound up.

It should be clear from the above discussion that partially oriented feed yarns for draw-texturing according to the invention must have higher denier per filament than highly oriented feed yarns by a factor equal to the draw ratio used in the draw-texturing operation. While ratio may vary according to tension and other factors, the maximum ration ratio (R) of output-to-input speed in the draw-texturing operation which is operable without excessive filament breakage is established by testing the feed yarn under a number of draw-texturing conditions. For high-speed spun partially oriented filaments, the ratio (R) is between 1.2 and 2. For slow speed spun partially oriented yarns, the ratio may be as high as 6. For so-called drawn yarns which are highly oriented, the maximum ratio may be as low as 1.1; in practice, such drawn yarns may be overfed to the machine to give an actual operating ratio as low as 0.90. The required denier per filament for partially oriented feed yarns as well as for highly oriented feed yarns is, therefore, between 3.8(R) and (5.88M - 10 + N) (R).

The following examples illustrate the effect which different combinations of the number of lobes, denier per filament, and modification ratio have on the amount of glitter from flattened surfaces on false-twist textured yarns. Products which meet the specified limits of the invention all have acceptable glitter ratings. Included for comparison therewith are products having unacceptable or borderline glitter ratings; these products have values (underlined in the tables) which are outside of the specified limits.

Examples I to VIII show feed yarns with a maximum operable output-to-input ratio (R) of about 1.1. Example IX illustrates a feed yarn with a maximum operable ratio (R) of about 2∅].

EXAMPLE I

This example illustrates the preparation of a series of octalobal (N=8) yarns with a range of deniers per filament d and modification ratios M from a copolymer of polyethylene terephthalate containing 2 mole percent of 5-sodium-sulfo-isophthalate units in the polymer chain.

A copolyester having an intrinsic viscosity of 0.53 was melt spun at 280°-300°C through orifices having 8 slots 0.0035 inch wide and 0.016 inch long symmetrically arranged and radiating from a common point, the length being measured from the common center point. After emerging from the spinneret, the filaments were quenched by a stream of air directed radially inwards against the threadline, the flow of quench air being adjusted to produce the desired modification ratio. The quenched filaments passed over a finish applicator where about 1 percent of Finish B was applied. The bundle of filaments then passed around a feed roll into a steam jet where it was drawn. Several different yarn deniers and filament counts were prepared as shown in Table I. The filament count was varied by using spinnerets with the required number of orifices. The denier per filament was adjusted by adjusting the relationship between extrusion rate and wind-up speed after drawing. Finish B was applied to the drawn yarn before wind-up with pickup of about 0.8 to 1.4 percent by weight based on non-aqueous components.

The drawn yarns were false-twist textured on a Leesona 553 machine having a rotating hollow spindle; the machine being available from Leesona Corporation, Warwick, Rhode Island. The texturing conditions are shown in Table I. In each case the overfeed to the spindle was 1 to 2 percent, and the overfeed to the package was about 12 percent. The resulting yarns were knitted into fabric and the knitted fabric was then dyed a deep purple shade and evaluated for glitter. The results are shown in Table I. The data show that glitter was avoided by increasing the modification ratio and/or decreasing the denier per filament. Knit fabrics prepared from 4.4 denier per filament and 5.5 denier per filament yarns had a dry, crisp hand and high liveliness. On the other hand, knit fabrics from 2.1 denier per filament yarns had a soft hand and low liveliness.

EXAMPLE II

This example describes the results obtained with polyethylene terephthalate yarns having hexalobal cross section and indicates that there is a maximum usable modification ratio beyond which glitter reappears in fabrics made from the textured yarns.

Polyethylene terephthalate having intrinsic viscosities of 0.66 to 0.89 was melt spun as in Example I, except that the spinneret orifices were composed of six equispaced slots radiating from a central point. The slots for the first six itmes items (Table II) were 0.003 inch wide and 0.018 long while the slots for the seventh item was 0.003 inch wide × 0.024 long. Hexalobal filaments were produced. The modification ratio was adjusted by adjusting quench rate. The yarns were drawn similarly to those in Example I but in an aqueous draw bath at 95°C rather than in steam. The yarns were false-twist textured on a Leesona 555 machine and knitted into fabrics which were dyed and evaluated for glitter. The results in Table II show that 150/34 yarns give acceptable performance at modification ratios of 1.43 and 1.71, but that unacceptable glitter occurs in fabrics produced from 150/34 yarn having a modification ratio of 2.05.

EXAMPLE III

Polyethylene terephthalate having intrinsic viscosities of 0.66-0.89 was melt spun and drawn as in Example II. The spinneret orifices consisted of eight equally spaced radial slots 0.003 inch wide and 0.018 inch long for items III-1, III-2, III-4, and III-5 shown in Table III. The orifices for III-3 was composed of eight slots 0.003 inch wide and 0.026 inch long. The yarns after spinning and drawing were false-twist textured under the conditions shown in Table III and knit into fabrics. Fiber properties and glitter ratings are shown in Table III.

EXAMPLE IV

Polyethylene terephthalate was melt spun and drawn as in Example II, except that the spinneret orifices were ten equally spaced radial slots. The filaments were decalobal in cross section. These were false-twisted, false-twist textured, knitted, and dyed. Properties are listed in Table IV. Item IV-1 was produced from spinneret slots of size 0.003 × 0.015 inch and Item IV-2 from slots of size 0.003 × 0.024 inch.

EXAMPLE V

A series of 150 denier/34 filament yarns (d=4.4) of differing cross sections (round, and N=3, 5, 6, 8 and 10) were prepared from the copolymer of Example I using melt-spinning techniques. The yarns, which are identified in Table V, were false-twist textured on a Leesona 555 machine at the following conditions:

______________________________________
Spindle Speed     210.000 rpm
Twist             60 tpi
Temperature       193° C
First Overfeed    0
Second Overfeed   + 12%
______________________________________

After texturing, the yarns were knitted into fabrics, dyed and evaluated for glitter. In this series of textured samples, the round trilobal and pentalobal cross-section yarns exhibited objectionable glitter while hexalobal cross-section yarns exhibited objectionable glitter only in the lower modification ratios. All of the octalobal and decalobal yarns were acceptable in their glitter ratings.

EXAMPLE VI V

Polyethylene terephthalate was melt spun and drawn as in Example III to produce octalobal yarns having a range of deniers/filament and modification ratios. These were false-twist textured, knitted into fabrics, dyed and evaluated for glitter with the results shown in Table VI.

EXAMPLE VII VI

Polyethylene terephthalate was melt spun and drawn as in Example II, except that a spinneret containing 50 six-slotted (0.004 × 0.016 inch) orifices was used to produce filaments with a hexalobal cross section which were textured, knitted, dyed, and evaluated for glitter. The results are listed in Table VII VI.

EXAMPLE VIII VII

This example illustrates application of the principles of this invention to a copolyester different from that in Example I.

A copolymer of polyethylene terephthalate containing 10 mole percent of ethylene adipate units in the polymer chain, having an intrinsic visocisity viscosity of 0.75, was melt spun at 305°C through a spinneret containing 34 orifices each consisting of six equally spaced radial slots of 0.003 × 0.018 inch in size. The yarn passed around a feed roll operating at 1109 ypm, through a draw bath at 92°C and around draw rolls operating at 3000 ypm and heated to 130°C About 2 percent of Finish B was applied on the yarn which was found to have the following properties: 75 total denier, 1.66 modification ratio, 3.28 gpd tenacity and 31 percent elongation.

The yarn was textured at 193°C with 80 turns/inch, a spindle speed of 300,000 rpm and 0 percent first overfeed. The textured yarn was knitted into a fabric, dyed a deep navy blue shade and found to be free from objectionable glitter. Examination of the cross sections of the textured yarn indicated that there were no filaments with flattened sides greater than 10 microns in length.

EXAMPLE IX

Polyethylene terephthalate was melt-spun as in Example II, from a spinneret having 34 orifices consisting of eight slots 0.0035-inch wide and 0.0112-inch long arranged radially around a center point and intersecting at the center. The denier per filament was adjusted by the relationship between extrusion rate and wind-up speed. The drawability, degree of molecular orientation, and modification ratio were adjusted by control of the quenching air temperature and of the quenching air speed in conjunction with wind-up speed. Partially oriented, 235 denier, 34-filament yarns were obtained which had a break elongation of 112 percent and a tenacity of 2.2 gpd. The filaments had octalobal cross-sections (N=8); the modification ratio M being 1.22 and the denier per filament being 6.9. A finish was applied consisting of an aqueous dispersion of 12 percent by weight of a polyoxyalkylene block copolymer, about 0.1 percent of a surface-active agent, and a basic buffer. The block copolymer contains about 40 percent by weight of oxyethylene groups and 60 percent of oxy-1,2-propylene groups.

The partially-oriented yarns were then draw-textured on a conventional draw-texturing machine (ARCT-480 available from Ateliers Roannais De Construction Textile) and set (second heater) under the conditions shown in Table VIII. The textured yarns were knit into fabrics, dyed, finished, and evaluated for glitter. Yarn properties are shown in Table VIII. All had the glitter rating "A". The yarn 3 had 4 percent of the filaments with a cross-section having a flattened periphery greater than 10 microns in length. The maximum operable ratio (R) of output-to-input for these yarns was about 2. The actual operating draw ratios were somewhat less than 2, as shown in Table VIII

TABLE I
__________________________________________________________________________
PROCESS AND PRODUCT DATA FOR EXAMPLE I
__________________________________________________________________________
Filament Properties
Texturing Conditions
__________________________________________________________________________
Yarn Denier/       Ten.
Elong.
Turn/
Temp.
rpm. Glitter
Sample
No. of Filaments
N d   M   gpd.
%   Inch
°C
×10-3
Rating
__________________________________________________________________________
1-8  70/34   8 2.1 1.34
3.1 30  76  185 195  A
1-9  70/34   8 2.1 1.25
3.1 30  76  185 195  A
1-10
70/34   8 2.1 1.19
3.1 39  76  185 195  A
1-11
70/34   8 2.1 1.11
3.2 38  76  185 195  U
1-12
70/34   8 2.1 1.06
3.4 39  76  185 195  U
1-1 150/34   8 4.4 1.36
3.6 25  60  193 210  A
1-2 150/34   8 4.4 1.28
3.2 34  60  193 210  A
1-3 150/34   8 4.4 1.20
3.5 35  60  193 210  A
1-4 150/34   8 4.4 1.15
4.1 26  60  193 210  B
1-5 110/20   8 5.5 1.36
3.6 31  65  193 210  A
1-6 110/20   8 5.5 1.30
3.6 32  65  193 210  A
1-7 110/20   8 5.5 1.21
3.6 25  65  193 210  B
__________________________________________________________________________
Note
1: rpm is revolutions per minute
2: Glitter rating A = acceptable Glitter rating B = borderline Glitter
rating U = unacceptable

TABLE II
__________________________________________________________________________
PROCESS AND PRODUCT DATA FOR EXAMPLE II
__________________________________________________________________________
Nominal
Fiber Properties
Draw
Fin-
Yarn Den./       Ten.
Elong.
Sample
Ratio
ish No. of Fils.
N M   d   gpd.
%
__________________________________________________________________________
II-1
3.4 A    70/34 6 1.50
1.9 4.3 29
II-2
3.5 A    70/34 6 1.30
2.1 4.2 27
II-3
3.9 A   150/34 6 1.43
4.3 4.2 29
II-4
3.9 A   150/34 6 1.43
4.2 4.1 29
II-5
1.8 B   150/34 6 2.05
4.5 2.3 23
II-6
2.0 B   193/34 6 1.90
6.2 1.9 57
II-7
4.0 A   150/34 6 1.71
4.4 4.2 28
__________________________________________________________________________
Texturing Conditions
Turns               % of filaments
Per Temp.
RPM  Overfeed to
with flattened
Glitter*
Sample
Inch
° C
×10-3
Spindle, %
sides > 10μ
Rating
__________________________________________________________________________
II-1
68  227 210  +2     0       A
II-2
68  227 210  +2     0       A
II- 3
58  227 210  +2     3       A
II-4
58  227 210  +2     0       A
II-5
63  227 300  0      29      U
II-6
56  188 160  -10    39      U
II-7
60  210 210  +1     0       A
__________________________________________________________________________
.A = Acceptable; B = Borderline; U = Unacceptable

TABLE III
__________________________________________________________________________
PROCESS AND PRODUCT DESCRIPTION FOR EXAMPLE II
__________________________________________________________________________
Intrin-
Nominal Fiber Properties
Draw    sic   yarn Den/         Ten.
Elong.
Sample
Ratio
Finish
Viscosity
No. of Fils.
N M   d   gpd.
%
__________________________________________________________________________
III-1
2.8 A   0.7    70/34  8 1.3 2.2 3.6 31
III-2
4.0 A   0.7   150/34  8 1.2 4.3 4.3 28
III-3
3.8 A   0.66  150/34  8 1.47
4.3 4.1 23
III-4
4.0 A   0.7   150/34  8 1.2 4.4 4.5 29
III-5
2.5 B   0.89  415/34  8 1.6 13.4
2.3 85
__________________________________________________________________________
Texturing Conditions
Turns                              Glit-
per  Temp.
RPM   First % Filaments with
ter*
Sample
Inch °C
×10-3
Overfeed
Flattened sides > 10 μ
Rating
__________________________________________________________________________
III-1
68   227  210   +2    0            A
III-2
58   227  210   +2    0            A
III-3
60   210  210   +1    0            A
III-4
58   227  210   +2    0            A
III-5
56   178  100   - 10  30           U
__________________________________________________________________________
*A = Acceptable; B = Borderline; U = Unacceptable

TABLE IV
__________________________________________________________________________
Process and Product Description for Example IV
__________________________________________________________________________
Nominal Yarn Denier/
Draw        Intrinisic
Number of Fila-
Fiber Properties
Sample
Ratio
Finish
Viscosity
ments       N M   d   Ten. gpd
Elong. %
__________________________________________________________________________
IV-1
3.2 A   0.7   150/34      10
1.26
4.4 3.8  34
IV-2
3.2 A   0.7   360/34      10
1.20
10.6
2.51 46
__________________________________________________________________________
Texturing Conditions    % Filaments
Turns Temp.
RPM  First
with Flattened
Sample
Per Inch
°C
× 10-3
Overfeed
sides > 10 μ
Glitter* Rating
__________________________________________________________________________
IV-1
60    210 210  +1   0       A
IV-2
50    232 144  -7   18      U
__________________________________________________________________________
*A = Acceptable; B = Borderline; U = Unacceptable

TABLE V
__________________________________________________________________________
Process and Product Description for Example V
__________________________________________________________________________
Fiber properties
Sample
N   M   d   Ten. gpd.
Elong. %
Glitter* Rating
__________________________________________________________________________
V-1  Round
1.0 4.4 3.2  32   U
V-2  3   1.7 4.4 3.1  31   U
V-3  5   1.3 4.4 3.1  25   U
V-4  6   1.25
4.4 3.3  30   U
V-5  6   1.4 4.4 3.0  23   B
V-6  6   1.5 4.4 2.9  26   A
V-7  8   1.2 4.4 3.1  17   A
V-8  8   1.25
4.4 3.3  25   A
V-9  8   1.35
4.4 3.4  21   A
V-10
10  1.2 4.4 3.3  23   A
__________________________________________________________________________
*A = Acceptable; B = Borderline; U = Unacceptable

TABLE VIV
__________________________________________________________________________
Process and Product Description for Example VIV
__________________________________________________________________________
Draw        Fiber Properties
Sample
Ratio
Finish
N M   Ten. gpd.
d   Elong. %
__________________________________________________________________________
1 3.4 B 8 1.46 3.47
V-3.8
B   8   1.25
6.2 32
VIV-2
3.8 B   8 1.25
4.09 6.0 41
VIV-3
3.8 B   8 1.18
3.90 5.9 42
VIV-4
3.8 B   8 1.09
4.05 6.3 37
VIV-5
3.8 B   8 1.37
4.15 7.1 35
VIV-6
3.8 B   8 1.07
3.99 3.6 34
__________________________________________________________________________
Texturing Conditions       % Filaments with
Turns        RPM  First
Flattened sides
Sample
Per Inch
Temp. °C.
× 10-3
Overfeed
>10 μ Glitter* Rating
__________________________________________________________________________
VIV-1
60    225    250  0    6        A
VIV-2
60    "      "    0    13       B
VIV-3
60    "      "    0    12       B
VIV-4
60    "      "    -10  52       U
VIV-5
60    "      "    -10  20       U
VIV-6
70    "      "    0    27       U
__________________________________________________________________________
*A = Acceptable; B = Borderline; U = Unacceptable

TABLE VIIVI
__________________________________________________________________________
Process and Product Description for Example VIIVI
__________________________________________________________________________
Draw        Fiber Properties
Sample
Ratio
Finish
N M   d   Ten. gpd.
Elong. %
__________________________________________________________________________
VIIVI-1
3.6 B   6 1.09
2.1 3.97 34
VIIVI-2
3.6 B   6 1.37
4.5 3.61 38
VIIVI-3
3.6 B   6 1.4 4.6 3.70 39
VIIVI-4
3.7 B   6 1.42
5.5 3.55 40
__________________________________________________________________________
Texturing Conditions       % Filaments
Turns per    RPM  First
with Flattened
SAMPLE
Inch  Temp.°C
x 10-3             sides >10 μ Glitter*
Rating
__________________________________________________________________________
VIIVI-1
70 225 250 0 19 U
VIIVI-2
60 " " -10 17 U
VIIVI-3
60 " " -10 29 U
VIIVI-4
60 " " -10 24 U
__________________________________________________________________________
*A = Acceptable; B = Borderline; U = Unacceptable

TABLE VIII
__________________________________________________________________________
PROCESS AND PRODUCT DATA FOR EXAMPLE IX
__________________________________________________________________________
Texturing Conditions
(ARCT-480)1
Temp. of
Temp. of
Finish-    Textured Yarn Properties
w/Cooling
Turns/
First  Second RPM   Draw
Color
% on Yarn
Den Ten. (g/d)
Elong. (%)
Zone  inch
Heater (°  C)
Heater (°
×10-3
Ratio
__________________________________________________________________________
1/Brown
1.0   168 3.5   25    No    66  210°
230°
391   1.57X
2/Blue
1.0   171 3.5   31    No    60  210°
230°
363   1.50X
3/Green
1.0   178 3.4   36    Yes   60  210°
230°
363   1.46X
__________________________________________________________________________
Note 1: "RPM" is revolutions per minutes

Claims

1. An improvement in multifilament polyester yarn for false-twist texturing at a maximum ratio (R) of output-to-input of up to 6:1, wherein the improvement comprises yarn composed of polyester filaments of multilobal cross-section characterized by a total number (N) of 6 to 10 essentially symmetric lobes of substantially equal length, equispaced radially about the center of the filament, and having between 1.17 and 1.85 modification ratio (M), the filaments having a denier per filament between 3.8(R) and (5.88M - 10 + N)(R). at M = 1.85.

2. yarn as defined in claim 1 wherein said polyester is polyethylene terephthalate.

3. yarn as defined in claim 1 wherein said polyester is an ethylene terephthalate copolyester containing about .Badd.2 mole percent of 5-sodium-sulfo-isophthalate units in the polymer chain.

4. yarn as defined in claim 1 wherein said polyester filaments have octalobal cross-sections.

5. yarn as defined in claim 1 wherein said polyester filaments have positive lobe angles.

6. A false-twist textured yarn product of the polyester yarn defined in claim 1, wherein less than 12 percent of the filaments have a flattened cross-sectional periphery of greater than 10 microns and the filaments have a denier per filament between 3.8 and 5.88M - 10 + N. at M = 1.85.

7. polyester yarn as defined in claim 6 wherein said polyester is an ethylene terephthalate polymer.

8. polyester yarn as defined in claim 6 wherein said polyester is an ethylene terephthalate copolyester containing about 2 mole percent of 5-sodium-sulfo-isophthalate units in the polymer chain.

9. yarn as defined in claim 1, wherein the yarn contains a finish which provides it with a friction coefficient of less than 0.3 at the texturing temperature.

10. yarn as defined in claim 9 wherein the finish is 0.8-1.4 percent by weight of the yarn of (A) isocetyl stearate, sodium di(2-ethylhexyl)-sulfosuccinate, condensation product of 1 mole stearyl alcohol with 3 moles of ethylene oxide, triethanolamine and oleic acid or (B) coconut oil, sulfated glyceryl trioleate, glyceryl monooleate, condensation product of 1 mole nonyl phenol with 5-6 moles of ethylene oxide, oleic acid and triethanolamine.