Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1040403
EACKGROUND OF THE INVENTION
_
This invention relates to textured polyamide yarn
and lts productlon, and ls more particularly concerned with
- a novel feed yarn, a process for draw-texturlng lt and a
novel textured yarn suitable for knltting stretch fabrlcs.
; m e polyamlde yarns of commerce are of 6-6 nylon
(polyhexamethyleneadipamide) or 6-nylon (from a-amino-
caprolc acid or caprolactam). Only minor amounts o~ yarns
are manufactured from other polyamides, such as ones having
branched chains or aromatic groups in the chains. A vast
number of other polyamides are posslble, but prevlous ex-
tensive research had not found any as deslrable as 6-6 nylon
for textlle yarn, even among the linear aliphatic polyamides
mo~t clo~ely related to 6-6 nylon. It ls surprising, there-
~ore, to flnd that one can be prepared to have propertles
superlor to 6-6 nylon yarn, particularly for textile uses
~here texturlng 18 lmportant to provide bulk, sortness and
atretch ln fabrics.
SUMMARY OF THE INVENTION
The present lnvention provides a polyamlde feed
yarn for drawing and texturing into products whlch are
superior to comparable 6-6 nylon yarn for textile uses.
me invention also provides a draw-texturing process for
provlding lmproved crimp properties. An improved textured
yarn i8 provided which h~s tenacity and modulus properties
at least equivalent to comparable 6-6 nylon yarn under
normal conditions and is less sensitive to humidity, which
has lmproved ratio5 of crimp to turns per inch of twist
liveliness for better processibility when knitting, and
which can be knitted lnto more powerful stretch fabrics
' ~
_ 2 - ~
1040403
havlng better recovery from ætretchlng. Other advantages
of the inventlon will appear herelnafter.
The polyamide feed yarn of this invention ha3
a break tenaclty of at least 6.5 grams per denier and a
yarn-on-yarn coe~ficlent Or frlctlon of less than 0.50
whlch i8 free from stlck-slip behavlor when tested as
described subsequently. The po}yamide conslst~ essentlally
of polyhexamethylenedodecaned~oamlde of 30 to 70 relatlve
vlscosity havlng a triclinlc cryætallite cell structure
characterized by a crystal perfectlon index of less than
50 percent with substantlal freedom from the ~-crystalline
form. m e yarn 18 preferably an undrawn yarn suitable for
drawing at a draw ratio of 3.5X to 4.5X when the yarn is
textured. However, the yarn can be partially drawn or
fully drawn prior to the the texturlng operation. Yarn
whlch has been drawn to have ~ bresk elongatlon Or a~out
to 40 percent i8 usually used in conventional texturing
operations.
In a preferred proces~ of this lnvention for draw-
lng snd false-twist texturing hosiery yarn, undrawn feed
yarn Or 30 to 70 relative vlscosity polyhexamethylene-
dodecanedloamide, having a tricllnic crystallite cell struc-
ture characterlzed by a crystal perfection lndex of les~
than 50 percent wlth substantial freedom from the ~-crystal-
line form, ls draw-textured at an applled twlst Or 170 to
200 turns per inch and a texturlng temperature of 150 to
200-C. The draw-texturing can be per~ormed in three ways.
In the tandem process, drawine is completed in a separated
draw zoné and the drawn ysrn is lmmedlately fed lnto a false-
twlst te~turing zone. In the si~ultaneous process, drawlng
. .
_ 3 _
. - :
104~)403
i~ accompllshed in the false-twist texturing zone. In the
third process, part of the drawln~ is accomplished in a
sepsrate draw zone and drawing is completed in the false-
twlst texturing zone.
Textured polyamide yarn is readily produced which
ha8 a break tenacity of at least 6.5 grams per denier, a
yarn-on-yarn coefficient of frictlon of less than 0.50,
free from stick-slip behavior, about 45 to 65 crimps per
`inch (restrained), a crimp elongation of at least 40 percent
and a ratio of crlmps per lnch (restrained) to turns per
inch (off pirn) of at least 1.6; the polyamide consisting
Or polyhexamethylenedodecanedioamide of 30 to 70 relative
~coslty having a triclinic cell structure characterlzed by
a cry8tal perfection index of at least 75 percent and a
ratio of ~/B crystalline forms of at least 1Ø The ex-
cellent crimp properties obtained are believed to be due,
at least ln part, to the change in triclinic cell ~truc-
ture whlch occurs during texturlng. Accordingly, the ~eed
yarn 18 produced under conditions which provlde a crystal
perfectlon lndex of less than 50 percent and substantlal
rreedom from the -crystalline form, and heating of the
feed yarn prlor to the draw-texturing operation is avoided.
BRIEF DESCRIPTION OF THE DR~WINGS
FIGURES 1 and 2 are schematic representatlons of
preferred apparatus for practicing the draw-texturing
process. FIGURE 1 illustrntes a coupled drawing and tex-
turing operation and FIGURE 2 illustrates simultaneous
draw-texturing operation.
FIGURE 3 is a side vlew of a friction-twlst device
~0 for lmparting twist to yarn during draw-texturing Orien-
tation relatlve to yarn travel is indicated.
-- 4 --
-
1040403
DETAI~ED DESCRIPTION
FIaURES 1 and 2 repre~ent ~ingle positions of a
drawtwister modified to both cold-draw and f~lse-twist
texture a drawable nylon feed yarn. Correspondlng parts
are ldentlcally numbered. Drawable reed yarn 12 i8 prefer-
ably completely undrawn and fed directly from lts partially
shown spin bobbin 10. Via creel pigtail guide 14, creel
snub guide 16, and traverse guide 18, yarn 12 is led to
~ and partly around cott roll 20 before passing through the
; 10 nlp between cott roll 20 and driven feed roll 22.
Drsw roll 26 is driven and comprises two sections:
(1) ~.inor ~tep 30 servlng as a first drawing stage, and (2)
maJor step 28 serving as a second drawing stage. Separator
roll 32 i~ al80 provided,as ls well understood. From feed
i5 roll 22, yarn 12 first p~sses about draw pln 24 and then to
8everal wrap~ around ~inor step 30 and separator roll ~2.
I Because the peripheral velocity of minor step 30 is greater
- than that o~ feed roll 22, yarn 12 becomes drawn.
~ Yarn 12 next passes in contact with hot plate ~4
:
(or other known heating means) which is sized and operated
to produce a predetermined yarn-temperature at its outlet.
False-twisting occurs on passage of yarn 12 through rotating
frlction-tube twl~ter 36 (descrlbed more fully hereinafter).
V1~ guide 38, y~rn 12 takes several wraps around maJor step
; 25 28 and separator roll 32, whereby further drawlng occurs,
~ince maJor step 28 and minor step 30 have dlfferent di-
ameters, but rotate at the ~ame aneular veloclty. Passlng
through balloon gùide 40, the false-twist textured yarn is
wound on pirn 42 using a convent~onal ring and traveler
(not shown).
.
- .
. . .
1040403
The larger the ma~or ~tep 28 i8 with respect to
the minor step 30, the more the yarn is drawn whlle belng
~alse-twisted as compared to the draw occurring between
reed roll 22 and minor step 30. mis treatment is labeled
"underfeed". A 4% underfeed i9 used for Examples 3 and C;
i.e~" the dlameter of ma~or ~tep 28 ls 4% greater than that
o~ mlnor step 30. To prevent the passage of applied false-
twist further upstream, a nip roll (not shown) bears against
ya m 12 on minor step 30 at the point where yarn 12 tan-
gentially departs toward heater ~4.
A special case of the`above-described underfeed
process is one in which major step 28 and minor step 30
have the same diameter. In thls case, all the drawing
occurs between feed roll 22 and mlnor step 30. All the
texturing occurs wlthout any further drawing ln the travel
from minor ~tep 30 to ma~or step 28. This 0~ underfeed i8
herein labeled "tandem" to designate serial coupling, but
conplete separation of the draw$ng and ~alse-twisting
operations.
A thlrd varlatlon is repreæented by FIGURE 2.
It dlffers from the above-described arrangements, as
follows:
Departing from feed roll 22, yarn 12 inltially
bypasses draw roll 44 v~a guldes 46. It is then heated by
hot plate 34, ~alse-twlsted via twlster 36, and dlrected
via guide 38 to several wraps around draw roll 44 and lts
~; separator roll 32. It is packaged as before. Thu~, all
the drawing and all the ~alse-twistlng occur ln the same
zone. Thls variatiffn i8 labeled "simultaneous".
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104~)403
While the above proce~se~ are preferred, other
texturlng processes~are also suitable. It 1~, for example~,
erfective to draw the yarn in a first separ~te operation
and then subsequently to feed the drawn yarn to custom~ry
~alse-twlsting and heat-setting wlth or without further
drawlng. In additlon to false-twist texturing, other tex-
turing processes such as Rtuffer-box crimping, knit-deknit
texturing, gear crimplng, and the like, are effective for
texturing yarns o~ thls invention.
Rotating frictlon-tube twister 36 of FIGURES 1
and 2 is shown in more detail in FIGURE ~. Dashed lines
represent pertinent lnternal structure. Twister 36 ls
baslcally an electrlc motor 50 havlng hollow rotor 52.
Fltted onto each end of rotor 52 is a ring-like bushing 54
having lts inner surfaces 56 outwardly flared. At least a
portion Or the yarn-contacting surfaces of bushings 54
ha8 a high coefficlent of frictlon with the running yarn.
Yarn 12 enters twlster 36 vla guide 58 positioned to provlde
a preselected entrance angle,B, wlth respect to the center
llne (axis of rotatlon). Likewise, on exit, yarn 12 travels
over gulde 60 positloned to provide exit angle Y. Ordi-
narlly, for most satisfactory performance, the center line
of twister 36 is at angle ~ wlth respect to the horizontal.
e yarn of this invention melts at about 215C.
The heat-setting temperature is also lower than that of
6-6 nylon, ~hich is an advantage in high speed texturing
processes because heat-settlng temperatures can be reached
more quickly. This means that the ~ame texturing equip-
ment can be operated at higher speeds or a simpler heating
device can be used. The inltial tensile modulus ia about
. . .
-- 7 --
1040403
the ~ame as that of ~-6 nylon at room temperature, but
decreases much more rapidly at elev~ted temperatures. At
150C. lt is only about 1/4 that of 6-6 nylon. The re-
slstance to applied torque is correspondingly reduced, BO
the yarn of this invention textures more readily and be-
comes more highly crimped than does 6-6 nylon in com-
parable processes.
The yarn of this invention is qulte strong. In
order to avold confusion when comparing yarns which have
been drawn to different extents or have been draw-textured
under different condltions, tenacities given herein are
calculated from stres~ in grams and denler at the instsnt
of yarn Pallure. Thls "break tenacity" is at least 6.5
g~ams per denier for yarns Or the present invention, and
preferred embodiments have break tenacitles of at least
8.o gpd.
Iow sensitivity to moisture i8 an important
attribute of the textured yarns of this invention. At
100% relative humidity (RH) and 25C., a desslcated yarn
regains 2.6% by weight water, whereas the corresponding
regain for 6-6 nylon ls 8%. At the same condltions sus-
pended under a load of 4 mg./denier, yarn Or the present
inventlon extend~ only about 20% as much as 6-6 nylon
(moiæture plasticization). As shown in the examples, the
lnltlal modulu~ of textured yarn of this inventlon is much
more constant than that of 6-6 nylon over the whole RX
range, a property leading to improved respon6e and sta-
bllity of garments worn during a variety of weather con-
ditions.
io4~)403
Textured nylon yarns are frequently used for
knlttlng ladles' stretch sheer ho~lery. Hlgh shape re-
covery a~ter stretching i8 an important property. Much
experlence wlth 6-6 nylon stretch hosiery has taught that
the higher ls the degree of crlmp Or the yarns, the lower
1B the recovery. Thls i8 belleved due to dirflculty yarn
portlons have in slidlng past other yarn portions as re-
covery ~orces approach zero. Surprislngly, the textured
yarn of the present inventlon exhiblts recoveries at least
egulvalent to 6-6 nylon even though lts level Or crimp i8
dlstlnctly higher.
A rinal advantage of false-twist textured ysrn
o~ thls invention, as compared to simllarly processed 6-6
nylon ya m, i8 that, lmmediately on removal fro~ its
psckage, it is conslderably less twlst-lively and, there-
ore, easier to proce~s into f~brics. me improved cr~mp
propertles csn be regenerated ~g a slmple heat trest~lent
~ter a rabrlc i8 prepared. ~ -
Derinitlons and Test ~ethods
.
Cold-drawln~. The terms "dr~wing" and "cold-
drawlng" are used lnterch~nge~bly hereln. They describe
~; su~lcient stretchin~ of a yarn in lt~ solld state (l.e.,
usually between room temperature and about 100C.) to
result in a per~anent reduction in denier.
Draw-ratlo. When ~ yarn ls fed into a zone at
one llnear velocity and removed from the zone st a hlgher
llnear veloclty, the draw-rstio (DR) ls the ratlo of the
hlgher to the lower Or the llnear veloclties.
Relntlve Viscosity ('~V). Relative vlscoslty ls
the ratlo Or visco51ties st 25 + 0.05C. of s solutlon of
! .
nylon and the solvent a~ one. For 6-6 nylon, the solvent
i8 90% by welght formlc scid (10~ water), and the solution
~B ~onmed ~rom 5.500 gm. of dry 6-6 ~ylon in 50 ml. (25C.)
. or 90% ~ormlc ecid. For 6-12 nylon, the solvent ls 50~ by
weight phenol and 50% by weight 98% formic acld. A 901ution
Or 3.700 gm. o~ polymer ln 50 ml. (25C.) Or the solvent is
employed.
Denler. Denler ls the welght in grams of 9000
meter8 o~ a yarn. It 18 ordlnarlly calculated from the
welght o~ a known shorter length.
Tenslle Testlng. Tenslle determination~ referred
to hereln include tenacity, bresk tenacity, elongation,
lnltlal modulus, and work recovery. These are all cslcu-
lated fror.~ ~.essurements on the trace o~ A record~ng ~tress/
atraln analyzer. Sample length ls 10 inches, and elongation
8t ~he r~tc o~ 6C~ per minute.
For the tests reported ln Table I, packaged yarn
18 e~uillbrated for at least 24 hours in the test atmos-
phere ~t 72% RH and 25C.
Tenaclty (T~ 18 the rorce ln grams per denler
where the rorce in grams ls that indlcated at the point Or
ten811e ~ailure and denier is th~t obtained for the lnltlal
8~mple before elongation.
Break tenacity (Tg) 18 the force ln grams per
denler at break when tbe denier employed ls that Or the
elongated speclmen at the polnt o~ tenslle failure. Math-
ematlcally TB 3 T tl + (E/100)1.
Elon~stion 18 expressed a~ the percentage ln-
crease in length o~ a yarn beyond its unstretched lnitlal
leneth.
- 10 -
~ i . . .
1040403reak eloneati~n (E) is elongatlon at tenslle
~ailure.
Modulus is expressed ln grams per denler and ls
~ ~easure at any polnt on the stre3s/strain curve Or the
change ln stress (gm./denler) per unlt increase ln elongH-
tlon (fractlonal, unitless).
Initial modulus as shown in ~able T iS calculated
rrom the measured stress ln grams pér denier at precise
the polnt where 1.425% elongation of the structural ele-
ments ha8 occurred (followlng stralghtening o~ crimp).m e measured stress 18 divlded by 1.425 and multiplied by
100 to obtaln the llsted initial moduli.
For the lnltial modulus results of Table II, a
~odi~ied testing procedure 18 used. Each yarn ls rirst
wcund Or~ it9 package into skeins, e~ullibrated in the
teat ~tmosphere, ard the.. tested. For q~ble III, the skeins
arc 8teamed while preventing any twisting Or the skeins
exactly as described belo~J under "Cri~p elongation".
Initlal moduluæ (W ) is computed from a straight line
drawn to coincide with the initial steepest ætraight line
~arlation Or stress with ~traln as recorded by the analyzer.
me 810pe o~ thls llne is Ml i~ ccmputed as the increase in
load (gm./denier) divided by unit increase in elongation
(~ractional, unltles8).
ApPlled twlst i5 the amount Or twist accumulated
. . .
~long a yarn at the tlme twist is heat-set in the yarn. A
8prlng-loaded device is used to take a sample Or the
traveling yarn Just upstream of the false-twlster (ro-
tating frlctlon-tube or splndle, etc.). The sampllng
device clamps two location3 on a twisted length about 1.5
- 11 -
104~403
lnches apart and simultaneously cuts the yarn Ju~t outslde
both clamped places. m e number o~ twlsts per inch (tpl)
o~ this twisted sample is counted under a microscope.~
Twists per lnch Or product (TPI o~f-pirn and TPI
steamed) are measures of twlst-livellness ln yarns after
being packaged at least a week. The packaged yarn ls
egullibrated for at least 24 hours at 72% RH and 25C.
After unwlnding to remove outer layers of the package, a
s~ple about 24 inches long ls carefully removed by un-
~0 ~lndlng the package (not over its end) while preventlngdevelopment Or twist and without stretching the yarn. The
sample is then doubled without allow~ng any twisting, and
teped at the Joined ends to form a loop. The loop is
pulled very gently until there are no twist kinks in any
~llament. Wlth the loop suspended at one end, twist of
one leg around the other is permitted in ~mal; in~re~ents
worklng from the bottom to the supported end. The twlsted
~ample i9 then mounted in a twist counter provldlng a 10-
lnch sample length under a tenslon Or 6 grams. The number
of rotations at one end required to ellminate sny twisting
o~ the leg~ Or the loop about one another, divided by 10,
18 labeled "TPI ofr-pirn." Another sample is identically
prepared, except that, Just before mountlng it in the twist
counter, lt is steamed to fully develop any latent twl~t.
Steamlng ls for 2 minutes ln saturated steam at atmospherlc
- pressure. The value calculated as above ls labeled "TPI-
~teamed. n
Crimps per inch (CPI). Thls characterizatlon ls
obtained ln elther Or 2 ways, wlth dlfferent results. "CPI-
restrained" is measured as follows:
- 12 _
$04U403
(1) Tape a length of yarn stralght from
lts supply package onto a black felt board while
carefully preventing any twisting;
(2) Separate out 2 fllaments from the yarn
and attach ad~acent ends of each to a piece of
masking tape cut to provide 7 mg./denier tension
when hanging (weight in mg. i8 14 times the denier
per filsment);
(3) Tape the remainlng ends to another piece
of masking tape to leave 6-8 inches between pleces
Or tape and about 0.75-inch bétween filaments;
(4) Mount the pair of filaments for steaming
and play stmospheric steam on them for 60 second~;
(5) Tape the steamed filaments to a glass
sllde while still hanging, then cut off excess
extending beyond the ends of the slide; and
~ (6) Count crimps per lnch by proJecting a
- half-inch section of the slide onto a screen,
counting the crimps, and multiplying the result
by 2.
Thç other measurement, "CPI-unrestrained", is obtained
identically, except that:
(1) Only one filament is handled; and
(2) It is allowed to rotate freely while
belng steamed under 5 mg /denier load.
CrlrnP elon~ation (C.E.). A 630-denler skein of
test yarn is prepared while preventing any twisting. (This
denler i8 twice the number of loops Or yarn in the skein
times the denier of a sin~le yarn). The skeln is hung from
the top pin of a skein-testin~ board, and from lts bottom i8
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104~)403
hung a welghted hook. The skein-testing board 1~ a ver-
tically supported board having (1) the nbove-mentioned
pin, (2) sn attached skein-length scale, and (3) two ver-
tlcal rods parallel to, one-inch from either side Or, and
~11 along the length of the suspended skein. The weighted
bottom hook has flne laterally extending pins, ~ pair ex-
tending to e~ch side and spaced apart just enough that one
goes before and the other behind the respective vertical
rods. This prevents rotation of the skein. Weight is
added to the bottom hook until a total Or 3.15 gm. (5 mg./
denier) is suspended. ~he skein, which h~d been wound
under 0.1-gm./denier tension, ls not relaxed until the 3.15
gm. weight is in place. Atmospheric steam ls directed onto
the skein until no more shortening in len~th occurs. m e
unextended length (Lu) is read from the attached sc~le.
Then ~nother 205.64 gm. ls edded to the hook. Arter 30
8econds, extended lengt`n (Le) is read.
% Crlmp Elongation z C.E. = Le Lu x 100
Hose Power and Recovery. Hose to be submitted to
thls test should be plain-stitch,circular-knit hose Or cus-
tomary degree9 o~ stretch. Results are relatively lnsensi-
tl~e to the number of stitches per course, to the number
1 o~ courses, and t~tlth less leeway) to tensions employed
I during knitting, a~suming the latter are custom~ry ones.
I 25 To sssure obtaining comparable results each time, the
¦ oircular-knltting machine preferably has 400 needles and
knits 1780 total courses. Selected yarn tenslons during
knlttin~ are such that, after sub~ecting the knitted hose
- 14 -
O
~04~4Q3
to boiling water for 30 mlnutes and drying, the Jonea
Stretch is measured at 13.0 + 1.0 inches at the knee (4
lnches below the shadow welt for hose, or 4 lnches below
the Junctlon of panty and leg portions for pantyhose), and
~t 11.0 + 1.0 at the ankle (2 inches above the heel). The
~one~ Tester is a commonly-used test device which has its
own bullt-ln indlcator for Jones Stretch in inches, whlch
i8 manufactured by Jones Machine Company of Burlington,
North Carolina, and which is as described ln U.S. Patent
- 10 No. 2,706,402 to Galther M. Jones, Sr.
Rose po~er and recover~ are measured as follows:
m e bolled-off test hose is laid onto a table and carefully
rlattened and straightened without any stretching The
unstretched inltial léngth (Io) of the completely relaxed
hose i8 measured from the toe to the Junction of the leg
~nd welt portions (if pantyhose, measure to the Junction
Or the leg and panty portions). A bulldog clamp (less
th~n 100 gm. and preferably about 40 gm.) is fastened at
each end of Io, and the hose is supported by the clamp at
2ff the welt end. A 100 gm. weight is added to the toe clamp
~nd, after 30 seconds, a new len~th (Ll) is measured.
Ihl8 last step is repeated until the welght added in 100
gm. lncrements totals 1000 6m. Thusly is generated a list
Or ~dded weights (100 i + w) and corresponding lengths (Ll),
where 1 18 1 to 10 and w is the welght in ~rams of the
bulldog clamp. The (100 i + w) data are plotted aeainst
corresponding Li data. Hose power is read rrom the plot
a8 the weight in grams at length L where
= 0.75.
, . 10 0
_
. _
104~403
Immediately arter the Llo measurement is taken,
and before the above-indicated plottlng and calculating
occur, the added wei~hts are slowly and carefully removed.
After a 30 second walt, the toe cla~p is removed and the
hose is taken out Or the welt clamp. It ls laid on a table,
carefully straiehtened without stretching, and allowed to
relax until no further shortening is observed (about 5 min.).
m e recovered length (L~) corresponding to the origlnal un-
stretched length (Lo) is measured. Recovery ln percent ls
cal~ulated as
Recovery = Llo - LR x 100.
Llo ~ Lo
Yarn-on-yarn coe~ficient Or frictlon ls a
measure Or the ease with whlch filaments slip by each
other. About 700 yards of yarn are wound uniformly along
a 2-1/2 inch portlon Or a cylinder 2 inches in diameter,
uslng a winding tension of about 5 grams. The cyllnder is
~ounted for rotatlon about lts central axis. A 12-inch
length Or the same yarn is laid over the cylinder so that
it rests on the wrapped yarn and ls parallel to the turns
thereof. A 30-eram weight ls attached to one end and the
other end is attached to a straln gauge. The cylinder ls
then rotated at least 180 at a peripheral speed Or O.OQ16
cn./second so that the straln gauge is under tension. The
tenslon ls recorded contlnuously by an automatlc device on
a plot o~ force in 6ram3 Y8. ti~e. m e coefriclent Or
friction (r) is calculated from the rormula
~ ~ 1 ln (F/30)
where F i5 the average o~ at least 25 peak tension values
i~ the values vsry, ln ind~c~tes the natural logarithm,
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.. .
104~)403
and'~is the constant 3.14159. D~ta on samples in whlch
perm~nent elongation occurs durlng testing are not used;
such yarn should be cold-drawn before testlng. All data
~re collected at room temperature (about 23C.).
~ . The textured 6-12 nylon yarns Or thls
lnventlon are partlcularly ~ulted to the knlttlng Or stretch
~abrlcs and especlally well to knltting ladies' sheer stretch
hosiery. The hose power developed (i.e., greater than about
500 gm.) is greater then heretofore provided by nylons and
the hose recovery is at least equivalent. When trans-
parency, clarity, and luster are desired, they are readily
provided at heretofore unobtainable levels by simply omitting
delusterant ~rom the polymer. High inltial modulus, low
degree o~ molsture sensltlvity, and low coefficient of
y~rn-on-yarn frlction combine to provlde a new level of
~2ns~0na~ stabi~ity in nylon stretch ~abrlc.
EXAMPLES
A ?q% by weieht aqueous solution or the salt
Or dodecanedloic acid (DDA) and hexamethylene diamine (HMD)
ls prepared in a mixing tank filled to the deslred level by
simultaneously charging 1.00 lb./min. of solid DDA, 1.26
lb./mln. o~ a 40% by weight aqueous solution of HMD, and
3.54 lb./~in. of water. This solution is maintained at
44 + 2C. and finally ad~usted to pH 7.60 ~ 0.04 by lncre-
mental addltion of whichever ingredlent is requlred. Atthl~ polnt, any deslred antloxidants and/or sntifoam agents
~re added, as ls also a small a~ount of acetlc acld for
~olecular weiGht control. The lnitlal salt solutlon ls
then evaporated to about 75% by wei~ht salt ln an evaporator
heated wlth steam at 300 psl~. (21.1 kg./cm.2 gauge). Vapor
104V403
temperature at thls point is 141C. Polymerizatlon-is
then carried out in an autoclave in four stages. In the
~irst stage, pressure increases from 150 to 250 pounds
per square lnch absolute (psla.) (10.5 to 17.6 kg.~cm.2)
~hlle temperature increases to 160C. Constant pressure
of 265 psla. (17.6 kg./cm.2) ls maintained ln the second
8tage until temperature reaches 227.9C. ~'ressure ls
reduced to 14.8 psia. (1.04 kg./cm. ) in the third stage
whlle temperature rises to 237C. In the fourth sta~e,
poly~lerlzation is completed by msintainlng the 14.8 psia.
(1.04 kg./cm. ) pressure until temperature reaches 254C.
Delustrant, lf deslred, is added bet~een the first and
second stages. Finally, the molten 6-12 nylon ls extruded
under pressure of inert gas, quenched with water, and cut
lnto flake for subsequent use. The polymer flake has a
relative vlscoslty (RV) of 27.
m e ysrn for Examples 1, 2 and 3 is melt-spun
rrom the above polymer flake at a spinning speed of 517
yards per minute. Melt-spinnin~ co~ditions are used which
are consldered opti~.um for ~.elt-spinning conventional 6-6
nylon, exceFt that the temperature of the melt just prlor
to extrusion i~ 260C. m e as-~pun yarn has a denler of
~bout 72 to y~eld 18 denier y~rn when dr~wn, and consists
Or three fllaments, each about 24 denier per filament.
m e yarn for comparison ln Examples A, B and C
melt-spun from conventionnl 6-6 nylon flake of 37
relatlve vlscosity. The melt-spinning conditlons are
ldentic~l to those used for Examples 1-3, except that the
temperature Or the melt ~ust prlor to extruslon is 293C.
.
18 -
1~4~403
The as-3pun yarn also ha~ n denier of about 72 to yield 18
denier yarn ~hen drawn, and consists of three filaments.
Each yarn 13 draw-textured using each Or the 3
processes descrlbed in connection wlth FIGURES 1 and 2.
In all, the orientatlon of fal~e-twister 36 is character-
lzed by the fo~lo~lng angle~:
~ ~ 21, B z 85, and r = 56.
Table I llsts remainlng process conditions for drawlng and
~alae-twlstlng. Examples 1 to 3 are textured 6-12 nylon
yarns Or thls inventlon. Examples A to C are com~arison
textured 6-6 nylon yarns. Each Or the pairs, 1 and A, 2
and B, and ~ and C, 18 ldentically textured, with one ex-
~eptlon. As shown on Table I by "Yarn Temperature at
Heater Exlt-(C.)", lt ls necessary to lower the temper-
ature ~or the 6-12 yarn~ because of thelr lower meltlng
polnt.
. .
.
- 19 -
~ 1040403
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Tables II and III present the variatlons of lnitial
modulus with relative humldity, modulus being determined by
the Rkein method described hereinabove. Results in Table II
are obtained on textured yarns before they are steamed. It
18 apparent that, although the 6-12 nylon yarns have lower
moduli than correspondlngly processed 6-6 nylon yarns when
desRicated (dry), they have greater moduli at all relative
~ humidities ordinarlly encountered. Results in Table III
-~ are obtalned on textured yarns after they are ~teamed.
; 10 Greater shrinkage of the 6-12 nylon yarns on steaming re-
duces the dry moduli more. In no case, however, is the
modulus of a 6-12 nylon yarn more than 20% less then the
dry modulus (percentages of dry modulus are shown in par-
entheses). At 55% RH, the modulus is at least equlvalent
to the dry modulus. Steaming or boiling in water slmulates
processlng treatments usually given to knlt fabrics.
..-
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- 21 -
1040403
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- 23 -
. ~04~403
The 6 textured yarns o~ the examples are separately
knltted into legs of women's shee~ stretch hoslery. Slngle-
reed, plain-stltch circular knittlng 18 used. ~ose power
snd percent recovery are measured as described hereinabove.
Results are ln Tsble TV.
TABLE IV
WER AND ~ECOVERY OF InNIT ~OSE~
ExsmPle Jones Stretch (in.) P~wer (gm.) Recovery (%)
Knee Ankle
1 12.8 10.8 547 79
2 12.8 10.7 554 79
13.4 10.5 588 76
A 13.4 11.5 373 79
~ 13.5 11.7 400 77
C~* 12.8 10.1 500 76
* ~laln-stltch circular-knit on 400-needle machine.
~* All had 1780 total courses except that Examp~e C
had 2~04 courses.
It 18 apparent that the 6-12 nYlon hose (Examples 1 to 3)
have hlgher power in excess Or 500 gm. and that they have
at least equlvalent recovery ln spite of thelr higher crl~p
levels (see Table I).
. Table V presents coefficients of frictlon messured
- ror all 6 examples. Surprisingly, the yarn-on-yarn co-
e~lclent o~ rrictlon for the yarn of this lnventlon is
slways less than for correspondingly textured 6-6 nylon
ysrn, and ls always le~ than 0.5. Moreover, it behaves dif-
erently ln that, whlle slldine on ltself at 0.0016 cm./sec.,
;~`
_ 24 -
. ...~_
1~46)403
lts frictlonal force, F, i8 invariant rather than the
repetltlve stlck-sllp phenomenon characteristic Or all
common yarns.
TABLE V
YARN-ON-YA~N CoEFFICIE~TS OF FRICTION AT 0.0016 CM./SEC.
Example 1 A 2 B ~ C
Coefrlcient 0.48 o.65 o.46 o.64 0.25 o.38
The yarns of the examples are also submitted to
~lat-rllm X-ray difrraction. Mlcrodensltometer traces along
the equator, the meridian, and a speciric azlmuth are used
to compute both XPI ("crystal perfection lndex" expressed
~8 a percentage) and ~/B ratios of ~mounts o~ crystal forms
(thc even-even allphatlc polyamides like 6-6 and 6-12 have
trlcllnlc crystallite cells wlth elther a or B crystalline
~orm~). P. F. Dlsmore and W, O. Statton, J. Poly. Scl.,
Part C. No. 13 (1966~, page 134, describe~ the mcasurement
~nd calculation Or XP}. The /B ratio of crystalline forms
1- obtalned from mlcrodensltometer traces or the same film
u8ed to determlne XPI. Triclinic difrraction patterns are
characterlzed by orf-equator layer lines. The percentage
o~ B form is taken as proportlonal to the maxl~um lntensity
at the second layer llne along the merldian. Difrraction
~pot8 at each end Or each layer line are contributed by
the ~ rOrm. The azlmuthal maxlmum intensity through one
o~ the spots on the Eecond layer llne 18 taken as pro-
portlonal to the percentage Or ~ form. Baseline and back-
ground correctlons customary for X-ray diffraction measure-
~ents are, Or course, made. The ~/B ratio is, then, the
dlrect ratio Or two measured scatterine intensitles.
.
lQ4~)403
Table VI æummarlzes the X-ray results. XPI and
~/B ratio are given, where applicable, for each yarn as
drawn before heat-settin~ and twlstin~ and as textured after
heat-setting and twistin~. ~lso listed are ~ ) and ~ XPI,
l.e;, the chflngeæ between the two states. Given the experi-
mentally determined ratio R of a and B forms, and remembering
th~t ~ ~ t mu~t be 100%, then % a (percentage of crystallltes
Sn the ~ form) can be computed from
(% a ) = 100 R
l~R.
~0 TABLE VI
X-Ra~ Characteri~ations
Drswn
Luntextured) Textured
Ex mple ~/B XPI a/B XPI (~ XPI
~ ~ (6-12) o 48.8 1.20 ô6.9 56.1 38.1
~5 2 (6-12) _ _ 1.12 79.2
3 (6-12) o 48.8- 1.16 8~.5 53-7 ~4-7
A (6-6) 1.17 47.8 ~.04 96.2 21.~ 48.4
B (6-6) - - 1.82 82.4
` C (6-6) 1.17 47.8 2.75 91.2 19.4 43.4
~ - me yarn was also tested for t~lst-llveliness by
messurlng the values for "TPI off-pirn" and "TPI stesmed."
These results are æhown in Table VII slong with the ratios
Or CPI (restrslned) to TPT (æee Table I ~or CPI).
~'`; ' .
~ ..
- 26 -
O
~ 4V403
TABLE VII
TPI Results
Example 1 2 3 A ~ C
Off-plrn TPI 30.2 12.3 28.6 ~5.6 20.8 40.2
Steamed TPI 64.4 45.4 62.1 69.9 50.7 7~.6
CPI(R)/TPI off-plrn1.62 4.55 2.16 0.77 1.59 1.04
CPI(R)/TPI steamed0.76 1.23 1.00 0.39 0.65 0.57
me 6-12 nylon yarns of Examples 1 to 3 are to be
compared with 6-6 nylon yarns Or Examples A to C. Whlle
the TPI results ror the yarns of this invention are less
than rOr 6-6 nylon yarns, the really slgniflcant comparlson
; ~e ln the CPI/TPI ratios. For improved buh`~ and stretch,
the numbers of crlmps per inch (CPI) are preferably as
large as posslble. False-twist crimping ls always accom-
panle~ wlth yarn-torque (here measured as ~PI~. Torque
o~ the pirn causes difficulties in knitting, and the higher
torque ln steamed yarns causes stltch dlstortions in knltted
rsbrlcs. Thus, where CPI i8 preferably maxlmlzed, TPI
~` should be minimized. The CPI/TPI ratio off-pirn for the
6-12 nylon yarns Or Examples 1 to 3 is seen to be at least
1.6~ ~nd is more than twice the ratlo for the slmilarly
proces-ed 6-6 nylon yarns. Slmilarly, the ratlo after
~teamlng 18 at least 0.75 for the yarns of Examples 1 to
~ and 1~ about twlce that of slmllarly processed 6-6
nylon yarns. It i~ not under3tood why the false-twist
textured 6-12 n~rlon yarn of this inventlon should have such
remarkably lmproved ratlcs of crln~p to twist-ll~eline-~s.
- 27 -
