Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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NYLON YARN FOR ~UUSHED FABRICS
SPECIFICATION
The invention relates to the art of making
napped fabrics, and more particularly to the making of
polyamide yarns suitable f'or use in napped fabrics.
~ rushed or napped fabrics have long been known,
particul~rly in fabrics made f'rom staple yarns. Such
fabrics are typically rnade by abrading the fabric
surface by contact with wire cardine cloth (see textbook
"Textile Finishing" by Hall, published 196~, American
Elsevier, pages 105-10~). When a very short pile or nap
is to be raised, the cloth surf'ace may be subjected to
abrasion by contact with emery or other similar material
(page 107 of the Hall text). Fabrics made of continuous
filament nylon have not been used extensively for many
types of brushed fabrics, since conventional nylon yarns
give poor results in the napping operation when using
conventional brushing equipment.
It has been discovered that the napping
operation can be successful with fabrics containing
continuous filament nylon yarns if the properties of the
nylon yarns are properly selected as disclosed below.
Broadly, the yarns of the invention are characterized by
having elongations less than 52% and tenacities less
25 than the lesser of 5 grams per denier and [7 - (0.06 X
elongation %)] grams per denier.
According to a f'irst principal aspect of the
invention there i6 provided a process for making a
polyamide yarn for use in brushed fabrics, comprising
metering a plurali-ty of molten streams of polyamide
polymer through ~pinneret orifices into a quench zone,
quenching the streams into filaments in the quenoh zone,
merging the filarnents into a yarn, contacting the yarn
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with a snubbing device, withdrawing the yarn from the
snubbing device at a speed of at least 2500 MPM, and
winding the yarn on a bobbin. The metering rate, the
forwarding speed, the elevated tension, the winding
tension, and the construction and arrangement of the
snubbing device, are selected and correlated such that
the yarn ~ound on the bobbin forms a stable package and
has an elongation less than 52~ and a -tenacity less than
the lesser of 5 Krams per denier and [7 - (0.06 X
elongation ~0)] erams per denier.
According to other specific aspects in
practicing the process, the polymer is preferably nylon
66. The snubbing device is preferably constructed and
arranged such that the yarn wound on the bobbin has a
tenacity less than the lesser of 5 grams per denier and
[6.8 - (0.06 times elongation ~)] grams per denier. The
filaments preferably have breaking strengths less than
12 grams. The polymer metering rate advantageously
selected such that the filaments have deniers greater
than 1.4. The snubbing device is preferably located
more than 2 meters below the spinneret. The winding
tension is preferably between 0.05 and about 0.35 grams
per denier.
According to a second principal aspect of the
invention, there is provided a polyamide flat yarn wound
on a bobbin, the yarn being suitable for forming into
brushed fabrics. The yarn haa filaments having
individual deniers le~s than 10, an elongation le~s than
52%; a Kanebo maximum shrinkage force at a temperature
less than 150 degrees C., a SAXS discrete scattering
halfwidth of at least 3.6 degrees, and a tenacity less
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than the lesser of 5 grams per denier and [6.8 - (0.06 X
elongation ~0)] grams per denier. The preferred tenacity
range is between 1.5 and 4 grams per denier, and the
filaments preferably have deniers greater than 1.4.
According to other preferred aspect~ in
accordance with the second principal aspect, the yarn is
nylon 66, preferably with no twist. The yarn preferably
has an elongation less than 50%. A yarn tenaci-ty less
than H4 grams per denier and an elongation less than 50
are particularly desirable, and advantageously the
filaments have deniers between 2 and 4.5. The yarn
preferably has a density less than 1.14.
Other aspects of the invention will appear in
the following detailed description.
Example 1
This is an example of attempts to brush f~brics
made of conventional nylon apparel yarns. A
conventional apparel 34 filament nylon 66 yarn is spun
at 1400 MPM, steamed in a conventional interfloor tube,
and wound, the spun denier being selected such that the
drawn yarn will have 70 denier. The spun yarn is cold
drawn to an elongation of 40~c, yielding a drawn yarn
having a tenacity of 5.6 grams per denier. A warp knit
fabric is formed from the yarn. Attempts to brush the
fabric using a Gessner knit goods napping apparatus are
unsuccessful due to rapid dulling of the wires on the
napping apparatus and failure of the filaments to
cleanly break.
The spinning and drawing operations are
modified to provide a 70 denier drawn yarn having an
elongation of 60/S, resulting in a tenacity of ~.2 grams
per denier, and a 70 denier drawn yarn having an
elongation of ~0~0, resulting in a -tenaci-ty of 6.5 grams
per denier. Similar unsuccessful resul-ts are obtained
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when it is attempted to brush warp knit fabrics formed
from either of the drawn yarns of this paragraph.
Example 2
This is an example according to the invention.
A 34 filament yarn is spun f'rom ~0 RV nylon 66 at a melt
temperature of 285 degrees C., the molten streams being
conventionally quenched and converged into a yarn 52
inches (132 C~i) below the face of' the spinneret. The
yarn next passes downwardly through an unheated
interfloor tube to a metered finish applicator located
3.3 meters below the spinneret face, then in a partial
wrap about each of two ceramic snubbing pins prior to
being forwarded by contact with a feed roll running a-t a
surface speed of 3800 MPM. Each of the pins has a
surface roughness of 80 RMS, and the pins are adjustably
mounted such that the wrap anEle or degree of wrap of
the yarn on each pin may be selected. The snubbing pins
constitute an adjustable snubbing device for controlling
the yarn tension. After passing in a partial wrap about
the f'eed roll, the yarn passes in a partial wrap about a
delivery roll running at a surface speed of 3710 MPM,
then is wound at a winding tension of about 7 grams.
The snubbing pins are adjusted and arranBed such that
the yarn tension between the snubbing pins and the feed
roll (the "snubbing tension") is 55 grams.
The resulting 70 denier yarn has an elongation
of 44~ and a tenacity of 3.9 grams per denier. When
examined by X-ray, the yarn has a SAXS scattering
half-width of 4.79 degrees. The yarn has a ~anebo
maximum shrinkage force at a temperature of about 100
degrees C. and a densi-ty less than 1.14. A warp knit
f'abric formed from the yarn is brushed with excellent
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processability, and the resulting napped fabric is of
excellent quali-ty.
If the snubbing pins are adjusted to provide a
snubbing tension below about 0.57 grams/denier, the yarn
would elongate on the packaee, thus preventing formation
of a stable package. Conversely, a snubbing tension
ereater than about 0.~6 grams/denier causes the yarn to
crush the bobbin, again preventing forrnation of a stable
package.
Test Methods and Defirlitions
For the tests in this paragraph, -the yarn
packages to be tested are conditioned at 21 degrees C.
and 65% relative humidity for one day prior to testing.
Fifty yards of yarn are stripped from the bobbin and
discarded. Elongation-to-break is determined using an
Instron tensile testing instrument. The gage length
(initial length of yarn sample between clamps on the
instrument) is 25 CM, and the crosshead speed is 30 CM
per minute. The yarn is extended until it breaks.
Elongation-to-break is defined as the increase in sample
length at the time of maximum load or force (stress)
applied, expressed as a percentage of the original length
(25 CM). Tenacity is the maximum load in grams divided
by the yarn denier.
Relative viscosity (R.V.) is determined by ASTM
D789-~1, using 90~ formic acid.
Kanebo maximum shrinkage force is measured using
a Type KE-2 Thermal Stress Tester manufactured by Kanebo
Engineering, Ltd. A 10 CM loop of yarn is pretensioned
at 5 milligrams/denier and heated from room temperature
to 300 degrees C. at a constant heating rate of 1.67
degrees C. per second. The shrinkage force response is
measured with a stress transducer and plot-ted with a dual
channel X-Y recorder.
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X-Ray Techniques
The X-ray diffraction pat-terns (small angle
X-ray scattering, or SAXS) are recorded on NS54T Kodak
no-screen medical X-ray film using evacuated fi~lat plate
Laue cameras (Statton type). Specimen to film distance
is 32.0 C~; incident beam collimator length is 3.0 inches
(7.62 C~) and exposure time i5 16 hours. Interchangeable
S-tatton type yarn holdsrs with 0.5 i~ diaMeter pinholes
and 0.5 l~M yarn sheath thickness are used throughout as
well as 0.5 MM entrance pinholes. The filamentE of each
sheath of yarn are aligned parallel to one another and
perpendicular to the X-ray bearn. A copper fine focus
X-ray tube (~ = 1.5~18 Angstrom units) is used with
nickel filter at 40 KV and 26.26 I~A ~ 85~o of their rated
load. For each X-ray exposure a single film is used in
the film cassette. This film is evaluated on a scanning
P-1000 Obtronics Densitometer for information concerning
scattering intensity and discrete scattering distribution
characteristics in the equatorial and meridional
directions. A curve fitting procedure, using Pearson VII
functions [see H. M. Heuvel and R. Huisman,
J.Appl.Poly.Sci., 22, 2229-2243 (1978)] together with a
second order polynomial background function, is used to
fit the experimental data prior to calculation. A
meridional scan is performed, the discrete scattering
fitted, equatorial scans are performed through each
discrete scattering maxima and then again the data is
fitted via a parameter fit procedure.
The SAXS discrete scattering equatorial
half-wid-ths (degrees) are used to de-termine the average
lamellar dimensions. In the equatorial direction this is
taken here to be proportional to the average size of the
lamellae scattered in a direction perpendicular to the
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fiber direction. These sizes are measured from the
reciprocal breadth of the SAXS diffraction maxima
(degrees 1), taken in the equatorial direction at a point
in which the SAXS intensity has fallen to one-half its
peak intensity value.
