Field of the Invention
[0001] The instant invention is directed to an as-spun polyester yarn having small crystals
and a high orientation.
Background of the Invention
[0002] Since fiber-forming, melt-spinnable, synthetic polymers were introduced, fiber manufacturers
have looked for ways to increase the strength and stability properties of the fibers
made from those polymers. The additional strength and stability properties of the
fibers are needed so that applications beyond textile uses could be opened for their
products. Such non-textile uses (also known as "industrial uses") include: tire cord;
sewing thread; sail cloth; cloth, webs or mats used for road bed construction or other
geo-textile applications; industrial belts; composite materials; architectural fabrics;
reinforcement in hoses; laminated fabrics; ropes; and the like.
[0003] Originally, rayon was used in some of these industrial uses. Thereafter, nylon supplanted
rayon as the material of choice. In the 1970's, conventional polyesters, such as polyethylene
terephthalate, were introduced into competition against nylon. In about 1985, higher
performance polyesters, i.e. higher strength and greater stability, were introduced.
[0004] A brief review of some of the patent prior art, summarized below, indicates that
three general areas have been investigated as possible ways of enhancing the strength
and stability properties of these synthetic fibers. Those general areas include: processes
directed to drawing; processes directed to the polymer; and processes directed to
the spinning. Hereinafter, the term "drawing" shall refer to the heating and stretching
performed on an as-spun yarn. The term "treatment to the polymer" shall refer to those
things done to the polymer prior to spinning. The term "spinning" shall refer to processes
for forming filaments from polymer, but excluding drawing.
[0005] The processes directed to drawing are as follows:
[0006] In U. S. Patent No. 3,090,997, multistage drawing of polyamides, for use as tire
cords, is disclosed. The fibers (nylon) are melt-spun in a conventional fashion. Thereafter,
spun fibers are drawn in a three-stage process (drawn, then heated, then drawn again)
to obtain a drawn nylon having the following properties: tenacity ranging from 10.4
to 11.1 grams per denier (gpd); elongation ranging from 12.9 to 17.1%; and initial
modulus of 48 to 71 gpd/100%.
[0007] In U. S. Patent No. 3,303,169, there is disclosed a single-stage drawing process
for polyamides that yields high modulus, high tenacity, and low shrinkage polyamide
yarns. The spun polyamide is drawn and heated to at least 115°C to obtain a yarn having:
tenacity in the range of 5 to 8.7 gpd; elongation ranging from 16.2 to 30.3%; initial
modulus of 28 to 59gpd/100%; and shrinkage ranging from 3.5 to 15%.
[0008] In U. S. Patent No. 3,966,867, a two-stage drawing process for polyethylene terephthalate
having a relative viscosity of 1.5 to 1.7 is disclosed. In the first stage, the fibers
are subjected to a temperature between 70 and 100°C and a draw ratio of 3.8 to 4.2.
In the second stage, the fibers are subjected to a temperature between 210 and 250°C
and a draw ratio, in the aggregate of the first draw ratio and second draw ratio,
in the range of 5.6 to 6.1. The drawn yarn obtained has the following properties:
tenacity, 7.5 and 9.5 gpd; elongation, approximately 2 to 5% at a load of 5 gpd; elongation
at break, 9 to 15%; and shrinkage, 1 to 4%.
[0009] In U. S. Patent No. 4,003,974, polyethylene terephthalate spun yarn, having an HRV
of 24 to 28, is heated to 75 to 250°C while being drawn, is then passed over a heated
draw roll, and finally relaxed. The drawn yarn has the following properties: tenacity,
7.5 to 9 gpd; shrinkage, about 4%; elongation at break, 12 to 20%; and load bearing
capacity of 3 to 5 gpd at 7% elongation.
[0010] Those processes directed to enhancing yarn properties by treatment to the polymer
are as follows:
[0011] In U. S. Patent Nos. 4,690,866 and 4,867,963, the intrinsic viscosity (I.V.) of the
polyethylene terephthalate is greater than 0.90. In U. S. Patent No. 4,690,868, the
as-spun (undrawn) fiber properties are as follows: elongation at break, 52 to 193%;
birefriengence, 0.0626 to 0.136; and degree of crystallinity, 19.3 to 36.8%. The drawn
fiber properties are as follows: tenacity, 5.9 to 8.3 gpd; elongation, 10.1 to 24.4%;
and dry shrinkage (at 210°C), 0.5 to 10.3%. In U. S. Patent No. 4,867,936, the drawn
fiber properties are follows: tenacity, about 8.5 gpd; elongation at break, about
9.9%; and shrinkage (at 177°C), about 5.7%.
[0012] Those processes directed to spinning are as follows:
[0013] In U. S Patent No. 3,053,611, polyethylene terephthalate after leaving the spinneret
is heated to 220°C in a spinning shaft two meters long. Thereafter, cold water is
sprayed onto the fibers in a second shaft. The fibers are taken up at a speed of 1,600
meters per minute (mpm) and are subsequently drawn to obtain a tenacity of 3.5 gpd.
[0014] In U. S. Patent No. 3,291,880, a polyamide is spun from a spinneret and then cooled
to about 15°C, then the fiber is sprayed with live steam. The as-spun fiber has a
low orientation and a low birefriengence.
[0015] In U. S. Patent No. 3,361,859, a synthetic organic polymer is spun into a fiber.
As the fibers exit the spinneret, they are subjected to "controlled retarded cooling".
This cooling is conducted over the first seven inches from the spinneret. At the top
(i.e. adjacent the spinneret), the temperature is 300°C and at the bottom (i.e. approximately
7 inches from the spinneret), the minimum temperature is 132°C. The as-spun yarn has
a low birefriengence (11 to 35 x 10⁻³) and drawn yarn properties are as follows: tenacity,
6.9 to 9.4 gpd; initial modulus, 107 to 140 gpd/100%; and elongation at break, 7.7
to 9.9%.
[0016] In U. S. Patent Nos. 3,936,253 and 3,969,462, there is disclosed the use of a heated
shroud (ranging in length from one-half foot to two feet) with temperatures ranging
from about 115 to 460°C. In the former, the temperature is greater at the top of the
shroud than at the bottom. The drawn yarn properties of the former are as follows:
tenacity, 9.25 gpd; elongation, about 13.5%; and shrinkage, about 9.5%. In the latter,
the temperature is constant within the shroud and the drawn yarn properties are as
follows: tenacity, 8 to 11 gpd; and elongation at break, 12.5 to 13.2%.
[0017] In U. S. Patent No. 3,946,100, fibers are spun from a spinneret and solidified at
a temperature below 80°C. The solidified fibers are then reheated to a temperature
between the polymer's glass transition temperature (Tg) and its melting temperature.
This heated fiber is withdrawn from the heating zone at a rate of between 1,000 to
6,000 meters per minute. Spun yarn properties are as follows: tenacity, 3.7 to 4.0
gpd; initial modulus, 70 to 76 gpd/100%; and birefriengence, 0.1188 to 0.1240.
[0018] In U.S. Patent No. 4,491,657, polyester multifilament yarn is melt-spun at high speed
and solidified. Solidification occurs in a zone comprising, in series, a heating zone
and a cooling zone. The heating zone is a barrel shaped heater (temperature ranging
from the polymer's melting temperature to 400°C) ranging in length from 0.2 to 1.0
meters. The cooling zone is cooled by air at 10° to 40°C. Drawn yarn made by this
process has the following properties: initial modulus, 90 - 130 gpd; and shrinkage
(at 150°C) less than 8.7%.
[0019] In U. S. Patent No. 4,702,871, fiber is spun into a chamber having a subatmospheric
pressure. Spun yarn properties are as follows: strength, 3.7 to 4.4 gpd; birefriengence,
104.4 to 125.8 (x 10⁻³); and dry heat contraction, 4.2 to 5.9% at 160°C for 15 minutes.
[0020] In U. S. Patent No. 4,869,958, the fiber is spun in the absence of heat and then
taken up. At this point, the fiber has a low degree of crystallinity, but it is highly
oriented. Thereafter, the fiber is heat treated. The drawn fiber properties are as
follows: tenacity, 4.9 to 5.2 gpd; initial modulus, 92.5 to 96.6 gpd/100%; and elongation,
28.5 to 32.5%.
[0021] The foregoing review of patents indicates that while some of the fibers produced
by these various processes have high strength or low shrinkage properties, none of
the foregoing patents teach of a yarn or a process for producing such a drawn yarn
having the combination of high tenacity, high initial modulus, and low shrinkage.
[0022] The patents which come closest to teaching such a drawn yarn are U. S. Patent Nos.
4,101,525 and 4,195,052, related patents that are assigned to the assignee of the
instant invention. In these patents, the polyester filaments (the polymer having an
intrinsic viscosity of 0.5 to 2.0 deciliters per gram) are melt spun from a spinneret.
Molten filaments are passed through a solidification zone where they are uniformly
quenched and transformed into solid fibers. The solid fibers are drawn from the solidification
zone under a substantial stress (0.015 to 0.15 gpd). These as-spun solid fibers exhibit
a relatively high birefriengence (about 9 to 70 x 10⁻³). The as-spun fibers are then
drawn and subsequently heat treated. The drawn filament properties are as follows:
tenacity, 7.5 to 10 gpd; initial modulus, 110 to 150 gpd/100%; and shrinkage, less
than 8.5% in air at 175°C.
Summary of the Invention
[0023] The instant invention is directed to as-spun polyester yarn having small crystals
and a high orientation. The as spun polyester yarn is characterized by a crystal size
less than 55A and either an optical birefringence greater than 0.090 or an amorphous
birefringence greater than 0.060 or a long period spacing less than 300A.
Description of the Drawing
[0024] For the purpose of illustrating the invention, there is shown in the drawing a schematic
of the process which is presently preferred; it being understood, however, that this
invention is not limited to the precise arrangement and instrumentalities shown.
[0025] Figure 1 is a schematic elevational view of the spinning process.
[0026] Figure 2 is a schematic elevational view of the drawing process.
Detailed Description of the Invention
[0027] High tenacity, high initial modulus, and low shrinkage drawn yarns, the as-spun yarn
from which such drawn yarn is made, and the process by which such yarns are spun are
discussed hereinafter. The term "yarn" or "filament" or "fiber" shall refer to any
fiber made from a melt spinnable synthetic organic polymer. Such polymers may include,
but are not limited to, polyesters and polyamides. The invention, however, has particular
relevance to polyesters such as, for example, polyethylene terephthalate (PET), blends
of PET and polybutylene terephthalate (PBT), and PET cross-linked with multifunctional
monomers (e.g. pentaerithritol). Any of the foregoing polymers may include conventional
additives. The yarn I.V. (for PET based polymer) may be between 0.60 and 0.87. The
instant invention, however, is not dependent upon the intrinsic viscosity (I.V.) of
the polymer.
[0028] Referring to Figure 1, a spinning apparatus 10 is illustrated. A conventional extruder
12 for melting polymer chip is in fluid communication with a conventional spinning
beam 14. Within spinning beam 14, there is a conventional spinning pack 16. Pack 16
may be of an annular design and it filters the polymer by passing the polymer through
a bed of finely divided particles, as is well known in the art. Included as part of
the pack 16 is a conventional spinneret (not shown). Flow rates of polymers through
the pack may range from about 10 to 55 pounds per hour. The upper limit of 55 pounds
is defined only by the physical dimensions of the pack 16 and greater flow rates may
be obtained by the use of larger packs. The spun denier per filament (dpf) ranges
from 3 to 20; it being found that the optimum properties and mechanical qualities
for the yarn appear between 5 and 13 dpf.
[0029] Optionally, the fiber, as it leaves the spinneret, may be quenched with a hot inert
gas (e.g. air). See U. S. Patent No. 4,378,325 which is incorporated herein by reference.
Typically, the gas is about 230°C and is provided at about six standard cubic feet
per minute (scfm). If the air is too hot, i.e. over 260°C, the spun yarn properties
are significantly deteriorated.
[0030] Immediately below and snugly (i.e. airtight) mounted to spinning beam 14 is an elongated
column 18. The column comprises an insulated tube having a length of about 5 meters
or greater. Column length will be discussed in greater detail below. The tube's internal
diameter is sufficiently large (e.g. twelve inches) so that all filaments from the
spinneret may pass the length of the tube without obstruction. The column is equipped
with a plurality of conventional band heaters so that the temperature within the tube
can be controlled along its length. Column temperatures will be discussed in greater
detail below. The column is, preferably, subdivided into a number of discrete temperature
zones for the purpose of better temperature control. A total of 4 to 7 zones have
been used. Optionally, the column 18 may include an air sparger 17 that is used to
control temperature in the column. Sparger 17 is designed to evenly distribute an
inert gas around the circumference of the column.
[0031] Inside the bottom-most end of the column 18 is a perforated, truncated cone 19, i.e.
a means for reducing air turbulence. The cone 19, which is preferably three feet in
length and having a diameter co-extensive with the tube diameter at its uppermost
end and a diameter of about one half that at the bottom end, is used to exhaust air,
via a valved exhaust port 21, from the bottom-most end of the tube so that movement
in the thread line, due to air turbulence, is substantially reduced or eliminated
completely.
[0032] Below the bottom-most end of the column, the thread line is converged. This convergence
may be accomplished by a finish applicator 20. This is the first contact the yarn
encounters after leaving the spinneret.
[0033] The length of the column, non-convergence of the individual filaments, and the air
temperature profile within the column are of particular importance to the instant
invention. With regard to the temperature profile, it is chosen so that the fibers
are maintained at a temperature above their Tg over a significant length of the column
(e.g. at least 3 meters). This temperature could be maintained over the entire length
of the column, but the wound filaments would be unstable. Therefore, for practical
reasons, the temperature within the column is reduced to below the Tg, so that the
filaments will undergo no further changes in crystal structure before being wound
up. Preferably, the temperature profile is chosen to reflect the temperature profile
that would be established within the tube if no external heat was applied. However,
the "no external heat" situation is impractical because of numerous variables that
influence the column temperature. So, the temperature profile is controlled, preferably
in a linear fashion, to eliminate temperature as a variable in the process.
[0034] The air temperature within the column is controlled by the use of the band heaters.
Preferably, the column is divided into a plurality of sections and the air temperature
in each section is controlled to a predetermined value. Thus, the temperature within
the column can be varied over the length of the column. The temperature within the
column may range from as high as the polymer spinning temperature to at or below the
glass transition (Tg) temperature of the polymer (Tg for polyester is about 80°C).
The polymer spinning temperature occurs around the spinneret, i.e. as the molten polymer
exits the spinneret. However, air temperatures within the column are preferably controlled
from about 155°C to about 50°C. At wind-up speeds less than 14,000 feet per minute,
the first section adjacent the spinneret is preferably controlled to a temperature
of about 155°C and the section furthest from the spinneret is controlled to about
50°C.
[0035] However, a linear temperature profile is not the only temperature pattern that will
yield the beneficial results disclosed herein. At take-up (or wind-up) speeds greater
than 14,000 fpm (4,300 mpm), the temperature profile (when the column is divided into
four discrete zones) may be as follows: (starting from the spinneret down) the first
zone - about 105°C to about 110°C; the second zone - about 110°C to about 115°C; the
third zone - about 125° to about 130°C; and the fourth zone - 115°C to about 120°C.
[0036] With regard to column length, a minimum column length of five meters (with column
temperature over the polymer's Tg for at least 3 meters) with filament convergence
thereafter appears to be necessary for the instant invention. Column lengths between
five and nine meters are suitable for the invention. The upper limit of nine meters
is a practical limit and may be increased, room permitting. To optimize the tenacity
properties, a column length of about seven meters is preferred.
[0037] The fibers are converged after exiting the column 18. This convergence may be accomplished
by use of a finish applicator.
[0038] Following the first application of the finish (i.e. at finish applicator 20), the
yarn is taken around a pair of godet rolls 22. Thereafter, a second application of
finish may be made (i.e. at finish applicator 23). The first finish application may
be made to reduce static electricity built up on the fibers. But this finish is sometimes
thrown off as the fibers pass over the godet rolls. Thus, the finish may be reapplied
after the godet rolls.
[0039] The fibers are then passed onto a conventional tension control winder 24. The wind-up
speed is typically greater than 3,000 mpm (9,800 fpm) with a maximum speed of 5,800
mpm (19,000 fpm). An optimum range exists of about 10,500 to 13,500 fpm (about 3,200-4,100
mpm). The most preferred range exists between about 3200 and 3800 mpm (10,500 and
12,500 fpm). At speeds below 9,800 fpm (3,000 mpm), the yarn uniformity properties
deteriorate.
[0040] The as spun polyester yarn produced by the foregoing process may be generally characterized
as having relatively small crystals and a relatively high orientation. It is believed
that these qualities of the as spun yarn enable the attainment of the unique drawn
yarn properties discussed below.
[0041] To quantify the general characterization of the as spun polyester yarn, the small
crystals are defined in terms of crystal size (measured in Å) and orientation is defined
in one of the following terms: optical birefringence; amorphous birefringence; or
crystal birefringence. Additionally, the spun polyester yarn is characterized in term
of crystal size and long period spacing (the distance between crystals). In broad
terms, the as spun polyester yarn may be characterized as having a crystal size less
than 55Å and either an optical birefringence greater than 0.090 or an amorphous birefringence
greater than 0.060 or a long period spacing of less than 300Å. More preferred, the
as spun polyester yarn may be characterized as having a crystal size ranging from
about 20 to about 55Å and either an optical birefringence ranging from about 0.090
to about 0.140 or an amorphous birefringence ranging from about 0.060 to about 0.100
or a long period spacing ranging from about 100 to about 250Å. Most preferred, the
as spun polyester yarn may be characterized as having a crystal size ranging from
about 43 to about 54Å and either an optical birefringence ranging from about 0.100
to about 0.130 or an amorphous birefringence ranging from about 0.060 to about 0.085
or a long period spacing ranging from about 140 to about 200Å.
[0042] As will be apparent to those of ordinary skill in the art, the crystal size of the
spun yarn is about 1/3 that of conventional yarns in the optimum wind-up speed range.
The crystal size increases with speed, but it still remains low. The spun amorphous
orientation is very high, about twice normal. This spun yarn has such a high orientation
and low shrinkage, that it could be used without any drawing.
[0043] In addition, the spun polyester yarn has the following properties: a crystal content
(i.e. crystallinity level as determined by density) of 10 to 43%; a spun tenacity
of about 1.7 to 5.0 gpd; a spun modulus in the range of 10 to 140 gpd/100%; a hot
air shrinkage of about 5 to 45%; and an elongation of 50-160%.
[0044] Thereafter, the spun yarn is drawn. Refer to Figure 2. Either a one or two stage
drawing operation may be used. However, it has been determined that a second stage
offers little-to-no additional benefit. It is possible that the spinning operation
may be coupled directly to a drawing operation (i.e., spin/draw process).
[0045] The as-spun yarn may be fed from a creel 30 onto a feed roll 34 that may be heated
from ambient temperatures up to about 150°C. Thereafter, the fiber is fed onto a draw
roll 38 which may be heated from ambient temperatures to approximately 255°C. If heated
rolls are not available, a hot plate 36, which may be heated from 180° - 245°, may
be used. The hot plate 36 (having a six inch curved contact surface) is placed in
the draw zone, i.e., between feed roll 34 and draw roll 38. The draw speed ranges
from 75 to 300 meters per minute. The typical draw ratio is about 1.65 (for spun yarn
made at about 3,800 meters per minute). The optimum feed roll temperature, giving
the highest tensile strength, was found to be about 90°C. The optimum draw roll temperature
is about 245°C. If the hot plate is used, the optimum temperature is between about
240° - 245°C. The draw roll temperature gives some control over hot air shrinkage.
In general, low shrinkages are desirable as they give rise to the best treated cord
stability ratings. However, at least one end use, sail cloth, requires higher drawn
yarn shrinkages and these can be controlled with lower draw roll temperatures.
[0046] Based on the foregoing, the drawn fiber properties may be controlled as follows:
Tenacity may range from 4.0 to 10.8 grams per denier. The elongation may range from
7% to approximately 80%. The initial secant modulus may range from 60 to 170 gpd/100%.
The hot air shrinkage (at 177°C) is 6% to 15%. The denier of the fiber bundle may
range from 125 to 1100 (the latter number may be obtained by plying tows together)
and the denier per filament ranges from 1.5 to 6 dpf. Such a yarn could be used as
the fibrous reinforcement of a rubber tire.
[0047] Polyester (i.e., PET) drawn yarns, made according to the process described above,
ran obtain an initial secant modulus greater than 150 grams per denier/100. Moreover,
those yarns may also have a shrinkage of less than 8%, or those yarns may have a tenacity
of greater than 7.5 grams per denier.
[0048] Another preferred embodiment of the drawn polyester yarn may be characterized as
follows: a tenacity of at least 8.5 grams per denier; an initial modulus of at least
150 grams per denier/100%, and a shrinkage of less than 6%. Another preferred embodiment
of the drawn polyester yarn may be characterized as follows: a tenacity of at least
10 grams per denier; an initial modulus of at least 120 grams per denier/100%; and
a shrinkage of less than 6%. Yet another preferred embodiment of the drawn polyester
yarn may be characterized as follows: a tenacity ranging from about 9 to about 9.5
grams per denier; an initial modulus ranging from about 150 to about 158 grams per
denier/100%; and a shrinkage less than 7.5%.
[0049] Any drawn yarn, made according to the above described process, may be utilized in
the following end uses: tire cord, sewing thread; sail cloth; cloth, webs or mats
used in road bed construction or other geo-textile applications; industrial belts;
composite materials; architectural fabrics; reinforcement in hoses; laminated fabrics;
ropes; etc.
[0050] The following critical tests, which are used in the foregoing discussion of the invention
and the subsequent examples, were performed as follows:
[0051] Tenacity refers to the "breaking tenacity" as defined in ASTM D-2256-80.
[0052] Initial modulus (or "initial secant modulus") is defined per ASTM D-2256-80, Section
10.3, except that the line representing the initial straight line portions of the
stress-strain curve is specified as a secant line passing through the 0.5% and 1.0%
elongation points on the stress-strain curve.
[0053] All other tensile properties are as defined in ASTM D-2256-80.
[0054] Shrinkage (HAS) is defined as the linear shrinkage in a hot air environment maintained
at 177
+1°C per ASTM D-885-85.
[0055] Density, crystal size, long period spacing, crystal birefringence, and amorphous
birefringence are the same as set forth in U.S. Patent No. 4,134,882 which is incorporated
herein by reference. Specifically, each of the foregoing may be found in U.S. Patent
No. 4,134,882 at or about: density - column 8, line 60; crystal size - column 9, line
6; long period spacing - column 7, line 62; crystal birefringence - column 11, line
12; and amorphous birefringence - column 11, line 27.
[0056] Birefringence (optical birefringence or Δn) is as set forth in U.S. Patent No. 4,101,525
at column 5, lines 4-46. U.S. Patent No. 4,101,525 is incorporated herein by reference.
"Bi CV" is the coefficient of variation of optical birefringence between filaments
calculated from 10 measured filaments.
[0057] Other tests referred to herein are performed by conventional methods.
[0058] Reference should now be made to the Examples which will more fully illustrate the
instant invention.
Example I
[0059] In the following set of experimental runs, a conventional polyester polymer (PET,
IV-0.63) was spun. The spinning speeds were increased from 12,500 fpm to 19,000 fpm.
The column length was 6.4 meters and divided into four temperature control zones.
The temperature was controlled by measuring the air temperature close to the wall
at the center of each zone. The polymer was extruded at a rate of 22.9 pounds per
hour through a spinning beam at 285°C and a 40 hole spinneret (hole size 0.009 inches
by 0.013 inches). The fibers were not quenched. The spun fibers were not drawn, but
they were heat set. The results are set forth in TABLE I.

Example II
[0060] In the following set of experimental runs, a conventional polyester (PET, IV-0.63)
was spun, The column temperatures were varied as indicated (air temperature, center
of zones). The column length was 6.4 meters. The polymer was extruded at a rate of
23.1 pounds per hour through a spinning beam at 300°C and a 72 hole spinneret (hole
size 0.009 inches by 0.012 inches). The fibers were not quenched. The spun fibers
were subsequently drawn (as indicated). The results are set forth in TABLE II.

[0061] In the above set of experimental runs (i.e., those set forth in TABLE II), Nos. 4,
5, 6 and 7 represent the instant invention.
Example III
[0062] In the following sets of experimental runs, conventional polyester (PET, IV-0.63)
was spun. The fibers were wound up at a rate of 10,500 fpm. The polymer was extruded
at a rate of 19.5 pounds per hour through a 72 hole spinneret (hole size 0.009 inches
by 0.012 inches) and a spinning beam at 300°C. The fibers were quenched with 6.5 scfm
air at 232°C. The column was 6.4 meters long and divided into 4 sections having the
following air temperature profile (in descending order): 135°C; 111°C; 92°C; and 83°C
at the center of the zones. The spun yarn had the following properties: denier - 334;
tenacity - 4.09 gpd; elongation 71.7%; initial modulus - 55.0 gpd/100%; hot air shrinkage
- 11.8% at 350°F.; Uster 1.10; I.V. -0.647; FOY - 0.35%; birefringence - 110 x 10⁻³;
and crystallinity - 21.6%.
[0063] In TABLE IIIA, the effect of draw ratio on drawn yarn properties is illustrated.

[0064] In Table IIIB, the effect of the heating method during stretching is illustrated
(the draw ratio was 1.65 and the yarn was not relaxed).

[0065] In Table IIIC, the effect of higher drawing temperatures and draw ratios is illustrated
(the feed roll is at ambient temperature and the draw roll is at 240°C).

Example IV
[0066] In the following set of experimental runs, a conventional polyester (PET, IV-0.92)
was spun. In runs Nos. 1-5, the fibers were spun and drawn in accordance with the
methods set forth in U. S. Patent Nos. 4,101,525 and 4,195,052. Nos. 6-9 were made
as follows:
[0067] PET with a molecular weight characterized by an I.V. of 0.92 was dried to a moisture
level of 0.001% or less. This polymer was melted and heated to a temperature of 295°C
in an extruder and subsequently forwarded to a spinning pack by a metering pump. This
pack was of an annular design, and provided filtration of the polymer by passing it
through a bed of finely divided metal particles. After filtration the polymer was
extruded through an 80 hole spinneret. Each spinneret hole had a round cross section
with a diameter of 0.457 mm and a capillary length of 0.610 mm.
[0068] An insulated heated tube 9 meters in length was mounted snugly below the pack and
the multifilament spinning threadline passed through the entire lengt of this tube
before being converged or coming into contact with any guide surfaces. The tube was
divided down its length into seven zones for the purposes of temperature control.
Individual controllers were used to set the air temperature at the center of each
of these zones. Using a combination of process heat and the external heaters around
the tube, individual controller settings were selected to arrive at a uniform air
temperature profile down the vertical distance of this tube. In a typical situation
the air temperature was 155°C at the top zone of the tube and the temperature was
reduced in an approximately uniform gradient to 50°C at the bottom.
[0069] Approximately 10 cm below the tube the threadline was brought into contact with a
finish applicator which also served as the convergence guide and the first contact
that the yarn encountered. At the exit of the tube the cross section of the un-converged
yarn was very small due to the proximity of the finish guide. This permitted a very
small aperture to be used, thus minimizing the amount of hot air lost from the tube.
[0070] Following the application of spin finish the yarn was taken to a pair of godet rolls
and then to a tension controlled winder. Wind up speeds were typically in the range
3200 - 4100 mpm.
[0071] Drawing of this yarn was effected in a second step, in which the as spun yarn was
passed over one set of pretension rolls to a heated feed roll maintained at a temperature
set between 80 and 150°C. The yarn was then drawn between these rolls and a set of
draw rolls maintained at a set point chosen in the range 180 to 255°C. A typical draw
ratio for a spun yarn made at 3800 mpm would be 1.65, with samples spun at higher
and lower speeds requiring lower or higher draw ratios, respectively.
[0072] The results are set forth in TABLE IV.

EXAMPLE V
[0073] Polyester with a molecular weight characterized by an I.V. of 0.92 was dried to a
moisture level of 0.001%. This polymer was melted and heated to a temperature of 295°C
in an extruder and the melt subsequently forwarded to a spinning pack by a metering
pumn. After filtration in a bed of finely divided metal particles, the polymer was
extruded through an 80 hole spinneret. Each spinneret hole had a diameter of 0.457
mm and a capillary length of 0.610 mm. On extrusion the measured I.V. of this polymer
was 0.84.
[0074] The extruded polymer was spun into heated cylindrical cavity 9 meters in length.
An approximately linear temperature profile (gradient) was maintained over the length
of this tube. At the center of the top zone the air temperature was 155°C and at the
bottom of the tube this temperature was 50°C. The multifilament yarn bundle was not
converged until it came in contact with a finish guide just below the exit of the
heated tube. From this point the yarn was advanced by a pair of godet rolls to a tension
controlled winder. Under these conditions a series of four spun yarns were made at
different spinning (wind-up) speeds. These yarns are referred to as examples A through
D in Table V. A.
[0075] In another series of experiments the heated tube was shortened by taking out some
of its removable sections. Examples E and F in Table V. A were spun through 7 and
5 meter columns. Other polymers with different molecular weights (I.V.'s) were also
spun on this system to give Examples G and H. Example I in Table VA illustrates a
case in which lower column temperatures were used. In this case a linear gradient
from 125°C to 50°C was established down the column.
[0076] All spun yarns in the series A through I were drawn in a single stage process using
an ambient feed roll and a 245°C draw roll.
[0077] In a further series of tests the same spun yarn which was described in Example A
was drawn using different feed roll temperatures. The results from testing these yarns
are given in Examples A, J and K in Table V. B.

EXAMPLE VI
[0078] In the following experimental run, a conventional polymer, nylon, was spun according
to the inventive process and compared to nylon made by conventional processes.
[0079] The nylon made by the inventive process was spun under the following conditions:
throughput- 37 lbs. per hour; spinning speed - 2,362 fpm; denier - 3500; number of
filaments - 68; spun relative viscosity - 3.21 (H₂ SO₄) or 68.4 (HCOOH equiv.) quench
air - 72 scfm; winding tension 80g; column length - 24 ft; column temperature top
240°C and bottom 48°C. The as-spun properties of this yarn were as follows: tenacity
- 0.95 gpd; elongation 235%; TE
1/2 - 14.6. Thereafter the yarn was drawn under the following conditions: draw ratio
3.03; draw temperature 90°C. The drawn yarn properties are as follows: tenacity 6.2
gpd; elongation -70%; TE
1/2 - 52; 10% modulus - 0.87 gpd; hot air shrinkage (HAS) at 400°F - 1.4%.
[0080] One comparative nylon was spun in the following conventional fashion: throughput
- 23.4 lbs. per hour; spinning speed - 843 fpm; denier - 5556; number of filaments
- 180; spun relative viscosity - 3.3 (H₂ SO₄) or 72.1 (HCOOH equiv.); quench - 150
scfm. Thereafter, the yarn was drawn under the following conditions: Draw ratio -
2.01; draw temperature - 90°C. The drawn yarn properties are as follows: tenacity
3.8 gpd; elongation - 89%; TE
1/2 - 33; 10% modulus - .55 gpd.
[0081] Another comparative yarn was spun in the following conventional fashion: throughput
- 57.5 lbs. per hour; spinning speed - 1048 fpm; denier - 12400; number of filaments
- 240; spun relative viscosity - 42 (HCOOH equiv.); quench air - 150 scfm. Thereafter,
the yarn was drawn under the following conditions: draw ratio - 3.60; draw temperature
- 110°C. The drawn yarn properties are as follows: tenacity - 3.6 gpd; elongation
- 70%; TE
1/2 - 30.1; modulus at 10% elongation - 0.8 gpd; HAS (at 400°F) - 2.0%.
EXAMPLE VII
[0082] In the following experimental runs, low I.V. (e.g. 0.63) and high I.V. (e.g. 0.92)
conventional polyester (i.e. PET) as spun yarn is compared with as spun yarn set forth
in U.S. Patent No. 4,134,882. Examples 1-8 are low I.V. polyester (PET) and are made
in the manner set forth in Example I. Examples 9-11 are high I.V. polyester (PET)
and are made in the manner set forth in Example V. Examples 12-17 correspond to Examples
1, 5, 12, 17, 36 and 20 of U.S. Patent No. 4,134,882.
[0083] For each example, the spinning speed (fpm), density (gms/cc), crystal size (Å, 010),
long period spacing (LPS), birefringence (biref.), crystal birefringence and amorphous
birefringence are given. The results are set forth in Table VII.

[0084] The present invention may be embodied in other specific forms without departing from
the spirit or essential attributes thereof and, accordingly, reference should be made
to the appended claims, rather than to the foregoing specification, as indicating
the scope of the invention.