U.S. patent application number 11/001138 was filed with the patent office on 2005-05-05 for method for high-speed spinning of bicomponent fibers.
This patent application is currently assigned to E.I. DuPont de Nemours and Company, E.I. DuPont de Nemours and Company. Invention is credited to Chang, Jing Chung, Kurian, Joseph V., Nguyen, Young D., Van Trump, James E., Vassilatos, George.
Application Number | 20050093196 11/001138 |
Document ID | / |
Family ID | 27413816 |
Filed Date | 2005-05-05 |
United States Patent
Application |
20050093196 |
Kind Code |
A1 |
Chang, Jing Chung ; et
al. |
May 5, 2005 |
Method for high-speed spinning of bicomponent fibers
Abstract
Highly crimped, fully drawn bicomponent fibers, prepared by
melt-spinning, followed by gas-flow quenching, heat treatment and
high speed windup, are provided, as are fine-decitex and highly
uniform polyester bicomponent fibers.
Inventors: |
Chang, Jing Chung;
(Columbia, SC) ; Kurian, Joseph V.; (Newark,
DE) ; Nguyen, Young D.; (Charlottesville, VA)
; Van Trump, James E.; (Wilmington, DE) ;
Vassilatos, George; (Wilmington, DE) |
Correspondence
Address: |
INVISTA NORTH AMERICA S.A.R.L.
THREE LITTLE FALLS CENTRE/1052
2801 CENTERVILLE ROAD
WILMINGTON
DE
19808
US
|
Assignee: |
E.I. DuPont de Nemours and
Company
Wilmington
DE
19805
|
Family ID: |
27413816 |
Appl. No.: |
11/001138 |
Filed: |
December 2, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11001138 |
Dec 2, 2004 |
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10743976 |
Dec 22, 2003 |
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6841245 |
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10743976 |
Dec 22, 2003 |
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09758309 |
Jan 11, 2001 |
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6692687 |
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09758309 |
Jan 11, 2001 |
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09708314 |
Nov 8, 2000 |
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09708314 |
Nov 8, 2000 |
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09488650 |
Jan 20, 2000 |
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Current U.S.
Class: |
264/172.14 ;
264/172.15; 264/210.2; 264/210.8 |
Current CPC
Class: |
Y10T 428/2924 20150115;
Y10T 428/2904 20150115; D01F 8/14 20130101; Y10T 428/2913 20150115;
Y10T 428/2929 20150115; Y10T 428/2931 20150115 |
Class at
Publication: |
264/172.14 ;
264/172.15; 264/210.2; 264/210.8 |
International
Class: |
D01D 005/22 |
Claims
1-26. (canceled)
27. A process for preparing a bicomponent fiber comprising the
steps of: (a) providing poly(trimethylene terephthalate) and a
polyester selected from the group consisting of poly(ethylene
terephthalate) and a copolyester of poly(ethylene terephthalate)
having different intrinsic viscosities; (b) melt-spinning the two
polyesters from a spinneret to form at least one bicomponent fiber
having a cross-section selected from the group consisting of
side-by-side and eccentric sheath-core; (c) providing at least one
flow of gas to at least one quench zone below the spinneret and
accelerating the flow to a maximum velocity in the direction of
fiber travel; (d) passing the fiber through the quench zone; (e)
withdrawing the fiber at a withdrawal speed in the range of about:
820 to 4,000 meters per minute when co-current quench gas flow is
used, and in the range of about 1,000 to 3,000 meters per minute
when cross or radial quench gas flow is used; and (f) winding up
the fiber without drawing.
28. The process of claim 27 further comprising, after step (f), the
steps of: (g) drawing; and (h) heat-treating the fibers.
29. The process of claim 28, wherein the fibers have, after step
(h), an after-heat-set crimp contraction value of at least about
30%.
30. The process of claim 28, wherein step (g) follows step (f) by
less than about 35 days.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of copending
application Ser. No. 09/708,314, filed Nov. 8, 2000, which in turn
is a continuation-in-part of copending application Ser. No.
09/488,650, filed Jan. 20, 2000.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to a process for preparing fully
drawn bicomponent fibers at high speeds and, more particularly, to
a process of extruding two polyesters from a spinneret, passing the
fibers through a cooling gas, drawing, heat-treating, and winding
up the fibers at high speeds.
[0004] 2. Description of Background Art
[0005] Synthetic bicomponent fibers are known. U.S. Pat. No.
3,671,379 discloses such fibers based on poly(ethylene
terephthalate) and poly(trimethylene terephthalate). The spinning
speeds disclosed in this reference are uneconomically slow.
Japanese Patent Application Publication JP11-189923 and Japanese
Patent JP61-32404 also disclose the use of copolyesters in making
bicomponent fibers. U.S. Pat. No. 4,217,321 discloses spinning a
bicomponent fiber based on poly(ethylene terephthalate) and
poly(tetramethylene terephthalate) and drawing it at room
temperature and low draw ratios. Such fibers, however, have low
crimp levels, as do the polyester bicomponent fibers disclosed in
U.S. Pat. No. 3,454,460.
[0006] Several apparatuses and methods have been proposed for
melt-spinning partially oriented monocomponent fibers at high
speeds, as disclosed in U.S. Pat. Nos. 4,687,610., 4,691,003,
5,034,182, and 5,824,248 and in International Patent Application
WO95/15409. Generally, in these methods a cooling gas is introduced
into a zone below the spinneret and accelerated in the travel
direction of the newly formed fibers. However, such fibers do not
crimp spontaneously and, therefore, do not have desirable high
stretch-and-recovery properties.
[0007] An economical process for making highly crimpable polyester
bicomponent fibers is still needed.
SUMMARY OF THE INVENTION
[0008] The process of the present invention for preparing fully
drawn crimped bicomponent fibers, having after-heat-set crimp
contraction values above about 30%, comprises the steps of:
[0009] (A). providing two compositionally different polyesters;
[0010] (B) melt-spinning the two polyesters from a spinneret to
form at least one bicomponent fiber;
[0011] (C) providing at least one flow of gas to at least one
quench zone below the spinneret and accelerating the gas flow to a
maximum velocity in the direction of fiber travel;
[0012] (D) passing the fiber through said zone(s);
[0013] (E) withdrawing the fiber at a withdrawal speed such that
the ratio of the maximum gas velocity to the withdrawal speed is so
chosen to achieve a specific draw ratio range;
[0014] (F) heating and drawing the fiber at a temperature of about
50-185.degree. C. at a draw ratio of about 1.4-4.5;
[0015] (G) heat-treating the fiber by heating it to a temperature
sufficient to result in an after-heat-set contraction value above
about 30%; and
[0016] (H) winding up the fiber at a speed of at least about 3,300
meters per minute.
[0017] Another process of the present invention for preparing fully
drawn bicomponent fibers, having after-heat-set crimp contraction
values above about 30%, comprises the steps of:
[0018] (A) providing poly(ethylene terephthalate) and
poly(trimethylene terephthalate) polyesters having different
intrinsic viscosities;
[0019] (B) melt-spinning said polyesters from a spinneret to form
at least one bicomponent fiber having either a side-by-side or
eccentric sheath core cross-section;
[0020] (C) providing a flow of gas to a quench zone below the
spinneret;
[0021] (D) passing the fiber through the quench zone;
[0022] (E) withdrawing the fiber;
[0023] (F) heating and drawing the fiber to a temperature of about
50-185.degree. C. at a draw ratio of about 1.4-4.5;
[0024] (G) heat-treating the fiber by heating it to a temperature
sufficient to result in an after-heat-set contraction value above
about 30%; and
[0025] (H) winding up the fiber at a speed of at least about 3,300
meters per minute.
[0026] The bicomponent fiber of this invention is of about 0.6-1.7
dtex/filament, the fiber having after-heat-set crimp contraction
values of at least 30% and comprising poly(trimethylene
terephthalate) and a polyester selected from the group consisting
of poly(ethylene terephthalate) and copolyesters of poly(ethylene
terephthalate), having a side-by-side or eccentric sheath core
cross-section and a cross-sectional shape which is substantially
round, oval or snowman.
BRIEF DESCRIPTION OF THE FIGURES
[0027] FIG. 1 illustrates a cross-flow quench melt-spinning
apparatus useful in the process of the present invention.
[0028] FIG. 2 illustrates a co-current, superatmospheric quench
melt-spinning apparatus useful in the process of the present
invention (as shown in U.S. Pat No. 5,824,248, FIG. 2).
[0029] FIG. 3 illustrates an example of a roll arrangement that can
be used in the process of the present invention.
[0030] FIG. 4 illustrates a co-current, superatmospheric quench
spinning apparatus useful in the process of the present invention,
in which two quench zones are used.
[0031] FIG. 5 is a graphical representation of the relationship
between fiber crimp contraction ("CC.sub.a") and windup speed for
Examples 1 and 2.
[0032] FIG. 6 shows a co-current, subatmospheric quench spinning
apparatus useful in the process of the present invention.
[0033] FIG. 7 is a schematic of another embodiment of a roll and
jet arrangement that can be used in the process of the
invention.
[0034] FIG. 8 illustrates examples of cross-sectional shapes that
can be made by the process of the invention and of
fine-denier(decitex) polyester bicomponent and highly uniform
polyester bicomponent cross-sectional shapes of the invention.
[0035] FIG. 9 is a schematic representation of another cross-flow
quench system which can be used in the process of the
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0036] It has now been found surprisingly that bicomponent fibers
can be spun with either crossflow, radial flow or co-current flow
quench gas, withdrawn, fully drawn, and heat-treated at very high
speeds to give high crimp levels. It was unexpected that such
highly crimped bicomponent fibers can be prepared in view of the
high withdrawal speeds and high draw ratios (that is, high windup
speeds).
[0037] As used herein, "bicomponent fiber" means a fiber comprising
a pair of polymers intimately adhered to each other along the
length of the fiber, so that the fiber cross-section is for example
a side-by-side, eccentric sheath-core or other suitable
cross-section from which useful crimp can be developed. "IV" means
intrinsic viscosity. "Fully drawn" fiber means a bicomponent fiber
which is suitable for use, for example, in weaving, knitting, and
preparation of nonwovens without further drawing. "Partially
oriented" fiber means a fiber which has considerable but not
complete molecular orientation and requires drawing or
draw-texturing before it is suitable for weaving or knitting.
"Co-current gas flow" means a flow of quench gas which is in the
direction of fiber travel. "Withdrawal speed" means the speed of
the feed rolls, which are positioned between the quench zone and
the draw rolls and is sometimes referred to as the spinning speed.
The notation "//" is used to separate the two polymers used in
making a bicomponent fiber. "2G" means ethylene glycol, "3G" means
1,3-propane diol, "4G" means 1,4-butanediol, and "T" means
terephthalic acid. Thus, for example, "2G-T//3G-T" indicates a
bicomponent fiber comprising poly(ethylene terephthalate) and
poly(trimethylene terephthalate).
[0038] In the process of the invention, two compositionally
different polyesters are melt-spun from a spinneret to form a
bicomponent fiber. The spinneret can have a design such as that
disclosed in U.S. Pat. No. 3,671,379. Either post-coalescence (in
which the polymers first contact each other after being extruded)
or pre-coalescence (in which the polymers first contact each other
before being extruded) spinnerets can be used. As illustrated in
FIG. 8, side-by-side fibers made by the process of the invention
can have a "snowman" ("A"), oval ("B"), or substantially round
("C1", "C2") cross-sectional shape. Eccentric sheath-core fibers
can have an oval or substantially round cross-sectional shape. By
"substantially round" it is meant that the ratio of the lengths of
two axes crossing each-other at 900 in the center of the fiber
cross-section is no greater than about 1.2:1. By "oval" it is meant
that the ratio of the lengths of two axes crossing each other at
90.degree. in the center of the fiber cross-section is greater than
about 1.2:1. A "snowman" cross-sectional shape can be described as
a side-by-side cross-section having a long axis, a short axis and
at least two maxima in the length of the short axis when plotted
against the long axis.
[0039] Regardless of whether co-current or cross-flow quench gas
flow is used, 2G-T can be typically heated to about 280.degree. C.
for transfer to the spinneret, while the corresponding temperature
for 3G-T can be less than 280.degree. C., with a transfer holdup
time up to 15 minutes.
[0040] FIG. 1 illustrates a crossflow melt-spinning apparatus which
is useful in the process of the invention. Quench gas 1 enters zone
2 below spinneret face 3 through plenum 4, past hinged baffle 18
and through screens 5, resulting in a substantially laminar gas
flow across still-molten fibers 6 which have just been spun from
capillaries (not shown) in the spinneret. Baffle 18 is hinged at
the top, and its position can be adjusted to change the flow of
quench gas across zone 2. Spinneret face 3 is recessed above the
top of zone 2 by distance A, so that the quench gas does not
contact the just-spun fibers until after a delay during which the
fibers may be heated by the sides of the recess. Alternatively, if
the spinneret face is not recessed, an unheated quench delay space
can be created by positioning a short cylinder (not shown)
immediately below and coaxial with the spinneret face. The quench
gas, which can be heated if desired, continues on past the fibers
and into the space surrounding the apparatus. Only a small amount
of gas can be entrained by the moving fibers which leave zone 2
through fiber exit 7. Finish can be applied to the now-solid fibers
by optional finish roll 10, and the fibers can then be passed to
the rolls illustrated in FIG. 3.
[0041] Various methods of providing co-current quench gas flow can
be used in the present invention. Referring to FIG. 2 for example,
fibers 6 are melt-spun into zone 2 from optionally recessed
spinneret face 3. Using a recessed spinneret face creates a heated
"quench delay" space, typically identified by its length. If the
spinneret face is not recessed, and a short cylinder (not shown) is
positioned coaxially below the spinneret face, an unheated quench
delay space can be created. Quench gas 1, for example, air,
nitrogen, or steam, enters quench zone 2 below spinneret face 3
through annular plenum 4 and cylindrical screen 5. When the gas is
air or nitrogen, it can be used for example at room temperature,
that is, about 20.degree. C. or it can be heated, for example to
40.degree. C.; the relative humidity of the gas is typically about
70%. Tube 8, which. at its upper end can be conical as illustrated,
is sealed to inner wall 9 of plenum 4 and provides the only outlet
for quench gas 1 and fibers 6. The pressure of the quench gas
introduced into zone 2 and the constriction provided by tube 8
create a superatmospheric pressure in zone 2, for example in the
range of about 0.5-5.0 inches of water (about 1.3.times.10.sup.-3
to 1.3.times.10.sup.-2 kg/cm.sup.2), more typically about 0.5-2.0
inches of water (about 1.3.times.10.sup.-3-5.1.times.10.sup- .-3
kg/cm.sup.2). The pressure used depends on the geometry of the
quench chamber and the withdrawal speed of the fiber. The quench
gas can be introduced from above, for example, from an annular
space around the spinneret, or from the side, as shown in FIG. 2 of
U.S. Pat. No. 5,824,248. Introduction from the side is preferred to
allow better contact of the gas with the fibers for better cooling.
The fibers and quench gas are passed through zone 2 below the
spinneret to exit 7, the quench gas being accelerated in the
direction of fiber travel due to the constriction of tube 8. The
maximum velocity of the quench gas is at the narrowest point of the
tube. When a tube having a minimum inner diameter of one inch (2.54
cm) is used, the maximum gas velocity can be in the range of about
330-5,000 meters/minute. The ratio of maximum gas velocity to the
withdrawal speed of the fiber in the present invention is so chosen
that the fiber can be drawn between the feed roll and draw roll at
a draw ratio of about 1.4-4.5 at a temperature of about
50-185.degree. C. Having been sufficiently cooled by the quench gas
to solidify, fibers 6 can then be contacted by optional finish roll
10 and passed to the rolls illustrated in FIG. 3.
[0042] The process of the present invention can also be carried out
with the co-current quench gas flow apparatus shown in FIG. 4. In
this process, fibers 6 are melt-spun into zone 2a from optionally
recessed spinneret face 3. A first flow of quench gas 1a enters
first quench zone 2a below optionally recessed spinneret face 3
through first annular plenum 4a and first cylindrical screen 5a.
First tapered or conical tube 8a is connected to first inner wall
9a of plenum 94a. The inner diameter of tube 8a can continually
converge as illustrated or can initially converge for a
predetermined length and then remain of substantially constant
internal diameter. A second flow of quench gas 1b enters second
quench zone 2b through second annular plenum 4b through second
cylindrical screen 5b and is combined in the second quench zone
with the first flow of quench gas. Second tube 8b is connected to
second inner wall 9b of plenum 4b. As illustrated, the inner
diameter of tube 8b can initially converge and then diverge; but
other geometries can also be used. Quench gas 1 is accelerated in
the direction of fiber travel by tubes 8a and 8b and can then exit
through last exit 7 and optional perforated exhaust diffuser cone
11. The maximum gas velocity is at the narrowest point of either
tube 8a or tube 8b, depending on the gas flows 1a and 1b. Fibers 6
pass through quench zones 2a and 2b, exit the quench apparatus
through fiber exit 7, can then be contacted by optional finish roll
10, and then passed around heating, drawing, and heat-treating
rolls and jets, for example as illustrated in FIGS. 3, 7, and 9.
The pressure used in the first quench zone is typically higher than
that in the second quench zone.
[0043] The preparation of bicomponent polyester fibers using quench
gas which is accelerated in the direction of fiber travel by
application of subatmospheric pressure in the zone below the
spinneret is also contemplated by the process of the present
invention. For example, the apparatus illustrated in FIG. 6 can be
used. In FIG. 6, newly formed fibers 6 leave spinneret face 3 and
enter quench zone 2. Vacuum source 37 pulls quench gas (for
example, room air or heated air) into zone 2 through perforated
cylinders 5a and 5b, which reduce turbulence. Optionally, ring 64
can be provided to shield the newly spun fibers from immediate
contact with the quench gas. Similarly, shield 74 can be positioned
to control quench gas flow. The quench gas and fibers 6 pass
through funnel 8, the gas velocity accelerating as it does so.
Additional gas can be drawn in between the bottom of funnel 8 and
the top 39 of tube 35, and optionally gas jets 60 can be arranged
to supply still more gas, especially along the inside of tube 35 to
minimize the risk of fibers 6 touching the inside of tube 35. Tube
35 flares outward at trumpet 58. The shapes of both funnel 8 and
trumpet 58 are designed to minimize turbulence. Quench gas velocity
is reduced when it enters chamber 43 and further reduced when it
enters chamber 49, thus reducing the risk of turbulence. Perforated
cylinder 47 further assists in reducing turbulence. Increased
control of quench gas velocity can be attained by various means,
for example by use of valve 53, throttle 55, and velocimeter 57.
Fibers 6 leave this part of the apparatus through exit 7, pass by
optional finish roll 10, and can then be additionally processed,
for example by means of the roll and jet systems illustrated in
FIGS. 3, 7, and 9. Optionally, ceramic fiber guides 46 can be
provided at exit 7.
[0044] The speed of feed rolls 13 determines and is substantially
equal to the withdrawal speed. When crossflow, radial flow or the
like flow of gas is used, the withdrawal speed can be in-the range
of about 700-3,500 meters per minute, commonly about 1,000-3,000
meters per minute. When co-current quench gas flow is used, the
withdrawal speed can be in the range of about 820-4,000 meters per
minute, typically about 1,000-3,000 meters per minute.
[0045] The bicomponent fiber can then be heated and drawn, for
example, by heated draw rolls, draw jet or by rolls in a hot chest.
It can be advantageous to use both hot draw rolls and a steam draw
jet, especially when highly uniform fibers having a linear density
of greater than 140 dtex are desired. The arrangement of rolls
shown in FIG. 3 is the system that was used in Examples 1, 2, and 4
and has been found useful in the present process. However, other
roll arrangements and apparatus that accomplish the desired results
can also be used (for example, those illustrated in FIGS. 7 and 9).
Drawing can be done via a single-stage or two-stage draw. In FIG.
3, fiber 6, which has just been spun for example from the apparatus
shown in FIGS. 1, 2, 4, or 6, can be passed by (optional) finish
roll 10, around driven roll 11, around idler roll 12, and then
around heated feed rolls 13. The temperature of feed rolls 13 can
be in the range of about 20.degree. C.-120.degree. C. The fiber can
then be drawn by heated draw rolls 14. The temperature of draw
rolls 14 can be in the range of about 50-185.degree. C., preferably
about 100-120.degree. C. The draw ratio (the ratio of wind-up speed
to withdrawal or feed roll speed) is in the range of about 1.4-4.5,
preferably about 2.4-4.0. Each of the rolls within pair of rolls 13
can be operated at the same speed as the other roll, as can those
within pair 14.
[0046] After being drawn by rolls 14, the fiber can be heat-treated
by rolls 15, passed around optional unheated rolls 16 (which adjust
the yarn tension for satisfactory winding), and then to windup 17.
Heat treating can also be carried out with one or more other heated
rolls, steam jets or a heating chamber such as a "hot chest" or a
combination thereof. The heat-treatment can be carried out at
substantially constant length, for example, by rolls 15 in FIG. 3,
which can heat the fiber to a temperature in the range of about
140.degree. C.-185.degree. C., preferably about 160.degree.
C.-175.degree. C. The duration of the heat-treatment is dependent
on yarn denier; what is important is that the fiber can reach a
temperature sufficient to result in an after-heat-set contraction
value above about 30%. If the heat-treating temperature is too low,
crimp can be reduced under tension at elevated temperatures, and
shrinkage can be increased. If the heat-treating temperature is too
high, operability of the process becomes difficult because of
frequent fiber breaks. It is preferred that the speeds of the
heat-treating rolls and draw rolls be substantially equal in order
to keep fiber tension substantially constant (for example 0.2
cN/dtex or greater) at this point in the process and thereby avoid
loss of fiber crimp.
[0047] An alternative arrangement of rolls and jets is illustrated
in FIG. 7. Just-spun bicomponent fiber 6 can be passed by optional
primary finish roll 10a and optional interlace jet 20a and then
around feed rolls 13, which can be unheated. The fiber can be drawn
through draw jet 21, which can be operated at pressures of 0.2-8.0
bar (2040-81,600 Kg/m.sup.2) and temperatures of 180.degree.
C.-400.degree. C., and both heat-treated and drawn by rolls 14,
which can heat the fiber to a temperature of about 140.degree.
C.-185.degree. C., preferably about 160.degree. C.-175.degree. C.
The draw ratio used can be in the same range as described above for
the arrangement shown in FIG. 3. Fiber 6 can then be passed around
optional roll 22 (optionally operated at speeds lower than rolls 14
in order to relax the fiber) in preparation for optional
interlacing by interlace jet 20b, and can be passed around optional
roll 16 (to adjust the fiber tension for satisfactory winding),
past optional finish roll 10b, and finally to windup 17.
[0048] Finally, the fiber is wound up. When cross-flow quench gas
flow is used, the windup speed is at least about 3,300 meters per
minute, preferably at least about 4,000 meters per minute, and more
preferably at about.4,500-5,200 meters per minute. When co-current
quench gas flow and one quench zone are used, the windup speed is
at least about 3,300 meters per minute, preferably at least about
4,500 meters per minute, and more preferably about 5,000-6,100
meters per minute. If co-current quench gas flow and two quench
zones are used, the windup speed is at least about 3,300 meters per
minute, preferably at least about 4,500 meters per minute and more
preferably about 5,000-8,000 meters per minute.
[0049] The wound fiber can be of any size, for example 0.5-20
denier per filament (0.6-22 dtex per filament). It has now been
found that novel poly(ethylene terephthalate)//poly-(trimethylene
terephthalate) fibers of about 0.5-1.5 denier per filament (about
0.6-1.7 dtex per filament) having a side-by-side or eccentric
sheath core cross-section and a substantially round, oval, or
snowman cross-sectional shape can be made at low, intermediate, or
high spinning speeds. For high crimp contraction levels, for
example above about 30%, it is preferred that such novel fibers
have a weight ratio of poly(ethylene terephthalate) to
poly(trimethylene terephthalate) in the range of about 30/70 to
70/30. It was unexpected that such fine fibers could reliably be
drawn sufficiently to give such high crimp levels.
[0050] When a plurality of fibers of the invention are combined
into a yarn, the yarn can be of any size, for example up to 1300
decitex. Any number of filaments, for example 34, 58, 100, 150, or
200, can be spun using the process of the invention.
[0051] It was found unexpectedly that highly uniform bicomponent
fibers, comprising two polymers that react differently to their
environment as indicated by their spontaneous crimp, can be made
with a low average decitex(denier) spread of less than about 2.5%,
typically in the range of 1.0-2.0%. Uniform fibers are valuable
because mill efficiency and processing are improved due to fewer
fiber breaks, and fabrics made from such fibers are visually
uniform.
[0052] The process of the present invention can be operated as a
coupled process or as a split process in which the bicomponent
fiber is wound up after the withdrawing step and later backwound
for the hot-drawing and heat-treating steps. If a split process is
used, the next steps are accomplished without excessive delay,
typically less than about 35 days and preferably less than about 10
days, in order to achieve the desired bicomponent fiber. That is,
the drawing step is completed before the as-spun fiber becomes
embrittled due to aging in order to avoid excessive fiber breaks
during drawing. Undrawn fiber can be stored refrigerated, if
desired, to diminish this potential problem. After the drawing
step, the heat-treating step is completed before the drawn fiber
relaxes significantly (typically in less than a second).
[0053] The weight ratio of the two polyesters in the bicomponent
fibers made by the process of the invention is about 30/70-70/30,
preferably about 40/60-60/40, and more preferably about
45/55-55/45.
[0054] The two polyesters used in the process of the present
invention have different compositions, for example 2G-T and 3G-T
(most preferred) or 2G-T and 4G-T and preferably have different
intrinsic viscosities. Other polyesters include poly(ethylene
2,6-dinaphthalate, poly(trimethylene 2,6-dinaphthalate),
poly(trimethylene bibenzoate), poly(cyclohexyl 1,4-dimethylene
terephthalate), poly(1,3-cyclobutane dimethylene terephthalate),
and poly(1,3-cyclobutane dimethylene bibenzoate). It is
advantageous for the polymers to differ both with respect to
intrinsic viscosity and composition, for example, 2G-T having an IV
of about 0.45-0.80 dl/g and 3G-T having an IV of about 0.85-1.50
dl/g, to achieve an after heat-set crimp contraction value of at
least 30%. When 2G-T has an IV of about 0.45-0.60 dl/g and 3-GT has
an IV of about 1.00-1.20 dl/g, a preferred composition, after
heat-set crimp contraction values of at least about 40% can be
achieved. Nevertheless, the two polymers must be sufficiently
similar to adhere to each other; otherwise, the bicomponent fiber
will split into two fibers.
[0055] One or both of the polyesters used in the process of the
invention can be copolyesters. For example, a copoly(ethylene
terephthalate) can be used in which the comonomer used to make the
copolyester is selected from the group consisting of linear,
cyclic, and branched aliphatic dicarboxylic acids having 4-12
carbon atoms (for example butanedioic acid, pentanedioic acid,
hexanedioic acid, dodecanedioic acid, and
1,4-cyclo-hexanedicarboxylic acid); aromatic dicarboxylic acids
other than terephthalic acid and having 8-12 carbon atoms (for
example isophthalic acid and 2,6-naphthalenedicarboxylic acid);
linear, cyclic, and branched aliphatic diols having 3-8 carbon
atoms (for example 1,3-propane diol, 1,2-propanediol,
1,4-butanediol, 3-methyl-1,5-pentanediol,
2,2-dimethyl-1,3-propanediol, 2-methyl-1,3-propanediol, and
1,4-cyclohexanediol); and aliphatic and araliphatic ether glycols
having 4-10 carbon atoms (for example, hydroquinone
bis(2-hydroxyethyl) ether, or a poly(ethyleneether) glycol having a
molecular weight below about 460, including diethyleneether
glycol). The comonomer can be present in the copolyester at levels
of about 0.5-15 mole percent.
[0056] Isophthalic acid, pentanedioic acid, hexanedioic acid,
1,3-propane diol, and 1,4-butanediol are preferred because they are
readily commercially available and inexpensive.
[0057] The copolyester(s) can contain minor amounts of other
comonomers, provided such comonomers do not have an adverse affect
on the amount of fiber crimp or on other properties. Such other
comonomers include 5-sodium-sulfoisophthalate, at a level of about
0.2-5 mole percent. Very small amounts of trifunctional comonomers,
for example trimellitic acid, can be incorporated for viscosity
control.
[0058] As wound up, the bicomponent fiber made by the present
process exhibits considerable crimp. Some crimp may be lost on the
package, but it can be "re-developed" upon exposure to heat in a
substantially relaxed state. Final crimp development can be
attained under dry heat or wet heat conditions. For example, dry or
wet (steam) heating in a tenter frame and wet heating in a jig
scour can be effective. For wet heating of polyester-based
bicomponent fibers, a temperature of about 190.degree. F.
(88.degree. C.) has been found useful. Alternatively, final crimp
can be developed by a process disclosed in U.S. Pat. No. 4,115,989,
in which the fiber is passed with overfeed through a bulking jet
with hot air or steam, then deposited onto a rotating screen drum,
sprayed with water, unraveled, optionally interlaced, and wound
up.
[0059] In the Examples, the draw ratio applied was the maximum
possible without generating a significant increase in the number
and/or frequency of broken fibers and was typically at about 90% of
break-draw. Unless otherwise indicated, rolls 13 in FIG. 3 were
operated at about 60.degree. C., rolls 14 at about 120.degree. C.
and rolls 15 at about 160.degree. C.
[0060] Intrinsic viscosity ("IV") of the polyesters was measured
with a Viscotek Forced Flow Viscometer Model Y-900 at a 0.4%
concentration at 19.degree. C. and according to ASTM D-4603-96 but
in 50/50 wt % trifluoroacetic acid/methylene chloride instead of
the prescribed 60/40 wt % phenol/1,1,2,2-tetrachloroethane. The
measured viscosity was then correlated with standard viscosities in
60/40 wt % phenol/1,1,2,2-tetrachloroethane to arrive at the
reported intrinsic viscosity values. IV in the fiber was measured
by exposing polymer to the same process conditions as polymer
actually spun into bicomponent fiber except that the test polymer
was spun through a sampling spinneret (which did not combine the
two polymers into a single fiber) and then collected for IV
measurement.
[0061] Unless otherwise noted, the crimp contraction in the
bicomponent fiber made as shown in the Examples was measured as
follows. Each sample was formed into a skein of 5000.+-.5 total
denier (5550 dtex) with a skein reel at a tension of about 0.1 gpd
(0.09 dN/tex). The skein was conditioned at 70.+-.2.degree. F.
(21.+-.1.degree. C.) and 65.+-.2% relative humidity for a minimum
of 16 hours. The skein was hung substantially vertically from a
stand, a 1.5 mg/den (1.35 mg/dtex) weight (e.g. 7.5 grams for a
5550 dtex skein) was hung on the bottom of the skein, the weighted
skein was allowed to come to an equilibrium length, and the length
of the skein was measured to within 1 mm and recorded as "C.sub.b".
The 1.35 mg/dtex weight was left on the skein for the duration of
the test. Next, a 500 gram weight (100 mg/d; 90 mg/dtex) was hung
from the bottom of the skein, and the length of the skein was
measured to within 1 mm and recorded as "L.sub.b". Crimp
contraction value (percent) (before heat-setting, as described
below for this test), "CC.sub.b", was calculated according to the
formula
CC.sub.b=100.times.(L.sub.b-C.sub.b)/L.sub.b
[0062] The 500-g weight was removed and the skein was then hung on
a rack and heat-set, with the 1.35 mg/dtex weight still in place,
in an oven for 5 minutes at about 225.degree. F. (107.degree. C.),
after which the rack and skein were removed from the oven and
conditioned as above for two hours. This step is designed to
simulate commercial dry heat-setting, which is one way to develop
the final crimp in the bicomponent fiber. The length of the skein
was measured as above, and its length was recorded as "C.sub.a".
The 500-gram weight was again hung from the skein, and the skein
length was measured as above and recorded as "La". The after
heat-set crimp contraction value (%), "CC.sub.a", was calculated
according to the formula
CC.sub.a=100.times.(L.sub.a-C.sub.a)/L.sub.a.
[0063] CC.sub.a is reported in the Tables. After-heat-set crimp
contraction values obtained from this test are within this
invention and acceptable if they are above about 30% and,
preferably, above about 40%.
[0064] Decitex Spread ("DS"), a measure of the uniformity of a
fiber, was obtained by calculating the variation in mass at regular
intervals along the fiber, using an ACW/DVA (Automatic Cut and
Weigh/Decitex Variation Accessory) instrument (Lenzing Technik), in
which the fiber was passed through a slot in a capacitor which
responded to the instantaneous mass of the fiber. The mass was
measured every 0.5 m over eight 30-m lengths of the fiber, the
difference between the maximum and minimum mass within each of the
lengths was calculated and then averaged over the eight lengths,
and the average difference divided by the average mass of the
entire 240-m fiber length was recorded as a percentage. To obtain
"average Decitex Spread", such measurements were made on at least
three packages of fiber. The lower the DS, the higher the
uniformity of the fiber.
[0065] In spinning the bicomponent fibers in Examples 1-4, the
polymers were melted with Werner & Pfleiderer co-rotating 28-mm
extruders having 0.5-40 pound/hour (0.23-18.1 kg/hour) capacities.
The highest melt temperature attained in the 2G-T extruder was
about 280-285.degree. C., and the corresponding temperature in the
3G-T extruder was about 265-275.degree. C. Pumps transferred the
polymers to the spinning head. In Examples 1-4, the fibers were
wound up with a Barmag SW6 2s 600 winder (Barmag AG, Germany),
having a maximum winding speed of 6,000 meters per minute.
[0066] The spinneret used in Examples 1-4 was a post-coalescence
bicomponent spinneret having thirty-four pairs of capillaries
arranged in a circle, an internal angle between each pair of
capillaries of 30.degree., a capillary diameter of 0.64 mm, and a
capillary length of 4.24 mm. Unless otherwise noted, the weight
ratio of the two polymers in the fiber was 50/50. Total yarn
decitex in Examples 1 and 2 was about 78.
EXAMPLE 1
[0067] A. 1,3-Propanediol ("3G") was prepared by hydration of
acrolein in the presence of an acidic cation exchange catalyst, as
disclosed in U.S. Pat. No. 5,171,898, to form
3-hydroxypropionaldehyde. The catalyst and any unreacted acrolein
were removed by known methods, and the 3-hydroxypropionaldehyde was
then catalytically hydrogenated using a Raney Nickel catalyst (for
example as disclosed in U.S. Pat. No. 3,536,763). The product
1,3-propanediol was recovered from the aqueous solution and
purified by known methods.
[0068] B. Poly(trimethylene terephthalate) was prepared from
1,3-propanediol and dimethylterephthalate ("DMT") in a two-vessel
process using tetraisopropyl titanate catalyst, Tyzor.RTM. TPT (a
registered trademark of E. I. du Pont de Nemours and Company) at 60
ppm, based on polymer. Molten DMT was added to 3G and catalyst at
185.degree. C. in a transesterification vessel, and the temperature
was increased to 210.degree. C. while methanol was removed. The
resulting intermediate was transferred to a polycondensation vessel
where the pressure was reduced to one millibar (10.2 kg/cm.sup.2),
and the temperature was increased to 255.degree. C. When the
desired melt viscosity was reached, the pressure was increased and
the polymer was extruded, cooled, and cut into pellets. The pellets
were further polymerized in a solid-phase to an intrinsic viscosity
of 1.04 dl/g in a tumble dryer operated at 212.degree. C.
[0069] C. Poly(ethylene terephthalate) (Crystar.RTM. 4415, a
registered trademark of E. I. du Pont de Nemours and Company),
having an intrinsic viscosity of 0.54 dl/g, and poly(trimethylene
terephthalate), prepared as in step B above, were spun using the
apparatus of FIG. 2. The spinneret temperature was maintained at
about 272.degree. C. In the spinning apparatus, the internal
diameter of cylindrical screen 5 was 4.0 inches (10.2cm), the
length B of screen 5 was 6.0 inches (15.2cm), the diameter of cone
8 at its widest was 4.0 inches (10.2cm), the length of cone C2 was
3.75 inches (9.5cm), the length of tube C3 was 15 inches (38.1cm),
and the distance C1 was 0.75 inch (1.9 cm). The inner diameter of
tube 8 was 1.0 inch (2.5 cm), and the (post-coalescence) spinneret
was recessed into the top of the spinning column by 4 inches (10.2
cm) ("A" in FIG. 2) so that the quench gas contacted the just-spun
fibers only after a delay. The quench gas was air, supplied at a
room temperature of about 20.degree. C. The fibers had a
side-by-side cross-section and an oval cross-sectional shape.
[0070] About 10 wraps were taken around the heat-treating
rolls.
1TABLE I Air Air Withdrawal Speed/ Windup Speed (1) Speed
Withdrawal Draw Speed CC.sub.a Sample (mpm) (mpm) Speed Ratio (mpm)
(%) 1 560 875 0.6 4.0 3500 51 2 560 1000 0.6 4.0 4000 55 3 560 1125
0.6 4.0 4500 57 4 1141 1250 0.9 4.0 4975 54 5 906 1250 0.7 4.0 5000
54 6 1141 1336 0.9 3.7 4975 54 7 1472 1388 1.1 3.6 4940 51 8 1472
1571 0.9 3.5 5440 51 9 1695 1714 1.0 3.5 5930 44 (1) In the 2.54-cm
inner diameter tube fiber exit
[0071] The data show that good crimp can be attained at high
withdrawal and windup speeds using the process of the invention and
two polyesters. The data also suggest that windup speeds of up to
at least about 6,100 meters per minute can be successfully used in
the present co-current gas flow process when one co-current quench
zone is used (see curve "1" in FIG. 5, which shows an extrapolation
of windup speed).
EXAMPLE 2
[0072] Crystar.RTM. 4415 and poly(trimethylene terephthalate) as
prepared in Example 1 were spun into a side-by-side oval
bicomponent fiber using the cross-flow quench apparatus of FIG. 1.
The spinneret temperature was maintained at about 272.degree. C.
For samples 10-15, the (post-coalescence) spinneret was recessed
into the top of the spinning column by six inches (15.2 cm) ("A" in
FIG. 1). The height of the zone below the spinneret ("2" in FIG. 1
was 172 cm. For samples 10-13, the flow of quench air had the
following profile, measured 5 inches (12.7 cm) from screen 5 (see
FIG. 1):
2 Distance below Air speed spinneret (cm) (mpm) 15 8.5 30 9.4 46
9.4 61 11.0 76 11.0 91 11.3 107 11.6 122 16.5 137 34.1 152 39.6 168
29.6
[0073] For samples 14 and 15, the quench air velocity was
approximately 50% higher.
[0074] For samples 16 and 17, no recess (no heated quench delay
space) was used, and the quench air flow had the following profile,
also measured 5 inches (12.7 cm) from screen 5:
3 Distance below Air spinneret speed (cm) (mpm) 2.5 15.2 30.5 12.2
61.0 11.3 91.4 9.8 121.9 9.8 152.4 9.8
[0075] Properties of the resulting fibers are given in Table II and
illustrated as curve "2" in FIG. 2. The data show that high crimp
levels can be obtained at surprisingly high speeds with crossflow
quench gas. Above about 3,500 mpm feed roll speed (withdrawal
speed), fiber breaks prevented the application of sufficient draw
to attain high crimp contraction levels.
4TABLE II Withdrawal Windup Speed Draw Speed CC.sub.a Sample (mpm)
Ratio (mpm) (%) 10 750 4.0 2980 56 11 933 3.7 3470 57 12 1176 3.4
3960 51 13 1406 3.2 4455 53 14 2000 2.4 4750 45 15 3250 1.6 5150 45
16 4417 1.2 5250 13 17 4818 1.1 5270 2
EXAMPLE 3
[0076] Using the same spinning equipment as employed in Example 1,
poly(ethylene terephthalate) and poly(trimethylene terephthalate),
prepared as in Example 1, side-by-side oval cross-section
bicomponent yarns of 34 filaments and 49-75 dtex (1.4-2.2 dtex per
filament) were spun at withdrawal speeds of 2,800-4,500 meters per
minute. The fibers were wound up on bobbins without drawing. The
fibers were stored at room temperature (about 20.degree. C.) for
about three weeks and at about 5.degree. C. for about fifteen days,
after which they were drawn over a 12-inch (30 cm) hot shoe held at
90.degree. C. at a feed roll speed of 5-10 meters per minute and
heat-treated by passing them at constant length through a 12-inch
(30 cm) glass tube oven held at 160.degree. C. The fibers were
drawn at 90% of the draw at which they broke. In this Example,
crimp contraction levels were measured immediately after drawing
and heat-treating by hanging a loop of fiber from a holder with a
1.5 mg/denier (1.35 mg/dtex) weight attached to the bottom of the
loop and measuring the length of the loop. Then a 100 mg/den (90
mg/dtex) weight was attached to the bottom of the loop, and the
length of the loop was measured again. Crimp contraction was
calculated as the difference between the two lengths, divided by
the length measured with the 90 mg/dtex weight. This method gives
crimp contraction values up to about 10% (absolute) higher than the
method described for "CC.sub.a" so that values above about 40% are
acceptable. Results are summarized in Table III.
5TABLE III Air Air Withdrawal Speed/ Crimp Speed (1) Speed
Withdrawal Draw Contraction Sample (mpm) (mpm) Speed Ratio (%) 18
1200 2800 0.43 2.0 50 19 1515 3500 0.43 1.6 42 20 1712 4000 0.43
1.4 51 21 -- 4500 -- 1.2 19 (1) In the 2.54-cm inner diameter tube
fiber exit
[0077] The results showed that, after spinning, drawing can be
delayed by about five weeks (for example, in a split process) and
still be effective in generating crimp in bicomponent fibers spun
with co-current air flow and that useful crimp levels can be
attained with draw ratios as low as about 1.4.
EXAMPLE 4
[0078] The same apparatus and polymers as in Example 1 were used,
but with an unheated quench delay space (created by an unheated
cylinder coaxial with the spinneret) of 2 inches (5.1 cm). The
withdrawal speed was 2,000 m/min, the draw ratio was 2.5-2.6, and
the windup speed was 5,000-5,200 m/min. Oval side-by-side
bicomponent fibers were produced with single superatmospheric
quench zone pressures so that the corresponding air speeds at exit
7 of tube 8 (see FIG. 2) were 1141 m/min and 1695 m/min,
respectively. The resulting 2G-T//3G-T bicomponent yarns of 34
filaments and 42 decitex (38 denier) [1.1 denier (1.2 dtex) per
filament] had unexpectedly high crimp contraction ("CCa") levels,
49-62%, which were comparable to crimp levels obtained in Example 1
for filament of nearly twice the dtex/filament. At this low
decitex, higher speeds were not possible with this apparatus
geometry and process conditions, due to breaks in the fibers during
drawing and heat-treating and on the wound package. However, when
the cylinder creating the 2-inch (5.1 cm) quench delay space was
heated with a band heater at 250.degree. C. and the position of
tube 8 (see FIG. 2) was raised so that distance "C1" in FIG. 2 was
reduced substantially to zero, even finer 2G-T//3G-T bicomponent
yarns of 38 decitex (34 denier) and 34 filaments [1.0 denier(1.1
dtex) per filament] and having good crimp contraction ("CCa")
levels (40-49%) were produced at up to 5,700 m/min with a draw
ratio of 2.85. Thus, heating the quench delay space and shortening
the quench zone improved high speed process continuity for very
fine polyester bicomponent fibers. Knit and woven and woven fabrics
prepared from these filaments had a very soft hand.
EXAMPLE 5
[0079] This example illustrates the use of a two-zone co-current
quench under a variety of conditions. In each of Examples 5A, 5B,
and 5C, poly(ethylene terephthalate) (Crystar.RTM. 4415-675) having
an intrinsic viscosity of 0.52 dl/g, and poly(trimethylene
terephthalate) prepared as in step B of Example 1, were spun into
34 side-by-side bicomponent filaments using the spinning apparatus
of FIG. 4 and the roll-and-jet arrangement of FIG. 7. The extruder
used for 2G-T was a single-screw Barmag model 4E10/24D with a
4E4-41-2042 model screw. The extruder used for 3G-T was a
single-screw Barmag Maxflex (single zone heating, 30 mm internal
diameter) with a MAF30-41-3 model single flight screw. The
residence times in the transfer lines between the extruder
discharge and the spinneret face were measured by adding briefly
dye chips to the polymers and determining the time it took for the
dye to appear in, and then disappear from, the fiber. For the 2G-T
line, the appearance time was 61/2 minutes, and the disappearance
time was over 40 minutes. For the 3G-T line, the appearance time
was 43/4 minutes, and the disappearance time was 10 minutes. The
poly(tri-methylene terephthalate) was discharged from the extruder
at a temperature less than about 260.degree. C. and the transfer
line was at about the same temperature. The angle between the
capillaries in the post-coalescence spinneret was 3.degree., and
the distance between the capillaries at their exits was 0.067 mm.
The pre-coalescence spinneret had a combined capillary and
counterbore length of 16.7 mm. The quench gas entered the spinning
column at least 90 mm below the spinneret ("A" in FIG. 4) so that
the gas first contacted the just-spun fibers only after a delay;
the recess was not intentionally heated. The quench gas was air,
supplied at a temperature of 20.degree. C. and a relative humidity
of 65%. The minimum inner diameter of tube 8a was 0.75 inch (1.91
cm) and the minimum inner diameter of tube 8b was 1.5 inch (3.81
cm). Five-and-a-half wraps were taken around unheated feed rolls
13. Draw jet 21 was operated at 0.6 bar (6118 Kg/cm.sup.2) and
225.degree. C., and the steam flow was adjusted to control the
position of the drawpoint. Draw rolls 14 also functioned as
heat-treating rolls and were operated at 180.degree. C.;
five-and-a-half wraps were taken around these rolls, too. The
winder was a commercial Barmag CRAFT 8-end winder capable of 7000
m/min winding speed. The fibers had a side-by-side cross-section,
and the total yarn denier was 96 in Examples 5A and 5C and 108 in
Example 5B (107 decitex and 120 decitex, respectively). Other
spinning conditions and the cross-sectional shapes and crimp
contraction levels are summarized in Table IV.
6TABLE IV Example 5A 5B 5C Polymer Weight Ratio 60/40 50/50 45/55
(2G-T//3G-T) 2G-T Transfer Line(.degree. C. 278 263 278 Spinneret
Type Post- Pre- Post- Coalescence Coalescence Coalescence Spin
Block(.degree. C.) 278 263 278 1st Quench Zone Max. 3180 3180 3180
Air Speed (m/min) 2nd Quench Zone Max. 2152 2184 2152 Air Speed
(m/min) Feed Rolls 13 Speed 2715 2100 2870 (m/min) Draw Rolls 14
Speed 6810 6835 6833 (m/min) Draw Ratio 2.5 3.2 2.4 Roll 22 Speed
(mpm) 6810 6835 6833 Roll 16 Speed (mpm) 6770 6775 6793 Winder 17
Speed (mpm) 6702 6710 6700 Fiber Cross-sectional Snowman Round
Snowman Shape CC.sub.a, % 55 67 58
[0080] The decitex spread for Example 5B, based on data from a
single package, was 1.36%. The data in Table IV show that very high
crimp levels can be attained at very high speeds by using the
process of the invention.
EXAMPLE 6
[0081] This example relates to novel, highly uniform bicomponent
fibers comprising poly(ethylene terephthalate) and
poly(trimethylene terephthalate) The polymers, extruders, spinning
apparatus, spinneret recess, quench gas, winder, and roll-and-jet
arrangement used were the same as in Example 5. The
post-coalescence spinneret of Example 5 was used, and the fiber
cross-sectional shape in each case was "snowman". The temperature
of the poly(trimethylene terephthalate) as it left the extruder was
less than about 260.degree. C., and the transfer line was at about
the same temperature. The recess was not intentionally heated
except in Example 6.C, in which it was heated to 120.degree. C.
Feed rolls 13 were not intentionally heated except in Example 6.B.,
in which they were heated to 55.degree. C. The steam flow in draw
jet 21 was adjusted to control the location of the drawpoint. Draw
rolls 14 also functioned as heat-treating rolls and were again
operated at 180.degree. C. Five-and-a-half wraps were taken around
the feed rolls and draw rolls. Other spinning conditions and crimp
contraction levels are given in Table V. Decitex Spread data are
presented in Table VI.
7TABLE V Example 6A 6B 6C Decitex 174 172 82 Number of filaments 68
34 34 Polymer Weight Ratio 60/40 50/50 50/50 (2G-T//3-GT) 2G-T
transferline (Dowtherm 264 262 280 temp. .degree. C.) Spin block
(Dowtherm temp., .degree. C.) 264 262 280 1st Quench Zone Max. Air
Speed 3079 3180 2980 (m/min) 2nd Quench Zone Max. Air Speed 1895
2184 1766 (m/min) Steam draw jet pressure (kg/m.sup.2) 7134 29,572
5099 Steam draw jet temp. (.degree. C.) 237 240 224 Feed Rolls 13
speed (m/min) 1915 2140-2210 1300-1380 Draw Rolls 14 speed (m/min)
6123 6845 4300 Draw Ratio 3.2 3.1-3.2 3.1-3.3 Roll 22 Speed (m/min)
6123 6845 4300 Roll 16 Speed (m/min) 6081 6775 4275 Winder 17 Speed
(m/min) 6001 6710 4200 Crimp Contraction ("CC.sub.a"), % 57 55
56
[0082]
8TABLE VI Example Package DS(%) 6A 1 1.8 2 2.2 3 2.0 4 2.1 5 1.9
Average 2.0 6B 1 1.9 2 2.1 3 1.8 Average 1.9 6C 1 1.3 2 1.8 3 1.7 4
1.8 Average 1.6
EXAMPLE 7 (COMPARISON)
[0083] This Example shows what levels of uniformity can be obtained
using conventional cross-flow quench in making polyester
bicomponent fibers. Poly(trimethylene terephthalate) containing 0.3
wt % TiO2 and prepared as described in Example 1 but having an IV
of 1.02-1.06, and poly(ethylene terephthalate) (Crystar.RTM. 4415,
IV 0.52) were used. The polymers were melted in independent
extruders and separately transported to a pre-coalescence spinneret
at a melt temperature of 256.degree. C. (3G-T) or 285.degree. C.
(2G-T). In the fibers, the 3G-T IV was about 0.93, and the 3G-T IV
was about 0.52. The weight ratio of 2G-T to 3G-T was 41/59. The
extruded bicomponent multifilament yarn was cooled in a cross flow
quench unit using an air speed of 16 m/min, supplied from a plenum
through a vertical diffuser screen. The roll-and-jet arrangement of
FIG. 9 was used. 5 wt % (based on fiber) of an ester-based finish
was applied 2 meters below spinneret face 3 (see FIG. 9) by an
applicator not shown. Yarn 6 was passed 2.5 times around feed roll
13 and associated separator roll 13a, through steam draw jet 21
(operated at 180.degree. C.) and then around draw roll 14 and
associated separator roll 14a. The yarn was then drawn a second
time between draw roll 14 and pair of rolls 15 in hot chest 76,
which was heated to 170.degree. C. A total of 7.5 wraps were taken
around the two hot chest rolls. The yarn was passed around roll 22,
through dual interlace jets 20, and then around roll 16. The same
finish was reapplied at finish applicator 10, again at the same 5
wt %. Finally, the yarn was wound onto a paper core tube at windup
17. The roll and windup speeds (in meters/minute) are summarized in
Table VII, and the resulting average Decitex Spreads are reported
in Table VIII.
9 TABLE VII Example 7A 7B 7C Yarn decitex 167 167 83 Number of
filaments 68 34 34 Speeds, m/min: Feed roll 13 840 325 840 Draw
roll 14 2560 1052 2560 Hot chest rolls 15 3110 1495 3110 Roll 22
2970 1480 2970 Roll 16 2912 1429 2912 Windup 17 2876 1413 2876
Total draw ratio 3.7 4.6 3.7
[0084]
10 TABLE VIII Example Package DS(%) 7A 1 2.2 (1) 2 3.1 3 2.9 4 2.9
5 3.2 6 3.0 Average 2.9 7B 1 3.9 2 2.9 3 3.7 4 3.4 5 3.6 6 2.6
Average 3.3 7C 1 3.5 2 2.7 3 3.0 4 2.8 5 3.0 Average 3.0
[0085] (1)The decitex spread for Example 7A, Package 1 is a
statistical outlier and believed not to be representative of the
true value of decitex spread in polyester bicomponent fibers
obtained with conventional quench methods, as evidenced by the high
average Decitex Spread obtained in Example 7A.
[0086] Comparison of the results for Examples 6 and 7 shows that
unusually uniform 2G-T//3G-T bicomponent fibers can now be
made.
* * * * *