Note: Descriptions are shown in the official language in which they were submitted.
12~30216~i
TITLE
NEW WATER-DISPERSIBLE SYNTHETIC FIBER
TECHNICAL FIELD
5~hi invention concerns new water-disper~ible
synthetic polymer fiber, particularly of poly(ethylene
terephthalate), and its preparation.
9AC~GROUND OF INVENTION
There has been increased ;nterest in recent years
10 in water-di6persible synthetic fiber, e~pecially of
polyester. Such water-di~persible fiber i~ used in
various non-woven applications, including paper-making and
wet-laid non-woven fabrics, so~etimes as part of a blend,
often with large amounts of wood pulp, or fiberglas~, but
15 also in applications requiring only polyester fiber, i.e.,
unblended with other fiber. This use, and the
requirements therefor, are entirely different from
previous more conventional use as tow or ætaple fiber for
conver~ion into tsxtile yarns for eventual use in woven or
20 knitted fabrics, because of the need to di~perse this
fiber in water instead of to convert the fiber into y~rns,
e.g., by processes such as carding, e.y. in the cotton
6ystem. It i6 this requirement for water-dispersibility
that distinguishe~ the field of the invention from
25 previous, more conventional polyester staple fiber.
~ ost ~uch water-dispersible polye~ter fiber i6 of
poly(ethylene terephthalate), and i~ prepared in
essentially the ~ame general way as conventional textile
polye~ter staple fiber, except that most water-dispersible
30 polyester fiber is not crimped, whereas any polyester
staple fiber for use in textile yarns is generally crimped
while in the form of tow, before conversion into staple
DP-3995A 35
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fiber. ~hu~, waterdi6persible polyester fiber has
generally been prepared by melt-spinning the polyester
into filaments, combining the filaments to form a tow,
drawing, applying a suitable coating to impart
5 water-dispersible properties, generally in the ~ame way as
¦ a fini~h is applied to a tow of conventional textile
! filaments, and then, generally without any crimpin~ (or
with imparting only soms mild wavy undulations in ~ome
ca~es to provide extra bulk and a three-dimen~ional
10 matrix), converting the tow into staple. Some prior
polyester staple fiber has been prepared in uncrimped
form, e.g. for use as flock in pile fabrics, but for such
use, water-dispersibility has not been required.
Polyester fibers are naturally hydrophobic, so it
5 i5 necessary to apply to the polye~ter a euitable coating,
a~ disclosed by Ring et al. in U.S. Patent No. 4,007,083,
~awkins in U.S. Patent No~. 4,137,181, 4,179,543 and
4,294,883, and Viscose Suisse in British Patent No.
958,350, to overcome the inherent hydrophobic character of
20 the polyester fiber without creating foam or causing the
fibers to flocculate. It is this coating that has
distinguished water-di~persible polyester fiber from more
conventional polyester ~taple fiber, rather than any
inherent characteristic feature of the polyester it~elf,
25 or of its shape, ~uch as the cross-~ection. ~eretofore,
so far as i8 known, the cross-~ection of all commercial
water-di~persible polye~ter fiber has been round. Indeed
the cross-~ection of mo~t commercial polye~ter staple
fiber has generally been round, because this has been
30 preferred.
Although, hitherto, most ~ynthetic polymeric
water-dispersible fiber ha~ been formed of polyester,
being inexpensive and plentiful, increasing amount~ of
polyolefins and polyamides are beginning to be used for
35 water-dispersible fibers, and so the invention is not
~3~ ~ 2 80 ~ 6~
limited only to polyesters, but covers other synthetic
polymers.
SUMMARY OF INVENTION
According to the present invention, there i~
provided new synthetic polymer water-dispersible fiber,
especially polyester fiber, characterized in that the
fibers are of cruciform cross-section.
A cruciform cross-section has been used heretofore
for other polyester fiberæ, as described herein. Other
than the cross-section, the water-dispersible fiber of the
invention may be e sentially similar to prior
water-dispersible polyester or other synthetic polymer
fibers, although the advantages described hereinafter may
provide the opportunity for additional modifications. The
invention will be described hereinafter with ~pecial
reference to polyester fiber, although it will be
recognized that other synthetic polymers, such as
polyamides and polyolefins, may also be used.
The fibers of the invention may be made
conveniently by melt-spinning and drawing polye~ter
filAments of appropriate denier per filament (dp~), and
applying thereto a suitable coating to impart
water-disper6ible characteristics. The filaments ~re then
generally cut into staple of whatever length is desired
25 for the end-use contemplated.
The use of a cruciform cro6s-~ection for
the water-dispersible fiber of the invention has,
~urprisingly, been found to promote dispersibility, in
comparison with a round cross-section, and this imparts to
30 the resulting wet-laid fiber~ better uniformity, more
opacity, good permeability, and an attractive flannel-like
hand as will be seen in the Example.
BRIEF DESCRIPTION OF DRAWINGS
Figure 1 shows a cruciform cross-section for a
35 stylized fiber according to the invention.
~2~0Z6~
Figure 2 shows a typical spinneret orifice for
spinning fil~ments of the invention.
DISCLOSURE OF THE INVENTION
As indicated above, a cruciform cro~ ection has
already been used for more conventional polyester staple
fiber, that has been spun into filaments and drawn, cut,
converted into spun yarn, and used in woven or knitted
fabrics. Such fiber had the water-dispersible
characteristics required for this invention. Similarly,
10 polyester filaments having a cruciform cross-~ection are
alread~ known from Lehmicke U.S. Pat. No. 2,945,739, which
discloses a process for melt-spinning polyamide and
polyester filaments of, inter alia cruciform
cross-6ection, and woven and knitted fabrics from staple
15 fibers, and from Jamisson U.S. Pat. No. 3,249,669, which
discloses a process for making a multifilament yarn of
polyester filament6 of various cro6s-sections, including a
cruciform cross-section. Oriented polyester filaments o
non-round cross-section have also been described by
20 Frankfort et al. in U. S. Pat. Nos. 4,134,882 and
4,195,051, having been prepared by spinning at a very high
speed (6,000 ypm), which high speed could al60 be used to
prepare oriented polyester filaments of cruciform
cross-section as a substrate for applying thereto a
uitable coating to impart water-di~persible
characteristics, ~nd thereby obtaln water-dispersible
fiber according to the invsntion. None of this art
concerns the field of the present invention. ~owever, the
polye6ter filamentary ~ubstrates for making the
30 water-di8persible fiber of the invention may be prepared
by the techniques described therein, or by appropriate
modifications of these or other known techniques of making
polyester filament~ of non-round cross-section.
The prior art references disclose parameters for a
35 cruciform cross-~ection and Figure 1 is essentially as
shown therein.
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Th6 preparatlon of the polye~ter ~taplæ Xiber
otherwi~e conventlonal, involving th~ 6tep~ of
melt-splnning polymer into filament~, collecting the
filaments ~nto a tow, drawinq the tow, ~nd ~pplying a
~uitable coating water-dispersible to impart
characteri~tic~. If low ~hrinkage i~ de~ired, the drdwn
~ilament~ are ~enerally annealed.
Selection of ~n appropriate coating to promote
w~ter-di~persibility i~ lmportant, and more of ~ueh
coating i6 generally required than for compar~ble weight~
of ~iber of round cros6-æectio:n o~ lar dpf, because of
the larger 6urface area of the periphery of the cruciform
cross-~ection. It i~ especially important to provide qood
boundary lubrication properties. For thi6 re~60n, an
15 ethoxylated coa~ing i~ preferred.
Suitable coating~ are disclo6ed ~n ~awkln6, V. S.
Pat. No~. 4,13~ ,179,543 and 4,294,883 disclosLng ~ use of
. _ .a syn~hetic copolyester.. o~ poly(ethylene terephthalate)
unit6 and poly(oxyalkylene) of groups derived from a
20 poly(oxyalkylene~ glycol having an average molecul~r
weight in the ranqe of 300 to 6,000, ~ di~clo6ed, e.g. in
McIntyre, ~t al. V.S. Pat. No6. 3,416,952, 3,557,039 and
3,619,269, referred to there$n; other u6eful ~egmented
copolye~ter6 ar~ disclosed ln Raynolds U.S. Patent No.
25 3,981,807; all the~e disclosures are lncorpor~t~d her~ln --
by reference.
Such polyester fiber i~ generally prepared f$r~t
in the ~orm of ~ continuous filamentary uncrimped tow or,
if extra bul~ i6 required, and a more three-dimen6ional
30 matrix, the filament~ may be provided with mild wave-like
undulations by a mild crimping-type proce~s, and the
uncrimped or ~ildly wave-like filament6 are cut t~ the
desired cut len~th, $.e. to form the water-dlspersible
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fiber, which is generally ~old in the ~orm of bales, or
other packages of cut fiber. Suitable cut lengths are
generally from about 5 to about 90 mm tl/4 to 3 inches),
generally up to 60 mm (2-1/2 inches), and of
length/diameter (L/D) ratio from about 100:1 to about
2000:1, preferably about 150:1 to about 2000:1, it being
an advantage of the invention that good performance has
been obtainable with preferred water-dispersible fiber of
the invention with ~n L/D ratio higher than we h~ve
¦ 10 considered satisfactory with prior art water-dispersible
polyester fiber. For instance, machine manufacturers have
generally recommended that the L/D ratio not exceed 500:1,
and many operators have considered even this figure
unrealistically high. A suitable denier per filament is
generally from ~bout 0.5 to about 20. The coating i~
generally present in amount about 0.04 to about 1.0~ of
the weight of fiber (OWF~), it being an advantage that
smaller amounts may generally be used than we have
i considered satisfactory according to the prior art.
There is al60 provided ~ process for preparing
such water-dispersible polyester fiber, comprising the
steps of melt-spinning the polyester into filaments of
cruciform oros~-section, forming a tow of such filaments,
drawinq, and then coating the filaments in the tow with
25 ~uch synthet~c copolyester, and, at an appropr~ate time,
converting 6uch coated filaments into staple fiber.
The coatIng is preferably cured on the filaments
by heating the coated filaments, or the resulting staple
fiber, if desired, to a temperature of about 100 to about
30 190 to improve durability.
The invention is further illustrated in the
~ollowing Example, in which all parts and percentages are
by weiqht, unless otherwi~e indicated, and OWF is tsolids)
"of weight of fiber". Reference is made to several
35 measurements of yarn properties, such as tensile
~7~ ~2~6~
properties (tenacity and elongation-to break), which are
measured according to the methods described in Frankfort
et al. U.S. Patent No. 4,134,882. It will be understood
that other conditions can be used e.q., other designs of orifice, 6uch as are shown in the art.
Example
The following fiber&, Fiber A, a compari~on of
round cross section, and Fiber N, a fiber of the invention
of cruciform cros~ section, were both spun from
10 poly(ethylene t~rephthalate) of intrinsic viscosity 0.64,
containing 0.3% Tio2 as a delusterant.
Fiber A was spun at 1600 ypm into filaments with
conventional radial air quenchinq using a 900 hole
~pinneret, with round holes 0.015 inche~ in diameter ~nd
15 capillary length of 0.030 inches, a 270C block, and
polymer throughput 68.2 pounds/hour. Denier per filament
was 3.67. Fiber A was then oriented by running over a set
of feed rool~ at 29.3 ypm, followed by a set of draw roll~
at 80.0 ypm, and delivered to a conveyer by puller rolls
20 at 80.1 ypm. Between feed roll sections the filaments
were treated in a 45C water bath. Between feed and draw
rolls the rope w~s sprayed with water at 9BC. Between
draw ~nd puller roll~ a commercial water-dispersible
coating (50/50 mixture of pota~ium ~alt of mono and
25 diacid phosphate ~sters of lauryl alcohol/tallow alcohol
ethoxylated with 25 ~ole~ of ethylene oxide) was applied.
The filaments were then relaxed free in ~n oven at 150C
for 6 minutes.
Fiber N was produced in a similar manner to Fiber
30 A excep~ that 625 filaments of 3.22 dpf and cruciform
cro~6-section were ~pun through capillaries as shown in
Figure 2, with block temperature 273C, and throughput
42.9 pound6/hour. -Roll 6peeds for the orientation were
feed roll~ 32.1 ypm, draw rolls 80.2 ypm and puller rolls
3579.2 ypm, and a somewhat higher level of water-dispersible
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coating wa~ used to offset approximately 57% higher
surface area of the cruciform cross-section.
The properties of the drawn coated filaments are
compared in Table 1.
Ta'ole_1
Sample A N
Cross-section Round cruciform
dpf 1.47 1.5
coating OWF(~) 0.4 0.44
Boil-off shrinkage(%) 1.0 0
Dry heat shrinkaye
(196C) (~) 2.45 3.6
Tenacity at break (g/d) 4.5 4.8
Elongation at break(%) 42 26
Tenacity at
2% elonyation(g/d) 0.93 0.93
~oth types were cut to form water-di6persible
i fiber of 1/4, 3/8, 1/2 and 3/4 inch cut lengths and were
tested on an inclined wire Fourdrinier machine. Fibers
were dispersed for three minutes in a s~all pulper at
0.75% consifitency (lbs. fiber per 100 lbs. slurry, or
furni~h). The cylindrical nulper wa~ approximately 3 feet
in dii~,meter by 6 feet deep. Fibers were then mixed with
unrefined sulphite pulp to form a 50% polye,ter blend and
diluted to 0.1~ consistency in a 10 cubic meter stock
tank. This stock was further diluted in the headbox of
-the machine to 0.0143% consistency and ~ormed into ia 0.5
meter wide wet lay nonwoven fabric at 20 ~eters/minute. A
~priay of an acrylic binder, Acronyl 240D was spray applied
at the end of the Fourdrinier wire. The fabric was then
cured in a through air drier at 150C. Finished fabric
weight averaged 40 grams/square meter.
Dispersion quality can be judged by the uniformity
of the fabric produced from ia given sample. As cut length
increases, the uniformity of the fabric can generally be
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expected to suffer significantly. However, great
advantages can result from using a longer fiber because
the fabric tear strength increases, for example. In
practice, therefore, a fabric producer will generally wish
5 to use the longe~t fiber that will meet his uniformity
standards. Thus, a longer fiber with improved, or
equivalent uniformity would be preferred.
The di6persion quality of fabrics from Fiber6 A
and N were rated as they were produced on the machine by
10 observing the fabrics as the water drained from them on
the Fourdrinier wire6. Results of this comparison ~re in
Table 2 and indicate good disper6ion for the cruciform in
spite of its 57% greater surface area.
TABLE 2
DISPERSION DESCRIPTION
ROUND CRUCIFORM
cu'r LENGTH I TEM A ITEM N
1/4 inch good dispersion good dispersion
few log defects few log defects
3/8 inch some log defects good dispersion
general quality not fair fabric cover
80 good as 1/4 inch (opacity)
1/2 inch fairly good dispersion normal dispersion
25 3/4 inch di6percion definitely very good di6persion
poor, cover lower
Standard physical propertie6 were mea,~ured for the
set of fabrics at Herty Foundation, Savannah, GA.
Compared each time to Fiber A as 100%, Fiber N had the
30 following average properties:
-1 o ~28026~
Air Permeability, Gurley 112%
Opacity, ISO 2471 111%
Bulk, TAPPI T410 om-83 and T411 om-83 118%
Tensile Strength, TAPPI T494 om-81 100%
5 Tensile Stretch, TAPPI T49~ om-81 B5
Tear Strength, TAPPI T414 om-82 104~
On balance, Item N exhibi~ed advantaye6 in the
important ~reas of higher permeability, opacity, bulk and
10 tear ~trength compared to the control at equivalent
ten~ile strength with a small reduction in ~tretch. The
cover advantage is important because less fiber can be
used for a nonwoven fabric with similar performance
characteri6tics, thereby saving material6 cost. The
~ 15 fabrics of Item N also have an attractive flannel-like
? hand.
j When used with the appropriate water-disper6ible
coating in appropriate amount, the cruciform cross-section
fiber of the invention has given a fabric with
20 6urprisingly good dispersion uniformity, and the
properties indicated.
; From theoretical con6iderations, water-dispersible
fibers of conventional round cross-6ection would have been
expected to give more uniform disper6ion6, and, therefore,
~5 more uniform wet-l~id fabrics. Thi6 ~s bec~use the
surface energy requlred to disper~e a fiber (or other
article~) is given by:
Ener~y ~ (Surface Tension) X (Dispersed ~urface area -
Undisper~ed surface area).
The undispersed fiber exists in logs or clumps of
many hundreds of fibers, most of which are on the inside
of the logs. Therefore the undi6persed surfa~e area is
~ negligible compared to the dispersed area, and the energy
term can be expressed approximately as:
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128 [)~66
Energy ~ (Surface Ten6ion~ X (Number of fibers) X
(Surface area of a fiber).
This energy term describes both the energy
required to disperse the fiber, and the free energy
5 driving force for reagglomeration. Therefore, for any
given coating, and fiber dpf, fibers with lower area would
be expected to provide a more uniform dispersion, hence
more uniform fabric. Ths minimum surface area per unit
weight for a given fiber occurs when the cross-6ection is
round, which would be expected, therefore, to be
preferred.
¦ Surprisingly, however, these cruciform fibers, in
spite of about 60% greater surface area gave more uniform
fabrics. Without limiting the invention to any theory,
th~ may result from the fiber'~ hydrodynamic shape, which
may more effectively use the energy available in the mixer
shear field.
.
.
3 30
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