Note: Descriptions are shown in the official language in which they were submitted.
8~`~
IMPROVED F~BERS AND FILTERS
CONTAINING SAID FIBERS
BACKGROUND OF THE INVENTION
1. Field of the Invention
- _
This invention relates to improved filter fibers
and filters comprising said fibers. More particularly,
this invention relates to such filter fibers comprising
a polyester and a polyolefin, and filters comprising
said fibers.
2. Prior Art
Polyesters are well known materials for the
manufacture of fibers. Illustrative of such fibers are
those described in United States Patent Nos. 4,454,196;
4,410,473; and 4,359,557.
Polyolefinic materials are well known articles of
commerce which have expèrienced wide acceptance in
forming shaped objects and film or sheet material. The
use of such materials has extended to the fiber and
fabric industries. For example, U. S. Patent Nos.
4,587,154; 4,567,092; 4,562,869; and 4,559,862.
Fibers containing mixtures of polyolefins and
polyesters are known. For example, U.S. Patent No.
3,639,505 describes fibers and films composed of a
polymer alloy comprising an intimate blend of
polyolefin, a minor amount of polyethylene terephthalate
and 0.2 to 5 parts per hundred parts of polymer of a
toluene sulfonamide compound which are described as
having improved receptivity to dispersed dyes.
Bicomponent fibers are known in the art. For
example, Textile World, June 1986 at page 29 describes
sheath/core fibers which have an inner core of polyester
and have an outer core of polypropylene or
polyethylene, Also see Textile World, April 1986, page
31.
~b
. .
1L7
--2--
Bicomponent textile filaments of polyester and
nylon are known in the art, and are described in U.S.
Pat. No. 3,489,641. According to the aforesaid patent,
a yarn that crimps but does not split on heating is
obtained by using a particular polyester.
It is also known to employ as the polyester
component of the bicomponent filament a polyester which
is free from antimony, it having been determined that
antimony in the polyester reacts with nylon to form a
deposit in the spinneret which produces a shorter
junction line, and thus a weaker junction line.
It is also known to make bicomponent filaments
using poly[ethylene terephthalate/5-(sodium sulfo)
isophthalate~ copolyester as the polyester component.
U.S. Patent No. 4,118,534 teaches such bicomponents.
It is also known to make bicomponent filaments in
which the one component partially encapsulates the
other component. U.S Patent No. 3,607,611 teaches such
a bicomponent filament.
It is also known to produce bi componenet filaments
in which the interfacial junction between the two
polymeric components is at least in part jagged. U.S.
Patent N. 3,781,399 teaches such a bicomponent
filament. Bicomponent filaments having a cross
sectional dumbell shape are known in the art. U.S.
Patent No. 3,092,892 teaches such bicomponent
filaments. Other nylon/polyester bicomponent fibers
having a dumbell across sectional shape having a jagged
interfacial surface, the polyester being an
antimony-free copolyester having 5-(sodium sulfo)
isophthalate units are known. U.S. Patent No.
4,439,487 teaches such fibers. The surface of such
bicomponent filament is at least 75% of one of the
polymeric components. Still other nylon/polyester
bicomponent sheath/core fibers are described in Japan
Patent Nos. 49020424, 48048721, 70036337 and 68022350;
and U.S. Patent Nos. 4,610,925, 4,457,974 and 4,610,928.
A
--3--
Fibers have previously been prepared from blends of
polyamides with minor amounts of polyesters such as
poly(ethylene terephthalate). Intimate mixing before
and during the spinning process has been recognized as
necessary to achieve good properties in such blended
fibers. It is furthermore known that the fine
dispersions in fibers of polymer blends are achieved
when both phases have common characteristics such as
melt viscosity. See D~R. Paul, "Fibers From Polymer
Blends" in Polymer Blends, vol. 2, pp. 167-217 at 184
(D.R. Paul & S. Newman, ehs., Academic Press 1978).
Graft and block copolymers of nylon 6/nylon 66,
nylon 6/poly(ethylene terephthalates) and nylon
6/poly(butylene terephthalate) have been formed into
grafts which can be spun into fibers. For example, U.S.
Patent 4,417,031, and S. Aharoni, Polymer Bulletin, vol.
10, pp. 210-214 (1983) disclose a process for preparing
block and/or graft copolymers by forming an intimate
mixture of two or more polymers at least one of which
includes one or more amino functions, as for example a
nylon, and at least one of the remaining polymers
includes one or more carboxylic acid functions, as for
example a polyester, and a phosphite compound; and
thereafter heating the intimate mixture to form the
desired block and/or graft copolymers. U.S. Patent No.
4,417,031 disclose that such copolymers can be spun into
fibers.
The use of polyester fibers as the filter element
for air filters of air breathing engines is known. For
example, the use of such fibers is described in Lamb,
George, E.R. et al., "Influence of Fiber Properties on
the Performance of Nonwoven Air Fillers,"
Proc. Air Pollut. Control Assoc., vol. S, pp. 75-57
... .
(June 15-20 1975) and Lamb, George E.R. et al.
"Influence of Fiber Geometry on the Performance of Non
Woven Air Filters," Textile Research Journal," vol. 45
No. 6 pp. 452-463 (1975).
--4--
SUMMARY ~F THE INVENTION
The present invention is directed to a polyester
based fiber useful for the filter element of air
filters. More particularly, this invention comprises a
polymer fiber comprising predominantly one or more melt
spinnable polyesters having non uniformly dispersed
therein one or more polyolefins; the concentration of
said polyolefin at or near the outer surface of said
fiber being greater than the concentration of said
polyester at or near the surface of the fiber. As used
herein, a "fiber" is an elongated body, the length
dimension of which is greater than the transverse
dimensions of width and thickness. Accordingly, the
term fiber includes single filament, ribbon, strip and
the like, having regular or irregular cross-section.
The fiber of this invention exhibits improved capacity
when used as the fibers of the filter element of an air
filter.
Yet another aspect of this invention relates to a
process of forming the fiber of this invention which
comprises melt spinning a molten mixture comprising as a
major component one or more melt spinnable polyesters
and as a minor component one or more polyolefins forming
a polymer fiber comprising predominantly said one or
more polyesters having non uniformly dispersed therein
said one or more polyolefins, the concentration of said
polyolefins being greater at or near the outer surfaces
of said fiber being greater than the concentration of
said polyesters at or near the center of said fiber.
Surprisingly, it has been discovered that during the
melt spinning of the fibers, a portion of the
polyolefins migrates to the surface of the fiber such
that even though it is the minor component, the
concentration of the polyolefins at or near the surface
of the polyolefins at or near the surface of the fiber
is greater than the concentration of polyesters at or
near the surface.
--5--
BR~EF DESCRIPTION OF T~E DRAWINGS
.
FIGs. 1 to 10 are cross-sections of various
"Multilobal" fibers for use in this invention.
DESCRIPTION OF THE INVENTION
The fiber of this invention comprises two essential
components. The fiber is predominantly a melt
processible polyester of "fiber forming molecular
weight." As used herein, "fiber forming molecular
weight" is a molecular weight at which the polymer can
be melt spun into a fiber. Such molecular weights are
well known to those of skill in the art and may vary
widely depending on a number of known factors, including
the specific type of polymer. In the preferred
embodiments of the invention, the molecular weight of
the polyester is at least about 5,000, and in the
particularly preferred embodiments the molecular weight
of the polyester is from about 8,000 to about 100,000.
Amongst these particularly preferred embodiments, most
preferred are those embodiments in which the molecular
weight of the polyester is from about 15,000 to about
50,000.
Polyester useful in the practice of this invention
may vary widely. The type of polyester is not critical
and the particular polyester chosen for use in any
particular situation will depend essentially on the
physical properties and features, i.e., desired in the
final filter element. Thus, a multiplicity of linear
thermoplastic polyesters having wide variations in
physical properties are suitable for use in this
invention.
The particular polyester chosen for use can be a
homo-polyester or a co-polyester, or mixtures thereof as
desired. Polyesters are normally prepared by the
condensation of an organic dicarboxylic acid and an
organic diol, and, therefore illustrative examples of
useful polyesters will be described hereinbelow in terms
of these diol and dicarboxylic acid precursors.
Polyesters which are suitable for use in this
invention are those which are derived from the
condensation of aromatic, cycloaliphatic, and aliphatic
diols with aliphatic, aromatic and cycloaliphatic
dicarboxylic acids. Illustrative of useful aromatic
diols, are those having from about 6 to about 12 carbon
atoms. Such aromatic diols include bis-(p-hydroxy-
phenyl) ether; bis-(p-hydroxyphenyl) thioether; (bis-(p-
hydroxyphenyl)-sulphone; bis-(p-hydroxyphenyl)-methane;
1,2-(bis-(p-hydroxyphenyl)-ethane; l-phenyl-(p-hydro-
xyphenyl)-methane; diphenyl-bis(p-hydroxyphenyl)-
methane; 2,2-bis(4'-hydroxy-3'-dimethylphenyl)propane;
1,1- bis(p-hydroxyphenyl)-butane; 2,2-(bis(p-
hydroxyphenyl)-butane l,l-(bis-(p-hydroxyphenyl)-
cyclopentane; 2,2-(bis-(p-hydroxyphenyl)-propane
(bisphenol A); l,l-(bis-(p-hydroxyphenyl)-cyclohexane
(bisphenol C); p-xylene glycol; 2,5 dichloro-p-xylylene
glycol; p-xylene-diol; and the like.
Suitable cycloaliphatic diols include those having
from about 5 to about 8 carbon atoms. Exemplary of such
useful cycloaliphatic diols are l,4-dihydroxy
cyclohexane; 1,4-dihydroxy methylcyclohexane; l,3-
dihydroxycyclopentane; 1,5-dihydroxycycloheptane; 1,5-
dihydroxycyclooctane; 1,4-cyclohexane dimethanol; and
the like. Polyesters which are derived from aliphatic
diols are preferred for use in this invention. Useful
and preferred aliphatlc and cycloaliphatic diols
includes those having from about 2 to about 12 carbon
atoms, with those having from about 2 to about 6 carbon
atoms being particularly preferred. Illustrative of
such preferred diol precursors are propylene glycols;
ethylene glycol, pentane diols, hexane diols, butane
diols and geometrical isomers thereof. Propylene
glycol, ethylene glycol, 1,4-cyclohexane dimethanol, and
1,4-butanediol are particularly preferred as diol
precursors of polyesters for use in the conduct of this
invention.
--7
Suitable dicarboxylic acids for use as precursors
in the preparation of useful polyesters aee linear and
branched chain saturated aliphatic dicarboxylic acids,
aromatic dicarboxylic acids and cycloaliphatic dicar-
boxylic acids. Illustrative of aliphatic dicarboxylic
acids which can be used in this invention are those
having from about 2 to about 50 carbon atoms, as for
example, oxalic acid, malonic acids, dimethyl-malonic
acid, succinic acid, octadecylsuccinic acid, pimelic
acid, adipic acid, trimethyladipic acid, sebacic acid,
suberic acid, azelaic acid and dimeric acids (dimeri-
sation products of unsaturated aliphatic carboxylic
acids such as oleic acid) and alkylated malonic and
succinic acids, such as octadecylsuccinic acid, and the
like.
Illustrative of suitable cycloaliphatic dicarboxy-
lic acids are those having from about 6 to about 15
carbon atoms~ Such useful cycloaliphatic dicarboxylic
acids include 1,3-cyclobutanedicarboxylic acid, 1,2-
cyclopentanedicarboxylic acid, 1,3- and 1,4-cyclo-
hexanedicarboxylic acid, 1,3- and 1,4-dicarboxymethyl-
cyclohexane and 4,4'-dicyclohexydicarboxylic acid, and
the like.
Polyester compounds prepared from the condensation
of a diol and an aromatic dicarboxylic acid are
preferred for use in this invention. Illustrative of
such useful aromatic carboxylic acids are terephthalic
acid, isophthalic acid and a o-phthalic acid, 1,3-,
1,4-, 2,6 or 2,7-naphthalenedicarboxylic acid, 4,4'-
diphenyldicarboxylic acid, 4,4'-diphenylsulphone-dicar-
boxylic acid, 1,1,3-trimethyl-5-carboxy-3-(p-carboxy-
phenyl)-indane, diphenyl ether 4,4'-dicarboxylic acid
bis-p~carboxyphenyl)methane and the like. Of the afore-
mentioned aromatic dicarboxylic acids, those based on a
benzene ring such as terephthalic acid, isophthalic
acid, and ortho-phthalic acid are preferred for use and
amongst these preferred acid precursors, terephthalic
acid is particularly preferred.
--8--
In the most preferred embodiments of this inven-
tion, poly(ethylene terephthalate), poly~butylene
terephthalate), and poly(l,4-cyclohexane dimethylene
terephthalate), are the polyesters of choice. Among
these polyesters of choice, poly(ethylene terephthalate
is most preferred.
The amount of polyester included in the fiber of
this invention may vary widely. In general, the amount
of polyester will vary from about 99.5 to about 75
percent by weight based on the total weight of the
fiber. In the preferred embodiments of the invention
the amount of polyester in the fiber may vary from about
99 to about 85 percent by weight based on the total
weight of the fiber, and in the particularly perferred
embodiments of the invention the amount of polyester in
the fiber may vary from about 90 to about 98 weight
percent on the aforementioned basis. Amongst these
partcularly preferred embodiments, most preferred are
those embodiments in which the amount of polyester in
the fiber is from about 92 to abo~t 95 weight percent
based on the total weight of the fiber.
As a second essential component, the fiber of this
invention includes one or more polyolefins. The
molecular weight of the polyolefin may vary widely. For
example, the polyolefin may be a wax having a relatively
low molecuar weight i.e., 500 to 1,000 or more. The
polyolefin may also be melt spinnable and of fiber
forming molecular weight. Such polyolefins Eor use in
the practice of this invention are well known. Usually,
the polyolefin is of fiber forming molecular weight
having a molecular weight of at least about 5,000. In
the preferred embodiments of the invention the molecular
weight of the polyolefins is from about ~,000 to about
1,000,000 and in the particularly preferred embodiments
is from about 25,000 to about 750,000. Amongst the
particularly preferred embodiments most preferred are
those in which the molecular weight of the polyolefins
is from about 50,000 to about 500,000. Illustrative of
~1 2~
polyolefins for use in the practice of this invention
are those formed by the polymerization of olefins of the
formula:
RlR2CH = CH2
wherein:
Rl and R2 are the same or different and are
hydrogen or substituted or unsubstituted alkylphenyl,
phenylalkyl, phenyl, or alkyl. Useful polyolefins
include polystyrene, polyethylene, polypropylene,
polyl(l-octadecene), polyisobutylene, poly(l-pentene),
poly(2-methylstyrene), poly(4-methylstyrene), poly(l-
hexene), poly(5-methyl-1-hexene), poly(4-methylpentene),
poly(l-butene), poly(3-methyl-1-butene), poly(3-phenyl-
l-propene), polybutylene, poly(methyl pentene-l),
poly(l-hexene), poly(5-methyl-1-hexene), poly(l-
octadecene), poly(vinyl cyclopentane),
poly(vinylcyclohexane), poly( a-vinylnaphthalene), and
the like.
Preferred for use in the practice of this invention
are polyolefins of the above referenced formula in which
20 R is hydrogen or alkyl having from 1 to about 12 carbon
atoms such as polyethylene, polypropylene, poly-
isobutylene, poly(4-methyl-1-pentene), poly(l-butene),
poly(l-pentene), poly(3-methyl-1-butene), poly(1-
hexene), poly(5-methyl-1-hexene), poly(l-octene), and
the like.
In the particularly preferred embodiments of this
invention, the polyolefins of choice are those in which
Rl is hydrogen and R2 is hydrogen or alkyl having from 1
to about 8 carbon atoms such as polyethylene,
polypropylene, poly(isobutylene), poly(l-pentene),
poly(3-methyl-1-butene), poly(l-hexene), poly(4-methyl-
l-pentene), and poly(1-octene). Amongst these
particularly preferred embodiments, most preferred are
those embodiments in which R1 is hydrogen and R2 is
hydrogen or alkyl having from 1 to about 6 carbon atoms
3~L~
--10--
_uch as polyethylene, polypropylene, poly(4-methyl-1-
pentene), and polyisobutylene, with polypropylene being
the polyolefin of choice.
The amount of polyolefins included in the fiber of
the invention may vary widely and is usually from about
0.5 to about 25 percent by weight based on the total
weight of the fiber. In the preferred embodiments of
this invention, the amount of melt spinnable polyolefins
is from about 1 to about 15 weight percent based on the
total weight of the fiber; and in the particularly
preferred embodiments of the invention the amount of
melt spinnable polyolefins in the fiber is from about 2
to about 10 weight percent based on the total weight of
the fiber. Amongst the particularly preferred
embodiments, most preferred are those embodiments in
which the amount of melt spinnable polyolefins is from
about 3 to about 8.5 percent by weight based on the
total weight of the fiber.
Surprisingly, it has been discovered that in the
fiber of this invention the polyolefins are not
uniformly dispersed throughout the polyester continuous
phase. Rather, the concentration of the melt spinnable
polyolefins at or near the surface of the fiber is
higher than the concentration of the melt spinnable
polyester at or near the surface of the iber. The
result is a fiber which when used in a iber ~ilter
element has a higher capacity and efficiency as compared
to polyester fibers which do not contain melt spinnable
polyolefins. As used herein "at or near" the surface of
the fiber is at least about 50 Rof the fiber surface.
In the preferred embodiments of this invention, the
weight percent of the polyolefin component in the
portion of the fiber forming a sheath about all or a
portion of the longitudinal axis of the fiber said
sheath having a thickness of at least about 50 Ais at
least about 50 weight percent based on the total weight
of the sheath. In the particularly preferred
embodiments of the invention, the amount of polyolefins
--ll--
contained in said sheath is at least about 80 percent by
weight based on the total weight of the sheath, and in
the most preferred embodiments the amount of polyolefins
contained in the sheath is at least about ~5 weight
percent to about 98 weight percent being the amount of
choice.
Various other optional ingredients, which are
normally included in polyester fibers, may be added to
the mixture at an appropriate time during the conduct of
the processr Normally, these optional ingredients can
be added either prior to or after melting of the
polyester or polyolefin or a mixture of the polyester
and polyolefin Such optional co~ponents include
fillers, plasticizers, colorants, mold release agents,
antioxidants, ultra violet light stabilizers,
lubricants, anti-static agents, fire retardants, and the
like. These optional components are well known to those
of skill in the art, accordingly, only the preferred
optional components will be described herein in detal.
While certain cross-sections are preferred for
certain uses, in ~eneral the cross-sectional shape of
the fiber is not critical and can vary widely. The
fiber may have an irregular cross section or a regular
cross section. For example, the fiber can be flat
sheets or ribbons, regular or irregular cylinders, or
can have two or more regular or irregular lobes or vanes
projecting from the center o~ axis of the fiber, such
fibers are hereinafter referred to as "multilobal"
fibers. Illustrative of such ~ultilobal fibers are
trilobal, hexalobal, pentalobal, tetralobal, and
octalobal filament fibers. In the preferred embodiments
of the invention the fibers are filament fibers having a
multilobal cross section such that the surface area of
the fiber is maximized, such as fibers having the
representative cross-sections depicted in FIGs 1 to
10. Illustrative of such preferred fibers are those
fibers ~hich are multilobal and having at least about
three projecting lobes, or vanes or projections, and in
\
-12-
the particularly preferred embodiments of the invention
the fiber is multilobal having at least about five
projecting lobes, vanes or projections such as hexalobal
or octalobal fibers.
In the preferred embodiments of the invention in
which fibers are multilobal, the "modification ratio" of
the fiber can affect the effectiveness of the fiber as
the filter element of a filter. As used herein, the
"modification ratio" is the ratio of the average
distance from the tip of the lobes or vanes of the fiber
to the longitudinal center of axis of the fiber to the
average distance from the base of the lobes or vanes of
the fiber to the longitudinal center of axis of the
fiber. In general, the greater the modification ratio
of the fiber, the greater the effectiveness of the fiber
as a filtering element; and conversely, the less the
modification ratio of the fiber, the less its
effectiveness as a filtering element. In the preferred
embodiments of the invention, the modification ratio of
20the fiber is at least about 18, and in the particularly
preferred embodiments of the invention is from about 2
to about 7. Amongst these preferred embodiments, most
preferred are those embodiments in which the
modification ratio of the fiber is from about 2.2 to
25about 5.
In the preferred embodiments of this invention,
foamed ~ibers are implied in the fabrication of the
filter elements. Such foamed fibers can be prepared by
using conventional foaming techniques, as for example
30U.S. Patent Nos. 4,562,022, 4,544,594, 4,380,594 and
4,164,603.
The fiber of this invention is prepared by the
process of this invention which comprises:
(a) forming a molten mixture comprising as a major
35amount one or more polyesters of fiber forming molecular
weight and as a minor amount of one or more polyolefins;
and
-13-
(b) melt spinning said mixture to form a fi~er
which comprises a major amount of a continuous phase
comprising said polyesters and a minor amount of said
polyolefins non-uniformly dispersed in said continuous
phase such that the concentration of said polyolefins
at or near the surface of said fiber is greater than
the concentration of said polyesters at or near the
center of said fiber.
A molten mixture is formed in the first process
step. As used herein, "molten mixture" is an intimate
mixture which has been heated to a temperature which is
equal to or greater than the melting point of the
highest melting polymer component of the mixture or an
intimate mixture formed by melting one polymer and
dispersing the other polymer in the molted polymer.
The manner in which the molten mixture is formed is not
critical ad conventional method can be employed. For
example, in the preferred embodiments of the invention,
the molten mixture can be formed through use of
conventional polymer and additive blending means, in
which the polymeric components are heated to a
temperature equal to or greater than the melting point
of the highest melting polymer, and below the
degradation temperature of each of the polymers.
In the preferred embodiment, the components of the
intimate mixture can be granulated, and the granulated
components mixed dry in a suitable mixture, as for
example a tumbler or a Branbury* Mixer, or the iike, as
uniformly as possible. Thereafter, the composition is
30 heated in an extruder until the polymer components are
melted.
Fibers can be melt supun from the molten mixture by
conventional spinning techniques. For example, the
compositions can be melt spun in accordance with the
3~ procedures of U.S. Patent Nos. 4,454,196 and
4,410,473. Foamed fibers can be melt spun using
conventional procedures, as for example by the
procedures of U.S. Patent No,s. 4,562,022 and 4,164,603.
* Trademark
~'
,~, "~,
-14-
The fibers produced from the composition of this
invention can be employed in the many applications in
which synthetic ~ibers are used, and are particularly
suited for use in the fabrication of filter elements of
5various types of air and liquid filters, such as air and
liquid filters for industrial applications as for
example filters for internal combustion engines,
clarification filters for water and other liquids,
compressed air filters, industrial air filters and the
like employing conventional techniques. Fibers of this
invention exhibit enhanced capacity and efficiency when
are used as filter elements, as compared to polyesters
which do not include minor amounts of the polyolefin.
The fibers of this invention are also useful in the
15fabrication of coverstock. For example, such fibers can
be used as coverstock for absorbant materials in the
manufacture of diapers, incontinence pads and the like
The following examples are presented to more
particularly illustrate the invention and should not be
20construed as limitations thereon.
EXAMPLES I to VI
Fibers Containing Polyethylene Terephthalate and
Polypropylene and Containing Polyethylene
Terephthate and Polv Methvlpentene
Polyethylene terephthalate (PET) received from St.
2sJude as chopped preforms was granulated into 1/8"
(0.3175 cm) to 1/4" ~0.635 cm) pieces which were then
dried in a Stokes vacuum tray drier at 0.5 mm Hg for 16
hrs. at 160C. The dry PET was sealed in a jar along
with a polyolefin and tumbled for fifteen minutes for
30uniform blending. The anhydrous mixture was placed in
the hopper of a one inch (2.54 cm) diameter MPM extruder
which was preheated to the desired temperature profile
along the barrel of the extruder to yield a polymer melt
temperature at the exit of the extruder of about 540F
35(282 C). The screw was 1 inch (2.54 cm) in diameter
and 30 inches (76.2 cm) long with a 4:1 compression
ratio. It had a standard feed screw configuration with
a modified mixing section consisting of a four inch
-15-
(10.2 cm) long cross hatched zone located seven inches
(17.8 cm) from the end of the screw. The extruder was
equipped with a metering pump and a spinning block
containing screens (eight layers, 90, 200, 200, 200,
5200, 200, 200, 90 mesh top to bottom) and a
spinnerette. The spinnerette had twenty (20)
symmetrical hexalobal orifices, wherein each lobe has
dimension of 4 mils (0.1 mm) (width) x 25 mils (0.635
mm) (length) x 20 mils (0.508 mm) (depth). The polymer
mixture was extruded at a rate of 13 g/min. The
filaments exiting from the spinnerette orifices were
drawn down while being cooled in air to a temperature at
which the filaments did not stick to the surface of a
first take-up ro]l. Just above the first take-up roll,
15a finish was applied to the yarn to aid further
processing and to dissipate any static charge buildup.
The yarn on the first take-up roll was then drawn in
line. The yarn on the first take-up roll which turned
at 1670 rpm (2800 ft/sec) (853 m/sec) yarn speed was
20advanced to a second roll which turned at 4482 rpm (6500
ft/sec) (1981 ~/sec) and from a second roll onto a third
roll which turned also at 4482 rpm (6500 ft/sec) (1981
m/sec). The yarn was then advanced from the third roll
to a Leesona winder at 6500 ft/sec (1981 m~sec), which
25wound the yarn upon a sleeve. The temperature of the
rolls (heated by induction heating) were 120C, 160C
and 23C for rolls 1, 2 and 3 respectively. The results
are set forth in the following Table I.
TABLE I
Amount of Amount of wt~
Ex. No. ~ ) Polymer (a~ Polymer
I 1900g 100g ppl 5% PP
II 975g 259 PP 2.5~ PP
III 925g 759 PP 7.5% PP
IV 9509 50g pMp2 5% PMP
V 925g 759 PMP 7.5% PMP
VI 962,5g 37.59 PMP 3.75~ PMP
1 "PP" is spinning grade polypropylene obtained
from Soltex Corporation under the trade name Soltex*
3606.
2 "PMP" is spinning grade polymethylpentene
obtained from Mitsui Corporation under the trade name
TPX*.
COMPARATIVE EXAMPLE I
Fibers Containina Polycaprolactam and PolY~ropylene
Using the procedure of Examples I to VI, 9509 of
~pinning grade polycaprolactam obtained from Allied
Corporation under the trade name Capron~ LS~, an
grams of spinning gra~e polypropylene obtained from
SOLTEX Corporation under the trade name Soltex* 3606,
were mixed and melt spun to obtain a 15 denier fiber
containing five percent by weight of polypropylene.
COMPARATIVE EXAMPI.E II
Analysis and Determination of the Nature
o~ the Dispersion of the Components in the Fiber
A series of experiments were conducted to
illustrate the unique nature of fibers containing
polyethylene terephthalate and a polyolefin as
compared to fibers containing polycaprolactam and
such polymers. The fibers of this invention selected
for testing are those of Examples III and IV, and the
nylon based fiber selected for testing is that of
Comparative Example I. In these experiments, x-ray
Photoelectron Spectroscopy (XPS) studies were carrier
out to determine the distribution of the minor amount
of the polyolefin
* Trademark
, . ~.
-17-
in the fiber. ~rocedure employed was as followso The
above fibers were wrapped around a strip of ~olybdenum
foil in order to provide a support for mounting on the
sample holder. After introduction into the analysis
5cha~ber of the spectrometer, liquid nitrogen was passed
through the sample holder to cool the specimen to a
temperature o~ ca. -70C as measured by a thermo-
couple. The analysis was performed on a PHI Model 560
electron spectrometer using MgK radiation as the
excitation source.
In addition, spectra of the pure PET, PP, nylon and
PMP were taken for reference. Calculations of the
surface composition were based on fitting of lineshapes
of the pure components to the convoluted envelope of the
mixture. As a secondary measure of the composition,
peaks heights ratios were used for those cases involving
PET utilizing the C=O and C-H peaks for deter~ination of
the relative quantity of PET. ~greement between the two
methods of calculation was within 10~. Esti~ates of the
20sampling depth for the sa~ples are on the order of 50-
60~. In order to mini~ize decomposition under X-ray
exposure, the samples were cooled to a temperature of
ca. -70C during analysis.
The results indicated that the distribution of PP
25was substantially uniform in the fiber containing 5% PP
(bulk concentration) o~ Comparative Example I and no
segregation of PP at or near the surface regions of the
fiber was not detected. For PET/7.5~ PP fibers of
Example III, the PP concentration within that portion of
30the fiber from 50 to 60 Aof the surface was determined
to be 95-100% and the COnCeQtratiOn of PFT within this
region was from 5 to 0~. This indicated that in
contrast to the nylon/PP fiber of Comparative Example I,
the concentration of PP in that region within 60 ~of
35the surface of the fiber is greater than the
concentration of PET within that region, even though the
concentration of PET within the ~iber as a whole is very
much greater than that of PP. Similarly, for PET/5% PMP
'7
-18-
fibers of Example IV, the concentration in the region
within 60 ~ of the surface o~ the eiber was determined
to be 85-90~, while concentration of PET in this region
was 15-10~. For the present experiments, it was not
5possible to determine i~ the PP or PMP distribution is
homogeneous throughout the analysis volume or if a
concentration gradient e~isted.
EXA~PLE VII
A series of experiments were carried out to compare
the efficacy o~ the fibers of this invention as filter
mediums to the efficacy o~ polyester alone for such
use. Filter media used in these experiments were
fabricated as ~ollows:
The experimental ~ibers were crimped or texturized
and cut into staple length of ap~roximately 11/2 inch
(3.81 cm). The fibers were pre-opened on a roller top
card and blended with 3DPF 11/4 inch (3.17 cm) staple
crimped Vinyon Fibers (a copolymer binding fiber
20co~prising 85~ polyvinyl chloride 15~ polyvinyl
acetate). The blend comprising 2/3 by weight of the
experimental fiber or control fiber and 1/3 by weight of
the binder ~iber. A 6 ounce/yd2 (0.02g/cm2) air laid
batting was made on a 12 inch wide laboratory air laying
25machine known as a Rando Webber. The air laid batting
was needle locked on a needle punching machine. The
needle locked batting was then needle punched to a spun
bonded material known as DuPont's Reemay~ 2470, a 3
ounce/yd2 (O.Olg/cm2) fabric. Two control fibers were
30employed: (1) A 3,DPF trilobal cross section DuPont
Dacron~ Polyester Fiber (crimped, 11/2inch (3.81 cm)
staple length) and (2) and experimental 3DPF 100~
polyester 3 DPF hexalobal cross section ~iber crimped or
texturized and cut into a 11/2 inch (3.81 cm) staple
351ength. Both the unbacked needle locked air laid
batting, and the reemay backed batting were heat
stabilized for 5 minutes at 275F (135C) in a
mechanical convection oven prior to ~lat sheet
. ,
t7
--19--
filtration performance testing.
After fabrications the filter ~ediums were
evaluated. The properties selected for evaluation were
capacity and efficiency because these properties are
5ulti~ately deter~inative of the effectiveness of a
filter medium. The procedure employed is as follows:
On a flat sheet test apparatus, a ~/2' x ~/2" (16.5
cm x 16.5 cm) specimen was clamped. A 4 x 4 (10.16 cm x
10.16 cm) mesh screen was used to support the unbacked
test specimen; no screen was used to support the Reemay~
backed test specimen. A six inch (15.24 cm) diameter
circle of the test specimen was subjected to an air flow
of 25 CFM AC dust fine or coarse (1.0 g/in) was
interspersed into the air stream by a feeder-aspirator
mechanism. Air flow was straigtened by a horn to
produce uniform air flow velocity or laminar flow
through the specimen. A tared absolute filter
consisting of a micro glass phenolic bonded batting
classified as AF 3 1/2inch (8.9 cm) by the fiher glass
20insulation industry, 10 inches (25.4 cm) in diameter
below the test specimen was used for determining AC dust
removal efficiency. The backed specimens were run until
a 10 inch (25.4 cm) of water rise in pressure differen-
tial across the specimen is reached.
The test contaminant was a natural siliceous
granular powder obtained from the Arizona desert
classified to a speci~ic particle size distribution and
marketed by the ~C Spark Plug Division of General
Motors. The particle size distributions of the two test
30dusts are set forth in the following Table II.
-20-
Table II
AC Fine AC Coarse
Particle Particle
Size ( um) ~ Size ( ~m) %
_
5.5 <38+3 5.5 <13+3
11 <54+3 11 <24t3
22 <71+3 22 <37+3
44 <89+3 44 <56+3
88 --- 88 <84+3
176 <100 176 <100
Dust Removal efficiency of fine and coarse
particles was determined by obtaining the weight
increase of both the test specimen and the absolute
15filter:
W
Dust re~oval efficiency ~ Wl + W2 x 100
Where Wl is the weight increase of the test speci~en and
2~2 is the weight increase o~ the absolute ~ilter.
Capacity is calculated as follows:
Capacity in - W
GMS
The results o~ this evaluation are set ~orth in the
following Table III;
TA~LE III
30Filter AC Course Test Dust AC Fine Test Dust
Medium Capaclty Efflclency CaPacltV Efficlency
Polyester(l) 12.9 99.3 8.29 99.0
Polyester(2) 9.8 99.0 8.14 98.9
Example I15.34 99.3 8.17 99.0
1. The Polyester fiber is hexalobal.
2. The Polyester obtained from duPont Co. under
-21-
the tradename Dacron~ is trilobal.
COMPARATIVE EXAMPLE I~I
A series of experiments were carried out to demon-
strate that when a polyamide is substituted for a
5polyester in this invention, the polyolefin is more
uniformly dispersed which results in inferior
performance when used as a filter medium. The fiber of
this invention used in the comparison study was the
trilobal fiber prepared as described in Example I
containing polyethylene terephthalate and 5% by weight
PP, and the fiber of Comparative Example 1 containing
polypoprolactam and 5% by weight PP.
The fibers were fabricated into a ~ilter element
and evaluated in accordance with the procedure of
Example IV. The results are set forth in the following
Table III.
TABLE III
Filter AC Course Test Dust AC Fine Test Dust
Medium Capacity EfficiencY CapacitY Efficiency
20Nylon/PP 10.3 99.3 6.8 98.7
Example I lS.34 99.3 8.17 99.0
