Note: Descriptions are shown in the official language in which they were submitted.
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MnCROPOROUS ~BERS .
Field of the Invention
The present invention relates to fibers. More particularly, the invention relates to
synthetic, porous fibers which are wettable and which exhibit improved me~,hanical
5 properties.
Back~round of the Invention
Porous fibers have included stnuctures made by employing conventional phase
10 separation methods. Such methods generally involve mixing a polymer resin with a
diluent or a plasticizer, quenching the polymer solution in a liquid medium to induce
phase separation, and washing away the diluent to leave behind an interconnectedporous structure. Other porous fibers have been produced by techniques which employ
a blowing agent or a swelling agent to create a ,,,;c~uporuus structure. Still other porous
15 materials have been produced by employing an environmental crazing technique.
Conventional porous fibers, such as those described above, have not been able toprovide desired cor.,bi"~Lions of mechanicai properties and water accessihi~ity. In
addition, the techniques have not adequately produced porous fibers having desired
20 combinations of small diameter, low denier, high weLLdbiliLy, high permeability to liquid,
and high tensile strength. As a result, there has been a continued need for fibers having
improved porous structures.
Brief Desc. il.tion of the Invention
Generally stated, the present invention provides a distinctive porous fiber which
includes voids therein to achieve desired levels of wettability and liquid penetration while
still having good mechanical properties. The fiber can have a denier of not more than
about 50, and can have a percent elongation at break of not less than about 30%. The
30 fiber can also have a tensile strength at break of not less than about 200 Mpa.
In its various aspects, the porous fiber of the invention can effectively and efficiently
produce fibers having desired combinations of small size, high w~LLabiiily, high water-
accessihility, high tensile strength and high elongation. As a result, the fiber can have an
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improved ability to be further processed to form nonwoven fabrics and other articles of
manufacture.
Brief Description of the Drawin~s
The present invention will be more fully understood and further advantages will become
apparent when reference is made to the followed detailed description of the invention
and the drawings, in which:
10 Fig. 1 is a scanni,)g electron photo"~ic ug(aph, taken at a ",a~.,iricalion of 850X, showing
a representative cross-sectional view of the porous fiber of the present invention;
Fig. 2 is a scan~l;, ,g electron phoLomi-,- ugraph, taken at a magnification of 1 ,700X,
showing an enlarged view of a portion of the cross-section shown in Fig. 1;
Fig. 3 is a scanning electron photomicrograph, taken at a magnification of 250X, showing
a representative cross-sectional view of a prior art fiber which includes a lumen;
Fig. 4 is a scanui"g electron photomicrograph, taken at a "-ay..iricdLion of 8,000X,
20 showing an enlarged view of the cross-section shown in Fig. 3 at a location adjacent to
the outer surface of the fiber;
Fig. 5 is a scann ,g electron photo-~ic.ugraph, taken at a magnification of 250X, showing
a representative cross-section view of another prior art fiber which includes a lumen, and
25 was produced by an incremental sL,~Lchi-,g process;
Fig. 6 is a scanni--g electron photomicrograph, taken at a ma~"iricaLion of 5,000X,
showing an enlarged view of a portion of the cross-section shown in Fig. 5;
30 Fig. 7 is an optical photomicrograph, based on oil-immersion optical microscopy taken at
a magnification of 1500X, showing a representative view of the voids on the surface and
in the bulk of a porous fiber of the invention;
Fig. 8 is an optical photo"-k,,ugraph, based on oil-immersion optical ~ uscopy taken at
35 a magnification of 1,500X, showing another view of the voids along the surface and in
the bulk of a porous fiber of the invention;
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Fig. 9 shows a representative view of the voids along the outer surface of another porous
fiber of the invention, taken at a mayl ,iricalion of 3,000X;
5 Fig. 9A representatively shows a schematic view of particular pores shown in Fig. 9;
Fig. 10 is a scanning electron photomicrograph, taken at a ,.,a~"iricdlion of 15,000X,
providing a representative view of the surface of the fiber shown in Fig. 3;
Fig. 11 is a scannillg electron phoLc",,;~,lugraph, taken at a magnification of 15,00ûX,
providing a representative view of the surface of the fiber shown in Fig. 5;
Fig. 12 shows a backscattered electron photo~ ,ugraph, taken at a ,,,ayniricalion of
5,000X, showing a representative cross-sectional view of a fiber of the invention;
Fig. 13 shows a representative version of Fig. 12 which has been riigiti,ed for image
analysis;
Fig. 14 shows a representative, graphical plot of the gained weight of water versus time
for a porous fiber sample.
Detailed DescriPtion of the Invention
With reference to Figs. 1, 2, 7, 8, 9, 9A and 12, a porous fiber 20 includes a length-wise
dimension 44 and a generally cross-wise dimension 38. The porous fiber has a di:,lin. ~ e
configuration of voids or pores 22 therein to achieve desired levels of wei' '~ ' ~, Iiquid
penetration and other liquid acces-cihility. The fiber can have a denier (d) per fiber of not
more than about 50, and desirably has a percent elongation at break of not less than
about 30%. The fiber can also have a tensile strength at break of not less than about
200 MPa. In particular aspects of the invention, the porous fiber 54 can also include
other properties, and can include voids or pores having distinctive shapes, sizes,
distributions and configurations.
In its various aspects, the microporous fiber of the invention can provide for improved
3~ wicking can more quickly bring water or other liquid into the interior of a fibrous article,
and can accelerate the dissolution kinetics for fibrous articles which are intended to be
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flushable. In addition, the microporous fiber can help provide for improved absorbency,
improved distribution of li~uid, improved the breathability in articles, such as surgical
gowns and diapers, improved tactile and aesthetic properties, and/or enhanced
biodegradability. The fibers can be forrrled directly into nonwoven webs with
conver,lional forming prooesses, such as the well known spunbond process.
Altematively, the fiber may be cut into staple fibers, and may be blended with other fibers
for sl Ihsequent formation into nonwoven, fibrous webs employing conventional air-laying
te~l1r~ es. The nonwoven webs may be particularly useful for producing flushablepersonal care products, such as diapers, tampons, feminine pads, pantiliners, tampon
10 strings and the like.
In the various configurations of the present invention, the porous fiber 54 can be a
synthetic fiber produced from a source material which includes a thermoplastic,
orientable material, such as thermoplastic and orientable polymers, copolymers, blends,
15 mixtures, compounds and other combinations thereof. t)esirably, the thermoplastic
materials do not include highly reactive groups.
In particular arrangements of the invention, the source material can be a polyolefinic
n,ate,ial. For example, the source material may include homopolymers of polyethylene
20 or polypropylene, or may include copolymers of ethylene and polypropylene. In other
arrangements, the source material may include another polymer l"~enal, such as apolyether, a copolyether, a polyamid, a copolyamid, a polyester or a copolyester, as well
as copolymers, blends, mixtures and other combinations thereof.
25 The the~ oplasLic material is melt processible, and in particular aspects of the invention,
the material can have a melt flow rate (MFR) value of not less than about 1 g/10 minutes
(based on ASTM D1238-~). Alternatively, the MFR value can be not less than about1Qg/10 minutes, and optionally, can be not less than about 20 g/10 minutes. In other
aspects of the invention, the MFR value can be not more than 200 9/10 minutes.
30 Alternatively, the MFR value can be not more than about 100g/10 minutes, and
optionally, can be not more than about 40 g/10 minutes to provide desired levels of
process~ ity.
Such melt p,ucessible, thel"~oplastic material can, for example, be provided by a
35 homopolymer polypropylene. Commercially available polyolefins, such as HimontPF 301, PF 304, and PF 305, Exxon PP 3445, Shell Polymer E5D47, are aiso
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represenLaLi~te of suitable materials. Still other suitable materials can include, for
example, random copolymers, such as a random copolymer conLai, .i"g propylene and
ethylene (e.g. Exxon 9355 conLa;"ing 3.5 % ethylene), and homopolymers, such as
homopolymer polyethylene, which have MFR values similar to those mentioned herein.
5 The polymer resins may contain small amounts (e.g. about 0.05 to 5 parts of additive to
100 parts of resin) of processing additives, such as calcium sterate or other acid
scavengers. Other additives can include, for example, silicon glycol copolymers,organosilicone compounds, olefinic elastomers, and low molecular weight parafins or
other lubricating additives. Various pigment additives may also be incorporated. For
10 ~Xdlll, le, pigment concentrates such as a titanium dioxide pigment concentrate with low
molec~ r weight polyethylene plasticizer can be employed as a processing additive. The
various additives can have a plasticizing effect, can improve the strength and softness of
the fiber, and can help facilitate one or more of the extrusion, fiber spil Ini, ,9, and
aLIt:L11lill9 processes.
The source material for the fiber 54 can also include a further supplemental material, and
the supplemental material may include a filler material, and/or a surfactant or other
surface-active ",~Lerial. The filler material can be a particulate maLelial which can help
provide porosity-initiating, debonding sites to enhance the desired formation of pores
20 during the various ~ Lcl ~ ,9 operations applied to the fiber. The filler material can help
provide a desired suRace-modified fiber, and can help enhance a desired "sliding effect~
generated during subsequent sLI~t-,hillg operations. In addition, the filler material help
preserve the pores that are generated during the various stretching operations.
25 Where the supplemental material includes a surface-active material, such as a surfactant
or other ",~Lerial having a low surface energy (e.g. silicone oil), the surface-active
"~aLerial can help reduce the surface energy of the fiber as well as provide lubricdLion
among the polymer segments which form the fiber. The reduced surface energy and
lubrication can help create the "sliding effect" during the subsequent sl,~Lchin g
30 operations.
The supplemental filler material can be organic or inorganic, and the filler material is
desirably in the form of individual, discrete particles. The fillers may be subjected to a
surface treatment with various coatings and su, ~a.;L~nLs to impart an affinity to the
35 polymer resin in the source material, to reduce agglomeration, to improve filler
dispersion, and to provide a conL~olled interact;on with fluids, such as body fluids, blood
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orwater. i=xamples of an inorganic filler can include metal oxides, as well as hydroxides,
carbonates and sulfates of metals. Other sui~hle inorganic filler n~dlelials can include,
for e~cd,nl~le~ calcium carbonate, various kinds of clay, silica, alumina, barium sulfate,
sodium cd,Londle, talc, magnesium carbonate""ay"esium sulfate, barium ca,i onale,
kaolin, mica, carbon, calcium oxide, magnesium oxide, aluminum hydroxide, titanium
dioxide, powdered metals, glass ll,ic,uspheres, orvugularvoid-conld;. ,9 pariicles. Still
other inorganic fillers csn include those with particles having higher aspect ratios, such
as talc, mica, and wollaslv, ,ile, but such fillers may be less effective. Represel ,lali~e
organic fillers can inciude, for example, pulp powders, wood powders, c~11~ ~'.,se
10 derivatives, chitin, c.l,ilosan powder, powders of highly crystalline, high melting polymers,
beads of highly crosslinked polymers, powders of organo~ ' ~ 3nes, and the like; as well
as con,b;.,dlions and derivatives thereof.
In particular aspects of the invention, the fillers can have an average particle size which
15 is not more than about 10 microns (~lm). Alternatively, the average particle size can be
not more than about 5 ~Lm, and optionally, can be not more than about 1 ~Lm to provide
improved processibility. In other aspects of the invention, the top cut particle size is not
more than about 25 ,~Lm. Altematively, and the top cut particle size can be not more than
about 10 ~Lm, and optionally can be not more than about 4 ~lm to provide improved
20 process~hility during the formation of fibers having the desired size and porous
structure. The fillers may also be surface-modified by the incorporation of surFactants,
and /or other materials, such as stearic or behenic acid, which can be employed to
improve the process~ ity of the source material.
25 Examples of suitable filler materials can include one or more of the following:
(1) Dupont R-101 TiO2, which is available from E.l. DuPont de Nemours, and can
be sl ~pp'.ed in a conce, ILI dle form by Standrich Color Corporation, a business having
offices located in Social Circle, Georgia 30279. This material can provide good
process~ y.
(2) Pigment Blue 15:1(10 % copper), which is distributed by Standridge Color
Corporation. Fibers produced with this ~ eri~l may break more often.
(3) OMYACARB ~ UF CaCO3, which is available from OMYA, Inc., a business
having offices located in Proctor, Vermont 05765. This ~I;alerial can have a top cut
particle size of about 4 ~rn and a average particle size of about ().7~1m, and can provide
35 good processibiiity. This filler can be coated with a surfactant, such as Dow Corning 193
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surfactant, before the compoundin~ or other combining with the source material 56. The
filler can also be coated with other appropriate surfactants, such as those mentioned
elsewhere in the present description.
(4) OMYACARB ~ UFT CaCO3 coated with stearic acid, which is available from
5 OMYA, Inc. This m~lerial can have a top cut particle size of about 4 llm and a mean
particle size of about 0.7,um, and can provide good proces ~ y.
(5) SUPERCOATrM CaCO3which is available from ECC International, a business
having offices located in Atlanta, Geor~ia 30342, ~775 Peachtree-Dunwoody Road. This
material can have a top cut particle size of about 8 ,Lm and a mean particle size of
10 about 1 ~Lm. Fibers produced with this ",dl~rial may break more often.
(6) Powdered polydimethyl silses~uioxane (#22 or #23 Dow Coming Additive),
which is available from Dow Coming, a business having offices located in Midland,
Michigan 48628-0997. This material can provide good procescihility, while some
a~_1cn,e,dlions may be observed.
The suFplemental material can optionally include a surface-active material, such as a
surfactant or other material having a low surface energy (e.g. silicone oil). In particular
aspects of the invention, the surfactant, or other surface-active ",aLerial, can have a
Hydrophile-Lipophile Balance (HLB) numberwhich is not more than about 18.
20 Altematively, the HLB number is not more than about 16, and optionally is not more than
about 15. In other aspects of the invention, the HLB number is not less than about 6.
Alternatively, the HLB number is not less than about 7, and optionally the HLB number is
not less than about 12. When the HLB number is too low, there can be insufficient
w:lLdbilily. When the HLB number is too high, the su,ra~.lahl may have insufficient
25 adhesion to the polymer matrix of the source material, and may be too easily washed
away during use. The HLB numbers of commercially available SUI ra~,la"l:. can, for
example, be found in McCUTCHEON's Vol 2: Functional Materials, 1995.
A suitable surfactant can include silicon glycol copolymers, carboxilated alcohol
30 ethoxylates, various ethoxylated alcohols, ethoxylated alkyl phenols, ethoxylated fatty
esters and the like, as well as combinations thereof. Other sl lit~hle su, raclanLs can, for
example, include one or more of the following:
(1) su,ra~,Lal1ts composed of ethoxylated alkyl phenols, such as IGEPAL RC-620,
RC-630, CA- 620, 630, 720, C0-530, 61Q, 630, 660, 710 and 730, which are available
35 from Rhone-Poulenc, a business having offices located in Cranbury, New Jersey.
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(2)su,rd-,lan~scomposed of silicone glycol copolymérs, such as Dow Corning
D190, D193, FF400, and D1315, which are available from Dow Coming, a business
having omces located in Midland, ~ higan.
(3) surfactants co,nposed of ethoxylated mono- and diglycerides, such as Mazel 80
5 MGK, Masil SF 19, and Mazel 165C, which are available from PPG Industries, a
business having offices located in Gumee, lL 60031.
(4) sulrd1l;3nis cG",posed of ethoxylated alcohols, such as Genapol 26-L-98N,
Genapol 26-L-6aN~ and Genapol 26-L-5, which are available from Hoechst Celanese
Corp., a business having offices located in Charlotte, NC 28217.
(5) su.racl~nls co.l"oosed of carboxilated alcohol ethoxylates, such as Marlowet4700 and Marlowet 4703, which are available from Huls America Inc., a business having
offices located in riscaLd~vay, NJ 08854.
(6) ethoxylated fatty esters, such as Pationic 138C, Pationic 122A, and PationicSS~, which are avaiiable from R.l.T.A. Corp., a business having offices located in
Woodstock, lL60098.
The source material for the porous fiber 54 can include not less than about 0.35 wt% of
the supplemental material, where the weight percentage is determined with respect to the
total weight of the combined source material. In particular aspects of the invention, the
20 amount of supplemental l,lal~rial is not less than about 0.~ wt%, and may desirably be at
least about 1 wt%. Alternatively, the amount of supplemental material is not less than
about 5 wt%, and optionally is not less than about 10 wt%. In other aspects of the
invention, the amount of supplemental material can be up to about 50 wt% or more. The
amount of supplemental material is desirably not more than about 30 wt%. Alternatively,
25 the amount of supplemental material can be not more than about 20 wt% and oplionally
can be not more than about 15 wt% to provide desired p,~,cessiL,il;ly chc,rdcLe~ ics.
In particular aspects of the invention, the source material can include not less than about
0.35 wt% of the filler material. In particular aspects of the invention, the amount of filler
30 material is not less than about 0.5 wt%. Alternatively, the amount of filler material is not
less than about 1 wt%, and optionally is not less than about 5 wt%. In other ~spectc of
the invention, the amount of filler material can up to about 50 wt% or more. The amount
of flller material may desirably be not more than about 30 wt%. Alternatively, the amount
of filler material can be not more than about 20 wt% and optionally can be not more than
35 about 10 wt%.
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In further aspects of the invention where the supplemental ~I,aLe,ial includes a surface-
active material, the amount of surface-active male~ ial, such as s~" r~-,lant, may be at least
about 0.1 wt%. Alternatively, the amount of surface-active ",dLe,ial is at least about
5 1 wt%, and oplionalJ~, is at least about 3 wt%. In other aspects of the invention, the
amount of surface-active material is not more than about 20 wt%. Alternatively, the
amount of surface-active material is not more than about 15 wt%, and optionally, is not
more than about 10 wt%.
10 A s~ lit~hle technique for forming the porous fiber 54 is described in U.S. Patent
Appl ~ ~"on Serial No. 08/697,996 entitled METHOD AND APPARATUS FOR MAKING
MICROPOROUS FIBERS WITH IMPROVED PROPERTIES, filed September 4, 1996 by
F. J. Tsai et al. (attorney docket No. 12,242), the entire disclosure of which is hereby
incorporated by reference in a manner that is consi~l~nt (not in contradiction) herewith.
Conventional porous fibers have often included lumens therein. The lumen is typically a
bore extending through a tube of fiber material, as representatively shown in Figs. 3 and
5. Accordingly, the lumen typically provides a hollow fiber in which the ratio of the outer
diameter of the tube to the diameter of the bore can be within the range of 50:1 to 50:48.
20 Fibers with lumens usually are more tedious to manufacture, and can be susceptible to
undesired collapse when the fibers are processed at high speeds. In addition, such
fibers have exhibited inadequate mechanical strength properties, which have made it
difficult to further process the fibers to form nonwoven fabrics.
25 The porous fiber 54 of the present invention, however, is subslanlially free of lumens. As
a result, the fiber can exhibit an increase in melt strength during the fiber formation, and
the greater melt strength can improve the in-line ~.. "~ability and stretchability of the fiber.
For example, simpler die designs can be employed to form the nascent fiber. The porous
fiber can also exhibit increased mechanical strength to provide improved dimensional
30 stability, and can exhibit other improved me~.hanical properties to f~ t~ thesl Ihsequent processing of the fiber. For example, the improved me~i ,anical properties
can improve the ability to further process the fibers to produce nonwoven fabric webs.
In its various aspects, the porous fiber 54 can also exhibit improved con,bi"dlions of
small diameter, low denier, tensile strength, elongation, and toughness (where toughness
35 is the ability to absorb energy, as described in the Dictionarv of Fiber & Textile
Technoloqv, HoechstCelanese, 1990).
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The various configurations of the porous fiber 54 can have relatively low diameter and
relatively low denier. In particular aspects, the porous fiber can have a fiber denier of not
more than about 50 . Alternatively, the porous fiber denier can be not more thanabout 20, and oplionall~/ can be not more than about 10. In other ~cr~ectC, the porous
fiber can have a denier of about 0.5, or less, and optionally can have a denier of about
0.1, or less to provide improved perfommance.
In other aspects, the tensile sLr~nglh at break of the porous fiber 54 can be not less than
10 about 200 mega-Pascal (MPa). Alternatively, the tensile strength can be not less than
about 250 MPa, and optionally can be not less than about 300 MPa. In other aspectc,
the method and apparatus of the invention can provide for a fiber tensile strength which
is not more than about 1000 mega-Pascal (MPa). Altemativeiy, the fiber tensile strength
can be not more than about 750 MPa, and optionally can be not more than about
15 450 MPa to provide improYed performance and processibility during sl~hseqLIent
manufaGturing operations.
In further aspects, the porous fiber 54 can exhibit a percent elongation to break of not
less than about 30%, as determined by the formula: (LF- Li)/ L~; where L, is the final
20 length of the fiber at break, and Lj is the initial length of the fiber prior to elongation.
Alternatively, the elongation to break can be not less than about 50%, and optionally can
be not less than about 90%. In further aspects, the method and appardLus of the
invention provides for a porous fiber 54 which can exhibit a percent elongation to break
of up to about 500%, or more. Alternatively, the elongation to break can be not more
25 than about 200%, and optionally can be not more than about 160% to provide desired
pe,rulmance attributes and processing capabilities.
In still other aspects of the invention, the porous fiber 54 can have a toughness index of
not less than about Q. 1 gram-ce- ,Li, ~ ,t:ler per denier-centimeter (g-cm/denier-cm).
30 Alternatively, the fiber toughness can be not less than about 1.5 g-cm/denier-cm, and
optionally can be not less than about 2 g-cm/denier-cm. AddiLional aspects of the
invention can provide for a porous fiber 54 which has a toughness index of not more than
about 20 g-cm/denier-cm. Altematively, the fiber toughness index can be not more than
about 10 g-cm/denier-cm, and optionally can be not more than about 5 g-cm/denier-cm to
35 provide improved performance. The toughness index represents the ability of the fiber to
absorb energy, and is determined by multiplying the fiber tenacity times the fiber
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elong~Lion-at-break, and then dividing by 2. For example, a typical c~ tion would be
(grams load-at-break x elongation-at-break)/(denier x 2), and may have the units of
(grams-cm)/(denier-cm)
5 ~Su ' ' le testing techniques for obtaining the data for delelllli, l;~ lg the various mechanical
properties of the porous fiber are further described in the Test Procedures section, set
forth hereinbelow.
The porous fiber 54 can advantageously provide improved water accessi~ ty. In
10 particular aspects of the invention, the water uptake rate of the porous fiber 54 can be
not less than 0.1 mg/sec. Alternatively, the water uptake rate can be not less than about
0.15 mg/sec, and optionally can be not less than about 0.2 mglsec. In other as~e.;L:" the
water uptake rate can be not more than about 15 mg/sec. Altematively, the water uptake
rate can be not more than about ~ mg/sec, and optionally can be not more than about
15 1.5 mg/sec to provide improved benefits. In comparison, a norlporuus fiberwill have a
water-uptake rate of less than 0.1 mg/sec, as illustrated by Examples 8, 9 and 10 set
forth hereinbelow.
In addition, the water-uptake amount of the porous fiber 54 can be not less than 0.1 mg
20 in 60 sec. Alternatively, the water uptake amount can be not less than about 0.2 mg in
60 sec, and optionally can be not less than about 0.3 mg in 60 sec. In other aspects, the
water uptake amount may be not more than about 25 mg in 60 sec. Alternatively, the
water uptake amount can be not more than about 5 mg in 60 sec, and optionally can be
not more than about 2.5 mg in 60 sec to provide improved benefits. In CG~ arisOn, a
25 nonporous fiberwill have a water-uptake amount of less than 0.1 mg in 60 sec, as
illustrated by Examples 8, 9 and 10 set forth below.
Suitable testing techniques for obld;";ng the data for determining the various water
accessiLllity properties of the porous fiber are further described in the Test Procedures
30 section, set forth below.
A plurality of the voids or pores 52 which impart the desired porosity to the fiber 54 can
be distributed over the outer surface of the fiber and can also be distributed through the
interior of the fiber. In particular aspects, the porous stnucture of the fiber 54 includes
35 elongate voids of generally ellipsoidal and/or double-conical shape, such as those
representatively shown in Figs. 7, 8, 9 and 9A. Desirably, the elongate voids 52 have
11
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their long, major axes 46 aligned substantially along a length-wise, iongitudinal
dimension 44 of the fiber. In particular aspects of the invention, the elongate voids can
have a major axis 46 wherein the length 42 of the major axis is not less than about
0.1,um. Alternatively, the major axis length is not less than about 0.2~m, and optionally is
not less than about 0.25,um. In other aspects, the length of the major axis is not more
than about 30,um. Alternatively, the major axis length 42 is not more than about 1 O~um,
and optionally is not more than about 7,um to provide improved pe~ ru~ ance~
To help provide for the desired combination of mechanical strength and water
10 ~Ccescihility~ particular aspects of the invention have fibers in which the voids of desired
pore size dimensions constitute at least about 30% of the total number of pores on either
or both of the fiber outer surface or fiber cross-section. Alternatively, the voids of the
desired pore size dimensions constitute at least about 50%, and optionally constitute at
least about 60% of the total number of pores on either or both of the fiber outer surface
15 or fiber cross-section.
In further aspects of the porous fibers of the invention, the voids having a maior axis
length within the range of about 0.25 - 10 um constitute at least about 30% of the total
number of pores on either or both of the fiber outer surface or fiber cross-section.
20 Alternatively, the voids of the 0.25 - 10 ,um pore size dimensions constitute at least about
50%, and opLionally constitute at least about 60% of the total number of pores on either
or both of the fiber outer surface or fiber cross-section to provide improved mechanical
and water accessibility properties.
25 The elongate pores or voids can also have an aspect ratio value which is determined by
the ratio of the length 42 of the pore major axis 48 to the length 40 of a pore minor
axis 46 which is aligned perpendicular to the major axis, as observed in the
phoLc"": Uyl dph or other imaging or measuring mecha,1is", employed to determine the
aspect ratio. In further aspects of the invention, the aspect ratio is not less than
30 about 1.3. Alternatively, the aspect ratio is not less than about 1.5, and oplionally is not
less than about 2. In other aspects, the aspect ratio is not more than about 50.Alternatively, the aspect ratio is not more than about 20, and optiol-ally is not more than
about 15 to provide improved porosity .:hdldcLeristics and fiber pe, rùl ",ance. The major
axis of each elongate pore or void is typically an axis aligned sul,sLantially along the
35 longitudinal dimension of the fiber, and can typically be represented by the largest length
measurement of each pores.
12
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As illustrated in Figs. 7, 8, 9 and 9A, the porous structure of the fiber 54 can have pores
distributed along the outer surface of the fiber. The surface pores have a distribution
with a pore number per unit of outer surface area of not less than about 0.01 /,um2.
5 Altematively, the pore number per unit of outer surface area is not less than about
Q.015 /I~mZ, and optionally is not less than about 0.05 /,um2. In further aspects, the pore
number per unit of outer surface area is not more than about 10 /,um2. Altematively, the
pore number per unit of outer surface area is not more than about 8 /,um2, and opLionF'~y
is not more than about 5 /,um2 to provide improved wt:lLdbiliLy and liquid penel~dlion.
As illustrated in Figs. 1, 2, 12 and 13, the porous structure of the invention, with respect
to the cross-sectional area of the fiber 54, can exhibit pore voids with an average pore
area (per pore) of not less than about 0.001 micron2 (,um2). Altematively, the average
pore area (per pore) is not less than about 0.002 ,um2, and optionally is not less than
15 about 0.03 ,um2 . In other aspects, the average pore area (per pore) is not more than
about 20 ,um2. Alternatively, the average pore area (per pore) is not more than about
10 l~m2, and optionally is not more than about 3 ,um2 to provide improved ~Llat "Ly and
liquid penetration.
20 The porous stnucture of the fiber 54 can also have pores distributed along its cross-
sectional area to provide a pore number per unit area which is not less than about
0.01/um2. Altematively, the pore number per unit of area is not less than about
0.015/,um2, and optionally is not less than about 0.1/,um2. In other aspects, the pore
number per unit area is not more than about 1 0/~um2. Alternatively, the pore number per
25 unit area is not more than about 8/um2, and optionally is not more than about 5/,um2 to
provide improved welldbiliL~I and liquid penetration.
In further aspects, the porous structure of the fiber 54 has pores distributed along the
fiber cross-section wherein a sum of the areas of the individual, cross-sectioned pores
30 provides a total pore area which not less than about 0.1% of the total area encompassed
by the cross-sectioned fiber (a percent pore area of not ~ess than about 0.1%).
Alternatively, the percent pore area is not less than about 1%, and optionally is not less
than about 2%. In other aspects, the percent pore area is not more than about 70%.
Altematively, the percent pore area is not more than about 50~/0, and optionally is not
35 more than about 20% to provide improved wettability and liquid penetration.
13
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With reference to Figs. 1, 2, 9, 9A and 12, particular aspects of the porous fiber can
include a plurality of voids or pores which are mainly initiated at structural irregularities or
other physical non-homogenities of the fiber material, and which are stretched and
5 expanded therefrom. Such initiator, structural non-homogenities can be provided by one
or more of the following meci-anis"~s: particulate filler/polymer resin interfaces, density
and/or modulus fluctuations in a fiber materiai, submicron size voids and/or air bubbles,
any type of inclusions having a modulus and /or density which varies from that of the
fibem.,~L~rial, as well as corlJh..,aLions of the mechanisms. More particularly, the fiber
10 can desirably include a plurality of stretched or otherwise extended voids wherein each of
the voids can be assouidl~d with a particulate initiator 50 provided by a rllal~lial
composed of a multiplicity of individual particles, such as a particulate filler material.
The pores or voids can subslal llially surround the initiators or can be immediately
15 adjacent to the il lilidlor~. The pores may also be located in the areas bet\,veen individual
in;tialur:,. Additionally, each of the extended voids can have a length which is larger than
a length of its associated initiator, as observed when viewing the voids in a length-wise
section taken along the fiber length. With respect to a direction along the fiber length,
the voids can have a sub~l~"Lially elongated elliptical shape, andlor may have a20 sub5Ldl ,lially double-cone configuration with the two cones arranged base-to-base. With
respect to a cross-section taken perpendicular to the fiber length, the voids can have a
generally spherical shape or a slightly oval or egg shape. In a particular aspect of the
microporous fibers of this invention, substantially no specific pattem or regular
arrangement of the voids is observed in a surface view or other lengthwise view of the
25 fiber. In another aspect, substantially no specific pattem or regular arrangement of the
voids is observed in a representative cross-sectional view of the fiber. Accordingly, the
a,l~ngement of the voids in the fiber material can be irregular, and may be suL,~ ,';-'ly
random, with some irregular clustering. For example, there may be such clustering in the
areas of agglomeration of any incorporated filler material. The observed stnucture of the
30 porous fiber of the invention can have a broad pore size distribution in a particular cross-
section of the fiber due to scattered pore distributions and the nature of the changing,
tapering cross-sections of the pores along the length of the fiber. The elongated shapes
(e.g. elliptical or double-conical shapes) of the voids and the lack of specific void
distribution patterns can clearly differentiate microporous fiber structure of this invention
35 from the porous fibers obtained by a phase separation method or by other sL, ~Luhil lg
CA 022~7862 1998-12-lO
W O 98/03706 PCTAJS97/10715
methods such as the incremental sL~ t:tchi, l9 method employed for producing CELGARD
microporous fibers.
In a surface view of a CELGARD fiber at a "~ay,lifiGalion of 15 000X as ,c:p,~se,lLdLi~ely
5 shown in Fig. 11 numerous Ill;.,lupOl~S of generally oval or rectangular-like shape are
arranged into strips of generally planar microporous zones aligned app,uxi,,,~Lely along
the direction perpendicular to the fiber length. These strips of microporous zones are
further arranged into arrays in which the strips occur in a nearly periodic regular fashion.
10 With ~efer~nce to Figs. 3 4 and 10 a porous fiber obtained by a conver,lional phase
sepa,~Lion method includes a sponge-like system of pores or voids separated by
relatively thin walls The system is assembled into a lacy interconnected structure which
defines the pores with membrane-like walls. In the shown configuration the system
forms layers of finger-like macrovoids located adjacent to the hollow fiber lumen. The
15 arrangement of the voids particularly along the fiber cross-section provides for a
s~b:,L~nLially regular array. With reference to Fig. 10 the surface of the fiber appears
subsLarlLially nonporous undera ,lla~niricaLion of 15 000X.
In conLIasL particular aspects of the porous fiber of the invention can include pores
20 bounded by tensile-stressed elongated regions which can for example be provided by a
plastic defol",aLion in the fiber material. The stressed regions can be observed at least
along boundary edges of the extended surface voids present on the exposed oute""osL
surface of the fiber. In the porous fiber of the invention the edge boundaries and edge
perimeters of the fiber material are angular sharply defined subsLd"Lially nonfilamented
25 and substantially non-spongiform in the areas surrounding the extended elongated void.
Accordingly, the voids are effectively bounded by fiber material having such boundary
edges and these boundary edges may be observed along any or all of the surface view
cross-sectional view or bulk view of the fiber. The fiber material in the regions observed
between the voids generally has the form of a plateau interrupted by the voids.
Suitable techniques for obtaining the data for determining the various pore sizeproperties and pore distributions of the porous fiber are further described in the Test
Procedures section set forth below.
,
CA 022~7862 1998-12-10
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Testinq Procedures
Mec,l,anicai Properties:
5 A suitable technique for determining the mechanical properties of the porous fiber 54 can
employ a Sintech tensiie tester (SINTFCH 1tD) and Testworks 3.03 software. The
tensile tester is a device available from MTS System Co., a business having offices
located in Cary, NC 27513. The software is available from MTS System Co., Sintech
Division, a business having offices located in Cary, NC 27513. Equipment and software
10 having su~ala~.lially equivalent cal~kililies may also be employed.
Mecha,~i_al properties can be evaluated with the tensile tester using its fiber-testing
configuration. The testing is conducted with a 10 pound (44.5 N) load cell, and air
actuated, rubber coated 3 inch (7.6 cm) grips. The fiber testing is conducted with a 2 inch
(5.08 cm) gauge length and a 500.00 mm/min crosshead speed. A single sample fiber is
loaded perpendicular to and in the center of the grips, and is held in place when air
pressure closes the grips together. The diameter of the fiber is inputted by the user
before beginning the tensile testing. For the hollow fiber s~""~l~s, such as those shown
in Examples 11 and 12, the annular cross-sectional area,7~ ((outer radius)2 - (inner
20 radius)2), was used for the calculation of the tensile strength. In each experiment, the
fiber is stretched until breakage occurs, and the equipment software or other equipment
proy~d~ lg creates a stress-versus-strain plot and c~culat~s the desired mechanical
properties for the sample. The mechanical properties can include, for example, Young's
modulus, stress at break, and % strain or elongation at break.
Water accese ' l~
A suitable technique for determining the comparative water accessil-ility properties of the
fiber can employ a CAHN DCA 322 microbalance, a device which is available from ATI
30 (Analytical Technology, Inc.), a business having office located in Madison, Wl. The
balance is sensitive to force changes as liKle as 0.1 micrograms and is equipped with two
weighing positions (the "A" loop and the "B" loop), and a tare position (the "C" loop). The
"A" loop can support a maximum load of 1.5 grams and the "B" loop can support a load of
3.5 grams. Thus, the A loop has better sensitivity while the B loop can support a heavier
35 load. It is understood that the operator will select the loop which provides the greater
measurement sensitivity while also remaining c~r~le of measuring the maximum load
16
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WO 98/03706 PCT~US97/10715
expected during the testing. The fiber testing for the ex~,o?ios set forth herein was
conducted on the "A" loop of the balance. Each fiber sample has a sufficient length (e.g
about 15 mm) which allows the fiber to be operabiy taped or otherwise secured along
and against a hanging wire or similar support to provide a test sample. In the test
sample, a 5 mm length of the support wire and its adjacenLly held fiber sampie extends
below the tape and remains exposed and available for contact with the water during
testing.
The CAHN system includes a movable stage which can be l~anslaLed at a steady rate up
10 and down. The test sample is hung from or otherwise mounted onto the selected loop of
the balance, and a beaker of water is placed on the moveable stage. The stage isbrought up so that the lower edge of the sample is just above the water surface, and the
test is begun. Software, which is provided with the CAHN system, conL,ols the
experiment in accordance with parameters which are input by the user. For the fiber
15 testing, the test sample is installed on the balance, and the balance is tared to provide a
measure of water uptake as the sample is in contact with the water. The software is
instructed to collect force readings at one second intervals. A 2 mm length of the
exposed portion of the test sample is immersed into the water, and the stage is stopped.
The test sample is left in the water for 1 minute as the software collects force readings at
20 the one second intervals. The test sample is then pulled back out of the water.
The data collected from an experiment is then evaluated. In particular, the data can be
exported into suitable spreadsheet software, such as ~l~i.,,usc,~( Exce/ ver~Jon 5.0, and
processed to generate a plot of wei~ht versus time for the 1 minute soak in the water.
25 The plot shows the trend of water uptake for the test sample, and provides a convenient
basis for co, npa, i"g the relative water uptake pe, ru" "ance and the relative levels of
water a-~e s ~ ' ."ly of different fiber samples. To allow a better co" ,parison between
sd"~Fles of different size fiber, the plotted data of the weight gain as function of time for
the different samples were normalized based on a fiber having a weight of 0.0416 mg.
30 The norm~'i~tion factor was the ratio of the dry weight of the tested fiber to 0.0416 mg.
The water uptake rate is determined at the two-second time mark of the curve generated
by plotting the no""ali~ed weight increase versus the amount of elapsed time during the
one minute soaking period. The water uptake rate shown in the examples was
determined by c~lculating the slope of the plotted curve at the data point recorded in the
3~ first second of the data measurement, as representatively shown in Fig. 14. The water
uptake amount listed in the examples was the total weight gain recorded at the 1 minute
17
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W 098/03706 PCTrUS97/10715
(60 sec) time of measurement in the data plot. It should be noted that the measured and
recorded weight gain may include a weight gain due to the water absorbed into the initial
porous stnJcture, as well as weight gains due to other i"Lera.,Lions between the fiber and
water. For example, a coating layer of water can form on the fiber. In addition, the fiber
5 structure can swell to provide pores with increased void volume, or the fiber can
othe~wise change in configuration to provide an increased capacity for acquiring and
holding absorbed water.
Scannin~ Electron Microscopy and Imaqe Analysis:
Electron photon.:~,ùgraphs can be generated by conventional techniques which are well
known in the imaging art. In addition, the samples can be prepared for the desired
i",ay;.lg by employing well known, conventional preparation techniques.
15 Since the porous fiber of the invention can be very ductile even at low temperatures, it is
important to avoid an excessive smearing of the fiber ~aLerial wllen the fiber sample is
being cut and prepared for an imaging of the fiber cross-section. In a suitable
p,~:pa,dLion technique, the samples can, for example, be submerged in ethanol for 1 hour
and then plunged into liquid nitrogen. For the fiber cross-sections, the surfaces can be
20 prepared by cryorl~ ulo~y, such as by using a Reichert Ultracut S microtome with FCS
cryo-sectioning system (Leica, Deerfield, IL), in which a fresh 6 mm glass knife at
temperatures of -180 ~C is used. The resulting fiber can then be mounted on an
app,upriate stub and coated with gold orAu/Pd (gold/palladium). The fiber
Il u:,L,ucture can be imaged by scanning electron microscopy, such as by using a JSM
25 6400 (JEOL, Peabody, MA) scanning electron microscope with both secondary and bac.kscdLler electron detectors.
Automated image analyses of voids and fiber pores can be conducted by well known,
conventional techniques. Ex&lllples of such techni~ues are described in "APPLICATION
30 OF AUTOMATED ELECRON MICROSCOPY TO INDIVIDUAL PARTICLE ANALYSISU by
Mark S. Germani, AMERICAN LABORATORY, published by Inter"aLional Sci 3r)liliC
Communications, Inc.; and in "INTRODUCTION TO AUTOMATED PARTICLE
ANALYSIS" by T. B. Vander Wood (copyright 19g4, MVA, Inc., 550 Oakbrook Parkway
#200, Norcross, GA 30093), Proc. 52nd Annual Meetinq of the Mk,luscopv Society of
35 America. G. W. Bailey and A. J. Garratt-Reed, Eds., published by San Francisco Press.
18
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The image analyses to provide pore distribution data for Example 1 was conducted by
Materials Analytical Services, a laboratory having offices located at Norcross, GA. The
image analyses to provide pore distribution data for Example 4 was conducted by MVA,
Inc., a laboratory having offices located at Norcross, GA.
The various image analyses can, for ekd"~ le, be done with a Noran Voyager imageanalysis system employing a may"iriuc,lion of 5,000X. The data are gener~led by taking
average of a total of twelve fields. The system is avaiiable from NORAN Instnument, Inc.,
10 a business having offices in Middleton, Wl, and systems c~r~ of providing
substantially equivalent pe,~o,i"ance may also be er", '~yed. During the course of the
image analyses, the image of the porous stnucture can be digltized employing
conventional techniques. An example of a digitized image is representatively shown in
Fig. 13.
Optical Microscopy
To examine the microstructure along the outside surface of the porous fiber, optical
microscopy can be a suitable technique. In particular, conventional oil-i,l".,er:,;on optical
microscopy can be employed . With this technique, the sa""~lEs are pr~pal~d by placing
20 in an immersion oil having a refractive index (Nd) of 1.516 at 23 ~C on a glass slide, and
are coverslipped. The immersion oil can be an oil available from OLYMPUS OPTICALCO. LTD., a business having offices in Lake Success, NY. The samples are
photographed using an oil immersion 100X objective, a high-speed film, such as Kodak
Gold 400 ASA, 35 mm film, and using daylight temperature illumination. A sl l L I 'e
25 ,,,;c,uscope is a OLYMPUS BH-2 optical mic,uscope, which is available from OLYMPUS
OPTICAL CO. LTD.,, a business having offices in Lake .Success, NY. Other opticalmicroscopes and equipment having substantially equivalent c~p~hi"lies may also be
employed.
30 The following Examples are to provide a more detailed understanding of the invention.
The examples are representative and are not intended to specifically limit the scope of
the invention.
19
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W 098/03706 PCTAUS97/10715
ExamPle 1:
A resin composed of polypropylene (Himont PF301) ( 90 wt%3 and TiO2 filler particles
(SCC 4837 by Standridge Color Corporation) (10 wt%) was i"te"-,;xed with Dow Coming
5 D193 su, rdcldl ,l (6 wt%, based on the total weight of the filler and the resin) by extruding
twice through laboratory Haake twin screw extruder. The TiO2 particie size was in the
r~nge of about 0.1 to 0.5 microns (~m), as measured by a scanning electron ~ r~copy
(SEM). The concentrations of the fillers were measured by ashes analysis. The
SIJI racLa~ ,t Dow Coming D193 had a HLB number of 12.2. The fiber spinning process
10 included feeding the COIll~ ed materials into a hopper and extruding the materials
through a single-screw extruder having a length-to-cJid",eler ratio of 24 (L/D = 24/1). The
extruder had three heating zones, a metering pump, an on-line static mixer, and a
spinpack with 4 holes, each hole having a diameter of 0.3 mm. During the spinning
extrusion of the fiber, the fiber was subjected to a draw-down ratio of 40. During the
15 quenching of the fiber, the nascent fiber was pre-wetted with a first surface-active liquid
delivered through a metering coating die. The first surface-active liquid was a solution
cor"posed of isopropanol and water mixed in a ratio of 9-parts isopropanol to 1-part
water, by volume. The fiber was then stretched in air by 2X (a draw ratio of 2), followed
by sL,~tcl,ing by 1.7X (a draw ratio of 1.7) in a bath provided by a second surface-active
2Q liquid. The second surface-active liquid was a solution composed of isop~upanol and
water mixed in a volume ratio of 9-parts isopropanol to 1-part water. The fiber was then
heat-set at 80 ~C before accumulation onto a winder. The mechanical prupei lies of the
resultant porous fiber were then measured by a Sintech tensile tester, and are
su."illdli~ed in the following TABLES 1 and 2. The number of pores per l-m2 of cross-
25 section of the fiber was about 0.74 and the number of pores per IJm2 of extemal surfacewas about 0.08.
ExamPle 2:
A resin composed of polypropylene 95.3 % (Himont PF301); 1.4 % TiO2concentrate,
i"o,gar,ic filler (SCC 4837 by Standridge Color Cor~ordiion) and 3.3 wt.% of powdered
polydimethyl silsesquioxane, organic filler (Dow Coming #23 Additive); was intermixed
with 6 wt.% (based on the total weight of the resin and the filler) of a silicone glycol
surfactant ~Dow Corning D193) by extruding twice through laboratory Haake twin-screw
extruder. The particle size of the organic filler ranged from 1 to 5 ",i~,,c"~s as measured
by SEM. The combined material was then extruded through a single-screw extruder
CA 022~7862 1998-12-lO
W O 98103706 PCT~US97/10715
(UD = 24/1), which included three heating zones, an on-line static mixer, a metering
pump, and a spi"pack with 4 holes, each hole having a dialneLer of 0.3 mm. During the
spi. .ni. ,g extrusion of the fiber, the fiber was subjected to a draw-down ratio of 33.
During the quenching of the fiber, the nascent fiber was pre-wetted with a first surface-
5 active liquid delivered through a metering coating die. The first surface-active liquid was
a solution composed of 2 wt.% of a s~" racLdnl (IGEPAL RC-630) in a isoprupanol/water
solvent. The solvent was composed of isopropanol and water mixed in a volume ratio of
9-parts isopropanol to 1 -part water. The fiber was then stretched in air by 1.1 7X, and
subsequently stretched by 2X in bath provided by a second suRace-active liquid. The
10 second surface-active liquid was a solution composed of isopropanol and water mixed in
a ratio of 9-parts isopropanol to 1-part water, by volume. The fiber was then heat-set at
8~; ~C in an on-line oven before accumulation onto a winder. The mechanical properties
of the porous fiber were then measured by a Sintech tensile tester, and are summarized
in the following TABLE 1.
ExamPle 3:
A resin composed of 93.2 wt.% polypropylene (Himont PF301); 1.4 wt.% TiO2
concenl,dLe (SCC 4837 by Standridge Color Corporation) and 5.4 wt.% CaC03
20 ~Omyacarb UF from Omya Inc.), which was suriace-modified with 6 wt% (based on the
weight of the filler) of silicone glycol D193 surfactant, was intermixed by extruding twice
through a laboratory Haake twin-screw extruder. The particle sizes of the CaC03 filler
were within the range of 1 to 3 microns, as measured by SEM. The combined material
was then extruded through a single-screw extruder (i~D = 24/1), which include an on-line
25 static mixer, a metering pump, and a spinpack with 8 holes, each hole having a clia"leter
of 0.3 mm. During the spinning extrusion, the fiber was subjected to a draw-down ratio of
33. During the quenching of the fiber, the nascent fiber was pre-wetted with a first
surface-active liquid delivered through a metering coating die. The first surface-active
liquid was a solution composed of isopropanol and water mixed in a volume ratio of 9-
30 parts isopropanol to 1-part water. The fiber was then stretched in air by 1 .17X, and
subsequently stretched 2X stretching in a bath provided by a second quantity of surface-
active liquid. The second surface-active iiquid was a solution composed of 1 wt%IGEPAL RC-630 in a isopropanol/water solvent. The solvent was composed of
isop.opanol and water mixed in a volume ratio of 9-parts isopropanol to 1-part water.
35 The fiber was then heat-set at 80 ~C before accumulation onto a winder. The
CA 022~7862 1998-12-10
W 098~,.C PCTrUS97/10715
mechanical properties of the porous fiber were then measured by a Sintech tensile
tester, and are su, l " "a, i~ed in the following TABLE 1
ExamPie 4:
A resin composed of 88.8 wt% polypropylene (Himont PF301), 1.3 wt% TiO2 concentrate
(SCC 4837 by Standridge Color Corporation), and 9.9 wt% CaC03 (Omyacarb UF from
Omya, Inc.) which was surface-modified by 6 wt% (based on the weight of the filler) of
silicone glycol D193 surfactant, was intermixed by extruding twice through a laboratory
Haake twin-screw extruder. The particle sizes of the CaC03 were within the range of 1
to 3 ~ uns as measured by SEM. The combined ~"alerial was then extruded through a
single-screw extruder (L /D = 24/1), which included three heating zones, an on-line static
mixer, a metering pump, and a spinpack with 15 holes, each hole having a diameter of
0.5 mm. During the extrusion-spinning operation, the fiber was suhjer-t~d to a draw-down
ratio of 4û. During quenching, the nascent fiberwas pre-wetted with a first surfacs-active
liquid delivered through a metering coating die. The first surface-active liquid was
composed of a mixture of isopropanol and water provided at a volume ratio of 9.8-parts
of isopropanol to 0.2-parts water. The fiberwas then stretched in air by 1.5X, and
sl Ihsec~Llently stretched by 1 .4X in a bath provided by a second quantity of surface-active
liquid. The second surface-active liquid was composed of isop, c,panol and water mixed
in a volume ratio of 9-parts isopropanol to 1-part water. The fiber was then heat-set at
90 ~C with an on-line oven, followed by collecting through a web forming box. The
me~;hanical properties of the porous fiber were then measured by a Sintech tensile
tester, and are summarized in the following TABLES 1 and 2. The number of pores per
,um2 of cross-section of the fiber was about 0.19.
ExamPle 5:
A resin composed of polypropylene (Himont PF301) ( 90 wt%) and TiO2 filler particles
(SCC 4837 by Standridge Color Corporation) (10 wt%) was intermixed with Dow Corning
D193 surfactant (6 wt%, based on the total weight of the filler and the resin) by extnuding
twice through laboratory Haake twin screw extruder. The TiO2 particle size was in the
range of 0.1 to 0.5 ",;~,,uns, as measured by a scanning electron microscopy (S~M). The
concenl, dliol Is of the fillers were measured by ashes analysis. The s-, r~cldnl Dow
Coming D193 had a HLB number of 12.2. The fiber spi,)ni. ,g process included feeding
the combined materials into a hopper and extruding the materials through a single-screw
22
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W 098/03706 PCT~US97/10715
extruder having a length-to-diameter ratio of 24 (UD = 24/1). The extruder had three
heating zones, a metering pump, an on-line static mixer, and a spinpack with 4 holes,
each hole having a diameter of 0.3 mm. During the spinning extrusion of the fiber, the
fiber was subjected to a draw-down ratio of 11. During the quenching of the fiber, the
nascent fiber was pre-wetted with a first surface-active liquid delivered through a
metering coating die. The first surFace-active liquid was a solution composed ofisop,upallol and water mixed in a ratio of 9-parts isopropanol to 1-part water, by volume.
The fiber was then stretched in air by 1 .58X followed by stretching by 2.2X in a bath
provided by a second surface-active liquid. The second surface-active liquid was a
10 solution composed of isopropanol and water mixed in a volume ratio of 9-partsisoprupanol to 1-part water. The fiber was then heat-set at 80 ~C before accumulation
onto a winder. The mechanical properties of the resultant porous fiber were thenmeasured by a Sintech tensile tester, and are su~lmdli~ed in the following TABLE 1.
15 Example 6:
A resin composed of polypropylene (Itimont PF301) ( 90 wt%) and TiO2 filler particles
(SCC 4837 by Standridge Color Corporation) (~0 wt%) was intermixed with Dow Coming
D193 surFactant (6 wt%, based on the total weight of the filler and the resin) by extruding
20 twice through laboratory Haake twin screw extnuder. The TiO2 particle size was in the
range of 0.1 to 0.5 ~ uns, as measured by a scanr,;ng electron Illi~.~Uscopy (SEM). The
concenL,~Iions of the fillers were measured by ashes analysis. The surfactant Dow
Corning D193 had a HLB number of 12.2. The fiber spinning process included feeding
the combined materials into a hopper and extruding the materials through a single-screw
25 extruder having a length-to-dian~eler ratio of 24 (UD = 24/1). The extruder had three
heating zones, a metering pump, an on-line static mixer, and a sp;npac,lc with 4 holes,
each hole having a dia~eLer of 0.3 mm. During the spinning extrusion of the fiber, the
fiber was subjected to a draw-down ratio of 11. During the quenching of the fiber, the
nascent fiber was pre-wetted with a first surface-active liquid delivered through a
30 metering coating die. The first surface-active liquid was a solution composed of
isopropanol and water mixed in a ratio of 9-parts isopropanol to 1-part water, by volume.
The fiber was then sLI~t~;hed in air by 1 .17X followed by ~LIeIUI ,i"g by 1 .5X in a bath
provided by a second surface-active liquid. The second surface-active liquid was a
solution cor,.posed of isopropanol and water mixed in a volume ratio of 9-parts
35 isoprupanol to 1-part water. The fiber was then heat-set at 80 ~C before accumulation
23
CA 022~7862 1998-12-lO
W 098/03706 PCT~US97/10715
onto a winder. The mechanical properties of the resultant porous fiber were thenmeasured by a Sintech tensile tester, and are summarized in the foilowing TABLE 1.
E-xamPle 7:
A resin composed of polypropylene (Himont PF301) ( 90 wt%) and TiO2 filler pdl'- '-S
(SCC 4837 by Standridge Color Corporation) (10 wt%) was intermixed with Dow Corning
D193 surfactant (6 wt%, based on the total weight of the filler and the resin) by extruding
twice through laboratory Haake twin screw extruder. The TiO2 particle size was in the
10 range of 0.1 to 0.5 m;_~unS, as measured by a scanr,;.,g electron ",;c,uscopy (SEM). The
conce~,L(dlions of the fillers were measured by ashes analysis. The surfactant Dow
Coming D193 had a HLB number of 12.2. The fiber spinning process included feeding
the combined ,I,aLerials into a hopper and extruding the ll,~lerials through a single-screw
extruder having a length-to-diameter ratio of 24 (UD = 24t1). The extruder had three
15 heating zones, a metering pump, an on-line static mixer, and a spinpack with 4 holes,
each hole having a diameter of 0.3 mm. During the spinning extrusion of the fiber, the
fiber was subjected to a draw-down ratio of 33. During the quenching of the fiber, the
nascent fiber was pre-wetted with a first surface-active liquid delivered through a
",ete,i"g coating die. The first surface-active liquid was a solution composed of
20 isopru~ar,ol and water mixed in a ratio of 9-parts isop, upanol to 1 -part water, by volume.
The fiberwas then stretched in air by 1.17X followed by ~llelCh;~l9 by 1.5X in a bath
provided by a second surface-active liquid. The second surface-active liquid was a
solution composed of isopropanol and water mixed in a volume ratio of 9-parts
isopropanol to 1-part water. The fiber was then heat-set at 80 ~C before accumulation
25 onto a winder. The mechanical properties of the resultant porous fiber were then
measured by a Sintech tensile tester, and are sun""d,i~ed in the following TABLE 1.
Example 8:
A resin composed of polypropylene (Himont PF301 ) ( 90 wt%) and TiO2 flller pa, Licl&s
(SCC 4837 by Standridge Color Corporation) (10 wt%) was intermixed with Dow Coming
D193 su, faulanl (6 wt%, based on the total weight of the filler and the resin) by extruding
twice through laboratory Haake twin screw extruder. The TiO2 particle size was in the
range of 0.1 to 0.5 ~ U1~5, as measured by a s~ann;.,g electron microscopy (SEM). The
cûl)cenlralions of the fillers were measured by ashes analysis. The surraclant Dow
Corning ~193 had a HLB number of 12.2. The fiber spinning process included feeding
24
CA 022~7862 1998-12-lO
W O 98/03706 PCTrUS97/10715
the combined materials into a hopper and extruding the rnaleriais through a single-screw
extruder having a length-to-diameter ratio of 24 (UD = 24/1). The extruder had three
heating zones a metering pump an on-line static mixer and a spinpack with 4 holes
each hole having a diameter of 0.3 mm. During the spinning extrusion of the fiber the
5 fiber was allowed to free-fall. During the quenching of the fiber the nascent fiber was
pre-wetted with a surface-active liquid delivered through a metering coating die. The
surface-active liquid was a solution composed of isop,upa"ol and water mixed in a ratio
of 9-parts isopropanol to 1-part water by volume. The mecha~ properties of the
resultant porous fiber were then measured by a Sintech tensile tester and are
10 su",n~a,i ed in thefollowing TABLE 1.
ExamPle 9:
This sample was composed of a commercially available polypropylene staple fiber which
15 was obtained from American E~armag a business having offices located in Chariotte
North Carolina. The staple fiber had a fiber length of 38 mm and was SUI taclanl-
modified by in""e,~i"g in a solution of 10 wt% hyd,uphilic silicon glycol (Dow Coming
193) su, r~la"l in acetone for 1 hour and drying at ~0 ~C for 6 hours before testing. The
properties of the fiberwere measured and are su,.""a,i,ed in the following TABLE 1.
Example 10:
This sample was composed of a commercially available polypropylene staple fiber
having a fiber length of 38 mm and was obtained from American Barrnag a business25 having oflices located in Charlotte North Carolina. The properties of the fiber were
measured and are summarized in the following TABLE 1.
ExamPle 11:
30 This sample is a conventional porous fiber obtained from Asahi Medical Co. Ltd. a
business having offices located in Tokyo .lapan. As representatively shown in Figs. 3
4 and 10 the fiber had a lumen which extended longitudinally along the fiber length
through the fiber interior. It is believed that the porous structure in the illustrated fiber
was created by a solution spinning technique where the lumen configuration aliowed an
35 introduction of the coagulation liquid to contact the nascent fiber along both an inside
and outside surface of the fiber material. The structure has large finger-like pores within
CA 022~7862 l998-l2-lO
W O 98/03706 PCTAUS97/10715
the inner wall of the fiber and has a sponge-like configuration of lacy pores in the vicinity
of the outer wall. In addition, the fiber typically has a thin, skin layer at its outer surface,
which may prevent the penetration water into the fiber. The properties of the flber were
measured and are su~""ldli~ed in the following TABLE 1.
ExamPle 12:
This sample is another conventional porous fiber distributed under the tradenameCELGARD by Hoechst Celanese, a business having offices in Cha~lolle, North Carolina.
10 As representatively shown in Figs. 5 ,6, and 11, the fiber had a longit~c'i ,al lumen, and it
is believed that the porous stnucture of the fiberwas created by a prucess whichemployed a piurality of incremental sll~t~hillg steps. The structure, as shown in the
cross-sectional view, includes a lamellar-like structure produced by creating inter-lamellar
volume in a pre-crystalline structure. In this structure, the pore conldil Is rr,:. uriL,rils that
15 orienL~d in the length-wise direction of the fibers and joint portions which are con,~osed
of stacked lamella. The properties of the fiberwere measured and are su..,l..a~i~ed in the
following TABLE 1
Example 13:
This sample is a microporous polypropylene fiber which is shown in example 1 of
U.S.P. 4,550,123 owned by Albany Intemational, a business having offices located in
Mansfield, MA. According to the descl i~lion of example 1 in the patent, the fiber had a
denier of 8.8 d. Other properties of the fiber are listed in the following TABLE 1.
26
CA 02257862 1998-12-10
WO 98/03706 PCTrUS97/1071S
TABLE 1
Example Water- Water- Break F.long~tion Fiber Tvu~lu~
No. uptake rateuptakestressat break size index
(mg/sec) (mg per(MPa)(~/O) ~g-cm per
1 min.) denier-cm)
0.79 1.2 427 157 4.7 d 4.2
2 0.58 1.1 391 111 5.7 d 2.7
3 0.84 1.5 310 95 5.8 d 1.8
4 0.89 1.3 358 150 1.8 d 3.3
1.01 1.8 295 119 16 d 2.2
6 0.67 1.4 231 168 18 d 2.4
7 0.21 0.3 251 183 5.6 d 2.9
8 0.014 0.015 47 966 68 d 2.8
9 0.02 0.25 220 55 2.8 d 0.75
0.002 0.005 362 60 2.8 d 1.30
11 --- --- 8.4 10.1 300 0.003
microns
12 --- -- -- 51 207 300 0.65
microns
13 -- --~ 217 23 8.8 d 0.30
5 Having thus described the invention in rather full detail, it will be readily apparent that
various changes and modifications can be made without departing from the spirit of the
invention. All of such changes and modifications are contemplated as being within the
scope of the invention, as defined by the subjoined claims.
