U.S. patent application number 09/816822 was filed with the patent office on 2002-09-26 for fluid management composite.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to Seth, Jayshree.
Application Number | 20020137418 09/816822 |
Document ID | / |
Family ID | 25221701 |
Filed Date | 2002-09-26 |
United States Patent
Application |
20020137418 |
Kind Code |
A1 |
Seth, Jayshree |
September 26, 2002 |
Fluid management composite
Abstract
A composite fabric for use in dewatering high solids content
fluid materials comprising a multiplicity of corrugated strands of
compression resistant material, and one or more sheets of porous
material bonded along its length at sheet bonding locations to the
strands, some of which strands have arcuate portions projecting
from the strands between those sheet bonding locations. The
sheet-like composite may be incorporated where there is a need to
dewater high solids content fluids such as in disposable garments
such as diapers or training pants.
Inventors: |
Seth, Jayshree; (Woodbury,
MN) |
Correspondence
Address: |
Attention: William J. Bond
Office of Intellectual Property Counsel
3M Innovative Properties Company
P.O. Box 33427
St. Paul
MN
55133-3427
US
|
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
25221701 |
Appl. No.: |
09/816822 |
Filed: |
March 23, 2001 |
Current U.S.
Class: |
442/334 ;
442/327; 442/333; 442/359; 442/363; 442/364 |
Current CPC
Class: |
D04H 1/559 20130101;
Y10T 442/60 20150401; D04H 3/14 20130101; Y10T 442/607 20150401;
D04H 3/04 20130101; B32B 5/08 20130101; Y10T 442/641 20150401; Y10T
442/64 20150401; Y10T 442/608 20150401; Y10T 442/635 20150401; D04H
3/07 20130101 |
Class at
Publication: |
442/334 ;
442/327; 442/359; 442/333; 442/363; 442/364 |
International
Class: |
D04H 001/00; D04H
003/00; D04H 005/00; D04H 013/00; D04H 001/06 |
Claims
We claim:
1. A composite fabric comprising: (a) a porous backing layer; and
(b) a plurality of mutually parallel thermoplastic filaments
extending in a first direction bonded to the porous backing layer
at spaced apart bonding locations along the lengths of the
filaments where the filaments form compression resistant arcuate
portions between the bonding locations.
2. The composite fabric of claim 1 wherein the porous backing layer
is a nonwoven fibrous web formed of thermoplastic fibers.
3. The composite fabric of claim 2 wherein the fibrous backing
layer is a bonded carded web.
4. The composite fabric of claim 2 wherein the nonwoven fibrous web
has a basis weight of from 10 to 20 g/m.sup.2.
5. The composite fabric of claim 2 wherein the nonwoven fibrous web
has a basis weight of from 20 to 100 g/m.sup.2.
6. The composite fabric of claim 2 wherein the arcuate portions of
the filaments have a height from the front surface of the backing
layer of greater than 0.2 mm.
7. The composite fabric of claim 6 wherein the arcuate portions of
the filaments have a height from the front surface of the backing
layer of less than 4.0 mm.
8. The composite fabric of claim 6 wherein the filaments diameter
is from 10 to 100 mils.
9. The composite fabric of claim 6 wherein the filaments diameter
is from 10 to 50 mils.
10. The composite fabric of claim 8 wherein the filaments are
homogeneous polymers or polymer blends.
11. The composite fabric of claim 8 wherein the filaments are
multi-component filaments.
12. The composite fabric of claim 11 wherein the filaments are
sheath core filaments.
13. The composite fabric of claim 12 wherein the multicomponent
filaments have sheath layers have a melting or softening point less
than the core layer material.
14. The composite fabric of claim 8 wherein the filament is formed
at least in part of a polymer having a softening point less than
the softening point of the fiber forming the backing layer.
15. The composite fabric of claim 14 wherein the filament is a
polyolefin fiber and the backing layer is a polyolefin.
16. The composite fabric of claim 8 wherein the filaments have a
compression resistance such that it retains at least 50% of its
initial caliper under a load of at least one pound per square inch.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a liquid permeable fluid
management nonwoven composite fabric for use in filtration, fluid
transfer and absorption, for example, in disposable absorbent
articles such as diapers, adult incontinence products, sanitary
napkins and the like. The invention further relates to methods of
producing such liquid permeable composite fabrics.
[0002] It is known, for example, in European Patent No. 963 747,
that it is desirable to provide a fluid management member in a
disposable absorbent article which is able to collect and retain
low viscosity, high solid materials such as fecal matter, while
still permitting passage of liquids such as urine. In order to
manage low viscosity fecal matter the patent document proposes a
structure where a fluid permeable support has a plurality of fibers
woven into the support, which fibers project outwardly from the
support. The support is described variously as nonwoven webs,
breathable films, microporous films, apertured nonwoven webs and
the like. The fibers woven into the supporting member extend
generally greater than 1 mm above the support member, preferably
higher. The individual fibers are preferably from 15 to 30 denier
and are woven in regular intervals into arc-like forms. The woven
fibers provide the laminate composite structure with a compression
resistance of at least 30% under an applied pressure of about 1,000
newtons per cm.sup.2, most preferably, at least 50% under this
applied pressure. Also the materials are able to resume its shape
after being subjected to this type of pressure after about 30
seconds to recover by at least 50 to 85%. The fluid management
member is provided to minimize the amount of low viscosity fecal
material on the skin of the wearer, preventing movement of the
fecal material and also separating the fecal material into its
solid and liquid components allowing the liquid components to be
transported to the underlying absorbent structure.
[0003] A similar-like structure is described in U.S. Pat. No.
5,705,249. In this patent, the composite material described
includes a nonwoven onto which filaments having a diameter of 0.05
to 5 mm are deposited. The filaments can be preformed or directly
extruded onto the nonwoven. Following this, the filaments are
intermittently bonded to the nonwoven resulting in bulges, which
are created by elastic deformation of the large diameter filaments
where they are not bonded. These filaments separate the nonwoven
fabric from the wearer's skin. However no discussion of fecal
management is described relative to this material. This material is
designed solely to increase the comfort of the wearer by separating
a liquid absorbent layer or fluid transport nonwoven from the
wearer's skin.
[0004] U.S. Pat. No. 5,976,665 describes another approach to
address the problems faced by the above U.S. Pat. No. 5,705,249
patent. A nonwoven fluid transport layer or absorbent is separated
from a wearer's skin by attaching a corrugated perforated film or
nonwoven. The corrugated material is formed into a series of
wave-crests and wave-troughs. The wave-crests contact the wearer's
skin and reduce the perceived wetness of the article. However in
this patent the wave-like structure is also stated as useful in
handling the solid discharges in a diaper or menstrual discharges
in a sanitary appliance by trapping the solids in the wave-troughs.
The corrugated layer is corrugated between the annealing surfaces
of two mutually engaging corrugating cylinders and for example,
thermally bonded to the underlying layer.
[0005] It is also known in the filtration area to provide netting
or like material prior to a porous filter for dewatering high solid
content materials. Such an approach is described in U.S. Pat. No.
5,776,567, where a multilayer laminate of flexible filter material
is separate by polymeric netting that serves as a dewatering layer
for high solids content material. The filter and nesting materials
are simply laid up against one another and placed in a framing
device.
[0006] European Patent No. 976 375 describes a fecal management
member where the material structure is similar to that described in
the U.S. Pat. No. 5,976,665 patent above. A sheet of fibers,
preferably a nonwoven web, is corrugated and attached to an
additional liquid permeable web. For example, a nonwoven sheet of
fibers is fed between the enmeshed engaging portions of the mating
corrugating members and joined to a second nonwoven web by
thermally bonding the corrugated nonwoven. Additional fibers are
deposit on top of the corrugated web. Although these various
designs for fecal and fluid management members are advantageous,
there remains a need for methods and materials that can do at least
one, or more, of directly producing a fluid management member which
is flexible, allows for good bonding between the separation member
and the fluid transport member, creates a low outer surface contact
area and/or can function effectively to separate high solids
materials from liquids.
DISCLOSURE OF THE INVENTION
[0007] The present invention provides improved fluid management
composites and their method of manufacture comprising a
multiplicity of corrugated strands of resilient material and one or
more sheets of porous material intermittently bonded to the
corrugated strands. The corrugated strands have arcuate portions
projecting from the porous material between portions of the strands
that are bonded to the porous material. These corrugated strands
are resistant to compression. These fluid management composites
provides advantages when used in disposable garments such as
diapers, training pants, adult incontinence briefs or sanitary
napkin products or for dewatering high solid content fluids.
[0008] The present invention also provides novel methods for making
the fluid management composites. The fluid management composites
are well constructed for their intended end uses and yet simple and
inexpensive to manufacture. The method is also flexible affording
versatility in selecting characteristics of the fluid management
composites to be produced without major modifications of the
equipment.
[0009] According to the present invention there is provided a
method for forming a fluid management composite which comprises (1)
providing at least a sheet of porous material (e.g., a perforated
polymeric film, or a sheet of woven natural or polymeric fibers, or
a coherent nonwoven web of natural or polymeric fibers); (2)
extruding spaced generally parallel elongate strands of molten
thermoplastic material that are resilient when cooled (e.g.,
polyolefins); (3) forming the extruded stands to have arcuate
portions projecting in the same direction from spaced anchor
portions of the extruded strands; and (4) attaching the anchor
portions of the extruded strands to form a porous laminate material
with the arcuate portions of the extruded strands projecting
outward from the porous material.
[0010] By this method there is provided a novel fluid management
composite comprising a multiplicity of corrugated strands of
resilient thermoplastic material extending in a generally parallel
spaced relationship. The corrugated strands have anchor portions
bonded at first strand bonding locations to longitudinally spaced
sections of the porous material. The strands have arcuate portions
projecting between the strand bonding locations.
[0011] Extruding the strands between opposing corrugating members
generally causes the strands to flatten and form into corrugations
having arcuate portions. The spaced apart anchor portions when
joined to the porous material at the bonding locations are
flattened further or indented along the parts of the strand's
surfaces that are closely adjacent the anchor portions. The
solidified strands generally have uniform morphology along their
lengths, however the bonding locations can see a different thermal
history and have a slightly different morphology. The strands can
be pressed against the surfaces of the porous material at the
bonding locations of the anchor portion so that the strands have a
greater width between the opposite elongate side surface portions
of the strands along the bonding locations than between the bonding
locations to provide very firm attachment between the porous
material and the strands.
[0012] In the method described above for forming a fluid management
composite the forming step can comprise the steps (which can be
performed in any order and may omit some steps) of (1) providing
first and second generally cylindrical corrugating members each
having an axis and including a multiplicity of spaced ridges
defining the periphery of the corrugating member, the ridges having
outer surfaces and defining spaces between the ridges adapted to
receive portions of the ridges of the other corrugating member in
meshing relationship with the multiple strand material
therebetween; (2) mounting the corrugating members in axially
parallel relationship with portions of the ridges in meshing
relationship; (3) rotating at least one of the corrugating members;
(4) extruding the multiple strand material onto at least one
corrugating member so that the strands are fed between the meshed
portions of the ridges to generally conform the strand material to
the periphery of a first corrugating member to form the arcuate
portions of the strand material in the spaces between the ridges of
the first corrugating member and the anchor portions of the strand
material along the outer surfaces of the ridges of the first
corrugating member; and (5) retaining the formed strand material
along the periphery of one of the first corrugating members for a
predetermined distance after movement past the meshing portions of
the ridges. The extruding step includes providing an extruder that,
through a die with spaced openings, extrudes the spaced strands of
molten thermoplastic material along the periphery of a first
corrugating member within the predetermined distance. This method
allows the diameter of the strands to be easily varied by either
changing the pressure in the extruder by which the strands are
extruded (e.g., by changing the extruder screw speed or type)
and/or by changing the speed at which the first corrugating member,
is moved (i.e., for a given rate of output from the extruder,
increasing the speed the corrugating member is moved will decrease
the diameter of the strands, whereas decreasing the speed at which
the corrugating member is moved will increase the diameter of the
strands). Also, the die through which the extruder extrudes the
thermoplastic material can have an easily changeable die plate in
which are formed a row of spaced openings through which the strands
of molten thermoplastic material are extruded. Such die plates with
openings of different diameters and different spacings can
relatively easily be formed by electrical discharge machining or
other known methods to afford different spacings and diameters for
the strands. Varied spacing and/or diameters for the openings along
the length of the row of openings in one die plate can be used, for
example, to produce a fluid management composite which will have
greater or less compression resistance as may be required for a
given end use. Different effects can be achieved by shaping and or
modifying the die to form hollow strands, strands with shapes other
than round (e.g., square or cross-shaped) or bi- or multi-component
strands.
[0013] As indicated above, the fluid management composite according
to the present invention can further include a second set of strand
material having anchor portions thermally bonded at second sheet
bonding locations to longitudinally spaced portion of the porous
material along corresponding second elongate surface portions
thereof, and having arcuate portions projecting from the second
elongate surface portions of the elastic strands between the second
sheet bonding locations.
[0014] Using the method described above, such a second set of
strand material can be provided in the fluid management composite
in at least two different ways. One way is to form the second set
of strand material to have arcuate portions projecting in the same
direction from spaced anchor portions of the second set of strand
material; and positioning the spaced anchor portions of the second
set of strand material in closely spaced opposition to the spaced
anchor portions of the first set of strand material with the
arcuate portions of the first and second set of strand material
projecting in opposite directions so that the porous material is
fed between the anchor portions of both the first and second sets
of strand material to bond simultaneously to the anchor portions of
both the first and second sets of strand material. Another way is
to provide a second set of strand material after the first set of
strand material is bonded to the porous material and bond the
second set of strand material to at least some of the spaced apart
bond portion of the porous material.
[0015] The porous material in the fluid management composite can be
any porous material that would allow the passage of fluid into the
porous material and optional into and through the porous material.
The porous material could be a (1) polymeric perforated film (e.g.,
polypropylene, polyethylene or polyester); (2) conventional woven,
knitted, stitch bonded or like fibrous material; (3) nonwoven
fibrous materials or laminates of a porous material to a second
needle punched porous material or nonporous material. The nonwoven
fibrous material can be stabilized by bonding or entangling the
fibers each to the other such by hydroentangling, spunbonding,
thermal bonding or bonding by various types of chemical bonding
such as latex bonding, powder bonding, etc. Alternatively the
fibers could be bonded externally to a second sheet material that
has at least some mechanical stability. The fibers can be formed of
any suitable polymer or other fiber forming materials such as of
polypropylene, polyethylene, polyester, nylon, cellulose,
superabsorbent fibers or polyamides Also bi- or multi-component
fibers can be used, for example, a core of polyester and a sheath
of polypropylene can be used which provides relatively high
strength due to its core material and is easily bonded due to its
sheath material. The fibers can also be mixed or blended with
particles or other fibers of different materials or material
combinations.
[0016] The fluid management composite can be conveniently included
in a disposable garment (e.g., a disposable diaper or training
pants, adult incontinence brief or sanitary napkin product) at a
location where there is encountered fluid discharge. The fluid
management composite can be adhered to an external surface or
placed in a structure between a fluid transport cover layer and a
further layer such as an absorbent layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The present invention will be further described with
reference to the accompanying drawing wherein like reference
numerals refer to like parts in the several views, and wherein:
[0018] FIG. 1 is a schematic view illustrating a first embodiment
of a method and equipment according to the present invention for
making a first embodiment of a fluid management composite according
to the present invention;
[0019] FIG. 2 is a perspective view of an embodiment of the fluid
management composite according to the present invention made by the
method and equipment illustrated in FIG. 1 and 5;
[0020] FIG. 3 is a fragmentary enlarged sectional view taken
approximately along line 3A-3A of FIG. 2;
[0021] FIG. 4 is a fragmentary enlarged top view of FIG. 2;
[0022] FIG. 5 is a schematic view illustrating a second embodiment
of a method and equipment according to the present invention for
making a second embodiment of a fluid management composite
according to the present invention;
DETAILED DESCRIPTION OF THE INVENTION
[0023] Referring now to FIG. 1 of the drawing, there is
schematically illustrated a first embodiment of a method and
equipment according to the present invention for making a first
embodiment of a fluid management composite 11 according to the
present invention which is illustrated in FIGS. 2 and 3.
[0024] Generally the method illustrated in FIG. 1 involves
providing a sheet of porous material 7; extruding spaced generally
parallel elongate strands 13 of molten thermoplastic material on a
first rotating corrugating roll 4 forming the plurality of extruded
strands 11 to have arcuate portions 14 projecting in the same
direction from spaced anchor portions 13 of the plurality strand
material; thermally bonding the anchor portions 13 of strand
material to the porous material with the arcuate portions 14 of the
strand material projecting from corresponding elongate side surface
portions of the porous material 7.
[0025] As illustrated in FIG. 1, the equipment for performing the
method includes first and second generally cylindrical corrugating
members 4 and 5 each having an axis and including a multiplicity of
spaced ridges 9 defining the periphery of the corrugating member 4
or 5, the ridges 9 having outer surfaces and defining spaces
between the ridges adapted to receive portions of the ridges 9 of
the other corrugating member in meshing relationship with the
strand material 3 therebetween; means for mounting the corrugating
members 4 and 5 in axially parallel relationship with portions of
the ridges 9 in meshing relationship; means for rotating at least
one of the corrugating members 4 or 5 so that when the strand
material 3 is fed between the meshed portions of the ridges 9 the
strand material will generally conform to the periphery of one of
the corrugating members 4 or 5 to form arcuate portions 14 of the
strand material in the spaces between the ridges 9 of a corrugating
member 4 or 5 and to form anchor portions 13 of the strand material
along the outer surfaces of the ridges 9 of a first corrugating
member 4 or 5; optionally means (e.g., including a surface of a
corrugating member 4 or 5 being roughened by being sand blasted or
chemically etched or being heated to a temperature generally in the
range of 25 to 150 Fahrenheit degrees above the temperature of the
first sheet 12 of flexible material) for retaining the strand
material along the periphery of a corrugating member 4 or 5 for a
predetermined distance after movement past the meshing portions of
the ridges 9; means in the form of an extruder feeding a die with a
changeable die plate 2 (see FIG. 1) with spaced through openings
for extruding thermoplastic material to form a multiplicity of
generally parallel elongate molten strands 13 of the thermoplastic
material extending in generally parallel spaced relationship and
for positioning the molten strands 13 along the periphery of a
corrugating member 4 within the predetermined distance. Also, that
equipment further includes a feed means such as roll 10 for feeding
the porous material to a nip between the generally cylindrical
bonding roll 6 having an axis and the corrugation member 5 carrying
the strands 3; means for rotatably mounting the bonding roll 6 in
axially parallel relationship with the corrugating members 4 and 5
with the periphery of the bonding roll 6 closely spaced from and
defining a nip with the periphery of the corrugating member 5 at a
predetermined distance from the meshing portions of the ridges 9;
optionally the bonding roll and/or the corrugating roll can be
supplied with heating means to assist in bonding the strands to the
porous material 7; and means including a nipping roller 25 for
moving the sheet-like composite 10 for a predetermined distance
around the periphery of the cooling roll 24 past the nip with the
strands 16 in contact with the cooling roll 24 to cool and solidify
the strands 16.
[0026] The structure of the sheet-like composite 10 made by the
method and equipment illustrated in FIG. 1 is best seen in FIGS. 2,
3 and 4. The fluid management composite 11 comprises the
multiplicity of generally parallel elongate strands 3 of
thermoplastic material extending in generally parallel spaced
relationship. Each of the strands 3 is generally a flattened
cylindrical or oval-like shape that is spaced from and is adjacent
another strand. The spaced anchor portions 13 of the strand are
thermally bonded at strand bonding locations 12 to longitudinally
spaced sections of the porous material 7 along its first surface
18, and the arcuate portions 14 of the strand material project from
the first surface 18 of the porous material 7 between the strand
bonding locations 12. The first strand bonding 17 locations are
spaced about at predetermined distances from each other and aligned
in generally parallel rows extending transverse to the strands 3 to
form continuous rows of the arcuate portions 14 projecting at a
predetermined first distance from the first surface 18 of the
porous material. Because the strands 13 have been extruded in
molten form the anchor portions 13 of the strand material can
generally be pressed onto the first surface 18 of the porous
material the ridges 9 on the corrugating member 5 and the periphery
of the bonding roll 6, in which case the still mobile thermoplastic
polymer strands 16 form around and are indented by the ridges 9.
The bonds between the strand 3 anchor portions 13 and the porous
material 7 at the first strand bonding locations extend along the
entire part of the strand's surfaces that are closely adjacent the
ridges 9. As is illustrated in FIG. 4, those parts of the strand's
surfaces that are closely adjacent the ridge 9 are widened along
the surfaces of the anchor portions 13 by indentations of the
strands 16 by the ridges 9. Thus the areas of bonding between the
strands 3 and the porous material can advantageously be made wider
at the strand bonding locations to increase bond levels.
[0027] Alternative structures that could be provided for the fluid
management composite include spacing the ridges 9 around the
corrugating members 4 and 5 to produce repetitive patterns of
different spacings between the anchor portions 13 of the strands 3,
thereby causing the continuous rows of the arcuate portions 14 to
project at different distances from the first surface 18 of the
porous material 7.
[0028] FIG. 5 illustrates a second embodiment of a method and
equipment according to the present invention for making a second
embodiment of a fluid management composite 31 according to the
present invention, which is generally identical in structure to the
fluid management composite shown in FIGS. 2-4. The method
illustrated in FIG. 5 is somewhat similar and uses much of the same
equipment as is illustrated in FIG. 1, and similar portions of that
equipment and product have been given the same reference numerals
and perform the same functions as they do in the equipment
illustrated in FIG. 1. In addition to the general method steps
described above with reference to FIG. 1, the method illustrated in
FIG. 5 further generally includes the step of directly extruding
the strand material 3 into the nip formed by corrugating members 4
and 5. This decreases the distance from the extruder to the bonding
roll 6 reducing or eliminating the need for additional heat to be
supplied to bonding roll 6 and/or corrugating member 5. However,
additional heat can of course be supplied if needed to increase the
bond level to a desired level. The structure of the fluid
management composite 3 made by the method and equipment illustrated
in FIG. 5 is identical to that seen in FIGS. 2-4.
[0029] The fluid management composite fabric is used primarily in
dewatering high solids content fluid materials in low flow
conditions. The product is also generally disposable where the
basis weight of the porous media and the fiber denier of the
filaments or strands are low to enhance bondability at low heat
bonding levels. These conditions are found often in personal
hygiene products such as incontinence products, baby diapers or
menstrual pads. Low flow high solids content conditions are also
possible in fluid filtration such as pool drain filters, medical
filters or the like.
[0030] The porous backing layer is a preferably a nonwoven fibrous
web formed of thermoplastic fibers such as a bonded carded web, a
spunlace fabric, a melt blown web, a spun bond web, a needletacked
nonwoven or the like. Generally the porous backing and preferably
the nonwoven fibrous web has a basis weight of from 10 to 200
g/m.sup.2, preferably from 20 to 100 g/m.sup.2. At higher basis
weights the web can become difficult to bond to the corrugated
strands and provides lower fluid passthrough. At lower basis
weights the web becomes difficult to handle and unstable in its
final use form. However additional porous support webs can be used
if desired and joined to the porous backing layer.
[0031] The filaments or strands generally are any resilient
thermoplastic material capable of being extruded, such as
polyesters, polyamides or polyolefins with polyolefin such as
polyethylenes or polypropylene polymers (including copolymers or
blends) being preferred.
[0032] The filaments can also be multi-component filaments such as
sheath core filaments where the sheath layers have a melting or
softening point less than the core layer material. This can aid in
bonding difficult to bond or incompatible strand or filament
material. Preferably the filament is formed at least in part of a
polymer having a softening point less than the softening point of
the fiber forming the porous backing layer. The composite fabric in
a preferred embodiment is one where the filament is a polyolefin
fiber and the back layer is a polyolefin.
[0033] The parallel longitudinally oriented thermoplastic filaments
are bonded to the fibrous backing layer at spaced apart bonding
locations along the lengths of the filaments where the filament
form compression resistant arcuate portions between the bonding
locations. The arcuate portion of the filaments will generally have
a height from the front surface of the backing layer of greater
than 0.2 mm but less than 4 mm, preferably from 0.5 mm to 3 mm. The
filaments generally will have a diameter of from 10 mil to 100 mil,
preferably from 10 mil to 50 mil. The web should be compression
resistant such that it retains at least 50% of its initial caliper
under a load of one pound per square inch.
EXAMPLES
Example 1
[0034] A nonwoven filter sheet composite similar to the sheet-like
composite 17 illustrated in FIG. 2 was made using equipment similar
to that illustrated in FIG. 1. A thermoplastic ethylene-propylene
impact copolymer (8 MFI) commercially available under the
designation 7C50 from the Union Carbide Corporation of Danbury,
Conn. was placed in a 51 mm single screw extruder to form the
filaments 3. About 4.7 filaments per centimeter of the 7C50
copolymer were extruded at a melt temperature of about 238.degree.
C. through 0.76 mm orifices at 17 RPM onto an upper corrugating
roll 4. The upper corrugating roll was machined to have 4 axially
parallel ridges per centimeter located completely around the
periphery of the roll with a groove between each ridge. Each ridge
was machined to have a flat top-surface having a width of about 0.7
mm. The upper corrugating roll was at about 88.degree. C. The
partially cooled strands were then corrugated in a nip formed by
the upper corrugating roll and a lower corrugating roll 5. The
lower corrugating roll (113.degree. C.) was machined with the same
ridge and groove geometry as the upper corrugating roll and was in
meshing relationship with the upper roll. A nip pressure of 100
pounds per lineal inch was used with a line speed of about 7.6
meters per minute. The corrugated strands were then bonded to a 30
gram per square meter spunbonded type polypropylene nonwoven 7
(available from Amoco Fabrics and Fibers Company of Atlanta, Ga.,
under the designation `RFX`) in a nip formed by the lower
corrugating roll 5 and a smooth metal chill roll 6. The chill roll
was maintained at about 150.degree. C. A nip pressure of 300 pounds
per lineal inch was used to bond the strands to the nonwoven. The
resulting nonwoven filter sheet composite had a basis weight of 58
grams per square meter with arcuate strand portions 11 of about 15
mm in height projecting from the nonwoven sheet 13. The composite
had a compression resistance of 93% measured as a ratio of initial
caliper and caliper under a load of one pound per square inch.
* * * * *