U.S. patent application number 16/990165 was filed with the patent office on 2020-11-26 for absorbent core for disposable absorbent article.
The applicant listed for this patent is The Procter & Gamble Company. Invention is credited to Kelyn Anne ARORA, Gary Wayne GILBERTSON, Brian Francis GRAY, Karen Denise MCAFFRY, John Richard NOEL, Jean Jianqun ZHAO.
Application Number | 20200368961 16/990165 |
Document ID | / |
Family ID | 1000005008410 |
Filed Date | 2020-11-26 |
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United States Patent
Application |
20200368961 |
Kind Code |
A1 |
ZHAO; Jean Jianqun ; et
al. |
November 26, 2020 |
ABSORBENT CORE FOR DISPOSABLE ABSORBENT ARTICLE
Abstract
A method of integrating a first fibrous web with a second
fibrous web, said method comprising the steps of: a. providing a
first absorbent fibrous web material; b. providing a topsheet
comprising a second fibrous web material; c. providing an
integrating means; and d. integrating said first absorbent fibrous
web material and said second fibrous web material by processing
through said integrating means. The step of integrating said first
absorbent fibrous web material and said second fibrous web material
comprises inter-entangling fibers from the first absorbent fibrous
web and fibers from the second fibrous web.
Inventors: |
ZHAO; Jean Jianqun;
(Cincinnati, OH) ; NOEL; John Richard;
(Cincinnati, OH) ; MCAFFRY; Karen Denise;
(Cincinnati, OH) ; GILBERTSON; Gary Wayne;
(Liberty Township, OH) ; GRAY; Brian Francis;
(Cincinnati, OH) ; ARORA; Kelyn Anne; (Cincinnati,
OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
The Procter & Gamble Company |
Cincinnati |
OH |
US |
|
|
Family ID: |
1000005008410 |
Appl. No.: |
16/990165 |
Filed: |
August 11, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15156970 |
May 17, 2016 |
10766186 |
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16990165 |
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13073185 |
Mar 28, 2011 |
9358705 |
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15156970 |
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11713992 |
Mar 5, 2007 |
7935207 |
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13073185 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B29C 43/222 20130101;
B29C 2043/464 20130101; B29K 2995/0065 20130101; Y10T 156/101
20150115; B29C 43/46 20130101; B29K 2105/04 20130101; A61F 13/15723
20130101; Y10T 156/1074 20150115; B29C 59/046 20130101; A61F
13/15699 20130101; B29C 65/02 20130101; B29K 2313/00 20130101; B29L
2031/4878 20130101; Y10T 156/1007 20150115; Y10T 156/102
20150115 |
International
Class: |
B29C 59/04 20060101
B29C059/04; A61F 13/15 20060101 A61F013/15; B29C 43/22 20060101
B29C043/22; B29C 43/46 20060101 B29C043/46; B29C 65/02 20060101
B29C065/02 |
Claims
1. A method of integrating a first fibrous web with a second
fibrous web, said method comprising the steps of: a. providing a
first absorbent fibrous web material; b. providing a topsheet
comprising a second fibrous web material; c. providing an
integrating means; and d. integrating said first absorbent fibrous
web material and said second fibrous web material by processing
through said integrating means; wherein the step of integrating
said first absorbent fibrous web material and said second fibrous
web material comprises inter-entangling fibers from the first
absorbent fibrous web and fibers from the second fibrous web.
2. The method of claim 1, wherein the integrating means is selected
from the processes consisting of creping, necking/consolidation,
corrugating, embossing, button break, hot pin punching, ring
rolling, SELF, micro-SELF, needle-punching, hydroentangling,
thermal point bonding, and rotary knife aperturing.
3. The method of claim 1, wherein one of the first fibrous web or
the second fibrous web is a pre-bonded web.
4. The method of claim 3, wherein the pre-bonded web is bonded by
combination technique selected from the group consisting of
applying latex binder and drying, thermally bonding thermoplastic
fibers in the web, hydrogen or embossed bonding or a combination
thereof.
5. The method of claim 1, wherein the first fibrous web is a
secondary topsheet.
6. The method of claim 1, wherein one of the first fibrous web or
the second fibrous web is a nonwoven.
7. The method of claim 1, wherein the first fibrous web is a tissue
layer.
8. The method of claim 1, wherein one of permeability, capillarity,
fiber type, fiber size, or combinations thereof are varied within a
layered web.
9. The method of claim 1, wherein said first absorbent fibrous web
material or said second fibrous web material is selected from the
group consisting of meltblown, spunbond, carded, wetlaid and
airlaid webs.
10. The method of claim 1, wherein the fibres of the first
absorbent fibrous web material comprise bicomponent fibers,
nano-fibers, shaped fibers, meltblown fibers, spunbond fibers,
carded web fibers, wet-laid web fibers, and combinations
thereof.
11. The method of claim 1, wherein said first or second fibrous
webs comprise an airlaid web formed of discrete layers, each said
layer comprising a different type or blend of fibers.
12. A method of integrating a first fibrous web with a second
fibrous web, said method comprising the steps of: a. providing a
first absorbent fibrous web material; b. providing a secondary
topsheet comprising a second fibrous web material; c. providing an
integrating means; and d. integrating said first absorbent fibrous
web material and said second fibrous web material by processing
through said integrating means; wherein the step of integrating
said first absorbent fibrous web material and said second fibrous
web material comprises inter-entangling fibers from the first
absorbent fibrous web and fibers from the second fibrous web.
13. The method of claim 12, wherein the integrating means is
selected from the processes consisting of creping,
necking/consolidation, corrugating, embossing, button break, hot
pin punching, ring rolling, SELF, micro-SELF, needle-punching,
hydroentangling, thermal point bonding, and rotary knife
aperturing.
14. The method of claim 12, wherein one of the first fibrous web or
the second fibrous web is a pre-bonded web.
15. The method of claim 14, wherein the pre-bonded web is bonded by
combination technique selected from the group consisting of
applying latex binder and drying, thermally bonding thermoplastic
fibers in the web, hydrogen or embossed bonding or a combination
thereof.
16. The method of claim 12, wherein the first fibrous web is a
topsheet.
17. The method of claim 12, wherein the first fibrous web is a
tissue layer.
18. The method of claim 12, wherein one of permeability,
capillarity, fiber type, fiber size, or combinations thereof are
varied within a layered web.
19. The method of claim 12, wherein said first absorbent fibrous
web material or said second fibrous web material is selected from
the group consisting of meltblown, spunbond, carded, nonwoven,
wetlaid and airlaid webs.
20. The method of claim 12, wherein the fibres of the first
absorbent fibrous web material comprise bicomponent fibers,
nano-fibers, shaped fibers, meltblown fibers, spunbond fibers,
carded web fibers, wet-laid web fibers, and combinations thereof.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to absorbent cores for
disposable absorbent articles such as sanitary napkins and
disposable diapers.
BACKGROUND OF THE INVENTION
[0002] Disposable absorbent articles such as disposable diapers and
feminine hygiene articles are well known in the art. Such articles
are designed to absorb exudates from the wearer's body. Disposable
absorbent articles typically have a fluid permeable body contacting
layer called a topsheet, a fluid impermeable layer called a
backsheet joined to the topsheet, and an absorbent layer referred
to as an absorbent core sandwiched between the topsheet and
backsheet. In operation fluid exiting the wearer's body enters the
disposable absorbent article through the topsheet and is stored in
the absorbent core. The backsheet prevents any excess fluid that is
not absorbed from exiting the disposable absorbent article. For
disposable absorbent articles like sanitary napkins intended to be
worn with other clothing, the backsheet can be a garment-facing
layer, and typically aids in preventing soiling of the
clothing.
[0003] Other elements can be included in disposable absorbent
articles, including additional absorbent layers having structures
designed for certain functions. For example, a secondary topsheet
can be an absorbent layer placed between the topsheet and the
absorbent core, and having a structure designed to wick fluid
quickly away from the topsheet and into the absorbent core.
Likewise, multiple layers of absorbent cores can be used, each
layer having fluid handling properties designed to securely move
fluid into the absorbent core for secure storage. Additionally,
each layer of absorbent core material can itself be a layered or
laminate structure having discrete layers as is known in the art of
air laying webs using multiple air laying heads or beams. In a
layered absorbent core material, any one discrete layer can
comprise a different type or blend of fibers with respect to one
other discrete layer.
[0004] It is known to design absorbent cores having a structure
such that fluid movement from the topsheet toward the backsheet,
i.e., away from the wearer's body, is facilitated. For example,
fibrous layered absorbent cores in which the capillarity of the
fibrous layers is increased with each layer are known. Likewise, it
is known to have layered absorbent cores wherein with each
succeeding layer in a direction away from the topsheet the
permeability is decreased. In this manner, fluid entering through
the topsheet first encounters a layer having high permeability and
low capillarity to facilitate quick fluid uptake. From this first
layer, the fluid can encounter a layer having less permeability and
higher capillarity, such that the fluid continues to move away from
the topsheet, but at a slower rate. This is generally acceptable
because once the fluid is away from the wearer's body the rate at
which it moves to other portions of the absorbent core is not
critical.
[0005] In known absorbent cores there is a well-known tradeoff
between the permeability of a material and its capillarity. In
general, known materials that are relatively higher in permeability
are relatively lower in capillarity, and vice versa. For disposable
absorbent articles, in which it is desirable to have both
parameters uncoupled, a positive change in one of these parameters
results in a corresponding negative change in the other. Because
permeability directly affects a material's acquisition rate and
capillarity directly impacts the movement of fluid due to limits in
capillary pressure, this tradeoff in properties has, in the past,
resulted in an absorbent core chosen for a balance of properties.
The necessary tradeoff, however, has resulted in absorbent
structures, including absorbent cores, in which the desired levels
of acquisition rate and effective fluid movement to secure storage
cannot be achieved simultaneously.
[0006] Accordingly, it would be desirable to have an absorbent
article and an absorbent core material in which both permeability
and capillarity pressure can be maintained at desirable levels
simultaneously in an absorbent core.
[0007] Additionally, it would be desirable to have an absorbent
article and an absorbent core material in which the negative
aspects of either of permeability or capillarity pressure when one
or the other is more optimized, are minimized.
[0008] Further, it would be desirable to have an absorbent article
and an absorbent material in which the tradeoff between
permeability and capillarity pressure is managed such that
delivering relatively higher permeability can be accomplished
without a decrease in capillarity pressure.
SUMMARY OF THE INVENTION
[0009] A method of integrating a first fibrous web with a second
fibrous web is disclosed. The method includes the steps of: a.
providing a first absorbent fibrous web material; b. providing a
topsheet comprising a second fibrous web material; c. providing an
integrating means; and d. integrating said first absorbent fibrous
web material and said second fibrous web material by processing
through said integrating means. The step of integrating said first
absorbent fibrous web material and said second fibrous web material
comprises inter-entangling fibers from the first absorbent fibrous
web and fibers from the second fibrous web.
[0010] Also disclosed is a method of integrating a first fibrous
web with a second fibrous web. The method includes the steps of: a.
providing a first absorbent fibrous web material; b. providing a
secondary topsheet comprising a second fibrous web material; c.
providing an integrating means; and d. integrating said first
absorbent fibrous web material and said second fibrous web material
by processing through said integrating means. The step of
integrating said first absorbent fibrous web material and said
second fibrous web material comprises inter-entangling fibers from
the first absorbent fibrous web and fibers from the second fibrous
web.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a partial cut-away perspective view of a sanitary
napkin embodying the present invention.
[0012] FIG. 2 is a schematic representation of a process for
mechanical modification of web materials through a nip of a pair of
inter-meshing rolls.
[0013] FIG. 3 is schematic representation of a pair of
inter-meshing rolls of a process commonly referred to as
ring-rolling.
[0014] FIG. 4 is an enlarged, fragmentary, cross-sectional view
showing the interengagement of teeth and grooves of respective
rolls of a ring-rolling apparatus as shown in FIG. 3.
[0015] FIG. 5 is an even further enlarged view of a ring-rolling
apparatus as shown in FIG. 3 showing several interengaged teeth and
grooves with a web of material therebetween.
[0016] FIG. 6 is schematic representation of a pair of
inter-meshing rolls of a process commonly referred to a SELF
process.
[0017] FIG. 7 is a schematic representation of a process for
modifying a web by the SELF process.
[0018] FIG. 8 is a schematic representation of a web after it has
passed between a pair of inter-meshing SELF rolls.
[0019] FIG. 9 is a pattern that can be produced in an absorbent
material by passing the material between a pair of inter-meshing
SELF rolls.
[0020] FIG. 10 is a pattern that can be produced in an absorbent
material by passing the material between a pair of inter-meshing
SELF rolls.
[0021] FIG. 11 is a side view of a roll for use in a micro-SELF
process.
[0022] FIG. 12 is a perspective representation of roll for use in a
micro-SELF apparatus.
[0023] FIG. 13 is an enlarged perspective representation of the
teeth on a micro-SELF roll.
[0024] FIG. 14 is a schematic representation of a rotary knife
apparatus (RKA) and process.
[0025] FIG. 15 is a portion of one embodiment of a roller of a
rotary knife apparatus, the roller having a plurality of teeth
useful for making an apertured web.
[0026] FIG. 16 is an enlarged perspective representation of one
embodiment of teeth on the toothed roll of a rotary knife
apparatus.
[0027] FIG. 17 is a side view of a SELF roll showing typical
dimensions useful in some embodiments of the present invention.
[0028] FIG. 18 is a cross-sectional view of the roll shown in FIG.
17, taken along line 18-18, showing typical dimensions useful in
some embodiments of the present invention.
[0029] FIG. 19 is a cross-sectional view of the teeth of a SELF
roll showing typical dimensions useful in some embodiments of the
present invention.
[0030] FIG. 20 is an enlarged side view of the teeth of the roll
shown in FIG. 17, showing typical dimensions useful in some
embodiments of the present invention.
[0031] FIG. 21 is a flat layout view of an SELF roll having a
staggered tooth pattern and showing typical dimensions useful in
some embodiments of the present invention.
[0032] FIG. 22 is a cross-sectional view of a portion of the SELF
roll shown in FIG. 20, taken along line 22-22.
[0033] FIG. 23 is an enlarged plan view of some of the teeth of the
SELF roll shown in FIG. 20 showing typical dimensions useful in
some embodiments of the present invention.
[0034] FIG. 24 is a partial perspective view showing one embodiment
of teeth on an RKA roll, and showing typical dimensions useful in
some embodiments of the present invention (in mm).
[0035] FIG. 25 is a plan view of the teeth of an RKA roll as shown
in FIG. 24, and showing typical dimensions useful in some
embodiments of the present invention (in mm).
[0036] FIG. 26 is a cross-sectional view of teeth on an RKA roll of
FIG. 24 taken along line 26-26 of FIG. 25, and showing typical
dimensions useful in some embodiments of the present invention (in
mm).
[0037] FIG. 27 is a cross-sectional view of teeth on an RKA roll of
FIG. 24 taken along line 27-27 of FIG. 24, and showing typical
dimensions useful in some embodiments of the present invention (in
mm).
[0038] FIG. 28 is a side view of a SELF roll suitable for the
present invention.
[0039] FIG. 29 is a view of the outer surface of the SELF roll
shown in FIG. 28.
[0040] FIG. 30 is a schematic detail of the teeth of the roll shown
in FIGS. 28 and 29, and showing typical dimensions (in inches).
[0041] FIG. 31 is a partial perspective view showing one embodiment
of teeth on an RKA roll, and showing typical dimensions useful in
some embodiments of the present invention (in mm).
[0042] FIG. 32 is a plan view of a portion of the RKA roll shown in
FIG. 31, and showing typical dimensions useful in some embodiments
of the present invention (in mm).
[0043] FIG. 33 is a partial cross-sectional view of 33-33 in FIG.
32 showing one embodiment of teeth on an RKA roll, and showing
typical dimensions useful in some embodiments of the present
invention (in mm).
[0044] FIG. 34 is a side view showing the teeth in FIG. 31, and
showing typical dimensions useful in some embodiments of the
present invention (in mm).
[0045] FIG. 35 is a partial perspective view showing one embodiment
of teeth on an RKA roll, and showing typical dimensions useful in
some embodiments of the present invention (in mm).
[0046] FIG. 36 is a plan view of a portion of the RKA roll shown in
FIG. 35, and showing typical dimensions useful in some embodiments
of the present invention (in mm).
[0047] FIG. 37 is a partial cross-sectional view of 37-37 in FIG.
36 showing one embodiment of teeth on an RKA roll, and showing
typical dimensions useful in some embodiments of the present
invention (in mm).
[0048] FIG. 38 is a side view showing the teeth in FIG. 35, and
showing typical dimensions useful in some embodiments of the
present invention (in mm).
[0049] FIG. 39 is a schematic representation of a web of the
present invention.
[0050] FIG. 40 is a schematic representation of a web of the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0051] One embodiment of the invention is an absorbent core having
utility as the fluid storage component of a disposable absorbent
article, such as a feminine hygiene article. One embodiment of a
feminine hygiene article of the present invention, a sanitary
napkin 10, is shown in perspective view in FIG. 1. While the
invention is disclosed in FIG. 1 as an embodiment of a sanitary
napkin 10, the disclosed features of the invention can also be
useful when incorporated in other feminine hygiene articles, such
as incontinence pads and pantiliners. Therefore, the description
below is in the context of a sanitary napkin, but it is applicable
to feminine hygiene articles in general. Likewise, the absorbent
core of the present invention can find utility in other disposable
absorbent articles, including disposable diapers, adult incontinent
devices, hemorrhoid treatment pads, bandages, and the like. Still
further, the structure produced by the methods and apparatus
disclosed herein can find utility in other webs for which surface
texture of heterogeneous fiber structure is beneficial, such as
wipes, scouring pads, dry-mop pads (such as SWIFFER.RTM. pads), and
the like.
[0052] Sanitary napkin 10 can be considered in three regions, two
end regions 12 and 14 each comprising about one-third of the
overall length, and a middle region 16. Sanitary napkin 10 has a
body-facing surface (or side) 15 that is in contact with the user's
body during use and a garment-facing surface (or side) 17 that is
in contact with the user's undergarment during use. In general,
each component layer of the sanitary napkin 10 can be said to have
a body-facing side and a garment-facing side, the sides being
determined by their orientation relative to the in-use orientation
of the article. Sanitary napkin 10 has a longitudinal centerline L
and a transverse centerline T, the centerlines being perpendicular
to one another in the plane of the sanitary napkin when in a flat
out configuration, as shown in FIG. 1. In one embodiment the
sanitary napkin can be generally symmetric about both centerlines,
while in other embodiments the sanitary napkin can be generally
asymmetric about either centerline. In the embodiment shown in FIG.
1, sanitary napkin 10 is symmetric about the longitudinal
centerline L and symmetric about transverse centerline T. Feminine
hygiene articles can also be provided with lateral extensions known
in the art as "flaps" or "wings" (not shown in FIG. 1) intended to
fold over and cover the panty elastics in the crotch region of the
user's undergarment.
[0053] Sanitary napkin 10 can have any shape known in the art for
feminine hygiene articles, including generally symmetric
"hourglass" shaped as shown in FIG. 1, or tapering inwardly from a
relatively greater transverse width in a portion of one of the end
regions to a relatively smaller transverse width at the middle
region, such that the maximum transverse width of one end, e.g.,
end region 12, of the pad is greater than the maximum transverse
width of the other end, e.g., end region 14. Transverse width is
defined herein as the edge-to-edge dimension across the article,
measured parallel to the transverse centerline T. Such pads can be
described as pear shaped, bicycle-seat shaped, trapezoidal shaped,
wedge shaped, or otherwise described in a manner that connotes a
two-dimensional shape having two ends in which one end is larger
than the other in a maximum width dimension.
[0054] Sanitary napkin 10 can have an absorbent core 20 to absorb
and store bodily fluids discharged during use. In some embodiments
of sanitary napkins, pantiliners, incontinence pads, or other such
devices of the present invention, an absorbent core is not
necessary, the pad consisting only of a topsheet (that can have
some absorbency) and a fluid impermeable backsheet. Absorbent core
20 can be formed from any of the materials well known to those of
ordinary skill in the art. Examples of such materials include
multiple plies of creped cellulose wadding, fluffed cellulose
fibers, wood pulp fibers also known as airfelt, textile fibers, a
blend of fibers, a mass or batt of fibers, airlaid webs of fibers,
a web of polymeric fibers, and a blend of polymeric fibers.
[0055] In one embodiment absorbent core 20 can be relatively thin,
less than about 5 mm in thickness, or less than about 3 mm, or less
than about 1 mm in thickness. Thickness can be determined by
measuring the thickness at the midpoint along the longitudinal
centerline of the pad by any means known in the art for doing while
under a uniform pressure of 0.25 psi. The absorbent core can
comprise absorbent gelling materials (AGM), including AGM fibers,
as is known in the art.
[0056] Absorbent core 20 can be formed or cut to a shape, the outer
edges of which define a core periphery 30. The shape of absorbent
core 20 can be generally rectangular, circular, oval, elliptical,
or the like. Absorbent core 20 can be generally centered with
respect to the longitudinal centerline L and transverse centerline
T. The profile of absorbent core 20 can be such that more absorbent
is disposed near the center of the absorbent article. For example,
the absorbent core can be thicker in the middle, and tapered at the
edges in a variety of ways known in the art.
[0057] Absorbent core 20 can be an airlaid core of the type
disclosed in U.S. Pat. No. 5,445,777; or 5,607,414. Absorbent core
can comprise a high capacity and highly absorbent core material of
the type generally referred to as HIPE foams, such as those
disclosed in U.S. Pat. Nos. 5,550,167; 5,387,207; 5,352,711; and
5,331,015. In one embodiment, the absorbent core can have a
capacity after desorption at 30 cm of less than about 10% of its
free absorbent capacity; a capillary absorption pressure of from
about 3 to about 20 cm; a capillary desorption pressure of from
about 8 to about 25 cm; a resistance to compression deflection of
from about 5 to about 85% when measured under a confining pressure
of 0.74 psi; and a free absorbent capacity of from about 4 to 125
grams/gram. Each of these parameters can be determined as set forth
in U.S. Pat. No. 5,550,167, issued Aug. 27, 1996 to DesMarais. One
advantage of utilizing the airlaid or HIPE foam cores as disclosed
is that the absorbent core can be made very thin. For example, an
absorbent core of the present invention can have an average caliper
(thickness) of less than about 3 mm, or less than about 2 mm, and
the thickness can be less than about 1 mm.
[0058] To prevent absorbed bodily exudates from contacting the
wearer's garments, sanitary napkin 10 can have a liquid impermeable
backsheet 22. Backsheet 22 can comprise any of the materials known
in the art for backsheets, such as polymer films and film/nonwoven
laminates. To provide a degree of softness and vapor permeability
for the garment-facing side of sanitary napkin 10, backsheet 22 can
be a vapor permeable outer layer on the garment-facing side of the
sanitary napkin 20. The backsheet 22 can be formed from any vapor
permeable material known in the art. Backsheet 22 can comprise a
microporous film, an apertured formed film, or other polymer film
that is vapor permeable, or rendered to be vapor permeable, as is
known in the art. One suitable material is a soft, smooth,
compliant, vapor pervious material, such as a nonwoven web that is
hydrophobic or rendered hydrophobic to be substantially liquid
impermeable. A nonwoven web provides for softness and
conformability for comfort, and can be low noise producing so that
movement does not cause unwanted sound.
[0059] To provide for softness next to the body, sanitary napkin 10
can have a body-facing layer, referred to herein as topsheet 26.
Topsheet 26 can be formed from any soft, smooth, compliant, porous
material which is comfortable against human skin and through which
fluids such as urine or vaginal discharges can pass. Topsheet 26
can comprise fibrous nonwoven webs and can comprise fibers as are
known in the art, including bicomponent and/or shaped fibers.
Bicomponent fibers can comprise polypropylene (PP) and polyethylene
(PE) in known configurations, including core/sheath, side by side,
islands in the sea, or pie. Shaped fibers can be tri-lobal,
H-shaped in cross section, or any other known cross-sectional
shape. Topsheet 26 can also be a liquid permeable apertured polymer
film, such as an apertured film, or an apertured three-dimensional
formed film as is known on sanitary napkins such as ALWAYS.RTM.
brand sanitary napkins.
[0060] At least one, and preferably both, of topsheet 26 and
backsheet 22 define a shape, the edge of which defines an outer
periphery 28 of the sanitary napkin 10. In one embodiment, both
topsheet 26 and backsheet 22 define the sanitary napkin 10 outer
periphery 28. The two layers can be die cut, as is known in the
art, for example, after combining all the components into the
structure of the sanitary napkin 10 as described herein. However,
the shape of either topsheet 26 or backsheet 22 can be
independently defined.
[0061] Disposable absorbent articles can include a lotion, skin
care ingredients, fragrances, odor control agents, and other
components. In one embodiment, a lotion that can include a skin
care composition can be added by spraying, extrusion or slot
coating to a topsheet. The skin care composition can be hydrophilic
or hydrophobic, and can have from about 0.001% to about 0.1% by
weight of hexamidine, from about 0.001% to about 10% by weight of
zinc oxide, from about 0.01% to about 10% by weight of niacinamide,
and a carrier such as petrolatum. The lotion can include glycols,
including poly propylene glycol, either in a compound or neat.
Lotions and skin care agents can be those described in co-owned and
co-pending U.S. Ser. No. 10/152,924, filed on May 21, 2002, U.S.
Ser. No. 09/968,154, and U.S. Ser. No. 10/152,924, filed on May 21,
2002.
[0062] Interposed between the absorbent core 20 and topsheet 26 can
be at least one fluid permeable secondary topsheet 24. Secondary
topsheet 24 can aid in rapid acquisition and/or distribution of
fluid and is preferably in fluid communication with the absorbent
core 20. In one embodiment, the secondary topsheet 24 does not
completely cover the absorbent core 20, but it can extend laterally
to core periphery 30. In one embodiment, topsheet, secondary
topsheet, or the absorbent core can be layered structures, the
layers facilitating fluid transport by differences in fluid
transport properties, such as capillary pressure. In one embodiment
secondary topsheet can function primarily as an absorbent core
layer and can be considered to be one of a multiple layer absorbent
core system.
[0063] Each web of absorbent core material can itself be a layered
structure having discrete layers as is known in the art of air
laying webs using multiple air laying heads or beams. In a layered
absorbent core material, any one discrete layer can comprise a
different type or blend of fibers with respect to one other
discrete layer.
[0064] In one embodiment, absorbent core 20 does not extend
laterally outward to the same extent as either topsheet 26 or
backsheet 22, but the sanitary napkin 10 outer periphery 28 can be
substantially larger than the core outer periphery 30. In this
manner, the region of sanitary napkin 10 between the core periphery
30 and the sanitary napkin 10 outer periphery 28 can define a
breathable zone that permits vapors to go through portions of the
sanitary napkin, thereby escaping and providing for dryer comfort
when worn. A sanitary napkin having a breathable zone can be
according to the teachings of U.S. Ser. No. 10/790,418, filed Mar.
1, 2004.
[0065] All the components can be adhered together by means well
known in the art with adhesives, including hot melt adhesives, as
is known in the art. The adhesive can be Findlay H2128 UN or Savare
PM 17 and can be applied using a Dynafiber HTW system.
[0066] As is typical for sanitary napkins and the like, the
sanitary napkin 10 of the present invention can have panty
fastening adhesive 18 disposed on the garment-facing side 17 of
backsheet 22. Panty fastening adhesive 18 can be any of known
adhesives used in the art for this purpose, and can be covered
prior to use by a release paper 19, as is well known in the art. If
flaps or wings are present, panty fastening adhesive can be applied
to the garment facing side so as to contact and adhere to the
underside of the wearer's panties.
[0067] The above disclosure is meant to give a general description
of the basic parts of feminine hygiene articles such as sanitary
napkins and the like as they are known in the art. The description
is not intended to be limiting. Any and all of various known
elements, features and processes of known sanitary napkins,
pantiliners, sanitary napkins, and the like can be incorporated in
the feminine hygiene article of the present invention as desired or
needed for commercial manufacture, or for particular use benefits.
For example, sanitary napkins can be according to the disclosure of
U.S. Pat. No. 4,950,264 issued to Osborn III Aug. 21, 1990, and an
incontinence pad can be according to the disclosure of U.S. Pat.
No. 5,439,458 issued to Noel et al. Aug. 8, 1995.
[0068] The present invention utilizes absorbent materials that for
sanitary napkins can include a secondary topsheet and/or an
absorbent core that have been modified from an as-made state to
exhibit higher permeability without a corresponding decrease in
capillary pressure, such that the secondary topsheet and/or core of
the present invention provides for faster acquisition rates and
greater retained capacity relative to the unmodified material, and
with respect to known materials. These desirable properties can be
imparted to known fibrous web materials by forming them by one or
more of known formation means, such as by known methods for making
extruded nonwoven webs and airlaid fibrous webs. Without being
bound by theory, it is believed that the modifications disclosed
herein produce modifications of the base web in the form of
relatively small, localized, discrete regions of increased
permeability, which together with the substantially unmodified
regions, produce an average, or "macro" effect of a web in which
the either the permeability or capillary pressure can be improved
without the expected negative impact on the other.
[0069] In one aspect, known absorbent web materials in an as-made
can be considered as being homogeneous throughout. Being
homogeneous, the fluid handling properties of the absorbent web
material are not location dependent, but are substantially uniform
at any area of the web. Homogeneity can be characterized by
density, basis weight, for example, such that the density or basis
weight of any particular part of the web is substantially the same
as an average density or basis weight for the web. By the apparatus
and method of the present invention, homogeneous fibrous absorbent
web materials are modified such that they are no longer
homogeneous, but are heterogeneous, such that the fluid handling
properties of the web material are location dependent. Therefore,
for the heterogeneous absorbent materials of the present invention,
at discrete locations the density or basis weight of the web is
substantially different than the average density or basis weight
for the web. The heterogeneous nature of the absorbent web of the
present invention permits the negative aspects of either of
permeability or capillarity pressure to be minimized by rendering
discrete portions highly permeable and other discrete portions to
have high capillarity. Likewise, the tradeoff between permeability
and capillarity pressure is managed such that delivering relatively
higher permeability can be accomplished without a decrease in
capillarity pressure. The heterogeneous web of the present
invention appears to uncouple the permeability/capillarity pressure
tradeoff. The formation means and the absorbent core materials made
thereby are described below.
[0070] Four formation means known for deforming a generally planar
fibrous web into a three-dimensional structure are utilized in the
present invention to modify as-made absorbent materials into
absorbent materials having relatively higher permeability without a
significant corresponding decrease in capillary pressure. Each of
the four formation means disclosed herein are disclosed as
comprising a pair of inter-meshing rolls, typically steel rolls
having inter-engaging ridges or teeth and grooves. However, it is
contemplated that other means for achieving formation can be
utilized, such as the deforming roller and cord arrangement
disclosed in US 2005/0140057 published Jun. 30, 2005. Therefore,
all disclosure of a pair of rolls herein is considered equivalent
to a roll and cord, and a claimed arrangement reciting two
inter-meshing rolls is considered equivalent to an inter-meshing
roll and cord where a cord functions as the ridges of a mating
inter-engaging roll. In one embodiment, the pair of intermeshing
rolls of the instant invention can be considered as equivalent to a
roll and an inter-meshing element, wherein the inter-meshing
element can be another roll, a cord, a plurality of cords, a belt,
a pliable web, or straps. Likewise, while the disclosure of four
formation means is illustrated herein, other known formation
technologies, such as creping, necking/consolidation, corrugating,
embossing, button break, hot pin punching, and the like are
believed to be able to produce absorbent materials having some
degree of relatively higher permeability without a significant
corresponding decrease in capillary pressure.
[0071] The first formation means useful in the present invention is
a process commonly referred to as "ring rolling". Referring to the
drawings, and particularly to FIG. 2 thereof, there is
schematically illustrated at 32 apparatus and a method for
modifying the physical and performance properties of a web by the
process commonly referred to as ring rolling, for example, a
nonwoven web 34 that is carried on and that is drawn from a supply
roll 36. For absorbent core materials, such as air laid nonwoven
webs, the ring rolling apparatus and method can produce a
physically modified web having improved fluid handling properties
and modified dimensions that may serve to improve both the
performance and the fit of disposable articles that incorporate
such modified materials. Additionally, after being modified in the
disclosed apparatus and after having acquired the desired physical
properties hereinafter described, such modified nonwoven webs are
capable of further processing, if desired, whether alone or
together with other materials, and without the modified nonwoven
web experiencing disintegration, rupture, or loss of integrity.
[0072] Referring again to FIG. 2, nonwoven web 34 is withdrawn from
supply roll 36 and travels in the direction indicated by the arrow.
Nonwoven web 34 is fed to the nip 38 formed by a pair of opposed
forming rolls 40 and 42 that together define a first forming
station 6. The structure and relative positions of forming rolls 40
and 42 of first forming station 50 are shown in an enlarged
perspective view in FIG. 3. As shown, rolls 40 and 42 are carried
on respective rotatable shafts 44, 46, having their axes of
rotation disposed in parallel relationship. Each of rolls 40 and 42
includes a plurality of axially-spaced, side-by-side,
circumferentially-extending, equally-configured ridges 52 that can
be in the form of thin fins of substantially rectangular cross
section, or they can have a triangular or an inverted V-shape when
viewed in cross section. If they are triangular, the vertices of
ridges 52 are outermost with respect to the surface of rolls 40 and
42. In any configuration, the outermost tips of the teeth are
preferably rounded, as shown in greater detail in FIGS. 4 and 5, to
avoid cuts or tears in the materials, such as nonwoven web 34, that
pass between the rolls.
[0073] The spaces between adjacent ridges 52 define recessed,
circumferentially-extending, equally configured grooves 54. The
grooves 54 can be of substantially rectangular cross section when
the teeth are of substantially rectangular cross section, and they
can be of inverted triangular cross section when the teeth are of
triangular cross section. Thus, each of forming rolls 40 and 42
includes a plurality of spaced ridges 52 and alternating grooves 54
between each pair of adjacent teeth. The teeth and the grooves need
not each be of the same width, however, and preferably the grooves
have a larger width than that of the teeth, to permit the material
that passes between the interengaged rolls to be received within
the respective grooves and to be locally stretched, as will be
explained hereinafter.
[0074] FIG. 4 is an enlarged, fragmentary, cross-sectional view
showing the interengagement of ridges 52 and grooves 54 of the
respective rolls. Ridges 52 have a tooth height TH and are spaced
apart from one another by a preferably uniform distance to define a
tooth pitch P. As shown, ridges 52 of one roll extend partially
into grooves 54 of the opposed roll to define a "depth of
engagement", E, as shown in FIG. 4. The respective axes of rotation
of rolls 40 and 42 are spaced from each other such that there is a
predetermined space or gap between the opposed sidewalls of the
interengaged teeth and grooves of the respective rolls. Also shown
is the tooth angle TA, which is the angle formed by adjacent
teeth.
[0075] FIG. 5 is an even further enlarged view of several
interengaged ridges 52 and grooves 24 with a web 25 of material
therebetween. As shown, a portion of a web, which can be nonwoven
web 34 as shown in FIG. 1, is received between the interengaged
teeth and grooves of the respective rolls. The interengagement of
the teeth and grooves of the rolls causes laterally spaced portions
of web 34 to be pressed by ridges 52 into opposed grooves 54. In
the course of passing between the forming rolls, the forces of
ridges 52 pressing web 34 into opposed grooves 54 impose within web
34 tensile stresses that act in the cross-web direction. The
tensile stresses can cause intermediate web sections 58 that lie
between and that span the spaces between the tips of adjacent
ridges 52 to stretch or extend in a cross-web direction, which can
result in a localized reduction of the web thickness at each of
intermediate web sections 58. For nonwoven webs, including airlaid
webs, the stretching can cause fiber reorientation, a reduction in
basis weight, and or controlled fiber destruction in the
intermediate web sections 58.
[0076] Although the portions of web 34 that lie between the
adjacent ridges are locally stretched, the portions of the web that
are in contact the tips of the ridges may not undergo a similar
degree of extension. Because of the frictional forces that exist
between the surfaces at the rounded outer ends of ridges 52 and the
adjacent areas 60 of web 34 that are in contact with the ridge
surfaces at the outer ends of the ridges, sliding movement of those
portions of the web surfaces relative to the ridge surfaces at the
outer ends of the ridges is minimized. Consequently, in some cases,
the properties of the web 34 at those areas of the web that are in
contact with the surfaces of the ridge tips changes only slightly,
as compared with the web property changes that occur at
intermediate web sections 58.
[0077] Because of the localized cross-web stretching of web 34 that
has taken place, with the consequent increase in web width, the web
material that exits from the forming rolls can have a lower basis
weight than that of the entering web material, provided the exiting
material remains in a substantially flat, laterally extended state.
The laterally-stretched web as it exits from between the forming
rolls may contract laterally to its original width, in that the web
is placed under some tension in the web movement direction, in
which case the exiting, modified web may have the same basis weight
as it had in its entering condition. If, however, the exiting web
is subjected to a sufficiently high web machine direction tension,
the exiting web can be made to contract to a smaller width than its
original width, in which case the web will have a greater basis
weight than its original basis weight. On the other hand, if the
web is subjected to sufficient additional cross-web stretching by
passing the modified web between so-called Mount Hope rolls,
tentering frames, angled idlers, angles nips, or the like as
described above, the exiting, modified web can have less than its
original basis weight. Thus, by selecting a suitable forming roll
tooth and groove configuration, by selecting a suitable web
movement direction tension level, and by selecting whether or not
to subject the web to additional cross-web stretching, the
resulting modified nonwoven web can have a web width that can range
from about 25% to about 300% of the initial web width and a basis
weight that is less than, equal to, or greater than the web's
original basis weight.
[0078] Ridges 52 can be generally triangular in cross section
having generally rounded ridge tips, as shown in FIGS. 4 and 5, and
preferably each of ridges 52 is of the same size so that each of
the opposed ridges and grooves on respective forming rolls 40 and
42 interengage with each other along the entire axial lengths of
each of the rolls. As shown ridges 66 have a ridge height RH (note
that RH can also be applied to groove depth; in one embodiment
tooth height and groove depth can be equal), and a ridge-to-ridge
spacing referred to as the pitch P. The depth of engagement E,
ridge height RH, and pitch P can be varied as desired depending on
the properties of the nonwoven webs being processed and the desired
characteristics of the processed webs. For example, in general, the
greater the level of engagement E, the greater the necessary
elongation or fiber-to-fiber mobility characteristics the fibers of
the processed web must possess.
[0079] By way of example, and not by way of limitation, ridges
having a peak-to-peak pitch P of the order of about 0.150 inches,
having sidewalls disposed at an included angle of the order of
about 120 and having a uniformly rounded ridge tip radius, and
having a tip-to-base ridge height RH (and groove depth) of the
order of about 0.300 inches can be employed in carrying out the
present invention. As will be appreciated by those skilled in the
art, the sizes of the respective ridges and grooves can be varied
within a wide range and would still be effective to carry out the
present invention. In that regard, additional structural details of
suitable forming rolls are provided in U.S. Pat. No. 5,156,793,
entitled "Method for Incrementally Stretching Zero Strain Stretch
Laminate Sheet in a Non-Uniform Manner to Impart a Varying Degree
of Elasticity Thereto," which issued on Oct. 20, 1992, to Kenneth
B. Buell et al.; in U.S. Pat. No. 5,167,897 entitled "Method for
Incrementally Stretching a Zero Strain Stretch Laminate Sheet to
Impart Elasticity Thereto," which issued on Dec. 1, 1992, to Gerald
M. Sheeter et al.; and in U.S. Pat. No. 5,518,801, entitled "Sheet
Materials Exhibiting Elastic-Like Behavior," which issued on May
21, 1996, to Charles W. Chappell et al.
[0080] The second means for deforming a web of the present
invention is a process commonly referred to as a "SELF" or
"SELF'ing" process, in which SELF stands for Structural Elastic
Like Film. While the process was originally developed for deforming
polymer film to have beneficial structural characteristics, it has
been found that the SELF'ing process can be used to produce
beneficial structures in nonwoven webs useful as absorbent core
materials, including air laid absorbent cores, as disclosed
herein.
[0081] Referring to FIG. 6, there is shown a configuration of
opposed forming rolls for use in a SELF process that can be
employed to expand portions of a nonwoven web in the web thickness
dimension, by expanding portions of the web out of the X-Y plane in
the Z-direction. As shown in FIG. 7, an unmodified nonwoven web 34
can be fed from a supply roll 36 into the nip 38 of opposed forming
rolls 62 and 64. Roll 64 includes a plurality of
circumferentially-extending, axially-spaced circumferential ridges
52 and grooves 54 similar to those described with respect to the
rolls 40 and 42 above. Roll 62 includes a plurality of
circumferentially-extending, axially-spaced circumferential ridges
52 wherein portions of the circumferential ridges 52 of roll 62
have been removed to form notches 66 that define a plurality of
circumferentially-spaced teeth 68. As shown in FIG. 6, notches 66
on respective axially adjacent circumferential ridges 52 can be
aligned laterally to define a plurality of circumferentially-spaced
groups of notched regions about the periphery of roll 62. The
respective laterally-extending groups of notched regions each
extend parallel to the axis of roll 62. Teeth 68 can have a tooth
height TH corresponding to ridge height RH, and a tooth pitch
corresponding to the ridge pitch P.
[0082] As web 34 passes through nip 38, the teeth 68 of roll 62
press a portion of web 34 out of plane to cause permanent,
localized Z-direction deformation of web 34. But the portion of the
web 34 that passes between the notched regions 66 of roll 62 and
the teeth 68 of roll 62 will be substantially unformed in the
Z-direction, i.e., the nonwoven web will not be deformed or
stretched in that area to the same degree as that of the toothed
regions, and can remain substantially planar, while the portions of
the web passing between toothed regions of roll 62 and the ridges
52 of roll 64 can be deformed or stretched beyond the elastic limit
of the nonwoven, resulting in a plurality of deformed, raised,
rib-like elements.
[0083] Referring now to FIG. 8, there is shown a schematic
representation of a portion of a SELF'ed nonwoven web 70 after it
has passed between a pair of opposed, interengaged forming rolls 62
and 64 of a SELF process, the rolls having the tooth configurations
similar to that shown in FIG. 6. SELF'ed nonwoven web 70 includes a
network of distinct regions. The network includes at least a first
region 72, a second region 74, and a transitional region 76, which
is at the interface between the first region 72 and the second
region 74. SELF'ed nonwoven web 70 also has a first surface 78 and
an oppositely-facing second surface 80. In the embodiment shown in
FIG. 8, SELF'ed nonwoven web 70 includes a plurality of
substantially flat, spaced first regions 72 and a plurality of
alternating rib-like elements 84. In the preferred embodiment of
FIG. 8, the first regions 72 and the second regions 74 are
substantially linear, each extending continuously in a direction
substantially parallel to the longitudinal axis of the web.
[0084] In the embodiment shown in FIG. 8 first regions 72 are
substantially planar. That is, the material within first regions 72
is substantially flat and is in substantially the same condition
after the modification step undergone by nonwoven web 60 by passage
between interengaged rolls 62 and 64 shown in FIG. 6 as it was in
before the web 34 was passed between the forming rolls.
[0085] In an air laid absorbent core, it has been found that the
rib-like elements 84 can beneficially be adjacent to one another
and can be separated from each other by an unformed first region 72
which can include the valleys 86 separating adjacent rib-like
elements 84. Unformed first region 72 can be areas that have
substantially the same material properties as the homogeneous air
laid absorbent core before SELF'ing, and can have a width of less
than about 0.10 inches measured perpendicular to the x-axis as
shown in FIG. 8. The dimensions of the rib-like elements can also
be varied, if desired. The rib-like elements protruding in the
Z-direction with respect to the plane of the web are raised
portions that increase the bulk or caliper of the web, without
necessarily increasing the basis weight thereof. The raised
portions also define a continuous network of channels in the
unformed first regions 72, which channels define a void region
between the surface of the web and any adjacent webs when the web
is combined into a layered absorbent core for a disposable
absorbent product, for example. In one embodiment, the continuous
network of channels can define a void region adjacent the topsheet.
The void regions can serve to provide void volume in an absorbent
core, such that the absorbent core has greater permeability, and
can handle "gushes" of fluid more effectively. An interconnected
continuous network of channels has channels running in both the MD
and the CD directions in the plane of the absorbent core. Channels
can facilitate lateral "run off" of fluid such that fluid can more
effectively be distributed across the length and width of an
absorbent core as well.
[0086] In one embodiment, the nonwoven web processed by the SELF
process described herein can be a web having absorbency
characteristics suitable for use as an absorbent core in a
disposable absorbent article. In one embodiment, the web can be an
airlaid web of fibers, including cellulosic fibers, synthetic
fibers, and blends and combinations thereof. In one embodiment, the
airlaid web can be a layered airlaid web, formed of layers in which
each layer can differ from an adjacent layer in fiber type,
density, basis weight, or combinations thereof. In one embodiment
an absorbent core material having rib-like elements formed therein
can be used in a layered relationship with a topsheet, wherein the
rib-like elements are oriented toward, and are in a contacting
relationship with, the topsheet. In one embodiment an absorbent
core material having rib-like elements formed therein can be used
in a layered relationship with a secondary topsheet, wherein the
rib-like elements are oriented toward, and are in a contacting
relationship with, the secondary topsheet. A secondary topsheet can
be what is commonly referred to as a distribution layer, which can
be an absorbent material having fluid handling properties suitable
for rapidly distributing fluid in a lateral direction.
Alternatively, in another embodiment, the rib-like elements can be
used in a layered relationship with a topsheet or secondary
topsheet, wherein the rib-like elements are oriented away from, and
are not in a contacting relationship with, the topsheet or
secondary topsheet.
[0087] In addition to the surface pattern illustrated in FIG. 8 in
the form of rib-like elements each having substantially equal
lengths and arranged in rows to define generally rectangular areas
of deformation separated by linear first regions 72, the desired
formation of a nonwoven web can, if desired, be effected by other
forming roll tooth and groove configurations that can cause
localized stretching and/or deformation of the nonwoven material.
For example, as shown in FIG. 10, instead of spaced rectangular
arrays of rib-like elements the deformation pattern can be in the
form of rib-like elements defining an array of spaced,
diamond-shaped second regions 74 with intervening undeformed first
regions 72. Each such diamond-shaped second region 74 is defined by
alternating rib-like elements 84 and intervening valleys 86.
Examples of methods and apparatus for formation of such
diamond-shaped elements are disclosed in U.S. Pat. No. 5,650,214,
entitled, "Sheet Materials Exhibiting Elastic-Like Behavior and
Soft, Cloth-Like Texture", which issued on Jul. 22, 1997, to Barry
J. Anderson, et al., and U.S. Pat. No. 6,383,431, entitled, "Method
of Modifying a Nonwoven Fibrous Web For Use as a Component of a
Disposable Absorbent Article," which issued May 7, 2002, to Dobrin,
et al.
[0088] As shown in FIG. 10, the deformation pattern can also be in
the form of rib-like elements 84 that together define an array of
spaced, circularly-shaped second regions 74. Each such circular
element can be defined by appropriately spaced, varying-length
rib-like elements 84 and intervening valleys 86. Between respective
circularly-shaped elements 108 are unformed intervening first
regions 72. As will be apparent to those skilled in the art, other
deformation patterns can also be employed, if desired, such as
those illustrated and described in U.S. Pat. No. 5,518,801.
[0089] The third means for deforming a web of the present invention
is a process that can best be described as "micro-SELF". Micro-SELF
is a process that is similar in apparatus and method to that of the
SELF process described with reference to FIGS. 6 and 7. The main
difference between SELF and micro-SELF is the size and dimensions
of the teeth 68 on the toothed roll, i.e., the micro-SELF roll 82
in FIG. 11, which corresponds to roll 62 of FIG. 6. Referring to
FIG. 11 there is shown a schematic side view representation of a
micro-SELF roll 82 that can be one of the rolls forming a nip roll
arrangement in a preferred configuration having one patterned roll,
e.g., micro-SELF roll 82, and one non-patterned grooved roll (not
shown) similar to that shown as roll 64 in FIG. 6. However, in
certain embodiments it may be preferable to use two micro-SELF roll
82 having either the same or differing patterns, in the same or
different corresponding regions of the respective rolls. Such an
apparatus can produce webs with deformations that, in nonwoven
webs, can be described as tufts or loops protruding from one or
both sides of the processed web. The tufts can be closely spaced,
but at least at their base can be spaced apart sufficiently to
define void region between tufts that permits fluid flow between
adjacent tufts. The existing between tufts can define a continuous
network of channels. In the micro-SELF roll of FIG. 11, individual
teeth 68 can have a tooth length TL of about 0.051 inch (about 1.27
mm) with a distance between teeth TD of about 0.062 inch (about
1.57 mm) and a pitch of about 0.060 inch (about 1.52 mm). In one
embodiment the circumference of roll 82 can be such that there are
158 teeth 68 separated by 159 cuts between teeth 68.
[0090] As shown in the partial perspective view of FIG. 12 and the
enlarged partial perspective view of FIG. 13, the teeth 68 of a
micro-SELF roll 82 have a specific geometry associated with the
leading and trailing edges of teeth 68 that permit the teeth to
essentially "punch" through the nonwoven web 34 as opposed to, in
essence, deforming the web into bumps or ridges as shown in FIGS.
8-10. In some embodiments of a nonwoven web 34 suitable for use in
an absorbent core, the teeth 68 urge fibers out-of-plane and to
form what can be described as "tufts" or loops of fibers. In one
embodiment, the web is punctured, so to speak, by the teeth 68
pushing the fibers through to form tufts or loops. Therefore,
unlike the "tent-like" rib-like elements of SELF webs which each
have continuous side walls associated therewith, i.e., a continuous
"transition zone," the tufts or loops forced out-of-plane in a
micro-SELF process can have a discontinuous structure associated
with the side wall portions of the Z-direction deformations.
Additionally, when utilized for relatively high basis weight
absorbent core materials, the "tufting" can be somewhat invisible
as fibers are urged out of the plane in a Z-direction with respect
to one of the web surfaces, the Z-direction deformation may be
muted or non-existent in the other web surface. Further, when a
laminate material is involved, the Z-direction deformations of one
web material may be pushed into and "hidden" by the second material
of the laminate, such that the "tufting" is essentially invisible
to the naked eye.
[0091] As shown in FIGS. 12 and 13, each tooth 68 has a tooth tip
112, a leading edge LE and a trailing edge TE. The tooth tip 112 is
elongated and has a generally longitudinal orientation. It is
believed that to get tufted, looped tufts in the processed web, the
LE and TE should be very nearly orthogonal to the local peripheral
surface 90 of roll 80. As well, the transition from the tip 112 and
LE or TE should be a sharp angle, such as a right angle, having a
sufficiently small radius of curvature such that teeth 68 push
through web 34 (as shown in FIG. 14) at the LE and TE. Without
being bound by theory, it is believed that having relatively
sharply angled tip transitions between the tip 112 of tooth 68 and
the LE and TE permits the teeth 68 to punch through nonwoven webs
"cleanly", that is, locally and distinctly, so that one side of the
resulting web can be described as "tufted" or otherwise
"deformed."
[0092] The teeth 68 of a micro-SELF roll 82 can have a uniform
circumferential length dimension TL measured generally from the
leading edge LE to the trailing edge TE at the tooth tip 112 of
about 1.25 mm and are uniformly spaced from one another
circumferentially by a distance TD of about 1.5 mm. For processing
a web having a total basis weight in the range of about 30 to about
500 gsm, teeth 110 of roll 104 can have a length TL ranging from
about 0.5 mm to about 3 mm and a spacing TD from about 0.5 mm to
about 3 mm, a tooth height TH ranging from about 0.5 mm to about 5
mm, and a pitch P between about 1 mm (0.040 inches) and about 5 mm
(0.200 inches). Depth of engagement E can be from about 0.5 mm to
about 5 mm (up to a maximum equal to tooth height TH). Of course,
E, P, TH, TD and TL can be varied independently of each other to
achieve a desired size, spacing, and area density of web
deformations.
[0093] The fourth means for deforming a web suitable for use as an
absorbent material is a process that can best be described as
"rotary knife aperturing" (RKA). In RKA, a process and apparatus
using counter-rotating meshing nip rolls 92 similar to that
described above with respect to SELF or micro-SELF rolls is
utilized, as shown in FIG. 14. As shown, the RKA process differs
from SELF or micro-SELF in that the relatively flat, elongated
teeth of a SELF or micro-SELF roll have been modified to be
generally pointed at the distal end. Teeth 68 can be sharpened to
cut through as well as deform nonwoven web 34 to produce a
three-dimensionally apertured web 94 as shown in FIG. 14. In other
respects such as tooth height, tooth spacing, pitch, depth of
engagement, and other processing parameters, RKA and the RKA
apparatus can be the same as described above with respect to SELF
or micro-SELF.
[0094] FIG. 15 shows a portion of one embodiment of an RKA toothed
roller having a plurality of teeth 68 useful for making an
apertured web 94. An enlarged view of the teeth 68 is shown in FIG.
16. As shown in FIGS. 15 and 16, each tooth 68 has a base 111, a
tooth tip 112, a leading edge LE and a trailing edge TE. The tooth
tip 112 can be generally pointed, blunt pointed, or otherwise
shaped so as to stretch and/or puncture the precursor web 34. Teeth
68 can have generally flattened, blade-like shape. Teeth 68 can
have generally flattened distinct sides 114. That is, as opposed to
round, pin-like shapes that are generally round in cross section,
teeth 68 can be elongated in one dimension, having generally
non-round, elongated cross-sectional configurations. For example,
at their base, teeth 110 can have a tooth length TL and a tooth
width TW exhibiting a tooth aspect ratio AR of TL/TW of at least 2,
or at least about 3, or at least about 5, or at least about 7, or
at least about 10 or greater. In one embodiment, the aspect ratio
AR of cross-sectional dimensions remains substantially constant
with tooth height.
[0095] In one embodiment of an RKA toothed roll, teeth 68 can have
a uniform circumferential length dimension TL of about 1.25 mm
measured generally from the leading edge LE to the trailing edge TE
at the base 111 of the tooth 110, and a tooth width TW of about 0.3
mm which is the longest dimension measured generally
perpendicularly to the circumferential length dimension at the
base. Teeth can be uniformly spaced from one another
circumferentially by a distance TD of about 1.5 mm. For making a
soft, fibrous three-dimensional apertured web from a precursor web
20 having a basis weight in the range of from about 5 gsm to about
500 gsm, teeth 68 can have a length TL ranging from about 0.5 mm to
about 3 mm, a tooth width TW of from about 0.3 mm to about 1 mm,
and a spacing TD from about 0.5 mm to about 3 mm, a tooth height TH
ranging from about 0.5 mm to about 10 mm, and a pitch P between
about 1 mm (0.040 inches) and 2.54 mm (0.100 inches). Depth of
engagement E can be from about 0.5 mm to about 5 mm (up to a
maximum approaching the tooth height TH).
[0096] Of course, DOE, P, TH, TD and TL can each be varied
independently of each other to achieve a desired size, spacing, and
area density of apertures (number of apertures per unit area of
apertured three-dimensionally apertured). For example, to make
apertured films and nonwovens suitable for use in sanitary napkins
and other absorbent articles, tooth length TL at the base can range
between about 2.032 mm to about 3.81 mm; tooth width TW can range
from about 0.508 mm to about 1.27 mm; tooth spacing TD can range
from about 1.0 mm to about 1.94 mm; pitch P can range from about
1.106 mm to about 2.54 mm; and tooth height TH can be from about
2.032 mm to about 6.858 mm. Depth of engagement DOE can be from
about 0.5 mm to about 5 mm. The radius of curvature R of the tooth
tip 112 can be from 0.001 mm to about 0.009 mm. Without being bound
by theory, it is believed that tooth length TL at the base can
range between about 0.254 mm to about 12.7 mm; tooth width TW can
range from about 0.254 mm to about 5.08 mm; tooth spacing TD can
range from about 0.0 mm to about 25.4 mm (or more); pitch P can
range from about 1.106 mm to about 7.62 mm; tooth height TH can
range from 0.254 mm to about 18 mm; and depth of engagement E can
range from 0.254 mm to about 6.35 mm. For each of the ranges
disclosed, it is disclosed herein that the dimensions can vary
within the range in increments of 0.001 mm from the minimum
dimension to the maximum dimension, such that the present
disclosure is teaching the range limits and every dimension in
between in 0.001 mm increments (except for radius of curvature R,
in which increments are disclosed as varying in 0.0001 mm
increments).
[0097] RKA teeth can have other shapes and profiles and the RKA
process can be used to aperture fibrous webs, as disclosed in
co-pending, commonly owned patent applications US 2005/0064136A1,
filed Aug. 6, 2004, US 2006/0087053A1, filed Oct. 13, 2005, and US
2005/021753 filed Jun. 21, 2005.
[0098] Each of the web deforming processes described above is known
in the art for processing various webs of an absorbent article. For
example, ring rolling is known to be used in combination with a
thermal melt weakening step to produce apertures, as disclosed in
U.S. Pat. Nos. 5,628,097 and 5,916,661, and US 2003/0028165A1. As
well, the SELF process is well known for making stretch portions of
a topsheet as disclosed in US 2004/0127875A1, filed Dec. 18, 2002.
Micro-SELF rolls are known to produce beneficially-modified
topsheets as disclosed in US 2004/0131820A1, WO 2004/059061A1 and
WO 2004/058118A1. And RKA is known to produce apertured formed
films, nonwoven webs, and laminates, as disclosed in US
2005/021753. Absorbent cores have also been modified by micro-SELF
rolls as disclosed in WO 2004/058497A1 in which a laminate of two
webs is made by processing two webs together to form a
fiber-integrated composite absorbent core.
[0099] In each of the processes described above heat can be
utilized, either by heating the web before the nip of the rollers
or by way of heated rollers, or heating the web after leaving the
nip rollers. If any of the rollers of the apparatuses as described
above are to be heated, care must be taken to account for thermal
expansion. In one embodiment, the dimensions of ridges, grooves,
and/or teeth are machined to account for thermal expansion, such
that the dimensions described herein can be dimensions at operating
temperature.
[0100] In one embodiment, processing of an absorbent core material
can be achieved by the method disclosed in commonly-owned,
co-pending US Application No. 2006/0286343A1 entitled Tufted
Fibrous Web. This method can include a heating means in which the
tips, or distal ends, of web features such as ribs or tufts can be
heated and/or bonded. Such heating and/or bonding can increase the
crush-resistance of an absorbent core, and can improve its
resiliency, which is important for maintaining permeability under
pressure. Resiliency can be improved by incorporating thermoplastic
bonding powders, such as polyethylene powder into the fibrous web,
and then heating in regions where bonding is desired. Resiliency
can also be improved by application of coatings, such as latex
coatings, that can tend to stiffen fibers, for example.
[0101] In one embodiment, multiple absorbent core layers can be
integrated by inter-entangling fibers from adjacent webs. Fiber
entanglement of adjacent layers can be achieved by the processes
described herein, and also by known means such as needle-punching,
hydroentangling, and thermal point bonding. By the same processes
and means, it may be desirable to integrate the topsheet of an
absorbent article with an underlying layer, such as a secondary
topsheet modified by the processes disclosed herein.
[0102] While the various web deforming processes described above
are known for topsheets, backsheets, and composite absorbent cores,
the novel feature of the present invention is the application of
these processes to achieve unexpected fluid handling property
results in absorbent homogeneous webs processed individually to be
heterogeneous, and then combined in a layered relationship with
other webs that can also have been processed by a web deforming
process to be heterogeneous. Combined webs need not be affixed in a
joined relationship, but can be joined if desired by means known in
the art, such as by adhesive bonding, thermal bonding, fiber
entangling, latex bonding, and combinations thereof. The invention
is believed to be applicable to a wide variety of fibers, including
bicomponent fibers, nano-fibers, shaped fibers, and combinations
thereof, as well as a wide variety of webs by various forming
processes, including meltblown, spunbond, and carded webs, wet-laid
webs including tissue paper, or combinations of these processes.
The invention is described below in a specific embodiment of
airlaid absorbent fibrous webs, i.e., core materials made by air
laying processes.
[0103] Air laying is a process for making nonwoven webs in which
cut staple fibers are introduced into an air stream which forces
the fibers onto a laydown belt in a controlled manner. The fibers
may be natural or synthetic, and may be bonded by thermal,
chemical, or mechanical means into a consolidated nonwoven web.
When fibers are supplied as cut, stable fibers in compacted form,
the airlaid process begins with a defibration system to open and
feed the staple fibers into an air stream. Other functions can also
be carried out, such at the dosage and introduction of super
absorbents or other powders. The fibrous and/or other materials are
suspended in air within a forming system and subsequently deposited
onto a moving forming screen or rotating perforated cylinder to
form a randomly oriented air formed batt. The air formed batt can
be bonded by applying latex binder and drying, thermally bonding
thermoplastic staple fibers in the web, hydrogen or embossed
bonding or a combination of these consolidation techniques. Airlaid
web formation is taught in U.S. Pat. No. 4,640,810, to Laursen et
al. Airlaid webs can be made by air laying a blend of fibrous
materials, or by air laying discrete layers, each layer having a
different type or blend of fibers.
[0104] In general, known methods of making airlaid materials
produce homogeneous webs of airlaid material. As used herein,
"homogeneous" refers to the uniformity of the web in the MD-CD
plane, as indicated in FIG. 14, for example. As shown in FIG. 14,
prior to formation through nip 38, web 34 can be formed by a
typical airlaid process so that in the MD-CD plane the web is
substantially uniform in bulk properties such as density and basis
weight. Virtually any discrete region chosen in the MD-CD plane of
a homogeneous web would have the same material handling properties
as an immediately adjacent region. Note that homogeneous does not
refer to the nature of the web in the "Z-direction," i.e., in a
direction perpendicular to the MD-CD plane, which can be considered
as being the thickness of the web. Web properties can vary in the
Z-direction by layering fibers in a non-uniform manner through the
thickness of the web.
[0105] As used herein, "heterogeneous" refers to the non-uniformity
of the web in the MD-CD plane, as indicated in FIG. 14, for
example. As shown in FIG. 14, after formation through nip 38, web
34 has been rendered heterogeneous such that in the MD-CD plane the
web is substantially non-uniform in bulk properties such as density
and basis weight. Discrete regions of the web have been
mechanically deformed into tufts, apertures, or other
three-dimensionally formed structures, such that discrete portions
of the web in the MD-CD plane would have the very different
material handling properties compared to immediately adjacent
regions.
[0106] The size of the discrete portions under consideration can
vary depending on the size of the web and the purpose of the
heterogeneous web. In general, however, it is desirable to have
closely spaced discrete portions on the order of from about 1 to
about 30 per square centimeter, including every whole number in
between, including from about 5 to about 10 per square centimeter.
By having relatively closely spaced (in the MD-CD plane) discrete
portions in the form of ribs, tufts, or apertures, for example,
fluid handling is improved by increasing the probability that a
given drop of fluid on the web can experience both high
permeability and high capillarity options upon contact with the
web.
[0107] To illustrate the present invention, generally homogeneous
absorbent airlaid fibrous web materials were modified by one or
more of the four processes described above to achieve a
heterogeneous absorbent core material having the ability to
advantageously move fluid rapidly into secure storage in the
absorbent core when used in a sanitary napkin. In one aspect, the
heterogeneity of the absorbent core permits the core to exhibit
fluid moving properties generally laterally, that is, in the plane
of the web material. That is, rather than exhibit heterogeneity in
the Z-direction, i.e., in a direction through the thickness of the
web, the web of the present invention can exhibit heterogeneity in
the "X-Y" plane, i.e., in a plane parallel with the plane of the
web in generally flattened condition, referred to herein as lateral
fluid movement.
[0108] Tables 1 and 2 below illustrate the benefits of processing
an airlaid fibrous absorbent material by one or more of the four
formation means described above. For all dimensions 1 inch equals
25.4 mm.
[0109] Table 1 shows variations in fluid handling properties for a
web referred to herein as Absorbent Core I, made from an unmodified
precursor web described in Table 1 as Control Absorbent I. The
Control Absorbent I web is an airlaid absorbent core material
having a basis weight of about 180 grams per square meter (gms) and
comprising cellulosic fibers and bicomponent fibers blended in an
air laying process together with 30 gsm of absorbent gelling
material (AGM). The cellulosic fibers are Weyco NB416 obtained from
Weyerhaeuser Co. The bicomponent fibers are Invista #35160A
(PE/PET, 2.0 denier and 4 mm length) obtained from Invista and the
proportion of cellulosic fibers to bicomponent fibers is 5 gram to
1 gram. The AGM is Degussa 23070G obtained from Degussa, and is
dispersed substantially uniformly throughout the web. About 5 wt %
latex AF 192 obtained from Air Products is sprayed on the surface
of both sides and allowed to cure.
[0110] Table 2 shows variations in fluid handling properties for a
web referred to herein as Absorbent Core II, made from an
unmodified precursor web described in Table 1 as Control Absorbent
II. The Control Absorbent II is an airlaid absorbent material
suitable for use as a secondary topsheet and is a laminate having a
basis weight of about 82 grams per square meter (gsm). One layer of
the laminate of Control Absorbent II is a spunbond polypropylene
(PP) hydrophilic nonwoven having a basis weight of about 22 gsm.
The spunbond web layer can be obtained as P9 from Fiberweb. The
spunbond polypropylene web is laminated to a web produced in an air
laying process, the air laid web being a 60 gsm web of cellulosic
fibers and polyethylene power binder blended in the air laying
process. About 5 wt % latex AF 192 obtained from Air Product was
sprayed on the surfaces of the air laid web prior to lamination to
the spunbond material. The cellulosic fibers are Weyco NB416
obtained from Weyerhaeuser Co. The polyethylene powder binder is
Dow Low Density polyethylene 959s obtained from Dow, and the
proportion of cellulosic fibers to polyethylene powder binder is 3
g to 1 g. After air laying, the laminate web is processed through a
heating step to effect the binding properties of the polyethylene
binder powder.
[0111] As shown in Table 1, the absorption capillary pressure and
desorption capillary pressure, the grams per gram capacity, the
permeability, and the flow rate can each be changed in a
beneficially positive manner by formation by the denoted processes.
Each of the parameters were determined by the tests shown in the
Test Methods section below.
TABLE-US-00001 TABLE 1 Fluid Handling Properties of Modified
Airlaid Fibrous Absorbent Core I Absorption Desorption Capillary
Capillary Flow Sample Formation Potential Potential Capacity
Permeability Rate No. Process Type (mJ/m.sup.2) (mJ/m.sup.2) (g/g)
(Darcy's) (g/sec) 1 Control 636 1111 4.14 171 5.65 Absorbent I 2
SELF 707 1297 6.76 360 8.8 3 SELF 632 1257 6.04 271 7.66 4 RKA 677
1167 5.03 240 6.96 5 SELF 732 1260 6.01 348 9.12 6 SELF 614 1172
6.15 399 11
[0112] Sample No. 2 was made by processing Control Absorbent I
through a SELF'ing process in which the toothed roll had the
dimensions shown in FIGS. 17-20. As shown in FIG. 19, the teeth had
a pitch P of 0.100 inches, a tooth height TH of about 6.86 mm
(about 0.270 inches), and a tooth angle TA between teeth of about
9.478 degrees. As shown in FIG. 20, each tooth had a tooth length
TL of about 5.33 mm (about 0.2101 inches), a tooth spacing TD of
about 1.98 mm (about 0.0781 inches), and a diverging tooth angle DA
of about 2.903 degrees. The mating roll was an un-toothed roll,
that is, a roll having circumferentially extending ridges and
grooves, similar to that shown in FIG. 6 above, and engaged at a
DOE of about 1.78 mm (about 0.070 inch). The SELF'ing process was
carried out at room temperature at a rate of about 1-5 m/min.
[0113] Sample No. 3 was made by processing Control Absorbent I
through a SELF'ing process in which the toothed roll had dimensions
as shown in FIGS. 21-23. FIG. 21 is a flat-out view of the
circumference of a toothed roll. One difference from the tooth
configuration of the rolls shown in FIGS. 21-23 and those used to
make Sample 2 is that the teeth, rather than having a generally
rectangular shape when viewed from the top (i.e., in plan view,
looking down on the surface of the roll), each tooth has a
generally diamond shape as shown in FIG. 23. Also, the pitch P from
tooth to tooth in a row is 0.200 inch, which results in a 0.100
pitch P from tooth to tooth in a stagger pattern. Teeth 68 have a
tooth length TL of about 5 mm, and a tooth distance TD of about 4
mm. The mating roll was an un-toothed roll, that is, a roll having
circumferentially extending ridges and grooves, similar to that
shown in FIG. 6 above, wherein the two mating rolls meshed at a DOE
of about 1.78 mm (about 0.070 inch). The SELF'ing process was
carried out at room temperature at a rate of about 1-5 m/min.
[0114] Sample No. 4 was made by processing Control Absorbent I
through a RKA process in which the toothed roll had teeth having
the dimensions shown in FIGS. 24-27. As shown in FIGS. 24-27, the
teeth of the toothed RKA roll were configured in a staggered
pattern having a row to row pitch P of about 2.54 mm (about 0.100
inch). The teeth 68 have a tooth length (measured at the base) TL
of about 3.81 mm (about 0.150 inch) and a tooth distance TD of
about 1.94 mm (about 0.076 inch). As shown in FIG. 26, teeth 68
have a tooth width at the base of about 1.27 mm and a tooth height
TH of about 6.858 mm (about 0.270 inch). The mating roll was an
un-toothed roll, that is, a roll having circumferentially extending
ridges and grooves, similar to that shown in FIG. 6 above, and
engaged at a DOE of about 6.35 mm (about 0.250 inch). The RKA
process was carried out at room temperature at a rate of about 1-5
m/min.
[0115] Sample 5 was made by processing Control Absorbent I through
a SELF'ing process in which the toothed roll had a configuration
shown in FIGS. 28-30. The teeth 68, rather than being in straight
rows across the width of the roll, are placed in staggered groups
of three teeth that make a generally circular shape to form a
pattern on a processed web similar to that shown in FIG. 10. As
shown in FIG. 30, teeth 68 have a tooth height TH of about 3.6 mm
(0.145 inches) and a pitch P of about 1.524 mm (about 0.060 inch).
The toothed roll was engaged with a mating ring roll having fully
circumferential ridges and grooves similar to that shown in FIG. 6
above, engaged at a DOE of about 1.9 mm (about 0.075 inch). The
SELF'ing process was carried out at room temperature at a rate of
about 1-5 m/min.
[0116] Sample 6 was made by processing Control Absorbent I through
a modified SELF'ing process in which an upper toothed roll had the
configuration described for the toothed roll of Sample 5. However,
the inter-meshing (inter-engaging) roll, rather than having fully
circumferential ridges and grooves similar to that shown in FIG. 6
above, was another toothed micro-SELF'ing roll similar to that
shown in FIGS. 11-13, with a pitch of about 1.52 mm (about 0.060
inch) to match the upper toothed roll. The rolls were operated at a
DOE of about 1.65 mm (about 0.065 inch). The process was carried
out at room temperature at a rate of about 1-5 m/min.
[0117] As can be seen in Table 1, in all cases the grams (of
absorbed fluid) per gram (of absorbent material) capacity, the
permeability and the flow rate, all increased significantly, as did
the capillary pressure in most cases. All these improvements are a
result of simply processing a web material through the nip of a
pair of intermeshing (or inter-engaging) rollers as described
above. Therefore, there is no new material content or new
composition that would increase costs associated with the much
better fluid acquisition properties.
TABLE-US-00002 TABLE 2 Fluid Handling Properties of Modified
Airlaid Fibrous Absorbent Core II Absorption Desorption Formation
Capillary Capillary Flow Sample Process Potential Potential
Capacity Permeability Rate No. Type (mJ/m.sup.2) (mJ/m.sup.2) (g/g)
(Darcy's) (g/sec) 7 Control 301 596 3.75 106 15 Absorbent II 8 Ring
roll 321 683 5.39 201 22 9 SELF 323 738 10.43 327 13 10 micro-SELF
342 724 8.59 204 18 11 micro-SELF 324 696 6.07 185 18 12 RKA 323
496 6.71 204 24 13 RKA 343 649 6.39 174 19 14 RKA 316 644 6.8 175
20 15 RKA 321 651 5.39 121 16 16 SELF 322 657 8.24 165 15 17 SELF
309 670 8.54 246 21 18 SELF 295 672 7.39 186 17 19 1.sup.st pass:
Ring 361 641 7.68 208 23 roll 2.sup.nd pass: RKA 20 1.sup.st pass:
.quadrature..quadrature.- 367 757 8.58 252 20 SELF 2.sup.nd pass:
RKA 21 1.sup.st pass : .quadrature..quadrature.- 340 742 8.16 254
20 SELF 2.sup.nd pass: RKA
[0118] Sample No. 8 was made by processing Control Absorbent II
through a ring rolling apparatus as described with reference to
FIGS. 2 and 3. The ring rolls had a pitch of about 1.016 mm (about
0.040 inch) and were meshed at a DOE of about 1.016 mm (about 0.040
inch). The process was carried out at room temperature.
[0119] Sample 9 was made by processing Control Absorbent II through
intermeshing SELF rollers as described for Sample 2 above, with a
DOE of about 2.45 mm (about 0.100 inch). The spunbond PP side of
Control Absorbent II faced the non-toothed roll of the apparatus.
The process was carried out at room temperature.
[0120] Sample 10 was made by processing Control Absorbent II
through intermeshing micro-SELF rollers having a pitch P of about
1.52 mm (about 0.060 inch) as described with respect to FIG. 11,
and with a DOE of about 1.9 mm (about 0.075 inch). The spunbond PP
side of Control Absorbent II faced the non-toothed roll of the
apparatus. The process was carried out at room temperature.
[0121] Sample 11 was made by processing Control Absorbent II
through intermeshing micro-SELF rollers having a pitch of about
1.52 mm (about 0.060 inch) as described with respect to FIG. 11,
and with a DOE of about 3.43 mm (about 0.135 inch). The spunbond PP
side of Control Absorbent II faced the toothed micro-SELF roll of
the apparatus. The process was carried out at a temperature of 300
degrees F.
[0122] Sample 12 was made by processing Control Absorbent II
through an RKA process in which the toothed roll had teeth having
the dimensions shown in FIGS. 31-34. The spunbond PP side of
Control Absorbent II faced the RKA roll of the apparatus. As shown
in FIGS. 31-34, the teeth of the toothed RKA roll were configured
in a staggered pattern having a row to row pitch of about 1.016 mm
(about 0.040 inch). Both the tooth height TH and tooth length TL
were each about 2.032 mm (about 0.080 inch). Tooth distance TD was
about 1.626 mm (about 0.64 inch) and the tooth width TW was about
0.510 mm (about 0.020 inch) Other dimensions were as shown. The
mating roll was an un-toothed roll, that is, a roll having
circumferentially extending ridges and grooves, similar to that
shown in FIG. 6 above at a DOE of about 6.35 mm (about 0.250 inch).
The RKA process was carried out at a temperature of 250 degrees F.
at a rate of about 1-5 m/min.
[0123] Sample 13 was made by processing Control Absorbent II
through an RKA process in which the toothed roll had teeth having
the dimensions shown in FIGS. 35-38. The spunbond PP side of
Control Absorbent II faced the RKA roll of the apparatus. As shown
in FIGS. 35-38, the teeth 68 of the toothed RKA roll were
configured in a staggered pattern having a row to row pitch P of
about 1.524 mm (about 0.060 inch). The tooth height TH was about
3.683 mm (about 0.145 inch), the tooth distance TD was about 1 mm
(about 0.039 inch), and the tooth length TL was about 2.032 mm
(about 0.080 inch). Other dimensions were as shown. The mating roll
was an un-toothed roll, that is, a roll having circumferentially
extending ridges and grooves, similar to that shown in FIG. 6 above
at a DOE of about 3.43 mm (about 0.135 inch). The RKA process was
carried out at a temperature of 300 degrees F. at a rate of about
1-5 m/min.
[0124] Sample 14 was made by processing Control Absorbent II
through an RKA process in which the toothed roll had teeth having
the dimensions shown in FIGS. 24-27, as described above. The
spunbond PP side of Control Absorbent II faced the RKA roll of the
apparatus. The mating roll was an un-toothed roll, that is, a roll
having circumferentially extending ridges and grooves, similar to
that shown in FIG. 6 above at a DOE of about 6.35 mm (about 0.250
inch). The RKA process was carried out at a temperature of 350
degrees F. at a rate of about 1-5 m/min.
[0125] Sample 15 was made by processing Control Absorbent II
through an RKA process in which the toothed roll had teeth having
the dimensions shown in FIGS. 24-27 as described above. The
spunbond PP side of Control Absorbent II faced the RKA roll of the
apparatus. The mating roll was an un-toothed roll, that is, a roll
having circumferentially extending ridges and grooves, similar to
that shown in FIG. 6 above at a DOE of about 6.35 mm (about 0.250
inch). The RKA process was carried out at room temperature at a
rate of about 1-5 m/min.
[0126] Sample 16 was made by processing Control Absorbent II
through a SELF'ing process in which the toothed roll had teeth
having the dimensions as described with respect to Sample 5 above.
The spunbond PP side of Control Absorbent II faced the SELF roll of
the apparatus. The mating roll was an un-toothed roll, that is, a
roll having circumferentially extending ridges and grooves, similar
to that shown in FIG. 6 above at a DOE of about 1.9 mm (about 0.075
inch). The process was carried out at room temperature at a rate of
about 1-5 m/min.
[0127] Sample 17 was made by processing Control Absorbent II
through a SELF'ing process in which the toothed roll had teeth
having the dimensions as described with respect to Sample 5 above.
The spunbond PP side of Control Absorbent II faced the SELF roll of
the apparatus. The mating roll was an un-toothed roll, that is, a
roll having circumferentially extending ridges and grooves, similar
to that shown in FIG. 6 above at a DOE of about 1.9 mm (about 0.075
inch). The process was carried out at a temperature of 300 degrees
F. at a rate of about 1-5 m/min.
[0128] Sample 18 was made by processing Control Absorbent II
through a SELF'ing process in which the toothed roll had teeth
having the dimensions as described with respect to Sample 5 above.
The spunbond PP side of Control Absorbent II faced the SELF roll of
the apparatus. The mating roll was an un-toothed roll, that is, a
roll having circumferentially extending ridges and grooves, similar
to that shown in FIG. 6 above at a DOE of about 1.65 mm (about
0.065 inch). The process was carried out at room temperature at a
rate of about 1-5 m/min.
[0129] Sample 19 was made by processing Control Absorbent II
through two separate inter-engaging rollers. First, Control
Absorbent II was processed at room temperature through the nip of a
ring roller having a pitch of about 1.016 mm (about 0.040 inch),
and a DOE of about 1.016 mm (about 0.040 inch). Next, the ring
rolled web was processed through an RKA process in which the
toothed roll had teeth having the dimensions shown in FIGS. 31-34.
The mating roll was an un-toothed roll, that is, a roll having
circumferentially extending ridges and grooves, similar to that
shown in FIG. 6 above at a DOE of about 1.143 mm (about 0.045
inch). The RKA process was carried out at a temperature of 220
degrees F. at a rate of about 1-5 m/min.
[0130] Sample 20 was made by processing Control Absorbent II
through two separate inter-engaging rollers. First, Control
Absorbent II was processed at room temperature through the nip of a
micro-SELF roller having a pitch of about 1.524 mm (about 0.060
inch), a DOE of about 1.9 mm (about 0.075 inch), and at room
temperature. The spunbond PP side of Control Absorbent II faced the
ring roll (non-toothed roll) of the apparatus. Next, the
micro-SELF'ed web was processed through an RKA process in which the
toothed roll had teeth having the dimensions shown in FIGS. 31-34.
The spunbond PP side of Control Absorbent II faced the RKA roll of
the apparatus. The mating roll was an un-toothed roll, that is, a
roll having circumferentially extending ridges and grooves, similar
to that shown in FIG. 6 above at a DOE of about 2.16 mm (about
0.085 inch). The RKA process was carried out at a temperature of
300 degrees F. at a rate of about 1-5 m/min.
[0131] Sample 21 was made by processing Control Absorbent II
through two separate inter-engaging rollers. First, Control
Absorbent II was processed at room temperature through the nip of a
micro-SELF roller having a pitch P of about 1.52 mm (about 0.060
inch), a DOE of about 1.9 mm (about 0.075 inch), and at room
temperature. The spunbond PP side of Control Absorbent II faced the
ring roll (non-toothed roll) of the apparatus. Next, the
micro-SELF'ed web was processed through an RKA process in which the
toothed roll had teeth having the dimensions shown in FIGS. 24-27.
The spunbond PP side of Control Absorbent II faced the RKA roll of
the apparatus. The mating roll was an un-toothed roll, that is, a
roll having circumferentially extending ridges and grooves, similar
to that shown in FIG. 6 above at a DOE of about 2.54 mm (about
0.100 inch). The RKA process was carried out at a temperature of
300 degrees F. at a rate of about 1-5 m/min.
[0132] As can be seen in Table 2, in almost all cases the capacity
efficiency in grams (of absorbed fluid) per gram (of absorbent
material) capacity, the permeability and the flow rate, all
increased significantly, as did the capillary pressure in most
cases. All these improvements are a result of simply processing a
web material through the nip of a pair of inter-engaging rollers as
described above. Therefore, there is no new material content or new
composition that would increase costs associated with the much
better fluid acquisition properties.
[0133] As shown above in Tables 1 and 2, processing the airlaid
webs by the web deforming methods shown can have an immediate
beneficial effect on the fluid handling properties of the web
material. Without being bound by theory it is believed that this
beneficial effect is due to the disruption of fibers in closely
spaced discrete locations that produces discrete, but relatively
closely spaced, regions of high or low permeability (depending on
the specific web deformation process) surrounded by regions of low
or high permeability, respectively. For example, in the example of
ring rolling, the nature of the process is to produce rows of high
density, high capillarity material, separated by rows of low
density, low capillarity materials. While it is recognized that
ring rolling is well known in the art, it is believed that the
application of ring rolling to air laid materials is a new
application providing for new and beneficial results in the art of
absorbent core materials.
[0134] In addition to the benefits observed when individual webs
are processed as shown in Tables 1 and 2, additional surprising and
unexpected benefits can be achieved when webs processed by one or
more of the web deforming processes described above are combined
with other webs so processed, or processed by different web
deforming processes. The present invention is particularly valuable
in the context of sanitary napkins when one of the processed webs
is used as a secondary topsheet and one of the webs is used as an
absorbent core. The nomenclature "secondary topsheet" and
"absorbent core" is not to be limiting. That is, the secondary
topsheet can be considered to be an absorbent core also, but the
term is used herein in its normal sense as developed in the art of
sanitary napkins as a material used under and adjacent to a
topsheet and having properties to move fluid away from the topsheet
and into the absorbent core. That is, while a secondary topsheet
can have absorbent properties, it is not intended to keep fluid
retained but is intended to give up fluid to an absorbent storage
medium, e.g., an absorbent core material, which absorbent core
material is intended to retain fluid securely to ensure fluid does
not return to the skin of the wearer.
[0135] The beneficial properties of the present invention can be
illustrated with reference to Table 3. In Table 3 is shown fluid
handling properties of a variety of combinations of web materials
from Tables 1 and 2, i.e., the web materials having been deformed
by one or more of the processes described above. In Table 3, each
combination of web materials from Tables 1 and 2 was tested in a
configuration to model a sanitary napkin, and each sample was
tested with an apertured formed film web of the type disclosed in
U.S. Pat. No. 4,629,643 issued to Curro et al. Dec. 16, 1986 and as
marketed by The Procter & Gamble Co. on its line of ALWAYS.RTM.
brand sanitary napkins.
[0136] Therefore, for each Sample in Table 3, the structure tested
was a layered structure comprising, in order, an apertured formed
film topsheet, secondary topsheet (STS) of Core II, and an
absorbent core of Core I. Table 3 designates the particular air
laid fibrous structures by reference to their respective sample
numbers in Tables 1 and 2 above.
TABLE-US-00003 TABLE 3 Fluid Handling Properties of Combined
Modified Airlaid Fibrous Absorbent Cores I and II Free HGW Gush
Rewet Retained Sample Core I/ Run-off Acquisition Pressure Capacity
No. Core II (%) (ml/sec) (psi) (g) 22 Sample 7/ 47 0.06 0.86 25
sample 1 23 Sample 12/ 39 0.07 1.62 26 sample 1 24 Sample 12/ 34
0.10 1.61 26 sample 2 25 Sample 13/ 40 0.19 1.36 30 sample 2 26
Sample 14/ 35 0.11 1.19 28 sample 2 27 Sample 10/ 37 0.09 1.07 29
sample 1 28 Sample 10/ 28 0.13 0.87 29 sample 2 29 Sample 21/ 38
0.11 0.82 27 sample 2 30 Sample8/ 52 0.07 1.00 26 sample 1 31
Sample8/ 37 0.12 0.96 26 sample 2 32 Sample 19/ 40 0.06 1.10 26
sample 1 33 Sample 19/ 35 0.08 0.88 27 sample 2
[0137] As shown in Table 3, the 2-layer absorbent cores of the
present invention (as shown in Samples 23-33) can break the
permeability versus capillarity pressure tradeoff, by delivering
relatively higher permeability (as shown by Free Gush Run-off,
Acquisition speed, and Retained Capacity) without a significant
decrease in capillary pressure (as shown by Rewet Pressure)
compared to the Control (Sample 22).
[0138] The web of the present invention, used as an absorbent core
in an absorbent product, exhibits properties that appear to have
uncoupled the permeability versus capillarity pressure tradeoff.
Without being bound by theory, it is believed that this apparent
uncoupling is due to the creation of structures that have the
effect of providing fluid handling properties in both of the
tradeoff areas. For example, it is believed that the processes
disclosed produce discrete locations of greater void volume, which,
particularly in multiple layer cores permits the core materials to
exhibit desirable benefits of both properties. The greater void
volume in a fibrous material can result in greater permeability.
These regions of greater permeability are relatively closely
spaced, separated by the unmodified regions of the web, such
regions exhibiting relatively lower permeability but relatively
high capillary pressure. Thus, fluid impinging on the core, such as
menses absorbed through a topsheet of an absorbent article during
use, is presented with the possibility of both fluid dynamics, high
permeability and high capillarity pressure. In effect, the fluid
dynamics of such cores can be the result of taking advantage of the
best of both material properties.
[0139] The material properties of the core of the present
invention, whether single core or multiple core, can be further
enhanced by additional core layers, or additional layers of
material in a given core material. That is, for example, additional
airlaid webs can be modified by the methods disclosed herein and
added in layered relationship with the other two or more. As well,
any one of the airlaid webs can itself be a layered structure
exhibiting therein a Z-direction gradient in fluid handling
properties. For example, for any one of the absorbent cores
disclosed herein, including airlaid webs, the core can exhibit a
Z-direction density gradient from low density on one side of the
web to relatively high density on the other. Likewise,
permeability, capillarity, fiber type and size, and other physical
properties can be varied in various combinations within a layered
web, such that a Z-direction gradient of virtually any physical
property of the web can be envisioned as being useful in the
present invention.
[0140] In one embodiment of a layered absorbent core, such as a
layered airlaid web, it is contemplated that one layer could be
designed to fracture upon treatment by the processes described
herein, while other layer(s) do not. For example, a middle layer of
a three layer airlaid web could comprise a material, such as a
fibrous material, which fractures at low levels of strain, such
that upon application of stress by the methods described herein,
the middle layer fractures to form discrete, spaced apart
apertures, while the remaining layers do not. In like manner a
layer of a multi-layer web could be rendered into strips.
[0141] In one embodiment of a layered absorbent core, it is
contemplated that a laminate could be formed in which one or more
of the layers is a non-fibrous material, such as a foam or film
web. For example, an absorbent core of the present invention can
comprise, or be combined with, an absorbent foam material, such as
high internal phase emulsions (HIPE) foams.
[0142] In one embodiment, the pattern of modification, such as by
teeth on a SELF roll, can be varied across the width of the web
being modified. For example, the rolls of a SELF process can be
designed such that the pitch P of the teeth and grooves varies
across the width of the rolls, and, consequently, across the width
of the web. In this manner, for example, an absorbent core can be
produced in which the central region corresponding to the
longitudinal centerline region of an absorbent article, can have a
pattern of ridges, tufts, apertures, or other feature, that is
different from either or both side regions.
[0143] A schematic representation of two cores of the present
invention for the purpose of illustrating density variation is
shown in FIGS. 39 and 40. FIG. 39 shows a schematic representation
of Sample 2 as detailed above with respect to Table 1. FIG. 40
shows a schematic representation of Sample 10 as detailed above
with respect to Table 2. For both schematic representations, the
out of plane, localized Z-direction deformations of the base web
are indicated as rectangles. The rectangles shown are approximate
representations of the relative X-Y boundaries of the Z-direction
deformations, where X and Y can correspond to the cross-direction
(CD) and machine-direction (MD), respectively. The rectangles show
approximate representations of the "tent-like" rib-like elements of
Sample 2, and the tufts of Sample 10, each of which can have a
distinct aspect ratio of length divided by width, the aspect ratio
of at least about 1.5 to 1, or 1.7 to 1, or 2.0 to 1 or 2.7 to 1,
or 3 to 1, or 5 to 1, or 10 to 1, and including all numerical
values between 1.5 and 10 in increments of one-tenth. The
dimensions and shape of rectangles as well as the spacing of
adjacent rectangles can be produced using visual imaging
techniques, as is known in the art.
[0144] As shown in FIG. 39, rib-like elements indicated as "a" can
be about 5.5 mm long and about 2 mm wide. Each element can be
separated from adjacent elements in the CD by a region indicated as
"b" which can be about 0.6 mm. Each element can be separated from
adjacent elements in the MD by a region indicated as "c" which can
be about 1.3 mm. Density measurements of the various regions "a",
"b", and "c" show that SELF'ing of a nonwoven web, such as a
fibrous airlaid web, can make relatively low density out-of-plane
deformations. In the embodiment depicted in FIG. 39, the base
material had a density of about 0.221 g/cc, region "a" had a
density of about 0.128 g/cc, region "b" had a density of about
0.199 g/cc, and region "c" had a density of about 0.226 g/cc.
[0145] As shown in FIG. 40, tuft elements indicated as "a" can be
about 1.7 mm long and about 1 mm wide. Each tuft element can be
separated from adjacent elements in the CD by a region indicated as
"b" which can be about 0.6 mm. Each element can be separated from
adjacent elements in the MD by a region indicated as "c" which can
be about 1.2 mm. Density measurements of the various regions "a",
"b", and "c" show that micro-SELF'ing of a nonwoven web, such as a
fibrous airlaid web, can make low density out-of-plane
deformations. In the embodiment depicted in FIG. 40, the base
material had a density of about 0.088 g/cc, region "a" had a
density of about 0.0.072 g/cc, region "b" had a density of about
0.0.093 g/cc, and region "c" had a density of about 0.0.101
g/cc.
[0146] It is understood that the density values described above
with respect to Samples 2 and 10 shown in FIGS. 39 and 40 are
approximate, and the density values can vary depending on the base
material properties, the process used to make Z-direction
deformations, and other material and process variables. In general,
it is believed that for airlaid webs having at least a portion of
fibers being cellulosic fibers, that a density difference between
the density of the base web and the density of the Z-direction
deformation of at least about 18% to about 50% is beneficial for
the present invention. The density difference between the density
of the base web and the density of the Z-direction deformation can
be 20%, 30%, 40% or greater than 50%. The density difference is
believed to be most beneficial when the density of the Z-direction
deformation is less than the density of the base material. The
density of the base material can be considered to be essentially
the same as the density of region "c" in FIGS. 39 and 40 in a web
processed by the methods of the present invention.
[0147] It is understood that the density values provided herein are
values for uncompressed webs processed to make absorbent cores as
described herein. The absorbent cores described herein may be used
in folded, compressed, packaged, and/or stored disposable absorbent
articles. Therefore, the as-used density differences may be
different than the as-made density differences. Therefore, it is
believed that an absorbent core material used in a packaged
disposable absorbent article can exhibit a density difference
between the density of the regions between Z-direction deformations
(e.g., the regions noted as "b" and "c" in FIGS. 39 and 40) and the
density of the Z-direction deformation can be 5%, 10%, 20%, 30%, or
greater than 40%. Currently it is believed that an airlaid nonwoven
absorbent core comprising cellulosic fibers is most beneficial when
the density differences above are due to the density of the
Z-direction deformations being relatively lower than the density of
the regions between Z-direction deformations.
[0148] The density data as discussed above with respect to Samples
2 and 10 shown in FIGS. 39 and 40 were obtained by using a
MicroCT40 (Scanco Medical, Bassersdorf, Switzerland) x-ray scanner
at high resolution, 35 KeV energy, 300 micron integration time and
10 averaging. A field of view of 20.times.20 mm in X/Y and 2-3 mm
in Z (depending on the sample) with an x/y/z resolution of 10
microns in all directions was used for the tomographic
reconstruction of the datasets. Each dataset was approximately
2048.times.2048 in x/y and around 200-300 slices in the z
direction. After removing the sample holder from the field of view,
the remaining stack of slices was analyzed as follows:
[0149] 1) A threshold of 1000 was used to distinguish between a
fiber and background.
[0150] 2) The Thickness at each x/y point was determined by finding
the first fiber (any pixel >1000) along the Z direction
(perpendicular to the wipe surface) and the last fiber along the Z
direction. The difference between these two Z values provided the
thickness at each location in X/Y. This image was saved in TIFF
format.
[0151] 3) The Basis Weight image at each x/y point was determined
by summing all the values >1000 along the Z direction. This
image was saved in TIFF format.
[0152] 4) The Density image at each x/y point was determined to be
the value of the basis weight image at (X,Y) divided by the value
of the thickness image at (X,Y). Images of 0 thickness were set to
0 in the Density image. This image was saved in TIFF format.
[0153] 5) The user then selects regions within the thickness image.
Each region is labeled either thick or thin. The thickness mean and
standard deviation, basis weight mean and standard deviation, and
density mean and standard deviation are then calculated for the
region chosen (in each respective image) and reported out as
desired, for example to a .csv file to an Excel.RTM.
spreadsheet.
Test Methods
1. Artificial Menstrual Fluid Preparation
[0154] For each of the tests using Artificial Menstrual Fluid
(AMF), prepare as follows: [0155] Step 1: Dilute 10 ml of reagent
grade 85-95% w/w lactic acid to 100 ml with distilled water. Label
as 10% v/v lactic acid. [0156] Step 2: Add 11.76 g of reagent grade
85% w/w potassium hydroxide (KOH) to a flask and dilute to 100 ml
with distilled water. Mix until completely dissolved. Label as 10%
w/v KOH. [0157] Step 3: Add 8.5 g sodium chloride and 1.38 g of
hydrous monobasic sodium phosphate to a flask and dilute to 1000 ml
with distilled water. Mix until completely dissolved. Label as
monobasic sodium phosphate solution. [0158] Step 4: Add 8.5 g
sodium chloride and 1.42 g anhydrous dibasic sodium phosphate to a
flask and dilute to 1000 ml with distilled water. Mix until
completely dissolved. Label as dibasic sodium phosphate solution.
[0159] Step 5: Add 450 ml of dibasic phosphate solution to a 1000
ml beaker and add monobasic sodium phosphate solution until the PH
is lowered to 7.2.+-.0.1. Label as phosphate solution. [0160] Step
6: Mix 460 ml of phosphate solution and 7.5 ml of 10% KOH in a 1000
ml beaker. Heat Solution to 45.degree. C..+-.5.degree. C. and then
add 28 sterilized gastric mucin (ICN Biomedical Inc., Cleveland,
Ohio). Continue heating for 2.5 hours to completely dissolve the
gastric mucin. Allow the solution to cool to less than 40.degree.
C. and then add 1.8.+-.0.2 ml of 10% v/v lactic acid solution.
Autoclave the mixture at 121.degree. C. for 15 minutes, then allow
to cool to room temperature. Mucous mixture should be used within 7
days. Label as gastric mucin solution. [0161] Step 7: Mix 500 ml of
gastric mucin solution and 500 ml of fresh, sterile defibrinated
sheep blood (Cleveland Scientific, American Biomedical, Bath, Ohio)
in a beaker. Label as artificial menstrual fluid. Store
refrigerated and use within 7 days.
2. Absorption Capillary Potential and Desorption Capillary
Potential
[0162] Absorption Capillary Potential, also referred to as
absorption energy, and Desorption Capillary Potential, also
referred to as desorption energy, can be determined by evaluating
capillary work potential for each tested material.
[0163] The ability of absorbent materials to absorb or desorb fluid
via capillary potential is measure by the Capillary Work Potential.
[0164] Step 1: A TRI Autoporosimeter from TRI, Princeton, N.J., is
used to measure percentage of fluid saturation as a function of
pressure of the absorbent core I and II samples listed in table 1
and 2. [0165] Step 2: The testing fluid used here is n-hexadecane.
[0166] Step 3: There are three testing cycles to generate three
capillary pressure vs. percent saturation curves:
[0167] 1) 1st Absorption with dry material (imbibition)
[0168] 2) Draining
[0169] 3) 2nd Absorption with wet material [0170] Step 4: The
Absorption Capillary Potential (absorption Capillary Work Potential
(CWP)) is calculated by the integration of the 1st absorption curve
of capillary potential as a function of uptake volume.
[0170] W=.intg.P.sub.cap(CV)dCV (mJ/m.sup.2) [0171] Where CV is the
measured cumulative uptake volume (convertible to saturation)
[0172] Step 5: The Desorption Capillary Pressure (desorption
Capillary Work Potential (CWP)) is calculated by the integration of
the draining curve of capillary pressure as a function of uptake
volume.
[0172] W=.intg.P.sub.cap(CV)dCV (mJ/m.sup.2) [0173] Where CV is the
measured cumulative uptake volume (convertible to saturation) 3.
Permeability (Darcy's) and Flow Rate (g/sec)
[0174] Permeability is determined from the mass flow rate of any
given fluid through a porous medium. The procedure for determining
both is as follows: [0175] Step 1: A through plane permeability
device is used to automatically dispense and measure flow of liquid
through a sample by monitoring the distance a column of water drops
in relation to time and pressure measure. [0176] Step 2: The
pressure drop determines the mass flow rate of a fluid through a
porous medium across the sample. [0177] Step 3 (for flow rate of
Table 1): The flow rate is determined at a variable pressure in the
falling hydro head mode using a salt solution containing 2.75%
Calcium Chloride as the fluid for all of the Absorbent I samples in
Table 1. [0178] Step 3 (for flow rate of Table 2): The flow rate is
determined at constant pressure using the constant hydro head mode
using distilled/de-ionized water as the fluid for all of the
Absorbent II samples in Table 2. [0179] Step 4: Darcy permeability
and Flow Rate is calculated by the equations below:
[0179] F=k(A/.quadrature.)(.quadrature.p/l) (1)
K=9.87.times.10.sup.-13k (2) [0180] Where: F=flow Rate (g/s) [0181]
k=permeability of the porous material (m.sup.2) [0182] A=Cross
sectional area available for flow (m.sup.2) [0183] 1=Thickness of
the material (m) [0184] .quadrature..quadrature.=Fluid viscosity
(cP) [0185] .quadrature..quadrature.p=Pressure Drop (cm H.sub.2O)
[0186] K=permeability (Darcy's)
4. Free Gush Run-Off (%)
[0187] This test measures the weight percentage of fluid not being
acquired (% run-off) by an absorbent pad. The protocol includes
loading 10 ml of artificial menstrual fluid (AMF) on an unloaded
(fresh) sanitary napkin which is placed at 150 incline angle in the
CD direction (i.e., the width of a sanitary napkin in a flat
condition). Reported values are the average of N=3.
AMF Preparation:
[0188] Condition AMF at 73.+-.4.degree. F. (23.+-.2.degree. C.) for
2 hours before drawing fluid for testing.
Sample Preparation and Apparatus:
[0189] Step 1: Pre-stress each pad to be tested by: holding the
ends of the pad and twisting it 10 times followed by folding the
pad approximately 90 degrees to make the ends meet 10 times. [0190]
Step 2: Allow samples to be equilibrated for at least two hours in
a room conditioned to 73.+-.4.degree. F. (23.+-.2.degree. C.)
temperature and 50.+-.4% relative humidity prior to testing. [0191]
Step 3: Mark the center point at the narrowest width of the pad as
the target fluid loading point. [0192] The apparatus includes a
sample holder ring stand with 15.degree. fixed incline base, a
fluid delivery separatory funnel with a nozzle, and a run-off
basin.
Procedures:
[0192] [0193] Step 1: Weigh each sample pad to be tested. [0194]
Step 2: Place the pad onto the sample holder in the CD direction
with 15.degree. incline angle and adjust the fluid delivery nozzle
to be centered over the marked center point and 0.5 inches (12.7
mm) above the pad surface. [0195] Step 3: Fill 10 ml of AMF into
the separatory funnel. [0196] Step 4: Quickly open the valve of the
funnel and allow the 10 ml fluid drained completely from the funnel
onto the pad surface in 3 seconds or less. [0197] Step 5: Weigh the
wet pad [0198] Step 6: Subtract the pad's dry weight from the wet
weight to determine the amount of fluid absorbed. Subtract this
number from 10 to get the amount of fluid not absorbed (run-off).
Then divide the run-off amount by 10 and multiply the result times
100 to report as the 10 ml Free Gush Run-Off.
5. HGW Retained Capacity
[0199] HGW is an absorbency test that measures the uptake of fluid
by an absorbent pad as a function of time.
AMF Preparation:
[0200] Condition AMF at 73.+-.4.degree. F. (23.+-.2.degree. C.) for
2 hours before drawing fluid for testing.
Sample Preparation and Apparatus:
[0201] Allow sample pads to be equilibrated for at least two hours
in a room conditioned to 73.+-.4.degree. F. (23.+-.2.degree. C.)
temperature and 50.+-.4% relative humidity prior to testing.
Procedure:
[0202] Step 1: Place the sample pad upside (top sheet side) down
horizontally in a holder basket suspended from an electronic
balance. Supply desired confining air pressure for either 0.06 psi
or 0.25 psi to the sample holder basket. [0203] Step 2: A fluid
loading column's tube, containing AMF and connected to a fluid
reservoir at zero hydrostatic head relative to the pad, is allowed
to contact the topsheet of the pad as a point source and the
increase in weight of the sample is used as a fluid uptake versus
time. [0204] Step 3: The test proceeds until the pad is fully
saturated. [0205] Step 4: 7-piles of filter paper are placed over
the saturated pad and a load of 0.25 psi (17.6 g/cm2), followed by
1.0 psi (70.3 g/cm2) is applied to squeeze-out the fluid. [0206]
Step 5: HGW Retained Capacity is the weight in grams of fluid
remaining in the sample post squeeze-out. Reported values are the
average of N=3.
6. Rewet Pressure
[0207] Rewet Pressure is the amount of pressure needed to cause
liquid to emerge back through a previously wetted topsheet from a
wet underlying absorbent core.
AMF Preparation:
[0208] Condition AMF at 73.+-.4.degree. F. (23.+-.2.degree. C.) for
2 hours before drawing fluid for testing.
Sample Preparation and Apparatus:
[0209] Step 1: Allow sample pads to be tested to equilibrate for at
least two hours in a room conditioned to 73.+-.4.degree. F.
(23.+-.2.degree. C.) temperature and 50.+-.4% relative humidity
prior to testing. [0210] Step 2: The apparatus used to measure the
loading force is a Tensile Tester with light duty jaws such as EME
model 607, model 627, or model 599A, available from the EME Co.,
Newbury, Ohio. It is equipped with a sample holder base plate and a
compression sensor foot which are also available form EME.
Procedure:
[0210] [0211] Step 1: Place the sample pad topsheet side up and
place a Plexiglas fluid loading strike through cap, with a center
hole, on the center of the pad. [0212] Step 2: Dispense 7.5.+-.0.3
ml of AMF through the center hole of the strike through cap in 5
second or less. [0213] Step 3: As soon as the pad completely
absorbs the fluid, remove the strike through cap, then start the
time for 5 minute. [0214] Step 4: Place the loaded sample pad onto
the sample holder base plate and center the compression sensor foot
directly above the stain area. [0215] Step 5: At the end of the 5
minute, start the tensile tester. The cross head should move down
to compression the sample until the fluid is detected. [0216] Step
6: The rewet pressure is the compression force divided by the area
of the compression sensor foot. Reported values are the average of
N=3. 7. Acquisition Rate (ml/sec)
[0217] This test measures gush acquisition rate, i.e., how fast the
absorbent pad acquires fluid.
AMF Preparation:
[0218] Condition AMF at 73.+-.4.degree. F. (23.+-.2.degree. C.) for
2 hours before drawing fluid for testing.
Sample Preparation:
[0219] Allow test pad samples to be equilibrated for at least two
hours in a room conditioned to 73.+-.4.degree. F. (23.+-.2.degree.
C.) temperature and 50.+-.4% relative humidity prior to
testing.
Procedures:
[0220] Step 1: Place a 4 inch square block with a 1 inch by 0.6
inch opening (generally oval in shape) over the center of the
sample pad to be tested. Add sufficient weight to the block to
achieve a 0.25 psi pressure, without obstructing opening. [0221]
Step 2: Add AMF through the top of the opening to the sample pad at
a rate of 2 ml/hr for 2.25 hour via a Low Flow Syringe Pump from
Harvard Apparatus, Southnatick, Mass. [0222] Step 3: Then, add 3 ml
AMF at once through the opening to the sample pad using a Eppendorf
Maxipipetter from Fisher Scientific. Time the interval between the
first drop of 3 ml AMF and no AMF is visible on the top surface of
the sample. [0223] Step 4: Calculate the Acquisition rate in ml/sec
by dividing the amount (3 ml) by the time in seconds measured in
Step 3. Reported values are the average of N=3.
[0224] The dimensions and values disclosed herein are not to be
understood as being strictly limited to the exact numerical values
recited. Instead, unless otherwise specified, each such dimension
is intended to mean both the recited value and a functionally
equivalent range surrounding that value. For example, a dimension
disclosed as "40 mm" is intended to mean "about 40 mm".
[0225] All documents cited in the Detailed Description of the
Invention are, in relevant part, incorporated herein by reference;
the citation of any document is not to be construed as an admission
that it is prior art with respect to the present invention. To the
extent that any meaning or definition of a term in this document
conflicts with any meaning or definition of the same term in a
document incorporated by reference, the meaning or definition
assigned to that term in this document shall govern.
[0226] While particular embodiments of the present invention have
been illustrated and described, it would be obvious to those
skilled in the art that various other changes and modifications can
be made without departing from the spirit and scope of the
invention. It is therefore intended to cover in the appended claims
all such changes and modifications that are within the scope of
this invention.
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