Note: Descriptions are shown in the official language in which they were submitted.
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ABSORBENT ARTICLE WITH IMPROVED COMBINATION OF
SKIN FEEL AND FLUID HANDLING
This is a continuation-in-part of application Serial No. 60/128,267, filed in
the name of
Walker, et al. on April 8, 1999, pending, which is a continuation-in-part of
application Serial
No. 08/832,715, filed in the name of Ouelette, et al. on April 11, 1997,
pending, which is a
continuation of application Serial No. 08/442,935, filed on May 31,
1995,abandoned, which is a
continuation-in-part of application Serial No. 08/326,571, filed on October
20, 1994, abandoned,
which is a continuation-in-part of application Serial No. 08/268,404, filed on
June 30, 1994,
abandoned.
FIELD OF THE INVENTION
The present invention relates to absorbent articles such as sanitary napkins,
panty liners,
diapers, adult incontinence pads and briefs, and the like having an improved
combination of skin
feel and fluid handling properties, such as fluid acquisition and retention.
BACKGROUND OF THE INVENTION
Absorbent articles such as diapers, sanitary napkins, panty liners,
incontinence pads and
briefs, tampons, and the like are well known and widely used to absorb bodily
exudates such as
urine, feces, and menses. Typical disposable absorbent articles often comprise
a liquid pervious
body side liner and an underlying absorbent core. The absorbent core may be
sandwiched
between the body side liner and a liquid impervious backsheet, which backsheet
serves to protect
garments and skin from contact with absorbed bodily discharges. Typically body
side liners may
comprise a topsheet such as an apertured formed film or a nonwoven topsheet
layer. A body side
liner may also comprise a multiple layer structure such as a topsheet in
liquid communication
with a secondary topsheet (which is also sometimes referred to as a
distribution layer, surge
management layer, wicking layer, or similar term).
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In order to meet the fluid handling needs of a user, such absorbent articles
need to rapidly
remove deposited bodily exudates from the body-contacting surface of the
absorbent article
(acquisition) and retain such acquired fluids away from the body surface
(retention or rewet
prevention). Typically, the fluid handling performance of an absorbent article
represents a
balance between acquisition requirements and fluid retention requirements
(rewet prevention). In
general, the properties of the core and the topsheet interact to determine the
balance.
Users of absorbent articles have other needs that also must be met to the
greatest degree
possible. For example, the body-contacting surface of the absorbent article
should be as skin
friendly as possible. Skin friendliness includes properties such as softness,
compressibility, not
retaining fluid adjacent to the skin, contains no irritating components, not
occluding the skin so as
to cause a hot, sweaty feel. For users of catamenial products, it is also
important that menses that
has been absorbed by the core be hidden from view as much as possible
(masking). Properties of
this type, while there is some performance requirement for the core, depend
more on the
performance of the topsheet.
The core of the typical absorbent article described above has two basic
requirements: to
drain the topsheet of deposited fluids and draw these fluids into the
absorbent core for storage,
and to resist subsequent release of previously absorbed fluid as a result of
pressure exerted on the
core or article as a whole (i.e. avoid "squeeze out" of the core which can
cause rewet of the body
surface). Other considerations, such as the overall capacity of the absorbent
core, its thickness,
and its stiffness are also important with respect to the design of superior
absorbent articles.
A wide variety of fibrous web structures suitable for use as core components
are known in
the art, and many of these have attempted to provide high capillary pressure
and other desirable
properties. For example, US Patents 5,009,650 and 4,699,619 both issued to
Bernardin. The
Bernardin devices incorporate a layer of primarily softwood pulp fiber
overlaying a layer of
primarily hardwood pulp fiber. The Bernardin device, however, does not achieve
the benefits of
high capillary pressure and fluid retention demonstrated by the present
invention. Additionally,
the Bernardin device fails to incorporate superabsorbent particles throughout
the layer. The use of
bicomponent fibers for improved retention properties is also not described.
The topsheet of absorbent articles preferably allows deposited fluids to
quickly penetrate
the surface thereof (i.e. the topsheet should exhibit high liquid strike-
through). Additionally, once
fluids penetrate the topsheet, they should not flow back to the surface of the
liner (i.e. the topsheet
should inhibit rewet). Preferred topsheets are also as soft, comfortable, and
as non-irritating to the
skin of the user as possible.
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The art has continually attempted to improve topsheet properties to address
such needs. For
example, one prior art approach has been to utilize a topsheet which comprises
a web of formed,
apertured thermoplastic film. Commonly assigned US Patent 4,342,314, issued to
Radel et al. on
August 3, 1982, the disclosure of which is hereby incorporated herein by
reference, discloses a
representative formed film of this variety. Such webs utilize capillary fluid
transport to conduct
fluid away from one surface (wearer-contacting) into and through the web via
three-dimensional
capillaries formed in the material, and then into the underlying absorbent
structure. In order to
address consumer concerns with regard to plastic-like appearance and feel,
apertured, formed
thermoplastic film webs have been developed which further include microscopic
surface texturing
(microtexture) and/or microscopic apertures (microapertures) to further
enhance the visual and
tactile impression of such webs. Representative film webs of this variety are
discloses in
commonly assigned US Patents 4,463,045, issued to Ahr et al. on July 31, 1984,
and 4,629,643,
issued December 16, 1986 to Curro et al., the disclosures of which are hereby
incorporated herein
by reference. While such formed film topsheets have enjoyed wide commercial
success, many
users still perceive them as being plastic-like and not particularly soft.
Another prior art approach is the use of nonwoven webs as a topsheet material.
For
example, nonwoven materials said to have desirable skin feel benefits compared
to the
aforementioned formed film topsheet materials are described in laid open
Japanese Patent
Application 7-119012, published in the name of Kao Corp. on May 9, 1995. While
the fibrous
nature of such nonwoven topsheets may have some desirable skin feel benefits,
nonwoven
materials are widely known to be deficient in preventing rewet.
One approach to combining the benefits of formed film materials and nonwoven
materials
has been to utilize a fibrous material as an overlay or laminate over a formed
film. Representative
topsheet structures of this variety are disclosed in Statutory Invention
Registration H 1670
published in the name of Aziz et al. on July l, 1997, which describes nonwoven
materials which
overlay a formed film material; and in US Patent Application Serial No.
08/744,892, filed in the
name of Sugahara on November 8, 1996 and published as WO 93/09744 on May 27,
1993, which
describes a structure having a central region comprising a formed film and
laterally outboard
regions where a nonwoven material overlies the formed film; the disclosure of
each of which is
hereby incorporated herein by reference. In addition to transport through the
formed film, webs of
this variety also exhibit capillary fluid transport characteristics via the
three-dimensional
capillaries formed by inter-fiber spaces, likewise conducting fluid away from
the wearer-
contacting surface and toward the underlying absorbent structure. Such webs
can exhibit an
aesthetically-pleasing, cloth-like surface appearance and tactile impression
due to the fibrous
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nature of the surface. However, as will be recognized, such webs are much more
expensive than a
topsheet comprising a unitary material both because of the additional material
used to produce the
laminated web and the additional processing steps required for the production.
Further, such webs
may still be deficient in fluid handling because fluids can "hang up" in small
inter fiber capillaries
of the nonwoven portion so they remain near the body contacting surface.
The art has also attempted to provide fluid handling benefits of the three
dimensional
capillaries discussed above while reducing the plastic-like feel of such
formed films using
apertured (not formed) film that is bonded to an underlying nonwoven layer in
a manner so as to
provide a series of raised peaks that are separated by valleys. Such
structures are described in US
Patent 5,536,555, issued in the name of Zelazoski, et al. on July 16, 1996 and
in PCT application
Serial No. WO 97/02133, published in the name of Kimberly-Clark Corporation on
January 23, 1997. While such structures may reduce the area of contact between
the topsheet
material and a wearer's body, a film material still contacts the wearer with
the resulting plastic-
like feel. Such materials also have the cost disadvantages of laminated
materials discussed above.
US Patent 5,643,240, issued to Jackson, et al. on July 1, 1997 describes body
side liners
(topsheets) for absorbent articles that have a multi-layer structure with an
apertured film layer
superposed over a nonwoven web where the film layer and the nonwoven web have
properties,
such that when the layers are used in combination, an absorbent article using
such a body side
layer is said to have a good penetration rate and good rewet. However, when
the claimed
penetration rate and rewet values for the claimed absorbent article are
compared to the values for
the prior art absorbent article having a formed film topsheet that is
described in the examples of
the reference, the performance of the prior art article and the claimed
article are very similar.
Also, since the body contacting surface of the '240 patent is a formed film
the body feel
deficiencies of formed films discussed above would also be present.
Thus there is a continuing need for improved absorbent articles that combine
improved
fluid handling characteristics with improved body feel. As noted above, the
desired characteristics
of the topsheet and the absorbent core are related. For example, a core which
exhibits a high
capillary pressure capability will also have an increased tendency to drain
fluids from the
topsheet, thus assisting the topsheet in inhibiting rewet. Consequently, the
design of an overall
absorbent article may involve several tradeoffs in design considerations. For
example, absorbent
cores having high capillary pressure and topsheets having an improved balance
of skin feel and
fluid handling performance can be combined as described herein. In other
words, by utilizing a
core of the present invention and the topsheets of the present invention,
absorbent articles having
both improved skin feel and fluid handling properties are envisioned.
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SUMMARY OF THE INVENTION
The present invention relates to absorbent articles such as sanitary napkins,
panty liners,
diapers, adult incontinence pads and briefs, and the like having an improved
combination of skin
feel and fluid handling properties, such as fluid acquisition and retention.
Such improved
properties are achieved by combining improved cores with improved topsheets.
Particularly
preferred embodiments of the present invention have a Drop Acquisition Time
less than about 35
seconds, a Strikethrough Time less than about 55 seconds, a Wetback of less
than 30 milligrams,
and a panel softness score of between 30 and 60 PSU. These properties are
provided by
combining improved absorbent core structures with topsheet designs having
improved skin feel
and fluid handling properties.
In one preferred embodiment of the present invention, the improved cores
comprise a
multiplicity of hardwood pulp fibers, a mult~licity of softwood pulp fibers,
and superabsorbent
particles. Both fiber types and the superabsorbent particles are present in a
substantially uniform
admixture throughout the web which is an airlaid web structure. The hardwood
pulp fibers may
preferably comprise eucalyptus fibers, which eucalyptus fibers are preferably
from about 10% to
about 50% by weight of the web. The softwood pulp fibers may preferably
comprise southern
softwood kraft fibers, which fibers are preferably from about 20% to about 60%
by weight of the
web. Alternatively, the pulp fibers may also be combined with bicomponent
thermoplastic fibers.
Preferred topsheets according to the present invention have improved skin feel
with
excellent fluid handling properties. The topsheets are fluid permeable but
provide a barrier to
rewet. The topsheets according to the present invention also preferably have a
multiplicity of
fibrils that project above the underlying surface of the topsheet material
where the fibrils originate
which produces a soft, velutinous surface.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a plan view of a preferred embodiment of an absorbent article in
the form of a
sanitary napkin which includes an absorbent core and topsheet according to the
present invention.
Figure 2 is a cross-sectional view along line 2-2, of the preferred embodiment
of the
present invention shown in Figure 1.
Figure 3 is a cross-sectional view along line 3-3, of the preferred embodiment
of the
present invention shown in Figure 1.
DETAILED DESCRIPTION OF THE INVENTION
The Absorbent Article
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The present invention relates to absorbent articles having an improved
combination of
surface feel and fluid handling properties. The absorbent articles, such as
sanitary napkins,
diapers, adult incontinence pads and briefs, panty liners, and the like, as
are described herein,
generally comprise three basic structural components. One such component is a
substantially
liquid impervious backsheet. On top of this backsheet is disposed an absorbent
core such as any
of the structures of the present invention described herein. On top of this
absorbent core and
joined to the backsheet at least about the periphery of the absorbent article
is a fluid pervious
topsheet. Optionally, at least one acquisition component (also sometimes
referred to as a fluid
distribution layer), may be located between the topsheet and the absorbent
core.
The present invention uses novel combinations of topsheets and absorbent cores
to provide
absorbent articles having the aforementioned improved combination of fluid
handling and surface
feel. Prior art absorbent articles have been able to provide either, but not
both of these properties
in one article. In particular, the absorbent articles of the present invention
have rapid fluid
acquisition (low strikethrough and drop acquisition times) and low rewet (low
wetback amount)
in combination with excellent softness. Example 1 below compares the fluid
handling properties
and softness of several embodiments of the present invention with exemplary
prior art absorbent
articles. These examples clearly demonstrate the improved performance of the
absorbent articles
of the present invention.
As noted above, the absorbent articles of the present invention generally
provide rapid
acquisition of bodily fluids that are deposited thereon. While fluid
acquisition may be evaluated in
many ways using a variety of test fluids, the methods for Drop Acquisition
Time and Liquid
Strike-Through Time, given in the ANALYTICAL METHODS section below, are
believed to
provide useful information about an absorbent article's ability to rapidly
acquire bodily fluids.
Both methods determine the time required for a sample to acquire a controlled
volume of fluid
that is rapidly deposited on the body surface of the sample. As such, a
suitable absorbent article
according to the present invention has a Drop Acquisition Time of less than
about 35 seconds,
preferably less than about 30 seconds, more preferably 25 seconds, still more
preferably less than
about 20 seconds, and most preferred less than about 15 seconds. Similarly, a
suitable absorbent
article according to the present invention will have a Liquid Strike-Through
Time of less than
about 60 seconds, preferably less than about 55 seconds, and more preferably
less than about 50
seconds.
Absorbent articles according to the present invention also inhibit absorbed
bodily fluids
from moving from the interior of the absorbent article back to the body
surface thereof when the
absorbent article is exposed to forces due to wearer movement so as to
minimize rewet. The
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7
Wetback Test described in the ANALYTICAL METHODS section below is a laboratory
measure
of rewet. The test describes a method that determines the amount of absorbed
test fluid that
returns to the surface of a sample after it has absorbed a controlled amount
of fluid and is then
loaded with a controlled pressure. When evaluated according to this method a
suitable absorbent
article according to the present invention has a Wetback of less than about 40
milligrams,
preferably less than 30 milligrams, more preferably less than 20 milligrams.
The absorbent articles of the present invention also have a desirable skin
feel. While not
being bound by theory, it is believed that the primary contributor to the skin
feel of the absorbent
articles of the present invention is the interaction between a wearer's skin
and the body surface of
the absorbent article. As is discussed in detail below, it is believed that
the body surface has a
soft, velutinous texture due to a multiplicity of fibrils that project above
underlying structure of
the topsheet material and a compressible, low density body-contacting surface.
While the present invention is suitable for all types of absorbent articles,
including baby
diapers and adult incontinence products, it will be illustrated in a
particularly preferred
embodiment, a catamenial pad, sanitary napkin 20, shown in Figure 1. As used
herein, the term
"sanitary napkin" refers to an absorbent article which is worn by females
adjacent to the pudendal
region, generally external to the urogenital region, and which is intended to
absorb and contain
menstrual fluids and other vaginal discharges from the wearer's body (e.g.,
blood, menses, and
urine). Interlabial devices which reside partially within and partially
external of the wearer's
vestibule are also within the scope of this invention. As used herein, the
term "pudendal" refers to
the externally visible female genitalia. It should be understood, however,
that the present
invention is also applicable to other feminine hygiene or catamenial pads such
as pantiliners, or
other absorbent articles such as incontinence pads, tampons, and the like.
Figure 1 is a plan view of the sanitary napkin 20 of the present invention in
its flat-out state
with portions of the structure being cut-away to more clearly show the
construction of the sanitary
napkin 20. The portion of the sanitary napkin 20 which faces or contacts the
wearer 20A is
oriented towards the viewer. As shown in Figure l, the sanitary napkin 20
preferably comprises a
liquid pervious topsheet 21, a liquid impervious backsheet 23 joined with the
topsheet 21, and an
absorbent core 25 of the present invention positioned between the topsheet 21
and the
backsheet 23. The sanitary napkin 20 depicted in Figure 1 is a simplified
absorbent article that
could represent a sanitary napkin prior to its being placed on a wearer's
undergarment. It should
be understood, however, that the present invention is not limited to the
particular type or
configuration of sanitary napkin shown in Figure 1.
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8
The sanitary napkin 20 has two surfaces, a body-contacting surface or "body
surface" 20A
and a garment surface. The sanitary napkin 20 is shown in Figure 1 as viewed
from its body
surface. The body surface is intended to be worn adjacent to the body of the
wearer while the
garment surface is on the opposite side and is intended to be placed adjacent
to the wearer's
undergarments when the sanitary napkin 20 is worn.
The sanitary napkin 20 has two centerlines, a longitudinal centerline "L" and
a transverse
centerline '°T". The term "longitudinal", as used herein, refers to a
line, axis or direction in the
plane of the sanitary napkin 20 that is generally aligned with (e.g.,
approximately parallel to) a
vertical plane which bisects a standing wearer into left and right body halves
when the sanitary
napkin 20 is worn. The terms "transverse" or "lateral" as used herein, are
interchangeable, and
refer to a line, axis or direction which lies within the plane of the sanitary
napkin 20 that is
generally perpendicular to the longitudinal direction.
Figure 1 also shows that the sanitary napkin 20 has a periphery 30 which is
defined by the
outer edges of the sanitary napkin 20 in which the longitudinal edges (or
"side edges") are
designated 26 and the end edges (or "ends") are designated 28. In the
embodiment depicted in
Figure 1, the sanitary napkin 20 is preferably symmetrical with respect to
both the longitudinal
and transverse centerlines although asymmetry about one of the centerlines is
within the scope of
the invention. Sanitary napkin 20 preferably includes side flaps or "wings" 34
that are folded
around the crotch portion of the wearer's panties. The side flaps 34 can serve
a number of
purposes, including, but not limited to, protecting the wearer's panties from
soiling and keeping
the sanitary napkin secured to the wearer's panties. While the topsheet, the
backsheet, and the
absorbent core may be assembled in a variety of well known configurations
(including so called
"tube" products or side flap products), preferred sanitary napkin
configurations are described
generally in US Patent No. 4,950,264, issued to Osborn on Aug. 21, 1990; US
Patent
No. 4,425,130, issued to DesMarais on Jan. 10, 1984; US Patent No. 4,321,924,
issued to Ahr on
Mar. 30, 1982; US Patent No. 4,589,876, issued to Van Tilburg on Aug. 18,
1987.
Figure 1 shows a preferred embodiment of the sanitary napkin 20 in which the
topsheet 21
and the backsheet 23 have length and width dimensions generally larger than
those of the
absorbent core 25. The topsheet 21 and the backsheet 23 extend beyond the
edges of the
absorbent core 25 to thereby form not only portions of the periphery but also
side flaps. As best
seen from Figure 1, the backsheet 23 and the topsheet 21 are positioned
adjacent the garment
surface and the body surface, respectively, of sanitary napkin 20 and are
preferably joined to each
other to form a perimeter 30. For example, the backsheet 23 and the topsheet
21 can be secured to
each other by a uniform continuous layer of adhesive, a patterned layer of
adhesive, or an array of
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9
separate lines, spirals, or spots of adhesive. Adhesives that have been found
to be satisfactory are
manufactured by H. B. Fuller Company of St. Paul, MN under the designation HL-
1258 or
H-2031. Alternatively, topsheet 21 and backsheet 23 can be joined to each
other by heat bonding,
pressure bonding, ultrasonic bonding, dynamic mechanical bonding, or any other
suitable method
for joining topsheets and backsheets known in the art.
Figures 1-3 show the individual components of the main body portion 22 of the
sanitary
napkin 20 of the present invention. The main body portion 22 of the sanitary
napkin comprises at
least three primary components. These include a liquid pervious topsheet 38, a
liquid impervious
backsheet 40, and absorbent core 42 positioned between the topsheet 38 and the
backsheet 40.
Preferably, the main body portion 22 of the sanitary napkin 20 also comprises
at least one
optional acquisition component 44. The acquisition component 44 may either be
a separate
component positioned between the topsheet 38 and the absorbent core 42, or it
may comprise part
of a composite topsheet or part of the absorbent core 42.
The Topsheet
The topsheet 38 is a liquid pervious component that permits liquids (e.g.,
menses and/or
urine) to readily penetrate through its thickness. The topsheet 38 is
preferably compliant, soft
feeling, and non-irntating to the wearer's skin. As noted above, preferred
topsheets according to
the present invention have both excellent skin feel and fluid handling
properties
In preferred embodiments of the present invention, at least a portion of the
body surface of
the topsheet 38 is hydrophilic so that liquids will be transferred through the
topsheet more readily.
This diminishes the likelihood that bodily fluids will flow off the topsheet
ratherthan flowing into
and being absorbed by the absorbent core 42. The body surface of the topsheet
38 can be made
hydrophilic by treating it with a surfactant. Suitable methods of treating a
topsheet with a
surfactant are described in US Patent 4,950,254 issued to Osborn and in US
Patent 5,520,875,
issued to Wnuk, et al. on May 28, 1996. Particularly preferred surfactant
materials are described
in copending, commonly assigned US Patent application Serial No. 09/287,986,
filed in the name
of Stone on April 8, 1999.
Preferred topsheets 38 according to the present invention achieve their
desirable balance of
skin feel and fluid handling properties by having means so bodily fluids that
are deposited on the
body surface 20A of sanitary napkin 20 rapidly pass through the topsheet 38
for absorption by the
absorbent core 42. Such preferred topsheets also provide a barrier that
inhibits such absorbed
fluids from moving in the opposite direction when the sanitary napkin 20 is
exposed to forces due
to wearer movement so as to minimize rewet. The topsheet also has desirable
skin feel properties
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as are provided by a multiplicity of fibrils that project above the underlying
structure of the
topsheet material where the fibrils originate so as to provide a substantially
uniform soft and silky
skin feel.
A suitable topsheet 38 may be manufactured from a wide range of materials such
as woven
and nonwoven materials; polymeric materials such as apertured formed
thermoplastic films,
apertured plastic films, and hydroformed thermoplastic films; porous foams;
reticulated foams;
reticulated thermoplastic films; and thermoplastic scrims. Suitable woven and
nonwoven
materials can be comprised of synthetic fibers (e.g., polymeric fibers such as
polyester,
polypropylene, or polyethylene fibers). Such suitable topsheets may also be
composite structures
comprising both a formed thermoplastic film layer and a fibrous layer or two
thermoplastic film
layers that are subsequently formed.
As noted above, such preferred topsheets 38 are liquid permeable so as to
provide rapid
strikethrough of deposited bodily fluids for absorption by the core 42. One
means of achieving
rapid strikethrough is to provide a multiplicity of apertures through the
topsheet. Such apertured
topsheets are described in greater detail in the aforementioned US Patent
application Serial
No. 08/832,715, which describes formed films having microscopic spaced apart
depositions of a
low surface energy material thereon and in US Patent application Serial No.
09/217,736 filed in
the names of Curro, et al. on December 21, 1998, which describes a laminate of
an aperlured
nonwoven and a formed apertured thermoplastic film. Preferably, the body
contacting surface is
provided with a plurality of microscopic, discontinuous, spaced regions that
comprise depositions
of a low surface energy material. The depositions have a surface energy that
is lower than the
surface energy of the underlying polymeric substrate which creates a surface
energy gradient
between the depositions and the underlying substrate. This surface energy
gradient exerts a force
on fluid contacting the body contacting surface of the topsheet to direct to
direct fluids away from
the body contacting surface and through the topsheet for absorption by the
core 42. Such surface
depositions are described in greater detail in US Patent 6,025,049 issued in
the names of Ouelette,
et al. on February 15, 2000.
While a topsheet 38 may have rapid strikethrough (i.e. rapid movement of fluid
from the
body surface 20A of the sanitary napkin 20 to the core 42), it is also
important for purposes of the
present invention that a suitable topsheet 38 also inhibit rewet of such
acquired fluids. As is well
known, wearer movement applies forces to absorbent articles that can cause
fluid movement from
the core toward the body surface of the article which can cause the fluids to
rewet the body
surface. Rewet can be inhibited by providing a barrier to such reverse fluid
flow toward the body
surface. Such a barrier can have many forms. For example, the structures
described in the
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aforementioned US Patent 4,342,314 use capillary size to partially inhibit
reverse fluid flow. In
addition, the formed film webs disclosed therein are somewhat resistant to the
shear forces caused
by bodily movement and provide some separation between the body surface and
the top of the
absorbent core. Another means of inhibiting rewet is to provide a surface
chemical barner to
reverse fluid flow. The surface energy gradients disclosed in the
aforementioned US
Patent 6,025,049 and in the aforementioned US Patent application Serial No.
08/832,715 are
believed to provide such a surface chemical barrier to rewet.
In addition to the fluid handling properties discussed above the topsheets of
the present
invention have desirable skin feel. As noted above, it is believed that such
desirable skin feel is
due to the presence of a multiplicity of fibrils that project above the
underlying surface of the
topsheet material where the fibrils originate. Such fibrils produce a soft,
velutinous surface which
contacts the wearer's body and enhances the skin feel of the topsheet.
Depending on the structure
of the topsheet 38, such fibrils can comprise the microapertures discussed in
the aforementioned
US Patent 6,025,049 or the portion of the fibers of a nonwoven structure that
may extend above
the bulk of the structure.
This softness is readily perceivable by tactile evaluation. As can clearly be
seen in
Examples 1 and 2, when topsheets 38 according to the present invention are
evaluated for
softness using the Panel Softness method given in the ANALYTICAL METHODS
section below,
graders rate the topsheets 38 of the present invention very highly. Suitably,
an absorbent article
using a topsheet 38 according to the present invention has a softness rating
of between about 30
panel score units (PSU) and about 60 PSU. Preferably, the softness rating is
between about 35
PSU and about 60 PSU. More preferably, the softness is between about 40 PSU
and about 60
PSU.
The fibrils provide a compressibility to the body surface 20A of the sanitary
napkin 20
because they project above the underlying surface of the topsheet material. As
will be recognized
such compressibility depends both on the dimensions of the individual fibrils
and the mechanical
properties of the fibrils. The Thickness Under Load Test described in the
ANALYTICAL
METHODS section below evaluates both of these contributors to provide an
overall response that
relates to this aspect of body feel. As can be seen therein this method
measures the force
necessary to compress a sample by the approximate length of the fibrils. Thus,
samples having a
low compressibility value are believed to be particularly preferred because of
their "cushy" feel.
Exemplary compressibility data are given in Example 2 which compares topsheets
according to
the present invention with various prior art topsheets. Suitably, a topsheet
according to the present
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invention has a compressibility less than, about 400 grams/cm3. Preferably,
the compressibility is
less than about 375 grams/cm3; more preferably, less than about 350 grams/cm3.
This compressibility is believed to be due to a region of the topsheet that is
defined by the
volume that lies between the underlying surface of the topsheet material and
the distal ends of the
fibrils. As will be recognized, because this region is occupied only by the
material comprising the
fibrils, the region has a low density. A method for determining this surface
density is given in the
Thickness Under Load method that is described in the ANALYTICAL METHODS
section
below. The reason the compressibility of this region is low is that the only
material resisting
compression is the material that comprises the fibrils. As compression
continues so as to bring the
fibrils into closer contact such that the density in the region begins to
approach the density of the
underlying topsheet material, the compressive force must, of necessity
increase. It has been found
that a material having a Surface Density that is less than about 0.035
grams/cubic centimeter has
desirable softness. Preferably, the Surface Density is less than 0.03 about
grams/cubic centimeter.
The fibrils that provide such desirable surface feel to topsheets according to
the present
invention can be provided using various means. Suitable means include:
hydroforming as
described in the aforementioned US Patent 4,629,643; body surfaces comprising
a nonwoven
material as disclosed in the aforementioned US Patent application Serial No.
08/832,715; napping
and separation of softened polymeric material from a template as disclosed in
PCT application
Serial No. WO 99/06623 published in the name of Minnesota Mining and
Manufacturing
company on February 11, 1999; printing a hot melt material on the body surface
as described in
commonly assigned US Patent 5,763,044, issued to Ahr, et al on June 9, 1998;
brushing; and
other means as would be known to those having skill in the art.
Topsheets 38 having the particularly preferred combination of fluid handling
and skin feel
include: the formed thermoplastic film materials having a plurality of
macroapertures and a
multiplicity of microapertures wherein land area between the microapertures
and the
macroapertures is also provided with a plurality of microscopic,
discontinuous, spaced regions
that comprise depositions of a low surface energy material. Such a structure
creates a surface
energy gradient between the depositions and the underlying polymeric structure
of the formed
film as described in the aforementioned US Patent 6,025,049; the nonwoven
materials having
depositions of a low surface energy material that create a surface energy
gradient between the
depositions and the underlying polymeric structure of the nonwoven material as
described in US
Patent application Serial No. 08/832,715 filed in the names of Ouelette, et
al. on April 11, 1997
and in US Patent 5,792,404, issued to Cree, et al. on August 11, 1998. The
disclosure of each of
which is incorporated herein by reference.
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13
Other suitable materials for use as the topsheet 38 include the nonwoven
materials provided
with apertures according to US Patent, 5,628,097, issued in the name of
Benson, et al. on
May 13, 1997; the laminate of a nonwoven material and a formed apertured
thermoplastic film,
the nonwoven material having depositions of a low surface energy material that
create a surface
energy gradient between the depositions and the underlying polymeric structure
of the nonwoven
material as described in US Patent application Serial No. 08/761,905 filed in
the name of Bien on
December 5, 1996 and in the aforementioned US Patent application Serial No.
09/217,736; the
permanently hydrophilic formed film materials described in US Patent
application Serial
No.09/344,161, filed in the name of Lee, et al. on June 24, 1999; and in the
textured,
microapertured polymeric film webs that are described in US Patent application
Serial
No. and the apertured polymeric webs having a multiplicity of three
dimensional surface
structures as described in US Patent application Serial No. , both filed in
the name of Lee,
et al. on April 7, 2000 (P&G Case Nos. 8011 and 8012 respectively; the
Applicant will add the
filing information when it is known). The disclosure of each of which is
incorporated herein by
reference.
The Backsheet
The backsheet 40 prevents the exudates absorbed and contained in the absorbent
core 42
from wetting articles which contact the sanitary napkin 20 such as pants,
pajamas and
undergarments. The backsheet 40 is preferably resistant to the flow of
liquids, and more
preferably is impervious to liquids (e.g., menses and/or urine). The backsheet
40 is preferably
manufactured from a flexible material. As used herein, the term "flexible"
refers to materials
which are compliant and will readily conform to the general shape and contours
of the human
body. The backsheet 40 may comprise a woven or nonwoven material, polymeric
films such as
thermoplastic films of polyethylene or polypropylene, or composite materials
such as a film-
coated nonwoven material. Preferably, the backsheet 40 is a polyethylene film
having a thickness
of from about 0.012 mm (0.5 mil) to about 0.051 mm (2.0 mils). The backsheet
40 may be
embossed and/or matte finished to provide a more clothlike appearance.
Further, the backsheet 40
may permit vapors to escape from the absorbent core 42 (i.e., breathable)
while still preventing
exudates from passing through the backsheet 40. A suitable backsheet material
is obtained as
product No. 18-1401 from the Clopay Corporation of Cincinnati, OH. A suitable
breathable
backsheet material is a laminate of an apertured film such as that described
in US Patent
3,929,135 issued to Thompson which is inverted so that the smaller openings of
the tapered
capillaries face the absorbent core 42 which is adhesively laminated to a
microporous film such as
that described in Exxon's US Patent 4,777,073.
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The Absorbent Core
The absorbent core 42 may be any absorbent means which is capable of absorbing
and
retaining liquids (e.g., menses and/or urine). A suitable core for purposes of
the present invention
has a high affinity for such liquids. Because of this high affinity, the
absorbent core 42 is
particularly effective in drawing such liquids from the topsheet 38 and in
retaining such acquired
liquids. Suitable structures for the core 42 have a high capillary pressure
which allows the core 42
to effectively draw liquids that are deposited on the body surface 20A of
sanitary napkin 20
through the topsheet 38 for storage. Suitable core structures also retain
fluids well either because
of a high capillary desorption pressure or because the core structure also
comprises a
superabsorbent material which can store acquired fluids by osmotic means.
As noted above, cores 42 of the present invention, because of their high
capillary
absorption pressure, can more fully dry the topsheet 38 than cores with a
lower capillary
absorption pressure. A method for measuring absorption pressure is provided in
the
ANALYTICAL METHODS section below. Because the cores 42 have a particularly
high
absorption pressure, they are very effective in acquiring fluids that are
deposited on the topsheet
38. Suitably the mean absorption pressure is at least about 7 cm. Preferably,
the mean absorption
pressure is at least about 10 cm; more preferably, at least about 12 cm.
Typically, the mean
absorption pressure is between about 7 cm and about 25 cm. More typically, the
mean absorption
pressure is between about 10 cm and about 25 cm.
The absorbent core 42 may be manufactured in a wide variety of sizes and
shapes (e.g.,
rectangular, oval, hourglass, dog bone, asymmetric, etc.). The configuration
and construction of
the absorbent core 42 may also be varied (e.g., the absorbent core may have
varying caliper zones
(e.g., profiled so as to be thicker in the center), or may comprise one or
more layers or structures.
The total absorbent capacity of the absorbent core should, however, be
compatible with the
design loading and the intended use of the sanitary napkin. Further, the size
and absorbent
capacity of the absorbent core may be varied to accommodate different uses
such as incontinence
pads, pantiliners, regular sanitary napkins, or overnight sanitary napkins.
A wide variety of liquid-absorbent materials commonly used in sanitary napkins
and other
absorbent articles are suitable for manufacture of the absorbent core 42, such
as blends
comprising comminuted wood pulp which is generally referred to as airfelt.
Examples of other
suitable absorbent materials meltblown polymers including coform; chemically
stiffened,
modified or cross-linked cellulosic fibers; synthetic fibers such as crimped
polyester fibers; peat
moss; tissue including tissue wraps and tissue laminates; absorbent foams;
absorbent sponges;
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superabsorbent polymers; absorbent gelling materials; or any equivalent
material or combinations
of materials, or mixtures of these. The configuration and construction of the
absorbent core may
also be varied (e.g., the absorbent core may have varying caliper zones (e.g.,
profiled so as to be
thicker in the center), hydrophilic gradients, superabsorbent gradients, or
lower density and lower
average basis weight acquisition zones; or may comprise one or more layers or
structures).
A particularly preferred absorbent core 42 according to the present invention
utilizes a
combination of hardwood pulp fibers and softwood pulp fibers in an airlaid
fibrous web. The
incorporation of the hardwood fibers in the combinations described allows for
increased capillary
pressure and improved fluid distribution compared to absorbent webs without
such fiber content.
Additionally, by making the structure an airlaid structure, it is possible to
incorporate
superabsorbent particulate material throughout the core 42 and to achieve
improved stiffness
control over the resulting core as compared to the prior art. Consequently,
the absorbent core 42
of the present invention is particularly well suited for use with the above-
described topsheet
materials due to its high capillary pressure, its high capacity through the
use of superabsorbent
material, and its high control over stiffness and other physical properties.
The particularly preferred absorbent core 42 of the present invention is an
airlaid fibrous
web comprising a substantially uniform admixture of hardwood pulp fibers and
softwood pulp
fibers. Preferably, the fibrous absorbent web also incorporates superabsorbent
particles
throughout the web. Additionally, the fibrous web layer may also incorporate
synthetic fibers,
such as bicomponent binder fibers, in the uniform admixture of fibers
described above.
Unless otherwise noted, all composition percentages given below are expressed
in terms of
weights of the quantities being considered. Preferably, the fibrous absorbent
web 40 of the
present invention includes a ratio of softwood pulp fibers to hardwood pulp
fibers in the range of
from about 4:1 to about 1:2, more preferably from about 3:1 to about 1:1, most
preferably about
2:1. A particularly preferred hardwood pulp fiber is a eucalyptus fiber. A
particularly suitable
eucalyptus fiber includes those of the eucalyptus grandis species. The
hardwood pulp fibers, and
eucalyptus in particular, have high surface area, thereby providing the
absorbent web with a high
capillary pressure. Too much hardwood pulp fiber, however, in the web will
reduce its overall
absorbent capacity. Additionally, the presence of excess hardwood pulp fiber
may lower the fluid
handling speed of the web to an unacceptably low level. Other suitable pulp
fibers for use as a
hardwood fiber in the absorbent core 42 of the present invention may include
acacia, oak, maple,
or cherry fibers.
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The hardwood pulp fibers are blended in the absorbent core 42 with a
multiplicity of
softwood pulp fibers. The softwood pulp fibers are preferably blended into the
structure in the
ratios indicated above. A particularly preferred softwood pulp fiber is
southern softwood kraft
fibers. Other suitable softwood fibers include western and northern softwood
kraft fibers.
The blend of hardwood pulp fibers and softwood pulp fibers provides a web with
different
sized fibers incorporated throughout. This provides a good distribution of
fiber surface area and
provides, in preferred embodiments, a high overall surface area. As noted
above, the use of
hardwood fibers involves tradeoffs between capillary pressure, and capacity
and/or fluid handling
speed. Because the cores 42 of the present invention are airlaid, they are
readily amenable to the
inclusion of a superabsorbent material. Such superabsorbent material will
improve the overall
capacity of the core 42, thereby advantageously combining high capacity and
high capillary
pressure.
The preferred absorbent core 42 of the present invention preferably also
incorporates
bicomponent binder fibers and/or superabsorbent particles. In more preferred
embodiments, both
the bicomponent fibers and the superabsorbent particles are present in the web
and are blended in
a substantially uniform mixture throughout the web thickness.
As will be recognized, the addition of bicomponent fibers allows for thermal
bonding
processes, such as through air bonding, bonding using heated rolls, ultrasonic
bonding, and other
means wherein a bonding material is melted. Such bonding also enables positive
stiffness control
of the overall layer. The stiffness of the web is controlled by adjusting the
amount of
bicomponent fiber as well as the time and temperature parameters of the
thermal bonding process.
Suitably, between about S% and about 30% of the web is bicomponent fibers. In
a particularly
preferred embodiment, between about 15% and about 25% of the web is
bicomponent fibers. A
preferred fiber comprises a polyethylene/polypropylene fiber in which the
polypropylene core is
surrounded by a polyethylene sheath Such a suitable 50%/50% concentric
bicomponent fiber is
available from Danaklon of Varde, Denmark.
Other binder materials may be included within the web structure as well.
Polyethylene
powder binders and/or latex binder material may be, but need not be,
incorporated into the web
structure. The use of a powder binder such as polyethylene allows the web to
be a thermally
bonded structure as is the case with the bicomponent binder fibers described
above. If latex, or a
similar binder is used, the latex will act as the binder and the structure may
be described as "latex
bonded."
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While the foregoing discussion indicates how the components of the fibrous
portion of the
particularly preferred core structure interact to provide high capillary
pressure, other components
of the absorbent core 42 can also contribute to the performance thereof.
Specifically, as noted
above, the use of superabsorbent materials in the cores 42 of the present
invention is preferred.
An exemplary superabsorbent material is SAB 960, as is available from
Stockhausen Louisiana
Limited of Garyville, LA. Preferred superabsorbent particulate materials for
use in the present
invention have high permeability because and reduced gel blocking compared to
commonly used
superabsorbent materials. Exemplary preferred materials include surface
crosslinked
polyacrylates such as ASAP 2300 as is available from Chemdal, Corp. of
Palatine, IL and the
mixed bed materials described in copending, commonly assigned US Patent
application Serial
No. 09/258,890, filed in the names of Hird, et al. on March 1, 1999. The AGM
particles
preferably comprise from about 10% to about 50% of the absorbent core 42. A
higher amount of
such superabsorbent material increases the overall capacity of the absorbent
core 42. Excess
superabsorbent material, however, may reduce the permeability of the core 42
due to gel blocking
or similar effects.
The fibrous absorbent web of the present invention may be made by any suitable
airlaying
technique known in the art. The use of airlaying allows the incorporate of
particulate
superabsorbent material throughout the structure, as well as greater positive
control over the web
physical properties than may be possible with other web forming techniques.
When the web incorporates bicomponent fibers, the web is preferably formed
using a
thermally bonded airlaid technique as described above. In such a construction,
the use of
additional binder material such as powder binder or latex is not required.
Such additional
materials may, nonetheless, be included in order to form a mufti-bonded
airlaid web. Additionally
the web need not incorporate any bicomponent fiber, and may use latex in
combination with the
superabsorbent particles and hardwood and softwood pulp fibers as described
above to form a
latex bonded airlaid structure. Suitable methods of forming such airlaid
structures are well known
in the art. Another alternative includes the use of a powdered binder such as
polyethylene
together with a multiplicity of hardwood pulp and softwood pulp fibers to form
a thermally
bonded airlaid web.
U.S. Patent 5,445,777 describes a preferred method of adding a particulate
superabsorbent
material and/or a powdered binder material (such as the polyethylene binder
described above) to a
fibrous airlaid web. Such techniques are suitable for construction of the
fibrous absorbent webs
40 of the present invention.
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The airlaid structure of the present invention may be made with any suitable
basis weight
and density for the article in which is to be utilized. Suitably, the basis
weight can be between
about 60 g/mz and about 400 g/m2and the density can be between about 0.05 g/cc
and about 0.2
g/cc. A preferred structure for use in a sanitary napkin may have a total
basis weight of about 200
g/mz, a preferred density of about 0.13 g/cc, and a caliper of about 1.5 mm.
For thicker products, the absorbent core 42 of the present invention may
comprise a fluff of
hardwood pulp fibers and softwood pulp fibers wherein the caliper and basis
weight are tailored
to meet the needs of users who desire such products. Optionally, a
superabsorbent material may
be incorporated homogeneously throughout the structure.
An alternative preferred material for the absorbent core 42 comprises
polymeric foams
formed from high internal phase emulsions (HIPE foams) as are described in US
Patent 5,795,921
issued in the name of Dyer, et al. on August 18, 1998. Such foam materials can
be produced so as
to have a suitably small cell size so as to provide the high capillary
absorption pressure that is
discussed above, yet have sufficient openness to allow free movement of the
insoluble
components in blood-based fluids such as menses. These absorbent foams are
made by
polymerizing HIPEs where the volume to weight ratio of the water phase to the
oil phase is in the
range of from about 20:1 to about 125:1.
In addition to the absorbent materials described above, the absorbent core 42
may comprise
other types of absorbent materials known in the art such as, creped cellulose
wadding; meltblown
polymers including coform; chemically stiffened, modified or cross-linked
cellulosic fibers;
synthetic fibers such as crimped polyester fibers; peat moss; tissue including
tissue wraps and
tissue laminates; absorbent foams; absorbent sponges; or any equivalent
material or combinations
of materials, or mixtures of these. Such additional materials can either be in
the form of additional
layers as are discussed below with respect to the acquisition component 44 or
can comprise
alternative preferred structures for the absorbent core 42.
While such alternative preferred structures must still meet the fluid handling
requirements
for the absorbent core 42 discussed above, the structures provide the designer
of an absorbent
article with additional design flexibility to meet performance requirements
other than those
discussed herein while still providing absorbent articles having the overall
desirable fluid
handling and skin feel of the absorbent articles of the present invention.
Exemplary core
structures that are also suitable for purposes of the present invention
include an acquisition
component that is pattern bonded to the topsheet so as to create an unbonded
window which
overlies an absorbent core comprising a mufti-bonded air laid nonwoven
material comprising
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a blend of cellulose fibers, bi-component fibers, superabsorbent particles,
and latex binder
as is described in commonly assigned and copending US Patent Application
Serial
No. 09/074,909 filed on May 8, 1998, in the name of Daniels et al. and in
International Patent
Application Serial No. PCT/US96/20873, filed on December 20, 1996, in the name
of Lynard et
al., which application designates the United States; and the blends of
chemically stiffened,
twisted, and curled bulking fibers, high surface area fibers, and
thermoplastic binding fibers as
described in US Patent 5,549,589 issued the name of Horney et al on August 27,
1996. The
disclosure of each of which is incorporated herein by reference. Absorbent
cores 42 may also
comprise blends or combinations of fibrous materials and HIDE foams wherein
the foam is either
in sheet or particulate form.
The acquisition component (or "acquisition layer" or "distribution layer") 44,
if used, lies
beneath the topsheet 38. The terms "layer" or "web", as used herein, include
but are not limited to
single unfolded sheets, folded sheets, strips of material, loose or bonded
fibers, multiple layers or
laminates of material, or other combinations of such materials. These two
terms are thus, not
limited to single unfolded layers or sheets of material. The acquisition
component 44 may provide
void volume beneath the topsheet 38 to increase the ability of the sanitary
napkin to draw liquids
through the topsheet 38. In the preferred embodiment described herein, the
acquisition component
44 preferably provides resiliency to lateral compressive forces so that the
sanitary napkin 20 has
improved resistance to bunching.
The acquisition layer serves to quickly collect and temporarily hold
discharged bodily
fluids, as well as facilitating transport of the fluid from the point of
initial fluid contact to other
parts of the acquisition layer and the absorbent core. There are several
reasons why the improved
transport of exudates is important, including providing a more even
distribution of the exudates
throughout the absorbent core and allowing the sanitary napkin 20 to be made
relatively thin. The
transport referred to herein may encompass the transportation of liquids in
one, two or all
directions (i.e., in the x-y plane and/or in the z-direction). The acquisition
layer may be comprised
of several different materials including nonwoven or woven webs of synthetic
fibers including
polyester, polypropylene, or polyethylene, natural fibers including cotton or
cellulose, blends of
such fibers, or any equivalent materials or combinations of materials.
Examples of sanitary
napkins having an acquisition layer and a topsheet are more fully described in
US Patent
No. 4,950,264 issued to Osborn, US Patent application Ser. No. 07/810,774,
Dec. 17, 1991 filed
in the names of Cree, et al. and published as PCT application Serial No. WO
93/117,725 on
June 24, 1993, and the aforementioned International Patent Application Serial
No. PCT/US96/20873. The disclosure of each of these references is incorporated
herein by
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reference. In a preferred embodiment, the acquisition layer may be joined with
the topsheet by
any of the conventional means for joining webs together, most preferably by
fusion bonds as is
more fully described in the above-referenced Cree application.
The acquisition component 44 should be liquid permeable. The acquisition
component 44 is
also preferably compliant, soft feeling, and non-irritating to the user's
skin. The acquisition
component 44 has a body-facing face (or side), and a garment-facing face. The
acquisition
component 44 may be of any suitable size and shape. In the embodiment shown in
Figure 1, the
acquisition component 44 is in the shape of a race track with slightly concave
side edges, as is the
portion of the topsheet 38 that overlies the main body portion 22 of the
sanitary napkin 20. The
dimensions of the acquisition component 44, however, are preferably not as
large as those of the
topsheet 38.
The acquisition component 44 can be made from any materials suitable for the
above
purposes that are capable of having the topsheet 38 fused to them. The
acquisition component 44
may, for example, be comprised of woven or nonwoven materials. The fibers or
other
components of these materials may be synthetic, or partially synthetic and
partially natural.
Suitable synthetic fibers include polyester, polypropylene, polyethylene,
nylon, viscous rayon, or
cellulose acetate fibers. Suitable natural fibers include cotton, cellulose,
or other natural fibers.
The acquisition component 44 may also be at least partially comprised of cross-
linked cellulose
fibers. The acquisition component 44, if nonwoven, can be made by a number of
different
processes. These include, but are not limited to: air laid, wet laid,
meltblown, spunbonded,
carded, thermally bonded, air-through bonded, powder bonded, latex bonded,
solvent bonded,
spunlaced, and combinations of the foregoing.
The acquisition component 44 may be constructed in the manner described in the
aforementioned US Patent 5,549,589 with respect to the distribution layer
described therein.
Another preferred construction for the acquisition component 44 is a laminate
of two nonwoven
materials. The uppermost layer of this laminate (or "secondary topsheet") 46
preferably comprises
an 19 g/yd2 (22.5 g/m2) spunbonded polypropylene nonwoven material referred to
as product No.
065MLPV60U (or "P-9") obtained from Fiberweb, North America of Washougal, WA.
The
underlying layer of the laminate (or "tertiary topsheet") 48 preferably
comprises a multi-bonded
air laid nonwoven material that is thermally bonded using powder bonding and
latex bonding. In a
preferred embodiment, this mufti-bonded air laid nonwoven material comprises
about 77%
cellulose fibers, about 20% powder binder, and about 3% latex binder (1.5%
sprayed on each side
of the web) and has a basis weight of about 50 g/ydz (about 60 g/mz). (Unless
otherwise stated, all
percentages herein are by weight.) Such a mufti-bonded air laid nonwoven is
preferably obtained
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21
as product No. 90830X312 from Merfin Hygienic Products, Ltd. of Delta, British
Columbia,
Canada. These two nonwoven layers are preferably laminated together by
depositing the multi-
bonded air laid nonwoven material on the spunbonded polypropylene nonwoven
material. The
spunbonded material is used as a process aid or carrier web in the process of
forming this
laminate.
In alternative embodiments, the spunbonded polypropylene nonwoven material may
have a
greater or a lower basis weight, or it may be replaced by an air laid tissue,
a wet laid tissue, or any
of the materials described above. If a wet laid tissue is used instead of a
polypropylene nonwoven
material, the orientation of the laminate is preferably reversed so that in
the finished product, the
multi-bonded air laid nonwoven material lies above the wet laid tissue layer.
In the case of thicker
sanitary napkins, any of the acquisition components described above can be
used. Additionally, in
one preferred thicker sanitary napkin embodiment, a low density latex bonded
air laid material
can be used as the entire acquisition component (that is, no tertiary topsheet
is required). A low
density latex bonded air laid material suitable for this purpose is a material
having a basis weight
of about 80 g/mz known as product No. FG413MHB, which is obtained from
Walkisoft, USA of
Mt. Holly, NC.
The topsheet 38 described herein is preferably fused to the acquisition
component 44 or to
the absorbent core 42, or to both. A suitable manner for fusing (or
integrating) the topsheet to
underlying components at discrete sites is described in the aforementioned US
Patent Application
Serial No. 09/074,909. As described in the above-referenced applications, the
bonding of the
topsheet to underlying layers is preferably done at discrete locations and the
center of the article
is provided with an "un-bonded window."
Assembly of the Sanitary Napkin
The topsheet 38, the acquisition component 44, if included, the backsheet 40,
and the
absorbent core 42 may be assembled in a variety of configurations known in the
art (including
layered or "sandwich" configurations and wrapped or "tube" configurations).
Figures 1 and 2
show a preferred embodiment of the sanitary napkin 20 assembled in a sandwich
construction. In
Figures 1-3, the topsheet 38 and the backsheet 40 have length and width
dimensions generally
larger than those of the absorbent core 42. The topsheet 38 and the backsheet
40 extend beyond
the edges of the absorbent core 42 to form portions of the periphery 30. The
garment-facing side
of the topsheet 38 is preferably joined to the body-facing side of the
acquisition component 44 as
described above. The acquisition component 44 may be joined to the absorbent
core 42, if
desired. If these components are joined, they can be joined in any of the
manners described herein
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for joining the topsheet 38 to the acquisition component 44. However, in the
embodiment shown
in the drawings, the acquisition component 44 is not directly joined to the
absorbent core 42. The
backsheet 40 is preferably joined to the garment-facing side of the absorbent
core by adhesives.
The portions of the topsheet 38 and backsheet 40 that extend beyond the edges
of the
absorbent core 42 and the acquisition component 44 are preferably also joined
to each other.
These portions of the topsheet 38 and backsheet 40 can be joined in any
suitable manner known
in the art. The term "joined", as used in this specification, encompasses
configurations in which
an element is directly secured to another element by affixing the element
directly to the other
element; configurations in which the element is indirectly secured to the
other element by affixing
the element to intermediate members) which in turn are affixed to the other
element; and
configurations in which one element is integral with another element, i.e.,
one element is
essentially part of the other element. Preferably, in the embodiment shown,
these portions of the
topsheet 38 and backsheet 40 are joined using adhesives over substantially the
entire portions that
extend beyond the edges of the absorbent core 42 and a crimp seal at the end
edges 28 of the main
body portion where the topsheet 38 and backsheet 40 are densifled by the
application of pressure
or heat and pressure.
Exemplary Absorbent Article Structure
One particularly preferred embodiment of the present invention comprises a
topsheet
according to the aforementioned US Patent 6,025,049 and the particularly
preferred core
described above. The performance of this particularly preferred structure is
shown as Sample 2 in
Table 1 below. As can be seen in the data presented in Table 1, this
particularly preferred
embodiment has a very desirable balance of fluid handling properties and
softness.
In particular, the topsheet 38 of this particularly preferred embodiment
comprises a formed
thermoplastic film having a plurality of macroaperlures that allow fluids
contacting the body
surface of the topsheet 38 to pass therethrough and a multiplicity of
microapertures that extend
upward and form the body contacting surface 20A when the formed film is used
as a topsheet.
The land area between the microapertures and the macroapertures is also
provided with a plurality
of microscopic, discontinuous, spaced regions that comprise depositions of a
low surface energy
material. There is a surface energy gradient between the depositions and the
underlying polymeric
structure of the particularly preferred topsheet 38 that creates a force which
encourages bodily
fluids deposited on the body surface 20A to move to the macroapertures and
therethrough for
absorption by the core 42.
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This preferred embodiment also comprises an acquisition component 44 which
underlies
the topsheet 38 as described above. A acquisition component 44 comprises
secondary topsheet 46
of spunbonded polypropylene nonwoven material and a tertiary topsheet 48 of a
multi-bonded air
laid nonwoven material that is thermally bonded using powder bonding and latex
bonding as is
described above and in the aforementioned US Patent 5,549,589.
The core 42 for this preferred embodiment is described in detail above and in
greater detail
in commonly assigned, copending US Patent Application serial No. 60/128,352,
filed in the name
of Noel, et al on April 8, 1999. As noted above, these preferred structures
for core 42 comprise
blends of hardwood and softwood fibers that provide high capillary pressure
and superabsorbent
polymers that provide a high osmotic storage capability.
The preferred components discussed above, along with a liquid impervious
backsheet 40 as
may be known to the art are assembled into a preferred embodiment of the
sanitary napkin 20 of
the present invention according to the configuration discussed in the Assembly
of the Sanitary
Napkin section above
Optional Components
Flaps
The sanitary napkin 20 shown in Figures 1-2, as discussed above, preferably
comprises an
optional pair of flaps 24 that are joined to the main body portion 22. The
flaps 24 extend laterally
outward beyond the longitudinal side edges 26 of the main body portion 22 from
their proximal
edges 60 to their distal edges (or "free end") 62. The flaps 24 extend outward
from at least the
central region 36 of the main body portion 22. As shown in Figure 1, each flap
24 is divided into
a front half 64, and a back half 66 by a flap transverse centerline T1. The
flap transverse
centerline T1 may coincide with the principal transverse centerline T of the
sanitary napkin, but
this is not absolutely required.
The flaps 24 can be joined to the main body portion 22 in any suitable manner.
Preferably,
in the embodiment shown in Figures 1-3, the flaps 24 are integral with the
main body portion 22
(that is, the flaps 24 comprise integral extensions of the topsheet 38 and
backsheet 40). In other
alternative embodiments, the flaps 24 can comprise separate components that
are joined to the
main body portion 22. The flaps 24 are each joined to (or associated with)
main body portion 22
along a juncture. This is typically a longitudinally-oriented (or
"longitudinal") juncture, such as
lines of juncture 68. As used herein, the terms "juncture" (or "line of
juncture") refer to regions
where the flaps 24 extend from or are joined to the main body portion 22. The
line of juncture 68
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24
in the embodiment illustrated in the drawings can be considered to be defined
by concave
inwardly-oriented regions or lines.
The flaps 24 can be in any suitable configuration. Suitable flaps are
described in
Reexamined Patent No. B 1 4,589,876, issued to Van Tilburg, Certificate of
Reexamination issued
April 27, 1993; US Patent 4,687,478, which issued to Van Tilburg on August 18,
1987; US
Patent 5,389,094 issued to Lavash, et al. on February 14, 1995; US Patent
5,558,663 issued to
Weinberger, et al. on September 24, 1996 (which describes an alternative to
flaps that are applied
by the wearer); and in International Patent Application Serial No. PCT US
96/15957 filed on
October 3, 1996, in the name of Lash, et al. Other preferred features for the
flaps 24 including a
deformed region that forms a hinge and zones of extensibility or zones of
differential extensibility
are described in US Patent Application Serial No. 09/074,909 filed on May 8,
1998, in the name
of Daniels et al. and International Patent Application Serial No.
PCTlCTS96/2087, filed on
December 20, 1996, in the name of Lynard et al., which application designates
the United States.
Attachment Means
The garment surface 20B of the sanitary napkin 20 may include, and preferably
does
include, fasteners for attaching the sanitary napkin to the wearer's
undergarment. Figure 3 shows
the central pad fastener 82 which is adapted to secure the main body portion
22 of the sanitary
napkin to the crotch region of an undergarment. Any types of fasteners known
in the art, such as
adhesive fasteners and mechanical fasteners can be used. Fasteners comprising
adhesives have
been found to work well for this purpose, with pressure-sensitive adhesives
being preferred. In a
preferred embodiment, the central pad fastener 82 comprises a pair of spaced
apart longitudinally-
oriented strips or zones of adhesive that are centered about the longitudinal
centerline L.
The outer surface of the flaps 24, adjacent the distal edges 62 of the flaps,
is preferably
provided with a flap adhesive 84. The flap adhesive 84 is used to assist in
maintaining the flaps
24 in position after they are wrapped around the edge of the crotch portion of
the panty. Suitable
adhesive fasteners are described in greater detail in US Patent 4,917,697. The
flaps 24 can be
maintained in position by attaching the flaps 24 to the undergarment, or to
the opposing flap.
The fasteners used with the present invention are not limited to adhesive
attachment means.
Any type of fastener used in the art can be used for such purpose. For
example, the sanitary
napkin 20 could be secured to the wearer's undergarment by mechanical
fasteners, such as
VELCRO, or the fasteners described in US Patent 4,946,527 issued to Battrell
on August 7, 1990,
or US Patent 5,392,498 issued to Goulait, et al. on February 28, 1995. For
simplicity, however, the
fasteners will be described in terms of adhesive attachment means.
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The adhesive attachment means are respectively covered by removable release
liners,
central pad release liner and flap release liner, both designated 86. The
pressure-sensitive
adhesives should be covered with release liners 86 to keep the adhesives from
sticking to
extraneous surfaces prior to use. Suitable release liners are described in US
Patent 4,917,697. A
particularly preferred release liner which also serves as an individual
package for wrapping the
sanitary napkin is described in US Patent 4,556,146 issued to Swanson, et al.
The sanitary napkin 20 of the present invention is utilized by removing the
release liners 86
and placing the sanitary napkin 20 in a panty. The main body portion 22 is
placed in the crotch
portion of the panty with one end of the main body portion 22 extending
towards the front section
of the panty and the other end towards the back section of the panty. The
backsheet 40 is placed
in contact with the inner surface of the center of the crotch portion of the
panty. The central pad
adhesive fastener 82 maintains main body portion 22 in position. The distal
portions of the flaps
24 are folded around the side edges of the panty. The flap adhesives 84 secure
the flaps 24 to the
underside of the panty or to the opposing flap.
EXAMPLES
Example 1.
This example compares fluid handling and softness, as evaluated according to
the methods
given in the ANALYTICAL METHODS section below, of various embodiments of a
sanitary
napkin form of the present invention with exemplary prior art sanitary napkins
and commercially
available sanitary napkins that are believed to represent best in class of the
prior art.
Table 1
Sample StrikethrouahWetback Drop AcquisitionSoftness
No.
(Seconds) (Milligrams)(Seconds) (PSU)
1 43 45 3 34
2 47 9 5 35
3 10 S 5 37
4 13 5 6 8
5 95 11 25 31
6 55 11 6 9
7 195 330 0.2 49
8 33 749 18 49
9 38 8 8 g
10 134 19 0.2 22
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11 11 4 0.3 5
12 49 43 49 41
13 63 6 52 36
14 60 46 3 38
15 SS 28 0.6 36
16 64 83 47 26
17 71 30 O.S 23
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Sample No. Sample Description
1 Prior Art: topsheet according to US Patent 6,025,049, core according to
application Serial No. 09/074,909
2 Present invention: topsheet according to US Patent 6,025,049, particularly
preferred core described above
3 Present invention: topsheet according to US Patent 6,025,049, thick, airfelt
core
4 Prior art: topsheet according to US Patent 4,342,314, thick, airfelt core
Present invention: topsheet according to application Serial No. 09/217,736,
particularly preferred core described above
6 Prior art: topsheet according to US Patent 4,342,314, core according to
application Serial No. 09/074,909
7 Prior art: A thin sanitary napkin available in Japan from Kao Mfg. Co. as
Laurier Softmesh Ultra
8 Prior art: A thick sanitary napkin available in Japan from Kao Mfg. Co. as
Laurier Softmesh Slim
9 Prior art: A thin sanitary napkin available in Japan from UniCharm as Sofy
Sara
Prior art: A thin sanitary napkin available from Personal Products Co. of
Skillman, NJ as Stayfree Ultra Thin
11 Prior art: A thick sanitary as available in Venezuela from Johnson &
Johnson de Venezuela as Stayfree Alas Normal Malla Siempre
Seca
12 prior art: A thin sanitary napkin as available in Germany from Kimberly-
Clark GmbH as Kotex Camelia
13 Prior art: A thin sanitary napkin as is available in Korea from elleair as
elis
14 Present Invention: Permanently hydrophilic topsheet according to the
aforementioned US Patent application Serial No.
(P&G Case 8012 Applicant will add application Serial
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No. when known) having a core according to described
in US Patent 5,795,921
15 Present Invention: Formed film polyethylene topsheet according to the
aforementioned US Patent application Serial No.
(P&G Case 8012 Applicant will add application Serial
No. when known) having a core according to described in
US Patent 5,795,921
16 Prior Art: Hydrophobic nonwoven topsheet available from Corovin GmbH of
Penne, Germany as Corolind and apertured so as to have a basis
weight of 20 grams/m' according US Patent 5,628.,097,
Sample No. Sample Description
17 Prior Art: Surfactant treated hydrophobic nonwoven topsheet available from
Corovin GmbH of Penne, Germany as Corolind and apertured so
as to have a basis weight of 20 grams/m'- according US Patent
5,628,097
Example 2
This example compares the softness-related properties of topsheets according
to the present
invention and according to the prior art.
Table 2
Sample Softness CompressibilitySurface Density
No.
(PSU) (g/cubic (g/cubic
cm) cm)
1 32 325 0.027
2 4 549 0.037
3 43 581 0.072
4 46 226 0.018
- 714 0.050
6 - 592 0.073
7 - 653 0.150
8 - 488 0.058
9 - 205 0.037
47 339 -
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11 33 430 -
12 48 939 -
13 - 250 -
14 41 350 -
Sample No. Sample Description
1 Topsheet according to US Patent 6,025,049
2 Topsheet according to US Patent 4,342,314
3 Topsheet according to application Serial No. 09/217,736
4 A nonwoven used as a topsheet on the thin sanitary napkin available in
Japan from Kao Mfg. Co. as Laurier Softmesh Ultra
A formed film used as a topsheet on the thin sanitary napkin available in
Japan from UniCharm. as Sofy Sara
6 A nonwoven used as a topsheet on the thin sanitary napkin available from
Personal Products Co. of Skillman, NJ as Stayfree Ultra Thin
Sample No. Sample Description
7 A formed film used as a topsheet on the thick sanitary napkin as available
in Venezuela from Johnson & Johnson de Venezuela as Stayfree Alas
Normal Malla Siempre Seca
8 A nonwoven used as a topsheet on the thin sanitary napkin as available in
Germany from Kimberly-Clark GmbH as Kotex Camelia
9 A nonwoven used as a topsheet on the thin sanitary napkin as is available
in Japan from elleair as elis
A formed film polyethylene topsheet according to the aforementioned US
Patent application Serial No. (P&G Case 8012 Applicant will add
application Serial No. when known)
11 A formed film topsheet according to US Patent 4,629,643
12 A hydrophobic nonwoven nonwoven as is available from Corovin GmbH
of Penne, Germany as Corolind that is apertured according US Patent
5,628,097 so as to have a basis weight of 20 grams/m'
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13 A permanently hydrophilic formed film topsheet according to the
aforementioned US Patent application Serial No. (P&G Case 8012
Applicant will add application Serial No. when known)
14 A permanently hydrophilic textured, formed film according to the
aforementioned US Patent application Serial No. (P&G Case 8011
Applicant will add application Serial No. when known)
ANALYTICAL METHODS
Drop Acquisition Time
1) Place a topsheet sample, approximately 18 cm x 28 cm, over one layer of
BOUNTY towel
(available from Procter & Gamble of Cincinnati, OH) on a flat surface. Place a
clear Lexan~
5 plate, 15 cm long by 20 cm wide by 1 cm thick, with eighteen 1.9 cm (3/4")
holes drilled 2.5
cm apart in 3 rows of six holes each, on top of the topsheet sample. The
pressure exerted on
the sample by this plate is 0.02 psi(0.14 kPa), ensuring intimate contact
between the
topsheet and the Bounty towel.
Alternatively, if complete products are to be evaluated, the plate is not
used. Instead, eighteen
10 drops (see Step 2) are applied to the product sample in a pattern wherein:
six drops are
applied adjacent the intersection of the longitudinal and lateral centerlines
of the product;
three drops are applied adjacent each end adjacent the longitudinal
centerline; and three drops
are applied adjacent each side, adjacent the lateral centerline.
2) Deliver a 45 microliter drop of sheep blood from a pipette (A 100
microliter capacity
1 S Eppendorf Air Displacement Pipette has been found to be satisfactory) onto
the surface of the
sample within one of the holes in the plate. The pipette tip should be
approximately 3-5 mm
above the topsheet surface, and the drops should be applied in such a manner
that the force
exerted by delivery from the pipette is minimized.
3) Start timing acquisition as soon as the drop contacts the sample.
20 4) Stop timing when the top surface plane of the sample again becomes
visible as a result of the
drop passing into or through the sample. Record this drop acquisition time.
5) If the acquisition time exceeds 60 seconds, record the result as 61
seconds.
6) Repeat steps 1 through S an additional seventeen times through the
remaining holes in the
Lexan plate so as to provide eighteen measurements per sample.
25 7) Repeat steps 1 through 6 on two more topsheet samples.
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8) Calculate the mean drop acquisition time, using 61 seconds for those drops
which did not
pass into or through the sample within 60 seconds.
Liquid Strike-Through Time
This test method measures the strike-through time, i.e. the time required for
a known
volume of liquid applied to the body surface of a topsheet material or
absorbent article, which is
in fluid contact with an underlying absorbent, to pass through the sample. The
method used herein
is described in European Disposables and Nonwovens Association (Brussels,
Belgium) standard
method number 150.3-96 with the following differences:
Test Condition EDANA Method 150.3-96 Method of Present Invention
Environmental Temperature 202°C ~ 22t1°C
Relative Humidity 6512% 502%
Test Fluid Synthetic Urine Sheep's Blood
Underlying Absorbent Filter Paper Finished Absorbent Article
Confining Pressure SOOg/(l2.Scm)z(~0.3 kPa) 0.25 psi (1.7 kPa)
Volume of Fluid to Acquire Sml, one insult 10 ml, one insult
Wetback
Wetback is a test designed to measure the amount of liquid which emerges from
an
absorbent structure through a topsheet to cause wetness on the surface of the
topsheet. The
method used herein is described in European Disposables and Nonwovens
Association (Brussels,
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Belgium) standard method number 151.1-96 with the following differences:
Test Condition EDANA Method 151.1-96Method of Present Invention
Environmental Temperature202C 221C
Environmental Relative6512% SOt2%
Humidity
Filter Paper Type ERT FF3 Ahlstrom (Mt. Holly Springs,
PA) #632
Number of Pieces of 5 7
Filter Paper
Confining Pressure 4000g/( l Ocm)Z(~3.90.77 psi (5.2 kPa)
kPa)
Test Fluid Synthetic Urine Sheep's Blood
Fluid Loading 3.3 times wt of 7.5 ml
filter paper
Exposure Time:
Distribution 3 Minutes Under 15 Minutes
Load
Rewet 2 Minutes 15 Seconds
Panel Softness
Overview
A trained panel of graders is used to compare the tactile softness of a series
of test products
or topsheet materials.
Graders
Graders are all female and are selected and trained for ability to
discriminate small
differences in tactile softness. As part of this training, each grader
identifies a "dominate" (i.e.
most sensitive) hand which is used in all evaluations. Graders are monitored
on a study to study
basis and retrained as needed to minimize drift with time.
Apparatus
Sensory Box While a room designed for sensory evaluations having features such
as, grader
separation from other graders, barrier between sample and panelist which
allows
sample access through slit, and other features as are known to the art is
preferred,
the sensory box described hereafter has been found to be suitable for softness
evaluations. A 33 cm X 43 cm (face) X 20 cm (deep) rectangular box having an
open back for sample presentation and a front opening screened by a black
curtain (the curtain is in 2 portions each about 21 centimeters wide and
separated
in the middle to allow easy grader access).
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Felt A 23 cm X 18 cm felt is used as a substrate when topsheet-only samples
are graded. A
suitable material is 54 Polyester felt, Rainbow Classic, Royal Blue as is
available
from Kunin Felt of Hampton, NH.
Method
1) The panel moderator introduces the first sample into the sensory box. Up to
six test samples
may be evaluated in any one test period. Two control samples, one with a
relatively high
softness reading (a hydroformed film made according to the aforementioned US
Patent
4,629,643 ~35) and one with a relatively low softness reading (a formed film
made
according to the aforementioned US Patent 4,342,314 ~5) are used in each
series. Samples
are presented to each grader in a random order. When topsheet-only 'samples
are evaluated,
the sample is first spread smoothly on the surface of the felt before
presentation to the
grader. Each sample is only graded one time.
2) The grader grades each sample using a 60 point scale for softness where,
for softness, 0 is
identified as not soft at all and 60 is identified as very soft/fluffy. The
grader uses the finger
tips of the first three forgers of her dominant hand to determine a softness
grade for the
sample (the fingers are arched so only the tips contact the sample). The
control samples are
used to maintain consistency between tests. The grade for each sample is
recorded by
marking the grade on a linear scale on the sample data sheet.
3) Steps 1 and 2 are repeated for a minimum of 12 graders.
Report
Report the mean and standard deviation for each sample tested, including the
control
samples. Known methods of determining statistically significant differences
(e. g. analysis of
variance, Newman-Keuls Multiple Range Test, etc.) may be used.
Thickness Under Load
Overview:
This test procedure determines material thickness as a function of applied
load. Data generated
using this procedure can be used to calculate compressibility and surface
density as functions of
applied load.
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S
Sc- ope:
This procedure applies to materials from 0.2 mm to 5 mm thick. Samples tested
by this
procedure should be flat and not have significant curvature. Top and bottom
surfaces of the
material should be essentially parallel.
Sampling
Samples should be cut such that they are larger than the 25.4 mm diameter
platen used to
compress the sample. A rectangular cutting die 3.81 cm by 6.99 cm is suitable.
The area to be
tested must be able to lie flat. Samples may be cut from individual materials
or finished products
but the cut area must be free from wrinkles or curvature and the sampling
procedure should not
distort the dimensions of the material. For example, when sampling finished
products, the sample
material must be cleanly separable from other materials. At least three
different samples should
be measured with the average result reported.
Apparatus:
Use a constant rate of extension (CRE) tester. A suitable CRE tester is the
Instron
Model 5564, available from the Instron Corporation, Canton, MA. The CRE tester
must have
accurate control and measurement of crosshead position to O.Olmm. The CRE
tester must be able
to measure load accuracy to 0.5 gram force (5 mN). The CRE tester should have
less than 0.02
mm compliance at 1N applied load. The moving crosshead should be fitted with a
25.4 mm
diameter (5.07 cm2 area) circular, flat platen disk, rigidly attached to the
load cell. A circular, flat
platen at least 100 mm in diameter should be rigidly fixed to the lower
stationary clamp. The
faces should be parallel with each other with a tolerance of 0.02 mm or less.
Procedure:
1. The grammage of the topsheet sample should be determined by weighing a
precisely known
area of 100 cmz or larger on an analytical balance to the nearest 0.0002 g.
2. With the parallel platens a known distance apart, the flat sample is placed
on the lower platen.
For a 1.00 mm thick sample, 3.00 mm is the recommended starting separation.
The CRE load
cell should be zeroed at the start of each test while the platens are not
contacting the sample.
3. The CRE tester lowers the upper platen toward the sample at a rate of 2.54
mm per minute,
recording at least 100 data points per mm of travel, until the sample is
compressed and a load
of 500 grams is reached.
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4. The thickness of the material at any given load is determined by the
position of the upper
platen. Thickness should be measured at a load of 5 grams force and 50 g
force,
corresponding to 100 Pa and 1000 Pa pressure on the sample.
Calculations:
5 Compressibility is determined by calculating the secant slope of the
stress/strain
compression curve between Sg and SOg and dividing this slope by the area
compressed. Units for
compressibility are grams per cm3. This slope is calculated by dividing the
change in load by the
change in thickness. For example, if a material was 1.00 mm thick under a Sg
load and
compressed to 0.70 mm thick under a 50 g load:
10 SOe-5~ = 150 g/mm Compression Slope
l.OOmm-0.70 mm
Compressibility = (150 g/mm) (lOmm/cm) (1/5.07 cm2) = 296 g/ cm3
Similarly, surface density at a given load is calculated by dividing the
grammage (grams material
per square centimeter) by the thickness under the load of interest.
15 Surface Density at X load = rg-amma~
thickness under X load
for example, the surface density of a material that has a grammage of 0.00325
grams/cm' and a
thickness of 0.065 cm at an applied pressure of 100 Pascals is:
0.00325 Qrams/cmz = 0.0500 g/cm3
20 0.065 cm
Mean Absomtion Pressure
This test measures the height at which the amount of fluid absorbed or
desorbed is equal to one
half the amount absorbed at a height of 0 centimeters (free absorbent
capacity). The method for
Capillary Sorption as described in US Patent Application Serial No. 09/258,889
entitled
25 Absorbent Members comprising a High Surface Area Material for Absorbing
Body fluids which
was filed in the name of Young, et al. on March l, 1999, was used with the
following differences.
1) The initial suction height is 50 centimeters instead of 200 centimeters.
2) The test is conducted at ambient laboratory conditions instead of
controlled temperature and
relative humidity.
30 3) The glass frit 202 is not jacketed.
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4) The reservoir 206 and the balance 207 are not enclosed.
5) Cylinder 266 and piston 288 are not equilibrated at 31°C.
6) An occlusive film is used instead of an apertured film to minimize
evaporation.
7) The set up height is 50 centimeters.
8) There is no evaporation loss correction.
9) The mean capillary absorption pressure is determined from the absorption
isotherm as the
height where the sample uptake is equal to one half the sample uptake at a
height of 0
centimeters.
The disclosures of all patents, patent applications (and any patents which
issue thereon, as
well as any corresponding published foreign patent applications), and
publications mentioned
throughout this patent application are hereby incorporated by reference
herein. It is expressly not
admitted, however, that any of the documents incorporated by reference herein
teach or disclose
the present invention. It is also expressly not admitted that any of the
commercially available
materials or products described herein teach or disclose the present
invention.
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.
