Note: Descriptions are shown in the official language in which they were submitted.
s~
-1- JBP 191
~bsorbent Struc e with Reservoir
Background of the Invention
Disposable absorbent structures such as disposable diapers,
sanitary napkins and incontinence pads have met with
increased commercial acceptance in recent years primarily
because of their convenience. Many different constructions
have been proposed and used and some have met ~lith wide-
spread commercial success in spite of certain inadequzcies
in functional properties.
One of the most serious prior art problems has been the
inability to provide a suitable construction that can
accept a large void of body fluids. This is particularly
true of the adult incontinent whether the incontinent be
active and l~orking or ill and bedridden. Various attempts
have been made to provide special structures to absorb a
large body fluid void. These include U. S. Patent
3,441,024 to H. J. Ralph, U. S. Patent 3,747,602 to
H. J. Ralph, U. S. Patent 3,968,79~ to ~. C. Hokanson,
and U. S Patent 4,067,366 to R. L. Johnson. I~'hile these
various constructions were designed to assist the adult
incontinent, the problem of providing an overall absorbent
structure which ~ill handle a full volume discharge of
urine without leakage s,ill remains.
Whether the incontinent be an adult or an infant, disposable
structures generally have not accepted and held a full
volume discharge of urine without leakage onto clothingr
Similarly, the sanitary nap~ins known in the art will no~
necessarily hold a full volume dischar~e o F menstrual
fluid. The present invention provides an absorbent
structure which may be used as an infant diaper, an adult
--2--
incontinence device, a sanitary napkin, an incontinence
pad, or the like.
~ummary o the Invention
The present invention provides, froln one of its broad
S aspects, an absorbent structure suitable for absorption of
body fluids and comprising a moisture-impermeable backing
sheet. An absorbent, loosely-compacted, cellulosic fibrous
bat-t is su~erimposed on the backing sheet. A moisture-
permeable fabric ~over covers at least the side of the
absorben-t batt opposite the backing sheet. The absorbent
batt is provided with a reservoir having a capacity of at
least 10 cc and covers at least one square inch of surface.
The reservoir is situated in a void zone between the center
and one transverse end and ls formed by compression of -the
cellulosic fibrous batt.
The absorbent structure may be incorporated in a disposable
diaper such as for an infant or in an adult diaper with a
larger liquid holding capacity. Furthermore, the absorbent
structure may be incorporated in a sanitary napkin as well
as in an incontinence pad. In each instance the opening of
the reservoir is placed in -the void zone allowing immediate
acceptance by the reservoir of the body fluid discharge.
Generally, the discharge capacity of the reservoir will be
at least 10 cc.
The reservoir is created by compression of the loosely-
compacted, cellulosic fibers in the reservoir area. The
compaction may be carried out by application of pressure
in the shape desired for the reservoir. This may be done
by a stam,oing-type operation or by an embossing roll or
the like.
35~
-i- JBP 191
rief Descrip~ion of the Drawings
FI~. 1 is a perspective view of one embodiment o~ the
present invention;
FIG. 2 is a cross-sectional view taken along line 2--2
of the embodiment of FIG. l;
FIG. 3 is a top view of another embodiment of the present
ln invention;
FIG. 4 is a top view o still another embodiment of the
present invention;
FI~. 5 is a perspective view of a disposable diaper
utilizing the absorbent structure of the present invention;
FIG. 6 is a perspecti~e view of a sanitary napkin incorpor-
ating the absorbent structure of the present invention; and
FIG. 7 is a cross-sectional view taken along line 7--7
of ~IG. 6.
Detailed Description of the Invention
l~ile this invention is susceptible of embodiment in many
different forms, there is shown in the dra-~in~s, and herein
will be described in detail~ preferred embodiments of ~he
invention and modifications thereof. I~ is understood th;t
the present disclosure is to be considered as an e~emplifi-
cation of the principles of the invention and is not
in~ended to limit the invention to the embodiments
illustrated. The scope of the invention will be pointed
out in the appended claims.
5~S~L
-4- JBP 191
Referrin~ to the dra~ings and particularly to FIG. 1, an
absorben-t structure 10 is provided with a reservoir 12
lying belo~ the cover 13. The cover is a moisture-
permeable non--~oven fabric. FIG. 2 shows the absorbent
S structure of FIG. 1 in cross-sectional vie~ along line 2--2.
The moisture-per~eable exterior cover 18 completely ~raps
the absorben~ structure. A moisture barrier 16 ~hich is
a moisture-impermeable backing sheet, covers the bottom
area as well as both sides of the structure. Immediately
adjacent the cellulosic batt 22 is a wrap of tissue 14.
It may not be necessary to have a tissue wrapping the
cellulosic batt but if the cellulosic batt is quite thick,
such as an inch or more, it may be desirable to provide
a tissue wrap to assist with maintenance of the desired
shape of the absorbent structure. The cellulosic fibrous
batt 22 is provided with a reservoir 20 and a densified
fibrous region 24. the surface of the fibrous ba~t
containing the opening of the reservoir 20 is placed
toward the wearer with the opening in the void zone.
release liner 26 is re~oved to expose adhesive so as to
secure the structure to the underwear of the ~earer.
FIGS. 3 and 4 are top views of typical cellulosic bat~s
used in the absorbent structure of the invention. The
cellulosic batt ~0 contains a reservoir 32 having the
shape of a rectangle. The reservoir may be located nearer
one end of the cellulosic batt sO, e.g., one-ti~ird of the
way, or between the center and end, to assist in location
in the ~oid 70ne of the wearer. In FIG. 4 a cellulosic
batt 40 is provided with a reservoir ~2 having an oval
sllape. Any desired shape and size may be used so long as
the reservoir covers at least one square inch of surface
and contains at least 10 cc in volume.
5 ~
-5- J~P 191
Referrin~ now to FIG. 5, a disposable diaper 50 is shown
ha~ing a moisture-impermeable backing sheet 52. Super-
imposed upon the backing sheet 52 is a loosely-compacted,
cellulosic fibrous batt 54. The fibrous batt contains a
reservoir 56 created by compression or compaction of the
fibers in ehat re~ion. The cellulosic batt 54 is covered
by a moisture-permeable facing 58 of non-woven fabric.
The facin~ and the backing are adhered in the margin
regions. In addition, glue lines 57 are used to secure
the fibrous batt to the backing. Tape tabs S9 are provided
to secure the diaper abowt the wearer.
Referring now to ~IGS. 6 and 7, a sanitary napkin 60 is
depicted. The cover 62 shown in FIG. 6 is a moisture-
permeable non-woven fabric. FIG. 7 is a cross-sectional
view taken along line 7--7 of FIG. 6. A cellulosic
fibrous batt 64 is partially surrounded by a moisture
barrier 70. The entire structure is wrapped in the
moisture-permeable cover 72. The cellulosic batt 6~
contains a reservoir 66. At the bottom of the reservoir
is a dense fibrous area 6S. The dense fibrous area 68 is
created when the reser~oir 66 is formed.
The loosely-compacted, cellulosic fibrous batt uscd in
the absorbent structure of the present invention is formed
from wood pulp fibers, rayon fibers, or cotton linters,
or mixtures thereof. The batt is primarily held together
by interfiber bonds requirin~ no added adhesive. In some
instances, the batt may contain synthetic fusible fibers,
such as polyethylene, polypropylene and the like. The
batt is a low bulk density coheren~ web of loosely-compac~ed
- cellulosic fibers pre~erably comminuted wood pulp fibers
in the form of so-called '7fluff."
x~
-6- JBP 191
lhe reservoir in the ccllulosic batt is creatcd by
compressing the portion of the batt ~hich it is desired
become a reservoir. The compression should be sufficient
to create a reservoir of suEficient depth to hold at
least 10 cc. The base of the reservoir is a densified
fibrous region l~herein the fibers are compacted. The
densified region quickly absorbs the body fluid and
commences distribution of the fluid to other parts of
the cellulosic batt. In addition, it may be desirable
to provide a paper-like densified layer on the side of
the batt opposite the reservoir. The paper-like
densified layer is formed by a slight moistening of
the surface of the batt follo~ed by light compaction using
the application of pressure. U. S. Patent 3,017,304,
Burgeni, provides such a densified layer in a loosely-
compacted, cellulosic fibrous batt.
The cover provided on the absorbent structure of the
present invention is a non-woven fabric having a high
degree of moisture permeability. For e~ample, the fabric
may be polyester, polyethylene, polypropylene, nylon~
rayon, or the like. Preferably, the fabric used for the
cover is a light~eight fabric in the range of 0.3 to
5.0 oz. per square yard and ~ith a density less than
0.2 gms/cc. The most suitable fabrics have unusually
high elongation, loft, softness and drape characteristics.
Though the cover is moisture^permeable, it is preferably
of ~he type which after permeation of the moisture,
prevents strike-bac~ of the body fluid when the absorbent
structure is approachina saturation.
5(~S~
-7- JBP 191
The body of the ce~ losic Eibrous ba~t is substantially
more wettable than the cover and tends to draw liquid
away from the facing layer. Thus the void occurs and the
cover is permeated and the liquid deposi~ed in the
reservoir. The individual fibers of the batt are extremely
wettable and thus draw the liquid into the fibrous batt.
The base of the reservoir is a densified fibrous region
wher~n the capillary radius is quite small. Thus the
capillary pressure is increased and ~he liquid is rapidly
distributed to portions of ~he cellulosic batt. The
densified fibrous region at the base of the reservoir
provides the ma~imum capillary pressure because it combines
the very low contact angle of the fibers of the batt with
the high density of the densified fibers.
The individual fibers of the batt are extremely wettable,
generally having liquid-fiber contact angles below about
15 and approaching zero in the optimum embodiment. The
wickability or preferential absorptivi~y of the body of
the ba~t for water is limited, however, by its low density
which results in large effective capillary radius for the
capillaries between a~jacent fibers.
The pressure causing a liquid to enter a cylindrical
capillary is e~pressed by the equation
2~cos
p _ r
wherein
P is the capillary pressure,
30 ~' 3.5 the surface tension of the liquid,
~ is the liquid-fiber contact angle, and
r is the capillary radius.
^LI ~S~5il
-8- JBP 191
l~ith a given liquid, the pressure (capillary force)
increases with thc cosine of the liquid-fiber contact
angle (reaching a ma~imum where thc angle is zero) and
increases with narrower capillary radii so that narrower
capillaries will draw liquid from wider ones.
The relative wickability be~ een the cover layer and the
body of the fibrous batt is affected b;- both the relative
densities of the layers and the relative wettability of
the individual fibers in each layer. The individual fibers
of the batt have substantially smaller liquid-fiber contact
angles than those of the cover layer overcoming the
density difference and providing a substantial overall
increase in capillary pressure to absorb liquid into the
body of the batt.
A densified fiber layer such as that at the base of the
reservoir provides the maximum capillary pressure because
it combines the very low contact angle of the fibers of
the batt with the high density (small capillary radius)
of the densified fibers.
Thus when urine is voided into an area in the cover layer,
it partially wets a small portion of the cover layer and
is passed through the cover layer, almost instantaneously,
to the reservoir. It then comes into contact Wit]l the
body of the batt surrounding the reservoir and is
preferentially absorbed into the body of the batt
because of the enhanced wettability of the reservoir
and particularly the base of the reservoir. The same is
true when the body fluid is a menstrual Lluid or other
liquid exudate.
-9- JBP 191
It .~ill be understood by those s~illed in the art that
variations and modifications of the speciEic embodiments
described above may be employed without departin~ from
the spirit and scope of the invention as defined in the
S appended claims.
SUPPLEMENTARY DISCLOSURE
In the principal disclosure there is described and claimed
an absorbent structure wherein an absorbent batt of loosely-
compacted, cellulosic fibers is provided with a reservoir
having a discharge capacity of at least 10 cc. It has now
been found that in a preferred embodiment of the present
invention the reservoir should not cover more than 25% of
the surface of the absorbent batt and should have a depth
of more than one-half the thickness of the absorbent batt.
The reservoir of the present invention is formed by compres-
sion of the fibers in the reservoir ~one and is located so
that the product, when worn, re-tains the proper shape. The
absorbent structure receives and contains body fluids,
particularly urine.
In one of its embodiments the absorbent batt is substan-
tially rectangular in shape and is provided with a reservoir
which (1) has a capacity of at least 10 cc, (2) which covers
at least one square inch of surface, (3) which is situated
between the center and one transverse end of the substan-
tially rectangular absorbent batt, (4) which covers less
than about 25% of the surface area of the absorbent batt,
and (5) is formed by compression OI the cellulosic fibrous
batt so that the depth of the reservoir is more than half
the thickness of the absorbent batt.
In U.S. Patent No. 4,184,498, there is provided a sanitary
napkin which by its appearance would seem to be a structure
which might be used for the deposit of urine and the
containment thereof. It has been found, however, that a
single depression such as is provided by the patent extend-
ing substantially the length of the structure does not
contain a substantial discharge of urine when being worn
-- 10 --
in place. This is because the structure folds on the
depression the entire length of the structure and fails
to provide a substantial reservoir whic'n retains its shape
and consequently high volume of discharge. The single
reservoir provided by the present invention does not permit
the folding or collapse of the central portion behind the
reservoir in such a way that liquid could leak. Instead,
the reservoir of the present invention, as it is defined
above, provides an absorbent structure which retains the
reservoir substantially in its originally shaped state when
the product is being used so that the entire absorbent
structure is available for proper use without collapsing
or folding to permit leakage. The absorbent structure of
the present invention, when utilized either in a diaper-type
structure or in a simple pad-type structure when worn
between the legs of the wearer, attains a boat-like shape
due to the compression on each side near -the reservoir
caused by the legs of the wearer. This boat-like shape
keeps the reservoir available for substantially all of its
holding capacity and keeps the ends and sides of the pad in
a position such that leakage does not occur.
According to a broad aspect of the present invention there
is provided an absorbent structure suitable for absorbtion
of body fluids comprising a moisture-impermeable backing
sheet. An absorbent, loosely-compacted, cellulosic fibrous
batt is superinposed on the backing sheet. A moisture-
permeable fabric cover covers at least the side of the
absorbent batt opposite the backing sheet. The absorbent
batt is provided with a reservoir having a capacity of at
least 10 cc and covers at least one square inch but does
not cover more than 25% of the surface of the absorbent
batt. The reservoir is situated between the center and one
transverse end and is fonned by compression of the cellulo~
sic fibrous batt such that the depth of the reservoir is
more than one-half the thickness of the absorbent batt.
11 --
Generally, -the discharge capaci-ty of the reservoir is
sufficient to hold at least 75% of the urine discharged
in one second.
In the drawings supported by the Supplem~ntary Disclosure
FIGURE 8 is a cross-section view taken across the reser-
voir provided with an absorbent batt.
As can be seen in Figure 8, there is shown an absorbent
batt 22 provided with a reservoir 20 therein. A moisture-
permeable exterior cover 18 completely wraps the absorbent
structure. A moisture barrier 16, which is a moisture-
impermeable backing sheet, covers the bottom area as well
as both sides of the structure. Immediately adjacent the
cellulosic batt 22 is a wrap of tissue 14. It may not be
necessary to have a tissue wrapping the cellulosic batt
but if the cellulosic batt is quite thick, such as an
inch or more, it may be desirable to provide a tissue wrap
to assist with maintenance of the desired shape of the
absorbent structure. The cellulosic fibrous batt 22 is
provided with a reservoir 20 and a densified fibrous
region 24. The surface of the fibrous batt containing the
opening of the reservoir 20 is placed toward the wearer
with the opening in the void zone. A release liner 26 is
removed to expose adhesive so as to secuxe the structure
to the underwear of the wearer. The reservoir does not cover
more than 25% of the sur~ace and the depth thereof is more
than one-half the thickness of the uncom~ressed batt. This
structure may be used as a urine pad or an incontinence pad.
It is also pointed out that the cover provided on the
absorbent structure may also be a film ~lich is perforated
or non-continuous. Also, the individual fibers of the batt
are extremely wettable and may have liquid-fiber contact
angle~ below about 30 and approaching 20 in the optimum
embodiment. The wickability or preferential absorptivity
of the body of the batt for water is limited, however, by
lts low density which results in large effective capi-
llary radii for the capillaries bet~een adjacent fibers.
- 13 -
