Note: Descriptions are shown in the official language in which they were submitted.
1 333951
LaW BULK DISPOSABLE DIAPER
Technical Field
The present invention relates generally to
disposable absorbent articles including diapers and
incontinent products, and more particularly to a low
bulk disposable diaper configured for improved fit
and comfort while exhibiting enhanced absorptive and
leakage-resistant characteristics.
Background of the Invention
The use of disposable diapers for infant
care has become increasingly widespread in recent
years, with these disposable products providing
substantial advantages and convenience over reuseable
diapers. A typical disposable diaper structure
includes a layer of liquid-retaining absorbent
material sandwiched between a moisture pervious
facing layer positioned adjacent the skin of the
wearer, and a moisture impervious plastic backing
sheet to confine moisture within the absorbent layer.
In the past, the absorbent layer has
typically been comprised of batt of loosely compacted
cellulosic fibers, usually comminuted wood pulp or
"fluff~. While such absorbent material is relatively
inexpensive and is capable of quickly absorbing
liquids, the typical diaper structure including such
material is configured such that it detracts from the
comfort of the wearer.
Specifically, typical disposable diaper
products are relatively thick and exhibit high bulk.
Such arrangements were thought to be desirable
because consumers showed a preference for thicker
diapers in view of their higher absorptive capacity
and reduced tendency to leak. Even those products
which include hydrocolloid or superabsorbent
. ~
1 333951
materials in combination with wood pulp are
relatively thick.
The appearance of bulkiness of a diaper is
related to the panel thickness and to the volume of
the diaper absorbent panel. The volume of the panel
affects the comfort of the product as felt by the
wearer, typically infants, and also affects consumer
preferences.
With regard to wearer comfort, testing has
shown that a standing infant of five months of age or
older, and weighing approximately 16 pounds and up,
has only a very small distance between its upper
thighs, typically 0.5 inches or less. As will be
appreciated, whatever thickness a diaper exhibits
between the infant's legs that is in excess of the
child's natural crotch width will necessarily press
against the child's thighs, spreading the thighs
apart to accommodate the diaper. This unnatural
displacement oE the child's thighs encumbers the
child's mobility, and is typically perceived as
uncomfortable.
Further, consumers prefer a snug-fitting
diaper not only because of its aesthetic appeal, but
also because of the desired ease with which outer
clothing can be fit over the diaper. It is therefore
preferred that a diaper does not tend to hang low
between an infant's legs with a bagging or pouch-like
appearance. As will be appreciated, however, in
order for the diaper to fit close to the body in the
limited space between the thighs, the diaper must
fold or corrugate. As a consequence of this
multiplying effect of the diaper thickness,
undesirable bulk is created in the crotch region
which is larger than the natural space provided
1 333951
--3--
between the thighs, with the resultant decrease in
comfort.
In view of the foregoing, it is desirable to
provide a disposable diaper product which is
configured to exhibit desirably low bulk for improved
fit and comfort, while at the same time exhibiting
enhanced absorptive capacity per unit volume of the
absorbent diaper panel so that the diaper can be used
effectively while minimizing leakage.
Summary of the Invention
The disposable diaper embodying the
principles of the present invention has been
particularly configured for improved fit and comfort
by providing a construction which exhibits relatively
low bulkiness, while at the same time providing
efficient absorbency so as to avoid leakage while in
use. Thls is achieved by providing the diaper with
an absorbent panel structure which is relatively thin
and narrow, yet exhibits a high absorptive capacity
per unit volume of the panel to obtain the desired
characteristics. In particular, the structure is
configured so as to minimize the unnatural outward
displacement of an infant's thighs while wearing the
product, thus enhancing comfort.
In accordance with the illustrated
embodiment, the present disposable diaper includes an
absorbent panel, with a moisture-pervious facing
layer positioned in overlying relationship on one
side of the absorbent panel. The facing layer is
adapted for positioning adjacent the wearer of the
diaper, and may typically comprise non-woven fabric
or the like.
The diaper construction further includes a
backing layer positioned on the side of the absorbent
panel opposite the facing layer. While the backing
1 33395 1
--4--
layer may be formed from moisture-impervious plastic
sheet material, the illustrated embodiment is
configured such that a moisture-impervious barrier
layer is provided in association with a
moisture-pervious backing layer. The barrier layer
has a surface area which is less than that of the
backing layer, thereby minimizing the occlusion of
the diaper for improved breathability, further
enhancing comfort.
The absorbent panel of the present
disposable diaper comprises a matrix of absorbent
material, and includes an impact or target zone,
defined as the second and third fifths of the panel
length, measured from the front of the diaper. In
1~ achieving the desired comfort and performance
characteristics, the present diaper is configured
such that the minimum transverse dimension of the
absorbent panel at the impact zone is no more than
about 40 times the thickness dimension panel in this
region. Additionally, the absorbent panel is
configured so as to exhibit sufficient inherent
absorbency to provide the impact zone with an
absorbency efficiency index of at least 1.5. This
absorbency efficiency index is determined by
2~ ascertaining the absorptive characteristics of a
diaper's absorbent panel as it relates to the bulk of
the panel. Comparison tests with numerous commercial
products show that a diaper embodying the principles
of the present invention exhibits a desirably high
efficiency index.
In achieving the desired characteristics for
the present diaper construction, the preferred
absorbent matrix of the absorbent panel comprises
superabsorbent material, preferably in combination
3~ with a fibrous web wherein the superabsorbent
- ~ ~33`951
23158-1598
materlal comprlses from about 200 to about 1500 percent, by dry
welght basls, of the flbrous materlal ln the web. In the pre-
ferred form, the flbrous materlal ls ln the form of a substan-
tlally hlgh loft, resllient flbrous web layer, wlth the super-
absorbent materlal dlstrlbuted wlthln the flbrous web layer. The
flbrous web layer ls malntalned ln a compressed state by the
superabsorbent materlal, whereupon wettlng of the absorbent matrlx
wets the superabsorbent materlal so that the flbrous web layer
expands from lts compressed state due to the lnherent reslllence
of the layer, thereby facllltatlng swelllng of the superabsorbent
materlal. An absorbent panel so-conflgured ls dlsclosed ln U.S.
Patents No. 4,500,315, No. 4,537,590, and No. 4,573,988.
In the most preferred form, the absorbent matrlx further
lncludes llquid transport means comprlslng at least one wlcklng
layer of denslfled hydrophlllc flbers, typlcally denslfled wood
pulp flbers. The wlcklng layer ls coextenslve wlth at least a
portlon of a respectlve expanslve surface of the compressed
flbrous web layer, and thus promotes llquld transport wlthln the
absorbent matrlx to maxlmlze utlllzatlon of the absorptlve
capaclty of the flbrous web layer and the assoclated superabsor-
bent materlal.
As discussed above, lt ls typlcally necessary that the
cross-sectlonal bulk of a dlaper be accommodated between the
thlghs of a wearer by foldlng or corrugatlon of the dlaper's
absorbent panel. Experlence has shown that when the dlaper ls
fitted wlth one or more elastlc elements at each of lts leg
openings for conformlng the dlaper to the wearer, lt ls the
distance between the innermost
6 1 3 3 3 9 5 1 23l58-l598
elastlc elements, as measured across the abæorbent panel, that
determines the wldth of the diaper whlch must be accommodated in
the space between the wearer's thighs by foldlng or corrugatlng.
To thls end, the present dlaper has been conflgured such that the
mlnlmum dlmenslon between the opposlte, lnnermoæt ones of such
elastlc elements at the lmpact zone of the dlaper ls no more than
about 1.25 tlmes the mlnlmum transverse dlmenslon of the absorbent
panel of the impact zone. Thls relatlonshlp has been found to
deslrably mlnlmlze the bulk of the materlal whlch must be
accommodated, whlle at the same tlme malntalnlng the deslgn
functlonallty of the dlaper as lt relates to waste contalnment.
In accordance wlth the present invention there is
provlded a dlsposable diaper havlng lmproved flt and comfort, the
dlaper having front and back walst end portlons and comprislng:
an absorbent panel; a moiæture-pervlouæ faclng layer posltloned ln
overlylng relatlonshlp on one slde of sald absorbent panel, sald
faclng layer belng adapted for posltionlng ad~acent the wearer of
the diaper; and an outer backing layer posltioned on the side of
sald absorbent panel opposlte sald faclng layer; the absorbent
panel and outer backlng layer belng secured together at the walst
portlons of the dlaper; sald abæorbent panel comprlslng a matrix
of absorbent material and havlng an impact zone whlch comprlses
the second and thlrd flfths of sald abæorbent panel ln a
longltudlnal dlrectlon as measured from the front thereof sald
lmpact zone lncludlng a portlon posltlonable between the thlghs of
the wearer, which sald portlon has a transverse dlmension and a
thlckneæs dlmension to provlde a crosæ-æectlonal area for æald
portion of no more than about 0.6 square inches, sald matrlx of
B
~a 1 333951 23158-1598
said absorbent panel havlng sufflcient lnherent absorbency to
provlde sald absorbent wlth an absorbency efflclency lndex of at
least 1.5, thereby provldlng sufflclent absorbent capaclty for
absorblng antlclpated volumes of volded llquld with a structure
which is sufficiently narrow and thin so as to minimize discomfort
to the wearer.
In accordance with another aspect of the present
invention there ls provided an absorbent panel for use in an
absorbent article having a facing layer and a backing layer on
respectlve opposlte sldes of said absorbent panel, said absorbent
panel providing the absorbent artlcle with improved comfort and
fit for the wearer, said absorbent panel comprising: a matrix of
absorbent materlal having a sufficient inherent absorbency to
provide a volumetrlc storage capaclty of at least about 220 cc. of
liquid, said absorbent panel having a bulk volume ln a portlon of
the panel posltionable between the thighs of the wearer, which
sald bulk volume ls derived from said panel portion having a
transverse dimension of about 4.5 inches and a thickness dimension
of about 0.13 inches to provide a cross-sectlonal area for sald
portlon of about 0.6 s~uare lnches, and to thereby provide sald
absorbent panel wlth an absorbency efficiency index of about 2.29,
whereln said absorbent panel includes an impact zone comprising
th~ second and third fifths of said absorbent ln a longltudlnal
dlrection thereof, sald lmpact zone lncludlng sald portlon of sald
panel, sald absorbent matrlx comprlslng superabsorbent materlal
and flbrous materlal, sald superabsorbent materlal comprlslng 200-
1,500 percent, by dry weight basls of sald flbrous materlal, said
absorbent panel having a denslty of at least about 0.25
B
_ 6b l 333~1 23158-1598
grams/cubic centlmeters, whereby a sufflclent abæorbent capaclty
for absorbing anticlpated volumes of voided liquid is provided by
a structure whlch ls sufflclently narrow and thln so as to
mlnlmlze dlscomfort to the wearer.
Other features and advantages of the preset lnventlon
will become readily apparent from the following detailed
description, the accompanylng drawlngs, and the appended clalms.
Brief Descrlptlon of the Drawinqs
FIGURE 1 is an exploded perspective view of a disposable
diaper embodylng the prlnclples of the present invention;
FIGURE 2 is a perspectlve vlew, partlally cut-away, of
the present dlsposable dlaper;
FIGURE 3 ls a cross-sectlonal vlew taken along llnes 3-
3 of FIGURE 2;
FIGURES 4 and 5 are lllustratlons made from photographs
of an lnfant wearlng a dlaper embodylng the prlnciples of the
present lnventlon, and a conventlonal dlsposable dlaper,
respectlvely;
FIGURE 6 ls a perspectlve vlew, partlally cut-away, of
an alternate embodlment of the present dlsposable dlaper; and
FIGURE 7 ls a cross-sectlonal vlew taken along llnes 7-
7 of FIGURE 6.
_7_ 1 333951
Detailed Description
While the present invention is susceptible
of embodiment in various forms, there is shown in the
drawings and will hereinafter be described presently
preferred embodiments of the invention, with the
understanding that the present disclosure is to be
considered as an exemplification of the invention,
and is not intended to limit the invention to the
specific embodiments illustrated.
As used in the present disclosure, the term
diaper is intended to refer to an absorbent article
which is worn by an individual for absorbing urine
and/or fecal matter. It is to be understood that
diapers embodying the principles of the present
invention can be appropriately sized for use by
infants or babies, and can further be sized for use
by incontinent adults. It will be further understood
that absorbent articles other than disposable diapers
can be provided with an absorbent unit or structure
embodying the principles of the present invention.
Such articles can include sanitary napkins, tampons,
incontinent pads, wound dressings, absorbent wipes,
and the like.
~eferring now to the drawings, therein is
illustrated a disposable diaper 10 embodying the
principles of the present invention. Diaper 10
includes a facing layer or topsheet 12 formed of
moisture pervious material, with the facing layer
being adapted for positioning adjacent to the wearer
of the diaper. The diaper further includes an
absorbent panel 14, which in the illustrated
embodiment, is generally rectangular, but which may
be otherwise shaped, such as T-shaped, I-shaped,
hourglass-shapea, or otherwise contoured. As will be
further described, absorbent panel 14 preferably
1 333~51
comprises an absorbent matrix of a resilient fibrous
web with hydrocolloid or superabsorbent material
distributed therein, with an associated wicking layer
of densified cellulosic fibers provided on one or
both of the expansive surfaces of the fibrous web for
enhancing liquid transport within the absorbent
matrix.
Disposable diaper 10 further includes a
backing layer 16 positioned on the side of the
absorbent panel 14 which is opposite the facing layer
12. While the backing layer may comprise
moisture-impervious material, such as plastic film or
sheet, it is presently preferred that the backing
layer 16 comprise a moisture-pervious material, such
as a non-woven fabric as used for facing layer 12,
except backing layer 16 is preferably more
hydrophobic than the facing layer to repel urine. If
desired, the non-woven fabric used for the backing
layer 16 is not treated with a surfactant compound in
order to maintain the typical hydrophobicity of the
fabric. In order to obviate passage of liquid from
absorbent panel 14 through pervious backing layer 16,
a moisture-impervious barrier layer 18 is preferably
provided so that it underlies the absorbent panel,
but is positioned inwardly of the backing layer 16.
A suitable material for the barrier layer 18
is an opaque polyolefin, for example, polyethylene
about 0.0005-0.001 inches thick. Another suitable
material for this purpose is polyethylene
terephthalate having a thickness of about
0.0005-0.001 inches. Additionally, coatings of
liquid impervious material, such as hot-melt
adhesives, or hydrophobic coatings of silicone or
flurocarbon compounds, can be applied to the layer 16
to provide the desired barrier properties.
-
1 333~51
g
The preferred relative dimensioning of the
barrier layer 18 and the backing layer 16 should be
noted. In particular, it is preferred that the
barrier layer have a surface area which is less than
the surface area of the backing layer, most
preferably with the surface area of the barrier layer
being no more than about 75 percent of the surface
area of the backing layer. By this construction,
breathability of the diaper is enhanced, thereby
helping to avoid discomfort for the wearer by
minimizing occlusion of the diaper. Additionally,
this construction positions the preferably non-woven
backing layer 16 at the exterior of the diaper, with
its cloth-like texture desirably lending aesthetic
appeal to the construction.
As will be recognized by those familiar with
the art, several different types of facing materials
may be used for facing layer 12, as well as for the
moisture-pervious backing layer 16. For example,
these layers may comprise a non-woven web made of a
mixture of fibers consisting predominantly of
inexpensive, short, cellulosic fibers such as wood
pulp fibers or cotton linters in amounts of about 75
percent to 98 percent, with the balance being textile
2S length fibers such as rayon as described in U.S.
Patent No. 3,663,348, to Liloia, et al. The
non-woven fabrics may also be formed from polyester,
polyethylene, polypropylene, nylon, rayon, or the
like.
Non-woven materials for the facing layer 12
of the present diaper can have fabric weights in the
range of from about 0.3 to 5 ounces per square yard
and densities of less than 0.2 grams/cc, generally in
the range of 0.05 to about 0.1 grams/cc. The dry
strength of the facing sheet material for a fabric
1 333951
--10--
having a weight of about 1.5 ounces per square yard
is at least 0.15 pounds per inch of width, in the
machine direction, and at least 0.1 pound per inch of
width in the cross direction. Such fabrics have good
elongation, loft, softness, and drape characteristics.
Facing layer 12 and backing layer 16 may
also be made of an apertured non-woven fabric which
is formed, for example, in accordance with the
teachings of U.S. Patents No. 2,862,251, No.
3,081,514, and No. 3,081,515. Furthermore, these
layers may also be made from other types of fabrics
such as those disclosed and described in U.S. Patent
No. 3,485,706, to Evans. Such fabrics can be made of
naturally occurring fibers, synthetic fibers, or
blends thereof. Typical facing sheets made of
polypropylene type fibers may have a weight of about
0.7 ounces per square yard.
In addition, the facing layer and backing
layer of the present construction may be made from
non-apertured materials such as non-woven isotropic
webs or apertured polyolefin or polyester films
having the desired moisture permeability.
Spun-bonded and melt-blown fabrics can also be
employed. In all of the aforementioned materials,
the materials should be relatively hydrophobic so as
to retard wicking within the material.
Referring again to the drawings, it is
presently preferred that facing layer 12, absorbent
panel 14, and barrier layer 18 all be of a
rectangular configuration, while backing layer 16 be
of a generally I-shaped, contoured configuration for
the desired fit. Specifically, the backing layer 16
includes a pair of rearward ear portions 20, and a
pair of forward ear portions 22, between which are
defined a pair of generally cut-out leg openings 24.
1 333951
The desired fit and leakage-resistant
characteristics for the present disposable diaper are
achieved by providing each leg opening 24 with one or
more associated elastic elements whereby a gathering
S or contracting force is created at the leg openings
so that the diaper conforms to and follows the
movements of the wearer's legs. For purposes of the
present discussion, reference to elastic members or
the like is intended to encompass elastic materials,
pre-stretched monofilament strands, polyurethane
films or foams, elastomeric films, shrink film and
other materials and structures which can be arranged
to exert a gathering force on the associated diaper
components. As used herein, the term "elastic~
refers to sheets, films, ribbons, strands, elastic
hot melt adhesives, elastomeric foams and nettings
and the like which preferably have a recovery of at
least 50 percent, when elongated at least 10 percent
of their yield point, and measured in accordance with
the following formula:
Percent retraction = (Le - Lt) X 100
(Le Lo)
where Lo = original length of sample
Le = fully extended length
Lt = length of sample measured three
seconds after released from
extended length.
The thickness of monofilament elastic
members is generally 10 mils or less. The thickness
of elastic film material is typically about 0.5 to
2.0 mils. Elastomeric foam materials typically have
a thickness of 1-2 mm. The elastic members have an
-12- 1 33395 1
extensibility to rupture of at least about 150
percent, and a recovery at 50 percent elongation of
at least about 50 percent, and preferably at least
about 75 percent.
In the illustrated embodiment of the present
diaper, each leg opening 24 is provided with a
plurality of generally parallel, elastic members 26
which cooperate to provide the desired sealing or
gasketing effect at the leg opening, without applying
undue force to the wearer of the diaper. Elastic
elements 26 may be adhesively secured in position, or
otherwise secured, such as ultrasonically, as is
known in the art.
As will be further discussed, specific
dimensional configurations of the present disposable
diaper have been selected to enhance its desired
conformity and fit, and wearer comfort. In this
regard, it has been determined that the distance
between the innermost ones of elastic elements 26
bears directly on the fit characteristics of the
diaper.
Experience has shown that during wearing of
the diaper, the innermost stretch elements will be
located, for the most part, in the fold of the groin
of the infant while the other stretch elements and
the sides of the diaper fold onto the infant's upper
thigh. Therefore, the distance between the innermost
stretch elements, measured across the absorbent
panel, determines the width of the diaper which must
be accommodated in the space between the thighs by
folding or corrugating. If this distance is
relatively large, excessive bagging or hanging of the
diaper between the infant's thighs will occur. For a
diaper to exhibit the desired fit, the distance
between the innermost stretch elements should be
-13- 1 333951
minimized, while still maintaining design
functionality as it relates to waste containment. In
this regard, it has been determined that the minimum
distance between the innermost elastic elements, WE
as shown in FIGURE 3, should be no more than about
1.25 times the width Wp of the associated absorbent
panel 14.
In accordance with the above preferred
dimensioning, the minimum dimension between the
opposite, innermost ones of the elastic elements 26
of diaper 10 is preferably less than the minimum
transverse dimension of the moisture impervious
barrier layer 18, with the innermost elastic elements
26 positioned on top of the barrier layer 18 in the
lS illustrated embodiment.
The superposed, multiple layers of the
disposable diaper 10 may be secured together by any
manner of known bonding techniques, including use of
adhesives in the form of glue lines or sprays, and/or
by ultrasonic bonding. When assembled in a typical
fashion, barrier layer 18 is secured to backing layer
16, with absorbent panel 14 in turn then secured to
the barrier layer. Facing layer 12 is superposed on
the absorbent panel, and is secured, typically with
glue lines, to the backing layer 16, barrier layer
18, and to the absorbent panel 14.
As shown in FIGURE 2, disposable diaper 10
is generally in position for fitting to a wearer
(although in FIGURE 2, for purposes of clarity, the
product has been shown substantially stretched in
opposition to elastic members 26). With the diaper
in a position generally as shown, a baby is placed
face up on the diaper. The forward portion of the
diaper having ear portions 22 is brought up between
the baby's legs to a position covering the perineum
-14- 1 333951
and contiguous with the front portion of the baby's
waist. The diaper is thereafter secured to the baby
by bringing the rearward ear portions 20 around the
baby into overlapping relation with the forward ear
portions 22.
In order to secure the diaper in position,
adhesive tape fasteners 28, as are well known in the
art, are provided on the rearward ear portions 20.
Each of these fasteners 28 include a tab-like element
having pressure-sensitive adhesive thereon which,
when brought into contact with the forward, outer
waist portion of the diaper, secures the diaper in
position. To this end, the outer forward waist
portion of the diaper is preCerably provided with a
fastener-receiving strip 30 (sometimes referred to as
a "target tape" or a ~tape landing zone~) to which
the adhesive fasteners 28 are respectively secured.
The use of the fastener-receiving strip 30,
which typically comprises a strip of plastic film
adhesively secured to backing layer 16, is preferred
for a variety of reasons. First of all, the use of
strip 30 assists in the correct positioning of the
tape fasteners 28 for achieving the desired fit of
the diaper. Additionally, the strip 30 can be
configured to cooperate with the adhesive of the tape
fasteners 28 to provide a secure, yet releasable
adhesive bond; a mother can thereby easily check to
see whether a diaper needs changing.
Further, the strip 30 desirably acts to
reinforce the forward portion of the diaper, thus
facilitating the above opening and resealing without
rupture of the diaper backing layer; this is a
particularly desirable feature when the backing layer
16 is made from plastic film material. When the
backing layer 16 is made from a breathable non-woven
-15- 1 333951
fabric as is presently preferred, the provision of
strip 30 further desirably functions to provide the
desired adhesive coaction with tape fasteners 28,
which is desirable since the fibrous nature of a
non-woven backing layer does not lend itself to
secure bonding with adhesives such as typically used
for tape fasteners 28.
Referring now to FIGURES 6 and 7, therein is
illustrated an alternate embodiment of the present
low bulk disposable diaper, designated 110. In most
respects, the various elements of diaper 110 function
in a manner similar to those elements in the
previously-described embodiment 10, and such like
elements are designated by like reference numerals in
the one hundred-series.
Accordingly, the disposable diaper 110
comprises a topsheet or facing layer 112, preferably
of moisture-pervious non-woven fabric, which is
superposed on an absorbent panel 114. The absorbent
panel 114 is positioned atop of a backing layer 116,
preferably also comprising a non-woven fabric, with a
moisture-impervious barrier layer 118 positioned
between the absorbent panel and the backing layer.
In distinction from the previous embodiment,
the opposite lateral edges of barrier layer 118 are
folded inwardly over the opposite lateral edges of
absorbent panel 114, with the opposite lateral edges
of the absorbent panel also folded inwardly in the
illustrated embodiment. This alternate construction
can enhance containment of waste material generally
upon and within the absorbent panel 114, thus
obviating leakage of the diaper, while at the same
time promoting diaper breathability by relatively
increasing the surface area of the breathable backing
-16- 1 333951
layer 116 which is not covered by the impervious
barrier layer 118.
As in the previous embodiment, backing layer
116 is of a contoured configuration, including
5 rearward ear portions 120, and forward ear portions
122, be tween which are defined a pair of leg openings
124. A plurality of elastic elements 126 are
provided in operative association with each of the
leg openings 124, and as will be observed in the
10 cross-sectional view of FIGURE 7, the innermost ones
of the elastic elements 126 are positioned from each
other a distance which is no more than about 1.25
times the transverse dimension of the absorbent panel
114. Adhesive tape fasteners 128 are respectively
15 provided on the rear ear portions 120 for securing
the diaper in position on a wearer.
In devel;~ping the present invention,
extensive testing was performed so as to optimize the
preferred dimensional configuration of the present
20 diaper, with like testing performed on a wide variety
of commercial disposable diaper products. It is
believed that these test results, as reported below,
highlight the novel combination of fit and absorptive
characteristics which are achieved with the present
25 construction, enhancing the comfort provided during
wearing of the diaper, yet without compromise of the
absorptive and leakage-resistant characteristics for
the construction.
The tested embodiment of the present low
30 bulk diaper tdesignated LBD in the test data) was
configured in accordance with the illustrated
embodiment of FIGURES 1-3. In this regard, the test
samples included an absorbent panel in accordance
with the preferred embodiment of the invention, and
which is disclosed in U.S. Patents No. 4,500,315, No.
17 l 3 3 3 9 5 l 23158-1598
4,537,590, and No. 4,573,998, and whlch panel can be formed ln
accordance wlth the method of U.S. Patent No. 4,540,454, all to
Plenlak, et al. Thls absorbent panel comprlses an absorbent
matrlx of a substantlally hlgh loft, reslllent flbrous web layer,
wlth superabsorbent materlal dlstrlbuted wlthln the fibrous web
layer. The superabsorbent materlal ls preferably in the form of a
plurallty of partlcles or globules of superabsorbent dlsposed ln a
random and lntermlttent arrangement throughout the flbrous web.
The partlcles or globules are of a slze and spaclng so that they
do not lnterfere wlth the absorptlon of llquld by ad~acent
partlcles.
Notably, the flbrous web layer is malntained ln a
compressed state by the superabsorbent materlal, after undergolng
compression during manufacture of the panel. By thls arrangement,
wetting of the absorbent matrix wets the superabsorbent materlal,
so that the flbrous web layer expands from its compressed state
due to the lnherent resillence of the flbrous materlal. Thls
facllltates swelllng of the superabsorbent materlal wlthout lnter-
ference with ad~acent particles or globules of the materlal.
In the preferred form, the absorbent matrlx of the panel
further lncludes llquld transport means ln operative assoclatlon
wlth the absorbent flbrous web. The transport mechanlsm comprlses
at least one wicklng layer of denslfled hydrophlllc flbers, wlth
the wlcklng layer belng coextenslve wlth at least a portlon of a
respectlve expanslve surface of the flbrous web layer of the
absorbent matrlx. Notably, thls arrangement has been found to
provlde a very efflcient absorbent structure, ln that the densi-
fied wlcklng layer promotes liquld transport from a polnt
X
1 33395 1
-18-
of introduction to various portions of the associated
fibrous web and superabsorbent. One of the problems
typically encountered in employing superabsorbent
materials in absorbent articles is the fact that such
superabsorbents typically do not transport or wick
liquid effectively, but rather can exhibit ~gel
blocking" upon wetting which can inhibit liquid
transport through the material. Thus, the wicking
layer of the absorbent matrix desirably promotes
liquid transport for efficient utilization of the
superabsorbent.
In the low bulk diapers used for generating
the following test data, an absorbent matrix in
accordance with the above patents was employed having
a density of 0.26 grams/cc, and a mean thickness of
0.13 inches. The above-described wicking layer is
provided on each side of the compre~sed fibrous web
of the structure, thus enhancing liquid transport.
It is presently preerred that the superabsorbent
material provided in the absorbent matrix comprise
200 to lS00 percent, by dry weight basis, of the
fibrous material in the fibrous web, with the
superabsorbent in the samples tested comprising about
1,000 percent add-on, by dry basis weight.
The absorbent composite is made by four
steps. First, a structure is made by blending
polyester fiber~T-375W manufactured by DuPont and
~BICO 1040 fiber, made by BASF, in a ratio of 67/33%.
this blend is carded into a high bulk non-woven web
structure of approximately 1.20 oz/yd2 weight and
passed through an air bonder at a temperature of
325 F. for a duration of 5.6 seconds and at a
pressure differential of .25 inches of water. This
heat process bonds the web by melting the BICO fiber.
-~ \ 'i ~,r l~tltt~
1 333q5 1
--19--
The second step consists of applying a
coating of potassium acrylate solution at a
consistency of 65% solids and 60% neutralized. The
monomer is added by suction coating to a level of
12.0 oz/yd2 of dry coating weight. The coating is
polymerized and cross-linked into a superabsorbent
polymer by multiple electron beam irradiations of 2
MRAD, 2MRAD, 8 MRAD, 8 MRAD, 8 MRAD with an ESI 300
KV electron accelerator.
Pulp wicking layers are attached as the
third step. Prior to this, the polymer was adjusted
to 25~ moisture content. It is passed through the
suction zone of a ~ammermill where pulp is
defiberized and deposited at a weight of
4.8 oz/yd . ~ulp is applied to the other side
similarly and the entire composite is lightly sprayed
with water and com?ressed to a thickness of .143
inches.
The fourth step consists of drying the
composite in a rotary thru air dryer at 400 F. until
it has a moisture content of less than 10%. It is
softened by passing through embossing rolls as
described in U.S. Patent No. 4,605,402.
For comparison purposes, a number of
different commercially available disposable diaper
products were tested, with these designated Samples
A-Q in the following test data. Between 10 and 20
individual samples were measured for generating the
following data, with the arithmetic mean of data
collected from like samples set forth in the
following tables.
-20- 1 33395 1
TABLE I
Diaper Cross Sectional
Thickness PanelBulk (Panel Width
Diaper Type In Crotch WidthX Thickness)
5Inches Inches Sq. Inches
Sample LBD .13 4.5 0.585
Sample A .15 6.0 0.900
Sample B .21 5.1881.089
Sample C .22 5.511.210
Sample D .25 5.241.313
Sample E .27 5.1251.384
Sample F .27 5.0 1.350
Sample G .28 5.8751.610
Sample H .31 5.0 1.550
Sample I .35 6.6252.319
Sample J .40 5.0 2.000
Sample R .40 5.592.200
Sample L .43 5.0 2.150
Sample M .44 5.252.220
Sample N .45 6.8753.094
Sample O .45 4.1251.856
Sample P .46 3.751.725
Sample Q .63 6.754.253
Referring first to Table I, the thickness of
the absorbent panels of the various samples,
(measured at 0.5 psi) and the panel widths, measured
at the center of the panel, are set forth. Table I
further sets forth the resultant cross-sectional bulk
of each panel sample, which directly relates to the
comfort or discomfort of a disposable diaper.
Specifically, a measure of comfort can be
determined by comparing the cross-section of a diaper
crotch area in relation to the distance between the
upper thighs of infants. In order for a relatively
1333951
-21-
wide diaper of a certain panel thickness and width to
fit between the infant's legs, the diaper, and
specifically the panel, has to fold and/or
corrugate. The extent to which the diaper
cross-section (cross-sectional diaper bulk) exceeds
the distance between the infant's legs is a measure
of discomfort.
Attendant to testing, the distance between
the legs of male and female infants, in the crotch
area, was measured. It was found that the most
common range for infants between 16-24 pounds and
9-18 months was between 0.0 an~ 1.0 inches, with a
mean of 0.46 inches.
Referring again to Table I, it will be noted
that the present low bulk diaper is clearly the
thinnest one of the samples tested, and is
substantially thinner than a number of the samples.
This suggests that the present low bulk diaper will
be the least bulky when worn.
1 333~51
-22-
TABLE II
Cross-Sectional Diaper Thickness When
Diaper Is Folded To Fit Between Crotch
Panel Thicknesses:
X2 X4 X6 X8
Diaper Type Inches Inches Inches Inches
Sample LBD 0.26 0.52 0.78 1.04
Sample A 0.30 0.60 0.90 1.20
Sample B 0.42 0.84 1.26 1.68
Sample 5 0.44 0.88 1.32 1.76
Sample D 0.50 1.00 1.50 2.00
Sample E 0.54 1.08 1.62 2.16
Sample F 0.54 1.08 1.62 2.16
Sample G 0.56 1.12 1.68 2.24
Sample H 0.62 1.24 1.86 2.48
Sample I 0.70 1.40 2.10 2.80
Sample J 0.80 1.60 2.40 3.20
Sample K 0.80 1.60 2.40 3.20
Sample L 0.86 1.72 2.58 3.44
Sample M 0.88 1.76 2.64 3.52
Sample N 0.90 1.80 2.70 3.60
Sample O 0.90 1.80 2.70 3.60
Sample P 0.92 1.84 2.76 3.68
Sample Q 1.26 2.52 3.78 5.04
Referring now to Table II, the
cross-sectional diaper width o' the various samples
tested is shown when the panel is folded once (twice
the panel thickness) to four times (eight times the
panel thickness). Folding of the diaper between
twice (four times panel thickness) and three times
(six times panel thickness) is very commonly observed
when infants wear diapers. As will be observed from
Table II, all of the diapers except the present low
-23- 1 33395 1
bulk diaper exceed by far the space t0.0 to 0.46
inches) provided for between the infant's thighs.
The differences between the fit
characteristics of the various diaper samples can be
expressed as a Diaper Compression Index. For a
diaper that is folded twice between the infant's legs
(i.e., four times panel thickness), this number
indicates how much more width the diaper occupies
between the legs than is available when the infant is
naturally standing without the diaper. This number
can be calculated as follows:
DIAPER COMPRESSION INDEX
Diaper Thickness When Corrugated Twice
15(4 x diaper thickness)
Distance between infants thighs (without diaper)
Example:
Diaper Thickness When corrugated Twice
20(4 x dia~er thickness) = 0.S3 in. = 1.13
Distance Between infant's thighs 0.46 in.
(without Diaper)
The following Table III shows the Diaper
Compression Index for the various samples tested.
This Table indicates that the present low bulk diaper
has a negligible effect in encumbering the infant,
while the other diapers tested far exceed the space
available between the infant's legs.
1 333~5 1
--24--
TABLE III
Diaper Compression Index
Diaper Type Diaper Type
Sample LBD 1.13 Sample I 3.04
Sample A 1.30 Sample J 3.48
Sample B 1.8 3 Sample R 3.48
Sample C 1.91 Sample L 3.74
Sample D 2.17 Sample M 3.83
Sample E 2.35 Sample N 3.91
Sample F 2.35 Sample O 3.91
Sample G 2.43 Sample P 4.00
Sample H 2.70 Sample Q 5.48
As will be appreciated, the above test data
15 relates to multiples of panel/diaper thickness in
relation to the distance between the infant's legs.
Another consideration for diaper fit and comfort is
panel width and diaper width. Consumers prefer a
snug fitting diaper because of its aesthetically
20 appealing appearance, and the ease with which outer
clothing can be applied over the diaper. It is
therefore undesirable for the diaper to hang or bag
in a pouch-like manner between the infant's legs.
Accordingly, it is believed that a further,
25 and perhaps better, expression of diaper bulk between
the infant's legs is the cross-sectional area of the
panel occupying the space between the legs (i.e.,
panel width multiplied by panel thickness). To this
end, the diaper with the smallest cross-sectional
30 area should be the least bulky and hence the most
comfortable. As shown on Table I, the present low
bulk diaper creates just slightly more than one-half
as much cross-sectional bulk area (in square inches)
between the infant's legs (0.585 square inches)
35 compared to the next best product tested, Sample A
1 333951
-25-
(0.90 square inches). It will be noted that some of
the samples are many times bulkier than the present
low hulk diaper. It is presently preferred that a
medium sized diaper (for infants between 12 and 24
pounds) have a cross-sectional bulk at that portion
of the diaper absorbent panel that fits between the
thighs of no more than about 0.6 square inches.
The significance of this data was verified
during testing on infants wearing the present low
bulk diaper, as well as a variety of the commercial
test samples. Referring to Table IV, the distance
between the legs of several infants was measured with
the infants standing without diapers. The various
samples listed in Table IV were then fitted to the
infants, and the distance between their legs again
measured. Arithmetic means for the distances, as
well as the percent increases, are shown on Table IV.
1 33395 1
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1 33395 1
-27-
It is believed that the data in this table
is particularly significant in ascertaining the
comfort of diaper fitting. As will be observed, the
present low bulk diaper exhibited a mean increase in
the distance between the infants' legs of 59
percent. In comparison, the mean increases for the
other samples tested varied from 414 percent to 536
percent. The significance of these numbers can be
readily observed in FIGURES 4 and 5. These drawings
were prepared from and closely correspond to
photographs taken during the above testing. These
drawings show the same infant (female, 18 months) for
which the distance between the infant's thighs was
measured at 0.13 inches when stan3ing without a
diaper. In FIGURE 4, the infant is shown wearing the
present low bulk diaper, with an increase of the
distance between the legs being 0.62 inches. In
marked contrast, the commercial product, Sample D,
was fitted to the same infant, which resulted in the
infant's legs being further spaced apart an increased
distance of 2.37 inches.
Another manner in which the bulk differences
between various diapers can be expressed in relation
to the anatomy of infants is the Diaper Discomfort
Factor. In this calculation, as shown below for the
low bulk diaper, panel volume of the diaper impact
zone (within the crotch region) is related to the
distance between the infant's thighs without a diaper
in a natural standing position. As designated I in
FIGURE 2, the impact zone is defined as the second
and third fifths of the diaper absorbent panel, as
measured from the front of the panel.
Moisture-impervious barrier layer 18 of the
illustrated embodiment is at least coextensive with
this portion of the absorbent panel 14, and
- .~
-28- 1 333951
preferably coextensive with substantially the entire
panel.
The length of the impact zone of the diaper
where urination is most likely to occur is, for
S mid-size diapers (for infants 12-24 pounds)
approximately 6 inches in length. Accordingly, the
six inch dimension was used in calculation of the
Discomfort Factor. Noting that the smaller the
number, the smaller the discomfort for the infant,
this factor for the present low bulk diaper is
calculated as follows:
DISCOMFORT FACTO~
15Crotch region panel bulk (i.e., panel width x
impact zone x thickness)
Distance between infants thighs (without diaper)
Example:
204 1/2" x 6" x .13 = 57.5 = 49.1
0.46" 1.17
Note: The smaller the number the smaller the
discomfort for the infant.
2~
The following Table V again shows that the
present low bulk diaper results in significantly less
discomfort for the wearer than other commercial
diaper products.
1 33395~
-29-
TABLE ~
Discomfort Factor
Diaper Type Diaper Type
Sample LBD 49.15 Sample I 194.82
Sample A 75.63 Sample J 168.06
Sample B 91.45 Sample R 187.82
Sample C 101.82 Sample L 180.67
Sample D 110.08 Sample M 194.11
Sample E 116.24 Sample N 259.94
Sample F 113.44 Sample O 155.88
Sample G 138.23 Sample P 144.95
Sample ~ 130.24 Sample Q 3S7.29
Another factor which determines the fit and
comfort level of a diaper relates to the distance
between the innermost elastic elements at the leg
openings of the product. Elastic elements tend to
contract or gather the side portions of the diaper in
order for the diaper to conform snugly to the
infant's body, specifically through the groin and
along the upper thighs for the desired waste
containment.
Experience has shown that the innermost ones
of the elastic elements of a diaper will be located,
for the most part, in the fold of the groin of the
infant, with other elastic elements in the sides of
the diaper folded onto the infant's upper thigh. It
is therefore the distance between the innermost
elastic members, measured across the absorbent panel,
that determines the width of the diaper which has to
be accommodated in the space between the thighs via
folding or corrugating. As will be appreciated, if
this distance is large, excessive bagging or hanging
of the diaper between the infant's thighs will
3~ occur. Accordingly, it is desirable to minimize this
_30_ 1 33395 1
distance, while still providing the desired waste
containment characteristics.
A sample calculation for Diaper Fit Index is
shown below, with the following Table VI showing
values for the present low bulk diaper, as well as
for the commercial products which were tested. As
will be observed, this index is a ratio of the
distance between the innermost elastic elements of a
diaper product, measured across the diaper panel in
the crotch area, and the distance between the upper
thighs of infants.
DIAPER FIT INDEX
Example:
15 Distance between innermost
stretch number = 5 1/2" = 11.9
Distance between infants 0.46"
thighs (without diaper)
TABLE VI
Diaper Fit Index
Diaper Type Diaper Type
Sample LBD 12.52 Sample I 15.97
Sample A 16.76 Sample J 16.45
Sample B 16.54 Sample R 16.60
Sample C 13.17 Sample L 16.36
Sample D 16.80 Sample M 16.52
Sample E 16.58 Sample N 16.02
Sample F 17.41 Sample O 18.23
Sample G 14.78 Sample P 18.15
Sample H 16.43 Sample Q 15.86
As will be appreciated, due to the fact that
the present low bulk diaper, when compared to other
commercial products, has one of the narrowest diaper
-31- 1 3 3 3 q 5
panels and the smallest distance between the
innermost stretch elements of all of the commercially
available diapers, it has the preferred Diaper Fit
Index.
The final parameter of the present low bulk
diaper relates to its absorptive characteristics,
thus providing a diaper which provides improved fit
and comfort, while at the same time providing
enhanced absorptivity and leakage-resistance. As
noted above, the parameters of diaper comfort and fit
are associated with a thin, narrow pad, with the
innermost elastic elements along each panel edge
placed as close to the panel as feasible.
It has been determined that an appropriate
standard in ascertaining functionality with respect
to absorptive capacity is that the impact zone of the
diaper be capable of absorbing about 220 cc of urine
throughout its usage (this representing the 9Oth
percentile of void volume for diapers during
overnight usage). Approximately 60 percent of the
urine introduced into the impact zone remains there
while the other 40 percent distributes throughout the
rest of the panel.
In order to combine the features of a thin
and narrow panel with high absorptive capacity, the
diaper panel in the impact zone has to be able to
absorb anticipated volumes of voided liquid in a
relatively small panel volume. The present low bulk
diaper is designed in such a way that the panel bulk
(i.e., the volume of the absorptive medium) in the
crotch area (i.e., impact zone) is mimimized while
the absorptive capacity in the impact zone is at the
required level as to assure a low probability of
diaper failure due to urine leakage.
1 33395 1
The relationship between diaper bulk and
absorptive capacity can be expressed as the
Absorbency Efficiency Index. As shown below, this
number is derived by dividing the urine volume at the
90th percentile level in the impact zone (of a
mid-size diaper) by the volume of the impact zone
absorptive medium. The impact zone is defined as
before as the 6 inches of panel located at the second
and third fifths of the panel length, as measured
from the front of the diaper.
ABSORBENCY EFFICIENCY INDEX
Urine volume 90th percentile in overnight
use: 220 cc.
Volume in crotch region approximately 60% of
1~ the total volume. Crotch area impact zone 6".
Crotch area impact zone is defined by the
second and third fifths of the panel length measured
from front end of diaper. This length is
approximately 6 inches for mid-size disposable
diapers.
Definition of panel bulk of impact zone in
crotch area: panel volume of the 6 inch panel length
(panel thickness measured at 0.5 psi).
Example:
2~ 220 cc X 0.6 220 cc x 0.6 = 2.29
bulk of 4.5 in. (panel width ) x 0.13 in.
crotch area (Panel thickness) x 6 in. (impact
zone length) x 16.39 cc/cu in.
Note: The highest number denotes a diaper which absorbs
the largest with the least panel volume.
3~
_33_ 1 33395 1
TABLE VII
Absorbency Efficiency Index
Diaper Type Diaper Type
Sample LBD 2.29 Sample I 0.58
Sample A 1.49 Sample J 0.67
Sample B 1.23 Sample R 0.60
Sample C 1.11 Sample L 0.62
Sample D 1.02 Sample M 0.58
Sample E 0.97 Sample N 0.43
Sample F 0.99 Sample O 0.72
Sample G 0.81 Sample P 0.78
Sample H 0.86 Sample Q 0.32
As clearly shown on the above Table VII, the
present low bulk diaper design has by far the highest
Absorbency Efficiency Index of the commercially
available diapers tested. It is believed that this
number is particularly significant, since it
indicates that a diaper having improved fit and
comfort characteristics can nevertheless be
effectively made without compromising the desired
absorbent characteristics of the product.
Summarizing, the disposable diaper embodying
the principles of the present invention enhances the
comfort for the wearer since the diaper can be worn
without forcing a dramatic dislocation of the thighs
and legs of an infant as is the usual case with
currently available commercial products. Not only
does this provide greater comfort, it is believed
that the present diaper construction could provide
pediatric benefits to the infants by avoiding
artificial dislocation of the limbs.
Additionally, the present diaper is
configured to provide high absorptive capacity in the
impact zone while at the same time exhibiting low
1 333q51
-34-
panel bulk, i.e., exhibits high absorbency
efficiency. Additionally, the manner in which the
present diaper is configured so that the innermost
ones of the elastic elements of the leg openings are
spaced as closely together provides a snug fit
between the infant's legs, thus facilitating
convenient consumer use.
From the foregoing, it will be observea that
numerous modifications and variations can be effected
without departing from the true spirit and scope of
the novel concept of the present invention. It is to
be understood that the present disclosure is to be
considered as an exemplification of the invention,
and is not intended to limit the invention to the
specific embodiments illustrated. The disclosure is
intended to cover by the appended claims all such
modifications as fall within the scope of the claims.
