Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
The present invention relates to disposable ahsorbent
articles.
A varlous assortment o~ disposable absorbent articles
have been proposed for use in receiving and retaining body fluids.
Such articlesJ e.g., disposable diapers, sanitary napkins and
the like, have normally b~en constructed with a fluid impervious
backing sheet, a f`luid pervious cover or top sheet, an absorbent
pad intermediate the backing and cover sheets, such as comminuted
wood pulp termed in the art as fluff. Although increasingly
popular due to disposabilityJ certain problems remain associated
with the absorbent pads which prevent the articles ~rom being
totally satisfactory. I
First, it is necessary that the pads rapidly spread
body fluids ~rom the point of application toward remote locations
of` the pads in order to minimize pad saturation in localized
areas and make maximum use of the full pad capacity. Second,
it is desirable that the pads preferentially retain the body
fluids at locations spaced from the cover sheet in order to
minimize back wetting through the cover sheet with attendant
discom~ort to the wearer. Third, the pads should be soft and
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conformable to the shape of the wearer in order to provide a
proper fit of the articles and maximum comfort. Finally, the
pads should be made in accordance with simplified manufacturing
techniques in order to reduce the cost of the disposable
articles to the consumer.
In the applicant's earlier filed application No. 248,289
filed August 8, 1977, there is disclosed, in a disposable
absorbent article, having a fluid impervious back sheet and a
fluid pervious top sheet, a pad assembly comprised of a loosely
formed bat adjacent the cover sheet and a second bat or pad
between the first one and the backing sheet and having
compressed regions throughout a substantial part of the second
pad and also having uncompressed areas adjacent said compressed
regions. Such a pad is functionally superior to a conventional
single pad type disposable product.
In United States patent 3,612,055 there is disclosed a
single pad diaper construction wherein the one surface not in
contact with the top sheet is processed to form a paper-like
skin to effect fluid spread to the backside of the diaper.
SUMMARY OF THE INVENTION
The aim of the present invention is the provision of an
absorbent article of simplified construction having improved
fluid dispersing and retention capabilities.
The present invention provides a disposable absorbent
article comprising a backing sheet of fluid impervious material,
a fluid pervious cover sheet, a first absorbent pad adjacent
said cover sheet comprising a loosely formed fibrous mass of
wood fluff, and a separate second absorbent pad intermediate
said first pad and backing sheet, said second pad comprising a
mass of fibers of wood fluff which are more dense than said
first pad throughout said second pad with interfiber spacings in
said second pad being substantially less than interfiber spacings
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in said first pad, said second pad thereby having its compressed
regions extending throughout at least said second pad, said
compressed regions rapidly transmitting body fluids to remote
locations of the second pad for retention in said compressed
regions at a location spaced from the cover sheet.
Thus, the pads minimize back wetting of the body fluids
through the cover sheet and maintain the cover sheet in a
relatively dry condition during use of the article.
The pads may be made in a simplified manner and at a
reduced cost.
DESCRIPTION OF THE DRAWINGS
In the drawings:
Figure l is a fragmentary front plan view of an
absorbent article of the present invention being illustrated in
the form of a disposable diaper.
Figure 2 is a fragmentary sectional view taken
substantially as indicated along the line 2-2 of Figure 1.
Figure 3 is a perspective view of the article of Figure
1 as folded into a box-pleat configuration.
Figure 4 is a top plan view partly broken away for
clarity of another form of a disposable diaper.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to Figures 1 and 2, there is shown a
disposable absorbent article generally designated 20 which is
illustrated in the form of a disposable diaper. Although for
convenience the article described will be a disposable diaper,
it will be understood that the principles of the invention are
equally applicable to other disposable absorbent articles, such
as sanitary napkins and underpads. As shown, the article or
diaper 20 has an absorbent pad assembly 21 having a fluid
impervious backing sheet 22, such as polyethylene, defining a
back surface 23 of the pad assembly, which covers the back
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surface 28 of pad 26, a fluid pervious top or cover sheet 24,
such as nonwoven material, defining a substantial portion of a
front surface 25 of the
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pad assembly, and an absorbent pad generally designated 26
intermediate the backing sheet 22 and cover sheet 24. With
reference to Fig. 1, the diaper 20 may have a pair of tape
fasteners 38 for securing the diaper about an infant during
placement, and the backing sheet 22 may have lateral side
margins 32 folded over and secured to the cover sheet 24 such
that the margins 32 cover side portions of the pad 26.
As sho~n in Figs. 1 and 2~ the absorbent pad 26 has
a first absorbent pad or layer 40 located adjacent the cover
sheet 24 and a second absorbent pad or layer 42 located inter-
mediate the first pad 40 and the backing sheet 22. The pad
26 may have a top wadding sheet 34 covering a front surface
30 of the upper first pad 40 and a back wadding sheet 36
covering a back surface 28 of the lower second pad 42. In
one form, as shown, a back surface 41 of the first pad 40 may
be placed against a front surface 43 of the second pad 42, or,
in an alternative form, a fluid pervious sheet, such as a
wadding sheet, may be interposed between the first and second
pads 40 and 42, respectively.
The first pad 40 is made from a loosely formed mass
of fibers, such as comminuted wood pulp termed in the art as
fluff. Although the first pad may be compacted, if desired,
the first pad 40 may have minimal compression in order to
obtain a soft, fluffy front pad 40 with relative~y large
interfiber spacings.
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The density of top pad 40 should be between about
0.03g/cm3 and about 0.07g/cm3 ~ preferably between about 0~04g/
cm3 and about 0.07g/cm3 and more preferably between about
0.06g/cm and about 0.07g/cm3 . The second lower pad 42 is also
made from a mass o~ fibers, such as comminuted wood pulp,
similar to pad 40 but this pad is prepared as by compression
or any other suitable conventional means, to a density of
between about 0.14g/cm3 and about 0.22 g/cm3, preferably from
about 0 16g/cm3 and 0.20 g/cm3 , and more preferably from about
0.18g/cm3 and 0.20g/cm3 . Within the aforedescribed parameters
of densities, lt is desirable that the ratlo of the density of
the lower pad 42 to that o~ the top pad 40 be ~rom about 1.5:1
to about 7:1, preferably about '2:1 to about 5:1 and more
preferably ~rom about 2:1 to 4:1. The densitles are, of
course, simply determined from a given weight of a measured
volume (length x width x thickness with the latter measured
as described below).
The thicknesses of the pads may vary widely but, in
general, they are combined to give an overall thickness of about
40 mils to 1500 mils (about lmm to about 40 mm) with ratios of
thicknesses of top to bottom pad ranging from about 50:1 to 1:1,
preferably 20:1 to 2:1, and more preferably 10:1 to 4:1. All
thicknesses are based upon measurements with a load of 4.1g/cm
on the pad since without such an applied load the loftiness and
resiliency of the fluff pad would give varying values. Density
11535~1
parameters are then based on such thickness determinations.
For infant diapers total pad thickness will, obvious-
ly, generally be lower than for adult incontinence pads and
diapers and for feminine sanitary napkins ! Typical newborn
infant diapers may have total pad thickness of about lmm
to about 6 mm or about 2mm to about lOmm depending on the
diaper style. For larger babies, pad thickness totals may
range from about 2mm to about 8mm or about 3mm to about 12mm.
Sanitary napkin pad totals typically may range from about 3mm
to about lOmm, or about 4mm to about 20mm or more, e.g. about
6mm to about 40 mm, again, depending on the particular style
of the sanitary napkin.
Further, it may be desirable to point out that total
pad fluff weights will, of course, vary considerably as do the
thicknesses and sizes of the pads. ~s a guide, such weights
may vary from about 10 to 20 grams up to about 100 grams.
Again, generally, the ratio of the weights of the top to
bottom pads may vary from about 2:1 to 1:2 but preferably will
be about the same, particularly as this permits the greatest
facility in manufacture. Thus, for example, a single web of
fluff can be formed in any of the conventional ways, then split
and the one for the bottom layer compressed as desired in
accordance with the present invention.
In use, the dlaper 20 is secured about an infant by
the tape fasteners 38. During voiding, urine passes through
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the cover sheet 24 into a localized portion of the first pad 40,
and due to the relatively small interfiber spacings in the
compressed second pad 42, the fluids are rapidly absorbed from
the first pad 40 by the second pad 42. Also, the compressed
pad 42 rapidly transmits the fluids to pad portions which are
remote the point of urine application to the diaper. Although
a relatively large amount of fluff material has been compressed
in producing the pad 42 and thu~ it has a smaller fluid holding
capacity than the pad 40 due to the relative size of their
interfiber spacings, the rapid spreading of the fluid through-
out pad 42 permits the overall pad composite 26 to retain sub-
stantially as much fluid as an equivalent weight uncompressed
pad assembly much like reservoirs which retain the body fluids
in localities but due to the more rapid and efficient spreading
of the urine there is much less leakage after each urination and
also a marked reduction in back wetting thereby maintaining the
top sheet 24 in a relatively dry condition. In this manner,
the first and second pads 40 and 42, respectively, cooperate
to rapidly disperse fluids throughout the second pad 42 while
making maximum use of the pad material and maintaining the top
sheet 18 in a relatively dry state.
As previously indicated, the first pad 40 is relative-
ly soft and conformable since it is relatively uncompressed.
Accordingly, the first and second pads 40 and 42 respectively,
provide a pad structure for the diaper which is soft and conform-
able to the shape of the wearer in order to maximize comfort and
provide an excellent fit of the diaper. In addition~ the pad 26
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o~ the present invention may be made in a simplified manner
by compressing the second pad 42 and by then placing the first
pad 40 against the second pad 42 during manufacture of the
diaper. Thus, the diaper is made without the necessity of
wetting and drying the compressed regions which would otherwise
add to the complexity and cost o~ manufacture.
Referring to Fig. 3, the pad assembly 21 of Fig. 1 may
be ~olded along a plurality of longitudinally extending fold
lines to define a box-pleat configuration of the diaper. Thus,
the diaper is folded along a pair of first fold lines 50 to
de~ine a longitudinally extending central panel 52 and along
a pair o~ s~econd fold lines 54 to define a pair of longitudin-
ally extending first panels 56 intermediate the ~old lines
50 and ~4 and a pair of outermost panels 58 extending from the
second fold lines 54.
Re~erring to Fig. 4, the diaper 60 is of an hour-glass
configuration having a crotch area 62 and four portlons of
greater width defining ears 64, 66, 68 and 70. The diaper
includes a backing sheet 72 of polyethylene or the like and a
top sheet 74, similarly as the box-pleated diaper. An
absorbent pad assembly 75 similar to pads 26, 40 and 42 of the
box-pleated diaper is disposed between the top and backsheets.
Waddings 77 similar to 34 and 36 of the box-pleated diaper may
be provided similarly as in the box-pleated diaper. The pad
assembly including wadding sheets are of lesser dimensions, as
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indicated than the top and backsheets which are o~ similar
dimensions.
In a product blind test of 106 users comprising a
first standard pad diaper (pad of 36 grams wood fluff of iniform
density of 0.1 g/cc - pad size 300mm x 409mm) with a second
2-layer pad diaper of the present invention of similar dimenslons
and weight as the first diaper but wherein the top pad of the
second diaper has a density of o~06g/cc and the second bottom
pad a density of 0.2g/cc, it was found as ~ollows :
prefer prefer no pre- ratio
double std. ference
flu~f
Layer
_____ ______ _______ ______
B B B
- o~rerall preference 41 21 38 + 1.49
- drier bottom 35 20 45 ~ 1.36
- strength 34 9 57 + 1.65
- absorption 37 21 42 ~ 1.38
- overall fit + 1.02
- fit at thighs - 1. o8
- thickness 33 15 52 ~ 1.44
Leakage occurence
33 40
diaper could absorb if needed.
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The overall preference ratio o~ + 1.49 is statistically
equivalent to a ~2 sigma preference for the 2-layer pad diaper
and indicates at a 95~ confidence level that a majority would
prefer the 2~1ayer pad di~per to the conventional single pad
diaper.
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