U.S. patent number 3,763,863 [Application Number 05/187,248] was granted by the patent office on 1973-10-09 for disposable diaper.
This patent grant is currently assigned to Johnson & Johnson. Invention is credited to Frederick K. Mesek, Virginia L. Repke.
United States Patent |
3,763,863 |
Mesek , et al. |
October 9, 1973 |
DISPOSABLE DIAPER
Abstract
A disposable multi-layer diaper including at one side a porous
fibrous facing layer to be brought into contact with an infant's
skin, and including at the other side a water-impervious backing
sheet, with a multi-layer batt being interposed between the facing
layer and backing sheet. The batt layers are of different size,
with the smaller layer being positioned in face-to-face engagement
with the backing sheet, and with the larger layer having lateral
extremities which extend beyond the smaller layer on each side
thereof. The smaller batt layer and the lateral extremities of the
larger layer are each adhered to the backing sheet. In a preferred
embodiment of the invention, a paper-like, densified, highly
compacted cellulosic layer is formed integrally with the smaller
batt layer, and is positioned in face-to-face engagement with the
backing sheet.
Inventors: |
Mesek; Frederick K. (Downers
Grove, IL), Repke; Virginia L. (Oak Forest, IL) |
Assignee: |
Johnson & Johnson (New
Brunswick, NJ)
|
Family
ID: |
22688198 |
Appl.
No.: |
05/187,248 |
Filed: |
October 7, 1971 |
Current U.S.
Class: |
604/365; 604/377;
604/389; 604/374; 604/378 |
Current CPC
Class: |
A61F
13/535 (20130101); A61F 2013/1543 (20130101) |
Current International
Class: |
A61F
13/15 (20060101); A61f 013/16 () |
Field of
Search: |
;128/284,287,29R,29W |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Rosenbaum; Charles F.
Claims
What is claimed is:
1. A multi-layer diaper comprising: a water-impervious backing
sheet; an absorbent batt in juxtaposition with said backing sheet,
said batt including a first highly porous, loosely compacted,
cellulosic fibrous layer having a paper-like, densified, compacted
cellulosic fibrous layer of relatively high wettability and
relatively high fluid retentivity formed integrally therewith, said
densified layer being positioned in face-to-face engagement with
said backing sheet, said batt further including a second highly
porous, loosely compacted, cellulosic fibrous layer wider than said
first layer and being of uniform density throughout its thickness,
said second layer having its midportion positioned face-to-face
engagement with said first layer with marginal portions of said
second layer extending outwardly beyond the sides of the first
layer, said marginal portions being disposed in face-to-face
engagement with said backing sheet and adhered thereto; and a
porous facing layer disposed over the second layer of said batt,
said loosely compacted batt layers having greater wettability to
water than said facing layer.
2. The diaper of claim 1 wherein said backing sheet and said facing
layer are substantially rectangular and substantially coextensive,
said second batt layer is substantially rectangular, narrower than
said backing sheet and facing layer, and centrally disposed with
respect thereto to provide marginal portions of said diaper in
which said backing sheet and said facing web are in direct contact
with each other.
3. The diaper of claim 2 wherein said first batt layer is also
substantially rectangular and disposed centrally of said second
batt layer.
4. The diaper of claim 1 wherein the fiber content of said facing
layer comprises from about 75 to about 98 weight percent of short
fibers having a fiber length less that 1/4 inch and from about 2 to
about 25 weight percent of long fibers having a fiber length
between about 1/2 and about 21/2 inches.
5. The diaper of claim 1 wherein the fibers of said facing layer
are bonded together by a water repellent polymeric bonding agent
and wherein the fibers of said facing layer are coated with a
surfactant.
6. The diaper of claim 1 wherein said first batt layer and the
marginal portions of said second batt layer are adhered to said
backing sheet by an adhesive discontinuously distributed over the
entire interface between them.
7. The diaper of claim 6 wherein said first batt layer and the
marginal portions of said second batt layer are adhered to said
backing sheet by parallel lines of adhesive.
8. A multi-layer diaper comprising: a water-impervious backing
sheet; an absorbent batt in juxtaposition with said backing sheet,
said batt including a first highly porous, loosely compacted,
cellulosic fibrous layer having a paper-like, densified, compacted
cellulosic fibrous layer of relatively high wettability and
relatively high fluid retentivity formed integrally therewith, said
densified layer being positioned in face-to-face engagement with
said backing sheet and adhered thereto by parallel lines of
adhesive, said batt further including a second highly porous,
loosely compacted cellulosic fibrous layer wider than said first
layer, said second layer having its mid-portion positioned in
face-to-face engagement with said first layer with marginal
portions of said second layer extending outwardly beyond the sides
of the first layer, said marginal portions being disposed in
face-to-face engagement with said backing sheet and adhered thereto
by parallel lines of adhesive; and a porous facing layer disposed
over the second layer of said batt, said batt layers having greater
wettability to water than said facing layer.
9. The diaper of claim 8 wherein said backing sheet and said facing
layer are substantially rectangular and substantially coextensive,
said second batt layer is substantially rectangular, narrower than
said backing sheet and facing layer, and centrally disposed with
respect thereto to provide marginal portions of said diaper in
which said backing sheet and said facing web are in direct contact
with each other.
10. The diaper of claim 9 wherein said first batt layer is also
substantially rectangular and disposed centrally of said second
batt layer.
11. The diaper of claim 8 wherein the fiber content of said facing
layer comprises from about 75 to about 98 weight percent of short
fibers having a fiber length less than 1/4 inch and from about 2 to
about 25 weight percent of long fibers having a fiber length
between about 1/2 and about 21/2 inches.
12. The diaper of claim 8 wherein the fibers of said facing layer
are bonded together by a water repellent polymeric bonding agent
and wherein the fibers of said facing layer are coated with a
surfactant.
Description
BACKGROUND OF THE INVENTION
Disposable diapers have met with increasing commercial acceptance
in recent years, primarily because of their convenience. Such
diapers have conventionally included a facing layer to be brought
into contact with an infant's skin, an absorbent panel adjacent
thereto, and a water-impervious or a water repellent outer
layer.
Known types of disposable diapers have had many functional
deficiencies including inadequate absorptive capacity and inability
to keep moisture away from the surface of the diaper which comes
into contact with the infant's skin. Another serious drawback of
prior art diapers is the tendency for liquid to leak around the
edges of the diaper, particularly at night during periods of heavy
discharge.
A significant advance in the art is provided by the diaper
constructions disclosed and claimed in commonly assigned, copending
Mesek et al. application Ser. No. 6,864 filed Jan. 29, 1970. The
diaper structure illustrated therein includes, in order; a fibrous
facing layer which is to be brought into contact with the infant's
skin; an absorbent panel comprising a batt of highly porous,
loosely compacted cellulose fibers having a paper-like, densified,
highly compacted cellulosic fibrous layer integral with the loosely
compacted batt; and an impervious backing sheet adhered to the
densified layer portion of the batt throughout the interface
therebetween. The facing layer is of porous construction and its
fibers have less wettability for water than the fibers of the
loosely compacted batt, resulting in a tendency for liquid to flow
from the facing web into the batt. The densified fibrous layer has
a smaller average pore size than the lossely compacted batt
resulting in a tendency for liquid to flow from the batt into the
densified layer.
In one embodiment of the diaper disclosed in the above mentioned
application, having particular utility during periods of heavy
discharge, the absorbent panel of the diaper includes a relatively
small second batt, similar to the batt already named, superimposed
on the larger first named batt. This construction not only provides
an increased absorptive capacity for the diaper, but also provides
for greater compressibility at the center of the diaper because of
the increased batt thickness. When the batt portion of the diaper
is compressed by the infant's weight, the distances between
adjacent fibers is decreased, i.e., there is a smaller effective
capillary radius between adjacent fibers, particularly in the
center section of the batt portion of the diaper. In consequence of
this, there is a greater wickability at the more highly compressed
center portion of the batt as compared to the less compressed
marginal portions. This latter construction tends to keep liquid in
place in the center portion of the diaper, and prevents it from
leaking around the edges thereof.
In the last mentioned diaper embodiment, the integral densified
layer portion of the larger batt is in face-to-face engagement with
the backing sheet, thus helping the urine to spread laterally
throughout the length and width of the batt beyond the edges of the
smaller batt. The rapid spread of the urine by means of the
densified layer is desirable, but carrying the liquid to the
peripheral edges of the larger batt increases the likelihood of
leakage at the edges of the diaper.
SUMMARY OF THE INVENTION
The diaper of the present invention represents an improvement upon
the multi-layer batt, heavy discharge type of diaper disclosed in
the above mentioned Mesek et al. application, by virtue of
minimizing the likelihood of urine leaking from the edges of the
diaper. To achieve this important result, the diaper of the present
invention includes an absorbent panel consisting of two differently
sized, superposed batt layers of highly porous, loosely compacted
cellulose fibers, sandwiched between a porous facing layer and a
water-impervious sheet, with the smaller of the batt layers being
positioned adjacent the backing sheet, and with the larger batt
layer being positioned over the smaller batt layer. The marginal
side portions of the larger batt layer extend outwardly beyond the
sides of smaller batt layer and are adhered to the backing sheet.
The smaller batt layer includes a paper-like, densified, highly
compacted cellulosic fibrous layer integral therewith, which is in
face-to-face engagement with the water-impervious sheet and adhered
thereto.
In consequence of the construction of the diaper of the present
invention, urine passing into the superposed layers of the
absorbent batt through the facing layer flows preferentially into
the densified layer of the smaller batt to draw the liquid away
from the infant's skin. The urine flowing into the densified layer
tends to spread laterally because of its wicking action, but
because the densified layer is confined to the central portion of
the diaper, the urine is similarly confined, and any tendency for
urine to leak around the edges of the diaper is minimized. The
increased compressibility resulting from the double thickness at
the center of the diaper, combined with the compression caused by
the infant's weight, provides for greater wickability at the center
of the diaper, so that there is a cooperative relationship with the
centrally located densified layer which tends to concentrate urine
away from the side edges of the diaper. Further, the less dense
overhanging extremities of the larger batt layer provide, in
effect, a barrier which also contributes to the retention of urine
in the center of the diaper.
The construction of the diaper of the invention, as a whole,
provides a mechanism for rapidly transporting urine laterally from
the point of discharge from the infant, and for spreading urine
throughout most of the absorbent panel, while at the same time
retarding the lateral flow before the urine reaches the edges of
the batt. It also provides a mechanism for holding a urine
discharge of limited content within the central portion of the
diaper by a combination of a densified layer of limited area in the
central region of the diaper and a greater overall batt density in
the central region, provided by the action of the infant's weight
on the thickened central portion (the superposed batts) of the
diaper.
In addition to the advantages described above with respect to the
handling of urine discharge by the diaper of this invention, it
also provides enhanced structural stability. As described above,
both of the batt layers are directly adhered to the backing sheet
(which is ordinarily the strongest structural element of the
diaper), the smaller batt layer being adhered to the backing sheet
throughout the interface therebetween, and the larger batt layer
having its marginal side portions adhered to the backing sheet.
Thus, each of the batt layers is positively anchored to the backing
sheet against movement and against disintegration. The increased
structural integrity is of especial importance in a diaper that can
hold a large volume of urine since the increased weight of the
urine-saturated diaper subjects it, and particularly its relatively
flimsy absorbent panel, to increased stress.
The improved structural stability is of particular importance in
embodiments of the diaper in which the facing layer is relatively
weak in comparison to the backing sheet, such as in embodiments in
which the facing layer is a bonded mixture of long and short fibers
and the backing sheet is a polyethylene film.
The increased strength imparted to the diaper by virtue of having
both layers of the absorbent panel directly adhered to the backing
sheet has applicability even in diaper structures which have no
densified layer and in which each batt is loosely compacted
throughout its thickness. In fact, the increased strength imparted
by direct adhesion to the backing sheet is more advantageous in a
diaper without a densified layer since a densified layer provides
structural strength to a loosely compacted batt of cellulosic
fibers and the absence of such a layer makes external reinforcement
all the more desirable.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view, with certain portions broken away, of
an open unfolded diaper in accordance with one embodiment of this
invention;
FIG. 2 is a partial cross-section of the diaper of FIG. 1 taken
generally along line 2--2 of FIG. 1;
FIG. 3 is a partial cross-sectional view similar to FIG. 2
illustrating an alternate embodiment of this invention; and
FIG. 4 is a perspective view on a reduced scale of the diaper in
its configuration after being put on an infant.
DETAILED DESCRIPTION OF THE INVENTION
Referring to the drawings, and particularly to FIGS. 1 and 2,
diaper assembly 10, when fully opened and laid out flat, comprises,
in order, fibrous facing layer 16 adapted to be positioned adjacent
the skin of an infant, absorbent fibrous panel, or batt 14, and a
water-impervious sheet 12. Fibrous layer 16 is rectangular in
shape, equal in dimension, and coterminous with backing sheet
12.
Batt 14 includes a first layer 14a in a face-to-face juxtaposition
with backing sheet 12, and layer 14a is also rectangular in shape,
but substantially smaller than backing sheet 12 and facing layer
16, and disposed centrally thereof. Batt 14 includes a second
rectangular layer 14b wider than batt layer 14a, but smaller than
backing sheet 13 and facing layer 16. Batt layer 14b is disposed
centrally above batt layer 14a to provide marginal side portions
14c that extend outwardly an equal amount beyond the sides of batt
layer 14a, with side portions 14c being sandwiched between
intermediate portions 12a of backing sheet 12 and downwardly
stepped intermediate portions 16a of facing layer 16. The marginal
portions 12b and 16b (i.e., the portions extending beyond batt
layer 14b) of sheet 12 and facing layer 16, respectively, are in
face-to-face engagement with one another. Backing sheet 12 is
adhered to layers 14a, 14b and 16 at the interface therebetween, as
will hereinafter be described.
In the preferred embodiment of the invention, moisture-impervious
sheet 12 is formed of polyethylene having a thickness of
approximately 0.001 inch. The sheet may be smooth, or may be
embossed to improve its drape and feel. Other suitable flexible
moisture-impervious sheets may be used in accordance with the
invention, such as, for example, polyethylene terephthalate sheets
having a thickness of about 0.0005 inch.
Batt layers 14a and 14b are formed of loosely compacted short
cellulose fibers, such as wood pulp fibers, or cotton linters, or
mixtures thereof, which are primarily held together by interfiber
bonds requiring no added adhesive, as is known in the art. Briefly,
this batt is a low bulk density coherent web of loosely compacted
cellulose fibers, preferably comminuted wood pulp fibers in the
form of so-called "fluff."
The term "short fibers," as used herein, refers to fibers less than
about 1/4 inch in length, in contrast to "long fibers," or "textile
length fibers," which are longer than about 1/4 inch in length, and
generally are between about 1/2 and 21/2 inches in length. The
former are substantially less costly than the latter. The
classification of fibers by length may be carried out by the Clark
Classification procedure described in the test manual of the
Technical Association of Pulp and Paper Industry (TAPPI-T233
SU64).
Paper-like densivied layer 18 of batt layer 14a is formed by a
slight moistening of one surface of the batt followed by the
application of pressure thereto. The nature of the batt and of its
densified layer and the method of producing the same are described
in U.S. Pat. No. 3,017,304, dated Jan. 16, 1962.
The composite density of batt 14, including the densified layer of
batt layer 14a, should be above about 0.07 gm./cc., and preferably
between about 0.10 and 0.15 gm./cc. The foregoing density values
are applicable to the diaper as produced. In storage and handling,
the loft or thickness of the batt is increased to some extent,
resulting in lowered densities.
Facing layer 16 is made up of a mixture of fibers consisting
predominantly of short cellulosic fibers such as wood pulp fibers
or cotton linters, in amounts of about 75 percent to about 98
percent, the balance being textile length fibers such as rayon.
Short cellulsoic fibers such as wood pulp fibers or cotton linters
are substantially less expensive than textile length cellulosic
fibers such as cotton and rayon, and this low cost is a factor in
reducing the cost of the facing layer component of the diaper of
this invention.
In facing layer 16, the short fibers are in uniform admixture with
2 percent to 25 percent by weight of textile length fibers, such as
1.5 denier rayon fibers uniformly cut to 11/2 inches length. The
short and long fibers are randomly and substantially uniformly
dispersed and bonded with a bonding agent such as a
self-cross-linking acrylic emulsion. One bonding agent that has
been applied with considerable success is a latex of a
polyethyl-acrylate copolymer containing small amounts of
acrylonitrile and a cross-linking monomer sold under the trademark
HYCAR 2600 .times. 120. The bonding agent should be of the low
viscosity type with a viscosity less than 5 centipoises. The facing
web is also treated with a wetting agent, preferably an anionic
surfactant, to partially counteract the water repellency of the
bonding agent and bring the facing layer to the desired degree of
wettability. A typical surfactant which has been found to be
suitable is the ionic sulfonated alkyl ester sold under the
trademark TRITON GR-5. Facing layers of this character are
described in greater detail in commonly-owned copending United
States patent application Ser. No. 729,784.
Facing layers suitable for use in this invention have fabric
weights in the range of 1 to 5 oz./yd..sup.2 and densities less
than 0.15 gm./cc., generally in the range between 0.05 and 0.01
gm./cc. The dry strength of the facing layer, for a fabric having a
weight of about 1.5 oz/yd..sup.2, is at least 0.15 lbs./in. of
width in the machine direction and at least 0.08 lbs./in. of width
in the cross direction. The fabrics have unusually good elongation,
loft, softness and drape characteristics in comparison to prior
products incorporating any substantial amount of short fibers.
For a more detailed description of facing layers and batt layers,
such as fibrous layer 16 and batt layers 14a and 14b, as well as
the methods of producing them, reference may be made to the above
mentioned application Ser. No. 6,864, the disclosure of which is
hereby incorporated herein in its entirety by this reference.
As is explained in application Ser. No. 6,864, an important aspect
of the improved diaper is the provision for selective wettability
among the above described fibrous components, such that the
moisture is selectively drawn from the facing layer into the body
of the batt and then from the body of the batt into the densified
layer thereof. Specifically, when liquid, such as urine, flows into
a small area on the outer surface of facing layer 16, it flows
preferentially into underlying batt layer 14b rather than to other
areas of the facing layer, thus tending to restrict wetting in the
facing layer to a small area and to move the liquid away from the
infant's skin.
When an infant's weight rests on the aforedescribed diaper
construction having the stepped batt panels, there is a tendency
for the uncompressed absorbent material of batt layers 14a and 14b
to be compressed by the weight. Since there is a greater thickness
of material in the center of the diaper than at the margins
thereof, there will be greater pressure (and hence more
compression) at the center. This results in a smaller effective
capillary radius in the central section, and greater wickability of
the more highly compressed center portion as compared to the less
compressed marginal portions 14c. As a result, urine passing into
the central portion of batt layer 14b tends to flow preferentially
into the underlying batt layer 14a, rather than into the marginal
portions 14c of batt layer 14b.
The liquid which flows through batt layer 14b and into batt layer
14a flows preferentially into underlying densified layer 18, rather
than to other areas of the loosely compacted batt layer, thus
tending to move the liquid farther from the infant's skin. The
liquid flowing into densified layer 18 tends to spread laterally
because of its wicking action, and liquid which might pass through
the densified layer during discharge (when flow is rapid) is held
back by the impervious backing sheet for sufficient time to permit
absorption to take place.
Since the densified layer is confined to the central portion of the
diaper, the capacity of the diaper to retain and confine liquid in
this area, as compared to prior art diapers, is markedly improved.
Liquid in excess of the absorptive capacity of densified layer 18
is forced back by impervious layer 12 into the dry portion of
loosely compacted batt layer 14a, thus utilizing the additional
absorptive capacity therein. Once batt layer 14a becomes saturated,
liquid will migrate into the superposed dry portions of batt layer
14b to take advantage of the additional absorptive capacity
thereof, and it will be appreciated that liquid will initially flow
into the dry portions of the relatively highly compressed central
portion of batt layer 14b before it flows into the less highly
compressed marginal portions 14c thereof. The net result is that
the loosely compacted marginal portions 14c act as dam-like
barriers that cooperate with the densified portion 18 of batt layer
14a to confine liquid at the central portions of the diaper. Only
after the relatively highly compressed central portions of batt
layers 14a and 14b become saturated will liquid flow into the
marginal portions 14c, and thus it will be appreciated that the
diaper of the present invention effectively minimizes the
likelihood that liquid will escape around the edges of the
diaper.
As noted above, because of the increased absorptive capacity
provided by the double layer batt construction, the aforedescribed
diaper is especially adapted for use during periods of heavy
discharge. In previous types of heavy duty type diapers, problems
have been encountered in retaining the various batt layers in place
when the diaper becomes saturated, since the increased weight
attributable to the larger absorbed volume subjects the diaper to
increased stresses not normally encountered in a diaper having a
smaller absorptive capacity. This problem is particularly acute,
since the loosely compacted fibrous layers that are conventionally
used as the absorbent panel of the diaper are usually relatively
flimsy and weak when compared to the facing layer and particularly
to the backing layer, which ordinarily has much greater structural
integrity than the other layers of the diaper.
The diaper of the present invention obviates the problems noted in
the preceding paragraph by having both layers of the absorbent
panel and facing layer adhered to the backing sheet substantially
through the interface therebetween. With reference to FIGS. 1 and
2, it will be noted that parallel lines of adhesive 22 are utilized
to adhere the densified layer 18 of batt layer 14a, as well as the
marginal portions 14c of batt layer 14a and 16b of facing layer 16,
to the backing sheet 12. Other adhesive patterns may be utilized,
as will occur to those skilled in the art. In any event, since
marginal portions 14c of batt layer 14b and batt layer 14a in its
entirety are each secured to backing sheet 12, both batt layers are
firmly anchored in place against movement and against
disintegration.
Referring now to FIG. 3, the diaper construction illustrated
therein is similar to the previously described embodiment, so that
the same reference numerals are used to designate the common
elements. The diaper of FIG. 3 differs from the previously
described embodiment in that the densified layer 18 has been
eliminated from the lower batt layer 14a . However, as with the
previous embodiment, batt layer 14b is a loosely compacted fibrous
member that is rectangular in shape and wider than the underlying
rectangular batt layer 14a to provide overhanging marginal side
portions 14c that are adhered to backing sheet 12, along with batt
layer 14a, by parallel lines of adhesive 22. Batt layer 14a is
loosely compacted throughout its thickness and hence is relatively
weak, as contrasted to the batt layer 14a of the embodiment of
FIGS. 1 and 2 whose strength is augmented by the presence of
densified layer 18. Nevertheless, by virtue of having both batt
layers secured to backing sheet, the diaper construction of FIG. 3
has adequate strength to withstand the increased stresses which
occur when the diaper becomes saturated.
The diaper is normally packaged and sold in a folded condition, as
is described in detail in the above mentioned application Ser. No.
6,864. Briefly, the opposite sides of the diaper are folded
inwardly toward one another, with the folded portions then being
folded outwardly to provide a three ply arrangement, as is shown in
FIG. 3. The folded over portions are adhered to the main body of
the diaper by centrally disposed spots of adhesive, and when it is
desired to use the diaper, the folds of the diaper are opened on
opposite sides of the adhesive spots, and the end portions of the
diaper are placed around the waist of the infant. The overlapping
corners of the end portions of the diaper are secured together by
pinning, or by adhesive strips 26 that may be attached to the
backing sheet 12.
It will be understood by those skilled in the art that variations
and modifications of the specific embodiments described above may
be employed without departing from the scope of the invention as
defined in the appended claims.
* * * * *