U.S. patent number 3,777,758 [Application Number 05/198,381] was granted by the patent office on 1973-12-11 for disposable diaper.
Invention is credited to Gerald J. Liloia, Louis F. May, Jr., Frederick K. Mesek, Norman Schiff, Robert C. Shepherd, William R. Strickel.
United States Patent |
3,777,758 |
Mesek , et al. |
December 11, 1973 |
DISPOSABLE DIAPER
Abstract
A disposable multi-layer diaper is disclosed in which a first
layer to be brought into contact with an infant's skin, is a
through bonded non-woven fabric of predominantly short length
fibers mixed with long, i.e., textile length, fibers. The fabric is
treated with a rewetting agent so as to have the desired degree of
wettability and absorbency. A second layer, in juxtaposition to the
facing layer, is a highly absorbent pad of short length fibers. The
final layer, positioned on the side of said pad opposite said
facing layer, is also through bonded non-woven fabric of
predominantly short length fibers in admixture with long or textile
length fibers. In each of the layers of the diaper the short length
fibers are naturally occurring cellulosic fibers, e.g., wood pulp
fibers and cotton linters having a length not exceeding about
one-quarter inch.
Inventors: |
Mesek; Frederick K. (Downers
Grove, IL), Shepherd; Robert C. (Oak Lawn, IL), Strickel;
William R. (Chicago, IL), Liloia; Gerald J. (North
Brunswick, NJ), May, Jr.; Louis F. (Old Bridge, NJ),
Schiff; Norman (Kendall Park, NJ) |
Family
ID: |
26893729 |
Appl.
No.: |
05/198,381 |
Filed: |
November 12, 1971 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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729784 |
May 16, 1968 |
3663348 |
|
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515874 |
Dec 23, 1965 |
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Current U.S.
Class: |
604/365; 604/375;
604/377 |
Current CPC
Class: |
A61F
13/51 (20130101); A61F 13/51104 (20130101); D21H
27/00 (20130101); A61F 13/51113 (20130101); A61F
13/51474 (20130101); A61F 13/51401 (20130101); D21H
5/26 (20130101); A61F 13/51121 (20130101) |
Current International
Class: |
A61F
13/15 (20060101); A61f 013/16 () |
Field of
Search: |
;128/284,286,287,290,296 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Rosenbaum; Charles F.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part of our copending
application Ser. No. 729,784, filed May 16, 1968, and now U.S. Pat.
No. 3,663,348 which in turn is a continuation-in-part of our
application Ser. No. 515,874 filed Dec. 23, 1965 (now abandoned).
Claims
What is claimed is:
1. A multi-layer diaper comprising: a facing layer; a highly
absorbent pad disposed in face-to-face juxtaposition to said facing
layer; and a backing layer on the side of said pad opposite said
facing layer, said facing layer comprising a through bonded
non-woven fabric of mixed short and long fibers, said fabric having
a short fiber content of at least about 75 percent by weight of the
fabric, said short fibers having a length less than one-fourth inch
and said long fibers having a length greater than three-fourths
inch, said fibers being bonded by a cross-linked binder applied
throughout said fabric in an amount between about 1 percent and
about 30 percent of the weight of the fibers on a dry solids basis,
said fabric having a weight of less than 8 oz./yd..sup.2 and a
density of 0.05 to 0.15 gm./cc.
2. The diaper of claim 1 wherein both said facing layer and said
backing layer are formed of said through bonded non-woven
fabric.
3. The diaper of claim 2 wherein said facing layer is treated with
a rewetting agent to make it water-wettable.
4. The diaper of claim 1 wherein said facing layer and said backing
layer are rectangular and substantially co-extensive, said pad is
substantially rectangular, narrower than said facing layer and said
backing layer and centrally disposed with respect thereto to
provide marginal portions of said diaper in which said facing layer
and said backing layer are in direct contact with each other.
5. The diaper of claim 4 wherein said marginal portions of said
facing layer and said backing layer are adhered to one another.
6. The diaper of claim 2 in which the through-bonded fabric of said
facing layer and the through-bonded fabric of said backing layer
each have one surface in which the fiber loft is substantially
greater than the fiber loft of the other surface, the surfaces of
greater fiber loft of said fabrics facing one another to
mechanically interlock said facing layer and said backing layer at
least in part through the interlocking of fibers on the surfaces of
greater fiber loft.
7. The diaper of claim 6 in which a strip of open mesh fabric is
placed between said facing layer and said backing layer at opposite
ends of the diaper to reinforce the diaper in these areas.
8. The diaper of claim 1 wherein the short fiber content of the
facing layer is in the range of about 75 to about 98 percent by
weight of the fabric.
9. The diaper of claim 1 wherein said short and long fibers are
randomly disposed and uniformly distributed.
10. A multi-layer diaper comprising: a water-wettable facing layer
adapted to be positioned adjacent the skin of an infant; a highly
absorbent pad disposed in face-to-face juxtaposition to said facing
layer; and a backing layer on the side of said pad opposite said
facing layer, said backing layer comprising a through bonded
non-woven fabric of mixed short and long fibers, said fabric having
a short fiber content of at least about 75 percent by weight of the
fabric, said short fibers having a length less than one-fourth inch
and said long fibers having a length greater than three-fourths
inch, said fibers being bonded by a cross-linked binder applied
throughout said fabric in an amount between about 1 percent and
about 30 percent of the weight of the fibers on a dry solids basis,
said fabric having a weight of less than 8 oz./yd..sup.2 and a
density of 0.05 to 0.15 gm./cc.
11. The diaper of claim 10 wherein both said facing layer and said
backing layer are formed of said through bonded non-woven fabric,
said facing layer being treated with a rewetting agent to make it
water-wettable.
12. The diaper of claim 10 wherein said facing layer and said
backing layer are rectangular and substantially coextensive, said
pad is substantially rectangular, narrower than said facing layer
and said backing layer and centrally disposed with respect thereto
to provide marginal portions of said diaper in which said facing
layer and said backing layer are in direct contact with each
other.
13. A multi-layer diaper comprising: a facing layer; a highly
absorbent fibrous pad disposed in face-to-face juxtaposition to
said facing layer; and a backing layer on the side of said pad
opposite said facing layer, said facing layer comprising a nonwoven
fabric of mixed short and long fibers having one surface in which
the fiber loft is substantially greater than the fiber loft of the
other surface, the surface of greater fiber loft facing inwardly
and in direct contact with a surface of said pad, the fibers in
said contacting surfaces being mechanically interlocked with each
other.
14. The diaper of claim 13 wherein said facing layer is embossed on
at least the outer surface thereof, whereby the drape
characteristics of the diaper are enhanced.
15. The diaper of claim 13 wherein said facing layer and said
backing layer are rectangular and substantially coextensive, said
pad is substantially rectangular, narrower than said facing layer
and said backing layer and centrally disposed with respect thereto
to provide marginal portions of said diaper in which said facing
layer and said backing layer are in direct contact with each other,
said backing layer comprising a nonwoven fabric of mixed short and
long fibers having one surface in which the fiber loft is
substantially greater than the fiber loft of the other surface, the
surface of greater fiber loft in said backing layer facing inwardly
and in direct contact in said marginal portions with the surface of
greater fiber loft of said facing layer, the fibers on said
contacting surfaces in said marginal portions being interlocked
with each other.
16. The diaper of claim 1 wherein said facing layer is embossed on
at least the outer surface thereof whereby the drape
characteristics of the diaper are enhanced.
Description
BACKGROUND OF THE INVENTION
Disposable diapers have met with widespread commercial acceptance
in the recent past, primarily because of their convenience. Even
though such diapers are functionally inadequate in certain
respects, and more expensive to use than cloth diapers, consumers
have exhibited an increased tendency to accept these deficiencies
as part of the price for convenience.
Typical disposable diapers include a fabric facing layer to be
placed adjacent an infant's skin, an absorbent pad or batt, and a
moisture-impervious backing sheet.
One of the problems of the prior art has been the inability to
provide a suitable lightweight, inexpensive facing material, i.e.,
one which would be pliable, soft, comfortable and non-irritating to
an infant's skin, while at the same time having adequate strength,
dimensional stability, and loft; and the desired degree of
water-wettability and absorbency. Since cost is a vital factor in
disposable diapers, it is essential that the foregoing properties
be obtained in a facing fabric made of low cost fibers.
Cost savings in a diaper facing fabric can be realized by using
short length fibers, such as the fibers of wood pulp or cotton
linters, and because of this it has been a desideratum in the
manufacture of facing layer fabrics and fabric-like materials to
use such fibers as compared to the generally used longer fibers of
one-half inch or more in length. However, prior to this invention,
it has not been possible to utilize such short length cellulosic
fibers in a diaper facing fabric having desired loft and strength
characteristics, since short length fibers as conventionally used
interlock to form a coherent layer of relatively high density. Such
relatively high density layers have been used as diaper facing
materials, but the use has not been entirely successful because
they do not have the loft which is required in a facing material to
help in keeping an infant's skin relatively dry.
Another problem that has confronted the disposable diaper industry
is the inability to provide a relatively inexpensive backing member
having adequate water repellency from naturally occurring
cellulosic fibers. It is conventional to use a plastic
moisture-impervious sheet, such as a polyethylene sheet, as a
backing member in a disposable diaper to provide the desired water
repellency, but while such diapers are satisfactory as a single use
item, they are not truly disposable, since the entire diaper
structure is not completely biodegradable. In addition, a plastic
sheet tends to impart stiffness and clamminess to the diaper.
SUMMARY OF THE INVENTION
In accordance with the present invention a multi-layer diaper is
provided which includes (1) an absorbent facing layer to be brought
into contact with the infant's skin and consisting predominantly of
low cost, short length, naturally occurring cellulosic fibers in
admixture with a small proportion of textile length fibers, with
the resulting layer being bonded throughout its thickness with a
cross-linked bonding agent, (2) a highly absorbent pad formed of
short length, naturally occurring cellulosic fibers positioned in
juxtaposed relationship with respect to said facing layer, and (3)
a backing layer on the side of the pad opposite of said facing
layer, and also consisting predominantly of short length, naturally
occurring cellulosic fibers in admixture with a small proportion of
textile length fibers, and also bonded throughout its thickness
with a cross-linked bonding agent.
The textile length fibers in the facing layer cooperate with the
short fibers to give the facing layer loft and strength, which loft
is more or less maintained, and which strength is augmented, by a
binder. The resulting layer is of relatively low density, and in
addition to having high loft and strength, the layer is soft and
conformable, thus making it ideally well suited for use as a diaper
facing.
In a preferred embodiment of the invention, the fibers of the
facing layer are in uniform admixture throughout the thickness of
the layer, and the fibers are held in their lofted state by a
binder, such as those of the self-curing acrylic latex family, the
urethane family, or other binders which can be utilized in low
viscosity solutions or suspensions. The binder add-on is in the
range of from about 1 percent to about 30 percent of the weight of
the fibers on a dry solids basis. While such binder materials have
the effect of interferring with the normal water-absorbency of the
mixture of fibers constituting the facing layer, because the binder
coats the individual fibers, in accordance with the present
invention the facing layer including the binder is made absorbent
by treatment of the layer with a rewetting agent (surfactant).
Hence, urine may pass through the facing layer and be absorbed in
the absorbent pad, thus, desirably carrying the urine away from the
skin of the infant. The ability of urine to pass through the lofted
mixture of fibers, bonded as described above, and into the
absorbent pad, is an important feature of the diaper of the present
invention. Without treating the bonded facing layer, the binder
component could interfere with the normal water-absorbent
characteristics of the fibers, and the facing layer would not
adequately serve for use in accordance with the present
invention.
In the backing layer, water repellency is desired and the wetting
agent is preferably omitted from its binder, so that the backing
layer is sufficiently water repellent to prevent urine absorbed in
the pad from striking through the diaper.
The overall combination provides a diaper in which all components
are fibrous, and therefore, has the desirable feel and drape
qualities of a cloth diaper. Since all the layers of the diaper are
formed of cellulosic fibers, the diaper is disposable in the true
sense of the word.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view of a production line showing the
preparation of a fabric used as facing or backing in the diaper of
the present invention;
FIG. 2 is a perspective view illustrating a swatch of fabric used
as facing or backing in the diaper of the present invention;
FIG. 3 is a perspective view illustrating a modification of the
fabric used as facing or backing in the diaper of the present
invention;
FIG. 4 is a perspective view illustrating a further modification of
the fabric used as facing or backing in the diaper of the present
invention;
FIG. 5 is a schematic view of a production line showing the
preparation of a modified fabric used as facing or backing in the
diaper of the present invention;
FIG. 6 is a perspective view illustrating a swatch of fabric
prepared in the manner of FIG. 5;
FIG. 7 is a perspective view of an open unfolded diaper of the
present invention, with a portion of the top layer broken away to
illustrate the internal construction;
FIG. 8 is a cross-sectional view taken along line 8--8 of FIG. 7;
and
FIG. 9 is a perspective view, partly in phantom, illustrating the
manner in which the diaper of FIGS. 7 and 8 is folded.
FIG. 10 is a fragmentary perspective view, with a portion of the
top layer broken away to show an internal end reinforcement.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the drawings, a diaper of simple inexpensive
construction is illustrated in FIGS. 7, 8 and 9. The diaper is
formed of a top fabric sheet 29 and a bottom fabric sheet 30, the
fabric sheets 29 and 30 being made in the manner hereinafter
described. Between fabric sheets 29 and 30 is an absorbent pad 31
formed of wood pulp, or other highly absorbent material. The
absorbent pad 31 is substantially narrower in width than the top
and bottom fabric sheets 29 and 30 and is spaced from the edges of
sheets 29 and 30 to lie along the center portion of the diaper,
i.e., the portion which would, in use, be positioned at the crotch
of the infant. The bottom fabric sheet 30 may be longer than the
top fabric sheet 29, the extending ends 32 and 33 being folded over
to form reinforced areas 34 and 35 for receiving safety pins and
the like when applying the diaper. However, if desired, the top and
bottom sheets may be of substantially the same length and a strip
of gauze or other woven fabric, 41 in FIG. 10, inserted between the
two sheets at each end to reinforce the diaper in these areas.
As is hereinafter explained, fabric sheets 29 and 30 are both
comprised of a mixture of short and long fibers that are through
bonded by a bonding agent that tends to make the sheets water
repellent. The water repellency may be modified, or overcome, by
use of a rewetting agent. In forming the diaper, both the top
fabric sheet 29 and the bottom fabric sheet 30 may be formed of a
readily wettable and highly absorbent fabric, i.e., one which
contains a rewetting agent, or the diaper may be formed with only
the top fabric 29 and the absorbent filler 31 being absorbent while
the bottom fabric 30 is nonabsorbent as hereinafter described, the
same having been prepared without being rendered readily wettable
and highly absorbent through the inclusion of a rewetting agent,
also as hereinafter described.
The fabrics used as facing sheets and backing sheets in the diaper
of the present invention have a fiber content which is
predominantly short fibers. By way of definition, "short fibers,"
as used herein, means wood pulp, cotton linters or the like where
the fiber lengths are less than one-fourth inch in length. Between
75 percent and 98 percent of the total fiber content in the fabrics
of this invention are such short fibers. Both wood pulp and cotton
linters are substantially less expensive than the textile length
cellulosic fibers of cotton and rayon generally employed in making
both woven and non-woven cellulosic fabrics. In the preferred
embodiments, the wood pulp fibers and the second cut cotton linters
generally have a length not exceeding about one-fourth inch with
the average length being from about one-sixteenth to
three-sixteenths inch. Accordingly, the fabrics of the present
invention have a fiber content in which between 75 percent and 98
percent of the fibers are less than one-fourth inch in length.
"Textile length fibers" or "long fibers" in this specification
means fibers at least three-fourths inch in length, and in the
preferred forms of the invention the long fibers are all of
substantially the same length, preferably produced synthetically
and preferably at least 1 inch long. In one preferred embodiment
made in accordance with Example I, 1.5 denier rayon long fibers
were used which were uniformly cut to about 11/2 inch lengths and
homogeneously and randomly dispersed with the short fibers.
Surprisingly high tensile strengths are thereby attainable provided
the short fibers are thoroughly and efficiently separated and the
short and long fibers are carefully and thoroughly blended and
intermixed.
The fabrics used in the diaper of the present invention have fabric
weights in the range of 1 to 8 oz./yd..sup.2 ; a density of less
than 0.15 gm./cc., the density generally being in the range of
0.100 gm./cc. to 0.050 gm./cc.; and for a fabric having a weight of
about 1.5 oz./yd..sup.2, a dry strength of at least 0.15 lbs./in.
of width in machine direction and 0.10 lbs./in. of width in the
cross direction. The fabrics have unusually good elongation, loft,
softness and drape characteristics when compared with prior
products incorporating any substantial amount of short fibers.
The fabrics are prepared by first forming a web of randomly laid
dry fibers, the web when laid having a density of about 0.09
gm./cc. to 0.025 gm./cc. measured by ASTM Method D-1777 at 0.16
lbs./sq.in. (test procedure set forth in the manual of The American
Society for Testing Materials). Where wood pulp fibers are used,
the same are generally obtained in the form of a fiberboard of
fairly dense construction from which the fibers must be separated.
These wood pulp fibers generally have a fiber length ranging from a
fine dust to about one-fourth inch.
Short-length fibers are best classified by the Clark Classification
procedure described in the test manual of The Technical Association
of Pulp and Paper Industry (TAPPI-T233 SU64). In this procedure a
water slurry of the fibers is passed through a series of graded
screens. Using this technique, which avoids grinding the fibers,
second cut cotton linters are found to have the following
composition:
30 percent retained by a 12 mesh screen
22 percent retained by an 18 mesh screen
14 percent retained by a 30 mesh screen
16 percent retained by a 50 mesh screen
18 percent passed through 50 mesh screen
In making the short fiber fabrics used in the diapers of the
present invention a web of dry fibers is first formed. In the
preferred method of manufacture, the web is then impregnated with a
binder fluid by flowing a solution or dispersion of the binder
through the web. The impregnated web is then subjected to suction
to remove excess binder fluid and assure uniform distribution of
binder fluid throughout the fiber web. This impregnation by binder
fluid followed by suction is hereinafter referred to as
suction-bonding. The fiber web at this point has, in one embodiment
on a solids basis, 4 percent to 6 percent dry solids add-on by
weight of the web. Depending upon the strength requirements of the
web, the loft and the softness desired in the end product, the
range of dry solids added on may vary over the range of about 1
percent to about 30 percent. The web so formed is then dried and
heated to cure the binder. This can be done simultaneously by
passing into a drying oven heated to a temperature of about
310.degree.F. to 320.degree.F. where the same is dried and the
binder cured. The preferred binders are of the self-curing acrylic
latex family, the urethane family, or other binders which can be
utilized in low viscosity solutions or suspensions.
The diaper of this invention has especial advantages by virtue of
the facing and backing layers being formed of lightweight, low
density, lofty, and soft fabrics. The especially useful range of
fabric densities in accordance with this invention is from about
0.05 gm./cc. to about 0.15 gm./cc. By the use of the teachings set
forth herein, and specifically the combination of fibers and other
parameters, it has been found possible to manufacture lightweight
fabrics, that is, fabrics having weights of less than 8 oz./sq.yd.
and handle the product, air blown or otherwise assembled dry,
during further processing. Thereby unusually desirable weights,
densities and other physical characteristics are obtained rendering
the fabrics particularly useful in the diaper of the present
invention.
The preparation of predominantly short fiber fabrics for use in the
diaper of the present invention is illustrated schematically, for
example, in FIG. 1. Referring to FIG. 1, a web 10 of mixed randomly
disposed short fibers 11 and long fibers 19 is deposited from
fiber-laying equipment 12 onto a foraminous moving screen or belt
13. The fiber-laying equipment 12 is preferably of the air
deposition type such as a modified RANDO WEBBER made by the
Curlator Co. The low density fiber web 10 is moved by belt 13 below
a screen containing a weir box 14 of binder in fluid form, i.e., in
solution or aqueous dispersion. The binder fluid is flowed onto and
through the web 10 in quantities substantially in excess of the
ultimate amount to be deposited on the fibers completely
impregnating the web. The web 10, immediately after impregnation
with the binder fluid, passes over a suction box 15 where excess
binder fluid is removed. The impregnated web 10 is conveyed by belt
13 through a dryer 16. The fabric is then removed from belt 13 and
collected, for example, on fabric roll 17. A section of fabric so
formed is illustrated, for example in FIG. 2 of the drawings
showing a very small percentage of long fibers 19. An alternate
construction with a larger percentage of long fibers 19 is shown
diagrammatically in FIG. 3. The binder fluid should be of the low
viscosity type to maintain the features of the invention described.
A "low viscosity binder" is generally one having the desired
adhesive qualities and having, in fluid form, a viscosity less than
5 centipoises.
The binder fluid, in the preferred method of manufacture, is flowed
onto the fabric from the weir box 14 and a major proportion thereof
is withdrawn in the suction box 15 before the fabric enters the
dryer 16. It is important in attaining the lofty and soft character
of the fabrics made hereunder that the application, removal and
drying of the binder fluid be without substantial compression of
the fabric. In many conventional methods of processing fabrics,
excess binder fluids are squeezed out of the fabric with
compression rollers or the like and such processes would generally
produce products that would not be satisfactory for use in the
diaper of this invention.
It has been found that the elongation characteristics are enhanced
in fabrics made in accordance with the teachings set forth above.
One set of samples was constructed with about 21/2 oz./yd..sup.2 of
fiber weight and utilizing wood pulp as the short fibers and about
11/2 inch 1.5 denier rayon staple as the long fibers. In the set,
the percentage of long fibers was varied, and the elongation tests
were performed on the unbonded web. Over the range of interest, the
percentage of elongation varied from about 60 percent to 94
percent. The elongation was measured by stretching a sample of the
fabric between two clamped ends and measuring the percentage
increase in length before the two ends separated.
Based on the samples tested, a fabric made of 98 percent short
fibers has about a 60 percent elongation, both in the machine
direction and in the cross direction. Samples made of 85 percent
short fibers with 15 percent long fibers exhibited an elongation of
about 88 percent, and samples containing 75 percent short fibers
showed an elongation of about 94 percent. It has been found that
there is a substantial increase in elongation characteristics with
the addition of about 2 percent of long fibers to an otherwise
short fiber fabric. The percentage of elongation rises very rapidly
with the addition of long fibers up to about 2 percent and
continues to increase for increases in long fibers up to 10 percent
at a diminishing rate. As the percentage of long fibers is
increased from about 10 percent to about 25 percent, the elongation
characteristics improve rather consistently and more gradually.
However, it has been found that additional long fibers in excess of
about 25 percent do not increase the elongation characteristics at
the same rate and actually reduce the elongation in some cases. A
sample made of 100 percent long fibers and no short fibers showed
an elongation in both directions of approximately 60 percent and a
sample made of 100 percent short fibers exhibited an elongation of
28 percent.
It is extremely difficult to handle a web of randomly disposed dry
fibers of predominantly short fiber length in webs of 8
oz./yd..sup.2 or less through the bonding equipment and
subsequently through the drying apparatus. In fact, handling of
fabrics having weights of less than 2 oz./yd..sup.2 had heretofore
been considered unworkable. It has been found that this problem can
be overcome through use of the teachings contained herein.
Referring to FIG. 5, a means is schematically shown for
manufacturing a fabric having two distinctly different surface
characteristics. A relatively thin web 21 of dry, mixed fibers 11
and 19 is first laid down, superimposing on the same is a loose
weave fabric 22 such as a low count gauze, cotton scrim, or the
like. A second relatively thin web 23 of dry fibers 11 and 19 is
then deposited onto the loose weave fabric 22. The dry laminate so
formed is suction-bonded, dried, and cured in the manner previously
described. The laminate is then split into two fabrics 24 and 25,
the laminate separating at the point of intersection of the loose
weave fabric. The loose weave fabric 22 is removed and the fabrics
24 and 25 wound on separate rolls 26 and 27. Other methods of
splitting may be employed with or without an actual dividing web
22.
By first forming and then splitting the web, fabrics having unique
surface characteristics are formed including short fibers, the
fabrics having excellent drape, loft and elongation
characteristics. A section of fabric formed by the split web
technique is illustrated in FIG. 6. The fabric is quite similar to
that of FIG. 2 differing primarily in that the fibers 28, on the
surface previously adjacent the loose weave fabric 22, have
substantially more loft than the fibers on the other surface of the
fabric. The apparatus of FIG. 5 is schematically illustrated as in
FIG. 1, 12' indicating fiber-layer equipment, 13' a moving belt,
14' a binder container and dispenser, 15' a suction box, and 16'
heating and drying apparatus.
In some constructions, it is desirable to have even greater
drapability than would result from the construction features
already described. Increased drape can be attained without
significant loss of loft, softness or strength by embossing the
fabric after completion of the processes shown in FIGS. 1 and 5.
This produces a fabric such as shown in FIG. 4 where the fibers 11
and 19 have been subjected to embossing pressure along the lines
20.
The fabrics so far described are not in and of themselves water
absorbent as the bonding agent appears to sufficiently coat the
individual fibers as to interfere with their normal water-absorbent
characteristics. Absorbent fabrics can be made, however, by
treating the fabric with a rewetting agent such, for example, as an
anionic sulfonated alkyl ester. In the preferred practice of making
facing fabrics for the diapers of the present invention, the
rewetting agent is included in the impregnating solution or
suspension together with the binder. By including the rewetting
agent at this step in the manufacture of the fabrics, the same are
found to be readily wettable and highly absorbent.
The preparation of fabrics for the diapers of the present invention
are further illustrated by the following examples. The examples are
given for the purpose of illustration only, and the invention is
not limited thereto.
EXAMPLE I
A fibrous web composed of approximately 15 percent textile length
fibers such as uniformly cut 11/2 inch 1.5 denier rayon fibers and
85 percent fibers of individualized second cut cotton linters is
made on a web laying device to a weight of 2 oz./yd..sup.2 This web
is then conveyed into a bonder as heretofore described using a
preferred bonding agent such as a self-cross-linking acrylic
emulsion. The composition of the binder suspension and the amount
of suction at the suction slot is controlled so as to give the
fabric a dry solids add-on of 4.75 percent based on the fabric
weight. The wet web is conveyed into a drying oven having a
temperature of 310.degree.-320.degree.F. where it is dried and the
resin binder cured. The resultant material has a density of 0.05 to
0.07 gm./cc., a dry strength of about 1.4 lbs./in. of width in the
machine direction and about 0.8 lbs./in. of width in the cross
direction. The wet strengths are about 0.9 lbs./in. of width in the
machine direction and about 0.5 lbs./in. of width in the cross
direction. The fabric has excellent hand or feel and drape.
EXAMPLE II
A fibrous web composed of approximately 25 percent textile length
fibers such as uniform 1.5 denier 1 inch rayon fibers and 75
percent fibers of ground up douglas fir bleached kraft pulp is made
on a web laying device to a weight of 1.5 to 2 oz./yd..sup.2 The
web is then conveyed into a suction bonder heretofore described
using the bonding agent HYCAR 2,600 .times. 120. The composition of
the binder suspension and the amount of suction at the suction slot
is controlled to give the fabric a dry solids add-on of about 25
percent based on the fiber weight. The wet web is conveyed into a
drying oven having a temperature of 310.degree.-320.degree.F. where
it is dried and the resin binder cured. The resultant web has a
density of 0.08 gm./cc.; a dry strength of about 7 lbs./in. of
width and a wet strength of about 2.2 lbs./in. of width in the
machine direction.
EXAMPLE III
A fibrous web composed of approximately 10 percent textile length
fibers such as uniform 1.5 denier 11/2 inch rayon fibers and 90
percent douglas fir pulp is made to a weight of 1.5 oz./yd..sup.2
The web is then passed through a suction bonder and receives
thorough impregnation wity HYCAR 2,600 .times. 120. The composition
and viscosity of the binder suspension and amount of suction are
controlled to give the fabric a dry solids add-on of about 1
percent based on the fiber weight.
The wet web is conveyed into a drying oven having a temperature of
310.degree. to 320.degree.F. where it is dried and the resin cured.
The resultant fabric has a density of 0.06 gm./cc., a dry tensile
strength of 0.18 lbs./in. in the machine direction and 0.13
lbs./in. in the cross direction, and the bonded fabric shows an
elongation of 50 percent before separation.
EXAMPLE IV
A fibrous web composed of approximately 13 percent textile length
fibers such as uniform 1.5 denier 11/2 inch rayon fibers and 87
percent douglas fir pulp is made to a weight of 8 oz./yd..sup.2.
The web is then passed through a suction bonder and receives
thorough impregnation with HYCAR 2600 .times. 120. The composition
and viscosity of the binder suspension and amount of suction are
controlled to give the fabric a dry solids add-on of about 1.5
percent based on the fiber weight.
The wet web is conveyed into a drying oven having a temperature of
310.degree. to 320.degree.F. where it is dried and the resin cured.
The resultant fabric has a density of 0.09 gm./cc., a dry tensile
strength of 1.9 lbs./in. in the machine direction and 1.4 lbs./in.
in the cross direction, and the bonded fabric shows an elongation
of 70 percent before separation.
EXAMPLE V
A fibrous web composed of approximately 5 percent textile length
fibers such as uniform 1.5 denier 11/2 inch rayon fibers and 95
percent douglas fir pulp is made to a weight of 2.3 oz./yd..sup.2.
The web is then passed through a suction bonder and receives
thorough impregnation with HYCAR 2600 .times. 120. The composition
and viscosity of the binder suspension and amount of suction are
controlled to give the fabric a dry solids add-on of about 2
percent based on the fiber weight.
The wet web is conveyed into a drying oven having a temperature of
310.degree. to 320.degree.F. where it is dried and the resin cured.
The resultant fabric has a density of 0.07 gm./cc., a dry tensile
strength of 0.56 lbs./in. in the machine direction and 0.40
lbs./in. in the cross direction, and the bonded fabric shows an
elongation of 46 percent before separation.
The excellent hand, feel and drape qualities of the fabrics given
diapers made therefrom much the same feel and handling qualities as
diapers formed of woven fabrics. However, the use of the short
textile fibers, such as wood pulp and cotton linters, permits the
same to be manufactured at a price substantially below that of
woven fabrics or the conventional non-woven fabrics thus keeping
the cost of the final diaper well within a price such that the same
can be disposed of after use.
Where the fabrics 29 and 30 of the diaper are made through the
split web technique heretofore described, the side of each fabric
sheet which was in the inner portion of the web prior to splitting
has appreciably more fiber loft than the other side of the fabric.
This loft is quite beneficial in forming a several ply construction
such as the diaper construction just described. The loft sides of
the fabrics are placed in face-to-face contact with each other on
either side of the filler or absorbent pad 31. The loft fibers tend
to interlock when the surfaces are pressed together. The fabrics 29
and 30 are thus mechanically united along their edges on each side
of the absorbent pad 31 to give the appearance and feel of a single
fabric. This also prevents the absorbent pad 31 from shifting its
position. The side edges 36 and 37 of the diaper may or may not be
further secured through spot bonding along the edge to prevent an
initial separation of the fabrics 29 and 30 along such edges if
desired.
As the fibers of fabrics 29 and 30 are through bonded, there is no
problem with fraying edges and the like so that hems or other
structure for prevention of edge fraying is not necessary. Because
of its simple construction, the whole diaper can be assembled
relatively easily.
In order to improve the ease with which the diaper is applied, the
portions extending along each side of absorbent pad 31 are folded
in towards the center of the diaper and then back on themselves to
form two double folds 38 and 39, one along each side of the diaper.
This is illustrated in FIG. 9. The double fold along each side is
stabilized by adhesive 40 and 41 being applied near the center
portion of each double fold as measured from the diaper ends. This
may either be a permanent or temporary adhesive as the primary
purpose of the adhesive is to hold the center portion of the folds
in place while the end portions of the folds are opened in applying
the diaper.
As is evident from the above description, the present invention
provides a unique diaper construction wherein all of the layers of
the diaper are comprised entirely of cellulosic fibers. The facing
and backing layers, despite their low density and despite the fact
that they are comprised predominantly of short fibers, are held
together as a lofty assemblage of fibers by the inclusion of a
minor proportion of textile length fibers and a binder.
Furthermore, the fibers of the facing material have the desired
degree of wettability and absorbency, by virtue of the fabric
having been treated with a rewetting agent, which counteracts the
interfering effect that the binder has upon the normal
water-absorbent characteristics of the fibers. As a result, urine
can readily pass through the facing layer and into the highly
absorbent pad in juxtaposition therewith. The backing layer of the
diaper is not treated with a rewetting agent, and thus the backing
layer tends to repel urine and prevent urine absorbed in the pad
from striking through the diaper.
Illustratively, the facing layer may be prepared in accordance with
Example I, as set forth above, except that a rewetting agent is
included in the impregnating solution, thus imparting to the facing
layer the desired degree of wettability and absorbency. The backing
layer may be prepared in accordance with Example II, also set forth
above; however, there is no rewetting agent in the impregnating
solution for the backing layer.
It is believed that one of the factors that enables the facing
layer of the diaper of the present invention to keep liquid away
from the infant's skin is that the fibers of the pad have greater
wettability for water than the fibers of the facing layer. It is
thought that since the pad is substantially more water-wettable
than the facing layer, it tends to draw liquid preferentially away
from the facing layer and into the pad. It is also thought that the
bonding agent, in addition to retaining the fibers of the facing
layer in their lofted relationship, serves the further function, in
cooperation with the rewetting agent, of giving the facing layer a
controlled amount of water absorbency, so that urine that has
passed through the facing layer and into the absorbent pad is
preferentially retained therein rather than soaking back into the
facing layer. The backing layer, by virtue of not being treated
with a rewetting agent, resists any tendency for urine to strike
through the diaper, and causes urine to spread out and soak into
unwetted portions of the pad.
A particular embodiment of the invention has been used to
illustrate the same. The invention, however, is not limited to the
specific embodiment. In view of the foregoing disclosure,
variations or modifications thereof will be apparent, and it is
intended to include within the invention all such variations and
modifications except as do not come within the scope of the
appended claims.
* * * * *