U.S. patent number 3,721,242 [Application Number 05/023,752] was granted by the patent office on 1973-03-20 for disposable diapers.
This patent grant is currently assigned to Scott Paper Company. Invention is credited to Evelyn H. Krusko.
United States Patent |
3,721,242 |
Krusko |
March 20, 1973 |
DISPOSABLE DIAPERS
Abstract
Disposable diaper having a moisture absorbent fluff pad which is
contoured in the crotch area and which is disposed between a facing
sheet and a backing sheet, said facing sheet being adapted to
contact the body of a child. Both the facing sheet and backing
sheet have a basis weight in the range of approximately 1.0-2.0
ounces per square yard, and each are comprised of a batt of
moisture-absorbent, self-sustaining, adhesively bonded,
intermingled cellulosic fibers. The outer surface of the facing and
backing sheets each have a pattern defined by ridges and valleys
extending over substantially the entire surface of the batt, the
density of the sheets in the regions of said valleys being greater
than the density of the sheets in the regions of said ridges. A
method for manufacturing the facing sheet and backing sheet of the
disposable diaper by forming a randomly arranged, intermingled
cellulosic fibrous batt having a basis weight of approximately 1.0
ounces per square yard, passing said batt through a nip defined
between a patterned roll and a moistened rubber roll to provide a
pattern in one surface of the batt and raise a nap on the other
surface, spraying opposite surfaces of said batt with adhesive,
drying said adhesive and setting said adhesive.
Inventors: |
Krusko; Evelyn H.
(Philadelphia, PA) |
Assignee: |
Scott Paper Company (Delaware
County, PA)
|
Family
ID: |
21816991 |
Appl.
No.: |
05/023,752 |
Filed: |
March 30, 1970 |
Current U.S.
Class: |
604/365; 604/370;
604/375; 604/378; 604/380 |
Current CPC
Class: |
A61F
13/15585 (20130101); A61F 13/533 (20130101); A61F
2013/15284 (20130101); A61F 2013/4958 (20130101); A61F
2013/51078 (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.
Claims
What is claimed is:
1. A throw-away diaper having an elongate absorbent layer disposed
between a facing sheet and a backing sheet, said facing sheet being
soft and moisture pervious; said elongate absorbent layer having a
transverse dimension defined by spaced, elongate said margins, at
least a portion of said side margins being recessed to define a
narrow crotch region adapted to be positioned in the perineal
region of a wearer; said facing and backing sheets having side
margins extending transversely beyond the spaced side margins of
said absorbent layer and having a substantially uniform transverse
dimension in the region of the diaper disposed in longitudinal
alignment with the recessed portions of the side margins of said
absorbent layer.
2. The throw-away diaper according to claim 1, wherein said
absorbent layer is comprised of a fluff batt of wood pulp
fibers.
3. The throw-away diaper according to claim 2, wherein said facing
sheet and said backing sheet are substantially rectangular.
4. The throw-away diaper according to claim 3, wherein said
elongate absorbent layer has a forward region and a rearward region
disposed, respectively, on opposite sides of the crotch region,
said forward and rearward regions having a greater transverse
dimension than said crotch region.
5. The throw-away diaper according to claim 3, wherein said backing
sheet is comprised of a thin plastic water repellent material.
6. A throw-away diaper according to claim 1, wherein said facing
sheet comprises a moisture absorbent, self-sustaining, adhesively
bonded, fibrous batt including randomly arranged, intermingled
cellulosic fibers, said batt having a substantially uniform weight
of fibers per unit area throughout substantially its entire extent,
an embossed pattern providing a plurality of ridge regions and
valley regions extending over substantially its entire extent, the
density of said facing sheet in the regions of said valleys being
greater than the density of said facing sheet in the regions of
said ridges.
7. The throw-away diaper according to claim 6, wherein said backing
sheet is comprised of a thin plastic water-repellant material.
8. A throw-away diaper according to claim 6, wherein said facing
sheet comprises up to about 30 percent long reinforcing fibers, and
the remainder of said facing sheet comprises relatively short
cellulosic fibers.
9. The throw-away diaper according to claim 8, wherein the short
cellulosic fibers of said facing sheet are wood pulp fibers.
10. The throw-away diaper according to claim 9, wherein said
reinforcing fibers are rayon.
11. The throw-away diaper according to claim 10, wherein said
adhesive is a cross-linkable acrylic latex.
12. The throw-away diaper according to claim 9, wherein said facing
sheet has a basis weight up to about 2 ounces per square yard.
13. The throw-away diaper according to claim 12, wherein said
facing sheet has a basis weight in the range of approximately
1.1-1.6 ounces per square yard.
14. The throw-away diaper according to claim 6, having a second
embossed pattern in said facing sheet and underlying elongate
absorbent layer, whereby the moisture absorption rate into and
along said facing sheet and underlying absorbent layer is
enhanced.
15. The throw-away diaper according to claim 14, wherein said
backing sheet is comprised of a thin plastic water repellent
material.
16. The throw-away diaper according to claim 14, wherein said
second embossed pattern is comprised of spaced, continuous embossed
lines in said facing sheet and elongate absorbent layer.
17. The throw-away diaper according to claim 16, comprising two
sets of spaced, continuous embossed lines, one of said sets of
embossed lines being disposed transversely to the other of said
sets of embossed lines.
18. The throw-away diaper according to claim 17, wherein said
backing sheet is water repellent.
19. A throw-away diaper according to claim 6, wherein said backing
sheet is comprised of a self-sustaining, adhesively bonded, fibrous
batt including randomly arranged, intermingled cellulosic
fibers.
20. The throw-away diaper according to claim 19, wherein said
backing sheet contains a water-repellant agent. 21. A throw-away
diaper according to claim 1, wherein said elongate absorbent layer
has a forward region and a rearward region disposed, respectively,
on opposite sides of the crotch region, said forward and rearward
regions having a greater transverse
dimension than said crotch region. 22. The throw-away diaper
according to claim 1, wherein said backing sheet is comprised of a
thin plastic water
repellent material. 23. A throw-away diaper or the like having an
elongate, moisture-absorbent layer disposed between a backing sheet
and a facing sheet, said facing sheet being a moisture absorbent,
self-sustaining, adhesively bonded, fibrous batt including randomly
arranged, intermingled cellulosic fibers, said batt having a
substantially uniform weight of fibers per unit area throughout
substantially its entire extent, a first embossed pattern disposed
only in said fibrous batt providing a plurality of ridge regions
and valley regions extending over substantially the entire extent
of said facing sheet, the density of said facing sheet in the
regions of said valleys being greater than the density of said
facing sheet in the region of said ridges, and a second embossed
pattern impressed into said facing sheet and underlying
moisture-absorbent layer whereby the moisture absorption rate into
and along said facing
sheet and moisture-absorbent layer is enhanced. 24. The throw-away
diaper according to claim 23, wherein said facing sheet comprises
up to about 30 percent long reinforcing fibers, and the remainder
of said facing sheet
comprises relatively short cellulosic fibers. 25. The throw-away
diaper according to claim 24, wherein said facing sheet has a basis
weight of up
to about 2.0 ounces per square yard. 26. The throw-away diaper
according to claim 25, wherein said facing sheet has a basis weight
approximately in
the range of 1.1 - 1.6 ounces per square yard. 27. The throw-away
diaper according to claim 24, wherein said short cellulosic fibers
are wood pulp fibers. 28The throw-away diaper according to claim
27, wherein said long
reinforcing fibers are rayon fibers. 29. The throw-away diaper
according to claim 28, wherein a cross-linkable acrylic latex bonds
the fibers in
said facing sheet. 30. The throw-away diaper according to claim 28,
wherein said elongate absorbent layer has a transverse dimension
defined by spaced, elongate side margins, at least a portion of
said side margins being recessed toward each other to define a
narrow crotch region adapted
to be positioned in the perineal region of a wearer. 31. The
throw-away diaper according to claim 24, wherein said elongate
absorbent layer has a transverse dimension defined by spaced,
elongate side margins, at least a portion of said side margins
being recessed toward each other to define a narrow crotch region
adapted to be positioned in the perineal region of
the wearer. 32. The throw-away diaper according to claim 23,
wherein said backing sheet is comprised of a self-sustaining,
adhesively bonded,
fibrous batt of randomly arranged, intermingled cellulosic fibers.
33. The throw-away diaper according to claim 23, wherein said
backing sheet is
water repellent. 34. The throw-away diaper according to claim 23,
wherein said second embossed pattern provides spaced, continuous
compressed lines
in said facing sheet and said moisture-absorbent layer. 35. The
throw-away diaper according to claim 23, wherein said second
embossed pattern provides two sets of spaced, continuous embossed
lines in said facing sheet and said moisture-absorbent layer, the
embossed lines in one of said sets extending substantially
transverse to the embossed lines in the other
of said sets. 36. The throw-away diaper according to claim 23,
wherein said elongate absorbent layer has a transverse dimension
defined by spaced, elongate side margins, at least a portion of
said side margins being recessed toward each other to define a
narrow crotch region adapted
to be positioned in the perineal region of a wearer. 37. A
throw-away diaper according to claim 36, wherein said elongate
absorbent layer has a forward region and a rearward region
disposed, respectively, on opposite sides of the crotch region,
said forward and rearward regions having a
greater transverse dimension than said crotch region. 38. The
throw-away diaper according to claim 36, wherein said second
embossed pattern is impressed into said facing sheet substantially
only in regions overlying
said elongate absorbent layer. 39. The throw-away diaper according
to claim 38, wherein said elongate absorbent layer is a fluff batt
of cellulosic fibers.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method for manufacturing nonwoven cover
sheets for a disposable diaper and to a disposable diaper formed
from said cover sheets.
2. Description of the Prior Art
A demand exists for a disposable diaper of the non-flushable,
throwaway type which is inexpensive and possesses the mechanical
and physical properties to perform as well, or better, than
conventional textile cloth diapers. A non-flushable, throwaway
diaper which is intended to serve as a satisfactory replacement for
the conventional textile cloth diaper should have sufficient
strength in both the dry and wet condition to retain its shape,
sufficient abrasion resistance to prevent the surface adjacent the
baby from shredding or "pilling up" and sufficient flexibility to
be worn comfortably. In addition, the disposable diaper should
closely resemble a conventional textile cloth diaper in hand feel
and appearance, and should be low cost to justify disposing of the
diaper after each use.
Prior art non-flushable, throwaway diapers have not been
commercially accepted to any substantial degree. This lack of
acceptance is believed to be attributable to the inability of
others to produce a product having the requisite mechanical and
physical properties to replace conventional textile cloth
diapers.
A representative prior art non-flushable throwaway diaper is
disclosed in U.S. Pat. No. 3,402,715, issued to Liloia et al.,
taken in conjunction with abandoned application Ser. No. 515,874,
which is referred to in the Liloia et al patent. This prior art
diaper has an absorbent fluff pad sandwiched between a pair of
non-woven fabrics formed predominately of short cellulosic fibers,
such as wood pulp or cotton linters, and the remainder of the
fibers are longer synthetic fibers such as rayon. This diaper does
not possess sufficient dry tensile strength and wet tensile
strength to perform satisfactorily unless an excessive quantity of
adhesive is utilized. Excessive quantities of adhesive will impair
flexibility and cause a reduction in the fluid retaining capacity
of the cover material. Also, excessive adhesive application may
impair the surface feel characteristics of the cover sheet.
SUMMARY OF THE INVENTION
The disposable diaper of this invention is comprised of a moisture
absorbent pad sandwiched between a nonwoven facing sheet, and a
backing sheet. In the preferred embodiment of the invention, the
backing sheet is identical in construction to the facing sheet;
however, the backing sheet could be a thin film of waterproof,
flexible material such as polyethylene, vinyl plastic, etc. In the
preferred embodiment of the invention the facing sheet and backing
sheet are each defined by a substantially rectangular nonwoven,
moisture-absorbent, self-sustaining, adhesively bonded, fibrous
batt of randomly arranged, intermingled cellulosic fibers
predominately consisting of short wood pulp fibers and the moisture
absorbent pad is contoured to provide a reduced width in the crotch
area. The outwardly facing surfaces of each nonwoven batt is
provided with an embossed pattern therein defined by a plurality of
ridges and valleys extending over substantially the entire surface
area of the batt, the density of said batt in the regions of said
valleys being greater than the density of said batt in the regions
of said ridges. The embossed pattern is produced by passing said
batt through a nip defined between a patterned roll and a
substantially smooth-surfaced roll such as one made of rubber.
Sufficient pressure is applied to the rolls to insure that the
pattern is retained in the fibrous batt during subsequent
operations. After the embossed pattern is formed in the batt an
adhesive, such as an acrylic latex, is sprayed on opposed surfaces
of said batt to enhance the strength and abrasion resistance of the
batt, while not destroying the hand and flexibility thereof. By
applying adhesive to the batt after embossing, the batt was
approximately 30 percent stronger than a batt which was embossed
after the adhesive was applied to opposed surfaces of said batt and
cured. The embossing operation compresses the fibers of the batt
into close proximity with respect to each other, and therefore, the
adhesive is more effectively utilized to bond fibers together than
when said adhesive is applied to an unembossed batt.
In the preferred embodiment of the invention, the patterned roll is
provided with a terry cloth pattern, which is formed in the roll by
a photoengraving process which utilizes the negative of a
photograph of a terry cloth pattern. After embossing the fibrous
batt has the physical appearance of a terry cloth woven product. In
this embodiment, the extremely close pattern of ridges and valleys
making up the terry cloth pattern provides excellent abrasion
resistance to the fabric. Other patterns such as straight line
regions of alternating ridges and valleys simulating a corduroy
pattern can also be impressed into the fibrous batt.
The nonwoven facing and backing sheets of the disposable diaper of
this invention are manufactured by forming a bonded batt of
randomly arranged, intermingled fibers comprised of predominately
short cellulosic fibers, such as wood pulp fibers, and the
remainder of said batt is comprised of longer synthetic fibers,
such as high tenacity rayon fibers. The batt is then passed through
the nip defined between a patterned roll and a rubber roll,
moisture being added to the surface of the rubber roll to moisten
the fibrous batt as it passes through the nip. Applying moisture to
the batt enhances the ability of the batt to retain the embossed
pattern therein during subsequent operations, and also aids in
releasing the batt from the rolls. The side of the batt which
contains the rubber roll is provided with a loose fiber nap which
is capable of mechanically interlocking with a loose fiber nap of a
like batt, or with the fibers of the absorbent pad of the diaper.
After the embossing operation the patterned batt passes
adhesive-applying stations whereat an adhesive, such as an acrylic
latex, is sprayed onto opposite surfaces of said batt. A vacuum
assist is provided at each adhesive-applying station to insure that
adequate adhesive penetration into the batt occurs, and to minimize
back-splash and adhesive drift. After the adhesive has been sprayed
on the opposed surfaces of the fibrous batt, the batt is
transported through an oven wherein the batt is dryed and the
adhesive is set. The finished nonwoven fabric is then wound into a
roll for subsequent use in the manufacture of disposable diapers
and the like.
It is an object of this invention to provide a disposable diaper of
the throwaway type which has sufficient strength and abrasion
resistance to serve as a replacement for conventional textile
diapers.
It is a further object of this invention to provide a throwaway
diaper having excellent hand feel and drape characteristics.
It is a further object of this invention to provide a throwaway
diaper having a textile fabric appearance.
It is a further object of this invention to provide a throwaway
diaper which is extremely absorbent.
It is a further object of this invention to provide a throwaway
diaper having a moisture absorbent inner pad covered on at least
one side thereof by a nonwoven, moisture absorbent facing
sheet.
It is a further object of this invention to provide a throwaway
diaper having a nonwoven facing sheet, one side of which is
provided with an embossed pattern defined by a plurality of ridges
and valleys, the density of the facing sheet in the regions of said
valleys being greater than the density of the facing sheet in the
regions of said ridges.
It is a further object of this invention to provide a throwaway
diaper having a water repellent backing sheet.
It is a further object of this invention to provide a throwaway
diaper having a nonwoven randomly arranged, intermingled cellulosic
fiber batt as a backing sheet thereof, said backing sheet being
chemically treated with a moisture repellent material.
It is a further object of this invention to provide a throwaway
diaper having a facing sheet defined by a bonded fibrous batt of
randomly arranged, intermingled cellulosic fibers, said batt being
provided with an embossed relief pattern in its outer surface
thereof, which extends over substantially the entire surface of the
batt, and a second embossed pattern extending through said facing
sheet and into a moisture absorbent pad over which said facing
sheet is disposed to provide mechanical entanglement between the
fibers of the facing sheet and the fibers of the moisture absorbent
pad whereby fluid communication through said facing sheet into said
pad, and also along said pad and facing sheet are enhanced.
It is a further object of this invention to provide a method for
manufacturing a facing sheet of a throwaway diaper wherein an
adhesive is applied to an embossed fibrous batt of randomly
arranged, intermingled cellulosic fibers, and said adhesive is
subsequently dried and set.
It is a further object of this invention to provide a method for
manufacturing a facing sheet of a throwaway diaper wherein a
fibrous batt is moistened by water sprayed upon the surface of a
rubber roll which defines, in conjunction with a patterned
embossing roll, a nip region through which said fibrous batt
passes.
Other objects and advantages of this invention will be readily
understood by referring to the detailed description which follows
taken in conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic representation of the sequential steps
performed in manufacturing a nonwoven cover material for a
throwaway diaper;
FIG. 2 is an enlarged sectional view along line 2--2 of FIG. 1
showing details of construction of the non-woven facing sheet
utilized in the disposable diapers of this invention;
FIG. 3 is a perspective view of the disposable diaper of this
invention; and
FIG. 4 is a sectional view taken along line 4--4 of FIG. 3, with
the specific embossed pattern shown in FIG. 2 omitted for purposes
of clarity.
DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
The method of manufacturing a moisture absorbent, nonwoven,
self-sustaining, absorbent fabric suitable for use as a cover
material in disposable diapers and the like can best be understood
by referring to the schematic representation of the process shown
in FIG. 1. A loosely compacted, randomly arranged, intermingled
fibrous batt 10, comprised of approximately 75 percent wood pulp
fibers and approximately 25 percent longer synthetic fibers, such
as rayon, is formed by conventional web-forming equipment which
does not form a part of the present invention but which will be
discussed briefly for purposes of clarity. Baled rayon is opened by
feeding it through a Rando Prefeeder and Rando Opener-Blender, both
of which are manufactured by the Curlator Corporation of Rochester,
New York. A continuous roll of pulp lap is fiberized by passing it
through a fiberizer, such as the one manufactured by Joa, Inc. of
North Wales, Fla. The opened rayon fibers and defibered wood pulp
fibers are blended in a Rando Feeder, and are air-laid by a Rando
Webber to form a randomly arranged, intermingled fibrous batt
containing approximately 75 percent wood pulp fibers and 25 percent
rayon fibers and having approximately 8 percent moisture regain.
The Rando Feeder and Rando-Webber are manufactured by the Curlator
Corporation. The wood pulp lap preferably is provided with a
suitable debonding agent to insure that the pulp lap can be
uniformly defibered in the fiberizer.
In the preferred embodiment of the invention, a high wet modulus
rayon of 1.5 denier and 1 9/16 inch length is used; however, other
synthetic fibers can be utilized. A high wet modulus rayon fiber
can be purchased from FMC Corporation and is designated as FMC
Fiber 410.
The fibrous batt can be formed with a basis weight up to about 2
ounces per square yard; however, in the preferred embodiment of the
invention the fibrous batt, as initially formed by the
Rando-Webber, has a basis weight in the range of approximately
0.9-1.1 ounces per square yard.
The fibrous batt formed by the web forming equipment is embossed on
one surface 32 (FIG. 2) thereof by feeding said batt through a nip
defined between an upper patterned roll 12 and a lower rubber roll
14. In the preferred embodiment of this invention, the upper
pattern roll 12 is loaded by hydraulic cylinders to provide the
necessary pressure to form the embossed pattern in the batt 10.
Moisture is sprayed from a nozzle 16 onto the surface of rubber
roll 14 just prior to the nip, whereby the moisture is transferred
from the rubber roll to the batt 10 as the batt passes through the
nip to insure that the pattern formed in said batt will be retained
therein during subsequent operations and to aid in releasing the
web from the rolls. In the event that the initially formed batt 10
has sufficient moisture to retain an embossed pattern therein
during subsequent operations, the application of moisture prior to
embossing can be eliminated.
In the preferred embodiment of the invention, a terry cloth pattern
is formed on the surface of roll 12 by a photoengraving process
well known in the art. It is understood that other patterns and
other methods of applying a pattern to a roll can be utilized. The
patterned embossing roll is heated by steam within the range of
approximately 190.degree.F to 210.degree.F, and a pressure of the
order of magnitude of 0.5 to 20 pounds per linear inch is applied
at the nip of rollers 12 and 14.
The temperature of the embossing roll 12 can be varied depending
upon the particular embossing pressure imposed on the batt 10,
i.e., lower temperatures can be used with increasing pressures. In
addition, various percentages of moisture add-on can be applied
through nozzle 16, depending on the pressure-temperature parameters
of the embossing step, i.e., lower percentages of moisture can be
utilized by increasing the embossing pressure and/or temperature.
The moisture level of the batt must be sufficient to insure that
the batt will retain its embossed pattern during subsequent
operations.
After the pattern has been embossed into the upper surface 32 of
the web, the batt 10 is fed past successive adhesive-applying
stations. At the first station, adhesive is applied to the lower
surface of the web through an adhesive nozzle 18, and a vacuum
assist 20 is provided from the opposite side of said batt to
improve adhesive penetration and minimize backsplash and adhesive
drift. At the second adhesive-applying station, the adhesive is
sprayed onto the upper surface 32 of the batt 10 through an
adhesive spray nozzle 22, and a vacuum assist 24 is provided from
the opposite side of the batt for the same reason that the vacuum
assist 20 is provided at the first adhesive-applying station.
In the preferred embodiment of this invention a self cross-linkable
acrylic latex sold by Rohm & Haas under the trade name Rhoplex
HA8 is utilized. The total adhesive solids add-on is approximately
8-12 percent by weight.
After the batt 10 has passed the second adhesive-applying station,
it is fed through an oven 26 which is maintained at approximately
300.degree.F to dry the web, and subsequently at about 320.degree.F
to cure said web. The web, as it enters the oven has approximately
200 percent moisture add-on by weight which resulted from the
moisture application through nozzle 16 and the moisture application
through adhesive nozzles 18 and 20. The dryed and cured batt is
then rolled in a roll 28 for subsequent use as a nonwoven cover
material for disposable diapers.
Although the self cross-linkable acrylic latices are preferred in
the manufacture of the nonwoven fabric of this invention, other
adhesives may be utilized, and when other adhesives are utilized
the batt 10 will be subjected to an adhesive-setting process
appropriate for the particular adhesive used.
It is highly desirable to utilize a predominate amount of wood pulp
fibers in the nonwoven fabric of this invention, since wood pulp is
relatively inexpensive as compared to the cost of longer textile
fibers, such as rayon and cotton, and since wood pulp has excellent
absorbency characteristics.
The nonwoven cover material formed according to the above-described
method has a basis weight up to or about 2.0 ounces per square
yard, but preferably is in the range of approximately 1.1 to
approximately 1.6 ounces per square yard. Manufacturing a nonwoven
fabric of predominately short cellulosic fibers, such as wood pulp,
in the basis weight range referred to above, requires extreme care
in handling during the fabrication thereof. This is particularly
true prior to embossing at which time the formed batt 10 has
relatively little integrity. By applying moisture from nozzle 16
onto the surface of rubber roll 14 for transfer to the batt 10,
instead of applying moisture directly against the surface of the
web, the batt is not physically disturbed, and therefore the chance
of destroying the uniformity of the batt is reduced.
The fiber construction in the finished fabric is shown in FIG. 2.
The finished fabric has an upper embossed surface 32 which is
defined by the pattern contained in the outer periphery of pattern
roll 12, and a lower, loose fiber nap surface 30 formed by its
engagement with the periphery of rubber roll 14 during the
embossing operation. The function of the loose fiber nap surface 30
will be described in detail with respect to the disposable diaper
construction shown in FIGS. 3 and 4.
Referring to FIGS. 3 and 4, the diaper 40 of this invention is
comprised of a moisture absorbent pad 46 extending longitudinally
along the center of the diaper and adapted to fit between the legs
of an infant in the crotch area. The pad 46 is preferably made of
fluffed wood pulp fibers, and is contoured in the crotch area to
define an hourglass configuration for reducing unneeded bulk to
provide comfort for the baby. The absorbent pad is sandwiched
between a facing sheet 42 adapted to be positioned against the skin
of the baby, and a backing sheet 44. In the preferred embodiment of
the invention, both the facing sheet 42 and the backing sheet 44
are comprised of randomly arranged intermingled cellulosic fibers
manufactured according to the process described in detail, supra
and both the facing and backing sheets are substantially
rectangular as is shown in FIG. 3.
To prevent moisture strikethrough during use of the diaper, a fluid
impermeable material, such as polyethylene can be placed between
the absorbent fluff pad 46 and the backing sheet 44, or to retard
the rate of moisture strikethrough, the backing sheet 44 may be
coated or chemically treated in a suitable manner to render it
substantially water impermeable. For example, a material such as an
emulsion of wax and poly(vinyl acetate) sold by Du Pont under the
trade name Nalan GN is extremely effective for retarding moisture
strikethrough when applied to both surfaces of the backing sheet
44.
The outer surfaces of facing sheet 42 and backing sheet 44 are
provided with the embossed pattern formed by embossing roll 12, and
therefore, the loose fiber nap layer 30 of the facing sheet 42
faces the corresponding loose fiber nap surface 30 of the backing
sheet 44. When the sheets are assembled to produce disposable
diaper 40, the fibers of the loosely napped surfaces tend to
mechanically interlock with each other and with the fibers of the
absorbent fluff pad 46 to thereby provide a relatively stable
product. In addition, any suitable adhesive, such as hot melt can
be utilized to bond the facing sheet to the backing sheet, and to
retain the fluff pad 46 in proper position therebetween.
To enhance the capillary flow characteristics between the facing
sheet 42 and the absorbent pad 46, a substantially broad pattern is
embossed into the absorbent pad 46 through the facing sheet 42, to
define compressed lines 54, and high loft, bulk regions 52. This
embossed pattern produces a continuous fiber network between the
facing sheet 42 and the fluff in the compressed regions 54 to
enhance the fluid distribution along lines 54 and into the fluff
pad 46. As can be seen in FIG. 3, two sets of spaced, continuous
embossed lines 54 are formed in the facing sheet and underlying
absorptive layer 46. One of the sets of embossed lines 54 extends
in the long direction of the diaper, and the second set of embossed
lines extends substantially transverse to the first set of embossed
lines.
In the preferred embodiment of the invention, the backing sheet 44
has a longitudinal length slightly in excess of the longitudinal
length of facing sheet 42, and the end portions of the backing
sheet 44 are folded over the upper surface of facing sheet 42 to
provide strengthened regions 48 and 50 for receiving pins.
Alternatively, the facing sheet and backing sheet can be
manufactured of the same length, and a print bonded pattern can be
applied to the longitudinally spaced edges of the diaper to provide
the needed pin strength, or alternatively a gauze insert can be
sandwiched between the sheets at the longitudinally spaced edges to
provide the necessary pin strength.
* * * * *