U.S. patent number 3,741,212 [Application Number 05/168,133] was granted by the patent office on 1973-06-26 for diaper system and absorbent pad therefor.
This patent grant is currently assigned to Scott Paper Company. Invention is credited to Richard W. Schutte.
United States Patent |
3,741,212 |
Schutte |
June 26, 1973 |
DIAPER SYSTEM AND ABSORBENT PAD THEREFOR
Abstract
A diaper system having an elongate, fluid impervious
pad-retaining garment and an elongate, disposable absorbent pad
removably retained in the garment. The elongate, disposable
absorbent pad includes an absorbent layer disposed within a
covering envelope having a porous, elongate, adhesively bonded,
fibrous facing cover web, and a backing cover web of a wet-strength
paper stock. The absorbent layer includes a fluff batt of
cellulosic fibers, and a lower layer of creped paper wadding
disposed adjacent the bottom face of the fluff batt and having a
transverse dimension at least substantially equal to the transverse
dimension of the fluff batt. The facing cover web overlies a facing
surface of the absorbent layer and has elongate side margins
extending around elongate sides of the absorbent layer and
overturned upon, and secured to the backing cover web. The backing
cover web has a lower wet-cross-direction energy absorption level
than the facing cover web, a higher wet-cross-direction energy
absorption level than the lower layer of creped paper wadding, and
is less permeable to the passage of urine than the facing cover web
and the lower layer of creped paper wadding. Side regions of the
absorbent pad include the absorbent layer and are infolded to
define side panels having upper exposed surfaces defined by
portions of the facing cover web. The backing cover web has
elongate side margins terminating short of the infolded side
regions so that the backing cover web is not disposed to underlie
the portions of the facing cover web defining the upper exposed
surfaces of the side panels.
Inventors: |
Schutte; Richard W. (Newton
Square, PA) |
Assignee: |
Scott Paper Company (Delaware
County, PA)
|
Family
ID: |
22610266 |
Appl.
No.: |
05/168,133 |
Filed: |
August 2, 1971 |
Current U.S.
Class: |
604/375; 604/364;
604/373; 604/386; 604/365; 604/378 |
Current CPC
Class: |
A61F
13/505 (20130101); A61F 13/533 (20130101); A61F
13/53418 (20130101) |
Current International
Class: |
A61F
13/15 (20060101); A61f 013/16 () |
Field of
Search: |
;128/284,286,287,290 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Rosenbaum; Charles F.
Claims
What is claimed is:
1. An elongate, disposable, absorbent pad for use as an insert in a
pad-retaining garment, comprising:
A. an elongate, absorbent layer having a facing and backing
surface, comprising;
1. an elongate, fluff batt of cellulosic fibers having top and
bottom faces and a transverse dimension defined by spaced, elongate
side margins, and
2. a lower layer of creped paper wadding disposed adjacent the
bottom face of said fluff batt for defining the backing surface of
said absorbent layer, said lower layer of creped paper wadding
having a transverse dimension at least substantially equal to the
transverse dimension of said fluff batt;
B. a covering envelope comprising;
1. a fluid pervious, adhesively bonded fibrous facing cover web,
and
2. a backing cover web of wet-strength paper stock, said backing
cover web having a lower wet-cross-direction energy absorption
level than said facing cover web, a higher wet-cross-direction
energy absorption level than said lower layer of creped paper
wadding, and a lower permeability to the passage of urine than said
facing cover web and said lower layer of creped paper wadding;
c. said absorbent layer disposed within said covering envelope with
said facing cover web overlying the facing surface of said
absorbent layer, and said backing cover web overlying and disposed
adjacent the backing surface of said absorbent layer, said facing
cover web having elongate side margins extending around the
elongate side margins of said absorbent layer and in overlapping
relationship with said backing cover web for substantially the
entire elongate extent of the absorbent pad, securing means
adhering overlapping sections of the facing cover web and the
backing cover web together along substantially the entire elongate
extent of overlap;
D. said absorbent pad having elongate side regions defined between
a center region and opposed side edges, the side regions of said
absorbent pad including said absorbent layer being infolded to form
side panels in overlying relationship with said center region, said
side panels having upper exposed surfaces defined by portions of
said facing cover web, said backing cover web having elongate side
margins terminating short of the side regions of said absorbent pad
which are infolded to form the side panels so that the backing
cover web is excluded from underlying said portions of said facing
cover web defining the upper exposed surfaces of said side panels,
said backing cover web being adapted to be disposed on a surface of
a pad-retaining garment.
2. The elongate, disposable, absorbent pad according to claim 1,
wherein said absorbent layer includes an upper layer of creped
paper wadding disposed adjacent the top face of said fluff batt for
defining the facing surface of said absorbent layer.
3. The elongate, disposable, absorbent pad according to claim 2,
wherein said backing cover web has a wet-cross-direction energy
absorption level in the range of approximately 0.01 to 0.06
inch-pounds, and a fluid permeability of less than 5 darcies.
4. The elongate, disposable, absorbent pad according to claim 3,
wherein said backing cover web has a wet-cross-direction energy
absorption level in the range of approximately 0.01 to 0.03
inch-pounds, and a fluid permeability in the range of approximately
2.7 to 4.0 darcies.
5. The elongate, disposable, absorbent pad according to claim 3,
wherein said facing cover web has a wet-cross-direction energy
absorption level in the range of approximately 0.11 to 0.19
inch-pounds, and a fluid permeability of greater than 15
darcies.
6. The elongate, disposable, absorbent pad according to claim 4,
wherein said facing cover web has a wet-cross-direction energy
absorption level in the range of approximately 0.16 to 0.19
inch-pounds, and a fluid permeability in the range of approximately
16.2 to 18.2 darcies.
7. The elongate, disposable, absorbent pad according to claim 5,
wherein said facing cover web is a nonwoven fabric comprising
synthetic fibers.
8. The elongate, disposable, absorbent pad according to claim 7,
wherein said nonwoven fabric is a carded rayon web.
9. The elongate, disposable, absorbent pad according to claim 6,
wherein said facing cover web is a nonwoven fabric comprising
synthetic fibers.
10. The elongate, disposable, absorbent pad according to claim 9,
wherein said nonwoven fabric is a carded rayon web.
11. In a diaper system:
A. an elongate, fluid impervious pad-retaining garment terminating
in opposed forward and rearward marginal edges, said forward and
rearward marginal edges being adapted to be fastened around the
front and rear area, respectively, of a child;
B. an elongate, disposable absorbent pad positioned on a surface of
said pad-retaining garment;
C. holding means secured to said pad-retaining garment for
removably retaining said absorbent pad within said pad-retaining
garment, said absorbent pad comprising:
1. an elongate, absorbent layer having a facing and backing
surface, comprising;
a. an elongate, fluff batt of cellulosic fibers having a top and
bottom face, and a transverse dimension defined by spaced, elongate
side margins, and
b. a lower layer of creped paper wadding disposed adjacent the
bottom face of said fluff batt for defining the backing surface of
said absorbent layer, said lower layer of creped paper wadding
having a transverse dimension at least substantially equal to the
transverse dimension of said fluff batt;
2. a covering envelope comprising;
a. a fluid pervious, adhesively bonded fibrous facing cover web
and
b. a backing cover web of wet-strength paper stock, said backing
cover web having a lower wet-cross-direction energy absorption
level than said facing cover web, a higher wet-cross-direction
energy absorption level than said lower layer of creped paper
wadding, and a lower permeability to the passage of urine than said
facing cover web and said lower layer of creped paper wadding;
3. said absorbent layer disposed within said covering envelope with
said facing cover web overlying the facing surface of said
absorbent layer, and said backing cover web overlying and disposed
adjacent the backing surface of said absorbent layer, said facing
cover web having elongate side margins extending around the
elongate side margins of said absorbent layer and in overlapping
relationship with said backing cover web for substantially the
entire elongate extent of the absorbent pad, securing means
adhering overlapping sections of the facing cover web and the
backing cover web together along substantially the entire elongate
extent of overlap;
4. said absorbent pad having elongate side regions defined between
a center region and opposed side edges, the side regions of said
absorbent pad including said absorbent layer being unfolded to form
side panels in overlying relationship with said center region, said
side panels having upper exposed surfaces defined by portions of
said facing cover web, said backing cover web having elongate side
margins terminating short of the side regions of said absorbent pad
which are infolded to form the side panels so that the backing
cover web is excluded from underlying said portions of said facing
cover web defining the upper exposed surfaces of said side panels,
said backing cover web being disposed on a surface of said
pad-retaining garment.
12. The diaper system according to claim 11, wherein said backing
cover web has a wet-cross-direction energy absorption level in the
range of approximately 0.01 to 0.06 inch-pounds, and a fluid
permeability of less than 5 darcies; and wherein said facing cover
web has a wet-cross-direction energy absorption level in the range
of approximately 0.11 to 0.19 inch-pounds, and a fluid permeability
of greater than 15 darcies.
13. The diaper system according to claim 11 wherein said backing
cover web has a wet-cross-direction energy absorption level in the
range of approximately 0.01 to 0.03 inch-pounds, and a fluid
permeability in the range of approximately 2.7 to 4.0 darcies; and
said facing cover web has a wet-cross-direction energy absorption
level in the range of approximately 0.16 to 0.19 inch-pounds, and a
fluid permeability in the range of approximately 16.2 to 18.2
darcies.
14. The diaper system according to claim 12, wherein said facing
cover web is a nonwoven fabric comprising synthetic fibers.
15. The diaper system according to claim 13, wherein said facing
cover web is a nonwoven fabric comprising synthetic fibers.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a diaper system, and to an absorbent pad
for use in said diaper system. More specifically, this invention
relates to a diaper system having an elongate, disposable absorbent
pad for use with a fluid impervious pad-retaining garment; and to
the elongate, disposable absorbent pad per se.
2. Description of the Prior Art
Absorbent pads for use with fluid impervious pad-retaining garments
in a diaper system are known in the prior art. One such absorbent
pad is disclosed in U.S. Pat. application Ser. No. 108,560, filed
Jan. 21, 1971, and assigned to Scott Paper Company. This prior art
absorbent pad is from about 4 to 5 inches wide and is disposed in
its flat condition within a water-proof pouch or channel of a fluid
impervious pad-retaining garment. This absorbent pad includes a
composite absorbent member comprising a fluff batt of short, wood
pulp fibers disposed between upper and lower layers of creped paper
wadding which are free of wet-strength resins. A porous, nonwoven
facing cover web is disposed over the upper layer of creped paper
wadding and has elongate side margins extending around elongate
sides of the composite absorbent member and overturned upon and
bonded to the lower layer of creped paper wadding so as to leave
exposed the central portion of the lower layer of creped paper
wadding. This construction of an absorbent pad permits the lower
layer of creped paper wadding to contact moisture instantly and to
immediately physically disintegrate when the absorbent pad is held
within the vortex of a flushed toilet or other stream of water.
This physical disintegration of the creped paper wadding exposes
the inner fluff batt to water, which causes said inner fluff batt
to disintegrate. The facing cover web of nonwoven material is
non-bulky, flexible, and also is disposable in an ordinary toilet
bowl. Therefore, the entire absorbent pad is disposable in an
ordinary toilet.
The lower layer of creped paper wadding in the prior art absorbent
pad had insufficient wet-cross-direction wet toughness to maintain
its structural integrity when saturated with urine, and therefore,
failed to function satisfactorily as part of the covering envelope
to maintain the structural integrity of the inner components of the
absorbent pad during use of the diaper system. Supporting the lower
layer of creped paper wadding on a surface of a pad-retaining
garment of the diaper system did not overcome this strength
deficiency. Furthermore, the lower layer of creped paper wadding
was so highly permeable to the passage of urine that urine
penetrating through the thickness of the absorbent pad during use
of the diaper system was easily transmitted through the lower layer
of creped paper wadding to flow along the pad-retaining garment and
leak from marginal regions thereof. Stating this another way, the
lower layer of creped paper wadding did not provide a sufficient
barrier to urine transmission to prevent leakage from the diaper
system. Another disadvantage encountered in the above-described
absorbent pad was the inefficient distribution of absorbent
material for adequately retaining urine to prevent leakage from the
diaper system.
The problem of inefficient distribution of absorptive material in
the above-described absorbent pad was overcome by widening the
absorbent pad, and infolding side regions of the pad to define
elongate side panels having upper exposed surfaces positioned
adjacent a child during use of the diaper system. In use, the rear
portions of the side panels were flared open to define a wide
confining region for fecal matter, and the forward portions of the
side panels were maintained in their infolded position to provide
double thick portions having a sufficient quantity of absorbent
material for retaining a sufficient quantity of urine to prevent an
undesirable level of leakage from the diaper system. To enhance the
strength of the covering envelope, and to alleviate the problem of
high fluid transmission through the bottom of the covering
envelope, the lower layer of creped paper wadding was replaced with
a backing cover web of a wet-strength paper stock having a greater
wet-cross-direction energy absorption level than the creped paper
wadding, and being less permeable to the passage of urine than said
lower layer of creped paper wadding. This backing cover web
extended the full width of the absorbent pad to thereby be included
in the side panels to aid in maintaining the structural integrity
of the fluff batt in the regions of said side panels. The backing
cover web, in the region of the side panels, was therefore disposed
between the porous, nonwoven facing cover web and the fluff batt.
Since, as stated above, the backing cover web was purposefully
designed to be less permeable to the passage of urine than the
previously utilized lower layer of creped paper wadding, it
provided a physical impediment to the passage of urine from the
porous, nonwoven cover web into the fluff batt in the side panels
of said absorbent pad. This impediment to urine passage resulted in
a flooding condition on the upper exposed surfaces of the side
panels thereby causing excessive leakage of urine from the diaper
system.
SUMMARY OF THE INVENTION
The elongate, disposable absorbent pad of this invention includes
an elongate absorbent layer and a covering envelope. The absorbent
layer comprises a fibrous fluff batt and a layer of creped paper
wadding disposed in intimate contact with at least a lower face of
said fluff batt and having a transverse dimension at least
substantially equal to the transverse dimension of said fluff batt.
This absorbent layer is disposed within the covering envelope which
comprises a fluid pervious, adhesively bonded fibrous facing cover
web and a backing cover web of wet-strength paper stock. The
backing cover web is disposed contiguous to and in overlying
relationship with the lower layer of creped paper wadding. The
facing cover web has elongate side margins extending around
elongate sides of the absorbent layer, and overturned upon and
secured to the backing cover web. Side regions of the absorbent pad
are infolded to define elongate side panels having upper exposed
surfaces defined by the facing cover web, and the backing cover web
terminates short of the elongate sides of the absorbent layer so as
not to be disposed in underlying relationship with the portions of
the facing cover web defining the upper exposed surfaces of the
side panels.
The backing cover web has a higher wet-cross-direction energy
absorption level than creped paper wadding, and has sufficient
strength to maintain the structural integrity of the absorbent pad
during its use in the diaper system. In addition, the backing cover
web has a lower wet-cross-direction energy absorption level than
the facing cover web to act as a shock absorber to loads
encountered by the absorbent pad during use of the diaper system of
this invention. To further explain, the loads which are initially
applied to the facing cover web during use of the diaper system are
transmitted around marginal edges of the absorbent pad to the
backing cover web. Since the backing cover web has a lower
wet-cross-direction energy absorption level than the facing cover
web, it will tend to tear and relieve stresses prior to the applied
load reaching, or exceeding the energy absorption level of the
facing cover web to thereby prevent the facing cover web from
tearing and exposing inner components of the absorbent pad to the
skin of a child during use of the diaper system.
The backing cover web is sufficiently less permeable to the passage
of urine than the lower layer of creped paper wadding to constitute
a partial moisture barrier for inhibiting the passage of urine
through the back surface of the absorbent pad. By reducing the
permeability of the backing cover web to the passage of urine,
excessive leakage through the absorbent pad, onto the fluid
pervious pad-retaining garment, and past marginal edges of said
pad-retaining garment is reduced. The backing cover web is excluded
from the side panels of the absorbent pad so that it will not
provide an impediment to urine transmission from the upper exposed
surfaces of the side panels into the highly absorbent fluff
batt.
The lower layer of creped paper wadding is included in the side
panels between the facing cover web and the absorbent fluff batt.
This lower layer of creped paper wadding has been found to have
sufficient strength in conjunction with the overlying facing cover
web to provide support for said fluff batt in the regions of said
side panels when said lower layer is positioned in the perineal
region of the child to initially receive the impingement of urine
thereon. By maintaining the side panels infolded in this forward
region, a large absorptive capacity for urine is provided. Since
the backing cover web is disposed on a surface of the pad-retaining
garment, it will not engage the skin of a child, and therefore any
tearing of this backing cover web resulting from excessive laods
encountered by the absorbent pad during use of the diaper system
will not expose inner components of the absorbent pad to the skin
of a child.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an isometric view of the absorbent pad of this invention
with parts broken away to show details of construction;
FIG. 2 is a plan view of the diaper system of this invention;
and
FIG. 3 is a sectional view along line 3--3 of FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION
Referring to FIGS. 1 and 2, the diaper system 10 of this invention
includes a pad-retaining garment 12 and a unique, elongate
disposable absorbent pad 14. The disposable absorbent pad 14 is
comprised of an elongate, absorbent layer 16 disposed within a
covering envelope 18. The elongate, absorbent layer 16 of the
disposable absorbent pad 14 includes an elongate fluff batt 20
having a lower layer of creped paper wadding 22 disposed adjacent
the bottom face of the fluff batt to define a backing surface 23 of
the absorbent layer 16. This lower layer of creped paper wadding is
highly permeable to the passage of urine, and has a transverse
dimension at least substantially equal to the transverse dimension
of the fluff batt for a purpose to be described hereinafter. An
upper layer of creped paper wadding 24 is disposed adjacent the top
face of the fluff batt 20 to define the facing surface 25 of the
absorbent layer 16. It is within the purview of this invention to
eliminate the upper layer of creped paper wadding 24, although in
the preferred embodiment of this invention the upper layer of
creped paper wadding performs the desirable function of cooperating
with the lower layer of creped paper wadding to support the fluff
batt 20. The number of plies of creped paper wadding which is
utilized in each of the upper and lower layers can be varied within
wide limits. In practice, two plies of creped paper wadding in each
of the upper and lower layers have proven satisfactory to aid in
supporting the fluff batt 20.
The fluff batt 20 preferably is comprised of short cellulosic
fibers of a paper-making length less than one-fourth inch, and
preferably is an air-laid batt manufactured on a Joa Fiberizer,
Hammermill, or the like. This fluff batt 20 preferably is profiled
to define a forward one-half section 26 having a greater weight of
fibers therein than a rearward one-half section 28 whereby the
forward section 26 is thicker and/or more dense than the rearward
section 28. An embossed pattern is impressed into the fluff batt 20
through the upper and lower layers of creped paper wadding 22 and
24 to define compressed regions in the form of transversely spaced,
elongate channels 30 separated by elongate high loft regions 32 to
aid in directing fluid along the elongate direction of the fluff
batt. In addition, the formation of an embossed pattern in the
fluff batt 20 through the upper and lower layers of creped paper
wadding functions to stabilize the fluff batt to prevent splitting
of the fluff batt into separated clumps which impairs the fluid
absorbing capability of said fluff batt. It is within the purview
of this invention to utilize fluff batts other than the
above-described profiled, embossed fluff batt 20 in the absorbent
layer 16. The above-described structure of the absorbent layer,
including a profiled, embossed fluff batt therein, forms the
subject matter of a separate patent application titled DIAPER
SYSTEM AND ABSORBENT PAD THEREFOR, filed on even date, and is the
invention of George G. DeNight et al.
The covering envelope 18 has forward and rearward end margins 40
and 42 which extend beyond end margins of the fluff batt 20, and
which are closed by transverse end seal bands 41 and 43. The upper
and lower layers of creped paper wadding 22 and 24 also extend
beyond the end margins of the fluff batt 20 and are included in the
seal bands 41 and 43. The specific structure of the transverse end
seal bands does not form a part of the present invention but is
preferably of the structure indicated in copending application Ser.
No. 137,839, filed Apr. 27, 1971, and assigned to Scott Paper
Company, the subject matter of which is hereby incorporated by
reference.
The covering envelope 18 includes a porous, elongate, adhesively
bonded fibrous facing cover web 44, and a backing cover web 46 of a
wet-strength paper stock. The elongate backing cover web 46 is
disposed adjacent the backing surface 23 of the absorbent layer 16,
and the porous, elongate, facing cover web 44 is disposed adjacent
the facing surface 25 of said absorbent layer. The facing cover web
44 has side margins 48 and 50 which extend around side margins of
the absorbent layer 16, and which are overturned upon and secured
to the backing cover web 46 adjacent side margins 52 and 54 of said
backing cover web. The facing cover web 44 is secured to the
backing cover web 46 by elongate, securing stripes 57 of any
suitable adhesive material, but preferably, a hot melt adhesive is
utilized (FIG. 3).
Referring to FIGS. 2 and 3, side regions of the absorbent pad 14
are infolded along elongate fold lines 58 and 60 to form side
panels 62 and 64 in overlying relationship with the elongate,
facing cover web 44 in a center region 66 of said absorbent pad 14.
Side panels 62 and 64 have upper exposed surfaces 68 and 70,
respectively, and inner end margins 69 and 71 which terminate short
of each other to leave exposed a portion of the facing cover web 44
in the center region 66. This exposed portion of center region 66,
in conjunction with upper exposed surfaces 68 and 70 of the side
panels 62 and 64 defines the upper exposed surfaces of the
absorbent pad 14 when said absorbent pad is positioned on a
fluid-impervious retaining garment 12 to form the diaper system 10
of this invention. The side panels 62 and 64 are retained in their
infolded positions by a suitable securing means, such as securing
dots or tacks 72, 74, of adhesive, or the like, disposed adjacent
the forward end margin 40 of the covering envelope 18 between the
side panels 62 and 64 and the facing cover web 44. The upper
exposed surfaces 68 and 70 of the side panels are defined by
portions of the facing cover web 44 initially disposed on the back
side of the absorbent pad 14 prior to folding, and therefore, the
lower layer of creped paper wadding 22 is disposed between the
facing cover web 44 and the fluff batt 20 in said side panels. The
lower layer of creped paper wadding, in conjunction with the
overlying facing cover web provides support for the fluff batt in
the side panels to maintain the structural integrity of the fluff
batt in this region. The elongate, side margins 52 and 54 of the
backing cover web 46 are disposed adjacent the fold lines 58 and
60, respectively, so that the backing cover web 46 is not disposed
in underlying relationship with the portions of the facing cover
web defining the upper exposed surfaces 68 and 70 of the side
panels 62 and 64. The unique structural relationship among the
facing cover web 44, the backing cover web 46 and the lower layer
of creped paper wadding 22, which structural relationship is the
essence of this invention, is dictated by the required physical
properties in the absorbent pad 14 of this invention as will be
explained hereinafter.
The facing cover web 44 must have sufficient strength to assure
that the structural integrity of the disposable absorbent pad 14 is
maintained during its use in the diaper system 10. Since the facing
cover web 44 is in contact with a child during use of the diaper
system 10, the integrity of said facing cover web must be
maintained to prevent inner components of the absorbent pad 14,
such as the fluff batt 20, from coming into contact with, and
sticking to a child's skin. In addition to the abovedescribed
strength requirement, the facing cover web 44 must be highly
permeable to urine to permit the urine to pass substantially
instantaneously into the absorbent layer 16 which has a high
absorptive capacity, i.e., ability to store large quantities of
urine without leaking.
The strength of the facing cover web 44 is determined by its energy
absorption level, i.e., the ability to absorb energy without
tearing or losing its structural integrity. The energy absorption
level is a function of both tensile strength and extensibility of
said web, and is measured in units of work, i.e., inch-pounds. The
critical strength property of the facing cover web 44 is its
wet-cross-direction energy absorption level, since the greatest
amount of work is absorbed in the cross-direction of the facing
cover web during use of the diaper system 10, and the criticality
of the strength requirement in the facing cover web exists when the
disposable absorbent pad 14 is wet. The method of determining
wet-cross-direction energy absorption levels will be described
later in this application. The wet-cross-direction energy
absorption level in acceptable facing cover webs of this invention
is in the range of from about 0.11 to about 0.19 inch-pounds, and
preferably in the range of from about 0.16 to about 0.19
inch-pounds.
An acceptable facing cover web 44 according to this invention has a
fluid permeability of greater than 15 darcies, and preferably in
the range of from about 16.2 to about 18.2 darcies as calculated in
a manner which is described later in this application. One facing
cover web 44 which has both the requisite wet-cross-direction
energy absorption level and fluid permeability is a pattern bonded,
carded web of 100 percent rayon staple fibers 11/2 denier, 2-inch
length. The adhesive utilized to pattern bond such a web is
preferably an acrylic latex, such as E-32, manufactured by Rohm and
Haas, and this latex accounts for approximately 18-20 percent by
weight of the web. It is contemplated that any adhesively bonded,
fibrous web having the requisite wet-cross-direction energy
absorption level and fluid permeability, as set forth above, will
be acceptable as a facing cover web in the disposable absorbent pad
14 of this invention. Such webs may be nonwoven, apertured webs
comprising 100 percent wood pulp fibers of a short papermaking
length less than one-fourth inch; 100 percent longer staple
synthetic fibers; or blends of short paper-making fibers and longer
synthetic fibers.
The backing cover web 46 must have sufficient structural integrity
when wet, i.e., a sufficiently high wet-cross-direction energy
absorption level, to function as part of the covering envelope 18
in maintaining the structural integrity of the disposable absorbent
pad during its use in the diaper system 10. The backing cover web
46 has a lower wet-cross-direction energy absorption level than the
facing cover web 44 to act as a shock, or load-absorbing member for
forces applied directly to the facing cover web 44 during use of
the diaper system 10. Since the backing cover web 46 has a lower
wet-cross-direction energy absorption level than the facing cover
web 44, the backing cover web will tend to tear, and leave the
facing cover web 44 intact, when the energy applied to the cover
envelope 18 during use of the absorbent pad 14 exceeds the
wet-cross-direction energy absorption level of said backing cover
web. Since this lattermentioned energy absorption level will be
exceeded before the wet-cross-direction energy absorption level of
the facing cover web 44 is reached, the backing cover web will tear
first to thereby reduce the stress level in the cross-direction of
the wet facing cover web and prevent the energy applied to the
facing cover web from exceeding its wet-cross-direction energy
absorption level. The backing cover web 46 has a greater
wet-cross-direction energy absorption level than the lower layer of
creped paper wadding 22 to function properly as part of the
covering envelope 18 to aid in maintaining the structural integrity
of the absorbent pad 14. In the preferred embodiment of this
invention, the backing cover web 46 has a wet-cross-direction
energy absorption level in the range of from about 0.01 to about
0.06 inch-pounds, and preferably, the wet-cross-direction energy
absorption level is in the range of from about 0.01 to about 0.03
inch-pounds. The backing cover web 46 has a permeability to urine
which is less than the permeability of the porous facing cover web
44 and the lower layer of creped paper wadding 22. This lower fluid
permeability is required so that the backing cover web 46 can
suitably act as a barrier to prevent urine from easily passing
therethrough to thereby prevent excessive urine leakage from the
diaper system 10. In the preferred embodiment of this invention,
the backing cover web 46 has a fluid permeability of under 5
darcies, and preferably in the range of from about 2.7 to about 4.0
darcies, as calculated in a manner to be described later. In
addition, the backing cover web has absorbent qualities to aid in
storing urine which strikes completely through the thickness of the
fluff batt and lower layer of creped paper wadding to thereby
function as an absorbent component of the absorbent pad 14.
Any fibrous web having the requisite wet-cross-direction energy
absorption level and fluid permeability, as set forth above, is
acceptable as a backing cover web. Preferably, the backing cover
web is a wet-laid web having a fiber content of 100 percent short,
wood pulp, paper-making fibers of less than one-fourth inch, said
web containing a polymeric, water soluble, thermosetting resin in
the range of from about 2 percent to about 4 percent by weight of
the backing cover web to provide wet strength in said web. The
wet-strength resins utilized in the backing cover web 46 of this
invention are preferably cationic, such as melamine and urea
formaldehyde composites; however, it is contemplated that other
polymeric, water soluble, thermosetting resins can be utilized,
such as those which are anionic or nonionic.
In the preferred embodiment of this invention the creped paper
wadding has a wet-cross-direction energy absorption level in the
range of from about 0.001 to about 0.003 inch-pounds; and a fluid
permeability exceeding 5 darcies, and preferably exceeding 5.6
darcies. "Creped paper wadding," as utilized throughout the
specification and claims, refers to a wet-formed web of 100 percent
short, wood pulp fibers of a paper-making length of less than
one-fourth inch, said web being free of wet-strength resins and
having a crepe ratio of from about 50 percent to about 225 percent,
wherein said crepe ratio is defined as 100 times the difference
between the dryer and reel speed divided by the reel speed.
Referring to FIG. 2, the pad-retaining garment 12 of diaper system
10 preferably is made from a fluid impervious, flexible sheet
material, such as polyethylene, polypropylene, or polyvinyl
chloride. The garment 12 has a forward marginal edge 80 adapted to
be positioned around the front area of a child and a rearward
marginal edge 82 adapted to be positioned around the rear area of a
child (FIG. 2). A forward region 84 of the regaining garment 12 is
interconnected to a rearward region 86 through an intermediate
region 88. The intermediate region 88 has a reduced transverse
dimension defining the crotch and thigh encircling region of the
retaining garment 12. Opposite transverse edges of the forward
region 84 are provided with male snap elements 90, 92 which are
adapted to cooperate with opposed female snaps 94, 96,
respectively, which are disposed adjacent opposite transverse edges
of the rearward region 86 to permit the retaining garment to be
fastened about a child. The diaper system 10 is worn by a child in
a bikini fashion with the forward marginal edge 80 of the
pad-retaining garment 12 disposed below the abdomen of a child
about 2 or 3 inches above the crotch area. Any suitable fastening
means can be utilized in place of the male and female snap
fasteners; the particular fastening means not forming a part of
this invention. Elastic material is fastened adjacent the forward
marginal edge 80, the rearward marginal edge 82 and opposed
longitudinal edges 97, 99 defining the intermediate region 88 of
the retaining garment 12 to insure that the impervious retaining
garment 12 closely conforms to the legs and waist region of a
child. A holding device 98 is secured to the forward marginal edge
80 of the pad-retaining garment and has a stem portion 100
extending rearwardly from said forward marginal edge and
terminating in a cross member 102. The cross member 102 has
pad-retaining members 104, 106, respectively disposed rearwardly of
the securing tacks 72, 74 to retain the absorbent pad 14 within the
pad-retaining garment 12. This holding device 98 is the invention
of Paul J. Jarusik et al., and is covered in copending application
Ser. No. 101,292 assigned to Scott Paper Company.
In use, the rear portion of the absorbent pad 14 is manually flared
open as is shown in FIG. 2 to provide a wide confining region for
fecal matter. This wide region is desirable to prevent the fecal
matter from escaping from the diaper system 10 to soil the
retaining garment 12. A wide confining structure is not required in
the forward section of the diaper into which urine is initially
directed, and this portion remains folded during use to provide a
high absorptive capacity for urine. Since the backing cover web is
in contact with the retaining garment 12, tears in the backing
cover web will not expose wet inner components, such as fluff batt
20, to a child to permit such inner components to stick to the
child.
Since the backing cover web is excluded from the side panels 62 and
64, its lower permeability will not affect the transmission of
fluid from the upper exposed surfaces of the side panels into the
fluff batt 20. It has been found that while the lower layer of
creped paper wadding does not function suitably as a part of the
covering envelope 18 by itself, it does have sufficient strength to
maintain the integrity of the fluff pad in the side panels of the
absorbent pad 14 when it is disposed between the facing cover web
and the fluff batt in said side panels. Furthermore, the lower
layer of creped paper wadding is highly permeable to the passage of
urine, and therefore permits rapid transmission of urine into the
fluff batt from the upper exposed surface of the facing cover web
of the side panels to thereby prevent excessive flooding on the
upper exposed surface of the side panels, which causes excessive
leakage from the diaper system 10.
CALCULATION OF WET-CROSS-DIRECTION ENERGY ABSORPTION LEVEL
The wet-cross-direction energy absorption level, E, in inch-pounds,
is obtained by clamping a strip of a water saturated specimen which
is 1-inch wide in the jaws of an Instron tensile tester. The jaws
are initially separated 2 inches apart, with any noticeable slack
being pulled out of the strip before clamping. The cross machine
direction of formation of the strip is aligned with the direction
of jaw separation, and strain is applied to the specimen by moving
the jaws apart at a constant rate of 2 inches/minute. The area
under the load-elongation curve is measured by an Instron
integrator which is described in Instron Manual No. 10-1-1 (C). The
reading from the integrator is converted directly into work, or
energy by the following formula:
E = X/5,000 (l) (s) (units in inch-pounds) wherein:
E = wet-cross-direction energy absorption level in inch-pounds,
l = full-scale load in pounds (this value is set on the Instron
tensile tester),
s = rate of sample extension in inches/minutes, and
X = the integrator reading.
The integrator reading is divided by 5,000 because the full-scale
integration carried out for 1 minute results in a count of 5,000,
and we are concerned with the fraction of this full-scale
integration which results from testing the specific specimen.
Therefore, the energy absorption level is the amount of work which
can be absorbed by a 1-inch specimen under the above-described test
conditions prior to breaking of the specimen, and all values of
energy absorption level set forth in this application are
calculated values resulting from the data obtained in the
above-described test.
CALCULATION OF FLUID PERMEABILITY
The permeability, K, in darcies, is determined by placing a 21/8
inch diameter sample consisting of five plies of the material to be
tested between a pair of 21/8 inch diameter porous screens. The
porous screens utilized in this test are manufactured by Perforated
Products, Inc., 68 Harvard St., Brookline, Mass., and are
identified as "30 G." Each perforated screen has the following
specifications:
Number of openings -- 30/lineal inch
Whole diameter -- 0.024 inch
Plate thickness -- 0.0028 inch
Percent Open area -- 50 percent.
The dry basis weight of the five-ply sample, and the dry thickness
is determined prior to disposing the sample between the screens.
Five plies of material are utilized to insure a greater accuracy in
the testing procedure, than if only one ply is utilized. The
sample-screen assembly is inserted into a 21/8 inch diameter
tubular vessel, and disposed on a bottom supporting surface
thereof. The region of the bottom surface of the vessel underlying
the sample-screen assembly is porous, and a water inlet is disposed
adjacent the bottom surface of the tubular vessel to pass water
through the sample-screen assembly. After the sample is saturated
with water, the thickness of the specimen is adjusted to the
previously determined original dry thickness of the sample by
compressing the specimen-screen assembly with a foot extending from
a caliper from which the thickness can be directly read. The
caliper is adjusted for screen thickness to permit an accurate
setting of the sample thickness by itself. A pressure head of 3
inches of water is created through the sample-screen assembly, and
water is passed through said assembly and exits through an outlet
nozzle where it is collected in a graduated container over a known
increment of time to determine the flow rate of the water through
the sample-screen assembly. The pressure drop across the screens as
a function of flow rate is determined prior to disposing the
specimen between the screens, and the appropriate pressure drop
across the screens is subtracted from the preset pressure head of 3
inches to thereby calculate the pressure drop across the sample
itself. The permeability, K, in darcies, is calculated from the
following formula:
K = q .eta. L / [ A .DELTA. P - .rho. g L ]
where:
q = flow rate (centimeters.sup.3 /second)
.eta. = viscosity of water (poise)
L = sample thickness (centimeters)
A = area of sample (centimeters.sup.2)
.DELTA.P = pressure drop across the sample
(dynes/centimeters.sup.2)
.rho. = density of the sample (grams/cubic centimeter)
g = acceleration due to gravity (centimeters/seconds.sup.2)
All tests were run with water since water is more readily available
than urine, and because water has a viscosity which is extremely
close to that of urine, and therefore, behaves very similar to
urine. The viscosity of water is approximately 0.01 poise, whereas
the viscosity of urine is approximately 0.008 poise. All values of
fluid permeability, K, which are set forth in this application
relate to the calculated fluid permeabilities predicated on the use
of water, rather than urine.
* * * * *