U.S. patent number 3,729,005 [Application Number 05/111,229] was granted by the patent office on 1973-04-24 for disposable diaper.
This patent grant is currently assigned to International Paper Company. Invention is credited to Charles A. Lee, Frank D. Sorrells.
United States Patent |
3,729,005 |
Lee , et al. |
April 24, 1973 |
DISPOSABLE DIAPER
Abstract
A disposable diaper of generally rectangular outline having
longitudinal and transverse directions including a pad of absorbent
matter encompassed by a cover sheet comprising a laminated nonwoven
fibrous fabric including fibrous web plies having respective
longitudinal directions, the web plies being reinforced in their
respective longitudinal directions and bonded in superposed
relation with their respective longitudinal directions at angle to
each other and at angle to the longitudinal direction of the diaper
thereby reinforcing the diaper at angles to its longitudinal and
transverse directions. The diaper includes wing folds extending
longitudinally along the side edges of the diaper to provide a seal
around the legs of the child and prevent body exudate from passing
outwardly of the diaper in the vicinity of the legs. In one aspect
of the inveniton, fibers of the web plies are bonded to the
reinforcing medium in a manner such that the fibers are retained in
the fabric cover sheet and do not become dislodged to deposit upon
the child or other surface even though the diaper becomes wet and
is subected to abrasion in the course of normal movements of the
child. The desirable absorptivity of the fibrous webs is retained
in the product.
Inventors: |
Lee; Charles A. (Knoxville,
TN), Sorrells; Frank D. (Knoxville, TN) |
Assignee: |
International Paper Company
(New York, NY)
|
Family
ID: |
22337285 |
Appl.
No.: |
05/111,229 |
Filed: |
February 1, 1971 |
Current U.S.
Class: |
604/366; 604/378;
604/371; 604/375 |
Current CPC
Class: |
A61F
13/53418 (20130101); A61F 13/49406 (20130101) |
Current International
Class: |
A61F
13/15 (20060101); A61f 013/16 () |
Field of
Search: |
;128/284,287,290 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Rosenbaum; Charles F.
Claims
1. A disposable diaper of rectangular outline having longitudinal
and transverse dimensions comprising a pad of absorbent matter, a
cover sheet encompassing said pad to form an encompassed
assemblage, the opposite side margins of said encompassed
assemblage being folded along longitudinal fold lines inwardly
toward the longitudinal centerline of said assemblage and further
folded along longitudinal fold lines back upon themselves to define
wing folds extending along the opposite side edges of said diaper,
said cover sheet comprising laminated nonwoven fabric having
longitudinal and transverse directions including a first web ply, a
first ply of discrete linear reinforcements aligned generally in
the longitudinal direction of said first web ply and bonded thereto
to reinforce it in its longitudinal direction, a second web ply, a
second ply of discrete linear reinforcements aligned generally in
the longitudinal direction of said second web ply and bonded to
said second web ply to reinforce it in its longitudinal direction,
each of said web plies comprising creped tissue having a basis
weight between about 5 and about 10 pounds per 2,880 square feet
and a crepe ratio between about 1.2 and about 1.5, said first and
second web plies being bonded together and disposed with their
longitudinal directions crossing each other and directed obliquely
with respect to the longitudinal and transverse directions of said
fabric, said reinforced directions of the respective plies of said
fabric being disposed at angle to the longitudinal direction of
said diaper, said reinforcements being spaced apart on a respective
web ply by a distance about twice the usual fiber length of the
fibers of said webs and extending into substantially all areas of
said diaper and being bonded one to another at their crossings to
develop a system of interconnected reinforcements defining regions
between adjacent interconnected filaments encompassing fibers
therein which are bonded to not more than one reinforcing filament
leaving substantial portions of such fibers free to work as the
diaper is stressed.
2. The disposable diaper of claim 1 wherein said pad of absorptive
matter terminates inwardly from the side edges of said cover sheet
by an amount such that when said encompassed assemblage is folded
into wing folds from the side edges of said cover sheet said pad is
included in the first fold of each wing fold and the upper fold of
each of said wing folds is free of said pad thereby reducing the
transport of fluid exudate into said upper fold.
3. The disposable diaper of claim 1 wherein said linear
reinforcements are extensible and when said diaper is stressed,
said creped webs extend to absorb the initial stress and said
linear reinforcements assume the stress as the webs approach their
rupture stress, thereby providing a strong extensible nonwoven
diaper.
4. The disposable diaper of claim 1 wherein said linear
reinforcements of said webs are spaced apart from one another by a
distance such that when said reinforcements are bonded to said webs
many of the fibers of each web are bonded to at least one
reinforcement and thereby are retained adhered to said
reinforcement and are not dislodged from said diaper even though
said fibers become loosened from their respective web.
5. The disposable diaper of claim 1 wherein said quantity of
absorptive matter terminates inwardly from opposite ends of said
diaper to leave said encapsulating cover sheet free of such
absorptive matter in the regions thereof which encircle the waist
when said diaper is worn.
6. The disposable diaper of claim 1 and including a moisture
barrier substantially coextensive in length and breadth as said
absorptive matter and interposed between said absorptive matter and
said cover sheet on that side of said absorptive matter opposite
the side thereof which receives liquid exudate.
7. The disposable diaper of claim 6 wherein said moisture barrier
is impervious to fluid body exudates.
8. The disposable diaper of claim 7 wherein said moisture barrier
comprises a plastic sheet.
9. The disposable diaper of claim 6 wherein said moisutre barrier
is pervious to air to permit significant transfer of air
therethrough and limitedly pervious to liquid body exudates thereby
restricting the transfer of such exudates whereby said cover sheet
receives a limited amount of wetting during the interval between a
period of discharge of body exudate into the diaper and its
subsequent removal from the body of the wearer and does not become
wet to the touch.
10. The disposable diaper of claim 9 wherein said moisture barrier
comprises a cellulosic sheet including a water repellent.
11. The disposable diaper of claim 1 and including an adhesive
bonding said plies one to another in superposed relation.
12. The disposable diaper of claim 1 wherein said filaments are
thermoplastic and said plies are bonded one to another by heating
said filaments while said plies are in superposed relation.
13. The disposable diaper of claim 1 wherein said filaments
comprise nylon of about 40 denier per filament.
14. The disposable diaper of claim 1 wherein said plies of linear
reinforcements each comprise a plurality of spaced apart lines of a
thermoplastic which are aligned generally parallel to the
longitudinal direction of the respective web ply.
15. The disposable diaper of claim 14 wherein said lines of
thermoplastic are spaced apart of the order of five lines per inch
of web width.
Description
This invention relates to disposable diapers.
Disposable diapers, in general, serve as throwaway replacements for
the common cloth diaper. For a disposable diaper to be attractive
to the consumer, it should exhibit the physical properties of a
cloth diaper and be available at a low cost approximating the cost
per use of the conventional cloth diaper which may be washed and
reused many times.
Whereas low cost materials such as loosely felted cellulosic fluff
possessing acceptable absorbency characteristics have been
available and used in the manufacture of disposable diapers, such
materials possess minimal tensile strength and tend to disintegrate
when wet and hence must be supported in position within the diaper.
Creped tissue which is desirable as a cover sheet has a low wet rub
resistance and when the diaper becomes wet and the child is active,
the cellulosic tissue may fragment and deposit objectionable
cellulosic matter on a child's body.
In another aspect of diapers, the usual procedure for securing a
diaper on a child is to fold opposite ends of a diaper about the
child's waist and pin opposite corners of the diaper to each other
as is well understood. Particularly in the pinning area, it is
desirable to have high strength so that the diaper may be pulled
and held snugly against the child's body.
Accordingly, it is a general object of the present invention to
provide an improved disposable diaper. It is also an object to
provide an improved cover sheet for a disposable diaper. It is a
still further object to provide a cellulosic disposable diaper
wherein the cellulosic fibrous matter thereof resists abrasion and
fragmentation, especially when wet.
Other objects and advantages of the invention will be apparent from
the following description with the accompanying drawings in
which:
FIG. 1 is a representation of a diaper depicting various features
of the invention;
FIG. 2 is a representation showing one manner of folding the cover
sheet of the disclosed diaper;
FIG. 3 is a sectional view taken along line 3--3 of the diaper
shown in FIG. 1.
FIG. 4 is a representation of one type of laminated reinforced
nonwoven fabric employed to make the diaper cover sheets disclosed
herein;
FIG. 5 is a fragmentary sectional view taken along line 5--5 of the
fabric shown in FIG. 4;
FIG. 6 is a fragmentary representation, partly cut-away, showing
the web and filament plies of the laminated fabric of FIG. 4;
FIG. 7 is a fragmentary representation showing the bonding of web
fibers to the reinforcing filaments of the fabric of FIG. 4;
FIG. 8 is a sectional view of the disclosed diaper wherein the
absorbent pad is provided with additional material in its central
portion and showing a diaper having no pad material in the wing
folds and including a water repellent in a portion of the cover
sheet in the wing fold areas; and
FIG. 9 is a sectional view of the disclosed diaper having a
moisture barrier included therein.
Broadly stated, the diaper disclosed herein is of the disposable
type and fabricated of low-cost materials. The diaper is of
rectangular outline and includes a pad of absorbent matter
encompassed by a cover sheet comprising a laminated fabric
including a plurality of creped cellulosic tissue web piles
reinforced in their respective longitudinal directions by means of
one or more plies of reinforcing matter and bonded in superposed
relation with their respective reinforced directions at an angle to
each other and to the longitudinal direction of the laminated
fabric. As a cover sheet, this reinforced laminated fabric,
referred to herein at times as "reinforced bias laid" fabric or
cover sheet, is disposed with its longitudinal direction aligned
with the longitudinal direction of the diaper thereby placing the
reinforced directions of the plies at angle to the longitudinal
direction of the diaper and reinforcing the diaper at angles to its
longitudinal direction. As illustrated in accompanying drawings,
the diaper is folded along its longitudinal side margins with wing
folds which gather the diaper in its central section to cause it to
conform to the crotch of the child and which expands in its end
portions to provide areas suitable for encompassing the waist of
the child and providing overlapping portions for pinning to secure
the diaper in position on the child.
The preferred reinforcing provided each of the web plies of the
laminated fabric comprising the cover sheet serves also as anchor
points for the fibers of the web plies thereby increasing the wet
rub resistance of the diaper and substantially eliminating the
prior art problem of cover sheet fragmentation and resultant
adhesion of tissue to the body of a child.
Bonding of the several plies of tissue one to another and anchoring
of the fibers to the reinforcing matter is achieved without
deleterious loss of absorptivity of the diaper materials thereby
creating a diaper capable of satisfactorily receiving and retaining
exudates.
With reference to FIGS. 1 and 3, one embodiment of the diaper 10
disclosed herein is of rectangular outline having a longitudinal
central portion 12 flanked by longitudinal wing folds 14, 16
extending parallel to the central portion 12 on opposite sides
thereof and coextensive in length with the longitudinal dimension
of the diaper.
As depicted in FIG. 2, the illustrated diaper is assembled by
depositing a pad 22 of absorbent loosely felted cellulosic matter
in the approximate center of a cover sheet 24 and subsequently
folding the side edges 26, 28 of the cover sheet inwardly of the
diaper and overlying the pad 22 thereby causing the coversheet to
envelop the pad. These side edges 26, 28 are preferably folded
along fold lines A, B which are spaced inwardly toward the
centerline of the cover sheet 24 to provide sufficiently wide side
edge portions as will cause the folded cover sheet to fully overlie
the pad and overlap sufficiently to assure complete encirclement of
the pad and prevent the cellulosic matter comprising the pad from
escaping even though the overlapped edges are not held in position
by an adhesive or similar sealing means. Alternatively the side
edge portions of the cover sheet overlap only a small amount and
are secured in position by a seam formed of an adhesive or as by
the application of sufficient heat and/or pressure to glassine, and
thereby seal, the overlapping edges of the cover sheet. This latter
alternative is useful in reducing the quantity of cellulosic matter
employed in the cover sheet and thereby reducing the overall cost
of the diaper, consideration being given to the cost involved in
making the seal along the overlapped edges of the cover sheet.
In a continuous diaper manufacturing process, it is advantageous to
utilize a cellulosic carrier sheet 30 of slightly greater width
than the pad for receiving the pad. This carrier sheet 30 is
disposed between the pad and the cover sheet 24 with the pad 22
being deposited on the carrier sheet 30 as illustrated. The ends of
the enveloped assemblage are sealed as by embossments 32, 33 (FIG.
1) to prevent the loss of cellulosic pad matter from the ends. The
assemblage is folded with the wing folds 14, 16 which extend
longitudinally along the side edges of the diaper to bring the side
margins of the diaper toward the longitudinal center of the diaper
and thereby accumulate the diaper into a relatively narrow
configuration in the central part thereof. This folded central part
of the diaper is comfortably received in a child's crotch and the
folded end portions of the diaper are expandable to develop
portions of the diaper which encircle the waist of the child and
receive the pins that hold the diaper in position on the child's
body. Additionally, the wing folds in the central portion of the
diaper provide good contact with the child's legs and develop a
seal around the legs of the child to prevent body exudate from
passing outwardly of the diaper in the vicinity of the legs. In
this instance, the wing folds are formed by bringing longitudinal
side edge portions of the diaper inwardly toward the center of the
diaper. Each such folded side edge portion extends inwardly of the
diaper a distance less than about one-third the width of the diaper
to form a first longitudinal fold along each side of the diaper. As
thus folded, each longitudinal side edge of the diaper overlies the
longitudinal central portion of the diaper and extends the length
of the diaper. Each of these first folds is next folded back upon
itself to form a second fold extending along the length of the
diaper and overlying the first fold, thereby providing two folds
34, 35 and 36, 37 (FIG. 3) in each wing fold 14, 16, respectively,
overlying the marginal edges of a central portion 12 of the diaper.
Herein, the first folds 35 and 37 are secured to the underlying
center portion to cause the folded diaper to retain its folded form
at least while the diaper is being secured to the child's body
thereby insuring that the accumulated configuration of the central
portion of the diaper comfortably and snugly resides within the
child's crotch and in position to efficiently receive body exudate.
These first folds 35 and 37 preferably are held in their folded
position by points of bonding 38, 39 (FIG. 1) located generally
centrally of the fold, i.e. medially of both the longitudinal and
transverse dimensions of each fold. Spot embossures made with
sufficient pressure to glassine the cellulose have been found
effective to hold the folds 35 and 37 in place. Spots of adhesive
have also been found suitable for this purpose but may be less
desirable in a manufacturing operation.
In the folded diaper illustrated in FIG. 3 in cross section, it is
shown how that, by appropriate selection of the width of the
cellulosic pad 22 and by folding the diaper in wing folds as noted
above, the diaper may be provided with the desired absorptive
matter thereof disposed in the central portion of the diaper and in
the first folds 35, 37 of the wing folds 14 and 16, respectively.
When the illustrated folded diaper is pinned in position on a
child's body the upper folds 34 and 36 of the wing folds 14 and 16,
respectively, encircle the child's legs and secure the diaper
against leakage of exudate in this region. These upper folds, being
unattached to the lower folds 35, 37 permit the absorptive central
portion of the diaper to fall somewhat free of the child's body
thereby forming a type of receptacle whose walls comprise the
absorptive matter of the cellulosic pad 22. This type of cellulosic
receptacle receives the body exudate and efficiently absorbs the
exudate to draw it away from the child's body and maintain it
therein and away from the child's body to reduce the possibility of
irritation due to prolonged contact between the child's body and a
soiled diaper. Both of the folds 34, 35 and 36, 37 of each wing
fold 14 and 16, respectively, are spot bonded to the underlying
central portion 12 of the diaper when it is desired to maintain the
wing folds more completely in their folded state.
A cover sheet 24 for the illustrated diaper comprises a soft,
strong, reinforced, nonwoven fabric as depicted in FIGS. 4-6, which
encompasses the relatively weak absorbent pad 22 and imparts
strength, integrity and shape to the diaper. In accordance with one
aspect of the invention, this fabric 32 includes a plurality of
reinforcing filamentary plies 41, 42 interposed between outer web
plies 44, 46, the several plies being bonded to at least adjacent
plies to develop a coherent fabric whose reinforced plies are
oriented at an angle of between about 60.degree. and about
90.degree. to each other and at an angle of between about
25.degree. and about 45.degree. to the transverse direction of the
fabric, i.e. perpendicular to the machine direction of the fabric,
which is also the longitudinal direction thereof in the
accompanying drawings. One method for manufacturing the fabric
includes bonding a plurality of strong reinforcing filaments to a
tissue web with the filaments generally aligned with the machine
direction of the web, simultaneously spirally winding two such
filament-bearing webs 48 and 50 (FIG. 4) into a tubular
configuration with the webs overlapping along their side margins
52, 54, respectively, and collapsing the tube to form a flat sheet
comprising inner plies 41, 42 of crossing filaments interposed
between outer web plies 44, 46 whose machine directions are
disposed at an angle, e.g. obliquely, with respect to the
longitudinal direction (i.e. machine direction) of the fabric 40.
The cross filaments and/or the overlaid webs are bonded one to
another to impart integrity and strength to the fabric. When
spirally wound, the superposed web plies preferably are disposed
with their reinforced longitudinal directions at an angle of about
80.degree. to each other thereby positioning the reinforced
directions at an angle of about 40.degree. to the longitudinal
direction and at an angle of about 50.degree. to the transverse
direction of the resultant fabric. Smaller angles of crossing of
the filaments are acceptable but result in increased usage of raw
material (more reinforced web per linear foot of fabric product).
Angles of filament crossing greater than about 90 degrees are
generally undesirable from a manufacturing standpoint and normally
no strength advantage is obtained through the use of such larger
angles of filament crossing.
Creped cellulosic tissue is preferred as the material for the web
plies 38, 40 of the cover sheet 24. One acceptable web is creped
cellulosic tissue having a crepe ratio of between about 1.2 and 1.5
and a basic weight between about 5 and 10 pounds per ream of 2,880
sq. ft. Other weights of cellulosic tissue webs are suitable,
however, as the weight is increased the softness and hand of the
product decrease. Crepe ratios of the individual cellulosic tissue
webs greater than about 1.5 are acceptable but are not necesary to
produce a diaper having the improved qualities referred to herein.
Typically, the fibers in the creped tissue have a length between
about one thirty-second and one-eighth inch, but other fiber
lengths are acceptable for use in the web plies of the present
diaper covers.
As noted hereinbefore, the creped tissue webs generally possess low
resistance to rupture, at least in the cross direction, but are
soft, pliable, relatively inexpensive and possess desirable
absorptivity characteristics. Each web presents a relatively even
surface irrespective of the creping of the respective web fibers
and when serving as an outermost layer of the fabric imparts good
hand to the fabric.
Each of the web plies 44, 46 of the cover sheet illustrated in
FIGS. 4-6 is reinforced with discrete filaments 52 aligned
generally parallel to the longitudinal direction of the web prior
to its incorporation into the fabric 40 so as to impart strength to
the web ply. Synthetic filaments, particularly those which possess
thermoplastic properties such as the polyester and polyamide resins
in filament form, have been found suitable as reinforcements.
Mineral filament, such as glass filaments, provide strength when
employed as reinforcements but lack the degree of stretchability
displayed by the resin filaments. Each filament 52 of a given ply
is preferably spaced apart from adjacent filaments within the same
ply without interfilament contact, but a filamentary mat having
entanglement or contact between the individual filaments thereof,
such as an expanded tow web, is likewise suitable for reinforcing
the web ply. In any event, the reinforcing filaments 50 of a web
ply are bonded to the respective web ply to insure the desired
enhancement of the web strength. This bonding is accomplished by
means of an adhesive 54 disposed between the web and filaments, or
in some instances, the filaments are heat-bondable to the web so as
to require only the application of heat to effect the desired
bonding.
In one method for bonding the individual filaments 52 to a base
web, the individual filaments are passed over a smooth-surfaced
printing roll which is provided with a film of adhesive on its
outer surface so as to transfer a quantity of adhesive from the
roll to each filament. Preferably, the thickness of the film on the
printing roll is maintained sufficiently great so that a filament
passing over the roll in contact therewith will be completely
covered with adhesive and pick up a uniform coat of adhesive. The
adhesive-bearing filaments are laid down, preferably in a
continuous fashion, upon a base web and subsequently directed to a
heating station maintained at a temperature at least as high as the
film-forming temperature of the adhesive to insure that the
adhesive thoroughly coats each filament and also to cause the
adhesive to migrate from each filament into the web. As the web and
adhesive-bearing filaments pass through the heating station, the
adhesive is at least partly dried and filaments adhered to the
web.
Adhesive migration laterally from each filament and contact between
the adhesive and individual fibers of the web is depicted in FIG.
7. Preferably, the adhesive is of a type which will not penetrate
the fibers to destroy their absorptivity but will remain as a film
on the portion of the outer fiber surface. Moreover, control over
the quantity and viscosity of the adhesive deposited on each
filament is maintained so as to limit the lateral migration of the
adhesive and prevent substantial blocking of the interstices
between fibers with resultant stiffness in the fabric and
destruction of its softness and absorptivity. A film of adhesive
over the entire surface of each filament assures that presence of
adhesive at each filament-to-filament intersection when the
reinforced web is bias-laid, and hence insures a bond at each such
intersection. One suitable adhesive is an acrylic latex adhesive
sold by B. F. Goodrich Company under the trade name of Geon
Latex.
The individual reinforcing filaments 52 preferably are generally
aligned in a single direction and are bonded to their respective
web ply with their alignment direction substantially parallel to
the machine direction of the creped tissue web ply. The filaments
thus are disposed generally perpendicular to the lines of creping
56, 58 of their respective web ply. The reinforcing filaments thus
reinforce the creped tissue and strengthen it in its machine
direction. When the reinforced creped tissue subsequently is
overlaid upon itself or upon another reinforced web with the
respective directions of increased strength disposed obliquely to
each other, and obliquely to the longitudinal direction of the
fabric product, the resultant multi-ply fabric exhibits generally
omnidirectional improvement in strength. The fabric 40 (see FIG. 4)
is divided transversely thereof as at lines D, E, F and G into
cover sheets 24 for individual diapers.
The omnidirectionally improved strength of the fabric is
transferred to a diaper when the fabric is used as the cover sheet
of the diaper in the manner disclosed herein. When the cover sheet
24 is folded about the pad 22 to envelop the pad and form a diaper
of rectangular outline, the strong reinforced longitudinal
directions of the web plies of the cover sheet are aligned at angle
to the longitudinal and transverse directions of the resultant
diaper, thereby developing a diaper which is of generally
omnidirectionally improved strength. Specifically, the cover sheet
of the resultant diaper is divided into many relatively small
interconnected squares or diamond-shaped regions 60 (FIG. 6) whose
peripheries are defined by the cross linear reinforcements 52. The
reinforcements are bonded to one another at their crossings and to
at least their adjacent web ply. Substantial area of fibrous web
ridges each such square or diamond-shaped region 60, the individual
fibers of such web region being bonded to a reinforcement as by an
end of a fiber being joined to a reinforcement, leaving substantial
portions of the fibers free to work as the diaper is stressed first
in one direction then in another direction as a child moves. The
fibers are held against separating when stressed beyond their
ability to remain interlocked within the web by reason of the
strong interconnected reinforcements to which the fibers are
bonded. Because individual ones of the reinforcements extend at
angle to both the longitudinal and transverse direction of the
diaper, the diaper itself exhibits improved resistance to rupture
when stressed at an angle to its longitudinal or transverse
direction. When the diaper is stressed in a direction generally
parallel to its longitudinal or transverse direction, the
interconnected reinforcements articulate about their bonded
crossings and combine in function to reinforce the diaper in these
latter directions, thereby providing a diaper which strongly
resists rupture irrespective of the directionality of the applied
stress. When a diaper is pinned in position on a child's body and
the child subsequently engages in normal body movement and
activities, the diaper is subjected to stresses in many and varied
directions. These stresses, of course, also vary in magnitude over
a wide range. In the present diaper, the reinforcements extend into
all areas of the diaper to provide strength in each area of the
diaper. Accordingly, the present diaper resists splitting in the
crotch area by reason of the reinforcements which extend at angles
to the longitudinal and transverse directions of the diaper. These
reinforcements and their generally omnidirectional strengthening
effect extend also into all other areas of the diaper such as in
the pinning areas where the diaper is strengthened against tears
and resultant falling away of the diaper from the child. The
present diaper, therefore, is strong in all areas thereof with its
strength being exhibited in many directions to withstand the many
and varied stresses to which it is subjected during normal use.
Preferably, the reinforcing filaments 52 are sufficiently small in
diameter as will permit their being disposed between two outer web
plies 44, 46 without producing undesirable ridges or impressions on
the outer surfaces of the fabric. Larger diameter filaments may be
used with an accompanying degradation in surface characteristics.
Nylon filaments each of about 40 denier have been found
satisfactory as reinforcing filaments for creped tissue webs of the
kind referred to hereinbefore. Such nylon filaments normally
exhibit an extensibility of about 8 percent thereby imparting a
degree of elasticity to the strengthened diaper and causing it to
more nearly exhibit the desirable extensibility found in the woven
diapers and which contributes to the soft hand of the diaper. Less
elasticity is obtainable through the use of mineral fibers or
certain of the organic synthetic fibers but the resultant diaper
posseses a less desirable hand. A diaper having a cover sheet
fabricated from creped tissue webs reinforced with nylon filaments
as disclosed herein exhibits extensibility and strength
characteristics which indicate that the creped webs initially
absorb applied stress by extending toward their uncreped lengths.
The stronger nylon filaments initially stretch with the creped webs
but before the webs reach their rupture stress, the nylon filaments
assume the stress and prevent failure of the diaper.
As illustrated in FIG. 7 and described hereinbefore, many of the
individual fibers 62, 64 of the respective web plies are adhered to
the respective reinforcing filaments 52 which are bonded to the
respective web plies. As indicated above, preferably the aligned
reinforcing filaments are spaced apart from one another on a
respective web ply. The filaments, however, are sufficiently close
to one another to permit many of the fibers of the respective web
ply to be bonded to the filaments. In one embodiment, the
interfilament spacing is not greater than of the order of the
typical fiber length of the fibrous web ply plus about twice the
average distance which the adhesive extends laterally of each
filament into the web ply. Thus substantial numbers of individual
fibers of a web ply will be adjacent at least one of its
reinforcing filaments and be bonded thereto, creating a desirably
coherent fabric. Creped tissue webs provided with between about 5
and 10 40-denier nylon filaments per inch of web width are
sufficiently reinforced for producing a diaper having the strength
referred to herein and provide sufficiently closely spaced
filaments for anchoring many of the fibers of the web. As a result
of the preferred fiber to filament bonding pattern, the fibers
remain secured to a filament even when the fiber to fiber
interlocking bond is broken due to overstressing of the diaper
beyond the tensile strength of an individual web ply. Consequently,
when the diaper becomes wet and is stressed locally by the child's
movements, fibers which are caused to separate from other fibers in
their respective web do not become dislodged from the diaper but
instead are retained, attached to a filament. The surface of the
diaper thus does not fragment with the deposition of fibers on the
child or upon floors, bedding or the like. Since many of the
individual fibers of a tissue web ply are bonded to at least one of
a plurality of the reinforcing filaments, the individual fibers
remain adhered to such filaments upon the fabric 40 being subjected
to rupture or abrasive forces. As noted above, the individual
fibers of each tissue web ply tend to remain attached to the
reinforcing filaments even when the diaper is wet.
It is preferred to space the reinforcing filaments 52 as set forth
above, but fabrics having fewer reinforcing filaments per unit of
web width are acceptable in certain instances. Such fabrics are
weaker, however, and exhibit increased tendency to deposit lint,
etc. Moreover, it is acceptable to overlay two reinforced web
plies, one web ply having closely spaced reinforcing filaments
(e.g. about one fiber length apart) and the other web ply having
more widely spaced filaments.
In accordance with a further aspect of the invention, the outer web
plies of the cover sheet fabric are each reinforced in their
respective longitudinal directions by means of a plurality of lines
of thermoplastic matter. These lines of thermoplastic are similar
to the individual filaments 52 described hereinbefore in that
preferably they are disposed on each of the web plies and the
reinforced web plies are superposed with the thermoplastic lines
facing each other and crossing one another at an angle, the several
plies being bonded to at least adjacent plies to develop a coherent
fabric whose reinforced plies are oriented at an angle to each
other and at angle to the longitudinal and transverse directions of
the fabric as is shown in FIGS. 4-7 in connection with filamentary
reinforcements.
One method for manufacturing a fabric reinforced with lines of a
thermoplastic includes printing a plurality of continuous lines of
thermoplastic such as a polyvinyl chloride onto a creped tissue web
of the kind described hereinbefore as the web is fed forwardly
between the nip between a smooth roll and a printing roll having a
plurality of thermoplastic-bearing circumferential projections on
its exterior surface so as to transfer the thermoplastic to the
tissue web in the form of a plurality of generally parallel lines
of thermoplastic extending along the longitudinal direction of the
web. The preferred lines of thermoplastic are of the order of 0.050
inch in width. Preferably, about 15 grams of the thermoplastic are
picked up on each 100 grams of web when printing five lines of
thermoplastic per each inch of web width. Whereas five lines of
thermoplastic per inch of web width is preferred, other lateral
spacings are suitable, as are other rates of thermoplastic pick-up,
consistent with maintaining the desired tactile properties in the
product, particularly its hand, strength and absorptivity.
The thermoplastic, when applied to the web in its liquid state, is
solidified as by curing or drying as appropriate for the chosen
thermoplastic. Because the thermoplastic is heat-bondable, the
biased superposed web plies having their respective plies of
thermoplastic facing inwardly of the multi-ply product, are bonded
in their mutually angular orientation by passing the superposed
plies through a heated nip to enhance the adhesion of the fibers of
the webs to the lines of thermoplastic. The reinforced web may be
overlaid on itself or another reinforced web as described
hereinbefore. The lines of thermoplastic on the overlaid webs are
bonded to each other at their crossings as by passing the overlaid
webs through a set of heated nip rolls. The bonded reinforced webs
provide a coherent fabric useful as a diaper cover sheet as noted
before. The strength of this latter described fabric when
incorporated into a diaper as a cover sheet, is normally less than
the strength of diapers having cover sheets whose web plies are
reinforced with filaments; however, the thermoplastic reinforcing
matter is less expensive and is useful in producing diapers which
exhibit many of the desirable properties referred to herein in
connection with filament-reinforced diapers.
In the illustrated fabrics, the reinforcing matter of the
respective reinforcing plies are bonded to their respective web
plies and the reinforcing matter of one ply is bonded to the
reinforcing matter of the other ply at the points where the
reinforcements cross. This bonding at the cross-overs securely
interconnects the reinforcements, and consequently their respective
web plies, at spaced points throughout the respective fabric to
develop a network of crisscrossing strengthening elements within
the fabric which makes the fabric much stronger with less bulk than
if an equal number of web plies were laminated. Being bonded to one
another at only their crossings, the strengthening reinforcements
articulate about their crossover bonds to give the laminated fabric
flexibility which carries over into the diaper causing it to
display many of the tactile properties of a cloth diaper. Contrary
to certain prior art diaper constructions wherein the components
contributed significantly toward increasing the weight and bulk of
the fabric and the resultant diaper, the multi-ply fabrics
disclosed herein comprise a combination of tissue webs, each having
a substantially continuous surface for reasons of hand, integrity
and pleasing appearance, and a plurality of reinforcing plies
preferably disposed between the web plies and strengthening the web
plies without undesirably adding to the weight, stiffness, and bulk
of the diaper. As disclosed, the spaced-apart reinforcements of
each reinforcing ply reinforce the web plies while leaving
significant areas of tissue between reinforcements free of
reinforcing matter. Accordingly, the illustrated reinforced fabric
strengthens the diaper in its several directions as has long been
desired, but does not adversely affect the drape and hand
characteristics thereof. In addition, the expanses of tissue web
between the reinforcements are substantially free of adhesive and
the fibers of the web in such regions readily accept liquid exudate
and rapidly transmit the liquid matter to the absorbent pad of the
diaper where it is retained. The illustrated reinforced cover sheet
provides the desired improvement in strength and tactile properties
while employing a minimum number of web plies thereby reducing any
tendency toward blocking the transfer of liquid exudate to the
internal absorptive pad by the more dense web plies, particularly
when such web plies are multi-plies excessively. Economically, the
present diaper is stronger and has good absorptivity while
utilizing less raw material in its manufacture.
The absorptive pad 22 of the diaper 10 illustrated in FIG. 3 is of
constant cross section throughout its longitudinal length. To
enhance an efficient reception and retention of body fluids, the
pad 22 in the exemplary embodiments of FIGS. 8 and 9 each are
provided with a non-uniform cross-sectional configuration having
the longitudinally extending portion 66 of greater thickness than
flanking side portions 68, 70. For example, the central portion 66
is approximately one-quarter inch in thickness while the outer
portions 68, 70 are approximately one-eighth inch in thickness.
Thus, the central portion has an increased fluid retaining capacity
as compared to the central portion of a pad of uniform
cross-sectional configuration and, generally speaking, fluid will
flow to the side edges of the diaper only when this capacity is
exceeded.
In the preferred diaper 10, the child's skin is protected against
lint emanating from the wood pulp pad 22 by the bias laid cover
sheet 24. Also, the cover sheet protects against the loss of fluid
and absorbent pad material which tends to disintegrate when wetted.
As large quantities of fluids are received over a short period of
time, they rapidly penetrate the upper central portion 12 of the
cover sheet and are absorbed and spread by the pad 22. The wing
folds 14 and 16 form effective seals about the child's legs and
thereby prevent the escape of fluid from about the child's legs.
The lower portion of the bias laid cover sheet also assists in
preventing the fluids from "striking through" the diaper. Because
of the increased strength provided by the bias laid cover sheet the
diaper is protected against failures which reduce the effective
absorptive capacity of the diaper. Thus by assuring against
failures, the amount of absorbency can be closely approximated and
it is possible to eliminate excessive fibers or plies of material
heretofore added to increase the diaper strength.
Whereas suitable diapers have been made using pads of loosely
felted wood fibers, enhanced lateral distribution of body fluids
has been accomplished by embossing a plurality of intersecting
channels 72 in the pad 22, preferably prior to enveloping the pad
with the cover sheets as shown in FIG. 2. Alternatively, the diaper
is embossed with such intersecting channels after the side edges of
the cover sheet have been folded inwardly to overlie the pad and
prior to folding of the wing folds 14, 16. Body fluids received in
the diaper flow along the channels 72 in bulk quantities thereby
rapidly distributing the fluids to the absorptive pad and causing
the fluids to be quickly taken up by the pad.
A still further feature of the diaper disclosed herein includes
selective disposition of the absorbent cellulosic matter within the
diaper for controlling the flow of exudate within the diaper. In
accordance with this additional feature, the highly absorptive pad
22, e.g. cellulosic fluff, is restricted to those areas of the
diaper 10 which are adjacent to the point of exudate discharge,
that is, the fluff is eliminated from the margins of the diaper,
thereby restricting the dispersion of the exudate to the central
area of the diaper. A diaper having this kind of pad is shown in
FIG. 8. Sufficient absorptive fluff is provided in such central
area 66 for receiving and retaining the anticipated exudate. The
reduction of absorptive capacity brought about by removing fluff
from the diaper margins is compensated by increasing the quantity
of fluff in the central region of the diaper as desirable. In the
margin areas of the diaper from which fluff is eliminated there is
no vehicle other than the cover sheet 24 for the transport of
liquid exudate into the margin areas and they remain relatively
free of liquid and retain their relatively greater dry strength,
resulting in a stronger diaper. Also in these areas of little or no
fluff or other highly absorptive matter, there is a reduction in
the quantity of exudate which is transferred to these areas and
resultant less leakage or strike-through of liquid matter in these
areas. When the usual fluff pad is eliminated in at least the top
fold of each of the longitudinal wing folds of the diaper, thus
limiting the flow of liquid exudate into these areas, there is an
accompanying reduction in the tendency of the diaper to leak in the
leg areas and less likelihood that a wet margin of the diaper will
contact and transfer moisture to items of outer clothing or bed
clothes.
Alternatively or in addition, the absorbent fluff is eliminated
from the ends of the diaper, that is, in the region often referred
to as the "belley band" of the diaper. Here again, the absence of
fluff reduces wicking, hence wetness, in the belly band and limits
the leakage of exudate in this area. The degree of wetness of the
diaper in the belly band is particularly important when the diaper
is worn by a child who is in a reclined position where soilage of
bed covering or the child's clothing could occur upon leakage of
exudate. The reduction of wetness in the belly band area also
permits retention of the relatively greater dry pinning strength of
the cover sheet in this area. With reference to the diaper pinning
strength, because of the increased strength provided by the bias
laid cover sheet, employed in the present diaper, particularly at
an angle of about 45.degree. to the transverse direction of the
diaper, the ends of the diaper may be fastened relatively tightly
and securely about the baby's waist by conventional fasteners such
as safety pins and, even when wet, the bias laid cover sheet
protects against failures occasioned by inordinate stressing of the
diaper in the pinning areas. Accordingly, in the illustrated diaper
there is less of the annoyance and frustration which heretofore
accompanied many of the prior art disposable diapers due to their
failure because of low pinning strength.
The diaper disclosed herein, having a reinforced bias laid cover
sheet, is made more resistant to the strike-through of liquid
exudate to the outer surface of the diaper by providing an internal
moisture barrier 74 within the diaper as illustrated in FIG. 9. A
preferred barrier 74 is a thin sheet of a plastic such as
polyethylene, the impervious plastic precluding leaking or moisture
transmission from the fluff pad through the cover sheet.
Accordingly, this barrier sheet is preferably dimensionally
coextensive with the fluff pad and disposed between the pad 22 and
cover sheet 24. In those diapers where a carrier sheet is used, the
barrier preferably is disposed between the carrier sheet and the
cover sheet.
Contrary to the harsh plastic outer liners heretofore used in
disposable diapers, the present plastic sheet moisture barrier is
disposed fully within the enveloping fibrous cover sheet.
Accordingly, the child's body is not exposed to the irritating
effects of the plastic and the diaper is more pleasing to both the
child and mother. The fabric cover sheet of the present diaper
provides a soft surface for contacting the child but exudate
discharged into the diaper is held within the diaper by the
absorptive matter and the impervious sheet. The inner plastic liner
is notably useful in preventing strike-through of exudate to the
outer surface of the diaper. When a child sits, lays, or falls to a
sitting position, etc., its body presses the diaper against the
supporting surface. If the diaper is wet, under such circumstances
there is a significant hydrostatic pressure developed which forces
liquid through the diaper such as would not occur by the usual
wicking and absorption mechanisms. The liquid impervious sheet
disposed between the fluff pad and cover sheet of the present
diaper blocks this movement of liquid toward the outer surface of
the diaper as a consequence of hydrostatic pressure.
Another useful barrier sheet material is a tissue web having a
water-repellent included therein. In this diaper assemblage there
is a controlled transfer of moisture to the outside of the diaper
which becomes damp rather than wet after a relatively extended
period of use. This damp condition signals that the diaper has not
utilized its full capacity and is more than adequate to the job.
But more importantly, the damp diaper as distinguished from a wet
diaper, eliminates the unpleasantness of handling a diaper that is
soaking wet on the outside. In addition, this assemblage offers the
convenience of putting a soiled diaper down without worrying about
contaminating the bed, furniture, floor covering or any other
surface where a diaper must temporarily be placed during the
process of replacing a soiled diaper. Still further, a soiled
diaper which is merely damp on the outside, as opposed to being
soaking wet, provides greater pleasantness and/or peace of mind
which comes from removing a diaper which does not feel wet on the
outside.
While the present description has included specific examples and
embodiments, it will be understood that there is no intent to limit
the invention by such disclosure, but, rather, it is intended to
cover all modifications and alternate constructions falling within
the spirit and scope of the invention as defined in the appended
claims. What is claimed is:
* * * * *