Note: Descriptions are shown in the official language in which they were submitted.
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LAYERED ABSORBENT PRODUCTS
Field of the Tnvents~n
The present invention relates to a multilayered
absorbent feminine hygiene product. In particular, it
relates to a stacked or layered product containing
individual absorbent pads which are releasably attached
one to another.
Backaround of the TnvA rinn
Absorbent products have long been used in feminine
hygiene products. Discretion in the use of these products
has been a goal of manufacturers and users alike.
Absorbent pads and napkins used for feminine hygiene
provide some specific capacity for absorbing body fluids.
Once soiled, a product must be replaced by an unsoiled
product. Unfortunately, a woman is not always at home or
otherwise conveniently near a supply of these absorbent
products, and it may be necessary for her to keep a
minimal supply of products with her. Thus, feminine
hygiene products have been manufactured to be carried
conveniently in a woman's purse or pocketbook. These
products have also been manufactured in convenient,
individual packages to keep the product clean until use.
However, more discrete ways to keep a ready supply of
feminine hygiene products handy are constantly sought.
Poulsen, U.S. Patent No. 2,929,379, suggested that a
woman might carry a supply of three sanitary napkins in a
sanitary napkin product having multiple layers. Aside
from the multiple layers of absorbent pads which made up
the sanitary napkin product, it incorporated cloth tabs
which extended from the front and rear of the absorbent
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pad which were secured to a belt. This belt was
separately worn about the user s waist. The use of the
belt in conjunction with sanitary napkins allowed the
napkins to be held closely to the user s body. The
5 plurality of absorbent layers of the Poulsen product are
stacked and attached in one general location proximate the
front of the sanitary napkin product. The back of the
upper individual layers was not anchored to the adjacent
layer. It was constrained only by the nature of the
belted product.
In more recent times, belted feminine hygiene
products have generally been replaced by products which
are releasably secured to a user s undergarments by means
of a layer or strip of pressure sensitive adhesive
disposed upon a garment-facing surface of the product. In
addition, new and thinner products, including thin
sanitary napkins and panty liners, have been developed.
Panty liners may be used for applications other than those
for which traditional sanitary napkins were designed.
These feminine hygiene products are substantially thinner
than conventional sanitary napkins and have a
substantially concentratedabsorbent volume. Thin
feminine hygiene products therefore, have less of the
absorbent fluff layer which helps to provide flexibility
to the product.
Most feminine hygiene products have a body-facing
absorbent side and a garment facing barrier side. A
pressure sensitive adhesive is generally disposed on the
garment facing side as oneor more lines to provide
attachment means to removably fix the product to the
garment. This pressure sensitive adhesive is protected
from contamination until use with a piece of release
liner. When the product is to be used, the user must
first remove the release liner and dispose of it. The
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disposal of a piece of release liner with each panty liner
increases the waste generated by the use of these
products. Thus, it is desirable to reduce the amount of
release liner used in conjunction with panty liners in an
era of increased environmental awareness.
Absorbent products have a finite absorbent capacity,
and they must be periodically replaced. Manufacturers
continue to search for products which are easily carried
by a user, are convenient and discrete. One solution is
discussed in Takao et al., Japanese Utility Model 5-177
(Y2), which discloses a panty liner product having three
single layers stacked and secured together. The bottom
panty liner has a conventional adhesive disposed for
positioning the product in the crotch area of a users
undergarment. Each remaining layer is releasably attached
to the layer below it in the stack by adhesive or
embossing (heat sealing) means. The Takao et al.
reference illustrates that the adhesive is to be applied
in two relatively small areas proximate the front and rear
ends of the layer, or adjacent layers may be embossed at
four discrete positions of the layers.
Additionally, Fuji Kikaku, Ltd, Japanese Utility
Model Application No 60-175230 (U), discloses a
multilayered sanitary napkin product having smaller pads
stacked on top of larger pads and secured with two
discrete strips of adhesive tape. Again, these strips are
at the ends of the pad layers.
After a substantial amount of research into the
problems associated in developing panty liners having
several removable absorbent layers, it has been discovered
that panty liners having only one local attachment point
between individual layers are susceptible to substantial
movement of the unsecured portions of the panty liner
layers. The forces acting on such pads tend to displace
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at least the topmost pad as the user moves. The
displacement allows the pad to intrude into the area
between the buttocks where it can be wedged, causing
discomfort and painful chafing. This movement presents a
major problem for users of thinner panty liners. Merely
adding a second minor spot of adhesive cannot guarantee a
firm attachment of the topmost panty liner through
intermediate panty liner layers to the user s
undergarment.
Using two small areas of adhesive spaced apart at the
ends of a panty liner pad presents an additional problem.
The adhesive may effectively attach adjacent pads at the
adhesive application sites, but the adhesive cannot always
prevent separation of the pads away from the application
sites. Thus, when the application sites are located at
the panty liner pad ends, the center section of adjacent
pads can separate, causing problems similar to those
identified above. Finally, while it is important that
the absorbent layers of the panty liner product be secured
together, the final product should be flexible enough to
generally conform to the user to reduce chafing and other
irritation.
Therefore, a new and useful panty liner product is
needed having a plurality of absorbent pads which are
releasably attached together in a secure manner. It is
desirable that the product be flexible and comfortable to
wear.
Sum_marv of the Tnvention
The present invention relates to an absorbent
feminine hygiene product configured for releasable
attachment to an undergarment. The product has several
individual absorbent pad layers releasably joined
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together. Each of the absorbent pads has an absorbent layer
and a liquid-impermeable barrier layer. An upper surface of
each absorbent pad is defined by the top surface of the
absorbent layer. A bottom, garment-facing surface of a
first absorbent pad is configured for releasable attachment
to a user's garment. A bottom surface of a second absorbent
pad is releasably attached to the top absorbent surface of
the first absorbent pad in a manner to prevent separation of
significant portions of the absorbent pads during use.
Preferably, the absorbent pads are releasably attached using
attachment means which have a plurality of attachment points
or areas distributed about the contact area of adjacent
pads. Thus, in a preferred embodiment, the attachment means
covers a substantial portion of the contact area. The first
absorbent pad can be releasably attached to a user's garment
with a first separation force, and the second absorbent pad
is releasably attached to the first absorbent pad with a
second separation force, less than the first separation
force.
A broad aspect of the invention provides an
absorbent feminine hygiene product which is configured for
releasable attachment to a user's garment, the product
comprising three stacked individual absorbent pads, each of
said pads comprising a top liquid-permeable surface opposite
a bottom surface and having disposed therebetween an
absorbent layer and a barrier layer, wherein a first of said
absorbent pads having a peripheral edge, is configured for
releasable attachment of the bottom surface of said first
absorbent pad to the user's garment with a first attachment
strength; a second of said absorbent pads having a
peripheral edge and attachment means for releasably
attaching the second pad to the top surface of the first
absorbent pad, thereby forming a contact area between the
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first and second absorbent pads, with a second attachment
strength, less than the first, in a manner to prevent
separation of significant portions of the first absorbent
pad from the second pad during use, at least a portion of
the peripheral edge of the second absorbent pad extends
beyond at least a corresponding portion of the peripheral
edge of the first absorbent pad-; and a third of said
absorbent pads having a peripheral edge and attachment means
for releasably attaching the third pad to the top surface of
the second absorbent pad, thereby forming a contact area
between the second and third absorbent pads, with a third
attachment strength, not greater than the second, in a
manner to prevent separation of significant portions of the
second absorbent pad from the third absorbent pad during
use, at least a portion of the peripheral edge of the third
absorbent pad extends beyond at least a corresponding
portion of the peripheral edge of the second absorbent pad,
wherein the attachment means is a layering adhesive which is
applied to form a plurality of attachment zones having void
areas, each void area having a major dimension of less than
about ~ inch; said attachment means covers at least about
400 of the contact area between the first and second
absorbent pads and the second and third absorbent pads.
Another broad aspect of the invention provides a
method of forming an absorbent feminine hygiene product
which is configured for releasable attachment to a user's
garment comprising the steps of: a) forming a plurality of
individual absorbent pads, each of said pads having a
peripheral edge and comprising a top liquid-permeable
surface opposite a bottom surface and having disposed
therebetween an absorbent layer and a barrier layer;
b) configuring the bottom of a first of said absorbent pads
for releasable attachment having a first attachment strength
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to the user's garment; and c) releasably attaching, at a
second attachment strength, less than the first attachment
strength, the bottom surface of a second of said absorbent
pads to the top surface of the first of said absorbent pads,
thereby forming a contact area between the first and second
absorbent pads, wherein the attachment means is a layering
adhesive which is applied to form a plurality of attachment
zones having void areas, each void area having a major
dimension of less than about ~ inch; said attachment means
covers at least about 400 of the contact area between the
first and second absorbent pads, wherein at least a portion
of the peripheral edge of the second absorbent pad extends
beyond at least a corresponding portion of the peripheral
edge of the first absorbent pad.
In a preferred embodiment, each absorbent pad has
a peripheral edge, and at least a portion of the peripheral
edge of the second absorbent pad extends beyond at least a
corresponding portion of the peripheral edge of the first
absorbent pad.
In another preferred embodiment, the absorbent
pads are stacked together and releasably attached with a
layering adhesive. The layering adhesive is applied at low
coating weights per unit area in a pattern over a
substantial portion of the contact area between adjacent
pads. The application pattern of the layering adhesive
keeps the individual pad layers of the product secured one
to another and prevents gapping, curling and other
separation during use.
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While individual pad layers are secured to adjacent
layers, the individual pad layers can, nonetheless, slip
along one another when subjected to shear forces. This
allows the absorbent product of the present invention to
remain as flexible as some single pad absorbent products
of the same class which are commercially available.
Unless otherwise stated, when used in conjunction
with adhesive coating and/or terms relating to surface
areas, the term "coverage" and related forms of the word
including the verb "to cover" as used in the specification
and claims includes both a continuous layer of adhesive
and a regular or random pattern of an adhesive coating
having void areas. In particular, "coverage" includes the
application of a pattern of discrete dots, fibrils,
continuous or discontinuous lines, etc., over an area or
substantially enclosing an area, even if the adhesive
particles, fibers, etc., coat only a fraction of that
area. Thus, the area "covered" by an adhesive is that
area defined by the boundaries of the applied adhesive
pattern.
As used in the specification and the claims, the
phrase "contact area" means the area of a first absorbent
pad contacted by a second absorbent pad stacked on the
first.
Figure 1 shows a perspective view of a multilayered
panty liner according to the present invention.
Figure 2 shows a cross section of the multilayered
panty liner along line 2-2 in Figure 1.
Figure 3 shows a cross section of an individual pad
along the line 2-2 in Figure 1.
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Figures 4a and 4b show line depictions of two
' alternative embodiments of the arrangement of absorbent
pads having overlapping portions.
Figure 5 shows a perspective view of an alternative
embodiment of the present invention incorporating
laterally extending tabs proximate a center section of a
bottom absorbent pad.
F~.gures 6a shows an alternative embodiment of the
present invention in which the absorbent pad layers are
releasably attached with a thermal bonding pattern.
Figure 6b illustrates a cross-section of Fig. 6a
along line 6-6.
Figures 7a shows a top view of an alternative
embodiment of the present invention in which the absorbent
pad layers are releasably attached by embossing/heat
sealing along the side edges and in which the absorbent
pads are removed by tearing along perforations inside the
heat sealed lines.
Figure 7b shows a cross-section of Fig. 7a along line
7-7.
Figure 7c shows a side view of the embodiment of Fig.
7a during the removal of the top absorbent pad.
Figure 8 shows a cross section along line 2-2 of Fig.
1 of an alternative embodiment employing fiber
entanglement.
Figure 9 shows a cross section along line 2-2 of Fig.
1 of an alternative embodiment employing hook-and-loop
type fasteners.
Figure 10 shows a perspective view of a multilayered
thin sanitary napkin according to the present invention.
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Detailad peSC ip ion O the Prafcrra
d EmbodimPr,t
The absorbent product of the present invention has a
plurality of releasably attached absorbent pads which are
stacked together. The pads may be attached by any means
which provide sufficient attachment strength to maintain
product integrity during use. Preferably, the stacked
pads are held together in a manner to prevent separation
of significant portions of the absorbent pads during use.
Thus, the attachment means should be able to continue to
hold adjacent pads together_ under both shear and peel
forces likely to be encountered during product use.
The attachment means may be adhesive, thermal or
compressive such as heat sealing and embossing, and
mechanical such as fiber entanglement or hook-and-loop
type fasteners. Preferably, the attachment means provides
varied attachment strength between adjacent pads and
between the bottom pad and the user's garment to which it
is attached. The first, garment-facing pad may be
releasably attached to the user's garment with a first
attachment strength, and a second absorbent pad is
releasably attached to the first pad with a second
attachment strength which is preferably less than the
first attachment strength. Additional pads may be
releasably attached in a stacked manner to the top of the
second absorbent pad with attachment strengths, preferably
not greater than the second attachment strength.
The absorbent pads which are stacked in the absorbent
product may be of any geometry normally used in the
feminine hygiene field, including strip-like (See Fig. 1),
dog-bone or hourglass shaped, and the like. Referring to
Fig. 5, the pads 50 may also have laterally extending tabs
51 proximate a center portion 52 of the pad 50 for at
least partially wrapping around a user's undergarment. In
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the stacked multilayered absorbent product, each pad may
have substantially similar geometry, i.e., all strip-like
or hourglass shaped, while having identical or
substantially similar geometry. Where the pads are of
substantially similar geometry, the may have slightly
different proportions. Thus, successive absorbent pads
may be proportionately longer or shorter in length.
Alternatively, the pads may have different geometry. For
example, only the first, garment-facing absorbent pad may
have tabs 51. In another embodiment, the ratio of length
to width may be substantially altered, e.g., one layer
long and narrow, and a second layer short and wide.
Referring to Figs 4a and 4b, the geometry of the
individual absorbent pads 41 may therefore allow for
partial or complete overlap of one absorbent pad in
relation to an adjacent pad. Preferably, at least a
portion of the peripheral edge 42 of an upper absorbent
pad overlaps at least a portion of an adjacent lower
absorbent pad 43 in the stacked product. This overlap can
protect the lower pad from soiling or staining by body
fluids during use and facilitates the removal of a soiled
pad from the pad immediately below it. Where the
absorbent product is constructed Pram identically-sized
individual pads, the overlap of at least one edge of the
uppermost pad is achieved by staggering the pads as in Fig
4b, Where the pads are of different sizes, the pads may be
stacked in a manner to cover each pad with the absorbent
pad immediately above it. Thus, the first, garment-facing
pad may be completely covered by a second absorbent pad,
and a third absorbent pad may completely cover the second
absorbent pad. Additionally, each upper pad may extend
beyond the peripheral edge of the pad immediately below it
in the stack.
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The individual absorbent pads of the multilayered
product are preferably relatively thin. This allows
several absorbent pads to form an absorbent product which
will not be too thick fox the average product user. The
individual pads may be panty liners, thin sanitary napkins
or even ultrathin sanitary napkins, and possibly thin
incontinence pads. Preferably, the individual absorbent
pads of the invention have a thickness of less than about
mm, more preferably, less than about 5 mm, and most
10 preferably, less than about 2.5 mm.
The absorbent product- of the present invention
remains flexible. Indeed, preferred multilayered
absorbent products have a flexural resistance according to
the test method of Example V, below, in the range of
equivalent absorbent products. Thus, multilayered
sanitary napkins have a flexural resistance in the range
of conventional sanitary napkins, and multilayered panty
liners have a flexural resistance in the range of
conventional panty liners. Preferred multilayered panty
liners have a flexural resistance of less than about 0.25
lbs, and more preferred multilayered panty liners have a
flexural resistance of less than about 0.2 lbs.
Referring to Fig. 1, there is depicted, a
multilayered panty liner l0 having a top pad 12, a center
pad 14 and a bottom pad 16. Figure 2 shows a cross
section of the multilayered panty liner 10, including the
attachment means 18a and 18b which releasably attach the
top pad 12 to the center pad 14 and the center pad 14 to
the bottom pad 16, respectively. In addition, the bottom
pad has a positioning means 20, illustrated in Fig. 2 as
an adhesive layer.
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Indiv~',dual Absorbent Pads
A detail of an individual absorbent pad is depicted
in Figure 3. The individual absorbent pad 12 comprises a
top, liquid permeable layer 22, an absorbent structure 24
and a bottom, barrier film 26. The absorbent pad 12 can
be any conventional panty liner pad. To keep lower pads
clean until use, the absorbent pads 12,14,16 preferably
decrease in size from top to bottom. In a particularly
preferred embodiment, the top pad 12 is about 6 to 8
inches (15 to 20 cm) long and 1 3/4 to 2 1/2 inches (4.4
to 6.4 cm) wide, the center pad 14 is about 5 3/4 to 7 3/4
inches (14.6 to 19.7 cm) long and 1 3/4 to 2 1/4 inches
(4.4 to 5.7 cm) wide and the bottom pad 16 is about 5 to
7 1/2 inches (12.7 to 19 cm) long and 1 1/2 to 2 1/4
inches (3.8 to 5.7 cm) wide. Examples of single layered
panty liner products currently on the market include
CAREFREE PANTY SHIELDS, KOTEX LIGHTDAYS PANTILINERS,M NEW
FREEDOM PANTILINERST, ALWAYS PANTILINERSTM and the like.
These products generally have an absorbent structure 24,
and a plastic barrier film 26. The absorbent structure
may include several layers, or it may be a single layer
having an upper liquid pervious surface. Preferably, the
absorbent structure has several layers, the top layer
forming the liquid pervious layer 22. The liquid
permeable layer 22 may be a nonwoven fabric such as a
spunbonded fabric, a thermal bonded fabric, a resin bonded
fabric, and the like; an apertured film such as DRI-WEAVE,M
TM TM
RETICULON, APEX, and the like; a densified top layer
formed with hydrogen bonding; or any other suitable
covering surface. The rest of the absorbent structure 24
may be cellulosic fibers, including wood pulp and cotton
pulp; synthetic fibers, including polyolefins and
polyesters; and the like. Preferably, the absorbent
structure includes wood fluff pulp and about 5 to 80% of
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fusible, thermoplastic fibers. Useful absorbent
structures and top surfaces are disclosed in Cancian et
al., U.S. Patent No. 4,592,943; Mays, et al. U.S. Patent
No. 4,713,134; Mays U.S. Patent No. 4,787,947 and Shimalla
et al., U.S. Patent No. 4,774,124.
A particular preferred class of individual absorbent
pads 12 is a fusible fiber pulp structure (FFP). It is
constructed with a liquid permeable layer 22. In one
embodiment, the layer 22 comprises a nonwoven fibrous web
formed of staple hydrophobic textile fibers. Such fibers
may be unified by being coated with a water-insoluble
rubbery fiber-binding resin so that all of the individual
fibers are substantially covered with a resin coat, thus
bonding them together at their crossing points while
leaving the interstices of the web unfilled.
The liquid permeable layer 22 can also be a porous,
substantially planar flexible polymeric coating on the
surface of a bonded staple hydrophobic fiber web or on the
outermost surface of a lofty web of blended fibers in a
pad construction wherein each component is essentially
completely secured to adjacent components. Such a
surface, due to the flatness of the polymeric coating, has
an unusually soft, smooth feeling and is pleasing to the
touch.
Preferably, the fibers of the liquid permeable layer
22 are thermoplastic or, more preferable, a mixture of two
or more types of thermoplastic fibers having different
melting points. Upon application of heat and pressure
sufficient to melt at least one of the fiber types, the
remaining unmelted fibers will be thermobonded or fused
together into a porous web. This processing step is
described more fully in Lauritzen, U.S. Patent No.
4,622,089.
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The fibrous materials found to be satisfactory in the
making of the liquid permeable layer have been found to be
blends of two thermoplastic fibers having distinguishable
melting temperatures. Bicomponent fibers, fibers with an
inner core of a thermoplastic fiber, e.g., polyester,
surrounded by an outer sheath of thermoplastic e.g.,
polyethylene, having a melting point much lower than the
core, have been found to be the best fibers to work with
from processing and performance standpoints in this class
of absorbent pads. It is also conceivable that the
material for liquid permeable layer 22 may be coformed
blends of pulp fluff and thermoplastic fibers, e.g.,
polypropylene.
It has been found to be acceptable to use fibrous
materials for the liquid permeable layer 22 having a
denier in the range of from about 1.0 to about 4Ø Fiber
length for the liquid permeable layer 22 has been found to
be satisfactory if in the range of from about 0.5 inches
to about 2.5 inches.
The resulting web is a thin, pliable, resilient,
porous, cloth-like fabric whose top surface has a soft,
smooth, pleasing, tactile quality. This web may be fed
directly and continuously into the manufacturing process
for the individual absorbent pad of this invention. It
may also be collected and stored for later use.
In heat bonded relationship with liquid permeable
layer 22 is an absorbent structure 24 comprising a blend
of thermoplastic fibers in this class of absorbent pads.
It is preferable that the thermoplastic fibers of
absorbent structure 24 be a mixture of two or more types
of thermoplastic fibers having different melting points.
Bicomponent fibers having a melting point much lower than
the core, have been found to be the best fibers to work
with from processing and performance standpoints. Like
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layer 22 above it, upon application of heat and pressure
sufficient to melt at least one of the fiber types, the
remaining unmelted fibers will be thermobonded or fused
together into a porous web.
It is also preferable to include cellulosic pulp
fibers with the thermoplastic fibers in absorbent
structure 24. Since thermoplastic fibers, without further
treatment, are essentially hydrophobic, absorbent
structure 24 will not effectively draw fluid away from
liquid permeable layer 22- absent some hydrophilic
material. It is important to have sufficient pulp to
absorb fluid. An acceptable amount of pulp for effective
absorbency is from about 20% to about 95% by weight.
Conversely, an acceptable amount of thermoplastic fibers
is from about 5% to about 80% by weight. A preferred
amount of pulp would be in the range of from about 20% to
about 60% by weight (with thermoplastic fibers being in
the range of from about 40% to about 80%).
A second fusible fiber layer, made from the same or
similar material as liquid permeable layer 22, may be used
to "sandwich" the absorbent structure 24. Pulp fluff is
very dusty. By sandwiching the absorbent layer containing
pulp between two fibrous thermoplastic layers, the dust in
the operating environment is greatly reduced. In this
construction, the layer first laid down in manufacture is
generally smoother.
The ratio of thermoplastic fiber to pulp fluff may be
characterized by comparing the total amount of pulp and
thermoplastic fibers in both the total absorbent structure
including the liquid permeable layer 22 and the bottom
outside "sandwiching" layer (not shown) and absorbent
structure 24. Since they are to be in heat bonded
relationship, it is preferable that, when looking at the
fusible fiber layers 22 together with absorbent structure
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24, there is at least 35% by weight thermoplastic fibers.
It is more preferable that there be at least 60% by weight
thermoplastic fibers in both "sandwiching" layers.
The fibrous materials found to be satisfactory in the
making of the absorbent structure 24 are the same or
similar fibrous materials used for the liquid pervious
layer 22. Bicomponent polyester/polyethylene fibers have
been found to be the best fibers to work with from
processing and performance standpoints in this class of
l0 absorbent layers. Although it has been found that using
fibers having a denier of about 1.8 in liquid pervious
cover layer 22 results in improved comfort, it is not
necessary to use fibers of this denier for absorbent
structure 24. Although any denier in the range of from
about 1.0 to about 4.0 will suffice, from a cost
standpoint a denier of from about 2.5 to about 3.5 will
yield good performance with acceptable manufacturing
costs. Fiber length for absorbent structure 24 has been
found to be satisfactory if in the range of from about 0.5
to about 2.5 inches.
It is clear that the major distinctions between the
liquid permeable layer 22 and absorbent structure 24 is
the presence of pulp in absorbent structure 24 and the
possibility of finer denier fibers in liquid permeable
layer 22. However, since the ranges for each layer
overlap, it is possible and acceptable to use the same
denier fibers for both the liquid permeable layer 22 and
absorbent structure 24. In such a case, there is no real
need for two separate and distinct layers. Instead, it is
possible to construct the pad using one layer that has a
body contacting surface and a surface which faces barrier
film 26 (which is described in more detail below) . In
such a case, however, it is important to remember that the
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body contacting surface should be substantially devoid of
pulp.
The plastic barrier film may be any barrier film
useful in the panty liner and sanitary napkin art. Useful
films include, without limitation, polyolefin films such
as polyethylene and polypropylene; polyvinyl films such as
polyvinyl acetate, polyvinyl chloride, and polyvinylidene
chloride; copolymeric films such as ethylene-vinyl
acetate, and blends or laminates of one or more of the
above polymers. Preferred barrier films include ethylene-
vinyl acetate/polyethylene laminate films and
polypropylene films.
attachment Means
The absorbent pads 12, 14, 16 generally and
particularly described above are stacked and releasably
attached to form the absorbent product 10 of the present
invention. The pads 12, 14, 16 may be attached by any
attachment means 18a, 18b which provide sufficient
attachment strength to maintain product integrity during
use. The attachment means 18a, 18b may be adhesive,
thermal or compressive such as heat sealing and embossing,
mechanical such as fiber entanglement or hook-and-loop
type, and the like.
The attachment means may be a single attachment zone
such as a solid area, a series of lines, a pattern of
attachment points which cover an area, and the like.
Preferably, if a plurality of attachment zones are used,
each attachment zone is within 2 inches of an adjacent
attachment zone. This helps to limit the separation of
adjacent absorbent pads in the product according to the
present invention.
In a preferred embodiment, the attachment zones may
also include void areas. These void areas preferably have
SUBSTITUTE SNEET (RULE 26)
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i WO 95129655 - PCT/U595104485
- 17 -
a major axis of less than about 1/2 inch and more
preferably less than about 1/4 inch.
I~dhesive
In one preferred embodiment, the adhesive may be
applied to the bottom surface 28 of an individual
absorbent pad 12, 14, 16. Preferably, the adhesive is
disposed upon a substantial portion of the contact area of
the bottom surface 28. The adhesive is also preferably
applied at relatively low coating levels, i.e., low
to coating weights per unit area. The low coating weight
over relatively large surface area provides a secure
attachment between the adjacent absorbent pads in the
multilayered product.
The relative adhesion between the adjacent absorbent
pads in the panty liner product in comparison with the
strength of the attachment means 20 between the panty
liner product and the garment to which it is attached is
a characteristic of one embodiment of the present
invention. Preferably, the attachment strength between
adjacent absorbent pads 12, 14, 16 should be less than the
strength of the attachment means 20 between the panty
liner product and the garment. In the case of adhesive
attachment to the garment (positioning adhesive), this can
be achieved by selective use of adhesives for both the
layering adhesive and the positioning adhesive 20. For
example, an adhesive which adheres more strongly to cotton
than synthetic polymers would adhere more strongly to
cotton undergarments. In a particularly preferred
embodiment, the attachment strength between layers
decreases with increasing vertical distance from the
- bottom pad. Thus, in a three layered panty liner
product, the positioning adhesive 20 or other attachment
- means between the product and garment would have the
highest attachment strength, the attachment strength of
SUBSTITUTE SHEET (RULE 2fi)
WO 95129655 PCTIU595104485
.. ~ ,.. '.: ,;. V ,:
- 18
the layering adhesive 18b between the bottom absorbent pad
16 and the center absorbent pad 14 would be less than the
attachment strength between the bottom pad 16 and the
undergarment, and the attachment strength of the layering
adhesive 18a between the top pad 12 and the center pad 14
would be less than that between the center pad 14 and the
bottom pad 16. In addition, the attachment strength
between adjacent pads in the construction is preferably
substantially less than the force necessary to delaminate
the individual absorbent pads.
In general, the layering adhesive has an average peel
strength of at least about 0.02 lb/in according to the
test method of Example II, below, to allow it to maintain
the structural integrity of the panty liner product during
use. More preferably, the layering adhesive has an
average peel strength of at least about 0.04 lbs/in and a
peak peel strength of less than about 5 lbs/in according
to the test method of Example I to allow the layering
adhesive to maintain the integrity of the panty liner
product without resulting in delamination of the
individual absorbent pads when the user removes the top
pad in a stack. Most preferably, the layering adhesive
has an average peel strength of greater than about 0.04
lbs/in and a peak peel strength of less than about 3
lbs/in.
Generally, these adhesive peel strength ranges relate
to an average attachment strength of at least about 0.04
1b for an absorbent pad layer of the present invention.
This can be determined for the product according to the
test method of Example II. The peak attachment strength
of the absorbent pad layer is preferably less than about '
10 lbs for the product, more preferably, less than about
5 lbs when measured according to the test method of
Example I.
SUBSTITUTE SHEET (RULE 26)
W095I29655 '~ PCTIUS95/04485
- 19 -
Preferably, the layering adhesive covers least about
40% of the contact area of the bottom surface 28. More
preferably, it covers about 60% to 95% of the contact
area, and most preferably, about 75% to 95%. It is
preferred that the layering adhesive not be applied at the
extreme longitudinal ends of the barrier film. The lack
of adhesive at the longitudinal ends of the barrier film
provides finger tabs 30 to enable a user to more easily
separate adjacent absorbent-pads.
l0 The layering adhesive can be classified by method of
setting: solvent-releasing, e.g., emulsion or organic
solvent based; curing, e.g., radiation cure, electron
beam, or catalytic cure; or hot melt. Preferred adhesives
are pressure sensitive adhesives (PSA). PSAs can allow
adjacent pads to be reattached if they are prematurely
separated. However, PSAs have the potential of
transferring to the cover material on an absorbent layer
and forming a somewhat tacky surface an the cover
material. Therefore, if a PSA is used as the layering
adhesive, it is preferred that it be selected such that a
minimal amount, if any, of the PSA transfers to the cover
material from the barrier film. If a non-PSA is used, it
is preferred that the adhesive remain flexible after
setting so that the cover material remains supple and
relatively soft to the touch. A representative, non-
limiting list of useful PSAs includes those based on
natural rubber, styrene/butadiene latex, A-B-A block
copolymer, butyl rubber and polyisobutylene, acrylics
including vinyl acetate-acrylate copolymers, vinyl ether
polymers, polyalkene polymers, polyurethane, ethylene-
vinyl acetate copolymers and polypropylene including
atactic polypropylene. A representative, non-limiting
list of useful non-PSAs includes latexes based on the
above-listed resins and hot melts based on these resins.
SUBSTITUTE SHEET (RULE 26)
~~$~~~s
,.
WO 95/29655 PCTIUS95104485
- 20
Preferably, the adhesive is a PSA, and more preferably,
the PSA is an A-B-A block copolymer, an acrylic resin, or
an ethylene-vinyl acetate copolymer. Most preferably, the
PSA is based on an A-B-A block copolymer. The adhesive
can be applied to the absorbent pad in any manner known to
the ordinary practitioner. Such application methods
include, without limitation, spraying, roll coating, slot
coating, gravure rolling, etc.
The selection of the adhesive for use as a layering
adhesive 18a, 18b is also dependent upon the composition
of the bottom surface 28 and the covering layer 22 of the
individual absorbent pads 12, 14, 16 which make up the
multilayered product. In particular, if a PSA is used,
adhesive transfer can be noticeable. Also, if the cover
sheet and barrier film of adjacent absorbent pads are
formed from similar material, there may be a greater
tendency for a PSA to transfer to the cover sheet.
Generally, the adhesives described above adhere to
bottom surfaces 28 formed by barrier films 26.
Preferably, the adhesives adhere strongly to the selected
barrier film 26. The adhesives described above also
adhere to the cover sheet 22, although it is preferred
that the adhesion to the cover sheet 22 be less than that
to the barrier film 26.
The choice of adhesive used to practice the invention
depends in part on the barrier film, and perhaps more
particularly, the cover sheet used. The selection of
adhesive to use with a given cover sheet and barrier film
will be readily determined by one of ordinary skill in the
art. Preferably, the adhesive adheres strongly to the
barrier film, less strongly to the cover sheet of an
adjacent absorbent pad, and does not transfer from the
barrier film to the cover sheet. As a guideline, it has
been determined that A-B-A block copolymers work well with
SUBSTITUTE SNEET (RULE 26)
CA 02189037 2005-03-24
74484-85
- 21 -
polyolefin barrier films and nonwoven cover sheets. These
block copolymers also work with apertured film cover
materials. Acrylics, EVA and other similar adhesives also
work with these materials.
According to a preferred embodiment of the present
invention, a block copolymer PSA, such as National Starch
X34-5539, or an atactic polypropylene adhesive, such as
TM
LUNATACK ~ 3457C from H.B. Fuller Co., is used at low
coating weight over a large surface are. Preferably, the
adhesive is applied at about 0.5 mg/inz to 6 mg/inz. More
preferably, the adhesive is applied at about 0.5 to about
4 mg/in2. Most preferably, the adhesive is applied at
about 0.75 mg/ini to substantially cover the bottom surface
of the top absorbent pad and at about 1 mg/inz to
substantially cover the bottom surface of the middle
absorbent pad in a three-layered product. The bottom pad
may be anchored to a user's garment with about 8 mg/inz of
a block copolymer adhesive such as HM-1972 positioning
adhesive from H.B. Fuller Co. The coating weight is
determined by weighing the absorbent pad before and after
application of the adhesive and dividing the weight (in
grams) by the area covered by the adhesive.
Thermal and/or Compressive Means
In another embodiment, thermal and/or compressive
attachment means 18a, 18b can be used to releasably attach
the absorbent pads in the multilayered product. Thermal
attachment means include, without limitation, heat
sealing, embossing at elevated temperatures, ultrasonic
sealing, and the like. Compressive attachment means
include, without limitation, cold flow embossing,
crimping, and the like. Generally, the thermal attachment
means include an element of compressive force, as well.
WO 95129655 PCTIIJS95104485
v...
- 22 -
Thus, embossing with applied heat is included in this
category of attachment means.
Referring to Figs 6a-7c, the absorbent pads 60, 70
may be heat sealed or embossed with applied heat in a
pattern (See Figs 6a and 6b) as described for the adhesive
attachment means, or the absorbent pads 60, 70 may be heat
sealedJembossed along their side edges (See Figs 7a-7c).
If the thermal attachment means are applied in a pattern
61 over a substantial surface of the absorbent pads 60,
the individual heat sealed or embossed attachment points
62 should leave a soft surface on the upper, absorbent
surface 63 to avoid irritating the user. The thermal
attachment means 71 can also be used to substantially
permanently seal the side edges 72 of the pads 70 in the
absorbent product while allowing a perforated portion 70a
of the pad defined by perforations 73 to be removed as
illustrated in Figure 7,c. In addition, a combination of
thermal and adhesive attachment can be used. An example
of such a combination would be to apply an adhesive in the
region designated as R in Figure 7b to more securely
attach the center portions of the absorbent pads during
use.
Mechanical Attachmen Moa n
In another embodiment illustrated in Figs. 8 and 9,
mechanical attachment means 81, 91 may be used to
releasably attach the absorbent pads 80, 90 in the
multilayered product. Mechanical attachment means
include, without limitation, fiber entanglement, hook-and-
loop type fasteners and the like. Fiber entanglement
involves the use of a fibrous top surface 82 in
conjunction with a fibrous bottom surface 83 of adjacent
absorbent pads 80 in the stacked product. In this
embodiment, fibers from these adjacent surfaces come into
SUBSTITUTE SNEET (RULE 26)
CA 02189037 2005-03-24
74484-85
- 23 -
close contact and become entangled to releasably attach
the two layers 82, 83 together. Any fibrous surfaces can
be used in this embodiment provided that the fibers
forming the surface have sufficient crimp to enable the
fibers from adjacent layers to become entangled and catch.
Examples of fibers useful in this invention include
natural fibers having crimp such as cotton, wool, and the
like; and synthetic fibers which have a coiled or crimped
nature such as rayon, polyester, nylon, and the like.
Preferred synthetic fibers are relatively thick and
resilient, having a denier of about 1 to 15, preferably
about 3 to 10. This allows the entanglement of the
adjacent layers to have sufficient attachment strength to
hold the product together during use. In a preferred
embodiment of this invention, the adjacent fibrous layers
82, 83 of adjacent absorbent pads 80 are different, e.g.,
3 in top surface 82 and l0 in bottom surface 83 to allow
the fibers of one layer to intrude to a greater extent
into the fibers of the adjacent layer. However, it may
also be desirable to use fibrous layers having similar
fibers to allow the entanglement to be more uniform.
Alternative mechanical attachment means includes
hook-and-loop type fasteners 91. These fastener systems
are well known to those of ordinary skill in the art, are
widely available and include VELCROMbrand fasteners and
the like. These fasteners generally have a first
attachment surface 92 having an array of relatively rigid
hooks (not shown in detail) and a second attachment
surface 93 of looped fibers. In using this type of
attachment means, the array of hooks can be secured on the
bottom or barrier side 94 of the individual absorbent pads
90, and the second attachment surface 93 can be located on
the top, absorbent surface of the individual absorbent
pads 90. The second attachment surface 93 can comprise
CA 02189037 2005-03-24
' 74484-85
24
looped fibers, or the fibers can result from a relatively
loose, woven or nonwoven fabric. It is merely required
that the array of hooks can contact and hold securely onto
the second fibrous attachment surface.
~ltei;~,stiva Embodim~gnts
While the above discussion refers primarily to panty
liner products, the practitioner will recognize with
reference to Fig. 10 that the multilayered product of, the
present invention can be a thin sanitary napkin 100.
to Commercially available thin napkins include SURE & NATURAL
THIN, ULTRA THIN, and PRIMAM napkins, STAYFREE THINTM and
ULTRA THIN~napkins, ALWAYS ULTRA napkins, and KOTEX ULTRA
THINTnapkins, etc. These products generally have a liquid
permeable overwrap 101 which encloses an absorbent
structure and a liquid impervious barrier sheet (not
shownj.. The overwrag 101 is sealed together about the
periphery or at the ends 102 of the product. The
materials of the exterior surfaces of thin sanitary
napkins may be similar to those used in panty liners. The
dimensions of the sanitary napkin are generally larger
than corresponding panty liner. For example, the napkin
pads may be about 6 to 13 inches (15 to 33 cm) long and
about 2 to 5 ( 5 to 13 cm) inches wide. 'The teaching of
this invention relating to panty liners can therefore be
used to create a multilayered sanitary napkin as well.
Method of O~e
In use, a consumer would remove the release liner
which protects the positioning adhesive from the
multilayered panty liner product and secure the product in
the crotch area of her undergarment. After some period of
time when the top absorbent pad has become soiled, the
user can simply remove the soiled pad to expose the next
absorbent pad. This procedure can be continued until all
W095129655 ~ PCTIUS95I04485
- 25 -
absorbent pads have been soiled and a new multilayered
product is needed.
The present invention will be further understood by
reference to the following specific Examples which are
illustrative of the composition, form and method of
producing the multilayered panty liner product of the
present invention. It is to be understood that many
variations of composition, form and method of producing
the panty liner product would be apparent to those skilled
in the art. The following Examples, wherein parts and
percentages are by weight unless otherwise indicated, are
only illustrative.
EBAMPLE I
A series of delamination tests were run on several
commercial panty liners to determine a maximum
commercially useful peel strength of the layering
adhesive.
Samples were prepared as follows:
A 7'° x 2" strip of Permacel Professional Grade
Gaffer~s Tape was cut, one end was folded onto itself to
create a 1/2'° tab. A 2 1/2" x 3 1/2" piece of release
paper was placed on the tape, with the 2 1/2" side
parallel to the 2" edge of the tape, leaving a 4" length
of adhesive exposed. The adhesive coated side of the tape
was then placed on the surface of a test product such that
the sides of the tape strip lined up with the edges of the
product, the folded tab of the tape did not overlap with
the test product but extended past its end to provide a
constant thickness over the surface of the product, and
the edge of the exposed adhesive did not overlap any crimp
or curve on either end of the test product.
The test product was then placed in a Jenkins press
between two platens heated to 100°F and pressed at 150 psi
SUBSTITUTE SHEET (RULE 2B)
CA 02189037 2005-03-24
' ~ 74484-85
- 26 -
for 3 minutes. One minute after removal from the heated
platens, the sample is secured to a TMI tester sled and
the top cover is clamped for peel testing. The TMI tester
is engaged to remove the tap cover at a rate of 1200
in/min. The force of removal, as well as adhesive tear-
out and/or transfer, is recorded. The TMI tester is a
Release and Adhesive Tester, Model #80-14, available from
Testing Machines, Inc. of Amityville, NY. In order to get
more detailed output than the test method describes, the
to dial strain gauge on the TMI Release and Adhesive Tester
was replaced with an Entran Devices, Inc. model
ELF-TC500-10 10 1b. load cell. The load cell was fed
into a Tektronix TEK 2430A digital oscilloscope and the
force profile over the entire peel was captured and
15~ plotted.
Each prepared sample was placed on the sled with the
barrier side of the product down. The end of the test
product closest to the tab on the Gaffer~s Tape was
anchored to the sled using 3M Duct Tape. The release
20 paper patch was removed from the Gaffer's Tape and the
tabbed end of the tape was held by jaws attached to the
load cell. As each sample was run, the force profile over
the peel of the test sample, the maximum force over the:
peel and the mean force were captured by the oscilloscope
25 and plotted.
Between each sample tested the oscilloscope was
zeroed to within o.04 V using the mean force read-out at
zero load. The oscilloscope was calibrated using the dial
strain gauge to verify two or three force read-outs at the
30 start of each test session. All tests were run at 1 volt
- 1 pound.
The samples tested were ALWAYS LONGS with DRI-WEAVE
(longs were used to avoid tape over the crimped ends and
rn
still allow a 4" peel), ALWAYS SHEER CONFIDENCE (cut to a
CA 02189037 2005-03-24
74484-85
- 27 -
2" width to avoid edge effects), KOTEX LIGHTDAYS
TM
WRAPAROUND (cut to a 2" width), and Product A, an example
of the present invention.
Product A was produced by forming a 2.5 oz/yd1
absorbent structure having a first veneer layer of 0.3
oz/ydz BASFM1040 bicomponent fiber, 1.8 denier, nonwoven
fabric, a 1.9 oz/yd~ air-laid core of 1.14 oz/ydi BASFM1039
bicomponent fiber, 3.0 denier, and 0.76 oz/yd2 ITT XJ-HM E
Type Cellulosic Fluff Pulp (a 60:40 ratio by weight of
bicomponent fiber:fluff pulp), and a second veneer of 0.3
oz/yd~ BASFM1039 bicomponent fiber, 3.0 denier, nonwoven
fabric. The absorbent structure is thermobonded by
passing hot air (about 300°F) through the structure from
the BASF 1039 veneer side to the BASF 1040 side for about
2 sec. The absorbent structure has a "smooth side"
comprising the BASF 1040 veneer which is formed against a
screen in the preparation of the structure. The surface
opposite the "smooth side" of the absorbent structure is
adhered to a 1.25 mil PE/EVA laminate barrier film using
about 3 mg/in2 National Starch #34-5539 adhesive coated on
the EVA (top) side of the laminated barrier film. The
resultant absorbent pad is thermally bonded about its
perimeter to seal the absorbent structure to the barrier
film, maintaining its integrity.
Each type of sample had a characteristic force
profile. For example, the KOTEX LIGHTDAYSMproducts have
a very sharp force increase at the very beginning of the
peel to a peak force value and then a sharp drop to a
relatively steady peel. However, the Product A samples
have a jump in force at the beginning when the veneer
initially tears, which holds for a short time creating a
TM
broader peak than the KOTEX products and another more
narrow peak at the end when the seal breaks. Depending on
the Product A sample's seal strength, the veneer tear
~~~9~37
WO 95129655 PCTIU595104485
,:.: _ 28
force peak may or may not correspond to the maximum force
displayed. The results shown in Table 1 were calculated
using the peak force of the veneer tearing as the inherent
strength of the material and assume a normal distribution.
SUBSTITUTE SHEET (RULE 26)
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WO 95129655 PCTIUS95104485
Z 9
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R'O 95119655 ~ PCTIUS95104485
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30 -
Under these test conditions the lower limit of each
product type s confidence interval would be the upper
limit for a layer adhesive s peel force. However, it
would be wise to make the upper limit for the layer
adhesive some safety factor below the lower confidence
limit to ensure that there is no tearing of the surface of
the lower layer. For example, calculating a 25% or 50%
reduction of the lower confidence limit of the inherent
strength of a product s surface material to determine the
new upper limit for a layer adhesive s peel force would
yield the values shown in Table 2, below.
SUBSTITUTE SHEET (RULE 26)
WO 95129655 - ~ ~ pCT/US95/04485
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CA 02189037 2005-03-24
74484-85
- 32 -
ERAMBLE II
A series of tests were run to determine the amount of
adhesive which transfers from a barrier film to an
adjacent cover sheet after aging with a 2kg weight for 1
hour. The products were formed as follows:
TOP LAYER: 6.5" long, rectangular with curved ends.
The absorbent pad used in the top layer was
prepared in the same manner as Product A of Example
I with the following changes: The absorbent
structure had a basis weight of 3.3 oz/ydi and the
air-laid core had a basis weight of 2.7 oz/ydZ.
BOTTOM LAYER: 6.0" long, rectangular .with curved
ends.
The absorbent pad used in the bottom layer was
prepared from the same material as the top layer. In
addition, 10 mg/ini of HM-1972 positioning adhesive
from H.B. Fuller Co. was slot coated onto the bottom
(PE) side of the barrier film in a pattern 5.25" long
x 1.75" wide.
Varying costing levels of a layering adhesive,
National Starch #34-5539 adhesive, were spray coated on
the bottom (PE) side of the barrier film of the top layer
in a pattern covering the entire exposed surface.
TEST CONDITIONS
TM
After preparation, samples were run on an INST~tON Model
No. 1122 apparatus equipped with a moveable sled. The
sample is placed in the test apparatus horizontally, and
the leading edge of the sample is lifted to be attached to
the test arm at a 90° orientation. Under the test
W~ 95129655 ~ PCT/US95104485
- 33 -
conditions, the leading edge of the sample is pulled
upwards at 12 in/min, and the moveable sled is moved at 12
in/min toward the point of separation of the sample to
maintain the 90° orientation. A four inch peel was
recorded. The results are shown in Table 3, below.
SUBSTITUTE SHEET (RULE 26)
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WO 95129655
PC1'IUS95104485
34
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Wm 95129655
PCT/ITS95104J85
- 35 -
The amount of adhesive transfer increased with
increasing coating level. All coating levels exhibited
some trace of adhesive transfer. Transfer was extremely
sparse at coating levels of 0.5 and 0.75 mg and was not
present in most of the samples. Samples were prepared
using 0.3 mg coating level but would not stay assembled
long enough to be put in test. Samples were tested from
coating levels of 0.5mg to 8mg. 5% of the 0.5 mg samples
were positive for transfer and 10% were positive for the
0.75 mg samples. Between coating levels 2 and 6 mg,
substantial fiber pull and bagging of the veneer occurred.
Coating levels 7 to 8 mg had a significant decrease of
fiber pull and bagging.
ERPiMPLE r_Tr
In order to identify a maximum desired peel strength
between individual absorbent pads, the adhesion between a
bottom pad layer and a cotton undergarment was tested.
The test pad layer was identical to the bottom layer of
Example II.
90° peel strength testing was performed on 20 samples of
this product using the procedures outlined in Example II.
The results are shown in Table 4, below.
SUBSTITUTE SHEET (RULE 26)
~~~~(l3'~
WO 95129655 ~ PCTIUS95104485
36
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WO 95129655
PCTIUS95I04485
- 37 -
The testing continued to evaluate the 90 peel
strength between individual pad layers. The test products
had 3 individual absorbent pads. The test data relates to
' the separation of a top pad from a middle pad while the
middle and lower most pad remained adhered to a cotton
undergarment panel.
Product B was prepared as follows:
TOP LAYER: 6.5" long, rectangular with curved ends.
The absorbent pad used in the top layer was
prepared in the same manner as Product A of Example
I with the following changes: The barrier film was
replaced with 0.6 mil polypropylene XP-544 FS/P, from
Edison Plastics, Edison, New Jersey, the absorbent
structure was adhered to the barrier film with 2.5
mg/in~ of the National Starch X34-5539 adhesive, and
0.75 mg/in~ of a layering adhesive, H.B. Fuller Co.
HM-1972 hot melt adhesive was coated onto the bottom
side of the barrierfilm in a pattern 5.25" long x
1.75" wide.
MIDDLE LAYER: 6.25" long, rectangular with curved
ends.
The absorbent layer used in the middle layer was
prepared in the same manner as the top layer with the
following changes: 0.75 mg/inZ of the H.B. Fuller Co.
HM-1972 hot melt adhesive was coated onto the bottom
side of the barrier film in a pattern 5.5" long x
1.75" wide.
BOTTOM LAYER: 6.0" long, rectangular with curved
ends.
SUBSTITUTE SHEET (RULE 26)
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W0 95129655 PCTIUS95f044S5
.= 38 -
The absorbent pad used in the bottom layer was
prepared in the same manner as the top layer with the
following changes: 8 mg/in2 of HM-1972 adhesive from
H.B. Fuller Co. was coated onto the bottom side of
the barrier film in a pattern 5.25" long x 1.75"
wide.
The products were assembled to be staggered at both
ends.
Product C was prepared as follows:
TOP LAYER: 6.0'° long, rectangular with curved ends.
The absorbent pad used in the top layer was
prepared in the same manner as the top layer of
Product B with the following changes: The layering
adhesive was 0.75 mg/in~ H.B. Fuller Co. HM-1335X hot
melt adhesive.
MIDDLE LAYER: 6.0" ,long, rectangular with curved
ends.
The middle layer was the same as the top layer.
BOTTOM LAYER: 6.0°' long, rectangular with curved
ends.
The absorbent pad used in the bottom layer was
prepared in the same manner as the top layer with the
following changes: The positioning adhesive was 8
mg/in~ of HM-1335X adhesive from H.B. Fuller Co.
90° peel strength testing was performed on 20 samples
of each product using the procedures outlined in Example
II. The data relate to removing the top pad layer from
the middle pad layer and the middle layer from the bottom
layer. The results are shown in Table 5, below.
SUBSTITUTE SHEET (RULE 26)
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/ 39
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WO 95129655 PCTII1S95104455
- '40 -
EXAMPLE IV
Individual absorbent pads were prepared in the same
manner as Product A of Example I with the following
changes: The surface opposite the "smooth side" of the
absorbent structure is adhered to a 0.6 mil polypropylene
barrier film using about 2.5 mg/in2 National Starch
X34-5539 adhesive coated on the top side of the barrier
film. The pads were rectangular with curved ends, 6" long
by 2" wide, and had a surface area of 11.5 in2. Finished
pads having no adhesive on the exposed barrier film
surface were taped to a roll of paper and run through a
spray coating line to be exposed to adhesive for=the
trial. The entire exposed surface of the barrier film was
coated with adhesive (the taped area was considered to be
negligible). The adhesive coating weights of the
resulting samples of Products D-K are shown in Table 6.
TABLE 6
Coating Peel
Product Adhesive WeiQht* Substrate
D Atactic polypropylene' 0.02 FFP~
E Atactic PP' 0.04 FFP~
F Atactic PP' 0.06 FFP~
Ethylene-vinyl acetateb 0.03 FFPs
H Acrylic' N/A FFFe
I Acrylic° 0.06 FFP~
J SBS/SIS' 0.02 FFP~
K SBS/SIS' 0.04 FFPf
*grams/pad
'H. B. Fuller Co. LUNATACK D 3457C
bH.B. Fuller Co. LUNATACK D 3446C
'Schenectady International HRJ 10127
°Schenectady International HRJ 4326
'H. B. Fuller Co. 1280
The structure of Product A, thermobonded @ 265°F, 2 sec.
=The absorbent structure of Product A.
The samples were prepared and tested (90° Peel) according
to the test method described in Example II. The results
are shown in Table 7.
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WO 95/29655 PCTIUS95I04485
- 42 -
The results suggest that several classes of adhesives
are useful in the practice of the present invention.
While the results using acrylic adhesives were not
optimal, they suggest that acrylics can be formulated to
work.
The flexural resistance of three types of commercial
panty liners and two embodiments of the present invention
(Product L and Product M) was tested using the following
test protocol:
Ten (10) samples of each product were obtained and
conditioned for 24 hours at 72°F, 65% relative humidity.
Each product sample was placed in a modified INSTRON
Flexure Fixture, Model X2810-020. The fixture was
modified to provide an adjustable roller gap, the gap was
set at 1-1/2", and the Fixture was placed in the INSTRON
Model X1122 test device described in Example II, above,
with a 2,000 gram compression cell. A sample product was
placed across the two rollers, and the transverse beam of
the test device was adjusted to 1/2" above the rollers.
The transverse beam descended toward the sample at 5"/min
and continued until it had traveled 1-1/2" and the
measured deflection values had passed the maximum value
and began to decrease. The maximum force of the
deflection was measured in grams and converted to lbs.
Product L was prepared in the same manner as Product
B of Example III with the following changes: The seal
pattern around the perimeter of the individual pad layers
was a repeating flower pattern having a space of about 3
mm between adjacent flowers, the absorbent structure was
SUBSTITUTE SHEET (RULE 26)
WO 95/29655 PCTIUS95104485
- 43
thermobonded at 300 °F for 2 sec., and the layering
adhesive is coated at 0.75 mg/in2 in a pattern 2" by 5.75".
Product M was prepared in the same manner as Product
L with the following changes: The seal pattern around the
perimeter of the individual pad layers was a continuous
embossed line, the absorbent structure is formed like that
of Product A of Example I - and the layering adhesive is
coated at 0.75 mg/in2 in a pattern 1.75" by 5.75".
The results of this testing are shown in Table 8,
below.
Table 8
Average Flexural
Fore llb~- ) Ranae llbs. 1
ALWAYS DRY-WEAVE 0.029 0.028-0.030
KOTEX LIGHT DAYS
Comfort Design 0.065 0.060-0.073
STAYFREE Panty Liner 0.234 0.214-0.256
Product L 0.167 0.141-0.185
Product M 0.215 0.194-0.231
Both embodiments of the present invention fall within
the flexural resistance range of currently available
commercial panty liners.
The specification and examples above are presented to
aid in the complete and non-limiting understanding of the
invention disclosed herein. Since many variations and
embodiments of the invention can be made without departing
from its spirit and scope, the invention resides in the
claims hereinafter appended.
SUBSTITUTE SHEET (RULE 26)
