Note: Descriptions are shown in the official language in which they were submitted.
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PATENT
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ABSORBENT ARTICLE HAVING A FOAM BAFFLE
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FIELD OF THE INVENTION ~
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This invention relates to a disposable absorbent article having
a liquid-permeable cover sheet, a foam baffle, and an absorbent ~ -
therebetween. More particularly, this invention relates to an
absorbent article that uses a foam as a liquid-impervious baffle and
hot melt adhesive to bond the foam to the absorbent.
BACKGROUND OF THE INVENTION
Disposable absorbent articles, such as sanitary napkins ~
catamenial pads, panty liners, training pants, incontinent garments, ~ ~ -
diapers, and the like are designed to be worn adjacent to a human
body to absorb discharged body liquids. Conventionally, disposable ~ ~-
absorbent articles comprise an absorbent pad positioned between a
liquid-permeable nonwoven top sheet and a liquid-impermeable back
sheet. The nonwoven top sheet draws the waste away from the
contacting skin and into the absorbent core while the liquid
impermeable back sheet prevents the absorbed liquids from leaking out
of the absorbent article. Numerous variations of, and elements in
addltion to, these basic components have been taught with each
variation or additional element being directed to improving specific
characteristics of the article. Regardless of the particular
construction, however, it is expected that the absorbent article will
have characteristics which permit liquid to penetrate the
liquid-permeable top sheet while quantities of liquid are absorbed by -~
the core.
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The body fluid which penetrates the thickness of the core will
be pr~vented from wetting the surrounding undergarment by a liquid-
impermeable baffle. Usually, the baffle is a polyethylene film
having a thickness of about .001 to about .005 of an inch (.025 to
.13 millimeters). Optionally, the absorbent article may provide for
a pressure sensitive adhesive applied to the garment facing side of
the baffle. The adhesive is of the type that is capable of securing
the absorbent article to the crotch portion of an undergarment, yet
permitting removal of the article when soiled.
For convenience in the description, a panty liner or a very thin
absorbent pad used primarily for feminine hygiene, which may be used
for undergarment protection between menstrual periods as well as
absorbing light flow between and during periods will be described
herein. However, it is to be understood that this preferred
embodiment of this invention is not limiting the invention only to
panty liners.
Heretofore, in constructing a panty liner, some means was
provided for holding the fibers constructing the absorbent core
together to form a layer so the laminate does not fall apart and/or
for bonding the layer of fibers to adjoining layers.
Several approaches have been taken in the prior art. One
technique is to seal the fibers within an envelope. The envelope is
formed by sealing or adhesively attaching the cover sheet and the
baffle together about their perimeters. These layers are typically a
nonwoven material and are bonded to each other by application of heat
or with adhesive.
Another approach has been to add thermoplastic powders, fibers,
or fibrils to the fiber layer and to apply heat during lamination to
form a supporting web of thermoplastic material throughout the
fibrous layer as well as a bond between the thermoplastic web and
adjoining thermoplastic liquid-permeable and liquid-impermeable
layers. Typically, the laminate is embossed during application of
heat so that bonding occurs primarily in embossed areas.
Crosslinkable latex adhesives have also been employed in bond~ng
the absorbent fibers together and to bond the adjacent layers
together. One problem in using latex adhesives in this manner is
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that the adhesive is at least partially absorbed into the absorbent
fibers. This can redu~e the efficiency of the absorbent fibers.
Another problem with using a latex adhesive to bond the adhesive
fibers together is that upon drying the absorbent fibers have an
increased stiffness, resulting in an article that is less comfortable
to the wearer. ~
Embossing has also been used in such constructions to cause the ~ -
latex adhesive to migrate into the embossed layers prior to curing.
Other patent literature discloses a pad having the absorbent
fibers enclosed in a tissue or a nonwoven wrap. The edges are sealed
by highly compressing the pad around its entire periphery. However,
when the panty liner's entire periphery is compressed or compacted
sufficiently to seal the edges, relatively harsh and sharp edges are
formed which tend to be abrasive.
It is therefore desirable in the art to produce a panty liner
that would have a low cost for manufacturing and would be soft and
comfortable to the wearer yet resilient and absorbent in use.
SUMMARY OF THE INVENTION
Briefly, this invention relates to an absorbent article having a
liquid-permeable cover sheet; an absorbent; a liquid-impermeable foam
baffle having a thickness ranging from about 0.51 millimeters to
about 1.54 millimeters, a density of from about 0.0225 g/cm3 to about
0.0962 g/cm3, and having an absorbent facing surface and a garment -
facing surface; and a layer of hot melt adhesive applied to the
absorbent facing surface to bond the absorbent to the foam.
In a preferred embodiment, the absorbent article is a thin
elongated panty liner in which a polyethylene foam baffle is utili ed
as a liquid-impervious backing. The cover sheet, the absorbent core,
and the foam baffle can have coterminous edges.
The completed panty liner may be used in combination with a -
tight fitting undergarment without supplementary attachment means, if
desired. Preferably, a pressure sensitive, garment attachment - .
adhesive is disposed on a least a portion of the garment facing
surface of the polyolefin foam baffle and covered with a removable
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peel strip which may be peeled off by the user for more positive
attachment purposes.
The general object of this invention is to provide an absorbent
article utilizing a polyolefin foam as a liquid-impermeable baffle.
A more specific object of this invention is to provide a panty liner
that is simpler, less expensive to manufacture, and has greater
comfort to the wearer.
Another object of the invention provides an absorbent article
wh;ch is softer and provides improved fluid management.
Other objects and advantages of the present invention will
become more apparent to those skilled in the art in view of the
following description and the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a plan view of an absorbent article such as a panty
liner.
FIG. 2 is an enlarged sectional view taken along 2--2 of FIG. 1.
FIG. 3 is a perspective view of the bottom of the absorbent
article showing a garment adhesive strip.
FIG. 4 is schematic of a method for producing the absorbent
article shown in FIG 1.
DETAI~ED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIGS. 1 and 2, an absorbent article 10 in the form
of a panty liner is shown. Although not depicted, other absorbent
articles contemplated to be within the scope of the invention include
diapers, adult incontinent garments, training pants, sanitary
napkins, and the like. The panty liner 10 has a top cover 12 of a
nonwoven material with a pattern of spaced longitudinally extending -
line embossments 14 impressed therein. The line embossments 14
extend the full length of the panty liner 10 and intersect the end
and edges of the panty liner 10 at intervals indicated at 15, leaving
35 major portions 16 of the periphery unembossed and therefore unbonded ~ -
in the z-direction (see FIG. 2). An absorbent 17 consisting of
absorbent fibers is positioned below the cover 12 and is compressed
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along the line embossments 14 which provide hydrogen bonding of the
fibers in areas 18. It is this hydrogen bonding which provides the
absorbent 17 and the cover 12 with sufficient integrity to prevent
delamination in the z.-direction. The cover 12 is puffed up and has
rounded cushion-like contours between the line embossments 14 where
uncompressed and unbonded portions of the absorbent 17 press upwardly
against the cover 12. A hot melt adhesive 19 is sprayed onto the
absorbent 17 and a foam baffle 20 is adhesively attached thereto.
The nonwoven cover 12 may be any of the many known types of
liquid-pervious, nonwoven materials that are liquid-permeable and
non-irritating to the skin. For example, the cover 12 may be made
from a carded web of polyester, polypropylene, nylon, or other heat
bondable fibers. A preferred material is a nonwoven web of stable
linked rayon fibers. A more preferred material is a spunbond
polypropylene fabric. Spunbonded webs of continuous filaments such
as polyethylene, polypropylene, polyester, nylon and the like retain
a much drier surface when in use. The most preferred materials are -
spunbond polypropylene webs having a basis weight from about 10 gsm
to about 40 gsm. A spunbond material containing a whitener such as
titanium dioxide (TiO2) or ralcium carbonate (CaC03) is desirable
because the color exhibits good stain masking properties to hide body
fluid that has permeated into the absorbent 17. Spunbond also has
sufficient strength so that the cover 12 does not tear or fall apart
in use.
The absorbent 17 may be of any desired moisture absorbent
material. Typical materials include wood pulp, cotton, rayon,
polyesters, coforms, and combinations of these absorbent fibers. A
preferred material is devilizated wood fiber fluff as it is low in
cost. The fluff may further contain crosslinked highly absorbent
polymers ordinarily referred to as superabsorbents either as a
separate layer or mixed with the fibers. Preferably, the fibers have
a length of from about 0.5 to about 10 millimeters. Many methods for
making absorbents are known in the art, so there is no need to
describe such method here.
The line embossing 14 binds the short wood pulp fibers in the
absorbent 17 to the cover 12 by means of hydrogen bonding and heat.
Hydrogen bonding of wood pulp fibers are bonds which develop when the
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hydroxyl groups of adjacent fibrillae in the cellulosic fibers form
hydrogen bonds when the web dries. In this instance, the bonds are
formed during the embossing process. Such bonding serves as a means
for maintaining the strength and integrity of the absorbent 17 in the
z-direction. Sufficient strength and integrity in the x and y
directions are provided by adhesively attaching the foam baffle 20 to
the absorbent 17. The x, y and z designations are used herein in the
customary manner, see FIGS. 1 and 2, i.e. x and y are the
longitudinal and traverse directions respectively, while the z-
direction is perpendicular thereto. An objective of the lineembossing arrangement, in addition to providing the hydrogen bonding
which is the primary means for providing z-direction integrity in the
panty liner, is to provide the entire surface of the panty liner,
including the edges with a soft, cushion-like structure.
Undulating or wavy lines are also preferred for the line
embossments 14. When the panty liner is bent into an arcuate shape
during use, the wavy or undulating lines permit flexing much more
than straight lines. The flexing produces only small scale wrinkles
which do not appear to interfere with tactile comfort as large scale
wrinkles have been found to do.
The line embossments 14 also direct the migration of the
absorbed fluid along the X--X axis. Since the edges of the panty
liner are unsealed, it is desirable to keep any of the absorbed
liquid away from these edges as long as possible. The longitudinally
extending embossments 14 serve this purpose well by acting as
conduits which, due to their compressed condition, provide small
pores in the absorbent 17 which can enhance capillary suction
pressures.
The adhesive 19 can be virtually any water insoluble or water ~ -
impermeable hot melt adhesive composition. For convenience, it is
generally preferred to employ one of the hot melt adhesives already
utilized by the manufacturer in the construction of the particular
absorbent article. The hot melt adhesive 19 has a cold tack to
improve its adherence and bonding of the absorbent 17 to the foam
baffle 20. The adhesive 19 can be applied by spraying a uniform
pattern, atomized with heated air into very small spherical or fiber-
like particles, onto the foam baffle 20. Suitable hot melt adhesives
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are Findley 593-335, an ethylene vinyl acetate blend, and Findley
582-371, as well as various amorphous polypropylenes, all available
from Findley Adhesives Inc., located at 11320 Watertown Plank Road,
Wauwatosa, Wisconsin. Practical ranges on the amounts of hot melt ~ -
adhesive to be applied range from about 1 gsm to about 15 gsm.
Preferably, the amount of adhesive ranges from about 5 gsm to about
12 gsm.
Referring now to FI6S. 2 and 3, the foam baffle 20 may be made
from any light weight polyolefin foam material having two or more
surfaces capable of being adhesively coated. Such foams may be a
closed cell, crosslinked or a non-crosslinked polyolefin foam.
Desirably, the foam is a polypropylene or a polyethylene foam, with
polyethylene being preferred. Particularly preferred is a non^
crosslinked polyethylene foam.
The foam must be flexible and capable of being formed into
sheets. The foam should have a thickness, as measured by ASTM D3575,
ranging from about 0.51 millimeters to about 6.35 millimeters.
Preferably, a thickness of from about 0.51 millimeters to about 1.54
millimeters, more preferably from about 0.76 millimeters to about
1.27 millimeters, and most preferably from about 0.76 millimeters to
about 1.02 millimeters.
The foam should have a density ranging from about 0.0225 g/cm3
to about 0.0962 g/c3. Preferably, the density ranges from about
0.0322 g/cm3 to about 0.0642 g/cm3, and most preferably, from about
0.0354 g/cm3 to about 0.0482 g/cm3. The foam should have the
thickness and density measured just after extrusion, prior to any
compaction of the foam's cells that may occur through subsequent
handling, packaging, or other methods or processes that may alter the
foam's characteristics. Examples of commercially available foams
contemplated for use in this invention include the trade name CA-30
foam manufactured by Sealed Air Corp. located at 19-01 State Highway
208, Fair Lawn, New Jersey and trade name AF-030 manufactured by
Astro-Valcour, Inc. located at 18 Peck Ave., Glens Falls, New York.
Referring to FIG. 3, disposed on the foam baffle's 20 garment ~ `
facing surface is a long~tudinally extending pressure sensitive
adhesive means 22, provided for attaching the panty liner 10 to a
crotch portion of an undergarment. While such adhesive means are
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illustrated in the preferred form of a longitudinal strip, it is
understood that various patterns such as spots, or transverse lines
will be suitable.
The adhesive employed may be any of the large number of
pressure-sensitive adhesives. Non-limiting examples of such
adhesives are those hot melt adhesive compositions based on
ethylene/vinyl acetate copolymers, isotactic or atactic
po1ypropylene, styrene-butadiene, styrene-isoprene, or styrene-
ethylene-butylene A-B-A or A-B-A-B block copolymers. Such adhesives
are sold under the Kraton~, Solprene~ and Stereon~ trade names. In
addition to a base polymer, the hot melt adhesive is composed of
tackifiers, oils and/or waxes as well as conventional additives
including stabilizers, anti^oxidants, pigments and the like. A
preferred adhesive is 34-2823 from National Starch and Chemical Co.
located at Finderne Ave., Bridgewater, New Jersey.
Generally, the garment attachment adhesive 22 is applied to the
peel strip 24 by suitable methods known in the art. For example,
slot coating or spraying. Desirably, the amount of adhesive 22
ranges from about 10 gsm to about 40 gsm, preferably from about 18
gsm to about 30 gsm and most preferably from about 18 gsm to 25 gsm.
It should be recognized that even though this amount of adhesive 22
is adequate to anchor a panty liner, greater amounts of adhesive may
be required for anchoring particular structures.
A preferred method of bonding the garment adhesive 22 to : :~
the foam baffle 20 is disclosed in the commonly assigned, : :
copending, Canadian patent application No. ,
corresponding to patent application US Serial No. 055,052 filed
on April 28, 1993. This disclosure is incorporated by reference
and made a part hereof.
Overlying the adhesive 22 is the protective peel strip 24 which
is provided to protect the adhesive 22 from contamination and
unintended adhesion prior to use. A particularly useful material is
a semi-bleached Kraft paper, the adhesive contacting side of which
has been silicone treated to provide easy release from the adhesive
elements.
Referring to FIG. 4, a suitable method of fabricating the panty
liner 10 will now be described. A liquid-pervious cover 110 has a
thin, uniform layer of absorbent 130 air-laid onto one surface
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thereof. The cover 110 and the layer of absorbent 130 are pressed
between two rollers 140 and 145 to densify the absorbent.
Optionally, the rollers 140 and 145 may supply sufficient pressure,
and heat if required, to hydrogen bond the cover 110 to the absorbent
130 as well as to emboss a pattern thereon. A foam baffle 150 is
unwound from a supply roll 160 and sprayed with a hot melt
construction adhesive 165 from a sprayer 17Q. Although not shown,
alternatively, the hot melt adhesive 165 may be sprayed onto the
adhesive 130 prior to contacting it with the foam baffle 150. The
foam baffle 150 is applied to the absorbent 130. An applicator 175
applies a garment attachment adhesive 177 onto one surface of peel
strip 180. The adhesive 177 is heated by a heater 190 so that when
the adhesive 177 contacts the foam baffle 150 the adhesive 177 will
be properly melted to permit bonding. Although not necessary,
bonding of the garment attachment adhesive 177 may be enhanced by one
or more compression rollers 195, 196 and 197. After bonding, the
laminate (consisting of the cover 110, the absorbent 130, the
adhesive 177 and the foam baffle 180) is die cut into a desired
shape 200 and packaged for shipment.
In using the panty liner of this invention it is preferred that
the peel strip 24 be removed from the foam baffle 20 exposing the
garment attachment adhesive 22. The panty liner 10 is then centered
and mounted in the crotch portion of an undergarment in the usual
way. -
Panty liners constructed in accordance with the present
invention have been found to possess a high liquid absorption
capacity. In addition, the panty liner is thin, soft and flexible so -
it is comfortable to the wearer.
Another advantage is that the panty liner is resilient and
conforms well to the surface of the body to which it is applied to
achieve good gasketing effects.
While the invention has been described in conjunction a specific
embodiment, it is to be understood that many alternatives,
modifications and variations will be apparent to those skilled in the
art in light of the foregoing description. For example, a wide
variety of absorbent products including baby diapers, adult :~
incontinent garments, training pants, wound dressing, sanitary
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napkins, and the like can incorporate this invention. Accordingly,
this invention is intended to embrace all such modifications and
variations which fall within the spirit and scope of the appended
claims.
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