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Description  |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to female sanitary napkins. Particularly, the
present invention concerns thin, flexible sanitary napkins offering
enhanced fit and comfort through a construction which promotes a
continuously self-conforming anatomical cooperation of the sanitary napkin
to the wearer to yield a highly effective absorbent device.
2. Background Art
All manner and variety of absorbent articles configured for the absorption
of body fluids such as menses, urine and feces are, of course, well known.
With respect to feminine protection devices, the art has offered two basic
types; sanitary napkins have been developed for external wear about the
pudendal region while tampons have been developed for internal wear within
the vaginal cavity for interruption of menstrual flow therefrom. Such
tampon devices are disclosed in U.S. Pat. No. 4,412,833, entitled "Tampon
Applicator", which patent issued to Weigner at al. on November 1, 1983,
and U.S. Pat. No. 4,413,986, entitled "Tampon Assembly With Means For
Sterile Insertion", which patent issued to Jacobs on November 8, 1983.
Hybrid devices which attempt to merge the structural features of the
sanitary napkins and the tampons into a single device have also been
proposed. Such hybrid devices are disclosed in U.S. Pat. No. 2,092,346,
entitled "Catamenial Pad", which patent issued to Arone on September 7,
1937, and U.S. Pat. No. 3,905,372, entitled "Feminine Hygiene Protective
Shield", which patent issued to Denkinger on September 16, 1975. Other
less intrusive hybrid devices are known as labial or interlabial sanitary
napkins and are characterized by having a portion which at least partially
resides within the wearer's vestibule and a portion which at least
partially resides external of the wearer's vestibule. Such devices are
disclosed in U.S. Pat. No. 2,662,527, entitled "Sanitary Pad", which
patent issued to Jacks on December 15, 1953, and U.S. Pat. No. 4,631,062,
entitled "Labial Sanitary Pad", which patent issued to Lassen et al. on
December 23, 1986.
With respect to sanitary napkins, at least two general classes pertinent to
the present invention exist. One such class is for the absorption of
medium to high menstrual flows. These sanitary napkins offer a fairly high
absorptive capacity. Absorptive capacity is commonly achieved by providing
the napkins with a fairly thick and bulky absorbent member, commonly fluff
pulp. Sanitary napkins of this class are disclosed in U.S. Pat. No.
3,294,091, entitled "Sanitary Napkin", which patent issued to Morse on
December 27, 1966, U.S. Pat. No. 4,654,040, entitled "Smooth-Edged
Contoured Sanitary Napkin", which patent issued to Luceri on March 31,
1987, and U.S. Pat. No. 4,687,478, entitled "Sanitary Napkin With Flaps",
which patent issued to Van Tilburg on August 18, 1987. Such sanitary
napkins theoretically have a high absorptive capacity, however, when the
sanitary napkin is worn and subjected to the compressive forces of the
wearer's thighs and pudendal region, the fluff pulp core simply compacts
or bunches into an arbitrary, but generally rope-like shape. Such napkins
commonly shift from their original placement so that after only a short
wearing time, the napkin might only partially, if at all, be beneath the
wearer's vaginal orifice or vestibule. Thus, in use, these sanitary
napkins sometimes offer very little absorption. Further, the rolling and
twisting of these napkins may create soiling on the wearer's panties and
skin surfaces. In addition, the bulkiness of these napkins causes a high
degree of wearing awareness and may make them quite obtrusive when worn
with tight fitting slacks, body suits or bathing suits.
A second class of sanitary napkins are intended for light or low menstrual
flows and are commonly referred to as panty liners or panty shields.
Sanitary napkins of this type are disclosed in U.S. Pat. No. 4,681,578,
entitled "Pantiliner With Ventilation Areas", which patent issued to
Anderson and Brandt on July 21, 1987. Sanitary napkins of this class, as a
group, are thinner, somewhat more flexible and generally more comfortable
than those of the first class, however, they lack the absorptive capacity
of the napkins of the frist class.
Therefore, there exists a real consumer need for a sanitary napkin which is
thin and flexible, thereby offering enhanced fit and comfort, yet having a
fluid capacity great enough for use with medium to high menstrual flows
thereby allaying consumer fears of leakage and staining.
Therefore, it is an object of the present invention to provide a sanitary
napkin which is thin and flexible and which is absorbent enough to absorb
and contain medium to high menstrual flows.
It is an additional object of the present invention to provide a sanitary
napkin which will closely conform to the various anatomical shapes of the
female urogenital and buttocks region.
It is an additional object of the present invention to provide a sanitary
napkin which offers enhanced fit and comfort and a low degree of wearing
awareness.
It is an additional object of the present invention to provide a thin
flexible sanitary napkin having laterally extending flaps configured to
drape over the side edges of the wearer's panties in the crotch portion
thus being disposed between the side edges of the wearer's panties in the
crotch portion and the wearer's thighs.
It is an additional object of the present invention to provide the
laterally extending flaps with an attachment means on their garment facing
surface so that the flaps can wrap around the side edges of the wearer's
panties in the crotch portion and be attached to the garment facing side
of the wearer's panties in order to provide protection from soiling and so
as to keep the napkin properly positioned in the wearer's panties.
These and other objects of the present invention will be more readily
apparent when considered in reference to the following description and
when taken in conjunction with the accompanying drawings.
SUMMARY OF THE INVENTION
In accordance with the present invention, a sanitary napkin having a body
surface and a garment surface and being comprised of an absorbent means
underlayed by a liquid barrier means, wherein the sanitary napkin is
relatively highly flexible and has a capacity great enough to handle
medium to high menstrual flows, is provided. In a preferred embodiment,
the sanitary napkin comprises, from the body surface down, an apertured
formed film topsheet, an apertured nonwoven wipe acquisition sheet, a
wet-laid tissue, a superabsorbent core, and a barrier sheet. Preferably,
the central width of the absorbents is at least about 7.0 centimeters and
the caliper of the napkin as a whole is less than about 2.5 millimeters.
In a preferred embodiment, the napkin has laterally extending flaps which
drape over the edges of the wearer's panties in the crotch and are
attachable to the garment side of the wearer's panties.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a top plan view of a preferred sanitary napkin embodiment of the
present invention with portions being torn away to show underlying
structure.
FIG. 2 is a lateral cross-sectional view of the preferred sanitary napkin
embodiment shown in FIG. 1 taken along line 2--2 of FIG. 1.
FIG. 3 is a top plan view of a preferred topsheet and wipe acquisition
sheet laminate with portions of the topsheet being torn away to show
underlying structure.
FIG. 4 is a top plan view of an alternatively preferred sanitary napkin
embodiment of the present invention with portions being torn away to show
underlying structure.
FIG. 5 is a top plan view of another alternatively preferred sanitary
napkin embodiment of the present invention with portions being torn away
to show underlying structure.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The present invention relates to female sanitary napkins and in particular
to sanitary napkins which are thin and flexible and offer enhanced fit,
comfort, and containment.
As used herein, the term "sanitary napkin" refers to an article which is
worn by females adjacent to the pudendal region and which is intended to
absorb and contain the various exudates which are discharged from the body
(e.g., blood, menses and urine) and which is intended to be discarded
after a single use (i.e., it is not intended to be laundered or otherwise
restored or reused). Interlabial devices which reside partially within and
partially external of the wearer's vestibule are also within the scope of
this invention. As used herein, the term "pudendal" refers to the
externally visible femal genitalia and is limited to the labia majora, the
labia minora, the clitoris, and the vestibule.
A preferred embodiment of a sanitary napkin 10 of the present invention is
shown in FIGS. 1 and 2. As can be seen in FIGS. 1 and 2, a preferred
sanitary napkin 10 basically comprises an absorbent means 13 and a liquid
impermeable barrier means 16. The absorbent means 13 may be any means
which is generally compressible, conformable, non-irritating to the
wearer's skin and capable of absorbing and containing body exudates such
as menses, blood and urine. Preferably, the absorbent means 13 maintains
integrity when wetted, in use. The absorbent means 13 has a first major
surface 19 and a second major surface 22. The barrier means 16 is adjacent
the second major surface 22 of the absorbent means 13. The barrier means
16 may be any means which is flexible and liquid impervious and which
prevents the exudates absorbed and contained in the absorbent means 13
from wetting articles which contact the sanitary napkin 10 such as
panties.
In the preferred embodiment shown in FIGS. 1 and 2, the absorbent means 13
is comprised of a liquid permeable topsheet 25, a liquid permeable wipe
acquisition sheet 28, a wet-laid tissue sheet 31 and an absorbent core 34.
In the preferred embodiment shown in FIGS. 1 and 2, the barrier means 16
is a barrier sheet. The absorbent core 34 is comprised of hydrogel-forming
material 37 disposed between two air-laid tissue sheets 40 and 43. The
sanitary napkin 10 has side edges 11 and end edges 12 which together form
the periphery 15 of the sanitary napkin 10. The sanitary napkin 10 has a
body surface 26 which is generally defined by the topsheet 25 and a
garment surface 17 which is generally defined by the barrier sheet 16.
Looking at some of the elements of the sanitary napkin 10 more
specifically, the absorbent core 34 may be any means which is generally
compressible, conformable, non-irritating to the wearer's skin and capable
of absorbing and containing body exudates. The absorbent core 34 has a
first major surface 46, a second major surface 49, a pair of end edges 52
and a pair of side edges 55. The absorbent core 34 may be manufactured in
a wide variety of sizes and shapes (e.g., rectangular, hourglass, etc.). A
preferred shape of the absorbent core 34 is the dogbone shape shown in
FIG. 1. This preferred absorbent core 34 is about 22.0 centimeters long
(longitudinal dimension along the longitudinal centerline 58), about 7.0
centimeters wide across its midportion (lateral dimension along the
lateral centerline 61) and about 8.0 centimeters wide across its widest
portion (lateral dimension). The absorbent core 34 is symmetrically
configured for ease of manufacture and so that no conscious effort is
required by the wearer to properly place the napkin 10 in the direction it
should be worn. The midportion is configured to basically conform to the
wearer's thighs and to the thinner crotch portion of the wearer's panties
so as to prevent excessive bunching. The size of the absorbent core 34 may
be varied to accommodate wearers ranging in size and also ranging in the
expected amount of exudate fluid volume. The absorbent core 34 may be
attached over the core's first or second major surfaces 46 and 49,
respectively, to adjacent members such as the topsheet 25 and barrier
sheet 16 by any of the means well known in the art, such as by
spray-gluing or lines or spots of adhesive. Such attachment facilitates
integrity and recoverability of the absorbent materials in use so as to
maintain an optimum degree of absorbency. Preferably, the absorbent core
34 has a wet-tensile strength in the cross-direction of at least about
100.0 grams per centimeter. Wet tensile strength is determinable by ASTM
Standard D 829-49.
The absorbent core 34 may be manufactured from a wide variety of liquid
absorbent materials commonly used in disposable sanitary napkins, diapers,
and other absorbent articles. Examples of suitable absorbent materials
include comminuted wood pulp which is generally referred to as airfelt,
creped cellulose wadding, absorbent foams, absorbent sponges, synthetic
staple fibers, polymeric fibers, hydrogel-forming polymer gelling agents,
or any equivalent materials or combinations of materials. A particularly
preferred absorbent material are polymeric gelling agents. Polymeric
gelling agents are those materials which, upon contact with fluids (i.e.,
liquids) such as water or body fluids, imbibe such fluids and thereby form
hydrogels. In this manner, fluid discharged into the absorbent core 34 can
be acquired and held by the polymeric gelling agent, thereby providing the
articles herein with enhanced absorbent capacity and/or improved fluid
retention performance.
The polymeric gelling agent which is employed in the absorbent core 34 will
generally comprise particles of a substantially water-insoluble, slightly
cross-linked, partially neutralized, hydrogel-forming polymer material.
Such polymer materials can be prepared from polymerizable, unsaturated,
acid-containing monomers. Suitable unsaturated acidic monomers for use in
preparing the polymeric gelling agents used in this invention include
those listed in U.S. Pat. No. 4,654,039, entitled "Hydrogel-Forming
Polymer Compositions For Use In Absorbent Structures", which issued to
Brandt, Goldman and Inglin on March 31, 1987, and which patent is
incorporated herein by reference. Preferred monomers include acrylic acid,
methacrylic acid, and 2-acrylamido-2-methyl propane sulfonic acid. Acrylic
acid itself is especially preferred for preparation of the polymeric
gelling agent material.
In the hydrogel-forming polymeric gelling agent the polymeric component
formed from unsaturated, acid-containing monomers may be grafted onto
other types of polymer moieties such as starch or cellulose. Polyacrylate
grafted starch materials of this type are especially preferred for use
herein.
Preferred polymer gelling agents which can be prepared from conventional
types of monomers include hydrolyzed acrylonitrile grafted starch,
polyacrylate grafted starch, polyacrylates, maleic anhydride-based
copolymers and combinations thereof. Especially preferred are the
polyacrylates and polyacrylate grafted starch.
Whatever the nature of the basic polymer components of the hydrogel-forming
polymeric gelling agents used in the absorbent core 34 herein, such
materials will in general be slightly cross-linked. Cross-linking serves
to render the hydrogel-forming polymer gelling agents used in this
invention substantially water-insoluble, and cross-linking thus in part
determines the gel volume and extractable polymer characteristics of the
hydrogels formed from the polymeric gelling agents employed. Suitable
cross-linking agents are well known in the art and include, for example,
those described in greater detail in U.S. Pat. No. 4,076,663, which patent
issued to Masuda el al. on February 28, 1978, and which patent is
incorporated herein by reference. Preferred cross-linking agents are the
di- or polyesters of unsaturated mono- or polycarboxylic acids with
polyols, the bisacrylamides and the di- or triallyl amines. Especially
preferred cross-linking agents are N,N'-methylenebisacrylamide,
trimethylol propane triacylate and trially amine. The cross-linking agent
can generally comprise from about 0.001 mole percent to 5.0 mole percent
of the resulting hydrogel-forming polymer material. More preferably, the
cross-linking agent will comprise from about 0.01 mole percent to 3.0 mole
percent of the hydrogel-forming polymeric gelling agent used herein.
The slightly cross-linked, hydrogel-forming polymeric gelling agents which
may be used in the articles of the present invention are generally
employed in their partially neutralized form. For purposes of this
invention, such materials are considered partially neutralized when at
least 25.0 mole percent, and preferably at least 50.0 mole percent of
monomers used to form the polymer are acid group-containing monomers which
have been neutralized with a salt-forming cation. Suitable salt-forming
cations include alkali metal, ammonium, substituted ammonium, and amines.
This percentage of the total monomer utilized which are neutralized acid
group-containing monomers is referred to herein as the "degree of
neutralization."
The polymeric gelling agent materials used in the absorbent articles herein
must have a relatively high capacity for imbibing fluids encountered in
such article. The absorbent capacity of these materials can be quantified
by referencing the "gel volume" of the polymeric gelling agents which are
to be selected for use in the present invention.
For purposes of this invention, gel volume can be define in terms of the
amount of syntheic urine absorbed by any given polymeric gelling agent and
is specified as grams of synthetic urine per gram of polymeric gelling
agent. Gel volume in synthetic urine can be determined by forming a
suspension of about 0.1-0.2 parts of dried polymeric gelling agent to be
tested with about 20 parts of synthetic urine. This suspension is
maintained at ambient temperature under gentle stirring for a time
sufficient, e.g., about 1 hour, for swelling equilibrium to be attained.
The gel volume of the polymeric gelling agent in grams of synthetic urine
per gram of polymeric gelling agent is then calculated from the weight
fraction of the polymeric gelling agent in the suspension and the ratio of
the liquid volume excluded from the formed hydrogel to the total volume of
the suspension.
The gel volume of the gelling agents used in the absorbent core 34 herein
will generally be at least about 20.0 grams of synthetic urine per gram of
polymeric gelling agent. More preferably, the gel volume of the materials
employed will range from about 20.0 to about 60.0, most preferably from
about 22.0 to about 35.0 grams of synthetic urine per gram of polymeric
gelling agent.
Within the webs which form the layers of the absorbent core 34, the
particles of the polymeric gelling agent should be thoroughly dispersed
but may or may not be uniformly distributed. In particular, there may be
regions or zones of the core layers which have higher concentrations of
gelling agent particles than do other regions or zones of the layers.
In a preferred embodiment, the sanitary napkin 10 of the present invention
will have a hydrogel-forming polymeric gelling agent distributed
throughout at least about 17.0 square centimeters of the napkin, more
preferably throughout at least about 50.0 square centimeters of the
napkin, and most preferably throughout at least about 100.0 square
centimeters of the napkin. Preferably, the hydrogel-forming polymeric
gelling agent will be distributed in an amount of from about 0.001 grams
per square centimeter to about 0.009 grams per square centimeter, more
preferably of from about 0.003 grams per square centimeter to about 0.008
grams per square centimeter, and most preferably from about 0.004 grams
per square centimeter to about 0.007 grams per square centimeter.
Preferably. the absorbent core 34 will contain from about 5.0% to about
85.0% by weight of hydrogel-forming polymeric gelling agent, more
preferably from about 10.0% to about 70.0%, and most preferably from about
15.0% to about 55.0%.
In the preferred embodiment shown in FIG. 2, the absorbent core 34 is a
laminate comprised of a layer of superabsorbent polymer material 37
disposed between two air-laid tissues 40 and 43. A suitable laminate is
the superabsorbent laminate WATER-LOCK L-535 available from the Grain
Processing Corporation of Muscatine, Iowa (WATER-LOCK registered TM by
Grain Processing Corporation). Such superabsorbent laminates are disclosed
in U.S. Pat. No. 4,467,012, entitled "Composition For Absorbent Film And
Method Of Preparation", which patent issued to Pedersen et al. on August
21, 1984, and U.S. Pat. No. 4,260,443, entitled "Laminated Absorbent
Process", which patent issued to Lindsay et al. on April 7, 1981, and
which patents are incorporated herein by reference. The WATER-LOCK L-535
has a hydrogel polymer loading of 0.005 grams per square centimeter,
however, loadings of 0.001-0.009 grams per square centimeter have been
found acceptable. The first and second tissue layers 40 and 43 provide
containment of the superabsorbent polymer material 37, improve lateral
wicking of the absorbed exudates throughout the absorbent core 34 and
provide a degree of absorbency. In the case of non-particulate
hydrogel-forming polymer gelling agents which can be formed into fibrous
sheets, foams or films, the non-particulate gelling agent may comprise
from about 15% to about 100% by weight of the absorbent core 34, more
preferably of from about 40% to about 100%, and most preferably of from
about 60% to about 100%. The basis weight of such non-particulate
superabsorbents may be from about 0.002 to about 0.028 grams per square
centimeter, more preferably of from about 0.003 to about 0.018, and most
preferably of from about 0.004 to about 0.010. Two suitable and
commercially available non-particulate absorbent materials for the
absorbent core 34 are a double layer acrylic fibrous material available
under the tradename Lanseal F from the Choli Company, LTD., of Higashi,
Osaka Japan and a carboxymethylcellulose fibrous material available under
the tradename Aqualon C from Hercules, Inc. of Wilmington, Delaware.
The total absorbent capacity of the absorbent core 34 should be compatible
with the design exudate loading for the intended use of the sanitary
napkin 10. Further, the absorbent capacity of the absorbent core 34 may be
varied to accommodate wearers ranging in the expected amount of exudate
fluid volume. For instance, a different absorbent capacity may be utilized
for sanitary napkins intended for daytime use as compared with those
intended for nightime use, or for sanitary napkins intended for use by
teenage females as compared with those intended for use by more mature
women.
It should be noted that the scope of the present invention is not intended
to extend to sanitary napkins which are void of any superabsorbent
material and which have a central absorbent member overlayed solely by
nonwoven materials, wherein the nonwoven materials have caliper of less
than 0.50 millimeters, as determined by the caliper test, as later
defined.
Superimposed over the absorbent core 34 and extending about 3.0 millimeters
beyond the edges 52 and 55 of the absorbent core 34 is the wet-laid tissue
31. The wet-laid tissue 31 is liquid permeable. A satisfactory wet-laid
tissue 31 has a basis weight of about 15.8 grams per square meter and an
air permeability of about 30.5 cubic meters per minute per square meter at
a pressure differential of about 12.8 millimeters of water. Preferably,
the wet-laid tissue 31 maintains integrity when wetted, in use. The
wet-laid tissue 31 preferably has a wet tensile strength in the
cross-direction of at least about 15.0 grams per centimeter. Suitable
tissue 31 and their manufacture are disclosed in U.S. Pat. No. 3,301,746,
entitled "Process For Forming Absorbent Paper By Imprinting A Fabric
Knuckle Pattern Thereon Prior To Drying And Paper Thereof", which patent
issued to Sanford and Sisson on January 31, 1967, and which patent is
incorporated herein by reference. In a preferred embodiment, those parts
of the wet-laid tissue 31 which extend beyond the edges 52 and 55 of the
absorbent core 34 are associated with the barrier sheet 16. The wet-laid
tissue 31 may be associated with the barrier sheet 16 by attachment means
as are well known in the art such as by spray-gluing or lines or spots of
adhesive. The wet-laid tissue 16 serves a number of purposes. The tissue
31 serves to confine any loose superabsorbent material 37 between the
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