Note: Descriptions are shown in the official language in which they were submitted.
2122660
PATENT
ABSORBENT ARTICLE HAVING A BODY ADHESIVE
FIELD OF THE INVENTION
This invention generally relates to disposable absorbent
articles, and particularly to absorbent articles adapted to be self
supporting and secured to the wearer. More particularly, this
invention relates to sanitary napkins for personal feminine hygiene
that may be secured to the wearer's body.
BACKGROUND OF THE INVENTION
All manner and variety of absorbent articles configured for the
absorption of body fluids such as menses, urine and feces are well
known. With respect to feminine protection devices, the art has
offered two basic types: sanitary napkins and tampons. Sanitary
napkins, for the purposes described herein includes thin devices
denoted as panty liners and interlabial pads, have been developed for
external use about the pudendal region of a female while tampons have
been developed for internal use within the vaginal cavity for
interruption of menstrual flow therefrom. Each has offered distinct
advantages.
2122660
~ A tampon is constructed of natural absorbent material such as
cotton, synthetic materials, such as polyethylene or rayon or
combinations thereof. Because the tampon is hidden and does not
disclose the fact that the wearer is menstruating, it is
stylistically preferable to the sanitary napkin. However, its use is
interdicted in a number of situations: in some women use of a tampon
is physically uncomfortable; its use is not acceptable immediately
after childbirth or during post-surgical periods, or when
pathological conditions exist; and lastly when menstrual flow is very
heavy, the tampon may have insufficient capacity to absorb secretions
making the sanitary napkin necessary to supplement or supplant the
tampon.
With respect to sanitary napkins, an important objective is to
control the absorption and flow of exudate or body fluids in a manner
which obtains maximum utilization of the available absorbent.
Ideally, a sanitary napkin is expected to immediately accept all body
fluid discharged, rapidly transport the fluid away from the point of
discharge, contain the transported fluid within the marginal confines
of the napkin, and maintain the body contacting surface as dry as
possible.
The prior art describes many sanitary napkins that have
addressed one or more of the above expectations. Improvements to the
sanitary napkin's absorbency have included, among other things, the
addition of superabsorbents into the absorbent batt and various
methods to improve body contact. In the latter, at least three
general designs exist. One design includes forming the napkin into a
cup or boat shape which is intended to catch the menses as it exits
the vaginal orifice.
. 2122660
- A second design includes those sanitary napkins that are raised
upwardly or humped in their medial portions so as to be near or in
contact with the pudendal region when worn. These sanitary napkins
attempt to contact and absorb menses immediately as it leaves the
vestibule. Such humps or raised areas have been formed from
additional medial absorbent or the incorporation of a
flexure-resistant deformation element.
The third design include those sanitary napkins that are not
predisposed to have a trough or a hump shape when worn, but instead
have a more or less rope-like shape when worn. Such sanitary napkins
typically have a fluff pulp absorbent core surrounded by flexible
outer wraps.
Securement of the sanitary napkin during use is generally
accomplished by attaching the sanitary napkin to the wearer's
undergarment by a pressure sensitive adhesive. The prior art also
teaches the use of wings and flaps which fold over the edges of the
elastic sides of the crotch portion of an undergarment and which may
then be secured underneath using an adhesive. The prior art further
teaches using panels with mechanical fasteners.
These methods of securing a sanitary napkin to an undergarment
can exhibit a number of drawbacks. One drawback is that the adhesive
can stick to the inside surface of the undergarment and cause
discoloration. Another is the napkin will tend to move with the
undergarment rather than the body of the wearer. This can result in
a less secure fit and increase incidence of fluid leakage,
irritation, and chafing.
2122660
,
Now a sanitary napkin with a body adhesive has been invented
which improves the fit with the curve of the human body, is
comfortable to wear, and is effective in preventing fluid leakage.
SUMMARY OF THE INVENTION
Briefly, this invention relates to a disposable absorbent
article having a total weight greater than about 5 grams and adapted
to be secured to the torso about the pudendal region of a human. The
absorbent article includes an absorbent and a body side adhesive
secured to the absorbent. The absorbent materials are designed to
absorb body exudates, including menstrual fluids, catamenial fluids,
blood and urine.
The body side adhesives used in the invention are of the type
that exhibit suitable adhesion properties to skin but which can be
removed without appreciable discomfort. The purpose of the adhesive
is to secure the absorbent proximate the wearer, improving body to
article contact. The adhesives typically have a peel force of from
about 25 to about 700 grams. Because of the absorbent articles
intimate contact with the wearer, it is also advantageous for the
absorbent's surface distal the wearer to be liquid-impermeable.
Liquid impermeability can be accomplished by means well known in the
art, and include securing a thin polyethylene backsheet to the
absorbent or coating the absorbent fibers with a hydrophobic
material.
2122660
In general, the present invention provides an
absorbent article, such as a sanitary napkin, disposable diaper,
incontinent pad, and the like, that is adhesively secured to the
wearer's body.
Another aspect of this invention is to provide a thin and
flexible absorbent article which will, by the mere act of putting it
on, will closely conform to and fit the external body surfaces.
Still another aspect of this invention is to provide an
absorbent article which obviates the need for a frictional supporting
means, resulting in a more comfortable body conforming absorbent
article.
Another aspect of the invention is to provide a sanitary napkin
that uses an adhesive applied to the body facing surface to secure
the napkin to the wearer.
Yet another aspect of this invention is to provide a sanitary
napkin which when secured to the wearer's body is, for all practical
purposes, invisible in outline underneath the wearer's garments.
These and other aspects of the present invention will be more
fully apparent from the following description when taken in
connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective view of an absorbent article having a
body adhesive located about its periphery and having a body side,
removable member partially pulled back.
Figure 2 is a perspective view of another embodiment of an
absorbent article showing a longitudinally and transversely centered
aperture through the topsheet and absorbent.
2122660
Figure 3 is a cross-sectional view of Figure 2 taken along
line 3--3.
Figure 4 is a top view of another embodiment of an absorbent
article having an upper surface which is at least partially overlaid
by a backsheet.
Figure 5 is a cross-sectional view of Figure 4 taken along
line 5--5 showing the adhesive partially residing on the topsheet and
the backsheet.
Figure 6 is an alternative cross-sectional view of an
alternative embodiment of Fig. 5 taken along line 5--5 showing the
backsheet extending over the absorbent's periphery and the adhesive
residing completely on the backsheet.
Figure 7 is a top view of another embodiment showing an aperture
in the topsheet and having a flattened front portion and a rearward
portion having a ridge or peak.
Figure 8 is a side view of Figure 8 illustrating the flattened
front portion and the peaked rearward portion. The body adhesive is
shown around the periphery of the absorbent.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention relates generally to disposable absorbent
articles having a total weight greater than about 5 grams that are
secured to the body of a user by a pressure sensitive body adhesive.
For convenience of description of only, the invention will be
described as applied to a catamenial device, i.e. a sanitary napkin,
but is not limited thereto. It is to be understood that the
invention may be adapted for use in other absorbent articles such as
diapers, incontinent devices and the like.
- 2122fi60
For ease of understanding, when referring to the Figures, the
same numeral designates the same part in the different views and
embodiments. Referring to Figure 1, an embodiment of a sanitary
napkin 10 is shown.
In the most basic embodiment, the sanitary napkin 10 includes an
absorbent 12 and a body side adhesive 14 disposed toward the wearer's
body and secured to the absorbent 12. The adhesive 14 secures the
sanitary napkin 10 to the wearer's body.
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 various exudates which are
discharged from the body such as blood, menses, and urine, and which
is intended to be discarded after a single use. Interlabial devices
which reside partially within and partially external of the female
wearer's vestibule are also within the scope of this invention.
The sanitary napkin 10 preferably has a total weight of less
than about 12 grams. The sanitary napkin 10 an oval shape, but it
can be an hourglass, racetrack or any other design that will allow
the absorbent article to come into intimate contact with the wearer.
The sanitary napkin 10 has a body side surface 15 which can include a
liquid-permeable topsheet 16 proximate the wearer's body; a
liquid-impermeable backsheet or baffle 18 that is distal the wearer's
body; an absorbent 12 positioned intermediate the topsheet 16 and the
backsheet 18; and a pressure sensitive, body side adhesive 14 secured
to the body side surface 15. The adhesive 14 secures the sanitary
napkin 10 to the wearer's body. Generally, the sanitary napkin 10 is
provided with a removable member 20 that is a releasably secured
material for protecting the adhesive 14 from contamination and which
- 2122660
advantageously protects the topsheet 16 from preplacement soiling
until the member 20 is removed and the sanitary napkin 10 is
appropriately positioned for use.
Referring to Figures 2 and 3, the sanitary napkin 10'
illustrates the topsheet 16 and the backsheet 18 having generally a
length and a width dimension sized larger than the absorbent 12 so
that they extend beyond the outer perimeter 22 of the absorbent 12 to
form a peripheral edge 24. The backsheet 18 is coextensive and in
face to face contact with the topsheet 16, and includes a surface 26
facing toward and disposed under the absorbent 12. The topsheet 16
and the backsheet 18 are sealed together from the absorbent
perimeter 22 to the peripheral edge 24 in any suitable manner that
does not leave a hard, uncomfortable residue that would be annoying
to the wearer. As used herein, the term "sealed" encompasses
configurations whereby a first member is directly joined to a second
member and configurations whereby a first member is indirectly joined
to a second member by affixing the first member to intermediate
members which in turn are affixed to the second member. Means of
attachment are well known to those skilled in the art and include the
use of hot melt adhesives in a uniform and continuous layer,
patterned adhesives, pressure sensitive adhesives, double sided tape,
sonic bonding, and heat sealing.
The absorbent 12 has a first surface 28 and a second surface 30.
The first surface 28 is disposed toward the topsheet 16 and the
second surface 30 is disposed toward the backsheet 18. The absorbent
article can include a wicking layer 32. The wicking layer 32 is
positioned adjacent to the second surface 30. The purpose of the
wicking layer 32 is to route body fluid which contacts the
2122660
-
topsheet 16 down to the absorbent 12. The wicking layer 32 may
include more than one material having wicking characteristics.
The first and second surfaces 28 and 30 respectively, of the
absorbent 12 have a coaxially aligned aperture 34 formed
therethrough. Although not a necessary feature, the aperture 34 can
extend through the topsheet 16 so that body fluid will not have to
permeate through the topsheet 16 before contacting the absorbent 12.
Preferably, the aperture 34 extends through the wicking layer 32.
This arrangement allows the aperture 34 to act as a conduit to
rapidly transport any sudden gush of body fluid away from the point
of discharge to the absorbent's second surface 30, which is
positioned on the bottom of the absorbent 12. This arrangement also
allows the topsheet 16, the absorbent 12, and the backsheet 18 to act
as a reservoir to surround and contain the discharged body fluid
until it is absorbed by the absorbent 12. The backsheet 18 can have
between about 5% to about 95% of its surface 26 bonded to the
adjacent layer 32. Most preferably, the backsheet 18 is marginally
secured to the adjacent layer 32.
As shown in Figures 1-3, the body adhesive 14 is positioned
inward from the peripheral edge 24 of the sanitary napkin 10 and 10'.
The purpose of the adhesive 14 is to secure the sanitary napkin 10
and 10' to the body of the wearer. As illustrated in Figure 3, the
adhesive 14 is disposed adjacent to the topsheet 16, overlying the
perimeter 22 but can be secured up to about 3 centimeters from the
perimeter 22 of the absorbent 12. Although the adhesive 14 is
depicted as a continuous, uniform layer, it is to be understood that
those skilled in the art can readily select a different pattern for
adhesive attachment. For example, an intermittent pattern of
2122660
adhesive 14 may be applied. The adhesive 14 is superimposed over
less than about 85% of the body side surface 15 of the sanitary
napkin 10, more preferably less than about 50%, and most preferably
less than about 25%.
The adhesive 14 is usually covered, prior to the time sanitary
napkin 10 is affixed to the person, with a removable member 20. The
removable member 20 serves to protect the adhesive 14 from adhering
to extraneous surfaces prior to use and to prevent contamination of
the adhesive 14. Advantageously, the member 20 also prevents the
topsheet 16 from becoming prematurely soiled prior to placement
against the wearer's body. Suitable cover materials can be any
material that is capable of being releasably secured to the
adhesive 14 and includes-those materials commonly used to protect the
garment attachment adhesive presently used on commercially sold
sanitary napkins. Non-limiting examples include a silicone coated
Kraft paper, SILOX E1-0 and BL30MG-A SILOX 4P/O manufactured by
Akrosil Corporation.
The liquid-permeable topsheet 16 is designed to contact the body
of the wearer and can be constructed of a woven or nonwoven, natural
or synthetic material which is easily penetrated by body fluid.
Suitable materials include bonded carded webs of polyester,
polypropylene, polyethylene, nylon, or other heat-bondable fibers.
Other polyolefins, such as copolymers of polypropylene and
polyethylene, linear low-density polyethylene, finely-perforated film
webs and net material, also work well. Particularly preferred are
composite materials of a polymer and a nonwoven fabric material. The
composite sheets are generally formed by extrusion of the polymer
onto a web of spunbonded material to form an integral sheet. This
- 10 -
- 2122660
material is preferred, because the outer fabric surface is not
irritating to the skin of the wearer. Still another material for the
topsheet 16 is a spunbond web of polypropylene. The web can contain
about 1% to about 6% titanium dioxide pigment to give it a clean,
white appearance. A uniform spunbond material is desirable, because
it has sufficient strength, after being perforated in the
longitudinal direction, to resist being torn or pulled apart during
use. The most preferred polypropylene webs have a weight of between
about 18 and 40 grams per square meter. An optimum weight is between
about 30 and about 40 grams per square meter.
The topsheet 16 can also be treated with a surfactant to improve
its hydrophilic characteristics and, thereby, aid in the absorption
of the liquid. The surfactant can include topical additions or
internally applied materials like polysiloxanes.
The backsheet 18 can permit the passage of air or vapor out of
the sanitary napkin 10 while blocking the passage of body fluids and
liquids from the absorbent 12. A good material is a micro-embossed,
polymeric film, such as polyethylene or polypropylene. Bi-component
films can also be used as well as woven and nonwoven fabrics which
have been treated to render them liquid-impermeable. The
backsheet 18 can be made from a polyethylene film. Most preferably,
the backsheet 18 comprises a polyethylene film having a thickness in
the range of from about 0.012 mm to about 1.0 mm. The backsheet 18
should be soft and compliant. As used herein, the term "compliant"
refers to materials which will readily conform to the general
external shape and contours of the human anatomy.
- 2122660
In a preferred embodiment of the present invention, the
backsheet 18, besides being secured to the topsheet 16 as described
above, can have from about 5% to about 95% of the surface 26
positioned underneath the absorbent 12 secured to the adjacent
layer 32. Preferably, less than about 50% of the surface 26 is
secured, and more preferably, less than about 20%. Most preferably,
the surface 26 is only marginally secured to the adjacent layer 32.
This arrangement allows the backsheet 18 to separate, distending
downward, from the absorbent 12, thereby acting similar to a fluid
reservoir for holding sudden rushes of body fluid.
The topsheet 16 and the backsheet 18 will, in combination,
enclose the absorbent 12, substantially defining the absorbent's
perimeter 22. The absorbent materials used in the absorbent
article 10 are designed to absorb body exudates, including menstrual
fluids, catamenial fluids, blood and urine. Suitable materials
include wood pulp fluff, rayon, cotton and meltblown polymer, such as
polyester, polypropylene or coform. Coform is an air-formed
combination of meltblown polymers, such as polypropylene, and
absorbent staple fibers, such as cellulose. A preferred material is
wood fluff, for it is low in cost, relatively easy to form and has
good absorbency. The absorbent 12 may be a composite comprised of a
hydrophilic material that can be formed from various natural or
synthetic fibers, wood pulp fibers, regenerated cellulose or cotton
fibers, an airlaid tissue or a blend of pulp and other fibers. The
absorbent 12 can be made from other well known materials used in
absorbent articles, including multiple layers of cellulose wadding,
rayon fibers, cellulose sponge, hydrophilic synthetic sponge, such as
polyurethane, and the like. The absorbent 12 can have varying
2122660
densities in the Z direction. The term "Z direction" as used herein
means in the direction of the sanitary napkin thickness, where X and
Y directions would be along the length (longitudinally) and width
(transversely) of the sanitary napkin 10, respectively, see Figure 2.
Preferably, the first surface 28 of the absorbent 12 is of a lower
density than the second surface 30. This assists in drawing any body
fluid toward the backsheet 18 and in reducing and/or preventing the
fluid from permeating back toward the wearer a phenomenon known as
"rewet."
Although the sanitary napkin 10 is described as having a single
layer of absorbent material forming the absorbent 12, the
absorbent 12 may include more than one layer of absorbent material.
As viewed looking downward from the topsheet 16 toward the
backsheet 18, each successive absorbent layer, if used, preferably
has a density and a liquid absorption capacity greater than the
preceding absorbent layer. It should be emphasized that the values
relating to absorbency are relative for any particular style of
absorbent article. It is, therefore, quite possible that one
particular style of absorbent article may utilize the same material
in its second absorbent layer as that utilized as the first absorbent
layer in another absorbent article.
The absorbent 12 may contain superabsorbent particles which are
extremely effective in retaining body fluids. Superabsorbents have
the ability to absorb a large amount of fluid in relation to their
own weight. Typical superabsorbents used in absorbent articles, such
as sanitary napkins, can absorb anywhere from about 5 to about 60
times their weight in body fluids. However, the absorption mechanism
- 2122660
~ of the superabsorbents is usually slower than the rate of fluid
absorption by cellulose fluff material.
It has been found that superabsorbents have a high mechanical
stability in the swollen state, an ability to rapidly absorb fluid,
and those having a strong liquid-binding capacity perform well in
catamenial devices. Hydroxyfunctional polymers have been found to be
good superabsorbents for this application. The superabsorbent can be
a hydrogel forming polymer composition which is water-insoluble,
slightly cross-linked, and partially neutralized. Such
superabsorbents can be obtained from Dow Chemical, Hoechst-Celanese,
and Stockhausen, Inc.
The sanitary napkin 10 and 10' can include a wicking layer 32.
The wicking layer 32 is positioned adjacent to the second surface 30
of the absorbent 12. The wicking layer 32 performs the function of
distributing the body fluid to and across the second surface 30 of
the absorbent 12. Thus, any material having sufficient capillary
activity, or other means to attract and transport body fluid coming
into intimate contact with its surface, and thereby distributing the
discharges across the whole of the absorbent 12, can be used. The
wicking layer 32 can be comprised of a fibrous material having little
absorption ability. Suitable materials include blends of polyester
and rayon that have minimum fluid retaining character. Other
materials may be airformed or carded webs of polyester, rayon, or
polypropylene. A preferred material for the wicking layer 32 is a
meltblown polypropylene layer having a thickness of about 0.6 mm, a
weight of about 60 grams per square meter, a pore size of about
10.6 micrometers, and a mean fiber diameter of about 3.9 micrometers.
- 14 -
- 2122660
. ~
The wicking layer 32 can be coextensive with the second
surface 30 of the absorbent 12. Preferably it is of a size less than
that of the absorbent 12, thereby having a peripheral edge 36 located
inboard from the outer perimeter 22 of the absorbent 12. The wicking
layer 32 can range from about 10 mm to about 65 mm in width and from
about 5 mm to about 180 mm in length. The wicking layer 32 can have a
wicking rate equal to the wicking rate of the second surface 30 of
the absorbent 12 to facilitate liquid transport. Preferably, the
wicking layer 32 has a wicking rate greater than that of the second
surface 30. Wicking rates may be determined in accordance with the
procedure set forth in U.S. Pat. No. 4,256,111, issued to Lassen on
March 17, 1981.
The sanitary napkins 10 and 10' are provided with similar body
side adhesive 14 for retaining the sanitary napkin 10 and 10' against
the wearer's vulvar region so only 10' will be described in detail.
The body facing surface 15 is coated with the body side adhesive 14.
The adhesive 14 is generally disposed within a distance of about
3 centimeters (cm) from the perimeter 22 of the absorbent 12,
including the outer perimeter 22 thereof. The adhesive 14 may be
applied as a continuous or intermittent pattern. The thickness and
surface area of the adhesive 14 may also vary. The adhesive 14
should be superimposed over less than about 85% of the body facing
surface 15 of the sanitary napkin 10', preferably less than about
50%, and most preferably, less than about 25%. Nonlimiting factors
which effect the adhesion of the sanitary napkin 10' to a wearer
include: the strength of the adhesive 14; the location of the
adhesive 14 on the sanitary napkin 10'; whether the adhesive 14 will
- 15 -
2122660
lie on the wearer's skin or will primarily be intermingled with body
hair; and the size, weight, and shape of the sanitary napkin 10'.
Accordingly, adhesives for use in this invention should have an
adequate adhesive force to retain the sanitary napkin 10' against the
wearer during static and dynamic conditions but will release from the
skin and hair without a high level of discomfort. In a preferred
embodiment, the sanitary napkin 10' has a total weight ranging from
between about 5 grams and less than about 12 grams. The term "total
weight" as used herein means the weight of the sanitary napkin 10'
without the removable member 20 and before it has acquired any fluids
in use. It has been discovered that suitable adhesives for use have
an adhesive peel force, as determined by a modified Pressure
Sensitive Tape Council peel resistance test (PSTC-1) described below,
of from about 25 grams to about 700 grams. The peel force is
preferably from about 100 grams to about 650 grams, more preferably
from about 100 grams to about 450 grams, and most preferably from
about 100 grams to about 400 grams. PSTC-1 is a standardized test
procedure that is described in greater detail on page 23 of the tenth
edition of Test Methods copyright 1992, available from Pressure
Sensitive Tape Council 401 North Michigan Ave., Chicago, Ill.
60611-4267.
Additionally, suitable adhesives have the rheological properties
loss modulus (G"), storage modulus (G') and loss tangent (tan ~)
falling within the ranges of Table 1 below. The terms "loss tangent"
(tan ~ or G"/G') and "storage modulus" (G'), are defined according to
established principles of dynamic mechanics. These rheological
quantities are measured on bulk adhesive samples not suspended on any
substrate and having a thickness of approximately 0.56 mm. The
- 16 -
- 2122660
adhesive is cut into a 25 centimeter (cm) circle and placed between
two 25 cm parallel plate fixtures of a Rheometrics Dynamic
Spectrometer (RDS), which can be obtained from Rheometrics located at
1 Possum Town Road, Piscataway, New Jersey 08854. The upper platen
is lowered onto the sample until the normal force meter indicates a
slight deflection. The samples are allowed to equilibrate at the
test temperature (e.g. 25C. and 37C.) before testing. A
minicomputer governs the application of a 5% peak-to-peak shear
strain to the sample. The frequency of the application can be
controlled to a fraction of a radian/sec (one radian is equal to
6.28 Hz). The values of the complex modules (G*) and loss tangent
(tan ~) are calculated by the computer from geometry factors, peak-
to-peak amplitude of the torque signal, and phase lag of the torque
output wave. The definition of loss tangent (tan ~) and the
relationship between G*, G', and G" provide two equations in two
unknowns which can be solved by the computer to provide G" and G',
since G* and loss tangent (tan ~) are both known values calculated as
described previously. For any of these values, the frequency is 10
radian/sec.
TABLE 1
Values in 104 dynes/cm2 at
PropertY 25-37C.
Loss Modulus (G") 0.5 to 20
Storage Modulus (G') 0.2 to 45
Loss Tangent (tan ~ = G"/G') 0.1 to 1.0
- 17 -
- 212266~
.~. .
Nonlimiting examples of suitable adhesives include a
pressure-sensitive, hydrophilic hydrogel adhesive material. Such
hydrogel adhesives are marketed by Promeon Division of Medtronic,
Inc., of Minneapolis, Minnesota, under the trademark "PROMEON" and
include a commercial medical grade hydrogel marketed as PROMEON
RG-63B. A detailed description of such a hydrogel composition is
contained in U.S. Pat. No. 4,593,053, issued to Jevne et al., on
June 3, 1986. Another suitable hydrogel adhesive is described in
U.S. Pat. No. 4,699,146, issued to Sieverding on October 13, 1987.
The peel force of the adhesive is determined by a test which is
modeled after the PSTC-1 90~ PEEL ADHESION PROCEDURE, the procedure
being modified and performed as follows. The PEEL ADHESION PROCEDURE
gives a force value related to a unidirectional removal force from a
test subject's forearm.
APPARATUS
The apparatus used for the Peel Adhesion Procedure is an Instron
model 4201 materials testing instrument or equivalent. Instron
materials testing instrument is available from Instron Engineering
Corporation, Canton Massachusetts.
PREPARATION OF SPECIMENS
In order to perform the procedure for this task, as explained
below, no less than 5 test specimens are prepared. The test
specimens are approximately 0.635 cm (1/4 inch) wide with a degree of
variance no greater than 0.04 cm (1/64 of an inch). The test
- 18 -
2122660
specimens are approximately 15.24 cm (6 inches) in length. In the
case where a non-hydrogel adhesive is to be tested, it is conditioned
by placing the adhesive laminate strips in a 73 ~ 2 degree Fahrenheit
and a relative humidity of 50 ~ 2 percent for 24 hours. The adhesive
5 strips do not have the peel strip removed.
In the case where the adhesive is a hydrogel, it is tested at a
residual moisture content of 25 percent, 35 percent, and 45 percent.
In preparing the hydrogel samples for testing, all of the samples are
conditioned to achieve the proper moisture content. Samples having a
10 25 percent moisture content are prepared by placing the hydrogel
having a thickness of 15 + 1 millimeters on a nonwoven substrate.
These laminates are placed in a 130 ~ 2 degree Fahrenheit oven with
the adhesives exposed. After 45 minutes, the release liner is
replaced on the samples and then they are sealed in a polyethylene
15 bag.
Samples having a 35 percent moisture content are prepared by
placing the adhesive laminates of hydrogel having a thickness of 15 +
1 millimeter on a nonwoven substrate. The laminates are then placed
in a chamber having a temperature of 73 + 2 degrees Fahrenheit and a
20 relative humidity of 50 + 2 percent for 6 hours. The samples are
removed and the release liner is replaced on the samples and then
they are sealed in a polyethylene bag.
Samples having 45 percent hydration are prepared by placing the
adhesive laminates of hydrogel having a thickness of 15 + 1
millimeter on a nonwoven substrate. The laminates are placed in a
chamber having a temperature of 100 , degrees fahrenheit and relative
humidity of 80 ~ 2 percent for 6 hours. The samples are removed and
2122660
. .
the release liner is replaced on the samples and then they are sealed
in a polyethylene bag.
The percent hydration is determined by evaporating the moisture
from the adhesive laminate at 234 degrees Fahrenheit for eight (8) to
twelve (12) hours. Hydration is determined by weight differences,
that is, the weight of the nonwoven substrate is subtracted off the
sample weights, then the weight of the sample having the moisture
evaporated is divided by the original weight of the hydrogel
adhesive.
PROCEDURE
The procedure for PEEL ADHESION PROCEDURE is as follows: The
specimens are tested in a room having a temperature of 73 ~ 3 degrees
Fahrenheit and a relative humidity of 50 ~ 2 percent. Because the
adhesive is for attaching an absorbent article onto the body of a
wearer, adhesion is tested on human arms. Attach one end of the
15.24 cm specimen to the forearm and drape the specimen along the
length of the arm. Roll the test specimen lengthwise, once in each
direction, using a 2.043 kilogram (4.5 pound) roller, at a speed of
approximately 0.3048 meters per minute (twelve (12) inches per
minute). After 5 minutes, peel back the free end of the test
specimen at an angle of 90 degrees and peel 2.54 cm (1 inch) of the
test specimen from the subject's forearm. Clamp that end from which
the test specimen has been peeled into the movable jaw of the
adhesion testing machine, allowing the subject's forearm to rest on
the stationary portion of the adhesion testing apparatus. Operate
the movable jaw at 5.08 and 10.16 meters per minute (200 and 400
inches per minute). After the movable jaw is started in motion,
- 20 -
2122660
disregard the values obtained while the first 2.54 cm of tape is
removed. Use the average peel value obtained during the next 5.08 cm
(2 inches) of removal as the adhesion value. The above steps are
repeated until at least 5 similar specimens have been tested.
CALCULATIONS
The peel adhesion for each specimen is the average force reading
for that specimen.
Comparative Example
The rheological data for an adhesive that is considered to be
too aggressive for use but which can be used as a bandage adhesive is
"DURO-TAK~ 9908" from National Starch and Chemical Company, 10
Finderne Avenue, P O Box 6500, Bridgewater, New Jersey 08807-3300.
The test specimen was prepared according to the above procedure for
determining rheological data. The results appear in TABLE 2 below.
TABLE 2
Values in 104 dynes/cm2 at
25-37C and a frequency of
Pro~ertY 10 radians/second
25C 37C
Loss Modulus (G") 31 16
Storage Modulus (G') 62 52
Loss Tangent (Tan ~) 0.46 0.32
EXAMPLE 2
In accordance with the above procedures, a number of peel
strength test specimens were run using PROMEON hydrogel RG 63B as the
adhesive.
2I22660
The results appear in TABLE 3. Rheological data for the
hydrogel appears in TABLE 4. All values are in 104 dynes/cm2 and a
frequency of 10 radians/second.
TABLE 3
90 PEEL STRENGTH
Contact Speed Number Peel Range Average
10 HYdration Time (in/min) of Tests (Grams) (Grams)
25% 5 min. 200 45 31-402 164
5 min. 400 44 58-405 190
35% 5 min. 200 46 83-601 236
5 min. 400 46 81-628 268
44% 5 min. 200 46 57-386 169
5 min. 400 46 70-511 218
TABLE 4
% Water Content
ProPertY 25% 35% 45%
Loss Modulus (G") @ 25C 21 4.2 0.76
Storage Modulus (G') @ 25C 37 7.5 1.5
Loss Tangent (Tan t ) 0.63 0.55 0.47
Loss Modulus (G") @ 37C 14 3.4 0.92
Storage Modulus (G') @ 37C 24 6.3 2.0
Loss Tangent (Tan t ) 0.59 0.55 0.47
Referring to Figures 4-6, another embodiment of a sanitary
napkin 10" is shown. The sanitary napkin 10" has a body facing
surface 15, a backsheet 18, an absorbent 12, and a wicking layer 22.
The absorbent 12 is advantageously provided with an aperture 34
extending through first and second surfaces, 28 and 30 respectively
of the absorbent 12. The body facing surface 15 of the sanitary
napkin 10" includes the liquid-permeable topsheet 16 and a portion of
the backsheet 18.
- 22 -
2122660
The aperture 34 can be a variety of geometric configurations.
The aperture 34 is coaxially aligned and extends through the
topsheet 16 and more preferably extends through the wicking layer 32.
The aperture can be substantially symmetrical in its shape and can be
positioned along the longitudinal axis X--X. Preferably, the
aperture 34 is longitudinally and transversely centered along the
X--X and Y--Y axes, see Figure 4. The aperture 34 allows the
sanitary napkin 10" to more completely acquire the sometimes highly
viscous menses by allowing the backsheet 18 to accumulate the excess
menses away from the topsheet 16 and proximate the second surface 30
of the absorbent 12. Without the aperture 34, less absorption of
exudates may take place and the unabsorbed exudates may lay in
contact with the body and cause irritation or may overflow the
peripheral edge 24 of the sanitary napkin 10" and cause soiling. The
aperture 34 preferably has an area great enough to be in contact with
the menses as it exits the wearer's vagina yet not so large as to
contact surrounding skin surfaces which could be soiled or irritated
by rewet. The aperture 34 should be positioned on the body so that
menses will contact the aperture 34 before contacting the rest of the
topsheet 16.
Dimensionally, the aperture 34 ranges in size from about 10 mm
to about 65 mm. If elliptical or of a similar shape having unequal
dimensions, the aperture 34 may have a minor axis of from about 10 mm
to about 35 mm and a major axis of from about 15 mm to about 85 mm
and appropriately positioned on the sanitary napkin 10.
Referring to Figure 5 a cross-sectional view of Figure 4 along
transverse axis Y--Y is shown. In forming the body facing
surface 15, the backsheet 18 partially overwraps the topsheet 16.
The backsheet 18 can extend over the topsheet 16, inward from the
outer peripheral edge 24 of the sanitary napkin 10", by a distance
from about 0.1 mm to about 30 mm.
Figure 6 shows a cross-sectional view taken along axis Y--Y of
another embodiment of the sanitary napkin 10", as illustrated in
Figure 4. The difference between the embodiments illustrated in
Figures 5 and 6 is that in Figure 6 the backsheet 18 extends over the
topsheet 16 by a sufficient distance to allow the adhesive 14 to
reside on the backsheet 18 which is proximate the wearer. The
- 23 -
222660
backsheet 18 can extend over the topsheet 16 sufficiently to allow
the adhesive 14 to be completely affixed to the backsheet 18 facing
the wearer's torso and inward from the perimeter 22. The
backsheet 18 may be affixed to the topsheet 16 by means well known to
those skilled in the art such as spaced apart strips of construction
adhesive.
Referring to Figures 7 and 8, another embodiment of a sanitary
napkin 100 is shown. The sanitary napkin 100 has the same plan form
as sanitary napkin 10', illustrated in Figure 2 but with the
following difference. The sanitary napkin 100 has a rearward
portion 38 and a front portion 40. The rearward portion 38 includes
a raised peak 42. The peak 42 forms a gradual rise from its
beginning area immediate the aperture 34 to an end section 44 of the
sanitary napkin 100. The raised peak 42 assists the wearer in
properly placing the sanitary napkin 100 between her legs at the
perineum and between her buttocks. The front portion 40 is generally
flat as is best shown in Figure 8.
The raised peak 42 may be formed completely prior to delivery of
the sanitary napkin to the consumer. Alternatively, the raised
peak 42 may only be present in a precursor state that allows the user
to form the peak 42 in its correct shape by folding the sanitary
napkin 100 in the preferential fold that the precursor allows. This
assists the user in forming the profile of the pad. Depending on the
nature and composition of the absorbent and backing material, the
raised peak 42 may be formed in may ways, including heat setting,
thermoplastic containing absorbents, thermoplastic backing members,
and scoring the components comprising the sanitary napkin 100 so that
the raised peak 42 is formed when in use. Other approaches will
occur to the skilled artisan for achieving the goal of providing the
peak 42 fold line.
The length and height of the ridge or raised peak 42 in the
rearward portion 38 of the sanitary napkin 100 is determined by the
sharpness of the fold and the arrangement of the absorbent 12. The
fold is useful for aligning the sanitary napkin 100 so that the
aperture 34 is correctly aligned under the vestibule, and preferably
under the vaginal opening, as the sanitary napkin 100 is being
positioned on the body of the user. In use, the flattened portion 40
- 24 -
2122660
would be concave and extend generally over the mons pubis of the
female anatomy and the forward portion of the labia. The raised
peak 42 generally begins in the pudendal cleft rearward portion of
the labia, adjacent the vestibule and extends toward the perineum and
buttocks.
Use of the sanitary napkins 10, 10', 10" or 100 is similar. The
removable member 20 is first removed, exposing the body adhesive 14
upward and toward the user. The aperture 34 can be used to assist
the wearer in positioning the sanitary napkin 10' so that the
aperture 34 is underneath the vaginal opening. The sanitary
napkin 10' is then placed adjacent to the wearer by applying a
sufficient pressure on the backsheet 18 of the sanitary napkin 10'
toward the wearer's body, to secure the napkin 10' to the wearer.
The sanitary napkins 10, 10', 10" and 100 may be formed in any
size suitable for absorption of body exudate and can have a total
weight of between about 5 grams and 12 grams. Generally, the
sanitary napkin 10' has a length between about 17.78 cm to about 25.4
cm (7 inches to about 10 inches). The preferred length is generally
between about 12.7 cm and 20.32 cm (5 inches to about 8 inchesJ as
this length is discreet, effective and easily placed in the correct
position. The width generally between about 5.08 cm to about 10.16
cm (2 inches to about 4 inches). The preferred width is about 6.35
cm (2.5 inches) for comfort and effectiveness in absorption of
menstrual fluids.
Manufacturing the sanitary napkin 10, 10', 10" and 100 is in
accordance with known methods in the art for making such laminated
structures. In securing the adhesive 14 to the body facing
surface 15, preferably an intermediate adhesive is used to increase
the adhesive's 14 bonding to the body facing surface 15. Suitable
adhesives include hot melt construction adhesives, cohesive
adhesives, and particularly preferred is a two sided tape identified
as 465 double sided transfer tape available from the 3M Corporation.
While the invention has been discussed with reference to
catamenial pads, the invention is also desirable for absorbent
articles for use as incontinence protection. Furthermore, the
absorbent article may be formed in various sizes and shapes to best
conform to the body of the user. These and other variations of the
- 2122660
. .
invention are intended to be included by the invention which is only
to be limited by the scope of the claims attached hereto.
- 26 -
