Note: Descriptions are shown in the official language in which they were submitted.
' CA 02203796 1997-04-25
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', Flexible And Water Vapour Permeable Absorbent Articles And '
Their Fixation To Undergarments
. .
Meld of the invention
j
', The present invention relates to water vapour permeable
absorbent articles such as sanitary napkins, panty liners, and
incontinence pads which are adhered to an undergarment
',, during use. More particularly the present invention relates to
articles which are water vapour permeable and which have a
I flexibility in a longitudinal direction which provides improved
comfort to the wearer of the article.
Background of the invention:
Disposable absorbent articles such as baby diapers, adult
incontinence articles, sanitary napkins and panty liners are well
known in the art. These articles have a wearer facing side
through which they typically absorb liquids discharged by the
wearer. The liquid is stored in an absorbent structure. Liquid
leakage from the article through the surface opposite the
wearer facing side is usually prevented by incorporating a liquid
impermeable backsheet on that side.
It is well established in the art that a backsheet allowing air
communication with the environment, usually referred to as
breathability, is highly desirable. Breathability improves with the
', amount of air permeating through a backsheet. This amount is
' ', proportional to the open area (the sum of the area of all
apertures) in the backsheet. Obviously improvements in
" ~, breathability lead to compromising the liquid leakage prevention,
', which is the primary function of a backsheet.
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2
Many suggestions how to provide breathable backsheets have
been recorded in the art. Numeral attempts , of combining the
mutual contradicting features of air permeability and liquid
impermeability have been documented in patents and patent
applications. However the lack of commercially available
breathable disposable absorbent articles, which are also very
flexible, indicates that the technology so far suggested has not
provided an all around satisfactory result for the desired
technical requirements at commercially acceptable conditions.
Sanitary napkins, panty liners, and incontinence pads are
typically worn in the crotch region of an undergarment and
attached to the undergarment by a so called panty-fastening-
adhesive. They are intended for daily use and providing them
with breathability is desirable to increase the comfort of the
wearer of such articles. In particular it is believed that the water
vapour loss from such articles provides a reduced sweaty,
stuffy and hot feeling.
It is also well established that in order to be comfortable for the
wearer these articles need to be flexible. It is believed that the
more flexible an absorbent article is the less will it be noticeable
to the wearer. Hence this provides comfort by more closely
resembling the situation when no such absorbent article is
worn.
Flexibility can easily be achieved by reducing the amount of
material in an absorbent article or replacing stiff or inflexible
components by more flexible ones. However it has long been
recognised that extreme flexibility can also reduce the
absorbent performance of these articles, for example by an
h
insufficient amount of absorbent material or by bunching or
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3
I densifying of the absorbent material during use. A too flexible
article may be difficult to handle for the wearer wh_ en attaching
' it to the undergarment.
i
The problem of too much flexibility in an article due to a low
amount of inflexible material has been addressed for example in
U.S. 4,217,901 where particularly the stiffness of an absorbent
article is increased in order to provide satisfactory performance.
This prior art reference accepts the comfort implications caused
by its stiffness requirement. Also breathability is not even
considered in this document.
', Therefore absorbent articles having a high degree of flexibility
and breathability would be very desirable. However providing an
apertured backsheet in conjunction with a flexible i.e. thin
absorbent article, would accept too much risk of leakage
through the backsheet. Hence the lack of breathability of the
backsheet has been accepted heretoforth for the sake of
leakage prevention especially for thin low absorbent products.
Only now novel multilayer breathable backsheets suggested in
simultaneously filed applications entitled "Breathable backsheet
design for disposable absorbent articles" and "Breathable dual
layer backsheet design for disposable absorbent articles" both
assigned to The Procter and Gamble company and designating
' M.Depner and M. Divo as co-inventors have been suggested ,
and could be considered alternatives. However even these multi
layer backsheet designs are somewhat counter productive to
improved flexibility since the addition of layers increases
', stiffness rather then supports flexibility.
Other prior art attempts to provide breathable backsheet
assemblies comprising more than one layer are e. g.
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4
documented in US 4,341,216. EP-A-109 126 or EP-A-203 821.
Single layer breathable backsheets are known for example from
G&A-2184391, GB-A-2184390, GB-A-2184389, US
4,591,523. US 4.839,216 or EP 156471. None of the
mentioned disclosures attempts however to address the
comfort problems associated with stiff or not sufficiently
flexible absorbent articles. Some of them actually suggest to
provide sufficient absorbent material to cover possible leakage
situations. This is however increasing stiffness at the cost of
breathablitity.
Therefore it is an objective of an aspect of the present
invention to address
the problem of conflict between leakage through the backsheet,
flexibility and breathability. The benefits of breathability and
flexibility, in particular the ability to bend and twist easily in
longitudinal and preferably in all directions, has however
become of key importance especially for everyday usage
absorbent articles such as panty liners, sanitary napkins and
incontinence pads.
It now has been found that the leakage problem associated with
apertured breathable backsheets can be prevented while
substantially maintaining the benefit by use of water vapour
permeable films. At the same time the comfort of absorbent
articles can be drastically improved when providing a high
flexibility in longitudinal direction in combination with a
particular panty-fastening-adhesive configuration so as to
maintain the water vapour permeable article flat relative to the
undergarment of the wearer. The flexibility then becomes
limited only by material strength requirements and by handling
requirements of the absorbent article .
CA 02203796 2000-08-11
S
It is therefore an objective of an aspect of the present invention to provide
sanitary
napkins with an improved flexibility without the previously experienced
drawbacks.
In particular a high degree of flexibility and the benefits of breathability
without
aperturing the backsheet in the absence of bunching problems or major handling
difficulties is achieved by the selected ranges of design parameters of the
articles
according to the present invention.
These and other objectives of aspects of the present invention will be more
readily
apparent when considered in reference to the following description.
Summary of the invention
The present invention provides a water vapour permeable absorbent article such
as a
sanitary napkin, an incontinence pad and particularly a panty liner for use in
an
undergarment. The absorbent article has a water vapour permeable backsheet
which is
not apertured and comprises a garment facing surface. On the garment facing
surface
is an adhesive to adhere the article to the undergarment.
In accordance with one embodiment of the present invention, there is provided
a
flexible absorbent article for use in an undergarment, said article comprising
an
absorbent core and a backsheet having a garment facing suface;
said garment facing surface comprising an adhesive to adhere said article to
said
undergarment, said adhesive having an actual adhesive surface and said
adhesive
defining a theoretical adhesion surface inside of an endless line which is the
shortest
encircling line of the adhesive without extending beyond the periphery of the
garment
facing surface;
said backsheet being water vapour permeable and comprising a liquid impervious
but
water vapour permeable layer;
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Sa
said article being characterised in that
- the surface ratio of said actual adhesive surface to said garment facing
surface is in
the range of 0.2 to 0.8;
- the surface ratio of said theoretical adhesion surface to said garment
facing surface
is in the range of 0.6 to 1 .0;
and
said article has a flexibility of 1300 mg x cm to 5000 mg x cm measured
according to
modify ASTM D1388.
In accordance with another embodiment of the present invention, there is
provided a
flexible absorbent article for use in an undergarment, said article comprising
protective side flaps, said article comprising a backsheet having a garment
facing
surface and said article comprising an absorbent core;
said garment facing surface comprising an adhesive to adhere said article to
said
undergarment, said adhesive having an actual adhesive surface and said
adhesive
defining a theoretical adhesion surface inside of an endless line which is the
shortest
encircling line of the adhesive without extending beyond the periphery of the
garment
facing surface;
said backsheet being water vapour permeable and comprising a liquid impervious
but
water vapour permeable layer;
said article being characterised in that
- the surface ratio of said actual adhesive surface to said garment facing
surface is in
the range of 0.2 to 0.8;
- the surface ratio of said theoretical adhesion surface to said garment
facing surface
CA 02203796 2000-08-11
Sb
is in the range of 0.5 to 1.0 for articles with said protective side flaps;
and
said article has a flexibility of 1300 mg x cm to 5000 mg x cm measured
according to
modify ASTM Dl 388.
The article may optionally comprise protective side-flaps which during use are
folded
around the side edges in the crotch region of the undergarment so as to
improve
soiling protection for the undergarment. The absorbent article also comprises
the other
typical components of such articles namely an absorbent core and a liquid
pervious
wearer facing surface which is preferably provided by a liquid pervious
topsheet. The
absorbent article comprises a water vapour permeable backsheet which usually
provides the garment facing surface of the absorbent article. If topsheet and
backsheet
are present the absorbent core is
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6
enclosed by them on the wearer and on the garment side
respectively.
The adhesive can be provided across the whole, part or several
distinct parts of the garment facing surface. The adhesive is
provided so as not to clog the full surface area. If it covers the
whole garment facing surface it can be in a filamentary fashion
which is random or in a defined design like spirals. The total
area of all adhesive on the garment facing surface of the
absorbent article defines the actual adhesive surface. ~ In
addition a theoretical adhesion surface is given by the periphery
of an endless line which is the shortest encircling line of the
adhesive without extending beyond the periphery of the
garment facing surface itself.
The absorbent article according to the present invention has a
surface ratio of theoretical adhesion surface to the garment
facing surface in a range of 0.6 to 1, preferably 0.85 to 1 for
articles without the protective side flaps and in a range of 0.5
to 1, preferably from 0.7 to 0.9 for articles with protective side
flaps. In a preferred embodiment the theoretical adhesion
surface is substantially coextensive to the actual surface
covered by the adhesive.
In order to realise the benefits of the present invention the
absorbent article as a whole needs to provide exceptional
flexibility. The flexibility is measured by the modified ASTM
method D1388 as described herein below in longitudinal
direction. The expression "flexibility" is also referred to as
"drapability" due to the particular method. It should be
understood that stiffness is characteristic of the opposite
behaviour of a material. The flexibility should be in the range of
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7
1300 to 5000, preferably from 2000 to 3500, most preferably
2000 to 3000, mg x cm.
These flexibility values in combination with the surface ratio
indicated above provide exceptional wearer comfort without
soiling and/or absorbent performance problems due to bunching
or densification of the absorbent material and still allows the
wearer to attach the article to the undergarment without undue
effort. According to the present invention flexibility is measured
in longitudinal direction because this is the value more readily
measurable and important. in principle the transverse flexibility
also could be used, possibly at different values. Due to the
small extension of articles in the transverse direction it is
however usually not possible to properly measure flexibility in
this direction.
The thickness of a preferred embodiment of the present
invention especially for panty liners is less than 3 mm and even
more preferably in the range of 0.5 to 1.5 mm according to the
thickness measurement method described herein below.
The combination of appropriate panty-fastening adhesive
coverage and flexibility is particularly useful in the context of
stretchable absorbent articles. Absorbent articles being
stretchable in one direction and more so absorbent articles
being stretchable in two for all) directions are inherently flexible.
Stretchability in itself already provides an improvement for
comfort ' such that the absorbent articles combining
stretchability w'tth the present invention are particularly
desirable.
Particularly useful are stretchable absorbent articles having the
stretch characteristics described in application number
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g
WO 95/20431 filed February 4, 1994 and indicated in the Table
of Figure 7 and the respective description of that application.
The second key aspect according to the present invention is the
water vapour permeability of the backsheet of the absorbent
articles. The articles according to the present invention have a
water vapour permeable backsheet without apertures. The
backsheet is liquid impervious. To achieve this the backsheet
comprises a water vapour permeable layer which also is liquid
impervious. It can be provided with one or several additional
layers which provide different functions. in particular it can
have e.g. a very thin film of water vapour permeable
thermoplastic provided with another e.g. discontinuous film
having apertures (so as not to retard the water vapour
permeability) but to enhance material strength and/or yet
another layer to provide e.g. desirable appearance such as a
fibrous layer on the garment facing side of the backsheet to
better resemble fabric appearance.
Brief description of the drawings
Figure 1 shows a plan view of the garment facing surface of a
panty liner without protective side flaps according to the
present invention.
Figure 2 shows the garment facing surface of a sanitary napkin
having protective side flaps according to an alternative
embodiment of the present invention.
Detailed description of the present invention
The present invention will be described by reference to panty
liners. It is however equally well applicable to sanitary napkins
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9
' or . adult incontinence articles which are worn in an
I undergarment and are joint to the undergarment during wearing
of the absorbent article .
Absorbent articles according to the present invention comprise
typically three main components: a liquid pervious topsheet, a
water vapour permeable backsheet and an absorbent core. The
absorbent core is enclosed by the backsheet and the topsheet
and the article is worn such that the exposed surface of the
topsheet faces the wearer of the absorbent article while the
exposed surface of the backsheet faces the undergarment to
which the article is joint by a panty-fastening attachment
means. Typically this is an adhesive but could also be a
mechanical attachment.
The present invention is concerned with the flexibility of the
article and its water vapour permeability. The degree of
flexibility is determined by the selection of the materials for the
components of the article as mentioned above and their
respective quantity. It will be apparent to those skilled in the art
- that, in order to achieve the flexibility according to the present
invention, the selection of kind and quantity of raw materials
' has to be balanced with other desired characteristics of the
absorbent article such as for example absorbent capacity,
absorption speed and surface dryness on the outside of the
', topsheet during use. '
Therefore the following description of typical materials of the
'; main components of the absorbent article will allow to provide
an almost infinite number of article variants inside and outside
', the flexibility limitations according to the present invention.
Whether or not an absorbent article meets the requirements of '
_ . _._~. _ . .. . ...
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PCflUS95113_cd6
10
flexibility of the present invention can then be confirmed by
simple measurements according to the method described below.
The absorbent articles according to a preferred embodiment of
the present invention are elastically stretchable. The term
"elastically stretchable", as used herein, means that when the
stretching forces are removed, the article will tend to return
toward its unextended or unstretched for 'original' dimensionsl.
It need not return all the way to its unstretched dimensions,
however. If the absorbent article is elastically stretchable it may
be stretchable in one or two directions (which are not-parallel)
within the plane of the article i.e. parallel to the garment facing
surface.
Materials for elastically stretchable articles can be elastically
stretchable per se or be treated so as to provide elastic
stretchability. In particular elastic backsheet material, elastic
topsheet material, filamentary materials combined with elastic
strands, threads or webs as well as shirring, pleating or ring
rolling of the materials may be employed in this context.
Suitable material and methods are knov~c~., in the art and e.g.
disclosed in detail in W0 95/20431 of February 4,
1994 speciticaUy referred to in order to facilitate selection of
materials if .stretchable absorbent articles according to the
present invention are made.
In the following, non-limiting embodiments of the main elements
of the absorbent article are described which can be employed in
elastically stretchable or non-stretchable designs.
Absorbent core
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The absorbent core typically includes the following
components: (a) optionally a primary fluid distribution layer; (b) '
optionally, but preferably, a secondary fluid distribution layer;
(c) a fluid storage layer; (d) optionally a fibrous ("dusting") layer
underlying the storage layer; and (e) other optional components.
a. Primary Fluid Distribution Layer
One optional component of the absorbent cores according to
the present invention is the primary fluid distribution layer. This
primary distribution layer typically underlies the topsheet and is
I, in fluid communication therewith. The topsheet transfers the
' acquired menstrual fluid to this primary distribution layer for
ultimate distribution to the storage layer. This transfer of fluid
through the primary distribution layer occurs not only in the
' thickness, but also along the length and width directions of the
', absorbent article . -
b. Optional Secondar~r_ Fluid Distribution Layer
i ,
Also optional but a preferred component of the absorbent cores
according to the present invention is a secondary fluid
' distribution layer. This secondary distribution layer typically
underlies the primary distribution layer and is in fluid
I, communication therewith. The purpose of this secondary
distribution layer is to readily acquire menstrual fluid from the
primary distribution layer and transfer it rapidly to the
I
underlying storage layer. This helps the fluid capacity of the
I underlying storage layer to be fully utilised.
c. Fluid Storage Layer
',
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I2
Positioned in fluid communication with, and typically underlying
the primary or secondary distribution layers, is a fluid storage .
layer comprising certain absorbent gelling materials andlor other
absorbent materials, which can form the carrier matrix for the
absorbent gelling materials. Absorbent gelling materials are
usually referred to as "hydrogels," "superabsorbent"
"hydrocolloid" materials. Absorbent gelling materials are those
materials that, upon contact with aqueous fluids, especially
aqueous body fluids, imbibes such fluids and thus form
hydrogels. These absorbent gelling materials are typically
capable of absorbing large quantities of aqueous body fluids,
and are further capable of retaining such absorbed fluids under
moderate pressures. These absorbent gelling materials are
typically in the form of discrete, non-fibrous particles.
The fluid storage layer can comprise solely absorbent gelling
materials, or these absorbent gelling materials can be dispersed
homogeneously or non-homogeneously in a suitable carrier or it
can comprise solely an absorbent carrier material. Suitable
carriers include cellulose fibres, in the form of fluff, tissues or
paper such as is conventionally utilised in absorbent cores.
Modified cellulose fibres such as the stiffened cellulose fibres
can also be used. Synthetic fibres can also be used and include
those made of cellulose acetate, polyvi T~I fluoride,
polyvinylidene chloride, acrylics !such as Orlon), polyvinyl
acetate, non-soluble polyvinyl alcohol, polyethylene,
polypropylene, poiyamides !such as nylon), polyesters,
bicomponent fibres, tricomponent fibres, mixtures thereof and
the Like. Preferred synthetic fibres have a thickness of from
about 3 denier per filament to about 25 denier per filament,
more preferably from about 5 denier per filament to about 16
denier per filament. Also preferably, the fibre surfaces, are
hydrophilic or are treated to be hydrophilic. The storage layer
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1
13
can also includiller materials, such as Perlite, diatomaceous
earth, Vermiculite, etc., that lower rewet problems.
If dispersed non-homogeneously in a carrier, the storage layer
can be locally homogeneous, i.e. have a distribution gradient in
one or several directions within the dimensions of the storage
layer. Non-homogeneous distribution can also refer to laminates
of carriers enclosing absorbent gelling materials partially or
fully.
If absorbent gelling materials are present, preferably the storage
layer comprises from about 15 to 100°~ absorbent Belting
materials and from 0 to about 85 % carrier. Preferably, the
storage layer comprises from about 30 to 100 %, most
preferably from about 60 to 100°~ absorbent gelling materials
and from 0 to about 70 %, most preferably from 0 to about 40
%, carrier.
Suitable absorbent gelling materials for use herein will most
often comprise a substantially water-insoluble, slightly
crosslinked, partially neutralised, polymeric gelling material. This
material forms a hydrogel upon contact with water. Such
polymer materials can be prepared from poiymerizable,
unsaturated, acid-containing monomers. Suitable unsaturated
acidic monomers for use in preparing the polymeric absorbent
gelling material used in this invention include those listed in
U.S. Patent 4,654,039 and reissued as RE 32,649. 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
material. The polymeric component formed from the
unsaturated, acid-containing monomers can be grafted onto
other types of polymer moieties such as starch or cellulose.
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14
Polyacrylate grafted starch materials of this type are especially
preferred. Preferred polymeric absorbent gelling materials that
can be prepared from conventional types of monomers include
hydrolysed acrylonitrile grafted starch, polyacrylate grafted -
starch, polyacrylates, malefic anhydride-based copolymers and
combinations thereof. Especially preferred are the polyacrylates
and polyacrylate grafted starch.
While these absorbent gelling materials are typically in particle
form, it is also contemplated that the absorbent gelling material
can be in the form of macrostructures such as fibres, sheets or
strips. These macrostructures are typically prepared by forming
the particulate absorbent gelling material into an aggregate,
treating the aggregated material with a suitable crosslinking
agent, compacting the treated aggregate to densify it and form
a coherent mass, and then curing the compacted aggregate to
cause the crosslinking agent to react with the particulate
absorbent gelling material to form a composite, porous
absorbent macrostructure. Such porous, absorbent
macrostructures are disclosed, for example, in U.S. Patent
5,102, 597.
d. Optional Fibrous ("Dustin "~ 1 Layer
An optional component for inclusion in the absorbent cores
according to the present invention is a fibrous layer adjacent to,
and typically underlying the storage layer. This underlying
fibrou$ layer is typically referred to as a "dusting" layer since it
provides a substrate on which to deposit absorbent gelling
material in the storage layer during manufacture of the
absorbent core. This layer can comprise all those materials
disclosed above as carrier materials for the storage layer.
Indeed, in those instances where the absorbent gelling material
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is .in the form of macrostructures such as fibres, sheets or
strips, this fibrous "dusting" layer need not be included.
However, because this "dusting" layer provides some additional
fluid-handling capabilities such as rapid wicking of fluid along
the length of the pad, its inclusion is typically prefe_ rred in
absorbent cores according to the present invention.
e. Other Optional Components
The absorbent cores according to the present invention can
I~ include other optional components normally present in
absorbent webs. For example, a reinforcing scrim can be
positioned within the respective layers, or between the
respective layers, of the absorbent cores. Such reinforcing
scrims should be of such configuration as to not form interfacial
barriers to fluid transfer, especially if positioned between the
respective layers of the absorbent core. Given the structural
integrity that usually occurs as a result of thermal bonding,
reinforcing scrims are usually not required for the absorbent
structures according to the present invention and indeed may
cause the desired flexibility to be unachievable.
Another component which can be included in the absorbent
core according to the invention and preferably is provided close
i to or as part of the primary or secondary fluid distribution layer
..a...l .. ."+.. T...,C~..~11.~ ~nt:we i.'rhnn nn~tml vmith nr
arts vuvul huum age~aw. ~ yfrwomy ov.a~vw.u....r,. vvc.w.. ...~.. ...
in addition to other odour control agents, in particular suitable
zeolite or clay materials, are optionally incorporated in the
absorbent core. These components can be incorporated in any
I desired form but often are included as discrete, non-fibrous
particles.
To~sheet
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16
The topsheet is compliant, soft feeling, and non-irritating to the -
wearer's skin. As indicated above the topsheet also can be
elastically stretchable in one or two directions. Further, the
topsheet is fluid pervious permitting fluids (e.g., menses and/or
urine) to readily penetrate through its thickness. A suitable
topsheet can be manufactured from a wide range of materials
such as woven and non-woven materials; polymeric materials
such as apertured formed thermoplastic films, apertured plastic
films, and hydroformed thermoplastic films; porous foams;
reticulated foams; reticulated thermoplastic films; and
thermoplastic scrims. Suitable woven and non-woven materials
can be comprised of natural fibres (e.g., wood or cotton fibres),
synthetic fibres (e.g., polymeric fibres such as polyester,
polypropylene, or polyethylene fibres) or from a combination of
natural and synthetic fibres.
Preferred topsheets for use in the present are selected from
high loft non-woven topsheets and aperture formed film
topsheets. Apertured formed films are especially preferred for
the topsheet because they are pervious to body exudates and
yet non-absorbent and have a reduced tendency to allow fluids
to pass back through and rewet the wearer's skin. Thus, the
surface of the formed film that is in contact with the body
remains dry, thereby reducing body soiling and creating a more
comfortable feel for the wearer. Suitable formed films are
described in U.S. Patent 3,929,135; U.S. Patent 4,324,246;
U.S. Patent 4,342,314; U.S. Patent 4,463,045; and U.S.
5,006,394. Particularly preferred micro-apertured formed film
topsheets are disclosed in U.S. patent 4,609,518 and U.S.
patent 4,629,643. The preferred topsheet for the present
invention is the formed film described in one or more of the
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I7
above patents and marketed on sanitary napkins by The Procter
& Gamble Company of Cincinnati, Ohio as "DRI-WEA E."
Topsheets having not a homogeneous distribution of liquid
passage ways but only a portion of the topsheet comprising
liquid passage ways are also useful for the present invention.
Typically such topsheets would have the liquid passage ways
oriented such that they result in a centrally permeable and
peripherally impermeable topsheet for liquids.
The body surface of the formed film topsheet can be
hydrophilic so as to help liquid to transfer through the topsheet
faster than if the body surface was not hydrophilic. !n a
preferred embodiment, surfactant is incorporated into the
polymeric materials of the formed film topsheet such as is
described in PCT application number US 92/09227.
Alternatively, the body surface of the topsheet can be made
hydrophilic by treating it with a surfactant such as is described
in the above referenced U.S. 4,950,254.
Water vapour oermeable back heel
The water vapour permeable and liquid impervious backsheet
prevents the exudates absorbed and contained in the absorbent
core from wetting articles that contact the sanitary napkin such
as pants, pyjamas and undergarments. The backsheet
comprises at least a layer of water vapour permeable material.
The backsheet can also comprise a polymeric film having
apertures to provide structural strength to the backsheet. Also a
layer of fibrous fabric particularly forming the garment facing
surface can be comprised of the backsheet.
CA 02203796 1997-04-25
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ig
The water vapour permeable layer can be provided by a
polymeric film having molecular size apertures. The film can be
e.g. a Goretex (TM) or Sympatex (TM) type of structure well
known in the art of providing breathable clothing. Also films
according to EP-A-293482 are considered useful in the context
of the present invention. Another example of a commercially
available water vapour permeable film useful as backsheet for
the present invention is designated XMP-1001 of the Minnesota
Mining and Manufacturing Company, St. Paul, Minnesota, USA.
Th~panty-fastening-adhesive
The backsheet typically forms the garment facing surface on
which the panty fastening adhesive is placed.
According to the present invention it is important that the ratio
of theoretical adhesion surface to actual garment facing surface
is within the range according to the claims of the present
invention. The theoretical adhesion surface is defined by the
surface area inside the shortest possible endless line encircling
the panty-fastening adhesive however without extending
beyond the periphery of the garment facing surface.
In addition the ratio of actual adhesive surface to garment
facing surface is in the range of 0.2 to 0.8. If there is for
example one rectangular adhesive area on the garment facing
surface then the theoretical adhesion surface and the actual
adhesive surface are identical, this can be seen in Figure 1
where the adhesive 22 is indicated by hatching. The encircling
line 26 results in a theoretical adhesion surface 24 identical to
the surface covered by the adhesive 22. For absorbent articles
.. -- m having protective side flaps Figure 2 shows that the three
adhesive areas 22 are smaller in surface area than the
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19
theoretical adhesion surface 24 encircled by line 26. If the
backsheet is elastically stretchable the adhesive surfaces are
measured on the unstretched backsheet prior to initial
stretching thereof.
Panty-fastening-adhesives can comprise any adhesive or glue
', used in the art for such purposes with pressure-sensitive
adhesives being preferred. Suitable non-extensible adhesives
are Century A-305-IV manufactured by the Century Adhesives
Corporation, Instant lock 34-2823 manufactured by the
National Starch Company , 3 Sigma 3153 manufactured by 3
~I .Sigma, and Fuller H-2238ZP manufactured by the H.B. Fuller
Co. Suitable adhesive fasteners are also described in U.S.
Patent 4,917,697.
In order to maintain the water vapour permeability of the
backsheet according to the present invention it is-important that
', the panty fastening adhesive does not close or clog the whole
surface of the garment facing side of the backsheet. For this
' purpose it is possible to use an adhesive in such a pattern to
i
', only seal off a fraction of the surface such that no more than
80% of the actual garment facing surface is covered by
', adhesive. On the other hand 20°~ adhesive coverage has been
I found necessary to provide the benefit of proper attachment to
the undergarment of the absorbent article.
', Therefore, preferably the panty fastening adhesive is applied in
intermittent patterns such as for example intermittent dots,
intermittent strips, random or designed filamentary patterns like
spirals to permit the sanitary napkin to remain water vapour
permeable.
__
_ __M_ . _ _ .
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' 20
In addition, other types of fasteners can be used instead of , or
in addition to adhesives. These other types of fasteners are
arranged in patterns similar to those of the adhesive. Suclrhi
fasteners include, but are not limited to conventional VELCRO
hook material or similar fasteners.
The protective side flaps can have optional fasteners thereon
for additional security. The optional protective side flap
fasteners can be any of the types of fastening materials herein
above. The fasteners assist the protective side flaps in staying
in position after they are wrapped around the edges of the
crotch surface of the protective side flaps.
Prior to use of the absorbent article the panty fastening
adhesive is typically protected from contamination and from
sticking to any surface where this is not desired by a protective
cover means such as a silicone coated release paper, a plastic
film or any other easily removable cover. The protective cover
means can be provided as a single piece or in a multitude of
pieces e.g. to cover the individual adhesive areas.
The procedure for measuring the flexibility/drapability of the
absorbent article is as follows:
ASTM Method D1388-64: Standard Methods for Test for
Stiffness of Fabrics (modified as described herein).
i _
', CA 02203796 1997-04-25
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21
This test is based on the cantilever beam principle. The distance
a strip of sample can be extended beyond a flat platform before
it bends through a 41.5° angle is measured. The inter-action
between sample weight and sample stiffness measured as the
sample bends or drapes under its own weight through the given
angle under specified test conditions is used to calculate the
I Flexibility/Drapability.
GENERAL COMMENTS
The flexibility test is only one way of measuring a sample's
', flexibility and is believed to be one of the components which
users of absorbent articles often refer to as softness. This
measurement method should be followed as closely as possible
I and should not be confused with the multidirectional flexibility
', described in US 5,009,653. Even so testing of samples in only
the longitudinal direction is described and necessary for the
present invention it is also possible for very wide or
exceptionally flexible articles to measure flexibility in the
transverse direction.
In general, a single sample strip should be tested only ~ time.
The two sides of the sample should be tested on different
sample strips. Likewise, sample strips for use in this test must
be very carefully handled to prevent folds, wrinkles, bends, etc.
This test is intended to be used on articles before they have
been folded or bent for packaging by the manufacturer. If the
sample is placed by the manufacturer in a folded configuration,
it should be gently unfolded for the test. If only folded articles
', are available, the Flexibility/Drapability can be approximated by
measuring a sample taken from between the fold lines. The test
', ~ should be used on cornplete samples, i.e. with all layers
having the same shape extending to the complete sample
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22
surface and fully glued together. For each sample four different
strips with topsheet up and four different strips with topsheet
down should be measured. Samples should be measured in
longitudinal direction. .
To note for relative stiff absorbent articles measurements even
in longitudinal direction may not be obtainable due to the
sample length being insufficient for bending through 41.5°.
APPARATUS
Cantilever Drape Stiffness-Tester Type SDL 0038 SDL
International
Obtain form Carl von Gehlen/Germany
(Te1.:02168/2910; Fax 02168/24570)
1-inch Wide Cutter Double edge cutter, 25.4 mm wide
(1 inch)
Conditioned Room A room conditioned to 21.7°C -
23.9°C, 50 %,~ 2 % Relative Humidity
Talcum Powder
Zerostat Anti-Static To eliminate static charge on the
drape Pistol (optional) tester and/or tissue. Distributed
in the
USA by Dishwasher, Inc., Columbia,
MO 65201. May be obtained from
Morgan Instruments, Inc., P.O. Box
46442, 113 Circle Freeway Dr.,
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23
.
Cincinnati, OH 45246. Morgan
Catalogue No. 70-35-00. Also available
from record shops and photographic
. ' supply stores. Use of this pistol is an
approved way to remove static
charges for this test. Never use fabric
softener to remove static char e~1' from
a drab Operate the Anti-Static
', Pistol according to the manufacturer's
instructions.
SAMPLE PREPARATION
The samples should be placed in an area of the room permitting '
maximum recirculation of air and maximising equilibration with
the humidity and temperature conditions.
', 1. Cut 8 samples using a 1-finch wide cutter. The sample
strip has to be cut lengthwise from the centre of the
absorbent article to be rectangular without crimp. Usual
~I sample dimensions for measurements are 2.54 cm x 14.0
', cm = 35.56 cm2. The samples may be shorter but must
comprise
absorbent material throughout.
2. Remove the release paper and weight the sample tmg).
Round the weight to the nearest 1 mg.
3. Carefully powder the PFA with the minimum amount of
talcum sufficient to avoid sticking. Blow out the
', remaining talcum from the sample.
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24
4. Weight the sample strip with talcum (mg). Round the
weight to the nearest 1 mg.
5. For each sample calculate the basis weight of the sample
based on weight measurement with and without talcum
and the actual surface area of the sample.
s~ Discard the sample if its weight increased more than 2.0
mg/cm2 after adding the talcum.
INSTRUMENT OPERATION
Drape-tester should be placed on a bench directly in front of the
operator. It is important that the bench is relatively free of
vibration, that there is no air flow during the measurement and
that the bench is free of draft.
The operator may either sit or stand in front of the tester while
it is being used. Then the operator has to chose his position so
that looking in the mirror of the tester he sees the front
reference line covering the back reference tine. If he sees only
one line he has the right position for the measurement.
The tester shall:
1. Remove the sample slide bar from the sample slot on the
top platform of the drape tester.
2. Place the sample trip on the sample slot so that one end
of the strip is exactly even with the vertical edge of the
tester. The strip should be placed as close as possible to
the side rail of the sample slot but not touching it.
_.. _..
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3. Place the sample slide bar on top of the sample strip so
I
that its front edge is aligned with the edge of the-sample strip
in the tester and so that it touches the side rail. The sample
' slide bar must be carefully placed so that the sample is
', not wrinkled or moved forward.
4. Pulling from its free edge and using very light, gentle
I pressure, move the slide bar slowly and steadily forward
with a speed of about 1 cm/s. As the slide bar moves
', forward, the sample should move at an equal stow
rate. As the slide bar and the sample strip project
over the edge of the tester, the sample strip will begin to
i
~I bend or drape downward. Stop moving the slide bar the
instant when the leading edge of the sample strip falls level
with the 41.5 ° reference lines.
If the sample has a tendency to twist, take the reference
point at the centre of its leading edge. Samples which
j
twist more than 45° cannot be measured. Samples can only be
I~ measured if the sample length. is at least 0.5 cm longer
than the overhang length. For non measurable samples, the
overhang length can be measured only if a long enough
strip can be obtained which is at least 0.5 cm longer than
the overhang length.
5. Mark the overhang length on top of the sample
(Overhang length : distance from the start point of movement
until the point where the sample bends through 41.5°1.
6. Measure the overhang length in cm with a ruler. Read the
overhang length to the nearest 1 mm.
_. _ - CALCULATION
_
_~a_
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26
The equation used to express Flexibility/Drapability according to
the present invention is as follows:
G = WL3
Where G equals the Flexibility/Drapability, W is the sample basis
weight including talcum in milligrams/cm2, and L is the length
of the overhang in cm. Results are expressed in milligrams x cm
or grams x cm.
Thickness measurement
The thickness should always be measured at the thickest
possible place, usually in the centre of the absorbent article. For
convenience the measurement is conducted on the absorbent
article inclusive any protective cover means present. The article
should be reconditioned at 50 °~ humidity and 23° C for two
hours
within its usual package and be removed not more than five
minutes prior to the measurement.
The thickness is measured with a micrometer gauge having a
range of 0 to 30 mm and capable of plus minus 0.5 mm
tolerance. The gauge must not be spring loaded and should
have a foot moving downwards under gravity. The micrometer
foot has a diameter of 40 mm and is loaded with a 80 gram
weight. The measurement is taken between 5. and 10 seconds
after the foot has been lowed to come into contact with the
absorbent article. Measurements should be taken often enough
to allow statistical analysis to determine average thickness
within a sigma of plus minus 0.1 mm. A detailed description of
the thickness measurement can also be found in US-Patent 5,
009, 653.
