Note: Descriptions are shown in the official language in which they were submitted.
CR121/AA
21~9966
ABSORBENT SANITARY DEVICE
This invention relates to an absorbent sanitary
device, for example in the form of a catamenial or a
sanitary pad. However, it relates particularly to
incontinence devices, and, more particularly, device for
handling light or moderate incontinence in adult
females. One characteristic which is particularly
important in an incontinence device is its ability to
conform to the adjacent part of the wearer's body, so
that urine and other body fluids are directed into the
device and do not bypass it. It is an object of the
present invention to provide a device in which this is
achieved to a particularly great extent. This is
achieved by use of an advantageous system of
elastication.
According to one aspect of the present invention
there is provided an absorbent sanitary device having a
top side adapted in use to face the user and a back side
adapted to face away from the user, the device being
elongate and having its end regions directed generally
upwardly as viewed from the top side, the device
comprising, as considered from the top side to the back
side, a topsheet which is liquid permeable, a fluid
storage core, and a liquid-impermeable backsheet sealed
to the topsheet at least along a pair of laterally
spaced, longitudinally extending, sealing lines, the
device being provided with upstanding, elasticated,
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spaced apart barriers which extend longitudinally of the
devlce along at least part of the length thereof,
adjacent laterally opposite side edges thereof, inwardly
of the said sealing lines, which barriers, in
cooperation with the said end regions, define a
user-engaging surface, the barriers being formed by
upstanding, elasticated portions of the topsheet.
According to another aspect thereof there is
provided an absorbent sanitary device having a top side
adapted in use to face the user and a back side adapted
to face away from the user, the device being elongate
and having its end regions directed generally upwardly
as viewed from the top side, the device comprising, as
considered from the top side to the back side, a
topsheet which is liquid permeable, a fluid storage
core, and a liquid-impermeable backsheet sealed to the
topsheet at least along a pair of laterally spaced,
longitudinally extending, sealing lines, the device
being provided with upstanding, elasticated, spaced
apart barriers which extend longitudinally of the device
along at least part of the length thereof, adjacent
laterally opposite side edges thereof, which barriers,
in cooperation with the said end regions, define a user-
engaging surface, the barriers being formed by
upstanding, elasticated portions of the topsheet, the
topsheet material having a greater width than the
backsheet material.
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According to yet another aspect there is provided
an absorbent sanitary device having a top side adapted
in use to face the user and a back side adapted to face
away from the user, the device being elongate and having
its end regions directed generally upwardly as viewed
from the top side, the device comprising, as considered
from the top side to the back side, a topsheet which is
liquid permeable, a fluid storage core, and a
liquid-impermeable backsheet sealed to the topsheet at
least along a pair of laterally spaced, longitudinally
extending, sealing lines, the device being provided with
upstanding, elasticated, spaced apart barriers which
extend longitudinally of the device along at least part
of the length thereof, adjacent laterally opposite side
edges thereof, which barriers, in cooperation with the
said end regions, define a user- engaging surface, the
barriers being formed by upstanding, elasticated
portions of the topsheet, the elastication of said
elasticated portions extending over at least 35% of the
length of the device.
Each of the said barriers may be elasticated by
means of a line of hot melt adhesive material, and the
said material may be deactivated in at least one zone to
cause it to be inelastic in the said zone, thereby to
influence the shape of the device and/or increase the
adhesion of the said material.
The invention will now be described with reference
to the accompanying drawings, in which:
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Figure 1 is a perspective view of a first
embodiment showing the user side (i.e. the side which,
in use faces the body of the wearer);
Figure 2 is a top plan view of the device of Figure
1 in a tensioned condition, i.e. with the elasticatlon
therein stretched to cause the device to assume a planar
configuration;
Figure 3 is a diagrammatic cross section through
the centre of the device of Figure 1, showing the layers
of which it is formed;
Figure 4 shows the patterns of adhesive applied to
the various layers of the device of Figure 1;
Figure 5 is a view similar to Figure 3 but showing
a second embodiment; and
Figure 6 is a view similar to Figure 3 but showing
a third embodiment.
Referring first to Figure 3, it can be seen that,
considered starting from the user side thereof, the
device comprises the following layers:
(a) Topsheet
The top layer (user side) is a topsheet 20 that
must be comfortable to the touch, provide a dry feeling
over an absorbent core filled with liquid, and pass
fluid rapidly into the interior of the core. It is
liquid permeable in the central longitudinal zone 22 and
is liquid impermeable at least in the two lateral zones
24. As can be seen in Figure 3, the boundary between
the central zone and each of the lateral zones coincides
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with a line of elastic glue, which is described in more
det~il below, though it is not essential that this
should be so.
The topsheet can be of a variety of known
materials, provided that it has a fluid-permeable
central region and a fluid-impermeable edge region, for
example: (a) a formed-film topsheet as described in
U.S. Patent 3929135, or any of European Patent
specifications Nos. EP-A-0018020, EP-A-0018684 and
EP-A-0059506, (b) a partially perforated fibre/film
composite described in EP-A-207904, the perforated area
thereof providing a liquid permeable area, and the
unperforated area thereof providing a liquid
impermeable area, (c) a nonwoven film produced by the
spunbonding or by a carded, thermal-bonded process,
treated by appropriate hydrophobic finishing agents to
give areas that are liquid permeable and liquid
impermeable respectively, or (d) a sheet produced by
various other processes currently practised.
(b) Secondary Topsheet
This element 26 has the characteristics of
accepting a high rate of fluid intake, serving as a
temporary reservoir for the fluid, and then draining
substantially completely into the storage core in order
to remain empty for subsequent fluid loadings. In
addition, this element must resist collapse when wet so
that it maintains its performance through multiple
loadings. This element must do all these things while
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also remaining extremely thin. An airlaid web of
synthetic fibres can be used for this purpose. The
secondary sheet should preferably have hydrophilic
properties.
This material preferably has the following
characteristics:
(a) A thickness of from 1 to lOmm, more preferably from
1.5 to lOmm, still more preferably from 1.8 to 7.5mm,
and even more preferably from 2 to 6mm, the thickness
being measured with the sheet under a pressure of 2kPa.
(b) A basis weight of from 35 to 300 g/m2, more
preferably from in excess of 40 up to 200 g/m2, and
still more preferably from 42 or 43 to 200 g/m2.
(c) The sheet has a bulkiness of at least 15 cm3/g,
when the sheet is under a pressure of 2kPa. More
preferably, the bulkiness is from 15 to 65 cm3/g, still
more preferably from 30 to 50 cm3/g. Yet more
preferably, the minimllm value for the bulkiness is 32,
33, 34 or 35 cm3/g.
(d) The ability to discharge to the storage core at
least 95%, and more preferably at least 99% of the fluid
which it receives in a loading.
(e) A wet collapse at 2.7kPa of not more than 45%, and
more preferably not more than 40%.
(f) A wet resilience at 0.1 kPa of not more than 40%,
more preferably not more than 30%, and still more
preferably not more than 25%.
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(g) A wetting time of not more than 5 seconds, and
preferably not more than 2 seconds.
(h) It is formed of fibres having a diameter of not
more than about 20 um, more preferably from about 15 to
about 20um, and a length, at least when the sheet is an
airlaid web, of not more than 20mm, preferably not more
than 12mm, and most preferably about 6mm.
One suitable form of secondary topsheet is
described in our Italian Patent Application No. TO 93a
000 402. In the embodiment illustrated in Figure 3
there are two secondary sheets 28, 30 each of which has
the above mentioned characteristics.
The two layers of the secondary topsheet are
adhered to one another by, for example a spiro hot melt
adhesive, the term "spiro" referring to adhesive which
is applied in a spiral pattern. The use of a pattern,
as opposed to a continuous layer, keeps to ensure that
fluid permeability is not significantly impaired.
(c) Storage Core
The storage core 32 is a thin, high-capacity
absorbent core. While thin when dry, this element of
the structure preferably expands when wetted to provide
a high, tenacious fluid-holding ability, and it must
avoid collapse when wet. The storage core is itself
preferably formed, as illustrated, of a plurality of
layers. For example, as shown in Figure 3 it may be a
three layer structure in which the upper and lower
layers are of a cellulose tissue material ~and may be
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the same as, or different from, one another). The upper
layer 34 is a thermobonded, airlaid, nonwoven, of short
cellulose fibres, the lower layer 36 is an airlaid
nonwoven also of short cellulose fibres, and the middle
layer 38 is of a water-insoluble hydrogel. This is a
polymeric material in particulate form, capable of
absorbing a large quantity of liquid and retaining it
under moderate pressures. It is commonly known by the
abbreviation "AGM".
It is important that the secondary sheet and the
storage core work together. In particular, given the
form of secondary sheet described above, it is possible
in this structure to avoid the typical problem of gel
blocking in the storage core, because the secondary
sheet provides total distribution of the fluid, and then
drains into the storage core whenever the storage core
has not yet received fluid.
As an alternative to the form of storage core
described above, it can be one of a number of thin, high
capacity materials. For example, the storage core can
be a sheet of fused AGM particles as described in
International Patent Applications Nos. WO91/14733,
WO91/14734, WO91/15352 and WO91/15368 or a high capacity
foam, as described, for example, in International Patent
Publications Nos. W093/04092, W093/03699, W093/04093,
WO93/04113 and WO93/04115.
Another possibility is to use a core which is a
mixture of cellulose fluff and AGM.
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g
Still more preferably, the storage core can be an
AGM- comprising core as described in International
Patent Application No. PCT/US93/06128, or as described
in Italian Patent Application No. TO 93 A 01028 filed on
31st December 1993. TO 93A01028 describes a layered,
absorbent structure, characterised in that it comprises,
in combination, first and second layers of fibrous
material and an intermediate layer comprising a
hydrogelling, ~bsorbent material, in an amount exceeding
120g/m2, distributed between the first and second
fibrous layers, at least one of the first and second
layers being permeable to liquids, and the intermediate
layer also comprising a thermoplastic material, the
intermediate layer bonding the first and second fibrous
layers together, with the intermediate layer between
them.
(d) Impervious backsheet
The backsheet 40 is impervious to liquids and,
thus, prevents fluid which may be expressed from the
absorbent core from soiling the body or clothing of the
user. Suitable materials are well known in the art,
including woven and nonwoven fabrics which have been
treated to render them liquid repellent. Breathable or
vapour pervious, liquid resistant materials, and those
materials described in US-A-3,881,489 and US-A-3,989,867
can also be used. Preferred materials are those
materials that are fluid and vapour impervious, because
they provide additional fluid strikethrough protection.
- 21S9966
- ' 10
Especially preferred materials include formed
thermoplastic films.
(e) Panty fastening adhesive
A layer of pressure-sensitive adhesive 42 is
provided on the reverse side of the backsheet to enable
it to be adhesively attached to the user's panties.
(f) Release paper
A silicone release paper 44 removably covers the
panty fastening a&esive 42, to enable the incontinence
device to be packaged, and handled by the user prior to
use, without it becoming unintentionally adhered to
itself or to anything else. The release paper 44 is
removed by the user prior to use. Such release papers
are well-known in the art.
The various layers are adhered to one another by
adhesives disposed in suitable patterns, and these are
shown in Figure 4. This shows:
(i) The release paper 44 and its adjacent layer of
panty fastening adhesive 42 (the paper 44 extends beyond
the adhesive 42 both at its ends and at its side edges).
(ii) The backsheet 40 and a layer of spiro hot melt
adhesive 46 extending the full length thereof, by which
it is attached to the core 32.
(iii) The secondary topsheet layers 28, 30, each
with a respective layer 48, 50 of spiro hot melt
adhesive extending the full length thereof, by which,
respectively, the layer 28 is attached to the layer 30
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and the layer 30 attached to core 32. (In the drawing
of the layer 30 in Figure 4 the lateral extent of the
absorbent core is indicated by broken lines).
(iv) A plurality of spaced, longitudinally
extending lines of hot-melt adhesive 52 by means of
which the topsheet 20 is attached to the secondary
topsheet layer 28, and laterally outermost lines 53 by
which the topsheet is attached to the backsheet 40.
The device 10 as thus far described with reference
to the drawings would lie in a flat plane. As
illustrated in Figure 1, the device in fact has a
generally flat central region 12 and an upwardly sloping
region 14, 16 at each end. However, the basic
requirements is for a device which is generally curved
as viewed in longitudinal section, and this may take the
form of a smooth curve extending from one end of the
device to the other, rather than there being a distinct
flat central region and distinct upwardly sloping end
regions. The generally curved shape, whichever way it
is achieved, enables the device to conform to a
considerable degree to the user's body, with
advantageous consequences in terms of its ability to
catch urine and other body fluids.
The effect just described is achieved by two lines
of elastication 54, 56 which are applied to the
underside of the topsheet 30. The elastication
preferably takes the form of two lines of a hot melt
glue which is capable of being deactivated, a phenomenon
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12
described in more detail below. Suitable compositions
for~the purpose of the present invention are described
in our copending Italian Patent Application No. [ ]
entitled [title of DR52].
By way of giving some theoretical background, it
should be noted that for any elastic adhesive
composition the elastic modulus G' can be measured as a
function of the temperature. At room temperature G'>G",
where G" is the viscous modulus. At a certain
temperature, which coincides with the softening point of
the material, G' and G" cross each other. At even
higher temperatures G">G' and the material is liquid,
while when G'>G" the material is solid. At any
temperature below the softening point the value of G'is
related to the storing of elastic tension. So if we
subject the material at a certain temperature to a
pressure at least equal or higher than the value of G'
at that temperature, the material itself, even if still
solid, flows and the internal tensions are relaxed.
When this occurs the material ceases to be elastic, and
is said to be "deactivated". The necessary pressure is
zero at the softening point (at this temperature the
material begins to turn into a liquid and any internal
stress disappears spontaneously), while at lower
temperatures G' increases as the temperature decreases,
These facts are used in providing the lines of
elastication 54, 56. A hot melt adhesive, preferably
having a composition as described in the last mentioned
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13
copending Italian Patent Appli~ation, is extruded to
give elongate pieces of adhesive, for example threads
thereof. These are cooled, stretched to the desired
elongation and tension and applied to the lower surface
of the topsheet. A method of carrying out this
procedure is described in our copending Italian Patent
Application No. [ ] filed on [ ] and entitled
[title of DR3.l]. Adhesion between the threads and the
topsheet can be improved by exerting pressure, for
example with a roll. This roll can be heated to a
moderate temperature, to improve the adhesion between
the threads and the topsheet. The combination of
temperature and pressure must not be so great as to
cause deactivation, at least not over the whole length
of the threads. As described in Italian Patent
Application No. [ ] [title of DR3.1], the roll can
have a smooth surface, or it can have a toothed surface
so that it presses the threads into contact with the
topsheet only in selected zones.
Although, as already stated, the adhesive threads
must not be deactivated through their entire length,
they can be, and preferably are, deactivated over
certain regions. At a plurality of points spaced along
the central part thereof, where it runs alongside the
central region 12, the adhesive threads can be
subjected to a temperature, or a pressure, or,
preferably, a combination of temperature and pressure
which, though sufficient to improve the adhesion of the
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threads to the topsheet at those points, is insufficient
to cause deactivation. However, each thread is
deactivated over the whole of each of its end parts,
where it runs alongside the upwardly sloping regions 14,
16. This is done so that the threads are not in a
tensioned state in these parts, and the sections 14, 16
do not curve, as viewed in side elevation.
The improved adhesion at selected points, and the
deactivation along the regions 14, 16 can be carried out
using heat and/or pressure applied by the same member,
e.g. a single roll, or by different members, e.g. rolls.
When a single member is used to carry out both
functions, the single member can have a first zone where
the temperature and/or pressure applied are sufficient
to cause adhesion but insufficient to cause
deactivation, and a second zone where the temperature
and/or pressure are sufficient to cause deactivation.
Typically, deactivation is carried out with a
combination of temperature and pressure, so that the
temperature required is less than or equal to the
softening point.
In one example, the article has end regions each
45mm in length, over which the threads are completely
deactivated, and a central region 156mm in length over
which the threads are adhered to the topsheet over a
plurality of short elements each 3mm in length, the
centre- to-centre spacings of these elements being
7.8mm. It must be understood that these values are
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given by way of example only. The measure~ents apply to
the article in its extended state, i.e. before the
adhesive threads are allowed to cause contraction of the
central region. The threads need not extend over the
whole length of the article, and may extend only over
part of the length thereof. Preferably, however, the
threads, whether or not they are full length, have an
elasticated portion which extends over at least 35% of
the length of the article, and they may extend over 40%,
45%, 50%, or even more. In the example just quoted, the
value is over 60%.
Once the lines of elastication 54, 56 have been
applied to the topsheet 20, it is thermally crimped to
the backsheet 40, adhesion being assisted in the crotch
region by means of the lines of adhesive 53. At this
stage, the lines of elastication 54, 56 are in tension.
When this tension is released, the elasticity therein
causes the adjacent parts of the topsheet (which are not
adhered to the secondary topsheet situated below them)
to stand up, thus producing side barriers 60, 62 (see
Figure 3), and causing the incontinence device as a
whole to assume the curved shape shown in Figure 1.
Typically, the width of the topsheet, before assembly,
exceeds that of the backsheet by about 45mm, so
permitting the formation of two barriers each about 10mm
high. These barriers 60, 62, together with the upwardly
sloping end regions 14, 16, define, so to speak, a kind
of gasket which engages the body of the user and helps
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16
to prevent fluid escaping past the edges of the device
before the device has had time to absorb it. It will be
seen that each barrier has a triangular cross-section,
with the generally upright walls of each triangle not
being adhered to one another. All or part of the inner
one of these walls may be fluid permeable, but the other
one of these walls should be fluid impermeable.
An example of an incontinence device according to
the invention will now be set out in more detail.
EXAMPLE
This is a light incontinence device for use by an
adult female. The device is hourglass shaped as
indicated in the drawings, and has a length of 246mm, a
width at its widest point of 98mm, a width at its
narrowest point of 76mm, and a weight of lO.58g. The
details of the components used in the construction are
shown in the following Table. Corresponding
measurements appear on the drawings, all of which are in
mm.
~ABLe
~aterial Length (mm) Width (mm)
ABSORBENT CORE 219 56
TOPSHEET 246 98 (wide~t)
76 (narrowe~t)
SECONDARY TOPSHEET 219 78 (wideqt)
(2 LAYERS. EACH LAYER) 60 (narrowe~t)
BA~K~ 246 98 (wide~t)
76 (narrowe~t)
ELASTIC GLUE 246 (in ~tretched 2
(2 line~ - each line) ~tate)
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17
With reference to the above Table, the topsheet is
a partially perforated fibre/film laminated composite
as already mentioned with reference to EP-A-207904; the
composite may be ring rolled, and the perforated region
is 65mm wide. Ring-rolling is used to provide the
composite with a degree of extensibility. Suitable
processes for ring-rolling are described in US Patents
4107364, 4834741, 5143679, 5156793 and 5167897.
The absorbent core is a layered structure of the
type described above. The upper fibrous layer is a
thermal bonded airlaid (about 76% cellulose fibres and
about 24% bicomponent PE-PP fibres) 219mm long 56mm wide
and with a basis weight of 75 g/m2; the intermediate
layer, 219mm long and 48mm wide, ~comprises particles of
AGM (XZ 91002.01 by Dow Chemical) with a basis weight of
385 g/m2; the lower fibrous layer is a latex bonded
airlaid (100% cellulose fibres) 219mm long, 56mm wide
and with a basis weight of 55 g/m2.
The secondary topsheet is a 100% bicomponent PE-PP
fibres thermal bonded air laid.
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.
18
The backsheet is a thermoplastic film 40 ~m thick.
The elastic glue is of the type described above.
The embodiment shown in Figure 5 is similar in most
respects to that of Figure 3, and the same references
are used for corresponding elements, but increased by
100. The two embodiments differ in that in Figure 5 the
topsheet 20 wraps around the edges of the backsheet 40,
so avoiding the laterally extending flanges of topsheet
and backsheet which are present in Figure 3 in the
region wherein the two are bonded together.
The embodiment shown in Figure 6 is similar to the
two previous embodiments, and the same reference
numerals are used as for Figure 3, but increased by 200.
The principal difference from the previous embodiments
is that the topsheet is turned over at its outer lateral
edges and sealed to itself, enclosing the lines of
elastication.
A number of tests are referred to in the preceding
description, and the following gives details of how
those tests are conducted.
Wet collapse
The samples 39 x 50mm are made of as many
superimposed layers of material as are needed to get an
overall basis weight of 500 g/m2. The samples are
completely plunged in synthetic urine (the composition
of which is given below) and left in it for 1 minute.
They are then placed on a perforated plexiglass plate
and subjected to three dynamic cycles of compression and
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19
decompression (speed of the pressing head lOmm/min,
maximum load for each cycle 2.7 kPa). The minimum
thickness of the sample under compression is measured.
The wet collapse is:
(initial thickness - minimum thickness/initial
thickness of the sample) x 100 (%).
Wet resilience
In the above described test the final thickness of
the sample after the last decompression is measured.
The wet resilience is then obtained as:
(initial thickness - final thickness)/initial
thickness) x 100 (%).
Wetting time
In this test, samples of the secondary sheet having
a volume of about 5cc are tested. The samples are
placed horizontally onto the surface of synthetic urine
by means of a metallic net. The wetting time is the
time needed for each sample to get completely soaked.
Synthetic urine
The synthetic urine used was a solution in
distilled water of the following salts tin weight %)
Urea 2%, sodium chloride 0.9%, magnesium sulfate
(heptahydrate) 0.11%, calcium chloride (anhydrous)
0.06%.
