Note: Descriptions are shown in the official language in which they were submitted.
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short title: WASHABLE ABSORBENT PAD AND A METHOD FOR MANUFACTERING SAME
The invention relates firstly to a washable pad, at
least comprising an assembly of a moisture-absorption element
which is positioned between a moisture-permeable top-layer
material and a moisture-impermeable bottom-layer material, each
with a thickness and an area which are such that the materials
have substantially the same surface area and, in the position of
use, the top surface of the moisture-absorption element bears
against the bottom surface of the moisture-permeable top-layer
material and the bottom surface of the absorption element bears
against the top surface of the moisture-impermeable bottom-layer
material, and in which the moisture-permeable top-layer
material, the moisture-absorption element and the moisture-
impermeable bottom-layer material are joined together to form a
single unit,
Washable pads of this nature are used as protection on,
for example, a mattress, in order to prevent them from becoming
soiled, for example when used by incontinent patients.
The pad collects any soiling instead of the mattress;
once it has been washed, the pad can be reused.
In the preceding text, the terms top and bottom surface
relate to the orientation of these surfaces in the position of
use of a pad, i.e. on top of a mattress or other base, with the
moisture-permeable top-layer material facing upwards.
A washable pad of this nature is known from
US-A-3,965,503. This publication describes a washable pad of the
type described in which the join between the above layers is
brought about by stitching.
The moisture-impermeable character of the bottom-layer
material is brought about by providing the bottom-layer material
with a moisture-impermeable coating subsequent to the stitching
operation, for example by applying a molten coating of polyvinyl
chloride, followed by cooling of this coating so that it
solidifies.
One drawback of this known washable pad is that, owing
to the presence of a sealing coating layer on the outside of the
bottom-layer material, it becomes stiff since this coating
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layer, in order to be moisture-impermeable, has to be relatively
heavy.
Sealing is necessary because moisture can pass downwards
from the patient along the stiches, so that a good seal is
necessary.
The object of the present invention is to provide an
improved washable pad of the above type and is characterized in
that between two out of the moisture-permeable top-layer
material, the moisture-absorption element and the moisture-
impermeable bottom-layer material, there is a form of bonding,
over at least part of the surface thereof, which differs from
the form of bonding between the third out of the moisture-
permeable top-layer material, the moisture-absorption element
and the moisture-impermeable bottom-layer and one of the above
two, or there is no bonding at all, while the moisture-
impermeable bottom-layer material is intrinsically moisture-
impermeable. Intrinsically moisture-impermeable is intended to
mean that the material in question is impermeable to moisture
without requiring any further treatment.
Starting from an intrinsically moisture-impermeable
bottom-layer material makes the pad easier to manufacture,
considerably improves the flexibility of the washable pad and,
as a result of the layers being attached to one another in
different ways, the flexibility of the pad can be optimized on
the one hand and, on the other hand, optimum fixing of the
layers with respect to one another is achieved.
In connection with the invention described above,
reference is also made to US-A-5,099,532, which describes a
principle for joining together the various layers which exhibits
some resemblance to the method used in the present invention.
In the above publication, a moisture-permeable top layer
is joined to an absorption body by means of stitching; then,
strips of material are placed against the moisture-absorption
body on the underside and are then joined to the assembly of top
layer and absorption body by additional stitching. On their side
which is remote from the absorption body, the strips have a
thermoplastic coating. Then, a moisture-impermeable bottom-layer
material is placed against the underside of the absorption body;
on the side facing towards the absorption body, the bottom-layer
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material has a layer of thermoplastic. By exerting pressure
and/or supplying heat, the thermoplastic layer of the strips is
joined to the thermoplastic layer of the bottom-layer material,
so that the three layers are joined together.
The use of a number of ways of joining moisture-
permeable top-layer material to moisture-absorption element and
of special strips for securing purposes make this pad
complicated to manufacture, while the presence of strips which
are coated with thermoplastic and joined to the bottom layer has
an adverse effect on the flexibility of the pad.
In an attractive embodiment of the washable pad
according to the invention, bonding is present between the
moisture-permeable top-layer material and the moisture-
impermeable bottom-layer material via perforations, which are
present in the moisture-absorption element, in the form of
bonding points.
The presence of a bond between the moisture-permeable
top-layer material and the moisture-impermeable bottom-layer
material firstly produces excellent fixing of the various layers
with respect to one another; there is no need for any further
bonding of the third layer, which in this case is therefore the
moisture-absorption element. The dimensions of the perforations
are selected in such a manner that the moisture-permeable top-
layer material of the moisture-impermeable bottom-layer material
can easily make contact with one another in order to be bonded
together under the influence of heat and/or pressure. Bonding
can be brought about using, for example, HF, ultrasonic or
thermal spot welding; obviously, bonding can also be achieved
with the aid of a locally applied bonding agent. The dimensions
of the perforations are not critical, provided that the
abovementioned condition concerning contact is satisfied. Good
results are obtained with perforations with a diameter of
between 10 and 50 mm; in one specific case, perforations with a
diameter of 25 mm gave good results. The centre-to-centre
distance may be from 50-400 mm, preferably 100-200 mm.
In the case outlined here, there is bonding between the
moisture-permeable top-layer material and the moisture-
impermeable bottom-layer material, while there is no bonding
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between the moisture-absorption element and one of the other
layers.
The use of a moisture-absorption element with
perforations is known per se from NL-B-1009034, in the name of
the applicant. The perforations allow rapid drying of the
absorption element following washing of the pad. The
perforations for promoting drying are generally of smaller
dimensions than those discussed above for forming the bond
between the moisture-permeable top-layer material and the
moisture-impermeable bottom-layer material. The perforations
which promote drying may, for example, have a diameter of 1-5 mm
with a centre-to-centre distance of S-30 mm. A practical
embodiment has perforations with a diameter of approximately
3 mm and a centre-to-centre distance of approximately 12 mm. In
the embodiment outlined above, in which there are relatively
large perforations for bonding the moisture-permeable top-layer
material to the moisture-impermeable bottom-layer material,
there may therefore be two types of perforations: small
perforations in a relatively large density for drying purposes
and large perforations in a relatively small density for bonding
purposes. Obviously, it is also possible only to have
perforations for bonding purposes. To provide a border finish,
the absorption element may be of smaller size than the moisture-
permeable top-layer material and the moisture-impermeable
bottom-layer material, and the said top-layer material and
bottom-layer material are then bonded together.
If appropriate, to promote the bonding, thermoplastic
may be arranged on the top and/or bottom surface of the
moisture-permeable top-layer material, or the top surface of the
moisture-impermeable bottom-layer material, at the location of
the borders and/or the perforations for bonding, in order to
promote the bonding between top-layer material and bottom-layer
material in those regions.
In the washable pad described above, there is also
expediently a border finish in which the moisture-impermeable
bottom-layer material is turned over onto the top surface of the
moisture-permeable top-layer material and is bonded thereto.
In an alternative embodiment of the washable pad
according to the invention, the moisture-impermeable bottom-
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layer material, on the side which faces towards the moisture
absorption element, is coated, over at least part of its
surface, with a layer of bonding material which bonds the
moisture-absorption element and the bottom-layer material
together.
The bonding between the moisture-absorption element and
moisture-permeable top-layer material may be of numerous types,
as will be explained in more detail below; it is possible to
select stitching; stepping/quilting; needling, HF/ultrasonic
welding, etc.
In the case described above, it is also expedient to
have a border finish in which moisture-impermeable bottom-layer
material bears against and is bonded to the moisture-permeable
top-layer material, for example by turning over the bottom-layer
material so that it bears against and bonds to the top-layer
material.
The latter embodiment can be used to very good effect if
there is no bonding between the moisture-absorption element and
the moisture-permeable top-layer material.
Starting from an intrinsically moisture-impermeable
bottom-layer material and bonding the said material to the
moisture-absorption element with the aid of a layer of bonding
material also results in a considerably more flexible washable
pad compared with the pad which is known from the prior art as
described above.
The bonding material as referred to above may, on the
one hand, be a thermoplastic bonding material which displays its
action as a result of heat being supplied, with the result that
the bonding material melts and materials which are bearing
against one another stick together.
Bonding is brought about by cooling to below the melting
point of the thermoplastic. The bonding material may also be a
material which crosslinks, optionally with heat being supplied,
which can no longer be reactivated once it has carried out a
bonding action of this type.
The moisture-impermeable bottom-layer material may be
combined with any desired moisture-permeable top-layer material
and moisture-absorption element, and the join between the
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moisture-absorption element and the moisture-permeable top-layer
material may also be of any desired type.
As is discussed in more detail below, this join between
the moisture-absorption element and the moisture-permeable top
s layer material may be brought about by stitching or
stepping/quilting which is known in the prior art.
Stepping/quilting involves making up two or more layers, for
example of moisture-permeable top-layer material and moisture-
absorption element, over the entire surface thereof in a
preselected pattern. It is also possible for moisture-permeable
top-layer material and moisture-absorption element to be bonded
together using, for example, a spot coating layer of bonding
material which, as stated above, is a thermoplastic material or
a material which crosslinks, optionally with heat being
supplied.
The invention also relates to a method for forming a
washable pad in which a moisture-permeable top-layer material is
placed against the top surface of a moisture-absorption element,
and a moisture-impermeable bottom-layer material is placed
against the bottom surface thereof, and the moisture-permeable
top-layer material, the moisture-absorption element and the
moisture-impermeable bottom-layer material are joined together
to form a single unit, which is characterized in that, between
two out of the moisture-permeable top-layer material, the
moisture-absorption element and the moisture-impermeable bottom-
layer material, over at least part of the mutually facing
surfaces thereof, bonding is brought about by supplying heat
and/or exerting pressure, while bonding of a different type is
brought about between the third out of the moisture-permeable
top material, the moisture-absorption element and the moisture-
impermeable bottom-layer material and one of the said two, or
there is no bonding whatsoever, while the starting material for
the moisture-impermeable bottom-layer material is intrinsically
moisture-impermeable.
As described above with regard to the product, it is
possible, by suitably selecting the bonding methods, to provide
the washable incontinence pad with a high level of flexibility;
optimum fixing of the layers with respect to one another is
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ensured, and, as will be explained in more detail, the method is
suitable for a high degree of automation.
In an advantageous embodiment, the washable pad
according to the invention also includes bottom-layer material,
or a similar material, in the border regions, and this material
bears against and bonds to the top-layer material.
The moisture-absorption element used may be any known
moisture-absorption element which generally comprises a
combination of moisture-absorbent fibres and, if appropriate, a
moisture-dispersing layer on one or both sides.
Very good results are obtained with a moisture-
absorption element such as that which is described in
WO-97/34554 in the name of the applicant, in which a moisture-
absorption element comprises a mixture of chemical and synthetic
fibres which are brought together in a layer, with liquid-
dispersing layers of synthetic fibres present on the top and
bottom sides of the layer.
A moisture-absorption element of this nature typically
comprises <100%, for example 90-10%, chemical fibres and up to
100, for example 10-90%, synthetic fibres, while one or more
liquid-dispersing layers which substantially comprise synthetic
fibres are bonded to the top and bottom sides (percentages are
by weight). In a specific case, the liquid-absorbent layer
contains 90-60% chemical fibres, such as viscose or modified
viscose, and 10-40% synthetic fibres, such as polyester,
polyamide, polyacrylate, polypropylene, and the like.
In the present context, the term chemical fibre is
understood to mean a fibre which is based on a natural product,
such as cellulose, and has been made into a form which is
suitable for human use by means of a chemical treatment. A
synthetic fibre is a fibre which is produced from a polymer
which is prepared entirely by chemical synthesis and in which
there is no natural product base.
Another advantageous embodiment of the absorption
element described above and produced by the applicant is
described in Dutch Patent 1009034, in the name of the applicant,
as referred to above, in which the absorption element, in order
to improve its drying properties, is provided with a large
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number of perforations which extend over at least part of the
height of the absorption element.
The top-layer material may also be of numerous types,
provided that it exhibits good permeability to moisture and is
substantially hydrophobic.
Expediently, the top-layer material is, for example, a
knitted fabric comprising fibres, such as polyester, polyamide,
polyethylene, etc. It should be noted that good results have
also been obtained with mixed materials, such as with
synthetic/natural fibres, one example of which is 50%/50%
polyester/cotton. It is even possible to use 100% cotton, if the
absorption capacity of the absorption element is sufficiently
high.
Suitable results are obtained, for example, with a
polyester knitted fabric which, on the side which comes into
contact with the patient, has been roughened so that a soft
surface is obtained.
In an attractive embodiment, the method which is
described in general terms above is characterized in that a
moisture-absorption element is provided with perforations
distributed over its surface, which perforations extend through
the entire thickness of this element, and in at least some of
the perforations the moisture-permeable top-layer material and
the moisture-impermeable bottom-layer material are brought into
contact with one another and bonded to one another by supplying
heat and/or exerting pressure, so that bonding points are
formed.
The embodiment described above is eminently suitable for
automation in a production line.
The moisture-permeable top-layer material, the
absorption-body material which is provided with perforations and
the moisture-impermeable bottom-layer material are for this
purpose fed to a processing unit in the form of webs; by
exerting pressure, for example air pressure, contact is brought
about between the moisture-permeable top-layer material and the
moisture-impermeable bottom-layer material in the region of the
perforations; bonding between the said layers is brought about
in the region of a selected number of perforations with the aid
of the abovementioned techniques, such as welding or adhesive
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bonding; the assembled web which is formed in this way is
divided into pieces in the size of a washable pad by cutting
and, in line or off line, a border finish is produced, if
necessary, as will be described in more detail below.
The border finish may firstly be brought about by making
the moisture-absorption element smaller than the moisture-
permeable top-layer material and the moisture-impermeable
bottom-layer material and by bonding the top-layer material and
bottom-layer material together at the borders. To improve the
bonding, it is possible, at the location of the borders and/or
the perforations for bonding, to provide the top-layer material
(which is permeable), on the top and/or bottom surface, or the
top surface of the moisture-impermeable bottom-layer material,
with thermoplastic which contributes to the ease and speed of
bonding.
With regard to the border finish, in the embodiment
described above this may expediently be carried out in such a
manner that the surface area of the moisture-impermeable bottom-
layer material is made larger than the surface area of the
moisture-absorption element and the moisture-permeable top-layer
material, and in the border regions the moisture-impermeable
bottom-layer material is turned over onto the moisture-permeable
top-layer material and is joined thereto.
In a fully automated method, if this embodiment is used,
it will be possible for the border finish to be realized in the
transverse direction of the web by carrying this finish out
after the web has been divided into pieces with a longitudinal
border finish, for which purpose a strip of moisture-permeable
top-layer material/moisture-absorption material is cut away at
the location of the transverse edge. It is also possible to feed
pieces of assembled moisture-permeable top-layer
material/moisture-absorption element of suitable dimensions to a
web of moisture-impermeable bottom-layer material, and the
entire border finish can be carried out after the materials
which have been assembled to form the pad sandwich structure
have been divided into pieces.
In another embodiment of the method according to the
invention, an assembly is formed from a moisture-absorption
element and a moisture-permeable top-layer material which bears
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against its top surface, and then a moisture-impermeable bottom-
layer material is placed against the bottom surface of the
moisture-absorption element, a layer of bonding material being
provided over at least part of the surface of the moisture-
s impermeable bottom-layer material, on its side facing towards
the moisture-absorption element, after which this moisture-
impermeable bottom-layer material is joined to the moisture-
absorption element, which forms part of the assembly, by
supplying heat and/or exerting pressure.
The assembly of a moisture-absorption element and a top-
layer material, to which the moisture-impermeable bottom-layer
material is joined, may, in an expedient embodiment, be formed
in a step which precedes the method described above.
The moisture-absorption element and the top-layer
material can be joined in various ways, for example by:
a) stitching;
b) stepping/quilting;
c) needling;
d) joining by means of high-frequency or ultrasonic welding;
e) joining using a spot coating layer of bonding material which
is present on that side of the top-layer material which faces
towards the moisture-absorption element, by supplying heat
and/or exerting pressure; and
f) joining using a spot coating layer of bonding material on that
side of the moisture-absorption element which faces towards
the top-layer material by supplying heat and/or exerting
pressure.
If options a or f are used for the assembly, a coating
method which differs from the spot coating method will
expediently be selected for bonding together the moisture
impermeable bottom-layer material and the moisture-absorption
element by means of a bonding agent.
In the embodiment described under a and f above, it is
possible, in a first option, for a thermoplastic material to be
present in the interface between top-layer material and
moisture-absorption element. The thermoplastic material may form
part of the said layers; it may also be applied separately.
However, the top-layer material and moisture-absorption
element may also be joined together as a result of the presence
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of a crosslinkable material. With a view to the speed of
production, crosslinking will generally be brought about under
the influence of heat. If a very high speed is not required, it
is possible to use materials which crosslink under ambient
conditions. In the latter case, pressure will generally be
applied in order to hold the materials in good contact with one
another during crosslinking of the bonding material.
Examples of thermoplastic bonding materials which may be
mentioned are polyvinyl chloride, polyethylene, polypropylene,
polyurethane and the like.
Examples of bonding materials which crosslink,
optionally with heat being supplied, which may be mentioned are
isocyanates and cyanoacrylates which crosslink under the
influence of atmospheric humidity (for example crosslinkable
PU); epoxy resin/hardener combinations; polyester resin/hardener
combinations, etc.
In another attractive embodiment of the method according
to the invention, the assembly of a moisture-absorption element
and a top-layer material is formed at the same time as the
moisture-impermeable bottom-layer material and the moisture-
absorption element are joined together.
The formation of the assembly as referred to above may
be carried out in numerous ways, as indicated; in one attractive
embodiment, this formation takes place either by using a spot
coating layer of bonding material which is present on that side
of the top-layer material which faces towards the moisture-
absorption element or by using a spot coating layer of bonding
material on that side of the moisture-absorption element which
faces towards the top-layer material. The (spot) coating of
bonding material may be thermoplastic or, as stated above,
crosslinkable, optionally under the influence of heat.
If the bonding material between the top-layer material
and the moisture-absorption element and between the moisture-
absorption element and the bottom-layer material is
thermoplastic, when a heat treatment, if appropriate with the
application of pressure, which is used to join the bottom-layer
material to the moisture-absorption element in the latter
embodiment, is carried out, the thermoplastic bonding material
which is present in the interface region between the top-layer
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material and the moisture-absorption element will also be
activated, with the result that the top-layer material and the
moisture-absorption element will be stuck together.
If the bonding material in the boundary layer between
the top-layer material and the moisture-absorption element and
in the boundary layer between the moisture-absorption element
and the bottom-layer material crosslinks under the action of
heat, once again the formation of the assembly is brought about
and the bottom-layer material is bonded to this assembly in a
single heat treatment.
If the bonding material in both boundary layers is
crosslinkable under ambient conditions, it is generally
sufficient to apply pressure for a sufficient time.
The bonding material which is present in the boundary
region between the top-layer material and the moisture
absorption element is generally, if used, present in the form of
a spot coating layer, in order to present the minimum possible
obstacle to the passage of moisture from the patient side of the
pad to the moisture-absorption element.
The thermoplastic bonding material which is present as a
component of the bottom-layer material may either be present in
a spot coating layer or as a completely covering layer.
The bottom-layer material may be a moisture-impermeable
material such as polyvinyl chloride, polyethylene or
polyurethane which is itself thermoplastic or may be a rubber
like non-thermoplastic material which, on the bonding side, is
coated with a bonding layer of thermoplastic material.
On the outer side which is directed away from the
moisture-absorption element, the moisture-impermeable bottom
layer material may, if appropriate, be in the form of a layer
which reduces the sliding properties and/or a decorative layer.
The decorative layer may be obtained by printing or by
lamination of, for example, a textile layer.
To join the moisture-impermeable bottom-layer material
and the moisture-absorption element it is possible, for example,
to select heating and/or the exertion of pressure over the
entire surface of the bottom-layer material; however, it is also
possible to select heating and/or exertion of pressure in a
pattern.
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In the latter method according to the invention, it is
also important to ensure a good border finish of the washable
pad.
In certain cases, there is no need for a special border
finish to take place, and at the border the stacked arrangement
of at least the moisture-impermeable bottom-layer material, the
moisture-absorption element and the moisture-permeable top-layer
material, as well as any other layers, is visible. This
embodiment will be sufficient in particular if the bonding layer
of thermoplastic or crosslinkable material is applied over the
entire surface of the bottom-layer material.
If the bottom-layer material is provided with a layer of
bonding material over part of its surface, for example in the
form of a spot coating layer, it is recommended to provide
finishing material which is expediently formed by bottom-layer
material or a similar material. In a first embodiment of the
method according to the invention, the surface area of the
bottom-layer material is larger than the surface area of the
assembly of the top-layer material and the moisture-absorption
element and projects partially beyond this assembly; by folding
over the projecting parts and bringing them into contact with
the top-layer material, it is possible, by suitable heating
and/or exertion of pressure, to join the bottom-layer material
to the outside of the top-layer material.
In this context, heating is also understood to include
welding, such as HF or ultrasonic welding.
In this method, the bonding layer of thermoplastic or
crosslinkable material is activated in such a way that bonding
has occurred after sticking followed by cooling.
In another embodiment, separate strips of bottom-layer
material are brought into contact with the top side of the top-
layer material and the bottom side of the bottom-layer material
by being folded over, and this bottom-layer material is then
joined to the top-layer material and the bottom-layer material.
In yet another embodiment, the bottom-layer material is
selected to be of larger surface area than the absorption
element and a top-layer material which bears against the latter;
the bottom-layer material is folded upwards along the borders of
the pad and is fixed around the top surface of the top-layer
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material using a separate strip of bottom-layer material. The
strip of bottom-layer material on one side is bonded to the
bottom-layer material which has the bonding layer facing upwards
and on the other side it is joined to the top-layer material.
The invention will now be described with reference to
the drawing, in which:
Fig. 1 shows a diagrammatic cross-sectional view through
a pad according to the invention;
Fig. 2 shows a border finish of the pad from Fig. 1, in
a first embodiment;
Fig. 3 shows a border finish in a second embodiment; and
Fig. 4 shows a border finish in a third embodiment;
Fig. 5 diagrammatically depicts an embodiment in which
the moisture-permeable top-layer material and the moisture
impermeable bottom-layer material are joined to one another via
perforations which are present in the moisture-absorption
element;
Fig. 6 shows an embodiment as in Fig. 5, with an
alternative border finish.
Fig. 1 shows a diagrammatic cross section through a pad,
in which the moisture-absorption element is denoted by 1, the
moisture-permeable top-layer material is denoted by 2 and the
moisture-impermeable bottom-layer material is denoted by 3. The
boundary surface between the moisture-absorption element 1 and
the moisture-permeable top-layer material 2 is formed by 4; in
the case illustrated, bonding has been effected with the aid of
a layer of thermoplastic bonding material which is arranged in
the said boundary surface 4 in the form of a spot coating layer.
The spot coating layer is expediently applied to that side of
the top-layer material 2 which faces towards the moisture-
absorption element 1.
The boundary surface between the moisture-absorption
element 1 and the moisture-impermeable bottom layer 3 is formed
by the boundary surface 5.
In this arrangement, although not shown, a layer of
thermoplastic bonding material is also used to join the
moisture-absorption element 1 and the moisture-impermeable
bottom layer 3.
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The layer of thermoplastic bonding material is applied
to the bottom layer 3 over the entire surface. The thermoplastic
may also be arranged in the form of a pattern.
The above text has made numerous references to a layer
of thermoplastic bonding material which is present as a separate
layer on the moisture-impermeable bottom layer 3.
Obviously, it is also possible for the entire layer 3 to
be made from a thermoplastic material which is the same as the
material of the bonding layer. In the latter case, it is
possible, by suitably selecting the thickness of the layer 3, to
ensure the desired flexibility of the washable pad.
The assembly of moisture-absorption element 1 and
moisture-permeable top-layer material 2 may obviously also be
produced, as described above, by stitching or stepping/quilting.
In the cases discussed here, however, the moisture-impermeable
bottom-layer material 3 is joined to the moisture-absorption
element 1 with the aid of a layer of thermoplastic bonding
material, in which case the layer of bonding material and the
moisture-impermeable bottom-layer material 3 may, if
appropriate, have the same function.
The bonding material used in this embodiment shown in
Figure 1 was crosslinkable polyurethane which was applied by
spraying. Another application techniques involves screen-
printing.
Bonding took place by applying a pressure of 2-10 kg/cmz
and by heating at 135°C.
If an isocyanate coating which cures under the influence
of atmospheric humidity is used, curing took place under ambient
conditions (15-25°C), likewise with the application of pressure
(2-10 kg/cm2) .
An excellent flexible pad material was obtained both
when using a thermoplastic material and when using a curable
bonding material.
In addition to the above-described bottom-layer material
3, moisture-absorption element 1 and top-layer material 2, it is
possible for a plurality of further layers of material to be
present, depending on the precise function of the washable pad.
Additional layers of material may, for example, be
formed by a spacer layer, such as a knitted fabric of synthetic
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fibres, between the top-layer material 2 and the absorption
element 1, in order to prevent the patient/user from suffering
bed sores (decubitus) and to shorten the drying time still
further.
It is also possible for a PU foam layer of the type
described in Hygienic Products with superabsorbent polyurethane
foam; Jeff Patterson, Nonwovens World, April/May 1999 to be
included, for example between the bottom-layer material 3 and
the absorption element 1.
The PU foam layer consists of hydrophilic PU.
The function of a layer of this nature is to absorb
moisture, prevent decubitus and to accelerate drying after
washing. Fig. 2 shows the same cross section as that shown in
Fig. 1, but in this case, to finish the pad, the moisture-
impermeable bottom layer 3 has been folded over so that it bears
against the top side of the top-layer material 2, after which
the bottom-layer material 3 can be bonded to the top-layer
material 2 by means of a heat treatment, so as to form boundary
layers 6 and 7. In this way, an excellent liquid-tight border
finish is obtained.
Fig. 3 shows an alternative form of finish for a
washable pad according to the invention, in which a strip 8 of
bottom-layer material which is provided with a bonding layer of
thermoplastic material is placed against the moisture-permeable
top layer 2 and the moisture-impermeable bottom layer 3 by being
folded over. Bonding between the strip 8 and the top-layer
material 2 and the bottom-layer material 3 is brought about by
heat treatment. The strip of material 8 may consist of the same
material as the bottom-layer material 3; obviously, it is also
possible to select another material with a similar action. This
border finish is likewise extremely liquid-tight.
Fig. 4 shows yet another variant of a liquid-tight
border finish in which the bottom-layer material 3 of the
washable pad projects beyond the surface of the moisture-
absorption element, is folded upwards and is then fixed to a
separate strip 12 of bottom-layer material 3 or similar material
on the top side of the top-layer material 2.
It should be noted that it is not strictly necessary to
fold the bottom-layer material upwards; in view of the
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relatively small thickness of the pad, the projecting part of
the bottom-layer material 3 and the separate strip 12 can also
be bonded together without any folding.
The pad according to the invention is extremely flexible
and pleasant for the patient to use; it can be washed without
boiling at 95°C, while sterilization can be carried out in an
autoclave at 135°C. The bonding material used was in this case a
thermoplastic polyurethane material.
As the bonding layer of thermoplastic material it is
possible to select from numerous thermoplastic materials, such
as polyvinyl chloride, polyethylene, polyamide, polyurethane,
etc.; numerous other materials will be immediately obvious to
the person skilled in the art.
In connection with the embodiments described above as
shown in Figs. 2, 3 and 4, it is pointed out that, due to the
border finish shown in those figures, which is always produced
by fixing bottom-layer material around the borders, it is
possible to obtain an absolutely liquid-tight border finish
which substantially prevents moisture from flowing towards the
region outside the pad.
In US-A-3,965,503, referred to above, by way of example
a border finish using a bias strip or an overcast seam is
described, the attachment being brought about by means of
stitching. Obviously, leakage can still occur at these stitches.
This is prevented altogether with the border finish according to
the invention.
The invention makes it possible to provide a washable
pad which, starting from the separate components or partial
assemblies thereof, makes it possible to produce the pad in a
fully automated and continuous method.
The various components or assemblies thereof can be
supplied in web form and then, by suitable processing and/or
heat treatment, formed into separate, completely finished,
washable pads according to the invention.
Figure 5 diagrammatically depicts a washable pad having
a moisture-absorption body 21, a top layer 22 of moisture-
permeable material and a bottom layer 23 of moisture-impermeable
material.
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Perforations in the moisture-absorption body 21 are
denoted by 28.
In the perforations 28, contact is brought about between
the moisture-permeable top-layer material 22 and the moisture
s impermeable bottom-layer material 23, and bonding has taken
place so as to form bonding points 29.
The number of bonding points is not critical, provided
that good fixing of the layers 21, 22 and 23 with respect to one
another is obtained. In a test, good results were obtained with
a tetragonal arrangement of perforations with a side of 10 cm.
Distances between the points of between 5 and 25 cm are
generally suitable. The size of the perforations is equally
uncritical provided that they do allow the moisture-permeable
top-layer material 22 and moisture-impermeable bottom-layer
material to be joined to one another.
In addition to the perforations 28 which have suitable
dimensions for bonding, it is also possible, as discussed above,
for smaller perforations to be present, the purpose of which is
primarily to assist with drying.
As can be seen in the figure, the moisture-impermeable
bottom-layer material 23 is turned over at the borders and is
bonded to the top side of the moisture-permeable top-layer
material 22 using a bonding surface 26.
As stated above, the bonding points 29 may be formed in
numerous ways; thermal, high-frequency or ultrasonic spot
welding are attractive options in those cases in which both the
moisture-permeable top-layer material 22 and the moisture
impermeable bottom-layer material 23 consist at least to a
significant extent of thermoplastic fibres or materials.
It is also possible for the border finish to be brought
about under the same condition using one of the said welding
techniques; with surface contact being used instead of a spot
action. If the moisture-absorption element also consists to a
large extent of thermoplastic material, it is also possible for
the border of the entire pad to be compressed over its thickness
so as to fuse together, with the result that a very good
moistureproof border is obtained.
Figure 6 shows a situation in which the moisture-
absorption element 21 is smaller than the moisture-permeable
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top-layer material 22 and moisture-impermeable bottom-layer
material 23 and bonds 29 are also formed in the border regions.
The bonds may be made between the two materials directly;
bonding can be promoted by the presence of thermoplastic (PE,
PP, PU) on the top and/or bottom surface of the moisture-
permeable top-layer material 22 at the location of the borders
and/or the perforations 28. Due to the moisture-permeable nature
of the top-layer material 22, good bonding promotion will also
be found when thermoplastic is applied to the top surface of the
top-layer material; in the situation represented
diagrammatically in Figure 6, thermoplastic was applied to the
top surface.
It is preferable for thermoplastic to be applied only to
the borders; in addition to promoting adhesion, the application
of thermoplastic also causes the top layer to become impermeable
to liquid, with the result that excellent closure is obtained at
the borders.
The above text has always referred to a washable pad for
use as such. In an adapted size and/or shape, the washable pad
can also function as a sanitary towel, incontinence products, a
bib for babies or adults, a medical bandage, an operation pad,
etc. This technique can also be employed for the manufacture of
washable diapers and washable incontinence pants for adults, and
washable cleaning cloths.
