Absorbent composite

An absorbent composite, in particular for diapers, sanitary pads or napkins, mattress pads, incontinence briefs and liners or the like, has a support layer onto which a layer of a superabsorbent granular material is applied. A portion of the absorbent material is intimately connected to, particularly glued to, the support layer.

BACKGROUND OF THE INVENTION 
The present invention relates to an absorbent composite especially for 
diapers, mattress pads, sanitary napkins, incontinence briefs and liners, 
comprising a support layer onto which is applied a layer of absorbent 
material. 
Numerous attempts have been undertaken to produce an absorbent composite, 
which, on the one hand, is impermeable with respect to the outside, on the 
other hand, however, gives the impression of being dry on the inside even 
after being wetted. In order to solve this problem, absorbent bodies, for 
example, made of polyacrylate, have been used which when wetted with 
water, urine or other aqueous solutions, for example, with blood, will 
swell forming a gel and thus exhibit a high degree of absorbent capacity. 
For this purpose a superabsorbent granular material is used and in this 
respect reference is, for example, to DE-A1-42 07 465. Granular materials 
are preferred to compact swelling bodies since the swelling capacity, 
especially with small grain size, is better due to the increased surface 
area. In order to improve the swelling capacity and thus the absorbent 
capacity, it is known to use grain sizes as small as possible adjacent to 
a layer impermeable to moisture and larger grain sizes preferably on the 
side facing the body. 
Superabsorbent materials are those materials which, upon contact with 
liquids, imbibe such liquids and thereby form hydrogels. In this manner, 
liquids discharged into the absorbent composites of the present invention 
can be absorbed and held by the particles, thereby providing absorbent 
composites with enhanced absorbent capacity and/or improved liquid 
retention performance. 
The superabsorbent material particles which are employed will generally 
comprise a substantially water-insoluble, slightly cross-linked, partially 
neutralized, hydrogel-forming polymer material. Such absorbent materials 
can be prepared from polymerizable, unsaturated, acid-containing monomers. 
Thus, such monomers include the olefinically unsaturated acids and 
anhydrides which contain at least one carbon-to-carbon olefinic double 
bond. More specifically, these monomers can be selected from olefinically 
unsaturated carboxylic acids and acid anhydrides, olefinically unsaturated 
sulfonic acids and mixtures thereof. Another example of such 
superabsorbent materials are polyacrylates of small grain sizes which are 
also capable to form hydrogels. 
However, especially granular material of a small grain size tends to shift 
in an undesired manner. If diapers, sanitary napkins or pads or liners and 
so on were stored in a compactly compressed shape, this danger would be 
relatively little. However, especially in the case of diapers a certain 
"fluffiness", i.e. a smooth character of the liner or pad is desired, so 
that storage in an only slightly compressed form is often preferred. 
During transport, but also in use, the granules can thus shift. 
In order to prevent this, it is known to provide the granules within a 
compact absorbent body. In this context reference is made, for example, to 
DE- A1-37 38 601, which shows such an absorbent body covered by a layer of 
cellulose flocks of a thickness of 0.5 to 10 mm and these cellulose flocks 
are covered by a layer of nonwoven material. 
However, an unequal distribution of the granular bodies cannot be prevented 
by means of this solution. 
The production process provides, granular bodies in the form of relatively 
sharp-edged grains. In view of the largest possible surface a rather 
hackly grain structure is even desired. The retaining layer in diapers, 
pads, etc., by means of which leakage of liquids to the outside is to be 
prevented, thus must be relatively thick when composites are made of 
granular material in order to prevent damage to the retaining layer by the 
granules. However, a relatively thick retaining layer or outer shell is 
unfavorable, not only with respect to the weight in transport and use but 
also with respect to disposal. 
This effect is especially relevant with respect to sanitary mattress pads 
and composites for incontinence diapers and liners since the granules 
before being wetted can behave just like abrasive granules when the 
patient's movement and weight acts upon the sanitary mattress, pads, etc. 
It is therefore an object of this invention to provide an absorbent 
composite with a comparably thin outer shell, that nevertheless provides 
an excellent absorbent capacity for liquids while providing a composite 
that is unaffected even by changing compressive stresses. 
SUMMARY OF THE INVENTION 
An absorbent composite for absorbing liquids according to the present 
invention is primarily characterized by: 
a main support layer; 
a layer of absorbent material positioned on the main support layer; 
the absorbent material comprised of a superabsorbent granular component; 
at least a first portion of the superabsorbent granular component being 
intimately bonded to the main support layer. 
Preferably, the absorbent composite further comprises an adhesive for 
gluing at least the first portion of the superabsorbent granular component 
to the main support layer. 
The adhesive is preferably a spray adhesive. 
Advantageously, first the adhesive is applied to the main support layer and 
the superabsorbent granular component is subsequently placed onto the 
adhesive on the main support layer. 
Alternatively, the adhesive is applied to a layer of the superabsorbent 
granular component and the main support layer is placed onto the adhesive 
applied to on the layer of the superabsorbent granular component. 
The superabsorbent granular component is preferably comprised of acrylate 
granules or of a biodegradable material. 
Expediently, the adhesive has a reduced moisture contents. 
The adhesive forms an adhesive layer and at least the first portion of the 
superabsorbent granular component is bonded to the adhesive layer. The 
adhesive layer preferably extends over the entire surface area of the main 
support layer. 
The main support layer is expediently comprised of a material selected from 
the group consisting of tissue and non-woven material. 
The superabsorbent composite may further comprise an intermediate support 
layer, wherein the first portion of the superabsorbent granular component 
is bonded to the main support layer and a second portion of the 
superabsorbent granular component is bonded to the intermediate support 
layer. 
The first portion of the superabsorbent granular component is arranged in a 
layer such that the granules of the granular component form a single layer 
within a common plane. 
The first portion of the superabsorbent granular component preferably has 
smaller granules than the second portion of the superabsorbent granular 
component. 
The second portion of the superabsorbent component is glued to the 
intermediate support layer with an adhesive. 
The superabsorbent composite further comprises a cover layer positioned 
opposite the main support layer for covering the superabsorbent component. 
The cover layer is preferably comprised of non-woven material comprised of 
at least 20% of viscose and at most 80% of polypropylene. Alternatively, 
the non-woven material may be tissue or can be comprised of 100% viscose, 
that is preferably hydrophilic. 
The composite may comprise a cover strip positioned on top of the cover 
layer. The cover strip is comprised of non-woven material having a 
hydrophobic inner side facing the cover layer. The non-woven material is 
preferably comprised of at least 80% of polypropylene and at most 20% 
viscose. The non-woven material may be comprised of 100% viscose that is 
preferably hydrophilic. 
The absorbent composite further comprises a substantially 
moisture-impermeable outer shell positioned exterior to the main support 
layer. The outer shell is expediently made of a material selected from the 
group consisting of polypropylene and amylose. 
The main support layer is substantially moisture-impermeable and made of a 
material selected from the group consisting of polypropylene and amylose. 
In this embodiment, there is no need for an outer shell. 
Due to the fact that the support layer is intensively connected to the 
small-size granular component or materials, the risk of damaging the outer 
surface may surprisingly be reduced drastically even if a very thin 
retaining layer or outer shell is used. The lowermost granules or grains 
of the granular component are each fixed on the support layer by gluing 
with a moisture-reduced spray adhesive so that these grains cannot damage 
the outer shell. With a correspondingly high density of these lower most 
granules it is additionally prevented that the adjacent layer of granules 
can come into contact with the outer surface at all. Surprisingly, 
penetration of the outer shell is thus impossible, in spite of a 
relatively small amount of spray adhesive, even in the case of intensive 
back and forth movement of the patient. 
The adhesive can be applied to the support layer and the granules can then 
be placed thereon. It is also possible to apply the adhesive to a layer of 
granules and then place the support layer thereon. Another alternative is 
to soak the support layer with the adhesive and apply the granules on one 
side and the outer shell on the other side. 
According to an alternative embodiment intensive connection is not provided 
by gluing but by melting the granulated bodies at the side facing the 
outer shell. They are thus intimately connected by fusing. It is to be 
understood that this embodiment is only possible if the melting point of 
the granular bodies is at least somewhat lower than the melting point of 
the outer shell or at least of the support layer. 
According to the invention the lowermost support layer may either consist 
of non-woven fabric or tissue or may even be formed by the outer shell 
itself. When being separate from the outer shell the support layer is so 
dense that, together with the grains of superabsorbent material connected 
to it, it forms a support structure for the further layers of the 
composite. 
It is to be understood that, if necessary, further layers of the composite 
may be embodied in a corresponding manner. Instead of a spray adhesive a 
hot-melt glue can also be used which is compatible with the superabsorbent 
material, which, however, should not wet the superabsorbent material too 
much in order not to affect the absorbent capacity thereof. 
It is further to be understood that, instead of the preferred polyacrylates 
with hydroxyl groups, other superabsorbent materials may be used in the 
same manner. 
It is especially advantageous that according to the invention sharp-edged 
and rough granular bodies may also be used. The individual granular body 
is smoothly covered by the spray adhesive the side facing outwardly and 
away from the penetrating moisture. Thus, the risk of scratching is 
strongly reduced with respect to the outer shell. For example, the support 
layer that has already been provided with the grains of superabsorbent 
material can have applied thereto a moisture-reduced spray adhesive from 
the outside, and immediately subsequently the outer shell may be applied 
so that the desired intimate connection will result. This process may 
possibly be improved by applying pressure for a short period. According to 
another embodiment of the invention, the outer shell is provided with 
spray adhesive and then the support layer and the superabsorbent grains 
are placed on the outer shell. Thus, the outer shell and the support layer 
can be glued together in this manner. 
The adhesives to be used should have a reduced moisture contents in order 
to prevent swelling and absorption of moisture by the granules. The 
adhesives can be physically or chemically bonding adhesives. The solvents 
used should not impair the swelling of the granules. Conventional 
adhesives such as animal-product based adhesive (casein, glutin), 
plant-based adhesives (starch, dextrin, cellulose ether) or synthetic 
adhesives (polyacrylic acid-based, polyvinylalcohol-based, 
polyvinylpyrrolidone-based) can be used with water as a solvent. When 
using water, the water content of the adhesive should be reduced by 
20-80%, especially 40-70% and preferably 60%, relative to the contents of 
the commercial product. A reduction of the moisture contents to 0 can, of 
course, be achieved with non-water based adhesives, especially with 
hot-melt adhesives. 
It is possible to use a separate support layer, which is comprised of a 
non-woven material, or to use the outer shell as a support layer. In the 
latter case it is to be understood that due to the intimate application of 
the granulated material, for example, acrylate, a protective layer is 
formed for the outer shell. 
According to the invention, it is especially advantageous that due to the 
concentration of superabsorbent material adjacent to the cover layer, an 
especially good absorbent capacity and a dry surface of the diaper or the 
incontinence brief may be obtained. For this purpose a two-layer structure 
of the inventive composite, with a smaller grain size adjacent to the 
outer shell and a larger grain size adjacent to the cover layer, is 
especially preferred. This embodiment makes possible an absorbent capacity 
with which only a very small amount of residual moisture can be felt by 
the patient at the inner surface of the absorbent composite. 
According to a further preferred embodiment of the invention, the composite 
may be covered by a cover strip of non-woven fabric (fibrous web material) 
with a hydrophobic inner side. By means of this covering strip it is 
ensured that the liquid will quickly penetrate the composite. After 
penetration the liquid is effectively prevented from leaking outwardly due 
to the water-repellent effect of the hydrophobic inner side.

DESCRIPTION OF PREFERRED EMBODIMENTS 
FIG. 1 shows an incontinence liner with its outer shell (the side to be 
placed remote from the patient's skin) facing downward. The outer shell is 
a plastic sheet that may be breathable and/or textured in order to impart 
a fabric-like character to the outer surface. However, the outer shell 
should be impermeable to moisture. The outer shell, for example, consists 
of polypropylene. 
Further, as may be taken from FIG. 2, the absorbent composite 14 comprises 
a lower main support layer 16 to which a layer 18 of granular acrylate is 
applied. In order to make the granular material of the layer 18 adhere 
reliably and non-slidingly to the support layer 16, it is fixed to the 
support layer 16 by means of a spray adhesive with a very low moisture 
contents. The fact that the spray adhesive has a low moisture contents 
will ensure that the granulated material will not swell and absorb 
moisture already when the adhesive is sprayed onto the material. In order 
to impart a very low moisture contents to the spray adhesive, it is 
sprayed onto the support layer 16 via compressed air after being molten as 
usual. Prior to this the compressed air is past through a drying agent 
such as silica gel in order to be dried so that only a very small amount 
of residual moisture of less than 0.5% will remain. 
In connection with dried compressed air a hot-melt spray adhesive may also 
be used. It is to be understood that such an adhesive must both be 
compatible with the support layer and with the acrylate. 
As a support layer 16, a non-woven fabric, weighing, for example, 24 
g/m.sup.2, or a fine and superabsorbent, wet strength paper material known 
as "tissue" may be used. 
It is to be understood that, instead of substances reacting with urine, 
other materials may also be used for the support layer, for example, a 
material comprised of polypropylene and viscose or comprised completely of 
polypropylene. Thus, the unpleasant odor of the absorbent composite after 
being wetted with urine will be further reduced. 
In the embodiment shown, the layer of the granular component comprises a 
top layer and a bottom layer 18, 18'. A further intermediate support layer 
16' is provided which is somewhat lighter than the main support layer 16 
and is arranged on the bottom layer 18 of granulated grains. For example, 
a non-woven fabric material weighing 18 g/m.sup.2 may be employed for the 
intermediate support layer. A further top layer 18' of granulated 
acrylate, which has a somewhat larger grain size and thus a relatively 
smaller surface, is fixed on this support layer 16' with a spray adhesive. 
It is to be understood that the spray adhesive is applied such that it 
will not affect the penetration of moisture into the main support layer 
16'. 
The second layer 18' of superabsorbent granular material is covered by a 
cover layer 20, for example, of tissue or non-woven fabric weighing 24 
g/m.sup.2. 
Together with a covering strip 26, which may be placed on the cover layer 
20, both support layers 16 and 16', the granulate layers 18 and 18' as 
well as the outer shell 12 form a superabsorbent composite 14. As a 
semifinished product this composite may be employed for numerous purposes, 
for example, for producing diapers, sanitary napkins, incontinence briefs 
and liners or sanitary mattress pads. 
As an example, FIG. 1 illustrates such an incontinence liner. As may be 
taken from FIG. 2, the longitudinal edges 22 of the outer shell 12 may be 
folded upwardly and inwardly. A cover strip 26 is glued onto the folded 
edges by means of glue 24 or by hot stamping. The inner side 28 of the 
cover strip 26 exhibits hydrophobic characteristics. A non-woven material 
of about 15 g/m.sup.2 is suitable for such a cover strip. 
The nonwoven material used for the support layers 16, 16', the cover layer 
20, and the cover strip 26 preferably consists of a compound of about 80% 
polypropylene and 20% viscose, however, it may also consist of 100% of 
polypropylene. 
Two further embodiments of a composite according to the invention may be 
taken from FIGS. 3a and 3b. FIG. 3a, represents one embodiment, showing 
the way in which spray adhesive 30 embeds the lowermost layer 18 of the 
granulated bodies and at the same time protects the support layer 16. 
Beneath the support layer 16 the outer shell 12 is provided. Thus, 
granules located above the glued-on layer of granular bodies will not come 
into contact with the support layer 16 and also not with the outer shell 
12. Above the layer 18, a further support layer 16' and a further layer of 
granulated material are provided. 
The embodiment illustrated in FIG. 3b shows the outer shell 12 functioning 
as a support layer 16. The spray adhesive 30 ensures in this case that the 
lowermost layer of granulated bodies 18 is reliably embedded. Apart from 
this difference, the embodiment of FIG. 3b corresponds to the one of FIG. 
3a. 
It may be taken from FIG. 4 that grains of acrylate having edges that are 
quite sharp may also be used, without having to worry about damaging the 
outer shell 12 or the support layer 16. The spray adhesive 30 will adapt 
to the contour of the granular bodies 18 and embed them so that there will 
be a smooth connection. 
In the alternative shown in FIG. 5, the granules of acrylate 18 are 
virtually molten onto the support layer 16. It is to be understood that 
this support layer may again be formed by the outer shell if desired. In 
this embodiment, too, the granules are affixed and will thus form a 
barrier against the penetration of further granules of acrylate into the 
outer shell. 
It is also possible to use a biodegradable superabsorbent material instead 
of a superabsorbent material of polyacrylate. For this purpose chemically 
modified natural substances such as higher sugars or starch products may 
be employed. In the case of such biodegradable superabsorbent materials, 
the grain size and thus the relative surface may also be adjusted over a 
wide range and may accordingly be adapted to the desired specifications. 
The present invention is, of course, in no way restricted to the specific 
disclosure of the specification and drawings, but also encompasses any 
modifications within the scope of the appended claims.