AN ABSORBENT LAMINATE

Abstract: An absorbent laminate (1) has a first outer layer (2) comprising an absorbent material, an intermediate layer (3) one face of which is in contact with and attached to one face of the first outer layer (2), the intermediate layer (3) being effective to prevent or moderate liquid transmission therethrough, characterised by a second outer layer (4) of an absorbent material in contact with and attached to the other face of the intermediate layer (3). Preferably the intermediate layer (3) comprises an adhesive which also serves the purpose of securing the first and second outer layers (2, 4) together. In a preferred embodiment the first outer layer (2) comprises super absorbent crystals e.g. sodium polyacrylate, the intermediate layer (3) comprises a cross-linked polyvinyl acetate adhesive, and the second outer layer (4) is used as the bottom layer and comprises an absorbent material such as blotting paper. A layer of non-woven cellulose tissue paper (5) e.g. toilet tissue is preferably disposed on top of the super absorbent crystals forming part of the first outer layer (2).

Description: TITLE: AN ABSORBENT LAMINATE DESCRIPTION Technical Field The invention relates to an absorbent laminate. More particularly, but not exclusively, the invention relates to an absorbent laminate which may be used for example to line a litter tray arranged under the perforated floor of an animal cage for the absorption of urine and the like. Other possible uses include the absorption of chemicals. Background Art It is known to provide an absorbent laminate as a lining for a litter tray below an animal cage formed with a perforated floor for the absorption of urine and the like and which consists of a layer of a highly absorbent material, e.g. cellulose, which may be of the kind known for use in human incontinence pads, and which may be impregnated with a super-absorbent material to enhance the liquid-carrying capacity of the layer. It is also known to back the absorbent layer with a liquid impervious layer of, for example, a plastics material which has the function both of keeping the liquid material from contacting the surface of the supporting tray and of providing mechanical strength to the laminate whereby it can be removed as a single sheet from the tray after the laminate has become loaded with liquid. It is a disadvantage of the known absorbent laminates that liquid can sometimes find its way round the edge of the laminate and can thus end up between the impervious layer of the laminate and the surface of the tray. This can be undesirable since, in some circumstances such as when it has dried to powder form, animal urine can constitute a significant health hazard. Disclosure of Invention It is an object of the invention to mitigate against the disadvantage of the known absorbent laminate. According to the invention an absorbent laminate has a first outer layer comprising an absorbent material, an intermediate layer one face of which is in contact with and attached to one face of the first absorbent layer, the intermediate layer being effective to prevent or moderate liquid transmission therethrough and a second outer layer comprising an absorbent material and in contact with and attached to the other face of the intermediate layer. Preferably the intermediate layer comprises an adhesive which also serves the purpose of securing the first and second outer layers together. In a preferred embodiment the first outer layer will comprise super absorbent crystals e.g.sodium polyacrylate, the intermediate layer will be a cross-linked polyvinyl acetate adhesive, and the second outer layer will be used as the bottom layer and will be of an absorbent material such as blotting paper. In this arrangement, a layer of non-woven cellulose tissue paper is preferably disposed on top of the super absorbent crystals forming part of the first outer layer and facilitating transmission of liquid thereto. The intermediate layer may be applied directly as a liquid on the second outer layer after which the crystals of super-absorbent are scattered on the wet adhesive so that they are retained by the adhesive layer and so that they project from the adhesive layer. A layer of tissue paper is then applied so that it becomes bonded to the adhesive. Preferably a soft roller is used to apply light pressure to the laminate to ensure intimate contact between the layers. Preferably the adhesive layer is not entirely covered by the crystals, as this would make it more difficult for the adhesive to bond to the layer of tissue especially bearing in mind that the adhesive layer must be thin so that the crystals are not entirely immersed in and coated with adhesive. If the crystals do cover 100% of the surface of the adhesive layer a patterned, e.g. knobbly, roller may be used to transmit localised pressure to some of the crystals forcing the adhesive in these local areas to the surface of the crystals so that the adhesive then bonds to the tissue layer. This manufacturing process has the virtue that no heat is required to produce the laminate, but if desired other adhesives, such as hot melt adhesives, could be used to form the intermediate layer. Brief Description of Drawings The invention is diagrammatically illustrated by way of example in the accompanying drawing, which is a cross- sectional view through a typical laminate made in accordance with the invention, with a detail shown enlarged. Best Mode for Carrying Out the Invention In the drawing there is shown an absorbent laminate 1 particularly intended for use in lining a droppings tray disposed beneath the perforated floor of an animal cage and consisting of a first outer layer 2 of a liquid absorbent material, an intermediate layer 3 forming a liquid barrier, and a second outer layer 4 of liquid absorbent material disposed below the intermediate layer. The first outer layer 2 is super absorbent crystals, e.g. sodium polyacrylate, and the second outer layer 4 is of blotting paper. The intermediate layer 3 is of cross- linking polyvinyl acetate adhesive. A layer of tissue 5 , e.g. toilet tissue, is disposed on top of the super absorbent crystals forming part of the first outer layer. The layer of super absorbent crystals 2 is a single layer and is arranged to cover 100% of the surface of the intermediate layer. The intermediate layer is thin so that the crystals project from the layer or at least so that they are not entirely immersed in and coated by the adhesive. A knobbly roller is then used to apply localised pressure to some of the crystals forcing adhesive to the surface in these local areas, to which adhesive the tissue layer then becomes bonded. As an alternative the tissue paper may be replaced by a more absorbent material e.g. blotting paper or the intermediate layer may be of a material such as polyethylene or water retardant paper. Industrial Applicability The embodiment of the invention particularly described with reference to the drawings thus provides a simple laminate which will provide improved performance compared to the known laminates. In particular the laminate can be sterilised in an autoclave prior to use and can be disposed of after use by burning or composting.

Claims: CLAIMS 1. A liquid absorbent laminate (1) comprising a first outer layer (2) of a liquid absorbent material, an intermediate layer (3) one face of which is in contact with and attached to one face of the first outer layer (2) , the intermediate layer (3) being effective to prevent or moderate liquid transmission therethrough, characterised by a second outer layer (4) of a liquid absorbent material in contact with and attached to the other face of the intermediate layer (3) . 2. A liquid absorbent laminate according to claim 1, characterised in that the first outer layer (2) comprises super absorbent crystals. 3. A liquid absorbent laminate according to claim 1 or claim 2, characterised in that the intermediate layer (3) comprises an adhesive which also serves the purpose of securing the first and second outer layers (2) , (4) together. 4. A liquid absorbent laminate according to any one of claims 1 to 3, characterised in that the second outer layer (4) is of blotting paper. 5. A liquid absorbent laminate according to any one of claims 1 to 4, characterised in that a layer of non-woven cellulose tissue paper (5) is disposed on top of the first outer layer (2) forming part of the first outer layer (2) . 6. A method of making a liquid absorbent laminate (1) as claimed in any preceding claim, characterised in that the intermediate layer (3) is applied directly as a liquid on the second outer layer (4) after which crystals of super- absorbent material are scattered on the wet adhesive so that they are retained by the adhesive layer and so that they project from the adhesive layer. 7. A method according to claim 6, characterised in that a layer of tissue paper (5) is applied over the layer of super absorbent crystals so that it becomes bonded to the adhesive. 8. A method according to claim 7, characterised in that a soft roller is used to apply light pressure to the laminate (1) to ensure intimate contact between the layers.

Inventors: FARMER HARLEY, FARMER, HARLEY
Applicants: ICHOR LIMITED
Application year: 1992
Main classification: A01K1
IPC codes: A01K1, B32B29