WO1996013382A1

WO1996013382A1 - Absorbent materials and uses thereof

Info

Publication number: WO1996013382A1
Application number: PCT/GB1995/002537
Authority: WO
Inventors: Dermot Christopher John Barrow
Original assignee: Dermot Christopher John Barrow
Priority date: 1994-10-27
Filing date: 1995-10-27
Publication date: 1996-05-09
Also published as: AU3706895A

Abstract

The invention provides a lightweight, flexible, laminar fabric comprising a supporting membrane (1) and, bonded to the supporting membrane (1), an absorbent air-laid paper layer (5) capable of absorbing at least five times its own weight of aqueous fluid. The invention also provides a covering sheet or containing structure for covering or containing all or part of a body, the covering sheet or containing structure being formed from the laminar fabric.

Description

ABSORBENT MATERIALS AND USES THEREOF

The invention relates to a lightweight, flexible laminar fabric having the ability to absorb aqueous fluids, and to covering and containing structures formed from the fabric.

Blankets formed from woven materials such as wool, or synthetic equivalents, are used in numerous situations to provide warmth and shelter. A problem with conventional blankets is that due to their weight and thickness, and the materials from which they are made, they are notoriously expensive to clean and this is a particular problem in circumstances where they are liable to become heavily soiled. For example, paramedic teams and ambulances routinely carry blankets for keeping patients warm on route to hospital. Frequently, the para-medic or ambulance crew will be called upon to take accident victims to a hospital, and in such circumstances, blankets will often become soiled with blood and other bodily fluids thereby necessitating a thorough cleaning afterwards. As a result of the somewhat harsh conditions needed to provide effective cleaning of the blanket to remove heavy soils, the lifetime of the blanket is rather short and typically is measured in terms of months rather than years. A further problem with such blankets is that the weight of the blanket itself pressing against a wound can exacerbate the discomfort or pain experienced by the patient.

There are other circumstances in which conventional woven blankets are far from ideal. For example, in relief operations following disasters, whether man-made such as wars, or natural disasters such as floods, famines, earthquakes, hurricanes etc, where people are displaced from their homes without adequate protection against the elements, it is usual for relief agencies to issue blankets as a means of providing warmth and shelter for the victims of the disaster. A problem here is that in addition to the initial cost of the blanket, the bulk of the blanket inevitably places a restriction upon the number of blankets that can be transported in a given operation. Moreover, under the circumstances existing on the ground, the blankets quickly become soiled and thereafter are not easily reusable by the relief agencies.

In the circumstances described above, and indeed in many other circumstances, it would be advantageous to be able to provide a blanket or covering structure for the body which was light in weight, had good thermally insulating properties, absorbed bodily fluids emanating from the body, was relatively cheap to produce, and could readily be disposed of after use.

GB-A-1 353 028 discloses a laminar fabric comprising a layer of fibrous tissue material embossed with a cellular pattern and laminated to a flexible moisture-proof material. However, so far as the present applicant is aware, the material disclosed in GB-A-1353028 has not found acceptance, at least insofar as the circumstances described above are concerned.

It is an object of the present invention to provide a covering material which meets the aforementioned objects.

Accordingly, the invention provides a lightweight, flexible laminar fabric comprising a supporting membrane and, bonded to the supporting membrane, an absorbent air- laid paper layer capable of absorbing at least five times its own weight of aqueous fluid.

The absorbent material is preferably an air-laid wet- strength substantially non-linting paper. The air-laid paper is formed by an air-laying technique in which individual fibres are generally oriented in one direction by means of a current of air. The air-laid paper is thus distinguished from conventional wet-laid paper in which the wood pulp fibres tend to be randomly oriented. The air- laid paper is typically formed from fluff pulp and a latex binder. The latex binder should generally be dermatologically compatible ie it should be inter alia non- allergenic and non-irritating to the skin. The latex binder preferably is not a natural rubber-based binder. A particularly preferred binder is ethylene-vinyl acetate (EVA).

The air-laid paper preferably has a wet-strength of at least 0.1 kN/m. Preferably it is capable of absorbing up to 40 times its own weight of aqueous fluid, for example 15-35 times, eg approximately 30 times its own weight.

The use of an air-laid paper as defined above represents an important feature of the present invention and distinguishes the laminar fabrics of the invention from the fabrics disclosed in GB-A-1353 028.

The absorbent layer may be a unitary layer or may have a multilaminar structure, for example, the absorbent layer can comprise an air-laid paper layer as hereinbefore defined along with a layer of superabsorbent polymer bonded thereto.

Examples of superabsorbent polymers include superabsorbent acrylic polymers ("superacrylics") of the type available from Allied Colloids, Bradford, Yorkshire, UK under the name "Salsorb 90". The absorbent layer is configured so as to provide a one-way capillary action drawing fluids from the surface thereof into the layer so that the surface appears relatively dry.

The supporting membrane can be a polymeric membrane or it could, for example, be formed from a paper.

In one embodiment of the invention, the polymeric membrane is a waterproof membrane.

In another embodiment of the invention the polymeric membrane is gas-permeable, e.g. the membrane may be microporous or micro-perforated. Such a membrane is advantageous in that it can allow the patient's or user's skin to breathe. The membrane porosity can be such as to allow water vapour to pass through the membrane whilst preventing the passage of water in liquid form.

It will be appreciated from the foregoing that the supporting membrane, e.g. the polymeric membrane, can be both waterproof and gas-permeable.

The polymeric membrane can be made from polymers such as polyvinyl chloride (PVC), polyvinyl dichloride (PVDC), ethylene vinyl alcohol co-polymer (EVOH), ethylene vinyl acetate (EVA), polyalkylenes such as polyethylenes and polypropylene, polyamides such as nylon, and polyesters such as polyethylene terephthalate, by way of example. The polymeric membrane preferably is formed from polyester, polyamide or polypropylene and most preferably is formed from polyester.

The supporting membrane may consist of a single layer, or it may be a laminate formed from a plurality of layers. The laminate may be formed from a plurality of paper layers, or a plurality of polymeric layers, or a mixture of paper and polymeric layers. Where a plurality of polymeric layers is present, the individual layers may be formed of the same or different polymer. For example, the membrane may consist of a laminate of polyester and polyethylene.

The supporting membrane preferably has a thickness in the range 6μm to lOOum for example lOum to 15um and preferably approximately 12um.

The supporting membrane may advantageously have a heat-reflective metallic layer on one side thereof in order to improve the heat retention properties of the fabric.

Accordingly, in one embodiment of the invention there is provided a lightweight flexible laminar fabric comprising a supporting membrane having a heat-reflective metallic layer on one side thereof and, bonded to the metallic layer, an absorbent air-laid paper layer capable of absorbing at least five times its own weight of aqueous fluid. The heat-reflective metallic layer may be a discrete layer of metal foil, such as aluminium foil, bonded to the supporting membrane, e.g. by means of an adhesive system. Alternatively, the metallic layer may be a coating applied by a vapour deposition technique onto the surface of the supporting membrane.

Where the supporting membrane is provided with a metallic layer, the surface of the absorbent material to which the metallic layer is adhered is preferably lightly calendered to give a smooth surface to which the adhesive can bond, but the opposite surface of the sheet is most preferably left uncalendered.

The polymeric supporting membrane is typically adhesively bonded to the absorbent layer, and the adhesive used to effect the adhesive bonding may be selected from one of a number of types, both in terms of the method of application and the type of adhesive employed.

Extrusion laminating may be employed whereby a molten plastics material such as polyethylene is the adhesive. Similarly, heat-activated hot melt adhesives may also be used. Aqueous and solvent-based adhesives can be used in the laminar fabrics of the invention. As an alternative to "wet-adhesive" types, dry-bonding adhesive types can be used. Dry bonding types can be single component or two part curing systems, for example polyurethane or epoxy adhesives.

A preferred adhesive is a polyurethane adhesive available from DRG Rexham, Bristol, UK under the code number SLA 075.

The flexible laminar fabric of the invention can comprise a reinforcing material to increase the resistance of the fabric to tearing. The reinforcing material may be present as a discrete layer which may be interposed, for example, between the absorbent layer and the polymeric membrane. The reinforcing material can be a layer of non- woven fibrous mesh, for example a lattice of criss-crossing polymeric fibres. The reinforcing layer can be bonded to the other layers by means of adhesives, for example hot melt adhesives. For example, the reinforcing layer can be co-extruded with the polymeric membrane, a layer of polyethylene therebetween serving as a hot-melt adhesive.

The laminar fabric of the invention is a lightweight material and typically has a weight of 20 to 100 grammes per square metre, preferably 40 to 60 grammes per square metre, and most preferably approximately 48 grammes per square metre.

The laminar fabric of the invention is advantageously formed into a covering sheet or containing structure for covering or containing all or part of a body.

For example, the laminar fabric of the invention can be formed into sheets, blankets, sleeping bags, temporary wound dressings, and liner materials for clothing, to name but a few uses. Furthermore, the fabric can be made up into items of clothing, such as protective clothing. For example, the fabric can be made up into overalls, full body suits, boots, gloves, headwear etc. The fabric can also be made up into body bags for conveying corpses.

In each of the aforementioned embodiments, the fabric offers the advantage that it can absorb bodily fluids such as blood and sweat, thereby minimising any discomfort to the user or, in the case of blankets used in accident or casualty situations, or wound dressings or body bags, minimising the potential for undesirable and messy leakage.

In one particular embodiment of the invention, there is provided a covering sheet or blanket for covering a body, the sheet or blanket being formed from a laminar fabric as hereinbefore defined.

The sheet may be provided in the form of a roll, and in a further embodiment, the invention provides a dispenser having mounted thereon or therein a roll of the lightweight flexible laminar fabric of the invention. The blankets formed from the fabric of the invention are of particular use in accident situations where, for example, they can be used to cover a victim during transport to a hospital. The thermal insulating ability of the absorbent layer, and the heat-reflective property of the metal layer ensure that the victim remains warm. Moreover, thanks to the highly absorbent nature of the absorbent layer, blood, perspiration and other bodily fluids are rapidly taken up thereby eliminating or substantially reducing a possible further source of discomfort for the victim.

When intended for use in accident situations, the absorbent layer may be coloured red so as to mask the colour of blood, and thereby reducing the psychological trauma induced by bleeding.

An advantage of the blankets formed from the fabric of the invention is that they may be made more economically than conventional woven blankets and are readily disposable, by burning , thereby avoiding the need for cleaning.

As a result of the lightness of the blankets, and their non-bulky nature, they are more easily transported and can be transported in greater numbers for the same load volume, a feature giving rise to clear advantages in emergency relief operations. The fabric of the invention can be formed into sleeping bags intended for a single night's use after which the sleeping bag is thrown away. Such sleeping bags are envisaged as being particularly useful in an outdoor pursuits or military context where a user could carry four or five disposable sleeping bags in place of a conventional sleeping bag.

A further use of the fabric of the present invention is as a temporary wound dressing, the absorbent nature of the absorbent layer allowing it to soak up blood until such time as a more permanent dressing can be applied to a wound. For example, with head wounds, where bleeding is often profuse, a shaped cap or head bandage formed from the fabric of the invention would contain the flow of blood and would reduce the visual impact of the bleeding to the victim. In the context of temporary wound cover applications, it is important that the surface of the absorbent layer does not break up or form lint which can become entrapped in the wound thereby causing complications when the wound dressing is removed, and for this purpose, non-linting synthetic non-woven fabrics are preferred.

A still further use is for the preparation of disposable protective clothing, for example in situations where the wearer requires protection from surrounding environmental hazards. In such cases, the absorbent air- laid paper layer minimises the discomfort caused by perspiration. Also, the protective properties of the fabric can be used in preparing insulating clothing for the victims of exposure e.g. to extreme weather conditions.

The invention will now be illustrated, by way of example, by reference to the accompanying drawings in which:

Figure 1 is a schematic cross sectional view through a piece of fabric according to one embodiment of the invention;

Figure 2 is a schematic cross-sectional view through a piece of fabric according to a second embodiment of the invention; and

Figure 3 is a schematic cross-sectional view through a piece of fabric according to a third embodiment of the invention.

As shown in Figure 1, the fabric comprises a layer 1 of polyester of approximately 12um thickness which has a coating 3 of aluminium on one side 2 thereof. The metallic layer, which is approximately 400 Angstroms thick has been applied by means of vapour deposition. A suitable grade of metallised polyester is available from Camvac Europe Ltd of Thetford, UK.

Secured to the metallic layer 3 by means of a layer of adhesive 4 is a layer 5 of absorbent material. The adhesive 4 is of a type which remains flexible over a prolonged period and does not become brittle or crack after curing. A preferred adhesive is a polyurethane adhesive available from DRG Rexham, Bristol, UK under the code number SLA 075.

The absorbent layer 5 in this embodiment, which is approximately 1mm thick, is an air laid, latex bonded wet strength paper comprising fluff pulp and latex binder.

The absorbent layer has the capacity to absorb up to 15 times its own weight of aqueous fluid.

The fabric illustrated in Figure 1 is a lightweight material and typically has a weight of approximately 75 grammes per square metre.

The absorbent potential of the blanket may be significantly increased, where required, by the incorporation of a super-absorbent polymer. Examples of such super-absorbent polymers include superabsorbent acrylic polymers ("superacrylics") of the type available from Allied Colloids, Bradford, Yorkshire, UK under the name "Salsorb 90".

The super-absorbent polymer can form part of the absorbent layer 5 or may be a discrete layer between the metallic layer 3 and the absorbent material 5. A second embodiment of the invention is shown in Figure 2. The fabric of this embodiment is formed of similar materials, and has a similar structure, to the embodiment shown in Figure 1 except that the heat- reflective metallic layer 3 has been omitted. Fabrics of this type are, for example, suitable for use in hospital situations where the presence of a metallic layer could create problems. Thus, a metallic layer would be undesirable in situations where, for example, high voltage heart-starter or defibrillator apparatus was to be used, or where X-ray examination was to be undertaken.

Figure 3 illustrates a fabric similar to that illustrated in Figure 1 except that a reinforcing layer 6 of "scrim" or non-woven material formed from a lattice of criss-crossed polymeric fibres has been interposed between the absorbent air-laid paper layer and the other layers. The reinforcing layer 6 is bonded to the absorbent layer 5 by means of a layer 7 of polyethylene hot melt adhesive within which the reinforcing material is embedded. The reinforcing layer 6 greatly increases the resistance of the fabric to tearing and is particularly beneficial when the fabric is made up into clothing or other items such as sleeping bags where it is likely to be subjected to greater stresses and strains.

It will be appreciated that the reinforcing layer 6 could also be included in the embodiment shown in Figure 2. It will readily be apparent that numerous modifications and alterations may be made to the fabric illustrated in the drawing without departing from the principles underlying the invention and all such modifications and alterations are within the scope of this application.

Claims

1. A lightweight, flexible laminar fabric comprising a supporting membrane and, bonded to the supporting membrane, an absorbent air-laid paper layer capable of absorbing at least five times its own weight of aqueous fluid.

2. A laminar fabric according to claim 1 wherein the supporting membrane is a polymeric membrane or is formed from a paper.

3. A laminar fabric according to claim 2 wherein the supporting membrane is a waterproof polymeric membrane.

4. A laminar fabric according to any one of the preceding claims wherein the membrane porosity is such as to allow water vapour to pass through the membrane whilst preventing the passage of water in liquid form.

5. A laminar fabric according to any one of claims 2 to 4 wherein the supporting membrane is a gas-permeable polymeric membrane.

6. A laminar fabric according to any of the preceding claims wherein the supporting membrane is both waterproof and gas-permeable.

7. A laminar fabric according to any one of the preceding claims wherein the polymeric membrane is formed from a polymer selected from polyvinyl chloride, polyvinyl dichloride, ethylene vinyl alcohol co-polymer, ethylene vinyl acetate, polyalkylenes, polyamides and polyesters.

8. A laminar fabric according to claim 7 wherein the supporting membrane is formed from polyester, polyamide or polypropylene.

9. A laminar fabric according to any one of the preceding claims wherein the supporting membrane consists of a single layer.

10. A laminar fabric according to any one of claims 1 to 8 wherein the supporting membrane is a laminate formed from a plurality of layers.

11. A laminar fabric according to any one of the preceding claims wherein the supporting membrane has a thickness in the range 6um to lOOum.

12. A laminar fabric according to any one of the preceding claims wherein the supporting membrane has a heat- reflective metallic layer on one side thereof.

13. A laminar fabric according to claim 12 wherein the heat-reflective layer is present on the inner side of the supporting membrane.

14. A laminar fabric according to claim 12 or claim 13 wherein the heat-reflective metallic layer is a discrete layer of metal foil bonded to the supporting membrane.

15. A laminar fabric according to claim 12 or claim 13 wherein the metallic layer is a coating applied by a vapour deposition technique onto the surface of the supporting membrane.

16. A laminar fabric according to any one of the preceding claims wherein the absorbent layer is capable of absorbing up to 40 times its own weight of aqueous fluid.

17. A laminar fabric according to claim 16 wherein the absorbent layer is capable of absorbing 15 to 35 times its own weight of aqueous fluid.

18. A laminar fabric according to any one of the preceding claims which has a weight of 20 to 100 grammes per square metre.

19. A laminar fabric according to any one of the preceding claims further comprising a reinforcing material.

20. A laminar fabric according to Claim 19 wherein the reinforcing material is present as a discrete layer.

21. A laminar fabric according to Claim 20 wherein the layer of reinforcing material is interposed between the absorbent layer and the supporting membrane.

22. A laminar fabric according to Claim 20 or claim 21 wherein the layer of reinforcing material is a layer of non-woven fibrous mesh.

23. A laminar fabric according to Claim 22 wherein the reinforcing material is a lattice of criss-crossing polymeric fibres.

24. A covering sheet or containing structure for covering or containing all or part of a body, the covering sheet or containing structure being formed from the laminar fabric of any one of the preceding claims.

25. A covering sheet or containing structure according to claim 24 in the form of a sheet, blanket, sleeping bag, temporary wound dressing, or a liner material for clothing .

26. A covering sheet or blanket for covering a body, the sheet or blanket being formed from a laminar fabric as defined in any one of claims 1 to 23.

27. A dispenser having mounted thereon a roll of the laminar fabric according to any one of claims 1 to 23.

28. An item of clothing formed from a laminar fabric as defined in any one of claims 1 to 23.

29. A laminar fabric substantially as described herein with reference to the accompanying drawings.