WOUND DRESSING

Abstract

Wound dressings displaying improved adhesion and breathability and methods for their manufacture, the wound dressing comprising a backing layer, a layer of pressure-sensitive adhesive and a perforated layer of silicone gel, wherein the layer of pressure-sensitive adhesive is disposed between the substrate and the perforated layer of silicone gel, and wherein the layer of pressure-sensitive adhesive is moisture-permeable.

Claims

1. A wound dressing comprising a backing layer, a layer of pressure-sensitive adhesive and a perforated layer of silicone gel, wherein the layer of pressure-sensitive adhesive is disposed between the backing layer and the perforated layer of silicone gel, and wherein the layer of pressure-sensitive adhesive is moisture-permeable.

2. The wound dressing of claim 1, wherein the pressure-sensitive adhesive is rubber/resin adhesive, acrylic adhesive or acrylate adhesive.

3. The wound dressing of claim 1, wherein the layer of pressure-sensitive adhesive is applied to, and extends across the whole surface of, the backing layer.

4. The wound dressing of claim 1, wherein the layer of pressure-sensitive adhesive is a discontinuous layer of pressure-sensitive adhesive.

5. The wound dressing of claim 4, wherein the layer of pressure-sensitive adhesive comprises apertures that are irregularly shaped and/or sized.

6. The wound dressing of claim 5, wherein the layer of pressure-sensitive adhesive is formed from intermingling fibres of adhesive that form an irregular mat or mesh on the backing layer.

7. The wound dressing of claim 1, wherein the layer of pressure-sensitive adhesive comprises apertures having a mean average area of from 0.1 mm.sup.2 to 5 mm.sup.2, or from 0.1 mm.sup.2 to 4 mm.sup.2, or from 0.1 mm.sup.2 to 3 mm.sup.2.

8. The wound dressing of claim 7, wherein the apertures in the layer of pressure-sensitive adhesive account for at least 1%, at least 3%, at least 5%, at least 10%, at least 20%, or at least 30%, of the area covered by the pressure-sensitive adhesive and up to 80%, or up to 70%, or up to 60%, or up to 50%, or up to 40% of the area covered by the pressure-sensitive adhesive.

9. The wound dressing of claim 1, wherein the backing layer is a film of polyurethane, polyvinylchloride, polypropylene and regenerated cellulose.

10. The wound dressing of claim 1, wherein a layer of perforated silicone gel overlays the layer of pressure-sensitive adhesive and extends across the whole wound contacting surface of the wound dressing, forming the wound contacting layer.

11. The wound dressing of claim 1, wherein coating weight of the silicone gel layer is less than 600 g/m.sup.2, less than 400 g/m.sup.2, less than 300 g/m.sup.2 or about 200 g/m.sup.2.

12. The wound dressing of claim 1, wherein the perforations in the layer of silicone gel have a diameter of between 1 mm and 15 mm, between 3 mm and 10 mm, between 5 mm and 8 mm, or about 6 mm.

13. The wound dressing of claim 1, wherein the silicone gel layer is carried on a substrate layer.

14. The wound dressing of claim 13, wherein the substrate layer is melt-blown polyurethane.

15. A method for the production of a wound dressing, said method comprising: a) providing a backing layer; b) applying a discontinuous layer of pressure-sensitive adhesive to the backing layer by fiberization, to form a moisture-permeable layer of pressure-sensitive adhesive; and c) applying a perforated layer of silicone gel to the layer of pressure-sensitive adhesive.

16. The method of claim 15, wherein fiberization comprises extruding the adhesive into a stream of heated air and depositing the adhesive onto the substrate.

17. The method of claim 15, wherein fiberisation produces a layer of pressure-sensitive adhesive in the form of intermingling fibres of adhesive that form an irregular mat or mesh on the backing layer.

18. The method of claim 15, wherein the layer of pressure-sensitive adhesive comprises apertures having a mean average area of from 0.1 mm.sup.2 to 5 mm.sup.2, or from 0.1 mm.sup.2 to 4 mm.sup.2, or from 0.1 mm.sup.2 to 3 mm.sup.2.

19. The method of claim 15, wherein the apertures in the layer of pressure-sensitive adhesive account for at least 1%, at least 3%, at least 5%, at least 10%, at least 20%, or at least 30%, of the area covered by the pressure-sensitive adhesive and up to 80%, or up to 70%, or up to 60%, or up to 50%, or up to 40% of the area covered by the pressure-sensitive adhesive.

20. The method of claim 15, wherein the backing layer is a film of polyurethane, polyvinylchloride, polypropylene and regenerated cellulose.

21. The method of claim 15, wherein coating weight of the silicone gel layer is less than 600 g/m.sup.2, less than 400 g/m.sup.2, less than 300 g/m.sup.2 or about 200 g/m.sup.2.

22. The method of claim 15, wherein the perforations in the layer of silicone gel have a diameter of between 1 mm and 15 mm, between 3 mm and 10 mm, between 5 mm and 8 mm, or about 6 mm.

23. The method of claim 15, wherein the perforated silicone gel layer is carried on a substrate layer and is adhered to the backing layer via the substrate.

24. The method of claim 23, wherein the substrate layer is melt-blown polyurethane.

Description

[0057] The invention will now be described in greater detail, by way of example only, with reference to the accompanying drawings, in which:

[0058] FIG. 1 is a schematic plan view of the top face of a wound dressing according to the invention;

[0059] FIG. 2 is a cross-sectional view of the wound dressing of FIG. 1, taken along line X-X;

[0060] FIG. 3 is a photograph of the wound contacting side of a wound dressing according to the invention;

[0061] FIGS. 4a and 4b are photographs of a backing layer coated with a layer of pressure-sensitive adhesive;

[0062] FIG. 5 is an explodied view of an island dressing according to the invention.

[0063] FIG. 1 depicts a wound dressing 10 comprising a backing layer 11 formed of polyurethane film which overlays a sheet of an absorbent polyurethane foam pad 13 depicted by dashed lines. A circular hole in the backing layer above the superabsorbent material forms a port 12, which enables the wound dressing to be connected to a suction tube for use in NPWT. The dressing 10 is supplied with the port 12 covered by a releasable cover (not shown). The releasable cover may be left in place and the dressing used as a simple island dressing, or the releasable cover may be removed, exposing the port 12 and enabling the dressing to be used in NPWT.

[0064] The layered structure of the wound dressing 10 is shown in FIG. 2, which shows a cross-section of the wound dressing of FIG. 1 taken along the line X-X. The polyurethane film backing layer 21 forms the top surface of the wound dressing which, in use, faces away from the wound. A moisture permeanle layer of acrylic pressure-sensitive adhesive 22 is applied across the whole surface of the backing layer 21 by fiberization. This produces a discontinuous layer of adhesive having randomly arranged and irregularly shaped apertures across its surface, which permit the passage of moisture vapour through the pressure-sensitive adhesive. A pad of absorbent polyurethane foam material 23 is situated in the centre of the dressing 20 and is retained in place by the layer of pressure-sensitive adhesive 22. The adhesive layer 22 extends beyond the edge of the absorbent pad 23 on all sides, such that the superabsorbent pad 23 forms an island in the centre of the dressing 20. A perforated laminate 24 comprising a layer of perforated silicone gel overlays the absorbent pad 23 and pressure-sensitive adhesive layer 22, and forms the skin contact layer of the dressing 30. The perforated laminate 24 comprises a layer of silicone gel applied to a melt-blown polyurethane substrate.

[0065] Regions of the layer of pressure-sensitive adhesive 23 are thus exposed through the perforations in the laminate 24. When the dressing 20 is applied to a wound, these exposed regions of pressure-sensitive adhesive 23 contact the skin surrounding the wound, increasing adhesion of the wound dressing to the healthy skin. The discontinuous nature of the pressure-sensitive adhesive 23 permits the passage of moisture vapour through the dressing, which reduces the rate at which moisture builds up under the dressing.

[0066] The wound dressing may be supplied with a protective releasable liner (not shown) adhered to the silicone gel. The releasable liner is removed to expose the adhesive wound contacting face of the dressing immediately prior to application of the dressing to the wound site.

[0067] The wound contacting layer can be seen in FIG. 3. The wound dressing 30 shown in FIG. 3 has the same layered structure as the wound dressings of FIGS. 1 and 2. It can be seen that the layer of perforated silicone gel 31 extends across the whole wound contacting surface of the wound dressing, while the pressure sensitive adhesive is exposed through the perforations in the silicone gel 32 in the area surrounding the sheet of superabsorbent material 33.

[0068] A layer of acrylic pressure-sensitive adhesive 40 applied by fiberization to a polyurethane film with a paper carrier is shown in FIGS. 4a and 4b. The use of fiberization results in a discontinuous layer of pressure-sensitive adhesive with numerous irregularly shaped, closely spaced apertures or gaps in the adhesive 41 through which moisture vapour can egress. It has the form of an open, net-like structure.

[0069] An island dressing 50 according to the invention may be seen in FIG. 5. The island dressing 50 comprises a backing layer of polyurethane film 501 coated with a layer of moisture-permeable pressure sensitive adhesive on its wound facing surface. The absorbent portion of the island dressing comprises a composite absorbent body, the composite absorbent body comprising two layers of a superabsorbent polymer 502, each layer of superabsorbent polymer 502 sandwiched between a layer of wicking material 503 on its underside and a layer of welding material 504 on its topside. This layered structure comprises a further layer of wicking material 505 on its non wound facing surface, and is fused to the backing layer 501.

[0070] The wound contacting surface of the wound dressing 50 carries a perforated laminate 506 comprising a layer of perforated silicone gel. The surface area of the composite absorbent body is smaller than the surface area of the backing layer 501 and perforated laminate 506, such that the backing layer 501 and perforated laminate 506 extend beyond the edges of the composite absorbent body on all sides. This ensures good adhesion of the wound dressing to the skin.

[0071] The backing layer 501 further comprises a port for connection to a vacuum for negative pressure wound therapy. The port comprises a circular aperture 507 in the backing layer 501, positioned above the composite absorbent body. The circular aperture 507 has a diameter of approximately 5 mm. The port further comprises an adhesive ring 508 positioned about the aperture 507. In use, a moulded connection pad 509, connected to a vacuum tube 510, is bonded to the adhesive ring 508. The port is positioned such that, in use, the moulded connection pad 509 sits entirely within the area of the composite absorbent body, to protect the patient’s skin.

[0072] The dressing may be manufactured by the following general method.

[0073] First, a sheet of breathable polyurethane film (which constitutes the backing layer 11 of wound dressing 10) is coated with a layer of pressure sensitive adhesive using a fiberization process. An ITW Dynatec UFD Spray Applicator is used to apply a randomised, fibrous pattern of monofilament strands of an acrylic pressure-sensitive adhesive to one surface of the polyurethane film. An ordered pattern may alternatively be produced.

[0074] Second, a perforated laminate comprising a melt-blown polyurethane (MBPU) carrying silicone gel on one side and acrylic adhesive on the other is produced in the manner described in WO2007/113597. In general terms, this involves applying silicone gel precursors to a sheet of MBPU, the underside of which carries a coating of acrylic adhesive and a temporary protective backing, eg of plastics film or paper. Once the silicone gel precursors have cured, to produce a hydrophobic silicone gel, a temporary cover, again of plastics film or paper material, is applied to the gel. The perforations are then formed in the laminate by a suitable method. A preferred silicone gel for use in the wound dressing is Dow Corning™ 7-9700 Soft Skin Adhesive.

[0075] In a separate operation, the absorbent body is produced, and individual squares or other appropriate shapes are cut out. A preferred superabsorbent material for use in the absorbent body is polyurethane foam, although superabsorbent materials such as Gellok® 20040 S/S White may also be used.

[0076] The squares of the absorbent body are then positioned on the adhesive coated sheet of breathable polyurethane film. The temporary protective backing is removed from the underside of the MBPU to expose the acrylic adhesive and the laminate is applied to the polyurethane film. Finally, the temporary protective cover is removed from the silicone gel and replaced with appropriately formed release liners, and individual dressings 10, 20, 30 are punched out and sterile-packaged.

EXAMPLE

Comparison of the Moisture Vapour Transmission Rate of Polyurethane Films Carrying Different Coatings of Acrylic Adhesive

[0077] The moisture vapour transmission rate (MVTR) of standard polyurethane (PU) films carrying a continuous flood coating of acrylic adhesive versus an irregular porous coating of acrylic adhesive produced by a fiberization method was compared.

[0078] The PU film carrying the irregular porous coating of acrylic adhesive was prepared by applying acrylic adhesive to the film using an ITW Dynatec UFD Spray Applicator.

[0079] The MVTR of the coated PU films were tested in accordance with the standard test methods for primary wound dressings set out in BS EN 13726-2:2002. In particular, deionised water was introduced into containers, the openings of the containers were sealed with samples of the coated PU film and the containers were weighted. The containers were then inverted such that the water remained in contact with the coated film and places in an incubator at a temperature of 37° C. A sufficient gap was maintained between the surface of the film samples and the incubator in order to ensure sufficient air flow across the surface of the film samples.

[0080] The containers were incubated for 4 hours under these conditions, following which they were removed from the incubator and weighed, with the reduction in weight indicating the amount of water that had been able to pass through the film during incubation. The experiment was repeated five times for PU film carrying each of a continuous flood coating of acrylic adhesive and an irregular porous coating of acrylic adhesive.

[0081] The mean reduction in weight was 309.08 g for the film carrying the continuous coating of acrylic adhesive and 814.82 g for the film carrying the irregular porous coating of acrylic adhesive. The ITW Dynatec UFD Spray Applicator is therefore able to apply an irregular porous coating of acrylic adhesive to a PU film that has a significantly higher MVTR than the same film carrying a continuous coating of adhesive while still providing effective adhesion.