GB2425487A

GB2425487A - Wound dressing and method of preparation

Info

Publication number: GB2425487A
Application number: GB0607716A
Authority: GB
Inventors: Xavier Thomas; Gerald K Schalau; John Robert Biddle; Frederick Edward Ennis
Original assignee: POLYMER SCIENCE Inc; Dow Corning Corp
Current assignee: POLYMER SCIENCE Inc; Dow Silicones Corp
Priority date: 2005-04-26
Filing date: 2006-04-20
Publication date: 2006-11-01
Also published as: GB0607716D0

Abstract

This invention describes a method for preparing wound dressings by applying a adhesive to the dressing by forcing it through an orifice. The method used herein produces a wound dressing with variable adhesive free area on a selected substrate. The method comprises altering the amount of adhesive placed on the substrate; thereby providing an adhesive dressing with adjustable adhesive and moisture barrier characteristics. The adhesive may be a silicone 'hot melt' or pressure sensitive adhesive. The method may be used to prepare a transdermal drug delivery service.

Description

100011 This invention describes a method for preparing wound dressings

that are useful for human and veterinary applications. The method used herein produces a wound dressing with variable adhesive free area on a selected substrate. The method comprises altering the amount of adhesive placed on the substrate; thereby providing an adhesive dressing with adjustable adhesive and moisture barrier characteristics.

100021 Some occiusivity of a wound dressing is necessary to provide an environment that is ideal for wound healing. However, dressings that are too occlusive (i.e. do not allow moisture from under the dressing to escape) can cause excessive moisture levels at or around a wound.

Excessive moisture can cause the wound to macerate. The problems of excessive dressing occlusivity have been avoided in the past by preparing dressings of discontinuous surfaces with a continuous coating of adhesive. These dressings allow some moisture vapor to be transmitted from the wound bed through the discontinuities on the surface of the adhesive.

The method of adhesive application described herein and the resulting wound dressings may employ either a continuous or a discontinuous substrate. The key distinction of this method is that the adhesive coating is also discontinuous.

100031 The wound dressings prepared herein are useful in healthcare applications such as OTC bandages, medical, athletic or surgical tape, medical device anchorage, and professional wound dressings where atraumatic dressings are needed for efficacious treatment, including the treatment of geriatric, pediatric neo-natal and other patients who have delicate, thin or abraded skin, as well as patients who suffer from eczema, psoriasis and other chronic skin disorders. Wound dressings prepared using the described technique are especially useful in treatment of pressure sores, diabetic ulcers, venous ulcers, burns and other wounds and skin disorders that are difficult to treat. Other potential applications include sports applications, such as blister prevention, and scar management where excessive sweating caused by more occlusive dressings may cause delamination of the adhesive from the skin. The adhesive may also create an occlusive environment to allow for better autolytic enzymatic debridement.

Other potential applications include transdermal drug delivery patches and topical therapeutic plasters where there is a need to increase the flow of skin moisture into the medicated device or to increase the flow of the active molecules from the matrix or reservoir containing the actives.

100041 The method used herein comprises applying an adhesive to a substrate using a means to create a pattern on the substrate. For example, the adhesive is applied to the substrate by allowing the adhesive to pass through an orifice onto a substrate that may move or be stationary beneath the flowing adhesive to create the pattern on the substrate.

Alternatively, the adhesive dispensing apparatus and orifice may move in addition to or instead of the substrate. The adhesive apparatus may move via mechanical, pneumatic or physical means. Patterns include but are not limited to boxes, continuous perpendicular lines (exterior window pane), unidirectional lines, irregular overlapping and non-overlapping lines, spots, dots, spirals, zigzag as well as other regular and irregular patterns.

[00051 The adhesive free area of a dressing is defined as areas where no adhesive is applied or exists. This method is applicable to prepare dressings with adhesive free areas from as low as 5% adhesive free area to those having as much as 95% adhesive free area.

[00061 To apply the adhesive to the substrate, the adhesive may be forced through the orifice via pneumatic, mechanical, electrical, or gravity feed mechanisms. The orifice can be circular, oval, linear, or geometric (such as star, cross, radius slit, etc.) in shape and typically has a diameter and/or width of 0.001 inch to 0.25 inches. Further, the orifice can be constructed of plastic components (including polyethylene, polypropylene polyurethane, polycarbonate, etc.), metallic components (including stainless steel, brass, copper, etc.), thermoset rubbers, or other non-reactive materials (such as Teflon, nylon, and etc.). The adhesive delivery apparatus may or may not contain a static mixing mechanism in the case of multipart adhesive systems, a heat source in the case of applying a "Hot Melt" adhesive.

100071 Suitable substrates for the wound dressings or other medical and pharmaceutical constructions include films (defined as nearly occlusive, continuous sheets of material), non- woven materials (defined as a breathable substrate whose fibers are held together by chemical or physical interlocking or bonding as opposed to being held together by knitting) foams, (defined as a porous, mass of interlacing fibers of natural or synthetic origin) or textiles (defined as a breathable substrate whose fibers are held together by being interwoven). The substrates can be plastic (such as polyethylene, polypropylene, polycarbonate, PTFE and similar products), film products with release coatings (coating based on silicone, fluorosilicone, fluorine and others), alginate (materials of botanical (i.e. algal) origin), thermoset or room temperature vulcanized rubber (such as silicone), hydrocolloid, hydrogel, or silicone derivation, as well as textiles of natural (such as cotton, silk or wool, etc.) or synthetic sources (such as nylon, polyester, polyurethane, polyvinyl chloride, polyvinyl acrylate, etc.).

100081 Alternatively, the substrate may consist of multiple layers rather than the two layers described above. When the substrate consists of multiple layers, typically the adhesive pattern is applied to at least one of the outermost layers. This could be a double-sided tape type of construction where at least one side of the tape is coated in a pattern with adhesive- free area as described above. Other examples of multi-layer constructs include transdermal or topical drug delivery devices consisting of one or multiple film layers, an active pharmaceutical either incorporated into an adhesive layer or maintained as a reservoir, and a pattern coated exterior surface.

[00091 Traditional pattern coating techniques such as Gravure and coating are most suited for one part adhesive systems. These traditional coating pattern techniques will not work for adhesives having a viscosity of over 6000 mPa.s and will not consistently apply a coating thickness greater than 4 mil (0.1mm). Traditionally, thicker coat weights have been applied with a stencil or mask that is removed to display the adhesive pattern. This method of adhesive application differs from these traditional pattern coating methods in that thicker coat weights, multipart systems, hot melt adhesives and a wide variety of adhesive viscosities can be applied in a pattern without a stencil or expensive tool. Lower adhesion adhesives (such as Dow Corning 7-9800 Soft Skin Adhesive) are typically applied in a thicker coat weight than are most pressure sensitive adhesives. Prior to this development, Soft Skin adhesives and their kind could not be readily coated in a pattern. The described method is applicable to one part or multiple part adhesive systems with a solid content from 30 wt. % to 100 wt.% and a viscosity of 0.1 Pa.s to 600 Pa.s.

100101 Suitable adhesives for use in this preparation technique include solvent-based acrylic adhesives, emulsion acrylic adhesives, and hot melt acrylic adhesives, multi-part silicone elastomeric tacky gels, hot melt silicone adhesives, solvated and solventless silicone pressure sensitive adhesives, emulsion (water-in-silicone or silicone-in-water) silicone pressure sensitive adhesives, and solvated or hot melt synthetic or natural rubber based adhesives and hydrogels. Additionally, blends of any of the aforementioned adhesive types with other materials (such as hydrocolloids, active ingredients, drugs) may be used.

[00111 Using the method herein adhesive coat thicknesses of 0.1 mil (0. 0025 mm) up to mil (5.1 mm) are possible and will depend on the viscosity, thixotropic properties, and cure profile of the adhesive used.

100121 The method used herein and the resulting dressings differ from previous methodologies and products in that the prepared dressing may be a continuous surface or discontinuous surface (i.e. perforated or have voids in the surface). A continuous surface can be of distinct advantage in the utility of the resulting dressings. The dressings of discontinuous construction have been utilized as "under dressings" that contact the skin.

These under dressings must utilize a separate absorbent dressing to soak up any fluids that exude from the wound. The disclosed invention does not require additional layers to be used when a continuous surface is employed, in that the adhesive may be applied directly to an absorbent substrate (such as a sponge, non-woven or textile fabric), thereby eliminating the necessity of additional absorbent dressings.

[00131 An additional benefit of the continuous or discontinuous dressing substrate is found in the ability to "fine-tune" the Moisture Vapor Transmission Rate (MVTR) of the dressing by using substrates with differing vapor permeability rates (i.e. the same pattern of the same adhesive cast on vastly different substrates will produce a dressing with widely different MVTR properties). The substrates can be varied to create a reasonably occlusive barrier dressing that will allow some moisture to be left near the wound to prevent drying, or conversely a very breathable and absorbent substrate may be used for wounds with a high levels of exudates. One skilled in the art will be able to fine-tune the moisture vapor transmission rate.

100141 Similarly, adjusting the amount of adhesive free area left after applying adhesives can modify moisture vapor transmission rates of a dressing. Generally, adhesives are at least somewhat occlusive. Therefore, adjusting the amount adhesive applied to a substrate, can dramatically affect the MVTR of the dressing. Adhesive free area can also act to channel the exudate away from the wound by providing a route away from the wound site.

[00151 Modifying the amount of adhesive free area may also decrease the adhesion level, creating a more "skin friendly" contact surface. For patients with fragile skin, dressings with complete adhesive coverage are more likely to damage or strip the skin, than a pattern coated dressing. Therefore the pattern coated dressing will be less damaging to the skin when the dressing is removed. The benefice can be useful to reduce the adhesion to the release liner and allowing for a lower peel release force.

(00161 This dressing may also be used for the delivery of actives, including antibiotics, pain relievers, hormones, steroids, vitamins and other active ingredients including active pharmaceutical ingredients. Metallic species such as silver, and copper that work to reduce bacterial infections may also be added as long as the additives are compatible with the adhesive curing conditions.

Claims

1. A method for producing a wound dressing comprising forming a pattern coating on a substrate wherein the pattern coating is formed by passing an adhesive through an orifice onto the substrate in a manner to create a pattern on the substrate.

2. The method as claimed in claim I wherein the substrate is selected from films, non- woven materials, foams, and textiles.

3. The method as claimed in claim 1 or 2 wherein the substrate has a continuous surface.

4. The method as claimed in claim I or 2 wherein the substrate has a discontinuous surface.

5. The method as claimed in claim 1 wherein the adhesive is selected from acrylic adhesives, multi-part silicone elastomeric tacky gels, hot melt silicone adhesives, silicone pressure sensitive adhesives as solvent based solutions or emulsions, synthetic rubber based adhesives, natural rubber based adhesives, hydrogels and mixtures thereof.

6. The method as claimed in claim 1 wherein the adhesive is selected from hot melt silicone adhesives, and silicone pressure sensitive adhesives.

7. The method as claimed in claim 1, 5 or 6 wherein the adhesive has a viscosity of 0.1 Pa.s to 600 Pa.s.

8. The method as claimed in claim 1, 5, 6 or 7 wherein the adhesive has a solid content of from 30 wt% to 100 wt%.

9. The method as claimed in claim 1 wherein the adhesive is applied to a thickness in the range of 0.0025 mm to 5.1 mm.

10. The method as claimed in claim 1, 2 or 3 wherein the substrate is comprised of more than 1 layer.

11. The method as claimed in claim 10 wherein the adhesive is applied to the outermost layer.

12. The method as claimed in claim 1 wherein the adhesive is applied in a pattern selected from boxes, continuous perpendicular lines, unidirectional lines, irregular overlapping and non-overlapping lines, spots, dots, spirals and zigzags.

13. The method as claimed in claim I wherein the wound dressing has adhesive free areas.

14. The method as claimed in claim 1 wherein the adhesive free area is in the range of 5% to 95% of the wound dressing.

15. The method as claimed in claim 1 wherein the substrate moves during the application of the adhesive.

16. The method as claimed in claim I wherein the orifice moves during the application of the adhesive.

17. The method as claimed in claim 1 wherein the substrate and the orifice move during the application of the adhesive.

18. A would dressing comprising a patterned adhesive on a substrate.

19. A method for producing a transdermal drug delivery system or a topical therapeutic plaster comprising forming a pattern coating on a substrate wherein the pattern coating is formed by passing an adhesive through an orifice onto the substrate in a manner to create a pattern on the substrate.

20. The method as claimed in claim 1 wherein the wound dressing contains an active molecule or an active pharmaceutical ingredient.

21. The method as claimed in claim 19 wherein the wound dressing contains an active molecule or an active pharmaceutical ingredient.