SUPERABSORBENT WOUND DRESSING WITH SILICONE WOUND CONTACT LAYER

Abstract

Wound dressing (10, 30) comprising a backing layer(11, 31), an absorbent pad (12, 32) and a wound contact layer(13, 33), wherein the backing layer (11, 31) comprises a water vapour-permeable and substantially liquid-impermeable film material, wherein the absorbent pad (12, 32) comprises an absorbent core (15, 35) having a proximal side and a distal side, and an envelope (14, 34) surrounding the absorbent core(15, 35), the absorbent core (15, 35) comprising an absorbent material, and wherein the wound contact layer (13, 33) comprises a layer of a skin-friendly silicone adhesive(13b, 33b), characterized in that the envelope (14, 34) comprises a first layer (14a, 34a) of a first liquid-permeable material and a second layer (14b, 34b) of a second material different from the first material, wherein the first layer (14a, 34a) of the envelope (14, 34) covers the proximal side of the absorbent core (15, 35) and wherein the second layer (14b, 34b) of the envelope (14, 34) covers the distal side of the absorbent core(15, 35), and wherein the first layer (14a, 34a) of the envelope(14, 34) extends over the proximal side of the absorbent core (15, 35) and the second layer (14b, 34b) of the envelope(14, 34) extends over the distal side of the absorbent core (15, 35) each of them forming a border area (16, 36) surrounding the absorbent core(15, 35), the first (14a, 34a) and second layer (14b, 34b) of the envelope (14, 34) being joined to each other along the border area (16, 36) surrounding the absorbent core(15, 35).

Claims

1. A wound dressing (10, 30) comprising a backing layer (11, 31), an absorbent pad (12, 32) and a wound contact layer (13, 33), wherein the backing layer (11, 31) comprises a water vapour-permeable and substantially liquid-impermeable film material, wherein the absorbent pad (12, 32) comprises an absorbent core (15, 35) having a proximal side and a distal side, and an envelope (14, 34) surrounding the absorbent core (15, 35), the absorbent core (15, 35) comprising an absorbent material, and wherein the wound contact layer (13, 33) comprises a layer of a skin-friendly silicone adhesive (13b, 33b), wherein the envelope (14, 34) comprises a first layer (14a, 34a) of a first liquid-permeable material and a second layer (14b, 34b) of a second material different from the first material, wherein the first layer (14a, 34a) of the envelope (14, 34) covers the proximal side of the absorbent core (15, 35) and wherein the second layer (14b, 34b) of the envelope (14, 34) covers the distal side of the absorbent core (15, 35), and wherein the first layer (14a, 34a) of the envelope (14, 34) extends over the proximal side of the absorbent core (15, 35) and the second layer (14b, 34b) of the envelope (14, 34) extends over the distal side of the absorbent core (15, 35) each of them forming a border area (16, 36) surrounding the absorbent core (15, 35), the first (14a, 34a) and second layer (14b, 34b) of the envelope (14, 34) being joined to each other along the border area (16, 36) surrounding the absorbent core (15, 35).

2. The wound dressing (10, 30) of claim 1, wherein the first layer (14a, 34a) of the envelope (14, 34) comprises a first material exhibiting hydrophilic properties and the second layer (14b, 34b) of the envelope (14, 34) comprises a second material exhibiting hydrophobic properties.

3. The wound dressing (10, 30) according to claim 1, wherein the second layer (14b, 34b) of the envelope (14, 34) comprises a substantially liquid-impermeable material.

4. The wound dressing (10, 30) of claim 1, wherein the first (14a, 34a) and the second layer (14b, 34b) of the envelope (14, 34) comprise a material exhibiting thermoplastic properties.

5. The wound dressing (10, 30) of claim 4, wherein the second layer (14b, 34b) of the envelope (14, 34) comprises a thermoplastic material that has hydrophobic properties, and wherein the first layer (14a, 34a) of the envelope (14, 34) comprises a thermoplastic material that is the same material as in the first layer (14b, 34b) and that has been treated chemically and/or physically to exhibit hydrophilic properties.

6. The wound dressing (10, 30) according to claim 5, wherein the thermoplastic material of both the first layer (14a, 34a) and the second layer (14b, 34b) of the envelope (14, 34) comprises polypropylene.

7. The wound dressing (10, 30) of claim 4, wherein the first layer (14a, 34a) and the second layer (14b, 34b) of the envelope (14, 34) have been joined by a thermic process and therefore comprise a welding connection (18).

8. The wound dressing (10, 30) of claim 7, wherein the welding connection (18) comprises at least one non-continuous welding line (19).

9. The wound dressing (10, 30) of claim 8, wherein the welding connection (18) comprises four to six parallel non-continuous welding lines (19).

10. The wound dressing (10, 30) of claim 8, wherein the at least one non-continuous welding line (19) is arranged parallel to the machine direction of the manufacturing process.

11. The wound dressing (10, 30) according to claim 1, wherien the wound contact layer (13, 33) has an open area of between 10 to 25% of the entire area of the wound contact layer (13, 33).

12. The wound dressing (10, 30) of claim 1, wherein the wound contact layer (13, 33) comprises apertures (13c, 33c) having an essentially circular shape with an average diameter of between 0.2 mm to 3.0 mm.

13. The wound dressing (10, 30) of claim 1, wherein the absorbent pad (14, 34) comprises a proximal surface and a distal surface and the backing layer (11, 31) comprises a coating of a pressure-sensitive adhesive, and that the backing layer (11, 31) extends over the distal surface of the absorbent pad (12, 32) forming an adhesive border area (17, 37) that surrounds the absorbent pad (12, 32).

14. The wound dressing (10) of claim 13, wherein the wound contact layer (13) is coextensive with the backing layer (11).

15. The wound dressing (10, 30) of claim 1, wherein the absorbent core (15, 35) comprises an absorption capacity of at least 100 g/100 cm2.

16. The wound dressing (10, 30) of claim 1, wherein the absorbent core (15, 35) comprises a mixture of absorbent fibers and superabsorbent particles.

17. The wound dressing (10, 30) of claim 1, wherein the first layer (14a, 34a) of the envelope (14, 34) and the second layer (14b, 34b) of the envelope (14, 34) are joined along the border area (16, 36) surrounding the absorbent core (15, 35) in a joining area, the joining area having an inner margin and an outer end, and that the envelope (14, 34) comprises a space between the first (14a, 34a) and the second layer (14b, 34b) of the envelope (14, 34), wherein the absorbent core (15, 35) is placed, the space being limited by the inner margin of the joining area, and the space having an area A1, the absorbent core (15, 35) having an area A2, wherein the area A2 is at least 80% of the area A1.

Description

[0064] FIG. 1 shows a wound dressing in a top view of a preferred embodiment of the invention.

[0065] FIG. 2 shows the wound dressing of FIG. 1 in a cross-section view along the cutting line A-A of FIG. 1.

[0066] FIG. 3 shows a wound dressing in a cross-section view representing an island-type embodiment of the invention.

[0067] FIG. 1 shows a top view of a wound dressing (10) having a backing layer (11) and an absorbent pad (12). A wound contact layer is present on the side of the dressing facing away from the viewer. The absorbent pad (12) comprises an absorbent core (15) and an envelope (14) surrounding the absorbent core (15). The envelope (14) comprises a first, proximal layer (facing away from the viewer) of a liquid-permeable nonwoven material and a second, distal layer (14b, see FIG. 2) of a substantially liquid-impermeable nonwoven material. The proximal layer of the envelope (14) covers the proximal side of the absorbent core (15) and extends over the proximal side of the absorbent core (15), thereby forming a border area (16) surrounding the absorbent core (15). The distal layer (14b) of the envelope (14) covers the distal side of the absorbent core (15) and extends over the distal side of the absorbent core (15), thereby forming a border area (16) surrounding the absorbent core (15). The proximal layer of the envelope (14) and the distal layer (14b) of the envelope (14) are joined along the border area (16) surrounding the absorbent core (15) by a thermic process and therefore comprise a welding connection (18). The welding connection (18) is formed by five non-continuous welding lines (19). The backing layer (11) extends over the absorbent pad (12), thereby forming a border area (17) surrounding the absorbent pad (12).

[0068] FIG. 2 shows a cross-sectional view of the wound dressing (10) of FIG. 1 along the cutting line A-A from FIG. 1, having an absorbent pad (12), a backing layer (11) and a wound contact layer (13). The absorbent pad (12) comprises an absorbent core (15) and an envelope (14). The envelope (14) is formed from a proximal layer (14a) and a distal layer (14b). The wound contact layer (13) is formed from a layer of a perforated sheet material (13a) and a layer of skin-friendly silicone adhesive (13b). The backing layer (11) is made from a vapour-permeable and liquid-impermeable polyurethane film material with low friction characteristics having a thickness of 30 μm. The backing layer (11) is coated with a layer of acrylate-based adhesive (not shown). The absorbent core (15) comprises a mixture of cellulose fibers and superabsorbent sodium polyacrylate particles in a pre-fabricated airlaid material. The absorbent core (15) further comprises a diffusion layer (not shown) in form of a sheet of cellulose tissue that is wrapped around the airlaid mixture of cellulose fibers and polyacrylate particles. The proximal layer (14a) of the envelope (14) is a nonwoven made from a mixture of viscose fibers and polyamide fibers. The distal layer (14b) of the envelope (14) is a nonwoven made from polypropylene fibers. The proximal layer (14a) of the envelope (14) covers the proximal side of the absorbent core (15) and extends over the proximal side of the absorbent core (15), thereby forming a border area (16) surrounding the absorbent core (15). The distal layer (14b) of the envelope (14) covers the distal side of the absorbent core (15) and extends over the distal side of the absorbent core (15), thereby forming a border area (16) surrounding the absorbent core (15). The proximal layer (14a) of the envelope (14) and the distal layer (14b) of the envelope (14) are joined along the border area (16) surrounding the absorbent core (12). The perforated sheet material (13a) of the wound contact layer (13) is made from a polyurethane film that comprises apertures (13c) having a circular shape. These apertures (13c) have similar shapes having an average diameter of 2.4 mm and are arranged in a regular pattern resulting in an open area of 15%. The backing layer (11) extends over the absorbent pad (12), thereby forming a border area (17) surrounding the absorbent pad (12). The wound contact layer (13) extends over the absorbent pad (12), thereby forming a border area (17) surrounding the absorbent pad (12). The backing layer (11) and the wound contact layer (13) are coextensive.

[0069] FIG. 3 shows a cross-sectional view of a wound dressing (30) of an island-type having an absorbent pad (32), a backing layer (31) and a wound contact layer (33). The absorbent pad (32) comprises an absorbent core (35) and an envelope (34). The envelope is formed from a proximal layer (34a) and a distal layer (34b). The wound contact layer (33) is formed from a layer of a perforated sheet material (33a) and a layer of skin-friendly silicone adhesive (33b). The backing layer (31) is made from a vapour-permeable and liquid-impermeable polyurethane film material with low friction characteristics having a thickness of 30 μm. The backing layer (31) is coated with a layer of acrylate-based adhesive (not shown). The absorbent core (35) comprises a mixture of cellulose fibers and superabsorbent sodium polyacrylate particles in a pre-fabricated airlaid material. The absorbent core (35) further comprises a diffusion layer (not shown) in form of a sheet of cellulose tissue that is wrapped around the airlaid mixture of cellulose fibers and polyacrylate particles. The proximal layer (34a) of the envelope (34) is a nonwoven made from a mixture of viscose fibers and polyamide fibers. The distal layer (34b) of the envelope (34) is a nonwoven made from polypropylene fibers. The proximal layer (34a) of the envelope (34) covers the proximal side of the absorbent core (35) and extends over the proximal side of the absorbent core (35), thereby forming a border area (36) surrounding the absorbent core (35). The distal layer (34b) of the envelope (34) covers the distal side of the absorbent core (35) and extends over the distal side of the absorbent core (35), thereby forming a border area (36) surrounding the absorbent core (35). The proximal layer (34a) of the envelope (34) and the distal layer (34b) of the envelope (34) are joined along the border area (36) surrounding the absorbent core (35). The perforated sheet material (33a) of the wound contact layer (33) is made from a polyurethane film that comprises apertures (33c) having a circular shape. These apertures (33c) have similar shapes having an average diameter of 2.4 mm and are arranged in a regular pattern resulting in an open area of 15%. The wound contact layer further comprises a layer of skin-friendly silicone adhesive (33b). The backing layer (31) extends over the absorbent pad (32), thereby forming a border area (37) surrounding the absorbent pad (32).

EXAMPLES

Example 1: Wound Dressing

[0070] The wound dressing has an absorbent pad, a backing layer and a wound contact layer. The absorbent pad comprises an absorbent core and an envelope. The envelope is formed from a proximal layer and a distal layer. The wound contact layer is formed from a layer of a perforated sheet material and a layer of skin-friendly silicone adhesive. The backing layer is made from a vapour-permeable and liquid-impermeable polyurethane film material with low friction characteristics having a thickness of 30 μm. The absorbent core comprises a mixture of cellulose fibers and superabsorbent sodium polyacrylate particles in a pre-fabricated airlaid material. The absorbent core further comprises a diffusion layer in form of a sheet of cellulose tissue that is wrapped around the airlaid mixture of cellulose and polyacrylate particles. The proximal layer of the envelope is a nonwoven made from a mixture of viscose and polyamide fibers. The distal layer of the envelope is a nonwoven made from polypropylene fibers. The perforated sheet material of the wound contact layer is made from a polyurethane film that comprises apertures having a circular shape. These apertures exhibit similar shapes having an average diameter of 2.4 mm and are arranged in a regular pattern resulting in an open area of 15%. The wound contact layer further comprises a layer of skin-friendly silicone adhesive without occluding the apertures of the perforated sheet material.

Example 2: Test Solutions Used in the Characterization of Wound Dressings

[0071] Solution A (saline solution)

[0072] 2 L Deionized water

[0073] 0.74 g Calcium chloride dihydrate (CaCl.sub.2.2H.sub.2O, CAS: 10035-04-5)

[0074] 16.6 g Sodium chloride (NaCl, CAS: 7647-14-5)

[0075] Solution B (exudates solution)

[0076] 1 L Deionized water

[0077] 70 g Albumin from chicken egg white (No CAS 9006-59-1)

[0078] 0.2 g Allura Red AC (CAS 25956-17-6)

[0079] 9 g Sodium chloride (NaCl, No CAS: 7647-14-5)

[0080] 0.37 g Calcium chloride dihydrate (CaCl.sub.2.2H.sub.2O, No CAS: 10035-04-5)

[0081] 2 g Methyl 4-hydroxybenzoate (CAS: 99-76-3)

[0082] 1 g Propyl 4-hydroxybenzoate (CAS: 94-13-3)

Example 3: Test Method Absorption Velocity

[0083] The absorption velocity of a dressing is determined by the time necessary to completely absorb a test solution. Test solutions can be either saline solution (solution A) or exudate solution (solution B). Solutions (saline solution or exudates solution) as well as test products must be preconditioned at room temperature prior to testing by leaving the test products and the solutions for two hours at 22° C.

[0084] A 50 mL buret is filled with the test solution. The liquid level should be fixed at 15mL. The dressing is placed under the buret, that surface which in use faces the wound now faces the buret. The distance between the buret and the dressing is adjusted to 1 cm. The tap of the buret is opened, and simultaneously a stopwatch is started, while 2 mL of test solution are allowed to flow out. The stopwatch is stopped immediately when the 2 mL of test solution are completely absorbed by the dressing, i.e. when no drop is remaining over the perforation of the wound contact layer. If the dressing is big enough, 1 to 3 measurements can be made on the same dressing.

[0085] Positions of the tests on a dressing are one in the centre, two further points along a diagonal in direction to the corners of the dressing, similar to the position of the three points on a regular die.

[0086] At least five samples have to be investigated.

[0087] Each value has to be classified in the following categories

TABLE-US-00001 Time (s) [0 [5.0 [11.0 [31.0 to 4.9] to10.9] to 30.9] to 60.0] >60 category Immediate Very quick quick Average slow

[0088] A dressing according to the invention has been compared with commercially available competitor dressings Biatain® silicone, Allevyn® Life, Mepilex® border (which is considered as being a dressing according to the disclosure of WO93/19709 and WO93/19710).

[0089] Absorption Velocity:

TABLE-US-00002 Absorption velocity [percentage of samples] Dressing immediate Very quick quick average slow Example 1 20%  80%  0% 0% 0% Biatain ® 0% 0% 0% 20%  80%  silicone Allevyn ® Life 0% 0% 100%  0% 0% Mepilex ® 0% 0% 0% 100%  0% border

Example 4: Test Method Absorption Capacity

[0090] Solutions (saline solution or exudates solution) as well as test products must be preconditioned at room temperature prior to testing by leaving the test products and the test solutions for two hours at 22° C.

[0091] The basic mass (m.sub.1) of a dressing is determined after removal of the release liners. The length and width of the absorbent core is determined so that the absorbent core surface (S) can be determined. A bowl is filled with the test solution. The weight of testing solution should be at least 40 times higher than the dressing itself. The dressing is put into the bowl, and simultaneously a stopwatch is started. That side of the dressing which in use faces the wound side should face the bottom of the bowl, the back side of the dressing should be on the top. The dressing should not be glued to the bottom of the bowl. The dressing is left within the bowl for 30 min+/−1 min. After 30 min, the dressing is removed from the bowl. The dressings should only be manipulated via the borders and not the absorbent core itself. The dressings are fixed on one corner to a stand with a clamp and allowed to hang for 20 min at room temperature. The wet mass (m.sub.2) of the dressing is determined. The amount of liquid (m.sub.liquid) absorbed is calculated:

m.sub.liquid=m.sub.2−m.sub.1

[0092] The absorption capacity is the amount of liquid absorbed (m.sub.2−m.sub.1) by the absorbent core surface (S) and is given in g/100 cm.sup.2:

[0093] absorption capacity=m.sub.2−m.sub.1/S×100

[0094] A dressing according to the invention has been compared with commercially available competitor dressings Biatain® silicone, Allevyn® Life, Mepilex® border (which is considered as being a dressing according to the disclosure of WO093/19709 and WO093/19710).

[0095] Comparison of Absorption Capacities:

TABLE-US-00003 Dressing Absorption capacity in g/100 cm.sup.2 Example 1 147 Biatain ® silicone 116 Allevyn ® Life 87 Mepilex ® border 54

Example 5: Test Method for Adhesiveness on Skin—Peel Test

[0096] Subjects came to the Study Site. They were informed about the study and gave their written consent. Test products were applied to the back of each subject (two samples per test product): One sample of each test product was adhered to the upper part of the back. The second sample of each test product was adhered to the lower part of the back at the same position as the first sample in the upper part.

[0097] The lower end of each sample was folded on the length of approximately 0.5 cm, in order to obtain a starting point for removing the sample from downside to upside with the universal test machine. The test materials were applied by a technician and pressed to the skin with the use of a metal roll (1 kg, 5 times of rolling back and forth).

[0098] Subjects came to the Study Site 3 hours and 50 minutes after the product application. They stayed in the air-conditioned room for at least 10 minutes. It was checked that the subjects did not sweat. Then, samples were removed 4 hours after application by using a universal test machine, set up for determining adhesive forces.

[0099] Universal Test Machine: Zwick 1120 (Zwick GmbH, Ulm, Germany). The universal test machine measures the force needed to pull off the adhesive-coated backings from the skin. For removal of the samples the subjects were positioned in a sitting position. The samples were removed under an angle of approximately 135°.

[0100] 1 measurement per sample, 2 samples per product

Example 6: Test Method for Welding Strength

[0101] The test for welding strength is carried out with Tensile Tester MTS C42.503E (MTS Systems Corporation, Eden Prairie, USA); cell strength 50N.

[0102] Test samples are prepared by stamping a part of the absorbent pad including the welding line having a rectangular shape of 15 mm in width and 25 mm in length, wherein the 15 mm side corresponds to the welding line. The sample must be at a distance of at least 2 mm from the corner. After stamping, the absorbent material is removed. The sample to be tested is only made of 2 nonwovens welded together. The clamp jaws of the tensile tester are placed in a way that the distance between the 2 jaws is 2 cm. Each nonwoven is placed in a separate jaw. The tensile tester is started at a speed of 200 mm/min until the 2 nonwovens are separated. This can happen either after a complete break of the weld or after complete tearing of the nonwovens themselves.

[0103] The welding strength is the average strength over the testing period. It is given in N/15 mm.