Wound dressing

Abstract

The present invention relates to a multilayered wound dressing particularly for wound treatment in the granulation and epithelization phase. The wound dressing comprises a) a first layer as a wound contact layer having a first side and a second side, and b) at least one second layer as an absorbent layer having a first side and a second side and comprising a hydrophilic polyurethane foam, wherein the polyurethane foam comprises a water fraction of at least 10% by weight of water.

Claims

1. A multilayered wound dressing comprising a) a first layer as a wound contact layer having a first side and a second side, and a multiplicity of channels, and including a hydrogel matrix which comprises a polyurethane-polyurea copolymer formed from a prepolymer having aliphatic diisocyanate groups and a polyamine based on polyethylene oxide, and wherein the hydrogel matrix contains from 20% to 80% of wound deliverable water; b) at least one second layer as an absorbent layer having a first side and a second side and comprising a hydrophilic polyurethane foam which has a water fraction of at least 10% by weight and at most 80% by weight of water, a free absorbency A.sub.2 of at least 10 g/g determined by DIN-EN13726-1 and a swell capacity V.sub.1 of at most 60%; and, c) a transition layer disposed between the first layer and the second layer and which transition layer consists of a portion of the hydrogel matrix of the first layer which has penetrated into a portion of the polyurethane foam of the second layer, said transition layer having channels which are filled with only polyurethane foam from the second side of the second layer and which channels are disposed congruent relative to the channels in the hydrogel matrix of the first layer.

2. The wound dressing of claim 1 , wherein the wound contact layer further comprises one or more of a polymer film, a hydrocolloid matrix, a polymer net, a nonwoven material or an adhesive.

3. The wound dressing according to claim 1 wherein the prepolymer having aliphatic diisocyanate groups includes isophorone diisocyanate.

4. The wound dressing according to claim 1, wherein the hydrogel matrix has channels from a first side to an opposite second side to allow liquids to pass through the hydrogel matrix.

5. The wound dressing of claim 1, wherein the wound dressing further comprises a water impermeable and moisture vapor permeable polymer film or a water impermeable and moisture vapor permeable polymer foam as a backing layer.

6. The wound dressing of claim 5 wherein the backing layer is the water impermeable and moisture vapor permeable polymer foam.

7. A multilayered wound dressing comprising a) a first layer as a wound contact layer having a first side and a second side, and a plurality of channels extending from the first side to the second side, and including a hydrogel matrix which comprises a polyurethane-polvurea copolymer formed from a prepolymer having aliphatic diisocyanate groups and a polyamine based on polyethylene oxide, and wherein the hydrogel matrix contains from 20% to 80% of wound deliverable water; b) at least one second layer as an absorbent layer having a planar first side and a second side and comprising a hydrophilic polyurethane foam, the first side being in contact with the wound contact first layer and, which has a water fraction of at least 10% by weight and at most 80% by weight of water, a free absorbency A.sub.2 of at least 10 g/g determined by DIN-EN13726-1 and a swell capacity V.sub.1 of at most 60%; c) a transition layer disposed between the first layer and the second layer and which transition layer consists of a portion of the hydrogel matrix of the first layer which has penetrated into a portion of the polyurethane foam of the second layer, said transition layer having channels which are filled with only polyurethane foam from the second side of the second layer and which channels are disposed congruent relative to the channels in the hydrogel matrix of the first layer; and, d) a water impermeable and moisture vapor permeable polymer film or a water impermeable and moisture vapor permeable polymer foam as a backing layer bonded to the second side of the polyurethane foam by a discontinuous layer of adhesive.

8. The multilayered wound dressing of claim 7 wherein the wound contact first layer comprises a hydrogel matrix and the channels are conically shaped.

9. The multilayered wound dressing of claim 7 wherein the wound contact first layer further comprises a hydrocolloid matrix comprising a tacky polymer into which hydrocolloid particles have been dispersed.

10. The multilayered wound dressing of claim 9 wherein the hydrocolloid particles comprise one or more of alginic acid, salts of alginic acid. chitin, chitosan, pectin, cellulose, cellulose ethers, cellulose esters, crosslinked or uncrosslinked carboxyalkylcellulose or hydroxyalkylcellulose, polyvinyl alcohol, polyvinylpyrrolidone, agar, guar gum, gelatin, and combinations thereof.

11. The multilayered wound dressing of claim 9 wherein the tacky polymer matrix comprises at least one block copolymer selected from the group consisting of AB diblock copolymers and ABA triblock copolymers, wherein said block copolymers are constructed from the monomers selected from the group consisting of styrene, butadiene and isoprene.

12. The wound dressing of claim 1 wherein the hydrogel matrix includes 5-40 wt % of a polyhydric alcohol.

13. The wound dressing of claim 12 wherein the polyhydric alcohol is selected from the group consisting of ethylene glycol, polypropylene glycol, sorbitol, glycerol and combinations thereof.

14. The wound dressing of claim 1 wherein the hydrogel matrix includes 0.1-3.0 wt % of a salt.

15. The wound dressing of claim 14 wherein the salt is selected from the group consisting of sodium chloride, potassium chloride, magnesium chloride, calcium chloride and combinations thereof.

16. The wound dressing of claim 1 wherein the hydrogel matrix is formed from a 6-30 wt % of a prepolymer having aliphatic diisocyanate groups, 4-20 wt % of a diamine based on polyethylene oxide, 10-30 wt % polyhydric alcohol selected from ethylene glycol, polypropylene glycol, sorbitol, glycerol and combinations thereof, 10-30 wt % of a polyhydric alcohol selected from polypropylene glycol and/or glycerol, 0.5-1.5 wt % salt selected from sodium chloride, potassium chloride, magnesium chloride, calcium chloride and combinations thereof, and at least 30 wt % water.

17. The wound dressing of claim 16 wherein the prepolymer having aliphatic diisocyanate groups includes isophorone diisocyanate.

18. The wound dressing of claim 1, wherein the hydrophilic polyurethane foam has a water content of at least 35 wt % of water and at most 65 wt % of water.

19. The wound dressing of claim 1 wherein the transition layer forms an adhesive bond between the first layer and the second layer.

20. The wound dressing of claim 1 wherein the polyurethane foam is capable of rereleasing at least some of the water present in the polyurethane foam.

21. The wound dressing of claim 1 wherein the wound dressing has a smaller shearing stress on a wound than an identical wound dressing comprising a dry hydrophilic polyurethane foam.

22. The wound dressing of claim 1 wherein the wound dressing has a smaller shearing stress on further plies or materials and a smaller shearing stress on a wound than an identical wound dressing comprising a dry hydrophilic polyurethane foam.

23. A laminate dressing consisting essentially of: a) a first layer as a wound contact layer having a first side and a second side, and a multiplicity of channels, and including a hydrogel matrix which comprises a polyurethane-polyurea copolymer formed from a prepolymer having aliphatic diisocyanate groups and a polyamine based on polyethylene oxide, and wherein the hydrogel matrix contains from 20% to 80% of wound deliverable water; b) at least one second layer as an absorbent layer having a first side and a second side and comprising a hydrophilic polyurethane foam which has a water fraction of at least 10% by weight and at most 80% by weight of water, a free absorbency A.sub.2 of at least 10 g/g determined by DIN-EN13726-1 and a swell capacity V.sub.1 of at most 60%; and, c) a transition layer disposed between the first layer and the second layer and which transition layer consists of a portion of the hydrogel matrix of the first layer which has penetrated into a portion of the polyurethane foam of the second layer, said transition layer having channels which are filled with only polyurethane foam from the second side of the second layer and which channels are disposed congruent relative to the channels in the hydrogel matrix of the first layer.

24. The laminate of claim 23 wherein the transition layer forms an adhesive bond between the first layer and the second layer.

25. The laminate of claim 23 wherein the polyurethane foam is capable of rereleasing at least some of the water present in the polyurethane foam.

26. The laminate of claim 23 wherein the laminate has a smaller shearing stress on a wound than an identical laminate comprising a dry hydrophilic polyurethane foam.

27. The laminate of claim 23 wherein the laminate has a smaller shearing stress on further plies or materials and a smaller shearing stress on a wound than an identical laminate comprising a dry hydrophilic polyurethane foam.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1: shows a first inventive wound dressing,

(2) FIG. 2: shows a second inventive wound dressing in cross section,

(3) FIG. 3 shows a third inventive wound dressing in cross section, and

(4) FIG. 3a shows a detail from the third inventive wound dressing in cross section.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

(5) FIG. 1 shows a first inventive wound dressing (10) with the wound contact layer in plan view. The wound dressing (10) is fabricated as a so-called island dressing and consists of a backing layer (11) composed of a water impermeable and moisture vapor permeable polyurethane film uniformly coated with an acrylate adhesive (12). In the center of the backing layer the acrylate adhesive (12) has been used to apply an absorbent hydrophilic polyurethane foam layer (not depicted here) onto which a polyurethane film (15) has been applied as wound contact layer. This hydrophilic polyurethane foam layer comprises a water fraction of 40% by weight of water. Therefore, 100 g of a polyurethane foam used in this example comprise 40 g of water and 60 g of polyurethane matrix. The polyurethane film (15) is adhesively bonded to the absorbent polyurethane foam (not depicted here). A multiplicity of circular holes (16) have been made in the polyurethane film to allow wound exudate to flow therethrough from the wound into the absorbent layer. The polyurethane film prevents ingrowth of newly formed cells into the pores of the polyurethane foam.

(6) FIG. 2 shows a further embodiment of an inventive wound dressing. The wound dressing (20) comprises a backing layer (21) which is congruent to an absorbent layer (23), is composed of a water impermeable and moisture vapor permeable polyurethane foam and is bonded by a discontinuous adhesive layer (22) of an acrylate adhesive to the absorbent layer (23). The discontinuous add on means that there are regions (27) of the absorbent layer and of the backing layer which remain unconnected. The wound dressing comprises an absorbent layer (23) having a layer thickness of 4 mm and a backing layer (11) having a layer thickness of 1.5 mm. The absorbent layer (23) is formed from an open-celled hydrophilic polyurethane foam having an average pore size of 220 m. The polyurethane foam in question comprises a water fraction of 70% by weight. On the first side of the polyurethane foam is a polyurethane adhesive applied as a wound contact layer (25). The form in which the polyurethane adhesive has been applied to the polyurethane foam at a basis weight of 75 g/m.sup.2 is not continuous, so that the wound contact layer (25) has circular holes (26) for improved passage of wound exudate. The polyurethane foam comprises a first side having an area of 25 cm.sup.2, of which the holes (26) altogether occupy an area of 5 cm.sup.2.

(7) FIG. 3 shows a third embodiment of an inventive wound dressing. The wound dressing (30) comprises a backing layer (31) composed of a water impermeable and moisture vapor permeable polyurethane film, an absorbent layer (33) composed of an open-celled hydrophilic polyurethane foam having a water fraction of 52.8% by weight (based on the polyurethane foam) and a wound contact layer (35) composed of a water-containing hydrogel matrix having a water fraction of about 63.5% by weight (based on the hydrogel). The backing layer (31) is uniformly laminated onto the hydrophilic polymer foam by means of an acrylate adhesive (32) applied to the polymer film. A water-containing hydrogel matrix (35) comprising a polyurethane-polyurea copolymer has been applied to the absorbent layers first side, which faces the wound in use. The hydrogel matrix is endowed with conical channels (36) which are circular in cross section (parallel to the wound), and so an improved wound exudate flow from the wound into the absorbent hydrophilic foam can take place (cf. FIG. 3a). In the course of the production of the wound dressing, the still viscous hydrogel matrix has slightly penetrated into the polyurethane foam, forming between the hydrogel matrix and the hydrophilic polyurethane foam a transition layer (34) which consists of the hydrogel matrix and the hydrophilic polyurethane foam. The transition layer in turn has channels (37) which are filled with polyurethane foam only and which are disposed congruent relative to the channels in the hydrogel matrix.

EXAMPLE

(8) The wound dressing has the construction described using FIG. 3.

(9) A) Producing the Hydrogel

(10) The hydrogel is produced using the following aqueous solutions and components (components A, B, C):

(11) Component A

(12) TABLE-US-00001 Propylene glycol Hedinger Aug. GmbH; 23.24% by weight USP30 (99.8%) Stuttgart, Germany Aqua purificata Water treatment plant 75.41% by weight NaCl, purest, USP Hedinger Aug. GmbH; 1.35% by weight Stuttgart, Germany

(13) Component A is produced by combining the ingredients and stirring until the salt has completely dissolved. Component A is cooled down to 2 C.

(14) Component B

(15) TABLE-US-00002 Jeffamin ED-2003 Huntsman; Everberg, Belgium 52.5% by weight Aqua purificata Water treatment plant 47.5% by weight

(16) The aqueous component B is produced by melting the solid Jeffamin at 50 C. and adding the melt to the initially charged water with stirring. Component B is cooled down to room temperature.

(17) Component C

(18) TABLE-US-00003 Aquapol PI-13000-3 Carpenter; Richmond, USA 100.0% by weight

(19) Component C is brought to room temperature.

(20) The ready-made components A, B and C are combined with each other in a ratio of 75.4:14.0:10.6 and homogenized by means of a rotating mixing system to form a homogeneous mixture which is poured ideally without bubbles into the molds provided.

(21) B1) Polyurethane Foam Used

(22) A hydrophilic polyurethane foam is used (polyurethane foam MCF.03R; from Corpura,Etten Leur, Netherlands). The dry hydrophilic polyurethane foam has the following characteristics: a) density: 77.9-83.7 kg/m.sup.3 (EN ISO 845) b) average pore size: 208 m (determined by microscope) c) layer thickness: 2.7 mm (thickness measuring instrument with 25 cm.sup.2 plate, 2 g/cm.sup.2 load, measured to EN ISO 9073-2) d) moisture vapor transmission rate: MVTR (upright)=3593 g/m.sup.2/24 h (measured to DIN EN 13726-2) e) absorbency: free absorbency A.sub.1=20.5 g/g (measured to DIN EN 13726-1) f) swell capacity: V.sub.0=89.7% The swell capacity V.sub.0 of a polyurethane foam describes the volume change experienced by a dry polyurethane foam after it has reached its maximum absorption. To determine swell capacity V.sub.0 the spatial dimensions of a sample piece of the dry polymer foam and the spatial dimensions of this sample piece after complete absorption as per the free absorbency of DIN EN 13726-1 are determined. The thickness (height) is determined using a thickness measuring instrument having a 25 cm.sup.2 plate adjusted to a loading of 2 g/cm.sup.2 as per EN ISO 9073-2. The lateral extent (length, width) is determined by means of a vernier without deforming the sample piece. To determine the extent, the particular sample piece is laid tensionlessly onto a smooth surface. The volume change after absorption corresponds to the swell capacity V.sub.0 of the dry polyurethane foam, taking account of all three spatial directions.

(23) TABLE-US-00004 Sam- Sam- Sam- ple 1 ple 2 ple 3 Mean Change/mm (%) Length (l.sub.0)/mm 50.0 50.0 50.0 50.0 Width (b.sub.0)/mm 50.0 50.0 50.0 50.0 Height (h.sub.0)/mm 2.80 2.81 2.81 2.81 Length (l.sub.2)/mm 60.2 61.9 61.3 61.1 11.1 mm (22.2%) Width (b.sub.2)/mm 61.7 63.5 62.8 62.7 12.7 mm (25.4%) Height (h.sub.2)/mm 3.47 3.47 3.49 3.48 0.67 mm (23.8%) $V_0=\frac{V_2-V_0}{V_0}.Math.100\%=\frac{\left(l_2.Math.b_2.Math.h_2\right)-\left(l_0.Math.b_0.Math.h_0\right)}{\left(l_0.Math.b_0.Math.h_0\right)}.Math.100\%=89.7\%$
where: V.sub.0=the volume of the sample piece before absorption (measured under standard conditions (23 C., 50% relative humidity), and V.sub.2=the volume of the sample piece after complete absorption. g) Retention value: R=52.8% The retention value R describes the amount of water which the polyurethane foam can maximally bind in its polyurethane matrix disregarding the water which might be imbibed into the pores. The retention value is determined by die cutting a sample piece of 5 cm5 cm (stored under standard conditions) out of a hydrophilic polyurethane foam not more than 5 mm in thickness, the weight of which is measured under standard conditions. The sample piece is thereafter subjected to a free absorbency test with water similar to DIN EN 13726-1. The water imbibed by the pores is squeezed out of the sample piece by means of a roller (weight 5000 g, diameter 10 cm, width 5 cm) by the sample being repeatedly placed between fresh paper tissues and rollered. This operation is repeated until there is no visible water absorption in the paper tissues. To determine the retention value R, the water fraction W.sub.ww, which is present in the polyurethane foam following the absorbing and squeezing out, is measured as per DIN EN 14079 and computed as follows:

(24) TABLE-US-00005 Sample 1 Sample 2 Mean Weight dry (W.sub.tt) 0.57 g 0.58 g 0.58 g Weight after absorption 11.44 g 11.75 g 11.60 g Weight after squeezing out (W.sub.gg) 1.22 g 1.24 g 1.23 g

(25) The thickness of the sample pieces measured is 2.80 mm.

(26) $R=W_{\mathrm{ww}}=\frac{W_{\mathrm{gg}}-W_{\mathrm{tt}}}{W_{\mathrm{gg}}}.Math.100\%=52.8\%$$\left(\mathrm{measured}\mathrm{to}\mathrm{DIN}\mathrm{EN}14079\right)$
where: W.sub.ww=weight of water present in the polyurethane foam after absorption and squeezing out W.sub.tt=weight of sample piece after drying, and W.sub.gg=weight of sample piece after absorption and squeezing out

(27) B2) Conditioning the Polyurethane Foam

(28) The dry hydrophilic polyurethane foam is cut to a size of 2030 cm and dipped in water for 3 minutes, so that the polyurethane foam reaches its maximum absorption. The polyurethane foam is removed from the water and carefully squeezed out by hand. The polyurethane foam is thereafter repeatedly placed between dry paper tissues and squeezed out by means of a roll (linear pressure 10 N/cm) until no water absorption is visible in the paper tissues. Therefore, the possibility of no water being present in the pores of the foam can be ruled out.

(29) The water-containing polyurethane foam has the following characteristics: a) Water content: The hydrophilic polyurethane foam has a water fraction W.sub.w=52.8% by weight (measured to DIN EN 14079), which corresponds to the retention value R of the dry polyurethane foam. b) Absorbency: Free absorbency A.sub.2=16.2 g/g (measured to DIN EN 13726-1) c) Swell capacity: V.sub.1=4% The swell capacity of the water-containing polyurethane foam is determined similarly to the dry polymer foam.

(30) TABLE-US-00006 Sam- Sam- Sam- ple 1 ple 2 ple 3 Mean Change/mm (%) Length (l.sub.1)/mm 62.8 64.3 64.15 63.75 Width (b.sub.1)/mm 63.4 64.45 64.3 64.05 Height (h.sub.1)/mm 3.4 3.38 3.39 3.39 Length (l.sub.2)/mm 60.2 61.9 61.3 61.1 2.65 mm (4.3%) Width (b.sub.2)/mm 61.7 63.5 62.8 62.7 1.35 mm (2.2%) Height (h.sub.2)/mm 3.47 3.47 3.49 3.48 0.09 mm (2.5%) $V_1=\frac{V_2-V_1}{V_1}.Math.100\%=\frac{\left(l_2.Math.b_2.Math.h_2\right)-\left(l_1.Math.b_1.Math.h_1\right)}{\left(l_1.Math.b_1.Math.h_1\right)}.Math.100\%=4\%$ where: V.sub.1=volume of water-containing sample piece and V.sub.2=volume of sample piece after complete absorption.

(31) C) Further Materials Used

(32) The backing layer used is a water impermeable polyurethane film 60 m in thickness (from Exopack-Wrexham, United Kingdom). This film is coated with an acrylate-based pressure sensitive adhesive in a layer 30 m in thickness. The film has a moisture vapor transmission rate MVTR (upright) of 1100 g/m.sup.2/24 h (DIN EN 13726-1).

(33) D) Producing the Wound Dressings

(34) The wound dressings (specimens) are fabricated by hand in accordance with the following sequence: 1. The polyurethane foam is preconditioned as per B) and provided. 2. To produce a hydrogel matrix having channels a PTFE mold having a pimpled texture is provided. The pimples of the pimpled texture are cone-shaped and have an average diameter of 1.38 mm (base 1.56 mm, tip 1.2 mm). The pimples are 1.35 mm high and are spaced 5 mm apart in a rectangular pattern. 3. The hydrogel is produced as per A) and provided, although the hydrogel has to be further processed without delay after the commixing and homogenizing. To this end, the hydrogel is poured ideally without bubbles into the provided molds to form the hydrogel matrix. 4. The gel is distributed with a PTFE blade such that the gel layer has the height of the pimples (1.35 mm). Excess gel is removed from the mold. 5. After about 3 minutes, the preconditioned polyurethane foam is laid onto the gel surface. A pressure of 200 N/m.sup.2 is applied to the foam to press and hold it down. 6. After about 7 minutes more, the gel has become bonded to the foam, so that the laminate of water-containing polyurethane foam and water-containing hydrogel matrix can be removed from the mold. A transition layer consisting of water-containing hydrogel matrix and water-containing polyurethane foam has formed in a thickness of 0.3 mm. 7. The laminate is placed with the hydrogel side face down onto the prepared release film (the siliconized side faces the gel), so that the side facing the wound is protected. 8. The assembly is covered on the foam side with a self-adhesive polyurethane film (cf. D), and the polyurethane film is firmly pressed in place using a pressure of 200 N/m.sup.2. 9. Wound dressings having an edge length of 1010 cm are die cut out of the multi-ply material assembly.

(35) The wound dressing thus produced has the construction described using FIG. 3, although FIG. 3 does not show a release liner. The wound dressing thus consists of a laminate composed of a flexible water-containing hydrogel matrix as wound contact layer, which contains 63.5% by weight of water (based on the hydrogel matrix), and an absorbent layer composed of an open-celled hydrophilic polyurethane foam having a water fraction of 52.8% by weight (based on the polyurethane foam).

(36) The wound dressing further has the following characteristics: a) Basis weight: 1550 g/m.sup.2 (measured to DIN EN 29073-1) b) Absorbency: free absorbency A.sub.1=56 g/100 cm.sup.2 (measured to DIN EN 13726-1) c) Water content in total:

(37) $W_w=\frac{W_g-W_t}{W_g}.Math.100\%=58.8\%$ d) Swell capacity: V=10% (measured as per method described above)

(38) The present wound dressing thus has a high water fraction, a high absorbency and a low swell. The wound dressing is thus optimally suitable for use in wound healing phases 2 and 3 (granulation phase and epithelization phase).