Composite foam in wound treatment

1. A composite material comprising:

a first foam layer comprising a first hydrophilic polyurethane foam material, wherein said first foam layer has a first side adapted to face an area of application in use,

a second foam layer comprising a second hydrophilic polyurethane foam material, wherein the fluid retention capacity of said second foam layer is at least 20% greater than the fluid retention capacity of said first foam layer, wherein said fluid retention capacity is defined as the capability of retaining Solution A having first absorbed a maximum amount of Solution A, according to EN 13726-1:2002, when exposed to a pressure of 40 mmHg for two minutes,

and wherein a plurality of channels extends from said first side of said first foam layer through the entire first foam layer into at least a portion of said second foam layer, wherein the channels have an average diameter of from 0.1 mm to 4.0 mm, wherein each channel of the plurality of channels is an open structure.

2. A composite material comprising:

a first foam layer comprising a first hydrophilic polyurethane foam material, wherein said first foam layer has a first side adapted to face an area of application in use,

a second foam layer comprising a second hydrophilic polyurethane foam material,

wherein an interfacial bonding volume exists between said first and said second foam layer,

wherein said interfacial bonding volume comprises a mixture of the materials making up said first and said second foam layer,

and wherein said interfacial bonding volume has a thickness of less than 200 μm,

and wherein a plurality of channels extends from said first side of said first foam layer through the entire first foam layer into at least a portion of said second foam layer, wherein the channels have an average diameter of from 0.1 mm to 4.0 mm, wherein each channel of the plurality of channels is an open structure.

3. A composite material comprising:

a first foam layer comprising a first hydrophilic polyurethane foam material, wherein said first foam layer has a first side adapted to face an area of application in use,

a second foam layer comprising a second hydrophilic polyurethane foam material,

wherein a plurality of channels extends from said first side of said first foam layer through the entire first foam layer into at least a portion of said second foam layer, wherein the channels have an average diameter of from 0.1 mm to 4.0 mm, wherein each channel of the plurality of channels is an open structure.

4. The composite material according to claim 3 , wherein a fluid retention capacity of said second foam layer is at least 20% greater than a fluid retention capacity of said first foam layer, said fluid retention capacity is defined as the capability of retaining Solution A having first absorbed a maximum amount of Solution A, according to EN 13726-1:2002, when exposed to a pressure of 40 mmHg for two minutes.

5. The composite material according to claim 2 , wherein at least one physical property of the material comprised in the interfacial bonding volume is different vis-à-vis the material making up said first foam layer and said second foam layer, respectively.

6. The composite material according to claim 3 , wherein the thickness of the first foam layer is less than the thickness of the second foam layer.

7. The composite material according to claim 3 , wherein said second foam layer has a fluid retention capacity of at least 800 kg/m3.

8. The composite material according to claim 3 , wherein said first foam layer has a speed of absorption of at least 10 μL/sec, as measured according to TAPPI standard T558 OM-97, using 30 μL Solution A, according to EN 13726-1:2002, as test solution.

9. The composite material according to claim 3 , wherein at least one of said first foam layer and/or said second foam layer is obtained by a process, in which an aqueous mixture comprising a prepolymer, leading to the hydrophilic polyurethane foam layer, comprises less than 40% of water.

10. The composite material according to claim 3 , wherein said first hydrophilic polyurethane foam material is obtained from a first prepolymer comprising or being an isocyanate-capped polyol or isocyanate-capped polyurethane, and/or wherein said second hydrophilic polyurethane foam material is obtained from a second prepolymer comprising or being an isocyanate-capped polyol or isocyanate-capped polyurethane.

11. The composite material according to claim 10 , wherein said polyol is selected from the group consisting of a polyester polyol, polyacrylate polyol, polyurethane polyol, polycarbonate polyol, polyether polyol, polyesterpolyacrylate polyol, polyurethane polyacrylate polyol, polyurethane polyester polyol, polyurethane polyether polyol, polyurethane polycarbonate polyol, and polyester polycarbonate polyol.

12. The composite material according to claim 10 , wherein said first and/or second prepolymer derive(s) from a reaction between a polyol, and a diisocyanate compound selected from the group consisting of hexamethylene diisocyanate (HDI), toluene diisocyanate (TDI), methylene diphenyl diisocyanate (MDI), and isophorone diisocyanate (IPDI), or any mixture thereof.

13. A medical dressing comprising a composite material according to claim 3 .

14. The medical dressing according to claim 13 , wherein said medical dressing further comprises at least one further layer.

15. A method for producing the composite material of claim 3 , comprising the steps of:

(i) preparing an aqueous mixture comprising a polyurethane prepolymer, wherein the water content of said aqueous mixture is less than 40% w/w relative to the total weight of said aqueous mixture;

(ii) applying said aqueous mixture from step (i) onto a carrier material;

(iii) applying, before said aqueous mixture is essentially completely cured, an already cured hydrophilic polyurethane foam layer on top of said aqueous mixture as cast onto said carrier material in step (ii);

(iv) allowing said aqueous mixture to essentially completely cure, thereby producing a composite material comprising a first foam layer comprising a first hydrophilic polyurethane foam material and a second foam layer comprising a second hydrophilic polyurethane foam material; and

(v) forming the plurality of channels extending from said first side of said first foam layer through the entire first foam layer into at least a portion of said second foam layer, wherein the channels have an average diameter of from 0.1 mm to 4.0 mm, wherein each channel of the plurality of channels is an open structure.

16. The method according to claim 15 , wherein the degree of curing of said aqueous mixture is between 50 to 90%, at the stage of applying said layer of an already cured hydrophilic polyurethane foam layer in step (iii).