METHOD FOR MANUFACTURING A WOUND DRESSING AND A WOUND DRESSING

Abstract

A method for manufacturing a wound dressing having a substrate, and a wound dressing manufactured by such a method are described. The method has a step of providing a sacrificial layer of material to be perforated by means of a hot pin perforator, in order to remove any molten residues on the heated pins of the hot pin perforator, before the same pins are used to make holes in the substrate. The presented method is cost effective, robust and reduces the risk of contaminating substances being embedded in the substrate during the hole making process.

Claims

1. A method for manufacturing a wound dressing having a substrate, said method comprising: providing a hot pin perforator having an array of heated pins; providing a sacrificial layer of material adapted to be perforated by the heated pins; perforating the sacrificial layer with said heated pins; making holes in the substrate with the heated pins of said hot pin perforator.

2. The method according to claim 1, wherein said hot pin perforator is arranged so that the heated pins perforate the sacrificial layer before reaching a proximal surface of the substrate in order to remove residues on the heated pins before they are brought in contact with the substrate.

3. The method according to claim 1, wherein the step of providing a sacrificial layer of material comprises positioning the sacrificial layer of material between said hot pin perforator and the substrate.

4. The method according to claim 1, further comprising: applying an adhesive layer onto a perforated surface of the substrate.

5. The method according to claim 1, further comprising applying a backing layer onto a distal surface of the substrate, wherein the backing layer comprises a liquid impervious material.

6. The method according to claim 1, wherein the sacrificial layer comprises a material selected from the group consisting of a plastic film, a thin paper material, and a nonwoven material.

7. The method according to claim 1, wherein the heated pins have a temperature at or above the melting point temperature of the substrate.

8. The method according to claim 1, wherein the step of making holes in the substrate, comprises making through holes in the substrate.

9. The method according to claim 1, wherein the step of making holes in the substrate, comprises making blind holes in the substrate.

10. The method according to claim 9, wherein the step of making blind holes in the substrate comprises making blind holes having a depth in the range of 0.2 mm-6.0 mm.

11. The method according to claim 1, wherein the array of heated pins has a pin density in the range of 3-10 pins per cm.sup.2.

12. The method according to claim 1, wherein the substrate comprises an absorbent foam.

13. The method according to claim 1, wherein the substrate comprises an absorbent nonwoven material.

14. The method according to claim 1, wherein the hot pin perforator includes a roller having a plurality of heated pins mounted on an outer surface thereof.

15. The method according to claim 1, further comprising: providing a supporting surface for the substrate on the opposite sides of the sacrificial layer and the substrate relative to the hot pin perforator, such that the hot pin perforator and the supporting surface form a gap through which the substrate and the sacrificial layer passes.

16. The method according to claim 15, wherein the supporting surface is an outer surface of a counter roller.

17. A wound dressing having a substrate, wherein said wound dressing is manufactured by the method according to claim 1.

18. The wound dressing according to claim 17, wherein the substrate has an open surface area in the range of 0.1-20%.

19. The wound dressing according to claim 17, wherein the substrate comprises an absorbent material.

20. The wound dressing according to claim 19, wherein the absorbent material is selected from the group consisting of a polymeric foam, non-woven material, fibrous material, gel forming fibres, hydrogel, a matrix containing hydrocolloids, woven fibres, and knitted fibres.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0045] For exemplifying purposes, the invention will be described in close detail in the following with reference to embodiments thereof illustrated in the attached drawings, wherein:

[0046] FIG. 1 illustrates a schematic flow chart representation of a manufacturing method in accordance with an embodiment of the present invention;

[0047] FIG. 2A illustrates a schematic cross-sectional view of a system or apparatus for manufacturing a wound dressing in accordance with an embodiment of the present invention;

[0048] FIG. 2B illustrates a schematic cross-sectional view of a system or apparatus for manufacturing a wound dressing in accordance with another embodiment of the present invention;

[0049] FIG. 2C illustrates a schematic cross-sectional view of a system or apparatus for manufacturing a wound dressing in accordance with yet another embodiment of the present invention;

[0050] FIG. 2D illustrates a schematic cross-sectional view of a system or apparatus for manufacturing a wound dressing in accordance with yet another embodiment of the present invention;

[0051] FIG. 3 illustrates a schematic perspective view of a method step for applying a layer of skin adhesive gel onto a proximal surface of a substrate layer, in accordance with an embodiment of the present invention;

[0052] FIG. 4 illustrates a schematic perspective view of a method step for applying a layer of liquid impervious material onto a distal surface of a substrate layer, in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION

[0053] In the following detailed description, some embodiments of the present invention will be described. However, it is to be understood that features of the different embodiments are exchangeable between the embodiments and may be combined in different ways, unless anything else is specifically indicated. Even though in the following description, numerous specific details are set forth to provide a more thorough understanding of the present invention, it will be apparent to one skilled in the art that the present invention may be practiced without these specific details. In other instances, well known constructions or functions are not described in detail, so as not to obscure the present invention.

[0054] FIG. 1 shows a schematic flow chart representation of a method 10 for manufacturing a wound dressing having a substrate 4 in accordance with an embodiment of the present invention. The inventive method is particularly suitable for making holes in open cell absorbent foam materials, thus, the substrate 4 may for example be an absorbent foam material with open pores or cells, such as e.g. a polyurethane foam produced from a composition comprising a prepolymer based on: hexamethylene diisocyante (HDI), toluene diisocyanate (TDI), or methylene diphenyl diisocyanate (MDI). The substrate is preferably selected to have a pore size in the range of 30 m to 1000 m. However, as previously mentioned the absorbent material may also be an absorbent non-woven material such as e.g., poly(vinyl alcohol) fibres, carboxymethyl cellulose (CMC) fibres, or any other equivalent and suitable material.

[0055] The substrate 4 is here in the form of a substrate layer 4 preferably having a thickness in the range of 0.25-10 mm, such as in the range of 2-8 mm, depending on requirements in terms of absorption capacity and flexibility. However, in other embodiments of the invention (not shown), the substrate 4 comprises a first sublayer and a second sublayer. Stated differently, the substrate 4 may comprise a plurality of superimposed sublayers.

[0056] Firstly, a hot pin perforator 2, 2 is provided 11. The hot pin perforator may for example be roller 2 having a plurality of heated pins arranged on an outer surface thereof (may also be called a spiked pin roller 2) as indicated in the leftmost illustration to the right of the box 11. However, the hot pin perforator may also be in the form of a pressing arrangement 2, as indicated in the rightmost illustration next to the box 11. Further, a sacrificial layer 3 of material adapted to be perforated by the heated pins is provided 12. The sacrificial layer 3 is preferably made of a material that has a melting point temperature below the operating temperature of the hot pin perforator 2, 2, i.e. below the temperature of the heated pins. The sacrificial layer 3 may for example be made from nonwoven or plastic film, such as e.g. polyester or polypropylene, alternatively the sacrificial layer may be made from thin paper materials. The sacrificial layer 3 may have a thickness in the range of 50 m to 200 m, or if the sacrificial layer 3 is in the form of a nonwoven or thin paper material the thickness may be in the range of 50 g/m.sup.2 to 200 g/m.sup.2.

[0057] Moving on, holes are made 13 in the substrate 4. In more detail, the holes are made in a piercing operation in which the heated pins 21 of the hot pin perforator 2, 2 are brought in contact with a proximal surface 61 of the substrate 4 and allowed to penetrate into the material, effectively melting a hole into the material. However, the hot pin perforator 2, 2 is arranged such that the heated pins 21 perforate the sacrificial layer 3 before reaching the proximal surface 61 of the substrate 4 (as exemplified in the illustrations to the right of box 13). Although the illustrations in FIG. 1 show an example where the sacrificial layer 3 is provided between the heated pin 21 (i.e. the hot pin perforator) and the substrate 4, other arrangements are feasible and will be further discussed in reference to e.g. FIG. 2B. Furthermore, by having a material in the sacrificial layer 3 that slightly melts upon contact with the heated pins 21, i.e. having a melting point below the operating temperature of the hot pin perforator 2, 2, the perforations made by the heated pins 21 will be distinct and well-defined while the risk of cracks or tears in the sacrificial layer 3 is reduced. Consequently, the amount of residue 101 caught by the sacrificial layer 3 increases, and the efficiency of the manufacturing process and particularly the efficiency of the cleaning of the pins 21 by means of the sacrificial layer 3 is increased. The sacrificial layer 3 preferably has a melting point in the range of 30% to 100% of the temperature of the heated pins 21, i.e. 30% to 100% of the operating temperature of the hot pin perforator 2, 2. For example, if the heated pins have a temperature of 400 C., the sacrificial layer 3 is preferably arranged to have a melting point in the range of 120 C. to 400 C.

[0058] Moreover, the sequence of figures to the right of box 13 illustrate an example of the cleaning process of the heated pins 21. Firstly, a heated pin 21 with contaminating residual material 101 (residues from a preceding hole making operation) is positioned to make a hole in the substrate. Subsequently the pin 21 is moved towards the substrate 4, through the sacrificial layer 3, in order to make a hole in the substrate 4. Finally, the heated pin 21 is retracted whereby a resulting hole is formed in the substrate 4. As indicated in the rightmost illustration, and particularly in the enlarged view 100, the sacrificial layer 3 has collected or scraped off the contaminating residual material 101 from the heated pin 21 during its passage through the sacrificial layer 3. As can also be seen, the heated pin 21 is again contaminated by molten residues from the substrate from the hole making operating (middle illustration). Thus, upon another sequence of making a hole in the substrate, these residues will again be caught by the sacrificial layer 3 when the heated pin 3 perforates an unperforated area of the sacrificial layer 3.

[0059] The resulting holes in the substrate 4 are preferably blind holes, but may in some applications be through holes, where in the latter case the heated pins 21 pass all the way through the layer of absorbent foam material 4. A combination of blind holes and through holes is also conceivable, for example, the heated pins 21 of the hot pin perforator 2 may have different lengths.

[0060] Further the method 10 comprises the optional steps of applying 14 an adhesive layer 32 onto a proximal surface 61 of the substrate 4, and applying 15 a backing layer 33 onto a distal surface 62 of the substrate 4. However, these steps will be further discussed in reference to FIGS. 3 and 4.

[0061] FIG. 2A is a schematic cross-sectional view of a manufacturing apparatus or manufacturing arrangement 1 for manufacturing a wound dressing 50 in accordance with an embodiment of the invention. The manufacturing arrangement 1 comprises a hot pin perforator 2, here in the form of a spiked pin roller, having an array of heated pins 21 arranged on an outer surface thereof. The arrangement 1 further has a set of rolling conveyor elements 22a, 22b, 24 in order to bring the substrate 4 and the sacrificial layer 3 in contact with the heated pin 21 of the hot pin perforator 2. The pins may for example be heated by infrared radiation, suitably arranged heating elements, gas burners, etc. Stated differently, the hot pin perforator may comprise any suitable means for heating the pins. The pin temperature, i.e. the operating temperature of the hot pin perforator 2, may for example be in the range of 200 C. to 600 C., though, the temperature is preferably set in relation to the melting point temperature of the substrate. For example, the temperature of the heated pins 21 may be in the range of 100% to 200% of the melting point temperature of the substrate 4.

[0062] Further, each of the heated pins 21 may have a length in the range of 1 to 15 mm, preferably in the range of 5 to 10 mm, and a diameter in the range of 1 to 5 mm. The heated pins 21 may have a substantially cylindrical shape with a conical or tapering tip. Also, the pin density of the hot pin perforator 2 is in the range of 3-10 pins per cm.sup.2, preferably in the range of 4-8 pins per cm.sup.2, and more preferably in the range of 4-7 pins per cm.sup.2. The pin density of the hot pin perforate 2, 2 and consequently the resulting hole density and open surface area of the substrate is suitably selected in order to control the flexibility of the resulting dressing, i.e. a higher hole density or larger open surface area will result in a more flexible wound dressing.

[0063] In FIG. 2A, the substrate 4 is fed from left to right and in close proximity to the hot pin perforator 2, whereby, due to the rotation of the hot pin perforator 2, the heated pins 21 penetrate into the substrate 4 as indicated in the illustration. The manufacturing arrangement 2 also has a supporting surface 23, here in the form of an outer surface of a counter roller which is included in the conveyor elements 22a, 22b, 24. The counter roller 24 together with the hot pin perforator 2 form a gap through which the substrate 4 passes. The sacrificial layer 3 travels in parallel to the substrate 4, and is also fed, by means of the rolling conveyor elements 22a, 22b, through the gap formed by the hot pin perforator 2 and the counter roller 24. Accordingly, the heated pins 21 first penetrate the sacrificial layer 3 before reaching the proximal surface 61 of the substrate 4. Thus, residues stuck to the heated pins 21 are scraped off when the heated pins pass through the sacrificial layer 3. The sacrificial layer 3 can be discarded after it has been perforated. Preferably, the sacrificial layer is made of a material suitable for recycling, such that it can be molten and re-shaped into a thin sheet or layer in order to be used in the inventive manufacturing method again.

[0064] Further, by providing a supporting surface 23 onto which the substrate 4 is positioned during the hole making operation, the depth of the holes can be controlled by controlling the distance between the hot pin perforator 2 and the supporting surface 3. However, the substrate 4 can, in alternative embodiments, be transported under tension (not shown), the hole making operation then occurs in free space and no supporting surface 23 needs to be used to press the substrate 4 towards the heated pins 21, thereby alleviating the need for a supporting surface 23.

[0065] Even further, the hot pin perforator is preferably arranged to make holes in the substrate at a rate of 1-20 m per minute. The manufacturing rate is biased towards the lower or upper end of the abovementioned range based on the material choice for the substrate. Since the holes are formed in a melting process, a material with a lower melting point can be processed faster, and analogously, a material with a higher melting point requires more time for proper hole formation.

[0066] FIGS. 2B-2D show schematic cross-sectional views of a manufacturing arrangement 1 for manufacturing a wound dressing 50 in accordance with different embodiments of the invention. The operational principle is largely analogous to the one previously described in reference to FIG. 2A, and will for the sake of brevity not be unnecessarily repeated.

[0067] However, in the alternative embodiment illustrated in FIG. 2B, the sacrificial layer 3 is positioned at an opposite side of the spiked pin perforator 2 in reference to the substrate 4. Stated differently, the substrate is arranged to be pierced at a 6 o'clock position relative to the hot pin perforator 2, while the sacrificial layer is arranged to be perforated at a 12 o'clock position relative to the hot pin perforator 2 in the illustrated embodiment of FIG. 2B. Accordingly, after the heated pins 21 of the hot pin perforator 2 have pierced through a portion of the substrate 4 there will be some residues of molten material stuck to the outer surface of the heated pins 21. The heated pins 21 are then subsequently cleaned by perforating the sacrificial layer 3 before reaching the proximal surface 61 of the substrate 4 in the subsequent piercing operation.

[0068] FIG. 2C shows a manufacturing arrangement 1 for manufacturing a wound dressing 50, where the supporting surface comprises a resilient material, such as e.g. a silicone or rubber layer. In more detail, the counter roller 24 has a resilient sheet arranged about its outer surface. Hereby, the risk of damaging the tips of the heated pins 21 during the piercing operation is reduced, particularly in a scenario, where the manufacturing arrangement 1 is configured to make through holes in the substrate 4. In an alternative embodiment (not shown) the supporting surface 23 may be arranged with indentations or recesses into which the heated pins 21 may protrude during the hole making operation.

[0069] In FIG. 2D the manufacturing arrangement 1 comprises a conveyor belt acting as a supporting surface 23. Preferably the conveyor belt comprises a layer of resilient material. The resilient material may for example be a foam material having naturally occurring pores. Similar to the arrangement in FIG. 2C, the conveyor belt yields when the heated pins 21 apply a pressing force onto the first substrate 4 during the piercing operation.

[0070] FIG. 3 shows a schematic perspective view of a two-step sequence illustrating a method step of coating the proximal surface 61 of the substrate 4 with an adhesive layer 32. The substrate 4 is preferably provided with the adhesive layer 32 after it has been provided with an array of holes 40 in a hole making operation. The holes 40 are preferably blind holes with an opening in the proximal surface 61 of the substrate 4.

[0071] In embodiments of the invention, the adhesive layer 32 may comprise a silicone based adhesive, acrylic adhesive, or a pressure-sensitive adhesive (PSA) holtmelt. For example, the silicone based adhesive may be a soft silicone gel adhesive which adhesive is known for its advantageous skin friendly properties as inter alia no or little skin is stripped off when an adhesive layer of soft silicone gel adhesive is removed from a dermal surface. The term silicone gel refers to a silicone gel that comprises a cross-linked network including silicone of lower molecular weight. For example, suitable soft silicone gel adhesives can be composed of an addition-cured RTV (Room Temperature Vulcanizing) silicone system which, after admixture, crosslinks and forms a self-adhesive elastomer. One example of a commercially available RTV addition-cured silicone system is Wacker SilGel 612 which is a two-component system, wherein the softness and degree of adherence of the formed elastomer can be varied by varying the proportions of the two components A:B from 1.0:0.7 to 1.0:1.3. Other examples of silicone based adhesives include inter alia NuSil MED-6340, NuSil MED3-6300 and NuSil MED 12-6300 from NuSil Technology, Carpinteria, Ga., USA, and Dow Corning 7-9800 from Dow Corning Corporation, Midland, USA. Furthermore, the adhesive layer may have a coating weight of from 20 to 300 g/m.sup.2, for example from 50 to 200 g/m.sup.2 such as from 80 to 150 g/m.sup.2.

[0072] The coating operation is in FIG. 3 shown as an application of a transfer paper 31 having a layer of uncured adhesive mixture 34 applied onto the proximal surface 61 of the substrate 4. The transfer paper 31 is, after a curing process, stripped off the proximal surface 61 of the substrate 4, leaving a layer of (cured) adhesive 32 thereon.

[0073] The resulting adhesive layer 32 will have through holes 41 in the corresponding positions as the underlying substrate 4 since the adhesive will be drawn in by capillary action into the holes 40 and partly provide a thin adhesive coating on an inner surface of each hole 40. Stated differently, the adhesive layer 32 will slightly extend into the holes 40 and cover the circumferential rims of the holes 40 without entirely blocking the holes. Curing of the adhesive mixture 34 is preferably carried out in an oven with air in the range of 50 to 200 C. Small amounts of the adhesive substance may remain on the transfer paper 31 on the corresponding positions as the underlying holes 40, 41 as the transfer paper 31 is stripped off.

[0074] Further details of the coating process and alternative methods for applying an adhesive layer onto a substrate of a wound dressing are readily understood by the skilled artisan, and for example disclosed in EP0855921, by the present applicant, incorporated herein by reference.

[0075] Because the adhesive layer 32 will not seal off or close the holes 40, but rather covers a part of the inner walls of each hole 40, more specifically the inner walls of an end portion of the holes that faces the wound when the dressing is worn. Excess wound exudate can still be drawn into the substrate 4 and be retained therein. Similar action will take place in and around any naturally occurring pores that are open up to the proximal surface 61 of the substrate 4 (not shown).

[0076] The thickness of the adhesive layer 32 is preferably in the range of 0.1 to 1.0 mm, excluding any penetration into the substrate 4.

[0077] Moreover, the substrate 4 functions both as an absorbent and as a carrier for the adhesive layer 32, the dressing 50 as a whole will therefore be very soft and pliant. Because the adhesive layer 32 will adhere to the skin surrounding a wound, the dressing 50 will be held firmly in place while the adhesive layer 32 affords a sealing function and prevents maceration, i.e. prevents wound exudate from reaching healthy surrounding skin. The open structure of the adhesive layer 32 and the substrate 4 also enables the skin to breathe.

[0078] FIG. 4 shows a perspective view of a two-step sequence illustrating a method step of coating the distal surface 62 of the substrate 4 with a backing layer 33. In this particular illustration the backing layer 33 is for illustrative purposes shown as being sprayed onto the distal surface 62 of the substrate 4, however, the backing layer 33 may be applied onto the distal surface 62 by e.g. printing, rolling, or similar. More specifically the step of applying a backing layer may include coating the distal surface of the substrate with an (acrylic) adhesive in order to subsequently adhere the backing layer 33 to the substrate 4.

[0079] The backing layer 33 is preferably in the form of a thin liquid impervious, but vapour permeable, film or membrane. This is advantageous in order to provide a wound dressing 50 that has a dry outer surface, and to prevent any wound fluid from leaking out of the dressing 50 during use.

[0080] The backing layer 33 may be in the form of a film, foil, foam, or membrane. The backing layer may be realized to be pervious to water vapour in accordance to DIN 53333 or DIN 54101.

[0081] Preferably, the backing layer 33 may comprise a thermoplastic polymer, for example as a coating, or may consist thereof. A thermoplastic polymer, at first, is to be understood as a polymer that remains thermoplastic if the same is repeatedly heated and cooled within a temperature that is typical for the respective processing or application conditions. Being thermoplastic is understood to be the property of a polymer material to repeatedly soften upon application of heat and to repeatedly harden when cooled down, within a temperature range that is typical for the respective material, wherein the material remains capable of being formed, in the softened stage, and repeatedly, by way of flowing, for example as a shaped article, extruded or otherwise.

[0082] Preferred thermoplastic polymers are polyurethane, polyethylene, polypropylene, polyvinyl chloride, polystyrol, polyether, polyester, polyamide, polycarbonate, polyether polyamide copolymers, polyacrylate, polymethacrylate, and/or polymaleate. Preferably, the thermoplastic polymers are elastomeric. It is particularly preferred that the carrier foil comprises thermoplastic polyurethanes (TPU), or consists thereof. Thermoplastic polyurethanes selected from the group comprising aliphatic polyester polyurethanes, aromatic polyester polyurethanes, aliphatic polyether polyurethanes and/or aromatic polyether polyurethanes are particularly suitable. By using these polymers, it is possible to obtain backing layers 33 as breathable elastic membrane films. These are characterized by high flexibility and elasticity over a broad range of temperatures, also having advantageous sealing properties for (liquid) water while having a high water vapour permeability. These materials are further characterized by low noise, advantageous textile feel, resistance against washing and cleaning, very good chemical and mechanical resistance and the fact they are free of plasticizers.

[0083] Particularly preferred is also a backing layer 33 that acts as a barrier for germs and has a high sealing capability against exudate emanating from the wound while, at the same time, being permeable for water vapour. In order to achieve the same, the backing layer 33 may, for example, be realized as a semipermeable membrane. The backing layer may be a plastic film, for example, comprising or consisting of polyurethane, polyethylene, or polypropylene. In embodiments of the invention, the backing layer is a polyurethane film having a thickness in the range of 5 to 100 m, for example, 10 to 80 m such as 10 to 50 m, preferably from 10 m to 30 m.

[0084] The invention has mainly been described above with reference to specific exemplifying embodiments, many different alterations, modifications and the like will become apparent for those skilled in the art. For example, the dressings may further be sterilized, e.g. by ethylene oxide sterilization or steam sterilization, and is intended to be realized in different shapes and sizes suitable for different types of wounds. Furthermore, the illustrated holes have for the sake of convenience been circular, however, other suitable cross-sectional shapes are feasible, e.g. oval, square, rectangular, etc. Moreover, different substances, such as e.g. active carbon, silver, different salts, bactericides, etc., may be mixed into the substrate in order to achieve a desired pharmacological effect. The word comprising does not exclude the presence of other elements or steps than those listed in the claim. The word a or an preceding an element does not exclude the presence of a plurality of such elements.