Wound dressing and method for manufacturing the same

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WO 2005/034797 PCT/US2004/025594

WOUND DRESSING AND METHOD FOR MANUFACTURING THE SAME

BACKGROUND

Historically, many diverse materials of various origins have been used to treat wounds by absorbing wound fluids and tissue, hereinafter generally referred to as exudate, from a wound site with some type of absorbent material. In recent years, use of polymeric-based wound care products have become increasingly popular to control wound site environmental factors such as water vapor, oxygen permeability, bacterial impermeability, and absorption of exudate. Such wound care products are tailored to meet specific requirements including conformability to a body portion, selective adherence to a wound bed, and adhesiveness to the skin surrounding the wound site.

Recently, occlusive or moisture-retentive dressings have gained increasing acceptance in treating wounds, in particular pressure sores and ulcers. A wide variety of types of structures are known in the art for use in or as occlusive dressings and generally comprise components for receiving, absorbing and retaining exudate. Typically, these wound care products include polymeric foams, polymeric films, particulate and fibrous polymers, hydrogels and hydrocolloids. Dressings with at least one of these components promote wound healing by providing a moist environment, while removing excess exudate and toxic components, and further serve as a barrier to protect the wound from secondary bacterial infection. While these known occlusive wound dressings can effectively manage a wound, many have been found to possess certain limitations or disadvantages.

Developments in the field of siliconé manufacturing have led Ossur hf of Reykjavik, Iceland, and assignee of the present invention, to produce silicone products adapted for skin contact that provide superb softness, and gentle skin contact. In particular, such silicone manufacturing has led to advances in improved comfort and cushioning of prosthetic suspension liners that have excellent durability and intimacy using proprietary silicone technology of Ossur hf. It has been found that by applying the silicone

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WO 2005/034797 PCT/US2004/025594 technology of Ossur hf to produce a discrete ultra-thin, perforated tacky silicone sheet, a silicone adhesive layer can be produced that possesses superior gentle adherence to wound sites while not damaging skin and the wound bed due to single or repeated removal of the silicone layer.

While a wound dressing having an absorbent core with a silicone adhesive layer provides gentle adhesion to the wound and the surrounding skin, there are many instances where it is required that the wound dressing has greater tackiness in outer lying regions bordering the wound. Difficulties arise in that there must be a balance of gentle adhesion at the wound site and adjacent areas of skin so as to avoid disrupting the wound, while still providing sufficient adhesion of the dressing to accommodate movement of a patient or at wound sites difficult to maintain adhesion.

Efforts have been made to apply a wound dressing having a silicone adhesive layer with sufficient gentle adhesive properties to a wound and further secured to the outer lying skin by the application of medical tape over the wound dressing. While this has proven effective at maintaining a wound dressing on a patient’s body, more time and care is required to apply the wound dressing. Furthermore, the adhesive on the medical tape may be too tacky and irritate the skin upon which it is applied during application and removal thereof.

Despite the ready availability of medical tape, it is desirable to provide a wound dressing that possesses the adherence capabilities of medical tape in a stand alone form yet gentle to the shin.

From a standpoint of ease of application and comfort to a patient, it is desirable that a wound dressing include different areas of adhesion, wherein an adhesive layer disposed on the absorbent core has gentle skin adherence while a portion of the wound dressing bordering the absorbent core has greater skin adherence. Thus, with such a wound dressing, the need for medical tape is mitigated and the wound dressing can be applied in a simpler fashion without discomfort to a patient.

For the foregoing reasons, there is a demand for an improved wound dressing which prevents wound trauma upon wound dressing changes,

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WO 2005/034797 PCT/US2004/025594 improves the durability and lifetime of the wound dressing, anatomically conforms to a wound, possesses improved fluid uptake, retention and removal properties, and can be securely maintained on a patient’s body. It. is thus desired to produce a wound dressing having an adhesive layer that does not possess the drawbacks of known adhesive layers, and instead, gently adheres and detaches from a wound site while providing superior fluid uptake. Moreover, there is a demand for a wound dressing that includes adhesive means having greater skin adherence than an adhesive layer disposed over a wound.

SUMMARY

The present invention is directed to an improved wound dressing possessing superior skin adherence capabilities. In an embodiment of the wound dressing, the dressing includes a backing layer defining opposed proximal and distal surfaces including a center portion and a border portion, and an absorbent core having proximal and distal surfaces. A carrier layer is secured to the proximal surface of the border portion of the backing layer and defines an opening that surrounds the center portion of the backing layer. A first skin adherent facing layer is secured to a proximal surface of the carrier layer and generally corresponds to the border portion of the backing layer. A distal surface of an absorbent core is secured to the proximal surface of the center portion of the backing layer and extends through the opening of the carrier layer. A second skin adherent facing layer is secured to a proximal surface of the absorbent core.

According to one embodiment, the first facing layer has greater skin adhesive properties than the second facing layer. In this embodiment, the second facing layer is a discrete layer of silicone gel having a plurality of through extending apertures arranged in a pattern. The first facing layer is an imperforate layer of silicone gel, and may be applied to the backing layer with or without the aforementioned carrier layer as a reinforcement element. An advantage to this embodiment is that the dressing can provide greater adhesion to outlying areas of a wound while still maintaining gentle contact to

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WO 2005/034797 PCT/US2004/025594 the wound itself. Moreover, by using a carrier layer, the border portion of the wound dressing is reinforced and can be placed onto skin in greater tension without tearing the backing layer.

According to yet another embodiment, the backing layer defines contoured peripheral edges wherein the absorbent core has corresponding contoured peripheral edges generally corresponding in shape to the contoured shape of the backing layer. In a variant of this embodiment, the peripheral edges of both the backing layer and absorbent core define a substantially non-linear profile. An advantage to this embodiment lies in that the wound dressing may be configured to be particularly applied to various body parts, thereby assuring greater adherence to skin and more aptly absorbing wound exudate. Due to the border portion of the dressing, this embodiment is advantageous since it is configured to respond to the movement of a body part, thereby reducing the likelihood of the dressing being pulled or loosening from the skin due to such movement.

According to yet another embodiment, the combination of the backing and carrier layers defines a plurality of pleats, and the center portion of the backing layer has a generally planar configuration. In a variant of this embodiment, the pleats generally taper from the peripheral outer edges of the backing layer to the boundary between the center portion and border portion of the backing layer. Similar to, the contoured dressing embodiment, the pleats of this embodiment are advantageous in that they reduce the magnitude of tensile forces created in the border portion of the dressing in response to body movement, and thereby reduce the likelihood of the dressing being pulled or loosening from the skin due to such movement.

According to yet another embodiment, the backing and carrier layers define an undulating profile in the areas of the border portion of the dressing, and the central portion of the dressing is substantially planar. The corrugations are defined as parallel rows having a generally undulating form. This embodiment is advantageous in that the backing and carrier layers are stretchable over outlying areas of the wound and thereby provide greater tension of the dressing against the skin. Moreover, this embodiment accommodates movement and swelling of the wound area.

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According to yet another embodiment of the dressing, the absorbent core has an undulating profile and the backing layer closely adheres to the distal surface of the absorbent core. In a variant of this embodiment, the dressing includes a plurality of discrete hydrophilic particles enmeshed in the absorbent core. Furthermore, the border portion in a variant of this dressing may remain in a substantially planar configuration. This embodiment is particularly advantageous when the dressing is to be placed on an exuding joint wound so as to accommodate for movement and swelling of the wound area itself while being secured to the outlying areas of the wound.

Also provided are methods of manufacturing the embodiments of the wound dressing of the invention. According to one method, the method for manufacturing a wound dressing comprises the steps of providing a carrier layer having first and second surfaces, applying a first skin adherent facing layer onto the carrier layer, removing a center portion of the carrier layer to define an opening in the carrier layer, inserting an absorbent core having first and second surfaces within the opening of the carrier layer and securing a first surface of the backing layer having first and second surfaces over the second surface of the absorbent core and the second surface of the carrier layer.

In conjunction with the methods of manufacturing the embodiments of the wound dressing, numerous methods may be employed to secure the backing layer to the carrier layer and the absorbent core. According to one method a platen is provided which has a generally planar border region and a recessed center region relative to the border region that generally corresponds to the shape of the absorbent core. The platen is heated to an elevated temperature sufficient to thermal bond the carrier and backing layers, and secures the backing layer to the absorbent core. The platen is subsequently urged against the second surface of the backing layer to generate pressure thereon, the pressure being sufficient to substantially cause thermal bonding of the backing and carrier layers. The platen is then removed from the second surface of the backing layer after the first surface of the backing layer has thermal bonded to the second surface of the carrier layer and a portion of the absorbent core.

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BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where:

FIG. 1 is perspective view showing an embodiment of a wound dressing;

FIG. 2 is a sectional view of the wound dressing in FIG. 1 taken along line ll-ll;

FIG. 3 is a top plan view of the wound dressing in FIG. 1;

FIG. 4 is a bottom plan view of the wound dressing in FIG. 1 ;

FIG. 5 is a bottom plan view of an embodiment of a wound dressing;

FIG. 6 is a sectional view of the wound dressing in FIG. 5 taken along line VI-VI;

FIG. 7 is a top plan view of an embodiment of a wound dressing having contoured peripheral edges;

FIG. 8 is a top plan view of an embodiment of a wound dressing having contoured peripheral edges;

FIG. 9 is a top plan view of an embodiment of a wound dressing having contoured peripheral edges;

FIG. 10 is a perspective view of an embodiment of a wound dressing having a pleated border portion;

FIG. 11 is a sectional view of the wound dressing in FIG. 10 taken along line XI-XI;

FIG. 12 is a perspective view of an embodiment of a wound dressing having a border portion with an undulating profile;

FIG. 13 is a sectional view of the wound dressing in FIG. 12 taken along line XIII-XIII;

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FIG. 14 is a perspective view of an embodiment of a wound dressing with an absorbent core with an undulating profile;

FIG. 15 is a sectional view of the wound dressing in FIG. 14 taken along line XV-XV;

FIG. 16 is a schematic view showing a process for making features of a wound dressing; and

I

FIG. 17 is a schematic view showing a process for making features of a wound dressing.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

A. Overview

A better understanding of different embodiments of the invention may be had from the following description read in conjunction with the accompanying drawings in which like reference characters refer to like elements.

While the disclosure is susceptible to various modifications and alternative constructions, certain illustrative embodiments thereof are shown in the drawings and will be described below in detail. It should be understood, however, that there is no intention to limit the disclosure to the specific embodiments disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, combinations, and equivalents falling within the spirit and scope of the disclosure and defined by the appended claims.

It will be understood that, unless a term is expressly defined in this patent to possess a described meaning, there is no intent to limit the meaning of such term, either expressly or indirectly, beyond its plain or ordinary meaning.

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B. Environment and Context of Embodiments

Various embodiments of the invention are provided to variously be used to absorb exudate, combat odor and infection, relieve pain, wound cleanse and maintain a moist environment at a wound surface to facilitate healing of the wound. The embodiments of the invention are particularly configured to absorb exudate or wound fluid and may therefore be suitable for application for a variety of different wound types.

The various embodiments are conformable to a variety of locations on a living body, and may be dimensioned to accommodate different types and sizes of wounds. Moreover, the adhesive properties may be modified according to the location and type of wound to be treated while taking into consideration the potential for the dressing to cause sensitivity reactions, the ease of application and removal including the production of pain and trauma to wound surfaces, and the interval between wound dressing changes.

Thus, it is to be clearly understood that the various embodiments of the wound dressing according to invention may be made in any desired sizes and shapes, for example in various standardized sizes and shapes, for use over any afflicted portion of a human or other living body.

While features are shown in the drawing figures that are not described in detail in the description that follows, a detailed description of such features is found in U.S. Patent 7,696,400.

C. Various Embodiments of the Wound Dressing

As shown in FIG. 1, an embodiment of a wound dressing 20 includes a liquid impervious, vapor permeable backing layer 22 having proximal (first) and distal (second) surfaces. The backing layer 22 defines a center portion 32, and a border portion 34 surrounding the center portion 32. A carrier layer 26 is provided which has proximal and distal surfaces wherein the distal surface of the carrier layer 26 is secured to the proximal surface of the border portion 34 of the backing layer 22 and borders the center portion 32. A first skin adherent facing layer 28 is secured to the proximal side of the carrier layer 26.

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The carrier layer 26 defines an opening corresponding to the center portion 32 of the backing layer 22, and substantially outlines the border portion 34.

As exemplified in FIGS. 2 and 3, an absorbent core 24 is secured to the proximal surface of the center portion 32 of the backing layer 22. The absorbent core 24 is positioned on the backing layer 22 such that the absorbent core 24 extends through the opening of the carrier layer 26. A second skin adherent facing layer 36 is disposed along a proximal surface of the absorbent core 24. According to this embodiment, the first facing layer 28 has greater skin adherence properties than the second facing layer 36.

In the embodiment shown in FIGS. 1-4, the backing layer 22 is thermal bonded to the carrier layer 26, and at least portions of the backing layer 22 are secured to the distal surface of the absorbent core 24. Moreover, the backing layer 22 may be thermal bonded to the absorbent core 24 at a boundary region 30 near or at the peripheral edges of the proximal surface thereof. By thermal bonding the absorbent core 24 to the backing layer 22, a seal may be formed along the regions of bonding. A bevel may also be defined near the peripheral edges of the absorbent core to gradually reduce stresses of the absorbent core as it absorbs wound exudate and to minimize imprints on skin of a wearer.

It will be understood that the backing layer may be secured to the carrier layer and the absorbent core in any manner known to one skilled in the art of wound dressings, and any such methods are within the scope of this application. Such other methods include using an adhesive, pressure molding, or mechanical fixation with elements such as stitches, pins or staples.

Preferably, the first facing layer 28 is a silicone gel coated onto the carrier layer 26, and the second facing layer 36 is a discrete sheet of silicone gel directly secured to the absorbent core 24. As shown more fully in FIG.4, the second facing layer 36 includes a plurality of apertures 38 that are preferably arranged in a predetermined pattern such that they are equally spaced from one another and possess a generally uniform size and shape.

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While the first facing layer 28 is shown in FIG. 4 as not including apertures, the first facing layer 28 may be configured to include a plurality of apertures in a similar formation as those described above in reference to the second facing layer 26. Furthermore, alternative embodiments regarding the pattern, configuration and dimension of the apertures of the facing layers is provided in U.S. Patent 7,696,400.

FIGS. 5 and 6 show another embodiment of the wound dressing including a backing layer 23 having proximal and distal surfaces. The backing layer defines a center portion 39 and a border portion 41 surrounding the center portion 39. A first skin adherent facing layer 29 is secured to the proximal surface of the backing layer 23. The first facing layer 29 defines a plurality of apertures 31.

A substantially planar distal surface, of an absorbent core 25 is secured to the proximal surface of the center portion 39 of the backing layer 23. A second skin adherent facing layer 33 is secured to a proximal surface of the absorbent core 25. The second facing layer 33 defines a plurality of apertures 35 arranged in a pattern. A boundary 37 delimits the first and second facing layers 29, 33, and distinguishes the center and border portions 39, 41 of the dressing

In addition to the basic footprint or configuration of the wound dressing exemplified in FIGS. 1-4, other configurations are possible and are fully within the scope of the present invention. FIGS. 7-9 show exemplary wound dressing embodiments generally having the same backing layer and absorbent core relationship as in the wound dressing of FIG. 1. In each of the embodiments, the backing layer defines contoured outer edges and the absorbent core has contoured outer edges generally corresponding in shape to the contoured outer edges of the backing layer.

FIG. 7 illustrates a dressing 40 having a backing layer 42 and an absorbent core 44 each with a generally elongate profile such that the outer edges 46, 48 of both the backing layer 42 and the absorbent core 44 are concave and convex at certain portions thereof. FIG. 8 shows another embodiment of a dressing 50 wherein a backing layer 52 and an absorbent

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WO 2005/034797 PCT/US2004/025594 core 54 each have generally equal length outer sides 56, 58 that are both concave and convex. FIG. 9 shows yet another embodiment of a dressing 60 wherein the backing layer 62 and the absorbent core 64 have peripheral edges 66, 68 that are generally circular and concentric with one another.

Turning to FIGS. 10 and 11, another embodiment of a wound dressing 70 is shown having a center portion 90 and a border portion 92. In the dressing 70, a proximal surface of a backing layer 72 is secured to a distal surface of an absorbent core 74 wherein a boundary 80 generally defined as the peripheral edges of the absorbent core 74 delimits the center portion 90 and border portion 92 of the dressing 70. A distal surface of a carrier layer 76 is secured to the proximal surface of the backing layer 72 and has an opening that generally surrounds the absorbent core 74, whereby the carrier layer 76 is associated with the border portion 92 and the absorbent core 74 is associated with the center portion 90 of the dressing 70. A first facing layer 78 is secured to the proximal surface of the carrier layer 76. A second facing layer 86 is secured to the proximal surface of the absorbent core 74 and defines a plurality of apertures 88. _t

In observing FIG. 11, the border portion 92 of the backing layer 72 defines a plurality of pleats 82 that extend from the peripheral edge 84 of the backing layer 72, and have a taper 86 that leads from the edge 84 towards the boundary 80. The pleats 82 are generally arranged around the border portion 92 of the dressing 70 and extend towards the center portion 90. The pleats 82 are equally formed by the carrier layer 76 and the first facing layer 78 as these layers generally follow the contours of the backing layer 72 within the border portion 92 thereof.

According to variations of this embodiment, the pleats may not include a taper and, moreover, the backing layer may comprise at least two discrete portions whereby each portion corresponds to a center portion and a border portion of the dressing. Such two backing layer portions may be joined at the boundary between the center and border portions of the dressing.

As illustrated in FIGS. 12 and 13, another embodiment of a wound dressing 93 is shown having a center portion 111 and a border portion 113.

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In the dressing 93, a proximal surface of a backing layer 95 is secured to a distal surface of an absorbent core 97 wherein a boundary 101 generally defined as the peripheral edges of the absorbent core 97 delimits the center and border portions 111, 113 of the dressing 93. A distal surface of a carrier layer 115 is secured to the proximal surface of the backing layer 95 and has an opening that generally surrounds the absorbent core 97, whereby the carrier layer 115 is associated with the border portion 113 and the absorbent core 97 is associated with the center portion 111 of the dressing 93. A first facing layer 99 is secured to the proximal surface of the carrier layer 115. A second facing layer 107 is secured to the proximal surface of the absorbent core 97 and defines a plurality of apertures 109.

In observing FIG. 13, the border portion 113 of the backing layer 95 has an undulating profile comprising alternating ridges 103 and grooves 105. In this embodiment, the ridges 103 and grooves are generally in a parallel arrangement and laterally extend across the width of the dressing 93. The ridges 103 and grooves 105 are equally formed by the carrier layer 115 and the first facing layer 99, and these layers generally follow the contours of the backing layer 95 within the border portion 113 of the dressing 93.

According to variations of this embodiment, the undulating profile may extend across or in portions along the border and center portions of the dressing. Moreover, the pitch and depth of the ridges and grooves may be modified as deemed necessary to provide capabilities such as a desired stretchability of the dressing. Moreover, the cross-section of the ridges and grooves may also be modified as considered necessary to provide optimum stretchability, absorbency and skin adhesion.

As illustrated in FIGS. 14 and 15, another embodiment of a wound dressing 110 is shown having a center portion 132 and a border portion 134. In the dressing 110, a proximal surface of a backing layer 112 is secured to a distal surface of an absorbent core 114 wherein a boundary 120 generally defined as the peripheral edges of the absorbent core 114 delimits the center and border portions 132, 134 of the dressing 110. A distal surface of a carrier layer 116 is secured to the proximal surface of the backing layer 112 and has an opening that generally surrounds the absorbent core 114, whereby the

CA 02539945 2012-06-08 carrier layer 116 is associated with the border portion 134 and the absorbent core 114 is associated with the center portion 132 of the dressing 110. A first facing layer 118 is secured to the proximal surface of the carrier layer 116. A second facing layer 126 is secured to the proximal surface of the absorbent core 114 and defines a plurality of apertures 128.

In observing FIG. 15, the absorbent core 114 has an undulating profile comprising of alternating ridges 122 and grooves 124. In this embodiment, the ridges 122 and grooves 124 are generally in a parallel arrangement and laterally extend across the width of the absorbent core 114. As shown, the side portion 125 of the ridges 122 and grooves 124 is generally tapered to provide features such as greater conformability and absorption. The absorbent core 114 includes a plurality of hydrophilic particles 130 enmeshed therein, as explained in greater detail in U.S. Patent 7,696,400.

Variations of the embodiment shown in FIGS. 14 and 15 are possible in that the undulating profile may be modified according to a desirable configuration. For example, the ridges and grooves may be increased or decreased, and the cross-sectional profile of the ridges and grooves can be modified as considered necessary to provide features such as improved stretchability, absorbency and skin adherence.

The facing layers used in each of the embodiments of the present invention are preferably hydrophobic, and liquid and moisture impervious layers that are bonded to the proximal surface either the carrier layer or absorbent core. In a preferred embodiment, the facing layers comprise a cross-linked silicone elastomer gel, such as, for example, a cross-linked silicone (polydimethyl siloxane gel) manufactured by NuSil Technology (Carpenteria, CA) under product designations MED-6340 or MED-6345 which is tackier than MED-6340. Preferably, the first facing layer comprises silicone gel under product designation MED-6345 and the second facing layer comprises silicone gel under product designation MED-6340.

According to the preferred embodiment, the method used to evaluate adhesion between the different facing layers is to measure the force needed to peel a 25 mm wide sample comprising a silicone gel layer from a stainless

CA 02539945 2012-06-08 steel plate. The differences in the force (measured in N/25 mm) used to remove the sample indicate the difference in the skin adhesion. In the embodiments of the facing layers described herein, the adhesion level on stainless steel of the facing layers are as follows: border portion (first facing layer: 1-3 N/25mm) and center portion (second facing layer: 0.1-0.3 N/25mm). It will be noted, however, that the adhesion levels described herein are only exemplary and may be modified according to desired adhesion levels.

In alternative variations, the facing layers may comprise a pressure sensitive adhesive known to those skilled in the art of adhesives and wound dressings and described in U.S. Patent 7,696,400. Moreover, the first facing layer may be provided with or without apertures, such as those defined by the second facing layer in each of the embodiments particularly described herein.

The facing layers preferably have a thickness in the range of 0.05 mm to 0.5 mm, and more preferably 0.1 mm. The conformability of the dressing to the wound is somewhat dependent on thickness of the components, such that when the dressing is applied to a body portion, it conforms to the surface even when the surface is moved. When the surface is flexed and then returned to an un-flexed position, the facing layer stretches to accommodate the flexation of the joint but is resilient enough to continue to conform to the surface when the surface is returned to its unflexed condition.

The preferred embodiments for the backing and carrier layers is a thin polymeric elastic or flexible film coating providing a bacterial barrier formed from a water vapor permeable pliable elastomer material. The film is continuous in that it has no perforations or pores which extend through the thickness of the film. Films of this type are known and generally are hydrophilic polymeric materials through which water vapor is capable of diffusing.

The backing layer is bonded to the distal surface of the absorbent core, and in a preferred embodiment, the backing layer is bonded only to the distal surface of the absorbent core and does not penetrate any pores, cells or cavities therein. Generally, the film used for the backing and carrier layers is

CA 02539945 2006-03-13 cells or cavities therein. Generally, the film used for the backing and carrier layers is 15 to 45 micrometers in thickness, with a preferred thickness of about 30 micrometers for the backing layer. For the carrier layer, the film may have the same thickness as in the backing layer. It is preferred, however, that the carrier layer possess a greater stiffness than the backing layer so as to provide greater control of applying the border portion of the dressing on skin and preventing curling, wrinkling or sticking of parts of the first facing layer to each other upon repeated application and removal of the dressing.

The backing layer may comprise polyurethane, such as a polyurethane film available from InteliCoat Technologies (South Hadley, MA) under product designation INSPIRE, elastomeric polyester, blends of polyurethane and polyester, polyvinyl chloride, and polyether-amide block copolymer. The preferred backing layer for use in the embodiments described herein is a polyurethane film since it exhibits a resilient property that allows the film to have good conformability and further has a high degree of stretchability.

The backing layer may be at least translucent, or sufficiently transparent so that the wound site to which the dressing is applied can be viewed through the dressing. It is advantageous to view the wound and healing thereof without removal of the dressing so as to avoid unnecessary handling of the dressing and exposure of the wound to the environment, and to reduce the likelihood of contamination.

The preferred carrier layer is a polyurethane film (such as Inspire 2301 from InteliCoat Technologies) that can be thermal bonded to the backing layer. Alternatively, other films, foams and mesh substrates may be employed that can be thermal bonded to the backing layer, or secured to the backing layer by other methods including the use of adhesives, stitching, pins, and staples. Preferably, the carrier layer should be sufficiently stiff so as to reinforce the border portion of the backing layer.

Suitable continuous conformable backing layers have a moisture vapor transmission rate (MVTR) of the backing layer alone of 1,500 to

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The backing layer thickness is preferably in the range of 10 to 1,000 micrometers, more preferably 10 to 100 micrometers.

Suitable continuous conformable carrier layers have a moisture vapor transmission rate (MVTR) of the carrier layer alone of 1,500 to 14,600 g/m^A2 /24 hrs, preferably 2000-3000 g/m^A2 /24 hrs at 38°C. The carrier layer thickness is preferably in the range of 20 -100 micrometers, more preferably 80 micrometers.

The absorbent core may be selected from a variety of different types known within the art of wound dressings, and the construction thereof may be configured in a variety of different arrangements as discussed more fully in U.S. Patent 7,696,400.

Numerous methods of manufacturing may be employed to make the embodiments of the wound dressing described herein. According to one method exemplified in FIGS. 16 and 17, the method for manufacturing a wound dressing comprises the steps of providing a carrier layer 202 having removable paper 204 thereon dispensed from a carrier layer roll 206. The carrier layer 202 is transported and a surface treatment substance 208 is applied on a proximal surface of the carrier layer 202. Preferably, the substance 208 is permitted to remain on the carrier layer 202 for approximately 30 minutes and maintained at 25 °C prior to the next step of the method to allow for any solvents in the primer to evaporate.

A suitable surface treatment substance includes silicone primers, such as those discussed more fully in U.S. Patent 7,696,400.

Next, a layer of an uncured silicone gel 210 is extruded onto the proximal surface of the carrier layer 202 over the substance 208. The carrier layer 202 with the uncured silicone gel layer 210 is transported over a drum 212 having a surface temperature of approximately 130 °C and maintained on the drum 212 for approximately 20 minutes. The drum 212 may be coated with any suitable release agent, such as Teflon, that will prevent adherence of the silicone gel 210 after curing thereof.

After the silicone gel layer 210 has cured and the carrier layer 202 is removed from the drum 212, a die cutter 216 is used to remove a center

CA 02539945 2012-06-08 portion from the carrier layer 202. The removal of a center portion of the carrier layer 202 effectively forms an opening 222 through the carrier layer 202 and the cured silicone gel layer 210. Subsequently, the carrier layer paper 204 is removed from the distal surface of the carrier layer 202 onto a roll 220. A release paper or film 218 is applied to the proximal surface of the silicone gel layer 210.

As shown in FIG. 17, an absorbent core 224 is inserted within the opening 222 of the carrier layer 202 and the layer of silicone gel 210. A second facing layer 226 is provided on a proximal surface of the absorbent core 224. The second facing layer 226 is preferably an apertured discrete layer of silicone gel. Methods for making the apertured second facing layer 226 are discussed more fully in U.S. Patent 7,696,400.

According to the method exemplified in FIG. 17, a backing layer 228 is disposed over the distal surfaces of the carrier layer 202 and absorbent core 224. A platen 230 is provided as having a generally planar border region 232 and a recessed center region 234 relative to the planar border region 232 that generally corresponds to the shape of the absorbent core 224. The platen 230 is preferably heated to an elevated temperature suitable to thermal bond the backing layer 228 and the carrier layer 202 to one another and secure the absorbent core 224 thereon.

The platen 230 is urged against the distal surface of the backing layer 228 to generate pressure thereon sufficient to substantially cause thermal bonding of the backing layer 228 to the carrier layer 202. After a period of time sufficient to thermal bond the backing layer 228 to the carrier layer 202 and to at least portions of the absorbent core 224, the platen 230 is removed from the distal surface of the backing layer 228.

Subsequent to the thermal bonding of the backing layer 228 to the carrier layer 202 and the absorbent core 224, the wound dressing is cut to size with a die cutter 236.

In variations of the described method, the platen 230 may be modified to impart the pleated or undulating profile of the embodiments of the wound dressing described herein. Alternatively, other platen systems may be used

CA 02539945 2012-06-08 after the backing layer is secured to the carrier layer that has the pleated or undulating profiles. Such platen systems may include mutually opposed platens having the impression of the different bordered profiles described herein, and which are suitably heated to impart the aforementioned bordered profiles.

Suitable platens or die cutters may be employed that impart the undulating profile of the absorbent core described herein. Moreover, the undulating profile may be formed by methods including cutting the absorbent core, forming the absorbent core, and molding the absorbent core in the configuration described herein. Such configuration of the absorbent core is preferably achieved prior to the application of the backing layer. Moreover, the impregnation of the hydrophilic particles in the absorbent core mav be accomplished as discussed more fully in U.S. Patent 7,696,400, and is performed prior to the application of the backing layer.

Methods for applying the apertured facing layer onto the absorbent core are described more fully in U.S. Patent 7,696,400.