CA2092704A1 - Bilayer wound dressing - Google Patents

Abstract

A skin covering material, e.g. for covering wounds, burns and the like, to protect them during the healing process, includes a tacky polymer complex layer (24) for adhesively contacting the skin, and a water vapour-permeable backing layer (22, 26) carrying the polymer. The polymer complex is produced by mixing together solutions of two hydrophilic polymers which are coprecipitatable, when mixed together, to form a water-insoluble complex. An example of a pair of such polymers is polyacrylic acid and polyethylene oxide. The assembly is suitably packaged in a sealed pouch (13) with high barrier properties towards water vapour and containing an atmosphere of high humidity.

Description

W092/049~3 PCT/CA91/00327 ~ 9 2 7 0 ~
This invention relates to wound coverings, of the type commonly applied adhesively to minor cuts, burns, post-operative incision sites and wounds. ~ore particular-ly, the invention relates to adhesive bandages or patches which ar~ applied domestically to cover and protect such wounds, by adhesion to the wound itself or to its periph-ery~ The best known examples of such adhesive patches are those sold under the names BAND-AID (trade-mar~ of Johnson & Johnson, Inc.), ELASTOPLAST (trade-mark of Smith & Nephew Limited) and HANSAPLAST (txade-mark of Beiersdorf A.G.).

These familiar s~rip bandages commonly comprise a patch of sterile gauze mounted on a plastic or fabric strip, with an adhesive coating for attachment to the skin.
The gauze may be covered with a perforated plastic strip, to prevent adhesion of the gauze to the wound surface. It is known also to incorporate medicaments such as antisep-tics in the gauze patches thereof.
'~,, Although simple, convenient and generally effec-tive in their use on the household or domestic scale, the commonly available strip bandages have certain disadvan-tages. For example, frequent and sometimes painful changes of such bandages are necessary in order to check the healing process and apply medications. In many cases moisture cannot adequately escape through them, so that the tissue swells and healing is retarded. When the wound site is washed, the bandage may be removed or loosened. When it is wetted, a retained water layer in the fibrous material favours microbial growth and swelling of the tissue.
Application to highly contoured parts of the body is difficult.
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An important factor in the wound healing process ;~ is the maintenance of an appropriately moist environment around the wound site. Wound coverings~which may protect ` the wound site from contamination, or which promote drying ,~
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wo92/n4923 PCT/CA91/003V

2~927 ~ 2 -and scab formation, are not totally satisfactory. The healing process is ~etter promoted by contact of the wound with an appropriately moisture controlled atmosphere, as well as protection of the wound from contamination.

U,S. Patent 4,750.482 (SieverdingL discloses a water-insoluble, hydrophilic, pressure-sensitive adhesive useful for attaching electrodes and wound dressings and the like to mammalian tissue. The adhesiYe composition ; includPs an irradiation crosslinked synthetia organic polymer formed from a solution or dispersion of at least one gel-forming, uncrosslinked synthetic organic polymer, in the solubilizing plasticizer. On irradiation crosslink-ing, a gel is ~ormed which retains a solubilizing plasticizer within the three dimensional network. Poly-acrylic acid admixed with polyethylene oxidet in the weight ratio of 14:1, is given as one example of an uncrosslinked synthetic organic polymer suitable for subsequent irradi-~ ation crosslinking. The solubilizing plasticizer includes a non-volatile elasticizer, which is generally a liquid at room temperature.

! C~a~ian ~ent 1 180,244 ~Muchin) discloses a medical covering for adhesive fixing to a subject, and comprising a stretchable film sheet of polyurethane or other copolymer material carrying an adhesive on one surface, and an unstretchable, rigid film sheet carrier on the oppo~ed surface, removable from the stretcha~le sheet after adhesive application of the assemblv to a patient.
The adhesive is of conventional form.
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U.S. Patent 3 419.006 (Kin~) discloses a polyethylene oxide polymer complex dressing. The polymer complexes disclosed have a very high water content.
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W092tO4923 PCT/CA91/00327 _ 3 ~ 27~ :

An object o~ the present invention is to provide novel skin and wound coverings employing polymer complexes as skin and wound contacting material.
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The present invPntion provides a novel adhesive covering for application to skin lesions (this term being understood to cover cuts, burns, abrasions, lesions due to skin infection or skin disorder, post-operative incision sites and other skin damaged or skin punctured locations~
as well as bruised areas and skin locations overlying damaged or inflamed tissues, bruised bones or muscles which can when appropriate be applied at the domestic or housa-hold level. The adhesive covering according to this invention has a water vapour permeable self-supporting outer backing layer and a wound contacting layer of biocom-patib~e high water content polymer complex capable of adhering to the wound site, and supported by the backing layer. It has been found according to the present inven-tion that biocompatible, wound and skin adhesive polymer complexes as described herein, in combination with an appropriate backing layer, provide a highly satisfactory, controlled-moisture environment for the promotion of healing of skin lesions.

The polymer complexes used as the skin lesion-contacting layer in the products of the present invention are tack~, solid or semi-solid materials. In order for them to be skin adherent, they typically have a water content of from about 20 - 70% by weight. The complexes are swellable in water but essentially water-insoluble.
They are prepared by coprecipitation from mixed solutions, preferably aqueous solutions, of a~ least two hydrophillic polymers, followed by removal of the coprecipitate from the medium, op~ionally followed by adjustment of the residual water content of the coprecipitate. The polymer complexes lose substantial amounts of water when exposed to a normal , : .

W092~0~923 PCT/CA91/003~7 '~09'~7~4 - 4 - ;

room environment, but this is essentially rev~rsible upon immersion in wa~er or exposure to very high humidity. The polymer complexes are inter-reacted products of the indi-vidual polymers in the sense that they are not physically separable into ~heir individual polymeric constituents, but are essentially chemically non-crosslinked. Tac~iness of them is increased by moistening.

Thus according to one aspect of the present invention, there is provided an adhesive covering suitable for adhesive attachment to mammalian tissue for contacting treatment areas thereof, and comprising:

an outer layer of self-supporting, water vapour permeable film;

an inner, treatment-area contacting layer of high water content, tacky polymer complex supported by the outer layer;

the polymer complex layer composition being substantially wound- and skin-compatible, having a water content sufficient to render it skin-adhesive, and compris-ing the tacky, polymer complex product produced by copreci-pitation as a result of mixing solutions of first and second coprecipitatable hydrophilic polymers, and optional-ly ad;usting the water content thereof.
According to another aspect of the invention, there is provided a process for making an adhesive covering material suitable for adhesive attachment to mammalian tissue for contacting treatment areas thereof, which comprises: :

mixing together solutions of coprecipitatable, hydrophilic polymers and forming a solid or semi-solid . ~.
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coprecipitated wound-compatible polymer complex thereof;

forming a laminate of said polymer complex with a self-supporting water vapour-permeable film by applica-tion of the polymer complex to a surface of said film;

and, before or after its application to the film surface, if necessary, adjusting the water content o~ said polymer complex as necessary to render it skin adhesive.

The coverings of the presant invention are thus produced bv a simple procedure easily adapted to an.econ- ~
omically large scale, in order to produce materials of the :
desired structure and composition. .

In the accompanying drawings~

FIGURE 1~ is a diagrammatic cross-section of a basic structure o~ a packaged bilayer adhesive wound :~
dressing of the invention;
; FIGURE 1~3 and FIGURE lC are similar views of modifications of the embodiment of FIGURE lA; ~:
FIGURE 2 is a similar diagrammatic cross-section :
of an alternative embodiment of the invention;
FIGURE 3A is a similar diagrammatic cross-section of a further embodiment of the invention; ` -.
FIGURE 3B is a similar view of a modified form of .:~
the FIGURE 3A embodiment; ::.~ ` ;
FIGURE 3C is an underneath plan view o~ the embodiment of FIGURE 3A and FIGURE 3B with the bottom : release sheet removed fcr application; .
FIGURE 4 is.a similar diagrammatic cross-section of a further embodiment of the invention;. - :.
FIGU~E 5 and 6 are similar diagrammatic cross- . :
` sections of further and most preferred embodiments of the invention, in packaged form. -i , 20927~4 - 6 -In the drawings, like reference numerals indicats like parts.
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With reference to FIGURE 1 of the accompanying drawings, this basic embodiment includes an outer package 13 with ~ood water vapour barrier properties to enclose an atmosphere 20 of high humidity around the packaged wound covering. The wound covering itself comprises a sel~-supporting layer 22 o~ ~ilm ~optionally perforated)l foam or fabric of high water vapour transmission, a polymer complex layer 24 supported by layer 22 and release sheet 30 protecting the undersurface of the polymer complex layer 24. Release sheet 30 is provided with an end-projecting tab 32 to facilitate its removal prior to application~ In the modification shown in FIGURE lB, the tab is replaced by an integral lateral extension 32b. In the modification shown in FIGUR~ lC, the release sheet 30 is provided in two parts, each with a projection 32c to facilitate removal.
The high humidity atmosphere 20 within the package 13 prevents drying out of the polymer complex layer 24.
Release sheet 30 preven~s adhesion of the assembly to the package. `~

~ ith reference to FIGURE 2, the embodiment shown thereon (omitting the package) is essentially similar to that of FIGURE 1 with the dif~erence that an adhesive layer 26 i5 interposed between the top, self-supporting layer 22 and the polymer complex 24, to improve the adhesion of the polymer complex to the supporting carrier layer. The - ~`
combination of adhesive layer 26 and self-supporting layer 22 must have ade~uate water vapour transmission.
, ; With reference to FIGURE 3A, this embodiment (also omitting the package) include~ a rim 36 of adhesive material surrounding the polymer complex layer 24. The ~ .

W092tO4923 PCr/CA91/00327 - 7 - 2~9270'1 adhesive rim 36 is provided on the underside of the lat-erally extending periphery o~ the self-supporting layer 22.
In FIGURE 3A, this rim 36 cons~itutes ~he only portion of adhesive, other ~han polymer complex 24, in the structure.
In FIGURE 3B, this rim 36 is formed by the peripheral extension of the adhesive layer 26, which bonds the self-supporting layer 22 to the polymer complex layer 24, beyond the layer 24. In either case the adhesive rim 36 is dis-posed between the top layer and the release sheet 30, to become exposed for skin adhesion when the release sheet 30 is removed. Then the underneath of the assembly has the appearance shown in FIGURE 3C in either embodiment. The adhesive 26 in this embodiment is skin compatible.
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With reference to FIGURE 4, this embodiment includes a covering for the top layer 22, in the form of a self-supporting film 34 and a weak adhesive layer 46 to attach Xilm 34 to top layer 22. Tabs 42 and 32 are pro-vided to facilitate the removal of the release sheets 34 and 30 respectively. With this embodiment, the top layer 22 is protected until application. The weak adhesive layer 46 should be strong enough to hold the film 34 in position while release sheet 30 is removed. Adhesive 46 remains attached to film 34 a~ter removal of film 34 from the structure.

The embodiments shown in FIGURES 5 and 6, which are the most preferred embodiments, have a release sheet 34 attached over the top layer 22, as in the embodiment shown in FIGURE 4. In the FIGURE S embodiment, the upper release sheet 34 has a lateral extension 43 forming a tab to facilitate its removal, and is attached to the top layer 22 by means of an adhesive layer 46. The portion of the adhesive layer 46 underlying the extension 43 is provided with a protective patch 44 of suitable mzterial. The release sheet 30 covering the polymer complex layer 24 has J ' ' ' ~

2~ r~4 - 8 -a tab 32 to facilitate its removal. An adhesive layer 26 is pxovided, as in FIGU~E 3B, to protrude peripherally beyond the layer 24 for adhesion to the skin. The whole is packaged in a sealed outer package 13, preferably contain-ing an atmosphere of high humidity, to keep the polymer complex 24 in moist condition prior to application. The package 13 is suitably of aluminum Poil/thermoplastic laminate or metallized thermoplastic film, so as to be heat sealahle. The hea~ seal should allow convenient package opening by peeling apart of the pac~age edges. Alterna-tively, the package may be suitably marginally notched for ease of opening. In the FIGURE 6 embodiment, the release sheet 34 is non-adhesively attached to the top layer 22, e.g. by solution casting o~ the top layer 22 onto the release sheet surface. Otherwise it is the same as the FIGURE 5 embodiment.

It will be appreciated that the illustrated embodiments are exemplary only, and do not limit the scope of the invention.

In use, the sealed outer package is opened and the assembly removed fxom its package. The release sheet 30 covering the polymer complex layer 24 is removed and the patch is applied to the wound site with the layer 24 contactirg the wound. Adhesion of the patch to the wound is effe~ted by the inherently adhesive nature of the polymer complex layer 24 and, in the embodiments of FIGURES

3, 5 and 6, by the adhesion of the peripheral adhesive layer 36 to the skin surrounding of the wound site.
Substantially immediately after the patch has been applied to the wound site, pressure can be applied on or through the top layer 22, to retard bleeding from the wound site.
Thereafter, the patch provides an appropriately moist environment to the wound site.

W092/04923 PCr/CA91/00327 209270~
The polymer complex compositions used as the wound-contacting layer in the coverings of the present invention are substantially wound compatible and skin compatibïe. The term "wound compatible" used herein - describes materials which can be applied to a flesh wound site of a human or other animal and will not deleteriously interfere with the normal healthy biological processes encounte.ed at the wound si~e. The term "skin compatible"
means not deleterious to normal healthy skin on which it is applied. ~he adhesive coverings of the present invention provide appropriate wa~er vapour transmission between the wound site and the environment, and act as suitable bar-riers for the wound against microorganisms including viruses, and agatnst harmful contaminations and physical ~
contact damage, which would otherwise impede the healing ~ -process. After removal of these adhesive coverings, the skin surrounding the wound area is relatively free from swelling and discoloration, largely due to the appropriate water vapour transmission properties of the assembly. ~
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~ oth the polymer complex layer and the outer layer and, i~ present, the adhesive layer between them, remain overlying the wound after application, and can if desired be made transparent, so that the wound can be inspected and process in its healing can be monitored visually. Moreover, such an adhesive covering can be made ~; cosmetically appealing, e.g. by coloration, opacity or gloss reduction, and can carry medication to treat the wound site. These layers are all suitably permeable to ; water vapour, for best healing properties. Preferably, '~ they are also oxygen permeable.

` The polymer complexes used in the present inven-tion are wound compatible, tacky products produced by -~
coprecipitation from solution of at least two water-sol-uble, hydrophilic polymers. Preferably, the polymers are ',`; ~ '' .:,; .
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`' '`' '; ` ' ` ' ` i '~ i ' - ~ , , W092/04923 PCT/CA91/00327_ 20927~ - 10 - '"

coprecipitated fo~m aqueous solution. The two polymers are chosen, in relationship to one another so that, when solution~; o~ the two pol~mers are mixed together, a copre-cipitate of the two polymers forms, either on mixing, after standing, or on subsequen~ concentration of, p~ adjustment of or addition of a suitable solu~e to, the resultant solution.

The coprecipitate is usually of a semi-solid "gummy" consistency, and may be separated by decantation and dissolved in an appropriate solvent such as aqueous ethanol, aqueous acetone or aqueous isoprapanol, at room or slightly elevated temperatures. Then this solution can be applied to the self-supporting, outer layer and allowed to dry. Alternatively, the polymer solution may be cast on a suitable transfer surface, allowed to dry, applied to the self-supporting outer layer as a transfer coating and, if deemed necessary subsequently rehydrated to some extent to increase tack, before the final assembly of the product, with release`sheets etc. Preferred polymer complexes used in the present invention are those which can be dried to a non-tacky, self supporting film, and subsequently remoist-ened to a taaky condition. Such materials are convenient to handle in their dry film form, e.g. in manufacturing and cutting machines.

If the gummy coprecipitate is sufficiently mobile at room cr elevated temperatures, dissolution in a solvent may not be necessary, and the coprecipitate may be case directly onto the outer layer or onto a suitable transfer -surface. After formation and application to the self-supporting layer, the polymer complexes are preferably maintained in a moist condition until use, e.g. by packag-ing in a sealed, water vapour containing envelope as previ- , -ously described. ~

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W092/0~923 PCT/CA91/00327 When it is desired to a~d additional ingredient~
such as plasticizers, colourants, medicaments, etc. for in¢orporation in th~ polymer complex layer, these are suitably mixed with the coprecipitate or ~he coprecipitate solution.

Thus it is necessary, in accordance with the present invention, to choose polymers which are hydrophi-lic, water-soluble, coprecipitatable together from sol-utions, preferably aqueous solutions, to form a wound compatible polymer complex coprecipitate. The choice oP
first polymer may be made from polymers and copolymers of acxylic acid (PAA), polymers and copolymers of methacrylic acid (PMA), polymers and copolymers of itaconic acid (PIA), polymers and copolymers of maleic acid (PMLA), and combina-tions thereof. The second hydrophilic polymer may be selected from polymers or copolymers o~ vinyl pyrrolidone, polymers or copolymers of ethylene oxide, including copolymer combina~ions of propylene oxide and ethylene oxide [P(E0/P0)], chitosan, derivatives of chitosan such as N,O-carbomethoxy chitosan, gelatin, and combinations ; -thereof. -At the time of application to the self-supporting layer and when packaged in the envelope, the polymer complex layer has a very substantial water content, i.e. 20 - 70% by weight of the total, the corresponding 80 - 30% by weight being solid polymer. After application to the wound site, the water content of the polymer complex comes to an ;~
equilibrium, dependent upon the rate of water vapour loss through the wound dressing as a whole, and the rate of water vapour production by the wound and skin beneath the dressing. The contac~ of the wound site with the assembly ~1 of the polymer complex of Z0 - 70% water content and the self sup~orting layer has a beneficial effect on wound healing, by avoiding dehydration of the wound site. ~;~

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WOg2/04923 PCT/CA91/00327 2~9270~
Additional benefits may be obtained, on occasion, by inclusion of appropriate medicaments such as antibiotics, anti-infectives, analgesics, antipruritics, growth factors and the like, in the polymer complex layer. Such materials are particularly easy to incorporate in the polymer com-plexes of the present invention, since the polymer com-plexes, after formation by coprecipitation, are subsequently redissolved in organic solvents, generally a particularly good medium in which to add the medicaments to the polymer complex.

Accordingly, the adhesive coverings of the present invention can serve as an especially useful trans-dermal drug delivery system, for example, for delivery of medicaments to alleviate the discomfort of muscle pains, bruises and the like. In addition, these adhesive coverings are particularly valuable ~or delivery oP those drugs which penetrate the skin with difficulty and consequently are unsuitable for membrane rate controlling or membrane based transdermal drug delivery devices.

When adherent to a treatment site, the assembly of the polymer complex layer and the self-supporting backing film provides an effective barrier to microorgan-isms and other healing-inhibiting foreign substances. The adherent assembly will withstand immersion in sea water or tap water, or normal washing, and will withstand applica-tions of common skin creams and lotions.
,.

The tacky polymer complex layer may also incl~de a reinforcing mesh disposed within the thicXness of the polymer complex layer, to strengthen it and to increase its cohesiveness. Such a reinforcing mesh may be a non-woven, fibrous sheet, consisting essentially of cellulose fibres and of high porosity, resembling tea-bag tissue. Such ..

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materials are known for use in connection with hydrogel wound dressing materials.

Examples of suitable commercially available such material are high strength, ligh~weight, high porosity tissues comprised of a special blend of hemp and other selected cellulose fibres, marketed by The Nonwoven Di~i-sion of lhe Dexter Corporation, Windsor Locks, Connecticut, as Dexter Grades 785D and 198T.

Alternatively, the reinforcing mesh may be a thermoplastically welded fibrous web, of thermoplastic fi~res such a polypropylene, high density polyethylene or polyester. An example of a suitable, commercially avail- ~ ;
able such web is that sold under the trade name DELNE~, by Applied Extrusion Technology, Middleton, Delaware. ~`
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Such reinforcing meshes may be incorporated into the polymer layer during or after the application of the polymer in liquid form to the self-supporting outer layer.
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Particularly preferred for use as `the second hydrophilic polymer is a polymer or copolymer of ethylene ox$de, or a polymer or copolymer of vinyl pyrrolidone, especially polyethylene oxide or polyvinyl pyrrolidone. ~ ~ -, Acrylic acid polymers or copolymers, especially polyacrylic acid, are particularly preferred choices of first hydrophilic polymer for forming the polymer complex adhesive layer in the adhesive patches of the present invention. A wide range of grades and molecular weights of P~A may be used, choioe of which is within the skill of the art. Suitable PAA has a molecular weight of at least 2,500 and preferably 5,000 - 4S0,000.

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W092/04923 PCT/CA91/0032~
:~ '2~3~27~ - 14 -Especially preferred for use in the present invention are polymer complexes derived from PAA as first polymer and PE0 as second polymer. PE0 of widely varying molecular weights, from about 2,500 up, can be used, with those of molecular weight 6,000 to 600,000 being especially suitable.

As noted, plasticizers can be incorporated in the polymer complex layers of this invention, to adjust the final consistency of the layer. Suitable such plasticizers include urea, propylene glycol, polyhydroxy compounds of low molecular weight including glycerol, sorbitol, glucono-lactone, triethanolamine and gluconic acid. Alkaline plasticizers such as triethanolamine can be used to reduce the level of complexation in the polymer complex, by neutralization of some of the carboxylic acid groups of the first hydrophilic polymer, to increase the tackiness on rehydration. Conventional alXalies e.g. caustic soda or ammonia may also be advantageous for the same purpose in some instances. Additionally, the wound contacting polymer complex material may include suitable preservatives to control microbial growth. Many frequently used preserv-atives known in the art are suitable for this use, includ-ing sodium benzoate and sorbic acid.
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In another embodime~t of the present invention, the polymer complex layer is subjected, after application to the outer film layer, to a crosslinking process, to effect a limited degree of crosslin~ing of the polymers for strength improvement and sterilization purposes. This is conveniently effected by subjecting the polymer layer to a controll~d dose of suitable radiation, e.g. gamma radiation of 3 - 4 Mrad, arter application to the film layer. In practice, it is found that the irradiated products tend to give better bleeding control when applied to wound sites, as compared with non-irradiated products.

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. , . ," .. ". I ~ -2~27~ll The outer layer of the assembly according to the invention is self-supporting and has a high water vapour transmission, which may result from high inherent permea- I
bility,~from microporosity or from perforations. Preferab- j ly, it also has high oxygen transmission, good drape properties so as to be conformable to wound sites, and good extensibility and elasticity.
.~ . ' -The combination of the outer layer and the polymer complex acts as a barrier to ~he dehydration of the wound site, but must permit adequate water vapour trans-mission away from the wound site such that the wound site and adj~cent skin do not become edematous (swollen), thereby having a deleterious effect on wound healing, or - -resulting in fluid build-up at the patc~-wound interface ~ -such that the adhesion is lost. For this purpose the backing layer suitably has a water vapour permeability o~
at least l~O gm/m2/24 hours. When necessarv, the water `~
vapaur permeability can be increased by introduction of perforations or microporosity. The degree of perforation is not critical, and is determined by the requirement for ~ the backing layer to protect and hold the polymer complex.
`;~Thus the size and nature of any such perforation should not be such as to interfere with the function of the bac~ing sheet to protect the polymer complex. It must of course hold the polymer complex in position, and not allow diffu-sion of the polymer through the backing sheet. For a discussion of water vapour permeability of wound dressings and their methods of measurement, reference may be made to ;i an article by Marcel F. Jonkman et al., "New Method to Assess the Water Vapour Permeance of Wound Dressings", ~iomaterials, 1988, Volume 9, May, pages 263 - 267. ~-~

`Perforations provided in the outer layer also serve the additional purpose of enhancing the bonding of .~, . . ~` .' .. , ;': ' - ::

2~9270~
the polymer complex layer to the outer layer, and counter-acting the tendency towards delamination. In effect, the perforations form a ~ype of physical interlock between the outer layer and the polymer complex. Advantageously, the per~orations are in the form of lacerations, i.e. a series of slits. The physical interlock can also be provided by embossing, pin pointing or roughening the surface of the outer film layer which is to receive the polymer complex or adhesive The outer layer can be made of substantially any skin compatible material exhibiting suita~le properties of permeability. It may be a self-supporting film, foam or fabric. Suitable such materials are known in the prior art, and those useful in prior art adhesive wound covering patchas are generally use~ul in the present invention.
Examples include polyester polyure~hanes, polyether polyurethanes, silicones, polyethylene, polypropylene, ethylene-vinyl acetate copolymers, polyvinyl chloride, etc.
It may be opaque, semi-opaque, coloured or transparent, or printed with designs or character.
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Ultra-thin polyurethane films which are semi-permeable to water vapour, as exemplified by the commer-cially available wound dressing OP-SITE, which consists of a polyurethane film coated with a medical grade adhesive, are particularly preferred. These often have appropriate permeability without perforation. Elastic silicone mem-branes constitute another preferred film outer layer. They need to be perforated to provide appropriate permeability.

Foam sheets, preferably of open cell foam or perforated closed cell foam, non-woven or woven fabric bandages of natural, synthetic of mixed fibres, may also be used as the outer layer for the assembly of the invention.

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W092/04923 PCr/CA91/00327 - 17 ~ 2~927 04 Similarly, non-polymer complex adhesives used for skin contacting layers in the assembly of embodiments of the present inven~ion are suitably those known from the prior art for use with conventional wound dressing patches.
Pressure sensitive, skin-compatible adhesives are commonly used. Porous adhesive coatings are especially preferred.
These adhesives may comprise acrylic polymers or silicones (e.g. Dow Corning Medical adhesive); these are merely exemplary of suitable, available materials.
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With reference again to the accompanying draw-ings, and specifically to FIGURES 4 and 5, the adhesion of upper release sheet 34 to the outer self-supporting layer 22 ef~ected by adhesive layer 46, should be strong enough to withstand the removal of lowermost release sheet 30 but :. ~
significantly weaker than the adhesion of the polymer complex layer 24 to the wound site (augmented, in the embodiment shown in FIGURE 5, by the adhesion of adhesive 26 to the wound surrounds). This will permit the removal of release sheet 34 after application of the dressing to the wound area. The adhesive 46 should have sufficiently stronger adhesive bonding to the upper release sheet 34 than to the outex, self-supporting layer 22. Thus the choice o~ material of adhesive 46 will be determined to some extent by the nature of the top surface of layer 22.

For polyurethane films, the adhesive 46 would be much weaker than the adhesive 26. Such weak adhesives are often referred to in the art as ~repositionable adhesives".
If still weaker adhesion is required, the adhesive may be applied to a part only of the surface of ~heet 34, or a backside coating may be applied to the top surface of top layer 22.

Another preferred embodiment of the invention is as illustrated in FIGURE 6. As compared with that shown in .
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20 92rl Oll - 18 -FIGURE 5, it omits the adhesive layer 46 so that the top release sheet 34 is in direct adhesive contact with the top surface of backing s~ee~ 22. This can be accomplished by solution casting of a solution of the backing sheet 22 onto the appropriate isur~aca of the top release sheet, and allowing it to dry and if neces5ary, curing. Alternatively it may be applied to the release sheet by a hot melt process. The end result is adhesion of the backing sheet to the release sheet, by direct contact, without the inter-mediary of a layer of adhesive~

~ he invention is further described in the follow-ing illustrative but non-limiting examples.

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WO 92/04923 PCI'/CA91/00327 19 209270~ ~

EXAMPLE 1 -- PREPARATION OF }: OLYMEE~< COMPLEX LAYER--PAA/PEO WITH PLASTICIZERS
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A solutlon of 30 g of poly~thylene oxide (Polyox WSR-205 from Union Carbide) in 600 ml of distilled water wa~ stirre~ rapidly at room temperature as 120 g of Acrysol A-3 (a 25~ aqueous solution of polyacrylic acid from Rohm and Haas) were added. After completion of the addition, tha mixture was stirred for 25 minutes. It was the~ covered and allowed to stand at room temperature for 6 weeks. At the end of this time, the mixture consisted of a turbid, non-viscous liquid and a translucent, rubbery solid. The liquid phase was discarded. The rubbery solid waighed 143 g. A total of 91 g of ethanol was worked into the rubbery solid by gentle warming (bath at 35-60C) and by kneading/stirring with a stiff rod having a rlng at the bottom. The following materials, in order, were then worked into the mixture by stirring at room temperature:

a solution o~ 6 g of urea in a mixture of 7 g o~ distilled water and 20 g of ethanol, a solution of 5 g of triethanolamine and 2.3 g of tartaric acid B.P. in 24 g of distilled water and 8 g ~thanol:
and a total of 80 g of distilled water and 267 g of ethanol added in portions individually and as mixtures. The mixture was allowed to stand for 2 days, and finally was diluted with a total of 58 g of distilled water and 1~5 g of ethanol. The hazy, viscous solution was cast on a sheet of low dens1ty polyethylene attached to a levelled glass plate. The cast liquid was left exposed to the laboratory atmosphere (about 40%
relative humidity) for 17 days, after which it was a _ transparent and somewhat elastic film. The top of the film was covered with #1361 release liner (3M Co.).

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W092/04g23 PCT/CA91/00327 2~9~7~20 Sectlons of film about 0.17 mm thlck were used as the polymer complex layer of bilayer wound coverings~ The requlred shape was cut while the polyethylene and #1361 release liner were stlll attached.
' EXAMP~E 2 -- PREPARATION OF POLYMER COMPLEX LAYER--PAA/PEO WIT~OUT PLASTICIZERS

A solution of 60 g of polyethylene oxide(Polyox WSRN-750 from Union Carbide) in 1050 g of distilled water was rapidly stirred at room temperature as 240 g of Acrysol A-1 (a 25% aqueous solu~ion of PAA
from Rohm & ~aas) diluted with 250g of distilled water were added over a period of 5 minutes. The mixture was stlrred for a further 5 minutes after completion of the additlon, and was then allowed to stand for 22 hours.
At the end of this time, it consisted of a translucent gum and a semi-opaque, mobile liquid. The liquid was decanted, and the gum was kneaded to express occluded liquid. The resulting gum weighed 282 y. Of this, 56.2 g were separated and allowed to stand at room tempera~ure in a covered vessel for 4 months. The gum was then diæsolved to form a solution suitable for castln~ by the addition, in portions, o ethanol/water ml~tures ollowed by stirring at room temperature. In total, 154.8 g o ethanol and 82.3 g of distilled water were used. The solution was cast on sheets of 7 mil high density polyethylene secured to levelled glass plates. The cast liquid was exposed to the laboratory atmosphere (relatlve humidity 30-37%) for 4 days, after which the resulting film was transparent and elastic.
It was cooled to 4C to facilitate removal from the polyethylene. The film was----stored with` #W-89-SPiP
release liners (Mead Release Products) on either side.
Sections of film about 0.11 mm thick were used for the polymer complex layer of bilayer wound coverings. The ., ~ .
.
, ' ', ', , , . . ,~. .

W0~2/04923 PCT/CA91/00327 - 21 ~ 2~927 0~

required shape was cut while the release liners were still attached.

EXAMPLE 3 ~- ASSEMBLY AND PERFORM~NCE OF_A 8ILAYER
POLYMER COMPLEX WOUND COVERING

The bilayer wound covering for this example was produced in accordance with the preferred embodimen~
of the invention, FIGURE 5. The adhesive layer 46, which was supplied as a weak film between two release sheets, was placed on the self-supporting top film 34.
One release sheet was removed to leave a sandwich of adhesive between a release sheet and film 34. Then the assembly was cut to an appropriate rectangular shape and size, and the release sheet was removed. Tha rectangular tab 44 was next applied over adhesive 46.
An o~al shape of top layer 22 with adhesive 26 thereon, and having a release sheet protecting the adhesive 26, was placed over the adhesive 46 on top film 34 and pressed firmly into place. The release sheet was removed. Cast polymer complex film was cut to the appropriate size and shape, and after removal of one of :
the release sheets, was applled over top layer 22 with the exposed face of the polymer complex against the top layer. It was pressed firmly in place, and the remaining release sheet was removed. The assembly was malntained under conditions of high humidity to hydrate the polymer complex untll it became tacky. The bottom release sheet 30, wlth removal tab 32, was then applied, to complete the assembly. It was then heat sealed into a laminated aluminum foil package 13.

The above-described procedure was used to assemble a bilayer wound covering from the following specific components, reference numbered to accord with the drawlngs, especially FIGURE 5: ;

.
.. .. ..

W092/04923 PCT/CA9l/00327 '~a927~1~

top layer rslease sheet 34 and adhesive layer 46 -- 2 mil polyester backing coated wi~h strips of a re-positionable adhesive 2 mm wide placed 2 mm apart.
The adhesive strlps were parallel to the long direction of the patch:
. , tab 44 covering part of adhesiYe 46 -- 5 mil high density polyethylene;

top layer 22 and adhesive coating 26 -- 1.5 mil polyester polyurethane coa~ed with a porous pressure sensitive adhesive (PSA) (#KM1393-OO from Semex Medical~;

polymer complex layer 24 -- film from Example 2;

; polymer complex release sheet 30 -- 3 mil high density polyethylene with a silicone coating cured with an electron beam (#3-H~D-S233~-WHITE from Mead ~elease Products).

TEST ON HEALTHY SKIN
, The complete, assembled wound covering was -removed from its hermetically sealed pouch and applied to a forearm test site of a human volunteer. A~ter 11 -~
days, 95~ of the area o~ the wound covering was still ;
adherent to the skin. During the entire test period, there was no discomfort, an~ no evidence of skin ;irritation. At lS days, when the wound covering was removod, there was no noticeable edema.

, :, .
'~-. ~ ., ... , , , - , .. ~.. . . .. - - : . :: . - . : ,: . . :: - : .. . - . : , :~

", ",, ,, ,, ~ ,, .,, ,.,, ....... .. ~ :` ' ` "' ' ' " ' ' ' ~' ' '' WO 92/M923 PCltCA91/00327 2~27~
- 23 - :

TEST ON FINGER CUT

A male, q7, in good health, suffered a paper ' cut on the end of the ring finger, perpendicular to the plane of the hand. The cut wa~ 5 mm long and had an estimated dep~h of 2 mm. Bleedlng was substantlal.
Blood wa~ absar~ed wi~h a facial tissue for about 60 seconds, and the~ a complete, assembled wound covering prepared aæ described above wa~ removed from its hermetically sealed pouch and applied. The patch was left on the injury for ~ive continuous days. During this time, ~he hand was involved in all narmal activities, except that it was kept from immersion in water. ;

The patch remained transparent during the five day period. Inflammatlon at the edges of the cut disappeared over the first few days, leaving a thin raddish brown line as the only evidence of in~ury. At -~
no tlme was there any fluid buildup beneath the dressing. On the fith day, the patch was st~ll adherent to the skin surrounding the in~ury, although by this time there had been peripheral detachment correspondlng to about half of the area of the patch.
The patch was pulled off. The inJury appeared completely healed, and the ad~acent skin which had been covered continuously for five days appeared quite healthy.

TEST ON AN ABRASION INJURY UNDER ADVERSE CONDITIONS
. . .
A male, 37, in good health sustained an abrasion injury to the ring finger of the right hand in a routine domestic accident. The injury was located on the top of the finger a~out 1 cm from the central s knuckle toward the end of the finger. The zbrasion was :' .

;: ' . ~ , . .

wo 92/M9t3 Pcr/cA91/oo32l 209270~

, .

.
about 6 mm in diamg~er and extended well into the dermis~
., .
Bleeding was stopped by absorption with facial tissue. The wound was left exposed for about four hours, and then a complete, assembled wound covering was removed from its henmetically sealed pouch and applied~
There was no sensation on application. Af~er application, the volunteer was involved in vigorous outdoor activities including swimming, water skiing and chopping wood. During these activities, the patch remained adherent to the wound and to immediately ad~acent healthy skin for about 36 hours, after which i~
; there was some peripheral detachment. The patch was removed at thls tlme. The wound appeared hea~thy and -was left exposed. Subsequent healing was highly satisfactory.
,~ .

POLYMER COMPLEX WOUND_COVERING `

The procedure outlined in Example 3 was used i,, to assemble a bilayer covering from the following ccmponents, referring to the drawings as regards the ~
speaiflc componentsl ;

top layer release sheet 34 and adhesive 46-~as in Example 3;
tab 44 coverlng part of adhesive 46 -- as in ` Example 3; -top layer 22 and adhesive coating 26 -- 0.7 mil polyether polyurethane coated with a porous pressure ! `~
~i s~nsitive adheslve ~#KM1391-02 from Semex Medical);
polymer complex layer 24 -- film from Example 2;
.,, :"

' " ' ,. '' .'` ' ' . ' .' .,. .. . .: : . , . ,:, ,`,.,:`' ,"' :. ::.: ;:, ' :' :,` . ~' .'` ,,` ' ,~' ' ' ' : ' . :

, polymer complex layer release sheet 30 -- as I -in Example 3.

The polymer complex layer was moisturized by exposure to an atmosphere of lOO~ relative humidity for - 3.5 hours. The complete, assei~bled wound covering was kept in a hermetically sealed pouch for 1 day before application to a forearm test site of a human pa~ient.
After 5 days, 88~ of the area of the covering was still adherent to the skin. During the 5-day period, there was no discomfort and no evidence of skin irritation. ;
When the wound covering was removed, there was no noticeable edema.

EXAMPLE 5 -- ASSEM~LY AND TEST OF BILAYER POLYMER -~
COMPLEX WOUND COVERING
. ~
The procedure outllned in Example 3 was used to assemble a bilayer covering from the followlng components, referring to the drawings:

` top layer release sheet 34 -- laminate of an outer layer o 2.8 mil low density polyethylene bonded to a film of 0.5 mil polyester bonded by a layer of polyacrylate adhesive;
adhesive 46 - repositionable adhesive on the 0.5 mil polyegter component of the laminate formin~ top ` layer release sheet 34 described above; ~-tab 44 covering part of adhesive on 46 -- as , in Example 3;
top layer 22 and adhesive c~ating 26 -- 1.5 ~
mil polyether polyurethane coated with a porous pressure ~ -sensitive adhesive (#KM-1393-02 from Semex Medical);
polymer complex layer 24 -- film from Example ;:
`,!

~ W092/04923 PCT/CA91/003~
20~270~

polymer complex layer release sheet 30 -- as in Example 3~

The polymer oomplex layer was moisturi~ed by exposure to an atmosphere of 100% relative humidity for 16.5 hours. The complete, assembled wound covering was kept in a hermetically sealed pouch one day. The pouch was opened and the covering was applied to a forearm test site o~ a human patient. Af~er 18 days, 96~ of the area of the wound covering was still adherent to the skin. During the 18 day period, the test si~e was exposed to five warm showers. At the end of the 18 day period, the covering was still transparent. There was never any dlscomfort or evidence of skin irritation.

EXAMPLE 6 -- ASSEM~LY AND TEST OF BILAYER POLYMER ~ `
COMPLEX WOUND COVERING ~" ~
' ' ~`" ., A complete, assembled wound covering identical with the one described in Example 5 was kept in a hermetically sealed pouch for a total of 25 days. On the 13th day, while still sealed in the pouch, it was given a dose of 1.92 Mrad of gamma radiation, for sterilizatlon purpogeg. ~he pouch was opened at 25 days and the covering was applied to a forearm test site of a human patient. After six days, 94% of the area of the wound covering was still adherent to the skin. During the six-day period, there was no discomfort, and no evidence of skin irritation.
,: , .:

:........... , I
The procedure outlined in Example 3 was used to assemble a bilayer covering from the following ;
components, referring to the drawings:
, . ~ .

", I '`', ~270'1 top layer release sheet 34 and adhesive layer 46 -- as in Example 3;
tab 4~ covering part of adhesive 46 -- as in ~xample 3;
- top layer 22 and adhesive coating 26 -- 3 mil polyvinyl chloride, yellowish tan ("flesh colour"), partially transparent, coated with a pressure sensitive adhesive (No. 1103-5 from Betham Corporation);
polymer complex layer 24 -- fllm from Example ~; 2;
polymer complex release sheet 30 -- as in Example 3. -The polymer complex layer was moisturized by exposure to an atmosphere of 100~ relative humidity for 18 hours. The complete, assembled wound covering was kept in a hermetlcally se~led pouch for 40 days before application to a forearm test site of a human patient.
After six days, 93% o~ the area of the wound coverlng was still adherent to` the skin. Hairs and veins were visible through the dressing. At 11 days, when the wound covering was removed, the skin whlch had been adherent to the covaring was much whiter than the surrounding skin. Th~s whiteness had disappeared after exposure to ambient air or 30 minutes. During the entire test period, there was no discomfort, and no evidence of skin irritation.
.` ' '' - The procedure outlined in Example 3 was used to assemble a bilayer covering from the following components, referring to the drawings:

top layer release sheet 3~ and adhesive layer ~8 20927~

46 -- 1 mil polyester backing coated with a repositionable adhesi~e;
tab 44 covering part of adhesive 46 -- as in ~xample 3;
top layer 22 and adhesive coating 26--porous, spunlaced polyes~er non-wo~en fabric, fabric weight 1.2 oz/s~.yd., coated with a porous pressure sensitive adhesi~e ~No. PA 1251-01 from Semex Medical);
polymer complex layer 2~ -- film from Example 2;
polymer complex release shee~ 30 -- as in Example 3.

The polymer complex layer was moisturized by ~ exposure to an atmosphere of 100~ relative humidity for ; 22 hours. ~he complete, assembled wound covering was kept in a hermetically sealed pouch for one day before application to a test site on the back of a finger of a human patient between the first (closest to the fingernail) and second ~oints. After 3.5 days, 80~ of the area o~ the wound covering was still adherent to the skln. The wound covering was removed at this time;
there was no noticeable edema or evidence of skin 'r irritation. All normal activitieg were carried out ~ -during the test period, including approximately 16 washings of the hands with soap and warm water.

:' . ' ,:
The procedure outlined in Example 3 was used to assemble a bilayer covering from the following components, referring to the drawings:
,~
top layer release sheet 34 and adhesive layer 46 -- as in Example 3;

. 1 .. . .:, ...

::'i,:., : . . :. : :. . ';. : :: : ' ' : . ''' ~ :~.. : . ' W0~2/04923 PCT/CA91/00327 ~927~

tab 44 covering part of adhesive 46 -- as in Example 3;
top layer 22 -- 1 mil microporous polypropylene (45% porosity, oblong pores about O.04 x 0.2 micrometers), Celyard 2500 from Celanese Corporation;
adhesive 26 -- approximately 0.6 mil coating of polydimethylsiloxane applied to one side of the top layer as follows: the spray from an aerosol can of Hollister Medical Adhesive (No. 7730 from Hollister Incorporated) was directed onto a small jar until about 15 ml had been collected. A portion of thls liquid was spread on one side of the top layer material, which had been secured to a levelled surface by taping the edges.
The solvent in the coating was allowed to evaporate by exposure to the laboratory a~mosphere. The tacky residue was then protected by application of a release `
sheet of 3 mil polyester; "
polymer complex layer 24 -- film from Example 2:
polymer complex ralease sheet 30 -- as in Example 3.

The polymer complex layer was moisturized by exposure to an atmosphere of 100% relative humidity for 68 hours. The complete, assembled wound covering was ~ept in a hermetically gealed pouch for one day before application to a forearm test site of a human patient.
After four days, 85~ of the area of the wound covering was still adherent to the skin. About 8~ of this adherent area had become transparent, possibly because of migration of low molecular weight silicone polymers into the top layer. One day later, after five days, 65%
of the area of the wound covering was still adherent to the skin, and 85~ of this adherent area was transparent.

W092/04923 PCr/CA91/003~7 Q~ :

When the wound covering wa removad at six days, there was no edema and no evidence of skin irritation.

This example shows that, under favourable ~:
conditions, a polymer complex layer 24 which displays little or no adhesion to skin becausa it has not been moisturized, can become adherent a~ter application of a bilayer wound covering if the wound covering has a peripherally protrud~ng adhesive layer 26 as shown in FIGURES 3-6.
::
The procedure outlined in Example 3 was used to assemble a bilayer coverlng, except that the polymer complex layer was never moisturized, the assem~ly was never completed by the additlon of a polymer complex release sheet and was never placed in a hermeticallY :
sealed package.

The components used were as follows, with reference to FIGURE 5:
: .
top layer release sheet 34 -- laminate of an ~' outer layer of 2.8 mil low density polyethylene bonded to a film of 1 mil polyester with an adhesive layer;
adhesive 46 -- repositionable adhesive on the 0.5 mil polyester component of the laminate forming top layer release sheet 34 described above;
. tab 44 covering part of adhesive 46 -- as in ;~
Example 3; ~
top layer 22 and adhesive coating 26 -- as in . ::
Example 3;
2 polymer complex layer 24 -- film from Example . .

, ' `: :
: . . . . .

WO9~/04923 PCT/CA91/OU327 - 31 ~ 7 ~ ~

The assembly, complete except for the addition of polymer comple~ release s~aet 30, was kept at ambient temperature and relative humidity (23%) for no more than 30 minutes and was then applied to a test site on the back of a finger of a human patient between the first and second ~oints. During the next 33 hours, the hand was never in contact wl~h water, but otherwise all normal hand activlties were carried ou~. At the end of the 33-hour period, the entire area covered by the peripherally protruding part of the bllayer wound covering was stlll adherent. The polymer complex layer had very good adhesion to the skin of the test site.

The procedure outlined in Example 3 was used to assemble a bilayer covering from the following components, referring to the drawings:

top layer release sheet 34 -- as in Example 9;
. tab 44 covering part o adhesive ~6 -- as in . Example 3:
top layer 22 and adhesive coating 26--polyethylene foam, 1/16th inch thick (4 lbs.), coated with an acrylic pressure~sensitive adhesive (No. 1117-W
from ~tham Corporation);
. polymer complex layer 24 -- film from Example ; 2;
polymer complex release sheet 30 -- as in Example 3.
,. . .
The polymer complex layer was moisturized by ' exposure to an atmosphere of 100~ relative ~umidity for 21 hours. The complete, assembled wound covering was . kept in a hermetically sealed pouch for one day before : application to a test site on the back of a finger of a , 92~'~ - 32 -human patient between the first and second joints.
After one day, only 50% of the bllayer wound covering was still adherent to the skin. This exceptionally rapid loss of adhesion can be attributed to a combination of the s~iffness of the foam and the high curvature of the finger. The covering was removed at this time. The area under that part of the wound covering which had maintained adhesion was whitish.

The bilayer wound covering for this example was produced in accordance with the embodiment shown in FIGURE 4, except ~or the presence of layer 26 between the top layer 22 and the polymer complex layer 24 as shown in FIGURE 2. Tab 42 in FIGURE 4 was present as an extension of top layar release sheet 34 and adhesive layer 46. The protruding adhesive portion of layer 46 was covered wlth a tab of 5 mil high density polyethylene. Tab 32 on polymer complex release sheet 30 was present as a ~olded back extenslon of sheet 30.

The general method of assembly is as described for Example 3, using the following speci~ic components: ~
; ;-top layer release sheet 34 and adhesive layer 46 -- 2 mil polyester backing coated with strips of a repositionable adhesive 2 mm wide placed l.5 mm apart;
top layer 22 and adhesive coating 26 -- as in Example 3;
polymer complex layer 24 -- film from Example 2;
polymer complex release sheet 30 - as in Example 3.

.

- 33 - 2~92 ~0~

The polymer complex layer, which was an oval with maximum dimensions 27 x 16 mm, was moisturized by exposure to an atmosphere of 100% relative humidity for four hours, application of approximately 25 mg of distllled watèr to the surface in the form of 2 drops from a syrlnge followed by spreading over the surface, and continued exposure to an atmosphere of 100~ relative humidlty for 2.5 hours. The complete, assembled wound coverlng was kept in a hermetically sealed pouch for two days before application to a test site on the back of a finger of a human patient between the first and second ~oints. After three hours, the test area with the attached wound covering was immersed in a 5~ solution of soap at 39C for one minute and then towelled dry.
Thereafter, contact with water was avoided, but all normal hand activities were undertaken. During days two and three, prolonged operation of a power tool with a two-handed overlapping grip caused a significant creep of the wound covering. After four days, 75% of the area of the wound covering was still adherent to the s~in, and the adhesion was ~ound to be very good. There was no evldence of skin irritation.
'' ~
The performance of an identical bilayer wound coverlng, which had been placed on a similar test site on an ad~acent finger and which had been immersed for one minute in distilled water at 39C instead of a soap solution, was indistinguishable.

COMPLEX LAYER - PAA/PVP WITH PLASTICIZERS ~;

100 grams of polyvinylpyrrolidone tPVP) (Plasdone ~-29/32 from GAF Corporation) were dissolved in 100 grams of distilled water. 400 grams of AcrySol A-l (a 25% aqueous solution of PAA from Rohm and Haas) .

~, W092/04923 PCT/CA91/003~7 Z~27 ~

were stlrred as the PVP solution was added to lt. A gum separated during the addit~on. The liquid phase was decanted and discarded. The gum was kneaded to express occluded liquid, which was discarded. The gum was dlssolved in 32 grams of ethanol by heating and stirring, and the solu~ion was diluted with 8 grams of ethanol. ~he resulting solution was labelled 81-B. To 50.2 grams of 81-~, while kept warm in a hot water bath, were added, in order, with stirring, 12.0 grams of propylene glycol USP (Daminco Inc.) 9.0 grams of urea (BDH Chemicals), 8 grams of ethanol, and finally a mixture of 8.4 grams of distilled water and 7 grams of ethanol. The warm solution, labelled 97-C, was cast on a polyethylene surface kept at 53 C. After one day, the dry film was transparent and flexible.
. .
To 0.70 grams of the dry film in a small pouch of 3 ml polyethylene were added 0.4 grams of distilled water, and the pouch was sealed. After 2.5 days at room temperature, the pouch was cut open and the tack of the film was assessed by pressing clean, dry skin on the end of a finger against it for three seconds. Its tack level was ~udged "very good".

EXAMP~E 14 -- PREPARATION AND EVALUATION OF POLYMER
COMP EX - PAA/PVP WITH PLASTICIZERS

50.9 grams of 81-B from EXAMPLE 13 were warmed in a hot water bath, and the following additions were made in order with stirring 5.5 grams of propylene glycol: a solution of 4.0 grams of triethanolamine (Fisher Scienti~iC) in 7 grams of ethanol; 16 grams of 1 ~`
ethanol. ~
, I , .
, The resulting solution, while still warm, was cast on a level glass surface kept at room temperature-WO 92/04923 PCr/CA91/00327 2 ~ s3 ~

To 0 .70 gram~ of the dr~ fllm in a small pouchof 3 ml polyethylene wer2 added 0.14 yrams of distilled water, znd the pouch was sealed. Af~er 2.5 days at room temperature, the pouch was cut open and the tack o ~he film was assessed by pressing clean, dry skin on the Pnd of a finger against it for three seconds. The tack was judged "good".

Claims (24)

What we claim is:

1. An adhesive covering for adhesive attachment to mammalian tissue for contacting treatment areas thereof, and comprising:

an outer layer of self-supporting, water vapour-permeable film:
an inner, treatment area contacting layer of tacky polymer complex supported by the outer layer;
the polymer complex layer composition being substantially wound- and skin-compatible, having a water content sufficient to render it skin adhesive, and being formed from the tacky, polymer complex product produced by coprecipitation as a result of mixing solutions of first and second coprecipitatable hydrophilic polymers, and optionally adjusting the water content thereof.

2. The adhesive covering of claim 1 wherein the polymer complex product is produced by coprecipitation form mixed aqueous solution.

3. The adhesive covering of claim 2 further includ-ing an intermediate layer of skin compatible adhesive disposed between the outer self-supporting layer and the polymer complex layer.

4. The adhesive covering of claim 3 wherein said intermediate layer and said outer layer extend peripherally beyond the edge of said polymer complex layer to provide additional bonding of the covering to the wound location.

5. The adhesive covering according to any preceding claim further including a removable release sheet applied to the potential wound-contacting surface of the polymer complex layer, said release sheet being removable by peeling prior to application of the covering to the wound site.

6. The adhesive covering of claim 1 further includ-ing an adhesive release sheet applied to the outer surface of the outer supporting film, the adhesive release sheet being removable by peeling after application of the covering to the wound site.

7. The adhesive covering according to any preceding claim wherein the polymer complex has one or more thera-peutic agents incorporated therein.

8. The adhesive covering of any preceding claim wherein the polymer complex layer consists essentially of a complex of a polymer or copolymer of acrylic acid and a polymer or copolymer of ethylene oxide.

9. The adhesive covering of claim 8 wherein the polymer complex layer consists essentially of polyacrylic acid and polyethylene oxide.

10. The adhesive covering of any of claims 1 - 7 wherein the polymer complex layer consists essentially of a complex of a polymer or copolymer of acrylic acid and a polymer or copolymer of vinyl pyrrolidone.

11. The adhesive covering of claim 10 wherein the polymer complex layer consists essentially of a complex of polyacrylic acid and polyvinyl pyrrolidone.

12. A sealed package containing an adhesive wound covering suitable for application to wounds, said package comprising a sealed film envelope confining an atmosphere of high water vapour content in which the adhesive wound covering is stored;

the adhesive wound covering comprising an outer layer of self-supporting, water vapour-permeable film, an inner wound contacting layer of tacky polymer complex having a water content sufficient to render it skin adhes-ive supported by said outer layer, the polymer complex layer being essentially wound and skin compatible.

13. The sealed package of claim 12 including a removable release sheet applied to the potential wound-contacting surface of the polymer complex layer.

14. The sealed package of claim 12 or claim 1 including an adhesive release sheet applied to the outer surface of the outer supporting film.

15. The sealed packed of claim 12, claim 13 or claim 14 wherein said sealed film envelope is a heat-sealable laminated aluminium foil.

16. A process for making an adhesive covering material suitable for adhesive attachment to mammalian tissue for contacting treatment areas thereof, which com-prises:

mixing together solutions of coprecipitatable, hydrophilic polymers and forming a solid or semi-solid wound compatible polymer complex thereof;
forming a laminate of said polymer complex with a self-supporting, water vapour permeable film by applica-tion of the polymer complex to a surface of said film;
and, before or after its application to the film surface, adjusting the water content of said polymer complex as necessary to render it skin adhesive.

17. The process of claim 16 wherein the coprecipi-tated polymer complex is separated from the precipitation medium, dissolved in water-compatible organic solvent, applied to the self supporting film as a liquid solution and dried thereon.

18. The process of claim 16 wherein the coprecipi-tated polymer complex is separated from the precipitation medium, dissolved in water compatible organic solvent, the solution so formed is cast onto a transfer surface and dried thereon to form a film, and applied to the self-supporting film surface as a film.

19. The process of claim 16, claim 17 or claim 18, wherein the solutions of coprecipitatable, hydrophilic polymers are both aqueous solutions.

20. The process of any of claims 16 - 19 wherein the polymer complex film is subsequently rehydrated.

21. The process of any of claims 15 - 19 wherein the polymers are a polymer or copolymer of acrylic acid, and a polymer or copolymer of ethylene oxide.

22. The process of claim 20 wherein the polymers are polyacrylic acid and polyethylene oxide.

23. The process of any of claims 15 - 19 wherein the polymers are a polymer or copolymer of acrylic acid and a polymer or copolymer of vinyl pyrrolidone.

24. The process of claim 22 wherein the polymers are polyacrylic acid and polyvinyl pyrrolidone.