A DRESSING

Abstract: A dressing comprising a skin friendly pressure-sensitive continuous or discontinuous adhesive layer (2), which is coated on one side with a non-adhesive flexible polymer film (1a) and which is optionally coated on the other side with a removable release layer (3), said polymer film (1a) consisting of an uppermost layer (4) of a material which is relatively hard, and a lowermost layer (5) of a material which is relatively soft, said lowermost layer (5) being thicker than the uppermost layer (4). The dressing has a low surface friction and a good flexibility.

Description: A dressing The present invention concerns a dressing of the type com¬ prising a skin friendly pressure-sensitive continuous or discontinuous adhesive layer, which is coated on one side with a non-adhesive flexible polymer film, optionally with a flexible foam layer interposed between the film layer and the adhesive layer, and which is optionally coated on the other side with a removable release layer. Dressings of the above-mentioned type are extensively used for the treatment of wounds, in particular cronic wounds, burns and surgical wounds. Dressings of the above- mentioned type are also used for the treatment of blisters, minor wounds and chafe wounds, as wells as prophylactically to avoid the same, e.g. in connection with the practice of sports or manual labour and the like, where the skin areas, such as heels, elbows, knees and palms of the hand are subject to particularly severe stresses which easily give rise to the above-mentioned minor injures. Dressings of the above-mentioned type con¬ tinue to find new fields of application. It may e.g. be mentioned that such dressings have also been found useful as a transcutaneous dosing means for the dosing of various medicaments, such as hormones or nicotine. Thus, a large number of products of the above-mentioned type are known. The products most used are the so-called liquid absorbing bandages, e.g. hydrocolloid plasters and hydrogel plasters. Hydrogel bandages consist of a liquid abosorbing cross- linked polymer, such as colagen, polyvinyl alcohol and gelatine, as well as of a non-adhesive watertight film having a low water vapour permeability arranged on the side of the bandage which is not intended to face the ski of the patient. A hydrogel bandage contains a large amount of water already prior to use. In the cases where -the bandage is approximately saturated with water, the bandage is fre- • quently not adhesive and must therefore be secured to the skin in another manner, e.g. by means of a plaster. An example of this is the so-called 2ND SKIN® dressing which is commercially available from Spenco Medical Ltd., U.K. Other hydrogel bandages having a lower content of water exhibit excellent adhesive properties. Certain modified gellable polymers, however, are capable of maintaining a reasonably good adhesive capability, even when they are essentially saturated with water. Hydrogel bandages are known e.g. EP Patent Applications 97846 and 415183, SE Published Application 365 410, WO Patent Application 88/6894 and US Patent Specification 4 093 673. Hydrocolloid plasters normally consist of (a) and adhesive material consisting of (i) a continuous phase containing an adhesive and composed of e.g. an elastomer, a plasticizer for elastomers, atack promoting resin and optionally an oilbased extender as well as an antioxidant, and (ii) a discontinuous phase dispersed therein and consisting of one or more water soluble or water swellable hydrocolloids, such as starch or cellulose derivatives or other hydrophillic polymers, and (b) a non-adhesive watertight film arranged on the side o the bandage which is not intended to face the patient's skin. Such a dressing is known e.g. from the Applicant's own DK Patent Specifications 147 034 and 147 035 (corresponding to US Patent Specifications 4 231 369 and 4 367 632). The products mentioned in these consist of an adhesive mate- rial consisting of (I) a continuous phase containing (a) a physically cross-linked elastomer in the form of one or more styrene olefin styrene block copolymers or ethylene propylene block copoly¬ mers, (b) a hydrocarbon adhesive resin in the form of a polymer or copolymer of cyclopentadiene, dicyclo- pentadiene, α-pinene and/or 0-pinene, (c) an antioxidant, (d) optionally an oil extender consisting of one or more mineral oils, and (e) an elastomer polar plasticizer, such as e.g. an ester of a polyethylene glycol or polypropylene glycol, or an ester of a di- or polybasic car¬ boxylic acid with a preferably aliphatic alcohol, as well as (II) a phase dispersed in the continouus phase and consisting of one or more water swellable hydro- colloids. Also other elastomers may occur in known dressings, e.g. natural rubber, synthetic resins of a nature similar to natural rubber and silicone rubbers. Further, polyisobu- tylene in a suitable molecular weight distribution is also frequently used as an adhesive material and texture im¬ parting component in dressings, e.g. as stated in US Patent Specification 3 339 546. Other dressings of a similar type are known from e.g. NO Published Application 157 686 as well as DK Patent Speci¬ fications 154 806, 147 226, 157 899 and 154 747. Mention should also be made of WO Patent Application 90/01911, GB Patent Specification 128 631 and DK Published Application 158 493, which concern bandages that essen¬ tially do not contain components which are actively water absorbing. In particular, thin, non-liquid absorbing pro¬ ducts are greatly used. Mention may here be made of e.g. "the dressing Tegaderm® which is marketed by 3M, the dressing Bioclosure® which is marketed by Johnson & John¬ son, the dressing Up-Site® which is marketed by Smith & Nephew, and the dressing Uniflex® which is marketed by Howmedica. The thin non-absorbing products are extremely flexible and often transparent. They consist of a non-absorbing adhe¬ sive, such as rubber, various acrylates or copolymerisates thereof, polyvinyl ether and synthetic or natural resins and a film cover layer which is frequently watertight, but has a relatively great water vapour permeability. In con¬ trast to the absorbing bandages, this water vapour permea¬ bility is very important, because the skin constantly secretes a certain amount of liquid which may give rise to maceration. In case of very suppurating wounds these thin non-absorbing bandages cannot always be applied success- fully . A development of recent years is the combination of these different types of bandages. For example, also hydro- colloid bandages as thin as 0.3 mm are now available. Such thin hydrocolloid bandages are not always capable of ab¬ sorbing all the liquid secreted from the skin and possible wounds, and it is thus important that these thin hydro- colloid bandages have a cover film with a reasonably great water vapour permeability. This water vapour permeability, as mentioned before, has no significant importance for the thicker hydrocolloid bandages of e.g. 1.0 mm or more, since these bandages are essentially capable of absorbing the amount of liquid secreted from the skin and possible wounds. Another type of bandage consisting of a combination of the above-mentioned types of bandages is the one known from the above-mentioned DK Published Application 157 899, in which the bandage has an adhesive layer consisting of various types of adhesives arranged juxtaposed in a pattern. DK Published Application 147 226 mentions a bandage which comprises an adhesive layer, a film layer and a flexible film layer interposed therebetween. Like the previously mentioned adhesive layers, the ad¬ hesive layer may e.g. contain rubber-like elastomers and liquid absorbing hydrocolloid. The foam layer is a non- compressed semi-open cell layer of e.g. polyurethane which, in addition to being flexible, can also be elastic. The film layer has a water vapour permeable water imper- meable flexible polymer film, such as polyurethane. Such bandages containing a foam layer may have an overall thickness of down to about 0.6 mm. A common feature of all the above-mentioned bandages is that they are relatively thin, i.e. thinner than 3.0 mm and in particular thinner than 1.0 mm. Furthermore, they are flexible and frequently elastic so that when being used they can be shaped and conform to the bends and shapes of the skin surface. The elastic property of the bandages is very essential, because it is precisely this property which enables a bandage to conform to the skin upon movements and the like, and moreover the elasticity of a bandage is of great importance for the comfort when using it. For a bandage to have a sufficient elasticity to satisfy the functional requirements, as stated above, it is essen¬ tial that each individual one of the constituent layers is sufficiently elastic, since it is the least elastic layer that determines the elasticity of the assembled product. The elasticity of the non-adhesive film usually determines the elasticity of the entire dressing, in particular in case of the quite thin dressings, because the adhesive mass is relatively more elastic than even the most elastic non-adhesive polymer film.- Foam layers frequently also possess a sufficient elastici- ty, in particular the non-compressed foam layers. Bandages containing a polymer foam layer are frequently just as elastic as bandages without a foam layer. The film layer on bandages with a foam layer and bandages without a foam layer, respectively, serve several pur¬ poses. The film layer on bandages having a foam layer serves i.a. to strengthen the foam layer, cf. DK Published Applicatio 147 226, page 5, lines 9-10. The film layer on bandages without a foam layer, i.e. where the film layer is in direct contact with the adhe¬ sive layer, serves to cover the adhesive face facing away from the skin, so that clothes and other objects do not stick to the adhesive. Whether or not the bandage has a foam layer, the film serves to protect against contaminations and ingress of bacteria, etc. and another essential purpose of the film is to impart a smooth surface to the bandage. In the use of the bandage the film is subjected to several wear forces, such as rubbing against clothes or other ob¬ jects, tension and stretching as caused by the movements of the user, as well as removal of the bandage. Thus, it is very important that the film has a sufficient strength to resist these external impacts. It is thus clear that the most important properties of the film are that it must be elastic and wear resistant. Both the elasticity and strength properties depend upon the composition of the material and the thickness of the film layer, the elasticity of the film decreasing with increasing thickness, and the strength of the film increasing with increasing thickness. Thus, it has been necessary to weigh the desired elasticity and strength properties. The non-adhesive films in known dressings of the type described in the opening paragraph thus typically have a thickness of 20-40 um. Films in this thickness range of a material having a reasonable elasticity can thus essen¬ tially satisfy the requirements made both of the elastici¬ ty and the wear strength. The film materials most used are different polyurethanes, which are selected in particular because of their excel¬ lent elastic properties and possibly water vapour per¬ meability properties, but also other polymer types, in particular elastomers, are used as non-adhesive films in dressings. The more elastic a film in a given thickness is, the lower hardness the film material has. The non-adhesive film used for the known dressings thus consists of a polymer material which is relatively soft either per se or after addition of a plasticizer. The known dressings consisting of a skin friendly pres¬ sure-sensitive adhesive layer and a non-adhesive, rela¬ tively soft film, optionally with an elastic foam material layer interposed therebetween, thus have a good flexibi¬ lity, and the known dressings in which the adhesive layer or the sum of the adhesive layer and the foam layer is 2.0 mm or thinner, have a particularly good flexibility and elasticity, so that they can easily conform to the body to provide great comfort in use. However, the existing dressings have the drawback that after some time they very frequently roll off completely or partly. This drawback is caused by the fact that in addition to the desirable elasticity, the non-adhesive, relatively soft film also exhibits a high friction in par- ticular with relation to skin, leather, plastics and cer¬ tain fabrics. In case of external forces, such as friction agains articles, clothing or other skin surfaces, the edges of the dressing thus work loose and roll up, causin the adhesive layer to turn away from the skin surface to which it is intended to adhere so that instead it sticks to garments and the like, whereby the dressing is easily torn off or rolled up completely or the foam layer is tor to pieces. This is a long-known problem, but the only known solution proposed is the one mentioned in EP Patent Application 40 587, in which the employed non-adhesive film is embossed in relief so that the bandage surface area offering resistance upon rubbing against another plain surface is significantly diminished. The coefficient of friction between the embossed bandage surface and a given plane surface, e.g. a non-woven fabric surface, is thus un¬ changed, but since the contact area is reduced, the resulting friction is likewise reduced. Howver, the embossed bandage surface only gives rise to reduced friction upon rubbing against plain or approxi¬ mately plain surface. Rubbing against irregular surfaces, such as certain knitted or woven fabric surfaces, fre¬ quently causes the resulting friction to be considerably greater than if the bandage surface was not embossed. Additionally, protruding parts and edges on e.g. garments or footwear can very easily grip the bosses and thus cause the bandage to be removed. Furthermore, the embossed areas in the bandage frequently collect dirt and bacteria, which is very inexpedient and inacceptable to the users. An essential reason why no other solutions have been developed, as far as is known, is presumably that the elastic property of the dressing has been given priority, because lack of said property would involve even easier undesirable removal of the dressing. In an attempt at solving the above-mentioned problem of friction the inventors of the present invention tested how polymer materials having a greater hardness than the mate¬ rials normally used operated as non-adhesive films in a dressing. As might expected, it was found that the surface friction of the non-adhesive film decreased with increas- ing hardness of the material, but at the same time the elasticity decreased so drastically that the selection of a polymer material having a hardness giving even a tole¬ rably acceptable low value of friction resulted in such an inelastic polymer film that in the employed thicknesses for use for dressings it would be quite inapplicable. To obtain even a tolerably acceptable elasticity it was thus found that the film of the higher hardness should be thinner than 10 urn and preferably 5 urn or less. When testing a dressing consisting of an adhesive layer and a film with a higher hardness in a thickness of 10 urn or less, it was found that the film tore easily in use, because it did not possess a sufficient strength or elasticity to conform to the movements of the skin or to absorb other effects occurring in use, and it was simul¬ taneously found that large areas, in particular edge areas, were worn in use. It was additionally found that the dressing having the very thin and relatively hard film was significantly more difficult to remove than the known dressings, because the film broke during removal and thus was not capable of holding the adhesive material together, which was left on the skin in major and minor spots. The object of the present invention is thus to provide a dressing which comprises an elastic adhesive layer and a non-adhesive film and optionally an elastic foam layer interposed between these, and which has a sufficient elas ticity to conform to the skin surfaces of the body, follo the skin during movement, and where the non-adhesive film has a sufficient wear strength to absorb the forces to which the product is subjected in use, and where the non- adhesive film additionally has a surface of less friction than the surface on existing dressings. Another object of the present invention is to provide an elastic dressing comprising an adhesive layer and a non- adhesive film and optionally a foam layer, which dressing does not break easily in use or during removal of the pro duct, and which has a dynamic friction of less than 5 N, preferably less than 4 N, and in particular a friction of less than 3 N, measured as stated below. A third object of the present invention is to provide a flexible dressing having a low surface friction, where th non-adhesive film has a sufficient mechanical strength to resist the wear to which it is subjected in the use of th product. These objects are achieved by the dressing of the inven¬ tion, which is of the type stated in the introductory por¬ tion of claim 1, and which is characterized by the fea¬ tures defined in the characterizing portion of claim 1. Thus, it has surprisingly been found that by applying a film layer of a polymer material having a relatively low hardness between the adhesive layer and a film having a thickness of 10 urn or less of a material having a higher hardness, the film of the higher hardness does not break easily in use or upon removal of the product. It has moreover surprisingly been found that the dressing of the invention provides a product having a high flexibi¬ lity and simultaneously a low surface friction. Additionally, it has surprisingly been found that the dressing of the invention provides a product which has a sufficient mechanical strength to resist wear in use. Thus, the present invention has made it possible to achieve a dressing having a lower surface friction than the known dressings, while essentially retaining both the essential elastic property and the essential wear strength. As mentioned, the dressing of the invention comprises an adhesive layer coated on one side with a polymer film, optionally with an intermediate polymer foam layer, said polymer film consisting of an uppermost film layer of a material having a relatively high hardness and a lowermost film layer consisting of a material having a relatively low hardness. The film layer may have an overall thickness of between 20 and 80 μm, preferably between 25 and 35 μm, and parti- cularly about 27 μm and an E-.-„ value of between 1.0 and 2.5 N, preferably between 1.0 and 2.0 N. The E 50S _ value is an expression of the force used for stretching the film layer and is thus an expression of the flexibility of the film layer. For some materials the E__„ value is very dependent on the temperature at which it is measured. The E--_. value is moreover linearly dependent on the thickness of the material. E 50°- is measured according to DS/ISO 1184, the test piece being constructed as a dumb bell sample having a width of 12.5 mm, the initial spacing between the jaws being 100 mm, and the pull rate being 100 mm/min. All measurements are made at about 20 °C. The E- π „ values of the non-adhesive film layers used for the dressings of the invention have been found to be of the same order as for the non-adhesive film layers used i the known dressings having the higher surface friction. The desired water vapour permeability greatly depends upo which type of adhesive and which thickness of the adhesive the film is to be combined with, and upon whether an intermediate foam layer is provided and the thickness and nature of this optional foam layer. By nature is meant the porosity of the foam, and whether it is open cell, semi- open cell or closed cell foam. Thus, the water vapour permeability of the film may be between 2 and 20,000 g/m 2 /24h. In case of hydrogel adhesives the film layer can thus have a water vapour permeability of as low as 2 g/m 2 /24h, but a water vapour permeability of above 500/g/m 2 /24h is preferred in case of the non-saturated hydrogel adhesives, while the film is preferably to have a water vapour per- meability of above 1000 g/m 2 /24h when used in combination with an essentially non-liquid absorbing adhesive. For use in connection with a hydrocolloid adhesive a water vapour permeability of above 500 g/m 2 /24h is preferred. The adhesive layer may be of any pressure-sensitive adhe¬ sive material which lends itself for use on skin. The ad¬ hesive layer may e.g. comprise rubber, rubber-like synthe¬ tic homopolymers, copolymers or block polymers, poly- acrylate and copolymerisates thereof, polyurethane, sili- cone, polyisobutylene, polyvinyl ether and natural or synthetic resins or mixtures of these. The adhesive layer may moreover be a hydrogel adhesive of e.g. one of the previously mentioned types. The adhesive matrix may additionally contain various additives, such as plasticizers, thickeners, alcohols and others, as well as optionally hydrocolloids and/or various drugs, such as antiseptics, hormones, nicotine, etc. These adhesive materials are generally known and further information on these can be found e.g. in the previously mentioned publications. The adhesive layer may be continuous and cover the entire one side of the dressing. It may discontinuous in strips or points or cover an edge width of the product, or the adhesive layer may consist of two or more different adhe¬ sives arranged juxtaposed in a pattern, as known from DK Published Application 157 899. The adhesive layer prefer¬ ably has a thickness not exceeding 3 mm and in particular a thickness not exceeding 2 mm. A thickness of between 0.3 and 1.1 mm is particularly preferred. If the dressing has an intermediate foam layer, this layer may e.g. consist of an open celled, a semi-open celled or a closed celled foam material of e.g. polyurethane, poly- acrylate or natural rubber. Such an intermediate foam layer preferably has a thickness of between 0.3-1.5 mm. The lowermost film layer of the polymeric non-adhesive film consists of a material such as polyurethane, poly¬ ethylene, polybutadiene, polyvinyl chloride, polyvinyl- idene chloride, polyvinyl alcohol, polyacrylate, poly- sulphone, polystyrene, polypropylene, polyamide, ethylenevinyl cetate copolymer, polyester, polycarbonate, polyvinyl fluoride, copolyester ether, synthetic or natural rubbers, silicone and mixtures of these. Particu- larly preferred are elastomers, such as polyurethane, co- polyester ether and synthetic or natural rubbers. The lowermost film layer may additionally contain various additives, such as plasticizers, e.g. dioctyl adipate, as well as fillers, e.g. SiO-, and pigments. The lowermost film layer is of a material which, either per se or after addition of a plasticizer, has a rela- tively low hardness and is thus very elastic. The lowermost film layer preferably has a thickness of between 15 and 70 μm, in particular of between 15 and 35 If a greater water vapour permeability, through the dressing is desired, the lowermost film may optionally be discontinuous, i.e. the film layer does not cover the entire face, but the film layer is preferably to cover at least 50% of the face, and in particular it is advan¬ tageous if each of the non-covered areas does not have an extent of more than 25 mm 2 , preferably less than 10 mm 2 . The uppermost film layer of the polymeric non-adhesive film consists of a material such as polyurethane, poly¬ ethylene, polybutadiene, polyvinyl chloride, polyvinyl- idene chloride, polyvinyl alcohol, polyacrylate, poly- sulphone, polystyrene, polypropylene, polyamide, ethylene vinylacetate copolymer, polyester, polycarbonate, poly- vinyl fluoride, copolyester ether, synthetic or natural rubbers, silicone and mixtures of these. Particularly pre¬ ferred are elastomers, such as polyurethane, copolyester ether and synthetic or natural rubbers. The uppermost film layer may additionally contain various additives, such as an antiblocking agent, e.g. SiO_, friction-reducing agents, such as SiO- and talc which have well-known but only less friction-reducing effects, as well as optionally minor amounts of a plasticizer. The uppermost film layer is of a material having a rela¬ tively high hardness and a thickness of up to 10 μ , in particular of between 2 and 5 μm. This material of the high hardness, i.e. a hardness higher than the hardness of the lowermost film material, is thus less elastic than the material of the lower hardness, but since the thickness of the uppermost film layer is smaller than the thickness of the lowermost film layer, the resulting elasticity of the sum of the two film layers is essentially of the same order as the elasticity of the film layers which are used in the known dressings. On its adhesive side the dressing may be provided with a removable cover layer, which can optionally be formed in a manner such that the product can be applied without the adhesive layer being touched by the fingers, as is known from e.g. NO Published Application 156 035 and from EP Patent Application 189 999. The dressing may moreover be covered on the film side with a removable cover layer, as is known from e.g. WO Patent Application 90/01915. If the dressing is very thin, such a cover layer is particularly desirable, because it imparts a stiffness to the product which makes it easier to posi¬ tion the product at the moment of application, while preventing the product from sticking together. The dressing of the invention can be manufactured in several different ways in principle. The manufacture can e.g. take place in the following steps: a) The polymer material for the uppermost film layer is dissolved in a suitable solvent, and optional addi¬ tives are admixed, following which the mixture is applied in a thin layer to a suitable carrier material which easily releases the finished polymer and is dried. b) The polymer material for the lowermost film layer is dissolved in a suitable solvent, and optional addi¬ tives are admixed, following which the mixture is applied optionally in a pattern on the uppermost film and is dried. c) An adhesive material is applied to the film layer, with a foam layer optionally interposed between the adhesieve material and the film material, and the adhesive material is optionally covered with a removable release layer. d) The skin sheets are punched after optional bevelling, e.g. as mentioned in DK Published Application 154 747. The amount of the mixture applied in b) is of an order such that the lowermost film layer after drying is thicker than the uppermost film layer, the uppermost film layer being preferably smaller than 10 μm. The application of the adhesive material stated in c) can take place in several ways, e.g. by a hot melt method, in¬ cluding extrusion or spreading of the adhesive or by coat- ing with a dissolved or emulsified adhesive material followed by drying. The process described in a)-d) can take place in-line, or each step can be performed separately, so that the carrier material with the applied material is rolled up after one or more of the stated steps, optionally after application of a removable cover paper layer. If such cover paper has been applied, it is removed again when the carrier material is rolled out at the beginning of the next step, it being unnecessary to remove the cover paper at the beginning of step c), because bevelling and punching can be performed very well while this cover paper is on. The dressing of the invention is useful for all forms of treatment of skin surfaces, and it is particularly useful in the situation where the product is particularly sub¬ jected to external impacts, such as friction against other objects and wear. The dressing of the invention is thus particularly useful for ambulant treatment where the patients are not physi¬ cally impaired, for treatment of in bedridden patients, since these patients as well as all other humans are restless in their sleep in many cases, as well as for pro¬ phylactic treatment of exposed skin areas, such as heels, elbows, knees and palms. The invention will be described more fully below with reference to examples and the drawing, in which fig. 1 shows a cross-section of a known dressing, fig. 2 shows a cross-section of a dressing according to the invention, fig. 3 is a top view of an embodiment of a dressing according to the invention with parts of the uppermost film layer removed, fig. 4 shows a cross-section of a second embodiment of the bandage according to the invention, and fig. 5 schematically shows an apparatus for in-line pro¬ duction of the dressing according to the invention. The known dressing shown in fig. 1 consists of a non-ad¬ hesive polymer film (1), a skin friendly pressure-sensi¬ tive adhesive (2) and a removable cover layer (3). In some of the known dressings a foam layer (not shown) is more- over interposed between the film layer (1) and the adhe¬ sive layer (2) . The dressing of the invention, which is illustrated in fig. 2, likewise consists of a non-adhesive polymer film (la), a skin friendly pressure-sensitive adhesive (2) and a removable cover layer (3) . In contrast to the dressing shown in fig. 1, the non-adhesive film (la) is a laminate consisting of an uppermost film layer (4) and a lowermost film layer (5). The uppermost film layer (4) is of a relatively hard mate¬ rial, and the surface of the film (4) has a relatively low friction. The lowermost film layer (5) is of a relatively soft mate¬ rial and is thicker than the uppermost film layer (4). As mentioned before, the two film layers (4, 5) may con¬ sist of a large number of various materials, and the same or a different polymer may be used as the basic component in the two layers. Preferably, polyurethane is used in both layers. The two materials must have a sufficient affinity to each other so that they do not delaminate in use. The materials are additionally selected on the basis of the water vapour permeability desired. It will be possible to a person skilled in the field to find useful materials by an ordinary optimization process which give the desired water vapour permeability and whic do not delaminte. In a special embodiment of the dressing of the invention, see fig. 3, the dressing 6 consists of an adhesive (not shown) having a removable cover layer (not shown) as well as an uppermost film layer (7) with a surface which has a low friction, and a lowermost film layer (9) which is applied discontinuously so that there are areas (9) which are not covered by the lowermost film. With a bandage like the one shown in fig. 3 it is possible to obtain a dressing having a particularly great water vapour permeability, and a great water vapour permeability is obtained in particular if the film layer (7) consists of a material which is very water vapour permeable per se. The areas which are not covered by the lowermost film in the special embodiment, do not give rise to any signifi- cant reduction in the wear strength of the dressing, in particular not if their extent is limited, and the overall area not covered by the lowermost film consitutes less than 50%, and in particular not if it just constitutes about 15% of the face area like in the embodiment shown in fig. 3, or less. Additionally, it is particularly advantageous if the indi¬ vidual non-covered areas have an extent of 25 mm 2 or below, and in particular below 10 mm 2 . The bandange of the invention shown in fig. 4 consists of a skin friendly pressure-sensitive adhesive 12, which is coated with a removable cover layer (13) on one side and is coated on the other side with a foam layer (16) of e.g semi-open celled polyurethane and a non-adhesive polymer film (11a) consisting of an uppermost film layer (14) and a lowermost film layer (15). The layers 12, 13, 14 and 15 correspond to the layers 2, 3, 4 and 5 in the bandage shown in fig. 2. The apparatus shown in fig. 5 comprises a means (20) on which a roll of carrier material (11) can be mounted, as well as a means (not shown) capable of pulling the carrie material through the various treatment stations. The carrier material (10) is pulled off the roll (11), past a application means (12a) in which the uppermost film layer is applied, the application material, which consists of a dissolved polymer and optional additives, fillers, etc., being conveyed from a container (12) to the application means (12a). The carrier material with the uppermost film layer is pulled further on through a drying station (13) and past a second application means (14a), which receives application material from a container (14) containing material for the lowermost film layer which consists of a dissolved polymer and optional additives, fillers, etc. The carrier material with the two film layers is pulled past a second drying station (15), and then an adhesive layer (16) is fed from an adhesive roll (not shown), said adhesive layer being provided with a removable cover laye on the side facing away from the laminate, said adhesive layer being applied to the film layer by means of an application roller (17), with optional addition of heat t improve the bonding between the adhesive layer and the film laminate. The carrier material is moved further on past a bevelling station (18) and a punching station (19). If desired, a station may be inserted after the drying station (15) for applying a foam layer, which can be bonded to the film layer by slight heating. EXAMPLE The samples shown in fig. 1 were manufactured. S stands for an aromatic polyether-based polyurethane ESTANE® 5714 having a hardness of 80 A shore. H stands for an aromatic polyester-based polyurethane ESTANE® 5707 having a hardness of 95 A Shore. The ESTANE® products are available from BF Goodrich Chemical, Belgium. Syloid® (Syloid® ED-30) is an Si0 2 product available from W.R. Grace, and DOA stands for dioctyl adipate. All percentages are per cent by weight, unless otherwise s ated. The samples were tested, and the results appear from table 2. The following methods of measurement were used: Force for 50% elongation (E- Q - . E 50% was measure d according to DS/ISO 1184, the test piece being constructed as a dumb bell sample having a width of 12.5 mm, the initial spacing the jaws being 100 mm, and the pull rate being 100 mm/min. The measurements were performed at about 20 °C. Elasticity The test piece was elongated to 50% elongation, and then the application of force was removed. This was repeated 5 times. The elasticity was calculated as: E 50%, 5th time Elasticity = X 100% 50%, 1st time E--- . , 1st time and E_-~ . , 5th time were measured according to DS/ISO 1184, the test piece being constructed a dumb bell sample having a width of 12.5 mm, the initial spacing between the jaws being 100 mm, and the pull rate being 510 mm/min. The measurements were performed at about 20 °C. Tensile strength/Elongation at break Tensile strength and elongation at break were measured according to DS/ISO 1184, the test piece being constructed as a dumb bell sample having a width of 12.5 mm, the ini¬ tial spacing between the jaws being 100 mm, and the pull rate being 100 mm/min. The measurement were performed at about 20 °C. Friction The friction was measured as the dynamic friction accord¬ ing to ISO 8295, 1986, the base used being a teflon coated glass tissue of the type: Acoflon G 13 A from Aco-plast A/S, Helsingør, DK, the weight of the carriage being 500 9- Water Vapour Permeability The water vapour permeability of the films was measured by water contact with the soft PU film as described in ASTM E96-80. The stated values were measured on a circular test piece with a diameter of 20 mm and at a temperature of 37 °C and a relative air humility of 30%. Results It will be seen clearly from the results in table 2 that the surface friction of ESTANE® 5707 (samples 5, 6, 7 and 8) is considerably lower than of the softer ESTANE® 5714 (samples 1 and 2). On the other hand, the E 5-0-%- . values of the hard ESTANE alone are inacceptably high (sample 3). As mentioned before, ' the E5 cn 0% o value of the non-adhesive film is of great importance for the flexibility of the dressing. In the samples of the invention, in which the non-adhesive film consists of an uppermost hard material and a lower¬ most soft material (samples 5, 6, 7 and 8), E_ n5 , is at the same level as that obtained by using a relatively soft material of the type employed in the known dressings (samples 1 and 2). The E-. os , value of sample no. 9 according to the invention is somewhat higher-^ but still within the acceptable limit. With the relatively hard film layer without a laminated lowermost film layer and in a thickness of 10 μm (sample 4) the E__ o , value is at the same level as for the samples U_ 1 and 2. The E_- 0 value of sample 4 is thus quite good, _>U. but on the other hand the tensile strength is inacceptabl low. Thus, the products of the invention (samples 5, 6, 7, 8 and 9 ) have a reduced surface friction with respect to th known products (samples 1 and 2), while the flexibility, elasticity, tensile strength and elongation at break are kept at the same level. TABLE 1 Samples No. Lowermost film layer Uppermost film layer 1 S + 5% syloid - 27 μm 2 S + 4% syloid, 7% DOA - 27μm 3 - H + 20% syloid - 27 4 - H + 20% syloid - 10 5 S + 4% syloid, 7% DOA - 24 μm H + 5% syloid - 3 7 " H + 20% syloid - 3 8 " H + 20% syloid - 3 9 S + 4% syloid, 7% DOA - 17 μm H + 20% syloid - 10 TABLE 2 Elasti- Tensile Elongation Water Vapou Friction E, -e- city Strength at Break Permeabilit J 50^ (N) (N) (%) (N) (%-) (g/m 2 24h) 3* 3* 3* 3* 4* + 10** + 3** + 3 _.* + 15** + 10** + 2** 7.6 1.6 92 10.1 491 4 1.6 1.4 84 1.7 153 2.2 1.7 91 7.6 468 6. 2.4 1.8 92 8.3 487 1278 1.6 2.3 90 8.4 487 *) Average of (number of samples) **) Uncertainty (%) User Test - Comparative Example Two dressings were moreover manufactured, one according t the invention, hereinafter called A, and one according to the prior art, hereinafter called B. The dressings consisted of a 1.00 mm thick adhesive layer and a 27 μm thick film layer. The adhesive composition was identical for the two dressings, viz. the following: The components for the adhesive matrix were mixed with heating to 135 °C. Thus, dressing A according to the invention consisted of 1.00 mm thick adhesive layer, as stated above, as well as a film material coated thereon and having a composition like the film sample no. 7 previously stated (see table 1). Dressing B according to the prior art consisted of a 1.00 mm thick adhesive layer, as stated above, and a film layer coated thereon and having a composition like the previous- ly stated film sample no. 1 (see table 1). Both faces on both products A and B were coated with a removable cover layer. The dressings were bevelled under the action of pressure and heat, as described in DK Published Application 154 747, and punched in oval pieces with a surface area of about: 22 cm 2 . The dressings were tested via a user test performed as follows: 100 randomly chosen Compeed® users received a letter of introduction with instructions, a questionnaire as well as one of each of the dressings A and B. The letter of introduction informed the users that they participated in a development test of plasters. The instructions read as follows: 1. Place the plaster marked V on the left heel. HI on the right heel. 2. The area where the plaster is placed must be totally clean and dry, and you must not have used cream with¬ in the last 24 hours. 3. It is important that the plasters are placed uniform¬ ly on the right and left heels. 4. Remove the paper on both sides of the plaster prior to application. 5. Stretch the skin - tip the foot upwardly prior to application. 6. Apply the plaster carefully. Take special care that the edges adhere firmly. 7. Warm the plaster with the hand for about 1 minute. 8. When one of the plasters loosens, remove both plasters, and complete the questionnaire. 9. Remove the plaster by elongating it along the skin surface. Result: 35 of the user test participants answered the following questions: I How did the plasters fit? II Did the plasters tend to adhere to the stockings? III Which plaster is the best? YES NO Dressing A 30% 70% Dressing B 48% 52% Question III The user test result shows clearly that the dressing of the invention is a better fit and provides a better co - fort than the known dressings, and that these improvement are exclusively due to the fact that the dressing of the invention has a smaller surface friction than the dressin of the prior art. The above-mentioned test therefore shows clearly that the dressing of the invention provides a product which has th advantages stated in the preamble to the description over the known dressings, without this being at the expense of the generally good properties in use.

Claims: P a t e n t C l a i m s: 1. A dressing comprising a skin friendly pressure-sentive continuous or discontinuous- adhesive layer (2, 12), which is coated on one side with a non-adhesive flexible polymer film (la, 11a) and which is optionally coated on the other side with a removable release layer (3, 13), c h a r a c t e r i z e d in that the polymer film (la, 11a) consists of an uppermost film layer (4, 7, 14) of a material which is relatively hard, and a lowermost film layer (5, 9, 15) of a material which is relatively soft, said lowermost film layer being thicker than the uppermost one. 2. A dressing according to claim 1, c h a r a c t e r ¬ i z e d in that the uppermost film layer (4, 7, 14) has a thickness not exceeding 10 μm, preferably between 2 and 5 3. A dressing according to any of claims 1-2, c h a r a c t e r i z e d in that the uppermost film layer (4, 7, 14) has a dynamic friction not exceeding 5 N, preferably not exceeding 4 N, and in particular not exceeding 3 N. 4. A dressing according to any of claims 1-3, c h a r a c t e r i z e d in that the lowermost film layer (5, 9, 15) has a thickness of between 15 and 70 μm, preferably of between 15 and 35 μm. 5. A dressing according to any of claims 1-4, c h a r a c t e r i z e d in that the polymer film (la, 11a) is liquid impermeable. 6. A dressing according to any of claims 1-5, c h a r a c t e r i z e d in that the uppermost film layer (4, 7, 14) consists of an elastomeric material selected from polyurethane, copolyester ether, synthetic and natural rubbers as well as mixtures thereof. 7. A dressing according to claim 6, c h a r a c t e r ¬ i z e d in that the film layer (4, 7, 14) consists of polyurethane, and that an antiblocking agent is additio- nally admixed. 8. A dressing according to claim 7, c h a r a c t e r ¬ i z e d in that the film layer (4, 7, 14) consists of an aromatic polyester-based polyurethane having a hardness of 95 A shore or above, and that 5-20% Si0 2 is additionally admixed, said film layer (4, 7, 14) having a thickness of 9. A dressing according to any of claims 1-8, c h a r a c t e r i z e d in that the lowermost film layer (5, 9, 15) consists of an elastomeric material selected from polyurethane, copolyester ether, synthetic and natural rubbers as well as mixtures thereof. 10. A dressing according to claim 9, c h a r a c t e r ¬ i z e d in that the film layer (5, 9, 15) consists of polyurethane, and that a filler and a plasticizer are additionally admixed. 11. A dressing according to claim 10, c h a r a c t e r ¬ i z e d in that the film layer (5, 9, 15) consists of an aromatic polyether-based polyurethane having a hardness of 80 A shore or less, and that up to 5% SiO- and up to 7% dioctyl adipate are additionally admixed, said film layer (5, 9, 15) having a thickness of between 17 and 25 μm. 12. A dressing according to any of claims 1-11, c h a r a c t e r i z e d in that the skin friendly adhe sive (2, 12) is an adhesive which is substantially not liquid absorbing, and that the non-adhesive polymer film (la, 11a) has a water vapour permeability of more than 1000 g/m 2 /24h. 13. A dressing according to any of claims 1-11, c h a r a c t e r i z e d in that the skin friendly adhe sive (2, 12) is a hydrocolloid adhesive or an unsaturated hydrogel adhesive, and that the non-adhesive polymer film (la) has a water vapour permeability of more than 500 g/m 2 /24h, preferably more than 1000 g/m 2 /24h: 14. A dressing according to any of claims 1-13, c h a r a c t e r i z e d in that the adhesive (2) has a thickness of up to 3 mm, preferably of between 0.3 and 2. mm.

Inventors: JENSEN HANNE, NAESTOFT ROLAND, JENSEN, HANNE, NAESTOFT, ROLAND
Applicants: COLOPLAST AS, COLOPLAST A/S
Application year: 1993
Main classification: A61F13
IPC codes: A61F13, A61L15