the adhesive layer is deformable under the influence of weak and rapidly acting forces , thus having a low elasticity modulus and a large elongation . it has a very low flowing when dry and not exposed to outer forces . with the expression that the elastomer must be physically cross - linked is meant that the cross links in the polymer of which it consists is not of a chemical ( covalent ) nature but of a physical nature which means that there are areas or domains within the elastomer which have a high crystallinity , i . e . a high glass transition temperature . precisely this property of the material known from u . s . pat . no . 4 , 231 , 369 causes that when absorbing moisture it expands largely uniformly in all three dimensions . it has surprisingly been found that a limited plastification of the physical cross - links in the elastomer with the plasticizer mentioned under ( c ), which must be compatible with the styrene domains of the elastomer , causes that absorption of moisture in the adhesive material in use precominantly expresses itself as an increase in dimension in the thickness direction and only very small expansion in the two other dimensions . thereby the puckering of the adhesive material , discussed hereinabove , is avoided even at high moisture absorption , and hence also that the adhesion gets lost in parts of the adhesive material . especially it is obtained that sealing problems when using the material for ostomy adhesive and sealing gaskets are avoided . the lesser elasticity and higher plasticity of the material caused by the plasticizer , which may give a tendency to some degree of permanent change of shape or &# 34 ; set &# 34 ; after deformation is counteracted thereby that the watertight film is elastic , whereby the combination adhesive layer - film has the desired properties with respect to a low elasticity modulus and a small or no permanent change of shape or &# 34 ; set &# 34 ; after deformation . because of this the skin barrier according to the invention is not only suited as sealing and adhesive gasket for ostomy pouches and other ostomy closure means , but also for bandaging purposes where skin , mucous membranes or wounds are to be protected against the immediate surroundings such as intestinal , wound or glandular secretions or again bacterial attack , the action of the air , evaporation , light , impact and pressure . if the skin barrier is to be used in connection with real bandages change of these may take place without disturbing the surface of the skin or wound since the skin barrier is retained on the skin at the change , and moreover it will in itself limit bandage changes to a minimum . the material is skin and wound friendly and because of the elastic properties it may in many cases draw edges of wounds together and render superfluous the use of clips , which may give a less visible wound healing than would otherwise be the case . by use around movable parts of the body , e . g . joints , or on soft parts of the body , which for instance are apt to form folds , the mobility is preserved and the skin barrier follows the movements . the skin barrier seals well around protruding part of the body , e . g . ostomies . as elastomer there is used as mentioned styrene - olefin - styrene block copolymers . they are a - b - a block copolymers having polystyrene end blocks which are thermodynamically incompatible with the polyolefin rubber middle blocks . consequently there is phase separation in the solid state . the polystyrene constitutes about a third of the molecule and hard polystyrene domains are therefore a kind of discontinuous phase distributed in a rubber matrix . the hard areas constitute the physical cross - links which bind the ends of the molecules together to a network reminding of that formed by a conventional vulcanized rubber ( caoutchouc ). since the high cohesive strength of the block copolymer originates from the physical cross - links ( instead of from the chemical cross - links as in vulcanized materials ) it is easy to work . in comparison with conventional rubbers the styrene - olefin - styrene block copolymers have low molecular weights , of the a - blocks around 2000 - 100 , 000 and of the b - blocks around 25 , 000 - 200 , 000 . the content of styrene units is normally below 40 %. these block copolymers have two glass transition temperatures , one below , the other considerably above room temperature . the aliphatic blocks may be based on isoprene , butadiene , other short chain alkadienes or alkenes such as mixtures of ethylene and butylene , or polyisobutylene . it has been found according to the invention that the elastomer particularly advantageously is a styrene - isoprene - styrene block copolymer . very suitable is the material sold under the registered trade mark &# 34 ; cariflex &# 34 ; tr - 1107 , which contains about 28 % by weight styrene units . as softener for the two types of blocks of the elastomer , or at least for the hard styrene blocks a plasticizer must be present . the plasticizer especially has to decrease the higher of the glass transition temperatures . as this plasticizer in principle may be used a series of substances having polar nature to a substantial degree , thus for instance naphthenic oils , which however should be avoided because they may be cancerogenic and / or allergenic . the best suitable are esters of di - and polybasic organic acids which have been fully esterified with aliphatic monovalent alcohols , especially those having 6 - 12 carbon atoms , and esters of polyethylene and polypropylene glycols with carboxylic acids , for the above reason preferably aliphatic acids . particularly suitable are dioctyl adipate and dioctyl pthalate and of these dioctyl adipate is preferred according to the invention , firstly because it has been found to give to the invention , firstly because it has been found to give the best results with respect to a moderate decrease of the elasticity of the elastomer , and secondly as a consequense of a general tendency to prefer aliphatic to aromatic compounds for materials for use on the human body . for the same reasons esters of the said acids with phenols are avoided . the tackifier resin is necessary to give the needful adhesion to the skin and is an integral component of the continuous phase . the antioxidant is necessary to maintain the properties of the elastomer ; some commercial elastomers of the type concerned incidentally contain antioxidant from the factory . the type of antioxidant is not critical and ordinary reference books will give examples . suitable antioxidants are butylated hydroxy toluenes such as methylene - bis -( 4 - methyl - 6 - t - butylphenol ) or 1 - hydroxy - 2 , 6 - di - t - butyl - 4 - methylbenzene . apart from the above described plasticizer there may be an oily extender present . it is substantially incompatible with the styrene domains of the elastomer but compatible with the soft olefin moiety . as oily extender there may especially be used paraffinic oils or vaseline . if desired vegetable oils may be used but since they have a somewhat polar nature they may also act on the styrene domains and thereby increase the effect of the plasticizer to a degree not fully clear ; they are therefore preferably avoided . the discontinuous phase consists of the hydrocolloid . its purpose first and foremost is to ensure the adhesion of the skin barrier to skin and mucous membranes even when they are moist . it is well - known that conventional plasters lose the grip and adherence to the skin when exposed to moisture . the hydrocolloid must be capable of swelling rapidly under the influence of water , and of transporting water rapidly . it should preferably also be soluble in water . suitable hydrocolloids are carboxymethyl celluloses and carboxymethyl starches and alkali metal derivatives thereof , polyvinyl alcohol , gelatin , powdered pectin , vegetable gums such as gum guar , gum arabic , locust bean gum , karaya , high molecular weight polyethylene or polypropylene glycols , polyoxymethylene and similar polymers . according to the invention sodium carboxymethylcellulose is preferred ; also a blend of sodium carboxymethylcellulose and gum guar in the proportion about 36 : 16 by weight is suitable . in the continuous phase or as a further dispersed phase additives having various skin - friendly and / or therapeutic purposes may be present . such additives may for instance be ph controlling systems such as sodium , potassium or magnesium citrates , or bacteriocidal , bacterostatic , fungicidal or fungistatic agents and special proteins which might contribute to a fast wound healing , e . g . collagen . as mentioned it is important that the watertight film is elastic . comparatively few plastic foil materials are elastic but suitable films for the purpose consist of polyurethane , styrene - isoprene copolymers , styrene - butadiene block copolymers , butadiene rubbers , isoprene rubbers , neoprene rubbers , silicone rubbers , butyl rubbers , chloroprene rubbers or mixtures thereof . according to the invention it is particularly preferred that the watertight elastic film is a polyurethane film . the proportions of the several components may vary within rather wide limits . the amount of the elastomer , however , is normally somewhat higher than in the material known from u . s . pat . no . 4 , 231 , 369 and according to the invention constitutes 10 - 40 % by weight of the adhesive layer , preferably 20 - 40 %. according to the invention the composition of the adhesive layer expressed in % by weight may be : elastomer 10 - 40 %, preferably 20 - 40 %; tackifier resin 15 - 45 %, preferably 30 - 40 %; plasticizer for the two domains of the elastomer as defined 2 - 12 %, preferably 8 - 12 %; antioxidant 0 . 5 - 2 . 5 %; oily extender 0 - 25 % and hydrocolloid 10 - 55 %, preferably 20 - 40 %. an especially preferred composition is about 25 % styrene - isoprene block copolymer ( notably one containing about 20 % styrene unites , &# 34 ; cariflex &# 34 ;® tr 1107 ), about 35 % tackifier resin , about 9 % dioctyl adipate , about 1 % antioxidant and about 30 % sodium carboxymethylcellulose . for special purposes the adhesive layer in the skin barrier may have a high thickness , e . g . up to 6 mm or more , but according to the invention the thickness is normally 0 . 25 - 3 mm , preferably about 1 . 1 mm , and the thickness of the elastic watertight film normally according to the invention 10 - 15μ , preferably about 30μ . in practice the skin barrier is prepared by pouring the adhesive material in molten condition on the film , after which there is rolled to the desired thickness of the adhesive layer . if desired the adhesive material may be rolled onto the film in a non - molten state , but softened by heat . during the application of the adhesive layer the film must be supported on a suitable material because the film will absorb plasticizer from the adhesive material and swell ; because of physical forces ( e . g . van der waal &# 39 ; s forces ) the swelling only takes place in the thickness dimension when the film is fixed to the backing , but otherwise may take place in all directions and involve puckering . when the adhesive layer is cold the connection between the same and the film will remain smooth , even if the film has swelled . some films when supplied by the manufacturer are supported on a suitable material and a particularly suitable material is paper coated with polyethylene on the side facing the adhesive material and on the other side with a silicone wax . this support material may remain on the skin barrier as a protective cover which is only removed when it is to be taken into use . the adhesive material may be prepared in a manner similar to that described in u . s . pat . no . 4 , 231 , 369 . preferably the physically cross - linked styrene - olefin - styrene elastomeric copolymer is mixed with the antioxidant ( if not present from the factory of the copolymer ), the hydrocarbon resin tackifier , the plasticizer and optionally the oily extender , after which the blend is heated at a suitable temperature , normally within the range of 80 °- 170 ° c . when the desired temperature has been reached and the blend is homogenuous , optionally by agitation , the hydrocolloid is added at the same temperature and the mixture stirred until the hydrocolloid has been evenly dispersed in the mixture of the other components . thereafter the mass is cooled for later used , or directly used for pouring onto the supported fiom as described above . a skin barrier having the structure schematically shown in the drawing was prepared in the following manner a web of paper 10 which on the underside 12 had silicone wax and on the top side was coated with a thin film 14 of polyethylene , and above that an elastic film 16 of polyurethane having a thickness of about 28μ , was coated with a melt of adhesive material having the following composition : 25 . 1 % &# 34 ; cariflex &# 34 ;® tr 1107 , 35 . 1 % &# 34 ; arkon &# 34 ;® p 90 ( a hydrogenated polycyclopentadiene adhesive from arkawa forest chemical industries ltd . ), 8 . 8 % dioctyl adipate , 30 % sodium carboxymethylcellulose and 1 . 0 % antioxidant , viz , methylene - bis -( 4 - methyl - 6 - t - butylphenol ). after partial solidification the melt was rolled to a thickness of 1 . 1 mm whereby the adhesive material constituted a layer 18 . after cooling the whole was wound to a roll of the web . the paper with polyethylene layer and silicone wax layer is an extra protective cover to be removed when the skin barrier , consequently consisting of the layers 16 and 18 , is taken into use . on top of the adhesive layer a protective cover may be placed , consisting of a paper web 20 coated on the side facing the adhesive layer with a layer of silicone was 22 . when the skin barrier is taken into use , pieces of desired shape and size are cut out .
a skin barrier consisting of an elastic film , secured to the film a layer of at least weakly elastic adhesive material , these two components together having low resistance to quick deformation and rapid recovery to substantially the original shape after deformation , the plastic properties of the adhesive thereby being compensated by the elasticity of the film . optionally there may be a releasable protective cover on the other side of the adhesive layer . the adhesive material consists of a hydrocolloid , preferably sodium carboxymethylcellulose , dispersed in a continuous phase consisting of a mixture of a physically cross - linked elastomer which is a styrene - olefin - styrene block copolymer , a hydrocarbon resin tackifier which is a polymer or copolymer of cyclopentadiene , dicyclopentadiene or α - or β - pinene , a plasticizer for the elastomer which is compatible at least with the styrene blocks thereof and decreases the upper glass transition temperature thereof , preferably dioctyl adipate , an antioxidant , and optionally an oily extender compatible with the olefin blocks of the elastomer .