CA2212028C - Adhesive sheet articles - Google Patents

Abstract

Provided is an adhesive sheet article comprised of at least three layers comprising a porous backing, a migration barrier and an adhesive wherein said migration barrier is juxtaposed between said porous backing and said adhesive so that said migration barrier substantially prevents said adhesive from migrating into said porous backing; wherein said article does not include an additional adhesive layer between said migration barrier and said porous backing and wherein said migration barrier is comprised of an alkyl acrylate-N-alkylacrylamide copolymer or polyurethane. A method of manufacturing such an article is also disclosed.

Description

ADHESIVE SHEET ARTICLES
Field of the Invention The invention relates to adhesive sheet articles comprising porous s sheets with a polymeric composition adhered thereto which is further coated with an adhesive. The invention further relates to adhesive articles such as tapes or wound dressings made from the adhesive sheet articles and methods for making the adhesive articles.
1o Background of the Invention Sheet materials having physical characteristics which allow for air permeability and moisture vapor permeability are well known and are generally referred to as porous sheets. Porous sheet materials are typically non-woven, woven or knitted constructions although foamed sheets, microporous films and 1s perforated films also provide certain degrees of permeability.
Porous sheet materials have many applications and are particularly useful as backings for tapes in the medical field. This is particularly tnie when it is desirable to allow the skin covered by the sheet material to breathe. When an adhesive is coated onto a porous sheet, the adhesive sheet article will exhibit 2o varying degrees of breathability depending upon the nature of both the porous sheet and the adhesive coated thereon. For example, Copeland in U.S. Patent 3,121,021 describes a breathable surgical tape made of a non-woven backing and a microporous layer of pressure-sensitive adhesive.
Certain porous sheets coated with adhesive may permit or even 2s facilitate the migration of adhesives into the porous sheet layer. Such migration of adhesives is not always detrimental to the performance of the adhesive tape article. This is true if a heavy adhesive coating is used or if the adhesive is used for transdermal delivery of a bioactive molecule. However, it is sometimes detrimental when the adhesive migrates into the porous sheets. This is true when 3o adhesion of the resulting article is reduced due to the migrated adhesive.

When it is necessary to control or limit the migration of adhesive, a few strategies are available. Generally, one should avoid "soft" adhesives which readily migrate into the interstices of porous backings. "Soft"
adhesives include adhesives such as acrylate ester-acrylic acid-polyethylene oxide acrylate s macromer copolymers which provide adhesive coated sheet materials having a ' skin adhesion value of at least about 2.2 Newtons per 100 millimeters of width.
However, such "soft" adhesives are very desirable for adhering to skin because "soft" adhesives are generally very conformable and usually adhere well to skin, and may adhere to moist skin.
1o U.S. Patent 5,344,415 of DeBusk and Felice (hereinafter "DeBusk") describes a mufti-component system which includes a web and adhesive layer, a barrier layer and a second adhesive layer. The DeBusk barrier layer is a distinct and separate transparent nonexclusive film material such as a polyurethane film. As is generally known in the art, films must be at least 25 is micrometers thick in order to allow handling of the film. The DeBusk barrier layer (film) is sandwiched between 2 layers of adhesive and does not directly contact the web. DeBusk teaches that the barrier layer provides a barrier to external contaminants, restricts drainage strike-through and helps maintain a desirable moist environment.
2o It is an object of the present invention to provide porous adhesive sheet articles wherein the migration of the soft adhesives into the porous sheeting is limited or prevented.
Description of the Drawings 25 Fig. 1 is a 500 times magnification scanning electron micrograph (SEM) of a nonwoven web coated with an adhesive.
Fig. 2 is a 500 times magnification SEM of an embodiment of the invention.
Fig. 3 is a 100 times magnification SEM of a migration 3o barrier/adhesive/release liner composite.

-2-Figure 3.
Figure 2.
Fig. 4 is a 500 times magnification of the composite shown in Fig. 5 is a 900 times magnification of the sample shown in SummarJr of the Invention The present invention provides adhesive sheet articles. More specifically, it provides adhesive sheet articles comprising porous backings with a polymeric composition juxtaposed between said backing and the adhesive layer to Io prevent migration of the adhesive into the porous backing.
This invention further provides such adhesive sheet articles which are converted to provide pressure-sensitive adhesive tape articles or first aid dressings. Although sheet articles comprising porous backings adhered to non-tacky polymeric migration barriers and further adhered to skin adhesives are a preferred sub-class, sheet articles comprised of porous backings with any non-film barrier layer which adheres to both the backing and the adhesive are broadly described. This invention further relates to nontacky or tacky migration barrier layers which are polymeric coatings of acrylate copolymers or polyurethanes juxtaposed between an adhesive and a porous backing. Preferred polymeric 2o coatings are acrylate copolymers.
This invention also provides a process for preparing a pressure-sensitive adhesive tape article comprising depositing a polymeric migration barrier coating on one side of a pressure-sensitive adhesive layer, then adhering the exposed side of the polymeric migration barrier coating to a porous backing.

-3-According to one aspect of the present invention, there is provided an adhesive sheet article comprised of at least three layers comprising a porous backing, a migration barrier and an adhesive wherein said migration barrier is juxtaposed between said porous backing and said adhesive so that said migration barrier substantially prevents said adhesive from migrating into said porous backing; wherein said article does not include an additional adhesive layer between said migration barrier and said porous backing and wherein said migration barrier is comprised of an alkyl acrylate-N-alkylacrylamide copolymer or polyurethane.
According to another aspect of the present invention, there is provided a method of making an adhesive sheet article described herein, comprising: a) coating an adhesive on a liner, b) bonding a migration barrier to the surface of the adhesive, and c) bonding a porous backing to the surface of the migration barrier.
According to yet another aspect of the present invention, there is provided a first aid dressing comprising an adhesive sheet, wherein said adhesive sheet is comprised of at least three layers, said three layers comprised of a porous backing, a migration barrier and an adhesive wherein said migration barrier is juxtaposed between said porous backing and said adhesive, and wherein said migration barrier comprises alkyl acrylate-N-alkylacrylamide copolymer or polyurethane and does not readily migrate into interstices of the backing; wherein said adhesive sheet has a moisture vapor transmission rate of at least 400 g/m2 per 24 hours and further wherein an absorbent layer is adhered to at least a portion of said adhesive.
-3a-According to still another aspect of the present invention, there is provided a first aid dressing comprising the adhesive sheet article as described herein, and an absorbent layer, wherein the absorbent layer is adhered to at least a portion of the adhesive of the adhesive sheet article.
Definitions As used herein the term "coating" refers to an essentially continuous macroscopically nonporous chemically homogeneous layer which has been deposited on or bonded to or adhered to a separately nonsimultaneously formed, deposited or otherwise provided layer.
-3b-As described herein the term "breathable" refers to materials which are penetrable by air and water vapor preferably to the extent that they provide a moisture vapor transmission rate (MVTR) of at least 200 g/m2 per 24 hours when measured in accordance with ASTM E 96-80 or minor modifications s thereof. ' As used herein the term "porous" refers to materials or surfaces which are penetrable by smaller objects or materials. Such porous materials or surfaces do not necessarily have visible openings, although they may, but have visible characteristics consistent with permeability and penetration. Some to . examples of porous materials are nonwoven polymeric webs, woven cloth or polymeric fabrics, knitted cloth or nonwoven fabrics, absorbent spongelike foams and the like but do not include films or other nonbreathable layers.
Detailed Description of the Invention 15 The articles of the invention comprise an adhesive sheet article with moisture vapor transmission rates of at least 400 g/m2 per 24 hours. The adhesive sheet articles of the invention comprise a porous backing, a migration barrier layer comprised of a polymeric composition coated on the backing with an adhesive layer coated on the barrier layer. The migration barrier is preferably 20 less than 20 ~.m thick. The adhesives are first described, followed by a discussion of the porous backings and a discussion of the polymeric migration barrier.
Adhesive 2s As stated earlier, the adhesives which are preferred for contact with human skin are "soft" adhesives. Such soft adhesives would readily migrate into a porous backing. Nonlimiting examples of soft adhesives include hydrophilic adhesives or blends including hydrophilic adhesive components.
Examples of suitable soft hydrophilic adhesives for use on the articles of the invention include pressure sensitive adhesives which are water r

-4-insoluble and not significantly water absorbent and water tolerant such as polyacrylates, polyolefins e.g. polyalpha-olefins, polyethers, polyisoprenes, butyl rubbers, natural rubbers, styrene-butadiene rubbers, polyurethanes, polyesters and the like. It is anticipated that blends or mixtures of such adhesives are useful s in the present invention and the adhesives may optionally include tacldfiers.
Preferred adhesives are acrylate ester-acrylic acid-polyether macromer copolymers described below as second polymeric components and polymer blends thereof. The blends are novel materials described in U.S. Patent No. 5,648,210.
Such adhesive blends comprise primarily two components. The components are each described in detail below followed by a description of the method of blending the two components.
First Polymeric Component of a Preferred Adhesive Blend z5 The first polymeric component increases the initial adhesion of the adhesive blend to the skin while retaining the typical advantages of acrylate ester adhesives when used as medical adhesives. This component is comprised of certain copolymers which are used as skin adhesives for medical applications and are described in U.S. Patent 4,693,776 of Krampe, Moore and Taylor (Ksampe) 2o entitled "Macromer Reinforced Pressure Sensitive Skin Adhesive." The typical advantages of these adhesives include ease of manufacture, an excellent safety history and profile, high shear strength, low cost and chemical stability.
This first polymeric component comprises certain copolymers, especially the A-B-C
type copolymers of (A) acrylate esters, (B) ethylenically unsaturated compounds 25 copolymerizable with acrylate esters such as acrylic and methacrylic acid and (C) macromolecular monomers as described hereinafter. The acrylic esters may be esters of acrylic or methacrylic acid and are preferably acrylic acid esters.
The alcohol portion of the ester is typically a non-tertiary alcohol having one to fourteen carbon atoms with the average number of carbon atoms being about four 3o to twelve. In a preferred embodiment the average number of carbon atoms is

-5-about six to ten, and most preferably about eight. Nonlimiting examples include isooctyl acrylate and ethyl(hexyl) acrylate.
The ethylenically unsaturated compounds (B monomers) copolymerizable with acrylate (and methacrylate) esters include acrylic acid, s methacrylic acid, itaconic acid, acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, vinyl acetate and N-vinylpyrrolidone, but acrylic acid is used in a preferred embodiment.
The macromolecular monomers (macromers) useful as C
monomers have the general formula: X-(Y),~ Z wherein X is a vinyl group to copolymerizable with said A and B monomers; Y is a divalent linking group;
where " can be zero or 1; and Z is a monovalent polymeric moiety having a Tg greater than about 20° C. and a molecular weight in the range of about 2,000 to about 30,000 and being essentially unreactive under copolymerization conditions;
wherein said vinyl group and said A and B monomers form a polymeric 15 backbone having pendant therefrom said polymeric moieties (Z) and wherein the molecular weight of said C macromer and the inherent viscosity of the copolymer are such that the adhesive composition has a creep compliance value of at least about 1.2 x 10-SCm2/dyne. In a preferred embodiment C macromers are polystyrylethyl methacrylate macromers having a weight average molecular 2o weight of about 8,000 to 15,000 g/mol. and most preferably about 10,000 g/mol.
as described in Example M-3 of U.S. Patent 4,693,776 and hereinafter in Example 1. These macromers are prepared by reaction of styrene with secondary-butyl lithium in cyclohexane to form "living polymers" of polystyryl lithium, "capping" with ethylene oxide, followed by reaction with methacryloyl 25 chloride to obtain a macromer of about 10,000 weight average molecular weight.
Some macromers useful in the present invention are commercially available, e.g.
polystyrylethyl methacrylate (13,000 M. wt.) is available as Chemlink~ 4500 from Sartomer Chemical Company of West Chester, PA.
The amounts of A, B and C monomers in these copolymers are so typically 90 percent or more by weight of A monomer and about equal amounts

-6-of B and C monomers. A nonlimiting example of the amounts of monomer in the copolymer is 96 parts A monomer, 2 parts of B monomer and 2 parts of C
monomer.
s Second Polymeric Gomnonent of a Preferred Adhesive Blend The second main component of the polymer blends useful in the present invention promotes prolonged adhesion to skin, which is a relatively moist substrate. Medical tapes which adhere well to moist skin generally require adhesives which are substantially hydrophilic and polar in character. One such to class of adhesives is described in PCT Application WO 84/03837 of Snyder and Silence (Snyder) entitled "Adhesive and Adhesive-Coated Sheet Material for Moist Skin."
These second copolymers include three comonomers. A first comonomer is an acrylic acid ester of a non-tertiary alcohol, said alcohol having is from about 4 to 14 carbon atoms. In a preferred embodiment the alcohol has about 8 carbon atoms. Examples include but are not limited to isooctyl or ethylhexyl alcohol. In a preferred embodiment the alcohol is isooctyl alcohol.
The second copolymer includes a second comonomer which is a hydrophilic monomer having a vinyl group copolymerizable with the acrylate 2o ester monomer, a divalent linking group and a monovalent polyether group.
The polyether group should be essentially unreactive under conditions used for forming the copolymer. Many such second comonomers are described in Snyder. These comonomers contain a plurality of hydrophilic sites such as ether groups. Preferred second comonomers are macromolecular monomers of the 25 formula:
_7_ RI O
Formula III CH2=C-C-W-OR2 wherein Rl is hydrogen or methyl, R2 is hydrogen, phenyl, substituted phenyl or ' lower alkyl and W is a divalent poly(lower alkylene oxide) group containing 2 to 250 repeating alkoxy units and selected from the group consisting of a polyethylene oxide) radical, a polypropylene oxide) radical, a radical of a to copolymer of ethylene oxide and propylene oxide and a polytetrahydrofuran radical.
In a preferred embodiment the W moiety contains about 5 to 25 repeating alkoxy units, most preferably ethylenoxy units, and R2 is hydrogen or lower alkyl. Such second monomers are commonly commercially available as is alkoxypoly(ethylenoxy)alcohols such as methoxypoly(ethylenoxy)ethanols of various molecular weights. Synthesis and description of various additional suitable materials as found in Snyder is as follows:
A variety of second monomers are or have been available commercially. For example, suitable commercially available monomers are the 20 2-(2-ethoxyethoxy)ethyl acrylate available under the trade designation "SR-256"
from Sartomer Company, West Chester, PA; the methoxy polyethylene oxide)lo acrylate available under the trade designation "No. 8816" from Monomer-Polymer & Dajac Laboratories, Inc., Trevose, PA; the methoxy polyethylene oxide) methacrylates of 200 Daltons, 400 Daltons, and 1000 Daltons available 25 under the trade designations "No. 16664", "No. 16665" and "No. 16666", respectively, from Polysciences, Inc., Warrington, PA; the hydroxy polyethylene oxide)5 methacrylate available under the trade designation "No.
16712" from Polysciences, Inc., Warrington, PA.
Other preferred second monomers may be prepared using 3o commercially available starting materials and conventional methods. For example, the preferred second monomers wherein R2 of Formula III is lower _g_ W O 96/26251 CA 0 2 212 0 2 8 19 9 7 - 0 7 - 31 pC~~~S96/00794 alkyl may be prepared by reacting an a,b-unsaturated carboxylic acid such as acrylic acid or methacrylic acid with an equimolar amount of a mono-alcohol of a poly(lower alkylene oxide). The esterification reaction is generally conducted under anhydrous conditions in an organic solvent such as toluene which s preferably will form an azeotropic mixture with the water which is generated as the esterification reaction proceeds. A suitable solvent is toluene.
Typically, the alcohol is combined with the organic solvent and the unsaturated carboxylic acid is then added to the alcohol/solvent mixture. In the event that the alcohol is a solid at room temperature, it is first melted by heating prior to addition of the to unsaturated carboxylic acid. The reaction is conducted in the presence of an acid catalyst such as para-toluenesulfonic acid and a free-radical inhibitor such as copper powder. The reaction mixture is refluxed, generally for 16 to 18 hours under a nitrogen atmosphere, and the water generated is removed by azeotrophic distillation, for example, using a Dean Stark trap.
is Examples of suitable mono-hydroxyl-terminated poly(lower alkylene oxides) which may be used to prepare the preferred second monomers using the above-described procedure include Carbowax~ 350, Carbowax~ 550, Carbowax~ 750, Carbowax~ 2000 and Carbowax~ 5000 (i.e., the methoxy-poly(ethylene oxide) ethanols of about 350 MW, 550 MW, 750 MW, 2000 MW
2o and 5000 MW, respectively, commercially available from Union Carbide Corp).
The Carbowax~ family of monomers are methoxy(polyethylene oxide)ethanols possessing an average molecular weight expressed by the numeral e.g. the 5000 of Carbowax~ 5000 denotes an average molecular weight of 5000. A
monoalcohol of a polytetrahydrofuran of about 16,000 MW prepared as 2s described in Snyder by polymerization of tetrahydrofuran in the presence of methyl trifluoromethanesulfonate as shown in Examples for Monomer "B-9" in

7 cited above; UCOh1~ LB-285 (an n-butoxy polypropylene oxide) propanol having about a 1000 MW, commercially available from Union Carbide Corp.); UCON~ 50-HB260 (an n-butoxy polyethylene oxide/propylene oxide) 30 (50:50 by weight) alcohol having about a 1000 MW, available from Union Carbide Corp.); and 1'ycal~ 94 ( a phenoxy polyethylene oxide)4 ethanol, available from Atlas Chemical Industries).
Second monomers wherein R2 is hydrogen may be prepared by reacting an a,b-unsaturated carboxylic acid or hydroxyalkyl ester with an s anhydride selected from monoepoxides, lactones or mixtures thereof.
A suitable commercially available poly(alkylene oxide) acrylate ester is NK-Ester AM 90G~ available from Shin-Nakamura.
The preferred second monomer for employment in preparing the pressure-sensitive adhesive copolymer is the acrylate ester of above-described 1o Carbowax~ 750.
It is to be understood that the pressure-sensitive adhesive copolymer may comprise a single type of second monomer or may comprise two or more different second monomers.
The third monomeric component of the second copolymer is 1s generally acrylic acid or methacrylic acid, preferably acrylic acid monomer.
Preparation of the First and Second Polymeric Components of a Preferred Adhesive Blend Either of the pressure-sensitive adhesive copolymer components of 2o the adhesive blends useful in the invention may be prepared using conventional free-radical-polymerization methods. One particularly convenient method is the following. The desired amounts of each of the different monomers and an organic solvent in which the monomers are soluble are combined in a sealable bottle. A particularly suitable solvent is ethyl acetate. A solvent such as 25 isopropyl alcohol which functions as a chain-transfer agent is also present in the reaction medium in order to control the molecular weight of the resulting adhesive copolymer. A catalytic amount of a free-radical initiator such as a,a'-azobisisobutyronitrile is then added to the solution. Nitrogen is bubbled through the solution to purge air from within the bottle, and the bottle is then sealed.
3o The sealed bottle is tumbled in a heated water bath for a period of time sufficient to effect essentially complete polymerization. Generally, 24 hours has been found to be sufficient time to effect essentially complete polymerization when the water bath is maintained at about 55°C.
The hydrophilic adhesives used as the second main component of the polymer blends described above are also useful as the sole adhesive on the tape articles of the present invention.
Preparation of an Adhesive Blend Useful for the Invention The process of blending the two copolymer components of the to preferred blend adhesive of the present invention to provide a useful homogeneous pressure-sensitive adhesive requires that each of the copolymer components is dissolved in a solvent or solvent mixture. The solvents used for each of the copolymer components are preferably at least partially miscible in order to obtain good blending. Suitable solvents include esters such as ethyl 15 acetate, dimethyl sulfoxide and N,N-dimethylformamide. Cyclohexane may be used to allow dispersions in solvent. Blending is observed visually to determine that incompatible phases are not present. It may be useful to heat one or more of the solvent mixtures to improve blending. Once mixing of the solutions of the copolymers has provided a homogeneous blend, it is preferred to coat the 2o adhesives onto a substrate as soon as practical, but in all cases before any significant non-homogeneity of the blend is observed. Non-homogeneity would be observed e.g. by formation of heterogeneous regions (known as heterogeneous "domains"). In a preferred embodiment this coating is accomplished in one to three hours. Once the adhesive blends are coated onto substrates e.g. backings 2s and any remaining solvent is removed, the coatings of pressure-sensitive adhesive blend have been observed to remain stable and functional for extended periods.
Preferred blends contain ratios of about 90:10 to 10:90 of the two components, but preferably 40 to 80 parts of the hydrophilic component.
The pressure-sensitive adhesive copolymer blends or the one 3o component adhesives e.g. hydrophilic adhesives of the invention may be applied to a carrier release liner by conventional methods. As is known to those skilled in the art, the particular method selected may depend upon the nature of the liner being employed. A suitable method for applying the adhesive involves coating a solution of the adhesive in water or an organic solvent or a solvent blend onto a release liner e.g. a silicone coated or fluorochemical coated liner. ' It is possible to crosslink the adhesives with gamma radiation by means of the normal sterilization dose. This may be done with or without added cross-linking agents. It is preferably done without added cross-linking agents.
The doses of gamma radiation used are generally 5 to 60 kilograys total dose, to preferably 20 to 40 kilograys.
Porous Backin~,s Suitable porous backings for use in the invention are any backings which find use in medical or surgical fields. In particular the porous backings are those which are susceptible to adhesives migrating into the backing. Such backings include any of the conventional nonwoven fabrics, woven fabrics, knits, foams and the like, particularly those which permit transpiration of perspiration or wound exudate therethrough. Suitable woven, knit and nonwoven fabrics include those formed from fibers or threads of synthetic or natural materials 2o including cotton, rayon, nylon, polyester, polyurethane and the like.
Nonwoven polyurethane backings are used in a preferred embodiment. Other backings may be laminated onto selected barrier layers and adhered thereto by conventional methods such as heating, irradiation and pressure.
Nonwoven polyurethane backings which are particularly useful in the present invention can be melt blown into a separate web or directly onto a substrate for which it will serve as a backing. The polyurethane can be melt blown using a process similar to the process reported in Wente, Van A. , "Superfine Thermoplastic Fibers" in Industrial En ig nag Chemistry, Vol. 48, pages 1342 et seq (1965), or in Report No. 4364 of the Naval Research 3o Laboratories, published May 25, 1954 titled "Manufacture of Superfine Organic Fibers" by Wente, Van A., Boone, C.D. and Fluharty, E.L. The process is exemplified hereinafter (Example 9) but is known to those skilled in the art.
Typical polyurethanes useful in the process are commercially available e.g.
Morthanes~, available from Morton International Inc. and Pellthanes~, available from Dow Chemical.
The backing may be of any desired shape to provide adhesive coated sheet materials embodied as adhesive tapes, strips, wound dressings, monitoring or neuro-stimulating electrodes, drapes or the like. These tapes are converted by conventional methods.
Polymeric Migration Barriers Suitable migration barriers used in articles of the present invention are coatings of polymers which will adhere to both the porous backings and any adhesives used. Therefore, the invention does not require the additional adhesive layer required in Debusk to adhere the migration barrier to the porous backing.
When coated on porous backings the migration barrier does not readily migrate into the interstices of the backing but instead adheres substantially to the surface of the backing. An adhesive coated on the migration barrier is therefore prevented from contacting the porous backing and is also prevented from 2o migrating into the interstices of the backing. The migration barrier provides a continuous surface to which the adhesives adheres. Without being bound by theory it is believed that the migration barrier maintains a substaintially continuous and smooth surface of the adhesive thus increasing the liklihood that the adhesive will adhere to any surface, particularly a rough surface such as human skin.
The migration barrier of the invention is either non-adhesive or adhesive under ambient conditions. Suitable non-adhesive coatings are polymeric coatings such as lower alkyl acrylate copolymers or polyurethanes which are not pressure-sensitive at room temperature, although these may be adhesive at higher 3o temperatures. Such non-adhesive migration barriers are in some ways easier to process during manufacturing because they are not sticky. A preferred non-adhesive migration barrier is an ethyl acrylate N/tertiary butyl acrylamide copolymer. In order to adhere such non-adhesive migration barriers to a backing, the non-adhesive migration barriers are heated to a temperature above their softening point where the migration barrier is sufficiently tacky to allow adherence to the backing, then cooled to provide a secure bond.
Migration barriers are generally selected which will adhere to an adhesive coated thereon, i.e. an adhesive with enough chemical similarity to the migration barrier to facilitate adherence. Many suitable combinations are 1o possible, and one skilled in the art is familiar with such suitable combinations.
When polyurethane non-wovens are used as the porous backings, it has been found that migration barriers selected from polyurethane and lower alkyl acrylate-N-lower alkylacrylamide copolymers and the like are suitable.
Preferred migration barriers for polyurethane non-woven backings made from Dow Chemical Co. Pellthane~ polymers or Morton International Inc. Morthane~
polymers include lower alkyl acrylate-N-lower alkylacrylamide copolymers e.g.
a copolymer of ethyl acrylate and tertiary butylacrylamide.
The copolymers of lower alkyl acrylates and acrylamides such as N-lower alkylacrylamides which are useful in the present invention are readily 2o prepared using conventional free radical catalyzed processes such as those taught in Ulrich, Re 24,906 and illustrated in Example 6 hereafter.
Typically, the thickness of a migration barrier is relatively thin, e.g. 1 to 2 grains per 4 by 6 inch (4 to 8 g/m2), which provides a coating thickness of about 6 to 8 microns. The migration barrier, as analyzed by scanning electron microscopy, is found to be essentially continuous.
Absorbent Pads for use in First Aid Dressings The first aid dressings of the present invention will generally have an absorbent pad adhered thereto, either over a portion of the adhesive or in WO 96/26251 PC'~YUS96100794 place of a portion of the adhesive and adjacent to the migration barrier as the pads are conventionally provided.
A preferred absorbent layer is a foam, woven or nonwaven material including but not limited to rayon, polyester, polyurethane, polyolefin, cellulose, cellulose derivatives, cotton, orlon, nylon, or hydrogel polymeric materials. Most preferred are woven and nonwoven materials. See, e.g., U.S.
Patent No. 4,773,903 to Weisman et al. An alternative absorbent layer includes a composite material comprising a nonwoven polymeric matrix and a highly hydrophilic fluid absorbing material. Another preferred composite material is a 1o nonwoven matrix combined with a highly hydrophilic fluid absorbing material such as a polymeric absorbent fiber or particle selected from the group consisting of modified starches and high molecular weight acrylic polymers containing hydrophilic groups such as acrylonitrile fibers treated with alkali metal hydroxides. Suitable absorbent materials will preferably absorb at least about 25 % by weight of fluid or exudate, and more preferably greater than about 100 by weight, when measured using test methods reported in U.S. Patent No.
4,957,795 to Riedel. Another preferred class of pads is conventional non-stick pads used on first aid dressings. Nonwoven rayon web laminated to a porous high density polyethylene web such as to the 3.2 ounce single side laminate of 2o P530 high density polyethylene mesh available from Applied Extrusion Technologies, Inc., Middletown, DE is a preferred absorbent layer.
Suitable absorbent materials include composite materials such as nonwoven polymeric matrices combined with highly hydrophilic fluid absorbing materials. Highly hydrophilic fluid absorbing materials include polymeric absorbent fibers or particles selected from the group consisting of modified polysaccharides, modified polyurethanes, and high molecular weight acrylic polymers containing hydrophilic groups. A preferred highly hydrophilic fluid absorbing material is acrylonitrile fibers treated with alkali metal hydroxides. A
commercially available hydrogel polymeric material is available under the 3o tradename LANSEAL fiber (Japan Exlan Co., Ltd., Osaka, Japan). These types of composite absorbent materials are readily prepared using well known methods such as the method reported in U.S. Patent 4,957,795 to Riedel.
A variety of means are suitable for attaching or fixing the elastic substrate to the absorbent layer such as stitching, needle-tacking, ultrasonic welding or bonding with a suitable adhesive. A preferred adhesive is a biocompatible adhesive that is selected from the group consisting of natural rubber based adhesives and acrylic based adhesives.
The following test methods were employed to evaluate the properties of articles and compositions of the invention. The present invention 1o provides adhesive sheet articles which have desirable moisture vapor transmission rates and also maintain desirable adhesivity because the adhesives of the invention do not disappear by migrating into the porous backings of the invention. Additionally, the adhesive sheet articles of the invention are able to maintain soft textures and good conformability ratings because the migration barriers of the invention are not unduly thick or stiff.
Moisture Vapor Transmission Rate (Upright) The Moisture Vapor Transmission Rate (MVTR"p) for the 2o composite samples is measured in accordance with ASTM E 96-80 as modified below.
The adhesive sheet article samples are sandwiched between the adhesive surfaces of two axially aligned foil adhesive rings having 2.54 cm diameter holes. Each sample is assembled to ensure a flat, wrinkle-free and void-free foil/sample/foil laminate.
A four-ounce (0.14 kg) glass jar is filled half full with distilled water. The jar is fitted with a screw-on cap having a 3.8 cm diameter hole concentrically aligned with a rubber washer having a 4.445 cm outside-diameter and a 2.84 cm inside-diameter.

W 0 96/26251 CA 0 2 212 0 2 8 19 9 7 - 0 7 - 31 pC r~S96/00794 The foil/sample/foil laminate is concentrically positione~.d on the rubber washer and the sample-containing sub-assembly screwed loosely onto the jar.
The assembly is placed into a chamber maintained at a temperature s of 40°C and 20% relative humidity. The assembly is removed from the chamber after four hours, weighed to the nearest 0.01 gram (WI), and immediately returned to the chamber. The cap is now screwed tightly onto the jar without bulging of the sample. The assembly is again removed from the chamber after an additional eighteen hours and weighed to the nearest 0.01 gram (W2).
1o The MVTRup T24 of the adhesive (measured in grams of water transmitted per square meter of sample area over a twenty four hour period) may then be calculated according the formula set forth below:
MVTRup T2a = (Wi - W2)(4.74 x 104)/t where:
15 (WIJ is the initial weight of the assembly (grams) (W~ is the final weight of the assembly (grams), and (t) is the time period between Wl and W2 (hrs).
Three samples of each adhesive were run and the average of the three samples reported.
2o The following examples are provided to illustrate specific embodiments of the invention, but are not intended to be limiting thereof.
Examples 1 and 3 illustrate the preparation of monomers not conveniently available from commercial sources which are necessary to make copolymers of the First and Second Polymeric Components of a preferred 2s adhesive described hereinabove.
Examples 2, 4 and 5 describe preparation of adhesives suitable for use in the present invention.
Examples 2, 6 and 12 describe preparation of migration barriers suitable for use in the present invention.

Examples 8 - 19 describe preparation of samples. Table 1 provides a key which outlines construction of the samples prepared in Examples

8-19.
Example 1: Preparation of a Polystyrylethyl Methacrylate Macromonomer PREPARATION OF MACROMER
The "C" moiety of the general formula A-B-C is a polymeric material which has a copolymerizable vinyl group which copolymerizes with monomers A and B under polymerizing conditions. The C moiety, while being to polymeric in one sense, actually behaves as a monomer and is referred to in the literature as a macromolecular monomer which is shortened to the term "macromer" for convenience. For the purposes of this invention, a representative preparation of the macromers that are used follows.

is This methacrylate-terminated styrene macromer having an average molecular weight of about 9000 was prepared using a five-liter four-necked flask, fitted with a thermometer, mechanical stirrer, septum, Dean-Stark trap and condenser. 150 grams (1.44 moles) of styrene were charged into the flask which contained 1155 grams of cyclohexane, resulting in an 11.5 % by weight solution.
2o The solution was heated to about 50°C. and a 1.4 molar solution of secondary-butyl lithium in cyclohexane was added dropwise until a faint yellow color persisted, then 10.7 ml of additional sec-butyl lithium cyclohexane solution was added rapidly. The reaction mixture was maintained at 65° C. by cooling. After about one hour, the solution was allowed to cool to 35° C. and then ethylene 25 oxide gas was introduced over the reaction mixture which was agitated rapidly for 15 minutes until the orange color of polystyryl lithium had disappeared.
The reaction was then quenched with 5 ml (51.2 meq. ) of methacryloyl chloride.
The polymer solution was reduced in volume and the polymer gradually precipitated and was separated and dried. Gel permeation chromatography W O 96/26251 CA 0 2 212 0 2 8 19 9 7 - 0 7 - 31 pCT~S96/00794 revealed a number average molecular weight of 8394, weight average molecular weight of 8842 and polydispersity of 1.05.
In addition to the above macromer the following macromers are prepared by the process described in Example M-1 above but gradually s decreasing the amount of secondary-butyl lithium initiator to obtain higher moledular weight macromer. The macromer's molecular weight is higher if less initiator is used, as is known to the art. See e.g. U.S. Patent 4,693,776.
Example M-2: a methacrylate-terminated polystyrene macromer having a weight average molecular weight of about 10,000 g/mol.
1o Example M-3: a methacrylate-terminated polystyrene macromer having a weight. average molecular weight of about 13,000 g/mol.
Example M-4: a methacrylate-terminated poly(methyl methacrylate) macromer having a weight average molecular weight of about 13,000 g/mol.
15 Example M-5: an acrylate-terminated polymethyl methacrylate polymeric monomer having an average molecular weight of 10,000 was prepared. Recrystallized dried fluorene, five parts, was placed in a 1,000 ml three-necked flask fitted with stirrer, thermometer, argon inlet and rubber septum, all of which were previously flamed under argon. Dried 2o tetrahydrofuran, 400 parts, was distilled into the flask and 15 parts of a 1.4N
solution of sec-butyllithium in cyclohexane were added through the septum, producing an orange-red solution of "fluorenyl lithium" under slight argon pressure. The flask contents were cooled to -76°C and 65 parts of dried, freshly distilled methyl methacrylate (MMA) were rapidly added through the septum.
2s The reaction temperature quickly rose to -20°C and then was gradually returned to -76°C by cooling. After one hour of stirring, 3 parts of ethylene oxide were bubbled into the flask and the flask was warmed to -10°C, causing the liquid to change from orange-red to light yellow. Acryloyl chloride (3 parts) was then added to quench the reaction. The reaction mixture was then warmed to room 3o temperature and added dropwise with vigorous stirring to 4 liters of hexane, causing a white solid to precipitate. The solid was filtered, dried, redissolved in toluene, filtered to remove impurities and precipitated in methanol. The resulting white solid was a polymeric monomer having the following properties:
weight average molecular weight 10,420 and polydispersity 2.6.
Examgle 2~ Preparation of Macromer Reinforced Pressure Sensitive Adhesive Copolymer ("MRP Adhesive") The copolymerization reaction was carried out in a sealed, one quart bottle. The one quart (0.95 liter) glass bottle was charged with 190 grams of isooctyl acrylate, 4 grams of acrylic acid, 4 grams of 2-polystyrylethyl methacrylate macromonomer prepared according to Example 1 plus 300 grams of ethyl acetate, 0.6 grams of 2,2'-azobisisobutyronitrile (available from DuPont of Wilmington, DE as Vazo~ 64), and 2.5 grams of a 1 % solution of carbon tetrabromide in isooctyl acrylate that results in a 0.012 % by weight charge of carbon tetrabromide. The mixture was deoxygenated by purging with nitrogen at a rate of one liter per minute for two minutes. The bottle was sealed and placed in a rotating water bath for twenty-four hours at 55°C to effect essentially complete polymerization. The resulting copolymer was separated by partial evaporation of the solvent, filtration and drying, then resuspended and dissolved 2o in ethyl acetate and was used in Example 5 to form an adhesive blend useful for the present invention. The copolymer can also be used as a Migration Barrier in the present invention.
F~cam~le 3~ Preparation of an Acr~late Ester of a Polvether An acrylate ester of a polyether containing an average of about 16 repeating ethoxy units was prepared as follows.
Two hundred eighty-eight g (0.4 m) of Carbowax~ 750 (a methoxy polyethylene oxide) ethanol of approximately 750 MW, available from Union Carbide Corp.) was melted in a 1000 ml round bottom flask fitted with a so magnetic stirrer and a Dean Stark trap. Toluene, 288 g, was added to the flask and the solution was refluxed, with stirring and under a nitrogen stream, for hours to remove dissolved oxygen. To this solution was then added 33.8 g (0.5 m) of acrylic acid, 9.2 g of p-toluenesulfonic acid, and 0.16 g of copper powder.
The resulting mixture was then refluxed, with stirring and under a nitrogen s stream, for 16 hours with generated water collected in the Dean Stark trap.
The mixture was cooled to room temperature and 10 g of calcium hydroxide was added thereto. The mixture was stirred for 2 hours and then filtered through an inorganic filter aid. This polyether acrylate ester monomer was then used to prepare copolymers as described in the examples below.
Ex~nple 4: Preparation of a Hydrophilic Adhesive The copolymerization reaction is carried out in a sealed, four ounce bottle. The bottle is charged with 21.0 grams of isooctyl acrylate, 9.54 grams of an acrylate ester of methoxy polyethylene oxide) ethanol of approximately 750 molecular weight in toluene at 47.16 % solids prep~~red according to Example 2, 4.5 grams of acrylic acid, 0.06 grams of 2,2'-azobisisobutyronitile (available from DuPont as Vazo~ 64), 5.7 grams of isopropanol, and 19.26 grams of ethyl acetate. The mixture is deoxygenated by purging with nitrogen at a rate of one liter per minute for thirty-five seconds.
2o The bottle is sealed and placed in a rotating water bath for twenty-four hours at 55°C. to effect essentially complete polymerization. The resulting copolymer product was isolated using the method described in Example 2. The copolymer product was combined with the adhesive of Example 2 and was used in Example 5 to form an adhesive blend useful for the present invention.
Example 5: Preparation of an Adhesive Blend A mixture of 887.5 g (32 % of weight of solids) of the lvIRP
Adhesive of Example 2 (43 % solids in ethyl acetate) and 1612.5 g (68 % by weight of solids) of the Hydrophilic Adhesive of Example 4 (50 % solids in ethyl acetate) was blended in a roller mill blender under ambient conditions for 96 hours to provide a solvent blend which was homogeneous to visual inspection.
Example 6: Preparation of N-Tertiary Butyl Acr~lamide-Ethyl Acr~late ~~uolymer Migration Barrier A pre-infix of 680.4 kg of deionized water and 177 kg of N-tertiary butyl acrylamide was prepared by mixing at high speed until the mixture was uniform. The pre-mix was charged to a 1892 liter, glass-lined reactor and agitation was set at 60 rpm. To the charged, rotating reactor was added 411.9 kg to of ethyl acrylate, 371.9 kg of deionized water, 42.5 kg of Triton~ X-200 (available from Union Carbide, Danbury, CT), and 294 grams of carbon tetrabromide. The reaction mixture was heated to 50°C., and deoxygenated using inert gas. When the temperature stabilized at 50°C, 294 grams of potassium persulfate dissolved in 2.72 kg of deionized water were charged to the reactor. The reaction was allowed to generate heat exothermically, after which the temperature was increased to 85°C and the batch was held for thirty minutes at 85°C. The batch was then cooled to 38°C and diluted with deionized water to 33 % solids. The weight of solids present per unit volume was determined by drying an aliquot of the reaction mixture, weighing the polymeric residue and 2o calculating the percent solids. The amount of water needed for the dilution was then calculated. 74.2 kg of Triton~ X-200 was charged to the batch and mixed for thirty minutes after which the batch was drained through an 80 mesh screen filter to provide a 25 % solids batch of the desired copolymer.
Example 7~ Preparation of Adhesive Blend Coated on a Release Liner A Blended Adhesive of Example 5 was coated from a hopper knife water of suitable size onto a 50 yard (45.7 m) length of a 4 mil (1.02 mm) thick and 20 in (50.8 cm) wide, silicone-coated release liner (available from Release International, Iowa City, IA as 211A 72# Stick-Not Grade 8527) at a coating 3o weight of 12 grains per 4 x 6 inch sample (50 grams per square meter) and dried WO 96/26251 PC7.'/US96/00794 by heating in an oven at temperatures of 110°F (43°C) for Zone 1, 165°F
(74°C) for Zone 2 and 225°F (107°C) for Zone 3 at a line speed of about 16.5 feet per minute (5.03~'/,";,~.

Table 1 Sample:;:Porous.-:. . Migration BarrierAdhesive 'Silicone:
' :..':. .

:, ;tCoated::

Ex. None Ethyl acrylate/tertiaryAdhesive Yes 8 Blend butylacrylamide copolymer(prepared in (hereinafter EA/t Ex.S) as prepared in Ex.6) Ex. MeltblownEA/t (Ex.6) Adhesive Yes

9 Blend Polyurethane (Ex.S) Ex.lO None None Hydrophilic Yes Adhesive (prepared in Ex.4) Ex. None EA/t (Ex.6) Hydrophilic Yes Adhesive (Ex.4) Ex. None Polyurethane BarrierHydrophilic Yes Adhesive (Ex.4) Ex. MeltblownPolyurethane BarrierHydrophilic Yes 13 (Ex.12) Polyurethane Adhesive (Ex.4) (Ez.9) Ex. None MRP Adhesive (describedHydrophilic Yes 14 in Ex.2) Adhesive (Ex.4) Ex. None EA/t (Ex.6) with Hydrophilic Yes Adhesive (Ex.2) coatedAdhesive (Ex.4) thereon ControlMeltblownNone Hydrophilic Yes Ex. Polyurethane Adhesive 16 (Ex.4) Ex. MeltblownEA/t (Ex.6) Hydrophilic Yes Polyurethane Adhesive (Ex.4) (Ex.9) Pressure Laminated Ex. MeltblownMRP Adhesive (Ex.2) Hydrophilic Yes Polyurethane Adhesive (Ex.4) (Ex.9) Ex. MeltblownEA/t (Ex.6) with Hydrophilic Yes PolyurethaneAdhesive (Ex.2) coatedAdhesive (Ex.4) (Ez.9) thereon WO 96/26251 PC7ClUS96100794 Example 8: Coating Migration Barrier Layer onto Adhesive Blend The dried adhesive cc~~ ::qlymer blend o~~ _release liner from Example 7 was flood coated with a 3:3'~ solids batch vi the ethyl acrylate-N-tertiary butylacrylamide copolymer made as described in Example 6 using a s Meier bar apparatus at a line speed of about 20 yards per minute at a coating weight of 2 grains per 4 x 6 inch sample (8 g/m2). The article obtained was dried at an oven temperature of 225 ° F ( 107 ° C) .
Examule 9: Preaaration of an Article of the Invention Using Blend Adhesive to and Polyurethane Non-Woven Backing The barrier layer/adhesive blend/release liner composite from Example 8 was used to collect a non-woven polyurethane backing layer.
The polyurethane was melt blown using a process similar to the process reported in Wente, Van A., "Superfine Thermoplastic Fibers" in 15 Industrial En ineering Chemistry, Vol. 48, pages 1342 et seq (1965), or in Report No. 4364 of the Naval Research Laboratories, published May 25, 1954 titled "Manufacture of Superfine Organic Fibers", by Wente, Van A., Boone, C.
D. and Fluharty, E.L. Molten polyurethane was forced by a ram extruder through a row of orifices that had smooth surface orifices (10/cm) with an 8:1 20 length to diameter ratio. The polyurethane was forced through the orifices directly into two converging high velocity streams of heated air. The die temperature was maintained at 226°C, the primary air temperature and pressure were 235 ° C and 150 kPa, respectively (0.76 mm gap width), and the polymer throughput rate was 131 gm/hr/cm. The resulting webs had an average fiber 2s diameter of about 10-15 microns, basis weight of 102 g/m2 and thickness of about 13 mils (.33 min) and were extruded at about 14 pounds per hour (6.36 kg per hour) directly onto the adhesive layer on a heated (88 to 93 ° C) collector positioned 6 inches (15.2 cm) from the die to provide a backing. The polyurethane used for the backing was Morton PUR 440-200 (available from 3o Morton International Inc. , Chicago, IL) with 4 percent tan pigment (color number 1093538 available from Reed Spectrum, a division of Sandoz Chemicals Corp., Minneapolis, MN). The tape was allowed to cool under ambient conditions.
The tape was gamma irradiated using conventional production equipment to a total dose of about 30-35 Kilograys. The tape was tested for MVTR and the results are provided in Table 2.
Example 10: Preparation of a Liner Coated with Hydrophilic Pressure-Sensitive Adhesive to A 50% solids hydrophilic adhesive from Example 4 was knife coated from solution onto a 4 mil ( 1 mm) thick and 9 in (23 cm) wide silicone-coated liner (as used in Example 7) at about 11 grains per 4 by 6 inch section (46 g/m2) at a knife water gap of about 5 mil (12.6 mm). The adhesive layer was dried as described in Example 7.
Example 11: Preparation of Migration Barrier Coated H~philic Adhesive The adhesive coated on release liner from Example 10 was flood coated with a coating of about 2 grains per 4 x 6 inch section (8 g/m2) of the copolymer of ethyl acrylate/N-tertiary butylacrylamide prepared as described in 2o Example 6 using a Meier bar water from solution The article was oven dried.
Figures 3 and 4 are scanning electron micrographs of a sample prepared according to Example 11. Figure 3 is a 100 times magnification and Figure 4 is a 500 times magnification of the sample. Although it is not essential to the present invention that the migration barrier and the adhesive layer remain as disinct layers, Figures 3 and 4 illustrate that the migration barrier 20 is apparent as a distinct layer apart from the adhesive layer 22. The silicone coated release liner is depicted as 24 in both Figures 3 and 4.

Example 12: Preparation of a Polyurethane Migration Barrier Layer Coated on hydrophilic Adhesive A batch of an aqueous (62 % solids) dispersion of a polyurethane polymer, Witcobond-290H diluted to 31 % solids (available from Witco Corp., s Greenwich, CT) was flood coated using a method similar to the method described in Example 8. That is, it was coated by pouring the polyurethane dispersion over the adhesive side of the adhesive coated release liner article of Example 10 and the polyurethane was then spread with a 0.5 inch (1.27 cm) diameter cylindrical rod to a coating weight of 2 grains per 4 x 6 inch section to (8g/m2). The article was dried at 225°F (107°C) in an oven for 10 minutes.
Exam~le 13: Preparation of a Tape Article of the Invention The article of Example 12 was coated as described in I~xample 9 with the same melt blown polyurethane backing and the collector drum used was is heated at 180 to 190°F (82 to 88°C). The pressure-sensitive adhesive tape article was gamma irradiated to a total dose of 30 to 40 kilograys and. tested for moisture vapor transmission. Moisture vapor transmission results are provided in Table 2.
2o Example 14: Preparation of a MiEration Barrier Iayer-Adhesive Article A hydrophilic adhesive/silicone release liner composite prepared as described in Example 10 was coated with a barrier layer comprising the copolymer of Example 2 using a knife coater with a coating gap of 2 mils (0.051 mm). The wet coating was dried at room temperature for 10 minutes, then in an 25 oven at 225°F (107°C) for 25 minutes to achieve a dry coating weight of 6 grains per 4 by 6 inch section (24 g/m2).
Example 15: Preparation of Multiple Layer Adhesive Article A 36 inch length (0.91 m) x 6 inch width (15.2 cm) of the 3o migration barrier/hydrophilic adhesive/liner composite described in Example was coated with a dispersion of the copolymer (MRP Adhesive) described in Example 2 using a knife water with a gap of 2 mils (0.051 mm). The resulting article was dried at room temperature (about 25 ° C) for 10 minutes and then dried in an oven at 225°F (107°C) for 25 minutes to obtain a dry coating weight of 6 s grains per 4 by 6 inch section (24 g/m2).
Comparative Example 16~ Preparation of a Control Tape Article A polyurethane non-woven web was melt blown using the method described in Example 9 to provide a nonwoven web with a basis weight of 120 to g/m, a thickness of 15.8 mil (0.40 mm) and an average fiber diameter of about

10-15 microns. The nonwoven web was then pressure laminated onto the hydrophilic adhesive on silicone-coated liner prepared as described in Example 10. The lamination was accomplished at room temperature and at a pressure of 20 psi with a line speed of 3 feet (0.91 m) per minute. A portion of this sample 15 was gamma irradiated at 30 to 35 kGy total dose to crosslink the adhesive.
The irradiated portion of the sample was tested for MVTR and the results are provided in Table 2.
Figure 1 is a scanning electron micrograph of the sample prepared according to Example 16. The sample shown in Figure 1 was held for 14 days at 20 120°F at 90% relative humidity. These are the parameters at which samples are generally held to accelerate the aging process. Eleven days at 120°F
(49°C) and 90% relative humidity is considered a good approximation of one year aging under ambient conditions. Since the sample in Figure 1 lacks the migration barrier, the adhesive 14 freely migrates into the interstices of the nonwoven web 25 16 and settles between the individual fibers 18 which comprise the nonwoven web 16.
Example 17~ Preparation of a Tape Article of the Invention The article of Example 11 (migration barrier of ethyl acrylate/N-3o tertiary butylacrylamide copolymer/Hydrophilic Adhesive/liner composite) was coated with the same melt blown polyurethane backing as described in Example 9. The backing had a basis weight of 122 g/m, web thickness of 15.7 mil (0.40 mm) and effective fiber diameter of 17.8 microns. The collector drum was heated to about 190 to 200°F (88 to 93°C). The pressure-sensitive adhesive tape s article was gamma irradiated to a total dose of 30 to 35 kGy and tested for moisture vapor transmission. The resulting article had an acceptable moisture vapor transmission rate and results are given in Table 2.
Example 18: Preparation of a Porous Backing Tage Article of the lfnvention to The article of Example 14 (migration barrier of the isooctyl acrylate-acrylic acid-macromer copolymer of Example 2 coated on the hydrophilic adhesive of Example 4 on a silicone-coated liner) was coated as described in Example 9 with the same melt blown polyurethane backing at the same basis weight, web thickness and effective fiber diameter but the collector 15 drum was not heated. The resultant composite was dried in an oven as detailed in Example 7. The dried article was gamma irradiated to a total dose of 30 to kilograys. The article was tested for MVTR and the results are shown in Table 2.
Figures 2 and 5 are scanning electron micrographs of the sample 2o prepared according to Example 17 and held for 14 days at 120 ° F and relative humidity (accelerated aging described above in Example 16). At the times magnification used for Figure 2, the migration barrier is not evident as a distinct layer apart from the adhesive layer. However, Figure 2 shows that the adhesive (10) does not migrate into the interstices of the nonwoven backing 12 2s comprised of fibers 17. Figure 5 (900x magnification) more clearly shows the migration barrier 30 as a distinct layer apart from the adhesive 32. Figure 5 also shows that the adhesive 32 does not flow into the interstices of the nonwoven web 34 comprised of fibers 37. The migration barrier 30 shown best in Figure 5 is about 6-7~m thick.

Example 19: Preparation of a Tape Article The article of Example 15 (first layer of silicone-coated liner, second layer of hydrophilic adhesive, third layer of ethyl acrylate/N-tertiary butylacrylamide copolymer migration barrier and fourth layer of isooctyl acrylate-acrylic acid-macromer copolymer) was used to collect a melt blown ' polyurethane backing prepared as described in Example 9 at the same basis weight, web thickness and fiber diameter but the collector drum was not heated.
The finished article was gamma irradiated to a total dose of 30 to 35 kilograys.
The resultant article was tested for MVTR and the results are provided in Table 2.
Example 20:
The moisture vapor transmission rate of the tape articles described in Examples 9, 13, 16, 17, 18 and 19 above was measured using the test method described above.
The results are shown in Table 2.
Table 2 A~t'~'~CrLE ~F:~XANiPLE Nt'~. MVTR, (glm~l?.4 hours3' :.:

Example 16 (Control) 712.8 Example 9 689.9 Example 13 809.6 Example 17 933.6 Example 18 581.1 Example 19 594.1 The conclusion derived from this data is that MVTR is not 2o substantially reduced by the presence of a barrier layer.

The migration barriers were examined by scanning electron microscope. For examples 9, 13, ~~', 18 and 19~a barrier was detected, preventing the migration of adhesive into the interstices of the porous backing.

Claims (8)

CLAIMS:

1. An adhesive sheet article comprised of at least three layers comprising a porous backing, a migration barrier and an adhesive wherein said migration barrier is juxtaposed between said porous backing and said adhesive so that said migration barrier substantially prevents said adhesive from migrating into said porous backing; wherein said article does not include an additional adhesive layer between said migration barrier and said porous backing and wherein said migration barrier is comprised of an alkyl acrylate-N-alkylacrylamide copolymer or polyurethane.

2. The adhesive sheet article of claim 1, wherein said porous backing is comprised of a woven, non-woven or knitted fabric.

3. The adhesive sheet article of claim 1 or 2, wherein said porous backing is a non-woven web.

4. The adhesive sheet article of any one of claims 1 to 3, wherein said migration barrier is 20 micrometers or less thick.

5. The adhesive sheet article of any one of claims 1 to 4, wherein said adhesive sheet article has a moisture vapor transmission rate of at least 400 g/m2 per 24 hours.

6. A method of making an adhesive sheet article according to any one of claims 1 to 5, comprising:
a) coating an adhesive on a liner, b) bonding a migration barrier to the surface of the adhesive, and c) bonding a porous backing to the surface of the migration barrier.

7. A first aid dressing comprising an adhesive sheet, wherein said adhesive sheet is comprised of at least three layers, said three layers comprised of a porous backing, a migration barrier and an adhesive wherein said migration barrier is juxtaposed between said porous backing and said adhesive, and wherein said migration barrier comprises alkyl acrylate-N-alkylacrylamide copolymer or polyurethane and does not readily migrate into interstices of the backing;
wherein said adhesive sheet has a moisture vapor transmission rate of at least 400 g/m2 per 24 hours and further wherein an absorbent layer is adhered to at least a portion of said adhesive.

8. A first aid dressing comprising the adhesive sheet article of any one of claims 1 to 5, and an absorbent layer, wherein said absorbent layer is adhered to at least a portion of the adhesive of the adhesive sheet article.