CA1218954A - Hydrophilic, elastomeric, pressure-sensitive adhesive - Google Patents

Abstract

HYDROPHILIC, ELASTOMERIC, PRESSURE-SENSITIVE ADHESIVE
Abstract The present invention concerns a novel water-insoluble, hydrophilic, pressure-sensitive adhesive that has a number of unique characteristics including being elastomeric and ultraconformable. This adhesive includes an irradiation cross-linked synthetic organic polymer having a three-dimensional matrix, and an adhesive plasticizer. The plasticizer includes a substantially non-volatile elasticizer. The adhesive is useful either as a coating on a supporting web-like substrate or as a self-supporting layer. Also provided are various articles made using the adhesive such as a bandage or ostomy device, a method of making the adhesive, and methods of using the adhesive.
In one embodiment, the adhesive is electroconductive, and is useful for attaching an electrically conductive member of an electrode to a selected surface such as mammalian tissue. Also provided is an electrode having a layer of this adhesive, and a method of adhering this electrode to mammalian tissue.

Description

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HYDROPHILIC, El.ASTOMERIC, PREssuRE-sENsITIvE ADHESIVE

Technical Field This invention relates to a novel pressure-sensitive adhesive, and particularly relates to a water-insoluble, hydrophilic, elastomeric, pressure-sensitive adhesive.
This invention additionally rela~es to a supportive web-like substrate such as that of an ostomy appliance, coated with this adhesive, to a self-supporting layer of the adhesive, to various articles made of this self-supporting layer, to methods of using the self-supporking layer, to a method of making the adhesive~ to a type of the adhesive that is electroconductive, and to an electrode such as an electrosurgical return electrode comprising this type of the adhesive.
Background Art A polymeric hydrophobic substance is the most common type of conventional pressure-sensitive adhesive used to secure s~bstrates to the human body. The ma~ority of all adhesive bandages are made with this broad class of adhesive, which is used as a thin film. These polymeric hydrophobic substances are frequen~ly produced by homopolymerization or copolymerization of one or more vinyl type monomers, especially acrylic esters, metha-crylic estersj vinyl alcohol esters and vinyl ethers.
Natural rubber and gum have also found use in con-ventional adhesive formulae.
When these prior art thin film, hydrophobic, polymeric, pressure-sensitive adhesives are used to secure a device such as an EKG monitoring electrode ox to secure a bandage, removal frequently causes trauma, discomfort

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and soreness to the skin to which the adhesive was adhered. Skin trauma of this type may take the form of pulled hair, bruises, erythema, edema, blistering, removal of some epidermis, or tearing of the skin.
The severity of the discomfort and trauma appears to be greater when the adhesive is allowed to contact the skin for an extended time. Frequently, EKG
monitoring electrodes and postsurgical bandages are left on a patient's skin for up to a week and some-times longer. Thus, the removal of these bandages andelectrodes, quite often, is very painful, and soreness persists for some time.
- Hydrophilic polymeric pressure-sensitive adhesives are also known in the prior art. Adhesives of this type are much less common than hydrophobic pressure-sensitive adhesives. Major uses of hydrophilic pressure-sensitive adhesives include use as an ostomy adhesive and as a conductive adhesive for securing an electrode to the human body. These pressure-sensitive adhesives are much less likely to cause skin trauma than the hydrophobic-type adhesives.
Some hydrophilic-type adhesives are made by chemically cross-linking a polymeric material to form the adhesive. Illustrative of this type of prior art are U. S. Patent 3,998,215 to Anderson et al, U. S. Patent 4,125,110 to Hymes, British Patent Appli-cation 2,034,184 of Hymes, U. S. Patent-4,066,078 to Berg, and U. S. Patent 4,~94,822 to Xater. The ad-hesive of each of these documents is used in a patient electrode, and is conductive per se or provided with conductivity by, for example, using the adhesive to bond strands of a conductive material. In the Anderson et al, Hymes and Kater documents, it is stated that the adhesive is formed from an aqueous solution of the polymeric material.

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In the ~nderson et al patent, a porous webbed material is dipped into an aqueous solution of a hydro-gel former, for example, polyvinyl alcohol, to wet the webbed material, excess solution is scraped off, and the webbed material is then dipped into a solution of a gel-forming agent or a cross-linker for the hydrogel former, in order to form a hydrogel throughout the webbed material. ~he hydrogel is said to be lightly adherent to the body surface but sufficiently co-hesive so that no residue remains upon removal thereof.
The Hymes patent relates to an electrode havingan electrically conductive adhesive that contains a hydrophilic polysaccharide material ~karaya), a hydric alcohol (glycerin) to provide plasticity, an electro-lS lytic salt and propylene glycol. An alternate embodl-ment of this adhesive includes additive materials or cross-linking the hydrophilic polysaccharide material.
These chemical cross-linking agents are said to in-clude, for example, gelatin, polyvinyl acetate, certain polyesters and calcium salts.
The British patent application in the name of Hymes is similar to the U. S. pa~ent to Hymes. The adhesive of this document is formed from dry karaya gum powder and a non-volatile liquid carrying either an ionizable salt or finely powdered silver or alumi-num. In an alternate embodiment, the adhesive is comprised of 15-70% aqueous polyacrylic acid ~25%
concentration), 15-45% karaya, 10-35% water, 0-35%
isopropyl alcohol, and 1-3% electrolyte. Additive materials for chemically cross-linking the karaya are said to include polymers such as vinyl ace~ate-ethylene copolymers and polyacrylic acid. At page 7, lines 48-S0, it is mentioned that the substrate compound can be subjected to radiation to inhibit microbial growth, and that such radiation should be below 2.5 megarads gamma radiation.

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The Kater patent pertains to an electrode having an adhésive-electrolyte material. Polyvinyl alcohol adhesives are said to be preferred, and a formulation is provided for an adhesive of this type, in which there is present 15-25% polyvinyl alcohol having a de-gree of polymerization equal to 1700 and being 88%
hydrolyzed, and 5-10% glycerol. Suitably, the adhesive electrolyte material is based upon polyvinylpyrrolidone (PVP), polyacrylamide or polyvinylpyridines.
The Berg patent, mentioned above, is concerned with an electrode having an electrically conductive, hydrophilic adhesive that is a chemically cross-linked hydrophilic interpolymer composition. The starting materials for preparing this interpolymer composition may be (a) an ester of an ~,~-olefinically unsaturated carboxylic acid and a monohydric or polyhydric alcohol having a terminal quaternary ammonium group, and (b) an ~ olefinically unsaturated comonomer.
Other documents relating to an adhesive for use in a patient electrode include British Patent Appli-cation 2,045,088 in the name of Larimore, U. S. Patent 4,237,8~6 to Sakurada et al, U. S. Patent 4,243,051 ~
to Wittemann, U. S. Patent 4,243,052 to Bailey, U. 5.
Patent 4,248,247 to Ware et al, U. S. Patent 4,267,840 25 to Lazar et al, U. S. Patent 3,547,105 to Paine, U. S. I
Patent 3,565,059 to Hauser et al, U. S. Patent 3,607,788 to Adolph et al, U. S. Patent 3,911,9a6 to Reinhold, Jr., U. S. Patent 3,993,049 to Kater, U. S. Patent 4,008,721 to Burton, U. S. Patent 4,016,869 to Reichen-berger, U. S. Patent 4,067,34~ to Burton, U. S. Patent 4,112,941 to Larimore, V. S. Patent 4,141,366 to Cross, Jr. et al, Reissue Patent 24,906 to Ulrich, U. S.
Patent 3,845,757 to Weyer and U. S. Patent 3,265,638 to Goodman et al. The Larimore British patent appli-~ation and the Sakurada et al, Wittemann, Bailey, ~z~

Ware et al and Lazar et al patents appear to be con-cerned with adhesives ~ased upon cross-linked polymers.
The patents to Reinhold, Jr., Larimore, Burton and Cross, Jr. et al pertain to an adhesiue material based upon an acrylic polymer. Of these patents, the patent to Reinhold, Jr., has electrically conductive par-ticles dispersed throughout the adhesive material thereo~; An adhesive layer of this type can create non-uniform electrical transmission, provide lower conductivity, require a high cost for manu~acture, be difficult to manufacture, have lower adh~sivity, and be unable to absorb perspiration, with there being a tendency to lose adhesion if only a slight amount of moisture is present. The Kater patent discloses that the lS adhesive thereof is suitabl~ PVP-based. The Goodman et al patent is concerned with an electrolyte composi- !
tion comprising an aqueous solution of sodium chloride that is preferably completely saturated with silver chloride and that contains up to 7 5% polyvinyl alco-hol as a thickening agent. It is said that borax may be used to aid the polyvLnyl alcohol in its thickening action.
Other patents pertaining to chemically cross-linking an aqueous solution of a polymeric material 25 include U. S. Patent 3,087,920 to Suzumura et al, U. S. Patent 4,036,808 to Rembaum et al, U. S. Patent

3,932,311 to Caldwell et al, U. S. Patent 2,616,~18 to Azorlosa, U. S. Patent 4,089,832 to Yamauchi ~ ;
et al, U. S. Patent 3,220,960 to Wichterle, U. S.
30 Patent 3,545,230 to Morse, U. S. Patent 3,336,129 to Herrett et al, and U. S. Patent 2,838,421 to Sohl.
The Suzumura et al patent is concerned with a cold water-soluble polyvinyl alcohol that includes an admixture of partially saponified polyvinyl alcohol having a hydrolysis of 75-90%, a diaminostilbene optical 3L2~ 5~L

bleaching agent, and a surfactant~ At column 3, lines 33~35, of this patent, it is stated that in water, the partially saponified polyvinyl alcohol reacts with the diaminostilbene to form a three-dimensional bridge, thereby assuming a gel form, and at column 3, line 47, the cold water-soluble polyvinyl alcohol is stated to be useful as an adhesive.
The Rembaum et al patent relates to a conductive hydrogel formed by reacting the cationic polyelectro-lyte thereof with a gel-forming polymer such as poly-vinyl alcohol, polyacrylic acid or a polyether.
At column 8, lines 19-22, it is explained that a cross-linked hydrogel can be prepared from aqueous solutions of a mixture of polyvinyl alcohol and poly-acrylic acid or polyhydroxyethylmethacrylate. Thegels of this patent appear to be adhesive.
The Caldwell et al patent is concerned with an electrically conducting adhesi~e composition con-taining a cross-linked acrylate and/or methacrylate polymer and silver particles. The Azorlosa patent relates to a process for preparing a coated paper in which polyacrylamide or a copolymer of acryl-amide and acrylic acid is used as an adhesive. In a preferred embodiment, the coated paper is treated with a cross-linking agent so as to render the ad-hesive highly insoluble and stron~ly adhesi~e.
The Yamauchi et al patent pertains to a water-containing plastic composition that contains a water-containing powdery gel obtained by subjecting a water-soluble polymer such as polyvinyl alcohol, poly~acrylamide or PVP to a cross~linking reaction and then pulverizing the cross~ ked product. Ionizing radiation can be used to effect the cross-linking.
The plastic composition is suitable for manufacturin~
poorly combustible molding materials.

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The Wichterle patent is concerned with a hydrogel essentially consisting of a cross-linked hydrophilie ; polymer and 20-97% of an aqueous liquid. The hydrogel can be made, cut, or otherwise shaped to produee, for example, a lens, a pessary, or a dia:Lyzer diaphragm.
Medicinally active agents such as antibiotics may be dissolved in the aqueous constituent to provide medi-cation over an extended period.
The Morse patent relates to a flexible cooling device comprised of a reinforced layer of an insoluble hydrophilic gel. If desired, the gel can include materials to control the physical and ehemieal pro-perties sueh as freezing point and ehemieal stability.
~xemplary starting materials for preparing the gel in-elude poly(ethylene oxide), PVP, polyacrylamide, poly-vinyl alcohol, maleic anhydride-vinyl ether copolymers, polyacrylic acid, ethylene-maleic anhydride copolymers, polyvinyl ether, polyethyleneimine, polyvinyl alkyl pyridinium halides, and polymethacrylic acid. Insolu-! 20 bilization ean be effected by ionizing radiation or chemical cross-linking. The gel must be capable of retaining relatively large quantities of a liquid.
Water can be employed as the sole liquid, other liquids such as alcohols can be used, or mixtures of water and other li~uids or solutes can be employed. When it is desirable to use more than one gel layer, a thin film of an inert material such as polyethylene or a metal foil is used to separate the gel layers and thereby effectively prevent adhesion of the layers when staeked.

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The Herrett et al patent pertains to a plant growth medium containing an active agent and a water-insoluble, cross-linked polymeric material that serves as a matrix for the active agent. The polymeric material is illustratively polyvinyl alcohol, PVP, polyacrylic acid, polyvinyl acetate, polyacrylamide, and a copolymer of vinyl alcohol and vinyl acetate. The polymeric material i5 cross-linked either chemically or by ionizing radiation. Irradiation is carried out in the solid phase or in solution using water, for example, as the solvent. In one embodiment, a homogeneous water solution of the polymeric material is prepared and then irradiated for a period of time sufficient to cause the formation of a gel-like material, ! 15 and the gel-like material is dewatered. Exemplary active agents are quaternary ammonium salts, copper sulfate, , antibiotics and propylene glycol insect repellants.
At column 10, lines 39-44, it is said that the roots of plants grown in soil formulations containing the cross-linked poly(ethylene oxide) of Herrett et al had adhered thereto particles of the polymeric matrix.
The Sohl patent is concerned with an adhesive tape having a water-soluble adhesive composition that is essentially a blend of a solid water-soluble poly-vinyl carboxylic acid such as polyacrylic acid, anda compatible hydroxy-polyalkylene permanent elasti-9 ~ 54 cizer such as polyethylene glycol or polypropyleneglycol~ Another exemplary polyvinyl carboxylic acid is a 50/50 copolymer of polyvinyl methyl ether and maleic anhydride. Internal strength of the adhesive is in-creased by including in the adhesive mixture a chemicalcross-linking agent. The cured type of adhesive is said to be more resistant to water but to dissolve in water when mechanically agitated or mixed.
Other prior art patents that in addition to the Morse and Herrett patents discussed above, pertain to a hydrogel based upon N-vinyl-2-pyrrolidone include U. S. Patent 3,878,175 to Steckler, U. S. Patent 3,759,880 to Hoffmann et al and U. S. Patent 4,226,247 to Hauser et al. The Steckler patent is concerned with a highly spongy polymeric material characterized by swelling in water and being soft when wet. This spongy polymer is prepared by simultaneously copolymerizing and partially cross-linking 30-90 weight percent of an N-vinyl lactam monomer and 10~70 weight percent of an 2a acrylate monomer. The spongy material is said to be adaptable for industrial applications, human use in toiletry, and as a sterile surgical dressing for sponging, wiping, or absorbing pus, blood and other body fluids during surgical operations. The Hoffman et al patent relates to the manufacture of insoluble and only slightly swellable poly-N-vinylpyrrolidone-2.
The polymeric material of this patent is said to be a valuable absorbant for many purposes, especially as a beverage clarifying agent. The Hauser et al patent relates to an electrode having an adhesive that is preferably PVP-based. The adhesive is com-pounded by mixing with an active agent such as PVP, a plasticizer such as dioctyl phthalate, camphor or glycerin, and, alternatively, a conventional tackifier.

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The Herrett et al, Yamauchi et al and Morse patents, discussed above~ describe the ~se of radia-tion to cross-link a polymeric material. Similarly, U. S. Patent 3,897,295 to Dowbenko, U. S. Patent 3,264,202 to King, U. S. Patent 2,964,455 to Graham, U. S. Patent 3,841,985 to OIDriscoll et al, an~ U. S.
Patent 4,115,339 to Restaino pertain to the irradia-tion of polymeric materials.
In the Dowbenko et al patent, a solventless or nearly solventless solution of a polymer in a monomer is irradiated. The King patent pertains to forming a gel-li~e material by treating polymers of ethylene oxide with radiation. The gel-like material of this patent is said to have utility as a humidifier.
The O'Driscoll et al patent is concerned with irradiation of a solid, dry material containing PVP, and the Graham patent relates to the use of irradia-tion to modify solid articles made from polymeric alkylene oxides and polyvinyl ethers. At column 3, lines 59-61 of the Graham patent, it is disclosed that a benzene-soluble polytetramethylene oxide was soaked in water prior to irradiation. In the Restaino patent, an aqueous solution of a water soluble vinyl monomer is irradiated for the purpose of forming high molecular weight water-soluble polymers.
I believe this prior art and the other prior art of which I am aware,fails to provide a novel water-insoluble, hydrophilic, elastomeric, pressure-sensitive adhesive that is transparent, ultra-conformable and a soft, but strong, rl~bber-like solid that will absorb moisture that cannot be squeezed out; that will transmit oxygen, moisture, and druqs or salts soluble in the adhesive: and that will serve as a barrier to bacteria.

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This adhesive could be useful as a coating on a supportive web-like substrate. The adhesive-coated web-like substrate could be used as a bandage, a burn or wound dressing, an ostomy device, a decubitus ulcer pad, 05 a sanitary napkin, a diaper, a vibration or impact absorbing material such as a padding in shoes, splints, casts and orthopedic devices or an athletic padding, a sound absorhing material, or a medium for delivering a pharmacologically active agent. Additionally, a self-supporting layer of this adhesive could serve these same uses, and furthermore be useful as a cosmetic face mask and to secure a prosthesis or article of apparel to a mammalian body. One type of the novel adhesive could be electroconductive and function to attach an electrically conductive member of an electrode to a selected surface such as mammalian tissue.

~isclosure of the Invention It is accordingly one object of the present invention to provide a novel water-insoluble, hydrophilic elastomeric, pressure-sensitive adhesive.
This adhesive absorbs moisture that cannot be s~ueezed out; is transparent, ultra-conformable, and a sof-t, yet strong, rubber-like solid that serves as a barrier to bacteria; and transmits oxygen, moisture, and drugs or salts soluble in the adhesive.
A further object is to provide a supportive, web-like substrate coated with the adhesive.
A stil] further object is to provide a bandage, a wound or burn dressing, a sanitary napkin, a diaper, an ostomy device, a decubitus ulcer pad, a vibration or impact absorbing material, a sound absorbing material, and a medium for delivering a pharmacologically active agent having a layer of the adhesive supported by a web-3 like substrate.
An even further object is to provide a self-supporting layer of the adhesive that will serve these ,~

same uses, and furthermore be useful as a cosmetic face mask and to secure a prosthesis or article of apparel to a mammalian body.
A yet further object is to provide a method of S making the adhesive.
An additional object of the present invention is to provide an adhesive of this type that is electro-conductive and useful Eor attaching an electrically conductive member of an electrode to a selected surface such as mammalian tissue.
An even additional object is to provide an electrode having a layer of such an adhesive.
Other objects and advantages of the present invention will become apparent as the description thereof proceeds.
In satisfaction of the foregoing objects and objectives, there is provided by this invention a water-insoluble, hydrophilic, elastomeric, pressure-sensitive adhesive comprising at least one irradiation cross-linked synthetic organic polymer comprising repeating units derived from an N-vinyl lactam monomer, a polyalkylene glycol plasticizer and water, the polyalkylene glycol plasticizer being present in an amount sufficient to maintain the elastomeric state of the adhesive; and wherein the cross-linked polymer is water-insoluble, has a three-dimensional matrix, and is formed from a solution or dispersion of at least one suitable gel-forming, uncrosslinked water-soluble synthetic organic polymer comprising repeating units derived from an N-vinyl lactam monomer, and the plasticizer in water, and the relative proportions of the uncrosslinked polymer, plasticizer and water are such that the gel formed upon irradiation crosslinking retains said plasticizer and water within the three-dimensional matrix.
Also in satisfaction of the foregoing objects andobjectives, there is provided by this inven-tion a water-insoluble, electroconductive, hydrophilic, elastomeric, pressure-sensitive adhesive comprising at least one - 13 ~ 5~
irradiation cross~linked synthetic organic polymer, a conductivity-enhancing amount of at least one salt, a polyalkylene glycol plasticizer and water, the plasticizer being present in an amount su~ficient to 05 main~ain the elastomeric state of the adhesive; and wherein the cross-linked polymer is water-insoluble, has a three-dimensional matrix, and is formed from a solution or dispersion of at least one suitable gel-forming, uncrosslinked synthetic organic polymer and the l~ plasticizer in waterr and the relative proportions of the uncrosslinked polymer, plasticizer and water are such that the gel formed upon irradiation cross-linking, retains said plasticizer and water within the three-dimensional matrix.
Still further, in satisfaction of the foregoing objects and objectives, there is provided by this invention a process for making a water-insoluble, hydrophilic, elastomeric, pressure-sensitive adhesive comprising at least one irradiation cross-linked synthetic organic polymer comprising repeating units derived from an N-vinyl lactam monomer, a polyalkylene glycol plasticizer and water, the polyallcylene glycol plasticizer being present in an amount suEficient to maintain the elastomeric state of the adhesive;
comprising (a) solubilizing or dispersing at least one of said suitable gel-forming, uncrosslinked water-soluble synthetic organic polymer in the polyalkylene glycol plasticizer and water, and (b) subjecting the resulting solution or dispersion to a dosage of irradiation sufficient to produce the cross-linked polymer having a three-dimensional matrix and thereby form the adhesive, wherein the relative proportions of the uncrosslinked water-soluble polymer, plasticizer and water are such that the gel formed upon irradiation crosslinking, retains the plasticizer and water in the matrix.

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Brief Description of the Drawing Reference is hereby made to the accompanying drawing, which forms a part of the specification of the present invention.
05 Figure 1 shows an electrosurgical return electrode (with certain areas cut away) having a layer 1~ of an electroconductive, water-insoluble, hydrophilic, elastomeric, pressure-sensitive adhesive, with a portion of release liner 28 peeled back for attaching to arm 16.
Figure 2 depicts a supportive web-like substrate 18 with a layer 20 of a water-insoluble, hydrophilic, elastomeric pressure-sensitive adhesive coated thereon.
Figure 3 shows a self-supporting layer 35 of the adhesive of Figure 2.
Best Mode for Carrying Out the Invention As discussed above, the present invention pertains to a novel pressure-sensitive adhesive. This adhesive is a water-insoluble, hydrophilic, elastomeric, pressure-sensitive adhesive; is a soft, yet strony, rubber-like solid; and is Eurther characterized by belng transparent and ultra conformable. In fact, my adhesive has much higher drape than the skin itself. My adhesive absorbs moisture that cannot be squeezed out, transmits oxygen, moisture, and drugs or salts soluble in the adhesive, and functions as a barrier to bacteria.

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My adhesive adheres aggressively to skin but does not appear to stick well to hair, thus eliminating or greatly reducing the discomfort that Erequently accom-panies removal of a pressure-sensi~ive adhesive coated substrate from an area of human body having hair present.
My adhesive can be left on the human body several hours or even days, and discoloration and wrinkled appearance of the skin does not result.
My adhesive can absorb a significant amount of mois-ture without significant reduction in adhesion, and in this regard will absorb or transmit perspiration as it leaves the skin surface including moisture, salt~ urea, ammonia and other waste products. My adhesive can be prepared to contain a significant amount of water, or can be prepared in a dehydrated state and thus have even greater capability for absorbing moisture. My 'Idry'' adhesive, as illustrated in Example 1 and Table 1, has unexpected high oxygen permeance (the meaning of the term "dry" is explained below). The presence of a signi-ficant water phase in the adhesive is expected to produceeven higher oxygen permeability.
In most embodiments, my adhesive is suberabsorbant.
By superabsorbant, I mean that the adhesive will absorb an amount of water equal to approximately its own weight, without a loss in adhesivity. Exemplary embodiments in which the adhesive is not superabsorbant exis~ when the plasticizer is substantially polypropylene glycol, or substantially a copolymer of about 25 mole percent ethylene oxide and about 75 mole percent propylene oxide, such as is sold commercially by Union Carbide under the trademark Ucon 75-H 90,000. In most of the uses for the adhesive set forth in this description of my inven~
tion, it is advantageous that the adhesive is super-absorbant. However, when used as an ostomy adhesive or possibly when used as a drug delivery medium ~de-pending on the solubility characteristics of the drug), the adhesive should be absorbant, not 16 ~2~895~
superabsorban~ and thus plasticizers of the type just mentioned should be used.
My adhesive wiIl filter out microorganism con-taminants by presenting a tortuous path for the influx of the bacteria. As a result, antibiotics in a wound dressing may be unnecessary in most cases.
My adhesive so closely matches the fluid transmission and bacteria barrier characteristics of human skin as to be like an instantly healing injury as far as in-fection is concerned. It is believed that scar tissueformation would be retarded.
In one embodiment, the adhesive is electroconductive and is particularly ~uitable for use with an electrode.
~eferring to Figure 1, there is illustrated an electro-surgical return pad 10 that includes a conventionalelectrically conductive member 12 and an electroconductive, water-insoluble, h~vdrophilic, elastomeric, pressure-sensitive adhesive 14, in accordance with the invention.
Also shown in this Figure is an arm 16, which serves as a surface to which electrosurgical return pad 10 is attached.
Referring to Figure 2, there is shown a bandage 17 having a supportive web like substrate 18 and an adhesive layer 20, in accordance with'the invention, coated thereon. This general structure is typical o a bandage, sanitary nap]cin, burn or wound dressing, ostomy device, decubitus ulcer pad, diaper, a vibration or impact absorbing material such as a padding, a sound absorbing material, and a medium for delivering a pharmac'ologically active agent, in accordance with the''invention.
~owever, the size and thickness of substrate 18 and adhesive layer 20 will vary depending upon the use selected.
Also shown in Figure 1 are foam l'ayers 22 and 23, non-woven fabric layer 24, adhesive layers 26 and 27, release liners 28, 30 and 32, and electrical connection holes 34. These aspects of the pad are conventional.

~3L89S~l Adhesive layer 26 serves to bond fabric layer 24 to foam layer 22. Foam layer 22 is conveniently a polyethylene foam, and fabri~ layer 24 is suitably a polyester material such as Nexus(-~ polyester rnaterial sold by Burlington. Pad 10 is attached to arm 16 after re-lease liner 28 is removed.
Pad 10 is advantageously manufactured in part by coating foam layer 22 with adhesive layer 26l laying down fabric layer 24 on the adhesive to form a lami-nate, placing conductive member 12 on fabric layer 24,applying a solution or dispersion of an uncrosslinked, appropriate synthetic organic polymer in a suitable plasticizer to fabric layer 24 and conductive member 12, and subjecting the resulting laminate to ionizing radiation. Release liner 28 is then put into place.
The synthetic organic polymer and plasticizer are described below.
Referring to Figure 3, there is shown a self-supporting layer 3G of the adhesive of the present invention. This general structure is typical for all uses of the adhesive as a self-supporting layer. However, the size and thickness of layer 3~ will vary depending upon the use selected.
Preferably, a self-supporting layer of the adhesive ranges in thickness from about 3-6 mm. When prepared for use as a self-supporting layer, the adhesive layer, of course, could be sandwiched between a pair of conventional release liners.
My adhesive includes at least one irradiation cross-linked synthetic organic polymer and a sufficient amount o~ an adhesive plasticizer to maintain the elas-tomeric state of the adhesive. The cross-linked polymer is formed by dispersing or solubilizing at least one suitable gel-forming, uncrosslinked synthetic organic polymer in a plasticizer that has a composition the same as or different than the adhesive plasticizer, and then subjecting the resulting solution or dispersion 18 1~ 5~
to an appropriate dosage of irradiation. Use of an appropriate dosage of irradiation produces an adhesive with the properties described herein. The cross-linked polymer of the adhesive is water-insoluble and has a three-dimensional matrix.
Conveniently, the uncrosslinked synthetic organic polymer includes repeating units derived from a carboxy vinyl monomer, a vinyl ester monomer, an ester of a carboxy vinyl monomer, a vinyl amide monomer, a hydroxy vinyl monomer, a cationic vinyl monomer containing an amine or a quaternary ammonium group, or an N-vinyl lactam monomer.
Alternatively, the uncrosslinked polymer is conveniently a homopolymer or copolymer of a polyvinyl ether, or a copolymer derived from a half ester of maleic anhydride. A polymer formed from a compatible monomer mixture may be used such as a polymer formed from a mixture of an N-vinyl lactam monomer and an ester of a carboxy vinyl monomer. Also r compatible uncrosslinked polymers may be used, in appropriate amounts, such ~s about 11.25 ~eight percent polyvinyl alcohol (88% hydro-lyzed) and about 3.75 weight percent polyacrylic acid having a molecular weight of about 450,000. Advantageously, the uncrosslinked polymer is water(-soluble, and includes, for example, re~eating units derived from a carboxy vinyl monomer, is a homopolymer or copolymer of a poly~
vinyl alcohol, or is a copolymer formed from approxi-mately substantially equal amounts of methyl vinyl ether and maleic anhydride.
Preferably, the uncrosslinked polymer includes repeating units derived from an N-vinyl lactam monomer.
Illustrative N-vinyl lactam monomers are N-vinyl-2-pyrrolidone, N-vinyl--caprolactam and mixtures thereof. The N-vinyl lactam monomer is suitably either a homopolymer of N-vinyl-2 pyrrolidone, or a copolymer of N-vinyl-2-pyrrolidone and at least one vinyl monomer that is compatible with solubility ~L895~

or dispersability of the uncrosslinked copolymer in the solubilizing or dispersing plasticizer and that is com-patible with solubility or dispersability of the cross-linked copolymer in the adhesive plasticizer.
Vinyl monomers of this type include vinyl acetate, and an ester of an ~,~-olefinically unsaturated car-boxylic acid and an amino group-containing alcohol. When the vinyl monomer is vinyl acetate, the mole ratlo of vinyl acetate and N-vinyl-2-pyrrolidone is advantageously such that the copolymer is water-soluble. A commercially available copolymer of this type is sold by BASF under the - ~ name Luviskol VA.
A copolymer of N-vinyl-2-pyrrolidone and the carboxylic acid ester is preferred, with the copolymer suitably con-taining about 20 mole percent of the ester~ It is par-ticularly preferred for the ester to be either dimethyl-aminoethyl methacrylate or the partially or ully ~ua-ternized salt of this methacrylate. A partially quaternized salt-containing copolymer of N-vinyl-2-pyrrolidone (having a X value of approximately 90) is sold as a 20~ aqueous solution under the trademark Gafquat 755 N. This com-mercially available copolymer contains 20 ~ole percent of dimethylaminoethyl methacrylate partially ~uaternized with diethyl sulfateO An advantageous polyvinyl pyrrolidone is K-90 PVPj and is available from GAF as Type NP-K90.
For purposes of this specification, the term "carboxy vinyl monomer" includes a water-soluble salt of a carboxy vinyl monomer with, for example, an alkali metal, ammonia or an amine. Exemplary carboxy vinyl monomers include acrylic acid, methacrylic acid, crotonic acid, isocrotonic acid, itaconic acid and anhydridej a 1,2-dicarboxylic acid such as maleic acid or fumaric acid, maleic anhydride, and mixtures thereof. Conveniently, the carboxy vinyl monomer is acrylic acid.
When the carboxy vinyl monomer is a 1,2-dicarboxylic acid or maleic anhydride, the uncrosslin~ed polymer includes ~ Jrr~cjc~ ~lr~rl~ .

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a comonomer. The comonomer is, for example, a C2- C4 olefinic monomer such as ethylene, propylene, n-butylene or isobutylene; a C4 diolefinic monomer such as buta-diene; a Cl-C4 alkyl vinyl ether such as methyl vinyl ether; styrene; or vinyl acetate. The amount of the 1,2-dicarboxylic acid or maleic anhydride is substantially equivalent, on a molar basis, to the amount of the co-monomer. Vinyl acetate is a suitable comonomer in an amount up to as much as about 20 weight percent, with an~ of the other carboxy vinyl monomers.
As the polyvinyl alcohol, one or more water-soluble polyvinyl alcohols are used. A convenient polyvinyl alcohol is a high molecular weight, 88~ hydrolyzed polyvinyl alcohol prepared through hydrolysis of polyvinyl acetate. This polyvin~l alcohol is com-mercially available as Gelvatol ~ 20-90 and is a product of Monsanto.
The irradiation cross-linked polymer is produced by carrying out the irradiation on a solution or dis-persion of the suitable gel-forming, uncrosslinked synthetic organic polymer in a plasticizer that is water-soluble or water-dispersible, into which the uncrosslinked polymer can be dissolved or dis-persed, and into which water and the uncrosslinked polymer can be dissolved or dispersed. The term "solubilizing plasticizer" is used in this description to designate this plasticizer. This plasticizer is irradiation cross-linking compatible. For purposes of this specification, the term "irradiation cross-linking compatible" means that the solubilizing plastiaizer does not inhibit irradiation-caused cross-linking of the polymer.
The solubilizing plasticizer includes at least one substantially non-volatile elasticizer, and con-veniently includes a volatile solvent that in combina-2~ 5~
tion with the elasticizer serves to disperse ordissolve the polymer. The volatile solvent is either aqueous, non-aqueous, or a mixture, and is selected in conjunction with the elasticizer to form a plas-ticizer composition into which the uncrosslinked polymercan be dissolved or dispersed, and to form an adhesive plasticizer that will dissolve or disperse the cross-linked polymerO Conveniently, the volatile solvent is aqueous, and it is especially convenient for the vola-tile solvent to ke water. When the volatile solventis water, up to about 90% of the solubilizing plasticizer may be water. A very important feature that separates my unique adhesive from the prior art is that it re-tains its adhesivity upon removal of the volatile solvent. In contrast, an aqueous solvent gel such as disclosed by Steckler, Herrett et al, and Kater will become hard and non-adhesive upon removal of the volatile solvent.
The substantially non~volatile elasticizer is present in an amount su~ficient to maintain adhesivity of the cross-linked polymer-containing adhesive when the adhesive plasticizer is substantially made up of the elasticiæer. By "substantially" in reference to the plasticizer is meant that only as much ~.s about 2 weight percent of the volatile solvent is present.
Advantageously, the elasticizer is present in an amount ranging from about 0.5 to 4:1, on a weight basis, of the cross-linked polymer.
The solution or dispersion formed from combining the uncrosslinked polymer with the solubilizing plasticizer is either clear or hazy in appearance.
The relative proportions of the uncrosslinked polymer and the plasticizer are such that the gel formed upon irradiation crosslinking, retains this plasticizer within the three-dimensional matrix.

~ ~2~ 5~
Conveniently, the substantially non-volatile elasticizer is a suitable polyhydric alcohol, mono- or diether of a poly-alkylene glycol, mono- or diester of a polyalkylene glycol, imidazoline derivative amphoteric surfactant, lactam, N-substituted lactam, amide, polyamide, amine, polyamine, condensate of poly-ethylene imine with epichlorohydrin, polyquaternary ammonium compound or compatible mixture thereof. The polyhydric alcohol is used with particular advantage, and it is very advantageous that the polyhydric alcohol is a polyalkylene glycol, in particular a polyethylene glycol. Other suitable polyalkylene glycols include a copolymer made from about 25 mole percent ethylene oxide and about 75 mole percent propylene oxide. A copolymer of this type is sold under the trademark Ucon 75-H 90,000 by Union Carbide. Other useful polyhydric alcohols include sorbitol, 1,3-butane diol, 1,4-butane diol, 1,4-butene diol, a suitable corn sugar derivative, pentaerythritol, trimethylolethane, glycerine, propylene glycol, 1,3-propane diol, polyglycerine, ethylene glycol, and compatible mixtures.
~t is necessary that the elasticizer present during the irradi~tion treatment step is irradiation cross-linking com-p~tible. Thus, for example, glycerine, which tends to reduce the effectiveness of irradiation cross-linking, should not be present as the elasticizer prior to irradiation treatment in an amount greater than about 5~ of the total formula weight, depending upon the polymer upon which the adhesive is based.
This amount of glycerine can be present as the elasticizer and can accordingly be added to the elasticizer, once the cross-linking step has been completed. It is to be understood that, if, for example, the elasticizer is the amide or amine, the amide or amine is sub-stantially non-volatile. Also, as explained below, the elasticizer is typically a liquid at room temperature.

23 ~2~8~5~
Once the irradiation treatment is completed, another way of altering the composition of the adhesive plasticizer in those cases in which this plasticizer contains a volatile solvent, is to remove some of the volatile solvent. When the volatile solvent is water, it is preferable to remove some of the water so that only a small amount, say up to about 5%, of water is present as part of the adhesive plasticizer. In fact, it is even more preferable to remove a sufficient amount of water so that the adhesive is "dry", as defined below. An advantage of these dewatered adhesives is their capability for greatly increased moisture absorption.
Additionally, as shown in the Examples, the dewatered or "dry" adhesive is superior in its adhesivity to the "wet"
adhesive, has markedly superior water vapor transmission, and has unexpectedly high oxygen permeance. By "dry", for purposes of this specification, is meant that an adhesive has a degree of dryness that is minimally that produced by allowing an adhesive to air dry for about 48 hours at approximatel~ 30~ relative humidity and 20C. By "wet", for purposes of this specification, is meant that the adhesive contains at least about 55% water.
Generally, as noted above, the elasticizer is a liquid at room temperature. However, it is possible for the elasticizer to be a solid at room temperature when a freezing point depression results from the combination of the elasticizer with the uncrosslinked polymer, some other component of the solubilizing plasticizer, or a suitable additive material that is placed into the formulation prior to the cross-linking step. A material that is normally solid but that experiences freezing point depression in the presence of an appropriate . ~

~Z 8~5~

uncrosslinked polymer such as polyacrylic acid having a molecular weight of approximately 450,000, is a polyethylene glycol having a molecular weight from about 600 to about 20,000. Particularly advantageous polyethylene glycols, for use in my invention, have a molecular weight of about 300 or about 600. A
polyethylene glycol (PEG) having a molecular weight of 300 is sold by Union Carbide under the trademark Carbowax 300, and a PEG having a molecular weight of 600 is sold under the trademar~ Carbowax 600. It is also possible for an elasticizer that is solid at room temperature to be used, if the remainder of the plasticizer composition is capable of solubilizing or dispersing both a mixture of this and the uncrosslinked polymer, and a mixture of this and the cross-linked polymer.
As discussed, the elasticizer ls illustratively the polyhydric alcohol, the mono- or diether of a poly-alkylene glycol or the N-substituted lactam. It is very advantageous when the polyhydric alcohol is a polyalkylene glycol, with polyethylene glycol, polypropylene glycol and the copoiymer of ethylene oxide and propylene oxide being exemplary polyalkylene glycols. A mono- or diether of polyethylene glycol is suitably the mono- or diether of a polyalkylene glycol, and a polyethoxylated fatty alcohol, poly-ethoxylated nonyl phenol or a polyethoxylated octyl phenol is convenlently the monoether of the polyethylene glycol. Illustrative N-substituted lactams include N-isopropyl-2-pyrrolidone, N-(~,N-dimethylamino)propyl-2-pyrrolidone, and N-cyclohexyl-2-pyrrolidone.
Suitably, the uncrosslin~ed polymer includes repeating units derived from a vinyl amide monomer.

~2~8~3159L
A particularly suitable monomer of this type is an amide of a ~ olefinically unsaturated carboxylic acid, with acrylamide and dimethylaminopropyl methacrylamide being exemplary. Another amide of this type is methacrylamido propyl trimethylammonium chloride.
As explained earlier, it is advantageous for the uncrosslinked polymer to include repeating units derived from a carboxy vinyl monomer. When the carboxy vinyl monomer is acrylic acid, the polymer may be a copolymer of acrylic acid and ethylene, vinyl acetate or an acrylate ester. With this copolymer, there is included an amount of a base sufficient to solubilize the polymer, with the base being an amine, a quaternary ammonium or an alkali metal hydroxide. When the carboxy vinyl monomer is maleic acid, an advantageous comonomer is methylvinyl ether, ethylene, vinyl acetate, styrene or butadiene, with the amount of the comonomer being substantially equivalent, on a molar basis, to the amount of the maleic acid. When the comonomer is styrene or vinyl acetate, there is included enough of a base sufficient to solubilize the copolymer.
An adhesive in accordance with my invention prepared from an uncrosslinked polymer or plasticizer that is skin irritating, or that otherwise contains a skin-irritating additive is better employed so as not to be in contact with skin. An exemplary polymer of this type predominantly includes repeating units derived from a carboxy vinyl monomer such as acrylic acid, and an illustrative plasticizer contains a surfactant or detergent as ~he elasticizer. Otherwise, my adhesive has the substantial advantage of being hypo-allergenic.
When the uncrosslinked polymer includes repeating units derived from an N-vinyl lactam monomer, particu-larly useful elasticizers include a polyethylene glycol, an imidazoline derivative amphoteric sur~actant, a 895igL

polyethoxylated fa~ty alcohol, a polyethoxylated fatty acid, a polyethoxylated nonyl phenol, and a polyethoxy~
lated octyl phenol. A polyethoxylated octyl phenol surfactant is sold under the Triton brandname by Rohm & Haas.
A convenient polyvinyl ether ~or use as the un-crosslinked polymer starting material is polymethyl-vinyl ether or polyethyl vinyl ether. Particularly suitable elasticizers include the monoether of a poly-alkylene glycol or the monoester of a polyalkylene glycol.~n illustrative monoether of a polyalkylene glycol is polyethoxylated octyl phenol, and an exemplary monoester of a polyal~ylene glycol is a fatty acid ester of polyethylene glycol such as polyethylene glycol 300 monostearate. Other use~ul elasticizers include an N-substituted lactam and, of course, polyethylene glycol An N-substituted lactam is also a particularly convenient elasticizer for use with an uncrosslinked pol~mer derived from an N-vinyl lactam monomer.
When the uncrosslinked polymer includes repeating units derived from a vinyl ester monomer, the polymer contains an amount of a second comonomer sufficient to make the polymer soluble or dispersible in the plasti-cizer prior to the irradiation treatment stepj and also soluble in the adhesive plasticizer. Exemplary vinyl esters include vinyl acetate and vinyl propionate, and the comonomer is illustratively an N-substituted lactam, a vinyl alcohol, a hydrolyzed maleic anhydride, or crotonic acid. A copolymer containing the vinyl ester and vinyl alcohol may be prepared through in-complete hydrolysis of the vinyl ester. A copolymer of vinyl acetate and maleic anhydride is prepared through hydrolysis and base treatment. When the comonomer is crotonic acid, a sufficient amount of an appropriate base is added to dissolve the polymer in the plasticizer prior to the irradiation treatment.
~c~c/~

8~
~7 Conveniently, this copolymer contains vinyl acetate and crotonic acid in an about 19:1 mole ratio.
When the uncrosslinked polymer is a copolymer derived from a half ester of maleic anhydride, the half ester is suitably the methyl half ester or the ethyl half ester, and the comonomer is advantageously a Cl-C~ vinyl ether such as methyl vinyl ether, or etllylene.
Other exemplary vinyl amide monomers are prepared from an ~ olefinically unsaturated carboxylic acid and a diamine such as dimethylaminoethylamine and aminoethyl trimethylammonium chloride. Illustra-tive hydroxy vinyl monomers, for use as the uncross-linked polymer starting material, include allyl alcohol, hydroxyethyl acrylate and hydroxypropyl acrylate. Vinyl benzyl trimethylammonium chloride exemplifies a cationic vinyl monomer containing an amine or a quaternary ammonium group.
As e~plained earlier, the relative proportions of the uncrosslinked polymer and the solubilizing plas-ticizer are such that the gel formed upon theirradiation cross-linking, retains this plasticizer within the three-dimensional matrix. When the un-crosslinked polymer includes repeating units derived from a carboxy vinyl monomer, a vinyl ester monomer, an ester of a carboxy vinyl monomer, a vinyl amide monomer, a hydroxy vinyl monomer, or a cationic vinyl monomer containing an amine or a quaternary ammonium group, the solution or dispersion to be irradiated conveniently contains about 5-50 weight percent of the uncrosslinked polymer. Also, when the uncross-linked polymer is a copolymer derived from a half ester of maleic anhydride, the solution or dispersion advantageously contains about 5-50 weight percent of the uncrosslinked polymer. It is suitable for the solution or dispersion to contain about 7-60 weight 2g ~2~ 5~

percent of the uncrosslinked polymer, in the case that the uncrosslinked polymer in~ludes repeating units derived from an N-vinyl lactam monomer. When the uncrosslinked polymer is a homopolymer or copolymer of a polyvinyl ether, it is convenient for the solution or dispersion to contain about 5-60 weight percent of the uncrosslinked polymer. In the case where the uncrosslinked polymer is a homopolymer or copolymer of a polyvinyl alcohol, the solution or dispersion to be irradiated advantageously contains about 5-30 weight percent of the uncrosslinked polymer. When the un-crosslinked polymer includes repeating units derived from a carboxy vinyl monomer, it is especially suitable for the solution or dispersion to contain about 14-20 wei~ht pexcent of the uncrosslinked polymer, with about 20 weight per~ent being preferred. When the uncross-linked polyrner includes repeating units derived from an N-vinyl lactam monomer, it is particularly advan-tageous for the solution or dispersion to contain about 12.5 - 22.5 weight percent of the uncrosslinked polymer, with about 20 weight percent again being preferred.
A particularly convenient concentration of the un-crosslinked polymer in the solution or dispersion is about 7-25 weight percent when the uncrosslinked poly-mer is a homopolymer or copolymer of a polyvinylalcohol, with about 10 weight percent being preferred.
When the uncrosslinked polymer includes repeating units derived from a carboxy vinyl monomer, a particu-larly suitable ratio of the elasticizer to the carboxy vinyl monomer is an about 1:1 ratio, on a weight basis.
~hen the uncrosslinked polymer is polyacrylic acid, the polyacrylic acid conveniently has a molecular weight of about 450,000 - 500,000. Polyacrylic acid having a molecular weight of about 500,000 is sold in a 15%
aqueous solution by ~. F. Goodrich as Carbopol ~ Ex-17, l.Z:1.~39591 and polyacrylic acid having a molecular weight of 450,000 is sold as Carbopol ~ 9Q7. A particularly advantageous adhesive, as discussed earlier, is "dry". Removal of the volatile solvent to form this adhesive is achieved as explained above, or by using equivalent techniques.
When the adhesive includes irradiation cross-linked K-90 polyvinyl pyrrolidone and polyethylene glycol having a molecular weight of about 300, it is highly preferred for the polyethylene glycol to be present in an amount that is about 0.75 - 1.5 times the amount, on a weight basis, of the polyvinyl pyrrolidone.
These particular compositions and similar compositions in which the polyvinyl pyrrolidone is a copolymer of N-vinyl-2-pyrrolidone and either dimethylaminoethyl methacrylate or the partially quaternized salt of this methacrylate, are the very preferred compositions of this invention. -The dosage of irradiation to produce my adhesivedepends upon factors that include the concentration of the uncrosslinked~polymer in the solubilizing plasticizer, and the molecular weight of the uncrosslinked polymer.
For instance, a relatively lower dosage of irradiation is required by a relatively higher concentration of the uncrosslinked polymer or a relatively higher molecular weight uncrosslinked polymer; whereas a relatively higher amount of irradiation is required by a relatively lower concentration of the uncrosslinked polymer or a relatively lower molecular weight uncrosslinked polymer. The choice of elasticizer and the relative proportions of the elasticizer, the remaining plasti-cizer components, and the uncrosslinked polymer also affect the dosage requirements.

3~

In addition, when the irradiation is carried out at a relatively low rate, and in the presence o~ a free radical scavenger such as oxygen, relatively higher dosages are required; whereas, when the irradi-ation is carried out under conditions that favor therelatively long existence of the free radicals pro-duced, as for example, when the irradiation is carried out with a high dose rate, in the absence of oxygen, or in solution where oxygen is rapidly used up, a relatively lower dosage is necessary-.
The term "irradiationl' as used herein, means high energy radiation and/or the secondary energies resulting from conversion of electron or other particle energy to neutron or gamma radiation. ~hese energies are at least equivalent to about 100,000 electron volts. While var.ious types of irradiation are suitable for this pur-pose, such as x-ray and gamma and beta rays, the radia-tion produced by accelerated high energy electrons is conveniently and economically applicable. However, regardless o the type of radiation and the types of equipment used for its generation or application, the ionization radiation need only be equivalent to at least about 100,000 electron volts.
While there is no upper limit to the electron energy that can be applied advantageously, the effects desired in the practice of this invention can be accom-plished without having to exceed about 20 million electron volts. Generally, the higher the electron energy used, the greater is the depth of penetration into the struc-ture of the materials to be treated, and the shor~er is the time of exposure required. For other types of radiation, such as gamma and x~rays, eneryy systems equivalent to the above range of electron volts are desirable.
It is intended that the term "irradiation" include ~2~

"ionizing radiation" which has been defined as radiationpossessing an energy at least sufficient to produce ions or to break chemical bonds and thus includes "ionizing particle radiation" as well as radiations of the type termed "ionizing electromagnetic radiation".
The term "ionizing particle radiation" has been used to designate the emission of electrons or highly accelerated nuclear particles such as protons, neutrons, alpha-particles, deuterons, or beta-particles, directed in such a way that the particle is projected into the mass to be irradiated. Charged particles can be accele-rated by the aid of voltage gradients by such devices as accelerators with resonance chambers, Van der Graaff generators, betatrons, synchrotons, cyclotrons, dyna-matrons and insulated core transformers. Neutron radi-ation can be produced by bombarding a selected light metal such as beryllium with positive particles of h~gh energy. Particle radiation can also be obtained by the use of an atomic pile, radioactive isotopes or other natural or synthetic radioactive materials.
"Ionizing electromagnetic irradiation" is pro-duced when a metallic target, such as tungsten, is bombarded with electrons of suitable energy. This energy is conferred to the electrons by potential accelerators of over 0.1 million electron volts. In addition to irradiation of this type, commonly called x-ray, an ionizing electromagnetic irradiation suitable for the practice of this invention can be obtained by means of a nuclear reactor (pile) or by the use of natural or synthetic radioacti~e material, for example, cobalt 60.
Dosages of irradiation ranging from about 0.5 - 4.5 megarads are useful for cross-linking the uncrosslinked polymer, with a dosage of about 3.5 - 4.5 megarads being particularly suitable. Thus, this dosage range is es-pecially useful for a composition substantially containing 1~8~

about 18-22 weight percent, K-90 polyvinyl pyrrolidone, about 10-70 weight percent polyethylene glycol having a molecular weight of about 300, and water. The adhesive produced is a preferred adhesive, and can be made electro-conductive by including an appropriate amount of aconductivity enhancer such as about 6-8 weight percent.
It is very preferred for this adhesive to contain about 25-30 weight percent of PEG 300, and about 20 weight percent PVP.
My adhesive optionally contains a compatible preservative such as methyl paraben or propyl paraben.
Mixtures of preservatives may be used, and, when used, a preservative is used in an amount sufficient to achieve a preservative effect. Also, my adhesive may contain a dye such as FD&C Blue # 2.
My adhesive is useful as a coating on a suppor-tive web-like substrate. As a result of high cohesion, and by a judicious choice of the web-like substrate so that there is a very high adhesion of the adhesive to the substrate, my adhesive does not leave behind an adhesive residue. When polystyrene, for example, is used as the supportive substrate, very high adhesion of the adhesive to the polystyrene results if irradiation is carried out with the solution or dispersion of the un-crosslinked polymer in dlrect contact with polystyrene. A
particular advantage of my adhesive is that it tends to be re-applicable. As a result, the adhesive may be re-posi-tioned several times without loss of adhesive performance.
My adhesive is elastomeric and undergoes elastic deformation. When my adhesive is strained, a restoring static stress develops. Even after undergoing several hundred percent strain, there is little if any visually detectable permanent set, after relaxation of my adhesive.
My adhesive is very low in stiffness and has a modulus as low as gelatin desserts or even lower.
Since my adhesive is elastomeric and does not 33 ~L2~8~
exhibit excessive cold flow, it is possible to produce my adhesive in a very thick layer form, even as great as about 40 mm or more. However, a layer having a thickness of about 3-6 mm is preferable, especially when a layer of my adhesive is self-supporting, and has the advantage of allowing articulation of a patient's body with a minimum of re-triction and a minimum of painful pulling. A self-sup-porting layer of my adhesive could be a coating on a non-supportive thickness of a web-like substrate such as gauze or a non-woven fabric. In this instance, the web-like substrate would function to increase dimensional stability and enable the adhesive to be cut more easily.
A supportive web-like substrate coated with a layer of my adhesive has a multiplicity of uses, and the web-like substrate is selected according to the desired use.
~uitably, the web-like substrate is non-conductive. If it i is desired to use the coated substrate as an adhesive tape, for example, a cellophane~film may be used as the substrate.
A number of uses exist for the coated substrate such as a bandage, a burn or wound dressing, a sanitary napkin, an ostomy device, a diaper, a decubitus ulcer pad, a vibration or impact absorbing material, a sound absorbing material, and a medium for delivering an adhesive-soluble pharma-cologically active agent. In certain of these uses, the adhesive includes a pharmacologically active agent that is soluble in the adhesive.
When used as a self-supporting layer, my adhesive has the uses described above for the coated substrate. A self supporting layer of my adhesive is also useful as a cosmetic 3~ face mask, and to secure a prosthesis or an article of apparel to a mammalian body.
When used in a bandage, my adhesive material is able to replace all three parts of the bandage, that is, the adhesive, gauze and su~strate, and may be the best material known for any of these three parts. As the adhesive part of the bandage, it is non-traumatic, ~r a ~Je~ r ~

~8~S~L

does not pull hair, does not induce painful pulling in use, does not cause discomfort or injury upon removal, and does not cause the skin-wrinkling moisture retention observed with many other adhesives. As a gauze material, my adhesive allows continual observation of a patient's condition without disturbing the patient. Being a soft elastomer, it provides superior padding as well. Being non-fibrous, it does not strongly adhere to a scab, and usually will be removed without scab trauma. My adhesive will significantly reduce bacterial influx by filtering bacteria out. Being elastomeric in nature, my adhesive can be used without a supporting substrate when an appropriate thickness is provided. Its superior drape will allow it to conform to the most intricate body contours, remaining attached even during vigorous movement. Its high oxygen and moisture permeability is most beneficial in bandage applications, particularly as a means of controlling anaerobic bacterial infection.
My adhesive can absorb the fluid exuded from a minor injury and thus serve as both adhesive and absorbant pad. A
substantial advantage of this is that if an appropriately-sized sheet of adhesive-coated substrate is available, one can cut a special size or shape of bandage to fit the exact need. This is in contrast to commercially available bandages that are made of an absorbant pad secured to an adhesive tape, and that require providing a gauze pad of appropriate size and shape and also an adhesive tape of appropriate size and shape.
When gauze is used to cover an injury site, a frequent problem is that the coagulated blood and body fluids tend to encapsulate the gauze fibers, as a result of which the gauze becomes adhered to the injury site. In contrast, my ad-hesive is less likely to adhere to the injury. When used as a gauze replacement, my adhesive can be prepared to contain an amount of moisture ranging 8~5~ 1l from about zero to ninety percent so that one can maintain either a high moisture environment or a low moisture environment over the area being treated.
As a burn dressingt it is believed my adhesive will function as an artificial skin graft that will stabilize a patient until grafts of his own tissue are available.
When used as a sanitary napkin, a layer of my adhesive can serve as all three parts of the sanitary napkin, that is, as the absorbant material, the adhesive, and the supporting structural member. The ability of my adhesive to adhere to the contours of the vaginal area even during vigorous movement, to absorb menstrual fluid, and to provide a seal over the vaginal area makes this adhesive material an ideal sanitary napkin. An about 3/16" sheet of this ma-terial could be used alone, without support. When un-supported, the opposite side of the adhesive could have an undergarment adhesion preventing coating provided, for example, by dusting this side with talc or treating it with ~ silicone Eluid. Since my adhesive does not absorb particulates, it is advantageous to use a pad o-f another absorbant material over the center portion of the sanitary napkin.
As a cosmetic face mask, my adhesive is soft enough to be comfortably used over the entire face. Moisturizers could be added in an appropriate amount in order to provide an o~ernight beauty treatment which, being continuous through the night, will provide a most effective "youth restoring" beauty aid. Additionally, pharmacologically active agents such as those useful against acne or pro-viding sunburn pain relief could be included in the ad-hesive~
When used as a delivery medium for a pharma-cologically active agent, a layer of my adhesive can be applied to skin areas other than the face. This use is particularly advantageous when the pharma-36 ~Z~L~95~

cologically active agent is able to pass through theskin. In addition to applying my adhesive to the skin, my adhesive may be located in the vagina, rectum or mouth, and even under the skin for subcutaneous administration. In S an interesting use of my adhesive as a drug delivery medium, my adhesive is prepared so as to include an aqueous solution of epsom salt. A layer of the adhesive is applied to the feet, and the user is able to freely move about and still "soak" his feet. The adhesive will retain the epsom salt solution, and even if compressed will not release moisture.
The pharmacologically active agent should be soluble in the plasticizer phase of the adhesive, and must be present in an amount sufficient to bring about the desired pharma-cological effect. Exemplary pharmacologically active agents include hormones such as estrogen, analgesics, and antirheumatics. Additionally, the adhesive may be used as a carrier for a depilatory agent.
My adhesive is especially useful as a vibration or impact absorbing material such as a padding since it is very ~oft and can undergo considerable shear strain and yet not transmit very high stresses. A self-supporting layer of the adhesive may be used as pad~ing in shoes, orthopedic devices, casts and splints. In another use as a padding, a layer of the adhesive may be used as a saddle blanket so as to reduce saddle sores of horses. My adhesive is useful for attenuating vibration in motion picture equipment, and in various sensitive instruments. Additionally, my adhesive provides good sound attenuation.
The properties of my adhesive result in useful-ness for treating or preventing bed sores or decubitusulcers. This is accomplished by applying a layer of my adhesive to a selected area of the body, as a result of which rubbing of this area is reduced.

~2~89~i~

My adhesive may contain beneficial ingredients such as humectants, skin conditioners, depilatories, hormones, perfumes, cleansing agents, acne medication, antiperspirants, astringentsl sun screens, and arti-ficial sun tanning materials. When used as a mediumfor delivering an adhesive-s oluble pharmacologically active agent, my adhesive may function to provide continuous drug delivery by providing an appropriate con-centration of the drug in a suitable adhesive. In addition to those drug types set forth above, the drug could be nitroglycerin or a motion sickness treatment drug. In situations where it is desirable to have a bacteriastatic agent in the adhesive, for example, where the adhesive is to be applied to the face of a person for treatment of acne or is to be applied topically to the skin for treatment of a topical infection, my adhesive includes a quaternary ammonium compound. For treatment of ringworm, athlete's foot, jock itch or other topical fungal infections, an appropriate antifungal compound is added to my adhesive.
As a self-supporting layer, my adhesive may also be used to secure a prosthesis to a mammalian body. Also, an article of apparel may be secured to a mammalian body by use of a self-supporting layer of my adhesive.
In forming my adhesive, irradiation is used to induce cross~linking of an appropriate synthetic organic polymer.
The use of an irradiation processing technique enables in situ preparation of films and coatings to be done con-tinuously, and additionally enables bulk cross-linking, especially if gamma rays from cobalt 60 are used. Using irradiation to cross-link the syn-thetic organic polymer allows the use of high speed web processing techniques and thereby results in high volume continuous production of adhesive-coated 38 ~2~5~
substrate. Simple liquid handling equipment can be used to dispense the uncrosslinked formulation onto a moving web of substrate, which then passes under a scanning electron beam.
One potential problem of a polymer that has been chemically cross-linked may exist in the situation where an ester linkage has been formed by the reaction of a carboxyl group o~ the polymer with an oxirane or aziridine group of the cross-linker, and a significant amount of wa~er is present. In this instance, the ester linkage may not be hydrolytically stable over a period of several weeks. Similarly, an amide bond formed between the carboxyl group of a polymer and the amine group of a cross-linking agent may not be hydro-lytically stable. On the other hand, the carbon-carbon bonds formed between adjacent polymer molecules during irradiation are very stable. Further advantages of using irradiation are high efficiency, ease of handling, and the elimination of potentially toxic chemicals.
Irradiation is a clean process that is thought to impart no residual chemical toxins. The advantages of easy handling and rapid processing equipment make the use of irradiation very cost effective. Cross-linking can be accomplished instantly rather than requiring prolonged care cyc]es such as are required with an epoxy cure. A further advantage is that in certain instances when chemical cross-linking is used, the cross-linked polymeric material would have to be air dried to remove the water in order to convert the material from a flow-able liquid state to a pressure-sensitive adhesive.
In contrast, use of an appropriate dosage of irradia-tion would convert such a compositlon instantly to a pressure-sensitive adhesive.
A theoretical dose rate can be calculated for an electron beam by using the equation:

dt = 1.1 A~
assuming an energy loss similar to water, where d is the dose in megarads, t is the time in minutes, A is the area of the scanning electron beam in space meters, I is the current in milliamperes, and 1.1 is an empirical constant dependent upon the material being irradiated and a beam energy of 2 Mev. Using a scanning electron beam of 152.4 cm scanning width and a scanning length of 5.08 cm, and using current of 3-30 milliamperes, the theoretical dose rate is calculated to be 2.5 -25 x 109 rads per hour. The material to be irradiated is passed under the scanning beam on a moving conveyor.
In this instance, the conveyor travels in the direction of the 5.0~ cm scanning coordinate so as to allow the conveyor to take advantage of the 152.~ cm width.
Using a 100 milliamp irradiation source, it may be possible to reach production rates as high as a million square feet per day. Since, in most embodi-ments, a volatile organic solvent is not used in making my adhesive, solvent removal to produce a "dry" adhesive does not necessitate expensive pollution control and explosion prevention equipment.
Under certain circumstances, a cross-lin~ing promoter is advantageously added to the solution or dispersion of the uncrosslinked polymer. Exemplary promoters include polymercaptans such as 2,2-dimercapto diethylether, dipentaerythritol hexa~3-mercaptopropionate), ethylene bis(3-mercaptoacetate), pentaerythritol tetra(3-mer-captopropionate), pentaerythritol tetrathioglycolate, polyethylene glycol dimercaptoacetate, polyethylene glycol di(3-mercaptopropionate), trimethylolethane tri(3-mercaptopropionate), trimethylolethane trithio-glycolate, trimethylolpropane tri(3-mercaptopropionate), trimethylolpropane trithioglycolate, dithioethane, di- or trithiopropane and 1,6-hexane dithiol.

~ % ~
In another embodiment of my invention, my adhesive is electroconductive and useful for attaching an elec-trically conductive member of an electrode to a selected surface such as mammalian tissue. Basically, this adhesive is the same adhesive as that discussed above excep. that a conductivity-enhancing material is in-cluded in the adhesive composition. Conveniently, the conductivity-enhancing material is added to the solution or dispersion of the uncrosslinked polymer prior to the irradiation treatment step. Preferably, the con-ductivity-enhancing material is a non-polymeric, ionizable organic or inorganic salt. The amount of the conductivity-enhancer to be used in my adhesive depends upon factors such as the conductivity-enhancing material selected, with a relatively smaller amount of a more conductive material being required, and a relatively greater amount of a material providing relatively less conductivity, being needed. Exem-plary non-polymeric, ionizable organic or inorganie salts include ammonium sulfamate, monoethanolamine aeetate, diethanolamine acetate, sodium lac-tate, sodium eitrate, sodium chloride, magnesium sulfate, and poly-ethylene glyeol-soluble salts such as ammonium acetate, magnesium ehloride and magnesium acetate. About 5% of magnesium sul~ate or about 7% of ammonium acetate is suitably used as the conductivity-enhancer in my adhesive.
Mixtures of conductivity-enhancing materials may be used.
Thus, for example, a mixture of magnesium chloride and magnesium aeetate could be utili~ed.
My electroconductive adhesive is particularly suitable for use as an electrode adhesive, and thus is eonveniently used as a eoating on an electrically conductive substrate such as member 12 of Figure 1.
Electrieally conductive members are well known in the electrode art. Thus, a discussion is not provided con-cerning such a member excep-t to point out that the selection of the particular material to be used to form the member, as well as selection of the size, shape and thickness, is dependent on the end use contemplated -for the electrode.
Generally, member 12 has a thickness ranging from about 15 thousandths up to about 1/8 inch. As shown in Figure 1, electroconductive adhesive 14 serves to attach member 12 to a surface 16. The electroconductivlty of the adhe~ive promotes the transfer of electric signals between member 12 and surface 16. Exemplary electrodes for attachment to mammalian skin include a transcutaneous electrical nerve stimulation electrode, an electrosurgical return electrode and an EKG monitoring electrode.
Examples of my invention will now be provided in order to illustrate the invention. These examples are to be regarded as exemplary only. All percentages are weight percent unless otherwise indicated.

A solution containing 20~ PVP, 25% PEG and 55% water is prepared, and a 1.5 mm coating of the solution is applied to one side of a white polyester cloth. The PVP is PVP K-90 sold by GAF, the PEG is Carbowax ~ 300 sold by Union Carbide, and the cloth is similar to the fabric customarily making up a nurse's uniform. A protective polyethylene film is applied to the coated fabric, and the sample is subjected to an ionizing irradiation dose of 3.5 megarads using a 2.5 Mev elèctron beam source. This procedure is repeated several times to produce a number of samples. The poly ethylene film is removed from approximately half of the samples, and these particular samples are allowed to air dry for about ~8 hours at approximately 30% relative humidity and 20C, to form "dry" samples.
The "wet" and "dry" samples are then subjected to a rolling ball tack test, and tested for peel strength and lap shear. The rolling ball tack test is conducted as 5~

follows: A steel ball is rolled ~own an inclined trough o~ 8.3" length and having a cross-sectional width of 0.53 inches (the trough being inclined at an angle of 21 degrees 30 minutes from the horizontal).
The adhesive sample is positioned so that as the ball rolls off the end of the trough, the ball begins contacting the surace of the adhesive sample. A relatively lower number means the adhesive has a better tack.
The samples are tested for 180 peel as follows:
~ 4" lengtl~ of a specimen of 1" width is caused to adhere to one surface of a vertically-oriented steel plate, the remaining length of the specimen is doubled back, and the loose end of the remaining length is anchored.
The steel plate is pulled vertically upward at a speed of 6" per minute, and the force to strip the adhesive sample from the vertically oriented steel plate surface is measured.
Each sample is analyzed for 90 peel as follows:
A 6" length of a specimen of 1" width is caused to adhere to one surface of a vertically-oriented steel plate and the remaining 6" length of the specimen is caused to adhere to the top surface of a horizontally oriented steel plate. The vertically oriented steel plate is moved vertically upward at a speed of 6"
per minute, and the force to strip the adhesive sample from the horizontal plate surface is measured. The specimens for the peel strength testing showed a wide varlance in thickness within a given specimen type.
Also, the specimens contained air bubbles.
In addition, the solution of PVP, PEG, and water is used to saturate a piece of gauze with about 1 mm of adhesive, and the saturated gauze is placed between two polyethylene sheets, and irradiated in like manner as before. This procedure is repeated to produce additional samples for testing for water vapor transmission and oxygen permeance. Prior to this testing~ the upper layer of 5~

polyethylene is removed in the case of about half the samples, and these particular samples are allowed to air dry for about 48 hours at approximately 30~ relative humidity and 20C to produce "dr~" samples.
Oxygen permeance is measured as follows: An adhesive sample having an area of 3.4 in2 and a thick-ness of 0.15 inches is located between two chambers, with one side of the adhesive sample forming a portion of one chamber wall, and the other side of the sample forming a portion of the other chamber wall. Oxygen is flowed rom a regulator through a gas flow meter into a reservoir connected to a manometer. A 1 psi O2 pressure difference is set up between the two chambers, and the oxygen permeance is measured.
The results for the rolling ball tack test, peel strength test, lap shear test, and oxygen permeance are shown in Table 1. The water vapor transmission results are set forth in Table 2.

Adhesives in accordance with the invention, certain of which are conductive, are prepared using the formulations shown in Table 3. In each case, a solution or dispersion is formed, and a layer ranging from about 1~6 mm in thick-ness is subjected to a dose of a 2.5 Mev electron beam radiation souce, as indicated in the Table. The layer thickness ranges from about 1-3 mm for formulations con-taining PVP and PEG, and ranges from about 2-6 mm for the other formulations. In each instance, the resulting cross-linked material is adhesive.
In addition, several of the cross-linked adhesives are allowed to air dry for about 48 hours at approximately 30% relative humidity and 20C. For these particular for-mulations, the theoretical formula of the corresponding dry adhesive is shown in the Table. In all cases, the cor responding "dry" material is a good adhesive.

~4 Following the procedure of Examples 2-44, a solution or dispersion of each of the'formulations shown in Table

4 is prepared, and a layer ranging in thickness from about 2-6 mm is subjected to a dose of 2.5 Mev electron beam radiation, as indicated in this Table. In each case, the resulting cross-linked material is adhesive. Each of these adhesives is allowed to air dry in the same manner as each of the adhesives of Examples 2-44 for which a theo-retical formula of the corresponding "dry" adhesiveis shown. "Dry" comparative material 1 is a non-adhesive, brittle film, and the other four "dry" comparative materi,als are non-adhesive flexible films.

A conductive adhesive is prepared using the following formulation:
Polyvinyl pyrrolidone tPVP K-90, GAF) 20%
Polyethylene glycol 300 (Carbowax 300 Sentry Grade, Union Carbide) 25%
20 Magnesium Acetate (Reagent Grade, J. T. Baker) 7%
Methyl paraben (Inolex*) .037%
Propyl Paraben ~Inolex*) .012%
FD&C Blue #2 (H. Kohnstamm)~0012%
2S Water Balance A 1/15 inch thick layer of the vlscous liquid is applied to the electrosurgical return electrode pad of Figure 1. This pad has 20 square inches of electrode area.
The coated pad is then subjected to 3.5 megarads of 2.5 Mev beam radiation.
The electrical impedance of the electrode is measured by constructing a circuit in which an electrical current is passed through the entire area of the electrode.
This is done by first securing the full surface of the electrode to a stainless steel plate. The stainless steel plate is then connected to the active electrode of a * - Trade Mark

5~
~5 Valleylab ssE3-s electrosurgical generator, while the electrode being tested is grounded to the generator ground.
A Simpson radiofrequency am~eter is connected in series with the electrode/stainless plate and a Fluke model 8920A
true RMS voltmeter is connected between the steel plate and the electrode. The SSE3-B generator is adjusted to produce a 750,000 hertz sine wave signal, and the current is adjusted to one amp using the Simpson ammeter as a reference. The voltage is read on the voltmeter and recorded. The result is shown in Table 5, as average impedance per square inch.
The peel strength at 180 is tested using a steel plate, as in the Table l peel strength data, and is also tested using the skin of female and male human test subjects. The procedure used is essentially the same as that set forth with respect to the 180 peel test of Table 1, except that the tensile tester is used to peel off the electrode at a rate of 12 inches per second. Furthermore, in carrying out the test with human test subjects, the electrode pad is pulled off manually using a hand-held Ametek*0-30 pound scale.
In each of these experiments, the electrode pad is secured to the thigh of the test subject. Attention is invited to Table 6, which shows the results.
The adhesive of the electrode pad is tested for any irritating effect upon human subjects, with particular attention being given to discomfort upon removal, pulling of hair, edema, erythema, bruising and removal of epidermis.
The electrode pad is applied to the subject and removed within ten minutes, with the runs being uniformly carried out. The data obtained is set forth in Table 7.
Electrical impedance of the electrode is tested on human test subjects using one amp of current at 750,000 hertz. The runs are uniformly conducted, and the data obtained is shown in Table5, asaverage impedance per square inch.
* - Trade Mark ~L2~ S~

Further testing of the electrode pad is carried out by weighing the pad and hea-t sealing it into an aluminum foil laminate pouch having a moisture vapor transmission rate not ~reater than 0.016 g/lOOin /24 hrs. when tested 05 at 37C with 90% relative humidity on one side and dry air on the other. This procedure is repea-ted several times, and the sealed ~ads are placed into a Blue M oven at the same time. At two week intervals, six of the pouches are removed and allowed to stand at room temperature for 18 hours. The pouches are then opened, the pads removed, the pads reweighed, and then electrical impedance and adhesion to a ~metal plate are tested. The results oE this testing are set forth in Table 8.
lS Petri dish samples of the irradiated adhesive are prepared and tested to see whether the irradiated adhesive supports bacterial or mold growth. Each of , four plates is inoculated with Serratia marcescens, Micrococcws lutea, E. coli and Candida albicans. One o-f these inoculated plates is incubated for two weeks at 2C, another at 25C, a third at 37C and the fourth at 55C. A fifth plate is left sealed at room temperature as a negative control. A sixth plate is left open for 15 minutes to room air in a biology lab and allowed to inc~bate at 25C for one week and 37C for an additional week. None of the six plates showed any colony growth.
As a positive control, an agar plate containing minimum nutrients is inoculated with the same bacteria and yeast and incubated at 37C. Colony growth is seen on this plate after 24 hours.
COMPARATIVE EXAMPLE ~;
-A commercially available electrosurgical pad is used ~or comparison with the electrode pad of Example 45. This pad, which is designated "Comparative Pad"
throughout this specification, has a viscous gel impregnated in a reticulated polyurethane sponge) and has a conventional pressure-sensitive adhesive along the border for adhering the pad to a surface such as mammalian skin. The electroconductive member of -the pad .: .

is a ~ickel alloy, and the viscous gel is ~omprised of 3% Carbopol ~ 934, 3% sodium sodium chloride, suf-ricient sodium hydroxide to adjust the pH to 7.0, and water.
The various testing carried out on the electrode pad of Example ~5 is repeated in the same manner, except that inocula~ion with bacteria and yeast is not carried out.
Additionally, the testing involving use of the Blue M oven is conducted so that these samples and the other samples are placed into the oven at the same time and also removed from the oven and otherwise treated at the same time. In Tables 5-8, the data ob-tained are set forth.
Industrial Applicability The present invention is concerned with a novel water-insoluble, hydrophilic, elastomeric, pressure-sensitive adhesive. This adhesive is useful either as a coating on a supportive web-like substrate or as a self-supporting layer. When supported by a web-like substrate, this adhesive is useful as an adhesive on a bandage, a wound or burn dressing, a sanitary napkin, a diaper, an ostomy device, a decubitus ulcer pad, a vibration or impact absorbing material, a sound absorbing material, and a medium for delivering a pharmacologically active agent (drug). In addition, 2S when used as a self-supporting layer, this adhesive is useful as a cosmetic face mask and for securing a prosthesis or article of apparel to a mammalian body.
In one embodiment of the adhesive, the adhesive is electrically conductive and is useful as an electrode adhesive. Illustrative electrodes include a transcutaneous electrical nerve stimulation electrode, an electrosurgical return electrode, and an EKG monitoring electrode.

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Water Vapor Transmission (ASTM 3833) .
Wet Dry Al A2 Bl B2 __ Initial Weight CaC12(g)22.36 13.8023.97 20.39 Initial Weight Sample (g)12.0414.70 7.73 6.40 .
H2O Absorbed cacl2(g)12.3211.02 14.30 15.40 .
H2O Absorbed as a percent of initial sample weight11~89 4.63 28.98 29.84 .
Actual Weight Gain Sample (g)1~430.68 2.24 1.91 .
Water Vapor Transmission Rate g/100 in2353.94316.67 410.92 442.43 . . ~
Thickness (inches) 0.12 0.10 0.07 0.06 Std. Dev. 0.03 0.04 0.01 0.01 .

lThe conditions maintained in the sealed chamber were 90-95% humidity and 100F ~ 1. The samples were conditioned for 24 hours. Since the dessicant, CaC12, reached 100% absorbency in 24 hours, the test was concluded.

2Each value represents an average of 5 readings across each sample.

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TABLE 3 - Footnotes PVA is polyvinyl alcohol.
PAA is polyacrylic acld having a molecular weight of approximately 450,000 and sold by B. F. Goodrich as Carbopol ~ 907.
MVE/MA is GAF's brand of copolymer of methyl vinyl ether and maleic anhydride.
The PVP is PVP K-90.
The "wet" formula additionally contains 7~ ammonium acetate. This is a conductive adhesive.
3This formula additionally contains 5% magnesium sulfate. This is a conductive adhesive.
4This formula additionally contains 8% of 30 ammonium hydroxide solution.
5This formula additionally contains 7% of 30% ammonium hydroxide solution.
6This formula additionally contains 8% of 30 ammonium hydroxide solution.
7This formula additionally contains 8~ of 30%
ammonium hydroxide solution.
8This formula additionally contains 7% of 3~%
ammonium hydroxide solution.
9This is a 4 million molecular weight polymer sold by Union Carbide under the trademark Polyox WSR-Coag.

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(Impedance Test) Standard Ratio of Std.
Average Impedance DeviationDeviation per sq.
per square inchl Per sq.in. in. to A~g.
(ohms/sq. in.) (ohms/sq.in.~ Impedance per sq. in.
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-Using Stainless Steel Plate A) Example 45 Pad2 0.070 0.020 B) Comparative Pad3 0.078 0.018 Using Human Subjec~s I. Male A. Example 0.586 0.163 0.279 45 Pad2 B~ Comparlson Pad3 0.387 0.108 0.323 II. Female A. Example 45 Pad2 0~878 0.267 0.304 B. Comparison Pad3 0.574 0.185 0.322 .

Each value represents 15 runs.
2This pad has an active electrode area of 20 square inches.
3This pad has an active electrode area of 24 square inches.

58 ~2~

(Peel Strength - 180)1 Average Standard Ratio of Standard Adhesion Deviation Deviation to Average (lbs/in. (lbs/in. Adhesion - width) width) (Measure of Pro-duct Uniformity) I. Using Steel Plate A. Example 2 45 Pad 0.362 0.043 0.121 B. Comparative 2 Pad0.945 0.196 0.207 II. Using Thigh of Female Human Subjects A- Example 3 45 Pad0.42 0.043 0.24 B. Comparative Pad0.793 0.31 0.39 III. Using Thigh of Male Hu-man Subjects A. Example 3 45 Pad0.43 0.09 0.21 B. Comparative Pad4 - - ` ~
_ In carrying out these tests, it is noted that the pull force remains relatively more constant with the Example 45 pad than the comparative pad.
This value represents 30 runs.

This value represents 15 runs.
4Data are not taken since the male subjects, with their unshaven legs, experience pain~ul pulling upon pad removal.

8~

of Human Subjects Experiencing Irritation Upon Pad Removal*

I, Male A) Example 45 Pad 0 B) Comparative Pad 47 II. Female A) Example 45 Pad .06 B) Comparative Pad 66 *Fifteen tests are carried out for each pad type.

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Claims (32)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A water-insoluble, hydrophilic, elastomeric, pressure-sensitive adhesive comprising at least one irradiation cross-linked synthetic organic polymer comprising repeating units derived from an N-vinyl lactam monomer, a polyalkylene glycol plasticizer and water, the polyalkylene glycol plasticizer being present in an amount sufficient to maintain the elastomeric state of the adhesive; and wherein the cross-linked polymer is water-insoluble, has a three dimensional matrix, and is formed from a solution or dispersion of at least one suitable gel-forming, uncrosslinked water-soluble synthetic organic polymer comprising repeating units derived from an N-vinyl lactam monomer, and the plasticizer in water, and the relative proportions of the uncrosslinked polymer, plasticizer and water are such that the gel formed upon irradiation crosslinking retains said plasticizer and water within the three-dimensional matrix.

2. The adhesive of claim 1, wherein the uncrosslinked water-soluble polymer is polyvinyl pyrrolidone.

3. The adhesive of claim 1, wherein the polyalkylene glycol plasticizer is a polyethylene glycol, a polypropylene glycol or a copolymer of ethylene oxide and propylene oxide.

4. The adhesive of claim 3, wherein the polyalkylene glycol plasticizer is polyethylene glycol having a molecular weight of about 300 or about 600.

5. The adhesive of claim 1, wherein the uncross-linked polymer is a copolymer of a N-vinyl lactam monomer and an ester of an .alpha.,.beta.-olefinically unsaturated carboxylic acid and an amino group-containing alcohol.

6. The adhesive of claim 5, wherein the carboxylic acid ester is dimethylaminoethyl methacrylate or is the partially or fully quaternized salt of this methacrylate.

7. The adhesive of claim 1, wherein the uncrosslinked water-soluble polymer is polyvinyl pyrrolidone and the plasticizer is a polyethylene glycol.

8. The adhesive of claim 7, wherein said adhesive comprises an irradiation cross-linked K-90 polyvinyl pyrrolidone and polyethylene glycol having a molecular weight of about 300; said polyethylene glycol being present in an amount that is about 0.75 to 1.5 times the amount, on a weight basis, of said polyvinyl pyrrolidone.

9. The adhesive of claim 1, wherein said plasticizer is present in an amount ranging from about 0.5 - 4:1, on a weight basis, of said uncrosslinked polymer.

10. A water-insoluble, electroconductive, hydrophilic, elastomeric, pressure-sensitive adhesive comprising at least one irradiation cross-linked synthetic organic polymer, a conductivity-enhancing amount of at least one salt, a polyalkylene glycol plasticizer and water, the plasticizer being present in an amount sufficient to maintain the elastomeric state of the adhesive; and wherein the cross-linked polymer is water-insoluble, has a three-dimensional matrix, and is formed from a solution or dispersion of at least one suitable gelforming, uncrosslinked synthetic organic polymer and the plasticizer in water, and the relative proportions of the uncrosslinked polymer, plasticizer and water are such that the gel formed upon irradiation cross-linking, retains said plasticizer and water within the three-dimensional matrix.

11. The adhesive of claim 10, wherein the uncross-linked polymer comprises repeating units derived from a carboxy vinyl monomer, a vinyl ester monomer, an ester of a carboxy vinyl monomer, a vinyl amide monomer, a hydroxy vinyl monomer, a cationic vinyl monomer containing an amine or a quaternary ammonium group, or an N-vinyl lactam monomer; or wherein the uncrosslinked polymer is a copolymer derived from a half ester of maleic anhydride, is a homopolymer or copolymer of a polyvinyl ether, or is a homopolymer or copolymer of a polyvinyl alcohol.

12. The adhesive of claim 10, wherein the uncross-linked polymer is a water-soluble polymer.

13. The adhesive of claim 10, wherein the uncross-linked polymer is polyvinyl pyrrolidone.

14. The adhesive of claim 10, wherein said salt is ammonium acetate or magnesium acetate.

15. The adhesive of claim 10, wherein the polyalkylene glycol is a polyethylene glycol, a polypropylene glycol or a copolymer of ethylene oxide and propylene oxide.

16. The adhesive of claim 15, wherein the polyalkylene glycol is polyethylene glycol having a molecular weight of about 300 or about 600.

17. The adhesive of claim 10, wherein the uncross-linked polymer is a copolymer of a N-vinyl lactam monomer and an ester of an .alpha.,.beta.-olefinically unsaturated carboxylic acid and an amino group-containing alcohol.

18. The adhesive of claim 17, wherein the carboxylic acid ester is dimethylaminoethyl methacrylate or is the partially or fully quaternized salt of this methacrylate.

19. The adhesive of claim 10, wherein the uncross-linked polymer is polyvinyl pyrrolidone and the elasticizer is a polyethylene glycol.

20. The adhesive of claim 10, wherein said adhesive comprises an irradiation cross-linked K-90 polyvinyl pyrrolidone and polyethylene glycol having a molecular weight of about 300; said polyethylene glycol being present in an amount that is about 0.75 to 1.5 times the amount, on a weight basis, of said polyvinyl pyrrolidone.

21. The adhesive of claim 10, wherein said plasticizer is present in an amount ranging from about 0.5 - 4:1, on a weight basis, of said uncrosslinked polymer.

22. An electrode comprising an electrically conductive member and the electroconductive adhesive of claim 10.

23. The electrode of claim 22, wherein said electrode is a transcutaneous electrical nerve stimulation electrode, an electrosurgical return electrode, or an EKG monitoring electrode.

24. The adhesive of claim 1, further comprising a pharmacologically active ingredient in a therapeutically effective amount.

25. The electroconductive adhesive of claim 12, wherein the uncrosslinked polymer is water-soluble and is selected from polyvinyl pyrrolidone, polyacrylic acid, a polyvinyl alcohol, and a copolymer formed from approximately substantially equal amounts, on a molar basis, or methyl vinyl ether and maleic anhydride.

26. The adhesive of claim 1, wherein said adhesive is formed from a solution or dispersion of about 18-22 weight percent PVP K-90 in water; wherein the plasticizer is polyethylene glycol 300 and ranges in amount from about 10 - 70 weight percent of the solution or dispersion that is irradiated, with the balance of the solution or dispersion being substantially water, and wherein about 3.5 - 4.5 megarads of irradiation is used.

27. The adhesive of claim 26, wherein about 20%
weight percent PVP is present, and the amount of the polyethylene glycol 300 is about 25 - 30 weight percent.

28. The electroconductive adhesive of claim 10, wherein about 18-22 weight percent of polyvinyl pyrrolidone K-90 is solubilized or dispersed in water, wherein about 10 - 70 weight percent polyethylene glycol 300 is present in the water as the plasticizer, wherein about 6 - 8 weight percent of the salt is present in the water, wherein the balance of the formulation prior to irradiation is substantially water, and wherein about 3.5 - 4. 5 megarads of irradiation is used.

29. The electroconductive adhesive of claim 28, wherein about 20 weight percent of PVP is present, wherein approximately 25 - 30 weight percent of the polyethylene glycol 300 is present in the water, and wherein the salt is magnesium acetate.

30. An adhesive-supporting web-like substrate coated with the adhesive of claim 1.

31. A self-supporting layer of the adhesive of claim 1.

32. A process for making a water-insoluble, hydrophilic, elastomeric, pressure-sensitive adhesive comprising at least one irradiation cross-linked synthetic organic polymer comprising repeating units derived from an N-vinyl lactam monomer, a polyalkylene glycol plasticizer and water, the polyalkylene glycol plasticizer being present in an amount sufficient to maintain the elastomeric state of the adhesive;
comprising (a) solubilizing or dispersing at least one of said suitable gel-forming, uncrosslinked water-soluble synthetic organic polymer in the polyalkylene glycol plasticizer and water, and (b) subjecting the resulting solution or dispersion to a dosage of irradiation sufficient to produce the cross-linked polymer having a three-dimensional matrix and thereby form the adhesive, wherein the relative proportions of the uncrosslinked water-soluble polymer, plasticizer and water are such that the gel formed upon irradiation crosslinking, retains the plasticizer and water in the matrix.