CA1263978A - Macromer reinforced pressure sensitive skin adhesive - Google Patents

Abstract

Abstract of the Invention A skin adhesive coated sheet material is provided which is coated with a polymer that exhibits an enhanced level of initial adhesion when applied to skin but resists objectionable adhesion build up over time. The skin adhesives are comprised of a macromer reinforced acrylate copolymer which has a creep compliance value at least about 1.2 X 10-5 cm2/dyne. A stable chemical complex of iodine, iodide and a pressure-sensitive adhesive is also provided wherein the adhesive has a creep compliance value of at least about 1.0 x 10-5 cm2/dyne measured when the adhesive composition is substantially free of iodine.

Description

~i39~3 ~ 1 --This application is based on a United States application which is now United States Patent No. 4,693,776.

- Field of the Invention . .
This invention relates to a skin adhesive composition and to a tape utilizing such an adhesive. More particularly, the inven-tion relates to a skin adhesive comprised of an acrylate copolymer having an enhanced level of initial adhesion to skin and resistance to objectionable adhesion build over time. This invention also re-lates to a stable chemical complex of iodine, iodide and the skin adhesive described above.
Background of the Invention Pressure sensitive adhesive tapes have been usecl for more than hal a centur~ for a variet~ o:E markin~, holclin~, protect:Ln~, sealin~ and maskin~ purposes. The earliest medical applications where the product was referred to as an adhesive plaster were not pressure sensitive adhesives. These were, in fact, crude mixtures of natural rubber plasticized and tackified with wood rosin deriva-tives:and turpentine and heavily pigmented with zinc oxide. These tape-like products served their purpose but, with the adve.nt of the truly pressure sensitive adhesives, they were replaced. The term PSA has a very precise technical definition and has been dealt with extensively in the technical literature, examples of which are Chapter 17 of Houwink and Salomon "Adhesion and Adhesives", Vol. 2, : Elsiviex Publishing Company, 1967, and the "Handbook of Pressure-Sensitive Technology" edited by Donatas Satas, published by Van Nostrand:Reinhold Company, 1982.

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~j39 ~ ~3 Fundamentally, PSA's require a delicate balance of viscou5 and elastic properties which result in a four-fold balance of adhesion, cohesion, stretchiness and elasticity.
In essence, PSA products have sufficient cohesiveness and elasticity so that, despite their aggressive tackiness, they can be handled with the fingers and removed from smooth surfaces without leaving residue. General trade usage does not sanction the extension of the term PSA to embrace tapes and adhesives merely because they are l'sticky" or because they adhere to a particular type of surface.
The prior art relating to ~raft copolymers is directed to modifying systems for the purpose of i~parting flexibility to rigid or semi-rigid polymeric backbones. The patents of Behrens (U.S. Patent No. 3,004,958), Gregorian (U.S. Patent No. 3,135,717), and Milkovich tU.S. Patent Nos.
3,786,116; 3,832,423; 3,862,267) teach how to graft side chains of polystyrene or acrylate esters onto rigid or semi-rigid backbones o~ polyvinyl chloride or methacrylate esters to provide flexibility and temperature and impact resistance.
Block copolymers of the ~tyrene-isoprene-styrene type have had their adhesion enhanced by grafting of methyl methacrylate as taught by Harlan (U.S. Patent No. 4,007,311).
This was done without regard for elasticity or cohesiveness.
In Ambrose (U.S. Patent No. 4,075,186), a butadiene side chain i~ grafted to an acrylate polymer backbone to produce a molded product which has improved impact resistance but which is tack-free. British Patent No. 872,532 is a process patent which deals fundamentally with the preparation of ~raft copolymers and clearly demonstrates the advantages of grafting using different methods of grafting polystyrene onto poly~ethacrylate.
U.S. Patent No. 4,563,389, discloses macromer reinforced copolymers for use as pressure-sensitive adhesives. That patent discloses that such macromer-reinforced copolymers have high shear strength. Somecomparative examples are disclosed which do not have the requisite shear strength. However, the adhesives of these examples are applied to relatively non-conformable backings, i.e., polyethylene terephthalate.
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i3~3'7~3 The difficulty of adhering tape or other devices to the human skin has long been recognized. The irregular and complex surface of the skin presents obstacles in itself and the wide variation in the skin surface from individual to individual and from site to site compound these obstacles. Acrylic PSAs have been used for many years in medical and surgical applications. An outstanding acrylic copolymer, of the type described in U.S.

2,8~4,126/RE 24,906 (Ulrich) has been employed in a porous, surgical adhesive tape, U.S. Patent No. 3,121,0~1 (Copeland) with very accept~ble skin adhesion performance.
The desirable features of an acrylic PSA in medical applications, .such as less irritation to the skin, were recognized in U.S. Patent No. 3,321,451 (Gander), as well lS as the disadvantages which result from adhesion buildup when the acrylic PSA is in contact with the skin for lonc~
periods of ~ime. According to this patent, the irritation caused by removal of the tape was overcome by including in the acrylate adhesive polymer certain amine salts which made it possible to remove the tape by washing with water which is not always feasible where high standards of sterility are being maintained.
In Gander (U.S. Patent No. 3,475,363), the inventor has attempted to overcome the objectionable compliance failure in the acrylate PSA by employing as a crosslinking agent dimethylaminoethyl methacrylate to ensure adhesion to the skin without deleterious effects.
Zang ~U.S~ Patent No. 3,532,652) recognizes that acrylate PSAs suffer when used on surfaces which promote migration of oils and the like to the adhesive, thereby weakening their cohesive strength. Zang overcomes this by partially crosslinking his acrylate interpolymer with polyi~ocyanate.
In Schonfeld (U.S. Patent No. 4,140,~15), the inventor reduces the stripping of tis~ue cells when his acrylate PSA is remo~ed from the skin by blending the PSA with an unreacted polyol having a fatty acid ester pendant moiety. This adhe~ive has a tendency to leave ohjectionable residue.
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~3~8 Another approach to modifying PSA tape for the purpose of controlling the degree of elastic compliance and viscous flow can be found in Gobran (United States Patent No. 4,260,659) which relies upon and teaches how a plurality of superimposed adhesive layers having different gradients of shear creep eompliance can meet the requirement of releasable adhesion to a plastic surface such as polyethylene. In Winslow (United States Patent No.
4,374,883) the shear creep compliance is achieved and the cohesive strength maintained by combining two layers of adhesive which reinforce each other. While both of these address the problem of modifying a PSA to improve compliance, neither deals with the kind of precision and control required :L~ medieal products which are adhered to the skin.
United States Patent No. 4,323,557 discloses a stable ehemical complex of iodine, iodide and a dermatologically acceptable room temperature tacky pressure sensitive adhesive which is sub-stantially free of aeidic eomponents.
Summary of the Invention According to one aspect of the present invention there is provided an adhesive sheet material suitable for application to skin, said adhesive sheet material comprising a conformable backing member and a skin adhesive composition which is applied to at least a por-tion of one surface of said conformable backing member, said skin adhesive composition comprising a copolymer of copolymerized A mono-mers, C macromers, and optionally B monomers, wherein.
A is a monomeric acrylate or methaerylate ester of a i ;397~

non-tertiary alcohol, said alcohol having from about 1 to about 14 carbon atoms with the average number of carbon atoms being from about 4 to about 12;
s, when used, is at least one ethylenically unsaturated compound copolymerizable with said A monomer, with B monomers com-prising from about 0% to about 25% of the total weight of A and B
monomers; and C is a macromer having the general formula:
X~ (Y)n~Z
10 wherein X is a vinyl group copolymerizable with said A and B
monomers, X having the general formula:
R R' CH=C-wherein R is a hydrogen atom or COOH group, and R' is a hydrogen atom or a methyl group;
Y is a divalent linking group with n being either 0 or l; and Z i.s a monovalent polymeric moiety having a Tg greater than about 20C. and a weight average molecular weight in the range of about 2,000 to about 30,000 and being essentially unreactive under copolymerization conditions, Z having the general formula:

: - 5 -~i3~3~3 - 5a - 60557-3037 ~C-CH2~nR

wherein R2 is a hydrogen atom or a lower alkyl group, R is a lower alkyl group, n is an integer from about 20 to about 500, and R is a monovalent radical selectecL from the group consis-ting of:

~ R5 and -CO2R whereln R ls a hydrogen atom or a lower alkyl group, and R6 is a lower alkyl group; wherein the number and composi-tion of said C macromers is such that the skin adhesive composition has a creep compliance of at least about 1.2X10 5 cm /dyne when measured after about 3 minutes of subjection to stress.
The skin adhesi.ve coated sheet is preferably in the form of a tape or dressing which can be applied to this skin to yield an enhanced level of initial adhesion to the skin without objectionable adhesion build over time.
This invention also relates to a method of adherlng a sub-~20 strat~e to skin comprising interposing between said substrate andskin an effecti~e amount of the skin adhesive described above.
~ ; In the present invention, the PSA has been chemically ; - 5a ~, ~3~3"~
- Sb ~ 60557-3037 tailored to produce within physically defined parameters a skin adhesive for a tape which is a significant advance over the prior art in its ability to conform to the human skin surface and be removed after a reasonable period of time without undue irritation to the ::~
~ - 5b _ i3"178 skin and without leaving objectionable residue. The optimization of these ~wo properties without upset~ing the delicate four-fold balance of adhesion, cohesion, stretchiness and elasticity ha~ required a unique combination of polymerization techniques which control the rheological propertie3 which contribute to the bond-making (compliance) and the bond-breaking (release) properties of a PSA coated material which has been in moderately long contact with the human skin.
This invention also relates to a stable chemical complex of iodine, iodide and a pressure-sensitive adhesive compriqed of a polymerized monomeric acrylate or methacrylate ester of a non-tertiary alcohol, said alcohol having from 1 to 14 carbon atoms with the average number of carbon atoms being about 4 to 12, ancl having attached to qaid backbone polymeric moietie~ having a weight average molecular weight above about 2,000 and a Tg above about 20C; wherein the number and compo~ition of the polymeric moietie~ in said polymer and the inherent viscosity of said polymer are such as to provide said adhesive composition with a creep compliance value of at least about 1~0 x 10-5 cm2Jdyne .

Detailed Description_of the Invention In accordance with the invention, a skin adhesive comprises a polymer having in its backbone at least a major portion by weight of polymerized monomeric acrylic or methacrylic acid e~ter of a non-tertiary alcohol having from 1 to 14 carbon atoms with the average number of carbon atoms being 4-12 and grafted to the backbone polymeric moieties having a Tg greater than about 20C~ and a weight average molecular weight above about 2,000. The number and compo~ition of the attached polymeric moieties in the polymer and the inherent viscosity of the polymer are such as to provide an adhesive composition with a creep compliance value of greater than 1.2 x 10-5 cm2/dyne.

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~ 7~37~3 Preferably the skin adhesive composition comprises a copolymer which consists essentially of copolymerized repeating unit~ from A monomers and C
macromers and optionally B monomers. A is a monomeric acrylic or methacrylic acid ester of a non-tertiary alcohol, said alcohol having from 1 to 14 carbon atoms with the average number of carbon atoms being about 4-12. When used, B is at least one ethylenically unsaturated compound copolymerizable with the monomeric acrylic acid ester. B
monomers generally reduce the flexibility of the copolymer.
Preferred B monvmers are acrylic acid, methacrylic acid, itaconic acid, acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, vinyl acetate and N-vinylpyrrolidone. C
is a macromer having the general ~ormula X-(X)n-Z wherein X
is a vinyl group copolymerizable with the ~ and ~ monomers.
Y is a divalent linking group where n can be zero or one.
Z is a monovalent polymeric moiety having a Tg greater than 20Co and a weight average molecular weight in the range of about 2,000 to 30,000 preferably 4,000 to 20,000, and being essentially unreactive under copolymerization conditions.
The vinyl group of the C macromer and the A and B monomers are copolymerized to form a backbone having pendant therefrom the polymeric moieties.
The number and composition of C macromers and the inherent viscosity of the polymer are adjusted to obtain the desired degree of creep compliance. For a polymer of given flexibility, i.e. a given A and B composition, an increase in the amount of C macromer will decrease the level of creep compliance of the polymer. Likewise, an increase in the inherent viscosity of the copolymer adhesive will decrease the level of creep compliance.
Accordingly as the amount of C macromer is increased, the inherent viscosity of the copolymer adhesive should be decreased to obtain a comparable level of creep compliance.

3 5 For example, a preferred composition of the copolymer adhesive is 96 parts isooctyl acrylate, 2 parts acrylic acid and 2 parts of a polystyrene macromer having a ~ 3~J~

molecular weight of about 8,000 to about 15,000~ For ~his particular composition, the inherent viscosity of the resulting copolymer should be from about .85 to about .95.
If the amount of C macromer is decreased, the inherent viscosity of the copolymer adhesive should be increased to obtain comparable level of creep compliance and, likewise, if the amount of C macromer is increased the inherent viscosity should be decreased to obtain a comparable level o~ creep compliance.
In general, the inherent visco~ity of the copolymer adhesive should range from about 0.5 to about 1.4, more preferably 0.55 to 1.1. The inherent viscosities ~IV) reported herein were obtained by conventional methods used by those skilled in the art. The so-called IV's were obtained using a Cannon-Fenske #50 viscometer in a water bath controlled at 25C to measure the flow time of 10 ml of a polymer solution (0.2g per deciliter polymer in ethyl acetate)~ The test procedure followed and the apparatus used are de~cribed in detail in "Textbook of Polymer Science", F.W. Billmeyer, Wiley-Interscience, Second Edition, 1971, Pages 84 and 85.
The weight of C macromer is generally within the range of about 1% to 30%, preferably 1% to 7%, of the total weight of all monomers in the copolymer.
Monomer A, as previously mentioned, is a monomeric acrylic or methacrylic acid ester of a non-tertiary alcohol, said alcohol having from 1 to 14 carbon atoms with the ave~age number o carbon atoms being about 4-12. Examples of such monomers include the esters of acrylic acid or methacrylic acid with non-tertiary alkyl : alcohols such as l-butanol, l-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, l-methyl-l-butanol, l-methyl-l-pentanol, 2-methyl-1-pentanol, 3-methyl-1-pentanol, 2-ethyl-1-butanol, 35 3,5,5-trimethyl-1-hexanol, 3-heptanol~ 2-octanol, l-decanol~ l-dodecanol, and the like. Such monomeric , , .

3~3~3 acrylic or methacrylic esters are known in the art and many are commercially available.
As mentioned above, the s monomer :is an ethylenically unsaturated compound copolymerizable with the monomeric acrylic acid ester and is employed to modify the flexibil:ity of the copolymer.
In general/ the addition of the B monomer reduces the flexibility of the copolymer. Preferred B monomers are acrylic acid, methacrylic acid, itaconic acid/ acrylamide/ methacrylamide/ acrylonitrile/
methacrylonitrile/ vinyl acetate/ and N-vinylpyrrolidone. The B
monomer is not necessary to produce the skin adhesive/ but up to 25% of the total weight of all monomers of B monomer may be included.
The preferred skin adhesive according to the present invention will contain from about 1% to about 15% by weight o:E B monomer o:E the total weic~ht of all monomers. In the preferred skin adhesive/ the amount of acrylic acid or acrylamide will range from about 1% to about 4% by weight of total monomer. In skin adhesives containing N-vinylpyrrolidone as the B monomer/ the preferred copolymer will contain from about 5% to about 15% of N-vinylpyrrolidone by weight of total monomers.
The C macromer is a polymeric material having a copoly-merizable vinyl group with which the A monomer and the B monomer will copolymerize under the polymerization conditions. The C macro~
mer as defined above/ is represented by the general formula : X~(~)n~Z wherein Y is a divalent linking group where n can be zero or one; X is a~vinyl group which has the general formula R R' ; C=C-_ g _ ~3~3~

wherein R is a hydrogen atom or a COOH group and R' is a hydrogen atom or methyl group. The double bond between the ¢arbon atoms pro-vides a copolymerizable moiety capable of copolymerizing with the A
and B monomers.
Z is a monovalent polymeric moiety having a Tg greater than 20C. and a weight average molecular weight in the range of about 2,000 to 30,000 and being essentially unreactive under copo-lymerization conditions, Z having the general formula tC-CH2tnR
R

wherein R2 is a hydrogen atom or a lower alkyl group, R3 is a lower alkyl grou,p, n is an integer from 20 to 500 ancl R4 ig a monovalent radical selected from the group consisting oE

~>

and -CO2R6 wherein R is a hydrogen atom or a lower alkyl group and R is a lower alkyl group.
Preferably, the C macromer has a general formula selected from the group consisting of O H
, .
X-C-O-C-CH -Z

R

O O H
: X-c-o-cH2cH2-NH-c-o-c-cH2-z ; R7 ~i3~3'7 - lOa -X-CH -O-C-CH - Z

H

~CH2 -0-C-CH2 - Z
X R

, ` ~ :

- lOa ,'f"`' `'.~

~i3~378 11 E~

H

X-OCH2CH2 -0-(~-CH2 -Z

wherein R7 is a hydrogen atom or a lower alkyl group.
The C macromer is a functionally terminated polymer having a single functional group (the vinyl group) and is some-times ldentified as a "semitelechelic" polymer. (Vol. ~7 "Func-tionally Terminal Polymers Via Anionic Methods" D.N. Schultz et al, pages 427-440, Anionic Polymerization, American Chemical Society ~19~1].) Such macromers are known and may be prepared by the method disclosed by Milkovich et al in U.S. Pat. Nos.
3,786,116 and 3,842,059. ~s disclosed therein, vinyl-terminated macromer is prepared by anionic polymerization o~ a po~ymerizable monomer to form a living polymer. Such monom~rs include those having an olefinic group, such as the vinyl-containing compounds.
Living polymers are conveniently prepared by contacting the monomer with an alkali metal hydrocarbon or allcoxide salt in the presence of an inert organic diluent which does not participate in or interfere with the polymerization process. Monomers which are susceptible to anionic polymerization are well known. Illus-trative species include vinyl aromatic compounds such as styrene, alpha-methylstyrene, vinyltoluene and its isomers or non-aromatic vinyl compounds such as methyl methacrylate. Other monomers susceptible to anionic polymerization are also useful.
The initiators for anionic polymerization may be any of the alkali metal hydrocarbons or alkoxide salts which produce a mono-functional living polymer, i.e., only 3S3~

one end of the polymer contains a reactive ion. Such initiators include the hydrocarbons of lithium, ~odium or potas~ium, for example, having an alkyl radical containing up to 20 carbon atoms or more, and preferably up to 8 carbon atoms. Illustrative alkali metal hydrocarbons include ethylsodium, propylsodium, butylpotassium/
octylpotassium, phenylsodium, ethyllithium, butyllithium, sec-butyllithium, isobutyllithium, tert-butyllithium and ~ 2-ethylhexyllithium. Sec-butyllithium is the preferred initiator.
The inert organic diluent utilized to facilitate heat transfer and adequate mixing of the initiator and monomer preferably is a hydrocarbon or an ether. Useful diluents include ~aturated aliphatic and cycloaliphatic hydrocarbon~ ~uch aq hexane, heptane, octane, cyclohexane and the like. In addition, aliphatic and cyclic ether solvent~ may be u3ed, for exa~ple, dimethyl ether, diethyl ether, and tetrahydrofuran.
The amount of initiator usually dictates the molecular weight of the living polymer. If a ~mall portion of initiator is used, with respect to the amount of monomer, the molecular weight of the living polymer will generally be larger than if a large portion of initiator is used. It is generally advisable to add initiator dropwise to the monomer until the persistence of the characteri~tic color of the organic anion is observed, then the calculated amount of the initiator is added for the molecular weight desired. The preliminary dropwi~e addition ~erves to destroy contaminants and thus permits better control of the polymerization. Generally, the initiator concentration can vary from about 0.01 to about 0.1 mole of active alkali metal per mole of monomer, or higher~ Preferably, the concentration of the initiator will be from about 0.01 to about 0.04 mole of active alkali metal per mole of monomer.
The temperature of the polymerization will depend upon the monomer. ~enerally, the reaction can be carried .

39~

out at a temperature ranging from about -100C. up to about 100C.
The anionic polymerization must be carried out under controlled conditions so as to exclude substances which destroy the initiator or living anion. Water and oxygen must be excluded. The polymerization therefore is carried out under anhydrous conditions in an inert atmosphere such as nitrogen, helium or argon.
The living polymers may be terminated in several ways. It is important, however, that conditions be selected to provide a quantitative termination free from side reactions. Under certain conditions the liviny polymeric anion may be allowed to react directly with halogen-containing terminating agents to produce, for example, vinyl-terminated macromers. In many cases, however, the polymeric anion i9 highly reactive and non-selective in its reaction with the terminating agent.
In addition to displacement o the halogen atom, it may abstract hydrogen atoms or react with other functional groups present, including the vinyl group itself. This results in polymer chains which are non-functional or of unwanted functionality and molecular weight. Occasionally, under these conditions, a vinyl-terminated polymer may be attacked by living anion and its functionality destroyed.
One means for overcoming the foregoing problem is to render the living anion less reactive, thuæ less suscept-ible to side reactions, by ~Icapping~ with a less reac~ive end group prior to actual termination. Examples of suitable "capping agents" include lower alkylene oxides such aæ ethylene and propylene oxide, and l,l-diphenyl-ethylene, etc. A preferred capping agent is an alkylene oxide, such as ethylene oxide. The capping agent reacts with the living polymer, destroying its oxirane ring. The alkoxide anion then displaces the halogen atom of the terminating agent selectively, leaving the vinyl group intact, 3~J~3 ~14-The cappiny reaction is carried out quite simply, as in the case of the terminating reaction, by adding the capping reactant to the living polymer at the polymeriza-tion temperature. The reaction occurs immediately. As in the case of the termination reaction, a slight molar excess of the capping reactant with respect to the amount of initiator may be used. The reaction occurs on a mole for mole basis. This reaction is de~cribed in Milko~ich, U.S.
Pat. No. 3,842,059. Reaction with the terminating agent provides the desired vinyl-terminated macromer.
A second method of termination, also useful for synthesis of the vinyl-terminated polymeric monomers, involves capping the living anion performed as described previously, and then protonating the alkoxide ion to produce a hydroxyl-terminated polymer. The hydroxyl group is then allowed to react with a terminating agent containing an isocyanate group (lnstead of a halogen atom) to produce the vinyl termlnation. Suitable terminating agents for thiq reaction are isocyanato alkyl acrylates and methacrylates having 1 to 4 carbon atoms in the alkyl group. The hydroxyl and isocyanato groups react to form a urethane linkage between the polymeric segment and the "monomeric" end group. Intermediate protonation of the alkoxide is necessary to prevent unwanted side reactions upon termination.
Although U.S. Pat. No. 3,786,116 teaches that the molecular weight distribution o~ the polymer chains of the vinyl-terminated macromer prior to copolymerization must be narrow, i. e., le~ than 1.1 polydispersity, it has been found that useful psa compositions according to the present invention may employ polymeric monomer having a polydispersity of up to about 3 without deleterious effects on the adhesive propertiesO These broader molecular weight distributions may be obtained by known ~ariations in tem~
perature o~ polymerization and the lithium alkali initiator used.

~i39~3 - 15 ~ 60557-3037 The vinyl-terminated macromers useful in the present invention may also be prepared by free-radical polymerization (rather than anionic polymerization). Known methods can be used to prepare semi-telechelic polymers using thermal free-radical initiators. An illustrative method is described in Y. Yamashita, K. Ito, H. Mizuno and H. Okada, Polymer Journal 14, 255-260 (1982) and K. Ito, N. Usami, and ~. Yamashita, Macromolecules 13, 216-221 (1980). These functional polymers can then be converted into vinyl- terminated monomers using standard condensation chemistry, ring opening reactions, etc. Specifically, carboxylic-acid terminated low molecular weight polystyrene can be prepared using 4,4'-azobis-(4-cyanovaleric acid) as an initiator and an acid-containing chain transfer agent such as HS-CH2-COOH. The semi-telechelic polystyrene can then be vinyl terminated via, for example, ring opening of glycidyl methacrylate. These vinyl-terminated polymers have a high polydispersity.
The copolymeriz.ation oE the A monomer, B ~onomer, iE
used, and C macromer is by conventional Eree-radical polymeriza-tion, for example, as described by Ulrich, U.S. Reissue Pat. ~o.
24,906 issued December 13, 1960. The monomers and macromers are dissolved in a suitable inert organic solvent and polymerized by standard free radical polymerization utilizing a suitable free-radical initiator. Suitable free-radical initia-tors which may be utilized include azo compounds such as 2,2'-azobis~isobutyro-nitrile), hydroperoxides such as tert-butyl hydroperoxide, peroxides such as benzoyl peroxide or cyclohexanone peroxide.
Generally, from about O.Ol -to about 5% by weight of thermally activatable initiator based upon the total polymerizable composition is used.
The organic solvent utilized in the latter free-radical polymerization may be any organic liquid which is inert to the reactants and product and will not otherwise adversely affect the reaction. Suitable solvents include ethyl acetate and mixtures such as ethyl acetate with ~

i3~3~

toluene, heptane with toluene and isopropyl alcohol and heptane with toluene and methyl alcohol. Other solvent systems are useful. The amount of solvent is generally about 30-80% by weight based on the total weight of the reactants and solvent. In addition to solution polymeriza-tion herein described, said copolymerization may be carried out by other well known techniqueq such as suspension, emulsion and bulk polymerization.
As described above, the preferred grafting technique involves copolymerization of monomer A, B ~if used) and macromer C with C being a chemically tailored macromolecular monomer of controlled molecular weight and selected to have a T~ sufficiently high to optimize the creep compliance of the compliant acrylic backbone. Other polymer grafting techniques may also be employed to produce the improved creep compliant ~kin adhesive compos;tions of the invention. Each oE the ~rafting methods provides a high degree o~ predictability o~ the properties o~ the end product.
An alternative grafting technique involves preforming the compliant, acrylic polymeric backbone, then copolymerizing the preformed polymeric backbone with monomer to produce high Tg polymeric moieties on the backbone to obtain the desired creep complianceO Such a composition may be obtained, for example, by grafting methyl methacrylate monomer to a preformed acrylic polymer backbone r Another equally effective approach is to graft preformed high Tg polymeric moieties to a preformed compliant acrylic polymeric backbone. Such a composition ; may be obtained, for example, by grafting hard hydroxy-terminated polystyrene moieties to a preformed acrylic polymer backbone.
Theæe and other useful polymer grafting techniques are well known as described in overview in Chapter ~, pages 13-16 Block Copoly~ers by Noshay and McGrath, Academic Press (1977) and in greater detail in ~:

.~

~i39~8 Graft Copolymers, Battaerd and Tregear, J. Wiley & Sons (:L967).
When the B monomer chosen is one which will form a stable chemical complex with iodine, the skin adhesive can be glven antimicrobial activity by the formation of a stable chemical complex of iodine, iodide and the skin adhesive. Suitable iodine complexing monomers include ~-vinyl-pyrrolidone. U.S. Patent No.
~,323,557, generally discloses the process of forming a stable chemical complex of iodine, iodide and a pressure-sensitive adhesive without regard to the creep compliance of the adhesive.
The process for forming the composition of the present invention involves Eorming a pressure sensitive adhesive and mixing into it an antimicrobial treating solution comprising iodine, iodide, and a solvent. The resulting composition preferably contains N-vinyl-pyrrolidone (NVP) in the backbone of the pressure-sensitive adhesive which serves to complex iodine.
It is believed that complexation provides stability while main-taining an appropriate equilibrium to provide sustain~cl release of iodine.
The composition which is the resulting chemical complex of the aforementioned process is stable, non-irritating, non-sensitizing, non-toxic and non-trauma-tizing to skin or other tissues. Although it is generally recognized that an acid medium renders many broad-spectrum antimicrobial agents more stable, i.e.
PVP-I, it was disclosed in U.S. Patent No. 4,323,557 that a pressure-sensitive adhesive having a significant acidic content caused a negative alteration in -the stability of iodine in the system disclosed therein. However, it has been found that inclusion of small amounts of acidic monomers does not appreciably affect the stability of -the present adhesive system. Accordingly, additional monomers containing substituent groups which e~hibit acid functionality, e.g., acrylic acid, methacrylic acid, i3~3"J~3 itaconic acid, etc., may be copolymeri~ed with the other comporsents and used to form a useful adhesive of this invention.
It i~ believed that the iodine release is controlled by the copolymerization of low levels of the NVP
into the adhesive backbone. The iodine release from the adhesive matrix is a function of the level of NVP
copolymerized into the adhesive backbone. For a given iodine content, the higher the NVP level, the lower the antimicrobial activity. For this invention, the useful NVP
comonomer level is less than 30% (preferentially 5-10%) of the total adhesive solids. At higher NVP levels, skin adhesion and antimicrobial activity are reduced.
An antimicrobial solution is used to incorporate iodine into the pressure-sensitive adhesive. This solution contains iodine ~as used herein, iodine ~hall refer to I2)~
inorganic io-Jide ~e.g., pota~sium iodide) and a suitable solvent compatible with the adhe~ive and the iodine and iodide components. A solution recommended for use with the 5-10~ NVP copolymer adhesive above would have a 0.5:1 to

4:1 molar ratio of iodide:iodine dissolved in acetone (preferred solution, 2:1 molar ratio of iodide-iodine)~
For example, a solution utilizing sodium iodide would have a formulation of 1-20 wt. ~ iodine, 1.2-24 wt.% sodium iodide and 97.8-56 wt.% acetone.
In particular, an IOA/NVP/Macromer: 88/9/3 adhesive (40% solids in ethyl acetate) to which has been added a solution containing 2% iodine and 2.4~ ~odium iodide in acetone to obtain an adhesive containing 2%
iodine by weight of polymer solids is preferred. This adhesive is then coated onto a release liner at 6 grains per ~4 sq. inches solids, dried and transfer coated onto a polyurethàne film. Typical adhesion values are 70 grams per lineal inch width initially and 180 g/in. after 48 hrs.
Although the mèchanism of complexation of iodine into the adhesive matrix of this invention is not completely understood, it is believed to have some analogy :
-, ~2~

to the complexation of iodine with polyvinylpyrrolidone~
The skin adhesive compositions prepared in accordance with the present invention are easily coated upon suitable conformable backing materials by conventional coating techniques to produce skin adhesive coated sheet materials in accordance with the present invention.
Suitable backings include any of the well-known backings which find use in medical or surgical fields. Typical examples of conformable backing materials which may be useful for the adhesive compositions of the present invention include those made of nonwoven fabric, woven fabric, knit, o~ medium to low tensile modulus synthetic films such as polypropylene, polyethylene, polyvinyl chloride, polyurethane, low modulus polyester, and ethyl cellulose. With respect to the con~ormable synthetic film backings, the ~ilm ~hould have a tensile moclulus of less than about 400,000 psi as me~sured in accordance with ~Srl'~l D-638 and D-882, preEerably less thall about 300,000 psi. As noted above, backings may be prepared of fabric such as woven fabric formed of threads of synthetic or natural materials such as cotton, nylon, or rayon, and the like or nonwoven fabric such as air laid webs of natural or synthetic fibers or blends of these. Conformable fabric backings should be as conformable as synthetic films having a tensile modulus of less than about 4000,000 p9i preferably less than about 300,000 psi.
Preferred backings are those which permit transpiration of perspiration and/or tissue or wound ex~date therethrough, e.g., nonwoven fabrics, woven fabrics, knits and the like. Preferred backings are, accordingly, moisture vapor permeable in that they have a high rate of transmission of moisture vapor therethrough.
These preferred backings have moisture vapor transmission values, when tested in accordance with ASTM E 96-80, of at leac;t about 500 gjm2, over 24 hours at 100F (38C) with a humidity differential of 80%, more preferably at least about 1000 g/m2. For example, a continuous film backing , .

~39'~3 prepared from a polyurethane sold under the tradename Estane, available from B. F. Goodrich, and a continuous film backing prepared from a polyester sold under the tradename Hytrel, available from DuPont, each have values of about 1000 to about 1500 g/m2 and woqen backings such that those used for ~RAPORE~ tape, available from 3M, have even higher values. In contrast, conventional polyethylene terephthalate films have approximate values of abou~ 50 9/m2 .
The coated sheet materials may take the form of any article conventionally known to be utilized with skin adhesives such as tapes, patches, strips, wound dressings, monitoring or neuro-stimulating electrodes, drapes or the like. These articles may be dispensed from any convenient ~ispensing orm, e.g., multi layered pads, etc.
'rhe skin a~he~ive composition~ of the pre~ent invention may be coated by any of a variety of conventional coating techniques such as roll coating, spray coating, curtain coating, and the like. As is known to those skilled in the art, the particular method selected may depend upon the nature of the backing being employed. For example, where the backing is a nonwoven fabric, a suitable method for applying the adhesive copolymer thereto involves coating a solution of the adhesive copolymer in an organic solvent onto a release liner, followed by lamination of the nonwoven fabric backing to the lsemi-dry) adhesive coating.
The compositions may also be coated without modification by extrusion coating, coextrusion, hot-melt coating and the like by employing suitable conventional coating devices for this purpose. Primers may be used but they are not always necessary~
The ~kin adhesives of this invention may also be used in a method of adhering a substrate skin. In this method an effective amount of a skin adhesive of this inyention is interposed between the substrate and s~in and pressure is applied to activate the skin adhesive. The subst~ate is preferably a sheet material as described above .. . .

~39~

which i~ applied to the skin as a cover, patch or tape for the conventional purposes thereof.

CREEP COMPLIANCE TEST ~
In order to understand the advantages of this invention, it is necessary to understand how a fundamental rheological property of the pressure sensitive adhesives being used enables one to ascertain when and how the advantages of the invention are being obtained. The measurement of this property, which is the creep compliance of the PSA used to coat the tape backing, will be covered in detail later. The fundamentals of creep compliance as they relate to polymeric materials and, in particular, to viscoeleastic polymers is covered in "Viscoela3tic Properties of Polymers"~ John D. Ferry, 3rd Edition, John Wiley and Sons~ 1980~ Chapter 1. Also in "Treatise on Adhe~ion and Adhesive~"~ Volume ~, "Material~", "Pressure Sen~itive Adhe~lves"~ R.l. Patrick, Editor, Marcel Dekker, Inc., 1969. In "Properties and Structure of Polymers", Tobolsky, John Wiley and Sons, 1960, Chapter II, Section 6, the five regions of viscoelastic behavior are discussed.
C.A. Dahlquis~ in "Handbook of Pressure Sensitive Adhesive ~` Technology", edited by Donatas Satas, Van Nostrand Reinhold Company, lg82, Chapter 5 covers the entire stres~-stain behavior of pressure sensitive adhesives and how this can be treated as a creep compliance phenomenon.

CREEP COMPLIANCE PROCEDURE
.
To ineàsure the creep compliance of the skin adhe~ive of this invention, a 150-micrometer thickness of the skin adhesive is knife-coated onto a smooth film of polytetrofluorethylene.~The coated film is then dried to -~ constant weight by placing the samples in an air-circulating oven genera}ly for at least five minutes at 110C. The skin adhesive, thus dried, is stripped from the polytetrafluoro~thylene and two test pieces of equal area are die-cut and placed in the parallel pla~e creep , ~.., 3~3'~

compliance rheometer, one piece being on each side of the center plate, wit}) an outer plate contacting the exposed surface of each. Screws which connect the two outer plates are then tightened so as to compress thle interposed layers of sXin adhesive approximately 10%~ The parallel plates are placed in horizontal arrangement and one end of the center plate is connected to a linear variable transducer which measures the plate displacement (due to adhesive flow) and outputs an electrical signal, proportional to the displacementl to a chart recorder. A hook is attached to the opposite end of the center plat~ with a flexible wire extending horizontally from the hook and then downward over a pulley, the outer plates being held in a fixed position.
A suitable weight (one which is sufficient to measurably deform the sample a distance no greater than it~ thickness) is attached to the free end of the wire, then the strip chart recorder is ~tarted. The weight typically used to exert the stress on the skin adhesive films oE thi~
invention is S00 grams. From the ~trip chart recorder, the time and the diqplacement (strain) are read and the applied force (stress) is recorded. The creep compliance at a given temperature is then calculated using the equation:
J(t) hf where t i8 the time at which the measurement is taken, A is - 25 the area of one face of the adhesive samples, h is the thickness of the adhesive mass, X i~ the displacement at time t (where X is les~ than h) and f is the force due to the mass attached to the wire connected to the middle plate. Where A is expressed in cm2, h in cm, X in cm, and f in dynes, thsn the compliance value J(t) is given in cm2/dyne.
It has been found that the skin adhesive films of thi invention have the required degree of compliance and the short term creep to function as an exceptionally fine ~p~essure sensitive skin adhesive for medical and surgical applications, when the J value measured at ambient ,, ~ ~3 9 ~58 conditions at the end of a 3 minute period of subjection to stres3 is at least about 1.2 x 10-5 cm~/dyne to about 2.3 x lQ-5 cm2/dyne, preferably about 1.3 x 10-5 cm2/dyne to about 2.0 x 10-5 cm2/dyne. It has been found that the higher the creep compliance, the greater the adhesive residue left on the skin after removal of the skin adhesive coated sheet material. Accordingly, creep compliance values greater than 2.3 x 10-5 cm2/dyne are not preferred.
When the skin adhesive is to form a complex with iodine, e.g., a skin adhesive which has NVP as a B monomer, J values as low as l.O x 10~5cm2/dyne are acceptable.
These J values are measured when the adhesive i~
substantially free of iodine, e.g, preferably less than about 0.1% by weigh~. This measurement is taken before trea~ment of the uncomplexed adhesive with the lodine/iodide solution or after the iodine has been vola~ilized from the complexed adhesive composition.

SKIN_ADHESION TEST
The evaluation of the skin adhesives of this invention i9 highly subjective when the performance in contact with and upon removal from the human s~in surface becomes part of the evaluation. For this reason a protocol was developed using a prescribed test panel of individuals who were selected to embrace the normal variations in skin surface that are encountered in medical practice. The result of this designed study enables one to get vaiue~
which can be considered controlled and comparative~ While the~e value~ are observational in respect to adhesive residue, sample lift and adhesion buildup, the procedures followed are in accord with carefully developed assessments of similar properties as described in detail in the Clinical Research Manualj Methodological Procedures for Adhesion Studies.
~: :
SKIN ADHESION PROCE _RE
The i~nital skin adhesion value (To) and the s~in adhesion value after 24 or 48 hours in contact with the ;, ' 3~

skin (T24 or T4g) are essentially the widely accepted PSTC-l, peel adhe3ion test for single coated skin adhe3ive tapes measured at 180 angle. PSTC-l is test method No. 1 of the Pressure Sensitive Tape Council, Glenview, Illinois, Seventh Edition (1976); developed by the Specifications and Technical Committee of the Council. The test has been modified only to the extent that the tape is applied to the human skin surface on a selected area on the individual's back. Otherwise the steps in the procedure are as follow~:
1. Tape samples 2.54 cm wide hy 5.08 cm long are placed on the back of a human subject.
2. Each tape is rolled down with one forward and one reverse pass, using a l-kilogram tape roller (described in Appendix B~ Sections 2.7 1, 2.8.1 and 2.8.2 of Pressure Sensitive Tape Council) moved at the rate of about 30 cm per minute.
3. Adhesion to the skin is measured as the peel force required to remove the tape at 180 angle (PSTC-l)~ The peel force values are measured through the use of a strain-gauge mounted on a motor-driven carriage. The force of removal is reported in grams of adhesion per 2.54 cm of width of sample. The rate of removal is 15 cm per minute.
4. The adhesion to skin is measured immediately after intial application (To) and after 24 or 48 hours of continuous contact with the skin (T24 or T48)-Preferred skin adhesive will generally exhibit a 30 To of between 50 grams to about 100 grams and a T48 ~
between about 150 grams to about 300 grams.

Adhesive Residue Test When the skin adhesion test described above is performed, the skin underlying the tape sample is visually inspected to determine the amount of adhesive residue left ~æ~

on the ~urface of the skin. Each ~ample is assigned a numerical rating from 0 to 5 based on the following scale~
Rating Definition 0 No visible residue;
S 1 Only residue at edges of tape;
2 Residue covering 1% to ~5~ of tested area:
3 Residue ~overing 25~ to 50% of tested area;
4 Residue covering 50% to 75~ of tested area;
S Residue covering 75% to 100% of tested area.
The re~ults of all tape samples of a given panel were averaged and are reported below. Due to the subjectivity of the v~sual inspection for residue, no degree of precision should be in~erred from the number~ to the right o~ the decimal point and those numbers should be treated a~ only rough approximations.
Preferred skin adhesives will generally exhibit an average rating below about 2.5.

EXAMPLES
In the following examples, an arabic numeral denote~ an example of a copolymer contemplated as a skin adhesive of this invention, a capital letter denotes a comparative example and the denotation "M-X", wherein X is an arabic numeral, denotes a macromer useful in preparing the skin adhesivss of thiQ invention.
:~ PREPARATION OF MACROMER
The "C" moiety of the general formula A-B-C is a polymeric material which has a copolymerizable vinyl group which copolymerizes with monomers A and B under poly-merizing conditions. The C moiety, while being polymeric in one sense, actually behaves as a monomer and is referred to in the literature as a macromolecular monomer which is - shortened to the term "macromer" for convenienc~. For the ..
: --~ ~3~3~,18 purpose of this invention, representative preparations of the macromers that are used follow~.

EXAMPLE M-l This methacrylate-terminated styrane macromer having an average molecular weight of about 9000 was prepared using a five-liter four-necked flask, fitted with a thermometer, mechanical stirrer, septum, Dean-Stark trap and condenser. 150 grams ~1.44 moles) of styrene were charged into the flask which contained 1155 grams cyclohexane, resulting in an 11.5~ by weight solution. Ths solution wa~ heated to about 50C and a 1.4 molar solution of sec-butyl lithium in cyclohexane was added dropwise until a faint yellow color persisted, then 10.7 ~1 oE
additional sec-butyl lithium cyclohexane solution was added rapidly. The reaction mixture was maintained at 65C by cooling. After about one hour, the ~olution was ~llowed to cool to 35C and then ethylene oxide gas was introduced over the reaction mixture which wa~ agitated rapidly for 15 minutes until the orange color of polystyryl lithium had di~appeared. The reaction was then quenched with 5 ml (51.~ meq.) of methacryloyl chloride. The polymer solution was reduced in volume and the polymer was precipitated and dried. Gel permeation chromatography revealed a number average molecular weight of 8394, weight average molecular 25 weight of 8842 and polydispersity of 1.05.

An acrylate-terminated polymethyl methacrylate polymeric monomer having an average molecular weight of 10,000 was prepared. Recry~tallized dried fluorene, five 30 parts, was placed in a 1,000 ml three-necked 1ask fitted with stir~er, thermometer, argon inlet and rubber septum, all of which had been previously flamed under argon. Dried tetrahydrofuran, ~00 parts, was distilled into the flask and 15 parts of a 1.4 N solution o sec-butyllithium in cyclohexane were added through the septum, producing an 3'7 orange-red solution of "fluorenyl lithium" under slight argon pressure. The flask contents were cooled to -76C and 65 parts dried, freshly distilled methyl methacrylate (MMA) were rapidly added through the septum. Tha reaction ~emperature quickly rose to -20C and then was gradually returned to -76C by cooling. After one hour of stirring, 3 parts of ethylene oxide were bubbled into the flask and the flask was warmed to -10C, causing the liquid to change from orange-red to light yellow. Acryloyl chloride (3 parts) was then added to quench. The reaction mixture was then warmed to room temperature and added dropwiRe with vigorous stirring to 4 liter~ of hexane, causing a white solid to precipitate. The solid was filtered, dried, redis~olved in toluene, filtered to remove impurities and precipitated in methanol. The resulting white solid was a polymeric monomer having the ~ollowing prop~rties: weight average molecular weight 10,420 and polydispersity 2.6.
In addition to the above macromers the following macromers prepared by means similar to those used above, were used to prepare the skin adhesives shown in the following examples:
Example M-3: a methacrylate-terminated polystyrene macromer having a weight average molecular weight of about 10,000 g/mol.
Example M-4: a methacrylate-terminated polystyrene rnacromer having a weight average molecular weight of about 13,000 g/mol.
Example M-5: a methacrylate-terminated poly(methyl methacrylate) macromer having a weight average molecular weight of about 13,000 gjmol.

Pre~aration of Skin Adhesive This is a representative preparation of the skin 3S adhesives which are comprised of the A-B-C moieties of the general formula of thi~ inventionn The copolymerization reaction takes place in a ~ealed, one-quart amber bottle which has been purged by bubbling nitrogen through the solution at a flow rate of one liter per minute for two minutes after which the bottle is ~ealed~ The solution through which the nitrogen has been bubbled is comprised of 190 grams of isooctyl acrylate monomer (IOA), 4 gram~ of acrylic acid (AA~, 4 grams of 2-polystyrylethyl methacrylate macromer ~commercially available as CHEMLINK~ 4500, 13,O00 M.W. from Sartomer Chemical Company), 300 grams of ethyl acetate tA~R. grade), 0.6 gram 2,2'-azobisisobutyronitrile (commercially available from DuPont as VAZOo 64), plu~ 2.5 grams of a 1 solution of carbon tetrabromide in isooctyl acrylate which re~ults in a CBr4 charge of 0.012%. The bottle thus charged is tumbled ~or 2~ hour~ in a water bath at 55C to efeect essentially complete polymerization. The yield for this charge was a solution containing 38.65% of copolymer comprised of 96% isooctyl acrylate/2% acrylic acid/2%
2-polystyrylethyl methacrylate macromer. The inherent viscosity of this adhesive polymer mea~ured in dilute solution of ethyl acetate was 0.904~ The Brookfield viscosity measurement was 6,000 centipoise.

The following tables, Tables 1, 2 and 3, ~et forth the composition, inherent vi3cosity and creep compliance values of copolymers prepared in a manner similar to that of Example 1. The abbreviations ACM, MA
and NVP were used for acrylamide, methacrylic acid and N-vinylpyrrolidone, respectively.

~: :

i3~3"~3 TABLE I
~kin Adhesives from Acryli~ Acid Copolymers Ex. IOA AA Macromer J
No. (pbw)(pbw) (pbw(identi~ m(X10~5cm2/dyne) 1 96 2 2(M-4) 0.901.g8 2 96 2 2(M-4) 0.802.49 3 96 2 2(M-4) 0.742.80 4 96 2 2(M-4) 0.673.70 96 2 2(M-4) 0.931.80 6 95 2 3(M-4) 0.811.79 7 95 2.52.5(M-4) 0.801.73 8 96 1 3(M-4) 0.782.25 9 95 2 3(M-4) 0.722.45 2.52.5(M-4) 0.712.41 11 9~ 1 3(M-4) 0.692.90 12 96 2 2~M-4) 0.91l.aS
13 96 2 2(M-3) 0.891.72 14 96 2 2(M-3) 0.941.46 98 1 l(M-3) 0.783.36 16 96 1 3(M-3) 0.83l.S9 17 96 13(M 3) ~ 0.751.59 18 94 3 3~M-3) 0.781.31 19 98 1l(M 3) 0.5712.70 96 13(M 3) 0.605.21 21 96 3 1(M-3) 0.553,36 22 94 3 3(M-3) 0.582.18 23 96 2 2(M-3) 0.653.60 24 98 1 l(M-3) 0.892.77 97 1.51.5(M-3) 0.861.98 26 97 0 3(M-3) 0.801.71 27 96 3 l(M-3) 0-90 1.71 28 96 2 2(M-3) 0.871.6S
29 96 1 3(M-3) 0u831. 38 9S 2.52.5(M-3) 0.871.24 31 95 0 S(M-3) ~ 0.830.96 3~ ~ 96 2 2(M-5) 0.822.99 33 80 020(M-5) 0.760.23 :,, .

~i3'~3'78 Skin Adhesives from~ ylamide Copolymers Ex. IOA ACM Macromer J
No. (~bw) (pbw) (pbw(identity) IV (X10~5cm2 ~ me) 34 go 46(M-1) 0.58 0.39 97 2l(M-3) 0.86 3.25 36 95 23(M-3) 0.82 2.20 37 95 4l(M-3) 0.92 1.15 38 93 43(~-3) 0.87 0.94 39 97 2l(M-3) 0.53 8.57 23(M-3) 0.53 3.48 41 95 4l~M-3) 0.58 1.62 42 93 43(M-3) 0.60 1.20 43 95 32(M-3) 0.67 2.04 4~ 98 1.50.5(M-3) 1.03 1.98 98 0.51.5(M-3) 0.94 2.0~
46 97 2l(M-3) 1.05 1.20 47 97 12(M-3) 0.95 1.41 48 96 3l(M-3) 1~10 0.87 49 96 22(M-3) 1.06 1.04 96 13(M-3) 0.98 1.22 51 94 2~53.5(M-3) 1.09 0.81 52 95 05tM-3) 0~90 0.88 53 97 2l(M-5) 0.95 2.27 :

....

~i3~
~31-Skin Adhesives from N-viny~pyrrolidone~ lymers Ex. IOA NVP Macromer J
No (pbw) (pbw) (pbw(identit~ IV (X10~5cm2/d 54 93 5 2(M-31 1.04 1.60 91 6 3(M-3) 1~05 1006 5G 89 7 4(M-3) 1.09 0.86 57 89 5 6(M-3) 0.99 0.69 58 88 10 2(M-3) 1.20 1.11 59 87 8 5(M-3) 1.14 0.70 86 10 4(M-3) 1~19 0.79 61 85 12 3(M-3) 1.28 0.76 62 84 1~ 2(M-3) 1.36 0.78 63 8~ 10 6(M-3) 1.26 0.58 64 84 1~ 2(M-5) 0.~2 1.23 87 10 3(M-5) 0.~3 1.66 The following Skin Adhesion Tests from four separate testing panels illustrate the general rule that copolymers having creep compliance values within the range of 1.2 to 2.3 X 10~5cm2/dyne give adhesive tape~ having higher initial adhesion without objectionable adhesion build over time. The tapes were comprised of the adhesive~
shown 011 a woven backing such as that of DURAPORE~
available from 3M, St. Paul, MN~ The control is a copolymer of isooctyl acrylate and acrylic acid, 95.5 and 4.5 parts by weight respectively, haYing the IV and J
valueq shown commercially available as D~RAPORE~ tape from : :3M~

3~3'~

_ Skin Adhe~ion Tests Ex. Skln Adhesion ~esidue No. CoE~ymer IV J Tn ~ Rating Panel 1 66 IQA/AA/M 3:96/2/2 O.g41.46 76 157 1.17 67 IOA/AA/M-3:96/2/2 0.84 1.65 8S 190 1.11 68 IOA/ACM/M-3:97/2/1 0.832.15 225 471 2.89 t 69 IOA/NVP/M-3:87/10/3 0.931.61 102 268 2.17 IOA/NVP/M-3:84/14/2 0.911.74 291 388 2~44 A Control 1.55 0.84 67 234 1l78 Panel 2 71 IOAjAA/M-3:96/2/2 0.89 1.72 69 270 0.67 72 IOA/NVP/M-3:87/10/3 1.331.09 91 366 0.78 73 IOA/ACM/M-3:97/2/1 1.101.39 106 499 1.61 Control 1.55 0.84 38 242 0.72 Panèl 3 74 IOA/AA/M-3:96/2/2 0.93 1.80 79 128 1.00 IOA/AA/M-3:96/2/2 0.93 1.80 76 127 0.88 C Control 1.55 0.84 60 317 2.39 Panel 4 76 IOA/ M /M-3:96/2/2 0.931.80 56 228 0.78 D Control 1.55 0.84 36 256 1.]1 Panel 5 77 IOA/AA/M~3:96/2/2 0.941.46 53 219 1.22 E Control 1.55 0.8~ 30 216 1.00 :

3'~'3'7~3 - 33 - ~0557-3037 The adhesives o~ U.S. Patent No. 4,554,324 having a shear strength value below 50 minutes were tested for their utility as skin adhesives by testing their creep compliance. (The high shear strengths of the adhesives having shear strengths above 50 minutes will prevent these adhesives from creep compliance v~lues low enough to act as a skin adhesive.) The results of these -tests are shown in Table 5, below:

3 ~ 3g78 r O~
u u~ 7 ~ O
10 .
l r-l r-l ~ (q) o x -O ~ O 0 H

O
CO --` O
rl ~ JJ
O Q~
Z; E ~ O
O ~ ~ ~ ~ O
~1 ~ u~ Ei r-l .,1 ,~ D u :~:
~n ~ o U~ ~
U~ ~, :~
E~ ~J
~J
~a aJ
~ F 3 O C
U
.~ a~
bq D
., ~ 3 ~
s o ~ a~ ~ o o o o co H

CD
.
O
Z;
Ln I` ~ U~
~r x ~r ~r ~ u~ I
E~

:

~ Z ~ 'r ~

~ 3~
- 35 - 60557-30~7 It can be seen from the above table tha-t out of the many adhesives disc]osed in U.S. Patent No. 4,554,324 only two have the creep compliance required to act as skin adhesives in accordance with this invention and only one within the preferred ran~e of creep compliance.

The IV and compliance (J) values were taken by measurements on the adhesive without the Iodine/NaI. A solution of 2% iodine and 2~4% NaI (by weight) in acetone was added to each adhesive to achieve an overall composition of 2% iodine and 204%
~aI by weight o~ adhesive solids. The adhesives were coated onto a silicone liner, dried to evaporate the solvents, and laminated to a polyurethane backing so as to achieve a dried coating weight o~ approximate]y 25.1 g/m2. The skin adhesion procedure described above was then followed to obtain the results shown in Table 6 below.

Adhesive Skin Adhesion Sample Terpolymer IV ~ TO T48 Resldue 92/6/2 1.042.11 88 222 2.0 76 91/6/3 1.201.25 75 137 2.2 77 90.5/7.5/2 1.24 1.29 75 212 1.7 78 90/7/3 1.081.36 71 159 1.9 79 90/6/4 1.20.9g 58 124 1.8 89.5/8.5/2 1.29 1.11 69 183 1.9 81 89/8/3 1.28.94 69 154 1.2 82 88.5/g.5/2 1.18 1.29 80 230 2.0 83 88.5/7.5/4 1.28 .92 54 104 1.5 84 88/9/3 1.141.06 72 159 1.8 87/11/2 1.211.14 81 190 1.5 86 87/9/4 1.15.91 60 167 1.8

Claims (38)

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

1. An adhesive sheet material suitable for application to skin, said adhesive sheet material comprising a conformable backing member and a skin adhesive composition which is applied to at least a portion of one surface of said conformable backing member, said skin adhesive composition comprising a copolymer of copolymerized A
monomers, C macromers, and optionally B monomers, wherein:
A is a monomeric acrylate or methacrylate ester of a non-tertiary alcohol, said alcohol having from about 1 to about 14 car-bon atoms with the average number of carbon atoms being from about 4 to about 12;
B, when used, is at least one ethylenically unsaturated compound copolymerizable with said A monomer, with B monomers com-prising from about 0% to about 25% of the total weight of A and monomers; and C is a macromer having the general formula:
X-(Y)n-Z
wherein:
X is a vinyl group copolymerizable with said A and B
monomers, X having the general formula:
wherein R is a hydrogen atom or COOH group and R' is a hydrogen atom or a methyl group;

Y is a divalent linking group with n being either 0 or 1; and Z is a monovalent polymeric moiety having a Tg greater than about 20°C. and a weight average molecular weight in the range of about 2,000 to about 30,000 and being essentially unreactive under copolymerization conditions, Z having the general formula:
wherein R2 is a hydrogen atom or lower alkyl group, R3 is a lower alkyl group, n is an integer from about 20 to about 500, and R4 is a monovalent radical selected from the group con-sisting of:
and -CO2R6 wherein R5 is a hydrogen atom or a lower alkyl group and R6 is a lower alkyl group; wherein the number and composi-tion of said C macromers is such that the skin adhesive composition has a creep compliance of at least about 1.2X10-5 cm2/dyne when measured after about 3 minutes of subjection to stress.

2. An adhesive sheet material as defined in claim 1 wherein said copolymer contains from about 1% to about 7% by weight of C
macromer.

3. An adhesive sheet material as defined in claim 1 wherein said copolymer has an inherent viscosity of about 0.5 to about 1.4.

4. An adhesive sheet material as defined in claim 1 wherein the conformable backing member has a water vapor permeability of at least about 500 g/m when measured over about 24 hours at a tempera-ture of about 100°F. under a humidity differential of about 80%.

5. An adhesive sheet material as defined in claim 1 wherein the conformable backing member has conformability which is at least equivalent to that of a film having a tensile modulus of less than about 400,000 psi.

6. An adhesive sheet material as defined in claim 1 wherein said B monomer is selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, acrylamide, methacrylamide, acrylo-nitrile, methacrylonitrile, vinyl acetate, and N-vinylpyrrolidone.

7. An adhesive sheet material as defined in claim 1 wherein said A monomer is isooctylacrylate, said B monomer is present and is acrylic acid, and said C macromer is methacrylate-terminated polystyrene.

8. An adhesive sheet material as defined in claim 7 wherein said copolymer contains from about 1% to about 7% by weight of C macromer and from about 1% to about 4% by weight of B monomer.

9. An adhesive sheet material as defined in claim 1 wherein said copolymer contains from about 1% to about 4% by weight of acrylic acid as the B monomer.

10. An adhesive sheet material as defined in claim 1 wherein said copolymer contains from about 1% to about 4% by weight of acrylamide as the B monomer.

11. An adhesive sheet material as defined in claim 1 wherein said B monomer is present and is N-vinylpyrrolidone.

12. An adhesive sheet material as defined in claim 11 wherein said copolymer contains from about 5% to about 15% by weight of N-vinylpyrrolidone as the B monomer.

13. An adhesive sheet material as defined in claim 11 wherein said copolymer is complexed with iodine or iodide and wherein said creep compliance is measured before complexing with the iodine or iodide.

14. An adhesive sheet material as defined in claim 13 wherein the amount of iodine or iodide in said copolymer complex is from about 1% to about 3% by weight of the copolymer.

15. An adhesive sheet material as defined in claim 1 wherein said A monomer is isooctyl acrylate, said B monomer is present and is N-vinylpyrrolidone, and said C macromer is methacrylate-terminated polystyrene.

16. An adhesive sheet material as defined in claim 1 wherein N-vinylpyrrolidone and an acidic monomer selected from the group consisting of acrylic acid, methacrylic acid, and itaconic acid are both included in the copolymer as B monomers.

17. An adhesive sheet material as defined in claim 1 wherein said conformable backing member is made from a synthetic film.

18. An adhesive sheet material as defined in claim 1 wherein said conformable backing member is made from a conformable fabric.

19. An adhesive sheet material as defined in claim 1 wherein the number and composition of said C macromers is such that the skin adhesive composition has a creep compliance of between about 1.2X10-5 cm2/dyne and about 2.3X10-5 cm2/dyne when measured after about 3 minutes of subjection to stress.

20. A method of adhering a substrate to skin comprising the step of interposing between the substrate and the skin an adhesive composition comprising a copolymer of copolymerized A monomers, C
macromers, and optionally B monomers, wherein:
A is a monomeric acrylate or methacrylate ester of a non-tertiary alcohol, said alcohol having from about 1 to about 14 car-bon atoms with the average number of carbon atoms being from about 4 to about 12;
B, when used, is at least one ethylenically unsaturated compound copolymerizable with said A monomer, with B monomers comprising from about 0% to about 25% of the total weight of A and B monomers; and C is a macromer having the general formula:
X-(Y)n-Z
wherein:

X is a vinyl group copolymerizable with said A and B
monomers, X having the general formula:
wherein R is a hydrogen atom or a COOH group and R' is a hydrogen atom or a methyl group;
Y is a divalent linking group with n being either 0 or 1; and Z is a monovalent polymeric moiety having a Tg greater than about 20°C. and a molecular weight in the range of about 2,000 to about 30,000 and being essentially unreactive under copolymeriza-tion, conditions, Z having the general formula:
wherein R2 is a hydrogen atom or a lower alkyl group, R3 is a lower alkyl group, n is an integer from about 20 to about 500, and R4 is a monovalent radical selected from the group con-sisting of:
and -CO2R6 wherein R5 is a hydrogen atom or a lower alkyl group and R6 is a lower alkyl group; wherein the number and composi-tion of said C macromers is such that the adhesive composition has a creep compliance of at least about 1.2X10-5 cm2/dyne when measured after about 3 minutes of subjection to stress.

21. A method as defined in claim 20 wherein said copolymer contains from about 1% to about 7% by weight of C macromer.

22. A method as defined in claim 20 wherein said copolymer has an inherent viscosity of about 0.5 to about 1.4.

23. A method as defined in claim 20 wherein the substrate comprises a skin conformable backing member having a water vapor permeability of at least about 500 g/m when measured over about 24 hours at a temperature of about 100°F. under a humidity differential of about 80%.

24. A method as defined in claim 20 wherein the substrate comprises a skin conformable backing member having conformability which is at least equivalent to that of a film having a tensile modulus of less than about 400,000 psi.

25. A method as defined in claim 20 wherein said B monomer is selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, vinyl acetate and N-vinylpyrrolidone.

26. A method as defined in claim 20 wherein said A monomer is isooctyl acrylate, said B monomer is present and is acrylic acid, and said C macromer is methacrylate-terminated polystyrene.

27. A method as defined in claim 26 wherein said copolymer contains from about 1% to about 7% by weight of C macromer and from about 1% to about 4% by weight of B monomer.

28. A method as defined in claim 20 wherein said copolymer contains from about 1% to about 4% by weight of acrylic acid as the B monomer.

29. A method as defined in claim 20 wherein said copolymer contains from about 1% to about 4% by weight of acrylamide as the B monomer.

30. A method as defined in claim 20 wherein said B monomer is present and is N-vinylpyrrolidone.

31. A method as defined in claim 30 wherein said copolymer contains from about 5% to about 15% by weight of N-vinylpyrrolidone as the B monomer.

32. A method as defined in claim 30 wherein said copolymer is complexed with iodine.

33. A method as defined in claim 32 wherein the amount of iodine in said copolymer complex is from about 1% to about 3% by weight of the copolymer.

34. A method as defined in claim 20 wherein said A monomer is isooctyl acrylate, said B monomer is present and is N-vinyl-pyrrolidone, and said C monomer is methacrylate-terminated poly-styrene.

35. A method as defined in claim 20 wherein N-vinylpyrrolidone and an acidic monomer selected from the group consisting of acrylic acid, methacrylic acid, and itaconic acid are both included in the copolymer as B monomers.

36. A method as defined in claim 20 wherein said substrate is made from a synthetic film.

37. A method as defined in claim 20 wherein said substrate is made from a conformable fabric.

38. A method as defined in claim 20 wherein the number and composition of said C macromers is such that the adhesive composi-tion has a creep compliance of between about 1.2X10-5 cm2/dyne and about 2.3X10-5 cm2/dyne when measured after about 3 minutes of subjection to stress.