Note: Descriptions are shown in the official language in which they were submitted.
9~
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
2 ~2~ 9~
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.
, _, _ ,,, __ , , . , . _, ,_ . _ ,,, . . ~.. ~ . , .. _ _ . . . .....
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.
s~
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.
7 ~ 5~L
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.
9~;~
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.
10 ~ 89~;~
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.
2 iL~9~
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
,~
- 12 -
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.
~ i~..,
- 14 - ~ 95~
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.
J'~.
~2~gs~
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
17
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~
19
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~ .
~2~39S~
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~
24
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
26
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,
29
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.
954
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~
31
"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~
32
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
34
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~
37
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:
39
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
41
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.
EXAMPLE 1
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~
42
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~
43
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.
EXAMPLES 2-44
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
COMPARATIVE EXAMPLES 1-5
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.
EXAMPLE 45
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~
- 46 -
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
.: .
47
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.
~,~l ;
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49
TABLE 2
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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P;
_ In In U~
Q)
~0 ~_
a) ~ ^ ~0\O 0~O _~
o\ o\ o In 0\0
O ~ ~ ~ ~ O
~ 0\~ o\O ~ ~,o
N ~ ~1 0 Ll'l --O
F. ~1 u~
O o o ~O `-- o `-- o--
C) ~rl O ~ ~ O
u~ O Q a~ Q
~ F~ ~O ~ O
E~
o\
_ o\ O
~ o\ o\O ~
~1 a:~ o o
O
X
~ 39~i~
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.
-
56
~ .
a
O ~r~
1:' -
o o o
o o o o
o
~ ~1 P~
h
O o o\ o\O o\o o\O o\O o\O o\O
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~ .
o\
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o o\ ~ o~ ~ o\ CO o\o
h ~ . ~ . ~ . t~
-a) oP ,~ . ~ . r~ .
N o -- cr~
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O O O O
u~ o) a) a) a
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57
TABLE 5
(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.
(Measure of Pro-
duct Uniformity~
-
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~
TABLE 6
(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~
59
TABLE 7
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.
54L
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