Note: Descriptions are shown in the official language in which they were submitted.
W096/26251 CA 02212028 1997-07-31
PCT/US96/00794
ADHESIVE SHEET ARTICLES
Field of the Invention
The invention relates to adhesive sheet articles comprising porous
s sheets with a polymeric composition adhered thereto which is further coated
with
an adhesive. The invention further relates to adhesive articles such as tapes
or
wound dressings made from the adhesive sheet articles and methods for making
the adhesive articles.
1o Background of the Invention
Sheet materials having physical characteristics which allow for air
permeability and moisture vapor permeability are well known and are generally
referred to as porous sheets. Porous sheet materials are typically non-woven,
woven or knitted constructions although foamed sheets, microporous films and
1s perforated films also provide certain degrees of permeability.
Porous sheet materials have many applications and are particularly
useful as backings for tapes in the medical field. This is particularly tnie
when it
is desirable to allow the skin covered by the sheet material to breathe. When
an
adhesive is coated onto a porous sheet, the adhesive sheet article will
exhibit
2o varying degrees of breathability depending upon the nature of both the
porous
sheet and the adhesive coated thereon. For example, Copeland in U.S. Patent
3,121,021 describes a breathable surgical tape made of a non-woven backing and
a microporous layer of pressure-sensitive adhesive.
Certain porous sheets coated with adhesive may permit or even
2s facilitate the migration of adhesives into the porous sheet layer. Such
migration
of adhesives is not always detrimental to the performance of the adhesive tape
article. This is true if a heavy adhesive coating is used or if the adhesive
is used
for transdermal delivery of a bioactive molecule. However, it is sometimes
detrimental when the adhesive migrates into the porous sheets. This is true
when
3o adhesion of the resulting article is reduced due to the migrated adhesive.
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When it is necessary to control or limit the migration of adhesive,
a few strategies are available. Generally, one should avoid "soft" adhesives
which readily migrate into the interstices of porous backings. "Soft"
adhesives
include adhesives such as acrylate ester-acrylic acid-polyethylene oxide
acrylate
s macromer copolymers which provide adhesive coated sheet materials having a '
skin adhesion value of at least about 2.2 Newtons per 100 millimeters of
width.
However, such "soft" adhesives are very desirable for adhering to skin because
"soft" adhesives are generally very conformable and usually adhere well to
skin,
and may adhere to moist skin.
1o U.S. Patent 5,344,415 of DeBusk and Felice (hereinafter
"DeBusk") describes a mufti-component system which includes a web and
adhesive layer, a barrier layer and a second adhesive layer. The DeBusk
barrier
layer is a distinct and separate transparent nonexclusive film material such
as a
polyurethane film. As is generally known in the art, films must be at least 25
is micrometers thick in order to allow handling of the film. The DeBusk
barrier
layer (film) is sandwiched between 2 layers of adhesive and does not directly
contact the web. DeBusk teaches that the barrier layer provides a barrier to
external contaminants, restricts drainage strike-through and helps maintain a
desirable moist environment.
2o It is an object of the present invention to provide porous adhesive
sheet articles wherein the migration of the soft adhesives into the porous
sheeting
is limited or prevented.
Description of the Drawings
25 Fig. 1 is a 500 times magnification scanning electron micrograph
(SEM) of a nonwoven web coated with an adhesive.
Fig. 2 is a 500 times magnification SEM of an embodiment of the
invention.
Fig. 3 is a 100 times magnification SEM of a migration
3o barrier/adhesive/release liner composite.
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60557-5574
Figure 3.
Figure 2.
Fig. 4 is a 500 times magnification of the composite shown in
Fig. 5 is a 900 times magnification of the sample shown in
SummarJr of the Invention
The present invention provides adhesive sheet articles. More
specifically, it provides adhesive sheet articles comprising porous backings
with a
polymeric composition juxtaposed between said backing and the adhesive layer
to
Io prevent migration of the adhesive into the porous backing.
This invention further provides such adhesive sheet articles which
are converted to provide pressure-sensitive adhesive tape articles or first
aid
dressings. Although sheet articles comprising porous backings adhered to non-
tacky polymeric migration barriers and further adhered to skin adhesives are a
preferred sub-class, sheet articles comprised of porous backings with any non-
film barrier layer which adheres to both the backing and the adhesive are
broadly
described. This invention further relates to nontacky or tacky migration
barrier
layers which are polymeric coatings of acrylate copolymers or polyurethanes
juxtaposed between an adhesive and a porous backing. Preferred polymeric
2o coatings are acrylate copolymers.
This invention also provides a process for preparing a pressure-
sensitive adhesive tape article comprising depositing a polymeric migration
barrier coating on one side of a pressure-sensitive adhesive layer, then
adhering
the exposed side of the polymeric migration barrier coating to a porous
backing.
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According to one aspect of the present invention,
there is provided an adhesive sheet article comprised of at
least three layers comprising a porous backing, a migration
barrier and an adhesive wherein said migration barrier is
juxtaposed between said porous backing and said adhesive so
that said migration barrier substantially prevents said
adhesive from migrating into said porous backing; wherein
said article does not include an additional adhesive layer
between said migration barrier and said porous backing and
wherein said migration barrier is comprised of an alkyl
acrylate-N-alkylacrylamide copolymer or polyurethane.
According to another aspect of the present
invention, there is provided a method of making an adhesive
sheet article described herein, comprising: a) coating an
adhesive on a liner, b) bonding a migration barrier to the
surface of the adhesive, and c) bonding a porous backing to
the surface of the migration barrier.
According to yet another aspect of the present
invention, there is provided a first aid dressing comprising
an adhesive sheet, wherein said adhesive sheet is comprised
of at least three layers, said three layers comprised of a
porous backing, a migration barrier and an adhesive wherein
said migration barrier is juxtaposed between said porous
backing and said adhesive, and wherein said migration
barrier comprises alkyl acrylate-N-alkylacrylamide copolymer
or polyurethane and does not readily migrate into
interstices of the backing; wherein said adhesive sheet has
a moisture vapor transmission rate of at least 400 g/m2 per
24 hours and further wherein an absorbent layer is adhered
to at least a portion of said adhesive.
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According to still another aspect of the present
invention, there is provided a first aid dressing comprising
the adhesive sheet article as described herein, and an
absorbent layer, wherein the absorbent layer is adhered to
at least a portion of the adhesive of the adhesive sheet
article.
Definitions
As used herein the term "coating" refers to an
essentially continuous macroscopically nonporous chemically
homogeneous layer which has been deposited on or bonded to
or adhered to a separately nonsimultaneously formed,
deposited or otherwise provided layer.
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As described herein the term "breathable" refers to materials
which are penetrable by air and water vapor preferably to the extent that they
provide a moisture vapor transmission rate (MVTR) of at least 200 g/m2 per 24
hours when measured in accordance with ASTM E 96-80 or minor modifications
s thereof. '
As used herein the term "porous" refers to materials or surfaces
which are penetrable by smaller objects or materials. Such porous materials or
surfaces do not necessarily have visible openings, although they may, but have
visible characteristics consistent with permeability and penetration. Some
to . examples of porous materials are nonwoven polymeric webs, woven cloth or
polymeric fabrics, knitted cloth or nonwoven fabrics, absorbent spongelike
foams
and the like but do not include films or other nonbreathable layers.
Detailed Description of the Invention
15 The articles of the invention comprise an adhesive sheet article
with moisture vapor transmission rates of at least 400 g/m2 per 24 hours. The
adhesive sheet articles of the invention comprise a porous backing, a
migration
barrier layer comprised of a polymeric composition coated on the backing with
an adhesive layer coated on the barrier layer. The migration barrier is
preferably
20 less than 20 ~.m thick. The adhesives are first described, followed by a
discussion of the porous backings and a discussion of the polymeric migration
barrier.
Adhesive
2s As stated earlier, the adhesives which are preferred for contact
with human skin are "soft" adhesives. Such soft adhesives would readily
migrate
into a porous backing. Nonlimiting examples of soft adhesives include
hydrophilic adhesives or blends including hydrophilic adhesive components.
Examples of suitable soft hydrophilic adhesives for use on the
articles of the invention include pressure sensitive adhesives which are water
r
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insoluble and not significantly water absorbent and water tolerant such as
polyacrylates, polyolefins e.g. polyalpha-olefins, polyethers, polyisoprenes,
butyl
rubbers, natural rubbers, styrene-butadiene rubbers, polyurethanes, polyesters
and the like. It is anticipated that blends or mixtures of such adhesives are
useful
s in the present invention and the adhesives may optionally include
tacldfiers.
Preferred adhesives are acrylate ester-acrylic acid-polyether macromer
copolymers described below as second polymeric components and polymer
blends thereof. The blends are novel materials described in
U.S. Patent No. 5,648,210.
Such adhesive blends comprise primarily two components. The
components are each described in detail below followed by a description of the
method of blending the two components.
First Polymeric Component of a Preferred Adhesive Blend
z5 The first polymeric component increases the initial adhesion of the
adhesive blend to the skin while retaining the typical advantages of acrylate
ester
adhesives when used as medical adhesives. This component is comprised of
certain copolymers which are used as skin adhesives for medical applications
and
are described in U.S. Patent 4,693,776 of Krampe, Moore and Taylor (Ksampe)
2o entitled "Macromer Reinforced Pressure Sensitive Skin Adhesive." The
typical
advantages of these adhesives include ease of manufacture, an excellent safety
history and profile, high shear strength, low cost and chemical stability.
This
first polymeric component comprises certain copolymers, especially the A-B-C
type copolymers of (A) acrylate esters, (B) ethylenically unsaturated
compounds
25 copolymerizable with acrylate esters such as acrylic and methacrylic acid
and (C)
macromolecular monomers as described hereinafter. The acrylic esters may be
esters of acrylic or methacrylic acid and are preferably acrylic acid esters.
The
alcohol portion of the ester is typically a non-tertiary alcohol having one to
fourteen carbon atoms with the average number of carbon atoms being about four
3o to twelve. In a preferred embodiment the average number of carbon atoms is
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about six to ten, and most preferably about eight. Nonlimiting examples
include
isooctyl acrylate and ethyl(hexyl) acrylate.
The ethylenically unsaturated compounds (B monomers)
copolymerizable with acrylate (and methacrylate) esters include acrylic acid,
s methacrylic acid, itaconic acid, acrylamide, methacrylamide, acrylonitrile,
methacrylonitrile, vinyl acetate and N-vinylpyrrolidone, but acrylic acid is
used
in a preferred embodiment.
The macromolecular monomers (macromers) useful as C
monomers have the general formula: X-(Y),~ Z wherein X is a vinyl group
to copolymerizable with said A and B monomers; Y is a divalent linking group;
where " can be zero or 1; and Z is a monovalent polymeric moiety having a Tg
greater than about 20° C. and a molecular weight in the range of about
2,000 to
about 30,000 and being essentially unreactive under copolymerization
conditions;
wherein said vinyl group and said A and B monomers form a polymeric
15 backbone having pendant therefrom said polymeric moieties (Z) and wherein
the
molecular weight of said C macromer and the inherent viscosity of the
copolymer
are such that the adhesive composition has a creep compliance value of at
least
about 1.2 x 10-SCm2/dyne. In a preferred embodiment C macromers are
polystyrylethyl methacrylate macromers having a weight average molecular
2o weight of about 8,000 to 15,000 g/mol. and most preferably about 10,000
g/mol.
as described in Example M-3 of U.S. Patent 4,693,776 and hereinafter in
Example 1. These macromers are prepared by reaction of styrene with
secondary-butyl lithium in cyclohexane to form "living polymers" of polystyryl
lithium, "capping" with ethylene oxide, followed by reaction with methacryloyl
25 chloride to obtain a macromer of about 10,000 weight average molecular
weight.
Some macromers useful in the present invention are commercially available,
e.g.
polystyrylethyl methacrylate (13,000 M. wt.) is available as Chemlink~ 4500
from Sartomer Chemical Company of West Chester, PA.
The amounts of A, B and C monomers in these copolymers are
so typically 90 percent or more by weight of A monomer and about equal amounts
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of B and C monomers. A nonlimiting example of the amounts of monomer in
the copolymer is 96 parts A monomer, 2 parts of B monomer and 2 parts of C
monomer.
s Second Polymeric Gomnonent of a Preferred Adhesive Blend
The second main component of the polymer blends useful in the
present invention promotes prolonged adhesion to skin, which is a relatively
moist substrate. Medical tapes which adhere well to moist skin generally
require
adhesives which are substantially hydrophilic and polar in character. One such
to class of adhesives is described in PCT Application WO 84/03837 of Snyder
and
Silence (Snyder) entitled "Adhesive and Adhesive-Coated Sheet Material for
Moist Skin."
These second copolymers include three comonomers. A first
comonomer is an acrylic acid ester of a non-tertiary alcohol, said alcohol
having
is from about 4 to 14 carbon atoms. In a preferred embodiment the alcohol has
about 8 carbon atoms. Examples include but are not limited to isooctyl or
ethylhexyl alcohol. In a preferred embodiment the alcohol is isooctyl alcohol.
The second copolymer includes a second comonomer which is a
hydrophilic monomer having a vinyl group copolymerizable with the acrylate
2o ester monomer, a divalent linking group and a monovalent polyether group.
The
polyether group should be essentially unreactive under conditions used for
forming the copolymer. Many such second comonomers are described in
Snyder. These comonomers contain a plurality of hydrophilic sites such as
ether
groups. Preferred second comonomers are macromolecular monomers of the
25 formula:
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RI O
Formula III CH2=C-C-W-OR2
wherein Rl is hydrogen or methyl, R2 is hydrogen, phenyl, substituted phenyl
or '
lower alkyl and W is a divalent poly(lower alkylene oxide) group containing 2
to
250 repeating alkoxy units and selected from the group consisting of a
polyethylene oxide) radical, a polypropylene oxide) radical, a radical of a
to copolymer of ethylene oxide and propylene oxide and a polytetrahydrofuran
radical.
In a preferred embodiment the W moiety contains about 5 to 25
repeating alkoxy units, most preferably ethylenoxy units, and R2 is hydrogen
or
lower alkyl. Such second monomers are commonly commercially available as
is alkoxypoly(ethylenoxy)alcohols such as methoxypoly(ethylenoxy)ethanols of
various molecular weights. Synthesis and description of various additional
suitable materials as found in Snyder is as follows:
A variety of second monomers are or have been available
commercially. For example, suitable commercially available monomers are the
20 2-(2-ethoxyethoxy)ethyl acrylate available under the trade designation "SR-
256"
from Sartomer Company, West Chester, PA; the methoxy polyethylene oxide)lo
acrylate available under the trade designation "No. 8816" from Monomer-
Polymer & Dajac Laboratories, Inc., Trevose, PA; the methoxy polyethylene
oxide) methacrylates of 200 Daltons, 400 Daltons, and 1000 Daltons available
25 under the trade designations "No. 16664", "No. 16665" and "No. 16666",
respectively, from Polysciences, Inc., Warrington, PA; the hydroxy
polyethylene oxide)5 methacrylate available under the trade designation "No.
16712" from Polysciences, Inc., Warrington, PA.
Other preferred second monomers may be prepared using
3o commercially available starting materials and conventional methods. For
example, the preferred second monomers wherein R2 of Formula III is lower
_g_
W O 96/26251 CA 0 2 212 0 2 8 19 9 7 - 0 7 - 31 pC~~~S96/00794
alkyl may be prepared by reacting an a,b-unsaturated carboxylic acid such as
acrylic acid or methacrylic acid with an equimolar amount of a mono-alcohol of
a poly(lower alkylene oxide). The esterification reaction is generally
conducted
under anhydrous conditions in an organic solvent such as toluene which
s preferably will form an azeotropic mixture with the water which is generated
as
the esterification reaction proceeds. A suitable solvent is toluene.
Typically, the
alcohol is combined with the organic solvent and the unsaturated carboxylic
acid
is then added to the alcohol/solvent mixture. In the event that the alcohol is
a
solid at room temperature, it is first melted by heating prior to addition of
the
to unsaturated carboxylic acid. The reaction is conducted in the presence of
an acid
catalyst such as para-toluenesulfonic acid and a free-radical inhibitor such
as
copper powder. The reaction mixture is refluxed, generally for 16 to 18 hours
under a nitrogen atmosphere, and the water generated is removed by azeotrophic
distillation, for example, using a Dean Stark trap.
is Examples of suitable mono-hydroxyl-terminated poly(lower
alkylene oxides) which may be used to prepare the preferred second monomers
using the above-described procedure include Carbowax~ 350, Carbowax~ 550,
Carbowax~ 750, Carbowax~ 2000 and Carbowax~ 5000 (i.e., the methoxy-
poly(ethylene oxide) ethanols of about 350 MW, 550 MW, 750 MW, 2000 MW
2o and 5000 MW, respectively, commercially available from Union Carbide Corp).
The Carbowax~ family of monomers are methoxy(polyethylene oxide)ethanols
possessing an average molecular weight expressed by the numeral e.g. the 5000
of Carbowax~ 5000 denotes an average molecular weight of 5000. A
monoalcohol of a polytetrahydrofuran of about 16,000 MW prepared as
2s described in Snyder by polymerization of tetrahydrofuran in the presence of
methyl trifluoromethanesulfonate as shown in Examples for Monomer "B-9" in
WO 84/03837 cited above; UCOh1~ LB-285 (an n-butoxy polypropylene oxide)
propanol having about a 1000 MW, commercially available from Union Carbide
Corp.); UCON~ 50-HB260 (an n-butoxy polyethylene oxide/propylene oxide)
30 (50:50 by weight) alcohol having about a 1000 MW, available from Union
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Carbide Corp.); and 1'ycal~ 94 ( a phenoxy polyethylene oxide)4 ethanol,
available from Atlas Chemical Industries).
Second monomers wherein R2 is hydrogen may be prepared by
reacting an a,b-unsaturated carboxylic acid or hydroxyalkyl ester with an
s anhydride selected from monoepoxides, lactones or mixtures thereof.
A suitable commercially available poly(alkylene oxide) acrylate
ester is NK-Ester AM 90G~ available from Shin-Nakamura.
The preferred second monomer for employment in preparing the
pressure-sensitive adhesive copolymer is the acrylate ester of above-described
1o Carbowax~ 750.
It is to be understood that the pressure-sensitive adhesive
copolymer may comprise a single type of second monomer or may comprise two
or more different second monomers.
The third monomeric component of the second copolymer is
1s generally acrylic acid or methacrylic acid, preferably acrylic acid
monomer.
Preparation of the First and Second Polymeric Components of a Preferred
Adhesive Blend
Either of the pressure-sensitive adhesive copolymer components of
2o the adhesive blends useful in the invention may be prepared using
conventional
free-radical-polymerization methods. One particularly convenient method is the
following. The desired amounts of each of the different monomers and an
organic solvent in which the monomers are soluble are combined in a sealable
bottle. A particularly suitable solvent is ethyl acetate. A solvent such as
25 isopropyl alcohol which functions as a chain-transfer agent is also present
in the
reaction medium in order to control the molecular weight of the resulting
adhesive copolymer. A catalytic amount of a free-radical initiator such as
a,a'-
azobisisobutyronitrile is then added to the solution. Nitrogen is bubbled
through
the solution to purge air from within the bottle, and the bottle is then
sealed.
3o The sealed bottle is tumbled in a heated water bath for a period of time
sufficient
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to effect essentially complete polymerization. Generally, 24 hours has been
found to be sufficient time to effect essentially complete polymerization when
the
water bath is maintained at about 55°C.
The hydrophilic adhesives used as the second main component of
the polymer blends described above are also useful as the sole adhesive on the
tape articles of the present invention.
Preparation of an Adhesive Blend Useful for the Invention
The process of blending the two copolymer components of the
to preferred blend adhesive of the present invention to provide a useful
homogeneous pressure-sensitive adhesive requires that each of the copolymer
components is dissolved in a solvent or solvent mixture. The solvents used for
each of the copolymer components are preferably at least partially miscible in
order to obtain good blending. Suitable solvents include esters such as ethyl
15 acetate, dimethyl sulfoxide and N,N-dimethylformamide. Cyclohexane may be
used to allow dispersions in solvent. Blending is observed visually to
determine
that incompatible phases are not present. It may be useful to heat one or more
of
the solvent mixtures to improve blending. Once mixing of the solutions of the
copolymers has provided a homogeneous blend, it is preferred to coat the
2o adhesives onto a substrate as soon as practical, but in all cases before
any
significant non-homogeneity of the blend is observed. Non-homogeneity would
be observed e.g. by formation of heterogeneous regions (known as heterogeneous
"domains"). In a preferred embodiment this coating is accomplished in one to
three hours. Once the adhesive blends are coated onto substrates e.g. backings
2s and any remaining solvent is removed, the coatings of pressure-sensitive
adhesive
blend have been observed to remain stable and functional for extended periods.
Preferred blends contain ratios of about 90:10 to 10:90 of the two components,
but preferably 40 to 80 parts of the hydrophilic component.
The pressure-sensitive adhesive copolymer blends or the one
3o component adhesives e.g. hydrophilic adhesives of the invention may be
applied
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to a carrier release liner by conventional methods. As is known to those
skilled
in the art, the particular method selected may depend upon the nature of the
liner
being employed. A suitable method for applying the adhesive involves coating a
solution of the adhesive in water or an organic solvent or a solvent blend
onto a
release liner e.g. a silicone coated or fluorochemical coated liner. '
It is possible to crosslink the adhesives with gamma radiation by
means of the normal sterilization dose. This may be done with or without added
cross-linking agents. It is preferably done without added cross-linking
agents.
The doses of gamma radiation used are generally 5 to 60 kilograys total dose,
to preferably 20 to 40 kilograys.
Porous Backin~,s
Suitable porous backings for use in the invention are any backings
which find use in medical or surgical fields. In particular the porous
backings
are those which are susceptible to adhesives migrating into the backing. Such
backings include any of the conventional nonwoven fabrics, woven fabrics,
knits,
foams and the like, particularly those which permit transpiration of
perspiration
or wound exudate therethrough. Suitable woven, knit and nonwoven fabrics
include those formed from fibers or threads of synthetic or natural materials
2o including cotton, rayon, nylon, polyester, polyurethane and the like.
Nonwoven
polyurethane backings are used in a preferred embodiment. Other backings may
be laminated onto selected barrier layers and adhered thereto by conventional
methods such as heating, irradiation and pressure.
Nonwoven polyurethane backings which are particularly useful in
the present invention can be melt blown into a separate web or directly onto a
substrate for which it will serve as a backing. The polyurethane can be melt
blown using a process similar to the process reported in Wente, Van A. ,
"Superfine Thermoplastic Fibers" in Industrial En ig nag Chemistry, Vol. 48,
pages 1342 et seq (1965), or in Report No. 4364 of the Naval Research
3o Laboratories, published May 25, 1954 titled "Manufacture of Superfine
Organic
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Fibers" by Wente, Van A., Boone, C.D. and Fluharty, E.L. The process is
exemplified hereinafter (Example 9) but is known to those skilled in the art.
Typical polyurethanes useful in the process are commercially available e.g.
Morthanes~, available from Morton International Inc. and Pellthanes~,
available
from Dow Chemical.
The backing may be of any desired shape to provide adhesive
coated sheet materials embodied as adhesive tapes, strips, wound dressings,
monitoring or neuro-stimulating electrodes, drapes or the like. These tapes
are
converted by conventional methods.
Polymeric Migration Barriers
Suitable migration barriers used in articles of the present invention
are coatings of polymers which will adhere to both the porous backings and any
adhesives used. Therefore, the invention does not require the additional
adhesive
layer required in Debusk to adhere the migration barrier to the porous
backing.
When coated on porous backings the migration barrier does not readily migrate
into the interstices of the backing but instead adheres substantially to the
surface
of the backing. An adhesive coated on the migration barrier is therefore
prevented from contacting the porous backing and is also prevented from
2o migrating into the interstices of the backing. The migration barrier
provides a
continuous surface to which the adhesives adheres. Without being bound by
theory it is believed that the migration barrier maintains a substaintially
continuous and smooth surface of the adhesive thus increasing the liklihood
that
the adhesive will adhere to any surface, particularly a rough surface such as
human skin.
The migration barrier of the invention is either non-adhesive or
adhesive under ambient conditions. Suitable non-adhesive coatings are
polymeric
coatings such as lower alkyl acrylate copolymers or polyurethanes which are
not
pressure-sensitive at room temperature, although these may be adhesive at
higher
3o temperatures. Such non-adhesive migration barriers are in some ways easier
to
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process during manufacturing because they are not sticky. A preferred non-
adhesive migration barrier is an ethyl acrylate N/tertiary butyl acrylamide
copolymer. In order to adhere such non-adhesive migration barriers to a
backing, the non-adhesive migration barriers are heated to a temperature above
their softening point where the migration barrier is sufficiently tacky to
allow
adherence to the backing, then cooled to provide a secure bond.
Migration barriers are generally selected which will adhere to an
adhesive coated thereon, i.e. an adhesive with enough chemical similarity to
the
migration barrier to facilitate adherence. Many suitable combinations are
1o possible, and one skilled in the art is familiar with such suitable
combinations.
When polyurethane non-wovens are used as the porous backings,
it has been found that migration barriers selected from polyurethane and lower
alkyl acrylate-N-lower alkylacrylamide copolymers and the like are suitable.
Preferred migration barriers for polyurethane non-woven backings made from
Dow Chemical Co. Pellthane~ polymers or Morton International Inc. Morthane~
polymers include lower alkyl acrylate-N-lower alkylacrylamide copolymers e.g.
a copolymer of ethyl acrylate and tertiary butylacrylamide.
The copolymers of lower alkyl acrylates and acrylamides such as
N-lower alkylacrylamides which are useful in the present invention are readily
2o prepared using conventional free radical catalyzed processes such as those
taught
in Ulrich, Re 24,906 and illustrated in Example 6 hereafter.
Typically, the thickness of a migration barrier is relatively thin,
e.g. 1 to 2 grains per 4 by 6 inch (4 to 8 g/m2), which provides a coating
thickness of about 6 to 8 microns. The migration barrier, as analyzed by
scanning electron microscopy, is found to be essentially continuous.
Absorbent Pads for use in First Aid Dressings
The first aid dressings of the present invention will generally have
an absorbent pad adhered thereto, either over a portion of the adhesive or in
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place of a portion of the adhesive and adjacent to the migration barrier as
the
pads are conventionally provided.
A preferred absorbent layer is a foam, woven or nonwaven
material including but not limited to rayon, polyester, polyurethane,
polyolefin,
cellulose, cellulose derivatives, cotton, orlon, nylon, or hydrogel polymeric
materials. Most preferred are woven and nonwoven materials. See, e.g., U.S.
Patent No. 4,773,903 to Weisman et al. An alternative absorbent layer includes
a composite material comprising a nonwoven polymeric matrix and a highly
hydrophilic fluid absorbing material. Another preferred composite material is
a
1o nonwoven matrix combined with a highly hydrophilic fluid absorbing material
such as a polymeric absorbent fiber or particle selected from the group
consisting
of modified starches and high molecular weight acrylic polymers containing
hydrophilic groups such as acrylonitrile fibers treated with alkali metal
hydroxides. Suitable absorbent materials will preferably absorb at least about
25 % by weight of fluid or exudate, and more preferably greater than about 100
by weight, when measured using test methods reported in U.S. Patent No.
4,957,795 to Riedel. Another preferred class of pads is conventional non-stick
pads used on first aid dressings. Nonwoven rayon web laminated to a porous
high density polyethylene web such as to the 3.2 ounce single side laminate of
2o P530 high density polyethylene mesh available from Applied Extrusion
Technologies, Inc., Middletown, DE is a preferred absorbent layer.
Suitable absorbent materials include composite materials such as
nonwoven polymeric matrices combined with highly hydrophilic fluid absorbing
materials. Highly hydrophilic fluid absorbing materials include polymeric
absorbent fibers or particles selected from the group consisting of modified
polysaccharides, modified polyurethanes, and high molecular weight acrylic
polymers containing hydrophilic groups. A preferred highly hydrophilic fluid
absorbing material is acrylonitrile fibers treated with alkali metal
hydroxides. A
commercially available hydrogel polymeric material is available under the
3o tradename LANSEAL fiber (Japan Exlan Co., Ltd., Osaka, Japan). These types
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of composite absorbent materials are readily prepared using well known methods
such as the method reported in U.S. Patent 4,957,795 to Riedel.
A variety of means are suitable for attaching or fixing the elastic
substrate to the absorbent layer such as stitching, needle-tacking, ultrasonic
welding or bonding with a suitable adhesive. A preferred adhesive is a
biocompatible adhesive that is selected from the group consisting of natural
rubber based adhesives and acrylic based adhesives.
The following test methods were employed to evaluate the
properties of articles and compositions of the invention. The present
invention
1o provides adhesive sheet articles which have desirable moisture vapor
transmission
rates and also maintain desirable adhesivity because the adhesives of the
invention do not disappear by migrating into the porous backings of the
invention. Additionally, the adhesive sheet articles of the invention are able
to
maintain soft textures and good conformability ratings because the migration
barriers of the invention are not unduly thick or stiff.
Moisture Vapor Transmission Rate
(Upright)
The Moisture Vapor Transmission Rate (MVTR"p) for the
2o composite samples is measured in accordance with ASTM E 96-80 as modified
below.
The adhesive sheet article samples are sandwiched between the
adhesive surfaces of two axially aligned foil adhesive rings having 2.54 cm
diameter holes. Each sample is assembled to ensure a flat, wrinkle-free and
void-free foil/sample/foil laminate.
A four-ounce (0.14 kg) glass jar is filled half full with distilled
water. The jar is fitted with a screw-on cap having a 3.8 cm diameter hole
concentrically aligned with a rubber washer having a 4.445 cm outside-diameter
and a 2.84 cm inside-diameter.
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The foil/sample/foil laminate is concentrically positione~.d on the
rubber washer and the sample-containing sub-assembly screwed loosely onto the
jar.
The assembly is placed into a chamber maintained at a temperature
s of 40°C and 20% relative humidity. The assembly is removed from the
chamber
after four hours, weighed to the nearest 0.01 gram (WI), and immediately
returned to the chamber. The cap is now screwed tightly onto the jar without
bulging of the sample. The assembly is again removed from the chamber after
an additional eighteen hours and weighed to the nearest 0.01 gram (W2).
1o The MVTRup T24 of the adhesive (measured in grams of water
transmitted per square meter of sample area over a twenty four hour period)
may
then be calculated according the formula set forth below:
MVTRup T2a = (Wi - W2)(4.74 x 104)/t
where:
15 (WIJ is the initial weight of the assembly (grams)
(W~ is the final weight of the assembly (grams),
and (t) is the time period between Wl and W2 (hrs).
Three samples of each adhesive were run and the average of the
three samples reported.
2o The following examples are provided to illustrate specific
embodiments of the invention, but are not intended to be limiting thereof.
Examples 1 and 3 illustrate the preparation of monomers not
conveniently available from commercial sources which are necessary to make
copolymers of the First and Second Polymeric Components of a preferred
2s adhesive described hereinabove.
Examples 2, 4 and 5 describe preparation of adhesives suitable for
use in the present invention.
Examples 2, 6 and 12 describe preparation of migration barriers
suitable for use in the present invention.
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Examples 8 - 19 describe preparation of samples. Table 1
provides a key which outlines construction of the samples prepared in Examples
8-19.
Example 1: Preparation of a Polystyrylethyl Methacrylate Macromonomer
PREPARATION OF MACROMER
The "C" moiety of the general formula A-B-C is a polymeric
material which has a copolymerizable vinyl group which copolymerizes with
monomers A and B under polymerizing conditions. The C moiety, while being
to polymeric in one sense, actually behaves as a monomer and is referred to in
the
literature as a macromolecular monomer which is shortened to the term
"macromer" for convenience. For the purposes of this invention, a
representative preparation of the macromers that are used follows.
EXAMPLE M-1
is This methacrylate-terminated styrene macromer having an average
molecular weight of about 9000 was prepared using a five-liter four-necked
flask, fitted with a thermometer, mechanical stirrer, septum, Dean-Stark trap
and
condenser. 150 grams (1.44 moles) of styrene were charged into the flask which
contained 1155 grams of cyclohexane, resulting in an 11.5 % by weight
solution.
2o The solution was heated to about 50°C. and a 1.4 molar solution of
secondary-
butyl lithium in cyclohexane was added dropwise until a faint yellow color
persisted, then 10.7 ml of additional sec-butyl lithium cyclohexane solution
was
added rapidly. The reaction mixture was maintained at 65° C. by
cooling. After
about one hour, the solution was allowed to cool to 35° C. and then
ethylene
25 oxide gas was introduced over the reaction mixture which was agitated
rapidly
for 15 minutes until the orange color of polystyryl lithium had disappeared.
The
reaction was then quenched with 5 ml (51.2 meq. ) of methacryloyl chloride.
The polymer solution was reduced in volume and the polymer gradually
precipitated and was separated and dried. Gel permeation chromatography
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revealed a number average molecular weight of 8394, weight average molecular
weight of 8842 and polydispersity of 1.05.
In addition to the above macromer the following macromers are
prepared by the process described in Example M-1 above but gradually
s decreasing the amount of secondary-butyl lithium initiator to obtain higher
moledular weight macromer. The macromer's molecular weight is higher if less
initiator is used, as is known to the art. See e.g. U.S. Patent 4,693,776.
Example M-2: a methacrylate-terminated polystyrene macromer
having a weight average molecular weight of about 10,000 g/mol.
1o Example M-3: a methacrylate-terminated polystyrene macromer
having a weight. average molecular weight of about 13,000 g/mol.
Example M-4: a methacrylate-terminated poly(methyl
methacrylate) macromer having a weight average molecular weight of about
13,000 g/mol.
15 Example M-5: an acrylate-terminated polymethyl methacrylate
polymeric monomer having an average molecular weight of 10,000 was
prepared. Recrystallized dried fluorene, five parts, was placed in a 1,000 ml
three-necked flask fitted with stirrer, thermometer, argon inlet and rubber
septum, all of which were previously flamed under argon. Dried
2o tetrahydrofuran, 400 parts, was distilled into the flask and 15 parts of a
1.4N
solution of sec-butyllithium in cyclohexane were added through the septum,
producing an orange-red solution of "fluorenyl lithium" under slight argon
pressure. The flask contents were cooled to -76°C and 65 parts of
dried, freshly
distilled methyl methacrylate (MMA) were rapidly added through the septum.
2s The reaction temperature quickly rose to -20°C and then was
gradually returned
to -76°C by cooling. After one hour of stirring, 3 parts of ethylene
oxide were
bubbled into the flask and the flask was warmed to -10°C, causing the
liquid to
change from orange-red to light yellow. Acryloyl chloride (3 parts) was then
added to quench the reaction. The reaction mixture was then warmed to room
3o temperature and added dropwise with vigorous stirring to 4 liters of
hexane,
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causing a white solid to precipitate. The solid was filtered, dried,
redissolved in
toluene, filtered to remove impurities and precipitated in methanol. The
resulting white solid was a polymeric monomer having the following properties:
weight average molecular weight 10,420 and polydispersity 2.6.
Examgle 2~ Preparation of Macromer Reinforced Pressure Sensitive
Adhesive Copolymer ("MRP Adhesive")
The copolymerization reaction was carried out in a sealed, one
quart bottle. The one quart (0.95 liter) glass bottle was charged with 190
grams
of isooctyl acrylate, 4 grams of acrylic acid, 4 grams of 2-polystyrylethyl
methacrylate macromonomer prepared according to Example 1 plus 300 grams of
ethyl acetate, 0.6 grams of 2,2'-azobisisobutyronitrile (available from DuPont
of
Wilmington, DE as Vazo~ 64), and 2.5 grams of a 1 % solution of carbon
tetrabromide in isooctyl acrylate that results in a 0.012 % by weight charge
of
carbon tetrabromide. The mixture was deoxygenated by purging with nitrogen at
a rate of one liter per minute for two minutes. The bottle was sealed and
placed
in a rotating water bath for twenty-four hours at 55°C to effect
essentially
complete polymerization. The resulting copolymer was separated by partial
evaporation of the solvent, filtration and drying, then resuspended and
dissolved
2o in ethyl acetate and was used in Example 5 to form an adhesive blend useful
for
the present invention. The copolymer can also be used as a Migration Barrier
in
the present invention.
F~cam~le 3~ Preparation of an Acr~late Ester of a Polvether
An acrylate ester of a polyether containing an average of about 16
repeating ethoxy units was prepared as follows.
Two hundred eighty-eight g (0.4 m) of Carbowax~ 750 (a
methoxy polyethylene oxide) ethanol of approximately 750 MW, available from
Union Carbide Corp.) was melted in a 1000 ml round bottom flask fitted with a
so magnetic stirrer and a Dean Stark trap. Toluene, 288 g, was added to the
flask
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and the solution was refluxed, with stirring and under a nitrogen stream, for
2
hours to remove dissolved oxygen. To this solution was then added 33.8 g (0.5
m) of acrylic acid, 9.2 g of p-toluenesulfonic acid, and 0.16 g of copper
powder.
The resulting mixture was then refluxed, with stirring and under a nitrogen
s stream, for 16 hours with generated water collected in the Dean Stark trap.
The
mixture was cooled to room temperature and 10 g of calcium hydroxide was
added thereto. The mixture was stirred for 2 hours and then filtered through
an
inorganic filter aid. This polyether acrylate ester monomer was then used to
prepare copolymers as described in the examples below.
Ex~nple 4: Preparation of a Hydrophilic Adhesive
The copolymerization reaction is carried out in a sealed, four
ounce bottle. The bottle is charged with 21.0 grams of isooctyl acrylate, 9.54
grams of an acrylate ester of methoxy polyethylene oxide) ethanol of
approximately 750 molecular weight in toluene at 47.16 % solids prep~~red
according to Example 2, 4.5 grams of acrylic acid, 0.06 grams of 2,2'-
azobisisobutyronitile (available from DuPont as Vazo~ 64), 5.7 grams of
isopropanol, and 19.26 grams of ethyl acetate. The mixture is deoxygenated by
purging with nitrogen at a rate of one liter per minute for thirty-five
seconds.
2o The bottle is sealed and placed in a rotating water bath for twenty-four
hours at
55°C. to effect essentially complete polymerization. The resulting
copolymer
product was isolated using the method described in Example 2. The copolymer
product was combined with the adhesive of Example 2 and was used in Example
5 to form an adhesive blend useful for the present invention.
Example 5: Preparation of an Adhesive Blend
A mixture of 887.5 g (32 % of weight of solids) of the lvIRP
Adhesive of Example 2 (43 % solids in ethyl acetate) and 1612.5 g (68 % by
weight of solids) of the Hydrophilic Adhesive of Example 4 (50 % solids in
ethyl
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acetate) was blended in a roller mill blender under ambient conditions for 96
hours to provide a solvent blend which was homogeneous to visual inspection.
Example 6: Preparation of N-Tertiary Butyl Acr~lamide-Ethyl Acr~late
~~uolymer Migration Barrier
A pre-infix of 680.4 kg of deionized water and 177 kg of N-
tertiary butyl acrylamide was prepared by mixing at high speed until the
mixture
was uniform. The pre-mix was charged to a 1892 liter, glass-lined reactor and
agitation was set at 60 rpm. To the charged, rotating reactor was added 411.9
kg
to of ethyl acrylate, 371.9 kg of deionized water, 42.5 kg of Triton~ X-200
(available from Union Carbide, Danbury, CT), and 294 grams of carbon
tetrabromide. The reaction mixture was heated to 50°C., and
deoxygenated
using inert gas. When the temperature stabilized at 50°C, 294 grams of
potassium persulfate dissolved in 2.72 kg of deionized water were charged to
the
reactor. The reaction was allowed to generate heat exothermically, after which
the temperature was increased to 85°C and the batch was held for thirty
minutes
at 85°C. The batch was then cooled to 38°C and diluted with
deionized water to
33 % solids. The weight of solids present per unit volume was determined by
drying an aliquot of the reaction mixture, weighing the polymeric residue and
2o calculating the percent solids. The amount of water needed for the dilution
was
then calculated. 74.2 kg of Triton~ X-200 was charged to the batch and mixed
for thirty minutes after which the batch was drained through an 80 mesh screen
filter to provide a 25 % solids batch of the desired copolymer.
Example 7~ Preparation of Adhesive Blend Coated on a Release Liner
A Blended Adhesive of Example 5 was coated from a hopper knife
water of suitable size onto a 50 yard (45.7 m) length of a 4 mil (1.02 mm)
thick
and 20 in (50.8 cm) wide, silicone-coated release liner (available from
Release
International, Iowa City, IA as 211A 72# Stick-Not Grade 8527) at a coating
3o weight of 12 grains per 4 x 6 inch sample (50 grams per square meter) and
dried
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by heating in an oven at temperatures of 110°F (43°C) for Zone
1, 165°F
(74°C) for Zone 2 and 225°F (107°C) for Zone 3 at a line
speed of about 16.5
feet per minute (5.03~'/,";,~.
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Table 1
Sample:;:Porous.-:. . Migration BarrierAdhesive 'Silicone:
' :..':. .
:, ;tCoated::
Ex. None Ethyl acrylate/tertiaryAdhesive Yes
8 Blend
butylacrylamide copolymer(prepared
in
(hereinafter EA/t Ex.S)
as prepared
in Ex.6)
Ex. MeltblownEA/t (Ex.6) Adhesive Yes
9 Blend
Polyurethane (Ex.S)
Ex.lO None None Hydrophilic Yes
Adhesive
(prepared
in
Ex.4)
Ex. None EA/t (Ex.6) Hydrophilic Yes
11
Adhesive
(Ex.4)
Ex. None Polyurethane BarrierHydrophilic Yes
12
Adhesive
(Ex.4)
Ex. MeltblownPolyurethane BarrierHydrophilic Yes
13 (Ex.12)
Polyurethane Adhesive
(Ex.4)
(Ez.9)
Ex. None MRP Adhesive (describedHydrophilic Yes
14 in
Ex.2) Adhesive
(Ex.4)
Ex. None EA/t (Ex.6) with Hydrophilic Yes
15 MRP
Adhesive (Ex.2) coatedAdhesive
(Ex.4)
thereon
ControlMeltblownNone Hydrophilic Yes
Ex. Polyurethane Adhesive
16 (Ex.4)
Ex. MeltblownEA/t (Ex.6) Hydrophilic Yes
17
Polyurethane Adhesive
(Ex.4)
(Ex.9)
Pressure
Laminated
Ex. MeltblownMRP Adhesive (Ex.2) Hydrophilic Yes
18
Polyurethane Adhesive
(Ex.4)
(Ex.9)
Ex. MeltblownEA/t (Ex.6) with Hydrophilic Yes
19 MRP
PolyurethaneAdhesive (Ex.2) coatedAdhesive
(Ex.4)
(Ez.9) thereon
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Example 8: Coating Migration Barrier Layer onto Adhesive Blend
The dried adhesive cc~~ ::qlymer blend o~~ _release liner from
Example 7 was flood coated with a 3:3'~ solids batch vi the ethyl acrylate-N-
tertiary butylacrylamide copolymer made as described in Example 6 using a
s Meier bar apparatus at a line speed of about 20 yards per minute at a
coating
weight of 2 grains per 4 x 6 inch sample (8 g/m2). The article obtained was
dried at an oven temperature of 225 ° F ( 107 ° C) .
Examule 9: Preaaration of an Article of the Invention Using Blend Adhesive
to and Polyurethane Non-Woven Backing
The barrier layer/adhesive blend/release liner composite from
Example 8 was used to collect a non-woven polyurethane backing layer.
The polyurethane was melt blown using a process similar to the
process reported in Wente, Van A., "Superfine Thermoplastic Fibers" in
15 Industrial En ineering Chemistry, Vol. 48, pages 1342 et seq (1965), or in
Report No. 4364 of the Naval Research Laboratories, published May 25, 1954
titled "Manufacture of Superfine Organic Fibers", by Wente, Van A., Boone, C.
D. and Fluharty, E.L. Molten polyurethane was forced by a ram extruder
through a row of orifices that had smooth surface orifices (10/cm) with an 8:1
20 length to diameter ratio. The polyurethane was forced through the orifices
directly into two converging high velocity streams of heated air. The die
temperature was maintained at 226°C, the primary air temperature and
pressure
were 235 ° C and 150 kPa, respectively (0.76 mm gap width), and the
polymer
throughput rate was 131 gm/hr/cm. The resulting webs had an average fiber
2s diameter of about 10-15 microns, basis weight of 102 g/m2 and thickness of
about 13 mils (.33 min) and were extruded at about 14 pounds per hour (6.36 kg
per hour) directly onto the adhesive layer on a heated (88 to 93 ° C)
collector
positioned 6 inches (15.2 cm) from the die to provide a backing. The
polyurethane used for the backing was Morton PUR 440-200 (available from
3o Morton International Inc. , Chicago, IL) with 4 percent tan pigment (color
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WO 96/26251 PCTIUS96/00794
number 1093538 available from Reed Spectrum, a division of Sandoz Chemicals
Corp., Minneapolis, MN). The tape was allowed to cool under ambient
conditions.
The tape was gamma irradiated using conventional production
equipment to a total dose of about 30-35 Kilograys. The tape was tested for
MVTR and the results are provided in Table 2.
Example 10: Preparation of a Liner Coated with Hydrophilic Pressure-
Sensitive Adhesive
to A 50% solids hydrophilic adhesive from Example 4 was knife
coated from solution onto a 4 mil ( 1 mm) thick and 9 in (23 cm) wide silicone-
coated liner (as used in Example 7) at about 11 grains per 4 by 6 inch section
(46
g/m2) at a knife water gap of about 5 mil (12.6 mm). The adhesive layer was
dried as described in Example 7.
Example 11: Preparation of Migration Barrier Coated H~philic Adhesive
The adhesive coated on release liner from Example 10 was flood
coated with a coating of about 2 grains per 4 x 6 inch section (8 g/m2) of the
copolymer of ethyl acrylate/N-tertiary butylacrylamide prepared as described
in
2o Example 6 using a Meier bar water from solution The article was oven dried.
Figures 3 and 4 are scanning electron micrographs of a sample
prepared according to Example 11. Figure 3 is a 100 times magnification and
Figure 4 is a 500 times magnification of the sample. Although it is not
essential
to the present invention that the migration barrier and the adhesive layer
remain
as disinct layers, Figures 3 and 4 illustrate that the migration barrier 20 is
apparent as a distinct layer apart from the adhesive layer 22. The silicone
coated
release liner is depicted as 24 in both Figures 3 and 4.
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Example 12: Preparation of a Polyurethane Migration Barrier Layer Coated
on hydrophilic Adhesive
A batch of an aqueous (62 % solids) dispersion of a polyurethane
polymer, Witcobond-290H diluted to 31 % solids (available from Witco Corp.,
s Greenwich, CT) was flood coated using a method similar to the method
described in Example 8. That is, it was coated by pouring the polyurethane
dispersion over the adhesive side of the adhesive coated release liner article
of
Example 10 and the polyurethane was then spread with a 0.5 inch (1.27 cm)
diameter cylindrical rod to a coating weight of 2 grains per 4 x 6 inch
section
to (8g/m2). The article was dried at 225°F (107°C) in an oven
for 10 minutes.
Exam~le 13: Preparation of a Tape Article of the Invention
The article of Example 12 was coated as described in I~xample 9
with the same melt blown polyurethane backing and the collector drum used was
is heated at 180 to 190°F (82 to 88°C). The pressure-sensitive
adhesive tape
article was gamma irradiated to a total dose of 30 to 40 kilograys and. tested
for
moisture vapor transmission. Moisture vapor transmission results are provided
in Table 2.
2o Example 14: Preparation of a MiEration Barrier Iayer-Adhesive Article
A hydrophilic adhesive/silicone release liner composite prepared
as described in Example 10 was coated with a barrier layer comprising the
copolymer of Example 2 using a knife coater with a coating gap of 2 mils
(0.051
mm). The wet coating was dried at room temperature for 10 minutes, then in an
25 oven at 225°F (107°C) for 25 minutes to achieve a dry coating
weight of 6
grains per 4 by 6 inch section (24 g/m2).
Example 15: Preparation of Multiple Layer Adhesive Article
A 36 inch length (0.91 m) x 6 inch width (15.2 cm) of the
3o migration barrier/hydrophilic adhesive/liner composite described in Example
11
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was coated with a dispersion of the copolymer (MRP Adhesive) described in
Example 2 using a knife water with a gap of 2 mils (0.051 mm). The resulting
article was dried at room temperature (about 25 ° C) for 10 minutes and
then dried
in an oven at 225°F (107°C) for 25 minutes to obtain a dry
coating weight of 6
s grains per 4 by 6 inch section (24 g/m2).
Comparative Example 16~ Preparation of a Control Tape Article
A polyurethane non-woven web was melt blown using the method
described in Example 9 to provide a nonwoven web with a basis weight of 120
to g/m, a thickness of 15.8 mil (0.40 mm) and an average fiber diameter of
about
10-15 microns. The nonwoven web was then pressure laminated onto the
hydrophilic adhesive on silicone-coated liner prepared as described in Example
10. The lamination was accomplished at room temperature and at a pressure of
20 psi with a line speed of 3 feet (0.91 m) per minute. A portion of this
sample
15 was gamma irradiated at 30 to 35 kGy total dose to crosslink the adhesive.
The
irradiated portion of the sample was tested for MVTR and the results are
provided in Table 2.
Figure 1 is a scanning electron micrograph of the sample prepared
according to Example 16. The sample shown in Figure 1 was held for 14 days at
20 120°F at 90% relative humidity. These are the parameters at which
samples are
generally held to accelerate the aging process. Eleven days at 120°F
(49°C) and
90% relative humidity is considered a good approximation of one year aging
under ambient conditions. Since the sample in Figure 1 lacks the migration
barrier, the adhesive 14 freely migrates into the interstices of the nonwoven
web
25 16 and settles between the individual fibers 18 which comprise the nonwoven
web 16.
Example 17~ Preparation of a Tape Article of the Invention
The article of Example 11 (migration barrier of ethyl acrylate/N-
3o tertiary butylacrylamide copolymer/Hydrophilic Adhesive/liner composite)
was
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coated with the same melt blown polyurethane backing as described in Example
9. The backing had a basis weight of 122 g/m, web thickness of 15.7 mil (0.40
mm) and effective fiber diameter of 17.8 microns. The collector drum was
heated to about 190 to 200°F (88 to 93°C). The pressure-
sensitive adhesive tape
s article was gamma irradiated to a total dose of 30 to 35 kGy and tested for
moisture vapor transmission. The resulting article had an acceptable moisture
vapor transmission rate and results are given in Table 2.
Example 18: Preparation of a Porous Backing Tage Article of the lfnvention
to The article of Example 14 (migration barrier of the isooctyl
acrylate-acrylic acid-macromer copolymer of Example 2 coated on the
hydrophilic adhesive of Example 4 on a silicone-coated liner) was coated as
described in Example 9 with the same melt blown polyurethane backing at the
same basis weight, web thickness and effective fiber diameter but the
collector
15 drum was not heated. The resultant composite was dried in an oven as
detailed
in Example 7. The dried article was gamma irradiated to a total dose of 30 to
35
kilograys. The article was tested for MVTR and the results are shown in Table
2.
Figures 2 and 5 are scanning electron micrographs of the sample
2o prepared according to Example 17 and held for 14 days at 120 ° F and
90
relative humidity (accelerated aging described above in Example 16). At the
500
times magnification used for Figure 2, the migration barrier is not evident as
a
distinct layer apart from the adhesive layer. However, Figure 2 shows that the
adhesive (10) does not migrate into the interstices of the nonwoven backing 12
2s comprised of fibers 17. Figure 5 (900x magnification) more clearly shows
the
migration barrier 30 as a distinct layer apart from the adhesive 32. Figure 5
also
shows that the adhesive 32 does not flow into the interstices of the nonwoven
web 34 comprised of fibers 37. The migration barrier 30 shown best in Figure 5
is about 6-7~m thick.
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Example 19: Preparation of a Tape Article
The article of Example 15 (first layer of silicone-coated liner,
second layer of hydrophilic adhesive, third layer of ethyl acrylate/N-tertiary
butylacrylamide copolymer migration barrier and fourth layer of isooctyl
acrylate-acrylic acid-macromer copolymer) was used to collect a melt blown '
polyurethane backing prepared as described in Example 9 at the same basis
weight, web thickness and fiber diameter but the collector drum was not
heated.
The finished article was gamma irradiated to a total dose of 30 to 35
kilograys.
The resultant article was tested for MVTR and the results are provided in
Table
2.
Example 20:
The moisture vapor transmission rate of the tape articles described
in Examples 9, 13, 16, 17, 18 and 19 above was measured using the test method
described above.
The results are shown in Table 2.
Table 2
A~t'~'~CrLE ~F:~XANiPLE Nt'~. MVTR, (glm~l?.4 hours3'
:.:
Example 16 (Control) 712.8
Example 9 689.9
Example 13 809.6
Example 17 933.6
Example 18 581.1
Example 19 594.1
The conclusion derived from this data is that MVTR is not
2o substantially reduced by the presence of a barrier layer.
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The migration barriers were examined by scanning electron
microscope. For examples 9, 13, ~~', 18 and 19~a barrier was detected,
preventing the migration of adhesive into the interstices of the porous
backing.
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