Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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ACRYLIC PRESSURE-SENSITIVE ADHESIVE
FTELD OF THE INVENTION
This invention relates to pressure-sensitive adhesive compositions, and,
more particularly, pressure-sensitive adhesive compositions formed from at
least
two polymeric materials at least one of which is a pressure-sensitive
adhesive, and
to methods for making pressure-sensitive adhesives and articles having
pressure-
sensitive adhesives components.
BACKGROUND OF THE INVENTION
Pressure-sensitive adhesive tapes have been used for more than half a
century for a variety of marking, holding, protecting, sealing and masking
purposes. Pressure-sensitive adhesive tapes comprise a backing, or substrate,
and
a pressure-sensitive adhesive. Pressure-sensitive adhesives are materials
which
adhere with no more than applied finger pressure and are aggressively and
permanently tacky. Pressure-sensitive adhesives require no activation other
than
the finger pressure, exert a strong holding force and should be removable from
a
smooth surface without leaving a residue.
Some of the earliest applications of adhesives in the medical field, where
the product was referred to as an adhesive plaster, were not pressure-
sensitive
adhesives. These were, in fact, crude mixtures of natural rubber plasticized
and
tackified with wood resin derivatives and turpentine and heavily pigmented
with
zinc oxide. These tape-like products served their purpose but, with the advent
of
the truly pressure-sensitive adhesives they were replaced.
In the medical field, pressure-sensitive adhesive tapes are used for many
different applications in the hospital and health areas, but basically they
perform
one of two functions. They are used to pull something in place, restricting
movement such as in various strapping applications, or they are used to hold
something in place, such as a wound dressing. It is important in each fimction
that
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the pressure-sensitive adhesive tape be compliant with and non-irntating to
the
skin and adhere well to the skin without causing skin damage on removal.
Similarly, early electrical tapes were black friction tape which is not
pressure-sensitive; the adhesive is very soft and it splits when unwound. With
the
development of truly pressure-sensitive adhesives, these were also replaced. .
Generally, more current electrical tape has a pressure-sensitive adhesive
applied to
a plasticized polyvinyl chloride backing or a polyethylene or rubber film
backing.
Electrical tape is used to insulate, hold, reinforce and protect electrical
wires.
Other uses include providing a matrix for varnish impregnation, identifying
wires
in electrical circuitry, and protecting terminals during manufacture of
electrical
circuit boards. With electrical tape, it is important that the tape be
stretchable,
conformable and meet nonflammability requirements.
Packaging applications require a large variety of tapes for uses such as
closing packages, protecting labels, sealing packages from moisture, and
strapping
and bundling loose parts. Packaging tapes are subjected to continuous shear
and
low angle peel forces. Generally, if the adhesive mass is of low cohesive
strength,
it fails in shear; if the shear resistance is improved by adding firmness to
the
adhesive, it has tendency to be less tacky and fail adhesively.
Pressure-sensitive adhesives require a delicate balance of viscous and
elastic properties which result in a four-fold balance of adhesion, cohesion,
stretchiness and elasticity. Pressure-sensitive adhesives generally comprise
elastomers which are either inherently tacky, or elastomers or thermoplastic
elastomers which are tackified with the addition of tackifying resins. They
can be
coated in solvent or as water-based emulsions to reduce the material viscosity
to a
level that is easily applied to a substrate of choice.
Major classes of pressure-sensitive adhesives include tackified natural
rubbers; synthetic rubbers such as butyl rubber; and tackified linear, radial,
star,
branched and tapered block copolymers such as styrene-butadiene, styrene-
ethylene/butylene and styrene-isoprene; polyvinyl ethers; acrylics, especially
those ,
having long chain alkyl groups; poly-oc-olefins; and silicones.
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Generally, when additives are used to enhance properties of pressure-
sensitive adhesives they are required to be miscible with the pressure-
sensitive
adhesive or to have some common blocks or groups to permit homogeneous
blends to form at the molecular level. Pressure-sensitive adhesives have been
modified to extend their applicability into new areas. Tackified thermoplastic
elastomers have been dissolved in acrylic monomers and subsequently cured.
Tackified thermoplastic elastomers have also been added to polymerized acrylic
pressure-sensitive adhesives in solvent where each component contains a common
segment to permit compatibility. The general purpose is to combine the high
shear
properties of elastomers with the high tack performance of acrylics. Further
improvements and better balance of properties continue to be sought.
SUMMARY OF THE INVENTION
The present invention provides a pressure-sensitive adhesive composition
comprising a blend of about 5 to 95 weight percent of at least one acrylic
pressure-sensitive adhesive and about 5 to 95 weight percent of at least one
thermoplastic elastomeric material, said composition having a morphology
comprising at least two distinct domains, a first domain being substantially
continuous in nature and said second domain being fibrillose to schi:>tose in
nature
parallel to the major surface of the adhesive composition within said first
domain.
The thermoplastic elastomeric material may optionally contain a taclcifying
resin or
plasticizer, in which case it also may be an adhesive.
The present invention further provides a process for preparing a pressure-
sensitive adhesive composition comprising the steps of
(1) melt blending about 5 to 95 weight percent of at least one acrylic
pressure-sensitive adhesive and about 5 to 95 weight percent of at
least one thermoplastic elastomeric material,
(2) (a) forming said melt blended materials under shear and
extensional conditions or
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(b) forming and drawing said melt blend
to form a pressure-sensitive composition having a morphology comprising
at least two distinct domains, a first domain being substantially continuous
in nature and said second domain being fibrillose to schistose in nature
parallel to the major surface of the adhesive within said first domain, and
(3) allowing said composition to cool.
The present invention further provides a pressure-sensitive adhesive tape
comprising a substrate with a pressure-sensitive adhesive composition
comprising
a blend of about 5 to 95 weight percent of acrylic pressure-sensitive adhesive
and
about 5 to 95 weight percent of thermoplastic elastomeric material, said
composition having a morphology comprising at least two distinct domains, a
first
domain being substantially continuous in nature and said second domain being
fibrillose to schistose in nature parallel to the major surface of the
adhesive within
said first domain on the face of the substrate.
The present invention also provides an electrical pressure-sensitive
adhesive tape comprising a substrate and on the substrate a pressure-sensitive
adhesive composition comprising a blend of about 5 to 95 weight percent of
acrylic pressure-sensitive adhesive and about 5 to 95 weight percent of
thermoplastic elastomeric material, said composition having a morphology
comprising at least two distinct domains, a first domain being substantially
continuous in nature and said second domain being fibrillose to schistose in
nature
parallel to the major surface of the adhesive within said first domain. The
substrate is preferably a polyvinyl chloride film or a film of a blend of
ethylene-
vinyl acetate and ethylene-propylene-diene rubber.
The present invention also provides a process for preparing a pressure-
sensitive adhesive tape comprising the steps of
(1) melt blending about 5 to 95 weight percent of at least one acrylic
pressure
sensitive adhesive and about 5 to 95 weight percent of at least one
thermoplastic elastomeric material,
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(2) (a) forming said melt blended materials under shear or extensional
conditions or both or
(b) forming and drawing said melt blend,
said blend forming an adhesive composition and said composition being
extruded onto a face of a substrate to form a pressure-sensitive adhesive
tape, said adhesive having a morphology comprising at least two distinct
domains, a first domain being substantially continuous in nature and said
second domain being fibrillose to schistose in nature in the adhesive
forming direction within said first domain, and
(3) allowing said adhesive to cool.
The present invention also provides a process for preparing a pressure-
sensitive adhesive tape comprising the steps of
(1) melt blending about 5 to 95 weight percent of at least one acrylic
pressure-sensitive adhesive and about 5 to 95 weight percent of at
least one thermoplastic elastomeric material,
(2) (a) forming said melt blended materials under shear or
extensional conditions or both or
(b) forming and drawing said melt blend to form a pressure-
sensitive adhesive composition and
(c) coextruding a film forming polymeric resin with said
adhesive composition,
said adhesive composition having a morphology comprising at least two
distinct domains, a first domain being substantially continuous in nature
and said second domain being fibrillose to schistose in natur<; in the
adhesive forming direction within said first domain, and
(3) allowing said composition and said polymeric resin to cool.
The present invention also provides a double coated pressure-sensitive
adhesive tape comprising a substrate having on a first face a pressure-
sensitive
adhesive composition comprising a blend of about 5 to 95 weight percent of an
acrylic pressure-sensitive adhesive and about 5 to 95 weight percent of a
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thermoplastic elastomeric material, said composition having a morphology
comprising at least two distinct domains, a first domain being substantially
continuous in nature and said second domain being fibrillose to schistose in
nature
parallel to the major surface of the adhesive within said first domain and
having on
a second face a pressure-sensitive adhesive which may be the same or different
,
from that on the first face.
The present invention still fizrther provides a process for forming a double
coated pressure-sensitive adhesive tape comprising the steps of
(1) melt blending about S to~95 weight percent of at least one acrylic
pressure-sensitive adhesive and about 5 to 95 weight percent of a
thermoplastic elastomeric material,
(2) (a) forming said melt blended materials under shear or
extensional conditions or both or
(b) forming and drawing said melt blend, to form a pressure-
sensitive adhesive composition,
said composition being fed to the outer portions of a feed block having at
least three layers and a film forming polymeric resin being fed to a middle
portion of said feed block to form a double-coated pressure-sensitive
adhesive tape, said adhesive composition having a morphology comprising
at least two distinct domains, a first domain being substantially continuous
in nature and said second domain being fibrillose to schistose in nature in
the adhesive forming direction within said first domain, and
(3) allowing said tape to cool.
The present invention also provides a pressure-sensitive adhesive
composition for adhesion to skin comprising a substrate and on the substrate a
pressure-sensitive adhesive composition comprising a blend of about 5 to 95
weight percent of acrylic pressure-sensitive adhesive and about 5 to 95 weight
percent of thermoplastic elastomeric material, said composition having a
morphology comprising at least two distinct domains, a first domain being ,
substantially continuous in nature and said second domain being fibrillose to
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schistose in nature parallel to the major surface of the
adhesive within said first domain. Suitable substrates, or
backings include occlusive, i.e., substantially non-
breathable, backings such as, for example, films, foam
materials and laminates thereof, and non-occlusive, i.e.,
breathable, backings such as, for example, perforated
polymeric film, woven fabrics, nonwoven fabrics such as
hydroentangled or melt blown webs and thermally embossed
nonwoven webs.
Increased peel adhesion over the acrylic pressure-
sensitive adhesive alone and solution blended
acrylic/thermoplastic elastomeric pressure-sensitive
adhesives can be observed when the continuous domain is a
pressure-sensitive adhesive and the fibrillose to schistose,
i.e., discontinuous or co-continuous domain has elastic
properties but is not pressure-sensitive. Controlled tack
and peel adhesion properties can be observed when the
continuous domain is not a pressure-sensitive adhesive.
When each of the polymeric materials is a pressure-sensitive
adhesive, the composition exhibits enhanced peel adhesion
over similar blends of pressure-sensitive adhesives formed
and coated from solvent.
According to one aspect of the present invention,
there is provided a pressure-sensitive adhesive composition
comprising a blend of about 5 to 95 weight percent of an
acrylic pressure-sensitive adhesive and about 5 to 95 weight
percent of a thermoplastic elastomeric copolymer, said
composition having a morphology comprising at least two
distinct domains, a first domain being substantially
continuous and said second domain being one or both of
fibrillose and schistose.
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According to another aspect of the present
invention, there is provided a process for preparing a
pressure-sensitive adhesive comprising the steps of (1) melt
blending 5 to 95 weight percent of at least one acrylic
pressure-sensitive adhesive and 5 to 95 weight percent of at
least one thermoplastic elastomeric material, (2) (a)
forming said melt blended materials under shear or
extensional conditions or both or (b) forming and drawing
said melt blend to form a pressure-sensitive adhesive
composition having a morphology comprising at least two
distinct domains, a first domain being substantially
continuous and said second domain being one or both of
fibrillose and schistose, and (3) allowing said composition
to cool.
According to still another aspect of the present
invention, there is provided a pressure-sensitive adhesive
electrical tape comprising a polyvinyl chloride substrate or
a substrate film of a blend of ethylene-vinyl acetate and
ethylene-propylene-dime rubber and on the substrate, a
pressure-sensitive adhesive composition comprising a blend
of about 5 to 95 weight percent of an acrylic pressure-
sensitive adhesive and about 5 to 95 weight percent of a
thermoplastic elastomeric block copolymer, said composition
having a morphology comprising at least two distinct
domains, a first domain being substantially continuous and
said second domain being one or both of fibrillose and
schistose.
According to yet another aspect of the present
invention, there is provided a pressure-sensitive adhesive
tape comprising a substrate and on the substrate the
pressure-sensitive adhesive composition described herein on
which the fibrillose or schistose morphology lies parallel
to the substrate.
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According to a further aspect of the present
invention, there is provided a double coated pressure-
sensitive adhesive tape comprising a substrate and on a
first face of the substrate the pressure-sensitive adhesive
composition described herein and on a second surface of said
substrate, a pressure-sensitive adhesive.
According to yet a further aspect of the present
invention, there is provided a process for preparing a
pressure-sensitive adhesive tape comprising the steps of (1)
melt blending 5 to 95 weight percent of at least one acrylic
pressure-sensitive adhesive and 5 to 95 weight percent of at
least one thermoplastic elastomeric material, (2) (a)
forming said melt blended materials under shear or
extensional conditions or both or (b) forming and drawing
said melt blend, said blend forming an adhesive composition
and said composition being extruded onto a substrate to form
a pressure-sensitive adhesive tape, said adhesive having a
morphology comprising at least two distinct domains, a first
domain being substantially continuous and said second domain
being one or both of fibrillose and schistose in the
adhesive forming direction, and (3) allowing said adhesive
to cool.
According to still a further aspect of the present
invention, there is provided a process for preparing a
pressure-sensitive adhesive tape comprising the steps of (1)
melt blending 5 to 95 weight percent of at least one acrylic
pressure-sensitive adhesive and 5 to 95 weight percent of at
least one thermoplastic elastomeric material, (2) (a)
forming said melt blended materials under shear or
extensional conditions or both or (b) forming and drawing
said melt blend to form a pressure-sensitive adhesive
composition and coextruding a film forming polymeric resin
with said adhesive composition, said adhesive composition
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having a morphology comprising at least two distinct
domains, a first domain being substantially continuous and
said second domain being one or both of fibrillose and
schistose in the adhesive forming direction, and (3)
allowing said composition and said polymeric resin to cool.
According to another aspect of the present
invention, there is provided a process for forming a double
coated pressure-sensitive adhesive tape comprising the steps
of (1) melt blending 5 to 95 weight percent of at least one
acrylic pressure-sensitive adhesive and 5 to 95 weight
percent of at least one thermoplastic elastomeric material,
(2) (a) forming said melt blended materials under shear or
extensional conditions or both or (b) forming and drawing
said melt blend, to form a pressure-sensitive adhesive
composition, said composition being fed to the outer
portions of a feed block having at least three layers and a
film forming polymeric resin being fed to a middle portion
of said feed block to form a double-coated pressure-
sensitive tape, said adhesive composition having a
morphology comprising at least two distinct domains, a first
domain being substantially continuous and said second domain
being one or both of fibrillose and schistose in the
adhesive forming direction, and (3) allowing said tape to
cool.
According to yet another aspect of the present
invention, there is provided a pressure-sensitive adhesive
tape for adhesion to skin comprising a substrate and on the
substrate a pressure-sensitive adhesive composition
comprising a blend of about 5 to 95 weight percent of
acrylic pressure-sensitive adhesive and about 5 to 95 weight
percent of thermoplastic elastomeric material, said
composition having a morphology comprising at least two
distinct domains, a first domain being substantially
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continuous and said second domain being one or both of
fibrillose and schistose parallel to the substrate.
The pressure-sensitive adhesives of the present
invention are useful in such applications as in medical
tapes; in box sealing tape; in electrical tape; and in
repositionable tapes, removable tapes, and sheet materials.
By proper selection of the polymeric materials, a variety of
desirable end use properties can be designed into the
adhesive. When used as adhesives for contact with skin, the
compositions of the invention have enhanced initial adhesion
over acrylic pressure-sensitive adhesives or the
thermoplastic elastomeric material. Further, the aged
adhesion to skin can be manipulated by, for example,
adjusting the relative amounts of the acrylic pressure-
sensitive adhesive and thermoplastic elastomer components.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view of the adhesive
layer of Example 5 taken along the film forming directional
1000X using scanning electron microscopy (SEM).
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FIG. 2 is a surface view of the adhesive layer of Comparative Example C6
at lOX using optical microscopy.
FIG. 3 is a cross-sectional view of the adhesive layer of Example 7 taken
along the film forming direction at 6000X using transmission electron
microscopy
(TEM).
FIG. 4 is a cross-sectional view of the adhesive layer of Example 8 taken
along the film forming direction at 6000X using TEM.
FIG. S is a cross-sectional view of the adhesive layer of Example 9 taken
along the film forming direction at 6000X using TEM.
FIG. 6 is a cross-sectional view of the adhesive layer of Example 11 taken
along the film forming direction at 3000X using SEM.
FIG. 7 is a cross-sectional view of the adhesive layer of Example 13 taken
along the film forming direction at 2000X using SEM.
FIG. 8 is a cross-sectional view of the adhesive layer of Example 13 taken
along the cross web direction at 2000X using SEM.
FIG. 9 is a cross-sectional view of the adhesive layer of Example 18 taken
along the film forming direction at 1000X using SEM.
FIG. 10 is a cross-sectional view of the adhesive layer of Example 18
taken along the cross web direction at 1000X using SEM.
FIG. 11 is a cross-sectional view of the adhesive layer of Example 22
taken along the film forming direction at 2000X using SEM.
FIG. 12 is a cross-sectional view of the adhesive layer of Example 22
taken along the cross web direction at 2000X using SEM.
FIG. 13 is a cross-sectional view of the adhesive layer of Example 40
taken along the film forming direction at 1000X using SEM.
FIG. 14 is a plot of the dynamic mechanical analysis of Examples 24 - 26.
DETAILED DESCRIPTION OF TFIE INVENTION
Acrylic pressure-sensitive adhesives generally have a glass transition
temperature of about -20°C or less and may comprise from 100 to 80
weight
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percent of a C3-C~2 alkyl ester component such as, for
example, isooctyl acrylate, 2-ethyl-hexyl acrylate and
n-butyl acrylate and from 0 to 20 weight percent of a polar
component such as, for example, acrylic acid, methacrylic
acid, ethylene vinyl acetate, N-vinyl pyrrolidone and
styrene macromer. Preferably, the acrylic pressure-
sensitive adhesives comprise from 0 to 20 weight percent of
acrylic acid and from 100 to 80 weight percent of isooctyl
acrylate. The acrylic pressure-sensitive adhesives may be
self tacky or tackified. Useful tackifying resins for
acrylics are rosin esters such as FORALTM 85, available from
Hercules, Inc., aromatic resins such as PICCOTEXTM LC-55WK,
available from Hercules, Inc., aliphatic resins such as
ESCOREZTM 1310LC, available from Exxon Chemical Co.
The second component of the pressure-sensitive
adhesive compositions of the present invention is a
thermoplastic elastomeric material which is blended with the
acrylic pressure-sensitive adhesive. Thermoplastic
elastomeric materials are materials which contain at least
two segments, i.e., a hard segment and a soft segment, have
a glass transition temperature greater than 50°C and exhibit
elastic properties in one of the segments. The material is
selected such that it is sufficiently incompatible and
nonreactive with the pressure-sensitive adhesive at the use
temperature to result in the pressure-sensitive adhesive
composition having at least two distinct domains. Of
course, more than one second component may be combined with
the pressure-sensitive adhesive. The second component may
or may not also be a pressure-sensitive adhesive.
Thermoplastic elastomeric materials useful in the
present invention may comprise linear, radial, star, tapered
or branched copolymers and include, for example, linear,
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radial, star and tapered styrene-isoprene block copolymers
such as KRATONTM D1107P, available from Shell Chemical Co.
and EUROPRENETM SOL TE 9110, available from EniChem
Elastomers Americas, Inc., linear styrene-(ethylene
butylene) block copolymers such as KRATONTM 61657, available
from Shell Chemical Co., linear styrene-(ethylene-propylene)
block copolymers such as KRATONTM 61657X, available from
Shell Chemical Co., styrene-isoprene-styrene block
copolymers such as KRATONTM D1119P, available from Shell
Chemical Co., linear, radial, and star styrene-butadiene
block
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copolymers such as KRATONTM Dl 118X, available from Shell Chemical Co.,
EUROPRENETM SOL TE 6205, available from EniChem Elastomers Americas,
Inc., polyetheresters such as HY7:'RELTM 63548, available from DuPont Co., and
poly-a-olefin-based thermoplastic elastomeric materials such as those
represented
by the formula -(CH2 CHR)X where R is an alkyl group containing 2 to 10 carbon
atoms and poly-a-olefins based on metallocene catalysis such as ENGAGETM
EG8200, an ethylene/1-octene copolymer available from Dow Plastics Co.
These thermoplastic elastomeric materials can be modified with tackifying
resins or plasticizers to lower their melt viscosity to facilitate the
formation of fine
dispersions, with the smallest phase dimension preferably less than about 20
microns when blended with the acrylic pressure-sensitive adhesive. Tackifying
resins or plasticizers usefizl with the thermoplastic elastomeric materials
are
preferably miscible at the molecular level, i.e., soluble in, any or all of
the
polymeric segments of the thermoplastic elastomeric material. The tackifying
resins or plasticizers may or may not be miscible with the acrylic pressure-
sensitive
adhesive. The tackifying resin, when present can generally comprises about 5
to
300 parts by weight, more typically up to about 200 parts by weight, based on
100
parts by weight of the thermoplastic elastomeric material.
The acrylic pressure-sensitive adhesive and the thermoplastic elastomeric
material are blended and coated using melt extrusion techniques. Mixing can be
done by any method that results in a substantially homogeneous distribution of
the
acrylic pressure-sensitive adhesive and the thermoplastic elastomeric material
.
The blend of the acrylic pressure-sensitive adhesive and the thermoplastic
elastomeric material is prepared by melt mixing the components in the molten
or
softened state using devices that provide dispersive mixing, distributive
mixing, or
a combination of dispersive and distributive mixing. Both batch and continuous
methods of blending may be used. Examples of batch methods include
BrabenderTM or BanburyTM internal mixing, and roll milling. Examples of
continuous methods include single screw extruding, twin screw extruding, disk
extruding, reciprocating single screw extruding, and pin barrel single screw
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extruding. The continuous methods can include both distributive elements such
as
cavity transfer elements such as CTMTM, available from RAPRA Technology,
Ltd., Shrewsbury, England, pin mixing elements, and static mixing elements and
dispersive elements such as Maddock mixing elements or Saxton mixing elements.
After the mixing step, the softened or molten acrylic pressure-sensitive
adhesive and thermoplastic elastomeric material blend is formed into coatings
which have a morphology such that the pressure-sensitive adhesive i.-'orms a
substantially continuous domain and the thermoplastic elastomeric material
forms
a domain which is fibrillose to schistose in nature by processes that involve
either
shear or extensional deformations or both. When a tackifying agent is blended
with the thermoplastic elastomeric material such that this too is now an
adhesive
material, then either adhesive domain may be continuous or the domains may be
co-continuous. These processes may be either batch or continuous.
An example of a batch process is the placement of a portion of the blend
between the desired substrate to be coated and a release liner, pressing this
composite structure in a heated platen press with sufficient temperature and
pressure to form a pressure-sensitive coating of the desired thickness and
cooling
the resulting coating.
Continuous forming methods include drawing the pressure-sensitive
adhesive composition out of a film die and subsequently contacting a moving
plastic web or other suitable substrate. A related continuous method involves
extruding the pressure-sensitive adhesive composition and a coextruded backing
material from a film die and subsequently cooling to form a pressure-sensitive
adhesive tape. Other continuous forming methods involve directly contacting
the
pressure-sensitive adhesive blend to a rapidly moving plastic web or other
suitable
substrate. In this method, the pressure-sensitive adhesive blend can be
applied to
the moving web using a die having flexible die lips such as a reverse orifice
coating
die. After forming, the pressure-sensitive adhesive coatings are solidified by
quenching using both direct methods, such as chill rolls or water baths, and
indirect methods, such as air or gas impingement.
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Preferably, each of the polymeric components has similar melt viscosity.
The ability to form a finely dispersed morphology is related to the viscosity
ratio
and concentration of the components. The shear viscosity is determined using
capillary rheometry at a shear rate approximating extrusion blending
conditions,
i.e., 100s'' and 175°C. When a higher viscosity polymeric material is
present as
the minor component, the viscosity ratio of the minor component to the major
component is preferably less than about 20:1, more preferably less than about
10:1. When a lower viscosity polymeric material is present as the minor
component, viscosity ratios of the minor component to the major component are
preferably greater than about 1:10, more preferably greater than about 1:5.
The
melt viscosities of individual polymeric materials may be altered by the
addition of
plasticizers, tackifying resins or solvents or by varying mixing temperatures.
If the
use of solvent is required, the solvent is preferably removed before the
coating
step to prevent foaming.
It is also preferable that at least one of the polymeric materials be easily
extended in the melt blending and coating operations to form a finely
dispersed
morphology with domains which are fibrillose to schistose, e.g., forming
sheets,
ribbons, fibers, ellipsoids or the like, oriented in the web formation
direction in the
substantially continuous or co-continuous domain of the other polymeric
material.
Sufficient interfacial adhesion between the acrylic pressure-sensitive
adhesive
component and the thermoplastic elastomeric component preferably exists to
withstand the shear and extensional deformation present during the forming
step
and to promote formation of a continuous film.
If none of the polymeric materials can be easily extended in the melt
blending and coating or sufficient interfacial adhesion is not present, a
pressure-
sensitive adhesive coating may be produced which has gross discontinuities and
is
grainy in texture. Through use of suitably selected conditions of mixing,
closeness
of melt viscosities, and shear/stretch conditions during extrusion, the
thickness of
the fibrillose to schistose domains can be made sufficiently thin that
delamination
from the substantially continuous or cocontinuous domain will not occur.
r
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Preferably, the thickness of the fibrillose to schistose domains is less than
about 20
microns, more preferably less than about 10 microns, and most preferably less
than
about 1 micron although the size will vary depending on specific blends, i.e.,
polymer types, concentration, viscosity, and the like.
This invention is fiarther illustrated by the following examples which are
not intended to limit the scope of the invention. In the examples, all parts,
ratios
and percentages are by weight unless otherwise indicated. The following test
methods were used to evaluate and characterize polymeric materials and the
pressure-sensitive adhesive compositions produced in the examples.
Shear Viscosity
Shear viscosity was determined using a high pressure capillary rheometer
(RHEOGRAPH 2001, available from Gottfert Co.) operated with a capillary die
30 mm long and 1 mm in diameter at a temperature of 175°C. At a 100s''
shear
rate, the apparent viscosity was calculated from Poiseuille's equation and
converted to true viscosity using the Weissenberg-Rabinovitch correction.
180° Peel Adhesion Test
Pressure-sensitive adhesive tape samples 1.25 cm wide and 15 cm long
were tested for 180° peel adhesion to glass and/or smooth cast
biaxialliy oriented
polypropylene films. The samples were adhered to the test surfaces by rolling
the
tapes with a 2.1 Kg (4.5 1b.) roller using 4 passes. After aging at ambient
temperatures (~22°C) for approximately 1 hour, the tapes were tested
using a
Model 3M90 slip/peel tester, available from Instrumentors, Inc., in
180° geometry
at 30.5 cm/min (12 in/min) peel rate, unless otherwise noted.
Shear Strength Test
Shear strength was measured on pressure-sensitive adhesive tape samples
at ambient temperatures. A 12.7 mm x 12.7 mm (0.5 in x 0.5 in) section of the
tape was adhered to a stainless steel sheet with a 2.1 Kg (4.5 Ib.) roller
using 4
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passes. A 1000 gram weight was adhered to the sample. The amount of time for
the weight to drop was recorded.
Rolling Ball Tack Test
The rolling ball tack test was performed according to Pressure-Sensitive
Tape Council Test PSTC-6 wherein a 7/16 inch steel ball was rolled down an
inclined (21 °30') runway onto a sample of tape placed at the bottom of
the runway
on a flat surface. The result was the distance the ball rolls on the tape
before
stopping.
Electrical Tape Adhesion Test
Pressure-sensitive adhesive electrical tape samples were tested against steel
panel (adhesion to steel) and against web material (adhesion to backing) at a
speed
of 30.5 cm/min according to the American Society for Testing and Materials
(ASTM) Standard Methods of Testing Pressure-Sensitive Adhesive-Coated Tapes
Used for Electrical Insulation, ASTM D 1000-79, Procedure A.
Skin Adhesion Test
Skin adhesion testing was carned out by placing tape samples 2.5 cm
wide by 7.5 cm long on the back of a human subject. Each tape was rolled down
with one forward and one reverse pass using a 2 Kg roller moved at a rate of
about 30 cm/min. Adhesion to the skin was measured as the peel force required
to remove the tape at 180° angle at a 15 cm/min rate of removal.
Adhesion was
measured immediately after initial application (To) and after either 24 hours
(T2a)
or 48 hours (T48). Preferred skin adhesion generally exhibits a To of between
about 30 and 100 grams (1.2 to 3.8 N/dm), a T24 of between about 150 and 300
grams (5.8 to 11.5 N/dm), and a T4g of between about 150 and 300 grams (5.8 to
11.5 N/dm).
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Skin Adhesion Lift Test
When either the 24 hour or 48 hour skin adhesion test was performed,
the tape sample was examined for the amount of area that was lifted (released)
A
from the skin prior to removal of the tape and ratings were given as:
- 5 0 no visible lift
1 lift only at edges of tape
2 lift over 1% to 25% of test area
3 lift over 25% to 50% of test area
4 lift over 50% to 75% of test area
5 lift over 75% to 100% of test area
Results of 9 tests were averaged. Preferred skin adhesives will generally
exhibit
an average rating below about 2.5.
Skin Adhesive Residue Test
When either the 24 hour or 48 hour skin adhesion test was performed,
the skin underlying the tape sample was visually inspected to determine the
amount of adhesive residue on the skin surface and was rated as:
0 no visible residue
1 residue only at edges of tape
2 residue covering 1% to 25% of test area
3 residue covering 25% to 50% of test area
4 residue covering 50% to 75% of test area
S residue covering 75% to 100% of test area
Results of 9 tests were averaged. Preferred skin adhesives will generally
exhibit
an average rating below about 2.5.
Examples 1-6 and Comparative Example Cl
In Example 1, an acrylic pressure-sensitive adhesive (95 weight percent
isooctyl acrylate/5 weight percent acrylic acid, water emulsion polymerized,
shear
viscosity - 150 Pa-s), prepared according to U.S. Pat. No. RE 24,906, (Ulrich)
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and dried, and thermoplastic
elastomeric KItATONTM D 1107P (styrene-isoprene-styrene block copolymer,
shear viscosity 1250 Pa-s) which was preblended with 1 weight percent
IRGANOX'~'M 1010 antioxidant, available from Ciba-Geigy Corp. were melt-
blended in a 34 mm diameter fully intermeshing co-rotating twin-screw extruder
(LEISTRTTZTM Model LSM34GL, available from Leistritz, Inc.). The
thermoplastic elastomeric block copolymer was introduced into the feed throat
of
the extruder and the acrylic pressure-sensitive adhesive was introduced in
zone 4.
The temperature was progressively increased from 38°C to
177°C (100°F to
350°F) from zone 1 to zone 4. The temperature of the remaining zones
was
maintained at 177°C to 191°C (350°F to 375°F). The
feed rates were adjusted to
provide a ratio of pressure-sensitive adhesive to thermoplastic elastomeric
block
copolymer of 75:25.
The twin-screw eactruder was continuously discharged at a pressure of at
least about 0.69 MPa (100 psi) into a three-layer feed block (CLOEItENTM Model
92-1033, available from The Cloeren Co.) mounted on a 25.4 cm (10 inch) wide
film die (UTLTRAFLEXT~ 40 die, Model 89-12939, available from Extrusion
Dies, Inc.). The die was maintained at 177°C to 191°C
(350°F to 375°F) and the
die gap was 0.5 to 0.8 mm (20 to 30 mils). The blended adhesive composition
was extruded through the outer two portions of the feed block, with the center
portion of the feed block not used, and was fed between a 51 pm (2 mil) thick
biaxially oriented polyethylene terephthalate film and a release coated paper
web
at a rate of 6.4 Kg/hr ( 14 lbs/hr). The film and the web were fed at a rate
of 7.3
m/min (24 fpm) between chill rolls maintained at a temperature of 21 °C
(70°F) to
form a pressure-sensitive adhesive tape. In Examples 2, 3 and 4, the
thermoplastic
elastomeric block copolymer, KRATONTM D1117P (styrene-isoprene-styrene
block copolymer; shear viscosity 690 Pa-s) preblended with 1 weight percent
IRGANOXTM 1010, was added to the acrylic pressure-sensitive adhesive at ratios
of acrylic adhesive to thermoplastic elastomeric block copolymer of 75:25,
63:37,
and 25:75, respectively. In Example 5, the thermoplastic elastomeric block
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copolymer was KRATONTM D1118X (butadiene-styrene block copolymer; shear
viscosity 1160 Pa-s), which was added to the acrylic pressure-sensitive
adhesive at
a ratio of acrylic adhesive to thermoplastic elastomeric block copolymer of
82:18.
In Example 6, the thermoplastic elastomeric polymer was STEREOrd 827,
(styrene-butadiene mufti-block copolymer available from Firestone Synthetic
Rubber & Latex Co.; shear viscosity 2040 Pa-s) which was added to the acrylic
adhesive at a ratio of acrylic adhesive to thermoplastic elastomeric block
polymer
of 82:18. In Comparative Example CI, only the acrylic pressure-sensitive
adhesive, with no other polymer was used to prepare the pressure-sensitive
adhesive tape.
The viscosity ratio of the discontinuous to substantially continuous
component and the thickness of adhesive on samples of each pressure-sensitive
adhesive tape were determined and the 180° peel adhesion test on glass
and the
180° peel adhesion test on biaxially oriented polypropylene (BOPP) were
carried
out. The results are set forth in Table 1. The morphology of the adhesive
compositions of Examples 1-6 was also determined. -
Table I
Example Viscosity Thickness 180 eel
adhesion
/dm
Ratio (pm) Glass BOPP
1 8.3:1 36 60 26
2 4.6:1 41 78 23
3 4.6:1 41 64 25
4 1:4.6 46 36 20
C1 - 76 48 27
5 7.7:1 76 76 32
6 13.6:1 76 86 ~ 29
As can be seen from the data in Table 1, the addition of the thermoplastic
elastomeric block copolymers to the acrylic pressure-sensitive adhesive
increased
the peel adhesion of the adhesive to both glass and biaxially oriented,
polypropylene in Examples 1, 2, 3, 5, and 6. Example 4 demonstratE;s that the
adhesive properties of the adhesive composition can be controlled wfien
excessive
thermoplastic elastomeric block copolymer is used. The peel values of this
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adhesive indicate that it would be suitable as a repositionable adhesive. In
the
Examples, the acrylic adhesive formed a substantially continuous domain and
the
morphology was schistose or ribbon-like. In Example 4, the thermoplastic
f
elastomeric block copolymer formed a substantially continuous domain and the
S morphology was schistose. A scanning electron microscope (SEM)
photomicrograph of a cross-section of an osmium stained adhesive layer of
Example 5 is shown in FIG. 1, with the acrylic adhesive the dark portion.
Examples 7-9 and Comparative Examples C2-C6
In Examples 7-9, pressure-sensitive adhesive tapes were prepared as
Example 1 except a thermoplastic elastomeric pressure-sensitive adhesive
prepared from a thermoplastic elastomer (50 parts by weight KRATONTM
D 1107P) with tackifying resin (50 parts by weight WINGTACK PLUSTM,
available from Goodyear Tire and Rubber Co.) and antioxidant (1 part by weight
IRGANOXTM 1010) was substituted for the thermoplastic elastomeric block
copolymer. This adhesive had a shear viscosity of35 Pa-s at 191°C
(375°F). The
ratio of acrylic pressure-sensitive adhesive to thermoplastic elastomeric
pressure-
sensitive adhesive was 70:30, 50:50 and 25:75, respectively, and the acrylic
adhesive was added to the extruder at the feed throat and the thermoplastic
elastomeric adhesive was added in zone 4. The pressure-sensitive adhesive tape
of
Comparative Example C2 was prepared using only the acrylic pressure-sensitive
adhesive with no other polymer. The pressure-sensitive adhesive tape of
Comparative Example C3 was prepared using only the thermoplastic elastomeric
block copolymer KRATONTM D 1107P preblended with antioxidant, with
tackifying resin WINGTACKTM Plus at a 50/50 weight ratio.
The thickness of each adhesive was determined and the 180° peel
adhesion
to glass test and the 180° peel adhesion to biaxially oriented
polypropylene
(BOPP) test were carned out. The results are set forth in Table 2.
In Comparative Examples C4, C5, and C6, the acrylic pressure-sensitive ,
adhesive and the pressure-sensitive adhesive prepared with the block copolymer
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KRATONTM D 1107P and the tackifying resin WINGTACKTM PLUS used in
Examples 6-8 were dissolved in tetrahydrofuran at ratios of acrylic adhesive
to
block copolymer/tackifying resin adhesive of 70:30, 50:50 and 25:75,
respectively,
with solutions containing 20 weight percent adhesives and 80 weiglot percent
solvent. The solutions were coated on 76 llm (3 mil) thick biaxially oriented
polyethylene terephthalate film and dried at room temperature to obtain
coating
thicknesses of 38pm. The thus-prepared pressure-sensitive adhesive tapes were
tested for 180° peel adhesion to glass. The results are set forth in
'1f able 3.
Table 2
Example Thickness 180 peel adhesion
(pm) (IV/dm)
Glass B OPP
C2 48 S1 26
7 43 64 3 9
8 48 81 43
9 64 75 _ 49
C3 56 95 65
As can be seen from the data in Table 2, addition of the thermoplastic
elastomeric pressure-sensitive adhesive to the acrylic pressure-sensitive
adhesive
increased both 180° peel adhesion to glass and biaxially oriented
polypropylene.
With regard to the morphologies of these adhesive compositions, each of
Examples 7-9 was schistose in nature, i.e., stratified. In Example 7, the
acrylic
adhesive formed a substantially continuous domain, while the thermoplastic
elastomer adhesive was discontinuous. In Example 8, the domains were
substantially co-continuous. In Example 9, the thermoplastic elast~omer
adhesive
was substantially continuous, while the acrylic adhesive was discontinuous.
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Table 3
Example Peel Adhesion (N/dm)
C4 35
CS 33
C6 30
As can be seen from the data in Tables 2 and 3, the extrusion melt blended
adhesives of the invention perform significantly better than the same adhesive
compositions prepared by a solvent coating procedure. With regard to the
morphologies of these solution coated adhesives, each had a continuous domain
of
acrylate adhesive in Comparative Examples C4 and CS or thermoplastic elastomer
adhesive in Comparative Example C6 with discontinuous spheres of thermoplastic
elastomer adhesive in Comparative Examples C4 and CS and discontinuous
spheres of acrylic adhesive in Comparative Example C6.
Examples 10-11 and Comparative Example C7
Double coated pressure-sensitive adhesive tape was prepared in Examples
10 and 11 using the melt blending and extrusion procedures as in Example 1
except the weight ratio of acrylic pressure-sensitive adhesive to
thermoplastic
elastomeric polymer was 85:15 and 70:30, respectively, and a polypropylene
melt
was fed to the middle portion of the CLOERENTM feed block. The melts were
coextruded to produce a double-coated pressure-sensitive adhesive tape having
a
polypropylene core of about 76 to 127 pm (3 to 5 mil) thickness with 25 and 38
pm (1.0 and 1.5 mil) thick adhesive coatings. In Comparative Example C7, a
double-coated pressure-sensitive adhesive tape was prepared as in Example 10
and 11 except the thermoplastic elastomer was omitted. Each double-coated
pressure-sensitive tape was tested for 180° peel adhesion from glass.
The results
of Examples 10, and 11 and Comparative Example C7 were 67 N/dm ( 173 0 g/in),
74 N/dm (1913 g/in) and 51 N/dm (1332 g/in), respectively. As can be seen, the
addition of the thermoplastic elastomer to the acrylic adhesive increased the
180°
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peel adhesion of the adhesive significantly. In each of Examples 10 .and 11,
the
morphology was schistose with the acrylic adhesive forming a substantially
continuous domain with the thermoplastic elastomer forming a ribbon-like
discontinuous domain. FIG. 6 shows the adhesive of Example 11 in cross-section
viewed in the film forming direction after staining with osmium tetroxide at
3000X.
Examples 12 and 13 and Comparative Example C8
In Examples 12 and 13, double-boated pressure-sensitive adhesive tapes
were prepared as in Examples 10 and 11, respectively except for the
replacement
of the water emulsion polymerized acrylic pressure-sensitive adhesive with a
suspension polymerized composition. The suspension polymerized ;acrylic
pressure-sensitive adhesive was prepared in accordance with U.S. Peat. No.
4,833,179 (Young et al.) in the following manner: A two liter split reactor
equipped with condenser, thermowell, nitrogen inlet, stainless steel motor-
driven
agitator, and a heating mantle with temperature control was charged with 750g
deionized water, to which was added 2.5 g of zinc oxide and 0.75 g hydrophilic
silica (CAB-O-SILTM EH-S, available from Cabot Corp.) and was hated to
55°C
while purging with nitrogen until the zinc oxide and silica were thoroughly
dispersed. At this point, a charge of 480 g isooctyl acrylate, 20 g
methacrylic
acid, 2.5 g initiator (VAZOTM 64, available from DuPont Co.) and 0.5 g
isooctyl
thioglycolate chain transfer agent were mixed together. The resulting solution
with initiator and chain transfer agent was then added to the initial aqueous
mixture while vigorous agitation (700 rpm) was maintained to obtain a good
suspension. The reaction was continued with nitrogen purging for at least 6
hours, during which time the reaction was monitored to maintain a reaction
temperature of less than 70°C. The resulting pressure-sensitive
adhesive was
collected and machine pressed to at least 90% solids by weight. In Comparative
. Example C8, a double-coated pressure-sensitive adhesive tape was prepared as
in
Examples 12 and 13 except the thermoplastic elastomer adhesive w,as omitted.
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Each tape was tested for 180° peel adhesion to glass. The results
for
Examples 12 and 13 and Comparative Example C8 were 32 N/dm (830 g/in), 74
N/dm (1913 g/in) and 24 N/dm (615 g/in), respectively, demonstrating that the
r
addition of the thermoplastic elastomer, particularly at higher levels
increases the
peel strength of the acrylic adhesive.
In Examples 12 and 13, the acrylic adhesive domain was substantially
continuous and the thermoplastic elastomer formed ribbon-like layers, i.e.,
was
schistose in nature. FIG. 7 shows the adhesive of Example 13 in cross-section
viewed in the film forming direction after staining with osmium tetroxide at
2000X. FIG. 8 shows the adhesive of Example 13 in cross-section viewed
perpendicular to the film-forming direction after staining with osmium
tetroxide at
2000X.
examples 14-17 and Comparative Example C9
In Examples 14 and 15, double-coated pressure-sensitive adhesive tapes
were prepared as in Examples 12 and 13, respectively, except the acrylic
adhesive
used was an acrylic pressure-sensitive adhesive prepared by water suspension
polymerization of 465 g isooctyl acrylate, 20 g methacrylic acid, 15 g
methacrylate-terminated polystyrene macromer (CHEMLINKTM 4500, available
from Sartomer Co.) 0.25 g acryloxybenzophone and 0.35 g isooctyl
thiogylcolate.
In Comparative Example C9, a double-coated pressure-sensitive adhesive tape
was prepared as in Examples 14 and 15 except the thermoplastic elastomeric
block copolymer KRATONTM D 1107P was omitted. In Examples I 6 and 17,
double-coated pressure-sensitive adhesive tapes were prepared as in Examples
14
and 15, respectively, except the thermoplastic elastomeric block copolymer
KRATONTM 61657 (styrene -(ethylene-butylene)-styrene) was substituted for the
KRATONTM D 1107P. The peel adhesion to glass was determined for each
pressure-sensitive adhesive tape. The results are set forth in Table 4.
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Table 4
Example 180 Peel AdhesionShear Strength
/dm minutes
' C9 32 27
14 55 37
15 66 29
16 17 43
17 22 38
As can be seen from the data in Table 4, addition of the KRATONTM
D1107P improved the 180° peel adhesion of the suspension polymerized
acrylic
adhesive, while addition of the KRATONTM' 61657 improved the shear strength
of the adhesive. The addition of the KRATONTM 61657 did not improve the
180° peel adhesion of the adhesive because the elastic properties
oiFthe
thermoplastic elastomer were insufficient in this particular blend. In each of
Examples 14 to 17, the acrylic adhesive domain was substantially continuous
with
the thermoplastic elastomer domain being schistose in Examples lit and 15 and
fibrillose in Examples 16 and 17.
examples 18 and 19
In Example 18, the acrylic pressure-sensitive adhesive used in Example 1
was melt-blended with a thermoplastic elastomeric block copolymer KRATONTM
D1320X, (a mufti-arm star styrene/isoprene polymer available from Shell
Chemical Co., which had been preblended with 1 weight percent IItGANOXTM
1010) at a ratio of acrylic adhesive to thermoplastic elastomeric block
copolymer
of 80:20 using a corotating twin screw extruder (Model ZSK 30, available from
Werner & Pfleiderer Corp., Ramsey, NJ, having a 30 mm diameter barrel and a
length to diameter ratio of 45 :1 ) with the thermoplastic elastomeric block
copolymer being fed into zone I and the acrylic pressure-sensitive adhesive
being
fed into zone 3. The blend was extruded onto polyethylene film usiing a
contact die
with rates similar to those used in Example 1 to form a pressure-sensitive
adhesive
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tape. In Example 19, a pressure-sensitive adhesive tape was prepared as in
Example 24 except a polyolefin thermoplastic elastomer (ENGAGETM EG8200,
available from Dow Plastics Co.; shear viscosity 1030 Pa-s) was substituted
for
the thermoplastic elastomeric block copolymer and the ratio of acrylic
adhesive to
thermoplastic elastomer was 90:10. The adhesive thickness and 180° peel
.
adhesion value from glass were determined and are set forth in Table 5.
Table 5
Example Adhesive Peel Adhesion
Thickness (N/dm)
m
18 47 >77
19 36 63
As can be seen from the data in Table 5, the adhesive composition
prepared from the acrylic pressure-sensitive adhesive and the thermoplastic
elastomeric polymers had excellent 180° peel adhesion values. Each of
Examples
18 and 19 had a substantially continuous acrylic adhesive domain. In Examples
18
and 19, the thermoplastic elastomers formed schistose and fibrillose domains,
respectively. FIG. 9 shows the adhesive of Example 18 in cross-section in the
film
forming direction after staining with osmium tetroxide. FIG. 10 shows the
adhesive of Example 18 in cross-section along the cross direction after
staining
with osmium tetroxide.
Examples 20-23 and Comparative Example C 10
In Example 20, 75 parts by weight of the acrylic pressure-sensitive
adhesive used in Example 1, and a blend of 12.5 parts by weight thermoplastic
elastomeric block copolymer KRATONTM D 1107P, 1 part by weight antioxidant ,
IRGANOXTM 1010 and 12.5 parts by weight tackifying resin ESCOREZTM
13 l OLC, available from Exxon Chemical Co., were melt-blended and extruded as
-
in Example 18 to form a pressure-sensitive adhesive tape. In Example 21, a
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pressure-sensitive adhesive tape was prepared as in Example 20 except the
proportions were 50 parts by weight acrylic adhesive, 25 parts by weight
thermoplastic elastomeric block copolymer, 1 part by weight antioxidant, and
25
parts by weight tackifying resin. In Example 22, a pressure-sensitive adhesive
. 5 tape was prepared as in Example 20 except the proportions were 25 parts by
weight acrylic adhesive, 37.5 parts by weight thermoplastic elastomnric block
copolymer, 1 part by weight antioxidant, and 37.5 parts by weight t~~ckifying
resin.
In Example 23, a pressure-sensitive adhesive was prepared as in Example 20
except the thermoplastic elastomeric block copolymer was KRATONTM D1112P
(styrene isoprene-styrene block copolymer) and the proportions were 50 parts
by
weight acrylic adhesive, 25 parts by weight thermoplastic elastomeric block
copolymer, 1 part by weight antioxidant, and 25 parts by weight tackifying
resin.
Each adhesive was 25 pm ( 1 mil) thick.
Comparative Example C 10 was prepared as in Example 20, but contained
only the acrylic pressure-sensitive adhesive. The pressure-sensitive adhesive
tapes
were tested for 180° peel adhesion to glass, shear strength to
fiberboard and
polished steel and rolling ball tack. The results are set forth in Table 6.
Table 6
Example Shear Strength Rolling Ball Peel Adhesion
(min) Tack /dm
FB SS m
C10 5 31 35 32
- I4 36 38
21 9 15 44 35
22 6 26 43 59
23 7 26 38 50
As can be seen from the data in Table 6, addition of the thermoplastic
elastomeric block copolymer and tackifying resin improve the 180° peel
adhesion
of the acrylic pressure-sensitive adhesive with the greater improvement being
seen
in Example 22 of the adhesive compositions prepared with KRATO~NTM D 1107P
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as the thermoplastic elastomer block copolymer and a dramatic increase in peel
adhesion being seen in the adhesive prepared with KRATONTM D 1112 as the
thermoplastic elastomeric block copolymer. The adhesives of Examples 20-23
retained the excellent rolling ball tack of the adhesive containing only
acrylic
pressure-sensitive adhesive even when the amount of tackified thermoplastic
elastomer was as high as 75 weight percent. In Example 20, the acrylic
adhesive
formed a continuous domain with the thermoplastic elastomer/tackifying resin
forming a ribbon-like schistose structure. In Example 21 the structure was
schistose in nature with the acrylic adhesive domain and the thermoplastic
elastomer/tackifying resin domain being substantially co-continuous. In
Example
22, the thermoplastic elastomer/tackifying resin formed a substantially
continuous
domain with the acrylic adhesive being in a ribbon-like schistose form. FIG.
11
shows the adhesive of Example 22 in cross-section in the film forming
direction at
2000X magnification after staining with osmium tetroxide. FIG. 12 shows the
adhesive of Example 22 in cross-section along the cross-web direction after
staining with osmium tetroxide. In Example 23 the structure was schistose in
nature with the acrylic adhesive domain and the thermoplastic
elastomer/tackifying
resin domain being substantially co-continuous.
Examples 24-27 and Comparative Examples C 11 and C 12
In Examples 24-27, an acrylic pressure-sensitive adhesive was prepared as
described in Example 1. Core-sheath strands were prepared having a core of the
acrylic adhesive and a sheath of thermoplastic elastomeric polymer (99 parts
by
weight KRATONrM D 1107P) blended with an antioxidant ( 1 part by weight
IRGANOXTM 1010, available from Ciba-Geigy Corp.). The weight ratios of
acrylic adhesive, thermoplastic elastomer and antioxidant used in Examples 24-
27
was 70:30:1, 75:25:1, 80:20:1 and 70:30:1, respectively. The strands were
quenched in water, dried and fed into a corotating twin screw extruder, Model
ZSK 30, available from Werner & Pfleiderer Corp. In Examples 24-27, the
adhesives were coated at coating weights of approximately 25 g/m2 (6 gr1155
cm2)
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onto a polyvinyl chloride-free film comprising a blend of 80 pans by weight
ethylene-vinyl acetate and 20 parts by weight ethylene-propylene-diene rubber
and
a flame retardant system comprising 20 parts by weight alumina trihydrate, 11
parts by weight decabromodiphenyl oxide and 5 parts by weight antimony
trioxide, prepared as described in U.S. Pat. No. 5,284,889 .
In Example 30, the adhesive was coated at a coating weight
of 35 g/m2 (8.4 gr/155 cm2) onto a polyvinyl chloride film backing designated
SA1Q801-l, available from Namra Plastics Corp. In Comparative Example CI 1,
the polyvinyl chloride-free tape backing was coated with a blend of 100 parts
by
weight thermoplastic elastomer (KRATONT"s D 1107P) and 1 part by weight
antioxidant (IRGANOX''~' 1010) at a coating weight of 75 g/m2.(18 gr/155 cm2)
In Comparative Example C 12, the polyvinyl chloride-free backing was coated at
a
coating weight of 47 g/m2 ( 11.4 g/ 15 5 cm2 ) using only the acrylic
adhesive.
Peel adhesion of the adhesives to steel and backing at 20°C and -
18°C was
determined using the Electrical Tape Adhesion Test, the data from which was
normalized to a coating weight of 29 g/m2 (7 gr/155 cm2 ) using the formula
Measured Adhesion x 0.45
Normalized Adhesion = ----------- -------------------
Measured Coating Weight (g)
where coating weight is the weight of adhesive per 155 cm2 (4 in x 6 in) area.
The
results are set forth in Table 7.
Table 7
Example C 11 C 12 24 25 26 27
Adhesion /dm
Steel @ 20C 0.7 I2 17 26 23 20
Backing @ 20C 0.4 5.2 4.7 7.5 6. S 22
Steel @ -18C 0 26 38 54 45 -
Backing @-18C 0 13 31 41 37 -
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As can be seen from the data in Table 7, the pressure-sensitive adhesive
tapes of the present invention, Examples 24-27, perform better than either
component alone on steel at 20°C and generally on backing at
20°C. At -18°C,
the pressure-sensitive electrical tapes of Examples 24-27 performed
significantly
better than the tapes of Comparative Examples C 11 and C 12. .
During coating of the adhesive materials in Examples 24-26,
approximately 1 to 2 mm thick samples of adhesive were collected from the die
onto a polyester release liner. These samples were examined by dynamic
mechanical analysis using a RHEOMETRICTM dynamic analyzer (available from
Rheometric Scientific, Inc.). FIG. 14 shows the dynamic mechanical properties
G'(cu) and tan28 obtained from this measurement, where dashed lines represent
Example 24, dotted lines represent Example 25 and solid lines represent
Example
26. The compliance values were calculated using the equation J(t) _
1/~G'(w)x(1+tan2S) where G'(w) is the shear storage modulus equal to (tensile
storage modulus)/3 and J(t) is the shear creep compliance, a measure of the
softness of the adhesive. The higher the J(t) value, the better the contact
between
the adhesive and the surface to which it is bonded. The results in cm2/dyne
are set
forth in Table 8.
Table 8
Example 24 25 26
Tan 8 @ -20C 0.79 0.82 1.13
@ -10C 0.39 0.44 0.56
@ 23C 0.30 0.33 0.32
G'(dynes/cm ) @ -20C5.0x106 4.3x106 6.5x106
@ -10C 3.0x106 2.0x106 2.9x106
@ 23C ?.8x105 6.4x10s 7.5x105
J(t) (cm /dyne) @ 1.6x10'' 1.8x10-' 1.0x10-'
-20C
@ -10C 3.1x10-' 4.6x10-' 3.0x10-'
@ 23C 12.0x10-' 15.0x10'' 13.0x10'' '
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As can be seen from the data in Table 8, each of the pressure-sensitive
adhesive tapes of Examples 24-26 has excellent compliance, with the best
performance shown by the tape of Example 25. Such compliance, or softness,
indicates that the adhesive of this invention would make good contact with a
S surface to which it is bonded and that the adhesive would generally have
good
peel adhesion.
Example 28 and Comparative Example C 13
Pressure-sensitive adhesive tape's were prepared as in Example 15 and
Comparative Example C9. Samples of each tape were subjected to ultraviolet
irradiation using a UV Processor Model #QC 120244ANIR available from RPC
Industries, Inc. with medium mercury lamps. The irradiation was performed in
an
inert nitrogen atmosphere at a calibrated dose of 100 mJ/cm2 at 36'> nm. The
tapes were tested for 180° peel adhesion and for shear strength. The
results are
set forth in Table 9 together with the results of the tests on Example 15 and
Comparative Example C9. -
Table 9
Example Peel Adhesion Shear Strength (min)
/dm ailure Mocle
C9 31.5 27 (cohesive:)
15 55.3 37 (cohesive)
C13 37.1 21 (adhesive: pop-ofd
28 71.7 216 (adhesive: pop-ofd
Radiation curing with ultraviolet light to increase crosslinking, caused
greater increases in peel adhesion with the tape prepared with the adhesive of
the
invention. However, the most significant increase due to irradiating the
samples
' was seen in the shear strength where the irradiated adhesive of the
invention
increased in shear strength more than five times over the non-irradiated tape,
while
the irradiated tape prepared with only acrylate adhesive decreased inn shear
strength after irradiation.
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Examples 29-3 5 and Comparative Examples C 14-C 15.
The acrylic pressure-sensitive adhesive described in Example 1 was
blended with KRATONTM D1107P at various ratios and coated using batch
mixing and coating processes. For Examples 29-35, a total of 45 grams of
acrylic
pressure-sensitive adhesive and KRATONTM D 1107P (99 parts preblended with 1 .
part IRGANOXTM 1010 antioxidant) were charged into a 50 gram BrabenderTM
sigma blade mixer operating at 175°C (347°F). The KRATONTM
D1107P was
added first, followed by the acrylic pressure-sensitive adhesive. The blend
was
mixed at 50-75 rpm for S minutes. The relative amounts of acrylic pressure-
sensitive adhesive and KRATONTM D1107P that were blended correspond to 40.5
grams and 4.5 grams for Example 29, 33.75 grams and 11.25 grams for Example
30, 22.5 grams and 22.5 grams for Example 31, 18 grams and 27 grams for
Example 32, 11.25 grams and 33.75 grams for Example 33, 6.75 grams and 38.25
grams for Example 34, and 2.25 grams and 42.75 grams for Example 35.
Pressure-sensitive adhesive coated tapes were prepared for each example by
placing approximately 1-5 grams of blended material between a sheet of release
coated paper and a 50-75 micron thick biaxially oriented polyethylene
terephthalate film. This was then placed between two aluminum plates in a
hydraulic platen press having two steel plates measuring 152 mm (6 inches) by
152 mm (6 inches). Application of 28 NfPa (4000 psi) at 138°C
(280°F) and 0.6
second dwell time produced pressure-sensitive adhesive coatings having
thickness
ranging from 76 pm (3 mils) to 102 pm (4 mils). The tapes were tested for
180°
peel adhesion to glass. The results are set forth in Table 10.
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Table 10
Example Acrylic Pressure-KRATONTM 180 Peel (N/dm)
sensitive D 1107P (Wt.
Adhesive %)
Wt.
C14 100 0 61
29 90 10 71
30 75 25 81
31 50 50 81
32 40 ' 60 59
33 25 75 49
34 15 85 29
35 5 95 26
C15 0 100 0
The morphologies of the adhesives of Examples 29 and 30 were a
continuous acrylic pressure-sensitive adhesive phase with schistose
thermoplastic
elastomer phase. The adhesives ofExamples 31 and 32 had co-continuous
schistose phases of acrylic pressure-sensitive adhesive and thermoplastic
elastomer. Examples 33-35 had a continuous non-tacky thermoplastic elastomer
phase with discontinuous pressure-sensitive adhesive schistose phase. Due to
the
axial deformation of the platen press coating method, the phases are formed
parallel to the plane of the coating. As can be seen from Table 10, the
180° peel
adhesion to glass can be controlled by varying the ratio of acrylic p~ressure-
sensitive adhesive to thermoplastic elastomer. Behavior ranging from enhanced
180° peel adhesion (Examples 29-31) to reduced 180° peel
adhesion and easier
removal (Examples 32-35) is demonstrated.
Examples 36 - 37
Acrylic pressure-sensitive adhesive tapes were prepared as in Example
29 except different acrylic pressure-sensitive adhesives were used ;~.nd the
ratio of
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acrylic pressure-sensitive adhesive to thermoplastic elastomer was 80:20. For
Example 36, the acrylic pressure-sensitive adhesive used was 2-ethylhexyl
acrylic
pressure-sensitive adhesive prepared by feeding a premix of isooctylacrylate
acrylic acid : isooctylthioglycolate : VAZO''"~ 64 (available from DuPont) in
a
ratio of 90:10:0.05:0.3 into an 18 mm Leistritz counterrotating twin screw
extruder equipped with fully intermeshing, integrated screws according to the
general method described in U.S. Pat. No. 4,619,979 (Kotnour, et al),
The extruder was not vented and the screw
speed was maintained at 50 rpm. The temperatures in zones 1 through 8 were
maintained at 72°C, 82°C, 92°C, 96°C,
100°C, 110°C, 115°C and 120°C,
respectively. For Example 37, the acrylic pressure-sensitive adhesive used was
n-
butyl acrylic pressure-sensitive adhesive prepared in a similar manner as the
2-
ethyl hexyl acrylic pressure-sensitive adhesive of Example 36 except the
materials
used were n-butyl acrylate : N,N-dimethylacrylamide : acrylic acid : 4-
acryloxy-
I S benzophenone : isopropanol : and VAZOTM 64 in a ratio of 83
:15:2:0.2:2:0.3, the
extruder rpm was 70 and temperatures in zones 1 through 8 were maintained at
70°C, 81°C, 92°C, 96°C, 105°C,
110°C, 115°C and 120°C, respectively. For
each example, the relative amount of acrylic pressure-sensitive adhesive and
preblended KR.ATONTM D 1107P and IRGANOXTM 1010 blended at 100 parts
thermoplastic elastomer to 2 parts antioxidant. Comparative Examples C 16 and
C17 were made as in Examples 36 and 37, respectively, except only the acrylic
pressure-sensitive adhesive was used with no thermoplastic elastomer. The
samples were tested for 180° peel adhesion from glass and the adhesive
thickness
and peel adhesion values are listed in Table 10.
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Table 10
Example Adhesive Peel Adhesion
Thickness (N/dm)
m
36 100 78
C16 100 63
37 100 108
C17 100 92
As can be seen by the data in Table 10, the adhesive compositions
prepared from the acrylic pressure-sensitive adhesives and the thermoplastic
elastomer block copolymer had superior 180° peel adhesion values than
the
comparative examples containing no thermoplastic elastomer. The morphologies
of the adhesive compositions were a continuous acrylic pressure-sensitive
adhesive
phase with a schistose thermoplastic elastomer phase.
Example 38
In Example 38, pressure-sensitive adhesive tape was prepared as in
Example 1 with the acrylic pressure-sensitive adhesive used in Example 1 and
with
the thermoplastic elastomeric polymer HYTRELTM 5326, a polyethnrester
available from DuPont Co., shear viscosity - 495 Pa-s, which had been
preblended
with 1 weight percent IRGANOXTM 1010, such that the ratio of acrylic adhesive
to thermoplastic elastomeric polymer was 80:20. The adhesive thickness was 60
pm and the 180° peel adhesion value from glass was 40 N/dm. The
morphology
of the adhesive was a continuous acrylic pressure-sensitive adhesives phase
with a
schistose thermoplastic elastomer phase.
Examples 39-42 and Comparative Examples C 18 and C 19
In Examples 39, 40 and 41, the water suspension polymerized acrylic
pressure-sensitive adhesive described in Example 12 and 13 was melt blended
with
a thermoplastic elastomeric adhesive (prepared by blending SO part:.
thermoplastic
elastomeric block copolymer KRATONTM D1107P, 1 part antioxidant
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IRGANOXTM 1010 and 50 parts tackifying resin ESCOREZTM 13 l OLC) in a
corotating twin screw extruder, Model ZSK 30, having 30 mm diameter barrel and
a length to diameter ratio of 37:1 with the acrylic adhesive to thermoplastic
elastomer adhesive ratio being 75:25, 50:50 and 25:75, respectively. The
thermoplastic elastomer block copolymer was fed into zone 1, the tackifying
resin
in zone 2 and the acrylic pressure-sensitive adhesive in zone 3. Temperatures
were
maintained between 149°C and 165°C. In Example 42, a pressure-
sensitive
adhesive tape was prepared as in Example 39 using the water emulsion
polymerized acrylic pressure-sensitive adhesive described in Example 1 and the
thermoplastic elastomer described in Example 29 with the acrylic pressure-
sensitive adhesive to thermoplastic elastomer block copolymer ratio being
75:25.
In Comparative Example C 18, the pressure-sensitive adhesive tape was prepared
using only acrylic adhesive. In Comparative Example C 19, the pressure-
sensitive
adhesive tape was prepared using only the tackified thermoplastic elastomeric
adhesive. All samples had an adhesive coating thickness of about 50 pm (2
mils)
and were coated onto non-occlusive, i.e. breathable, woven backing which has
an
180 x 48 plain weave acetate taffeta cloth, 75 denier fiber in the warp
direction
and 150 denier fiber in the fill direction, available from Milliken and Co.,
Spartanburg, GA. The adhesive compositions in Example 39 and 42 showed a
substantially continuous acrylic adhesive domain with the thermoplastic
elastomer/tackifying resin forming schistose ribbon-like domains. In the
adhesive
composition of Example 40, the acrylic adhesive and the thermoplastic
elastomer/tackifying resin formed substantially co-continuous schistose
domains.
In Example 41, the thermoplastic elastomer/tackifying resin formed a
substantially
continuous domain, while the acrylic adhesive formed schistose ribbon-like
domains. FIG. 15 shows the adhesive of Example 40 in cross-section in the film
forming direction after staining with osmium tetroxide. The pressure-sensitive
adhesive tapes were tested for skin adhesion immediately after application,
To, and
after 24 hours, T24, skin adhesion lift after 24 hours and skin adhesion
residue after
24 hours. The results are set forth in Table 11.
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Table 11
Example To (N/dm)T24 (N/dm)T24 Lift 'r2a Residue
C18 2.2 7.9 1.8 1.0
39 3.0 11.2 1.6 0.8
40 4.0 7.7 1.6 0.6
4 1 3.4 4.3 1.6 0.3
C19 3.0 3.3 1.3 0.1
42 2.0 2.7 0.3 1.0
I
As can be seen from the data in Table 11, the pressure-sensitive adhesive
S tapes on Examples 39-42 had enhanced peel performance from skin and the
To:T2a
adhesion can be controlled by appropriate blending of the acrylic adhesive and
the
tackified or untackified thermoplastic elastomer. In particular, the tape of
Example 40 had between 180 percent and 33 percent higher initial adhesion to
skin than tapes prepared of either of the component pressure-sensitive
adhesives,
Comparative Examples C 18 and C 19. Additionally, all Examples provided
adhesives with acceptable 24 hour aged adhesion to skin.
Examples 43-45
In Example 43, the acrylic pressure-sensitive adhesive used in Example
12 was melt-blended with a thermoplastic elastomeric adhesive (prepared by
preblending 100 parts thermoplastic elastomeric block copolymer KRATONTM
D1107P, 1.5 parts antioxidant IRGANOXTM 1076, available from Ciba-Geigy
Corp, 1.5 parts antioxidant CYANOXTM LTDP, available from American
Cyanamide Corp., Wayne, NJ, and 70 parts tackifying resin WINGTACKTM Plus,
available from Goodyear Chemical Co., Akron, OIT) with the acrylic adhesive to
thermoplastic elastomer adhesive ratio being 65:35 using an 8.9 cm diameter
screw pin barrel mixer, available from The French Oil Mill Machinery Co.,
Piqua,
OH, with zone temperatures rising from 106°C to 144°C and water
injected at 1
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part per 100 parts pressure-sensitive adhesive composition as the composition
leaves the pin barrel mixer. A gear pump attached to the output end of the pin
barrel mixer by a heated pipe delivered the pressure-sensitive adhesive
composition to a wipe-film coating die, maintained at a temperature of
160°C, for
coating the adhesive composition at a rate of 1.8 kg/hour/25 cm die width onto
a
non-occlusive woven backing as used in Examples 39-42. The backing speed was
adjusted to provide adhesive coatings having an average thickness of about 50
~m
(2 mils): In Example 44, a pressure-sensitive adhesive tape was prepared as in
Example 42 except the thermoplastic elastomeric adhesive was prepared by
blending 50 parts thermoplastic elastomeric block copolymer KRATONTM D 1119,
a styrene-isoprene-styrene block copolymer, shear viscosity - 17 Pa-s,
available
from Shell Chemical Co), 2 parts antioxidant IRGANOXTM 1076 and 48 parts
tackifying resin WINGTACKTM Plus. In Example 45, a pressure-sensitive
adhesive tape was prepared as in Example 43 except the acrylic pressure-
sensitive
adhesive used in Example 1 was melt-blended with a thermoplastic elastomeric
adhesive, prepared by blending 50 parts thermoplastic elastomeric block .
copolymer KRATONTM D1107P, 1 part antioxidant IRGANOXTM 1010, and SO
parts tackifying resin ESCOREZTM 13 l OLC, with the acrylic adhesive to
thermoplastic elastomer adhesive ratio being 25:75, the pressure-sensitive
adhesive composition being fed at 15.1 Kg/hr and the zone temperatures
maintained between 124°C and 131°C. The adhesive compositions in
Example 43
and 44 showed a substantially continuous acrylic adhesive domains with the
thermoplastic elastomer/tackifying resin forming schistose ribbon-like
domains.
The adhesive compositions in Example 45 showed a substantially continuous
thermoplastic elastomer/tackifying resin domain with the acrylic adhesive
forming
schistose ribbon-like domains. The pressure-sensitive adhesive tapes were
tested
for skin adhesion immediately after application, To, and after 48 hours, T48,
skin ,
adhesion lift after 48 hours and skin adhesion residue after 48 hours. The
results
are set forth in Table 12.
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Table 12
Example To (N/dm)T48 (N/dm)T4g Lift 7.'48 Residue
- 43 4.9 12.0 1.9 1.6
44 4.6 10.8 1.9 1.7
45 2.1 5.4 0.7 0.3
As can be seen from the data in Table 12, the pressure-sensitive adhesive
tapes on Examples 43, 44 and 45, with non-occlusive woven backings and with
different acrylic pressure-sensitive adhesives and thermoplastic elastomeric
adhesives, had acceptable peel performance from skin.
Examples 46-48
In Examples 46-48, pressure-sensitive adhesive tapes were made with
various non-occlusive backings using the same thermoplastic
elastomer/tackifying
resin adhesive, melt-mixing and coating process as in Example 45. The acrylic
adhesive was as used in Example 12 and 13. In Example 46, the acrylic adhesive
to thermoplastic elastomer adhesive ratio was 60:40 and the pressure-sensitive
adhesive composition was coated onto a release liner and laminated to a
nonwoven rayon fiber backing. The backing was formed by first passing 2.5 to 5
cm long, 1.5 denier viscose-rayon staple fibers through a twin cylinder card
(available from Spinnbau GmbH, Bremen, Germany) to form a fluffy fiber web
with a fiber weight of between 41 g/m2 and 54 g/mz. The fluffy fiber web was
simultaneously compacted to a tissue-like condition and sized by bE;ing fed
through the nip of a pair of horizontal squeeze rolls, the lower one of which
dips
in an aqueous bath of fiber-binding rubbery acrylate sizing latex (R:EiOPLEXTM
B-
15, available from Rohm and Haas Co.), diluted with water to provide a size
weight approximately equal to the weight of the fiber; and then dried. In
Example
47, the acrylic adhesive to thermoplastic elastomer adhesive ratio vvas 50:50
and
the pressure-sensitive adhesive composition was applied to a liner ~~nd melt
blown
microfiber was blown onto the adhesive at 450 g/hr/cm to form an 80 p,m thick
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backing with a basis weight of 20 g/m2. The melt blown microfibers had a
diameter of between about 5 and 10 p,m and were prepared using PS 440-200
polyurethane, available from Morton International, Inc., Seabrook, NI3, and a
_
process similar to that describe in U. S. Pat. No. 5,230,701, Example 1. In
Example 48, the acrylic adhesive to thermoplastic elastomer adhesive ratio was
'
60:40 and the pressure-sensitive adhesive composition was applied to 0.65 mm
thick SONTARATM 8010 backing, a 44 g/mz basis weight hydroentangled
polyester nonwoven substrate available from DuPont Co. In the adhesive
composition of Example 46, 47 and 48, the acrylic adhesive and the
thermoplastic
elastomer/tackifying resin adhesive formed substantially co-continuous
schistose
domains. The pressure-sensitive adhesive tapes were tested for skin adhesion
immediately after application, To, and after 48 hours, T4g, skin adhesion lift
after
48 hours and skin adhesion residue after 48 hours. The thickness of each of
the
adhesive composition examples and the test results are set forth in Table 13.
Table 13
Example ThicknessTo Tas T48 LiftTas Residue
m (N/dm) (N/dm)
46 21 2.1 6.5 0.1 0.6
47 39 2.6 6.1 0.5 0.0
48 32 3.5 12.0 0.9 4.8
As can be seen from the data in Table 13, the pressure-sensitive adhesive
tapes on Examples 46, 47 and 48, with non-occlusive woven backings and with
different acrylic pressure-sensitive adhesives and thermoplastic elastomeric
adhesives, had acceptable peel performance from skin.
Examples 49-52
In Examples 49-52, pressure-sensitive adhesive tapes were made as in
Examples 46-48 except various occlusive non-breathable backings were used. In
Example 49, the acrylic adhesive to thermoplastic elastomer adhesive ratio was
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60:40 and the pressure-sensitive adhesive composition was applied to a 117 ~m
thick polyethylene/vinyl acetate copolymer film prepared using ESC:ORENETM :S-
31209, available from Exxon Chemical Co. The film was perforated with about
100 holes/cm2. In Example 50, the acrylic adhesive to thermoplastic elastomer
adhesive ratio was 60:40 and the pressure-sensitive adhesive composition was
applied to a 76 p,m thick low density polyethylene film, prepared u.~ing NA
964-
085 resin, available from Quantum Chemical Co. In Example 51, tlhe acrylic
adhesive to thermoplastic elastomer adhesive ratio was 50:50 and the pressure-
sensitive adhesive composition was applied to 0.57 mm thick plasticized
polyvinyl
chloride foam (available as No. 9058 TA 022 Fleshtone from General Foam
Corp., Carlstat, NJ. In Example 52, the acrylic adhesive to thermoplastic
elastomer adhesive ratio was 50:50 and the pressure-sensitive adhesive
composition was applied to the polymer side of a white polymer/cloth laminate
composed of ENGAGETM 8200 (a polyolefin elastomer available fc~om Dow
Plastics Co) extrusion coated onto 44x36 woven cloth (available from Burcott
Mills). White backing was produced by dry blending 1 part of 50:50 titanium
dioxide in low density polyethylene (available as PWC00001 from lEZeed
Spectrum,
Holden MA) with 3 parts ENGAGETM 8200; forming pigmented pellets by melt
mixing the blend in a 40 mm twin screw extruder (available from Berstorf~ at
200°C and extruding and pelletizing strands; dry blending the pigmented
pellets
with more unpigmented ENGAGETM 8200 in a ratio of 1:25; melt mixing the
blend and feeding the blend at approximately 270 g/min into the feed throat of
a
6.4 cm diameter Davis Standard Model N 9485 Single Screw Extn.~der, available
from Davis Standard Div., Crompton and Knowles Corp., Pawcatuck, CT, at
204°C (400°F) and extruding a 66 ~m (2.6 mil) thick film onto
the cloth with the
casting roll temperature set at 93°C (200°F) to form a laminate;
and passing the
laminate through the nip of two horizontal rolls at a pressure of 350 N/cm at
approximately 11 m/min (approximately 35 fpm). In the adhesive composition of
Examples 49, 50 and 52, the acrylic adhesive and the thermoplastic;
elastomer/tackifying resin adhesive formed substantially co-continuous
schistose
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domains. In the adhesive composition ofExample 51, the acrylic adhesive formed
a substantially continuous domain and the thermoplastic elastomer/tackifying
resin
adhesive formed ribbon-like schistose domains. The pressure-sensitive adhesive
_
tapes were tested for skin adhesion immediately after application, To, and
after 48
hours, T48, skin adhesion lift after 48 hours and skin adhesion residue after
48
hours. The thickness of each of the adhesive composition examples and the test
results are set forth in Table 14.
Table 14
Example ThicknessTo T~g T48 Lift T4g
m (Nldm) (N/dm) Residue
49 29 2.4 1.8 1.3 0.6
50 39 2.1 1.5 0.9 0.6
51 39 5.6 7.6 0.3 1.8
52 SO 1.5 3.7 1.1 0.3
As can be seen from the data in Table 14, the pressure-sensitive adhesive
tapes of Examples 49 to 52 with occlusive nonbreathable backings had varying
peel performance from skin.
Exam In a 53
Pressure-sensitive adhesive tape was prepared using the procedure of
Example 18 and the materials described in Example 52 except 10 parts
NiICRALTM 1500, an alumina trihydrate, available from Salem Industries, Inc.,
Norcross, GA, per 100 parts thermoplastic elastomeric adhesive was preblended
with the thermoplastic elastomeric adhesive. The pressure-sensitive adhesive
had
a thickness of about 50 p,m. The acrylic adhesive and the thermoplastic
elastomer/tackifying resin adhesive formed substantially co-continuous
schistose
domains. The pressure-sensitive adhesive tape was tested for skin adhesion
immediately after application, To, and after 48 hours, T4g, skin adhesion lift
after
48 hours and skin adhesion residue after 48 hours. The skin adhesion was 1
N/dm
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initially and 3.1 N/dm after 48 hours. After 48 hours the skin adhesion lift
was 1
and the skin adhesion residue was 0.
The various modifications and alterations of this invention will be apparent
S to those skilled in the art without departing from the scope and spirit of
this
invention and this invention should not be restricted to that set forth herein
for
illustrative purposes only.
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