Note: Descriptions are shown in the official language in which they were submitted.
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IMPROVED MASKING FILM
AND METHOD FOR PRODUCING SAME
INTRODUCTION:
'The present invention relates to masking films and, more specifically, to a
masking film which removably adheres to rigid, relatively smooth-surfaced
substrates under a variety of conditions without the need for corona treatment
or an
adhesive, and a method for producing same.
BACKGROUND OF THE INVENTION
Masking films are used in numerous applications as a protective coating or
covering for surfaces, particularly smooth surfaces, such as acrylics, glass,
polished
or painted metals, glazed ceramics, and other smooth, relatively rigid
surfaces. The
masking film is applied to the surface to be protected and acts as a physical
barrier
to prevent scratching, scuffing and marring of the surface. Protection
provided by
masking films is particularly useful while these surfaces are being printed,
transported, or otherwise handled prior to use.
Traditionally, protection for smooth surfaces has been provided via corona
treated films and/or adhesive coated masking paper. Corona treated films are
films
exposed to an electrostatic discharge to increase the adhesion level of the
film.
This is accomplished through the production of surface oxidation of the film
via the
electrostatic discharge, increasing the attraction between the nonpolar
surface of the
film and the polar surface of the material to be protected. Such corona
treated films
are typically non-embossed and rely on a very narrow window of corona
treatment
to facilitate enhanced adhesion. However, disadvantages exist with this
technique.
For example, where too little corona treatment occurs, the masking film will
not
adhere to the surface to be protected. Conversely, where too much corona
treatment occurs, it is common to fmd the masking film laminating to itself
and/or
laminating completely to the surface to be protected, at best requiring
additional
time, effort and costs to completely unwind the masking film and/or remove the
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masking material from the protected surface, and, at worst, ruining the
protected
material for its intended end use. Additionally, since corona treated masking
films
have a relatively high surface coefficient of friction, rigid wrinkles
commonly form
in the masking film. Such wrinkles are difficult, if not impossible, to
remove, thus
S precluding the film from adequately protecting the surface to be protected
and/or
permanently distorting the surface to be protected, again ruining it for its
intended
purpose. Finally, corona treated polyethylene films commonly have numerous
large
gels and carbon specks associated with them which can produce dimples in, or
otherwise mar, the surface to be protected.
Disadvantages are also associated with masking films using an adhesive
coated paper. For example, where a masking material requiring an adhesive
coating is used, moisture from humidity or elsewhere can permeate the masking
material and loosen or completely separate the masking material from the
surface to
be protected. The tendency for moisture to adversely affect the performance of
this
type of masking film is increased where heat is required to activate the
adhesive
coating. Additionally, even where the masking material remains firmly adhered
to
the surface to be protected until its removal is desired, such removal can
require the
use of a solvent to remove trace amounts of the adhesive coating. The adhesive
residue left behind on the surface is of particular concern where the surface
being
protected is to be used in a context where sanitary conditions are desired,
such as in
food industry applications. The use of an adhesive coating also requires the
additional steps of applying the adhesive coating to the preformed film, as
well as
the expense of using, activating and storing one or more adhesives to be used
as a
coating. Finally, where heat-activated adhesive coatings are used, the time
and
expense of providing the proper amount of heat to the process to facilitate
proper
adhesion further complicates the process.
Recent advances in masking film technology have produced improved
masking films formed without corona treatment or the use of adhesive coatings,
including one side smooth, one side matted ("OSM") masking films. Such OSM
films are more fully described in U.S. PatentNos. 4,895,760 and 5,100,709,
both
assigned to Tredegar Industries, Inc., Richmond, VA. These advanced masking
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films rely upon the tendency for smooth surfaces to adhere to each other to
produce
an adequate and constant level of adhesion without the need for corona
treatment
and the use of adhesive coatings. Additionally, the matted side of the OSM
films
prevents blocking and wrinkling of such films by preventing a meastn~e of
intimate
contact between the surfaces. Importantly, these improved OSM films avoid the
numerous problems associated with the use of corona treatment and adhesives
and
are stable over time, even when exposed to moisture and ultraviolet light.
Despite the advanced nature of the OSM films, however, it was discovered
that the level of adhesion produced by these improved masking films can vary
with
temperature and other conditions associated with the production and use of
such
improved films. At times, such conditions can result in a masking film
exhibiting
either too much or not enough adhesion level for the desired application. In
other
applications, it can result in the need for heaters to raise the temperature
of the film
so thatproper application and adequate adhesion level are achieved. Moreover,
since the level of adhesion produced is primarily a function of the
interaction
between the smooth surface of the masking film and the smooth surface to be
protected, the smoothness of the surface requiring protection is a significant
factor.
This factor can present difficulties, and masking films of this type are of
limited
utility, where the surface to be protected is not particularly smooth.
Methods for producing such prior art films are relatively rigid and do not
offer flexibility in the recipe for such films, thus producing films incapable
of
producing a variety of adhesion levels under a variety of production
conditions for
a variety of applications.
Variable adhesive masking films are now known in the art and ate more
fully described in U.S. Patent No. 6,040,046 issued March 21, 2000,
assigned to Tredegar Industries, Inc. Such variable adhesive masking
films are based upon polymer/co-polymer additives within the adhesive
layer of the masking film.
Thus there remains a need for a polymer/comonomer-based masking film
capable of providing an adequate level of protection to merely relatively
smooth
surfaces by providing a functional, adjustable and controlled level of
adhesion
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between the masking film and the surface to be protected without the use of
corona
treatment or an adhesive and their associated disadvantages and under a
variety of
production and application conditions, and a method for producing same.
SUMMARY OF THE INVENTION
In accordance with the present invention there is provided a masking film
which adheres to and provides protection for a relatively smooth surface
without
the need for a separate adhesive layer or corona treatment. Additionally, the
improved film is preferably of the OSM type so that blocking and wrinkling of
the
film are substantially minimized, if not completely eliminated. Moreover, the
adhesion produced is not as dependent upon the smoothness of the surface to be
protected. Importantly, the level of adhesion produced by the improved OSM
film
is adjustable so as to accommodate a variety of production and application
conditions. For example, the improved masking film of the present invention
will
provide a functional level of adhesion to uncoated polycarbonates, acrylics
and
PETG at room or ambient temperature. Accordingly, for virtually any given
processing environment, including temperature and line equipment layout, and
desired application, the improved masking film of the present invention can
provide an adequate level of adhesion to the substrate of interest. The
improved
masking film of the present invention also remains removably attached to a
substrate surface even after the application of post-production heat loading
processes, including, but not limited to, thermoforming, drape-forming and
heat-
bending.
The improved masking film of the present invention comprises a film
preferentially having a smooth side, a rough side and, optionally, one or more
core
layers interposed between the smooth side and the rough side. The monolayer is
preferably extruded and the multiple layers are preferably coextruded. The
smooth
side comprises at least one layer of a thermoplastic film. In use, the smooth
side is
applied to the relatively smooth surface to be protected. The rough side is
also
comprised of at least one layer of a thermoplastic film. The rough side is
preferably
matte embossed, but can be roughened via any suitable means. The rough side
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prevents the film from contacting as much surface area of itself, or any other
surface, preventing blocking and wrinkling of the film. At least one core
layer may
be interposed between the smooth side and the rough side of the improved
masking
film and, if present, is also comprised of a thermoplastic film. In the
monolayer
embodiment, the smooth side and rough side are opposing sides of the single
layer
of the film.
The level of adhesion produced between the smooth side of the masking
film of the present invention and the surface to be protected is adjustable
via the
introduction of certain copolymers associated with the smooth side of the
film. The
controlled combination of such palymers/comonomers has the affect of adjusting
the level of adhesion produced between the smooth side of the masking film and
the surface to be protected by the masking film. The identity, mixture and
quantities of these polymers/comonomers are dictated by the conditions {e.g.,
temperature) under which the masking film will be applied and ultimately used.
1 S Thus, for example, the masking film of the present invention can be
produced so as
to provide a functional and controlled level of adhesion to acrylics at room
temperature without subsequent laminating or welding during heat-loading
processes, such as thermobending or thermoforming. The level of adhesion can
be
adjusted to provide adequate levels of adhesion with substrates at a higher
temperature.
In other embodiments of the improved masking film of the present
invention, a one, two or multilayered masking film is produced which includes
certain copolymer capable of adjusting the level of adhesion produced by the
film.
These films can be blown or cast. Monolayer or coextrusion of multiple layers
may
be employed. Additionally, in the multilayered embodiment, the layer including
the smooth side of the improved masking film of the present invention may be
laminated to the layer including the rough side, if desired. The blending of
two or
more copolymers (or homopolymers) of the smooth side of the masking film is
controlled to produce desired tackiness of the resulting masking film.
According to the method of the present invention, the improved masking
film is produced by preselecting the one or more primary components comprising
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the first skin of the improved masking film of the present invention. It is
the surface
of this first skin layer which will ultimately intimately contact and adhere
with the
surface of the substrate to be protected. Once selected, the relative
percentages of
the one or more components is also predetermined so as to produce a functional
and
controlled level of adhesion force produced under a given set of the
substrate's
production conditions and environment.
The remaining skin and core layers, if present, are formed of a
thermoplastic. The skin and core layers are preferably coextruded to form the
improved masking film of the present invention. Due to the preselection of the
components and their relative amounts, the resulting masking film is tailored
to
perform in the given production environments under the given conditions.
In a particularly preferred embodiment there is provided an improved
adhesiveless masking film, comprising: a first side of the film having a
smooth
adhesive-free surface; a second side of the film having a rough surface;
wherein the
smooth surface of the film ranges in smoothness from 0-60 Ra and the rough
surface of the film ranges in roughness from 65-600 Ra; said smooth surface of
the
first side of the film adapted for removably adhering to a surface of a
substrate
when placed in intimate contact with said surface of a substrate; said first
side
comprising at least two components preselected to affect the amount of
adhesion
produced between the smooth surface of the first side and the surface of the
substrate at a given temperature; wherein one of said at least two components
comprises a metallocene catalyzed copolymer of ethylene with a comonomer
selected from the group consisting of octene, hexane, and butene; and wherein
another of said at least two components is selected from the group consisting
of
polyolefins (homopolymers and copolymers), polyvinyl alcohol, nylon,
polyester,
polystyrene, polymethylpentene, polyoxymethylene, and blends thereof.
In a further preferred embodiment there is provided an improved
adhesiveless masking film, comprising: a first side of the film having a
smooth
adhesive-free surface; a second side of the film having a rough surface;
wherein the
smooth surface of the film ranges in smoothness from 0-60 Ra and the rough
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surface of the film ranges in roughness from 65-600 Ra; said smooth surface of
the
first side of the film adapted for removably adhering to a surface of a
substrate
when placed in intimate contact with said surface of a substrate; said first
side
comprising one or more components preselected to affect the amount of adhesion
produced between the smooth surface of the first side and the surface of the
substrate at a given temperature; wherein the one or more components is a
polyethylenic material including a copolymer selected from the groups
consisting of
octene comonomers, hexane comonomers, and butene comonomers; and wherein
the amount of adhesion produced between the smooth surface of the first side
and
the surface of the substrate at a given temperature is a function of the
amount of the
one or more components present in the masking film.
BRIEF DESCRIPTION OF THE FIGURES
A more complete understanding of the present invention may be had by
reference to the following detailed description when taken in conjunction with
the
accompanying figures wherein:
FIGURE 1 is a graph depicting peel adhesion values for polycarbonate and
acrylic substrates masked at 180°F and as a function of the percentage
of the
comonomer component of the masking film; and
FIGURE 2 is a graph depicting peel adhesion values for polycarbonate and
acrylic substrates as a function of temperature for 18% octene comonomer
component of the masking film.
DETAILED DESCRIPTION OF FIGURES
In a preferred embodiment of the improved masking film of the present
invention, a first layer having at least one smooth surface and a second layer
having
at least one rough surface and, optionally, at least one core layer are
coextruded to
form an improved masking film. Each of the layers is comprised of a
thermoplastic
film. Preferred films include metallocene catalyzed polyethylenic films
containing
octene comonomers, including, but not limited to, DuPont-Dow Engage
Polyolefin Elastomers (POEs) and AffinityTM Polyolefin Plastomers (POPs),
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available from DuPont Company or Dow Chemical Company. The thermoplastic
films making up the layers of the improved masking film of the present
invention
also may include films of other polyolefins (homopolymers and copolymers),
polyvinyl alcohol, nylon, polyester, polystyrene, polymethylpentene,
polyoximethylene, and the like, or blends thereof. Films of polyethylene are
particularly suited and therefore preferred and films of low density
polyethylene
homopolymers are even more particularly suited and therefore more preferred
due
to their relatively low flexure modulus which tends to conform better to
surfaces.
The rough side of the second layer is preferably embossed to produce the
desired roughness. The roughness of the second layer is important to prevent
blocking and wrinkling of the masking film. The rough surface prevents
blocking
by precluding such intimate contact between the surfaces of the masking film
and
another surface such that the masking film can be easily unrolled and/or
peeled
away from another smooth surface. This feature also prevents the wrinkling so
often associated with traditional masking films.
In a preferred embodiment, the first layer includes a surface having a
measure of smoothness of from about between 0 Ra and 60 Ra, and more
preferably, between 0 Ra and 30 Ra. In a preferred embodiment, the relatively
rough surface of the second layer includes a measure of roughness of from
between
65 Ra and 600 Ra, and more preferably, between 100 Ra and 300 Ra. For purposes
of this application, smoothness and roughness will be defined as the
arithmetic
average height of the micropeaks and microvalleys of a surface to the center
line of
such surface as measured by a profilometer. Smoothness and roughness defined
in
this manner is typically expressed with units of microinches (l0~binches)
(Ra). All
testing of surface textures {relative smoothness and roughness) were conducted
in
accordance with ANSI/ASME Test Method B46.1-1985, the entire content of
which is incorporated herein by reference. Although measures of smoothness of
from about between 0 Ra and 60 Ra are preferred and measures of roughness from
about between 65 Ra and 600 Ra are preferred, it is noted that the improved
masking film may have virtually any level of relative smoothness or roughness
and
still prevent much of the blocking and wrinkling associated with traditional
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masking films. Matte embossing is a preferred technique for imparting a
sufficient
level of roughness to the second layer. Although matte embossing has been
described as a preferred technique by which the second layer is provided with
roughness, it should be noted that the roughing of the surface of the second
layer
may be accomplished via any suitable method or means, if desired.
It is noted that although the preferred embodiment includes at least a first
layer and a second layer, the relatively smooth side and the relatively rough
side of
the improved masking film of the present invention can be formed on opposite
sides of a single layer of thermoplastic material, if desired. In such an
embodiment, no core layers would be present.
Returning now to the preferred embodiment, fillers added to the second
layer will provide certain desired characteristics, including, for
illustrative purposes
only, roughness, abrasion resistance, printability, writeability, opacity and
color.
Such fillers are well known in the industry and include, for illustrative
purposes
only, calcium carbonate (abrasion resistance), mica (printability), titanium
dioxide
(color and opacity) and silicon dioxide (roughness).
The degree of relative smoothness/roughness desired can be imparted via
any suitable means known in the art, including, without limitation, air
impingement, air jets, water jets, and combinations thereof.
In a preferred embodiment, the multiple layers of the improved masking
film of the present invention are coextruded using any coextrusion process
known
in the art. The use of coextrusion allows for the relatively simple and easy
manufacture of a multilayered masking film composed of distinct layers, each
performing specific functions. Although coextrusion of the improved
multilayered
masking film of the present invention is preferred, it is again noted that the
improved masking film can be monolayered or multilayered and that, regardless
of
form, the improved masking film can be produced using any other suitable
method,
if desired.
In use, the relatively smooth surface of the first layer of the improved
masking film of the present invention is brought into intimate contact with a
relatively smooth surface to be protected. While not wishing to be bound by
the
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following theory, the Applicants believe that the smooth surface of the
masking
film adheres to the smooth surface of the substrate to be protected through
intimate
contact via the natural blocking adhesion which exists between a very smooth
surface and another smooth surface via polar bonding, ionic bonding and, in
some
instances, hydrogen bonding, and/or Van der Waals secondary bonding. Preferred
substrates for such surfaces include, by way of illustration only,
polycarbonates,
acrylics, PET, PETG, glass, ceramics and metals.
While the foregoing theory also applies to prior art OSM type films, it has
been discovered that the relative smoothness/roughness of the smooth side of
the
improved film of the present invention plays a less important role in the
production
of adhesion, thus allowing the improved masking film of the present invention
to
be used under a wider variety of conditions (e.g., temperature at the time the
masking film is applied). Generally, it has been discovered that the relative
smoothness of the smooth side of film will be of greater importance where
application temperatures during the masking process are lower. Conversely, the
higher the application temperature, the less important a role the relative
smoothness
plays.
Any one or more of a number of conventional application methods can be
used to bring the smooth side of the first layer of the improved masking film
into
intimate contact with the smooth surface of the substrate to be protected by
the
masking film. Typically, the improved masking film will be applied to the
surface
to be protected via a nip roll or similar system through which the
multilayered film
and the substrate surface to be protected are passed simultaneously. If
desired, the
resulting article can be passed through compression rolls or the like for
further
processing. Any other suitable method for combining the multilayer film with
the
substrate surface to be protected can be used, if desired.
Turning now to the level of adhesion produced between the smooth side of
the first layer of the improved masking film of the present invention and the
substrate surface to be protected, a significant improvement in OSM masking
films
has been achieved with the improved masking film of the present invention due
to
its ability to have the adhesion level adjusted according to specific
production and
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application conditions. Adjustment of the adhesion level allows the improved
masking film of the present invention to provide a functional level of
adhesion in
connection with certain substrates at room temperature. Traditional OSM
masking
films typically require heat to produce the desired level of adhesion. For
example,
in some applications, latent heat within the substrate's surface to be
protected
creates a desired adhesion level. However, this will vary from machine to
machine
in a single process, and even more widely between processes, thus making the
use
of OSM masking films more difficult and expensive since adjustments in
procedure
and/or equipment are needed to consistently achieve a desired level of
adhesion.
Additionally, in some instances where post-production heat-loading processes,
including, but not limited to, thermoforming, drape-forming and heat-bending,
are
employed with masking films which do not provide adequate adhesion at room
temperature, the masking film is destroyed upon subsequent attempts to remove
the
film. Destruction of the masking film occurs in these attempts at removal
since the
heat-loading has increased the adhesion force between the substrate surface
and the
masking film to a point where the peel strength needed to remove the masking
film
exceeds the tensile strength of the masking film itself thus causing the film
to tear
or break before it will peel away from the substrate.
Adjustment of the adhesion level produced in the present invention is
accomplished through the introduction of certain polymex/copolymers into the
smooth side of the thermoplastic film. A preferred copolymer associated with
the
smooth side of the first layer to affect the adhesion level produced is a
metallocene
catalyzed polyethylene with octene comonomer, such as EG-8200 or PFl 140,
available from either Dow Chemical Company or DuPont Chemical Company. In
such copolymers, it has been discovered that the percentage of octene
comonomer
influences the level of adhesion of the film to the substrate.
As previously discussed, depending upon the desired application, the
polymerl copolymer blends may be modified for improved performance. It is
noted
that embodiments of the present invention masking film including only a
primary
component exist and are useful as described herein.
A further understanding of the improved masking film of the present
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invention can be obtained by reference to FIGURES 1 and 2. FIGURE 1 depicts a
graph illustrating the peel adhesion values measured on acrylic and
polycarbonate
substrates using a masking film as a function of percentage comonomer
component
of the masking film. FIGURE 2 depicts a graph illustrating peel adhesion
values to
polycarbonate and acrylic substrates as a function of application temperature
for a
18% octene comonomer content masking film. The test data were produced and
gathered according to the following test procedures.
TEST PROCEDURES
FIGURE 1
The smooth side of a coextruded film was made by blending varying
percentages of an copolymers with varying percentages of octene comonomers.
The resulting film was then masked to a sheet of 1/8" acrylic or polycarbonate
by
contacting the sheet with the masking film at room temperature and nip rolling
the
masked sheet to remove any air. The resulting masked sheet was then placed
into
an oven at various temperatures for a period of 8 minutes for each
temperature.
The masked sheet was then removed from the oven and nip rolled again. A one
inch strip of the masking film was used in a 180 ° peel test. The peel
tests were
conducted according to a modified version of ASTM Standard D3330-90. An
Instron tensile testing machine was used to measure the force required to peel
4-6
inches of a one inch-wide strip of masking film from the acrylic sheet. The
results
of the above-identified tests are summarized in FIGURE 1
As is demonstrated in the graph of FIGURE 1, there is a strong relationship
between the percentage comonomer component present and the strength of
adhesion produced by the resultant masking film. At a given temperature, the
higher the percentage of comonomer, the higher the adhesion to the substrate.
As
previously mentioned, the addition of other polyethylenes can also adjust the
adhesion level produced.
FIGURE 2
The smooth side of a coextruded film was made by blending two
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copolymers with varying percentages of octene comonomer contents in such ratio
so as to obtain an overall 18% comonomer content. The resulting film was then
masked to a sheet of 1/8" acrylic or polycarbonate by contacting the sheet
with the
masking film at room temperature and nip rolling the masked sheet to remove
any
air. The resulting masked sheet was then placed into an oven at various
temperatures for a period of 8 minutes for each temperature. The masked sheet
was
then removed from the oven and nip rolled again. A one inch strip of the
masking
film was used in a 180° peel test. The peel tests were conducted
according to a
modified version of ASTM Standard D3330-90. An Instron tensile testing machine
was used to measure the force required to peel 4-6 inches of a one inch-wide
strip
of masking film from the acrylic sheet. The results of the above-identified
tests are
summarized in FIGURE 2. As illustrated in FIGURE 2, the peel strength values
increase with temperature.
All of the samples tested above were further tested for performance
subsequent to undergoing a heat-loading process, such as thermoforming,
drape-forming and heat-bending. In the heat-bending procedure, the sample
sheet
was heated to its softening point using a conventional "strip heater". The
softening
point was visually inspected by recording the temperature at which the sheet
bent
over the strip heater to a predetermined angle. The temperature of such
bending
was at or above 100°C for acrylic and 150°C for polycarbonate.
Once the sheet
was bent to the predetermined angle, the sheet was allowed to cool to maintain
the
desired angle. For thermoforming, the sheet samples were heated to their glass
transition temperature and then forced via vacuum into a desired shape using a
vacuum mold.
All of the samples performed well under these heat-loading tests in that the
improved masking sheets of the present invention were peeled from the surface
after such heat-loading treatment without destruction of the masking film.
The results of the above-identified tests are summarized in Tables I and II
below.
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TABLE 1
Peel Strength on Polycarbonate Substrate - 3 Hours Post Masking
Application Temp.Prior Art AdhesionPresent Invention
(F) (g/in) Adhesion ( in)
73 0-25 0-32
120 10-70 3-70
200 30 to Destruct 54-500
After Heat LoadingDestructs Peels
Process
TABLE 2
Peel Strength on Acrylic Substrate - 3 Hours Post Masking
Application Temp Prior Art AdhesionPresent Invention
(F) (g/in) Adhesion ( in)
73 0-25 0-25
120 10-70 3-36
200 30 to Destruct 27-250
After Heat LoadingDestructs Peels
Process
As evidenced by the foregoing, by varying the comonomer content (e.g.,
blend components and percentages thereof) comprising the improved masking film
of the present invention, the level of adhesion produced between the improved
masking film of the present invention and the substrate surface to be
protected, as
expressed by the peel force numbers in the TABLES, is also adjusted. Thus,
using
the improved masking film of the present invention, it is possible to: (a)
produce a
desired level of adhesion by selecting the appropriate blend of copolymer and
octene comonomer (and/or blend or materials and percentages thereofj; and (b)
use
the improved masking film of the present invention on substrates subject to
post-
production heat-loading processes (e.g., thermoforming, drape-forming and heat-
bending) without destruction of the film upon subsequent removal thereof.
SUBSTITUTE SHEET (RULE 26)
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Importantly, the desired level of adhesion is achieved despite the processing
environment and application constraints under which such masking film is used.
For example, if the desired application and application context is to
functionally
adhere the masking film to polycarbonate at..room temperature the appropriate
copolymer or combination of copolymers can be selected and produced using the
improved masking film of the present invention. Even where the masking film is
to protect a relatively rough surface, the blend and temperature can be
altered to
produce the appropriate level of adhesion. With prior art masking films, the
processing environment (e.g., equipment placement) and/or desired application
temperature were often altered in an effort to obtain the desired adhesion
level from
the masking film.
The improved masking film of the present invention is thus capable of
providing a controlled, adjustable and adequate level of protection to smooth
surfaces of substrates by providing a controlled level of adhesion between the
masking film and the surface to be protected without the use of corona
treatment or
an adhesive and their associated disadvantages and under a variety of
production
and application conditions. The unique advantages of the improved masking film
of the present invention allow the film to be modified to meet the desired
application and processing environment.
According to the method of the present invention, the above-identified
improved masking film is produced employing the steps of preselecting one or
more primary copolymers of the at least one first skin layer of the film,
preferably
copolymers which include octene comonomer content varying from about 5% to
about 30% (hexene and butene comonomers can also be used); predetermining the
relative percentages of each constituent element selected. The density of the
at
least one first layer of polymer can vary from about (>.86 to 0.92 g/cm3;
coextruding
the at least one first layer with the at least one second layer and the at
least one core
layer to form a multilayered masking film. The resulting masking film is
tailored
made to perform (i.e., produce a desired level of adhesion) under a given set
of
production conditions and environment.
Although preferred embodiments of the invention have been described in
CA 02349255 2001-05-02
WO 00/27614 PCTNS98/23602
-15-
the Graphs, Tables and foregoing Detailed Description, it will be understood
that
the invention is not limited to the embodiments disclosed, but is capable of
numerous rearrangements and modifications of parts and elements without
departing from the spirit of the invention.
