Note: Descriptions are shown in the official language in which they were submitted.
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DECORATIVE SHEET MATERIAL
WITH CHLORINATED POLYOLEF1N ADHESIVE LAYER
FIELD OF THE INVENTION
The present invention relates to sheet materials generally and more
particularly
relates to a sheet material suitable for use as a flexible, weatherable paint
film.
S
BACKGROUND OF THE INVENTION
Manufacturers have shown increasing interest in using paint films in lieu of
spray painting for providing a decorative surface finish for parts, such as
automobile
body parts. This manufacturing technique reduces the environmental concerns
associated with painting and has the potential to reduce manufacturing costs.
An
automobile body part utilizing a plastic paint film to provide a high quality
base
coat/clear coat automotive finish is disclosed, for example, in U.S. Patent
No.
4,810,540, which is incorporated by reference herein in its entirety. In
producing the
part, the paint film is typically formed into a contoured three-dimensional
configuration corresponding to the shape of the outer surface of the part by
suitable
methods, such as by thermoforming.
Automotive manufacturers, for example, require that automotive parts have an
exterior paint appearance which meets demanding performance and appearance
specifications, such as weatherability, resistance to ultraviolet light
degradation, high
gloss, and high distinctness-of image (DOI). In addition, the adhesive layer
used to
bond the paint film to a substrate must withstand the effects of changes in
temperature
over a wide range of temperatures without losing adhesion or cohesive
strength. For
instance, some industry tests involve subjecting the paint film to an abrupt
change in
temperature from approximately 0°C to approximately 100°C. The
adhesive must be
capable of withstanding such a temperature change without delamination of the
paint
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film from the substrate occurring. Further, since the paint film may be used
to surface
parts having complex three-dimensional configurations, the adhesive must
exhibit
good elongation properties at thermoforming temperatures. There remains a need
for
an adhesive material that possesses the characteristics listed above.
SUMMARY OF THE INVENTION
The adhesive composition of the present invention comprises a mixture
or blend of a chlorinated polypropylene and a higher molecular weight
chlorinated
polyolefin that provides both good adhesion to adjacent film layers and good
elongation and cohesive strength over a wide range of temperatures. The
chlorinated
polypropylene has a higher softening point than the chlorinated polyolefm,
which
enhances the cohesive strength of the adhesive composition, while the
chlorinated
polyolefin component provides good adhesion at room temperature. The two
chlorinated components have comparable chlorine content in order to ensure
chemical
1 S compatibility.
The adhesive composition of the present invention includes a chlorinated
polypropylene component having a peel strength of at least about 0.8 lbs./in.
at 100°C
and a chlorinated polyolefin component having a peel strength of at least
about 5
lbs./in. at room temperature. Room temperature is defined as about 15°C
to about
30°C. In one embodiment, the chlorinated polypropylene component has a
peel
strength of at least about 1.0 lbs./in. at 100°C, and the chlorinated
polyolefm
component has a peel strength of at least about 7 lbs./in. at room
temperature.
Preferably, the chlorinated polyolefin is present in the composition at a
concentration
of about 1 to about 10 weight percent and the chlorinated polypropylene is
present in
an amount of about 5 to about 20 weight percent. The adhesive composition may
further comprise any compatible solvent known in the art.
Preferably, the chlorinated polypropylene component has a peel strength of at
least about 0.8 lbs./in. at room temperature, and the chlorinated polyolefm
component
has a peel strength of at least about 0.2 lbs./in. at 100°C. Most
preferably, the
chlorinated polypropylene component has a peel strength of at least about 1.0
lbs./in.
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at room temperature, and the chlorinated polyolefin has a peel strength of at
least
about 0.4 lbs./in. at 100°C.
The two chlorinated components have similar chlorine contents. Preferably,
both components have a chlorine content of about 20 to about 40 weight
percent.
Additionally, the chlorinated polypropylene has a softening point of at least
about
85°C, and preferably at least about 100°C.
The adhesive composition may also comprise an epoxy component, preferably
in an amount of about 0.1 to about 2.0 weight percent on a dry solids basis.
Additionally, the adhesive composition may contain a pigment component, such
as
carbon black, titanium oxide, and mixtures thereof. The adhesive composition
may
also contain further additives such as IJV screeners, heat stabilizers,
antioxidants, and
mixtures thereof.
Preferably, the adhesive composition is in the form of a film layer. In dried
film form, the adhesive layer comprises about 30 to about 70 weight percent
chlorinated polyolefin component and about 30 to about 70 weight percent
chlorinated
polypropylene component. In one embodiment, the adhesive layer comprises about
30
weight percent chlorinated polyolefm and about 70 weight percent chlorinated
polypropylene.
For example, the present invention provides a flexible, weatherable decorative
sheet material comprising a decorative paint film and an adhesive layer
overlying the
inner surface of the decorative paint film, wherein the adhesive layer
comprises the
chlorinated polypropylene and chlorinated polyolefin components described
above.
Preferably, the decorative paint film has a 60 degree gloss value of at least
60.
Further, the decorative sheet material may include a primer layer adhering the
inner surface of the decorative paint film to the adhesive layer. Preferably,
the primer
layer comprises an acrylic polymer composition. The decorative sheet material
may
further include a thermoformable backing layer adhered to the opposing surface
of the
adhesive layer. Additionally, the decorative sheet material may include an
extensible
mask layer releasibly adhered to the outer surface of the paint film to form a
protective
film overlying the paint film. For example, a mask layer comprising a polymer
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selected from the group consisting of polyurethane, polyolefin, polyester, and
polyamide may be used.
The present invention also includes a method of making a flexible weatherable
decorative sheet material. The method includes the steps of forming a
thermoformable
decorative paint film and applying a coating of an adhesive composition to the
inner
surface of the paint film to form an adhesive layer, wherein the adhesive
composition
comprises the chlorinated components described above. The method may also
include
the steps of applying a primer layer to the inner surface of the decorative
paint film
prior to application of the adhesive layer. Also, the method may include the
step of
applying a thermoformable backing layer to the exposed surface of the adhesive
layer,
such that the adhesive layer bonds the backing layer to the paint film.
The decorative paint film may be formed by applying at least one coating layer
to a smooth flexible casting surface and drying the coating layer on the
casting surface
to produce a paint film so that the outer surface of the paint film is
releasably bonded
to the casting surface. The decorative paint film may comprise a single layer
of a
pigmented polymer or may comprise both a clear coat layer and a pigmented
color
coat layer.
The decorative sheet material constructed using the method outlined above
may be thermoformed into a three-dimensional shape and the exposed surface of
the
thermoformable backing layer may be bonded to a substrate to form a composite
shaped part. The decorative sheet material of the present invention may be
inserted
into a mold, such as a compression mold or an injection mold, and bonded to
the
substrate to form the composite shaped part. The decorative sheet material may
be
inserted into the mold in the form of a substantially flat sheet or after
thermoforming
the sheet material into a preform.
BRIEF DESCRIPTION OF THE DRAWINGS
Having thus described the invention in general terms, reference will now be
made to the accompanying drawings, which are not necessarily drawn to scale,
and
wherein:
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Figure 1 is a perspective view of an automobile illustrating the front fascia
of
the automobile having a decorative paint film applied thereto;
Figure 2 is a front view of an automobile front fascia having a decorative
paint
film applied thereto;
S Figure 3 is a cross-sectional view of the fascia shown in Figure 2 taken
along
line 3-3 of Figure 2;
Figure 4 is a cross-sectional view of the decorative sheet material of the
present invention adhered to a substrate;
Figure 5 is a cross-sectional view of the decorative sheet material of the
present invention including a clear coat and a color coat layer;
Figure 6 is a cross-sectional view of the decorative sheet material of the
present invention having a single paint film layer;
Figure 7 is a schematic illustration of a process for construction of the
decorative sheet material of the present invention;
Figure 8 is a schematic illustration of a process for applying the mask layer
to
the outer surface of a decorative paint film;
Figures 9A-9D are schematic illustrations of the steps in a thermoforming
process used to construct a preform; and
Figures l0A-lOC are schematic illustrations of steps in an injection molding
process for forming a composite shaped part.
DETAILED DESCRIPTION OF THE INVENTION
The present invention now will be described more fully hereinafter with
reference to the accompanying drawings, in which preferred embodiments of the
invention are shown. This invention may, however, be embodied in many
different
forms and should not be construed as limited to the embodiments set forth
herein;
rather, these embodiments are provided so that this disclosure will be
thorough and
complete, and will fully convey the scope of the invention to those skilled in
the art.
Like numbers refer to like elements throughout.
Figure 1 illustrates an automobile 10 having a composite shaped part 12. As
shown, the composite shaped part 12 is a complex, contoured three-dimensional
front
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fascia of the automobile 10. The composite shaped part 12 has a decorative
sheet
material 14 applied thereto. Although not limited to such applications, the
decorative
sheet material 14 of the present invention is particularly advantageous for
providing a
decorative surface on a composite shaped part 12 of an automobile 10. However,
those skilled in the art will appreciate that the present invention could be
used in a
variety of applications requiring a weatherable, decorative surface.
Figure 2 is a front view of the composite shaped part 12 having the decorative
sheet material 14 applied thereto. Figure 3 is a cross-sectional side view of
the
composite shaped part 12 comprising a substrate 16 having a decorative sheet
material
14 applied thereto. As illustrated in Figure 3, the decorative sheet material
14
undergoes different amounts of elongation at different points along the
contoured
surface of the composite shaped part 12. In one embodiment, the decorative
sheet
material 14 of the present invention has a three-dimensional configuration in
which
certain areas of the sheet material have been subjected to elongation in
excess of about
300%, and other areas of the sheet material are substantially non-elongated.
However,
the difference in gloss value between the elongated areas and the non-
elongated areas
should be no more than 10 gloss units with a minimum 60 degree gloss value of
at
least 60. The decorative sheet material 14 of the present invention is capable
of
maintaining a high level of gloss regardless of the amount of elongation
experienced
by the decorative sheet material during a thermoforming or molding process.
Figure 4 shows a greatly expanded cross-sectional view of a composite shaped
part 12 comprising a decorative sheet material 14 of the present invention
adhered to a
substrate 16. The decorative sheet material includes a mask layer 20, a clear
coat layer
22, a color coat layer 24, a primer layer 26, an adhesive layer 28, and a
thermoformable backing layer 30.
The extensible mask layer 20 is designed to maintain gloss and DOI during
forming processes and molding processes. Forming processes include, but are
not
limited to, thermoforming, cold stretching, and vacuum forming. Molding
processes
include, but are not limited to, injection molding, compression molding, and
blow
molding. The mask layer 20 also adds strength to the decorative sheet material
14 and
improves process uniformity during the thermoforming process. Additionally,
the
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extensible mask layer 20 protects the underlying layers of the decorative
sheet
material 14 from scratching or marnng until the part is ready for display. The
mask
layer 20 is capable of stretching up to about 600 percent during thermoforming
and
has a room temperature elongation at break of at least about 200 percent.
The mask layer 20 may be retained as the outer layer of the decorative sheet
material 14 during construction of the final product, such as an automobile.
Thereafter, the mask layer 20 may be removed to reveal the underlying
decorative
paint film 18. For instance, the extensible mask layer 20 can be maintained as
a
protective layer and removed only after the vehicle has completed shipment and
is
ready for delivery to a customer. The extensible mask layer 20 is releasably
bonded to
the underlying decorative paint film 18 and may be stripped away from the
underlying
layers in a single piece. In a preferred embodiment, the mask layer 20 is
transparent
or substantially transparent to permit visual inspection of the part for
surface defects
without removal of the mask layer.
1 S Additionally, the extensible mask layer 20 maintains high gloss and DOI
during injection or compression molding, such as thermoplastic or thermoset
compression molding, where the mold is roughened or deglossed. Roughened molds
are less expensive than highly polished molds and are also functionally
superior to
highly polished molds because the rough mold surface enhances air removal from
the
mold as the mold closes. The extensible mask layer 20 protects the paint film
18 from
loss of gloss or other damage caused by the mold without resorting to the use
of highly
polished molds.
Preferably, the extensible mask layer 20 is about 0.3 mils to about 3.0 mils
in
thickness. The extensible mask layer ZO comprises polyurethane, polyolefin,
such as
polyethylene and polypropylene, polyester, such as polyethylene terephthalate,
or
polyamide. Preferably, the mask layer 20 comprises a dried film of an
aliphatic or
aromatic polyester or polyether polyurethane in the form of a dispersion or a
solution.
For example, polyurethane polymers QA 5218 and QA 5026, manufactured by Mace
Adhesives and Coatings of Dudley, Massachusetts, may be used to form the mask
layer 20. In one embodiment, the mask layer 20 comprises about 85 to about
99.5
weight percent polyurethane water-borne dispersion. Advantageously, a small
amount
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of surfactant (about 0.05 to about 0.2 weight percent), such as SURFYNOL 104H
manufactured by Air Products of Allentown, PA, is added to lower surface
tension.
The mask layer 20 composition may include additional additives designed to
migrate into the clear coat layer 22 to enhance weatherability or other
desirable
properties of the clear coat layer or to prevent migration of additives from
the clear
coat into the mask layer. Migratory additives suitable for use with the
present
invention include, but are not limited to, hardness enhancers, release agents,
ultraviolet
light stabilizers, antioxidants, dyes, lubricants, surfactants, catalysts, and
slip
additives.
More specifically, the migratory additives useful in the present invention
include benzophenone, silicones, waxes, triazoles, and triazines. The
migratory
additives are encouraged to migrate into the outer surface of the clear coat
layer 22 by
the heat and/or pressure present during thermoforming processes and in-mold
processes. Additionally, the presence of these additives in the mask layer 20
prevents
migration of additive components from the clear coat layer 22 into the mask
layer.
Ultraviolet light stabilizers, such as TINUVIN 1130 and TINUVIN 292, both
manufactured by Ciba Geigy of Hawthorne, NY, can be added as migratory
additives
in the mask layer 20 composition. Silicone additives, such as BYK333
manufactured
by BYK Chemie of Wallingford, CT, can be added to lower the coefficient of
friction
of the clear coat layer 22. The migratory additives are generally added in
amounts
ranging from about 0.01 to about 2.0 weight percent, with all additives
accounting for
no more than about 5.0 weight percent of the mask layer 20 composition.
Figures 5 and 6 are greatly expanded cross-sectional views of two
embodiments of the decorative sheet material 14 of the present invention. The
decorative paint film 18 may comprise a single layer 25 of a pigmented
polymer, as
shown in Figure 6, or may comprise multiple layers, as shown in Figures 4 and
5. If a
single layer 25 of pigmented polymer is used, the polymer may be selected from
the
group consisting of urethane polymers, acrylic polymers, fluoropolymers, and
alloys
of a fluoropolymer and an acrylic polymer. FLUOREX~ films manufactured by
Rexam are examples of alloys of a fluoropolymer and an acrylic polymer. The
single
layer 25 of pigmented polymer may also include UV screeners to enhance
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weatherability, antioxidants, heat stabilizers, and other conventional
additives. The
pigmented polymer layer 25 may further include pigments, dyes, and/or flakes
to
enhance visual appearance.
As shown in Figures 4 and 5, the decorative paint film 18 may also comprise
both a clear coat layer 22 and a color coat layer 24. The clear coat layer 22
is formed
from a substantially transparent weatherable polymer composition selected to
provide
a film which will not significantly fade, peel, crack, or chalk when exposed
to the
environment for the intended life of the part 12. Additionally, the clear coat
layer 22
must be formable from a two-dimensional surface to a three-dimensional surface
without objectionable loss of appearance or performance properties.
Advantageously,
the clear coat layer 22 is selected from the group consisting of urethane
polymers,
acrylic polymers, fluoropolymers, and alloys or a fluoropolymer and an acrylic
polymer (such as FLUOREX~ films). As with the single pigmented polymer layer
25, the clear coat layer 22 may include UV screeners, antioxidants, heat
stabilizers,
and other conventional additives. Preferably, the clearcoat layer 22 is about
0.3 to
about 3 mils in thickness.
The color coat layer 24 is formed of a polymer composition containing a
uniformly dispersed pigment to provide the appearance necessary for exterior
automobile use. Preferably, the color coat layer 24 is selected from the group
consisting of urethane polymers, acrylic polymers, fluoropolymers, and alloys
of a
fluoropolymer and acrylic polymer (such as FLUOREX~ films). The color coat
layer
24 may include pigments, dyes, and/or flakes to enhance visual appearance and
improve weatherability. Preferably, the color coat layer 24 is about 0.3 to
about 3 mils
in thickness.
If desired, a color adjustment layer 27 may be added between the clear coat
layer 22 and the color coat layer 24 to enhance visual appearance. The color
adjustment layer 27 can be applied in coating form and include pigments, dyes
and/or
flakes or applied as a graphic design using printing methods such as gravure,
rotary
screen, flat bed step-and-repeat screen, ink jet, flexographic or other
printing
techniques.
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The primer layer 26 improves adhesion between the color coat layer 24 and the
adhesive layer 28. The primer layer 26 preferably comprises an acrylic polymer
prepared in solution using any compatible solvent known in the art, such as
toluene.
In one embodiment, the primer layer 26 is prepared from a solution comprising
about
65 to about 85 weight percent acrylic composition and about 5 to about 10
weight
percent solvent. An acrylic polymer suitable for use in the primer layer 26 is
acrylic
adhesive 68070 manufactured by DuPont. The primer layer 26 may be opaque,
colored or clear. Opaque is defined as less than 1 percent transmission at a
wavelength of less than 400 nm. The primer layer 26 is preferably about 0.2 to
about
2 mils in thickness. The primer layer 26 may be colored or opaque to protect
the
underlying thermoformable backing layer 30 from damage caused by UV exposure.
Pigments such as carbon black, titanium oxide, and mixtures thereof may be
added to
impart color to the acrylic polymer composition used in the primer layer 26.
Additionally, additives such as UV screeners, antioxidants, and heat
stabilizers may be
added to the primer layer 26.
The adhesive layer 28 adheres the decorative paint film 18 to a
thermoformable backing layer 30. The adhesive layer 28 comprises a mixture or
blend of a chlorinated polypropylene and a higher molecular weight chlorinated
polyolefin. In one embodiment, the adhesive layer 28 is formed from a mixture
of
about 5 to about 20 weight percent chlorinated polypropylene and about 1 to
about 10
weight percent of a higher molecular weight chlorinated polyolefm formed in
solution.
A compatible solvent known in the art, such as toluene, is present in an
amount of
about 60 to about 80 weight percent. After evaporation of the solvent, the
dried
adhesive layer 28 comprises about 30 to about 70 weight percent chlorinated
polyolefm and about 30 to about 70 weight percent chlorinated polypropylene.
In one
embodiment, the adhesive layer 28 comprises about 30 weight percent
chlorinated
polyolefin and about 70 weight percent chlorinated polypropylene. A
chlorinated
polypropylene suitable for use with the present invention is HARDLEN 13-LP
manufactured by Advanced Polymer. A higher molecular weight chlorinated
polyolefin suitable for use with the present invention is SUPERCHLON 8225
manufactured by CP/Phibrochem of Fort Lee, NJ. The adhesive layer 28 should be
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capable of stretching about 300 to about 600 percent. Due to the substantial
elongation capability of the adhesive layer 28, the adhesive layer maintains
the
necessary adhesive strength to prevent delamination of the decorative paint
film 18
from the thermoformable backing layer 30 over a wide temperature range. The
adhesive layer 28 must have good adhesion to the backing layer 30 and the
primer
layer 26. Additionally, the adhesive layer 28 must exhibit good cohesive
strength at
100°C and good elongation properties at thermoforming temperature
(about 190° to
about 200°C).
The blend of chlorinated polypropylene and higher molecular weight
chlorinated polyolefin provides both good adhesion to adjacent film layers and
good
elongation and cohesive strength over a wide range of temperatures. The
chlorinated
polypropylene component, such as HARDLEN 13-LP, has a higher softening point
than the chlorinated polyolefin component, which enhances the cohesive
strength of
the adhesive layer 28, particularly at elevated temperatures. The higher
molecular
weight chlorinated polyolefin component, such as SUPERCHLON 8225, provides
good adhesion at room temperature. The two chlorinated components should have
comparable chlorine content in order to ensure chemical compatibility. The two
chlorinated components preferably have a chlorine content of about 20 to about
40
weight percent, and most preferably, a chlorine content of about 20 to about
30 weight
percent.
The higher molecular chlorinated polyolefin should have a peel strength at
room temperature of at least about 5 lbs./in., and preferably about 7 lbs./in.
Additionally, the chlorinated polyolefm should have a peel strength at
100°C of at
least about 0.2 lbs./in., and preferably at least about 0.4 lbs./in. The
chlorinated
polypropylene should have a peel strength of at least about 0.8 lbs./in at
room
temperature, and preferably at least about 1.0 lbs./in. Further, the
chlorinated
polypropylene should have a peel strength at 100°C of at least about
0.8 lbs./in., and
preferably at least about 1.0 lbs./in. The softening point of the chlorinated
polypropylene component should be at least about 85°C, and preferably
at least about
100°C. Peel strength at room temperature was measured using Sintech
System I
manufactured by Sintech, Inc. Peel strength at elevated temperature was
measured
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using an INSTRON machine, model 4467, coupled with a heating unit that allows
temperature control of the sample. Using either machine, peel strength was
measured
using a 180 degree peel with a cross head speed of 4 inches/minute.
An epoxy component, such as EPON 828RS manufactured by Shell Chemical,
may be added in small amounts (approximately about 0.1 to about 2.0 weight
percent
on a dry solids basis) as an acid scavenger. As with the primer layer 26, the
adhesive
layer 28 may be colored or opaque to protect the underlying thermoformable
backing
layer 30 from damage caused by UV exposure. Pigments such as carbon black,
titanium oxide, and mixtures thereof may be added to impart color to the
polymer
composition used in the adhesive layer 28. Additives such as UV screeners,
antioxidants, and heat stabilizers may be added to the adhesive layer 28.
Preferably,
the adhesive layer 28 is about 0.2 to about 2 mils in thickness.
The thermoformable backing layer 30 bonds the decorative paint film 18 of the
decorative sheet material 14 to the substrate 16. In addition, the backing
layer 30
provides bulk and/or rigidity for handling the decorative sheet material 14 as
a
thermoformed preform. The backing layer 30 also provides thickness to prevent
glass
fibers, fillers or other sources of visual roughening or "orange peel" from
the substrate
16 from affecting the visual appearance of the decorative sheet material 14.
The
backing layer 30 must bond well with both the substrate 16 and the adhesive
layer 28.
The backing layer 30 may be selected from the group consisting of
thermoplastic
olefin, acrylonitrile-butadiene-styrene terpolymer, polypropylene,
thermoplastic
polyimide, polyethylene oxide, polycarbonate, polyvinyl chloride, polystyrene,
styrene/polyphenylene oxide (NORYEL), polybutylene terephthalate, nylon, PETG
copolyester, and mixtures, laminates and copolymers thereof, depending on the
material used as the substrate 16.
Figure 7 illustrates a process for constructing the decorative sheet material
14
of the present invention. As shown, a film Garner 33 is advanced from a supply
roll 38
through a series of process steps. The film carrier 33 preferably comprises a
polyester
casting film having a high gloss surface. The film carrier 33 is important for
high
gloss applications because it imparts high gloss and DOI to the decorative
sheet
material 14. Advantageously, the film carrier 33 comprises polyethylene
terephthalate
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(PET) in a grade without slip additives. The film carrier 33 is about 1 to
about 3 mils
in thickness, preferably about 2 mils in thickness.
The film Garner 33 passes through a first coating station 40. If a single
pigmented layer 25 is used as the decorative paint film 18, the pigmented
layer is
deposited onto the film carrier 33 using coating station 40 and the resulting
film is
dried by dryer 46. If a decorative paint film 18 having multiple coatings is
desired, the
first coating station 40 may deposit the clear coat layer 22. The clear coat
layer 22
then passes through a dryer 42. Thereafter, a color coat layer 24 is deposited
on the
dried clear coat layer 22 using coating station 44. The color coat layer 24 is
then dried
using dryer 46. Optionally, the dried color coat layer 24 can be subjected to
a corona
treatment (not shown).
The coating stations 40 and 44 may utilize any conventional coating or casting
techniques, such as reverse roll coating or slot die coating techniques. Slot
die coating
methods are preferred.
The dryers 42 and 46 may utilize any conventional drying technique.
Preferably the dryers 42 and 46 are ovens having multiple heating zones
wherein each
successive heating zone operates at a progressively higher temperature. For
example,
an oven having four to six heating zones ranging in temperature from about 200
F to
about 400 F may be used. Alternatively, dryer 42 may be eliminated from the
process
such that the color coat 24 is applied to the clear coat 22 while the clear
coat is still
wet.
After the decorative paint film 18 is applied to the film carrier 33, the film
carrier advances to a primer coating station 48, where the primer layer 26 is
deposited
onto the exposed layer of the decorative paint film 18. The primer layer 26 is
then
dried using dryer 49. Thereafter, the film Garner advances to an adhesive
coating
station 50, where the adhesive layer 28 is deposited onto the primer layer 26.
Thereafter, the adhesive layer 28 is dried using dryer 51. The primer coating
station
48 and adhesive coating station 50 may utilize any conventional coating or
casting
technique, such as reverse roll coating or slot die coating techniques. The
dryers 49
and 51 may utilize any conventional drying technique.
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A thermoformable backing layer 30 is advanced from a supply roll 52 and
laminated to the adhesive-coated surface of the film Garner 33. Optionally,
the
backing layer 30 can be subjected to a corona treatment (not shown) prior to
lamination. The resulting laminate is collected by product roll 54.
Figure 8 illustrates a process for preparing a decorative sheet material 14
having a mask layer 20. A non-extensible carrier 34 is advanced from a supply
roll
58. The Garner 34 may be constructed of the same material used for the film
carrier
33. Preferably, the carrier 34 comprises a polyethylene terephthalate film.
The Garner
34 advances through a coating station 60, where the mask layer 20 is deposited
onto a
surface of the carrier. The coating station 60 may utilize any coating or
casting
technique known in the art, such as reverse roll coating or slot die coating
techniques.
Thereafter, the coated carrier 34 passes through a dryer 62 to form a dried
mask layer
20. As discussed above in connection with dryers 42 and 46 used to dry the
decorative
paint film 18, the dryer 62 used to dry the mask layer 20 may utilize any
conventional
drying technique. Preferably, the dryer 62 comprises an oven with multiple
heating
stages. The dryer 62 evaporates the solvents present in the mask layer 20
composition.
The layers of the decorative sheet material 14 formed in the process
illustrated
in Figure 7 are advanced from a supply roll 56. The film carrier 33 is
stripped away
from the remaining layers to expose either the single pigmented layer 25 or
the clear
coat layer 22 of the decorative paint film 18, depending on the construction
of the
paint film used. The exposed outer layer of the decorative paint film 18 is
laminated
and releasably bonded to the mask layer 20 by nipping the two films between
two
rollers, 64 and 65, with or without applying heat to the layers. The resulting
decorative sheet material 14 is collected by product roll 67. The non-
extensible Garner
34 may be stripped away to expose the mask layer ZO before or after collection
of the
sheet material 14 by product roll 67.
In another embodiment, the decorative paint film 18, primer layer 26, and
adhesive layer 28 are coated directly onto the dried mask layer 20 rather than
laminating the coated films together. In a further embodiment, the mask layer
is
coated onto the clear coat layer 22. For example, a decorative sheet material
14
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prepared according to Figure 7 could be stripped from carrier 33 so that the
mask layer
20 can be coated directly onto the clear coat layer 22.
The decorative sheet material 14 of the present invention can be adhered to a
supporting substrate 16 in accordance with known laminating or bonding
techniques.
Illustrative examples of supporting substrates 16 include metal, wood, and
molded
polymer substrates. As explained above, exterior automobile parts are
particularly
suitable as the substrate 16. Suitable polymers for use as the substrate 16
include, for
example, thermoplastic olefin, acrylonitrile-butadiene-styrene terpolymer,
polypropylene, thermoplastic polyimide, polyethylene oxide, polycarbonate,
polyvinyl
chloride, polystyrene, styrene/polyphenylene oxide (NORYEL), polybutylene
terephthalate, nylon, PETG copolyester, Sheet Molding Compounds (SMC), RIM
urethanes, and mixtures, laminates and copolymers thereof.
The decorative sheet material 14 may be applied to the substrate 16 by a
variety of methods. These methods include, but are not limited to, compression
molding, such as thermoplastic or thermoset compression molding, injection
molding
and the like. In an injection molding process, the decorative sheet material
14 may be
preformed as described below or placed in the mold as a substantially flat
sheet. If the
sheet material 14 is placed in the mold without performing, the heat and/or
pressure of
the molding process conforms the sheet material to the desired shape.
Figures 9A-9D illustrate the steps in a thermoforming process.
Thermoforming is often used to create a preform in a three-dimensional
configuration
that roughly approximates the three-dimensional configuration of the final
product.
The preform is then placed in a mold for in-mold surfacing of a desired
substrate 16 to
form the final product. Figure 9A shows heating of the decorative sheet
material 14 of
the present invention by heating elements 70. The heating step softens and
increases
the extensibility of the decorative sheet material 14 so that the sheet
material will
readily conform to the contoured outer surface of the mold 74. As shown in
Figure
9C, the mold 74 is brought into contact with the heated decorative sheet
material 14
and a vacuum is drawn to encourage conformity of the sheet material 14 to the
contours of the mold 74. Thereafter, the mold 74 is removed from the
decorative sheet
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material 14 and the sheet material is allowed to cool and harden into the
three-
dimensional configuration.
Figures l0A-l OC illustrate steps in an in-mold surfacing process. As shown in
Figure 10A, the thermoformed decorative sheet material 14 is placed in the
mold
cavity 78 of an injection mold 76. The decorative sheet material is placed in
the mold
cavity 78 with the mask layer 20 facing the inner surface of the injection
mold 76.
Alternatively, the decorative sheet material 14 may be placed in the mold
cavity 78 as
a flat, two-dimensional insert rather than as a preform. As noted above, the
mold 76
may have a roughened inner surface: The injection mold 76 is shut and a
moldable
polymer 82 is introduced into the mold 76 through the injection mold barrel
80. The
polymer 82 bonds to the backing layer 30 and conforms to the contoured shape
of the
mold cavity 78. Thereafter, the moldable polymer 82 is allowed to cool and
harden
into a composite shaped part 12 comprising a substrate 16 bonded to a
decorative
sheet material 14, as shown in Figure l OC. The mask layer 20 of the
decorative sheet
material may be stripped from the composite shaped part 12 to expose the paint
film
finish when desired.
EXAMPLE 1
The peel strength data shown in Table 1 illustrates the good balance of
adhesion and cohesive strength provided by a blend of chlorinated
polypropylene
(HARDLEN 13-LP) and a higher molecular weight chlorinated polyolefin
(SUPERCHLON 8225). The HARDLEN 13-LP component exhibits good peel
strength at 100°C, while the SUPERCHLON 8225 component adds good peel
strength
at room temperature (about 15 to about 30°C). The two chlorinated
components have
similar chlorine contents: 24.5 weight percent for SUPERCHLON 8225 and 26
weight percent for HARDLEN 13-LP.
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Table 1
~~L~L~ 5~'.E~t,~H~'B~~S PEI ~..1~.~T~ Peel c~ lt~l
:. " :::: G.' :
C~ . P.. . ..: .:. .
r ' ~t a ;
~;~v~.~.~ ~~ .:.~~~er4al~ ~~~w'r9~ ~~
: ..
100 0 1-2 1.2
70 30 7-8 0.9
50 50 7-8 0.9-1.0
30 70 7-8 0.8-0.9
0 100 7-8 0.3-0.4
EXAMPLE 2
An adhesive layer of the present invention was compared to two
S available adhesives: Eastman 343-1 and Novacote 222. Adhesive layers were
formed
as described above and subjected to peel strength testing using the peel
strength
equipment described above. The adhesive layer of the present invention
comprised
about 30 weight percent SUPERCHLON 822s and about 70 weight percent
HARDLEN 13-LP. As shown by the data, the adhesive of the present invention
provides a better combination of room temperature and elevated temperature
peel
strength than the comparative examples.
Table 2
Adhe~~v~ ' % a~f Stretch Peel ~ Room Peel G 10~J!
'~"empezae (lb~~~~
# ~lb~.h~~
Adhesive of 0 7-8 1.1
the
present invention approx. 300 6-7 0.9-1.0
Eastman 343-1 0 7-8 0.1-0.2
approx. 300 7-8 0.1-0.2
Novacote 222 0 7-8 1-2
approx. 3 00 1-2 --
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Many modifications and other embodiments of the invention will come to
mind to one skilled in the art to which this invention pertains having the
benefit of the
teachings presented in the foregoing descriptions and the associated drawings.
Therefore, it is to be understood that the invention is not to be limited to
the specific
embodiments disclosed and that modifications and other embodiments are
intended to
be included within the scope of the appended claims. Although specific terms
are
employed herein, they are used in a generic and descriptive sense only and not
for
purposes of limitation.
