Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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COMPOSITIONS AND METHODS FOR RESTORING
PLASTIC COVERS AND LENSES
CROSS-REFERENCE TO RELATED APPLICATIONS
Not applicable.
BACKGROUND OF THE INVENTION
1. The Field of the Invention
The present invention is directed to compositions and methods for removing
scratches and oxidative damage from plastic covers and lenses. In particular,
the
present invention is directed to restoring clarity and shine to plastic
headlight covers,
optical lenses, other plastic surfaces, and preventing future damage due to
scratching
and oxidation.
2. The Relevant Technology
Plastic materials have largely replaced glass as an optically transparent
covering for automotive headlights. A typical plastic headlight cover is
composed of
a molded polycarbonate plastic that is formed into an aerodynamic shape that
fits the
profile of the front of the automobile.
Plastics are superior to glass in a number of respects. Plastics are lighter
than
glass while having similar clarity, they are more flexible and able to absorb
small
impacts, and they are much less likely to shatter in response to large
impacts. In
addition, plastics can readily be molded into a variety of aerodynamic shapes
that are
more compatible with modern automotive design.
Plastics, however, present a number of disadvantages. For example, they are
prone to scratching and UV-induced oxidative damage. And while plastic
headlight
covers are typically endowed with coatings that protect against scratching and
UV
damage, such coatings do not provide 100% protection over time. For example,
road
particles and other hard, abrasive substances can penetrate the protective
coating and
cause scratching that degrades the optical properties of the plastic. In
addition to
physically degrading the optical properties of the cover, scratching leads to
a number
of other processes that can damage the plastic. For example, scratches (from
washing
and cleaning the surface) that penetrate the protective coating can allow
access to the
plastic substrate by exhaust emissions and the chemicals in acid rain.
Scratches that
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penetrate the UV coating also allow UV radiation and/or oxygen to access the
plastic
substrate leading to oxidative damage of the plastic. In addition, heating of
the cover
produced by high intensity headlights can cause scratches to expand and
contract,
allowing greater access to the plastic substrate for UV radiation and/or
oxygen. Over
time, if these processes are left unchecked, plastic headlight covers can
become
almost opaque, reducing the Lumens, or light output. This naturally creates a
safety
issue due to reduced headlight intensity and effectiveness.
Replacement is one option for car owners with headlight covers that have been
badly damaged by scratching and/or oxidation. Replacing the plastic covers is,
however, cost prohibitive for many consumers. For example, the typical cost
for
replacing headlight covers can run anywhere between $200 and $500 per
headlight,
not including installation costs.
There are products that are available that purport to restore plastic
headlight
covers. Most of these products, however, use harsh cleaners or processes,
cheap
waxes, and metal polish intended for other applications. These products can be
very
detrimental to the fragile plastic of the lens. Also, whatever benefit is
derived from
these products is often short lived, as the uncoated lens will quickly become
crazed
when again exposed to environmental forces.
One example of a product that has been used to remove scratches from plastics
is a system called Micro-MeshTm. Another is Permatex, which used sand paper.
The
MiCrO-MeshTm system removes scratches from plastics using a series of rubber-
backed sanding cloths with differing sizes of grit. The first step uses a
sanding cloth
having 2,400 gauge grit. In subsequent steps, sanding cloths of finer grades
up to
12,000 gauge grit are used. In addition to using the rubber sanding block, a
small
amount of antistatic cream is applied after polishing is complete.
The Micro-MeshTm system, however, has many negative aspects. One
negative aspect of using the Micro-MeshTm system is that a large amount of
plastic
must be sanded away in order to remove even the tiniest of scratches. That is,
it is
necessary to remove enough of the plastic surface to at least equal the depth
of the
scratch. In addition, a sizable area of plastic must be removed in order to
avoid
causing optical distortion of the plastic in the surrounding area where the
scratch was
removed. To avoid optical distortion, the user must possess a high level of
skill and
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patience, which requires a high amount of training. Moreover, repeated scratch
removals using this system will greatly reduce the thickness of the plastic
and destroy
its desired protective properties. Another negative aspect of the Micro-MeshTm
sanding system is the large amount of time it takes to perform each of the
series of
sandings for each type of grit. Yet another negative aspect of the Micro-
MeshTm
sanding system is that extensive sanding removes the protective UV coating
from the
plastic along with the scratches.
Other products use varnishes, such as acrylic spar varnish, to essentially
fill in
and cover scratches in plastic head light cover. These products are easy and
quick to
use, but they ultimately do not restore the plastic. A coat of varnish merely
covers the
scratching and oxidation and does nothing to repair the underlying damage to
the
plastic. Varnishes and paint generally do not adhere to plastic very well and
the
varnish is likely to flake off in a short period of time. Moreover, if the
refractive
index of the varnish coating is dissimilar to that of the underling plastic,
each of the
filled in scratches will act as a micro lens scattering the light from the
headlight.
While the headlight may look better after applying the coat of varnish, the
varnish
will not in fact restore the optical properties of the cover.
BRIEF SUMMARY OF THE INVENTION
The present invention encompasses novel compositions and methods
configured to restore the clarity and light transmission properties of a
plastic surface
that has been damaged by scratching and ultraviolet induced oxidation. It has
been
found that such imperfections or flaws in the surface of the plastic can be
removed by
applying to the plastic surface renewal compositions described herein. The
compositions may include, for example, one or more polishing compositions for
removing scratches and oxidation from a plastic surface, one or more
lusterizing
compositions for further smoothing the polished plastic surface and restoring
luster,
and one or more compositions for restoring UV protection to the plastic
surface.
Restoring a plastic surface according to the present invention provides long-
lasting
clarity, light transmission, and a UV protective finish.
The polishing compositions include an abrasive material having an initial grit
size in a range of about 50 microns to about 400 microns, preferably in a
range of
about 60 microns to about 300 microns, and more preferably in a range of about
70
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microns to about 200 microns, and most preferably in a range of about 75
microns to
about 150 microns. A medium grit polishing composition preferably has an
initial grit
size of about 50-100 microns, preferably about 60-90 microns, and a heavy grit
polishing composition preferably has an initial grit size in a range of about
80-200
microns, preferably about 100-150 microns. The abrasive material is dispersed
within
an appropriate carrier suitable for use in making polishing compositions.
According
to one embodiment, the abrasive material in the polishing composition
comprises
abrasive particles that break down into smaller size particles (e.g., to about
10-50
microns, preferably about 15-45 microns, more preferably about 20-40 microns,
and
most preferably about 25-35 microns) when exposed to mechanical pressure and
oxygen during the polishing process. Prior to use, the polishing compositions
are
advantageously manufactured and stored in an environment that is substantially
oxygen free (e.g., under inert nitrogen).
The lusterizing compositions include an abrasive material having an initial
grit
size in a range of about 10 microns to about 60 microns, preferably in a range
of about
15 microns to about 50 microns, more preferably in a range of about 20 microns
to
about 45 microns, and most preferably in a range of about 25 microns to about
40
microns. A light abrasive lusterizing composition has an initial grit size in
a range of
about 20-60 microns, preferably about 25-55 microns. A finish lusterizing
composition has an initial grit size of about 10-50 microns, preferably about
15-40
microns. The abrasive material is dispersed within an appropriate carrier
suitable for
use in making fine polishing compositions. According to one embodiment, the
abrasive material comprises abrasive particles that break down into smaller
size
particles (e.g., about 1-20 microns, preferably about 2-15 microns, more
preferably
about 2.5-10 microns, and most preferably about 3-8 microns) when exposed to
mechanical pressure and oxygen during the luster restoring process. Prior to
use, the
lusterizing compositions are advantageously manufactured and stored in an
environment that is substantially oxygen free (e.g., under inert nitrogen).
The abrasives of the polishing and lusterizing compositions advantageously
dispersed within an appropriate liquid or gel carrier known in the art for
manufacturing polishing materials. Exemplary carriers may include solvents,
such as
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colorants, and
the like.
According to one embodiment, the abrasive particles in the polishing and/or
lusterizing compositions are in the form of agglomerates having an initial
particle size
when stored in a substantially oxygen free environment but progressively break
down
into smaller particles having a smaller final particle size when exposed to
oxygen and
mechanical pressure during the polishing and/or lusterizing process. The
agglomerates advantageously break down into smaller particles having a final
particle
size that is less than about 75% of the initial particle size. Preferably, the
agglomerates break down into particles having a final particle size that is
less than
about 50% of the initial particle size, more preferably less than about 33% of
the
initial particle size, and most preferably less than about 20% of the initial
particle size.
The UV protective composition includes a UV protective material dispersed
within a carrier having a solvent that, when the composition is worked into a
plastic
surface by buffing, advantageously causes the UV protective composition to
effectively become annealed or melted into the plastic surface. The result is
a
hardened UV protective coating on the plastic surface that is optically
transparent and
smooth. The UV protective coating may optionally include a polymerizable
material
that helps bond the coating to the prepared plastic surface. It is postulated
that the
polishing and lusterizing compositions may assist in preparing the plastic
surface so
as to receive and form a stronger bond with the UV protective coating.
The polishing and lusterizing compositions of the invention can be applied in
the same manner as conventional polishing compositions, although the results
are far
superior to conventional compositions. Exemplary apparatus for applying the
polishing and lusterizing compositions of the invention include a hand-held
buffing or
polishing machine, such as rotary, orbital, cordless drills, or oscillating
polishing
machines, or an open-cell polyurethane buffing pad impregnated with glass
fibers.
For lighter scratches, it may be advantageous to manually apply the
compositions
with the open-cell polyurethane buffing pad or with a soft cotton cloth. The
compositions of the invention are compatible with existing polishing systems
presently used but yield better and longer lasting results.
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Almost any type of buffing cloth may work with the compositions of the
present invention, including the aforementioned open-cell polyurethane
material and
cotton pads. Fleece wool, linen, rigid polyurethane, glass wool, and most
other
natural and synthetic materials work well. The only restraints are that the
buffing pad
or cloth be sufficiently durable to withstand the mechanical forces of the
buffing
process, that its stiffness be commensurate with the difficulty of the job in
question,
and that its component materials not be so hard that they will scratch the
plastic
surface or heat it up causing it to burn or melt.
According to one embodiment, the invention includes a kit for restoring light
transmission and clarity to a scratched and/or oxidized plastic surface. The
kit
includes at least one polishing composition for removing scratches, oxidative
damage
and damaged UV protective coating from the plastic surface, at least one
lusterizing
composition for restoring luster and optical clarity to the plastic surface
following use
of the polishing composition, and at least one UV protective composition for
application to the plastic surface following use of the lusterizing
composition. The kit
may optionally include other components, such as one or more cleaning cloths
and/or
compositions for use in removing residues from the polishing and lusterizing
compositions prior to application of the UV protective composition and one or
more
polishing or buffing pads or cloths (e.g., two buffing pads composed of
reticulated
open-cell polyurethane impregnated with glass fibers).
In one embodiment, the invention includes a method for restoring light
transmission and clarity to a scratched and/or oxidized plastic surface. The
method is
designed to allow a practitioner to restore essentially any plastic surface,
including but
not limited to, plastic headlight covers, other automotive plastic light
covers, plastic
sunglass lenses, and plastic corrective eyeglass lenses.
An exemplary method according to the invention includes (1) applying a
polishing composition to a buffing pad or cloth for polishing and removing
scratches
and oxidative damage from a plastic surface using the polishing composition
and the
buffing pad or cloth, (2) applying a lusterizing composition to the same or
different
buffing pad or cloth and restoring luster and optical clarity to the headlight
using the
lusterizing composition and the buffing pad or cloth, (3) cleaning the plastic
surface to
remove any residues from the polishing and lusterizing compositions, and (4)
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applying an ultraviolet protective composition to the plastic surface. In one
embodiment, the open-cell polyurethane buffing pad is impregnated with glass
fibers.
These and other advantages and features of the present invention will become
more fully apparent from the following description and appended claims, or may
be
learned by the practice of the invention as set forth hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
To further clarify the above and other advantages and features of the present
invention, a more particular description of the invention will be rendered by
reference
to specific embodiments thereof which are illustrated in the appended
drawings. It is
appreciated that these drawings depict only typical embodiments of the
invention and
are therefore not to be considered limiting of its scope. The invention will
be
described and explained with additional specificity and detail through the use
of the
accompanying drawings in which:
Figure 1 depicts a profilometric scan of an exemplary plastic headlight cover
showing undamaged and scratched regions, and a region restored according to an
embodiment of the present invention; and
Figure 2 is a flow-chart of a method according an embodiment of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
I. Introduction and Defmitions
The present invention extends to compositions and methods configured to
restore clarity and light transmission properties to a plastic headlight
cover. In
particular, the present invention encompasses novel compositions and methods
configured to restore the clarity and light transmission properties of a
surface that has
been damaged by scratching and ultraviolet induced oxidation. It has been
found that
such imperfections or flaws in the surface of the plastic can be removed by
applying
to the plastic surface renewal compositions described herein. The compositions
may
include, for example, compositions for removing scratches and oxidation from a
plastic surface, as well as compositions for polishing, lusterizing, and
reapplying an
ultraviolet protective coating to the plastic surface. The compositions and
methods
disclosed herein provide restoration of a damaged plastic surface with the use
of
abrasives and polishes. The compositions and methods disclosed herein further
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include compositions for reapplying a UV protective coating. Restoring a
plastic
surface according to the present invention provides long-lasting clarity,
light
transmission, and finish.
As used herein, the term "plastic headlight cover" refers to the molded
plastic
headlight covers that cover the primary lights on late model automobiles.
These
plastic headlight covers, which are typically made of polycarbonate, are
ubiquitous on
today's cars because they are generally more durable than glass and plastic
can
readily be molded into a variety of aerodynamic shapes that fit seamlessly
into the
front end of the automobile.
One will appreciate, however, that there are many plastic surfaces that can be
restored according to the compositions and methods described herein. The
methods,
and kits disclosed herein are configured to allow a user to efficiently
restore any
plastic surface that has been damaged by scratching and/or ultraviolet induced
oxidation.
Figure 1 depicts a profilometric scan of an exemplary plastic surface showing
undamaged and scratched regions, and a region restored according to an
embodiment
of the present invention. Profilometry is a technique that detects
irregularities in a
surface as a probe scans across the surface. The x-axis of a typical
profilometric scan,
as shown in Figure 1, displays the linear distance traveled by the probe
across the
surface. In this case, the x-axis of Figure 1 shows that the probe collected
data across
a linear distance of about 10,000 microns, or about 1 cm. The y-axis of a
profilometric scan generally records the magnitude of any irregularities
detected as
the probe travels linearly across the surface. In this case, the
irregularities in the
surface are scratches in the plastic.
To prepare the surface of the plastic headlight cover depicted in Figure 1
some
portions were masked off with tape to preserve an undamaged surface while
other
regions were scratched and then restored. The unmasked region was thoroughly
scratched with coarse sandpaper (80 grit) to mimic the scratching and UV
damage
that occurs over time to a typical plastic headlight cover. Some portions of
the
scratched surface were then masked off to preserve an example of a damaged
surface.
The unmasked, damaged region was then restored using the systems and methods
disclosed herein.
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The scan depicted in Figure 1 shows these undamaged 10, damaged 12, and
restored 14 regions. Undamaged region 10, which ranges on the x-axis from
about 0
microns to about 1000 microns, shows a substantially flat surface depicted by
the
dotted line at Y=0 microns. In contrast, the damaged region 12, which ranges
on the
x-axis from about 1,000 microns to about 7,500 microns, shows a wavy profile
indicative of many deep scratches. In contrast, the restored region 14, which
ranges
on the x-axis from about 7,500 microns to about 10,000, was restored according
the
methods of the present invention. Restored region 14 has a substantially more
regular
profile relative to the damaged region 12. And while the surface of restored
region 14
is not perfect, it is greatly improved over the level of scratching observed
in scratched
region 12.
By comparing the undamaged region 10 to the restored region 14 in Figure 1,
one can appreciate that the restoration process tends to remove a thickness of
material
from the surface of the plastic of only about 30 microns, or about three one
hundredths of a millimeter. This is a very small amount of material,
particularly when
one considers that the typical headlight cover is several millimeters thick.
The plastic
surface is restored according to the present invention with the removal of
such a small
amount of material because the compositions of the invention remove scratches
and/or oxidation from the plastic surface without creating additional
scratches that
have to be removed by progressively finer abrasives. It is also believed that
the
compositions of the present invention are able to penetrate larger scratches
and reform
them such that a deep v-shaped cut may be reformed into a shallow u-shaped
depression.
The polishing and lusterizing compositions of the present invention can be
applied the same way as any polishing compound, although the results are far
superior
to any of the prior art compounds presently available. The presently preferred
method
of application for removing scratches from plastic headlight covers and other
plastic
surfaces is to apply the polishing compounds by means of conventional hand-
held
buffing or polishing machines, such as rotary, orbital, or oscillating
polishing
machines, using an open-cell polyurethane buffing pad impregnated with glass
fibers.
For lighter scratches, it may be preferable to manually apply the compounds
with the
open-cell polyurethane buffing pad or with a soft cotton cloth. Finally, the
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polishing systems
presently used but yield better results.
It should be understood that almost any type of buffing cloth will work with
the compounds of the present invention including the aforementioned open-cell
polyurethane material and cotton pads. Fleece wool, linen, rigid polyurethane,
glass
10 wool, and most other natural and synthetic materials work well. The only
restraints
are that the buffing pad or cloth be sufficiently durable to withstand the
mechanical
forces of the buffing process, that its stiffness be commensurate with the
difficulty of
the job in question, and that its component materials not be so hard that they
will
scratch the plastic surface or heat it up causing it to burn or melt.
II. Exemplary Kits for Restoring Plastic Surfaces
In one embodiment, the present invention includes a kit for restoring optical
clarity and light transmission properties to a plastic surface damaged by
scratching
and/or UV-induced oxidation, comprising. The kit includes at least one
polishing
composition formulated to readily remove scratches and oxidation from the
plastic
surface, optionally at least one lusterizing composition for finishing the
plastic
surface, and at least one UV protective composition.
The polishing compositions comprise an abrasive material having an initial
grit size in a range of about 50 microns to about 400 microns, preferably in a
range of
about 60 microns to about 300 microns, more preferably in a range of about 70
microns to about 200 microns, and most preferably in a range of about 75
microns to
about 150 microns. The polishing abrasive may be "heavy grit" or "medium
grit",
Heavy grit polishing abrasives have an initial grit size of about 80-200
microns,
preferably about 100-150 microns. Medium grit polishing abrasives have an
initial
grit size of about 50-100 microns, preferably about 60-90 microns.
The polishing abrasive is advantageously dispersed within an appropriate
liquid or gel carrier suitable for use in making polishing compositions.
Exemplary
carriers may include solvents, such as water and/or organic solvents,
thickening
agents, emulsifying agents, colorants, and the like.
In one embodiment, the abrasive material comprises abrasive particles that
progressively break down into smaller size particles when exposed to oxygen
and
mechanical pressure during the polishing process. According to one embodiment,
the
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polishing abrasive breaks down to a particle size of about 10-50 microns,
preferably
about 15-45 microns, more preferably about 20-40 microns, and most preferably
about 25-35 microns when exposed to mechanical pressure and oxygen during the
polishing process. Prior to use, the polishing compositions are advantageously
manufactured and stored in an environment that is substantially oxygen free
(e.g.,
under inert nitrogen).
One will of course appreciate that this phenomenon produces a polishing
composition that becomes progressively finer during use. This is advantageous
when
one considers that typical polishing techniques involve using a series of
progressively
finer abrasives to remove scratches left by the previous abrasive. The
polishing
composition of the present invention is advantageously formulated to avoid
having to
use several polishing compositions to achieve a final polished surface in that
the
polishing composition encompasses many polishing steps in a single step by
virtue of
the fact that the abrasive particles become progressively finer as the
polishing process
continues.
The kit may include at least one lusterizing composition formulated to readily
restore optical clarity and light transmission properties to the plastic
surface following
use of the polishing composition. The lusterizing compositions comprise an
abrasive
material having an initial grit size in a range of about 10 microns to about
60 microns,
preferably in a range of about 15 microns to about 50 microns, more preferably
in a
range of about 20 microns to about 45 microns, and most preferably in a range
of
about 25 microns to about 40 microns. The lusterizing abrasive may be "light
grit" or
"fine grit", Light grit polishing abrasives have an initial grit size of about
20-60
microns, preferably about 25-55 microns. Fine grit polishing abrasives have an
initial
grit size of about 10-50 microns, preferably about 15-40 microns.
The lusterizing abrasive is advantageously dispersed within an appropriate
liquid or gel carrier suitable for use in making polishing and/or finishing
compositions. Exemplary carriers may include solvents, such as water and/or
organic
solvents, thickening agents, emulsifying agents, colorants, and the like.
In one embodiment, the lusterizing composition comprises abrasive particles
that progressively break down into smaller size particles when exposed to
oxygen and
mechanical pressure and oxygen during the lusterizing process. According to
one
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embodiment, the lusterizing abrasive breaks down to a particle size of about 1-
20
microns, preferably about 2-15 microns, more preferably about 2.5-10 microns,
and
most preferably about 3-8 microns when exposed to mechanical pressure and
oxygen
during the lusterizing process. Prior to use, the lusterizing compositions are
advantageously manufactured and stored in an environment that is substantially
oxygen free (e.g., under inert nitrogen).
One will of course appreciate that this phenomenon produces a lusterizing
composition that becomes progressively finer during use. This is highly
advantageous
when one considers that typical finishing techniques involve using a series of
progressively finer abrasives to remove scratches left by the previous
abrasive. The
lusterizing composition of the present invention is advantageously formulated
to
avoid having to use several lusterizing compositions to achieve a final
lustrous surface
in that the lusterizing composition encompasses many lusterizing steps in a
single step
by virtue of the fact that the abrasive particles become progressively finer
as the
lusterizing process continues.
According to one embodiment, the abrasive particles in the polishing and/or
lusterizing compositions are in the form of agglomerates having an initial
particle size
when stored in a substantially oxygen free environment but progressively break
down
into smaller particles having a smaller final particle size when exposed to
oxygen and
mechanical pressure during the polishing and/or lusterizing process. The
agglomerates advantageously break down into smaller particles having a final
particle
size that is less than about 75% of the initial particle size. Preferably, the
agglomerates break down into particles having a final particle size that is
less than
about 50% of the initial particle size, more preferably less than about 33% of
the
initial particle size, and most preferably less than about 20% of the initial
particle size.
The kit includes at least one composition for applying a UV protective coating
to the plastic surface following application of the polishing and lusterizing
compositions. Unfortunately, the process of restoring a plastic surface with
the above
described kit typically removes the factory applied UV protective coating from
the
plastic surface. Without a protective coating, the surface would quickly be
degraded
by scratching and UV induced oxidation. The UV protective composition includes
a
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UV protective material dispersed within a carrier having a solvent that
advantageously causes the UV protective composition to effectively become
annealed
or melted into the plastic surface during the buffing process. The result is a
hardened
UV protective coating on the plastic surface that is optically transparent and
smooth.
The UV protective coating may optionally include a polymerizable material that
helps
bond the coating to the prepared plastic surface. It is postulated that the
polishing and
lusterizing compositions may assist in preparing the plastic surface so as to
receive
and form a stronger bond with the UV protective coating by activating the
surface and
creating bonding sites where the protective composition can form physical and
chemical bonds to the plastic surface.
In the past, transparent protective coatings of high optical quality for UV
protection have been obtained on plastic substrates by spin and dip coating,
followed
by baking. The UV protective compositions of the invention allow for low
temperature application (T < 130 F), which is achieved by the chemical
dispersion of
the UV protective coating within a solvent carrier, which causes the coating
to anneal
itself to a headlight lens similar to the way it is done in the original
manufacturing
process. It is believed that solids in the coating are made of crystalline and
UV
protective nano particles that coalesce into larger particles by means of a
polyermizable material. This causes deposition of the UV protective particles
as a
thick single layer (>400 nm). The transparency in the visible range is high, T
7-z; 87%,
the abrasion resistance is in agreement with DIN 58-196-G10, and the hardness
according to ASTM D 3363-92a is 1H. The application process allows for
antiglare
coatings with an adjustable gloss of 60 to 80 GU and an optical resolution >8
lines/mm.
The kit may include at least one buffing pad or buffing cloth for applying the
polishing and lusterizing compositions to the plastic surface. The buffing pad
or
buffing cloth can either be used manually or they can be attached to a drill
or a
mechanical polisher. In one embodiment, the buffing pad or buffing cloth are
impregnated with glass fibers to enhance the action of the polishing and
lusterizing
compounds. It is believed that the glass fibers enhance the action of the
polishing and
lusterizing compounds by penetrating or "reaching" into deep scratches such
that deep
scratches are reformed from deep v-shaped grooves to shallow u-shaped
depressions.
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By reforming the surface, the glass fibers allows some scratches to be
restored
without having to remove a layer of plastic from the plastic surface without
having to
remove a layer of plastic equal to the depth of the deepest scratch.
III. Exemplary Methods for Restoring Plastic Surfaces
In one embodiment, the present invention includes a method for restoring light
transmission and clarity to a scratched and/or oxidized plastic surface. The
method is
configured to allow a practitioner to restore essentially any plastic surface.
Examples
of plastics surfaces that can be restored according to the present invention
include
plastic headlight covers, other plastic automotive light covers, and plastic
eyeglass
lenses, including sunglass lenses and plastic corrective lenses.
An exemplary method according to the invention includes (1) applying a
polishing composition to a buffing pad or cloth for polishing and removing
scratches
and oxidative damage from a plastic surface using the polishing composition
and the
buffing pad or cloth, (2) applying a lusterizing composition to the same or
different
buffing pad or cloth and restoring luster and optical clarity to the headlight
using the
lusterizing composition and the buffing pad or cloth, (3) cleaning the plastic
surface to
remove any residues from the polishing and lusterizing compositions, and (4)
applying an ultraviolet protective composition to the plastic surface. In one
embodiment, the open-cell polyurethane buffing pad is impregnated with glass
fibers.
Figure 2 depicts a flow-chart 20 of one embodiment of a method for restoring
essentially any type of plastic surface that has been damaged by scratching
and/or
UV-induced oxidation. Flow-chart 20 starts at 22 and ends at 40. In one
embodiment, the method includes applying a polishing composition to an open-
cell
polyurethane buffing pad 24. The polishing composition and the buffing pad are
used
for polishing and removing scratches and oxidative damage from a plastic
surface 26.
In one embodiment, the open-cell polyurethane buffing pad may be impregnated
with
glass fibers. It is believed that the polishing composition and the glass
fibers are able
to penetrate or reach into larger scratches in the plastic surface and reform
the
scratches from a deep v-shaped gouge to a u-shaped depression. It is this
property of
the polishing system that allows larger scratches to be removed without having
to
remove a layer of plastic equal to the depth of the deepest scratch.
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5 The
buffing pad and the polishing composition may be used for polishing and
removing scratches and oxidative damage from a plastic surface by attaching
the
buffing pad to a conventional hand-held polishing or buffing machine.
Alternatively,
the buffing pad can be used manually with the first abrasive composition for
polishing
and removing scratches and oxidative damage from a plastic surface. The
plastic
10 surface
can be rinsed as necessary 28 in order to wash away dirt and/or plastic
residue, and to provide lubrication between the plastic surface and the
buffing pad and
polishing composition.
One will of course appreciate that this phenomenon produces a polishing
composition that becomes progressively finer during use. This is highly
advantageous
15 when one
considers that typical polishing techniques involve using a series of
progressively finer abrasives to remove scratches left by the previous
abrasive. The
polishing composition of the present invention is advantageously formulated to
avoid
having to use several polishing compositions to achieve a final polished
surface in
that the polishing composition encompasses many polishing steps in a single
step by
virtue of the fact that the abrasive particles become progressively finer as
the
polishing process continues.
In one embodiment, the method includes applying a lusterizing composition to
the open-cell polyurethane buffing pad 30. The lusterizing composition and the
buffing pad are used for restoring the lumonious output and luster to the
plastic
surface 32. The buffing pad and the lusterizing composition may be used for
restoring luster to the plastic surface by attaching the buffing pad to a
conventional
cordless drill or air and electric hand-held polishing or buffing machine.
Alternatively, the buffing pad can be used manually with the lusterizing
composition
for restoring luster to the plastic surface. The plastic surface can be rinsed
as
necessary 34 in order to wash away dirt and/or plastic residue, and to provide
lubrication between the plastic surface and the buffing pad and lusterizing
composition.
One will of course appreciate that this phenomenon produces a lusterizing
composition that becomes progressively finer during use. This is highly
advantageous
when one considers that typical lusterizing techniques involve using a series
of
progressively finer abrasives to remove scratches left by the previous
abrasive. The
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lusterizing composition of the present invention is advantageously formulated
to
avoid having to use several lusterizing compositions to achieve a final
lustrous surface
in that the lusterizing composition encompasses many lusterizing steps in a
single step
by virtue of the fact that the abrasive particles become progressively finer
as the
lusterizing process continues.
In one embodiment, the method includes cleaning the plastic surface to
remove residues from the polishing and luster restoring steps 36. Cleaning can
be
achieved with a spray of water or with a damp cloth. Generally, the cleaning
step
should be conducted with care to avoid rescratching the plastic surface.
Moreover,
the cleaning step should be conducted with utmost care to remove all of the
residues
from the polishing and luster restoring steps prior to the application of a UV-
protective coating.
In one embodiment, the method includes a step of applying a UV-protective
composition to the plastic surface 38. Generally, the factory-applied UV-
protective
coating is removed in the process of polishing and restoring luster to the
plastic
surface. If a new UV-protective coating is not applied, exposure to the
elements
would quickly degrade the plastic surface and the benefits of the restoration
would be
lost.
In one embodiment, the ultraviolet protective composition comprises at least
one solvent that allows the coating to anneal to the plastic surface, at least
one
polymer or polymerizable compound that forms a hard, clear coating on the
plastic
surface, and at least one ultra-violet protective compound that protects the
plastic
surface from future UV induced damage.
In one embodiment, the solvent in the UV protective composition includes at
least one ether compound. In an alternative embodiment, the solvent is an
alcohol.
When ether is the main solvent, the ether compound preferably constitutes
about 1%
to about 20% of the UV protective composition, calculated on a weight/weight
basis.
More preferably, the ether compound constitutes about 5% to about 15% and most
preferably, about 8-12%. When alcohol is the main solvent, the alcohol
preferably
constitutes about 70% to about 98% of the UV protective composition,
calculated on a
weight/weight basis. More preferably, the alcohol constitutes about 80% to
about
95% of the UV protective composition. Most preferably, the alcohol constitutes
about
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87% to about 93%. Exemplary ether compounds include dipropylene glycol n-butyl
ether and ethylene glycol monobutyl ether. Exemplary alcohols include
isopropyl
alcohol. The solvent may also consist of a blend of alcohol and ether
compounds.
In one embodiment, the polymer or polymerizable compound that forms a
hard, clear coating on the plastic surface includes at least one acrylic-
urethane hybrid
polymer dispersion. Exemplary acrylic-urethane hybrid polymer dispersions
include
Hybridur 570" and Hybridur 580TM, which are available from Air Products and
Chemical, Inc. Hybridur 570TM and Hybridur 580TM may be used alone or in
combination. Preferably, Hybridur 570TM constitutes about 40% to about 65% of
the
ultraviolet protective composition, calculated on a weight/weight basis. More
preferably, Hybridur 570TM constitutes about 45% to about 60% of the
ultraviolet
protective composition, calculated on a weight/weight basis. Most preferably,
Hybridur 570TM constitutes about 50% to about 55% of the ultraviolet
protective
composition, calculated on a weight/weight basis. Preferably, Hybridur 580TM
constitutes about 10% to about 35% of the ultraviolet protective composition,
calculated on a weight/weight basis. More preferably, Hybridur 580TM
constitutes
about 15% to about 30% of the ultraviolet protective composition, calculated
on a
weight/weight basis. Most preferably, Hybridur 580' constitutes about 20% to
about
25% of the ultraviolet protective composition, calculated on a weight/weight
basis.
In another embodiment, the polymer or polymerizable compound that forms a
hard, clear coating on the plastic surface includes at least one acrylic
polymer. An
exemplary acrylic polymer is Elvacite 2776TM, which is available from Lucite
International. Preferably, Elvacite 2776TM constitutes about 0.5% to about 10%
of the
ultraviolet protective composition, calculated on a weight/weight basis. More
preferably, Elvacite 2776TM constitutes about 1% to about 8% of the
ultraviolet
protective composition, calculated on a weight/weight basis. Most preferably,
Elvacite 2776TM constitutes about 2% to about 5% of the ultraviolet protective
composition, calculated on a weight/weight basis.
The ultraviolet protective coating includes at least one ultraviolet
protective
compound to protect the plastic surface from UV-induced damage. Exemplary
ultraviolet protective compounds are hindered amine compounds, such as Tinuvin
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384Tm and Tinuvin 292T1, which are available from Ciba, benzophenones,
benzotriazoles, hydroxyphenyltriazines, and hydroxyphenylbenzotriazoles.
Preferably, the ultraviolet protective compound or compounds constitute about
0.01%
to about 1% of the ultraviolet protective coating, calculated on a
weight/weight basis.
More preferably, the ultraviolet protective compound or compounds constitute
about
0.05% to about 0.5% of the ultraviolet protective coating, calculated on a
weight/weight basis. Most preferably, the ultraviolet protective compound or
compounds constitute about 0.1% to about 0.3% of the ultraviolet protective
coating,
calculated on a weight/weight basis.
Additional ingredients which may be included in the ultraviolet protective
composition include wetting agents to improve the uniformity of the coating,
plasticizers to increase the durability of the coating, and antifoaming agents
to
discourage the formation of air bubbles in the ultraviolet protective coating
as it is
applied to the plastic surface. Exemplary wetting agents include polyether
modified
siloxanes, such as BYK345TM, BYK346TM, BYK347TM, BYK348TM, BYK349TM,
which are available from BYK Chemie, Inc, and sodium dioctyl sulfosuccinate,
which
is available from Cytec. Exemplary plasticizers include derivatives of citric
acid,
such as triethyl citrate, acetyl triethyl citrate, tributyl citrate, acetyl
tributyl citrate, and
tri-(2-ethylhexyl)-citrate. Exemplary defoamers include the SurfynolTM line of
chemicals available from Air Products and Chemicals, Inc.
EXAMPLES OF SPECIFIC FORMULAS
Below are specific examples of compositions and methods which have been
created according to the present invention.
Example 1
A medium abrasive polishing composition in accordance with the present
invention was prepared with the following formulation:
% wiw
Solid abrasive material 30.0
Propylene Glycol 5.0
Carboxymethyl Cellulose 1.0
Ethylene Oxide/Propylene 2.5
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Oxide Block Copolymer
Fragrance 98164 0.2
1 -(3 -chloro ally1)-3 ,5 ,7- Triaza-1 - 0.2
azonia adamantane chloride
Sufficient deionized water was added to bring the total volume to 100 percent
(w/w).
The composition is prepared, packaged, and stored in a substantially oxygen
free environment. For example, the dry material is added to a mixing
apparatus.
Subsequently, the dry materials and the mixer are exposed to a vacuum such
that
essentially all oxygen is evacuated from the dry ingredients. An inert gas
such as
nitrogen is added back to the mixing apparatus, the liquid ingredients are
added, and
the composition is mixed. The composition is subsequently packaged in a
substantially oxygen free environment.
It is believed that preparing and packaging the composition under oxygen free
conditions allows the abrasive particles to agglomerate into larger particles.
It is
postulated that this aggregation occurs in a substantially oxygen free
environment
because the lack of oxygen alters the surface charge properties of the
abrasive
particles. A person having ordinary skill in the art will appreciate that this
aggregation is progressively reversed when the abrasive particles are exposed
to
oxygen and mechanical pressure during the polishing process.
This formulation exhibited a creamy viscous lotion consistency, and was
cream in color. In this and other examples coconut fragrance was added for
aesthetic
purposes only, and it should be understood that fragrance could be omitted or
substituted without altering the efficiency of the polishing composition. This
formulation has a wide variety of uses for removing scratches from plastic
surfaces.
It is a presently preferred composition for initial treatment for polishing
and removal
of scratches and oxidative damage from plastic headlight covers.
A heavy to medium abrasive formula in accordance with this example would
also be useful for initial treatment in restoring and repairing plastic
material such as
plastic windows, plastic or acrylic furniture, plastic shields on face masks,
light bars
on police vehicles, ski trams or gondolas, the faces of advertising signs, and
many
other applications.
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5 Although
the formulation set forth above is the presently preferred
formulation, it should be understood that various alterations may be made
without
departing from the broader teachings of the present invention. In this
example, the
solid polishing material may include a blend of kaolinitic quartz, silicon
dioxide, and
calcined alumina. The particle size of the polishing materials ranged from
about 50
10 microns
to about 400 microns. Although it is preferred that the total abrasives
content
be about 23%, a broader range of abrasive content is about 15% to about 35%
with a
more preferred range being about 20% to about 30%. In formulating a heavy to
medium abrasive formulation of the type set forth in this example, it is to be
understood that variations in the ratio of amounts of the remaining
constituents may
15 be made as required to maintain their function.
Example 2
A light abrasive lusterizing composition in accordance with the present
invention was prepared with the following formulation:
% W/W
Solid abrasive material 30.0
Propylene Glycol 5.0
Carboxymethyl Cellulose 1.0
Ethylene Oxide/Propylene 2.5
Oxide Block Copolymer
Fragrance 98164 0.2
1-(3-chloroally1)-3,5,7- Triaza-1- 0.2
azonia adamantane chloride
20
Sufficient deionized water was added to bring the total volume to 100 percent
(w/w),
which yielded a viscous, creamy fluid with a lotion-like consistency. In this
and other
examples coconut fragrance was added for aesthetic purposes only, and it
should be
understood that fragrance could be omitted or substituted without altering the
efficiency of the polishing composition.
The composition is prepared, packaged, and stored in a substantially oxygen
free environment. For example, the dry material is added to a mixing
apparatus.
Subsequently, the dry materials and the mixer are exposed to a vacuum such
that
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21
essentially all oxygen is evacuated from the dry ingredients. An inert gas
such as
nitrogen is added back to the mixing apparatus, the liquid ingredients are
added, and
the composition is mixed. The composition is subsequently packaged in a
substantially oxygen free environment.
It is believed that preparing and packaging the composition under oxygen free
conditions allows the abrasive particles to aggregate into larger particles.
It is
postulated that this aggregation occurs in a substantially oxygen free
environment
because the lack of oxygen alters the surface charge properties of the
abrasive
particles. A person having ordinary skill in the art will appreciate that this
aggregation is progressively reversed when the abrasive particles are exposed
to
oxygen and mechanical pressure during the polishing process.
This light abrasive formulation has a variety of uses, but is particularly
preferred as a lusterizing treatment for plastics first treated with the
polishing
composition of Example 1. It is preferred for use on plastic headlight covers,
plastic
windows, plastic or acrylic furniture, plastic shields on face masks, light
bars on
police vehicles, ski trams or gondolas, the faces of advertising signs, and
many other
applications. It would also be useful for buffing or removing minor scratches,
hazing
and discoloration from other plastics, particularly for removing scratches
from
eyeglass lenses (e.g., sunglass lenses and/or corrective lenses.
Although the formulation set forth above is the presently preferred
formulation, it should be understood that various alterations may be made
without
departing from the broader teachings of the present invention. In this
example, the
solid polishing material included a blend of kaolinitic quartz, silicon
dioxide, and
calcined alumina. The particle size of the polishing materials ranged from
about 1
micron to about 50 microns. Although it is preferred that the total abrasives
content
be about 23%, a broader range of abrasive content is about 15% to about 35%
with a
more preferred range being about 20% to about 30%. In formulating a light
abrasive
formulation of the type set forth in this example, it is to be understood that
variations
in the ratio of amounts of the remaining constituents may be made as required
to
maintain their function.
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Example 3
A heavy abrasive polishing composition in accordance with the present
invention was prepared with the following formulation:
Ingredient Trade Name/Supplier
% W/W
Magnesium Aluminum Silicate (5% Van Gel /RT Vanderbilt
30.0
dispersion)
Propylene Glycol Propylene Glycol 5.0
Carboxymethyl Cellulose CMC 7H or CMC
1.0
9M31XF/Aqualon-Hercules
Aluminum Silicate Kaopolite/Kaopolite Co.
18.0
Fused Silica (8.8 microns average) Siltex 44/Kaopolite Co.
3.0
Boehmite Alumina (60 microns average) Catapal D/ Sasol (formerly Vista)
2.0
Ethylene Oxide/Propylene Oxide Block Tergitol 15-S-7/Dow
2.5
Copolymer
Fragrance 98764 Fragrance 98764/Noville 0.2
1-(3-chloroally1)-3,5,7-Triaza- 1-azonia- Dowicil 75
0.2
adamantane chloride
Deionized water q.s. to 100
This heavy formulation is useful for quick removal of scratches from most of
the plastic materials listed in Example 1, although it would not likely be
used with
compact discs or the like. A medium formulation such as set forth in Example 1
and/or a light formulation as set forth in Example 2 might be used to complete
the
repair after an initial treatment with this heavy formulation.
Example 4
A medium abrasive polishing composition in accordance with the present
invention was prepared with the following formulation:
Ingredient Trade Name/Supplier
% W/W
Magnesium Aluminum Silicate (5% Van Gel /RT Vanderbilt
30.0
dispersion)
Propylene Glycol Propylene Glycol 5.0
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23
Carboxymethyl Cellulose CMC 7H or CMC
1.0
9M31XF/Aqualon-Hercules
Aluminum Silicate Kaopolite/Kaopolite Co.
8.0
Celite Diatomaceous Silica Super Floss or Snow Floss/Celite
7.0
Boehmite Alumina Catapal D/ Sasol (formerly Vista)
8.0
Ethylene Oxide/Propylene Oxide Block Tergitol 15-S-7/Dow
2.5
Copolymer
Fragrance 98764 Fragrance 98764/NoviIle
0.2
1-(3-chloroally1)-3,5,7-Triaza- 1-azonia- Dowicil 75
0.2
adamantane chloride
Deionized water
q.s. to 100
This formulation is suitable for many uses, such as those described in Example
1. The boehmite aluminum has the advantage of being relatively soft. It will
break
into smaller fragments during use, assisting in repair of the increasingly
small
scratches which exist during the course of repair.
Example 5
A fine abrasive lustering composition in accordance with the present invention
was prepared with the following formulation:
Ingredient Trade Name/Supplier
% W/W
Magnesium Aluminum Silicate (5% Van Gel /RT Vanderbilt
30.0
dispersion)
Propylene Glycol Propylene Glycol
5.0
Carboxymethyl Cellulose CMC 7H or CMC
1.0
9M31XF/Aqualon-Hercules
Aluminum Silicate Kaopolite/Kaopolite Co.
23.0
Ethylene Oxide/Propylene Oxide Block Tergitol 15-S-7/Dow
2.5
Copolymer
Fragrance 98764 Fragrance 98764/Noville
0.2
1-(3-chloroally1)-3,5,7-Triaza- 1-azonia- Dowicil 75
0.2
adamantane chloride
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Deionized water q.s. to 100
_____________________________________________ .-
This fine abrasive formulation is similar to Example 2 but has a finer
abrasive.
As with Example 2, this lusterizing composition has a variety of uses, but is
particularly preferred as a final treatment for plastic surfaces first treated
with the
composition of Example 1 and/or Example 3.
Example 6
A light abrasive polishing composition has the following formulation:
Ingredient Trade Name/Supplier
% W/W
Magnesium Aluminum Silicate (5% Van Gel /RT Vanderbilt
30.0
dispersion)
Propylene Glycol Propylene Glycol 5.0
Carboxymethyl Cellulose CMC 7H or CMC
1.0
9M31XF/Aqualon-Hercules
Aluminum Silicate Kaopolite/Kaopolite Co.
11.5
Zirconia (2-4 microns average)
11.5
Ethylene Oxide/Propylene Oxide Block Tergitol 15-S-7/Dow
2.5
Copolymer
Fragrance 98764 Fragrance 98764/Noville 0.2
1-(3-chloroally1)-3,5,7-Triaza- 1-azonia- Dowicil 75
0.2
adamantane chloride
Deionized water q.s. to 100
This example includes zirconia (zirconium oxide) as an abrasive. This is a
hard material that should be used with care.
Example 7
An ultraviolet protective coating was prepared in accordance with the present
invention with the following formulation:
Ingredient description Trade name %
W/W
Dipropylene Glycol n-Butyl Ether Arcosolve DPnB
9.8
Polyether modified BYK-346 0.5
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polydimethylsiloxane
Light stabilizer Tinuvin 384 0.7
Light stabilizer Tinuvin 292 0.4
Urethane Hybrid Polymer Hybridur 570 Polymer
51.5
Dispersion
Urethane Hybrid Polymer Hybridur 580 Polymer
22.1
Dispersion
Defoamer Surfynol DF-58 0.2
Water, DI Water, DI
14.9
TOTAL 100.0
5
The coating composition appeared as a uniform flowable liquid. This light
ultraviolet protective coating has a variety of uses, but is particularly
preferred as a
coating for restoring a UV protective layer to plastic surfaces treated with
one or more
of the compositions of Examples 1-6. It is preferred for use on plastic
headlight
10 covers, plastic windows, plastic or acrylic furniture, plastic
shields on face masks,
light bars on police vehicles, ski trams or gondolas, the faces of advertising
signs, and
many other applications. It would also be useful for applying a UV protective
coating
to other plastics, particularly eyeglass lenses (e.g., sunglass lenses and/or
corrective
lenses.
15 Although the formulation set forth above is the presently preferred
formulation, it should be understood that various alterations may be made
without
departing from the broader teachings of the present invention. In formulating
an
ultraviolet protective coating formulation of the type set forth in this
example, it is to
be understood that variations in the ratio of amounts of the remaining
constituents as
20 required to maintain their function.
Example 8
An ultraviolet protective coating was prepared in accordance with the present
invention with the following formulation:
Ingredient Trade Name/Supplier
%w/w
Isopropyl alcohol Any suitable vendor
88.85
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17400.1a 26
Acrylic polymer Elvacite 2776/Lucite 3.0
International
Sodium dioctyl sulfosuccinate, Aerosol OT-75/Cytec
0.05
75%
Triethyl citrate Citroflex 2/Morflex
0.3
Ethylene Glycol monobutyl ether Dowanol EB/Dow
7.0
Light stabilizer Tinuvin 384/Ciba 0.5
Light stabilizer Tinuvin 292/Ciba 0.3
TOTAL 100.0
The coating composition appeared as a uniform flowable liquid and dried to a
hard, clear surface in approximately 30 minutes.
Example 9
An ultraviolet protective coating was prepared in accordance with the present
invention with the following formulation:
Ingredient Trade Name/Supplier
%w/w
Isopropyl alcohol Any suitable vendor 90.95
Acrylic polymer Elvacite 2776/Lucite 3.0
International
Sodium dioctyl sulfosuccinate, Aerosol OT-75/Cytec
0.05
75%
Dipropylene Glycol n-Butyl Ether Arcosolve DPnB/Arco
5.0
Light stabilizer Tinuvin 384/Ciba 0.5
Light stabilizer Tinuvin 292/Ciba 0.3
Antifoam Surfynol DF-58/Air Products
0.2
TOTAL 100.0
The coating composition appeared as a uniform flowable liquid and dried to a
hard, clear surface in approximately 30 minutes.
The scope of the claims should not be limited by the preferred embodiments
' 15
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set forth in the examples, but should be given the broadest interpretation
consistent
with the description as a whole.
