Note: Descriptions are shown in the official language in which they were submitted.
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UV CURABLE COMPOSITIONS FOR PRODUCING
DECORATIVE METALLIC COATINGS
TECHNICAL FIELD
The present invention relates to ultraviolet light curable compositions
that may be utilized to produce a decorative metallic coating on a substrate.
BACKGROUND OF THE INVENTION
UV radiation curable paint compositions are applied to a substrate
through spraying, screen printing, dipping or brushing for the protection or
decoration of the substrate. In the usual application, a substrate such as
metals,
glass, or plastics is coated with the paint composition and then UV light is
introduced to complete the curing process. The UV curable paint compositions
offer
many advantages over typical heat curable compositions.
Heat curable compositions require the use of organic solvents that
contain a significant amount of volatile organic compounds (VOCs). These VOCs
escape into the atmosphere while the heat curable composition dries. Such
solvent
based systems are undesirable because of the hazards and expenses associated
with
VOCs. The hazards include water and air pollution and the expenses include the
cost of complying with strict government regulation on solvent emission
levels. In
contrast, UV curable compositions contain reactive monomers instead of
solvents;
thus eliminating the detrimental effects of the VOCs.
The use of heat curable compositions not only raises environmental
concerns but other disadvantages exist with their use as well. Heat curable
compositions suffer from slow cure times which lead to decreased productivity.
These compositions require high energy for curing due to energy loss as well
as the
energy required to heat the substrate. Additionally, many heat curable
compositions
yield poor film properties that result in decreased value of the end product.
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Although UV curable compositions exhibit superior properties and
performance over their heat curable counterparts, UV curable compositions
themselves suffer from certain disadvantages. Generally, UV compositions have
high molecular weights and a substantial degree of cross linkage due to the
highly
reactive nature of the composition. As a result, many of these compositions
suffer
from low durability and resin shrinkage. With the use of many such
compositions,
an inordinately high amount of UV light is required to cure. New formulations
that
lessen these problems typically suffer from diminished abrasion, chemical, and
scratch resistance as well as low thermal stability and adhesion.
An addition disadvantage of typical UV compositions is their lack of
stability which results in dispersion. With some compositions, suspended
solids fall
out of solution after a period of one to two days. Dispersion adversely
affects the
gloss and clarity of the finished product. To combat this problem, new
compositions
have been formulated with higher viscosities which often lessen the
flowability of the
composition. These viscous formulations rule out spray application and provide
for
an unsuitably high dipping thickness.
Accordingly, there exists a need to provide environmentally safe UV
curable paint compositions which exhibit improved weatherability, corrosion
resistance and workability. Additionally, there is a need to provide a method
of
applying the composition which furthers the goal of improved performance.
SUMMARY OF INVENTION
It is an object of the present invention to provide an improved
composition that upon curing by ultraviolet light produces a decorative
metallic
coating.
It is another object of the present invention to provide an improved
decorative metallic composition that can be applied by spraying, screen
printing,
dipping, and brushing.
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The present invention discloses an ultraviolet light curable decorative
metallic composition and method for making such a composition that may be used
to produce a decorative metallic layer. The disclosed composition does not
contain
any significant amount of volatile organic solvents that do not become
incorporated
in the active layer after curing. Specifically, the decorative metallic
composition
contains 5 % or less volatile organic solvents by weight.
In accordance with one aspect of the invention, an ultraviolet light
curable decorative metallic composition is provided. The decorative metallic
composition comprises an acrylated epoxy oligomer in an amount of about 20 %
to
45 % , an isobornyl acrylate monomer in an amount of about 15 % to 40 % of the
decorative metallic composition, a photoinitiator in an amount of about 4 % to
14
of the decorative metallic composition, a flow promoting agent in an amount of
0%
to 8 %of the decorative metallic composition, and a metallic pigment in an
amount
of 5 % to 40 % . All percentages of the decorative metallic composition as
expressed
in this document refer to the weight percentage of the stated component to the
total
weight of the decorative metallic composition in its fluid state at standard
temperature and pressure.
In accordance with yet another aspect of the invention, a method is
provided for depositing a decorative metallic coating on a substrate. The
method
comprises a first step of applying to the substrate a decorative metallic
fluid-phase
composition ("decorative metallic composition"). The decorative metallic
composition includes an acrylated epoxy oligomer in an amount of about 20% to
45 % , an isobornyl acrylate monomer in an amount of about 15 % to 40 % of the
decorative metallic composition, a photoinitiator in an amount of about 4 % to
14 %
of the decorative metallic composition, a flow promoting agent in an amount of
0 %
to 8 % of the decorative metallic composition, and a metallic pigment in an
amount
of 5 % to 40 % .
The method also includes a second step of illuminating the decorative
metallic composition on the substrate with an ultraviolet light to cause the
decorative
metallic composition to cure into the decorative metallic coating.
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In accordance with this method, the decorative metallic composition
can be selectively deposited on the substrate at specific locations where
decorative
metallic plating is desired. It need not be applied to the entire substrate.
BEST MODE FOR CARRYING OUT THE INVENTION
Decorative metallic Compositions
Reference will now be made in detail to presently preferred
compositions or embodiments and methods of the invention, which constitute the
best modes of practicing the invention presently known to the inventor.
In accordance with one aspect of the invention, a presently preferred
ultraviolet light curable decorative metallic composition ("decorative
metallic
composition") is provided. In this preferred embodiment, the decorative
metallic
composition includes an acrylated epoxy oligomer. The acrylated epoxy oligomer
is
present in an amount of about 20 % to 45 % . The acrylated epoxy oligomer is
more
preferably present in an amount of about 35 % to 45 % , and most preferably
about
40 % . Suitable acrylated epoxy oligomers include Radcure Ebecryl 3603
(novolac
epoxy acrylate diluted 20 % by weight with tripropylene glycol diacrylate),
commercially available from Radcure UCB Corp.; Sartomer CN-120 (difunctional
bisphenol based epoxy acrylate) and CN-124 (difunctional bisphenol based epoxy
acrylate), commercially available from Sartomer Corp.; and Echo Resin THE 9310
and 9345, commercially available from Echo Resins. The preferred acrylated
epoxy
oligomer is Ebecryl 3603, which is a tri-functional acrylated epoxy novolac.
Combinations of these materials may also be employed herein.
The preferred decorative metallic composition also includes an
isobornyl acrylate monomer in an amount of about 15 % to 40 % . The isobornyl
acrylate monomer is more preferably present in an amount of about 25 % to 35 %
,
and most preferably about 28 % . Suitable isobornyl acrylate monomers include
Sartomer SR-423 (isobornyl methacrylate):
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CH3 CH3
CH3
O
I
C=O
I
H3C-C
I I
CH2
and SR-506 (isobornyl acrylate):
CH3 CH3
CH3 O
I I
O-C-C=CH2
available from Sartomer Corp.; Radcure IBOA (isobornyl acrylate), commercially
available from Radcure Corp.; IBOA and IBOMA, commercially available from CPS
Chemical; and Genomer 1121, commercially available from Rahn Radiation Curing.
The preferred isobornyl acrylate monomers is Radcure IBOA, commercially
available from Radcure Corp. Radcure IBOA is a high purity, low color monomer.
Combinations of these materials may also be employed herein.
This preferred decorative metallic composition also includes a
photoinitiator in an amount of about 4 % to 14 % of the decorative metallic
composition. The photoinitiator is more preferably present in an amount of
about
8 % to 12 % , and most preferably about 10 % . Suitable photoinitiators
include
Irgacure 184 (1-hydroxycyclohexyl phenyl ketone); Irgacure 907 (2-methyl-1-[4-
(methylthio)phenyl]-2-morpholino propan-1-one); Irgacure 369 (2-benzyl-2-N,N-
dimethylamino-1-(4-morpholinophenyl)-1-butanone); Irgacure 500 (the
combination
of 50 % by weight 1-hydroxy cyclohexyl phenyl ketone and 50 % by weight
benzophenone); Irgacure 651 (2,2-dimethoxy-2-phenyl acetophenone); Irgacure
1700 (the combination of 25 % by weight bis(2,6-dimethoxybenzoyl-2,4-,4-
trimethyl
pentyl phosphine oxide and 75 % by weight 2-hydroxy-2-methyl-1-phenyl-propan-1-
one); Darocur 1173 (2-hydroxy-2-methyl-lphenyl-1-propane); and Darocur 4265
(the
combination of 50 % by weight 2,4,6-trimethylbenzoyldiphenyl- phosphine oxide
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and 50 % by weight 2-hydroxy 2-methyl-1-phenyl-propan-1-one)available
commercially from Ciba-Geigy Corp., Tarrytown, N.Y.; CYRACURE UVI-6974
(mixed triaryl sulfonium hexafluoroantimonate salts) and CYRACURE UVI-6990
(mixed triaryl sulfonium hexafluorophosphate salts) available commercially
from
Union Carbide Chemicals and Plastics Co. Inc., Danbury, Conn.; and Genocure
CQ,
Genocure BOK, and Genocure M.F., commercially available from Rahn Radiation
Curing. The preferred photoinitiator is IRGACURE 1700 commercially available
from Ciba-Geigy of Tarrytown, New York. Combinations of these materials may
also be employed herein.
The composition still further includes a flow promoting agent in an
amount of about 0.0 % to 8.0 % , and preferably about 6.0 % , of the topcoat
composition. Suitable flow promoting agents include Genorad 17, commercially
available from Rahn Radiation Curing; and Modaflow, commercially available
from
Monsanto Chemical Co., St. Louis, Missouri. The preferred flow promoting agent
is Modaflow which is an ethyl acrylate and 2-ethylhexyl acrylate copolymer
that
improves the flow of the composition. Combinations of these materials may also
be
employed herein.
The preferred paint composition also includes a pigmented
composition in an amount of about 5 % to 40 % of the decorative metallic
composition. The pigmented composition is more preferably present in an amount
of about 10 % to 25 % , and most preferably about 20 % . Suitable pigmented
compositions includeVenus #91 pigment and Palegold #400 available from NazDar;
and A1 #200 pigment available from Silberlne. The preferred pigment used will
depend on the desired color of the paint. Combinations of these materials may
also
be employed herein.
To illustrate, the following example sets forth a presently preferred
decorative metallic composition according to this aspect of the invention.
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Example 1
This example provides a preferred gold decorative metallic
composition according to the invention. The decorative metallic composition
was
made from the following components:
Component Approximate
Weight %
IBOA 25.5
IRGACURE 17009.1
Ebecryl 3603 34.5
Modaflow 3 .6
Venus #91 27.3
Gold
Total 100.00
In this example the IBOA and Irgacure 1700 are mixed in a pan with
a propeller blade mixer for 30 seconds at a speed of 500 to 1000 rpm. In the
next
step, the Modaflow and the Ebecryl 3603 are introduced into the pan and mixed
for
1 to 2 minutes at a speed of 2000 rpm. In the final step, the Venus #91 is
introduced
into the pan and mixed for 1 to 2 minutes at a speed of 2000 rpm. The
temperature
during mixing is monitored. The mixing is temporarily suspended if the
temperature
exceed 100°F.
Example 2
This example provides a preferred aluminum decorative metallic
composition according to the invention. The decorative metallic composition
was
made from the following components:
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Component Approximate
Weight
IBOA 31.1
IRGACURE 170011.1
Ebecryl 3603 42.2
Modaflow 4.5
A1#200 11.1
Total 100.00
In this example the IBOA and Irgacure 1700 are mixed in a pan with
a propeller blade mixer for 30 seconds at a speed of 500 to 1000 rpm. In the
next
step, the Modaflow and the Ebecryl 3603 are introduced into the pan and mixed
for
1 to 2 minutes at a speed of 2000 rpm. In the final step, the Aluminum #200 is
introduced into the pan and mixed for 1 to 2 minutes at a speed of 2000 rpm.
The
temperature during mixing is monitored. The mixing is temporarily suspended if
the
temperature exceed 100°F.
Example 3
This example provides a preferred copper decorative metallic
composition according to the invention. The decorative metallic composition
was
made from the following components:
Component Approximate
Weight
IBOA 28.0
IRGACURE 1700 10.0
Ebecryl 3603 38.0
Modaflow 4.0
Palegold #400 20.0
Copper
Total 100.00
_g_
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In this example the IBOA and Irgacure 1700 are mixed in a pan with
a propeller blade mixer for 30 seconds at a speed of 500 to 1000 rpm. In the
next
step, the Modaflow and the Ebecryl 3603 are introduced into the pan and mixed
for
1 to 2 minutes at a speed of 2000 rpm. In the final step, the Palegold #400 is
introduced into the pan and mixed for 1 to 2 minutes at a speed of 2000 rpm.
The
temperature during mixing is monitored. The mixing is temporarily suspended if
the
temperature exceed 100°F.
Method for Depositing an Decorative Metallic Coating on a Substrate
In accordance with still another aspect of the invention, a method is
provided for depositing an decorative metallic coating on a suitable
substrate. The
method comprises a first step of applying a decorative metallic fluid-phase
composition ("decorative metallic composition") to the substrate.
The decorative metallic composition comprises an acrylated epoxy
oligomer in an amount of about 20 % to 45 % , an isobornyl acrylate monomer in
an
amount of about 15 % to 40 % of the decorative metallic composition, a
photoinitiator
in an amount of about 4 % to 14 % of the decorative metallic composition, a
flow
promoting agent in an amount of 0 % to 8 % of the decorative metallic
composition,
and a metallic pigment in an amount of 5 % to 40 % . The preferred decorative
metallic compositions according to this method are those described herein, for
example, including the compositions described in examples 1, 2, and 3.
The decorative metallic composition may be applied to the substrate
using a number of different techniques. The decorative metallic composition
may
be applied, for example, by direct brush application, dipping, or it may be
sprayed
onto the substrate surface. It also may be applied using a screen printing
technique.
In such screen printing technique, a "screen" as the term is used in the
screen
printing industry is used to regulate the flow of liquid composition onto the
substrate
surface. The decorative metallic composition typically would be applied to the
screen as the latter contacts the substrate. The decorative metallic
composition flows
through the silk screen to the substrate, whereupon it adheres to the
substrate at the
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desired film thickness. Screen printing techniques suitable for this purpose
include
known techniques, but wherein the process is adjusted in ways known to persons
of
ordinary skill in the art to accommodate the viscosity, flowability, and other
properties of the liquid-phase composition, the substrate and its surface
properties,
etc. Flexographic techniques, for example, using pinch rollers to contact the
decorative metallic composition with a rolling substrate, also may be used.
The method includes a second step of illuminating the decorative
metallic fluid-phase composition on the substrate with an ultraviolet light to
cause
the decorative metallic fluid-phase composition to cure into the decorative
metallic
coating. This illumination may be carried out in any number of ways, provided
the
ultraviolet light or radiation impinges upon the decorative metallic
composition so
that the decorative metallic composition is caused to polymerize to form the
coating,
layer, film, etc., and thereby cures.
Curing preferably takes place by free radical polymerization, which
is initiated by an ultraviolet radiation source. The photoinitiator preferably
comprises
a photoinitiator, as described above.
Various ultraviolet light sources may be used, depending on the
application. Preferred ultraviolet radiation sources for a number of
applications
include known ultraviolet lighting equipment with energy intensity settings
of, for
example, 125 watts, 200 watts, and 300 watts per square inch.
While embodiments of the invention have been illustrated and
described, it is not intended that these embodiments illustrate and describe
all
possible forms of the invention. Rather, the words used in the specification
are
words of description rather than limitation, and it is understood that various
changes
may be made without departing from the spirit and scope of the invention.
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