Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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METHODS OF DISPENSING POWDER COATING COMPOSITIONS
AND ARTICLES COATED THEREWITH
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S. Patent Application
Serial No.
11/337,016, entitled "Decorative And Durable Coatings Having A Homogeneous
Hue, Methods
For Their Preparation, And Articles Coated Therewith", filed January 20, 2006,
incorporated
herein by reference. This application also claims priority under 35 U.S.C.
119 to Provisional
Application Serial No. 61/118,761, filed December 1, 2008, incorporated herein
by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to methods of dispensing thermoset powder
coating
compositions, a system for dispensing a plurality of thermoset powder coating
compositions, and
methods of coating substrates with the dispensed thermoset powder coating
compositions.
BACKGROUND INFORMATION
[0003] Powder coatings compositions for use in coating various types of
substrates are
often desired. Such coating compositions can greatly reduce, or even
eliminate, the use of
organic solvents that are often used in liquid coating compositions. When a
powder coating
composition is cured by heating, little if any volatile material is driven
into the surrounding
environment. This is a significant advantage over liquid coating compositions
in which organic
solvent is volatized into the surrounding atmosphere when the coating
composition is cured by
heating.
[0004] Powder coating compositions are typically produced by a complex process
that
includes dry blending various coating components, such as color pigments, film-
forming resins,
curing agents, and other additives, such as flow control agents and charge
control agents,
subjecting the resulting blend to heating, melting and kneading by the use of
an extruder or the
like, and then subjecting the resulting extrudate to cooling, grinding and
classification (referred to
herein as the "Extrusion Process"). Thus, the Extrusion Process requires many
steps.
[0005] Many customers, such as those customers in the industrial business,
change colors
frequently in production during the coating process. Often, customers wish to
make these color
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changes in a short period of time. One disadvantage to the use of powder
coatings has been the
difficulty of coatings' manufacturers to produce and supply small batches of
powder coating
compositions in a variety of colors to customers in a short period of time and
in a cost effective
manner so that the customers can in turn rapidly change colors during
production.
[0006] Another disadvantage to the use of powder coating compositions has been
that, to
obtain various coatings of different hues, the production of a separate powder
coating
composition for each desired hue has been required. When liquid coating
compositions of
different hues are mixed, it is possible to obtain a coating having a
homogeneous hue that is
different from the hue of each mixed liquid coating composition. On the other
hand, when typical
powder coating compositions of different hues are dry-blended and the
resultant blend applied to
a substrate, the result is that each hue can be generally distinguished by
visual examination with
the naked eye, resulting in a "salt and pepper" effect. Thus, it has
previously been difficult, if not
impossible, to achieve a coating of a desired hue from a dry blend of two or
more powder coating
compositions of different hues.
[0007] As a result, it would be desirable to have a method of dispensing a
plurality of
powder coating compositions to provide small batches of powder coating
compositions in a
variety of colors to the customer in a very short period of time. It would
also be desirable to
provide powder coating compositions suitable for producing a decorative and
durable coating
having a selected homogeneous hue from a dry blend of two or more powder
coating
compositions each having a different hue dispensed according to these methods.
SUMMARY OF THE INVENTION
[0008] In certain respects, the present invention provides a method of
dispensing a
thermoset powder coating composition, comprising: metering a controlled amount
of at least one
of a plurality of thermoset powder coating compositions from at least one of a
plurality of
containers to a common receptacle, wherein at least one of the plurality of
thermoset powder
coating compositions comprises: (a) a colorant; (b) a particulate film-forming
resin; and (c) a
curing agent for the film-forming resin, and wherein each one of the thermoset
powder coating
compositions provides a fmished decorative and durable coating when deposited
onto a substrate
and cured.
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[0009] In other respects, the present invention a method of dispensing a
plurality of
thermoset powder coating compositions, comprising: metering a controlled
amount of a first
thermoset powder coating composition having a first hue from a first container
and a second
powder coating composition having a second hue different from the hue of the
first powder
coating composition from a second container to a common receptacle to form a
mixture, wherein
the first powder coating composition and the second powder coating composition
each comprise:
(a) a colorant; (b) a particulate film-forming resin; and (c) a curing agent
for the film-forming
resin, wherein each of the first thermoset powder coating composition and the
second thermoset
powder coating composition provides a fmished decorative and durable coating
when deposited
onto a substrate and cured, and wherein the mixture provides a fmished
decorative and durable
coating having a homogeneous hue different from the hue of the first powder
coating composition
and the hue of the second powder coating composition when the mixture is
applied to a substrate
and cured.
[0010] In yet other respects, the present invention is directed to a system
for dispensing a
plurality of thermoset powder coating compositions, the system comprising: (a)
a plurality of
containers having at least one thermoset powder coating composition therein;
and (b) a means for
metering a controlled amount of at least one of the thermoset powder coating
compositions from
at least one of the containers to a common receptacle, wherein the thermoset
powder coating
compositions comprise: (i) a colorant; (ii) a particulate film-forming resin;
and (iii) a curing agent
for the film-forming resin, and wherein each one of the thermoset powder
coating compositions
provides a fmished decorative and durable coating when deposited onto a
substrate and cured.
[0011] These and other respects will become more apparent from the following
description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The Figure schematically illustrates a system and method of metering
and
dispensing a plurality of thermoset powder coating compositions in accordance
with an
embodiment of the invention.
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DETAILED DESCRIPTION
[0013] For purposes of the following detailed description, it is to be
understood that the
invention may assume various alternative variations and step sequences, except
where expressly
specified to the contrary. Moreover, other than in any operating examples, or
where otherwise
indicated, all numbers expressing, for example, quantities of ingredients used
in the specification
and claims are to be understood as being modified in all instances by the term
"about".
Accordingly, unless indicated to the contrary, the numerical parameters set
forth in the following
specification and attached claims are approximations that may vary depending
upon the desired
properties to be obtained by the present invention. At the very least, and not
as an attempt to limit
the application of the doctrine of equivalents to the scope of the claims,
each numerical parameter
should at least be construed in light of the number of reported significant
digits and by applying
ordinary rounding techniques.
[0014] Notwithstanding that the numerical ranges and parameters setting forth
the broad
scope of the invention are approximations, the numerical values set forth in
the specific examples
are reported as precisely as possible. Any numerical value, however,
inherently contains certain
errors necessarily resulting from the standard variation found in their
respective testing
measurements.
[0015] Also, it should be understood that any numerical range recited herein
is intended to
include all sub-ranges subsumed therein. For example, a range of "1 to 10" is
intended to include
all sub-ranges between (and including) the recited minimum value of 1 and the
recited maximum
value of 10, that is, having a minimum value equal to or greater than 1 and a
maximum value of
equal to or less than 10.
[0016] In this application, the use of the singular includes the plural and
plural
encompasses singular, unless specifically stated otherwise. In addition, in
this application, the use
of "or" means "and/or" unless specifically stated otherwise, even though
"and/or" may be
explicitly used in certain instances.
[0017] As previously mentioned, certain embodiments of the present invention
are
directed to methods of dispensing a plurality of thermoset powder coating
compositions. As used
herein, the term "thermoset" refers to compositions that set irreversibly upon
curing or
crosslinking wherein the polymer chains of the polymeric components are joined
together by
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covalent bonds. As used herein, the term "powder coating compositions" refers
to compositions
suitable for producing a coating on a substrate, which is embodied in a solid
particulate form, as
opposed to liquid form.
[0018] In certain embodiments, the methods of the present invention comprise
metering a
controlled amount of at least one of a plurality of thermoset powder coating
compositions from at
least one of a plurality of containers to a common receptacle, wherein at
least one of the plurality
of thermoset powder coating compositions comprises: (a) a colorant; (b) a
particulate film-
forming resin; and (c) a curing agent for the film-forming resin, and wherein
each one of the
thermoset powder coating compositions provides a finished decorative and
durable coating when
deposited onto a substrate and cured.
[0019] Any suitable dispensing apparatus may be used to meter the thermoset
powder
coating compositions according to the methods of the present invention.
Various types of
dispensing apparatus include dispensers with rotating screws, pistons, and
pumps. Examples of
suitable dispensing apparatus include, but are not limited to, those available
from IDEX
Corporation and Fast & Fluid Management (a division of IDEX Corporation), for
example, under
the tradenames ACCUTINTER, XFAST, BLENDORAMA, COLORPRO, TINTMASTER,
HARBIL, and LEOLUX. Non-limiting suitable dispensing apparatus that may be
used to meter
the thermoset powder coating compositions in accordance with the invention
include those
disclosed in U.S. Patent No. 7,134,573, col. 3, line 13 through col. 5, line
6, the cited portion
incorporated herein by reference, and U.S. Patent No. 7,311,223, col. 3, line
32 through col. 7,
line 11, the cited portion incorporated herein by reference. U.S. Patent Nos.
7,134,573 and
7,311,223 disclose a dispensing apparatus with several containers, each
container having a meter
pump with two screws, a large and small screw, capable of dispensing powdered
materials into a
common receptacle. The plurality of containers and common receptacle described
in U.S. Patent
Nos. 7,134,573 and 7,311,223 may be adapted and used in the methods of the
present invention.
The plurality of metering powder pumps as described in U.S. Patent Nos.
7,134,573 and
7,311,223 may be used herein to meter a controlled amount of the thermoset
powder coating
compositions. The screws located inside the metering pumps as described in
U.S. Patent Nos.
7,134,573 and 7,311,223 may also be used in the metering step described herein
to meter a
controlled amount of the thermoset powder coating compositions.
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[0020] Other suitable dispensing apparatus that may be used to meter the
thermoset
coating powders in accordance with the invention include those disclosed in
U.S. Patent No.
7,360,564, col. 4, line 47 through col. 9, line 32, the cited portion
incorporated herein by
reference.
[0021] The Figure schematically illustrates a system and method of metering
and
dispensing a plurality of thermoset powder coating compositions in accordance
with an
embodiment of the present invention. The system 10 can include multiple
containers 12A-F, each
of which contains at least one thermoset powder coating composition that can
be the same or
different. In certain embodiments, at least two, or, in some cases all, of the
thermoset powder
coating compositions have a different hue. The powder coating compositions are
selectively fed
from the containers 12A-F to a common receptacle 20. In the embodiment shown
in the Figure,
each container has a coarse feedline and a fine feedline extending from the
container to the
common receptacle 20. For example, the container 12A communicates with a first
feedline 14A
and a second feedline 16A. The first feedline 14A may be used to meter a
coarse amount of the
powder coating composition to the common receptacle 20, while the second
feedline 16A may be
used to meter a fine amount of the powder coating composition to the common
receptacle 20.
Each of the containers 12A-F are thus equipped with a coarse feedline 14A-F
and a fine feedline
16A-F, respectively. As shown in the Figure, after the selected types and
amounts of powder
coating compositions are fed to the common receptacle, the powders may be fed
to a powder
coating sprayer for application to various substrates by known techniques,
such as electrostatic
spray deposition. A mixer (not shown) may be used to blend the multiple powder
coating
compositions prior to feeding the mixture to the powder coating sprayer 30.
[0022] There may be any number of containers present to hold the plurality of
thermoset
powder coating compositions in the methods of the present invention. The
number of containers
may vary depending on, for example, the number of thermoset powder coating
compositions to be
dispensed, and other similar factors. In certain embodiments, there may be a
small number of
containers, for example, up to ten containers, while in other embodiments,
there may be a larger
number of containers, for example, more than ten containers, such as twenty
containers, in some
cases, thirty containers.
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[0023] In certain embodiments, each of the plurality of containers has one
thermoset
powder coating composition therein. In certain embodiments, the thermoset
powder coating
composition in each one of the containers is different from the thermoset
powder coating
composition in the other containers. In other embodiments, the thermoset
powder coating
composition differs from the other thermoset powder coating compositions in
hue, as discussed in
more detail below.
[0024] In other embodiments, each of the plurality of containers has two or
more
thermoset powder coating compositions therein.
[0025] The containers may be any suitable size and shape and may have the
capacity to
hold any suitable amount of thermoset powder coating composition. The
containers may be
covered or uncovered by any suitable means and may be made of any suitable
material including
but not limited to, plastic, metal, for example, stainless steel, aluminum,
and the like.
[0026] In certain embodiments, the containers may have an associated mixing
apparatus
so that the thermoset powder coating compositions may be agitated while
present inside the
containers prior to being dispensed. In other embodiments, the containers
themselves may be
capable of rotation and/or vibration to agitate the powder coating
compositions held within the
containers. In still other embodiments, the containers do not require any such
mixing apparatus.
[0027] In certain embodiments, the containers may have a heating apparatus
associated
with them, for example, to provide heat to the thermoset powder coating
compositions provided
the temperature does not reach a level that would prematurely soften and/or
melt the powder
coating compositions present inside the containers. In other embodiments, no
such heating
apparatus is required.
[0028] In certain embodiments, the containers may be portable, while in other
embodiments, they may be non-portable.
[0029] In certain embodiments, the containers may be disposable. In these
embodiments,
once the thermoset powder coating composition held inside the container is
used and the empty
container is no longer desired, it may be discarded. A different container
filled with the same or
different thermoset powder coating composition may be used in its place. The
disposable
containers filled with thermoset powder coating composition may be provided by
any suitable
supplier, for example, by the manufacturer of the thermoset powder coating
compositions or a
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third party supplier. The containers may be provided individually, i.e., a
single full disposable
container may be obtained to replace a single empty one. The containers may
also be provided as
a kit, i.e., a kit of more than one container may be obtained, the disposable
containers in the kit
filled with a variety of thermoset powder coating compositions having
different hues. As used
herein, the term "kit" refers to a collection of articles usable together. As
used herein, the term
"hue" refers to the quality of a color, as determined by its dominant
wavelength. For example, the
kits may comprise (a) a first container comprising a powder coating
composition having a first
hue, and (b) a second container comprising a powder coating composition having
a second hue
different from the first hue. There may be additional containers containing
thermoset powder
coating compositions of other different hues. The kits are discussed in more
detail below. In
other embodiments, the disposable containers may be filled with an additive
that may be used in
combination with the thermoset powder coating compositions in the methods of
the present
invention as discussed in further detail below.
[0030] In other embodiments, the plurality of containers used in the methods
of the
present invention may be refillable. In these embodiments, once the thermoset
powder coating
composition is used, the container may be refilled, i.e., more powder coating
composition, either
the same or different, may be added to the container. Any suitable method for
refilling the
containers may be employed.
[0031] As mentioned, at least one of a plurality of thermoset coating
compositions is
metered from at least one of a plurality of containers. Containers may also be
present which hold
materials other than the thermoset powder coating compositions. In certain
embodiments, there
may be additive containers, wherein the additive container holds at least one
additive selected
from a flatting agent, a UV absorber, a texture agent, a catalyst, a flow
control agent, a charge
control agent, a mar resistant agent, a flame retardant, an anti-microbial
additive, an
electrochromic particle, an effect pigment, and a mixture thereof.
[0032] As used herein, the term "effect pigment" refers to a material that
provides visual
effects to a coating and includes, but is not limited to, micas, metallic
pigments, and the like. As
used herein, the term "electrochromic particle" refers to a material that
causes a color change in a
coating in response to an applied electrical potential. Such materials are
known in the art.
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[0033] The additives are not necessary for the powder coating compositions to
provide a
finished decorative and durable coating when deposited onto a substrate and
cured, as discussed
in more detail below. The additives may optionally be added to the thermoset
powder coating
compositions to provide a variety of appearance and/or performance properties.
Some of these
additives may not be present for the purpose of providing appearance and/or
performance
properties to the powder compositions, but may be present for other purposes
associated with the
methods of the present invention, such as solvent used to clean the
containers.
[0034] As mentioned, the methods of the present invention comprise metering a
controlled amount of at least one of a plurality of thermoset powder coating
compositions from at
least one of a plurality of containers to a common receptacle. The thermoset
powder coating
composition is dispensed, in a controlled amount, from the container which
holds it to the
common receptacle. In certain embodiments, the amount of the thermoset coating
composition
dispensed is selectably controlled so that a particular chosen amount may be
dispensed.
[0035] In certain embodiments, a single thermoset powder coating composition
may be
dispensed in a controlled amount from the container that holds it to the
common receptacle, while
in other embodiments, two or more of the thermoset powder coating compositions
may be
dispensed in controlled amounts from their individual containers to the common
receptacle.
[0036] The common receptacle may have any of the characteristics described
above with
respect to the containers. Similar to the containers, the common receptacle
may have an
associated mixing apparatus so that the thermoset powder coating compositions
may be agitated
after being dispensed into the common receptacle. In other embodiments, the
mixing apparatus is
not necessarily associated with the common receptacle, but may exist
separately from the
common receptacle and used as necessary. In these embodiments, the common
receptacle
containing the plurality of thermoset coating compositions may be taken to a
separate mixing
apparatus and mixed prior to application to a substrate. In still other
embodiments, the common
receptacle may be capable of rotation and/or vibration to agitate the
thermoset powder coating
compositions that have been dispensed. In yet other embodiments, no mixing
apparatus is
present.
[0037] In certain embodiments, a heating apparatus may be associated with the
common
receptacle that provides heat to the thermoset coating compositions as desired
provided the
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temperature does not reach a level that would prematurely soften and/or melt
the powder coating
compositions present inside the common receptacle. In other embodiments, the
common
receptacle has no such heating apparatus.
[0038] In certain embodiments of the methods of the present invention, the
metering step
comprises determining a desired amount of the thermoset powder coating
composition; drawing
the desired amount of the thermoset powder coating composition from the
container; and
dispensing the desired amount of the thermoset powder coating composition into
the common
receptacle.
[0039] In other embodiments, the metering step further comprises measuring a
first
amount of the thermoset powder coating composition dispensed into the common
receptacle;
comparing the first amount dispensed to the desired amount to calculate a
difference between the
first amount dispensed and the desired amount; using the difference between
the first amount
dispensed and the desired amount to calculate a second amount of the thermoset
powder coating
composition to be dispensed; and dispensing the second amount of the thermoset
powder coating
composition into the common receptacle to provide the desired amount.
[0040] The desired amount of the thermoset powder coating composition to be
dispensed
may be derived from a formula and/or recipe containing a list of one or more
of the thermoset
powder coating compositions, wherein the formula and/or recipe, as followed,
results in a desired
hue once the final coating film is applied to a substrate and cured. In
certain embodiments, the
formula and/or recipe may be stored on a computer, which may communicate with
the metering
system.
[0041] As mentioned, once the desired amount of the thermoset powder coating
composition is determined, the desired amount is drawn from the appropriate
container and
subsequently dispensed into the common receptacle. In certain embodiments, the
thermoset
powder coating compositions may be gravimetrically dispensed from the
container by weight. In
other embodiments, the compositions may be volumetrically dispensed.
[0042] The metering step may be accomplished in any suitable manner that draws
the
thermoset powder coating composition from the container holding it and
dispenses the
composition from the container into the common receptacle. In certain
embodiments, the
metering step comprises the use of a meter mechanism. Any suitable meter
mechanism may be
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used. Non-limiting examples include pistons, as described in U.S. Patent No.
7,360,564, col. 4,
line 47 through col. 9, line 32, the cited portion incorporated herein by
reference; rotating screws
as described in U.S. Patent No. 7,134,573, col. 3, line 13 through col. 5,
line 6, the cited portion
incorporated herein by reference, and U.S. Patent No. 7,311,223, col. 3, line
32 through col. 7,
line 11, the cited portion incorporated herein by reference; and the like.
[0043] In certain embodiments, the meter mechanism is positioned to be able to
dispense
the powder coating compositions into the common receptacle. The capacity of
the meter
mechanism may be selectable, that is, the amount of thermoset powder coating
composition to be
dispensed may be varied, which may improve dispense times as well as accuracy
of the amounts of
dispensed compositions that may be present.
[0044] In certain embodiments, there may be a single meter mechanism which
meters a
controlled amount of the plurality of thermoset powder coating compositions
from the plurality of
containers into the common receptacle. In these embodiments, the plurality of
containers and/or
the single meter mechanism may be movable so that each of the plurality of
containers may come
in contact with the single meter mechanism as necessary to be dispensed. In
other embodiments,
there may be a plurality of meter mechanisms. In these embodiments, at least
one meter
mechanism is connected to each of the plurality of containers.
[0045] The meter mechanism may be releasably connected to a container so that
it may be
removed, if desired. As previously mentioned, in certain embodiments, the
containers may be
portable. In these embodiments, the meter mechanism is capable of detachment
from and
reattachment to the container as desired. As would be recognized, similar
releasable properties of
the meter mechanisms would be desired in embodiments where the containers are
disposable
and/or refillable.
[0046] In certain embodiments, the meter mechanisms may be individually
controlled, that
is, a meter mechanism may be controlled separately from other meter
mechanisms.
[0047] In certain embodiments, the metering step comprises the use of a meter
mechanism
comprising at least two pump screws. In certain embodiments, the at least two
pump screws
present in the meter mechanism comprise one screw having a relatively large
dispensing capacity
and another screw having a relatively small dispensing capacity. The pump
screws may be
individually controlled and/or operated so that they may dispense varying
amounts of the
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thermoset powder coating compositions. In certain embodiments, the screw
having a relatively
large dispensing capacity dispenses a larger amount of the thermoset powder
coating composition,
and the screw having a relatively small dispensing capacity dispenses a lesser
amount of the
thermoset powder coating composition than the screw having a relatively large
capacity. In other
embodiments, the screw having a relatively large dispensing capacity is larger
in diameter than the
screw having a relatively small dispensing capacity. In yet other embodiments,
the larger screw
has a diameter over twice the diameter of the small screw.
[0048] The pump screws may be made of any suitable material, including but not
limited
to metal, for example, stainless steel; plastic, for example, polyproplene,
polytetrafluroethylene,
and the like. In certain embodiments, the meter mechanism may be operated by
use of a motor.
[0049] Any suitable dispensing capacity may exist for the meter mechanism. In
certain
embodiments, the dispensing capacity of the meter mechanism may range from 1
milligram to 10
kilograms, such as from 1 milligram to 5,000 grams, such as from 10 milligrams
to 1,000 grams,
such as from 10 milligrams to 500 grams.
[0050] As mentioned, once the desired amount of the thermoset powder coating
composition has been drawn from the container and dispensed into the common
receptacle, a first
amount that has been dispensed into the receptacle may be measured. As one
would recognize,
measuring of the first amount may be accomplished by any suitable measuring
device including,
for example, by devices that measure weight, by devices that measure volume,
or other similar
devices. The measuring device may be associated with the common receptacle,
i.e., attached in a
suitable manner, to enable rapid measurements as the powder coating
compositions are dispensed.
The measuring device may also be separate from the common receptacle.
[0051] Subsequently, the first amount dispensed into the receptacle may be
compared to
the desired amount to calculate a difference between the first amount
dispensed and the desired
amount. The difference between the first amount dispensed and the desired
amount may then be
used to calculate a second amount of the thermoset powder coating composition
to be dispensed,
if a second amount of the thermoset powder coating composition is necessary.
As one would
recognize, if the difference between the first amount dispensed and the
desired amount is zero, no
second amount of the thermoset powder coating composition is necessary to be
dispensed. Next,
the second amount of the thermoset powder coating composition may be dispensed
into the
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common receptacle. Typically, the second amount is less than the first amount
dispensed. In
certain embodiments, a rotating screw having a relatively large dispensing
capacity may be used to
dispense the first amount, and a rotating screw having a relatively small
dispensing capacity may
be used to dispense the second amount.
[0052] In certain embodiments, the determination of the first and second
amounts may be
used to calibrate the metering mechanism for future dispenses.
[0053] The above-described method may be used to dispense any of the plurality
of
thermoset powder coating compositions present in the plurality of containers.
In certain
embodiments of the methods of the present invention, at least one of the
plurality of thermoset
powder coating compositions may be dispensed into a common receptacle
sequentially one at a
time. In other embodiments, more than one of the plurality of thermoset powder
coating
compositions may be dispensed simultaneously into the common receptacle as dry
powder coating
compositions. In certain embodiments, the plurality of thermoset powder
coating compositions
may be dispensed without the presence of heat and/or agitation. In other
embodiments, as
discussed above, agitation and/or heating of one or more of the plurality of
thermoset powder
coating compositions may be used, for example, while the compositions are
present in the
containers and/or in the common receptacle after the compositions have been
dispensed.
[0054] As previously mentioned, at least one of the plurality of thermoset
powder coating
compositions dispensed according to the methods of the present invention
comprises: (a) a
colorant; (b) a particulate film-forming resin; and (c) a curing agent for the
film-forming resin,
and wherein each one of the thermoset powder coating compositions provides a
fmished
decorative and durable coating when deposited onto a substrate and cured.
Suitable thermoset
powder coating compositions include those disclosed in U.S. Patent Application
Publication No.
2006/0251891, paragraphs [0019] through [0148] and U.S. Patent Application
Publication No.
2007/0172662, paragraphs [0015] through [0125], the cited portions
incorporated herein by
reference.
[0055] As used herein, the term "colorant" means any substance that imparts
color and/or
other visual effect to the composition. The colorant can be added to the
thermoset powder
coating composition in any suitable form, such as discrete particles,
dispersions, solutions and/or
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flakes. A single colorant or a mixture of two or more colorants can be used in
the thermoset
powder coating compositions of the present invention.
[0056] In certain embodiments, the powder coating compositions comprise from
0.1 to 50
percent by weight, such as 1 to 20 percent by weight, of colorant, based on
the total weight of the
powder coating composition.
[0057] In certain embodiments, the colorant comprises polymer-enclosed color-
imparting
nanoparticles. As used herein, the term "nanoparticles" refers to particles
that have an average
particle size of less than 1 micron. In certain embodiments, the nanoparticles
used in the present
invention have an average particle size of 300 nanometers or less, such as 200
nanometers or less,
or, in some cases, 100 nanometers or less. It will be appreciated, of course,
that a powder coating
composition comprising nanoparticles may also include particles that are not
nanoparticles.
[0058] For purposes of the present invention, average particle size can be
measured
according to known laser scattering techniques. For example, average particle
size can be
determined using a Horiba Model LA 900 laser diffraction particle size
instrument, which uses a
helium-neon laser with a wave length of 633 nm to measure the size of the
particles and assumes
the particle has a spherical shape, i.e., the "particle size" refers to the
smallest sphere that will
completely enclose the particle. Average particle size can also be determined
by visually
examining an electron micrograph of a transmission electron microscopy ("TEM")
image of a
representative sample of the particles, measuring the diameter of the
particles in the image, and
calculating the average primary particle size of the measured particles based
on magnification of
the TEM image. One of ordinary skill in the art will understand how to prepare
such a TEM
image and determine the primary particle size based on the magnification. The
primary particle
size of a particle refers to the smallest diameter sphere that will completely
enclose the particle.
As used herein, the term "primary particle size" refers to the size of an
individual particle.
[0059] As mentioned, in certain embodiments, the powder coating compositions
comprise
color-imparting nanoparticles that are polymer-enclosed and, therefore, not
significantly
agglomerated. As used herein, the term "polymer-enclosed nanoparticles" refers
to nanoparticles
that are at least partially enclosed by, i.e., confined within, a polymer to
an extent sufficient to
separate particles from each other within the resulting coating, such that
significant agglomeration
of the particles is prevented. It will be appreciated, of course, that a
powder coating composition
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comprising such "polymer-enclosed nanoparticles" may also include
nanoparticles that are not
polymer-enclosed particles. As used herein, the term "color-imparting
nanoparticle" refers to a
particle that significantly absorbs some wavelengths of visible light, that
is, wavelengths ranging
from 400 to 700 nm, more than it absorbs other wavelengths in the visible
region.
[0060] The shape (or morphology) of the polymer-enclosed color-imparting
nanoparticles
can vary. For example, generally spherical morphologies (such as solid beads,
microbeads, or
hollow spheres), can be used, as well as particles that are cubic, platy, or
acicular (elongated or
fibrous). Additionally, the particles can have an internal structure that is
hollow, porous or void
free, or a combination of any of the foregoing, e.g., a hollow center with
porous or solid walls.
For more information on suitable particle characteristics see H. Katz et al.
(Ed.), Handbook of
Fillers and Plastics (1987) at pages 9-10.
[0061] Depending on the desired properties and characteristics of the
resultant powder
coating composition (e.g., coating hardness, scratch resistance, stability, or
color), mixtures of
one or more polymer-enclosed color-imparting nanoparticles having different
average particle
sizes can be employed.
[0062] The polymer-enclosed color-imparting nanoparticles can be formed from
polymeric
and/or non-polymeric inorganic materials, polymeric and/or non-polymeric
organic materials,
composite materials, as well as mixtures of any of the foregoing. As used
herein, "formed from"
denotes open, e.g., "comprising," claim language. As such, it is intended that
a composition or
substance "formed from" a list of recited components be a composition
comprising at least these
recited components, and can further comprise other, non-recited components,
during the
composition's formation. Additionally, as used herein, the term "polymer" is
meant to encompass
oligomers, and includes without limitation both homopolymers and copolymers.
[0063] As used herein, the term "polymeric inorganic material" means a
polymeric
material having a backbone repeat unit based on an element or elements other
than carbon.
Moreover, as used herein, the term "polymeric organic materials" means
synthetic polymeric
materials, semi-synthetic polymeric materials and natural polymeric materials,
all of which have a
backbone repeat unit based on carbon.
[0064] The term "organic material", as used herein, means carbon containing
compounds
wherein the carbon is typically bonded to itself and to hydrogen, and often to
other elements as
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well, and excludes binary compounds such as the carbon oxides, the carbides,
carbon disulfide,
etc.; such ternary compounds as the metallic cyanides, metallic carbonyls,
phosgene, carbonyl
sulfide, etc.; and carbon-containing ionic compounds such as metallic
carbonates, for example
calcium carbonate and sodium carbonate.
[0065] As used herein, the term "inorganic material" means any material that
is not an
organic material.
[0066] As used herein, the term "composite material" means a combination of
two or
more differing materials. The particles formed from composite materials
generally have a
hardness at their surface that is different from the hardness of the internal
portions of the particle
beneath its surface. More specifically, the surface of the particle can be
modified in any manner
well known in the art, including, but not limited to, chemically or physically
changing its surface
characteristics using techniques known in the art.
[0067] For example, a particle can be formed from a primary material that is
coated, clad
or encapsulated with one or more secondary materials to form a composite
particle that has a
softer surface. In certain embodiments, particles formed from composite
materials can be formed
from a primary material that is coated, clad or encapsulated with a different
form of the primary
material. For more information on particles useful in the present invention,
see G. Wypych,
Handbook of Fillers, 2nd Ed. (1999) at pages 15-202.
[0068] As aforementioned, the particles useful in the present invention can
include any
inorganic materials known in the art. Suitable particles can be formed from
ceramic materials,
metallic materials, and mixtures of any of the foregoing. Non-limiting
examples of such ceramic
materials can comprise metal oxides, mixed metal oxides, metal nitrides, metal
carbides, metal
sulfides, metal silicates, metal borides, metal carbonates, and mixtures of
any of the foregoing. A
specific, non-limiting example of a metal nitride is boron nitride; a
specific, non-limiting example
of a metal oxide is zinc oxide; non-limiting examples of suitable mixed metal
oxides are aluminum
silicates and magnesium silicates; non-limiting examples of suitable metal
sulfides are molybdenum
disulfide, tantalum disulfide, tungsten disulfide, and zinc sulfide; non-
limiting examples of metal
silicates are aluminum silicates and magnesium silicates, such as vermiculite.
[0069] In certain embodiments of the methods of the present invention, the
nanoparticles
of the thermoset powder coating compositions comprise inorganic materials
selected from
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aluminum, barium, bismuth, boron, cadmium, calcium, cerium, cobalt, copper,
iron, lanthanum,
magnesium, manganese, molybdenum, nitrogen, oxygen, phosphorus, selenium,
silicon, silver,
sulfur, tin, titanium, tungsten, vanadium, yttrium, zinc, and zirconium,
including oxides thereof,
nitrides thereof, phosphides thereof, phosphates thereof, selenides thereof,
sulfides thereof,
sulfates thereof, and mixtures thereof. Suitable non-limiting examples of the
foregoing inorganic
particles are alumina, silica, titania, ceria, zirconia, bismuth oxide,
magnesium oxide, iron oxide,
aluminum silicate, boron carbide, nitrogen doped titania, and cadmium
selenide.
[0070] The particles can comprise, for example, a core of essentially a single
inorganic
oxide, such as silica in colloidal, fumed, or amorphous form, alumina or
colloidal alumina,
titanium dioxide, iron oxide, cesium oxide, yttrium oxide, colloidal yttria,
zirconia, e.g., colloidal
or amorphous zirconia, and mixtures of any of the foregoing; or an inorganic
oxide of one type
upon which is deposited an organic oxide of another type.
[0071] Non-polymeric, inorganic materials useful in forming the particles used
in the
present invention can comprise inorganic materials selected from graphite,
metals, oxides,
carbides, nitrides, borides, sulfides, silicates, carbonates, sulfates, and
hydroxides. A non-limiting
example of a useful inorganic oxide is zinc oxide. Non-limiting examples of
suitable inorganic
sulfides include molybdenum disulfide, tantalum disulfide, tungsten disulfide,
and zinc sulfide.
Non-limiting examples of useful inorganic silicates include aluminum silicates
and magnesium
silicates, such as vermiculite. Non-limiting examples of suitable metals
include molybdenum,
platinum, palladium, nickel, aluminum, copper, gold, iron, silver, alloys, and
mixtures of any of
the foregoing.
[0072] In certain embodiments, the particles can be selected from fumed
silica, amorphous
silica, colloidal silica, alumina, colloidal alumina, titanium dioxide, iron
oxide, cesium oxide,
yttrium oxide, colloidal yttria, zirconia, colloidal zirconia, and mixtures of
any of the foregoing. In
certain embodiments, the particles comprise colloidal silica. As disclosed
above, these materials
can be surface treated or untreated. Other useful particles include surface-
modified silicas, such
as are described in U.S. Patent No. 5,853,809 at column 6, line 51 to column
8, line 43,
incorporated herein by reference.
[0073] As another alternative, a particle can be formed from a primary
material that is
coated, clad or encapsulated with one or more secondary materials to form a
composite material
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that has a harder surface. Alternatively, a particle can be formed from a
primary material that is
coated, clad or encapsulated with a differing form of the primary material to
form a composite
material that has a harder surface.
[0074] In one example, and without limiting the present invention, an
inorganic particle
formed from an inorganic material, such as silicon carbide or aluminum
nitride, can be provided
with a silica, carbonate or nanoclay coating to form a useful composite
particle. In another non-
limiting example, a silane coupling agent with alkyl side chains can interact
with the surface of an
inorganic particle formed from an inorganic oxide to provide a useful
composite particle having a
"softer" surface. Other examples include cladding, encapsulating or coating
particles formed from
non-polymeric or polymeric materials with differing non-polymeric or polymeric
materials. A
specific non-limiting example of such composite particles is a synthetic
polymeric particle coated
with calcium carbonate that is commercially available under the tradename
DUALITE particles
from Pierce and Stevens Corporation of Buffalo, N.Y.
[0075] In certain embodiments, the particles used in the present invention
have a lamellar
structure. Particles having a lamellar structure are composed of sheets or
plates of atoms in
hexagonal array, with strong bonding within the sheet and weak van der Waals
bonding between
sheets, providing low shear strength between sheets. A non-limiting example of
a lamellar
structure is a hexagonal crystal structure. Inorganic solid particles having a
lamellar fullerene
(i.e., buckyball) structure are also useful in the present invention.
[0076] Non-limiting examples of suitable materials having a lamellar structure
include
boron nitride, graphite, metal dichalcogenides, mica, talc, gypsum, kaolinite,
calcite, cadmium
iodide, silver sulfide, and mixtures thereof. Suitable metal dichalcogenides
include molybdenum
disulfide, molybdenum diselenide, tantalum disulfide, tantalum diselenide,
tungsten disulfide,
tungsten diselenide, and mixtures thereof.
[0077] The particles can be formed from non-polymeric, organic materials. Non-
limiting
examples of non-polymeric, organic materials useful in the present invention
include, but are not
limited to, stearates (such as zinc stearate and aluminum stearate), diamond,
carbon black, and
stearamide.
[0078] The particles used in the present invention can be formed from
inorganic polymeric
materials. Non-limiting examples of useful inorganic polymeric materials
include
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polyphosphazenes, polysilanes, polysiloxanes, polygernanes, polymeric sulfur,
polymeric selenium,
silicones, and mixtures of any of the foregoing. A specific, non-limiting
example of a particle
formed from an inorganic polymeric material suitable for use in the present
invention is Tospearl,
which is a particle formed from cross-linked siloxanes and is commercially
available from Toshiba
Silicones Company, Ltd. of Japan.
[0079] The particles can be formed from synthetic, organic polymeric
materials. Non-
limiting examples of suitable organic polymeric materials include, but are not
limited to, thermoset
materials and thermoplastic materials. Non-limiting examples of suitable
thermoplastic materials
include thermoplastic polyesters, such as polyethylene terephthalate,
polybutylene terephthalate
and polyethylene naphthalate, polycarbonates, polyolefms, such as
polyethylene, polypropylene
and polyisobutene, acrylic polymers, such as copolymers of styrene and an
acrylic acid monomer
and polymers containing methacrylate, polyamides, thermoplastic polyurethanes,
vinyl polymers,
and mixtures of any of the foregoing.
[0080] Non-limiting examples of suitable thermoset materials include thermoset
polyesters, vinyl esters, epoxy materials, phenolics, aminoplasts, thermoset
polyurethanes and
mixtures of any of the foregoing. A specific, non-limiting example of a
synthetic polymeric
particle formed from an epoxy material is an epoxy microgel particle.
[0081] The particles can also be hollow particles formed from materials
selected from
polymeric and non-polymeric inorganic materials, polymeric and non-polymeric
organic materials,
composite materials, and mixtures of any of the foregoing. Non-limiting
examples of suitable
materials from which the hollow particles can be formed are described above.
[0082] In certain embodiments, the nanoparticles used in the present invention
comprise
an organic pigment, for example, azo compounds (monoazo, di-azo, .beta.-
Naphthol, Naphthol
AS salt type azo pigment lakes, benzimidazolone, di-azo condensation,
isoindolinone,
isoindoline), and polycyclic (phthalocyanine, quinacridone, perylene,
perinone, diketopyrrolo
pyrrole, thioindigo, anthraquinone, indanthrone, anthrapyrimidine,
flavanthrone, pyranthrone,
anthanthrone, dioxazine, triarylcarbonium, quinophthalone) pigments, and
mixtures of any of the
foregoing. In certain embodiments, the organic material is selected from
perylenes,
quinacridones, phthalocyanines, isoindolines, dioxazines (that is,
triphenedioxazines), 1,4-
diketopyrrolopyrroles, anthrapyrimidines, anthanthrones, flavanthrones,
indanthrones, perinones,
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pyranthrones, thioindigos, 4,4'-diamino-1,1'-dianthraquinonyl, as well as
substituted derivatives
thereof, and mixtures thereof.
[0083] Perylene pigments used in the practice of the present invention may be
unsubstituted or substituted. Substituted perylenes may be substituted at
imide nitrogen atoms for
example, and substituents may include an alkyl group of 1 to 10 carbon atoms,
an alkoxy group of
1 to 10 carbon atoms and a halogen (such as chlorine) or combinations thereof.
Substituted
perylenes may contain more than one of any one substituent. The diimides and
dianhydrides of
perylene-3,4,9,10-tetracarboxylic acid are preferred. Crude perylenes can be
prepared by
methods known in the art.
[0084] Phthalocyanine pigments, especially metal phthalocyanines may be used.
Although
copper phthalocyanines are more readily available, other metal-containing
phthalocyanine
pigments, such as those based on zinc, cobalt, iron, nickel, and other such
metals, may also be
used. Metal-free phthalocyanines are also suitable. Phthalocyanine pigments
may be
unsubstituted or partially substituted, for example, with one or more alkyl
(having 1 to 10 carbon
atoms), alkoxy (having 1 to 10 carbon atoms), halogens such as chlorine, or
other substituents
typical of phthalocyanine pigments. Phthalocyanines may be prepared by any of
several methods
known in the art. They are typically prepared by a reaction of phthalic
anhydride, phthalonitrile,
or derivatives thereof, with a metal donor, a nitrogen donor (such as urea or
the phthalonitrile
itself), and an optional catalyst, preferably in an organic solvent.
[0085] Quinacridone pigments, as used herein, include unsubstituted or
substituted
quinacridones (for example, with one or more alkyl, alkoxy, halogens such as
chlorine, or other
substituents typical of quinacridone pigments), and are suitable for the
practice of the present
invention. The quinacridone pigments may be prepared by any of several methods
known in the
art but are preferably prepared by thermally ring-closing various 2,5-
dianilinoterephthalic acid
precursors in the presence of polyphosphoric acid.
[0086] Isoindoline pigments, which can optionally be substituted symmetrically
or
unsymmetrically, are also suitable for the practice of the present invention
can be prepared by
methods known in the art. A suitable isoindoline pigment, Pigment Yellow 139,
is a symmetrical
adduct of iminoisoindoline and barbituric acid precursors. Dioxazine pigments
(that is,
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triphenedioxazines) are also suitable organic pigments and can be prepared by
methods known in
the art.
[0087] Mixtures of any of the previously described inorganic particles and/or
organic
particles can also be used.
[0088] As mentioned, the thermoset powder coating compositions used in certain
embodiments of the methods of the present invention comprise polymer-enclosed
color-imparting
nanoparticles. In certain embodiments, the nanoparticles are formed in situ
during formation of
an aqueous dispersion of polymer-enclosed particles, as described in more
detail below. In other
embodiments, however, the nanoparticles are formed prior to their
incorporation into such an
aqueous dispersion. In these embodiments, the nanoparticles can be formed by
any of a number
of various methods known in the art. For example, the nanoparticles can be
prepared by
pulverizing and classifying the dry particulate material. For example, bulk
particles such as any of
the inorganic or organic particles discussed above, can be milled with milling
media having a
particle size of less than 0.5 millimeters (mm), or less than 0.3 mm, or less
than 0.1 mm. The
particles typically are milled to nanoparticle sizes in a high energy mill in
one or more solvents
(either water, organic solvent, or a mixture of the two), optionally in the
presence of a polymeric
grind vehicle. If necessary, a dispersant can be included, for example, (if in
organic solvent)
SOLSPERSE 32000 or 32500 dispersant available from Lubrizol Corporation, or
(if in water)
SOLSPERSE 27000 dispersant, also available from Lubrizol Corporation. Other
suitable
methods for producing the nanoparticles include crystallization,
precipitation, gas phase
condensation, and chemical attrition (i.e., partial dissolution).
[0089] In certain embodiments, the polymer-enclosed color-imparting
nanoparticles are
formed from an aqueous dispersion of polymer-enclosed color-imparting
nanoparticles. As used
herein, the term "dispersion" refers to a two-phase system in which one phase
includes finely
divided particles distributed throughout a second phase, which is a continuous
phase. The
dispersions often are oil-in-water emulsions, wherein an aqueous medium
provides the continuous
phase of the dispersion in which the polymer-enclosed particles are suspended
as the organic
phase.
[0090] As used herein, the term "aqueous", "aqueous phase", "aqueous medium,"
and the
like, refers to a medium that either consists exclusively of water or
comprises predominantly
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water in combination with another material, such as, for example, an inert
organic solvent. In
certain embodiments, the amount of organic solvent present in the aqueous
dispersions is less than
20 weight percent, such as less than 10 weight percent, or, in some cases,
less than 5 weight
percent, or, in yet other cases, less than 2 weight percent, with the weight
percents being based on
the total weight of the dispersion. Non-limiting examples of suitable organic
solvents are
propylene glycol monobutyl ether, ethylene glycol monohexyl ether, ethylene
glycol monobutyl
ether, n-butanol, benzyl alcohol, and mineral spirits.
[0091] The polymer-enclosed color-imparting nanoparticles used in the present
invention
may comprise, for example, a polymer selected from acrylic polymers,
polyurethane polymers,
polyester polymers, polyether polymers, silicon-based polymers, co-polymers
thereof, and
mixtures thereof. Such polymers can be produced by any suitable method known
to those skilled
in the art to which the present invention pertains. Suitable polymer include
those disclosed in
U.S. patent application Ser. No. 10/876,031 at [0061] to [0076], the cited
portion of which being
incorporated by reference herein, and U.S. Patent Application Publication No.
2005/0287348 Al
at [0042] to [0044], the cited portion of which being incorporation by
reference herein.
[0092] In certain embodiments, such aqueous dispersions comprise color-
imparting
nanoparticles enclosed by a friable polymer. As used herein, the term "friable
polymer" refers to a
polymer that is easily pulverized at ambient conditions. That is, upon removal
of liquid materials
from the dispersion, the resulting solid material does not coalesce and is
easily broken into small
fragments or pieces, such as would be suitable as a dry feed material to an
extruder to produce a
powder coating composition. A film-forming polymer, on the other hand, would,
upon removal
of liquid materials from the dispersion, form a self-supporting continuous
film on at least a
horizontal surface of a substrate. As used herein, the term "ambient
conditions" refers to
surrounding conditions, which is often around one atmosphere of pressure, 50%
relative humidity,
and 25 C.
[0093] In certain embodiments, the friable polymer comprises the reaction
product of (i) a
polymerizable polyester polyurethane, and (ii) an ethylenically unsaturated
monomer. As used
herein, the term "polymerizable polyester polyurethane" refers to a polymer
that includes a
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R1 -C-O-R2
O
plurality of ester units, , and a plurality of urethane units
H
R3 N-C-O- R 2
0
has functional groups that are capable of being polymerized to form
a larger polymer, and wherein R' is an alkyl, cycloalkyl or oxyalkyl moiety,
R2 is an alkyl or
cycloalkyl moiety, and R3 is alkyl, cycloalkyl, arakyl, or aromatic moiety. In
certain embodiments,
the polymerizable polyester polyurethane comprises a polyester polyurethane
having terminal
ethylenic unsaturation. As used herein, the phrase "terminal ethylenic
unsaturation" means that at
least some of the terminal ends of the polyester polyurethane contain a
functional group
containing ethylenic unsaturation. Such polyester polyurethanes may also
include, but need not
necessarily include, internal ethylenic unsaturation. As a result, in certain
embodiments, the
aqueous dispersion comprises a polymerizable polyester polyurethane having
terminal ethylenic
unsaturation which is prepared from reactants comprising (a) a polyisocyanate,
(b) a polyester
polyol, and (c) a material comprising an ethylenically unsaturated group and
an active hydrogen
group. In certain embodiments, the polymerizable polyester polyurethane is
formed from
reactants further comprising (d) a polyamine, and/or (e) a material comprising
an acid functional
group or anhydride and a functional group reactive with isocyanate or hydroxyl
groups. As used
herein, the term "active-hydrogen group" refers to functional groups that are
reactive with
isocyanates as determined by the Zerewitnoff test as described in the JOURNAL
OF THE
AMERICAN CHEMICAL SOCIETY, Vol. 49, page 3181 (1927).
[0094] Polyisocyanates suitable for use in preparing the polymerizable
polyester
polyurethane include aliphatical, cycloaliphatical, araliphatical, and/or
aromatic isocyanates, and
mixtures thereof.
[0095] Examples of useful aliphatic and cycloaliphatic polyisocyanates include
4,4-
methylenebisdicyclohexyl diisocyanate (hydrogenated MDI), hexamethylene
diisocyanate (HDI),
isophorone diisocyanate (IPDI), methylenebis(cyclohexyl isocyanate), trimethyl
hexamethylene
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diisocyanate (TMDI), meta-tetramethylxylylene diisocyanate (TMXDI), and
cyclohexylene
diisocyanate (hydrogenated XDI). Other aliphatic polyisocyanates include
isocyanurates of IPDI
and HDI.
[0096] Examples of suitable aromatic polyisocyanates include tolylene
diisocyanate (TDI)
(i.e., 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate or a mixture
thereof), diphenylmethane-
4,4-diisocyanate (MDI), naphthalene- 1,5-diisocyanate (NDI), 3,3-dimethyl-4,4-
biphenylene
diisocyanate (TODI), crude TDI (i.e., a mixture of TDI and an oligomer
thereof),
polymethylenepolyphenyl polyisocyanate, crude MDI (i.e., a mixture of MDI and
an oligomer
thereof), xylylene diisocyanate (XDI), and phenylene diisocyanate.
[0097] Polyisocyanate derivatives prepared from hexamethylene diisocyanate, 1-
isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane ("IPDI"), including
isocyanurates
thereof, and/or 4,4'-bis(isocyanatocyclohexyl)methane are suitable.
[0098] In certain embodiments, the amount of polyisocyanate used to prepare
the
polymerizable polyester polyurethane ranges from 20 to 70 percent by weight,
such as 30 to 60
percent by weight or, in some cases, 40 to 50 percent by weight, with the
weight percents being
based on the total weight of resin solids used to prepare the polymerizable
polyester polyurethane.
[0099] Polyester polyols suitable for use in preparing the polymerizable
polyester
polyurethane may be prepared by any suitable method, e.g., using saturated
dicarboxylic acids or
anhydrides thereof (or combination of acids and anhydrides) and polyhydric
alcohols, or by ring
opening of caprolactones, e.g., epsilon caprolactone. Such polyester polyols
are commercially
available in various molecular weights. Aliphatic dicarboxylic acids suitable
for preparing
polyesters include those containing from 4 to 14, such as 6 to 10, carbon
atoms inclusive.
Examples of such dicarboxylic acids include: succinic acid, glutaric acid,
adipic acid, pimelic acid,
suberic acid, azelaic aid, and sebacic acid. Corresponding anhydrides can also
be used. Typically,
adipic and azelaic acids are used.
[00100] Polyhydric alcohols used in the preparation of polyester polyols
suitable for
use in preparing the polymerizable polyester polyurethane include, without
limitation, aliphatic
alcohols containing at least 2 hydroxy groups, e.g., straight chain glycols
containing from 2 to 15,
such as 4 to 8, carbon atoms inclusive. In certain embodiments, the glycols
contain hydroxyl
groups in the terminal positions. Non-limiting examples of such polyhydric
alcohols include
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WO 2010/065390 PCT/US2009/065654
ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol,
1,3-propane diol, 1,3-
butane diol, 1,4-butane diol, 1,5-pentane diol, 2,2-dimethylpropane diol, 1,5-
hexane diol, 1,7-
heptane diol, 1,8-octane diol, 1,10-decane diol, and mixtures of such
polyhydric alcohols.
[00101] In certain embodiments, the polyester polyol is prepared by reacting a
dicarboxylic acid (or anhydride thereof) with a polyhydric alcohol in the
presence of an
esterification catalyst, such as an organo tin catalyst. The amount of acid
and alcohol used will
vary and depend on the molecular weight polyester desired. Hydroxy terminated
polyesters are
obtained by utilizing an excess of the alcohol, thereby to obtain linear
chains containing a
preponderance of terminal hydroxyl groups. Examples of polyesters include:
poly(1,4-butylene
adipate), poly(1,4-butylene succinate), poly(1,4-butylene glutarate), poly(1,4-
butylene pimelate),
poly(1,4-butylene suberate), poly(1,4-butylene azelate), poly(1,4butylene
sebacate), and
poly(epsilon caprolactone). In certain embodiments, the polyester polyol
utilized in preparing the
friable, polymerizable polyester polyurethane has a weight average molecular
weight from 500 to
3000, such as 500 to 2500, or, in some cases, 900 to about 1300.
[00102] In certain embodiments, the amount of polyester polyol used to prepare
the
polymerizable polyester polyurethane included in certain embodiments of the
present invention
ranges from 10 to 60 percent by weight, such as 20 to 50 percent by weight or,
in some cases, 30
to 40 percent by weight, with the weight percents being based on the total
weight of resin solids
used to prepare the polymerizable polyester polyurethane.
[00103] As indicated, the polymerizable polyester polyurethane present in
certain
embodiments of the present invention is formed from a material comprising an
ethylenically
unsaturated group and an active hydrogen group. Suitable ethylenically
unsaturated groups
include, for example, acrylates, methacrylates, allyl carbamates, and allyl
carbonates. The acrylate
CH2-C(R,) -C(0)0-
and methacrylate functional groups may be represented by the formula,
wherein Rl is hydrogen or methyl. The allyl carbamates and carbonates may be
represented by the
CH2-CH-CH2-NH-C(O)O- CH2=CH-CH2 0-(0)0-
formulae, , and , respectively.
[00104] In certain embodiments, the material comprising an ethylenically
unsaturated group and an active hydrogen group utilized in preparing the
polymerizable polyester
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polyurethane comprises a hydroxyalkyl(meth)acrylate. Suitable
hydroxyalkyl(meth)acrylates
include those having from 1 to 18 carbon atoms in the alkyl radical, the alkyl
radical being
substituted or unsubstituted. Specific non-limiting examples of such materials
include 2-
hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, 2-
hydroxybutyl(meth)acrylate,
hexane-1,6-diol mono(meth)acrylate, 4-hydroxybutyl(meth)acrylate, and mixtures
thereof. As
used herein, the term "(meth)acrylate" is meant to include both acrylates and
methacrylates.
[00105] In certain embodiments, the amount of the material comprising an
ethylenically unsaturated group and an active hydrogen group used to prepare
the polymerizable
polyester polyurethane ranges from 1 to 12 percent by weight, such as 2 to 8
percent by weight
or, in some cases, 4 to 6 percent by weight, with the weight percents being
based on the total
weight of resin solids used to prepare the polymerizable polyester
polyurethane.
[00106] As previously indicated, in certain embodiments, the polymerizable
polyester polyurethane is formed from a polyamine. Useful polyamines include,
but are not
limited to, primary or secondary diamines or polyamines in which the groups
attached to the
nitrogen atoms can be saturated or unsaturated, aliphatic, alicyclic,
aromatic, aromatic-
substituted-aliphatic, aliphatic-substituted-aromatic, and heterocyclic.
Exemplary suitable
aliphatic and alicyclic diamines include 1,2-ethylene diamine, 1,2-porphylene
diamine, 1,8-octane
diamine, isophorone diamine, propane-2,2-cyclohexyl amine, and the like.
Exemplary suitable
aromatic diamines include phenylene diamines and the toluene diamines, for
example, o-phenylene
diamine and p-tolylene diamine. These and other suitable polyamines are
described in detail in
U.S. Patent No. 4,046,729 at column 6, line 61 to column 7, line 26, the cited
portion of which
being incorporated herein by reference.
[00107] In certain embodiments, the amount of polyamine used to prepare the
polymerizable polyester polyurethane ranges from 0.5 to 5 percent by weight,
such as 1 to 4
percent by weight or, in some cases, 2 to 3 percent by weight, with the weight
percents being
based on the total weight of resin solids used to prepare the polymerizable
polyester polyurethane.
[00108] As previously indicated, in certain embodiments, the polymerizable
polyester polyurethane is formed from a material comprising an acid functional
group or
anhydride and a functional group reactive with the isocyanate or hydroxyl
groups of other
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components from which the polyurethane material is formed. Useful acid
functional materials
X-Y-Z
include compounds having the structure:
wherein X is OH, SH, NH2, or NHR, and R includes alkyl, aryl, cycloalkyl,
substituted alkyl,
substituted aryl, and substituted cycloalkyl groups, and mixtures thereof; Y
includes alkyl, aryl,
cycloalkyl, substituted alkyl, substituted aryl, and substituted cycloalkyl
groups, and mixtures
thereof; and Z includes OSO3H, COOH, OP03H2, SO2OH, POOH, and P03H2, and
mixtures
thereof.
[00109] Examples of suitable acid functional materials include hydroxypivalic
acid,
3-hydroxy butyric acid, D,L-tropic acid, D,L hydroxy malonic acid, D,L-malic
acid, citric acid,
thioglycolic acid, glycolic acid, amino acid, 12-hydroxy stearic acid,
dimethylol propionic acid,
mercapto propionic acid, mercapto butyric acid, mercapto-succinic acid, and
mixtures thereof.
[00110] Useful anhydrides include aliphatic, cycloaliphatic, olefinic,
cycloolefinic
and aromatic anhydrides. Substituted aliphatic and aromatic anhydrides also
are useful provided
the substituents do not adversely affect the reactivity of the anhydride or
the properties of the
resultant polyurethane. Examples of substituents include chloro, alkyl, and
alkoxy. Examples of
anhydrides include succinic anhydride, methylsuccinic anhydride, dodecenyl
succinic anhydride,
octadecenylsuccinic anhydride, phthalic anhydride, tetrahydrophthalic
anhydride,
methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, alkyl
hexahydrophthalic
anhydrides such as methylhexahydrophthalic anhydride, tetrachlorophthalic
anhydride,
endomethylene tetrahydrophthalic anhydride, trimellitic anhydride, chlorendic
anhydride, itaconic
anhydride, citraconic anhydride, maleic anhydride, and mixtures thereof.
[00111] In certain embodiments, the acid functional material or anhydride
provides
the polymerizable polyester polyurethane with anionic ionizable groups which
can be ionized for
solubilizing the polymer in water. As a result, in certain embodiments, the
polymerizable polyester
polyurethane is water-dispersible. As used herein, the term "water-
dispersible" means that a
material may be dispersed in water without the aid or use of a surfactant. As
used herein, the term
"ionizable" means a group capable of becoming ionic, i.e., capable of
dissociating into ions or
becoming electrically charged. An acid may be neutralized with base to from a
carboxylate salt
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group. Examples of anionic groups include
OS03 , -COO , -OP03-, -S020, -POO , and P03=-
[00112] In certain embodiments, the amount of the material comprising an acid
functional group or anhydride and a functional group reactive with isocyanate
or hydroxyl groups
used to prepare the polymerizable polyester polyurethane ranges from 5 to 20
percent by weight,
such as 7 to 15 percent by weight or, in some cases, 8 to 12 percent by
weight, with the weight
percents being based on the total weight of resin solids used to prepare the
polymerizable
polyester polyurethane.
[00113] As indicated, in certain embodiments, the acid groups are neutralized
with
a base. Neutralization can range from 0.6 to 1.1, such as 0.4 to 0.9, or, in
some cases, 0.8 to 1.0,
of the total theoretical neutralization equivalent. Suitable neutralizing
agents include inorganic
and organic bases such as sodium hydroxide, potassium hydroxide, ammonia,
amines, alcohol
amines having at least one primary, secondary, or tertiary amino group and at
least one hydroxyl
group. Suitable amines include alkanolamines, such as monoethanolamine,
diethanolamine,
dimethylaminoethanol, diisopropanolamine, and the like.
[00114] The polymerizable polyester polyurethane present in certain
embodiments
of the present invention may be formed by combining the above-identified
components in any
suitable arrangement. For example, the polymerizable polyester polyurethane
may be prepared by
solution polymerization techniques understood by those skilled in the art to
which the present
invention pertains.
[00115] As should be apparent from the foregoing description, the
polymerizable
polyester polyurethane can be nonionic, anionic, or cationic. In certain
embodiments, the
polymerizable polyester polyurethane will have a weight average molecular
weight of less than
150,000 grams per mole, such as from 10,000 to 100,000 grams per mole, or, in
some cases, from
40,000 to 80,000 grams per mole. The molecular weight of the polyurethane and
any other
polymeric materials described herein is determined by gel permeation
chromatography using a
polystyrene standard.
[00116] As previously indicated, in certain embodiments of the present
invention, a
friable polymer is present that comprises the reaction product of (i) a
polymerizable polyester
polyurethane, such as that previously described, and (ii) an ethylenically
unsaturated monomer.
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Suitable ethylenically unsaturated monomers include any of the polymerizable
ethylenically,
unsaturated monomers, including vinyl monomers known in the art. Non-limiting
examples of
useful ethylenically unsaturated carboxylic acid functional group-containing
monomers include
(meth)acrylic acid, beta-carboxyethyl acrylate, acryloxypropionic acid,
crotonic acid, fumaric acid,
monoalkyl esters of fumaric acid, maleic acid, monoalkyl esters of maleic
acid, itaconic acid,
monoalkyl esters of itaconic acid and mixtures thereof. As used herein,
"(meth)acrylic" and terms
derived therefrom are intended to include both acrylic and methacrylic.
[00117] Non-limiting examples of other useful ethylenically unsaturated
monomers
free of carboxylic acid functional groups include alkyl esters of
(meth)acrylic acids, for example,
ethyl(meth)acrylate, methyl(meth)acrylate, butyl(meth)acrylate, 2-
ethylhexyl(meth)acrylate, 2-
hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, hydroxy
butyl(meth)acrylate,
isobornyl(meth)acrylate, lauryl(meth)acrylate, and ethylene glycol
di(meth)acrylate; vinyl
aromatics such as styrene and vinyl toluene; (meth)acrylamides such as N-
butoxymethyl
acrylamide; acrylonitriles; dialkyl esters of maleic and fumaric acids; vinyl
and vinylidene halides;
vinyl acetate; vinyl ethers; allyl ethers; allyl alcohols; derivatives thereof
and mixtures thereof.
[00118] The ethylenically unsaturated monomers also can include ethylenically
unsaturated, beta-hydroxy ester functional monomers, such as those derived
from the reaction of
an ethylenically unsaturated acid functional monomer, such as a monocarboxylic
acid, for
example, acrylic acid, and an epoxy compound which does not participate in the
free radical
initiated polymerization with the unsaturated acid monomer. Examples of such
epoxy compounds
are glycidyl ethers and esters. Suitable glycidyl ethers include glycidyl
ethers of alcohols and
phenols such as butyl glycidyl ether, octyl glycidyl ether, phenyl glycidyl
ether, and the like.
[00119] In certain embodiments, the polymerizable polyester polyurethane and
the
ethylenically unsaturated monomer are present in the aqueous dispersion in a
weight ratio of 95:5
to 30:70, such as 90:10 to 40:60, or, in some cases, from 80:20 to 60:40.
[00120] The aqueous dispersions described herein can be prepared by any of a
variety of methods. For example, in certain embodiments, the aqueous
dispersion is prepared by a
method comprising (A) providing a mixture, in an aqueous medium, of (i) color-
imparting
nanoparticles, (ii) one or more polymerizable, ethylenically unsaturated
monomers; and/or (iii) a
mixture of one or more polymerizable unsaturated monomers with one or more
polymers; and/or
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(iv) one or more polymers, and then subjecting the mixture to high stress
shear conditions in the
presence of an aqueous medium. Such methods are described in detail in U.S.
patent application
Ser. No. 10/876,031 at [0054] to [0090], the cited portion of which being
incorporated by
reference herein, and U.S. Patent Application Publication No. 2005/0287348 Al
at [0036] to
[0050], the cited portion of which being incorporation by reference herein.
[00121] In certain embodiments, however, the aqueous dispersions are made by a
method comprising (1) providing a mixture, in an aqueous medium, of (i) color-
imparting
particles, (ii) a polymerizable ethylenically unsaturated monomer, and (iii) a
water-dispersible
polymerizable dispersant, and (2) polymerizing the ethylenically unsaturated
monomer and
polymerizable dispersant to form polymer-enclosed color-imparting
nanoparticles comprising a
water-dispersible polymer. In these embodiments, the polymerizable dispersant
may comprise any
polymerizable material that is water-dispersible and which, upon
polymerization with the
ethylenically unsaturated monomer, produces polymer-enclosed color-imparting
nanoparticles
comprising a water-dispersible polymer, in some cases, a water-dispersible,
friable polymer. In
certain embodiments, the polymerizable dispersant comprises the previously
described water-
dispersible, polymerizable polyester polyurethane having terminal ethylenic
unsaturation.
[00122] In these embodiments, the water-dispersible polymerizable dispersant
is
capable of dispersing itself and other materials, including the ethylenically
unsaturated monomers,
in the aqueous medium without the need for surfactants and/or high shear
conditions. As a result,
the foregoing method for making an aqueous dispersion of polymer-enclosed
color-imparting
nanoparticles is particularly suitable in situations where use of the high
stress shear conditions
described in U.S. patent application Ser. No. 10/876,031, at [0081] to [0084]
and U.S. Patent
Application Publication No. 2005/0287348 Al at [0046] is not desired or
feasible. Therefore, in
certain embodiments, the aqueous dispersion of polymer-enclosed color-
imparting nanoparticles is
prepared by a method that does not include the step of subjecting the mixture
of color-imparting
nanoparticles, polymerizable ethylenically unsaturated monomer, and water-
dispersible
polymerizable dispersant to high stress shear conditions.
[00123] In addition, the foregoing method enables the formation of
nanoparticles in
situ, rather than requiring their formation prior to the preparation of the
aqueous dispersion. In
these methods, particles having a primary particle size of 1 micron or more,
after being mixed
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with the ethylenically unsaturated monomer and the water-dispersible
polymerizable dispersant in
the aqueous medium, may be formed into color-imparting nanoparticles (i.e.,
the nanoparticles are
formed in situ). In certain embodiments, the color-imparting nanoparticles are
formed by
subjecting the aqueous medium to pulverizing conditions. For example, the
particles can be
milled with milling media having a particle size of less than 0.5 millimeters,
or less than 0.3
millimeters, or, in some cases, less than 0.1 millimeters. In these
embodiments, the color-
imparting particles can be milled to nanoparticle size in a high energy mill
in the presence of the
aqueous medium, the polymerizable ethylenically unsaturated monomer, and the
water-dispersible
polymerizable dispersant. If desired, another dispersant can be used, such as
SOLSPERSE 27000
dispersant, available from Avecia, Inc.
[00124] As indicated, the foregoing methods for making aqueous dispersions of
polymer-enclosed color-imparting nanoparticles include the step of
polymerizing the ethylenically
unsaturated monomer and polymerizable dispersant to form polymer-enclosed
color-imparting
nanoparticles comprising a water-dispersible polymer. In certain embodiments,
at least a portion
of the polymerization occurs during formation of nanoparticles, if applicable.
Also, a free radical
initiator may be used. Both water and oil soluble initiators can be used.
[00125] Non-limiting examples of suitable water-soluble initiators include
ammonium peroxydisulfate, potassium peroxydisulfate, and hydrogen peroxide.
Non-limiting
examples of oil soluble initiators include t-butyl hydroperoxide, dilauryl
peroxide and 2,2'-
azobis(isobutyronitrile). In many cases, the reaction is carried out at a
temperature ranging from
20 C to 80 C. The polymerization can be carried out in either a batch or a
continuous process.
The length of time necessary to carry out the polymerization can range from,
for example, 10
minutes to 6 hours, provided that the time is sufficient to form a polymer in
situ from the one or
more ethylenically unsaturated monomers.
[00126] Once the polymerization process is complete, the resultant product is
a
stable dispersion of polymer-enclosed color-imparting nanoparticles in an
aqueous medium which
can contain some organic solvent. Some or all of the organic solvent can be
removed via reduced
pressure distillation at a temperature, for example, of less than 40 C. As
used herein, the term
"stable dispersion" or "stably dispersed" means that the polymer-enclosed
color-imparting
nanoparticles neither settle nor coagulate nor flocculate from the aqueous
medium upon standing.
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[00127] In certain embodiments, the polymer-enclosed nanoparticles are present
in
the aqueous dispersions in an amount of at least 10 weight percent, or in an
amount of 10 to 80
weight percent, or in an amount of 25 to 50 weight percent, or in an amount of
25 to 40 weight
percent, with weight percents being based on weight of total solids present in
the dispersion.
[00128] In certain embodiments, the dispersed polymer-enclosed nanoparticles
have
a maximum haze of 10%, or, in some cases, a maximum haze of 5%, or, in yet
other cases, a
maximum haze of 1%, or, in other embodiments, a maximum haze of 0.5%. As used
herein,
"haze" is determined by ASTM D1003.
[00129] The haze values for the polymer-enclosed nanoparticles described
herein
are determined by first having the nanoparticles, dispersed in a liquid (such
as water, organic
solvent, and/or a dispersant, as described herein) and then measuring these
dispersions diluted in a
solvent, for example, butyl acetate, using a Byk-Gardner TCS (The Color
Sphere) instrument
having a 500 micron cell path length. Because the % haze of a liquid sample is
concentration
dependent, the % haze as used herein is reported at a transmittance of about
15% to about 20% at
the wavelength of maximum absorbance. An acceptable haze may be achieved for
relatively large
particles when the difference in refractive index between the particles and
the surrounding medium
is low. Conversely, for smaller particles, greater refractive index
differences between the particle
and the surrounding medium may provide an acceptable haze.
[00130] In certain embodiments, particularly wherein the polymer-enclosed
nanoparticles comprise a friable polymer, the aqueous dispersion of polymer-
enclosed color-
imparting nanoparticles may then be further processed by (1) removing water
from the aqueous
dispersion to form a solid material comprising the polymer-enclosed color-
imparting
nanoparticles, and (2) fragmenting the solid material. In these embodiments,
the water can be
removed from the aqueous dispersion by any suitable drying method, such as
through the use of a
drum dryer, a roller dryer, a spray dryer, or the like. Moreover, the solid
material can be
fragmented by any suitable technique, such as through the use of a hammer mill
or the like.
Following fragmentation, the resultant granules may be further processed, such
as by being
screened in a classifier, before packaging.
[00131] In the thermoset powder coating compositions of the methods of the
present invention, the polymer-enclosed color-imparting nanoparticles are
incorporated into a
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powder coating composition. In certain embodiments, such powder coating
compositions
comprise from 0.1 to 50 percent by weight, such as 1 to 20 percent by weight,
of polymer-
enclosed nanoparticles, based on the total weight of the powder coating
composition.
[00132] As mentioned, in addition to the colorant, the thermoset powder
coating
composition comprises a particulate film-forming resin. Suitable film-forming
resins include, for
example, an epoxy resin, such as an epoxy group-containing acrylic polymer or
a polyglycidyl
ether of a polyhydric alcohol and a suitable curing agent for the epoxy resin,
such as a
polyfunctional carboxylic acid group-containing material or a dicyanamide.
Examples of curable
particulate resinous materials are described in U.S. Patent No. RE 32,261 and
U.S. Patent No.
4,804,581, incorporated by reference herein. Examples of other suitable
particulate film-forming
resins are carboxylic acid functional resins, such as carboxylic acid
functional polyesters and
acrylic polymers and suitable curing agents for such materials, such as
triglycidyl isocyanurate and
beta-hydroxyalkylamide curing agents as described, for example, in U.S. Patent
No. 4,801,680
and U.S. Patent No. 4,988,767, incorporated by reference herein.
[00133] In certain embodiments, such powder coating compositions comprise from
50 to 90 percent by weight, such as 60 to 80 percent by weight, of the
particulate film-forming
resin, based on the total weight of the powder coating composition.
[00134] As mentioned, the thermoset powder coating composition comprises a
curing agent for the film-forming resin. Suitable curing agents include,
without limitation,
blocked isocyanates, uretidiones, polyepoxides, polyacids, polyols,
anhydrides, polyamines,
aminoplasts and phenoplasts. As previously indicated, the appropriate curing
agent can be
selected by one skilled in the art depending on the polymer used. For example,
blocked
isocyanates are suitable curing agents for hydroxy and primary and/or
secondary amino group
containing materials. Examples of blocked isocyanates are those described in
U.S. Pat. No.
4,988,793, at col. 3, lines 1-36, the cited portion of which being
incorporated by reference herein.
Polyepoxides suitable for use as curing agents for COOH functional group-
containing materials
are described in U.S. Pat. No. 4,681,811 at col. 5, lines 33-58, the cited
portion of which being
incorporated by reference herein. Polyacids as curing agents for epoxy
functional group-
containing materials are described in U.S. Pat. No. 4,681,811 at col. 6, line
45 to col. 9, line 54,
the cited portion of which being incorporated by reference herein. Polyols,
materials having an
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average of 2 or more hydroxyl groups per molecule, can be used as curing
agents for NCO
functional group-containing materials and anhydrides, and are well known in
the art. Polyols for
use in the present invention are typically selected such that the resultant
material has a Tg greater
than about 30 C., in some cases greater than 50 C. Anhydrides as curing agents
for epoxy
functional group-containing materials include, for example, trimellitic
anhydride, benzophenone
tetracarboxylic dianhydride, pyrrolmellitic dianhydride, tetrahydrophthalic
anhydride, and the like
as described in U.S. Pat. No. 5,472,649 at col. 4, lines 49-52, the cited
portion of which being
incorporated by reference herein. Aminoplasts as curing agents for hydroxy,
COOH, and
carbamate functional group-containing materials are well known in the art.
Examples of such
curing agents include aldehyde condensates of glycol urea, which give high
melting crystalline
products useful in powder coatings. While the aldehyde used is typically
formaldehyde, other
aldehydes such as acid aldehyde, crotonaldehyde, and benzaldehyde can be used.
In certain
embodiments, the curing agent is present in an amount of 5 to 50 weight
percent, such as from 5
to 30 weight percent, based on the total weight of the powder coating
composition.
[00135] These thermoset powder coating compositions can optionally include
other
materials such as other pigments, fillers, light stabilizers, flow modifiers,
anti-popping agents, and
anti-oxidants. Suitable pigments include, for example, titanium dioxide,
ultramarine blue,
phthalocyanine blue, phthalocyanine green, carbon black, graphite fibrils,
black iron oxide,
chromium green oxide, ferride yellow and quindo red. In certain embodiments,
these other
pigments are not nanoparticles.
[00136] Anti-popping agents can be added to the composition to allow any
volatile
material to escape from the film during baking. Benzoin is a commonly
preferred anti-popping
agent and when used is generally present in amounts of from 0.5 to 3.0 percent
by weight based
on total weight of the powder coating composition.
[00137] Such powder coating compositions may also include fumed silica and/or
fumed aluminum oxide or the like to reduce caking of the powder during
storage. An example of
a fumed silica is sold by Cabot Corporation under the trademark CAB-O-SIL
silica. An example
of fumed aluminum oxide is sold by Evonik Corporation under the trademark
AEROXIDE, for
example, AEROXIDE Aluminum Oxide C. The fumed silica and/or fumed aluminum
oxide may
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be present in amounts ranging from 0.1 to 1 percent by weight based on total
weight of the
powder coating formulation.
[00138] The polymer-enclosed color-imparting nanoparticles may be incorporated
into the powder coating composition by any of a variety of methods. For
example, in
embodiments wherein the polymer-enclosed nanoparticles comprise a friable
polymer, the
polymer-enclosed color-imparting nanoparticles and other coating components
are all embodied in
a dried, particulate form, blended together, and then melt blended in an
extruder. In other
embodiments, however, such as those cases wherein an aqueous dispersion of
polymer-enclosed
nanoparticles is used that does not comprise a friable polymer, the polymer-
enclosed color-
imparting nanoparticles are incorporated into the powder coating composition
by a method
comprising (1) introducing to an extruder powder coating composition
components comprising:
(a) an aqueous dispersion of polymer-enclosed color-imparting nanoparticles,
and (b) dry
materials; (2) blending (a) and (b) in the extruder; (3) devolatilizing the
blend to form an
extrudate; (4) cooling the extrudate, and (5) milling the extrudate to a
desired particle size. As
used herein, the term "devolatilizing" means to remove volatile materials,
including water and
organic solvents. In certain embodiments, such powder coating compositions are
made by a
method and/or apparatus described in U.S. Patent Application Publication Nos.
2005/0212159A1;
2005/0212171A1; and/or 2005/0213423A1, the relevant disclosures of which being
incorporated
herein by reference.
[00139] In the foregoing methods, the dry materials may include the
particulate
film-forming resin described earlier as well as any other composition
additives. The dry materials
may be first blending in a high shear mixer such as a planetary mixture. In
certain embodiments,
the dry materials and the aqueous dispersion of the present invention are then
blended in an
extruder at a temperature ranging from 80 C to 150 C. The extrudate is then
cooled and
pulverized into a particulate blend. In certain embodiments, the average
particle size of the
extrudate after if has been pulverized into particulate form ranges from 1 to
200 microns, such as
from 10 to 100 microns, such as from 15 to 50 microns.
[00140] As mentioned, each one of the thermoset powder coating compositions
provides a fmished decorative and durable coating when deposited onto a
substrate and cured. As
used herein, the term "finished decorative and durable coating" refers to a
finished coating, i.e.,
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the coating is at a colorant, i.e., pigment, to film-forming resin
concentration that is suitable for a
powder coating composition in its final form as it is applied to a substrate;
the colorant
concentration is not at a concentration higher than what is to be applied to a
substrate; the
finished coating is both decorative, i.e., it provides a desired appearance to
the substrate, and
durable, i.e., it does not significantly chip, peel, mar, or delaminate when
subjected to
environmental conditions, such as humidity and abrasion typically experienced
by a coating, such
as coatings used on automotive and truck components, such as bodies, door
panels, cabs, trailer
bodies; airplane components, such as fuselage and wings; architectural
components; consumer
electronic equipment, such as computers and telephones; as well as other
articles. As a result, the
"finished decorative and durable coatings" of the present invention are
distinct from decorative
coatings formed from the use of dyes or inks that are not durable as well as
from coatings that are
at a higher colorant concentration than what is to be subsequently applied to
a substrate.
[00141] Because each one of the thermoset powder coating compositions provides
a finished decorative and durable coating when deposited onto a substrate and
cured, no further
ingredients are necessary to be combined with the thermoset powder coating
compositions in
order to provide a cured coating layer. In other words, each of the powder
coating compositions
of the methods of the present invention is a complete coating composition
itself and may be
applied as a coating layer without the addition of any other ingredients.
[00142] As would be recognized, because each one of the thermoset powder
coating compositions provides a finished decorative and durable coating as
described above, the
thermoset powder coating composition formed from a mixture of one or more of
the plurality of
thermoset powder coating compositions dispensed according to the methods of
the present
invention also provides a finished decorative and durable coating when
deposited onto a substrate
and cured.
[00143] As mentioned above, in certain embodiments of the methods of the
present
invention, in addition to the containers holding the thermoset powder coating
compositions, there
may also be containers that hold various additives. These additives include
materials other than
thermoset powder coating compositions, and the additives are not necessary to
the formation of a
finished decorative and durable coating when the thermoset powder coating
compositions are
applied to a substrate and cured. The additives may be added to the thermoset
powder coating
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compositions to provide various desired appearance and/or properties to the
coating film, for
example, variations to gloss and/or texture; control of cure rates; UV
durability; coefficient of
friction; weatherability.
[00144] In accordance with certain embodiments of the methods of the present
invention, a controlled amount of a thermoset powder coating composition
comprising a colorant,
a particulate film-forming resin, and a curing agent is metered into the
common receptacle
followed by metering a controlled amount of another thermoset powder coating
composition
comprising a colorant, a particulate film-forming resin, and a curing agent to
form a mixture of
the powder coating composition in the common receptacle. In certain
embodiments, the
particulate film-forming resin present in the first powder coating composition
is the same as, or at
least compatible with, the particulate film-forming resin present in the
second powder coating
composition.
[00145] In certain embodiments of the methods of the present invention, each
one
of the plurality of thermoset powder coating compositions has a different hue.
[00146] In other embodiments, at least two of the plurality of the thermoset
powder
coating compositions have different hues such that when combined to form a
mixture, the mixture
upon direct application to at least a portion of a substrate and cure,
produces a decorative and
durable coating having a homogeneous hue different from the hues of each of
the individual
thermoset powder coating compositions. As used herein, the term "direct
application", and the
like, means that the powder coating composition need not be subject to the
Extrusion Process
prior to application. As used herein, the term "homogeneous hue different from
the hues of each
of the individual themoset powder coating compositions" means that the coating
is recognized by
a person as having a uniform hue that is different from the hues of each of
the individual
thermoset powder coating compositions when viewed with the naked eye at any
distance from the
coating, including distances of one foot or less. Stated differently, the
coating does not have a
"salt and pepper" appearance wherein each of the hues is distinguishable by
visual examination
with the naked eye.
[00147] In yet other embodiments of the methods of the present invention, a
controlled amount of a first thermoset powder coating composition having a
first hue is metered
into a common receptacle and a controlled amount of a second thermoset powder
coating
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composition having a second hue different from the hue of the first thermoset
powder coating
composition is metered into the common receptacle to provide a mixture,
wherein the mixture of
the first powder coating with the second powder coating composition produces a
powder coating
composition that, upon direct application to at least a portion of a substrate
and cure, produces a
decorative and durable coating having a homogeneous hue different from the
first hue and the
second hue from which it is formed. As discussed above, the coating does not
have a "salt and
pepper" appearance of the first and second hues. As would be recognized, one
or more additional
thermoset powder coating compositions may also be added, each having a hue
different from the
hues of the first and second powder coating compositions, to provide a desired
homogeneous hue.
[00148] In certain embodiments, the powder coating compositions provided from
the plurality of thermoset powder coating compositions dispensed according to
the methods of
the present invention comprise a mixture of a first thermoset powder coating
composition having
a first hue and a second thermoset powder coating composition having a second
hue different
from the first hue. As used herein, the term "mixture" refers to a
heterogeneous association of the
first powder coating composition and the second powder coating composition,
wherein the
powder coating compositions are not chemically combined and can be separated
by mechanical
means. The first powder coating composition and the second powder coating
composition may
be dispensed according to the methods of the present invention, as described
above, and
subsequently mixed by any method, such as, for example, dry-blending methods
using high speed
agitators, such as a Henchsel mixer. In the methods of the present invention,
as described herein,
by dispensing thermoset powder coating compositions of a limited number of
colors (fundamental
colors) and by examining, in advance, the relation between the proportions of
these colored
powder coating compositions and the hues of the coatings obtained therefrom, a
powder coating
composition of virtually any desired hue can be produced by appropriately
selecting the colored
powder coating compositions, dispensing them in the proper proportion
according to the present
invention, and mixing them so as to give a desired homogeneous coating hue
without the need to
subject the mixture to the Extrusion Process.
[00149] In those methods of the present invention wherein the plurality of
thermoset powder coating compositions are provided in a kit, upon dispensing
and mixture of the
contents of the first container in the kit with the contents of the second
container in the kit, a
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powder coating composition is formed that, upon direct application to at least
a portion of a
substrate and cure, produces a decorative and durable coating having a
homogeneous hue
different from the first hue and the second hue.
[00150] The present invention is also directed to a method of coating a
substrate
comprising: (a) metering a controlled amount of at least one of a plurality of
thermoset powder
coating compositions from at least one of a plurality of containers to a
common receptacle; and
(b) applying the at least one thermoset powder coating composition from the
common receptacle
to a substrate, wherein at least one of the thermoset powder coating
compositions comprises: (i) a
colorant; (ii) a particulate film-forming resin; and (iii) a curing agent for
the film-forming resin,
and wherein the thermoset powder coating composition from the common
receptacle provides a
finished decorative and durable coating when deposited onto the substrate and
cured.
[00151] In certain embodiments, more than one thermoset powder coating
composition is present in the common receptacle. In these embodiments, the
thermoset powder
coating compositions in the common receptacle are mixed prior to application
to the substrate.
[00152] The thermoset powder coating compositions provided from the plurality
of
thermoset powder coating compositions dispensed according to the methods of
the invention can
be applied to a variety of substrates including metallic substrates, for
example, aluminum and steel
substrates. The powder coating compositions are often applied by spraying, and
in the case of a
metal substrate, by electrostatic spraying, or by the use of a fluidized bed.
The powder coating
compositions can be applied in a single sweep or in several passes to provide
a film having a
thickness after cure of from about 1 to 10 mils (25 to 250 micrometers),
usually about 2 to 4 mils
(50 to 100 micrometers). In many cases, after application of the powder
coating composition, the
coated substrate is heated to a temperature sufficient to cure the coating,
often to a temperature
ranging from 250 F to 500 F. (121.1 C to 260.0 C) for 1 to 60 minutes, such as
300 F to 400 F
(148.9 C to 204.4 C) for 15 to 30 minutes.
[00153] As a result, the present invention is also directed to a substrate at
least
partially coated with a powder coating composition deposited from the
plurality of thermoset
powder coating compositions dispensed according to the methods of the present
invention. In
certain embodiments, the powder coating composition provided from the
plurality of thermoset
powder coating compositions dispensed according to the methods of the present
invention and
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coated onto a substrate is a finished decorative and durable coating having a
homogeneous hue.
The decorative and durable coating is deposited directly from the plurality of
thermoset coating
compositions comprising a mixture of a first thermoset powder coating
composition having a first
hue and a second thermoset powder coating composition having a second hue
different from the
first hue, wherein the first powder coating composition and/or the second
powder coating
composition comprises polymer-enclosed color-imparting nanoparticles and a
particulate film-
forming resin. In the articles of the present invention, the homogeneous hue
is different than the
first hue and the second hue.
[00154] In certain embodiments, the decorative and durable coating deposited
from
the plurality of thermoset coating compositions dispensed according to the
methods of the present
invention is a non-hiding coating. As used herein, the term "non-hiding
coating" refers to a
coating layer deposited upon a substrate wherein the surface beneath the
coating layer is visible to
the naked eye. In certain embodiments of the present invention, the surface
beneath the non-
hiding coating layer is visible when the non-hiding layer is applied at a dry
film thickness of 0.5 to
5.0 mils (12.7 to 127 microns). One way to assess non-hiding is by measurement
of opacity. As
used herein, "opacity" refers to the degree to which a material obscures a
substrate.
[00155] "Percent opacity" refers herein to the ratio of the reflectance of a
dry
coating film over a black substrate of 5% or less reflectance, to the
reflectance of the same
coating film, equivalently applied and dried, over a substrate of 85%
reflectance. The percent
opacity of a dry coating film will depend on the dry film thickness of the
coating and the
concentration of color-imparting nanoparticles. In certain embodiments of the
present invention,
the color-imparting non-hiding coating layer has a percent opacity of no more
than 90 percent,
such as no more than 50 percent, at a dry film thickness of one (1) mil (about
25 microns).
[00156] In certain embodiments, the powder coating compositions provided from
the plurality of thermoset powder coating compositions dispensed according to
the methods of
the present invention are deposited over a reflective surface. In these
embodiments, the coating
deposited over the reflective surface is a non-hiding coating as described
above. As used herein,
the term "reflective surface" refers to a surface comprising a reflective
material having a total
reflectance of at least 30%, such as at least 40%. "Total reflectance" refers
herein to the ratio of
reflected light from an object relative to the incident light that impinges on
the object in the visible
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spectrum integrating over all viewing angles. "Visible spectrum" refers herein
to that portion of
the electromagnetic spectrum between wavelengths 400 and 700 nanometers.
"Viewing angle"
refers herein to the angle between the viewing ray and a normal to the surface
at the point of
incidence. The reflectance values described herein may be determined, for
example, by using a
Minolta Spectrophotometer CM-3600d according to the manufacturer supplied
instructions.
[00157] In certain embodiments, the reflective surface comprises a substrate
material such as, for example, polished aluminum, cold roll steel, chrome-
plated metal, or vacuum
deposited metal on plastic, among others. In other embodiments, the reflective
surface may
comprise a previously coated surface which may, for example, comprise a
reflective coating layer
deposited from a coating composition, such as, for example, a silver metallic
basecoat layer, a
colored metallic basecoat layer, a mica containing basecoat layer, or a white
basecoat layer,
among others.
[00158] Such reflective coating layers may be deposited from a film-forming
composition that may, for example, include any of the film-forming resins
typically used in
protective coating compositions. For example, the film-forming composition of
the reflective
coating may comprise a resinous binder and one or more pigments to act as the
colorant. Useful
resinous binders include, but are not limited to, acrylic polymers,
polyesters, including alkyds and
polyurethanes. The resinous binders for the reflective coating composition
may, for example, be
embodied in a powder coating composition, an organic solvent-based coating
composition or a
water-based coating composition.
[00159] As noted, the reflective coating composition can contain pigments as
colorants. Suitable pigments for the reflective coating composition include,
for example, metallic
pigments, which include aluminum flake, copper or bronze flake and metal oxide
coated mica;
non-metallic color pigments, such as titanium dioxide, iron oxide, chromium
oxide, lead chromate,
and carbon black; as well as organic pigments, such as, for example,
phthalocyanine blue and
phthalocyanine green.
[00160] The reflective coating composition can be applied to a substrate by
any
conventional coating technique such as brushing, spraying, dipping or flowing,
among others.
The usual spray techniques and equipment for air spraying, airless spraying
and electrostatic
spraying in either manual or automatic methods can be used. During application
of the basecoat
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to the substrate, the film thickness of the basecoat formed on the substrate
often ranges from 0.1
to 5 mils (2.5 to 127 micrometers), or 0.1 to 2 mils (2.5 to 50.8
micrometers).
[00161] After forming a film of the reflective coating on the substrate, the
reflective
coating can be cured or alternatively given a drying step in which solvent is
driven out of the
basecoat film by heating or an air drying period before application of
subsequent coating
compositions. Suitable drying conditions will depend on the particular
basecoat composition, and
one the ambient humidity if the composition is water-borne, but often, a
drying time of from 1 to
15 minutes at a temperature of 75 F to 200 F (21 C to 93 C) will be adequate.
[00162] As mentioned above, the reflective surfaces are at least partially
coated
with a non-hiding coating layer deposited from a powder coating composition
provided from a
plurality of thermoset powder coating compositions dispensed according to the
methods of the
present invention. In certain embodiments, a clearcoat layer is deposited over
at least a portion of
the non-hiding coating layer. The clearcoat layer may be deposited from a
composition that
comprises any typical film-forming resin and can be applied over the color-
imparting non-hiding
layer to impart additional depth and/or protective properties to the surface
underneath. The
resinous binders for the clearcoat can be embodied as a powder coating
composition, an organic
solvent-based coating composition, or a water-based coating composition.
Optional ingredients
suitable for inclusion in the clearcoat composition include those which are
well known in the art of
formulating surface coatings, such as those materials described earlier. The
clearcoat composition
can be applied to a substrate by any conventional coating technique such as
brushing, spraying,
dipping or flowing, among others.
[00163] The thermoset powder coating compositions provided from the plurality
of
thermoset powder coating compositions dispensed according to the methods of
the present
invention may be used to form a single decorative and durable coating, for
example, a monocoat,
a base coat in a two-layered system or both; or as one or more layers of a
multi-layered system
including a clear top coating composition, a colorant layer and/or a base
coating composition,
and/or a primer layer, including, for example, an electrodeposition primer
and/or a primer-surfacer
layer.
[00164] The present invention is also directed to substrates at least
partially coated
with a multi-layer composite coating wherein at least one coating layer is
deposited from a
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powder coating composition provided from the plurality of thermoset powder
coating
compositions dispensed according to the methods of the present invention. In
certain
embodiments, for example, the powder coating composition provided from the
methods of the
present invention comprises the basecoat layer in a multi-layer composite
coating comprising a
basecoat and a topcoat. As a result, in these embodiments, after application
and curing of the
powder coating composition provided from the methods of the present invention,
at least one
topcoat layer can be applied to the basecoat layer. The topcoat can, for
example, be deposited
from a powder coating composition, an organic solvent-based coating
composition or a water-
based coating composition, as is well known in the art. The film-forming
composition of the
topcoat can be any of the compositions useful in coatings applications,
including, for example, a
film-forming composition that comprises a resinous binder selected from
acrylic polymers,
polyesters, including alkyds, and polyurethanes. The topcoat composition can
be applied by any
conventional coating technique such as brushing, spraying, dipping or flowing,
but they are most
often applied by spraying. The usual spray techniques and equipment for air
spraying, airless
spray and electrostatic spraying in either manual or automatic methods can be
used.
[00165] In certain embodiments, coatings deposited from a powder coating
composition provided from the plurality of thermoset powder coating
compositions comprising
polymer-enclosed color-imparting nanoparticles having a maximum haze of 10%
dispensed
according to the methods of the present invention exhibit a "richer" color as
compared to similar
powder coating compositions provided from thermoset powder coating
compositions that do not
include a plurality of polymer-enclosed color-imparting nanoparticles having a
maximum haze of
10%, such as those described above. As used herein, the term "color richness"
refers to the L*
value in the CIELAB color system as described in U.S. Pat. No. 5,792,559 at
col. 1, lines 34 to
64, the cited portion of which being incorporated herein by reference, wherein
a lower L* value
corresponds to a higher level of color richness. For purposes of the present
invention, color
measurements at various angles can be made using an X-RITE spectrophotometer,
such as an
MA681 Multi-angle spectrophotometer, commercially available from X-Rite
Instruments, Inc.
[00166] The inventors have discovered that, unlike prior art powder coating
compositions, the powder coating compositions provided from the plurality of
thermoset powder
coating compositions comprising a colorant, a particulate film-forming resin,
and a curing agent
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for the film-forming resin dispensed according to the methods of the present
invention are capable
of producing coatings that exhibit color properties similar to coatings
deposited from liquid
coating compositions. As a result, the powder coating compositions dispensed
according to the
methods of the present invention can be used for color matching of coatings
deposited from liquid
coating compositions. These color-matching methods comprise: (a) determining
the visible color
of the preselected liquid coating by measuring the absorbance or reflectance
of the preselected
liquid coating; (b) determining a recipe and/or formula for a thermoset powder
coating
composition wherein a coating deposited from the thermoset powder coating
composition
matches the visible color of the preselected liquid coating, and wherein the
recipe and/or formula
contains a list of a plurality of thermoset powder coating compositions
comprising polymer-
enclosed color-imparting nanoparticles and particulate film-forming resin; (c)
dispensing the
plurality of thermoset powder coating compositions comprising a colorant, a
particulate film-
forming resin, and a curing agent for the film-forming resin present on the
list according to the
methods of the present invention. In these methods, the absorbance or
reflectance of the
preselected liquid coating is determined using a spectrophotometer (as
described above) and a
curve of the absorbance or reflectance across the range of wavelengths
corresponding to the
visible spectrum is produced. This curve is referred to as the visible
absorbance or reflectance
spectrum. A powder coating composition is produced from the plurality of
thermoset powder
coating compositions dispensed according to the methods of the present
invention such that the
coating deposited from the powder coating composition has a visible absorbance
or reflectance
spectrum closely matching that of the preselected liquid coating.
[00167] The present invention is also directed to a system for dispensing a
plurality
of thermoset powder coating compositions, the system comprising: (a) a
plurality of containers
having at least one thermoset powder coating composition therein; and (b) a
means for metering a
controlled amount of at least one of the thermoset powder coating compositions
from at least one
of the containers to a common receptacle, wherein the thermoset powder coating
compositions
comprise: (i) a colorant; (ii) a particulate film-forming resin; and (iii) a
curing agent for the film-
forming resin, and wherein each one of the thermoset powder coating
compositions provides a
finished decorative and durable coating when deposited onto a substrate and
cured.
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[00168] Whereas particular embodiments of this invention have been described
above for purposes of illustration, it will be evident to those skilled in the
art that numerous
variations of the details of the present invention may be made without
departing from the
invention as defined in the appended claims.
