U.S. patent application number 17/285640 was filed with the patent office on 2021-12-16 for system for electrocoating conductive substrates.
This patent application is currently assigned to PPG Industries Ohio, Inc.. The applicant listed for this patent is PPG Industries Ohio, Inc.. Invention is credited to Judith A. Bethoski, Mark L. Follet, Amy E. Harrison, Tammy L. Hutchinson, Brent A. Schwartz, Irina G. Schwendeman, Dennis J. Siefer.
Application Number | 20210388525 17/285640 |
Document ID | / |
Family ID | 1000005850517 |
Filed Date | 2021-12-16 |
United States Patent
Application |
20210388525 |
Kind Code |
A1 |
Schwartz; Brent A. ; et
al. |
December 16, 2021 |
System for Electrocoating Conductive Substrates
Abstract
The present invention is directed towards an electrocoating
system for electrocoating a substrate (500), the system comprising
a tank (100) configured to hold an electrodepositable coating
composition; at least one pump (200) in fluid communication with
the tank, at least one return conduit (210) connecting the tank
with an inlet of the pump, at least one recirculating pipe (300)
comprising a first end in fluid communication with an outlet of the
pump and a second end having at least one aperture, and the at
least one recirculating pipe comprising at least one external
electrode (400) positioned at least partially outside of the tank.
Also disclosed herein are methods of coating substrates, systems
for coating a substrate, and coated substrates.
Inventors: |
Schwartz; Brent A.;
(Wapakoneta, OH) ; Hutchinson; Tammy L.; (Lima,
OH) ; Siefer; Dennis J.; (Findlay, OH) ;
Bethoski; Judith A.; (Pittsburgh, PA) ; Schwendeman;
Irina G.; (Wexford, PA) ; Follet; Mark L.;
(Allison Park, PA) ; Harrison; Amy E.;
(Monroeville, PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
PPG Industries Ohio, Inc. |
Cleveland |
OH |
US |
|
|
Assignee: |
PPG Industries Ohio, Inc.
Cleveland
OH
|
Family ID: |
1000005850517 |
Appl. No.: |
17/285640 |
Filed: |
October 14, 2019 |
PCT Filed: |
October 14, 2019 |
PCT NO: |
PCT/US2019/056107 |
371 Date: |
April 15, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62745494 |
Oct 15, 2018 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C25D 13/20 20130101;
C25D 21/18 20130101; C25D 13/04 20130101 |
International
Class: |
C25D 21/18 20060101
C25D021/18; C25D 13/20 20060101 C25D013/20; C25D 13/04 20060101
C25D013/04 |
Claims
1. An electrocoating system for electrocoating a substrate, the
system comprising a tank configured to hold an electrodepositable
coating composition; at least one pump in fluid communication with
the tank, at least one return conduit connecting the tank with an
inlet of the pump, at least one recirculating pipe comprising a
first end in fluid communication with an outlet of the pump and a
second end having at least one aperture, and the at least one
recirculating pipe comprising at least one external electrode
positioned at least partially outside of the tank, wherein: the
substrate has a first surface and a second surface; the pump is
configured to receive the electrodepositable coating composition
from the return conduit and deliver the electrodepositable coating
composition into the tank through the recirculating pipe; the
external electrode is configured to provide an electric charge to
the electrodepositable coating composition; and the recirculating
pipe is configured to extend into the interior of the tank and
position the aperture of the second end to deliver at least a
portion of the electrically charged electrodepositable coating
composition to the first surface of the substrate.
2. The electrocoating system of claim 1, wherein the external
electrode comprises at least 50% of the recirculating pipe.
3. The electrocoating system of claim 1, wherein the external
electrode has an internal surface configured to contact the
electrodepositable coating composition, and the electrocoating
system is configured such that a ratio of a total combined surface
area of the external electrode based on the surface area of the
external surface area of the external electrode to a surface area
of the first surface of the substrate is from 1:7 to 1:1.
4. The electrocoating system of claim 1, wherein the external
electrode comprises a section of the recirculating pipe located
outside of the tank.
5. The electrocoating system of claim 1, wherein the second end of
the recirculating pipe comprises at least one nozzle comprising the
aperture.
6. The electrocoating system of claim 1, wherein the second end of
the recirculating pipe is branched and comprises at least two
apertures configured to deliver at least a portion of the
electrodepositable coating composition charged by the external
electrode to different surface sections of the first surface of the
substrate.
7. The electrocoating system of claim 1, wherein the recirculating
pipe comprises a plurality of apertures configured to deliver the
electrodepositable coating composition charged by the external
electrode to different sections of the first surface of the
substrate.
8. The electrocoating system of claim 1, wherein the electrocoating
system comprises a plurality of recirculating pipes configured to
deliver the electrodepositable coating composition charged by the
external electrode to different sections of the first surface of
the substrate.
9. The electrocoating system of claim 8, wherein the plurality of
recirculating pipes is positioned equidistant along a length of the
tank.
10. The electrocoating system of claim 1, further comprising at
least one internal electrode positioned inside the tank.
11. The electrocoating system of claim 10, wherein the
recirculating pipe comprises a plurality of the internal electrodes
positioned along a length of the tank.
12. The electrocoating system of claim 11, wherein the plurality of
internal electrodes is positioned equidistant along the length of
the tank.
13. The electrocoating system of claim 10, wherein the
electrocoating system is configured such that a ratio of a total
combined surface area of the internal electrode to the surface area
of the second surface of the substrate is from 1:7 to 1:1.
14. The electrocoating system of claim 1, further comprising at
least one power source to provide an electrical current to the
electrocoating system, wherein the power source is electrically
coupled to the external electrode and the substrate, wherein the
substrate comprises a counter-electrode to the external
electrode.
15. The electrocoating system of claim 10, further comprising at
least one power source to provide an electrical current to the
electrocoating system, wherein the power source is electrically
coupled to the external electrode, the internal electrode, and the
substrate, wherein the substrate comprises a counter-electrode to
the external electrode and the internal electrode.
16. The electrocoating system of claim 1, wherein the tank, the
return conduit, the pump and the recirculating pipe are directly
coupled to form at least one continuous and uninterrupted loop
configured for constrained flow of the electrodepositable coating
composition through the return conduit, pump and recirculating
pipe.
17. The electrocoating system of claim 1, wherein the tank
comprises a base portion and at least one side wall extending up
from the base portion.
18. The electrocoating system of claim 1, wherein the substrate
comprises an open-polygon cross-sectional shape.
19. The electrocoating system of claim 1, wherein the substrate
comprises a rectangular cross-sectional shape.
20. The electrocoating system of claim 1, wherein the substrate is
a container.
21. The electrocoating system of claim 1, wherein the substrate has
a cross-sectional area of at least 40 m.sup.2.
22. A method for coating a substrate comprising electrophoretically
applying a coating deposited from an electrodepositable coating
composition to at least a portion of the substrate using the
electrocoating system of claim 1.
23. The method of claim 22, wherein the electrodepositable coating
composition comprises a cationic film-forming resin comprising
sulphonium groups.
24. The method of claim 22, wherein the method further comprises
applying a topcoat coating composition to at least a portion of the
substrate coated with the coating deposited from the
electrodepositable coating composition.
25. The method of claim 22, wherein the method further comprises
pretreating the substrate with a pretreatment composition prior to
applying the coating deposited from the electrodepositable coating
composition.
26. The method of claim 22, wherein the method further comprises
priming the substrate with a priming composition prior to applying
the coating deposited from the electrodepositable coating
composition.
27. The method of claim 22, wherein the substrate comprises an
open-polygon cross-sectional shape or a rectangular cross-sectional
shape.
28. The method of claim 22, wherein the substrate is a
container.
29. A substrate coated by the method of claim 22.
30. A system for coating a substrate comprising the electrocoating
system of claim 1, and further comprising at least one of: a
pretreatment system for pretreating the substrate prior to
processing the substrate in the electrocoating system; a priming
system for priming the substrate prior to processing the substrate
in the electrocoating system; and/or a topcoat system for applying
a topcoat coating to the substrate after processing the substrate
in the electrocoating system.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to electrocoating systems for
electrocoating a substrate. The present invention also relates to a
system for coating substrates, methods for coating substrates, and
coated substrates.
BACKGROUND INFORMATION
[0002] Electrodeposition as a coating application method involves
the deposition of a film-forming composition onto a conductive
substrate under the influence of an applied electrical potential.
Electrodeposition has gained popularity in the coatings industry
because it provides higher paint utilization, outstanding corrosion
resistance, and low environmental contamination as compared with
non-electrophoretic coating methods. However, some conductive
substrates are more difficult to coat by electrodeposition because
of a number of factors, including the shape and size of the
substrate. For example, it may be difficult to coat both the
internal and external surfaces of substrates having an open-pocket
shape, such as a container, using conventional electrocoat systems.
Therefore, an electrocoating system that is capable of coating a
wide range of substrates is desired.
SUMMARY OF THE INVENTION
[0003] Disclosed herein is an electrocoating system for
electrocoating a substrate, the system comprising a tank configured
to hold an electrodepositable coating composition; at least one
pump in fluid communication with the tank, at least one return
conduit connecting the tank with an inlet of the pump, at least one
recirculating pipe comprising a first end in fluid communication
with an outlet of the pump and a second end having at least one
aperture, and the at least one recirculating pipe comprising at
least one external electrode positioned at least partially outside
of the tank, wherein: the substrate has a first surface and a
second surface; the pump is configured to receive the
electrodepositable coating composition from the return conduit and
deliver the electrodepositable coating composition into the tank
through the recirculating pipe; the external electrode is
configured to provide an electric charge to the electrodepositable
coating composition; and the recirculating pipe is configured to
extend into the interior of the tank and position the aperture of
the second end to deliver at least a portion of the electrically
charged electrodepositable coating composition to the first surface
of the substrate.
[0004] Also disclosed herein is a method for coating a substrate
comprising electrophoretically applying a coating deposited from an
electrodepositable coating composition to at least a portion of the
substrate using the electrocoating system of the present
invention.
[0005] Further disclosed herein are substrates coated by the method
of the present invention.
[0006] Still further disclosed herein is a system for coating a
substrate comprising the electrocoating system of the present
invention, and further comprising a pretreatment system for
pretreating the substrate prior to processing the substrate in the
electrocoating system; a primer system for applying a primer to the
substrate prior to processing the substrate in the electrocoating
system; and/or a topcoat system for applying a topcoat coating to
the substrate after processing the substrate in the electrocoating
system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is an illustration of an electrocoating system with a
recirculating pipe comprising an external electrode and extending
into the tank, according to the present invention.
[0008] FIG. 2 is an illustration of an electrocoating system of
FIG. 1 with an insulating part extending out of the tank the length
of the recirculating pipe to the pump.
[0009] FIG. 3 is an illustration of an electrocoating system of
FIG. 1 without internal electrodes.
DETAILED DESCRIPTION OF THE INVENTION
[0010] The present invention is directed to an electrocoating
system for electrocoating a substrate. The present specification
also discloses systems for coating a substrate, methods for coating
substrates, substrates coated in accordance with one or more of the
methods described herein, and/or through the use of one or more the
systems described herein.
Electrocoating System
[0011] As shown in FIG. 1, the present invention is directed to an
electrocoating system 10 for electrocoating a substrate, the system
comprising a tank 100 configured to hold an electrodepositable
coating composition; at least one pump 200 in fluid communication
with the tank 100, at least one return conduit 210 connecting the
tank 100 to an inlet of the pump 200, at least one recirculating
pipe 300 comprising a first end 310 in fluid communication with an
outlet of the pump 200 and a second end 320 having at least one
aperture 330, the at least one recirculating pipe 300 comprising at
least one external electrode 400 positioned at least partially
outside of the tank 100, wherein the substrate has a first surface
and a second surface; the return conduit 210 is configured to
connect the tank 100 to an inlet of the pump 200; the pump 200 is
configured to receive the electrodepositable coating composition
600 from the return conduit 210 and deliver the electrodepositable
coating composition 600 into the tank 100 through the recirculating
pipe 300; the external electrode 400 is configured to provide an
electric charge to the electrodepositable coating composition 600;
and the recirculating pipe 300 is configured to extend into the
interior of the tank 100 and position the aperture 330 of the
second end 320 to deliver at least a portion of the electrically
charged electrodepositable coating composition 600 to the first
surface of the substrate.
[0012] According to the present invention, and as shown in FIGS. 1,
2, and 3, the tank 100 is configured to hold an electrodepositable
coating composition. The tank 100 may comprise any material known
in the art. For example, the tank 100 may comprise plastic, metal
having an insulating liner such as metal having an internal plastic
liner, or metal having an insulating coating. The tank 100 may
comprise any geometric shape. For example, the tank 100 may be
generally rectangular or generally round or spherical. The tank 100
may comprise a base portion 110 and at least one side wall 120
extending up from the base portion 110 to form a cavity within
which the electrodepositable coating composition 600 may be
held.
[0013] The tank 100 is also configured to contain, at least
partially, a substrate 500 for electrocoating. The substrate 500
may be a grounded electrical conductor and may generally be
substantially configured of a conductive substance, such as, for
example, a metallic substance. The substrate 500 serves as a
counter-electrode in electrical communication with the internal
electrode(s) 400 (if present) and external electrode(s) 400. The
substrate 500 may comprise any cross-sectional shape, or multiple
cross-sectional shapes if the substrate 500 does not have a uniform
cross-sectional shape. The substrate may comprise any dimensions.
The substrate 500 may comprise an open-polygon cross-sectional
shape, such as an open-pocket cross-sectional shape. The
cross-sectional shape may comprise a generally rectangular or a
generally round cross-sectional shape. The substrate may comprise a
first surface 510 and a second surface 520. The first surface 510
may comprise an internal surface of the substrate 500, and the
second surface 520 may comprise an external surface of the
substrate 500. For example, as shown in FIGS. 1, 2, and 3, when the
substrate 500 has a generally rectangular cross-sectional shape,
the first surface 510 may comprise the internal surface of the
substrate 500, and the second surface 520 may comprise the external
surface of the substrate 500. The substrate 500 may comprise a
container, such as, for example, an intermodal container. For
example, the substrate 500 may have an external length of 8 feet
(2.44 m), 10 feet (3.05 m), 20 feet (6.10 m), 40 feet (12.19 m), 45
feet (13.72 m) or 53 feet (16.15 m); an external width of 7 feet
(2.13 m) or 8 feet (2.44 m); and an external height of 7.5 feet
(2.29 m), 8.5 feet (2.59 m) or 9.5 feet (2.90 m). The substrate 500
may have a length of at least 8 feet (2.44 m), such as at least 10
feet (3.05 m), such as at least 20 feet (6.10 m), such as at least
40 feet (12.19 m), such as at least 45 feet (13.72 m) or such as at
least 53 feet (16.15 m).
[0014] The first surface 510 of the substrate 500 may have a
surface area that varies based on the length of the substrate 500.
The first surface 510 of the substrate 500 may have a surface area
of at least 285 ft.sup.2 (26.48 m.sup.2), such as at least 340
ft.sup.2 (31.59 m.sup.2), such as at least 600 ft.sup.2 (55.74
m.sup.2), such as at least 1,145 ft.sup.2 (106.37 m.sup.2), such as
at least 1,275 ft.sup.2 (118.45 m.sup.2), such as at least 1,490
ft.sup.2 (138.43 m.sup.2). The first surface 510 of the substrate
500 may have a surface area of 285 ft.sup.2 (26.48 m.sup.2) to
1,890 ft.sup.2 (175.59 m.sup.2) or larger. With respect to a
container, the surface area may vary depending upon the length of
the substrate 500. For example, the first surface 510 of an 8 foot
substrate 500 may have a surface area of 285 ft.sup.2 (26.48
m.sup.2) to 400 ft.sup.2 (37.16 m.sup.2), the first surface 510 of
a 10 foot substrate 500 may have a surface area of 340 ft.sup.2
(31.59 m.sup.2) to 460 ft.sup.2 (42.74 m.sup.2), the first surface
510 of a 20 foot substrate 500 may have a surface area of 600
ft.sup.2 (55.74 m.sup.2) to 795 ft.sup.2 (73.86 m.sup.2), the first
surface 510 of a 40 foot substrate 500 may have a surface area of
1,145 ft.sup.2 (106.37 m.sup.2) to 1,460 ft.sup.2 (135.64 m.sup.2),
the first surface 510 of a 45 foot substrate 500 may have a surface
area of 1,275 ft.sup.2 (118.45 m.sup.2) to 1,620 ft.sup.2 (150.50
m.sup.2), and the first surface 510 of a 53 foot substrate 500 may
have a surface area of 1,490 ft.sup.2 (138.43 m.sup.2) to 1,890
ft.sup.2 (175.59 m.sup.2).
[0015] The second surface 520 of the substrate 500 may have a
surface area that varies based on the length of the substrate 500.
The second surface 520 of the substrate 500 may have a surface area
of at least such as at least 330 ft.sup.2 (30.66 m.sup.2), 380
ft.sup.2 (35.30 m.sup.2), such as at least 675 ft.sup.2 (62.71
m.sup.2), such as at least 1,250 ft.sup.2 (116.13 m.sup.2), such as
at least 1,390 ft.sup.2 (129.14 m.sup.2), such as at least 1,630
ft.sup.2 (151.43 m.sup.2). The second surface 520 of the substrate
500 may have a surface area of 330 ft.sup.2 (30.66 m.sup.2) to
1,750 ft.sup.2 (162.58 m.sup.2) or larger. With respect to a
container, the surface area may vary depending upon the length of
the substrate 500. For example, the second surface 520 of an 8 foot
substrate 500 may have a surface area of 330 ft.sup.2 (30.66
m.sup.2) to 440 ft.sup.2 (40.88 m.sup.2), the second surface 520 of
a 10 foot substrate 500 may have a surface area of 380 ft.sup.2
(35.30 m.sup.2) to 520 ft.sup.2 (48.31 m.sup.2), the second surface
520 of a 20 foot substrate 500 may have a surface area of 675
ft.sup.2 (62.71 m.sup.2) to 865 ft.sup.2 (80.36 m.sup.2), the
second surface 520 of a 40 foot substrate 500 may have a surface
area of 1250 ft.sup.2 (116.13 m.sup.2) to 1,575 ft.sup.2 (146.32
m.sup.2), the second surface 520 of a 45 foot substrate 500 may
have a surface area of 1,390 ft.sup.2 (129.14 m.sup.2) to 1,750
ft.sup.2 (162.58 m.sup.2), and the second surface 520 of a 53 foot
substrate 500 may have a surface area of 1,630 ft.sup.2 (151.43
m.sup.2) to 2,030 ft.sup.2 (188.59 m.sup.2).
[0016] The substrate may have a cross-sectional area of at least 40
m.sup.2, such as at least 45 m.sup.2, such as at least 50 m.sup.2,
and may be no more than 100 m.sup.2, such as no more than 85
m.sup.2, such as no more than 80 m.sup.2. The substrate may have a
cross-sectional area of 40 m.sup.2 to 100 m.sup.2, such as 45
m.sup.2 to 85 m.sup.2, such as 50 m.sup.2 to 80 m.sup.2. As used
herein, the term "cross-sectional area" with respect to the
substrate refers to the largest cross-sectional area of the
substrate as measured perpendicular to the longest axis of the
substrate. With respect to a container-shaped substrate, the
cross-sectional area will be the width multiplied by the
height.
[0017] The substrate may comprise any conductive substrate. For
example, the substrate may comprise a metal, metal alloy, and/or
materials that have been metallized, such as nickel-plated plastic.
Additionally, substrates may comprise non-metal conductive
materials including composite materials such as, for example,
materials comprising carbon fibers or conductive carbon. The metal
or metal alloy may comprise, for example, cold rolled steel, hot
rolled steel, steel coated with zinc metal, zinc compounds or zinc
alloys, such as electrogalvanized steel, hot-dipped galvanized
steel, galvanealed steel, nickel-plated steel, and steel plated
with zinc alloy. The substrate may comprise an aluminum alloy.
Non-limiting examples of aluminum alloys include the 1XXX, 2XXX,
3XXX, 4XXX, 5XXX, 6XXX, or 7XXX series as well as clad aluminum
alloys and cast aluminum alloys. The substrate may comprise a
magnesium alloy. The substrate used in the present invention may
also comprise other suitable non-ferrous metals such as titanium or
copper, as well as alloys of these materials.
[0018] As illustrated in FIGS. 1, 2, and 3, the electrocoating
system 10 also comprises a return conduit 210 that connects the
tank 100 to the pump 200. The return conduit 210 is configured to
recycle the electrodepositable coating composition 600 from the
tank 100 to the pump 200. The return conduit 210 may comprise any
combination of pipes, hoses, valves, and any other fluid conveying
devices configured to perform the purposes stated herein.
[0019] As shown in FIGS. 1, 2, and 3, the pump 200 is in fluid
communication with the tank 100. The pump 200 is configured to
receive the electrodepositable coating composition 600 from the
return conduit 210 and deliver the electrodepositable coating
composition 600 into the tank 100 through a recirculating pipe 300.
The recirculating pipe 300 comprises a first end 310 in fluid
communication with an outlet of the pump 200 and a second end 320
having at least one aperture 330. The recirculating pipe 300 is
configured to extend into the interior of the tank 100, immersed in
the electrodepositable coating composition, to position the
aperture(s) 320 of the second end 310 to deliver at least a portion
of the electrodepositable coating composition 600 to the first
surface 510 of the substrate 500. The return conduit 210, pump 200,
and recirculating pipe 300 may be directly coupled to form at least
one continuous and uninterrupted loop for constrained flow of the
electrodepositable coating composition 600 through the return
conduit 210, pump 200 and recirculating pipe 300. The pump 200 is
configured to deliver the electrodepositable coating composition
600 into the tank 100 through the recirculating pipe 300 at a flow
rate and pressure appropriate for electrocoating a substrate 500,
as described herein. For example, but not by way of limitation, the
pump may deliver the electrodepositable coating composition 600 to
the tank 100 at a pressure from about 1 psi to about 50 psi, such
as from about 15 psi to about 40 psi, and at a flow rate from about
0.1 liters per second to about 65.0 liters per second. The pump 200
may comprise, for example, a centrifugal pump. It is contemplated,
however, that any pump 200 configured to perform the purposes
stated herein may be utilized in the electrocoating system 10 of
the present invention.
[0020] As shown in FIGS. 1, 2, and 3, the external electrode 400 is
positioned outside of the tank 100. The external electrode 400 is
configured to provide an electric charge to the electrodepositable
coating composition 600 delivered by the pump 200 into the tank 100
through the recirculating pipe 300. As such, the external electrode
400 provides the electric charge to the electrodepositable coating
composition 600 prior to its delivery into the tank 100 for
electrocoating. The pump 200 generally delivers the
electrodepositable coating composition 600 past the external
electrode 400 through the recirculating pipe 300 and into the tank
100 at a flow rate appropriate for the external electrode 400 to
sufficiently electrically charge the electrodepositable coating
composition 600. This flow rate of the electrodepositable coating
composition 600 delivered past the external electrode 400 may vary
depending upon a volume of the electrodepositable coating
composition 600 delivered by the pump 200 relative to the surface
area of the external electrode 400. For example, it is contemplated
that as a volume of the electrodepositable coating composition 600
increases, a slower flow rate of the electrodepositable coating
composition 600 may be provided to increase a contact time between
the electrodepositable coating composition 600 and the external
electrode 400 and enable the external electrode 400 to sufficiently
electrically charge the electrodepositable coating composition 600.
Likewise, it is contemplated that an increase in the surface area
of the external electrode 400 requires less contact time with the
external electrode 400 in order to sufficiently electrically charge
the electrodepositable coating composition 600. The external
electrode 400 may be configured in any variety of cross-sectional
shapes, such as, for example, tubular, flat plate, C-shape, fanned,
or annular, and may comprise, for example, a conductive pipe or
pipe section, such as a metal pipe. For example, the external
electrode 400 may have an internal surface configured to contact
the electrodepositable coating composition 600, and the
electrocoating system 10 may be configured such that the ratio of a
total combined surface area of an external surface of the external
electrode(s) 400 to a surface area of the first surface 510 of the
substrate 500 is from 1:7 to 1:1, such as 1:6 to 1:2, such as 1:5
to 1:3, such as about 1:4.
[0021] At least a portion of the recirculating pipe 300 comprises
the external electrode, and the portion of the recirculating pipe
300 comprising the external electrode 400 is located at least
partially or completely outside of the tank 100. As used herein, at
least partially or completely outside of the tank 100 means that at
least a portion of the external electrode 400 is present outside of
the tank 100 and not immersed in the electrodepositable coating
composition 600, or that the entire external electrode 400 is
located outside of the tank 100 and not immersed in the
electrodepositable coating composition 600. In other words, at
least a portion or all of the recirculating pipe 300 that comprises
the external electrode 400 is not immersed in the
electrodepositable coating composition 600 held within the tank
100. Alternatively, substantially all of the recirculating pipe 300
may comprise the external electrode 400. For example, the external
electrode 400 may comprise at least 50% of the recirculating pipe
300, such as at least 60%, such as at least 75%, such as at least
85%, such as at least 95%, such as 100%. The remainder of the
recirculating pipe 300 may comprise a combination of non-conductive
and/or conductive materials. The recirculating pipe 300 may
comprise any combination of pipes, hoses, valves, and any other
fluid conveying devices configured to perform the purposes stated
herein.
[0022] The external electrode 400 may be contained within an
insulating part 410. The insulating part 410 may prevent a user of
the electrocoating system 10 from being exposed to the electric
charge of the external electrode 400 when an electrical potential
is applied to the electrocoating system 10. The insulating part 410
may alternatively, or in addition to, be located on the
recirculating pipe 300 that extends into the tank 100. The
insulating part 410 may comprise, for example, a polyvinyl chloride
(PVC) pipe in which the external electrode 400 is contained. It is
contemplated, however, that any insulating part 410 configured to
perform the purposes stated herein may be utilized according to the
electrocoating system 10 of the present invention.
[0023] Further, if the external electrode 400 comprises an anode, a
membrane may be used to cover the internal surface of the external
electrode 400 so as to remove acid build-up from the
electrodepositable coating composition 600 during the process of
electrocoating a substrate 500. For example, about 50%, such as
about 75%, such as about 80%, or more of the internal surface area
of an external electrode 400 may be covered by a membrane to
control pH of the electrodepositable coating composition through
the removal of acid generated during electrocoating. Membrane
covered anodes generally are referred to in the industry as anolyte
cells. An external electrode 400 that is substantially
membrane-free is one that is membrane-free to an extent that any
existing membrane does not interfere, to any significant degree,
with the electric charging of the electrodepositable coating
composition 600 by the external electrode 400. In addition, the
external electrode 400 may be completely membrane-free.
[0024] The external electrode 400 may comprise, for example, a
membrane-free 316 type stainless steel pipe. The entirely exposed
wall of the channel of the membrane-free metal pipe external
electrode 400 combined with the flow of the electrodepositable
coating composition 600 through the external electrode 400 may aid
in the external electrode 400 providing the electric charge
substantially uniform to the electrodepositable coating composition
600 so as to promote substantially equal electric charge
distribution throughout the electrodepositable coating composition
600. Substantially equal electric charge distribution throughout
the electrodepositable coating composition 600 optimizes the
electrocoating of the substrate 500 by providing a substantially
uniform attraction of charged molecules of the electrodepositable
coating composition 600 to the oppositely charged substrate 500.
Further, it is contemplated that as a volume of the
electrodepositable coating composition 600 delivered to the
external electrode 400 by the pump 200 increases, a greater surface
area of the external electrode 400 may be provided to sufficiently
electrically charge the electrodepositable coating composition 600
delivered by the pump 200. Thus, it is contemplated that a minimum
surface area of the external electrode 400 per unit volume of
electrodepositable coating composition 600 flow may be provided to
sufficiently charge the electrodepositable coating composition 600
prior to its delivery to the tank 100 for electrocoating a
substrate 500. As discussed above, the surface area of the external
electrode 400 may be manipulated by, for example, increasing the
length of the external electrode 400 (i.e., increasing the length
of the portion of the recirculating pipe 300 that comprises the
external electrode 400, or, if the entire recirculating pipe 300
comprises the external electrode 400, increasing the length of the
recirculating pipe 300), or changing the cross-sectional shape of
the external electrode 400.
[0025] The second end 320 of the recirculating pipe 300 may
comprise a nozzle which comprises the aperture 330. The nozzle may
comprise any nozzle known in the art. In addition, the second end
320 of the recirculating pipe 300 may comprise a plurality of
apertures 330 through which the electrodepositable coating
composition 600 may pass. The recirculating pipe may also comprise
a plurality of second ends 320. For example, as shown in FIGS. 1,
2, and 3, the recirculating pipe may be branched with each branch
comprising a second end 320 comprising at least one aperture 330.
Each second end 320 of the branched recirculating pipe 300 may be
configured to deliver at least a portion of the electrodepositable
coating composition 600 electrically charged by the external
electrode 400 to different sections of the first surface 510 of the
substrate 500.
[0026] As discussed above, the electrocoating system 10 may
comprise a plurality of return conduits 210, pumps 200, and/or
recirculating pipes 300. For example, the electrocoating system 10
may comprise a plurality of recirculating pipes 300 configured to
deliver the electrodepositable coating composition 600 charged by
the external electrode(s) 400 to different sections of the first
surface 510 of the substrate 500. Each recirculating pipe 300 may
be fed by a different pump 200, or a pump 200 may pump the
electrodepositable coating composition 600 to multiple
recirculating pipes 300. Likewise, each pump 200 may be fed by a
return conduit 210, or a return conduit 210 may feed multiple pumps
200. The number of each component (i.e., return conduit 210, pump
200, recirculating pipe 300) present in the electrocoating system
10 may depend upon a variety of factors, including, for example,
the length of the substrate 500, the surface area of the first
surface 510 of the substrate 500, the resin solids present in the
electrodepositable coating composition 600, the charge density of
the electrodepositable coating composition 600, the voltage applied
during electrocoating of the substrate, the shape of the substrate,
among other factors. The return conduits 210, pumps 200, and/or
recirculating pipes 300 may be positioned along a length of the
tank 100 such that the electrodepositable coating composition 600
is deposited substantially uniform along the length of the
substrate 500 to be electrocoated. For example, the return conduits
210, pumps 200, and/or recirculating pipes 300 may be positioned
equidistant along a length of the tank 100. The electrodepositable
coating composition 600 flowed into the tank 100 through the
recirculating pipe 300 may be substantially deposited onto the
first surface 510 of the substrate 500 during electrocoating.
Without intending to be bound by any theory, it is believed that
positioning the recirculating pipe 300 of the electrocoating system
10 inside the tank 100 to provide a flow of electrodepositable
coating composition 600 charged by the external electrode 400 to
the first surface 510 of the substrate 500 allows for the
deposition of a more uniform coating to be applied to the first
surface 510 of the substrate 500 in comparison to an electrocoating
system that does not include the recirculating pipe 300 and
external electrode 400.
[0027] When a power source provides an electrical current to the
electrocoating system 10, the electrodepositable coating
composition 600 is charged by the external electrode 400 and, if
present, the internal electrode 700, and is attracted to, and
deposits on, the oppositely charged substrate 500. Equal, or
substantially equal, charge distribution throughout the
electrically charged fluid provided by the electrocoating system 10
of the present invention enhances the electrocoating process by
generally providing a substantially uniform coating thickness of
the electrodepositable coating composition 500 deposited on the
substrate 500.
[0028] The electrocoating system 10 optionally may further comprise
at least one internal electrode 700 positioned inside the tank 100
to provide additional electric charge to the electrodepositable
coating composition 600, as shown in FIGS. 1 and 2. The internal
electrode 700 may comprise any suitable conductive material known
in the art. For example, the internal electrode 700 may comprise a
pipe electrically coupled with the power source. The internal
electrode(s) 700 may be membrane-free, or substantially
membrane-free, or substantially covered by a membrane. The
electrocoating system 10 may comprise a plurality of internal
electrodes 700, and the internal electrodes 700 may be positioned
along a length of the tank 100 such that the electrodepositable
coating composition 600 is deposited substantially uniform along
the length of the substrate 500 to be electrocoated. For example,
the internal electrode 700 may be positioned equidistant along a
length of the tank 100. The electrocoating system 10 may be
configured such that the ratio of a total combined surface area of
the internal electrode(s) 700 to the surface area of the second
surface 510 of the substrate 500 may be from 1:7 to 1:1, such as
1:6 to 1:2, such as 1:5 to 1:3, such as 1:4. In contrast to the
recirculating pipe 300 comprising the external electrode 400, the
internal electrode 700 does not recirculate or transport the
electrodepositable coating composition 600 within the
electrocoating system 10.
[0029] Without intending to be bound by any theory, it is believed
that the use of the internal electrode 700 in an electrocoating
system will not provide a sufficient charge to the
electrodepositable coating composition 600 to enable a uniform
deposition of the electrodepositable coating composition 600 over
the entire surface of the substrate 500 without the recirculating
pipe 300 comprising the external electrode 400 also being present.
For example, the internal electrode 700 may provide a sufficient
charge to the electrodepositable coating composition 600 to deposit
a coating on a surface of the substrate 500 located near the
internal electrode 700, such as, for example, the second surface
520 of the substrate 500, but may not provide a sufficient charge
to enable deposition on other portions of the substrate, such as,
for example, the first surface 510 of the substrate 500.
[0030] The electrocoating system 10 further comprises at least one
power source (not shown) to provide an electrical current to the
electrocoating system 10. The power source may optionally include a
rectifier. The power source is electrically coupled to the external
electrode(s) 400, the substrate 500, and, if present, the internal
electrodes 700, with one pole of the power source coupled to the
substrate, and the other pole of the power source coupled to the
external electrode(s) 400 and, if present, the internal
electrode(s) 700, such that the substrate serves as a
counter-electrode to the external electrode 400 and, if present,
internal electrode 700. For example, if the electrodepositable
coating composition 600 is a cationic electrodepositable coating
composition, the substrate 500 serves as the cathode and the
external electrode 400 and, if present, internal electrode 700
serve as anodes, with the polarities reversed for an anionic
electrodepositable coating composition. The power source provides
an electric current to the electrocoating system 10 such that the
external electrode 400 and, if present, internal electrode 700,
provide an electric charge to the electrodepositable coating
composition 600 sufficient for electrocoating purposes. For
example, but not by way of limitation, the electric current
provided to the power source may be, but is not limited to, about
25 volts to about 600 volts or higher. The voltage provided to the
power source may vary according to a volume of the
electrodepositable coating composition 600 delivered by the pump
200. For example, a higher voltage may be provided to the external
electrode 400 to sufficiently charge an increased volume and/or
increased flow rate of the electrodepositable coating composition
600 delivered by the pump 200. The electrocoating system 10 may
also comprise any additional or other electrical circuitry desired
or needed to perform the purposes stated herein.
[0031] The electrodepositable coating composition 600 may comprise
any electrodepositable coating composition known in the art. As
used herein, the term "electrodepositable coating composition"
refers to a composition that is capable of being deposited onto an
electrically conductive substrate under the influence of an applied
electrical potential. For example, as mentioned above, the
electrodepositable coating composition 600 may comprise a cationic
or anionic electrodepositable coating composition.
[0032] The electrodepositable coating composition comprises a
film-forming binder. The film-forming binder may comprise an ionic
salt group-containing film-forming polymer and, optionally, a
curing agent.
[0033] According to the present invention, the ionic salt
group-containing film-forming polymer may comprise a cationic salt
group-containing film-forming polymer. The cationic salt
group-containing, film-forming polymer may be used in a cationic
electrodepositable coating composition. As used herein, the term
"cationic salt group-containing film-forming polymer" refers to
polymers that include at least partially neutralized cationic
groups, such as sulfonium groups and/or ammonium groups, that
impart a positive charge to the polymer. As used herein, the term
"polymer" encompasses, but is not limited to, oligomers and both
homopolymers and copolymers. The cationic salt group-containing
film-forming polymer may comprise active hydrogen functional
groups. As used herein, the term "active hydrogen functional
groups" refers to those groups that are reactive with isocyanates
as determined by the Zerewitinoff test described in the JOURNAL OF
THE AMERICAN CHEMICAL SOCIETY, Vol. 49, page 3181 (1927), and
include, for example, hydroxyl groups, primary or secondary amino
groups, and thiol groups. Cationic salt group-containing
film-forming polymers that comprise active hydrogen functional
groups may be referred to as active hydrogen-containing, cationic
salt group-containing film-forming polymers.
[0034] Examples of polymers that are suitable for use as the
cationic salt group-containing film-forming polymer in the present
invention include, but are not limited to, alkyd polymers, acrylic
polymers, polyepoxide polymers, polyamide polymers, polyurethane
polymers, polyurea polymers, polyether polymers, and polyester
polymers, among others.
[0035] The cationic salt groups may be incorporated into the
cationic salt group-containing film-forming polymer as follows: The
film-forming polymer may be reacted with a cationic salt group
former. By "cationic salt group former" is meant a material which
is reactive with epoxy groups present and which may be acidified
before, during, or after reaction with the epoxy groups on the
film-forming polymer to form cationic salt groups. Examples of
suitable materials include amines such as primary or secondary
amines which can be acidified after reaction with the epoxy groups
to form amine salt groups, or tertiary amines which can be
acidified prior to reaction with the epoxy groups and which after
reaction with the epoxy groups form quaternary ammonium salt
groups. Examples of other cationic salt group formers are sulfides
which can be mixed with acid prior to reaction with the epoxy
groups and form ternary sulfonium salt groups upon subsequent
reaction with the epoxy groups.
[0036] More specific examples of suitable active
hydrogen-containing, cationic salt group containing film-forming
polymers include polyepoxide-amine adducts, such as the adduct of a
polyglycidyl ether of a polyphenol, such as Bisphenol A, and
primary and/or secondary amines, such as are described in U.S. Pat.
No. 4,031,050 at col. 3, line 27 to col. 5, line 50, U.S. Pat. No.
4,452,963 at col. 5, line 58 to col. 6, line 66, and U.S. Pat. No.
6,017,432 at col. 2, line 66 to col. 6, line 26, these portions of
which being incorporated herein by reference. A portion of the
amine that is reacted with the polyepoxide may be a ketimine of a
polyamine, as is described in U.S. Pat. No. 4,104,147 at col. 6,
line 23 to col. 7, line 23, the cited portion of which being
incorporated herein by reference. Also suitable are ungelled
polyepoxide-polyoxyalkylenepolyamine resins, such as are described
in U.S. Pat. No. 4,432,850 at col. 2, line 60 to col. 5, line 58,
the cited portion of which being incorporated herein by reference.
In addition, cationic acrylic resins, such as those described in
U.S. Pat. No. 3,455,806 at col. 2, line 18 to col. 3, line 61 and
U.S. Pat. No. 3,928,157 at col. 2, line 29 to col. 3, line 21,
these portions of both of which are incorporated herein by
reference, may be used.
[0037] Besides amine salt group-containing resins, the cationic
salt group-containing film-forming polymer may comprise a
quaternary ammonium salt group-containing resin. As used herein, a
"quaternary ammonium salt group" refers to group comprising a
quaternary ammonium cation of the formula NR.sub.4.sup.+, wherein
each R group is independently an alkyl or aryl group, and a counter
anion. Examples of these resins are those which are formed from
reacting an organic polyepoxide with a tertiary amine acid salt.
Such resins are described in U.S. Pat. No. 3,962,165 at col. 2,
line 3 to col. 11, line 7; U.S. Pat. No. 3,975,346 at col. 1, line
62 to col. 17, line 25 and U.S. Pat. No. 4,001,156 at col. 1, line
37 to col. 16, line 7, these portions of which being incorporated
herein by reference.
[0038] Examples of other suitable cationic resins include ternary
sulfonium salt group-containing resins, such as those described in
U.S. Pat. No. 3,793,278 at col. 1, line 32 to col. 5, line 20, this
portion of which being incorporated herein by reference. Also,
cationic resins which cure via a transesterification mechanism,
such as described in European Patent Application No. 12463B1 at pg.
2, line 1 to pg. 6, line 25, this portion of which being
incorporated herein by reference, may also be employed.
[0039] Other suitable cationic salt group-containing film-forming
polymers include those that may form photodegradation resistant
electrodepositable coating compositions. Such polymers include the
polymers comprising cationic amine salt groups which are derived
from pendant and/or terminal amino groups that are disclosed in
U.S. Patent Application Publication No. 2003/0054193 A1 at
paragraphs [0064] to [0088], this portion of which being
incorporated herein by reference. Also suitable are the active
hydrogen-containing, cationic salt group-containing resins derived
from a polyglycidyl ether of a polyhydric phenol that is
essentially free of aliphatic carbon atoms to which are bonded more
than one aromatic group, which are described in U.S. Patent
Application Publication No. 2003/0054193 A1 at paragraphs [0096] to
[0123], this portion of which being incorporated herein by
reference.
[0040] The active hydrogen-containing, cationic salt
group-containing film-forming polymer may be made cationic and
water dispersible by at least partial neutralization with an acid.
Suitable acids include organic and inorganic acids. Non-limiting
examples of suitable organic acids include formic acid, acetic
acid, methanesulfonic acid, and lactic acid. Non-limiting examples
of suitable inorganic acids include phosphoric acid and sulfamic
acid. By "sulfamic acid" is meant sulfamic acid itself or
derivatives thereof such as those having the formula:
##STR00001##
wherein R is hydrogen or an alkyl group having 1 to 4 carbon atoms.
Mixtures of the above-mentioned acids also may be used in the
present invention.
[0041] The extent of neutralization of the cationic salt
group-containing film-forming polymer may vary with the particular
polymer involved. However, sufficient acid should be used to
sufficiently neutralize the cationic salt-group containing
film-forming polymer such that the cationic salt-group containing
film-forming polymer may be dispersed in an aqueous dispersing
medium. For example, the amount of acid used may provide at least
20% of all of the total theoretical neutralization. Excess acid may
also be used beyond the amount required for 100% total theoretical
neutralization. For example, the amount of acid used to neutralize
the cationic salt group-containing film-forming polymer may be
.gtoreq.0.1% based on the total amines in the active
hydrogen-containing, cationic salt group-containing film-forming
polymer. Alternatively, the amount of acid used to neutralize the
active hydrogen-containing, cationic salt group-containing
film-forming polymer may be .ltoreq.100% based on the total amines
in the active hydrogen-containing, cationic salt group-containing
film-forming polymer. The total amount of acid used to neutralize
the cationic salt group-containing film-forming polymer may range
between any combination of values, which were recited in the
preceding sentences, inclusive of the recited values. For example,
the total amount of acid used to neutralize the active
hydrogen-containing, cationic salt group-containing film-forming
polymer may be 20%, 35%, 50%, 60%, or 80% based on the total amines
in the cationic salt group-containing film-forming polymer.
[0042] The cationic salt group-containing film-forming polymer may
be present in the cationic electrodepositable coating composition
in an amount of at least 40% by weight, such as at least 50% by
weight, such as at least 60% by weight, and may be present in the
in an amount of no more than 90% by weight, such as no more than
80% by weight, such as no more than 75% by weight, based on the
total weight of the resin solids of the electrodepositable coating
composition. The cationic salt group-containing film-forming
polymer may be present in the cationic electrodepositable coating
composition in an amount of 40% to 90% by weight, such as 50% to
80% by weight, such as 60% to 75% by weight, based on the total
weight of the resin solids of the electrodepositable coating
composition. As used herein, the "resin solids" include the ionic
salt group-containing film-forming polymer, the curing agent (if
present), and any additional water-dispersible non-pigmented
component(s) present in the electrodepositable coating
composition.
[0043] According to the present invention, the ionic salt group
containing film-forming polymer may comprise an anionic salt group
containing film-forming polymer. As used herein, the term "anionic
salt group containing film-forming polymer" refers to an anionic
polymer comprising at least partially neutralized anionic
functional groups, such as carboxylic acid and phosphoric acid
groups that impart a negative charge. The anionic salt
group-containing film-forming polymer may comprise active hydrogen
functional groups. Anionic salt group-containing film-forming
polymers that comprise active hydrogen functional groups may be
referred to as active hydrogen-containing, anionic salt
group-containing film-forming polymers. The anionic salt group
containing film-forming polymer may be used in an anionic
electrodepositable coating composition.
[0044] The anionic salt group-containing film-forming polymer may
comprise base-solubilized, carboxylic acid group-containing
film-forming polymers such as the reaction product or adduct of a
drying oil or semi-drying fatty acid ester with a dicarboxylic acid
or anhydride; and the reaction product of a fatty acid ester,
unsaturated acid or anhydride and any additional unsaturated
modifying materials which are further reacted with polyol. Also
suitable are the at least partially neutralized interpolymers of
hydroxy-alkyl esters of unsaturated carboxylic acids, unsaturated
carboxylic acid and at least one other ethylenically unsaturated
monomer. Still another suitable anionic electrodepositable resin
comprises an alkyd-aminoplast vehicle, i.e., a vehicle containing
an alkyd resin and an amine-aldehyde resin. Another suitable
anionic electrodepositable resin composition comprises mixed esters
of a resinous polyol. Other acid functional polymers may also be
used such as phosphatized polyepoxide or phosphatized acrylic
polymers. Exemplary phosphatized polyepoxides are disclosed in U.S.
Patent Application Publication No. 2009-0045071 at [0004]-[0015]
and U.S. patent application Ser. No. 13/232,093 at [0014]-[0040],
the cited portions of which being incorporated herein by reference.
Also suitable are resins comprising one or more pendent carbamate
functional groups, such as those described in U.S. Pat. No.
6,165,338.
[0045] According to the present invention, the anionic salt
group-containing film-forming polymer may be present in the anionic
electrodepositable coating composition in an amount of at least 50%
by weight, such as at least 55% by weight, such as at least 60% by
weight, and may be present in an amount of no more than 90% by
weight, such as no more than 80% by weight, such as no more than
75% by weight, based on the total weight of the resin solids of the
electrodepositable coating composition. The anionic salt
group-containing film-forming polymer may be present in the anionic
electrodepositable coating composition in an amount 50% to 90%,
such as 55% to 80%, such as 60% to 75%, based on the total weight
of the resin solids of the electrodepositable coating
composition.
[0046] According to the present invention, the electrodepositable
coating composition of the present invention may further comprise a
curing agent. The curing agent may be reactive with the ionic salt
group-containing film-forming polymer. The curing agent comprises
functional groups that react with the reactive functional groups,
such as active hydrogen groups, of the ionic salt group-containing
film-forming polymer to effectuate cure of the coating composition
to form a coating. As used herein, the term "cure", "cured" or
similar terms, as used in connection with the electrodepositable
coating compositions described herein, means that at least a
portion of the components that form the electrodepositable coating
composition are crosslinked to form a coating. Additionally, curing
of the electrodepositable coating composition refers to subjecting
said composition to curing conditions (e.g., elevated temperature)
leading to the reaction of the reactive functional groups of the
components of the electrodepositable coating composition, and
resulting in the crosslinking of the components of the composition
and formation of an at least partially cured coating. Non-limiting
examples of suitable curing agents are at least partially blocked
polyisocyanates, aminoplast resins and phenoplast resins, such as
phenolformaldehyde condensates including allyl ether derivatives
thereof.
[0047] Suitable at least partially blocked polyisocyanates include
aliphatic polyisocyanates, aromatic polyisocyanates, and mixtures
thereof. The curing agent may comprise an at least partially
blocked aliphatic polyisocyanate. Suitable at least partially
blocked aliphatic polyisocyanates include, for example, fully
blocked aliphatic polyisocyanates, such as those described in U.S.
Pat. No. 3,984,299 at col. 1 line 57 to col. 3 line 15, this
portion of which is incorporated herein by reference, or partially
blocked aliphatic polyisocyanates that are reacted with the polymer
backbone, such as is described in U.S. Pat. No. 3,947,338 at col. 2
line 65 to col. 4 line 30, this portion of which is also
incorporated herein by reference. By "blocked" is meant that the
isocyanate groups have been reacted with a compound such that the
resultant blocked isocyanate group is stable to active hydrogens at
ambient temperature but reactive with active hydrogens in the film
forming polymer at elevated temperatures, such as between
90.degree. C. and 200.degree. C. The polyisocyanate curing agent
may be a fully blocked polyisocyanate with substantially no free
isocyanate groups.
[0048] The polyisocyanate curing agent may comprise a diisocyanate,
higher functional polyisocyanates or combinations thereof. For
example, the polyisocyanate curing agent may comprise aliphatic
and/or aromatic polyisocyanates. Aliphatic polyisocyanates may
include (i) alkylene isocyanates, such as trimethylene
diisocyanate, tetramethylene diisocyanate, pentamethylene
diisocyanate, hexamethylene diisocyanate ("HDI"), 1,2-propylene
diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate,
1,3-butylene diisocyanate, ethylidene diisocyanate, and butylidene
diisocyanate, and (ii) cycloalkylene isocyanates, such as
1,3-cyclopentane diisocyanate, 1,4-cyclohexane diisocyanate,
1,2-cyclohexane diisocyanate, isophorone diisocyanate, methylene
bis(4-cyclohexylisocyanate) ("HMDI"), the cyclo-trimer of
1,6-hexmethylene diisocyanate (also known as the isocyanurate
trimer of HDI, commercially available as Desmodur N3300 from
Convestro AG), and meta-tetramethylxylylene diisocyanate
(commercially available as TMXDI.RTM. from Allnex SA). Aromatic
polyisocyanates may include (i) arylene isocyanates, such as
m-phenylene diisocyanate, p-phenylene diisocyanate, 1,5-naphthalene
diisocyanate and 1,4-naphthalene diisocyanate, and (ii) alkarylene
isocyanates, such as 4,4'-diphenylene methane ("MDI"), 2,4-tolylene
or 2,6-tolylene diisocyanate ("TDI"), or mixtures thereof,
4,4-toluidine diisocyanate and xylylene diisocyanate.
Triisocyanates, such as triphenyl methane-4,4',4''-triisocyanate,
1,3,5-triisocyanato benzene and 2,4,6-triisocyanato toluene,
tetraisocyanates, such as 4,4'-diphenyldimethyl
methane-2,2',5,5'-tetraisocyanate, and polymerized polyisocyanates,
such as tolylene diisocyanate dimers and trimers and the like, may
also be used. The curing agent may comprise a blocked
polyisocyanate selected from a polymeric polyisocyanate, such as
polymeric HDI, polymeric MDI, polymeric isophorone diisocyanate,
and the like. The curing agent may also comprise a blocked trimer
of hexamethylene diisocyanate available as Desmodur N3300.RTM. from
Covestro AG. Mixtures of polyisocyanate curing agents may also be
used.
[0049] The polyisocyanate curing agent may be at least partially
blocked with at least one blocking agent selected from a 1,2-alkane
diol, for example 1,2-propanediol; a 1,3-alkane diol, for example
1,3-butanediol; a benzylic alcohol, for example, benzyl alcohol; an
allylic alcohol, for example, allyl alcohol; caprolactam; a
dialkylamine, for example dibutylamine; and mixtures thereof. The
polyisocyanate curing agent may be at least partially blocked with
at least one 1,2-alkane diol having three or more carbon atoms, for
example 1,2-butanediol.
[0050] Other suitable blocking agents include aliphatic,
cycloaliphatic, or aromatic alkyl monoalcohols or phenolic
compounds, including, for example, lower (e.g. C.sub.1-C.sub.6)
aliphatic alcohols, such as methanol, ethanol, and n-butanol;
cycloaliphatic alcohols, such as cyclohexanol; aromatic-alkyl
alcohols, such as phenyl carbinol and methylphenyl carbinol; and
phenolic compounds, such as phenol itself and substituted phenols
wherein the substituents do not affect coating operations, such as
cresol and nitrophenol. Glycol ethers and glycol amines may also be
used as blocking agents. Suitable glycol ethers include ethylene
glycol butyl ether, diethylene glycol butyl ether, ethylene glycol
methyl ether and propylene glycol methyl ether. Other suitable
blocking agents include oximes, such as methyl ethyl ketoxime,
acetone oxime and cyclohexanone oxime.
[0051] The curing agent may comprise an aminoplast resin.
Aminoplast resins are condensation products of an aldehyde with an
amino- or amido-group carrying substance. Condensation products
obtained from the reaction of alcohols and an aldehyde with
melamine, urea or benzoguanamine may be used. However, condensation
products of other amines and amides may also be employed, for
example, aldehyde condensates of triazines, diazines, triazoles,
guanidines, guanamines and alkyl- and aryl-substituted derivatives
of such compounds, including alkyl- and aryl-substituted ureas and
alkyl- and aryl-substituted melamines. Some examples of such
compounds are N,N'-dimethyl urea, benzourea, dicyandiamide,
formaguanamine, acetoguanamine, ammeline,
2-chloro-4,6-diamino-1,3,5-triazine,
6-methyl-2,4-diamino-1,3,5-triazine, 3,5-diaminotriazole,
triaminopyrimidine, 2-mercapto-4,6-diaminopyrimidine,
3,4,6-tris(ethylamino)-1,3,5-triazine, and the like. Suitable
aldehydes include formaldehyde, acetaldehyde, crotonaldehyde,
acrolein, benzaldehyde, furfural, glyoxal and the like.
[0052] The aminoplast resins may contain methylol or similar
alkylol groups, and at least a portion of these alkylol groups may
be etherified by a reaction with an alcohol to provide organic
solvent-soluble resins. Any monohydric alcohol may be employed for
this purpose, including such alcohols as methanol, ethanol,
propanol, butanol, pentanol, hexanol, heptanol and others, as well
as benzyl alcohol and other aromatic alcohols, cyclic alcohol such
as cyclohexanol, monoethers of glycols such as Cello-solves and
Carbitols, and halogen-substituted or other substituted alcohols,
such as 3-chloropropanol and butoxyethanol.
[0053] Non-limiting examples of commercially available aminoplast
resins are those available under the trademark CYMEL.RTM. from
Allnex Belgium SA/NV, such as CYMEL 1130 and 1156, and
RESIMENE.RTM. from INEOS Melamines, such as RESIMENE 750 and 753.
Examples of suitable aminoplast resins also include those described
in U.S. Pat. No. 3,937,679 at col. 16, line 3 to col. 17, line 47,
this portion of which being hereby incorporated by reference. As is
disclosed in the aforementioned portion of the '679 patent, the
aminoplast may be used in combination with the methylol phenol
ethers.
[0054] Phenoplast resins are formed by the condensation of an
aldehyde and a phenol. Suitable aldehydes include formaldehyde and
acetaldehyde. Methylene-releasing and aldehyde-releasing agents,
such as paraformaldehyde and hexamethylene tetramine, may also be
utilized as the aldehyde agent. Various phenols may be used, such
as phenol itself, a cresol, or a substituted phenol in which a
hydrocarbon radical having either a straight chain, a branched
chain or a cyclic structure is substituted for a hydrogen at the
aromatic ring. Mixtures of phenols may also be employed. Some
specific examples of suitable phenols are p-phenylphenol,
p-tert-butylphenol, p-tert-amylphenol, cyclopentylphenol and
unsaturated hydrocarbon-substituted phenols, such as the
monobutenyl phenols containing a butenyl group in ortho, meta or
para position, and where the double bond occurs in various
positions in the hydrocarbon chain.
[0055] Aminoplast and phenoplast resins, as described above, are
further described in U.S. Pat. No. 4,812,215 at col. 6, line 20 to
col. 7, line 12, the cited portion of which being incorporated
herein by reference.
[0056] The curing agent may be present in the cationic
electrodepositable coating composition in an amount of at least 10%
by weight, such as at least 20% by weight, such as at least 25% by
weight, and may be present in an amount of no more than 60% by
weight, such as no more than 50% by weight, such as no more than
40% by weight, based on the total weight of the resin solids of the
electrodepositable coating composition. The curing agent may be
present in the cationic electrodepositable coating composition in
an amount of 10% to 60% by weight, such as 20% to 50% by weight,
such as 25% to 40% by weight, based on the total weight of the
resin solids of the electrodepositable coating composition.
[0057] The curing agent may be present in the anionic
electrodepositable coating composition in an amount of at least 10%
by weight, such as at least 20% by weight, such as at least 25% by
weight, and may be present in an amount of no more than 50% by
weight, such as no more than 45% by weight, such as no more than
40% by weight, based on the total weight of the resin solids of the
electrodepositable coating composition. The curing agent may be
present in the anionic electrodepositable coating composition in an
amount of 10% to 50% by weight, such as 20% to 45% by weight, such
as 25% to 40% by weight, based on the total weight of the resin
solids of the electrodepositable coating composition.
[0058] The electrodepositable coating composition according to the
present invention may optionally comprise one or more further
components in addition to the film-forming binder described
above.
[0059] According to the present invention, the electrodepositable
coating composition may optionally comprise a catalyst to catalyze
the reaction between the curing agent and the polymers. Examples of
catalysts suitable for cationic electrodepositable coating
compositions include, without limitation, organotin compounds
(e.g., dibutyltin oxide and dioctyltin oxide) and salts thereof
(e.g., dibutyltin diacetate); other metal oxides (e.g., oxides of
cerium, zirconium and bismuth) and salts thereof (e.g., bismuth
sulfamate and bismuth lactate); or a cyclic guanidine as described
in U.S. Pat. No. 7,842,762 at col. 1, line 53 to col. 4, line 18
and col. 16, line 62 to col. 19, line 8, the cited portions of
which being incorporated herein by reference. Examples of catalysts
suitable for anionic electrodepositable coating compositions
include latent acid catalysts, specific examples of which are
identified in WO 2007/118024 at [0031] and include, but are not
limited to, ammonium hexafluoroantimonate, quaternary salts of
SbF.sub.6 (e.g., NACURE.RTM. XC-7231), t-amine salts of SbF.sub.6
(e.g., NACURE.RTM. XC-9223), Zn salts of triflic acid (e.g.,
NACURE.RTM. A202 and A218), quaternary salts of triflic acid (e.g.,
NACURE.RTM. XC-A230), and diethylamine salts of triflic acid (e.g.,
NACURE.RTM. A233), all commercially available from King Industries,
and/or mixtures thereof. Latent acid catalysts may be formed by
preparing a derivative of an acid catalyst such as
para-toluenesulfonic acid (pTSA) or other sulfonic acids. For
example, a well-known group of blocked acid catalysts are amine
salts of aromatic sulfonic acids, such as pyridinium
para-toluenesulfonate. Such sulfonate salts are less active than
the free acid in promoting crosslinking. During cure, the catalysts
may be activated by heating.
[0060] According to the present invention, the electrodepositable
coating composition may further comprise other optional
ingredients, such as a pigment composition and/or various additives
including fillers, plasticizers, anti-oxidants, biocides, UV light
absorbers and stabilizers, hindered amine light stabilizers,
defoamers, fungicides, dispersing aids, flow control agents,
surfactants, wetting agents, pH adjusters, buffering agents, or
combinations thereof. Alternatively, the electrodepositable coating
composition may be completely free of any of the optional
ingredients, i.e., the optional ingredient is not present in the
electrodepositable coating composition. The pigment composition may
comprise, for example, iron oxides, lead oxides, strontium
chromate, coal dust, titanium dioxide, talc, barium sulfate, as
well as color pigments such as cadmium yellow, cadmium red,
chromium yellow and the like. The pigment content of the pigment
composition, which excludes the electrically conductive particles
described above, may be expressed as the pigment-to-binder weight
ratio, and may be within the range of 0.03 to 0.1, when pigment is
used. The other additives mentioned above may be present in the
electrodepositable coating composition in amounts of 0.01% to 3% by
weight, based on total weight of the resin solids of the
electrodepositable coating composition.
[0061] According to the present invention, the electrodepositable
coating composition comprises an aqueous dispersion medium
comprising water and/or one or more organic solvent(s). Water can
for example be present in amounts of 40% to 90% by weight, such as
50% to 80% by weight, such as 60 to 75% by weight, based on total
weight of the electrodepositable coating composition. Examples of
suitable organic solvents include oxygenated organic solvents, such
as monoalkyl ethers of ethylene glycol, diethylene glycol,
propylene glycol, and dipropylene glycol which contain from 1 to 10
carbon atoms in the alkyl group, such as the monoethyl and
monobutyl ethers of these glycols. Examples of other at least
partially water-miscible solvents include alcohols such as ethanol,
isopropanol, butanol and diacetone alcohol. If used, the organic
solvents may typically be present in an amount of less than 10% by
weight, such as less than 5% by weight, based on total weight of
the electrodepositable coating composition. The electrodepositable
coating composition may in particular be provided in the form of a
dispersion, such as an aqueous dispersion.
[0062] According to the present invention, the total solids content
of the electrodepositable coating composition may be at least 1% by
weight, such as at least 10% by weight, such as at least 20% by
weight, and may be no more than 60% by weight, such as no more than
40% by weight, such as no more than 20% by weight, based on the
total weight of the electrodepositable coating composition. The
total solids content of the electrodepositable coating composition
may be from 1% to 60% by weight, such as 10% to 40% by weight, such
as 20% to 30% by weight, based on the total weight of the
electrodepositable coating composition.
Method for Coating a Substrate and Coated Substrates
[0063] The present invention is also directed to a method for
coating a substrate comprising electrophoretically applying a
coating deposited from an electrodepositable coating composition to
at least a portion of the substrate using the electrocoating system
10 described above.
[0064] The electrodepositable coating composition of the present
invention may be deposited upon an electrically conductive
substrate by placing the electrodepositable coating composition in
contact with an electrically conductive cathode and an electrically
conductive anode, with the surface to be coated being either the
anode or the cathode, depending upon the type of electrodepositable
coating composition being applied. Following contact with the
composition, an adherent film of the electrodepositable coating
composition is deposited on the substrate when a sufficient voltage
is impressed between the electrodes by a power source. The applied
voltage may be varied and can be, for example, as low as one volt
to as high as several thousand volts, such as between 25 and 600
volts. The current density may be between 0.5 ampere and 15 amperes
per square foot.
[0065] The electrodepositable coating composition that may be used
in the method of the present invention may comprise any of those
known in the art, including those described above. For example, the
electrodepositable coating composition may comprise a cationic
film-forming resin comprising sulphonium groups and/or ammonium
groups, or the electrodepositable coating composition may comprise
an anionic electrodepositable coating composition comprising
carboxylic acid and/or phosphoric acid groups.
[0066] According to the present invention, the method may further
comprise at least partially curing the electrophoretically applied
coating deposited from the electrodepositable coating composition
on the substrate. As discussed above, at least partially curing the
electrodepositable coating composition may comprise subjecting the
substrate to elevated temperature. With respect to cationic
electrodepositable coating compositions, the coated substrate may
be heated to a temperature ranging from, for example, 250.degree.
F. to 450.degree. F. (121.1.degree. C. to 232.2.degree. C.), such
as from 275.degree. F. to 400.degree. F. (135.degree. C. to
204.4.degree. C.), such as from 300.degree. F. to 360.degree. F.
(149.degree. C. to 180.degree. C.). With respect to anionic
electrodepositable coating compositions, the coated substrate may
be heated to a temperature ranging from, for example, 200.degree.
F. to 450.degree. F. (93.degree. C. to 232.2.degree. C.), such as
from 275.degree. F. to 400.degree. F. (135.degree. C. to
204.4.degree. C.), such as from 300.degree. F. to 360.degree. F.
(149.degree. C. to 180.degree. C.). The curing time may be
dependent upon the curing temperature as well as other variables,
for example, the film thickness of the electrodeposited coating,
level and type of catalyst present in the composition, type of
curing agent employed, and the like. For purposes of the present
invention, all that is necessary is that the time be sufficient to
effect cure of the coating on the substrate. For example, the
curing time can range from 10 minutes to 60 minutes, such as 20 to
40 minutes. For example, the thickness of the resultant cured
electrodeposited coating may range from 1 to 50 microns, such as 15
to 50 microns.
[0067] According to the present invention, the method for coating a
substrate may comprise (a) electrophoretically depositing onto at
least a portion of the substrate a coating deposited from an
electrodepositable coating composition using the electrocoating
system 10 described above and (b) heating the coated substrate to a
temperature and for a time sufficient to at least partially cure
the electrodeposited coating on the substrate. According to the
present invention, the method may optionally further comprise (c)
applying directly to the at least partially cured electrodeposited
coating one or more pigment-containing coating compositions and/or
one or more pigment-free coating compositions to form an additional
coating layer over at least a portion of the at least partially
cured electrodeposited coating, and (d) curing the additional
coating layer by allowing it to set at ambient temperature or by
applying a sufficient energy from an external energy source to the
coated substrate of step (c) to a condition and for a time
sufficient to at least partially cure the additional coating layer.
Non-limiting examples of external energy sources include thermal
energy and radiation such as ultraviolet, infrared or
microwave.
[0068] The optional additional coating layer may comprise one or
more primer layer(s) and suitable topcoat layer(s) (e.g., base
coat, clear coat layer, pigmented monocoat, and color-plus-clear
composite compositions). It is understood that suitable additional
coating layers include any of those known in the art, and each
independently may be waterborne, solventborne, in solid particulate
form (i.e., a powder coating composition), or in the form of a
powder slurry. The additional coating compositions may comprise a
film-forming polymer, crosslinking material and, if a colored base
coat or monocoat, one or more pigments. The primer layer(s) may
optionally be disposed between the electrocoating layer and the
topcoat layer(s). Alternatively, the topcoat layer(s) may be
omitted such that the composite comprises the electrocoating layer
and one or more primer layer(s).
[0069] Moreover, the topcoat layer(s) may be applied directly onto
the electrodepositable coating layer. In other words, the substrate
may lack a primer layer such that the composite comprises the
electrocoating layer and one or more topcoat layer(s). For example,
a basecoat layer may be applied directly onto at least a portion of
the electrodepositable coating layer.
[0070] It will also be understood that any of the topcoat layers
may be applied onto an underlying layer despite the fact that the
underlying layer has not been fully cured. For example, a clearcoat
layer may be applied onto a basecoat layer even though the basecoat
layer has not been subjected to a curing step (wet-on-wet). Both
layers may then be cured during a subsequent curing step thereby
eliminating the need to cure the basecoat layer and the clearcoat
layer separately.
[0071] According to the present invention, additional ingredients
such as colorants and fillers may be present in the various coating
compositions from which the top-coat layers result. Any suitable
colorants and fillers may be used. For example, the colorant may be
added to the coating in any suitable form, such as discrete
particles, dispersions, solutions and/or flakes. A single colorant
or a mixture of two or more colorants can be used in the coatings
of the present invention. It should be noted that, in general, the
colorant can be present in a layer of the multi-layer composite in
any amount sufficient to impart the desired property, visual and/or
color effect.
[0072] Example colorants include pigments, dyes and tints, such as
those used in the paint industry and/or listed in the Dry Color
Manufacturers Association (DCMA), as well as special effect
compositions. A colorant may include, for example, a finely divided
solid powder that is insoluble but wettable under the conditions of
use. A colorant may be organic or inorganic and may be agglomerated
or non-agglomerated. Colorants may be incorporated into the
coatings by grinding or simple mixing. Colorants may be
incorporated by grinding into the coating by use of a grind
vehicle, such as an acrylic grind vehicle, the use of which will be
familiar to one skilled in the art.
[0073] Example pigments and/or pigment compositions include, but
are not limited to, carbazole dioxazine crude pigment, azo,
monoazo, disazo, naphthol AS, salt type (lakes), benzimidazolone,
condensation, metal complex, isoindolinone, isoindoline and
polycyclic phthalocyanine, quinacridone, perylene, perinone,
diketopyrrolo pyrrole, thioindigo, anthraquinone, indanthrone,
anthrapyrimidine, flavanthrone, pyranthrone, anthanthrone,
dioxazine, triarylcarbonium, quinophthalone pigments, diketo
pyrrolo pyrrole red ("DPP red BO"), titanium dioxide, carbon black,
zinc oxide, antimony oxide, etc. and organic or inorganic UV
opacifying pigments such as iron oxide, transparent red or yellow
iron oxide, phthalocyanine blue and mixtures thereof. The terms
"pigment" and "colored filler" can be used interchangeably.
[0074] Example dyes include, but are not limited to, those that are
solvent and/or aqueous based such as acid dyes, azoic dyes, basic
dyes, direct dyes, disperse dyes, reactive dyes, solvent dyes,
sulfur dyes, mordant dyes, for example, bismuth vanadate,
anthraquinone, perylene, aluminum, quinacridone, thiazole,
thiazine, azo, indigoid, nitro, nitroso, oxazine, phthalocyanine,
quinoline, stilbene, and triphenyl methane.
[0075] Example tints include, but are not limited to, pigments
dispersed in water-based or water miscible carriers such as
AQUA-CHEM 896 commercially available from Degussa, Inc., CHARISMA
COLORANTS and MAXITONER INDUSTRIAL COLORANTS commercially available
from Accurate Dispersions division of Eastman Chemical, Inc.
[0076] The colorant may be in the form of a dispersion including,
but not limited to, a nanoparticle dispersion. Nanoparticle
dispersions can include one or more highly dispersed nanoparticle
colorants and/or colorant particles that produce a desired visible
color and/or opacity and/or visual effect. Nanoparticle dispersions
may include colorants such as pigments or dyes having a particle
size of less than 150 nm, such as less than 70 nm, or less than 30
nm. Nanoparticles may be produced by milling stock organic or
inorganic pigments with grinding media having a particle size of
less than 0.5 mm. Example nanoparticle dispersions and methods for
making them are identified in U.S. Pat. No. 6,875,800 B2, which is
incorporated herein by reference. Nanoparticle dispersions may also
be produced by crystallization, precipitation, gas phase
condensation, and chemical attrition (i.e., partial dissolution).
In order to minimize re-agglomeration of nanoparticles within the
coating, a dispersion of resin-coated nanoparticles may be used. As
used herein, a "dispersion of resin-coated nanoparticles" refers to
a continuous phase in which is dispersed discreet "composite
microparticles" that comprise a nanoparticle and a resin coating on
the nanoparticle. Example dispersions of resin-coated nanoparticles
and methods for making them are identified in U.S. patent
application Ser. No. 10/876,031 filed Jun. 24, 2004, which is
incorporated herein by reference, and U.S. Provisional Patent
Application Ser. No. 60/482,167 filed Jun. 24, 2003, which is also
incorporated herein by reference.
[0077] According to the present invention, special effect
compositions that may be used in one or more layers of the
multi-layer coating composite include pigments and/or compositions
that produce one or more appearance effects such as reflectance,
pearlescence, metallic sheen, phosphorescence, fluorescence,
photochromism, photosensitivity, thermochromism, goniochromism
and/or color-change. Additional special effect compositions may
provide other perceptible properties, such as reflectivity, opacity
or texture. For example, special effect compositions may produce a
color shift, such that the color of the coating changes when the
coating is viewed at different angles. Example color effect
compositions are identified in U.S. Pat. No. 6,894,086,
incorporated herein by reference. Additional color effect
compositions may include transparent coated mica and/or synthetic
mica, coated silica, coated alumina, a transparent liquid crystal
pigment, a liquid crystal coating, and/or any composition wherein
interference results from a refractive index differential within
the material and not because of the refractive index differential
between the surface of the material and the air.
[0078] According to the present invention, a photosensitive
composition and/or photochromic composition, which reversibly
alters its color when exposed to one or more light sources, can be
used in a number of layers in the multi-layer composite.
Photochromic and/or photosensitive compositions can be activated by
exposure to radiation of a specified wavelength. When the
composition becomes excited, the molecular structure is changed,
and the altered structure exhibits a new color that is different
from the original color of the composition. When the exposure to
radiation is removed, the photochromic and/or photosensitive
composition can return to a state of rest, in which the original
color of the composition returns. For example, the photochromic
and/or photosensitive composition may be colorless in a non-excited
state and exhibit a color in an excited state. Full color-change
may appear within milliseconds to several minutes, such as from 20
seconds to 60 seconds. Example photochromic and/or photosensitive
compositions include photochromic dyes.
[0079] The photosensitive composition and/or photochromic
composition may be associated with and/or at least partially bound
to, such as by covalent bonding, a polymer and/or polymeric
materials of a polymerizable component. In contrast to some
coatings in which the photosensitive composition may migrate out of
the coating and crystallize into the substrate, the photosensitive
composition and/or photochromic composition associated with and/or
at least partially bound to a polymer and/or polymerizable
component in accordance with the present invention, have minimal
migration out of the coating. Example photosensitive compositions
and/or photochromic compositions and methods for making them are
identified in U.S. patent application Ser. No. 10/892,919 filed
Jul. 16, 2004 and incorporated herein by reference.
[0080] The additional coating layers may be applied by a topcoat
system. The topcoat system may comprise any equipment and/or method
known in the art to apply a topcoat coating composition. For
example, the topcoat system may comprise equipment to apply a
powder coating composition or a liquid coating composition. For
example, the topcoat system may comprise a spray gun, a brush, a
roller, a tank for immersion coating, or combinations thereof. The
topcoat system may optionally further comprise a spraybooth, and
the spraybooth may optionally comprise a ventilation system.
[0081] As mentioned above, the coating composition may be a powder
coating composition. As used herein, "powder coating composition"
refers to a coating composition which is completely free of water
and/or solvent. Accordingly, the powder coating composition
disclosed herein is not synonymous to waterborne and/or
solvent-borne coating compositions known in the art.
[0082] According to the present invention, the powder coating
composition comprises (a) a film forming polymer having a reactive
functional group; and (b) a curing agent that is reactive with the
functional group. Examples of powder coating compositions that may
be used in the present invention include the polyester-based
ENVIROCRON line of powder coating compositions (commercially
available from PPG Industries, Inc.) or epoxy-polyester hybrid
powder coating compositions. Alternative examples of powder coating
compositions that may be used in the present invention include low
temperature cure thermosetting powder coating compositions
comprising (a) at least one tertiary aminourea compound, at least
one tertiary aminourethane compound, or mixtures thereof, and (b)
at least one film-forming epoxy-containing resin and/or at least
one siloxane-containing resin (such as those described in U.S. Pat.
No. 7,470,752, assigned to PPG Industries, Inc. and incorporated
herein by reference); curable powder coating compositions generally
comprising (a) at least one tertiary aminourea compound, at least
one tertiary aminourethane compound, or mixtures thereof, and (b)
at least one film-forming epoxy-containing resin and/or at least
one siloxane-containing resin (such as those described in U.S. Pat.
No. 7,432,333, assigned to PPG Industries, Inc. and incorporated
herein by reference); and those comprising a solid particulate
mixture of a reactive group-containing polymer having a T.sub.g of
at least 30.degree. C. (such as those described in U.S. Pat. No.
6,797,387, assigned to PPG Industries, Inc. and incorporated herein
by reference).
[0083] Suitable film forming polymers that may be used in the
powder coating composition of the present invention comprise a
(poly)ester (e.g., polyester triglycidyl isocyanurate), a
(poly)urethane, an isocyanurate, a (poly)urea, a (poly)epoxy, an
anhydride, an acrylic, a (poly)ether, a (poly)sulfide, a
(poly)amine, a (poly)amide, (poly)vinyl chloride, (poly)olefin,
(poly)vinylidene fluoride, or combinations thereof.
[0084] According to the present invention, the reactive functional
group of the film forming polymer of the powder coating composition
comprises hydroxyl, carboxyl, isocyanate (including blocked
(poly)isocyanate), primary amine, secondary amine, amide,
carbamate, urea, urethane, vinyl, unsaturated ester, maleimide,
fumarate, anhydride, hydroxyl alkylamide, epoxy, or combinations
thereof.
[0085] Suitable curing agents (crosslinking agents) that may be
used in the powder coating composition of present invention
comprise an aminoplast resin, a polyisocyanate, a blocked
polyisocyanate, a polyepoxide, a polyacid, a polyol, or
combinations thereof.
[0086] After deposition of the powder coating composition, the
coating is often heated to cure the deposited composition. The
heating or curing operation is often carried out at a temperature
in the range of from 150.degree. C. to 200.degree. C., such as from
170.degree. C. to 190.degree. C., for a period of time ranging from
10 to 20 minutes. According to the invention, the thickness of the
resultant film is from 50 microns to 125 microns.
[0087] As mentioned above, the coating composition may be a liquid
coating composition. As used herein, "liquid coating composition"
refers to a coating composition which contains a portion of water
and/or solvent. Accordingly, the liquid coating composition
disclosed herein is synonymous to waterborne and/or solvent-borne
coating compositions known in the art.
[0088] According to the present invention, the liquid coating
composition may comprise, for example, (a) a film forming polymer
having a reactive functional group; and (b) a curing agent that is
reactive with the functional group. In other examples, the liquid
coating may contain a film forming polymer that may react with
oxygen in the air or coalesce into a film with the evaporation of
water and/or solvents. These film-forming mechanisms may require or
be accelerated by the application of heat or some type of radiation
such as Ultraviolet or Infrared. Examples of liquid coating
compositions that may be used in the present invention include the
SPECTRACRON.RTM. line of solvent-based coating compositions, the
AQUACRON.RTM. line of water-based coating compositions, and the
RAYCRON.RTM. line of UV cured coatings (all commercially available
from PPG Industries, Inc.).
[0089] Suitable film forming polymers that may be used in the
liquid coating composition of the present invention may comprise a
(poly)ester, an alkyd, a (poly)urethane, an isocyanurate, a
(poly)urea, a (poly)epoxy, an anhydride, an acrylic, a (poly)ether,
a (poly)sulfide, a (poly)amine, a (poly)amide, (poly)vinyl
chloride, (poly)olefin, (poly)vinylidene fluoride, (poly)siloxane,
or combinations thereof.
[0090] According to the present invention, the reactive functional
group of the film forming polymer of the liquid coating composition
may comprise hydroxyl, carboxyl, isocyanate (including blocked
(poly)isocyanate), primary amine, secondary amine, amide,
carbamate, urea, urethane, vinyl, unsaturated ester, maleimide,
fumarate, anhydride, hydroxyl alkylamide, epoxy, or combinations
thereof.
[0091] Suitable curing agents (crosslinking agents) that may be
used in the liquid coating composition of the present invention may
comprise an aminoplast resin, a polyisocyanate, a blocked
polyisocyanate, a polyepoxide, a polyacid, a polyol, or
combinations thereof.
[0092] In addition, a colorant and, if desired, various additives
such as surfactants, wetting agents or catalyst can be included in
the coating composition (electrodepositable, powder, or liquid). As
used herein, the term "colorant" means any substance that imparts
color and/or other opacity and/or other visual effect to the
composition. The colorant can be added to the composition in any
suitable form, such as discrete particles, dispersions, solutions
and/or flakes. A single colorant or a mixture of two or more
colorants can be used.
[0093] Example colorants include pigments, dyes and tints, such as
those used in the paint industry and/or listed in the Dry Color
Manufacturers Association (DCMA), as well as special effect
compositions. A colorant may include, for example, a finely divided
solid powder that is insoluble but wettable under the conditions of
use. A colorant can be organic or inorganic and can be agglomerated
or non-agglomerated. Colorants can be incorporated by use of a
grind vehicle, such as an acrylic grind vehicle, the use of which
will be familiar to one skilled in the art.
[0094] Example pigments and/or pigment compositions include, but
are not limited to, carbazole dioxazine crude pigment, azo,
monoazo, disazo, naphthol AS, salt type (lakes), benzimidazolone,
condensation, metal complex, isoindolinone, isoindoline and
polycyclic phthalocyanine, quinacridone, perylene, perinone,
diketopyrrolo pyrrole, thioindigo, anthraquinone, indanthrone,
anthrapyrimidine, flavanthrone, pyranthrone, anthanthrone,
dioxazine, triarylcarbonium, quinophthalone pigments, diketo
pyrrolo pyrrole red ("DPPBO red"), titanium dioxide, carbon black
and mixtures thereof. The terms "pigment" and "colored filler" can
be used interchangeably.
[0095] Example dyes include, but are not limited to, those that are
solvent and/or aqueous based such as phthalo green or blue, iron
oxide, bismuth vanadate, anthraquinone, perylene, aluminum and
quinacridone.
[0096] Example tints include, but are not limited to, pigments
dispersed in water-based or water miscible carriers such as
AQUA-CHEM 896 commercially available from Degussa, Inc., CHARISMA
COLORANTS and MAXITONER INDUSTRIAL COLORANTS commercially available
from Accurate Dispersions division of Eastman Chemical, Inc.
[0097] As noted above, the colorant can be in the form of a
dispersion including, but not limited to, a nanoparticle
dispersion. Nanoparticle dispersions can include one or more highly
dispersed nanoparticle colorants and/or colorant particles that
produce a desired visible color and/or opacity and/or visual
effect. Nanoparticle dispersions can include colorants such as
pigments or dyes having a particle size of less than 150 nm, such
as less than 70 nm, or less than 30 nm. Nanoparticles can be
produced by milling stock organic or inorganic pigments with
grinding media having a particle size of less than 0.5 mm. Example
nanoparticle dispersions and methods for making them are identified
in U.S. Pat. No. 6,875,800 B2, which is incorporated herein by
reference. Nanoparticle dispersions can also be produced by
crystallization, precipitation, gas phase condensation, and
chemical attrition (i.e., partial dissolution). In order to
minimize re-agglomeration of nanoparticles within the coating, a
dispersion of resin-coated nanoparticles can be used. As used
herein, a "dispersion of resin-coated nanoparticles" refers to a
continuous phase in which is dispersed discreet "composite
microparticles" that comprise a nanoparticle and a resin coating on
the nanoparticle. Example dispersions of resin-coated nanoparticles
and methods for making them are identified in U.S. Patent
Application Publication No. 2005-0287348 A1, filed Jun. 24, 2004,
U.S. Provisional Patent Application Ser. No. 60/482,167 filed Jun.
24, 2003, and U.S. patent application Ser. No. 11/337,062, filed
Jan. 20, 2006, which is also incorporated herein by reference.
[0098] Example special effect compositions that may be used include
pigments and/or compositions that produce one or more appearance
effects such as reflectance, pearlescence, metallic sheen,
phosphorescence, fluorescence, photochromism, photosensitivity,
thermochromism, goniochromism and/or color-change. Additional
special effect compositions can provide other perceptible
properties, such as opacity or texture. According to the invention,
special effect compositions can produce a color shift, such that
the color of the coating changes when the coating is viewed at
different angles. Example color effect compositions are identified
in U.S. Pat. No. 6,894,086, incorporated herein by reference.
Additional color effect compositions can include transparent coated
mica and/or synthetic mica, coated silica, coated alumina, a
transparent liquid crystal pigment, a liquid crystal coating,
and/or any composition wherein interference results from a
refractive index differential within the material and not because
of the refractive index differential between the surface of the
material and the air.
[0099] According to the invention, a photosensitive composition
and/or photochromic composition, which reversibly alters its color
when exposed to one or more light sources, can be used.
Photochromic and/or photosensitive compositions can be activated by
exposure to radiation of a specified wavelength. When the
composition becomes excited, the molecular structure is changed,
and the altered structure exhibits a new color that is different
from the original color of the composition. When the exposure to
radiation is removed, the photochromic and/or photosensitive
composition can return to a state of rest, in which the original
color of the composition returns. According to the invention, the
photochromic and/or photosensitive composition can be colorless in
a non-excited state and exhibit a color in an excited state. Full
color-change can appear within milliseconds to several minutes,
such as from 20 seconds to 60 seconds. Example photochromic and/or
photosensitive compositions include photochromic dyes.
[0100] According to the invention, the photosensitive composition
and/or photochromic composition can be associated with and/or at
least partially bound to, such as by covalent bonding, a polymer
and/or polymeric materials of a polymerizable component. In
contrast to some coatings in which the photosensitive composition
may migrate out of the coating and crystallize into the substrate,
the photosensitive composition and/or photochromic composition
associated with and/or at least partially bound to a polymer and/or
polymerizable component in according to the invention, have minimal
migration out of the coating. Example photosensitive compositions
and/or photochromic compositions and methods for making them are
identified in U.S. patent application Ser. No. 10/892,919, filed
Jul. 16, 2004, incorporated herein by reference.
[0101] In general, the colorant can be present in the coating
composition in any amount sufficient to impart the desired visual
and/or color effect. The colorant may comprise from 1 to 65 weight
percent, such as from 3 to 40 weight percent or 5 to 35 weight
percent, with weight percent based on the total weight of the
composition.
[0102] According to the present invention, the method may
optionally further comprise pretreating the substrate with a
pretreatment composition prior to applying the electrodepositable
coating composition using the electrocoating system. As used
herein, the term "pretreatment composition" refers to a composition
that is capable of reacting with and chemically altering the
substrate surface and binding to it to form a film that affords
corrosion protection. Non-limiting examples of a pretreatment
composition include zinc phosphate pretreatment compositions such
as, for example, those described in U.S. Pat. Nos. 4,793,867 and
5,588,989, zirconium containing pretreatment compositions such as,
for example, those described in U.S. Pat. Nos. 7,749,368 and
8,673,091, and the like. The pretreatment composition may be
brought into contact with the substrate by any of a variety of
known techniques, such as dipping or immersion, spraying,
intermittent spraying, dipping followed by spraying, spraying
followed by dipping, brushing, or roll-coating. According to the
invention, the pretreatment composition when applied to the
substrate may be at a temperature ranging from, for example,
40.degree. F. to 160.degree. F. (4.4.degree. C. to 71.1.degree.
C.), such as 60.degree. F. to 110.degree. F. (15.6.degree. C. to
43.3.degree. C.), such as 70.degree. F. to 90.degree. F.
(21.1.degree. C. to 32.2.degree. C.). For example, the pretreatment
process may be carried out at ambient or room temperature. The
contact time is often from 1 second to 15 minutes, such as 4
minutes to 10 minutes, such as 5 seconds to 4 minutes.
[0103] Following the contacting with the pretreatment composition,
the substrate optionally may be dried in place, e.g., air dried at
room temperature or be dried with hot air, for example, by using an
air knife, by flashing off the water by brief exposure of the
substrate to a high temperature, such as by drying the substrate in
an oven at 15.degree. C. to 100.degree. C., such as 20.degree. C.
to 90.degree. C., or in a heater assembly using, for example,
infrared heat, such as for 10 minutes at 70.degree. C., or by
passing the substrate between squeegee rolls. The substrate surface
may be partially, or in some instances, completely dried prior to
any subsequent contact of the substrate surface with any water,
solutions, compositions, or the like. According to the present
invention, following the contacting with the pretreatment
composition, the substrate (either wet or dried) optionally may be
rinsed with tap water, deionized water, and/or an aqueous solution
of rinsing agents in order to remove any residue and then
optionally may be dried, for example air dried or dried with hot
air as described in the preceding sentence. According to the
present invention, such water rinses may be eliminated and the
substrate (either wet or dried in place) may be contacted with
subsequent treatment compositions.
[0104] The pretreatment composition may be applied to the substrate
by a pretreatment system. The pretreatment system may comprise
tanks for immersion, brushes, rollers, spray guns, or combinations
thereof to apply the pretreatment composition to the substrate. The
pretreatment system may further comprise tanks, brushes, rollers,
spray guns, or combinations thereof for applying rinse
compositions, such as water, to the substrate.
[0105] According to the present invention, the method may
optionally further comprise priming the substrate with a priming
composition prior to applying the electrodepositable coating
composition using the electrocoating system. The priming
composition may be used alone or in combination with the
pretreatment composition or other treatments prior to applying the
electrodepositable coating composition. The priming composition may
comprise a metal-rich coating composition. As used herein, the term
"metal-rich coating composition" refers to film-forming
compositions that include an organic or inorganic binder and at
least 65% by weight metal particles, based on the total solids
weight of the coating composition. As used herein, the term "metal
particles" refers to elemental (i.e., zerovalent) metal and metal
alloy particles. As used herein, the term "particles" refers to
material in the form of particulates, such as powder or dust, as
well as flakes, and may be in the form of any shape, such as, for
example, spherical, ellipsoidal, cubical, rod-shaped, disk-shaped,
prism-shaped, and the like. The metal may comprise zinc, aluminum,
or alloys thereof. The priming composition may be brought into
contact with the substrate by any of a variety of known techniques,
such as dipping or immersion, spraying, electrostatic spraying,
intermittent spraying, dipping followed by spraying, spraying
followed by dipping, brushing, or roll-coating. It is appreciated
that the metal-rich primer coatings can also be applied in dry
forms such as powder or films. The metal-rich primer coatings
formed from the priming composition can be applied to a dry film
thickness of, for example, 2.5 to 500 microns.
[0106] After application of the priming composition to the
substrate, a film formed on the surface of the substrate may be
dried by driving solvent out of the film by heating or by an
air-drying period. Suitable drying conditions will depend on the
particular priming composition and/or application, but an exemplary
drying time of from about 1 to 5 minutes at a temperature of about
60 to 250.degree. F. (15.6 to 121.degree. C.), such as 70 to
212.degree. F. (27 to 100.degree. C.) may be sufficient. More than
one primer coating layer may be applied if desired. Between coats,
the previously applied coat may be flashed; that is, exposed to
ambient conditions for a desired amount of time.
[0107] After application of the priming composition to a substrate,
the applied priming composition may be cured by any means known in
the art. For example, the coating may be subjected to curing
conditions sufficient to cure the priming composition. For example,
the coating composition may be subjected to curing conditions such
as ambient conditions, as discussed above, for a period of hours or
days. Alternatively, the substrate may be subjected to curing
conditions such as radiation (e.g., UV radiation) or heated to a
temperature and for a time sufficient to cure the priming
coating.
[0108] The priming composition may be applied to the substrate by a
priming system. The priming system may comprise tanks for
immersion, brushes, rollers, spray guns, or combinations thereof to
apply the priming composition to the substrate. The priming system
may further comprise tanks, brushes, rollers, spray guns, or
combinations thereof for applying rinse compositions, such as
water, to the substrate.
[0109] According to the present invention, the substrate may
optionally be subjected to other treatments prior to
electrocoating. For example, the substrate may be rinsed, cleaned,
deoxidized, cleaned and deoxidized, anodized, acid pickled, plasma
treated, laser treated, or ion vapor deposition (IVD) treated. At
least a portion of the surface of the substrate may be cleaned by
physical and/or chemical means, such as mechanically abrading the
surface and/or cleaning/degreasing the surface with commercially
available alkaline or acidic cleaning agents that are well known to
those skilled in the art. These optional treatments may be used on
their own or in combination with a pretreatment composition and/or
a priming composition.
[0110] The present invention is also directed towards a substrate
coated using the electrocoating system described above. The
substrate may optionally be coated using the topcoat system.
Accordingly, the substrate comprises an electrocoating layer and an
optional topcoat layer.
[0111] The present invention is also directed towards a substrate
coated using the pretreatment system and electrocoating system,
both as described above. The substrate may optionally be coated
using the topcoat system. Accordingly, the substrate comprises a
pretreatment layer, an electrocoating layer and an optional topcoat
layer.
[0112] The present invention is also directed towards a substrate
coated using the priming system and electrocoating system, both as
described above. The substrate may optionally be coated using the
topcoat system. Accordingly, the substrate comprises a priming
layer, an electrocoating layer and an optional topcoat layer.
[0113] The present invention is also directed towards a substrate
coated using the pretreatment system, priming system and
electrocoating system, each as described above. The substrate may
optionally be coated using the topcoat system. Accordingly, the
substrate comprises a pretreatment layer, a priming layer, an
electrocoating layer and an optional topcoat layer.
[0114] The present invention is also directed towards a substrate
coated according to the method of the present invention.
System for Coating a Substrate
[0115] The present invention is also directed towards a system for
coating a substrate comprising the electrocoating system as
described above. The system for coating a substrate may optionally
further comprise the pretreatment system, the priming system, the
topcoat system, or any combination thereof. For example, the system
for coating a substrate may comprise the pretreatment system for
pretreating the substrate; the priming system for priming the
substrate; the electrocoating system for electrocoating the
substrate; and the topcoat system for applying a topcoat coating to
the substrate. The system for coating a substrate may comprise any
combination of the systems discussed above applied sequentially.
For example, the system for coating a substrate may comprise the
pretreatment system followed by the electrocoat system; the system
for coating a substrate may comprise the pretreatment system
followed by the electrocoat system followed by the topcoat system;
the system for coating a substrate may comprise the priming system
followed by the electrocoat system; the system for coating a
substrate may comprise the priming system followed by the
electrocoat system followed by the topcoat system; the system for
coating a substrate may comprise the pretreatment system followed
by the priming system followed by the electrocoat system; the
system for coating a substrate may comprise the pretreatment system
followed by the priming system followed by the electrocoat system
followed by the topcoat system; or the system for coating a
substrate may comprise the electrocoat system followed by the
topcoat system.
[0116] For purposes of the 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 such as those expressing
values, amounts, percentages, ranges, subranges and fractions may
be read as if prefaced by the word "about," even if the term does
not expressly appear. 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. Where a closed or open-ended
numerical range is described herein, all numbers, values, amounts,
percentages, subranges and fractions within or encompassed by the
numerical range are to be considered as being specifically included
in and belonging to the original disclosure of this application as
if these numbers, values, amounts, percentages, subranges and
fractions had been explicitly written out in their entirety.
[0117] 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.
[0118] As used herein, unless indicated otherwise, a plural term
can encompass its singular counterpart and vice versa, unless
indicated otherwise. For example, although reference is made herein
to "a" pump, "a" recirculating pipe, "a" return conduit, "an"
internal electrode, and "an" external electrode, a combination
(i.e., a plurality) of these components can be used. 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.
[0119] As used herein, "including," "containing" and like terms are
understood in the context of this application to be synonymous with
"comprising" and are therefore open-ended and do not exclude the
presence of additional undescribed or unrecited elements,
materials, ingredients or method steps. As used herein, "consisting
of" is understood in the context of this application to exclude the
presence of any unspecified element, ingredient or method step. As
used herein, "consisting essentially of" is understood in the
context of this application to include the specified elements,
materials, ingredients or method steps "and those that do not
materially affect the basic and novel characteristic(s)" of what is
being described.
[0120] As used herein, the terms "on," "onto," "applied on,"
"applied onto," "formed on," "deposited on," "deposited onto," mean
formed, overlaid, deposited, or provided on but not necessarily in
contact with the surface. For example, an electrodepositable
coating composition "deposited onto" a substrate does not preclude
the presence of one or more other intervening coating layers of the
same or different composition located between the
electrodepositable coating composition and the substrate.
[0121] Whereas specific embodiments of the invention have been
described in detail, it will be appreciated by those skilled in the
art that various modifications and alternatives to those details
could be developed in light of the overall teachings of the
disclosure. Accordingly, the particular arrangements disclosed are
meant to be illustrative only and not limiting as to the scope of
the invention which is to be given the full breadth of the claims
appended and any and all equivalents thereof.
Aspects
[0122] In view of the foregoing, the present invention thus relates
inter alia, without being limited thereto, to the following
aspects:
[0123] 1. An electrocoating system for electrocoating a substrate,
the system comprising a tank configured to hold an
electrodepositable coating composition; at least one pump in fluid
communication with the tank, at least one return conduit connecting
the tank with an inlet of the pump, at least one recirculating pipe
comprising a first end in fluid communication with an outlet of the
pump and a second end having at least one aperture, and the at
least one recirculating pipe comprising at least one external
electrode positioned at least partially outside of the tank,
wherein:
[0124] the substrate has a first surface and a second surface;
[0125] the pump is configured to receive the electrodepositable
coating composition from the return conduit and deliver the
electrodepositable coating composition into the tank through the
recirculating pipe;
[0126] the external electrode is configured to provide an electric
charge to the electrodepositable coating composition; and
[0127] the recirculating pipe is configured to extend into the
interior of the tank and position the aperture of the second end to
deliver at least a portion of the electrically charged
electrodepositable coating composition to the first surface of the
substrate.
[0128] 2. The electrocoating system according to Aspect 1, wherein
the external electrode comprises at least 50% of the recirculating
pipe.
[0129] 3. The electrocoating system according to Aspects 1 or 2,
wherein the external electrode has an internal surface configured
to contact the electrodepositable coating composition, and the
electrocoating system is configured such that a ratio of a total
combined surface area of the external electrode based on the
surface area of the external surface area of the external electrode
to a surface area of the first surface of the substrate is from 1:7
to 1:1.
[0130] 4. The electrocoating system according to any one of the
preceding Aspects, wherein the external electrode comprises a
section of the recirculating pipe located outside of the tank.
[0131] 5. The electrocoating system according to any one of the
preceding Aspects, wherein the second end of the recirculating pipe
comprises at least one nozzle comprising the aperture.
[0132] 6. The electrocoating system according to any one of the
preceding Aspects, wherein the second end of the recirculating pipe
is branched and comprises at least two apertures configured to
deliver at least a portion of the electrodepositable coating
composition charged by the external electrode to different surface
sections of the first surface of the substrate.
[0133] 7. The electrocoating system according to any one of the
preceding Aspects, wherein the recirculating pipe comprises a
plurality of apertures configured to deliver the electrodepositable
coating composition charged by the external electrode to different
sections of the first surface of the substrate.
[0134] 8. The electrocoating system according to any one of Aspects
1-5, wherein the electrocoating system comprises a plurality of
recirculating pipes configured to deliver the electrodepositable
coating composition charged by the external electrode to different
sections of the first surface of the substrate.
[0135] 9. The electrocoating system according to Aspect 8, wherein
the plurality of recirculating pipes is positioned equidistant
along a length of the tank.
[0136] 10. The electrocoating system according to any one of the
preceding Aspects, further comprising at least one internal
electrode positioned inside the tank.
[0137] 11. The electrocoating system according to Aspect 10,
wherein the recirculating pipe comprises a plurality of the
internal electrodes positioned along a length of the tank.
[0138] 12. The electrocoating system according to Aspect 11,
wherein the plurality of internal electrodes is positioned
equidistant along the length of the tank.
[0139] 13. The electrocoating system of any of Aspects 10 to 12,
wherein the electrocoating system is configured such that a ratio
of a total combined surface area of the internal electrode to the
surface area of the second surface of the substrate is from 1:7 to
1:1.
[0140] 14. The electrocoating system according to any one of the
preceding Aspects, further comprising at least one power source to
provide an electrical current to the electrocoating system.
[0141] 15. The electrocoating system according to Aspect 14,
wherein the power source is electrically coupled to the external
electrode, the internal electrode, if present, and the substrate,
wherein the substrate comprises a counter-electrode to the external
electrode and the internal electrode, if present.
[0142] 16. The electrocoating system according to Aspect 15,
wherein the electrical connection to the power source is made such
that the external electrode and internal electrode, if present,
comprise anodes, and the substrate comprises a cathode.
[0143] 17. The electrocoating system according to any one of the
preceding Aspects, wherein the tank, the return conduit, the pump
and the recirculating pipe are directly coupled to form at least
one continuous and uninterrupted loop configured for constrained
flow of the electrodepositable coating composition through the
return conduit, pump and recirculating pipe.
[0144] 18. The electrocoating system according to any one of the
preceding aspects, wherein the tank comprises a base portion and at
least one side wall extending up from the base portion.
[0145] 19. The electrocoating system according to any one of the
preceding Aspects, wherein the substrate comprises an open-polygon
cross-sectional shape.
[0146] 20. The electrocoating system according to any one of the
preceding Aspects, wherein the substrate comprises a rectangular
cross-sectional shape.
[0147] 21. The electrocoating system according to any one of the
preceding Aspects, wherein the substrate is a container.
[0148] 22. The electrocoating system according to any one of the
preceding Aspects, wherein the substrate has a cross-sectional area
of at least 40 m.sup.2.
[0149] 23. A method for coating a substrate comprising
electrophoretically applying a coating deposited from an
electrodepositable coating composition to at least a portion of the
substrate using the electrocoating system according to any one of
preceding Aspects 1 to 18.
[0150] 24. The method according to Aspect 23, wherein the
electrodepositable coating composition comprises a cationic
film-forming resin comprising sulphonium groups.
[0151] 25. The method according to any one of Aspects 23 or 24,
wherein the method further comprises at least partially curing the
electrodepositable coating composition.
[0152] 26. The method according to any one of Aspects 23 to 25,
wherein the method further comprises applying a topcoat coating
composition to at least a portion of the substrate coated with the
electrodepositable coating composition.
[0153] 27. The method according to any one of Aspects 23 to 26,
wherein the method further comprises pretreating the substrate with
a pretreatment composition prior to applying the electrodepositable
coating composition.
[0154] 28. The method according to any of Aspects 23 to 27, wherein
the method further comprises priming the substrate with a priming
composition prior to applying the electrodepositable coating
composition.
[0155] 29. The method according to any one of Aspects 23 to 28,
wherein the substrate comprises an open-polygon cross-sectional
shape or a rectangular cross-sectional shape.
[0156] 30. The method according to any one of Aspects 23 to 29,
wherein the substrate is a container.
[0157] 31. The method according to any one of Aspects 23 to 30,
wherein the substrate has a cross-sectional area of at least 40
m.sup.2.
[0158] 32. A substrate coated by the method according to any one of
preceding Aspects 23 to 31.
[0159] 33. A system for coating a substrate comprising the
electrocoating system according to any one of Aspects 1 to 22, and
further comprising at least one of:
[0160] a pretreatment system for pretreating the substrate prior to
processing the substrate in the electrocoating system;
[0161] a priming system for priming the substrate prior to
processing the substrate in the electrocoating system; and/or
[0162] a topcoat system for applying a topcoat coating to the
substrate after processing the substrate in the electrocoating
system.
[0163] Illustrating the invention are the following examples,
which, however, are not to be considered as limiting the invention
to their details. Unless otherwise indicated, all parts and
percentages in the following examples, as well as throughout the
specification, are by weight.
Prophetic Example
[0164] In this prophetic example, an intermodal shipping container
is coated using the system and method of the present invention. The
intermodal shipping container has four enclosed sides (the top or
roof of the container, two side walls, and an enclosed end), an
opening at the opposing end which is covered by doors (which will
be open during the electrodeposition process), and a floor which
has rows of structural support members crossing over from the long
sides of the container and is not enclosed. The structural supports
are the members which are utilized to attach and support the floor
of the finished container (the floor is installed after painting).
The open-pocket shape of the container makes it difficult to fully
coat the inside surfaces of the container during an
electrodeposition process using standard technology, i.e.,
electrodes positioned along the inside walls of the tank. For the
electrophoresis process to work effectively (coat the entire inside
surface of the container), an electrical potential must be applied
at a rate and voltage potential adequate to initiate and maintain
the electrodeposition process.
[0165] To apply a coating deposited from the electrodepositable
coating composition to all the surfaces of the container, the
container must be fully immersed into an electrocoat bath large
enough to fully immerse the container. For intermodal shipping
containers, the electrocoat bath may exceed 80,000 gallons of
electrodepositable coating composition. The container may be lifted
by the four exterior, top corners by a lifting device (e.g., a
hoist or crane) and positioned above the electrocoat bath. Once in
the proper horizontal position, it will be lowered into the
electrocoat bath with care and manipulated in the tank during the
immersion process to minimize the air bubbles that may form in the
container. It is anticipated that the electrodepositable coating
composition may be maintained at a temperature between 80.degree.
F. and 95.degree. F. Cooling may be required as the
electrodeposition process should generate heat. In addition, anodes
with membranes may be present in the bath to remove acid which is
also released during the electrocoat deposition process. A proper
ratio of bare anode surface area and membrane area will need to be
maintained to provide proper pH control of the bath. The interior
surface, and exposed external surface area of the external
electrode (if the external electrode is an anode) will need to be
included in this calculation.
[0166] The external electrode will be electrically charged in the
same manner as a standard electrode in electrodeposition processes
with the container electrically coupled to the other pole and serve
as a counter-electrode. The applied DC voltage may vary from 100V
to 450V. Amperage will be dependent on coating application rate,
immersion time, coulombic efficiency of the specified
electrodepositable coating composition, application parameters, and
applied thickness. For example, anodes of 316SS may have an
effective electrical capacity of approximately 5 amps per ft.sup.2
of exposed anode area. For cationic electrodeposition, use of the
external anode may effectively double the effective surface area of
each anode. In addition, the fully charged electrodepositable
coating composition that flows through the external anode and
recirculating pipe may carry or drive the electrical energy to the
cathode (i.e., the container) at greater distances than a static
anode wherein the electrodepositable coating composition simply
contacts the surface of the anode. This allows for the
electrodepositable coating composition to coat the inside of the
container where it is difficult to get adequate throwpower because
of the limitations of standard electrocoat systems.
[0167] It will be appreciated by skilled artisans that numerous
modifications and variations are possible in light of the above
disclosure without departing from the broad inventive concepts
described and exemplified herein. Accordingly, it is therefore to
be understood that the foregoing disclosure is merely illustrative
of various exemplary aspects of this application and that numerous
modifications and variations can be readily made by skilled
artisans which are within the spirit and scope of this application
and the accompanying claims.
* * * * *