U.S. patent application number 11/552659 was filed with the patent office on 2007-03-08 for electrodepositable coating compositions and related methods.
This patent application is currently assigned to PPG INDUSTRIES OHIO, INC.. Invention is credited to Donald W. Boyd, Cheng-Hung Hung, James E. Poole, Noel R. Vanier.
Application Number | 20070051634 11/552659 |
Document ID | / |
Family ID | 39217950 |
Filed Date | 2007-03-08 |
United States Patent
Application |
20070051634 |
Kind Code |
A1 |
Poole; James E. ; et
al. |
March 8, 2007 |
ELECTRODEPOSITABLE COATING COMPOSITIONS AND RELATED METHODS
Abstract
An electrodepositable coating composition is provided including
a resinous phase and corrosion resisting particles dispersed in an
aqueous medium. Methods of preparing and using the composition also
are provided.
Inventors: |
Poole; James E.; (Gibsonia,
PA) ; Boyd; Donald W.; (Cheswick, PA) ;
Vanier; Noel R.; (Wexford, PA) ; Hung;
Cheng-Hung; (Wexford, PA) |
Correspondence
Address: |
PPG INDUSTRIES INC;INTELLECTUAL PROPERTY DEPT
ONE PPG PLACE
PITTSBURGH
PA
15272
US
|
Assignee: |
PPG INDUSTRIES OHIO, INC.
3800 West 143rd Street
Cleveland
OH
44111
|
Family ID: |
39217950 |
Appl. No.: |
11/552659 |
Filed: |
October 25, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11213174 |
Aug 26, 2005 |
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11552659 |
Oct 25, 2006 |
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11213136 |
Aug 26, 2005 |
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11552659 |
Oct 25, 2006 |
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Current U.S.
Class: |
205/109 |
Current CPC
Class: |
C09D 5/084 20130101;
C09D 5/4492 20130101 |
Class at
Publication: |
205/109 |
International
Class: |
C25D 15/00 20060101
C25D015/00 |
Claims
1. An electrodepositable coating composition comprising: (a) a
resinous phase comprising: (i) an active hydrogen-containing, ionic
salt group-containing resin; and (ii) at least one curing agent;
and (b) particles having a calculated equivalent spherical diameter
of no more than 200 nanometers and comprising a plurality of
inorganic oxides wherein at least one inorganic oxide comprises
zinc, cerium, yttrium, magnesium, lithium, aluminum, tin, or
calcium.
2. The electrodepositable coating composition of claim 1, wherein
the particles (b) comprise corrosion resisting particles.
3. The electrodepositable coating composition of claim 1, wherein
the particles are selected from (i) particles comprising oxides of
cerium, zinc, and silicon; (ii) particles comprising oxides of
calcium, zinc and silicon; (iii) particles comprising oxides of
phosphorous, zinc and silicon; (iv) particles comprising oxides of
yttrium, zinc, and silicon; (v) particles comprising oxides of
molybdenum, zinc, and silicon; (vi) particles comprising oxides of
boron, zinc, and silicon; (vii) particles comprising oxides of
cerium, aluminum, and silicon, (viii) particles comprising oxides
of magnesium or tin and silica, and (ix) particles comprising
oxides of cerium, boron, and silicon, or a mixture thereof.
4. The electrodepositable coating composition of claim 3, wherein
the particles comprise oxides of cerium, zinc, and silicon.
5. The electrodepositable coating composition of claim 1, wherein
the particles are selected from particles comprising: (i) 10 to 25
percent by weight zinc oxide, 0.5 to 25 percent by weight cerium
oxide, and 50 to 89.5 percent by weight silica; (ii) 10 to 25
percent by weight zinc oxide, 0.5 to 25 percent by weight calcium
oxide, and 50 to 89.5 percent by weight silica; (iii) 10 to 25
percent by weight zinc oxide, 0.5 to 25 percent by weight yttrium
oxide, and 50 to 89.5 percent by weight silica; (iv) 10 to 25
percent by weight zinc oxide, 0.5 to 50 percent by weight
phosphorous oxide, and 25 to 89.5 percent by weight silica; (v) 10
to 25 percent by weight zinc oxide, 0.5 to 50 percent by weight
boron oxide, and 25 to 89.5 percent by weight silica; (vi) 10 to 25
percent by weight zinc oxide, 0.5 to 50 percent by weight
molybdenum oxide, and 25 to 89.5 percent by weight silica; (vii)
0.5 to 25 percent by weight cerium oxide, 0.5 to 50 percent by
weight boron oxide, and 25 to 99 percent by weight silica; (viii)
0.5 to 25 percent by weight cerium oxide, 0.5 to 50 percent by
weight aluminum oxide, and 25 to 99 percent by weight silica; (ix)
0.5 to 75 percent by weight magnesium or tin oxide, and 25 to 99.5
percent by weight silica; (x) 0.5 to 25 percent by weight cerium
oxide, 0.5 to 25 percent by weight zinc oxide, 0.5 to 25 percent by
weight boron oxide, and 25 to 98.5 percent by weight silica; (xi)
0.5 to 25 percent by weight yttrium oxide, 0.5 to 25 percent by
weight phosphorous oxide, 0.5 to 25 percent by weight zinc oxide,
and 25 to 98.5 percent by weight silica; (xii) 0.5 to 5 percent by
weight yttrium oxide, 0.5 to 5 percent by weight molybdenum oxide,
0.5 to 25 percent by weight zinc oxide, 0.5 to 5 percent by weight
cerium oxide and 60 to 98 percent by weight silica; and (xiii)
mixtures thereof, wherein the percent by weights are based on the
total weight of the particles.
6. The electrodepositable coating composition of claim 1, wherein
the particles are prepared by a process comprising: (a) introducing
a reactant into a plasma chamber; (b) heating the reactant by means
of a plasma as the reactant flows through the plasma chamber,
yielding a gaseous reaction product; (c) contacting the gaseous
reaction product with a plurality of quench streams injected into
the reaction chamber through a plurality of quench gas injection
ports, wherein the quench streams are injected at a flow rate and
injection angle that results in the impingement of the quench
streams with each other within the gaseous reaction product stream,
thereby producing ultrafine solid particles; and (d) passing the
ultrafine solid particles through a converging member.
7. The electrodepositable coating composition according to claim 1,
wherein at least a portion of the particles are dispersed in one or
both of the resin (i) and the curing agent (ii) prior to dispersing
the resinous phase in the aqueous medium.
8. The electrodepositable coating composition according to claim 1,
further comprising catalyst particles selected from the group
consisting of bismuth oxide; bismuth silicate; bismuth titanate;
molybdenum oxide; molybdenum silicate; molybdenum titanate;
tungsten oxide; tungsten silicate; tungsten titanate; and
combinations thereof, wherein the catalyst nanoparticles have an
average B.E.T. specific surface area greater than 20 square meters
per gram (m.sup.2/g).
9. The electrodepositable coating composition according to claim 8,
wherein the catalyst particles comprise bismuth oxide.
10. The electrodepositable coating composition according to claim
1, wherein the catalyst nanoparticles are present in the coating
composition in an amount ranging from 0.1 to 5.0 percent by weight
of metal based on weight of total resin solids present in the
electrodepositable coating composition.
11. The electrodepositable coating composition according to claim
1, wherein the resin (a) comprises active hydrogens derived from
reactive hydroxyl groups and/or primary amine groups.
12. The electrodepositable coating composition according to claim
1, wherein the resin (a) comprises the reaction product of a
polyepoxide and a diglycidyl ether of a polyhydric phenol.
13. The electrodepositable coating composition according to claim
1, wherein at least a portion of the active hydrogens present in
the resin (a) comprise primary amine groups derived from the
reaction of a ketimine-containing compound and an epoxy
group-containing material.
14. The electrodepositable coating composition according to claim
1, wherein the curing agent (b) is at least partially blocked with
a blocking agent.
15. The electrodepositable coating composition according to claim
1, which is free of lead-containing compounds.
16. An electrodepositable coating composition comprising: (a) a
resinous phase comprising: (i) an active hydrogen-containing, ionic
salt group-containing resin; and (ii) a curing agent; (b) catalyst
particles selected from the group consisting of bismuth oxide,
bismuth silicate, bismuth titanate, molybdenum oxide, molybdenum
silicate, molybdenum titanate, tungsten oxide, tungsten silicate,
tungsten titanate, or a combination thereof, wherein the catalyst
particles have an average B.E.T. specific surface area greater than
20 square meters per gram; and (c) corrosion resisting particles
having a calculated equivalent spherical diameter of no more than
200 nanometers and comprising a plurality of inorganic oxides
comprising at least one inorganic oxide comprising zinc, cerium,
yttrium, manganese, magnesium, molybdenum, lithium, aluminum, or
calcium.
17. A method for electrocoating a conductive substrate serving as a
cathode in an electrical circuit comprising the cathode and an
anode, the cathode and anode being immersed in an aqueous
electrocoating composition, the method comprising passing electric
current between the cathode and anode to cause deposition of the
electrocoating composition onto the substrate as a substantially
continuous film, the aqueous electrocoating composition comprising
(1) a resinous phase comprising: (a) an active hydrogen
group-containing, ionic group-containing electrodepositable resin;
and (b) a curing agent, and (2) corrosion resisting particles
having a calculated equivalent spherical diameter of no more than
200 nanometers and comprising a plurality of inorganic oxides
wherein at least one inorganic oxide comprises zinc, cerium,
yttrium, magnesium, lithium, aluminum, tin, or calcium.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 11/213,174, which was filed on Aug. 26, 2005
and is entitled, "Electrodepositable Coating Compositions and
Related Methods". This application is also a continuation-in-part
of U.S. patent application Ser. No. 11/213,136, which was filed on
Aug. 26, 2005, and is entitled, "Coating Compositions Exhibiting
Corrosion Resistance Properties, Related Coated Substrates, And
Methods", each of which being incorporated by reference herein.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to electrodepositable coating
compositions comprising a resinous phase and certain catalyst
particles and/or corrosion resisting particles dispersed in an
aqueous medium, to methods of preparing such compositions; and to
methods for applying such compositions.
[0003] The application of a coating by electrodeposition involves
depositing a film-forming composition onto surfaces of an
electrically conductive substrate under the influence of an applied
electrical potential. Electrodeposition has gained prominence in
the coating industry because, in comparison with
non-electrophoretic coating methods, electrodeposition provides
higher paint utilization, excellent corrosion resistance and low
environmental contamination. Early attempts at commercial
electrodeposition processes used anionic electrodeposition where
the workpiece to be coated serves as the anode. However, cationic
electrodeposition has become increasingly popular and today is the
most prevalent method of electrodeposition. While electrodeposited
coatings often provide excellent corrosion resistance, further
improved corrosion resistance performance is sometimes
desirable.
SUMMARY OF THE INVENTION
[0004] In certain respects, the present invention provides
electrodepositable coating compositions comprising a resinous phase
and corrosion resisting particles dispersed in an aqueous medium,
the resinous phase comprising: (a) an active hydrogen-containing,
ionic salt group-containing resin; and (b) at least one curing
agent; and corrosion resisting particles having a calculated
equivalent spherical diameter of no more than 200 nanometers and
comprising a plurality of inorganic oxides. In certain embodiments,
at least one inorganic oxide comprises zinc, cerium, yttrium,
manganese, magnesium, molybdenum, lithium, aluminum, or
calcium.
[0005] In other respects, the present invention is directed to
electrodepositable coating compositions comprising a resinous
phase, catalyst particles, and corrosion resisting particles
dispersed in an aqueous medium, the resinous phase comprising: (a)
a active hydrogen-containing, ionic salt group-containing resin;
and (b) at least one curing agent; the catalyst particles being
selected from the group consisting of bismuth oxide, bismuth
silicate, bismuth titanate, molybdenum oxide, molybdenum silicate,
molybdenum titanate, tungsten oxide, tungsten silicate, tungsten
titanate, or a combination thereof, wherein the catalyst particles
have an average B.E.T. specific surface area greater than 20 square
meters per gram; the corrosion resisting particles having a
calculated equivalent spherical diameter of no more than 200
nanometers and comprising a plurality of inorganic oxides
comprising at least one inorganic oxide comprising zinc, cerium,
yttrium, manganese, magnesium, molybdenum, lithium, aluminum, or
calcium.
[0006] In yet another aspect, the present invention provides
methods for electrocoating a conductive substrate serving as a
cathode in an electrical circuit comprising the cathode and an
anode, the cathode and anode being immersed in an aqueous
electrocoating composition, the methods comprising passing electric
current between the cathode and anode to cause deposition of the
electrocoating composition onto the substrate as a substantially
continuous film, the aqueous electrocoating composition comprising
a resinous phase dispersed in an aqueous medium, the resinous phase
comprising: (a) a active hydrogen group-containing, ionic
group-containing electrodepositable resin; and (b) a curing agent,
and corrosion resisting particles having a calculated equivalent
spherical diameter of no more than 200 nanometers and comprising a
plurality of inorganic oxides. In certain embodiments, at least one
inorganic oxide comprises zinc, cerium, yttrium, manganese,
magnesium, molybdenum, lithium, aluminum, or calcium.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The foregoing summary, as well as the following detailed
description, will be better understood when read in conjunction
with the appended drawings. In the drawings:
[0008] FIGS. 1A and 1B are flow diagrams of certain embodiments of
suitable methods for making nanoparticles in accordance with the
present invention;
[0009] FIGS. 2A and 2B are schematic diagrams of an apparatus for
producing nanoparticles in accordance with certain embodiments of
the present invention;
[0010] FIG. 3 is a perspective view of a plurality of quench gas
injection ports in accordance with certain embodiments of the
present invention.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0011] Other than in the operating examples, or where otherwise
indicated, all numbers expressing quantities of ingredients,
reaction conditions and so forth used in the specification and
claims are to be understood as being modified in all instances by
the term "about". Accordingly, unless indicated to the contrary,
the numerical parameters set forth in the following specification
and attached claims are approximations that may vary depending upon
the desired properties sought 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.
[0012] 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 values, however,
inherently contain certain errors necessarily resulting from the
standard deviation found in their respective testing
measurements.
[0013] Also, it should be understood that any numerical range
recited herein is intended to include all sub-ranges subsumed
therein. For example, a range of "1 to 10" is intended to include
all sub-ranges between and including the recited minimum value of 1
and the recited maximum value of 10, that is, having a minimum
value equal to or greater than 1 and a maximum value of equal to or
less than 10.
[0014] In certain embodiments, the present invention provides
electrodepositable coating compositions comprising a resinous phase
and catalyst particles dispersed in an aqueous medium, the resinous
phase comprising: (a) at least one active hydrogen-containing,
ionic salt group-containing resin; and (b) at least one curing
agent. The catalyst particles effect or facilitate cure between the
resin and the curing agent, as described in detail below.
[0015] The catalyst particles are selected from the group
consisting of bismuth oxide; bismuth silicate; bismuth titanate;
molybdenum oxide; molybdenum silicate; molybdenum titanate;
tungsten oxide; tungsten silicate; tungsten titanate; a combination
of cerium oxide, zinc oxide and silicon dioxide; a combination of
cerium oxide and silicon dioxide; and combinations thereof, such as
composite particles of two or more of these compounds or
combinations.
[0016] In some embodiments, the catalyst particles comprise bismuth
oxide. In other embodiments, the catalyst particles comprise
bismuth oxide and silica. In other embodiments, the catalyst
particles comprise bismuth oxide and bismuth silicate. In other
embodiments, the catalyst particles comprise bismuth oxide, bismuth
silicate and silica.
[0017] In some embodiments, the catalyst particles may be a complex
metal oxide comprising a homogeneous mixture, or solid state
solution of two or more (up to x) metal oxides, labeled MO.sub.1,
MO.sub.2, . . . , MO.sub.x.
[0018] The catalyst particles have an average B.E.T. (Brunauer,
Emmett, and Teller) specific surface area greater than 20 square
meters per gram (m.sup.2/g), in some embodiments greater than 25
square meters per gram (m.sup.2/g), and in other embodiments
greater than 30 m.sup.2/g. In some embodiments, the average BET
specific surface area is less than 300 m.sup.2/g. The BET specific
surface area of particles can be measured by any method well known
to those skilled in the art, such as by nitrogen absorption
according to ASTM D 3663-78 standard based upon the Brunauer,
Emmett, and Teller method described in J. Am. Chem. Soc'y 60, 309
(1938). For example, the BET specific surface area of particles can
be measured using a Gemini Model 2360 surface area analyzer
(available from Micromeritics Instrument Corp. of Norcross,
Ga.).
[0019] In certain embodiments, the catalyst particles have a
calculated equivalent spherical diameter of less than 500
nanometers, in other embodiments less than 100 nanometers and in
still other embodiments less than 50 nanometers. As will be
understood by those skilled in the art, a calculated equivalent
spherical diameter can be determined from the B.E.T. specific
surface area according to the following equation: Diameter
(nanometers)=6000/[BET(m.sup.2/g)*.rho.(grams/cm.sup.3)]
[0020] In certain embodiments, the catalyst particles have an
average primary particle size of less than 500 nanometers. In some
embodiments, the catalyst particles have an average primary
particle size of less than 100 nanometers, and in other embodiments
less than 50 nanometers. In some embodiments, the catalyst
particles have an average primary particle size of less than 30
nanometers and in other embodiments less than 20 nanometers. The
particles typically have an average primary particle size greater
than 1 nm. The average primary particle size can be determined by
visually examining an electron micrograph of a transmission
electron microscopy ("TEM") image, measuring the diameter of the
particles in the image, and calculating the average particle size
("APS") based on the magnification of the TEM image. One of
ordinary skill in the art will understand how to prepare such a TEM
image and determine particle size based on the magnification. The
primary particle size of a particle refers to the smallest diameter
sphere that will completely enclose the particle. As used herein,
the phrase "primary particle size" refers to the size of an
individual particle as opposed to an agglomeration of two or more
individual particles.
[0021] It will be recognized by one skilled in the art that
mixtures of one or more catalyst particles having different average
particle sizes can be incorporated into the compositions in
accordance with the present invention to impart the desired
properties and characteristics to the compositions. For example,
catalyst particles of varying particle sizes can be used in the
compositions according to the present invention.
[0022] The catalyst particles can be present in the coating
composition in an amount sufficient to effect cure of the coating
composition at or below a temperature of 360.degree. F.
(182.2.degree. C.), such as at or below a temperature of
340.degree. F. (171.1.degree. C.), or, in some cases, at or below a
temperature of 320.degree. F. (160.degree. C.), or, in yet other
cases, at or below a temperature of 300.degree. F. (149.degree.
C.). One skilled in the art would understand that the cure
temperature can vary based upon the amount and type of catalyst
particles used.
[0023] In addition to or in lieu of the previously described
catalyst particles, the electrodepositable coating compositions of
the present invention, in certain embodiments, comprise corrosion
resisting particles. As used herein, the term "corrosion resisting
particles" refers to particles which, when included in a coating
composition that is electrodeposited upon a substrate, act to
provide a coating that resists the alteration or degradation of the
substrate, such as by a chemical or electrochemical oxidizing
process, to an extent greater than such a coating would otherwise
resist such alteration or degradation, if electrodeposited from a
similar composition that did not include such particles.
[0024] In certain embodiments, the present invention is directed to
electrodepositable coating compositions that comprise particles
comprising an inorganic oxide, in some embodiments a plurality of
inorganic oxides, such as, for example, zinc oxide (ZnO), magnesium
oxide (MgO), cerium oxide (CeO.sub.2), molybdenum oxide
(MoO.sub.3), and/or silicon dioxide (SiO.sub.2), among others. As
used herein, the term "plurality" means two or more. Therefore,
certain embodiments of coating compositions of the present
invention comprise corrosion resisting particles comprising two,
three, four, or more than four inorganic oxides. In certain
embodiments, these inorganic oxides are present in such particles,
for example, in the form of a homogeneous mixture or a solid-state
solution of the plurality of oxides.
[0025] In certain embodiments of the electrodepositable coating
compositions of the present invention, the particles comprising an
inorganic oxide, or, in certain embodiments, a plurality thereof,
comprise an oxide of zinc, cerium, yttrium, manganese, magnesium,
molybdenum, lithium, aluminum, magnesium, tin, or calcium. In
certain embodiments, the particles comprise an oxide of magnesium,
zinc, cerium, or calcium. In certain embodiments, the particles
also comprise an oxide of boron, phosphorous, silicon, zirconium,
iron, or titanium. In certain embodiments, the particles comprise
silicon dioxide (hereinafter identified as "silica").
[0026] In certain embodiments, the particles, such as corrosion
resisting particles, that are included within certain embodiments
of the electrodepositable coating compositions of the present
invention comprise a plurality of inorganic oxides selected from
(i) particles comprising an oxide of cerium, zinc, and silicon;
(ii) particles comprising an oxide of calcium, zinc and silicon;
(iii) particles comprising an oxide of phosphorous, zinc and
silicon; (iv) particles comprising an oxide of yttrium, zinc, and
silicon; (v) particles comprising an oxide of molybdenum, zinc, and
silicon; (vi) particles comprising an oxide of boron, zinc, and
silicon; (vii) particles comprising an oxide of cerium, aluminum,
and silicon, (viii) particles comprising oxides of magnesium or tin
and silicon, and (ix) particles comprising an oxide of cerium,
boron, and silicon, or a mixture of two or more of particles (i) to
(ix).
[0027] In certain embodiments of the electrodepositable coating
compositions of the present invention, the corrosion resisting
particles comprise 10 to 25 percent by weight zinc oxide, 0.5 to 25
percent by weight cerium oxide, and 50 to 89.5 percent by weight
silica, wherein the percents by weight are based on the total
weight of the particle.
[0028] In other embodiments of the electrodepositable coating
compositions of the present invention, the corrosion resisting
particles comprise 10 to 25 percent by weight zinc oxide, 0.5 to 25
percent by weight calcium oxide, and 50 to 89.5 percent by weight
silica, wherein the percents by weight are based on the total
weight of the particle.
[0029] In still other embodiments of the electrodepositable coating
compositions of the present invention, the corrosion resisting
particles comprise 10 to 25 percent by weight zinc oxide, 0.5 to 25
percent by weight yttrium oxide, and 50 to 89.5 percent by weight
silica, wherein the percents by weight are based on the total
weight of the particle.
[0030] In yet other embodiments of the electrodepositable coating
compositions of the present invention, the corrosion resisting
particles comprise 10 to 25 percent by weight zinc oxide, 0.5 to 50
percent by weight phosphorous oxide, and 25 to 89.5 percent by
weight silica, wherein the percents by weight are based on the
total weight of the particle.
[0031] In some embodiments of the electrodepositable coating
compositions of the present invention, the corrosion resisting
particles comprise 10 to 25 percent by weight zinc oxide, 0.5 to 50
percent by weight boron oxide, and 25 to 89.5 percent by weight
silica, wherein the percents by weight are based on the total
weight of the particle.
[0032] In certain embodiments of the electrodepositable coating
compositions of the present invention, the corrosion resisting
particles comprise 10 to 25 percent by weight zinc oxide, 0.5 to 50
percent by weight molybdenum oxide, and 25 to 89.5 percent by
weight silica, wherein the percents by weight are based on the
total weight of the particle.
[0033] In other embodiments of the electrodepositable coating
compositions of the present invention, the corrosion resisting
particles comprise 0.5 to 25 percent by weight cerium oxide, 0.5 to
50 percent by weight boron oxide, and 25 to 99 percent by weight
silica, wherein the percents by weight are based on the total
weight of the particle.
[0034] In still other embodiments of the electrodepositable coating
compositions of the present invention, the corrosion resisting
particles comprise 0.5 to 25 percent by weight cerium oxide, 0.5 to
50 percent by weight aluminum oxide, and 25 to 99 percent by weight
silica, wherein the percents by weight are based on the total
weight of the particle.
[0035] In yet other embodiments of the electrodepositable coating
compositions of the present invention, the corrosion resisting
particles comprise 0.5 to 25 percent by weight cerium oxide, 0.5 to
25 percent by weight zinc oxide, 0.5 to 25 percent by weight boron
oxide, and 25 to 98.5 percent by weight silica, wherein the
percents by weight are based on the total weight of the
particle.
[0036] In certain embodiments of the electrodepositable coating
compositions of the present invention, the corrosion resisting
particles comprise 0.5 to 25 percent by weight yttrium oxide, 0.5
to 25 percent by weight phosphorous oxide, 0.5 to 25 percent by
weight zinc oxide, and 25 to 98.5 percent by weight silica, wherein
the percents by weight are based on the total weight of the
particle.
[0037] In certain embodiments of the electrodepositable coating
compositions of the present invention, the corrosion resisting
particles comprise 0.5 to 75 percent by weight magnesium or tin
oxide, and 25 to 99.5 percent by weight silica, wherein the
percents by weight are based on the total weight of the
particle.
[0038] In some embodiments of the electrodepositable coating
compositions of the present invention, the corrosion resisting
particles comprise 0.5 to 5 percent by weight yttrium oxide, 0.5 to
5 percent by weight molybdenum oxide, 0.5 to 25 percent by weight
zinc oxide, 0.5 to 5 percent by weight cerium oxide and 60 to 98
percent by weight silica, wherein the percents by weight are based
on the total weight of the particles.
[0039] Certain embodiments of the electrodepositable coating
compositions of the present invention comprise ultrafine particles
comprising an inorganic oxide, or in some embodiments, a plurality
of inorganic oxides. As used herein, the term "ultrafine" refers to
particles that have a B.E.T. specific surface area of at least 10
square meters per gram, such as 30 to 500 square meters per gram,
or, in some cases, 80 to 250 square meters per gram. In certain
embodiments, the coating compositions of the present invention
comprise corrosion resisting particles having a calculated
equivalent spherical diameter of no more than 200 nanometers, such
as no more than 100 nanometers, or, in certain cases, 5 to 50
nanometers.
[0040] Certain embodiments of the electrodepositable coating
compositions of the present invention comprise corrosion resisting
particles having an average primary particle size of no more than
100 nanometers, such as no more than 50 nanometers, or, in certain
embodiments, no more than 20 nanometers.
[0041] When a coating composition of the present invention is in a
liquid medium, the catalyst and/or corrosion resisting particles
may have an affinity for the medium of the composition sufficient
to keep the particles suspended therein. The affinity of the
particles for the medium may be greater than the affinity of the
particles for each other, thereby preventing agglomeration of the
particles within the medium. This property can be due to the nature
of the particles themselves. The particles can also be
substantially free of any surface treatment. In certain
embodiments, the particles used in the composition of the present
invention may be added to the composition neat during the
formulation thereof, and may be added at high loadings without
appreciable viscosity increases, allowing for formulation of high
solids coating compositions.
[0042] The shape (or morphology) of the catalyst and/or corrosion
resisting particles can vary depending upon the specific embodiment
of the present invention and its intended application. For example,
generally spherical morphologies can be used, as well as particles
that are cubic, platy, or acicular (elongated or fibrous). In
general, the particles are substantially spherical in shape.
[0043] The catalyst and/or corrosion resisting particles may be
prepared by various methods, including gas phase synthesis
processes, such as, for example, flame pyrolysis, hot walled
reactor, chemical vapor synthesis, among other methods. In certain
embodiments, however, such particles are prepared by reacting
together one or more organometallic and/or metal oxide precursors
and any other ingredients in a fast quench plasma system. In
certain embodiments, the catalyst and/or corrosion resisting
particles are formed in such a system by: (a) introducing materials
into a plasma chamber; (b) rapidly heating the materials by means
of a plasma to a selection temperature sufficient to yield a
gaseous product stream; (c) passing the gaseous product stream
through a restrictive convergent-divergent nozzle to effect rapid
cooling and/or utilizing an alternative cooling method, such as a
cool surface or quenching stream, and (d) condensing the gaseous
product stream to yield ultrafine solid particles. Certain suitable
fast quench plasma systems and methods for their use are described
in U.S. Pat. Nos. 5,749,937, 5,935,293, and RE 37,853 E, which are
incorporated herein by reference. One process of preparing catalyst
and/or corrosion resisting particles suitable for use in certain
embodiments of the coating compositions of the present invention
comprises: (a) introducing one or more organometallic precursors
and/or inorganic oxide precursors into one axial end of a plasma
chamber; (b) rapidly heating the precursor stream by means of a
plasma to a selected reaction temperature as the precursor stream
flows through the plasma chamber, yielding a gaseous product
stream; (c) passing the gaseous product stream through a
restrictive convergent-divergent nozzle arranged coaxially within
the end of the reaction chamber; and (d) subsequently cooling and
slowing the velocity of the desired end product exiting from the
nozzle, yielding ultrafine solid particles.
[0044] The precursor stream may be introduced to the plasma chamber
as a solid, liquid, gas, or a mixture thereof. Suitable liquid
reactants that may be used as part of the precursor stream include
organometallics, such as, for example, cerium-2 ethylhexanoate,
zinc-2 ethylhexanoate, tetraethoxysilane, calcium methoxide,
triethylphosphate, lithium 2,4-pentanedionate, yttrium butoxide,
trimethoxyboroxine, aluminum sec-butoxide, molybdenum oxide
bis(2,4-pentanedionate), among other materials, including mixtures
thereof. Suitable solid precursors that may be used as part of the
precursor stream include solid silica powder (such as silica fume,
silica sand, or precipitated silica), bismuth oxide; bismuth
silicate; bismuth titanate; molybdenum oxide; molybdenum silicate;
molybdenum titanate; tungsten oxide; tungsten silicate; tungsten
titanate; cerium acetate, cerium oxide, magnesium oxide, tin oxide,
zinc oxide, silicon dioxide and other oxides, among other
materials, including mixtures thereof. The reactant stream may be
introduced to the reaction chamber as a solid, liquid, or gas, but
is usually introduced as solid.
[0045] In certain embodiments, the catalyst and/or corrosion
resisting particles are prepared by a method comprising: (a)
introducing a solid precursor into a plasma chamber; (b) heating
the precursor by means of a plasma to a selected reaction
temperature as the precursor flows through the plasma chamber,
yielding a gaseous product stream; (c) contacting the gaseous
product stream with a plurality of quench streams injected into the
plasma chamber through a plurality of quench gas injection ports,
wherein the quench streams are injected at flow rates and injection
angles that result in the impingement of the quench streams with
each other within the gaseous product stream, thereby producing
ultrafine particles; and (d) passing the ultrafine particles
through a converging member.
[0046] In certain embodiments, the catalyst and/or corrosion
resisting particles are prepared by a method comprising: (a)
introducing a solid precursor into a plasma chamber; (b) heating
the precursor by means of a plasma to a selected reaction
temperature as the precursor flows through the plasma chamber,
yielding a gaseous product stream; (c) passing the gaseous product
stream through a converging member; then (d) contacting the gaseous
product stream with a plurality of quench streams injected into the
plasma chamber through a plurality of quench gas injection ports,
wherein the quench streams are injected at flow rates and injection
angles that result in the impingement of the quench streams with
each other within the gaseous product stream, thereby producing
ultrafine particles; and (e) collecting the ultrafine
particles.
[0047] Referring now to FIGS. 1A and 1B, there are seen flow
diagrams depicting certain embodiments of suitable methods for
making catalyst and/or corrosion resisting particles. As is
apparent, in certain embodiments, at step 100, a solid precursor is
introduced into a feed chamber. As used herein, the term
"precursor" refers to a substance from which a desired product is
formed. Then, as is apparent from FIGS. 1A and 1B at step 200, in
certain embodiments, the solid precursor is contacted with a
carrier. The carrier may be a gas that acts to suspend the solid
precursor in the gas, thereby producing a gas-stream suspension of
the solid precursor. Suitable carrier gases include, but are not
limited to, argon, helium, nitrogen, oxygen, air, hydrogen, or a
combination thereof.
[0048] Next, in certain embodiments, the solid precursor is heated,
at step 300, by means of a plasma to a selected temperature as the
solid precursor flows through the plasma chamber, yielding a
gaseous product stream. In certain embodiments, the temperature
ranges from 2,500.degree. to 20,000.degree. C., such as
1,700.degree. to 8,000.degree. C.
[0049] In certain embodiments, the gaseous product stream may be
contacted with a reactant, such as a hydrogen-containing material,
that may be injected into the plasma chamber, as indicated at step
350. The particular material used as the reactant is not limited
and may include, for example, air, water vapor, hydrogen gas,
ammonia, and/or hydrocarbons, depending on the desired properties
of the resulting catalyst and/or corrosion resisting particles.
[0050] As is apparent from FIG. 1A, in certain embodiments, after
the gaseous product stream is produced, it is, at step 400,
contacted with a plurality of quench streams that are injected into
the plasma chamber through a plurality of quench stream injection
ports, wherein the quench streams are injected at flow rates and
injection angles that result in impingement of the quench streams
with each other within the gaseous product stream. The material
used in the quench streams is not limited, so long as it adequately
cools the gaseous product stream to cause formation of ultrafine
solid particles. Thus, as used herein, the term "quench stream"
refers to a stream that cools the gaseous product stream to such an
extent so as to cause formation of ultrafine particles. Materials
suitable for use in the quench streams include, but are not limited
to, hydrogen gas, carbon dioxide, air, water vapor, ammonia, mono,
di and polybasic alcohols, silicon-containing materials (such as
hexamethyldisilazane), carboxylic acids and/or hydrocarbons.
[0051] The particular flow rates and injection angles of the
various quench streams are not limited, so long as they impinge
with each other within the gaseous product stream to result in the
rapid cooling of the gaseous product stream to produce ultrafine
particles. This is different from certain fast quench plasma
systems that utilize Joule-Thompson adiabatic and isentropic
expansion through, for example, the use of a converging-diverging
nozzle or a "virtual" converging diverging nozzle, to form
ultrafine particles. In these embodiments, the gaseous product
stream is contacted with the quench streams to produce ultrafine
solid catalyst nanoparticles before passing those particles through
a converging member, such as, for example, a converging-diverging
nozzle, which, inter alia, can reduce the fouling or clogging of
the plasma chamber, thereby enabling the production of ultrafine
solid particles from solid reactants without frequent disruptions
in the production process for cleaning of the plasma system. In
these embodiments, the quench streams primarily cool the gaseous
product stream through dilution, rather than adiabatic expansion,
thereby causing a rapid quenching of the gaseous product stream and
the formation of ultrafine solid particles prior to passing the
particles into and through a converging member.
[0052] As used herein, the term "converging member" refers to a
device that includes at least a section or portion that progresses
from a larger diameter to a small diameter in the direction of
flow, thereby restricting passage of a flow therethrough, which can
permit control of the residence time of the flow in the plasma
chamber due to a pressure differential upstream and downstream of
the converging member. In certain embodiments, the converging
member is a conical member, i.e., a member whose base is relatively
circular and whose sides taper towards a point, wherein, in other
embodiments, the converging member is a converging-diverging nozzle
of the type described in U.S. Pat. No. RE 37,853 at col. 9, line 65
to col. 11, line 32, the cited portion of which being incorporated
herein by reference.
[0053] Referring again to FIG. 1A, it is seen that, in certain
embodiments, after contacting the gaseous product stream with the
quench streams to cause production of ultrafine solid particles,
the particles are, at step 500, passed through a converging member,
whereas in other embodiments, as illustrated in FIG. 1B, the
gaseous product stream is passed through a converging member at
step 450 prior to contacting the stream with the quench streams to
cause production of ultrafine particles at step 550. In either of
these embodiments, while the convergent-divergent nozzle may act to
cool the product stream to some degree, the quench streams perform
much of the cooling so that a substantial amount of ultrafine solid
particles are formed upstream of the convergent member in the
embodiments of FIG. 1A or downstream of the converging member in
the embodiments of FIG. 1B. Moreover, in either of these
embodiments, the converging member may primarily act as a choke
position that permits operation of the reactor at higher pressures,
thereby increasing the residence time of the materials therein. The
combination of quench stream dilution cooling with a converging
member appears to provide a commercially viable method of producing
ultrafine solid particles from solid precursors, since, for
example, (i) a solid precursor can be used effectively without
heating the feed material to a gaseous or liquid state before
injection into the plasma, and (ii) fouling of the plasma system
can be minimized, or eliminated, thereby reducing or eliminating
disruptions in the production process for cleaning of the plasma
system.
[0054] As shown in FIGS. 1A and 1B, in certain embodiments, after
the ultrafine solid particles are passed through a converging
member, they are harvested at step 600. Any suitable means may be
used to separate the ultrafine solid particles from the gas flow,
such as, for example, a bag filter or cyclone separator.
[0055] Now referring to FIGS. 2A and 2B, there are depicted
schematic diagrams of an apparatus for producing ultrafine solid
catalyst and/or corrosion resisting particles in accordance with
certain embodiments of the present invention. As is apparent, a
plasma chamber 20 is provided that includes a solid particle feed
inlet 50. Also provided is at least one carrier gas feed inlet 14,
through which a carrier gas flows in the direction of arrow 30 into
the plasma chamber 20. As previously indicated, the carrier gas
acts to suspend the solid reactant in the gas, thereby producing a
gas-stream suspension of the solid reactant which flows towards
plasma 29. Numerals 23 and 25 designate cooling inlet and outlet
respectively, which may be present for a double-walled plasma
chamber 20. In these embodiments, coolant flow is indicated by
arrows 32 and 34. Suitable coolants include both liquids and gasses
depending upon the selected reactor geometry and materials of
construction.
[0056] In the embodiments depicted by FIGS. 2A and 2B, a plasma
torch 21 is provided. Torch 21 vaporizes the incoming gas-stream
suspension of solid reactant within the resulting plasma 29 as the
stream is delivered through the inlet of the plasma chamber 20,
thereby producing a gaseous product stream. As shown in FIGS. 2A
and 2B, the solid particles are, in certain embodiments, injected
downstream of the location where the arc attaches to the annular
anode 13 of the plasma generator or torch.
[0057] A plasma is a high temperature luminous gas which is at
least partially (1 to 100%) ionized. A plasma is made up of gas
atoms, gas ions, and electrons. A thermal plasma can be created by
passing a gas through an electric arc. The electric arc will
rapidly heat the gas to very high temperatures within microseconds
of passing through the arc. The plasma is often luminous at
temperatures above 9000 K.
[0058] A plasma can be produced with any of a variety of gases.
This can give excellent control over any chemical reactions taking
place in the plasma as the gas may be inert, such as argon, helium,
or neon, reductive, such as hydrogen, methane, ammonia, and carbon
monoxide, or oxidative, such as oxygen, nitrogen, and carbon
dioxide. Air, oxygen, and/or oxygen/argon gas mixtures are often
used to produce ultrafine solid particles in accordance with the
present invention. In FIGS. 2A and 2B, the plasma gas feed inlet is
depicted at 31.
[0059] As the gaseous reaction product exits the plasma 29 it
proceeds towards the outlet of the plasma chamber 20. As is
apparent, an additional reactant, as described earlier, can be
injected into the reaction chamber prior to the injection of the
quench streams. A supply inlet for the reactant is shown in FIGS.
2A and 2B at 33.
[0060] As shown in FIGS. 2A and 2B, in certain embodiments, the
gaseous product stream is contacted with a plurality of quench
streams which enter the plasma chamber 20 in the direction of
arrows 41 through a plurality of quench gas injection ports 40
located along the circumference of the plasma chamber 20. As
previously indicated, the particular flow rate and injection angle
of the quench streams is not limited so long as they result in
impingement of the quench streams 41 with each other within the
gaseous reaction product stream, in some cases at or near the
center of the gaseous product stream, to result in the rapid
cooling of the gaseous product stream to produce ultrafine solid
particles. This results in a quenching of the gaseous product
stream through dilution to form ultrafine solid particles.
[0061] Referring now to FIG. 3, there is depicted a perspective
view of a plurality of quench gas injection ports 40 in accordance
with certain embodiments of the present invention. In this
particular embodiment, six (6) quench gas injection ports are
depicted, wherein each port disposed at an angle "0" apart from
each other along the circumference of the reactor chamber 20. It
will be appreciated that "0" may have the same or a different value
from port to port. In certain embodiments of the present invention,
at least four (4) quench gas injection ports 40 are provided, in
some cases at least six (6) quench gas injection ports are present.
In certain embodiments, each angle "0" has a value of no more than
90.degree.. In certain embodiments, the quench streams are injected
into the plasma chamber normal (90.degree. angle) to the flow of
the gaseous reaction product. In some cases, however, positive or
negative deviations from the 90.degree. angle by as much as
30.degree. may be used.
[0062] In certain embodiments, such as is depicted in FIG. 2B, one
or more sheath streams are injected into the plasma chamber
upstream of the converging member. As used herein, the term "sheath
stream" refers to a stream of gas that is injected prior to the
converging member and which is injected at flow rate(s) and
injection angle(s) that result in a barrier separating the gaseous
product stream from the plasma chamber walls, including the
converging portion of the converging member. The material used in
the sheath stream(s) is not limited, so long as the stream(s) act
as a barrier between the gaseous product stream and the converging
portion of the converging member, as illustrated by the prevention,
to at least a significant degree, of material sticking to the
interior surface of the plasma chamber walls, including the
converging member. For example, materials suitable for use in the
sheath stream(s) include, but are not limited to, those materials
described earlier with respect to the quench streams. A supply
inlet for the sheath stream is shown in FIG. 2B at 70 and the
direction of flow is indicated by numeral 71.
[0063] By proper selection of nozzle dimensions, the plasma chamber
20 can be operated at atmospheric pressure, or slightly less than
atmospheric pressure, or, in some cases, at a pressurized
condition, to achieve the desired residence time, while the chamber
26 downstream of the nozzle 22 is maintained at a vacuum pressure
by operation of vacuum pump 60. Following passage through nozzle
22, the ultrafine solid particles may then enter a cool down
chamber 26.
[0064] As is apparent from FIGS. 2A and 2B, in certain embodiments,
the ultrafine solid particles may flow from cool down chamber 26 to
a collection station 27 via a cooling section 45, which may
comprise, for example, a jacket cooled tube. In certain
embodiments, the collection station 27 comprises a bag filter or
other collection means. A downstream scrubber 28 may be used if
desired to condense and collect material within the flow prior to
the flow entering vacuum pump 60.
[0065] In certain embodiments, the residence times for materials
within the plasma chamber 20 are on the order of milliseconds. The
solid precursor may be injected under pressure (such as greater
than 1 to 100 atmospheres) through a small orifice to achieve
sufficient velocity to penetrate and mix with the plasma. In
addition, in many cases the injected stream of solid precursor is
injected normal (90.degree. angle) to the flow of the plasma gases.
In some cases, positive or negative deviations from the 90.degree.
angle by as much as 30.degree. may be desired.
[0066] The high temperature of the plasma rapidly vaporizes the
precursor. There can be a substantial difference in temperature
gradients and gaseous flow patterns along the length of the plasma
chamber 20. It is believed that, at the plasma arc inlet, flow is
turbulent and there is a high temperature gradient; from
temperatures of about 20,000 K at the axis of the chamber to about
375 K at the chamber walls.
[0067] The plasma chamber is often constructed of water cooled
stainless steel, nickel, titanium, copper, aluminum, or other
suitable materials. The plasma chamber can also be constructed of
ceramic materials to withstand a vigorous chemical and thermal
environment.
[0068] The plasma chamber walls may be internally heated by a
combination of radiation, convection and conduction. In certain
embodiments, cooling of the plasma chamber walls prevents unwanted
melting and/or corrosion at their surfaces. The system used to
control such cooling should maintain the walls at as high a
temperature as can be permitted by the selected wall material,
which often is inert to the materials within the plasma chamber at
the expected wall temperatures. This is true also with regard to
the nozzle walls, which may be subjected to heat by convection and
conduction.
[0069] The length of the plasma chamber is often determined
experimentally by first using an elongated tube within which the
user can locate the target threshold temperature. The plasma
chamber can then be designed long enough so that precursors have
sufficient residence time at the high temperature to reach an
equilibrium state and complete the formation of the desired end
products.
[0070] The inside diameter of the plasma chamber 20 may be
determined by the fluid properties of the plasma and moving gaseous
stream. It should be sufficiently great to permit necessary gaseous
flow, but not so large that recirculating eddies or stagnant zones
are formed along the walls of the chamber. Such detrimental flow
patterns can cool the gases. In many cases, the inside diameter of
the plasma chamber 20 is more than 100% of the plasma diameter at
the inlet end of the plasma chamber.
[0071] The catalyst particles described in detail above can be
present in the electrodepositable coating composition of the
present invention in an amount of at least 0.1 percent by weight of
metal (bismuth, molybdenum, tungsten, etc.) based on weight of
total resin solids present in the electrodepositable coating
composition. Also, the catalyst particles can be present in the
electrodepositable coating composition of the present invention in
an amount less than or equal to 5.0 percent by weight metal, often
less than or equal to 3.0 percent by weight metal, and typically
less than or equal to 1.0 percent by weight metal based on weight
of total resin solids present in the electrodepositable coating
composition. The level of catalyst particles present in the
electrodepositable coating composition can range between any
combination of these values, inclusive of the recited values. The
catalyst is present in an amount sufficient to effect cure
(determined by a method described in detail below) of the
composition at a temperature at or below 360.degree. F.
(182.2.degree. C.).
[0072] As used herein, the term "cure" as used in connection with a
composition, e.g., "composition when cured" or a "cured
composition", shall mean that any crosslinkable components of the
composition are at least partially crosslinked. In certain
embodiments of the present invention, the crosslink density of the
crosslinkable components, i.e., the degree of crosslinking, ranges
from 5% to 100% of complete crosslinking. In other embodiments, the
crosslink density ranges from 35% to 85% of full crosslinking. In
other embodiments, the crosslink density ranges from 50% to 85% of
full crosslinking. One skilled in the art will understand that the
presence and degree of crosslinking, i.e., the crosslink density,
can be determined by a variety of methods, such as dynamic
mechanical thermal analysis (DMTA) using a TA Instruments DMA 2980
DMTA analyzer conducted under nitrogen. This method determines the
glass transition temperature and crosslink density of free films of
coatings or polymers. These physical properties of a cured material
are related to the structure of the crosslinked network. In certain
embodiments of the present invention, the sufficiency of cure is
evaluated relative to the solvent resistance of the cured film. For
example, solvent resistance can be measured by determining the
number of double acetone rubs. For purposes of the present
invention, a coating is deemed to be "cured" when the film can
withstand a minimum of 100 double acetone rubs without substantial
softening of the film and no removal of the film.
[0073] The catalyst particles described herein are substantially
non-volatile at the curing temperature, that is, at temperatures at
or below 360.degree. F. (182.2.degree. C.). By "substantially
non-volatile" is meant that the catalyst particles do not
volatilize from the film into the curing oven environment at these
temperatures during the curing process.
[0074] In certain embodiments, one or more of the previously
described corrosion resisting particles are present in a coating
composition of the present invention in an amount of 3 to 50
percent by volume, such as 8 to 30 percent by volume, or, in some
cases, 10 to 18 percent by volume, based on the total volume of the
coating composition.
[0075] As aforementioned, in addition to the catalyst and/or
corrosion resisting particles, the electrodepositable coating
compositions of the present invention also comprise a resinous
phase comprising (a) one or more active hydrogen-containing, ionic
salt group-containing resins, and (b) one or more curing
agents.
[0076] In some embodiments, the active hydrogen-containing, ionic
salt group-containing resin is a cationic resin, for example such
as is typically derived from a polyepoxide and can be prepared by
reacting together a polyepoxide and a polyhydroxyl group-containing
material selected from alcoholic hydroxyl group-containing
materials and phenolic hydroxyl group-containing materials to chain
extend or build the molecular weight of the polyepoxide. The
reaction product can then be reacted with a cationic salt group
former to produce the cationic resin.
[0077] A chain extended polyepoxide typically is prepared as
follows: the polyepoxide and polyhydroxyl group-containing material
are reacted together neat or in the presence of an inert organic
solvent such as a ketone, including methyl isobutyl ketone and
methyl amyl ketone, aromatics such as toluene and xylene, and
glycol ethers such as the dimethyl ether of diethylene glycol. The
reaction typically is conducted at a temperature of 80.degree. C.
to 160.degree. C. for 30 to 180 minutes until an epoxy
group-containing resinous reaction product is obtained.
[0078] The equivalent ratio of reactants; i.e., epoxy:polyhydroxyl
group-containing material is typically from 1.00:0.50 to
1.00:2.00.
[0079] The polyepoxide typically has at least two 1,2-epoxy groups.
In general, the epoxide equivalent weight of the polyepoxide will
range from 100 to 2000, such as from 180 to 500. The epoxy
compounds may be saturated or unsaturated, cyclic or acyclic,
aliphatic, alicyclic, aromatic or heterocyclic. They may contain
substituents such as halogen, hydroxyl, and ether groups.
[0080] Examples of suitable polyepoxides are those having a
1,2-epoxy equivalency greater than one, such as two; that is,
polyepoxides which have on average two epoxide groups per molecule.
In some cases, the preferred polyepoxides are polyglycidyl ethers
of polyhydric alcohols such as cyclic polyols, such as polyglycidyl
ethers of polyhydric phenols such as Bisphenol A. These
polyepoxides can be produced by etherification of polyhydric
phenols with an epihalohydrin or dihalohydrin, such as
epichlorohydrin or dichlorohydrin, in the presence of alkali.
Besides polyhydric phenols, other cyclic polyols can be used in
preparing the polyglycidyl ethers of cyclic polyols, such as
alicyclic polyols, including cycloaliphatic polyols, such as
1,2-cyclohexane diol and 1,2-bis(hydroxymethyl)cyclohexane. In some
cases, the preferred polyepoxides have epoxide equivalent weights
ranging from 180 to 2000, such as from 186 to 1200. Epoxy
group-containing acrylic polymers can also be used. These polymers
often have an epoxy equivalent weight ranging from 750 to 2000.
[0081] Examples of polyhydroxyl group-containing materials used to
chain extend or increase the molecular weight of the polyepoxide
(i.e., through hydroxyl-epoxy reaction) include alcoholic hydroxyl
group-containing materials and phenolic hydroxyl group-containing
materials. Examples of alcoholic hydroxyl group-containing
materials are simple polyols, such as neopentyl glycol; polyester
polyols, such as those described in U.S. Pat. No. 4,148,772;
polyether polyols, such as those described in U.S. Pat. No.
4,468,307; and urethane diols, such as those described in U.S. Pat.
No. 4,931,157. Examples of phenolic hydroxyl group-containing
materials are polyhydric phenols, such as Bisphenol A,
phloroglucinol, catechol, and resorcinol. Mixtures of alcoholic
hydroxyl group-containing materials and phenolic hydroxyl
group-containing materials may be used.
[0082] As indicated, the active hydrogen-containing resin can
contain cationic salt groups, which can be incorporated into the
resin molecule as follows: The resinous reaction product prepared
as described above is further reacted with a cationic salt group
former. By "cationic salt group former" is meant a material which
is reactive with epoxy groups and which can be acidified before,
during, or after reaction with the epoxy groups 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.
[0083] When amines are used as the cationic salt formers,
monoamines typically are employed. Hydroxyl-containing amines are
suitable, and polyamines also may be used.
[0084] Tertiary and secondary amines are used more often than
primary amines because primary amines are polyfunctional with
respect to epoxy groups and have a greater tendency to gel the
reaction mixture. If polyamines or primary amines are used, they
should be used in a substantial stoichiometric excess to the epoxy
functionality in the polyepoxide so as to prevent gelation and the
excess amine should be removed from the reaction mixture by vacuum
stripping or other technique at the end of the reaction. The epoxy
may be added to the amine to ensure excess amine.
[0085] Examples of hydroxyl-containing amines include, but are not
limited to, alkanolamines, dialkanolamines, alkyl alkanolamines,
and aralkyl alkanolamines containing from 1 to 18 carbon atoms,
preferably 1 to 6 carbon atoms in each of the alkanol, alkyl and
aryl groups. Specific examples include ethanolamine,
N-methylethanolamine, diethanolamine, N-phenylethanolamine,
N,N-dimethylethanolamine, N-methyldiethanolamine,
3-aminopropyldiethanolamine, and N-(2-hydroxyethyl)-piperazine.
[0086] Amines such as mono, di, and trialkylamines and mixed
aryl-alkyl amines which do not contain hydroxyl groups or amines
substituted with groups other than hydroxyl may also be used.
Specific examples include ethylamine, methylethylamine,
triethylamine, N-benzyldimethylamine, dicocoamine,
3-dimethylaminopropylamine, and N,N-dimethylcyclohexylamine.
[0087] Mixtures of the above mentioned amines may also be used.
[0088] The reaction of a primary and/or secondary amine with the
polyepoxide takes place upon mixing of the amine and polyepoxide.
The amine may be added to the polyepoxide or vice versa. The
reaction can be conducted neat or in the presence of a suitable
solvent such as methyl isobutyl ketone, xylene, or
1-methoxy-2-propanol. The reaction is generally exothermic and
cooling may be desired. However, heating to a moderate temperature
of 50 to 150.degree. C. may be done to hasten the reaction.
[0089] The reaction product of the primary and/or secondary amine
and the polyepoxide is made cationic and water dispersible by at
least partial neutralization with an acid. Suitable acids include
organic acids, such as formic acid, acetic acid, methanesulfonic
acid, and lactic acid, and inorganic acids, such as phosphoric acid
and sulfamic acid, which refers to sulfamic acid itself or
derivatives thereof; i.e., an acid of the formula: ##STR1## wherein
R is hydrogen or an alkyl group having 1 to 4 carbon atoms.
Mixtures of the above mentioned acids may also be used.
[0090] The extent of neutralization of the cationic
electrodepositable composition varies with the particular reaction
product involved. However, sufficient acid should be used to
disperse the electrodepositable composition in water. Typically,
the amount of acid used provides at least 20 percent of all of the
total neutralization. Excess acid may also be used beyond the
amount required for 100 percent total neutralization.
[0091] In the reaction of a tertiary amine with a polyepoxide, the
tertiary amine can be pre-reacted with the neutralizing acid to
form the amine salt and then the amine salt reacted with the
polyepoxide to form a quaternary salt group-containing resin. The
reaction is conducted by mixing the amine salt with the polyepoxide
in water. Typically, the water is present in an amount ranging from
1.75 to 20 percent by weight based on total reaction mixture
solids.
[0092] In forming the quaternary ammonium salt group-containing
resin, the reaction temperature can be varied from the lowest
temperature at which the reaction will proceed, generally room
temperature or slightly thereabove, to a maximum temperature of
100.degree. C. (at atmospheric pressure). At higher pressures,
higher reaction temperatures may be used. Preferably, the reaction
temperature is in the range of 60 to 100.degree. C. Solvents such
as a sterically hindered ester, ether, or sterically hindered
ketone may be used.
[0093] In addition to the primary, secondary, and tertiary amines
disclosed above, a portion of the amine that is reacted with the
polyepoxide can be a ketimine of a polyamine, such as is described
in U.S. Pat. No. 4,104,147, column 6, line 23 to column 7, line 23.
The ketimine groups decompose upon dispersing the amine-epoxy resin
reaction product in water. In certain embodiments, at least a
portion of the active hydrogens present in the resin (a) comprise
primary amine groups derived from the reaction of a
ketimine-containing compound and an epoxy group-containing
material, such as those described above.
[0094] In addition to resins containing amine salts and quaternary
ammonium salt groups, cationic resins containing ternary sulfonium
groups may be used in the composition of the present invention.
Examples of these resins and their method of preparation are
described in U.S. Pat. Nos. 3,793,278 and 3,959,106.
[0095] Suitable active hydrogen-containing, cationic salt
group-containing resins can include copolymers of one or more alkyl
esters of acrylic acid or methacrylic acid optionally together with
one or more other polymerizable ethylenically unsaturated monomers.
Suitable alkyl esters of acrylic acid or methacrylic acid include
methyl methacrylate, ethyl methacrylate, butyl methacrylate, ethyl
acrylate, butyl acrylate, and 2-ethyl hexyl acrylate. Suitable
other copolymerizable ethylenically unsaturated monomers include
nitriles, such acrylonitrile and methacrylonitrile, vinyl and
vinylidene halides, such as vinyl chloride and vinylidene fluoride
and vinyl esters, such as vinyl acetate. Acid and anhydride
functional ethylenically unsaturated monomers, such as acrylic
acid, methacrylic acid or anhydride, itaconic acid, maleic acid or
anhydride, or fumaric acid may be used. Amide functional monomers
including acrylamide, methacrylamide, and N-alkyl substituted
(meth)acrylamides are also suitable. Vinyl aromatic compounds such
as styrene and vinyl toluene can be used.
[0096] Functional groups such as hydroxyl and amino groups can be
incorporated into the acrylic polymer by using functional monomers,
such as hydroxyalkyl acrylates and methacrylates or aminoalkyl
acrylates and methacrylates. Epoxide functional groups (for
conversion to cationic salt groups) may be incorporated into the
acrylic polymer by using functional monomers, such as glycidyl
acrylate and methacrylate, 3,4-epoxycyclohexylmethyl(meth)acrylate,
2-(3,4-epoxycyclohexyl)ethyl(meth)acrylate, or allyl glycidyl
ether. Alternatively, epoxide functional groups may be incorporated
into the acrylic polymer by reacting carboxyl groups on the acrylic
polymer with an epihalohydrin or dihalohydrin, such as
epichlorohydrin or dichlorohydrin.
[0097] The acrylic polymer can be prepared by traditional free
radical initiated polymerization techniques, such as solution or
emulsion polymerization, as known in the art, using suitable
catalysts which include organic peroxides and azo type compounds
and optionally chain transfer agents, such as alpha-methyl styrene
dimer and tertiary dodecyl mercaptan. Additional acrylic polymers
which are suitable for forming the active hydrogen-containing,
cationic resin, which can be used in the electrodepositable
compositions of the present invention, include the resins described
in U.S. Pat. Nos. 3,455,806 and 3,928,157.
[0098] Polyurethanes can also be used as the polymer from which the
active hydrogen-containing, cationic resin can be derived. Among
the polyurethanes which can be used are polymeric polyols which are
prepared by reacting polyester polyols or acrylic polyols, such as
those mentioned above, with a polyisocyanate such that the OH/NCO
equivalent ratio is greater than 1:1 so that free hydroxyl groups
are present in the product. Smaller polyhydric alcohols, such as
those disclosed above for use in the preparation of the polyester,
may also be used in place of or in combination with the polymeric
polyols.
[0099] Additional examples of polyurethane polymers suitable for
forming the active hydrogen-containing, cationic resin are the
polyurethane, polyurea, and poly(urethane-urea) polymers prepared
by reacting polyether polyols and/or polyether polyamines with
polyisocyanates, as described in U.S. Pat. No. 6,248,225.
[0100] Epoxide functional groups may be incorporated into the
polyurethane by, for example, reacting glycidol with free
isocyanate groups. Alternatively, hydroxyl groups on the
polyurethane can be reacted with an epihalohydrin or dihalohydrin
such as epichlorohydrin or dichlorohydrin in the presence of
alkali.
[0101] Sulfonium group-containing polyurethanes can also be made by
at least partial reaction of hydroxy-functional sulfide compounds,
such as thiodiglycol and thiodipropanol, which results in
incorporation of sulfur into the backbone of the polymer. The
sulfur-containing polymer is then reacted with a monofunctional
epoxy compound in the presence of acid to form the sulfonium group.
Appropriate monofunctional epoxy compounds include ethylene oxide,
propylene oxide, glycidol, phenylglycidyl ether, and CARDURA.RTM.
E, available from Resolution Performance Products.
[0102] Besides the above-described polyepoxide, acrylic and
polyurethane polymers, the active hydrogen-containing, cationic
salt group-containing polymer can be derived from a polyester. Such
polyesters can be prepared in a known manner by condensation of
polyhydric alcohols and polycarboxylic acids. Suitable polyhydric
alcohols include, for example, ethylene glycol, propylene glycol,
butylene glycol, 1,6-hexylene glycol, neopentyl glycol, diethylene
glycol, glycerol, trimethylol propane, and pentaerythritol.
Examples of suitable polycarboxylic acids used to prepare the
polyester include succinic acid, adipic acid, azelaic acid, sebacic
acid, maleic acid, fumaric acid, phthalic acid, tetrahydrophthalic
acid, hexahydrophthalic acid, and trimellitic acid. Besides the
polycarboxylic acids mentioned above, functional equivalents of the
acids such as anhydrides where they exist or lower alkyl esters of
the acids such as the methyl esters may be used.
[0103] The polyesters contain a portion of free hydroxyl groups
(resulting from the use of excess polyhydric alcohol and/or higher
polyols during preparation of the polyester) which are available
for cure reactions. Epoxide functional groups may be incorporated
into the polyester by reacting carboxyl groups on the polyester
with an epihalohydrin or dihalohydrin such as epichlorohydrin or
dichlorohydrin.
[0104] Sulfonium salt groups can be introduced by the reaction of
an epoxy group-containing polymer of the types described above with
a sulfide in the presence of an acid, as described in U.S. Pat.
Nos. 3,959,106 and 4,715,898. Sulfonium groups can be introduced
onto the polyester backbones described using similar reaction
conditions.
[0105] It should be understood that the active hydrogens associated
with the cationic resin include any active hydrogens which are
reactive with isocyanates at temperatures sufficient to cure the
electrodepositable composition as previously discussed, i.e., at
temperatures at or below 360.degree. F. (182.2.degree. C.). The
active hydrogens typically are derived from reactive hydroxyl
groups, and primary and secondary amino, including mixed groups
such as hydroxyl and primary amino. In one embodiment of the
present invention, at least a portion of the active hydrogens are
derived from hydroxyl groups comprising phenolic hydroxyl groups.
The cationic resin can have an active hydrogen content of 1 to 4
milliequivalents, such as 2 to 3 milliequivalents, of active
hydrogen per gram of resin solids.
[0106] The extent of cationic salt group formation should be such
that when the resin is mixed with an aqueous medium and other
ingredients, a stable dispersion of the electrodepositable
composition will form. By "stable dispersion" is meant one that
does not settle or is easily redispersible if some settling occurs.
Moreover, the dispersion should be of sufficient cationic character
that the dispersed resin particles will electrodeposit on a cathode
when an electrical potential is set up between an anode and a
cathode immersed in the aqueous dispersion.
[0107] Generally, the cationic resin in the electrodepositable
composition of the present invention contains from 0.1 to 3.0, such
as from 0.1 to 0.7, milliequivalents of cationic salt group per
gram of resin solids. The cationic resin typically is non-gelled,
having a number average molecular weight ranging from 2000 to
15,000, such as from 5000 to 10,000. By "non-gelled" is meant that
the resin is substantially free from crosslinking, and prior to
cationic salt group formation, the resin has a measurable intrinsic
viscosity when dissolved in a suitable solvent. In contrast, a
gelled resin, having an essentially infinite molecular weight,
would have an intrinsic viscosity too high to measure.
[0108] The active hydrogen-containing, cationic salt
group-containing resin can be present in the electrodepositable
composition of the present invention in an amount ranging from 40
to 95 weight percent, such as from 50 to 75 weight percent based on
weight of total resin solids present in the composition.
[0109] The electrodepositable compositions of the present invention
also comprise at least one curing agent, such as a polyisocyanate,
polyester or carbonate. The polyisocyanate curing agent may be a
fully blocked polyisocyanate with substantially no free isocyanate
groups, or it may be partially blocked and reacted with the resin
backbone as described in U.S. Pat. No. 3,984,299. The
polyisocyanate can be an aliphatic or an aromatic polyisocyanate or
a mixture of the two. Diisocyanates are often preferred, although
higher polyisocyanates can be used in place of or in combination
with diisocyanates.
[0110] Examples of suitable aliphatic diisocyanates are straight
chain aliphatic diisocyanates, such as 1,4-tetramethylene
diisocyanate, norbornane diisocyanate, and 1,6-hexamethylene
diisocyanate. Also, cycloaliphatic diisocyanates can be employed,
such as isophorone diisocyanate and 4,4'-methylene-bis-(cyclohexyl
isocyanate). Examples of suitable aromatic diisocyanates are
p-phenylene diisocyanate, diphenylmethane-4,4'-diisocyanate and
2,4- or 2,6-toluene diisocyanate. Examples of suitable higher
polyisocyanates are triphenylmethane-4,4',4''-triisocyanate,
1,2,4-benzene triisocyanate and polymethylene polyphenyl
isocyanate, and trimers of 1,6-hexamethylene diisocyanate.
[0111] Isocyanate prepolymers, for example, reaction products of
polyisocyanates with polyols such as neopentyl glycol and
trimethylol propane or with polymeric polyols such as
polycaprolactone diols and triols (NCO/OH equivalent ratio greater
than one) can also be used. A mixture of
diphenylmethane-4,4'-diisocyanate and polymethylene polyphenyl
isocyanate can be used.
[0112] Any suitable alcohol or polyol can be used as a blocking
agent for the polyisocyanate in the electrodepositable compositions
of the present invention provided that the agent will deblock at
the curing temperature and provided a gelled product is not formed.
Any suitable aliphatic, cycloaliphatic, or aromatic alkyl alcohol
may be used as a blocking agent for the polyisocyanate including,
for example, lower aliphatic monoalcohols, such as methanol,
ethanol, and n-butanol; cycloaliphatic alcohols such as
cyclohexanol; aromatic-alkyl alcohols such as phenyl carbinol and
methylphenyl carbinol. Glycol ethers 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.
[0113] In certain embodiments, the blocking agent comprises a
1,3-glycol and/or a 1,2-glycol. In certain embodiments, the
blocking agent comprises a 1,2-glycol, such as one or more C.sub.3
to C.sub.6 1,2-glycols. For example, the blocking agent can be
selected from at least one of 1,2-propanediol, 1,3-butanediol,
1,2-butanediol, 1,2-pentanediol and 1,2-hexanediol.
[0114] Other suitable blocking agents include oximes, such as
methyl ethyl ketoxime, acetone oxime and cyclohexanone oxime and
lactams, such as epsilon-caprolactam.
[0115] In some embodiments, the curing agent comprises one or more
polyester curing agents. Suitable polyester curing agents include
materials having greater than one ester group per molecule. The
ester groups are present in an amount sufficient to effect
cross-linking at acceptable cure temperatures and cure times, for
example at temperatures up to 250.degree. C., and curing times of
up to 90 minutes. Acceptable cure temperatures and cure times will
be dependent upon the substrates to be coated and their end
uses.
[0116] Compounds generally suitable as the polyester curing agent
are polyesters of polycarboxylic acids, including
bis(2-hydroxyalkyl)esters of dicarboxylic acids, such as
bis(2-hydroxybutyl)azelate and bis(2-hydroxyethyl)terephthalate;
tri(2-ethylhexanoyl)trimellitate; and poly(2-hydroxyalkyl)esters of
acidic half-esters prepared from a dicarboxylic acid anhydride and
an alcohol, including polyhydric alcohols. The latter type is
suitable to provide a polyester with a final functionality of more
than 2. One suitable example includes a polyester prepared by first
reacting equivalent amounts of the dicarboxylic acid anhydride (for
example, succinic anhydride or phthalic anhydride) with a trihydric
or tetrahydric alcohol, such as glycerol, trimethylolpropane or
pentaerythritol, at temperatures below 150.degree. C., and then
reacting the acidic polyester with at least an equivalent amount of
an epoxy alkane, such as 1,2-epoxy butane, ethylene oxide, or
propylene oxide. The polyester curing agent (ii) can comprise an
anhydride. Another suitable polyester comprises a lower
2-hydroxy-akylterminated poly-alkyleneglycol terephthalate.
[0117] In some embodiments, the polyester comprises at least one
ester group per molecule in which the carbon atom adjacent to the
esterified hydroxyl has a free hydroxyl group.
[0118] Also suitable is the tetrafunctional polyester prepared from
the half-ester intermediate prepared by reacting trimellitic
anhydride and propylene glycol (molar ratio 2:1), then reacting the
intermediate with 1,2-epoxy butane and the glycidyl ester of
branched monocarboxylic acids.
[0119] In some embodiments, where the active hydrogen-containing
resin comprises cationic salt groups, the polyester curing agent is
substantially free of acid. For purposes of the present invention,
by "substantially free of acid" is meant having less than 0.2 meq/g
acid. For aqueous systems, for example for cathodic
electrodepositable coating compositions, suitable polyester curing
agents can include non-acidic polyesters prepared from a
polycarboxylic acid anhydride, one or more glycols, alcohols,
glycol mono-ethers, polyols, and/or monoepoxides. Suitable
polycarboxylic anhydrides can include dicarboxylic acid anhydrides,
such as succinic anhydride, phthalic anhydride, tetrahydrophthalic
anhydride, trimellitic anhydride, hexahydrophthalic anhydride,
methylhexahydrophthalic anhydride,
3,3',4,4'-benzophenonetetracarboxylic dianhydride, and pyromellitic
dianhydride. Mixtures of anhydrides can be used. Suitable alcohols
can include linear, cyclic or branched alcohols. The alcohols may
be aliphatic, aromatic or araliphatic in nature. As used herein,
the terms glycols and mono-epoxides are intended to include
compounds containing not more than two alcohol groups per molecule
which can be reacted with carboxylic acid or anhydride functions
below the temperature of 150.degree. C.
[0120] Suitable mono-epoxides can include glycidyl esters of
branched monocarboxylic acids. Further, alkylene oxides, such as
ethylene oxide or propylene oxide, may be used. Suitable glycols
can include, for example, ethylene glycol and polyethylene glycols,
propylene glycol and polypropylene glycols, and 1,6-hexanediol.
Mixtures of glycols may be used.
[0121] Non-acidic polyesters can be prepared, for example, by
reacting, in one or more steps, trimellitic anhydride (TMA) with
glycidyl esters of branched monocarboxylic acids in a molar ratio
of 1:1.5 to 1:3, if desired with the aid of an esterification
catalyst, such as stannous octoate or benzyl dimethyl amine, at
temperatures of 50-150.degree. C. Also, trimellitic anhydride can
be reacted with 3 molar equivalents of a monoalcohol, such as
2-ethylhexanol.
[0122] Alternatively, trimellitic anhydride can be reacted first
with a glycol or a glycol monoalkyl ether, such as ethylene glycol
monobutyl ether, in a molar ratio of 1:0.5 to 1:1, after which the
product is allowed to react with 2 moles of glycidyl esters of
branched monocarboxylic acids. Furthermore, the polycarboxylic acid
anhydride i.e., those containing two or three carboxyl functions
per molecule, or a mixture of polycarboxylic acid anhydrides can be
reacted simultaneously with a glycol, such as 1,6-hexane diol
and/or glycol mono-ether and monoepoxide, after which the product
can be reacted with mono-epoxides, if desired. For aqueous
compositions these non-acid polyesters can also be modified with
polyamines, such as diethylene triamine, to form amide polyesters.
Such "amine-modified" polyesters may be incorporated in the linear
or branched amine adducts described above to form self-curing amine
adduct esters.
[0123] The non-acidic polyesters of the types described above often
are soluble in organic solvents, and often can be mixed readily
with the previously described active hydrogen-containing resin.
[0124] Polyesters suitable for use in an aqueous system or mixtures
of such materials disperse in water typically in the presence of
resins comprising cationic or anionic salt groups.
[0125] In some embodiments, the curing agent comprises one or more
cyclic or acyclic carbonates. Non-limiting examples of suitable
acyclic carbonates include dimethyl carbonate, diethyl carbonate,
methylethyl carbonate, dipropyl carbonate, methylpropyl carbonate,
and/or dibutyl carbonate.
[0126] In certain embodiments, the curing agent is present in the
electrodepositable composition in an amount ranging from 5 to 60
percent by weight, such as from 25 to 50 percent by weight, based
on total weight of resin solids.
[0127] It should be understood that the catalyst and/or corrosion
resisting particles can be incorporated into the electrodepositable
composition of the present invention by any method or means
provided that the stability of the composition is not compromised.
For example, such particles can be admixed with or dispersed in the
reactants used to form the resin (a) during preparation of the
resin (a). Also, such particles can be admixed with or dispersed in
one or more of the reactants used to form the resin (a) prior to
resin preparation. In addition, such particles can be admixed with
or dispersed in the resin (a) either prior to or subsequent to
neutralization with an acid. The particles also can be admixed with
or dispersed in the at least partially blocked polyisocyanate
curing agent (b) prior to combining the resin (a) and the curing
agent (b). Further, the particles can be admixed with or dispersed
in the admixture of the resin (a) and the curing agent (b).
Alternatively, the particles can be added to any of the optional
additives, solvents, or adjuvant resinous materials as described
below prior to addition of the optional ingredients to the
composition. Also, the particles can be directly admixed with or
dispersed in the aqueous medium, prior to dispersion of the
resinous phase in the aqueous medium. The particles also can be
added neat to the electrodepositable composition subsequent to
dispersion in the aqueous medium. Additionally, if desired, the
particles can be added on-line to the electrodeposition bath in the
form of an additive material.
[0128] The electrodepositable composition of the present invention
may contain a coalescing solvent such as hydrocarbons, alcohols,
esters, ethers and ketones. The coalescing solvent is usually
present in an amount up to 40 percent by weight, typically ranging
from 0.05 to 25 percent by weight based on total weight of the
electrodepositable composition.
[0129] The electrodepositable compositions of the present invention
may further contain conventional pigments and various other
optional additives such as plasticizers, surfactants, wetting
agents, defoamers, and anti-cratering agents, as well as adjuvant
resinous materials different from the resin (a) and the curing
agent (b).
[0130] Suitable pigments include, but are not limited to, iron
oxides, lead oxides, carbon black, coal dust, titanium dioxide,
talc, clay, silica, and barium sulfate, as well as color pigments
such as cadmium yellow, cadmium red, chromium yellow, and the like.
The pigment content of the aqueous dispersion, generally expressed
as the pigment to resin (or pigment to binder) ratio is often
0.05:1 to 1:1. In certain embodiments, the electrodepositable
coating composition of the present invention is free of
lead-containing compounds.
[0131] The electrodepositable coating compositions of the present
invention are used in an electrodeposition process in the form of
an aqueous dispersion. By "dispersion" is meant a two-phase
transparent, translucent, or opaque aqueous resinous system in
which the resin, pigment, and water insoluble materials are in the
dispersed phase while water and water-soluble materials comprise
the continuous phase. The dispersed phase can have an average
particle size of less than 10 microns, and can be less than 5
microns. The aqueous dispersion can contain at least 0.05 and
usually 0.05 to 50 percent by weight resin solids, depending on the
particular end use of the dispersion.
[0132] The electrodepositable compositions of certain embodiments
of the present invention in the form of an aqueous dispersion have
excellent storage stability, that is, upon storage at a temperature
of 140.degree. F. (60.degree. C.) for a period of 14 days, the
compositions are stable. By "stable dispersion" is meant herein
that the resinous phase and the nanoparticulate catalyst remain
uniformly dispersed throughout the aqueous phase of the
composition. Upon storage under the conditions described above, the
dispersions do not flocculate or form a hard sediment. If over time
some sedimentation occurs, it can be easily re-dispersed with low
shear stirring.
[0133] In certain processes of electrodeposition, the
electrodepositable composition of the present invention in the form
of an aqueous dispersion is placed in contact with an electrically
conductive anode and cathode, where the substrate serves as the
cathode. Upon passage of an electric current between the anode and
cathode while they are in contact with the aqueous dispersion, an
adherent film of the electrodepositable composition will deposit in
a substantially continuous manner on the cathode. The film will
contain the active hydrogen-containing resin, the blocked
polyisocyanate curing agent, the catalyst, and the optional
additives from the non-aqueous phase of the dispersion.
[0134] The thickness of the electrodepositable coating applied to
the substrate can vary based upon such factors as the type of
substrate and intended use of the substrate, i.e., the environment
in which the substrate is to be placed and the nature of the
contacting materials.
[0135] In yet other embodiments, the present invention is directed
to a coated substrate comprising a substrate and a composition
coated over the substrate, wherein the composition is selected from
any of the foregoing compositions. In still other embodiments, the
present invention is directed to a method of coating a substrate
which comprises applying a composition over the substrate, wherein
the composition is selected from any of the foregoing compositions.
In other embodiments, the present invention is directed to a method
for forming a cured coating on a substrate comprising applying over
the substrate a coating composition, wherein the composition is
selected from any of the foregoing compositions.
[0136] In other embodiments, the present invention is directed to a
method of coating a substrate further comprising a step of curing
the composition after application to the substrate. The components
used to form the compositions in these embodiments can be selected
from the components discussed above, and additional components also
can be selected from those recited above.
[0137] As used herein, a composition "over a substrate" refers to a
composition directly applied to at least a portion of the
substrate, as well as a composition applied to any coating material
which was previously applied to at least a portion of the
substrate.
[0138] Electrodeposition is usually carried out at a constant
voltage in the range of from 1 volt to several thousand volts,
typically between 50 and 500 volts. Current density is usually
between 1.0 ampere and 15 amperes per square foot (10.8 to 161.5
amperes per square meter) and tends to decrease quickly during the
electrodeposition process, indicating formation of a continuous
self-insulating film. Any electroconductive substrate known in the
art, especially metal substrates such as steel, zinc, aluminum,
copper, magnesium or the like can be coated with the
electrodepositable composition of the present invention. It is
customary to pretreat the substrate with a phosphate conversion,
usually a zinc phosphate conversion coating, followed by a rinse
which seals the conversion coating.
[0139] After deposition, the coating is often heated to cure the
deposited composition. The heating or curing operation can be
carried out at a temperature in the range of from 250 to
400.degree. F. (121.1 to 204.4.degree. C.), typically from 300 to
360.degree. F. (148.8 to 182.2.degree. C.), for a period of time
ranging from 1 to 60 minutes. The thickness of the resultant film
often ranges from 10 to 50 microns.
[0140] The invention will be further described by reference to the
following examples. Unless otherwise indicated, all parts and
percentages are by weight.
EXAMPLES
Particle Example 1
[0141] Particles were prepared using a DC thermal plasma system.
The plasma system included a DC plasma torch (Model SG-100 Plasma
Spray Gun commercially available from Praxair Technology, Inc.,
Danbury, Conn.) operated with 80 standard liters per minute of
argon carrier gas and 24 kilowatts of power delivered to the torch.
A liquid precursor feed composition comprising the materials and
amounts listed in Table 1 was prepared and fed to the reactor at a
rate of 5 grams per minute through a gas assisted liquid nebulizer
located 3.7 inches down stream of the plasma torch outlet. At the
nebulizer, a mixture of 4.9 standard liters per minute of argon and
10.4 standard liters per minute oxygen were delivered to assist in
atomization of the liquid precursors. Additional oxygen at 28
standard liters per minute was delivered through a 1/8 inch
diameter nozzle located 180.degree. apart from the nebulizer.
Following a 6 inch long reactor section, a plurality of quench
stream injection ports were provided that included 61/8 inch
diameter nozzles located 60.degree. apart radially. A 10 millimeter
diameter converging-diverging nozzle of the type described in U.S.
Pat. No. RE 37,853E was provided 4 inches downstream of the quench
stream injection port. Quench air was injected through the
plurality of quench stream injection ports at a rate of 100
standard liters per minute. TABLE-US-00001 TABLE 1 Material Amount
Cerium 2-ethylhexanoate.sup.1 163 grams Zinc 2-ethylhexanoate.sup.2
311 grams Tetraethoxysilane.sup.3 1056 grams .sup.1Commercially
available from Alfa Aesar, Ward Hill, Massachusetts.
.sup.2Commercially available from Alfa Aesar, Ward Hill,
Massachusetts. .sup.3Commercially available from Sigma Aldrich Co.,
St Louis, Missouri.
[0142] The produced particles had a theoretical composition of 18
weight percent zinc oxide, 6 weight percent cerium oxide, and 76
weight percent silica. The measured B.E.T. specific surface area
was 201 square meters per gram using the Gemini model 2360 analyzer
and the calculated equivalent spherical diameter was 23
nanometers.
Particle Example 2
[0143] Particles from liquid precursors were prepared using the
apparatus and conditions identified in Example 1 and the feed
materials and amounts listed in Table 2. TABLE-US-00002 TABLE 2
Material Amount Calcium methoxide.sup.4 116 grams Butanol 116 grams
2-ethylhexanoic acid 582 grams Tetraethoxysilane.sup.3 820 grams
.sup.4Commercially available from Sigma Aldrich Co., St Louis,
Missouri.
[0144] The produced particles had a theoretical composition of 21
weight percent calcium oxide, and 76 weight percent silica. The
measured B.E.T. specific surface area was 106 square meters per
gram using the Gemini model 2360 analyzer and the calculated
equivalent spherical diameter was 27 nanometers.
Particle Example 3
[0145] Particles from liquid precursors were prepared using the
apparatus and conditions identified in Example 1 and the feed
materials and amounts listed in Table 3. TABLE-US-00003 TABLE 3
Material Amount Cerium 2-ethylhexanoate.sup.1 41 grams
Trimethoxyboroxine.sup.5 50 grams Zinc 2-ethylhexanoate.sup.2 78
grams Tetraethoxysilane.sup.3 229 grams Hexanes.sup.6 76 grams
Methyl ethyl ketone 182 grams .sup.5Commercially available from
Alfa Aesar, Ward Hill, Massachusetts. .sup.6Commercially available
from Sigma Aldrich Co., St Louis, Missouri.
[0146] The produced particles had a theoretical composition of 6
weight percent cerium oxide, 10 weight percent boron oxide, 18
weight percent zinc oxide, and 66 weight percent silica. The
measured B.E.T. specific surface area was 175 square meters per
gram using the Gemini model 2360 analyzer and the calculated
equivalent spherical diameter was 13 nanometers.
Particle Example 4
[0147] Particles from liquid precursors were prepared using the
apparatus and conditions identified in Example 1 and the feed
materials and amounts listed in Table 4. TABLE-US-00004 TABLE 4
Material Amount Calcium methoxide.sup.4 55 grams Butanol 55 grams
2-ethylhexanoic acid 273 grams Zinc 2-ethylhexanoate.sup.2 160
grams Tetraethoxysilane.sup.3 809 grams
[0148] The produced particles had a theoretical composition of 10
weight percent calcium oxide, 12.3 weight percent zinc oxide, and
77.7 weight percent silica. The measured B.E.T. specific surface
area was 124 square meters per gram using the Gemini model 2360
analyzer and the calculated equivalent spherical diameter was 34
nanometers.
Example 5
[0149] A resinous composition was prepared from the ingredients of
Table 5: TABLE-US-00005 TABLE 5 Component Description Mass (/g) A
methyl isobutyl ketone 174.39 Tinuvin 1130.sup.7 17.68 B ethyl
acrylate 384.11 Styrene 294.00 Hydroxypropyl methacrylate 94.85
methyl methacrylate 33.19 glycidyl methacrylate 142.28 t-dodecyl
mercaptan 4.73 Vazo 67.sup.8 23.70 Dowanol PNB.sup.9 30.36 Dowanol
PM.sup.10 15.17 methyl isobutyl ketone 12.30 C Luperoxl 7M50.sup.11
19.01 Dowanol PNB 15.17 methyl isobutyl ketone 7.58 D
Diethanolamine 85.37 E DETA diketimine.sup.12 71.52 F
crosslinker.sup.13 1055.34 G sulfamic acid 60.68 deionized water
5547.04 .sup.7Light stabilizer available from Ciba Geigy
Corporation. .sup.82,2'-azobis(2-methylbutyronotrile) available
from Du Pont Specialty Chemicals. .sup.9N-butoxypropanol solvent
available from Dow Chemical Co. .sup.10Propylene glycol monomethyl
ether solvent available from Dow Chemical Co. .sup.1150% t-butyl
peroxyacetate in mineral spirits available from Arkema Inc.
.sup.12Diketimine formed from diethylene triamine and
methylisobutyl ketone (72.69% solids in methylisobutyl ketone).
.sup.13Blocked isocyanate curing agent, 79.5% solids in
methylisobutyl ketone. Prepared by reacting 10 equivalents of
isophorone diisocyanate with 1 equivalent of trimethylol propane, 3
equivalents of bisphenol A-ethylene oxide polyol (prepared at a
bisphenol A to ethylene oxide molar ratio of 1:6) and 6 equivalents
of primary hydroxy from 1,2-butane diol.
[0150] Components A were raised to reflux in a 3 liter flask fitted
with a stirrer, thermocouple, nitrogen inlet and a Dean and Stark
condenser. The temperature was adjusted throughout the process to
maintain reflux until noted otherwise. Components B were added at a
uniform rate over 150 minutes. After a further 30 minutes
components C were added over 10 minutes. 90 minutes later component
D was added followed, 90 minutes later by component E. After 60
minutes component F was added and the temperature was allowed to
fall to 105.degree. C. over 60 minutes.
[0151] Meanwhile components G were heated to 50.degree. C. in a
separate vessel. 2381.5 g of the reaction mixture were then poured
into components G under rapid agitation. The resulting dispersion
had a solids content of 25%.
[0152] Solvent was removed from the dispersion by distillation
under reduced pressure. The final dispersion had a solid content of
27.9%
Example 6
[0153] Pigment pastes 6A to 6E were prepared from the ingredients
of Table 6: TABLE-US-00006 TABLE 6 Ingredient Example 6A Example 6B
Example 6C Example 6D Example 6E Grind vehicle.sup.14 402.7 g 402.7
g 402.7 g 402.7 g 402.7 g Surfynol GA.sup.15 8.4 g 8.4 g 8.4 g 8.4
g 8.4 g pH additive.sup.16 13.2 g 13.2 g 13.2 g 13.2 g 13.2 g
Deionized water 110.1 g 110.1 g 110.1 g 110.1 g 110.1 g Titanium
dioxide 384.7 g 384.7 g 384.7 g 384.7 g 384.7 g Carbon black 6.9 g
6.9 g 6.9 g 6.9 g 6.9 g Clay 117.5 g -- -- -- -- Particle Example 1
-- 117.5 g -- -- -- Particle Example 2 -- -- 117.5 g -- -- Particle
Example 3 -- -- -- 117.5 g -- Particle Example 4 -- -- -- -- 117.5
g Dibutyl tin oxide 220.4 g 220.4 g 220.4 g 220.4 g 220.4 g paste
.sup.14A grind vehicle as described in Example 2 of United States
Patent No. 4,715,898 with 2 percent by weight on solids of Icomeen
T-2 (commercially available from BASF) added. .sup.15A surfactant
commercially available from Air Products and Chemicals, Inc.
.sup.16A 22% solution of lactic acid in deionized water.
[0154] The ingredients were milled in a Redhead mill using ceramic
media to a Hegman gauge reading of 7.
Example 7
[0155] Electrodepositable compositions were prepared from the
pigment pastes of Examples 6A and 6B from the ingredients of Table
7: TABLE-US-00007 TABLE 7 Ingredient Example 7A Example 7B Resin of
Example 5 1222.0 g 1222.0 g Plasticizer 15.9 g 15.9 g
Polyepoxide.sup.17 98.6 g 98.6 g Deionized water 100.0 g 100.0 g
Cationic epoxy resin.sup.18 784.5 g 784.5 g Example 6A 251.0 g --
Example 6B -- 251.0 g E-6278.sup.19 6.6 g 6.6 g Deionized water
1321.4 g 1321.4 g .sup.17A polyoxyalkylenepolyamine-polyepoxide
adduct derived from Jeffamine D400 (polyoxypropylenediamine
commercially available from Huntsman Corp.) and DER-732 (aliphatic
epoxide commercially available from Dow Chemical Co.) prepared as
described in U. S. Pat. No. 4,423,166. .sup.18Prepared as described
in Example H of United States Patent Application Publication
2003/0054193A1. .sup.19A dibutyl tin oxide containing pigment paste
commercially available from PPG Industries, Inc.
[0156] The 22 percent solids compositions of Examples 7A and 7B
which contained 1.5% tin level of weight of resin solids were
ultrafiltered with 20 percent by weight of the composition being
replaced with deionized water. CRS and EG panels were cathodically
electrodeposited in the composition at 0.9 mils thickness. The
coated panel was cured at 360.degree. F. (182.2.degree. C.) for 25
minutes. The cured coating was smooth, uniform and had good solvent
resistance. The coated panels were subjected to corrosion testing
according to General Motors Test Method GM9540P (GM APG scab
corrosion). This test measures loss of paint, adhesion and
corrosion of the base metal across a scribe line on the coated
panel after exposure to repeated cycles. After 20 cycles on the
bare substrates and 40 cycles on the phosphated substrates, the
coated panels are examined for corrosion creepback from the scribe
line. Results are reported in millimeters (mm) of creepage. Results
are reported in Table 8 with replicates. TABLE-US-00008 TABLE 8
Commercial Substrate/Cycles Control Example 7A Example 7B Bare
CRS/20 cycles 23/23 22/23 3-6/4-8 Bare EG/20 cycles 5-10/3-8
2-5/2-5 1-3/1-2 Phosphated CRS/40 cycles 4-5/4-5 4-5/4-5 3-4/2-4
Phosphated EG/40 cycles 1-3/1-2 1-3/1-2 1-2/1-2
[0157] It will be appreciated by those skilled in the art that
changes could be made to the embodiments described above without
departing from the broad inventive concept thereof. Whereas
particular embodiments of this invention have been described above
for purposes of illustration, it will be evident to those skilled
in the art that numerous variations of the details of the present
invention may be made without departing from the invention as
defined in the appended claims.
* * * * *