U.S. patent application number 11/213174 was filed with the patent office on 2007-03-01 for electrodepositable coating compositions and related methods.
Invention is credited to Cheng-Hung Hung, Alan J. Kaylo, Gregory J. McCollum, Noel R. Vanier, Michael White.
Application Number | 20070045116 11/213174 |
Document ID | / |
Family ID | 37802513 |
Filed Date | 2007-03-01 |
United States Patent
Application |
20070045116 |
Kind Code |
A1 |
Hung; Cheng-Hung ; et
al. |
March 1, 2007 |
Electrodepositable coating compositions and related methods
Abstract
An electrodepositable coating composition is provided including
a resinous phase and catalyst nanoparticles dispersed in an aqueous
medium, the resinous phase including (a) at least one active
hydrogen-containing, ionic salt group-containing resin; and (b) at
least one curing agent; and the catalyst nanoparticles for
effecting cure between the resin (a) and the curing agent (b). The
catalyst nanoparticles have an average BET specific surface area
greater than 20 square meters per gram (m.sup.2/g). Methods of
preparing and using the composition also are provided.
Inventors: |
Hung; Cheng-Hung; (Wexford,
PA) ; Kaylo; Alan J.; (Glenshaw, PA) ;
McCollum; Gregory J.; (Gibsonia, PA) ; Vanier; Noel
R.; (Wexford, PA) ; White; Michael; (Oswego,
IL) |
Correspondence
Address: |
PPG INDUSTRIES, INC.;Law Dept. - Intellectual Property
One PPG Place
Pittsburgh
PA
15272
US
|
Family ID: |
37802513 |
Appl. No.: |
11/213174 |
Filed: |
August 26, 2005 |
Current U.S.
Class: |
204/471 |
Current CPC
Class: |
C09D 5/4496
20130101 |
Class at
Publication: |
204/471 |
International
Class: |
C25B 7/00 20060101
C25B007/00 |
Claims
1. An electrodepositable coating composition comprising a resinous
phase and catalyst nanoparticles dispersed in an aqueous medium,
the resinous phase comprising: (a) a active hydrogen-containing,
ionic salt group-containing resin; and (b) a curing agent; and the
catalyst nanoparticles for effecting cure between the resin (a) and
the curing agent (b), the catalyst nanoparticles 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; a
combination of cerium oxide, zinc oxide and silicon dioxide; a
combination of cerium oxide and silicon dioxide; 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).
2. The electrodepositable coating composition according to claim 1,
wherein at least a portion of the catalyst nanoparticles are
dispersed in one or both of the resin (a) and the curing agent (b)
prior to dispersing the resinous phase in the aqueous medium.
3. The electrodepositable coating composition according to claim 1,
wherein the catalyst nanoparticles comprise bismuth oxide.
4. The electrodepositable coating composition according to claim 1,
wherein the catalyst nanoparticles comprise bismuth oxide and
bismuth silicate.
5. The electrodepositable coating composition according to claim 1,
wherein the catalyst nanoparticles further comprise silica.
6. The electrodepositable coating composition according to claim 1,
wherein the catalyst nanoparticles have an average B.E.T. specific
surface area greater than 25 square meters per gram
(m.sup.2/g).
7. The electrodepositable coating composition according to claim 6,
wherein the catalyst nanoparticles have an average B.E.T. specific
surface area greater than 30 square meters per gram
(m.sup.2/g).
8. The electrodepositable coating composition according to claim 1,
wherein the catalyst nanoparticles have an average primary particle
size of less than 500 nanometers.
9. The electrodepositable coating composition according to claim 1,
wherein the catalyst nanoparticles are present in the
electrodepositable coating composition in an amount sufficient to
effect cure of the electrodepositable composition at a temperature
at or below 360.degree. F. (182.2.degree. C.).
10. The electrodepositable coating composition according to claim
1, wherein the catalyst nanoparticles are present in the
electrodepositable coating composition in an amount sufficient to
effect cure of the electrodepositable composition at a temperature
at or below 340.degree. F. (171.1.degree. C.).
11. The electrodepositable coating composition according to claim
1, wherein the catalyst nanoparticles are present in the coating
composition in an amount sufficient to effect cure of the coating
composition at or below a temperature of 320.degree. F.
(160.degree. C.).
12. 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.
13. The electrodepositable coating composition according to claim
1, wherein the catalyst further comprises dioctyltin oxide and/or
its derivatives.
14. The electrodepositable coating composition according to claim
1, wherein the catalyst is substantially non-volatile at a
temperature at or below 360.degree. F. (182.2.degree. C.).
15. 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.
16. The electrodepositable coating composition according to claim
1, wherein the resin (a) compresses the reaction product of a
polyepoxide and a diglycidyl ether of a polyhydric phenol.
17. 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.
18. The electrodepositable coating composition according to claim
1, wherein the curing agent (b) is at least partially blocked with
a blocking agent.
19. The electrodepositable coating composition according to claim
1, which is free of lead-containing compounds.
20. 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
a resinous phase and catalyst nanoparticles dispersed in an aqueous
medium, the resinous phase comprising: (a) a active
hydrogen-containing, ionic salt group-containing resin; and (b) a
curing agent; and the catalyst nanoparticles for effecting cure
between the resin (a) and the curing agent (b), the catalyst
nanoparticles 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; a combination of cerium oxide, zinc
oxide and silicon dioxide; a combination of cerium oxide and
silicon dioxide; 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).
Description
BACKGROUND OF THE INVENTION
[0001] I. Field of the Invention
[0002] The present invention relates to cationic electrodepositable
coating compositions comprising a resinous phase and certain
catalyst nanoparticles dispersed in an aqueous medium, wherein the
catalyst nanoparticles have a specified B.E.T. specific surface
area to methods of preparing such compositions; and to methods for
applying such compositions.
[0003] II. Technical Considerations
[0004] The application of a coating by electrodeposition involves
depositing a film-forming composition onto the 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.
[0005] Many cationic electrodeposition compositions in use today
are based on active hydrogen-containing resins derived from a
polyepoxide and a capped or blocked polyisocyanate curing agent.
Typically, these cationic electrodeposition compositions also
contain organotin catalysts to lower the temperature at which the
blocking agent is released from blocked polyisocyanate and to
activate cure of the electrodeposition composition.
[0006] Most of the common dialkyltin oxide catalysts are high
melting, amorphous solid materials which must be introduced into
the composition in the form of a catalyst paste prepared by
dispersing the solid catalyst into a pigment wetting resin under
extremely high shear conditions. Preparation of stable catalyst
pastes can be very costly and time intensive. Further, it has been
noted that some of the aforementioned organotin catalysts can cause
a multitude of surface defects in the cured electrodeposited
coating composition. For example, dibutyltin oxide dispersions can
flocculate in the electrodeposition bath, resulting in oversized
dibutyltin oxide agglomerates or particles which can settle in
areas of the electrodeposition tank where agitation is poor. This
flocculation phenomenon constitutes a loss of catalyst from the
coating composition resulting in poor cure response. Moreover, the
flocculate particles can settle in the uncured electrodeposited
coating causing localized "hot spots" or pinholes in the surface of
the cured coating. Also, electrodeposition bath stability can be
adversely affected with the use of some organotin catalysts. It has
been observed that soft, floating foams can form from a mixture of
organotin catalyst, polyisocyanate curing agent and microscopic air
bubbles.
[0007] Triorganotin compounds are known for use as catalysts in
electrodepositable coating compositions comprised of an active
hydrogen-containing resin and a blocked polyisocyanate curing
agent. Such triorganotin compounds, however, have been observed to
have poor cure response when used in conjunction with resinous
components having phenolic hydroxyl groups. Moreover, some
trialkyltin compounds, for example, tributyltin compounds, are
known to be volatile at typical curing temperatures. Also, some
trialkyltin compounds can be toxic. Further, many triorganotin
compounds typically have the disadvantage of high cost.
[0008] In view of the foregoing, it would be advantageous to
provide a cationic electrodepositable coating composition including
a catalyst which overcomes the problems encountered with prior art
compositions containing such catalysts as discussed above. Such
compositions can provide improved storage stability and cure
response at lower cure temperatures, without compromising cured
film appearance and performance properties.
SUMMARY OF THE INVENTION
[0009] In one aspect, the present invention provides
electrodepositable coating compositions comprising a resinous phase
and catalyst nanoparticles 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; and
catalyst nanoparticles for effecting cure between the resin (a) a
curing agent (b), the catalyst nanoparticles 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; a
combination of cerium oxide, zinc oxide and silicon dioxide; a
combination of cerium oxide and silicon dioxide; 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).
[0010] In 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 catalyst nanoparticles for effecting cure between the resin (a)
and the curing agent (b), the catalyst nanoparticles 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; a
combination of cerium oxide, zinc oxide and silicon dioxide; a
combination of cerium oxide and silicon dioxide; 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).
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] 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:
[0012] FIG. 1 is a flow diagram of certain embodiments of suitable
methods for making catalyst nanoparticles in accordance with the
present invention;
[0013] FIG. 2 is a schematic diagram of an apparatus for producing
catalyst nanoparticles in accordance with certain embodiments of
the present invention;
[0014] FIG. 3 is a perspective view of a plurality of quench gas
injection ports in accordance with certain embodiments of the
present invention;
[0015] FIG. 4 is a micrograph of a TEM image of a representative
portion of the nanoparticles of Example 1 (10,000.times.
magnification); and
[0016] FIG. 5 is a micrograph of a TEM image of a representative
portion of the nanoparticles of Example 2 (210,000.times.
magnification).
DETAILED DESCRIPTION
[0017] 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.
[0018] 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.
[0019] 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.
[0020] The present invention provides electrodepositable coating
compositions comprising a resinous phase and catalyst nanoparticles
dispersed in an aqueous medium, the resinous phase comprising: (a)
at least one active hydrogen-containing, ionic salt
group-containing resin; (b) at least one curing agent. The catalyst
nanoparticles effect or facilitate cure between the resin (a) and
the curing agent (b), as described in detail below.
[0021] The catalyst nanoparticles 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.
[0022] In some embodiments, the catalyst nanoparticles 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.
[0023] In some embodiments, the catalyst nanoparticles 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,
[0024] The catalyst nanoparticles 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 ("SSA") 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 ("SSA") can be measured
using a Gemini Model 2360 surface area analyzer (available from
Micromeritics Instrument Corp. of Norcross, Ga.).
[0025] In certain embodiments, the catalyst nanoparticles 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)]
[0026] The catalyst nanoparticles can have an average primary
particle size of less than 500 nanometers. In some embodiments, the
catalyst nanoparticles can have an average primary particle size of
less than 100 nanometers, and in other embodiments less than 50
nanometers. In some embodiments, the catalyst nanoparticles 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 and the Examples
contained herein illustrate a suitable method for preparing a TEM
image. 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.
[0027] It will be recognized by one skilled in the art that
mixtures of one or more 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, particles of
varying particle sizes can be used in the compositions according to
the present invention.
[0028] The catalyst nanoparticles 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.). In some embodiments, catalyst nanoparticles are
present in the coating composition in an amount sufficient to
effect cure of the coating composition at or below a temperature of
340.degree. F. (171.1.degree. C.). In other embodiments, catalyst
nanoparticles are present in the coating composition in an amount
sufficient to effect cure of the coating composition at or below a
temperature of 320.degree. F. (160.degree. C.). In other
embodiments, catalyst nanoparticles are present in the coating
composition in an amount sufficient to effect cure of the coating
composition 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 nanoparticles used.
[0029] When the film-forming composition of the present invention
is in a liquid medium, the particles have an affinity for the
medium of the composition sufficient to keep the particles
suspended therein. The affinity of the particles for the medium is
greater than the affinity of the particles for each other, thereby
preventing agglomeration of the particles within the medium. This
property is due to the nature of the particles themselves. The
particles are also substantially free of any surface treatment. 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.
[0030] The shape (or morphology) of the 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.
[0031] The catalyst nanoparticles 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 particles may be 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
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
precursers into one axial end of a plasma chamber; (b) rapidly
heating the precurser stream by means of a plasma to a selected
reaction temperature as the precurser 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.
[0032] 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, 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, 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.
[0033] In certain embodiments, the catalyst nanoparticles 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 solid particles; and (d)
passing the ultrafine solid particles through a converging
member.
[0034] Referring now to FIG. 1, there is shown a flow diagram
depicting certain embodiments of suitable methods for making
catalyst nanoparticles. As is apparent, in certain embodiments, at
step 100, a solid precursor is introduced into a feed chamber.
Then, as is apparent from FIG. 1 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.
[0035] 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
ranging from 2,500.degree. to 20,000.degree. C., such as
1,7000.degree. to 8,000.degree. C.
[0036] 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 nanoparticles.
[0037] As is apparent from FIG. 1, 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. 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.
[0038] 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 catalyst
nanoparticles. 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 the present invention, 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 the
present invention, 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, such as a
converging-diverging nozzle, as described below.
[0039] Referring again to FIG. 1, 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, wherein the plasma system is designed
to minimize the fouling thereof. In certain embodiments, the
converging member comprises a converging-diverging (De Laval)
nozzle. In 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-divergent nozzle. In these embodiments, the
convergent-divergent nozzle 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
convergent-divergent nozzle 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.
[0040] As shown in FIG. 1, in certain embodiments of the methods of
the present invention, 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.
[0041] Now referring to FIG. 2, there is depicted a schematic
diagram of an apparatus for producing ultrafine solid catalyst
nanoparticles 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.
[0042] In the embodiment depicted by FIG. 2, 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 FIG. 2, 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.
[0043] 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.
[0044] 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 FIG. 2, the plasma gas feed inlet is depicted
at 31.
[0045] 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 FIG. 2
at 33.
[0046] As shown in FIG. 2, in certain embodiments of the present
invention, 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.
[0047] 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 ".theta." apart
from each other along the circumference of the reactor chamber 20.
It will be appreciated that ".theta." 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 ".theta." 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
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.
[0048] In certain methods of the present invention, contacting the
gaseous product stream with the quench streams results in the
formation of ultrafine solid particles, which are then passed into
and through a converging member. As used herein, the term
"converging member" refers to a device that restricts passage of a
flow therethrough, thereby controlling the residence time of the
flow in the plasma chamber due to pressure differential upstream
and downstream of the converging member.
[0049] In certain embodiments, the converging member comprises a
convergent-divergent (De Laval) nozzle, such as that which is
depicted in FIG. 2, which is coaxially positioned within the outlet
of the reactor chamber 20. The converging or upstream section of
the nozzle, i.e., the converging member, restricts gas passage and
controls the residence time of the materials within the plasma
chamber 20. It is believed that the contraction that occurs in the
cross sectional size of the gaseous stream as it passes through the
converging portion of nozzle 22 changes the motion of at least some
of the flow from random directions, including rotational and
vibrational motions, to a straight line motion parallel to the
reaction chamber axis. In certain embodiments, the dimensions of
the plasma chamber 20 and the material are selected to achieve
sonic velocity within the restricted nozzle throat.
[0050] As the confined stream of flow enters the diverging or
downstream portion of the nozzle 22, it is subjected to an ultra
fast decrease in pressure as a result of a gradual increase in
volume along the conical walls of the nozzle exit. 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.
[0051] As is apparent from FIG. 2, in certain embodiments of the
present invention, 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.
[0052] 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.
[0053] The high temperature of the plasma rapidly vaporizes the
solid precursor. There is 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. At the nozzle throat, it is believed,
the flow is laminar and there is a very low temperature gradient
across its restricted open area.
[0054] The plasma chamber is often constructed of water cooled
stainless steel, nickel, titanium, or other suitable materials. The
plasma chamber can also be constructed of ceramic materials to
withstand a vigorous chemical and thermal environment.
[0055] 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.
[0056] 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.
[0057] 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 eddys or stagnant zones
are formed along the walls of the chamber. Such detrimental flow
patterns can cool the gases prematurely and precipitate unwanted
products. 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.
[0058] In certain embodiments, the converging section of the nozzle
has a high aspect ratio change in diameter that maintains smooth
transitions to a first steep angle (such as >45.degree.) and
then to lesser angles (such as <45.degree. degree.) leading into
the nozzle throat. The purpose of the nozzle throat is often to
compress the gases and achieve sonic velocities in the flow. The
velocities achieved in the nozzle throat and in the downstream
diverging section of the nozzle are controlled by the pressure
differential between the plasma chamber and the section downstream
of the diverging section of the nozzle. Negative pressure can be
applied downstream or positive pressure applied upstream for this
purpose. A converging-diverging nozzle of the type suitable for use
in the present invention is described in U.S. Pat. No. RE37,853 at
col. 9, line 65 to col. 11, line 32, the cited portion of which
being incorporated by reference herein.
[0059] The methods and apparatus of the present invention, which
utilize quench gas dilution cooling in combination with a
converging member, such as a converging-diverging nozzle, have
several benefits. First, such a combination allows for the use of
sufficient residence times of solid material within the plasma
system that make the use of solid reactants practical. Second,
because ultrafine solid particles are formed prior to the flow
reaching the converging member, fouling of the plasma chamber is
reduced or, in some cases, even eliminated, since the amount of
material sticking to the interior surface of the converging member
is reduced or, in some cases, eliminated. Third, this combination
allows for the collection of ultrafine solid particles at a single
collection point, such as a filter bag, with a minimal amount of
such particles being deposited within the cooling chamber or
cooling section described earlier.
[0060] The catalyst nanoparticles 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, cerium, and/or zinc) based on
weight of total resin solids present in the electrodepositable
coating composition. Also, the catalyst nanoparticles 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
nanoparticles 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 (as determined by a method described in detail below)
of the composition at a temperature at or below 360.degree. F.
(182.2.degree. C.).
[0061] 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 an
embodiment 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.
[0062] It should be noted herein that the catalyst is characterized
in that the catalyst is 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 does not volatilize from the film into the curing oven
environment at these temperatures during the curing process.
[0063] As aforementioned, in addition to the catalyst, the
electrodepositable coating composition of the present invention
comprises (a) one or more active hydrogen-containing, ionic salt
group-containing resins, and (b) one or more curing agents.
[0064] 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.
[0065] 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.
[0066] The equivalent ratio of reactants; i.e., epoxy:polyhydroxyl
group-containing material is typically from 1.00:0.50 to
1.00:2.00.
[0067] 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, typically 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.
[0068] Examples of polyepoxides are those having a 1,2-epoxy
equivalency greater than one and preferably two; that is,
polyepoxides which have on average two epoxide groups per molecule.
The preferred polyepoxides are polyglycidyl ethers of polyhydric
alcohols such as cyclic polyols. Particularly preferred are
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. Examples of
other cyclic polyols include alicyclic polyols, particularly
cycloaliphatic polyols such as 1,2-cyclohexane diol and
1,2-bis(hydroxymethyl)cyclohexane. The preferred polyepoxides have
epoxide equivalent weights ranging from 180 to 2000, preferably
from 186 to 1200. Epoxy group-containing acrylic polymers can also
be used. These polymers typically have an epoxy equivalent weight
ranging from 750 to 2000.
[0069] 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 also be used. Bisphenol A is
preferred.
[0070] The 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.
[0071] When amines are used as the cationic salt formers,
monoamines typically are employed. Hydroxyl-containing amines are
suitable, and polyamines also may be used.
[0072] 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.
[0073] 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-methyidiethanolamine,
3-aminopropyldiethanolamine, and N-(2-hydroxyethyl)-piperazine.
[0074] 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 which do not negatively
affect the reaction between the amine and the epoxy may also be
used. Specific examples include ethylamine, methylethylamine,
triethylamine, N-benzyldimethylamine, dicocoamine,
3-dimethylaminopropylamine, and N,N-dimethylcyclohexylamine.
[0075] Mixtures of the above mentioned amines may also be used.
[0076] 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.
[0077] 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 and inorganic acids. Non-limiting examples of suitable
organic acids include formic acid, acetic acid, methanesulfonic
acid, and lactic acid. Non-limiting examples of suitable inorganic
acids include phosphoric acid and sulfamic acid. By "sulfamic acid"
is meant sulfamic acid itself or derivatives thereof; i.e., an acid
of the formula: ##STR1## wherein R is hydrogen or an alkyl group
having 1 to 4 carbon atoms. Sulfamic acid is preferred. Mixtures of
the above mentioned acids may also be used.
[0078] 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.
[0079] 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.
[0080] 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, but their use is not necessary.
[0081] 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 an embodiment of the present
invention, 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.
[0082] 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.
[0083] 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 so long as
photodegradation resistance of the polymer and the resulting
electrodeposited coating is not compromised.
[0084] 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.
[0085] 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 (a) which can be used in the electrodepositable
compositions of the present invention include those resins
described in U.S. Pat. Nos. 3,455,806 and 3,928,157.
[0086] 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.
[0087] Additional examples of polyurethane polymers suitable for
forming the active hydrogen-containing, cationic resin (a) include
the polyurethane, polyurea, and poly(urethane-urea) polymers
prepared by reacting polyether polyols and/or polyether polyamines
with polyisocyanates. Such polyurethane polymers are described in
U.S. Pat. No. 6,248,225.
[0088] Epoxide functional groups may be incorporated into the
polyurethane by methods well known in the art. For example, epoxide
groups can be incorporated by 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.
[0089] 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.
[0090] 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.
[0091] 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.
[0092] 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.
[0093] 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, typically 2 to 3 milliequivalents of active
hydrogen per gram of resin solids.
[0094] 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.
[0095] 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,
preferably 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.
[0096] The active hydrogen-containing, cationic salt
group-containing resin (a) can be present in the electrodepositable
composition of the present invention in an amount ranging from 40
to 95 weight percent, typically from 50 to 75 weight percent based
on weight of total resin solids present in the composition.
[0097] The electrodepositable composition of the present invention
also comprises 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 preferred, although higher
polyisocyanates can be used in place of or in combination with
diisocyanates.
[0098] 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.
Examples include isophorone diisocyanate and
4,4.degree.-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.
[0099] 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.
[0100] Any suitable alcohol or polyol can be used as a blocking
agent for the polyisocyanate in the electrodepositable composition
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.
[0101] In one embodiment of the present invention, the blocking
agent comprises one or more 1,3-glycols and/or 1,2-glycols. In one
embodiment of the present invention, the blocking agent comprises
one or more 1,2-glycols, typically 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. It has been observed that the
presence of such blocking agents facilitates dissolution or
dispersion of the organotin catalyst in the resinous phase or
components thereof.
[0102] Other suitable blocking agents include oximes such as methyl
ethyl ketoxime, acetone oxime and cyclohexanone oxime and lactams
such as epsilon-caprolactam.
[0103] 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. It should be understood that acceptable cure
temperatures and cure times will be dependent upon the substrates
to be coated and their end uses.
[0104] Compounds generally suitable as the polyester curing agent
are polyesters of polycarboxylic acids. Non-limiting examples
include 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.
[0105] 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.
[0106] 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.
[0107] 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.
[0108] 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.
[0109] 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. Additionally, trimellitic
anhydride can be reacted with 3 molar equivalents of a monoalcohol
such as 2-ethylhexanol.
[0110] Alternatively, trimellitic anhydride (1 mol.) 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.
[0111] The non-acidic polyesters of the types described above
typically are soluble in organic solvents, and typically can be
mixed readily with the active hydrogen-containing resin (i)
previously described.
[0112] 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.
[0113] 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. In some embodiments of the present
invention, the acyclic carbonate comprises dimethyl carbonate.
[0114] The curing agent (b) is usually present in the
electrodepositable composition in an amount ranging from 5 to 60
percent by weight, typically from 25 to 50 percent by weight based
on total weight of resin solids.
[0115] It should be understood that the catalyst nanoparticles 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, the
catalyst nanoparticles can be admixed with or dispersed in the
reactants used to form the resin (a) during preparation of the
resin (a). Also, the catalyst nanoparticles 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, the catalyst
nanoparticles can be admixed with or dispersed in the resin (a)
either prior to or subsequent to neutralization with an acid. The
catalyst nanoparticles 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
catalyst nanoparticles can be admixed with or dispersed in the
admixture of the resin (a) and the curing agent (b). Alternatively,
the catalyst nanoparticles 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 catalyst nanoparticles can be directly
admixed with or dispersed in the aqueous medium, prior to
dispersion of the resinous phase in the aqueous medium. The
catalyst nanoparticles also can be added neat to the
electrodepositable composition subsequent to dispersion in the
aqueous medium. Additionally, if desired, the catalyst
nanoparticles can be added on-line to the electrodeposition bath in
the form of an additive material. It should be understood that the
catalyst can be incorporated into the electrodepositable
composition by one or more of the above described methods.
[0116] The electrodepositable composition may optionally contain a
coalescing solvent such as hydrocarbons, alcohols, esters, ethers
and ketones. Examples of preferred coalescing solvents are
alcohols, including polyols, such as isopropanol, butanol,
2-ethylhexanol, ethylene glycol and propylene glycol; ethers such
as the monobutyl and monohexyl ethers of ethylene glycol; and
ketones such as methyl isobutyl ketone and isophorone. 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.
[0117] The electrodepositable composition of the present invention
may further contain 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).
[0118] 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 (P/B) is
usually 0.05:1 to 1:1. In a particular embodiment, the
electrodepositable coating composition of the present invention is
free of lead-containing compounds.
[0119] The electrodepositable coating composition of the present
invention is 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.
[0120] The electrodepositable compositions 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.
[0121] In the process 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.
[0122] 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.
[0123] In yet another embodiment, 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 another embodiment, 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 another embodiment, 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.
[0124] In another embodiment, 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.
[0125] 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.
[0126] 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. Steel
substrates are preferred. 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.
[0127] After deposition, the coating is 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
typically can range from 10 to 50 microns.
[0128] The invention will be further described by reference to the
following examples. Unless otherwise indicated, all parts and
percentages are by weight.
EXAMPLES
[0129] Nanoparticle catalyst materials according to the present
invention were prepared as follows:
[0130] Particles from solid precursors were prepared using a DC
thermal plasma reactor system of the type described in U.S. Pat.
No. RE 37,853E. The main reactor system included a DC plasma torch
(Model SG-100 Plasma Spray Gun commercially available from Praxair
Technology, Inc., Danbury, Conn.) operated with 60 standard liters
per minute of argon carrier gas and 28 kilowatts of power delivered
to the torch. Solid reactant feed compositions comprising the
materials and amounts listed in Tables 1-5 were prepared and fed to
the reactor at a rate of 2.5 grams per minute through a gas
assistant powder feeder (Model 1264, commercially available from
Praxair Technology, Inc., Danbury, Conn.) located at the plasma
torch outlet. At the powder feeder, 2.6 standard liters per minute
argon were used as carrier gas. Oxygen at 10 standard liters per
minute was delivered through two 1/8 inch diameter nozzles located
180.degree. apart at 0.69'' downstream of the powder injector port.
Following a 9.7 inch long reactor section, a quench system was
provided that included a quench gas injection port that included
61/8 inch diameter nozzles located 60.degree. apart radially and a
7 millimeter diameter converging-diverging nozzle located 3 inches
downstream of the quench gas injection port. Quench air was
injected at the quench gas injection port at a rate of 100 standard
liters per minute.
Example 1
[0131] TABLE-US-00001 TABLE 1 Material Amount Bismuth
Trioxide.sup.1 195 grams Fumed Silica.sup.2 5 grams
.sup.1Commercially available from Pharmacie Central de Guinea,
France. .sup.2Commercially available from Cabot Corporation,
Massachusetts; Cab-O-Sil M5 grade.
[0132] Nanoparticles having a theoretical composition of 97.5
weight percent bismuth oxide and 2.5 weight percent silica were
prepared by the above method using the feed composition listed in
Table 1. The measured B.E.T. specific surface area of the
nanoparticles was 32 square meters per gram using the Gemini model
2360 analyzer and the calculated equivalent spherical diameter was
21 nanometers. FIG. 4 is a micrograph of a TEM image of a
representative portion of the particles (10,000.times.
magnification). The micrograph was prepared by weighing out 0.2 to
0.4 grams of the particles and adding those particles to methanol
present in an amount sufficient to yield an adequate particle
density on a TEM grid. The mixture was placed in a sonicater for 20
minutes and then dispersed onto a 3 millimeter TEM grid coated with
a uniform carbon film using a disposable pipette. After allowing
the methanol to evaporate, the grid was loaded into a specimen
holder which was then inserted into a TEM instrument.
Example 2
[0133] Particles from solid precursors were prepared using the same
apparatus and operating conditions identified in Example 1, except
that the solid reactant feed composition comprised the materials
and amounts listed in Table 2. TABLE-US-00002 TABLE 2 Material
Amount Bismuth Trioxide.sup.3 20 grams Silica.sup.4 80 grams
.sup.3Commercially available from Sigma Aldrich Co., St Louis,
Missouri, having an average particle size of 3 microns.
.sup.4Commercially available under trade name WB-10 from PPG
Industries, Inc., Pittsburgh, PA.
[0134] Nanoparticles having a theoretical composition of 20 weight
percent bismuth oxide and 80 weight percent silica were prepared by
the above method using the feed composition listed in Table 2. The
measured B.E.T. specific surface area was 143 square meters per
gram using the Gemini model 2360 analyzer and the calculated
equivalent spherical diameter was 12 nanometers. FIG. 5 is a
micrograph of a TEM image of a representative portion of the
particles (210,000.times. magnification). The micrograph was
prepared in the manner described in Example 1.
Example 3
[0135] Particles from solid precursors were prepared using the same
apparatus and operating conditions identified in Example 1, except
that the solid reactant feed composition comprised the materials
and amounts listed in Table 3. TABLE-US-00003 TABLE 3 Material
Amount Bismuth Trioxide.sup.3 40 grams Silica.sup.4 60 grams
[0136] Nanoparticles having a theoretical composition of 40 weight
percent bismuth oxide and 60 weight percent silica were prepared by
the above method using the feed composition listed in Table 3. The
measured B.E.T. specific surface area was 80 square meters per gram
using the Gemini model 2360 analyzer and the calculated equivalent
spherical diameter was 15 nanometers.
Example 4
[0137] Particles from solid precursors were prepared using the same
apparatus and operating conditions identified in Example 1, except
that the solid reactant feed composition comprised the materials
and amounts listed in Table 4. TABLE-US-00004 TABLE 4 Material
Amount Bismuth Trioxide.sup.3 60 grams Fumed Silica.sup.4 40
grams
[0138] Nanoparticles having a theoretical composition of 60 weight
percent bismuth oxide and 40 weight percent silica were prepared by
the above method using the feed composition listed in Table 4. The
measured B.E.T. specific surface area was 62 square meters per gram
using the Gemini model 2360 analyzer and the calculated equivalent
spherical diameter was 16 nanometers.
Comparative Example 5
[0139] Bismuth silicate particles from a solution process were
prepared using feed composition comprised the materials and amounts
listed in Table 5. A solution was prepared by adding powder of
components 1, 2, and 3 to the liquid of component 4. The solution
was heated to 97 degrees Celsius to increase solubility of the
solid components. Component 5 was added to the solution to form
bismuth silicate particles. The precipitated particles were
collected by filtering from the solution and drying at room
temperature. TABLE-US-00005 TABLE 5 Component Material Amount 1
Bismuth Trioxide.sup.3 70.73 grams 2 Aminocaproic acid 81.22 grams
3 Sulfamic acid 30.03 grams 4 Deionized water 209.04 grams 5 Sodium
silicate 98.46 grams
[0140] Nanoparticles having a theoretical composition of 40 mole
percent bismuth oxide and 60 mole percent silica were prepared by
the above method using the feed composition listed in Table 5. The
measured B.E.T. specific surface area was 109 square meters per
gram using the Gemini model 2360 analyzer. The resulting product
was agglomerated porous material.
Coating Composition Examples 1A to 1D
[0141] Coating compositions were prepared using the components and
weights (in grams) shown in Table 6. Coatings were prepared by
adding components 1 to 3 to a suitable vessel under agitation with
a tong press for 3 minutes. TABLE-US-00006 TABLE 6 Comparative
Comparative Comparative Component Material Sample 1A Example 1B
Example 1C Example 1D 1 Resin.sup.5 30 30 30 30 2 MIBK 5 5 5 5 3
Example 1 catalyst 0.831 material Dibutyl tin dilaurate 1.982
Bi.sub.2O.sub.3.sup.1 0.831 Bismuth 6.007 methanesulfonate.sup.6
.sup.5The resin was prepared from the following components as set
forth below: weight 1 Epon 828.sup.5a 817.1 2 Bisphenol A 239.0 3
MACOL 98 A MOD 1.sup.5b 291.5 4 Methylisobutyl ketone (mibk) 70.93
5 Benzyldimethyl amine 0.92 6 Benzyldimethyl amine 2.64 7
Crosslinker.sup.5c 1429.2 8 Ketimine.sup.5d 98.23 9 N-methyl
ethanolamine 77.68 10 Epon 828 17.1 11 MIBK 2.56 12 Deionized
H.sub.2O 33.0 13 Epon 828 17.07 14 MIBK 2.56 15 MIBK 705.52
.sup.5aEpoxy resin available from Resolution Performance Products
.sup.5bBisphenol ethylene oxide adduct available from BASF
Corporation. .sup.5cThe crosslinker was prepared as follows: weight
1 PAPI 2940.sup.1 1320.00 2 Methyl isobutyl ketone (mibk) 626.47 3
trimethylolpropane 134.19 4 Dibutyltindilaurate 1.00 5
Diethyleneglycol monobutyl ether 1135.61 6 MIBK 61.96 TOTAL 3279.23
.sup.1Isocyanate, available from Dow Chemical Co Items 1 and 2 were
charged to a 4 neck round bottom flask, fit with a stirrer,
temperature measuring probe, N.sub.2 blanket and Dean-Stark trap
and heated to 80.degree. C. Charge 3 was added and the reaction
mixture exothermed to about 90.degree. C. and was then heated to
105.degree. C. The mixture was then held at this temperature until
the measured isocyanate equivalent is 297 .+-. 10. Charge 4 was
then added and charges 5 and 6 were added over about 30 minutes
without exceeding 110.degree. C. The mixture was then held at
110.degree. C. until the infrared spectrum indicated the absence of
isocyanate. .sup.5dMIBK diketimine of diethylene triamine at 72.7%
in MIBK All weights were in grams. Items 1, 2, 3, and 4 were
charged to a 4 neck round bottom flask, fit with a stirrer,
temperature measuring probe, N.sub.2 blanket and Dean-Stark trap
and heated to 130.degree. C. Charge 5 was added and the mixture
exothermed to about 150.degree. C. The temperature was allowed to
drop to 143.degree. C. and held at this temperature for 30 minutes.
Charge 6 was then added and the mixture was held until the epoxide
equivalent weight (based on solids) was 1087. Charges 7, 8, and 9
were added and the mixture was held at 123.degree. C. for one hour.
Charges 10 and 11 (mixed) were added and the mixture was cooled to
96-99.degree. C. over 90 minutes. Charge 12 was added over 15
minutes with the temperature at 96-99.degree. C. Charges 13 and 14
mixed were added, charge 15 was added. The mixture was then held at
96-99.degree. C. for two hours. The resin had a solids content of
about 75%. .sup.6Made using the material and process described in
the Example 2, Canadian patent # 2362073.
[0142] The compositions of Table 6 were applied to galvanized test
substrates (APR26917, ACT Laboratories, Hillsdale, Mich.) using a
draw down bar (PG&T Co.). Each composition was applied to form
a 5 mils (127 microns) thickness coating layer on a surface of the
substrate. Panels were placed in an electrical oven for 20 minutes.
Curing was tested using a double-rub method with acetone as
solvent. The film is marked as cured if no penetration or
significant scratch is observed after 100 times of double-rubbing.
Results of the testing are set forth in Table 7. Lower curing
temperature indicated better catalytic activity of the materials.
TABLE-US-00007 TABLE 7 Temperature (.degree. F.) 400 380 360 340
320 Example 1A Cured Cured Cured Cured Not cured Comparative Cured
Cured Cured Cured Not cured Example 1B Comparative Not cured Not
cured Not cured Not cured Not cured Example 1C Comparative Cured
Cured Not cured Not cured Not cured Example 1D
[0143] As shown in Table 7 above, the coating composition of
Example 1A according to the present invention successfully cured at
the same temperature (340.degree. F.) as Comparative Example 1B,
which contained more than twice as much of dibutyl tin dilaurate
catalyst. Also, the coating composition of Example 1A (having
bismuth oxide and silica) according to the present invention
successfully cured at a temperature of 340.degree. F., whereas the
coating composition of Comparative Example 1C using the same amount
of bismuth trioxide.sup.1 alone did not.
Coating Composition Examples 2A to 2C
[0144] Coating compositions were prepared using the components and
weights (in grams) shown in Table 8. Coatings were prepared by
adding components 1 to 3 to a suitable vessel under agitation with
a tong press for 3 minutes. TABLE-US-00008 TABLE 8 Example Example
Component Material Example 2A 2B 2C 1 Resin.sup.5 30 30 30 2 MIBK 7
6 5 3 Example 2 catalyst 4.158 material Example 3 catalyst 2.079
material Example 4 catalyst 1.386 material
[0145] The compositions of Table 8 were applied to galvanized test
substrates, cured and tested as above. Results are set forth in
Table 9. TABLE-US-00009 TABLE 9 Temperature (.degree. F.) 400 380
360 340 320 Example 2A Cured Cured Cured Cured Not cured Example 2B
Cured Cured Cured Cured Not cured Example 2C Cured Cured Cured
Cured Not cured
[0146] The coating compositions of Examples 2A-2C according to the
present invention cured at a temperature of 340.degree. F.
Coating Composition Examples 3A to 3D
[0147] Coating compositions were prepared using the components and
weights (in grams) shown in Table 10. Coatings were prepared by
adding components 1 to 3 to a suitable vessel under agitation with
a tong press for 3 minutes. TABLE-US-00010 TABLE 10 Example Example
Example Example Component Material 3A 3B 3C 3D 1 Resin.sup.5 10 10
10 10 2 MIBK 2 2 2 2 3 Example 2 0.284 catalyst material Example 3
0.284 catalyst material Example 4 0.284 catalyst material Example 1
0.284 catalyst material
[0148] The compositions of Table 10 were applied to galvanized test
substrates, cured and tested as above. Results are set forth in
Table 11. TABLE-US-00011 TABLE 11 Temperature (.degree. F.) 400 380
360 340 320 Example 3A Cured Cured Cured Cured Not cured Example 3B
Cured Cured Cured Cured Not cured Example 3C Cured Cured Cured
Cured Not cured Example 3D Cured Cured Cured Cured Not cured
[0149] The coating compositions of Examples 3A-3D according to the
present invention cured at a temperature of 340.degree. F.
Coating Composition Examples 4A to 4D
[0150] Coating compositions were prepared using the components and
weights (in grams) shown in Table 12. Coatings were prepared by
adding components 1 to 3 to a suitable vessel under agitation with
a tong press for 3 minutes. TABLE-US-00012 TABLE 12 Example Example
Component Material Example 4A 4B 4C 1 Resin.sup.5 20 20 20 2
Example 2 catalyst 0.480 material Example 2 catalyst 0.240 material
Example 2 catalyst 0.120 material
[0151] The compositions of Table 12 were applied to galvanized test
substrates, cured and tested as above. Results are set forth in
Table 13. TABLE-US-00013 TABLE 13 Temperature (.degree. F.) 400 380
360 340 320 Example 4A Cured Cured Cured Cured Not cured Example 4B
Cured Cured Cured Not cured Not cured Example 4C Cured Cured Not
cured Not cured Not cured
Coating Composition Examples 5A to 5D
[0152] Coating compositions were prepared using the components and
weights (in grams) shown in Table 14. Coatings were prepared by
adding components 1 and 2 to a suitable vessel under agitation with
a tong press for 3 minutes. TABLE-US-00014 TABLE 14 Comparative
Comparative Comparative Example Example Component Material Example
5A Example 5B Example 5C 5D 5E 1 Resin.sup.5 10 20 10 10 10 2
Bismuth Trioxide.sup.7 0.189 Bismuth Trioxide 0.5 and Silica.sup.8
Example 2 catalyst 0.5 material Example 5 catalyst 0.113 material
.sup.7Commercially available from Nanostructured and Amorphous
Materials Inc., Houston, TX. having a B.E.T. specific surface area
of 3.5 m.sup.2/g and a particle size of 193 nm. .sup.8A mixture of
20 weight percent Bismuth trioxide from Nanostructured and
Amorphous Materials and 80 weight percent precipitated silica from
PPG Industries under the trade name WB-10.
[0153] The compositions of Table 14 were applied to galvanized test
substrates, cured and tested as above. Results are illustrated in
Table 15. TABLE-US-00015 TABLE 15 Temperature (.degree. F.) 400 380
360 340 320 Comparative Not cured Not cured Not cured Not cured Not
cured Example 5A Comparative Cured Cured Not cured Not cured Not
cured Example 5B Comparative Cured Cured Not cured Not cured Not
cured Example 5C Example 5D Cured Cured Cured Cured Not cured
Example 5E Cured Cured Not cured Not cured Not cured
[0154] Both of the composition of Example 5D and the composition of
Comparative Example composition 5C contained similar amounts of
bismuth trioxide and silica. As shown in the above Examples, the
composition of Example 5D cured at a lower temperature (340.degree.
F.) compared to the Comparative Example composition 5C (380.degree.
F.).
Electrodeposited Coatings--Example 6
[0155] Electrodeposited coatings were prepared comprising catalyst
nanoparticles of Example 1 above using the components and weights
(in grams) shown in Table 16. TABLE-US-00016 TABLE 16 Pigment
Component Weight Resin solids Solids 1 Plasticizer.sup.9 76.9 26.9
2 Non-ionic surfactant.sup.10 6.8 6.8 3 Resin.sup.11 1057.5 396.6 4
Deionized water 350.5 5 Propylene glycol 12.5 monomethyl ether 6
Ethylene glycol 6.3 monohexyl ether 7 Plasticizer.sup.12 49.9 8
Deionized water 200 9 W9771-1P5 pigment 239.6 47.1 74.4
paste.sup.13 10 Deionized water 1800 Total 3800 495.7 74.4
.sup.9The plasticizer was prepared as follows: 711 g of DER732
aliphatic epoxy resin available from Dow Chemical Co., and 164.5 g
bisphenol A were charged to a suitably equipped 3-liter
round-bottomed flask. The mixture was heated to 130.degree. C. and
1.65 g benzyldimethyl amine was added. The reaction mixture was
held at 135.degree. C. until the epoxide equivalent weight of the
mixture was 1232. 78.8 g of butyl carbitol formal available as
Mazon 1651 from BASF Corporation was added and then the mixture is
cooled to 95.degree. C. 184.7 g Jeffamine D400 polyoxypropylene
diamine available from Huntsman Corp. was added and the reaction
held at 95.degree. C. until the Gardner-Holdt viscosity of a sample
of the resin diluted 50/50 in methoxy propanol was "HJ". A mixture
of 19.1 g Epon 828 and 3.4 g butyl Carbitol formal was added and
the mixture held until the Gardner-Holdt viscosity of a sample of
the resin diluted 50/50 in methoxy propanol was "Q-". 988.6 g of
this resin was poured into a mixture of 1242.13 g deionized water
and 30.2 g sulfamic and mixed for 30 minutes. 614.8 g deionized
water was then added and mixed well. The final aqueous dispersion
had a measured solids content of 35.8% .sup.10MAZON 1651 butyl
carbitol formal non-ionic surfactant commercially available from
BASF Corp. .sup.11The resin was prepared as follows: weight 1 Epon
828.sup.5a 476.6 2 Bisphenol A 139.4 3 MACOL 98 A MOD 1.sup.5b
170.0 4 Methylisobutyl ketone (MIBK) 41.37 5 Benzyldimethyl amine
0.54 6 Benzyldimethyl amine 1.54 7 Crosslinker.sup.5c 833.7 8
Ketimine.sup.5d 57.30 9 N-methyl ethanolamine 45.31 10 Epon 828
10.0 11 MIBK 1.49 12 Deionized H2O 19.3 13 Epon 828 9.96 14 MIBK
1.49 15 MIBK 99.22 16 Bi.sub.2O.sub.3 particles of Example 1 27.15
17 sulfamic acid 61.3 18 Deionized H.sub.2O 845.8 19 Deionized
H.sub.2O 1141 20 Deionized H.sub.2O 980 All weights were in grams.
Items 1, 2, 3, and 4 were charged to a 4 neck round bottom flask,
fit with a stirrer, temperature measuring probe, N.sub.2 blanket
and Dean-Stark trap and heated to 130.degree. C. Charge 5 was added
and the mixture exotherms to about 150.degree. C. The temperature
was allowed to drop to 143.degree. C. and held at this temperature
for 30 minutes. Charge 6 was then added and the mixture was held
until the epoxide equivalent weight (based on solids) was 1087.
Charges 7, 8, and 9 were added and the mixture is held at
123.degree. C. for one hour. Charges 10 and 11 (mixed) were added
and the mixture is cooled to 96-99.degree. C. over 90 minutes.
Charge 12 was added over 15 minutes with the temperature at
96-99.degree. C. Charges 13 and 14 mixed were added and a slurry of
items 15 and 16 was added. The mixture was then held at
96-99.degree. C. for two hours. 1644 g of the reaction mixture was
poured into a solution of items 17 and 18 with good stirring. The
resulting dispersion was mixed for thirty minutes and then charge
19 was added with stirring over about 30 minutes. Charge 20 was
added and mixed well. About 1000 g of water and solvent were
stripped off under vacuum at 60-65.degree. C. The resulting aqueous
dispersion had a solids content of 37.75% .sup.12The plasticizer
was prepared as follows: 1 MAZEEN 355 70.sup.12a 1423.49 2 acetic
acid 15.12 3 Dibutyltindilaurate 1.52 4 Toluene diisocyanate 80/20
200.50 5 acetic acid 49.32 6 deionized H2O 1623.68 7 deionized H2O
766.89 .sup.12aAmine functional diol of amine equivalent weight
1131 available from BASF Corporation Items 1 and 2 were charged to
a 4 neck round bottom flask, fit with a stirrer, temperature
measuring probe and N.sub.2 blanket and mixed for 10 minutes. Item
3 was added and then item 4 was charged over about 1 hour allowing
the reaction mixture to exotherm to a maximum temperature of
100.degree. C. The mixture was then held at 100.degree. C. until
the infrared spectrum indicates the absence of isocyanate
(approximately 1 hour). 1395 g of the reaction mixture was poured
into a mixture of items 5 and 6 and mixed for 1 hour. Item 7 was
then added over about 1 hour and mixed for about 1 hour. The
resulting aqueous solution had a solids content of about 36%.
.sup.13Commercially available from PPG Industries, Inc.
[0156] The components in Table 16 were mixed as follows: Charge 2
was added under mild agitation to charge 1, and then blended with
the mixture of charges 3 and 4. Charges 5, 6, and the mixture of
charges 7 and 8 were sequentially added. Charge 9 was diluted with
charge 10, and then added to the blend prepared above.
[0157] Phosphated cold rolled steel panels from ACT, C700/DI, were
electrocoated and cured as set forth below: TABLE-US-00017 TABLE 17
Film build Double Acetone Electrocoat Conditions Cure time/temp
(mils) Rubs 2 min/200volts/90.degree. F. 25'/360.degree. F. 0.76
>100 2 min/220volts/90.degree. F. 25'/340.degree. F. 0.81
>100 2 min/220volts/90.degree. F. 25'/320.degree. F. 0.86 10
[0158] Cure was determined by soaking a cotton cloth in acetone and
rubbing the cured film with an even back and forth stroke, up to
100 times. The films were evaluated for the degree of mar. As shown
in Table 17, an electrodeposited coating containing nanoparticles
according to the present invention (Example 6) showed acceptable
mar resistance at cure temperatures as low as 340.degree. F.
(171.1.degree. C.).
[0159] 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 numeous variations of the details of the present
invention may be made without departing from the invention as
defined in the appended claims.
* * * * *