US20070051634A1

US20070051634A1 - Electrodepositable coating compositions and related methods

Info

Publication number: US20070051634A1
Application number: US11/552,659
Authority: US
Inventors: James Poole; Donald Boyd; Noel Vanier; Cheng-Hung Hung
Original assignee: PPG Industries Ohio Inc
Current assignee: PPG Industries Ohio Inc
Priority date: 2005-08-26
Filing date: 2006-10-25
Publication date: 2007-03-08
Also published as: AR074031A1; WO2008051784A3; WO2008051784A2; EP2076571A2

Abstract

An electrodepositable coating composition is provided including a resinous phase and corrosion resisting particles dispersed in an aqueous medium. Methods of preparing and using the composition also are provided.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent application Ser. No. 11/213,174, which was filed on Aug. 26, 2005 and is entitled, “Electrodepositable Coating Compositions and Related Methods”. This application is also a continuation-in-part of U.S. patent application Ser. No. 11/213,136, which was filed on Aug. 26, 2005, and is entitled, “Coating Compositions Exhibiting Corrosion Resistance Properties, Related Coated Substrates, And Methods”, each of which being incorporated by reference herein.

BACKGROUND OF THE INVENTION

The present invention relates to electrodepositable coating compositions comprising a resinous phase and certain catalyst particles and/or corrosion resisting particles dispersed in an aqueous medium, to methods of preparing such compositions; and to methods for applying such compositions.
The application of a coating by electrodeposition involves depositing a film-forming composition onto surfaces of an electrically conductive substrate under the influence of an applied electrical potential. Electrodeposition has gained prominence in the coating industry because, in comparison with non-electrophoretic coating methods, electrodeposition provides higher paint utilization, excellent corrosion resistance and low environmental contamination. Early attempts at commercial electrodeposition processes used anionic electrodeposition where the workpiece to be coated serves as the anode. However, cationic electrodeposition has become increasingly popular and today is the most prevalent method of electrodeposition. While electrodeposited coatings often provide excellent corrosion resistance, further improved corrosion resistance performance is sometimes desirable.

SUMMARY OF THE INVENTION

In certain respects, the present invention provides electrodepositable coating compositions comprising a resinous phase and corrosion resisting particles dispersed in an aqueous medium, the resinous phase comprising: (a) an active hydrogen-containing, ionic salt group-containing resin; and (b) at least one curing agent; and corrosion resisting particles having a calculated equivalent spherical diameter of no more than 200 nanometers and comprising a plurality of inorganic oxides. In certain embodiments, at least one inorganic oxide comprises zinc, cerium, yttrium, manganese, magnesium, molybdenum, lithium, aluminum, or calcium.
In other respects, the present invention is directed to electrodepositable coating compositions comprising a resinous phase, catalyst particles, and corrosion resisting particles dispersed in an aqueous medium, the resinous phase comprising: (a) a active hydrogen-containing, ionic salt group-containing resin; and (b) at least one curing agent; the catalyst particles being selected from the group consisting of bismuth oxide, bismuth silicate, bismuth titanate, molybdenum oxide, molybdenum silicate, molybdenum titanate, tungsten oxide, tungsten silicate, tungsten titanate, or a combination thereof, wherein the catalyst particles have an average B.E.T. specific surface area greater than 20 square meters per gram; the corrosion resisting particles having a calculated equivalent spherical diameter of no more than 200 nanometers and comprising a plurality of inorganic oxides comprising at least one inorganic oxide comprising zinc, cerium, yttrium, manganese, magnesium, molybdenum, lithium, aluminum, or calcium.
In yet another aspect, the present invention provides methods for electrocoating a conductive substrate serving as a cathode in an electrical circuit comprising the cathode and an anode, the cathode and anode being immersed in an aqueous electrocoating composition, the methods comprising passing electric current between the cathode and anode to cause deposition of the electrocoating composition onto the substrate as a substantially continuous film, the aqueous electrocoating composition comprising a resinous phase dispersed in an aqueous medium, the resinous phase comprising: (a) a active hydrogen group-containing, ionic group-containing electrodepositable resin; and (b) a curing agent, and corrosion resisting particles having a calculated equivalent spherical diameter of no more than 200 nanometers and comprising a plurality of inorganic oxides. In certain embodiments, at least one inorganic oxide comprises zinc, cerium, yttrium, manganese, magnesium, molybdenum, lithium, aluminum, or calcium.

BRIEF DESCRIPTION OF THE DRAWINGS

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:
FIGS. 1A and 1B are flow diagrams of certain embodiments of suitable methods for making nanoparticles in accordance with the present invention;
FIGS. 2A and 2B are schematic diagrams of an apparatus for producing nanoparticles in accordance with certain embodiments of the present invention;
FIG. 3 is a perspective view of a plurality of quench gas injection ports in accordance with certain embodiments of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

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.
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.
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.
In certain embodiments, the present invention provides electrodepositable coating compositions comprising a resinous phase and catalyst particles dispersed in an aqueous medium, the resinous phase comprising: (a) at least one active hydrogen-containing, ionic salt group-containing resin; and (b) at least one curing agent. The catalyst particles effect or facilitate cure between the resin and the curing agent, as described in detail below.
The catalyst particles are selected from the group consisting of bismuth oxide; bismuth silicate; bismuth titanate; molybdenum oxide; molybdenum silicate; molybdenum titanate; tungsten oxide; tungsten silicate; tungsten titanate; a combination of cerium oxide, zinc oxide and silicon dioxide; a combination of cerium oxide and silicon dioxide; and combinations thereof, such as composite particles of two or more of these compounds or combinations.
In some embodiments, the catalyst particles comprise bismuth oxide. In other embodiments, the catalyst particles comprise bismuth oxide and silica. In other embodiments, the catalyst particles comprise bismuth oxide and bismuth silicate. In other embodiments, the catalyst particles comprise bismuth oxide, bismuth silicate and silica.
In some embodiments, the catalyst particles may be a complex metal oxide comprising a homogeneous mixture, or solid state solution of two or more (up to x) metal oxides, labeled MO₁, MO₂, . . . , MO_x.
The catalyst particles have an average B.E.T. (Brunauer, Emmett, and Teller) specific surface area greater than 20 square meters per gram (m²/g), in some embodiments greater than 25 square meters per gram (m²/g), and in other embodiments greater than 30 m²/g. In some embodiments, the average BET specific surface area is less than 300 m²/g. The BET specific surface area of particles can be measured by any method well known to those skilled in the art, such as by nitrogen absorption according to ASTM D 3663-78 standard based upon the Brunauer, Emmett, and Teller method described in J. Am. Chem. Soc'y 60, 309 (1938). For example, the BET specific surface area of particles can be measured using a Gemini Model 2360 surface area analyzer (available from Micromeritics Instrument Corp. of Norcross, Ga.).
In certain embodiments, the catalyst particles have a calculated equivalent spherical diameter of less than 500 nanometers, in other embodiments less than 100 nanometers and in still other embodiments less than 50 nanometers. As will be understood by those skilled in the art, a calculated equivalent spherical diameter can be determined from the B.E.T. specific surface area according to the following equation:
Diameter (nanometers)=6000/[BET(m²/g)*ρ(grams/cm³)]
In certain embodiments, the catalyst particles have an average primary particle size of less than 500 nanometers. In some embodiments, the catalyst particles have an average primary particle size of less than 100 nanometers, and in other embodiments less than 50 nanometers. In some embodiments, the catalyst particles have an average primary particle size of less than 30 nanometers and in other embodiments less than 20 nanometers. The particles typically have an average primary particle size greater than 1 nm. The average primary particle size can be determined by visually examining an electron micrograph of a transmission electron microscopy (“TEM”) image, measuring the diameter of the particles in the image, and calculating the average particle size (“APS”) based on the magnification of the TEM image. One of ordinary skill in the art will understand how to prepare such a TEM image and determine particle size based on the magnification. The primary particle size of a particle refers to the smallest diameter sphere that will completely enclose the particle. As used herein, the phrase “primary particle size” refers to the size of an individual particle as opposed to an agglomeration of two or more individual particles.
It will be recognized by one skilled in the art that mixtures of one or more catalyst particles having different average particle sizes can be incorporated into the compositions in accordance with the present invention to impart the desired properties and characteristics to the compositions. For example, catalyst particles of varying particle sizes can be used in the compositions according to the present invention.
The catalyst particles can be present in the coating composition in an amount sufficient to effect cure of the coating composition at or below a temperature of 360° F. (182.2° C.), such as at or below a temperature of 340° F. (171.1° C.), or, in some cases, at or below a temperature of 320° F. (160° C.), or, in yet other cases, at or below a temperature of 300° F. (149° C.). One skilled in the art would understand that the cure temperature can vary based upon the amount and type of catalyst particles used.
In addition to or in lieu of the previously described catalyst particles, the electrodepositable coating compositions of the present invention, in certain embodiments, comprise corrosion resisting particles. As used herein, the term “corrosion resisting particles” refers to particles which, when included in a coating composition that is electrodeposited upon a substrate, act to provide a coating that resists the alteration or degradation of the substrate, such as by a chemical or electrochemical oxidizing process, to an extent greater than such a coating would otherwise resist such alteration or degradation, if electrodeposited from a similar composition that did not include such particles.
In certain embodiments, the present invention is directed to electrodepositable coating compositions that comprise particles comprising an inorganic oxide, in some embodiments a plurality of inorganic oxides, such as, for example, zinc oxide (ZnO), magnesium oxide (MgO), cerium oxide (CeO₂), molybdenum oxide (MoO₃), and/or silicon dioxide (SiO₂), among others. As used herein, the term “plurality” means two or more. Therefore, certain embodiments of coating compositions of the present invention comprise corrosion resisting particles comprising two, three, four, or more than four inorganic oxides. In certain embodiments, these inorganic oxides are present in such particles, for example, in the form of a homogeneous mixture or a solid-state solution of the plurality of oxides.
In certain embodiments of the electrodepositable coating compositions of the present invention, the particles comprising an inorganic oxide, or, in certain embodiments, a plurality thereof, comprise an oxide of zinc, cerium, yttrium, manganese, magnesium, molybdenum, lithium, aluminum, magnesium, tin, or calcium. In certain embodiments, the particles comprise an oxide of magnesium, zinc, cerium, or calcium. In certain embodiments, the particles also comprise an oxide of boron, phosphorous, silicon, zirconium, iron, or titanium. In certain embodiments, the particles comprise silicon dioxide (hereinafter identified as “silica”).
In certain embodiments, the particles, such as corrosion resisting particles, that are included within certain embodiments of the electrodepositable coating compositions of the present invention comprise a plurality of inorganic oxides selected from (i) particles comprising an oxide of cerium, zinc, and silicon; (ii) particles comprising an oxide of calcium, zinc and silicon; (iii) particles comprising an oxide of phosphorous, zinc and silicon; (iv) particles comprising an oxide of yttrium, zinc, and silicon; (v) particles comprising an oxide of molybdenum, zinc, and silicon; (vi) particles comprising an oxide of boron, zinc, and silicon; (vii) particles comprising an oxide of cerium, aluminum, and silicon, (viii) particles comprising oxides of magnesium or tin and silicon, and (ix) particles comprising an oxide of cerium, boron, and silicon, or a mixture of two or more of particles (i) to (ix).
In certain embodiments of the electrodepositable coating compositions of the present invention, the corrosion resisting particles comprise 10 to 25 percent by weight zinc oxide, 0.5 to 25 percent by weight cerium oxide, and 50 to 89.5 percent by weight silica, wherein the percents by weight are based on the total weight of the particle.
In other embodiments of the electrodepositable coating compositions of the present invention, the corrosion resisting particles comprise 10 to 25 percent by weight zinc oxide, 0.5 to 25 percent by weight calcium oxide, and 50 to 89.5 percent by weight silica, wherein the percents by weight are based on the total weight of the particle.
In still other embodiments of the electrodepositable coating compositions of the present invention, the corrosion resisting particles comprise 10 to 25 percent by weight zinc oxide, 0.5 to 25 percent by weight yttrium oxide, and 50 to 89.5 percent by weight silica, wherein the percents by weight are based on the total weight of the particle.
In yet other embodiments of the electrodepositable coating compositions of the present invention, the corrosion resisting particles comprise 10 to 25 percent by weight zinc oxide, 0.5 to 50 percent by weight phosphorous oxide, and 25 to 89.5 percent by weight silica, wherein the percents by weight are based on the total weight of the particle.
In some embodiments of the electrodepositable coating compositions of the present invention, the corrosion resisting particles comprise 10 to 25 percent by weight zinc oxide, 0.5 to 50 percent by weight boron oxide, and 25 to 89.5 percent by weight silica, wherein the percents by weight are based on the total weight of the particle.
In certain embodiments of the electrodepositable coating compositions of the present invention, the corrosion resisting particles comprise 10 to 25 percent by weight zinc oxide, 0.5 to 50 percent by weight molybdenum oxide, and 25 to 89.5 percent by weight silica, wherein the percents by weight are based on the total weight of the particle.
In other embodiments of the electrodepositable coating compositions of the present invention, the corrosion resisting particles comprise 0.5 to 25 percent by weight cerium oxide, 0.5 to 50 percent by weight boron oxide, and 25 to 99 percent by weight silica, wherein the percents by weight are based on the total weight of the particle.
In still other embodiments of the electrodepositable coating compositions of the present invention, the corrosion resisting particles comprise 0.5 to 25 percent by weight cerium oxide, 0.5 to 50 percent by weight aluminum oxide, and 25 to 99 percent by weight silica, wherein the percents by weight are based on the total weight of the particle.
In yet other embodiments of the electrodepositable coating compositions of the present invention, the corrosion resisting particles comprise 0.5 to 25 percent by weight cerium oxide, 0.5 to 25 percent by weight zinc oxide, 0.5 to 25 percent by weight boron oxide, and 25 to 98.5 percent by weight silica, wherein the percents by weight are based on the total weight of the particle.
In certain embodiments of the electrodepositable coating compositions of the present invention, the corrosion resisting particles comprise 0.5 to 25 percent by weight yttrium oxide, 0.5 to 25 percent by weight phosphorous oxide, 0.5 to 25 percent by weight zinc oxide, and 25 to 98.5 percent by weight silica, wherein the percents by weight are based on the total weight of the particle.
In certain embodiments of the electrodepositable coating compositions of the present invention, the corrosion resisting particles comprise 0.5 to 75 percent by weight magnesium or tin oxide, and 25 to 99.5 percent by weight silica, wherein the percents by weight are based on the total weight of the particle.
In some embodiments of the electrodepositable coating compositions of the present invention, the corrosion resisting particles comprise 0.5 to 5 percent by weight yttrium oxide, 0.5 to 5 percent by weight molybdenum oxide, 0.5 to 25 percent by weight zinc oxide, 0.5 to 5 percent by weight cerium oxide and 60 to 98 percent by weight silica, wherein the percents by weight are based on the total weight of the particles.
Certain embodiments of the electrodepositable coating compositions of the present invention comprise ultrafine particles comprising an inorganic oxide, or in some embodiments, a plurality of inorganic oxides. As used herein, the term “ultrafine” refers to particles that have a B.E.T. specific surface area of at least 10 square meters per gram, such as 30 to 500 square meters per gram, or, in some cases, 80 to 250 square meters per gram. In certain embodiments, the coating compositions of the present invention comprise corrosion resisting particles having a calculated equivalent spherical diameter of no more than 200 nanometers, such as no more than 100 nanometers, or, in certain cases, 5 to 50 nanometers.
Certain embodiments of the electrodepositable coating compositions of the present invention comprise corrosion resisting particles having an average primary particle size of no more than 100 nanometers, such as no more than 50 nanometers, or, in certain embodiments, no more than 20 nanometers.
When a coating composition of the present invention is in a liquid medium, the catalyst and/or corrosion resisting particles may have an affinity for the medium of the composition sufficient to keep the particles suspended therein. The affinity of the particles for the medium may be greater than the affinity of the particles for each other, thereby preventing agglomeration of the particles within the medium. This property can be due to the nature of the particles themselves. The particles can also be substantially free of any surface treatment. In certain embodiments, the particles used in the composition of the present invention may be added to the composition neat during the formulation thereof, and may be added at high loadings without appreciable viscosity increases, allowing for formulation of high solids coating compositions.
The shape (or morphology) of the catalyst and/or corrosion resisting particles can vary depending upon the specific embodiment of the present invention and its intended application. For example, generally spherical morphologies can be used, as well as particles that are cubic, platy, or acicular (elongated or fibrous). In general, the particles are substantially spherical in shape.
The catalyst and/or corrosion resisting particles may be prepared by various methods, including gas phase synthesis processes, such as, for example, flame pyrolysis, hot walled reactor, chemical vapor synthesis, among other methods. In certain embodiments, however, such particles are prepared by reacting together one or more organometallic and/or metal oxide precursors and any other ingredients in a fast quench plasma system. In certain embodiments, the catalyst and/or corrosion resisting particles are formed in such a system by: (a) introducing materials into a plasma chamber; (b) rapidly heating the materials by means of a plasma to a selection temperature sufficient to yield a gaseous product stream; (c) passing the gaseous product stream through a restrictive convergent-divergent nozzle to effect rapid cooling and/or utilizing an alternative cooling method, such as a cool surface or quenching stream, and (d) condensing the gaseous product stream to yield ultrafine solid particles. Certain suitable fast quench plasma systems and methods for their use are described in U.S. Pat. Nos. 5,749,937, 5,935,293, and RE 37,853 E, which are incorporated herein by reference. One process of preparing catalyst and/or corrosion resisting particles suitable for use in certain embodiments of the coating compositions of the present invention comprises: (a) introducing one or more organometallic precursors and/or inorganic oxide precursors into one axial end of a plasma chamber; (b) rapidly heating the precursor stream by means of a plasma to a selected reaction temperature as the precursor stream flows through the plasma chamber, yielding a gaseous product stream; (c) passing the gaseous product stream through a restrictive convergent-divergent nozzle arranged coaxially within the end of the reaction chamber; and (d) subsequently cooling and slowing the velocity of the desired end product exiting from the nozzle, yielding ultrafine solid particles.
The precursor stream may be introduced to the plasma chamber as a solid, liquid, gas, or a mixture thereof. Suitable liquid reactants that may be used as part of the precursor stream include organometallics, such as, for example, cerium-2 ethylhexanoate, zinc-2 ethylhexanoate, tetraethoxysilane, calcium methoxide, triethylphosphate, lithium 2,4-pentanedionate, yttrium butoxide, trimethoxyboroxine, aluminum sec-butoxide, molybdenum oxide bis(2,4-pentanedionate), among other materials, including mixtures thereof. Suitable solid precursors that may be used as part of the precursor stream include solid silica powder (such as silica fume, silica sand, or precipitated silica), bismuth oxide; bismuth silicate; bismuth titanate; molybdenum oxide; molybdenum silicate; molybdenum titanate; tungsten oxide; tungsten silicate; tungsten titanate; cerium acetate, cerium oxide, magnesium oxide, tin oxide, zinc oxide, silicon dioxide and other oxides, among other materials, including mixtures thereof. The reactant stream may be introduced to the reaction chamber as a solid, liquid, or gas, but is usually introduced as solid.
In certain embodiments, the catalyst and/or corrosion resisting particles are prepared by a method comprising: (a) introducing a solid precursor into a plasma chamber; (b) heating the precursor by means of a plasma to a selected reaction temperature as the precursor flows through the plasma chamber, yielding a gaseous product stream; (c) contacting the gaseous product stream with a plurality of quench streams injected into the plasma chamber through a plurality of quench gas injection ports, wherein the quench streams are injected at flow rates and injection angles that result in the impingement of the quench streams with each other within the gaseous product stream, thereby producing ultrafine particles; and (d) passing the ultrafine particles through a converging member.
In certain embodiments, the catalyst and/or corrosion resisting particles are prepared by a method comprising: (a) introducing a solid precursor into a plasma chamber; (b) heating the precursor by means of a plasma to a selected reaction temperature as the precursor flows through the plasma chamber, yielding a gaseous product stream; (c) passing the gaseous product stream through a converging member; then (d) contacting the gaseous product stream with a plurality of quench streams injected into the plasma chamber through a plurality of quench gas injection ports, wherein the quench streams are injected at flow rates and injection angles that result in the impingement of the quench streams with each other within the gaseous product stream, thereby producing ultrafine particles; and (e) collecting the ultrafine particles.
Referring now to FIGS. 1A and 1B, there are seen flow diagrams depicting certain embodiments of suitable methods for making catalyst and/or corrosion resisting particles. As is apparent, in certain embodiments, at step 100, a solid precursor is introduced into a feed chamber. As used herein, the term “precursor” refers to a substance from which a desired product is formed. Then, as is apparent from FIGS. 1A and 1B at step 200, in certain embodiments, the solid precursor is contacted with a carrier. The carrier may be a gas that acts to suspend the solid precursor in the gas, thereby producing a gas-stream suspension of the solid precursor. Suitable carrier gases include, but are not limited to, argon, helium, nitrogen, oxygen, air, hydrogen, or a combination thereof.
Next, in certain embodiments, the solid precursor is heated, at step 300, by means of a plasma to a selected temperature as the solid precursor flows through the plasma chamber, yielding a gaseous product stream. In certain embodiments, the temperature ranges from 2,500° to 20,000° C., such as 1,700° to 8,000° C.
In certain embodiments, the gaseous product stream may be contacted with a reactant, such as a hydrogen-containing material, that may be injected into the plasma chamber, as indicated at step 350. The particular material used as the reactant is not limited and may include, for example, air, water vapor, hydrogen gas, ammonia, and/or hydrocarbons, depending on the desired properties of the resulting catalyst and/or corrosion resisting particles.
As is apparent from FIG. 1A, in certain embodiments, after the gaseous product stream is produced, it is, at step 400, contacted with a plurality of quench streams that are injected into the plasma chamber through a plurality of quench stream injection ports, wherein the quench streams are injected at flow rates and injection angles that result in impingement of the quench streams with each other within the gaseous product stream. The material used in the quench streams is not limited, so long as it adequately cools the gaseous product stream to cause formation of ultrafine solid particles. Thus, as used herein, the term “quench stream” refers to a stream that cools the gaseous product stream to such an extent so as to cause formation of ultrafine particles. Materials suitable for use in the quench streams include, but are not limited to, hydrogen gas, carbon dioxide, air, water vapor, ammonia, mono, di and polybasic alcohols, silicon-containing materials (such as hexamethyldisilazane), carboxylic acids and/or hydrocarbons.
The particular flow rates and injection angles of the various quench streams are not limited, so long as they impinge with each other within the gaseous product stream to result in the rapid cooling of the gaseous product stream to produce ultrafine particles. This is different from certain fast quench plasma systems that utilize Joule-Thompson adiabatic and isentropic expansion through, for example, the use of a converging-diverging nozzle or a “virtual” converging diverging nozzle, to form ultrafine particles. In these embodiments, the gaseous product stream is contacted with the quench streams to produce ultrafine solid catalyst nanoparticles before passing those particles through a converging member, such as, for example, a converging-diverging nozzle, which, inter alia, can reduce the fouling or clogging of the plasma chamber, thereby enabling the production of ultrafine solid particles from solid reactants without frequent disruptions in the production process for cleaning of the plasma system. In these embodiments, the quench streams primarily cool the gaseous product stream through dilution, rather than adiabatic expansion, thereby causing a rapid quenching of the gaseous product stream and the formation of ultrafine solid particles prior to passing the particles into and through a converging member.
As used herein, the term “converging member” refers to a device that includes at least a section or portion that progresses from a larger diameter to a small diameter in the direction of flow, thereby restricting passage of a flow therethrough, which can permit control of the residence time of the flow in the plasma chamber due to a pressure differential upstream and downstream of the converging member. In certain embodiments, the converging member is a conical member, i.e., a member whose base is relatively circular and whose sides taper towards a point, wherein, in other embodiments, the converging member is a converging-diverging nozzle of the type described in U.S. Pat. No. RE 37,853 at col. 9, line 65 to col. 11, line 32, the cited portion of which being incorporated herein by reference.
Referring again to FIG. 1A, it is seen that, in certain embodiments, after contacting the gaseous product stream with the quench streams to cause production of ultrafine solid particles, the particles are, at step 500, passed through a converging member, whereas in other embodiments, as illustrated in FIG. 1B, the gaseous product stream is passed through a converging member at step 450 prior to contacting the stream with the quench streams to cause production of ultrafine particles at step 550. In either of these embodiments, while the convergent-divergent nozzle may act to cool the product stream to some degree, the quench streams perform much of the cooling so that a substantial amount of ultrafine solid particles are formed upstream of the convergent member in the embodiments of FIG. 1A or downstream of the converging member in the embodiments of FIG. 1B. Moreover, in either of these embodiments, the converging member may primarily act as a choke position that permits operation of the reactor at higher pressures, thereby increasing the residence time of the materials therein. The combination of quench stream dilution cooling with a converging member appears to provide a commercially viable method of producing ultrafine solid particles from solid precursors, since, for example, (i) a solid precursor can be used effectively without heating the feed material to a gaseous or liquid state before injection into the plasma, and (ii) fouling of the plasma system can be minimized, or eliminated, thereby reducing or eliminating disruptions in the production process for cleaning of the plasma system.
As shown in FIGS. 1A and 1B, in certain embodiments, after the ultrafine solid particles are passed through a converging member, they are harvested at step 600. Any suitable means may be used to separate the ultrafine solid particles from the gas flow, such as, for example, a bag filter or cyclone separator.
Now referring to FIGS. 2A and 2B, there are depicted schematic diagrams of an apparatus for producing ultrafine solid catalyst and/or corrosion resisting particles in accordance with certain embodiments of the present invention. As is apparent, a plasma chamber 20 is provided that includes a solid particle feed inlet 50. Also provided is at least one carrier gas feed inlet 14, through which a carrier gas flows in the direction of arrow 30 into the plasma chamber 20. As previously indicated, the carrier gas acts to suspend the solid reactant in the gas, thereby producing a gas-stream suspension of the solid reactant which flows towards plasma 29. Numerals 23 and 25 designate cooling inlet and outlet respectively, which may be present for a double-walled plasma chamber 20. In these embodiments, coolant flow is indicated by arrows 32 and 34. Suitable coolants include both liquids and gasses depending upon the selected reactor geometry and materials of construction.
In the embodiments depicted by FIGS. 2A and 2B, a plasma torch 21 is provided. Torch 21 vaporizes the incoming gas-stream suspension of solid reactant within the resulting plasma 29 as the stream is delivered through the inlet of the plasma chamber 20, thereby producing a gaseous product stream. As shown in FIGS. 2A and 2B, the solid particles are, in certain embodiments, injected downstream of the location where the arc attaches to the annular anode 13 of the plasma generator or torch.
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.
A plasma can be produced with any of a variety of gases. This can give excellent control over any chemical reactions taking place in the plasma as the gas may be inert, such as argon, helium, or neon, reductive, such as hydrogen, methane, ammonia, and carbon monoxide, or oxidative, such as oxygen, nitrogen, and carbon dioxide. Air, oxygen, and/or oxygen/argon gas mixtures are often used to produce ultrafine solid particles in accordance with the present invention. In FIGS. 2A and 2B, the plasma gas feed inlet is depicted at 31.
As the gaseous reaction product exits the plasma 29 it proceeds towards the outlet of the plasma chamber 20. As is apparent, an additional reactant, as described earlier, can be injected into the reaction chamber prior to the injection of the quench streams. A supply inlet for the reactant is shown in FIGS. 2A and 2B at 33.
As shown in FIGS. 2A and 2B, in certain embodiments, the gaseous product stream is contacted with a plurality of quench streams which enter the plasma chamber 20 in the direction of arrows 41 through a plurality of quench gas injection ports 40 located along the circumference of the plasma chamber 20. As previously indicated, the particular flow rate and injection angle of the quench streams is not limited so long as they result in impingement of the quench streams 41 with each other within the gaseous reaction product stream, in some cases at or near the center of the gaseous product stream, to result in the rapid cooling of the gaseous product stream to produce ultrafine solid particles. This results in a quenching of the gaseous product stream through dilution to form ultrafine solid particles.
Referring now to FIG. 3, there is depicted a perspective view of a plurality of quench gas injection ports 40 in accordance with certain embodiments of the present invention. In this particular embodiment, six (6) quench gas injection ports are depicted, wherein each port disposed at an angle “0” apart from each other along the circumference of the reactor chamber 20. It will be appreciated that “0” may have the same or a different value from port to port. In certain embodiments of the present invention, at least four (4) quench gas injection ports 40 are provided, in some cases at least six (6) quench gas injection ports are present. In certain embodiments, each angle “0” has a value of no more than 90°. In certain embodiments, the quench streams are injected into the plasma chamber normal (90° angle) to the flow of the gaseous reaction product. In some cases, however, positive or negative deviations from the 90° angle by as much as 30° may be used.
In certain embodiments, such as is depicted in FIG. 2B, one or more sheath streams are injected into the plasma chamber upstream of the converging member. As used herein, the term “sheath stream” refers to a stream of gas that is injected prior to the converging member and which is injected at flow rate(s) and injection angle(s) that result in a barrier separating the gaseous product stream from the plasma chamber walls, including the converging portion of the converging member. The material used in the sheath stream(s) is not limited, so long as the stream(s) act as a barrier between the gaseous product stream and the converging portion of the converging member, as illustrated by the prevention, to at least a significant degree, of material sticking to the interior surface of the plasma chamber walls, including the converging member. For example, materials suitable for use in the sheath stream(s) include, but are not limited to, those materials described earlier with respect to the quench streams. A supply inlet for the sheath stream is shown in FIG. 2B at 70 and the direction of flow is indicated by numeral 71.
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.
As is apparent from FIGS. 2A and 2B, in certain embodiments, the ultrafine solid particles may flow from cool down chamber 26 to a collection station 27 via a cooling section 45, which may comprise, for example, a jacket cooled tube. In certain embodiments, the collection station 27 comprises a bag filter or other collection means. A downstream scrubber 28 may be used if desired to condense and collect material within the flow prior to the flow entering vacuum pump 60.
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° angle) to the flow of the plasma gases. In some cases, positive or negative deviations from the 90° angle by as much as 30° may be desired.
The high temperature of the plasma rapidly vaporizes the precursor. There can be a substantial difference in temperature gradients and gaseous flow patterns along the length of the plasma chamber 20. It is believed that, at the plasma arc inlet, flow is turbulent and there is a high temperature gradient; from temperatures of about 20,000 K at the axis of the chamber to about 375 K at the chamber walls.
The plasma chamber is often constructed of water cooled stainless steel, nickel, titanium, copper, aluminum, or other suitable materials. The plasma chamber can also be constructed of ceramic materials to withstand a vigorous chemical and thermal environment.
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.
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.
The inside diameter of the plasma chamber 20 may be determined by the fluid properties of the plasma and moving gaseous stream. It should be sufficiently great to permit necessary gaseous flow, but not so large that recirculating eddies or stagnant zones are formed along the walls of the chamber. Such detrimental flow patterns can cool the gases. In many cases, the inside diameter of the plasma chamber 20 is more than 100% of the plasma diameter at the inlet end of the plasma chamber.
The catalyst particles described in detail above can be present in the electrodepositable coating composition of the present invention in an amount of at least 0.1 percent by weight of metal (bismuth, molybdenum, tungsten, etc.) based on weight of total resin solids present in the electrodepositable coating composition. Also, the catalyst particles can be present in the electrodepositable coating composition of the present invention in an amount less than or equal to 5.0 percent by weight metal, often less than or equal to 3.0 percent by weight metal, and typically less than or equal to 1.0 percent by weight metal based on weight of total resin solids present in the electrodepositable coating composition. The level of catalyst particles present in the electrodepositable coating composition can range between any combination of these values, inclusive of the recited values. The catalyst is present in an amount sufficient to effect cure (determined by a method described in detail below) of the composition at a temperature at or below 360° F. (182.2° C.).
As used herein, the term “cure” as used in connection with a composition, e.g., “composition when cured” or a “cured composition”, shall mean that any crosslinkable components of the composition are at least partially crosslinked. In certain embodiments of the present invention, the crosslink density of the crosslinkable components, i.e., the degree of crosslinking, ranges from 5% to 100% of complete crosslinking. In other embodiments, the crosslink density ranges from 35% to 85% of full crosslinking. In other embodiments, the crosslink density ranges from 50% to 85% of full crosslinking. One skilled in the art will understand that the presence and degree of crosslinking, i.e., the crosslink density, can be determined by a variety of methods, such as dynamic mechanical thermal analysis (DMTA) using a TA Instruments DMA 2980 DMTA analyzer conducted under nitrogen. This method determines the glass transition temperature and crosslink density of free films of coatings or polymers. These physical properties of a cured material are related to the structure of the crosslinked network. In certain embodiments of the present invention, the sufficiency of cure is evaluated relative to the solvent resistance of the cured film. For example, solvent resistance can be measured by determining the number of double acetone rubs. For purposes of the present invention, a coating is deemed to be “cured” when the film can withstand a minimum of 100 double acetone rubs without substantial softening of the film and no removal of the film.
The catalyst particles described herein are substantially non-volatile at the curing temperature, that is, at temperatures at or below 360° F. (182.2° C.). By “substantially non-volatile” is meant that the catalyst particles do not volatilize from the film into the curing oven environment at these temperatures during the curing process.
In certain embodiments, one or more of the previously described corrosion resisting particles are present in a coating composition of the present invention in an amount of 3 to 50 percent by volume, such as 8 to 30 percent by volume, or, in some cases, 10 to 18 percent by volume, based on the total volume of the coating composition.
As aforementioned, in addition to the catalyst and/or corrosion resisting particles, the electrodepositable coating compositions of the present invention also comprise a resinous phase comprising (a) one or more active hydrogen-containing, ionic salt group-containing resins, and (b) one or more curing agents.
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.
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° C. to 160° C. for 30 to 180 minutes until an epoxy group-containing resinous reaction product is obtained.
The equivalent ratio of reactants; i.e., epoxy:polyhydroxyl group-containing material is typically from 1.00:0.50 to 1.00:2.00.
The polyepoxide typically has at least two 1,2-epoxy groups. In general, the epoxide equivalent weight of the polyepoxide will range from 100 to 2000, such as from 180 to 500. The epoxy compounds may be saturated or unsaturated, cyclic or acyclic, aliphatic, alicyclic, aromatic or heterocyclic. They may contain substituents such as halogen, hydroxyl, and ether groups.
Examples of suitable polyepoxides are those having a 1,2-epoxy equivalency greater than one, such as two; that is, polyepoxides which have on average two epoxide groups per molecule. In some cases, the preferred polyepoxides are polyglycidyl ethers of polyhydric alcohols such as cyclic polyols, such as polyglycidyl ethers of polyhydric phenols such as Bisphenol A. These polyepoxides can be produced by etherification of polyhydric phenols with an epihalohydrin or dihalohydrin, such as epichlorohydrin or dichlorohydrin, in the presence of alkali. Besides polyhydric phenols, other cyclic polyols can be used in preparing the polyglycidyl ethers of cyclic polyols, such as alicyclic polyols, including cycloaliphatic polyols, such as 1,2-cyclohexane diol and 1,2-bis(hydroxymethyl)cyclohexane. In some cases, the preferred polyepoxides have epoxide equivalent weights ranging from 180 to 2000, such as from 186 to 1200. Epoxy group-containing acrylic polymers can also be used. These polymers often have an epoxy equivalent weight ranging from 750 to 2000.
Examples of polyhydroxyl group-containing materials used to chain extend or increase the molecular weight of the polyepoxide (i.e., through hydroxyl-epoxy reaction) include alcoholic hydroxyl group-containing materials and phenolic hydroxyl group-containing materials. Examples of alcoholic hydroxyl group-containing materials are simple polyols, such as neopentyl glycol; polyester polyols, such as those described in U.S. Pat. No. 4,148,772; polyether polyols, such as those described in U.S. Pat. No. 4,468,307; and urethane diols, such as those described in U.S. Pat. No. 4,931,157. Examples of phenolic hydroxyl group-containing materials are polyhydric phenols, such as Bisphenol A, phloroglucinol, catechol, and resorcinol. Mixtures of alcoholic hydroxyl group-containing materials and phenolic hydroxyl group-containing materials may be used.
As indicated, the active hydrogen-containing resin can contain cationic salt groups, which can be incorporated into the resin molecule as follows: The resinous reaction product prepared as described above is further reacted with a cationic salt group former. By “cationic salt group former” is meant a material which is reactive with epoxy groups and which can be acidified before, during, or after reaction with the epoxy groups to form cationic salt groups. Examples of suitable materials include amines, such as primary or secondary amines, which can be acidified after reaction with the epoxy groups to form amine salt groups, or tertiary amines which can be acidified prior to reaction with the epoxy groups and which after reaction with the epoxy groups form quaternary ammonium salt groups. Examples of other cationic salt group formers are sulfides which can be mixed with acid prior to reaction with the epoxy groups and form ternary sulfonium salt groups upon subsequent reaction with the epoxy groups.
When amines are used as the cationic salt formers, monoamines typically are employed. Hydroxyl-containing amines are suitable, and polyamines also may be used.
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.
Examples of hydroxyl-containing amines include, but are not limited to, alkanolamines, dialkanolamines, alkyl alkanolamines, and aralkyl alkanolamines containing from 1 to 18 carbon atoms, preferably 1 to 6 carbon atoms in each of the alkanol, alkyl and aryl groups. Specific examples include ethanolamine, N-methylethanolamine, diethanolamine, N-phenylethanolamine, N,N-dimethylethanolamine, N-methyldiethanolamine, 3-aminopropyldiethanolamine, and N-(2-hydroxyethyl)-piperazine.
Amines such as mono, di, and trialkylamines and mixed aryl-alkyl amines which do not contain hydroxyl groups or amines substituted with groups other than hydroxyl may also be used. Specific examples include ethylamine, methylethylamine, triethylamine, N-benzyldimethylamine, dicocoamine, 3-dimethylaminopropylamine, and N,N-dimethylcyclohexylamine.
Mixtures of the above mentioned amines may also be used.
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° C. may be done to hasten the reaction.
The reaction product of the primary and/or secondary amine and the polyepoxide is made cationic and water dispersible by at least partial neutralization with an acid. Suitable acids include organic acids, such as formic acid, acetic acid, methanesulfonic acid, and lactic acid, and inorganic acids, such as phosphoric acid and sulfamic acid, which refers to sulfamic acid itself or derivatives thereof; i.e., an acid of the formula:

wherein R is hydrogen or an alkyl group having 1 to 4 carbon atoms. Mixtures of the above mentioned acids may also be used.
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.
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.
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° 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° C. Solvents such as a sterically hindered ester, ether, or sterically hindered ketone may be used.
In addition to the primary, secondary, and tertiary amines disclosed above, a portion of the amine that is reacted with the polyepoxide can be a ketimine of a polyamine, such as is described in U.S. Pat. No. 4,104,147, column 6, line 23 to column 7, line 23. The ketimine groups decompose upon dispersing the amine-epoxy resin reaction product in water. In certain embodiments, at least a portion of the active hydrogens present in the resin (a) comprise primary amine groups derived from the reaction of a ketimine-containing compound and an epoxy group-containing material, such as those described above.
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.
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.
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.
The acrylic polymer can be prepared by traditional free radical initiated polymerization techniques, such as solution or emulsion polymerization, as known in the art, using suitable catalysts which include organic peroxides and azo type compounds and optionally chain transfer agents, such as alpha-methyl styrene dimer and tertiary dodecyl mercaptan. Additional acrylic polymers which are suitable for forming the active hydrogen-containing, cationic resin, which can be used in the electrodepositable compositions of the present invention, include the resins described in U.S. Pat. Nos. 3,455,806 and 3,928,157.
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.
Additional examples of polyurethane polymers suitable for forming the active hydrogen-containing, cationic resin are the polyurethane, polyurea, and poly(urethane-urea) polymers prepared by reacting polyether polyols and/or polyether polyamines with polyisocyanates, as described in U.S. Pat. No. 6,248,225.
Epoxide functional groups may be incorporated into the polyurethane by, for example, reacting glycidol with free isocyanate groups. Alternatively, hydroxyl groups on the polyurethane can be reacted with an epihalohydrin or dihalohydrin such as epichlorohydrin or dichlorohydrin in the presence of alkali.
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® E, available from Resolution Performance Products.
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.
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.
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.
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° F. (182.2° C.). The active hydrogens typically are derived from reactive hydroxyl groups, and primary and secondary amino, including mixed groups such as hydroxyl and primary amino. In one embodiment of the present invention, at least a portion of the active hydrogens are derived from hydroxyl groups comprising phenolic hydroxyl groups. The cationic resin can have an active hydrogen content of 1 to 4 milliequivalents, such as 2 to 3 milliequivalents, of active hydrogen per gram of resin solids.
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.
Generally, the cationic resin in the electrodepositable composition of the present invention contains from 0.1 to 3.0, such as from 0.1 to 0.7, milliequivalents of cationic salt group per gram of resin solids. The cationic resin typically is non-gelled, having a number average molecular weight ranging from 2000 to 15,000, such as from 5000 to 10,000. By “non-gelled” is meant that the resin is substantially free from crosslinking, and prior to cationic salt group formation, the resin has a measurable intrinsic viscosity when dissolved in a suitable solvent. In contrast, a gelled resin, having an essentially infinite molecular weight, would have an intrinsic viscosity too high to measure.
The active hydrogen-containing, cationic salt group-containing resin can be present in the electrodepositable composition of the present invention in an amount ranging from 40 to 95 weight percent, such as from 50 to 75 weight percent based on weight of total resin solids present in the composition.
The electrodepositable compositions of the present invention also comprise at least one curing agent, such as a polyisocyanate, polyester or carbonate. The polyisocyanate curing agent may be a fully blocked polyisocyanate with substantially no free isocyanate groups, or it may be partially blocked and reacted with the resin backbone as described in U.S. Pat. No. 3,984,299. The polyisocyanate can be an aliphatic or an aromatic polyisocyanate or a mixture of the two. Diisocyanates are often preferred, although higher polyisocyanates can be used in place of or in combination with diisocyanates.
Examples of suitable aliphatic diisocyanates are straight chain aliphatic diisocyanates, such as 1,4-tetramethylene diisocyanate, norbornane diisocyanate, and 1,6-hexamethylene diisocyanate. Also, cycloaliphatic diisocyanates can be employed, such as isophorone diisocyanate and 4,4′-methylene-bis-(cyclohexyl isocyanate). Examples of suitable aromatic diisocyanates are p-phenylene diisocyanate, diphenylmethane-4,4′-diisocyanate and 2,4- or 2,6-toluene diisocyanate. Examples of suitable higher polyisocyanates are triphenylmethane-4,4′,4″-triisocyanate, 1,2,4-benzene triisocyanate and polymethylene polyphenyl isocyanate, and trimers of 1,6-hexamethylene diisocyanate.
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.
Any suitable alcohol or polyol can be used as a blocking agent for the polyisocyanate in the electrodepositable compositions of the present invention provided that the agent will deblock at the curing temperature and provided a gelled product is not formed. Any suitable aliphatic, cycloaliphatic, or aromatic alkyl alcohol may be used as a blocking agent for the polyisocyanate including, for example, lower aliphatic monoalcohols, such as methanol, ethanol, and n-butanol; cycloaliphatic alcohols such as cyclohexanol; aromatic-alkyl alcohols such as phenyl carbinol and methylphenyl carbinol. Glycol ethers may also be used as blocking agents. Suitable glycol ethers include ethylene glycol butyl ether, diethylene glycol butyl ether, ethylene glycol methyl ether and propylene glycol methyl ether.
In certain embodiments, the blocking agent comprises a 1,3-glycol and/or a 1,2-glycol. In certain embodiments, the blocking agent comprises a 1,2-glycol, such as one or more C₃to C₆1,2-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.
Other suitable blocking agents include oximes, such as methyl ethyl ketoxime, acetone oxime and cyclohexanone oxime and lactams, such as epsilon-caprolactam.
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° C., and curing times of up to 90 minutes. Acceptable cure temperatures and cure times will be dependent upon the substrates to be coated and their end uses.
Compounds generally suitable as the polyester curing agent are polyesters of polycarboxylic acids, including bis(2-hydroxyalkyl)esters of dicarboxylic acids, such as bis(2-hydroxybutyl)azelate and bis(2-hydroxyethyl)terephthalate; tri(2-ethylhexanoyl)trimellitate; and poly(2-hydroxyalkyl)esters of acidic half-esters prepared from a dicarboxylic acid anhydride and an alcohol, including polyhydric alcohols. The latter type is suitable to provide a polyester with a final functionality of more than 2. One suitable example includes a polyester prepared by first reacting equivalent amounts of the dicarboxylic acid anhydride (for example, succinic anhydride or phthalic anhydride) with a trihydric or tetrahydric alcohol, such as glycerol, trimethylolpropane or pentaerythritol, at temperatures below 150° 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.
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.
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.
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° C.
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.
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° C. Also, trimellitic anhydride can be reacted with 3 molar equivalents of a monoalcohol, such as 2-ethylhexanol.
Alternatively, trimellitic anhydride can be reacted first with a glycol or a glycol monoalkyl ether, such as ethylene glycol monobutyl ether, in a molar ratio of 1:0.5 to 1:1, after which the product is allowed to react with 2 moles of glycidyl esters of branched monocarboxylic acids. Furthermore, the polycarboxylic acid anhydride i.e., those containing two or three carboxyl functions per molecule, or a mixture of polycarboxylic acid anhydrides can be reacted simultaneously with a glycol, such as 1,6-hexane diol and/or glycol mono-ether and monoepoxide, after which the product can be reacted with mono-epoxides, if desired. For aqueous compositions these non-acid polyesters can also be modified with polyamines, such as diethylene triamine, to form amide polyesters. Such “amine-modified” polyesters may be incorporated in the linear or branched amine adducts described above to form self-curing amine adduct esters.
The non-acidic polyesters of the types described above often are soluble in organic solvents, and often can be mixed readily with the previously described active hydrogen-containing resin.
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.
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 certain embodiments, the curing agent is present in the electrodepositable composition in an amount ranging from 5 to 60 percent by weight, such as from 25 to 50 percent by weight, based on total weight of resin solids.
It should be understood that the catalyst and/or corrosion resisting particles can be incorporated into the electrodepositable composition of the present invention by any method or means provided that the stability of the composition is not compromised. For example, such particles can be admixed with or dispersed in the reactants used to form the resin (a) during preparation of the resin (a). Also, such particles can be admixed with or dispersed in one or more of the reactants used to form the resin (a) prior to resin preparation. In addition, such particles can be admixed with or dispersed in the resin (a) either prior to or subsequent to neutralization with an acid. The particles also can be admixed with or dispersed in the at least partially blocked polyisocyanate curing agent (b) prior to combining the resin (a) and the curing agent (b). Further, the particles can be admixed with or dispersed in the admixture of the resin (a) and the curing agent (b). Alternatively, the particles can be added to any of the optional additives, solvents, or adjuvant resinous materials as described below prior to addition of the optional ingredients to the composition. Also, the particles can be directly admixed with or dispersed in the aqueous medium, prior to dispersion of the resinous phase in the aqueous medium. The particles also can be added neat to the electrodepositable composition subsequent to dispersion in the aqueous medium. Additionally, if desired, the particles can be added on-line to the electrodeposition bath in the form of an additive material.
The electrodepositable composition of the present invention may contain a coalescing solvent such as hydrocarbons, alcohols, esters, ethers and ketones. The coalescing solvent is usually present in an amount up to 40 percent by weight, typically ranging from 0.05 to 25 percent by weight based on total weight of the electrodepositable composition.
The electrodepositable compositions of the present invention may further contain conventional pigments and various other optional additives such as plasticizers, surfactants, wetting agents, defoamers, and anti-cratering agents, as well as adjuvant resinous materials different from the resin (a) and the curing agent (b).
Suitable pigments include, but are not limited to, iron oxides, lead oxides, carbon black, coal dust, titanium dioxide, talc, clay, silica, and barium sulfate, as well as color pigments such as cadmium yellow, cadmium red, chromium yellow, and the like. The pigment content of the aqueous dispersion, generally expressed as the pigment to resin (or pigment to binder) ratio is often 0.05:1 to 1:1. In certain embodiments, the electrodepositable coating composition of the present invention is free of lead-containing compounds.
The electrodepositable coating compositions of the present invention are used in an electrodeposition process in the form of an aqueous dispersion. By “dispersion” is meant a two-phase transparent, translucent, or opaque aqueous resinous system in which the resin, pigment, and water insoluble materials are in the dispersed phase while water and water-soluble materials comprise the continuous phase. The dispersed phase can have an average particle size of less than 10 microns, and can be less than 5 microns. The aqueous dispersion can contain at least 0.05 and usually 0.05 to 50 percent by weight resin solids, depending on the particular end use of the dispersion.
The electrodepositable compositions of certain embodiments of the present invention in the form of an aqueous dispersion have excellent storage stability, that is, upon storage at a temperature of 140° F. (60° 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.
In certain processes of electrodeposition, the electrodepositable composition of the present invention in the form of an aqueous dispersion is placed in contact with an electrically conductive anode and cathode, where the substrate serves as the cathode. Upon passage of an electric current between the anode and cathode while they are in contact with the aqueous dispersion, an adherent film of the electrodepositable composition will deposit in a substantially continuous manner on the cathode. The film will contain the active hydrogen-containing resin, the blocked polyisocyanate curing agent, the catalyst, and the optional additives from the non-aqueous phase of the dispersion.
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.
In yet other embodiments, the present invention is directed to a coated substrate comprising a substrate and a composition coated over the substrate, wherein the composition is selected from any of the foregoing compositions. In still other embodiments, the present invention is directed to a method of coating a substrate which comprises applying a composition over the substrate, wherein the composition is selected from any of the foregoing compositions. In other embodiments, the present invention is directed to a method for forming a cured coating on a substrate comprising applying over the substrate a coating composition, wherein the composition is selected from any of the foregoing compositions.
In other embodiments, the present invention is directed to a method of coating a substrate further comprising a step of curing the composition after application to the substrate. The components used to form the compositions in these embodiments can be selected from the components discussed above, and additional components also can be selected from those recited above.
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.
Electrodeposition is usually carried out at a constant voltage in the range of from 1 volt to several thousand volts, typically between 50 and 500 volts. Current density is usually between 1.0 ampere and 15 amperes per square foot (10.8 to 161.5 amperes per square meter) and tends to decrease quickly during the electrodeposition process, indicating formation of a continuous self-insulating film. Any electroconductive substrate known in the art, especially metal substrates such as steel, zinc, aluminum, copper, magnesium or the like can be coated with the electrodepositable composition of the present invention. It is customary to pretreat the substrate with a phosphate conversion, usually a zinc phosphate conversion coating, followed by a rinse which seals the conversion coating.
After deposition, the coating is often heated to cure the deposited composition. The heating or curing operation can be carried out at a temperature in the range of from 250 to 400° F. (121.1 to 204.4° C.), typically from 300 to 360° F. (148.8 to 182.2° C.), for a period of time ranging from 1 to 60 minutes. The thickness of the resultant film often ranges from 10 to 50 microns.
The invention will be further described by reference to the following examples. Unless otherwise indicated, all parts and percentages are by weight.

EXAMPLES

Particle Example 1

Particles were prepared using a DC thermal plasma system. The plasma system included a DC plasma torch (Model SG-100 Plasma Spray Gun commercially available from Praxair Technology, Inc., Danbury, Conn.) operated with 80 standard liters per minute of argon carrier gas and 24 kilowatts of power delivered to the torch. A liquid precursor feed composition comprising the materials and amounts listed in Table 1 was prepared and fed to the reactor at a rate of 5 grams per minute through a gas assisted liquid nebulizer located 3.7 inches down stream of the plasma torch outlet. At the nebulizer, a mixture of 4.9 standard liters per minute of argon and 10.4 standard liters per minute oxygen were delivered to assist in atomization of the liquid precursors. Additional oxygen at 28 standard liters per minute was delivered through a ⅛ inch diameter nozzle located 180° apart from the nebulizer. Following a 6 inch long reactor section, a plurality of quench stream injection ports were provided that included 6⅛ inch diameter nozzles located 60° apart radially. A 10 millimeter diameter converging-diverging nozzle of the type described in U.S. Pat. No. RE 37,853E was provided 4 inches downstream of the quench stream injection port. Quench air was injected through the plurality of quench stream injection ports at a rate of 100 standard liters per minute.

	TABLE 1


	Material	Amount

	Cerium 2-ethylhexanoate¹	163 grams
	Zinc 2-ethylhexanoate²	311 grams
	Tetraethoxysilane³	1056 grams

	¹Commercially available from Alfa Aesar, Ward Hill, Massachusetts.
	²Commercially available from Alfa Aesar, Ward Hill, Massachusetts.
	³Commercially available from Sigma Aldrich Co., St Louis, Missouri.

The produced particles had a theoretical composition of 18 weight percent zinc oxide, 6 weight percent cerium oxide, and 76 weight percent silica. The measured B.E.T. specific surface area was 201 square meters per gram using the Gemini model 2360 analyzer and the calculated equivalent spherical diameter was 23 nanometers.

Particle Example 2

Particles from liquid precursors were prepared using the apparatus and conditions identified in Example 1 and the feed materials and amounts listed in Table 2.

	TABLE 2


	Material	Amount

	Calcium methoxide⁴	116 grams
	Butanol	116 grams
	2-ethylhexanoic acid	582 grams
	Tetraethoxysilane³	820 grams

	⁴Commercially available from Sigma Aldrich Co., St Louis, Missouri.

The produced particles had a theoretical composition of 21 weight percent calcium oxide, and 76 weight percent silica. The measured B.E.T. specific surface area was 106 square meters per gram using the Gemini model 2360 analyzer and the calculated equivalent spherical diameter was 27 nanometers.

Particle Example 3

Particles from liquid precursors were prepared using the apparatus and conditions identified in Example 1 and the feed materials and amounts listed in Table 3.

	TABLE 3


	Material	Amount

	Cerium 2-ethylhexanoate ¹	41 grams
	Trimethoxyboroxine⁵	50 grams
	Zinc 2-ethylhexanoate²	78 grams
	Tetraethoxysilane³	229 grams
	Hexanes⁶	76 grams
	Methyl ethyl ketone	182 grams

	⁵Commercially available from Alfa Aesar, Ward Hill, Massachusetts.
	⁶Commercially available from Sigma Aldrich Co., St Louis, Missouri.

The produced particles had a theoretical composition of 6 weight percent cerium oxide, 10 weight percent boron oxide, 18 weight percent zinc oxide, and 66 weight percent silica. The measured B.E.T. specific surface area was 175 square meters per gram using the Gemini model 2360 analyzer and the calculated equivalent spherical diameter was 13 nanometers.

Particle Example 4

Particles from liquid precursors were prepared using the apparatus and conditions identified in Example 1 and the feed materials and amounts listed in Table 4.

	TABLE 4


	Material	Amount

	Calcium methoxide⁴	55 grams
	Butanol	55 grams
	2-ethylhexanoic acid	273 grams
	Zinc 2-ethylhexanoate²	160 grams
	Tetraethoxysilane³	809 grams

The produced particles had a theoretical composition of 10 weight percent calcium oxide, 12.3 weight percent zinc oxide, and 77.7 weight percent silica. The measured B.E.T. specific surface area was 124 square meters per gram using the Gemini model 2360 analyzer and the calculated equivalent spherical diameter was 34 nanometers.

Example 5

A resinous composition was prepared from the ingredients of Table 5:

TABLE 5


Component	Description	Mass (/g)

A	methyl isobutyl ketone	174.39
	Tinuvin 1130⁷	17.68
B	ethyl acrylate	384.11
	Styrene	294.00
	Hydroxypropyl methacrylate	94.85
	methyl methacrylate	33.19
	glycidyl methacrylate	142.28
	t-dodecyl mercaptan	4.73
	Vazo 67⁸	23.70
	Dowanol PNB⁹	30.36
	Dowanol PM¹⁰	15.17
	methyl isobutyl ketone	12.30
C	Luperoxl 7M50¹¹	19.01
	Dowanol PNB	15.17
	methyl isobutyl ketone	7.58
D	Diethanolamine	85.37
E	DETA diketimine¹²	71.52
F	crosslinker¹³	1055.34
G	sulfamic acid	60.68
	deionized water	5547.04

⁷Light stabilizer available from Ciba Geigy Corporation.
⁸2,2′-azobis(2-methylbutyronotrile) available from Du Pont Specialty Chemicals.
⁹N-butoxypropanol solvent available from Dow Chemical Co.
¹⁰Propylene glycol monomethyl ether solvent available from Dow Chemical Co.
¹¹50% t-butyl peroxyacetate in mineral spirits available from Arkema Inc.
¹²Diketimine formed from diethylene triamine and methylisobutyl ketone (72.69% solids in methylisobutyl ketone).
¹³Blocked isocyanate curing agent, 79.5% solids in methylisobutyl ketone. Prepared by reacting 10 equivalents of isophorone diisocyanate with 1 equivalent of trimethylol propane, 3 equivalents of bisphenol A-ethylene oxide polyol (prepared at a bisphenol A to ethylene oxide molar ratio of 1:6) and 6 equivalents of primary hydroxy from 1,2-butane diol.

Components A were raised to reflux in a 3 liter flask fitted with a stirrer, thermocouple, nitrogen inlet and a Dean and Stark condenser. The temperature was adjusted throughout the process to maintain reflux until noted otherwise. Components B were added at a uniform rate over 150 minutes. After a further 30 minutes components C were added over 10 minutes. 90 minutes later component D was added followed, 90 minutes later by component E. After 60 minutes component F was added and the temperature was allowed to fall to 105° C. over 60 minutes.
Meanwhile components G were heated to 50° C. in a separate vessel. 2381.5 g of the reaction mixture were then poured into components G under rapid agitation. The resulting dispersion had a solids content of 25%.
Solvent was removed from the dispersion by distillation under reduced pressure. The final dispersion had a solid content of 27.9%

Example 6

Pigment pastes 6A to 6E were prepared from the ingredients of Table 6:

TABLE 6


Ingredient	Example 6A	Example 6B	Example 6C	Example 6D	Example 6E

Grind vehicle¹⁴	402.7 g	402.7 g	402.7 g	402.7 g	402.7 g
Surfynol GA¹⁵	8.4 g	8.4 g	8.4 g	8.4 g	8.4 g
pH additive¹⁶	13.2 g	13.2 g	13.2 g	13.2 g	13.2 g
Deionized water	110.1 g	110.1 g	110.1 g	110.1 g	110.1 g
Titanium dioxide	384.7 g	384.7 g	384.7 g	384.7 g	384.7 g
Carbon black	6.9 g	6.9 g	6.9 g	6.9 g	6.9 g
Clay	117.5 g	—	—	—	—
Particle Example 1	—	117.5 g	—	—	—
Particle Example 2	—	—	117.5 g	—	—
Particle Example 3	—	—	—	117.5 g	—
Particle Example 4	—	—	—	—	117.5 g
Dibutyl tin oxide	220.4 g	220.4 g	220.4 g	220.4 g	220.4 g
paste

¹⁴A grind vehicle as described in Example 2 of United States Patent No. 4,715,898 with 2 percent by weight on solids of Icomeen T-2 (commercially available from BASF) added.
¹⁵A surfactant commercially available from Air Products and Chemicals, Inc.
¹⁶A 22% solution of lactic acid in deionized water.

The ingredients were milled in a Redhead mill using ceramic media to a Hegman gauge reading of 7.

Example 7

Electrodepositable compositions were prepared from the pigment pastes of Examples 6A and 6B from the ingredients of Table 7:

TABLE 7


Ingredient	Example 7A	Example 7B

Resin of Example 5	1222.0 g	1222.0 g
Plasticizer	15.9 g	15.9 g
Polyepoxide¹⁷	98.6 g	98.6 g
Deionized water	100.0 g	100.0 g
Cationic epoxy resin¹⁸	784.5 g	784.5 g
Example 6A	251.0 g	—
Example 6B	—	251.0 g
E-6278¹⁹	6.6 g	6.6 g
Deionized water	1321.4 g	1321.4 g

¹⁷A polyoxyalkylenepolyamine-polyepoxide adduct derived from Jeffamine D400 (polyoxypropylenediamine commercially available from Huntsman Corp.) and DER-732 (aliphatic epoxide commercially available from Dow Chemical Co.) prepared as described in U. S. Pat. No. 4,423,166.
¹⁸Prepared as described in Example H of United States Patent Application Publication 2003/0054193A1.
¹⁹A dibutyl tin oxide containing pigment paste commercially available from PPG Industries, Inc.

The 22 percent solids compositions of Examples 7A and 7B which contained 1.5% tin level of weight of resin solids were ultrafiltered with 20 percent by weight of the composition being replaced with deionized water. CRS and EG panels were cathodically electrodeposited in the composition at 0.9 mils thickness. The coated panel was cured at 360° F. (182.2° C.) for 25 minutes. The cured coating was smooth, uniform and had good solvent resistance. The coated panels were subjected to corrosion testing according to General Motors Test Method GM9540P (GM APG scab corrosion). This test measures loss of paint, adhesion and corrosion of the base metal across a scribe line on the coated panel after exposure to repeated cycles. After 20 cycles on the bare substrates and 40 cycles on the phosphated substrates, the coated panels are examined for corrosion creepback from the scribe line. Results are reported in millimeters (mm) of creepage. Results are reported in Table 8 with replicates.

TABLE 8


	Commercial
Substrate/Cycles	Control	Example 7A	Example 7B

Bare CRS/20 cycles	23/23	22/23	3-6/4-8
Bare EG/20 cycles	5-10/3-8	2-5/2-5	1-3/1-2
Phosphated CRS/40 cycles	4-5/4-5	4-5/4-5	3-4/2-4
Phosphated EG/40 cycles	1-3/1-2	1-3/1-2	1-2/1-2

It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. Whereas particular embodiments of this invention have been described above for purposes of illustration, it will be evident to those skilled in the art that numerous variations of the details of the present invention may be made without departing from the invention as defined in the appended claims.

Claims

1. An electrodepositable coating composition comprising:

(a) a resinous phase comprising:

(i) an active hydrogen-containing, ionic salt group-containing resin; and

(ii) at least one curing agent; and

(b) particles having a calculated equivalent spherical diameter of no more than 200 nanometers and comprising a plurality of inorganic oxides wherein at least one inorganic oxide comprises zinc, cerium, yttrium, magnesium, lithium, aluminum, tin, or calcium.

2. The electrodepositable coating composition of claim 1, wherein the particles (b) comprise corrosion resisting particles.

3. The electrodepositable coating composition of claim 1, wherein the particles are selected from (i) particles comprising oxides of cerium, zinc, and silicon; (ii) particles comprising oxides of calcium, zinc and silicon; (iii) particles comprising oxides of phosphorous, zinc and silicon; (iv) particles comprising oxides of yttrium, zinc, and silicon; (v) particles comprising oxides of molybdenum, zinc, and silicon; (vi) particles comprising oxides of boron, zinc, and silicon; (vii) particles comprising oxides of cerium, aluminum, and silicon, (viii) particles comprising oxides of magnesium or tin and silica, and (ix) particles comprising oxides of cerium, boron, and silicon, or a mixture thereof.

4. The electrodepositable coating composition of claim 3, wherein the particles comprise oxides of cerium, zinc, and silicon.

5. The electrodepositable coating composition of claim 1, wherein the particles are selected from particles comprising:

(i) 10 to 25 percent by weight zinc oxide, 0.5 to 25 percent by weight cerium oxide, and 50 to 89.5 percent by weight silica;

(ii) 10 to 25 percent by weight zinc oxide, 0.5 to 25 percent by weight calcium oxide, and 50 to 89.5 percent by weight silica;

(iii) 10 to 25 percent by weight zinc oxide, 0.5 to 25 percent by weight yttrium oxide, and 50 to 89.5 percent by weight silica;

(iv) 10 to 25 percent by weight zinc oxide, 0.5 to 50 percent by weight phosphorous oxide, and 25 to 89.5 percent by weight silica;

(v) 10 to 25 percent by weight zinc oxide, 0.5 to 50 percent by weight boron oxide, and 25 to 89.5 percent by weight silica;

(vi) 10 to 25 percent by weight zinc oxide, 0.5 to 50 percent by weight molybdenum oxide, and 25 to 89.5 percent by weight silica;

(vii) 0.5 to 25 percent by weight cerium oxide, 0.5 to 50 percent by weight boron oxide, and 25 to 99 percent by weight silica;

(viii) 0.5 to 25 percent by weight cerium oxide, 0.5 to 50 percent by weight aluminum oxide, and 25 to 99 percent by weight silica;

(ix) 0.5 to 75 percent by weight magnesium or tin oxide, and 25 to 99.5 percent by weight silica;

(x) 0.5 to 25 percent by weight cerium oxide, 0.5 to 25 percent by weight zinc oxide, 0.5 to 25 percent by weight boron oxide, and 25 to 98.5 percent by weight silica;

(xi) 0.5 to 25 percent by weight yttrium oxide, 0.5 to 25 percent by weight phosphorous oxide, 0.5 to 25 percent by weight zinc oxide, and 25 to 98.5 percent by weight silica;

(xii) 0.5 to 5 percent by weight yttrium oxide, 0.5 to 5 percent by weight molybdenum oxide, 0.5 to 25 percent by weight zinc oxide, 0.5 to 5 percent by weight cerium oxide and 60 to 98 percent by weight silica; and

(xiii) mixtures thereof,

wherein the percent by weights are based on the total weight of the particles.

6. The electrodepositable coating composition of claim 1, wherein the particles are prepared by a process comprising:

(a) introducing a reactant into a plasma chamber;

(b) heating the reactant by means of a plasma as the reactant flows through the plasma chamber, yielding a gaseous reaction product;

(c) contacting the gaseous reaction product with a plurality of quench streams injected into the reaction chamber through a plurality of quench gas injection ports, wherein the quench streams are injected at a flow rate and injection angle that results in the impingement of the quench streams with each other within the gaseous reaction product stream, thereby producing ultrafine solid particles; and

(d) passing the ultrafine solid particles through a converging member.

7. The electrodepositable coating composition according to claim 1, wherein at least a portion of the particles are dispersed in one or both of the resin (i) and the curing agent (ii) prior to dispersing the resinous phase in the aqueous medium.

8. The electrodepositable coating composition according to claim 1, further comprising catalyst particles selected from the group consisting of bismuth oxide; bismuth silicate; bismuth titanate; molybdenum oxide; molybdenum silicate; molybdenum titanate; tungsten oxide; tungsten silicate; tungsten titanate; and combinations thereof, wherein the catalyst nanoparticles have an average B.E.T. specific surface area greater than 20 square meters per gram (m²/g).

9. The electrodepositable coating composition according to claim 8, wherein the catalyst particles comprise bismuth oxide.

10. The electrodepositable coating composition according to claim 1, wherein the catalyst nanoparticles are present in the coating composition in an amount ranging from 0.1 to 5.0 percent by weight of metal based on weight of total resin solids present in the electrodepositable coating composition.

11. The electrodepositable coating composition according to claim 1, wherein the resin (a) comprises active hydrogens derived from reactive hydroxyl groups and/or primary amine groups.

12. The electrodepositable coating composition according to claim 1, wherein the resin (a) comprises the reaction product of a polyepoxide and a diglycidyl ether of a polyhydric phenol.

13. The electrodepositable coating composition according to claim 1, wherein at least a portion of the active hydrogens present in the resin (a) comprise primary amine groups derived from the reaction of a ketimine-containing compound and an epoxy group-containing material.

14. The electrodepositable coating composition according to claim 1, wherein the curing agent (b) is at least partially blocked with a blocking agent.

15. The electrodepositable coating composition according to claim 1, which is free of lead-containing compounds.

16. An electrodepositable coating composition comprising:

(a) a resinous phase comprising:

(i) an active hydrogen-containing, ionic salt group-containing resin; and

(ii) a curing agent;

(b) catalyst particles selected from the group consisting of bismuth oxide, bismuth silicate, bismuth titanate, molybdenum oxide, molybdenum silicate, molybdenum titanate, tungsten oxide, tungsten silicate, tungsten titanate, or a combination thereof, wherein the catalyst particles have an average B.E.T. specific surface area greater than 20 square meters per gram; and

(c) corrosion resisting particles having a calculated equivalent spherical diameter of no more than 200 nanometers and comprising a plurality of inorganic oxides comprising at least one inorganic oxide comprising zinc, cerium, yttrium, manganese, magnesium, molybdenum, lithium, aluminum, or calcium.

17. A method for electrocoating a conductive substrate serving as a cathode in an electrical circuit comprising the cathode and an anode, the cathode and anode being immersed in an aqueous electrocoating composition, the method comprising passing electric current between the cathode and anode to cause deposition of the electrocoating composition onto the substrate as a substantially continuous film, the aqueous electrocoating composition comprising (1) a resinous phase comprising: (a) an active hydrogen group-containing, ionic group-containing electrodepositable resin; and (b) a curing agent, and (2) corrosion resisting particles having a calculated equivalent spherical diameter of no more than 200 nanometers and comprising a plurality of inorganic oxides wherein at least one inorganic oxide comprises zinc, cerium, yttrium, magnesium, lithium, aluminum, tin, or calcium.