PROCESSES

TECHNICAL FIELD

This invention generally relates to the field of autodeposition coatings on metallic surfaces of a substrate, and more particularly to operating autodeposition coating processes in a manner to extend the operative life of catalysts used in the production of articles having autodeposition coatings.

BACKGROUND OF THE INVENTION

Autodeposition has been in commercial use on steel for more than thirty years and is now well established for that use. For details, see for example, U.S. Pat. Nos. 3,063,877; 3,585,084; 3,592,699; 3,674,567; 3,791,431; 3,795,546; 4,030,945; 4,108,817; 4,178,400; 4,186,226; 4,242,379; 4,234,704; 4,636,264; 4,636,265; 4,800,106; and 5,342,694. The disclosures of all these patents are incorporated herein by reference in their entirety for all purposes. Epoxy resin-based autodeposition coating systems are described in U.S. Pat. No. 4,180,603; U.S. Pat. No. 4,289,826; U.S. Pat. No. 5,500,460; U.S. Pat. No. 7,388,044 and International Publication Number WO 00/71337, the teachings of each of which are incorporated by reference in their entirety for all purposes.

Autodeposition compositions are usually in the form of liquid, usually aqueous solutions, emulsions or dispersions in which active metal surfaces of inserted articles are coated with an adherent resin or polymer film that increases in thickness the longer the metal remains in the bath, even though the liquid is stable for a long time against spontaneous precipitation or flocculation of any resin or polymer, in the absence of contact with the active metal. When used in the autodeposition process, the composition when cured forms a polymeric coating. "Active metal" is defined as metal that spontaneously begins to dissolve at a substantial rate when introduced into the liquid solution or dispersion. Such compositions, and processes of forming a coating on a metal surface using such compositions, are commonly denoted in the art, and in this specification, as "autodeposition" or "autodepositing" compositions, dispersions, emulsions, suspensions, baths, solutions, processes, methods or a like term. Autodeposition is often contrasted with electrodeposition. Although each can produce adherent films with similar performance characteristics, the dispersions from which they are produced and the mechanism by which they deposit are distinctly different. Electrodeposition requires that metal or other articles to be coated be connected to a source of direct current electricity for coating to occur. No such external electric current is used in autodeposition.

Conventional autodeposition coatings are typically cured in two steps and require reaching a peak metal temperature (PMT) of about 200° C. This higher temperature cure coating provides improved properties such as resistance to temperatures up to about 220° C, but comes at a cost in time and energy for curing and limits the type of paints that can be applied to the uncured autodeposition coating.

The general difficulties facing any low temperature cure autodeposition coating composition (curable at oven temperatures of 130° C or less) have been poor performance of the cured coating with respect to corrosion resistance, chemical resistance and high temperature resistance compared to conventional higher temperature curing autodeposition coating compositions, as well as poor storage and heat stability of the coating compositions prior to application. This is reflected in the limited, if any, commercial successes of low temperature cure chemistry in the autodeposition industry.

U.S. Pat. No. 4,575,523 and U.S. Pat. No. 6,048,443 disclose low bake cathodic electrodeposition compositions, but the chemistry of these compositions is unstable in autodeposition bath conditions. U.S. Pat. No. 7,388,044 discloses single component autodeposition compositions, but the coatings are generally baked above 160° C. International patent publication WO 2002/042008 discloses rinse compositions of metal phosphates that are said to improve anticorrosive properties of autodeposition coatings, but these rinses cannot catalyze crosslinking or improve chemical resistance in the autodeposition coatings described therein. International patent publication WO 2012/174424 discloses an additive having one to two nitrogen-oxygen bonds that are said to improve autodeposition coating performance on multimetal substrates, but these additives cannot catalyze crosslinking or improve chemical resistance in the autodeposition coatings described therein, and the coatings are generally baked above 160° C.

Many problems with conventional low temperature autodeposition coatings are addressed by the teachings in International patent publication WO 2017/117169, which is also published as U.S. Pre-Grant Publication No. 2018/0304306 ("the '306 publication"), and both of which are incorporated herein by reference. The '306 publication provides various methods and compositions for creating autodeposition coatings at low cure temperatures of 140° C or less. Such coatings have corrosion resistance, chemical resistance and high temperature resistance properties comparable to conventional higher temperature curing autodeposition coating, and also provide good storage and heat stability of the coating compositions prior to application.

Although the teachings of the '306 publication represent an advancement over the state of the art, the inventors have determined that further improvements can be made to provide greater flexibility and efficiency when implementing processes such as those described in the '306 publication or other autodeposition coating processes.

SUMMARY OF THE INVENTION

According to one aspect of the present invention ("Aspect 1"), an autodeposition coating line is provided which is comprised of, consists essentially of, or consists of: an autodeposition coating bath configured to receive one or more articles therein, the autodeposition coating bath containing an autodeposition composition comprising an epoxy-based autodeposition coating material selected to form a layer of uncured autodeposition composition on an active metal surface of the one or more articles upon contact therewith; a catalyst rinse bath configured to receive the one or more articles therein following the autodeposition coating bath, the catalyst rinse bath containing an aqueous catalyst composition comprising a dissolved and/or dispersed crosslinking catalyst that is capable of reacting with and/or absorbing carbon dioxide; an ion exchange system comprising: an ion exchange column containing a strong base anion exchange resin; a plurality of fluid control circuits between the catalyst rinse bath and the ion exchange column; and one or more controls operatively connected to the plurality of fluid control circuits and configured to selectively operate the plurality of fluid control circuits to remove a quantity of the aqueous catalyst composition from the catalyst rinse bath, pass the quantity of the aqueous catalyst composition through the ion exchange column into contact with the strong base anion exchange resin capable of removing a quantity of carbon dioxide from the quantity of aqueous catalyst composition, and return the quantity of aqueous catalyst composition to the catalyst rinse bath; and a cure oven configured to receive the one or more articles therein following the catalyst rinse bath.

Further aspects of the invention may be summarized as follows: Aspect 2: The autodeposition coating line of any of the foregoing Aspects, wherein the aqueous catalyst composition within the catalyst rinse bath is in contact with atmospheric air.

Aspect 3: The autodeposition coating line of any of the foregoing Aspects, wherein the cure oven is operable at a temperature selected to cure the layer of uncured autodeposition composition on the one or more articles to full cure at 140° C or less.

Aspect 4. The autodeposition coating line of any of the foregoing Aspects, wherein the aqueous catalyst composition comprises an amine-based catalyst.

Aspect 5: The autodeposition coating line of any of the foregoing Aspects, wherein at least a portion of the amine-based catalyst is deactivated by carbonation of the portion with carbon dioxide.

Aspect 6: The autodeposition coating line of any of the foregoing Aspects, wherein the aqueous catalyst composition comprises one or more of: cyclic amidines, tertiary amines, quinuclidine-based catalysts, and triazine-based catalysts, preferably one or more of l,8-diazabicyclo[5.4.0]undece-l-ene; l,5-diazabicyclo[4.3.0]non-5-ene; 1,2-dimethyl- 1,4,5,6-tetrahydropyrimidine; N-(3-dimethylaminopropyl)-N,N-diisopropanolamine; diazabicyclo[2.2.2]octane; l,3,5-tris(3-(dimethylamino)propyl)-hexahydro-s-triazine; imidazole; 1,2-dimethylimidazole; and dicyandiamide.

Aspect 7: The autodeposition coating line of any of the foregoing Aspects, wherein the strong base anion exchange resin comprises quaternary ammonium functional groups in the OH-form substituted thereon.

Aspect 8: The autodeposition coating line of any of the foregoing Aspects, wherein the one or more controls operates manually or automatically.

Aspect 9: The autodeposition coating line of any of the foregoing Aspects, wherein the aqueous catalyst composition comprises an amidine.

Aspect 10: The autodeposition coating line of any of the foregoing Aspects, further comprising: a) a cleaning rinse bath configured to receive the one or more articles therein before the autodeposition coating bath, the cleaning rinse bath comprising a degreasing composition; b) a water rinse bath configured to receive the one or more articles therein following the cleaning rinse bath and before the autodeposition coating bath, the water rinse bath containing a quantity of water; and cl) a water rinse bath configured to receive the one or more articles therein following the autodeposition coating bath and prior to the catalyst rinse bath, the water rinse bath containing a quantity of water; or c2) a post-treatment rinse bath configured to receive the one or more articles therein following the autodeposition coating bath and prior to the catalyst rinse bath, the post-treatment rinse bath comprising a post-treatment reagent comprising at least one of: soluble zirconium compounds, soluble titanium compounds, and an alkaline earth metal compound.

According to another aspect of the present invention ("Aspect 11"), an open-to-air crosslinking catalyst rinse bath system method is provided which is comprised of, consists essentially of, or consists of: a catalyst rinse bath containing an aqueous catalyst composition in contact with atmospheric air and comprising a dissolved and/or dispersed crosslinking catalyst that is capable of reacting with and/or absorbing carbon dioxide; an ion exchange column containing a strong base anion exchange resin; a first fluid control circuit connecting an outlet of the catalyst rinse bath to an inlet of the ion exchange column; and a second fluid control circuit connecting an outlet of the ion exchange column to an inlet of the catalyst rinse bath; wherein the first fluid control circuit is configured to convey a quantity of the aqueous catalyst composition from the catalyst rinse bath to the ion exchange column into contact with the strong base anion exchange resin capable of removing a quantity of carbon dioxide from the quantity of aqueous catalyst composition, and the second fluid control circuit is configured to convey the quantity of the aqueous catalyst composition from the ion exchange column to the catalyst rinse bath.

Further aspects of the invention may be summarized as follows:

Aspect 12: The open-to-air crosslinking catalyst rinse bath system of any of the foregoing Aspects, wherein the first fluid control circuit comprises a first valve, the second fluid control circuit comprises a second valve, and at least one of the first fluid control circuit and the second fluid control circuit comprises a first pump.

Aspect 13: The open-to-air crosslinking catalyst rinse bath system of any of the foregoing Aspects, wherein at least one of the first fluid control circuit and the second fluid control circuit comprises a heat exchanger or a holding tank.

Aspect 14: The open-to-air crosslinking catalyst rinse bath system of any of the foregoing Aspects, further comprising a processor operatively connected to the first fluid control circuit and the second fluid control circuit, and configured to operate the first fluid control circuit to convey the quantity of the aqueous catalyst composition from the catalyst rinse bath to the ion exchange column and operate the second fluid control circuit to convey the quantity of the aqueous catalyst composition from the ion exchange column to the catalyst rinse bath.

Aspect 15: The open-to-air crosslinking catalyst rinse bath system of any of the foregoing Aspects, further comprising: a supply of regenerant; a third fluid control circuit extending from an outlet of the supply of regenerant to the inlet of the ion exchange column; and a fourth fluid control circuit extending from the outlet of the ion exchange column to a waste receptacle.

Aspect 16: The open-to-air crosslinking catalyst rinse bath system of any of the foregoing Aspects, wherein the regenerant comprises at least one of sodium hydroxide and potassium hydroxide.

Aspect 17 : The open-to-air crosslinking catalyst rinse bath system of any of the foregoing Aspects, further comprising a processor operatively connected to the third fluid control circuit and the fourth fluid control circuit, and configured to operate the third fluid control circuit to convey a quantity of the regenerant from the supply of regenerant to the ion exchange column and operate the fourth fluid control circuit to convey the quantity of the regenerant from the ion exchange column to the waste receptacle.

Aspect 18: The open-to-air crosslinking catalyst rinse bath system of any of the foregoing Aspects, wherein the processor is operatively connected to the first fluid control circuit and the second fluid control circuit, and configured to operate the first fluid control circuit to convey the quantity of the aqueous catalyst composition from the catalyst rinse bath to the ion exchange column and operate the second fluid control circuit to convey the quantity of the aqueous catalyst composition from the ion exchange column to the catalyst rinse bath.

Aspect 19: The open-to-air crosslinking catalyst rinse bath system of any of the foregoing Aspects, further comprising: a water supply; and a fifth fluid control circuit extending from an outlet of the water supply to the inlet of the ion exchange column.

Aspect 20: The open-to-air crosslinking catalyst rinse bath system of any of the foregoing Aspects, further comprising: a processor operatively connected to the fifth fluid control circuit and the fourth fluid control circuit, and configured to operate the fifth fluid control circuit to convey a first quantity of water from the water supply to the inlet of the ion exchange column and operate the fourth fluid control circuit to convey the first quantity of water from the ion exchange column to the waste receptacle.

Aspect 21 : The open-to-air crosslinking catalyst rinse bath system of any of the foregoing Aspects, wherein the processor is operatively connected to the third fluid control circuit and the fourth fluid control circuit, and configured to operate the third fluid control circuit to convey a quantity of the regenerant from the supply of regenerant to the ion exchange column and operate the fourth fluid control circuit to convey the quantity of the regenerant from the ion exchange column to the waste receptacle.

Aspect 22: The open-to-air crosslinking catalyst rinse bath system of any of the foregoing Aspects, wherein the processor is operatively connected to the first fluid control circuit and the second fluid control circuit, and configured to operate the first fluid control circuit to convey the quantity of the aqueous catalyst composition from the catalyst rinse bath to the ion exchange column and operate the second fluid control circuit to convey the quantity of the aqueous catalyst composition from the ion exchange column to the catalyst rinse bath.

Aspect 23: The open-to-air crosslinking catalyst rinse bath system of any of the foregoing Aspects, further comprising: a sixth fluid control circuit extending from the outlet of the water supply to the outlet of the ion exchange column; and a seventh fluid control circuit extending from the inlet of the ion exchange column to the waste receptacle.

Aspect 24: The open-to-air crosslinking catalyst rinse bath system of any of the foregoing Aspects, further comprising a processor operatively connected to the fourth fluid control circuit, the fifth fluid control circuit, the sixth fluid control circuit and the seventh fluid control circuit, the processor being configured to alternately: operate the fifth fluid control circuit to convey a first quantity of water from the water supply to the inlet of the ion exchange column and operate the fourth fluid control circuit to convey the first quantity of water from the ion exchange column to the waste receptacle; and operate the sixth fluid control circuit to convey a second quantity of water from the water supply to the outlet of the ion exchange column and operate the seventh fluid control circuit to convey the second quantity of water from the ion exchange column to the waste receptacle.

Aspect 25: The open-to-air crosslinking catalyst rinse bath system of any of the foregoing Aspects, wherein the aqueous catalyst composition comprises one or more of: cyclic amidines, tertiary amines, quinuclidine-based catalysts, and triazine-based catalysts; preferably one or more of l,8-diazabicyclo[5.4.0]undece-l-ene; l,5-diazabicyclo[4.3.0]non- 5-ene; 1, 2-dimethyl- 1,4, 5, 6-tetra hydropyrimidine; N-(3-dimethylaminopropyl)-N,N- diisopropanolamine; diazabicyclo[2.2.2]octane; l,3,5-tris(3-(dimethylamino)propyl)- hexahydro-s-triazine; imidazole; 1,2-dimethylimidazole; and dicyandiamide.

Aspect 26: The open-to-air crosslinking catalyst rinse bath system of any of the foregoing Aspects, wherein the aqueous catalyst composition comprises an amine-based catalyst, preferably comprising an amidine.

Aspect 27: The open-to-air crosslinking catalyst rinse bath system of any of the foregoing Aspects, wherein at least a portion on the amidine is deactivated by carbonation thereof with carbon dioxide.

Aspect 28: The open-to-air crosslinking catalyst rinse bath system of any of the foregoing Aspects, wherein the aqueous catalyst composition consists of at least one amidine and water.

Aspect 29: The open-to-air crosslinking catalyst rinse bath system of any of the foregoing Aspects, wherein the strong base anion exchange resin comprises quaternary ammonium functional groups in the OH-form substituted thereon.

Aspect 30: The open-to-air crosslinking catalyst rinse bath system of any of the foregoing Aspects, wherein the strong base anion exchange resin comprises a crosslinked resin having a vinyl aromatic or acrylic polymeric backbone and the quaternary ammonium groups are bonded to the backbone.

According to another aspect of the present invention ("Aspect 31"), a method for operating a crosslinking catalyst rinse bath system having a catalyst rinse bath containing an aqueous catalyst composition exposed to one or more sources of carbon dioxide, the aqueous catalyst composition comprising a dissolved and/or dispersed crosslinking catalyst that is capable of reacting with and/or absorbing carbon dioxide, and an ion exchange column, is provided which is comprised of, consists essentially of, or consists of the following steps: a) contacting one or more articles comprising a surface coated with an uncured composition film to the aqueous catalyst composition while at least a portion of the aqueous catalyst composition is deactivated by carbonation of the catalyst with carbon dioxide to a carbonated form; b) moving a quantity of the aqueous catalyst composition including at least some of the portion of the catalyst in the carbonated form to the ion exchange column; c) contacting the quantity of aqueous catalyst composition with a strong base anion exchange resin in the ion exchange column thereby converting at least some of the portion in the catalyst in the carbonated form to aqueous catalyst composition in a catalytically active free base form; and d) moving the quantity of aqueous catalyst composition to the catalyst rinse bath.

Further aspects of the invention may be summarized as follows:

Aspect 32: The method of any of the foregoing Aspects, wherein the source of carbon dioxide comprises atmospheric air in contact with the aqueous catalyst composition in the catalyst rinse bath.

Aspect 33: The method of any of the foregoing Aspects, wherein step b) is performed after determining, optionally by measuring, that a total quantity of aqueous catalyst composition in the free base form following step a) is less than a predetermined threshold quantity.

Aspect 34: The method of any of the foregoing Aspects, wherein step b) is performed a predetermined time after initiating step a).

Aspect 35: The method of any of the foregoing Aspects, further comprising, after step d): e) contacting the strong base anion exchange resin in the ion exchange column with a quantity of regenerant.

Aspect 36: The method of any of the foregoing Aspects, wherein the regenerant comprises sodium hydroxide or potassium hydroxide. Aspect 37: The method of any of the foregoing Aspects, further comprising, after step e): f) rinsing the ion exchange column with water to remove at least a portion of any remaining regenerant from the ion exchange column.

Aspect 38: The method of any of the foregoing Aspects, wherein step f) comprises backflushing the strong base anion exchange resin in the ion exchange column.

Aspect 39: The method of any of the foregoing Aspects, further comprising, before step e): rinsing the ion exchange column with water to remove at least a portion of any remaining aqueous catalyst composition from the ion exchange column.

Aspect 40: The method of any of the foregoing Aspects, wherein step e) is performed after a predetermined number of iterations of steps a) through d).

Aspect 41: The method of any of the foregoing Aspects, wherein step e) is performed after determining, optionally measuring, that a total quantity of aqueous catalyst composition in the free base form following step c) is less than a predetermined threshold quantity. Aspect 42: The method of any of the foregoing Aspects, wherein the aqueous catalyst composition comprises one or more of: cyclic amidines, tertiary amines, quinuclidine-based catalysts, and triazine-based catalysts.

Aspect 43: The method of any of the foregoing Aspects, wherein the aqueous catalyst composition comprises one or more of: l,8-diazabicyclo[5.4.0]undece-l-ene; 1,5- diazabicyclo[4.3.0]non-5-ene; l,2-dimethyl-l,4,5,6-tetrahydropyrimidine; N-(3- dimethylaminopropyl)-N,N-diisopropanolamine; diazabicyclo[2.2.2]octane; l,3,5-tris(3- (dimethylamino)propyl)-hexahydro-s-triazine; imidazole; 1,2-dimethylimidazole; and dicyandiamide.

Aspect 44: The method of any of the foregoing Aspects, wherein the aqueous catalyst composition comprises an amine-based catalyst.

Aspect 45: The method of any of the foregoing Aspects, wherein the aqueous catalyst composition comprises an amidine.

Aspect 46: The method of any of the foregoing Aspects, wherein the aqueous catalyst composition consists essentially of at least one amidine and water. Aspect 47: The method of any of the foregoing Aspects, wherein the aqueous catalyst composition consists of at least one amidine and water. Aspect 48: The method of any of the foregoing Aspects, wherein the strong base anion exchange resin comprises quaternary ammonium functional groups in the OH-form substituted thereon.

Aspect 49: The method of any of the foregoing Aspects, wherein the strong base anion exchange resin comprises a crosslinked resin having a vinyl aromatic or acrylic polymeric backbone and the quaternary ammonium groups are bonded to the backbone.

Aspect 50: The method of any of the foregoing Aspects, wherein step b) further comprises reducing temperature of the quantity of the aqueous catalyst composition including at least some of the portion of the catalyst in the carbonated form prior to entry into the ion exchange column.

According to another aspect of the present invention ("Aspect 51"), a method of controlling carbonate concentration in an open-to-air catalyst rinse bath is provided which is comprised of, consists essentially of, or consists of the following steps: providing a quantity of an aqueous catalyst composition comprising a dissolved and/or dispersed crosslinking catalyst that is capable of reacting with and/or absorbing carbon dioxide into the catalyst rinse bath; exposing the quantity of aqueous catalyst composition to a source of carbon dioxide to thereby convert a portion of the crosslinking catalyst to a carbonated form; temporarily immersing one or more articles coated with an autodeposition compound film in the aqueous catalyst composition; and upon determining that the amount of crosslinking catalyst in the carbonated form is above a predetermined amount, removing a quantity of carbon dioxide from the aqueous catalyst composition to thereby reduce the amount of crosslinking catalyst in the carbonated form below the predetermined amount, without adding water soluble ions or particulates to the catalyst rinse bath.

Further aspects of the invention may be summarized as follows:

Aspect 52: The method of any of the foregoing Aspects, wherein removing a quantity of carbon dioxide from the aqueous catalyst composition to thereby reduce the amount of crosslinking catalyst in the carbonated form below the predetermined amount comprises: contacting at least a portion of the quantity of aqueous catalyst composition with a strong base anion exchange resin to thereby convert at least some of the portion in the carbonated form to crosslinking catalyst in a free base form.

Aspect 53: The method of any of the foregoing Aspects, wherein the aqueous catalyst composition comprises one or more of: cyclic amidines, tertiary amines, quinuclidine-based catalysts, and triazine-based catalysts.

Aspect 54: The method of any of the foregoing Aspects, wherein the aqueous catalyst composition comprises one or more of: l,8-diazabicyclo[5.4.0]undece-l-ene; 1,5- diazabicyclo[4.3.0]non-5-ene; 1, 2-dimethyl- 1,4, 5, 6-tetra hydropyrimidine; N-(3- dimethylaminopropyl)-N,N-diisopropanolamine; diazabicyclo[2.2.2]octane; l,3,5-tris(3- (dimethylamino)propyl)-hexahydro-s-triazine; imidazole; 1,2-dimethylimidazole; and dicyandiamide.

Aspect 55: The method of any of the foregoing Aspects, wherein the aqueous catalyst composition comprises an amine-based catalyst.

Aspect 56: The method of any of the foregoing Aspects, wherein the aqueous catalyst composition comprises an amidine.

Aspect 57: The method of any of the foregoing Aspects, wherein the aqueous catalyst composition consists essentially of at least one amidine and water.

Aspect 58: The method of any of the foregoing Aspects, wherein the aqueous catalyst composition consists of at least one amidine and water.

Aspect 59: The method of any of the foregoing Aspects, wherein the strong base anion exchange resin comprises a crosslinked resin having a vinyl aromatic or acrylic polymeric backbone and quaternary ammonium groups substituted thereon.

Other than in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, or defining ingredient parameters used herein are to be understood as modified in all instances by the term "about". Throughout the description, unless expressly stated to the contrary: percent, "parts of", and ratio values are by weight or mass; the term "polymer" includes "oligomer", "copolymer", "terpolymer", and the like; the first definition or description of the meaning of a word, phrase, acronym, abbreviation or the like applies to all subsequent uses of the same word, phrase, acronym, abbreviation or the like and applies, mutatis mutandis, to normal grammatical variations thereof; the term "mole" and its variations may be applied to ions, moieties, elements, and any other actual or hypothetical entity defined by the number and type of atoms present in it, as well as to materials with well-defined neutral molecules; the description of a group or class of materials as suitable or preferred for a given purpose in connection with the invention implies that mixtures of any two or more of the members of the group or class are equally suitable or preferred; description of constituents in chemical terms refers to the constituents at the time of addition to any combination specified in the description or of generation in situ within the composition by chemical reaction(s) between one or more newly added constituents and one or more constituents already present in the composition when the other constituents are added; specification of constituents in ionic form additionally implies the presence of sufficient counterions to produce electrical neutrality for the composition as a whole and for any substance added to the composition; any counterions thus implicitly specified preferably are selected from among other constituents explicitly specified in ionic form, to the extent possible; otherwise, such counterions may be freely selected, except for avoiding counterions that act adversely to an object of the invention; molecular weight (MW) is weight average molecular weight; the word "mole" means "gram mole", and the word itself and all of its grammatical variations may be used for any chemical species defined by all of the types and numbers of atoms present in it, irrespective of whether the species is ionic, neutral, unstable, hypothetical or in fact a stable neutral substance with well-defined molecules; the term "latex" is to be understood to mean a dispersion in water of polymer particles, and the terms "storage stable" or "shelf stable" are to be understood as including dispersions that show no visually detectable tendency toward phase separation or show less than 75, 50, 40, 35, 30, 25, 20, 18, 16, 14, 12, 10, 9, 8, 7, 6, 5, 4, 3, 2 or 1 % cross-linking, calculated by GPC comparison to unaged dispersions, over a period of observation of at least 72, 96, 120, 150, 200, 250, 300, 320, or preferably at least 336, hours during which the material is mechanically undisturbed and the temperature of the material is maintained at ambient room temperatures (18 to 25° C.).

For a variety of reasons, it is preferred that catalyst rinse compositions according to the invention may be substantially free from many ingredients known to poison or irreversibly damage strong base anion exchange resins, as well as other undesirable chemistries. Specifically, it is increasingly preferred in the order given, independently for each preferably minimized ingredient listed below, that compositions according to the invention, contain no more than 1.0, 0.5, 0.35, 0.10, 0.08, 0.04, 0.02, 0.01, 0.001, or 0.0002 percent, more preferably said numerical values in grams per liter, most preferably in ppm, of each of the following constituents: chromium; vinyl chloride monomer, vinylidene chloride monomer. The following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims and equivalents thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a process flow diagram of an exemplary autodeposition process employing a catalyst rinse step.

Figure 2 is a schematic illustration of an exemplary catalyst bath treatment system.

Figure 3 is a process flow diagram of an exemplary method for operating a catalyst bath treatment system.

Figure 4 is a schematic illustration of an exemplary control system for operating a catalyst bath treatment system.

DETAILED DESCRIPTION

The embodiments described herein relate to methods and systems for maintaining the condition of an active catalyst in a crosslinker bath in autodeposition coating systems. Embodiments are provided in various forms, such as an autodeposition coating line and methods for operating the same, or a crosslinker rinse bath and regeneration system and methods for operating the same. It will be understood that the embodiments discussed herein are exemplary, and other embodiments may encompass various different aspects or combinations of features described herein.

As used herein, the listed abbreviations have the following meaning: DMP: 3,5- Dimethylpyrazole; DICY: Dicyandiamide; DMI: 1,2-Dimethylimidazole; DEM: Diethyl malonate; DBU: l,8-Diazabicyclo[5.4.0]undece-l-ene; DBN: l,5-diazabicydo[4.3,0]non-5- ene; MEKO: Methylethyl ketoxime; HDI: Hexamethylene diisocyanate; IPDI: Isophorone diisocyanate; MDI: Methylene diphenyl diisocyanate; SFS: Sodium formaldehyde sulfoxylate; tBHP: tert-Butylhydroperoxide 70%; CRS: Cold rolled steel; GPC: Gel permeation chromatography. Additional definitions may be included throughout this disclosure.

Figure 1 illustrates an exemplary embodiment of a generally complete autodeposition process 100 into which various aspects of the invention may be incorporated. The process steps may be performed using any suitable equipment, such as: racks to hold one or more articles; open-top baths containing the various cleaning solvents, water, liquid compositions and so on; spray stations; ovens; etc. Any suitable automated or manual conveyor system may be used to move the articles between stations for the various steps, and multiple steps may be performed at a single station (e.g., spraying degreasing agents and then water at a single station to perform steps 102 and 104). The selection and use of such industrial equipment is within the ordinary skill in the art, and need not be discussed in detail herein.

Exemplary details of the particular operation steps are now described in greater detail, beginning with step 102 and concluding at the oven cure step 114. It will be appreciated that various steps may be omitted combined and/or added.

Beginning with the cleaning step 102, a metal surface normally is degreased and rinsed with water before applying an autodeposition composition. Conventional techniques for cleaning and degreasing the metal surface to be treated according to the invention can be used for the present invention. The particular selection of cleaning agents and cleaning method (e.g., dip bath, spray, etc.) can vary depending on the nature of the article being treated, and earlier steps that may have been used to prepare the article for the coating process. In a typical case, the article may be a metallic article or an article comprising a combination of metals and plastics, natural rubber, polymers, or the like. If the article is free of contaminants, step 102 might be omitted.

Step 104 may be performed using tap water, deionized water or any other composition suitable for removing any trace chemicals that might affect the downstream processes. However, step 104 might be omitted if the incoming article is already sufficiently clean to perform the autodeposition process, or if the cleaning step 102 does not leave residual cleaning compositions that would interfere with autodeposition. Rinse step 104 may be performed using a spray, immersion in or exposure to running water, a dip bath, or other suitable systems. In some embodiments, the article may be immersed in water for 10 to 120 seconds, or preferably for 20 to 60 seconds, in water at ordinary ambient temperature, e.g. about 18°C - 45°C.

Step 106 is an autodeposition coating step, in which an article with an active metal surface is contacted with an autodeposition coating material, such as an autodeposition bath composition as described herein, for a sufficient time to cause formation of a film of uncured coating having a predetermined thickness on the metal surface. The film deposited in this step may also contain certain other components of the autodeposition bath composition, such as a curing agent.

The autodeposition coating material preferably is an epoxy-based autodeposition coating material with good chemical and corrosion resistance, and preferably is curable at temperatures of less than 135° C. In one embodiment, an epoxy pre-polymer is used. The epoxy pre-polymer is combined with ethylenically unsaturated monomer that desirably may comprise hydroxyfunctional monomer, to yield an epoxy-monomer blend, which may be blended with other coating components and additives. The resulting blend is then dispersed in water with surfactant and the ethylenically unsaturated monomer is polymerized (optionally in the presence of other formulation components) to yield an aqueous epoxy dispersion. (As used herein "aqueous epoxy dispersion" means a dispersion in water of polymer particles comprising an epoxy polymer or pre-polymer and polymerized ethylenically unsaturated monomer, and may comprise other additives.) Prior to being dispersed in water, at least one curing agent, e.g. a crosslinking agent, may be added to the blend. The curing agent should be stable in pH ranges of 1.5 to about 6, and desirably is a blocked or otherwise temporarily inactivated curing agent, preferably a blocked isocyanate. The curing agent may be added before, during or after the time the epoxy pre polymer is combined with the ethylenically unsaturated monomer and optionally other coating components and additives, and desirably is added prior to the resulting blend being dispersed in water.

The coating bath formulation can then be applied to the article, and particularly to an active metal substrate of the article, using a variety of techniques, such as autodeposition, spray, electrostatic, roll and brush application. However, an autodeposition application in which the article is immersed into a tank of the coating bath formulation, is preferred.

The aqueous epoxy dispersion may be made using any suitable process. For example, the process may comprise the steps of: (a) dissolving and/or dispersing an epoxy pre-polymer with at least one ethylenically unsaturated monomer to form a mixture; (b) dispersing the mixture of step (a) in water, optionally with at least one surfactant, to form a fine particle dispersion; and (c) polymerizing the at least one ethylenically unsaturated monomer contained in the fine particle dispersion to form an aqueous epoxy dispersion, wherein at least one water soluble initiator and/or at least one organic soluble initiator is added prior to step (c) and at least one latent curing agent such as, for example, a blocked isocyanate is incorporated into the mixture before the at least one ethylenically unsaturated monomer is polymerized. The type and concentration of epoxy pre-polymer and ethylenically unsaturated monomer used, as well as the type of initiator, can be varied to achieve specific performance properties such as corrosion resistance, flexibility, edge protection, and appearance properties such as gloss and smoothness.

Depending on the relative amounts of epoxy-prepolymer and ethylenically unsaturated monomer used, a solvent may also be used in conjunction with the ethylenically unsaturated monomer to form the crude or fine particle dispersions of the aqueous epoxy dispersion. Solvent, for the purposes of the present application, includes any suitable solvent other than water. A solvent component may be used as a medium for preparing the epoxy pre-polymer. The solvent may be used when combining the epoxy resin and any catalysts capable of accelerating the desired epoxy group reaction. Subsequently, the solvent may be removed by techniques known in the art. The solvent, in many cases, does not diminish the technical benefits of the final coating composition and may be left in place when the aqueous epoxy dispersion is added as a component of the final coating composition. The preferred solvents are mixtures of (i) aromatic hydrocarbons having 6 to 10 carbon atoms and (ii) ketones having 3 to 8 carbon atoms. Particularly preferred solvents include propylene carbonate, butyl benzoate, butylene carbonate, butoxyethanol acetate and 2,2,4-trimethyl-l,3-pentanediol mono(2-methylpropanoate).

The relative amounts of epoxy-prepolymer and ethylenically unsaturated monomer can be varied widely to yield a variety of performance attributes. Typical weight ratios of epoxy-prepolymer to ethylenically unsaturated monomer are about 90: 10 to about 15:85.

In one embodiment the weight ratios of epoxy-prepolymer to ethylenically unsaturated monomer are about 90: 10 to about 5:95. In another embodiment, weight ratios of epoxy- pre-polymer to ethylenically unsaturated monomer are about 70:30 to about 30:70. Other desired coating components, curing agents, and additives may be added to the epoxy pre- polymer-ethylenically unsaturated monomer mixture before, during, or after it is formed.

The resulting mixture of epoxy pre-polymer, ethylenically unsaturated monomer, curing agent and any other desired coating components are then dispersed in water.

The epoxy pre-polymers can be based on conventional epoxy resins. Such epoxy resins are well known substances and are described, for example, in the chapter entitled "Epoxy Resins" in Volume 6 of The Encyclopedia of Polymer Science and Engineering (Second Edition). Epoxy resins are often described by the type of central organic moiety or moieties to which the 1,2-epoxy moieties are attached. Non-exclusive examples of such central moieties are those derived from bisphenol A, bisphenol F, novolac condensates of formaldehyde with phenol and substituted phenols, the condensates containing at least two aromatic nuclei; triazine; hydantoin; and other organic molecules containing at least two hydroxyl moieties each, in each instance with as many hydrogen atoms deleted from hydroxy moieties in the parent molecule as there are epoxy moieties in the molecules of epoxy resin. Optionally, the 1,2-epoxy moieties may be separated from the central moieties as defined above by one or more, preferably only one methylene group. Oligomers of such monomers, either with themselves or with other organic molecules containing at least two hydroxyl moieties each, may also serve as the central organic moiety. Non-exclusive examples of epoxy resins for the present invention include glycidyl ethers of a polyhydric phenol, such as bisphenol A (a particularly preferred species of polyhydric phenol), bisphenol F, bisphenol AD, catechol, resorcinol, and the like. Primarily for reasons of economy and commercial availability, it may be preferred to utilize epoxy resins derived from bisphenol A. More particularly, epoxy moiety containing molecules utilized in this invention preferably conform to the general chemical formula: where:

A = and "n" is an integer from 0 to 50. If such epoxy resins are to be used directly as the resin component, "n" is preferably an integer within the range from about 1-30 so that each molecule contains at least one hydroxyl group. Commercially available epoxy resins of this type are normally mixtures of molecules having somewhat different "n" values and different numbers of epoxy groups. Preferably, the epoxy resin mixture used has a number average molecular weight in the range of from about 350 to about 5,000, more preferably in the range from about 400 to about 3000. Preferably, the average number of epoxide groups per molecule in the epoxy resin mixture is in the range from 1.7 to 2.5, more preferably in the range from 1.9 to 2.1. The epoxy resin mixture may contain resin molecules in which n=0.

In another embodiment, the epoxy pre-polymer may comprise the reaction product of aromatic polyepoxide and at least one co-reactant having one or more epoxy-reactive groups. The ratio of epoxy and epoxy reactive groups are chosen such that epoxy end groups remain once the reaction is essentially complete. Preferred molecular equivalent weight ranges for such pre-polymers range from 450-2000 grams/equivalent epoxy based on solids. In one embodiment the co-reactant containing epoxy reactive groups also comprises ethylenic unsaturation. Such co-reactants offer one of several means to control degrees of grafting, if any, onto the epoxy pre-polymer during the radical polymerization. Non-exclusive examples of such co-reactants include unsaturated acid esters such as acrylic and methacrylic acid, and unsaturated acids and unsaturated anhydrides such as maleic acid and maleic anhydride.

In one embodiment the pre-polymer comprises an additional monofunctional species that is capable of reacting with some of the epoxy functional groups of the pre-polymer.

The resulting pre-polymer has a lower viscosity and is therefore easier to process into a dispersion with a desired particle size. Non-exclusive examples of such monofunctional species include phenol, substituted phenols such as nonylphenol, and monocarboxylic acids such as alkylcarboxylic acids.

At least one ethylenically unsaturated monomer may be is used to prepare the autodeposition coating composition. Suitable ethylenically unsaturated monomers include, but are not limited to: vinyl aromatic hydrocarbons such as styrene and substituted styrenes, vinyl aliphatic hydrocarbons, ethylenically unsaturated acids such as acrylic and methacrylic acid as well as alkyl and hydroxy-alkyl esters of such acids. Non-exclusive examples include butyl acrylate, methyl methacrylate, and hydroxyethyl methacrylate. Acrylonitrile, methacrylonitrile, acrylamide, and methacrylamide are also suitable. Ethylenically unsaturated monomers with anionic functionality may be used. Anionic functional monomers, when co-polymerized into an emulsion or aqueous solution polymers, provide a "bound" source of ionic charges to effectively stabilize the emulsion polymer particles both during polymerization and subsequent formulation into autodeposition compositions.

Desirably, hydroxyl functional ethylenically unsaturated monomer is used. The use of hydroxyl functional ethylenically unsaturated monomer provides for a dispersion that has greater solvent resistance when used in conjunction with hydroxyl reactive crosslinking or curing agents. The improvement in solvent resistance is observed in the applied coating after curing. Without being bound to any theory of operation, it is believed that the improvement stems from crosslinking between hydroxyl groups on the acrylic chain and crosslinking agent utilized in the aqueous epoxy dispersion. Non-exclusive examples of hydroxyl functional ethylenically unsaturated monomer include 2-hydroxyethyl methacrylate, hydroxyethyl acrylate, and hydroxypropyl methacrylate.

The aqueous epoxy dispersions and coating compositions may also contain one or more substances capable of reacting with the polymer end product to provide a crosslinked polymeric matrix in the cured coating. In one embodiment, at least a portion of the curing agents (sometimes referred to as crosslinking agents) only react with the epoxy dispersion end-product at the elevated temperatures typically encountered during the curing stage of the composition. Such curing agents are often referred to in the art as "latent" curing agents or hardeners because they only become activated when heated to a temperature well in excess of normal room temperature. The use of latent curing agents is preferred so that substantial cross linking of the epoxy resin or epoxy pre-polymer may be avoided prior to and during deposition on the surface of an article. In the case of metallic articles, the deposition is typically carried out at temperatures of from about 20° C to about 60° C. However, if so desired, minor amounts of more reactive curing agents may also be present in addition to the latent curing agents so as to accomplish partial crosslinking prior to deposition on an article. In one embodiment, at least one latent curing agent such as, for example, a blocked isocyanate, is incorporated into the mixture before the at least one ethylenically unsaturated monomer is polymerized.

Blocked isocyanates are popular latent curing agents. Most commercial products in the industry use blocked isocyanates with alcohols or lactams as blocking groups because they generally deblock at fairly high temperatures in the presence of catalysts, and therefore, can ensure good shelf life for the paint formulations. Commercial blocked isocyanates that can de-block at relatively low temperatures are usually blocked with pyrazoles, oximes, phenols, malonates or amines et al. Many more blocking agents are available as discussed in [Douglas A. Wicks, Zeno W. Wicks Jr., Progress in Organic Coatings, 36 (1999) 148-172; 41 (2001) 1-83] but only a few of them have been commercialized. Because they deblock at lower temperatures, these blocked isocyanates are also more prone to deblock during transportation or storage, therefore, have inferior shelf or in-can stability. Some of them may also be prone to undergo other types of side reactions such as hydrolysis of oxime blocked isocyanates at low pHs and undesirable transesterification reactions of malonate based isocyanates.

In autodeposition paint bath, due to extremely low pHs and presence of strong oxidizer and heavy metal ions, it's generally very difficult to incorporate a blocked isocyanate that can survive the harsh bath condition, and at the same time can function properly. It has been found, however, that suitable blocked isocyanates can be those blocked with pyrazole, triazoles, oximes, phenols, malonate, amines and other amine-based blocking groups. DMP-blocked isocyanates are preferred. This includes DMP blocked aliphatic isocyanates, such as HDI, IPDI and derivatives, as well as aromatic isocyanates. Mixed blocked isocyanates such as DMP blocked HDI/IPDI mixtures or mixed blocked groups such as IPDI blocked with both DMP and DEM also may be suitable. Desirably, typical curing temperatures for such crosslinking agents are at or below 135° C. The deblocking temperature of the latent crosslinker, i.e. the curing agent, is at least in increasing order of preference about 55, 56, 58, 60, 62, 64, 66, 68, 70, 71, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 100, 102, 104, 106, 108, 110, 112, 114, 116, 118, 120, 122 or 124° C, and not more than in increasing order of preference about 140, 139, 138, 137, 136, 135, 134, 133, 132, 131, 130, 129, 128, 127, 126, 125 or 124° C.

Concentration of the blocked isocyanate in the aqueous epoxy dispersion may range for example from 0 to 20% of total monomer prior to polymerization, and desirably is at least about 2, 3, 4, 5, 6, 7, 8 or 10 wt.%, and not more than 20, 18, 16, 14 or 12 wt. %. Typical weight ratios of blocked isocyanate to ethylenically unsaturated monomer are about 1:99 to about 20:80. In one embodiment the weight ratios of blocked isocyanate to ethylenically unsaturated monomer are about 3:97 to about 15:85. In another embodiment, weight ratios of epoxy-pre-polymer to ethylenically unsaturated monomer are about 4:96 to about 10:90.

In some embodiments, a stabilizer may be included in the aqueous epoxy dispersion to stabilize the lower curing blocked isocyanates in the autodeposition compositions. Strong acids generally can slow down certain urethane reactions, and therefore can somewhat extend the shelf life of certain blocked isocyanates. Preferred acids are organic acids containing sulfur or phosphorus, for example sulfonic and phosphonic acids, as some of them are also used as corrosion inhibitors or as a component of corrosion inhibitor packages. Concentration of the strong organic acid in the mixture prior to polymerization may range from 0-5% by weight, measured as a percentage of total monomer present, i.e. 0-5 parts by weight acid to 100 parts by weight monomer. Desirably, the amount of organic acid present may range from about 0.05, 0.1, 0.3, 0.5, 1.0 or 1.5% by weight at the low end, and independently preferably is not more than, with increasing preference in the order given, 5, 4.8, 4.5, 4.2, 4, 3.8, 3.5, 3.2, 3.0, 2.8, 2.5, 2.2, 2.0, 1.9 or 1.8% by weight, at the high end.

Essentially any type of free radical generator can be used to initiate polymerization of the monomers. For example, free radical generating chemical compounds, ultraviolet light or radiation can be used. A radical initiator may be added to facilitate the polymerization of the ethylenically unsaturated monomer within the epoxy containing micelle of the dispersion. Relative degrees of grafting, if any, between epoxy pre-polymer and polymerized monomer can be achieved to provide for specific molecular weights and specific performance ends by careful selection of initiator type. Initiators may be added at various points in the process of forming the dispersion. In one embodiment, the initiator is organic soluble and is introduced in the organic phase prior to dispersion of the epoxy pre polymer, ethylenically unsaturated monomer, and curing agent in water. In another embodiment, the initiator is water-soluble and is introduced after dispersion of the epoxy pre-polymer/ethylenically unsaturated monomer/curing agent mixture in water. In another embodiment both organic soluble initiators and water-soluble initiators are added. In another embodiment an organic soluble initiator is introduced after the aqueous dispersion is formed. In this embodiment, the organic soluble initiator is added directly or dissolved in a co-solvent and dripped into the dispersion.

Non-exclusive examples of suitable organic soluble initiators, e.g. oxidants, include peroxides, peroxy esters as well as organic soluble azo compounds. Benzoyl peroxide is one preferred example. Non-exclusive examples of suitable water-soluble initiators include hydrogen peroxide, tert-butyl peroxide, t-butyl peroctoate, hydroperoxides such as t-butyl hydroperoxide, alkali metal (sodium, potassium or lithium) or ammonium persulfates; azo initiators such as azobisisobutyronitrile or 2,2'-azobis(2-amidinopropane)dihydrochloride; or mixtures thereof. Ammonium persulfate and Vazo ^® 68 WSP (Available from The Chemours Company of Wilmington, Delaware) are two preferred examples. In one embodiment such initiators may also be combined with reducing agents, e.g. reductant solutions, to form a redox system. Non-exclusive examples of reducing agents include sulfites such as alkali metal meta bisulfite, or hyposulfite, sodium thiosulfate, or isoascorbic acid, or sodium formaldehyde sulfoxylate. The free radical precursor and reducing agent together, referred to as a redox system herein, may be used at a level of from about 0.01% to 5%, based on the weight of monomers used. Non-exclusive examples of redox systems include: t-butyl hydroperoxide/sodium formaldehyde sulfoxylate/Fe(III); t-butyl hydroperoxide/isoascorbic acid/Fe(III); and ammonium persulfate/sodium bisulfite/sodium hydrosulfite/Fe(III). In another embodiment, sodium formaldehyde sulfoxylate is used to initiate polymerization in conjunction with at least one anionic surfactant, such as sulfates and sulfonates in the absence of peroxides. Incorporation of anionic end groups resulting from this method provides an increased level of stability for the emulsion as well as the corresponding autodeposition bath. Nonylphenol ethoxylate sulfate ammonium salt and sodium lauryl sulfate are two suitable non-exclusive examples.

The polymerization of the ethylenically unsaturated monomer may be carried out with applied heat. A wide variety of temperatures can be employed, and the specific optimum temperature varies with each initiator. Alternatively, redox initiation methods are known in the art by which polymerization can be conducted at ambient or near ambient conditions.

Coalescing agents may be incorporated into the dispersion. Coalescing agents will be apparent to those skilled in the art. Non-exclusive examples of coalescing agents include monoethers and monoesters of glycols, preferably glycols with at least one terminal hydroxy group. Monoethers of ethylene glycol are readily available. Monoethers of propylene glycol, particularly the methyl, t-butyl, n-butyl, and phenol monoethers of propylene glycol, dipropylene glycol and tripropylene glycol are preferred from this class.

The dispersion or coating bath composition may also contain a number of additional ingredients that are added before, during, or after the formation of the dispersion. Such additional ingredients include fillers, biocides, foam control agents, pigments and soluble colorants, and flow control or leveling agents. The compositions of these various components may be selected in accordance with the concentrations of corresponding components used in conventional epoxy resin-based autodeposition compositions, such as those described in U.S. Pat. Nos. 5,500,460, and 6,096,806 and U.S. Ser. No. 09/578,935, the teachings of which are hereby incorporated by reference in their entirety for all purposes. Pigments and soluble colorants may generally be selected from materials established as satisfactory for similar uses. Examples of suitable materials include carbon black, titania, phthalocyanine blue, phthalocyanine green, quinacridone red, hansa yellow, and/or benzidine yellow pigment, and the like, provided that they are sufficiently stable in the autodeposition coating bath.

To prepare a coating bath composition suitable for coating a metallic substrate by autodeposition, the epoxy dispersion is combined with at least one autodeposition accelerator component, which is capable of causing the dissolution of active metals (e.g., iron) from the surface of the metallic substrate in contact with the bath composition. Preferably, the amount of accelerator present is sufficient to dissolve at least about 0.020 gram equivalent weight of metal ions per hour per square decimeter of contacted surface at a temperature of 20° C. Preferably, the accelerator(s) are utilized in a concentration effective to impart to the bath composition an oxidation-reduction potential that is at least 100 millivolts more oxidizing than a standard hydrogen electrode. Such accelerators are well-known in the autodeposition coating field and include, for example, substances such as an acid, oxidizing agent, and/or complexing agent capable of causing the dissolution of active metals from active metal surfaces in contact with an autodeposition composition.

The autodeposition accelerator component may be chosen from the group consisting of hydrofluoric acid and its salts, fluosilicic acid and its salts, fluotitanic acid and its salts, ferric ions, acetic acid, phosphoric acid, sulfuric acid, nitric acid, hydrogen peroxide, peroxy acids, citric acid and its salts, and tartaric acid and its salts. More preferably, the accelerator comprises: (a) a total amount of fluoride ions of at least 0.4 g/L, (b) an amount of dissolved trivalent iron atoms that is at least 0.003 g/L, (c) a source of hydrogen ions in an amount sufficient to impart to the autodeposition composition a pH that is at least 1.6 and not more than about 5, and, optionally, (d) hydrogen peroxide. Hydrofluoric acid is preferred as a source for both the fluoride ions as well as the proper pH. Ferric fluoride can supply both fluoride ions as well as dissolved trivalent iron. Accelerators comprised of HF and FeF3 are especially preferred for use in the present invention.

In some embodiments, ferric cations, hydrofluoric acid, and hydrogen peroxide are all used to constitute the autodeposition accelerator component. In a working composition, independently for each constituent: the concentration of ferric cations preferably is at least, with increasing preference in the order given, 0.5, 0.8 or 1.0 g/l and independently preferably is not more than, with increasing preference in the order given, 2.95, 2.90, 2.85, or 2.75 g/l; the concentration of fluorine in anions preferably is at least, with increasing preference in the order given, 0.5, 0.8, 1.0, 1.2, 1.4, 1.5, 1.55, or 1.60 g/l and independently is not more than, with increasing preference in the order given, 10, 7, 5, 4, or 3 g/l; and the amount of hydrogen peroxide added to the freshly prepared working composition is at least, with increasing preference in the order given, 0.05, 0.1, 0.2, 0.3, or 0.4 g/l and independently preferably is not more than, with increasing preference in the order given, 2.1, 1.8, 1.5, 1.2, 1.0, 0.9, or 0.8 g/l.

In some embodiments, the autodeposition composition may further comprise at least one additive selected from zinc fluoride hydrate, sodium acetylacetonate hydrate and combinations thereof.

The autodeposition coating can be formulated by either a single emulsion containing both the aqueous epoxy dispersion and the crosslinker, or two distinct emulsions that separate the aqueous epoxy dispersion from the crosslinker until the two emulsions are combined to form the autodepositing coating bath. Being able to provide a two-pack of aqueous epoxy dispersion and crosslinker allows formulation flexibility and product customization based on customer requirements.

In another embodiment, autodeposition compositions can be formulated in a two- package product comprising two component emulsions, for example: Component A comprising a crosslinker for the aqueous epoxy dispersion and optional stabilizer; and Component B comprising the aqueous epoxy dispersion, a dispersion in water of polymer particles comprising an epoxy polymer or pre-polymer and polymerized ethylenically unsaturated monomer including but not limited to hydroxyfunctional monomer.

Alternatively, Component A may comprise all components of the single package latex, in the absence of epoxy resin, solvent and hydroxy functional monomer; while Component B may comprise all components of the single package latex, in the absence of curing agent and stabilizer, with amounts of other components adjusted to be comparable to the single package latex. Ratios between two resin packages A/B: 0/100-40/60. The two components may generally be kept separate until combined with water and other components to formulate an autodepositing coating bath.

A two-package product is also expected to be helpful in a low bake temperature autodeposition process to ensure that the curing agents do not deblock prior to the desired time. In conventional high bake temperature autodeposition products, such as the Bonderite ^® MPP 900 series, a single resin package contains both curing agents (or crosslinkers) and the chemical groups that react with them. The same is true for the current electro-deposition resin technology and or some other major commercial metal primer packages. Such formulations are typically baked at temperatures, such as 350° F/177° C or above to become fully cured, and the blocked isocyanates used in these products are mostly alcohol or lactam based products which are usually stable enough in a single package. However, when the autodeposition coating is designed to be baked at lower temperatures such as below 270° F/132° C, different curing agents that can deblock at these temperatures are usually needed and these curing agents generally also have poor in-can or shelf stability during transportation or shelf stability.

Thus, it is beneficial, at least for shelf stability, to put curing agents and the chemical groups that can react with them in different packages, therefore, they don't crosslink prematurely during storage and transportation in certain regions or seasons. For example, the blocked isocyanates may be incorporated in a resin package that does not have any chemical groups that can react with them, and all the epoxy resins and hydroxyl containing components may be incorporated in another package. These two resins can be blended in a designed ratio at a later stage or before charging into the autodeposition paint bath, thereby maintaining sufficient in-can stability prior to use. A second advantage of the two package system can allow customers to customize the paint bath by changing the ratio of the resin packages to maximize certain properties or attributes of the autodeposition technologies. This allows a greater flexibility compared with other technologies. As will be appreciated from the foregoing, the autodepositing liquid bath composition used in the autodeposition coating step 106 may be provided in a variety of forms. In one preferred embodiment, the autodepositing liquid bath composition comprises, preferably consists essentially of, or more preferably consists of, water and:

(A) a concentration of at least 1.0%, based on the whole composition, of dispersed or both dispersed and dissolved film forming polymer molecules, i.e. epoxy resin, acrylic monomer reaction products (as used herein, "film forming polymer molecules" found in the aqueous epoxy dispersion will be understood to mean at least the epoxy polymer or pre-polymer and polymerized ethylenically unsaturated monomer of the aqueous epoxy dispersion);

(B) a surfactant component in sufficient quantity to emulsify all dispersed constituent molecules of component (A) so that, in the autodepositing liquid composition, no separation or segregation of bulk phases that is perceptible with normal unaided human vision occurs during storage at 25° C for at least 24 hours after preparation of the autodepositing liquid composition, in the absence of contact of the autodepositing liquid composition with any metal, particularly any metal that dissolves in the autodepositing composition to produce therein metal cations with a charge of at least two, or other material that reacts with the autodepositing liquid composition;

(C) a curing component comprising at least one latent crosslinking agent, such as a blocked isocyanate, chemically reactive with constituents of component (A) at a temperature of 130° C or less; and

(D) a dissolved accelerator component, selected from the group consisting of acids, oxidizing agents, and complexing agents, sufficient in strength and amount to impart to the total autodepositing liquid composition an oxidation-reduction potential that is at least 100 millivolts hereinafter usually denoted "mV") more oxidizing than a standard hydrogen electrode (hereinafter usually abbreviated "SHE"); and optionally, one or more of the following: (E) a component of pigment, filler, or other dispersed solid phase materials other than the materials that constitute any part of any of the preceding components;

(F) a component of solvent in which constituents of component (A) that are insoluble in water were dissolved during some step in the preparation of the autodepositing liquid composition, other than materials that constitute any part of any of the preceding components;

(G) a component of organic acid stabilizer for component (C), other than materials that form any part of any of the preceding components;

(H) a component of coalescing agent, other than materials that form any part of any of the preceding components; and

(I) a plasticizer component, other than materials that constitute part of any of the preceding components.

The autodeposition composition preferably has a pH that is at least 1.6, or preferably is, with increasing preference in the order given, at least 1.7, 1.8, 1.9, 2.0, or 2.1 and independently preferably is, with increasing preference in the order given, not more than 5, 4.5, 3.8, 3.6, 3.4, 3.2, 3.0. 2.8, 2.6, 2.4, or 2.3.

The autodepositing liquid bath composition may be made using various methods. As one example, the process comprises the steps of: (a) dissolving and/or dispersing an epoxy resin or pre-polymer with at least one ethylenically unsaturated monomer to form a mixture; (b) dispersing the mixture of step (a) in water with at least one surfactant to form a fine particle dispersion; and (c) polymerizing the at least one ethylenically unsaturated monomer contained in the fine particle dispersion to form an aqueous dispersion. In this example, at least one water soluble initiator and/or at least one organic soluble initiator, e.g. promoter, reductant solution and/or oxidant solution may be added prior to or during step (c). Also, in this example, at least one latent curing agent having a deblocking temperature of no more than 135° C, and optionally one or more of a solvent and a stabilizer, may be incorporated into the mixture before the at least one ethylenically unsaturated monomer is polymerized.

Any method can be used for contacting a metal surface of the article with the autodeposition composition of the present invention. Examples include immersion (e.g., dipping), spraying or roll coating, and the like. Immersion is usually preferred. Preferably, contact between an active metal surface and the autodeposition bath compositions such as described herein is for a time between about 0.5 and about 10 minutes, more preferably between about 1 and about 3 minutes. Contact preferably is long enough to produce a final film thickness of from about 10 to about 50 microns (preferably about 18 to about 25 microns).

Still referring to Figure 1, in following step 106, the article with the film deposited thereon is removed from contact with the autodeposition bath composition and may be rinsed in step 108 to remove at least some of the absorbed but otherwise unadhered components of the bath composition from the more adherent portion of the coating. Water rinse step 108 may be performed using deionized water, or the like. As with the previous rinse step 104, any suitable rinsing mechanism (e.g., dip bath, spray, exposure to running water, etc.) may be used.

An optional post-treatment rinse step 110 may be performed after water rinse step 108 or immediately after autodeposition coating step 106. In this step, a post-treatment reagent capable of causing modifications of the coated film may be included in the rinse used after cessation of contact between the wet coated surface and the bulk of the autodeposition bath composition. Post-treatment rinse step 110 may be useful for various purposes. For example, in some embodiments, a post-treatment rinse step 110 may be used to improve the corrosion resistance of the final cured coating by rinsing with an aqueous post-treatment solution comprising soluble zirconium or titanium compounds, such as fluorometallate or carbonate compounds of these metals, e.g. ammonium zirconium carbonate; or an alkaline earth metal compound such as calcium nitrate, as described in co owned U.S. Pat. No. 6,613,387 and which is incorporated herein by reference in its entirety for all purposes. The concentration of the total of the post-treatment reagent present in the aqueous liquid rinse composition in this embodiment preferably is, with increasing preference in the order given, at least 0.001, 0.002, 0.004, 0.008, 0.016, 0.023, 0.033, 0.040, 0.047, 0.054, or 0.060 grams per liter and independently preferably is, with increasing preference in the order given, not more than 10.0, 9.0, 8.0, 7.0, 6.0, 5.0, 4.0, 2.0, 1.5, 1.3, 1.0, 0.7, 0.4, 0.20, 0.15, 0.100, 0.090, 0.080, 0.075, or 0.070 grams per liter. Contact time between the article and the post-treatment solution may be may vary.

Any suitable mechanism may be used to perform the post-treatment rinse step 110. A preferred mechanism is dipping the article in a bath filled with the post-treatment composition, but spraying or other comparable mechanisms may be used. In one embodiment, the contact duration preferably is at least 1 second and preferably is not more than 5 minutes. The autodeposition coating step 106 is followed by a catalyst rinse step 112, in which the article is contacted with an aqueous catalyst composition (also referred to herein as the catalyst bath or catalyst rinse bath). The catalyst rinse step 112 is performed after cessation of contact between the wet coated surface and the bulk of the autodeposition bath composition, and preferably after any water rinse step 108 or post-treatment rinse steps 110, but before the curing step 114. It has been found that contact with the aqueous catalyst composition can be used to improve the corrosion resistance and chemical resistance of the autodeposition coating, particularly when the autodeposition coating is cured at a low temperature, such as described herein. For example, rinsing the article with an aqueous catalyst composition comprising a catalyst for isocyanate reactions with active hydrogens, particularly catalysts for the blocked or inhibited isocyanates of the autodeposition coating composition in the wet coated films, can help improve final film quality.

The catalyst composition preferably is aqueous, and may be provided in a solution, dispersion, suspension, colloid or other form, but a solution is preferred. Suitable catalysts for use in the aqueous catalyst composition may include organic metallic compounds, nitrogen containing catalysts, as well as phosphorus-based compounds. The catalysts useful in this invention are those that can be incorporated and remain stably dissolved and/or dispersed in an aqueous formulation and can act as a catalyst, preferably for a urethane-type reaction of isocyanate (or blocked isocyanate) with an active hydrogen. Amine-based catalysts are preferred. By way of non-limiting example, suitable amine- based catalysts include: cyclic amidines, including bicyclic amidines such as DBU (1,8- diazabicyclo[5.4.0]undece-l-ene), DBN (1,5-diazobicydo (4:3:0) non-S-ene) and 1,2- dimethyl-l,4,5,6-tetrahydropyrimidine and the like; tertiary amines such as N-(3- dimethylaminopropyl)-N,N-diisopropanolamine, tributylamine, 1,2-dimethylimidazole (DMI)and diethylcyclohexylamine; diazabicyclo[2.2.2]octane (DABCO); quinuclidine-based catalysts; and triazine-based catalysts, such as l,3,5-tris(3-(dimethylamino)propyl)- hexahydro-s-triazine. Some primary or secondary amine containing compounds, such as imidazole, and dicyandiamide and the like, can work both as catalyst and curing agents, and therefore, are also suitable in this application. In some cases, a surfactant may be added to or combined with the catalyst composition to assist with penetrating into the uncured autodeposition coating film. In addition, a combination of catalysts optionally may be used. The concentration of the total amount of the catalyst present in the aqueous catalyst composition used according to the invention preferably is, with increasing preference in the order given, at least 0.1, 0.2, 0.4, 0.8, 0.016, 0.023, 0.033, 0.040, 0.047, 0.054, 0.061, or 0.068 grams per liter and independently preferably is, with increasing preference in the order given, not more than 10.0, 9.0, 8.0, 7.0, 6.0, 5.0, 4.0, 2.0, 1.5, 1.3, 1.0, 0.7, 0.4, 0.20, 0.15, 0.100, 0.090, 0.080, 0.075, or 0.072 grams per liter. Contact time with the aqueous catalyst composition preferably may be at least 1 second and preferably is not more than 10 minutes.

The catalyst bath may be maintained at a desirable operating temperature to help ensure efficacy of the process. For example, the catalyst bath may be provided as an aqueous catalyst composition in a bath maintained at least at, with increasing preference in the order given, 45°C, 48° C, 50° C, 51° C, 52° C, 53° C, 54° C, or 55° C, and independently preferably is, with increasing preference in the order given, not more than 70°C, 67° C, 65° C, 64° C, 63° C, 62° C, 61° C, or 60° C.

In step 114, the article is heated to cure the autodeposition coating. Final heating of the rinsed, wet coated and optionally post-treated autodeposited film is preferably at a temperature (PMT) of no more than 135° C. The curing temperature must be sufficiently high so as to effect reaction of the latent crosslinker (e.g., a blocked isocyanate) with the reactive epoxy- and/or hydroxyl functional groups of the epoxy dispersion present in the autodeposited film. As discussed above, the latent crosslinker preferably is selected such that deblocking of the curing agent does not take place to any significant extent during transportation or storage, and more preferably no deblocking takes place during these times. The deblocking temperature of the latent crosslinker, i.e. the curing agent, is at least in increasing order of preference about 55, 56, 58, 60, 62, 64, 66, 68, 70, 71, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 100, 102, 104, 106, 108, 110, 112, 114,

116, 118, 120, 122 or 124° C, and not more than in increasing order of preference about 140, 139, 138, 137, 136, 135, 134, 133, 132, 131, 130, 129, 128, 127, 126, 125 or 124°

C. Generally, the final heating temperature is selected to dry and cure the coating at a temperature of 140° C or less, and more preferably within the range from at least about 60° C to about 132° C, and more preferably between about 100° C and 125° C. The final heating temperature preferably is selected to ensure full curing of the coating, and may be, for example, for a time of about 3 to about 60 minutes, or more preferably for about 10 to about 30 minutes.

The heating can be performed in multiple stages, if desired, by adjusting temperature of the stages and selection of curing agent deblocking temperature. For example, in one embodiment, in a first stage lasting from about 5 to about 15 minutes, the coated substrate is heated to a peak temperature of about 55° C to about 65° C to flash off most of the residual water in the coating and in a second stage lasting from about 30 to about 50 minutes, the coated substrate is heated to a peak temperature of about 100° C to about 130° C, thereby unblocking the curing agent. The peak temperature preferably is attained in no more than about 10 minutes after the first heating stage has been completed. Any suitable oven or other heating system may be used to perform the final heating process.

Metal substrates coated according to embodiments described herein have been found to have a resulting cured autodeposition coating with a corrosion resistance comparable to conventional autodeposition coatings that require a higher cure temperature in the neutral salt spray ("NSS") test, such as ASTM B-117 and in chemical resistance tests, e.g. methylethyl ketone double rub testing (ASTM D4752). Such coatings are also compatible with co-cure processes wherein a paint is applied to a dewatered uncured autodeposited coating and the two layers are cured together, see for example WO 2009/088993, which is incorporated herein by reference in its entirety for all purposes. The lower curing temperature of autodeposition coatings provided herein enables use of a wider variety of paints in a process in which the uncured autodeposition coating is dewatered, paint is applied to the uncured autodeposition coating and then the paint and the autodeposition coating are cured in the same curing step by heating to temperatures of less than about 135° C, as disclosed herein.

Autodeposition compositions as described herein can be used for treating surfaces of iron, zinc, iron alloy and zinc alloy, and particularly steel portions of various components such as automobile sheet components and automobile components such as shock absorbers, jacks, leaf springs, suspension components and brackets, and the like, and components of furniture such as drawer rails, and the like. Autodeposition coatings are particularly well suited for indoor metal furniture that is subjected to wear and surface impacts, e.g., filing cabinets, filing shelves, desks, etc.

Further examples of autodeposition coatings and methods for preparing and applying the same are described in detail in previously-mentioned U.S. Pre-Grant Publication No. 2018/0304306 ("the '306 publication") (i.e., the publication of U.S. Application Ser. No. 16/021,954), which is incorporated by reference herein in its entirety for all purposes.

While the '306 publication provides useful advancements to the state of the art, the inventors have determined that the processes for implementing the autodeposition coatings described in the '306 publication can be improved, particularly in relation to the catalyst rinse step 112. More specifically, it has been found that the low cure temperature autodeposition paint processes described in the '306 publication and herein are subject to relatively rapid deactivation of the catalyst used in the catalyst rinse step, particularly when such catalyst is in an open-to-air bath and capable of reacting with and/or absorbing carbon dioxide from atmospheric air (typically about 0.04% carbon dioxide by volume), such as many of the amine-based catalysts discussed above, e.g. a urethane crosslinking catalyst.

The gas CO2 is quite soluble in water in which more than 99% exists as the dissolved gas and the remainder forms carbonic acid H2CO3, which partly dissociates to give H ⁺ ,

HC03 , and CCh ^-2 , based on thermodynamic equilibrium. For purposes of this disclosure, the term "carbon dioxide" encompasses any of the carbon containing molecules and/or ions in this equilibrium that are capable of contributing to deactivation of catalyst in the catalyst rinse bath and whose concentration in the catalyst rinse bath may be reduced by the ion exchange process and apparatus disclosed herein.

When certain amine-based catalyst reacts with and/or absorbs carbon dioxide, it converts free base catalyst to a carbonated form, such as bicarbonate or carbonate salt, which has little or none of the desired catalytic activity for curing the autodeposition coating. When the concentration of carbonated catalyst becomes too great or the concentration of free base catalyst becomes too low, efficacy of the catalyst rinse bath is reduced and becomes ineffective at providing the desired final cured coating quality. Thus, it is desirable to maintain a minimum concentration of free base (i.e., active, uncarbonated) catalyst in the catalyst rinse bath sufficient to provide the desired coating quality. It is furthermore desirable to reduce the amount of carbonated (i.e., deactivated) catalyst in the bath where it may undesirably affect solubility of catalyst or stability of the catalyst rinse bath.

The problem of carbonated catalyst accumulation in the catalyst bath, and consequent deterioration of coating quality is compounded by the use environment. Typical autodeposition processing lines utilize large open-air processing stations, such as spray stations or open-to-air dip baths, enabling coating of large parts, such as automobile chassis. Thus, the catalyst bath is generally in contact with atmospheric air during normal operation and during line shut-downs, and movement of parts into and out of the catalyst rinse bath introduces more air via turbulence. One could conceivably overcome this problem by operating the catalyst bath in an environment that does not contain carbon dioxide, such as a sealed chamber or an open chamber operating under a blanket of nitrogen that provides a barrier between the catalyst bath and the surrounding air.

However, such operations would require significant costs to implement and maintain. Furthermore, parts having complex shapes or pockets could capture environmental air and convey it through a nitrogen barrier and into the catalyst bath.

Another conventional way to remove carbonated catalyst from an aqueous catalyst composition is adding an alkali composition to neutralize the salts. For example, the absorbed carbon dioxide can be neutralized and the free base catalyst regenerated by adding an alkali, such as sodium hydroxide, to the catalyst bath. However, the inventors' testing showed residual water soluble ions in the catalyst bath negatively affect the final coating quality.

Still another potential approach is to treat the catalyst bath with calcium oxide. The calcium oxide reacts with bicarbonate salt to form insoluble carbonate salts and converts the carbonated catalyst to non-carbonated form. However, such treatment can be difficult to control, and forms insoluble particulates that remain in the bath as sludge that must be removed and remediated since build-up in the catalyst bath could affect the coating appearance or quality.

Another option for addressing the carbonated catalyst is to simply replace the entire catalyst bath, which is the approach taken in previous implementations of the inventions described in the '306 publication. However, this method is commercially undesirable due to significant costs to replace the catalyst bath and treat the resulting waste.

The inventors have determined that the problem of carbonated catalyst accumulation can be addressed by regenerating the catalyst bath in a separate ion exchange process. In general terms, the catalyst bath is treated by contacting the inactive carbonated salt form of the catalyst (which is typically dissolved in the catalyst bath in the form of an aqueous solution) with a strong base anion (SBA) exchange resin (also referred to herein as an SBA exchange resin) in the hydroxide form, to thereby convert the carbonated catalyst back to the catalytically active free base form. To avoid unnecessary waste of the SBA exchange resin, the SBA exchange resin may be periodically regenerated, while effectively isolating the catalyst bath from any potentially problematic products of the regeneration process. An example of a system for implementing this process is described in relation to Figure 2.

Figure 2 illustrates an exemplary catalyst bath treatment system 200 in the form of an ion exchange system. The system 200 includes a catalyst bath 202, which is configured to contain a quantity of aqueous catalyst composition such as described above. The aqueous catalyst composition may generally be in contact with atmospheric air, and thus carbon dioxide, while it resides in the catalyst bath 202. For example, the catalyst bath 202 may comprise a tank having an open top through which articles pass to contact them with the catalyst composition contained therein.

An outlet of the catalyst bath 202 is connected to an inlet of an ion exchange column 204 by a first fluid control circuit 206, and an outlet of the ion exchange column 204 is connected to an inlet of the catalyst bath 202 by a second fluid control circuit 208. As used herein, a "fluid control circuit" is any arrangement of flow passages, chambers, pumps, valves and the like that are configured to convey an aqueous composition between two points. The first and second fluid control circuits 206 and 208, respectively, may include any number of conduits (i.e., hoses, pipes, etc.) and fluid control mechanisms (e.g., pumps, valves, etc.) to effect transfer of aqueous catalyst composition from the catalyst bath 202 to the ion exchange column 204 and back. It will be appreciated that in all instances in which a single feature is identified (e.g., a valve), multiple like features may be implemented, and vice versa, and so references to a single feature both in the specification and the appended claims are understood to encompass one or more of the referenced feature. In the shown example, the first fluid control circuit 206 includes a first pump 210 configured to pump aqueous catalyst composition from the catalyst bath 202 to the ion exchange column 204, and a first valve 212 to selectively prevent or allow flow through the first fluid control circuit 206. Similarly, the second fluid control circuit 208 includes a second pump 214 configured to pump aqueous catalyst composition from the ion exchange column 204 to the catalyst bath 202, and a second valve 216 to selectively prevent or allow flow through the second fluid control circuit 208.

It will be appreciated that the pumps described herein may have any suitable construction for the desired liquid properties and flow rates, with centrifugal pumps being a common type of pump that is suitable for commercial operations. Similarly, the valves described herein may have any suitable construction (e.g., ball valves, butterfly valves, gate valves, etc.). It will also be appreciated that one or more pumps or valves may be omitted if unnecessary, such as omitting a pump where flow can be achieved by gravity or omitting a valve where a pump is sufficient to control forward flow and reverse flow is not possible.

One or both of the first fluid control circuit 206 and the second fluid control circuit 208 may also include a reservoir for temporarily holding a quantity of the aqueous catalyst composition. For example, the first fluid control circuit 206 may include a first reservoir 218, and the second fluid control circuit 208 may have a second reservoir 220. Other devices, such as a heat exchanger 222 may be provided in one or both of the first and second fluid control circuit 206, 208. The purposes of such devices are described in more detail below.

One or more filters or skimmers may be provided in the first and/or second fluid control circuits 206, 208 to remove foam, particulate matter or debris from the aqueous catalyst composition. For example, a filter 254 may be provided between the catalyst bath 202 and the ion exchange column 204 to capture particulate debris that may enter the catalyst bath 202. As another example, the outlet of the catalyst bath 202 to the first fluid control circuit 206 may include a weir and skimmer to remove debris from the surface of the aqueous catalyst composition. Preferably, the first and second fluid control circuits 206,

208 are generally air-tight to prevent the aqueous catalyst composition from absorbing additional carbon dioxide as it passes therethrough, preferably the outlet of the catalyst bath 202 may be located below the surface of the aqueous catalyst composition to avoid air intake. Similarly, it is preferred that any skimming or weir system used with the catalyst bath 202 be configured to minimize additional contact between the aqueous catalyst composition and the atmospheric air. Such devices are known in the art, and need not be described in detail herein.

The ion exchange column 204, first fluid control circuit 206 and second fluid control circuit 208 collectively form the core structural features of an ion exchange system for treating the aqueous catalyst composition. The ion exchange column 204 contains a strong base anion exchange resin (SBA exchange resin) useful for regenerating the catalyst from carbonated form to active form. The ion exchange system is operated by conveying a quantity of the aqueous catalyst composition to the ion exchange column 204 via the first fluid control circuit 206, passing the aqueous catalyst composition through the strong base anion exchange resin in the ion exchange column 204 and then returning the quantity of aqueous catalyst composition to the catalyst bath 202. Within the ion exchange column 204, the SBA exchange resin in the hydroxide form reacts with the carbonated salt form of the aqueous catalyst composition, converting the SBA exchange resin to a carbonated form (e.g., carbonate or bicarbonate form), and converting the carbonated catalyst compound into active free base catalyst compound.

The SBA exchange resin preferably is selected to adequately regenerate the selected aqueous catalyst composition to a usable state for performing additional catalyst rinse steps 112. The selection of the SBA exchange resin may include consideration of the resin's chemical properties, exchange capacity, temperature stability, kinetics and mass transfer characteristics, tendency towards organic fouling, tendency to generate detrimental channeling within the ion exchange column 204, osmotic and mechanical stability, cost, availability, and so on.

Suitable SBA exchange resins include resins which have polymeric, preferably organic polymeric, backbones substituted with quaternary ammonium groups (e.g. polymer backbone-NR3 ⁺ ). When used in the context of the present invention to regenerate free base catalyst from carbonated catalyst in a catalyst bath composition, the counterion to the quaternary ammonium groups typically is hydroxide (OH ). The exchanger -NR3 ⁺ in the OH ion form is able to exchange OH ions for carbonate ions on the catalyst and thus, to remove carbonate from the aqueous catalyst composition and replace it with an equivalent molar quantity of OH, thereby regenerating the catalytically active free base molecule. Quaternary ammonium groups (-NR3+) in the OH form are preferred as the functional groups for reactivating catalysts as disclosed herein, but other functional groups may be used provided that they do not interfere with the objects of the invention, such as reactivation of the catalyst and performance of the low temperature cure autodeposition coating.

Polymeric backbones of SBA exchange resins typically may be crosslinked (using, for example, a multifunctional comonomer such as divinyl benzene or a di(meth)acrylate).

Thus, according to certain embodiments of the invention, the SBA exchange resin may be a crosslinked organic resin having a vinyl aromatic or acrylic polymeric backbone and quaternary ammonium groups substituted thereon. SBA exchange resins are typically available in two types, based on which type of quaternary ammonium group is used: Type I with a trimethyl ammonium group, and Type II with a dimethylethanol ammonium group. Suitable SBA exchange resins may be made with a polystyrene backbone and cross-linked with divinyl benzene (DVB). Other suitable acrylic type SBA exchange resins typically may be made with an acrylate polymer backbone cross-linked with a DVB, but may be cross linked with other multifunctional monomers. Other polymeric materials may be used as the "backbone" and "cross-linking" reactants, provided that they do not interfere with the functioning of the IEX column and the goals of the invention.

SBA exchange resins are also available in various morphologies, including gel types and macroporous types. The different varieties of SBA exchange resin generally have different properties with respect to one or more operating variables, such as those listed above. For example, Type I gel SBA exchange resins generally can be advantageous for providing good thermal stability and lifetime, osmotic and mechanical stability, and low rinse water demands, but they can have relatively low working capacity and may be relatively prone to organic fouling. Type I macroporous SBA exchange resins can be advantageous over the gel type by providing higher resistance to organic fouling due to their larger surface area per unit volume, and can have better kinetics and resistance to osmotic shock, but can have a lower working capacity than the gel version. Type II gel SBA exchange resins have relatively high working capacity, but they typically may have relatively low thermal stability, and greater susceptibility to organic fouling. Type II macroporous SBA exchange resins typically may have a lower working capacity than the gel type, but offer better resistance to organic fouling, and better kinetics and resistance to osmotic shock. Acrylic type SBA exchange resins having the gel morphology typically may have good working capacity, good resistance to organic fouling, but have relatively low thermal stability (e.g., 35° C maximum operating temperature) and higher rinse water requirements, and are less efficient when operating at a high pressure drop. Acrylic type SBA exchange resins of the macroporous type are also available, and offer high reversible removal of organics, high surface area and good resistance to osmotic shock.

Non-limiting examples of commercially available SBA exchange resins that may be used in embodiments of the invention include, but are not limited to, the SBA exchange resins sold by: Aldex Chemical Co. under the brand name Aldex CRA, the Dow Chemical Company under the brand names "Amberlite" and "Dowex", Lanxess Aktiengesellschaft under the brand name "Lewatit", Mitsubishi Chemical Corporation under the brand name "Diaion", as well as the SBA exchange resins sold by Purolite and ResinTech, examples of which include those sold under the name Diaion SA10A (available from Mitsubishi Chemical Corporation of Japan), Dowex Monosphere 55a (available from Dow Chemical Company of Midland, Michigan), Lewatit Monoplus M 800 (available from Lanxess Aktiengesellschaft of Cologne, Germany), and SBG1 (available from ResinTech Inc. of West Berlin, New Jersey). In one preferred embodiment, the SBA exchange resin comprises a Type I, gel morphology, styrene-divinyl benzene (DVB) backbone. The SBA exchange resin may be in any suitable solid physical form or shape, including by way of non-limiting example in the form of pellets, powder or beads.

The construction and operation parameters of the ion exchange column 204 can vary depending on the particular application. The ion exchange column 204 may include various features, such as internal baffles and flow controllers, screens and perforated sheets for retaining resin, and other features such as known in the art. Factors that may be considered include the column dimensions and internal structure, SBA exchange resin volume, aqueous catalyst composition flow rate and residence time, operating temperature, and so on. An ion exchange column 204 suitable for use in the invention can be readily accomplished without undue experimentation based upon the disclosure herein in view of the desired operating parameters for the selected aqueous catalyst composition and SBA exchange resin.

The ion exchange system may be operated continuously or in a batch mode. The ion exchange system also may be operated in coordination with the remainder of the autodeposition coating line process, or it may be operated independently.

In an example of a continuous operation, the first fluid control circuit 206 and second fluid control circuit 208 are operated to continuously divert a portion of the aqueous catalyst composition through the ion exchange column 204, to thereby maintain the active catalyst concentration within the catalyst bath 202 within an acceptable level to perform the desired coating process. In such an embodiment, the first and second reservoirs 218, 220 may optionally be omitted. If continuous operation is used, it also may be desirable to include a heat exchanger 222 in one or both of the first fluid control circuit 206 and second fluid control circuit 208 to maintain the aqueous catalyst composition at the desired operating temperature for one or both of the ion exchange column 204 and the catalyst bath 202. For example, the heat exchanger 222 may be used to reduce the temperature of the aqueous catalyst composition to a temperature that will not risk premature thermal degradation of the selected SBA exchange resin.

In an example of a batch operation, the first fluid control circuit 206 and second fluid control circuit 208 may be operated to periodically remove a quantity of aqueous catalyst composition from the catalyst bath 202 and process it through the ion exchange column 204. For example, the ion exchange system may be operated to perform the steps of: (a) stopping operation of the catalyst bath 202 (i.e., suspending immersion of articles into the catalyst bath 202); (b) moving a first quantity of aqueous catalyst composition from the catalyst bath 202 to the first reservoir 218; (c) moving a second quantity of previously- treated reactivated aqueous catalyst composition from the second reservoir 220 to the catalyst bath 202; (d) resuming operation of the catalyst bath 202; (e) moving the first quantity of aqueous catalyst composition from the first reservoir 218 to the ion exchange column 204 for treatment; and (f) moving the first quantity of aqueous catalyst composition to the second reservoir 220 for storage until the next batch process begins.

As another example of a batch operation, the catalyst bath 202 operation may be suspended, and the entire volume of aqueous catalyst composition may be removed from the catalyst bath 202, treated in the ion exchange column 204, then returned to the catalyst bath 202. In this example, the combined volume of the first fluid control circuit 206, ion exchange column 204 and second fluid control circuit 208 preferably is selected to hold the entire volume of the aqueous catalyst composition. Depending on the relative sizes of the components, this may or may not require the inclusion of the first reservoir 218 or second reservoir 220.

Other processing methods will become apparent with further consideration of the present disclosure by persons of ordinary skill in the art.

In either a continuous operation or a batch operation, the ion exchange operation preferably is operated at a sufficient rate or frequency to ensure that the concentration of free base catalyst compound within the catalyst bath 202 is sufficient to maintain acceptable final coating quality results. The selection of a suitable rate or frequency will depend on factors such as the starting concentration of free base catalyst compound, through-put per unit time of coated parts and the efficacy of the ion exchange column 204 at reacting with the carbonated form of the catalyst. In one example, the concentration of free base catalyst in the catalyst bath 202 may be periodically tested using titration methods or the like, and the ion exchange operation performed when such testing indicates that the desired concentration of free base catalyst is approaching, at, or below the desired level.

In another example, the ion exchange process may be performed at a predetermined rate or frequency that has been determined via modeling or empirical testing to maintain the concentration of free base catalyst at the desired level. For example, a batch operation may be used to clean the entire amount of aqueous catalyst composition between each operating shift of the autodeposition coating line. Such a system could operate based on a simple timer, and forego the need to continuously or periodically test the concentration of free base catalyst to determine when to perform the ion exchange process. Similarly, such a system may operate based on the output of a thermocouple indicating that the aqueous catalyst composition has cooled to a certain temperature indicating a cessation of the autodeposition line's operation. The selected temperature value may also coincide with a temperature at which the selected SBA exchange resin can be used without risking premature thermal degradation, which eliminates the need for the heat exchanger 222 to cool the incoming aqueous catalyst composition.

The ion exchange process also may be performed after a predetermined amount of time has elapsed since the first article was treated in the catalyst bath, after a predetermined number of articles have been treated in the catalyst bath, or after a total elapsed active operating time. Using the active operating time to determine when to perform the ion exchange process can be useful if the catalyst bath is stored between uses (e.g., when the entire line is shut down) in a way that it does not absorb more carbon dioxide from the atmospheric air. For example, the aqueous catalyst composition could be pumped into an enclosed environment, or a blanket of nitrogen or floating balls can be placed over the surface of the aqueous catalyst composition, at times when it is not in use. The number of articles also may provide a suitable estimate for (or factor in estimating) when it is necessary to perform the ion exchange process, particularly where the articles are sized or shaped such that they convey air into the aqueous catalyst composition. Other alternatives and variations will be apparent to persons of ordinary skill in the art in view of the present disclosure.

The ion exchange process can be repeated until the SBA exchange resin is no longer capable of returning the aqueous catalyst composition to the desired concentration of free base catalyst. At this point, the SBA exchange resin may be regenerated by contacting it with a regenerant, such as sodium hydroxide or potassium hydroxide. To this end, the catalyst bath treatment system 200 preferably also includes a source of regenerant such as a regenerant tank 224 including dilute sodium hydroxide (e.g., a solution of about 1-15%, and more preferably 2-10%, and even more preferably 3-6% sodium hydroxide in water), or in one embodiment is desirably at least about 1, 2, 3, 4, 5, 6, 7, or 8 wt.% and not more than 20, 18, 16, 14, 12, 10 wt.%. A third fluid control circuit 226 connects an outlet of the regenerant tank 224 to the inlet of the ion exchange column 204 (or optionally to the outlet of the ion exchange column 204 if reverse regenerant flow is desired). The third fluid control circuit 226 may include, for example, a third pump 228 and a third valve 230 that are operated when it is desired to deliver the regenerant to the ion exchange column 204.

A fourth fluid control circuit 232 is also provided to connect an outlet of the ion exchange column 204 to a waste treatment tank 234 or the like. The fourth fluid control circuit may include, for example, a fourth valve 236 that is opened to convey the waste regenerant to a waste receptacle via gravity, or a pump (not shown) may be provided if gravity is not sufficient to drain the waste. If necessary, a vent (not shown) may be provided to prevent the generation of a vacuum within the ion exchange column 204 during the outflow of waste regenerant. The use of a vent also may be avoided if a replacement fluid is provided into the ion exchange column 204 as the waste regenerant is drained.

The SBA exchange resin typically can be regenerated multiple times to a condition that is suitable for removing the carbonated salt from the aqueous catalyst composition. Eventually, however, the SBA exchange resin may exhibit exchange capacity loss that cannot be sufficiently remedied by regeneration and can require replacement. Such replacement of exhausted SBA resin can be scheduled, for example, according to empirical testing, performance estimations based on the post-regeneration performance of the SBA exchange resin, or other methods.

As noted above, it has been found that exposing certain aqueous catalyst compositions to an alkali such as sodium hydroxide can leave water soluble ions in the aqueous catalyst composition. To avoid this, the catalyst bath treatment system 200 may incorporate a wash system to remove trace regenerant (e.g., sodium hydroxide) from the ion exchange column 204 after the SBA exchange resin regeneration process. For example, as shown in Figure 2, a wash tank 238 may be provided to contain a wash liquid, such as deionized water. A fifth fluid control circuit 240 connects an outlet of the wash tank 238 to an inlet of the ion exchange column 204, and is operative to convey a quantity of wash water from the wash tank 238 to the ion exchange column 204. The fifth fluid control circuit 240 may include a fifth valve 242 that control flow through the fifth fluid control circuit 240, and a wash system pump 244 may be provided to pump the wash water to and through fifth valve 242 when it is opened. During or following operation of the fifth fluid control circuit 240, the fourth fluid control circuit 232 may be operated to release the wash water to waste 234 or recycling, if available.

The wash system also may include a reverse-flow circuit comprising a sixth fluid control circuit 246 that extends from the wash tank outlet to the ion exchange column outlet. The sixth fluid control circuit 246 includes a sixth valve 248 to selectively control flow, and may overlap with the fifth fluid control circuit 240 to include the wash system pump 244, but such overlap is not strictly required, and a separate pump (not shown) may be provided for the sixth fluid control circuit 246. The reverse-flow circuit also includes a seventh fluid control circuit 250 that extends from an inlet of the ion exchange column 204 to the waste treatment tank 234. The seventh fluid control circuit 250 is operated to release the wash water during reverse flow through the ion exchange column 204, and may include a seventh valve 252 an optionally a separate pump (not shown) or other devices. When operated in reverse, the wash water backflushes the SBA exchange resin, which can provide several benefits, such as eliminating high-flow channels that might have formed in the SBA exchange resin during forward flow, expand the SBA exchange resin to re-expose blocked surfaces, and remove waste that is trapped from moving in the forward flow direction.

Figure 3 illustrates an exemplary process 300 for operating the catalyst bath treatment system 200. In step 302, catalyst reactivation is performed by operating the first fluid control circuit 206 to convey a quantity of the aqueous catalyst composition from an outlet of the catalyst bath 202 to an inlet of the ion exchange column 204, and operating the second fluid control circuit 208 to return the quantity of aqueous catalyst composition to the catalyst bath 202.

In step 304, it is determined whether the SBA exchange resin treatment is effective to reactivate the aqueous catalyst composition to the desired performance level (e.g., minimum concentration of free base catalyst to ensure the desired coating quality). Step 304 may be performed using testing, such as titration testing to determine the concentration of free base catalyst in the aqueous catalyst composition following reactivation in step 302. Alternatively, step 304 may be performed using calculations, estimations, modeling or empirical data that suggests, but does not necessarily confirm, that the latest catalyst reactivation 302 was not effective to return the aqueous catalyst composition to the desired performance level. Using such indirect methods has the benefit of avoiding potentially time-consuming testing but may lead to premature SBA exchange resin regeneration cycles. In one example, step 304 may be operated as a simple counter that determines whether a predetermined number of catalyst reactivations 302 have been performed, with the predetermined number being based on prior testing or estimations of SBA exchange resin efficacy.

If the catalyst reactivation by SBA exchange resin in step 302 is determined in step 304 to have been effective, the catalyst reactivation process 302 may be permitted to continue operating (if in a continuous operation mode), or permitted to perform one or more additional cycles (if operating in a batch operation mode). If the SBA exchange resin is not considered in step 304 to be effective, the process moves to step 306.

In step 306, any ongoing catalyst reactivation process is terminated, and future scheduled catalyst reactivation processes are suspended until the SBA exchange resin is regenerated, using for example steps 314 and 316 or the SBA resin is determined to be exhausted in step 320 and replaced in step 322.

Then the process moves to step 308, in which any catalyst remaining in the ion exchange column 204 is displaced, preferably back into the catalyst bath 202. This may be performed, for example, by operating the second fluid control circuit 208 (e.g., opening the second valve 216 and operating the second pump 214 (or using gravity)) to drain the contents of the ion exchange column 204 back to the catalyst bath 202. A vent (not shown) may be opened to prevent the generation of a vacuum in the ion exchange column 204 that might inhibit such flow. Alternatively, the fifth fluid control circuit 240 may be operated simultaneously with the second fluid control circuit 208 to fill the ion exchange column 204 with wash water.

Next, in step 310, the fifth fluid control circuit 240 may be activated (e.g., by opening the fifth valve 242 and operating the wash system pump 244) to continue pumping wash water to the ion exchange column 204, while the fourth fluid control circuit 232 is activated (e.g., by opening the fourth valve 232) to flush wash water through the ion exchange column 204 and to the waste treatment system 234.

Then, in step 312, the sixth fluid control circuit 246 is activated (e.g., by opening the sixth valve 248 and operating the wash system pump 244), and the seventh fluid control circuit 250 is activated (e.g., by opening the seventh valve 252), to thereby backflush the ion exchange column 204 with wash water.

In step 314, the SBA exchange resin is regenerated by contacting it with the regenerant from the regenerant tank 224. Any suitable flow process or sequence of flow processes may be used to perform the regeneration step 314. For example, in a basic system, the regeneration step 314 may be performed by simultaneously or sequentially activating the third fluid control circuit 226 (e.g., by opening the third valve 230 and operating the third pump 228) and the fourth fluid control circuit 232 (e.g., by opening the fourth valve 236). The volume of regenerant and duration of contact with the SBA exchange resin may depend on factors, such as the identity of the SBA exchange resin and the regenerant and the desired level of regeneration. In one preferred embodiment, the regenerant is in contact with the SBA exchange resin for at least one hour. More preferably a quantity of regenerant equal to approximately three times the volume of the SBA exchange resin bed (i.e., the "bed volume" or"BV") is pumped through the SBA exchange resin at a rate of three BVs per hour. Desirably, this rate of three BVs of regenerant for one hour may be effective to return a typical SBA exchange resin to about, in increasing order of preference, 20, 25, 30, 35, 40, 45, 50, 55, 60, 64, 66, 68, 70, 72, 74,75, 76, 78, 80, 82,

84, or 85% of the theoretical working capacity. Other embodiments may use other regenerant flow volumes and rates, as may be necessary or desirable depending on different combinations of the selected SBA exchange resin and regenerant.

In other embodiments, more complex regeneration processes may be performed.

For example, the regeneration step 314 may be performed by operating in a countercurrent flow configuration, using a two-column lead/lag process, a three-column lead/lag/lag process, and so on. Multiple ion exchange columns also may be used in parallel, or any suitable series arrangement, and bypass blending may be used to help improve efficiency. Other alternatives and variations will be apparent to persons of ordinary skill in the art in view of the present disclosure. The design and implementation of a suitable ion exchange regenerating process is within the ordinary skill in the art, and need not be described in more detail herein.

After the regeneration step 314 is complete, the process continues to a final rinse step 316, in which the ion exchange column 204 is again rinsed with wash water from the wash tank 238. This may be performed, for example, by activating the fifth fluid control circuit 240 (e.g., by opening the fifth valve 242 and operating the wash system pump 244) and activating the fourth fluid control circuit 232 (e.g., by opening the fourth valve 236). The final rinse step 316 may use any suitable amount of wash water to clean residual regenerant from the ion exchange column 204. For example, wash water may be pumped through the ion exchange column 204 at the same flow rate as the regenerant (e.g., 3 BVs per hour) until about 1 to 2 BVs of wash water have passed through the ion exchange column 204, and then the flow rate may be increased to pass an additional volume of wash water through ion exchange column 204 until any significant trace amount of regenerant is expected to be removed. If desired, the final rinse step 316 may be followed by an additional backflush rinse, such as performed in step 312.

After the final rinse step 316, the aqueous catalyst composition can be used to perform one or more additional autodeposition processes, as shown in step 318 (the autodeposition process itself is not necessarily considered part of the catalyst bath treatment process 300 itself).

The process 300 also may include steps to account for the eventual degradation of the SBA exchange resin to a state in which it can no longer be effectively regenerated to continue reactivating the aqueous catalyst composition (i.e. exhausted). For example, in step 320, it is determined whether the SBA exchange resin is considered to be exhausted, and no longer effective at reactivating the catalyst to the desired performance level. Step 320 may be performed using testing, such as titration testing to determine the concentration of free base catalyst in the aqueous catalyst composition following the catalyst reactivation step 302. Alternatively, step 320 may be performed using calculations, estimations, modeling or empirical data that suggests, but does not necessarily confirm, that the SBA exchange resin has reached an exhausted state. Making the determination that the SBA exchange resin is considered to be exhausted based on such indirect methods has the benefit of avoiding potentially time-consuming testing but may lead to some excess waste if the SBA exchange resin is disposed of prior to actually reaching a state in which it is not able to reactivate the catalyst to the desired performance level. In one example, step 320 may be performed based on counting the number of times the regeneration step 314 has been performed on a particular quantity of SBA exchange resin. For example, if it is determined through modeling or experimentation that the chosen SBA exchange resin cannot be regenerated more than a certain number of times without losing its efficacy, that number can be used as a cutoff to consider the SBA exchange resin exhausted in step 320.

If the SBA exchange resin is deemed to be exhausted in step 320, the process moves to step 322 to replace the SBA exchange resin. It may not be necessary to perform one or more of steps 306 through 316 following SBA exchange resin replacement. Thus, one or more of these steps may be skipped and the process can then proceed to step 318 in which the aqueous catalyst composition is used to perform additional autodeposition processes until it is necessary to return to the catalyst bath treatment process 300.

It will be appreciated that the foregoing process 300 may be modified in various ways. For example, one or both of steps 310 and 312 may optionally be omitted, or step 308 may be performed by displacing the catalyst directly to waste or to a holding tank. Other alternatives and variations will be apparent to persons of ordinary skill in the art in view of the present disclosure.

Figure 4 is a block diagram of exemplary hardware and computing equipment that may be used as an exemplary control system 400 for implementing one or more of the processes provided herein. The control system 400 comprises a signal processing unit 402 having a central processing unit (CPU) 404, which is responsible for performing calculations and logic operations required to execute one or more computer programs or operations.

The CPU 404 is connected via a data transmission bus to a memory 406 and a data interface 408. The CPU 404, memory 406 and data interface 408 may be embodiment in any suitable computing device, such as an INTEL ATOM E3826 1.46GHz Dual Core CPU or the like, being coupled to DDR3L 1066/1333 MHz SO-DIMM Socket SDRAM having a 4GB memory capacity or other memory (e.g., compact disk, digital disk, solid state drive, flash memory, memory card, USB drive, optical disc storage, etc.), and having one or more communication ports in the form of wired communication ports (e.g., serial, USB, or the like) and/or wireless communication ports (e.g., Zigbee, Bluetooth, NFC, WiFi, or other wireless communication transceivers and associated hardware and control software). The selection of appropriate hardware and operating systems for the control system 400 is within the skill in the art of automated and semi-automated industrial process design, and need not be discussed in greater detail herein. The control system 400 is operatively connected via wired or wireless communication to sensors 410 (e.g., thermocouples, fluid level sensors, valve position sensors, pressure sensors, and the like) to monitor the status of one or more aspects of the autodeposition or SBA regeneration processes 100, 300. The control system 400 is also operatively connected via wired or wireless communication to one or more of the pumps, valves, and other control equipment 412 provided in the catalyst bath treatment system 200 or other parts of the autodeposition line. The control system 400 is also operatively connected via wired or wireless communication to one or more user interfaces 414, such as output devices (e.g., touchscreens, gauges, monitors, printers, speakers, etc.) and input devices (e.g., touchscreens, keyboards, buttons, levers, knobs, microphones, etc.). The user interfaces 414 may be used to monitor one or more of the sensors 410 and operate one or more of the controls 412 via the control system 400, and may be used to program or reprogram the control system to perform automated processes or semi-automated processes.

It will be appreciated from the foregoing disclosure that the inventors have provided new and useful solutions to the problem of carbonated catalyst accumulation in catalyst baths used in autodeposition coating lines. Such solutions are expected to be particularly useful in autodeposition coating lines that operate at low bake temperatures. Such solutions are also expected to be particularly useful in autodeposition coating lines that operate with a urethane crosslinking catalyst that is capable of reacting with and/or absorbing carbon dioxide, and is also in contact with atmospheric air containing carbon dioxide. Advantageously, solutions provided herein are capable of reactivating an aqueous catalyst composition of amine crosslinking catalyst that is capable of reacting with and/or absorbing carbon dioxide, without leaving water soluble ions or particulates in the aqueous catalyst composition.

As noted previously, although the invention is illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the invention.

Within this specification, embodiments have been described in a way which enables a clear and concise specification to be written, but it is intended and will be appreciated that embodiments may be variously combined or separated without departing from the invention. For example, it will be appreciated that all preferred features described herein are applicable to all aspects of the invention described herein. While preferred embodiments of the invention have been shown and described herein, it will be understood that such embodiments are provided by way of example only. Numerous variations, changes and substitutions will occur to those skilled in the art without departing from the spirit of the invention. Accordingly, it is intended that the appended claims cover all such variations as fall within the spirit and scope of the invention.