DE102018107717A1 - An electrodeposition paint composition including an anticrater agent - Google Patents

Abstract

An electrocoating composition is provided herein. The electrodeposition coating composition includes an aqueous carrier. The electrodeposition coating composition further includes a film-forming binder. The film-forming binder includes an epoxy-amine adduct and a blocked polyisocyanate crosslinking agent. The electrodeposition paint composition further includes an anticrater agent selected from the group consisting of a polyester resin dispersion, a polyacrylate resin dispersion, and a combination thereof. The electrodeposition coating composition further includes a supplemental anticrater agent including a polyether-modified polysiloxane.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application is a non-provisional US patent application which is the priority of the provisional U.S. Application No. 62 / 479,589 , filed on Mar. 31, 2017, which is hereby incorporated by reference in its entirety.

TECHNICAL AREA

The technical field generally relates to electrodeposition coating compositions for coating substrates.

BACKGROUND

Coating of electrically conductive substrates by an electrodeposition process, also called electrocoating, is a well-known and important industrial process. Electrodeposition of primers on automotive substrates is widely used in the automotive industry. In this method, a conductive article such as a car body or a car part is immersed in a coating composition bath of an aqueous emulsion of a film-forming polymer and functions as an electrode in the electrodeposition process. An electric current is passed between the article and a counter electrode in electrical contact with the aqueous emulsion until a desired coating is deposited on the article. In a cathodic electrodeposition process, the article to be coated is the cathode and the counter electrode is the anode.

Resin compositions used in the bath of a typical cathodic electrodeposition process are also well known in the art. These resins are typically made from polyepoxide resins that have been chain extended and then an adduct is formed to include amine groups in the resin. Amine groups are typically introduced by reaction of the resin with an amine compound. These resins are mixed with a crosslinking agent and then neutralized with an acid to form a water emulsion, commonly referred to as the main emulsion.

The main emulsion is combined with a pigment paste, coalescing solvents, water and other additives to form the electrodeposition bath. The electrodeposition bath is placed in an insulated tank containing the anode. The object to be coated is the cathode and is passed through the tank containing the electrodeposition bath. The thickness of the coating deposited on the article being electrocoated is a function of bathing properties, electrical operating characteristics, dipping time, and the like.

The resulting coated article is removed from the bath after a predetermined period of time and rinsed with deionized water. The coating on the article is typically cured in an oven at a temperature sufficient to produce a crosslinked finish on the article.

One ongoing problem with cathodic electrodeposition coatings has been the presence of craters in the cured finish. Craters may be caused by oils from the manufacture of the article or by lubricants used in the conveyors. Conventional attempts to reduce the presence of craters have not only lessened the presence of craters, but have also had a negative impact on the properties of the electrodeposition coating layer, subsequent coating layers applied thereto, or both.

Accordingly, it is desirable to provide an electrocoating composition having reduced craters and excellent performance properties. Furthermore, other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, in light of this background.

SHORT SUMMARY

An electrocoating composition is provided herein. The electrodeposition coating composition includes, but is not limited to, an aqueous carrier. The Electrodeposition paint composition further includes, but is not limited to, a film-forming binder. The film-forming binder includes, but is not limited to, an epoxy-amine adduct and a blocked polyisocyanate crosslinking agent. The electrodeposition paint composition further includes, but is not limited to, an anti-crater agent selected from the group consisting of a polyester resin dispersion, a polyacrylate resin dispersion, and a combination thereof. The electrodeposition coating composition further includes, but is not limited to, an additional anticrater agent including a polyether-modified polysiloxane.

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature and is not intended to limit coating compositions as described herein. In addition, there is no intention to be bound by any theory presented in the preceding or the following detailed description.

An electrodeposition coating composition for coating a substrate is provided herein. The electrodeposition coating composition can be used to coat any type of substrate known in the art. In embodiments, the substrate is a vehicle, automobile, or motor vehicle. "Vehicle" or "automobile" or "motor vehicle" includes an automobile such as automobile, van, minivan, bus, SUV (Sport Utility Vehicle); TRUCK; Truck tractors; Tractor; Motorcycle; Pendant; ATV (off-road vehicle); Pick up; High performance machines, such as bulldozers, mobile cranes and earthmoving machines; aircraft; boats; Ships; and other means of transport.

The electrodeposition coating composition is used to form a coating layer on the substrate. The electrodeposition coating composition includes an anticratering agent to reduce the presence of craters in the coating layer. The term "crater" as used herein refers to surface defects in a surface of a coating layer that typically have the appearance of circular cavities extending into the surface of the coating layer. The anticrater agent may be selected from the group of a polyester resin dispersion, a polyacrylate resin dispersion and a combination thereof. The anticrater agent may be used in an amount of from about 0.01 to about 10 percent by weight, based on the total weight of the electrodeposition coating composition.

The polyester resin dispersion may be further defined as a highly branched water-reducible polyester. The polyester resin dispersion can be formed by first reacting a carboxylic acid anhydride and a hydroxy functional cyclic carbonate to form a first adduct having a primary carboxyl group at one end and a cyclic carbonate at the other end. In embodiments, this first reaction proceeds at a temperature of from about 90 ° C to about 150 ° C and in the presence of a catalyst. Examples of suitable catalysts include, but are not limited to, triphenylphosphine, ethyltriphenylphosphonium iodide, or a combination thereof. The first reaction is complete when a predetermined acid number of about 132 to about 136 mg KOH / g is reached. The first reaction may be completed after a period of about 10 minutes to about 24 hours. It should be noted that a reaction of a carboxylic acid in place of the carboxylic acid anhydride and the hydroxy functional cyclic carbonate may require esterification by condensation, thereby eliminating water, which may then require removal of the water by distillation. For this purpose, the polyesterification in various embodiments should be avoided.

In embodiments, the equivalent ratio of anhydride of the carboxylic acid anhydride to hydroxy of the hydroxy-functional cyclic carbonate is about 0.8: 1 to about 1.2: 1 (the anhydride being considered monofunctional) to obtain maximum conversion to the desired reaction product. In certain embodiments, the equivalent ratio of anhydride to hydroxy is about 1: 1. Equivalent ratios of less than 0.8: 1 may be used, but such ratios may result in increased formation of less desirable polyesterification products.

In embodiments, among the carboxylic acid anhydrides which may be used in the formation of the primary carboxyl groups of the first adduct are those containing from about 2 to 30 carbon atoms without the carbon atoms in the anhydride group. Examples include, but are not limited to, aliphatic, including cycloaliphatic, olefinic and cycloolefinic anhydrides, and aromatic anhydrides. Substituted aliphatic and aromatic anhydrides are also included within the definition of aliphatic and aromatic, provided that the substituents are the reactivity of the aliphatic and aromatic anhydrides Anhydride or the properties of the resulting polyester do not adversely affect. Examples of substituents include, but are not limited to, halo, alkyl and alkoxy groups. In embodiments, aromatic anhydrides are generally not preferred because of their poor weathering properties.

Examples of suitable aliphatic acid anhydrides include, but are not limited to, phthalic anhydride, maleic anhydride, succinic anhydride, hexahydrophthalic anhydride, tetrahydrophthalic anhydride and methylhexahydrophthalic anhydride. In embodiments, the carboxylic acid anhydride is further defined as succinic anhydride. Examples of suitable succinic anhydrides include, but are not limited to, hexadecenyl succinic anhydride, octenyl succinic anhydride, octadecenyl succinic anhydride, tetradecenyl succinic anhydride, dodecenyl succinic anhydride and octadecenyl succinic anhydride. In embodiments succinic anhydrides are useful because of their long hydrocarbon chains of at least 4 carbon atoms or alternatively of at least 6 to 18 carbon atoms without the carbon atoms in the anhydride group which provide good stability and proper hydrophilic / hydrophobic balance in the final coating composition. In certain embodiments, the carboxylic acid anhydride is selected from the group of dodecenyl succinic anhydride, octadecenyl succinic anhydride, and a combination thereof.

In embodiments, among the hydroxy-functional cyclic carbonates that may be used are those containing active hydrogens having one or more hydroxy-functional groups. These cyclic carbonates are well known in the art. Hydroxy functional cyclic carbonates having various ring sizes, as known in the art, can be used. In embodiments, five-membered-ring cyclic carbonates, six-membered-ring cyclic carbonates or a combination thereof can be used. In certain embodiments, five-membered-ring cyclic carbonates are used because of their higher degree of commercial availability. Examples of suitable five-membered cyclic carbonates containing a hydroxyl group include 1,3-dioxolan-2-one-4-propanol, 1,3-dioxolan-2-one-butanol, 1,3-dioxolan-2-one pentanol and the like, but are not limited thereto. Examples of suitable six-membered cyclic carbonates containing a hydroxyl group include but are not limited to 1,3-dioxolan-2-one-2,2-diethylpropanol, 1,3-dioxolan-2-one-2,2-dimethylpropanol and the like not limited to this. In certain embodiments, the hydroxy-functional cyclic carbonate is further defined as a five-membered cyclic carbonate that includes a 1,3-dioxolan-2-one group, such as 1,3-dioxolan-2-one-propanol, commonly referred to in U.S. Pat Technique referred to as glycerol carbonate.

In embodiments, the carboxyl group of the first adduct is chain extended to introduce additional hydrocarbon chains into the molecule for improved stability and improved hydrophilic / hydrophobic balance. In certain embodiments, the carboxyl group is chain extended by first reacting the carboxyl group of the first adduct with a monofunctional epoxy resin to form a second adduct having a hydroxy group at one end and a cyclic carbonate at the other end. This first part of the chain extension reaction is complete when a predetermined acid value of less than 20 mg KOH / g or alternatively less than 5 mg KOH / g is achieved. In certain embodiments, the monofunctional epoxy resin is further defined as a monoglycidyl ether. The chain extension reaction can be continued by reacting the hydroxyl group of the second adduct with additional acid anhydride to form a third adduct having a carboxyl group at one end and a cyclic carbonate at the other end. This second part of the chain extension reaction is complete when a predetermined acid number greater than 40 mg KOH / g or alternatively greater than 50 mg KOH / g is achieved. The chain extension reactions may proceed under similar conditions and use similar reagents as described above.

In embodiments, among the monoglycidyl ethers which may be used in the chain extension reaction are those having a 1,2-epoxy equivalence of about 1, that is, monoepoxides having an average of one epoxide group per molecule. These epoxy compounds may be saturated, unsaturated, aliphatic, cycloaliphatic, aromatic or heterocyclic. These epoxy compounds may contain substituents such as halo, hydroxy, ether, alkyl and / or aryl groups, provided that the substituents do not adversely affect the reactivity of the adduct or the properties of the resulting polyester.

In embodiments, suitable monoepoxide compounds are those containing from 4 to 18 carbon atoms without the carbon atoms in the epoxide group. In certain embodiments, the Monoepoxide compound further defined as a monoglycidyl ether of long chain, ie C4 or higher, monohydric alcohol. Examples of suitable monoglycidyl ethers include, but are not limited to, alkyl, cycloalkyl, alkylalkoxysilane, aryl, and mixed arylalkyl monoglycidyl ethers, such as o-cresyl glycidyl ether, phenyl glycidyl ether, butyl glycidyl ether, octyl glycidyl ether, dodecyl glycidyl ether, glycidoxypropyl trimethoxysilane, and glycidoxypropyl triethoxysilane, 2-ethylhexyl monoglycidyl ether. In various embodiments, the monoglycidyl ether may be selected from the group of 2-ethylhexyl monoglycidyl ether, the combination of glycidoxypropyltrimethoxysilane and 2-ethylhexyl monoglycidyl ether or a combination thereof. Other useful long chain epoxy compounds having an epoxide group will be readily apparent to one skilled in the art.

In embodiments, among the acid anhydrides, any of the aforementioned acid anhydrides can be used in the chain extension reaction. In embodiments, the equivalent ratio of carboxyl to hydroxyl groups in this chain extension reaction is from about 0.8: 1 to about 1.2: 1 to obtain maximum conversion to the chain-extended adduct. In certain embodiments, the equivalent ratio of carboxyl to hydroxyl groups is about 1: 1.

The formation of the polyester resin dispersion can be continued by reacting either the first adduct (not chain extended) or the third adduct (chain extended) with a coupling agent having two or more sites reactive with active hydrogen groups to form a di- or higher adduct (ie branched polyester adduct) with terminal cyclic carbonate groups. The amount of coupling agent is selected primarily relative to the carboxyl groups to ensure an acid number in the range of 0 to 10 for every 100 grams of resin to provide the best balance between water solubility and low excess carboxyl.

The reaction with the coupling agent is carried out under the same conditions as used above and is continued until the desired acidity is reached. In embodiments, the coupling agent used to form the anticrater agent includes a polyfunctional isocyanate compound. Any of the conventionally used aromatic, aliphatic or cycloaliphatic monomeric, polymeric or prepolymeric polyfunctional (i.e., difunctional or higher) isocyanate compounds may be used without particular limitation as long as the isocyanate compound has at least two isocyanate groups in the one molecule. In embodiments, the isocyanate compounds have on average from two to six isocyanate groups per molecule. In certain embodiments, the isocyanate compounds have, on average, two to three isocyanate groups per molecule.

Examples of suitable monomeric isocyanate compounds include, but are not limited to, 1,6-hexamethylene diisocyanate, isophorone diisocyanate, 2,4-toluene diisocyanate, diphenylmethane-4,4'-diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, tetramethylxylylene diisocyanate and the like. Typical examples of polymeric isocyanate compounds are isocyanurate of 1,6-hexamethylene diisocyanate, biuret of 1,6-hexamethylene diisocyanate, uretdione of 1,6-hexamethylene diisocyanate, isocyanurate of isophorone diisocyanate, biuret of isophorone diisocyanate, uretdione of isophorone diisocyanate, isocyanurate of diphenylmethane-4,4 '. diisocyanate and polymeric diphenylmethane diisocyanate.

Prepolymer isocyanate compounds formed from any of the above-mentioned organic polyisocyanates and a polyol can also be used. Polyols such as polyoxypropylene ethers of glycerine, trimethylolpropane, 1,2,6-hexanetriol, sorbitol can be used. A useful adduct is the reaction product of tetramethylxylylene diisocyanate and trimethylolpropane. In embodiments, an aromatic isocyanate is used for better emulsion stability, electrodeposition phenomena, and corrosion resistance. In certain embodiments, the aromatic isocyanate is the mixture of monomeric and polymeric compounds of diphenylmethane diisocyanate, such as Mondur® MR, commercially available from Bayer Corporation.

The terminal cyclic carbonate groups on the di- or higher branched polyester adduct may then be reacted in a subsequent reaction with a polyamine compound containing at least one free tertiary amine group, and also additionally containing a primary amine or secondary amine group, to give the final branched one Polyester-amine adduct containing terminal tertiary amine groups to form. Typical polyamines containing at least one tertiary amine and one primary amine or secondary amine which are used include N, N-dimethylaminopropylamine, aminopropylmonomethylethanolamine, N, N-diethylaminopropylamine, aminoethylethanolamine, N-aminoethylpiperazine, aminopropylmorpholine, tetramethyldipropylenetriamine and diketimine (a reaction product of 1 mole of diethylenetriamine and 2 moles Methyl isobutyl ketone). In certain embodiments, the polyamine compound is further defined as N, N-dimethylaminopropylamine. Typically, after the above-described cyclic carbonate end-adduct is formed, the amine containing the primary or secondary amine functions in addition to the tertiary amine functions and additional solvent are added to the reaction solution, and the reaction is continued at elevated temperature until all cyclic carbonate groups have been converted and converted into terminal tertiary amine groups. The amount of polyamine required varies from case to case depending on the desired level of water solubility required for the particular end use application. In general, an equimolar amount of amine to cyclic carbonate is used, but a slight excess of carbonate is acceptable.

In embodiments, a portion of the polyamine used in the above reaction may be replaced with an amino-functional alkylalkoxysilane compound to further improve crater resistance. The amino-functional alkylalkoxysilane compound is also reactive with the terminal cyclic carbonate groups and is capable of converting these groups into terminal alkoxysilane groups. Examples of suitable amino-functional alkylalkoxysilane compounds are gamma-aminopropyltriethoxysilane, gamma-aminopropyltrimethoxysilane and N- (2-aminoethyl) -3-aminopropyltrimethoxysilane. In certain embodiments, the amino-functional alkylalkoxysilane compound is further defined as gamma-aminopropyltrimethoxysilane.

In an exemplary embodiment, mixtures of polyamines and aminoalkylalkoxysilanes are used to react with the terminal cyclic carbonate groups to form tertiary amine groups and terminal alkoxysilane groups. The molar ratio of polyamines and aminoalkylalkoxysilanes in the blends can range from about 95: 5 to about 60:40, or alternatively from about 95: 5 to about 80:20.

The resulting polyester resin composition prepared above has a low to intermediate molecular weight having a number average molecular weight of from about 1,000 to about 10,000, or alternatively from about 2,000 to about 6,000, as determined by GPC (gel permeation chromatography) using polystyrene as the standard.

The resulting polyester resin composition is emulsified in water with an organic or inorganic acid such as lactic acid, acetic acid, formic acid, sulfamic acid and the like to completely or partially neutralize the tertiary amine functionality to form the polyester resin dispersion. The polyester resin dispersion may then be added to the electrocoating composition at almost any time. It can be added to the main emulsion, bath or pigment paste. In the pigment paste, the pigment is ground with a resin, which may be the polyester resin dispersion which also functions as a pigment dispersing resin.

The polyacrylate resin dispersion may be further defined as a water-reducible polyacrylate. The polyacrylate resin dispersion can be formed by first reacting a monomer reaction mixture that includes one or more acrylate monomers. In embodiments, the reaction proceeds in the presence of a solvent, such as methyl isobutyl ketone. In embodiments, this reaction proceeds at a temperature of about 115 ° C to about 125 ° C and in the presence of a catalyst. It should be noted that the reaction can proceed at a temperature of 110 ° C to 160 ° C, depending on the solvent used. An example of a suitable catalyst includes, but is not limited to, 2,2'-azodi (2-methylbutyronitrile). This first reaction can be completed in a period of at least 300 minutes.

The reaction mixture may include an alkyl (meth) acrylate monomer, a hydroxy-functional (meth) acrylate monomer, an amino-functional (meth) acrylate monomer, or combinations thereof. It is to be understood that the reaction mixture may include other monomers known in the art, provided that the monomers do not adversely affect the reactivity of the polyacrylate. The alkyl (meth) acrylate monomer may be included in the reaction mixture in an amount of from about 1 to about 99 percent by weight, based on the total weight of all monomers of the reaction mixture. The hydroxy-functional (meth) acrylate monomer may be included in the reaction mixture in an amount of from about 1 to about 99 percent by weight, based on the total weight of all monomers of the reaction mixture. The amino functional (meth) acrylate monomer may be included in the reaction mixture in an amount of from about 1 to about 99 percent by weight, based on the total weight of all monomers of the reaction mixture.

Examples of suitable alkyl (meth) acrylate monomers include methyl methacrylate, ethyl methacrylate, propyl methacrylate (all isomers), butyl methacrylate (all isomers), 2-ethylhexyl methacrylate, isobornyl methacrylate, methacrylonitrile, methyl acrylate, ethyl acrylate, propyl acrylate (all isomers), butyl acrylate (all isomers), 2 - Ethylhexyl acrylate, isobornyl acrylate, acrylonitrile and the like, but are not limited thereto. In certain embodiments, the alkyl (meth) acrylate monomer is further defined as butyl acrylate.

Examples of suitable hydroxy-functional (meth) acrylate monomers include, but are not limited to, 2-hydroxyethyl methacrylate (HEMA), 2-hydroxyethyl acrylate (HEA), hydroxypropyl methacrylate (HPMA) and hydroxypropyl acrylate (HPA). In certain embodiments, the hydroxy-functional (meth) acrylate monomer is further defined as hydroxypropyl methacrylate (HPMA).

Examples of suitable amino-functional (meth) acrylate monomers include t-butylaminoethyl methacrylate (t-BAEMA), N, N-dialkylaminoalkyl acrylates such as N, N-dimethylaminoethyl acrylate and N, N-diethylaminoethyl acrylate and N, N-dialkylaminoalkyl methacrylate such as N, N- Dimethylaminoethyl methacrylate and N, N-diethylaminoethyl methacrylate, but are not limited thereto. In certain embodiments, the amino-functional (meth) acrylate monomer is further defined as N, N-dimethylaminoethyl methacrylate.

The resulting polyacrylate resin composition prepared above has a low to intermediate molecular weight having a number average molecular weight of from about 4,000 to about 12,000, or alternatively from about 6,000 to about 10,000 as determined by GPC (gel permeation chromatography) using polystyrene as a standard.

The resulting polyacrylate resin composition is emulsified in water with an organic or inorganic acid such as lactic acid, acetic acid, formic acid, sulfamic acid and the like to form the polyacrylate resin dispersion. The polyacrylate resin dispersion can then be added to the electrocoating composition at almost any time. It can be added to the main emulsion, bath or pigment paste. In the pigment paste, the pigment is ground with a resin, which may be the polyacrylate resin dispersion which also functions as a pigment dispersing resin.

The electrodeposition coating composition may further contain a supplemental anticrater agent. The supplemental anticrater agent may be further defined as a polyether-modified polysiloxane. Examples of suitable polyether-modified polysiloxanes are commercially available from Momentive ™ under the trade name CoatOSil ™ such as CoatOSil ™ 2400, CoatOSil ™ 2812, CoatOSil ™ 2816, CoatOSil ™ 3500, CoatOSil ™ 3501, CoatOSil ™ 3505, CoatOSil ™ 3573, CoatOSil ™ 7001 CoatOSil ™ 7500, CoatOSil ™ 7510, CoatOSil ™ 7600, CoatOSil ™ 7602, CoatOSil ™ 7604, CoatOSil ™ 7605, CoatOSil ™ 7650, CoatOSil ™ 77 and CoatOSil ™ 7608, and under the trade name Silwet ™, such as Silwet ™ L-7200, Silwet ™ L-7210, Silwet ™ L-7220, Silwet ™ L-7230, Silwet ™ L-7280, Silwet ™ L-7550, Silwet ™ L-7607 and Silwet ™ L-8610. In embodiments, the additional anticrater agent is the polyether modified polysiloxane commercially available as CoatOSil ™ 7604. The additional anticratering agent may be used in an amount of from 0.01% to 20% by weight, based on the total weight of the anticrater agent used in the electrodeposition coating composition.

Back to the electrodeposition coating composition, many emulsions used in an electrodeposition coating composition include an aqueous emulsion of a binder of an epoxide amine adduct blended with a crosslinking agent that has been neutralized with an acid to form a water-soluble product. Examples of epoxy-amine adduct-based resins are generally in US Pat. No. 4,419,467 which is incorporated herein by reference. It should be noted, however, that the anticrater agent can also be used with a variety of cathodic electrodeposition resins. Examples of acids that can be used to neutralize the epoxide-amine adduct include lactic acid, acetic acid, formic acid, sulfamic acid, and the like.

Crosslinking agents for the electrodeposition coating composition are also well known in the art. The crosslinking agent may be aliphatic, cycloaliphatic and aromatic isocyanate including any of the above isocyanates such as hexamethylene diisocyanate, cyclohexamethylene diisocyanate, toluene diisocyanate, methylene diphenyl diisocyanate and the like. These isocyanates may be prereacted with a blocking agent, such as oximes, alcohols or caprolactams, which selectively block the isocyanate functionality. The isocyanates may be deblocked by heating to separate the blocking agent from the isocyanate group of the isocyanate to provide a reactive isocyanate group. Isocyanates and blocking agents are well known in the art and are also in the aforementioned U.S. Patent No. 4,419,467 which is incorporated herein by reference.

The cathodic binder of the epoxy-amine adduct and the blocked isocyanate are the major resinous ingredients in the electrodeposition coating composition and may be present in amounts of from about 10 to about 70 weight percent, alternatively from about 20 to about 60 weight percent, or alternatively about 30 to about 50 wt .-%, based on the total solids of the electrodeposition coating composition, be present. An electrocoating bath can be formed by diluting the solids with an aqueous medium.

The electrodeposition coating composition further includes a pigment which can be added to the composition in the form of a pigment paste. The pigment paste may be prepared by milling or dispersing a pigment in a pigment grinding vehicle and optionally additives such as wetting agents, surfactants and defoamers. The pigment grinding vehicle may be the anticratering agent, a conventional pigment grinding vehicle well known in the art, or a combination thereof. The pigment may be milled to a particle size of about 6 to about 8 according to a Hegman refiner.

The pigments may include titanium dioxide, carbon black, barium sulfate, clay and the like. In embodiments, pigments having high surface areas and high oil absorbency are used in a limited amount due to undesirable effects on coalescence and flowability of the coating layer.

The pigment to binder weight ratio may be less than 5: 1, alternatively less than 4: 1, or alternatively about 2: 1 to about 4: 1. In embodiments, higher pigment to binder weight ratios may adversely affect coalescence and flowability.

The electrodeposition coating composition may further include additives such as wetting agents, surfactants, defoamers, and the like. Examples of surfactants and additional wetting agents include acetylenic alcohols available from Air Products and Chemicals as "Surfynol 104". These additives, when present, may be present in an amount of from about 0.1 to about 20 percent by weight, based on the total binder solids of the electrodeposition coating composition.

The electrodeposition paint composition may further contain a plasticizer for promoting flowability. Examples of suitable plasticizers can be high boiling, water immiscible materials such as ethylene or propylene oxide adducts of nonylphenols or bisphenol A. The electrodeposition coating composition may include the plasticizer in an amount of from about 0.1 to about 15 percent by weight, based on the total resin solids of the electrodeposition coating composition.

The electrodeposition coating composition may be an aqueous dispersion. The terminology "dispersion" as used herein refers to a biphasic translucent or opaque aqueous resin binder system in which the binder is in the dispersed phase and water is the continuous phase. The average particle diameter of the binder phase is from about 0.01 to about 1 micrometer in size, alternatively from about 0.05 to about 0.15 micrometers, alternatively less than 1 micrometer, or alternatively less than 0.15 micrometer. While the concentration of the binder in the aqueous medium is generally not critical, in embodiments the majority of the aqueous dispersion is typically water. The aqueous dispersion may include the binder in an amount of from about 3 to about 50 weight percent solids, or alternatively from about 5 to about 40 weight percent solids, based on the total weight of the aqueous dispersion. In embodiments, aqueous binder concentrates, which are to be further diluted with water when added to an electrocoating bath, may have a range of binder solids of from about 10 to about 30 percent by weight.

Examples

The following examples describe the preparation, use, and evaluation of various electrodeposition coating compositions of this disclosure.

Preparation of a water-dilutable polyester resin dispersion (anticratering agent I)

A highly branched water-reducible polyester was prepared by placing 266 parts of dodecenylsuccinic anhydride, 125 parts of glycerol carbonate and 3 parts of triphenylphosphine in a suitable reaction vessel and heating to 116 ° C under a nitrogen atmosphere. The reaction was held at 132 ° C until an acid number of 132 to 136 was reached. 266 parts of 2-ethylhexyl monoglycidyl ether and 3 parts of triphenylphosphine were added and kept at 132 ° C until an acid number of 0 to 3 was reached. 266 parts of dodecenylsuccinic anhydride and 1 part of triphenylphosphine were added and kept at 132 ° C until an acid number of 56 to 62 was reached. Add 84 parts of xylene and drop the reaction temperature to 116 ° C. 127 parts of Mondur MR (methylene diphenyl diisocyanate) were slowly added to the reaction vessel. The reaction mixture was held at 116 ° C until all the isocyanate had reacted as indicated by infrared scan. 87 parts of dimethylaminopropylamine and 33 parts of aminopropyltrimethoxysilane were added and kept at 116 ° C for one hour. The reaction mixture is added to a mixture of 2150 parts deionized water and 83 parts lactic acid (80% concentration) and mixed for 30 minutes. The resulting resin dispersion had a nonvolatile content of 30% in water.

II. Preparation of a Water-Dilutable Polyacrylate Resin Dispersion (Anticcrating Agent II)

A water reducible polyacrylate was prepared by placing 102 parts of methyl isobutyl ketone in a suitable reaction vessel and refluxing with stirring under nitrogen. 58 parts of diethylaminoethyl methacrylate, 121 parts of hydroxypropyl acrylate and 270 parts of butyl acrylate were charged into the monomer feed tank and mixed well before being fed to the reaction vessel. 8 parts of 2,2'-azodi (2-methylbutyronitrile) and 98 parts of methyl isobutyl ketone were charged into the initiator feed tank before being fed to the reaction vessel and mixed well. The mixture of monomers was added to the reaction vessel within 300 minutes simultaneously with the initiator mixture. The initiator mixture was added to the reaction vessel simultaneously with the monomer mixture over 330 minutes. After the supply is complete, hold at reflux for 30 minutes. Methyl isobutyl ketone was evaporated until the percent solids was 90%. The resin was dropped into a mixture of 1086 parts of deionized water and 33 parts of lactic acid (80% concentration) and mixed for 30 minutes. The resulting resin dispersion had a non-volatile content of 26% in water.

III. Preparation of polyether-modified polysiloxane (additional anticrater agent)

Commercially available Momentif polyether-modified polysiloxane such as CoatOsil7604 is used in the blends of Table 1 below. Table 1 Mixture A Mixture B Mixture C Mixture D Antikratermi ttel I 1000 parts by weight 1000 parts by weight - - Antikratermi ttel II - - 1000 parts by weight 1000 parts by weight Complementary anti-cremation medication - 53 parts by weight - 46 parts by weight

IV. Preparation of a Conventional Crosslinking Resin Solution

A solution of alcohol-blocked polyisocyanate crosslinker resin was prepared by placing 317.14 parts of Mondur MR (methylene diphenyl diisocyanate), 105.71 parts of methyl isobutyl ketone and 0.06 part of dibutyltin dilaurate in a suitable reaction vessel and heating to 37 ° C under a nitrogen atmosphere. A mixture of 189.20 parts of propylene glycol monomethyl ether and 13.24 parts of trimethylolpropane was added slowly to the reaction vessel while keeping the reaction mixture below 93 ° C. The reaction mixture was then kept at 110 ° C. until substantially all of the isocyanate had reacted, as indicated by infrared scanning. 3.17 parts of butanol and 64.33 parts of methyl isobutyl ketone (MIBK) were then added. The resulting resin solution had a nonvolatile content of 75% of MIBK.

Preparation of a chain-extended polyepoxide emulsion with a conventional crosslinker resin solution

The following ingredients were added to a suitable reaction vessel: 520 parts Epon® 828 (epoxy resin of diglycidyl ether of bisphenol A having an epoxide equivalent weight of 188), 151 parts bisphenol A, 190 parts ethoxylated bisphenol A having a hydroxyl equivalent weight of 247 (Synfac®8009), 44 parts of xylene and 1 part of dimethylbenzylamine. The resulting reaction mixture was heated to 160 ° C under a nitrogen atmosphere and held at this temperature for one hour. 2 parts of dimethylbenzylamine were added and the mixture was kept at 147 ° C until an epoxide equivalent weight of 1050 was obtained. The reaction mixture was cooled to 149 ° C and then 797 parts conventional crosslinking resin (prepared as II) was added. At 107 ° C, 58 parts of diketimine (reaction product of diethylenetriamine and methyl isobutyl ketone at 73% nonvolatile) and 48 parts of methylethanolamine were added. The resulting mixture was maintained at 120 ° C for one hour and then dispersed in an aqueous medium of 1335 parts of deionized water and 61 parts of lactic acid (88% lactic acid in deionized water). It is further diluted with 825 parts of deionized water. The emulsion was stirred until methyl isobutyl ketone had evaporated. The resulting emulsion had a nonvolatile content of 38%.

VI. Preparation of quaternizing agent

The quaternizing agent was prepared by adding 87 parts of dimethylethanolamine to 320 parts of 2-ethylhexanol half-capped toluene diisocyanate in the reaction vessel at room temperature. An exothermic reaction occurred and the reaction mixture was stirred for one hour at 80 ° C. 118 parts of aqueous lactic acid solution (80% concentration) were then added, followed by the addition of 39 parts of 2-butoxyethanol. The reaction mixture was kept at 65 ° C for about one hour with constant stirring to form the quaternizing agent.

VII. Preparation of a pigment grinding vehicle

The pigment grinding vehicle was prepared by charging 710 parts of Epon828 (diglycidyl ether of bisphenol A having an epoxy equivalent weight of 188) and 290 parts of bisphenol A to a suitable vessel under a nitrogen atmosphere and heating to 150 ° C to 160 ° C to initiate an exothermic reaction. The exothermic reaction was continued for about 1 hour at 150 ° C - 160 ° C. The reaction mixture was then cooled to 120 ° C and 496 parts of 2-ethylhexanol half-capped toluene diisocyanate were added. The temperature of the reaction mixture was maintained at 110 ° C - 120 ° C for one hour, followed by the addition of 1095 parts of 2-butoxyethanol, the reaction mixture was then cooled to 85 ° C - 90 ° C and then 71 parts of deionized water was added followed by the addition of 496 parts of quaternizing agent (prepared above VI). The temperature of the reaction mixture was maintained at 85 ° C - 90 ° C until an acid value of about 1 was obtained.

Preparation of a pigment paste

parts by weight Pigment vehicle (as prepared above) 597.29 Deionized water 1,283.95 Lactic acid, 80% 21,02 bismuth 87.06 Titanium dioxide 419.28 aluminosilicate 246.81 soot 15.27 barium sulfate 329.32 3,000.00

The above ingredients were mixed until a homogeneous mixture was formed in a suitable mixing vessel. It was then dispersed by pouring into an egg mill and then grinding until it passed the Hegman test.

Production of electrocoating baths

Table 2 Bath 1 Bath 2 Bath 3 Bathroom 4 Emulsion (as prepared above V) 1650 1650 1650 1650 Deionized water 1982 1988 1974 1983 Pigment paste (as prepared above A) 314 314 314 314 Mixture A (prepared as above III) 54 - - - Mixture B (prepared as above III) - 48 - - Mixture C (prepared as above III) - - 62 - Mixture D (as prepared above III) - - - 53 Total (parts by weight) 4000 4000 4000 4000

Cationic electrodeposition baths were prepared by mixing the above ingredients. Each bath was then ultrafiltered. Each bath was electrocoated at 240-280 volts to obtain 0.8-1.0 mils (20.32-25.4 microns).

The surface roughness of the cured electrodeposition paint film was measured using a Taylor-Hobson Surtronic 3+ profilometer. The phosphated cold rolled steel plates were electrolytically coated and baked at 360 ° F for 10 minutes metal temperature. The film build up from 0.8 mils to 0.9 mils should be obtained. The surface roughness was then measured. The surface roughness of the panels with bath 1, bath 2, bath 3 and bath 4 was 9 μin.

1. A --- 0-10% defekt
2. B --- 11-20% defekt
3. C --- 21-40% defekt
4. D --- 41-80% defekt
5. E --- mehr als 80% defekt

ASPP Blowout Crater and Oil Contamination Tests are two commonly used test methods for checking the crater resistance of e-coat films. For the ASPP Blow-Off Crater Test, crater resistance was assessed according to the following rating scale of AE:

1. A --- 0-10% defect
2. B --- 11-20% defect
3. C --- 21-40% defective
4. D --- 41-80% defective
5. E --- more than 80% defect

The ASPP blowout crater resistance rating for bath 1 was D, bath 2 was A and bath 3 was D and bath 4 was B.

1. 1 --- weniger als 10 Krater
2. 2 --- 10 bis 20 Krater
3. 3 --- 30 bis 50 Krater
4. 4 --- 50 bis 100 Krater
5. 5 --- mehr als 100 Krater

To perform an oil contamination test, 50 ppm of Quicker oil was added to the e-coat bath and mixed for 24 hours with little agitation. Each bath was electrocoated to give a film build of 0.8 to 1.0 mils. For the oil contamination test, the crater resistance was rated according to the following rating scale from 1 to 5:

1. 1 --- less than 10 craters
2. 2 --- 10 to 20 craters
3. 3 --- 30 to 50 craters
4. 4 --- 50 to 100 craters
5. 5 --- more than 100 craters

The oil pollution test for bath 1 was 3, bath 2 was 1, bath 3 was 3 and bath 4 was 1.

The PVC seal adhesion test was also performed by applying a PVC sealer to an electrically baked e-coated panel. The thickness of the PVC sealer was 1 mm and baked at 140 ° C for 10 minutes of metal temperature. The adhesion was evaluated as passed if no sealant was peeled from the E-coated substrate can and fails if no sealant can adhere to the E-coated substrate. Bath 1, 2, 3 and 4 passed the PVC Sealer Adhesion Test.

While at least one exemplary embodiment has been illustrated in the foregoing detailed description, it should be appreciated that a large number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples and are not intended to limit the scope, applicability, or configuration in any way. Rather, the foregoing detailed description will provide those skilled in the art with a practical guide to implementing an exemplary embodiment. It should be understood that various changes in the function and arrangement of elements described in an exemplary embodiment may be made without departing from the scope as set forth in the appended claims.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 62479589 [0001]
• US 4419467 [0039, 0040]

Claims (16)

Claimed is: An electrodeposition paint composition comprising: an aqueous carrier; a film-forming binder comprising an epoxy-amine adduct and a blocked polyisocyanate crosslinking agent; an anticrater agent selected from the group consisting of a polyester resin dispersion, a polyacrylate resin dispersion and a combination thereof; and a supplemental anticrater agent comprising a polyether-modified polysiloxane. Electrocoating composition according to Claim 1 wherein the polyester resin dispersion is further defined as a highly branched water-reducible polyester. Electrocoating composition according to Claim 1 wherein the polyester resin dispersion comprises the reaction product of: a hydroxy-functional cyclic carbonate; and an aliphatic carboxylic acid anhydride. Electrocoating composition according to Claim 3 wherein the hydroxy-functional cyclic carbonate is further defined as glycerol carbonate. Electrocoating composition according to Claim 3 wherein the aliphatic carboxylic acid anhydride is selected from the group consisting of dodecenyl succinic anhydride, octadecenyl succinic anhydride and a combination thereof. Electrocoating composition according to Claim 3 wherein the polyester resin dispersion comprises the reaction product of: a hydroxy-functional cyclic carbonate; an aliphatic carboxylic acid anhydride; a polyfunctional isocyanate compound; and a polyamine compound. Electrocoating composition according to Claim 6 wherein the polyamine compound is selected from the group of: a polyamine having at least one free tertiary amine and one primary or secondary amine group; and a combination of a polyamine having at least one free tertiary amine and a primary or secondary amine group, and an aminoalkylalkoxysilane; wherein the reaction product is neutralized in the presence of acid and water. Electrocoating composition according to Claim 6 wherein the polyester resin dispersion comprises the reaction product of: a hydroxy-functional cyclic carbonate; an aliphatic carboxylic acid anhydride; a monofunctional epoxy resin; a polyfunctional isocyanate compound; and a polyamine compound selected from the group of: a polyamine having at least one free tertiary amine and a primary or secondary amine group, and a combination of a polyamine having at least one free tertiary amine and a primary or secondary amine group, and an aminoalkylalkoxysilane wherein the reaction product is neutralized in the presence of acid and water. Electrocoating composition according to Claim 1 wherein the polyacrylate resin dispersion is further defined as a water-dilutable polyacrylate. Electrocoating composition according to Claim 8 wherein the polyacrylate resin dispersion comprises the reaction product of alkyl (meth) acrylate monomer, a hydroxy functional (meth) acrylate monomer, an amino functional (meth) acrylate monomer or combinations thereof. Electrocoating composition according to Claim 10 wherein the alkyl (meth) acrylate monomer is further defined as butyl acrylate. Electrocoating composition according to Claim 10 wherein the hydroxy-functional (meth) acrylate monomer is further defined as hydroxypropyl methacrylate. Electrocoating composition according to Claim 10 wherein the amino-functional (meth) acrylate monomer is further defined as N, N-dimethylaminoethyl methacrylate. Electrocoating composition according to Claim 1 wherein the anticrater agent is used in an amount of from about 0.01% to about 10% by weight, based on the total weight of the anticrater agent used in the electrodeposition coating composition. Electrocoating composition according to Claim 1 wherein the supplemental anticrater agent is used in an amount of from about 0.01% to about 20% by weight, based on the total weight of the anticrater agent used in the electrodeposition coating composition.