HK1146292A - Method of stabilizing metal pigments against gassing - Google Patents

Description

Method for stabilizing metallic pigments against gassing

Technical Field

The application is a divisional application of Chinese invention patent application 200580022080. X. The present invention relates to a polymeric compound useful as a metallic flake pigment having both a corrosion or hydrolysis inhibitor and a surface modifier. The invention also relates to coating compositions comprising the treated metallic pigments.

Background

Metallic flake pigments, such as aluminum flake pigments, are widely used in decorative coatings to provide a metallic effect to the coating. This metallic effect is particularly popular with consumers in the automotive market who require "glamour finishes".

Automotive coatings may use a single uniform color layer. Alternatively, they may have two distinct layers, a first highly pigmented layer (basecoat) and a less or no pigmented coating (clearcoat) applied over it. This two-layer coating is referred to in the industry as a "basecoat/clearcoat". The "base coat/clear coat" coating introduces a high degree of gloss and depth of color, which can produce a particularly desirable appearance. Metallic flake pigments are typically added to the basecoat composition.

Waterborne automotive paints are gaining widespread use in the automotive industry due to concerns about organic solvent emissions during coating applications and processing. However, the aqueous paints have the disadvantage that the media used therein can corrode the metallic flake pigments. For example, hydrolysis of metallic pigments can occur in aqueous paints. In addition, the pH value of the general water-based acrylic coating composition can be 8.0-9.0, and the pH value of the general polyurethane coating composition can be 7.5-8.0. In an alkaline pH environment, the aluminum pigment will oxidize. Oxidation is a form of corrosion that destroys the metallic coloring properties of the mirror-like particles. When paints with oxidized metallic flake pigments are applied to a substrate, the coating exhibits discoloration and a diminished metallic effect.

Furthermore, hydrolysis or oxidation of the metal surface in aqueous paints can lead to the generation of hydrogen. The amount of hydrogen generated indicates the degree of oxidation (or corrosion) of the metallic pigment. If the coating composition is stored in a closed container, hydrogen gas can build up under pressure.

Hydrolysis of aluminum pigments in the presence of water can accelerate over time due to the alkaline pH environment of the continuous contact coating composition. Coating compositions containing metal flake pigments are typically stored for 6 months or more prior to use, which can result in significant corrosion of the pigment. If this corrosion persists unnoticed, it can render the coating composition unusable.

Considerable effort has been expended in the industry to treat or "passivate" the surface of metallic pigments to prevent corrosion of the metallic surface by water in aqueous coating compositions. For example, it is known to apply a chromium coating to the surface of aluminum pigments to prevent the corrosion and hydrogen generation described above. However, chromium is toxic and special handling and disposal procedures are therefore required for such chromium-coated metal pigment particles.

It would therefore be highly advantageous to provide a coating composition that can be used to passivate metallic pigments while reducing or completely eliminating at least some of the problems with known passivation processes.

Disclosure of Invention

In one embodiment, the present invention relates to a polymer suitable for passivating a metal surface. The polymer comprises (a) at least one nitro group, and/or pyridine group, and/or phenolic hydroxyl group; and (b) at least one group selected from a phosphorus-containing group and/or a carboxylic acid group, wherein the at least one phosphorus-containing group is selected from a phosphate, a phosphite, or a non-nitrogen substituted phosphonate.

Furthermore, the present invention provides a passivated metal pigment comprising at least one metal pigment particle and a passivating species formed on at least a portion of the at least one metal pigment particle. The passivating material can comprise a polymer comprising (a) at least one nitro group, and/or pyridine group, and/or phenolic hydroxyl group; and (b) at least one group selected from a phosphorus-containing group and/or a carboxylic acid group, wherein the at least one phosphorus-containing group is selected from a phosphate, a phosphite, or a non-nitrogen substituted phosphonate.

In another embodiment, the present invention relates to a coating composition comprising a diluent medium, a film-forming polymer, and at least one metallic pigment particle at least partially treated with a passivating material. The passivating material can comprise a polymer comprising (a) at least one nitro group, and/or pyridine group, and/or phenolic hydroxyl group; and (b) at least one group selected from a phosphorus-containing group and/or a carboxylic acid group, wherein the at least one phosphorus-containing group is selected from a phosphate, a phosphite, or a non-nitrogen substituted phosphonate.

Yet another embodiment provides a coating composition comprising an aqueous diluent medium, a film-forming polymer, and at least one metallic pigment particle at least partially treated with a passivating material. The passivating material can comprise a polymer comprising the reaction product of reactants comprising: diglycidyl ether of polyhydric alcohol, nitro-containing compound selected from at least one of alkyl-, aryl-and/or alkylaryl-nitro-containing compounds; and phosphorus-containing compounds, including phosphate and/or non-nitrogen substituted phosphonate.

The invention also provides a method of passivating a metal surface comprising contacting the metal surface with a passivating substance. The passivating material comprises a polymer comprising (a) at least one nitro group, and/or pyridine group, and/or phenolic hydroxyl group; and (b) at least one group selected from a phosphorus-containing group and/or a carboxylic acid group, wherein the at least one phosphorus-containing group is selected from a phosphate, a phosphite, or a non-nitrogen substituted phosphonate.

Detailed Description

As used herein, all numbers expressing dimensions, physical properties, processing parameters, quantities of ingredients, reaction conditions, and the like, used in the specification and claims are to be understood as being modified in all instances by the term "about". Accordingly, unless indicated to the contrary, the numerical values set forth in the following specification and claims can vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical value should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Moreover, all ranges disclosed herein are to be understood to encompass the beginning and ending range values and any and all subranges subsumed therein. For example, a range of "1 to 10" should be considered to include any and all subranges between (and inclusive of) the minimum value of 1 and the maximum value of 10; i.e., all small ranges starting with a minimum value of greater than or equal to 1 and ending with a maximum value of less than or equal to 10, such as 5.5 to 10, 3.7 to 6.4, or 1 to 7.8, to name just a few. The molecular weight numbers used herein, whether Mn or Mw, can be measured by gel permeation chromatography using polystyrene as a standard. Also, the term "polymer" as shown herein includes oligomers, homopolymers and copolymers. The terms "surface modification" and "modified surface" include all and any bonding, interaction or reaction between a metal surface and a compound or composition in accordance with the disclosed invention. The terms "passivation" and "passivation method" both mean that the surface has been modified to reduce its tendency to corrode and/or generate hydrogen gas when in contact with water. All references mentioned in this document should be understood to be incorporated in their entirety by reference. The term "non-nitrogen substituted phosphonate" as used herein means a group of the formula:

wherein R is₁Is any group that does not contain nitrogen.

Passivating materials suitable for use in the present invention generally include polymers having at least two substituents. In a non-limiting embodiment, the first substituent may include at least one nitro group, and/or at least one pyridine group, and/or at least one phenolic hydroxyl group. The second substituent may comprise at least one phosphorus-containing group and/or at least one carboxylic acid group.

In the broad practice of the invention, the passivating polymer may be a linear or branched polymer. The polymer may be or may be derived from, for example, an acrylic polymer, a polyester polymer, a polyurethane polymer, an epoxy polymer, a polyolefin polymer, a polyether polymer, or may be a copolymer comprising one or more of the foregoing. In one embodiment, the polymer may be or may be derived from a polymer containing hydroxyl or epoxy groups, including addition and condensation polymers, or mixtures of such polymers may also be used. The hydroxyl equivalent weight of the polymer may range from 100 to 1000, such as 200 to 400; or an epoxy equivalent in the range of 100 to 2000, for example 300 to 600.

Examples of hydroxyl-containing polymers that may be used include, but are not limited to: condensation polymers containing hydroxyl groups, such as polyesters containing hydroxyl functional groups. Examples of epoxy-containing polymers that may be used include polyglycidyl ethers of polyhydric alcohols, such as the reaction products of epichlorohydrin or dichloropropanol with aliphatic and alicyclic alcohols, such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, propylene glycol, butylene glycol, pentanediol, glycerol, 1, 2, 6-hexanetriol, pentaerythritol, and 2, 2-bis (4-hydroxycyclohexyl) propane.

Hydroxyl-or epoxy-containing addition polymers which may be used include hydroxyl-or epoxy-functional polymers or copolymers of ethylenically unsaturated monomers. Examples of suitable hydroxyl-functional monomers include hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate and allyl alcohol. Examples of suitable monomers with epoxy functional groups include glycidyl (meth) acrylate. The addition polymer may be a homopolymer of any of these hydroxy-or epoxy-functional monomers, or may be a copolymer of one or more of these hydroxy-or epoxy-functional monomers and at least one other non-hydroxy-or epoxy-functional ethylenically unsaturated monomer. Examples of such other monomers include, but are not limited to, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, styrene, and vinyl monomers such as styrene, vinyl toluene, and vinyl acetate.

Examples of the epoxy compound that can be used include compounds as simple as ethylene oxide, propylene oxide, butylene oxide, cyclohexene oxide, and the like.

Examples of the epoxy compound which can be used also include epoxy polyethers obtained by reacting an epihalohydrin (e.g., epichlorohydrin or epibromohydrin) with a polyhydric phenol in the presence of an alkali. Suitable polyhydric phenols include: 2, 2-bis (4-hydroxyphenyl) propane (i.e., bisphenol A), 1, 1-bis (4-hydroxyphenyl) isobutane, 2-bis (4-hydroxy-t-butylphenyl) propane, 4-dihydroxybenzophenone, 1, 1-bis (4-hydroxyphenyl) ethane, bis (2-hydroxynaphthyl) methane, 1, 5-dihydroxynaphthalene, 1, 1-bis (4-hydroxy-3-allylphenyl) ethane and hydrogenated derivatives of such compounds. Polyglycidyl ethers of polyhydric phenols of various molecular weights can be prepared, for example by varying the molar ratio of epichlorohydrin to polyhydric phenol in a known manner.

Examples of epoxy compounds which may be used also include polyglycidyl ethers of monocyclic polyhydric phenols, such as the polyglycidyl ethers of resorcinol, pyrogallol, hydroquinone and catechol, and monoglycidyl ethers of monohydric phenols, such as phenyl glycidyl ether, α -naphthyl glycidyl ether, β -naphthyl glycidyl ether and the corresponding compounds having one alkyl substituent on the aromatic ring.

Other non-limiting examples of epoxy compounds that can be used include glycidyl ethers of aromatic alcohols, such as benzyl glycidyl ether and phenyl glycidyl ether, or polyglycidyl ethers of polyhydric alcohols, such as epichlorohydrin or dichloropropanol, with aliphatic or alicyclic alcohols, such as the reaction products of ethylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, propylene glycol, butylene glycol, pentanediol, glycerol, 1, 2, 6-hexanetriol, pentaerythritol, and 2, 2-bis (4-hydroxycyclohexyl) propane.

Further non-limiting examples of epoxy compounds that may be used also include polyglycidyl esters of polycarboxylic acids, such as the commonly known polyglycidyl esters of adipic acid, phthalic acid, and the like. Other epoxy compounds that may be used include monoglycidyl esters of monocarboxylic acids, such as glycidyl benzoate, glycidyl naphthoate, and monoglycidyl esters of substituted benzoic and naphthoic acids.

Polyaddition resins containing epoxy groups can also be used. Such materials may be prepared by addition polymerization of epoxy-functional monomers with polymerizable ethylenically unsaturated and/or vinyl monomers. The epoxy functional monomers are typically, for example, glycidyl acrylate, glycidyl methacrylate, and allyl glycidyl ether. Such polymerizable ethylenically unsaturated and/or vinylic monomers are, for example, styrene, alpha-methylstyrene, alpha-ethylstyrene, vinyltoluene, tert-butylstyrene, acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, ethacrylonitrile, ethyl methacrylate, methyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, and the like.

Alternatively, the backbone of the polymer may comprise an acrylic, urethane, polyester, alkyd or epoxy polymer or oligomer. The main chain of the polymer when synthesized may include at least two isocyanate groups or blocked isocyanate groups thereon. This can be achieved by copolymerizing monomers bearing isocyanate or blocked isocyanate functional groups into the polymer backbone or by reacting one or more groups (e.g. hydroxyl or amine groups) with isocyanate or blocked isocyanate functional groups on the polymer. The reaction of the isocyanate or blocked isocyanate functional groups with the isocyanate-reactive functional groups of the first substituent or the second substituent may form suitable linking groups.

Illustrative examples of urethane backbones containing isocyanate or blocked isocyanate functional groups include urethane polymers with terminal isocyanate or blocked isocyanate functional groups. The urethane polymers may be synthesized by known techniques, such as bulk polymerization, e.g., solution polymerization, from the polymerization of polyisocyanates with polyfunctional polyisocyanate-reactive compounds (including, for example, polyols, polyamines and aminoalcohols), but with the sum of the equivalents of isocyanate and latent isocyanate groups exceeding the equivalents of polyfunctional polyisocyanate-reactive compounds employed. The polyisocyanate may be, for example, isophorone diisocyanate, p-phenylene diisocyanate, biphenyl 4, 4 ' diisocyanate, m-xylylene diisocyanate, toluene diisocyanate, 3 ' -dimethyl-4, 4 ' -biphenylene diisocyanate, 1, 4-tetramethylene diisocyanate, 1, 6-hexamethylene diisocyanate, 2, 4-trimethylhexane-1, 6-diisocyanate, 1, 3-bis- [2- (isocyanato) propyl ] benzene (also known as tetramethylxylylene diisocyanate, TMXDI), methylenebis- (phenylisocyanate), 1, 5-naphthylene diisocyanate, bis- (isocyanatoethyl fumarate), methylenebis- (4-cyclohexyl isocyanate) and biuret or the isocyanurates of any of these.

The polyfunctional compound reactive with the polyisocyanate may include any diol, triol or alcohol containing more functional groups, such as ethylene glycol, propylene glycol, 1, 4-butanediol, 1, 6-hexanediol, neopentyl glycol, trimethylolethane, trimethylolpropane, pentaerythritol, polyester polyols, polyether polyols, and the like; polyamines such as ethylenediamine and diethylenetriamine; or aminoalcohols such as diethanolamine and ethanolamine.

One of the polyisocyanates or polyfunctional compounds reactive with polyisocyanates may have more than two functional groups (including blocked functional groups). The reactants may be partitioned such that the polyurethane copolymer has terminal isocyanate functional groups.

An illustrative example of an isocyanate or blocked isocyanate functional acrylic is a copolymer of ethylenically unsaturated monomers containing isocyanate or blocked isocyanate groups. The copolymers may be prepared by using conventional techniques such as free radical, cationic or anionic polymerization, for example in a batch or semi-batch process. For example, the polymerization may be carried out by heating the ethylenically unsaturated monomer in bulk or organic solution in the presence of a free radical source (e.g., an organic peroxide or azo compound), optionally in a batch process with the addition of a chain transfer agent; or alternatively, the monomers and initiator may be added at a controlled rate in a heated reactor in a semi-batch process.

In a non-limiting embodiment, the first substituent can include a nitro group (NO)₂). The nitro substituent may be formed by reacting a nitro-containing material with an isocyanate group on the polymer backbone. Examples of such materials that may be used to form substituents that meet the above requirements include any nitro-containing compound having isocyanate-reactive groups (e.g., hydroxyl, amine, mercapto or oxirane groups). Useful nitro-containing compounds include those containing isocyanatesAlkyl, aryl or alkylaryl substituted compounds of the reactive group. Typically, non-limiting nitro-containing compounds useful in the present invention include 2-methyl-2-nitropropanol, 2-nitro-1-propanol, 2-nitroethanol, 4-nitroaniline, 5-nitrobenzyl alcohol, 4-nitrothiophenol, 2-nitrobenzoic acid, 4-nitrobenzoic acid, 2-4-dinitrobenzoic acid and/or mixtures thereof.

In another non-limiting embodiment, the first substituent can include at least one pyridine group and/or at least one phenolic hydroxyl group. Examples of materials suitable for forming a pyridine group include, but are not limited to, 2, 6-pyridinedimethanol, 2-pyridinepropanol, 3-pyridinepropanol, pyridineproronic acid, isonicotinic acid, picolinic acid, pyridinedicarboxylic acid, nicotinic diacid, cinchonic acid, isooctaconic acid, or mixtures thereof. Examples of materials suitable for forming phenolic hydroxyl groups include, but are not limited to: gallic acid, allylphenol, polyhydric phenols such as resorcinol, catechol, phloroglucinol, pyrogallol, 1, 2, 4-benzenetriol, or mixtures thereof.

In a non-limiting embodiment, the second substituent comprises a phosphorus-containing group, such as a phosphate, a non-nitrogen substituted phosphonate, orthophosphoric acid, an organic ester of phosphoric acid, and/or a phosphite compound. For example, the phosphate compound may be of the type described in US patent 4565716. Organophosphites are derivatives of phosphorous acid and not phosphoric acid used to prepare organophosphates. Exemplary organophosphates are described in U.S. patent 4808231.

Examples of phosphate esters useful in the practice of the present invention include mono-and di-C₄-C₁₈Alkyl esters, such as mono-and dibutyl phosphate, mono-and dipentyl phosphate, mono-and dihexyl phosphate, mono-and diheptyl phosphate, mono-and dioctyl phosphate, mono-and dinonyl phosphate, mono-and dihexadecyl phosphate, and mono-and dioctadecyl phosphate; and aryl and arylalkyl esters containing 6 to 10 carbon atoms in the aryl group, such as mono-and diphenyl phosphates and mono-and diphenyl phosphates.

In a specific non-limiting embodiment, the passivating polymer used in the present invention comprises an epoxy polymer having at least one nitro substituent and at least one phosphoric acid group, wherein the equivalent ratio of epoxy to nitro to phosphoric acid is from 3.8/0.3/4.8 to 3.8/3/0.8. In another non-limiting embodiment, the equivalent ratio of epoxy to nitro to phosphoric acid can be 3.8/0.8/4.2 to 3.8/1/3.2.

It has been found that contacting the metallic pigment with a passivating polymer, such as those described above, reduces or prevents hydrolysis or oxidation of the pigment and, thus, reduces and completely eliminates the generation of hydrogen gas. Furthermore, since the inclusion of such a polymer-treated metallic pigment in an aqueous coating composition does not adversely affect the moisture resistance of a dry film (coating) formed from the aqueous composition.

An exemplary aqueous coating composition of the present invention generally comprises a film-forming polymer, an aqueous diluent medium, and a metallic pigment at least partially treated with a passivating polymer of the present invention. By adding an effective amount of the passivating material of the present invention, the tendency of the pigment to react with aqueous media to emit gaseous species can be prevented or reduced.

Examples of metallic pigments suitable for use in the aqueous coating composition of the present invention include any of the metallic pigments generally known for coloring coating compositions. Examples include, but are not limited to: metallic pigments, such as metallic flake pigments, include, at least in part, aluminum, copper, zinc, iron, and/or brass, as well as other wrought metals and alloys, such as nickel, tin, silver, chromium, aluminum-copper alloys, aluminum-zinc alloys, and aluminum-magnesium alloys, among others. In addition, the aqueous coating composition of the present invention may also include one or more of a number of other pigments known for use in coating compositions, such as various color-producing and/or extender pigments. Examples of such pigments include, but are not limited to: generally known pigments based on metal oxides, metal hydroxides, metal sulfides, metal sulfates, metal carbonates, carbon black, china clay, phthalocyanine blues and greens, organic reds and organic dyes.

Passivation substances comprising the passivation polymers of the present invention, such as those described previously, can be added to a coating composition, such as, but not limited to, an aqueous coating composition of the present invention, using a variety of processes. By "aqueous" coating composition is meant a coating composition in which the dilution medium is predominantly an aqueous medium, i.e., an aqueous coating composition is free or substantially free of organic solvents. By "substantially free of organic solvent" is meant that if organic solvent is contained therein, it is less than 20 wt.%, e.g., less than 10 wt.%, e.g., less than 5 wt.%, e.g., less than 2 wt.%, e.g., less than 1 wt.%, of the total weight of the coating composition. One skilled in the art will recognize that in one non-limiting embodiment of the present invention, the aqueous coating composition may include a small amount of organic solvent to improve one or more coating properties, such as improving the flow or leveling of the coating composition, or reducing the viscosity as desired. One method of adding a passivating material comprising a polymer of the present invention is to contact the metallic pigment with the passivating material prior to adding the pigment to the aqueous coating composition. This can be achieved by adding the passivating substances according to the invention to the pigment paste (for example pigments which are generally commercially available) or they can be added at an earlier stage, for example during the actual production of the pigment. Alternatively, the passivating material may be incorporated into the aqueous coating composition of the present invention simply by adding it "neat", i.e., as another component in the aqueous coating composition formulation, for example during the mixing of the film-forming resin, metallic pigment, and aqueous medium, as well as other conventional and optional components (e.g., crosslinkers, co-solvents, thickeners, and fillers). Regardless of the manner in which the passivating material of the present invention is incorporated into the aqueous coating composition of the present invention, such compounds are generally employed in amounts effective to reduce or eliminate the evolution of gas from the metallic pigment in the aqueous medium. For example, the amount of passivating material can range from 5 wt.% to 200 wt.% passivating material solids, such as from 10 wt.% to 100 wt.%, such as from 10 wt.% to 80 wt.%, such as from 15 wt.% to 50 wt.%, such as from 16 wt.% to 25 wt.%, based on the weight of the pigment solids.

An exemplary substantially organic solvent-free composition of the present invention can be a thermoplastic film-forming composition, or alternatively a thermosetting composition. As used herein, "thermosetting composition" means that the compound is "fixed" irreversibly once cured or crosslinked, wherein the polymer chains of the polymer components are linked together by covalent bonds. This property is often associated with crosslinking reactions of the components of the composition, often caused by, for example, heat or radiation. Hawley, Gessner G., The Condensed Chemical Dictionary, Ninth edition, page 856; surface Coatings, vol.2, Oil and Colour Chemists' Association, Australia, TAFE equivalent Books (1974). The curing or crosslinking reaction may also be carried out under ambient conditions. Once cured or crosslinked, the thermosetting composition does not melt under heat and is insoluble in solvents. By comparison, a "thermoplastic composition" includes polymeric components that are not covalently linked, and thus are capable of achieving liquid flow upon heating, and are soluble in a solvent. Saunders, K.J., Organic Polymer chemistry, pp.41-42, Chapman and Hall, London (1973).

An exemplary coating composition of the invention comprises a diluent medium, a resin binder system, a passivating material comprising a polymer of the invention, and at least one metallic pigment particle. For example, the pigment particles may be at least partially treated with a passivating material of the invention.

The dilution medium may be a solvent-borne dilution medium or an aqueous (e.g. aqueous) dilution medium. By "solvent-borne" is meant that the diluting medium is essentially a non-aqueous material, such as an organic solvent.

The resinous binder system typically comprises (a) at least one film-forming polymer containing reactive functional groups, and (b) at least one crosslinker comprising functional groups capable of reacting with the functional groups of the film-forming polymer.

The film-forming polymer (a) may comprise various reactive group-containing polymers known in the art of surface coatings, provided that the polymer is sufficiently dispersible in the diluting medium. Suitable non-limiting examples can include acrylic polymers, polyester polymers, polyurethane polymers, polyether polymers, polysiloxane polymers, polyepoxide polymers, and copolymers and mixtures thereof. Also, the polymer may include a variety of reactive functional groups, such as functional groups selected from at least one of hydroxyl, carboxyl, epoxy, amine, amide, carbamate, isocyanate, and combinations thereof.

For example, suitable hydroxyl-containing polymers may include acrylic polyols, polyester polyols, polyurethane polyols, polyether polyols, and mixtures thereof.

Suitable hydroxyl-and/or carboxyl-containing acrylic polymers can be prepared from polymerizable ethylenically unsaturated monomers, which are typically copolymers of (meth) acrylic acid and/or hydroxyalkyl esters of (meth) acrylic acid with one or more other polymerizable ethylenically unsaturated monomers, such as alkyl esters of (meth) acrylic acid, including methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and 2-ethylhexyl acrylate, and vinyl aromatics, such as styrene, alpha-methylstyrene, and vinyl toluene.

In one embodiment of the invention, the acrylic polymer may be prepared from ethylenically unsaturated β -hydroxy ester functional monomers, such as those described above.

Epoxy functional groups may be added to acrylic copolymers prepared from polymerizable ethylenically unsaturated monomers by copolymerizing the ethylene oxide group-containing monomers with other polymerizable ethylenically unsaturated monomers, such as those described above. Oxirane group-containing monomers such as glycidyl (meth) acrylate and allyl glycidyl ether. The preparation of such epoxy-functional acrylic polymers is described in detail in U.S. patent 4001156, columns 3 to 6.

Carbamate functionality may be added to acrylic copolymers prepared from polymerizable ethylenically unsaturated monomers by copolymerizing polymerizable ethylenically unsaturated monomers such as those described above with carbamate-functional vinyl monomers such as carbamate-functional alkyl methacrylates. Useful carbamate-functional alkyl esters can be prepared, for example, by reacting a hydroxyalkyl carbamate (e.g., the reaction product of ammonia and ethylene or propylene carbonate) with methacrylic anhydride. Other useful carbamate-functional vinyl monomers include: such as the reaction product of hydroxyethyl methacrylate, isophorone diisocyanate, and hydroxypropyl carbamate; or the reaction product of hydroxypropyl methacrylate, isophorone diisocyanate, and methanol. Other urethane-functional vinyl monomers may also be used, such as the reaction product of isocyanic acid (HNCO) with a hydroxy-functional acrylic or methacrylic monomer (e.g., hydroxyethyl acrylate), as well as those described in U.S. patent 3479328. Carbamate functionality can also be incorporated into the acrylic polymer by reacting a hydroxy-functional acrylic polymer with a low molecular weight alkyl carbamate (e.g., methyl carbamate). Carbamate side groups can also be introduced into acrylic polymers by "transcarbamoylation" reactions in which hydroxy-functional acrylic polymers are reacted with low molecular weight carbamates derived from alcohols or glycol ethers. The urethane groups are exchanged with hydroxyl groups to form a urethane-functional acrylic polymer and the original alcohol or glycol ether. Furthermore, a hydroxyl functional acrylic polymer may be reacted with isocyanic acid to provide pendant carbamate groups. Likewise, a hydroxyl functional acrylic polymer may be reacted with urea to provide pendant carbamate groups.

Polymers prepared from polymerizable ethylenically unsaturated monomers can be prepared by solution polymerization techniques well known to those skilled in the art in the presence of suitable catalysts such as organic peroxides or azo compounds, for example benzoyl peroxide or N, N-bis (isobutyronitrile). The polymerization can be carried out in an organic solvent in which the monomers are soluble, using techniques common in the art. Alternatively, these polymers may be prepared by aqueous emulsion or dispersion polymerization techniques well known in the art. The selection of appropriate reactant ratios and reaction conditions produces an acrylic polymer with the desired pendant functional groups.

Polyester polymers may also be used in the film-forming compositions of the present invention. Useful polyester polymers generally include condensation products of polyhydric alcohols and polycarboxylic acids. Suitable polyols may include ethylene glycol, neopentyl glycol, trimethylolpropane and pentaerythritol. Suitable polycarboxylic acids may include adipic acid, 1, 4-cyclohexyldicarboxylic acid and hexahydrophthalic acid. In addition to the polycarboxylic acids mentioned above, functional equivalents of the carboxylic acids, such as the anhydrides or lower alkyl esters of the carboxylic acids, such as methyl esters, present therein, may also be used. In addition, small amounts of monocarboxylic acids, such as stearic acid, may also be used. The polyester polymer with the desired pendant functional groups (i.e., carboxyl or hydroxyl functional groups) is prepared by selecting the appropriate ratio of reactants and reaction conditions.

For example, hydroxyl group-containing polyesters can be prepared by reacting anhydrides of dicarboxylic acids (e.g., hexahydrophthalic anhydride) with diols (e.g., neopentyl glycol) in a 1: 2 molar ratio. When enhanced air drying is desired, suitable drying oil fatty acids may be used, including those derived from linseed oil, soya oil, tall oil, dehydrated castor oil or tung oil.

The carbamate-functional polyester may be prepared by first forming a hydroxyalkyl carbamate that is reactive with the polyacid and polyol used in forming the polyester. Alternatively, terminal carbamate functionality may be added to the polyester by reacting isocyanate with a hydroxy-functional polyester. Also, carbamate functionality can be added to the polyester by reacting the hydroxy polyester with urea. In addition, it is also possible to incorporate carbamate groups into the polyester by transamination. The process for preparing those suitable carbamate functional group containing polyesters is described in U.S. patent 5593733 at column 2, line 40 to column 4, line 9.

Polyurethane polymers containing terminal isocyanate groups or hydroxyl groups may also be used as polymers in the coating compositions of the present invention. Polyurethane polyols or NCO-terminated polyurethanes which may be used are those prepared by reacting polyols comprising polymeric polyols with polyisocyanates. Polyureas containing terminal isocyanate groups or primary and/or secondary amine groups which can also be used are those prepared by reacting polyamines comprising polymeric polyamines with polyisocyanates. The desired terminal group is obtained by adjusting the equivalent ratio of the hydroxyl group/isocyanate group or amino group/isocyanate group and selecting appropriate reaction conditions. Examples of suitable polyisocyanates include those described in U.S. patent 4046729 at column 5, line 26 to column 6, line 28, which is incorporated herein by reference. Examples of suitable polyols include those described in U.S. patent 4046729, column 7, line 52 to column 10, line 35. Examples of suitable polyamines include those described in column 6, line 61 to column 7, line 32 of U.S. patent 4046729 and column 3, lines 13 to 50 of U.S. patent 3799854.

Carbamate functionality can be incorporated into the polyurethane polymer by reacting a polyisocyanate with a polyester bearing hydroxyl functionality and containing pendant carbamate groups. Alternatively, the polyurethane may be prepared by reacting a polyisocyanate with a polyester polyol and a hydroxyalkyl carbamate or isocyanic acid as separate reactants. Examples of suitable polyisocyanates are aromatic isocyanates, such as 4, 4' -diphenylmethane diisocyanate, 1, 3-phenylene diisocyanate and toluene diisocyanate, and aliphatic polyisocyanates, such as 1, 4-tetramethylene diisocyanate and 1, 6-hexamethylene diisocyanate. Cycloaliphatic diisocyanates such as 1, 4-cyclohexyl diisocyanate and isophorone diisocyanate can also be used.

Examples of suitable polyether polyols include polyalkylene ether polyols, such as those having the following structural formula (I) or (II):

or

Wherein the substituent R is hydrogen or a lower alkyl group containing 1 to 5 carbon atoms, including mixed substituents, n is usually 2 to 6, and m is in the range of 8 to 100 or more. Exemplary polyalkylene ether polyols include poly (oxytetramethylene) glycol, poly (oxytetraethylene) glycol, poly (oxy-1, 2-propylene) glycol, poly (oxy-1, 2-butylene) glycol.

Polyether polyols prepared from various polyols (e.g., diols such as ethylene glycol, 1, 6-hexanediol, bisphenol a, etc., or other higher polyols such as trimethylolpropane, pentaerythritol, etc.) by alkoxylation may also be used. The higher functional polyols described above which may be used may be prepared, for example, by alkoxylation of compounds such as sucrose or sorbitol. One alkoxylation process that is commonly used is the reaction of a polyol with an alkylene oxide (e.g., propylene oxide or ethylene oxide) in the presence of an acidic or basic catalyst. Examples of polyethers include those available under the tradenames TERATHANE and TERACOL from E.I. Du Pont de Nemours and Company, Inc.

As previously mentioned, in certain embodiments of the present invention, the film-forming composition may also comprise (b) one or more crosslinkers suitable for reacting with the functional groups of the polymer and/or any of the aforementioned polymeric microparticles and/or additives used to cure the film-forming composition, if desired. Non-limiting examples of suitable crosslinking agents include any aminoplast and polyisocyanate known in the art of surface coating, provided that the crosslinking agent is suitable for water solubility or water dispersibility as described below, as well as polyacids, polyanhydrides, and mixtures thereof. In use, the cross-linking agent or mixture of cross-linking agents is selected based on the functional groups (e.g., hydroxyl and/or carbamate functional groups) associated with the polymeric microparticles. For example, when the functional group is a hydroxyl group, the hydrophilic crosslinker can be an aminoplast or a polyisocyanate crosslinker.

Examples of aminoplast resins suitable for use as crosslinking agents include those containing hydroxymethyl or hydroxyalkyl groups, a portion of which is etherified by reaction with a lower alcohol (e.g., methanol) to provide a water soluble/dispersible aminoplast resin. One suitable aminoplast resin is the partially methylated aminoplast resin CYMEL 385, which is available from cytec industries, inc. A blocked isocyanate that is water soluble/dispersible and suitable for use as a crosslinker is dimethylpyrazole blocked hexamethylene diisocyanate trimer available as BI 7986 from Baxenden Chemicals, ltd.

Polyacid crosslinking species suitable for use in the present invention may include: such as those which typically contain, on average, more than 1 acid group per molecule, sometimes 3 or more, sometimes 4 or more, which can react with the epoxy-functional film-forming polymer. The polyacid crosslinking agent may have two, three, or more functional groups. Suitable polyacid crosslinking agents that may be used include, for example, carboxylic acid group-containing oligomers, polymers, and compounds, such as acrylic polymers, polyesters, and polyurethanes, as well as compounds containing phosphorus-based acid groups.

Examples of suitable polyacid crosslinking agents include: for example, ester group-containing oligomers and polyesters containing half-esters derived from the reaction of a polyol and a cyclic 1, 2-anhydride or acid functional groups derived from a polyol and a polyacid or anhydride. These half-esters have a relatively low molecular weight and comparable reactivity towards epoxy functional groups. Suitable ester group-containing oligomers include those described in U.S. patent 4764430, column 4, line 26 to column 5, line 68, which are incorporated herein by reference.

Other useful crosslinking agents include acid functional acrylic crosslinking agents prepared by copolymerization of methacrylic and/or acrylic monomers and other ethylenically unsaturated copolymerizable monomers as polyacid crosslinking agents. Alternatively, the acid functional acrylic may be prepared by reacting a hydroxy functional acrylic with a cyclic anhydride.

In accordance with certain embodiments of the present invention, the crosslinking agent (b) is generally water soluble/dispersible, in the range of from 0 to at least 10 wt.%, or at least 10 to at least 20 wt.%, or at least 20 to at least 30 wt.%, as a component in the film-forming composition, based on the weight of total resin solids in the film-forming composition. In accordance with certain embodiments of the present invention, the crosslinker is present in the film-forming composition in an amount ranging from less than or equal to 70 to less than or equal to 60 wt.%, from less than or equal to 60 to less than or equal to 50 wt.%, or from less than or equal to 50 to less than or equal to 40 wt.%, based on the total resin solids weight in the film-forming composition. The amount of the crosslinker in the film-forming composition can range between any combination of these resins within the recited ranges.

The resin binder used for the primer layer may be an organic solvent based material such as those described in U.S. patent 4220679 document at column 2, line 24 through column 4, line 40. Also, water-based coating compositions such as those described in U.S. patent 4403003, U.S. patent 4147679, U.S. patent 5071904 may be used as binders in basecoat compositions.

The coating composition may include various other components commonly known for use in aqueous coating compositions. Examples of various other components include: fillers, plasticizers, antioxidants, mildewcides and fungicides, surfactants, various flow control agents, including for example thixotropic agents and anti-sagging additives and/or pigment orientation, such as precipitated silica, fumed silica, organically modified silica, bentonite, organically modified bentonite, and such additives based on polymer microparticles (sometimes also referred to as microgels) as described for example in us patents 4025474, 4055607, 4075141, 4115472, 4147688, 4180489, 4242384, 4268547, 4220679 and 4290932.

Examples of organic solvents and/or diluents that can be used in the organic solvent-borne coating compositions of the present invention include alcohols, such as lower alkanols containing 1 to 8 carbon atoms, including methanol, ethanol, n-propanol, isopropanol, butanol, sec-butanol, tert-butanol, pentanol, hexanol, and 2-ethylhexanol; ethers and ether alcohols such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol dibutyl ether, propylene glycol monomethyl ether, diethylene glycol monobutyl ether, diethylene glycol dibutyl ether, dipropylene glycol monomethyl ether and dipropylene glycol monobutyl ether; ketones such as methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone and methyl N-butyl ketone; esters such as butyl acetate, 2-ethoxyethyl acetate and 2-ethylhexyl acetate; aliphatic and alicyclic hydrocarbons such as various naphthas and cyclohexanes; and aromatic hydrocarbons such as toluene and xylene. The amount of organic solvent and/or diluent used in the organic solvent-borne coating compositions of the present invention can vary widely. However, in one non-limiting embodiment, the amount of organic solvent and/or diluent can vary from about 10% to about 50%, such as from 20% to 40%, based on the total weight of the organic solvent-borne coating composition.

The passivating materials of the present invention may also be used in powdered coating compositions comprising a film-forming polymer and a pigment, typically a metallic pigment.

The following examples illustrate the invention but should not be construed as limiting its scope. All percentages and amounts are understood to be by weight unless otherwise indicated.

Examples

The following examples describe the outgassing characteristics of exemplary coating compositions incorporating passivating materials including the polymers of the present invention in comparison to commercially available passivating materials.

Preparation of passivating substances

The polymer of the passivating material used in the present invention and the composition comprising the polymer are prepared as follows:

polymer Synthesis example 1(PE1)

One passivation polymer of the invention was prepared as described below using the following ingredients.

TABLE 1

Components	Content (g)
		1 EPON 82812N-Methylpyrrolidone 32-Nitrophenol 4 phosphate 5 propylene glycol propyl ether 6N, N-DimethylEthanolamine 7 deionized Water	358.5263.4106.173.1263.343.2671.0

¹EPON828 is a diepoxy having an epoxy equivalent weight of 188, available from Shell Oil and chemical co.

The first three components were charged to a reactor and heated to 100 ℃ under nitrogen and held at this temperature for about 1 hour. The reaction mixture was cooled to a temperature of 30 ℃ and then component 4 was added. The reaction temperature was then increased to 100 ℃ and the mixture was held at this temperature for about 2 hours. The product thus formed is then diluted by adding components 5, 6 and 7 with stirring. The product was cooled to room temperature. The reaction product had a solids content of about 32% and a pH of 5.7.

Polymer Synthesis example 2(PE2)

The polymer was prepared as in example 1 except that 2-nitrophenol was replaced with an equal amount of 4-nitrobenzoic acid.

Polymer Synthesis example 3(PE3)

The polymer was prepared as in example 2 except that half of the 4-nitrobenzoic acid was replaced with the same amount of isonicotinic acid.

Polymer Synthesis example 4(PE4)

The polymer was prepared as in example 2 except that the 4-nitrobenzoic acid was replaced with an equivalent amount of isonicotinic acid.

Polymer Synthesis example 5(PE5)

The polymer was prepared as in the preparation of the polymer of example 2 except that 4-nitrobenzoic acid was used only in place of all of EPON828 and no phosphoric acid was used.

Polymer Synthesis example 6(PE6)

The polymer was prepared as in the preparation of the polymer of example 2 except that 42 wt.% of the phosphoric acid was replaced with an equivalent amount of trimellitic anhydride.

Polymer Synthesis example 7(PE7)

The polymer was prepared as in example 2 except that the reaction product of phthalic anhydride and hydroxyethylethylene urea (prepared by reacting these two components at 120 ℃) was used in place of 50 equivalent% of 4-nitrobenzoic acid.

Polymer Synthesis example 8(PE8)

The polymer was prepared in the same manner as the polymer of example 2 except that 4-nitrobenzoic acid was replaced with an equal amount of isostearic acid.

Polymer Synthesis example 9(PE9)

The polymer was prepared as in example 8 except that EPON828 was replaced with an equivalent amount of EPON 872 (epoxy equivalent weight of 645).

Polymer Synthesis example 10(PE10)

An acrylate polyurethane was prepared using the following components as follows:

TABLE 2

Content (g)	Substance(s)
		1 934.02 108.03 1.24 1.25 157.26 262.2	Polyester polyol with hydroxyl number 120 (prepared from trimethylolpropane (15.2%), neopentyl glycol (35.3%) and adipic acid (49.5%)) hydroxyethyl acrylate (HEA) dibutyltin dilaurate butylated hydroxytoluene Hexamethylene Diisocyanate (HDI) Butyl Acrylate (BA)

The first four components were stirred in the flask while HDI was added over a period of 1 hour at a temperature of 70-80 ℃. The addition funnel was then flushed with 39g of butyl acrylate and the reaction mixture was held at a temperature of 70 ℃ for a further 2 hours while the isocyanate was fully reacted. The remaining butyl acrylate was then added to produce an 80% solution with a Gardner-Holdt viscosity of X.

A pre-emulsion was prepared with the following components:

TABLE 3

Content (g)	Components
		1 1003.802 120.403 147.004 20.605 13.526 46.167 17.928 1246.00	Acrylate polyurethane butyl acrylate Methyl Methacrylate (MMA) dodecyl benzene sulfonic acid dimethyl Ethanolamine 50% aqueous solution (DDBSA/DMEA) ALIPAL Co 436 prepared as above, anionic surfactant, deionized water available from Rhodia chemical sAEROSOL OT-75 (sodium dioctyl sulfosuccinate available from Cytec industries, Inc.)

The pre-emulsion was passed through a M110MICROFLUIDIZER RTM emulsifier at 7000psi pressure in one pass to form a microdispersion. The microdispersion was stirred in a round-bottomed flask at 22 ℃ under nitrogen, and the components listed in Table 4 below were added.

TABLE 4

Content (g)	Components
		1 429.902 2.003 2.864 2.945 21.50	Deionized water ferrous ammonium erythorbate sulfate (1% aqueous solution) hydrogen peroxide (30% aqueous solution) dimethylethanolamine

After addition of the components in table 4, the reaction temperature was naturally raised to 56 ℃ after about 15 minutes. The final product had the following characteristics:

total solid content: about 42 wt.%;

pH value: about 8.3; and

brookfield viscosity (50rpm, rotor # 1): about 14 cps.

Polymer example 11(PE11)

This example describes the preparation of an acrylic polyester polymer. The acrylic polyester is prepared from the components described below.

Polyester (P): the polyester was prepared in a four-necked round bottom flask equipped with a thermometer, mechanical stirrer, condenser, dry nitrogen sparge and heating mantle. The polyester was prepared from the components listed in table 5 below.

TABLE 5

Content (g)	Components
		1 1103.002 800.003 480.004 688.005 6.126 6.127 1200.00	Stearic acid pentaerythritol crotonic acid phthalic acid dibutyl tin dilaurate triphenyl phosphite butyl acrylate

The first six components were stirred in the flask at a temperature of 230 ℃. The distillate was collected in a dean Stark trap and the mixture was held at this temperature until the acidity dropped below 5. The product was then cooled to a temperature below 80 ℃ and diluted with butyl acrylate.

Preparation of polyester/acrylic latex

A pre-emulsion was prepared by stirring the following components together:

TABLE 6

Content (g)	Components
		1 1000.02 295.03 30.04 20.05 655.06 46.47 14.3	Deionized water polyester (P) ethylene glycol dimethacrylate butyl acrylate dodecyl benzene sulfonic acid dimethyl ethanol amine

The pre-emulsion was passed once through MICROFLUIDIZER RTMM110T at a pressure of 8000psi and transferred to a four-necked round bottom flask equipped with an overhead stirrer, condenser, thermometer and nitrogen atmosphere. MICROFLUIDIZER RTM was rinsed with 150.0g of deionized water and added to the flask. The polymerization was initiated by the addition of 4.0g of isoascorbic acid and 0.02g of ferrous ammonium sulfate dissolved in 120.0g of water, followed by the addition of 4.0g of 70% t-butyl hydroperoxide dissolved in 115.0g of water over a period of 30 minutes. During this time the reaction temperature rose from 24 ℃ to 85 ℃. 36g of 33.3% dimethylethanolamine in water and then 2.0g PROXEL GXL (a pesticide available from ICI America, Inc.) in 8.0g water were added and the temperature was lowered to 28 ℃. The latex thus formed had a pH of 7.9, a nonvolatile content of 42.0%, and a Brookfield viscosity of 17cps (rotor #1, 50 rpm).

Polymer example 12(PE12)

This example describes the preparation of an acrylic dispersion. The acrylic dispersion was prepared from the components listed in table 7 below as follows.

TABLE 7

Stage I	Content (g)
		Charge #1Deionized water dioctyl sulfosuccinateFeed AMethyl methacrylate butyl acrylate dioctyl sulfosuccinate deionized waterFeed BDeionized water ammonium persulfate	884.217.0441.6147.211.913.6423.3339.62.5
Stage II	Content (g)
		Feed CButyl methacrylate butyl acrylate dioctyl sulfosuccinate deionized waterFeed DDeionized water ammonium persulfate	71.035.06.92.475.2319.80.42
Stage III	Content (g)

Stage I	Content (g)
		Feed EMethyl methacrylate butyl methacrylate hydroxyethyl methacrylate ethylene glycol dimethacrylate dioctyl sulfosuccinate deionized waterFeed FDeionized water ammonium persulfate sodium bicarbonateFeed GDimethyl ethanolamine deionized water	71.012.330.840.222.734.52.497.5319.80.541.310.9176.0

Charge #1 was added to a reactor equipped with a thermocouple, stirrer, and reflux condenser. The contents of the reactor were then heated to a temperature of 80 ℃. Feeds a and B (stage I) were then added to the reactor over three hours and the reaction mixture was stirred at a temperature of 80 ℃ for 30 minutes. Feeds C and D (stage II) were then added over a period of 30 minutes, followed by stirring at 80 ℃ for 30 minutes. Feeds E and F (stage III) were then added over 30 minutes, stirred for 1 hour, and cooled to ambient temperature. Feed G was then added over 5 minutes, followed by stirring for an additional 10 minutes.

Polymer example 13(PE-13)

This example describes a process for preparing a polymer from the following components:

TABLE 8

Components	Content (g)
		1 Dimethylpropionic acid 2 neopentyl glycol 3 FORMREZ 55-5614 Poly THF25 Dibutyltin dilaurate 6 Butanol 7N-Methylpyrrolidone 8 DESMODUR W39N-methyl pyrrolidone 10 deionized water 11 ethylene diamine 12 dimethyl ethanol amine	79.214.9193.3193.31.73.87195.628.028.02366.414.251.8

¹Hydroxy-functional polyester, molecular weight 2000, obtainable from Witco Chemicals

²A hydroxy functional polyester, polymerized from tetrahydrofuran, having a molecular weight of 2000, available from e.i. dupont de Neumors and Co.

³Diisocyanates available from Bayer corporation

The first seven components were added to a reactor and heated to 80 ℃ under a nitrogen atmosphere until the mixture became homogeneous. It was then cooled to 55 ℃ and premixed components 8 and 9 were added over 30 minutes. The mixture temperature was increased up to 90 ℃. The mixture was then held at this temperature until the isocyanate equivalent weight became up to 1370. The premixed components 10, 11 and 12 are then added. The product was stirred for a further 30 minutes and cooled to room temperature. The final product had a total non-volatile content of 24% and a viscosity of less than 100 centipoise.

Preparation of aqueous compositions

Primer examples BC1-10

Aqueous metallic silver basecoat compositions comprising the passivates of examples 1-10 were prepared. For each basecoat composition (example BC1-10, below), aluminum pigment slurry, premix A1-10, respectively, the following components were prepared as described below. The following amounts are all in parts by weight (grams). The components of premix A1-10 were mixed with gentle stirring and the mixture was stirred for 30 minutes until completely dispersed. Premix A1 used a commercially available passivation substance (LUBRIZOL2062, available from Lubrizol Company).

The basecoat compositions (examples BC 1-BC 10) were prepared from the following ingredients as follows. The contents listed below are in parts by weight (g) unless otherwise specified. Primer composition BC1 was used for comparison and contained a commercially available passivation material.

Each of the aqueous basecoat compositions of examples BC 1-BC 10 was prepared by mixing the above-described components under agitation. The pH of each composition was adjusted to 8.4-8.6 using an appropriate amount of 50% aqueous DMEA. After a16 hour equilibration period at ambient conditions, the pH of each primer layer was again adjusted to 8.4-8.6 using an appropriate amount of a 50% aqueous solution of DMEA. The viscosity of each composition was then reduced to a spray viscosity of 24-26 seconds (Ford #4 cup) using deionized water. The samples were then subjected to the following gassing test.

Outgassing assay

Each of the waterborne basecoat compositions of examples BC 1-BC 10 was evaluated to measure the amount of gas released from a waterborne coating containing aluminum flakes. This test method was used to determine the effectiveness of an aluminum flake deactivator (i.e., gassing inhibitor) to prevent or inhibit the generation of hydrogen and heat by the reaction between the surface of the aluminum pigment and water. The method includes placing an aqueous coating containing aluminum flakes in a gassing test apparatus for measuring the amount of milliliters (ml) of gas released within 7 days per 200 grams of the basecoat composition.

After the final pH and viscosity adjustments described above, 200 grams of each basecoat composition was placed into a separate 250ml erlenmeyer flask, capped with a greased glass joint with a flexible connector tube (Tygon (polyethylene) tube). A tapered clamp is clamped at the joint of the flask and the joint. A plumb bob was placed around each charged erlenmeyer flask, and then each was placed in a pre-set thermostatic bath at 40 ℃. The temperature was then allowed to equilibrate in a constant temperature bath for 4 hours.

When the composition was allowed to equilibrate, the ring stand and burette were assembled in the Nalgene tub after the thermostatic bath. The ring frame was placed in a Nalgene tub filled with water. The burette clamp is connected with the ring frame. For each primer, a 250ml burette was filled with water and inverted in a Nalgene tub filled with water. The burette is inverted so that the top of the inverted burette is below the top of the horizontal plane in the tub. The burette was clamped in place with a burette clamp.

After the equilibration period, the polyethylene tube was inserted into an inverted burette and then connected to the hose connector end of the flask in a constant temperature bath. The internal water level (ml) of the burette was then recorded. The difference between the initial water level and the final water level after 7 days of standing in the test apparatus was recorded as the amount of gas released from the primer layer. Those skilled in the art will recognize that each deflation will result in a different result due to minor variations in the test conditions. The deflation results in table 11 should therefore be understood to have an error of ± about 5 ml.

The gassing data in Table 11 below shows that the aqueous metal basecoat compositions comprising the aluminum passivates of the invention (i.e., the compositions of examples BC 2-BC 14) have comparable or improved passivation properties on aluminum flakes as compared to the commercially available passivates (example BC 1).

TABLE 11

Base coat	Amount of released gas (ml)
		Example BC1	12-18
Example BC2	10
		Example BC3	0
Example BC4	3
		Example BC5	8

Base coat	Amount of released gas (ml)
		Example BC6	0
Example BC7	4
		Example BC8	0
Example BC9	6
		Example BC10	15

^*Comparative example

Primer examples BC 11-BC 13

The following examples BC 11-BC 13 describe the preparation of aqueous metallic silver basecoat compositions. For each of the basecoat compositions, aluminum pigment slurries, and premixes a11-13 of examples BC 11-BC 13, respectively, the following components were prepared as described below. The following amounts are all in parts by weight (grams). The components of premix A11-13 were mixed with stirring and the mixture was stirred for 30 minutes until completely dispersed. Premix A11 used a commercially available passivation substance (LUBRIZOL2062, available from Lubrizol Company).

TABLE 12

Premix A11-13

¹¹The reaction product of EPON828 and phosphoric acid (83: 17 by weight).

¹²Substituted benzotriazole UV light absorbers, available from Ciba Additives.

¹³Aluminum pigment paste ALPLATE 7670NS, available from Toyal Europe.

¹⁴60/36/4w/w of a solution of LUBRIZOL 2062/diisopropanolamine/propyleneglycol butylether, LUBRIZOL2062 available from Lubrizol Co.

¹⁵Methylated melamine formaldehyde resins available from Cytec Industries, inc.

Aqueous basecoat composition

The aqueous basecoat compositions of each of examples BC 11-BC 13 were then prepared as follows using the following ingredients. The contents listed below are in parts by weight (g) unless otherwise specified.

Watch 13

¹⁶PE-Polymer of the examples

¹⁷Mineral spirits, available from Shell Chemical Co.

¹⁸An aqueous polyurethane dispersion obtainable from Crompton corp.

¹⁹PE-Polymer of the examples

²⁰LAPONITE RD in 2% solution in deionized water. LAPONITE RD is a synthetic Clay available from Southern Clay Products, inc.

²¹Viscolam 330 is an acrylic thickener emulsion available from Lehmann& Voss。

Each of the aqueous basecoat compositions of examples BC 11-13 was prepared by mixing the above components under agitation. The pH of each composition was adjusted to 8.4-8.6 using an appropriate amount of 50% aqueous DMEA. The viscosity of each aqueous basecoat composition is then reduced to a spray viscosity (DIN #4 cup) of 33-37 seconds using deionized water.

Outgassing assay

Each of the aqueous basecoat compositions of examples BC 11-BC 13 was evaluated in accordance with the outgassing testing procedure set forth in examples BC 1-BC 10.

The gassing data in table 14 below shows that the aqueous metal primer composition comprising the aluminum passivator of the invention (i.e., the composition of examples BC 12-BC 13) has comparable or improved passivation properties on aluminum flakes compared to a comparative passivator comprising a commercially available passivation substance (i.e., the composition of example BC 11).

TABLE 14

Base coat	Amount of released gas (ml)
		Example BC11	9
Example BC12	0
		Example BC13	6

Examples BC14 to BC17

The following examples BC 14-BC 17 (Table 16) describe the preparation of aqueous metallic silver basecoat compositions containing the deactivators of examples A14-A17, respectively, of Table 15. For each of the basecoat compositions, aluminum pigment slurries, and premixes a14-17 of examples BC 14-BC 17, respectively, the following components were prepared as described below. The following amounts are all in parts by weight (grams). The components of premix A14-17 were mixed with stirring and the mixture was stirred for 30 minutes until completely dispersed.

As shown in Table 15, known passivation substances were contained in premixes 14, 16 and 17, while passivation substance of the present invention was contained in premix 15. All of the premixes in table 15 contained 15 wt.% of the passivating agent of the present invention, based on the total weight of the aluminum pigment.

Watch 15

Premix A14-17

Base coat	A14	A15	Comparative example A16	Comparative example A17
					DPM glycol ethers	56	56	56	56
Polypropylene glycol	57	57	57	57
					TINUVIN 1130	16	16	16	16
Aluminum paste	94	94	94	94
					Aluminum passivator
Lubrizol 2062	25	-	-	-
					PE 24	-	33	-	-
Comparative passivator #11	-	-	17	-
					Comparative passivator #22	-	-	-	24
Nitroethane3	-	-	-	8
					Phosphated epoxy resins	4	4	4	4

¹Such as the passivating species described in example 2 of us patent 5389139.

²Such as the passivating species described in example 1 of us patent 5215579.

³Obtained from Aldrich Chemical co.

⁴PE-Polymer of the examples

Aqueous basecoat composition

Aqueous basecoat compositions (examples BC 14-BC 17) were prepared from premixes A11-A14 as set forth in Table 16 below. Unless otherwise indicated, the following amounts are listed as parts by weight (grams) and contain 15 wt.% of the passivating agent based on the total weight of the aluminum pigment.

TABLE 16

	Comparative BC14 example	BC15	Comparative BC16 example	Comparative BC17 example
					Deionized water	291	291	291	291
PE-10	547	547	547	547
					50% aqueous DMEA solution	10	10	10	10
CYMEL 3851	205	205	205	205
					N-butoxypropanol	153	153	153	153
Mineral oil extract	23	23	23	23
					Premix A14	252	-	-	-
Premix A15	-	260	-	-
					Premix A16	-	-	244	-
Premix A17	-	-	-	259
					Polymer of example 13	15	15	15	15
Rheology modifier2	61	61	61	61

¹A melamine resin available from Cytec Industries, inc.

²Rheology modifier prepared by reacting 42.9g of 4-methylhexahydrophthalic anhydride, 18.4g of hexahydrophthalic anhydride and 38.7g of neopentyl glycol hydroxypivalate at 200 ℃ and then diluted with methyl isobutyl ketone to a solids content of 80% and an acid number of 165.

Each of the aqueous basecoat compositions of examples BC 14-BC 17 was prepared by mixing the above components under agitation. The pH of each composition was adjusted to 8.4-8.6 using an appropriate amount of 50% aqueous DMEA. After a16 hour equilibration period at ambient conditions, the pH of each primer layer was again adjusted to 8.4-8.6 using an appropriate amount of a 50% aqueous solution of DMEA. The viscosity of each composition was then reduced to a spray viscosity of 24-26 seconds (Ford #4 cup) using deionized water. The samples were then subjected to the outgassing test as described below.

Outgassing assay

Each of the water-borne base coat compositions of examples BC 14-BC 17 was evaluated according to the test method described below to measure the amount of gas released from the water-borne coating of aluminum-containing flakes. This test method was used to determine the effectiveness of an aluminum flake deactivator (i.e., gassing inhibitor) to prevent or inhibit the generation of hydrogen and heat by the reaction between the surface of the aluminum pigment and water. The method includes placing an aqueous coating containing aluminum flakes in a gassing test apparatus for measuring the amount of milliliters (ml) of gas released within 7 days per 250 grams of coating.

After the final pH and viscosity adjustments described above, 250 grams of each base coat was placed in a degassing cylinder and placed in a water bath at 40 ℃. Each sample was placed in the water bath as soon as possible until after it became available to capture all possible released gases. The results are given in table 17.

TABLE 17

Base coat	Amount of released gas (ml)
		BC14*	24
BC15	11.9
		BC16*	44.2
BC17*	17.4

From the results shown in table 17, it can be seen that the gassing properties of the passivation substances of the present invention are improved compared to other known passivation substances.

Example 2

This example describes the effect of the passivating materials of the present invention on the appearance properties of a coated article.

Various appearance properties of the coating compositions B15 and B18-20 were evaluated as given in Table 18 below. B18, B19 and B20 are identical to B14, B16 and B17, respectively, except that they contain 20 wt.% passivating agent instead of 15 wt.%.

Watch 18

	B18	B15	B19	B20
					Wt.% passivator	20	15	20	20
Flip/Flop1	1.54	1.52	1.44	1.46
					L152	132.08	131.13	126.91	126.49
CO3	49	51	30	52
					Air release amount4±5ml	＜5	＜5	33.7	＜5

¹Obtained by using L15, L45 and L110 obtained by X-RITE spectrophotometer and calculating flip/flop from these data. The larger the value, the brighter the L15 value and the darker the L110 value.

²Brightness measured at 15 ° using a spectrophotometer. The larger the value, the brighter the color.

³Autospec is the combined average of gloss, distinctness of image, and orange peel measured using a conventional Autospec Quality Measurement System (ASTM 0631).

⁴An outgassing amount of less than 10ml is considered acceptable.

Those skilled in the art will readily recognize that many changes may be made thereto without departing from the spirit and scope of the present invention, which is disclosed in the foregoing description. Accordingly, the particular embodiments described in detail herein are illustrative only and are not limiting to the scope of the invention, which is to be given the full breadth of the appended claims and any and all equivalents thereof.

Claims (17)

1. A passivated metal pigment comprising:

at least one metal pigment particle; and

a passivating species formed on at least a portion of the at least one metal pigment particle, the passivating species comprising a polymer, wherein the polymer comprises (a) at least one nitro group, and/or pyridine group, and/or phenolic hydroxyl group; and (b) at least one group selected from a phosphorus-containing group and/or a carboxylic acid group, wherein the at least one phosphorus-containing group is selected from a phosphate, a phosphite, or a non-nitrogen substituted phosphonate.

2. The pigment of claim 1, wherein the pigment particles are in the form of metal flakes.

3. The pigment of claim 1, wherein the metallic pigment particles comprise at least one of: aluminum, copper, zinc, brass, nickel, tin, silver, chromium, iron, and oxides thereof or alloys comprising at least one of the foregoing.

4. The pigment of claim 1, wherein the pigment particles are in the form of aluminum flakes.

5. The pigment of claim 1, wherein the at least one pigment particle comprises a mixture of aluminum pigment particles and iron oxide pigment particles.

6. A coating composition comprising:

(a) a diluting medium;

(b) a film-forming polymer; and

(c) at least one metal pigment particle at least partially treated with a passivating material comprising a polymer, wherein the polymer comprises (a) at least one nitro group, and/or pyridine group, and/or phenolic hydroxyl group; and (b) at least one group selected from a phosphorus-containing group and/or a carboxylic acid group, wherein the at least one phosphorus-containing group is selected from a phosphate, a phosphite, or a non-nitrogen substituted phosphonate.

7. The composition of claim 6 wherein the diluent medium is an aqueous diluent medium.

8. The composition of claim 6 wherein the diluting medium is a non-aqueous diluting medium.

9. The composition of claim 6, wherein the at least one metal pigment particle comprises flake aluminum.

10. The composition of claim 6, wherein the at least one pigment particle comprises a mixture of aluminum pigment particles and iron oxide pigment particles.

11. A coating composition comprising:

(a) an aqueous dilution medium;

(b) a film-forming polymer; and

(c) at least one metallic pigment particle at least partially treated with a passivating material, wherein the passivating material comprises a polymer comprising the reaction product of:

diglycidyl ethers of polyhydric alcohols;

a nitro-containing compound selected from at least one of alkyl-, aryl-and/or alkylaryl-nitro-containing compounds; and

phosphorus-containing compounds, including phosphate and/or non-nitrogen substituted phosphonate.

12. The composition of claim 11, wherein the at least one pigment particle is in the form of metal flakes.

13. The composition of claim 11, wherein the at least one metal pigment particle comprises at least one of: aluminum, copper, zinc, brass, nickel, tin, silver, chromium, iron, and oxides thereof or alloys comprising at least one of the foregoing.

14. The composition of claim 11 wherein the pigment particles are in the form of aluminum flakes.

15. The composition of claim 11, wherein the at least one pigment particle comprises a mixture of aluminum pigment particles and iron oxide pigment particles.

16. A method of passivating a metal surface, the method comprising:

contacting the metal surface with a passivating material comprising a polymer, wherein the polymer comprises (a) at least one nitro group, and/or pyridine group, and/or phenolic hydroxyl group; and (b) at least one group selected from a phosphorus-containing group and/or a carboxylic acid group, wherein the at least one phosphorus-containing group is selected from a phosphate, a phosphite, or a non-nitrogen substituted phosphonate.

17. The method of claim 16, wherein the metal surface comprises a pigment in the form of aluminum flakes.