HK1114813A - Methods of forming composite coatings - Google Patents

Description

Method for forming composite coating

Technical Field

The present invention relates to a method of forming composite coatings prepared from a variety of powder coating compositions that provide coatings with outstanding visual impact, good intercoat adhesion, and resistance to chipping and coating film defects (texturing).

Background

Today's vehicle bodies are treated with multiple coatings that not only enhance the appearance of the vehicle, but also provide protection from corrosion, chipping, ultraviolet light, acid rain, and other environmental conditions that may degrade the coating appearance and the underlying vehicle body.

These coating formulations can vary widely. However, a major challenge facing all automotive manufacturers is how to quickly apply and cure these coatings with minimal investment cost and indoor space, which is very valuable in manufacturing plants. The use of powder coatings is desirable because, when cured, they release very low levels of volatile materials into the environment and excess materials can be easily recycled.

Despite recent improvements in color and clear-coat (color-plus-clear) systems, there is still a need for powder coating composites in automotive coatings to reduce VOC of the overall painting process and minimize the cost of improvements to existing automotive coating assembly lines. In addition, it is desirable to reduce the number of heating steps in the composite powder coating process to reduce energy and equipment costs. Such composite coatings should have good intercoat adhesion and good resistance to film defects and chipping.

Disclosure of Invention

In one embodiment, the present invention provides a method of forming a composite coating on a surface of a substrate, the method comprising the steps of:

(a) applying a first powder basecoating composition to a substrate surface to form a first basecoat (base coat);

(b) applying a second powder basecoating composition to the first basecoat to form a second basecoat;

(c) applying a liquid or powder topcoat coating composition to the second basecoat to form a transparent topcoat and, in turn, a composite coating; and

(d) heating the composite coating to substantially cure the composite coating.

Wherein the applying and heating steps are performed in any one of the following ways:

(1) applying a second basecoat composition comprising an effect pigment in flake or platelet form to the first basecoat layer prior to heating the first basecoat layer, and then heating the first and second basecoat layers at a temperature and for a time period sufficient to melt and substantially level the second basecoat composition and allow the effect pigment to migrate to the surface area of the second basecoat layer, but not sufficient to cause the second basecoat layer to cure; and

(2) applying a topcoat coating composition over the second basecoat layer after the heating step and heating the resulting composite coating layer at a temperature and for a time period sufficient to cure substantially the entire composite coating layer;

or alternatively

(3) Applying a first basecoating composition to the substrate to form a first basecoat layer, and heating the first basecoat layer at a temperature and for a time period sufficient to melt and form a substantially continuous film of the first basecoat layer;

(4) applying a second basecoat composition comprising an effect pigment to the substantially cured first basecoat layer to form a second basecoat layer, and heating the second basecoat layer for a time period sufficient to melt and substantially level the second basecoat composition and allow the effect pigment to migrate to a surface area of the second basecoat layer; and

(5) applying a topcoat coating composition to the second basecoat layer, and heating the resulting composite coating at a temperature and for a time sufficient to substantially cure the composite coating.

Other than in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term "about". Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Further, where numerical ranges of varying ranges are set forth herein, it is contemplated that any combination of these values (including the endpoints of the recited values) can be used.

Moreover, it should be understood that any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, a range of "1 to 10" is intended to include all sub-ranges between and including the recited minimum value of 1 and the recited maximum value of 10, that is, having a minimum value equal to or greater than 1 and a maximum value of equal to or less than 10.

Detailed Description

The present invention relates to an environmentally friendly and cost effective method of forming composite coatings for substrates useful as panels and components, particularly for automotive applications. Many powder basecoats provide composite coatings with outstanding visual impact, good gloss, durability, scratch and moisture resistance, and resistance to paint-off incompatible coating defects, such as filming defects, chipping, and lack of intercoat adhesion. The powder basecoats are compatible with a wide range of conventional liquid or powder topcoats, providing versatility in automotive assembly lines. The composite coating can be applied directly to the metal and/or polymer substrate, thereby eliminating the need for a primer coating. Another advantage of the present invention is the ability to produce these panels and parts at high utilization rates using a substantially zero VOC basecoating system.

The method of the present invention provides a composite coated substrate having a composite coating applied over at least a portion of the substrate. Suitable substrates are selected from the group consisting of metal substrates, polymeric substrates, such as thermoset and thermoplastic materials, and combinations thereof.

Useful metal substrates include ferrous metals, non-ferrous metals, and combinations thereof. Suitable ferrous metals include iron, steel, and alloys thereof. Non-limiting examples of useful steel materials include cold rolled steel, zinc coated steel, such as hot dipped galvanized and electroless steel, stainless steel, pickled steel, zinc-iron alloys, such as GALVANEAL, zinc-aluminum alloys coated on steel, such as GALVALUME and GALFAN, and combinations thereof. Different forms of ferrous metal are possible for different parts of the same substrate, for example a zinc coating is applied to only a portion or one side of a steel substrate. Useful non-ferrous metals include aluminum, zinc, magnesium, and alloys thereof. Combinations or composites of ferrous and non-ferrous metals may also be used. Preferred metal substrates are corrosion resistant steels such as the zinc coated steels and zinc-iron alloys mentioned above, and zinc-aluminum alloys.

Useful thermosets include polyesters, epoxies, phenols, polyurethanes, such as reaction injection molded polyurethane (RIM) thermosets, and mixtures thereof. Useful thermoplastic materials include thermoplastic polyolefins such as polyethylene and polypropylene, polyamides such as nylon, thermoplastic polyurethanes, thermoplastic polyesters, acrylic polymers, vinyl polymers, polycarbonates, acrylonitrile-butadiene-styrene (ABS) copolymers, Ethylene Propylene Diene (EPDM) rubbers, copolymers and mixtures thereof.

Preferably, the substrate is used as a component for manufacturing motor vehicles, including, but not limited to, automobiles, trucks, and tractors. The substrate may have any shape, but is preferably an automotive body component, such as the body (frame), hood, door, fender, bumper and/or trim of a vehicle.

The present invention will first be generally discussed in the context of coating a metal automotive vehicle body. Those skilled in the art will appreciate that the method of the present invention may also be used to coat metal and/or polymer parts of non-automotive vehicles, as will be discussed below.

Before depositing the coating on the surface of the metal substrate, dust, oil or foreign substances are removed from the metal surface, preferably by thoroughly cleaning the surface and degreasing. The surface of the metal substrate may be cleaned by physical or chemical means, such as mechanically abrading the surface or by cleaning/degreasing with commercially available alkaline or acidic cleaning agents known to those skilled in the art, such as sodium metasilicate and sodium hydroxide. Non-limiting examples of suitable alkaline cleaners include CHEMKLEEN 163 and CHEMKLEEN 177 phosphate cleaners commercially available from PPG Industries, Inc. of Pittsburgh, Pa.

Following the cleaning step, the metal substrate is typically rinsed with water, preferably deionized water, to remove any residue. The metal substrate may optionally be dried using an air knife, by flashing off water with brief exposure to elevated temperatures, or by passing the metal between squeeze rolls.

Following the washing and optional drying steps, the metal substrate may optionally be pretreated with a thin layer of a pretreatment agent. Advantages of the pretreatment include protecting the metal substrate from corrosion and improving the adhesion of subsequent coatings to the substrate. The pretreatment may contain chromium or preferably no chromium. The choice of pretreatment is generally determined by substrate and environmental considerations. Suitable pre-treatments are well known to those skilled in the art. An example of a suitable chromium pretreatment is Granodine 1415A from HenkelSurface Technologies, NA. Examples of chromium-free pretreatments are Nupal 456BZ or CHEMFOS 700 zinc phosphate pretreatments available from PPG Industries, inc.

The pretreatment solution can be applied to the surface of the metal substrate in a batch or continuous process by any conventional application technique, such as spray coating, dip coating, or roll coating. The temperature of the treatment solution, when applied, is typically from about 10 ℃ to about 85 ℃, and preferably from about 15 ℃ to about 40 ℃. When applied, the preferred pH range of the treatment solution is generally from about 2.0 to about 9.0, and preferably from about 3 to about 5.

The film coverage of the residue of the pretreatment coating is generally in the range of about 0.1 to about 1000mg/m²And preferably from about 1 to about 400mg/m²。

Hereinafter the term "substrate" shall refer to a cleaned, optionally pretreated substrate.

Preferably, the substrate surface is substantially free of a conductive weldable primer coating prior to application of the composite coating, i.e., the substrate surface has less than about 5% of the surface area coated with the conductive weldable primer, and more preferably less than about 2%. More preferably, the substrate surface is free of a conductive weldable primer coating prior to application of the composite coating.

As used herein, "conductive solderable primer" or "conductive solderable primer coating" refers to a conductive, solderable coating formed from a composition that includes one or more conductive pigments that provide the conductivity of the solderable coating and one or more binders that bind the conductive pigments to the substrate, as described in U.S. patent No.6715196, which is incorporated herein by reference. Such conductive pigments include Zinc, iron phosphide, aluminum, iron, graphite, nickel, tungsten and mixtures thereof, such as StolbergerZINCOLI in the form of Zinc particles of zincoli 620, US Zinc superfines 7 Zinc powder or ferro Ferrophos Microfine grade 2132 iron phosphide available from Glenn Springs Holdings of Lexington, Ky. Such compositions include a significant amount of conductive pigment, typically greater than about 10 volume percent, and typically from about 30 to about 60 volume percent, based on the total volume of conductive pigment and binder.

In another embodiment, the substrate surface may be coated with an electrodeposited primer coating prior to application of the composite coating. Suitable electrodepositable coating compositions include conventional anionic or cationic electrodepositable coating compositions, such as epoxy-or polyurethane-based coatings, as described in U.S. patent nos.6217674, 5530043, 5760107, 5820987 and 4933056, which are incorporated herein by reference. It will be understood by those skilled in the art that such electrodepositable coating compositions are substantially free of conductive pigments, i.e., less than about 5 weight percent, preferably less than about 2 weight percent, and more preferably free of electrodepositable pigments, based on the total weight of the electrodepositable coating composition, since such conductive materials can interfere with the electrodeposition process. Methods of application and suitable coating thicknesses are well known to those skilled in the art and are disclosed in the foregoing references.

To provide additional cost savings, in another embodiment, the substrate surface is substantially free of the electrodeposited primer coating prior to application of the composite coating, i.e., the substrate surface has less than about 5% of the surface area coated with the electrodeposited primer, and more preferably less than about 2%. In another embodiment, the substrate surface is free of an electrodeposited primer coating prior to application of the composite coating.

Alternatively or additionally, the substrate may be coated with a powder primer, as described in U.S. patent nos. 4804581, 5212245, and 5248400 (which are incorporated herein by reference). Another example of a useful powder primer is the envirocon PCV70118 powder primer available from PPG Industries, inc.

The composite coating of the present invention has the advantage that it can be applied directly to bare metal, thereby eliminating the need for a primer coating. In addition to the significant cost savings of eliminating the coating and the energy savings through the elimination of the drying step, the elimination of the electrodeposited primer coating can significantly reduce the construction costs of the plant. Preferably, the bare metal is cold rolled steel or electroplated steel.

In the present invention, a first primer layer is deposited on a substrate surface. The first basecoat is formed from a powder basecoating composition comprising at least one film-forming material.

Preferably, the polymeric film-forming material in the powder basecoating composition is of the thermosetting type and comprises: (a) one or more polymers having reactive functional groups; and (b) one or more curing agents selected to react with the functional groups in (a).

(a) At least one polymer having reactive functional groups is a heat curable polyester. The thermally curable polyester may have reactive functional groups selected from the group consisting of hydroxyl, carboxylic acid, epoxy, carbamate, amide, carboxylate, and combinations thereof.

Preferably, the heat curable polyester has carboxylic acid functionality. The monomers used to synthesize the polyester polymer having carboxylic acid functionality suitable for use in the powder coating composition of the present invention are selected so that the resulting polyester polymer has a Tg of greater than 40 ℃.

Among the carboxylic acid group-containing polyesters, use may be made of those based on the condensation of aliphatic polyols, including cycloaliphatic polyols, with aliphatic and/or aromatic polycarboxylic acids and anhydrides. Examples of suitable aliphatic polyols include 1, 2-ethanediol, 1, 3-propanediol, 1, 4-butanediol, 1, 6-hexanediol, neopentyl glycol, cyclohexanedimethanol, trimethylolpropane and the like. Suitable polycarboxylic acids and anhydrides include succinic acid, adipic acid, azelaic acid, sebacic acid, terephthalic acid, isophthalic acid, tetrahydroterephthalic acid, hexahydroterephthalic acid, trimellitic acid, and the anhydrides of these acids.

In the case of an excess of acid compared to the alcohol, the polyol and the acid or anhydride are reacted together to form a polyester having free carboxylic acid groups. Preferably, the carboxylic acid group-containing polyester has an acid number of from about 20 to about 80, more preferably from about 30 to about 75, and is an amorphous solid at room temperature. The polyester is further characterized by a Tg of from about 30 ℃ to about 85 ℃, preferably from about 40 ℃ to about 75 ℃.

The Tg of a polymer is a measure of the hardness and melt flow of the polymer. The higher the Tg, the less melt flow and the harder the coating. Tg is disclosed in Principles of Polymer chemistry (1953), Cornell University Press. Tg may be actually measured or may be calculated as described by Fox in Bu ll. amer. physics soc.1, 3, page 123 (1956). Tg as used herein refers to the actual measured value. To measure the Tg of the polymer, Differential Scanning Calorimetry (DSC) can be used (heating rate 10 ℃/min and taking the Tg at the first point of inflow (entry point)).

If the Tg of the polyester is below 30 deg.C, the polymer and powder coating compositions containing this polymer may tend to be tacky and difficult to handle. If the Tg is higher than 85 ℃, the melt flowability of the polyester is low and the coating may have a poor appearance.

Examples of suitable carboxylic acid group containing polyester polymers are those disclosed in U.S. Pat. No.4801680 at column 5, line 65 to column 7, line 39, which is incorporated herein by reference. A preferred carboxylic acid functional polyester is DSM P880, available from DSM.

In addition to the heat-curable polyester, the powder basecoating composition may further comprise other oligomers or polymers containing functional groups such as hydroxyl, carboxylic acid, epoxy, carbamate, amide, and carboxylate functional groups.

The use of acrylic, polyester, polyether and polyurethane oligomers and polymers with hydroxyl functionality in powder coatings is well known in the art. The monomers for synthesizing such oligomers and polymers are selected such that the resulting oligomers and polymers have a Tg of greater than 40 ℃. Examples of such oligomers and polymers having hydroxyl functionality suitable for use in the powder coating compositions of the present invention are those described in U.S. Pat. No.5646228 at column 5, line 1 to column 8, line 7, which is incorporated herein by reference.

The use of acrylic polymers having carboxylic acid functionality in powder coatings is well known in the art. The monomers used to synthesize the acrylic polymer having carboxylic acid functionality suitable for use in the powder coating composition of the present invention are selected so that the Tg of the resulting acrylic polymer is greater than 40 ℃. Examples of carboxylic acid group containing acrylic polymers are those described in U.S. Pat. No.5214101, column 2, line 59-column 3, line 23, which is incorporated herein by reference.

Also useful in powder coating compositions are acrylic, polyester, and polyurethane polymers containing carbamate functionality and epoxy functionality, such as those well known in the art. Examples of such polymers with carbamate functionality suitable for use in the powder coating composition of the present invention are disclosed in international application WO 94/10213. Examples of polymers having epoxy functionality suitable for use in the powder coating compositions of the present invention are disclosed in U.S. patent No.5407707, which is incorporated herein by reference. The monomers used to synthesize such polymers for use in powder coating compositions are selected so that the resulting polymer has a high Tg, that is, a Tg greater than 40 ℃.

Suitable curing agents for the powder basecoating composition include aminoplasts, blocked polyisocyanates, polyacids, polyepoxides, polyols, polyanhydrides, hydroxyalkylamides, and mixtures thereof.

Blocked isocyanates as curing agents for (OH) and primary and/or secondary amino group-containing materials are well known in the art. Examples of blocked isocyanates suitable for use as curing agents in the powder coating compositions of the present invention are those disclosed in U.S. Pat. No.4988793 at column 3, lines 1-36, which is incorporated herein by reference.

Polyepoxides as curing agents for materials Containing (COOH) functional groups are well known in the art. Examples of polyepoxides suitable for use as curing agents in the powder coating compositions of the present invention are those disclosed in U.S. Pat. No.4681811 at column 5, lines 33-58, which is incorporated herein by reference.

Polyacids as curing agents for epoxy functional group containing materials are well known in the art. Examples of polyacids suitable for use as curing agents in the powder coating compositions of the present invention are those disclosed in U.S. Pat. No.4681811, column 6, line 45-column 9, line 54, which is incorporated herein by reference.

Polyhydroxy compounds, i.e., materials having an average of two or more hydroxyl groups per molecule, are useful as curing agents for materials containing (NCO) functional groups and anhydrides and are well known in the art. The polyhydroxy compounds used in the powder coating compositions of the present invention are selected so that the resulting materials have a high glass transition temperature, i.e. greater than 50 ℃.

Beta-hydroxyalkylamide materials are disclosed as cross-linking agents for carboxylic acid functional polymers (a) in U.S. patent No.4801680, which is incorporated herein by reference. To obtain the best cure profile, the hydroxyl functionality in the β -hydroxyalkylamide should average at least 2, preferably greater than 2, and more preferably from greater than 2 to about 4.

The β -hydroxyalkylamide materials may be described by the structural formula:

wherein R is₁Is H or C₁-C₅An alkyl group; r₂Is H, C₁-C₅Alkyl or:

wherein R is₁As described above; a is a bond, a monovalent or polyvalent organic radical derived from a saturated, unsaturated or aromatic hydrocarbon comprising a substituted hydrocarbon radical containing from 2 to 20 carbon atoms, m is equal to 1 to 2, n is equal to 0 or 2, and m + n is at least 2, preferably greater than 2, typically in the range of 2 to 4 (including 4). Preferably, A is alkylene- (CH)₂)_x-, where x is from 2 to 12, preferably from 4 to 10, preferred β -hydroxyalkylamides are N, N, N ', N' -tetrakis (2-hydroxyethyl) adipamide commercially available under the trade name PRIMID XL-552 from Ems-Chemie AG, Switzerland.

The β -hydroxyalkylamides may be prepared by reacting a mixture of lower alkyl esters or esters of carboxylic acids with a β -hydroxyalkylamide at a temperature in the range of from ambient temperature to about 200 ℃, depending on the choice of reactants and the presence or absence of catalyst. Suitable catalysts include base catalysts such as sodium methoxide, potassium methoxide, sodium butoxide, potassium butoxide, sodium hydroxide, potassium hydroxide and the like, present in amounts of about 0.1 to about 1 percent by weight based on the weight of the alkyl ester.

In order to bring about the most efficient curing of the powder coating composition, the equivalent ratio of β -hydroxyalkylamide (hydroxyl equivalent) to carboxyl group containing polyester (carboxylic acid equivalent) is preferably from about 0.6 to 1.6: 1, more preferably from 0.8 to 1.3: 1. Ratios outside the range of 0.6-1.6: 1 are undesirable because of poor cure.

Anhydrides as curing agents for epoxy functional group containing materials are well known in the art. Examples of such curing agents include trimellitic anhydride, benzophenone tetracarboxylic dianhydride, pyromellitic dianhydride, tetrahydrophthalic anhydride, and the like, as described in U.S. Pat. No.5472649 at column 4, lines 49-52, which is incorporated herein by reference.

Aminoplasts as curing agents for OH, COOH and carbamate functional group containing materials are well known in the art. An example of such a curing agent suitable for use in the present invention is an aldehyde condensate of glycoluril, which gives a crystalline product with a high melting point useful in powder coatings. While the aldehyde used is typically formaldehyde, other aldehydes such as acetaldehyde, crotonaldehyde, and benzaldehyde can be used.

The first powder basecoating composition comprises at least one reaction product of at least one cyclic carboxylic acid anhydride, at least one olefin, and at least one reactant selected from the group consisting of primary amines, aliphatic polyamines, primary amino alcohols, isocyanates, and mixtures thereof. The number average molecular weight of the copolymer ranges from about 1000 to about 20,000, preferably from about 3000 to about 10,000, and more preferably from about 3000 to about 6000, and most preferably from about 2000 to about 2500.

Non-limiting examples of suitable cyclic carboxylic acid anhydrides include maleic anhydride (preferred), chloromaleic anhydride, dichloromaleic anhydride, bromomaleic anhydride, citraconic anhydride, dimethylmaleic anhydride, ethylmaleic anhydride, itaconic anhydride, vinylsuccinic anhydride, and vinyltrimellitic anhydride.

Suitable olefins include cyclic olefins, alpha olefins, vinyl monomers, esters of acrylic or methacrylic acid, and mixtures thereof.

Examples of suitable alpha olefins include 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene (preferred), 2-methyl-1-butene, 2-ethyl-1-pentene, 2-methyl-1-pentene, and 2-ethyl-1-hexene.

The reaction product can be viewed as a substantially alternating copolymer of a cyclic carboxylic acid anhydride and an olefin. Theoretically, 1mol of the cyclic carboxylic anhydride or the substituted cyclic carboxylic anhydride is added to 1mol of the olefin to obtain a copolymer. However, it is preferred to use a molar excess of the olefin relative to the cyclic carboxylic anhydride. The reaction is carried out by heating the reactants together, preferably in the presence of an organic solvent and in the presence of a free radical initiator, such as an organic peroxide, e.g., t-amyl peroxyacetate, t-butyl perbenzoate, and the like, or an azo compound, e.g., azobisisobutyronitrile, and the like, at a temperature typically to achieve olefin reflux, typically a temperature of from about 30 ℃ to about 220 ℃, preferably from about 80 ℃ to 180 ℃, for a period of time sufficient to complete the copolymerization, typically a period of time ranging from 1 to 24 hours, preferably 1 to 3 hours. Organic peroxide free radical initiators are preferred.

The number average molecular weight of the reaction product is generally from about 1000 to about 20,000, preferably from about 3000 to about 10,000, and more preferably 3000 and 6000. The number average molecular weight of the copolymer can be determined by Gel Permeation Chromatography (GPC) using polystyrene standards. What is measured by this method is not the actual molecular weight but an indication of the molecular weight compared to polystyrene. The resulting values are often referred to as polystyrene values. However, for the purposes of this application, they are referred to as molecular weights. Molecular weights (number average) less than 1000 are undesirable because the copolymer will lose surface activity, i.e., flow control properties, while molecular weights greater than about 10,000 are less desirable and greater than about 20,000 are undesirable because high viscosity detracts from flow properties.

The reaction product is chemically modified by about 0.5 to about 100 mole percent, based on the moles of anhydride functional groups in the copolymer, of a reactant selected from the group consisting of primary amines, aliphatic polyamines, primary amino alcohols, isocyanates, and mixtures thereof. Preferably, the reaction product is chemically modified by about 2 to about 10 mol% or more of the reactants described.

Chemical modification with an alcohol will form a partial ester or half-ester derivative, while chemical modification with a primary amine will form an imide. Among the alcohols, there may be used alkanols, preferably alkanols containing 1 to about 10 carbon atoms, such as methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, and the like. More preferably, the alkanol is methanol, ethanol, butanol or 2-ethylhexanol. Aryl alkanols, such as benzyl alcohol, phenethyl alcohol and phenyl propyl alcohol, alkyl diols, such as ethylene glycol or propylene glycol, and substituted alkyl diols, such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, and ethylene glycol monohexyl ether, may also be suitable alcohols to form the half esters of the anhydride groups. The alcohol may also be a tertiary amine having at least one alkanol group, such as 2-dimethylaminoethanol, 1-diethyl (emthyl) aminomethylpropanol, 2-diethylaminoethanol and the like, or a diglycolamine, such as dimethyl or diethyl (aminoethoxy) ethanol. Chemical modification by the alcohol, i.e. esterification, can also be achieved by heating the copolymer and alcohol together, optionally with a catalyst such as sodium methoxide, at a temperature of 100 ℃ to 150 ℃ to accelerate the ring opening of the anhydride.

The copolymer may also be chemically modified with primary amines such as butylamine, isobutylamine, propylamine, isopropylamine, ethylamine, methylamine and pentylamine, aliphatic polyamines such as N, N-dimethylaminopropylamine, N-dimethylaminoethylamine, N-diethylaminopropylamine, N-diethylaminoethylamine and the like, or primary aminoalcohols such as ethanolamine (preferred) and propanolamine and the like. Primary amines, such as aliphatic polyamines, e.g., N-dimethylaminopropylamine, will yield imide-modified anhydrides having pendant tertiary amino groups, which can act as catalysts for the epoxy reaction and increase the crosslink density and electrical resistance properties of the cured coating. Primary aminoalcohols can result in imide-modified anhydrides having pendant alcohol functionality.

Examples of suitable isocyanates include alkyl substituted isocyanates such as MONDUR O octadecyl isocyanate.

Preferably, the reaction product is prepared from 1-decene, maleic anhydride, monoethanolamine, and octadecyl isocyanate, and has an acid number in the range of from about 8 to about 15, and a number average molecular weight in the range of from about 2000 to about 2500.

Typically, the first powder basecoating composition comprises from about 50 to about 85 weight percent of the film-forming material and from about 70 to about 80 weight percent of the reaction product. Preferably, the reaction product is included in the first powder basecoating composition in an amount of from about 0.1 to about 5 weight percent, more preferably from about 0.5 to about 3 weight percent, based on the total weight of the film-forming material and the reaction product.

The first powder basecoating composition comprises at least one flow control agent. Suitable as flow control agents are acrylic polymers (preferred), such as polylauryl acrylate, polybutyl acrylate, poly (2-ethylhexyl) acrylate, poly (ethyl-2-ethylhexyl) acrylate, polylauryl methacrylate, polyisodecyl methacrylate and the like, and fluorinated polymers, such as esters of polyethylene or polypropylene glycols with fluorinated fatty acids, such as esters of polyethylene glycol and perfluorooctanoic acid with molecular weights of more than about 2500. Polymeric siloxanes with molecular weights above 1000 may also be used as flow control agents, such as polydimethylsiloxane or poly (methylphenyl) siloxane. The flow control agent can help reduce surface tension during heating of the powder and avoid formation of coating defects. Preferably, the flow control agent is an acrylic copolymer prepared from 2-ethylhexyl acrylate and butyl acrylate, such as RESIFLOW PL200 available from Estron Chemical of CalvertCity, Kentucky. Generally, the flow control agent is present in an amount of about 0.05 to about 5 weight percent, based on the total weight of the first powder coating composition.

The one or more non-platelet pigments may typically be included in the coating composition in an amount of from about 1 to about 50 weight percent, based on the total weight of the first powder basecoating composition. Pigments suitable for powder coating compositions may be organic or inorganic pigments and include basic silica lead chromate, titanium dioxide, ultramarine blue, phthalocyanine green, carbon black, black iron oxide, green chromium oxide, iron yellow and quinto red. Platelet or flake pigments (described below) may optionally be included in the first powder basecoating composition.

An anti-popping agent (anti-popping agent) may be added to the composition to allow any volatile materials present to escape from the film during baking. Benzoin and/or zinc oxide are preferred degassing agents and, if used, are present in an amount ranging from about 0.5 to about 3 weight percent based on the total weight of the powder basecoating composition. The powder coating composition may also preferably contain a UV absorber, such as TINUVIN, which, if used, is typically present in the composition in an amount of from about 0.5 to about 6 weight percent, based on the total weight of the first powder basecoating composition.

Additionally, the first powder basecoating composition may contain fumed silica or the like as a powder flow additive to reduce caking of the powder during storage. An example of fumed silica is sold under the tradename CAB-O-SIL RTM by Cabot Corporation. The powder flow additive, if used, is typically present in an amount in the range of from about 0.1 to about 0.5 weight percent, based on the total weight of the first powder basecoating composition. After the preparation of the granular mixture, a powder flow additive is typically added to the granular powder basecoating composition.

An example of a suitable first powder basecoating is the ENVIRORON PZB90100 ferrous metal powder basecoating available from PPG Industries, Inc.

Powder coating compositions are typically prepared by blending the polymer containing functional groups, the crosslinker (for thermoset compositions) and optional ingredients in a Henschel blade blender for 15 minutes. The powder is then typically extruded, for example, through a Baker-Perkins twin screw extruder. The extrudate is typically pelletized by first being cut into flakes and then ground in a hammer mill. The final powder may then be classified in a cyclone/sieve into particle sizes typically 20 to 30 microns.

The powder coating can be applied by electrostatic spraying or by using a fluidized bed. Electrostatic spraying using a gun or bell (bell) at 55-80kV, 80-120g or more per minute is preferred. The powder basecoating composition can be applied in a single application or in several applications to provide a film thickness (about 0.5 to about 4 mils) of about 12.7 to about 102 micrometers after cure. Preferably the coating thickness is such that good chip resistance, uv opacity and visual hiding will be achieved. The preferred film thickness is from about 25 to about 50 micrometers (about 1 to about 2 mils). The substrate to be coated may optionally be preheated prior to application of the powder to promote more uniform deposition of the powder.

In a first embodiment of the method of the present invention, the second powder basecoating composition is applied directly onto the first basecoating layer without any heating or curing of the first basecoating layer.

In a second embodiment of the method of the present invention, the first basecoat is heated at a temperature and for a time period sufficient to degas, melt, and form a generally continuous first basecoat film prior to application of the second powder basecoat composition. The first basecoating is heated at a temperature of from about 110 c to about 170 c for a period of time of from about 4 to about 40 minutes. The first base coat may be partially or fully crosslinked, as described below.

The second powder basecoating composition comprises at least one heat-curable polyester having reactive functional groups as described above, one or more curing agents selected to react with the functional groups in the heat-curable polyester, at least one reaction product, and at least one flow control agent. The second powder basecoating composition may further comprise other polymers having reactive functional groups, curing agents, reaction products, flow control agents, non-platelet pigments and other additives as described above. In one embodiment, the second powder basecoating composition can include the same binder components and additives as the first powder basecoating composition.

The second powder basecoating composition is different from the first powder basecoating composition in that it comprises at least one visual effect additive different from that used in the first powder basecoating composition, i.e., the amount of visual effect additive or type of visual effect additive in the second powder basecoating composition is different from that of the first powder basecoating composition or the second powder basecoating composition comprises one or more visual effect additives, and the first powder basecoating composition is free of visual effect additives.

Examples of suitable visual effect additives include flake or plate-like pigments or metallized polymer particles. Examples of flake pigments include aluminum flake pigments, such as SilberlineTF4700/LE10521 aluminum flakes. Other metal platelet or flake compositions may be used, such as bronze flakes, stainless steel flakes, nickel flakes, tin flakes, silver flakes, copper flakes, and the like. Preferred flake pigments range in size from 1.0 to 50.0 microns. In addition to the flake pigments described, other metallized polymer particles may be used, such as aluminized Mylar (Mylar) and aluminized polyester fibers. Other suitable pigments include mica, coated mica, iron oxide, lead oxide, carbon black, titanium dioxide and colored organic pigments such as phthalocyanines. Suitable metal oxides for use as coatings on mica particles may include alumina or other metal oxides such as titanium dioxide, iron oxide, chromium hydroxide, and the like, and combinations thereof. Other useful pigments include heliocone HC silicone liquid crystal platelets.

The specific pigment to binder ratio can vary widely so long as it provides the requisite hiding at the desired film thickness and applied solids. The pigments are incorporated into the powder coating at a level of from 0.1% to 20.0% based on the total weight of the powder coating. Preferably, the flake pigment is used in an amount of 1.0% to 10.0% based on the total weight of the coating composition.

To achieve the attractive visual effects caused by orientation of the flake pigment in the resulting coating, the flake pigment particles are incorporated into the second powder coating composition by dry blending rather than extrusion. The dry blending operation can be carried out either with cooling or with heating. Dry blending under heating is referred to as "bonding". It is believed that the bonding method fixes the flake pigment to the binder particles and does not actually disperse the flake pigment within the binder powder particles. The "bonding" method of dispersion is particularly useful for metal flake particle dispersions because there is no undesirable electrostatic interaction that occurs in electrostatically spraying metal particles.

An example of a suitable second powder basecoating is ENVIRORON PZB43102 powder basecoating available from PPG Industries, Inc.

After the second powder basecoating is applied, the coated substrate is heated to a temperature sufficient to melt and coalesce the coating. In the present invention, this is an important step because when properly performed, the flake pigment migrates to the air interface and aligns itself in a direction substantially parallel to the substrate, resulting in a unique visually pleasing appearance. The heating step should be performed so that the second powder coating coalesces into a substantially continuous fluid layer, rather than so high as to cause an increase in viscosity and crosslinking of the coating before the flake pigment rises to the coating-air interface and aligns with the coating surface. The layer remains fluid for a period of time sufficient for the flake pigment to rise to the coating-air interface and align so that the two largest dimensions in the pigment flake are nearly parallel to the coating surface. After the pigments align themselves with the coating surface, heating of the coating is continued until, in the case of a thermosetting powder base coat, partial or complete curing is achieved. Alternatively, the coating may be cooled prior to curing. Typically, the pigmented coating layer is heated to a temperature of from about 110 ℃ to about 190 ℃ (preferably between about 110 ℃ to about 170 ℃) over a period of from about 4 to about 40 minutes. When a heat-curable, thermosetting clear coat is used, the color coat need not be fully cured and full curing can occur during the curing cycle of the thermosetting clear coat.

A topcoat is deposited over the basecoat and cured to provide a composite coated substrate of the present invention. The topcoat may be a liquid, a powder slurry (powder suspended in a liquid), or a powder, as desired. Preferably, the topcoat composition is a crosslinkable coating comprising one or more thermally curable film-forming materials and one or more crosslinking materials, such as those described above. Useful film-forming materials include epoxy-functional film-forming materials, acrylics, polyesters, and/or polyurethanes. The top coat composition may include additives such as those described above for the base coat, but preferably is not a pigment. If the topcoat is a liquid or powder slurry, volatile materials are included. Suitable waterborne topcoats (which are incorporated herein by reference) are disclosed in U.S. patent No.5098947 and are based on water-soluble acrylic resins. Useful solvent-based topcoats are disclosed in U.S. patent nos.5196485 and 5814410, which are incorporated herein by reference, and include an epoxy-functional material and a polyacid curing agent. Examples of useful solvent-based topcoats include SRC8002 and DIAMOND COAT solvent-based clear coating compositions available from PPGIndustries, inc. Suitable powder slurry top coat compositions include those disclosed in international publications WO96/32452 and 96/37561, european patents 652264 and 714958, and canadian patent No.2163831, which are incorporated herein by reference. Suitable powder topcoats are disclosed in U.S. patent nos.5407707 and 5663240, which are incorporated herein by reference, and include an epoxy-functional acrylic copolymer and a polycarboxylic acid crosslinking agent. Preferably, the topcoat is prepared from a powder topcoat composition such as ENVIRACRYL PZC10102 powder clearcoat available from PPG industries, Inc. The powder topcoat can be applied by electrostatic spraying using a gun or bell at 55-80kV, 80-120 g/min to achieve a film thickness of, for example, about 50-90 microns.

The amount of topcoat composition applied to the substrate can vary based on factors such as the type of substrate and the intended use of the substrate, i.e., the environment in which the substrate is placed, and the nature of the contacting materials. Typically, the topcoat composition is applied to provide a film thickness of about 12.7 to about 102 micrometers (0.5 to about 4 mils), preferably about 38.1 to about 68.6 micrometers (1.5 to about 2.7 mils) after curing. Typically, the composite coating is then heated to a temperature of about 110 ℃ to about 190 ℃ (preferably about 150 ℃ to about 190 ℃) over a period of about 4 to about 40 minutes.

The term "cured" as used herein in connection with a composition, e.g., "composition as cured" and "thermoset" as used in connection with a composition, e.g., "thermoset composition" shall mean that any crosslinkable components in the composition are at least partially crosslinked. In some embodiments of the invention, the cross-link density, i.e., the degree of cross-linking, of the cross-linkable component ranges from 5% to 100% of full cross-linking. In other embodiments, the crosslink density ranges from 35% to 85% of full crosslinking. In other embodiments, the crosslink density ranges from 50% to 85% of full crosslinking. It will be appreciated by those skilled in the art that the presence and extent of crosslinking, i.e., crosslink density, can be determined by various methods, such as Dynamic Mechanical Thermal Analysis (DMTA) using a TA Instruments DMA 2980 DMTA analyzer conducted under nitrogen. This method determines the glass transition temperature and crosslink density of a linerless film (freefilm) of a coating or polymer. These physical properties of the cured material relate to the structure of the crosslinked network.

The thickness of the sintered and crosslinked composite coating is generally from about 0.2 to about 5 mils (5 to 125 micrometers), and preferably from about 0.4 to about 4 mils (10 to 100 micrometers). The composite coating is cured so that any crosslinkable components in the coating are sufficiently fully crosslinked to the extent that the automotive industry accepts the coating process to transport the coated automotive body without damaging the coating.

The following examples illustrate the invention, however these examples should not be construed as limiting the invention to the details thereof. Unless otherwise indicated, in the following examples, as well as throughout the specification, all parts and percentages are by weight.

Examples

The following examples a-D illustrate the separate preparation of coated panels by the method of the present invention using a cleaned and pretreated electroplated substrate (optionally coated with an electrodeposited primer), two powder basecoats and a powder or liquid clearcoat. For comparison purposes, control panels were coated by conventional methods using the same electrodeposition primer, liquid color coating, liquid accept coating, and liquid clear coating. Table 1 below shows the physical property test results of the coated panels.

Preparation of pretreated Panels

Double-sided heat-dipped Galvaneal panels from USX Corporation, 15.3cm wide and 38.1cm long, were cleaned at 60 deg.C (135-. The panels were rinsed with deionized water and dried using a warm air blower. The duration of the cleaning step is adjusted to cause the rinse water to drain from the vertical surfaces of the metal panels in the water, in the sheet without breakpoints, thereby indicating that the surfaces are free of oil. The panels were pretreated on both sides with a CHEMPHOS C700/C59 zinc phosphate composition, then rinsed with deionized water and dried with a warm air blower. The dried panels were wrapped in paper and stored at ambient room temperature conditions.

Preparation of an electrodeposition Panel

An ED6100H electrodepositable primer (available from PPG industries, Inc.) was applied by electrodeposition to the selected pretreated panel and the panel was baked at 177 deg.C (350 deg.F) for 20 minutes to give a 20-30 micron (0.8-1.2mil) film.

Example A

Preparation of powder base coat/powder acid coat/powder clear coat

Example A1

ENVIRORON PZB90100 black powder basecoating (available from PPG Industries, Inc.) was applied to the pretreated panel by electrostatic spraying to provide a film thickness of 38-63 microns (1.5-2.5 mil). The panels were then coated with a second powder coating containing an accept pigment (ENVIROCRON PZB43102, available from PPGIndustries, inc.) and baked in an electronics box oven at 143 ℃ (290 ° f) for 20 minutes and allowed to air cool, providing a film thickness of 38-63 microns (1.5-2.5mil) for each layer, resulting in a 76-126 micron (3.0-5.0mil) total powder basecoat.

The ENVIRORORON PZB90100 and ENVIRORON PZB43102 powder basecoats each comprised a carboxylic acid functional polyester resin, a beta hydroxyalkylamide crosslinker, an acrylate copolymer, a reaction product as described below, a degassing agent, an antioxidant, a UV absorber, and a pigment.

The reaction product was prepared by the following method. A reaction vessel equipped with a condenser, thermometer, nitrogen purge inlet and stirrer was charged with 61.1 parts by weight (ppw) of 1-decene dissolved in 73.8ppw of butyl acetate. The 1-decene solution was heated to reflux temperature at 145 deg.C and a mixture of 1.8ppw t-amyl peroxyacetate (60 wt% in mineral spirits) obtained as LUPERSOL 555-M60 and 62.7ppw butyl acetate was added over a period of about 3 hours. A solution of 27.4ppw maleic anhydride in 98.8ppw butyl acetate was added over a period of about 2 hours. The reaction mixture was diluted with an additional 85.5ppw of butyl acetate and then heated at reflux for 1 hour. Monoethanolamine (16.2ppw) and 16.2ppw butyl acetate were added to the reaction mixture and the reaction mixture was heated to reflux and water was removed by azeotropic distillation when the water content in the reaction mixture was reduced to less than 0.2 wt%. The temperature of the reaction mixture was set at 115 ℃ and 1.6ppw of octadecyl isocyanate dissolved in 30.0ppw of butyl acetate was added to the reaction mixture. The reaction mixture was maintained at 115 ℃ until evidence of the absence of NCO by IR analysis. Thereafter, the solvent was removed by distillation until the reaction mixture reached a solids content of 65% by weight.

After the powder basecoat was applied as described above, ENVIRACRYL PZC10102 powder clearcoat (available from PPG Industries, Inc.) was applied to the above basecoat combination by electrostatic spraying and baked in an electronic box oven at 169 deg.C (335 deg.F) for 30 minutes to provide a clearcoat film having a film thickness of 50-75 microns (2.0-3.0 mil).

Example A2

ENVIRORON PZB90100 black powder basecoating was applied to the pretreated substrate by electrostatic spraying and baked at 143 deg.C (290 deg.F) for 20 minutes to provide a film thickness of 38-63 microns (1.5-2.5 mil).

The panels were then coated with a second powder coating containing an accept pigment (ENVIROCRON PZB43102 powder basecoating from PPGIndustries, inc.) and baked in an electronic box oven at 143 ℃ (290 ° f) for 20 minutes and allowed to air cool, providing a film thickness of 38-63 microns (1.5-2.5mil) for each layer, resulting in a 76-126 micron (3.0-5.0mil) total powder basecoat.

The ENVIRACRYL PZC10102 powder clearcoat was applied to the above combination of basecoats by electrostatic spraying and baked in an electronic box oven at 169 deg.C (335 deg.F) for 30 minutes to provide a clearcoat film having a film thickness of 50-75 microns (2.0-3.0 mil).

Example B

Preparation of electrodeposited primer/powder basecoat/powder accept coat/powder clearcoat

Example B1

ENVIRORON PZB90100 black powder basecoating was applied to the pretreated and electrodeposited primer panel by electrostatic spraying to give a 38-63 micron (1.5-2.5mil) film. The panels were then coated with a second powder coating containing an accept pigment (ENVIROCRON PZB43102 powder basecoating from PPGIndustries, inc.) and baked in an electronic box oven at 143 ℃ (290 ° f) for 20 minutes and allowed to air cool, providing a film of 38-63 microns (1.5-2.5mil) for each layer, resulting in a 76-126 micron (3.0-5.0mil) total powder basecoat.

ENVIRACRYL PZC10102 powder clearcoat was applied to the above combination of basecoats by electrostatic spraying and baked in an electronic box oven at 169 deg.C (335 deg.F) for 30 minutes to give clear coat films with film thicknesses of 50-75 microns (2.0-3.0 mil).

Example B2

ENVIRORON PZB90100 black powder basecoating was applied to the pretreated and electrodeposited primer panel by electrostatic spraying and baked at 143 deg.C (290 deg.F) for 20 minutes to give a 38-63 micron (1.5-2.5mil) film.

The panels were then coated with a second powder coating containing an accept pigment (ENVIROCRON PZB43102 powder basecoating from PPGIndustries, inc.) and baked in an electronic box oven at 143 ℃ (290 ° f) for 20 minutes and allowed to air cool, providing a film thickness of 38-63 microns (1.5-2.5mil) for each layer, resulting in a 76-126 micron (3.0-5.0mil) total powder basecoat.

ENVIRACRYL PZC10102 powder clearcoat was applied to the above-described primed panels by electrostatic spraying and baked in an electronics box oven at 169 deg.C (335 deg.F) for 30 minutes to give clear coat films with a film thickness of 50-75 micrometers (2.0-3.0 mils).

Example C

Preparation of powder base coat/powder acid coat/liquid clear coat

Example C1

ENVIRORORON PZB90100 black powder basecoating was applied to the pretreated panel by electrostatic spraying to give a 38-63 micron (1.5-2.5mil) film. The panels were then coated with a second powder coating containing an accept pigment (ENVIROCRON PZB43102 powder basecoating from PPG Industries, inc.) and baked in an electronic box oven at 169 ℃ (335 ° f) for 30 minutes and allowed to air cool, providing a film thickness of 38-63 microns (1.5-2.5mil) for each layer, resulting in a 76-126 micron (3.0-5.0mil) total powder basecoat.

The PPG CNCT-10 solvent-based clear composition (available from PPG Industries, Inc.) was then applied to the primed panel by spray application and baked at 121 deg.C (250 deg.F) for 30 minutes to give a film thickness of 38-64 micrometers (1.5-2.6 mils).

Example C2

ENVIRORON PZB90100 black powder basecoating was applied to the pretreated panel by electrostatic spraying and baked at 143℃ (290F) for 20 minutes to give a 38-63 micron (1.5-2.5mil) film. The panels were then coated with a second powder coating containing an accept pigment (ENVIROCRON PZB43102 powder basecoating from PPG Industries, inc.) and baked in an electronic box oven at 143 ℃ (290 ° f) for 20 minutes and allowed to air cool, providing a 38-63 micron (1.5-2.5mil) film for each layer, resulting in a 76-126 micron (3.0-5.0mil) total powder basecoat.

The PPG CNCT-10 solvent-based clear composition was then applied to the powder primed panels by spray application and baked at 121 deg.C (250 deg.F) for 30 minutes to give a film thickness of 38-64 micrometers (1.5-2.6 mil).

Example D

Preparation of electrodeposited primer/powder basecoat/powder accept coat/liquid clearcoat

Example D1

ENVIRORON PZB90100 black powder basecoating was applied to the pretreated and electrodeposited primer panel by electrostatic spraying to give a 38-63 micron (1.5-2.5mil) film. The panels were then coated with a second powder coating containing an accept pigment (ENVIROCRON PZB43102 powder basecoating from PPGIndustries, inc.) and baked in an electronic box oven at 169 ℃ (335 ° f) for 30 minutes and allowed to air cool, providing a film of 38-63 microns (1.5-2.5mil) for each layer, resulting in a 76-126 micron (3.0-5.0mil) total powder basecoat.

The PPG CNCT-10 solvent-based clear composition was then applied to the powder basecoat by spray application and baked at 121 deg.C (250 deg.F) for 30 minutes to give a film thickness of 38-64 microns (1.5-2.6 mil).

Example D2

ENVIRORON PZB90100 black powder basecoating was applied to the pretreated panel by electrostatic spraying and baked at 143℃ (290F) for 20 minutes to give a 38-63 micron (1.5-2.5mil) film. The panels were then coated with a second powder coating containing an accept pigment (ENVIROCRON PZB43102 powder basecoating from PPG Industries, inc.) and baked in an electronic box oven at 143 ℃ (290 ° f) for 20 minutes and allowed to air cool, providing a 38-63 micron (1.5-2.5mil) film for each layer, resulting in a 76-126 micron (3.0-5.0mil) total powder basecoat.

The PPG CNCT-10 solvent-based clear composition was then applied to the powder basecoat panels by spray application and baked at 121 deg.C (250 deg.F) for 30 minutes to give a film thickness of 38-64 microns (1.5-2.6 mil).

Control (comparison)

Liquid waterborne HWB 190430 base coat (available from PPG Industries, Inc.) containing pigmented mica pigments was applied to the electrodeposited primed panel by spray application and the panel was baked at 121 ℃ (250 ° f) for 10 minutes in an electronic box oven and allowed to air cool, providing a film thickness of 20-38 microns (0.8-1.5 mil).

The PPG CNCT-10 solvent-based clear composition was then applied to the powder basecoat by spray application and baked at 121 deg.C (250 deg.F) for 30 minutes to give a film thickness of 38-64 microns (1.5-2.6 mil).

Panel comparison

Tables 1-4 below show a direct comparison of panels coated by the method of the present invention (examples A, B, C and D, respectively) and panels coated with a commercial paint system (control). The panels prepared by the process of the invention generally corresponded to the control in terms of the following automotive test properties: 20 ℃ gloss (ASTM D523-89), chip resistance (ASTM 3170-03), scratch resistance (Chrysler test LP-463-PB-54-01 Break-old automotive Damage test: 20 ℃ gloss Retention), Dry Cross adhesion (ASTM D3359 method A), moisture resistance (ASTM D1735-02, 240 hours at 100 ℃ F. and 100% relative humidity), durability (24 months Florida Exposure, SAE J1976), and salt spray Corrosion resistance (ASTM B117-95).

TABLE 1

	Example A		Control
				Priming paint layer	Is free of		ED6100H
First base coat layer	ENVIROCRON Powder PZB90100		Liquid-Waterborne HWB 9517
				Accent coating	ENVIROCRON Powder PZB43102		Liquid-Waterborn HWB Clear + mica
Transparent coating	Envi racryl Powder PZC10102		PPG Solvent Borne NCT-10
						Example A1		Example A2	Control
Baking of the base coat		Dry on dry without baking								Flash bake 295 ° F.down 19'	Flash baking 10 'at 250 deg.F'
				Accent coating baking		Flash bake 295 ° F.down 19'		Flash bake 295 ° F.down 19'	Flash baking 10 'at 250 deg.F'
Baking of transparent coatings		Normal baked at 335 ℃ F. 30'								Normal baked at 335 ℃ F. 30'	Normal bake 30 'at 250 ° F'
				20 ℃ gloss ASTM D523-89		80-95		80-95	80-95
Chipping resistance ASTM3170-03 (grade 1 poor/10 good)		7-8								7-8	6-7
				Scratch resistance Chrysler Test LP-463-PB-54-01 (worn automobile Damage Test: 20 ℃ gloss Retention)		60-70％		65-75％	60-70％
Adhesion ASTM D3359 method A Dry Cross adhesion		100％								100％	100％
				Moisture resistance ASTM D1735-02 (100F. 100% relative humidity 240 hours)		100% adhesion, no blistering, no blush, no cracking		100% adhesion, no blistering, no blush, no cracking	100% adhesion, no blistering, no blush, no cracking
Durability (24 month Florida exposure) SAE J197620 ℃ gloss Retention% foam/Corona etch		80-90 none/none mild-moderate								80-88 none/none very slight-slight	80-92 none/none mild-moderate
				Durability (3000Kj Xenon Arc accelerated Exposure) SAEJ197620 ℃ gloss Retention%		90-95		90-95	90-95

Get upBubble/wet halo acid etch	None/none	None/none	None/none
				Corrosion resistance: ASTM B117-95 salt spray 500 hours salt spray scratch creep (mm) cell size/density	3-6mm very small/very small	2-6mm very small/very small	2-6mm very small/very small

TABLE 2

	Example B		Control
				First base coat layer	ENVIROCRON Powder PZB90100		Liquid-Waterborne HWB 9517
Accent coating	ENVIROCRON Powder PZB43102		Liquid-Waterborn HWBClerar + mica
				Transparent coating	Enviracryl Powder PZC10102		PPG Solvent Borne NCT-10
		Example B1						Example B2	Control
				Baking of the base coat		Dry on dry without baking				Flash bake 295 ° F.down 19'	Flash baking 10 'at 250 deg.F'
Accent coating baking		Flash bake 295 ° F.down 19'						Flash bake 295 ° F.down 19'	Flash baking 10 'at 250 deg.F'
				Baking of transparent coatings		Is normalBaking at 335 ℃ F. 30'				Normal baked at 335 ℃ F. 30'	Normal bake 30 'at 250 ° F'
20 ℃ gloss ASTM D523-89		80-95						80-95	80-95
				Chipping resistance ASTM3170-03 (grade 1 poor/10 good)		7-8				7-8	6-7
Scratch resistance Chrysler Test LP-463-PB-54-01 (worn automobile Damage Test: 20 ℃ gloss Retention)		60-70％						65-75％	50-70％
				Adhesion ASTM D3359 method A Dry Cross adhesion		100％				100％	100％
Moisture resistance ASTM D1735-02 (100F. 100% relative humidity 240 hours)		100% adhesionNo bubbling, no blush, and no cracking						100% adhesion, no blistering, no blush, no cracking	100% adhesion, no blistering, no blush, no cracking
				Durability (24 month Florida exposure) SAE J197620 ℃ gloss Retention% foam/blush		80-90 none/none				80-88 none/none	80-88 none/none

Acid etching	Mild-moderate	Very slight-slight	Mild-moderate
				Durability (3000Kj Xenon Arc accelerated Exposure) SAEJ197620 ℃ gloss Retention% bubble/Damp crack	90-95 none/none	90-95 none/none	90-95 none/none
Corrosion resistance: ASTM B117-95 salt spray 500 hours salt spray scratch creep (mm) bubble size/density	2-6mm very small/very small	2-6mm very small/very small	2-6mm very small/very small

TABLE 3

	Example C		Control
				Primer layer	Is free of		ED6100H
First base coat layer	ENVIROCRON Powder PZB90100		Liquid-Waterborne HWB 9517
				Accent coating	ENVIROCRON Powder PZB43102		Liquid-Waterborn HWBClerar + mica
Transparent coating	PPG Solvent Borne NCT-10		PPG Solvent Borne NCT-10
						Example C1		Example C2	Control
Baking of the base coat		Dry on dry without baking								Flash bake 295 ° F.down 19'	Flash baking 10 'at 250 deg.F'
				Accent coating baking		Fully baked at 335 ℃ F. 30'		Fully baked at 335 ℃ F. 30'	Flash baking 10 'at 250 deg.F'
Baking of transparent coatings		Normal bake 30 'at 250 ° F'								Normal roast 250 ° fLower 30'	Normal bake 30 'at 250 ° F'
				20 ℃ gloss ASTM D523-89		80-95		80-95	80-95
Chipping resistance ASTM3170-03 (grade 1 poor/10 good)		7-8								7-8	6-7

Scratch resistance Chrysler Test LP-463-PB-54-01 (worn automobile Damage Test: 20 ℃ gloss Retention)	60-70％	60-70％	60-70％
				Adhesion ASTM D3359 method A Dry Cross adhesion	100％	100％	100％
Moisture resistance ASTM D1735-02 (100F. 100% relative humidity 240 hours)	100% adhesion, no blistering, no blush, no cracking	100% adhesion, no blistering, no blush, no cracking	100% adhesion, no blistering, no blush, no cracking
				Durability (24 month Florida exposure) SAE J197620 ℃ gloss Retention% foam/Corona etch	80-88 none/none mild-moderate	80-88 none/none very slight-slight	80-90 none/none mild-moderate
Durability (3000Kj Xenon Arc accelerated Exposure) SAEJ197620 ℃ gloss Retention% bubble/Damp crack	90-95 none/none	90-97 none/none	90-95 none/none
				Corrosion resistance: ASTM B117-95 salt spray 500 hours salt spray scratch creep (mm) cell size/density	3-6mm very small/very small	2-6mm very small/very small	2-6mm very small/very small

TABLE 4

	Example D	Control
			First base coat layer	ENVIROCRON Powder PZB90100	Liquid-Waterborne HWB 9517
Accent coating	ENVIROCRON Powder PZB43102	Liquid-Waterborn HWBClerar + mica
			Transparent coating	PPG Solvent Borne NCT-10	PPG Solvent Borne NCT-10

	Example D1	Example D2	Control
				Baking of the base coat	Dry on dry without baking	Flash bake 295 ° F.down 19'	Flash baking 10 'at 250 deg.F'
Accent coating baking	Fully baked at 335 ℃ F. 30'	Fully baked at 335 ℃ F. 30'	Flash baking 10 'at 250 deg.F'
				Baking of transparent coatings	Normal bake 30 'at 250 ° F'	Normal bake 30 'at 250 ° F'	Normal bake 30 'at 250 ° F'
20 ℃ gloss ASTM D523-89	80-95	80-95	80-95
				Chipping resistance ASTM3170-03 (grade 1 poor/10 good)	7-8	7-8	6-7
Scratch resistance Chrysler TestLP-463-PB-54-01 (worn automobile Damage test: 20 ℃ gloss Retention)	60-70％	65-75％	60-70％
				Adhesion ASTM D3359 method A Dry Cross adhesion	100％	100％	100％
Moisture resistance ASTM D1735 (100F. 100% relative humidity 240 hours)	100% adhesion, no blistering, no blush, no cracking	100% adhesion, no blistering, no blush, no cracking	100% adhesion, no blistering, no blush, no cracking
				Durability (24 month Florida exposure) SAE J197620 ℃ gloss Retention% foam/Corona etch	80-90 none/none mild-moderate	80-89 none/none very slight-slight	80-92 none/none mild-moderate
Durability (3000Kj Xenon Arc accelerated Exposure) SAEJ197620 ℃ gloss Retention% bubble/Damp crack	90-95 none/none	90-95 none/none	90-95 none/none
				Corrosion resistance: ASTM B117-95 salt spray 500 hours salt spray scratch creep (mm) cell size/Density	2-6mm very small/very small	3-6mm very small/very small	2-6mm very small/very small

The above comparative examples show that the coating process of examples a-D of the present invention is very advantageous compared to conventional coating systems. The coating system of the present invention can be used with or without an electrolessly deposited primer, which provides greater flexibility than conventional coating processes, particularly in terms of efficiency and cost.

It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention, as defined by the appended claims.

Claims (20)

1. A method of forming a composite coating on a surface of a substrate, the method comprising the steps of:

(a) applying a first powder basecoating composition to the surface of the substrate to form a first basecoat;

(b) applying a second powder basecoating composition to the first basecoat to form a second basecoat;

(c) applying a liquid or powder topcoat coating composition to the second basecoat to form a transparent topcoat and, in turn, a composite coating; and

(d) heating the composite coating to substantially cure the composite coating;

wherein the applying and heating steps are performed in any one of the following ways:

(1) applying a second basecoat composition comprising an effect pigment in flake or platelet form to the first basecoat layer prior to heating the first basecoat layer, and then heating the first and second basecoat layers at a temperature and for a time period sufficient to melt and substantially level the second basecoat composition and allow the effect pigment to migrate to the surface area of the second basecoat layer, but not sufficient to cause the second basecoat layer to cure; and

(2) applying a topcoat coating composition over the second basecoat layer after the heating step and heating the resulting composite coating layer at a temperature and for a time period sufficient to cure substantially the entire composite coating layer;

or alternatively

(3) Applying a first basecoating composition to the substrate to form a first basecoat layer, and heating the first basecoat layer at a temperature and for a time period sufficient to melt and form a substantially continuous film of the first basecoat layer;

(4) applying a second basecoat composition comprising an effect pigment to the substantially cured first basecoat layer to form a second basecoat layer, and heating the second basecoat layer for a time period sufficient to melt and substantially level the second basecoat composition and allow the effect pigment to migrate to a surface area of the second basecoat layer; and

(5) applying a topcoat coating composition to the second basecoat layer, and heating the resulting composite coating at a temperature and for a time sufficient to substantially cure the composite coating.

2. The method of claim 1, wherein the first primer layer has a thickness ranging from about 0.5 to about 4.0 mils prior to heating.

3. The method of claim 1, wherein the thickness of the second primer layer ranges from about 0.5 to about 4.0 mils prior to heating.

4. The method of claim 1, wherein the topcoat has a thickness ranging from about 0.5 to about 4.0 mils prior to heating.

5. The method of claim 1, wherein in step (1), the first and second primer layers are heated at a temperature of about 110 ℃ to about 170 ℃ for a period of about 4 to about 40 minutes.

6. The method of claim 1, wherein in step (2), the composite coating is heated at a temperature of about 150 ℃ to about 190 ℃ for a period of time of about 20 to about 40 minutes.

7. The method of claim 1, wherein in step (3), the first primer layer is heated at a temperature of about 110 ℃ to about 170 ℃ for a period of time of about 4 to about 40 minutes.

8. The method of claim 1, wherein in step (4), the composite coating is heated at a temperature of about 110 ℃ to about 170 ℃ for a period of about 4 to about 40 minutes.

9. The method of claim 1, wherein in step (5), the composite coating is heated at a temperature of about 150 ℃ to about 190 ℃ for a period of time of about 20 to about 40 minutes.

10. The method of claim 1, wherein the first powder basecoating composition and the second powder basecoating composition each comprise at least one independently selected thermally curable film-forming material and at least one independently selected curing agent.

11. The method of claim 10 wherein the thermally curable film-forming material is selected from the group consisting of acrylics, polyesters, polyurethanes, epoxies, and mixtures thereof.

12. The method of claim 11, wherein the thermally curable film-forming material is a polymer having reactive functional groups selected from the group consisting of hydroxyl, carboxylic acid, epoxy, carbamate, amide, carboxylate, and combinations thereof.

13. The method of claim 1 wherein at least one of the first or second basecoating compositions further comprises at least one reaction product of at least one cyclic carboxylic acid anhydride, at least one olefin, and at least one reactant selected from the group consisting of primary amines, aliphatic polyamines, primary amino alcohols, isocyanates, and combinations thereof, wherein the number average molecular weight of the reaction product ranges from 1000-.

14. The process of claim 13, wherein the cyclic carboxylic acid anhydride is selected from the group consisting of maleic anhydride, itaconic anhydride, citraconic anhydride, vinyl succinic anhydride, and vinyl trimellitic anhydride.

15. The process of claim 13 wherein the olefin is selected from the group consisting of cyclic olefins, alpha-olefins, vinyl monomers, acrylates or methacrylates, and mixtures thereof.

16. The method of claim 1, wherein at least one of the first or second basecoating compositions further comprises at least one flow control agent.

17. The method of claim 16 wherein the flow control agent is an acrylic polymer flow control agent selected from the group consisting of polylauryl acrylate, polybutyl acrylate, poly (2-ethylhexyl) acrylate, poly (ethyl-2-ethylhexyl) acrylate, polylauryl methacrylate, polyisodecyl methacrylate, and copolymers thereof.

18. The method of claim 17 wherein the acrylic polymer flow control agent is a copolymer of 2-ethylhexyl acrylate and butyl acrylate.

19. The method of claim 1, wherein the topcoat coating composition is a powder coating composition.

20. The method of claim 1, wherein the topcoat coating composition is a liquid coating composition.