Epoxy functional acrylic coating powders and powder coatings therefrom having filiform corrosion resistance

The present invention relates to thermosetting coating powders of epoxy functional acrylic copolymers containing a copolymerization product of one or more hydrophobic acrylic monomers and one or more epoxies, and filament resistant coatings made therefrom. More particularly, the invention relates to coating powders comprising as an ingredient epoxy functional acrylic copolymer, which is an epoxy functional acrylic copolymer or a mixture of such a copolymer with one or more second copolymer, as well as coatings resistant to filamentous corrosion, e.g. coated wheels of aluminum or a light alloy.

[0002] The unshielded parts of the metal wheels of a moving car are subjected to the momentum of fine-grained materials that rubs off the protective coating. You need a hard and durable membrane. The ideal film should be non-porous and maintain high metal adhesion to prevent corrosion from spreading between the film and metal. However, the appearance of filiform corrosion precedes any signs of decay, e.g. visible pitting corrosion in the coating penetrating the metal surface of the organic coating is not necessary for the development of filiform corrosion. For example, protective acrylic and polyester transparent coatings of coating powders with comparable film thickness were used on aluminum wheels before the present invention. It was observed that such coatings did not prevent filiform corrosion over time, even if the coating itself did not experience visually unacceptable damage.

[0003] Currently, transparent coatings applied to aluminum wheels are applied to surfaces subjected to chromium-free pretreatment, such as treatment by applying a monoatomic layer (SAM), which maintains the bright color of the aluminum wheels. This type of pre-treatment avoids highly toxic treatment with hexavalent chromium; however, aluminum wheels and hubcaps having transparent acrylic powder coatings with epoxy functional groups do not provide resistance to filiform corrosion on pretreated wheels and hubcaps without the use of hexavalent chromium, resulting in unacceptable rejection rates. Such coatings provide the desired chemical resistance, scratch resistance and weathering.

[0004] Polyester transparent coatings of coating powders on wheels and hubcaps pretreated with hexavalent chromium provide adequate resistance to filiform corrosion. However, polyester powder coatings must be applied with a liquid to ensure adequate chemical, scratch and weather resistance.

[0005] Powder compositions of epoxy acrylic resins are known. St. Patents U.S. Patent Nos. 5,407,707 and 5,663,240, both to Simone et al., Are suitable references disclosing conventional coating powders containing epoxy functional acrylic polymers. Such compositions provide good appearance when applied to a colored coating, but do not provide sufficient resistance to atmospheric agents. In addition, DE 22 61 392 A1, belonging to Ford Werke AG, discloses powders for flexible products formed from glycidyl acrylic copolymers. Powders are not adapted to create coatings and do not provide resistance to atmospheric agents of products formed to weathering.

[0006] The publication of the patent application US 2007/0078235 A1, belonging to Lu et al., Discloses coating powders containing copolymers of glycidyl (meth) acrylate and caprolactone (meth) acrylate aimed at giving compatibility, renovation possibilities, flexibility and dispersion of pigments in coatings powder. However, the publication by Lu et al. does not disclose eye coating powders that would provide eye coatings having better thread corrosion resistance than conventional transparent epoxy functional acrylic coating powders.

[0007] Current inventors are looking for a solution to the problem of providing acrylic coating powders for producing filament-resistant coatings for aluminum, light metal alloy or metal substrates without compromising coating smoothness, transparency or stability of the coating powder, especially in powder coatings for wheels and car wheel hubcaps made of aluminum or a light-alloy alloy pretreated with hexavalent chromium.

Summary of the Invention [0008] The invention is in all aspects set out in the appended claims.

[0009] According to the invention, coating powders providing resistance to filiform corrosion in transparent coatings or transparent colored powder coatings containing as an ingredient an epoxy functional acrylic copolymer which is an epoxy functional acrylic copolymer or a mixture of two or more copolymers, a copolymer component acrylic with epoxy functional groups having a Tg from 40 ° C to 90 ° C and containing, as copolymerized monomers, i) from 10 to 40 wt. one or more epoxy functional unsaturated monomer, e.g. glycidyl (meth) acrylate; ii) from 2.0 wt. up to 13% by weight, or 12% by weight or less, or preferably, 8.0% or less, more preferably, 6.0 wt. or less one or more hydrophobic acrylic monomers that have a water solubility of 3.5 g / l or less and which would themselves form a homopolymer having a glass transition temperature (T_g) 50 ° C to 175 ° C, and iii) the residue of one or more nonionic comonomers that are different from the hydrophobic acrylic monomer ii), preferably a nonionic comonomer which has a water solubility of 30 g / L or less ii),% wt. each monomer based on the total weight of copolymerized monomers in the epoxy functional acrylic copolymer component; and one or more crosslinkers for the acrylic copolymer. Optionally, the coating powder additionally contains one or more excipients selected from hydrophobic submicron particles, adhesion promoter, light stabilizer and ultraviolet (UV) absorber. Preferably, the epoxy functional acrylic copolymer component contains 12 wt. or less, or preferably 8.5 wt. or less of an aromatic vinyl monomer iv), based on the total weight of copolymerized monomers in the epoxy functional acrylic copolymer component.

[0010] In one embodiment, when the epoxy functional acrylic copolymer component comprises one epoxy functional acrylic copolymer, the coating powder further comprises one or more excipients selected from hydrophobic submicron particles, adhesion promoter, light stabilizer and ultraviolet absorber ( UV).

[0011] Preferably, the hydrophobic acrylic monomer ii) comprises bicycloalkyl meth (acrylate) such as isobornyl (meth) acrylate or / and dicyclopentadienyl meth (acrylate). [0012] In another embodiment, the coating powders comprise an epoxy functional acrylic copolymer component which is a mixture of two or more copolymers, and one or more crosslinkers. Mixtures of copolymers may contain epoxy functional acrylic copolymer and one or more second copolymers selected from epoxy functional acrylic second copolymers, a product of the copolymerization of one or more carboxyl functional monomers and one or more nonionic comonomers, a copolymerization product of one or more phosphoric acid functionalized monomers and one or more nonionic comonomers, and mixtures and combinations thereof.

[0013] The coating powder may additionally contain one or more adhesion promoters, such as epoxy resin.

[0014] Preferably, the second copolymer is substantially free of copolymerized hydrophobic acrylic monomer (ii); i.e., the hydrophobic acrylic monomer ii) constitutes 2.0 wt. or less, based on the total weight of the copolymerized monomer in the copolymer.

[0015] Preferably, the epoxy functional acrylic copolymer component comprises a mixture of one or more epoxy functional acrylic copolymers substantially free of copolymerized vinyl aromatic monomer (iv), and one or more second copolymer which contains a copolymerization product of 30% by weight . or less one or more vinylaromatic (iv) comonomers, e.g. styrene or vinyltoluene, based on the total weight of copolymerized monomers in the second copolymer (calculus).

[0016] In another preferred embodiment, the epoxy functional acrylic copolymer component comprises epoxy functional acrylic copolymer and one or more second epoxy functional acrylic copolymer, substantially free of copolymerized hydrophobic acrylic monomer (ii), where the total amount of copolymerized the hydrophobic acrylic monomer (ii) ranges from 2.0 wt. up to 13% by weight, based on the total weight of copolymerized monomers in the epoxy functional acrylic copolymer component. More preferably, the second epoxy-functional acrylic copolymer further comprises in copolymerized form from 30 wt. one or more vinylaromatic monomers iv), based on the total weight of copolymerized monomers in epoxy functional acrylic copolymer.

[0017] Preferably, the one or more crosslinkers are an organic dicarboxylic acid or anhydride or an adduct thereof with a polyester or polyisocyanate.

[0018] Additionally, in accordance with the present invention, a powder coated metal substrate, for example aluminum or a light metal alloy, comprises a coating made of the coating powder of the invention. Preferably, the aluminum or light metal alloy substrate is cleaned and pretreated, for example with zinc phosphate or iron phosphate. The substrates can be, for example, aluminum wheels or automotive hubcaps.

[0019] All terms containing brackets mean a disjoint alternative of the content contained in brackets and the absence thereof. For example, the term "(co) polymer" includes, alternatively, a polymer, copolymer, or a mixture thereof.

[0020] Unless otherwise noted, all processes to which they relate and all examples were carried out under standard temperature and pressure (STP) conditions. [0021] All ranges cited herein are cumulative and cumulative. For example, if the ingredient may be present in amounts of 0.05 wt. or more to 1.0% by weight, and in amounts up to 0.5% by weight, this component may be present in amounts from 0.05% by weight. to 1.0% by weight, from 0.5 to 1.0% by weight or from 0.05 to 0.5% by weight

[0022] The term "average particle size" as used herein will mean, unless otherwise indicated, the diameter of the particles or the largest particle size in the particle distribution determined by laser light scattering using a Malvern Mastersizer ™ 2000 apparatus (Malvern Instruments Inc., Southboro, MA ) according to the procedures recommended by the manufacturer.

[0023] The term "coating powder" as used herein refers to a coating powder composition and the term "powder coating" refers to a coating formed from a coating powder composition.

[0024] As used herein, the term "copolymer" will mean any polymer made from two or more different monomers.

[0025] The term "glass transition temperature" or "Tg" of any resin or (co) polymer as used herein, unless otherwise indicated, is measured by differential scanning calorimetry (DSC) (heating rate 20 ° C per minute), reading Tg as mean at the inflection point. Alternatively, Tg can be calculated as described by Fox in Bull. Amer. Physics. Soc., 1, 3, p. 123 (1956).

[0026] As used herein, the term "hybrid" of any (co) polymer or resin will refer to adducts, grafted or block copolymers, and homogeneous or homogeneous blends of blends of such (co) polymers or resins, such as epoxy-polyester hybrids.

[0027] As used herein, the term "mass solubility" refers to the calculated solubility of a given material in water, calculated using Advanced Chemistry Development (ACD / Labs) V9.04 (© 1994-2007 ACD / Labs), available in Chemical Abstracts' Registry.

[0028] The term "(meth) acrylate" as used herein refers to acrylate or methacrylate and the term "(meth) acrylic" refers to acrylic or methacrylic.

[0029] As used herein, unless otherwise indicated, the term "molecular weight" refers to the number average molecular weight of a polymer, determined by gel permeation chromatography (GPC) with calibration using polystyrene as a standard.

[0030] As used herein, the term "nonionic comonomer" refers to monomers that do not have acidic groups or salts, basic groups or salts, polyial groups (e.g., OH, SH, NH) or condensation crosslinking groups.

[0031] As used herein, the term "organic oligosilane" includes any number of 2 to 20 silicon-containing units, and the prefix "organic polysilane" includes more than 20 silicon-containing units.

[0032] As used herein, the "phosphoric acid group" refers to oxophosphoric acids having a POH residue in which the hydrogen atom can be ionized. The term "phosphoric acid group" also includes salts of oxophosphoric acids, i.e. having a cation such as a metal ion or an ammonium ion, replacing at least one acid proton. Examples of phosphoric acid groups include groups formed from phosphinic acid, phosphonic acid, phosphoric acid, pyrophosphinic acid, pyrophosphoric acid, their partial esters and their salts.

[0033] The term "phr" as used herein means the amount, by weight, of the component per hundred parts of the resin system, in units of mass. The resin system includes a resin or polymer and a crosslinker or hardener.

[0034] The term "polymer" as used herein includes random, block, segmented and graft copolymers, and any mixture or combination thereof.

[0035] As used herein, the terms "resin" and "polymer" are used interchangeably. [0036] The term "resin system" as used herein refers to all epoxy resin, improvement resin and any crosslinking, curing or hardener (but not a catalyst) that becomes an integral part of the crosslinked structure. [0037] The term "substantially free of the (specified) copolymerized monomer" as used herein means that the acrylic copolymer contains 2 wt. or less specified copolymerizable monomer, based on the total weight of the copolymerized monomers.

[0038] As used herein, the term "wt.%" Refers to wt.%.

[0039] Unless otherwise noted, all percentages given herein are by weight.

[0040] Innovative coating powders provide transparent or colored powder coatings that exhibit excellent resistance to thread corrosion on aluminum or light metal alloy substrates, such as automotive wheel substrates, using traditional coating techniques and traditional acrylic copolymer resins that have previously produced powder coatings with an unacceptable frequency of filiform corrosion. Coating powders allow better filament corrosion resistance even in coatings without an adhesion promoter. Accordingly, the coating powders of the invention can significantly reduce the percentage of wheels and hubcaps rejected by customers due to filiform corrosion without a significant increase in the cost of the coating powder or its use. In addition, the coating powders of the present invention provide coatings resistant to filiform corrosion on iron, steel, magnesium alloy and brass substrates.

[0041] The coating powders of the invention contain an epoxy functional acrylic copolymer component which is a copolymer or a copolymer mixture containing, based on the total weight of the copolymerized monomers in the epoxy functional acrylic copolymer component, i) from 10 to 40 wt. one or more epoxy functional unsaturated monomer, e.g. glycidyl (meth) acrylate; ii) from 2.0 wt. up to 13% by weight, or 12% by weight or less, or preferably, 8.0% or less, more preferably, 6.0 wt. or less, one or more hydrophobic acrylic monomers that have a water solubility of 3.5 g / l or less and which would themselves form a homopolymer having a glass transition temperature (T_g) 50 ° C to 175 ° C, and iii) a residue of one or more nonionic comonomers that are different from the hydrophobic acrylic monomer ii). The epoxy-functional acrylic copolymer component may additionally contain copolymerized vinylaromatic monomer iv) in an amount of 3 wt. or more, or 12 wt. or less, or preferably 8.5 wt. or less, based on the total weight of copolymerized monomers in the epoxy functional acrylic copolymer component.

[0042] To make blends containing the copolymer components, the copolymers can be mixed, for example at any time after polymerization, or one copolymer can be copolymerized in the presence of an already formed copolymer.

[0043] Suitable second copolymers for admixing with epoxy functional acrylic copolymer may be selected from epoxy functional acrylic copolymers, epoxy functional vinyl copolymers, carboxyl functional acrylic copolymers, carboxyl functional vinyl copolymers, carboxyl functional vinyl copolymers phosphoric acid functional groups, phosphoric acid functional vinyl copolymers, mixtures and combinations thereof. The amount of one or more second acrylic copolymer, based on the total weight of the acrylic copolymer in the mixture, may range from 1 to 60% by weight, preferably, 10 to 50% by weight, or, more preferably, 40% by weight. or less.

[0044] In embodiments where the second acrylic copolymer comprises a copolymerization product of one or more carboxyl functional acrylic monomers and one or more comonomers, the carboxyl functional acrylic monomer may be used in amounts up to 10 wt.%, Or

0.1 wt. or more, preferably 5 wt. or less, based on the total weight of copolymerized monomers in the copolymer.

[0045] In embodiments where the second acrylic copolymer comprises a copolymerization product of one or more phosphoric acid functional monomers and one or more comonomers, phosphoric acid functional acrylic monomer may be used in amounts up to 5 wt.%, or 0.1 wt. or more, preferably 3 wt. or less, based on the total weight of copolymerized monomers in the copolymer.

[0046] In one embodiment, the epoxy functional acrylic copolymer component comprises a mixture of one or more epoxy functional acrylic copolymers and one or more second copolymer, substantially free of copolymerized hydrophobic acrylic monomer ii). Preferably, the second copolymer comprises a copolymerization product i) from 5 to 80% by weight, based on the total weight of the copolymerized monomers, one or more unsaturated epoxy functional monomers and one or more nonionic comonomers iii).

[0047] In another embodiment, the epoxy functional acrylic copolymer component comprises one or more acrylic copolymers substantially free of copolymerized vinyl aromatic monomer iv), and one or more second copolymer. Preferably, the second copolymer contains from 2 to 30% by weight, or 25% by weight or less copolymerized vinyl aromatic monomer iv), based on the total weight of copolymerized monomers in the second copolymer.

[0048] Other suitable polymer mixtures may comprise, for example, mixtures of one or more acrylic copolymers and a second copolymer selected from epoxy functional acrylic copolymer, substantially free of copolymerized vinyl aromatic monomer iv), carboxyl functional acrylic copolymer, essentially free from a copolymerized vinyl aromatic monomer iv), acrylic phosphoric acid functional copolymer substantially free of copolymerized vinyl aromatic monomer iv), and mixtures thereof.

[0049] Acrylic copolymers are described in more detail as follows:

The epoxy functional acrylic copolymer or mixture of copolymers contains a copolymerization product of 10 to 40 wt. unsaturated monomer with epoxy functional groups, based on the total weight of copolymerized monomers in the epoxy functional acrylic copolymer component. If the amount of unsaturated epoxy functional monomer used is less than 10% by weight, based on the total weight of the copolymerized monomers, it does not contribute significantly to the improvement of solvent resistance and mechanical strength.

On the other hand, if its amount exceeds 40% by weight, no further improvement in corrosion resistance is obtained.

[0050] A preferred epoxy functional acrylic copolymer or mixture of copolymer comprises the product of a copolymerization reaction of one or more epoxy functional monomers and from 2.0 wt. up to 13% by weight, or 12% by weight or less, or preferably, 8.0 wt. or less, or more preferably 6.0 wt. or less, based on the total weight of copolymerized monomers in the epoxy functional acrylic copolymer component, one or more hydrophobic acrylic monomer ii) which has a water solubility of 3.5 g / l or less, preferably 2.5 g / L or less, and which alone would form a homopolymer having a glass transition temperature (T_g) 50 ° C to 175 ° C, preferably 65 ° C or more, preferably bicycloalkyl (meth) acrylate. Maintaining an adequate Tg of acrylic copolymer ensures adequate blocking resistance or packaging stability while maintaining proper flow and film-forming properties.

[0051] To ensure proper resistance to filiform corrosion, the amount of copolymerized vinylaromatic (iv) comonomer such as, for example, styrene, vinyltoluene, α-methylstyrene and other α-alkyl substituted styrenes, in the epoxy functional acrylic copolymer component should in the range from 0 to 12 wt.%, preferably, 10 wt. or less or, more preferably, 8.5 wt. or less, based on the total weight of copolymerized monomers in the epoxy functional acrylic copolymer component. Accordingly, a 50/50 w / w mixture two acrylic copolymers may contain epoxy functional acrylic copolymer containing 0 wt. copolymerized styrene and a second copolymer having up to 24 wt. styrene, based on the total weight of copolymerized monomers in the second copolymer.

[0052] Suitable epoxy functional unsaturated monomers i) for use in the preparation of epoxy functional acrylic copolymer may include, for example, one or more α-glycidyl esters, β-ethylenically unsaturated carboxylic acids, such as (meth) acrylic acid, maleic acid or itaconic, and allyl glycidyl ethers. Preferably, the epoxy functional monomer is selected from glycidyl (meth) acrylate monomers of formula H2C = C (R⁸) C (O) OR⁹where R⁸ is H or lower alkyl and R⁹is a glycidyl terminal, branched or unbranched alkylene residue having from 1 to 4 carbon atoms, i.e. the glycidyl ring is located distally from the unsaturated group. Compounds illustrating this definition of formula (I) are glycidyl acrylate, glycidyl (meth) acrylate and 1,2-epoxybutyl acrylate, preferably glycidyl (meth) acrylate of formula (I) in which R⁸ is methyl and R⁹ is a glycidylmethylene group. Glycidyl (meth) acrylate monomers may contain a mixture of monomers of formula (I). Glycidyl (meth) acrylate can be obtained commercially from Eastman Chemical Co. (Calvert City, KY) or glycidyl (meth) acrylate monomer may be prepared under conventional reaction conditions known to those skilled in the art.

[0053] Suitable hydrophobic acrylic monomers ii) may contain, for example, one or more monomers selected from isobornyl (meth) acrylate, dicyclopentadienyl (meth) acrylate, dihydrocyclopentadienyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate , benzyl (meth) acrylate, phenyl (meth) acrylate and t-butyl (meth) acrylate. These monomers improve the filament corrosion resistance of aluminum-resistant coatings such as aluminum wheels. Preferably, the hydrophobic acrylic monomer is selected from cycloalkyl (meth) acrylates such as dicyclopentadienyl (meth) acrylates and isobornyl (meth) acrylates. Even in the amounts used in the acrylic copolymer of the invention, such bicyclic monomers improve the flow of the acrylic copolymer and the compatibility of the acrylic copolymer containing it with other polymers and resins.

[0054] Suitable nonionic comonomers iii) may include one or more acrylic, vinyl or allyl nonionic monomer, such as, for example, one or more monomers selected from alkyl (meth) acrylates, cycloalkyl (meth) acrylates, alkylaryl acrylates, vinyl esters (meth) acrylates, vinyl vinyl ethers, (meth) acrylonitriles, (meth) acrylamides, dialkyl esters of unsaturated dicarboxylic acids, poly (alkoxylated alkyl) (meth) acrylates having from 1 to 20 alkoxy groups and mixtures thereof. Unless otherwise indicated, nonionic comonomers include hydrophobic comonomers ii) and vinylaromatic (iv) monomers.

Preferably, the nonionic comonomer has a water solubility of 30 g / L or less, or preferably 25 g / L or less. Suitable examples of the comonomer may be selected from C1-C20- (cyclo) alkyl esters of (meth) acrylic acid, such as methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, eicosyl (meth) acrylate and cetyl (meth) acrylate as well as tridecyl (meth) acrylate, and mixtures thereof. Preferably, the comonomer includes one or more (meth) acrylic acid C 1 -C 8 (cyclo) alkyl esters, such as butyl (meth) acrylate and methyl methacrylate. Further, as examples, vinyl monomers may be selected from styrene, α-methylstyrene, α-ethylstyrene, vinyltoluene, divinylbenzene, vinyl esters, e.g. vinyl acetates, vinyl ethers, allyl ethers, allyl alcohols and mixtures thereof.

[0055] Suitable carboxyl functional acrylic copolymers for use in the epoxy functional acrylic copolymer component may be any copolymer having a weight average molecular weight between 1000 and 30,000, and a carboxylic acid equivalent weight of 300 to 1000, preferably at least 500, the product copolymerization from 2.5 to 25% by weight, based on the total weight of copolymerized monomers, one or more α, β-ethylenically unsaturated carboxylic acids, and one or more nonionic comonomers. Examples of suitable carboxy-functional acrylic copolymers are Joncryl ™ 819 and Joncryl ™ 821 from BASF Corporation, Wyandotte, MI.

[0056] Suitable α, β-ethylenically unsaturated carboxylic acid monomers for the production of carboxyl functional acrylic copolymers may include, for example, acrylic acid, methacrylic acid, acryloxypropionic acid, crotonic acid, fumaric acid, fumaric acid monolacyl esters, maleic acid, maleic acid monoalkyl esters, itaconic acid, itaconic acid monoalkyl esters and mixtures thereof.

[0057] Phosphoric acid functional acrylic copolymers for use in the epoxy functional acrylic copolymer component may include a copolymerization product i) from 0.5 wt. up to 10% by weight, preferably 1 to 5% by weight, based on the total weight of copolymerized monomers, one or more monomers with phosphorus groups and one or more nonionic comonomers. Acrylic phosphoric acid functional copolymers may further contain a copolymerization product of up to 10 wt.%, Preferably 1 to 5 wt.%, Based on the total weight of copolymerized monomers, one or more α, β-ethylenically unsaturated carboxylic acids. The acrylic copolymer may include mixtures of one or more phosphoric acid functional copolymers and one or more epoxy functional acrylic copolymers.

[0058] A suitable phosphoric acid monomer for the preparation of phosphoric acid functional acrylic copolymers may be any α, β-ethylenically unsaturated carboxylic acid having a phosphoric acid group, which may be in the form of an acid or salt of phosphoric acid. Phosphoric acid monomers may include, for example, phosphoalkyl (meth) acrylates, such as phosphoethyl (meth) acrylate, phosphopropyl (meth) acrylate, phosphobutyl (meth) acrylate; phosphoalkyl crotonates, phosphoalkyl maleates, phosphoalkyl fumarates, phosphodialkyl (meth) acrylates, phosphodialkyl crotonates, vinyl phosphates and (meth) allyl phosphate. Phosphoalkyl methacrylates are preferred. Other suitable phosphoric acid monomers may include functional dihydrophosphate monomers such as allumphosphate, fumarate mono- or diphosphate or bis (hydroxymethyl) itaconate; functional phosphonate monomers, including, for example, vinyl phosphonic acid, allyl phosphonic acid, 2-acrylamido-2-methylpropane phosphonic acid, α-phosphonostyrene, 2-methylacrylamido-2-methylpropane phosphonic acid; 1,2-ethylenically unsaturated (hydroxy) phosphinylalkyl (meth) acrylates monomers; and oligomeric phosphoric acid monomers such as diphosphononoalkyl (meth) acrylates, i.e. (meth) acryloyloxyalkyl diphosphonate, triphosphonoalkyl (meth) acrylates, and metaphosphomonoalkyl (meth) acrylates and polyphosphonoalkyl (meth) acrylates.

[0059] Suitable acrylic copolymers with functional phosphoric acid can be prepared by first forming a polymer precursor containing a pending first reactive epoxy group that can react with a compound containing a second reactive group and a phosphoric acid group. For example, a precursor polymer can be prepared using glycidyl (meth) acrylate. Suitable second reactive groups in a compound containing a second reactive group and a phosphoric acid group may be amino, hydroxyl and phosphoric anhydride. The epoxy-precursor polymer may be reacted with polyphosphoric acid or glyphosate to generate an acrylic copolymer with phosphoric acid functional groups with internal phosphoric acid waiting groups.

[006] Any suitable acrylic copolymers can be made by conventional polymerization methods in the presence of a thermal or redox initiator. Polymerization in an organic solvent can be carried out in the case of epoxy functional acrylic copolymers. In other cases, emulsion polymerization in water may be carried out.

[0061] The coating copolymer powders according to the invention also contain one or more crosslinking compounds, preferably a flexible crosslinking compound. The crosslinking compound is added in stoichiometry of 0.7 to 1.3: 1 acid to the epoxy in the acrylic copolymer, preferably 0.95 to 1.05: 1, and the appropriate amounts of crosslinking compound may range from 5 to 35% by weight. , calculated on the total weight of the coating powder. Suitable crosslinking compounds can be any compounds that react with epoxy groups without causing yellowing in the product coating, for example di- or polyacids, anhydrides and dihydrides. Preferred crosslinking compounds may be organic dicarboxylic acids and their anhydrides such as sebacic acid and dodecanediolic acid and adducts obtained by esterification of organic dicarboxylic acids or anhydrides with polyesters or polyols.

A crosslinking compound can help improve the breakability of coatings made of coating powder.

[0062] The coating powder may additionally contain one or more adhesion promoters including an epoxy resin or an isocyanate compound or a prepolymer having a Tg of 40 ° C or higher, such as, for example, epoxy resins, epoxyphenol novolac resins, dimers and trimers of isophorone diisocyanate (IPDI ), hexamethylene diisocyanate (HMDI) or toluene diisocyanate, block isocyanates such as IPDI block caprolactam, and isocyanate-terminated diisocyanate prepolymers or their dimers or trimers with polyol or glycol. Preferred adhesion promoters are bisphenol epoxy resins, more preferably bisphenol A or bisphenol F epoxy resins. Suitable amounts of adhesion promoter may range up to 10 wt.%, Based on the total weight of the coating powder, preferably from 0.2 to 3 wt%, or more preferably up to 1 wt% Amounts above 3 wt. may contribute to weathering problems.

[0063] To enhance the resistance to filiform corrosion, the coating powder may further contain up to 1.5 wt.%, Based on the total weight of the coating powder, of one or more hydrophobic submicron particles, such as inorganic oxides, e.g. metal oxide or silica , and an organic silicon compound, e.g., polydimethylsiloxane (PDMS) in a mixture with finely divided silica.

[0064] Hydrolysable silanes, e.g. alkoxysilanes, may be used in amounts of from 0.01 to 3% by weight, preferably 0.3% by weight or less, based on the total weight of the coating powder, to combine with the fillers and pigments of inorganic oxides into the coating matrix. Examples of suitable silanes include glycidyl alkoxysilanes and amino alkoxysilanes such as glycidyl trimethoxysilane.

[0065] Coating powder compositions further include one or more light stabilizers or ultraviolet (UV) absorbing compounds that enhance resistance to weathering. Light stabilizers or UV absorbing compounds can be used in amounts of 1 to 15 phr, preferably up to 5 phr. Suitable light stabilizers include, for example, sterically hindered amines such as poly (alkanoyl piperidine alcohols), e.g. dimethyl succinate oligomers with 4-hydroxytetramethylpiperidine ethanol, sterically hindered phenols or combinations thereof; suitable UV absorbing compounds include, for example, benzotriazoles, oxalic acid diarylamides and 2-hydroxybenzophenone.

[0066] Small amounts, for example up to 0.10 wt.%, Based on the total weight of the coating powder, preferably, up to 0.05 wt.%, Of organic pigments, such as phthalocyanines, may be incorporated to control yellowing. The coating powder may additionally contain from 0.001 to 1.0% by weight, based on the total weight of the coating powder, optical brighteners and / or leveling agents; from 0.1 to 10 phr, based on the total weight of the coating powder, one or more matting agents, such as copolymers of alkyl (meth) acrylates, up to 6 phr of one or more wax; and from 0.01 to 1.0% by weight, based on the total weight of the coating powder, auxiliaries added after mixing, such as flow agents such as silica and finely divided alumina. [0067] Coating powders according to the invention are produced by traditional methods. The ingredients can be blended and then mixed thoroughly, e.g. by melt mixing, so that no significant hardening occurs. The molten compound may be extruded and, after extrusion, rapidly cooled, then comminuted, and, if necessary, sorted into particles by size. Alternatively, coating powders can be prepared by combining particles containing an acrylic copolymer with hydrophobic submicron particles to form particle agglomerates.

[0068] Coating powders can be applied by conventional means. For electrostatic coating, the average particle size may be in the range of 5 to 200 μm or more, preferably 25 μιτι or more, or, 75 μm or less. [0069] Suitable substrates may include, for example, aluminum, light metal alloys, iron, steel, magnesium alloy, such as electronic and brass articles, such as door locks and fittings. Aluminum substrates may include, for example, aluminum silicon alloys, aluminum lithium alloys, aluminum magnesium, aluminum zinc, aluminum manganese and aluminum and copper based alloys, such as aluminum bronze. The alloys can be single, double or contain more than two metals. [0071] Preferably, the substrates are pre-treated. Aluminum and light metal alloy substrates may be pretreated, for example, with a self-assembled layer of organic phosphorus material, zirconium titanates or acrylate-modified zirconate titanates. Steel and aluminum substrates can be pre-treated with passivators such as zinc phosphate or iron phosphate. [0072] The following examples illustrate the usefulness of the present invention.

Examples: Test methodology [0073] Coating thickness: The thickness of the dried coating was measured using a POSITECTOR ™ Model 6000-FN 1 coating thickness gauge from DeFelsko Corporation, Ogdensburg, NY, the coating thickness was measured in accordance with ASTM D 1400-00 "Standard Test Methods for Nondestructive Measurement of Dry Film Thickeness of Nonconductive Coatings Applied to a Nonferrous Metal Base ”, 2000. The coating thickness is defined as the range (from low to high) of three readings measured in the middle of the sheet.

[0074] Rub resistance with methyl ethyl ketone (MEK): The applicator with the cotton cap is immersed in MEK and rubs the surface of the test coating a total of 50 times using 2.6 cm pulls under 2-2.5 kg pressure. One back and forth movement is equivalent to one double rub. The applicator is saturated with MEK during 50 double rubs. Coatings showing MEK resistance rated 4-5 have acceptable curing, physical properties, and solvent resistance. The tested sheets are evaluated as follows:

TABLE 1: MEK assessment card

<td>Rating resistance to rubbing MEK</td><td>attrition</td><td>Indicator strength chemical</td><td>Comments</td>

<td> 5</td><td>Lack</td><td>Perfect</td><td>No abrasion coating pigmentation; no softening or dull surface shell</td>

<td> 4</td><td>Light</td><td>Very good</td><td>Slight abrasion of the coating or pigmentation</td>

<td> 3</td><td>moderate</td><td>Satisfactory to good</td><td>Moderate abrasion coating or pigmentation</td>

<td> 2</td><td>Serious</td><td>Weak to satisfactory</td><td>Serious abrasion coating or pigmentation</td>

<td> 1</td><td>extreme</td><td>Very weak or no</td><td>Extreme abrasion of the coating or pigmentation, total chafing through the coating to ground</td>

[0075] Mesh crack resistance: To determine the relative resistance of a transparent powder coating when exposed to isopropyl alcohol, powder coated substrates were bent over a 165 ° tang. The sheets obtained are deflected 30 to 45 ° from the level, and isopropyl alcohol is applied to the coating at the place of maximum curvature. Immediately after this, the treated surface was observed for cracks. The reference point for the observed cracks was the perpendicular axis. A minute after applying isopropyl alcohol, visual inspection is made and the degree of cracking is noted.

[0076] Cut-out adhesion test: Coatings were tested according to the adhesion test method published by the American Society for Testing and Materials (ASTM) using method D3359-02, "Standard Test Methods for Measuring Adhesion by Tape Test", Test Method B - Cross-Cut Tape test (2002). The principle of measuring with this method is to cut the film into a grid pattern at specific distances and seal the cut surface with Permacel # 99, and then peel off the tape immediately. The surface is then observed to determine if the paint has loosened or removed and the surface is evaluated.

[0077] The 5B rating is an excellent rating, it requires that no coating be removed. A rating of 0B would indicate that 65% or more of the coating was removed, thereby indicating poor adhesion of the coating to the substrate. The minimum rating for acceptance of adhesion is 3B.

[0078] Chemical tests: reference fuel B and leaching fluid: A cotton swab moistened with a suitable solvent for a specified period of time is placed on coated sheets at room temperature, with a crucible on top to inhibit evaporation. In the test with fuel B as a standard (70% isooctane and 30% toluene), a cotton tampon is placed on the substrate for 1 hour, washed with DI water and dried with a paper towel. In the elution test (part No. 8710320, original Volvo), a mixture of 50% methyl acetate and 50% ethanol on a cotton tampon is placed on the substrate for 2 hours, washed with DI water and dried with a paper towel. The evaluation takes place 24 hours after the test. The film surface of the coating is rated for swelling on a scale of 0 to 3, with "0" meaning no signs of swelling, and "3" means severe swelling, and is also evaluated for discoloration from 0 to 3, where "0" means no discoloration, and "3" means severe discoloration of the paint coating. "Meets" means no surface change or softening. The coating is then subjected to an adhesion test. To pass the test, it should not be possible to remove the surface coating with a nail scratch.

[0079] Corrosion tests in atomized brine acidified with acetic acid with the addition of copper accelerator (CASS) DIN ISO EN 9227 (10/2006). The corrosion resistance tests of powder coatings applied to the substrate and at a certain thickness, presented in tables 3, 4 and 5 below, were carried out by cutting, in parts of the circles, two cuts per part (minimum cut length 100 mm), with a minimum distance between cuts 20 mm and cut width 1 mm, with the help of a Sikkens 1 mm / Erichsen model 463 hand-cutting device, deep into the coating to the metal substrate (Erichsen, Hemer, Germany) and placing a maximum of 20 samples of wheel parts in a saline spray chamber (Weiss Umwelttechnik GmbH, Reiskirchen, Germany, Type SC 1000 tester with saline spray) equipped with a pressure filtered air atomizer equipped with an acrylic glass nozzle and a deionized water saturation tower ( DI) adapted to receive 1.5 ml / h ± 0.5 ml / h, for every 80 cm² the ground surface of the wheel parts, a solution of 50 ± 5 g / l sodium chloride (NaCl) and

0.26 ± 0.02 g / l copper (II) chloride dihydrate (CuCl2^.2H2O) in DI water having a pH of

3.1 to 3.3 (VIN 50021 CASS solution) at 50 ° C ± 2 ° C for 24 hours. The thread lengths on each sample are measured with a metric ruler, average creep (thread length) and maximum creep (longest thread length) are noted in Tables 4 and 5 below.

[0080] Resistance to filamentous corrosion PPAP3002 (TA762) according to the Daimler DC procedure:

To measure the resistance to filiform corrosion in coated wheel parts, the procedure according to DIN ISO EN 9227 CASS was followed, without spraying. The samples obtained were then placed directly in RH 82% at 60 ° C for 672 hours. The thread lengths on each sample are measured with a metric ruler and the average creep (thread length) and maximum creep (longest thread length) are noted in Table 3 below.

[0081] Resistance to chipping before / after CASS: (DIN 55996-1B, April 2001). Both before and after the CASS test, the coated substrates were subjected to firing with 4-5 mm steel gravel in accordance with DIN EN ISO 11124-2 (2002) in the Erichsen model 508 sand test chamber (Erichsen, Hemer, Germany). The described range of K values ​​from 0.5 to 5, with an increase of 0.5 points, representing the degree of chipping and percentage surface damage, was evaluated by comparing with ten (10) photographs of the "K" standards in DIN 55996-1. K values ​​refer to the proportion of the damaged surface area. A lower K value is better; A value of K 2.0 or higher passes the test.

[0082] Appearance / Smoothness: They were evaluated by comparing the coatings with the standard Powder Coatings Institute (PCI) sheets, a score of 1 (poor) is rated as severe orange peel, and 10 means the highest smoothness rating.

[0083] QUV-B: The initial gloss and color (colorimetrically) of each coated sheet was evaluated, and then the sheets were exposed to radiation at an average wavelength of 313 nm for 3000 hours in a UV-B tester made by Pausch Messtechnik GmbH (Haan, Germany) , after which the final change in gloss and color was evaluated

Examples 1 (compare) to 5: Preparation and use [0084] Coating powders were prepared from the ingredients of Example 2 listed in

Table 2 by the method by which the raw materials were mixed in a Prism mixer for 30 seconds at 2100 rpm, then extruded in ZSK30 (Coperion Werner &amp; Pfleiderer,

Stuttgart, Germany) at 400 rpm, torque 15-30% and set drum temperature 90-130 ° C. The resulting molten extruded blend was fed to cooled hardened cast iron rollers to form a solid sheet, which was then granulated into chips. Dry flow aids were mixed with the chips by shaking the bag for 0.25-0.5 min. The shavings after forming the mix were ground to a fine powder in a ZM 100 laboratory mill (Retsch, Wuppertal-Haan, Germany) at 18,000 rpm using a 0.5 mm sieve. The obtained fine powder was sieved through a 125 μf mesh screen and then electrostatically applied to the indicated medium using a Nordson Versa-spray ™ spray gun (Nordson Corp., Amherst, Ohio) to the indicated thickness and then cured at 175 ° C for 20 minutes in an electrically heated laboratory oven to form powder coatings.

[0085] The coating powders of Examples 1 (Comp.), 3, 4 and 5 were prepared by simply melt-mixing the ingredients listed in the table in ZSK25 (Coperion Werner &amp; Pfleiderer, Stuttgart, Germany) at 500 rpm, torque 15- 30% and a set drum temperature of 90-130 ° C. The resulting molten extruded blend was fed to cooled hardened cast iron rollers to form a solid sheet, which was then granulated into chips. Dry flow aids were mixed with the chips by shaking the bag for 0.25-0.5 min. The shavings after forming the mix were ground to a fine powder in a ZM 100 laboratory mill (Retsch, Wuppertal 20 Haan, Germany) at 18,000 rpm using a 0.5 mm sieve. The obtained fine powder was sieved through a 125 μΐΗ screen and then electrostatically applied to the indicated substrate using a GEMA Optiflex-Optistar CG07 spray gun (St. Gallen, Switzerland) until the indicated thickness is obtained, then cured at 175 ° C for 20 minutes in an electrically heated Heraeus UT6025 6120 laboratory oven (Hanau, Germany).

Table 2: Compositions

<td>EXAMPLE</td><td>1 Comp.</td><td> 2</td><td> 3</td><td> 4</td><td> 5</td>

<td>Raw</td><td></td><td colspan="3">Quantity (parts by weight)</td><td></td>

<td>Second copolymer 24 wt. GMA; 40 wt. MMA; 23 wt. BMA, 13% Styrene</td><td> 2250</td><td> 825</td><td> 825</td><td></td><td></td>

<td>Acrylic copolymer with epoxy functional groups 28 wt. GMA; 12 wt. IBOMA; 34 wt. MMA; 22 wt. nBMA; 4 wt. styrene</td><td></td><td></td><td> 825</td><td> 1625</td><td> 1625</td>

<td>Acrylic copolymer with epoxy functional groups 28 wt. GMA; 47 wt. MMA; 8 wt. nBMA; 6 wt. IBOMA; 11 wt. styrene</td><td></td><td> 800</td><td></td><td></td><td></td>

<td>Second copolymer 23 wt. GMA; 38 wt. MMA; 11 wt. nBA, 28% Styrene</td><td> 750</td><td></td><td></td><td></td><td></td>

<td>Sebacic acid</td><td> 552,5</td><td> 310</td><td> 552,5</td><td> 552,5</td><td> 552,5</td>

<td>³Copolymer fluidity modifier acrylic</td><td> 30</td><td> 18</td><td> 30</td><td> 30</td><td> 30</td>

<td>¹benzoin</td><td> 15</td><td> 10</td><td> 15</td><td> 15</td><td> 15</td>

<td>Dioxazine violet</td><td> 0,0018</td><td> 0,0018</td><td> 0,0018</td><td> 0,0018</td><td> 0,0018</td>

<td>⁴benzotriazole</td><td> 15</td><td> 14</td><td> 15</td><td> 15</td><td> 15</td>

<td>Polyester dimethyl succinate with 4-hydroxytetramethylpiperidine-ethanol</td><td> 15</td><td> 14</td><td> 15</td><td> 15</td><td> 15</td>

<td>²Aerosil ™ R-972</td><td> -</td><td> 4</td><td> 4</td><td> 4</td><td> 4</td>

<td>⁵Epoxy-bisphenol A</td><td> -</td><td> -</td><td> -</td><td> -</td><td> 30</td>

<td>Glycidyl trimethoxysilane</td><td> 6</td><td> 6</td><td> 6</td><td> 6</td><td> 6</td>

<td>Fine alumina - dry flow</td><td> 0,20%</td><td> 0,20%</td><td> 0,20%</td><td> 0,20%</td><td> 0,20%</td>

<td colspan="2">1. Benzoin Mi Won, GCA Chemical Corp., Braden</td><td>ABOUT "Π r^-</td><td></td><td></td><td></td>

<td colspan="6">2. Aerosil ™ R-972, dimethyldichlorosilane in a mixture with finely divided</td>

<td colspan="4">silica with approx. 70% methylated hydroxyl groups</td><td colspan="2">on the surface,</td>

<td>Degussa Corp., Parsippany, NJ.</td><td></td><td></td><td></td><td></td><td></td>

<td colspan="4">3. Resiflow ™ PL 200, except Resiflow ™ PW 155 in Ex. 2</td><td colspan="2">Estron Chemical,</td>

<td>Calvert City, NY.</td><td></td><td></td><td></td><td></td><td></td>

<td>4. Tinuvin ™ 928, except Tinuvin</td><td colspan="5">™ 900 in Ex. 2, Ciba Specialty Chemicals,</td>

<td>Tarrytown, NY.</td><td></td><td></td><td></td><td></td><td></td>

<td colspan="4">5. Epikote ™ GT 1003, Hexion Specialty Chemicals, Columbus, OH.</td><td></td><td></td>

Application: Coating powders were applied to:

[0086] Wheel parts in Examples 1 (comp.) To 5: Machined aluminum alloy (Ford 7M2J-1007-AA (AlSi7Mgwa) spoke wheel) consisting of an aluminum alloy doped with 6.5 to 7.5 wt. silicon, from 0.25 to 0.45% by weight Mg, less than 0.10 wt. Fe, less than 0.03 wt. Cu, from 0.06 to 0.07 wt. Zn, 0.14 wt. Ti and 0.02 wt. Mn. Ford Motor Company, Dearborn, MI, pretreated with chromium-free self-assembled monolayer (Gardobond ™ X-4707 X-4661, Chemetall,

Frankfurt a. M, Germany).

[0087] Sheets in Examples 1 (compared) to 5: Gardobond ™ X-4707 aluminum sheets

Pre-treated X-4661, 10.16 cm x 15.24 cm (4 "x 6") AA6016, available with

Chemetall, Frankfurt a. M, Germany. The coatings were cured for 15 minutes until the substrate surface temperature reached 190.6 ° C (375 ° F), giving coatings 50-75 μιτι thick.

Table 3: Results

<td rowspan="2">Test</td><td colspan="5">Example</td>

<td>1 Comp.</td><td> 2</td><td> 3</td><td> 4</td><td> 5</td>

<td>Coating thickness (part of a circle)</td><td> 70-120</td><td> 70-120</td><td> 70-120</td><td> 70-120</td><td> 70-120</td>

<td></td><td>μιτ</td><td>μιτ</td><td>μιτ</td><td>um</td><td>um</td>

<td>MEK (50 strokes / sheet)</td><td> 4</td><td> 5</td><td> 5</td><td> 5</td><td> 5</td>

<td>Cracking (sheet)</td><td>Fulfills</td><td>Fulfills</td><td>Fulfills</td><td>Fulfills</td><td>Fulfills</td>

<td></td><td>the norm</td><td>the norm</td><td>the norm</td><td>the norm</td><td>the norm</td>

<td></td><td>5B</td><td>5B</td><td>5B</td><td>5B</td><td>5B</td>

<td></td><td></td><td></td><td></td><td></td><td></td>

<td></td><td>5B</td><td>5B</td><td>5B</td><td>5B</td><td>5B</td>

<td>Chemical test - fuel</td><td>0 (none)</td><td>0 (none)</td><td>0 (none)</td><td>0 (none)</td><td>0 (none)</td>

<td>reference B (sheet)</td><td>impact)</td><td>impact)</td><td>impact)</td><td>impact)</td><td>impact)</td>

<td>Chemical test - liquid</td><td>0 (none)</td><td>0 (none)</td><td>0 (none)</td><td>0 (none)</td><td>0 (none)</td>

<td>leaching (sheet)</td><td>impact)</td><td>impact)</td><td>impact)</td><td>impact)</td><td>impact)</td>

<td>Thread (part of a circle): max creep (Mm)</td><td> 5,75</td><td> 2,95</td><td> 2,8</td><td> 2,2</td><td> 2,15</td>

<td>Thread (part of a circle): avg. crawl (Mm)</td><td> 1,0</td><td> 0,12</td><td> 0,6</td><td> 0,4</td><td> 0,3</td>

<td>PCI smoothness (sheet)</td><td> 8</td><td> 8</td><td> 8</td><td> 8</td><td> 8</td>

<td>QUV-B sheet (behavior gloss% / Ae)</td><td> 63%/2,1</td><td> 79%/1,4</td><td></td><td></td><td></td>

[0088] As shown in Table 3 above, the coating powders of the invention in Examples 2, 3, 4 and 5 retain the appearance of traditional commercial powder coatings of epoxy functional acrylic copolymers in Example 1 (comparative).

In addition, Example 2 shows that the polymeric mixture of two epoxy functional acrylic copolymers containing 12 wt. vinylaromatic monomer iv) and only 2.95 wt. hydrophobic acrylic monomer ii), provides significantly better resistance to filiform corrosion compared to Example 1 (compare), while maintaining the chemical resistance properties of Example 1 (compare) and slightly improving the resistance to atmospheric factors QUV-B. Finally, compared to Example 4, the use of the epoxy adhesion promoter in Example 5 leads to resistance to filiform corrosion in coatings made of epoxy functional acrylic copolymer components having 12 wt. hydrophobic acrylic monomer ii).

Table 4: CASS results on wheel parts

<td>Example</td><td>Film thickness (Μιτι)</td><td>Creep max (ττ)</td><td>Medium crawl (Ττ)</td><td>Chips before / after CASS (TL239-VW; max. K2,0 before)</td>

<td>1 (compare)</td><td> 85-115</td><td> 1,0</td><td> 0,15</td><td>K1,5 / K2.0</td>

<td> 2</td><td> 70-105</td><td> 2,0</td><td> 0,35</td><td>K2.0 / K2.0</td>

<td> 3</td><td> 80-130</td><td> 1,2</td><td> 0,25</td><td>K2.0 / K2.0-2.5</td>

<td> 4</td><td> 95-115</td><td> 2,0</td><td> 0,60</td><td>K2.0 / K2.0-2.5</td>

<td> 5</td><td> 80-110</td><td> 1,8</td><td> 0,30</td><td>K2.0 / K2.0-2.5</td>

[0089] No edge corrosion was observed in any of the parts . The CASS test results show that the innovative powder coatings retain the chipping resistance of the traditional comparable coatings of Example 1. In addition, Examples 2 and 3 show that the copolymer mixture containing 2.95 wt. and 6 wt.

copolymerized hydrophobic acrylic monomer ii) and, respectively, 12 wt. and 8.5 wt. copolymerized vinyl aromatic monomer iv), based on the total weight of copolymerized monomers in all copolymers in the mixture, show the best combination of chipping strength and CASS corrosion resistance.

Rohm and Haas Company, USA Representative

EP 2 098 575 Z-7405/10