Binder compositions for direct-to-metal coatings

Details Binder compositions for direct-to-metal coatings Binder compositions for direct-to-metal coatings

2001-09-12

2004-06-29

Egwim, Kelechi C. (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C524S547000, C524S565000, C524S806000, C524S807000, C524S818000, C524S831000, C524S832000, C526S279000, C526S287000, C526S316000, C526S317100, C526S342000

Reexamination Certificate

active

06756459

ABSTRACT:

This invention relates to binder compositions in aqueous coatings that exhibit high gloss and superior corrosion resistance when applied to metal substrates and a method for achieving high gloss and superior corrosion resistance of metal substrates by coating a substrate with said compositions. More particularly this invention relates to binder compositions in aqueous coatings that exhibit high gloss and superior corrosion resistance when applied to metal substrates comprising an aqueous emulsion copolymer, the copolymer including as polymerized units, at least one ethylenically unsaturated monomer and an ethylenically unsaturated strong acid monomer, or salts thereof. Preferred strong acid monomers or salts thereof of the present invention are phosphorus containing monomers, particularly phosphoethylmethacrylate (“PEM”).
U.K. Patent No. 958,856, published May 27, 1964, discloses copolymers derived from (1) one or more esters of acrylic and/or methacrylic acid; (2) a methylol compound and/or an alkyl ether thereof of acrylic and/or methacrylic acid amide; and (3) a mixed ester of a diol esterified with acrylic or methacrylic acid and with a di or polybasic organic or inorganic acid having a pKa value of less than 4. Such copolymers include PEM and are adhesive, resistant to water, washing and solvents and are hardened at low ambient temperatures. However, specific copolymer formulations, including copolymers made from styrene based monomers, are not disclosed.
U.S. Pat. No. 3,449,303 discloses phosphate ester polymers for improved adhesion of dyes in textile fibers, yams and fabrics such as allyloxy and allyloxyalkoxy phosphates and homologs thereof, including PEM, and methods of producing such polymers. However, the use of the polymers in binder compositions for aqueous coatings is not disclosed, including in combination with at least one ethylenically unsaturated monomer.
U.S. Pat. No. 4,506,057 discloses a phosphorus modified latex composition useful in the coating of substrates with inorganic fillers. Disclosed is a latex particle having phosphorus groups intimately bound to the particle's surface formed by the emulsion polymerization of a latex with a phosphorus compound. However, specific quantitative and optimized combinations of at least one ethylenically unsaturated monomer and an ethylenically unsaturated strong acid monomer, or salts thereof, are not disclosed and no mention of achieving certain levels of corrosion resistance and high gloss is disclosed.
European Patent Application No. 86114977, published as EP 0 221 498, discloses anti-corrosive random copolymers, anti-corrosive random emulsion co-polymers, methods of inhibiting corrosion on a corrosion-susceptible substrate and methods of preparing random emulsion copolymers. In particular, a polymerizable surface active alkylphosphate monomer is reacted with an ethylenically unsaturated monomer resulting in an anti-corrosive copolymer. However, specific quantitative and optimized combinations of at least one ethylenically unsaturated monomer and an ethylenically unsaturated strong acid monomer, or salts thereof, are not disclosed and no mention of achieving high gloss is disclosed.
PCT Patent Application No. PCT/EP98/07284, published as WO 99/25780, discloses pigment-containing preparations, which contain as the binder at least one aqueous polymer dispersion, the polymer of which is functionalized with phosphonate groups. However, specific quantitative and optimized combinations of at least one ethylenically unsaturated monomer and an ethylenically unsaturated strong acid monomer, or salts thereof, are not disclosed.
The problem faced by the inventors is to optimize the levels of ethylenically unsaturated monomers and an ethylenically unsaturated strong acid monomer, or salts thereof, needed in binder compositions for aqueous coatings, in order to achieve high gloss and superior corrosion resistance when applied to metal substrates, without sacrificing properties expected of commercial aqueous coatings. Quite unexpectedly, the inventors discovered critical and optimum levels and ratios of such monomers in order to achieve high gloss and superior corrosion resistance when applied to metal substrates, without sacrificing properties expected of commercial aqueous coatings.
In one aspect of the present invention there is provided a binder composition for aqueous coatings that exhibit high gloss and superior corrosion resistance when applied to metal substrates comprising an aqueous emulsion copolymer, the copolymer including as polymerized units, at least one ethylenically unsaturated monomer and an ethylenically unsaturated strong acid monomer, or salts thereof. Preferred strong acid monomers or salts thereof of the present invention are phosphorus containing monomers, particularly phosphoethylmethacrylate (“PEM”).
In another aspect of the present invention there is provided a binder composition for aqueous coatings that exhibit high gloss and superior corrosion resistance when applied to metal substrates comprising an aqueous emulsion copolymer, the copolymer including as polymerized units, at least one ethylenically unsaturated monomer, an ethylenically unsaturated strong acid monomer and an additional ethylenically unsaturated acid monomer, or salts thereof, whereby the total acid level is less than about six percent (6%) by weight whereby the strong acid monomer is greater than about 45% of the total acid but not exceeding about 3.7% by weight of the copolymer binder composition. Preferably, the total acid level of the copolymer binder composition should be less than about six percent (6%) by weight whereby the strong acid monomer is greater than about 65% of the total acid but not exceeding about 3.7% by weight of the copolymer binder composition.
In another aspect of the present invention there is provided a method for achieving high gloss and superior corrosion resistance of metal substrates by coating a substrate with the compositions of the present invention and drying, or allowing to dry, the aqueous composition.
The aqueous emulsion copolymer includes at least one copolymerized ethylenically unsaturated monomer. The ethylenically unsaturated monomers include, for example, (meth)acrylic ester monomers including methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, lauryl acrylate, methyl methacrylate, butyl methacrylate, isodecyl methacrylate, lauryl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate; (meth)acrylonitrile; (meth)acrylamide; amino-functional and ureido-functional monomers; silane functional monomers, including methacryloxy-propyltrimethoxy silane(MATS); monomers bearing acetoacetate-functional groups; styrene and substituted styrenes; butadiene; ethylene, propylene, &agr;-olefins such as 1-decene; vinyl acetate, vinyl butyrate and other vinyl esters; and vinyl monomers such as vinyl chloride, vinylidene chloride. Preferred are all-acrylic, predominantly acrylic, styrene/acrylic, and vinyl acetate/acrylic copolymers.
The emulsion copolymer contains 0.1-3.7%, by weight based on the dry weight of the copolymer, copolymerized ethylenically unsaturated strong acid monomer, or salts thereof. “Ethylenically unsaturated strong acid monomer” means a monomer bearing a pendant acid group having a pKa (in water at 20 degree C.) less than 4, or a salt thereof. Strong acid monomers include, without limitation, 2-acrylamido-2-methylpropane sulfonic acid, vinyl sulfonic acid, styrene sulfonic acid, 1-allyloxy-2-hydroxypropane sulfonic acid, alkyl allyl sulfosuccinic acid, sulfoethyl (meth)acrylate, vinyl phosphonic acid, phosphoalkyl (meth)acrylates such as phosphoethyl (meth)acrylate (“PEM”), phosphopropyl (meth)acrylate, and phosphobutyl (meth)acrylate, phosphoalkyl crotonates, phosphoalkyl maleates, phosphoalkyl fumarates, phosphodialkyl (meth)acrylates, phosphodialkyl crotonates, and allyl phosphate. Preferred are phosphorous-containing strong acid monomers. It is also contemplated that the copolymerized ethylenically unsaturated strong acid monom

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