Aqueous coating compositions and methods for preparing same

Abstract

The aqueous coating composition comprises: (A) an emulsion polymer having, based on the weight of the emulsion polymer, 0.48% to 1.20% by weight of structural units of a phosphorous acid monomer, its salt, or a mixture thereof, 0.5% to 3% by weight of structural units of diacetone (meth)acrylamide, 10% to 80% by weight of structural units of a vinyl aromatic monomer, and C1 to C2 of (meth)acrylic acid. 24 (B) an emulsion polymer comprising structural units of an α,β-alkyl ester and, optionally, structural units of an α,β-ethylenically unsaturated carboxylic acid; (B) a specific amount of a dicarboxylic acid of formula (I) HOOC-R-COOH, its salt, or a mixture thereof; and (C) 0.05% to 5% by weight, based on the weight of the aqueous coating composition, of a flash rust inhibitor.

Description

[Technical Field]

[0001] The present invention relates to an aqueous polymer composition and a method for preparing the same. [Background technology]

[0002] Introduction Solvent-borne coating compositions containing epoxy, polyurethane, or alkyd resins are widely used for metal protective coatings due to their corrosion resistance, mechanical properties, and appearance. Water-based acrylic polymer dispersions are much less environmentally concerning than solvent-based dispersions and are typically used for light- to medium-grade metal protection. Ferrous metals, such as carbon steel and cast iron, and metal parts with welded seams are prone to rapid corrosion known as "flash rust." Flash rust tends to form as discrete rust spots visible to the naked eye immediately or shortly after conventional water-based coating compositions are applied to such metal surfaces, before the resulting coating film has completely dried. The formation of flash rust makes it more difficult to use water-based coating compositions in high-temperature (e.g., above 40°C) or high-humidity (e.g., above 90% relative humidity) environments.

[0003] Initial water resistance and long-term corrosion resistance are also important properties of metal protective coatings. Unlike flash rust, long-term corrosion refers to corrosion of the metal substrate that occurs after the coating film has completely dried. Long-term corrosion resistance is usually evaluated by a salt spray test. Adding a sufficient amount of a flash rust inhibitor, such as sodium nitrite, to an aqueous coating composition can reduce or eliminate the formation of flash rust, but typically impairs initial water resistance and / or long-term corrosion resistance. It is difficult for an aqueous composition to provide good flash rust resistance while achieving the desired initial water resistance and long-term corrosion resistance.

[0004] Therefore, there remains a need to provide an aqueous coating composition that has the above-mentioned balanced properties, including flash rust resistance, long-term corrosion resistance, and initial water resistance. Summary of the Invention

[0005] The present invention provides a novel aqueous coating composition that does not suffer from the above-mentioned problems. The aqueous coating composition comprises a novel combination of a specific emulsion polymer and a specific dicarboxylic acid, its salt, or a mixture thereof. The aqueous coating composition can provide excellent flash rust resistance (rated as "0") even under high temperature and humidity conditions (e.g., a temperature of 40°C and 90% relative humidity); good long-term corrosion resistance after 150 hours of exposure to a salt spray test, characterized by a blister rating of at least "6F" or "8M" and a rust rating of at least "9P" or "9S"; good initial water resistance, rated as a blister rating of at least "8M"; and a rust rating of at least "9P" or "9S." These properties can be measured according to the test methods described in the Examples section below.

[0006] In a first aspect, the present invention is an aqueous coating composition comprising: (A) an emulsion polymer, based on the weight of the emulsion polymer: 0.48% by weight to 1.20% by weight of structural units of a phosphorous acid monomer, a salt thereof, or a mixture thereof, 0.5% by weight to 3% by weight of structural units of diacetone (meth)acrylamide, 10% by weight to 80% by weight of structural units of a vinyl aromatic monomer, C1 to C6 of (meth)acrylic acid 24 an emulsion polymer comprising structural units of an alkyl ester, and optionally structural units of an α,β-ethylenically unsaturated carboxylic acid, its salt, or a mixture thereof; (B) a dicarboxylic acid, a salt thereof, or a mixture thereof, wherein the dicarboxylic acid is a compound of formula (I): HOOC-R-COOH(I) wherein R is alkylene, alkenylene, alkynylene, cycloalkylene, cycloalkenylene, cycloalkynylene, arylene, or heterocyclic arylene; and contains 6 to 18 carbon atoms; a dicarboxylic acid, its salt, or mixture thereof, wherein the dicarboxylic acid, its salt, or mixture thereof is present in an amount to provide an —OOC—R—COO— segment at a concentration of 0.28 wt % to 1.0 wt %, based on the weight of the aqueous coating composition; (C) 0.05% by weight to 5% by weight of a flash rust inhibitor, based on the weight of the aqueous coating composition.

[0007] In a second aspect, the invention is a method of preparing the aqueous coating composition of the first aspect, comprising combining an emulsion polymer and a dicarboxylic acid, its salt, or mixtures thereof with a flash rust inhibitor. DETAILED DESCRIPTION OF THE INVENTION

[0008] If a date is not given with the test method number, the test method refers to the test method most recent as of the priority date of this document. References to test methods include both a reference to the testing association and the test method number. The following test method abbreviations and identifiers apply herein: ASTM refers to ASTM International methods, ISO refers to International Organization for Standardization standards, and GB / T refers to Chinese national standards.

[0009] Products identified by trade names refer to compositions available under those trade names as of the priority date of this document. "And / or" means "and, or alternatively." All ranges are inclusive of endpoints unless otherwise indicated.

[0010] As used herein, an "aqueous" composition or dispersion means that the particles are dispersed in an aqueous medium. By "aqueous medium" herein is meant water and 0% to 30% by weight, based on the weight of the medium, of a water-miscible compound, such as, for example, an alcohol, a glycol, a glycol ether, a glycol ester, or a mixture thereof.

[0011] The fragment "(meth)acrylic" refers to both "methacrylic" and "acrylic." For example, (meth)acrylic acid refers to both methacrylic acid and acrylic acid, and methyl (meth)acrylate refers to both methyl methacrylate and methyl acrylate.

[0012] A "structural unit," also known as a "polymerized unit," of a specified monomer refers to the remainder of the monomer after polymerization, i.e., the polymerized monomer or the polymerized form of the monomer. For example, the structural unit of methyl methacrylate is:

[0013] [ka] (dotted lines represent points of attachment of structural units to the polymer backbone).

[0014] "Alkylene" means a branched or unbranched, saturated divalent hydrocarbon group. Exemplary alkylene groups include methylene (-CH-), ethylene (-CHCH-), -CHCH(CH)CH-, or combinations thereof. "Cycloalkylene" means a branched or unbranched divalent hydrocarbon group bonded to one or more cycloalkyl groups. Exemplary cycloalkylene groups include cyclohexylene, methylcyclohexylene, or combinations thereof. "Alkenylene" means a branched or unbranched divalent hydrocarbon group having one or more carbon-carbon double bonds. Exemplary alkenylene groups include ethenylene (-CH=CH-), -CH=CH-CH-, -CH=C(CH)-, or combinations thereof. "Cycloalkenylene" means a branched or unbranched divalent hydrocarbon group bonded to one or more cycloalkyl groups or having one or more carbon-carbon double bonds therein. Exemplary cycloalkenylene groups include cyclohexenylene, -CH=CH-CH 10 -, or combinations thereof. "Alkynylene" means a branched or unbranched divalent hydrocarbon group having one or more carbon-carbon triple bonds. Exemplary alkynylene groups include ethynylene, -C≡C-, -C≡C-CH2-, or combinations thereof. "Cycloalkynylene" means a branched or unbranched divalent hydrocarbon group having one or more cycloalkyl groups attached thereto or having one or more carbon-carbon triple bonds therein. Exemplary cycloalkynylene groups include -C≡C-CH6H 10 -, or combinations thereof. "Arylene" means a branched or unbranched divalent hydrocarbon group bonded to one or more aryl groups. Exemplary arylene groups include phenylene, -CH-, -CH-, -CH(CH)-, or combinations thereof. "Heterocyclic arylene" means a branched or unbranched divalent hydrocarbon group bonded to one or more heterocyclic aryl groups. Exemplary heterocyclic arylene groups include pyridylene, thiazylene, or combinations thereof.

[0015] The "glass transition temperature" or "T" reported herein g can be calculated using the following Fox formula (T.G. Fox, Bull. Am. Phys. Soc., Volume 1, Issue No. 3, page 123 (1956)). For example, the T g To calculate

[0016]

number

[0017] "Weight of emulsion polymer" refers to the dry weight of the emulsion polymer.

[0018] The aqueous coating compositions of the present invention typically contain one or more emulsion polymers in aqueous dispersion. The emulsion polymer may contain structural units of one or more phosphorous acid monomers, their salts, or mixtures thereof. The phosphorous acid monomers may have ethylenic unsaturation. The phosphorous acid monomers may be dihydrogen phosphate esters of alcohols, where the alcohol contains or is substituted with a polymerizable vinyl or olefin group. Phosphorous acid monomers and salts thereof include, for example, phosphoalkyl(meth)acrylates, such as phosphoethyl(meth)acrylate, phosphopropyl(meth)acrylate, phosphobutyl(meth)acrylate, salts thereof, or mixtures thereof; CH═C(R p1 )-C(O)-O-(R p2 O) q -P(O)(OH)2 (wherein, R p1 is H or CH3, and R p2is alkylene, such as an ethylene group, a propylene group, or a combination thereof, and q is 1 to 20 (e.g., SIPOMER PAM-100, SIPOMER PAM-200, SIPOMER PAM-300, and SIPOMER PAM-600, all available from Solvay); phosphoalkoxy(meth)acrylates such as phosphoethylene glycol (meth)acrylate, phosphodiethylene glycol (meth)acrylate, phosphotriethylene glycol (meth)acrylate, phosphopropylene glycol (meth)acrylate, phosphodipropylene glycol (meth)acrylate, phosphotripropylene glycol (meth)acrylate, salts thereof, or mixtures thereof. Desirably, the phosphorous acid monomer is selected from phosphoethyl methacrylate (PEM), phosphoethyl acrylate, allyl ether phosphate, phosphopropyl methacrylate, phosphobutyl methacrylate, or a mixture thereof, more preferably phosphoethyl methacrylate. The emulsion polymer may contain structural units of a phosphorous acid monomer, its salt, or mixtures thereof in an amount of 0.48% by weight or more, based on the weight of the emulsion polymer, but the concentration may be 0.50% by weight or more, 0.52% by weight or more, 0.55% by weight or more, 0.58% by weight or more, 0.60% by weight or more, 0.62% by weight or more, 0.65% by weight or more, 0.68% by weight or more, 0.70% by weight or more, 0.72% by weight or more, 0.75% by weight or more, 0.78% by weight or more, 0.80% by weight or more, 0.82% by weight or more, It may be 0.85% by weight or more, 0.88% by weight or more, or even 0.90% by weight or more, while generally comprising no more than 1.20% by weight, but the concentration may be 1.19% by weight or less, 1.18% by weight or less, 1.17% by weight or less, 1.16% by weight or less, 1.15% by weight or less, 1.12% by weight or less, 1.10% by weight or less, 1.08% by weight or less, 1.05% by weight or less, 1.02% by weight or less, 1.00% by weight or less, 0.98% by weight or less, 0.95% by weight or less, or even 0.92% by weight or less.

[0019] Emulsion polymers useful in the present invention may contain structural units of diacetone (meth)acrylamide, preferably diacetone acrylamide (DAAM). The emulsion polymer may contain structural units of diacetone (meth)acrylamide at a concentration of 0.5% to 3% by weight, based on the weight of the emulsion polymer, but the concentration may be 0.5% by weight or more, 0.6% by weight or more, 0.7% by weight or more, 0.8% by weight or more, 0.9% by weight or more, 1.0% by weight or more, 1.1% by weight or more, 1.2% by weight or more, 1.3% by weight or more, 1.4% by weight or more, 1.5% by weight or more, 1.6% by weight or more, 1.7% by weight or more, 1.8% by weight or more, 1.9 ...9% by weight or more, 1.9% by weight or more, 1.9% by weight or more, 1.9% by weight or more, 1.9% by weight or more, 1.9% It may be 0.7% by weight or more, or even 1.75% by weight or more, while generally the concentration is 3% by weight or less, and may be 3% by weight or less, 2.9% by weight or less, 2.8% by weight or less, 2.7% by weight or less, 2.6% by weight or less, 2.5% by weight or less, 2.45% by weight or less, 2.3% by weight or less, 2.2% by weight or less, 2.1% by weight or less, 2.0% by weight or less, 1.9% by weight or less, 1.8% by weight or less, or even 1.75% by weight or less.

[0020] The emulsion polymer useful in the present invention may contain structural units of one or more α,β-ethylenically unsaturated carboxylic acids, their salts, or mixtures thereof. Suitable α,β-ethylenically unsaturated carboxylic acids may include acrylic acid, methacrylic acid, maleic acid, itaconic acid, crotonic acid, fumaric acid, 2-carboxyethyl acrylate, or mixtures thereof. α,β-ethylenically unsaturated carboxylic acids also include monomers having acid-forming groups that generate or can subsequently be converted into acid groups such as those described above (e.g., anhydrides, (meth)acrylic anhydride, or maleic anhydride); or mixtures thereof. Desirably, the α,β-ethylenically unsaturated carboxylic acid is selected from acrylic acid, methacrylic acid, itaconic acid, 2-carboxyethyl acrylate, or mixtures thereof. The emulsion polymer may contain structural units of α,β-ethylenically unsaturated carboxylic acids and salts thereof at a concentration of 0 wt % to 5 wt %, based on the weight of the emulsion polymer, but the concentration may be 0 wt % or more, 0.3 wt % or more, 0.5 wt % or more, 0.8 wt % or more, 1.0 wt % or more, 1.2 wt % or more, 1.5 wt % or more, 1.8 wt % or more, or even 2 wt % or more. At the same time, the emulsion polymer may generally contain structural units of α,β-ethylenically unsaturated carboxylic acids and salts thereof at a concentration of 5 wt % or less, and the concentration may be 4.5 wt % or less, 4 wt % or less, 3.5 wt % or less, 3.2 wt % or less, 2.8 wt % or less, 3.0 wt % or less, 2.8 wt % or less, 2.5 wt % or less, 2.2 wt % or less, or even 2.0 wt % or less.

[0021] The emulsion polymer useful in the present invention may contain structural units of one or more vinyl aromatic monomers. Suitable vinyl aromatic monomers include, for example, styrene and substituted styrenes, such as α-methylstyrene, p-methylstyrene, t-butylstyrene, trans-β-methylstyrene, 2,4-dimethylstyrene, ethylstyrene, o-, m-, and p-methoxystyrene; p-trifluoromethylstyrene, or mixtures thereof. Preferably, the vinyl aromatic monomer is styrene. The emulsion polymer may contain structural units of the vinyl aromatic monomer in a concentration of 10% to 80% by weight, based on the weight of the emulsion polymer, which may be 10% by weight or more, 20% by weight or more, 30% by weight or more, 35% by weight or more, 40% by weight or more, 45% by weight or more, 50% by weight or more, or even 55% by weight or more, while generally at a concentration of 80% by weight or less, and may be 75% by weight or less, 70% by weight or less, 65% by weight or less, or even 60% by weight or less.

[0022] The emulsion polymers useful in the present invention may comprise one or more C1-C alkyl-containing alkyl groups having 1 to 24 carbon atoms. 24 The alkyl group may contain a structural unit of alkyl (meth)acrylate, and may have 1 to 20, 4 to 10, or 4 to 8 carbon atoms. The alkyl group may be a linear, branched, or cyclic alkyl, and is preferably a linear or branched alkyl. Suitable C1 to C 24Examples of alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, butyl (meth)acrylate, tert-butyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, dibutyl itaconate, diethyl itaconate, cycloalkyl (meth)acrylates such as cyclohexyl acrylate, cyclohexyl methacrylate, methylcyclohexyl (meth)acrylate, isobornyl methacrylate, isobornyl acrylate, dihydrodicyclopentadienyl (meth)acrylate, trimethylcyclohexyl (meth)acrylate, t-butyl (meth)cyclohexyl acrylate, or mixtures thereof; or combinations thereof. Preferably, C1 to C 24 The alkyl (meth)acrylate is selected from butyl acrylate, 2-ethylhexyl (meth)acrylate, ethyl (meth)acrylate, or a mixture thereof. 24 The total concentration of cycloalkyl (meth)acrylate structural units can be in the range of 10% to 70% by weight, based on the weight of the emulsion polymer, but can be 10% by weight or more, 15% by weight or more, 20% by weight or more, 25% by weight or more, 30% by weight or more, 35% by weight or more, or even 40% by weight or more. At the same time, the concentration is generally 70% by weight or less, and can be 65% by weight or less, 60% by weight or less, 55% by weight or less, 50% by weight or less, 45% by weight or less, or even 40% by weight or less. Desirably, the emulsion polymer may or may not contain cycloalkyl (meth)acrylate structural units. The concentration of cycloalkyl (meth)acrylate structural units in the emulsion polymer can be in the range of 0% to 5% by weight, based on the weight of the emulsion polymer, but can be less than 5% by weight, 4% by weight, 3% by weight, 2% by weight, 1% by weight, or even 0% by weight.

[0023] Emulsion polymers useful in the present invention may or may not contain structural units of one or more monoethylenically unsaturated functional monomers other than those having one or more functional groups selected from acetoacetate, acetoacetoxy or acetoacetamide, amide, silane, hydroxyl, ureido, imide, glycidyl, amino, and sulfonic acid; salts thereof; or combinations thereof. These monoethylenically unsaturated functional monomers include, for example, amino-functional monomers such as dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, dimethylaminopropyl methacrylate, dimethylaminopropyl acrylate, or mixtures thereof; monomers having an amide functionality such as acrylamide and methacrylamide; monomers having a glycidyl functionality such as glycidyl acrylate, glycidyl methacrylate, or mixtures thereof; vinyltrialkoxysilanes such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, vinyldimethylethoxysilane, vinylmethyldiethoxysilane, or mixtures thereof; and vinyltrialkoxysilanes such as (meth)acryloxyethyltrimethoxysilane, ( Examples of suitable monomers include (meth)acryloxyalkyltrialkoxysilanes, such as (meth)acryloxypropyltrimethoxysilane, or mixtures thereof; ureido-functional monomers; hydroxyl-functional monomers, such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxybutyl methacrylate, or mixtures thereof; acetoacetate-functional monomers, such as acetoacetoxyethyl (meth)acrylate, acetoacetoxypropyl (meth)acrylate, acetoacetoxybutyl (meth)acrylate, 2,3-di(acetoacetoxy)propyl (meth)acrylate, allyl acetoacetate, vinyl acetoacetate, acetoacetamide, or mixtures thereof; or combinations thereof. As used herein, the term "ureido-functional monomer" refers to an ethylenically unsaturated compound containing a cyclic ureido group (i.e., an imidazolidin-2-one group).The ureido-functional monomer may include a cyclic ureido-group-containing alkyl ester of (meth)acrylic acid. Examples of suitable ureido-functional monomers include N-(2-methacrylamidoethyl)ethyleneurea, N-(2-methacryloyloxyethyl)ethyleneurea, N-(diethyl maleate)ethyleneurea, or a mixture thereof, preferably N-(2-methacryloyloxyethyl)ethyleneurea. The sulfonic acid monomer may include sodium vinyl sulfonate (SVS), sodium styrene sulfonate (SSS), and acrylamido-methyl-propane sulfonate (AMPS), salts thereof; or a mixture thereof. The emulsion polymer may contain structural units of monoethylenically unsaturated functional monomers in a concentration of 0% or more, 0.05% or more, 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, or even 0.5% or more by weight, based on the weight of the emulsion polymer, while generally at a concentration of 5% or less by weight, and the concentration may be 4% or less, 3.5% or less, 3% or less, 2.5% or less, 2% or less, 1.5% or less, 1% or less, 0.8% or less, or even 0.6% or less by weight.

[0024] The emulsion polymer useful in the present invention may or may not contain structural units of one or more multi-ethylenically unsaturated monomers. Examples of suitable multi-ethylenically unsaturated monomers include alkylene glycol diacrylates and dimethacrylates, such as ethylene glycol di(meth)acrylate; 1,1,1-trimethylolpropane di(meth)acrylate; pentaerythritol trimethacrylate; vinyl (meth)acrylate; divinylbenzene; allyl (meth)acrylate; allyl (meth)acrylamide; allyloxyethyl (meth)acrylate, crotyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenylethyl (meth)acrylate; diallyl maleate; or mixtures thereof. The emulsion polymer may contain structural units of the multi-ethylenically unsaturated monomer in a concentration of 0% to 1% by weight, based on the weight of the emulsion polymer, but the concentration may be 0.05% by weight or more, 0.1% by weight or more, or even 0.15% by weight or more, while generally at a concentration of 1% by weight or less, and the concentration may be less than 1% by weight, 0.8% by weight or less, 0.5% by weight or less, 0.4% by weight or less, or even 0.3% by weight or less.

[0025] The emulsion polymers useful in the present invention may or may not contain structural units of one or more monoethylenically unsaturated benzophenones, monoethylenically unsaturated acetophenones, or mixtures thereof. Suitable monoethylenically unsaturated benzophenones can include, for example, vinylbenzophenone, (2-hydroxy-3-methacryloxy)propyl ortho-benzoyl-benzoate, (2-hydroxy-3-acryloxy)propyl ortho-benzoyl-benzoate, or mixtures thereof. The monoethylenically unsaturated benzophenone and / or acetophenone structural units may be present in a total concentration of 0% to 3% by weight, based on the weight of the emulsion polymer, and the concentration may be 0% or more, 0.1% or more, 0.3% or more, 0.5% or more, or even 0.7% or more by weight, while generally at a concentration of 3.0% or less by weight, the concentration may be 2.0% or less, 1.5% or less, 1.2% or less, 1.0% or less, or even 0.9% or less by weight.

[0026] Emulsion polymers useful in the present invention may contain, by weight, based on the weight of the emulsion polymer, 0.8% to 1.2% structural units of phosphoethyl methacrylate; 1.1% to 2.1% structural units of diacetone acrylamide; 40% to 70% structural units of styrene; 20% to 50% structural units of butyl acrylate, 2-ethylhexyl acrylate, butyl methacrylate, or mixtures thereof; and 0.3% to 4% structural units of acrylic acid, methacrylic acid, or mixtures thereof.

[0027] The total weight concentration of the structural units of the above monomers in the emulsion polymer can be equal to 100% by weight, based on the weight of the emulsion polymer. The types and concentrations of the above monomers for preparing the emulsion polymer can be selected to provide the emulsion polymer with a glass transition temperature (Tg) suitable for various applications. The Tg of the emulsion polymer, as calculated by the Fox equation, can be -10 degrees Celsius (°C) or higher, but can also be -5°C or higher, 0°C or higher, 5°C or higher, 10°C or higher, or even 15°C or higher, while generally being 40°C or lower, and can be 35°C or lower, 30°C or lower, 25°C or lower, or even 20°C or lower.

[0028] Desirably, the emulsion polymer is a multistage emulsion polymer comprising polymer A and polymer B. As used herein, "multistage emulsion polymer" refers to an emulsion polymer prepared by the sequential addition of two or more different monomer compositions, including polymer A and polymer B. "Polymer A" and "polymer B" refer to polymers having different compositions and formed in different stages of multistage emulsion polymerization when preparing a multistage emulsion polymer. Each stage is polymerized sequentially and differs from the previous and / or subsequent stage in terms of differences in monomer composition. Without being bound by theory, a multistage emulsion polymer may comprise multiple distinct phases or layers, which can be demonstrated by at least two Tg's measured by scanning transmission electron microscopy (STEM) or differential scanning calorimetry (DSC). Desirably, polymer A is the outer layer of the multistage emulsion polymer, and polymer B is the inner layer. A multistage emulsion polymer may consist of polymer A and polymer B. The types and concentrations of structural units of the above-mentioned monomers in polymer A and / or polymer B of the multistage emulsion polymer may be selected to provide the resulting emulsion polymer with the Tg values ​​just described. Desirably, polymer A has a Tg of less than 20°C, which may be 17°C or less, 14°C or less, 11°C or less, or even 8°C or less, while the Tg is generally -20°C or greater, and may be -15°C or greater, -10°C or greater, -5°C or greater, 0°C or greater, 4°C or greater, or even 6°C or greater. Polymer B may have a Tg greater than 30°C, but may be 35°C or greater, 40°C or greater, 45°C or greater, 49°C or greater, or even 52°C or greater, while the Tg may generally be less than 70°C, but may be 65°C or less, 60°C or less, 57°C or less, or even 54°C or less. Tg values ​​are calculated according to the Fox equation.

[0029] When the emulsion polymer is a multi-stage emulsion polymer, the structural units of the monomers described above in the emulsion polymer section can be present in one or both of Polymer A and Polymer B at a concentration such that the total concentration of structural units of each monomer relative to the weight of the multi-stage emulsion polymer is the same as the concentration of structural units of the same monomer relative to the emulsion polymer described above. For example, one or both of Polymer A and Polymer B in the multi-stage emulsion polymer can be a C1-C (meth)acrylic acid. 24 Polymer A and / or polymer B, preferably polymer A, in the multi-stage emulsion polymer may or may not contain structural units of an α,β-ethylenically unsaturated carboxylic acid.

[0030] One or both of polymer A and polymer B in the multistage emulsion polymer, preferably polymer A, may contain structural units of a phosphorous acid monomer, a salt thereof, or a mixture thereof. Polymer A may contain structural units of a phosphorous acid monomer, its salt, or a mixture thereof in a concentration of 0.3 wt. % to 2.4 wt. %, based on the weight of polymer A, but the concentration may be 0.3 wt. % or more, 0.5 wt. % or more, 0.6 wt. % or more, 0.7 wt. % or more, 0.8 wt. % or more, 0.9 wt. % or more, 1.0 wt. % or more, 1.1 wt. % or more, 1.2 wt. % or more, 1.3 wt. % or more, 1.4 wt. % or more, 1.5 wt. % or more, or even 1.6 wt. % or more; while the concentration is generally 2.4 wt. % or less, and the concentration may be 2.3 wt. % or less, 2.2 wt. % or less, 2.1 wt. % or less, 2.0 wt. % or less, 1.9 wt. % or less, 1.8 wt. % or less, or even 1.7 wt. % or less. Polymer B may contain structural units of a phosphorous acid monomer, its salt, or a mixture thereof in a concentration of 0% to 2.5% by weight, based on the weight of polymer B, but the concentration may be 0% by weight or more, 0.1% by weight or more, 0.2% by weight or more, 0.3% by weight or more, 0.4% by weight or more, or even 0.5% by weight or more; while the concentration is generally 2.5% by weight or less, and the concentration may be 2.2% by weight or less, 2.0% by weight or less, 1.8% by weight or less, 1.5% by weight or less, 1.2% by weight or less, 1.0% by weight or less, 0.9% by weight or less, or even 0.6% by weight or less.

[0031] One or both of polymer A and polymer B in the multistage emulsion polymer, preferably polymer A, may contain diacetone (meth)acrylamide structural units as described above. Polymer A may contain diacetone (meth)acrylamide structural units in a concentration of 0.5% to 6% by weight, based on the weight of polymer A, but the concentration may be 0.5% by weight or more, 0.8% by weight or more, 1.0% by weight or more, 1.2% by weight or more, 1.5% by weight or more, 1.8% by weight or more, 2.0% by weight or more, 2.2% by weight or more, 2.5% by weight or more, 2.8% by weight or more, or even 3% by weight or more; while the concentration is generally 6% by weight or less, and the concentration may be 6% by weight or less, 5.5% by weight or less, 5.2% by weight or less, 5% by weight or less, 4.8% by weight or less, 4.5% by weight or less, 4.2% by weight or less, 4% by weight or less, 3.8% by weight or less, 3.6% by weight or less, 3.5% by weight or less, or even 3.2% by weight or less. Polymer B may contain diacetone (meth)acrylamide structural units in a concentration of 0% to 2.5% by weight, based on the weight of polymer B, but the concentration may be 0.1% by weight or more, 0.2% by weight or more, 0.3% by weight or more, 0.4% by weight or more, or even 0.5% by weight or more; and at the same time, the concentration is generally 2.5% by weight or less, and may be 2.2% by weight or less, 2.0% by weight or less, 1.5% by weight or less, 1.0% by weight or less, or even 0.6% by weight or less.

[0032] One or both of polymer A and polymer B in the multistage emulsion polymer may contain structural units of a vinyl aromatic monomer. Polymer A may contain structural units of a vinyl aromatic monomer in a concentration of 10% to 75% by weight, based on the weight of polymer A, but the concentration may be 10% or more, 15% or more, 20% or more, 25% or more, 30% or more, 35% or more, 40% or more, 45% or more, or even 50% or more by weight, while the concentration is generally 75% or less, and the concentration may be 70% or less, 65% or less, 60% or less, or even 55% or less by weight. Polymer B may contain structural units of vinyl aromatic monomers in a concentration of 10% to 100% by weight, based on the weight of polymer B, but the concentration may be 10% by weight or more, 25% by weight or more, 30% by weight or more, 40% by weight or more, 50% by weight or more, 60% by weight or more, or even 70% by weight or more, while the concentration is generally 100% by weight or less, and may be 95% by weight or less, 90% by weight or less, 85% by weight or less, or even 80% by weight or less.

[0033] Polymer A may be present in the multistage emulsion polymer at a concentration of 50% to 80%, 52% to 78%, 55% to 75%, 58% to 74%, 60% to 72%, 62% to 71%, or 65% to 70% by weight, based on the weight of the multistage emulsion polymer. Polymer B may be present in the multistage emulsion polymer at a concentration of 20% to 50%, 22% to 48%, 25% to 45%, 26% to 42%, 28% to 40%, 29% to 38%, or 30% to 35% by weight, based on the weight of the multistage emulsion polymer. Preferably, the multi-stage emulsion polymer comprises 55% to 75% by weight of Polymer A and 25% to 45% by weight of Polymer B, based on the weight of the multi-stage emulsion polymer.

[0034] Desirably, the multistage emulsion polymer comprises 50% to 80% by weight of Polymer A and 20% to 50% by weight of Polymer B, based on the weight of the multistage emulsion polymer; Polymer A comprises, based on the weight of Polymer A, 0.3 wt % to 2.4 wt % structural units of a phosphorous acid monomer, a salt thereof, or a mixture thereof, 0.5 wt % to 6 wt % structural units of diacetone (meth)acrylamide, and 10 wt % to 75 wt % structural units of a vinyl aromatic monomer; Polymer B comprises, based on the weight of Polymer B, 0 wt % to 2.5 wt % structural units of a phosphorous acid monomer, a salt thereof, or a mixture thereof, 0 wt % to 2.5 wt % structural units of diacetone (meth)acrylamide, and 10 wt % to 100 wt % structural units of a vinyl aromatic monomer; At least one of polymer A and polymer B is a C1-C (meth)acrylic acid 24 -Alkyl ester structural units are further included.

[0035] Emulsion polymers useful in the present invention have an average molecular weight (Mn) of 5,000 grams per mole (g / mol) or greater, 8,000 g / mol or greater, 10,000 g / mol or greater, 11,000 g / mol or greater, 12,000 g / mol or greater, 14,000 g / mol or greater, 15,000 g / mol or greater, 17,000 g / mol or greater, 18,000 g / mol or greater, 20,000 g / mol or greater, 22,000 g / mol or greater, 24,000 g / mol or greater, or even 26,000 g / mol or greater, while generally having a molecular weight (Mn) of 100,000 g / mol or greater. The emulsion polymer may have a number average molecular weight of 80,000 g / mol or less, and may be 80,000 g / mol or less, 70,000 g / mol or less, 60,000 g / mol or less, 55,000 g / mol or less, 50,000 g / mol or less, 45,000 g / mol or less, 40,000 g / mol or less, 38,000 g / mol or less, 35,000 g / mol or less, 32,000 g / mol or less, 30,000 g / mol or less, 29,000 g / mol or less, 28,000 g / mol or less, 27,000 g / mol or less, or even 26,000 g / mol or less. The molecular weight of the emulsion polymer may be measured by gel permeation chromatography (GPC) (further details are provided in the GPC Analysis section below).

[0036] Emulsion polymers useful in the present invention can be prepared by emulsion polymerization of a monomer mixture containing the monomers described above. The total concentration of monomers in the monomer mixture for preparing the emulsion polymer is equal to 100% by weight, based on the total weight of the monomer mixture. For each monomer, the weight concentration of the monomer in the monomer mixture relative to the total weight of the monomer mixture is the same as the weight concentration of the structural unit of that monomer in the emulsion polymer, as described above, relative to the weight of the emulsion polymer. The monomer mixture can be added neat or as an emulsion in water; or in one or more portions or continuously, linearly or nonlinearly, over the reaction period to prepare the emulsion polymer. The monomer mixture can be added neat or as an emulsion in water; or in one or more portions or continuously, linearly or nonlinearly, over the reaction period to prepare the polymer. Suitable temperatures for the emulsion polymerization process can be below 100 degrees (°C), but the temperature can be within the range of 10°C to 99°C, or within the range of 50°C to 90°C. One or more surfactants may be used in the preparation of emulsion polymers. Emulsion polymers can be prepared by single-stage emulsion polymerization or by a multi-stage emulsion polymerization process to form multi-stage emulsion polymers. A multi-stage emulsion polymerization process includes at least two successively formed stages, which usually results in the formation of a multi-stage emulsion polymer containing at least polymer A and polymer B; optionally, the different stages can be formed in different reactors. Desirably, the multi-stage emulsion polymerization process includes a stage of preparing polymer A and a stage of preparing polymer B in an aqueous medium; both are prepared by emulsion polymerization. This process may include a stage of polymerizing a monomer mixture A to form polymer A and a stage of polymerizing a monomer mixture B to form polymer B. Desirably, the process for preparing a multi-stage emulsion polymer includes a first polymerization stage to form polymer A, optionally a stage of neutralizing polymer A, followed by a polymerization stage to form polymer B in the presence of polymer A.Monomer mixtures A and B can each independently contain the monomers described above for forming the structural units of polymers A and B, respectively. The total concentration of the monomer mixtures for preparing polymer A and polymer B relative to the total weight of monomers for preparing the multistage emulsion polymer can be equal to 100% by weight relative to the weight of the multistage emulsion polymer (e.g., the total weight of polymer A and polymer B). For each monomer, the concentration of the monomer relative to the total weight of monomers used in preparing a polymer (e.g., polymer A) is substantially the same as the concentration of the structural units of such monomer relative to the total weight of such polymer (e.g., polymer A).

[0037] One or more free radical initiators may be used in the polymerization process. The polymerization process may be a thermally initiated or redox-initiated emulsion polymerization. Examples of suitable free radical initiators include hydrogen peroxide, t-butyl hydroperoxide, cumene hydroperoxide, ammonium and / or alkali metal persulfates, sodium perborate, superphosphate, and salts thereof; potassium permanganate, and ammonium or alkali metal salts of peroxydisulfate. Free radical initiators may typically be used at concentrations of 0.01% to 3.0% by weight, based on the total weight of the monomers. Redox systems containing the above initiators combined with a suitable reducing agent may be used in the polymerization process. Examples of suitable reducing agents include sodium formaldehyde sulfoxylate, ascorbic acid, isoascorbic acid, alkali metal and ammonium salts of sulfur-containing acids, such as sodium sulfite, bisulfite, thiosulfate, hydrosulfite, sulfide, hydrogen sulfide, or dithionous acid, formamidine sulfinic acid, acetone bisulfite, glycolic acid, hydroxymethanesulfonic acid, glyoxylic acid hydrate, lactic acid, glyceric acid, malic acid, tartaric acid, and salts of the aforementioned acids. Metal salts of iron, copper, manganese, silver, platinum, vanadium, nickel, chromium, palladium, or cobalt may be used to catalyze the redox reaction. Chelating agents for metals may optionally be used.

[0038] One or more surfactants may be used in the polymerization process to prepare emulsion polymers. The surfactant may be added before or during polymerization of the monomers or combinations thereof. A portion of the surfactant may also be added after polymerization. The surfactant may be used in at least one or all stages of preparing a multistage emulsion polymer. The surfactant may include anionic and / or nonionic emulsifiers. The surfactant may be a reactive surfactant, such as a polymerizable surfactant. Examples of suitable surfactants include alkali metal or ammonium salts of alkyl, aryl, or alkylaryl sulfates, sulfonates, or phosphates; alkylsulfonic acids; sulfosuccinates; fatty acids; and ethoxylated alcohols or phenols. Preferably, alkali metal or ammonium salts of alkyl, aryl, or alkylaryl sulfate surfactants are used. The combined amount of surfactants used is typically 0% to 10% by weight, or 0.5% to 3% by weight, based on the weight of all monomers (i.e., the monomer mixture) used to prepare the emulsion polymer.

[0039] In order to control the molecular weight of the emulsion polymer, one or more chain transfer agents may be used in the polymerization process.Examples of suitable chain transfer agents include 3-mercaptopropionic acid, methyl 3-mercaptopropionate, butyl 3-mercaptopropionate, n-dodecyl mercaptan, n-hexadecanethiol, tert-dodecyl mercaptan, n-octadecanethiol, benzenethiol, alkyl mercaptan azelates, hydroxyl-containing mercaptans such as hydroxyethyl mercaptan, mercaptopropionic acid, and mixtures thereof. The chain transfer agent may be used at a concentration of 0% to 2% by weight, based on the total weight of monomers used to prepare the emulsion polymer, but the concentration may be 0.05% by weight or more, 0.1% by weight or more, or even 0.15% by weight or more, while the concentration is generally 2% by weight or less, 1.5% by weight or less, 1.0% by weight or less, 0.5% by weight or less, 0.3% by weight or less, 0.25% by weight or less, or even 0.20% by weight or less.

[0040] After polymerization is complete, the resulting aqueous dispersion (i.e., polymer emulsion) can be neutralized with one or more bases as neutralizing agents, for example, to a pH value of at least 5, 6 to 12, 7 to 10, or 8 to 9. The base can result in partial or complete neutralization of the ionic or potentially ionic groups of the emulsion polymer. Examples of suitable bases include ammonia; alkali metal or alkaline earth metal compounds, such as sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, and the like; primary, secondary, and tertiary amines, such as triethylamine, ethylamine, propylamine, monoisopropylamine, monobutylamine, hexylamine, ethanolamine, diethylamine, dimethylamine, tributylamine, triethanolamine, dimethoxyethylamine, 2-ethoxyethylamine, 3-ethoxypropylamine, dimethylethanolamine, diisopropanolamine, morpholine, ethylenediamine, 2-diethylaminoethylamine, 2,3-diaminopropane, 1,2-propylenediamine, neopentanediamine, dimethylaminopropylamine, hexamethylenediamine, 4,9-dioxadodecane-1,12-diamine, polyethyleneimine, or polyvinylamine; aluminum hydroxide; or mixtures thereof.

[0041] The emulsion polymer particles in the aqueous dispersion can have a particle size of 50 nanometers (nm) or more, 80 nm or more, or even 90 nm or more, and at the same time, 500 nm or less, 200 nm or less, or even 150 nm or less. Particle size herein refers to Z-average size and can be measured by a Brookhaven BI-90 Plus Particle Size Analyzer.

[0042] The aqueous coating compositions of the present invention may contain emulsion polymers at a concentration of 10% by weight or more, 15% by weight or more, 20% by weight or more, or even 25% by weight or more, based on the weight of the aqueous coating composition, while at the same time the concentration is generally 80% by weight or less, 70% by weight or less, 60% by weight or less, 50% by weight or less.

[0043] The aqueous coating composition of the present invention may further comprise one or more polyfunctional carboxylic acid hydrazides containing at least two hydrazide groups per molecule. The polyfunctional carboxylic acid hydrazides may be selected from adipic acid dihydrazide, oxalic acid dihydrazide, isophthalic acid dihydrazide, polyacrylic acid polyhydrazide, or mixtures thereof. The polyfunctional carboxylic acid hydrazide may be present at a concentration of 0% by weight or greater, based on the weight of the emulsion polymer, but the concentration may be 0.05% by weight or greater, 0.1% by weight or greater, 0.2% by weight or greater, 0.4% by weight or greater, or even 0.6% by weight or greater. At the same time, the concentration is typically 3% by weight or less, and the concentration may be 2% by weight or less, 1.5% by weight or less, or even 1% by weight or less.

[0044] The aqueous coating composition of the present invention also contains one or more dicarboxylic acids, their salts, or mixtures thereof, typically in the form of an aqueous solution. "Dicarboxylic acid" refers to a compound containing two carboxyl functional groups (-COOH). Dicarboxylic acids useful in the present invention are represented by the formula (I): HOOC-R-COOH(I) (wherein R is an alkylene group, an alkenylene group, an alkynylene group, a cycloalkylene group, a cycloalkenylene group, a cycloalkynylene group, an arylene group, or a heterocyclic arylene group; containing 6 to 18 carbon atoms (C6 to C 18 )). R can contain 6 to 18 carbon atoms, but R can have 7 or more carbon atoms, 8 or more carbon atoms, 9 or more carbon atoms, or even 10 or more carbon atoms; while R generally has 18 or fewer carbon atoms, the number of carbon atoms can be 17 or fewer, 16 or fewer, 15 or fewer, or even 14 or fewer. Desirably, the dicarboxylic acid is a straight-chain (i.e., unbranched) or branched-chain aliphatic dicarboxylic acid. Desirably, R is a C6-C 18 Alkylene groups (i.e., -(CH2) n -, where n is 6 to 18), more preferably C6 to C 14The dicarboxylic acid is preferably a saturated dicarboxylic acid. The aqueous coating composition may comprise a mixture of two or more dicarboxylic acids, a mixture of salts of two or more dicarboxylic acids, or a combination thereof.

[0045] Suitable dicarboxylic acids include, for example, sebacic acid (HOOC(CH2)8COOH), dodecanedioic acid (HOOC(CH2) 10 COOH), suberic acid (HOOC(CH2)6COOH), ancoic acid (HOOC(CH2)7COOH), undecanedioic acid (HOOC(CH2)9COOH), eicosanedioic acid (HOOC(CH2) 18 COOH), or mixtures thereof, but preferably sebacic acid.

[0046] Aqueous coating compositions typically contain a reaction mixture of at least one dicarboxylic acid (preferably sebacic acid) and at least one base. Bases useful for neutralizing (i.e., reacting with) the dicarboxylic acid may include those bases described above for neutralizing aqueous dispersions of emulsion polymer sections, particularly ammonia, N,N-dimethylethanolamine, 2-amino-2-methyl-1-propanol, or mixtures thereof. The amount of base used to neutralize the dicarboxylic acid to form the salt of the dicarboxylic acid (also referred to as the "dicarboxylate salt") may be in an amount that results in a dry weight ratio of neutralizing agent to dicarboxylic acid within the ranges of 30:70 to 70:30, 35:65 to 65:35, 40:60 to 60:40, or 45:55 to 55:45. Aqueous coating compositions typically contain one or more salts of the dicarboxylic acid. Depending on the type of base used, the resulting salt of the dicarboxylic acid may be an ammonium salt, an alkali metal salt, an amine salt, or a mixture thereof. These salts may be mono-neutralized salts of dicarboxylic acids, bis-neutralized salts of dicarboxylic acids, or mixtures thereof.

[0047] The dicarboxylic acid and / or salt thereof can be present in the aqueous coating composition in an amount that provides the -OOC-R-COO- segment in a concentration of 0.28 wt.% to 1.0 wt.%, based on the weight of the aqueous coating composition, but the concentration can be 0.28 wt.% or more, 0.29 wt.% or more, 0.30 wt.% or more, 0.35 wt.% or more, 0.40 wt.% or more, 0.45 wt.% or more, 0.50 wt.% or more, 0.60 wt.% or more, or even 0.70 wt.% or more, while the concentration is generally 1.0 wt.% or less, and the concentration can be 0.9 wt.% or less, 0.85 wt.% or less, 0.80 wt.% or less, or even 0.75 wt.% or less. The -OOC-R-COO- segment can be derived from a dicarboxylic acid and / or a salt of a dicarboxylic acid. The concentration of the -OOC-R-COO- segment can be determined by liquid chromatography-mass spectrometry (LC-MS), nuclear magnetic resonance (NMR) analysis, and / or extraction analysis. Alternatively, the concentration of the -OOC-R-COO- segment can be calculated by the weight of the original, unneutralized dicarboxylic acid added relative to the weight of the aqueous coating composition. In the case of an aqueous coating composition containing a salt of a dicarboxylic acid, the weight of the dicarboxylic acid used to form such salt, instead of the weight of the salt, is used to calculate the concentration of the -OOC-R-COO- segment.

[0048] The weight ratio of the -OOC-R-COO- segment to the emulsion polymer can be in the range of 0.008 to 0.08, and can be 0.008 or more, 0.01 or more, 0.011 or more, 0.012 or more, 0.015 or more, or even 0.017 or more, while the weight ratio is generally 0.08 or less, and can be 0.06 or less, 0.05 or less, 0.04 or less, 0.03 or less, or even 0.02 or less.

[0049] The aqueous coating composition of the present invention may contain one or more flash rust inhibitors. Flash rust inhibitors refer to monoacids, alkalis, and / or their salts that can (i) form a protective thin film with an inhibitory effect by chemical adsorption (chemisorption) on metal surfaces, (ii) form a film by oxide protection of the metal, (iii) react with potentially corrosive components present in aqueous media to form complex products, or (iv) act as a hydrophobic film by a surface adsorption process to provide a barrier against metal dissolution in a corrosion reaction. Flash rust inhibitors can include inorganic flash rust inhibitors, organic flash rust inhibitors, or mixtures thereof. Suitable flash rust inhibitors include, for example, sodium nitrite, sodium molybdate, sodium chromate, sodium phosphate, sodium phosphite, sodium silicate, phosphoric acid, phosphorous acid, and magnesium, zinc, or nickel ions (typically in the form of soluble salts of magnesium, zinc, or nickel) that can react with hydroxyl (—OH) groups in water to form insoluble hydroxides (e.g., Mg(OH)2, Zn(OH)2, or Ni(OH)2) that are deposited on cathodic sites on the metal surface; and may also include urea, mercaptobenzothiazole (MBT), benzotriazole, aldehydes, heterocyclic nitrogen compounds, sulfur-containing compounds, acetylenic compounds, ascorbic acid, benzoic acid, benzoates, caffeine, and extracts of natural substances, or mixtures thereof.The concentration of the flash rust inhibitor can be in the range of 0.05 wt.% to 5 wt.%, dry weight based on the weight of the aqueous coating composition, and the concentration can be 0.05 wt.% or more, 0.06 wt.% or more, 0.08 wt.% or more, 0.10 wt.% or more, 0.12 wt.% or more, or even 0.13 wt.% or more; while the concentration is generally 5.0 wt.% or less, and the concentration can be 4.5 wt.% or less, 4.0 wt.% or less, 3.5 wt.% or less, 3.0 wt.% or less, 2.5 wt.% or less, 2.0 wt.% or less, 1.0 wt.% or less, 0.9 wt.% or less, 0.8 wt.% or less, 0.7 wt.% or less, 0.6 wt.% or less, 0.5 wt.% or less, 0.4 wt.% or less, 0.3 wt.% or less, 0.2 wt.% or less, 0.18 wt.% or less, or even 0.15 wt.% or less.

[0050] The aqueous coating composition of the present invention may or may not contain one or more pigments. As used herein, "pigment" refers to a material that can substantially contribute to the opacity or hiding power of the composition. Such materials typically have a refractive index greater than 1.8. Inorganic pigments typically include metal oxides. Examples of suitable inorganic pigments include titanium dioxide (TiO), zinc sulfide, lithopone, carbon black, iron oxide red, iron oxide black, lemon chrome yellow, or mixtures thereof. Organic pigments typically include Prussian blue, organic pigment yellow, organic pigment red, anticorrosion pigments, or mixtures thereof. Preferably, the pigment is selected from TiO, carbon black, or mixtures thereof. The pigment may be present in a total concentration of 0% to 60%, 10% to 50%, 15% to 40%, or 20% to 35% by weight based on the weight of the aqueous coating composition. The pigment may or may not include an anticorrosion pigment. "Anti-corrosion pigment" refers to a pigment that can prevent or retard corrosion of steel by chemical reaction or chelation. Suitable anti-corrosion pigments can include, for example, zinc phosphate, zinc molybdate, zinc oxide, aluminum tripolyphosphate, zinc molybdenum phosphate, calcium-modified zinc phosphate, organic molecule-modified zinc phosphate, or mixtures thereof. The anticorrosion pigment may be present in a concentration of 0% to 10% by weight, based on the weight of the aqueous coating composition, and the concentration may be 0% by weight or more, 0.5% by weight or more, 1% by weight or more, 2% by weight or more, 3% by weight or more, or even 4% by weight or more, while the concentration is generally 10% by weight or less, and the concentration may be 9% by weight or less, 8% by weight or less, 7% by weight or less, or even 6% by weight or less, and the concentration may be 5.5% by weight or less, 5% by weight or less, 4.5% by weight or less, 4% by weight or less, 3.5% by weight or less, 3% by weight or less, 2.5% by weight or less, 2% by weight or less, 1.5% by weight or less, 1% by weight or less, or even 0.5% by weight or less.

[0051] The aqueous coating composition of the present invention may or may not contain one or more extenders. The term "extender" as used herein refers to a particulate inorganic material having a refractive index of 1.8 or less and greater than 1.3. Examples of suitable extenders include barium sulfate, talc, calcium carbonate, clay, calcium sulfate, aluminosilicates, silicates, zeolites, mica, diatomaceous earth, solid or hollow glass, ceramic beads, nepheline syenite, feldspar, diatomaceous earth, calcined diatomaceous earth, talc (hydrated magnesium silicate), silica, alumina, kaolin, pyrophyllite, perlite, barite, wollastonite, opaque polymers such as ROPAQUE™ Ultra E (ROPAQUE is a trademark of The Dow Chemical Company) available from The Dow Chemical Company, or mixtures thereof. The aqueous coating composition may include the extender at a concentration of 0% to 60% by weight, based on the weight of the aqueous coating composition, but the concentration may also be 10% to 50% by weight, 15% to 40% by weight, or 20% to 35% by weight.

[0052] The aqueous coating composition of the present invention may or may not contain one or more defoamers. "Defoamer," as used herein, refers to a chemical additive that reduces or prevents foam formation. The defoamer may be a silicone-based defoamer, a mineral oil-based defoamer, an ethylene oxide / propylene oxide-based defoamer, an alkyl polyacrylate, or a mixture thereof. Suitable commercially available defoamers include, for example, TEGO Airex 901W, TEGO Airex 902W, and TEGO Foamex 1488 polyether siloxane copolymer emulsions, all available from TEGO, and BYK-022 and BYK-024 silicone defoamers, available from BYK, and mixtures thereof. These defoamers may generally be present at a concentration of 0% to 0.5%, 0.02% to 0.4%, or 0.04% to 0.2% by weight, based on the weight of the aqueous coating composition.

[0053] The aqueous coating compositions of the present invention may or may not contain one or more thickeners (also known as "rheology modifiers"), which may include polyvinyl alcohol (PVA), clay materials, acid derivatives, acid copolymers, urethane associative thickeners (UAT), polyether urea polyurethanes (PEUPU), polyether polyurethanes (PEPU), or mixtures thereof. Examples of suitable thickeners include alkali-swellable emulsions (ASEs), such as sodium- or ammonium-neutralized acrylic acid polymers; hydrophobically modified alkali-swellable emulsions (HASEs), such as hydrophobically modified acrylic acid copolymers; associative thickeners, such as hydrophobically modified ethoxylated urethanes (HEURs); and cellulosic thickeners, such as methylcellulose ethers, hydroxymethylcellulose (HMC), hydroxyethylcellulose (HEC), hydrophobically modified hydroxyethylcellulose (HMHEC), sodium carboxymethylcellulose (SCMC), sodium carboxymethyl 2-hydroxyethylcellulose, 2-hydroxypropylmethylcellulose, 2-hydroxyethylmethylcellulose, 2-hydroxybutylmethylcellulose, 2-hydroxyethylethylcellulose, and 2-hydroxypropylcellulose. Preferably, the thickener is HEUR. These thickeners may be present in a concentration of 0% to 1.0%, 0.05% to 0.6%, or 0.1% to 0.4% by weight based on the weight of the aqueous coating composition.

[0054] The aqueous coating composition of the present invention may or may not contain one or more wetting agents. As used herein, the term "wetting agent" refers to a chemical additive that reduces the surface tension of the composition, allowing it to spread or penetrate more easily over the surface of a substrate. Wetting agents can be polycarboxylate, anionic, zwitterionic, or nonionic. Suitable commercially available wetting agents include, for example, SURFYNOL 104 and SURFYNOL TG nonionic wetting agents based on acetylenic diols, available from Evonik; BYK-190, TEGO-750W, and TEGO-755W solutions of high molecular weight block polymers with pigment-affinic groups, available from BYK and Evonik, respectively; BYK-346 and BYK-349 polyether-modified siloxanes, both available from BYK; or mixtures thereof. These wetting agents may be present at a concentration of 0% to 0.6%, 0.1% to 0.5%, or 0.2% to 0.4% by weight based on the weight of the aqueous coating composition.

[0055] The aqueous coating composition of the present invention may or may not contain one or more coalescents. As used herein, the term "coalescent" refers to a slow-evaporating solvent that coalesces polymer particles into a continuous film under ambient conditions. Examples of suitable coalescents include 2-n-butoxyethanol, dipropylene glycol n-butyl ether, propylene glycol n-butyl ether, dipropylene glycol methyl ether, propylene glycol methyl ether, propylene glycol n-propyl ether, diethylene glycol monobutyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, triethylene glycol monobutyl ether, dipropylene glycol n-propyl ether, n-butyl ether, or mixtures thereof. Preferred coalescents include dipropylene glycol n-butyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, n-butyl ether, or mixtures thereof. These coalescents may be present at a concentration of 0% to 10%, 0.2% to 8%, or 1% to 6% by weight based on the weight of the aqueous coating composition.

[0056] The aqueous coating compositions of the present invention may or may not contain one or more dispersants. The dispersants may be, for example, polyacrylic acid, polymethacrylic acid, or maleic anhydride with various monomers such as styrene, acrylate or methacrylate esters, diisobutylene, and other hydrophilic or hydrophobic comonomers; salts thereof; or mixtures thereof. The dispersants may be present in concentrations of 0% to 2%, 0.1% to 1.5%, or 0.2% to 1% by weight, based on the weight of the aqueous coating composition.

[0057] In addition to the above-mentioned components, the aqueous coating composition of the present invention may include any one or combination of the following additives: buffering agents, neutralizing agents, wetting agents, mildewcides, biocides, antiskinning agents, colorants, antioxidants, plasticizers, leveling agents, adhesion promoters, and grind vehicles. These additives may be present in a total concentration of 0% to 10%, 0.1% to 5%, or 0.2% to 1% by weight, based on the weight of the aqueous coating composition. The aqueous coating composition may also include water, at a concentration of 30% to 90%, 40% to 80%, or 50% to 70% by weight of the aqueous coating composition.

[0058] The aqueous coating composition of the present invention can be prepared by mixing an emulsion polymer, typically in an aqueous dispersion, and a dicarboxylic acid and / or its salt, typically in an aqueous solution, with a flash rust inhibitor, and optionally with a polyfunctional carboxylic acid hydrazide, a pigment, and other ingredients described above. Any of the optional ingredients described above can also be added during or before mixing to form the aqueous coating composition. The ingredients in the aqueous coating composition can be mixed in any order. For example, the emulsion polymer and the dicarboxylic acid and / or its salt (preferably in aqueous solution) can be mixed first, followed by the flash rust inhibitor and other ingredients (if present). Alternatively, the dicarboxylic acid and / or its salt can be added after the emulsion polymer has been mixed with the flash rust inhibitor and other ingredients (if present). Preferably, the pigment and / or extender are mixed with a dispersant to form a pigment and / or extender slurry.

[0059] The aqueous coating composition of the present invention is suitable for coating applications such as marine protective coatings, general industrial finishes, metal protective coatings, automotive coatings, traffic paints, exterior insulation and finish systems (EIFS), wood coatings, coil coatings, plastic coatings, can coatings, architectural coatings, and civil engineering coatings. The aqueous coating composition is particularly suitable for metal protective coatings. The aqueous coating composition can be used as a primer, a topcoat, a one-coat direct-to-metal coating, or in combination with other coatings to form multi-layer coatings.

[0060] The aqueous coating compositions of the present invention can be applied to and adhere to a variety of substrates, including wood, metals, particularly ferrous metals such as cast iron, welded seams, and carbon steel, plastics, foams, stone, elastomeric substrates, glass, textiles, concrete, or cementitious substrates. The aqueous coating compositions can be applied to substrates by conventional means, including brushing, dipping, rolling, and spraying. The aqueous coating compositions are preferably applied by spraying. Standard spraying techniques and equipment, including air-atomized spraying, air-free spraying, high-volume, low-pressure spraying, and electrostatic spraying, such as electrostatic bell application, can be used, and either manual or automated methods can be used. After the aqueous coating composition is applied to a substrate, the polymer composition can be dried at a temperature ranging from 0°C to 35°C, or at elevated temperatures, for example, from 35°C to 60°C, to form a film (i.e., coating).

[0061] The aqueous coating composition of the present invention can exhibit improved flash rust resistance, initial water resistance, and good long-term corrosion resistance, even in the absence of anticorrosion pigments. The present invention also provides a method for improving the flash rust resistance and long-term corrosion resistance of substrates susceptible to flash rust and corrosion, such as metals, particularly ferrous metals. The method includes providing a substrate, applying an aqueous coating composition to the substrate (i.e., coating the coating composition on the substrate), and drying the aqueous coating composition to form a coated substrate. For example, the aqueous coating composition can achieve a flash rust resistance rating of "0" when measured at a temperature of 40°C and a relative humidity (RH) of 90%. This method can also provide coatings with good initial water resistance, as indicated by a blister rating of "8M," preferably "8F" or "10," and a rust rating of "9P" or "9S," preferably "10." After the coating composition is completely dried to form a coated substrate, the long-term corrosion resistance is tested, for example, after drying at room temperature (20°C to 25°C) for 7 days. Good long-term corrosion resistance is characterized by a blister rating of "6F" or "8M," preferably "8F" or "10"; and a rust rating of "9P" or "9S," preferably "10," after at least 150 hours of exposure to a salt spray test in accordance with ASTM B117-2011. Flash rust resistance, initial water resistance, and long-term corrosion resistance can be measured according to the test methods described in the Examples section below. The present invention also relates to articles produced by the method. The present invention also relates to a process for preparing a coating. The process can include applying an aqueous coating composition to a substrate and drying the applied coating composition to form a coating. [Example]

[0062] Some embodiments of the present invention will now be described in the following examples, where all parts and percentages are by weight (i.e., % by weight), where the weight percent of the structural unit is based on the emulsion polymer weight, and the weight percent of the dicarboxylic acid (e.g., sebacic acid or adipic acid) is based on the weight of the aqueous coating composition, unless otherwise specified. Materials for use in the samples are those described herein below. OROTAN, RETAN, and ACRYSOL are trademarks of The Dow Chemical Company.

[0063] Styrene (ST) is available from Langyuan Chemical Co., Ltd.

[0064] Phosphoethyl methacrylate (PEM) is available from Solvay.

[0065] 2-Ethylhexyl acrylate (2-EHA), butyl acrylate (BA), ACRYSOL™ RM-8W thickener (nonionic urethane rheology modifier), and OROTAN™ 681 dispersant (polymethacrylic acid with a hydrophobic comonomer) are all available from The Dow Chemical Company.

[0066] Methacrylic acid (MAA), acrylic acid (AA), n-dodecyl mercaptan (n-DDM), aqueous ammonia (25%), sodium nitrite (NaNO2) anti-flash rust additive, sebacic acid, and adipic acid are all available from Sinopharm Chemical Reagent Co., Ltd.

[0067] Cyclohexyl methacrylate (CHMA) and DISPONIL™ FES32 surfactant (“Fes-32”, an alcohol ethoxylate sulfate surfactant) are both available from BASF.

[0068] Diacetone acrylamide (DAAM) and adipic acid dihydrazide (ADH) are both available from Kyowa Hakko Chemical Co., Ltd.

[0069] N-(2-methacryloyloxyethyl)ethyleneurea (MEUR), SURFYNOL™ TG (acetylene diol-based nonionic surfactant), and TEGO™ Airex 902W defoamer (polyether siloxane copolymer emulsion) are all available from Evonik Industries.

[0070] POLYSTEP™ B-11 surfactant (B-11), available from STEPAN, is an alcohol ethoxylate sulfate surfactant.

[0071] HITENOL™ AR-1025 surfactant (“AR-1025”) available from DKS Co., Ltd. is a tristyrylphenol ethoxylate sulfate surfactant.

[0072] Ti-PURE™ R-706 titanium dioxide is available from DuPont.

[0073] TEXANOL™ ester alcohols available from Eastman Chemical Company are used as coalescents.

[0074] Polymer emulsions for use as binders in the sample coating compositions were prepared according to the synthesis process described below.

[0075] Synthesis of Polymer Emulsion 11 ("E-11") Deionized (DI) water (518 grams (g)), Fes-32 surfactant (31%, 71 g), ST (1016 g), BA (694 g), AA (39 g), PEM (6 g), MEUR (50%, 7 g), and n-DDM (5 g) were mixed together to produce a stable monomer emulsion. Under a nitrogen (N) atmosphere at 90°C, Fes-32 surfactant (31%, 10 g) in DI water (20 g), the monomer emulsion prepared above (59 g), and APS (9 g) were added to DI water (896 g), followed by the addition of DI water (20 g) to form a reaction mixture. Next, the remaining monomer emulsion, ammonium persulfate (APS, 4 g) in DI water (78 g), and ammonia (25%, 9 g) in DI water (78 g) were added over 240 minutes at 86° C., followed by the addition of DI water (30 g). At the end of the polymerization, FeSO (0.01 g) in DI water (4 g) mixed with ethylenediaminetetraacetic acid (EDTA) sodium salt (0.02 g) in DI water (4 g), a solution of t-butyl hydroperoxide (t-BHP, 5.4 g) dissolved in DI water (35 g), and a solution of isoascorbic acid (IAA, 2.0 g) in DI water (35 g) were added, all at 60° C. Next, ammonia (17 g) in DI water (17 g) was added at 50° C. to obtain an aqueous dispersion.

[0076] Synthesis of Polymer Emulsion 05 ("E-05") A stable monomer emulsion was produced by mixing 363 g of DI water, 49.1 g of Fes-32 surfactant (31%), 711 g of ST, 481 g of BA, 14.8 g of AA, 22 g of PEM, 4.9 g of MEUR (50%), and 3.0 g of n-DDM. To 628 g of DI water at 90°C under N2, 6.8 g of Fes-32 surfactant (31%), 41 g of the monomer emulsion prepared above, and 6 g of APS were added, followed by 20 g of DI water, to form a reaction mixture. Next, the remaining monomer emulsion, 3 g of APS in 54 g of DI water, and 6 g of ammonia (25%) in 54 g of DI water were added over 240 minutes at 86°C, followed by 30 g of DI water. At the end of the polymerization, FeSO (0.01 g) in DI water (4 g) mixed with EDTA sodium salt (0.02 g) in DI water (4 g), a solution of t-BHP (3.8 g) dissolved in DI water (35 g), and a solution of IAA (1.4 g) in DI water (35 g) were added, all at 60° C. Ammonia (17 g) in DI water (17 g) was then added at 50° C. to obtain an aqueous dispersion.

[0077] Synthesis of Polymer Emulsion 61 ("E-61") A stable monomer emulsion was produced by mixing together 273 g of DI water, 22 g of AR-1025 surfactant (25%), 372 g of ST, 315 g of 2-EHA, 225 g of CHMA, 28 g of MAA, 21 g of PEM, 24.8 g of DAAM, 14 g of MEUR (50%), and 1.5 g of n-DDM. To 674 g of DI water at 90° C. under N2, 23 g of AR-1025 surfactant (25%), 60 g of the monomer emulsion prepared above in 20 g of DI water, and 1.9 g of APS, and 0.6 g of ammonia in 4 g of DI water were added, followed by 20 g of DI water to form a reaction mixture. Next, the remaining monomer emulsion, APS (1.2 g) in DI water (64 g), and ammonia (25%, 4 g) in DI water (64 g) were added over 120 minutes at 88°C, followed by the addition of DI water (30 g). At the end of the polymerization, FeSO (0.01 g) in DI water (4 g) mixed with EDTA sodium salt (0.02 g) in DI water (4 g), a solution of t-BHP (3.5 g) dissolved in DI water (45 g), and a solution of IAA (1.4 g) in DI water (45 g) were added, all at 60°C, followed by the addition of ammonia (30 g) in DI water (17 g) at 55°C. Next, ADH (15 g) in DI water (25 g) was added at 50°C to obtain an aqueous dispersion.

[0078] Synthesis of Polymer Emulsion 66 ("E-66") First-stage monomer emulsion (ME1) was prepared by mixing together 332 g of DI water, 18 g of B-11 surfactant (54%), 520 g of BA, 777 g of ST, 29 g of PEM, 33.5 g of MAA, 4.8 g of MEUR (50%), and 2.7 g of n-DDM to form a stable monomer emulsion. Second-stage monomer emulsion (ME2) was prepared by mixing together 142 g of DI water, 8 g of B-11 surfactant (54%), 223 g of BA, 363 g of ST, 3 g of MEUR (50%), and 1.2 g of n-DDM to form a stable monomer emulsion.

[0079] A 5-liter, four-necked round-bottom flask equipped with a paddle stirrer, thermocouple, nitrogen inlet, and reflux condenser was charged with DI water (953 g) and stirring was initiated. The contents of the flask were heated to 90°C under N2. B-11 surfactant (54%, 4 g), MAA (3 g), ME1 (98 g), and APS (5.5 g) in DI water (49 g) were added to the flask, followed by a DI water (25 g) rinse. The remaining ME1, APS (1.6 g) in DI water (48 g), and ammonia (25%, 16 g) in DI water (45 g) were then added over 87 minutes. After the ME1 feed was completed, DI water (22 g) was added as a rinse. ME2 and APS (0.7 g) in DI water (21 g) were then added over 33 minutes. After the ME2 feed was completed, DI water (30 g) was added as a rinse. The temperature of the flask contents was maintained between 87 and 89 °C during the addition. At the end of the polymerization, a mixture of FeSO 7H O (0.016 g) in DI water (5 g) and EDTA sodium salt (0.016 g) in DI water (5 g), a solution of t-BHP (70%, 3.7 g t-BHP dissolved in 39 g DI water), and a solution of IAA (2.6 g IAA dissolved in 41 g DI water), all at 60 °C, was added to the flask. Ammonia (25%, 28 g) in DI water (28 g) was then added to the flask at 50 °C to obtain an aqueous dispersion.

[0080] Synthesis of Polymer Emulsion 12 ("E-12") First-stage monomer emulsion (ME1) was prepared by mixing together 313 g of DI water, 17 g of B-11 surfactant (54%), 478 g of BA, 714 g of ST, 28 g of PEM, 32 g of MAA, 32 g of DAAM, 4.5 g of MEUR (50%), and 2.6 g of n-DDM to form a stable monomer emulsion. Second-stage monomer emulsion (ME2) was prepared by mixing together 134 g of DI water, 7 g of B-11 surfactant (54%), 210 g of BA, 342 g of ST, 2 g of MEUR (50%), and 1.0 g of n-DDM to form a stable monomer emulsion.

[0081] A 5-liter, four-necked round-bottom flask equipped with a paddle stirrer, thermocouple, nitrogen inlet, and reflux condenser was charged with 889 g of DI water and stirring was initiated. The contents of the flask were heated to 90°C under N2. B-11 surfactant (54%, 4 g), MAA (5.6 g), ME1 (93 g), and APS (5.2 g) in 46 g of DI water were added to the flask, followed by a 30 g DI water rinse. The remaining ME1, APS (1.6 g) in 45 g of DI water, and ammonia (25%, 15 g) in 43 g of DI water were then added over 87 minutes. After the ME1 feed was completed, 30 g of DI water was added as a rinse. ME2 and APS (0.7 g) in 20 g of DI water were then added over 33 minutes. After the ME2 feed was completed, DI water (30 g) was added as a rinse. The temperature of the flask contents was maintained between 87 and 89 °C during the addition. At the end of the polymerization, a mixture of FeSO 7H O (0.008 g) in DI water (5 g) and EDTA sodium salt (0.016 g) in DI water (5 g), a solution of t-BHP (70%, 3.5 g t-BHP dissolved in 36 g DI water), and a solution of IAA (2.4 g IAA dissolved in 38 g DI water), all at 60 °C, were added to the flask. Ammonia (25%, 26 g) in DI water (26 g) and ADH (19 g) in DI water (67 g) were then added to the flask at 50 °C to obtain an aqueous dispersion.

[0082] Synthesis of Polymer Emulsion 29 ("E-29") First-stage monomer emulsion (ME1) was prepared by mixing 301 g of DI water, 15 g of B-11 surfactant (54%, 560 g), 572 g of ST (572 g), 26 g of PEM, 30 g of MAA, 43 g of DAAM, 4.3 g of MEUR (50%, 50%), and 5 g of n-DDM to form a stable monomer emulsion. Second-stage monomer emulsion (ME2) was prepared by mixing 130 g of DI water, 7.6 g of B-11 surfactant (54%, 50%), 105 g of BA, 425 g of ST (425 g), 2 g of MEUR (50%, 50%), and 1.0 g of n-DDM to form a stable monomer emulsion.

[0083] A 5-liter, four-necked round-bottom flask equipped with a paddle stirrer, thermocouple, nitrogen inlet, and reflux condenser was charged with DI water (780 g) and stirring was initiated. The contents of the flask were heated to 90°C under N2. B-11 surfactant (54%, 4.7 g), MAA (5.3 g), ME1 (89 g), and APS (5 g) in DI water (44 g) were added to the flask, followed by a DI water rinse (45 g). The remaining ME1, APS (1.5 g) in DI water (71 g), and ammonia (25%, 15 g) in DI water (52 g) were then added over 87 minutes. After the ME1 feed was completed, DI water (30 g) was added as a rinse. ME2 and APS (0.7 g) in DI water (30 g) were then added over 33 minutes. After the ME2 feed was completed, DI water (30 g) was added as a rinse. The temperature of the flask contents was maintained between 87 and 89 °C during the addition. At the end of the polymerization, a mixture of FeSO 7H O (0.008 g) in DI water (5 g) and EDTA sodium salt (0.016 g) in DI water (5 g), a solution of t-BHP (70%, 3.4 g t-BHP dissolved in 43 g DI water), and a solution of IAA (2.3 g IAA dissolved in 78 g DI water), all at 60 °C, were added to the flask. Ammonia (25%, 26 g) in DI water (26 g) and ADH (26 g) in DI water (67 g) were then added to the flask at 50 °C to obtain an aqueous dispersion.

[0084] Synthesis of Polymer Emulsion 30 ("E-30") First-stage monomer emulsion (ME1) was prepared by mixing together 301 g of DI water, 15 g of B-11 surfactant (54%, 547 g), 554 g of ST (554 g), 26 g of PEM, 30 g of MAA, 74 g of DAAM, 4.3 g of MEUR (50%, 50%), and 5 g of n-DDM to form a stable monomer emulsion. Second-stage monomer emulsion (ME2) was prepared by mixing 130 g of DI water, 7.6 g of B-11 surfactant (54%, 50%), 105 g of BA, 425 g of ST (425 g), 2 g of MEUR (50%, 50%), and 1.0 g of n-DDM to form a stable monomer emulsion.

[0085] A 5-liter, four-necked round-bottom flask equipped with a paddle stirrer, thermocouple, nitrogen inlet, and reflux condenser was charged with DI water (780 g) and stirring was initiated. The contents of the flask were heated to 90°C under N2. B-11 surfactant (54%, 4.7 g), MAA (5.3 g), ME1 (89 g), and APS (5 g) in DI water (44 g) were added to the flask, followed by a DI water rinse (45 g). The remaining ME1, APS (1.5 g) in DI water (71 g), and ammonia (25%, 15 g) in DI water (52 g) were then added over 87 minutes. After the ME1 feed was completed, DI water (30 g) was added as a rinse. ME2 and APS (0.7 g) in DI water (30 g) were then added over 33 minutes. After the ME2 feed was completed, DI water (30 g) was added as a rinse. The temperature of the flask contents was maintained between 87 and 89 °C during the addition. At the end of the polymerization, a mixture of FeSO 7H O (0.008 g) in DI water (5 g) and EDTA sodium salt (0.016 g) in DI water (5 g), a solution of t-BHP (70%, 3.4 g t-BHP dissolved in 43 g DI water), and a solution of IAA (2.3 g IAA dissolved in 78 g DI water), all at 60 °C, were added to the flask. Ammonia (25%, 26 g) in DI water (26 g) and ADH (45 g) in DI water (115 g) were then added to the flask at 50 °C to obtain an aqueous dispersion.

[0086] Synthesis of Polymer Emulsion 31 ("E-31") First-stage monomer emulsion (ME1) was prepared by mixing together 301 g of DI water, 15 g of B-11 surfactant (54%, 570 g), 597 g of ST, 26 g of PEM, 30 g of MAA, 9 g of DAAM, 4.3 g of MEUR (50%, 50%), and 5 g of n-DDM to form a stable monomer emulsion. Second-stage monomer emulsion (ME2) was prepared by mixing 130 g of DI water, 7.6 g of B-11 surfactant (54%, 50%), 105 g of BA, 425 g of ST, 2 g of MEUR (50%, 50%), and 1.0 g of n-DDM to form a stable monomer emulsion.

[0087] A 5-liter, four-necked round-bottom flask equipped with a paddle stirrer, thermocouple, nitrogen inlet, and reflux condenser was charged with DI water (780 g) and stirring was initiated. The contents of the flask were heated to 90°C under N2. B-11 surfactant (54%, 4.7 g), MAA (5.3 g), ME1 (89 g), and APS (5 g) in DI water (44 g) were added to the flask, followed by a DI water rinse (45 g). The remaining ME1, APS (1.5 g) in DI water (71 g), and ammonia (25%, 15 g) in DI water (52 g) were then added over 87 minutes. After the ME1 feed was completed, DI water (30 g) was added as a rinse. ME2 and APS (0.7 g) in DI water (30 g) were then added over 33 minutes. After the ME2 feed was completed, DI water (30 g) was added as a rinse. The temperature of the flask contents was maintained between 87 and 89 °C during the addition. At the end of the polymerization, a mixture of FeSO 7H O (0.008 g) in DI water (5 g) and EDTA sodium salt (0.016 g) in DI water (5 g), a solution of t-BHP (70%, 3.4 g t-BHP dissolved in 43 g DI water), and a solution of IAA (2.3 g IAA dissolved in 78 g DI water), all at 60 °C, were added to the flask. Ammonia (25%, 26 g) in DI water (26 g) and ADH (5.3 g) in DI water (14 g) were then added to the flask at 50 °C to obtain an aqueous dispersion.

[0088] Synthesis of Polymer Emulsion 32 ("E-32") First-stage monomer emulsion (ME1) was prepared by mixing together 301 g of DI water, 15 g of B-11 surfactant (54%, 548 g), BA (548 g), ST (601 g), PEM (44 g), MAA (22 g), DAAM (44 g), 4.3 g of MEUR (50%, 500 g), and 5 g of n-DDM to form a stable monomer emulsion. Second-stage monomer emulsion (ME2) was prepared by mixing 130 g of DI water, 7.6 g of B-11 surfactant (54%, 500 g), BA (105 g), ST (425 g), 2 g of MEUR (50%, 500 g), and 1.0 g of n-DDM to form a stable monomer emulsion.

[0089] A 5-liter, four-necked round-bottom flask equipped with a paddle stirrer, thermocouple, nitrogen inlet, and reflux condenser was charged with DI water (780 g) and stirring was initiated. The contents of the flask were heated to 90°C under N2. B-11 surfactant (54%, 4.7 g), MAA (5.3 g), ME1 (89 g), and APS (5 g) in DI water (44 g) were added to the flask, followed by a DI water rinse (45 g). The remaining ME1, APS (1.5 g) in DI water (71 g), and ammonia (25%, 15 g) in DI water (52 g) were then added over 87 minutes. After the ME1 feed was completed, DI water (30 g) was added as a rinse. ME2 and APS (0.7 g) in DI water (30 g) were then added over 33 minutes. After the ME2 feed was completed, DI water (30 g) was added as a rinse. The temperature of the flask contents was maintained between 87 and 89 °C during the addition. At the end of the polymerization, a mixture of FeSO 7H O (0.008 g) in DI water (5 g) and EDTA sodium salt (0.016 g) in DI water (5 g), a solution of t-BHP (70%, 3.4 g t-BHP dissolved in 43 g DI water), and a solution of IAA (2.3 g IAA dissolved in 78 g DI water), all at 60 °C, were added to the flask. Ammonia (25%, 26 g) in DI water (26 g) and ADH (11 g) in DI water (28 g) were then added to the flask at 50 °C to obtain an aqueous dispersion.

[0090] Synthesis of Polymer Emulsion 41 ("E-41") First-stage monomer emulsion (ME1) was prepared by mixing together 301 g of DI water, 15 g of B-11 surfactant (54%, 560 g), 580 g of ST, 35 g of PEM, 26 g of MAA, 31 g of DAAM, 4.3 g of MEUR (50%, 50%), and 5 g of n-DDM to form a stable monomer emulsion. Second-stage monomer emulsion (ME2) was prepared by mixing 130 g of DI water, 7.6 g of B-11 surfactant (54%, 50%), 105 g of BA, 425 g of ST, 2 g of MEUR (50%, 50%), and 1.0 g of n-DDM to form a stable monomer emulsion.

[0091] A 5-liter, four-necked round-bottom flask equipped with a paddle stirrer, thermocouple, nitrogen inlet, and reflux condenser was charged with DI water (780 g) and stirring was initiated. The contents of the flask were heated to 90°C under N2. B-11 surfactant (54%, 4.7 g), MAA (5.3 g), ME1 (89 g), and APS (5 g) in DI water (44 g) were added to the flask, followed by a DI water rinse (45 g). The remaining ME1, APS (1.5 g) in DI water (71 g), and ammonia (25%, 15 g) in DI water (52 g) were then added over 87 minutes. After the ME1 feed was completed, DI water (30 g) was added as a rinse. ME2 and APS (0.7 g) in DI water (30 g) were then added over 33 minutes. After the ME2 feed was completed, DI water (30 g) was added as a rinse. The temperature of the flask contents was maintained between 87 and 89 °C during the addition. At the end of the polymerization, a mixture of FeSO 7H O (0.008 g) in DI water (5 g) and EDTA sodium salt (0.016 g) in DI water (5 g), a solution of t-BHP (70%, 3.4 g t-BHP dissolved in 43 g DI water), and a solution of IAA (2.3 g IAA dissolved in 78 g DI water), all at 60 °C, were added to the flask. Ammonia (25%, 26 g) in DI water (26 g) and ADH (18.5 g) in DI water (48 g) were then added to the flask at 50 °C to obtain an aqueous dispersion.

[0092] Synthesis of Polymer Emulsion 42 ("E-42") First-stage monomer emulsion (ME1) was prepared by mixing together 301 g of DI water, 15 g of B-11 surfactant (54%, 564 g), BA (564 g), ST (585 g), PEM (18 g), MAA (35 g), DAAM (31 g), 4.3 g of MEUR (50%, 50%), and 5 g of n-DDM to form a stable monomer emulsion. Second-stage monomer emulsion (ME2) was prepared by mixing 130 g of DI water, 7.6 g of B-11 surfactant (54%, 50%), BA (105 g), ST (425 g), 2 g of MEUR (50%, 50%), and 1.0 g of n-DDM to form a stable monomer emulsion.

[0093] A 5-liter, four-necked round-bottom flask equipped with a paddle stirrer, thermocouple, nitrogen inlet, and reflux condenser was charged with DI water (780 g) and stirring was initiated. The contents of the flask were heated to 90°C under N2. B-11 surfactant (54%, 4.7 g), MAA (5.3 g), ME1 (89 g), and APS (5 g) in DI water (44 g) were added to the flask, followed by a DI water rinse (45 g). The remaining ME1, APS (1.5 g) in DI water (71 g), and ammonia (25%, 15 g) in DI water (52 g) were then added over 87 minutes. After the ME1 feed was completed, DI water (30 g) was added as a rinse. ME2 and APS (0.7 g) in DI water (30 g) were then added over 33 minutes. After the ME2 feed was completed, DI water (30 g) was added as a rinse. The temperature of the contents of the flask was maintained between 87°C and 89°C during the addition. At the end of the polymerization, FeSO in DI water (5 g) was added. 4 A mixture of EDTA sodium salt (0.016 g) in 7H2O (0.008 g) and DI water (5 g), a solution of t-BHP (70%, 3.4 g t-BHP dissolved in 43 g DI water), and a solution of IAA (2.3 g IAA dissolved in 78 g DI water), all at 60° C., were added to a flask. Ammonia (25%, 26 g) in DI water (26 g) and ADH (18.5 g) in DI water (48 g) were then added to the flask at 50° C. to obtain an aqueous dispersion.

[0094] The as-prepared polymer emulsions were characterized according to the following test methods, and the properties of these aqueous polymer dispersions are shown in Table 1.

[0095] Solid content The solids content of the aqueous dispersion samples was measured by weighing 0.7±0.1 g of sample (the wet weight of the sample is designated "W1"), placing the sample in an aluminum pan (the weight of the aluminum pan is designated "W2") in a 150°C oven for 25 minutes, then cooling to room temperature and weighing the aluminum pan containing the dried sample (the total weight is designated "W3"). "W3-W2" refers to the dry weight or solids weight of the sample. The solids content was calculated by (W3-W2) / W1*100%.

[0096] GPC analysis The number average molecular weight (Mn) of the emulsion polymer is determined by GPC analysis, typically performed on an Agilent 1200. Samples were dissolved in tetrahydrofuran (THF) / formic acid (FA) (5%) at a concentration of 2 milligrams per milliliter (mg / mL), stirred for more than 1 hour, stored at room temperature overnight, and then filtered through a 0.45 micrometer (μm) polytetrafluoroethylene (PTFE) filter before GPC analysis. GPC analysis was performed using the following conditions:

[0097] Columns: one PL Gel GUARD column (10 μm, 50 millimeters (mm) × 7.5 mm) in tandem, two Mixed B columns (7.8 mm × 300 mm); column temperature: 40 °C; mobile phase: THF / FA (5%); flow rate: 1.0 mL / min; injection volume: 100 μL; detector: Agilent refractive index detector, 40 °C; and calibration curve: PL Polystyrene I Narrow standards with molecular weights ranging from 2,329,000 to 580 g / mol, polynom 3 fitness.

[0098] [Table 1] * Fox Tg was calculated by the Fox formula. Dry weight (エマルジョンポリマー) = weight (ポリマーエマルジョン) *Solid content (ポリマーエマルジョン)。 NA=not available.

[0099] Preparation of an aqueous solution of neutralized sebacic acid ("sebacic acid solution") Sebacic acid (6.00 g), aqueous ammonia (25%, 19.53 g), and water (1.74 g) were mixed and stirred to obtain a clear solution containing sebacic acid, monoammonium sebacate, bisammonium sebacate, or a mixture thereof.

[0100] Preparation of an aqueous solution of neutralized adipic acid ("adipic acid solution") Adipic acid (6.00 g), aqueous ammonia (25%, 19.53 g), and water (1.74 g) were mixed and stirred to obtain a clear solution containing adipic acid, monoammonium adipate, bisammonium adipate, or a mixture thereof.

[0101] Coating composition samples The formulations of the direct-to-metal (DTM) coating samples are reported in Tables 2 and 3, with the amount of each component expressed in grams (g). The as-prepared polymer emulsions described above were used as binders in the samples, and the specific binders used in each sample are listed in Table 4. The pigment grind was prepared by mixing the components in the grinding stage using a high-speed grinder at 1500 revolutions per minute (RPM) for 20 minutes. The binder was premixed with water and aqueous ammonia to adjust the pH value to greater than 8.5 to obtain a premix. The pigment grind was then added to the premix, followed by the addition of TEXANOL ester alcohol. To the resulting mixture, an aqueous solution of NaNO2 and the sebacic acid or adipic acid solution prepared above were further added. Finally, ACRYSOL RM-8W rheology modifier and water were added to adjust the KU viscosity of the resulting sample to 80-90 kreb units (KU), as measured at room temperature using a BROOKFIELD™ KU-3 viscometer. The resulting coating compositions were evaluated according to the following test methods, and the properties and characterization results are provided in Table 4.

[0102] Flash rust resistance test A cast iron panel (Model QT500-7 according to GB / T 1348-2009) was polished with 240-grit abrasive paper to remove loose rust on the panel surface. The panel surface was further treated with alcohol to remove anti-flash oil. Then, a coating composition sample (1.5 g) was brushed onto a 4 cm x 8 cm section of the panel using an art brush (Model 6713 from Shanghai Oil Paint Brush Manufactory) to obtain a final dry film thickness of 60 μm to 80 μm. The coated panel was immediately placed in an environmental chamber (LabEvent LC / 100 / 40 / 5) at 40°C and 90% relative humidity for 24 hours. The panel was then removed and evaluated for flash rust rating according to ISO 8501-4:2006, as shown in Table A below. A flash rust rating of "0" is acceptable.

[0103] [Table 2]

[0104] Initial water resistance test The coating composition samples were applied onto cold-rolled steel panels (R46 from Q-lab, Inc.) with a 150 μm applicator and then dried for 120 minutes at a temperature of 23° C. and a relative humidity of 50%. The resulting coated panels were partially immersed in DI water for 12 days at 23° C. The surfaces of the panels were then observed for rust spots and blisters after immersion.

[0105] Blister ratings are performed according to ASTM D714-02(2009) and include numbers and / or one or more letters, as shown in Table B. The letters F, M, MD, or D qualitatively describe the blister density. The numbers refer to the blister size, with 2 being the largest size, 8 being the smallest size, and 10 being no blisters. The higher the number, the smaller the blister size. Rust ratings are determined according to ASTM D610-2001, as shown in Tables C and D. Panels with a blister rating of "8M," preferably "8F" or "10"; panels with a rust rating of "9P" or "9S," preferably "10," are acceptable and exhibit good initial water resistance.

[0106] Long-term corrosion resistance test Long-term corrosion resistance is determined by exposing the panels to a salt spray environment (5% sodium chloride fog) according to ASTM B117-2011 test method (Q-Fog cyclic corrosion tester, model number Q-FOG / CCT1100).

[0107] Panels were prepared by drawing down coating composition samples onto cold-rolled steel (R46 from Q-lab, Inc.) with a 150 μm applicator and drying for 7 days at 23°C and 50% relative humidity to obtain a final dry film thickness of 40 μm to 60 μm. Prior to exposure, the exposed cold-rolled steel was covered with tape (3M Plastic Tape #471). A razor blade-made scribe mark was inscribed on the bottom half of the panel immediately prior to exposure. The panels were exposed to a salt spray environment for 150 hours, then removed, washed with DI water, and evaluated for rust and blistering. Panels with a blister rating of "6F" or "8M," preferably "8F" or "10," and panels with a rust rating of "9P" or "9S," preferably "10," were acceptable and demonstrated good long-term corrosion resistance.

[0108] [Table 3]

[0109] Table 4

[0110] Table 5

[0111] The properties and characterization of the coating composition samples are shown in Table 4. As shown in Table 4, samples CE1-3 used a conventional emulsion polymer (E-11) as the binder. Coating composition samples CE1 and CE2, which further contained 0.2 wt% and 0.3 wt% sebacic acid, respectively, failed to provide good flash rust resistance. Further increasing the sebacic acid content to 0.5 wt% improved flash rust resistance, but resulted in poor long-term corrosion resistance (CE3). Samples CE4-7, which used the E-05 binder without DAAM structural units, also exhibited poor flash rust resistance, even with the addition of 0.5 wt% sebacic acid. Samples CE8 and CE9, which contained the E-61 binder with DAAM structural units but either no sebacic acid or 0.05 wt% sebacic acid, both exhibited poor flash rust resistance and long-term corrosion resistance. Samples CE10 and CE11 show that, regardless of the amount of sebacic acid added, in the absence of a DAAM-containing binder, flash rust resistance or initial water resistance were poor. Among samples CE12-CE14 containing the E-12 binder with both DAAM and PEM structural units, sample CE12 without sebacic acid exhibited poor flash rust resistance and initial water resistance, sample CE13 with 0.25 wt% sebacic acid exhibited poor flash rust resistance, and sample CE14 with 1.5 wt% sebacic acid exhibited poor long-term corrosion resistance and initial water resistance. Sample CE15, containing the E-32 binder with 1.5 wt% PEM structural units, exhibited poor initial water resistance. Sample CE16, containing the E-30 binder with 4.2 wt% DAAM structural units, exhibited poor initial water resistance and long-term corrosion resistance. The CE17 sample containing a certain amount of adipic acid received a flash rust rating of "L", indicating poor flash rust resistance.

[0112] In contrast, all of the IE1-12 samples achieved excellent flash rust resistance and good initial water resistance and long-term corrosion resistance by using a novel combination of an emulsion polymer containing specific concentrations of PEM and DAAM structural units and a specific weight percent of sebacic acid. In this novel combination, sebacic acid not only contributed to improved flash rust resistance compared to the CE12 sample, but also demonstrated benefits in terms of initial water resistance. This indicates that the synergistic effect between the emulsion polymer containing both PEM and DAAM structural units and sebacic acid improves the above properties.

[0113] [Table 6] "Wt % of dicarboxylic acid" refers to "wt % of sebacic acid" for IE1-12 and CE1-16, calculated by the weight of the sebacic acid (raw material) initially added in forming the sebacic acid solution used in preparing the sample relative to the coating composition sample weight; or "wt % of adipic acid" for CE17, calculated by the weight of the adipic acid (raw material) initially added in forming the adipic acid solution used in preparing the sample relative to the coating composition sample weight.

[0114] [Table 7]

[0115] [Table 8] * Instead of sebacic acid solution, as prepared adipic acid solution was used in CE17. The present application also relates to the following aspects: (1) 1. An aqueous coating composition comprising: (A) an emulsion polymer, based on the weight of said emulsion polymer: 0.48% to 1.20% by weight of structural units of phosphorous acid monomer, its salt, or mixtures thereof; 0.5% by weight to 3% by weight of diacetone (meth)acrylamide structural units; 10% to 80% by weight of vinyl aromatic monomer structural units; (Meth)acrylic acid C 1 ~C 24 -alkyl ester structural units, and optionally, structural units of an α,β-ethylenically unsaturated carboxylic acid, a salt thereof, or a mixture thereof; an emulsion polymer comprising: (B) a dicarboxylic acid, a salt thereof, or a mixture thereof, wherein the dicarboxylic acid is a compound of formula (I): HOOC-R-COOH(I) wherein R is alkylene, alkenylene, alkynylene, cycloalkylene, cycloalkenylene, cycloalkynylene, arylene, or heterocyclic arylene; and contains 6 to 18 carbon atoms; a dicarboxylic acid, its salt, or mixture thereof, wherein the dicarboxylic acid, its salt, or mixture thereof is present in an amount to provide an —OOC—R—COO— segment at a concentration of 0.28 wt % to 1.0 wt %, based on the weight of the aqueous coating composition; (C) 0.05 to 5 wt. % of a flash rust inhibitor, based on the weight of the aqueous coating composition; 1. An aqueous coating composition comprising: (2) The aqueous coating composition according to (1) above, wherein the dicarboxylic acid is selected from sebacic acid, dodecanedioic acid, suberic acid, ancoic acid, undecanedioic acid, eicosanedioic acid, or a mixture thereof. (3) The aqueous coating composition according to (1) or (2), wherein the salt of the dicarboxylic acid is an ammonium salt, an alkali metal salt, an amine salt, or a mixture thereof. (4) The aqueous coating composition according to any one of (1) to (3) above, wherein the phosphorous acid monomer is selected from phosphoethyl methacrylate, phosphoethyl acrylate, allyl ether phosphate, phosphopropyl methacrylate, phosphobutyl methacrylate, or a mixture thereof. (5) The aqueous coating composition according to any one of (1) to (4) above, wherein the vinyl aromatic monomer is styrene. (6) The aqueous coating composition according to any one of (1) to (5), wherein the emulsion polymer contains 0.3 wt % to 5 wt % of structural units of the α,β-ethylenically unsaturated carboxylic acid, the salt thereof, and a mixture thereof, based on the weight of the emulsion polymer. (7) The aqueous coating composition according to any one of (1) to (6), wherein the emulsion polymer has a glass transition temperature of -10°C to 40°C, as calculated by the Fox equation. (8) The aqueous coating composition according to any one of (1) to (7) above, wherein the emulsion polymer contains 0% by weight to less than 5% by weight of cycloalkyl(meth)acrylate structural units. (9) the emulsion polymer comprises, based on the weight of the emulsion polymer, 0.8% to 1.2% by weight of structural units of phosphoethyl methacrylate; 1.1% to 2.1% by weight of structural units of diacetone acrylamide; 0.3% to 4% by weight of structural units of acrylic acid, methacrylic acid, or a mixture thereof; 40% to 70% by weight of structural units of styrene; and 20% to 50% by weight of structural units of butyl acrylate, 2-ethylhexyl acrylate, butyl methacrylate, or a mixture thereof. The aqueous coating composition according to any one of (1) to (8) above, comprising: (10) The aqueous coating composition according to any one of (1) to (9) above, wherein the emulsion polymer has a number average molecular weight of 10,000 to 60,000 g / mol as measured by gel permeation chromatography. (11) the emulsion polymer is a multistage emulsion polymer comprising, based on the weight of the multistage emulsion polymer, 50% to 80% by weight of polymer A and 20% to 50% by weight of polymer B; The polymer A contains, based on the weight of the polymer A, 0.3 wt % to 2.4 wt % of structural units of the phosphorous acid monomer, the salt thereof, or a mixture thereof; 0.5 wt % to 6 wt % of structural units of the diacetone (meth)acrylamide; and 10 wt % to 75 wt % of structural units of the vinyl aromatic monomer, the polymer B comprises, based on the weight of the polymer B, 0 wt % to 2.5 wt % of structural units of the phosphorous acid monomer, the salt thereof, or a mixture thereof; 0 wt % to 2.5 wt % of structural units of the diacetone (meth)acrylamide; and 10 wt % to 100 wt % of structural units of the vinyl aromatic monomer; At least one of the polymer A and the polymer B is a (meth)acrylic acid C 1 ~C 24 The aqueous coating composition according to any one of (1) to (10) above, further comprising a structural unit of an alkyl ester. (12) The aqueous coating composition according to any one of (1) to (11) above, further comprising a polyfunctional carboxylic acid hydrazide containing at least two hydrazide groups per molecule. (13) The aqueous coating composition according to (12) above, wherein the polyfunctional carboxylic acid hydrazide is selected from adipic acid dihydrazide, oxalic acid dihydrazide, isophthalic acid dihydrazide, polyacrylic acid polyhydrazide, or a mixture thereof. (14) A method for preparing the aqueous coating composition according to any one of (1) to (13), comprising mixing the emulsion polymer and the dicarboxylic acid, its salt, or a mixture thereof with the flash rust inhibitor.

Claims

1. 1. An aqueous coating composition comprising: (A) an emulsion polymer comprising, based on the weight of said emulsion polymer: 0.48% to 1.20% by weight of structural units of phosphorous acid monomer, its salt, or mixtures thereof; 0.5% to 3% by weight of diacetone (meth)acrylamide structural units; 10% to 80% by weight of vinyl aromatic monomer structural units; C of (meth)acrylic acid １ ~C ２４ - alkyl ester structural units, and optionally structural units of an α,β-ethylenically unsaturated carboxylic acid, a salt thereof, or a mixture thereof; an emulsion polymer comprising: (B) a dicarboxylic acid, a salt thereof, or a mixture thereof, wherein the dicarboxylic acid is represented by formula (I): HOOC-R-COOH(I) wherein R is alkylene, alkenylene, alkynylene, cycloalkylene, cycloalkenylene, cycloalkynylene, arylene, or heterocyclic arylene; and contains 6 to 18 carbon atoms; a dicarboxylic acid, its salt, or mixture thereof, wherein the dicarboxylic acid, its salt, or mixture thereof is present in an amount to provide an —OOC-R-COO- segment at a concentration of 0.28 wt % to 1.0 wt %, based on the weight of the aqueous coating composition; (C) 0.05 to 5 wt. % of a flash rust inhibitor, based on the weight of the aqueous coating composition; and Including, The flash rust inhibitor is selected from the group consisting of sodium nitrite, sodium molybdate, sodium chromate, sodium phosphate, sodium phosphite, sodium silicate, phosphoric acid, phosphorous acid, soluble salts of magnesium, soluble salts of zinc, soluble salts of nickel, urea, mercaptobenzothiazole (MBT), benzotriazole, aldehydes, heterocyclic nitrogen compounds, sulfur-containing compounds, acetylenic compounds, ascorbic acid, benzoic acid, benzoates, caffeine, and mixtures thereof. Aqueous coating compositions.

2. 10. The aqueous coating composition of claim 1, wherein the dicarboxylic acid is selected from sebacic acid, dodecanedioic acid, suberic acid, ancoic acid, undecanedioic acid, eicosanedioic acid, or mixtures thereof.

3. 3. The aqueous coating composition of claim 1 or 2, wherein the salt of the dicarboxylic acid is an ammonium salt, an alkali metal salt, an amine salt, or a mixture thereof.

4. 4. The aqueous coating composition of claim 1, wherein the phosphorous acid monomer is selected from phosphoethyl methacrylate, phosphoethyl acrylate, allyl ether phosphate, phosphopropyl methacrylate, phosphobutyl methacrylate, or mixtures thereof.

5. The aqueous coating composition of any one of claims 1 to 4, wherein the vinyl aromatic monomer is styrene.

6. 6. The aqueous coating composition of claim 1, wherein the emulsion polymer comprises from 0.3% to 5% by weight of structural units of the α,β-ethylenically unsaturated carboxylic acid, the salt thereof, and mixtures thereof, based on the weight of the emulsion polymer.

7. 7. The aqueous coating composition of any one of claims 1 to 6, wherein the emulsion polymer has a glass transition temperature of from -10°C to 40°C, calculated by the Fox equation.

8. The aqueous coating composition of any one of claims 1 to 7, wherein the emulsion polymer comprises from 0 to less than 5 wt% cycloalkyl (meth)acrylate structural units.

9. the emulsion polymer comprises, based on the weight of the emulsion polymer, 0.8% to 1.2% by weight structural units of phosphoethyl methacrylate; 1.1% to 2.1% by weight structural units of diacetone acrylamide; 0.3% to 4% by weight structural units of acrylic acid, methacrylic acid, or a mixture thereof; 40% to 70% by weight structural units of styrene; and 20% to 50% by weight structural units of butyl acrylate, 2-ethylhexyl acrylate, butyl methacrylate, or a mixture thereof. The aqueous coating composition of any one of claims 1 to 8, comprising:

10. 10. The aqueous coating composition of any one of claims 1 to 9, wherein the emulsion polymer has a number average molecular weight of 10,000 to 60,000 g / mol as determined by gel permeation chromatography.

11. the emulsion polymer is a multistage emulsion polymer comprising, by weight based on the weight of the multistage emulsion polymer, 50% to 80% of Polymer A and 20% to 50% of Polymer B; Polymer A comprises, based on the weight of Polymer A, 0.3 wt % to 2.4 wt % structural units of the phosphorous acid monomer, its salt, or a mixture thereof; 0.5 wt % to 6 wt % structural units of the diacetone (meth)acrylamide; and 10 wt % to 75 wt % structural units of the vinyl aromatic monomer; Polymer B comprises, based on the weight of Polymer B, 0 to 2.5 wt % structural units of the phosphorous acid monomer, the salt thereof, or a mixture thereof; 0 to 2.5 wt % structural units of the diacetone (meth)acrylamide; and 10 to 100 wt % structural units of the vinyl aromatic monomer; At least one of the polymer A and the polymer B is a (meth)acrylic acid C １ ~C ２４ 11. The aqueous coating composition according to claim 1, further comprising structural units of alkyl esters.

12. 12. The aqueous coating composition of any one of claims 1 to 11, further comprising a polyfunctional carboxylic acid hydrazide containing at least two hydrazide groups per molecule.

13. 13. The aqueous coating composition of claim 12, wherein the polyfunctional carboxylic acid hydrazide is selected from adipic acid dihydrazide, oxalic acid dihydrazide, isophthalic acid dihydrazide, polyacrylic acid polyhydrazide, or mixtures thereof.

14. 14. A method for preparing the aqueous coating composition of any one of claims 1 to 13, comprising mixing the emulsion polymer and the dicarboxylic acid, its salt, or mixture thereof with the flash rust inhibitor.

Images