BR112021003465B1 - AQUEOUS DISPERSION, PROCESS, AND AQUEOUS COATING COMPOSITION - Google Patents

Abstract

AQUEOUS DISPERSION, PROCESS, AND AQUEOUS COMPOSITION OF COATING. An aqueous dispersion and aqueous coating composition comprising the aqueous dispersion and the aqueous coating composition providing coatings made therefrom with improved anti-corrosion property and good water resistance and blocking resistance.

Description

FIELD OF THE INVENTION

[001] The present invention relates to an aqueous polymer dispersion and an aqueous coating composition comprising the same.

INTRODUCTION

[002] Solvent-based coating compositions comprising epoxy resins, polyurethane or alkyd resins are widely used in metal protective coatings due to their anti-corrosion performance, mechanical properties and appearance. Water-based acrylic polymer dispersions have far fewer environmental issues than solvent dispersions and are generally used for protection of light to medium metals.

[003] U.S. patent 6,756,459 discloses an aqueous coating composition comprising an aqueous emulsion copolymer comprising, as polymerized units, 55 to 58% styrene, 35 to 37% 2-ethylhexyl acrylate, 2 .5 to 3% methyl methacrylate, 2.5 to 3% phosphoethyl methacrylate, 0 to 0.25% methacryloxypropyltrimethoxysilane and 0 to 3.5% 2-(acetoacetoxy)ethyl methacrylate. Such an aqueous emulsion copolymer can provide coatings with corrosion resistance when applied to metal substrates, for example, exhibiting rust not greater than 20% or a bubble rating not greater than "M" after at least 7 days of exposure to saline spray according to ASTM B-117-97. For some coating applications, such as general industrial finishes and agricultural construction equipment coatings, coatings with even better anti-corrosion performance are required to sustain at least 230 hours of salt spray testing at a dry film thickness of about 40 to 80 μm. Furthermore, it is desirable for waterborne coatings in many applications to have sufficient water resistance and blocking properties to meet industry requirements.

[004] Therefore, there remains a need to provide an aqueous dispersion suitable for coating applications, which provides coatings with the anti-corrosion described above, as well as other desirable properties.

SUMMARY OF THE INVENTION

[005] The present invention achieves the anti-corrosion property described above by providing a new aqueous dispersion. The aqueous dispersion of the present invention comprises an emulsion polymer prepared from a novel combination of monomers including a phosphorous acid monomer and/or a salt thereof, a cycloalkyl (meth)acrylate, a monomer with acetoacetoxy or acetoacetamide functionality and a hydrophobic monomer. An aqueous coating composition comprising such an aqueous dispersion can provide coatings made therefrom with improved corrosion resistance. The aqueous coating composition can also provide coatings with good initial water resistance and/or satisfactory blocking resistance.

[006] In a first aspect, the present invention is an aqueous dispersion comprising an emulsion polymer, wherein the emulsion polymer comprises, by weight based on the weight of the emulsion polymer, (a) structural units of a monomer of phosphorous acid and/or a salt thereof, (b) from 5% to less than 40% of structural units of a cycloalkyl (meth)acrylate, (c) from 0.8% to 5% of structural units of a monomer with acetoacetoxy or acetoacetamide functionality, and (d) structural units of a hydrophobic monomer; wherein the emulsion polymer has a weight average molecular weight of 160,000 g/mol or more.

[007] In a second aspect, the present invention is a process for preparing the aqueous dispersion of the first aspect by polymerization process.

[008] In a third aspect, the present invention is an aqueous coating composition comprising the aqueous dispersion of the first aspect.

DETAILED DESCRIPTION OF THE INVENTION

[009] “Structural units”, also known as “polymerized units”, of the named monomer, refers to the remainder of the monomer after polymerization, that is, polymerized monomer or the monomer in polymerized form. For example, a structural unit of methyl methacrylate is as illustrated: where the dotted lines represent the points of attachment of the structural unit to the main structure of the polymer.

[0010] "Acrylic" in the present invention includes (meth)acrylic acid, (meth)alkyl acrylate, (meth)acrylamide, (meth)acrylonitrile and their modified forms, such as (meth)hydroxyalkyl acrylate. Throughout this document, the word fragment “(meth)acryl” refers to both “methacryl” and “acryl”. 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.

[0011] “Glass Transition Temperature” or “Tg” as used herein can be measured by various techniques including, for example, Differential Scanning Calorimetry (“DSC”) or calculation using a Fox equation. For example, Tg of an emulsion polymer comprising structural units of Monomers a, b and c is determined according to the following Fox equation: 1/Tg(calc.)=w(Ma)/Tg(Ma)+w(Mb)/Tg( Mb)+w(Mc)/Tg(Mc) where Tg(calc.) refers to the calculated glass transition temperature for the polymer; Tg(Ma), Tg(Mb) and Tg(Mc) refer to Tg of Monomer a homopolymer, Monomer b homopolymer and Monomer c homopolymer, respectively; and w(Ma), w(Mb) and w(Mc) refer to the weight fraction of Monomer a, Monomer b and Monomer c used to prepare the emulsion polymer, based on the weight of total monomers, respectively. Homopolymer glass transition temperatures can be found, for example, in the "Polymer Handbook", edited by J. Brandrup and E. H. Immergut, Interscience Publishers.

[0012] The aqueous dispersion of the present invention comprises one or more emulsion polymers. The emulsion polymer useful in the present invention may comprise structural units of one or more additional phosphorous acid monomers and/or salts thereof. Phosphorous acid monomers and/or salts thereof may have ethylenically unsaturation. Phosphorous acid monomers may be dihydrogen phosphate esters of an alcohol, in which the alcohol contains or is replaced by a polymerizable vinyl or olefinic group. Phosphorous acid monomers may include phosphoalkyl (meth)acrylates, such as phosphoethyl (meth)acrylate, phosphopropyl (meth)acrylate, phosphobutyl (meth)acrylate, salts thereof and mixtures thereof; CH2=C(R)-C(O)-O-(RpO)n-P(O)(OH)2, where R=H or CH3, Rp = alkylene, such as an ethylene group, a propylene group or a combination of the same; and n = 1 to 20, such as 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 and mixtures thereof. Preferred phosphorous acid monomers are selected from the group consisting of phosphoethyl methacrylate (PEM), phosphoethyl acrylate, allyl phosphate ether or mixtures thereof; more preferably, phosphoethyl methacrylate. The emulsion polymer may comprise, by weight based on the weight of the emulsion polymer, 0.1% or more, 0.2% or more, 0.3% or more, 0.5% or more, 0.6% or more, 0.8% or more, 1.0% or more, 1.2% or more, 1.3% or more, 1.4% or more, or even 1.5% or more, and at the same time , 5% or less, 4.5% or less, 4% or less, 3.5% or less, 3.2% or less, 3% or less, 2.8% or less, 2.5% or less , 2% or less, or even 1.8% or less, of structural units of phosphorous acid monomers and/or salts thereof. "Emulsion polymer weight" herein refers to the dry or solids weight of the emulsion polymer.

[0013] The emulsion polymer useful in the present invention may further comprise structural units of one or more cycloalkyl (meth)acrylates. Examples of suitable cycloalkyl (meth)acrylates include cyclohexyl (meth)acrylate, methcyclohexyl (meth)acrylate, isobornyl methacrylate, isobornyl acrylate, dihydrodicyclopentadienyl (meth)acrylate, trimethylcyclohexyl, (meth)cyclohexyl t-butyl acrylate or mixtures thereof. The preferred cycloalkyl (meth)acrylate is cyclohexyl methacrylate, cyclohexyl acrylate or a mixture thereof. The emulsion polymer may comprise, by weight, based on the weight of the emulsion polymer, less than 40% structural units of the cycloalkyl (meth)acrylate, for example, 5% or more, 6% or more, 7% or more, 8% or more, 9% or more, 10% or more, 11% or more, 12% or more, 13% or more, 14% or more, or even 15% or more and at the same time 40% or less, 39% or less, 38% or less, 36% or less, 35% or less, 32% or less, 30% or less, 28% or less, 25% or less, 24% or less, 22% or less, or even 20% or less, of structural units of the cycloalkyl (meth)acrylate.

[0014] The emulsion polymer useful in the present invention may also comprise structural units of one or more monomers with acetoacetoxy or acetoacetamide functionality. Monomers with acetoacetoxy or acetoacetamide functionality are monomers that have an ethylenically unsaturation and one or more acetoacetyl chemical moieties represented by: where R1 is hydrogen, an alkyl having 1 to 10 carbon atoms, or phenyl.

[0015] Examples of suitable acetoacetoxy or acetoacetamide functional groups include wherein X is O or N, R1 is a divalent radical and R2 is a trivalent radical which attaches the acetoacetoxy or acetoacetamide functional group to the backbone of the emulsion polymer.

[0016] Suitable acetoacetoxy or acetoacetamide functional monomers may include, for example, acetoacetoxyalkyl (meth)acrylates such as acetoacetoxyethyl methacrylate (AAEM), acetoacetoxyethyl acrylate, acetoacetoxypropyl methacrylate, acetoacetoxybutyl methacrylate and 2,3-di methacrylate (acetoacetoxy)propyl; allyl acetoacetate; vinyl acetoacetate; acetoacetamidoalkyl (meth)acrylates, such as acetoacetamidoethyl methacrylate and acetoacetamidoethyl acrylate; or combinations thereof. The emulsion polymer may comprise, by weight based on the weight of the emulsion polymer, 0.05% or more, 0.1% or more, 0.5% or more, 0.8% or more, 1% or more , 1.2% or more, 1.5% or more, 1.8% or more, 2% or more, 2.2% or more, 2.5% or more, and at the same time 20% or less , 15% or less, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4.5% or less, or even 4% or less, of monomer structural units with acetoacetoxy or acetoacetamide functionality.

[0017] The emulsion polymer of the present invention may also comprise structural units of one or more hydrophobic monomers. "Hydrophobic monomers" refer to monomers with a calculated Hansch parameter > 2.2. As used herein, the term "calculated Hansch parameter" for any molecule refers to parameters that represent an index of hydrophobicity of the polymer, with higher values indicating greater hydrophobicity, as calculated according to the Kowwin methodology. A tool for this can be downloaded from http://www.epa.gov/oppt/exposure/pubs/episuitedl.htm. The Kowwin methodology uses a corrected “fragment constant” methodology to predict the Hansch parameter, expressed as log P. For any molecule, the molecular structure is divided into fragments, each having a coefficient and all the values of the coefficients in the structure are summed to produce the log P estimate for the molecule. Fragments can be atoms, but are larger functional groups (eg, C=O) if the groups provide a reproducible coefficient. The coefficients for each individual fragment were derived by multiple regression of reliably measured log P values (KOWWIN's "reductionist" fragment constant methodology), where the log P is measured by testing the fragment in a mixture of water and a certain hydrophobic organic solvent. In the fragment constant corrected methodology, the group coefficients are adjusted by a correction factor to account for any differences between a measured log P coefficient value of one group and a log P coefficient for the same group that would result from summing the log P coefficients estimates of all atoms in the group alone. The KOWWIN calculation tool and estimation methodology were developed at Syracuse Research Corporation. A journal article by Meylan and Howard (1995) describes the program's methodology as the “Atom/fragment contribution method for estimating octanol-water partition coefficients”. J.Pharm. Sci. 1995, 84, 83 to 92. The Hansch parameters can be calculated from the values of the coefficients found on the listed website. Hansch parameters for common vinyl monomers are available in "Exploring QSAR: Volume 2: Hydrophobic, Electronic and Steric Constants", Hansch, C., Leo, A., Hoekman, D., 1995, American Chemical Society, Washington, D.C.

[0018] The hydrophobic monomer useful in the present invention may include styrene, substituted styrene, C4-C24-alkyl (meth)acrylates or mixtures thereof. C4-C24-alkyl (meth)acrylates refer to alkyl esters of (meth)acrylic acids that contain an alkyl having from 4 to 24 carbon atoms. Hydrophobic monomers preferably include styrene in combination with one or more C4-C12-alkyl (meth)acrylates. Suitable hydrophobic monomers may include, for example, styrene, substituted styrene, such as alpha-methylstyrene, trans-beta-methylstyrene, 2,4-dimethylstyrene, ethylstyrene, butylstriene and p-methoxystyrene; o-, m- and p-methoxystyrene; and p-trifluoromethylstyrene; 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, butyl methacrylate, tert-butyl methacrylate, tert-butyl acrylate, butyl acrylate, lauryl acrylate, lauryl methacrylate or mixtures thereof. The emulsion polymer may comprise, by weight based on the weight of the emulsion polymer, 30% or more, 35% or more, 40% or more, 45% or more, 50% or more, 55% or more, or even 60 % or more, and at the same time 90% or less, 85% or less, 80% or less, 75% or less, 70% or less or even 65% or less of structural units of hydrophobic monomers.

[0019] The emulsion polymer useful in the present invention may also comprise structural units of one or more additional acid monomers and/or salts thereof that are different from the phosphorous acid monomers and/or salts thereof described above. Additional acid monomers can be carboxylic acid monomers, sulfonic acid monomers and mixtures thereof. The carboxylic acid monomers can be α,β-ethylenically unsaturated carboxylic acids, monomers bearing an acid forming group which produces or is subsequently convertible to such an acid group (such as anhydride, (meth)acrylic anhydride or maleic anhydride); and mixtures thereof. Specific examples of carboxylic acid monomers include acrylic acid, methacrylic acid, maleic acid, itaconic acid, crotonic acid, fumaric acid, 2-carboxyethyl acrylate and mixtures thereof. Sulphonic acid monomers can include sodium vinyl sulfonate (SVS), sodium styrene sulfonate (SSS) and acrylamido-methyl-propane sulfonate (AMPS); salts thereof; or mixtures thereof. Preferably, the additional acid monomer is an α,β-ethylenically unsaturated carboxylic acid, for example acrylic acid, methacrylic acid, itaconic acid or mixtures thereof. The emulsion polymer may comprise, by weight, based on the weight of the emulsion polymer, from zero to 10%, from 0.5% to 5%, from 1% to 3%, or from 1.5% to 2% structural units of additional acid monomers and/or salts thereof.

[0020] The emulsion polymer useful in the present invention may further comprise structural units of one or more multiethylenically unsaturated monomers, which include di-, tri-, tetra- or more multifunctional ethylenically unsaturated monomers. Examples of suitable multiethylenically unsaturated monomers include butadiene, allyl (meth)acrylate, divinyl benzene, ethylene glycol dimethacrylate, butylene glycol dimethacrylate or mixtures thereof. The emulsion polymer may comprise, by weight, based on the weight of the emulsion polymer, from zero to 5% multiethylenically unsaturated monomer structural units, for example, 3% or less, 1% or less, 0.5% or less or even zero.

[0021] The emulsion polymer useful in the present invention may also comprise structural units of one or more ethylenically unsaturated monomers that have one or more functional groups selected from ureido, amide, amino, silane, hydroxyl or combinations thereof (hereinafter “ functional group-containing monomers”). Such functional group-containing monomers may include, for example, amino-functional monomers such as dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, dimethylaminopropyl methacrylate, dimethylaminopropyl acrylate; monomers bearing groups with amide functionality, such as acrylamide and methacrylamide; vinyltrialkoxysilane, such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, vinyldimethylethoxysilane, vinylmethyldiethoxysilane or (meth)acryloxyalkyltrialkoxysilane, such as (meth)acryloxyethyltrimethoxysilane and (meth)acryloxypropyltrimethoxysilane; monomers with ureido functionality; hydroxyl functional monomers such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate and 3-hydroxybutyl methacrylate; or mixtures thereof. Preferred functional group-containing monomers are ureido-functional monomers. As used herein, the term "ureido-functional monomers" refers to an ethylenically unsaturated compound comprising a cyclic ureido group (i.e., an imidazolidin-2-one group). Examples of suitable ureido-functional monomers include N-(2-Methacrylamidoethyl)ethyleneurea, N-(2-Methacryloyloxyethyl)ethyleneurea, N-(maleathoxy diethyl)ethyleneurea or mixtures thereof. Preferred ureido-functional monomers are cyclic ureido group-containing alkyl esters of (meth)acrylic acids, most preferably N-(2-methacryloyloxyethyl)ethylene urea. The emulsion polymer may comprise, by weight based on the weight of the emulsion polymer, zero or more, 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, 0.5% or more, 0.6% or more, or even 0.7% or more, and at the same time, 3% or less, 2.5% or less, 2% or less, 1.5% or less, 1.1% or less, 1% or less, 0.9% or less, or even 0.8% or less, functional group-containing ethylenically unsaturated monomer structural units.

[0022] The emulsion polymer useful in the present invention may also comprise structural units of one or more additional ethylenically unsaturated nonionic monomers. "Nonionic monomers" herein refers to monomers that do not carry an ionic charge between pH=1 and 14. Suitable additional ethylenically unsaturated nonionic monomers may include, for example, C1-C3-alkyl (meth)acrylates such as methacrylate methyl, ethyl methacrylate and ethyl acrylate; (meth)acrylonitrile or mixtures thereof. The emulsion polymer may comprise, by weight, based on the weight of the emulsion polymer, from zero to 10%, from 0.1% to 8%, from 0.5% to 6%, from 1% to 5%, from 2% to 4% structural units of the additional non-ionic ethylenically unsaturated monomers.

[0023] The emulsion polymer useful in the present invention may comprise, by weight based on the weight of the emulsion polymer, from 0.5% to 3% structural units of phosphorous acid monomer and/or salt thereof, from 10 % to 30% of cycloalkyl (meth)acrylate structural units, from 1.5% to 4% of monomer structural units with acetoacetoxy or acetoacetamide functionality, from 30% to 50% of styrene and substituted styrene structural units, of 20% to 40% structural units of C4-C12-alkyl (meth)acrylate, and zero to 3% structural units of ethylenically unsaturated monomers having one or more functional groups selected from ureido, amide, amino, silane, hydroxyl or combinations thereof.

[0024] The total weight concentration of the structural units above the emulsion polymer may be equal to 100%. The types and levels of monomers described above for preparing the emulsion polymer can be chosen to provide the emulsion polymer with a suitable glass transition temperature (Tg) for different applications. The Tg of the emulsion polymer can be 0°C or higher, 5°C or higher, 10°C or higher, 15°C or higher, 20°C or higher, 25°C or higher, or even 30°C or higher. and at the same time 60°C or less, 55°C or less, 50°C or less, 47°C or less, 44°C or less, or even 40°C or less, as calculated by the equation of Fox.

[0025] The emulsion polymer useful in the present invention may have a weight average molecular weight (Mw) of 160,000 g/mol or more, for example, 170,000 g/mol or more, 180,000 g/mol or more, 200,000 g/mol or more, 220,000 g/mol or more, 240,000 g/mol or more, 260,000 g/mol or more, 280,000 g/mol or more, 300,000 g/mol or more or even 320,000 g/mol or more and at the same time , 700,000 g/mol or less, 650,000 g/mol or less 600,000 g/mol or less, 580,000 g/mol or less, 550,000 g/mol or less, 520,000 g/mol or less, 500,000 g/mol or less, 480,000 g/mol or less 460,000 g/mol or less 450,000 g/mol or less 440,000 g/mol or less 420,000 g/mol or less 400,000 g/mol or less 390,000 g/mol or less or even 350,000 g/mol or less. The weight average molecular weight of the emulsion polymer can be determined by Gel Permeation Chromatography (GPC) with polystyrene standards as described in the Examples section below.

[0026] The aqueous dispersion of the present invention may further comprise one or more epoxy-functional silanes. The epoxy functional silanes can be an epoxy functional polysiloxane oligomer, an epoxy functional silane compound or mixtures thereof. Epoxy-functional polysiloxane oligomers useful in the present invention are typically saturated epoxy-functional polysiloxane oligomers. The "oligomer" herein refers to a polymer having a number average molecular weight of 100 to 3000, 300 to 2000, or 350 to 1000. The number average molecular weight (Mn) of epoxy-functional polysiloxane oligomers can be measured by GPC with polystyrene standards that have molecular weights ranging from 580 to 19,760 g/mol.

[0027] Polysiloxane oligomers with epoxy functionality useful in the present invention may have the structure of formula (I): wherein x is from 0 to 14; preferably from 0 to 4, from 1 to 4 or from 1 to 3; and R3 is -CH2CH2CH2-. Commercially available epoxy functional polysiloxane oligomers can include CoatOSil MP 200 polysiloxane oligomer available from Momentive Performance Materials Inc.

[0028] The silane compound with epoxy functionality useful in the present invention is typically a saturated alkoxylated silane having an epoxy group. The epoxy functional silane compound can have at least one hydrolyzable silane group. A preferred epoxy functional silane compound has the general formula (II): wherein each R3 independently represents an alkyl group having one to 6 carbon atoms; each OR3 group independently represents an alkoxy group having one to 6 carbon atoms including, for example, methoxy, ethoxy or a combination thereof; R4 represents a bivalent organic group having a molecular weight of 200 or less, preferably, R4 is a C1-C10, C1-C5 or C1-C3 alkylene group; R5 represents a hydrogen atom or an alkyl, aryl or aralkyl group having one to 20 carbon atoms; eq is one, 2 or 3. Examples of suitable epoxy functional silane compounds include 3-glycidyloxypropyl trimethoxysilane, 3-glycidyloxypropyl triethoxysilane, 3-glycidyloxypropyl methyldiethoxysilane, 3-glycidyloxypropyl methyldimethoxysilane or mixtures thereof. Commercially available epoxy functional silane compounds can include gamma-glycidoxypropyltrimethoxysilane Silquest A-187 from Momentive Performance Materials Inc.

[0029] The epoxy functional silanes useful in the present invention may be present in a combined amount of zero or more, 0.05% or more, 0.1% or more, 0.15% or more, 0.2% or more. more, 0.25% or more, 0.3% or more, or even 0.35% or more and at the same time 5% or less, 4% or less, 3% or less, 2.5% or less, 2% or less, 1.5% or less, 1.2% or less, 1% or less, 0.8% or less, or even 0.5% or less, by weight based on the weight of the emulsion polymer .

[0030] The aqueous dispersion of the present invention further comprises water, for example, in an amount of 30% to 90%, 40% to 80%, 50% to 70% or 55% to 60%, by weight with based on the total weight of the aqueous dispersion.

[0031] The aqueous dispersion of the present invention can be prepared by emulsion polymerization of a mixture of the monomers described above. The total weight concentration of the monomer mixture to prepare the emulsion polymer is equal to 100%. The dosage of such monomer, based on the total weight of the monomers, is substantially the same as the amount by weight of each of these monomers as structural units in the emulsion polymer. The monomer blend can be added neat or as an emulsion in water; or added in one or more additions or continuously, linearly or non-linearly, during the polymer preparation reaction period. The suitable temperature for the free radical polymerization process can be below 100 °C, in the range of 10 °C to 95 °C or in the range of 50 °C to 90 °C. One or more surfactants can be used in preparing the polymer. The epoxy-functional silane can be added after polymerization of the monomer mixture.

[0032] One or more radical initiators can be used in the polymerization process. The polymerization process may be a thermally initiated or a redox initiated emulsion polymerization. Examples of suitable free radical initiators include hydrogen peroxide, t-butyl hydroperoxide, cumene hydroperoxide, alkali metal and/or ammonium persulfates, sodium perborate, perphosphoric acid and salts thereof; potassium permanganate and alkali metal or ammonium salts of peroxydisulfuric acid. Free radical initiators can typically be used at a level of 0.01% to 3.0% by weight, based on total weight of monomers. Redox systems comprising the initiators described above coupled to a suitable reductant can be used in the polymerization process. Examples of suitable reductants include sodium formaldehyde sulfoxylate, ascorbic acid, isoascorbic acid, alkali metal and ammonium salts of sulfur-containing acids such as sodium sulfide, disulfide, thiosulfate, hydrosulfite, sulfide, hydrosulfide or dithionite, formadinesulfinic acid, acetone disulfide, glycolic acid, hydroxymethanesulfonic acid, glyoxylic acid hydrate, lactic acid, glyceric acid, malic acid, tartaric acid and salts of the acids thereof. Metal salts of iron, copper, manganese, silver, platinum, vanadium, nickel, chromium, palladium or cobalt can be used to catalyze the redox reaction. Chelating agents for the metals can optionally be used.

[0033] One or more chain transfer agents can be used in the polymerization process to control the molecular weight of the emulsion polymer. 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 azelaic mercaptan, hydroxy group-containing mercaptans, such as hydroxyethyl mercaptan, mercaptopropionic acid, and mixtures thereof. The chain transfer agent can be used in an amount from zero to 2%, for example, 1.5% or less, 1% or less, 0.5% or less, 0.3% or less, 0.2 % or less, or even 0.15% or less, by weight based on the total weight of the monomers used to prepare the emulsion polymer.

[0034] After completing the polymerization, the aqueous dispersion obtained can be neutralized by one or more bases as neutralizers at a pH value, for example, at least 6, 6 to 10 or 7 to 9. Bases can lead to partial or complete neutralization of the ionic or latently 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, zinc oxide, magnesium oxide, sodium carbonate; 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. The emulsion polymer particles in the aqueous dispersion can have a particle size from 50 nanometers (nm) to 500 nm, from 80 nm to 200 nm, or from 90 nm to 150 nm. average Z size and can be measured by a Brookhaven BI-90 Plus Particle Size Analyzer.

[0035] The present invention also relates to an aqueous coating composition comprising the aqueous dispersion of the present invention. Such an aqueous dispersion may be present in the aqueous coating composition, by weight based on the weight of the aqueous coating composition, in an amount of from 20% to 90%, from 30% to 80% or from 40% to 70%.

[0036] The aqueous coating composition of the present invention may further comprise pigments and/or extenders. "Pigment" herein refers to a material that has the ability to materially contribute to the opacity or concealment of a coating. Such materials typically have a refractive index greater than 1.8. Inorganic pigments typically include metal oxides. Examples of suitable pigments include titanium dioxide (TiO2), carbon black, zinc oxide, iron oxide, zinc sulfide, anti-corrosion pigments such as zinc phosphate and zinc molybdate, carbon black, barium sulfate, carbonate barium and mixtures thereof. TiO2 normally exists in two crystal forms, anastasis and rutile. Suitable commercially available TiO2 may include, for example, KRONOS 2310 available from Kronos Worldwide, Inc., Ti-Pure R-706 available from Chemours (Wilmington, Del.), TiONA AT1 available from Cristal, and mixtures thereof. TiO2 may also be available in concentrated dispersion form. “Extender” in this document refers to a particulate inorganic material having a refractive index less than or equal to 1.8 and greater than 1.3. Examples of suitable extenders include calcium carbonate, clay, calcium sulfate, aluminosilicates, silicates, zeolites, mica, diatomaceous earth, solid or hollow glass, ceramic microbeads, nepheline syenite, feldspar, diatomaceous earth, calcined diatomaceous earth , talc (hydrated magnesium silicate), silica, alumina, kaolin, pyrophyllite, perlite, barite, wollastonite, opaque polymers such as ROPAQUETM Ultra E available from The Dow Chemical Company (ROPAQUE is a registered trademark of The Dow Chemical Company) and mixtures thereof. The aqueous coating composition may have a pigment volume concentration (PVC) of 0% to 55%, 5% to 40%, or 10% to 35%. PVC can be determined according to the following equation:

[0037] The aqueous coating composition of the present invention may further comprise one or more defoamers. “Defoamers” in this document refer to chemical additives that reduce and impair foaming. Antifoams can be silicone based antifoams, mineral oil based antifoams, ethylene oxide/propylene oxide based antifoams, alkyl polyacrylates or mixtures thereof. Suitable commercially available defoamers may include, for example, TEGO Airex 902 W and TEGO Foamex 1488 polyether siloxane copolymer emulsions, both available from TEGO, silicone strainer BYK-024 available from BYK, and mixtures thereof. The additional defoamer can be present, by weight based on the total weight of the aqueous coating composition, generally in an amount of zero to 5%, 0.05% to 3%, or 0.1% to 2%.

[0038] The aqueous coating composition of the present invention may additionally comprise one or more thickeners, also known as "rheology modifiers". Thickeners can include polyvinyl alcohol (PVA), clay materials, acid derivatives, acid copolymers, urethane associated thickeners (UAT), polyether urea polyurethanes (PEUPU), polyether polyurethanes (PEPU) or mixtures thereof. Examples of suitable thickeners include alkaline swellable emulsions (ASE) such as sodium or ammonium neutralized acrylic acid polymers; hydrophobically modified alkaline swellable emulsions (HASE) such as hydrophobically modified acrylic acid copolymers; associative thickeners such as hydrophobically modified ethoxylated urethanes (HEUR); 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. The thickener may be present, by weight based on the total weight of the aqueous coating composition, in an amount of zero to 5%, 0.05% to 3%, or 0.1% to 1%.

[0039] The aqueous coating composition of the present invention may additionally comprise one or more wetting agents. "Wetting agents" herein refer to chemical additives that reduce the surface tension of a coating composition, causing the coating composition to more easily spread across or penetrate the surface of a substrate. Wetting agents can be polycarboxylates, anionic, zwitterionic or non-ionic. Suitable commercially available wetting agents include, for example, nonionic wetting agent SURFYNOL 104 and SURFYNOL TG based on an actatylene diol available from Evonik, polyether modified siloxanes BYK-346 and BYK-349, both available from BYK, or mixtures thereof. The wetting agent can be present, by weight based on the total weight of the aqueous coating composition, from zero to 5%, from 0.05% to 3%, or from 0.1% to 2%.

[0040] The aqueous coating composition of the present invention may further comprise one or more coalescents. “Coalescents” in this document refer to slow evaporating solvents that fuse 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, monobutyl ether ethylene glycol, 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. Coalescents can be present, by weight based on the total weight of the aqueous coating composition, from zero to 15%, from 0.5% to 8%, or from 2% to 5%.

[0041] The aqueous coating composition of the present invention may further comprise one or more dispersants. The dispersant may be polyacrylic acid or polymethacrylic acid or maleic anhydride with various monomers such as styrene, acrylate or methacrylate esters, diisobutylene and other hydrophilic or hydrophobic comonomers; salts thereof; and mixtures thereof. The dispersant may be present, by weight based on the total weight of the aqueous coating composition, in an amount of zero to 5%, 0.05% to 3%, or 0.1% to 1%.

[0042] In addition to the components described above, the aqueous coating composition of the present invention may additionally comprise any one of or a combination of the following additives: buffers, neutralizers, humectants, anti-mold agents, biocides, anti-fouling agents, colorants, flow agents , antioxidants, plasticizers, leveling agents, adhesion promoters, flash rust additives and grinding vehicles. These additives may be present in a combined amount of zero to 10% or 0.1% to 2% by weight, based on the total weight of the aqueous coating composition. The aqueous coating composition may also comprise water in an amount of 30% to 90%, 40% to 80% or 50% to 70% by weight of the aqueous coating composition.

[0043] The aqueous coating composition of the present invention can be prepared by a process comprising: addition mixing the aqueous dispersion with other optional components, for example, pigments and/or extenders, as described above. The components in the aqueous coating composition can be mixed in any order to provide the aqueous coating composition of the present invention. Any of the above-mentioned optional components can also be added to the composition during or before mixing to form the aqueous coating composition. When the aqueous coating composition comprises pigment and/or extender, the pigments and/or extender are preferably mixed with the dispersant to form a pigment and/or extender slurry.

[0044] The aqueous coating composition of the present invention can provide coatings produced therefrom with improved corrosion resistance. The present invention also provides a method for improving the corrosion resistance of a corrosion-susceptible substrate such as metal. The method comprises: supplying the aqueous coating composition of the present invention, applying the aqueous coating composition to a metal substrate, and drying or allowing the aqueous coating composition to dry to form a coating. Improved corrosion resistance means surface rust rating of 10 and bubble rating of 6M for a coating with a thickness of 40 to 80 µm after exposure to salt spray for at least 48 hours, for at least 100 hours, for at least 230 hours , for at least 240 hours, for at least 250 hours, for at least 270 hours, at least 340 hours, or at least 400 hours, according to the test method described in the Examples section.

[0045] The present invention also relates to a process for using the aqueous coating composition of the present invention. The process may comprise: applying the coating composition to a substrate and drying, or allowing to dry, the applied coating composition. The present invention also provides a method for preparing a coating. The method may comprise forming the aqueous coating composition of the present invention, applying the aqueous coating composition to a substrate and drying, or allowing to dry, the applied coating composition to form the coating.

[0046] The aqueous coating composition of the present invention can be applied to, and adhered to, various substrates. Examples of suitable substrates include wood, metals, plastics, foams, stone, elastomeric substrates, glass, fabrics, concrete or cementitious substrates. The aqueous coating composition, which preferably comprises the pigment, is suitable for various applications such as marine protective coatings, general industrial finishes, metal protective coatings, automotive coatings, traffic paint, 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, as a one-layer direct-to-metal coating, or in combination with other coatings to form multi-layer coatings.

[0047] The aqueous coating composition of the present invention can be applied to a substrate by incumbent means, which include brushing, dipping, laminating and spraying. The aqueous composition is preferably applied by spraying. Standard spraying techniques and standard spraying equipment, such as air atomized sprinkler, air sprinkler, airless sprinkler, low pressure high volume sprinkler, and electrostatic sprinkler, such as electrostatic bell application, and automatic or manual methods can be used. After the aqueous coating composition of the present invention has been applied to a substrate, the aqueous coating composition can be dried, or allowed to dry, to form a film (i.e., coating) at room temperature (20 to 35°C), or at an elevated temperature, for example from 35 to 240 °C.

EXAMPLES

[0048] Some embodiments of the invention will now be described in the Examples below, in which all parts and percentages are by weight, unless otherwise specified.

[0049] Cyclohexyl methacrylate (CHMA) is available from BASF.

[0050] Styrene (ST) is available from Langyuan Chemical Co., Ltd.

[0051] 2-Ethylhexyl acrylate (2-EHA) is available from The Dow Chemical Company.

[0052] Methacrylic acid (MAA) is available from Sinopharm Chemical Reagent Co., Ltd.

[0053] Phosphoethyl methacrylate (PEM) is available from Solvay.

[0054] N-(2-Methacryloyloxyethyl)ethylene urea (MEUR) is available from Evonik.

[0055] Acetoacetoxyethyl methacrylate (AAEM) is available from Eastman.

[0056] Diacetone acrylamide (DAAM) and adipic dihydrazide (ADH) are available from Kyowa Hakko Chemical Co., Ltd.

[0057] n-dodecyl mercaptan (n-DDM), available from Sinopharm Chemical Reagent Co., Ltd., is used as a chain transfer agent.

[0058] The surfactant POLYSTEP P-12A (P-12A), available from Stepan Co., is a phosphate surfactant based on alcohol ethoxylate.

[0059] The surfactant Disponil FES 32 (Fes 32), available from BASF, is an alcohol ethoxylate sulfate surfactant.

[0060] Silquest A-187 silane (A-187), available from Momentive Performance Materials, is glycidoxypropyltrimethoxysilane.

[0061] ACRYSOL™ RM-8W rheology modifier, available from The Dow Chemical Company, is a nonionic urethane rheology modifier.

[0062] OROTAN™ 681 dispersant, available from The Dow Chemical Company, is a hydrophobic acrylic copolymer pigment dispersant.

[0063] Ti-Pure pigment R-706, available from Chemours Titanium Technologies, is a titanium dioxide pigment.

[0064] SURFYNOL TG nonionic wetting agent and TEGO AIREX 902W defoamer (an emulsion of a polyether siloxane copolymer, which contains fumed silica) are available from Evonik.

[0065] TEXANOL ester alcohol, available from Eastman, is used as a coalescent.

[0066] Ammonia neutralizer (25%) and NaNO2 fast anti-rust agent are both available from Sinopharm Chemical Reagent Co., Ltd.

[0067] Sodium Nitrite (15%) is used as a rapid anti-rust additive.

[0068] OROTAN, TRITON and ACRYSOL are trademarks of The Dow Chemical Company.

[0069] The following standard analytical equipment and methods are used in the Examples.

RESISTANCE TEST TO SALINE SPRAYING

[0070] Coated panels were prepared by applying a test coating formulation onto Q panels (cold-rolled steel) by a 100 μm applicator. The resulting film was then allowed to dry at 23 °C and 50% relative humidity (RH) for 7 days. Salt spray resistance properties were tested by exposing prepared coated panels to a salt spray environment (5% sodium chloride spray) in accordance with ASTM B-117 (2011). The exposed cold rolled steel was taped (3M plastic tape #471) prior to exposure. A reference mark made with a razor blade was scratched on the bottom half of the panels obtained above immediately before exposure. For each formulation, a scratched panel (“scratched panel”) and a non-scratched panel (“non-scratched panel”) were exposed to the saline spray environment for certain hours and then moved from the saline spray environment to sort bubbles. and rust. For example, non-scratched panels were rated after 230 to 270 hours and scratched panels were rated after 400 hours. Results were presented as blister/rust ratings.

[0071] Bubble ratings were performed in accordance with ASTM D714-02 (2010) and comprised a number and/or one or more letters, as shown in Table A. The letters F, M, MD, or D are a qualitative representation bubble density. The number refers to the bubble size, where 2 is the largest size, 8 is the smallest size, and 10 is no bubble. The higher the number, the smaller the bubble size. Rust ratings are determined per ASTM D610-2001 as shown in Tables B and C. Acceptable blister rating is better than 6M and acceptable rust rating is “10” after 230 to 270 hours of salt spray exposure . TABLE A. BLISTER CLASSIFICATION CRITERIA TABLE B. RUST CLASSIFICATION BY GRADE OF RUST TABLE C. RUST CLASSIFICATION BY PERCENTAGE OF RUSTED SURFACE

INITIAL WATER RESISTANCE

[0072] Coated panels were prepared by applying a test coating formulation onto Q panels (cold-rolled steel) by a 100 μm applicator. The resulting film was then allowed to dry at 23°C and 50% RH for 1 hour. The coated panels were then soaked in deionized (DI) water for 7 days before recording the degree of rust and blistering. The degree of rust and blistering was evaluated and recorded according to ASTM D610-2001 and ASTM D714-02 (2010), respectively. Panels with a bubble rating of 10 and a rust rating of 10 for initial water resistance testing are acceptable.

GPC ANALYSIS

[0073] GPC analysis was generally performed by Agilent 1200. The sample was dissolved in tetrahydrofuran (THF)/formic acid (FA) (5%) at a concentration of 2 mg/ml, stirred for one hour , stored at room temperature (20 to 35 °C) overnight, and then filtered through a 0.45 µm polytetrafluoroethylene (PTFE) filter prior to GPC analysis. GPC analysis was conducted using the following conditions:

[0074] Column: One PLgel GUARD column (10 μm, 50 mm x 7.5 mm), two Mixed B columns (7.8 mm x 300 mm) in tandem; column temperature: 40 °C; mobile phase: THF/FA (5%); flow rate: 1.0 ml/minute; Injection volume: 100 μl; detector: Agilent refractive index detector, 40 °C; and calibration curve: Narrow PL Polystyrene I standards with molecular weights that are in the range of 2,329,000 to 580 g/mol, using polynomial fitness 3.

BLOCKING RESISTANCE

[0075] Blocking resistance was measured in accordance with GB/T 23982-2009. Coated panels were prepared by applying a test coating formulation to aluminum (Al) panels by a 100 µm applicator and allowing the panels to dry at 23°C, 50% RH overnight. Two coated panels were then stacked face to face (coating film to coating film) with 500g weight on top of them and then placed in an oven at 50°C for 4 hours. The two stacked panels were then separated from each other to assess blocking strength.

[0076] The evaluation of blocking resistance is defined by the separation force and the area of damage: A: separated without any force; B: separated by a light blow; C: separated by low force with the hands; D: separated by medium force with the hands; E: separated by enormous force with the hands; F: separated by tools The number means the damage area: 0: no damage; 1: = 1%; 2: > 1 and = 5%; 3: > 5 and = 20%; 4: > 20 and ^ 50%; 5: >50% A-0 represents the best and F-5 is the worst. Blocking resistance better than acceptable C-3.

EXAMPLE (EX.) 1

[0077] DI water (455 g), Disponil Fes 32 surfactant (31%, 25 g), ST (572 g), 2-EHA (462 g), CHMA (344 g), MAA (30 g), PEM ( 22 g), MEUR (50%, 22 g), and AAEM (75 g) were mixed to produce a stable monomer emulsion.

[0078] DI water (1,000 g) and Polystep P-12A Surfactant (28%, 33 g) were charged into a five-liter multineck flask equipped with mechanical stirring. The flask contents were heated to 90 °C under a nitrogen atmosphere. Then ammonia (25%, 1.3 g) in DI water (5 g), 85 g of the monomer emulsion and APS (2.95 g) in DI water (16.67 g) were added to the shake flask, followed by a DI water rinse (5 g). The remaining monomer emulsion, APS (1.75 g) in DI water (98.33 g) and ammonia (25%, 8.0 g) in DI water (93.33 g) were then added at 88 °C for 120 minutes, followed by a DI water rinse (25 g). At the end of polymerization, FeSO4 (0.0122 g) in DI water (5.75 g) is mixed with ethylenediamine tetraacetic acid sodium salt (0.0229 g) in DI water (5.75 g), a solution of t-butyl hydroperoxide (3.89 g) in DI water (30.83 g) and a solution of sodium formaldehyde sulfoxylate (2.44 g) in DI water (30 g), a solution of t-butyl hydroperoxide (30 g) butyl (3.44 g) in DI water (25 g) and a solution of sodium formaldehyde sulfoxylate (2.0 g) in DI water (27 g) were all added to the flask at 60 °C, then ammonia ( 25%, 14g) in DI water (15g) was added at 50°C to obtain the aqueous dispersion.

EX. 2 to 5 and 7

[0079] The aqueous dispersions of Exs. 2 to 5 and 7 were prepared, respectively, according to the same procedure as described above to prepare the aqueous dispersion of Ex. 1 above, based on monomer formulations and n-DDM dosage, as given in Table 1 .

EX. 6

[0080] The aqueous dispersion of Ex. 6 was prepared by mixing the prepared aqueous dispersion of Ex. 3 with 0.35% Silquest A-187 silane by weight based on the weight of solids of the aqueous dispersion of Ex. 3.

EX. COMPARATIVES (COMP.) A, D, F E G

[0081] These aqueous dispersions were prepared, respectively, according to the same procedure described above to prepare the aqueous dispersion of Ex. 1 above, based on monomer formulations and the dosage of n-DDM, if used, provided in Table 1.

EX. COMP. B

[0082] DI water (455 g), Disponil Fes 32 surfactant (31%, 25 g), ST (586 g), 2-EHA (401 g), CHMA (344 g), MAA (30 g), PEM ( 22 g), MEUR (50%, 22 g), and DAAM (23 g) were mixed to produce a stable monomer emulsion.

[0083] DI water (1,000 g) and Polystep P-12A surfactant (28%) (33 g) were charged into a five-liter multineck flask equipped with mechanical stirring. The flask contents were heated to 90 °C under a nitrogen atmosphere. Then ammonia (25%, 1.3 g) in DI water (5 g), 85 g of the monomer emulsion and APS (2.95 g) in DI water (16.67 g) were added to the flask, followed by by a DI water rinse (5 g). The remaining monomer emulsion, APS (1.75 g) in DI water (98.33 g) and ammonia (25%, 8.0 g) in DI water (93.33 g) were then added at 88 °C for 120 minutes, followed by a DI water rinse (25 g). At the end of polymerization, FeSO4 (0.0122 g) in DI water (5.75 g) is mixed with ethylenediamine tetraacetic acid sodium salt (0.0229 g) in DI water (5.75 g), a solution of t-butyl hydroperoxide (3.89 g) in DI water (30.83 g) and a solution of sodium formaldehyde sulfoxylate (2.44 g) in DI water (30 g), a solution of t-butyl hydroperoxide (3.44 g) in DI water (25 g) and a solution of sodium formaldehyde sulfoxylate (2.0 g) in DI water (27 g) were all added to the flask at 60 °C, then ammonia (25 %, 14g) in DI water (15g) was added at 50°C. Finally, ADH (14g) in DI water (20g) was added at 45°C to obtain an aqueous dispersion.

EX. COMP. W

[0084] DI water (455 g), Disponil Fes 32 surfactant (31%, 25 g), ST (586 g), 2-EHA (401 g), CHMA (344 g), MAA (30 g), PEM ( 22 g), MEUR (50%, 22 g), and DAAM (23 g) were mixed to produce a stable monomer emulsion.

[0085] DI water (1,000 g) and Polystep P-12A Surfactant (28%) (33 g) were charged into a five-liter multineck flask equipped with mechanical stirring. The flask contents were heated to 90 °C under a nitrogen atmosphere. Then ammonia (25%, 1.3 g) in DI water (5 g), 85 g of the monomer emulsion and APS (2.95 g) in DI water (16.67 g) were added, followed by a rinse with DI water (5 g). The remaining monomer emulsion, APS (1.75 g) in DI water (98.33 g) and ammonia (25%, 8.0 g) in DI water (93.33 g) were then added at 88 °C for 120 minutes, followed by a DI water rinse (25 g). At the end of the polymerization, FeSO4 (0.0122 g) in DI water (5.75 g) together with ethylenediamine tetraacetic acid sodium salt (0.0229 g) in DI water (5.75 g), a solution of t-butyl hydroperoxide (3.89 g) in DI water (30.83 g) and a solution of sodium formaldehyde sulfoxylate (2.44 g) in DI water (30 g), a solution of t-butyl hydroperoxide (3.44 g) in DI water (25 g) and a solution of sodium formaldehyde sulfoxylate (2.0 g) in DI water (27 g) were all added to the flask at 60 °C and then ammonia ( 25%, 14g) in DI water (15g) was added at 50°C. Finally, ADH (21g) in DI water (30g) was added at 45°C to obtain an aqueous dispersion.

EX. COMP. AND

[0086] DI water (455 g), Disponil Fes 32 surfactant (31%, 25 g), ST (586 g), 2-EHA (401 g), CHMA (344 g), MAA (30 g), PEM ( 22 g), MEUR (50%, 22 g), and DAAM (23 g) were mixed to produce a stable monomer emulsion.

[0087] DI water (1,000 g) and Polystep P-12A surfactant (28%) (33 g) were charged into a five-liter multineck flask equipped with mechanical stirring. The flask contents were heated to 90 °C under a nitrogen atmosphere. Then ammonia (25%, 1.3 g) in DI water (5 g), 85 g of the monomer emulsion and APS (2.95 g) in DI water (16.67 g) were added to the flask, followed by by a DI water rinse (5 g). The remaining monomer emulsion, APS (1.75 g) in DI water (98.33 g) and ammonia (25%, 8.0 g) in DI water (93.33 g) were then added at 88 °C to the over 120 minutes, followed by a DI water rinse (25g). At 60 minutes, a large amount of clot was observed in the flask and the experiment was stopped.

[0088] The compositions and properties of the aqueous dispersions obtained above are shown in Table 1. TABLE 1: COMPOSITIONS AND PROPERTIES OF AQUEOUS DISPERSSIONS * Numbers separated by a single slash indicate the percentage by weight of monomer structural units in the emulsion polymer, based on the weight of the emulsion polymer.

INK FORMULATIONS - INK-1, INK COMP. A-I, INK COMP. B E INK COMP. W

[0089] The aqueous dispersions obtained above were used as binders in the preparation of paint formulations, based on the formulations shown in Table 2. The ingredients in the grinding stage were mixed using a high-speed disperser (mixing speed: 800 to 1,800 revolutions per minute (rpm)). Then, the obtained grinding was mixed with the binder using a conventional laboratory mixer (mixing speed: 50 to 600 rpm). Then other ingredients in the release stage were added to obtain the ink compositions. The ink formulations obtained were evaluated according to the test methods described above. The properties of the paints obtained are presented in Table 2. TABLE 2. PAINT FORMULATIONS AND PAINT PROPERTIES

[0090] As shown in Table 2, the dispersion of Ex. 1 gave Paint-1 the best salt spray resistance among all test paints. Furthermore, paints comprising binders with ADH as post-crosslinking agents (Exs. Comp. B and C) showed worse initial water resistance than paints prepared from a binder without the post-crosslinking agent (Ex. Comp. A ) or inks with a binder comprising structural units of AAEM (Ex. 1).

INK FORMULATIONS - INK-2, INK-3-I, INK COMP. A-II AND INK COMP. D

[0091] These ink formulations were prepared according to the same procedure as for Ink-1 described above, based on the formulations provided in Table 3. The properties of the inks obtained are shown in Table 3. As shown in Table 3, all binders provided paints with acceptable initial water resistance. The dispersions of Exs. 2 and 3 provided paints with better salt spray resistance than Ex. Comp dispersion. D. The Ex. 3 dispersion provided paints with even better salt spray resistance than the Ex. 2 dispersion. In addition, the Exs. 2 and 3 provided paints with better blocking resistance than Ex. Comp. A and Ex. Comp. D. TABLE 3. PAINT FORMULATIONS AND PAINT PROPERTIES

INK FORMULATIONS - TINTA-4 AND INK COMP. A-III

[0092] These ink formulations were prepared according to the same procedure as for Ink-1 described above, based on the formulations provided in Table 4. The properties of the inks obtained are shown in Table 4. As shown in Table 4, the dispersion of Ex. 4 provided paints with comparable initial water resistance and better salt spray resistance than the dispersion of Ex. Comp. A. TABLE 4. PAINT FORMULATIONS AND SALINE SPRAY RESISTANCE PROPERTIES

INK FORMULATIONS - INK-3-II, INK-5, INK-6, INK-7, INK COMP. F E INK COMP. G

[0093] These ink formulations were prepared according to the same procedure as for Ink-1 described above, based on the formulations provided in Table 5. The properties of the inks obtained are shown in Table 5. As shown in Table 5, the dispersions of Exs. 3 and 5-7 provided paints with comparable initial water resistance and better salt spray resistance after 270 hours of salt spray exposure when coated on panels (no scratch) than Exs dispersion. Comp. F and G, where Ex. 6 dispersion provided paints with the best salt spray resistance. Furthermore, the dispersions of Exs. 3, 6 and 7 maintained good salt spray resistance even after 400 hours of salt spray exposure when coated in scored panels. TABLE 5. PAINT FORMULATIONS AND SALINE SPRAY RESISTANCE PROPERTIES

Claims (15)

1. Aqueous dispersion, characterized in that it comprises an emulsion polymer, wherein the emulsion polymer comprises, by weight based on the weight of the emulsion polymer, (a) structural units of a phosphorous acid monomer and/or a salt thereof, (b) from 5% to less than 40% of structural units of a cycloalkyl (meth)acrylate, (c) from 0.8% to 5% of structural units of a monomer with acetoacetoxy or acetoacetamide functionality, and (d) structural units of a hydrophobic monomer comprising styrene, substituted styrene, a C4-C12-alkyl (meth)acrylate, or mixtures thereof; wherein the emulsion polymer comprises from 30% to 50% styrene or substituted styrene structural units; wherein the emulsion polymer has a weight average molecular weight of 160,000 g/mol or more. 2. Aqueous dispersion according to claim 1, characterized in that the emulsion polymer further comprises structural units of an ethylenically unsaturated monomer having one or more functional groups selected from ureido, amide, amino, silane, hydroxyl or combinations thereof. 3. Aqueous dispersion according to claim 1 or 2, characterized in that the polymer in emulsion has a weight average molecular weight of 200,000 to 500,000 g/mol. 4. Aqueous dispersion according to claim 1 or 2, characterized in that the phosphorous acid monomer is selected from the group consisting of phosphoethyl methacrylate, phosphoethyl acrylate, allyl ether phosphate or mixtures thereof. 5. Aqueous dispersion according to claim 1 or 2, characterized in that the emulsion polymer comprises, by weight based on the weight of the emulsion polymer, from 0.5% to 3% of acid monomer structural units phosphorus and/or salt thereof. 6. Aqueous dispersion according to claim 1 or 2, characterized in that the monomer with acetoacetoxy or acetoacetamide functionality is selected from the group consisting of acetoacetoxyethyl methacrylate, acetoacetoxyethyl acrylate, acetoacetoxypropyl methacrylate, allyl acetoacetate, acetoacetoxybutyl methacrylate, 2,3-di(acetoacetoxy)propyl methacrylate or mixtures thereof. 7. Aqueous dispersion according to claim 1 or 2, characterized in that the emulsion polymer comprises, by weight based on the weight of the emulsion polymer, from 1.5% to 4% of monomer structural units with functionality acetoacetoxy or acetoacetamide. 8. Aqueous dispersion according to claim 1 or 2, characterized in that the emulsion polymer comprises, by weight based on the weight of the emulsion polymer, from 10% to 30% of structural units of (meth)acrylate of cycloalkyl. 9. Aqueous dispersion according to claim 1 or 2, characterized in that the cycloalkyl (meth)acrylate is cyclohexyl methacrylate, cyclohexyl acrylate or a mixture thereof. 10. Aqueous dispersion according to claim 1 or 2, characterized in that it further comprises a silane with epoxy functionality. 11. Aqueous dispersion according to claim 1 or 2, characterized in that the C4-C12-alkyl (meth)acrylate is selected from 2-ethylhexylacrylate, butyl methacrylate, tert-butyl methacrylate, tert-butyl acrylate or mixtures thereof. 12. Aqueous dispersion according to claim 1 or 2, characterized in that the polymer in emulsion has a measured glass transition temperature of 0 to 60°C. 13. Aqueous dispersion according to claim 1 or 2, characterized in that the emulsion polymer comprises, by weight based on the weight of the emulsion polymer, from 0.5% to 3% of acid monomer structural units phosphorous and/or salt thereof; from 10% to 30% of cycloalkyl (meth)acrylate structural units, from 1.5% to 4% of monomer structural units with acetoacetoxy or acetoacetamide functionality, from 30% to 50% of styrene or substituted styrene structural units , and from 20% to 40% C4-C12-alkyl (meth)acrylate structural units. 14. Process for preparing the aqueous dispersion as defined in any one of claims 1 to 13, characterized in that it is by polymerization process, in which the aqueous dispersion comprises an emulsion polymer comprising, by weight based on the weight of the emulsion polymer, (a) structural units of a monomer of phosphorous acid and/or a salt thereof, (b) from 5% to less than 40% of structural units of a cycloalkyl (meth)acrylate, (c) of 0.8% to 5% of structural units of a monomer with acetoacetoxy or acetoacetamide functionality, and (d) structural units of a hydrophobic monomer comprising styrene, substituted styrene, a C4-C12-alkyl (meth)acrylate, or mixtures thereof themselves; wherein the emulsion polymer comprises from 30% to 50% styrene or substituted styrene structural units by weight based on the weight of the emulsion polymer; wherein the emulsion polymer has a weight average molecular weight of 160,000 g/mol or more. 15. Aqueous coating composition, characterized in that it comprises the aqueous dispersion as defined in any one of claims 1 to 13.