Patent Description:
Aqueous or waterborne coating compositions are becoming increasingly more important than solvent-based coating compositions for less environmental problems. The coating industry is always interested in developing coating compositions without or with substantially reduced VOC content, for example, aqueous coating compositions comprising not greater than <NUM> grams (g) of VOCs per liter of coating compositions. However, aqueous coating compositions, particularly zero or low VOC paints and latex dispersions, usually suffer from a lack of freeze-thaw (F/T) stability, particularly during transportation and storage.

Addition of conventional anti-freeze agents to coating compositions can achieve FIT stability. Examples of these conventional anti-freeze agents include ethylene glycol (EG), propylene glycol (PG), diethylene glycol, and coalescents with low boiling point (<<NUM>). However, the zero or low VOC requirement means the level of these glycol derivatives or low boiling point coalescents that can be used has to be reduced or eliminated. Recently developed anti-freeze agents having no contribution to the VOC content, such as polyethylene glycol (PEG) and tristyrylphenol ethoxylate, can be used to improve FIT stability of coating compositions. For example, <CIT> discloses the use of alkoxylated tristyrylphenols or alkoxylated tributylphenols for improving FIT stability of latex dispersions and paint formulations. Unfortunately, the addition of these compounds hurts stain resistance of the resulting coatings. Some high-end applications require coatings with good stain resistance as indicated by a total stain removal score of at least <NUM> so as to meet the requirement of national standards such as the GB/T9780-<NUM> standard.

<CIT> describes an emulsion paint with improved stain resistance that comprises a polymer of styrene and a reactive emulsifier, a phosphate surfactant and an epoxy-functional polysiloxane oligomer.

<CIT> describes in Example <NUM> an aqueous emulsion of a copolymer of styrene, butyl acrylate, acrylic acid and a reactive emulsifier of Formula I in present claim <NUM> that is produced in the presence of a phosphate surfactant.

Therefore, there is a need to develop an aqueous coating composition which meets the zero or low VOC requirement and provides an FIT stable coating composition while improving stain resistance of coatings obtained therefrom.

The present invention uses a novel combination of a specific emulsion polymer, a polyoxypropylene polyol having a number average molecular weight of from <NUM> to <NUM>,<NUM>, a specific phosphate surfactant, and a functional silane selected from the group consisting of an epoxy functional silane compound and an epoxy functional polysiloxane oligomer. The aqueous coating composition of the present invention affords good FIT stability and provides coatings with surprisingly good stain resistance, as indicated by a total stain removal score of at least <NUM> as measured according to the GB/T <NUM>-<NUM> method, which is the test method for stain removal of films of architectural coatings and paints (issued date: November <NUM>, <NUM>; effective date: August <NUM>, <NUM>). In the meanwhile, the aqueous coating composition can achieve zero or low VOCs, that is, <NUM>/L VOCs or less as measured by the GB18582-<NUM> standard, which is the national standard for indoor decorating and refurbishing materials-Limit of harmful substances of interior architectural coatings (issued date: April <NUM>, <NUM>; effective date: October <NUM>, <NUM>). The above two standards were both published by General Administration of Quality Supervision, Inspection and Quarantine, and Standardization Administration of the P.

In a first aspect, the present invention is an aqueous coating composition comprising:.

In a second aspect, the present invention is a process of preparing the aqueous coating composition of the first aspect, by admixing the emulsion polymer, the polyoxypropylene polyol, the phosphate surfactant, and the functional silane.

"Aqueous" composition or dispersion herein means that particles dispersed in an aqueous medium. By "aqueous medium" herein is meant water and from <NUM> to <NUM>%, by weight based on the weight of the medium, of water-miscible compound(s) such as, for example, alcohols, glycols, glycol ethers and glycol esters.

"Acrylic" as used herein 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.

"Glass transition temperature" or "Tg" as used herein can be measured by various techniques including, for example, differential scanning calorimetry ("DSC") or calculation by using a Fox equation. The particular values of Tg reported herein are those calculated by using the Fox equation (<NPL>)). For example, for calculating the Tg of a copolymer of monomers M<NUM> and M<NUM>, <MAT> wherein Tg(calc. ) is the glass transition temperature calculated for the copolymer, w(M<NUM>) is the weight fraction of monomer M<NUM> in the copolymer, w(M<NUM>) is the weight fraction of monomer M<NUM> in the copolymer, Tg(M<NUM>) is the glass transition temperature of the homopolymer of monomer M<NUM>, and Tg(M<NUM>) is the glass transition temperature of the homopolymer of monomer M<NUM>, all temperatures being in K. The glass transition temperatures of the homopolymers may be found, for example, in "<NPL>.

"Structural units", also known as "polymerized units", of the named monomer, refers to the remnant 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:
<CHM>
where the dotted lines represent the points of attachment of the structural unit to the polymer backbone.

The emulsion polymer useful in the present invention comprises structural units of one or more vinyl aromatic monomers. The vinyl aromatic monomers may include styrene, substituted styrene including, for example, benzyl acrylate, <NUM>-phenoxyethyl acrylate, butylstryene; methylstyrene; p-methoxystyrene; o-, m-, and p-methoxy-, o-, m-, and p-chloro-, o-, m-, and p-trifluoromethyl-, and m- and p-nitrostyrene; and mixtures thereof. Preferred vinyl aromatic monomer is styrene. The emulsion polymer comprises, by weight based on the weight of the emulsion polymer, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, or even <NUM>% or more, and at the same time, <NUM>% or less, <NUM>% or less, <NUM>% or less, <NUM>% or less, <NUM>% or less, <NUM>% or less, <NUM>% or less, <NUM>% or less, <NUM>% or less, <NUM>% or less, <NUM>% or less, or even <NUM>% or less, of structural units of the vinyl aromatic monomer. "Weight of the emulsion polymer" in the present invention refers to the dry or solids weight of the emulsion polymer.

The emulsion polymer useful in the present invention further comprises structural units of one or more polymerizable surfactants. The polymerizable surfactants have the structure of formula (I),
<CHM>.

Specific examples of the polymerizable surfactants have the structure of formula (II),
<CHM>
wherein R<NUM>, m1, and n are as defined above in formula (I), and M is a counter ion such as NH<NUM>+, Li+, Na+ or K+.

In formula (I) or (II), preferred R<NUM> is a phenyl substituted alkyl group having the structure of
<CHM>
wherein R‴ is an alkylene group having from <NUM> to <NUM> carbon atoms, preferably from <NUM> to <NUM> carbon atoms, such as for example,
<CHM>
More preferably, m1 is <NUM>, <NUM> or <NUM>, n is an integer in the range of from <NUM> to <NUM>, and R<NUM> is
<CHM>.

The emulsion polymer useful in the present invention may comprise, by weight based on the weight of the emulsion polymer, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, or even <NUM>% or more, and at the same time, <NUM>% or less, <NUM>% or less, <NUM>% or less, <NUM>% or less, <NUM>% or less, <NUM>% or less, <NUM>% or less, <NUM>% or less, <NUM> % or less, <NUM>% or less, <NUM>% or less, or even <NUM>% or less, of structural units of the polymerizable surfactant.

The emulsion polymer useful in the present invention may further comprise structural units of one or more additional monoethylenically unsaturated nonionic monomers that are different from the vinyl aromatic monomer. "Nonionic monomers" herein refer to monomers that do not bear an ionic charge between pH=<NUM>-<NUM>. Examples of suitable additional monoethylenically unsaturated nonionic monomers include alkyl esters of (meth)acrylic acids, preferably, C<NUM>-C<NUM>, C<NUM>-C<NUM> or C<NUM>-C<NUM>-alkyl esters of (meth)acrylic acid, for example, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, <NUM>-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, or combinations thereof; (meth)acrylonitrile; butadiene; and mixtures thereof. Preferred additional monoethylenically unsaturated nonionic monomers are selected from methyl acrylate, methyl methacrylate, ethyl acrylate, butyl acrylate, butyl methacrylate, <NUM>-ethylhexyl acrylate and mixtures thereof. The emulsion polymer may comprise, by weight based on the weight of the emulsion polymer, from <NUM>% to <NUM>%, from <NUM>% to <NUM>%, from <NUM>% to <NUM>%, from <NUM>% to <NUM>%, or from <NUM>% to <NUM>%, of structural units of the additional monoethylenically unsaturated nonionic monomers.

The emulsion polymer useful in the present invention may also comprise structural units of one or more monoethylenically unsaturated monomers having one or more functional groups. The functional groups may be selected from a carboxyl, amide, sulfonate, acetoacetate, carbonyl, ureido, imide, amino, or phosphorous group, and combinations thereof. Sulfonate and phosphate groups herein in the ethylenically unsaturated monomers carrying at least one functional group may be in the salt form. Examples of such functional-group-containing monoethylenically unsaturated monomers include α, β-ethylenically unsaturated carboxylic acids including an acid-bearing monomer such as methacrylic acid, acrylic acid, itaconic acid, maleic acid, crotonic acid, acyloxypropionic acid, or fumaric acid; or a monomer bearing an acid-forming group which yields or is subsequently convertible to, such an acid group (such as anhydride, (meth)acrylic anhydride, or maleic anhydride); acrylamide, methacrylamide, N-methylacrylamide, N-ethylacrylamide, N-isopropylacrylamide, N-butylacrylamide, N-tertiary butylacrylamide, N-<NUM>-ethylhexylacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide and diacetoneacrylamide; sulfonate monomers such as sodium styrene sulfonate (SSS) and sodium vinyl sulfonate (SVS), salts thereof; acrylamido-<NUM>-methylpropanesulfonic acid (AMPS), salts thereof; phosphoalkyl (meth)acrylates such as phosphoethyl (meth)acrylate, phosphopropyl (meth)acrylate, phosphobutyl (meth)acrylate, salts thereof; diacetone acrylamide (DAAM), acetoacetoxyethyl (meth)acrylate, acetoacetoxypropyl (meth)acrylate, acetoacetoxybutyl (meth)acrylate, <NUM>,<NUM>-di(acetoacetoxy) propyl (meth)acrylate, allyl acetoacetates, or vinyl acetoacetates; and mixtures thereof. Preferred functional-group-containing monoethylenically unsaturated monomers are selected from the group consisting of acrylic acid, methyl acrylic acid, acrylamide and methylacrylamide. The emulsion polymer may comprise, by weight based on the weight of the emulsion polymer, from <NUM> to <NUM>%, from <NUM>% to <NUM>%, from <NUM>% to <NUM>%, or from <NUM>% to <NUM>%, of structural units of the functional-group-containing monoethylenically unsaturated monomer.

The emulsion polymer useful in the present invention may also comprise structural units of one or more multiethylenically unsaturated monomers including di-, tri-, tetra-, or higher multifunctional ethylenically unsaturated monomers. Examples of suitable multiethylenically unsaturated monomers include butadiene, allyl(meth)acrylate, divinyl benzene, ethylene glycol dimethacrylate, butylene glycol dimethacrylate and mixtures thereof. The emulsion polymer may comprise, by weight based on the weight of the emulsion polymer, from <NUM> to <NUM>% of structural units of the multiethylenically unsaturated monomer, for example, <NUM>% or less, <NUM>% or less, or even <NUM>% or less.

The emulsion polymer useful in the present invention preferably comprises, by weight based on the weight of the emulsion polymer, from <NUM>% to <NUM>% of structural units of styrene; from <NUM>% to <NUM>% of structural units of the polymerizable surfactant; from <NUM>% to <NUM>% by weight of structural units of the functional-group-containing monoethylenically unsaturated monomer selected from the group consisting of the α, β-ethylenically unsaturated carboxylic acid, acrylamide and methacrylamide; from <NUM> to <NUM>% of structural units of the multiethylenically unsaturated monomer; and the rest being the additional monoethylenically nonionic monomers.

The emulsion polymer useful in the present invention may have a Tg of from -<NUM> to <NUM>, -<NUM> to <NUM>, -<NUM> to <NUM>, -<NUM> to <NUM>, or -<NUM> to <NUM>.

The emulsion polymer useful in the present invention may be prepared by free-radical emulsion polymerization of the vinyl aromatic monomer, and other monomers described above in the presence of the polymerizable surfactant. Total weight concentration of the monomers and the polymerizable surfactant for preparing the emulsion polymer is equal to <NUM>%. A mixture of the monomers and the polymerizable surfactant may be added neat or as an emulsion in water; or added in one or more additions or continuously, linearly or nonlinearly, over the reaction period of preparing the emulsion polymer. Temperature suitable for emulsion polymerization processes may be lower than <NUM>, in the range of from <NUM> to <NUM>, or in the range of from <NUM> to <NUM>. Multistage free-radical polymerization using the monomers described above can be used, which at least two stages are formed sequentially, and usually results in the formation of the multistage polymer comprising at least two polymer compositions.

In the polymerization process of preparing the emulsion polymer, free radical initiators may be used. The polymerization process may be 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, perphosphoric acid, and salts thereof; potassium permanganate, and ammonium or alkali metal salts of peroxydisulfuric acid. The free radical initiators may be used typically at a level of from <NUM>% to <NUM>% by weight, based on the total weight of monomers and the polymerizable surfactant. Redox systems comprising the above described initiators coupled with a suitable reductant may be used in the polymerization process. Examples of suitable reductants include sodium sulfoxylate formaldehyde, ascorbic acid, isoascorbic acid, alkali metal and ammonium salts of sulfur-containing acids, such as sodium sulfite, bisulfite, thiosulfate, hydrosulfite, sulfide, hydrosulfide or dithionite, formadinesulfinic acid, acetone bisulfite, glycolic acid, hydroxymethanesulfonic acid, glyoxylic acid hydrate, lactic acid, glyceric acid, malic acid, tartaric acid and salts of the preceding 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 the metals may optionally be used.

In the polymerization process of preparing the emulsion polymer, one or more chain transfer agents may be used. Examples of suitable chain transfer agents include <NUM>-mercaptopropionic acid, n-dodecyl mercaptan, methyl <NUM>-mercaptopropionate, butyl <NUM>-mercaptopropionate, benzenethiol, azelaic alkyl mercaptan and mixtures thereof. The chain transfer agent may be used in an effective amount to control the molecular weight of the emulsion polymer, for example, from <NUM> to <NUM>%, from <NUM>% to <NUM>%, or from <NUM>% to <NUM>%, by weight based on the total weight of monomers and the polymerizable surfactant used for preparing the emulsion polymer.

After completing the polymerization of the emulsion polymer, the obtained aqueous polymer dispersion may be neutralized by one or more bases as neutralizers to a pH value, for example, at least <NUM>, from <NUM> to <NUM>, or from <NUM> to <NUM>. The bases may 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 triethyl amine, ethylamine, propylamine, monoisopropylamine, monobutylamine, hexylamine, ethanolamine, diethyl amine, dimethyl amine, di-n-propylamine, tributylamine, triethanolamine, dimethoxyethylamine, <NUM>-ethoxyethylamine, <NUM>-ethoxypropylamine, dimethylethanolamine, diisopropanolamine, morpholine, ethylenediamine, <NUM>-diethylaminoethylamine, aluminum hydroxide, and mixtures thereof. The aqueous polymer dispersion may be further subject to stream stripping to further reduce the VOC content of the emulsion polymer dispersion. Process for stream stripping polymer dispersions are known in the art such as those described in <CIT> and <CIT>.

The aqueous coating composition of the present invention further comprises one or more polyoxypropylene polyols, that is, poly(propylene oxide) homopolymers. The polyoxypropylene polyols have a number average molecular weight (Mn) of <NUM> or more, <NUM> or more, <NUM> or more, <NUM> or more, <NUM> or more, <NUM> or more, <NUM> or more, <NUM> or more, <NUM> or more, <NUM> or more, <NUM> or more, or even <NUM> or more, and at the same time, <NUM>,<NUM> or less, <NUM>,<NUM> or less, <NUM>,<NUM> or less, <NUM>,<NUM> or less, <NUM>,<NUM> or less, <NUM>,<NUM> or less, <NUM>,<NUM> or less, <NUM>,<NUM> or less, <NUM>,<NUM> or less, <NUM>,<NUM> or less, <NUM>,<NUM> or less, <NUM>,<NUM> or less, <NUM>,<NUM> or less, <NUM> or less, <NUM> or less, <NUM> or less, <NUM> or less, <NUM> or less, <NUM> or less, or even <NUM> or less. Mn herein may be measured by Gel Permeation Chromatography (GPC) or by calculation according to equation (i) below. For example, Mn of the polyoxypropylene polyol can be measured by SEC on two Polymer Laboratories Mixed E columns (in tandem) with refractive index detector at <NUM> using polystyrene narrow standards. Molecular weights of polystyrene standards used for calibration range from <NUM>,<NUM> to <NUM>/mol. Peak molecular weight (Mp) used for calibration are values converted from peak molecular weight of each PS standard ("Mp-PS") according to the following equation: Mp = <NUM>*Mp-PS<NUM>.

Mn of the polyoxypropylene polyol can also be calculated by the equation (i) below, <MAT> wherein hydroxy number, reported in units of milligrams of KOH/gram of polyol, is measured according to the ASTM D4274-<NUM> method (Standard Test Methods for Testing Polyurethane Raw Materials: Determination of Hydroxyl Numbers of Polyols).

Generally the polyoxypropylene polyol useful in the present invention may have an average hydroxy functionality of <NUM> or more or <NUM> or more, and at the same time, <NUM> or less, <NUM> or less, or even <NUM> or less.

The polyoxypropylene polyol useful in the present invention may be initiated with, for example, water, organic dicarboxylic acids such as succinic acid, adipic acid, phthalic acid, terephthalic acid; or polyhydric alcohols (such as dihydric to pentahydric alcohols or dialkylene glycols), for example, ethanediol, <NUM>,<NUM>- and <NUM>,<NUM>-propanediol, diethylene glycol, dipropylene glycol, <NUM>,<NUM>-butanediol, <NUM>,<NUM>-hexanediol, glycerol, trimethylolpropane, pentaerythritol, sorbitol, and sucrose or blends thereof; linear and cyclic amine compounds which may also contain a tertiary amine such as ethanoldiamine, triethanoldiamine, and various isomers of toluene diamine, methyldiphenylamine, aminoethylpiperazine, ethylenediamine, N-methyl-<NUM>,<NUM>-ethanediamine, N-methyl-<NUM>,<NUM>-propanediamine, N,N-dimethyl-<NUM>,<NUM>-diaminopropane, N,N-dimethylethanolamine, diethylene triamine, bis-<NUM>-aminopropyl methylamine, aniline, aminoethyl ethanolamine, <NUM>,<NUM>-diamino-N-methylpropylamine, N,N-dimethyldipropylenetriamine, aminopropyl-imidazole and mixtures thereof; or combinations thereof. Suitable commercially available polyoxypropylene polyols may include, for example, VORANOL™ 2000LM polyol, VORANOL CP450 polyol and VORANOL 3000LM polyol, all available from The Dow Chemical Company; and mixtures thereof (VORANOL is a trademark of The Dow Chemical Company).

The polyoxypropylene polyol useful in the present invention may be present, by weight based on the weight of the emulsion polymer, in an amount of <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or even <NUM>% or more, and at the same time, <NUM>% or less, <NUM>% or less, <NUM>% or less, <NUM>% or less, <NUM>% or less, <NUM>% or less, <NUM>% or less, <NUM>% or less, or even <NUM>% or less.

The aqueous coating composition of the present invention also comprises one or more phosphate surfactants having the structure of formula (III),
<CHM>
where R is a C<NUM>-C<NUM> alkyl group, A<NUM>O is an alkoxylated group (i.e., alkylene oxide), a1 is an integer from <NUM> to <NUM>, b1 is <NUM> or <NUM>, and N+ can be a metal ion or ammonium ion. R can be a C<NUM>-C<NUM> alkyl, C<NUM>-C<NUM> alkyl, C<NUM>-C<NUM> alkyl, or C<NUM>-C<NUM> alkyl group. A<NUM>O can be an ethoxylated group (i.e., ethylene oxide group, -CH<NUM>CH<NUM>O-), a propoxylated group (i.e., propylene oxide group), or combinations thereof, preferably an ethoxylated group. Preferably, the value of a1 ranges from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, or from <NUM> to <NUM>. Preferred b1 is <NUM>. More preferably, a1 is an integer of from <NUM> to <NUM>, b1 is <NUM>, A<NUM>O is -CH<NUM>CH<NUM>O-, and N+ is NH<NUM>+. Suitable commercially available phosphate surfactants may include RHODAFAC RS610 alkyl ethoxylated phosphate surfactant with six ethylene oxide units available from Solvay Company. The phosphate surfactant may be added in the polymerization process of preparing the emulsion polymer, e.g., prior to or during the polymerization of the monomers, after the polymerization, or combinations thereof.

The aqueous coating composition of the present invention may comprise, by weight based on the weight of the emulsion polymer, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, or even <NUM>% or more, and at the same time, <NUM>% or less, <NUM>% or less, <NUM>% or less, <NUM>% or less, <NUM>% or less, <NUM>% or less, <NUM>% or less, <NUM>% or less, <NUM>% or less, of the phosphate surfactant.

The aqueous coating composition of the present invention further comprises one or more functional silanes selected from epoxy functional polysiloxane oligomers, epoxy functional silane compounds and mixtures thereof. The epoxy functional polysiloxane oligomers useful in the present invention may have the structure of formula (IV):
<CHM>
where p is an integer of from <NUM> to <NUM>, preferably, from <NUM> to <NUM>, from <NUM> to <NUM>, or from <NUM> to <NUM>; and R" is -CH<NUM>CH<NUM>CH<NUM>-.

The epoxy functional polysiloxane oligomer useful in the present invention can be a mixture of oligomers having the structure of formula (IV) with different p values, for example, <NUM>, <NUM>, <NUM> or <NUM>. The epoxy functional polysiloxane oligomer may comprise, a polysiloxane of formula (IV), wherein p=<NUM>; a polysiloxane of formula (IV), wherein p=<NUM>; a polysiloxane of formula (IV), wherein p=<NUM>; and a polysiloxane of formula (IV), wherein p=<NUM>. Suitable commercially available epoxy-containing polysiloxane oligomers may include CoatOSil MP <NUM> silane available from Momentive Performance Materials Inc.

The epoxy functional silane compounds useful in the present invention are different from the epoxy functional polysiloxane oligomer, and are typically saturated alkoxylated silanes having an epoxy group. The epoxy functional silane compounds may have at least one hydrolysable silane group. A preferred epoxy functional silane compound has the structure of general formula (V):
<CHM>
where R<NUM> represents an alkyl group having one to <NUM> carbon atoms; OR<NUM> group represents an alkoxy group including, for example, methoxy group, ethoxy group, and combinations thereof; R<NUM> represents a bivalent organic group having a molecular weight of <NUM> or less, preferably, R<NUM> is a C<NUM>-C<NUM>, C<NUM>-C<NUM>, or C<NUM>-C<NUM> alkylene group; R<NUM> represents a hydrogen atom or an alkyl, aryl, or aralkyl group having <NUM> to <NUM> carbon atoms; and q is <NUM>, <NUM> or <NUM>. Examples of suitable epoxy functional silane compounds include gamma-glycidyloxypropyl trimethoxysilane, gamma-glycidyloxypropyl triethoxysilane, gamma-glycidyloxypropyl methyldiethoxysilane, gamma-glycidyloxypropyl methyldimethoxysilane and mixtures thereof. Suitable commercially available epoxy functional silane compounds may include SILQUEST A-<NUM> gamma-glycidoxypropyltrimethoxysilane from Momentive Performance Materials Inc.

The functional silane useful in the present invention may be present in a combined amount of, by weight based on the weight of the emulsion polymer, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, <NUM>% or more, or even <NUM>% or more, and at the same time, <NUM>% or less, <NUM>% or less, <NUM>% or less, <NUM>% or less, <NUM>% or less, <NUM>% or less, or even <NUM>% or less.

The aqueous coating composition of the present invention may comprise: the emulsion polymer comprising from <NUM>% to <NUM>% of structural units of the polymerizable surfactant, from <NUM>% to <NUM>% of the polyoxypropylene polyol, from <NUM>% to <NUM>% of the phosphate surfactant, and from <NUM>% to <NUM>% of the functional silane, by weight based on the weight of the emulsion polymer.

The aqueous coating composition of the present invention may comprise one or more additional anti-freeze agents that are different from the polyoxypropylene polyol described above and have no contribution to VOCs. Specific examples of additional anti-freeze agents include polyethylene glycol, RHODOLINE FT-<NUM> FIT stabilizer available from Solvay and mixtures thereof. The additional anti-freeze agent, if present, should be in an amount without compromising stain resistance of coatings made therefrom, for example, less than <NUM>%, less than <NUM>%, or even less than <NUM>%, by weight of the aqueous coating composition. Preferably, the aqueous coating composition is substantially free (e.g., includes less than <NUM>%, preferably less than <NUM>%, and more preferably zero) of the additional anti-freeze agents.

The aqueous coating composition of the present invention may further comprise pigments and/or extenders. "Pigment" herein refers to a particulate inorganic material which is capable of materially contributing to the opacity or hiding capability of a coating. Such materials typically have a refractive index greater than <NUM>. Inorganic pigments typically include metal oxides. Examples of suitable metal oxides include titanium dioxide (TiO<NUM>), zinc oxide, iron oxide, zinc sulfide, barium sulfate, barium carbonate and mixtures thereof. TiO<NUM> typically exists in two crystal forms, anastase and rutile. Suitable commercially available TiO<NUM> may include, for example, KRONOS <NUM> available from Kronos Worldwide, Inc. , Ti-Pure R-<NUM> available from DuPont (Wilmington, Del. ), TiONA AT1 available from Millenium Inorganic Chemicals, and mixtures thereof. TiO<NUM> may be also available in concentrated dispersion form. "Extender" herein refers to a particulate inorganic material having a refractive index of less than or equal to <NUM> and greater than <NUM>. Examples of suitable extenders include 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, baryte, wollastonite, opaque polymers such as ROPAQUE™ Ultra E available from The Dow Chemical Company (ROPAQUE is a trademark of The Dow Chemical Company), and mixtures thereof. The aqueous coating composition may have a pigment volume concentration (PVC) of from <NUM>% to <NUM>%, from <NUM>% to <NUM>%, or from <NUM>% to <NUM>%. PVC may be determined according to the following equation: <MAT>.

The aqueous coating composition of the present invention may further comprise one or more defoamers. "Defoamers" herein refer to chemical additives that reduce and hinder the formation of foam. Defoamers may be silicone-based defoamers, mineral oil-based defoamers, ethylene oxide/propylene oxide-based defoamers, alkyl polyacrylates and mixtures thereof. Suitable commercially available defoamers may include, for example, TEGO Airex <NUM> W and TEGO Foamex <NUM> polyether siloxane copolymer emulsions both available from TEGO, BYK-<NUM> silicone deformer available from BYK, and mixtures thereof. The defoamer may be present, by weight based on the total weight of the aqueous coating composition, generally in an amount of from <NUM> to <NUM>%, from <NUM>% to <NUM>%, or from <NUM>% to <NUM>%.

The aqueous coating composition of the present invention may further comprise one or more thickeners, also known as "rheology modifiers". The thickeners may include polyvinyl alcohol (PVA), clay materials, acid derivatives, acid copolymers, urethane associate thickeners (UAT), polyether urea polyurethanes (PEUPU), polyether polyurethanes (PEPU), or mixtures thereof. Examples of suitable thickeners include alkali swellable emulsions (ASE) such as sodium or ammonium neutralized acrylic acid polymers; hydrophobically modified alkali swellable emulsions (HASE) such as hydrophobically modified acrylic acid copolymers; associative thickeners such as hydrophobically modified ethoxylated urethanes (HEUR); and cellulosic thickeners such as methyl cellulose ethers, hydroxymethyl cellulose (HMC), hydroxyethyl cellulose (HEC), hydrophobically-modified hydroxy ethyl cellulose (HMHEC), sodium carboxymethyl cellulose (SCMC), sodium carboxymethyl <NUM>-hydroxyethyl cellulose, <NUM>-hydroxypropyl methyl cellulose, <NUM>-hydroxyethyl methyl cellulose, <NUM>-hydroxybutyl methyl cellulose, <NUM>-hydroxyethyl ethyl cellulose, and <NUM>-hydoxypropyl cellulose. Preferably, the thickener is a hydrophobically-modified hydroxy ethyl cellulose (HMHEC). The thickener may be present, by weight based on the total weight of the aqueous coating composition, in an amount of from <NUM> to <NUM>%, from <NUM>% to <NUM>%, or from <NUM>% to <NUM>%.

The aqueous coating composition of the present invention may further 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 may be polycarboxylates, anionic, zwitterionic, or non-ionic. Suitable commercially available wetting agents may include, for example, SURFYNOL <NUM> nonionic wetting agent based on an actacetylenic diol available from Air Products, BYK-<NUM> and BYK-<NUM> polyether-modified siloxanes both available from BYK, or mixtures thereof. The wetting agent may be present, by weight based on the total weight of the aqueous coating composition, from <NUM> to <NUM>%, from <NUM>% to <NUM>%, or from <NUM>% to <NUM>%.

The aqueous coating composition of the present invention may further comprise one or more coalescents with a high boiling point. "High boiling point" herein refers to a boiling point higher than <NUM>. Examples of suitable coalescents include COASOL <NUM> Plus coalescent (a mixture of di-esters) available from Chemoxy International Ltd. , OPTIFILM Enhancer <NUM> coalescent available from Eastman, or mixtures thereof. The coalescents may be present, by weight based on the total weight of the aqueous coating composition, from <NUM> to <NUM>%, from <NUM>% to <NUM>%, or from <NUM>% to <NUM>%.

The aqueous coating composition of the present invention may further comprise one or more dispersants. The dispersant can 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 of 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 from <NUM> to <NUM>%, from <NUM>% to <NUM>%, or from <NUM>% to <NUM>%.

In addition to the components described above, the aqueous coating composition of the present invention may further comprise any one or combination of the following additives: buffers, neutralizers, humectants, mildewcides, biocides, anti-skinning agents, colorants, flowing agents, anti-oxidants, plasticizers, leveling agents, adhesion promoters, and grind vehicles. When present, these additives may be present in a combined amount of from <NUM>% to <NUM>% or from <NUM>% to <NUM>%, by weight based on the total weight of the aqueous coating composition. The aqueous coating composition may comprise water in an amount of from <NUM>% to <NUM>%, from <NUM>% to <NUM>%, or from <NUM>% to <NUM>% by weight of the aqueous coating composition.

The aqueous coating composition of the present invention may be prepared by a process comprising: admixing the emulsion polymer, the phosphate surfactant, the polyoxypropylene polyol, the functional silane, and other optional components, e.g., pigments and/or extenders as described above. For example, the aqueous coating composition may be prepared by admixing a dispersion comprising the emulsion polymer and the functional silane with the phosphate surfactant and the polyoxypropylene polyol. Components in the aqueous coating composition may be mixed in any order to provide the aqueous coating composition of the present invention. Any of the above-mentioned optional components may also be added to the composition during or prior to the mixing to form the aqueous coating composition. The functional silane is preferably mixed with the emulsion polymer prior to mixing with other components in the aqueous coating composition. When the aqueous coating composition comprises pigment and/or extender, the pigments and/or extenders are preferably mixed with the dispersant to form a slurry of pigments and/or extender.

The aqueous coating composition of the present invention may comprise not greater than <NUM> grams of volatile organic compounds (VOCs) per liter (g/L) of the aqueous coating composition according to the GB <NUM>-<NUM> method, also known as "zero or low content of VOCs". Preferably, the VOC content of the aqueous coating composition is less than <NUM>/L, less than <NUM>/L, or even less than <NUM>/L. Surprisingly, the aqueous coating composition even with zero or low content of VOCs can still have good freeze-thaw stability while achieving good stain resistance sufficient to meet the requirement of the GB/T9780-<NUM> standard. "Good stain resistance" represents a total stain removal score of <NUM> or higher, <NUM> or higher, <NUM> or higher, <NUM> or higher, <NUM> or higher, <NUM> or higher, <NUM> or higher, <NUM> or higher, or even <NUM> or higher, as measured by the GB/T9780-<NUM> standard. "Good freeze-thaw stability", that is, being freeze-thaw stable, means that a composition can be subjected to three freeze-thaw cycles showing no coagulation, according to the test method described in the Examples section below.

The use of the aqueous coating composition of the present invention may comprise: applying the coating composition to a substrate, and drying, or allowing to dry, the applied coating composition.

A method of preparing a coating 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.

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, stones, elastomeric substrates, glass, fabrics, concrete, or cementitious substrates. The aqueous coating composition, preferably comprising the pigment, is suitable for various applications such as marine and protective coatings, automotive coatings, traffic paint, Exterior Insulation and Finish Systems (EIFS), roof mastic, wood coatings, coil coatings, plastic coatings, powder coatings, can coatings, architectural coatings, and civil engineering coatings. The aqueous coating composition is particularly suitable for architectural coatings.

The aqueous coating composition of the present invention can be applied to a substrate by incumbent means including brushing, dipping, rolling and spraying. The aqueous composition is preferably applied by spraying. The standard spray techniques and equipment for spraying such as air-atomized spray, air spray, airless spray, high volume low pressure spray, and electrostatic spray such as electrostatic bell application, and either manual or automatic methods can be used. After the aqueous coating composition of the present invention has been applied to a substrate, The aqueous coating composition can dry, or allow to dry, to form a film (this is, coating) at room temperature (<NUM>-<NUM>), or at an elevated temperature, for example, from <NUM> to <NUM>.

The following materials are used in the examples:.

The following polyols are all available from The Dow Chemical Company:.

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

Containers were filled with <NUM>% volume of a test coating composition. The containers were sealed and placed into a freezer at -<NUM> for <NUM> hours, and then taken out from the freezer to allow to thaw at ambient conditions (about <NUM>) for <NUM> hours. The above steps complete one F/T cycle. The FIT cycles were continued until the sample coagulated or to a maximum of three cycles. After each cycle, the cycle number was recorded if coagulation or gel had been observed. After the completion of <NUM> cycles, the sample was shaken manually and the appearance of the sample was observed by the naked eye. If the sample does not coagulate or shows no grits separated from the sample after the F/T test, the sample is rated as "Pass" indicating good FIT stability. Otherwise, if the sample coagulates or has grits separated, the sample is rated as "Fail" indicating poor FIT stability.

Stain removal ability was tested according to the GB/T <NUM>-<NUM> method. Test samples were casted on black vinyl scrub charts to form wet films (thickness: <NUM>) using a drawdown bar. The films on the resultant test panels were cured for <NUM> days at room temperature before stains were applied. Within test areas (<NUM> width and <NUM> length on the test panels), six types of stains (vinegar, black tea, ink, water black, alcohol black, and Vaseline black) were applied on the films, respectively. Liquid stains were applied over gauze to prevent the stain from running off from the test areas. Stains stayed on the test panels for <NUM> hours before excess stain was wiped off with dry tissue. The test panels were then placed on a scrub tester under a <NUM> weight, with a scrubbing cycle of <NUM> scrubs per minute. After the test panels were scrubbed for <NUM> cycles, it was removed from the tester, rinsed under running water, and hung up for drying. Then the cleaned stain area was evaluated by measuring the change of reflection index (X) using the formula below, <MAT> where Y<NUM> is reflection index after the stain removal test and Y<NUM> is reflection index before the stain removal test. Y<NUM> and Y<NUM> were tested by BYK spectro-guide instrument.

Based on the obtained reflection index value X, the stain removal score (Ri) for each stain, on a scale of <NUM> to <NUM>, can be obtained from the below table,.

The total stain removal score (R') was then calculated according to the formula below,
<MAT>
where Ri is the stain removal score for different stains and n is <NUM>. The stain removal score of at least <NUM> points represents for acceptable or good stain resistance. Otherwise, the total stain removal score less than <NUM> points is not acceptable. The higher the total stain removal score, the better the stain resistance.

VOCs of a coating composition were measured according to the GB18582-<NUM> method. Quantitative and qualitative analyses of VOCs' of a sample were performed on an Agilent 7890A Gas Chromatograph (GC), 5975C Mass Spectrometer (MS) with triple-axis detector.

An aliquot of <NUM> (recorded accurately) homogenized sample was weighted into a <NUM> centrifuge vial, added with an internal standard (<NUM>-(<NUM>-ethoxyethoxy)-ethanol) and a VOC marker (hexanedioic acid, diethyl ester), and then the exact weight was recorded. The sample was mixed in a vortex centrifuge vial for <NUM> minute, followed by <NUM>-minute standing, vortex mixing again for <NUM> minute, and then centrifuging at <NUM> rpm for <NUM> minutes. The supernatant of the sample was taken out and filtered through a <NUM> syringe filter. The filtration was then injected into a GC-MS system (injection volume: <NUM>µL) with conditions as follows,.

Oven Program: Initial <NUM>, held for <NUM> minutes, then at a rate of <NUM>/min to <NUM>, held for <NUM>; Run Time: <NUM>; Flow rate: <NUM>/min; Average Velocity: <NUM>/sec; Inlet: temperature: <NUM>, Split ratio: <NUM>:<NUM>; Column: HP-<NUM> <NUM>% Phenyl Methyl Siloxane; Length x Diameter x Film thickness: <NUM> x <NUM> x <NUM>; and MS detector parameters: Low Mass: <NUM>, High Mass: <NUM>, MS Source temperature: <NUM>, MS Quad temperature: <NUM>.

Monomer Emulsion (ME) was prepared by mixing <NUM> of deionized (DI) water, <NUM> of AR-<NUM>, <NUM> of ST, <NUM> of BA, <NUM> of AM, and <NUM> of AA.

In a <NUM>-liter, four necked round bottom flask equipped with a paddle stirrer, a thermometer, nitrogen inlet and a reflux condenser, <NUM> of DI water was added and heated to <NUM> under nitrogen atmosphere with stirring. <NUM> of AR-<NUM>, <NUM> of Na<NUM>CO<NUM>, and <NUM> of ME seed were then added into the flask, quickly followed by <NUM> of sodium persulfate dissolved in <NUM> of DI water. Upon holding the batch for <NUM> minute with stirring, ME was added into the flask while co-feeding <NUM> of sodium persulfate catalyst and <NUM> of sodium bisulfite activator in <NUM> minutes. When the ME feed was completed, a catalyst/activator feed (<NUM> of tert-Butyl hydroperoxide /<NUM> of iso-ascorbic acid) was added, and then another catalyst/activator feed (<NUM> of tert-Butyl hydroperoxide/<NUM> of iso-ascorbic acid) was added to the flask in <NUM> minutes to chase the residual monomer separately. Then MEA solution was added to adjust the pH to <NUM>-<NUM>. At last, <NUM> of CoatOSil MP <NUM> silane was post added slowly. The obtained polymer emulsion had a measured particle size of about <NUM> nanometers (nm) and solids of about <NUM>% (Fox Tg of the polymer: -<NUM>).

Monomer Emulsion (ME) was prepared by mixing <NUM> of DI water, <NUM> of AR-<NUM>, <NUM> of ST, <NUM> of BA, <NUM> of AM, and <NUM> of AA.

In a <NUM>-liter, four necked round bottom flask equipped with a paddle stirrer, a thermometer, nitrogen inlet and a reflux condenser, <NUM> of DI water was added and heated to <NUM> under nitrogen atmosphere with stirring. <NUM> of AR-<NUM>, <NUM> of Na<NUM>CO<NUM>, and <NUM> of ME seed were then added into the flask, quickly followed by <NUM> of sodium persulfate dissolved in <NUM> of DI water. Upon holding the batch for <NUM> minute with stirring, ME was added into the flask while co-feeding <NUM> of sodium persulfate catalyst and <NUM> of sodium bisulfite activator in <NUM> minutes. When the ME feed was completed, a catalyst/activator feed (<NUM> of tert-Butyl hydroperoxide /<NUM> of iso-ascorbic acid) was added, and then another catalyst/activator feed (<NUM> of tert-Butyl hydroperoxide/<NUM> of iso-ascorbic acid) was added to the flask in <NUM> minutes to chase the residual monomer separately. Then MEA solution was added to adjust the pH to <NUM>-<NUM>. At last, <NUM> of CoatOSil MP <NUM> silane was post added slowly. The obtained polymer emulsion had a measured particle size of about <NUM> and solids of about <NUM>% (Fox Tg of the polymer: - <NUM>).

Monomer Emulsion (ME) was prepared by mixing <NUM> of DI water, <NUM> of AR-<NUM>, <NUM> of MMA, <NUM> of BA, and <NUM> of MAA.

In a <NUM>-liter, four necked round bottom flask equipped with a paddle stirrer, a thermometer, nitrogen inlet and a reflux condenser, <NUM> of DI water was added and heated to <NUM> under nitrogen atmosphere with stirring. <NUM> of AR-<NUM>, <NUM> of Na<NUM>CO<NUM>, and <NUM> of ME seed were then added into the flask, quickly followed by <NUM> of sodium persulfate dissolved in <NUM> of DI water. Upon holding the batch for <NUM> minute with stirring, ME was added into the flask while co-feeding <NUM> of sodium persulfate catalyst and <NUM> of sodium bisulfite activator in <NUM> minutes. When the ME feed was completed, a catalyst/activator feed (<NUM> of tert-Butyl hydroperoxide /<NUM> of iso-ascorbic acid) was added, and then another catalyst/activator feed (<NUM> of tert-Butyl hydroperoxide/<NUM> of iso-ascorbic acid) was added to the flask in <NUM> minutes to chase the residual monomer separately. Then MEA solution was added to adjust the pH to <NUM>-<NUM>. At last, <NUM> of CoatOSil MP <NUM> silane was post added slowly. The obtained polymer emulsion had a measured particle size of about <NUM> and solids of about <NUM>% (Fox Tg of the polymer: -<NUM>).

In a <NUM>-liter, four necked round bottom flask equipped with a paddle stirrer, a thermometer, nitrogen inlet and a reflux condenser, <NUM> of DI water was added and heated to <NUM> under nitrogen atmosphere with stirring. <NUM> of AR-<NUM>, <NUM> of Na<NUM>CO<NUM>, and <NUM> of ME seed were then added into the flask, quickly followed by <NUM> of sodium persulfate dissolved in <NUM> of DI water. Upon holding the batch for <NUM> minute with stirring, ME was added into the flask while co-feeding <NUM> of sodium persulfate catalyst and <NUM> of sodium bisulfite activator in <NUM> minutes. When the ME feed was completed, a catalyst/activator feed (<NUM> of tert-Butyl hydroperoxide /<NUM> of iso-ascorbic acid) was added, and then another catalyst/activator feed (<NUM> of tert-Butyl hydroperoxide/<NUM> of iso-ascorbic acid) was added to the flask in <NUM> minutes to chase the residual monomer separately. Then MEA solution was added to adjust the pH to <NUM>-<NUM>. At last, <NUM> of CoatOSil MP <NUM> silane was post added slowly. The obtained polymer emulsion had a measured particle size of about <NUM> and solids of about <NUM>% (Fox Tg of the polymer: <NUM>).

Monomer Emulsion (ME) was prepared by mixing <NUM> of DI water, <NUM> of AR-<NUM>, <NUM> of ST, <NUM> of BA, <NUM> of AM, and <NUM> of AA, <NUM> of A-<NUM>.

In a <NUM>-liter, four necked round bottom flask equipped with a paddle stirrer, a thermometer, nitrogen inlet and a reflux condenser, <NUM> of DI water was added and heated to <NUM> under nitrogen atmosphere with stirring. <NUM> of AR-<NUM>, <NUM> of Na<NUM>CO<NUM>, and <NUM> of ME seed were then added into the flask, quickly followed by <NUM> of sodium persulfate dissolved in <NUM> of DI water. Upon holding the batch for <NUM> minute with stirring, ME was added into the flask while co-feeding <NUM> of sodium persulfate catalyst and <NUM> of sodium bisulfite activator in <NUM> minutes. When the ME feed was completed, a catalyst/activator feed (<NUM> of tert-Butyl hydroperoxide /<NUM> of iso-ascorbic acid) was added, and then another catalyst/activator feed (<NUM> of tert-Butyl hydroperoxide/<NUM> of iso-ascorbic acid) was added to the flask in <NUM> minutes to chase the residual monomer separately. Then MEA solution was added to adjust the pH to <NUM>-<NUM>. The obtained polymer emulsion had a measured particle size of about <NUM> and solids of about <NUM>% (Fox Tg of the polymer: -<NUM>).

In a <NUM>-liter, four necked round bottom flask equipped with a paddle stirrer, a thermometer, nitrogen inlet and a reflux condenser, <NUM> of DI water was added and heated to <NUM> under nitrogen atmosphere with stirring. <NUM> of AR-<NUM>, <NUM> of Na<NUM>CO<NUM>, and <NUM> of ME seed were then added into the flask, quickly followed by <NUM> of sodium persulfate dissolved in <NUM> of DI water. Upon holding the batch for <NUM> minute with stirring, ME was added into the flask while co-feeding <NUM> of sodium persulfate catalyst and <NUM> of sodium bisulfite activator solution in <NUM> minutes. When the ME feed was completed, a catalyst/activator feed (<NUM> of tert-Butyl hydroperoxide /<NUM> of iso-ascorbic acid) was added, and then another catalyst/activator feed (<NUM> of tert-Butyl hydroperoxide/<NUM> of iso-ascorbic acid) was added to the flask in <NUM> minutes to chase the residual monomer separately. Then MEA solution was added to adjust the pH to <NUM>-<NUM>. At last, <NUM> of A-<NUM> was post added slowly. The obtained polymer emulsion had a measured particle size of about <NUM> and solids of about <NUM>% (Fox Tg of the polymer: -<NUM>).

Monomer Emulsion (ME) was prepared by mixing <NUM> of DI water, <NUM> of A-<NUM>, <NUM> of ST, <NUM> of BA, <NUM> of AM, and <NUM> of AA.

The above obtained polymer emulsions were used to prepare coating compositions below, based on formulations given in Table <NUM>. Types of polymer emulsions, and dosage and types of anti-freeze agents used in preparing the coating compositions are given in Table <NUM>. The amount of water was adjusted to make up a total weight of each coating composition of <NUM>.

The aqueous coating composition of Ex <NUM> was prepared by a two-stage process. First, components in the grind stage (including water (<NUM>), NATROSOL <NUM> HBR (<NUM>), TAMOL 731A (<NUM>), TERGITOL <NUM>-S-<NUM> (<NUM>), AMP-<NUM> (<NUM>), R-<NUM> (<NUM>), CELITE 499SP (<NUM>), DB-<NUM> (<NUM>), Talc AT-<NUM> (<NUM>) and water (<NUM>)) were mixed with a high-shear mixer. Sufficient agitation (usually <NUM>,<NUM>-<NUM>,<NUM> rpm) was required to obtain a homogeneous dispersion of pigment. After the grind stage, a viscous mill base was obtained. The viscous mill base was then mixed with components in the letdown stage (including Polymer Emulsion <NUM> (<NUM>), CP450 polyol (<NUM>), ROPAQUE Ultra E polymer (<NUM>), P12A surfactant (<NUM>), Foamaster NXZ (<NUM>), COASOL <NUM> Plus (<NUM>), ACRYSOL RM-8W (<NUM>), ACRYSOL RM-<NUM> NPR (<NUM>) and water (<NUM>)). At the same time, a high shear agitator was replaced with a low shear mixer (usually <NUM>-<NUM> rpm) to avoid foaming and unstable grits. After all the components in the letdown stage were added into the mill base and agitated for about <NUM> minutes, a homogeneous coating composition was obtained.

The coating composition of Ex <NUM> was prepared according to the same procedure as described above in Ex <NUM>, except that CP450 polyol was replaced by RN482 polyol.

The coating composition of Ex <NUM> was prepared according to the same procedure as described above in Ex <NUM>, except that the polymer emulsion <NUM> was replaced by the polymer emulsion <NUM>.

The coating composition of Ex <NUM> was prepared according to the same procedure as described above in Ex <NUM>, except that CP450 polyol was replaced by 2000LM polyol.

The coating composition of Ex <NUM> was prepared according to the same procedure as described above in Ex <NUM>, except that CP450 polyol was replaced by 2000LM polyol and the amounts of 2000LM polyol and P12A surfactant, respectively, were doubled.

The coating composition of Ex <NUM> was prepared according to the same procedure as described above in Ex <NUM>, except that CP450 polyol was replaced by 3000LM polyol.

The coating composition of Comp Ex A was prepared according to the same procedure as described above in Ex <NUM>, except that the polymer emulsion <NUM> was replaced by the polymer emulsion <NUM>, CP450 polyol was replaced by ethylene glycol (EG), and P12A surfactant was removed.

The coating composition of Comp Ex B was prepared according to the same procedure as described above in Ex <NUM>, except that the polymer emulsion <NUM> was replaced by the polymer emulsion <NUM>, and CP450 polyol and P12A surfactant were both removed.

The coating composition of Comp Ex C was prepared according to the same procedure as described above in Ex <NUM>, except that the polymer emulsion <NUM> was replaced by the polymer emulsion <NUM>, and P12A surfactant was removed.

The coating composition of Comp Ex D was prepared according to the same procedure as described above in Ex <NUM>, except that the polymer emulsion <NUM> was replaced by the polymer emulsion <NUM> and CP450 polyol was removed.

The coating composition of Comp Ex E was prepared according to the same procedure as described above in Ex <NUM>, except that the polymer emulsion <NUM> was replaced by the polymer emulsion <NUM>.

The coating composition of Comp Ex F was prepared according to the same procedure as described above in Ex <NUM>, except that CP450 polyol and P12A surfactant were removed.

The coating composition of Comp Ex G was prepared according to the same procedure as described above in Ex <NUM>, except that the post-added P12A surfactant was removed.

The coating composition of Comp Ex H was prepared according to the same procedure as described above in Ex <NUM>, except that CP450 polyol was removed.

The coating composition of Comp Ex I was prepared according to the same procedure as described above in Ex <NUM>, except that P12A surfactant was replaced by <NUM>-s-<NUM> surfactant.

The coating composition of Comp Ex J was prepared according to the same procedure as described above in Ex <NUM>, except that P12A surfactant was replaced by Fes-<NUM> surfactant.

The coating composition of Comp Ex K was prepared according to the same procedure as described above in Ex <NUM>, except that P12A surfactant was replaced by A-<NUM> surfactant.

The coating composition of Comp Ex L was prepared according to the same procedure as described above in Ex <NUM>, except that CP450 polyol was replaced by 8000LM polyol.

The coating composition of Comp Ex M was prepared according to the same procedure as described above in Ex <NUM>, except that the polymer emulsion <NUM> was replaced by the polymer emulsion <NUM>, and CP450 polyol and P12A surfactant were both removed.

The coating composition of Comp Ex N was prepared according to the same procedure as described above in Ex <NUM>, except that the polymer emulsion <NUM> was replaced by the polymer emulsion <NUM>.

The coating composition of Comp Ex O was prepared according to the same procedure as described above in Ex <NUM>, except that the polymer emulsion <NUM> was replaced by the polymer emulsion <NUM>.

The coating composition of Comp Ex P was prepared according to the same procedure as described above in Ex <NUM>, except that CP450 polyol was replaced by <NUM> polyol.

The coating composition of Comp Ex Q was prepared according to the same procedure as described above in Ex <NUM>, except that CP450 polyol was replaced by <NUM>-060LM polyol.

The coating composition of Comp Ex R was prepared according to the same procedure as described above in Ex <NUM>, except that the polymer emulsion <NUM> was replaced by the polymer emulsion <NUM>.

Table <NUM> gives properties of the above prepared coating compositions and coatings made therefrom. As shown in Table <NUM>, the coating composition comprising <NUM>% EG had a high VOC content (Comp Ex A). The coating compositions comprising the polymer emulsions prepared in the presence of A-<NUM> surfactant all failed the FIT stability tests (Comp Exs B, C, D and E). The coating composition of Comp Ex F that didn't comprise a polyol or P-12A surfactant provided poor FIT stability and unsatisfactory stain resistance. Even addition of P-12A surfactant to Comp Ex F, the resultant coating composition of Comp Ex H still showed poor FIT stability. The coating composition of Comp Ex G comprising the combination of MP200 silane, CP450 polyol and the polymer emulsion <NUM> while containing no P-12A surfactant had no benefit on the stain resistance of the resultant coatings. The coating compositions comprising the polymer emulsion <NUM> in combination with <NUM>-S-<NUM> (Comp Ex I), Fes-<NUM> (Comp Ex J), or A-<NUM> (Comp Ex K) surfactants all showed no benefit on stain resistance of the resultant coatings. The coating composition of Comp Ex O also showed poor stain resistance. Coating compositions comprising a high molecular weight 8000LM polyol (Comp Ex L) or EO-PO polyols (Comp Exs P and Q) all showed poor stain resistance. The coating composition of Comp Ex R comprising the polymer emulsion prepared in the presence of A-<NUM> polymerizable silane failed the FIT stability test. No synergetic effect was shown for coating compositions comprising pure acrylic binders (Comp Exs M and N) or styrene-acrylic binders comprising more than <NUM>% of structural units of styrene (Comp Ex O).

The coating compositions of Exs <NUM>-<NUM> all had a VOC of less than <NUM>/L. Surprisingly, these coating compositions comprising emulsion polymers prepared in the presence of AR1025 reactive surfactant, in combination with P-12A phosphate surfactant, the polypropylene polyols (CP450, RN482, 2000LM, or 3000LM polyol), and the non-polymerizable silanes (e.g., A-<NUM> or MP200 functional silane) (Exs <NUM>-<NUM>) all showed synergetic effects in improving FIT stability and increasing stain resistance scores in zero addition coating compositions. In summary, the coating compositions of Exs <NUM>-<NUM> all passed the F/T stability tests and provided coatings with good stain resistance sufficient to meet the requirement of GB/T9780-<NUM> (including, for example, stain resistance score of <NUM> or higher).

Claim 1:
An aqueous coating composition, comprising:
(a) an emulsion polymer comprising, based on the weight of the emulsion polymer, from <NUM>% to <NUM>% by weight of structural units of a vinyl aromatic monomer, and structural units of a polymerizable surfactant having the structure of formula (I),
<CHM>
wherein R<NUM> is a phenyl group or a phenyl substituted alkyl group; m1 is <NUM>, <NUM>, <NUM> or <NUM>; R<NUM> is an alkyl or a substituted alkyl; m2 is <NUM> or <NUM>; R<NUM> is hydrogen or a C<NUM>-C<NUM> alkyl group; R<NUM> is hydrogen or a C<NUM>-C<NUM> alkyl group; A represents an alkylene group or a substituted alkylene group, having <NUM> to <NUM> carbon atoms; n is an integer in the range of from <NUM> to <NUM>; and X represents hydrogen or an anionic hydrophilic group selected from -(CH<NUM>)a-SO<NUM>M, -(CH<NUM>)b-COOM,
-PO<NUM>M<NUM>, -P(Z)O<NUM>M, or -CO-CH<NUM>-CH(SO<NUM>M)-COOM, wherein a and b are each independently an integer of from <NUM> to <NUM>, Z represents a residual obtained by removing X from the general formula (I), and each M represents hydrogen, an alkali metal atom, an alkaline earth metal atom, an ammonium residue, or an alkanolamine residue;
(b) a polyoxypropylene polyol having a number average molecular weight of from <NUM> to <NUM> as measured by Gel Permeation Chromatography as described in the description;
(c) a phosphate surfactant having the structure of formula (III),
<CHM>
wherein R is a C<NUM>-C<NUM> alkyl group, A<NUM>O is an alkoxylated group, a1 is an integer of from <NUM> to <NUM>, b1 is <NUM> or <NUM>, and N+ is a metal ion or ammonium ion; and
(d) a functional silane selected from an epoxy functional silane compound, an epoxy functional polysiloxane oligomer, and mixtures thereof.