Aqueous dispersion of a polymer additive and process thereof

Abstract

An aqueous dispersion of a polymer additive having a weight average molecular weight of 2,000 g / mol to 25,000 g / mol and comprising, by weight based on the weight of the polymer additive: (i) 20% to 85% of structural units of an ethylenically unsaturated siloxane monomer; (ii) 0.1% to 10% of structural units of an ethylenically unsaturated functional monomer bearing at least one functional group selected from amide, ureido, carboxyl, carboxylic anhydride, hydroxyl, phosphoric acid or sulfonic acid groups, salts thereof, or mixtures thereof; and (iii) 5% to 79.9% of structural units of an additional ethylenically unsaturated non-ionic monomer. The aqueous dispersion has a coagulum content of less than 2,000 ppm after filtration through a 44 micron screen. A coating composition comprising the aqueous dispersion of the polymer additive can provide a coating having corrosion resistance and / or stain removal properties.

Description

Technical Field

[0001] This invention relates to aqueous dispersions of polymer additives and methods for their preparation.

[0002] Foreword

[0003] Waterborne or water-based coating compositions are becoming increasingly important compared to solvent-based coating compositions due to fewer environmental concerns. Waterborne coating compositions are typically formulated using emulsion polymers as binders, which are usually prepared by emulsion polymerization of conventional monomers such as butyl acrylate, 2-ethylhexyl acrylate, styrene, methyl methacrylate, or mixtures thereof. The incorporation of more hydrophobic monomers (such as olefinically unsaturated siloxane monomers) into the polymer backbone of the binder during emulsion polymerization can be a method to further improve coating properties (such as corrosion resistance). However, when the binder includes more than 4.5% olefinically unsaturated siloxane monomers by weight of the total monomers, significant amounts of agglomerates (e.g., exceeding 2,000 ppm) can form in conventional emulsion polymerization methods, limiting the application of waterborne silicone-acrylic hybrid polymer binders. Waterborne coating compositions can possess other desired properties (such as stain resistance in external applications).

[0004] Therefore, it is desirable to provide an aqueous dispersion that does not have the aforementioned binder problems, which is particularly suitable for use in coating compositions and can provide coatings with improved properties such as corrosion resistance and stain removal properties. Summary of the Invention

[0005] This invention provides a novel aqueous dispersion of a polymer additive that does not suffer from the aforementioned problems. A method for preparing such an aqueous dispersion of the polymer additive yields an aqueous dispersion with a low condensate content (e.g., less than 2,000 parts per million (ppm) after filtration through a 44-micron sieve). Incorporating a specific amount of the aqueous dispersion of the polymer additive into a coating composition can improve the corrosion resistance and stain removal properties of the coating prepared from the coating composition.

[0006] In a first aspect, the present invention is an aqueous dispersion of a polymer additive having a weight-average molecular weight of 2,000 g / mol to 25,000 g / mol, wherein the polymer additive comprises, by weight based on the weight of the polymer additive:

[0007] (i) 20% to 85% of structural units of olefinic unsaturated siloxane monomers of formula (I), (II) or (III),

[0008]

[0009] In formula (I), R is an olefinic unsaturated group, and j and k are each independently in the range of 0 to 100, and j+k = 5 to 100;

[0010]

[0011] In formula (II), R is an olefinic unsaturated group, R1 is a hydroxyl, alkyl, aryl, alkoxy, aryloxy, alkyl ether or aryl ether group, and m is 1 to 100.

[0012]

[0013] In formula (III), R is an olefinic unsaturated group, R1 and R2 are each independently a hydroxyl, alkyl, aryl, alkoxy, aryloxy, alkyl ether or aryl ether group, n is 1 to 5, and p is 1 to 100.

[0014] (ii) 0.1% to 10% of structural units of an olefinically unsaturated functional monomer having at least one functional group selected from amide, urea, carboxyl, carboxylic anhydride, hydroxyl, phosphoric acid or sulfonic acid groups, their salts, or mixtures thereof; and

[0015] (iii) 5% to 79.9% of additional olefinic unsaturated nonionic monomer structural units;

[0016] The content of condensate in the aqueous dispersion is less than 2,000 ppm after filtration through a 44-micron sieve.

[0017] In a second aspect, the present invention is a method for preparing an aqueous dispersion according to the first aspect. The method comprises:

[0018] Emulsion polymerization of a monomer mixture is carried out in the presence of a chain transfer agent, wherein, based on the total weight of the monomer mixture, the monomer mixture comprises 20% to 85% olefinically unsaturated siloxane monomers, 0.1% to 10% olefinically unsaturated functional monomers, and 5% to 79.9% additional monoolefinically unsaturated nonionic monomers.

[0019] In a second aspect, the present invention is a coating composition comprising, by weight based on the total weight of the coating composition, (A) 0.8% to 8% of an aqueous dispersion of a polymer additive according to the first aspect, and (B) an emulsion polymer having a weight-average molecular weight greater than 25,000 g / mol. Detailed Implementation

[0020] In this document, "aqueous" dispersion refers to particles dispersed in an aqueous medium. "Aqueous medium" in this document refers to water and one or more water-miscible compounds, such as, for example, alcohols, glycols, glycol ethers, glycol esters, etc., at a weight of 0 to 30% based on the medium.

[0021] As used herein, "acrylic acid" 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)acryloyl" refers to both "methacryloyl" and "acryloyl". For example, (meth)acrylic acid refers to both methacrylic acid and acrylic acid, and methyl methacrylate refers to both methyl methacrylate and methyl acrylate.

[0022] The "structural unit" (also called the "polymer unit") of a named monomer refers to the residue of the monomer after polymerization, that is, the polymerized monomer or the monomer in polymerized form. For example, the structural unit of methyl methacrylate is shown below:

[0023] The dashed lines represent the connection points between the structural units and the polymer backbone.

[0024] The aqueous dispersion of the present invention comprises a polymer additive. The polymer additive comprises one or more olefinically unsaturated siloxane monomers, preferably one or more (meth)acrylate-functionalized siloxane structural units. The olefinically unsaturated siloxane monomers have a structure represented by formula (I), (II), or (III).

[0025]

[0026] In formula (I), R is an olefinic unsaturated group, including, for example, -CH=CH2, -R p -OC(=O)CH=CH2 or -R p -OC(=O)C(CH3)=CH2, where R p It is a C1-C6 divalent hydrocarbon group, preferably, R is -CH2CH2CH2OC(=O)CH=CH2 or

[0027] -CH2CH2CH2OC(=O)C(CH3)=CH2; and j and k are each independently in the range of 0 to 100, 0 to 80, 0 to 60, 5 to 50, 10 to 40 or 10 to 20, and j+k=5 to 100, for example, 5 to 50, 8 to 50, 10 to 40, 10 to 30 or 10 to 25;

[0028]

[0029] In formula (II), R is an olefinic unsaturated group, including, for example, -CH=CH2, -R p -OC(=O)CH=CH2 or -R p -OC(=O)C(CH3)=CH2, where R p It is a C1-C6 divalent hydrocarbon group, preferably, R is -CH2CH2CH2OC(=O)CH=CH2 or

[0030] -CH2CH2CH2OC(=O)C(CH3)=CH2; R1 is a hydroxyl, alkyl, aryl, alkoxy, aryloxy, alkyl ether, or aryl ether group, preferably a hydroxyl group, or an alkyl, alkoxy, or alkyl ether group having 1 to 15, 1 to 10, or 1 to 5 carbon atoms, for example,

[0031] -CH3, -OH, -OCH3 or -OCH2CH3; and m is 1 to 100, 5 to 80, 10 to 60, 10 to 40 or 10 to 20;

[0032]

[0033] In formula (III), R is an olefinic unsaturated group, including, for example, -CH=CH2, -R p -OC(=O)CH=CH2 or -R p -OC(=O)C(CH3)=CH2, where R p It is a C1-C6 divalent hydrocarbon group, preferably, R is -CH2CH2CH2OC(=O)CH=CH2 or

[0034] -CH2CH2CH2OC(=O)C(CH3)=CH2; R1 and R2 are the same or different and each independently is a hydroxyl, alkyl, aryl, alkoxy, aryloxy, alkyl ether or aryl ether group, preferably a hydroxyl group, or an alkyl, alkoxy or alkyl ether group having 1 to 15, 1 to 10 or 1 to 5 carbon atoms, for example -CH3, -OH, -OCH3 or -OCH2CH3; and n is 1 to 5, 1 to 4, 1 to 3 or 1 to 2; and p is 1 to 100, 5 to 80, 5 to 60, 8 to 40 or 8 to 20. Suitable commercially available olefinically unsaturated siloxane monomers may include, for example, DOWSIL TM 32. A methacrylate siloxane monomer available from The Dow Chemical Company (DOWSIL is a trademark of The Dow Chemical Company).

[0035] Based on the weight of the polymer additive, the polymer additive of the present invention comprises the following amounts of olefinic unsaturated siloxane monomer structural units: 20% or more, 21% or more, 22% or more, 23% or more, 24% or more, 25% or more, 26% or more, 27% or more, 28% or more, 29% or more, 30% or more, 31% or more, 32% or more, 33% or more, 34% or more, 35% or more, 36% or more, 37% or more, or even 38% or more, and simultaneously, 85% or less, 80% or less, 75% or less, 70% or less, 65% or less, 60% or less, 55% or less, 52% or less, 50% or less, 48% or less, 45% or less, 42% or less, or even 40% or less.

[0036] The polymer additives of the present invention comprise structural units of olefinically unsaturated functional monomers having at least one functional group selected from amide, urea, carboxyl, carboxylic anhydride, hydroxyl, phosphoric acid or sulfonic acid groups, their salts, or mixtures thereof. Examples of suitable olefinically unsaturated functional monomers include α,β-olefinically unsaturated carboxylic acids comprising acidic monomers such as methacrylic acid, acrylic acid, itaconic acid, maleic acid, or fumaric acid; or monomers having an acid-forming group that generates or can subsequently be converted to such an acid group, such as anhydrides, (meth)acrylic anhydride, or maleic anhydride; sodium styrene sulfonate (SSS), sodium vinyl sulfonate (SVS), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), sodium salts of 2-acrylamido-2-methyl-1-propanesulfonic acid, ammonium salts of 2-acrylamido-2-methyl-1-propanesulfonic acid; allyl ether sulfonate; and other olefinically unsaturated functional monomers. Sodium salts of acids; acrylamide, methacrylamide, monosubstituted (meth)acrylamide, N-methacrylamide, N-ethylacrylamide, N-isopropylacrylamide, N-butylacrylamide, N-tert-butylacrylamide, N-2-ethylhexylacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide; hydroxyl-functionalized alkyl methacrylates, such as hydroxyethyl methacrylate and hydroxypropyl methacrylate; urea-functionalized monomers, such as hydroxyethylvinyl urea methacrylate, hydroxyethylvinyl urea acrylate, such as SIPOMER WAM II, methacrylamide ethylvinyl urea, or mixtures thereof, available from Solvay. Preferred olefinically unsaturated functionalized monomers are selected from the group consisting of acrylic acid, sodium styrene sulfonate, acrylamide, methacrylamide, methacrylic acid, or mixtures thereof. Based on the weight of the polymer additive, the polymer additive may contain structural units of olefinically unsaturated ionic monomers in the following amounts: 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, 0.5% or more, 0.6% or more, 0.7% or more, 0.8% or more, 0.9% or more, or even 1.0% or more, and simultaneously 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4.5% or less, 4% or less, 3.5% or less, 3% or less, 2.5% or less, 2% or less, or even 1.5% or less.

[0037] The polymer additives of the present invention comprise structural units of one or more additional mono-olefinic unsaturated nonionic monomers different from the monomers described above. Hereinafter, the term "nonionic monomer" refers to a monomer that does not carry an ionic charge between pH 1 and 14. Additional mono-olefinic unsaturated nonionic monomers may include acrylic monomers, styrene monomers, combinations of acrylic and styrene monomers, vinyl ester monomers, or combinations of ethylene and vinyl ester monomers, vinyl silane monomers, or mixtures thereof. Examples of suitable acrylic monomers include alkyl esters of (meth)acrylic acid having 2 to 30 carbon atoms or 2 to 18 carbon atoms, such as methyl acrylate, methyl methacrylate, ethyl acrylate, 2-ethylhexyl acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, decyl acrylate, isodecyl methacrylate, lauryl (meth)acrylate, and stearyl (meth)acrylate; cycloalkyl (meth)acrylates, including cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, and cycloalkyl (meth)acrylate. Dihydrodicyclopentadienyl ester, trimethylcyclohexyl (meth)acrylate, tert-butylcyclohexyl (meth)acrylate, and (meth)acrylate-functionalized silanes, including, for example, (meth)acryloyloxyalkyltrialkoxysilanes (such as γ-methacryloyloxypropyltrimethoxysilane and methacryloyloxypropyltriethoxysilane; 3-methacryloyloxypropylmethyldimethoxysilane; 3-methacryloyloxypropyltrimethoxysilane; 3-methacryloyloxypropyltriethoxysilane; or mixtures thereof). Styrene. Examples of suitable vinyl silane monomers include vinyl acetate, vinyl butyrate, vinyl tert-carbonate, or mixtures thereof. Examples of suitable alkylalkylvinyldialkoxysilanes; and vinyltrialkoxysilanes (such as vinyltriethoxysilane and vinyltrimethoxysilane). Preferred additional olefinic monounsaturated nonionic monomers are butyl acrylate, butyl methacrylate, methyl methacrylate, ethyl acrylate, 2-ethylhexyl acrylate, vinyl acetate, (meth)acrylate functionalized silanes, styrene, or mixtures thereof. Based on the weight of the additive, the polymer additive may contain the following amounts of additional olefinic monounsaturated nonionic monomer structural units: 5% or more, 10% or more, 15% or more, 20% or more, 25% or more, 30% or more, 35% or more, 40% or more, 45% or more, while 79.9% or less, 79% or less, 78% or less, 75% or less, 72% or less, 70% or less, 68% or less, 65% or less, 62% or less, 60% or less, 59% or less, or even 57% or less.

[0038] The polymer additive of the present invention may optionally contain structural units of one or more polyene-bonded unsaturated monomers different from the monomers described above. Examples of suitable polyene-bonded unsaturated monomers include allyl (meth)acrylate, hexanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, butanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, divinylbenzene, allyl acetate, allyl (meth)acrylamide, allyloxyethyl (meth)acrylate, crotonyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyl ethyl (meth)acrylate, diallyl maleate, or mixtures thereof. The polymer additive may contain 0 to 5%, 0 to 2%, or 0.1% to 1% of structural units of polyene-bonded unsaturated monomers based on the weight of the polymer additive.

[0039] Preferably, the polymer additive comprises, by weight based on the polymer additive, 20% to 50% of structural units of olefinic unsaturated siloxane monomers, 1% to 5% of structural units of olefinic unsaturated functional monomers, and 45% to 79% of structural units of additional monoolefinic unsaturated nonionic monomers.

[0040] The polymer additives of this invention may have the following weight-average molecular weight (M). w ): 2,000 g / mol or more, 2,100 g / mol or more, 2,200 g / mol or more, 2,500 g / mol or more, 2,800 g / mol or more, 3,000 g / mol or more, 3,200 g / mol or more, 3,500 g / mol or more, 3,800 g / mol or more, 4,000 g / mol or more, 4,200 g / mol or more, 4,500 g / mol or more, 4,800 g / mol or more, 5,000 g / mol or more, 5,200 g / mol ol or more or even 5,500 g / mol or more, and simultaneously, 25,000 g / mol or less (i.e., ≤25,000 g / mol), 22,000 g / mol or less, 20,000 g / mol or less, 18,000 g / mol or less, 15,000 g / mol or less, 12,000 g / mol or less, 10,000 g / mol or less, 9,500 g / mol or less, 9,000 g / mol or less, 8,500 g / mol or less or even 8,000 g / mol or less. M n It can be determined by gel permeation chromatography (GPC) analysis as described in the example section below.

[0041] The aqueous dispersion of the polymer additive of the present invention has a low condensate content. "Low condensate content" means that the condensate content of the aqueous dispersion is less than 2,000 ppm, preferably less than 1,900 ppm, less than 1,800 ppm, less than 1,700 ppm, less than 1,600 ppm, less than 1,500 ppm, less than 1,400 ppm, less than 1,300 ppm, less than 1,200 ppm, less than 1,100 ppm, less than 1,000 ppm, less than 900 ppm, less than 800 ppm, less than 700 ppm, less than 600 ppm, or even less than 500 ppm. The condensate content can be determined by filtering the aqueous dispersion through a sieve having a mesh size of 44 micrometers (325 mesh) according to the test method described in the example section below.

[0042] The aqueous dispersion of the polymer additive of the present invention can be prepared by emulsion polymerization of a monomer mixture comprising the monomers described above for forming the structural units of the polymer additive in the presence of a chain transfer agent. The monomer mixtures usable in the present invention comprise olefinically unsaturated siloxane monomers, olefinically unsaturated functional monomers, additional monoolefinically unsaturated nonionic monomers, and optionally polyolefinically unsaturated nonionic monomers. The total concentration of the monomer mixture used to prepare the polymer additive is equal to 100%. Prior to polymerization (e.g., before adding the monomer mixture to the reaction vessel), the monomer mixture can be emulsified and typically homogenized by a homogenizer. The homogenization process can be carried out for a period of time to minimize condensation during polymerization, thereby obtaining an aqueous dispersion with low condensation content. For example, the homogenization process can be in the range of, for example, 1 minute to 5 minutes or 3 minutes to 5 minutes. Examples of suitable chain transfer agents include 3-mercaptopropionic acid, n-dodecyl mercaptan (nDDM), methyl 3-mercaptopropionate (MMP), butyl 3-mercaptopropionate, benzenethiol, alkyl azelaic acid mercaptan, or mixtures thereof. Chain transfer agents can be used in effective amounts to control the molecular weight of polymer additives. For example, the amount of chain transfer agent used may be 0.01% or more, 0.1% or more, 0.5% or more, or even 1% or more, based on the total weight of the monomer mixture used to prepare the polymer additive, while 5% or less, 4.5% or less, 4% or less, or even 3.5% or less.

[0043] The polymerization of monomer mixtures can be carried out using conventional free radical polymerization methods known in the art. Monomers used to prepare polymer additives can be added purely or as emulsions in water; or added in one or more forms during the reaction time for preparing the polymer additive, or in a continuous, linear, or non-linear manner, or a combination thereof. Temperatures suitable for emulsion polymerization methods can be below 95 degrees Celsius (°C), ranging from 50°C to 90°C or from 70°C to 90°C. Free radical initiators can be used in the polymerization methods for preparing polymer additives. The polymerization process can be thermally initiated or redox-initiated emulsion polymerization. Examples of suitable free radical initiators include hydrogen peroxide, tert-butyl hydroperoxide, tert-amyl hydroperoxide, cumene hydroperoxide, ammonium and / or alkali metal persulfates, sodium perborate, superphosphate and its salts; ammonium or alkali metal salts of potassium permanganate and peroxydisulfate. Free radical initiators can typically be used at levels of 0.01% to 1% or 0.05% to 0.6% by weight based on the total weight of the monomer mixture. In polymerization methods, redox systems comprising the aforementioned initiators and suitable reducing agents can be used. Examples of suitable reducing agents include sodium formaldehyde sulfoxylate, ascorbic acid, isoascorbic acid, alkali metal and ammonium salts of sulfur-containing acids (such as sodium sulfite, bisulfite, thiosulfate, hyposulfite, sulfide, hydrosulfide or disulfide, acetone bisulfite), glycolic acid, hydroxymethanesulfonic acid, hydrated glyoxylic acid, lactic acid, glyceric acid, malic acid, tartaric acid, and salts of the aforementioned acids. Metal salts of iron, copper, manganese, silver, platinum, vanadium, nickel, chromium, palladium, or cobalt can be used to catalyze redox reactions. Metal chelating agents may optionally be used.

[0044] In polymerization methods, one or more surfactants may be added before, during, or in combination with the polymerization of monomers. A portion of the surfactant may also be added after polymerization. These surfactants may include anionic and / or nonionic emulsifiers. Examples of suitable surfactants include alkali metal or ammonium salts of alkyl, aryl, or alkylaryl sulfates, sulfonates, or phosphates; alkyl sulfonic acids; sulfosuccinates; fatty acids; reactive surfactants; ethoxylated alcohols or phenols; and mixtures thereof. The amount of surfactant used is typically in the range of 0.1% to 6%, 0.3% to 3%, or 0.5% to 1.5% by weight of the total monomers used to prepare the polymer additive.

[0045] After polymerization, the resulting aqueous dispersion containing the polymer additive may optionally be neutralized to a pH value, for example, in the range of 6 to 11 or 7 to 9, by one or more bases acting as neutralizing agents. The base may cause partial or complete neutralization of the ionic or potential ionic groups of the polymer additive. Examples of suitable bases include 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 amine solutions, triethylamine, ethylamine, propylamine, monoisopropylamine, monobutylamine, hexylamine, ethanolamine, diethylamine, dimethylamine, di-n-propylamine, tributylamine, triethanolamine, dimethoxyethylamine, 2-ethoxyethylamine, 3-ethoxypropylamine, dimethylethanolamine, diisopropanolamine, morpholine, ethylenediamine, 2-diethylaminoethylamine, 2,3-diaminopropane, 1,2-propanediamine, neopentyldiamine, dimethylaminopropylamine, hexanediamine, 4,9-dioxadodecane-1,12-diamine, polyethyleneimine, or polyethyleneamine; aluminum hydroxide; and mixtures thereof.

[0046] The polymer additive particles in the aqueous dispersion may have a number-average particle size in the range of 50 nanometers (nm) to 500 nm, 60 nm to 400 nm, or 70 nm to 300 nm, as determined by a Brookhaven BI-90Plus particle size analyzer.

[0047] The aqueous dispersion of the polymer additive also contains, for example, 30% to 90%, 40% to 80%, or 50% to 70% water by weight based on the total weight of the aqueous dispersion.

[0048] The present invention also relates to a coating composition, typically an aqueous coating composition, comprising (A) an aqueous dispersion of a polymeric additive and (B) an emulsion polymer. Based on the total weight of the coating composition, the coating composition of the present invention may contain the following amounts of an aqueous dispersion of the polymeric additive: 0.8% or more, 0.9% or more, 1.0% or more, 1.1% or more, 1.2% or more, 1.3% or more, 1.4% or more, 1.5% or more, or even 1.6% or more, and simultaneously 8% or less, 7.9% or less, 7.8% or less, 7.7% or less, 7.6% or less, 7.5% or less, 7.4% or less, 7.3% or less, 7.2% or less, 7.1% or less, 7% or less, 6.9% or less, 6.8% or less, 6.7% or less, 6.6% or less, 6.5% or less, 6.4% or less, or even 6.3% or less. Preferably, the aqueous dispersion of the polymer additive is present in the coating composition in an amount providing the structural unit concentration of the olefinic unsaturated siloxane monomer, based on the total weight of the coating composition: 0.2% or more, 0.22% or more, 0.25% or more, 0.28% or more, 0.3% or more, 0.32% or more, 0.35% or more, 0.38% or more, or even 0.4% or more, and simultaneously 1.8% or less, 1.7% or less, 1.6% or less, 1.5% or less, 1.4% or less, 1.3% or less, 1.2% or less, 1.1% or less, 1.0% or less, 0.9% or less, 0.8% or less, 0.78% or less, 0.75% or less, 0.72% or less, or even 0.7% or less, based on the total weight of the coating composition: 0.2% or more, 0.22% or more, 0.25% or more, 0.25% or more, 0.25% or less, 0.75% or less, 0.72% or less, or even 0.7% or less.

[0049] The coating compositions of the present invention further comprise one or more emulsion polymers, which are also commonly referred to as binders and are typically in the form of emulsions or aqueous dispersions. The weight-average molecular weight (Mi) of the emulsion polymers usable in the present invention is... w Greater than 25,000 g / mol (i.e., >25,000 g / mol), for example, 30,000 g / mol or greater, 60,000 g / mol or greater, 80,000 g / mol or greater, 100,000 g / mol or greater, 200,000 g / mol or greater, 300,000 g / mol or greater, or even 400,000 g / mol or greater. M w The particle size can be determined using GPC analysis with polystyrene standards. Emulsion polymer particles can have sizes ranging from 30 nanometers (nm) to 500 nm, 70 nm to 300 nm, or 70 nm to 250 nm. The particle size of the emulsion polymer can be determined using a Brookhaven BI-90Plus particle size analyzer.

[0050] The emulsion polymer in the coating composition of the present invention may be selected from acrylic polymers, including acrylic copolymers and styrene-acrylic copolymers, polyurethane-acrylic blends, or mixtures thereof. Based on the weight of the acrylic polymer, the acrylic polymer used in the present invention may comprise 90% to 99.9% of the structural units of the aforementioned mono-olefin unsaturated nonionic monomers (such as styrene, butyl acrylate, 2-ethylhexyl acrylate, acetoacetoxyethyl methacrylate (AAEM), or mixtures thereof), and 0.1% to 10% of the structural units of the aforementioned olefin unsaturated functional monomers (such as acrylic acid, methacrylic acid, ethyl methacrylate, or mixtures thereof).

[0051] The coating compositions of the present invention may comprise pigments and / or extenders. As used herein, “pigment” refers to a material capable of substantially contributing to the opacity or hiding power 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), zinc oxide, iron oxide, zinc sulfide, anti-corrosion pigments (such as zinc phosphate and zinc molybdate), carbon black, barium sulfate, barium carbonate, and mixtures thereof. TiO2 is typically present in two crystalline forms: anatase 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.) of Wilmington, Delaware, TiONA AT1 available from Cristal, and mixtures thereof. TiO2 may also be obtained in concentrated dispersion form. In this article, "increaser" refers to particulate inorganic materials with a refractive index less than or equal to 1.8 and greater than 1.3. Examples of suitable increasers include calcium carbonate, clay, calcium sulfate, aluminum silicate, silicates, zeolite, mica, diatomaceous earth, solid or hollow glass, ceramic beads, nepheline syenite, feldspar, diatomaceous earth, calcined diatomaceous earth, talc (hydrated magnesium silicate), silica, alumina, kaolin, pyrophyllite, perlite, barite, wollastonite, and opaque polymers (such as ROPAQUE, available from Dow Chemical). TM Ultra E opaque polymers (ROPAQUE is a trademark of Dow Chemical Company) and mixtures thereof. Coating compositions 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:

[0052] The coating compositions of the present invention may contain one or more defoamers. As used herein, "defoamer" refers to a chemical additive that reduces and inhibits foam formation. Defoamers may be silicone-based defoamers, mineral oil-based defoamers, ethylene oxide / propylene oxide defoamers, alkyl polyacrylates, and mixtures thereof. The defoamer may be present in amounts of 0 to 5%, 0.05% to 3%, or 0.1% to 2% by weight based on the total weight of the coating composition.

[0053] The coating compositions of the present invention may further comprise one or more thickeners (also referred to as "rheology modifiers"). Thickeners may include polyvinyl alcohol (PVA), clay materials, acid derivatives, acid copolymers, urethane associative thickeners (UAT), polyether urea polyurethane (PEUPU), polyether polyurethane (PEPU), or mixtures thereof. Examples of suitable thickeners include alkali-swellable emulsions (ASE), such as sodium or ammonium-neutralized acrylic polymers; hydrophobically modified alkali-swellable emulsions (HASE), such as hydrophobically modified acrylic copolymers; associative thickeners, such as hydrophobically modified ethoxylated urethane (HEUR); and cellulose thickeners, such as methyl cellulose ether, hydroxymethyl cellulose (HMC), hydroxyethyl cellulose (HEC), hydrophobically modified hydroxyethyl cellulose (HMHEC), sodium carboxymethyl cellulose (SCMC), sodium carboxymethyl 2-hydroxyethyl cellulose, 2-hydroxypropyl methylcellulose, 2-hydroxyethyl methylcellulose, 2-hydroxybutyl methylcellulose, 2-hydroxyethyl ethyl cellulose, and 2-hydroxypropyl cellulose. Preferably, the thickener is HEUR, HEC, or a mixture thereof. The thickener may be present in amounts of 0 to 8%, 0.05% to 3%, or 0.1% to 1% based on the total weight of the coating composition.

[0054] The coating compositions of the present invention may further comprise one or more wetting agents. As used herein, "wetting agent" refers to a chemical additive that reduces the surface tension of the coating composition, thereby facilitating diffusion or penetration across or into the substrate surface. The wetting agent may be anionic, amphoteric, or nonionic polycarboxylate. The wetting agent may be present in amounts of 0 to 5%, 0.05% to 3%, or 0.1% to 2% by weight based on the total weight of the coating composition.

[0055] The coating compositions of the present invention may contain one or more coalescing agents. As used herein, "coalescing agent" refers to a slowly evaporating solvent that fuses polymer particles into a continuous film under ambient conditions. Examples of suitable coalescing agents include 2-n-butoxyethanol, dipropylene glycol n-butyl ether, propylene glycol n-butyl ether, dipropylene glycol methyl ether, propylene glycol methyl ether, propylene glycol n-propyl ether, diethylene glycol monobutyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, triethylene glycol monobutyl ether, dipropylene glycol n-propyl ether, n-butyl ether, or mixtures thereof. Preferred coalescing agents include dipropylene glycol n-butyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, n-butyl ether, or mixtures thereof. The coalescing agent may be present in amounts from 0 to 30%, 0.5% to 20%, or 2% to 10% by weight based on the total weight of the coating composition.

[0056] The coating compositions of the present invention may comprise one or more dispersants. Dispersants may include nonionic, anionic, and cationic dispersants, such as polybasic acids having suitable molecular weights, 2-amino-2-methyl-1-propanol (AMP), dimethylaminoethanol (DMAE), potassium tripolyphosphate (KTPP), trisodium polyphosphate (TSPP), citric acid, and other carboxylic acids. The polybasic acids used may include homopolymers and copolymers based on polycarboxylic acids (e.g., with a weight-average molecular weight in the range of 1,000 to less than 50,000, as measured by GPC), including those that have been hydrophobically or hydrophilically modified, such as polyacrylic acid or polymethacrylic acid or maleic anhydride, and various monomers (such as styrene, acrylates or methacrylates, diisobutylene, and other hydrophilic or hydrophobic comonomers); their salts; or mixtures thereof. The dispersant may be present in amounts of 0 to 5%, 0.05% to 3%, or 0.1% to 1% based on the total weight of the coating composition.

[0057] In addition to the components described above, the coating compositions of the present invention may further comprise any or a combination of the following additives: buffers, neutralizers, humectants, fungicides, insecticides, anti-skinning agents, colorants, flow agents, antioxidants, plasticizers, leveling agents, tackifiers, flash rust inhibitors, and abrasives. These additives may be present in amounts ranging from 0 to 10% or in combinations of 0.1% to 2% based on the total weight of the coating composition. The coating compositions may also comprise water in amounts ranging from 30% to 90%, 40% to 80%, or 50% to 70% by weight of the coating composition.

[0058] The coating compositions of the present invention can be prepared by blending an emulsion polymer with an aqueous dispersion of polymer additives and other optional components (e.g., pigments and / or extenders). The components in the coating composition can be mixed in any order to provide the coating compositions of the present invention. Any of the optional components described above can also be added to the composition during or before mixing to form the coating composition. When the coating composition contains pigments and / or extenders, it is preferable to mix the pigments and / or extenders with a dispersant to form a slurry of the pigments and / or extenders.

[0059] The coating compositions of the present invention provide coatings made therefrom with improved corrosion resistance. The present invention also provides a method for improving the corrosion resistance of easily corroded substrates, such as metals. The method comprises: applying a coating composition to a metal substrate; and drying or allowing the coating composition to dry to form a coating. According to ASTM B117-2011, for coatings having a thickness of 40 micrometers (μm) to 50 μm, improved corrosion resistance after exposure to salt spray for at least 300 hours means a blistering rating of "6F" or higher and a surface rust rating of "7S" or higher, preferably "7P", "9S", "9P", or "10". According to the test method of GB / T 9780-2013, the coating compositions provide coatings with good stain removal properties, such as a stain removal score indication of 65 or higher. Compared to binders containing structural units of olefinically unsaturated siloxane monomers, the aqueous dispersions of the polymer additives of the present invention provide greater efficiency in improving the corrosion resistance and stain removal properties of coating compositions containing them. For example, in order to achieve comparable corrosion resistance and stain removal performance, the coating compositions of the present invention require a lower concentration of structural units of olefinically unsaturated siloxane monomers based on the weight of the coating composition compared to coating compositions containing binders comprising structural units of olefinically unsaturated siloxane monomers.

[0060] This invention also relates to a method for preparing a coating on a substrate (preferably an outer surface), the method comprising: applying a coating composition to the substrate and drying or allowing the applied coating composition to dry to prepare a coating. The coating compositions of this invention can be applied to and adhered to a variety of substrates. Examples of suitable substrates include wood, metal, plastic, foam, stone, elastic substrates, glass, textiles, concrete, or cement substrates. Coating compositions preferably containing pigments can be used in a variety of applications, such as marine protective coatings, general industrial paints, metal protective coatings, automotive coatings, road marking paints, exterior insulation and finishing systems (EIFS), wood coatings, coil coatings, plastic coatings, can coatings, architectural coatings, and civil engineering coatings. The coating compositions are particularly suitable for metal protective coatings and architectural coatings. The coating compositions can be used as primers, topcoats, as single-coat coatings applied directly to metals, or in combination with other coatings to form multi-layer coatings.

[0061] The present invention also provides a method for improving the corrosion resistance of a metal substrate. The method includes: providing a coating composition; applying the coating composition to a metal substrate; and drying or allowing the coating composition to dry to form a coating with improved corrosion resistance as described above. The present invention also relates to a coated metal article comprising a coating having the improved corrosion resistance defined above.

[0062] The coating compositions of the present invention can be applied to a substrate by existing methods including brushing, dipping, rolling, and spraying. Spraying is preferred for application of the coating compositions. Standard spraying techniques and equipment, such as air atomization spraying, air spraying, airless spraying, high-volume low-pressure spraying, and electrostatic spraying (e.g., electrostatic bell application), as well as manual or automated methods, can be used. After the coating compositions of the present invention have been applied to the substrate, the coating compositions can be dried at room temperature (23°C ± 2°C) or at high temperatures (e.g., 35°C to 60°C) to form a film (i.e., a coating).

[0063] Example

[0064] Some embodiments of the invention will now be described in the following examples, wherein all parts and percentages are by weight unless otherwise stated. The following materials are used in the examples:

[0065] DOWSIL 32 additive (DC-32), available from Dow Chemical Company, is a methacrylate siloxane monomer with the following structure:

[0066] Where j+k=12-25.

[0067] The surfactant DISPONIL Fes993 (29%-31% solids content) available from BASF is the sodium salt of aliphatic polyethylene glycol ether sulfate.

[0068] HITENOL AR1025 (25% solids content), which is available from Dai-Ichi Kogyo Seiyaku Co. Ltd. of Japan, is an ammonium salt of polyoxyethylene styrene-propylene phenyl ether sulfate.

[0069] NATROSOL 250HBR thickener was purchased from Ashland Aqualon Company.

[0070] ACRYSOL is available from Dow Chemical Company. TMRM-8W thickener is a nonionic urethane rheology modifier.

[0071] OROTAN TM 681 (35% solids content) and OROTAN 1288 dispersant (45% solids content) and TRITON TM EF-406 nonionic surfactant (70% solids content) is available from Dow Chemical Company.

[0072] AMP-95 neutralizer is available from Sinopharm.

[0073] Nopco NXZ defoamer is available from Cognis Corporation.

[0074] Surfynol TG nonionic wetting agent and Tego Airex 902W defoamer are both available from Evonik.

[0075] Ti-Pure R-706 pigment, available from DuPont, is a titanium dioxide pigment.

[0076] Kaolin (DB-80) is available from Shanxi Jinyang Calcined Kaolin Ltd.

[0077] CC-700 extender is available from Guangfu Building Materials Group (China).

[0078] Washed clay, available from HuiLi (China), can be used as a bulking agent.

[0079] Adhesive 1, Adhesive 2, and Adhesive 3 were all purchased from Dow Chemical Company. Adhesive 1 was a 100% acrylic emulsion (solid content: 49.0% and M). w : 340,000 g / mol - 360,000 g / mol); Binder 2 is a styrene-acrylic emulsion (solid content: 47.0%, M w : 340,000 g / mol - 360,000 g / mol); and binder 3 is a styrene-acrylic emulsion (solid content: 47.5% and M w :90,000g / mol-110,000g / mol).

[0080] ROPAQUE TM Ultra E opaque polymer is available from Dow Chemical Company.

[0081] TEXANOL ester alcohol, available from Eastman, can be used as a coalescing agent.

[0082] Propylene glycol is used as an antifreeze.

[0083] Sodium nitrite (15%) is used as an anti-flash rust additive.

[0084] ACRYSOL, OROTAN, TRITON, and ROPAQUE are trademarks of Dow Chemical Company.

[0085] The following standard analytical equipment and methods were used in the embodiments and to determine the properties and characteristics described herein:

[0086] GPC Analysis

[0087] GPC analysis is generally performed using an Agilent 1200. The sample is dissolved in a 2 mg / mL solution of tetrahydrofuran (THF) / formic acid (FA) (5%) to form a sample solution, which is then filtered through a 0.45 μm polytetrafluoroethylene (PTFE) filter before GPC analysis. GPC analysis is performed under the following conditions:

[0088] Columns: One pre-column and two mixed B-columns (7.8 mm × 300 mm); Column temperature: 35 °C; Mobile phase: THF / FA (5%); Flow rate: 1.0 mL / min; Injection volume: 100 mL; Detector: Agilent refractive index detector, 35 °C; and Calibration curve: PL polystyrene (PS) narrow standard (part number: 2010-0101), PS equivalent molecular weight range from 2,329,000 g / mol to 162 g / mol.

[0089] Agglomerate content of aqueous dispersions of polymer additives

[0090] The aqueous dispersion sample was filtered through a 44-micron sieve. The residue remaining on the sieve was washed with water and then placed in an oven at 150°C for 20 minutes. The coagulant content was determined by dividing the dry weight of the residue on the sieve by the original wet weight of the aqueous polymer dispersion. Lower coagulant content indicates a more stable polymerization method for preparing the aqueous dispersion.

[0091] Salt spray resistance test

[0092] The coating composition was applied to a Q panel (cold-rolled steel) using a 150 μm applicator. The resulting coating film was allowed to dry for 7 days at 23°C and 50% relative humidity (RH). Salt spray resistance was tested according to ASTM B117-2011 by exposing the prepared coated panel to a salt spray environment (5% sodium chloride mist). Prior to exposure, the exposed cold-rolled steel was covered with tape (3M plastic tape #471). Just before exposure, scratches made with a razor blade were made on the lower half of the panel obtained above. The panel was exposed to the salt spray environment for several hours and then removed from the salt spray environment. The surface of the panel was first washed with deionized (DI) water before rating. The results are expressed as a blistering / rusting rating.

[0093] Bubble ratings are determined according to ASTM D714-02 (2009) and include numbers and one or more letters, as shown in Table 1. The letters F, M, MD, or D are qualitative representations of the bubble density. The numbers indicate the size of the bubbles, with 2 being the largest, 8 the smallest, and 10 indicating no bubbles. Higher numbers indicate smaller bubble sizes. Rust ratings are determined according to ASTM D610-2001, as shown in Tables 2 and 3. Panels with a bubble density rating of "6F" or higher and "7S" or higher are considered acceptable levels of rust, indicating good corrosion resistance of the coating.

[0094] Table 1. Foaming Grade Standards

[0095] Density of foam abbreviation Bubble size grade rare F Very large bubbles 2 medium M Large bubbles 4 Medium density MD Small to medium bubbling 6 dense D The smallest visible bubble 8 No bubbles formed 10

[0096] Table 2. Rust grades according to the degree of rust corrosion

[0097] degree of corrosion grade spotted S generally G needle-like P

[0098] Table 3. Rust grades by percentage of surface rust

[0099] Surface rust grade Less than or equal to 0.01% 10 Greater than 0.01% and at most 0.03% 9 Greater than 0.03% and at most 0.1% 8 Greater than 0.1% and at most 0.3% 7 Greater than 0.3% and a maximum of 1.0% 6 Greater than 1.0% and up to 3.0% 5 Greater than 3.0% and a maximum of 10.0% 4 Greater than 10.0% and up to 16.0% 3 Greater than 16.0% and up to 33.0% 2 Greater than 33.0% and up to 50.0% 1 Greater than 50.0% 0

[0100] Stain removal evaluation

[0101] The test coating composition was applied to a black vinyl scrubber card using a 150 μm applicator and dried for 7 days at a constant temperature (25°C) and humidity (50%) before staining. Stain removal performance was evaluated according to GB / T 9780-2013 (Test methods for stain resistance and stain removal properties of architectural coatings and paint films). Each stain (vinegar, black tea, blue-black ink, water-soluble black, alcohol-soluble black, and a mixture of petroleum jelly and carbon black, respectively) was then uniformly applied to a test area with a width of 25 mm and a card cross-sectional length. Liquid stains were applied to gauze to prevent them from flowing out of the test area. The stains were left on the panel for absorption for 2 hours, then wiped off with a dry paper towel. The panel was then placed on a 1.5 kg scratch tester and scrubbed with a 1% Aomo powder solution at a scrubbing rate of 37 cycles / min. After 200 cycles of scrubbing the panel, it was removed from the testing equipment, thoroughly rinsed under running water, and hung to dry. Finally, the change in reflectivity (X) was measured to evaluate each cleaned stained area.

[0102]

[0103] X: Removal efficiency (%) of each stain as measured by reflectance;

[0104] Y1: Reflectance after the stain removal test;

[0105] Y0: Reflectance before a stain is applied to the paint film.

[0106] Based on the different stains (X), the stain removal ability score (R) can be obtained from the table below:

[0107] Table 4. Scoring criteria for stain removal ability

[0108]

[0109]

[0110] The total score (R') for stain removal ability is calculated as follows:

[0111]

[0112] R i : The score for the removal ability of each type of stain;

[0113] R: The total score for the ability to remove all six types of stains from the paint film.

[0114] A higher score indicates better stain removal performance. A total stain removal score of at least 60 is acceptable.

[0115] Synthesis of Polymer Additive (PA) Dispersion 1 ("PA Dispersion 1")

[0116] Water (420.00 g) and Fes993 surfactant (1.95 g) were added to a 3-liter five-necked flask equipped with a mechanical stirrer, nitrogen (N2) purging, thermocouples, and a condenser. The resulting solution in the flask was heated to 86°C. An initiator solution (0.65 g sodium persulfate (SPS) dissolved in 5.00 g of water) was added. After two minutes, a monomer emulsion finely stirred by a homogenizer was added, which contained 2-ethylhexyl acrylate (EHA, 96.00 g), DC-32 (120.00 g), ethyl acrylate (EA, 75.00 g), methacrylic acid (MAA, 9.00 g), n-dodecyl mercaptan (nDDM, 9.81 g), and Fes993 surfactant (18.30 g) in water (130.00 g). Simultaneously, an initiator comprising SPS (0.53 g) and water (60.00 g) was co-fed, and the flask temperature was maintained at approximately 86 °C for 90 min. After feeding, the reactants were held for 5 min. After cooling to 60 °C, a tracker system comprising a solution of ferrous sulfate (4.00 g, 0.2% aqueous solution), a solution of tert-butyl hydroperoxide (t-BHP, 1.18 g) in water (5.00 g), and a solution of isoascorbic acid (IAA, 0.58 g) in water (5.00 g) was added. After holding for 15 min, the same tracker system was refilled. Finally, the resulting dispersion was cooled to ambient temperature and filtered through a 325-mesh sieve (i.e., a 44-micron sieve) to obtain PA dispersion 1 with a total solids content of 30%.

[0117] Synthesis of PA Dispersion A

[0118] The preparation of PA dispersion A is the same as that of PA dispersion 1 above, except that a solution of a monomer emulsion containing EHA (96.00 g), EA (195.00 g), MAA (9.00 g), nDDM (9.81 g) and Fes993 surfactant (18.30 g) in water (130.00 g) is used.

[0119] Synthesis of PA Dispersion B

[0120] The preparation of PA dispersion B is the same as that of PA dispersion 1 above, except that a solution of a monomer emulsion containing EHA (180.00 g), DC-32 (30.00 g), EA (75.00 g), MAA (15.00 g), nDDM (9.81 g) and Fes993 surfactant (18.30 g) in water (130.00 g) is used.

[0121] Synthesis of PA Dispersion 2

[0122] The preparation of PA dispersion 2 is the same as that of PA dispersion 1, except that a solution of a monomer emulsion containing EHA (150.00 g), DC-32 (60.00 g), EA (75.00 g), MAA (15.00 g), nDDM (9.81 g) and Fes993 surfactant (18.30 g) in water (130.00 g) is used.

[0123] Synthesis of PA Dispersion 3

[0124] The preparation of PA dispersion 3 is the same as that of PA dispersion 1, except that a solution of a monomer emulsion containing EHA (126.00 g), DC-32 (90.00 g), EA (75.00 g), MAA (9.00 g), nDDM (9.81 g) and Fes993 surfactant (18.30 g) in water (130.00 g) is used.

[0125] Synthesis of PA Dispersion 4

[0126] The preparation of PA dispersion 4 is the same as that of PA dispersion 1, except that a solution of a monomer emulsion containing EHA (102.00 g), DC-32 (120.00 g), EA (75.00 g), MAA (3.00 g), nDDM (9.81 g) and Fes993 surfactant (18.30 g) in water (130.00 g) is used.

[0127] Synthesis of PA Dispersion D

[0128] The preparation of PA dispersion D is the same as the synthesis of PA dispersion 1 above, except that the solution of the monomer emulsion containing EHA (180.00g), DC-32 (30.00g), EA (75.00g), MAA (15.00g), nDDM (9.81g) and Fes993 surfactant (18.30g) in water (130.00g) was not stirred by a homogenizer before being fed into the flask.

[0129] Synthesis of PA Dispersion C

[0130] The preparation of PA dispersion C is the same as that of PA dispersion 1 above, except that a solution of a monomer emulsion containing EHA (60.00 g), DC-32 (60.00 g), EA (45.00 g), MAA (135.00 g), nDDM (9.81 g) and Fes993 surfactant (18.30 g) in water (130.00 g) is used.

[0131] The properties of the obtained aqueous dispersions of polymer additives are given in Table 5. As shown in Table 5, PA dispersions 1-4 all exhibit lower agglomerate content compared to PA dispersion C, which contains a higher content of acid structural units, and PA dispersion D, which was prepared without homogenization.

[0132] Table 5. Compositions and properties of polymer additive dispersions

[0133]

[0134] Examples (Ex) 1-8 and Comparative (Comp) Examples AC Coating Compositions

[0135] Based on the formulations given in Table 6, the polymer additive dispersions obtained above (e.g., PA dispersions 1-4, A, and B) were used to prepare coating compositions. All components used in the grinding stage for preparing each coating composition were added sequentially and uniformly mixed for 30 min using a high-speed disperser at approximately 1,000 rpm to form a mill. The components in the premix from the thinning stage were first mixed, followed by the addition of the milled mixture described above. Then, based on the type and dosage given in Table 7, the PA dispersion was added at the end of the thinning stage. ACRYSOL RM-8W and water were then further added to obtain the coating compositions. The water load was adjusted to maintain a total weight of 1,000 g for each coating composition. The salt spray resistance of the resulting coating compositions was evaluated, and the results are given in Table 7.

[0136] Table 6. Coating compositions (40% PVC) used for salt spray resistance evaluation

[0137]

[0138]

[0139] As shown in Table 7, the coating compositions of Examples 1-8, containing 1.67%-6.67% of PA dispersions 1, 2, 3, or 4 (by weight based on the total weight of each coating composition), provided coatings with better salt spray resistance after 300 hours of salt spray exposure than the coating composition of Comparative Example A. Conversely, Comparative Example B, containing a polymer additive with 10% DC-32 structural units, exhibited worse salt spray resistance compared to Comparative Example A and Example 1. The coating composition of Comparative Example C, containing 8.89% of PA dispersion 3, provided worse salt spray resistance compared to Comparative Example A.

[0140] Table 7. Salt spray resistance

[0141]

[0142]

[0143] Examples 9-13 and Comparative Examples D and E: Coating Compositions

[0144] Based on the formulations shown in Table 8, the polymer additive dispersions obtained above (e.g., PA dispersions 1, 4, and A) were used to prepare coating compositions. All components used in the grinding stage for preparing each coating composition were added sequentially and uniformly mixed for 30 minutes at approximately 1,000 rpm using a high-speed disperser to form a slurry. Then, binders (binders 1 and 2) and other components (including the PA dispersions from the thinning stage) were added sequentially to obtain the coating composition. The dosages and types of binders and PA dispersions are given in Table 9. The stain removal resistance of the obtained coating compositions was evaluated, and the results are given in Table 9.

[0145] Table 8. Coating compositions used for stain removal evaluation (49% PVC)

[0146]

[0147]

[0148] As shown in Table 9, the coating compositions of Examples 9 and 10, which contain an acrylic silicone mixed polymer additive, provide coatings with improved stain resistance compared to the coating composition of Comparative Example D. In particular, when 2.0% of PA dispersion 1 (by weight of the total coating composition) is included, the resulting coating composition of Example 10 shows a 5-point improvement in total stain removal score compared to Comparative Example D. Furthermore, the coating compositions containing binder 2 and 1%-2.0% of polymer additive dispersion (PA dispersion 1 or 4) also show improved stain removal performance compared to the coating composition of Comparative Example E (Examples 11-13).

[0149] Table 9. Stain Resistance of Coating Compositions

[0150]

Claims

1. An aqueous dispersion of a polymer additive having a weight-average molecular weight of 2,000 g / mol to 25,000 g / mol, wherein, based on the weight of the polymer additive, the polymer additive comprises: (i) 20% to 85% by weight of structural units of olefinic unsaturated siloxane monomers of formula (I), (II) or (III). (I)， in, In formula (I), R is an olefinic unsaturated group, and j and k are each independently in the range of 0 to 100, and j+k=5 to 100; (II), In formula (II), R is an olefinic unsaturated group, R1 is a hydroxyl, alkyl, aryl, alkoxy, aryloxy, alkyl ether or aryl ether group, and m is 1 to 100. (III), In formula (III), R is an olefinic unsaturated group, R1 and R2 are each independently a hydroxyl, alkyl, aryl, alkoxy, aryloxy, alkyl ether or aryl ether group, n is 1 to 5, and p is 1 to 100. (ii) 0.5% to 8% by weight of structural units of alkene-bonded unsaturated functional monomers having at least one functional group selected from carboxyl, carboxylic anhydride, salts thereof, or mixtures thereof; and (iii) 5% to 79.9% by weight of mono-olefinic unsaturated nonionic monomer structural units; The total weight percentage of all individual structural units is 100%; The agglomerate content of the aqueous dispersion is less than 2,000 ppm after filtration through a 44-micron sieve.

2. The aqueous dispersion according to claim 1, wherein the olefinic unsaturated siloxane monomer has a structure represented by formula (I), wherein R is -CH=CH2, -R p -OC(=O)CH=CH2 or -R p -OC(=O)C(CH3)=CH2, where R p It is a C1-C6 divalent hydrocarbon group, and j+k is in the range of 5 to 50.

3. The aqueous dispersion according to claim 1 or 2, wherein, based on the weight of the polymer additive, the polymer additive comprises 20% to 50% by weight of the structural unit of the olefinic unsaturated siloxane monomer.

4. The aqueous dispersion according to claim 1 or 2, wherein, based on the weight of the polymer additive, the polymer additive comprises 1% to 5% by weight of the structural unit of the olefinic unsaturated functional monomer.

5. The aqueous dispersion according to claim 1 or 2, wherein the polymer additive has a weight-average molecular weight of 5,000 g / mol to 10,000 g / mol.

6. The aqueous dispersion according to claim 1 or 2, wherein the monoolefinic unsaturated nonionic monomer is selected from the group consisting of acrylic acid monomers, styrene monomers, combinations of acrylic acid and styrene monomers, vinyl ester monomers, combinations of ethylene and vinyl ester monomers, vinyl silane monomers, or mixtures thereof.

7. A method for preparing an aqueous dispersion according to any one of claims 1-6, the method comprising: Emulsion polymerization of a monomer mixture is carried out in the presence of a chain transfer agent, wherein, based on the total weight of the monomer mixture, the monomer mixture comprises 20% to 85% by weight of the olefinically unsaturated siloxane monomer, 0.5% to 8% by weight of the olefinically unsaturated functional monomer, and 5% to 79.9% by weight of the monoolefinically unsaturated nonionic monomer, wherein the total weight percentage of all monomers is 100%. The monomer mixture is emulsified and homogenized prior to polymerization.

8. A coating composition comprising, based on the total weight of the coating composition, (A) 0.8% to 8% by weight of an aqueous dispersion of a polymer additive according to any one of claims 1-6, and (B) an emulsion polymer having a weight-average molecular weight greater than 25,000 g / mol.

9. The coating composition according to claim 8, wherein the structural unit of the olefinic unsaturated siloxane monomer in the polymer additive is present in an amount of 0.2% to 1.8% by weight, based on the total weight of the coating composition.

10. The coating composition of claim 8, wherein, based on the weight of the coating composition, the coating composition comprises 1% to 7% by weight of an aqueous dispersion of the polymer additive.

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