Multistage emulsion polymer and method for preparing the same

Abstract

A multi-stage emulsion polymer comprises a first polymer and a second polymer of structural units of a nitrogen-containing heterocyclic monomer, the first polymer being in a specific weight ratio relative to the second polymer, and having a specific Tg difference between the first polymer and the second polymer; the multi-stage emulsion polymer is suitable for coating applications to provide a coating film with improved stain resistance without compromising film-forming properties.

Description

Technical Field

[0001] The present invention relates to multistage emulsion polymers and a method for preparing the same. Background Art

[0002] In exterior coating applications, dirt pick-up resistance (DPUR) is a key property that enables the coating to maintain its color and gloss when exposed to the elements, such as sunlight. Common approaches used to improve DPUR properties in the coatings industry include, for example, increasing the glass transition temperature of acrylic polymer binders or incorporating conventional photocrosslinkers such as benzophenone (BzP) into the coating. These approaches can require higher dosages of coalescing agents for film formation or suffer from performance variability issues because BzP's ultraviolet (UV) curing depends on weather conditions.

[0003] It would therefore be desirable to provide an emulsion polymer suitable for coating applications that provides exterior coatings, such as elastomeric wall coatings, with improved stain resistance without compromising film-forming properties. Summary of the Invention

[0004] The present invention provides a multi-stage emulsion polymer comprising a first polymer and a second polymer, wherein the weight ratio of the first polymer to the second polymer is in the range of 55:45 to 95:5, wherein the Tg of the first polymer is at least 35°C higher than the Tg of the second polymer. The multi-stage emulsion polymer of the present invention comprises a cycloalkyl (meth)acrylate, a C6-C8 (meth)acrylate, 10 The multi-stage emulsion polymer comprises a specific combination of structural units of an alkyl ester or a mixture thereof; and structural units of a nitrogen-containing heterocyclic monomer; wherein the structural units of the nitrogen-containing heterocyclic monomer are present in the second polymer and optionally also in the first polymer. Such multi-stage emulsion polymers are particularly suitable for coating applications to provide coating films with improved stain resistance without compromising film-forming properties.

[0005] In a first aspect, the present invention is a multistage emulsion polymer comprising a first polymer and a second polymer, wherein the multistage emulsion polymer comprises from 0.1 wt% to 10 wt% of structural units of nitrogen-containing heterocyclic monomers and 5 wt% or more of cycloalkyl (meth)acrylates, C6-C8 (meth)acrylates, based on the weight of the multistage emulsion polymer. 10 Structural units of alkyl esters or mixtures thereof;

[0006] wherein the second polymer comprises structural units of nitrogen-containing heterocyclic monomers;

[0007] wherein the Tg of the first polymer is at least 35° C. higher than the Tg of the second polymer;

[0008] The weight ratio of the first polymer to the second polymer is in the range of 55:45 to 95:5.

[0009] In a second aspect, the present invention is a method for preparing the multistage emulsion polymer of the first aspect by multistage free radical polymerization. The method comprises:

[0010] (i) preparing a first polymer by free radical polymerization in an aqueous medium; and

[0011] (ii) preparing a second polymer by free radical polymerization in the presence of the first polymer obtained in step (i) to form a multistage emulsion polymer comprising the first polymer and the second polymer; wherein the multistage emulsion polymer comprises 0.1 wt % to 10 wt % of structural units of nitrogen-containing heterocyclic monomers and 5 wt % or more of cycloalkyl (meth)acrylates, C6-C8 (meth)acrylates, and C12-C16-C18-C19 ... 10 Structural units of alkyl esters or mixtures thereof;

[0012] wherein the second polymer comprises structural units of nitrogen-containing heterocyclic monomers;

[0013] wherein the Tg of the first polymer is at least 35° C. higher than the Tg of the second polymer;

[0014] The weight ratio of the first polymer to the second polymer is in the range of 55:45 to 95:5. DETAILED DESCRIPTION

[0015] As used herein, an "aqueous" dispersion refers to particles dispersed in an aqueous medium. As used herein, "aqueous medium" refers to water and 0% to 30% by weight, based on the weight of the medium, of a water-miscible compound, such as an alcohol, glycol, glycol ether, glycol ester, or mixtures thereof.

[0016] As used herein, the term "acrylic acid" includes (meth)acrylic acid, (meth)alkyl acrylates, (meth)acrylamide, (meth)acrylonitrile, and modified forms thereof, such as (meth)hydroxyalkyl acrylates. Throughout the text, the phrase "(meth)acryloyl" refers to both "methacryloyl" and "acryloyl." For example, (meth)acrylic acid refers to methacrylic acid and acrylic acid, and methyl (meth)acrylate refers to both methyl methacrylate and methyl acrylate.

[0017] As used herein, the term structural unit (also called polymerized unit) of a given monomer refers to what remains of that monomer after polymerization. For example, the structural unit of methyl methacrylate is shown below: The dashed lines indicate the points of attachment of the structural units to the polymer backbone.

[0018] The "glass transition temperature" (T g ) can be measured by various techniques, including, for example, differential scanning calorimetry (DSC) or calculation using the Fox equation (TGFox, Bull. Am. Physics Soc., Vol. 1, No. 3, p. 123 (1956)). For example, to calculate the T of a copolymer of monomer M1 and monomer M2, g ,

[0019]

[0020] Where T g (calc.) is the glass transition temperature calculated for the copolymer, w(M1) is the weight fraction of monomer M1 in the copolymer, w(M2) is the weight fraction of monomer M2 in the copolymer, T g (M1) is the glass transition temperature of the homopolymer of monomer M1, and T g (M2) is the glass transition temperature of the homopolymer of monomer M2; all temperatures are in K. Glass transition temperatures of homopolymers can be found, for example, in “Polymer Handbook”, edited by J. Brandrup and EH Immergut, Interscience Publishers.

[0021] "Multi-stage emulsion polymer" herein means an emulsion polymer prepared by sequentially adding two or more different monomer compositions, comprising at least a first polymer and a second polymer. "First polymer" (also referred to as "first-stage polymer") and "second polymer" (also referred to as "second-stage polymer") are polymers having different compositions and formed in different stages of a multi-stage free radical polymerization process when preparing the multi-stage emulsion polymer. Each stage is polymerized sequentially and differs from the subsequent and / or immediately following stage due to differences in monomer composition. "The weight of the multi-stage emulsion polymer" herein refers to the dry weight or solid weight of the multi-stage emulsion polymer.

[0022] The multistage emulsion polymer of the present invention may comprise one or more cycloalkyl (meth)acrylates, C6-C8 (meth)acrylates, 10-alkyl ester or a mixture thereof; it may be present in the first polymer, the second polymer or a combination thereof. Suitable (meth)acrylate cycloalkyl esters may include, for example, (meth)acrylate cyclohexyl, (meth)acrylate methylcyclohexyl, (meth)acrylate dihydrodicyclopentadienyl, (meth)acrylate trimethylcyclohexyl, (meth)acrylate tert-butylcyclohexyl, or a mixture thereof. Preferred (meth)acrylate cycloalkyl esters include methacrylate cyclohexyl, acrylate cyclohexyl, acrylate methylcyclohexyl, or a mixture thereof. (Meth)acrylate C6-C 10 -Alkyl ester refers to an alkyl ester of (meth)acrylic acid containing a linear or branched alkyl group having 6 to 10 carbon atoms or 6 to 8 carbon atoms. Suitable (meth)acrylic acid C6-C 10 Examples of -alkyl esters include 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, or mixtures thereof. Preferably, the multistage emulsion polymer of the present invention comprises structural units of cyclohexyl methacrylate, 2-ethylhexyl acrylate, or mixtures thereof; which may be present in the first polymer, the second polymer, or a combination thereof. The multistage emulsion polymer may comprise, by weight of the multistage emulsion polymer, cycloalkyl (meth)acrylate, C6-C8 (meth)acrylate, C6-C6 (meth)acrylate, C6-C8 ... 10 -alkyl esters or mixtures thereof having a combined amount of 5 wt % or more, 6 wt % or more, 7 wt % or more, 8 wt % or more, 10 wt % or more, 12 wt % or more, 14 wt % or more, 15 wt % or more, 16 wt % or more, 18 wt % or more, or even 20 wt % or more and at the same time 90 wt % or less, 80 wt % or less, 70 wt % or less, 60 wt % or less, 50 wt % or less, 48 wt % or less, 45 wt % or less, 42 wt % or less, 40 wt % or less, 39 wt % or less, 38 wt % or less, 36 wt % or less, 35 wt % or less, 32 wt % or less, 31 wt % or less or even 30 wt % or less.

[0023] The multistage emulsion polymer of the present invention may also contain structural units of one or more nitrogen-containing heterocyclic monomers, which may be present in the second-stage polymer and optionally also in the first polymer. A nitrogen-containing heterocyclic monomer refers to a nitrogen-containing heterocyclic compound containing at least one ethylenically unsaturated bond that can be polymerized with other monomers. The nitrogen-containing heterocyclic monomer may be an ethylenically unsaturated imidazole, imidazoline, amidine, pyridine, pyrrole, pyrrolidine, pyrrolidone or caprolactam; or a combination thereof. A preferred nitrogen-containing heterocyclic monomer is vinyl pyrrolidone, including, for example, N-vinyl-2-pyrrolidone, N-methylvinyl pyrrolidone, N-(methyl)acryloyl-2-pyrrolidone, methylvinyl pyrrolidone or a mixture thereof. More preferably, the nitrogen-containing heterocyclic monomer is N-vinyl-2-pyrrolidone. The multi-stage emulsion polymer can include structural units of nitrogen-containing heterocyclic monomers in an amount of 0.1 wt% or more, 0.2 wt% or more, 0.3 wt% or more, 0.4 wt% or more, 0.5 wt% or more, 0.6 wt% or more, 0.7 wt% or more, 0.8 wt% or more, 0.9 wt% or more, or even 1.0 wt% or more, and at the same time 10 wt% or less, 9 wt% or less, 8 wt% or less, 7 wt% or less, 6 wt% or less, or even 5 wt% or less, based on the weight of the multi-stage emulsion polymer. For example, the second polymer in the multi-stage emulsion polymer can comprise structural units of nitrogen-containing heterocyclic monomers in an amount of 0.2 wt% or more, 0.4 wt% or more, 0.6 wt% or more, 0.8 wt% or more, 1.0 wt% or more, 1.2 wt% or more, 1.4 wt% or more, 1.6 wt% or more, 1.8 wt% or more, 2.0 wt% or more, or even 2.5 wt% or more, and at the same time 80 wt% or less, 70 wt% or less, 60 wt% or less, 50 wt% or less, 40 wt% or less, 30 wt% or less, or even 25 wt% or less, based on the weight of the second polymer. The first polymer in the multi-stage emulsion polymer may include structural units of nitrogen-containing heterocyclic monomers in an amount of 0% to less than 5% by weight, based on the weight of the first polymer, such as less than 4%, less than 3%, less than 2%, less than 1.5%, less than 1.25%, less than 1%, less than 0.5%, or even less than 0.2% by weight, based on the weight of the first polymer. In some embodiments, 50% to 100% of the structural units of the nitrogen-containing heterocyclic monomer in the multi-stage emulsion polymer are present in the second polymer, preferably 60% or more, 70% or more, 80% or more, 90% or more, or 95% or more.

[0024] The multistage emulsion polymer of the present invention may further comprise structural units of one or more monoethylenically unsaturated functional monomers carrying at least one functional group selected from the group consisting of carboxyl, carboxylic anhydride, sulfonic acid, amide, sulfonate, phosphoric acid, phosphonate, phosphate or hydroxyl, salts thereof, or combinations thereof; which may be present in the first polymer, the second polymer or a combination thereof, preferably in the first polymer. Examples of suitable monoethylenically unsaturated functional monomers include: α,β-ethylenically unsaturated carboxylic acids including acid-bearing monomers, such as methacrylic acid, acrylic acid, itaconic acid, maleic acid or fumaric acid; or acid-forming monomers containing acid-bearing monomers. group), the acid-forming group generates or can subsequently be converted into such an acid group, such as anhydride, (meth)acrylic anhydride or maleic anhydride; sodium styrene sulfonate (SSS), sodium vinyl sulfonate (SVS), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), the sodium salt of 2-acrylamido-2-methyl-1-propanesulfonic acid, the ammonium salt of 2-acrylamido-2-methyl-1-propanesulfonic acid; the sodium salt of sulfonic acid allyl ether; acrylamide, methacrylamide, monosubstituted (meth)acrylamide, N-methylacrylamide Acrylamide, N-ethylacrylamide, N-isopropylacrylamide, N-butylacrylamide, N-tert-butylacrylamide, N-2-ethylhexylacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide; hydroxy-functional alkyl (meth)acrylates, such as hydroxyethyl methacrylate and hydroxypropyl methacrylate; phosphoalkyl (meth)acrylates, such as ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, their salts and mixtures thereof; CH2=C(R p1 )-C(O)-O-(R p2 O) p -P(O)(OH)2, where R p1 =H or CH3, R p2= alkyl and p = 1-10, such as SIPOMER PAM-100, SIPOMER PAM-200 and SIPOMER PAM-300, all available from Solvay; phosphoalkoxy (meth)acrylates, such as ethylene glycol phosphate (meth)acrylate, diethylene glycol phosphate (meth)acrylate, triethylene glycol phosphate (meth)acrylate, propylene glycol phosphate (meth)acrylate, dipropylene glycol phosphate (meth)acrylate, tripropylene glycol phosphate (meth)acrylate, phosphate allyl ether, vinylphosphonic acid, salts thereof; or mixtures thereof. Preferred monoethylenically unsaturated functional monomers are phosphoethyl methacrylate (PEM), acrylic acid AA), acrylamide, methacrylic acid (MAA) or mixtures thereof. The multi-stage emulsion polymer can comprise zero or more, 0.1 wt% or more, 0.3 wt% or more, 0.5 wt% or more, 0.8 wt% or more, 0.9 wt% or more, 1.0 wt% or more, 1.1 wt% or more, 1.2 wt% or more, or even 1.5 wt% or more, and at the same time 10 wt% or less, 8 wt% or less, 6 wt% or less, 5 wt% or less, 4.5 wt% or less, 4 wt% or less, 3.5 wt% or less, 3 wt% or less, or even 2.8 wt% or less, based on the weight of the multi-stage emulsion polymer, of structural units of monoethylenically unsaturated functional monomers.

[0025] The multi-stage emulsion polymer of the present invention may further comprise structural units of one or more monoethylenically unsaturated nonionic monomers other than the above-mentioned monomers, which may be present in the first polymer, the second polymer, or a combination thereof. Additional monoethylenically unsaturated nonionic monomers may include C1-C4-alkyl (meth)acrylates, such as methyl acrylate, methyl methacrylate, butyl acrylate, butyl methacrylate, ethyl acrylate, and ethyl methacrylate; alkylvinyldialkoxysilanes; vinyltrialkoxysilanes, such as vinyltriethoxysilane and vinyltrimethoxysilane; (meth)acryloyl-functional silanes, including, for example, (meth)acryloyloxyalkyltrialkoxysilanes, such as γ-methacryloyloxypropyltrimethoxysilane and methacryloxypropyltriethoxysilane; 3-methacryloyloxypropylmethyldimethoxysilane; 3-methacryloyloxypropyltrimethoxysilane; 3-methacryloyloxypropyltriethoxysilane; or mixtures thereof. The multi-stage emulsion polymer can comprise from 0% to 90%, from 0.05% to 85%, from 0.1% to 80%, from 0.3% to 78%, from 0.5% to 75%, from 1% to 70%, from 5% to 65%, or from 10% to 60% by weight of structural units of the additional monoethylenically unsaturated nonionic monomer, based on the weight of the multi-stage emulsion polymer.

[0026] The multi-stage emulsion polymer of the present invention may include structural units of one or more polyethylenically unsaturated monomers, which may be present in the first polymer, the second polymer, or a combination thereof, preferably in the second polymer. Suitable polyethylenically unsaturated monomers may include, for example, butadiene, allyl (meth)acrylate, divinylbenzene, ethylene glycol dimethacrylate, butanediol dimethacrylate, or mixtures thereof. The multi-stage emulsion polymer may include 0% to 3.0%, 0.05% to 0.8%, or 0.1% to 0.5% by weight of the polyethylenically unsaturated monomer structural units, based on the weight of the multi-stage emulsion polymer.

[0027] Preferably, the first polymer in the multistage emulsion polymer comprises cycloalkyl (meth)acrylate, C6-C 10 -alkyl esters or mixtures thereof; structural units of monoethylenically unsaturated functional monomers, and optionally structural units of additional monoethylenically unsaturated nonionic monomers. Preferably, the second polymer in the multistage emulsion polymer comprises structural units of vinyl pyrrolidone; cycloalkyl (meth)acrylates, C6-C8 (meth)acrylates, 10 - structural units of alkyl esters, or mixtures thereof; and optionally additional structural units of monoethylenically unsaturated nonionic monomers.

[0028] In some embodiments, the multistage emulsion polymer comprises from 8 to 70 weight percent, based on the weight of the multistage emulsion polymer, of cycloalkyl (meth)acrylates, C6-C8 (meth)acrylates, 10 - structural units of alkyl esters or combinations thereof; and 0.5 to 10% by weight structural units of vinyl pyrrolidone.

[0029] The first polymer and the second polymer in the multistage emulsion polymer can be present in a weight ratio of the first polymer to the second polymer in the range of 55:45 to 95:5, 56:44 to 94:6, 57:43 to 93:7, 57.5:42.5 to 92.5:7.5, 58:42 to 92:8, 59:41 to 91:9, 60:40 to 90:10, 62.5:37.5 to 88:12, 65:35 to 87.5:12.5, 67.5:32.5 to 85:15, 70:30 to 82.5:17.5, 72.5:27.5 to 82:18, or 75:25 to 80:20. The multistage emulsion polymer can optionally include a small amount of a third polymer, for example, less than 10% by weight of the multistage emulsion polymer, without compromising DPUR and film-forming properties. In some embodiments, the total amount of the first polymer and the second polymer, based on the weight of the multi-stage emulsion polymer, is 90% to 100%, 92% to 100%, 95% to 100%, 98% to 100%, or 99% to 100% by weight of the multi-stage emulsion polymer.

[0030] The total concentration of structural units of the above-mentioned monomers in the multi-stage emulsion polymer is equal to 100%. The types and amounts of the above-mentioned monomers can be selected to provide a multi-stage emulsion polymer with a Tg suitable for different applications, for example, in the range of -30°C to 50°C, -25°C to 45°C, -20°C to 40°C, or -15°C to 35°C. The Tg of the first polymer is 35°C or higher than the Tg of the second polymer, for example, 36°C or higher, 37°C or higher, 38°C or higher, 39°C or higher, 40°C or higher, 41°C or higher, 42°C or higher, 43°C or higher, 44°C or higher, or even 45°C or higher. For example, the Tg of the first polymer can be -5°C to 55°C, 5°C to 45°C, or 15°C to 35°C. The Tg of the second polymer can be -55°C to 10°C, -45°C to 0°C, or -35°C to -10°C. The Tg values herein can be calculated using the Fox equation. Without being limited by theory, the multistage emulsion polymer may comprise a plurality of different phases (layers or domains) formed from at least the first polymer and the second polymer.The multistage emulsion polymer may have a core-shell structure.

[0031] The particle size of the multistage emulsion polymer of the present invention can be from 50 nanometers (nm) to 500 nm, from 60 nm to 300 nm, or from 70 nm to 180 nm. Particle size can be measured by a Brookhaven BI-90 Plus particle size analyzer as described in the Examples section below.

[0032] The multi-stage emulsion polymer of the present invention is typically present in the form of an aqueous dispersion comprising water. The water may be present in an amount of 30% to 90% by weight, or 40% to 80% by weight, based on the total weight of the aqueous dispersion. The aqueous dispersion of the multi-stage emulsion polymer may have a minimum film forming temperature (MFFT) in the range of -20°C to -80°C, for example, 0°C to 75°C, 10°C to 70°C, 20°C to 65°C, or 25°C to 60°C. The MFFT may be measured according to the test method described in the Examples section below.

[0033] The method for preparing the multi-stage emulsion polymer of the present invention may comprise a multi-stage free radical polymerization, preferably an emulsion polymerization, wherein at least two stages are formed sequentially, which typically results in the formation of a multi-stage emulsion polymer comprising at least two polymer compositions. Optionally, the different stages may be formed in different reactors. The method for preparing the multi-stage emulsion polymer may comprise (i) preparing a first polymer by free radical polymerization in an aqueous medium, and (ii) preparing a second polymer by free radical polymerization in the presence of the first polymer obtained in step (i). The method may comprise a stage of polymerizing a first monomer composition (also referred to as the "stage 1 monomer composition") to form the first polymer, and a stage of polymerizing a second monomer composition (also referred to as the "stage 2 monomer composition") to form the second polymer. Each stage of free radical polymerization may be carried out by polymerization techniques known in the art, such as emulsion polymerization of the monomers described above. The first monomer composition and the second monomer composition may each independently comprise the monomers described above for forming the structural units of the first and second polymers, respectively. For example, the second monomer composition comprises a nitrogen-containing heterocyclic monomer, such as vinylpyrrolidone. The total concentration of the monomer compositions used to prepare the first and second polymers, respectively, is equal to 100%. The monomer compositions used to prepare the first and second polymers can be added neat or as an emulsion in water, or added in one or more additions or continuously, linearly, or non-linearly during the reaction period for preparing the first and second polymers, or a combination thereof. Suitable temperatures for the emulsion polymerization process can be below 100° C., in the range of 30° C. to 95° C., or in the range of 50° C. to 90° C.

[0034] In a multistage free radical polymerization process, a free radical initiator can be used in each stage. The polymerization process can be either thermally initiated or redox-initiated emulsion polymerization. Examples of suitable free radical initiators include hydrogen peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, ammonium and / or alkali metal persulfates, sodium perborate, perphosphoric acid and its salts; potassium permanganate; and ammonium or alkali metal peroxodisulfate. Free radical initiators can generally be used in amounts of 0.01% to 3.0% by weight, based on the total weight of the monomers used to prepare the multistage emulsion polymer. A redox system comprising the above-mentioned initiators coupled with a suitable reducing agent can be used in the polymerization process. Examples of suitable reducing agents include sodium bisulphite formaldehyde, ascorbic acid, isoascorbic acid, alkali metal salts and ammonium salts of sulfur-containing acids (such as sodium sulfite, bisulfite, thiosulfate, sulfoxylate, sulfide, hydrosulfide or dithionite), methanesulfinic acid (formadinesulfinic acid), acetone bisulfite, glycolic acid, hydroxymethanesulfonic acid, glyoxylic acid hydrate, lactic acid, glyceric acid, malic acid, tartaric acid and salts of the foregoing acids. Metal chelators may optionally be used.

[0035] In a multistage free radical polymerization process, a surfactant may be used at each stage. The surfactant may be added before or during the polymerization of the monomers or a combination thereof. A portion of the surfactant may also be added after polymerization. These surfactants may include anionic and / or nonionic surfactants. Examples of suitable surfactants include alkali metal or ammonium salts of alkyl, aryl, or alkaryl sulfates, sulfonates, or phosphates; alkaryl sulfonic acids; sulfosuccinates; fatty acids; ethylenically unsaturated surfactant monomers; and ethoxylated alcohols or phenols. The surfactant may be used in amounts of 0.1% to 5% by weight, 0.15% to 4% by weight, 0.2% to 3% by weight, or 0.2% to 2% by weight, based on the total weight of the monomers used to prepare the multistage emulsion polymer.

[0036] In the multistage free radical polymerization method, a chain transfer agent can be used in each stage of polymerization. The example of a suitable chain transfer agent includes 3-mercaptopropionic acid, methyl mercaptopropionate, butyl mercaptopropionate, n-dodecyl mercaptan (nDDM), methyl 3-mercaptopropionate (MMP), butyl 3-mercaptopropionate (BMP), benzene mercaptan, azelaic acid alkyl mercaptan or a mixture thereof. The chain transfer agent can be used in an effective amount to control the molecular weight of the multistage emulsion polymer. By the gross weight of the monomers used to prepare the multistage emulsion polymer, the chain transfer agent can be used in an amount of 0 weight % to 3 weight %, 0.01 weight % to 2 weight %, 0.02 weight % to 1 weight % or 0.03 weight % to 0.5 weight %.

[0037] The pH of the obtained aqueous dispersion of the multistage emulsion polymer can be controlled, for example, by neutralization, to a value of at least 7. Neutralization can be performed by adding one or more bases which can lead to partial or complete neutralization of the ionic or potentially ionic groups of the multistage emulsion polymer. Examples of suitable bases include ammonia; alkali metal or alkaline earth metal compounds such as sodium hydroxide, potassium hydroxide, calcium hydroxide, zinc oxide, magnesium oxide, sodium carbonate; primary, secondary and tertiary amines such as triethylamine, ethylamine, propylamine, monoisopropylamine, monobutylamine, hexylamine, ethanolamine, diethylamine, dimethylamine, di-n-propylamine, tributylamine, triethanolamine, dimethoxyethylamine, 2-ethoxyethylamine, 3-ethoxypropylamine, dimethylethanolamine, diisopropanolamine, morpholine, ethylenediamine, 2-diethylaminoethylamine, 2,3-diaminopropane, 1,2-propylenediamine, neopentyldiamine, dimethylaminopropylamine, hexanediamine, 4,9-dioxadodecane-1,12-diamine, polyethyleneimine or polyethyleneamine; aluminum hydroxide; or mixtures thereof.

[0038] The multistage emulsion polymers of the present invention can be used as binders in a variety of applications, including, for example, wood coatings, metal protective coatings, architectural coatings, and road marking paints. The present invention also relates to an aqueous coating composition comprising the multistage emulsion polymer, typically in the form of an aqueous dispersion. The multistage emulsion polymer can be present in an amount of 10% to 90%, 20% to 80%, or 30% to 60% by weight, based on the dry weight of the aqueous coating composition.

[0039] The aqueous coating composition of the present invention may additionally comprise a pigment. "Pigment" herein refers to a granular inorganic material that can substantially contribute to the opacity or hiding power of the coating. The refractive index of such materials is generally greater than 1.8. The pigment may comprise, for example, titanium dioxide (TiO2), zinc oxide, iron oxide, zinc sulfide, barium sulfate, barium carbonate, or a mixture thereof. In a preferred embodiment, the pigment used in the present invention is TiO2. TiO2 typically exists in two crystalline forms, i.e., anatase and rutile. TiO2 can also be obtained in the form of a concentrated dispersion. The aqueous coating composition may also comprise one or more extenders. "Extender" herein refers to a granular material having a refractive index less than or equal to 1.8 and greater than 1.3. Examples of suitable extenders include calcium carbonate, clay, calcium sulfate, aluminosilicates, silicates, zeolites, mica, diatomaceous earth, solid or hollow glass, porcelain beads, nepheline syenite, feldspar, diatomaceous earth, calcined diatomaceous earth, talc (hydrated magnesium silicate), silica, alumina, kaolin, pyrophyllite, perlite, barite, wollastonite, opaque polymers (such as ROPAQUE available from The Dow Chemical Company), TMUltra E (ROPAQUE is a trademark of The Dow Chemical Company) or mixtures thereof. The pigment volume concentration (PVC) of the aqueous coating composition can be 10% to 80%, 20% to 70% or 30% to 60%. PVC can be determined by the following equation: PVC = [Volume (颜料+增量剂) / volume (颜料+增量剂+粘结剂) ]×100%.

[0040] The aqueous coating composition of the present invention may optionally contain a certain amount of one or more photocrosslinkers without compromising the properties of the DPUR. Preferably, the aqueous coating composition contains substantially no photocrosslinkers. In this context, the substantially no photocrosslinker means that the photocrosslinker is less than 0.6% by weight, for example, less than 0.5% by weight, less than 0.4% by weight, less than 0.3% by weight, less than 0.2% by weight, less than 0.1% by weight, or even zero, based on the weight of the multistage emulsion polymer. The photocrosslinker may include a benzophenone (BP) derivative, such as benzophenone or a 4-substituted (p-) benzophenone; a benzotriazole (BTA) derivative, such as benzotriazole, an acylphosphine oxide, a bisacylphosphine oxide, or a mixture thereof.

[0041] Waterborne coating composition of the present invention can further comprise one or more defoamers.Herein, " defoamer " refers to the chemical additive that reduces foam and stops foam from forming.Defoamer can be silicone-based defoamer, mineral oil-based defoamer, ethylene oxide-based / propylene oxide-based defoamer, polyalkyl acrylate or their mixture.Suitable commercially available defoamer comprises for example all purchased from TEGO Airex 902W and TEGO Foamex 1488 polyether siloxane copolymer emulsions of Di Gao (TEGO), can be purchased from BYK-024 silicone defoamer of Bi Ke (BYK), or their mixture.Press the total dry weight of waterborne coating composition, defoamer can exist with the amount of 0 % by weight to 1.0 % by weight, 0.1 % by weight to 0.6 % by weight or 0.2 % by weight to 0.4 % by weight.

[0042] The aqueous coating composition of the present invention may further comprise one or more thickeners. The thickener 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 urethanes (HEUR); and cellulosic thickeners, such as methyl cellulose ethers, 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 hydrophobically modified hydroxyethyl cellulose (HMHEC).The thickener may be present in an amount of 0 wt% to 5.0 wt%, 0.2 wt% to 4.0 wt%, or 0.3 wt% to 3 wt% by dry weight, based on the total dry weight of the aqueous coating composition.

[0043] The aqueous coating composition of the present invention may also include one or more wetting agents. "Wetting agent" herein refers to a chemical additive that reduces the surface tension of the coating composition, thereby making the coating composition more easily diffuse across the substrate surface or penetrate the substrate surface. The wetting agent may be an anionic, zwitterionic or nonionic polycarboxylate. By the total dry weight of the aqueous coating composition, the wetting agent may be present in an amount of 0 wt % to 5.0 wt %, 0.2 wt % to 4 wt % or 0.3 wt % to 3.0 wt %.

[0044] The aqueous coating composition of the present invention may also include one or more dispersants. Dispersants may include nonionic, anionic or cationic dispersants, such as polyacids with 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 polyacid 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 gel permeation chromatography (GPC)), including those homopolymers and copolymers that have been hydrophobically or hydrophilically modified, such as polyacrylic acid or polymethacrylic acid or maleic anhydride with various monomers such as styrene, acrylates or methacrylates, diisobutylene and other hydrophilic or hydrophobic comonomers; salts thereof; or mixtures thereof. The dispersant can be present in an amount of 0 wt% to 10 wt%, 0.2 wt% to 5.0 wt%, or 0.5 wt% to 3.0 wt% by dry weight, based on the total dry weight of the aqueous coating composition.

[0045] Waterborne coating composition of the present invention can also comprise one or more coalescents." coalescent " herein refers to the slow evaporation solvent that makes polymer particles merge into continuous film under ambient conditions.The example of applicable coalescent comprises 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 their mixture.Preferred coalescent comprises dipropylene glycol n-butyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, n-butyl ether or its mixture.By the weight of multistage emulsion polymer, coalescent can exist with the amount of 0 % by weight to 35 % by weight, 5 % by weight to 30 % by weight, or 10 % by weight to 25 % by weight.

[0046] In addition to the above components, the aqueous coating composition of the present invention may further include any one or a combination of the following additives: a buffer, a neutralizing agent, an antifreeze agent, a wetting agent, a mildewcide, a biocide, an anti-skinning agent, a colorant, a flow agent, an antioxidant, a plasticizer, a leveling agent, a thixotropic agent, a tackifier, and a grinding medium. Based on the dry weight of the aqueous coating composition, these additives may be present in a combined amount of 0% to 20%, 0.5% to 15%, or 1.0% to 10%.

[0047] The waterborne coating composition of the present invention can be prepared by blending a multistage emulsion polymer with other optional components, for example, pigments and / or extenders as described above. The components in the waterborne coating composition can be mixed in any order to provide the waterborne coating composition of the present invention. Any one of the above-mentioned optional components can also be added to the composition during or before mixing to form a waterborne coating composition. When the waterborne coating composition comprises pigment and / or extender, that is, when it is a pigment formulation, the pigment and / or extender are preferably mixed with an aqueous polymer dispersion as a dispersant to form a slurry of the pigment and / or extender. The mixture obtained can then be sheared in a grinding or milling device, as is well known in the pigment dispersion field. Such grinding or milling devices include roller mills, ball mills, bead mills, attritors, and include mills in which the mixture is continuously recycled. The shearing of the mixture continues for a sufficient time to disperse the pigment. The time sufficient to disperse the pigment generally depends on the properties of the pigment and the aqueous polymer dispersion as a dispersant and the grinding or milling device used, and will be determined by a skilled practitioner.

[0048] The present invention also relates to a method of using the aqueous coating composition of the present invention. The method may include applying the aqueous coating composition to a substrate; and drying or allowing the applied aqueous coating composition to dry. The present invention also relates to a method of making a coating on a substrate, comprising applying the aqueous coating composition of the present invention to the substrate, and drying or allowing the aqueous coating composition to dry to form a coating having improved stain resistance (DPUR) as described above. "Improved DPUR" herein means that the aqueous coating composition of the present invention provides a coating that, after outdoor exposure, has a ΔY value that is lower than the same coating composition in the absence of the multistage emulsion polymer as described above ("conventional coating composition"). For example, after one month of outdoor exposure, the ΔY value of a coating made from the aqueous coating composition of the present invention may be at least 0.4 lower, at least 0.5 lower, at least 0.6 lower, or at least 0.7 lower than the ΔY value of a conventional coating composition.

[0049] Waterborne coating composition of the present invention can be applied and adhered to various substrates.The example of suitable substrate comprises timber, metal, plastics, foam, stone, elastic substrate, glass, fabric, concrete or cement substrate.Preferably the coating composition that comprises pigment is applicable to various applications, such as marine and protective coating, automotive coating, traffic paint, exterior wall exterior insulation decorative system (Exterior Insulation and Finish Systems, EIFS), roofing mastic (roof mastic), wood coating, coil coating, plastic coating, powder coating, can coating, architectural coating and civil engineering coating.Coating composition is particularly suitable for architectural coating.

[0050] The aqueous coating compositions of the present invention can be applied to the substrate by existing methods including brushing, roller coating and spraying. The aqueous composition is preferably applied by spraying. Standard spraying techniques and spraying equipment can be used, such as air atomizing spraying, air spraying, airless spraying, high volume low pressure spraying and electrostatic spraying (such as electrostatic bell jar application) and manual or automatic methods. After the coating composition of the present invention has been applied to the substrate, the coating composition can be dried or allowed to dry at room temperature (20° C. to 25° C.) or at an elevated temperature (e.g., 25° C. to 50° C.) to form a film (i.e., a coating).

[0051] Example

[0052] Certain embodiments of the present invention will now be described in the following examples, in which all parts and percentages are by weight unless otherwise indicated.

[0053] Onist ABS-15 surfactant, available from Shanghai Honest Chem. Co., Ltd., is a sodium dodecylbenzenesulfonate surfactant.

[0054] Polystep P-12A surfactant, available from Stepan, is polyethylene glycol monotridecyl ether phosphate.

[0055] Tert-butyl acrylate (TBA) and cyclohexyl methacrylate (CHMA) are commercially available from BASF.

[0056] Butyl acrylate (BA), methyl methacrylate (MMA), 2-ethylhexyl acrylate (2-EHA) and methacrylic acid (MAA) were all purchased from Shanghai LangYuan Chemical Co., Ltd.

[0057] Silquest A-174 silane, available from Momentive, is gamma-methacryloxypropyltrimethoxysilane.

[0058] N-vinyl-2-pyrrolidone (NVP), n-dodecyl mercaptan (n-DDM), acrylamide (AM, 40%), ammonium persulfate (APS), tert-butyl hydroperoxide (t-BHP), isoascorbic acid (IAA), ferrous sulfate, ethylenediaminetetraacetic acid (EDTA) sodium salt, lauryl methacrylate (LMA) and ammonia (25% to 28%) were all purchased from Shanghai Chemical Reagent Co., Ltd.

[0059] The Fox Tg of the homopolymer of the above monomers is given as follows,

[0060]

[0061] The following standard analytical equipment and methods were used in the examples.

[0062] Particle size measurement

[0063] The particle size of polymer particles in aqueous dispersions is measured using a Brookhaven BI-90 Plus particle size analyzer that employs photon correlation spectroscopy (light scattering from sample particles). This method involves diluting two drops of the aqueous dispersion to be tested into 20 mL of 0.01 M sodium chloride (NaCl) solution and further diluting the resulting mixture in a sample cuvette to achieve the desired count rate (K) (e.g., for diameters in the range of 10-300 nm, K is in the range of 250 to 500 counts / second). The particle size of the aqueous polymer dispersion is then measured and reported as the Z-average diameter based on intensity.

[0064] MFFT

[0065] MFFT is determined using a Coesfeld MFFT instrument according to ASTM D2354-10e1 (2010) (Test Method for Minimum Film Formation Temperature). MFFT is measured by casting a 75 μm wet film of an aqueous dispersion sample onto a heated rod with a constant temperature gradient from the cool end to the hot end. After drying the film, the lowest temperature of the rod where the film remains continuous is recorded as the minimum film formation temperature.

[0066] Dirt resistance (DPUR) test

[0067] Paint panels were prepared for DPUR testing according to the following procedure:

[0068] (i) By having 150 g / m2 (g / m 2 ) was applied to the cement panel using a wet-loaded roller and cured for 2 hours in a constant temperature room (CTR) (25° C. and 50% relative humidity (RH));

[0069] (ii) Using 200g / m 2 The test coating composition was brush-applied to the above primer-coated panel obtained from step (i) with a wet load of 1000 rpm and then dried in a CTR for 2 hours;

[0070] (iii) a second coat of the test coating composition was brush-applied to the panel obtained from step (ii) at a wet load of 200 g / m 2;as well as

[0071] (iv) The obtained painted panels were dried in a CTR for 1 day before outdoor DPUR testing.

[0072] The initial Y* values of the painted panels obtained above were measured. These painted panels were then exposed outdoors. The exposure direction was a 45° angle from south. After one or two months of exposure, the changes in the appearance of the panels were observed, and the final Y* values were recorded as Y* 最终 Y* was measured by Spectro-guide Sphere Gloss portable spectrophotometer (BYK-Gardner) 初始 Value and Y* 最终 The change in reflected Y, expressed as ΔY, is calculated according to the following formula:

[0073] ΔY=Y* 初始 -Y* 最终

[0074] The smaller the ΔY value, the better the DPUR properties.

[0075] Durability testing

[0076] Paint panels were prepared for durability testing as follows:

[0077] First, a test coating composition of 4 wt% of an organic phthalocyanine blue colorant (888-7214 COLORTREND Phthalo BLUE E) was added, the weight of which was based on the total weight of the test coating composition. The obtained blue coating composition was applied to a Q-panel with a wet film thickness of 150 μm and then dried in a CTR (25° C. and 50% RH) for 7 days. The obtained blue paint panel was evaluated by using a Spectro-guide Sphere Gloss portable spectrophotometer (BYK-Gardner), and the L* was recorded. 初始 value, a* 初始 Value and b* 初始 value.

[0078] The blue painted panel was then placed in an accelerated weathering tester (Model QUV / SE, Q-Lab Corporation) for rapid ultraviolet (QUV) testing. After 1,000 hours of exposure to ultraviolet A (UVA wavelength: 340 nm), the L*, a*, and b* values were recorded as L*, L*, and L*, respectively. 最终 、a* 最终 and b* 最终 The ΔE value indicating the durability of the sample was calculated according to the following formula,

[0079]

[0080] The smaller the ΔE value, the better the durability.

[0081] Example (Ex) 1

[0082] First, monomer emulsion #1 (ME1) was prepared by mixing deionized (DI) water (278 g), AM (28.78 g, 40%), MAA (29.69 g), n-DDM (1.28 g), MMA (875.26 g), 2-EHA (365.96 g), and ABS-15 surfactant (58.73 g, 16.33%). Monomer emulsion #2 (ME2) was prepared by mixing DI water (67.52 g), 2-EHA (166.93 g), MMA (136.16 g), NVP (15.99 g), A-174 (1.60 g), ABS-15 surfactant (9.80 g, 16.33%), and P-12A surfactant (19.17 g, 25%).

[0083] Next, DI water (837.61 g) was added to a one-gallon container equipped with a reflux condenser and a stirrer at 130 RPM. Simultaneously, the temperature of the reaction vessel was raised to 91° C. A-19 surfactant (12.14 g, 19%) and a buffered solution of sodium carbonate (Na2CO3) (2.08 g in 12.82 g DI water) were then introduced into the reaction vessel.

[0084] Third, ME1 (51.7 g) and an initiator solution of APS (3.41 g in 17.09 g DI water) were injected into the reaction vessel. The reaction mixture was maintained at a temperature between 80°C and 95°C for 5 minutes (min). Thereafter, the remainder of ME1 was added to the reaction vessel over a span of 72 minutes. After the ME1 feed was completed, ME2 was added to the reaction vessel over a span of 18 minutes. During the addition of ME1 and ME2, another small cup of initiator solution of APS (1.45 g in 100 g DI water) and a buffer solution of Na2CO3 (0.79 g in 100 g DI water) were co-fed into the reaction vessel over a span of 90 minutes. The reaction temperature was maintained between 87°C and 89°C. After completing the above mixing steps, the reaction vessel was cooled. While the contents of the reaction vessel were cooled to room temperature, when the temperature dropped to 70° C., a primary reducing agent solution (0.0164 g of ferrous sulfate and 0.0164 g of sodium EDTA in 6.78 g of DI water), a secondary reducing agent solution (0.62 g of IAA in 18.8 g of DI water), and an initiator solution of t-BHP (1.12 g of a 70% aqueous solution in 18.8 g of DI water) were injected into the reaction vessel. Finally, when the temperature reached 50° C., an adjustable amount of ammonia solution was added to the resulting dispersion to maintain the pH between 7.5 and 8.5. Thus, Example 1 was obtained.

[0085] Comparative Example 1A

[0086] The aqueous dispersion of Comparative Example 1A was prepared as in Example 1, except that ME1 and ME2 were prepared as follows:

[0087] First, ME1 was prepared by mixing DI water (278 g), AM (28.78 g, 40%), MAA (29.69 g), n-DDM (1.28 g), MMA (875.26 g), 2-EHA (365.96 g), and ABS-15 surfactant (58.73 g, 16.33%). ME2 was prepared by mixing DI water (67.52 g), 2-EHA (166.93 g), MMA (152.18 g), A-174 (1.60 g), ABS-15 surfactant (9.80 g, 16.33%), and P-12A surfactant (19.17 g, 25%).

[0088] Comparative Example 2A

[0089] The aqueous dispersion of Comparative Example 2A was prepared as in Example 1, except that ME1 and ME2 were prepared as follows:

[0090] ME1 was prepared by mixing DI water (278 g), AM (28.78 g, 40%), MAA (29.69 g), n-DDM (1.28 g), MMA (554.88 g), CHMA (319.73 g), 2-EHA (365.96 g), and ABS-15 surfactant (58.73 g, 16.33%). ME2 was prepared by mixing DI water (67.52 g), 2-EHA (166.93 g), MMA (152.18 g), A-174 (1.60 g), ABS-15 surfactant (9.80 g, 16.33%), and P-12A surfactant (19.17 g, 25%).

[0091] Example 2

[0092] The aqueous dispersion of Example 2 was prepared as in Example 1, except that ME1 and ME2 were prepared as follows:

[0093] ME1 was prepared by mixing DI water (278 g), AM (28.78 g, 40%), MAA (29.69 g), n-DDM (1.28 g), MMA (554.88 g), CHMA (319.73 g), 2-EHA (365.96 g), and ABS-15 surfactant (58.73 g, 16.33%). ME2 was prepared by mixing DI water (67.52 g), 2-EHA (166.93 g), MMA (136.15 g), NVP (15.99 g), A-174 (1.60 g), ABS-15 surfactant (9.80 g, 16.33%), and P-12A surfactant (19.17 g, 25%).

[0094] Comparative Example E Single-stage polymerization

[0095] A monomer emulsion (ME) was prepared by mixing DI water (325 g), AM (28.78 g, 40%), MAA (29.69 g), n-DDM (1.28 g), MMA (1027.44 g), A-174 (1.6 g), 2-EHA (532.89 g), ABS-15 surfactant (68.52 g, 16.33%), and P-12A surfactant (19.17 g, 25%).

[0096] In a one-gallon container equipped with a reflux condenser and a stirrer, DI water (837.61 g) was added at a stirring rate of 130 RPM. At the same time, the temperature of the reaction vessel was raised to 91° C. A-19 surfactant (12.14 g, 19%) and a buffered solution of Na2CO3 (2.08 g in 12.82 g DI water) were then introduced into the reaction vessel.

[0097] The ME (51.7 g) obtained above and the initiator solution of APS (3.41 g in 17.09 g DI water) were injected into the reaction vessel. The reaction mixture was maintained at a temperature of 80° C. to 95° C. for 5 minutes. Thereafter, the remaining ME was added to the reaction vessel over a span of 90 minutes. During the addition of the ME, another small cup of initiator solution of APS (1.45 g in 100 g DI water) and a buffer solution of Na2CO3 (0.79 g in 100 g DI water) were co-fed into the reaction vessel over a span of 90 minutes. The reaction temperature was maintained between 87° C. and 89° C. After completing the above mixing steps, the reaction vessel was cooled. While the contents of the reaction vessel were cooled to room temperature, when the temperature dropped to 70° C., an initial reducing agent solution (0.0164 g of ferrous sulfate and 0.0164 g of sodium EDTA in 6.78 g of DI water), a secondary reducing agent solution (0.62 g of IAA in 18.8 g of DI water), and an initiator solution of t-BHP (1.12 g of a 70% aqueous solution in 18.8 g of DI water) were injected into the reaction vessel. Finally, when the temperature reached 50° C., an adjustable amount of ammonia solution was added to the resulting dispersion to maintain the pH between 7.5 and 8.5. Thus, Comparative Example E was obtained.

[0098] Comparative Example F Single-stage polymerization

[0099] An aqueous dispersion of Comparative Example F was prepared as in Comparative Example E, except that a monomer emulsion for preparing the emulsion polymer was prepared by combining DI water (325 g), AM (28.78 g, 40%), MAA (29.69 g), n-DDM (1.28 g), MMA (1011.42 g), A-174 (1.6 g), NVP (15.99 g), 2-EHA (532.89 g), ABS-15 surfactant (68.52 g, 16.33%), and P-12A surfactant (19.17 g, 25%).

[0100] Comparative Example G

[0101] An aqueous dispersion of Comparative Example G was prepared as in Example 1, except that ME1 and ME2 were prepared as follows:

[0102] ME1 was prepared by mixing DI water (165 g), AM (27.98 g, 40%), MAA (29.07 g), n-DDM (1.28 g), MMA (532.63 g), 2-EHA (228.73 g), and ABS-15 surfactant (34.23 g, 16.33%). ME2 was prepared by mixing DI water (181.45 g), 2-EHA (417.33 g), MMA (382.85 g), A-174 (1.60 g), ABS-15 surfactant (34.23 g, 16.33%), and P-12A surfactant (19.17 g, 25%).

[0103] Comparative Example H

[0104] The aqueous dispersion of Comparative Example H was prepared as in Example 1, except that ME1 and ME2 were prepared as follows:

[0105] ME1 was prepared by mixing DI water (165 g), AM (27.98 g, 40%), MAA (29.07 g), n-DDM (1.28 g), MMA (532.63 g), 2-EHA (228.73 g), and ABS-15 surfactant (34.23 g, 16.33%). ME2 was prepared by mixing DI water (181.45 g), 2-EHA (417.33 g), MMA (366.83 g), NVP (15.99 g), A-174 (1.60 g), ABS-15 surfactant (34.23 g, 16.33%), and P-12A surfactant (19.17 g, 25%).

[0106] Comparative Example 1

[0107] The aqueous dispersion of Comparative Example 1 was prepared as in Example 1, except that ME1 and ME2 were prepared as follows:

[0108] ME1 was prepared by mixing DI water (278 g), AM (28.78 g, 40%), MAA (29.69 g), n-DDM (1.28 g), MMA (811.19 g), BA (430.60 g), and ABS-15 surfactant (58.73 g, 16.33%). ME2 was prepared by mixing DI water (67.52 g), BA (199.23 g), MMA (120.14 g), A-174 (1.60 g), ABS-15 surfactant (9.80 g, 16.33%), and P-12A surfactant (19.17 g, 25%).

[0109] Comparative Example J

[0110] The aqueous dispersion of Comparative Example J was prepared as in Example 1, except that ME1 and ME2 were prepared as follows:

[0111] ME1 was prepared by mixing DI water (278 g), AM (28.78 g, 40%), MAA (29.69 g), n-DDM (1.28 g), MMA (811.19 g), BA (430.60 g), and ABS-15 surfactant (58.73 g, 16.33%). ME2 was prepared by mixing DI water (67.52 g), BA (199.23 g), MMA (104.12 g), NVP (15.99 g), A-174 (1.60 g), ABS-15 surfactant (9.80 g, 16.33%), and P-12A surfactant (19.17 g, 25%).

[0112] Comparative Example K

[0113] The aqueous dispersion of Comparative Example K was prepared as in Example 1, except that ME1 and ME2 were prepared as follows:

[0114] ME1 was prepared by mixing DI water (278 g), AM (28.78 g, 40%), MAA (29.69 g), n-DDM (1.28 g), MMA (859.24 g), CHMA (15.99 g), 2-EHA (365.96 g), and ABS-15 surfactant (58.73 g, 16.33%). ME2 was prepared by mixing DI water (67.52 g), 2-EHA (166.93 g), MMA (152.18 g), A-174 (1.60 g), ABS-15 surfactant (9.80 g, 16.33%), and P-12A surfactant (19.17 g, 25%).

[0115] Example 9

[0116] The aqueous dispersion of Example 9 was prepared as in Example 1, except that ME1 and ME2 were prepared as follows:

[0117] ME1 was prepared by mixing DI water (278 g), AM (28.78 g, 40%), MAA (29.69 g), n-DDM (1.28 g), MMA (875.26 g), 2-EHA (365.96 g), and ABS-15 surfactant (58.73 g, 16.33%). ME2 was prepared by mixing DI water (67.52 g), 2-EHA (166.93 g), MMA (72.08 g), NVP (79.95 g), A-174 (1.60 g), ABS-15 surfactant (9.80 g, 16.33%), and P-12A surfactant (19.17 g, 25%).

[0118] Comparative Example 3A

[0119] The aqueous dispersion of Comparative Example 3A was prepared as in Example 1, except that ME1 and ME2 were prepared as follows:

[0120] ME1 was prepared by mixing DI water (308 g), AM (28.78 g, 40%), MAA (29.69 g), n-DDM (1.28 g), MMA (989.71 g), 2-EHA (411.7 g), and ABS-15 surfactant (62.81 g, 16.54%). ME2 was prepared by mixing DI water (32 g), 2-EHA (83.47 g), MMA (75.29 g), A-174 (1.60 g), ABS-15 surfactant (4.84 g, 16.54%), and P-12A surfactant (19.17 g, 25%).

[0121] Example 3

[0122] The aqueous dispersion of Example 3 was prepared as in Example 1, except that ME1 and ME2 were prepared as follows:

[0123] ME1 was prepared by mixing DI water (308 g), AM (28.78 g, 40%), MAA (29.69 g), n-DDM (1.28 g), MMA (989.71 g), 2-EHA (411.7 g), and ABS-15 surfactant (62.81 g, 16.54%). ME2 was prepared by mixing DI water (32 g), 2-EHA (83.47 g), MMA (59.27 g), NVP (15.99 g), A-174 (1.60 g), ABS-15 surfactant (4.84 g, 16.54%), and P-12A surfactant (19.17 g, 25%).

[0124] Comparative Example 4A

[0125] The aqueous dispersion of Comparative Example 4A was prepared as in Example 1, except that ME1 and ME2 were prepared as follows:

[0126] ME1 was prepared by mixing DI water (243 g), AM (28.82 g, 40%), MAA (29.73 g), n-DDM (1.28 g), MMA (760.7 g), 2-EHA (320.22 g), and ABS-15 surfactant (50.72 g, 16.54%). ME2 was prepared by mixing DI water (102.52 g), 2-EHA (250.39 g), MMA (229.08 g), A-174 (1.60 g), ABS-15 surfactant (16.91 g, 16.54%), and P-12A surfactant (19.17 g, 25%).

[0127] Example 4

[0128] The aqueous dispersion of Example 4 was prepared as in Example 1, except that ME1 and ME2 were prepared as follows:

[0129] ME1 was prepared by mixing DI water (243 g), AM (28.82 g, 40%), MAA (29.73 g), n-DDM (1.28 g), MMA (760.7 g), 2-EHA (320.22 g), and ABS-15 surfactant (50.72 g, 16.54%). ME2 was prepared by mixing DI water (102.52 g), 2-EHA (250.39 g), MMA (213.08 g), NVP (15.99 g), A-174 (1.60 g), ABS-15 surfactant (16.91 g, 16.54%), and P-12A surfactant (19.17 g, 25%).

[0130] Comparative Example 5A

[0131] The aqueous dispersion of Comparative Example 5A was prepared as in Example 1, except that ME1 and ME2 were prepared as follows:

[0132] ME1 was prepared by mixing DI water (210 g), AM (28.78 g, 40%), MAA (29.74 g), n-DDM (1.28 g), MMA (646.16 g), 2-EHA (274.47 g), and ABS-15 surfactant (43.47 g, 16.54%). ME2 was prepared by mixing DI water (135 g), 2-EHA (333.86 g), MMA (305.96 g), A-174 (1.60 g), ABS-15 surfactant (24.15 g, 16.54%), and P-12A surfactant (19.17 g, 25%).

[0133] Example 5

[0134] The aqueous dispersion of Example 5 was prepared as in Example 1, except that ME1 and ME2 were prepared as follows:

[0135] ME1 was prepared by mixing DI water (210 g), AM (28.78 g, 40%), MAA (29.74 g), n-DDM (1.28 g), MMA (646.16 g), 2-EHA (274.47 g), and ABS-15 surfactant (43.47 g, 16.54%). ME2 was prepared by mixing DI water (135 g), 2-EHA (333.86 g), MMA (289.94 g), A-174 (1.60 g), NVP (15.99 g), ABS-15 surfactant (24.15 g, 16.54%), and P-12A surfactant (19.17 g, 25%).

[0136] Comparative Example 0

[0137] The aqueous dispersion of Comparative Example 0 was prepared as in Example 1, except that ME1 and ME2 were prepared as follows:

[0138] ME1 was prepared by mixing DI water (278 g), AM (28.78 g, 40%), MAA (29.69 g), n-DDM (1.28 g), MMA (849.63 g), 2-EHA (391.64 g), and ABS-15 surfactant (58.73 g, 16.33%). ME2 was prepared by mixing DI water (67.52 g), 2-EHA (147.03 g), MMA (172.04 g), A-174 (1.60 g), ABS-15 surfactant (9.80 g, 16.33%), and P-12A surfactant (19.17 g, 25%).

[0139] Comparative Example P

[0140] The aqueous dispersion of Comparative Example P was prepared as in Example 1, except that ME1 and ME2 were prepared as follows:

[0141] ME1 was prepared by mixing DI water (278 g), AM (28.78 g, 40%), MAA (29.69 g), n-DDM (1.28 g), MMA (849.63 g), 2-EHA (391.64 g), and ABS-15 surfactant (58.73 g, 16.33%). ME2 was prepared by mixing DI water (67.52 g), 2-EHA (147.03 g), MMA (156.02 g), NVP (15.99 g), A-174 (1.60 g), ABS-15 surfactant (9.80 g, 16.33%), and P-12A surfactant (19.17 g, 25%).

[0142] Comparative Example 6A

[0143] The aqueous dispersion of Comparative Example 6A was prepared as in Example 1, except that ME1 and ME2 were prepared as follows:

[0144] ME1 was prepared by mixing DI water (278 g), AM (28.78 g, 40%), MAA (29.69 g), n-DDM (1.28 g), MMA (834.26 g), BA (304.63 g), 2-EHA (102.52 g), and ABS-15 surfactant (58.73 g, 16.33%). ME2 was prepared by mixing DI water (67.52 g), 2-EHA (25.63 g), BA (170.31 g), MMA (123.34 g), A-174 (1.60 g), ABS-15 surfactant (9.80 g, 16.33%), and P-12A surfactant (19.17 g, 25%).

[0145] Example 6

[0146] The aqueous dispersion of Example 6 was prepared as in Example 1, except that ME1 and ME2 were prepared as follows:

[0147] ME1 was prepared by mixing DI water (278 g), AM (28.78 g, 40%), MAA (29.69 g), n-DDM (1.28 g), MMA (834.26 g), BA (304.63 g), 2-EHA (102.52 g), and ABS-15 surfactant (58.73 g, 16.33%). ME2 was prepared by mixing DI water (67.52 g), 2-EHA (25.63 g), BA (170.31 g), MMA (107.32 g), NVP (15.99 g), A-174 (1.60 g), ABS-15 surfactant (9.80 g, 16.33%), and P-12A surfactant (19.17 g, 25%).

[0148] Comparative Example 7A

[0149] The aqueous dispersion of Comparative Example 7A was prepared as in Example 1, except that ME1 and ME2 were prepared as follows:

[0150] ME1 was prepared by mixing DI water (278 g), AM (28.78 g, 40%), MAA (29.69 g), n-DDM (1.28 g), MMA (849.64 g), BA (186.38 g), 2-EHA (205.04 g), and ABS-15 surfactant (58.73 g, 16.33%). ME2 was prepared by mixing DI water (67.52 g), 2-EHA (51.26 g), BA (141.39 g), MMA (126.54 g), A-174 (1.60 g), ABS-15 surfactant (9.80 g, 16.33%), and P-12A surfactant (19.17 g, 25%).

[0151] Example 7

[0152] The aqueous dispersion of Example 7 was prepared as in Example 1, except that ME1 and ME2 were prepared as follows:

[0153] ME1 was prepared by mixing DI water (278 g), AM (28.78 g, 40%), MAA (29.69 g), n-DDM (1.28 g), MMA (849.64 g), BA (186.38 g), 2-EHA (205.04 g), and ABS-15 surfactant (58.73 g, 16.33%). ME2 was prepared by mixing DI water (67.52 g), 2-EHA (51.26 g), BA (141.39 g), MMA (110.52 g), NVP (15.99 g), A-174 (1.60 g), ABS-15 surfactant (9.80 g, 16.33%), and P-12A surfactant (19.17 g, 25%).

[0154] Comparative Example S

[0155] The aqueous dispersion of Comparative Example S was prepared as in Example 1, except that ME1 and ME2 were prepared as follows:

[0156] ME1 was prepared by mixing DI water (278 g), AM (28.78 g, 40%), MAA (29.69 g), n-DDM (1.28 g), MMA (834.26 g), BA (304.63 g), LMA (102.52 g), and ABS-15 surfactant (58.73 g, 16.33%). ME2 was prepared by mixing DI water (67.52 g), LMA (25.63 g), BA (170.31 g), MMA (123.34 g), A-174 (1.60 g), ABS-15 surfactant (9.80 g, 16.33%), and P-12A surfactant (19.17 g, 25%).

[0157] Comparative Example T

[0158] The aqueous dispersion of Comparative Example T was prepared as in Example 1, except that ME1 and ME2 were prepared as follows:

[0159] ME1 was prepared by mixing DI water (278 g), AM (28.78 g, 40%), MAA (29.69 g), n-DDM (1.28 g), MMA (834.26 g), BA (304.63 g), LMA (102.52 g), and ABS-15 surfactant (58.73 g, 16.33%). ME2 was prepared by mixing DI water (67.52 g), LMA (25.63 g), BA (170.31 g), MMA (107.32 g), NVP (15.99 g), A-174 (1.60 g), ABS-15 surfactant (9.80 g, 16.33%), and P-12A surfactant (19.17 g, 25%).

[0160] Comparative Example 8A

[0161] The aqueous dispersion of Comparative Example 8A was prepared as in Example 1, except that ME1 and ME2 were prepared as follows:

[0162] ME1 was prepared by mixing DI water (278 g), AM (28.78 g, 40%), MAA (29.69 g), n-DDM (1.28 g), MMA (606.15 g), BA (430.60 g), CHMA (205.04 g), and ABS-15 surfactant (58.73 g, 16.33%). ME2 was prepared by mixing DI water (67.52 g), CHMA (51.26 g), BA (199.23 g), MMA (68.88 g), A-174 (1.60 g), ABS-15 surfactant (9.80 g, 16.33%), and P-12A surfactant (19.17 g, 25%).

[0163] Example 8

[0164] The aqueous dispersion of Example 8 was prepared as in Example 1, except that ME1 and ME2 were prepared as follows:

[0165] ME1 was prepared by mixing DI water (278 g), AM (28.78 g, 40%), MAA (29.69 g), n-DDM (1.28 g), MMA (606.15 g), BA (430.60 g), CHMA (205.04 g), and ABS-15 surfactant (58.73 g, 16.33%). ME2 was prepared by mixing DI water (67.52 g), CHMA (51.26 g), BA (199.23 g), MMA (52.86 g), NVP (15.99 g), A-174 (1.60 g), ABS-15 surfactant (9.80 g, 16.33%), and P-12A surfactant (19.17 g, 25%).

[0166] The properties of the aqueous dispersions of the emulsion polymers prepared above are given in Table 1. The multistage emulsion polymers of Examples 1 to 9 provide comparable MFFTs to the same emulsion polymers without NVP structural units. These aqueous emulsion polymer dispersions were used as binders in the following preparations of coating compositions.

[0167] Table 1. Composition and properties of aqueous dispersions

[0168]

[0169]

[0170] 1 Solids content is measured by weighing 0.7 ± 0.1 g of a polymer emulsion sample (the wet weight of the sample is designated "W1"), placing the sample in an aluminum pan (the weight of the aluminum pan is designated "W2") in an oven at 150°C for 25 minutes, then cooling and weighing the aluminum pan with the dried sample, with the total weight designated "W3." "W3 - W2" refers to the dry weight or solids weight of the sample. Solids content is calculated as (W3 - W2) / W1 * 100%.

[0171] 2 Tg was calculated by Fox equation.

[0172] Coating composition

[0173] Coating compositions were prepared using a two-stage process based on the formulations given in Table 2. First, all ingredients from the grinding stage were added sequentially and mixed using a high-speed disperser at 1,000 rpm for 30 minutes to obtain a well-dispersed slurry. The ingredients from the letdown stage were then added sequentially to the slurry. The type of binder (i.e., the prepared aqueous dispersion) used for each coating composition is given in Tables 4 and 5. The resulting coating compositions each had a PVC of 40.33%, a solids volume of 38.71%, and a solids weight of 53.76%.

[0174] Table 2. Coating composition

[0175]

[0176] *OROTAN, ECOSURF, and ACRYSOL are trademarks of The Dow Chemical Company.

[0177] The resulting coating compositions were evaluated in two groups (Group I and Group II) according to the test method described above, and the results are summarized in Tables 4 and 5, respectively. In the DPUR test, the coating compositions in each of Groups I and II were tested together by exposure to the same outdoor conditions. When preparing the painted panels for the DPUR test, an exterior primer was prepared based on the primer composition given in Table 3 and according to the same method as for preparing the above-mentioned coating compositions.

[0178] Table 3. Exterior primer composition

[0179]

[0180] *CELLOSIZE and PRIMAL are trademarks of The Dow Chemical Company.

[0181] Table 4 presents the DPUR properties after outdoor exposure and the durability properties after QUV testing for the coating compositions in Group 1. As shown in Table 4, the multistage polymers in Examples 1, 2, and 9 provide coatings with improved DPUR properties, as indicated by a ΔY value that is at least 0.4 lower than those of Comparative Examples 1A, 2A, and 1A, respectively. In contrast, the addition of NVP to the preparation of the single-stage polymers resulted in a decrease in the DPUR performance of the coating containing NVP (Comparative Example F) compared to Comparative Example E. The multistage polymer containing structural units of NVP at a 50:50 stage ratio (Comparative Example H) did not show an improvement in the DPUR of the coating containing NVP compared to Comparative Example G. The multistage polymer that did not contain NVP structural units in the second stage (Comparative Example K) did not provide improved DPUR properties of the coating relative to Comparative Example 1A. The combination of NVP with the multistage polymer of Comparative Example J failed to provide a coating with an improved DPUR compared to Comparative Example I. Furthermore, Examples 1-2 and 9 exhibited comparable durability properties compared to the comparative coating compositions (Comparative Example 1A and Comparative Example 2A).

[0182] Table 4. Group I coating formulations and properties

[0183] coating adhesive <![CDATA[Stage ratio 1 > <![CDATA[Tg Gap 2 , °C]]> <![CDATA[DPUR(ΔY a )]]> Durability (ΔE) Paint 1A Comparative Example 1A 80:20 47.02 5.81(12.96b) 7.8 Paint 1 Example 1 80:20 48.28 5.28(10.6b) 8.0 Paint 2A Comparative Example 2A 80:20 44.98 16.73b 5.7 Paint 2 Example 2 80:20 46.24 14.46b 5.6 Paint E Comparative Example E a stage 0 7.20 not applicable Paint F Comparative Example F a stage 0 7.87 not applicable Paint G Comparative Example G 50:50 47.62 6.86 not applicable Paint H Comparative Example H 50:50 48.13 6.68 not applicable Paint I Comparative Example 1 80:20 44.81 7.17 not applicable Paint J Comparative Example J 80:20 46.21 6.99 not applicable Paint K Comparative Example K 80:20 46.57 6.06 6.6 Paint 9 Example 9 80:20 53.19 5.07 7.6

[0184] a : Unless otherwise stated, ΔY is after 1 month of outdoor exposure.

[0185] b : ΔY is after 2 months of outdoor exposure.

[0186] 1 : The stage ratio refers to the weight ratio of the first stage monomer to the second stage monomer.

[0187] 2 : Tg gap refers to the difference in Tg between the first polymer and the second polymer.

[0188] Table 5 presents the DPUR properties of the coating compositions in Group II. As shown in Table 5, the aqueous multistage polymer dispersions of Examples 3 through 8 provide coatings with improved DPUR properties, as indicated by ΔY values that are at least 0.4 lower than those of Comparative Examples 3A, 4A, 5A, 6A, 7A, and 8A, respectively. In contrast, the addition of NVP to the multistage polymers of Comparative Examples P and T, respectively, did not improve the DPUR properties of the coatings compared to Comparative Examples O and S.

[0189] Table 5. Group II coating formulations and properties

[0190]

[0191]

[0192] 1 : The stage ratio refers to the weight ratio of the first stage monomer to the second stage monomer.

[0193] 2 : Tg gap refers to the difference in Tg between the first polymer and the second polymer.

Claims

1. A multi-stage emulsion polymer comprising a first polymer and a second polymer, The multistage emulsion polymer comprises 0.1 to 10 wt% of a nitrogen-containing heterocyclic monomer and 5 wt% or more of a cycloalkyl (meth)acrylate, a C6-C8 ... 10 Structural units of alkyl esters or mixtures thereof; wherein the (meth) acrylate cycloalkyl ester, (meth) acrylic acid C6-C 10 Structural units of alkyl esters or mixtures thereof are present in the first polymer, the second polymer, or a combination thereof; wherein the second polymer comprises structural units of the nitrogen-containing heterocyclic monomer; wherein the Tg of the first polymer is at least 35° C. higher than the Tg of the second polymer; The weight ratio of the first polymer to the second polymer is in the range of 55:45 to 95:

5.

2. The multistage emulsion polymer of claim 1, wherein the nitrogen-containing heterocyclic monomer is an ethylenically unsaturated imidazole, imidazoline, amidine, pyridine, pyrrole, pyrrolidine, pyrrolidone, or caprolactam; or a combination thereof.

3. The multistage emulsion polymer of claim 1 wherein the nitrogen-containing heterocyclic monomer is vinyl pyrrolidone.

4. The multistage emulsion polymer of claim 1, wherein the multistage emulsion polymer comprises structural units of cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, or a mixture thereof.

5. The multi-stage emulsion polymer of claim 1, wherein the second polymer comprises from 0.2% to 80% by weight of structural units of the nitrogen-containing heterocyclic monomer, based on the weight of the second polymer.

6. The multi-stage emulsion polymer of claim 1, wherein the weight ratio of the first polymer to the second polymer is in the range of 60:40 to 90:

10.

7. The multistage emulsion polymer of claim 1 further comprising structural units of monoethylenically unsaturated functional monomers carrying at least one functional group selected from the group consisting of carboxyl, carboxylic anhydride, sulfonic acid, amide, sulfonate, phosphoric acid, phosphonate, phosphate ester, or hydroxyl, or salts thereof, or combinations thereof; and optionally additional structural units of monoethylenically unsaturated nonionic monomers.

8. A method for preparing a multistage emulsion polymer according to any one of claims 1 to 7 by multistage free radical polymerization, the method comprising: (i) preparing a first polymer by free radical polymerization in an aqueous medium; as well as (ii) preparing a second polymer by free radical polymerization in the presence of the first polymer obtained in step (i) to form the multistage emulsion polymer comprising the first polymer and the second polymer; The multistage emulsion polymer comprises 0.1 to 10 wt% of a nitrogen-containing heterocyclic monomer and 5 wt% or more of a cycloalkyl (meth)acrylate, a C6-C8 ... 10 Structural units of alkyl esters or mixtures thereof; wherein the (meth) acrylate cycloalkyl ester, (meth) acrylic acid C6-C 10 Structural units of alkyl esters or mixtures thereof are present in the first polymer, the second polymer, or a combination thereof; wherein the second polymer comprises structural units of the nitrogen-containing heterocyclic monomer; wherein the Tg of the first polymer is at least 35° C. higher than the Tg of the second polymer; The weight ratio of the first polymer to the second polymer is in the range of 55:45 to 95:

5.

9. An aqueous coating composition comprising the multistage emulsion polymer according to any one of claims 1 to 7 and a pigment and / or an extender.

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