Aqueous dispersion of multistage polymer particles

Abstract

An aqueous dispersion of a multi-stage polymer particle includes at least two polymers, and a coating composition including the aqueous dispersion of the multi-stage polymer particle can provide a coating having heat resistance, alcohol resistance, alkali resistance, and acetic acid resistance.

Description

Technical Field

[0001] This invention relates to aqueous dispersions of multi-stage polymer particles and methods for their preparation. Background Technology

[0002] Waterborne or water-based coating compositions are widely used in industrial and construction applications because they produce fewer volatile organic compounds (VOCs) compared to solvent-based coating compositions. However, limitations remain, such as insufficient water and chemical resistance, including insufficient resistance to alcohols, acetic acids, and alkalis. In particular, providing waterborne coating compositions with hot water resistance is challenging. For example, some applications, such as coatings for kitchen furniture and dining tables, require resistance to damage after exposure to hot water (i.e., water at 70 degrees Celsius or higher), especially boiling water.

[0003] Therefore, it is desirable to provide an aqueous polymer dispersion that is particularly suitable for coating applications that can provide a coating with hot water resistance while achieving the aforementioned good chemical resistance to alcohols, acetic acid and alkalis. Summary of the Invention

[0004] This invention provides novel aqueous dispersions of multi-level polymer particles, particularly suitable for coating applications. Coating compositions comprising such aqueous dispersions of multi-level polymer particles provide coatings prepared therefrom that exhibit excellent heat resistance rated 3 or higher, while also achieving good chemical resistance, including alcohol resistance rated 4 or higher, alkali resistance rated 3 or higher, and acetic acid resistance rated 3 or higher. These properties can be measured according to the test methods described in the Examples section below.

[0005] In a first aspect, the present invention is an aqueous dispersion of multi-stage polymer particles, wherein, based on the weight of the multi-stage polymer particles, the multi-stage polymer particles comprise 30% to 60% by weight of polymer A and 40% to 70% by weight of polymer B, wherein polymer A has a higher glass transition temperature than polymer B.

[0006] Based on the weight of the multi-level polymer particles, the multi-level polymer particles comprise:

[0007] 2% to 15% by weight of structural units of acetylacetamide functional monomers having the structure of formula (I):

[0008]

[0009] R1 is selected from the following structures:

[0010]

[0011] Among them, R2, R4, R8, R10 R 12 and R 13 Each is an alkylene group having 2 to 20 carbon atoms; R3, R5, R6, R7 and R 11 Each is independently hydrogen or an alkyl group having 1 to 8 carbon atoms; R9 is hydrogen or an alkyl group having 1 to 20 carbon atoms; and X is O or N;

[0012] 0.1% to 10% by weight of mono-olefinic unsaturated acid monomers, their salts or mixtures thereof as structural units;

[0013] The structural unit of polyene-bonded unsaturated monomers; and

[0014] The structural unit of a monoene bond-type unsaturated nonionic monomer.

[0015] In a second aspect, the present invention provides a method for preparing an aqueous dispersion of multi-stage polymer particles of the first aspect by multi-stage free radical polymerization, the method comprising at least one polymerization stage for forming polymer A and at least one polymerization stage for forming polymer B.

[0016] In a third aspect, the present invention is a coating composition comprising the aqueous dispersion of the first aspect. Detailed Implementation

[0017] In this invention, "acrylic acid" includes (meth)acrylic acid, alkyl (meth)acrylate, (meth)acrylamide, (meth)acrylonitrile, and modified forms thereof, such as hydroxyalkyl (meth)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 (meth)acrylate refers to both methyl methacrylate and methyl acrylate.

[0018] As used herein, the term structural unit, also known as a polymerization unit, refers to the monomer as the remaining portion of the monomer after polymerization, or the monomer in its polymerized form. For example, the structural unit of methyl methacrylate is shown below:

[0019] The dashed lines represent the connection points between the structural units and the polymer backbone.

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

[0021] The "glass transition temperature" (T) in this invention gIt can be measured by various techniques, including, for example, differential scanning calorimetry (DSC) or calculations using the Fox equation (TGFox, Bulletin of the American Physical Society, Vol. 1, No. 3, p. 123 (1956)). For example, the T used to calculate the copolymer of monomers M1 and M2 g ,

[0022]

[0023] Where T g (Calculated) 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 Kelvin. Glass transition temperatures of homopolymers can be found, for example, in "Polymer Handbook" edited by J. Brandrup and E. Himmergut, Interscience Publishers. The Fox Tg values ​​of some commonly used monomers are summarized in the table below:

[0024] Methyl methacrylate 105 Butyl acrylate -54 2-Ethylhexyl acrylate -85 styrene 100 methacrylic acid 185 Allyl methacrylate 94* acetyl acetylacetyl methacrylate 7 acetoacetaminoethyl methacrylate 12

[0025] *Paper submitted to the Graduate School of Natural and Applied Sciences of Middle East Technical University, Tugba Vardareli, Polymerization and Characterization of Allyl Methacrylate, 2006

[0026] "Multi-level polymer particles" herein refers to polymer particles prepared by sequentially adding two or more different monomer compositions, comprising at least two polymers, including polymer A and polymer B. "Polymer A" (also referred to as "first-level polymer") and "Polymer B" (also referred to as "second-level polymer") refer to these polymers having different compositions and formed at different stages of multi-level radical polymerization during the preparation of multi-level polymer particles.

[0027] Polymer A and / or polymer B, preferably polymer A, in the multi-level polymer particles may each independently comprise structural units of one or more mono-olefinically unsaturated acid monomers, their salts, or mixtures thereof. The mono-olefinically unsaturated acid monomers and / or their salts may be α,β-olefinically unsaturated carboxylic acids, monomers with acid-forming groups that generate or subsequently convert to such acid groups (such as acid anhydrides, (meth)acrylic anhydrides, or maleic anhydrides); phosphoric acid monomers or their salts, sulfonic acid monomers and their salts, or mixtures thereof. Suitable α,β-olefinically unsaturated carboxylic acids may include, for example, methacrylic acid, acrylic acid, 2-carboxyethyl (meth)acrylic acid, maleic acid, crotonic acid, acyloxypropionic acid, fumaric acid, itaconic acid, or mixtures thereof. The phosphorus-containing acid monomer may be an olefinically unsaturated phosphoric acid monomer, including, for example, dihydrogen phosphate esters of alcohols, wherein the alcohol contains or is substituted with polymerizable vinyl or olefinic groups. Suitable phosphate-containing monomers and their salts may include, for example, phosphonoalkyl methacrylates such as ethyl methacrylate, propyl methacrylate, butyl methacrylate, salts of phosphonoalkyl methacrylates, or mixtures thereof; CH2=C(R)-C(O)-O-(R p O) n -P(O)(OH)2, where R = H or CH3 and R p=alkyl, n is 1 to 20, such as SIPOMER PAM-100, SIPOMER PAM-200, SIPOMER PAM-300 and SIPOMER PAM-4000, all purchased from Solvay; (meth)acrylate phosphonoalkoxy esters, such as ethylene glycol (meth)acrylate, diethylene glycol (meth)acrylate, triethylene glycol (meth)acrylate, propylene glycol (meth)acrylate, dipropylene glycol (meth)acrylate, tripropylene glycol (meth)acrylate, allyl ether phosphate, their salts or mixtures thereof. Sulfonic acid monomers and their salts may include sodium vinyl sulfonate (SVS), sodium styrene sulfonate (SSS) and sodium acrylamide-meth-propane sulfonate (AMPS) or mixtures thereof. Preferred mono-olefinic unsaturated acid monomers include methacrylic acid. Based on the weight of the multi-level polymer particles, the multi-level polymer particles may contain a total amount of 0.1 wt% or more, 0.4 wt% or more, 0.7 wt% or more, 1.0 wt% or more, 1.3 wt% or more, 1.6 wt% or more, 1.8 wt% or more, 2.0 wt% or more, 2.2 wt% or more, 2.4 wt% or more, 2.6 wt% or more, or even 2.8 wt% or more, and simultaneously 10 wt% or less, 7 wt% or less, 5 wt% or less, 4.5 wt% or less, 4.2 wt% or less, 4.0 wt% or less, 3.8 wt% or less, 3.6 wt% or less, 3.4 wt% or less, 3.2 wt% or less, or even 3.0 wt% or less structural units of monoolefinic unsaturated acid monomers and their salts. Based on the weight of polymer A, polymer A in the multi-level polymer particles may contain 0.1 wt% or more, 0.4 wt% or more, 0.7 wt% or more, 1.0 wt% or more, 1.3 wt% or more, 1.6 wt% or more, 1.8 wt% or more, 2.0 wt% or more, 2.2 wt% or more, 2.4 wt% or more, 2.6 wt% or more, or even 2.8 wt% or more, and simultaneously 5 wt% or less, 4.5 wt% or less, 4.2 wt% or less, 4.0 wt% or less, 3.8 wt% or less, 3.6 wt% or less, 3.4 wt% or less, 3.2 wt% or less, or even 3.0 wt% or less structural units of monoolefinic unsaturated acid monomers and their salts.Based on the weight of polymer B, polymer B in the multi-level polymer particles may contain 2.0 wt% or more, 2.2 wt% or more, 2.4 wt% or more, 2.6 wt% or more, or even 2.8 wt% or more, and simultaneously 15 wt% or less, 10 wt% or less, 7 wt% or less, 5 wt% or less, 4.5 wt% or less, 4.2 wt% or less, 4.0 wt% or less, 3.8 wt% or less, 3.6 wt% or less, 3.4 wt% or less, 3.2 wt% or less, or even 3.0 wt% or less of monoolefinic unsaturated acid monomers and their salts.

[0028] Polymer A and / or polymer B, preferably polymer B, in the multi-level polymer particles may each independently contain structural units of one or more acetylacetamide functional monomers. An acetylacetamide functional monomer is a monomer containing at least one acetylacetamide group. The acetylacetamide functional monomers used in this invention may have the structure of formula (I):

[0029]

[0030] R1 is selected from the following structures:

[0031]

[0032] Among them, R2, R4, R8, R 10 R 12 and R 13 Each is independently an alkylene group having 2 to 20 carbon atoms, 3 to 12 carbon atoms, or 4 to 8 carbon atoms, such as ethylene (-CH2CH2-) and propylene (-CH2CH2CH2-); R3, R5, R6, R7, and R 11 Each of the following groups is independently hydrogen (H) or an alkyl group having 1 to 8 carbon atoms or 2 to 4 carbon atoms, such as methyl and ethyl; R9 is H or an alkyl group having 1 to 20 carbon atoms, 3 to 12 carbon atoms, or 4 to 8 carbon atoms; and X is O or N. Preferably, R1 has the structure (II-a), wherein X is O, R2 is -CH2CH2-, and R3 is -CH3. "alkyl" refers to a monovalent hydrocarbon group, such as methyl. "alkylene" refers to a divalent saturated aliphatic group, such as -CH2CH2-.

[0033] The alkyl acetoacetamide functional monomer can be an alkyl acetoacetyl (meth)acrylate. Examples of suitable alkyl acetoacetamide functional monomers include ethyl acetoacetyl methacrylate (N-AAEM), ethyl acetoacetyl acrylate, ethyl acetoacetyl (meth)acrylamide, ethyl acetoacetyl maleate, ethyl acetoacetyl itaconic acid, or mixtures thereof. Preferably, the alkyl acetoacetamide functional monomer is ethyl acetoacetyl methacrylate.

[0034] The olefinically unsaturated acetoacetamide functional monomers that can be used in this invention can be synthesized by reacting N-(2-hydroxyethyl)acetoacetamide with the aforementioned monoolefinically unsaturated acids and / or their anhydrides, alkyl esters of (meth)acrylic acid, or mixtures thereof, via esterification or transesterification. The alkyl esters of (meth)acrylic acid are described below. Preferably, anhydrides of monoolefinically unsaturated acids are used. More preferably, (meth)acrylic anhydrides are used.

[0035] Based on the weight of polymer A, polymer B may contain structural units of acetylacetamide functional monomers in amounts of zero wt% or more, 0.1 wt% or more, 0.2 wt% or more, 0.3 wt% or more, or even 0.5 wt% or more, and simultaneously 15 wt% or less, 10 wt% or less, 7 wt% or less, 5 wt% or less, 4 wt% or less, 3 wt% or less, 2 wt% or less, 1.5 wt% or less, 1.1 wt% or less, or even 1 wt% or less. Based on the weight of polymer B, polymer B may contain structural units of acetylacetamide functional monomers in amounts of 2.8 wt% or more, 3.0 wt% or more, 3.2 wt% or more, 3.5 wt% or more, 3.8 wt% or more, 4 wt% or less, 4.2 wt% or less, 4.5 wt% or less, 4.8 wt% or more, or even 5 wt% or more, and simultaneously 30 wt% or less, 25 wt% or less, 20 wt% or less, 15 wt% or less, 14 wt% or less, 13 wt% or less, 12 wt% or less, 11 wt% or less, 10 wt% or less, 9 wt% or less, 8 wt% or less, 7 wt% or less, or even 6 wt% or less. The structural units of the acetylacetamide functional monomer can be present in polymer A, polymer B, or both polymer A and polymer B; the condition is based on the weight of the multi-level polymer particles, and the total amount of structural units of the acetylacetamide functional monomer in the multi-level polymer particles can be 2% or more by weight, 2.1% or more by weight, 2.5% or more by weight, 2.8% or more by weight, 3.0% or more by weight, 3.1% or more by weight, 3.3% or more by weight, 3.5% or more by weight, 3.7% or more by weight, 4.0% or more by weight, 4.2% or more by weight, 4.5% or more by weight, or even 4.7% or more by weight, and simultaneously 15% or less by weight, 12% or less by weight, 10% or less by weight, 9% or less by weight, 8% or less by weight, 7% or less by weight, 6% or less by weight, or even 5% or less by weight.

[0036] Polymer A and / or polymer B in the multi-level polymer particles, preferably polymer A, may each independently contain structural units of one or more polyene-bonded unsaturated monomers, including difunctional, trifunctional, tetrafunctional, or higher-functional polyene-bonded unsaturated monomers. Preferably, the polyene-bonded unsaturated monomers contain two or more different polyene-bonded unsaturated polymerizable groups. The two or more different polyene-bonded unsaturated polymerizable groups generally have different reactivity. Each of the polyene-bonded unsaturated polymerizable groups may be selected from one of the following different categories (i), (ii), (iii), and (iv): (i) acryloyl, (ii) methacryloyl, (iii) allyl (H₂C=CH-CH₂-), and (iv) other polyene-bonded unsaturated groups besides (i), (ii), and (iii). Acryloyl may be acryloyloxy or acryloylamino. Methacryl may include methacryloyloxy or methacryloylamino. Other olefinically unsaturated groups may include vinyl, maleate, crotonyl, or dicyclopentenyl. More preferably, the polyolefinically unsaturated monomer contains at least one allyl group and at least one acryloyl or methacryloyl group. Suitable polyolefinically unsaturated monomers may include, for example, divinylbenzene (DVB), allyl (meth)acrylate, 2-methylallyl (meth)acrylate, allyl (meth)acrylamide, 2-methylallyl (meth)acrylamide, allyloxyethyl (meth)acrylate, 2-methylallyloxyethyl (meth)acrylate, crotonyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyl (meth)acrylate, diallyl maleate, or mixtures thereof. Based on the weight of the multi-level polymer particles, the multi-level polymer particles may contain structural units of polyene-bonded unsaturated monomers in a total amount greater than 0.1 wt%, for example, 0.3 wt% or more, 0.5 wt% or more, 0.7 wt% or more, 0.9 wt% or more, 1.1 wt% or more, 1.3 wt% or more, 1.5 wt% or more, 1.7 wt% or more, 1.9 wt% or more, 2.1 wt% or more, 2.3 wt% or more, or even 2.5 wt% or more, and simultaneously 7 wt% or less, 5 wt% or less, 4.8 wt% or less, 4.6 wt% or less, 4.4 wt% or less, 4.2 wt% or less, 4 wt% or less, 3.8 wt% or less, 3.6 wt% or less, 3.4 wt% or less, 3.2 wt% or less, 3.0 wt% or less, or even 2.8 wt% or less.Based on the weight of polymer A, polymer A may contain structural units of polyene-bonded unsaturated monomers in amounts of 0.1 wt% or more, 0.5 wt% or more, 1.0 wt% or more, 1.4 wt% or more, 1.8 wt% or more, 2.2 wt% or more, 2.5 wt% or more, 2.8 wt% or more, 3.1 wt% or more, 3.4 wt% or more, 3.7 wt% or more, 4.0 wt% or more, 4.3 wt% or more, or even 4.5 wt% or more, and simultaneously 12 wt% or less, 11 wt% or less, 10 wt% or less, 9 wt% or less, 8 wt% or less, 7 wt% or less, 6.5 wt% or less, 6 wt% or less, 5.5 wt% or less, or even 5 wt% or less. Based on the weight of polymer B, polymer B may contain structural units of polyene-bonded unsaturated monomers in amounts ranging from zero wt% to 1.0 wt%, for example, less than 0.8 wt%, less than 0.5 wt%, less than 0.3 wt%, less than 0.2 wt%, less than 0.1 wt%, less than 0.08 wt%, less than 0.05 wt%, less than 0.04 wt%, less than 0.02 wt%, less than 0.01 wt%, or even zero wt%. The content of structural units of polyene-bonded unsaturated monomers in polymer A and polymer B may be the same or different. Preferably, the content of structural units of polyene-bonded unsaturated monomers in polymer A is higher than the content of structural units of polyene-bonded unsaturated monomers in polymer B.

[0037] The multi-level polymer particles of the present invention may further comprise structural units of one or more mono-olefinically unsaturated nonionic monomers other than acetylacetamide functional monomers. The structural units of mono-olefinically unsaturated nonionic monomers may be present in polymer A, polymer B, or both polymer A and B. As used herein, the term "nonionic monomer M" refers to a monomer that does not carry an ionic charge between pH = 1 and 14. Mono-olefinically unsaturated nonionic monomers may include any combination of monomers selected from any one or more of the following types: alkyl esters of (meth)acrylic acid, vinyl aromatic monomers such as styrene and substituted styrene, vinyl esters of carboxylic acids, (meth)acrylamide, olefinically unsaturated nitriles such as (meth)acrylonitrile, (meth)acryloyl-functionalized silanes such as (meth)acryloyloxyalkyltrialkoxysilane, vinyl silanes such as vinyltrialkoxysilane, or mixtures thereof. The alkyl esters of (meth)acrylic acid used in the present invention may be C1-C64 of (meth)acrylic acid. 20 -、C1-C 10- or C1-C8-alkyl esters, including, for example, methyl acrylate, methyl methacrylate, ethyl acrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, isobutyl methacrylate, hexyl methacrylate, lauryl methacrylate, stearyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, oleic acid ester, palmitate methacrylate, nonyl methacrylate, decyl methacrylate, dodecyl methacrylate, pentadecyl methacrylate, hexadecyl methacrylate, octadecyl methacrylate, hydroxyethyl methacrylate, or hydroxypropyl methacrylate, or mixtures thereof. Vinylsilanes that can be used in this invention may include any combination of monomers selected from alkylvinyldialkoxysilanes, vinyltriethoxysilanes, vinyltrimethoxysilanes, or mixtures thereof, or more than one type of monomer. The (meth)acryloyl-functionalized silanes that can be used in this invention may include any combination of monomers selected from γ-methacryloyloxypropyltrimethoxysilane, methacryloyloxypropyltriethoxysilane, 3-methacryloyloxypropylmethyldimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropyltriethoxysilane, or mixtures thereof. Preferably, the monoolefinic unsaturated nonionic monomer is selected from methyl methacrylate, methacrylate, ethyl acrylate, butyl methacrylate, butyl acrylate, 2-ethylhexyl acrylate, styrene, or mixtures thereof. Based on the weight of the multi-level polymer particles, the multi-level polymer particles may contain structural units of mono-olefinic unsaturated nonionic monomers in total amounts of 70% or more, 75% or more, 80% or more, 82% or more, 85% or more, 87% or more, or even 88% or more, and simultaneously 92.9% or less, 92% or less, 91% or less, 90% or less, or even 89% or less.

[0038] Preferably, polymer A in the multi-level polymer particles comprises structural units of monoene-bonded unsaturated acid monomers and their salts, structural units of polyene-bonded unsaturated monomers (such as allyl methacrylate), structural units of monoene-bonded unsaturated nonionic monomers, and optionally structural units of acetylacetamide functional monomers. More preferably, based on the weight of polymer A, polymer A comprises 1% to 5% by weight of structural units of monoene-bonded unsaturated acid monomers and their salts, 1% to 6% by weight of structural units of polyene-bonded unsaturated monomers, 84% to 98% by weight of structural units of monoene-bonded unsaturated nonionic monomers, and 1% to 5% by weight of structural units of acetylacetamide functional monomers. Preferably, polymer B in the multi-level polymer particles comprises structural units of monoene-bonded unsaturated acid monomers and their salts, structural units of monoene-bonded unsaturated nonionic monomers, and structural units of acetylacetamide functional monomers. More preferably, based on the weight of polymer B, polymer B comprises 1% to 10% by weight of structural units of mono-olefinic unsaturated acid monomers and their salts, 78% to 92% by weight of structural units of mono-olefinic unsaturated nonionic monomers, and 5% to 12% by weight of structural units of acetylacetamide functional monomers. Based on the weight of the multi-level polymer particles, the multi-level polymer particles of the present invention may comprise 2% to 8% by weight of structural units of mono-olefinic unsaturated acid monomers and their salts, 2% to 8% by weight of structural units of acetylacetamide functional monomers, 0.5% to 5% by weight of structural units of polyolefinic unsaturated monomers, and 79% to 95.5% by weight of structural units of mono-olefinic unsaturated nonionic monomers.

[0039] The multi-level polymer particles of the present invention comprise polymer A and polymer B. Based on the weight of the multi-level polymer particles, the amount of polymer A present in the multi-level polymer particles can be 30% or more by weight, 32% or more by weight, 34% or more by weight, 36% or more by weight, 38% or more by weight, 39% or more by weight, 40% or more by weight, 41% or more by weight, 42% or more by weight, 43% or more by weight, 44% or more by weight, or even 45% or more by weight, and simultaneously 60% or less by weight, 59% or less by weight, 58% or less by weight, 57% or less by weight, 56% or less by weight, 55% or less by weight, 54% or less by weight, 53% or less by weight, 52% or less by weight, 51% or less by weight, or even 50% or less by weight. Based on the weight of the multi-level polymer particles, the amount of polymer B present in the multi-level polymer particles can be 40% or more by weight, 41% or more by weight, 42% or more by weight, 43% or more by weight, 44% or more by weight, 45% or more by weight, 46% or more by weight, 47% or more by weight, 48% or more by weight, 49% or more by weight, or even 50% or more by weight, and simultaneously 70% or less by weight, 68% or less by weight, 66% or less by weight, 64% or less by weight, 62% or less by weight, 61% or less by weight, 60% or less by weight, 59% or less by weight, 58% or less by weight, 57% or less by weight, 56% or less by weight, or even 55% or less by weight. The multi-level polymer particles can be two-level polymer particles, wherein the total weight concentration of polymer A and polymer B in the multi-level polymer particles is equal to 100%. The multi-level polymer particles of the present invention can comprise multiple different phases or layers formed of at least polymer A and polymer B. Multilevel polymer particles may contain two layers, such as an inner layer of polymer A and an outer layer of polymer B.

[0040] The types and contents of the aforementioned monomers can be selected to provide multi-level polymer particles with Tg suitable for different applications. The multi-level polymer particles can have Tg values ​​of -10°C or higher, -5°C or higher, 0°C or higher, 5°C or higher, 10°C or higher, 14°C or higher, 18°C ​​or higher, or even 22°C or higher, and simultaneously 80°C or lower, 70°C or lower, 65°C or lower, 60°C or lower, 55°C or lower, 50°C or lower, 45°C or lower, 40°C or lower, 35°C or lower, or even 30°C or lower. In the multi-level polymer particles, polymer A has a higher Tg than polymer B, for example, 20°C or higher, 30°C or higher, or even 40°C or higher. For example, polymer A can have a Tg greater than 30°C or higher, such as 33°C or higher, 36°C or higher, 39°C or higher, 42°C or higher, 45°C or higher, 48°C or higher, 50°C or higher, 51°C or higher or even 52°C or higher, and simultaneously 110°C or lower, 100°C or lower, 90°C or lower, 85°C or lower, 80°C or lower, 75°C or lower, 72°C or lower, 70°C or lower, 68°C or lower, 67°C or lower, 65°C or lower, 62°C or lower or even 60°C or lower. Polymer B can have a Tg of 30°C or lower, such as 25°C or lower, 21°C or lower, 17°C or lower, 13°C or lower, 9°C or lower, 6°C or lower, 3°C or lower, 0°C or lower, -3°C or lower, -6°C or lower, -8°C or lower, or even -10°C or lower, and simultaneously -40°C or higher, -35°C or higher, -30°C or higher, -25°C or higher, -22°C or higher, -19°C or higher, -17°C or higher, -15°C or higher, or even -13°C or higher. The Tg is calculated using the Fox equation described above.

[0041] The multi-level polymer particles in the aqueous dispersion of the present invention can have an average particle size of 50 nanometers (nm) or larger, 80 nm or larger, 90 nm or larger, 100 nm or larger, and simultaneously 500 nm or smaller, 300 nm or smaller, 200 nm or smaller, or even 150 nm or smaller. The particle size referred to herein is the exponential average particle size and can be measured using a Brookhaven BI-90Plus particle size analyzer.

[0042] In addition to the multi-level polymer particles, the aqueous dispersion of the present invention may also contain one or more polyfunctional carboxylic hydrazides containing at least two hydrazide groups per molecule. The polyfunctional carboxylic hydrazides can act as crosslinking agents and are optionally diacid hydrazides, oxalic acid hydrazides, isophthalic acid hydrazides, polyacrylic acid polyhydrazides, and mixtures thereof. Based on the weight of the multi-level polymer particles, the amount of polyfunctional carboxylic hydrazides present may be 0.05% or more, 0.1% or more, 0.2% or more, or even 0.5% or more, and simultaneously, 10% by weight or less, 7% by weight or less, 5% by weight or less, 2% by weight or less, or even 1% by weight or less.

[0043] The aqueous dispersion of the multi-stage polymer particles of the present invention further comprises water. Based on the total weight of the aqueous dispersion, the amount of water present may be 30% or more, 40% or more, or even 50% or more, and simultaneously 90% or less, 85% or less, or even 80% or less.

[0044] The present invention also relates to a method for preparing an aqueous dispersion comprising multi-level polymer particles by multi-level radical polymerization, comprising at least one polymerization stage for forming polymer A and at least one polymerization stage for forming polymer B. In multi-level radical polymerization, at least two stages are formed sequentially, which generally results in the formation of multi-level polymer particles comprising at least two polymer compositions such as polymer A and polymer B, optionally with different stages formed in different reactors. Each stage is polymerized sequentially and differs from the preceding and / or immediately following stage due to differences in monomer composition. Multi-level radical polymerization may include at least one stage in which polymer A is formed by polymerization of monomer mixture A in a first stage, followed by polymerization of monomer mixture B in a second stage in the presence of polymer A obtained from the first stage to form polymer B. Alternatively, multi-level radical polymerization may include polymerization of monomer mixture B in a first stage to form polymer B, followed by polymerization of monomer mixture A in a second stage in the presence of the previously formed polymer B to form polymer A. Each stage of radical polymerization may be carried out by polymerization techniques known in the art, such as suspension polymerization or emulsion polymerization of monomers such as monomer mixtures A and B. Emulsion polymerization is a preferred method. Monomer mixture A and monomer mixture B may each independently include the monomers described above for forming the structural units of polymer A and polymer B, respectively. The total weight concentration of monomers in monomer mixture A for preparing polymer A is equal to 100%. The total weight concentration of monomers in monomer mixture B is equal to 100%. For each monomer, the weight concentration of the monomer used to prepare the polymer (e.g., polymer A) in the total monomers is substantially the same as the aforementioned weight concentration of the structural unit of such monomer in such polymer (e.g., polymer A) as described above; for example, the weight concentration of each monomer in monomer mixture A (i.e., based on the total weight of monomer mixture A) is the same as the weight concentration of the structural unit of such monomer in polymer A (i.e., based on the weight of polymer A). Monomer mixtures A and B, respectively used to prepare polymer A and polymer B, may be added in pure form or as an emulsion in water; or may be added once or multiple times, or continuously, linearly, or non-linearly, during the reaction for preparing polymer A, polymer B, or combinations thereof, respectively. The applicable temperature for emulsion polymerization can be below 100°C, in the range of 10°C to 95°C, in the range of 30°C to 90°C, or in the range of 50°C to 88°C.

[0045] In a multi-stage free radical polymerization method for preparing aqueous dispersions of multi-stage polymer particles, one or more free radical initiators may be used in each stage. The polymerization process may be a 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, superphosphate and its salts; ammonium or alkali metal salts of potassium permanganate and peroxydisulfate. The free radical initiator may typically be used at levels from 0.01% to 3.0% by weight of the total monomers used to prepare the multi-stage polymer. A redox system comprising the above-mentioned initiators and a suitable reducing agent may be used in the polymerization method. Examples of suitable reducing agents include sodium formaldehyde sulfoxylate, ascorbic acid, isoascorbic acid, alkali metal salts and ammonium salts of sulfur-containing acids, such as sodium sulfite, bisulfite, thiosulfate, hyposulfite, sulfide, hydrosulfide, or dithionite; formadinesulfinic acid; acetone sulfite; glycolic acid; hydroxymethanesulfonic acid; glyoxylate hydrate; lactic acid; glyceric acid; malic acid; tartaric acid; and salts of the aforementioned acids. Metal salts of iron, copper, manganese, silver, platinum, vanadium, nickel, chromium, palladium, or cobalt can be used to catalyze redox reactions. Metal chelating agents may be used optionally.

[0046] In a multi-stage free radical polymerization method for preparing an aqueous dispersion of multi-stage polymer particles, one or more surfactants may be used in one or more stages of the polymerization process. Surfactants may be added before or during monomer polymerization, or in combination thereof. A portion of the surfactant may also be added after polymerization. Surfactants may be used in at least one or all stages of the preparation of multi-stage polymer particles. Surfactants may include anionic and / or nonionic emulsifiers. Surfactants may be reactive surfactants, such as polymerizable surfactants. 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; and ethoxylated alcohols or phenols. Preferably, alkali metal or ammonium salts of alkyl, aryl, or alkylaryl sulfate surfactants are used. The combined amount of surfactants used is typically from 0% to 10% by weight or from 0.5% to 3% by weight, based on the total monomers used to prepare the multi-stage polymer.

[0047] In a multi-stage free radical polymerization method for preparing an aqueous dispersion of multi-stage polymer particles, one or more chain transfer agents may be used in one or more stages of the polymerization process. Examples of suitable chain transfer agents include 3-mercaptopropionic acid, methyl mercaptopropionate, butyl mercaptopropionate, n-dodecyl mercaptan, benzene mercaptan, alkyl azelate mercaptan, or mixtures thereof. The chain transfer agent may be used in an effective amount to control the molecular weight of the polymer in the multi-stage polymer particles; for example, the chain transfer agent may be used in the polymerization stage for forming polymer A, the polymerization stage for forming polymer B, or in both stages. Based on the total weight of the monomers used to prepare the multi-stage polymer particles, the amount of chain transfer agent may be 0% by weight or more, 0.1% by weight or more, 0.15% by weight or more, or even 0.2% by weight or more, and simultaneously 2% by weight or less, 1% by weight or less, 0.5% by weight or less, or even 0.3% by weight or less.

[0048] The resulting aqueous dispersion of multi-level polymer particles can be neutralized to a pH of at least 5, such as 5 to 12, 6 to 11, 6.5 to 10, or 7 to 9. Neutralization can be achieved by adding one or more bases that result in partial or complete neutralization of the ionic or potential ionic groups of the multi-level polymer. Examples of suitable bases include ammonia; alkali metal or alkaline earth metal compounds, such as sodium hydroxide, potassium hydroxide, calcium hydroxide, zinc oxide, sodium carbonate; primary, secondary, and tertiary monoamines, including propylamine, monobutylamine, hexylamine, diethanolamine, triethanolamine, dimethylethanolamine, diethylamine, dimethoxyethylamine, triethylamine, tributylamine, 2-ethoxyethylamine, morpholine; and polyetheramines (e.g., JEFFAMINE M-600): primary diamines, secondary diamines, primary triamines, and secondary triamines, including 2-diethylaminoethylamine, 1,2-propanediamine, neopentyl diamine, hexamethylenediamine, 4,9-dioxadodecane-1,12-diamine; and polyetheramines selected from those having a polyethylene glycol or polypropylene glycol backbone (e.g., JEFFAMINE D-230, JEFFAMINE ED-600, JEFFAMINE M-600). The group consists of EDR-148, JEFFAMINE T403, JEFFAMINE SD401, or mixtures thereof.

[0049] The method for preparing the aqueous dispersion of the present invention may further include adding a polyfunctional carboxyhydrazide containing at least two of the above-mentioned hydrazide groups per molecule to the aqueous dispersion.

[0050] The aqueous dispersion of the multi-stage polymer particles of the present invention exhibits excellent film-forming properties at minimum film-forming temperatures (MFFTs) above 0°C, such as 10°C or higher, 15°C or higher, 20°C or higher, 25°C or higher, 30°C or higher, 35°C or higher, 40°C or higher, or even 45°C or higher, and simultaneously 75°C or lower, 70°C or lower, 65°C, 60°C or lower, or even 55°C or lower. MFFT is the lowest temperature at which the polymer particles of the aqueous dispersion will aggregate together and form a continuous film when the volatile component (e.g., water) evaporates. MFFT can be determined according to the test methods described in the Examples section below. The aqueous dispersion of the multi-stage polymer particles can be used in many applications, including, for example, wood coatings, metal coatings, architectural coatings, and traffic marking paints.

[0051] This invention also relates to coating compositions comprising aqueous dispersions of multi-level polymer particles. The coating composition may also contain one or more pigments. Pigments may include particulate inorganic materials capable of substantially contributing to the opacity or hiding power of the coating. Such materials typically have a refractive index greater than 1.8. Examples of suitable pigments include titanium dioxide (TiO2), zinc oxide, zinc sulfide, iron oxide, barium sulfate, barium carbonate, or mixtures thereof. The coating composition may contain one or more extenders. Extenders may include particulate inorganic materials typically having a refractive index less than or equal to 1.8 and greater than 1.5. Examples of suitable extenders include calcium carbonate, alumina (Al2O3), clay, calcium sulfate, aluminosilicates, silicates, zeolites, mica, diatomaceous earth, solid or hollow glass, ceramic beads, and opaque polymers (such as ROPAQUE, available from The Dow Chemical Company). TM Ultra E (ROPAQUE is a trademark of Dow Chemical Company), or mixtures thereof. Based on the total weight of the coating composition, the amount of pigment and / or extender present may be zero wt% or more, 5 wt% or more, 10 wt% or more or even 15 wt% or more, and simultaneously 40 wt% or less, 30 wt% or less, 25 wt% or less or even 20 wt% or less.

[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. The defoamer may be a silicone-based defoamer, a mineral oil-based defoamer, an ethylene oxide / propylene oxide defoamer, a polyalkyl acrylate, or a mixture thereof. Based on the total weight of the coating composition, the defoamer may be present in amounts of zero wt% or more, 0.01 wt% or more, or even 0.1 wt% or more and simultaneously 2 wt% or less, 1.5 wt% or less, or even 1 wt% or less.

[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 carbamates (HEUR); and cellulose thickeners, such as methylcellulose ethers, hydroxymethylcellulose (HMC), hydroxyethylcellulose (HEC), hydrophobically modified hydroxyethylcellulose (HMHEC), sodium carboxymethylcellulose (SCMC), sodium carboxymethyl 2-hydroxyethylcellulose, 2-hydroxypropyl methylcellulose, 2-hydroxyethyl methylcellulose, 2-hydroxybutyl methylcellulose, 2-hydroxyethyl ethylcellulose, and 2-hydroxypropyl cellulose. Preferred thickeners are based on HEUR. Based on the total weight of the coating composition, the thickener may be present in amounts of zero wt% or more, 0.01 wt% or more, or even 0.1 wt% or more and simultaneously 5 wt% or less, 4 wt% or less, or even 3 wt% or less.

[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, zwitterionic, or nonionic polycarboxylate. Based on the total weight of the coating composition, the amount of wetting agent present may be zero wt% or more, 0.01 wt% or more, or even 0.1 wt% or more, and simultaneously 5 wt% or less, 4 wt% or less, or even 3 wt% or less.

[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. Suitable coalescing agents may include, for example, 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. Based on the total weight of the coating composition, the coalescing agent may be present in amounts of zero wt% or more, 0.1 wt% or more, or even 1 wt% or more and simultaneously 12 wt% or less, 10 wt% or less, or even 9 wt% or less.

[0056] In addition to the components described above, the coating compositions of the present invention may also contain any one or more of the following additives in any combination: buffers, neutralizers, dispersants, wetting agents, biocides, anti-skinning agents, colorants, flow agents, antioxidants, plasticizers, freezing / thawing additives, leveling agents, thixotropic agents, tackifiers, anti-scratch additives, and abrasives. Based on the total weight of the coating composition, the combined amount of these additives may be zero wt% or more, 0.001 wt% or more, or even 0.1 wt% or more, and simultaneously 5 wt% or less, 3 wt% or less, or even 2 wt% or less.

[0057] The coating compositions of the present invention can be prepared using techniques known in the coatings industry, for example by mixing an aqueous dispersion comprising multi-level polymer particles with the other optional components described above. 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. The coating compositions of the present invention are generally water-based coating compositions, such as one-component water-based wood coating compositions.

[0058] The present invention also provides a method for preparing a coating. The method may include: forming a coating composition, applying the coating composition to a substrate, and drying or allowing the applied coating composition to dry to form a coating. The coating composition may be applied to the substrate by existing methods including brushing, dipping, rolling, and spraying. The coating composition is preferably applied by spraying. 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 cup application), can be used. i (c bell application) and manual or automated methods. After the coating composition is applied to the substrate, the coating composition can be dried or allowed to dry at room temperature (20°C to 25°C) or at elevated temperatures (e.g., 35°C to 60°C) to form a film (i.e., a coating). The coating composition can provide a coating (i.e., a film obtained after drying or allowing the coating composition applied to the substrate to dry) and a coated substrate with excellent hot water resistance obtained therefrom at temperatures of 70°C or higher, 80°C or higher, or between 90°C and 100°C, wherein the rating is 3 or higher or even 4 or higher. The coating and the coated substrate can also exhibit alcohol resistance (48% aqueous ethanol solution, 1 hour) with a rating of 4 or higher, alkali resistance (10% aqueous sodium carbonate solution, 16 hours) with a rating of 3 or higher or even 4 or higher, and acetic acid resistance (10% aqueous glacial acetic acid solution, 16 hours) with a rating of 4 or higher. These properties can be measured according to the test methods described in the Examples section below.

[0059] The coating compositions of this invention can be applied and adhered to a variety of substrates. Examples of suitable substrates include concrete, cementitious substrates, wood, metal, stone, resilient substrates, glass, or fabric; wood is preferred. The coating compositions are suitable for a wide range of coating applications, such as architectural coatings, marine and protective coatings, automotive coatings, wood coatings (including furniture coatings, joinery coatings, and floor coatings), coil coatings, road marking paints, and civil engineering coatings. The coating compositions can be used alone or in combination with other coatings to form multilayer coatings.

[0060] Example

[0061] 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 materials used in the examples and their abbreviations are as follows:

[0062] Methacrylic acid (MAA), methyl methacrylate (MMA), styrene (ST), 2-ethylhexyl acrylate (2-EHA) and allyl methacrylate (ALMA) were all purchased from Sinoreagent Group.

[0063] Purchased from Dow Chemical Company DOWANOL TM DPnB (dipropylene glycol n-butyl ether), DOWANOL DPM (dipropylene glycol methyl ether), and DOWANOL EB (ethylene glycol monobutyl ether) are used as coalescing agents.

[0064] The Tego Airex 902w defoamer was purchased from Evonik.

[0065] BYK-346 polyether-modified siloxane was purchased from BYK and used as a wetting agent.

[0066] Acetyl acetyloxyethyl methacrylate (AAEM) and ACRYSOL TM Both RM-8W and ACRYSOL RM-5000 nonionic polyurethane rheology modifiers were purchased from Dow Chemical Company.

[0067] ACRYSOL and DOWANOL are trademarks of Dow Chemical Company.

[0068] The following standard analytical equipment and methods were used in the embodiments and to determine the properties and characteristics described herein:

[0069] MFFT measurement

[0070] The MFFT was measured using a Coesfeld MFFT instrument by casting a 75 μm wet film of an aqueous dispersion sample onto a heated plate with a temperature gradient. The film was dried, and the lowest temperature at which a coherent film was formed was recorded as the MFFT.

[0071] Particle size measurement

[0072] The particle size of the polymer particles in the aqueous dispersion was measured using a Brookhaven BI-90Plus particle size analyzer employing photon correlation spectroscopy (light scattering of sample particles). This method involves diluting two drops of the aqueous dispersion to be tested in 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., K in the range of 250 counts / second to 500 counts / second for diameters in the range of 10 nm to 300 nm). The particle size of the aqueous polymer dispersion was then measured and reported as the Z-mean diameter in intensity.

[0073] Thermal aging stability test

[0074] A diamine, such as Jeffamine D-230 (Huntsman Corporation), was added to the aqueous polymer dispersion sample to form a mixture. The viscosity of the mixture was measured and recorded as the initial viscosity. The thermal aging stability of the aqueous polymer dispersion containing the diamine was measured by storing the mixture in an oven at 50°C and monitoring viscosity changes periodically. After 7 days, the viscosity of the mixture was measured and recorded as the final viscosity. If the final viscosity was less than 3 times the initial viscosity, the aqueous polymer dispersion passed the thermal aging stability test. Otherwise, if the final viscosity was equal to or greater than 3 times the initial viscosity, or if the mixture gelled after 7 days at 50°C, the sample failed the thermal aging stability test.

[0075] Water resistance test

[0076] By applying 80g / m² to each layer 2 Up to 90g / m 2 The test coating composition was applied in two coats to a black wood substrate. After the first coat, the panel was left at room temperature for 4 hours, then sanded. After the second coat, the panel was allowed to dry at room temperature for 4 hours, then dried in an oven at 50°C for 48 hours to obtain the coated panel for room temperature (RT) water resistance and hot water resistance testing.

[0077] RT water resistance test Place the water-soaked filter tray on the finished panel at room temperature and cover it with a lid to reduce water evaporation. After 24 hours, remove the lid. Wipe the test area with a damp paper towel and allow it to dry at room temperature to observe the extent of damage.

[0078] Hot water resistance testFirst, apply 10 mL to 20 mL of boiling water to the surface of the coated panel. Then, place a stainless steel cup containing 350 mL to 500 mL of boiling water on top of the coated panel, ensuring the boiling water remains between the bottom of the cup and the coated panel. After 30 minutes, remove the cup and wipe away any remaining water from the coated panel with a paper towel. After 1 hour, rate any marks left on the surface of the coated panel.

[0079] RT water resistance and hot water resistance are rated on a scale of 0 to 5, with 0 being the worst and 5 being the best, as follows:

[0080] 5 - No change: The test area cannot be distinguished from the surrounding adjacent areas.

[0081] 4. Slight changes: The test area can only be distinguished from the adjacent surrounding area when the light source shines on the test surface and reflects into the observer's eye. Examples include discoloration; changes in gloss and color; and / or no changes in surface structure, such as swelling, fiber bulging, cracking, and / or blistering.

[0082] 3- Moderate changes: The test area can be distinguished from the surrounding area and is visible in several observation directions, such as discoloration; changes in gloss and color; and / or no changes in surface structure, such as swelling, fiber bulging, cracking and / or blistering.

[0083] 2- Significant changes: The test area is clearly distinguishable from the surrounding area and is visible in all viewing directions, such as discoloration; changes in gloss and color; and / or slight changes in surface structure, such as swelling, fiber bulging, cracking and / or blistering.

[0084] 1- Strong changes: obvious changes in surface structure and / or discoloration, changes in gloss and color, and / or complete or partial removal of surface material, and / or filter paper adhering to the surface.

[0085] Acceptable hot water resistance is 3 or higher.

[0086] Alcohol resistance, acetic acid resistance and alkali resistance tests

[0087] Panel preparation: by applying 80g / m² to each type of wood. 2 Up to 90g / m 2 The panel was prepared by applying three coats. After the first coat, the panel was left at room temperature for 4 hours and then sanded. After the second coat, the panel was allowed to dry at room temperature for 4 hours, and then dried in an oven at 50°C for 48 hours. The following tests were then performed.

[0088] Alcohol resistance test: Place the filter tray soaked in an aqueous ethanol solution (48%) on the finished panel and cover it with a lid to reduce evaporation. After 1 hour, remove the lid. Wipe the test area with a damp paper towel and allow it to dry at room temperature to observe the degree of damage.

[0089] Acid resistance test: Place the filter tray soaked in a 10% aqueous solution of glacial acetic acid on the finished panel and cover it with a lid to reduce evaporation. After 16 hours, remove the lid. Wipe the test area with a damp paper towel and allow it to dry at room temperature to observe the degree of damage.

[0090] Alkali resistance test: Place a filter tray soaked in a 10% sodium carbonate (Na2CO3) aqueous solution on the finished panel and cover it with a lid to reduce evaporation. After 16 hours, remove the lid. Wipe the test area with a damp paper towel and allow it to dry at room temperature to observe the degree of damage.

[0091] The degree of damage in alcohol resistance, acetic acid resistance, and alkali resistance tests was rated on a scale of 0 to 5, with 0 being the worst and 5 being the best, as follows:

[0092] 5 - No change: The test area cannot be distinguished from the surrounding adjacent areas;

[0093] 4. Minor Changes: The test area can only be distinguished from the surrounding area when the light source shines on the test surface and reflects off it into the observer's eye. Minor changes may include slight discoloration and changes in gloss, but no changes in surface structure, such as swelling, fiber bulging, cracking, and / or blistering.

[0094] 3- Moderate changes: The test area can be distinguished from the surrounding area and is visible in several viewing directions, such as discoloration; changes in gloss and color; but no changes in surface structure, such as swelling, fiber bulging, cracking and / or blistering;

[0095] 2- Significant changes: The test area is clearly distinguishable from the surrounding area and is visible in all viewing directions, such as discoloration; changes in gloss and color; and / or slight changes in surface structure, such as swelling, fiber bulging, cracking and / or blistering.

[0096] 1- Strong changes: obvious changes in surface structure and / or discoloration, changes in gloss and color, and / or complete or partial removal of surface material, and / or filter paper adhering to the surface.

[0097] The higher the rating, the better the tolerance. Acceptable acetic acid resistance is 4 or higher. Acceptable alkali resistance is 3 or higher. Acceptable alcohol resistance is 4 or higher.

[0098] Synthesis of N-AAEM (acetylacetaminoethyl methacrylate)

[0099] Methacrylic anhydride (107.1 g, 0.695 mol) was slowly added to a solution of N-(2-hydroxyethyl)acetylacetamide (N-AAEM precursor) (77.6 g, 0.535 mol) in anhydrous tetrahydrofuran (THF) (200 mL). Pyridine (42.3 g, 43 mL, 0.535 mol) was then slowly added while stirring at 0 °C. The resulting yellow solution was stirred at 0 °C for 5 hours, then allowed to warm naturally to room temperature with stirring to complete the reaction. Thin-layer chromatography (TLC) confirmed the completion of the reaction. After cooling the resulting mixture to 0 °C, 450 mL of HCl (1 M) was slowly added to the cooled mixture and stirred for a period of time. The organic layer was then separated, washed twice with water (100 mL), and dried over anhydrous sodium sulfate, which was then removed by filtration. Butylated hydroxytoluene (BHT) (120 mg) was added to the resulting organic layer, and the mixture was then concentrated under reduced pressure at 25 °C. The residue was purified by rapid chromatography (silica gel column; fluid phase: petroleum ether: ethyl acetate = 1:1) to give a white solid (65 g, yield: 57%) with 300 ppm BHT. The structure of the obtained product (acetoacetaminoethyl methacrylate) was confirmed by 1H nuclear magnetic resonance (NMR) spectroscopy, with peaks having the following chemical shifts: 6.15 ppm, 5.60 ppm, and 1.956 ppm (hydrogen on the carbon-carbon double bond); 4.25 ppm and 3.59 ppm (hydrogen on the ethoxy ring); and 3.435 ppm and 2.26 ppm (hydrogen on the acetoacetate ester).

[0100] Examples (Ex) 1-3

[0101] Preparation of monomer emulsion 1 (ME1): SLS surfactant (4.5 g, 25% active material) was dissolved in deionized (DI) water (51.2 g) under stirring, and then the monomers of ME1 listed in Table 1 were slowly added to the stirred solution to obtain ME1.

[0102] Preparation of monomer emulsion 2 (ME2): SLS surfactant (4.5 g, 25% active material) was dissolved in DI water (54.5 g) under stirring, and then the monomers of ME2 listed in Table 1 were slowly added to the stirred solution to obtain ME2.

[0103] A solution containing SLS surfactant (7.6 g, 25% active material) and DI water (199.9 g) was placed in a 5-liter, 4-necked round-bottom flask equipped with a thermocouple, a cooling condenser, and a stirrer, and heated to 85°C under nitrogen. Sodium carbonate aqueous solution (0.6 g sodium carbonate in 16.2 g DI water), ammonium persulfate (APS) initiator aqueous solution (0.6 g APS in 6.5 g DI water), and 5% ME1 were added to the flask. The start of polymerization was confirmed within 5 minutes by increasing the temperature by 3°C and observing a change in the appearance of the reaction mixture. After the heating phase, the remaining ME1 was gradually added to the flask over a stirring period of 45 minutes. Simultaneously, APS aqueous solution (0.6 g APS in 42.7 g DI water) was gradually added to the flask over a stirring period of 45 minutes. The polymerization temperature was maintained between 84°C and 86°C. After the addition is complete, rinse the container holding ME1 and the feed tube leading to the flask with DI water (6.5 g), and then add the rinsing solution back into the flask. Afterward, maintain the reaction mixture at 82°C to 86°C for 30 minutes.

[0104] ME2 was then added over 45 minutes in the same manner as ME1. Simultaneously, an aqueous solution of APS (0.6 g APS in 42.7 g DI water) was gradually added to the flask over 45 minutes. After the addition was complete, the reaction mixture was maintained at 70°C for 60 minutes. An aqueous solution of t-BHP (0.5 g, 70% active material) in DI water (6.5 g) and an aqueous solution of IAA (0.2 g in 7.5 g DI water) were added to the flask. The contents of the flask were cooled to 50°C and then neutralized with ammonia (25%) to pH 7.0 to pH 8.0. The contents of the flask were maintained at 45°C to 50°C for 10 minutes. The resulting dispersion was cooled to room temperature and filtered to obtain an aqueous polymer dispersion.

[0105] Example 4

[0106] Preparation of monomer emulsion 1 (ME1): SLS surfactant (2.7 g, 25% active material) was dissolved in DI water (30.7 g) under stirring, and then the monomers listed in Table 1 were slowly added to the stirred solution to obtain ME1.

[0107] Preparation of monomer emulsion 2 (ME2): SLS surfactant (6.4 g, 25% active material) was dissolved in DI water (76.3 g) under stirring, and then the monomers listed in Table 1 were slowly added to the stirred solution to obtain ME2.

[0108] A solution containing SLS surfactant (7.6 g, 25% active material) and DI water (199.9 g) was placed in a 5-liter, 4-necked round-bottom flask equipped with a thermocouple, a cooling condenser, and a stirrer, and heated to 85°C under nitrogen. Sodium carbonate aqueous solution (0.6 g sodium carbonate in 16.2 g DI water), ammonium persulfate (APS) initiator aqueous solution (0.6 g APS in 6.5 g DI water), and 5% ME1 were added to the flask. The start of polymerization was confirmed within 5 minutes by increasing the temperature by 3°C and observing a change in the appearance of the reaction mixture. After the heating phase, the remaining ME1 was gradually added to the flask over a stirring period of 45 minutes. Simultaneously, APS aqueous solution (0.6 g APS in 42.7 g DI water) was gradually added to the flask over a stirring period of 45 minutes. The polymerization temperature was maintained between 84°C and 86°C. After the addition is complete, rinse the container holding ME1 and the feed tube leading to the flask with DI water (6.5 g), and then add the rinsing solution back into the flask. Afterward, maintain the reaction mixture at 82°C to 86°C for 30 minutes.

[0109] ME2 was then added over 45 minutes in the same manner as ME1. Simultaneously, an aqueous solution of APS (0.6 g APS in 42.7 g DI water) was gradually added to the flask over 45 minutes. After the addition was complete, the reaction mixture was maintained at 70°C for 60 minutes. An aqueous solution of t-BHP (0.5 g, 70% active material) in DI water (6.5 g) and an aqueous solution of IAA (0.2 g in 7.5 g DI water) were added to the flask. The contents of the flask were cooled to 50°C and then neutralized with ammonia (25%) to pH 7.0 to pH 8.0. The contents of the flask were maintained at 45°C to 50°C for 10 minutes. The resulting dispersion was cooled to room temperature and filtered to obtain an aqueous polymer dispersion.

[0110] Example 5

[0111] Preparation of monomer emulsion 1 (ME1): SLS surfactant (4.17 g, 25% active material) was dissolved in DI water (47.28 g) under stirring, and then the monomers listed in Table 1 were slowly added to the stirred solution to obtain ME1.

[0112] Preparation of monomer emulsion 2 (ME2): SLS surfactant (2.8 g, 25% active material) was dissolved in DI water (33.6 g) under stirring, and then the monomers listed in Table 1 were slowly added to the stirred solution to obtain ME2.

[0113] A solution containing SLS surfactant (5.8 g, 25% active material) and DI water (154 g) was placed in a 5-liter, 4-necked round-bottom flask equipped with a thermocouple, cooling condenser, and stirrer, and heated to 85°C under nitrogen. Sodium carbonate aqueous solution (0.45 g sodium carbonate in 15 g DI water), ammonium persulfate (APS) initiator aqueous solution (0.45 g APS in 5 g DI water), and 5% ME1 were added to the flask. The start of polymerization was confirmed within 5 minutes by increasing the temperature by 3°C and observing a change in the appearance of the reaction mixture. After the heating phase was complete, the remaining ME1 was gradually added to the flask over a stirring period of 54 minutes. Simultaneously, APS aqueous solution (0.24 g APS in 20 g DI water) was gradually added to the flask over a stirring period of 54 minutes. The polymerization temperature was maintained between 84°C and 86°C. After the addition was complete, the container holding the ME1 and the feed line to the flask were rinsed with DI water (5 g), and the rinse solution was returned to the flask. Then, maintain the reaction mixture at 82°C to 86°C for 30 minutes.

[0114] ME2 was then added over 36 minutes in the same manner as ME1. Simultaneously, an aqueous solution of APS (0.16 g APS in 13 g DI water) was gradually added to the flask over 36 minutes. After the addition was complete, the reaction mixture was maintained at 70°C for 60 minutes. An aqueous solution of t-BHP (0.8 g, 70% active material) in DI water (10 g) and an aqueous solution of IAA (0.4 g in 12 g DI water) were added to the flask. The contents of the flask were cooled to 50°C and then neutralized with ammonia (25%) to pH 7.0 to pH 8.0. The contents of the flask were maintained at 45°C to 50°C for 10 minutes. The resulting dispersion was cooled to room temperature and filtered to obtain an aqueous polymer dispersion.

[0115] Comparison (Comp) Example 1

[0116] Preparation of monomeric emulsion (ME): SLS surfactant (9.1 g, 25% active material) was dissolved in DI water (105.7 g) under stirring, and then the monomers listed in Table 1 were slowly added to the stirred solution to obtain ME.

[0117] A solution containing SLS surfactant (7.6 g, 25% active material) and DI water (199.9 g) was placed in a 5-liter, 4-necked round-bottom flask equipped with a thermocouple, a cooling condenser, and a stirrer, and heated to 85°C under nitrogen. Sodium carbonate aqueous solution (0.6 g sodium carbonate in 16.2 g DI water), ammonium persulfate (APS) initiator aqueous solution (0.6 g APS in 6.5 g DI water), and 2.5% ME were added to the flask. The start of polymerization was confirmed within 5 minutes by increasing the temperature by 3°C and observing a change in the appearance of the reaction mixture. After the heating phase, the remaining ME was gradually added to the flask over a stirring period of 90 minutes. Simultaneously, APS aqueous solution (0.6 g APS in 42.7 g DI water) was gradually added to the flask over a stirring period of 90 minutes. The polymerization temperature was maintained between 84°C and 86°C. After the addition is complete, rinse the container holding the ME and the feed tube leading to the flask with DI water (6.5g), and then add the rinsing solution back into the flask.

[0118] After the addition was complete, the reaction mixture was maintained at 70°C for 60 minutes. Then, an aqueous solution of t-BHP (0.5 g, 70% active material) in DI water (6.5 g) and an aqueous solution of IAA (0.2 g, in 7.5 g DI water) were added to the flask. The contents of the flask were cooled to 50°C and then neutralized with ammonia (25%) to pH 7.0 to pH 8.0. The contents of the flask were maintained at 45°C to 50°C for 10 minutes. The resulting dispersion was cooled to room temperature and filtered to obtain an aqueous polymer dispersion.

[0119] Comparative Example 2

[0120] Preparation of monomer emulsion 1 (ME1): Fes-32 surfactant (13.90 g, 31% active material) was dissolved in DI water (240.47 g) under stirring, and then the monomers listed in Table 1 were slowly added to the stirred solution to obtain ME1.

[0121] Preparation of monomer emulsion 1 (ME1): Fes-32 surfactant (10.31 g, 31% active material) was dissolved in DI water (76.03 g) under stirring, and then the monomers listed in Table 1 were slowly added to the stirred solution to obtain ME2.

[0122] A solution containing Fes-32 surfactant (2.53 g, 31% active material) and DI water (369.60 g) was placed in a 5-liter, 4-necked round-bottom flask equipped with a thermocouple, a cooling condenser, and a stirrer, and heated to 87°C under nitrogen. An aqueous solution of ammonium persulfate (APS) initiator (3.74 g APS in 10.56 g DI water) and 4.7% ME1 were added to the flask. The start of polymerization was confirmed within 5 minutes by increasing the temperature by 5°C and observing a change in the appearance of the reaction mixture. After the heating phase, the remaining ME1 was gradually added to the flask over 80 minutes with stirring. Simultaneously, an aqueous solution of ammonium persulfate (APS) (2.03 g APS in 50.69 g DI water) and an aqueous solution of ammonia (11.46 g 25% ammonia in 2.11 g DI water) were gradually added to the flask over 140 minutes. The polymerization temperature was maintained between 84°C and 86°C. After adding the solution, rinse the container holding ME1 and the feed tube leading to the flask with DI water (8.45 g) and add the rinsing solution back into the flask.

[0123] ME2 was then added over 60 minutes in the same manner as ME1. After the addition was complete, the reaction mixture was maintained at 85°C for 15 minutes. Then, an aqueous solution of t-BHP (1.19 g, 70% active material) in DI water (10.56 g) and a solution of IAA (0.84 g in 13.94 g DI water) were added to the flask. The contents of the flask were cooled to 50°C and maintained at 45°C to 50°C for 10 minutes. The resulting dispersion was cooled to room temperature and filtered to obtain the aqueous polymer dispersion.

[0124] Comparative Example 3

[0125] Preparation of monomer emulsion 1 (ME1): SLS surfactant (14.25 g, 25% active material) was dissolved in DI water (181.4 g) under stirring, and then the monomers listed in Table 1 were slowly added to the stirred solution to obtain ME1.

[0126] Preparation of monomer emulsion 1 (ME1): SLS surfactant (14.38 g, 25% active material) was dissolved in DI water (171.96 g) under stirring, and then the monomers listed in Table 1 were slowly added to the stirred solution to obtain ME2.

[0127] A solution containing SLS surfactant (23.87 g, 25% active material) and DI water (630.7 g) was placed in a 5-liter, 4-necked round-bottom flask equipped with a thermocouple, cooling condenser, and stirrer, and heated to 85°C under nitrogen. Sodium carbonate aqueous solution (1.84 g sodium carbonate in 61.20 g DI water), ammonium persulfate (APS) initiator aqueous solution (1.84 g APS in 23.8 g DI water), and 5% ME1 were added to the flask. The start of polymerization was confirmed within 5 minutes by increasing the temperature by 3°C and observing a change in the appearance of the reaction mixture. After the heating phase, the remaining ME1 was gradually added to the flask over a stirring process over 45 minutes. Simultaneously, ammonium persulfate (APS) aqueous solution (0.9 g APS in 67.30 g DI water) was gradually added to the flask over a stirring process over 45 minutes. The polymerization temperature was maintained between 84°C and 86°C. After the addition is complete, rinse the container holding ME1 and the feed tube leading to the flask with DI water (20.4 g), and add the rinsing solution back into the flask. Then, maintain the reaction mixture at 82°C to 86°C for 30 minutes.

[0128] ME2 was then added over 45 minutes in the same manner as ME1. Simultaneously, an aqueous solution of ammonium persulfate (APS) (0.9 g APS in 67.30 g DI water) was gradually added to the flask over 45 minutes. After the addition was complete, the reaction mixture was maintained at 70°C for 60 minutes. An aqueous solution of t-BHP (1.63 g, 70% active material) in DI water (27.2 g) and IAA (0.82 g in 30.6 g DI water) were added to the flask. The contents of the flask were cooled to 50°C, then neutralized to a pH of 7.0 to 8.0 with ammonia (25%), and maintained at 45°C to 50°C for another 10 minutes. The resulting dispersion was cooled to room temperature and filtered to obtain an aqueous polymer dispersion.

[0129] The properties of the MP dispersions prepared above are given in Table 1.

[0130] Table 1. Monomer composition and properties

[0131]

[0132]

[0133] 1Solid content is measured as follows: Weigh 0.7g ± 0.1g of sample (wet weight of sample denoted as "W1"), place the sample in an aluminum pan (weight of aluminum pan denoted as "W2") in an oven at 150°C for 25 minutes, and then cool and weigh the aluminum pan containing the dried sample, denoted as "W3". "W3 - W2" refers to the dry or solid weight of the sample. Solid content is calculated as (W3 - W2) / W1 * 100%. 2 Average PS: Particle size measured using a Brookhaven BI-90Plus particle size analyzer. *Tg of primary polymer.

[0134] Furthermore, the mixture prepared by adding Jeffamine D-230 (based on 2.7 wt% of the polymer solids in Comparative Example 3) gelled after 7 days at 50°C. Conversely, the mixture containing the aqueous polymer dispersion of Example 1 and Jeffamine D-230 (based on 2.7 wt% of the polymer solids in Example 1) passed the thermal aging stability test at 50°C for 7 days (i.e., no gelling), indicating that the aqueous polymer dispersion of Example 1 has good thermal aging stability.

[0135] Coating composition

[0136] The aqueous polymer dispersions prepared in Examples 1-5 and Comparative Examples 1 and 2 were used as binders to prepare coating compositions based on the compositions given in Table 2. All components were mixed sequentially under stirring at 600 rpm / min to form the coating compositions.

[0137] Table 2. Coating Compositions

[0138]

[0139]

[0140] The coating compositions obtained were evaluated according to the test methods described above, and the characteristic results are shown in Table 3. As shown in Table 3, the coating compositions containing the binders of Examples 1-5 all provided coatings with surprisingly good hot water resistance (rating ≥3) and good water, alcohol, alkali, and acetic acid resistance. In particular, the binder of Example 1 provided excellent hot water resistance with a rating up to 4, and the binders of Examples 1, 3-5 provided water, alcohol, alkali, and acetic acid resistance with ratings of 4 or higher. Compared with the binder of Example 1, the primary binder of Comparative Example 1 failed to provide a coating with the desired hot water resistance. The binder of Comparative Example 2, prepared by AAEM, provided a coating with poor acid resistance (Comparative Coating 2).

[0141] Table 3. Properties of Coatings

[0142]

Claims

1. An aqueous dispersion of multi-stage polymer particles, wherein, based on the weight of the multi-stage polymer particles, the multi-stage polymer particles comprise 30 wt% to 60 wt% of polymer A and 40 wt% to 70 wt% of polymer B, wherein polymer A has a higher glass transition temperature than polymer B. Based on the weight of the multi-level polymer particles, the multi-level polymer particles comprise: 2% to 15% by weight of structural units of acetylacetamide functional monomers having the structure of formula (I): R1 is selected from the following structures: Among them, R2, R4, R8, R 10 R 12 and R 13 Each is an alkylene group having 2 to 20 carbon atoms; R3, R5, R6, R7 and R 11 Each is independently hydrogen or an alkyl group having 1 to 8 carbon atoms; R9 is hydrogen or an alkyl group having 1 to 20 carbon atoms; and X is O or N; 0.1% to 10% by weight of mono-olefinic unsaturated acid monomers, their salts or mixtures thereof as structural units; The structural unit of polyene-bonded unsaturated monomers; and The structural unit of a monoene bond-type unsaturated nonionic monomer.

2. The aqueous dispersion according to claim 1, wherein the acetylacetamide functional monomer is acetylacetaminoalkyl ester of (meth)acrylate.

3. The aqueous dispersion according to claim 1, wherein the acetoacetamide functional monomer is selected from the group consisting of acetoacetaminoethyl methacrylate, acetoacetaminoethyl acrylate, acetoacetaminoethyl (meth)acrylamide, acetoacetaminoethyl maleate, acetoacetaminoethyl itaconic acid, or mixtures thereof.

4. The aqueous dispersion according to any one of claims 1 to 3, wherein, based on the weight of the polymer B, the polymer B comprises 2.8% to 30% by weight of the structural unit of the acetylacetamide functional monomer.

5. The aqueous dispersion according to any one of claims 1 to 3, wherein, based on the weight of the polymer A, the polymer A comprises 0 to 15% by weight of the structural unit of the acetylacetamide functional monomer.

6. The aqueous dispersion according to any one of claims 1 to 3, wherein, based on the weight of the polymer A, the polymer A comprises 0.1 wt% to 12 wt% of the structural units of the polyene-bonded unsaturated monomer.

7. The aqueous dispersion according to any one of claims 1 to 3, wherein the polyene unsaturated monomer contains two or more different olefin unsaturated polymerizable groups.

8. The aqueous dispersion according to claim 7, wherein the polyene-bonded unsaturated monomer is selected from the group consisting of (2-methyl)allyl (meth)acrylate, (2-methyl)allyl(meth)acrylamide, (2-methyl)allyloxyethyl (meth)acrylate, crotonyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyl (meth)acrylate, diallyl maleate, or mixtures thereof.

9. The aqueous dispersion according to any one of claims 1 to 3, wherein, based on the weight of the polymer B, the polymer B comprises 2% to 15% by weight of the mono-olefinic unsaturated acid monomer and its salt structural units.

10. The aqueous dispersion according to any one of claims 1 to 3, wherein, based on the weight of polymer A, polymer A comprises 0.1% to 5% by weight of the mono-olefinic unsaturated acid monomer and its salt structural units.

11. The aqueous dispersion according to any one of claims 1 to 3, wherein the monoolefinic unsaturated acid monomer is methacrylic acid, ethyl methacrylate, or a mixture thereof.

12. The aqueous dispersion according to any one of claims 1 to 3, wherein the multi-stage polymer particles have a glass transition temperature in the range of -10°C to 80°C.

13. The aqueous dispersion according to any one of claims 1 to 3, wherein the Tg difference between polymer A and polymer B is 20°C or higher.

14. A method for preparing the aqueous dispersion of the multi-stage polymer particles according to any one of claims 1 to 13 by multi-stage free radical polymerization, the method comprising at least one polymerization stage for forming polymer A and at least one polymerization stage for forming polymer B.

15. A coating composition comprising an aqueous dispersion according to any one of claims 1 to 13.

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