Aqueous emulsion and preparation method thereof, coating composition and product

Abstract

The invention relates to a water-based emulsion and a preparation method thereof, a coating composition and a product, the water-based emulsion comprises polymer particles with a core-shell structure, the core of the polymer particles is obtained by copolymerizing a monomer mixture I, and the shell of the polymer particles is obtained by copolymerizing a monomer mixture II, the monomer mixture I and the monomer mixture II each independently comprise: a) a C1-C20 alkyl (meth) acrylate; b) a vinyl aromatic compound optionally having up to 20 carbon atoms; c) an ethylenically unsaturated monomer having an acid functional group; and d) optionally a hydroxy C1-C20 alkyl (meth) acrylate; wherein the ethylenically unsaturated monomer having an acid functional group comprises a phosphoric acid-functionalized, carboxylic acid-functionalized or sulfonic acid-functionalized monomer and an unsaturated, radically polymerizable compound having a phosphate group or a phosphonate group or a sulfonate group; wherein the amount of ethylenically unsaturated monomers having acid functional groups is in the range of 0.04 to 3.5 wt%, based on the total weight of monomer mixture II.

Description

Technical Field

[0001] The present invention relates to an aqueous emulsion and a preparation method thereof, and a coating composition comprising the aqueous emulsion. The present invention also relates to a product comprising the aqueous emulsion or the coating composition. Background Art

[0002] In recent years, as people have become more concerned about the environment, many countries have enacted environmental laws and require further reductions in the amount of VOCs that coating compositions (particularly solvent-based coating compositions) are allowed to release into the air.

[0003] Therefore, with the enhancement of people's environmental awareness and the improvement of environmental regulations, water-based paints have received more and more attention. Water-based paints are a heterogeneous multi-interface mixture. In mature paint formulas, in addition to water-based emulsions as film-forming substances, there are also various additives and powders (powder additives). The wetting and dispersion between them is a very complex dynamic process, and eventually tends to a metastable state. In this complex dynamic process, the wetting of powders is very important. Poor powder wetting will lead to excessive fineness or paint gel.

[0004] Therefore, there is still a need in the coatings industry for a polymer emulsion that is suitable for use in waterborne coating compositions and that helps to wet powders. Summary of the invention

[0005] The first aspect of the present invention provides an aqueous emulsion comprising polymer particles having a core-shell structure, wherein the core of the polymer particles is obtained by copolymerization of a monomer mixture I, and the shell of the polymer particles is obtained by copolymerization of a monomer mixture II, and the monomer mixture I and the monomer mixture II each independently comprise:

[0006] a) (meth)acrylic acid C1-C20 alkyl ester;

[0007] b) vinylaromatic compounds, optionally having up to 20 carbon atoms;

[0008] c) ethylenically unsaturated monomers having acid functionality; and

[0009] d) optionally hydroxy C1-C20 alkyl (meth)acrylate;

[0010] The ethylenically unsaturated monomers having acid functional groups include phosphate-functionalized, carboxylic acid-functionalized or sulfonic acid-functionalized monomers and unsaturated, free-radically polymerizable compounds having phosphate groups, phosphonate groups or sulfonate groups, preferably include one or more of acrylic acid, methacrylic acid, crotonic acid, fumaric acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, α-linolenic acid and 10-hydroxy-2-decenoic acid, more preferably include one or more of acrylic acid, methacrylic acid, itaconic acid, α-linolenic acid and 10-hydroxy-2-decenoic acid;

[0011] Wherein, based on the total weight of the monomer mixture II, the amount of the ethylenically unsaturated monomer having an acid functional group in the monomer mixture II is in the range of 0.04 wt % to 0.5 wt %.

[0012] A second aspect of the present invention provides a method for preparing an aqueous emulsion, characterized in that the method comprises:

[0013] 1) a pre-emulsification step to obtain pre-emulsion liquid I and pre-emulsion liquid II,

[0014] wherein the pre-emulsion I is prepared by mixing at least one emulsifier with water and then adding the monomer mixture I;

[0015] wherein the pre-emulsion II is prepared by mixing at least one emulsifier with water and then adding the monomer mixture II;

[0016] 2) polymerization: (i) mixing the pre-emulsion I and at least one initiator to carry out a polymerization reaction; and (ii) adding the pre-emulsion II to the pre-emulsion I and the at least one initiator to carry out a polymerization reaction,

[0017] The monomer mixture I and monomer mixture II each independently comprise:

[0018] a) (meth)acrylic acid C1-C20 alkyl ester;

[0019] b) vinylaromatic compounds, optionally having up to 20 carbon atoms;

[0020] c) ethylenically unsaturated monomers having acid functionality; and

[0021] d) optionally hydroxy C1-C20 alkyl (meth)acrylate;

[0022] The ethylenically unsaturated monomers having acid functional groups include phosphate-functionalized, carboxylic acid-functionalized or phosphoric acid-functionalized monomers and unsaturated, free-radically polymerizable compounds having phosphate groups, phosphonate groups or sulfonate groups, preferably including one or more of acrylic acid, methacrylic acid, crotonic acid, fumaric acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, α-linolenic acid and 10-hydroxy-2-decenoic acid, more preferably including one or more of acrylic acid, methacrylic acid, itaconic acid, α-linolenic acid and 10-hydroxy-2-decenoic acid;

[0023] Wherein, based on the total weight of the monomer mixture II, the amount of the ethylenically unsaturated monomer having an acid functional group in the monomer mixture II is in the range of 0.04 wt % to 0.5 wt %.

[0024] A third aspect of the present invention provides an aqueous coating composition, characterized in that the coating composition comprises: a) the aqueous emulsion described herein, and b) at least one powder additive.

[0025] A fourth aspect of the present invention provides an article, characterized in that the article comprises: a substrate having at least one major surface; and the aqueous coating composition described herein coated on at least one major surface of the substrate.

[0026] The inventors surprisingly found that the aqueous emulsion of the present invention introduces one or more Lewis acids into its shell layer. These Lewis acids contain highly polar anchoring groups such as -COOH and sulfonic acid groups. These groups are grafted onto the main chain of the polymer, thereby improving the binding force between the polymer and the powder particles, thereby promoting the wetting and dispersion of the powder. In addition, the adhesion of the emulsion to the substrate is enhanced, and the encapsulation ability of the powder is improved.

[0027] In addition, the aqueous emulsion of the present invention can further improve the scrub resistance and provide excellent comprehensive performance in terms of water resistance, alcohol resistance, stain resistance and durability.

[0028] The above summary of the present invention is not intended to describe each disclosed embodiment or every implementation of the present invention. Illustrative embodiments are more particularly exemplified in the following description. DETAILED DESCRIPTION

[0029] definition

[0030] As used herein, "a", "an", "the", "at least one" and "one or more" and the absence of quantifiers may be used interchangeably unless otherwise indicated. Thus, for example, a coating composition comprising "an" additive may be interpreted to mean that the coating composition comprises "one or more" additives. Unless otherwise indicated herein, the use of the singular form herein is intended to include the plural form.

[0031] Unless otherwise expressly stated, the use of the terms "comprising", "including", "containing", "having" should generally be interpreted as open-ended and non-restrictive. For example, where a composition is described as comprising or including specific components, it is contemplated that optional components not covered by the present invention are not excluded from the composition, and it is contemplated that the composition can be composed of or consist of the components involved, or where a method is described as comprising or including specific process steps, it is contemplated that optional process steps not covered by the present invention are not excluded from the method, and it is contemplated that the method can be composed of or consist of the process steps involved.

[0032] For simplicity, only some numerical ranges are explicitly disclosed herein. However, any lower limit can be combined with any upper limit to form an unambiguous range; and any lower limit can be combined with other lower limits to form an unambiguous range, and any upper limit can be combined with any other upper limit to form an unambiguous range. In addition, although not explicitly stated, each point or single value between the range endpoints is included in the range. Thus, each point or single value can be combined with any other point or single value as its own lower limit or upper limit or with other lower limits or upper limits to form an unambiguous range.

[0033] Unless otherwise indicated, each point or single value between the endpoints of a range is included in the range. For example, a range of 1 to 5 includes the values ​​1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc. Moreover, a disclosed numerical range includes all subset ranges within the broader range, for example, a range of 1 to 5 includes subranges 1 to 4, 1.5 to 4.5, 1 to 2, etc. Thus, each point or single value can be combined as a lower limit or upper limit with any other point or single value or with other lower limits or upper limits, and the resulting range belongs to the content explicitly disclosed in this application.

[0034] As used herein, the term "or" is inclusive. That is, the phrase "A or (or) B" means "A, B, or both A and B", which may also be abbreviated as "A and / or B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist). In contrast, the exclusive "or (or)" is represented herein, for example, by terms such as "either A or B" and "one of A or B".

[0035] Unless otherwise specified, the term "emulsion" refers to a liquid polymer or a polymer dissolved in an organic solvent to form a solution emulsified in water with an emulsifier to form an emulsion, usually with a larger average particle size (eg, 0.1 to 1 μm) and an opaque appearance.

[0036] In the context of the present invention, the term "monomer mixture" refers to a mixture consisting of reactive monomers, excluding solvents that do not participate in the reaction.

[0037] Unless otherwise stated, reference to a "(meth)acrylate" compound is meant to include both acrylate compounds and methacrylate compounds.

[0038] "Powder (or powder additive)" herein means an additive in powder form.

[0039] The term "pigment volume concentration (PVC)" as used herein refers to the percentage of the volume of the coloring pigment and the extender pigment (i.e., non-binder solids) in the coating composition to the total volume of all non-volatile components (polymers, coloring pigments and extenders) present in the coating composition. PVC reflects the volume relationship of the pigments and polymer particles in the coating film. In the case where the binder solids (polymers) and the non-binder solids contain multiple components, it is assumed that ideal mixing and all volumes are added. In short, according to the present invention, the pigment volume concentration (PVC) can be expressed by the following formula:

[0040]

[0041] It is well known that the volume of a substance can be determined by the ratio of its mass to its density. In the present invention, the volume of each pigment filler is determined by the ratio of the mass of these solid particles to their density, and the volume of the pigment filler is the sum of the volumes of the solid particles of each pigment filler. Similarly, the volume of the polymer particles is determined by the ratio of the mass of the solid part in the aqueous emulsion to the density of the polymer particles, assuming that the density of the polymer particles is 1 g / cm 3 .

[0042] When used in the context of a "coating applied to a surface or substrate," the term "on" includes coatings applied directly or indirectly to a surface or substrate. Thus, for example, a coating applied to a primer layer on a substrate is counted as a coating applied to the substrate.

[0043] The terms "preferred" and "preferably" refer to embodiments of the present invention that may provide certain benefits under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. In addition, the recitation of one or more preferred embodiments does not mean that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the present invention.

[0044] Water-based emulsion

[0045] The aqueous emulsion according to the first aspect of the present invention comprises polymer particles having a core-shell structure, characterized in that the core of the polymer particles is obtained by copolymerization of a monomer mixture I, and the shell of the polymer particles is obtained by copolymerization of a monomer mixture II, and the monomer mixture I and the monomer mixture II each independently comprise:

[0046] a) (meth)acrylic acid C1-C20 alkyl ester;

[0047] b) vinylaromatic compounds, optionally having up to 20 carbon atoms;

[0048] c) ethylenically unsaturated monomers having acid functionality; and

[0049] d) optionally hydroxy C1-C20 alkyl (meth)acrylate;

[0050] The ethylenically unsaturated monomers having acid functional groups include phosphate-functionalized, carboxylic acid-functionalized or sulfonic acid-functionalized monomers and unsaturated, free-radically polymerizable compounds having phosphate groups, phosphonate groups or sulfonate groups, preferably include one or more of acrylic acid, methacrylic acid, crotonic acid, fumaric acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, α-linolenic acid and 10-hydroxy-2-decenoic acid, more preferably include one or more of acrylic acid, methacrylic acid, itaconic acid, α-linolenic acid and 10-hydroxy-2-decenoic acid;

[0051] Wherein, based on the total weight of the monomer mixture II, the amount of the ethylenically unsaturated monomer having an acid functional group in the monomer mixture II is in the range of 0.04 wt % to 0.5 wt %.

[0052] In the context of the present invention, the term "(meth)acrylate" refers to acrylate, methacrylate and mixtures of the two. Examples of suitable C1-C20 alkyl methacrylates for use in the present invention include, but are not limited to, methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, 2-methyloctyl methacrylate, 2-tert-butylheptyl methacrylate, 3-isopropylheptyl methacrylate, decyl methacrylate, undecyl methacrylate, 5-methylundecyl methacrylate, dodec ... 2-methyldodecyl methacrylate, tridecyl methacrylate, 5-methyltridecyl methacrylate, tetradecyl methacrylate, pentadecyl methacrylate, hexadecyl methacrylate, 2-methylhexadecyl methacrylate, heptadecyl methacrylate, 5-isopropylheptadecyl methacrylate, 5-ethyloctadecyl methacrylate, octadecyl methacrylate, nonadecyl methacrylate, eicosyl methacrylate, cycloalkyl methacrylates (e.g. cyclopentyl methacrylate, cyclohexyl methacrylate, 3-vinyl-2-butylcyclohexyl methacrylate, cycloheptyl methacrylate, cyclooctyl methacrylate), bornyl methacrylate and isobornyl methacrylate. Preferred are methyl methacrylate, ethyl methacrylate, butyl methacrylate or tert-butyl methacrylate, and particularly preferred are methyl methacrylate, tert-butyl methacrylate or butyl methacrylate.

[0053] Examples of suitable C1-C20 alkyl acrylates for use in the present invention include, but are not limited to, methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, sec-butyl acrylate, tert-butyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 2-octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, 2-methyl-octyl acrylate, 2-tert-butylheptyl acrylate, 3-isopropylheptyl acrylate, decyl acrylate, undecyl acrylate, 5-methylundecyl acrylate, dodec ... Methyl dodecyl acrylate, tridecyl acrylate, 5-methyl tridecyl acrylate, tetradecyl acrylate, pentadecyl acrylate, hexadecyl acrylate, 2-methyl hexadecyl acrylate, heptadecyl acrylate, 5-isopropyl heptadecyl acrylate, 5-ethyl octadecyl acrylate, octadecyl acrylate, nonadecyl acrylate, eicosyl acrylate, cycloalkyl acrylates such as cyclopentyl acrylate, cyclohexyl acrylate, 3-vinyl-2-butylcyclohexyl acrylate, cycloheptyl acrylate, cyclooctyl acrylate, bornyl acrylate and isobornyl acrylate. Preferred are ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate or cyclohexyl acrylate, and particularly preferred are ethyl acrylate, n-butyl acrylate or 2-ethylhexyl acrylate.

[0054] In some embodiments, the amount of component a) (meth)acrylate C1-C20 alkyl ester in monomer mixture I is in the range of 35 wt % to 75 wt % based on the total weight of monomer mixture I. For example, the amount of component a) in monomer mixture I can be about 35 wt %, 40 wt %, 45 wt %, 50 wt %, 55 wt %, 60 wt %, 65 wt %, 70 wt % or 75 wt % based on the total weight of monomer mixture I.

[0055] In some embodiments, the amount of component a) (meth) acrylic acid C1-C20 alkyl ester in monomer mixture II is in the range of 35 wt % to 99 wt % based on the total weight of monomer mixture II. For example, the amount of component a) in monomer mixture II can be about 35 wt %, 45 wt %, 55 wt %, 65 wt %, 75 wt %, 85 wt %, 95 wt %, 98 wt % or 99 wt % based on the total weight of monomer mixture II.

[0056] Examples of suitable vinyl aromatic compounds b) having up to 20 carbon atoms include, but are not limited to, styrene, vinyltoluene, o-methylstyrene, p-methylstyrene, methylstyrene, α-butylstyrene, 4-n-butylstyrene, 4-n-decylstyrene, halogenated styrenes (e.g. monochlorostyrene, dichlorostyrene, tribromostyrene or tetrabromostyrene). Styrene and methylstyrene are preferred.

[0057] In some embodiments, the amount of component b) of the vinyl aromatic compound having up to 20 carbon atoms in the monomer mixture I is in the range of 0 wt % to 20 wt % based on the total weight of the monomer mixture I. For example, the amount of component b) in the monomer mixture I can be about 0 wt %, 5 wt %, 10 wt %, 15 wt %, 18 wt % or 20 wt % based on the total weight of the monomer mixture I.

[0058] In some embodiments, the amount of component b) of the vinyl aromatic compound having up to 20 carbon atoms in the monomer mixture II is in the range of 0 wt % to 35 wt % based on the total weight of the monomer mixture II. For example, the amount of component b) in the monomer mixture II can be about 0 wt %, 5 wt %, 15 wt %, 20 wt %, 25 wt %, 30 wt % or 35 wt % based on the total weight of the monomer mixture II.

[0059] Examples of suitable ethylenically unsaturated monomers c) having acid functional groups include, but are not limited to, phosphate functionalized or carboxylic acid functionalized monomers, preferably carboxylic acid functionalized monomers such as acrylic acid, methacrylic acid, crotonic acid, fumaric acid, maleic acid, itaconic acid, α-linolenic acid, 10-hydroxy-2-decenoic acid, and monoalkyl esters or anhydrides of dibasic acids (e.g., monoalkyl maleates). Particularly preferred are one or more of acrylic acid, methacrylic acid, itaconic acid, α-linolenic acid, and 10-hydroxy-2-decenoic acid.

[0060] Likewise suitable as compounds of component c) are unsaturated, free-radically polymerizable compounds having phosphate or phosphonate groups or sulfonic acid or sulfonate groups, as described, for example, in WO 00 / 39181 (page 8, line 13 to page 9, line 19).

[0061] Therefore, preferred ethylenically unsaturated monomers c) having an acid functionality include one or more of acrylic acid, methacrylic acid, crotonic acid, fumaric acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, α-linolenic acid and 10-hydroxy-2-decenoic acid, and more preferably include one or more of acrylic acid, methacrylic acid, itaconic acid, α-linolenic acid and 10-hydroxy-2-decenoic acid.

[0062] In some embodiments, the amount of component c) an ethylenically unsaturated monomer having an acid functional group in the monomer mixture I is in the range of 5 wt % to 35 wt % based on the total weight of the monomer mixture I. For example, the amount of component c) in the monomer mixture I can be about 5 wt %, 10 wt %, 15 wt %, 20 wt %, 25 wt %, 30 wt % or 35 wt % based on the total weight of the monomer mixture I.

[0063] In some embodiments, based on the total weight of monomer mixture II, the amount of component c) ethylenically unsaturated monomers having acid functional groups in monomer mixture II is in the range of 0.05 wt % to 0.5 wt %. For example, based on the total weight of monomer mixture II, the amount of component c) in monomer mixture II can be about 0.05 wt %, 0.1 wt %, 0.1 wt %, 0.15 wt %, 0.2 wt %, 0.25 wt %, 0.3 wt %, 0.35 wt %, 0.4 wt %, 0.45 wt % or 0.5 wt %.

[0064] In some embodiments, monomer mixture II contains itaconic acid or itaconic anhydride or 10-hydroxy-2-decenoic acid or α-linolenic acid, and the amount of itaconic acid or itaconic anhydride or 10-hydroxy-2-decenoic acid or α-linolenic acid in monomer mixture II is in the range of 0.04 wt % to 0.5 wt % based on the total weight of monomer mixture II.

[0065] Examples of suitable (meth) hydroxy C1-C20 alkyl esters of acrylic acid include, but are not limited to, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate or hydroxybutyl acrylate. Preferably, the (meth) hydroxy C1-C20 alkyl ester of acrylic acid includes one or more of hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate and hydroxybutyl (meth) acrylate.

[0066] In some embodiments, the amount of component d) (meth) hydroxy C1-C20 alkyl acrylate in the monomer mixture I is in the range of 5 wt % to 35 wt % based on the total weight of the monomer mixture I. For example, the amount of component d) in the monomer mixture I can be about 5 wt %, 10 wt %, 15 wt %, 20 wt %, 25 wt %, 30 wt % or 35 wt % based on the total weight of the monomer mixture I.

[0067] In some embodiments, based on the total weight of monomer mixture II, the amount of component d) (meth) hydroxy C1-C20 alkyl acrylate in monomer mixture II is in the range of 0 wt % to 30 wt %. For example, based on the total weight of monomer mixture II, the amount of component d) in monomer mixture II can be about 0 wt %, 5 wt %, 10 wt %, 15 wt %, 18 wt %, 20 wt %, 25 wt % or 30 wt %.

[0068] In some embodiments, based on the total weight of monomer mixture I, the monomer mixture I includes: 35-75 wt % of component a), 0-20 wt % of component b), 5-35 wt % of component c), and 5-35 wt % of component d), based on the total weight of the monomer mixture I.

[0069] In some embodiments, based on the total weight of the monomer mixture II, the monomer mixture II includes: 35-99 wt % of component a), 0-35 wt % of component b), 0.04 wt % to 0.5 wt % of component c), and 0-30 wt % of component d).

[0070] In the present invention, the amount of the ethylenically unsaturated monomer having an acid functional group is controlled, so that in some embodiments, the carboxyl content of the polymer particles having a core-shell structure is 0.2% to 2.5% by weight.

[0071] The weight ratio of monomer mixture I to monomer mixture II is 1:9-9:1, preferably 1:6-2:1. For example, the weight ratio of monomer mixture I to monomer mixture II can be about 1:9, 1:8, 1:7, 1:6, 1:5, 1:4, 1:3, 1:2, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1. The inventors have found that by using the weight ratio within the above range, very excellent coating performance can be obtained.

[0072] In the aqueous emulsions described herein, the acid value of the polymer particles having a core-shell structure is in the range of 5-120 mg KOH / g. For example, the acid value of the polymer particles can be about 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110 or 120 mg KOH / g resin. The acid value is measured by ISO 2114 titration.

[0073] In some embodiments, the average particle size of the polymer particles is 50 to 300 nm, preferably 60 to 150 nm. For example, the average particle size of the polymer particles can be about 60 nm, 80 nm, 100 nm, 120 nm, or 140 nm. The size can be measured by the Z-average particle size known in the art, which refers to the particle size measured by dynamic light scattering, such as using a Marvlen Zetasizer 3000HS microscopic particle size analyzer.

[0074] The inventors surprisingly found that the aqueous emulsion of the present invention introduces a specific amount of one or more Lewis acids in its shell layer. These Lewis acids contain highly polar anchoring groups such as -COOH and sulfonic acid groups. These groups will be grafted onto the main chain of the polymer, thereby improving the binding force between the emulsion and the powder particles, thereby promoting the wetting and dispersion of the powder. In addition, the adhesion of the emulsion to the substrate is enhanced, and the encapsulation ability of the powder is improved.

[0075] Preparation of aqueous emulsion

[0076] A second aspect of the present invention provides a method for preparing an aqueous emulsion. The method comprises:

[0077] 1) a pre-emulsification step to obtain pre-emulsion liquid I and pre-emulsion liquid II,

[0078] wherein the pre-emulsion I is prepared by mixing at least one emulsifier with water and then adding the monomer mixture I;

[0079] wherein the pre-emulsion II is prepared by mixing at least one emulsifier with water and then adding the monomer mixture II;

[0080] 2) polymerization: (i) mixing the pre-emulsion I and at least one initiator to carry out a polymerization reaction; and (ii) adding the pre-emulsion II to the pre-emulsion I and at least one initiator to carry out a polymerization reaction,

[0081] Wherein the monomer mixture I and monomer mixture II each independently comprise:

[0082] a) (meth)acrylic acid C1-C20 alkyl ester;

[0083] b) vinylaromatic compounds, optionally having up to 20 carbon atoms;

[0084] c) ethylenically unsaturated monomers having acid functionality; and

[0085] d) optionally hydroxy C1-C20 alkyl (meth)acrylate;

[0086] The ethylenically unsaturated monomers having acid functional groups include phosphate functionalized or carboxylic acid functionalized monomers and unsaturated, free radical polymerizable compounds having phosphate groups or phosphonate groups or sulfonic acid groups or sulfonate groups, preferably include one or more of acrylic acid, methacrylic acid, crotonic acid, fumaric acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, α-linolenic acid and 10-hydroxy-2-decenoic acid, more preferably include one or more of acrylic acid, methacrylic acid, itaconic acid, α-linolenic acid and 10-hydroxy-2-decenoic acid;

[0087] Wherein, based on the total weight of the monomer mixture II, the amount of the ethylenically unsaturated monomer having an acid functional group in the monomer mixture II is in the range of 0.04 wt % to 0.5 wt %.

[0088] The emulsion polymerization technology for preparing aqueous emulsions from ethylenically unsaturated monomers is well known in the polymer field, and any conventional emulsion polymerization process can be used, such as a single-stage polymerization process, a multi-stage polymerization process, a continuous process, etc. It is well known that aqueous emulsions can be prepared using a seed polymerization process in order to control the structure and composition of the polymer particles contained in the aqueous emulsion.

[0089] In an exemplary embodiment of the present invention, the aqueous emulsion is prepared as follows: i) under the action of a suitable emulsifier, a monomer mixture for forming a polymer core is dispersed in water into an emulsion, and then the prepared emulsion is added dropwise to a polymerization reactor containing an initiator for polymerization, thereby forming a seed emulsion as the polymer core; ii) then in the presence of the above-mentioned seed emulsion and optionally in the presence of a suitable emulsifier, another monomer mixture for forming a polymer shell is further emulsion polymerized to form polymer particles having a core-shell structure.

[0090] The dispersion of the above-mentioned polymerizable monomers can be completed with the assistance of any suitable emulsifier. In some embodiments, at least one emulsifier is one or more of anionic emulsifiers and nonionic emulsifiers. For example, some surfactants suitable for emulsion polymerization are disclosed in McCutcheon's Detergents and Emulsifers (MC Publishing Co., Glen Rock, NJ). Other types of stabilizing agents, such as protective colloids, can also be used. Preferably, a combination of anionic emulsifiers and nonionic surfactants is used. Anionic surfactants include aliphatic carboxylates, aliphatic sulfonates, aliphatic sulfates and aliphatic phosphates. Preferably, alkali metals, such as Na, K or Li, or alkaline earth metal salts, such as Ca or Ba, are used. In a specific embodiment, aliphatic sulfonates are used, preferably dodecyl sulfonic acid alkali metal salts, more preferably dodecylbenzene sulfonate. In a specific embodiment, sodium dodecylbenzene sulfonate (e.g., Rhodacal DS-10) is used. Nonionic surfactants include alkylphenol polyoxyethylene ethers, fatty alcohol polyoxyethylene ethers or aliphatic phosphates. Preferably, alkylphenol polyoxyethylene ether or aliphatic phosphate ester is used. In a specific embodiment, aliphatic phosphate ester (such as RHODAFAC RS-610) is used.

[0091] Any known free radical initiator can be used to initiate the polymerization reaction. Examples of available initiators include initiators that thermally decompose at the polymerization temperature to generate free radicals. Examples include water-soluble and water-insoluble initiators. Examples of initiators that generate free radicals include persulfates, such as ammonium persulfate or alkali metal persulfates (including potassium, sodium or lithium); peroxides, such as cumene hydroperoxide, tert-butyl hydroperoxide, di-tert-butyl peroxide, dioctyl peroxide, tert-butyl pervalerate, tert-butyl perisononanoate, tert-butyl peroctanoate, tert-butyl perneodecanoate, di(2-ethylhexyl) peroxydicarbonate, di(isotridecyl) peroxydicarbonate; azo compounds, such as azobis(isobutyronitrile) and azobis(4-cyanovaleric acid); and conventional redox systems. Preferably, water-soluble initiator persulfates are used. More specifically, ammonium persulfate or sodium persulfate are used as free radical initiators.

[0092] In some embodiments, the at least one initiator is one or more of potassium persulfate, sodium persulfate, ammonium persulfate, potassium persulfate-sodium bisulfite, sodium persulfate-sodium bisulfite, ammonium persulfate-sodium bisulfite, and tert-butyl hydroperoxide-formaldehyde sodium bisulfite.

[0093] According to the present invention, during the preparation of the aqueous emulsion, a chain transfer agent is optionally added, wherein the chain transfer agent is selected from isopropanol, a halogenated compound, a linear or branched C4-C 22One or more of alkyl mercaptan, mercaptoalkanoic acid and mercaptoalkanoic acid alkyl ester, preferably a linear or branched C4-C 22 Alkyl mercaptan, more preferably one or more of n-dodecyl mercaptan and tert-dodecyl mercaptan.

[0094] According to the present invention, during the preparation of the aqueous emulsion, a redox initiation system is used to further polymerize the remaining monomer mixture. The redox initiation system comprises a second initiator, a reducing agent and optionally a metal catalyst.

[0095] Examples of the second initiator include, but are not limited to, peroxides such as hydrogen peroxide, sodium peroxide, potassium peroxide, tert-butyl hydroperoxide, tert-amyl hydroperoxide and cumyl hydroperoxide; persulfates such as ammonium persulfate, potassium persulfate, sodium persulfate; perborates; and one or more of perphosphates; preferably peroxides, more preferably one or more of hydrogen peroxide, tert-butyl hydroperoxide, tert-amyl hydroperoxide and cumyl hydroperoxide.

[0096] Examples of the reducing agent include, but are not limited to, one or more of sodium formaldehyde sulfoxylate, sodium sulfite, sodium bisulfite, sodium thiosulfate, sodium sulfide, sodium hydrosulfide, sodium pyrosulfite, sodium dithionite, formamidinesulfinic acid, hydroxymethanesulfonic acid, acetone bisulfite, ethanolamine, glycolic acid, hydrated glyoxylic acid, ascorbic acid, isoascorbic acid, lactic acid, malic acid, 2-hydroxy-2-sulfinyl acetic acid, tartaric acid, and salts of the acids; preferably one or more of sodium pyrosulfite, ascorbic acid, and isoascorbic acid.

[0097] The metal catalyst is selected from one or more of iron, copper, manganese, silver, platinum, vanadium, nickel, chromium, palladium and cobalt catalysts, preferably an iron catalyst.

[0098] In the preparation process of the aqueous emulsion of the present invention, the amount of emulsifier and initiator and the reaction conditions such as reaction temperature, stirring speed, etc. can be determined by those skilled in the art based on experience. Preferably, the pre-emulsification process of the monomer mixture is carried out at a stirring speed of 2000rpm or higher, preferably at a stirring speed of 4000rpm or higher. Preferably, the reaction temperature is maintained below 100°C throughout the reaction process, more preferably the reaction temperature is 30-95°C, and most preferably 50-90°C. In addition, the polymerization reaction is preferably carried out at a pH of 4-8.

[0099] Unless expressly indicated otherwise, what is described in the context of aqueous emulsions also applies to the preparation of aqueous emulsions.

[0100] Waterborne coating composition

[0101] A third aspect of the present invention provides an aqueous coating composition, characterized in that the aqueous coating composition comprises: A) the aqueous emulsion described herein, and B) at least one powder additive.

[0102] The term "filler" as used herein refers to any volume extender suitable for coatings, which may be organic or inorganic, for example in the form of particles. There are no particular restrictions on the shape of the particles, which may have any suitable shape. The average particle size of the filler may vary over a wide range, for example, in the range of about 10 nanometers to about 5 microns. Some fillers, in addition to acting as volume extenders for coatings, also impart one or more desired properties to the composition and / or the coating formed by the composition. For example, some fillers may impart the desired color to the composition and the coating obtained by the composition. In this case, this filler is also referred to as a "pigment". Some fillers may improve chemical and / or physical properties, particularly the mechanical properties of the coating obtained by the composition. In this case, this filler is also referred to as a "reinforcing filler". In the present invention, pigments and fillers are collectively referred to as pigments and fillers.

[0103] In some embodiments, the at least one powder additive comprises one or more of titanium dioxide, matting agent, and pigments and fillers.

[0104] In some embodiments of the present invention, the pigments and fillers are selected from one or more of copper chrome black, zinc flakes, mica powder, talcum powder, ceramic powder, quartz powder, barite powder, and glass powder. The pigments and fillers may constitute about 1 wt % to about 40 wt % of the aqueous coating composition, more preferably about 3 wt % to about 35 wt % of the aqueous coating composition.

[0105] In the water-based coating composition according to the present invention, conventional additives may also be included, and these additives will not adversely affect the water-based coating composition or the cured coating obtained therefrom. Suitable additives include, for example, those reagents that can improve the processing properties or manufacturing properties of the composition, enhance the aesthetic feeling of the composition, improve the coating composition or the specific functional properties or characteristics (such as adhesion to substrate) of the cured composition obtained therefrom, or reduce costs. The additive that may be included is, for example, a film-forming aid, a wetting agent, a plasticizer, a defoamer, a coloring agent, an antioxidant, a flow control agent, a thixotropic agent, a dispersant, an adhesion promoter, a thickener, a pH adjusting agent, a solvent, a cross-linking agent, or a combination thereof. The content of each optional component is enough to play its intended purpose, but preferably, such content will not adversely affect the water-based coating composition or the cured coating obtained therefrom. In some preferred embodiments, the water-based coating composition may include a defoamer, a film-forming aid, a wetting agent, a dispersant, or any combination thereof as conventional additives. According to the present invention, the total amount of these conventional additives is 0.1 wt % to about 30 wt % relative to the gross weight of the water-based composition.

[0106] As examples of film-forming aids, alcohols such as ethylene glycol, propylene glycol, hexylene glycol, benzyl alcohol, etc. can be used; alcohol esters such as dodecyl alcohol ester; alcohol ethers such as ethylene glycol butyl ether, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol n-propyl ether, propylene glycol butyl ether, dipropylene glycol methyl ether, dipropylene glycol propyl ether, dipropylene glycol butyl ether, tripropylene glycol n-butyl ether, etc. can be used; alcohol ether esters such as hexylene glycol butyl ether acetate, etc. As an example of a defoamer, BYK 028 available from BYK can be used. As an example of a wetting agent, BYK 348 available from BYK can be used. As an example of a dispersant, BYK-190 can be used.

[0107] The aqueous emulsion according to the present invention has good film-forming properties and only requires a small amount of film-forming aids to form a film, which greatly reduces the VOC content in the coating, making the coating more environmentally friendly. The inventors surprisingly found that the aqueous emulsion of the present invention helps to wet the powder, and the emulsion has very good wettability for various powders (including titanium dioxide, matting powder, and pigments and fillers), thereby greatly reducing the demand for dispersants and wetting agents in the coating composition.

[0108] The inventors speculate that the possible reason is that the aqueous emulsion according to the present invention introduces a specific amount of one or more Lewis acids into its shell layer. These Lewis acids contain highly polar anchoring groups such as -COOH and sulfonic acid groups. These groups will be grafted onto the main chain of the polymer, thereby improving the binding force with the powder particles, thereby promoting the wetting and dispersion of the powder. In addition, the adhesion of the emulsion to the substrate is enhanced, and the encapsulation ability of the powder is improved, thereby reducing the demand for dispersants and wetting agents; or when the same amount of dispersants and wetting agents is used, more powder can be included.

[0109] The inventors surprisingly found that the aqueous emulsion according to the present invention can be used alone or in combination with a crosslinking agent capable of crosslinking therewith.

[0110] Thus, the aqueous coating composition according to the invention may optionally comprise at least one crosslinking agent.

[0111] In the waterborne coating composition according to the present invention, the crosslinking agent is optional. Required crosslinking agent can be selected according to practical application requirements. In some embodiments of the present invention, the limiting examples of crosslinking agent include amino resin crosslinking agent. Amino resin resin refers to the condensation product of aldehydes (such as formaldehyde, acetaldehyde, crotonaldehyde and benzaldehyde) and amino or amide-containing substances (such as urea, melamine and benzoguanamine). The example of suitable amino plastic resin includes but is not limited to melamine-formaldehyde resin, benzoguanamine-formaldehyde resin, urea-formaldehyde resin. The condensation product of other amines and amides can also be used, such as triazine, diazines, triazoles, guanidines, guanamines and alkyl-substituted and aryl-substituted melamine aldehyde condensates. Some examples of such compounds are N,N′-dimethylurea, benzourea, dicyandiamide, methylguanidine, ethylguanidine, glycoluril, ammeline, 2-chloro-4,6-diamino-1,3,5-triazine, 6-methyl-2,4-diamino-1,3,5-triazine, 3,5-diaminotriazole, triaminopyrimidine, 2-mercapto-4,6-diaminopyrimidine, 3,4,6-tris(ethylamino)-1,3,5-triazine, etc. Although the aldehyde used is usually formaldehyde, other aldehydes such as acetaldehyde, crotonaldehyde, acrolein, benzaldehyde, furfural, glyoxal, etc., and mixtures thereof may also be used. According to the present invention, melamine-formaldehyde crosslinking agent, benzoguanamine-formaldehyde crosslinking agent, glycoluril-formaldehyde crosslinking agent or a combination thereof may be used as the amino resin crosslinking agent. Amino resin cross-linking agents are commercially available, and non-limiting examples of suitable commercially available amino resin cross-linking agents include Cymel 303LF, Cymel 1123, Cyeml 1170, and the like from Cytec.

[0112] The amount of crosslinking agent may depend on various factors, including for example the type of crosslinking agent, the time and temperature of baking, the molecular weight of polymer and required coating properties. The crosslinking agent is usually present in an amount of at most 50 wt %, preferably at most 30 wt %, more preferably at most 15 wt %, and even more preferably at most 5 wt %. If used, the crosslinking agent is usually present in an amount of at least 0.1 wt %, more preferably at least 1 wt %, even more preferably at least 1.5 wt %. These weight percentages are all based on the gross weight of the waterborne coating composition.

[0113] In a specific embodiment of the present invention, the aqueous coating composition according to the present invention comprises, relative to the weight of the aqueous coating composition, 30-85 wt % of the aqueous emulsion according to the present invention; 5-15 wt % of a powder additive; 0-15 wt % of a crosslinking agent; and 0-20 wt % of other additional additives selected from one or more of a film-forming aid, a defoaming agent, a dispersant, a wetting agent and a thickener.

[0114] According to the present invention, the aqueous coating composition can be prepared as follows: before application, the aqueous emulsion is simply mixed with a powder additive and optionally other additives in a predetermined weight ratio in a mixing device. The mixed coating composition can be applied using various methods familiar to those skilled in the art, including spraying (e.g., air-assisted, airless or electrostatic spraying), brushing, roller coating, overflow coating and dipping. In one embodiment of the invention, the mixed coating composition is applied by spraying. The coating composition can be coated with various wet film thicknesses. In an embodiment of the invention, the wet film thickness preferably provides a dry film thickness of about 13 to about 260 μm, and more preferably about 25 to about 150 μm. It can be cured by air-drying the applied coating or by accelerating curing using various drying devices familiar to those skilled in the art (e.g., oven).

[0115] Products

[0116] A fourth aspect of the present invention provides an article comprising: a substrate having at least one major surface; and an aqueous emulsion or aqueous coating composition as described herein coated on at least one major surface of the substrate. After curing, a coating is formed by the aqueous emulsion or aqueous coating composition on at least one major surface of the substrate.

[0117] In certain embodiments of the present invention, the aqueous coating composition of the present invention can be used in conjunction with a primer. In this case, the article of the present invention comprises a substrate, a primer layer and a coating layer formed by the coating composition of the present invention.

[0118] In other embodiments of the present invention, the aqueous coating composition of the present invention can be applied without a primer and directly coated on the major surface of the substrate.

[0119] A person of ordinary skill in the art will select and determine a suitable material as a substrate according to actual needs. The substrate includes a wooden substrate, a plastic substrate, a glass substrate, a ceramic substrate, a polymer composite material or a metal substrate. The substrate can be a non-thermosensitive substrate, such as glass, ceramic, fiber, cement board or metal (such as aluminum, copper or steel), or a thermosensitive substrate. Suitable thermosensitive substrates include wooden substrates, such as solid wood, such as hardwood, cork, plywood; veneer, particle board, low-density fiberboard, medium-density fiberboard and high-density fiberboard, OSB (oriented structural board), wooden laminate, chipboard and other substrates in which wood is an important component, such as a wooden substrate coated with metal foil, composite wood flooring, plastic-modified wood, plastic substrate or wood-plastic composite (WPC); a substrate with cellulose fibers, such as cardboard or paper substrate.

[0120] As the wooden substrate for making wood products, any suitable wooden substrate known in the art can be used. In the present application, the term "wood substrate" refers to any cellulose / lignin material of hard, fibrous structural organization in the stem and root of trees or other woody plants. Timber includes, for example, hardwood and softwood timber directly cut from trees, and engineered wood composites made of wood strips, wood chips, wood fibers or wood veneers. The example of wood composites includes but is not limited to plywood, oriented strand board (OSB), medium density fiberboard (MDF), particle board, etc. As exemplary wooden substrate, one or more of hardwood, chestnut, oak, red hook chestnut, oil tea, eucalyptus, Douglas fir, Japanese cedar, American cypress, Japanese red pine, Japanese cypress, water walnut, black walnut, maple, Japanese beech, Japanese paulownia, birch, sal, magnolia, ash, teak, oak, catalpa, mountain camphor, fir, oak, rubber wood can be used.

[0121] According to certain embodiments of the present invention, the substrate has at least one, preferably two, major surfaces that are opposite to each other.

[0122] According to certain embodiments of the present invention, the articles thus obtained can be used in the following applications, including, but not limited to: household furniture, such as tables, chairs, cabinets, etc.; bedroom and bathroom furniture; office furniture; custom furniture, such as school and children's furniture, hospital furniture, restaurant and hotel furniture, kitchen cabinets and furniture; panels for interior design; indoor and outdoor windows and doors; indoor and outdoor window frames and door frames; outdoor and indoor wainscoting and wood flooring.

[0123] The inventors of the present invention surprisingly found that, compared with commercially available aqueous acrylic emulsions, the coating formed by the aqueous emulsion of the present invention has particularly excellent scrub resistance, can provide excellent comprehensive performance in terms of water resistance, alcohol resistance, stain resistance and durability, and reduces the use of dispersants or wetting agents in the coating composition, thereby lowering the cost.

[0124] Example

[0125] The following examples more specifically describe the disclosure of the present invention, which are intended for illustrative purposes only, as it will be apparent to those skilled in the art that various modifications and variations will be made within the scope of the disclosure. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on weight. Moreover, all reagents used in the examples are commercially available and can be used directly without further processing.

[0126] Test Method

[0127] Wettability

[0128] The powder material is placed in a tubular container whose lower end is sealed with a microporous plate, and the powder material is pressed tightly; the tubular container is placed vertically so that its lower end contacts the emulsion, so that the emulsion infiltrates part of the powder layer, and the height and time of the emulsion infiltrating the powder layer are measured; according to the formula h 2 / t=crγ1cosθ / 2η to calculate the wetting contact angle of the powder material in the liquid, where

[0129] h: liquid wetting height, cm;

[0130] t: wetting time, s;

[0131] cr: constant, customized for the system of the same powder material;

[0132] γ1: surface tension of liquid, dyn / cm;

[0133] θ: wetting contact angle of powder material, °;

[0134] η: Viscosity of the liquid, Pa.s.

[0135] Pencil hardness

[0136] This test is used to measure the hardness of a cured coating. ASTM D3363 is used to assess pencil hardness. Data is reported as the pencil hardness of the last successful test before the coating broke. Thus, for example, if a coating does not break when tested with a 2H pencil, but breaks when tested with a 3H pencil, the coating is reported as having a pencil hardness of 2H.

[0137] Adhesion

[0138] Adhesion testing is performed to evaluate whether the coating adheres to the coated substrate. The adhesion test is performed according to ASTM D 3359 - Test Method B. Adhesion is generally rated on a scale of 0-5B, with 5B indicating the best adhesion.

[0139] Chemical resistance testing

[0140] According to ASTM F2250-Test Method B, resistance to solvents (such as ethanol, coffee, red wine, etc.) is tested to evaluate the "curing" or cross-linking of the coating. Finally, the integrity of the coating is determined. Chemical resistance is usually rated from 0 to 5, where 5 = coating is intact, no stains, no delamination (best), 4 = coating stains are barely noticeable, 3 = coating stains can be clearly identified, 2 = coating discoloration and partial delamination, 0 = coating peeling off (worst).

[0141] Example 1: Preparation of aqueous emulsion

[0142] The following steps were used to prepare the aqueous emulsion:

[0143] 1) Pre-emulsification

[0144] At normal temperature and pressure, an emulsifier and water are added into a reaction kettle and stirred to dissolve, and the temperature is raised to 80° C. and maintained at this temperature; then a monomer mixture I containing methyl methacrylate, n-butyl acrylate, itaconic acid and hydroxyethyl methacrylate is added and stirred to prepare a pre-emulsion I.

[0145] At room temperature and pressure, an emulsifier and water are added into a reaction kettle and stirred to dissolve, and then a monomer mixture II containing hydroxyethyl methacrylate, methyl methacrylate, n-butyl acrylate and 10-hydroxy-2-decenoic acid is added in sequence and stirred to prepare a pre-emulsion II.

[0146] 2) Aggregation

[0147] Mixing sodium persulfate with water to obtain an initiator (1); Mixing sodium persulfate with water to obtain an initiator (2);

[0148] Pre-emulsion I and initiator (1) were added into the reactor together. After the reactor reached the highest temperature 10 minutes later, pre-emulsion II and initiator (2) were added dropwise. After the addition was completed, the reactor was kept warm at 80°C for 30 min, 84°C for 50 min, 86°C for 50 min, and 90°C for 50 min.

[0149] 3) Post-processing

[0150] After the above steps are completed, the temperature is lowered to 60°C, and a redox initiator consisting of tert-butyl hydroperoxide, water, a reducing agent (Bruggolite FF6) and sodium pyrophosphite is added dropwise within 30 minutes. Then, the temperature is lowered to 45°C, stirred, and filtered.

[0151] The obtained aqueous emulsion contained polymer particles having a core-shell structure, the polymer particles having an acid value of 10 mg KOH / g and an average particle diameter of 120 nm.

[0152] Example 2-3

[0153] In Example 2, Example 1 was repeated, but 10-hydroxy-2-decenoic acid in the pre-emulsion II was replaced with α-linolenic acid, and the resulting polymer particles had an acid value of 10 mg KOH / g and an average particle size of 123 nm.

[0154] In Example 3, Example 1 was repeated, but 10-hydroxy-2-decenoic acid in the pre-emulsion II was replaced with itaconic acid, and the obtained polymer particles had an acid value of 10 mg KOH / g and an average particle size of 117 nm.

[0155] Comparative Examples 1-4

[0156] In Comparative Example 1-2, a commercially available acrylic emulsion was used instead of the aqueous emulsion in Example 1.

[0157] In Comparative Example 3, Example 1 was repeated, but n-butyl acrylate was used to replace 10-hydroxy-2-decenoic acid in the pre-emulsion II.

[0158] In Comparative Example 4, Example 1 was repeated, but the amount of 10-hydroxy-2-decenoic acid in the pre-emulsion II was changed.

[0159] According to the above steps and the formulations shown in Table 1, seven aqueous emulsions of Examples 1-3 and Comparative Examples 1-4 were obtained respectively.

[0160] Table 1

[0161]

[0162] Preparation of waterborne coating compositions and preparation of articles with coatings

[0163] The aqueous emulsions of Examples 1 and 2 and the aqueous latex of Comparative Example 1 prepared above were respectively formulated into white topcoats with a PVC content of about 8%.

[0164] The obtained white topcoat was applied on the GAL panels coated with epoxy acrylic primer, with a dry film thickness (DFT) of 30-36 μm and a curing temperature of 110-130°C.

[0165] The corresponding properties were measured and the results are summarized in Table 2 below.

[0166] Table 2

[0167]

[0168] The results of Tables 1 and 2 show that the aqueous emulsion of the present invention exhibits very excellent performance in wettability to powder, so when preparing an aqueous coating composition, the amount of wetting agent or dispersant used can be reduced under the same PVC condition. In addition, the technical solution of the present invention exhibits excellent scrub resistance.

[0169] Although the present invention is described with reference to a large number of embodiments and examples, it will be appreciated by those skilled in the art that other embodiments may be designed based on the content disclosed in the present invention. It will be readily apparent to those skilled in the art that changes may be made to the present application without departing from the principles disclosed in the foregoing specification. For example, without departing from the principles disclosed in the foregoing specification, a plurality of features or preferred embodiments described herein may be combined, and the resulting technical solutions should be understood to belong to the content recorded herein. Unless otherwise specified in the claims, such changes are deemed to be included in the claims. Accordingly, the embodiments described in detail herein are merely exemplary and are not intended to limit the scope of the present application, which is the full scope of the attached claims and any and all equivalents thereof.

Claims

1. An aqueous emulsion comprising polymer particles having a core-shell structure, characterized in that: The core of the polymer particle is obtained by copolymerization of a monomer mixture I, and the shell of the polymer particle is obtained by copolymerization of a monomer mixture II, wherein the monomer mixture I and the monomer mixture II each independently comprise: a) (meth)acrylate C1-C20 alkyl ester; b) vinylaromatic compounds, optionally having up to 20 carbon atoms; c) ethylenically unsaturated monomers having acid functionality; and d) optionally hydroxy C1-C20 alkyl (meth)acrylate; The ethylenically unsaturated monomers having acid functional groups include phosphoric acid functionalized, carboxylic acid functionalized or sulfonic acid functionalized monomers and unsaturated, free radical polymerizable compounds having phosphate groups, phosphonate groups or sulfonate groups, preferably include one or more of acrylic acid, methacrylic acid, crotonic acid, fumaric acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, α-linolenic acid and 10-hydroxy-2-decenoic acid, more preferably include one or more of acrylic acid, methacrylic acid, itaconic acid, α-linolenic acid and 10-hydroxy-2-decenoic acid; Wherein, based on the total weight of the monomer mixture II, the amount of the ethylenically unsaturated monomer having an acid functional group in the monomer mixture II is in the range of 0.04 wt % to 0.5 wt %.

2. The aqueous emulsion according to claim 1, characterized in that The polymer particles having a core-shell structure have a carboxyl content of 0.2% to 2.5% by weight.

3. The aqueous emulsion according to claim 1 or 2, characterized in that The vinyl aromatic compound having up to 20 carbon atoms includes one or more of styrene, vinyltoluene, o-methylstyrene, methylstyrene, p-methylstyrene, α-butylstyrene, 4-n-butylstyrene, 4-n-decylstyrene, and halogenated styrene, preferably styrene.

4. The aqueous emulsion according to any one of claims 1 to 3, characterized in that The C1-C20 alkyl (meth)acrylate includes methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, 2-methyloctyl (meth)acrylate, 2-tert-butylheptyl (meth)acrylate, 3-isopropylheptyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, 5-methylundecyl (meth)acrylate, dodecyl (meth)acrylate, 2-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, 2-methyloctyl (meth)acrylate, 2-tert-butylheptyl (meth)acrylate, 3-isopropylheptyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, 5-methylundecyl (meth)acrylate, dodecyl (meth)acrylate, One or more of 2-methyldodecyl (meth)acrylate, tridecyl (meth)acrylate, 5-methyltridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, 2-methylhexadecyl (meth)acrylate, heptadecyl (meth)acrylate, 5-isopropylheptadecyl (meth)acrylate, 5-ethyloctadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate, cycloalkyl (meth)acrylate, bornyl (meth)acrylate and isobornyl (meth)acrylate, preferably one or more of methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate and tert-butyl (meth)acrylate.

5. The aqueous emulsion according to any one of claims 1 to 4, characterized in that The hydroxy C1-C20 alkyl (meth)acrylate includes one or more of hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate and hydroxybutyl (meth)acrylate.

6. The aqueous emulsion according to any one of claims 1 to 5, characterized in that Wherein, the amount of itaconic acid or itaconic anhydride or 10-hydroxy-2-decenoic acid or α-linolenic acid in the monomer mixture II is in the range of 0.04 wt % to 0.5 wt % based on the total weight of the monomer mixture II.

7. The aqueous emulsion according to any one of claims 1 to 6, characterized in that The acid value of the core-shell polymer particles is in the range of 5-120 mg KOH / g.

8. The aqueous emulsion according to any one of claims 1 to 7, characterized in that Based on the total weight of the monomer mixture I, the monomer mixture I comprises: 35-75 wt % of component a), 0-20 wt % of component b), 5-35 wt % of component c), and 5-35 wt % of component d).

9. The aqueous emulsion according to any one of claims 1 to 8, characterized in that Based on the total weight of the monomer mixture II, the monomer mixture II includes: 35-99 wt% of component a), 0-35 wt% of component b), 0.04 wt% to 0.5 wt% of component c), and 0-30 wt% of component d).

10. The aqueous emulsion according to any one of claims 1 to 9, characterized in that The weight ratio of the monomer mixture I to the monomer mixture II is 1:9 to 9:

1.

11. The aqueous emulsion according to any one of claims 1 to 10, characterized in that The average particle size of the polymer particles is 50 to 300 nm, preferably 60 to 150 nm.

12. A method for preparing an aqueous emulsion according to any one of claims 1 to 11, characterized in that The method comprises: 1) a pre-emulsification step to obtain pre-emulsion liquid I and pre-emulsion liquid II, wherein the pre-emulsion I is prepared by mixing at least one emulsifier with water and then adding the monomer mixture I; wherein the pre-emulsion II is prepared by mixing at least one emulsifier with water and then adding the monomer mixture II; 2) Polymerization: (i) mixing the pre-emulsion I and at least one initiator to carry out a polymerization reaction; and (ii) adding the pre-emulsion II to the pre-emulsion I and the at least one initiator to carry out a polymerization reaction.

13. The method according to claim 12, characterized in that The at least one emulsifier is one or more of an anionic emulsifier and a nonionic emulsifier, or The at least one initiator is one or more of potassium persulfate, sodium persulfate, ammonium persulfate, potassium persulfate-sodium bisulfite, sodium persulfate-sodium bisulfite, ammonium persulfate-sodium bisulfite and tert-butyl hydroperoxide-formaldehyde sodium bisulfite.

14. A water-based coating composition, characterized in that: The coating composition comprises: a) an aqueous emulsion according to any one of claims 1 to 11 or prepared by the process of claim 12 or 13, and b) at least one powdered additive.

15. The water-based coating composition according to claim 14, characterized in that: The at least one powder additive comprises one or more of titanium dioxide, matting agent, and pigments and fillers.

16. A product, characterized in that The product comprises: a substrate having at least one major surface; and An aqueous emulsion according to any one of claims 1 to 11 or prepared by the method of claim 12 or 13 or an aqueous coating composition according to any one of claims 14 to 15 coated on the at least one major surface of the substrate.

17. The article of claim 16, wherein: The substrate includes a wood substrate, a plastic substrate, a glass substrate, a ceramic substrate, a polymer composite material or a metal substrate.

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