Water-based hydroxyl acrylate polymer microsphere emulsion, coating containing emulsion and preparation method of water-based hydroxyl acrylate polymer microsphere emulsion

Abstract

The invention belongs to the technical field of water-based coatings, and relates to a water-based hydroxyl acrylate polymer microsphere emulsion, a microsphere comprises a core layer and a shell layer structure, the core layer comprises a core layer monomer, and the core layer monomer comprises 1-10% by mass of an epoxy group polymerizable unsaturated monomer; the shell layer comprises a shell layer monomer, and the shell layer monomer comprises the following components in percentage by mass: 0-10% of monoolefinic unsaturated polycarboxylic acid and 0-35% of lactone modified (methyl) hydroxyl acrylate. An epoxy group polymerizable unsaturated monomer is introduced into a core layer for modification, the cohesive force of polymer particles is improved, the hardness and the adhesive force of the coating are improved, monoolefinic unsaturated polycarboxylic acid and lactone modified (methyl) hydroxyalkyl acrylate are introduced into a shell layer, carboxyl on the surface of the polymer microsphere reacts with an epoxy group, and the coating is formed. The hydroxyl functional groups form weak interaction, the cohesive force of polymer particles is further increased, the hardness and the impact resistance of the polymer are improved, and meanwhile, the flexibility of the polymer is improved through a lactone modified (methyl) hydroxyalkyl acrylate long-chain structure.

Description

Technical Field

[0001] The present application relates to the technical field of water-based coatings, and in particular to a water-based hydroxy acrylate polymer microsphere emulsion, a coating containing the emulsion, and a preparation method thereof. Background Art

[0002] Waterborne (hydroxy) acrylic resin has become one of the research hotspots in the field of waterborne industrial coatings due to its excellent weather resistance, decorative and mechanical properties, and is widely used in the fields of corrosion protection and weather resistance. Waterborne (hydroxy) acrylic resin is often used in combination with isocyanate curing agent to prepare waterborne two-component polyurethane coating (2K-WPU). The cured paint film has the characteristics of both acrylic and polyurethane, with excellent performance and outstanding resistance. Among them, the waterborne hydroxy acrylic emulsion in waterborne hydroxy acrylic resin has received widespread attention due to its characteristics such as fast drying speed and low volatile organic compounds (VOC), and is used in many fields, such as the preparation of waterborne two-component polyurethane coatings.

[0003] The performance of water-based two-component polyurethane coatings is directly related to the hydroxyl content of the hydroxylated acrylic emulsion. The higher the hydroxyl content of the hydroxylated acrylic emulsion, the more sites that react with the isocyanate curing agent and the higher the cross-linking density. The hardness, scratch resistance and other properties of the resulting paint film are also improved accordingly. However, at the same time, the flexibility and impact resistance of the paint film will decrease, making it difficult to achieve a balance in performance, which limits the application of water-based hydroxylated acrylic resins. Summary of the Invention

[0004] Based on this, the present application provides a water-based hydroxyacrylate polymer microsphere emulsion and a coating containing the emulsion and a preparation method thereof. The present application introduces an epoxy-based polymerizable unsaturated monomer into the core layer of the polymer microsphere for modification. The epoxy group can increase the cohesion of the polymer particles and improve the hardness and adhesion of the coating. Further, after introducing a monoethylenically unsaturated polycarboxylic acid and a lactone-modified (meth) hydroxyalkyl acrylate into the shell layer, the carboxyl groups on the surface of the polymer microspheres react with the epoxy groups and form a weak interaction with the hydroxyl functional groups, further increasing the cohesion of the polymer particles and improving the hardness and impact resistance of the polymer. At the same time, the long-chain structure of the lactone-modified (meth) hydroxyalkyl acrylate increases the flexibility of the polymer.

[0005] According to the first aspect of the present application, the present application provides an aqueous hydroxy acrylate polymer microsphere emulsion, wherein the polymer microsphere includes a core layer and a shell layer structure, the core layer includes a core layer monomer, and the core layer monomer includes an epoxy-based polymerizable unsaturated monomer; the shell layer includes a shell layer monomer, and the shell layer monomer includes a monoethylenically unsaturated polycarboxylic acid and a lactone-modified (meth) hydroxy acrylate; based on the total mass of the core layer monomer, the mass percentage of the epoxy-based polymerizable unsaturated monomer in the core layer monomer is 1-10%; based on the total mass of the shell layer monomer, the mass percentage of the monoethylenically unsaturated polycarboxylic acid in the shell layer monomer is 0-10%, and the mass percentage of the lactone-modified (meth) hydroxy acrylate in the shell layer monomer is 0-35%.

[0006] An epoxy-based polymerizable unsaturated monomer is introduced into the core layer of the microparticles for modification. The addition of epoxy groups can improve the cohesion and adhesion of the polymer particles, thereby improving the hardness, adhesion and other properties of the coating. After further introducing monoethylenically unsaturated polycarboxylic acids and lactone-modified (meth) hydroxyalkyl acrylates into the shell layer of the microparticles to modify the shell layer, the carboxyl groups on the surface of the microsphere particles react with the epoxy groups and form weak interactions with the hydroxyl functional groups, further increasing the cohesion of the polymer particles, thereby improving the hardness and impact resistance of the polymer. At the same time, the long-chain structure of the lactone-modified (meth) hydroxyalkyl acrylate increases the flexibility of the polymer.

[0007] In some embodiments, the core layer monomers further comprise an ester of an α,β-monoethylenically unsaturated monocarboxylic acid, a vinyl aromatic compound, and a hydroxyalkyl (meth)acrylate; based on the total mass of the core layer monomers, the mass percentage of the ester of the α,β-monoethylenically unsaturated monocarboxylic acid in the core layer monomers is 30-50%, the mass percentage of the vinyl aromatic compound in the core layer monomers is 30-45%, and the mass percentage of the hydroxyalkyl (meth)acrylate in the core layer monomers is 15-25%;

[0008] The shell monomers further include esters of α,β-monoethylenically unsaturated monocarboxylic acids, vinyl aromatic compounds, and hydroxyalkyl (meth)acrylates; based on the total mass of the shell monomers, the mass percentage of the esters of α,β-monoethylenically unsaturated monocarboxylic acids in the shell monomers is 30-50%, the mass percentage of the vinyl aromatic compounds in the shell monomers is 25-40%, and the mass percentage of the hydroxyalkyl (meth)acrylates in the shell monomers is 15-25%.

[0009] In some embodiments, the aqueous hydroxy acrylate polymer microsphere emulsion comprises the following components: water, a mixed emulsifier, a core layer pre-emulsion, an initiator aqueous solution, and a shell layer pre-emulsion;

[0010] The mixed emulsifier includes an anionic emulsifier and a nonionic emulsifier, and the weight ratio of the anionic emulsifier to the nonionic emulsifier is 1:(1-3); such as 1:1, 1:2, 1:3, etc.;

[0011] The core layer pre-emulsion comprises the following components: core layer monomer, mixed emulsifier and water; the core layer monomer comprises the following components in parts by weight:

[0012] 30-50 parts of an ester of an α,β-monoethylenically unsaturated monocarboxylic acid; such as 30 parts, 35 parts, 40 parts, 42 parts, 45 parts, 48 ​​parts, 50 parts, etc.;

[0013] 30-45 parts of vinyl aromatic compound; such as 30 parts, 35 parts, 40 parts, 42 parts, 45 parts, etc.;

[0014] 15-25 parts of hydroxyalkyl (meth)acrylate; such as 15 parts, 18 parts, 20 parts, 26 parts, 25 parts, etc.;

[0015] 1-10 parts of epoxy polymerizable unsaturated monomers; such as 1 part, 2 parts, 5 parts, 8 parts, 10 parts, etc.;

[0016] The shell pre-emulsion comprises the following components: shell monomer, water, and mixed emulsifier; the shell monomer comprises the following components in parts by weight:

[0017] 0-10 parts of monoethylenically unsaturated polycarboxylic acid; such as 0 parts, 3 parts, 5 parts, 8 parts, 10 parts, etc.;

[0018] 30-50 parts of ester of α,β-monoethylenically unsaturated monocarboxylic acid; such as 30 parts, 35 parts, 40 parts, 42 parts, 45 parts, 48 ​​parts, 50 parts, etc.;

[0019] 25-40 parts of vinyl aromatic compound; such as 25 parts, 28 parts, 30 parts, 32 parts, 35 parts, 38 parts, 40 parts, etc.;

[0020] 15-25 parts of hydroxyalkyl (meth)acrylate; such as 15 parts, 12 parts, 13 parts, 18 parts, 20 parts, 23 parts, 35 parts, etc.;

[0021] 0-35 parts of lactone-modified (meth)acrylate hydroxy ester, such as 0 parts, 5 parts, 10 parts, 15 parts, 20 parts, 25 parts, 35 parts, etc.

[0022] In some embodiments, the weight ratio of the anionic emulsifier to the nonionic emulsifier is 1:(1.5-2.5); such as 1:1.5, 1:2, 1:2.5, etc.

[0023] In some embodiments, the initiator aqueous solution is an ammonium persulfate aqueous solution, and the concentration of the initiator aqueous solution is 2-15%, such as 2%, 4%, 6%, 8%, 10%, 12%, 13%, 14%, 15%, etc.

[0024] In some embodiments, the concentration of the initiator aqueous solution is 4-10%, such as 4%, 6%, 8%, 10%, etc.

[0025] In some embodiments, the ester of an α,β-monoethylenically unsaturated monocarboxylic acid comprises an ester obtained by reacting an α,β-monoethylenically unsaturated monocarboxylic acid with a C1-C10 alkanol.

[0026] In some embodiments, the ester of α,β-monoethylenically unsaturated monocarboxylic acid includes an ester obtained by reacting (meth)acrylic acid with a C1-C10 alkanol.

[0027] In some embodiments, the ester of the α,β-monoethylenically unsaturated monocarboxylic acid comprises at least one of methyl (meth)acrylate, methyl ethyl acrylate, ethyl (meth)acrylate, ethyl ethyl acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, tert-butyl ethyl acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, n-decyl (meth)acrylate, isooctyl (meth)acrylate, and glycidyl (meth)acrylate.

[0028] In some embodiments, the vinyl aromatic compound is at least one of styrene, 2-methylstyrene, 4-methylstyrene, 2-butylstyrene, 4-butylstyrene, or 4-decylstyrene.

[0029] In some embodiments, the hydroxyalkyl (meth)acrylate is at least one of hydroxyethyl methacrylate and hydroxypropyl methacrylate.

[0030] In some embodiments, the epoxy polymerizable unsaturated monomer is at least one of glycidyl (meth)acrylate and an alicyclic epoxy-containing monomer.

[0031] In some embodiments, the monoethylenically unsaturated polycarboxylic acid is at least one of fumaric acid, maleic acid, itaconic acid, or salts, anhydrides, and mixtures thereof.

[0032] In some embodiments, the lactone-modified (meth)acrylate hydroxy ester has the following structure:

[0033]

[0034] Wherein, R is -H or -CH3, n is 2, 3 or 4, m is a natural number of 1-8, and g is a natural number of 1-6. Specifically, the lactone-modified (meth)acrylate is at least one of caprolactone-modified hydroxypropyl methacrylate, caprolactone-modified hydroxypropyl acrylate, caprolactone-modified hydroxyethyl methacrylate, caprolactone-modified hydroxyethyl acrylate, caprolactone-modified hydroxybutyl acrylate, caprolactone-modified hydroxybutyl methacrylate, caprolactone-modified hydroxyhexyl acrylate and caprolactone-modified hydroxyhexyl methacrylate.

[0035] In some embodiments, the anionic emulsifier is an organic sodium acid, including at least one of sodium lauryl sulfate, sodium dodecylbenzene sulfonate, sodium dodecyl diphenyl ether disulfonate, sodium styrene sulfonate, or sodium stearate.

[0036] In some embodiments, the nonionic emulsifier is an isomeric alcohol polyoxyethylene ether with the structural formula RO-(CH2CH2O) n -H, where R satisfies C m H 2m+1 In the general formula, m is 8, 10, 11 or 13; n is 3, 5, 6, 7, 8, 10 or 12.

[0037] On the other hand, the present application provides a method for preparing the above-mentioned aqueous hydroxy acrylate polymer microsphere emulsion, comprising the following steps:

[0038] Step 1: Prepare nuclear layer pre-emulsion

[0039] (1.1) Preparing a core layer monomer: mixing the vinyl aromatic compound styrene, an ester of an α,β-monoethylenically unsaturated monocarboxylic acid such as methyl methacrylate, butyl acrylate, a hydroxyalkyl (meth)acrylate, hydroxyethyl methacrylate, and an epoxy-based polymerizable unsaturated monomer to obtain a core layer monomer;

[0040] (1.2) Preparing a core layer pre-emulsion: mixing the core layer monomer prepared above with a mixed emulsifier and water to prepare a core layer pre-emulsion;

[0041] Step 2: Prepare shell pre-emulsion

[0042] (2.1) Preparing a shell monomer: mixing the vinyl aromatic compound, an ester of an α,β-monoethylenically unsaturated monocarboxylic acid, a hydroxyalkyl (meth)acrylate, a monoethylenically unsaturated polycarboxylic acid, and a lactone-modified hydroxyl (meth)acrylate to obtain a shell monomer;

[0043] (2.2) Preparing a shell pre-emulsion: mixing the shell monomer prepared above, water, and a mixed emulsifier to obtain a shell pre-emulsion;

[0044] Step 3: Preparation of water-based hydroxy acrylate polymer microsphere emulsion by emulsion polymerization

[0045] Mix water and mixed emulsifier to obtain kettle bottom material, heat it to 75-85℃, such as 75℃, 78℃, 80℃, 83℃, 85℃, etc., then add 5-15% of the core layer pre-emulsion and the initiator aqueous solution to the kettle bottom material, such as adding 5%, 8%, 10%, 13%, 15% and so on of the core layer pre-emulsion, keep warm for 15-45min, such as keeping warm for 15min, 18min, 20min, 22min, 25min, 28min, 30min, 33min, 35min, 38min, 40min, 42min, 45min, etc., then add the remaining core layer pre-emulsion and keep warm for 15-60mi n, such as keeping warm for 15min, 18min, 20min, 22min, 25min, 28min, 30min, 33min, 35min, 38min, 40min, 42min, 45min, 50min, 55min, 60min, etc., then add the initiator aqueous solution dropwise, stir at constant temperature for 0.5-1.5h, such as stirring for 0.5h, 0.8h, 1h, 1.2h, 1.5h, etc., then cool to below 50°C, add a neutralizer to adjust the pH to 6-8, such as pH 6, 6.5, 7, 7.5, 8, etc., and then filter to obtain a water-based hydroxy acrylate polymer microsphere emulsion.

[0046] In one embodiment, the neutralizing agent includes at least one of ammonia, sodium hydroxide, N,N-dimethylethanolamine or triethylamine.

[0047] On the other hand, the present application provides a water-based two-component polyurethane coating, comprising any one of the water-based hydroxy acrylate polymer microsphere emulsions described above.

[0048] In one embodiment, the water-based two-component polyurethane coating comprises the following components in parts by weight:

[0049] 30-40 parts of water-based hydroxy acrylate emulsion; such as 30 parts, 23 parts, 25 parts, 28 parts, 40 parts, etc.;

[0050] 2.5-4.5 parts of water; such as 2.5 parts, 2.8 parts, 3.0 parts, 3.2 parts, 3.5 parts, 4.0 parts, 4.5 parts, etc.;

[0051] 20-40 parts of titanium dioxide slurry; such as 20 parts, 23 parts, 35 parts, 38 parts, 40 parts, etc.;

[0052] 3-5 parts of film-forming aid; such as 3 parts, 3.3 parts, 3.5 parts, 3.8 parts, 4.0 parts, 4.5 parts, 5.0 parts, etc.;

[0053] Wetting agent 0.1-0.3 parts; such as 0.1 parts, 0.2 parts, 0.25 parts, 0.28 parts, 0.3 parts, etc.;

[0054] Thickener 0.2-0.4 parts, such as 0.2 parts, 0.25 parts, 0.35 parts, 0.38 parts, 0.4 parts, etc.

[0055] On the other hand, the present application provides a method for preparing the water-based two-component polyurethane coating, comprising the following steps:

[0056] S1. Preparing a base emulsion: mixing a water-based hydroxy acrylate emulsion, water, titanium dioxide slurry, a film-forming aid, a wetting agent, and a thickener to obtain a base emulsion;

[0057] S1. Prepare a water-based two-component polyurethane coating: add a hydrophilic modified isocyanate curing agent to the base emulsion under stirring, wherein the ratio of the hydroxyl group in the base emulsion to the isocyanate group in the hydrophilic modified isocyanate curing agent is 1:1.1-1.5, such as 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, etc., to obtain a water-based two-component polyurethane coating.

[0058] This application has at least one of the following beneficial effects:

[0059] By introducing an epoxy-based polymerizable unsaturated monomer into the core layer of the microparticles for modification, the addition of the epoxy group can improve the cohesion and adhesion of the polymer particles, thereby improving the hardness, adhesion and other properties of the coating. After further introducing a monoethylenically unsaturated polycarboxylic acid and a lactone-modified (meth) hydroxyalkyl acrylate into the shell layer of the microparticles to modify the shell layer, the carboxyl groups on the surface of the microsphere particles react with the epoxy groups and form weak interactions with the hydroxyl functional groups, further increasing the cohesion of the polymer particles, thereby improving the hardness and impact resistance and other properties of the polymer. At the same time, the long-chain structure of the lactone-modified (meth) hydroxyalkyl acrylate improves the flexibility of the polymer. DETAILED DESCRIPTION

[0060] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0061] As used herein, the terms "about," "approximately," or "substantially" are used to describe and illustrate small variations. When used in conjunction with an event or circumstance, the terms may refer to instances where the event or circumstance occurred precisely as well as instances where the event or circumstance occurred very approximately. For example, when used in conjunction with a numerical value, the terms may refer to a range of variation of less than or equal to ±10% of the numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%.

[0062] In addition, amounts, ratios, and other numerical values ​​are sometimes presented herein in a range format. It should be understood that such a range format is used for convenience and brevity and should be interpreted flexibly to include not only the values ​​explicitly specified as limits of the range, but also all individual values ​​or sub-ranges encompassed within the range, as if each value and sub-range were explicitly specified.

[0063] In the detailed description and claims, a list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C.

[0064] Hereinafter, the present application will be described in more detail through specific examples and comparative examples.

[0065] Example 1

[0066] A method for preparing a water-based hydroxyacrylate polymer microsphere emulsion, wherein the polymer microspheres include a core layer and a shell layer structure, and the preparation method comprises the following steps:

[0067] Step 1: Prepare nuclear layer pre-emulsion

[0068] (1.1) Preparation of core layer monomers: 38.3 g of styrene (vinyl aromatic compound), 23.4 g of methyl methacrylate (ester of α,β-monoethylenically unsaturated monocarboxylic acid), 15.1 g of butyl acrylate (ester of α,β-monoethylenically unsaturated monocarboxylic acid), 19.2 g of hydroxyethyl methacrylate (hydroxyalkyl (meth)acrylate), and 4 g of glycidyl methacrylate (epoxy-polymerizable unsaturated monomer) were mixed to obtain core layer monomers;

[0069] (1.2) Preparing a core layer pre-emulsion: The core layer monomers and mixed emulsifier I prepared above were dispersed with 100 g of deionized water using a shearing machine at 800 rpm for 10 min. After dispersion and mixing, a core layer pre-emulsion was prepared;

[0070] Among them, mixed emulsifier I was prepared by mixing 1.5g of anionic emulsifier sodium lauryl sulfate (anionic surfactant, also known as SDS) and 3g of nonionic emulsifier BASF Lutensol FT TO10 (a nonionic surfactant, the main component of which is polyoxyethylene ether);

[0071] Step 2: Prepare shell pre-emulsion

[0072] (2.1) Preparation of Shell Monomers: 38.3 g of styrene (vinyl aromatic compound), 27.4 g of methyl methacrylate (ester of α,β-monoethylenically unsaturated monocarboxylic acid), 19.2 g of hydroxyethyl methacrylate (hydroxyalkyl (meth)acrylate), and 15.1 g of butyl acrylate (ester of α,β-monoethylenically unsaturated monocarboxylic acid) were mixed to obtain shell monomers.

[0073] (2.2) Preparing a shell pre-emulsion: The shell monomer prepared above, 100 g of deionized water, and mixed emulsifier I were dispersed using a shearing machine at 800 rpm for 10 min. After dispersion and mixing, a shell pre-emulsion was obtained.

[0074] Among them, mixed emulsifier I was prepared by mixing 1.5g of sodium dodecyl sulfate (anionic surfactant, also known as SDS) and 3g of BASF Lutensol FT TO10 (a nonionic surfactant, the main component of which is polyoxyethylene ether);

[0075] Step 3: Preparation of water-based hydroxy acrylate polymer microsphere emulsion by emulsion polymerization

[0076] In a reaction kettle equipped with a stirrer, a condenser, and a thermometer, 105 g of deionized water and a mixed emulsifier II were added to obtain a bottom material; when the temperature in the reaction kettle reached 80±2° C., 10% of the core layer pre-emulsion and an initiator aqueous solution I were added to the bottom material, and the mixture was kept warm for 30 minutes. The remaining 90% of the core layer pre-emulsion was then added dropwise for 3 hours. After the addition was complete, the mixture was kept warm for 1 hour, and the shell layer pre-emulsion and the initiator aqueous solution II were then added dropwise. The shell layer pre-emulsion and the initiator aqueous solution II were added simultaneously. After the addition was completed over 3-4 hours, the mixture was stirred at a constant temperature for 0.5-1.5 hours, and then cooled to below 50° C. A neutralizing ammonia solution was added to adjust the pH to 7.0-9.0, and the mixture was filtered through a 200-mesh filter to obtain an aqueous hydroxy acrylate polymer microsphere emulsion;

[0077] Among them, the mixed emulsifier II is prepared by mixing 1g of sodium dodecyl sulfate (SDS) and 2g of BASF Lutensol FT TO10; the initiator aqueous solution I is prepared by mixing 1g of ammonium persulfate and 10g of deionized water; and the initiator aqueous solution II is prepared by mixing 1g of ammonium persulfate and 25g of deionized water.

[0078] In this embodiment, an epoxy-polymerizable unsaturated monomer is introduced into the core layer of the polymer particles to increase the cohesive force of the polymer particles, thereby improving the hardness and adhesion of the polymer.

[0079] Example 2

[0080] A method for preparing an aqueous hydroxyacrylate polymer microsphere emulsion, wherein the polymer microspheres include a core layer and a shell layer structure. The preparation method is based on Example 1, and itaconic acid (a monoethylenically unsaturated polycarboxylic acid) and caprolactone-modified hydroxyethyl methacrylate (lactone-modified hydroxy (meth)acrylate) are added to modify the shell monomer. The method comprises the following steps:

[0081] Step 1: Prepare nuclear layer pre-emulsion

[0082] (1.1) Preparation of core layer monomers: 38.3 g of styrene (vinyl aromatic compound), 23.4 g of methyl methacrylate (ester of α,β-monoethylenically unsaturated monocarboxylic acid), 15.1 g of butyl acrylate (ester of α,β-monoethylenically unsaturated monocarboxylic acid), 19.2 g of hydroxyethyl methacrylate (hydroxyalkyl (meth)acrylate), and 4 g of glycidyl methacrylate (epoxy-polymerizable unsaturated monomer) were mixed to obtain core layer monomers;

[0083] (1.2) Preparation of core layer pre-emulsion: The core layer monomers and mixed emulsifier I prepared above were dispersed with 100 g of deionized water using a shearing machine at 800 rpm for 10 min to prepare a core layer pre-emulsion;

[0084] Among them, mixed emulsifier I was prepared by mixing 1.5g of sodium dodecyl sulfate (anionic surfactant, also known as SDS) and 3g of BASF Lutensol FT TO10 (a nonionic surfactant, the main component of which is polyoxyethylene ether);

[0085] Step 2: Prepare shell pre-emulsion

[0086] (2.1) Preparation of Shell Monomers: 38.3 g of styrene (vinyl aromatic compound), 12 g of methyl methacrylate (ester of α,β-monoethylenically unsaturated monocarboxylic acid), 11.5 g of hydroxyethyl methacrylate (hydroxyalkyl (meth)acrylate), 19.1 g of butyl acrylate (ester of α,β-monoethylenically unsaturated monocarboxylic acid), 6 g of itaconic acid (monoethylenically unsaturated polycarboxylic acid), and 13.5 g of caprolactone-modified hydroxyethyl methacrylate (lactone-modified hydroxy (meth)acrylate) were mixed to obtain shell monomers.

[0087] (2.2) Preparation of shell pre-emulsion: The shell monomer prepared above, 100 g of deionized water, and mixed emulsifier I were dispersed using a shearing machine at 800 rpm for 10 min to obtain a shell pre-emulsion;

[0088] Among them, mixed emulsifier I was prepared by mixing 1.5g of sodium dodecyl sulfate (anionic surfactant, also known as SDS) and 3g of BASF Lutensol FT TO10 (a nonionic surfactant, the main component of which is polyoxyethylene ether);

[0089] Step 3: Preparation of water-based hydroxy acrylate polymer microsphere emulsion by emulsion polymerization

[0090] In a reaction kettle equipped with a stirrer, a condenser, and a thermometer, 105 g of deionized water and a mixed emulsifier II were added to obtain a bottom material; when the temperature in the reaction kettle reached 80±2° C., 10% of the core layer pre-emulsion and an initiator aqueous solution I were added to the bottom material, and the mixture was kept warm for 30 minutes. The remaining 90% of the core layer pre-emulsion was then added dropwise for 3 hours. After the addition was complete, the mixture was kept warm for 1 hour, and the shell layer pre-emulsion and the initiator aqueous solution II were then added dropwise. The shell layer pre-emulsion and the initiator aqueous solution II were added simultaneously. After the addition was completed over 3-4 hours, the mixture was stirred at a constant temperature for 0.5-1.5 hours, and then cooled to below 50° C., sodium hydroxide as a neutralizer was added to adjust the pH to 7.0-9.0, and the mixture was filtered through a 200-mesh filter to obtain an aqueous hydroxy acrylate polymer microsphere emulsion;

[0091] Among them, the mixed emulsifier II was prepared by mixing 1 g of sodium dodecyl sulfate (SDS) and 2 g of BASF Lutensol FT TO10; the initiator aqueous solution I was prepared by mixing 1 g of ammonium persulfate and 10 g of deionized water; and the initiator aqueous solution II was prepared by mixing 1.0 g of ammonium persulfate and 25.0 g of deionized water.

[0092] In this embodiment, monoethylenically unsaturated polycarboxylic acids and lactone-modified (meth) hydroxyalkyl acrylates are introduced into the shell pre-emulsion. The carboxyl groups on the surface of the microsphere particles react with the epoxy groups and form weak interactions with the hydroxyl functional groups, further increasing the cohesion of the polymer particles, thereby improving the hardness and impact resistance of the polymer. At the same time, the long-chain structure of the lactone-modified (meth) hydroxyalkyl acrylate increases the flexibility of the polymer.

[0093] Example 3

[0094] A method for preparing an aqueous hydroxyacrylate polymer microsphere emulsion, wherein the polymer microspheres include a core layer and a shell layer structure. The preparation method is based on Example 2, except that only the amounts of the components of the shell layer monomers are adjusted. Other aspects are consistent with Example 2, and the method comprises the following steps:

[0095] Step 1: Prepare nuclear layer pre-emulsion

[0096] (1.1) Preparation of core layer monomers: 38.3 g of styrene (vinyl aromatic compound), 23.4 g of methyl methacrylate (ester of α,β-monoethylenically unsaturated monocarboxylic acid), 15.1 g of butyl acrylate (ester of α,β-monoethylenically unsaturated monocarboxylic acid), 19.2 g of hydroxyethyl methacrylate (hydroxyalkyl (meth)acrylate), and 4 g of glycidyl methacrylate (epoxy-polymerizable unsaturated monomer) were mixed to obtain core layer monomers;

[0097] (1.2) Preparation of core layer pre-emulsion: The core layer monomers and mixed emulsifier I prepared above were dispersed with 100 g of deionized water using a shearing machine at 800 rpm for 10 min to prepare a core layer pre-emulsion;

[0098] Among them, mixed emulsifier I was prepared by mixing 1.5g of sodium dodecyl sulfate (anionic surfactant, also known as SDS) and 3g of BASF Lutensol FT TO10 (a nonionic surfactant, the main component of which is polyoxyethylene ether);

[0099] Step 2: Prepare shell pre-emulsion

[0100] (2.1) Preparation of Shell Monomers: 38.3 g of styrene (vinyl aromatic compound), 7.8 g of methyl methacrylate (ester of α,β-monoethylenically unsaturated monocarboxylic acid), 3.9 g of hydroxyethyl methacrylate (hydroxyalkyl (meth)acrylate), 17 g of butyl acrylate (ester of α,β-monoethylenically unsaturated monocarboxylic acid), 6 g of itaconic acid (monoethylenically unsaturated polycarboxylic acid), and 27 g of caprolactone-modified hydroxyethyl methacrylate (lactone-modified hydroxy (meth)acrylate) were mixed to obtain shell monomers.

[0101] (2.2) Preparation of shell pre-emulsion: The shell monomer prepared above, 100 g of deionized water, and mixed emulsifier I were dispersed using a shearing machine at 800 rpm for 10 min to obtain a shell pre-emulsion;

[0102] Among them, mixed emulsifier I was prepared by mixing 1.5g of sodium dodecyl sulfate (anionic surfactant, also known as SDS) and 3g of BASF Lutensol FT TO10 (a nonionic surfactant, the main component of which is polyoxyethylene ether);

[0103] Step 3: Preparation of water-based hydroxy acrylate polymer microsphere emulsion by emulsion polymerization

[0104] In a reaction kettle equipped with a stirrer, a condenser, and a thermometer, 105 g of deionized water and a mixed emulsifier II were added to obtain a bottom material; when the temperature in the reaction kettle reached 80±2° C., 10% of the core layer pre-emulsion and an initiator aqueous solution I were added to the bottom material, and the mixture was kept warm for 30 minutes. The remaining 90% of the core layer pre-emulsion was then added dropwise for 3 hours. After the addition was complete, the mixture was kept warm for 1 hour, and the shell layer pre-emulsion and the initiator aqueous solution II were then added dropwise. The shell layer pre-emulsion and the initiator aqueous solution II were added simultaneously. After the addition was completed over 3-4 hours, the mixture was stirred at a constant temperature for 0.5-1.5 hours, and then cooled to below 50° C. The neutralizer N,N-dimethylethanolamine was added to adjust the pH to 7.0-9.0, and the mixture was filtered through a 200-mesh filter to obtain an aqueous hydroxy acrylate polymer microsphere emulsion;

[0105] Among them, the mixed emulsifier II is prepared by mixing 1g of sodium dodecyl sulfate (SDS) and 2g of BASF Lutensol FT TO10; the initiator aqueous solution I is prepared by mixing 1g of ammonium persulfate and 10g of deionized water; and the initiator aqueous solution II is prepared by mixing 1g of ammonium persulfate and 25g of deionized water.

[0106] Example 4

[0107] A method for preparing an aqueous hydroxyacrylate polymer microsphere emulsion, wherein the polymer microspheres include a core layer and a shell layer structure. The preparation method is based on Example 2, except that only the amounts of the components of the shell layer monomers are adjusted. Other aspects are consistent with Example 2, and the method comprises the following steps:

[0108] Step 1: Prepare nuclear layer pre-emulsion

[0109] (1.1) Preparation of core layer monomers: 38.3 g of styrene (vinyl aromatic compound), 23.4 g of methyl methacrylate (ester of α,β-monoethylenically unsaturated monocarboxylic acid), 15.1 g of butyl acrylate (ester of α,β-monoethylenically unsaturated monocarboxylic acid), 19.2 g of hydroxyethyl methacrylate (hydroxyalkyl (meth)acrylate), and 4 g of glycidyl methacrylate (epoxy-polymerizable unsaturated monomer) were mixed to obtain core layer monomers;

[0110] (1.2) Preparation of core layer pre-emulsion: The core layer monomers and mixed emulsifier I prepared above were dispersed with 100 g of deionized water using a shearing machine at 800 rpm for 10 min to prepare a core layer pre-emulsion;

[0111] Among them, mixed emulsifier I was prepared by mixing 1.5g of sodium dodecyl sulfate (anionic surfactant, also known as SDS) and 3g of BASF Lutensol FT TO10 (a nonionic surfactant, the main component of which is polyoxyethylene ether);

[0112] Step 2: Prepare shell pre-emulsion

[0113] (2.1) Preparation of Shell Monomers: 28.9 g of styrene (vinyl aromatic compound), 15.6 g of methyl methacrylate (ester of α,β-monoethylenically unsaturated monocarboxylic acid), 0.9 g of hydroxyethyl methacrylate (hydroxyalkyl (meth)acrylate), 19.1 g of butyl acrylate (ester of α,β-monoethylenically unsaturated monocarboxylic acid), 6 g of itaconic acid (monoethylenically unsaturated polycarboxylic acid), and 32.4 g of caprolactone-modified hydroxyethyl methacrylate (lactone-modified hydroxy (meth)acrylate) were mixed to obtain shell monomers.

[0114] (2.2) Preparation of shell pre-emulsion: The shell monomer prepared above, 100 g of deionized water, and mixed emulsifier I were dispersed using a shearing machine at 800 rpm for 10 min to obtain a shell pre-emulsion;

[0115] Among them, mixed emulsifier I was prepared by mixing 1.5g of sodium dodecyl sulfate (anionic surfactant, also known as SDS) and 3g of BASF Lutensol FT TO10 (a nonionic surfactant, the main component of which is polyoxyethylene ether);

[0116] Step 3: Preparation of water-based hydroxy acrylate polymer microsphere emulsion by emulsion polymerization

[0117] In a reaction kettle equipped with a stirrer, a condenser, and a thermometer, 105 g of deionized water and a mixed emulsifier II were added to obtain a bottom material; when the temperature in the reaction kettle reached 80±2° C., 10% of the core layer pre-emulsion and an initiator aqueous solution I were added to the bottom material, and the mixture was kept warm for 30 minutes. The remaining 90% of the core layer pre-emulsion was then added dropwise for 3 hours. After the addition was complete, the mixture was kept warm for 1 hour, and the shell layer pre-emulsion and the initiator aqueous solution II were then added dropwise. The shell layer pre-emulsion and the initiator aqueous solution II were added simultaneously. After the addition was completed over 3-4 hours, the mixture was stirred at a constant temperature for 0.5-1.5 hours, and then the temperature was lowered to below 50° C. The neutralizing agent triethylamine was added to adjust the pH to 7.0-9.0, and the mixture was filtered through a 200-mesh filter to obtain an aqueous hydroxy acrylate polymer microsphere emulsion;

[0118] Among them, the mixed emulsifier II is prepared by mixing 1g of sodium dodecyl sulfate (SDS) and 2g of BASF Lutensol FT TO10; the initiator aqueous solution I is prepared by mixing 1g of ammonium persulfate and 10g of deionized water; and the initiator aqueous solution II is prepared by mixing 1g of ammonium persulfate and 25g of deionized water.

[0119] Example 5

[0120] A method for preparing a water-based two-component polyurethane coating comprises the following steps:

[0121] S1. Prepare a base emulsion: Mix 40 parts by weight of an aqueous hydroxy acrylate polymer microsphere emulsion; 3.5 parts of deionized water; 30 parts of a titanium dioxide slurry; 4 parts of a film-forming aid, diethylene glycol butyl ether; 0.2 parts of a wetting agent, BYK-345; and 0.3 parts of a thickener, WT-202. Shear and disperse the mixture for 15 minutes using a shearing machine to obtain a base emulsion. The titanium dioxide slurry is composed of 75 wt% of R930 titanium dioxide, 17.5 wt% of water, and 7.5 wt% of BYK-190, a polymer wetting and dispersing agent for aqueous systems produced by BYK.

[0122] S2. Prepare a water-based two-component polyurethane coating: dilute the hydrophilic modified isocyanate curing agent in a ratio of 1:1.1 between the hydroxyl group (-OH) in the base emulsion and the (-NCO) isocyanate group in the hydrophilic modified isocyanate curing agent, slowly add it to the base emulsion under stirring, and add an appropriate amount of deionized water to adjust to a suitable viscosity to obtain a two-component polyurethane coating, wherein the hydrophilic modified isocyanate curing agent is a hydrophilic modified isocyanate curing agent produced by Bayer, Bayer XP2655.

[0123] Comparative Example 1

[0124] A method for preparing a water-based hydroxyacrylate polymer microsphere emulsion, wherein the polymer microspheres include a core layer and a shell layer structure, and the preparation method comprises the following steps:

[0125] Step 1: Prepare nuclear layer pre-emulsion

[0126] (1.1) Preparation of core layer monomers: 38.3 g of styrene (vinyl aromatic compound), 27.4 g of methyl methacrylate (ester of α,β-monoethylenically unsaturated monocarboxylic acid), 15.1 g of butyl acrylate (ester of α,β-monoethylenically unsaturated monocarboxylic acid), and 19.2 g of hydroxyethyl methacrylate (hydroxyalkyl (meth)acrylate) were mixed to obtain core layer monomers;

[0127] (1.2) Preparation of a core layer pre-emulsion: The core layer monomers prepared above, mixed emulsifier III, and 200 g of deionized water were dispersed using a shearing machine and sheared at 800 rpm for 10 min to prepare a core layer pre-emulsion. The mixed emulsifier III was prepared by mixing 1 g of sodium dodecyl sulfate (SDS) and 2 g of BASF Lutensol FT TO10.

[0128] Step 2: Prepare shell pre-emulsion

[0129] (2.1) Preparation of Shell Monomers: 38.3 g of styrene (vinyl aromatic compound), 27.4 g of methyl methacrylate (ester of α,β-monoethylenically unsaturated monocarboxylic acid), 15.1 g of butyl acrylate (ester of α,β-monoethylenically unsaturated monocarboxylic acid), and 19.2 g of hydroxyethyl methacrylate (hydroxyalkyl (meth)acrylate) were mixed to obtain shell monomers.

[0130] (2.2) Preparing a shell pre-emulsion: The shell monomer prepared above, 100 g of deionized water, and mixed emulsifier I were dispersed using a shearing machine at 800 rpm for 10 min. After dispersion and mixing, a shell pre-emulsion was obtained.

[0131] Among them, mixed emulsifier I was prepared by mixing 1.5g of sodium dodecyl sulfate (anionic surfactant, also known as SDS) and 3g of BASF Lutensol FT TO10 (a nonionic surfactant, the main component of which is polyoxyethylene ether);

[0132] Step 3: Preparation of water-based hydroxy acrylate polymer microsphere emulsion by emulsion polymerization

[0133] In a reaction kettle equipped with a stirrer, a condenser, and a thermometer, 105 g of deionized water and a mixed emulsifier II were added to obtain a bottom material. When the temperature in the reaction kettle reached 80±2° C., 10% of the core layer pre-emulsion and an initiator aqueous solution I were added to the bottom material, the temperature was kept warm for 30 minutes, and the remaining 90% of the core layer pre-emulsion was added dropwise for 3 hours. After the addition was completed, the temperature was kept warm for 1 hour, and the initiator aqueous solution II was added dropwise. After the initiator aqueous solution was added dropwise for 3-4 hours, the temperature was continued to be constant for 0.5-1.5 hours, and then the temperature was lowered to below 50° C., sodium hydroxide as a neutralizer was added to adjust the pH to 7.0-9.0, and the mixture was filtered through a 200-mesh filter to obtain an aqueous hydroxy acrylate polymer microsphere emulsion.

[0134] Among them, the mixed emulsifier II is prepared by mixing 1g of sodium dodecyl sulfate (SDS) and 2g of BASF Lutensol FT TO10; the initiator aqueous solution I is prepared by mixing 1g of ammonium persulfate and 10g of deionized water; and the initiator aqueous solution II is prepared by mixing 1g of ammonium persulfate and 25g of deionized water.

[0135] Performance Testing

[0136] According to the above preparation method, the proportion of caprolactone-modified hydroxyethyl methacrylate in the shell monomer, the solid content, and the hydroxyl content of the aqueous hydroxyacrylate polymer microsphere emulsion in Examples 1-4 and Comparative Example 1 are shown in the following table:

[0137]

[0138] In Examples 1-4, glycidyl methacrylate (an epoxy-polymerizable unsaturated monomer) was added to modify the core monomer. In Example 1, the shell monomer was not modified. In Example 2, itaconic acid (a monoethylenically unsaturated polycarboxylic acid) and caprolactone-modified hydroxyethyl methacrylate (lactone-modified (meth) acrylate hydroxy ester) were added to modify the shell monomer on the basis of Example 1. In Examples 3 and 4, the amounts of the components used to prepare the shell monomer were adjusted on the basis of Example 2. In Comparative Example 1, the epoxy-polymerizable unsaturated monomer glycidyl methacrylate was not added to modify the core monomer, and itaconic acid (a monoethylenically unsaturated polycarboxylic acid) and caprolactone-modified hydroxyethyl methacrylate (lactone-modified (meth) acrylate hydroxy ester) were not added to modify the shell monomer to make the core and shell components consistent. Initiator aqueous solution II was added dropwise to the core pre-emulsion to carry out emulsion polymerization to prepare an aqueous hydroxy acrylate polymer microsphere emulsion. The solid content of Examples 1-4 and Comparative Example 1 was kept at 45%, and the hydroxyl content was kept at 2.5%.

[0139] According to the method in Example 5, the water-based hydroxy acrylate polymer microsphere emulsions prepared in Examples 1-4 and Comparative Example 1 and the existing hydroxy acrylate emulsion of a market competitor (as Comparative Example 2, having a solid content of 45% and a hydroxyl content of 2.5%) were respectively prepared into water-based two-component polyurethane coatings, wherein the ratio of the content of isocyanate (-NCO) to hydroxyl (-OH) was 1.25. The prepared water-based two-component polyurethane coatings were sprayed on a clean tinplate sheet, allowed to dry at room temperature, and then baked in an 80°C oven for 2 hours. The paint film properties of the prepared water-based two-component polyurethane coatings were measured according to the method in the table below.

[0140] Paint film test methods and standards:

[0141] Test items Detection method Pencil hardness GB / T6739—2022 Adhesion / Grade GB / T9286—2021 Impact resistance (positive and negative impact) / (kg·cm) GB / T1732—2020 Flexibility / mm GB / T1731—2020

[0142] The paint film properties of the water-based two-component polyurethane coatings prepared with the water-based hydroxy acrylate polymer microsphere emulsions prepared in Examples 1-4 and Comparative Examples 1-2 are shown in the following table:

[0143]

[0144] As can be seen from the above table, at the same solid content and hydroxyl content, the hardness of the coatings prepared using the aqueous hydroxyacrylate polymer microsphere emulsions in Examples 1-4 as raw materials is higher than the hardness of the coatings prepared using the existing commercially available aqueous hydroxyacrylate polymer microsphere emulsions in Comparative Example 2 as raw materials, and can achieve the same adhesion. In terms of flexibility and impact resistance, except that Example 1 is similar to Comparative Example 2, Examples 2-4 are all better than Comparative Example 2, indicating that the aqueous hydroxyacrylate polymer microsphere emulsion of the present invention has better performance when used as a raw material to prepare coatings.

[0145] Compared with Comparative Example 1, the coatings prepared using the water-based hydroxy acrylate polymer microsphere emulsions in Examples 1-4 as raw materials have better hardness, impact resistance and adhesion, and can achieve similar flexibility. It can be seen that modifying the core layer monomer by adding epoxy polymerizable unsaturated monomer glycidyl methacrylate is beneficial to improving the hardness, impact resistance and adhesion of the coating.

[0146] Compared with Example 1, Examples 2-4 further added itaconic acid (monoethylenically unsaturated polycarboxylic acid) and caprolactone-modified hydroxyethyl methacrylate (lactone-modified (meth) acrylate hydroxy ester) to modify the shell monomer. As a result, the hardness, flexibility and impact resistance of Examples 2-4 were further improved compared with Example 1. It can be seen that adding itaconic acid (monoethylenically unsaturated polycarboxylic acid) and caprolactone-modified hydroxyethyl methacrylate (lactone-modified (meth) acrylate hydroxy ester) to modify the shell monomer is beneficial to further improve the hardness, flexibility and impact resistance of the coating.

[0147] In summary, the present invention obtains hydroxy acrylate emulsion microsphere particles with a core-shell structure through emulsion polymerization, introduces an epoxy polymerizable unsaturated monomer in the core layer free radical polymerization, and improves the hardness and adhesion of the coating. Furthermore, a monoethylenically unsaturated polycarboxylic acid and a lactone-modified (meth) hydroxyalkyl acrylate are introduced in the shell layer polymerization. The carboxyl groups on the surface of the hydroxy acrylate emulsion microsphere particles react with the epoxy groups and form weak interactions with the hydroxyl functional groups, thereby increasing the cohesion of the polymer particles, thereby improving the hardness and impact resistance of the prepared coating. At the same time, the long-chain structure of the lactone-modified (meth) hydroxyalkyl acrylate increases the flexibility of the polymer.

[0148] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0149] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A water-based hydroxy acrylate polymer microsphere emulsion, characterized in that: The polymer microspheres include a core layer and a shell layer structure, wherein the core layer includes core layer monomers, which include epoxy-polymerizable unsaturated monomers; the shell layer includes shell layer monomers, which include monoethylenically unsaturated polycarboxylic acids and lactone-modified (meth)acrylate hydroxy esters; based on the total mass of the core layer monomers, the mass percentage of the epoxy-polymerizable unsaturated monomer in the core layer monomers is 1-10%; Based on the total mass of the shell monomers, the mass percentage of the monoethylenically unsaturated polycarboxylic acid in the shell monomers is 0-10%, and the mass percentage of the lactone-modified (meth)acrylate hydroxy ester in the shell monomers is 0-35%.

2. The aqueous hydroxy acrylate polymer microsphere emulsion according to claim 1, wherein The core layer monomers further comprise an ester of an α,β-monoethylenically unsaturated monocarboxylic acid, a vinyl aromatic compound, and a hydroxyalkyl (meth)acrylate; based on the total mass of the core layer monomers, the mass percentage of the ester of the α,β-monoethylenically unsaturated monocarboxylic acid in the core layer monomers is 30-50%, the mass percentage of the vinyl aromatic compound in the core layer monomers is 30-45%, and the mass percentage of the hydroxyalkyl (meth)acrylate in the core layer monomers is 15-25%; The shell monomers also include esters of α, β-monoethylenically unsaturated monocarboxylic acids, vinyl aromatic compounds, and hydroxyalkyl (meth)acrylates; based on the total mass of the shell monomers, the mass percentage of the esters of α, β-monoethylenically unsaturated monocarboxylic acids in the shell monomers is 30-50%, the mass percentage of the vinyl aromatic compounds in the shell monomers is 25-40%, and the mass percentage of the hydroxyalkyl (meth)acrylates in the shell monomers is 15-25%.

3. The aqueous hydroxy acrylate polymer microsphere emulsion according to claim 1, wherein The aqueous hydroxy acrylate polymer microsphere emulsion comprises the following components: water, a mixed emulsifier, a core layer pre-emulsion, an initiator aqueous solution and a shell layer pre-emulsion; The mixed emulsifier includes an anionic emulsifier and a nonionic emulsifier, and the weight ratio of the anionic emulsifier to the nonionic emulsifier is 1:(1-3); The core layer pre-emulsion comprises the following components: core layer monomers, a mixed emulsifier and water; the core layer monomers comprise the following components in parts by weight: 30-50 parts of an ester of an α,β-monoethylenically unsaturated monocarboxylic acid; 30-45 parts of a vinyl aromatic compound; 15-25 parts of a hydroxyalkyl (meth)acrylate; and 1-10 parts of an epoxy polymerizable unsaturated monomer. The shell pre-emulsion comprises the following components: shell monomer, water, mixed emulsifier; the shell monomer comprises the following components in parts by weight: 0-10 parts of monoethylenically unsaturated polycarboxylic acid; 30-50 parts of α,β-monoethylenically unsaturated monocarboxylic acid ester; 25-40 parts of vinyl aromatic compound; 15-25 parts of hydroxyalkyl (meth)acrylate; 0-35 parts of lactone-modified hydroxy (meth)acrylate; Preferably, the initiator aqueous solution is an ammonium persulfate aqueous solution, and the concentration of the initiator aqueous solution is 2-15%; Preferably, the concentration of the initiator aqueous solution is 4-10%.

4. The aqueous hydroxy acrylate polymer microsphere emulsion according to claim 2, wherein The esters of the α,β-monoethylenically unsaturated monocarboxylic acids include esters obtained by reacting α,β-monoethylenically unsaturated monocarboxylic acids with C1-C10 alkanols; Preferably, the ester of the α,β-monoethylenically unsaturated monocarboxylic acid comprises an ester obtained by reacting (meth)acrylic acid with a C1-C10 alkanol; Preferably, the ester of the α,β-monoethylenically unsaturated monocarboxylic acid includes at least one of methyl (meth)acrylate, methyl ethylacrylate, ethyl (meth)acrylate, ethyl ethylacrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, tert-butyl ethylacrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, n-decyl (meth)acrylate, isooctyl (meth)acrylate, and glycidyl (meth)acrylate.

5. The aqueous hydroxy acrylate polymer microsphere emulsion according to claim 2, wherein The vinyl aromatic compound includes at least one of styrene, 2-methylstyrene, 4-methylstyrene, 2-butylstyrene, 4-butylstyrene or 4-decylstyrene; The (meth)acrylate hydroxyalkyl ester includes at least one of hydroxyethyl methacrylate and hydroxypropyl methacrylate; The epoxy polymerizable unsaturated monomer includes at least one of glycidyl (meth)acrylate and alicyclic epoxy-containing monomers; The monoethylenically unsaturated polycarboxylic acid comprises at least one of fumaric acid, maleic acid, itaconic acid or salts, anhydrides and mixtures thereof; The lactone-modified (meth)acrylate hydroxy ester includes at least one of caprolactone-modified hydroxypropyl methacrylate, caprolactone-modified hydroxypropyl acrylate, caprolactone-modified hydroxyethyl methacrylate, caprolactone-modified hydroxyethyl acrylate, caprolactone-modified hydroxybutyl acrylate, caprolactone-modified hydroxybutyl methacrylate, caprolactone-modified hydroxyhexyl acrylate and caprolactone-modified hydroxyhexyl methacrylate.

6. The aqueous hydroxy acrylate polymer microsphere emulsion according to claim 3, characterized in that: The anionic emulsifier is an organic sodium acid, including at least one of sodium lauryl sulfate, sodium dodecylbenzene sulfonate, sodium dodecyl diphenyl ether disulfonate, sodium styrene sulfonate or sodium stearate; The nonionic emulsifier is an isomeric alcohol polyoxyethylene ether with the structural formula RO-(CH2CH2O) n -H, where R satisfies C m H 2m+1 In the general formula, m is 8, 10, 11 or 13; n is 3, 5, 6, 7, 8, 10 or 12.

7. A method for preparing the aqueous hydroxy acrylate polymer microsphere emulsion according to any one of claims 2 to 6, characterized in that: The following steps are involved: Step 1: Prepare nuclear layer pre-emulsion (1.1) Preparing a core layer monomer: mixing the vinyl aromatic compound, an ester of an α,β-monoethylenically unsaturated monocarboxylic acid, a hydroxyalkyl (meth)acrylate, and an epoxy-polymerizable unsaturated monomer to obtain a core layer monomer; (1.2) Preparing a core layer pre-emulsion: mixing the core layer monomer prepared above with a mixed emulsifier and water to prepare a core layer pre-emulsion; Step 2: Prepare shell pre-emulsion (2.1) Preparing a shell monomer: mixing the vinyl aromatic compound, an ester of an α,β-monoethylenically unsaturated monocarboxylic acid, a hydroxyalkyl (meth)acrylate, a monoethylenically unsaturated polycarboxylic acid, and a lactone-modified hydroxyl (meth)acrylate to obtain a shell monomer; (2.2) Preparing a shell pre-emulsion: mixing the shell monomer prepared above, water, and a mixed emulsifier to obtain a shell pre-emulsion; Step 3: Preparation of water-based hydroxy acrylate polymer microsphere emulsion by emulsion polymerization Mix water and a mixed emulsifier to obtain a kettle bottom material, heat the mixture to 75-85° C., add 5-15% of the total amount of the core layer pre-emulsion and an initiator aqueous solution to the kettle bottom material, keep the temperature for 15-45 minutes, then add the remaining core layer pre-emulsion, keep the temperature for 15-60 minutes, then dropwise add the initiator aqueous solution, stir at a constant temperature for 0.5-1.5 hours, cool the mixture to below 50° C., add a neutralizer to adjust the pH to 6-8, and filter the mixture to obtain a water-based hydroxy acrylate polymer microsphere emulsion.

8. A water-based two-component polyurethane coating, characterized in that: The invention comprises the aqueous hydroxy acrylate polymer microsphere emulsion according to any one of claims 1 to 6 or the aqueous hydroxy acrylate polymer microsphere emulsion prepared by the preparation method according to claim 7.

9. A water-based two-component polyurethane coating, characterized in that: The composition comprises the following components in parts by weight: 30-40 parts of water-based hydroxy acrylate polymer microsphere emulsion; 2.5-4.5 parts of water; 20-40 parts of titanium dioxide slurry; 3-5 parts of film-forming aid; 0.1-0.3 parts of wetting agent; 0.2-0.4 parts of thickener.

10. A method for preparing a water-based two-component polyurethane coating according to claim 9, characterized in that: The following steps are involved: S1. Preparing a base emulsion: mixing a water-based hydroxy acrylate emulsion, water, titanium dioxide slurry, a film-forming aid, a wetting agent, and a thickener to obtain a base emulsion; S2. Prepare a water-based two-component polyurethane coating: add a hydrophilic modified isocyanate curing agent to the base emulsion under stirring, wherein the ratio of the hydroxyl group in the base emulsion to the isocyanate group in the hydrophilic modified isocyanate curing agent is 1: 1.1-1.5, to obtain a water-based two-component polyurethane coating.

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