Continuous-phase pure acrylic emulsion, preparation method thereof and multicolor paint using continuous-phase pure acrylic emulsion

Abstract

The invention provides a preparation method of a continuous-phase pure acrylic emulsion. Raw materials for preparing the continuous-phase pure acrylic emulsion comprise an acrylate monomer, unsaturated organic acid and a functional monomer. The acrylate monomer comprises a long-chain acrylate monomer and a short-chain acrylate monomer; the preparation method of the continuous-phase pure acrylic emulsion comprises the following steps: S1, preparing a pre-emulsion A and a pre-emulsion B, wherein the pre-emulsion A comprises an acrylate monomer, unsaturated organic acid and a functional monomer; the pre-emulsion B comprises an acrylate monomer and a functional monomer; wherein in the raw materials for preparing the pre-emulsion A, the ratio of the acrylate monomer to the unsaturated organic acid is (3-5): 1 according to the mass ratio; the proportion of the unsaturated organic acid for preparing the pre-emulsified liquid A is not less than 90% in all the unsaturated organic acids contained in the raw materials for preparing the continuous-phase pure acrylic emulsion according to the mass percent; s2, under the condition that the temperature is 80-90 DEG C, the pre-emulsion A is subjected to a polymerization reaction, and a nuclear layer reaction solution is prepared; and then adding the pre-emulsified liquid B into the nuclear layer reaction liquid to carry out polymerization reaction. The continuous-phase pure acrylic emulsion prepared by the preparation method is suitable for being prepared into a multicolor coating with dispersed-phase base paint, and the obtained multicolor coating has relatively good heat storage stability, low-temperature storage stability and relatively high viscosity.

Description

Technical Field

[0001] This invention belongs to the field of acrylic emulsion technology, specifically relating to a continuous phase pure acrylic emulsion, its preparation method, and multicolor coatings using the same. Background Technology

[0002] Multicolor coatings typically consist of a continuous phase emulsion, a granulating agent, and a base coat, with the main component of the continuous phase emulsion being pure acrylic or silicone-acrylic emulsion. However, existing continuous phase emulsions suffer from several problems. Firstly, insufficient functional groups in the emulsion lead to low crosslinking density, poor interlayer adhesion, and poor water resistance in the coating film. Secondly, the flexibility of the coating film and interfacial bonding are difficult to optimize synergistically, causing film cracking or peeling. Furthermore, poor compatibility and insufficient viscosity among the continuous phase emulsion, granulating agent, and base coat exacerbate bleeding and particle settling after application. These problems result in multicolor coatings experiencing particle flocculation during storage, pigment migration and color mixing under high temperature and humidity conditions, final coating blooming, and decreased durability, severely restricting their decorative effects and application reliability. Summary of the Invention

[0003] This invention provides a continuous phase pure acrylic emulsion, its preparation method, and a multicolor coating using the same. The continuous phase pure acrylic emulsion prepared by the method of this invention is suitable for formulation with dispersed phase base paint to produce multicolor coatings. The resulting multicolor coatings have good thermal storage stability, low temperature storage stability, and high viscosity.

[0004] This invention provides a method for preparing a continuous-phase pure acrylic emulsion. The raw materials used to prepare the continuous-phase pure acrylic emulsion include the following materials: acrylate monomers, unsaturated organic acids, and functional monomers; the acrylate monomers include long-chain acrylate monomers and short-chain acrylate monomers; the method for preparing the continuous-phase pure acrylic emulsion includes the following steps: S1. Pre-emulsion A and pre-emulsion B: Pre-emulsion A includes acrylate monomers, unsaturated organic acids, and functional monomers; pre-emulsion B includes acrylate monomers and functional monomers; wherein, by mass ratio, in the raw materials used to prepare pre-emulsion A, the ratio of acrylate monomers to unsaturated organic acids is (3~5):1; by mass percentage, in all the unsaturated organic acids included in the raw materials used to prepare the continuous-phase pure acrylic emulsion, the proportion of unsaturated organic acids used to prepare pre-emulsion A is not less than 90%; S2. Under the condition of a temperature of 80~90℃, pre-emulsion A undergoes a polymerization reaction to obtain a core layer reaction liquid; subsequently, pre-emulsion B is added to the core layer reaction liquid to carry out a polymerization reaction.

[0005] The continuous-phase pure acrylic emulsion preparation method provided by this invention employs a stepwise polymerization process. This method controls the amount of unsaturated organic acid added during the nucleation stage by adjusting the feeding ratio of acrylate monomers and unsaturated organic acids in the pre-emulsion A. This allows for the formation of hard nuclei during the nucleation stage and effectively regulates the carboxylic acid content in the polymerization system. During the shell-forming stage, the acrylate monomers continue to participate in the polymerization reaction to form a shell layer, ensuring that carboxyl groups are mainly enriched on the surface of the latex particles and remain in an undissociated state. This continuous-phase pure acrylic emulsion is suitable for use in conjunction with dispersed-phase base paints in a weakly alkaline protective colloid system. In the weakly alkaline environment of the dispersed-phase base paint, the carboxyl groups on the surface of the latex particles dissociate into negatively charged carboxylate ions. These carboxylate ions and cations on the surface of the protective colloid undergo directional association through electrostatic attraction, forming a stable "carboxylate house" three-dimensional network. This network significantly increases the fluid resistance of the multicolor coating system, thereby achieving self-thickening of the system. High viscosity can be obtained without the addition of additional thickeners, effectively reducing the stratification of multicolor coatings. Therefore, the continuous phase pure acrylic emulsion prepared by the method of the present invention is suitable for formulation with dispersed phase base paint to form multicolor coatings. The resulting multicolor coatings have good thermal storage stability, low temperature storage stability, and high viscosity.

[0006] Preferably, S2 includes the following steps: after the pre-emulsion A is added at a temperature of 80~90℃, the temperature is adjusted to 85~90℃ and kept at this temperature for 30~60 minutes to obtain the core layer reaction solution.

[0007] Preferably, S2 includes the following steps: adding pre-emulsion B dropwise to the core layer reaction solution at a temperature of 80-90°C; after the dropwise addition is completed, adjusting the temperature to 85-90°C and maintaining this temperature for 60-90 minutes. The heat preservation process helps to improve the monomer conversion rate of acrylate monomers, reduce monomer residue, and allow the polymer chains inside the latex particles of the continuous phase pure acrylic emulsion to be fully and regularly arranged. Simultaneously, it makes the distribution of carboxyl groups on the surface of the latex particles more uniform and orderly, enabling the latex particles to achieve tight and uniform stacking during film formation, effectively reducing light scattering, thereby improving the permeability of the continuous phase pure acrylic emulsion.

[0008] Preferably, the alkyl chain of the long-chain acrylate monomer has ≥8 carbon atoms; the alkyl chain of the short-chain acrylate monomer has 1 to 4 carbon atoms.

[0009] Preferably, the short-chain acrylate monomers include at least one selected from methyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, and butyl acrylate. By using the aforementioned short-chain acrylate monomers, on the one hand, these monomers participate in polymerization during the reaction process while simultaneously promoting the migration of carboxyl groups to the surface of latex particles, thereby increasing the efficiency of carboxyl group migration to the latex particle surface. This effectively regulates the carboxyl content on the latex particle surface, thereby improving the thermal and low-temperature storage stability of the multicolor coatings prepared from continuous-phase pure acrylic emulsions. On the other hand, it improves the stability of the polymerization reaction of continuous-phase pure acrylic emulsions, allowing for the control of latex particle size within a suitable range and enhancing the permeability of the paint film formed by the continuous-phase pure acrylic emulsion.

[0010] Preferably, the short-chain acrylate monomers include methyl methacrylate and ethyl acrylate.

[0011] Preferably, the unsaturated organic acid includes at least one of acrylic acid, methacrylic acid, and itaconic acid. Using the above-mentioned unsaturated organic acid can optimize the carboxyl enrichment efficiency and water-whitening resistance of the latex particle surface. On the one hand, it can control the content of carboxyl groups on the latex particle surface to a suitable range, effectively reducing the risk of water-whitening in pure acrylic emulsions, and ensuring that sufficient carboxylate groups after carboxyl dissociation can directionally associate with the protective colloid components in the dispersed phase base paint. On the other hand, the unsaturated organic acid provides active crosslinking sites in the polymerization reaction, synergistically constructing a dense hydrophobic network with functional monomers, effectively reducing swelling and whitening caused by water molecules entering the paint film, and further improving the water-whitening resistance and water resistance of the paint film.

[0012] Preferably, the functional monomer includes at least one of vinyltrimethoxysilane, methacryloxypropyltrimethoxysilane, and allyl methacrylate silane polymers.

[0013] Preferably, the mass ratio of acrylate monomers in preemulsion A to acrylate monomers in preemulsion B is (2~5): (10~13).

[0014] Preferably, the functional monomer in preemulsion A : functional monomer in preemulsion B is calculated by mass ratio of 3~5:1.

[0015] The raw materials used to prepare continuous phase pure acrylic emulsion, by weight, include: 85-100 parts of acrylate monomer, 1-10 parts of unsaturated organic acid, and 0.1-0.8 parts of functional monomer.

[0016] Preferably, the raw materials used to prepare the continuous phase pure acrylic emulsion further include 0.5 to 2 parts of emulsifier, which includes at least one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, disodium salt of fatty alcohol polyoxyethylene ether succinate monoester sulfonate, and alkyl polyoxyethylene ether.

[0017] Preferably, the raw materials used to prepare the continuous phase pure acrylic emulsion further include 0.3 to 0.8 parts of an initiator, which includes at least one of ammonium persulfate, potassium persulfate, and sodium persulfate.

[0018] Preferably, the raw materials used to prepare the continuous phase pure acrylic emulsion further include 0.05-0.5 parts of oxidant and 0.05-0.5 parts of reducing agent.

[0019] Preferably, the oxidant includes tert-butyl hydroperoxide.

[0020] Preferably, the reducing agent includes at least one of sodium bisulfite, L-ascorbic acid, and sodium sulfite.

[0021] According to another aspect of the present invention, a continuous phase pure acrylic emulsion is provided, which is prepared by the above-described preparation method.

[0022] Preferably, the particle size of the continuous phase pure acrylic emulsion is 60~80 nm.

[0023] Preferably, the rotational viscosity of the continuous phase pure acrylic emulsion is 1~1000 cps (2#30r, 25℃).

[0024] According to another aspect of the present invention, a multicolor coating is provided, comprising a continuous phase pure acrylic emulsion and a dispersion-based base paint.

[0025] Preferably, the viscosity of the multicolor coating is 85~95 KU. Detailed Implementation

[0026] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0027] Example 1 This embodiment provides a method for preparing a continuous-phase pure acrylic emulsion. The raw materials used to prepare the continuous-phase pure acrylic emulsion, calculated by weight, consist of 95 parts of acrylate monomer, 5 parts of unsaturated organic acid, 0.6 parts of functional monomer, 1.3 parts of emulsifier, 0.4 parts of persulfate, 0.08 parts of oxidant, 0.08 parts of reducing agent, and 200 parts of water. The acrylate monomer consists of 20 parts of isooctyl acrylate, 40 parts of methyl methacrylate, and 35 parts of ethyl acrylate.

[0028] The preparation method of continuous phase pure acrylic emulsion includes the following steps: S1. Preparation of preemulsion A and preemulsion B: Preemulsion A is prepared by mixing 0.2 parts emulsifier, 10 parts water, 10 parts methyl methacrylate, 10 parts ethyl acrylate, 5 parts unsaturated organic acid, 0.5 parts functional monomer, and 0.05 parts persulfate; wherein the emulsifier is disodium salt of fatty alcohol polyoxyethylene ether succinate monoester sulfonate, the unsaturated organic acid is acrylic acid, the functional monomer is vinyltrimethoxysilane, and the persulfate is sodium persulfate. Preemulsion B is prepared by mixing 1 part emulsifier, 50 parts water, 30 parts methyl methacrylate, 25 parts ethyl acrylate, 20 parts isooctyl acrylate, 0.1 parts functional monomer, and 0.3 parts persulfate, and stirring until homogeneous; wherein the emulsifier is sodium dodecylbenzenesulfonate, the functional monomer is vinyltrimethoxysilane, and the persulfate is sodium persulfate.

[0029] S2. Mix 0.1 parts emulsifier and 140 parts water, then heat to 85°C and stir for 25 minutes. Add 0.05 parts persulfate and maintain the temperature for 5 minutes to obtain a mixture. Then, at 85°C, add pre-emulsion A dropwise to the mixture for polymerization over 45 minutes. After polymerization, adjust the temperature to 90°C and maintain this temperature for 45 minutes to obtain a core layer reaction solution. Next, adjust the temperature to 85°C and add pre-emulsion B dropwise to the core layer reaction solution for polymerization over 150 minutes. After polymerization, adjust the temperature to 90°C and maintain this temperature for 75 minutes. After maintaining this temperature, adjust the reaction system temperature to 62°C and add 0.08 parts oxidant and 0.08 parts reducing agent for post-treatment. After post-treatment, adjust the reaction system temperature to 50°C, filter, and obtain a continuous phase pure acrylic emulsion. The emulsifier is alkyl polyoxyethylene ether, the persulfate is sodium persulfate, the oxidant is tert-butyl hydroperoxide, and the reducing agent is sodium sulfite.

[0030] Example 2 This embodiment provides a method for preparing a continuous-phase pure acrylic emulsion. The raw materials used to prepare the continuous-phase pure acrylic emulsion, calculated by weight, consist of 95 parts of acrylate monomer, 5 parts of unsaturated organic acid, 0.6 parts of functional monomer, 1.3 parts of emulsifier, 0.4 parts of persulfate, 0.08 parts of oxidant, 0.08 parts of reducing agent, and 200 parts of water. The acrylate monomer consists of 20 parts of isooctyl acrylate, 45 parts of methyl methacrylate, and 30 parts of ethyl acrylate.

[0031] The preparation method of continuous phase pure acrylic emulsion includes the following steps: S1. Preparation of pre-emulsion A and pre-emulsion B: Pre-emulsion A is prepared by mixing 0.2 parts emulsifier, 10 parts water, 10 parts methyl methacrylate, 10 parts ethyl acrylate, 5 parts unsaturated organic acid, 0.5 parts functional monomer, and 0.05 parts persulfate; wherein the emulsifier is disodium salt of fatty alcohol polyoxyethylene ether succinate monoester sulfonate, the unsaturated organic acid is acrylic acid, the functional monomer is vinyltrimethoxysilane, and the persulfate is sodium persulfate. Pre-emulsion B is prepared by mixing 1 part emulsifier, 50 parts water, 35 parts methyl methacrylate, 20 parts ethyl acrylate, 20 parts isooctyl acrylate, 0.1 parts functional monomer, and 0.3 parts persulfate, and stirring until homogeneous; wherein the emulsifier is sodium dodecylbenzenesulfonate, the functional monomer is vinyltrimethoxysilane, and the persulfate is sodium persulfate.

[0032] S2. Mix 0.1 parts emulsifier and 140 parts water, then heat to 80°C and stir for 25 minutes. Add 0.05 parts persulfate and maintain the temperature for 5 minutes to obtain a mixture. Then, at 80°C, add pre-emulsion A dropwise to the mixture for polymerization over 45 minutes. After polymerization, adjust the temperature to 85°C and maintain this temperature for 60 minutes to obtain a core layer reaction solution. Next, adjust the temperature to 80°C and add pre-emulsion B dropwise to the core layer reaction solution for polymerization over 150 minutes. After polymerization, adjust the temperature to 85°C and maintain this temperature for 90 minutes. After maintaining this temperature, adjust the reaction system temperature to 62°C and add 0.08 parts oxidant and 0.08 parts reducing agent for post-treatment. After post-treatment, adjust the reaction system temperature to 50°C, filter, and obtain a continuous phase pure acrylic emulsion. The emulsifier is alkyl polyoxyethylene ether, the persulfate is sodium persulfate, the oxidant is tert-butyl hydroperoxide, and the reducing agent is sodium sulfite.

[0033] Example 3 This embodiment provides a method for preparing a continuous-phase pure acrylic emulsion. The raw materials used to prepare the continuous-phase pure acrylic emulsion, calculated by weight, consist of 90 parts of acrylate monomer, 5 parts of unsaturated organic acid, 0.1 parts of functional monomer, 1.3 parts of emulsifier, 0.4 parts of persulfate, 0.08 parts of oxidant, 0.08 parts of reducing agent, and 200 parts of water. The acrylate monomer consists of 10 parts of isooctyl acrylate, 30 parts of methyl methacrylate, and 50 parts of ethyl acrylate.

[0034] The preparation method of continuous phase pure acrylic emulsion includes the following steps: S1. Preparation of preemulsion A and preemulsion B: Preemulsion A is prepared by mixing 0.2 parts emulsifier, 10 parts water, 10 parts methyl methacrylate, 10 parts ethyl acrylate, 5 parts unsaturated organic acid, 0.5 parts functional monomer, and 0.05 parts persulfate; wherein the emulsifier is disodium salt of fatty alcohol polyoxyethylene ether succinate monoester sulfonate, the unsaturated organic acid is acrylic acid, the functional monomer is vinyltrimethoxysilane, and the persulfate is sodium persulfate. Preemulsion B is prepared by mixing 1 part emulsifier, 50 parts water, 20 parts methyl methacrylate, 40 parts ethyl acrylate, 10 parts isooctyl acrylate, 0.1 parts functional monomer, and 0.3 parts persulfate, and stirring until homogeneous; wherein the emulsifier is sodium dodecylbenzenesulfonate, the functional monomer is vinyltrimethoxysilane, and the persulfate is sodium persulfate.

[0035] S2. Mix 0.1 parts emulsifier and 140 parts water, then heat to 90°C and stir for 25 minutes. Add 0.05 parts persulfate and maintain the temperature for 5 minutes to obtain a mixture. Then, at 90°C, add pre-emulsion A dropwise to the mixture for polymerization over 45 minutes. After polymerization, adjust the temperature to 85°C and maintain this temperature for 60 minutes to obtain a core layer reaction solution. Next, adjust the temperature to 90°C and add pre-emulsion B dropwise to the core layer reaction solution for polymerization over 150 minutes. After polymerization, adjust the temperature to 85°C and maintain this temperature for 90 minutes. After maintaining this temperature, adjust the reaction system temperature to 62°C and add 0.08 parts oxidant and 0.08 parts reducing agent for post-treatment. After post-treatment, adjust the reaction system temperature to 50°C, filter, and obtain a continuous phase pure acrylic emulsion. The emulsifier is alkyl polyoxyethylene ether, the persulfate is sodium persulfate, the oxidant is tert-butyl hydroperoxide, and the reducing agent is sodium sulfite.

[0036] Example 4 This embodiment provides a method for preparing a continuous-phase pure acrylic emulsion. By weight, the raw materials for the continuous-phase pure acrylic emulsion consist of 95 parts acrylate monomer, 5 parts unsaturated organic acid, 0.8 parts functional monomer, 1.3 parts emulsifier, 0.4 parts persulfate, 0.08 parts oxidant, 0.08 parts reducing agent, and 200 parts water. The acrylate monomer consists of 20 parts isooctyl acrylate, 35 parts methyl methacrylate, and 40 parts ethyl acrylate.

[0037] The preparation method of continuous phase pure acrylic emulsion includes the following steps: S1. Preparation of pre-emulsion A and pre-emulsion B: Pre-emulsion A is prepared by mixing 0.2 parts emulsifier, 10 parts water, 10 parts methyl methacrylate, 10 parts ethyl acrylate, 5 parts unsaturated organic acid, 0.6 parts functional monomer, and 0.05 parts persulfate; wherein the emulsifier is disodium salt of fatty alcohol polyoxyethylene ether succinate monoester sulfonate, the unsaturated organic acid is methacrylic acid, the functional monomer is vinyltrimethoxysilane, and the persulfate is sodium persulfate. Pre-emulsion B is prepared by mixing 1 part emulsifier, 50 parts water, 25 parts methyl methacrylate, 30 parts ethyl acrylate, 20 parts isooctyl acrylate, 0.2 parts functional monomer, and 0.3 parts persulfate, and stirring until homogeneous; wherein the emulsifier is sodium dodecylbenzenesulfonate, the functional monomer is vinyltrimethoxysilane, and the persulfate is sodium persulfate.

[0038] S2. Mix 0.1 parts emulsifier and 140 parts water, then heat to 85°C and stir for 25 minutes. Add 0.05 parts persulfate and maintain the temperature for 5 minutes to obtain a mixture. Then, at 85°C, add pre-emulsion A dropwise to the mixture for polymerization over 45 minutes. After polymerization, adjust the temperature to 90°C and maintain this temperature for 45 minutes to obtain a core layer reaction solution. Next, adjust the temperature to 85°C and add pre-emulsion B dropwise to the core layer reaction solution for polymerization over 150 minutes. After polymerization, adjust the temperature to 90°C and maintain this temperature for 75 minutes. After maintaining this temperature, adjust the reaction system temperature to 62°C and add 0.08 parts oxidant and 0.08 parts reducing agent for post-treatment. After post-treatment, adjust the reaction system temperature to 50°C, filter, and obtain a continuous phase pure acrylic emulsion. The emulsifier is alkyl polyoxyethylene ether, the persulfate is sodium persulfate, the oxidant is tert-butyl hydroperoxide, and the reducing agent is sodium sulfite.

[0039] Example 5 This embodiment refers to the preparation method provided in Example 1 to prepare a continuous-phase pure acrylic emulsion. The difference between this embodiment and Example 1 is that in this embodiment, methyl acrylate of equal mass is used instead of ethyl acrylate in Example 1 in the raw materials used to prepare the continuous-phase pure acrylic emulsion. The remaining raw material ratios and preparation methods are strictly consistent with those in Example 1.

[0040] Example 6 This embodiment refers to the preparation method provided in Example 1 to prepare a continuous-phase pure acrylic emulsion. The difference between this embodiment and Example 1 is that in this embodiment, an equal mass of n-butyl acrylate is used instead of ethyl acrylate in Example 1 in the raw materials used to prepare the continuous-phase pure acrylic emulsion. The remaining raw material ratios and preparation methods are strictly consistent with those in Example 1.

[0041] Example 7 This embodiment refers to the preparation method provided in Example 1 to prepare a continuous-phase pure acrylic emulsion. The difference between this embodiment and Example 1 is that in this embodiment, an equal mass of amyl acrylate is used instead of ethyl acrylate in Example 1 in the raw materials used to prepare the continuous-phase pure acrylic emulsion. The remaining raw material ratios and preparation methods are strictly consistent with those in Example 1.

[0042] Example 8 This embodiment refers to the preparation method provided in Example 1 to prepare a continuous phase pure acrylic emulsion. The difference between this embodiment and Example 1 is that in this embodiment, itaconic acid of equal mass is used instead of acrylic acid in Example 1 in the raw materials used to prepare the continuous phase pure acrylic emulsion. The remaining raw material ratios and preparation methods are strictly consistent with those in Example 1.

[0043] Example 9 This embodiment refers to the preparation method provided in Example 1 to prepare a continuous phase pure acrylic emulsion. The difference between this embodiment and Example 1 is that in this embodiment, methacrylic acid of equal mass is used instead of acrylic acid in Example 1 in the raw materials used to prepare the continuous phase pure acrylic emulsion. The remaining raw material ratios and preparation methods are strictly consistent with those in Example 1.

[0044] Example 10 This embodiment refers to the preparation method provided in Example 1 to prepare a continuous-phase pure acrylic emulsion. The difference between this embodiment and Example 1 is that in the raw materials used to prepare the continuous-phase pure acrylic emulsion in this embodiment, the feeding amounts of acrylate monomers and unsaturated organic acids in pre-emulsion A are adjusted so that, while maintaining the total feeding amounts of acrylate monomers and unsaturated organic acids respectively, the mass ratio of acrylate monomers to unsaturated organic acids in pre-emulsion A is controlled to 3:1. The remaining raw material ratios and preparation methods are strictly consistent with those in Example 1.

[0045] Example 11 This embodiment refers to the preparation method provided in Example 1 to prepare a continuous-phase pure acrylic emulsion. The difference between this embodiment and Example 1 is that in the raw materials used to prepare the continuous-phase pure acrylic emulsion in this embodiment, the feeding amounts of acrylate monomers and unsaturated organic acids in pre-emulsion A are adjusted so that, while maintaining the total feeding amounts of acrylate monomers and unsaturated organic acids respectively, the mass ratio of acrylate monomers to unsaturated organic acids in pre-emulsion A is controlled to be 5:1. The remaining raw material ratios and preparation methods are strictly consistent with those in Example 1.

[0046] Example 12 This embodiment provides a method for preparing a continuous-phase pure acrylic emulsion. The raw materials used to prepare the continuous-phase pure acrylic emulsion, calculated by weight, consist of 95 parts of acrylate monomer, 5 parts of unsaturated organic acid, 0.6 parts of functional monomer, 1.3 parts of emulsifier, 0.4 parts of persulfate, 0.08 parts of oxidant, 0.08 parts of reducing agent, and 200 parts of water. The acrylate monomer consists of 20 parts of isooctyl acrylate, 40 parts of methyl methacrylate, and 35 parts of ethyl acrylate.

[0047] The preparation method of continuous phase pure acrylic emulsion includes the following steps: S1. Preparation of pre-emulsion A and pre-emulsion B: 0.2 parts emulsifier, 10 parts water, 10 parts methyl methacrylate, 10 parts ethyl acrylate, 5 parts unsaturated organic acid, 0.5 parts functional monomer, 0.05 parts persulfate, and 10 parts isooctyl acrylate are mixed to obtain pre-emulsion A; wherein, the emulsifier is disodium salt of fatty alcohol polyoxyethylene ether succinate monoester sulfonate, the unsaturated organic acid is methacrylic acid, the functional monomer is vinyltrimethoxysilane, and the persulfate is sodium persulfate. 1 part emulsifier, 50 parts water, 30 parts methyl methacrylate, 25 parts ethyl acrylate, 10 parts isooctyl acrylate, 0.1 parts functional monomer, and 0.3 parts persulfate are mixed and stirred evenly to obtain pre-emulsion B; wherein, the emulsifier is sodium dodecylbenzenesulfonate, the functional monomer is vinyltrimethoxysilane, and the persulfate is sodium persulfate.

[0048] S2. Mix 0.1 parts emulsifier and 140 parts water, then heat to 85°C and stir for 25 minutes. Add 0.05 parts persulfate and maintain the temperature for 5 minutes to obtain a mixture. Then, at 85°C, add pre-emulsion A dropwise to the mixture for polymerization over 45 minutes. After polymerization, adjust the temperature to 90°C and maintain this temperature for 45 minutes to obtain a core layer reaction solution. Next, adjust the temperature to 85°C and add pre-emulsion B dropwise to the core layer reaction solution for polymerization over 150 minutes. After polymerization, adjust the temperature to 90°C and maintain this temperature for 75 minutes. After maintaining this temperature, adjust the reaction system temperature to 62°C and add 0.08 parts oxidant and 0.08 parts reducing agent for post-treatment. After post-treatment, adjust the reaction system temperature to 50°C, filter, and obtain a continuous phase pure acrylic emulsion. The emulsifier is alkyl polyoxyethylene ether, the persulfate is sodium persulfate, the oxidant is tert-butyl hydroperoxide, and the reducing agent is FF6.

[0049] Example 13 This embodiment provides a method for preparing a continuous-phase pure acrylic emulsion. The raw materials used to prepare the continuous-phase pure acrylic emulsion, calculated by weight, consist of 95 parts of acrylate monomer, 5 parts of unsaturated organic acid, 0.6 parts of functional monomer, 1.3 parts of emulsifier, 0.4 parts of persulfate, 0.08 parts of oxidant, 0.08 parts of reducing agent, and 200 parts of water. The acrylate monomer consists of 20 parts of isooctyl acrylate, 40 parts of methyl methacrylate, and 35 parts of ethyl acrylate.

[0050] The preparation method of continuous phase pure acrylic emulsion includes the following steps: S1. Preparation of preemulsion A and preemulsion B: Preemulsion A is prepared by mixing 0.2 parts emulsifier, 10 parts water, 10 parts methyl methacrylate, 10 parts ethyl acrylate, 5 parts unsaturated organic acid, 0.5 parts functional monomer, and 0.05 parts persulfate; wherein the emulsifier is disodium salt of fatty alcohol polyoxyethylene ether succinate monoester sulfonate, the unsaturated organic acid is acrylic acid, the functional monomer is vinyltrimethoxysilane, and the persulfate is sodium persulfate. Preemulsion B is prepared by mixing 1 part emulsifier, 50 parts water, 30 parts methyl methacrylate, 25 parts ethyl acrylate, 20 parts isooctyl acrylate, 0.1 parts functional monomer, and 0.3 parts persulfate, and stirring until homogeneous; wherein the emulsifier is sodium dodecylbenzenesulfonate, the functional monomer is vinyltrimethoxysilane, and the persulfate is sodium persulfate.

[0051] S2. Mix 0.1 parts emulsifier and 140 parts water, then heat to 85°C and stir for 25 minutes. Add 0.05 parts persulfate and maintain the temperature for 5 minutes to obtain a mixture. Then, at 85°C, add pre-emulsion A dropwise to the mixture for polymerization over 45 minutes to obtain a core layer reaction solution. Next, adjust the temperature to 85°C and add pre-emulsion B dropwise to the core layer reaction solution for polymerization over 150 minutes. After the polymerization reaction is complete, adjust the temperature to 90°C and maintain this temperature for 75 minutes. After the maintenance, adjust the reaction system temperature to 62°C and add 0.08 parts oxidant and 0.08 parts reducing agent for post-treatment. After post-treatment, adjust the reaction system temperature to 50°C, filter, and obtain a continuous phase pure acrylic emulsion. The emulsifier is alkyl polyoxyethylene ether, the persulfate is sodium persulfate, the oxidant is tert-butyl hydroperoxide, and the reducing agent is sodium sulfite.

[0052] Example 14 This embodiment provides a method for preparing a continuous-phase pure acrylic emulsion. The raw materials used to prepare the continuous-phase pure acrylic emulsion, calculated by weight, consist of 95 parts of acrylate monomer, 5 parts of unsaturated organic acid, 0.6 parts of functional monomer, 1.3 parts of emulsifier, 0.4 parts of persulfate, 0.08 parts of oxidant, 0.08 parts of reducing agent, and 200 parts of water. The acrylate monomer consists of 20 parts of isooctyl acrylate, 40 parts of methyl methacrylate, and 35 parts of ethyl acrylate.

[0053] The preparation method of continuous phase pure acrylic emulsion includes the following steps: S1. Preparation of preemulsion A and preemulsion B: Preemulsion A is prepared by mixing 0.2 parts emulsifier, 10 parts water, 10 parts methyl methacrylate, 10 parts ethyl acrylate, 5 parts unsaturated organic acid, 0.5 parts functional monomer, and 0.05 parts persulfate; wherein the emulsifier is disodium salt of fatty alcohol polyoxyethylene ether succinate monoester sulfonate, the unsaturated organic acid is acrylic acid, the functional monomer is vinyltrimethoxysilane, and the persulfate is sodium persulfate. Preemulsion B is prepared by mixing 1 part emulsifier, 50 parts water, 30 parts methyl methacrylate, 25 parts ethyl acrylate, 20 parts isooctyl acrylate, 0.1 parts functional monomer, and 0.3 parts persulfate, and stirring until homogeneous; wherein the emulsifier is sodium dodecylbenzenesulfonate, the functional monomer is vinyltrimethoxysilane, and the persulfate is sodium persulfate.

[0054] S2. Mix 0.1 parts emulsifier and 140 parts water, then heat to 85°C and stir for 25 minutes. Add 0.05 parts persulfate and maintain the temperature for 5 minutes to obtain a mixture. Then, at 85°C, add pre-emulsion A dropwise to the mixture for polymerization over 45 minutes. After polymerization, adjust the temperature to 90°C and maintain this temperature for 45 minutes to obtain a core layer reaction solution. Then, adjust the temperature to 85°C and add pre-emulsion B dropwise to the core layer reaction solution for polymerization over 150 minutes. Adjust the reaction system temperature to 62°C and add 0.08 parts oxidant and 0.08 parts reducing agent for post-treatment. After post-treatment, adjust the reaction system temperature to 50°C, filter, and obtain a continuous phase pure acrylic emulsion. The emulsifier is alkyl polyoxyethylene ether, the persulfate is sodium persulfate, the oxidant is tert-butyl hydroperoxide, and the reducing agent is sodium sulfite.

[0055] Comparative Example 1 This comparative example prepares a continuous-phase pure acrylic emulsion according to the preparation method provided in Example 1. The difference between this comparative example and Example 1 is that unsaturated organic acids are not used in the preparation of the continuous-phase pure acrylic emulsion in this comparative example; instead, an aqueous solvent of the same mass is used to replace the unsaturated organic acids in Example 1. The remaining raw material ratios and preparation methods are strictly consistent with those in Example 1.

[0056] Comparative Example 2 This comparative example uses the preparation method provided in Example 1 to prepare a continuous phase pure acrylic emulsion. The difference between this comparative example and Example 1 is that in the process of preparing the continuous phase pure acrylic emulsion in this comparative example, part of the unsaturated organic acid is added to pre-emulsion A, and the remaining part of the unsaturated organic acid is added to pre-emulsion B. Specifically, pre-emulsion A consists of 0.2 parts emulsifier, 10 parts water, 10 parts methyl methacrylate, 10 parts ethyl acrylate, 0.5 parts functional monomer, and 0.05 parts persulfate; pre-emulsion B consists of 1 part emulsifier, 50 parts water, 30 parts methyl methacrylate, 25 parts ethyl acrylate, 20 parts isooctyl acrylate, 0.1 parts functional monomer, 0.3 parts persulfate, and 5 parts unsaturated organic acid. The remaining raw material ratios and preparation methods are strictly consistent with those in Example 1.

[0057] Comparative Example 3 This comparative example uses the preparation method provided in Example 1 to prepare a continuous-phase pure acrylic emulsion. The difference between this comparative example and Example 1 is that unsaturated organic acids are added to the pre-emulsion B during the preparation of the continuous-phase pure acrylic emulsion in this comparative example. Specifically, pre-emulsion A consists of 0.2 parts emulsifier, 10 parts water, 10 parts methyl methacrylate, 10 parts ethyl acrylate, 0.5 parts functional monomer, 0.05 parts persulfate, and 0.5 parts unsaturated organic acid; pre-emulsion B consists of 1 part emulsifier, 50 parts water, 30 parts methyl methacrylate, 25 parts ethyl acrylate, 20 parts isooctyl acrylate, 0.1 parts functional monomer, 0.3 parts persulfate, and 4.5 parts unsaturated organic acid. The remaining raw material ratios and preparation methods are strictly consistent with those in Example 1.

[0058] Preparation Example In this preparation example, the continuous phase pure acrylic emulsions provided in Examples 1-14 and Comparative Examples 1-3 were used to prepare multicolor coatings. The composition of the coating is shown in Table 1. The components of the coating are calculated by weight ratio as follows: continuous phase: granulation liquid: continuous phase = 6:2:2.

[0059] Table 1. Raw material composition of multicolor coatings

[0060] Note: The pure acrylic emulsions in Table 1 correspond to the continuous phase pure acrylic emulsions provided in Examples 1-14 and the continuous phase pure acrylic emulsions provided in Comparative Examples 1-3, respectively.

[0061] Test case 1. Test Object: The multicolor coating prepared in the preparation example is used as the test object for relevant performance tests.

[0062] 2. Test Content (1) Water resistance: The immersion test method in GB / T 1733-1993 "Determination of Water Resistance of Paint Film" was used. The paint film test panel prepared and dried according to the standard was immersed in distilled water at a temperature of (23±2)℃. The immersion time was set to 24 hours. After the specified time, the test panel was taken out and the surface moisture was absorbed with filter paper. It was then immediately observed under diffused light, and the presence of phenomena such as loss of gloss, discoloration, blistering, wrinkling, peeling, and rust was recorded.

[0063] (2) Freeze-thaw resistance: A three-cycle test was conducted according to Method A of GB / T 9268-2008 "Determination of Freeze-thaw Resistance of Latex Paints". After three cycles, the test subject was observed for any hardening, agglomeration, or separation. The freeze-thaw resistance of the test subject was rated according to the following standards: if the test subject showed no hardening, agglomeration, or separation under the above test conditions, it was rated as "no abnormality"; if the test subject showed hardening, agglomeration, or separation under the above test conditions, it was rated as "unqualified".

[0064] (3) Low-temperature storage stability: After the test subject is placed at a temperature of 5±1℃ for 7 days, observe whether there is any color bleeding in the dispersion medium of the test subject. The low-temperature storage stability of the test subject is rated according to the following standards: if the test subject does not show color bleeding after being placed under the above test conditions for 7 days, it is rated as "excellent"; if the test subject shows slight color bleeding after being placed under the above test conditions for 7 days, it is rated as "good"; if the test subject shows moderate color bleeding after being placed under the above test conditions for 7 days, it is rated as "average"; if the test subject shows severe color bleeding after being placed under the above test conditions for 7 days, it is rated as "unqualified".

[0065] (4) Thermal storage stability: Referring to "HG-T 4343-2012 Waterborne Multicolor Architectural Coatings", the test subjects were placed at a temperature of 50±2℃ for 7 days, and the dispersion medium of the test subjects was observed to see if there was any bleeding. The thermal storage stability of the test subjects was rated according to the following standards: if the test subjects showed no bleeding after 7 days under the above test conditions, it was rated as "excellent"; if the test subjects showed slight bleeding after 7 days under the above test conditions, it was rated as "good"; if the test subjects showed moderate bleeding after 7 days under the above test conditions, it was rated as "average"; if the test subjects showed severe bleeding after 7 days under the above test conditions, it was rated as "unqualified".

[0066] (5) Water resistance whitening: The test was conducted according to the immersion test method in GB / T 1733-1993 Test Method for Water Resistance of Paint Films. The paint film test panel prepared and dried according to the standard was immersed in distilled water at a temperature of (23±2)℃. The immersion time was set to 24 hours. After the specified time, the test panel was removed and the surface moisture was absorbed with filter paper. The whitening of the paint film surface was immediately observed under diffused light and recorded.

[0067] (6) Transparency: Referring to GB / T 1721-2008 Determination of Appearance and Transparency of Varnishes, Oils and Thinners, the test object is poured into a dry and clean colorimetric tube. Under the condition of 23±2℃, it is compared with a series of standard solutions of different turbidity under transmitted light in a dark box, and the grade of standard solution closest to the test object is selected. The transparency of the test object is rated according to the following standards: if the test object is completely clear, without any visible suspended matter, turbidity or milky luster, it is rated as "excellent"; if the test object shows a slight hazy milky white luster, good light transmission, and the outline of objects behind it is clearly distinguishable, it is rated as "good"; if the test object shows a moderate hazy milky white luster, poor light transmission, and objects behind it are only blurred, it is rated as "average"; if the test object shows a severe hazy milky white luster, opaque, it is rated as "unqualified".

[0068] 3. Test Results Table 2. Relevant performance test results of the test subjects

[0069] The test data of Examples 1-14 were compared with those of Comparative Examples 1-3, and the results are shown in Table 2. It can be found that the multicolor coatings prepared by the continuous phase pure acrylic emulsion provided in Examples 1-14 have both good thermal storage stability and low temperature storage stability. Compared with the continuous phase pure acrylic emulsion provided in Examples 1-14, the multicolor coatings prepared by the continuous phase pure acrylic emulsion provided in Comparative Examples 1, 2, and 3 all showed severe color bleeding after being placed at a temperature of 50±2℃ for 7 days, and their thermal storage stability was rated as "unqualified". They could not have both good thermal storage stability and low temperature storage stability.

[0070] The difference between the continuous-phase pure acrylic emulsion provided in Comparative Example 1 and Example 1 is that unsaturated organic acids were not used in the preparation process. Test results showed that the multicolor coatings prepared from the continuous-phase pure acrylic emulsion in Comparative Example 1 exhibited severe color bleeding after being placed at 50±2℃ and 5±1℃ for 7 days, and their thermal and low-temperature storage stability were rated as "unqualified." In the water-resistant whitening test, whitening occurred. This was because the continuous-phase pure acrylic emulsion in Comparative Example 1 did not use unsaturated organic acids in its preparation process, resulting in a lack of carboxyl group enrichment on the surface of the latex particles. In a weakly alkaline dispersed phase base paint environment, the latex particles could not form negatively charged carboxylate ions through carboxyl group dissociation, and therefore could not electrostatically associate with the cations on the protective colloid surface, thus failing to form a stable "carboxylate" three-dimensional network structure. This results in the lack of self-thickening ability and insufficient fluid resistance in the multicolor coating system, leading to stratification and color bleeding during hot and low-temperature storage. At the same time, due to the absence of carboxyl groups on the surface of latex particles, the interaction between them and the weakly alkaline protective colloid in the dispersion base paint is weakened, reducing the density and water resistance of the coating film, thus causing whitening in the water resistance whitening test.

[0071] Compared to Example 1, the difference in the composition of the continuous-phase pure acrylic emulsion provided in Comparative Example 2 is that, during the preparation process, a portion of the unsaturated organic acid was added to pre-emulsion A, and the remaining portion was added to pre-emulsion B. The test results show that the multicolor coating prepared from the continuous-phase pure acrylic emulsion provided in Comparative Example 2 exhibited severe bleeding after being placed at 50±2℃ for 7 days, and its thermal storage stability was rated as "unqualified"; after being placed at 5±1℃ for 7 days, it exhibited moderate bleeding, and its low-temperature storage stability was rated as "moderate"; in the water-resistant whitening test, a slight whitening phenomenon occurred. This is because, in the preparation process of Comparative Example 2, a portion of the unsaturated organic acid was added to pre-emulsion B, resulting in a reduced proportion of carboxylic acid input during the nucleation stage, failing to fully utilize the control effect of stepwise polymerization on the distribution of carboxyl groups. This results in insufficient carboxyl group enrichment on the surface of latex particles, leading to a limited number of carboxylate ions generated during dissociation in a weakly alkaline dispersed phase environment. These ions cannot fully electrostatically associate with the cations on the protective colloid surface, making it difficult to form a complete and stable "carboxylate" three-dimensional network structure. This network structure defect reduces the system's self-thickening ability and weakens its fluid support, resulting in severe bleeding during hot storage. Under low-temperature conditions, although the structural instability is slightly alleviated due to reduced mobility, moderate bleeding still occurs. Simultaneously, insufficient surface carboxyl group coverage also affects the interaction between latex particles and the weakly alkaline protective colloid in the dispersion base paint, leading to decreased water resistance of the coating film and slight whitening.

[0072] Compared to Example 1, the difference in the composition of the continuous-phase pure acrylic emulsion provided in Comparative Example 3 is that unsaturated organic acids were added to the pre-emulsion B during the preparation process. Test results show that the multicolor coatings prepared from the continuous-phase pure acrylic emulsion provided in Comparative Example 3 exhibited severe color bleeding after being placed at temperatures of 50±2℃ and 5±1℃ for 7 days, and their thermal and low-temperature storage stability were rated as "unqualified." In the water-resistant whitening test, slight whitening occurred. This is because, in Comparative Example 3, all unsaturated organic acids were added to the pre-emulsion B during the preparation process. Since the carboxyl groups were mainly introduced during the shell polymerization stage, they could not effectively participate in the construction of the hard core structure during the nucleation stage and were difficult to fully migrate to the surface of the latex particles in subsequent polymerization. Therefore, in a weakly alkaline dispersed phase environment, the number of dissociable carboxyl groups on the surface of the latex particles was insufficient, and enough carboxylate ions could not be generated to effectively electrostatically associate with the cations on the protective colloid surface, resulting in the inability to form the "carboxylate house" three-dimensional network structure. The system lacks self-thickening properties, resulting in insufficient viscosity and severe stratification and color bleeding during hot and low-temperature storage. At the same time, the absence of surface carboxyl groups weakens the interaction between latex particles and the weakly alkaline protective colloid in the dispersion base paint, as well as the density of the coating film, leading to a decrease in water-whitening resistance.

[0073] Compared to Example 1, the difference in the composition of the continuous-phase pure acrylic emulsions provided in Examples 5-7 lies in the different short-chain acrylate monomers used in the preparation process. From the test results, the multicolor coating prepared from the continuous-phase pure acrylic emulsion provided in Example 5 was rated as "good" in thermal storage stability, the multicolor coating prepared from the continuous-phase pure acrylic emulsion provided in Example 6 was rated as "fair," and the multicolor coating prepared from the continuous-phase pure acrylic emulsion provided in Example 7 was rated as "fair" in both thermal and low-temperature storage stability. The multicolor coating prepared from the continuous-phase pure acrylic emulsion provided in Example 1 exhibits the best overall performance. This demonstrates that by using at least one of methyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, and butyl acrylate as short-chain acrylate monomers, these short-chain acrylate monomers participate in polymerization during the reaction and simultaneously promote the migration of carboxyl groups to the surface of latex particles, improving the efficiency of carboxyl group migration to the latex particle surface. This effectively regulates the carboxyl content on the latex particle surface, thereby improving the thermal and low-temperature storage stability of the multicolor coating prepared from the continuous-phase pure acrylic emulsion.

[0074] Compared to Example 1, the difference in the composition of the continuous phase pure acrylic emulsions provided in Examples 8-9 lies in the different unsaturated organic acids used in the preparation process. Test results show that the multicolor coating prepared from the continuous phase pure acrylic emulsion provided in Example 8 exhibited slight bubbling in the water resistance test and general whitening in the water whitening test, indicating inferior water resistance and whitening resistance compared to Examples 1 and 9. This demonstrates that using acrylic acid and methacrylic acid as unsaturated organic acids can optimize the carboxyl enrichment efficiency and water whitening resistance of the latex particle surface. On one hand, it can control the carboxyl content on the latex particle surface to a suitable range, effectively reducing the risk of water whitening in the pure acrylic emulsion and ensuring sufficient carboxyl groups to directionally associate with the protective colloid components in the dispersed phase base paint after carboxyl dissociation. On the other hand, the unsaturated organic acids provide active crosslinking sites in the polymerization reaction, synergistically constructing a dense hydrophobic network with functional monomers, effectively reducing swelling and whitening caused by water molecules entering the paint film, further improving the water whitening resistance and water resistance of the paint film.

[0075] Compared to Example 1, the difference in the composition of the continuous phase pure acrylic emulsion provided in Example 13 is that, after the pre-emulsion A is added dropwise during the preparation process, the heat preservation operation is not included. From the test results, the multicolor coating prepared from the continuous phase pure acrylic emulsion provided in Example 13 was rated as "average" in the transparency test. Compared to Example 1, the difference in the composition of the continuous phase pure acrylic emulsion provided in Example 14 is that, after the pre-emulsion B is added dropwise during the preparation process, the heat preservation operation is not included. From the test results, the multicolor coating prepared from the continuous phase pure acrylic emulsion provided in Example 14 was rated as "average" in the transparency test. Therefore, the heat preservation process is beneficial for improving the monomer conversion rate of acrylate monomers, reducing monomer residue, and allowing the polymer chains inside the latex particles of the continuous phase pure acrylic emulsion to be arranged in a sufficiently regular manner. Simultaneously, it makes the distribution of carboxyl groups on the surface of the latex particles more uniform and orderly, enabling the latex particles to achieve tight and uniform stacking during film formation, effectively reducing light scattering, thereby improving the transparency of the continuous phase pure acrylic emulsion.

[0076] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention, but such modifications or substitutions are all within the scope of protection of the present invention.

Claims

1. A method for preparing a continuous phase pure acrylic emulsion, characterized in that, The raw materials used to prepare the continuous phase pure acrylic emulsion include the following materials: acrylate monomers, unsaturated organic acids, and functional monomers; The acrylate monomers include long-chain acrylate monomers and short-chain acrylate monomers; The method for preparing the continuous phase pure acrylic emulsion includes the following steps: S1. Preparation of preemulsion A and preemulsion B: Preemulsion A comprises the acrylate monomer, the unsaturated organic acid, and the functional monomer; Preemulsion B comprises the acrylate monomer and the functional monomer; wherein, by mass ratio, in the raw materials used to prepare preemulsion A, the ratio of acrylate monomer to unsaturated organic acid is (3~5):1; by mass percentage, in all the unsaturated organic acids included in the raw materials used to prepare the continuous phase pure acrylic emulsion, the proportion of unsaturated organic acids used to prepare preemulsion A is not less than 90%; S2. Under a temperature of 80~90℃, the pre-emulsion A undergoes a polymerization reaction to obtain a core layer reaction solution; subsequently, the pre-emulsion B is added to the core layer reaction solution to carry out a polymerization reaction.

2. The preparation method according to claim 1, characterized in that: S2 includes the following steps: After the pre-emulsion A is added at a temperature of 80-90°C, the temperature is adjusted to 85-90°C and kept at this temperature for 30-60 minutes to obtain the core layer reaction solution.

3. The preparation method according to claim 1, characterized in that: S2 includes the following steps: At a temperature of 80-90°C, pre-emulsion B is added dropwise to the core layer reaction solution; after the addition is completed, the temperature is adjusted to 85-90°C and kept at this temperature for 60-90 minutes.

4. The preparation method according to claim 1, characterized in that: The long-chain acrylate monomer has ≥8 carbon atoms in its alkyl chain; the short-chain acrylate monomer has 1 to 4 carbon atoms in its alkyl chain.

5. The preparation method according to claim 4, characterized in that: The short-chain acrylate monomers include at least one of methyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, and butyl acrylate.

6. The preparation method according to claim 1, characterized in that: The unsaturated organic acid includes at least one of acrylic acid, methacrylic acid, and itaconic acid.

7. The preparation method according to claim 1, characterized in that: The functional monomer includes at least one of vinyltrimethoxysilane, methacryloxypropyltrimethoxysilane, and allyl methacrylate silane polymers.

8. The preparation method according to claim 1, characterized in that: The mass ratio of the acrylate monomer in the preemulsion A to the acrylate monomer in the preemulsion B is (2~5): (10~13).

9. A continuous phase pure acrylic emulsion, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 8.

10. A multi-colored coating comprising a continuous phase pure acrylic emulsion prepared by any one of claims 1 to 8, or a dispersion base paint prepared by the continuous phase pure acrylic emulsion of claim 9; wherein the dispersion base paint comprises a weakly alkaline protective colloid.

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