Acrylic acid microgel emulsion with controllable particle size as well as preparation method and application of acrylic acid microgel emulsion

Abstract

The invention discloses an acrylic microgel emulsion with a controllable particle size as well as a preparation method and application of the acrylic microgel emulsion. The preparation method of the acrylic microgel emulsion comprises the following steps: (1) mixing a first dropping material and an initiator, heating to 50-80 DEG C, and preserving heat; (2) adding a second dropping material and an initiator into a reaction system in the step (1), heating to 50-80 DEG C, and keeping the temperature; and (3) adding the third dripping material and the initiator into the reaction system in the step (2), heating to 50-80 DEG C, and keeping the temperature. The acrylic microgel emulsion with different particle size ranges is successfully prepared by accurately regulating and controlling reaction parameters including monomer concentration, stirring rate, additive ratio and the like, and the particle size ranges are 50-500 nm, 0.5-5 [mu] m, 5-10 [mu] m and 10-50 [mu] m. The microgel emulsion is suitable for diversified application scenes and has a wide application prospect.

Description

Technical Field

[0001] The invention belongs to the field of multifunctional microgel emulsions, and in particular relates to an acrylic microgel emulsion with controllable particle size, a preparation method and an application thereof. Background Art

[0002] Microgels are cross-linked polymer particles ranging in size from nanometers to micrometers. They absorb solvents, swell, and respond rapidly to external stimuli such as temperature, pH, and light. They are composed of polymer networks, possess a high specific surface area, and exhibit good biocompatibility. They are typically prepared through techniques such as emulsion polymerization and microfluidics. Due to their tiny size and stimuli-responsiveness, microgels have been widely used in a variety of fields, including high-performance paints and coatings, polymer composites, drug delivery, tissue engineering, smart sensors, cosmetics, and pollutant adsorption. They are important functional materials in smart materials and biomedical research.

[0003] The size range of microgels significantly influences their application scenarios. Nanoscale microgels (20-200 nm) offer unique advantages in the biomedical field due to their ultra-small size and excellent permeability, making them particularly suitable for targeted drug delivery, gene therapy vectors, and in vivo imaging probes. They also exhibit excellent biosafety due to their renal clearance. Submicron-sized microgels (200 nm-1 μm) excel in in vitro diagnostics and are commonly used as signal amplification carriers in homogeneous immunoassays, biomimetic cell membrane interface modification, and sustained-release systems for active ingredients in high-end cosmetics. Their moderate size ensures colloidal stability while providing ample surface functional sites. Micron-sized microgels (1-100 μm) are widely used in tissue engineering due to their macroscopic controllability and structural rigidity. Examples include cell culture scaffolds for 3D-directed stem cell differentiation, temperature-sensitive "bioinks" for 3D bioprinting, and intelligent coatings in industrial applications, such as self-healing anti-corrosion coatings and oil-water separation membranes. Their larger size also facilitates the loading of micron-sized functional fillers, such as magnetic particles and quantum dots. It is worth noting that as the size of the microgel increases, the stimulus response speed decreases, but the mechanical strength and drug loading capacity increase significantly. This gradient between size and performance provides precise customized solutions for different application scenarios.

[0004] However, current research on microgels has primarily focused on synthesis methods and performance characterization, while research on how to prepare acrylic microgel emulsions with controllable particle size remains limited. Therefore, it is necessary to propose a new preparation strategy to obtain acrylic microgel emulsions with different particle size ranges to meet diverse application scenarios and functional requirements. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide an acrylic microgel emulsion with controllable particle size and its preparation method and application, aiming to solve the problem that the existing acrylic emulsion is difficult to adapt to diverse needs in practical applications.

[0006] The purpose of the present invention is achieved through the following technical solutions: A method for preparing an acrylic microgel emulsion with controllable particle size comprises the following steps: (1) Mixing the first drop material and the initiator, heating to 50-80°C and keeping the temperature constant; the first drop material comprises material A, a crosslinking agent, and an emulsifier; the material A comprises vinyl monomers, methacrylic acid and its ester monomers, and acrylic acid ester monomers; (2) adding the second drop material and the initiator to the reaction system of step (1), heating the temperature to 50-80°C and keeping the temperature; the second drop material is composed of material B, a crosslinking agent and an emulsifier; the material B includes vinyl monomers, methacrylic acid and its ester monomers, and acrylic acid ester monomers; (3) Adding the third drop of material and the initiator to the reaction system of step (2), heating to 50-80°C and keeping the temperature constant; the third drop of material is composed of material C and an emulsifier; the material C includes vinyl monomers, methacrylic acid and its ester monomers, acrylic acid and its ester monomers.

[0007] The present invention employs a phased monomer addition strategy, sequentially constructing a gradient structure (core (rigidity) - intermediate layer (transition) - shell (functionalization)) to improve the material's overall performance. Adding all monomers at once can lead to several drawbacks: 1. Reaction runaway: Excessive monomer concentration can lead to excessively rapid polymerization, concentrated exothermic heat, and the potential for implosion, broadening the molecular weight distribution, and even gelation failure. 2. Structural inhomogeneity: It's difficult to control the balance between nucleation and growth of the microgel, leading to uneven particle size, agglomeration, or a loose structure.

[0008] In the present invention, different monomers give the microgel specific properties (such as hydrophilicity, mechanical strength, and stimulus responsiveness), and their step-by-step introduction can avoid functional group interference and achieve precise functional integration (such as core-shell structure).

[0009] Preferably, in step (1), the first drop of material and the initiator need to be mixed within 5 to 20 minutes; and the insulation time is 40 to 90 minutes.

[0010] Preferably, in step (2), the second drop of material and the initiator need to be added to the reaction system of step (1) within 60 to 90 minutes; and the insulation time is 40 to 90 minutes.

[0011] Preferably, in step (3), the third drop of material and the initiator need to be added to the reaction system of step (2) within 60 to 90 minutes, and the insulation time is 40 to 90 minutes.

[0012] In the present invention, in the synthesis of acrylic microgels, the reaction rate and particle size distribution can be controlled by adding monomers and initiators in steps. The first drop of material is mixed within 5 to 20 minutes in order to form a uniform initial core and avoid explosive polymerization leading to uneven particle size. Insufficient holding time will result in insufficient core formation, while too much time may trigger side reactions or excessive cross-linking. The second drop of material is used for core growth and needs to be added slowly to maintain a stable monomer concentration. Too fast will lead to a widening of the particle size distribution, while too slow will result in incomplete reaction. The third drop of material is used to further regulate the structure and properties of the microgel, and its drop rate affects the final cross-linking density and swelling properties. The initiator must be added simultaneously in each step to ensure the continuous generation of free radicals and prevent reaction interruption or local over-polymerization. The core of the present invention is to achieve uniform nucleation, growth and cross-linking through step-by-step rate-controlled addition; at the same time, the holding time has an important influence on the particle size, monodispersity and structural integrity of the final product.

[0013] Preferably, in step (1), step (2) and step (3), the initiator is at least one of potassium persulfate, ammonium persulfate, azobisisobutyronitrile and di-tert-butyl peroxide.

[0014] Preferably, in step (1), step (2) and step (3), the vinyl monomer is at least one of styrene and vinyltoluene.

[0015] Preferably, in step (1), step (2) and step (3), the methacrylic acid and its ester monomers are at least one of methacrylic acid, methyl methacrylate, n-butyl methacrylate, isooctyl methacrylate, lauryl methacrylate, allyl methacrylate, glycidyl methacrylate and glycol dimethacrylate.

[0016] Preferably, in step (1) and step (2), the acrylic acid ester monomers are at least one of methyl acrylate, n-butyl acrylate, isooctyl acrylate, lauryl acrylate, allyl acrylate, hexanediol diacrylate, neopentyl glycol diacrylate and tripropylene glycol diacrylate.

[0017] Preferably, the acrylic acid and its ester monomer in step (3) is at least one of acrylic acid, methyl acrylate, n-butyl acrylate, isooctyl acrylate, lauryl acrylate, allyl acrylate, hexanediol diacrylate, neopentyl glycol diacrylate and tripropylene glycol diacrylate.

[0018] Preferably, in step (1) and step (2), the cross-linking agent is trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, or N,N'-methylenebisacrylamide.

[0019] Preferably, in step (1), step (2) and step (3), the emulsifier is at least one of sodium lauryl sulfate, sodium dodecylbenzene sulfonate, alkylphenol polyoxyethylene ether and fatty alcohol polyoxyethylene ether.

[0020] Preferably, in step (1), step (2) and step (3), the initiator needs to be prepared into a solution before use, and the solvent used is at least one of water, ethanol and toluene.

[0021] Preferably, in step (1), step (2) and step (3), the emulsifier needs to be prepared into an aqueous solution before use.

[0022] Preferably, in step (1), the amounts of material A, cross-linking agent, emulsifier and initiator are 15-20 parts, 0.8-1.5 parts, 0.6-1.0 parts and 0.05-0.15 parts respectively by mass; In step (2), the amounts of material B, cross-linking agent, emulsifier and initiator are 15-20 parts, 0.8-1.5 parts, 0.6-1.0 parts and 0.05-0.15 parts respectively; In step (3), the amounts of material C, emulsifier, and initiator are 18-25 parts, 0.6-1.0 parts, and 0.05-0.15 parts, respectively; During the addition and heat preservation processes of steps (1), (2) and (3), stirring is maintained, and the stirring rate is controlled within the range of 1000 to 2000 rpm. The microgel particle size of the obtained acrylic microgel emulsion is 50 nm to 500 nm.

[0023] Preferably, in step (1), the amounts of material A, cross-linking agent, emulsifier and initiator are 25-35 parts, 1.0-2.0 parts, 1.0-2.0 parts and 0.2-0.5 parts respectively by mass; In step (2), the amounts of material B, cross-linking agent, emulsifier and initiator are 25-35 parts, 1.0-2.0 parts, 1.0-2.0 parts and 0.2-0.5 parts respectively; In step (3), the amounts of material C, emulsifier, and initiator are 40-50 parts, 1.0-2.0 parts, and 0.2-0.5 parts, respectively; During the addition and heat preservation processes of steps (1), (2) and (3), stirring is maintained and the stirring rate is controlled within the range of 400 to 800 rpm. The microgel particle size of the obtained acrylic microgel emulsion is 0.5 μm to 5 μm.

[0024] Preferably, in step (1), the amounts of material A, cross-linking agent, emulsifier and initiator are 25-35 parts, 0.5-1.0 parts, 0.5-1.0 parts and 0.4-0.6 parts respectively by mass; In step (2), the amounts of material B, cross-linking agent, emulsifier and initiator are 25-35 parts, 0.5-1.0 parts, 0.5-1.0 parts and 0.4-0.6 parts respectively; In step (3), the amounts of material C, emulsifier, and initiator are 40-50 parts, 0.5-1.0 parts, and 0.4-0.6 parts, respectively; During the addition and heat preservation processes of steps (1), (2) and (3), stirring is maintained and the stirring rate is controlled within the range of 100 to 300 rpm. The microgel particle size of the obtained acrylic microgel emulsion is 5 μm to 10 μm.

[0025] Preferably, the first drop-added material, the second drop-added material and the third drop-added material further comprise a dispersant; when in step (1), by weight, the amount of material A, the cross-linking agent, the emulsifier, the initiator and the dispersant are 25-35 parts, 1.0-2.0 parts, 0.5-1.0 parts, 0.5-1.0 parts and 0.5-1.0 parts respectively; In step (2), the amounts of material B, cross-linking agent, emulsifier, initiator and dispersant are 25-35 parts, 1.0-2.0 parts, 0.5-1.0 parts, 0.5-1.0 parts and 0.5-1.0 parts respectively; In step (3), the amounts of material C, emulsifier, initiator and dispersant are 40-50 parts, 0.5-1.0 parts, 0.5-1.0 parts and 0.5-1.0 parts respectively; During the addition and heat preservation processes of steps (1), (2) and (3), stirring is maintained and the stirring rate is controlled within the range of 100 to 300 rpm. The microgel particle size of the obtained acrylic microgel emulsion is 10 μm to 50 μm.

[0026] Preferably, the dispersant is at least one of polyvinyl alcohol and hypromellose.

[0027] In the present invention, the particle size of acrylic microgel is precisely controlled by synergistically regulating emulsifier, initiator, stirring speed, monomer concentration, crosslinking agent and temperature: The emulsifier concentration determines the number of micelles. High concentration increases the nucleation sites to generate small micelles and reduce the particle size. The type and dosage of initiator affect the nucleation rate. Water-soluble initiators (such as persulfate) initiate quickly to promote multi-nucleation and achieve small particle size, while oil-soluble initiators (such as AIBN) initiate slowly to facilitate particle growth and form large particle size. The stirring speed regulates dispersion and aggregation. High-speed stirring enhances shear force to inhibit particle aggregation and reduce particle size, while low speed facilitates fusion and increases particle size. Monomer concentration dominates particle growth. Increased concentration provides more monomer sources to promote particle size increase, but the initiation rate needs to be matched to prevent excessive nucleation. The crosslinking agent ratio limits the swelling space, high crosslinking density compresses the network and reduces the particle size after drying, while low crosslinking allows swelling and expansion; the temperature range bidirectionally regulates the dynamics, and heating accelerates initiation and polymerization to promote the nucleation of small particles. However, excessively high temperatures (>80°C) may trigger side reactions or aggravate Ostwald ripening, leading to a wider distribution. The core principle of this invention is to construct the initial micelle template through emulsifiers, control the nucleation / growth balance through initiators and temperature, regulate the internal structure expansion through monomers and crosslinkers, and maintain dispersion stability through stirring. Multiple parameters work together to achieve precise design of particle sizes from nanometers to micrometers.

[0028] When synthesizing large acrylic microgels with particle sizes on the order of tens of microns, adding a dispersant is a key measure to prevent particle aggregation, maintain monodispersity, and ensure controllable reactions. This is because large particles, due to their large mass and rapid sedimentation, are more likely to collide and aggregate during the polymerization process. Dispersants form a protective layer on the particle surface through steric hindrance (such as adsorption and coating of particles by long PVA chains) or electrostatic repulsion (such as with ionic dispersants), isolating them from physical contact and thus preventing uncontrolled fusion caused by van der Waals forces.

[0029] An acrylic microgel emulsion with controllable particle size is prepared according to the preparation method of the acrylic microgel emulsion with controllable particle size.

[0030] The application of the above-mentioned acrylic microgel emulsion with controllable particle size in automotive coatings and adhesives.

[0031] Compared with the prior art, the present invention has the following beneficial effects: (1) The acrylic microgel emulsion provided by the present invention is synthesized by emulsion polymerization process. The preparation process has mild reaction conditions, simple operation, good process adaptability and broad application prospects.

[0032] (2) The present invention successfully prepared acrylic microgel emulsions with different particle size ranges by precisely controlling the reaction parameters, including monomer concentration, stirring rate, and additive ratio. These microgel emulsions are suitable for a variety of application scenarios and have broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1Transmission electron microscope (TEM) images of the acrylic microgel emulsions prepared in Examples 1 to 4.

[0034] Figure 2 This is a particle size distribution diagram of the gel particles in the acrylic microgel emulsion prepared in Example 1.

[0035] Figure 3 This is the particle size distribution diagram of the gel particles in the acrylic microgel emulsion prepared in Example 2.

[0036] Figure 4 This is the particle size distribution diagram of the gel particles in the acrylic microgel emulsion prepared in Example 3.

[0037] Figure 5 This is the particle size distribution diagram of the gel particles in the acrylic microgel emulsion prepared in Example 4.

[0038] Figure 6 These are actual photographs of the coating corresponding to the experimental group and the control group, where the left picture corresponds to the experimental group and the right picture corresponds to the control group. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0040] Example 1 The raw material statistics of an acrylic microgel emulsion with a microgel particle size of 50 nm to 500 nm are shown in Table 1.

[0041] Table 1 Statistics of raw materials for Example 1

[0042] Preparation before the experiment: In step (1), step (2) and step (3), the initiator needs to be prepared into an initiator solution before use. The solvent used is water, and the mass parts of the initiator and water are 0.1 parts and 4 parts respectively.

[0043] In step (1), step (2) and step (3), the emulsifier needs to be prepared into an emulsifier aqueous solution before use, with the mass proportions of emulsifier and water being 0.83 parts and 130 parts respectively.

[0044] Referring to Table 1, the corresponding parts by mass of material A, crosslinking agent and emulsifier aqueous solution were mixed uniformly to obtain the first drop of material; The corresponding parts by weight of material B, crosslinking agent and emulsifier aqueous solution are mixed uniformly to obtain the second drop material; The corresponding parts by mass of material C and the emulsifier aqueous solution were mixed uniformly to obtain the third drop-added material.

[0045] The preparation method of the acrylic microgel emulsion having a microgel particle size of 50 nm to 500 nm comprises the following specific steps: (1) Refer to the component ratio in Table 1, control the speed to 1200 rpm, mix the first drop of material and initiator within 10 minutes, raise the temperature to 75℃ and keep it warm for 1 hour; (2) Add the second drop of feed and initiator to the reaction system of step (1) within 60 minutes, raise the temperature to 80°C and keep it warm for 1 hour; (3) The third drop of material and the initiator are added to the reaction system of step (2) within 60 minutes, the temperature is raised to 80°C and kept warm for 1 hour, and then cooled to room temperature to prepare an acrylic microgel emulsion with a microgel particle size of 50 nm to 500 nm.

[0046] Example 2 The raw material statistics of an acrylic microgel emulsion with a microgel particle size of 0.5 μm~5 μm are shown in Table 2.

[0047] Table 2 Statistics of raw materials for Example 2

[0048] Preparation before the experiment: In step (1), step (2) and step (3), the initiator needs to be prepared into an initiator solution before use. The solvent used is water, and the mass parts of the initiator and water are 0.4 parts and 4 parts respectively.

[0049] In step (1), step (2) and step (3), the emulsifier needs to be prepared into an emulsifier aqueous solution before use, with the mass proportions of emulsifier and water being 1.32 parts and 130 parts respectively.

[0050] Referring to Table 2, the corresponding parts by mass of material A, crosslinking agent and emulsifier aqueous solution were mixed uniformly to obtain the first drop of material; The corresponding parts by weight of material B, crosslinking agent and emulsifier aqueous solution are mixed uniformly to obtain the second drop material; The corresponding parts by mass of material C and the emulsifier aqueous solution were mixed uniformly to obtain the third drop-added material.

[0051] The preparation method of the acrylic microgel emulsion having a microgel particle size of 0.5 μm to 5 μm comprises the following specific steps: (1) Refer to the component ratio in Table 2, control the speed to 600 rpm, mix the first drop of material and initiator within 10 minutes, raise the temperature to 75°C and keep it warm for 1 hour; (2) Add the second drop of feed and initiator to the reaction system of step (1) within 60 minutes, raise the temperature to 80°C and keep it warm for 1 hour; (3) The third drop of material and the initiator are added to the reaction system of step (2) within 60 minutes, the temperature is raised to 80°C and kept warm for 1 hour, and then cooled to room temperature to prepare an acrylic microgel emulsion with a microgel particle size of 0.5 μm to 5 μm.

[0052] Example 3 The raw material statistics of an acrylic microgel emulsion with a microgel particle size of 5 μm~10 μm are shown in Table 3.

[0053] Table 3 Statistics of raw materials for Example 3

[0054] Preparation before the experiment: In step (1), step (2) and step (3), the initiator needs to be prepared into an initiator solution before use. The solvent used is toluene, and the mass parts of the initiator and toluene are 0.5 parts and 3 parts respectively.

[0055] In step (1), step (2) and step (3), the emulsifier needs to be prepared into an emulsifier aqueous solution before use, with the mass parts of emulsifier and water being 0.66 parts and 80 parts respectively.

[0056] Referring to Table 3, the corresponding parts by mass of material A, crosslinking agent and emulsifier aqueous solution were mixed uniformly to obtain the first drop of material; The corresponding parts by weight of material B, crosslinking agent and emulsifier aqueous solution are mixed uniformly to obtain the second drop material; The corresponding parts by mass of material C and the emulsifier aqueous solution were mixed uniformly to obtain the third drop-added material.

[0057] The preparation method of the acrylic microgel emulsion having a microgel particle size of 5 μm to 10 μm comprises the following specific steps: (1) Refer to the component ratio in Table 3, control the speed to 200 rpm, mix the first drop of material and the initiator within 10 minutes, raise the temperature to 60°C and keep it warm for 1.5 hours; (2) Add the second drop of feed and initiator to the reaction system of step (1) within 60 minutes, raise the temperature to 65°C and keep it warm for 1.5 hours; (3) The third drop of material and the initiator are added to the reaction system of step (2) within 60 minutes, the temperature is raised to 70°C and kept warm for 1.5 hours, and then cooled to room temperature to prepare an acrylic microgel emulsion with a microgel particle size of 5 μm to 10 μm.

[0058] Example 4 The raw material statistics of an acrylic microgel emulsion with a microgel particle size of 10 μm~50 μm are shown in Table 4.

[0059] Table 4 Statistics of raw materials for Example 4

[0060] Preparation before the experiment: In step (1), step (2) and step (3), the initiator needs to be prepared into an initiator solution before use. The solvent used is toluene, and the mass parts of the initiator and toluene are 0.66 parts and 4 parts respectively.

[0061] In steps (1), (2), and (3), the emulsifier is prepared into an emulsifier aqueous solution before use, with the mass proportions of emulsifier and water being 0.66 parts and 40 parts, respectively. The dispersant is added to the emulsifier aqueous solution to obtain an emulsifier solution containing the dispersant.

[0062] Referring to Table 4, the corresponding parts by mass of material A, a cross-linking agent, and an emulsifier solution containing a dispersant were mixed uniformly to obtain the first drop of material; The corresponding parts by mass of material B, a cross-linking agent and an emulsifier solution containing a dispersant are mixed uniformly to obtain a second dropwise addition material; The corresponding parts by mass of material C and the emulsifier solution containing a dispersant are mixed uniformly to obtain a third dropwise addition material.

[0063] The preparation method of the acrylic microgel emulsion having a microgel particle size of 10 μm to 50 μm comprises the following specific steps: (1) Refer to the component ratio in Table 4, control the speed to 150 rpm, mix the first drop of material and the initiator within 10 minutes, raise the temperature to 60°C and keep it warm for 1.5 hours; (2) Add the second drop of feed and initiator to the reaction system of step (1) within 60 minutes, raise the temperature to 65°C and keep it warm for 1.5 hours; (3) The third drop of material and the initiator are added to the reaction system of step (2) within 60 minutes, the temperature is raised to 75°C and kept warm for 1.5 hours, and then cooled to room temperature to prepare an acrylic microgel emulsion with a microgel particle size of 10 μm to 50 μm.

[0064] Physical property characterization: 1. Microscopic morphology The acrylic microgel emulsions prepared in Examples 1 to 4 were tested by transmission electron microscopy (TEM). Figure 1 As shown. Figure 1 It can be seen that the acrylic microgel particles prepared in the present invention are spherical.

[0065] 2. Particle size distribution The particle size distribution of the gel particles in the acrylic microgel emulsion prepared in Examples 1 to 4 was tested and statistically analyzed using a HYL-2076 laser particle size distribution analyzer. The statistical results are as follows: Figures 2 to 5 As shown. Figures 2 to 5We can observe that the particle size distribution of the acrylic microgel emulsion prepared in the present invention conforms to the normal distribution, and the particle size range is relatively concentrated.

[0066] Performance testing: 1. Storage stability The acrylic microgel emulsions prepared in Examples 1 to 4 were placed at room temperature for 14 days. After 14 days, the appearance of the emulsions and the particle size of the microgels were evaluated. The evaluation results are shown in Table 5.

[0067] Table 5 Storage stability results

[0068] As shown in Table 5, the experiment shows that the acrylic microgel emulsion prepared in the present invention has good physical stability. No delamination is observed after storage at room temperature for 14 days, and the microgel particle size remains stable without obvious aggregation or change.

[0069] Application testing: 1. Application in automotive coatings The specific steps are as follows: Control group: Take a certain amount of base coating, specifically epoxy resin coating, purchased from Hubei Longsheng Sihai New Materials Co., Ltd., without adding any additives, and evenly apply the base coating on a clean and dry substrate (specifically tinplate) to a coating thickness of 30 μm ± 5 μm. Dry and cure at room temperature.

[0070] Experimental Group: 5 wt% of the acrylic microgel emulsion (prepared in Example 1) was added to the same amount of base coating and uniformly mixed to obtain a mixed coating. The mixed coating was evenly coated onto a clean, dry substrate to a thickness of 30 μm ± 5 μm and dried and cured at room temperature.

[0071] The actual photos of the coatings corresponding to the experimental group and the control group are shown in the figure below. Figure 6 As shown, the left picture corresponds to the experimental group, and the right picture corresponds to the control group. Figure 6 We can see that the control group coating has obvious orange peel effect and sagging problems, while the experimental group coating has a smooth and flat surface without similar defects, indicating that the addition of acrylic microgel emulsion significantly improves the quality of the coating.

[0072] 2. Application in adhesives The specific steps are as follows: Control group: A two-component epoxy resin adhesive and a polyetheramine curing agent (both purchased from Henkel Loctite Co., Ltd.) were mixed according to the manufacturer's recommended ratio (resin:curing agent = 2:1, by mass) and mechanically stirred for 5 minutes until uniform. The mixed adhesive was applied to the treated aluminum alloy specimens, pressure applied at 0.2 MPa for 10 seconds, and then cured at room temperature for 24 hours.

[0073] Experimental group: To a two-component epoxy resin adhesive of the same proportion (based on the total weight of the resin and curing agent), add 5 wt% of the acrylic microgel emulsion (prepared in Example 1). Premix and stir with the resin for 5 minutes. Then add the curing agent and continue stirring for 5 minutes until uniform. The coating and curing steps were the same as for the control group to ensure consistent coating thickness.

[0074] Mechanical properties test method: Tensile strength: According to ASTM D638, a universal testing machine (Instron 5967) was used at a tensile rate of 10 mm / min. Five specimens were tested in each group and the average value was taken.

[0075] Shear strength: Based on ASTM D1002, using single lap shear specimens, the test conditions are the same as tensile strength.

[0076] The mechanical properties of the corresponding adhesives in the control group and the experimental group were tested, and the test results are shown in Table 6.

[0077] Table 6 Mechanical properties test results

[0078] The test results in Table 6 show that the tensile strength and shear strength of the adhesive in the experimental group increased by 20% and 23% respectively compared with the control group, indicating that the mechanical properties of the adhesive were significantly improved after the addition of acrylic microgel emulsion.

[0079] The specific embodiments of the present invention described above do not limit the scope of protection of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A method for preparing an acrylic microgel emulsion with controllable particle size, characterized in that: The steps include: (1) Mixing the first drop of material and the initiator, heating to 50-80°C and keeping the temperature constant; the first drop of material consists of material A, a crosslinking agent and an emulsifier; material A includes vinyl monomers, methacrylic acid and its ester monomers, and acrylic acid ester monomers; (2) adding the second drop of feed and the initiator to the reaction system of step (1), heating the system to 50-80°C and keeping the temperature constant; The second drop-added material consists of material B, a cross-linking agent, and an emulsifier; material B includes vinyl monomers, methacrylic acid and its ester monomers, and acrylic acid ester monomers; (3) Add the third drop of material and the initiator to the reaction system of step (2), heat it to 50-80°C and keep it warm; the third drop of material consists of material C and an emulsifier; material C includes vinyl monomers, methacrylic acid and its ester monomers, acrylic acid and its ester monomers.

2. The method for preparing the acrylic microgel emulsion with controllable particle size according to claim 1, wherein: In step (1), the first drop of material and the initiator need to be mixed within 5 to 20 minutes; the insulation time is 40 to 90 minutes; and / or In step (2), the second drop of material and the initiator need to be added to the reaction system of step (1) within 60 to 90 minutes; the insulation time is 40 to 90 minutes; and / or In step (3), the third drop of material and the initiator need to be added to the reaction system of step (2) within 60 to 90 minutes, and the insulation time is 40 to 90 minutes.

3. The method for preparing the acrylic microgel emulsion with controllable particle size according to claim 1, wherein: In step (1), step (2) and step (3), the initiator is at least one of potassium persulfate, ammonium persulfate, azobisisobutyronitrile and di-tert-butyl peroxide; and / or In step (1), step (2) and step (3), the vinyl monomer is at least one of styrene and vinyltoluene; and / or In step (1), step (2) and step (3), the methacrylic acid and its ester monomers are at least one of methacrylic acid, methyl methacrylate, n-butyl methacrylate, isooctyl methacrylate, lauryl methacrylate, allyl methacrylate, glycidyl methacrylate and glycol dimethacrylate; and / or In step (1) and step (2), the acrylic acid ester monomers are at least one of methyl acrylate, n-butyl acrylate, isooctyl acrylate, lauryl acrylate, allyl acrylate, hexanediol diacrylate, neopentyl glycol diacrylate and tripropylene glycol diacrylate; and / or The acrylic acid and its ester monomer in step (3) is at least one of acrylic acid, methyl acrylate, n-butyl acrylate, isooctyl acrylate, lauryl acrylate, allyl acrylate, hexanediol diacrylate, neopentyl glycol diacrylate and tripropylene glycol diacrylate; and / or In step (1) and step (2), the cross-linking agent is trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, N,N'-methylenebisacrylamide; and / or In step (1), step (2) and step (3), the emulsifier is at least one of sodium lauryl sulfate, sodium dodecylbenzene sulfonate, alkylphenol polyoxyethylene ether and fatty alcohol polyoxyethylene ether.

4. The method for preparing the acrylic microgel emulsion with controllable particle size according to claim 1, wherein: In step (1), step (2) and step (3), the initiator needs to be prepared into a solution before use, and the solvent used is at least one of water, ethanol and toluene; and / or In step (1), step (2) and step (3), the emulsifier needs to be prepared into an aqueous solution before use.

5. The method for preparing the acrylic microgel emulsion with controllable particle size according to claim 1, wherein: In step (1), the amount of material A, cross-linking agent, emulsifier and initiator is 15-20 parts, 0.8-1.5 parts, 0.6-1.0 parts and 0.05-0.15 parts respectively by weight; In step (2), the amounts of material B, cross-linking agent, emulsifier and initiator are 15-20 parts, 0.8-1.5 parts, 0.6-1.0 parts and 0.05-0.15 parts respectively; In step (3), the amounts of material C, emulsifier, and initiator are 18-25 parts, 0.6-1.0 parts, and 0.05-0.15 parts, respectively; During the addition and heat preservation processes of steps (1), (2) and (3), stirring is maintained, and the stirring rate is controlled within the range of 1000 to 2000 rpm. The microgel particle size of the obtained acrylic microgel emulsion is 50 nm to 500 nm.

6. The method for preparing the acrylic microgel emulsion with controllable particle size according to claim 1, characterized in that: In step (1), the amounts of material A, cross-linking agent, emulsifier and initiator are 25-35 parts, 1.0-2.0 parts, 1.0-2.0 parts and 0.2-0.5 parts respectively by mass; In step (2), the amounts of material B, cross-linking agent, emulsifier and initiator are 25-35 parts, 1.0-2.0 parts, 1.0-2.0 parts and 0.2-0.5 parts respectively; In step (3), the amounts of material C, emulsifier, and initiator are 40-50 parts, 1.0-2.0 parts, and 0.2-0.5 parts, respectively; During the addition and heat preservation processes of steps (1), (2) and (3), stirring is maintained and the stirring rate is controlled within the range of 400 to 800 rpm. The microgel particle size of the obtained acrylic microgel emulsion is 0.5 μm to 5 μm.

7. The method for preparing the acrylic microgel emulsion with controllable particle size according to claim 1, characterized in that: In step (1), the amounts of material A, cross-linking agent, emulsifier and initiator are 25-35 parts, 0.5-1.0 parts, 0.5-1.0 parts and 0.4-0.6 parts respectively by mass; In step (2), the amounts of material B, cross-linking agent, emulsifier and initiator are 25-35 parts, 0.5-1.0 parts, 0.5-1.0 parts and 0.4-0.6 parts respectively; In step (3), the amounts of material C, emulsifier, and initiator are 40-50 parts, 0.5-1.0 parts, and 0.4-0.6 parts, respectively; During the addition and heat preservation processes of steps (1), (2) and (3), stirring is maintained and the stirring rate is controlled within the range of 100 to 300 rpm. The microgel particle size of the obtained acrylic microgel emulsion is 5 μm to 10 μm.

8. The method for preparing the acrylic microgel emulsion with controllable particle size according to claim 1, characterized in that: The first drop-added material, the second drop-added material and the third drop-added material further comprise a dispersant; when in step (1), by weight, the material A, the cross-linking agent, the emulsifier, the initiator and the dispersant are 25-35 parts, 1.0-2.0 parts, 0.5-1.0 parts, 0.5-1.0 parts and 0.5-1.0 parts respectively; In step (2), the amounts of material B, cross-linking agent, emulsifier, initiator and dispersant are 25-35 parts, 1.0-2.0 parts, 0.5-1.0 parts, 0.5-1.0 parts and 0.5-1.0 parts respectively; In step (3), the amounts of material C, emulsifier, initiator and dispersant are 40-50 parts, 0.5-1.0 parts, 0.5-1.0 parts and 0.5-1.0 parts respectively; During the addition and heat preservation processes of steps (1), (2) and (3), stirring is maintained, and the stirring rate is controlled in the range of 100 to 300 rpm. The microgel particle size of the obtained acrylic microgel emulsion is 10 μm to 50 μm.

9. An acrylic microgel emulsion with controllable particle size, characterized in that: The acrylic microgel emulsion is prepared according to the preparation method of any one of claims 1 to 8.

10. Use of the acrylic microgel emulsion with controllable particle size according to claim 9 in automotive coatings and adhesives.

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