Water-based acrylic emulsion and preparation method thereof

Abstract

The invention relates to the technical field of polymer chemistry, in particular to a water-based acrylic emulsion and a preparation method thereof.The preparation method comprises the following steps that water and an emulsifier A are mixed according to the formula ratio, and a kettle base solution is obtained; dropwise adding the core emulsion and an initiator A solution into the kettle bottom solution, and keeping the temperature at 82-85 DEG C to obtain a first reaction solution; dropwise adding a nucleation emulsion and an initiator B solution into the first reaction solution, and keeping the temperature at 82-85 DEG C to obtain a second reaction solution; and dropwise adding the shell emulsion and the initiator C solution into the second reaction solution at 84-86 DEG C, and carrying out heat preservation at 86-88 DEG C to obtain the water-based acrylic emulsion. The acrylic emulsion with a three-layer core-shell structure is prepared according to the principle of soft inside, medium hard and soft outside, so that the prepared paint surface combines rigidity and softness, is hard and sufficient in toughness, and meets the performance requirements of the finish paint in the water-based automobile coating.

Description

Technical Field

[0001] The invention relates to the technical field of polymer chemistry, and in particular to an aqueous acrylic emulsion and a preparation method thereof. Background Art

[0002] With the improvement of economic level, the demand for automobiles is increasing, and the amount of paint used for automobiles is also gradually increasing. At the same time, as the whole society pays more and more attention to environmental protection, the demand for automobile manufacturers to use environmentally friendly paints is becoming more and more urgent. Water-based acrylic emulsion paint has become the first choice for automobile coatings due to its excellent environmental protection.

[0003] Existing water-based acrylic emulsions have the characteristics of fast drying, good water resistance after film formation, and excellent weather resistance, but have the problem of poor stone impact resistance, which limits their application in the automotive industry. Summary of the invention

[0004] In order to solve the problem of poor anti-stone impact performance of water-based acrylic emulsion after film formation in the prior art, the present invention provides a method for preparing a water-based acrylic emulsion. The preparation method adopts multi-layer interpenetrating network advanced polymerization technology to prepare a water-based acrylic emulsion with a three-layer core-shell structure, which meets the performance requirements of automobile coatings and solves the problem of poor anti-stone impact performance of water-based acrylic emulsion after film formation in the prior art.

[0005] The technical solution adopted by the present invention to solve its technical problem is: A method for preparing an aqueous acrylic emulsion comprises the following steps: S1: Mix water and emulsifier A according to the formula, raise the temperature to 78-82°C, and obtain the bottom liquid; S2: adding the core emulsion and the initiator A solution dropwise to the bottom liquid of the kettle, and keeping the temperature at 82-85° C. to obtain a first reaction liquid; S3: adding the core emulsion and the initiator B solution dropwise to the first reaction solution, and keeping the temperature at 82-85° C. to obtain a second reaction solution; S4: adding the shell emulsion and the initiator C solution dropwise to the second reaction solution at 84-86° C., and keeping the temperature at 86-88° C. to obtain an aqueous acrylic emulsion.

[0006] Optionally, the raw materials of the kernel emulsion include the following components in parts by weight: 80-150 parts of water; Emulsifier B 0.5-2 parts; Functional monomer A 2-5 parts; Butyl acrylate 50-90 parts; Dimethyl ester 20-30 parts; Methacrylic acid 2-10 parts.

[0007] Optionally, the raw materials of the core emulsion include the following components in parts by weight: 80-150 parts of water; Emulsifier C 0.5-2 parts; Functional monomer B 2-5 parts; Butyl acrylate 40-50 parts; 40-60 parts of caprolactone-modified hydroxyethyl acrylate; Isobornyl methacrylate 20-40 parts; Styrene 100-150 parts; Methacrylic acid 2-10 parts.

[0008] Optionally, the raw materials of the shell emulsion include the following components in parts by weight: 80-150 parts of water; Emulsifier D 0.5-2 parts; Functional monomer C 2-5 copies; 2-Ethylhexyl acrylate 40-60 parts; 30-50 parts of dimethyl ester; 2-10 parts of acrylic acid; Allyl methacrylate 2-10 parts.

[0009] Optionally, the functional monomer A, the functional monomer B, and the functional monomer C are all selected from at least one of diacetone acrylamide, adipic acid dihydrazide, acrylamide, and N-hydroxymethyl acrylamide.

[0010] Optionally, the functional monomer A, the functional monomer B, and the functional monomer C are all mixtures of the diacetone acrylamide and the adipic acid dihydrazide in a mass ratio of 2:1.

[0011] Optionally, the emulsifier A, the emulsifier B, the emulsifier C, and the emulsifier D are all selected from at least one of SR10, SR30, ER30, and PP70.

[0012] Optionally, the emulsifier A, the emulsifier B, the emulsifier C, and the emulsifier D are all selected from at least one of SR10 and PP70.

[0013] Optionally, the initiator A, the initiator B, and the initiator C are all selected from at least one of ammonium persulfate, sodium persulfate, and potassium persulfate.

[0014] Another object of the present invention is to provide an aqueous acrylic emulsion, which is prepared by the above-mentioned method for preparing the aqueous acrylic emulsion.

[0015] The beneficial effects of the present invention are: The preparation method of the water-based acrylic emulsion provided by the present invention prepares an acrylic emulsion with a three-layer core-shell structure according to the principle of inner soft-middle hard-outer middle soft, so that the prepared paint surface combines rigidity and flexibility, is hard and has full toughness, has the effects of stone impact resistance, aging resistance, impact resistance, heat resistance, water resistance and solvent resistance, has a flat and smooth surface, and has good recoatability, thus meeting the performance requirements of the topcoat in the water-based automobile coating. DETAILED DESCRIPTION

[0016] The present invention is now further described in detail. The embodiments described below are exemplary and intended to be used to explain the present invention, but cannot be understood as limiting the present invention. All other embodiments obtained by ordinary technicians in this field without creative work based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0017] In order to solve the problem that the water-based acrylic emulsion in the prior art has poor anti-stone impact performance after film formation, the present invention provides a method for preparing a water-based acrylic emulsion, comprising the following steps: S1: Mix water and emulsifier A according to the formula, raise the temperature to 78-82°C, and obtain a bottom liquid; preferably, in this step, 180-220 parts of water and 0.3-0.6 parts of emulsifier A are mixed according to weight fraction; S2: adding the core emulsion and the initiator A solution dropwise to the bottom liquid of the kettle, and keeping the temperature at 82-85° C., preferably keeping the temperature for 30 minutes, to obtain a first reaction liquid; Preferably, the initiator A solution in this step is a solution consisting of 0.1-0.3 parts by weight of initiator A and 5-15 parts by weight of water; S3: adding the core emulsion and the initiator B solution dropwise to the first reaction solution, and keeping the temperature at 82-85° C., preferably keeping the temperature for 1 hour, to obtain a second reaction solution; Preferably, the initiator B solution in this step is a solution consisting of 0.4-0.5 parts by weight of initiator B and 15-25 parts by weight of water; S4: adding the shell emulsion and the initiator C solution dropwise to the second reaction solution at 84-86° C., and keeping the temperature at 86-88° C., preferably keeping the temperature for 1.5 hours, to obtain an aqueous acrylic emulsion; Preferably, the initiator C solution in this step is a solution consisting of 0.1-0.3 parts by weight of initiator C and 8-15 parts by weight of water.

[0018] To ensure product quality, after the insulation in step S4 is completed, the temperature is preferably lowered to 65-75°C for residual elimination treatment and vacuum deodorization; the temperature is lowered to 45°C for neutralization elimination treatment; the temperature is lowered to below 30°C for anti-corrosion and film-forming temperature treatment, and stirring is continued for 1 hour, and filtering and packaging are performed to obtain a multi-layer core-shell water-based acrylic automotive emulsion resin, that is, a water-based acrylic emulsion.

[0019] The preparation method of the water-based acrylic emulsion provided by the present invention adopts a multi-layer interpenetrating network polymerization technology to prepare an emulsion with a three-layer core-core-shell structure, so that the prepared coating film meets the performance requirements of automobile rigid-flexible combination, heat resistance, aging resistance, stone impact resistance, water resistance, solvent resistance, and smooth surface.

[0020] In order to ensure that the film-forming properties meet the performance requirements of the automobile, the raw materials of the core emulsion preferably include the following components in parts by weight: 80-150 parts of water; Emulsifier B 0.5-2 parts; Functional monomer A 2-5 parts; Butyl acrylate (BA) 50-90 parts; Dimethyl ester 20-30 parts; Methacrylic acid 2-10 parts.

[0021] The raw materials of the inner core emulsion are used to make the inner core layer have excellent flexibility, thereby ensuring the flexibility of the coating.

[0022] In the present invention, the raw materials of the core emulsion preferably include the following components in parts by weight: 80-150 parts of water; Emulsifier C 0.5-2 parts; Functional monomer B 2-5 parts; Butyl acrylate (BA) 40-50 parts; Caprolactone modified hydroxyethyl acrylate (FA2D) 40-60 parts; Isobornyl methacrylate (IBOMA) 20-40 parts; Styrene 100-150 parts; Methacrylic acid 2-10 parts.

[0023] The raw material composition of the core emulsion is such that the core layer has a relatively high hardness to ensure the structural strength of the coating.

[0024] Specifically, since the viscosity of the system provided in the present application is relatively high during the polymerization process, the present invention introduces the monomer IBOMA into the core emulsion to help reduce the viscosity and ensure the smooth progress of the reaction.

[0025] In order to effectively improve the impact resistance of the film after forming, the present invention introduces FA2D into the core emulsion, preferably introduces the monomer FA2D of Japan Daicel, and its structure is as follows: ; Wherein, N is a natural number greater than 1.

[0026] The primary hydroxyl group of the FA2D functional group is located at the end of the polycaprolactone chain with good flexibility, far away from the main chain skeleton, so it is easy to react with curing agents such as amino resins and polyurethane resins, and the bridging reaction can proceed very smoothly to form a coating film with elasticity and toughness. FA2D hydroxy acrylic monomer has better strong elasticity, high hardness, wear resistance, low temperature flexibility, adhesion and processability, so the use of this monomer in the middle hardness layer can well improve the hardness index performance of automotive coatings to resist stone impact.

[0027] In the present invention, the raw materials of the shell emulsion preferably include the following components in parts by weight: 80-150 parts of water; Emulsifier D 0.5-2 parts; Functional monomer C 2-5 copies; 2-Ethylhexyl acrylate 40-60 parts; 30-50 parts of dimethyl ester; 2-10 parts of acrylic acid; Allyl methacrylate (AMA) 2-10 parts.

[0028] In order to better aggregate the three-layer structure, the present invention introduces AMA, i.e., allyl methacrylate, into the shell emulsion, which can play a good bridge role between the three layers, so that the three layers are closely combined together to ensure the overall functional role of the emulsion.

[0029] The preparation method of the water-based acrylic emulsion provided by the present invention prepares an acrylic emulsion with a three-layer core-shell structure according to the principle of inner soft-middle hard-outer middle soft, so that the prepared paint surface combines rigidity and flexibility, is hard and has full toughness, has the effects of stone impact resistance, aging resistance, impact resistance, heat resistance, water resistance and solvent resistance, has a flat and smooth surface, and has good recoatability, thus meeting the performance requirements of the topcoat in the water-based automobile coating.

[0030] Specifically, the functional monomer A, the functional monomer B, and the functional monomer C in the present invention may be the same or different; in the present invention, preferably, the functional monomer A, the functional monomer B, and the functional monomer C are all selected from at least one of diacetone acrylamide, adipic acid dihydrazide, acrylamide, and N-hydroxymethyl acrylamide; further preferably, the functional monomer A, the functional monomer B, and the functional monomer C are all a mixture of diacetone acrylamide and adipic acid dihydrazide in a mass ratio of 2:1.

[0031] The emulsifier A, emulsifier B, emulsifier C and emulsifier D in the present invention may be the same or different; preferably, the emulsifier A, emulsifier B, emulsifier C and emulsifier D are all selected from at least one of SR10, SR30, ER30 and PP70; more preferably, the emulsifier A, emulsifier B, emulsifier C and emulsifier D are all selected from at least one of SR10 and PP70.

[0032] In the present invention, preferably, initiator A, initiator B and initiator C are all selected from at least one of ammonium persulfate, sodium persulfate and potassium persulfate, and further preferably, initiator A, initiator B and initiator C are all water-resistant aqueous high-temperature initiator potassium persulfate; the water in the present invention is preferably deionized water.

[0033] Another object of the present invention is to provide an aqueous acrylic emulsion, which is prepared by the above-mentioned method for preparing the aqueous acrylic emulsion.

[0034] The water-based acrylic emulsion provided by the present invention adopts a multi-layer interpenetrating network polymerization technology in the preparation process to prepare an emulsion with a three-layer core-core-shell structure, so that the prepared coating film meets the performance requirements of automobile rigid-flexible combination, heat resistance, aging resistance, stone impact resistance, water resistance, solvent resistance, and smooth surface.

[0035] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below.

[0036] Example 1 This embodiment provides a method for preparing an aqueous acrylic emulsion, comprising the following steps: S1: According to the weight ratio, 200 parts of water and 0.5 parts of emulsifier SR10 were mixed, and the temperature was raised to 80°C to obtain the bottom liquid; S2: Weigh and mix the following components in parts by weight to prepare a core emulsion: 100 parts water; Emulsifier SR10 1 part; DAAM 1; ADH 2 parts; Butyl acrylate 70 parts; Dimethyl ester 25 parts; 5 parts of methacrylic acid.

[0037] Mixing 0.2 parts by weight of an initiator potassium persulfate with 10 parts by weight of water to obtain an initiator A solution; After mixing the core emulsion with the initiator A solution, the mixture was added dropwise to the bottom liquid of the kettle within 45 minutes, and kept at 83°C for 30 minutes to obtain the first reaction liquid; S3: Weigh and mix the following components according to weight to prepare a core emulsion: 100 parts water; Emulsifier SR10 1 part; DAAM 1; ADH 2 parts; BA 45 copies; FA2D 50 copies; IBOMA 30 copies; 120 parts of styrene; 5 parts of methacrylic acid.

[0038] Mixing 0.45 parts by weight of an initiator potassium persulfate with 20 parts by weight of water to obtain an initiator B solution; The core emulsion was mixed with the initiator B solution, and then added dropwise to the first reaction solution within 2 hours, and kept at 83°C for 1 hour to obtain a second reaction solution; S4: Weigh and mix the following components according to weight to prepare a shell emulsion: 100 parts water; Emulsifier SR10 1 part; DAAM 1; ADH 2 parts; 50 parts of isooctyl acrylate; 40 parts of dimethyl ester; Acrylic acid 5 parts; AMA 5 copies.

[0039] Mixing 0.2 parts by weight of an initiator potassium persulfate with 10 parts by weight of water to obtain an initiator C solution; After mixing the shell emulsion with the initiator C solution, add it dropwise to the second reaction liquid at 85°C within 45 minutes, keep it at 87°C for 1.5 hours, cool it to 70°C, add tert-butyl hydroperoxide solution (0.9 parts by weight of tert-butyl hydroperoxide and 20 parts by weight of water) and M6 solution (0.8 parts by weight of M6 and 20 parts by weight of water) to eliminate the residue and vacuum it for deodorization; cool it to 45°C, add defoamer solution and neutralizer solution to neutralize and eliminate the residue; cool it to below 30°C, add preservative solution for preservative and film-forming temperature treatment, continue stirring for 1 hour, filter and package to obtain the water-based acrylic emulsion.

[0040] Example 2 This embodiment provides a method for preparing an aqueous acrylic emulsion, comprising the following steps: S1: According to the weight ratio, 200 parts of water and 0.5 parts of emulsifier SR10 were mixed, and the temperature was raised to 82°C to obtain the bottom liquid; S2: Weigh and mix the following components according to weight to prepare a core emulsion: 100 parts water; Emulsifier SR10 1 part; DAAM 1; ADH 2 parts; Butyl acrylate 80 parts; 30 parts of dimethyl ester; 2 parts of methacrylic acid.

[0041] Mixing 0.2 parts by weight of an initiator potassium persulfate with 10 parts by weight of water to obtain an initiator A solution; After mixing the core emulsion with the initiator A solution, the mixture was added dropwise to the bottom liquid of the kettle within 45 minutes, and kept at 85° C. for 30 minutes to obtain the first reaction liquid; S3: Weigh and mix the following components according to weight to prepare a core emulsion: 100 parts water; Emulsifier SR10 1 part; DAAM 1; ADH 2 parts; BA 50 copies; FA2D 60 copies; IBOMA 40 copies; 130 parts of styrene; 2 parts of methacrylic acid.

[0042] Mixing 0.45 parts by weight of an initiator potassium persulfate with 20 parts by weight of water to obtain an initiator B solution; The core emulsion was mixed with the initiator B solution, and then added dropwise to the first reaction solution within 2 hours, and kept at 85° C. for 1 hour to obtain a second reaction solution; S4: Weigh and mix the following components according to weight to prepare a shell emulsion: 100 parts water; Emulsifier SR10 1 part; DAAM 1; ADH 2 parts; 60 parts of isooctyl acrylate; 50 parts of dimethyl ester; 2 parts of acrylic acid; 2 copies of AMA.

[0043] Mixing 0.2 parts by weight of an initiator potassium persulfate with 10 parts by weight of water to obtain an initiator C solution; After mixing the shell emulsion with the initiator C solution, add it dropwise into the second reaction liquid at 86°C within 45 minutes, keep it at 88°C for 1.5 hours, cool it to 70°C, add tert-butyl hydroperoxide solution (0.9 parts by weight of tert-butyl hydroperoxide and 20 parts by weight of water) and M6 solution (0.8 parts by weight of M6 and 20 parts by weight of water) to eliminate the residue and vacuum it for deodorization; cool it to 45°C, add defoamer solution and neutralizer solution to neutralize and eliminate the residue; cool it to below 30°C, add preservative solution for preservative and film-forming temperature treatment, continue stirring for 1 hour, filter and package to obtain the water-based acrylic emulsion.

[0044] Example 3 This embodiment provides a method for preparing an aqueous acrylic emulsion, comprising the following steps: S1: According to the weight ratio, 200 parts of water and 0.5 parts of emulsifier SR10 were mixed, and the temperature was raised to 78°C to obtain the bottom liquid; S2: Weigh and mix the following components according to weight to prepare a core emulsion: 100 parts water; Emulsifier SR10 1 part; DAAM 1; ADH 2 parts; 600 parts of butyl acrylate; Dimethyl ester 20 parts; Methacrylic acid 10 parts.

[0045] Mixing 0.2 parts by weight of an initiator potassium persulfate with 10 parts by weight of water to obtain an initiator A solution; After mixing the core emulsion with the initiator A solution, the mixture was added dropwise to the bottom liquid of the kettle within 45 minutes, and kept at 82° C. for 30 minutes to obtain the first reaction liquid; S3: Weigh and mix the following components according to weight to prepare a core emulsion: 100 parts water; Emulsifier SR10 1 part; DAAM 1; ADH 2 parts; BA 40 copies; FA2D 40 copies; IBOMA 20 copies; 100 parts of styrene; Methacrylic acid 10 parts.

[0046] Mixing 0.45 parts by weight of an initiator potassium persulfate with 20 parts by weight of water to obtain an initiator B solution; The core emulsion was mixed with the initiator B solution, and then added dropwise to the first reaction solution within 2 hours, and kept at 82°C for 1 hour to obtain a second reaction solution; S4: Weigh and mix the following components according to weight to prepare a shell emulsion: 100 parts water; Emulsifier SR10 1 part; DAAM 1; ADH 2 parts; 40 parts of isooctyl acrylate; 30 parts of dimethyl ester; Acrylic acid 10 parts; AMA 10 copies.

[0047] Mixing 0.2 parts by weight of an initiator potassium persulfate with 10 parts by weight of water to obtain an initiator C solution; After mixing the shell emulsion with the initiator C solution, add it dropwise into the second reaction liquid at 84°C within 45 minutes, keep it at 86°C for 1.5 hours, cool it to 70°C, add tert-butyl hydroperoxide solution (0.9 parts by weight of tert-butyl hydroperoxide and 20 parts by weight of water) and M6 solution (0.8 parts by weight of M6 and 20 parts by weight of water) to eliminate the residue and vacuum it for deodorization; cool it to 45°C, add defoamer solution and neutralizer solution to neutralize and eliminate the residue; cool it to below 30°C, add preservative solution for preservative and film-forming temperature treatment, continue stirring for 1 hour, filter and package to obtain the water-based acrylic emulsion.

[0048] The following comparative examples are all used for comparison with Example 1.

[0049] Comparative Example 1 The difference between this comparative example and Example 1 is that in step S3, the following components are weighed and mixed according to parts by weight to prepare a core emulsion: 100 parts water; Emulsifier SR10 1 part; DAAM 1; ADH 2 parts; BA 95 copies; IBOMA 30 copies; 120 parts of styrene; 5 parts of methacrylic acid.

[0050] Comparative Example 2 The difference between this comparative example and Example 1 is that in step S4, the following components are weighed and mixed according to parts by weight to prepare a shell emulsion: 100 parts water; Emulsifier SR10 1 part; DAAM 1; ADH 2 parts; 55 parts of isooctyl acrylate; 40 parts of dimethyl ester; 5 parts of acrylic acid.

[0051] Comparative Example 3 This embodiment provides a method for preparing an aqueous acrylic emulsion, comprising the following steps: S1: According to the weight ratio, 200 parts of water and 0.5 parts of emulsifier SR10 were mixed, and the temperature was raised to 80°C to obtain the bottom liquid; S2: Weigh and mix the following components according to weight to prepare a core emulsion: 100 parts water; Emulsifier SR10 1 part; DAAM 1; ADH 2 parts; Butyl acrylate 70 parts; Dimethyl ester 25 parts; 5 parts of methacrylic acid.

[0052] Mixing 0.2 parts by weight of an initiator potassium persulfate with 10 parts by weight of water to obtain an initiator A solution; After mixing the core emulsion with the initiator A solution, the mixture was added dropwise to the bottom liquid of the kettle within 45 minutes, and kept at 83°C for 30 minutes to obtain the first reaction liquid; S3: Weigh and mix the following components according to weight to prepare a core emulsion: 100 parts water; Emulsifier SR10 1 part; DAAM 1; ADH 2 parts; 50 parts of isooctyl acrylate; 40 parts of dimethyl ester; Acrylic acid 5 parts; AMA 5 copies.

[0053] Mixing 0.45 parts by weight of an initiator potassium persulfate with 20 parts by weight of water to obtain an initiator B solution; The core emulsion was mixed with the initiator B solution, and then added dropwise to the first reaction solution within 2 hours, and kept at 83°C for 1 hour to obtain a second reaction solution; S4: Weigh and mix the following components according to weight to prepare a shell emulsion: 100 parts water; Emulsifier SR10 1 part; DAAM 1; ADH 2 parts; BA 45 copies; FA2D 50 copies; IBOMA 30 copies; 120 parts of styrene; 5 parts of methacrylic acid.

[0054] Mixing 0.2 parts by weight of an initiator potassium persulfate with 10 parts by weight of water to obtain an initiator C solution; After mixing the shell emulsion with the initiator C solution, add it dropwise to the second reaction liquid at 85°C within 45 minutes, keep it at 87°C for 1.5 hours, cool it to 70°C, add tert-butyl hydroperoxide solution (0.9 parts by weight of tert-butyl hydroperoxide and 20 parts by weight of water) and M6 solution (0.8 parts by weight of M6 and 20 parts by weight of water) to eliminate the residue and vacuum it for deodorization; cool it to 45°C, add defoamer solution and neutralizer solution to neutralize and eliminate the residue; cool it to below 30°C, add preservative solution for preservative and film-forming temperature treatment, continue stirring for 1 hour, filter and package to obtain the water-based acrylic emulsion.

[0055] The water-based acrylic emulsions provided in the above embodiments and comparative examples were used to prepare paint films, and the properties of the paint films were tested. The test methods and results are shown in Table 1: Table 1 Moisture and heat resistance / grade (240h) (GB / T1740) Pencil hardness (GB / T6739) Stone impact resistance / level (2bar, 2 times) (Q / 320412 SJT010.1) Impact strength (N.cm) GB / T1732 Acid resistance (immersed in 0.05mol / L H2SO4 solution, 23±2℃, 25h) (GB / T9274) Alkali resistance (immersed in 0.1mol / L NaOH solution, 23±2℃, 25h) (GB / T9274) Example 1 264h HB pass 50 Pass pass pass Example 2 288h HB pass 50 Pass pass pass Example 3 264h HB pass 50 Pass pass pass Comparative Example 1 240h 2B Not passed 50 Fail pass pass Comparative Example 2 216h 2B Not passed 50 Fail Not passed Not passed Comparative Example 3 264h HB Not passed 50 Fail Not passed Not passed It can be seen from the data in the above table that the paint surface made of the water-based acrylic emulsion prepared in each embodiment of the present invention is a combination of rigidity and flexibility, hard and tough, and meets the performance requirements of the topcoat in water-based automotive coatings.

[0056] The difference between Comparative Example 1 and Example 1 is that FA2D in the core emulsion is replaced by BA, and the anti-stone impact performance of the paint film becomes worse.

[0057] The difference between Comparative Example 2 and Example 1 is that the AMA in the shell emulsion is replaced with isooctyl acrylate, and the stone impact resistance, moisture and heat resistance, and solvent resistance of the paint film are all deteriorated.

[0058] The difference between Comparative Example 3 and Example 1 is that the raw materials of the shell emulsion and the core emulsion are exchanged, and the stone impact resistance and solvent resistance of the paint film are both deteriorated.

[0059] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A method for preparing an aqueous acrylic emulsion, characterized in that: The steps include: S1: Mix water and emulsifier A according to the formula, raise the temperature to 78-82°C, and obtain the bottom liquid; S2: adding the core emulsion and the initiator A solution dropwise to the bottom liquid of the kettle, and keeping the temperature at 82-85° C. to obtain a first reaction liquid; S3: adding the core emulsion and the initiator B solution dropwise to the first reaction solution, and keeping the temperature at 82-85° C. to obtain a second reaction solution; S4: adding the shell emulsion and the initiator C solution dropwise to the second reaction solution at 84-86° C., and keeping the temperature at 86-88° C. to obtain an aqueous acrylic emulsion.

2. The method for preparing the aqueous acrylic emulsion according to claim 1, wherein The raw materials of the kernel emulsion include the following components in parts by weight: 80-150 parts of water; Emulsifier B 0.5-2 parts; Functional monomer A 2-5 parts; Butyl acrylate 50-90 parts; Dimethyl ester 20-30 parts; Methacrylic acid 2-10 parts.

3. The method for preparing the aqueous acrylic emulsion according to claim 2, wherein: The raw materials of the core emulsion include the following components in parts by weight: 80-150 parts of water; Emulsifier C 0.5-2 parts; Functional monomer B 2-5 parts; Butyl acrylate 40-50 parts; 40-60 parts of caprolactone-modified hydroxyethyl acrylate; Isobornyl methacrylate 20-40 parts; Styrene 100-150 parts; Methacrylic acid 2-10 parts.

4. The method for preparing the aqueous acrylic emulsion according to claim 3, wherein: The raw materials of the shell emulsion include the following components in parts by weight: 80-150 parts of water; Emulsifier D 0.5-2 parts; Functional monomer C 2-5 parts; 2-Ethylhexyl acrylate 40-60 parts; 30-50 parts of dimethyl ester; Acrylic acid 2-10 parts; Allyl methacrylate 2-10 parts.

5. The method for preparing the aqueous acrylic emulsion according to claim 4, characterized in that: The functional monomer A, the functional monomer B and the functional monomer C are all selected from at least one of diacetone acrylamide, adipic acid dihydrazide, acrylamide and N-hydroxymethyl acrylamide.

6. The method for preparing the aqueous acrylic emulsion according to claim 5, characterized in that: The functional monomer A, the functional monomer B, and the functional monomer C are all mixtures of the diacetone acrylamide and the adipic acid dihydrazide in a mass ratio of 2:

1.

7. The method for preparing the aqueous acrylic emulsion according to claim 4, characterized in that: The emulsifier A, the emulsifier B, the emulsifier C, and the emulsifier D are all selected from at least one of SR10, SR30, ER30, and PP70.

8. The method for preparing the aqueous acrylic emulsion according to claim 7, characterized in that: The emulsifier A, the emulsifier B, the emulsifier C, and the emulsifier D are all selected from at least one of SR10 and PP70.

9. The method for preparing the aqueous acrylic emulsion according to any one of claims 1 to 8, characterized in that: The initiator A, the initiator B and the initiator C are all selected from at least one of ammonium persulfate, sodium persulfate and potassium persulfate.

10. A water-based acrylic emulsion, characterized in that: The aqueous acrylic emulsion is prepared by the preparation method of the aqueous acrylic emulsion according to any one of claims 1 to 9.