Acrylic acid microgel emulsion with core-shell structure as well as preparation method and application of acrylic acid microgel emulsion

Abstract

The invention discloses an acrylic microgel emulsion with a core-shell structure as well as a preparation method and application thereof, and belongs to the technical field of coatings. The preparation method comprises the following steps: adding a part of an emulsifier solution into a hard core monomer and a cross-linking monomer to obtain a core pre-emulsion; the other part of the emulsifier is added into a soft shell monomer and a functional monomer to obtain a shell pre-emulsion, so that the problem that the film-forming property becomes poor due to the fact that the emulsifier is added into the monomer at a time can be avoided; meanwhile, firstly adding an initiator solution into the core pre-emulsion to obtain a core emulsion, then adding the shell pre-emulsion and the residual initiator solution into the core emulsion, and carrying out polymerization reaction to prepare the acrylic acid microgel emulsion with the core-shell structure, of which the film-forming property is further enhanced; in addition, the preparation method is simple, the used raw materials are cheap and easy to obtain, and the preparation method is suitable for industrial large-scale production and application.

Description

Technical Field

[0001] The invention belongs to the technical field of coatings, and particularly relates to a core-shell structure acrylic microgel emulsion and a preparation method and application thereof. Background Art

[0002] Acrylic microgels, with their unique core-shell structure, have demonstrated significant application value in numerous fields. Their cross-linked core and linear shell composite structure, formed through emulsion polymerization, imparts the material with the dual advantages of high strength and flexibility.

[0003] The conventional preparation process for acrylic microgel emulsions, involving a single emulsifier addition, results in uneven interfacial tension distribution. During film formation, this unevenness can lead to internal stress differences within the film, resulting in cracks and severely impacting the microgel's practical application in coatings, adhesives, and other applications. Furthermore, when the hardshell monomers are mixed with the crosslinker, an aldol condensation reaction easily occurs. This reaction causes rapid polymerization of the monomers in localized areas, rapidly increasing the reactor temperature. This sudden temperature fluctuation not only affects the microgel's structure and properties but also poses significant safety risks, posing significant challenges to industrial production. Furthermore, when the glycidyl methacrylate (GMA) dosage exceeds 5%, a series of side reactions can occur, generating insoluble crosslinked products. These products form solid residues, which can reach as high as 28.4%. The generation of large amounts of solid residue not only wastes raw materials and increases production costs, but also severely damages production equipment, shortening its lifespan.

[0004] In view of this, it is necessary to provide a core-shell structure acrylic microgel emulsion to solve the deficiencies in the prior art. Summary of the Invention

[0005] The present invention aims to provide a core-shell structure acrylic microgel emulsion and its preparation method and application, so as to solve the problem of poor film-forming performance of existing acrylic microgel emulsions.

[0006] In a first aspect, the present invention provides a method for preparing a core-shell structured acrylic microgel emulsion, comprising the following steps: S1, dissolving an emulsifier in a first water and an initiator in a second water to obtain an emulsifier solution and an initiator solution, respectively; S2, mixing a hard core monomer, a cross-linking monomer, and 1 / 2-3 / 4 of the emulsifier solution to obtain a core pre-emulsion; mixing a soft shell monomer, a functional monomer, and the remaining emulsifier solution to obtain a shell pre-emulsion; S3, mixing the core pre-emulsion and 8 / 15-4 / 5 of the initiator solution to obtain a core emulsion; S4, mixing the core emulsion, the shell pre-emulsion, and the remaining initiator solution, reacting the mixture, and adjusting the pH to 6.5-7.5 to obtain a core-shell structured acrylic microgel emulsion; wherein the hard core monomer comprises at least one of methyl methacrylate, styrene, acrylonitrile, ethyl acrylate, butyl acrylate, and isooctyl acrylate.

[0007] In the present invention, the inventors have discovered that by adding a portion of the emulsifier solution to the hard core monomer and the cross-linking monomer to obtain a core pre-emulsion; and adding the other portion to the soft shell monomer and the functional monomer to obtain a shell pre-emulsion, the problem of poor film-forming performance caused by adding the emulsifier to the monomers at one time can be avoided; at the same time, by first adding the initiator solution to the core pre-emulsion to obtain a core emulsion, and then adding the shell pre-emulsion and the remaining initiator solution to the core emulsion to carry out a polymerization reaction, a core-shell structured acrylic microgel emulsion with further enhanced film-forming performance is prepared.

[0008] In some embodiments, in parts by weight, in step S1, the emulsifier is present in an amount of 1-20 parts, the first water is present in an amount of 90-100 parts, the initiator is present in an amount of 0.5-10 parts, and the second water is present in an amount of 6-10 parts; and / or in step S2, the hard-core monomer is present in an amount of 20-50 parts, the cross-linking monomer is present in an amount of 3-7 parts, the soft-shell monomer is present in an amount of 20-40 parts, and the functional monomer is present in an amount of 2-5 parts.

[0009] In some embodiments, in step S1, the emulsifier includes at least one of nonylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, polyoxyethylene fatty acid ester, polyoxyethylene stearate, sodium oleate, sodium stearate, sodium dodecylbenzene sulfonate, fatty alcohol polyoxyethylene ether sodium sulfate, and sodium lauryl sulfate.

[0010] In some embodiments, in step S1, the initiator includes at least one of potassium persulfate and azobisisobutyronitrile.

[0011] In some embodiments, in step S2, the cross-linking monomer includes at least one of trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, trimethylolpropane trimethacrylate, ethylene glycol dimethacrylate, zinc diacrylate, and zinc dimethacrylate; and / or the soft shell monomer includes at least one of methyl methacrylate, acrylic acid, styrene, acrylonitrile, ethyl acrylate, butyl acrylate, and isooctyl acrylate; and / or the functional monomer includes at least one of diacetone acrylamide, ethyl acetoacetate methacrylate, glycidyl methacrylate, and dimethylaminoethyl methacrylate.

[0012] In some embodiments, in step S3, the core pre-emulsion and 8 / 15-4 / 5 initiator solution are mixed to obtain the core emulsion, which specifically includes: adding 1 / 3-2 / 3 of the core pre-emulsion and 4 / 15-2 / 5 of the initiator solution by a first mixing to obtain a first core emulsion, and continuing to add the remaining core pre-emulsion and 4 / 15-2 / 5 of the initiator solution by a second mixing to obtain a core emulsion; wherein the temperature of the first mixing is 60-75°C, and the time is 30-100 min; the temperature of the second mixing is 75-90°C, and the time is 30-100 min; and the time of the second adding is 70-80 min.

[0013] In some embodiments, in step S4, the reaction after mixing the core emulsion, the shell pre-emulsion and the remaining initiator solution specifically includes: adding the shell pre-emulsion and the remaining initiator solution to the core emulsion for a third time for third mixing; wherein the temperature of the third mixing is 75-90°C, and the time is 30-100 minutes; and the time of the third addition is 55-65 minutes.

[0014] In some embodiments, in step S4, the solution for adjusting pH comprises 0.1 M NaHCO 3 solution.

[0015] In a second aspect, the present invention provides a core-shell structured acrylic microgel emulsion prepared by any of the above-mentioned preparation methods.

[0016] In some embodiments, the core-shell acrylic microgel emulsion has a particle size of 100-600 nm and a solid content of 34-38%.

[0017] In a third aspect, the present invention provides use of the core-shell acrylic microgel emulsion in coatings.

[0018] The beneficial effects of the present invention are as follows: unlike the prior art, the present invention adds a portion of the emulsifier solution to the hard core monomer and the cross-linking monomer to obtain a core pre-emulsion; and adds the other portion to the soft shell monomer and the functional monomer to obtain a shell pre-emulsion, thereby avoiding the problem of poor film-forming performance caused by adding the emulsifier to the monomers at one time; at the same time, by first adding the initiator solution to the core pre-emulsion to obtain a core emulsion, and then adding the shell pre-emulsion and the remaining initiator solution to the core emulsion to carry out a polymerization reaction, a core-shell structured acrylic microgel emulsion with further enhanced film-forming performance is prepared; in addition, the preparation method is simple, the raw materials used are cheap and easily available, and the preparation method is suitable for industrial large-scale production applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a flow chart of the preparation method of the core-shell structure acrylic microgel emulsion of the present invention; Figure 2 This is a morphology diagram of the solution after the insulation reaction in step S4 of Comparative Example 1 of the present invention; Figure 3 This is a morphology diagram of the solution after the insulation reaction in step S4 of comparative example 2 of the present invention; Figure 4 The film-forming performance results of Example 5 (C) of the present invention and commercially available acrylic microgel emulsions (A, B) are shown. DETAILED DESCRIPTION

[0020] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0021] For experimental methods in the examples where specific conditions are not specified, generally conventional conditions and conditions described in the manual or conditions recommended by the manufacturer were followed. The general equipment, materials, reagents, etc. used were all commercially available unless otherwise specified.

[0022] Currently, existing acrylic microgel emulsions have the problem of poor film-forming properties.

[0023] In order to solve the problem of poor film-forming performance of existing acrylic microgel emulsions, the present invention provides a core-shell structure acrylic microgel emulsion and a preparation method and application thereof.

[0024] In a first aspect, the present invention provides a method for preparing a core-shell structure acrylic microgel emulsion, comprising the following steps: S1, dissolving an emulsifier in a first water and an initiator in a second water to obtain an emulsifier solution and an initiator solution, respectively; S2, mixing a hard core monomer, a cross-linking monomer, and 1 / 2-3 / 4 (preferably 2 / 3) of the emulsifier solution to obtain a core pre-emulsion; mixing a soft shell monomer, a functional monomer, and the remaining emulsifier solution to obtain a shell pre-emulsion; S3, mixing the core pre-emulsion and 8 / 4 of the emulsifier solution to obtain a shell pre-emulsion. S4, mixing the core emulsion, the shell pre-emulsion and the remaining initiator solution and reacting them, adjusting the pH to 6.5-7.5, for example, 6.5, 6.7, 7, 7.3, 7.5 or other values within this range; obtaining a core-shell structured acrylic microgel emulsion; wherein the hard core monomer includes at least one of methyl methacrylate, styrene, acrylonitrile, ethyl acrylate, butyl acrylate and isooctyl acrylate.

[0025] In the present invention, the inventors have discovered that by adding a portion of the emulsifier solution to the hard core monomer and the cross-linking monomer to obtain a core pre-emulsion; and adding the other portion to the soft shell monomer and the functional monomer to obtain a shell pre-emulsion, the problem of poor film-forming performance caused by adding the emulsifier to the monomers at one time can be avoided; at the same time, by first adding the initiator solution to the core pre-emulsion to obtain a core emulsion, and then adding the shell pre-emulsion and the remaining initiator solution to the core emulsion to carry out a polymerization reaction, a core-shell structured acrylic microgel emulsion with further enhanced film-forming performance is prepared.

[0026] In some embodiments, in step S1, the amount of the emulsifier is 1-20 parts, for example, 1 part, 5 parts, 10 parts, 15 parts, 20 parts or other values within the range; the amount of the first water is 90-100 parts, for example, 90 parts, 92 parts, 95 parts, 97 parts, 100 parts or other values within the range; the amount of the initiator is 0.5-10 parts, for example, 0.5 parts, 1 part, 5 parts, 7 parts, 10 parts or other values within the range; the amount of the second water is 6-10 parts, for example, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts Or other values within this range; and / or in step S2, the number of hard-core monomers is 20-50 parts, for example, 20 parts, 30 parts, 40 parts, 50 parts or other values within this range; the number of cross-linking monomers is 3-7 parts, for example, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts or other values within this range; the number of soft-shell monomers is 20-40 parts, for example, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts or other values within this range; the number of functional monomers is 2-5 parts, for example, 2 parts, 3 parts, 4 parts, 5 parts or other values within this range.

[0027] In the present invention, the inventors further discovered that by controlling the contents of emulsifier, initiator, hard core monomer, crosslinking monomer and soft shell monomer within a specific range, a core-shell structured acrylic microgel emulsion with good film-forming performance, reduced solid residue and improved stability can be prepared.

[0028] In some embodiments, in step S1, the emulsifier includes at least one of nonylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, polyoxyethylene fatty acid ester, polyoxyethylene stearate, sodium oleate, sodium stearate, sodium dodecylbenzene sulfonate, fatty alcohol polyoxyethylene ether sodium sulfate, and sodium lauryl sulfate.

[0029] In the present invention, the emulsifier is preferably a compound of at least two of nonylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, polyoxyethylene fatty acid ester, polyoxyethylene stearate, sodium oleate, sodium stearate, sodium dodecylbenzene sulfonate, fatty alcohol polyoxyethylene ether sodium sulfate, and sodium lauryl sulfate. The composite emulsifier obtained after compounding can optimize the interfacial stability, ensure that the monomers can be evenly dispersed during the reaction, and improve the controllability of the reaction and the quality of the product.

[0030] In some embodiments, in step S1, the initiator includes at least one of potassium persulfate and azobisisobutyronitrile.

[0031] It is understood that the initiator can be selected from conventional initiators in the prior art according to actual use needs, as long as it can achieve polymerization. In the present invention, the initiator preferably includes at least one of potassium persulfate and azobisisobutyronitrile.

[0032] In some embodiments, in step S2, the cross-linking monomer includes at least one of trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, trimethylolpropane trimethacrylate, ethylene glycol dimethacrylate, zinc diacrylate, and zinc dimethacrylate; and / or the soft shell monomer includes at least one of methyl methacrylate, acrylic acid, styrene, acrylonitrile, ethyl acrylate, butyl acrylate, and isooctyl acrylate; and / or the functional monomer includes at least one of diacetone acrylamide, ethyl acetoacetate methacrylate, glycidyl methacrylate, and dimethylaminoethyl methacrylate.

[0033] In the present invention, by selecting specific types of cross-linking monomers, soft shell monomers and functional monomers, the strength and stability of the core-shell structure acrylic microgel emulsion can be further enhanced; in addition, the above raw materials are cheap and easily available, which is conducive to cost saving.

[0034] In some embodiments, in step S3, the step of mixing the core pre-emulsion and 8 / 15-4 / 5 initiator solution to obtain the core emulsion specifically includes: adding 1 / 3-2 / 3 (preferably 1 / 2) of the core pre-emulsion and 4 / 15-2 / 5 (preferably 1 / 3) of the initiator solution by a first dropwise addition, performing a first mixing to obtain a first core emulsion, and continuing to add the remaining core pre-emulsion and 4 / 15-2 / 5 (preferably 1 / 3) of the initiator solution by a second dropwise addition to the first core emulsion, and performing a second mixing to obtain a core emulsion; wherein the temperature of the first mixing is 60-75°C, for example, 60°C, 65°C, 70°C, 75°C or a temperature within the range thereof. time is 30-100 min, for example, 30 min, 50 min, 70 min, 100 min or other values within this range; the second mixing temperature is 75-90 ° C, for example, 75 ° C, 80 ° C, 85 ° C, 90 ° C or other values within this range; the time is 30-100 min, for example, 30 min, 50 min, 70 min, 100 min or other values within this range; the second dropping time is 70-80 min, for example, 70 min, 72 min, 75 min, 78 min, 80 min or other values within this range.

[0035] In the present invention, the core emulsion is synthesized in steps, thereby improving its performance. Further synthesizing the core emulsion through stepwise gradient temperature increase allows the reaction to proceed at the desired rate at each stage, promoting the orderly arrangement of the molecular chains and further optimizing the microgel structure. Furthermore, by controlling the time of the first and second additions within a specific range, the rate of free radical generation can be better controlled, preventing an overly vigorous reaction and ensuring reaction stability and product quality.

[0036] In some embodiments, in step S4, the reaction after mixing the core emulsion, the shell pre-emulsion and the remaining initiator solution specifically includes: adding the shell pre-emulsion and the remaining initiator solution to the core emulsion for a third mixing; wherein the temperature of the third mixing is 75-90°C, for example, it can be 75°C, 80°C, 85°C, 90°C or other values within the range; the time is 30-100min, for example, it can be 30min, 50min, 70min, 100min or other values within the range; the time of the third addition is 55-65min, for example, it can be 55min, 60min, 65min or other values within the range.

[0037] In some embodiments, in step S4, the solution for adjusting pH comprises 0.1 M NaHCO 3 solution.

[0038] It is understood that the solution for adjusting pH can be conventionally selected according to actual use needs, as long as the purpose of adjusting pH can be achieved. For example, in the present invention, the solution for adjusting pH preferably includes 0.1M NaHCO3 solution.

[0039] In a second aspect, the present invention provides a core-shell structured acrylic microgel emulsion prepared by any of the above-mentioned preparation methods.

[0040] The core-shell structure acrylic microgel emulsion of the present invention has the advantages of good film-forming performance, low solid residue content and high stability, and therefore has good application prospects.

[0041] In some embodiments, the particle size of the core-shell acrylic microgel emulsion is 100-600 nm, for example, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm or other values within this range; the solid content is 34-38%, for example, 34%, 35%, 36%, 37%, 38% or other values within this range.

[0042] The core-shell structured acrylic microgel emulsion of the present invention has uniform particle size and good solid content, and therefore, the acrylic microgel emulsion has good performance.

[0043] In a third aspect, the present invention provides use of the core-shell acrylic microgel emulsion in coatings.

[0044] Some specific embodiments are listed below. It should be noted that the embodiments described below are exemplary and are only used to explain the present invention, and should not be understood as limiting the present invention.

[0045] See also Figure 1 , which is a flow chart of the preparation method of the core-shell structure acrylic microgel emulsion of the present invention. Specifically, the preparation method includes the following steps: S1, dissolving an emulsifier in a first water solution and an initiator in a second water solution to obtain an emulsifier solution and an initiator solution, respectively; S2, mixing a hard core monomer, a cross-linking monomer, and 1 / 2-3 / 4 of the emulsifier solution to obtain a core pre-emulsion; mixing a soft shell monomer, a functional monomer, and the remaining emulsifier solution to obtain a shell pre-emulsion; S3, mixing the core pre-emulsion and 8 / 15-4 / 5 of the initiator solution to obtain a core emulsion; S4, mixing the core emulsion, the shell pre-emulsion, and the remaining initiator solution, reacting them, and adjusting the pH to 6.5-7.5 to obtain a core-shell structure acrylic microgel emulsion.

[0046] Example 1 In this embodiment, the raw materials for preparing the core-shell structure acrylic microgel emulsion include the following components, in parts by weight: hard core monomer: 20 parts of methyl methacrylate, 5 parts of butyl acrylate, and 15 parts of styrene, cross-linking monomer: 5 parts of trimethylolpropane trimethacrylate, soft shell monomer: 8 parts of methyl methacrylate, 6 parts of styrene, 2 parts of acrylic acid, and 15 parts of butyl acrylate, functional monomer: 3 parts of glycidyl methacrylate, emulsifier: 10 parts of a mixture of nonylphenol polyoxyethylene ether and sodium lauryl sulfate in a mass ratio of 1:2, and initiator: 5 parts of potassium persulfate.

[0047] The preparation method of the core-shell structure acrylic microgel emulsion comprises the following steps: S1, dissolving an emulsifier in 94 parts of the first water and an initiator in 8 parts of the second water to obtain an emulsifier solution and an initiator solution, respectively; S2, mixing the hard core monomer, the cross-linking monomer and 2 / 3 of the emulsifier solution, stirring for 2 hours to obtain a core pre-emulsion; mixing the soft shell monomer, the functional monomer and the remaining emulsifier solution, stirring for 2 hours to obtain a shell pre-emulsion; S3. In a 250 mL three-necked flask, 1 / 2 of the core pre-emulsion and 1 / 3 of the initiator solution were added dropwise for the first time, and the mixture was kept at 75° C. for 40 minutes to obtain a first core emulsion. At this time, the pH of the reaction system was measured to be 6.3. The remaining core pre-emulsion and 1 / 3 of the initiator solution were added dropwise for the second time (the addition was completed within 75 minutes) to the first core emulsion, and the mixture was kept at 80° C. for 40 minutes to obtain a core emulsion. S4. After adding the shell pre-emulsion and the remaining initiator solution to the core emulsion for the third time (addition completed within 60 minutes), the temperature was kept at 80° C. for 40 minutes, and then the pH was adjusted to 7.0 with 0.1 M NaHCO 3 to obtain a core-shell structured acrylic microgel emulsion.

[0048] In this embodiment, the core-shell structure acrylic microgel emulsion has a solid content of 35.8% and a particle size of 345 nm. At 85°C, the cross-linking self-repair time is about 86 minutes. After repair, the scratches on the paint film surface basically disappear, and no sagging occurs when the film thickness is 220 μm.

[0049] Example 2 In this embodiment, the raw materials for preparing the core-shell structure acrylic microgel emulsion include the following components, in parts by weight: hard core monomer: 19 parts of methyl methacrylate, 6 parts of butyl acrylate, and 15 parts of styrene, a cross-linking monomer: 5 parts of trimethylolpropane trimethacrylate, a soft shell monomer: 6 parts of methyl methacrylate, 5 parts of styrene, 2 parts of acrylic acid, and 14 parts of butyl acrylate, a functional monomer: 3 parts of glycidyl methacrylate, an emulsifier: 9 parts of a mixture of nonylphenol polyoxyethylene ether and sodium lauryl sulfate in a mass ratio of 1:2, and an initiator: 4 parts of potassium persulfate.

[0050] The preparation method of the core-shell structure acrylic microgel emulsion comprises the following steps: S1, dissolving an emulsifier in 94 parts of the first water and an initiator in 8 parts of the second water to obtain an emulsifier solution and an initiator solution, respectively; S2, mixing the hard core monomer, the cross-linking monomer and 2 / 3 of the emulsifier solution, stirring for 2 hours to obtain a core pre-emulsion; mixing the soft shell monomer, the functional monomer and the remaining emulsifier solution, stirring for 2 hours to obtain a shell pre-emulsion; S3. In a 250 mL three-necked flask, 1 / 2 of the core pre-emulsion and 1 / 3 of the initiator solution were added dropwise for the first time, and the mixture was kept at 75°C for 40 minutes to obtain a first core emulsion. At this time, the pH of the reaction system was measured to be 6.4. The remaining core pre-emulsion and 1 / 3 of the initiator solution were added dropwise for the second time (the addition was completed within 75 minutes) to the first core emulsion, and the mixture was kept at 80°C for 40 minutes to obtain a core emulsion. S4. After adding the shell pre-emulsion and the remaining initiator solution to the core emulsion for the third time (addition completed within 60 minutes), the temperature was kept at 80° C. for 40 minutes, and then the pH was adjusted to 7.0 with 0.1 M NaHCO 3 to obtain a core-shell structured acrylic microgel emulsion.

[0051] In this embodiment, the core-shell structure acrylic microgel emulsion has a solid content of 36.8% and a particle size of 312 nm. At 85°C, the cross-linking self-repair time is about 88 minutes. After repair, the scratches on the paint film surface basically disappear, and no sagging occurs when the film thickness is 240 μm.

[0052] Example 3 In this embodiment, the raw materials for preparing the core-shell structure acrylic microgel emulsion include the following components, in parts by weight: hard core monomer: 21 parts of methyl methacrylate, 6 parts of butyl acrylate, and 16 parts of styrene, cross-linking monomer: 6 parts of trimethylolpropane trimethacrylate, soft shell monomer: 9 parts of methyl methacrylate, 7 parts of styrene, 3 parts of acrylic acid, and 16 parts of butyl acrylate, functional monomer: 4 parts of glycidyl methacrylate, emulsifier: 11 parts of a mixture of nonylphenol polyoxyethylene ether and sodium lauryl sulfate in a mass ratio of 1:2, and initiator: 6 parts of potassium persulfate.

[0053] The preparation method of the core-shell structure acrylic microgel emulsion comprises the following steps: S1, dissolving an emulsifier in 94 parts of the first water and an initiator in 8 parts of the second water to obtain an emulsifier solution and an initiator solution, respectively; S2, mixing the hard core monomer, the cross-linking monomer and 2 / 3 of the emulsifier solution, stirring for 2 hours to obtain a core pre-emulsion; mixing the soft shell monomer, the functional monomer and the remaining emulsifier solution, stirring for 2 hours to obtain a shell pre-emulsion; S3. In a 250 mL three-necked flask, 1 / 2 of the core pre-emulsion and 1 / 3 of the initiator solution were added dropwise for the first time, and the mixture was kept at 75° C. for 40 minutes to obtain a first core emulsion. At this time, the pH of the reaction system was measured to be 6.5. The remaining core pre-emulsion and 1 / 3 of the initiator solution were added dropwise for the second time (the addition was completed within 75 minutes) to the first core emulsion, and the mixture was kept at 80° C. for 40 minutes to obtain a core emulsion. S4. After adding the shell pre-emulsion and the remaining initiator solution to the core emulsion for the third time (addition completed within 60 minutes), the temperature was kept at 80° C. for 40 minutes, and then the pH was adjusted to 7.0 with 0.1 M NaHCO 3 to obtain a core-shell structured acrylic microgel emulsion.

[0054] In this embodiment, the core-shell structure acrylic microgel emulsion has a solid content of 35.9% and a particle size of 318 nm. At 85°C, the cross-linking self-repair time is about 87 minutes. After repair, the scratches on the paint film surface basically disappear, and no sagging occurs when the film thickness is 210 μm.

[0055] Example 4 In this embodiment, the raw materials for preparing the core-shell structure acrylic microgel emulsion include the following components, in parts by weight: hard core monomer: 21 parts of methyl methacrylate, 6 parts of butyl acrylate, and 14 parts of styrene, a cross-linking monomer: 4 parts of trimethylolpropane trimethacrylate, a soft shell monomer: 9 parts of methyl methacrylate, 6 parts of styrene, 2 parts of acrylic acid, and 16 parts of butyl acrylate, a functional monomer: 3 parts of glycidyl methacrylate, an emulsifier: 9 parts of a mixture of nonylphenol polyoxyethylene ether and sodium lauryl sulfate in a mass ratio of 1:2, and an initiator: 5 parts of potassium persulfate.

[0056] The preparation method of the core-shell structure acrylic microgel emulsion comprises the following steps: S1, dissolving an emulsifier in 94 parts of the first water and an initiator in 8 parts of the second water to obtain an emulsifier solution and an initiator solution, respectively; S2, mixing the hard core monomer, the cross-linking monomer and 2 / 3 of the emulsifier solution, stirring for 2 hours to obtain a core pre-emulsion; mixing the soft shell monomer, the functional monomer and the remaining emulsifier solution, stirring for 2 hours to obtain a shell pre-emulsion; S3. In a 250 mL three-necked flask, 1 / 2 of the core pre-emulsion and 1 / 3 of the initiator solution were added dropwise for the first time, and the mixture was kept at 75° C. for 40 minutes to obtain a first core emulsion. At this time, the pH of the reaction system was measured to be 6.3. The remaining core pre-emulsion and 1 / 3 of the initiator solution were added dropwise for the second time (the addition was completed within 75 minutes) to the first core emulsion, and the mixture was kept at 80° C. for 40 minutes to obtain a core emulsion. S4. After adding the shell pre-emulsion and the remaining initiator solution to the core emulsion for the third time (addition completed within 60 minutes), the temperature was kept at 80° C. for 40 minutes, and then the pH was adjusted to 7.0 with 0.1 M NaHCO 3 to obtain a core-shell structured acrylic microgel emulsion.

[0057] In this embodiment, the core-shell structure acrylic microgel emulsion has a solid content of 36.2% and a particle size of 364 nm. At 85°C, the cross-linking self-repair time is about 89 minutes. After repair, the scratches on the paint film surface basically disappear, and no sagging occurs when the film thickness is 250 μm.

[0058] Example 5 In this embodiment, the raw materials for preparing the core-shell structure acrylic microgel emulsion include the following components, in parts by weight: hard core monomer: 19 parts of methyl methacrylate, 7 parts of butyl acrylate, and 13 parts of styrene, a cross-linking monomer: 6 parts of trimethylolpropane trimethacrylate, a soft shell monomer: 11 parts of methyl methacrylate, 7 parts of styrene, 3 parts of acrylic acid, and 14 parts of butyl acrylate, a functional monomer: 3 parts of glycidyl methacrylate, an emulsifier: 12 parts of a mixture of nonylphenol polyoxyethylene ether and sodium lauryl sulfate in a mass ratio of 1:2, and an initiator: 6 parts of potassium persulfate.

[0059] The preparation method of the core-shell structure acrylic microgel emulsion comprises the following steps: S1, dissolving an emulsifier in 94 parts of the first water and an initiator in 8 parts of the second water to obtain an emulsifier solution and an initiator solution, respectively; S2, mixing the hard core monomer, the cross-linking monomer and 2 / 3 of the emulsifier solution, stirring for 2 hours to obtain a core pre-emulsion; mixing the soft shell monomer, the functional monomer and the remaining emulsifier solution, stirring for 2 hours to obtain a shell pre-emulsion; S3. In a 250 mL three-necked flask, 1 / 2 of the core pre-emulsion and 1 / 3 of the initiator solution were added dropwise for the first time, and the mixture was kept at 75° C. for 40 minutes to obtain a first core emulsion. At this time, the pH of the reaction system was measured to be 6.3. The remaining core pre-emulsion and 1 / 3 of the initiator solution were added dropwise for the second time (the addition was completed within 75 minutes) to the first core emulsion, and the mixture was kept at 80° C. for 40 minutes to obtain a core emulsion. S4. After adding the shell pre-emulsion and the remaining initiator solution to the core emulsion for the third time (addition completed within 60 minutes), the temperature was kept at 80° C. for 40 minutes, and then the pH was adjusted to 7.0 with 0.1 M NaHCO 3 to obtain a core-shell structured acrylic microgel emulsion.

[0060] In this embodiment, the core-shell structure acrylic microgel emulsion has a solid content of 35.6% and a particle size of 337 nm. At 85°C, the cross-linking self-repair time is about 85 minutes. After repair, the scratches on the paint film surface basically disappear, and no sagging occurs when the film thickness is 230 μm.

[0061] Example 6 In this embodiment, the raw materials for preparing the core-shell structure acrylic microgel emulsion include the following components, in parts by weight: hard core monomer: 20 parts of methyl methacrylate, 5 parts of butyl acrylate, and 15 parts of styrene, cross-linking monomer: 4.5 parts of trimethylolpropane trimethacrylate, soft shell monomer: 9 parts of methyl methacrylate, 7 parts of styrene, 3 parts of acrylic acid, and 15 parts of butyl acrylate, functional monomer: 4 parts of glycidyl methacrylate, emulsifier: 12 parts of a mixture of sodium polyoxyethylene fatty alcohol ether sulfate and sodium lauryl sulfate in a mass ratio of 1:1, and initiator: 5 parts of potassium persulfate.

[0062] The preparation method of the core-shell structure acrylic microgel emulsion is the same as that in Example 5.

[0063] In this embodiment, the core-shell structure acrylic microgel emulsion has a solid content of 35.2% and a particle size of 335 nm. At 85°C, the cross-linking self-repair time is about 85 minutes. After repair, the scratches on the surface of the paint film basically disappear, and no sagging occurs when the film thickness is 220 μm. The solid residue content is 0.5%.

[0064] Example 7 In this embodiment, the raw materials for preparing the core-shell acrylic microgel emulsion include the following components, in parts by weight: hard core monomer: 22 parts of methyl methacrylate, 6 parts of butyl acrylate, and 5 parts of acrylonitrile; crosslinking monomer: 5 parts of ethylene glycol dimethacrylate; soft shell monomer: 8 parts of methyl methacrylate, 2 parts of acrylic acid, and 18 parts of butyl acrylate; functional monomer: 3 parts of diacetone acrylamide; emulsifier: 10 parts of a mixture of sodium dodecylbenzene sulfonate and fatty alcohol polyoxyethylene ether in a mass ratio of 3:1; and initiator: 3 parts of azobisisobutyronitrile.

[0065] The preparation method of the core-shell structure acrylic microgel emulsion is the same as that in Example 5.

[0066] In this embodiment, the core-shell structure acrylic microgel emulsion has a solid content of 34.8% and a particle size of 310 nm. At 85°C, the cross-linking self-repair time is about 35 minutes. After repair, the scratches on the surface of the paint film basically disappear, and no sagging occurs when the film thickness is 201 μm.

[0067] Example 8 In this embodiment, the raw materials for preparing the core-shell structure acrylic microgel emulsion include the following components, in parts by weight: hard core monomer: 10 parts of isooctyl acrylate and 12 parts of styrene, cross-linking monomer: 6 parts of trimethylolpropane triacrylate, soft shell monomer: 20 parts of butyl acrylate and 5 parts of ethyl acrylate, functional monomer: 4 parts of ethyl acetoacetate methacrylate, emulsifier: 11 parts of a mixture of nonylphenol polyoxyethylene ether and sodium oleate in a mass ratio of 1:2, and initiator: 4 parts of ammonium persulfate.

[0068] The preparation method of the core-shell structure acrylic microgel emulsion is the same as that in Example 5.

[0069] In this embodiment, the core-shell structure acrylic microgel emulsion has a solid content of 37.1% and a particle size of 350 nm. At 85°C, the cross-linking self-repair time is about 40 minutes. After repair, the scratches on the surface of the paint film basically disappear, and no sagging occurs when the film thickness is 210 μm.

[0070] Comparative Example 1 In this comparative example, the raw materials and preparation method for preparing the core-shell acrylic microgel emulsion are basically the same as those in Example 5, except that the emulsifier is nonylphenol polyoxyethylene ether.

[0071] It was found that in step S4, the solution after the insulation reaction was yogurt-like ( Figure 2 ), the results showed that the use of a single emulsifier would reduce the performance of acrylic microgel emulsion.

[0072] Comparative Example 2 In this comparative example, the raw materials and preparation method for preparing the core-shell acrylic microgel emulsion are basically the same as those in Example 5, except that the emulsifier is sodium lauryl sulfate.

[0073] The results showed that in step S4, the solution after the heat preservation reaction had a large amount of flocculation and was in the form of elastic jelly ( Figure 3 ), the results showed that the use of a single emulsifier would reduce the performance of acrylic microgel emulsion.

[0074] Comparative Example 3 In this comparative example, the raw materials and preparation method for preparing the core-shell acrylic microgel emulsion are basically the same as those in Example 5, except that in step S3, the second dropping time is 45 minutes.

[0075] The results showed that in step S4, a large amount of solid residue existed in the solution after the heat preservation reaction. The results showed that if the second dropwise addition time was too long, the performance of the acrylic microgel emulsion would be reduced.

[0076] Comparative Example 4 In this comparative example, the raw materials and preparation method for preparing the core-shell acrylic microgel emulsion are basically the same as those in Example 5, except that in step S3, the second dropping time is 115 minutes.

[0077] The results showed that in step S4, a small amount of solid residue existed in the solution after the heat preservation reaction, which had almost no effect, but increased the reaction time and caused waste.

[0078] Performance Testing The film-forming properties of Example 5 and the commercially available acrylic microgel emulsion were tested. Specifically, samples were spotted on a glass slide and the film structure was observed. The results are as follows: Figure 4 shown.

[0079] from Figure 4 It can be seen from the figures that the acrylic microgel emulsion of the present invention has good film-forming performance.

[0080] It should be noted that the above embodiments all belong to the same inventive concept, and the description of each embodiment has its own focus. For any details not described in individual embodiments, reference may be made to the description in other embodiments.

[0081] The above-described embodiments merely illustrate the implementation methods of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for preparing a core-shell structure acrylic microgel emulsion, characterized in that: The steps include: S1, dissolving an emulsifier in a first water and an initiator in a second water to obtain an emulsifier solution and an initiator solution, respectively; S2, mixing the hard core monomer, the cross-linking monomer and 1 / 2-3 / 4 of the emulsifier solution to obtain a core pre-emulsion; mixing the soft shell monomer, the functional monomer and the remaining emulsifier solution to obtain a shell pre-emulsion; S3, mixing the core pre-emulsion and the initiator solution in an amount of 8 / 15-4 / 5 to obtain a core emulsion; S4, mixing the core emulsion, the shell pre-emulsion and the remaining initiator solution, reacting the mixture, and adjusting the pH to 6.5-7.5 to obtain a core-shell structured acrylic microgel emulsion; Wherein, the hard core monomer includes at least one of methyl methacrylate, styrene, acrylonitrile, ethyl acrylate, butyl acrylate, and isooctyl acrylate.

2. The method for preparing the core-shell structure acrylic microgel emulsion according to claim 1, wherein In parts by weight, in step S1, the emulsifier is present in an amount of 1-20 parts, the first water is present in an amount of 90-100 parts, the initiator is present in an amount of 0.5-10 parts, and the second water is present in an amount of 6-10 parts; and / or In step S2, the hard core monomer is present in an amount of 20-50 parts, the cross-linking monomer is present in an amount of 3-7 parts, the soft shell monomer is present in an amount of 20-40 parts, and the functional monomer is present in an amount of 2-5 parts.

3. The method for preparing the core-shell structure acrylic microgel emulsion according to claim 1, wherein In step S1, the emulsifier includes at least one of nonylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, polyoxyethylene fatty acid ester, polyoxyethylene stearate, sodium oleate, sodium stearate, sodium dodecylbenzene sulfonate, fatty alcohol polyoxyethylene ether sodium sulfate, and sodium lauryl sulfate.

4. The method for preparing the core-shell structure acrylic microgel emulsion according to claim 1, wherein In step S1, the initiator includes at least one of potassium persulfate and azobisisobutyronitrile.

5. The method for preparing the core-shell structure acrylic microgel emulsion according to claim 1, wherein In step S2, the cross-linking monomer includes at least one of trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, trimethylolpropane trimethacrylate, ethylene glycol dimethacrylate, zinc diacrylate, and zinc dimethacrylate; and / or The soft shell monomer comprises at least one of methyl methacrylate, acrylic acid, styrene, acrylonitrile, ethyl acrylate, butyl acrylate, and isooctyl acrylate; and / or The functional monomer includes at least one of diacetone acrylamide, ethyl acetoacetate methacrylate, glycidyl methacrylate, and dimethylaminoethyl methacrylate.

6. The method for preparing the core-shell structure acrylic microgel emulsion according to claim 1, wherein: In step S3, the step of mixing the core pre-emulsion and 8 / 15-4 / 5 of the initiator solution to obtain the core emulsion specifically includes: first adding 1 / 3-2 / 3 of the core pre-emulsion and 4 / 15-2 / 5 of the initiator solution dropwise, followed by a first mixing to obtain a first core emulsion, and then adding the remaining core pre-emulsion and 4 / 15-2 / 5 of the initiator solution dropwise to the first core emulsion, followed by a second mixing to obtain a core emulsion; The temperature of the first mixing is 60-75° C., and the time is 30-100 min; the temperature of the second mixing is 75-90° C., and the time is 30-100 min; and the time of the second dropping is 70-80 min.

7. The method for preparing the core-shell structure acrylic microgel emulsion according to claim 6, wherein: In step S4, the reaction after mixing the core emulsion, the shell pre-emulsion and the remaining initiator solution specifically includes: adding the shell pre-emulsion and the remaining initiator solution to the core emulsion by a third dropwise addition for a third mixing; The temperature of the third mixing is 75-90° C. and the time is 30-100 min; and the time of the third dropping is 55-65 min.

8. A core-shell structure acrylic microgel emulsion, characterized in that: The method is prepared according to any one of claims 1 to 7.

9. The core-shell structure acrylic microgel emulsion according to claim 8, characterized in that: The core-shell structure acrylic microgel emulsion has a particle size of 100-600 nm and a solid content of 34-38%.

10. Use of the core-shell structure acrylic microgel emulsion according to claim 9 in coatings.

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