Methacrylate waterproof coating containing core-shell structure microspheres and preparation method thereof

Abstract

The invention relates to the field of building industry, in particular to a methacrylate waterproof coating containing core-shell structure microspheres and a preparation method of the methacrylate waterproof coating, modified micro-nano rigid materials are used as seeds, and the methacrylate waterproof coating containing the core-shell structure microspheres is obtained through control, coupling and graft polymerization reaction of a polymerization process. The core-shell structure microsphere sequentially comprises an inorganic rigid particle layer (core), a silane coupling layer, a methacrylate polymer layer, an acrylate polymer layer and an acrylic polymer layer from inside to outside, the particle size D50 is 10-1000 nm, the shell is excellent in viscoelasticity and can be subjected to toughness deformation filling, the core has high strength to resist stress, and the service life of the core-shell structure microsphere is prolonged. The waterproof coating prepared from the emulsion containing the core-shell structure microspheres ensures that the microspheres not only can be embedded into pores and block building cracks, but also are not easy to fall off, and the waterproof effect is excellent.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of the construction industry, and in particular to a methyl acrylate waterproof coating containing core-shell structure microspheres and a preparation method thereof. BACKGROUND

[0002] Butyl acrylate coating is an acrylate coating synthesized with butyl acrylate as the main raw material. It is made of acrylate organic monomers as the basis, and various additives and modifiers. It has excellent weather resistance, good flexibility, good environmental protection, strong adhesion and convenient construction, etc. Compared with traditional solvent-based coatings, it does not contain a large amount of organic solvents and volatile organic compounds, has little harm to the environment and human health, and is mostly water-based, which can reduce VOC emissions and meet environmental protection requirements.

[0003] Traditional acrylate emulsion is prone to brittle fracture at low temperature and sticky at high temperature, and has poor mechanical properties. In order to solve these problems, researchers have developed core-shell structure methyl acrylate waterproof coating. For example, Chinese patent CN108329417A discloses a nano-SiO2 / organic silicon modified core-shell acrylate emulsion and a preparation method. The core-shell structure design improves the low-temperature brittleness and high-temperature stickiness problems. The core layer is mainly composed of methyl methacrylate (MMA) with high glass transition temperature (Tg), which provides rigid support. The shell layer is mainly composed of butyl acrylate (BA) with low Tg, which gives flexibility and balances the low-temperature film-forming property and high-temperature stability of the coating. The water resistance is improved by modification with organic silicon (KH570) and nano-SiO2, and the mechanical properties are enhanced by inorganic-organic hybridization. However, the core-shell structure has an organic polymer core and an inorganic-organic hybrid shell, and the high cross-linking density of the shell layer leads to insufficient flexibility, which cannot effectively seal micron-sized pores on the building, resulting in limited waterproof effect. In addition, the use of multiple layers of polymers with different glass transition temperatures leads to differences in physical and chemical properties of polymers with different Tg and interface compatibility problems: thermodynamically, the chemical structure of polymers with different Tg is different, the polarity is not matched, the solubility parameter difference is large, and the reaction activity is not matched, etc. The intermolecular forces between the layers are weak, leading to poor interface compatibility and spontaneous tendency to phase separation; kinetically, the polymerization rate during preparation is not matched, the phase separation and migration are difficult to control, and the thickness uniformity is difficult to control. It is difficult to precisely control the morphology between the layers and realize the synergistic effect of "rigidity-tenacity".

[0004] Therefore, there is an urgent need to develop a new core-shell structure waterproof coating with micron-sized sealing capacity, dynamic flexibility and excellent waterproof effect. SUMMARY

[0005] In order to overcome the deficiencies of the prior art, the present application provides a kind of methyl methacrylate waterproof coating containing core-shell structure microspheres and its preparation method, by introducing acrylic monomer into emulsion polymerization whole system process, and by controlling emulsification process and inorganic-organic composite ratio, optimizing particle size core layer, core layer is micron rigid particle, shell layer is formed by gradient polymerization elastic coating, the waterproof coating prepared ensures that microspheres can be embedded in pores, block building cracks, and not easy to fall off, and the waterproof effect is excellent.

[0006] The technical scheme for solving the technical problems of the present application is: The present application provides a kind of methyl methacrylate waterproof coating containing core-shell structure microspheres and its preparation method, comprising: 1) mix silicone modifier, deionized water and acetic acid in a mass ratio of 0.5-1.5:8-12:0.03-0.06, hydrolyze at 23-26℃ for 8~16h to obtain a silicon hydroxyl active hydrolysate, add 10-500nm nano-silicon dioxide particles to the hydrolysate, stir at 55-65℃ for 2-4h, and mix evenly to obtain a water dispersion containing two-layer core-shell structure microspheres, the core layer of the two-layer core-shell structure microspheres is a nano-silicon dioxide particle layer, and the shell layer is a silane coupling layer; 2) mix and dissolve acrylic monomers, emulsifiers and deionized water in a mass ratio of 0.5-1:0.5-1:55-65, adjust the pH of the system to 6-7 with 20% sodium hydroxide solution to obtain an aqueous phase; 3) add the water dispersion containing two-layer core-shell structure microspheres and methyl methacrylate monomers in a mass ratio of 4-8:10-20 to the aqueous phase, and mechanically shear emulsify to obtain a pre-emulsion; 4) warm the pre-emulsion to 70-82℃, slowly add the first-stage initiator solution, uniformly mix and incubate for 40-80min to form a dispersion containing three-layer core-shell structure microspheres, the core layer of the three-layer core-shell structure microspheres is a nano-silicon dioxide particle layer, and the shell layer is a silane coupling layer, a methyl methacrylate polymer layer from inside to outside; 5) Heat the dispersion containing the three-layer core-shell structured microspheres to 82-85℃, add acrylate monomers dropwise, and add the second-stage initiator aqueous solution dropwise (controlling the polymerization rate of each polymerization stage of the shell layer to avoid excessive reaction or failure to react). During the dropwise addition, maintain a micro-reflux state in the reactor and control the pH of the system at 6-7 (ammonia can be added dropwise for adjustment). After the dropwise addition is completed, heat to 90-95℃ and maintain the temperature for polymerization for 1-3 hours. The acrylate monomers copolymerize with the acrylate monomers in the aqueous phase, thereby continuing to build an acrylate polymer layer and an outermost acrylate polymer layer on the surface of the methacrylate polymer layer, forming an emulsion containing five-layer core-shell structured microspheres. After the reaction is completed, cool to 30-45℃ and adjust the pH to 8-9 with ammonia to obtain a stable emulsion. The core layer of the five-layer core-shell structured microspheres is a nano-silica particle layer, and the shell layer is a silane coupling layer, a methacrylate polymer layer, an acrylate polymer layer, and an acrylate polymer layer. 6) Add film-forming aid (5%-8% of the total monomer mass), thickener (to adjust viscosity to 80-100 KU), and defoamer (0.1%-0.3% of the total monomer mass) to the stabilized emulsion, stir evenly, filter through a 120-mesh filter to remove impurities, and obtain a methacrylate waterproof coating containing core-shell structured microspheres.

[0007] Furthermore, the mass ratio of the organosilicon modifier to the micro / nano rigid microspheres is 0.5-1.5:10-20.

[0008] Furthermore, the organosilicon modifier is one or more of γ-methacryloxypropyltrimethoxysilane, vinyltriethoxysilane, γ-aminopropyltriethoxysilane, and vinyltris(β-methoxyethoxy)silane.

[0009] Furthermore, the acrylic monomer is one or more of acrylic acid, methacrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, and acrylamide.

[0010] Further, the emulsifier is one or more of the following: sorbitol fatty acid ester, polyoxyethylene octylphenol ether-10, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, polyoxyethylene sorbitol ether stearate, or polysorbate-80.

[0011] Furthermore, the mechanical shearing speed is 4000-6000 r / min; the mechanical shearing time is 10-30 min; and the mechanical stirring speed is 200-800 r / min.

[0012] Furthermore, the methacrylate monomer is one or more of methyl methacrylate (MMA), cyclohexyl methacrylate (CHMA), octyl methacrylate (EHMA), butyl methacrylate (MBA), and styrene (St).

[0013] Further, the initiator is one or more of ammonium persulfate (APS), azobisisobutyronitrile (AIBN), benzoyl peroxide (BPO), and potassium persulfate (KPS); the amount of initiator added is 0.1%-1% of the total monomers.

[0014] Furthermore, the drop acceleration rate is 2-10 drops / second.

[0015] Furthermore, the acrylate monomer is one or more of butyl acrylate (BA) and octyl acrylate (2-EHAM).

[0016] Furthermore, the film-forming aid is one or more of propylene glycol butyl ether, ethylene glycol butyl ether (EB), propylene glycol, benzyl benzoate, and dibutyl phthalate (DBP); the amount of the film-forming aid is 4%-10% of the monomer mass.

[0017] Furthermore, the thickener is one or more of hydroxyethyl cellulose (HEC), methyl cellulose (MC), bentonite, etc.

[0018] Furthermore, the defoamer is one or more of the following: polydimethylsiloxane, modified organosilicon defoamer, white oil, polyoxyethylene polyoxypropylene glycerol ether, polyether modified silicone oil, etc.

[0019] Another aspect of the present invention provides a methacrylate waterproof coating containing core-shell structured microspheres prepared by the preparation method described above. The core layer of the core-shell structured microspheres is a nano-silica particle layer, and the shell layer, from the inside out, consists of a silane coupling layer, a methacrylate polymer layer, an acrylate polymer layer, and an acrylic polymer layer, with a particle size D50 of 10~1000 nm.

[0020] Furthermore, the structural formula of the shell is formula (I): Formula (I); Wherein, R1 represents one or more of -CONHC(CH3)(CH3)CH2SO3Na, -COONa, and -CONH2; R2 represents -H or -(CH2). n1 CH3, n1 is between 0 and 4; R3 represents -(CH2). n2 CH3, n2 is between 0 and 18; R4 represents -(CH2). n3 -or -COO(CH2) n3-, n3 is between 0 and 4; molar ratio m:n:p:q = (1-10):(10-200):(10-200):(0.1-0.6).

[0021] To address the issues of mismatched particle size and limited shell function in existing core-shell waterproof coatings, this invention uses modified micro / nano rigid materials as seeds. Through controlled polymerization processes, coupling and graft polymerization reactions introduce acrylic monomers into the entire emulsion polymerization process. In this emulsion polymerization system, the acrylic monomers are not completely dissolved in the aqueous phase, but exist in a dynamic equilibrium of "dissolution-diffusion-polymerization" in the aqueous phase, micelles, and latex particles. The main effects are as follows: 1. "Monomer reserve": maintains the continuity and stability of the polymerization reaction; 2. Regulates the surface charge of latex particles: improves emulsion stability; 3. Improves the interfacial bonding between latex particles and substrate: enhances adhesion; 4. Regulates the polymerization rate and molecular weight distribution; 5. Imparts "functional groups" to the emulsion: reserves active sites for subsequent modification.

[0022] It is the dynamic effect of this small amount of monomers that gives acrylic emulsions their core advantages of "uniform particle size, high stability, and strong adhesion," making them the mainstream system in coatings, adhesives, and other fields.

[0023] Acrylic esters provide adhesion and contain hydrophobic groups (ester groups). However, this polymer lacks sufficient hydrophilicity and tends to aggregate in water, leading to poor coating stability and poor adhesion, failing to effectively adhere to the substrate. Acrylic acid can exist in dynamic equilibrium in the aqueous phase, micelles, and latex particles, and needs to play a role throughout the polymerization process. Providing hydrophilic groups (negative charge) enhances emulsion stability and adhesion.

[0024] In the presence of acrylic acid, the core-shell structured microspheres form, from the inside out, a layer of nano-silica particles, a layer of organosilicon modifier, a layer of methacrylate polymer, a layer of acrylate polymer, and a layer of acrylic polymer. The inorganic core is surface-modified with an organosilicon modifier, resulting in a hydrophobic structure containing double bonds, enabling graft copolymerization with the methacrylate polymer and improving the interfacial bonding strength of the core-shell structure. The methacrylate polymer has a high glass transition temperature and high strength at room temperature; the acrylate polymer has a low glass transition temperature and exhibits viscoelasticity; and the acrylic polymer has good hydrophilicity, enabling efficient bonding. Through this core-shell structure, the inorganic rigid particles and organic polymers with different glass transition temperatures work synergistically to effectively seal cracks in walls and other structures.

[0025] The advantages and positive effects of this invention are: 1) The core-shell structured microspheres in the methacrylate waterproof coating prepared by this invention have a particle size D50 of 10-1000nm. The outer shell has excellent viscoelasticity and can undergo tough deformation to fill the core, while the core has high strength to resist stress. It maintains toughness and deformability while having rigid pressure bearing capacity, effectively improving the sealing effect and waterproof effect.

[0026] 2) This material does not require drying and granulation, and can be used directly. It is convenient to use and easy to promote. Attached Figure Description

[0027] Figure 1 This is a particle size distribution diagram of core-shell structured microspheres in methacrylate waterproof coatings. Figure 2 Microscopic morphology diagram of core-shell structured microspheres in methacrylate waterproof coating; Figure 3 TEM image of core-shell structured microspheres; Figure 4 This is a schematic diagram of the core-shell structured microspheres of the present invention.

[0028] Figure 5 This is a schematic diagram showing the connection between the core layer and the shell layer of the core-shell structured microsphere of the present invention.

[0029] Figure 6 The FT-IR spectrum of the two-layer core-shell structured microspheres prepared in Example 1. Detailed Implementation

[0030] This invention provides a methacrylate waterproof coating containing core-shell structured microspheres and its preparation method. Those skilled in the art can refer to the content of this document and appropriately modify the process parameters to achieve the same result. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and fall within the scope of protection of this invention. The method and application of this invention have been described through preferred embodiments. Those skilled in the art can obviously modify or appropriately change and combine the method and application described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0031] This invention provides a method for preparing a methacrylate waterproof coating containing core-shell structured microspheres, comprising: 1) Mix organosilicon modifier, deionized water, and acetic acid in a mass ratio of 0.5-1.5:8-12:0.03-0.06, and hydrolyze at 23-26℃ for 8-16 hours to obtain a silanol active hydrolysate. Add 50-500nm nano-silica microspheres to the hydrolysate, stir at 55-65℃ for 2-4 hours, and mix well to obtain an aqueous dispersion containing two-layer core-shell structure microspheres, wherein the core layer of the two-layer core-shell structure microspheres is a nano-silica particle layer and the shell layer is a silane coupling layer. 2) Mix and dissolve acrylic monomers, emulsifiers, and deionized water in a mass ratio of 0.5-1:0.5-1:55-65, and adjust the pH of the system to 6-7 with 20% sodium hydroxide solution to obtain the aqueous phase; 3) Add an aqueous dispersion containing microspheres with a two-layer core-shell structure in a mass ratio of 4-8:10-20 and methacrylate monomers to the aqueous phase, and mechanically shear emulsify to obtain a pre-emulsion; 4) Heat the pre-emulsion to 70-82℃, slowly add the first stage initiator solution, mix evenly and keep warm for 40-80 minutes to form a dispersion containing microspheres with a three-layer core-shell structure. The core layer of the microspheres is a nano-silica microsphere layer, and the shell layer consists of a silane coupling layer and a methacrylate polymer layer from the inside out. 5) Heat the dispersion containing the three-layer core-shell structured microspheres to 82-85℃, add acrylate monomers dropwise, and add the second-stage initiator aqueous solution dropwise (controlling the crosslinking density of each polymerization segment of the shell layer to avoid over-crosslinking). During the dropwise addition, maintain a micro-reflux state in the reactor and control the pH of the system at 6-7 (ammonia can be added dropwise to adjust). After the dropwise addition is completed, heat to 90-95℃ and maintain the temperature for polymerization for 1-3 hours to form an emulsion containing five-layer core-shell structured microspheres. After the reaction is completed, cool to 30-45℃ and adjust the pH to 8-9 with ammonia to obtain a stable emulsion. The core layer of the five-layer core-shell structured microspheres is a nano-silica microsphere layer, and the shell layer is a silane coupling layer, a methacrylate polymer layer, an acrylate polymer layer, and an acrylic polymer layer. 6) Add film-forming aid (5%-8% of the total monomer mass), thickener (to adjust viscosity to 80-100 KU), and defoamer (0.1%-0.3% of the total monomer mass) to the stabilized emulsion, stir evenly, filter through a 120-mesh filter to remove impurities, and obtain a core-shell type methacrylate waterproof coating.

[0032] Furthermore, the mass ratio of the organosilicon modifier to the nano-silica particles is 0.5-1:10-20.

[0033] Preferably, the organosilicon modifier is one or more of γ-methacryloyloxypropyltrimethoxysilane, vinyltriethoxysilane, γ-aminopropyltriethoxysilane, and vinyltris(β-methoxyethoxy)silane.

[0034] Preferably, the acrylic organic monomer is one or more of acrylic acid, methacrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, N-vinylpyrrolidone, and acrylamide.

[0035] Preferably, the emulsifier is one or more of the following: sorbitol fatty acid ester, polyoxyethylene octylphenol ether-10, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, polyoxyethylene sorbitol ether stearate, and polysorbate-80.

[0036] Preferably, the mechanical shearing speed is 4000-6000 r / min; the mechanical shearing time is 10-30 min; and the mechanical stirring speed is 200-800 r / min.

[0037] Preferably, the methacrylate organic monomer is one or more of methyl methacrylate (MMA), cyclohexyl methacrylate (CHMA), octyl methacrylate (EHMA), butyl methacrylate (MBA), and styrene (St).

[0038] Preferably, the initiator is one or more of ammonium persulfate (APS), azobisisobutyronitrile (AIBN), benzoyl peroxide (BPO), or potassium persulfate (KPS); the amount of initiator added is 0.1%-1% of the total monomers.

[0039] Preferably, the drop acceleration rate is 2-10 drops / second.

[0040] Preferably, the acrylate organic monomer is one or more of butyl acrylate (BA) and octyl acrylate (2-EHAM).

[0041] Preferably, the film-forming aid is one or more of propylene glycol butyl ether, ethylene glycol butyl ether (EB), propylene glycol, benzyl benzoate, and dibutyl phthalate (DBP); the amount of the film-forming aid is 4%-10% of the monomer mass; Preferably, the thickener is one or a mixture of several of hydroxyethyl cellulose (HEC), methyl cellulose (MC), bentonite, etc.; the viscosity is adjusted to 80-100 KU. Preferably, the defoamer is one or a mixture of several of the following: polydimethylsiloxane, modified organosilicon defoamer, white oil, polyoxyethylene polyoxypropylene glycerol ether, polyether modified silicone oil, etc.; the amount of the defoamer is 0.1%-0.5% of the monomer mass.

[0042] The present invention provides a method for preparing a methacrylate waterproof coating containing core-shell structured microspheres. The core layer of the core-shell structured microspheres is a nano-silica particle layer, and the shell layer, from the inside to the outside, consists of a silane coupling layer, a methacrylate polymer layer, an acrylate polymer layer, and an acrylic polymer layer. The particle size D50 is 10-1000 nm.

[0043] Preferably, the chemical structural formula of the shell layer of the core-shell type methacrylate waterproof coating is formula (I): Formula (I); Wherein, R1 represents one or more of -CONHC(CH3)(CH3)CH2SO3Na, -COONa, and -CONH2; R2 represents -H or -(CH2). n1 CH3, n1 is between 0 and 4; R3 represents -(CH2). n2 CH3, n2 is between 0 and 18; R4 represents -(CH2). n3 -or -COO(CH2) n3 -, n3 is between 0 and 4; molar ratio m:n:p:q = (1-10):(10-200):(10-200):(0.1-0.6).

[0044] This invention relates to an acrylic waterproof coating containing core-shell structured microspheres with nano-micron particle sizes, produced by seed emulsion polymerization. The microspheres have a particle size of 10-1000 nm and exhibit good sealing properties.

[0045] This invention relates to an acrylic waterproof coating with micro-nano particle size, synthesized through seed polymerization, with a particle size D. 50 With a particle size of 10-1000 nm, it exhibits good sealing properties. The sealing agent prepared in this invention is a water-in-oil core-shell structured microsphere. This invention uses modified micro-nano rigid materials as seeds, and through controlled polymerization processes, coupling and graft polymerization reactions are carried out to form an inorganic material (core) - organosilicon modifier - methacrylate polymer - acrylate polymer - acrylic polymer from the inside out. The inorganic core is surface modified by the organosilicon modifier, resulting in a hydrophobic structure containing double bonds, which can be grafted and copolymerized with oil-phase monomers. The methacrylate polymer has a high glass transition temperature and high strength at room temperature; the acrylate polymer has a low glass transition temperature and viscoelasticity; the acrylic polymer has good hydrophilicity and can bond efficiently. Through this core-shell structure, the inorganic rigid particles and organic polymers with different glass transition temperatures work synergistically to effectively seal cracks in walls and other structures. This waterproof coating has a particle size D50 of 10-1000 nm, and the outer shell can undergo tough deformation filling while the core has high strength, resulting in excellent sealing and waterproofing effects.

[0046] This invention utilizes the flexible hydrophobic chains and C-Si bonds in the coupling agent to improve the hydrolysis resistance of the flexible shell.

[0047] The material adopts a core-shell structure, which maintains toughness and deformability while having rigid pressure-bearing capacity, effectively improving the sealing effect. This material does not require drying or granulation and can be used directly, making it convenient and easy to promote.

[0048] To further illustrate the present invention, the following describes in detail, with reference to embodiments, a methacrylate waterproof coating containing core-shell structured microspheres and its preparation method.

[0049] Example 1 A method for preparing a methacrylate waterproof coating containing core-shell structured microspheres, comprising: 1) Mix 1g KH-570 with 10g deionized water and 0.05g acetic acid, and hydrolyze at 25℃ with magnetic stirring for 9 hours to form a silanol (Si-OH) active solution; slowly add 11g 100nm SiO2 to the hydrolysate, stir at 60℃ for 2 hours at 800rpm, and mix well to obtain an aqueous dispersion containing two-layer core-shell structured microspheres, wherein the core layer of the two-layer core-shell structured microspheres is a nano-silica microsphere layer and the shell layer is a KH-570 coupling layer, for later use; the FT-IR spectra of the two-layer core-shell structured microspheres are shown below. Figure 6 As shown. 2950cm -1 The peaks at 813 and 1108 cm⁻¹ represent the asymmetric stretching vibrations of CH in the methylene group. -1 The absorption peaks at 1690 cm⁻¹ are the symmetric and asymmetric stretching vibration absorption peaks of Si-O-Si, respectively. -1 The C=C stretching vibration peak at 1720 cm⁻¹ -1 The peak at this point is a characteristic absorption peak of C=O. Infrared spectral analysis shows that the inorganic mineral surface modification was successful and that the surface contains C=C, which facilitates subsequent polymerization and grafting.

[0050] 2) Dissolve 0.24g of initiator (ammonium persulfate) in 6g of deionized water, and divide it into a first-stage initiator solution (2 / 3) and a second-stage initiator solution (1 / 3), for later use; 3) Add 60g of water, 0.8g of sodium alkylbenzene sulfonate, 0.8g of polyoxyethylene octylphenol ether-10, and 0.8g of acrylamide to a 250mL four-necked flask equipped with a condenser, stirrer, and N2 gas channel. Mix and dissolve the mixture. Adjust the pH of the system to 6-7 with 20% sodium hydroxide solution to obtain the aqueous phase. 4) Add 20g of methyl methacrylate and 6g of aqueous dispersion containing microspheres with a two-layer core-shell structure to the aqueous phase, and stir at a shear rate of 4000rpm for 30min under N2 atmosphere to obtain a preemulsion. 5) Raise the preemulsion to 70°C, stir at 450 rpm, slowly add 4g of a first-stage initiator solution, keep warm and polymerize for 1 hour to form a dispersion of microspheres with a core layer of micron-sized SiO2 particles, a shell layer consisting of a KH-570 coupling layer and a methacrylate polymer layer. 6) Heat the dispersion containing the three-layer core-shell structured microspheres to 82°C, slowly add 20g of butyl acrylate dropwise over 1 hour, and continue stirring for 2 hours after the addition is complete. Add the second-stage initiator solution dropwise, maintaining a micro-reflux state in the reactor during the dropwise addition process, and control the pH of the system at 6-7 (which can be adjusted by adding ammonia). After the dropwise addition is complete, heat to 90°C, maintain the temperature for polymerization and stirring for 3 hours. After the reaction is complete, cool to 30°C and adjust the pH to 8-9 with ammonia to obtain a stable emulsion. The core layer of the five-layer core-shell structured microspheres is micron-sized SiO2 particles, and the shell layers are KH-570 coupling layer, methacrylate polymer layer, butyl acrylate polymer layer, and acrylamide polymer layer, in sequence. 7) Add 1.5g of film-forming aid (propylene glycol butyl ether), thickener hydroxyethyl cellulose (to adjust viscosity to 80KU), and 0.06g of polydimethylsiloxane (defoamer) to the stable emulsion and stir evenly. Filter through a 120-mesh filter to remove impurities and obtain a methacrylate waterproof coating containing core-shell structured microspheres (the structural formula of the shell is Formula I-1).

[0051] Formula (I-1).

[0052] Example 2 A method for preparing a methacrylate waterproof coating containing core-shell structured microspheres, comprising: 1) Mix 1g of vinyltrimethoxysilane (A-171) with 10g of deionized water and 0.05g of acetic acid, and hydrolyze at 25°C with magnetic stirring for 10 hours to form a silanol (Si-OH) active solution; slowly add 11g of 100nm SiO2 to the hydrolysate, stir at 60°C for 2 hours at 800rpm to obtain a core layer of nano-silica microspheres and a shell layer of vinyltrimethoxysilane coupling layer, for later use; 2) Dissolve 0.24g of initiator (ammonium persulfate) in 6g of deionized water, and divide it into a first-stage initiator solution (2 / 3) and a second-stage initiator solution (1 / 3), for later use; 3) Add 60g of water, 0.8g of sodium alkylbenzene sulfonate, 0.8g of polyoxyethylene octylphenol ether-10, and 0.8g of acrylic acid to a 250mL four-necked flask equipped with a condenser, stirrer, and N2 gas channel. Mix and dissolve the contents. Adjust the pH of the system to 6-7 using a 20% sodium hydroxide solution to obtain the aqueous phase. 4) Add 20g of methyl methacrylate and 6g of aqueous dispersion containing microspheres with a two-layer core-shell structure to the aqueous phase, and stir at a shear rate of 4000rpm for 30min under N2 atmosphere to obtain a preemulsion. 5) Raise the pre-emulsion to 70°C, stir at 450 rpm, slowly add 4g of a first-stage initiator solution, keep warm and polymerize for 1 hour to form a dispersion of microspheres with a core layer of micron-sized SiO2 particles and a shell layer consisting of a vinyltrimethoxysilane coupling layer and a methacrylate polymer layer. 6) The dispersion of the three-layer core-shell structured microspheres was heated to 82 °C, and 20 g of isooctyl acrylate was slowly added dropwise over 1 hour. After the addition was complete, stirring was continued for 2 hours. The second-stage initiator solution was then added dropwise, maintaining a micro-reflux state in the reactor during the addition process. The pH of the system was controlled at 6-7 (ammonia water can be added dropwise for adjustment). After the addition was complete, the temperature was raised to 90 °C, and polymerization was carried out at this temperature with stirring for 3 hours to form an emulsion containing five-layer core-shell structured microspheres. After the reaction was completed, the temperature was cooled to 30 °C, and the pH was adjusted to 8-9 with ammonia water to obtain a stable emulsion. The core layer of the five-layer core-shell structured microspheres is a nano-silica microsphere layer, and the shell layer is a silane coupling layer, a methacrylate polymer layer, an acrylate polymer layer, and an acrylic polymer layer. 7) Add 1.5g of film-forming aid (propylene glycol butyl ether), thickener hydroxyethyl cellulose (to adjust viscosity to 80KU), and 0.06g of polydimethylsiloxane (defoamer) to the stable emulsion and stir until homogeneous; filter through a 120-mesh filter to remove impurities and obtain a methacrylate waterproof coating containing core-shell structured microspheres (the structural formula of the shell is Formula I-2).

[0053] Formula (I-2).

[0054] Example 3 A method for preparing a methacrylate waterproof coating containing core-shell structured microspheres, comprising: 1) The modified SiO2 aqueous dispersion is the same as in Example 2; 2)-7) Same as Example 1. The resulting core layer is composed of nano-silica particles, and the shell layers, from the inside out, are successively a vinyltrimethoxysilane coupling layer, a methacrylate polymer layer, a butyl acrylate polymer layer, and an acrylamide polymer layer. (The structural formula of the shell layers is Formula I-3) Formula (I-3).

[0055] Comparative Example 1 The only difference from Example 1 is that in step 6), the dispersion containing the three-layer core-shell structured microspheres is heated to 82°C, and a micro-reflux state is maintained in the reactor during the heating process, and the pH of the system is controlled at 6-7 (ammonia can be added dropwise to adjust); after the addition is completed, the temperature is raised to 90°C, and the polymerization is carried out by stirring for 3 hours; after the reaction is completed, the temperature is cooled to 30°C, and the pH is adjusted to 8-9 with ammonia to obtain a stable emulsion.

[0056] The core layer of the prepared core-shell structured microspheres is a layer of nano-silica particles, and the shell layer is a silane coupling layer, a methacrylate polymer layer, and an acrylic polymer layer.

[0057] Comparative Example 2 The difference from Example 1 is that SiO2 is not added; the specific preparation steps are as follows: 1) Mix 1g KH-570 with 10g deionized water and 0.05g acetic acid, and hydrolyze with magnetic stirring at 25℃ for 10 hours to form a silanol (Si-OH) active solution for later use; 2) Dissolve 0.24g of initiator (ammonium persulfate) in 6g of deionized water, and divide it into a first-stage initiator solution (2 / 3) and a second-stage initiator solution (1 / 3), for later use; 3) Add 60g of water, 0.8g of sodium alkylbenzene sulfonate, 0.8g of polyoxyethylene octylphenol ether-10, and 0.8g of acrylamide to a 250mL four-necked flask equipped with a condenser, stirrer, and N2 gas channel. Mix and dissolve the mixture. Adjust the pH of the system to 6-7 with 20% sodium hydroxide solution to obtain the aqueous phase. 4) Add 20g of methyl methacrylate and 6g of silanol (Si-OH) active solution to the aqueous phase, and stir at a shear rate of 4000rpm for 30min under N2 atmosphere to obtain a preemulsion; 5) Raise the preemulsion to 70°C, stir at 450 rpm, slowly add 4g of a first-stage initiator solution, keep warm and polymerize for 1 hour to form a dispersion of polymer microspheres consisting of a KH-570 coupling layer and a methacrylate polymer layer. 6) Heat the above dispersion to 82°C, slowly add 20g of butyl acrylate dropwise over 1 hour, and continue stirring for 2 hours after the addition is complete. Add the second-stage initiator solution dropwise, maintaining a micro-reflux state in the reactor during the dropwise addition process, and control the pH of the system at 6-7 (ammonia can be added dropwise to adjust). After the dropwise addition is complete, heat to 90°C, maintain the temperature and stir for 3 hours to form an emulsion containing microspheres with a five-layer core-shell structure. After the reaction is complete, cool to 30°C and adjust the pH to 8-9 with ammonia to obtain a stable emulsion, which consists of a KH-570 coupling layer, a methacrylate polymer layer, a butyl acrylate polymer layer, and an acrylamide polymer layer from the inside out. 7) Add 1.5g of film-forming aid (propylene glycol butyl ether), thickener hydroxyethyl cellulose (to adjust viscosity to 80KU), and 0.06g of polydimethylsiloxane (defoamer) to the stabilized emulsion and stir until homogeneous. Filter through a 120-mesh filter to remove impurities and obtain a core-shell type methacrylate waterproof coating.

[0058] The core layer of the prepared core-shell structured microspheres is a silane coupling layer, and the shell layer is a methacrylate polymer layer and an acrylic polymer layer.

[0059] Comparative Example 3 The difference from Example 1 is that acrylic acid is not initially added to the aqueous phase. The specific preparation steps are as follows: 1) Mix 1g KH-570 with 10g deionized water and 0.05g acetic acid, and hydrolyze at 25°C with magnetic stirring for 10 hours to form a silanol (Si-OH) active solution; slowly add the hydrolysate to 11g 100nm SiO2 aqueous dispersion (10%), stir at 60°C for 2 hours at 800rpm, and mix well to obtain an aqueous dispersion containing two-layer core-shell structured microspheres, wherein the core layer of the two-layer core-shell structured microspheres is a nano-silica particle layer and the shell layer is a KH-570 coupling layer, for later use; 2) Dissolve 0.24g of initiator (ammonium persulfate) in 6g of deionized water, and divide it into a first-stage initiator solution (2 / 3) and a second-stage initiator solution (1 / 3), for later use; 3) Add 60g of water, 0.8g of sodium alkylbenzene sulfonate, and 0.8g of polyoxyethylene octylphenol ether-10 to a 250mL four-necked flask equipped with a condenser, stirrer, and N2 gas channel. Mix and dissolve the mixture. Adjust the pH of the system to 6-7 with 20% sodium hydroxide solution to obtain the aqueous phase. 4) Add 20g of methyl methacrylate and 6g of aqueous dispersion containing microspheres with a two-layer core-shell structure to the aqueous phase, and stir at a shear rate of 4000rpm for 30min under N2 atmosphere to obtain a preemulsion. 5) Raise the preemulsion to 70°C, stir at 450 rpm, slowly add 4g of a first-stage initiator solution, keep warm and polymerize for 1 hour to form a dispersion of microspheres with a core layer of micron-sized SiO2 particles, a shell layer consisting of a KH-570 coupling layer and a methacrylate polymer layer. 6) The dispersion containing the three-layer core-shell structured microspheres is heated to 82°C, and 20g of butyl acrylate is slowly added dropwise over 1 hour. After the addition is complete, stirring is continued for 2 hours. The second-stage initiator solution is then added dropwise, maintaining a micro-reflux state in the reactor during the addition process. The pH of the system is controlled at 6-7 (ammonia can be added dropwise to adjust). After the addition is complete, the temperature is raised to 90°C, and polymerization is carried out at this temperature with stirring for 3 hours to form an emulsion containing five-layer core-shell structured microspheres. After the reaction is completed, the temperature is cooled to 30°C, and the pH is adjusted to 8-9 with ammonia to obtain a non-uniform emulsion. The core layer of the five-layer core-shell structured microspheres is micron-sized SiO2 particles, and the shell layers are KH-570 coupling layer, methacrylate polymer layer, butyl acrylate polymer layer, and acrylamide polymer layer, in sequence. 7) Add 1.5g of film-forming aid (propylene glycol butyl ether), thickener hydroxyethyl cellulose (to adjust viscosity to 80KU), and 0.06g of polydimethylsiloxane (defoamer) to the stabilized emulsion and stir until homogeneous. Filter through a 120-mesh filter to remove impurities and obtain a methacrylate waterproof coating.

[0060] Since no acrylic monomers were added initially, there was no dynamic equilibrium of "dissolution-diffusion-polymerization" in the solution, which could not provide hydrophilic groups for the acrylate polymers. As a result, the adhesion of the acrylate polymer layers decreased, and the core-shell structure became unstable.

[0061] Comparative Example 4 The difference from Example 1 is that in step 4), 20g of butyl acrylate and 6g of an aqueous dispersion containing microspheres with a two-layer core-shell structure are added to the aqueous phase, and the mixture is stirred at a shear rate of 4000rpm for 30min under a N2 atmosphere to obtain a pre-emulsion. 5) Raise the preemulsion to 70°C, stir at 450 rpm, slowly add 4g of a first-stage initiator solution, keep warm and polymerize for 1 hour to form a dispersion of microspheres with a core layer of micron-sized SiO2 particles, a shell layer of KH-570 coupling layer and an acrylate polymer layer. 6) Heat the dispersion containing the three-layer core-shell structured microspheres to 72°C, slowly add 20g of butyl acrylate dropwise over 1 hour, and continue stirring for 2 hours after the addition is complete. Add the second-stage initiator solution dropwise, maintaining a micro-reflux state in the reactor during the dropwise addition process, and control the pH of the system at 6-7 (which can be adjusted by adding ammonia). After the dropwise addition is complete, heat to 90°C, maintain the temperature for polymerization and stirring for 3 hours to form an emulsion containing four-layer core-shell structured microspheres. After the reaction is complete, cool to 30°C and adjust the pH to 8-9 with ammonia to obtain a stable emulsion. The core layer of the four-layer core-shell structured microspheres is micron-sized SiO2 particles, and the shell layers are, in sequence, a coupling layer, a butyl acrylate polymer layer, and an acrylamide polymer layer. 7) Add 1.5g of film-forming aid (propylene glycol butyl ether), thickener hydroxyethyl cellulose (to adjust viscosity to 80KU), and 0.06g of polydimethylsiloxane (defoamer) to the stable emulsion and stir evenly. Filter through a 120-mesh filter to remove impurities and obtain a methacrylate waterproof coating containing core-shell structured microspheres.

[0062] Comparative Example 5 The difference from Example 1 is that in step 6), the dispersion containing the three-layer core-shell structured microspheres is heated to 82°C, and 20g of methyl methacrylate is slowly added dropwise over 1 hour. After the addition is complete, the temperature is raised to 90°C, and the mixture is stirred and polymerized at this temperature for 3 hours to form an emulsion containing four-layer core-shell structured microspheres. After the reaction is complete, the mixture is cooled to 30°C, and the pH is adjusted to 8-9 with ammonia to obtain a stable emulsion. The core layer of the four-layer core-shell structured microspheres consists of micron-sized SiO2 particles, and the shell layers are, in sequence, a KH-570 coupling layer, a methyl methacrylate polymer layer, and an acrylamide polymer layer. 7) Add 1.5g of film-forming aid (propylene glycol butyl ether), thickener hydroxyethyl cellulose (to adjust viscosity to 80KU), and 0.06g of polydimethylsiloxane (defoamer) to the stable emulsion and stir evenly. Filter through a 120-mesh filter to remove impurities and obtain a methacrylate waterproof coating containing core-shell structured microspheres.

[0063] Performance testing and analysis (1) Particle size analysis The acrylic waterproof coating obtained in Example 1 was dispersed in deionized water, stirred evenly using a high-speed mixer, and then ultrasonically dispersed. The particle size was measured using a laser particle size analyzer. Figure 1 It is known that the acrylic waterproof coating obtained by the present invention is micro-nano grade, with a D50 of 10-1000nm, and can seal micro-cracks and pores.

[0064] (2) Morphological state The acrylic waterproof coating obtained in Example 1 was observed to have a microstructure under an optical microscope. Figure 2 , Figure 3 It can be seen that the microstructure of the material obtained by the present invention is, in sequence, an inorganic hard core and an organic polymer soft shell, the core layer is a layer of nano-silica particles, and the shell layers from the inside to the outside are, in sequence, a silane coupling layer, a methacrylate polymer layer, an acrylate polymer layer, and an acrylic polymer layer.

[0065] (3) Evaluation of water resistance The testing standards adopted are GB / T 1733-1993 Test Method for Water Resistance of Coating Film and GB / T 24368-2009 Test Method for Contact Angle Measurement of Hydrophobic Contaminants on Glass Surface to determine water resistance and static water contact angle.

[0066] Table 1

[0067] As shown in Table 1, the product of this invention exhibits good water resistance, good compressive strength in cracked concrete, a high static contact angle with water, and good hydrophobic properties. The comparative example shows weaker compressive strength and hydrophobicity than the example, and a weaker sealing effect in cracked concrete.

[0068] In summary, this product can effectively seal cracked concrete, improve the concrete's compressive strength and hydrophobicity, and can be used to seal tiny gaps in concrete.

[0069] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the inventive concept, and these all fall within the protection scope of the present invention.

Claims

1. A method for producing a methacrylate waterproof paint containing a microsphere having a core-shell structure, characterized by, Comprising: 1) mixing silicone modifier, deionized water and acetic acid with a mass ratio of 0.5-1.5:8-12:0.03-0.06, hydrolyzing at 23-26℃ for 8-16h to obtain a hydrolysis solution with active silicon hydroxyl, adding 10-500nm nano-silica particles to the hydrolysis solution, stirring at 55-65℃ for 2-4h, and uniformly mixing to obtain a water dispersion containing microspheres with a two-layer core-shell structure, wherein the core layer of the microspheres is a nano-silica particle layer, and the shell layer is a silane coupling layer; 2) mixing and dissolving acrylic monomers, emulsifiers and deionized water with a mass ratio of 0.5-1:0.5-1:55-65, adjusting the pH of the system to 6-7 to obtain an aqueous phase; 3) adding the water dispersion containing microspheres with a two-layer core-shell structure and methacrylate monomers with a mass ratio of 4-8:10-20 to the aqueous phase, and mechanically shearing and emulsifying to obtain a pre-emulsion; 4) transferring the pre-emulsion to a reaction kettle, mechanically stirring, heating to 70-82℃, adding a first-stage initiator solution dropwise, and maintaining at 40-80min to form a dispersion containing microspheres with a three-layer core-shell structure, wherein the core layer of the microspheres is a nano-silica particle layer, and the shell layer is sequentially from the inside to the outside a silane coupling layer and a methacrylate polymer layer; 5) heating the dispersion containing microspheres with a three-layer core-shell structure to 82-85℃, adding an acrylic monomer dropwise, and adding a second-stage initiator aqueous solution while controlling the pH of the system to 6-7, after the addition is completed, heating to 90-95℃, and maintaining at 1-3h for polymerization to form a dispersion containing microspheres with a five-layer core-shell structure, cooling after the reaction is completed, adjusting the pH to 8-9, and obtaining a stable emulsion, wherein the core layer of the microspheres is a nano-silica particle layer, and the shell layer is sequentially from the inside to the outside a silane coupling layer, a methacrylate polymer layer, an acrylic ester polymer layer, and an acrylic polymer layer; 6) adding film-forming aids, thickeners and defoaming agents to the stable emulsion, stirring uniformly, filtering, and obtaining a methacrylate waterproof coating containing microspheres with a core-shell structure.

2. The production method according to claim 1, characterized by, The acrylic monomer is one or two or more of acrylic acid, methacrylic acid, 2-acrylamide-2-methylpropanesulfonic acid and acrylamide, and the silicone modifier is one or two or more of γ-methacryloyloxypropyltrimethoxysilane, vinyltriethoxysilane, γ-aminopropyltriethoxysilane and vinyltri(β-methoxyethoxy)silane.

3. The method of claim 1, wherein, The emulsifier is one or two or more of sorbitan fatty acid ester, polyoxyethylene octyl phenol ether-10, sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, polyoxyethylene sorbitan ether stearate and polysorbate-80.

4. The method of claim 1, wherein, The mechanical shearing speed is 4000-6000r / min, and the mechanical shearing time is 10-30min.

5. The preparation method according to claim 1, characterized in that, The mechanical stirring speed is 200-800r / min. The methacrylate monomer is one or two or more of methyl methacrylate, cyclohexyl methacrylate, octyl methacrylate, butyl methacrylate and styrene, and the acrylic ester monomer is butyl acrylate or octyl acrylate.

6. The method of claim 1, wherein, The initiator is one or more of ammonium persulfate, azobisisobutyronitrile, dibenzoyl peroxide, potassium persulfate, and the initiator solution is obtained by mixing 0.04:1 initiator and deionized water by mass, and the first and second initiator solutions account for 2 / 3 and 1 / 3 of the total initiator solution, respectively.

7. The preparation method according to claim 1, characterized in that, The dropping rate is 2-10 drops per second.

8. The method of claim 1, wherein, The film-forming aid is one or more of propylene glycol butyl ether, ethylene glycol butyl ether, propylene glycol, benzyl benzoate, and dibutyl phthalate; the thickening agent is one or more of hydroxyethyl cellulose, methyl cellulose, and bentonite; and the defoaming agent is one or more of polydimethylsiloxane, modified silicone defoaming agent, white oil, polyoxyethylene polyoxypropylene glycerol ether, and polyether modified silicone oil.

9. The methyl acrylate waterproof coating containing microspheres with core-shell structure prepared by the preparation method according to any one of claims 1-8, characterized in that, The core layer of the core-shell structure microsphere is a nano-silicon dioxide particle layer, and the shell layer is sequentially a silane coupling layer, a methacrylate polymer layer, an acrylate polymer layer, and an acrylic polymer layer from inside to outside, and the particle size D50 is 10-1000 nm.

10. The methyl acrylate waterproof paint containing the microspheres of core-shell structure according to claim 9, characterized by, The structural formula of the shell layer is formula (I): Formula (I); wherein R1 represents one or more of -CONHC(CH3)(CH3)CH2SO3Na, -COONa and -CONH2; R2 represents -H or -(CH2) n1 CH3, n1 is between 0 and 4; R3 represents -(CH2) n2 CH3, n2 is between 0 and 18; R4 represents -(CH2) n3 - or -COO(CH2) n3 -, n3 is between 0 and 4; the molar ratio m:n:p:q = (1-10):(10-200):(10-200):(0.1-0.6).

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