Method for preparing styrene-acrylic / siloxane graft copolymerized composite emulsion

Abstract

A method for preparing a nano-modified styrene-acrylic / siloxane graft copolymerized composite emulsion. The prepared composite emulsion has a styrene-acrylic molecule with a glass transition temperatu

Description

[0001] This patent application claims the benefit and priority of Chinese Patent Application CN116285678A entitled “Preparation method of nano-modified styrene-acrylic-siloxane graft copolymerization composite emulsion”, filed with the China National Intellectual Property Administration on February 10, 2023, the disclosure of which is incorporated by reference herein in its entirety as part of the present application. TECHNICAL FIELD

[0002] The present disclosure relates to the technical field of composite emulsion preparation, in particular to a method for preparing a styrene-acrylic / siloxane graft copolymerized composite emulsion. BACKGROUND

[0003] The mechanical and durability properties of cement-based cementitious materials in coastal environments determine the safety and long-term reliability of hydraulic concrete structures. Due to the high degree of erosion, multiple erosion factors, and high uncertainty of degradation risk in the environment of coastal areas, it is extremely necessary to take necessary and durable protection measures for concrete materials in coastal environments. The use of multifunctional, fast acting, and easy-construction polymer protective coatings for surface protection of cementitious materials could significantly improve the durability performance of concrete structures. In recent years, they have been widely used in the durability protection of concrete materials in complex environments.

[0004] Styrene-acrylate coating is a surface film-forming polymer coating prepared by addition polymerization reaction of styrene and acrylic monomers, while siloxane coating is an infiltration crystalline protective coating of a spatial network molecular structure with Si-O-Si bond as a main chain. Both of the two have been proven to effectively improve the resistance of cementitious materials and rebars to external corrosive mediums. The styrene-acrylate coatings have advantages of good resistance to chemical corrosion, low cost, and great weather resistance, but have poor environmental stability, water resistance, and unstable bonding with cementitious materials. Silicone coatings have advantages such as high hydrophobicity, high leveling, and high infiltrability, but their poor corrosion resistance makes them unable to adapt well to the durability protection requirements of concrete materials in harsh environments. Therefore, some 25 03 25 scholars and engineering technicians have come up with the idea of using nanoscale intermolecular copolymerization to prepare styrene-acrylate siloxane composite coatings, in order to achieve the complementary advantages of two types of polymer coatings, and thus achieve a long-term stable dual protective effect of surface isolation and internal crystal hydrophobicity for cement-based materials. However, many technicians have also noticed significant differences in molecular structure and synthesis method between the styrene-acrylate component and the siloxane component. Therefore, in recent years, new molecular copolymerization pathways and chain segment control methods have been continuously proposed.

[0005] In prior arts, silane monomer or silane coupling agent containing an unsaturated bond is used in the preparation of the styrene-acrylate siloxane composite coating. The cross-linked composite polymer is prepared based on seed emulsion polymerization and controlled free radical polymerization. However, the interaction between styrene-acrylate components and siloxane components is poor, the physical and chemical stability is low, and the degree of phase separation is low during the film forming and curing process of the coating, which seriously reduces the synergistic protection effect of styrene-acrylate and siloxane on the cement matrix. SUMMARY

[0006] In view of this, an object of the disclosure is to provide a method for preparing a styrene-acrylate siloxane graft copolymer composite emulsion. The styrene-acrylate siloxane graft copolymer composite emulsion prepared by the method according to the present disclosure has good protective effects.

[0007] In order to achieve the above object, the present disclosure provides the following technical solutions:

[0008] Provided is a method for preparing a styrene-acrylate siloxane graft copolymer composite emulsion, including the steps of

[0009] (1) mixing ethyl orthosilicate, water, and anhydrous ethanol, and subjecting a resulting mixture to hydrolysis reaction in an alkaline environment, to obtain an SiO2 sol;

[0010] (2) mixing the SiCh sol, a buffering agent, and dopamine hydrochloride, and subjecting a resulting mixture to hydroxylamination polymerization reaction under an alkaline condition, to obtain a hydroxylamination polymerization reaction system;

[0011] (3) mixing the hydroxylamination polymerization reaction system with an amide compound, and subjecting a resulting mixture to hydroxylamination graft reaction, to obtain modified SiCh particles; 25 03 25

[0012] (4) mixing styrene monomer, an acrylate monomer, and the modified SiCh particles, to obtain a styrene-acrylate monomer mixture I;

[0013] (5) mixing styrene monomer, an acrylate monomer, and the modified SiO2 particles, to obtain a styrene-acrylate monomer mixture II;

[0014] (6) mixing an acrylate functional monomer with a vinylsilane, to obtain a composite crosslinking agent;

[0015] (7) mixing polydimethylsiloxane, a vinylsilane monomer, a hydrophilic chain extender, and the modified SiO2 particles, to obtain a silane monomer mixture III;

[0016] (8) mixing a hydrophobic silane, a chain extender, and the modified SiO2 particles, to obtain a silane monomer mixture IV;

[0017] (9) mixing the styrene-acrylate monomer mixture I, an emulsifier, an initiator, and water, and subjecting a resulting mixture to a first addition polymerization reaction, to obtain a pre-emulsion;

[0018] (10) mixing the pre-emulsion, the styrene-acrylate monomer mixture II, an emulsifier, an initiator, and water, and subjecting a resulting mixture to a second addition polymerization reaction, to obtain a second addition polymerization reaction system;

[0019] (11) mixing the second addition polymerization reaction system with the composite crosslinking agent, and subjecting a resulting mixture to a third addition polymerization reaction, to obtain a third addition polymerization reaction system;

[0020] (12) mixing the third addition polymerization reaction system, the silane monomer mixture III, an emulsifier, and water, and subjecting a resulting mixture to a first condensation polymerization reaction, to obtain a first condensation polymerization reaction system; and

[0021] (13) mixing the first condensation polymerization reaction system, the silane monomer mixture IV, an emulsifier, and water, subjecting a resulting mixture to a second condensation polymerization to obtain the styrene-acrylate siloxane graft copolymer composite emulsion, wherein

[0022] step (4), step (5), step (6), step (7), and step (8) are conducted in any order; and

[0023] in terms of a glass transition temperature, the styrene-acrylate monomer mixture I, the styrene-acrylate monomer mixture II, the silane monomer mixture III, and the silane monomer mixture IV are ranked as follows: the styrene-acrylate monomer mixture I >the styrene-acrylate monomer mixture II >the silane monomer mixture III >the silane monomer mixture IV;

[0024] in step (3), the amide compound includes at least one selected from the group consisting of acetamide, acrylamide, butenamide, V. V-dimethylformamide, and A'. A-dimethylacetamide;

[0025] in step (4) and step (5), the acrylate monomer in step (4) and the acrylate monomer in 25 03 25 step (5) each independently comprise at least one selected from the group consisting of methyl acrylate, methyl methacrylate, ethyl acrylate, butyl acrylate, butyl methacrylate, acrylic acid, and methacrylic acid; the styrene-acrylate monomer mixture I and the styrene-acrylate monomer mixture II each independently comprise 5% to 20% by mass of the styrene monomer; and the styrene-acrylate monomer mixture I and the styrene-acrylate monomer mixture II each independently comprise 0.05% to 0.3% by mass of the modified SiO2 particles;

[0026] in step (6), the acrylate functional monomer includes at least one selected from the group consisting of hydroxyethyl acrylate and hydroxypropyl acrylate; the vinylsilane includes at least one selected from the group consisting of vinyltriethoxysilane, dimethoxymethylvinylsilane, vinyltriisopropoxysilane, and methyl vinyldiethyl oxy silane; and a mass percentage content of the acrylate functional monomer in the composite crosslinking agent ranges from 30% to 80%;

[0027] in step (7), the vinylsilane monomer is of a same type as the vinylsilane in step (6); a mass of the hydrophilic chain extender is in a range of 5% to 25% of a mass of the polydimethylsiloxane; a mass of the vinylsilane is in a range of 10% to 30% of the mass of the polydimethylsiloxane; and a mass percentage content of the modified SiO2 particles in the silane monomer mixture III ranges from 0.05% to 0.3%;

[0028] in step (8), the hydrophobic silane includes at least one selected from the group consisting of n-octyltrimethoxysilane, n-octyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, and hexadecyltrimethoxysilane; a mass of the chain extender is in a range of 5% to 25% of a mass of the hydrophobic silane; and a mass percentage content of the modified SiO2 particles in the silane monomer mixture IV is in a range of 0.05% to 0.3%;

[0029] in step (9), a mass of the emulsifier is in a range of 2% to 10% of a mass of the styrene-acrylate monomer mixture I; a mass of water is in a range of 50% to 100% of the mass of the styrene-acrylate monomer mixture I; a mass of the initiator is in a range of 0.2% to 0.7% of the mass of the styrene-acrylate monomer mixture I; the first addition polymerization reaction is performed at a pH value of 7.5-8.3; and the first addition polymerization reaction is performed at a temperature of 70-85 °C for 2 h; and

[0030] in step (10), a mass of the emulsifier is in a range of 2% to 10% of a mass of the styrene-acrylate monomer mixture II; a mass of water is in a range of 50% to 100% of the mass of the styrene-acrylate monomer mixture II; the initiator is in a same amount as that of the initiator in step (9); the second addition polymerization reaction is performed at a pH value of 7.5-8.3; and the second addition polymerization reaction is performed at a temperature of 75-85 °C for 1-2 h; and

[0031] in step (11), a mass of the composite crosslinking agent is in a range of 5-20% of the 25 03 25 mass of the styrene-acrylate monomer mixture II; and the third addition polymerization reaction is performed at a temperature of 75-85 °C for 20-40 minutes; and

[0032] in step (12), a mass of the emulsifier is in a range of 2% to 10% of a mass of the silane monomer mixture III; a mass of water is in a range of 50% to 100% of the mass of the silane monomer mixture III; and the first condensation polymerization reaction is performed at a temperature of 40-60 °C for 0.5-2 h; and

[0033] in step (13), a mass of the emulsifier is in a range of 2% to 10% of a mass of the silane monomer mixture IV; a mass of water is in a range of 50% to 100% of the mass of the silane monomer mixture IV; and the second condensation reaction is performed at a temperature of 30-50 °C for 1-3 h.

[0034] In some embodiments, in step (7), the hydrophilic chain extender includes at least one selected from the group consisting of dihydroxymethylpropionic acid, dihydroxymethylbutyric acid, polyethyleneimine, and diethyltoluene diamine.

[0035] In some embodiments, in step (8), the chain extender includes at least one selected from the group consisting of 1,4-butanediol, 1,6-hexanediol, glycerol, di ethylene glycol, triethylene glycol, neopentyl glycol, tris(hydroxymethyl)propane, and ethylenediamine.

[0036] In some embodiments, in step (9), the emulsifier includes at least one selected from the group consisting of OP-10 (octylphenol polyoxyethylene ether), sodium dodecyl sulfate, sodium dodecyl sulfonate, and sodium dodecylbenzenesulfonate; the initiator includes at least one selected from the group consisting of sodium persulfate, ammonium persulfate, potassium persulfate, azodiisobutyronitrile, and dimethyl 2,2’-azodiisobutyrate; and the first addition polymerization reaction is performed under stirring, and the stirring is performed at a rotational speed of 200-500 r / min.

[0037] In some embodiments, in step (10), the emulsifier includes at least one selected from the group consisting of OP-10, sodium dodecyl sulfate, sodium dodecyl sulfonate, and sodium dodecylbenzenesulfonate; the initiator is of a same type as the initiator in step (9); and the second addition polymerization reaction is performed under stirring, and the stirring is performed at a rotational speed of 200-500 r / min.

[0038] In some embodiments, in step (11), the third addition polymerization reaction is performed under stirring, and the stirring is performed at a rotational speed of 200-400 r / min.

[0039] In some embodiments, in step (12), the emulsifier includes at least one selected from the group consisting of OP-10, Peregal (fatty alcohol polyoxyethylene ether), Span (RTM) 60 (sorbitan monosterate), Span (RTM) 80 (sorbitan monooleate), Tween (RTM) 60 (polyoxyethylene(20) sorbitan monostearate), and Tween (RTM) 80 (polyoxyethylene(20) 25 03 25 sorbitan monooleate); and the first condensation polymerization reaction is performed under stirring, and the stirring is performed at a rotational speed of 800-1200 r / min.

[0040] In some embodiments, in step (13), the emulsifier includes at least one selected from the group consisting of OP-10, Peregal, Span (RTM) 60, Span (RTM) 80, Tween (RTM) 60, and Tween (RTM) 80; and the second condensation reaction is performed under stirring, and the stirring is performed at a rotational speed of 800-1200 r / min.

[0041] The present disclosure provides a method for preparing a styrene-acrylate siloxane graft copolymer composite emulsion.

[0042] Compared with the prior art, the styrene-acrylate siloxane graft copolymer composite emulsion prepared by the method according to the present disclosure has the following excellent technical effects:

[0043] (1) The styrene-acrylate siloxane graft copolymer composite emulsion coating prepared by the method according to the present disclosure has excellent hydrophobic and waterproof properties:

[0044] The styrene-acrylate molecules with gradient changes in glass transition temperature in the composite emulsion prepared in the present disclosure is combined with the siloxane molecular chain via strong covalent bonds, so that the water molecular isolation and hydrophobic effect of the coating formed from the composite emulsion could be fully exerted. Due to the presence of a certain degree of microphase separation trend among several components at the nanoscale, the styrene-acrylate linear molecular network and the siloxane dendritic molecular chain could coexist on the surface and in internal capillary channels of the cementitious material matrix. After curing and forming film, the styrene-acrylate siloxane graft copolymer composite emulsion could not only form a relatively dense waterproof polymer film on the surface of cement-based materials, but also form a stable structure of new hydration products inside the cementitious materials through osmotic crystallization, thus effectively inhibiting water molecules in the external environment from diffusing and transmitting inside the matrix. In addition, the internal styrene-acrylate linear structure weakens the cohesion and disorder entanglement among siloxane molecules through swelling promotion, such that the hydrophobic hydrocarbon long chains in siloxane molecules could orderly and fully stretch and freely move in the hydration layer of latex particles. Importantly, the outer dendritic siloxane molecules have larger free volume and lower surface energy in the action of directional chain extension, endow the polymer system with hydrophobicity, and allow hydrophobicity of the polymer system to be fully exerted. 25 03 25

[0045] (2) The styrene-acrylate siloxane graft copolymer composite emulsion coating prepared by the method according to the present disclosure could provide stable and good adhesion performance with a surface of cement matrix:

[0046] The linear styrene-acrylate molecular chain as the backbone structure in the styrene-acrylate siloxane graft copolymer composite emulsion could fully improve the configuration and spatial state of the outer siloxane branch chain molecules, promote the further hydrolysis of the shell siloxane molecules, and increase the number of silicon hydroxyl groups in the composite latex particle structure and improve reactivity thereof. The free moving silicon hydroxyl groups and the silicon hydroxyl groups in the cement hydration products could undergo a more complete secondary hydration reaction, which enhances the bonding effect with the cement matrix. Moreover, due to the great adsorption and infi 1 trabi 1 ity of siloxane molecules, the evaporation of its peripheral free water during the film formation and the migration of small-molecular-weight styrene-acrylate components to the capillary channels and gel pores have been promoted, thus inducing the styrene-acrylate polymer network to be more stably adsorbed onto the surface of cement matrix.

[0047] (3) The styrene-acrylate siloxane graft copolymer composite emulsion coating obtained by the method according to the present disclosure has excellent resistance to chloride salts and sulfates:

[0048] After the styrene-acrylate siloxane graft copolymer composite emulsion forms a film on a surface of a cement-based material, not only a relatively dense barrier protective film of corrosive ions is formed on the surface of the cement matrix, but also a stable hydrophobic layer is formed by penetrating into gel pores of the cement-based material. The styrene-acrylate main chain improves the hydrophobicity and surface adhesion of siloxane molecules, and meanwhile the siloxane branch chain enhances crosslinking and cohesion, weakening the diffusion and transport of water molecules and corrosive ions such as chloride ions and sulfate ions on the surface of concrete and inside the capillary channels. Due to the strong covalent bonding between the styrene-acrylate component and the siloxane component, the bonding between the composite coating and the substrate is enhanced, thereby inhibiting the adsorption and diffusion of corrosive ions along the interface.

[0049] (4) The styrene-acrylate siloxane graft copolymer composite emulsion obtained by the method according to the present disclosure allows for excellent resistance of rebar to rusting:

[0050] The surface barrier film and internal hydrophobic permeation layer formed from the styrene-acrylate siloxane graft copolymer composite emulsion could inhibit the diffusion of water-soluble CO2 in the capillary channels of concrete, maintain the alkaline environment inside 25 03 25 the concrete, protect the passive membrane on the surface of rebar(s), and effectively inhibit the diffusion and transmission of chloride ions and sulfate ions in the concrete. Meanwhile, the styrene-acrylate siloxane graft copolymer composite emulsion coating has excellent electrochemical performance, and its high resistivity could effectively inhibit the diffusion and migration of corrosive ions. In addition, the styrene-acrylate siloxane graft copolymer composite emulsion could form a crystal layer of a stable secondary hydration product with a certain depth in the cementitious material matrix, which fully protects the internal rebar(s) from the interference of external complex and adverse environmental factors.

[0051] (5) The styrene-acrylate siloxane graft copolymer composite emulsion coating obtained by the method according to the present disclosure has excellent resistance to acid and alkali corrosions:

[0052] The styrene-acrylate siloxane graft copolymer composite emulsion has excellent leveling and bonding properties, could adapt to various complex rough interfaces, exhibit firm bonding properties, and could form a stable, long-term and efficient protective layer on the surface of various cement-based materials. There is a strong cross-linking and hydrophobic association between the styrene-acrylate main chain and the siloxane branch chain, which could effectively resist the continuous erosion and damage from H+ and OH’ to the cross-linked structure of the composite coating. Importantly, the styrene-acrylate siloxane graft copolymer composite emulsion coating has relatively high non-polar characteristics and internal hydrogen bonding, and its high polymer crystallinity could significantly resist the development of polar ionization.

[0053] (6) The styrene-acrylate siloxane graft copolymer composite emulsion coating obtained by the method according to the present disclosure has excellent anti-aging performance:

[0054] The styrene-acrylate siloxane graft copolymer structure in the styrene-acrylate siloxane graft copolymer composite emulsion not only guarantees the good anti-aging performance of the gradient styrene-acrylate main chain, but also promotes the strong action of grafting, cross-linking and bonding between styrene-acrylate molecules and siloxane molecules, improving their cooperative performance and environmental adaptability. Also, the styrene-acrylate siloxane graft copolymer composite emulsion coating has high cross-linking density and crystallinity, which is conducive to the realization of the anti-aging performance of the composite coating with heat resistance and radiation resistance. In addition, the styrene-acrylate siloxane graft copolymer composite emulsion coating has a gradient dendritic structure with dynamic and thermodynamic characteristics, which not only improves the bond energy of main chemical bonds in the system, but also facilitates the recovery of the molecular network from the electronic excited state to the ground state under the action of ultraviolet radiation and thermal radiation, and reduces the damage of free radicals to the polymer system. 25 03 25 BRIEF DESCRIPTION OF THE DRAWINGS

[0055] FIG. 1A to FIG. IF show photos of apparent morphology and optical microscope morphology of the composite emulsion obtained in each experimental group.

[0056] FIG. 2A to FIG. 2F show transmission electron microscope images of the composite emulsion obtained in each experimental group.

[0057] FIG. 3 shows diagrams of water contact angle and self-cleaning performance tests on a surface of cement slurry specimens in each experimental group.

[0058] FIG. 4 shows curves of the water static capillary adsorption of concrete specimens in each experimental group.

[0059] FIG. 5 shows diagrams of the carbonation depth test results of the cement mortar specimens in each experimental group.

[0060] FIG. 6 shows the morphologies of the composite coatings in each experimental group after ultraviolet (UV) aging and thermal aging.

[0061] FIG. 7 shows the apparent morphologies of cracked mortar specimens treated in each experimental group.

[0062] FIG. 8 shows diagrams of the static water adsorption test results of cracked mortar specimens treated in each experimental group.

[0063] FIG. 9A to FIG. 9F show scanning electron microscope (SEM) images of surfaces of the composite coatings in each experimental group. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0064] The present disclosure provides a method for preparing a styrene-acrylate siloxane graft copolymer composite emulsion, including the steps of

[0065] (1) mixing ethyl orthosilicate, water, and anhydrous ethanol, and subjecting a resulting mixture to hydrolysis reaction in an alkaline environment, to obtain an SiO2 sol;

[0066] (2) mixing the SiCh sol, a buffering agent, and dopamine hydrochloride, and subjecting a resulting mixture to hydroxylamination polymerization reaction under an alkaline condition, to obtain a hydroxylamination polymerization reaction system;

[0067] (3) mixing the hydroxylamination polymerization reaction system with an amide compound, and subjecting a resulting mixture to hydroxylamination graft reaction, to obtain modified SiO2 particles;

[0068] (4) mixing a styrene monomer, an acrylate monomer, and the modified SiO2 particles, to 25 03 25 obtain a styrene-acrylate monomer mixture I;

[0069] (5) mixing a styrene monomer, an acrylate monomer, and the modified SiOz particles, to obtain a styrene-acrylate monomer mixture II;

[0070] (6) mixing an acrylate functional monomer with vinylsilane, to obtain a composite crosslinking agent;

[0071] (7) mixing poly dimethylsiloxane, a vinylsilane monomer, a hydrophilic chain extender, and the modified SiO2 particles, to obtain a silane monomer mixture III;

[0072] (8) mixing a hydrophobic silane, a chain extender, and the modified SiOz particles, to obtain a silane monomer mixture IV;

[0073] (9) mixing the styrene-acrylate monomer mixture I, an emulsifier, an initiator, and water, and subjecting a resulting mixture to a first addition polymerization reaction, to obtain a pre-emulsion;

[0074] (10) mixing the pre-emulsion, the styrene-acrylate monomer mixture II, an emulsifier, an initiator, and water, and subjecting a resulting mixture to a second addition polymerization reaction, to obtain a second addition polymerization reaction system;

[0075] (11) mixing the second addition polymerization reaction system with the composite crosslinking agent, and subjecting a resulting mixture to a third addition polymerization reaction, to obtain a third addition polymerization reaction system;

[0076] (12) mixing the third addition polymerization reaction system, the silane monomer mixture III, an emulsifier, and water, and subjecting a resulting mixture to a first condensation polymerization reaction, to obtain a first condensation polymerization reaction system; and

[0077] (13) mixing the first condensation polymerization reaction system, the silane monomer mixture IV, an emulsifier, and water, subjecting a resulting mixture to a second condensation polymerization to obtain the styrene-acrylate siloxane graft copolymer composite emulsion, wherein

[0078] step (4), step (5), step (6), step (7), and step (8) are conducted in any order; and

[0079] in terms of a glass transition temperature, the styrene-acrylate monomer mixture I, the styrene-acrylate monomer mixture II, the silane monomer mixture III, and the silane monomer mixture IV are ranked as follows: the styrene-acrylate monomer mixture I >the styrene-acrylate monomer mixture II >the silane monomer mixture III >the silane monomer mixture IV;

[0080] in step (3), the amide compound includes at least one selected from the group consisting of acetamide, acrylamide, butenamide, W-dimethylformamide, and V,7V-dimethylacetamide;

[0081] in step (4) and step (5), the acrylate monomer in step (4) and the acrylate monomer in step (5) each independently comprise at least one selected from the group consisting of methyl 25 03 25 acrylate, methyl methacrylate, ethyl acrylate, butyl acrylate, butyl methacrylate, acrylic acid, and methacrylic acid; the styrene-acrylate monomer mixture I and the styrene-acrylate monomer mixture II each independently comprise 5% to 20% by mass of the styrene monomer; and the styrene-acrylate monomer mixture I and the styrene-acrylate monomer mixture II each independently comprise 0.05% to 0.3% by mass of the modified SiO2 particles;

[0082] in step (6), the acrylate functional monomer includes at least one selected from the group consisting of hydroxyethyl acrylate and hydroxypropyl acrylate; the vinylsilane includes at least one selected from the group consisting of vinyltriethoxysilane, dimethoxymethylvinylsilane, vinyltriisopropoxysilane, and methylvinyldiethyloxysilane; and a mass percentage content of the acrylate functional monomer in the composite crosslinking agent ranges from 30% to 80%;

[0083] in step (7), the vinylsilane monomer is of a same type as the vinylsilane in step (6); a mass of the hydrophilic chain extender is in a range of 5% to 25% of a mass of the polydimethylsiloxane; a mass of the vinylsilane is in a range of 10% to 30% of the mass of the polydimethylsiloxane; and a mass percentage content of the modified SiCh particles in the silane monomer mixture III ranges from 0.05% to 0.3%;

[0084] in step (8), the hydrophobic silane includes at least one selected from the group consisting of n-octyltrimethoxysilane, n-octyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, and hexadecyltrimethoxysilane; a mass of the chain extender is in a range of 5% to 25% of a mass of the hydrophobic silane; and a mass percentage content of the modified SiO2 particles in the silane monomer mixture IV is in a range of 0.05% to 0.3%;

[0085] in step (9), a mass of the emulsifier is in a range of 2% to 10% of a mass of the styrene-acrylate monomer mixture I; a mass of water is in a range of 50% to 100% of the mass of the styrene-acrylate monomer mixture I; a mass of the initiator is in a range of 0.2% to 0.7% of the mass of the styrene-acrylate monomer mixture I; the first addition polymerization reaction is performed at a pH value of 7.5-8.3; and the first addition polymerization reaction is performed at a temperature of 70-85 °C for 2 h; and

[0086] in step (10), a mass of the emulsifier is in a range of 2% to 10% of a mass of the styrene-acrylate monomer mixture II; a mass of water is in a range of 50% to 100% of the mass of the styrene-acrylate monomer mixture II; the initiator is in a same amount as that of the initiator in step (9); the second addition polymerization reaction is performed at a pH value of 7.5-8.3; and the second addition polymerization reaction is performed at a temperature of 75-85 °C for 1-2 h; and

[0087] in step (11), a mass of the composite crosslinking agent is in a range of 5-20% of the mass of the styrene-acrylate monomer mixture II; and the third addition polymerization reaction 25 03 25 is performed at a temperature of 75-85 °C for 20-40 minutes; and

[0088] in step (12), a mass of the emulsifier is in a range of 2% to 10% of a mass of the silane monomer mixture III; a mass of water is in a range of 50% to 100% of the mass of the silane monomer mixture III; and the first condensation polymerization reaction is performed at a temperature of 40-60 °C for 0.5-2 h; and

[0089] in step (13), a mass of the emulsifier is in a range of 2% to 10% of a mass of the silane monomer mixture IV; a mass of water is in a range of 50% to 100% of the mass of the silane monomer mixture IV; and the second condensation reaction is performed at a temperature of 30-50 °C for 1-3 h.

[0090] In the present disclosure, unless otherwise specified, raw materials used for the preparation are commercially available products.

[0091] In the present disclosure, ethyl orthosilicate, water, and anhydrous ethanol are mixed, and a resulting mixture is subjected to hydrolysis reaction in an alkaline environment to obtain an SiO? sol. In some embodiments of the present disclosure, the water includes deionized water. In some embodiments of the present disclosure, a mass of the ethyl orthosilicate is in a range of 1% to 6% of a mass of anhydrous ethanol, preferably 2% to 5%, and more preferably 3% to 4%. In some embodiments of the present disclosure, the mass of the water is in a range of 50% to 300% of the mass of the ethyl orthosilicate. In some embodiments of present disclosure, the alkaline environment has a pH value of 7.5 to 8.5. In some embodiments, the alkaline environment is provided by adjusting with an alkaline reagent. In some embodiments, the alkaline reagent includes one or more of ammonia, sodium bicarbonate, sodium carbonate, sodium hydrogen phosphate, Barbital (RTM, 5,5-diethyl-l,3-diazinane-2,4,6-trione) buffer, and acetate buffer. In some embodiments of the present disclosure, the hydrolysis reaction is performed at a temperature of 20 °C to 40 °C, and preferably 30 °C. In some embodiments, the hydrolysis reaction is performed for 0.5-2 h. In some embodiments, the hydrolysis reaction is performed under stirring. In some embodiments, the hydrolysis reaction is performed under stirring, and the stirring is performed at a rotational speed of 100-300 r / min.

[0092] In the present disclosure, after obtaining the SiO? sol, the SiO? sol, a buffering agent, and dopamine hydrochloride are mixed, and a resulting mixture is subjected to hydroxylamination polymerization reaction under an alkaline condition to obtain a hydroxylamination polymerization reaction system. In some embodiments of present disclosure, the buffering agent includes one or more of Barbital (RTM) buffer, tris(hydroxymethyl)aminomethane, and acetate buffer. In some embodiments of the present disclosure, a mass of the buffering agent is in a range of 0.5% to 3% of a mass of the SiO? sol. In some embodiments of the present disclosure, a mass 25 03 25 of dopamine hydrochloride is in a range of 0.1% to 1% of the mass of SiCh sol. In some embodiments of the present disclosure, the alkaline condition refers to having a pH value of 7.5-8.3. In some embodiments of the present disclosure, mixing the SiCh sol, the buffering agent, and dopamine hydrochloride, and subjecting a resulting mixture to hydroxylamination polymerization reaction under an alkaline condition includes ultrasonically dispersing the SiO2 sol, adding the buffering agent and dopamine hydrochloride sequentially thereto, and subjecting a resulting mixture to hydroxylamination polymerization reaction. In some embodiments of the present disclosure, ultrasonic dispersion is performed for 20-60 minutes. In some embodiments of the present disclosure, the hydroxylamination polymerization reaction is performed at room temperature. In some embodiments, the hydroxylamination polymerization reaction is performed for 0.5-2 h. In some embodiments, the hydroxylamination polymerization reaction is performed under an ultrasound condition. After the hydroxylamination polymerization reaction, the resulting system is directly used for the next step without any reactions.

[0093] In the present disclosure, after obtaining the hydroxylamination polymerization reaction system, the hydroxylamination polymerization reaction system is mixed with an amide compound, and a resulting mixture is subjected to hydroxylamination graft reaction to obtain modified SiO2 particles. In the present disclosure, the amide compound includes one or more of acetamide, acrylamide, butenamide, MA'-di methyl form am ide, and A'A-dimethylacetamide. In some embodiments of present disclosure, a mass of the amide compound is in a range of 1% to 10% of the mass of the ethyl orthosilicate. In some embodiments of present disclosure, the hydroxylamination graft reaction is performed at room temperature. In some embodiments, the hydroxylamination graft reaction is performed for 30 minutes to 60 minutes. In some embodiments, the hydroxylamination graft reaction is performed under an ultrasound condition. In some embodiments of the present disclosure, after the hydroxylamination graft reaction, the method further includes performing centrifugation, washing, drying, and grinding in sequence. In some embodiments of the present disclosure, the centrifugation is performed at a centrifugal speed of 8,000-20,000 r / min, and preferably 10,000 r / min. In some embodiments, the centrifugation is performed for 10-60 minutes. In some embodiments of the present disclosure, a reagent for the washing is an aqueous ethanol solution. In some embodiments, the aqueous ethanol solution has a mass concentration of 60-100%. In some embodiments, the washing is performed 3-6 times. In some embodiments of the present disclosure, the drying is performed at a temperature of 40-70 °C, and preferably 50-60 °C. In some embodiments, the drying is performed for 6 hours. In some embodiments of the present disclosure, the modified SiO2 particles obtained by grinding each have a fineness of 200 mesh (0.074 mm) to 800 mesh (0.015 25 03 25 mm).

[0094] The modified SiCh particles prepared in the present disclosure have greater surface activity and dispersibility.

[0095] In the present disclosure, styrene monomer and an acrylate monomer are mixed with the modified SiO2 particles to obtain a styrene-acrylate monomer mixture I. In the present disclosure, the acrylate monomer includes one or more of methyl acrylate, methyl methacrylate, ethyl acrylate, butyl acrylate, butyl methacrylate, acrylic acid, and methacrylic acid. In the present disclosure, a mass percentage content of styrene in the styrene-acrylate monomer mixture I is in a range of 5% to 20%. In the present disclosure, a mass percentage content of the modified Si O2 particles in the styrene-acrylate monomer mixture I is in a range of 0.05% to 0.3%, and preferably 0.1% to 0.2%. In some embodiments of the present disclosure, mixing styrene monomer, the acrylate monomer with the modified SiCh particles is performed under stirring. In some embodiments of the present disclosure, the styrene-acrylate monomer mixture I has a glass transition temperature of 270 K to 300 K.

[0096] In the present disclosure, the styrene monomer and the acrylate monomer are mixed with the modified SiO2 particles to obtain a styrene-acrylate monomer mixture II. In the present disclosure, the acrylate monomer includes one or more of methyl acrylate, methyl methacrylate, ethyl acrylate, butyl acrylate, butyl methacrylate, acrylic acid, and methacrylic acid. In the present disclosure, a mass percentage content of styrene in the styrene-acrylate monomer mixture II is in a range of 5% to 20%. In the present disclosure, a mass percentage content of the modified SiO2 particles in the styrene-acrylate monomer mixture II is in a range of 0.05% to 0.3%, and preferably 0.1% to 0.2%. In some embodiments of the present disclosure, mixing the styrene monomer, the acrylate monomer with the modified SiO2 particles is performed under stirring. In some embodiments of the present disclosure, the styrene-acrylate monomer mixture II has a glass transition temperature of 250 K to 270 K.

[0097] In terms of a glass transition temperature, the styrene-acrylate monomer mixture I has a glass transition temperature higher than that of the styrene-acrylate monomer mixture II.

[0098] In the present disclosure, an acrylate functional monomer is mixed with vinylsilane to obtain a composite crosslinking agent. In the present disclosure, the acrylate functional monomer includes hydroxyethyl acrylate and / or hydroxypropyl acrylate. In the present disclosure, the vinylsilane includes one or more of vinyltriethoxysilane, dimethoxymethylvinylsilane, vinyltriisopropyloxysilane, and methylvinyldiethyloxysilane. In the present disclosure, a mass percentage content of the acrylate functional monomer in the composite crosslinking agent is in a range of 30% to 80%, preferably 40% to 70%, and more preferably 50% to 60%. In some 25 03 25 embodiments of the present disclosure, mixing the acrylate functional monomer with vinylsilane is performed under stirring.

[0099] In the present disclosure, poly dimethyl siloxane, vinylsilane monomer, and a hydrophilic chain extender are mixed with the modified SiO2 particles to obtain a silane monomer mixture III. In the present disclosure, vinylsilane is of a same type as vinylsilane in the composite crosslinking agent. In some embodiments of the present disclosure, the hydrophilic chain extender includes one or more of dihydroxymethylpropionic acid, dihydroxymethylbutyric acid, polyethyleneimine, and di ethyltoluene diamine. In the present disclosure, a mass of the hydrophilic chain extender is in a range of 5% to 25%, and preferably 10% to 20% of a mass of the polydimethylsiloxane. In the present disclosure, a mass of the vinylsilane is in a range of 10% to 30%, and preferably 20% of the mass of the polydimethylsiloxane. In the present disclosure, a mass percentage content of the modified SiCh particles in the silane monomer mixture III is in a range of 0.05% to 0.3%, and preferably 0.1% to 0.2%. In some embodiments of the present disclosure, mixing polydimethylsiloxane, the vinylsilane monomer, the hydrophilic chain extender, and the modified SiO? particles is performed under stirring. In some embodiments of the present disclosure, the silane monomer mixture III has a glass transition temperature of 200 K to 250 K.

[0100] In terms of a glass transition temperature, the styrene-acrylate monomer mixture II has a glass transition temperature higher than that of the silane monomer mixture III.

[0101] In the present disclosure, the hydrophobic silane and the chain extender are mixed with the modified SiOz particles to obtain a silane monomer mixture IV. In the present disclosure, the hydrophobic silane includes one or more of n-octyltrimethoxysilane, n-octyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, and hexadecyltrimethoxysilane. In some embodiments of the present disclosure, the chain extender includes one or more of 1,4-butanediol, 1,6-hexanediol, glycerol, di ethylene glycol, tri ethylene glycol, neopentyl glycol, tris(hydroxymethyl)propane, and ethylenediamine, and preferably 1,4-butanediol. In the present disclosure, a mass of the chain extender is in a range of 5% to 25% of a mass of the hydrophobic silane. In the present disclosure, a mass percentage content of the modified SiOz particles in the silane monomer mixture IV is in a range of 0.05% to 0.3%, and preferably 0.1% to 0.2%. In some embodiments of the present disclosure, mixing the hydrophobic silane, the chain extender, and the modified SiOz particles are performed under stirring. In some embodiments of the present disclosure, the silane monomer mixture IV has a glass transition temperature of not higher than 200 K.

[0102] In terms of a glass transition temperature, the silane monomer mixture III has a glass 25 03 25 transition temperature higher than that of the silane monomer mixture IV.

[0103] In the present disclosure, the styrene-acrylate monomer mixture I, the emulsifier, the initiator and water are mixed, and a resulting mixture is subjected to a first addition polymerization reaction to obtain a pre-emulsion. In some embodiments of the present disclosure, the emulsifier includes one or more of OP-10, sodium dodecyl sulfate, sodium dodecyl sulfonate, and sodium dodecylbenzenesulfonate, and preferably OP-10 and sodium dodecylbenzenesulfonate. In the present disclosure, a mass of the emulsifier is in a range of 2% to 10%, preferably 4% to 8%, and more preferably 5% to 6% of the mass of the styrene-acrylate monomer mixture I. In some embodiments of the present disclosure, the initiator includes one or more of sodium persulfate, ammonium persulfate, potassium persulfate, azodiisobutyronitrile, and dimethyl 2,2’-azodiisobutyrate, and preferably ammonium persulfate. In the present disclosure, a mass of the initiator is in a range of 0.2% to 0.7%, and preferably 0.4% to 0.6% of the mass of the styrene-acrylate monomer mixture I. In some embodiments of the present disclosure, the water includes deionized water. In the present disclosure, a mass of the water is in a range of 50% to 100% of the mass of the styrene-acrylate monomer mixture I. In the present disclosure, the first addition polymerization reaction is performed at a pH value of 7.5 to 8.3. In the present disclosure, the first addition polymerization reaction is performed at a temperature of 70 °C to 85 °C for 2 hours. In some embodiments of the present disclosure, the first addition polymerization reaction is performed under stirring. In some embodiments, the first addition polymerization reaction is performed under stirring, and the stirring is performed at a rotational speed of 200-500 r / min, and preferably 300-400 r / min.

[0104] In some embodiments of the present disclosure, mixing the styrene-acrylate monomer mixture I, the emulsifier, the initiator, and water, and subjecting a resulting mixture to the first addition polymerization reaction includes: mixing the styrene-acrylate monomer mixture I and the emulsifier, dropping a resulting mixture into water, adjusting the pH value, adding the initiator thereto under stirring, and subjecting a resulting mixture to the first addition polymerization reaction. In the present disclosure, there is no specific requirement for the dropping rate when dropping the mixture obtained by mixing the styrene-acrylate monomer mixture I and the emulsifier. In some embodiments of the present disclosure, the timing of the addition polymerization reaction is started after the addition of the initiator is accomplished.

[0105] In the present disclosure, after the pre-emulsion is obtained, the pre-emulsion, the styrene-acrylate monomer mixture II, the emulsifier, and the initiator are mixed with water, and a resulting mixture is subjected to the second addition polymerization to obtain the second addition polymerization reaction system. In some embodiments of the present disclosure, the emulsifier 25 03 25 includes one or more of OP-10, sodium dodecyl sulfate, sodium dodecyl sulfonate, and sodium dodecylbenzenesulfonate. In the present disclosure, a mass of the emulsifier is in a range of 2% to 10%, preferably 4% to 8%, and more preferably 5% to 6% of a mass of the styrene-acrylate monomer mixture II. In some embodiments of the present disclosure, the initiator is of a same type as the initiator in the first addition polymerization reaction. In some embodiments of the present disclosure, the water includes deionized water. In the present disclosure, a mass of the water is in a range of 50% to 100% of the mass of the styrene-acrylate monomer mixture II. In the present disclosure, the second addition polymerization reaction is performed at a pH value of 7.5-8.3. The second addition polymerization reaction is performed at a temperature of 75-85 °C for 1-2 h. In some embodiments of the present disclosure, the second addition polymerization reaction is performed under stirring. In some embodiments, the second addition polymerization reaction is performed under stirring, and the stirring is performed at a rotational speed of 200-500 r / min and preferably 300-400 r / min. In some embodiments of the present disclosure, mixing the pre-emulsion, the styrene-acrylate monomer mixture II, the emulsifier, the initiator and water, and subjecting a resulting mixture to the second addition polymerization reaction includes: adding water, the styrene-acrylate monomer mixture II and the emulsifier to the pre-emulsion in sequence, adjusting a pH value of a resulting mixture, adding the initiator under stirring, and subjecting a resulting mixture to the second addition polymerization reaction. In some embodiments of the present disclosure, the timing of the second polymerization reaction is started after the addition of the initiator is accomplished.

[0106] In the present disclosure, after obtaining the second addition polymerization reaction system, the second addition polymerization reaction system is mixed with the composite crosslinking agent, and a resulting mixture is subjected to a third addition polymerization reaction to obtain the third addition polymerization reaction system. In the present disclosure, a mass of the composite crosslinking agent is in a range of 5% to 20%, and preferably 10% to 12% of a mass of the styrene-acrylate monomer mixture II. In the present disclosure, the third addition polymerization reaction is performed at a temperature of 75-85 °C for 20-40 minutes. In some embodiments of the present disclosure, the third addition polymerization reaction is performed under stirring. In some embodiments of the present disclosure, the third addition polymerization reaction is performed under stirring, and the stirring is performed at a rotational speed of 200-400 r / min.

[0107] In the present disclosure, after obtaining the third addition polymerization reaction system, the third addition polymerization reaction system, the silane monomer mixture III, the emulsifier, and water are mixed, and a resulting mixture is subjected to a first condensation 25 03 25 polymerization reaction, to obtain the first condensation reaction system. In some embodiments of the present disclosure, the emulsifier includes one or more of OP-10, Peregal, Span (RTM) 60, Span (RTM) 80, Tween (RTM) 60, and Tween (RTM) 80. In the present disclosure, a mass of the emulsifier is in a range of 2% to 10% of a mass of the silane monomer mixture III. In some embodiments of the present disclosure, the water includes deionized water. In the present disclosure, a mass of the water is in a range of 50% to 100% of the mass of the silane monomer mixture III. In the present disclosure, the first condensation polymerization reaction is performed at a temperature of 40 °C to 60 °C for 0.5-2 h. In some embodiments of the present disclosure, the first condensation reaction is performed under stirring. In some embodiments, the first condensation reaction is performed under stirring, and the stirring is performed at a rotational speed of 500-1200 r / min.

[0108] In the present disclosure, after the first condensation polymerization reaction system is obtained, the first condensation polymerization reaction system, the silane monomer mixture IV, the emulsifier, and water are mixed, and a resulting mixture is subjected to a second condensation polymerization to obtain the styrene-acrylate siloxane graft copolymer composite emulsion. In some embodiments of the present disclosure, the emulsifier includes one or more of OP-10, Peregal, Span (RTM) 60, Span (RTM) 80, Tween (RTM) 60, and Tween (RTM) 80. In the present disclosure, a mass of the emulsifier is in a range of 2% to 10% of a mass of the silane monomer mixture IV. In some embodiments of the present disclosure, the water includes deionized water. In the present disclosure, a mass of the water is in a range of 50% to 100% of a mass of the silane monomer mixture IV. In the present disclosure, the second condensation polymerization reaction is performed at a temperature of 30 °C to 50 °C, and preferably 40 °C, for 1-3 hours. In some embodiments of the present disclosure, the second condensation polymerization reaction is performed under stirring. In some embodiments, the second condensation polymerization reaction is performed under stirring, and the stirring is performed at a rotational speed of 800-1200 r / min, and preferably 1000 r / min.

[0109] The method for preparing the styrene-acrylate siloxane graft copolymer composite emulsion according to the present disclosure is described below in conjunction with the examples, but the examples could not be construed as limiting the scope of the present disclosure.

[0110] Example 1

[0111] (1)3 mL of ammonia water was added dropwise to a mixture of 3 g of ethyl orthosilicate, 3 g of deionized water, and 50 g of anhydrous ethanol, such that a pH value of a resulting system was 7-8.5. A resulting mixture was stirred at a rotational speed of 300 r / min at 30 °C for 30 25 03 25 minutes, to obtain 55 g of an SiCh sol.

[0112] (2) 55 g of the SiCh sol was sonicated and pre-dispersed for 1 hour, and 500 mg of tri(hydroxymethyl)aminomethane and 200 mg of dopamine hydrochloride were added thereto sequentially. A resulting mixture was sonicated at 30 °C for 2 hours. 100 mg of acrylamide was then added, and a resulting mixture was sonicated at 30 °C for 1 hour. Afterwards, a resulting mixture was centrifuged at a rotational speed of 10,000 r / min for 60 minutes, followed by separation. A resulting precipitate was collected, washed three times with an aqueous ethanol solution with a mass concentration of 50%, dried at 50 °C for 6 hours, and ground to obtain modified SiO2 particles with a fineness of 200 mesh (0.074 mm) to 800 mesh (0.015 mm).

[0113] (3) 20 g of methyl methacrylate, 15 g of butyl acrylate, 5 g of acrylic acid, and 10 g of styrene were mixed with 25 mg of the modified SiO2 particles, and a resulting mixture was stirred to be uniform, to obtain a styrene-acrylate monomer mixture I, which had a glass transition temperature of 290 ±2K.

[0114] (4) 10 g of methyl methacrylate, 25 g of butyl acrylate, 5 g of acrylic acid, and 10 g of styrene were mixed with 25 mg of the modified SiO2 particles, and a resulting mixture was stirred to be uniform, to obtain a styrene-acrylate monomer mixture II, which had a glass transition temperature of 260 ± 2 K.

[0115] (5) 10 g of poly dimethyl siloxane, 2 g of vinyltriethoxysilane, and 2 g of 2,2-bis(hydroxymethyl)butyric acid were mixed with 10 mg of the modified SiO2 particles, and a resulting mixture was stirred to be uniform, to obtain a silane monomer mixture III, which had a glass transition temperature of 240 ± 2 K.

[0116] (6) 40 g of n-octyltriethoxysilane and 10 g of 1,4-butanediol were mixed with 25 mg of the modified SiOi particles, and a resulting mixture was stirred to be uniform, to obtain a silane monomer mixture IV, which had a glass transition temperature of <200 K.

[0117] (7) 3 g of hydroxy ethyl acrylate was mixed with 3 g of vinyl triethoxysilane, and a resulting mixture was stirred to be uniform, to obtain a composite crosslinking agent.

[0118] (8) 50 g of the styrene-acrylate monomer mixture I, 1.2 g of OP-10 and 1.8 g of sodium dodecyl sulfate were mixed, and a resulting mixture was dropped into 50 g of deionized water. A pH value of the resulting system was adjusted to 7.5 with sodium bicarbonate. A resulting mixture was stirred at a rotational speed of 300 r / min at 78 °C, and meanwhile 200 mg of ammonium persulfate was added slowly thereto. After the addition of ammonium persulfate, a resulting mixture was further stirred for 2 h, to obtain a pre-emulsion.

[0119] (9) 50 g of deionized water, 50 g of the styrene-acrylate monomer mixture II, 1.2 g of OP-10 and 1.8 g of sodium dodecyl sulfate were added slowly into the pre-emulsion, and a pH 25 03 25 value of a resulting system was adjusted to 7-8.5. A resulting mixture was stirred at a rotational speed of 300 r / min at 83 °C. 200 mg of ammonium persulfate was added thereto. After the addition of ammonium persulfate, a resulting mixture was further stirred for 2 h.

[0120] (10) 6 g of the composite crosslinking agent was added slowly thereto, and a resulting mixture was further stirred at a rotational speed of 300 r / min for 20 minutes.

[0121] (11) The temperature of the mixture was dropped to 60 °C. With the stirring at a rotational speed of 500 r / min, 16 g of deionized water, 20 g of the silane monomer mixture III, 300 mg of OP-10 emulsifier, and 300 mg of Peregal 0-25 were added slowly thereto. After the addition of the materials, a resulting mixture was further stirred for 1 hour.

[0122] (12) The temperature of the mixture was dropped to 40 °C. With the stirring at a rotational speed of 1000 r / min, 40 g of deionized water, 50 g of the silane monomer mixture IV, 750 mg of Tween (RTM) 80, and 750 mg of Span (RTM) 80 were slowly added thereto. After the addition, a resulting mixture was further stirred for 3 hours, to obtain a styrene-acrylate siloxane graft copolymer composite emulsion.

[0123] Example 2

[0124] (1)3 mL of ammonia water was added dropwise to a mixture of 3 g of ethyl orthosilicate, 3 g of deionized water, and 50 g of anhydrous ethanol, such that a pH value of a resulting system was 7-8.5. A resulting mixture was stirred at a rotational speed of 300 r / min at 30 °C for 30 minutes, to obtain 55 g of an SiO2 sol.

[0125] (2) 55 g of the SiO2 sol was sonicated and pre-dispersed for 1 hour, and 400 mg of Barbital (RTM) buffer and 200 mg of dopamine hydrochloride were added thereto sequentially. A resulting mixture was sonicated at 30 °C for 2 hours. 120 mg of acrylamide was then added, and a resulting mixture was sonicated at 30 °C for 1 hour. Afterwards, a resulting mixture was centrifuged at a rotational speed of 10,000 r / min for 60 minutes, followed by separation. A resulting precipitate was collected, washed three times with an aqueous ethanol solution with a mass concentration of 50%, dried at 50 °C for 6 hours, and ground to obtain modified SiO2 particles with a fineness of 200 mesh (0.074 mm) to 800 mesh (0.015 mm).

[0126] (3) 20 g of methyl acrylate, 15 g of butyl acrylate, 5 g of acrylic acid, and 10 g of styrene were mixed with 75 mg of the modified SiO2 particles, and a resulting mixture was stirred to be uniform, to obtain a styrene-acrylate monomer mixture I, which had a glass transition temperature of 290 ± 2 K.

[0127] (4) 10 g of methyl acrylate, 25 g of butyl acrylate, 5 g of acrylic acid, and 10 g of styrene were mixed with 75 mg of the modified SiO2 particles, and a resulting mixture was stirred to be 25 03 25 uniform, to obtain a styrene-acrylate monomer mixture II, which had a glass transition temperature of 260 ± 2 K.

[0128] (5) 10 g of polydimethylsiloxane, 2 g of vinyltriethoxysilane, and 2 g of 2,2-bis(hydroxymethyl)butyric acid were mixed with 30 mg of the modified SiO2 particles, and a resulting mixture was stirred to be uniform, to obtain a silane monomer mixture III, which had a glass transition temperature of 240 ± 2 K.

[0129] (6) 40 g of n-octyltriethoxysilane and 10 g of 1,4-butanediol were mixed with 75 mg of the modified SiO2 particles, and a resulting mixture was stirred to be uniform, to obtain a silane monomer mixture IV, which had a glass transition temperature of <200 K.

[0130] (7) 3 g of hydroxyethyl acrylate was mixed with 3 g of vinyl triethoxysilane, and a resulting mixture was stirred to be uniform, to obtain a composite crosslinking agent.

[0131] (8) 50 g of the styrene-acrylate monomer mixture I, 1.2 g of OP-10 and 1.8 g of sodium dodecyl sulfonate were mixed, and a resulting mixture was dropped into 50 g of deionized water. A pH value of the resulting system was adjusted to 7.5 with sodium bicarbonate. A resulting mixture was stirred at a rotational speed of 300 r / min at 78 °C, and meanwhile 200 mg of ammonium persulfate was added slowly thereto. After the addition of ammonium persulfate, a resulting mixture was further stirred for 2 h, to obtain a pre-emulsion.

[0132] (9) 50 g of deionized water, 50 g of the styrene-acrylate monomer mixture II, 1.2 g of OP-10 and 1.8 g of sodium dodecyl sulfate were added slowly into the pre-emulsion, and a pH value of a resulting system was adjusted to 7-8.5. A resulting mixture was stirred at a rotational speed of 300 r / min at 83 °C. 200 mg of ammonium persulfate was added thereto. After the addition of ammonium persulfate, a resulting mixture was further stirred for 2 h.

[0133] (10) 6 g of the composite crosslinking agent was added slowly thereto, and a resulting mixture was further stirred at a rotational speed of 300 r / min for 20 minutes.

[0134] (11) The temperature of the mixture was dropped to 60 °C. With the stirring at a rotational speed of 500 r / min, 16 g of deionized water, 20 g of the silane monomer mixture III, 300 mg of OP-10 emulsifier, and 300 mg of Peregal 0-25 were added slowly thereto. After the addition of the materials, a resulting mixture was further stirred for 1 hour.

[0135] (12) The temperature of the mixture was dropped to 40 °C. With the stirring at a rotational speed of 1000 r / min, 40 g of deionized water, 50 g of the silane monomer mixture IV, 750 mg of Tween (RTM) 60, and 750 mg of Span (RTM) 80 were slowly added thereto. After the addition, a resulting mixture was further stirred for 3 hours, to obtain a styrene-acrylate siloxane graft copolymer composite emulsion. 25 03 25

[0136] Examples

[0137] (1)3 mL of ammonia water was added dropwise to a mixture of 3 g of ethyl orthosilicate, 3 g of deionized water, and 50 g of anhydrous ethanol, such that a pH value of a resulting system was 7-8.5. A resulting mixture was stirred at a rotational speed of 300 r / min at 30 °C for 30 minutes, to obtain 55 g of an SiO2 sol.

[0138] (2) 55 g of the SiO? sol was sonicated and pre-dispersed for 1 hour, and 500 mg of Barbital (RTM) buffer and 200 mg of dopamine hydrochloride were added thereto sequentially. A resulting mixture was sonicated at 30 °C for 2 hours. 100 mg of acrylamide was then added, and a resulting mixture was sonicated at 30 °C for 1 hour. Afterwards, a resulting mixture was centrifuged at a rotational speed of 10,000 r / min for 60 minutes, followed by separation. A resulting precipitate was collected, washed three times with an aqueous ethanol solution with a mass concentration of 50%, dried at 50 °C for 6 hours, and ground to obtain modified SiO2 particles with a fineness of 200 mesh (0.074 mm) to 800 mesh (0.015 mm).

[0139] (3) 20 g of methyl acrylate, 15 g of butyl acrylate, 5 g of acrylic acid, and 10 g of styrene were mixed with 50 mg of the modified SiO? particles, and a resulting mixture was stirred to be uniform, to obtain a styrene-acrylate monomer mixture I, which had a glass transition temperature of 290 ± 2 K.

[0140] (4) 10 g of methyl acrylate, 25 g of butyl acrylate, 5 g of acrylic acid, and 10 g of styrene were mixed with 50 mg of the modified SiCh particles, and a resulting mixture was stirred to be uniform, to obtain a styrene-acrylate monomer mixture II, which had a glass transition temperature of 260 ± 2 K.

[0141] (5) 10 g of polydimethylsiloxane, 2 g of vinyltriethoxysilane, and 2 g of 2,2-bis(hydroxymethyl)butyric acid were mixed with 20 mg of the modified SiO2 particles, and a resulting mixture was stirred to be uniform, to obtain a silane monomer mixture III, which had a glass transition temperature of 240 ± 2 K.

[0142] (6) 40 g of n-octyltriethoxysilane and 10 g of 1,4-butanediol were mixed with 50 mg of the modified SiO2 particles, and a resulting mixture was stirred to be uniform, to obtain a silane monomer mixture IV, which had a glass transition temperature of <200 K.

[0143] (7) 3 g of hydroxyethyl acrylate was mixed with 3 g of vinyl triethoxysilane, and a resulting mixture was stirred to be uniform, to obtain a composite crosslinking agent.

[0144] (8) 50 g of the styrene-acrylate monomer mixture I, 1.2 g of OP-10 and 1.8 g of sodium dodecyl benzenesulfonate were mixed, and a resulting mixture was dropped into 50 g of deionized water. A pH value of the resulting system was adjusted to 7.5 with sodium bicarbonate. A resulting mixture was stirred at a rotational speed of 300 r / min at 78 °C, and meanwhile 200 25 03 25 mg of ammonium persulfate was added slowly thereto. After the addition of ammonium persulfate, a resulting mixture was further stirred for 2 h, to obtain a pre-emulsion.

[0145] (9) 50 g of deionized water, 50 g of the styrene-acrylate monomer mixture II, 1.2 g of OP-10 and 1.8 g of sodium dodecyl benzenesulfonate were added slowly into the pre-emulsion, and a pH value of a resulting system was adjusted to 7-8.5. A resulting mixture was stirred at a rotational speed of 300 r / min at 83 °C. 200 mg of ammonium persulfate was added thereto. After the addition of ammonium persulfate, a resulting mixture was further stirred for 2 h.

[0146] (10) 6 g of the composite crosslinking agent was added slowly thereto, and a resulting mixture was further stirred at a rotational speed of 300 r / min for 20 minutes.

[0147] (11) The temperature of the mixture was dropped to 60 °C. With the stirring at a rotational speed of 500 r / min, 16 g of deionized water, 20 g of the silane monomer mixture III, 300 mg of OP-10 emulsifier, and 300 mg of Peregal 0-25 were added slowly thereto. After the addition, a resulting mixture was further stirred for 1 hour.

[0148] (12) The temperature of the mixture was dropped to 40 °C. With the stirring at a rotational speed of 1000 r / min, 40 g of deionized water, 50 g of the silane monomer mixture IV, 750 mg of Tween (RTM) 60, and 750 mg of Span (RTM) 60 were slowly added thereto. After the addition, a resulting mixture was further stirred for 3 hours, to obtain a styrene-acrylate siloxane graft copolymer composite emulsion.

[0149] Comparative Example 1

[0150] In this comparative example, a pure styrene-acrylate emulsion was prepared according to the procedures as described in Example 1, except that the preparation of modified SiO2 in steps (1) to (2), the preparation of the silane monomer mixture and the composite crosslinking agent in steps (5) to (7), and the preparation of the graft copolymer composite emulsion in steps (10) to (13) were omitted.

[0151] Comparative Example 2

[0152] In this comparative example, a styrene-acrylate siloxane random copolymer composite emulsion was prepared according to the procedures as described in Example 1, except that: step (8) and step (13) were omitted, and the four monomer mixtures prepared in step (3) to step (6), as well as the emulsifiers and initiators related in steps (7) to (10) were stirred at a rotational speed of 600 r / min at 70 °C for 5 h, and then gradually cooled to 50 °C.

[0153] Comparative Example 3 25 03 25

[0154] In this comparative example, steps (1) to (8) were performed according to the procedures as described in Example 3, while steps (9) to (10) were performed as follows:

[0155] 9) 50 g of deionized water, 50 g of mixture II, 1.2 g of OP-10, and 1.8 g of sodium dodecyl benzenesulfonate were mixed, and a pH value of a resulting mixture was adjusted to 7.5 with sodium bicarbonate. A resulting mixture was stirred at a rotational speed of 300 r / min at 83 °C for 2 h, to obtain a pre-emulsion B.

[0156] 10) The pre-emulsion B and the composite cross-linking agent were added dropwise slowly into the pre-emulsion, and a resulting mixture was stirred at a rotational speed of 500 r / min at 83 °C for 2 h, and 400 mg of ammonium persulfate was further added.

[0157] The following steps were the same as steps (11) to (12) in Example 3, finally obtaining the SiO2 styrene-acrylate siloxane block copolymer composite emulsion.

[0158] Performance test

[0159] The styrene-acrylate siloxane graft copolymer composite emulsion prepared in the present disclosure was applied in a total amount of 600 g / m2 onto a surface of the cement-based material specimen in two batches with an interval of 5-7 h.

[0160] FIG. 1A to FIG. IF show photos of apparent morphology and optical microscope morphology of the composite emulsion obtained in each experimental group. As can be seen from FIG. 1A to FIG. IF, the styrene-acrylate siloxane graft copolymer composite emulsion prepared in the present disclosure has superior homogeneity and stability, and the emulsion particles have greater dispersion and more concentrated particle size distribution. The composite emulsions prepared in examples do not flocculate, layer or segregate after being left to stand for a long time. Compared with the Comparative Example 1 and Comparative Example 2, the structural integrity of the latex particles in the composite emulsion prepared in examples is better, and the coalescence and demulsification of the latex particles are significantly alleviated.

[0161] FIG. 2A to FIG. 2F show transmission electron microscope images of the composite emulsion obtained in each experimental group. As can be seen from FIG. 2A to FIG. 2F, the composite emulsions prepared in Examples 1 to 3 have latex particles with more uniform particles size, which is consistent with the results observed by optical microscope. The dyeing characteristics inside the latex particles in examples reflects that the graft copolymerization synthesis method in the present disclosure could make the styrene-acrylate component and siloxane component well crosslinked together, and form a stable microphase separation structure inside the micellar cluster.

[0162] 1. Basic properties of the emulsions

[0163] Table 1 Basic performance parameters of the composite emulsions obtained in each experimental group Comparative Example 1 Comparative Example 2 Comparative Example 3 Example 1 Example 2 Example 3 Solid content 45.4% 43.9% 44.7% 46.5% 46.9% 47.6% Gel rate 1.4% 1.2% 1.1% 0.7% 0.7% 0.9% Conversion of monomer 86.8% 83.2% 86.1% 87.6% 88.2% 88.5% Grafting rate — 82.4% 83.6% 86.2% 87.3% 88.3% 25 03 25

[0164] As can be seen from Table 1, the solid contents of the composite emulsions obtained in Examples 1 to 3 are higher than that of Comparative Example 1, and significantly higher than those of Comparative Examples 2 and 3, all of which are maintained at 46.5% or higher. The gel rates of the composite emulsions obtained from Examples 1 to 3 are not more than 1.0, which are better than that of the Comparative Example 1 (the gel rate being 1.4%), indicating that no flocculation or implosion occurs during the synthesis of the composite emulsion. The monomer conversions and grafting rates of the composite emulsions obtained in Examples 1 to 3 are not less than 87.6% and not less than 86.2% respectively, indicating that the method for preparing the SiO2-modified styrene-acrylate siloxane graft copolymer composite emulsion according to the present disclosure not only promotes the free polymerization of each of styrene-acrylate component and siloxane component, but also improves their crosslinking and synergistic effects.

[0165] Table 2 Stability of composite emulsions obtained in each experimental group Comparative Example 1 Comparative Example 2 Comparative Example 3 Example 1 Example 2 Example 3 Centrifugation stability Better Bad Relatively bad Better Better Better Dilution stability Great Better Great Great Great Great Ca2+ stability Great Bad Bad Better Great Great Low temperature stability Bad Bad Relatively bad Better Better Better High temperature Relatively Bad Better Better Great Great stability bad

[0166] As can be seen from Table 2, the physical and chemical stability of the composite emulsions in Examples 1 to 3 are better than those in the Comparative Examples 1 to 3. It has dilution stability, Ca2+ stability and high temperature stability, indicating that the prepared composite emulsions have excellent synergistic performance among each component. Although the centrifugation stability and low temperature stability of the composite emulsions obtained in Examples 1 to 3 are not very ideal, are still significantly better than those in the Comparative Examples 1 to 3.

[0167] The particle size characteristics of the composite emulsions obtained in each experimental group were tested by using a nanoparticle size analyzer.

[0168] Table 3 Particle size and dispersity of the composite emulsion obtained in each experimental group 25 03 25 Comparative Example 1 Comparative Example 2 Comparative Example 3 Example 1 Example 2 Example 3 Average particle size / nm 119 123 111 105 108 96 PDI 0.185 0.216 0.162 0.172 0.166 0.159 Zeta potential / -mV 32.26 27.24 35.77 38.38 38.67 39.02

[0169] As can be found from Table 3, the average particle size of the composite emulsions obtained in Examples 1 to 3 are less than 110 nm, which indicates that the composite emulsions meet the basic requirements of uniform surface film formation and capillary penetration. The PDI homogeneity indexes of the composite emulsions obtained in Examples 1 to 3 are less than 0.172, and Example 3 achieves the highest emulsion micromorphological homogeneity. The absolute values of Zeta potentials of the composite emulsions obtained in Examples 1 to 3 are significantly higher than those of the Comparative Examples 1 to 3, reflecting the superior dispersity and stability of the composite dendritic structure. When the content of the modified SiO2 particles is 0.2%, the dispersion and stability of the composite emulsion are the best.

[0170] 2. Hydrophobic and waterproof properties of the composite emulsion

[0171] The water contact angle on the surface of cement paste treated with the composite emulsion obtained in each experimental group was measured with a static surface contact angle measuring instrument, and the self-cleaning performance of the surface of the specimen was evaluated accordingly.

[0172] FIG. 3 shows diagrams of the water contact angle and self-cleaning performance test on a surface of cement paste specimens in each experimental group.

[0173] Table 4 Static contact angles on the surfaces of cement specimens in each experimental group Comparative Example 1 Comparative Example 2 Comparative Example 3 Example 1 Example 2 Example 3 Contact angle / 0 83.4 95.9 111.7 123.7 129.2 135.6 25 03 25

[0174] As can be seen from FIG. 3 and Table 4, compared with the Comparative Examples 1 to 3, the static contact angles on surfaces of specimens in Examples 1 to 3 could be increased to 123° or more, demonstrating superior hydrophobic performance. Moreover, the surface of cement specimens treated with composite emulsions in Examples 1 to 3 have excellent self-cleaning performance, which could make the water slip freely down on the inclined surface. This indicates that a graft copolymerization system with styrene-acrylate molecules as the main chain could fully improve the molecular configuration of siloxane, allowing the outer alkyl long branch chains to freely stretch and fully exert the hydrophobic properties of the composite polymer components.

[0175] One non-cast surface of the dry concrete specimen was selected as a coating surface, and four side surfaces were sealed with epoxy resin. The coated surface of the specimen was placed facing downwards in distilled water, with the bottom surface of the specimen being about 5 mm away from the water surface, and the water static capillary adsorption rate of the concrete specimen was measured at different water adsorption times.

[0176] FIG. 4 shows curves of the water static capillary adsorption of concrete specimens in each experimental group.

[0177] Table 5 Water static capillary adsorption rates of concretes in each experimental group at 24 h, g / (m2 h0'5) Comparative Example 1 Comparative Example 2 Comparative Example 3 Example 1 Example 2 Example 3 Water capillary adsorption rate 25.6 27.7 22.9 17.2 16.1 15.3 25 03 25

[0178] As can be seen from FIG. 4 and Table 5, compared with the sty rene-acry late emulsion in Comparative Example 1 and the random copolymer emulsion in Comparative Example 2, the concrete specimens treated with the copolymer composite emulsions in Comparative Example 3 and Examples 1 to 3 have greatly reduced water static capillary adsorption rates. In particular, the waterproof performance of dendriform graft copolymer composite emulsion prepared by step graft polymerization is better than that of the block copolymer emulsion prepared by step graft polymerization in Comparative Example 3. Compared with the pure styrene-acrylate emulsion, the water static capillary adsorption rate of Example 1, Example 2 and Example 3 decreases by 26.6%, 32.8%, 37.1% and 40.2% respectively, among which the water static capillary adsorption rate of Example 3 decreases by the most degree.

[0179] 3. Resistance of concrete to chloride and sulfate corrosion

[0180] Similarly with the water static capillary adsorption experiment, the concrete specimens were immersed in NaCl and Na2SO4 solutions with a concentration of 10%, respectively. The penetration of chloride ions and sulfate ions inside the specimens were tested within 50 days.

[0181] Table 6: Amounts corroded by chloride ions and sulfate ions in concretes in each experimental group, g / m2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Example 1 Example 2 Example 3 Amount corroded by Cl' 503 612 343 312 298 286 Amount corroded by SO42' 364 408 316 267 251 237

[0182] Table 7 Erosion potentials of composite coatings in each experimental group under chloride and sulfate corrosions / -V Comparative Comparative Comparative Example Example Example Example 1 Example 2 Example 3 1 2 3 Cl’ corrosion 0.27 0.24 0.31 0.37 0.40 0.41 SO42’ corrosion 0.34 0.30 0.36 0.41 0.42 0.46 25 03 25

[0183] As can be seen from Table 6, concrete specimens treated with the styrene-acrylate siloxane graft copolymer composite emulsion have significantly decreased amounts corroded by chloride ions and sulfate ions. Compared with the concrete specimens treated with ordinary styrene-acrylate emulsion, the amounts corroded by chloride ions in Example 1, Example 2 and Example 3 decrease by 38.0%, 40.8% and 43.1% respectively, while the amounts corroded by sulfate ions in Example 1, Example 2 and Example 3 decrease by 26.6%, 31.0% and 34.9%, respectively. The amounts corroded by chloride ions and sulfate ions for the composite emulsion obtained in Example 3 decreases by the most degree, showing the best anti ion erosion performance. In addition, Table 7 also indicates that the corrosion potential of the graft copolymer coatings in Examples 1 to 3 under the erosion of chloride salts and sulfates are significantly higher than those in Comparative Examples 1 to 3. In particular, the absolute value of the corrosion potential of the composite coating in Example 3 under the attack of chloride salts and sulfates reaches 0.4 V or more. Compared with the ordinary styrene-acrylate coating, the absolute values of the corrosion potentials for the composite coating prepared in Example 3 under chloride and sulfate corrosions increases by 0.14 V and 0.12 V, respectively. This indicates that the styrene-acrylate siloxane graft copolymer structure could effectively inhibit the diffusion and transmission of corrosive ions in the pores of concrete.

[0184] 4. Resistance to acid and alkali corrosion

[0185] The latex film prepared in each experimental group was placed in a dilute hydrochloric acid solution with pH=3 and a sodium hydroxide solution with pH=12, and soaked for 72 hours. The mass loss rates and electrical resistance moduli thereof were measured.

[0186] Table 8: Mass loss rates of latex films in each experimental group under acid and alkali corrosion Comparative Example 1 Comparative Example 2 Comparative Example 3 Example 1 Example 2 Example 3 Acid corrosion 45% 43% 34% 31% 26% 22% Alkali corrosion 25% 26% 22% 18% 13% 12%

[0187] As can be seen from Table 8, the mass loss rates of the latex films in Examples 1 to 3 under acid and alkali corrosions are smaller than those in Comparative Examples 1 to 3, indicating that the graft copolymer composite coating has superior resistance to acid and alkali corrosion, and that the composite coating prepared in the present disclosure has more outstanding resistance to alkali corrosion. The composite coating prepared in Example 3 has the best resistance to acid and alkali corrosion, and the mass loss rates could be controlled at 22% and 12%, respectively.

[0188] Table 9: Electrical resistance modulus of latex films in each experimental group under acid and alkali corrosions / xlO5 Q / cm2 25 03 25 Comparative Example 1 Comparative Example 2 Comparative Example 3 Example 1 Example 2 Example 3 Acid corrosion 4.05 3.27 4.17 4.58 4.75 4.83 Alkali corrosion 6.23 5.66 6.51 6.95 7.10 7.21

[0189] As can be found from Table 9, compared with the styrene-acrylate coating in Comparative Example 1, the blend emulsion coating in Comparative Example 2, and the copolymer emulsion coating in Comparative Example 3, the graft copolymer coatings prepared in Examples 1 to 3 have higher electrical resistance moduli. The graft copolymer coating prepared in Example 3 achieves the highest electrical resistance modulus, reaching 4.83* 105 Q / cm2 and 7.21 * 105 Q / cm2 respectively in acidic and alkaline environments, which is 19.3% and 15.7% higher than that of the styrene-acrylate coating, respectively. Therefore, the composite emulsion prepared in the present disclosure could have a stable protective effect on the cement matrix in acid and alkali environments.

[0190] 5 Anti carbonization performance

[0191] The composite emulsion prepared in each experimental group was applied onto each surface of the cement mortar cube specimen, and the mortar specimen was then placed in the special carbonization test chamber. Carbon dioxide concentration in the chamber was set as (20 ± 2)%. The carbonation depth of the mortar specimen was tested after 28 days of carbonation.

[0192] FIG. 5 shows the carbonation depth test results of the cement mortar specimens in each experimental group.

[0193] Table 10 Carbonation depths of the mortar specimens in each experimental group at 28 days of carbonization age / mm Comparative Example 1 Comparative Example 2 Comparative Example 3 Example 1 Example 2 Example 3 Carbonation depth 7.7 6.9 3.8 2.7 2.4 2.2 25 03 25

[0194] FIG. 5 and Table 10 show that the cement mortar specimens treated with the composite emulsions prepared in Examples 1 to 3 have smaller carbonization depth, only 2.7 mm, 2.4 mm and 2.2 mm respectively, which indicates that the graft copolymer coating could effectively inhibit the diffusion and transmission of small molecules CO2 gas, thus maintaining the alkaline environment inside the cement matrix.

[0195] 6. Antiaging performance

[0196] The latex film prepared in each experimental group was irradiated by artificial ultraviolet with a radiosity of 50 w / m2 and a wavelength of 254 nm for 72 hours. Their surface glossiness loss, pulverization degree, and cracking degree were measured.

[0197] Table 11 Surface glossiness loss of latex films in each experimental group / % Comparative Example 1 Comparative Example 2 Comparative Example 3 Example 1 Example 2 Example 3 Glossiness loss 85.4 82.1 72.5 65.8 54.3 57.8

[0198] FIG. 6 shows the morphologies of the composite coatings in each experimental group after UV aging and thermal aging.

[0199] Table 12 Pulverization grade and cracking grade of the latex film in each experimental group Comparative Example 1 Comparative Example 2 Comparative Example 3 Example 1 Example 2 Example 3 Pulverization grade II III III II I I Cracking grade II V IV I I I 25 03 25

[0200] As can be seen from Table 11, the styrene-acrylate emulsion coating in Comparative Example 1 has poor UV aging resistance, and its surface glossiness loss is relatively high, and the glossiness losses of copolymer emulsions in Comparative Example 2 and 3 slightly decrease. However, the glossiness losses of the styrene-acrylate siloxane graft copolymer composite emulsion coatings prepared in Examples 1 to 3 are significantly reduced, among which, the surface glossiness loss in Example 2 is the lowest, being 54.3%. In addition, Table 12 also indicates that, compared with the Comparative Examples 1 to 3, the graft copolymer coatings prepared in Examples 1 to 3 have higher pulverization grade and higher cracking grade. Especially in Example 2 and Example 3, the pulverization grade and cracking grade reach Grade I, showing extremely excellent anti-aging performance.

[0201] 7. Protective performance of cement matrix with cracks

[0202] A crack of about 1 mm was set on one non cast surface of a dry cement mortar specimen, which served as the coating surface, and the four side surfaces were sealed with epoxy resin. The coated surface of the specimen was placed facing downward in distilled water, with a bottom surface of the specimen being about 5 mm away from the water surface. The water static capillary adsorption rate of the concrete specimen was determined at 10 h and 100 h.

[0203] FIG. 7 shows the apparent morphologies of cracked mortar specimens treated in each experimental group.

[0204] FIG. 8 shows diagrams of the static water adsorption test results of cracked mortar specimens treated in each experimental group.

[0205] FIG. 7 shows that, compared with Comparative Examples 1 to 3, the graft copolymer emulsion prepared in Examples 1 to 3 could better solidify and form a film at the crack of cement matrix, to realize external repairment. FIG. 8 shows that, the water adsorption amounts of the corresponding specimens in Examples 1 to 3 are significantly lower than those in Comparative Examples 1 to 3, indicating that the composite emulsion could effectively inhibit the transmission of water molecules by capillary along the defects of the substrate. Among them, Example 3 has the best protective effect, and its water adsorption amount at 10 h and 100 h is only 23.7% and 30.4% of that of ordinary styrene-acrylate coatings.

[0206] 8. Microscopic morphology of surfaces of composite coatings

[0207] The surface microscopic morphology of the composite emulsion coating prepared in each experimental group was observed by SEM.

[0208] FIG. 9A to FIG. 9F show SEM images of surfaces of the composite coatings in each experimental group.

[0209] FIG. 9A to FIG. 9F show that, the surfaces of the graft copolymer composite emulsion coating prepared in Examples 1 to 3 are flatter than those in Comparative Examples 1 to 3, and the number and size of cracks, holes and other defects on the surface are correspondingly reduced, indicating that the composite coating prepared in the present disclosure could better resist the damage of external erosion media to the cement matrix.

[0210] The above is only the preferred embodiment of the method according to the present disclosure. 25 03 25

Claims

16 01 251. A method for preparing a styrene-acrylate siloxane graft copolymer composite emulsion, characterized in that the method comprises the steps of(1) mixing ethyl orthosilicate, water, and anhydrous ethanol, and subjecting a resulting mixture to hydrolysis reaction in an alkaline environment, to obtain an SiO2 sol;(2) mixing the SiO2 sol, a buffering agent, and dopamine hydrochloride, and subjecting a resulting mixture to hydroxylamination polymerization reaction under an alkaline condition, to obtain a hydroxylamination polymerization reaction system;(3) mixing the hydroxylamination polymerization reaction system with an amide compound, and subjecting a resulting mixture to hydroxylamination graft reaction, to obtain modified SiO2 particles;(4) mixing styrene monomer, an acrylate monomer, and the modified SiO2 particles, to obtain a styrene-acrylate monomer mixture I;(5) mixing styrene monomer, an acrylate monomer, and the modified SiCh particles, to obtain a styrene-acrylate monomer mixture II;(6) mixing an acrylate functional monomer with a vinylsilane, to obtain a composite crosslinking agent;(7) mixing polydimethylsiloxane, a vinylsilane monomer, a hydrophilic chain extender, and the modified SiO2 particles, to obtain a silane monomer mixture III;(8) mixing a hydrophobic silane, a chain extender, and the modified SiO2 particles, to obtain a silane monomer mixture IV;(9) mixing the styrene-acrylate monomer mixture I, an emulsifier, an initiator, and water, and subjecting a resulting mixture to a first addition polymerization reaction, to obtain a pre-emulsion;(10) mixing the pre-emulsion, the styrene-acrylate monomer mixture II, an emulsifier, an initiator, and water, and subjecting a resulting mixture to a second addition polymerization reaction, to obtain a second addition polymerization reaction system;(11) mixing the second addition polymerization reaction system with the composite crosslinking agent, and subjecting a resulting mixture to a third addition polymerization reaction, to obtain a third addition polymerization reaction system;(12) mixing the third addition polymerization reaction system, the silane monomer mixture III, an emulsifier, and water, and subjecting a resulting mixture to a first condensation polymerization reaction, to obtain a first condensation polymerization reaction system; and16 01 25(13) mixing the first condensation polymerization reaction system, the silane monomer mixture IV, an emulsifier, and water, subjecting a resulting mixture to a second condensation polymerization reaction to obtain the styrene-acrylate siloxane graft copolymer composite emulsion, whereinstep (4), step (5), step (6), step (7), and step (8) are conducted in any order; andin terms of a glass transition temperature, the styrene-acrylate monomer mixture I, the styrene-acrylate monomer mixture II, the silane monomer mixture III, and the silane monomer mixture IV are ranked as follows: the styrene-acrylate monomer mixture I >the styrene-acrylate monomer mixture II >the silane monomer mixture III >the silane monomer mixture IV;in step (3), the amide compound comprises at least one selected from the group consisting of acetamide, acrylamide, butenamide, V. V-dimethylformamide, and V,7V-dimethylacetamide;in step (4) and step (5), the acrylate monomer in step (4) and the acrylate monomer in step (5) each independently comprise at least one selected from the group consisting of methyl acrylate, methyl methacrylate, ethyl acrylate, butyl acrylate, butyl methacrylate, acrylic acid, and methacrylic acid; the styrene-acrylate monomer mixture I and the styrene-acrylate monomer mixture II each independently comprise 5% to 20% by mass of the styrene monomer; and the styrene-acrylate monomer mixture I and the styrene-acrylate monomer mixture II each independently comprise 0.05% to 0.3% by mass of the modified S1O2 particles;in step (6), the acrylate functional monomer comprises at least one selected from the group consisting of hydroxyethyl acrylate and hydroxypropyl acrylate; the vinylsilane comprises at least one selected from the group consisting of vinyltriethoxysilane, dimethoxymethylvinylsilane, vinyltriisopropoxysilane, and methylvinyldiethyloxysilane; and a mass percentage content of the acrylate functional monomer in the composite crosslinking agent ranges from 30% to 80%;in step (7), the vinylsilane monomer is of a same type as the vinylsilane in step (6); a mass of the hydrophilic chain extender is in a range of 5% to 25% of a mass of the polydimethylsiloxane; a mass of the vinylsilane is in a range of 10% to 30% of the mass of the polydimethylsiloxane; and a mass percentage content of the modified SiO2 particles in the silane monomer mixture III ranges from 0.05% to 0.3%;in step (8), the hydrophobic silane comprises at least one selected from the group consisting of n-octyltrimethoxysilane, n-octyltri ethoxy silane, dodecyltrimethoxysilane,dodecyltriethoxysilane, and hexadecyltrimethoxysilane; a mass of the chain extender is in a range of 5% to 25% of a mass of the hydrophobic silane; and a mass percentage content of the modified SiO2 particles in the silane monomer mixture IV is in a range of 0.05% to 0.3%;in step (9), a mass of the emulsifier is in a range of 2% to 10% of a mass of the16 01 25styrene-acrylate monomer mixture I; a mass of water is in a range of 50% to 100% of the mass of the styrene-acrylate monomer mixture I; a mass of the initiator is in a range of 0.2% to 0.7% of the mass of the styrene-acrylate monomer mixture I; the first addition polymerization reaction is performed at a pH value of 7.5-8.3; and the first addition polymerization reaction is performed at a temperature of 70-85 °C for 2 h; andin step (10), a mass of the emulsifier is in a range of 2% to 10% of a mass of the styrene-acrylate monomer mixture II; a mass of water is in a range of 50% to 100% of the mass of the styrene-acrylate monomer mixture II; the initiator is in a same amount as that of the initiator in step (9); the second addition polymerization reaction is performed at a pH value of 7.5-8.3; and the second addition polymerization reaction is performed at a temperature of 75-85 °C for 1-2 h; andin step (11), a mass of the composite crosslinking agent is in a range of 5-20% of the mass of the styrene-acrylate monomer mixture II; and the third addition polymerization reaction is performed at a temperature of 75-85 °C for 20-40 minutes; andin step (12), a mass of the emulsifier is in a range of 2% to 10% of a mass of the silane monomer mixture III; a mass of water is in a range of 50% to 100% of the mass of the silane monomer mixture III; and the first condensation polymerization reaction is performed at a temperature of 40-60 °C for 0.5-2 h; andin step (13), a mass of the emulsifier is in a range of 2% to 10% of a mass of the silane monomer mixture IV; a mass of water is in a range of 50% to 100% of the mass of the silane monomer mixture IV; and the second condensation reaction is performed at a temperature of 30-50 °C for 1-3 h.

2. The method as claimed in claim 1, wherein in step (7),the hydrophilic chain extender comprises at least one selected from the group consisting of dihydroxymethylpropionic acid, dihydroxymethylbutyric acid, polyethyleneimine, and diethyltoluene diamine.

3. The method as claimed in claim 1, wherein in step (8),the chain extender comprises at least one selected from the group consisting of 1,4-butanediol, 1,6-hexanediol, glycerol, diethylene glycol, triethylene glycol, neopentyl glycol, tris(hydroxymethyl)propane, and ethylenediamine.

4. The method as claimed in claim 1, wherein in step (9),16 01 25the emulsifier comprises at least one selected from the group consisting of octylphenol polyoxyethylene ether, sodium dodecyl sulfate, sodium dodecyl sulfonate, and sodium dodecylbenzenesulfonate;the initiator comprises at least one selected from the group consisting of sodium persulfate, ammonium persulfate, potassium persulfate, azodiisobutyronitrile, and dimethyl 2,2’-azodiisobutyrate; andthe first addition polymerization reaction is performed under stirring, and the stirring is performed at a rotational speed of 200-500 r / min.

5. The method as claimed in claim 1, wherein in step (10),the emulsifier comprises at least one selected from the group consisting of octylphenol polyoxyethylene ether, sodium dodecyl sulfate, sodium dodecyl sulfonate, and sodium dodecylbenzenesulfonate;the initiator is of a same type as the initiator in step (9); andthe second addition polymerization reaction is performed under stirring, and the stirring is performed at a rotational speed of 200-500 r / min.

6. The method as claimed in claim 1, wherein in step (11),the third addition polymerization reaction is performed under stirring, and the stirring is performed at a rotational speed of 200-400 r / min.

7. The method as claimed in claim 1, wherein in step (12),the emulsifier comprises at least one selected from the group consisting of octylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, sorbitan monosterate, sorbitan monooleate, polyoxyethylene(20) sorbitan monostearate, and polyoxyethylene(20) sorbitan monooleate; andthe first condensation polymerization reaction is performed under stirring, and the stirring is performed at a rotational speed of 800-1,200 r / min.

8. The method as claimed in claim 1, wherein in step (13),the emulsifier comprises at least one selected from the group consisting of octylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, sorbitan monosterate, sorbitan monooleate, poly oxy ethylene(20) sorbitan monostearate, and polyoxyethylene(20) sorbitan monooleate; andthe second condensation reaction is performed under stirring, and the stirring is conducted at a rotational speed of 800-1,200 r / min.16 01 25

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