Method for preparing graphene oxide modified styrene acrylic Pickering emulsion and composite emulsion, and method for corrosion prevention of cement-based materials

Abstract

The present invention provides graphene oxide modified styrene acrylic Pickering emulsion and composite emulsion, as well as preparation methods and uses thereof. [Solution] In the present invention, graphene oxide is added during the polymerization process of styrene-acrylic monomer to form a styrene-acrylic core, and at the same time, graphene oxide is attached to the styrene-acrylic core interface, and a silane coupling agent is used to "stitch" the graphene oxide at the styrene-acrylic core interface, thereby giving the graphene oxide a better dispersion effect. After adding the shell phase emulsion, the styrene-acrylic core part that is not completely wrapped by the graphene oxide sheet is grafted with the shell phase, and the steric stability is further improved due to the cross-linking action between the core phase and the shell phase. The presence of graphene oxide can also completely connect the styrene-acrylic core and the siloxane shell, improving the molecular structure of the siloxane composition.

Description

[Technical field]

[0001] This application claims priority to a Chinese patent application filed with the China Patent Office on December 28, 2021, bearing application number CN202111624818.7 and entitled "Graphene oxide modified styrene acrylic Pickering emulsion and composite emulsion and preparation method and use thereof", the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to the technical field of protective coatings, in particular to graphene oxide modified styrene acrylic Pickering emulsion and composite emulsion, and its preparation method and application. [Background technology]

[0003] Concrete is the most widely used cement-based civil engineering construction material, and the durability of cement-based materials directly affects the safety and reliability of concrete structures. In coastal environments where large amounts of chloride ions exist, the main cause of deterioration of concrete structures is the corrosion of the cement matrix by chloride ions.

[0004] Using composite polymer coatings to treat the surface of cement matrix can improve the corrosion resistance of concrete structures and is an efficient, convenient and low-cost protection measure. Styrene-acrylic coatings (styrene-acrylate) and silane are the two most commonly used anticorrosive polymer coatings. Styrene-acrylic coatings have excellent chemical resistance and high weather resistance, and can form a stable water-repellent and anticorrosive protective layer on the surface of cement-based materials; silane coatings have excellent hydrophobicity, good leveling property and strong permeability, and are applicable to many kinds of cement-based materials. The preparation of styrene-acrylic and silane into a composite anticorrosive emulsion with a core-shell structure can fully exert the protective performance of the styrene-acrylic composition and the hydrophobic effect of the siloxane composition, and can make up for the shortcomings of the weak adhesion performance of the styrene-acrylic coating and the poor aging resistance performance of the silane coating.

[0005] Traditional core-shell emulsions are prepared by emulsifiers, in which the core and shell parts are difficult to form regular and stable graft layers and assembly structures, which greatly limits the further development of core-shell emulsions. As a two-dimensional carbon nanomaterial with abundant active oxygen-containing functional groups on the surface, graphene oxide can be covalently bonded to various polymer molecules to play a role in chemical modification and performance adjustment of polymer coatings. Graphene oxide can be used in in-situ polymerization, sol-gel method, physical mixing, intercalation and other methods to construct polymer molecules with ideal molecular structures and improve the adjustment of work performance between each composition of composite coatings. However, the graphene oxide sheets in the graphene oxide modified polymer coatings prepared by these traditional methods are mostly in a disordered and chaotic spatial state, which does not have a good modification effect on the polymer composition, and the graphene oxide sheets are very prone to aggregation, which adversely affects the stability and film-forming properties of composite coatings. Summary of the Invention [Problem to be solved by the invention]

[0006] In view of the above, the present invention provides a graphene oxide modified styrene acrylic Pickering emulsion and a composite emulsion, as well as a preparation method and use thereof. In the graphene oxide modified styrene acrylic Pickering emulsion provided by the present invention, graphene oxide is regularly dispersed and not easily aggregated, and the composite emulsion with a core-shell structure prepared thereby has excellent stability, film-forming property, water resistance, corrosion resistance, ion penetration resistance, aging resistance and mechanical properties, and the durability of concrete structures can be greatly improved by surface treating a cement matrix with the composite emulsion of the present invention. [Means for solving the problem]

[0007] In order to achieve the above objectives of the present invention, the present invention provides the following technical solutions: A method for preparing a graphene oxide modified styrene acrylic Pickering emulsion, comprising: The graphene oxide buffer solution and the styrene-acrylic monomer mixture are mixed and ultrasonically dispersed for the first time, and the resulting emulsion is mixed with a silane coupling agent and ultrasonically dispersed for the second time to obtain a graphene oxide modified styrene-acrylic Pickering emulsion; the graphene oxide buffer solution contains graphene oxide, water, and a pH buffer solution; the styrene-acrylic monomer mixture contains water, an initiator, styrene, and an acrylate monomer.

[0008] Preferably, the mass fraction of the initiator in the styrene-acrylic monomer mixture is 0.3% to 0.7%, and the styrene N The mass fraction is 10% to 30%, and the mass fraction of the acrylate monomer is 60% to 90%.

[0009] Preferably, the initiator in the styrene acrylic monomer mixture includes one or more of a persulfate and an azo-based initiator.

[0010] Preferably, the mass of graphene oxide in the graphene oxide buffer solution is 1% to 10% of the mass of the styrene-acrylic monomer mixed solution, and the mass of water in the graphene oxide buffer solution is 60% to 150% of the mass of the styrene-acrylic monomer mixed solution; The graphene oxide buffer solution has a pH value of 7 to 8.5.

[0011] Preferably, the pH buffering agent includes one or more of sodium bicarbonate, sodium carbonate, sodium hydrogen phosphate, barbital buffer, tris(hydroxymethyl)aminomethane and glycerol phosphate buffer.

[0012] Preferably, the temperature of the first ultrasonic dispersion is 30 to 60° C., and the time is 1 to 3 hours.

[0013] Preferably, the temperature of the second ultrasonic dispersion is 55 to 75° C., and the time is 0.5 to 2 hours.

[0014] The present invention also provides a graphene oxide modified styrene acrylic Pickering emulsion prepared by the preparation method described in the above technical solution, which has a graphene oxide modified styrene acrylic Pickering structure, comprises a styrene acrylic core and graphene oxide coated on the outer interface of the styrene acrylic core, and the graphene oxides are coupled to each other via a coupling agent.

[0015] The present invention further provides a method for preparing a graphene oxide modified styrene acrylic-siloxane Pickering composite emulsion, comprising the steps of: The shell phase emulsion, the graphene oxide modified styrene acrylic Pickering emulsion described in the above technical solution, and an aqueous initiator solution are mixed to carry out a polymerization reaction to obtain a graphene oxide modified styrene acrylic-siloxane Pickering composite emulsion, in which the components of the shell phase emulsion include a silane monomer, a functional acrylate monomer, an emulsifier, and water.

[0016] Preferably, the mass fraction of the silane monomer in the shell phase emulsion is 20%-50%; the mass of the functional acrylate monomer is 10%-50% of the mass of the silane monomer, and the mass of the emulsifier is 2%-5% of the total mass of the silane monomer and the functional acrylate monomer.

[0017] Preferably, the method for preparing the shell phase emulsion includes mixing a silane monomer, a functional acrylate monomer, an emulsifier and water, and stirring at low temperature and high speed to obtain a shell phase emulsion, wherein the temperature of the low temperature and high speed stirring is 30-50°C, and the rotation speed is 800-1200 r / min.

[0018] Preferably, the silane monomer is a long chain hydrocarbyl silane, and the hydrocarbyl group in the long chain hydrocarbyl silane has 4 to 18 carbon atoms.

[0019] Preferably, the long chain hydrocarbyl silane is one or more of n-butyltriethoxysilane, n-octyltrimethoxysilane, n-octyltriethoxysilane, dodecyltrimethoxysilane and dodecyltriethoxysilane.

[0020] Preferably, the functional acrylate monomer is hydroxyethyl acrylate and / or hydroxypropyl acrylate.

[0021] Preferably, the emulsifier is one or more of OP-10, Span 80, sodium lauryl sulfate, sodium dodecyl sulfonate and sodium dodecyl benzene sulfonate.

[0022] Preferably, the mass ratio of the graphene oxide modified styrene acrylic Pickering emulsion to the shell phase emulsion is 1:(1 to 5).

[0023] Preferably, the mass of the initiator in the aqueous initiator solution is 0.2 to 0.5% of the mass of the shell phase emulsion.

[0024] Preferably, the polymerization reaction is carried out under high-temperature, low-speed stirring conditions, the temperature of the high-temperature, low-speed stirring being 80-85° C., the rotation speed being 100-300 r / min, and the time being 1-3 hours.

[0025] Preferably, after the polymerization reaction, the emulsion obtained is subjected to repeated low-speed stirring and ultrasonic dispersion, with one cycle of low-speed stirring and one cycle of ultrasonic dispersion counted as one cycle, and the number of cycles is 3 to 6.

[0026] The present invention further provides a graphene oxide modified styrene acrylic-siloxane Pickering composite emulsion prepared by the preparation method described in the above technical solution, the composite emulsion having a core-shell structure, comprising a shell structure, a core structure and an intermediate transition layer connecting the shell structure and the core structure, wherein the shell structure is a silicone polymer, the core structure is a graphene oxide modified styrene acrylic Pickering structure, and the intermediate transition layer is a polymer formed from a functional acrylate monomer.

[0027] The present invention further provides the use of the graphene oxide modified styrene acrylic-siloxane Pickering composite emulsion described in the above technical solution for corrosion protection of cement-based materials.

[0028] The present invention provides a method for producing a graphene oxide modified styrene acrylic Pickering emulsion, the method including the steps of mixing a graphene oxide buffer solution and a styrene acrylic monomer mixed solution to perform a first ultrasonic dispersion, and mixing the obtained emulsion with a silane coupling agent to perform a second ultrasonic dispersion to obtain a graphene oxide modified styrene acrylic Pickering emulsion, the components of the graphene oxide buffer solution including graphene oxide, water, and a pH buffer solution, and the composition of the styrene acrylic monomer mixed solution including water, an initiator, styrene, and an acrylate monomer. In the present invention, the graphene oxide buffer solution and the styrene-acrylic monomer mixed solution are mixed and subjected to the first ultrasonic dispersion, in which the styrene-acrylic monomer is polymerized to form a styrene-acrylic core during the first ultrasonic dispersion, and at the same time, the graphene oxide is attached to the interface of the styrene-acrylic core; then, a silane coupling agent is added and the second ultrasonic dispersion is performed; in the second ultrasonic dispersion, the graphene oxide is coupled with each other under the action of the silane coupling agent, and the graphene oxide is "stitched" at the interface of the styrene-acrylic core, thereby dispersing the graphene oxide regularly and giving the graphene oxide a better dispersion effect, and improving the performance adjustment and modification effect; by adding a shell phase emulsion, the graphene oxide modified styrene-acrylic Pickering emulsion of the present invention can be further prepared into a composite emulsion with a core-shell structure, and the graphene oxide at the interface of the styrene-acrylic core can maintain a good dispersion state during the subsequent composite emulsion synthesis process or even after the composite emulsion film is formed.

[0029] The present invention further provides a method for preparing a graphene oxide modified styrene acrylic-siloxane Pickering composite emulsion, the method including the steps of mixing the graphene oxide modified styrene acrylic Pickering emulsion described in the above technical solution with an aqueous initiator solution and carrying out a polymerization reaction to obtain a graphene oxide modified styrene acrylic-siloxane Pickering composite emulsion; the composition components of the shell phase emulsion include a silane monomer, a functional acrylate monomer, an emulsifier and water. In the present invention, a shell phase emulsion is added to a graphene oxide modified styrene acrylic Pickering emulsion to carry out a polymerization reaction to form a composite emulsion with a core-shell structure. After the shell phase emulsion is added, the styrene acrylic core portion that is not completely wrapped by the graphene oxide sheet in the graphene oxide modified styrene acrylic Pickering emulsion is grafted with the shell phase, and the steric stability of graphene oxide is further improved due to the cross-linking action between the core phase and the shell phase. At the same time, the presence of graphene oxide can fully connect the styrene acrylic core and the siloxane shell structure, improve the molecular structure of the siloxane composition, and enhance the ability to adjust the chemical activity of the siloxane molecule.

[0030] The graphene oxide modified styrene acrylic-siloxane Pickering composite emulsion prepared by the present invention has excellent film-forming properties, and the principle is as follows: Graphene oxide sheets contain both hydrophilic and hydrophobic groups, which can effectively replace the emulsifier molecules in the composite emulsion and become a stable transition layer between the styrene-acrylic molecular micelles and the solvent water molecules, thereby reducing the adverse effects of the residual emulsifier composition on the film formation process. Graphene oxide also enhances the binding and synergistic performance between the styrene-acrylic composition and the siloxane composition, which is beneficial to the uniformity and stability of the coating system during the film formation process.

[0031] The graphene oxide modified styrene acrylic-siloxane Pickering composite emulsion prepared by the present invention has excellent hydrophobicity and water repellency, and the principle is as follows: graphene oxide improves the molecular structure of siloxane in the shell structure, makes the siloxane molecules orderly and tightly grafted to the core phase inside the composite emulsion, and can fully extend and align the hydrophobic alkane chains of the siloxane molecules, and further enhances the dispersion and stability of the styrene acrylic core structure, thereby fully improving the water resistance of the styrene acrylic composition and the hydrophobicity of the siloxane composition, thereby improving the hydrophobicity and stability after film formation. In addition, when the emulsion is formed into a film, the graphene oxide sheets can not only be deposited on the surface of the cement matrix to form a regularly distributed rough surface, but also promote the secondary hydration reaction between the siloxane molecules and the concrete hydration products, and prevent external moisture from entering the cracks and capillary channels inside the concrete.

[0032] The graphene oxide modified styrene acrylic-siloxane Pickering composite emulsion coating prepared by the present invention has excellent corrosion resistance against chloride salts and sulfate salts, and the principle is as follows: graphene oxide enhances the cross-linking degree of the silane emulsion, weakening the diffusion and transport of chloride ions and sulfate ions on the concrete surface and inside the capillary channels. The presence of graphene oxide reinforcement strengthens the cross-linking and bonding between the styrene acrylic micelles and the siloxane composition, improving the shielding performance of the composite coating against corrosive ions, and graphene oxide also has a blocking effect against corrosive ions, which can block and extend the transmission path of corrosive ions. In addition, graphene oxide can further improve the electrochemical performance of the emulsion and enhance the chemical resistance of the coating.

[0033] The graphene oxide modified styrene acrylic-siloxane Pickering composite emulsion coating prepared by the present invention has excellent anti-aging performance, and the principle is as follows: due to the evaporation of free water during the film formation process and the infiltration of small particle size latex particles, the graphene oxide continues to deposit and adhere to the surface of the substrate, forming a perfect heat-resistant and radiation-resistant reflective layer. At the same time, the graphene oxide promotes the formation of strong cross-links and bonds between the styrene acrylic molecules and the siloxane molecules, greatly increasing the cross-link density of the transition layer of the Pickering composite emulsion, which is beneficial to the absorption and dissipation of external energy by the composite coating, and thereby improves the aging resistance of the coating. [Brief description of the drawings]

[0034] [Figure 1] 1 shows optical photographs of the appearance of the multiple emulsions obtained in Examples 1 to 4 and Comparative Examples 1 to 3. [Diagram 2] FIG. 2 is a metallographic scanning micrograph of the multiple emulsions obtained in Examples 1 to 4 and Comparative Examples 1 to 3. [Diagram 3] FIG. 2 is a test diagram of the static contact angle of the coating formed on the surface of a cement test sample by the composite emulsions obtained in Examples 1 to 4 and Comparative Examples 1 to 3. [Figure 4] FIG. 2 is a static capillary water absorption curve diagram of concrete test samples after surface treatment with the composite emulsions obtained in Examples 1-4 and Comparative Examples 1-3. [Diagram 5] FIG. 2 is a fitting calculation diagram of the chloride ion erosion rate of concrete after surface treatment with the composite emulsions obtained in Examples 1 to 4 and Comparative Examples 1 to 3. [Figure 6] FIG. 2 is a fitting calculation diagram of the sulfate ion erosion rate of concrete after surface treatment with the composite emulsions obtained in Examples 1 to 4 and Comparative Examples 1 to 3. [Figure 7] FIG. 2 is a SEM scanning electron microscope test image of the latex film formed from the composite emulsion obtained in Examples 1 and 2. [Figure 8]FIG. 2 is a SEM scanning electron microscope test image of the latex film formed from the composite emulsion obtained in Examples 3 and 4. [Figure 9] FIG. 2 is a SEM scanning electron microscope test image of the latex film formed from the emulsion obtained in Comparative Examples 1 and 2. [Figure 10] FIG. 2 is a SEM scanning electron microscope test image of a latex film formed from the emulsion obtained in Comparative Example 3. [Figure 11] FIG. 2 is an AFM atomic force microscope test image of the latex film formed from the composite emulsion obtained in Examples 1 and 2. [Figure 12] FIG. 2 is an AFM atomic force microscope test image of the latex film formed from the composite emulsion obtained in Examples 3 and 4. [Figure 13] FIG. 2 is an AFM atomic force microscope test image of the latex films formed from the emulsions obtained in Comparative Examples 1 and 2. [Figure 14] FIG. 1 is an AFM atomic force microscope test image of a latex film formed from the emulsion obtained in Comparative Example 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] The present invention provides a method for preparing a graphene oxide modified styrene acrylic Pickering emulsion, comprising the following steps: The graphene oxide buffer solution and the styrene-acrylic monomer mixture are mixed and ultrasonically dispersed for the first time, and the resulting emulsion is mixed with a silane coupling agent and ultrasonically dispersed for the second time to obtain a graphene oxide modified styrene-acrylic Pickering emulsion; the graphene oxide buffer solution contains graphene oxide, water and a pH buffer; the styrene-acrylic monomer mixture contains water, an initiator, styrene and an acrylate monomer.

[0036] In the present invention, the mass fraction of the initiator in the styrene-acrylic monomer mixture is preferably 0.3% to 0.7%, more preferably 0.4% to 0.6%. N The mass fraction is preferably 10%-30%, more preferably 15%-25%, and the mass fraction of the acrylate monomer is preferably 60%-90%; in the present invention, the styrene-acrylic core structure obtained by using the above blending ratio has a high glass transition temperature and can ensure high spatial stability of the graphene oxide sheet.

[0037] In the present invention, the initiator preferably includes one or more of a persulfate and an azo-based initiator; the persulfate preferably includes one or more of sodium persulfate, ammonium persulfate, and potassium persulfate; the azo-based initiator preferably includes azobis(isobutyronitrile) and / or dimethyl azobis(isobutyrate); the acrylate monomer preferably includes one or more of methyl acrylate, methyl methacrylate, ethyl acrylate, butyl acrylate, butyl methacrylate, acrylic acid, and methacrylic acid; and the water is preferably deionized water.

[0038] In a particular embodiment of the present invention, it is preferred to first add an initiator to deionized water to obtain an initiator solution, then mix styrene and acrylate monomers to obtain a mixed monomer, and then add the mixed monomer to the aqueous initiator solution to obtain a styrene-acrylic monomer mixed liquid.

[0039] In the present invention, the graphene oxide buffer solution is preferably prepared by the following method: graphene oxide is added to deionized water and ultrasonically dispersed to obtain a graphene oxide aqueous solution, and then a pH buffer is added to the graphene oxide aqueous solution to obtain a graphene oxide buffer solution; the ultrasonic dispersion time is preferably 1 to 4 hours.

[0040] In the present invention, the pH buffer preferably comprises one or more of sodium bicarbonate, sodium carbonate, sodium hydrogen phosphate, barbital buffer, tris(hydroxymethyl)aminomethane and glycerol phosphate buffer.

[0041] In the present invention, the mass of graphene oxide in the graphene oxide buffer is preferably 1%-10% of the mass of the styrene-acrylic monomer mixture, more preferably 3%-8%, the mass of water in the graphene oxide buffer is preferably 60%-150% of the mass of the styrene-acrylic monomer mixture, more preferably 80%-120%; the pH value of the graphene oxide buffer is 7-8.5, and the dosage of the pH buffer is based on adjusting the pH value of the graphene oxide buffer solution to the above range. In the subsequent polymerization reaction process, the initiator lowers the pH value of the system when starting to generate free radicals, and the present invention uses the pH buffer to adjust the graphene oxide buffer to be weakly alkaline, so that the emulsion in the subsequent addition polymerization reaction process can be kept neutral, which is favorable for the progress of the reaction.

[0042] In the present invention, after obtaining a graphene oxide buffer solution and a styrene-acrylic monomer mixture, the graphene oxide buffer solution and the styrene-acrylic monomer mixture solution are mixed to perform a first ultrasonic dispersion, and the obtained dispersion solution and a silane coupling agent are mixed to perform a second ultrasonic dispersion to obtain a graphene oxide modified styrene-acrylic Pickering emulsion. In the present invention, preferably, the styrene-acrylic monomer mixture solution is slowly added to the graphene oxide buffer solution, and then the first ultrasonic dispersion is performed; the temperature of the first ultrasonic dispersion is preferably 30 to 60°C, and the time is preferably 1 to 3 hours, more preferably 1.5 to 2.5 hours. In a specific embodiment of the present invention, preferably, after mixing the graphene oxide buffer solution and the styrene-acrylic monomer mixture solution, the mixture is first stirred at 30 to 60°C for 30 minutes, and then the first ultrasonic dispersion is performed. During the first ultrasonic dispersion process, styrene and acrylate monomers are polymerized to form a styrene-acrylic polymer (i.e., a styrene-acrylic core), and at the same time, graphene oxide is attached to the surface of the styrene-acrylic core.

[0043] After the first ultrasonic dispersion is completed, the present invention preferably drops a silane coupling agent into the emulsion obtained, and then performs a second ultrasonic dispersion. In the present invention, the silane coupling agent is preferably one or more of KH-550, KH-560, and KH-570; the mass of the silane coupling agent is preferably 2% to 20% of the mass of graphene oxide in the emulsion obtained by the first ultrasonic dispersion; the temperature of the second ultrasonic dispersion is preferably 55 to 75°C, more preferably 60 to 70°C, and the time of the second ultrasonic dispersion is preferably 0.5 to 2 hours, more preferably 1 to 1.5 hours. In a specific embodiment of the present invention, the emulsion obtained by the first ultrasonic dispersion is preferably mixed with the silane coupling agent, and then stirred at 55 to 75°C for 20 minutes, and then the second ultrasonic dispersion is performed. In the second ultrasonic dispersion process, the graphene oxide is coupled with each other under the action of the silane coupling agent, and the graphene oxide is "stitched" at the interface of the styrene-acrylic core, thereby endowing the graphene oxide with a better dispersion effect.

[0044] The present invention further provides a graphene oxide modified styrene acrylic Pickering emulsion prepared by the preparation method described in the above technical solution, the graphene oxide modified styrene acrylic Pickering emulsion has a graphene oxide modified styrene acrylic Pickering structure, includes a styrene acrylic core and graphene oxide coated on the outer interface of the styrene acrylic core, and the graphene oxide is coupled to each other via a coupling agent. In the graphene oxide modified styrene acrylic Pickering emulsion provided by the present invention, graphene oxide has good dispersibility and is not easily aggregated, so it can be used to prepare a composite emulsion with a core-shell structure, and the graphene oxide at the styrene acrylic core interface can maintain a good dispersion state during the subsequent composite emulsion synthesis process or even after the composite emulsion film is formed.

[0045] The present invention further provides a method for preparing a graphene oxide modified styrene acrylic-siloxane Pickering composite emulsion, comprising the steps of: The shell phase emulsion, the graphene oxide modified styrene acrylic Pickering emulsion described in the above technical solution, and an aqueous initiator solution are mixed to carry out a polymerization reaction to obtain a graphene oxide modified styrene acrylic-siloxane Pickering composite emulsion, in which the composition of the shell phase emulsion includes a silane monomer, a functional acrylate monomer, an emulsifier and water.

[0046] In the present invention, the silane monomer is preferably a long-chain hydrocarbyl silane, and the number of carbon atoms of the hydrocarbyl group in the long-chain hydrocarbyl silane is 4 to 18. Specifically, the long-chain hydrocarbyl silane is preferably one or more of n-butyltriethoxysilane, n-octyltrimethoxysilane, n-octyltriethoxysilane, dodecyltrimethoxysilane and dodecyltriethoxysilane; the functional acrylate monomer is preferably hydroxyethyl acrylate and / or hydroxypropyl acrylate; in the present invention, the functional acrylate monomer is used to provide crosslinking points, promote the polymerization reaction between silane molecules, and appropriately increase the viscosity of the emulsion; the emulsifier is preferably one or more of OP-10, Span 80, sodium dodecylbenzenesulfonate, sodium dodecylsulfonate and sodium dodecylbenzenesulfonate; the water is preferably deionized water.

[0047] In the present invention, the mass fraction of the silane monomer in the shell phase emulsion is preferably 20% to 50%; the mass of the functional acrylate monomer is preferably 10% to 50%, more preferably 15% to 40%, of the mass of the silane monomer; and the amount of the emulsifier is preferably 2% to 5%, more preferably 3% to 4%, of the total mass of the silane monomer and the functional acrylate monomer.

[0048] In the present invention, the method for preparing the shell phase emulsion is preferably to mix silane monomer, functional acrylate monomer, emulsifier and water and stir at low temperature and high speed to obtain the shell phase emulsion; in a specific embodiment of the present invention, preferably, first, the emulsifier is added to water to obtain an aqueous solution of the emulsifier, and then the silane monomer and the functional acrylate monomer are added to the aqueous solution of the emulsifier and stirred at low temperature and high speed. In the present invention, the temperature of the low-temperature and high-speed stirring is preferably 30-50°C, more preferably 35-45°C, and the rotation speed of the low-temperature and high-speed stirring is preferably 800-1200r / min, more preferably 900-1000r / min. The present invention prepares the shell phase emulsion under the condition of low-temperature and high-speed stirring, which can prepolymerize siloxane molecules to form a molecular network structure with a low molecular weight, which is beneficial to the crosslinking effect of the siloxane molecular layer in the styrene acrylic core structure and the improvement of the chemical stability of the surface hydrophobic layer.

[0049] After the shell phase emulsion is obtained, the present invention mixes the shell phase emulsion, the graphene oxide modified styrene acrylic Pickering emulsion and an aqueous initiator solution to carry out a polymerization reaction, thereby obtaining a graphene oxide modified styrene acrylic-siloxane Pickering composite emulsion. In the present invention, the mass ratio of the graphene oxide modified styrene acrylic Pickering emulsion to the shell phase emulsion is preferably 1:(1-5), more preferably 1:(2-4); the mass of the initiator in the initiator aqueous solution is preferably 0.2%-0.5% of the shell phase emulsion mass, more preferably 0.3%-0.4%; the type of initiator in the initiator aqueous solution is consistent with the above technical solution, so it will not be repeated here; the polymerization reaction is preferably carried out under high-temperature low-speed stirring conditions; the temperature of the high-temperature low-speed stirring is preferably 80-85°C, more preferably 82-83°C, the rotation speed of the high-temperature low-speed stirring is preferably 100-300r / min, more preferably 150-250r / min, and the time of the low-temperature high-speed stirring is preferably 1-3 hours, more preferably 1.5-2.5 hours. In the present invention, the polymerization reaction is preferably carried out under high-temperature low-speed stirring conditions, which can avoid the occurrence of aggregation, gelation, etc. during the polymerization process. After the low-temperature high-speed stirring is completed, the present invention preferably keeps the resulting reaction solution for 2 hours to allow the reaction to complete, and then slowly cools it to 30° C. to obtain a graphene oxide modified styrene acrylic-siloxane Pickering composite emulsion. During the polymerization reaction process, the silane monomer and the functional acrylate monomer are polymerized to form a shell layer that is coated on the surface of the styrene acrylic Pickering structure, and at the same time, the part of the styrene acrylic Pickering structure that is not completely wrapped by the graphene oxide sheet is grafted to the shell structure, thereby enhancing the stability of the composite emulsion.

[0050] After the polymerization reaction is completed, the present invention preferably further includes repeating low-speed stirring and ultrasonic dispersion of the obtained emulsion, where one low-speed stirring and one ultrasonic dispersion are counted as one repetition, and the number of repetitions is preferably 3 to 6 times, more preferably 4 to 5 times; the rotation speed of the low-speed stirring is preferably 100 to 200 r / min, more preferably 130 to 150 r / min, the time of each low-speed stirring is preferably 5 to 60 minutes, and the time of each ultrasonic dispersion is preferably 20 to 60 minutes, more preferably 30 to 50 minutes. The present invention further improves the dispersibility of the composite emulsion and further increases the graft cross-linking rate between the shell structure in the composite emulsion and the graphene oxide sheet by repeating low-speed stirring and ultrasonic dispersion.

[0051] The present invention further provides a graphene oxide modified styrene acrylic-siloxane Pickering composite emulsion prepared by the preparation method described in the above technical solution, the composite emulsion has a core-shell structure, and includes a shell structure, a core structure and an intermediate transition layer connecting the shell structure and the core structure, where the shell structure is a silicone polymer, the core structure is a graphene oxide modified styrene acrylic Pickering structure, and the intermediate transition layer is a polymer formed from a functional acrylate monomer. The graphene oxide in the composite emulsion provided by the present invention has good dispersion and is not easily agglomerated, and the obtained composite emulsion has excellent stability, film-forming properties, water resistance, corrosion resistance, ion penetration resistance, aging resistance and mechanical properties.

[0052] The present invention further provides the application of the graphene oxide modified styrene acrylic-siloxane Pickering composite emulsion described in the above technical solution for the corrosion protection of cement-based materials. In the present invention, the cement-based material is preferably a concrete building structure; the present invention does not have any special requirements for the specific method of application, and the application can be performed using a method well known to those skilled in the art, specifically, the composite emulsion of the present invention is coated on the surface of the cement-based material to form an anticorrosive coating, thereby improving the durability of the cement-based material; in a specific embodiment of the present invention, the dosage of the composite emulsion is preferably 300-1000g / m 2 and more preferably 400 to 600 g / m 2 It is.

[0053] The technical solutions of the present invention are clearly and completely described below with reference to the embodiments of the present invention.

[0054] Example 1 1) 280 mg of ammonium persulfate was added to 10 g of deionized water to prepare an aqueous initiator solution; 2) 6 g of styrene, 6 g of methyl methacrylate, 8 g of butyl acrylate, and 4 g of acrylic acid were mixed, and 5 g of an aqueous initiator solution was added to prepare a styrene-acrylic monomer mixture; 3) 480 mg of graphene oxide powder was added to 20 g of deionized water, ultrasonically dispersed for 2 hours, and then 1 g of sodium bicarbonate was added to prepare a graphene oxide buffer solution; 4) 24 g of styrene-acrylic monomer mixture was slowly added to 21.48 g of graphene oxide buffer solution, stirred at 80°C at a rotation speed of 150 r / min for 30 minutes, and then ultrasonically dispersed for 3 hours to prepare a styrene-acrylic Pickering emulsion; 5) 50 mg of KH-570 silane coupling agent was dropped into the styrene-acrylic Pickering emulsion, stirred at 60°C at a rotation speed of 150 r / min for 20 minutes, and then ultrasonically dispersed at 60°C for 2 hours to prepare a graphene oxide modified styrene-acrylic Pickering emulsion; 6) 0.5g OP-10, 0.3g Span 80 and 0.3g sodium dodecylbenzenesulfonate were added to 25g deionized water, and a mixture of 5g vinyltriethoxysilane, 20g octyltriethoxysilane and 3g hydroxyethyl acrylate was slowly added, and the mixture was stirred at 40℃ at a rotation speed of 1000r / min for 2 hours to prepare a shell phase emulsion; 7) Slowly add the shell phase emulsion to the graphene oxide modified styrene acrylic Pickering emulsion according to a mass ratio (core-shell ratio) of 1:1, add 5g of initiator aqueous solution, stir at 83°C at a rotation speed of 100r / min for 2 hours, and then keep warm for 2 hours, then slowly cool to 30°C; 8) The emulsion obtained in step 7) was subjected to three cycles of slow stirring and ultrasonic dispersion, in which the rotation speed of the slow stirring was 100 r / min, the time of slow stirring for each cycle was 1 hour, and the time of ultrasonic dispersion for each cycle was 40 minutes, to obtain a styrene acrylic-siloxane Pickering composite emulsion with a graphene oxide content of 2%, and the graphene oxide content was calculated as the mass fraction of graphene oxide in the styrene acrylic monomer mixture in step 4).

[0055] Example 2 1) 280 mg of ammonium persulfate was added to 10 g of deionized water to prepare an aqueous initiator solution; 2) 6 g of styrene, 7 g of methyl acrylate, 7 g of butyl methacrylate, and 4 g of methacrylic acid were mixed, and 5 g of an aqueous initiator solution was added to prepare a styrene-acrylic monomer mixture; 3) 960 mg of graphene oxide powder was added to 20 g of deionized water, ultrasonically dispersed for 2 hours, and then 1 g of sodium carbonate was added to prepare a graphene oxide buffer solution; 4) 24 g of styrene-acrylic monomer mixture was slowly added to 21.96 g of graphene oxide buffer solution, stirred at 80°C at a rotation speed of 150 r / min for 30 minutes, and then ultrasonically dispersed for 3 hours to prepare a styrene-acrylic Pickering emulsion; 5) 100 mg of KH-570 silane coupling agent was dropped into the styrene-acrylic Pickering emulsion, stirred at 60°C at a rotation speed of 150 r / min for 20 minutes, and then ultrasonically dispersed for 2 hours to prepare a graphene oxide modified styrene-acrylic Pickering emulsion; 6) 0.6g of OP-10, 0.3g of Tween80 and 0.2g of sodium dodecylbenzenesulfonate were added to 25g of deionized water, and a mixture of 5g of vinyltriethoxysilane, 20g of octyltriethoxysilane and 3g of hydroxypropyl acrylate was slowly added, and the mixture was stirred at a rotation speed of 1000r / min at 40°C for 2 hours to prepare a shell phase emulsion; 7) Slowly add the shell phase emulsion to the graphene oxide modified styrene acrylic Pickering emulsion according to a mass ratio of 1:1, add 5g of initiator aqueous solution, stir at 83°C at a rotation speed of 100r / min for 2 hours, and then keep warm for 2 hours, and then slowly cool to 30°C; 8) The emulsion obtained in step 7) was subjected to three cycles of slow stirring and ultrasonic dispersion, in which the rotation speed of the slow stirring was 100 r / min, the time of slow stirring for each cycle was 1 hour, and the time of ultrasonic dispersion for each cycle was 40 minutes, to obtain a styrene acrylic-siloxane Pickering composite emulsion with a graphene oxide content of 4%, and the graphene oxide content was calculated as the mass fraction of graphene oxide in the styrene acrylic monomer mixture in step 4).

[0056] Example 3 1) 280 mg of ammonium persulfate was added to 10 g of deionized water to prepare an aqueous initiator solution; 2) 5 g of styrene, 5 g of methyl methacrylate, 9 g of ethyl acrylate, and 5 g of acrylic acid were mixed, and 5 g of an aqueous initiator solution was added to prepare a styrene-acrylic monomer mixture; 3) 1.44 g of graphene oxide powder was added to 20 g of deionized water, ultrasonically dispersed for 2 hours, and then 1 g of sodium hydrogen phosphate was added to prepare a graphene oxide buffer solution; 4) 24 g of styrene-acrylic monomer mixture was slowly added to 22.44 g of graphene oxide buffer solution, stirred at 80°C at a rotation speed of 150 r / min for 30 minutes, and then ultrasonically dispersed for 3 hours to prepare a styrene-acrylic Pickering emulsion; 5) 150 mg of KH-550 silane coupling agent was dropped into the styrene-acrylic Pickering emulsion, stirred at 60°C at a rotation speed of 150 r / min for 20 minutes, and then ultrasonically dispersed for 2 hours to prepare a graphene oxide modified styrene-acrylic Pickering emulsion; 6) 0.5g OP-10, 0.4g Span 60 and 0.4g sodium dodecylbenzenesulfonate were added to 25g deionized water, and a mixture of 5g vinyltriethoxysilane, 20g dodecyltriethoxysilane and 3g hydroxyethyl methacrylate was slowly added, and the mixture was stirred at 40℃ at a rotation speed of 1000r / min for 2 hours to prepare a shell phase emulsion; 7) Slowly add the shell phase emulsion to the styrene-acrylic Pickering emulsion according to a mass ratio of 1:1, add 5g of initiator aqueous solution, stir at 83°C at a rotation speed of 100r / min for 2 hours, and then keep warm for 2 hours, and then slowly cool to 30°C; 8) The emulsion obtained in step 7) was subjected to three cycles of slow stirring and ultrasonic dispersion, in which the rotation speed of the slow stirring was 100 r / min, the time of slow stirring for each cycle was 1 hour, and the time of ultrasonic dispersion for each cycle was 40 minutes, to obtain a styrene acrylic-siloxane Pickering composite emulsion with a graphene oxide content of 6%, and the graphene oxide content was calculated as the mass fraction of graphene oxide in the styrene acrylic monomer mixture in step 4).

[0057] Example 4 1) Prepare an aqueous initiator solution by adding 280 mg of ammonium persulfate to 10 g of deionized water; 2) 4 g of styrene, 8 g of methyl acrylate, 8 g of butyl acrylate, and 4 g of methacrylic acid were mixed, and 5 g of an aqueous initiator solution was added to prepare a styrene-acrylic monomer mixture; 3) 1.92 g of graphene oxide powder was added to 20 g of deionized water, ultrasonically dispersed for 2 hours, and then 1 g of sodium bicarbonate was added to prepare a graphene oxide buffer solution; 4) 24 g of styrene-acrylic monomer mixture was slowly added to 22.92 g of graphene oxide buffer solution, stirred at 80°C at a rotation speed of 150 r / min for 30 minutes, and then ultrasonically dispersed for 3 hours to prepare a styrene-acrylic Pickering emulsion; 5) 200 mg of KH-570 silane coupling agent was dropped into the styrene-acrylic Pickering emulsion, stirred at 60°C at a rotation speed of 150 r / min for 20 minutes, and then ultrasonically dispersed for 2 hours to prepare a graphene oxide modified styrene-acrylic Pickering emulsion; 6) 0.5g of OP-10, 0.25g of Tween 60 and 0.35g of sodium dodecylbenzenesulfonate were added to 25g of deionized water, and a mixture of 5g of vinyltriethoxysilane, 25g of octyltriethoxysilane and 3g of hydroxypropyl methacrylate was slowly added, and the mixture was stirred at a rotation speed of 1000r / min at 40°C for 2 hours to prepare a shell phase emulsion; 7) Slowly add the shell phase emulsion to the styrene-acrylic Pickering emulsion according to a mass ratio of 1:1, add 5g of initiator aqueous solution, stir at 83°C at a rotation speed of 100r / min for 2 hours, and then keep warm for 2 hours, and then slowly cool to 30°C; 8) The emulsion obtained in step 7) was subjected to three cycles of slow stirring and ultrasonic dispersion, in which the rotation speed of the slow stirring was 100 r / min, the time of slow stirring for each cycle was 1 hour, and the time of ultrasonic dispersion for each cycle was 40 minutes, to obtain a styrene acrylic-siloxane Pickering composite emulsion with a graphene oxide content of 8%, and the graphene oxide content was calculated as the mass fraction of graphene oxide in the styrene acrylic monomer mixture in step 4).

[0058] Comparative Example 1 In this comparative example, a core-shell emulsion is prepared using a method similar to that in Example 1, with the difference being that step 3) and step 5) are omitted, and step 4) is changed to the following: The styrene-acrylic monomer mixture was added to a pH buffer aqueous solution (specifically, sodium hydroxide solution, concentration 5 wt%) and stirred at 83°C for 3 hours to prepare a styrene-acrylic core phase emulsion; and the styrene-acrylic core phase emulsion was used to replace the styrene-acrylic Pickering emulsion in step 7); Step 8) was omitted. The other conditions were the same as in Example 1, and a styrene acrylic-siloxane composite core-shell emulsion was finally obtained.

[0059] Comparative Example 2 In this comparative example, the graphene oxide modified copolymer emulsion was prepared using a method similar to that in Example 1, with the difference being that step 4) and step 5) were omitted; Since the final emulsion obtained in Comparative Example 2 does not have a core-shell structure, the emulsion prepared according to step 6) in Example 1 was a siloxane pre-emulsion; Step 7) was changed as follows: graphene oxide buffer solution, styrene-acrylic monomer mixture and siloxane pre-emulsion (the amounts of graphene oxide buffer solution, styrene-acrylic monomer mixture and siloxane pre-emulsion are the same as those in Example 1) were mixed together, 5g of initiator aqueous solution was added, and the mixture was stirred at 83°C with a rotation speed of 100r / min for 2 hours, and then slowly cooled to 30°C after keeping for 2 hours; Other conditions were consistent with those in Example 1, and a modified styrene acrylic-siloxane copolymer emulsion with a graphene oxide content of 2% was finally obtained.

[0060] Comparative Example 3 In this comparative example, a graphene oxide modified styrene acrylic-siloxane copolymer emulsion was prepared using a method similar to that of Comparative Example 2, with the difference being that the graphene oxide content was 8%, i.e., in step 7), the dosage of graphene oxide was 8% by mass of the styrene acrylic monomer mixture, and finally, a modified styrene acrylic-siloxane copolymer emulsion with a graphene oxide content of 8% was prepared.

[0061] Functional testing (1) Visual and microscopic examination Fig. 1 is an optical photograph of the appearance of the composite emulsions obtained in Examples 1 to 4 and Comparative Examples 1 to 3. According to Fig. 1, the graphene oxide modified styrene acrylic-siloxane Pickering emulsions prepared in Examples 1 to 4 have good homogeneity and stability, and the emulsions have never undergone aggregation, separation or segregation, and the graphene oxide sheets on the outer surface of the Pickering structure did not aggregate, but the composite emulsions prepared in Comparative Examples 1 to 3 have non-uniform colors and exhibit slight aggregation phenomena.

[0062] Fig. 2 is a gold microscope scanning diagram of the composite emulsions obtained in Examples 1 to 4 and Comparative Examples 1 to 3. According to Fig. 2, the latex particle size of the composite emulsions obtained in Examples 1 to 4 is smaller than that of the core-shell emulsions and copolymer emulsions in Comparative Examples 1 to 3, and the particle size of the composite emulsions obtained in Examples 1 to 4 is relatively uniform, but the particle size distribution of the latex particles in the emulsions obtained in Comparative Examples 1 to 3 is relatively dispersed. The smaller the particle size of the emulsion, the larger the specific surface area of ​​the latex particles and the higher the content of the graphene oxide sheets wrapped and adsorbed in the Pickering structure. Therefore, the method for producing a Pickering emulsion proposed by the present invention can significantly improve the utilization rate and dispersibility of graphene oxide.

[0063] (2) Testing basic emulsion performance According to GB / T1728-2020 "Method for Determining Drying Time of Paint Film and Putty Film", the surface drying time and actual drying time of the composite emulsion coating are measured by finger touch method. The emulsion is placed in a weighing bottle and dried in an oven at 105 ° C for 3 hours, then cooled to room temperature in a dryer, and the mass of the emulsion before and after drying is weighed and expressed as m1 and m2, respectively. The emulsion is filtered through a 200 mesh copper screen, all the gel is collected and washed with deionized water, and the gel is dried in the same way, and the mass of the dried gel is expressed as m3. In addition, the emulsion is demulsified with ethanol, and the obtained precipitated solid is washed with deionized water several times and dried at 80 ° C for 6 hours. The precipitated solid is extracted according to the GB / T23530-2009 standard, and the weight before and after extraction is measured and expressed as m4 and m5, respectively. The calculation formulas for solid content, gelation rate, monomer conversion rate, and grafting rate are as follows:

[0064] JPEG0007678610000001.jpg4788

[0065] where m non is the mass of non-volatile matter (i.e., the total mass of other raw materials excluding the solvent water), and m M is the mass of all organic monomers in the feedstock, and P SE is the mass fraction of the silane monomer raw material in the composite emulsion.

[0066] The results are shown in Table 1. Table 1. Basic performance parameters of the multiple emulsions obtained in Examples 1 to 4 and Comparative Examples 1 to 3 [Table 1]

[0067] As can be seen from Table 1, there was no significant difference in the surface drying time and hard drying time between the composite emulsions obtained in Examples 1 to 4 and those obtained in Comparative Examples 1 to 3. Compared with Comparative Examples 1 to 3, the graphene oxide modified styrene acrylic-siloxane Pickering composite emulsions prepared by the present invention have a higher solid content and a lower gel ratio. In addition, the emulsions of Examples 1 to 4 have higher monomer conversion and grafting rates. This indicates that the graphene oxide modified Pickering structure provided by the present invention can significantly promote the polymerization reaction inside the styrene acrylic core structure and the siloxane shell structure, and also strengthen the cross-linking and bonding action between the styrene acrylic composition, the graphene oxide interface and the siloxane composition.

[0068] (3) Emulsion stability test The composite emulsions prepared in Examples 1 to 4 and Comparative Examples 1 to 3 were used as test specimens, and the following tests were carried out: the emulsions were diluted to a concentration of 2% using deionized water as a solvent, and the dilution stability of the emulsions was observed; The emulsion was centrifuged at a rotation speed of 2000 r / min for 5 min, and the centrifugal stability of the emulsion was observed; The emulsion was diluted to 10% with 5% CaCl2 solution and Ca 2+ Observe the stability of; The emulsion was left at 60°C for 24 hours to observe the high temperature stability of the emulsion. The emulsion was left at 0°C for 18 hours to observe its low temperature stability.

[0069] The results are shown in Table 2. Table 2. Stability of multiple emulsions in each test group [Table 2]

[0070] In Table 2: very good means that the composite emulsion can maintain good stability even after standing for 14 days, and the morphology of the emulsion basically does not change; good means that the composite emulsion has high stability at first, but after standing for 14 days, the emulsion shows phenomena such as slight aggregation, gelation, separation, or segregation; fair bad means that the composite emulsion shows slight aggregation, gelation, separation, or segregation at first, and after standing for 14 days, the stability of the emulsion further decreases and more serious aggregation, separation, or segregation occurs; bad means that the composite emulsion shows relatively serious aggregation or separation from the beginning.

[0071] (4) Emulsion particle size distribution and dispersibility The particle size distributions and zeta potentials of the emulsions obtained in Examples 1 to 4 and Comparative Examples 1 to 3 are shown in Table 3: Table 3 Particle size distribution and zeta potential of the multiple emulsions obtained in Examples 1 to 4 and Comparative Examples 1 to 3 [Table 3]

[0072] As can be seen from the data in Table 3, the average particle size of the composite emulsions obtained in Examples 1 to 4 is all less than 250 nm, but all are larger than the average particle size of the core-shell emulsions and copolymer emulsions in Comparative Examples 1 to 3, meeting the basic requirements of a penetrating protective emulsion. The PDI homogeneity index of the composite emulsions obtained in Examples 1 to 4 is all less than 0.35, but still shows a higher value than Comparative Examples 1 to 3, which also reflects that the molecular weight distribution of the composite emulsions prepared by the present invention has a relatively high discreteness, which is also one of the prominent features of the graphene oxide modified styrene acrylic Pickering emulsion. The absolute value of the zeta potential of the composite emulsions obtained in Examples 1 to 4 is significantly higher than that of Comparative Examples 1 to 3, indicating that the Pickering structure prepared by the present invention has excellent dispersibility, where the absolute value of the zeta potential of Example 4 is the largest, indicating that the increase in the interfacial graphene oxide content in the Pickering structure is favorable to improving the stability of the Pickering emulsion.

[0073] 4) Hydrophobicity and water repellency of emulsions The graphene oxide modified styrene acrylic-siloxane Pickering composite emulsions prepared in Examples 1 to 4 and the emulsions prepared in Comparative Examples 1 to 3 were mixed at 600 g / m 2 The emulsion was coated on the surface of the cement slurry test sample in two separate coats, with an interval of at least 6 hours between the two coats, and then subjected to a static water contact angle test after drying.

[0074] Static water contact angle test: A surface contact angle meter was used to measure the static water contact angle of the surface of the cement slurry test sample of each test group. The test diagram of the obtained static contact angle is shown in Figure 3, and the specific data of the contact angle is shown in Table 4.

[0075] Table 4. Static contact angles of the cement test sample surfaces of each test group [Table 4]

[0076] It can be seen from Figure 3 and Table 4 that the films formed by the emulsions prepared in Examples 1 to 4 have larger surface contact angles and exhibit higher hydrophobicity compared with Comparative Examples 1 to 3. This indicates that the hydrophobic performance of the coating formed by the composite emulsion prepared according to the present invention is superior to that of the core-shell emulsion and the graphene oxide modified copolymer emulsion, and indicates that the emulsification replacement effect and interface modification effect of graphene oxide in the Pickering emulsion can greatly improve the hydrophobicity of the coating.

[0077] Static water absorption test: One uncast surface of the dry concrete test sample was used as the coating surface, and 600 g / m of emulsion was applied to the surface of the cement slurry test sample. 2 The concrete test samples were placed in distilled water with the coated side facing down and about 0.5 cm away from the water surface to measure the change in static capillary water absorption of the concrete test samples with the penetration time, and the results are shown in Figure 4 and Table 5. Figure 4 shows the static capillary water absorption curves of the concrete test samples of each test group, and Table 5 shows the data of the 24-hour concrete capillary water absorption of each test group.

[0078] Table 5. Static capillary water absorption of concrete in each test group at 24 hours (g m -2 h -0.5 ) [Table 5]

[0079] As can be seen from FIG. 4 and Table 5, the static capillary water absorption of the concrete test sample treated with the graphene oxide modified Pickering composite emulsion prepared by the present invention is significantly reduced compared with the concrete test samples coated with the general core-shell emulsion and graphene oxide modified copolymer emulsion of Comparative Examples 1 to 3. Compared with the capillary water absorption of Comparative Example 1, the capillary water absorption of Examples 1 to 4 is reduced by 19.5%, 37.0%, 33.1%, and 25.9%, respectively, and the static capillary water absorption of Example 2 is the largest. It is shown that the preparation method provided by the present invention can maximize the interfacial modification property of graphene oxide to styrene acrylic-siloxane core-shell structure, improve the film formation and protective performance of Pickering emulsion on the surface of cement-based materials, and inhibit the diffusion and permeation of water molecules inside concrete.

[0080] (5) Resistance to corrosion by chlorides and sulfates Using the same method as the static water absorption test, one non-cast surface of the dry concrete test sample was used as the coating surface, the side was sealed with hardening adhesive, and then the test sample was immersed in 10% NaCl and Na2SO4 solutions respectively to test the penetration status of chloride ions and sulfate ions in the concrete test sample. The results obtained are shown in Figures 5-6, where Figure 5 is a fitting calculation diagram of the chloride ion erosion rate of concrete in each test group, and Figure 6 is a fitting calculation diagram of the sulfate ion erosion rate of concrete in each test group.

[0081] As can be seen from Figures 5 and 6, compared with Comparative Examples 1 to 3, the corrosion rates of chloride ions and sulfate ions of the concrete test samples treated with the graphene oxide modified styrene acrylic-siloxane Pickering composite emulsions of Examples 1 to 4 are reduced to different degrees, and the construction of a Pickering structure with a graphene oxide interface can greatly improve the ion penetration resistance performance of the styrene acrylic composition and siloxane composition. During the entire corrosion process, the corrosion rates of chloride ions and sulfate ions are relatively stable, indicating that the styrene acrylic-siloxane Pickering emulsion connected by the interfacial graphene oxide can effectively inhibit the diffusion and transport of corrosion ions in the concrete capillary pores, block the transport path of corrosion ions, and reduce the osmotic pressure of ions in the capillary pores.

[0082] (6) Acid and alkali resistance of latex film Latex films were prepared from the emulsions prepared in each test group, the specific preparation method was: the emulsion was poured into a polytetrafluoroethylene strip mold, dried at 40℃ for 48 hours, and demolded to form emulsion film samples, the size of which was 15mm×50mm×3mm. The obtained latex films were respectively placed in a dilute hydrochloric acid solution of pH=3 and a sodium hydroxide solution of pH=12 for 72 hours, and the mass loss rate was measured, as shown in Table 6.

[0083] Table 6. Mass loss rate of latex film for each test group under acid-alkali corrosion [Table 6]

[0084] As can be seen from Table 6, the mass loss rate of the latex films of Examples 1-4 under acid-alkali corrosion is smaller than that of Comparative Examples 1-3, and the coatings formed by the composite emulsions synthesized by the preparation method of the present invention have better acid-alkali corrosion resistance. Here, the mass loss rate of the latex film of Example 4 is the smallest, indicating that the higher interfacial graphene oxide content is beneficial to improving the acid-alkali corrosion resistance of Pickering emulsion coatings.

[0085] The cement test samples were prepared according to the same method as the static water absorption test, and then the same test method as the mass loss rate above was used to corrode the coating on the surface of the cement test samples. An adhesive strength tester and a pencil hardness tester were used to measure the surface adhesive bond strength and pencil hardness of the composite coating on the cement sample surface after 72 hours of acid-alkali corrosion, and the results are shown in Table 7.

[0086] Table 7. Surface coating adhesive bond strength and pencil hardness of cement test samples of each test group under acid-alkali corrosion [Table 7]

[0087] As can be seen from Table 7, there was a higher surface adhesion bond strength between the composite emulsions prepared in Examples 1 to 4 and the cement substrate under acid-alkali corrosion compared to the core-shell emulsion and graphene oxide modified copolymer emulsion in the comparative example. The pencil hardness of the latex film in the comparative example under acid-alkali corrosion was low, but the pencil hardness of the coating in Examples 1 to 4 was improved to various degrees. Among them, the surface adhesion bond strength and pencil hardness of Example 4 were the highest, indicating excellent acid-alkali corrosion resistance. Under acid-alkali corrosion, the pencil hardness of the latex film in the comparative example was low, but the pencil hardness of the coating in Examples 1 to 4 was improved to various degrees. Among them, the surface adhesion bond strength and pencil hardness of Example 4 were the highest, indicating excellent acid-alkali corrosion resistance.

[0088] (7) Anti-aging performance of latex film The emulsions prepared by each test group were used to prepare latex films (the preparation method was the same as that of the mass loss rate test), and the obtained latex films were exposed to an irradiance of 50 w / m 2 The sample was left exposed to artificial ultraviolet light with a wavelength of 254 nm for 72 hours without stopping, and the surface gloss loss rate and crosslink density loss rate were measured. The results are shown in Table 8.

[0089] Table 8. Loss of crosslink density / % of latex films in each test group [Table 8]

[0090] Table 9. Loss / % of Tensile Strength and Elongation at Break for Latex Films in Each Test Group [Table 9]

[0091] As can be seen from Table 8, the crosslink density loss rate of the composite emulsion coatings of Examples 1 to 4 was significantly lower than that of Comparative Examples 1 to 3, indicating excellent anti-UV aging performance. In addition, the tensile strength and elongation at break loss rates of the coatings obtained in Examples 1 to 4 were also significantly lower than those of Comparative Examples 1 to 3, and in particular, the elongation at break rate of the latex film after aging was significantly improved. Here, the crosslink density loss rate, tensile strength loss rate, and elongation at break loss rate of Example 4 were the lowest, indicating that the increase in the interfacial graphene oxide content is beneficial to improving the UV aging resistance and heat aging resistance of the Pickering emulsion coating.

[0092] (8) SEM and AFM observation of latex film 7 to 10 are SEM scanning electron microscope images of latex films formed from the emulsions obtained in Examples 1 to 4 and Comparative Examples 1 to 3; 11 to 14 are AFM atomic force microscope test images of latex films formed from the emulsions obtained in Examples 1 to 4 and Comparative Examples 1 to 3.

[0093] As can be seen from Figures 7 to 14, the surface roughness of the latex films formed in Examples 1 to 4 was obviously higher than that of the conventional core-shell emulsion coating and copolymer emulsion coating in the comparative example. The latex films formed by the emulsions obtained in Examples 1 to 4 contained fewer surface pores and had a typical scale-like surface morphology, indicating that the preparation method of the present invention can greatly improve the surface roughness and structural compactness of the composite coating, which is beneficial to improving the water repellency and ion corrosion resistance of the composite anticorrosive coating.

[0094] It should be noted that the above is only a preferred embodiment of the present invention, and many improvements and modifications can be made by those skilled in the art without departing from the principle of the present invention, and these improvements and modifications are also considered to be within the protection scope of the present invention.

Claims

1. A method for preparing a graphene oxide modified styrene acrylic Pickering emulsion, comprising: A preparation method comprising the steps of mixing a graphene oxide buffer solution and a styrene-acrylic monomer mixed solution to perform a first ultrasonic dispersion, mixing the obtained emulsion with a silane coupling agent to perform a second ultrasonic dispersion, thereby obtaining a graphene oxide modified styrene-acrylic Pickering emulsion, wherein the graphene oxide buffer solution has a composition including graphene oxide, water, and a pH buffer, and the styrene-acrylic monomer mixed solution has a composition including water, an initiator, styrene, and an acrylate monomer.

2. 2. The preparation method according to claim 1, wherein the initiator in the styrene-acrylic monomer mixture comprises one or more of persulfate and azo-based initiator.

3. 2. The method according to claim 1, wherein a mass of graphene oxide in the graphene oxide buffer is 1%-10% of a mass of the styrene-acrylic monomer mixed solution, a mass of water in the graphene oxide buffer is 60%-150% of a mass of the styrene-acrylic monomer mixed solution, and a pH value of the graphene oxide buffer is 7-8.

5.

4. A process according to any one of claims 1 to 3, comprising the steps of: The graphene oxide modified styrene acrylic Pickering emulsion prepared by the preparation method has a graphene oxide modified styrene acrylic Pickering structure, comprises a styrene acrylic core and graphene oxide coated on the outer interface of the styrene acrylic core, and the graphene oxides are coupled to each other via a coupling agent.

5. A method for preparing a graphene oxide modified styrene acrylic-siloxane Pickering composite emulsion, comprising the steps of: A preparation method for a graphene oxide modified styrene acrylic-siloxane Pickering composite emulsion, comprising mixing a shell phase emulsion, the graphene oxide modified styrene acrylic Pickering emulsion according to claim 4, and an aqueous initiator solution to carry out a polymerization reaction, and the graphene oxide modified styrene acrylic-siloxane Pickering composite emulsion is obtained, and the composition of the shell phase emulsion includes a silane monomer, a functional acrylate monomer, an emulsifier, and water.

6. 6. The preparation method according to claim 5, wherein the mass fraction of the silane monomer in the shell phase emulsion is 20%-50%; the mass of the functional acrylate monomer is 10%-50% of the mass of the silane monomer, and the mass of the emulsifier is 2%-5% of the total mass of the silane monomer and the functional acrylate monomer.

7. The method for preparing the shell phase emulsion according to claim 5, further comprising the steps of mixing silane monomer, functional acrylate monomer, emulsifier and water, and stirring at low temperature and high speed to obtain the shell phase emulsion, wherein the temperature of the low temperature and high speed stirring is 30-50°C, and the rotation speed is 800-1200 r / min.

8. 6. The method of claim 5, The composite emulsion has a core-shell structure including a shell structure, a core structure, and an intermediate transition layer connecting the shell structure and the core structure, wherein the shell structure is a silicone polymer, the core structure is a graphene oxide modified styrene acrylic Pickering structure, and the intermediate transition layer is a polymer formed from a functional acrylate monomer.

9. A method for corrosion protection of a cement-based material, comprising adding the graphene oxide modified styrene acrylic-siloxane Pickering composite emulsion according to claim 8 to the cement-based material.

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