A method for preparing porous hydrophobic phosphate coating by titanium dioxide / urea-formaldehyde resin microcapsules

Abstract

The present invention discloses a method for preparing a porous hydrophobic phosphate coating using titanium dioxide / urea-formaldehyde resin microcapsules. The method comprises: stirring a formaldehyde solution and urea at 50-70°C and a pH of 8-9 for 1 hour to react and generate a prepolymer; after the prepolymer is cooled to room temperature, titanium dioxide, an emulsifier, and an auxiliary agent are added, and stirring is performed at 50-70°C for 0.5 hour to acidify the pH of the system to 2-4; heating the prepolymer to 50-70°C and maintaining the temperature for 2-3 hours, filtering the prepolymer after cooling, washing the prepolymer with distilled water, and drying the prepolymer. During the heating and curing process of the phosphate coating, the capsule wall of the microcapsules in the present invention is thermally decomposed, leaving micron-sized circular holes on the surface of the coating, which facilitates the subsequent construction of micro-nanostructures to improve hydrophobic properties. The core titanium dioxide remains inside the coating, improving the wear resistance of the coating.

Description

Technical Field

[0001] The invention belongs to the field of material surface modification, and in particular relates to a method for preparing a porous hydrophobic phosphate coating by using titanium dioxide / urea-formaldehyde resin microcapsules. Background Art

[0002] Inorganic phosphate-based coatings are widely used in industrial production due to their excellent adhesion, thermal and chemical stability, and environmental friendliness. However, the hydrophilicity of inorganic phosphate coatings makes them susceptible to corrosion in humid environments. Therefore, they need to be hydrophobicized by creating micro-nanostructures on the coating surface using pore-forming agents and nanoparticles.

[0003] After decomposing at high temperature, the pore-forming agent will leave holes on the surface and inside the coating, affecting the hardness and long-term corrosion resistance of the coating. Therefore, it is necessary to prepare a pore-forming agent that only leaves holes on the surface of the coating and does not affect the internal structure of the coating.

[0004] Therefore, there is an urgent need in this field to explore a method with simple process and low cost to prepare microcapsules that meet the above requirements and successfully prepare porous hydrophobic phosphate coatings. Summary of the Invention

[0005] The purpose of this section is to summarize some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of this application to avoid obscuring the purpose of this section, the abstract and the title of the invention, and such simplifications or omissions should not be used to limit the scope of the present invention.

[0006] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0007] Therefore, the object of the present invention is to overcome the deficiencies in the prior art and provide a method for preparing titanium dioxide / urea-formaldehyde resin microcapsules.

[0008] In order to solve the above technical problems, the present invention provides the following technical solutions: a method for preparing titanium dioxide / urea-formaldehyde resin microcapsules, comprising:

[0009] Prepolymerization stage: Stir the mixture of formaldehyde solution, urea and water evenly, add alkaline solution to adjust the pH to 8-9, react at 50-70°C for 1 hour under stirring to form urea-formaldehyde resin prepolymer, and cool to room temperature;

[0010] Emulsification stage: evenly mix the cooled urea-formaldehyde resin prepolymer with the aqueous solution of titanium dioxide, emulsifier and additives, and react at 50-70°C for 0.5h under stirring to obtain an emulsion;

[0011] Encapsulation stage: The acid solution is added dropwise to the emulsion, the pH of the system is adjusted to 2-4, and the reaction is carried out under stirring at a temperature of 50-70°C for 2-3 hours to form the microcapsule wall and obtain a suspension;

[0012] Post-treatment: The obtained suspension is cooled to room temperature and filtered, and the obtained filter residue is washed with distilled water and dried to obtain microcapsules with a porous hydrophobic phosphate coating.

[0013] As a preferred embodiment of the preparation method of the present invention, the mass ratio of urea, formaldehyde solution and water is 1:2:0-1.

[0014] As a preferred embodiment of the preparation method of the present invention, the mass content of the formaldehyde solution is 37%.

[0015] As a preferred embodiment of the preparation method of the present invention, the emulsifier is one or more of polyvinyl alcohol, polyethylene glycol and sodium dodecylbenzenesulfonate.

[0016] As a preferred embodiment of the preparation method of the present invention, the auxiliary agent is one or more of resorcinol, hydroquinone, polyethylene glycol, polypropylene glycol and ammonium chloride.

[0017] As a preferred embodiment of the preparation method of the present invention, the mass ratio of the titanium dioxide, the emulsifier and the auxiliary agent is 2:0.5-1:0.5-1.

[0018] As a preferred embodiment of the preparation method of the present invention, the mass ratio of titanium dioxide to urea is 1:1.5-2.

[0019] As a preferred embodiment of the preparation method of the present invention, the alkaline solution is a sodium hydroxide aqueous solution, the acid solution is a hydrochloric acid aqueous solution, and the stirring speed is 100 to 300 rpm.

[0020] Another object of the present invention is to overcome the deficiencies in the prior art and provide a product obtained by a method for preparing titanium dioxide / urea-formaldehyde resin microcapsules.

[0021] Another object of the present invention is to overcome the deficiencies in the prior art and provide a use of titanium dioxide / urea-formaldehyde resin microcapsules in the preparation of porous hydrophobic phosphate coatings.

[0022] Beneficial effects of the present invention:

[0023] (1) The present invention provides a method for preparing titanium dioxide / urea-formaldehyde resin microcapsules. The prepared titanium dioxide / urea-formaldehyde resin microcapsules are used to prepare porous hydrophobic phosphate coatings. During the heating and curing process of the phosphate coating, the capsule wall of the microcapsules will be thermally decomposed to leave micron-sized circular holes on the surface of the coating, so that the subsequent micro-nano structure can be constructed to improve the hydrophobic performance. At the same time, the core titanium dioxide remains in the interior of the coating, thereby improving the wear resistance of the coating.

[0024] (2) The present invention prepares a porous hydrophobic phosphate coating by an in-situ polymerization method, and uses a urea-formaldehyde resin, an organic material that decomposes under heat, as a microcapsule wall material. The coating can be automatically decomposed when heated and cured without the need for other steps.

[0025] (3) The core material of the product of the present invention is titanium dioxide, which has high hardness, high temperature resistance, and does not react with the coating material, thereby improving the wear resistance of the coating; the reaction process of the present invention is simple, has low energy consumption, high speed, and the prepared microcapsules have a high embedding rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort. Among them:

[0027] Figure 1 This is the infrared spectrum of the microcapsules prepared in Example 1 of the present invention.

[0028] Figure 2 This is an optical microscope picture of the microcapsules prepared in Example 1 of the present invention.

[0029] Figure 3 This is the microscopic morphology of the coating prepared in Example 1 of the present invention.

[0030] Figure 4 This is a scanning electron microscope image of the microcapsules prepared in Example 2 of the present invention.

[0031] Figure 5 This is the TGA analysis of the microcapsules prepared in Example 2 of the present invention.

[0032] Figure 6 This is a scanning electron microscope image of the microcapsules prepared in Example 2 of the present invention after grinding.

[0033] Figure 7 This is a scanning electron microscope image of the urea-formaldehyde self-agglomerated microcapsules prepared in Comparative Example 2 of the present invention.

[0034] Figure 8This is a scanning electron microscope image of the microcapsules prepared in Comparative Example 3 of the present invention. DETAILED DESCRIPTION

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

[0036] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0037] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0038] In the present invention, the tribological test of microporous coating and micro-nano coating was carried out using MFT-5000 series universal friction and wear testing machine. The room temperature was 20-30°C, the test conditions were as follows: loading load 10N, test time 20min, speed 20mm / s, and the friction ball was a silicon nitride ball with a diameter of 9mm.

[0039] In the present invention, the contact angle of each coating to deionized water was measured by a contact angle meter (POWEREACH, Shanghai Zhongchen Digital Technology Equipment Co., Ltd.).

[0040] Example 1

[0041] (1) 3 g of urea and 6 g of a 37% formaldehyde solution were stirred evenly, sodium hydroxide was added to adjust the pH to 8.5, and the mixture was heated in a constant temperature water bath at 70° C. for 1 h while stirring to form a urea-formaldehyde resin prepolymer, and then cooled to room temperature;

[0042] (2) The cooled urea-formaldehyde resin prepolymer was then mixed with 1.5 g of titanium dioxide, 0.2 g of sodium dodecylbenzene sulfonate, 0.2 g of polyethylene glycol, 0.2 g of resorcinol, 0.2 g of ammonium chloride, and 60 ml of deionized water, and stirred for 40 minutes to obtain an emulsion;

[0043] (3) Slowly add hydrochloric acid dropwise to the emulsion to adjust the pH of the system to 2.5, and heat in a constant temperature water bath at 60°C for 3 h while stirring to obtain a suspension;

[0044] (4) Finally, the suspension was cooled to room temperature and filtered, and the filter residue was washed three times with distilled water and then dried in an oven to obtain microcapsules for preparing a porous hydrophobic phosphate coating.

[0045] Figure 1 This is the infrared spectrum of the microcapsules prepared in Example 1.

[0046] from Figure 1 From the infrared spectrum, we can see that 3343cm -1 The -NH imino stretching vibration absorption peak is at 1634 cm -1 The -C=0 carbonyl stretching absorption peak is 1555cm -1 The absorption peak of -CO-NH amide group is at 1381 cm -1 The peak at the center is the antisymmetric stretching vibration peak of nitrate, among which the imino group is the characteristic functional group of the condensation product of formaldehyde and urea, indicating that a condensation reaction does occur between formaldehyde and urea.

[0047] Figure 2 This is an optical microscope image of the microcapsules prepared in Example 1, combined with Figure 2 From the optical microscope photos, it can be seen that the microcapsules are in a state where the middle core material is surrounded by the outer capsule wall and are dispersed relatively evenly, indicating that the titanium dioxide / urea-formaldehyde resin microcapsules are successfully prepared. The microcapsules are spherical with a particle size of 1-2μm.

[0048] (5) A porous hydrophobic phosphate coating was prepared using the titanium dioxide / urea-formaldehyde resin microcapsules prepared in this example. The preparation steps were as follows:

[0049] Step 1: Aluminum oxide, aluminum dihydrogen phosphate, zinc oxide, and microcapsule powder were mixed in a mass ratio of 42:50:8:5 (8.4 g, 10 g, 1.6 g, and 1 g, respectively). After magnetic stirring for 6 h, the coating was applied to the substrate surface by brushing. After drying, the sample was obtained.

[0050] Step 2: Place the sample in a vacuum tube furnace for sintering and curing, raise the temperature to 280°C in stages, and keep the temperature for 1 hour at each 50°C increase. Finally, cool the furnace and take the sample to obtain a porous inorganic phosphate coating.

[0051] Step 3: Anhydrous ethanol, water, 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane and nano-titanium dioxide were mixed in a mass ratio of 18:1:1:1 (18 g, 1 g, 1 g, 1 g, respectively) and stirred at 80 ° C. for 3 h to fully hydrolyze to obtain a nano-titanium dioxide solution;

[0052] Step 4: Take 10ml of nano-titanium dioxide solution in a beaker, then immerse the microporous inorganic phosphate coating into it, and use a vacuum drying oven to use a vacuum dipping method to infiltrate the nano-titanium dioxide particles into the interior of the microporous coating to establish a micro-nano structure, thereby obtaining a porous hydrophobic phosphate coating with a micro-nano structure. Figure 3 shown.

[0053] The contact angle and wear rate of the coating were tested, and the test results are shown in Table 1.

[0054] Example 2

[0055] (1) 6 g of urea, 12 g of a 37% formaldehyde solution, and 6 ml of deionized water were mixed uniformly, sodium hydroxide was added to adjust the pH to 9, and the mixture was heated in a constant temperature water bath at 70° C. for 1 h while stirring to form a urea-formaldehyde resin prepolymer, and then cooled to room temperature;

[0056] (2) The cooled urea-formaldehyde resin prepolymer was then mixed with 4 g of titanium dioxide, 0.5 g of sodium dodecylbenzene sulfonate, 0.5 g of polyvinyl alcohol, 0.5 g of resorcinol, 0.5 g of ammonium chloride, and 60 ml of deionized water, and stirred for 40 min to obtain an emulsion;

[0057] (3) Slowly add hydrochloric acid dropwise to the emulsion to adjust the pH of the system to 3, and heat in a constant temperature water bath at 60°C for 3 h while stirring to obtain a suspension;

[0058] (4) Finally, the suspension was cooled to room temperature and filtered, and the filter residue was washed three times with distilled water and then dried in an oven to obtain microcapsules for preparing a porous hydrophobic phosphate coating.

[0059] Figure 4 This is an electron microscope image of the microcapsules prepared in Example 2. The microcapsules are spherical and have a particle size of 1-2 μm.

[0060] Figure 5 The following are the TGA analysis results and corresponding derivative curves for the microcapsules prepared in Example 2. The sample's weight loss process occurs in two stages: the first, from 38.34°C to 117.01°C, primarily due to water evaporation; the second, from 171.25°C to 425.73°C, due to the thermal decomposition and volatilization of the urea-formaldehyde resin in the microcapsule wall. The sample's residual content is 45.96%, representing undecomposed core titanium dioxide.

[0061] Figure 6 This is a scanning electron microscope image of the microcapsules prepared in Example 2 after grinding. It can be clearly seen that the microcapsules have a core-shell structure, indicating that the urea-formaldehyde resin is wrapped around the titanium dioxide core material.

[0062] (5) A porous hydrophobic phosphate coating was prepared using the titanium dioxide / urea-formaldehyde resin microcapsules prepared in this example, and the preparation steps were the same as those in Example 1.

[0063] The contact angle and wear rate of the coating were tested, and the test results are shown in Table 1.

[0064] Example 3

[0065] (1) 7 g of urea, 14 g of a 37% formaldehyde solution, and 5 ml of deionized water were mixed uniformly, sodium hydroxide was added to adjust the pH to 9, and the mixture was heated in a constant temperature water bath at 70° C. for 1 h while stirring to form a urea-formaldehyde resin prepolymer, and then cooled to room temperature;

[0066] (2) The cooled urea-formaldehyde resin prepolymer was then mixed with 3.5 g of titanium dioxide, 0.5 g of sodium dodecylbenzene sulfonate, 0.5 g of polyvinyl alcohol, 0.5 g of polyethylene glycol, 0.4 g of resorcinol, 0.2 g of ammonium chloride, and 60 ml of deionized water, and stirred for 40 minutes to obtain an emulsion;

[0067] (3) Slowly add hydrochloric acid dropwise to the emulsion to adjust the pH of the system to 3, and heat in a constant temperature water bath at 60°C for 2 h while stirring to obtain a suspension;

[0068] (4) Finally, the suspension was cooled to room temperature and filtered, and the filter residue was washed three times with distilled water and then dried in an oven to obtain microcapsules for preparing a porous hydrophobic phosphate coating.

[0069] (5) A porous hydrophobic phosphate coating was prepared using the titanium dioxide / urea-formaldehyde resin microcapsules prepared in this example, and the preparation steps were the same as in Example 1. The contact angle and wear rate of the coating were tested, and the test results are shown in Table 1.

[0070] Example 4

[0071] (1) 6 g of urea, 12 g of a 37% formaldehyde solution, and 10 ml of deionized water were mixed uniformly, sodium hydroxide was added to adjust the pH to 8.9, and the mixture was heated in a constant temperature water bath at 65° C. for 1 h while stirring to form a urea-formaldehyde resin prepolymer, and then cooled to room temperature;

[0072] (2) The cooled urea-formaldehyde resin prepolymer was then mixed with 3.5 g of titanium dioxide, 0.5 g of sodium dodecylbenzene sulfonate, 0.5 g of polyvinyl alcohol, 0.5 g of polyethylene glycol, 0.4 g of resorcinol, 0.2 g of ammonium chloride, and 60 ml of deionized water, and stirred for 40 minutes to obtain an emulsion;

[0073] (3) Slowly add hydrochloric acid dropwise to the emulsion to adjust the pH of the system to 2.9, and heat in a constant temperature water bath at 55°C for 3 h while stirring to obtain a suspension;

[0074] (4) Finally, the suspension was cooled to room temperature and filtered, and the filter residue was washed three times with distilled water and then dried in an oven to obtain microcapsules for preparing a porous hydrophobic phosphate coating.

[0075] (5) A porous hydrophobic phosphate coating was prepared using the titanium dioxide / urea-formaldehyde resin microcapsules prepared in this example, and the preparation steps were the same as those in Example 1.

[0076] The contact angle and wear rate of the coating were tested, and the test results are shown in Table 1.

[0077] Example 5

[0078] (1) 8 g of urea, 16 g of a 37% formaldehyde solution, and 10 ml of deionized water were mixed uniformly, sodium hydroxide was added to adjust the pH to 8.5, and the mixture was heated in a constant temperature water bath at 70° C. for 1 h while stirring to form a urea-formaldehyde resin prepolymer, and then cooled to room temperature;

[0079] (2) The cooled urea-formaldehyde resin prepolymer was then mixed with 4 g of titanium dioxide, 0.8 g of sodium dodecylbenzene sulfonate, 0.6 g of polyvinyl alcohol, 0.5 g of polyethylene glycol, 0.6 g of resorcinol, 0.4 g of ammonium chloride, and 60 ml of deionized water, and stirred for 40 min to obtain an emulsion;

[0080] (3) Slowly add hydrochloric acid dropwise to the emulsion to adjust the pH of the system to 3, and heat in a constant temperature water bath at 60°C for 3 h while stirring to obtain a suspension;

[0081] (4) Finally, the suspension was cooled to room temperature and filtered, and the filter residue was washed three times with distilled water and then dried in an oven to obtain microcapsules for preparing a porous hydrophobic phosphate coating.

[0082] (5) A porous hydrophobic phosphate coating was prepared using the titanium dioxide / urea-formaldehyde resin microcapsules prepared in this example, and the preparation steps were the same as in Example 1. The contact angle and wear rate of the coating were tested, and the test results are shown in Table 1.

[0083] Example 6

[0084] (1) 10 g of urea, 20 g of a 37% formaldehyde solution, and 12 ml of deionized water were mixed uniformly, sodium hydroxide was added to adjust the pH to 9, and the mixture was heated in a constant temperature water bath at 70° C. for 1 h while stirring to form a urea-formaldehyde resin prepolymer, and then cooled to room temperature;

[0085] (2) The cooled urea-formaldehyde resin prepolymer was then mixed with 5 g of titanium dioxide, 1 g of sodium dodecylbenzene sulfonate, 1 g of polyvinyl alcohol, 0.5 g of polyethylene glycol, 0.8 g of resorcinol, 0.8 g of ammonium chloride, and 60 ml of deionized water, and stirred for 40 minutes to obtain an emulsion;

[0086] (3) Slowly add hydrochloric acid dropwise to the emulsion to adjust the pH of the system to 3, and heat in a constant temperature water bath at 60°C for 3 h while stirring to obtain a suspension;

[0087] (4) Finally, the suspension was cooled to room temperature and filtered, and the filter residue was washed three times with distilled water and then dried in an oven to obtain microcapsules for preparing a porous hydrophobic phosphate coating.

[0088] (5) A porous hydrophobic phosphate coating was prepared using the titanium dioxide / urea-formaldehyde resin microcapsules prepared in this example, and the preparation steps were the same as in Example 1. The contact angle and wear rate of the coating were tested, and the test results are shown in Table 1.

[0089] Comparative Example 1

[0090] (1) Aluminum oxide, aluminum dihydrogen phosphate, and zinc oxide were mixed in a mass ratio of 42:50:8, and magnetically stirred for 6 h. The coating was then applied to the substrate surface by brushing, and the sample was obtained after drying.

[0091] (2) The sample is placed in a vacuum tube furnace for sintering and curing, and the temperature is raised to 280°C in stages, and the temperature is kept for 1 hour each time the temperature is raised by 50°C. Finally, the furnace is cooled and the sample is taken to obtain a non-porous inorganic phosphate coating.

[0092] The contact angle and wear rate of the coating were tested, and the test results are shown in Table 1.

[0093] Table 1

[0094] Coating contact angle / ° <![CDATA[Wear rate / mm 3 ·N -1 ·s -1 > Example 1 120.01 <![CDATA[0.675×10 -6 ]]> Comparative Example 1 64.21 <![CDATA[0.805×10 -6 ]]> Example 2 119.32 <![CDATA[0.701×10 -6 ]]> Example 3 118.34 <![CDATA[0.692×10 -6 ]]> Example 4 115.47 <![CDATA[0.715×10 -6 ]]> Example 5 118.52 <![CDATA[0.704×10 -6 ]]> Example 6 119.43 <![CDATA[0.726×10 -6 ]]>

[0095] As can be seen from Table 1, after the inorganic phosphate coating is modified by the method of the present invention, the hydrophobicity and wear rate of the obtained coating are greatly improved, indicating that the present invention has successfully prepared an inorganic phosphate coating with a micro-nano structure.

[0096] Comparative Example 2

[0097] (1) Preheat a water bath to 70°C; stir 3g of urea and 6g of a 37% formaldehyde solution, add sodium hydroxide to adjust the pH to 8.5, and heat in a constant temperature water bath at 70°C for 1 hour while stirring to form a urea-formaldehyde resin prepolymer, and then cool to room temperature;

[0098] (2) The cooled urea-formaldehyde resin prepolymer was then mixed with 1.5 g of titanium dioxide, 0.2 g of sodium dodecylbenzene sulfonate, 0.2 g of polyethylene glycol, 0.2 g of resorcinol, 0.2 g of ammonium chloride, and 60 ml of deionized water, and stirred for 40 minutes to obtain an emulsion;

[0099] (3) Slowly add hydrochloric acid dropwise to the emulsion to adjust the pH of the system to 2.5, and heat in a constant temperature water bath at 60°C for 3 h while stirring to obtain a suspension;

[0100] (4) Finally, the suspension was cooled to room temperature and filtered. The filter residue was washed three times with distilled water and then dried in an oven to obtain urea-formaldehyde self-agglomerated microcapsules. The core material was not coated. Figure 7 .

[0101] Comparative Example 3

[0102] (1) 1.5 g of urea, 3 g of a 37% formaldehyde solution, and 3 g of water were stirred evenly, sodium hydroxide was added to adjust the pH to 8.5, and the mixture was heated in a constant temperature water bath at 70° C. for 1 h while stirring to form a urea-formaldehyde resin prepolymer, and then cooled to room temperature;

[0103] (2) The cooled urea-formaldehyde resin prepolymer was then mixed with 1 g of titanium dioxide, 0.2 g of sodium dodecylbenzene sulfonate, 0.2 g of Triton, 0.2 g of polyethylene glycol, and 60 ml of deionized water, and stirred for 40 minutes to obtain an emulsion;

[0104] (3) Slowly add hydrochloric acid dropwise to the emulsion to adjust the pH of the system to 3.5, and heat in a constant temperature water bath at 60°C for 4 h while stirring to obtain a suspension;

[0105] (4) Finally, the suspension was cooled to room temperature and filtered. The residue was washed three times with distilled water and then dried in an oven to obtain incompletely coated microcapsules. Figure 8 .

[0106] The present invention constructs a micro-nanostructure by incorporating titanium dioxide / urea-formaldehyde resin microcapsules into an inorganic phosphate coating. This allows the urea-formaldehyde resin, the microcapsule wall, to decompose and volatilize during the coating's sintering and curing process, while leaving the titanium dioxide core unaffected and able to fill the internal pores. This approach achieves both surface hydrophobicity and wear resistance.

[0107] The present invention adopts a vacuum dipping method to coat a titanium dioxide solution on a phosphate coating, and uses atmospheric pressure to press nanoparticles into the coating, so that the titanium dioxide and the phosphate coating are more firmly bonded, while the phosphate coating can be tightly bonded to the substrate, thereby overcoming the technical problem of easy shedding of the nanocoating in the prior art.

[0108] The preparation process of the invention is simple, the inorganic materials used are pollution-free and environmentally friendly, and the cost is low, making it more suitable for industrial production.

[0109] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, and all of these should be included in the scope of the present invention.

Claims

1. A method for preparing a porous hydrophobic phosphate coating by titanium dioxide / urea-formaldehyde resin microcapsules, characterized in that: include, Prepolymerization stage: Stir the mixture of formaldehyde solution, urea and water evenly, add alkaline solution to adjust the pH to 8-9, react at 50-70°C for 1 hour under stirring to form urea-formaldehyde resin prepolymer, and cool to room temperature; Emulsification stage: evenly mix the cooled urea-formaldehyde resin prepolymer with the aqueous solution of titanium dioxide, emulsifier and additives, and react at 50-70°C for 0.5h under stirring to obtain an emulsion; Encapsulation stage: The acid solution is added dropwise to the emulsion, the pH of the system is adjusted to 2-4, and the reaction is carried out under stirring at a temperature of 50-70°C for 2-3 hours to form the microcapsule wall and obtain a suspension; Post-treatment: The obtained suspension was cooled to room temperature and filtered, and the obtained filter residue was washed with distilled water and dried to obtain porous hydrophobic phosphate-coated microcapsules; Aluminum oxide, aluminum dihydrogen phosphate, zinc oxide, and microcapsule powder were mixed in a mass ratio of 42:50:8:5, and after magnetic stirring for 6 hours, the coating was applied to the substrate surface by brushing. After drying, the sample was obtained. The masses of aluminum oxide, aluminum dihydrogen phosphate, zinc oxide, and microcapsule powder were 8.4 g, 10 g, 1.6 g, and 1 g, respectively. The sample was placed in a vacuum tube furnace for sintering and curing, and the temperature was raised to 280°C in stages, and the temperature was kept for 1 hour each time the temperature was raised by 50°C. Finally, the furnace was cooled and the sample was taken to obtain a porous inorganic phosphate coating. Anhydrous ethanol, water, 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane and nano-titanium dioxide were mixed in a mass ratio of 18:1:1:1 and stirred at 80°C for 3 hours to fully hydrolyze to obtain a nano-titanium dioxide solution, wherein the masses of anhydrous ethanol, water, 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane and nano-titanium dioxide were 18 g, 1 g, 1 g, and 1 g, respectively; Take 10mL of nano-titanium dioxide solution in a beaker, then immerse the microporous inorganic phosphate coating into it, and use a vacuum dipping method in a vacuum drying oven to infiltrate the nano-titanium dioxide particles into the interior of the microporous coating to establish a micro-nano structure, thereby obtaining a porous hydrophobic phosphate coating with a micro-nano structure.

2. The method according to claim 1, wherein: The mass ratio of the urea, formaldehyde solution and water is 1:2:0-1.

3. The method according to claim 1 or 2, wherein: The mass content of the formaldehyde solution is 37%.

4. The method according to claim 1, wherein: The emulsifier is one or more of polyvinyl alcohol, polyethylene glycol and sodium dodecylbenzene sulfonate.

5. The method according to claim 1 or 4, wherein: The auxiliary agent is one or more of resorcinol, hydroquinone, polyethylene glycol, polypropylene glycol and ammonium chloride.

6. The method according to claim 5, wherein: The mass ratio of the titanium dioxide, the emulsifier and the auxiliary agent is 2:0.5-1:0.5-1.

7. The method according to claim 6, wherein: The mass ratio of the titanium dioxide to urea is 1:1.5-2.

8. The method according to claim 7, wherein: The alkaline solution is a sodium hydroxide aqueous solution, the acid solution is a hydrochloric acid aqueous solution, and the stirring speed is 100-300 rpm.

9. Titanium dioxide / urea-formaldehyde resin microcapsules prepared by the method described in claims 1 to 8.

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