CN1312234C - Preparation of titanium dioxide nano water-based coating by alkali peptication process - Google Patents

Abstract

The preparation of titanium dioxide nanometer water-based paint by alkaline peptization belongs to the technical field of nanometer material preparation, and in particular relates to the preparation of titanium dioxide nanometer material. It is characterized in that it contains titanium-containing inorganic or organic matter through hydrolysis to form a hydrated ortho-titanic acid gel; the ortho-titanic acid gel is dispersed in an alkaline solution of a certain concentration, and peptization and crystallization are carried out under stirring. The step of obtaining titanium dioxide nano water-based paint. The titanium dioxide water-based coating prepared by the invention has the advantages of good crystallization performance and easy dispersion. When the coating is applied to the surface of the material, there will be no powder falling and film tearing after drying. The invention also has the advantages of simple preparation process and mild synthesis conditions. , no pollution to the environment, convenient for industrial production and so on.

Description

Preparation of Titanium Dioxide Nanoscale Waterborne Coatings by Alkaline Peptization

Technical field:

The preparation of titanium dioxide nanometer water-based paint by alkaline peptization belongs to the technical field of nanometer material preparation, and in particular relates to the preparation of titanium dioxide nanometer material.

Background technique:

TiO ₂ is a non-toxic, inexpensive new inorganic semiconductor antibacterial and purification material. Anatase and rutile belonging to the I4 ₁ /amd, P4 ₂ /mnm space group are the two most important crystal forms, both belonging to the tetragonal crystal system. The forbidden band width of anatase titanium oxide is 3.2eV. When irradiated by ultraviolet light with a wavelength of less than 387.5nm, the electrons in the valence band are excited and transition to the conduction band, leaving holes in the valence band. The valence band potential of the hole is about 3.0V (vs. NHE), and it is easy to combine with the hydroxyl group adsorbed on the surface of TiO ₂ to form a hydroxyl radical (OH), which is a natural substance with a strong oxidizing ability in nature. , has a strong oxidative and bactericidal effect, and can completely degrade most organic pollutants. At the same time, titanium oxide photocatalysts exhibit broad-spectrum bactericidal properties against most pathogenic microorganisms, including Gram-positive bacteria, negative bacteria, green algae, viruses (including RNA types) and tumors. Therefore, titanium dioxide has special applications in the fields of environmental governance, air purification, sterilization and self-cleaning.

The fixation of TiO ₂ is an important issue in the application process. It is a very convenient, economical and practical way to directly spray/brush the paint to form a film in various environments and material surfaces. Existing methods for preparing titanium dioxide water-based coatings mainly include: organic-inorganic composite method, peptization method, sol-gel method and the like.

The method described in Chinese Patent Publication No. CN1287144A, CN1287145A and CN1380369A overcomes the pollution problem of traditional organic solvent paints with nanometer titanium oxide and water-soluble organic emulsion paint and other filler preparations, but due to the presence of organic packages, reduces the Catalytic efficiency and activity of titania. Other coatings (such as light-cured titanium oxide) formed by compounding crystalline titanium dioxide and various organic binders and curing agents have similar shortcomings and deficiencies.

CN1295977A discloses a kind of convenient method that uses inorganic acid as phase change accelerator and debonding agent to prepare high concentration, high stability and transparent titanium dioxide sol at low temperature, the concentration of the inorganic acid used in this method is 0.05-2M, so the obtained Sol coatings are strongly acidic and are only suitable for use on acid-resistant surfaces. The method provided by CN1384165A is also an acid peptization method. By adding silicon dioxide (after hydrolysis) inorganic adhesive, the film-forming performance and hydrophilic property of the coating are improved, but it is only applicable to acid-resistant materials. In addition, due to the low peptization temperature of the above two methods, the obtained titanium dioxide crystals are too small (about 5 nm) to cause a blue shift in light absorption, which reduces their photocatalytic ability under visible light. CN1244516A Method for forming silica-titania composite coating by mixing and hydrolyzing silica sol, titanium sol and their corresponding organic precursors (titanate and silicate) at 0-90°C and pH=1-9 respectively There are the same or similar problems as CN1384165A and CN1295977A, and the mixed coating prepared under weak alkali and low temperature hydrolysis is not stable. Other titanium dioxide coatings formed by the sol-gel method using titanium organic matter have the same disadvantages and deficiencies.

The titanium dioxide ceramic paint provided by Publication No. 1169447 and its preparation method are characterized in that the titanium salt solution is heated at 50-100°C, and then treated with semi-permeable membrane dialysis, electrodialysis or ion exchange treatment, so that at least a part of the titanium salt is hydrolyzed and converted into Orthotitanic acid and TiO ₂ colloidal particles. Due to the hydrolysis at relatively low temperature in this method, the produced TiO ₂ colloidal particles are too small, which also affects its photocatalytic ability under visible light. In addition, since the pH of the water-based paint is in the range of pH2-5, which is located in the unstable region of silica sol, it is often unable to be used in combination with inorganic silica sol, and it is difficult to improve the strength and hydrophilicity of film formation.

Invention content:

The purpose of the present invention is to provide a method for preparing a well-crystallized and stably dispersed titanium dioxide nanometer water-based coating in a weak alkali system by hydrothermal peptization. The coating has good visible light catalytic activity and can be used in combination with silica sol, which is widely used in industry. The basic principle is that hydrated orthotitanic acid is intercalated and dehydrated by hydroxyl groups under hydrothermal conditions to form negatively charged colloids, and a stable colloid is formed due to electrostatic repulsion, while part of the titanyl group is hydrolyzed and crystallized. The alkaline hydrothermal peptization process can be expressed as:

[Ti(OH) ₄ (H ₂ O) ₂ ]+OH ^- [Ti(OH) ₅ (H ₂ O)] ^-1 +H ₂ O

[Ti(OH) ₅ (H ₂ O)] ^-1 +OH ^- [Ti(OH) ₆ ] ^-2 +H ₂ O

[Ti(OH) ₆ ] ^-2 TiO ₂ +2H ₂ O +2OH ^-

The method is characterized in that it contains the following steps in sequence:

1) Preparation of hydrated orthotitanic acid gel:

1.1) Prepare the titanium-containing inorganic substance into a 0.1-1.0M aqueous solution;

1.2) Warm up the solution prepared above to 10°C-70°C;

1.3) Add an inorganic base as a hydrolysis precipitant, the concentration of the inorganic base is 0.5-5M, neutralize the solution to neutral or weakly alkaline, and then obtain a hydrated ortho-titanic acid gel; use the hydrated ortho-titanic acid gel to Ionized water washing to remove impurities;

2) Hydrothermal peptization and crystallization:

2.1) Dispersing the washed orthotitanic acid gel in an alkaline solution, the concentration of the solution is 10 ^-5 -10 ^-3 M;

2.2) Under the condition of stirring, heat in water within the range of 100°C-250°C for 2-24 hours to obtain a titanium dioxide sol water-based paint.

The titanium-containing inorganic substance in the step 1.1) is one or a mixture of two or more of titanium sulfate, titanium oxysulfate, titanium tetrachloride, and ammonium fluotitanate. The inorganic base in the described 1.3) step is one or more mixtures of sodium hydroxide, potassium hydroxide, lithium hydroxide, ammoniacal liquor. The alkaline solution in said 2.1) is one or a mixture of two or more of sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonia, ethanolamine. The hydrothermal temperature range of the step 2.2) is preferably 100°C to 150°C.

Another kind of alkaline peptization method is characterized in that the method for preparing titanium dioxide nano water-based paint is that it contains the following steps successively:

1) Preparation of hydrated orthotitanic acid gel:

1.1) Prepare titanium-containing organic matter into 0.1-1.0M ethanol solution;

1.2) Warm up the solution prepared above to 10°C-70°C, and stir to obtain hydrated orthotitanic acid gel;

2) Hydrothermal peptization and crystallization:

2.1) Dispersing the above-mentioned E titanate gel in an alkaline solution, the concentration of the solution is 10 ^-5 -10 ^-3 M;

2.2) Under the condition of stirring, heat in water within the range of 100-250°C for 2-24 hours to obtain a titanium dioxide sol water-based coating;

In the second method, the titanium-containing organic matter in step 1.1) is butyl titanate or propyl titanate. The alkaline solution in said 2.1) is one or a mixture of two or more of sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonia, ethanolamine. The hydrothermal temperature range of the step 2.2) is preferably 100°C to 150°C.

Experiments have proved that the method proposed by the present invention can prepare titanium dioxide nanometer water-based coatings with good crystallization and stable dispersion, and the expected purpose is achieved.

Description of drawings:

Figure 1 is the transmission electron microscope micrograph of titanium dioxide sol prepared at a hydrothermal peptization temperature of 100°C, and the upper right corner of the photo is selected area diffraction.

Fig. 2 is a transmission electron microscope microscopic appearance of titanium dioxide sol prepared at a hydrothermal peptization temperature of 120°C.

Fig. 3 is a transmission electron microscope microscopic appearance of titanium dioxide sol prepared at a hydrothermal peptization temperature of 150°C.

Fig. 4 is a transmission electron microscope microscopic appearance of titanium dioxide sol prepared at a hydrothermal peptization temperature of 250°C.

Fig. 5 is the X-ray small-angle grazing diffraction spectrum of the titanium dioxide sol prepared by the hydrothermal peptization temperature of 100-150-250 °C after coating the glass surface at room temperature. It can be seen from the figure that the product prepared by this method is anatase titanium dioxide .

Detailed ways:

The steps of the method proposed by the present invention are as follows:

(1) Preparation of hydrated orthotitanic acid gel

Hydrated orthotitanic acid gel can be formed by hydrolyzing titanium-containing inorganic or organic substances. The titanium-containing inorganic salt and organic ester mentioned in the present invention can be titanium sulfate, titanium oxysulfate, titanium tetrachloride, ammonium fluotitanate, butyl titanate, propyl titanate. Prepare these titanium oxide precursors into 0.1-1.0 M aqueous or ethanol solutions, and stir and hydrolyze them at 10-70°C. For titanium-containing inorganic salts, add an inorganic base as a hydrolysis precipitation agent to neutralize the solution to neutral or weakly alkaline. The precipitation agent described in the present invention can be one of sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonia water or a mixture thereof, and its concentration is 0.5-5M. As for organic esters containing titanium, they can be directly hydrolyzed in aqueous solution. The orthotitanic acid gel obtained after the hydrolysis of the titanium-containing inorganic salt is washed with deionized water several times to remove the impurity ions adsorbed therein, while the titanium-containing organic ester hydrolysis obtained after the titanate gel does not contain inorganic ions , can be directly peptized.

(2) Hydrothermal peptization and crystallization

The cleaned ortho-titanic acid gel is redispersed in a certain concentration of alkaline solution, and placed in a sealed reaction vessel to carry out peptization and crystallization reactions under stirring. The peptizing base of the present invention can be one of sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonia water, ethanolamine or a mixture thereof. The concentration of the solution is 10 ^-5 -10 ^-3 M, if the concentration is too low, the peptization will not be complete; if the concentration is too high, titanate will be formed and the photocatalytic performance will be lost. The water heating temperature range is 100-250°C, and the holding time is 2-24 hours. If the hydrothermal peptization temperature is too low, the glue will not be disintegrated. If the temperature is too high, the grains of titanium dioxide will grow excessively. At the same time, the pressure of the high temperature system will increase rapidly, which is not conducive to safe production. The preferred hydrothermal temperature is 100-150°C. In this temperature range, elongated titanium oxide grains can be obtained, with a particle size of 10-20nm and a length of 50-100nm; at 150-250°C, a particle size of 40-60nm Short diameter or square grains.

(3) Colloid dilution and stabilization

The water-based paint of the present invention is obtained by diluting the white and blue titanium dioxide sol obtained by hydrothermal peptization with deionized water. In order to improve the stability of the coating and the binding force of film formation, organic or inorganic film-forming aids can be added to the titanium oxide sol of the present invention. Long strip titanium oxide sol prepared at -150℃.

The following non-limiting examples are used to further illustrate the implementation and effect of the present invention.

Example 1:

Dissolve 0.1M titanium sulfate in 200ml of deionized water, raise the temperature to 40°C, add 3M sodium hydroxide solution under vigorous stirring, and adjust the pH to 8. Wash with filtered water to remove impurity ions, redisperse the filtered and washed ortho-titanic acid gel in 10 ¹ M sodium hydroxide alkali solution, and hydrothermally peptize at 100°C for 24 hours under stirring to obtain uniformly dispersed strip-shaped oxide Titanium colloid, the grain size is 10-20nm, and the length is 200-300nm. As shown in Figure 1.

Example 2:

Dissolve 0.5M titanium sulfate in 1000 ml of deionized water, raise the temperature to 70°C, add 0.5M potassium hydroxide solution under vigorous stirring, and adjust the pH to 8. Filter and wash with water to remove impurity ions, redisperse the filtered and washed ortho-titanic acid gel in 10 ⁴ M ammonia lye, and hydrothermally peptize at 120°C for 5 hours under stirring to obtain uniformly dispersed elongated titanium oxide colloids , as shown in Figure 2.

Example 3:

Slowly titrate the mixed solution of 0.5M titanium sulfate and 0.5M titanium tetrachloride-ethanol in 1000 ml of deionized water, add 5M concentrated ammonia solution for hydrolysis at 20°C under strong stirring, and adjust the solution to neutral. Filter and wash with water to remove impurity ions, redisperse the filtered and washed titanic acid gel in 10 ^-5 M sodium hydroxide alkali solution, and hydrothermally peptize at 150°C for 3 hours under stirring to obtain uniformly dispersed titanium dioxide colloid. The particle size is 20-30nm, and the length is 30-60nm, as shown in Figure 3. Compared with Example 1 and Example 2, the grain size of titanium oxide colloid becomes thicker and shorter.

Example 4:

Add 115 ml of ethanol solution of butyl titanate directly into 10 ^-3 M ethanolamine alkali solution under strong stirring at 10°C, and hydrothermally peptize at 250°C under stirring for 2 hours to obtain uniformly dispersed titanium oxide colloids. The particle size is 30-50nm, as shown in Figure 3. Compared with Example 1, Example 2 and Example 3, the crystal grains of titanium oxide colloid have developed from elongated to thick and short.

Example 5:

The titanium oxide sol water-based coatings prepared in Examples 1-4 were sprayed on ceramic, glass, metal, plastic or wood substrates at room temperature, and dried naturally or below 200°C to form photocatalytic nano-films. The titanium oxide formed according to the preparation method provided in the embodiment of the present invention has an anatase structure by X-ray diffraction analysis, as shown in FIG. 5 .

The water-based paint prepared by the method proposed by the present invention has the following advantages:

(1) In a hydrothermal environment, titanium dioxide has good crystallization properties and is easy to disperse; titanium oxide crystals with different morphologies can be synthesized by controlling the hydrothermal temperature.

(2) The paint is stable at pH=7-10, and can be applied to almost all material surfaces, and the crystals of the paint are long strips at low temperatures, and there will be no powder falling and film tearing after drying.

(3) It has excellent compatibility with the weakly alkaline silica sol widely used in industry, and can be directly compounded with it to form good hydrophilicity and film-forming property;

(4) The raw materials of the coating are easy to obtain, the process is simple, the synthesis conditions are mild, the environment is not polluted, and it is convenient for industrialized production.

Claims (9)

1, alkaline peptization method prepares titanium dioxide nano water-based paint, is characterized in that, it contains following steps successively: 1) Preparation of hydrated orthotitanic acid gel: 1.1) Prepare the titanium-containing inorganic substance into a 0.1-1.0M aqueous solution; 1.2) Warm up the solution prepared above to 10°C-70°C; 1.3) Add an inorganic base as a hydrolysis precipitant, the concentration of the inorganic base is 0.5-5M, neutralize the solution to neutral or weakly alkaline, and then obtain a hydrated ortho-titanic acid gel; use the hydrated ortho-titanic acid gel to Ionized water washing to remove impurities; 2) Hydrothermal peptization and crystallization: 2.1) Dispersing the washed orthotitanic acid gel in an alkaline solution, the concentration of the solution is 10 ^-5 -10 ^-3 M; 2.2) Under the condition of stirring, heat in water within the range of 100°C-250°C for 2-24 hours to obtain a titanium dioxide sol water-based paint. 2, alkaline peptization method as claimed in claim 1 prepares titanium dioxide nano water-based paint, it is characterized in that, the inorganic matter containing titanium in the described 1.1) step is titanium sulfate, titanium oxysulfate, titanium tetrachloride, One or more mixtures of ammonium fluorotitanate. 3, the alkaline peptization method as claimed in claim 1 prepares titanium dioxide nano water-based paint, it is characterized in that, the inorganic base in the described 1.3) step is a combination of sodium hydroxide, potassium hydroxide, lithium hydroxide, ammoniacal liquor a mixture of two or more. 4, the alkaline peptization method as claimed in claim 1 prepares titanium dioxide nano water-based paint, is characterized in that, the alkaline solution in the described 2.1) is sodium hydroxide, potassium hydroxide, lithium hydroxide, ammoniacal liquor, ethanolamine one or a mixture of two or more. 5. The titanium dioxide nanometer water-based paint prepared by alkaline peptization method according to claim 1, characterized in that the hydrothermal temperature range of the step 2.2) is preferably 100°C-150°C. 6, alkaline peptization method prepares titanium dioxide nano water-based paint, is characterized in that, it contains following steps successively: 1) Preparation of hydrated orthotitanic acid gel: 1.1) Prepare titanium-containing organic matter into 0.1-1.0M ethanol solution; 1.2) Warm up the solution prepared above to 10°C-70°C, and stir to obtain hydrated orthotitanic acid gel; 2) Hydrothermal peptization and crystallization: 2.1) Dispersing the above-mentioned orthotitanic acid gel in an alkaline solution, the concentration of the solution is 10 ^-5 -10 ^-3 M; 2.2) Under the condition of stirring, heat in water in the range of 100-250° C. for 2-24 hours to obtain a titanium dioxide sol water-based coating. 7. The titanium dioxide nanometer water-based paint prepared by alkaline peptization method according to claim 6, characterized in that the titanium-containing organic matter in the step 1.1) is butyl titanate or propyl titanate. 8, the alkaline peptization method as claimed in claim 6 prepares titanium dioxide nano water-based paint, is characterized in that, the alkaline solution in the described 2.1) is sodium hydroxide, potassium hydroxide, lithium hydroxide, ammoniacal liquor, ethanolamine one or a mixture of two or more. 9. The titanium dioxide nanometer water-based paint prepared by alkaline peptization method as claimed in claim 6, characterized in that the hydrothermal temperature range of the step 2.2) is preferably 100°C-150°C.

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