A transparent titanium dioxide-coated pigment and its preparation method

Abstract

The present invention relates to the field of pigment technology, and in particular, to a transparent titanium dioxide coated pigment and a preparation method. The surface of organic pigment particles is pre-adsorbed and modified at least once by using a polyelectrolyte, the particle size of the pigment dispersion is reduced to nanometer level by grinding with a ball mill, and then a transparent titanium dioxide coated pigment is obtained by a sol-gel method. The method pre-adsorbs and modifies the surface of the organic pigment by using a polyelectrolyte, so that the surface of the pigment is charged, a layer of tetrabutyl titanate is adsorbed by electrostatic adsorption, and then a continuous titanium dioxide film is formed on the surface of the pigment particles by the hydrolysis of tetrabutyl titanate, thereby realizing the coating modification of the organic pigment. The method has simple steps, mild conditions, low cost, and the prepared pigment coating has good transparency, which expands the application range of the coated pigment.

Description

Technical Field

[0001] The present invention relates to the technical field of pigments, and more specifically, to a transparent titanium dioxide-coated pigment and a preparation method thereof. Background Art

[0002] Organic pigments are widely used in the ink printing industry. Organic pigments have the characteristics of bright colors, a wide variety of varieties, a complete chromatogram, and bright hues.

[0003] However, even if various anti-aging additives are added to a single organic pigment ink, it is relatively easy to age and fade in an outdoor environment with high temperature, high humidity, and high light, affecting its use. In this regard, the main technology in this field is to modify organic pigments.

[0004] Currently, the research on the technology of modifying organic pigments with inorganic materials mainly has the following three directions: one is the simple blending of inorganic materials and organic pigments; the second is using inorganic materials as the core and wrapping organic pigments on the surface of the inorganic materials; the third is using organic pigments as the core and wrapping inorganic materials on the surface of the organic pigments. The third method is the most effective modification method at present. It is mainly divided into the electrostatic self-assembly method and the sol-gel method of directly coating inorganic nanoparticles. The electrostatic self-assembly method has no industrial value due to its cumbersome and complex steps. Although the sol-gel method is relatively mature in technology, the pigments obtained by the existing technical solutions have a relatively large particle size and poor dispersibility, and it is difficult to fully exert the original advantages of organic pigments.

[0005] In addition, in the existing preparation process of inorganic material-coated pigments, there are also defects that are not conducive to actual production, such as complex preparation operation processes and too long cycles. In particular, the particle sizes of the pigments synthesized by the current research methods are all in the micron level, and it is difficult to form a transparent pigment coating, which limits the application range of the coated pigments. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a preparation method of a transparent titanium dioxide-coated pigment to solve the problems of poor weather resistance, poor dispersibility, low coloring power, especially poor transparency in the prior art.

[0007] The technical solution of the present invention to solve the above technical problems is as follows:

[0008] The present invention provides a preparation method of a transparent titanium dioxide-coated pigment, which pre-adsorbs and modifies the surface of organic pigment particles at least once with at least one polyelectrolyte, grinds the pigment dispersion with a ball mill to reduce the particle size to the nanometer level, and then coats titanium dioxide on the surface of the organic pigment particles by the sol-gel method to obtain the transparent titanium dioxide-coated pigment.

[0009] On the basis of the above technical solution, the present invention can also be improved as follows.

[0010] Furthermore, it includes the following steps:

[0011] S1. Disperse the organic pigment in an anionic polyelectrolyte solution to obtain a first dispersion;

[0012] S2. Grind the dispersion with a ball mill until the particle size of the dispersion is nanoscale;

[0013] S3. Wash away the free first polyelectrolyte in the first dispersion to obtain a first paste;

[0014] S4. Disperse the first paste in water, add a cationic polyelectrolyte solution, and obtain a second dispersion after static adsorption;

[0015] S5. Wash away the free second polyelectrolyte in the second dispersion to obtain a second paste;

[0016] S6. Mix the second paste with ethanol and water, and then add a tetrabutyl titanate ethanol solution. After reaction, obtain the titanium dioxide-coated pigment.

[0017] Furthermore, the anionic polyelectrolyte solution is an aqueous solution of sodium polystyrene sulfonate or sodium polyacrylate, and the second polyelectrolyte solution is one of an aqueous solution of polydimethyldiallylammonium chloride, an aqueous solution of polyacrylamide, and an aqueous solution of polyvinylamide.

[0018] Furthermore, in the anionic polyelectrolyte aqueous solution, the mass percentage of the anionic polyelectrolyte is 20%.

[0019] Furthermore, in the cationic polyelectrolyte aqueous solution, the mass percentage of the cationic polyelectrolyte is 5%-10%.

[0020] Furthermore, in step S2, the particle size of the dispersion is 100-200 nm.

[0021] Furthermore, in step S4, the specific method of adding the second polyelectrolyte solution is to perform ultrasonic treatment while stirring. After the second polyelectrolyte solution is completely added, continue the ultrasonic treatment; after the ultrasonic treatment ends, perform the static adsorption.

[0022] Furthermore, in step S6, the concentration of the tetrabutyl titanate ethanol solution is 0.011 mol / L-0.025 mol / L.

[0023] Further, the mass ratio of the second paste, ethanol, water, and the tetrabutyl titanate ethanol solution is 1:50:10:40; the tetrabutyl titanate ethanol solution is slowly added dropwise while stirring, and the dropping time is 0.5 - 2 h. After the dropping is completed, stir and react, and the reaction time is 10 - 18 h.

[0024] The present invention also provides a transparent titanium dioxide-coated pigment prepared by the method as described above.

[0025] The beneficial effects of the present invention are as follows:

[0026] (1) In the preparation method of the transparent titanium dioxide-coated pigment of the present invention, tetrabutyl titanate is used as a raw material, and a titanium dioxide thin film is generated by the sol-gel method to realize the surface coating modification of the inorganic material of the pigment.

[0027] (2) In the preparation method of the transparent titanium dioxide-coated pigment of the present invention, the particle size of the pigment is controlled at the nanometer level by grinding with a ball mill, so that the coated pigment has higher coloring power and transparency.

[0028] (3) The preparation method of the transparent titanium dioxide-coated pigment of the present invention has the advantages of simple steps, mild conditions, and low cost.

[0029] (4) The transparent titanium dioxide-coated pigment of the present invention has good weather resistance properties such as light resistance, heat resistance, and solvent resistance. Description of the Drawings

[0030] Figure 1 It is a sample diagram of the preparation method of the transparent titanium dioxide-coated pigment, prepared with the pigment of Example 2;

[0031] Figure 2 It is a sample diagram of the preparation method of the transparent titanium dioxide-coated pigment, prepared with the pigment of Comparative Example 1;

[0032] Figure 3 It is a sample diagram of the preparation method of the transparent titanium dioxide-coated pigment, prepared with the pigment of Comparative Example 2. Detailed Embodiments

[0033] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0034] The preparation method of the transparent titanium dioxide-coated pigment of the present invention is to pre-adsorb and modify the particle surface of the organic pigment with at least one polyelectrolyte at least once, and then generate a continuous titanium dioxide thin film on the particle surface of the organic pigment through the sol-gel method to obtain the titanium dioxide-coated pigment. This titanium dioxide thin film plays a role in isolating oxygen and reducing ultraviolet irradiation, thereby effectively improving the weather resistance of the modified pigment such as light resistance, heat resistance, and solvent resistance.

[0035] Due to the difficulty in controlling the pigment particle size in the prior art, only covering-type coated pigments can be obtained, and the coloring power is relatively low. In the present invention, the particle size of the pigment is controlled to the nanometer level by ball milling to obtain a transparent titanium dioxide-coated pigment with higher coloring power.

[0036] Preferably, the preparation method of the present invention includes the following steps:

[0037] S1. Disperse the organic pigment in an anionic polyelectrolyte solution to obtain a first dispersion.

[0038] Preferably, the first polyelectrolyte solution is an aqueous solution of sodium polystyrene sulfonate (PSS) or sodium polyacrylate, and the mass percentage of the polyelectrolyte is 20%.

[0039] S2. Grind the dispersion with a ball mill until the particle size of the dispersion reaches the nanometer level.

[0040] Preferably, the particle size of the dispersion is 100-200 nm.

[0041] S3. Wash away the PSS in the first dispersion to obtain a first paste.

[0042] S4. Disperse the first paste in water and add a cationic polyelectrolyte solution, and let it stand for adsorption to obtain a second dispersion.

[0043] Preferably, the cationic polyelectrolyte solution is one of an aqueous solution of polydimethyldiallylammonium chloride (PDADMAC), an aqueous solution of polyacrylamide, and an aqueous solution of polyvinylamide. In the cationic polyelectrolyte aqueous solution, the mass percentage of the polyelectrolyte is 5%-10%. Preferably, the specific method of adding the PDADMAC solution is to perform ultrasonic treatment while stirring. After the PDADMAC is completely added, continue the ultrasonic treatment; after the ultrasonic treatment is completed, let it stand for adsorption.

[0044] S5. Wash away the PDADMAC in the second dispersion to obtain a second paste.

[0045] In the above steps, the adsorption times of both polyelectrolytes are once. By washing multiple times to exclude the interference of unadsorbed polyelectrolytes, the adsorption degree and efficiency can be effectively improved.

[0046] S6. Mix the second paste with ethanol and water, then add the nano-titanium dioxide precursor substance solution, and obtain titanium dioxide-coated pigment after reaction.

[0047] Preferably, the nano-titanium dioxide precursor substance solution is tetrabutyl titanate (TBOT) ethanol solution, and the concentration of TBOT is 0.011 mol / L - 0.025 mol / L.

[0048] Preferably, the mass ratio of the second paste, ethanol, water and tetrabutyl titanate ethanol solution is 1:50:10:40; the tetrabutyl titanate ethanol solution is slowly added dropwise while stirring, and the dropping time is 0.5 - 2 h. After the dropping is completed, stir and react, and the reaction time is 10 - 18 h.

[0049] In the above preparation method, a ball mill is used for grinding and a centrifuge is used for washing.

[0050] A titanium dioxide-coated pigment of the present invention is prepared by the method as described above. The titanium dioxide-coated pigment is a transparent coated pigment, having good coloring power, transparency, and good weather resistance such as light resistance, heat resistance, and solvent resistance.

[0051] The present invention will be specifically described below through specific examples.

[0052] Example 1

[0053] In this example, the method of the present invention is used to prepare titanium dioxide-coated pigment, and the pigment used is Pigment Yellow 150. The specific steps are as follows:

[0054] 1) By mass, dissolve one part of PSS in four parts of aqueous solution, and then add one part of Pigment Yellow 150 to prepare a pigment PSS dispersion.

[0055] 2) Grind the Pigment Yellow 150 - PSS dispersion with a ball mill at a rate of 500 revolutions, test the particle size, and stabilize the particle size at about 100 nm.

[0056] 3) Use a high-speed centrifuge at a rate of 11000 revolutions, and wash the Pigment Yellow 150 PSS dispersion with deionized water for multiple times to remove the remaining PSS aqueous solution.

[0057] 4) By mass, disperse the washed Pigment Yellow PSS adsorbate in one part of deionized water, slowly pour one part of PDADMAC aqueous solution while stirring and ultrasonically, then ultrasonically for 20 min and stand for adsorption for 20 min.

[0058] 5) Use a high-speed centrifuge at a rate of 11000 revolutions, and wash the Pigment Yellow 150 PDADMAC dispersion with deionized water for multiple times to remove the remaining PDADMAC aqueous solution.

[0059] 6) By mass fraction, disperse one portion of the washed pigment yellow PDADMAC adsorbate into 50 portions of ethanol, then add 10 portions of water, and slowly dropwise add 40 portions of an ethanol solution of tetrabutyl titanate with a concentration of 0.011 mol / L within 2 h while stirring. Stir and react at room temperature for 12 h. Centrifuge, wash, and dry to obtain titanium dioxide-coated pigment yellow 150.

[0060] Example 2

[0061] In this example, the method of the present invention is used to prepare titanium dioxide-coated pigment, and the pigment used is pigment red 264. The specific steps are as follows:

[0062] 1) By mass fraction, dissolve one portion of PSS in four portions of aqueous solution, and then add one portion of pigment red 264 to prepare a pigment PSS dispersion.

[0063] 2) Grind the pigment red 264 PSS dispersion with a ball mill at a rate of 500 revolutions, test the particle size, and stabilize the particle size at about 100 nm.

[0064] 3) Use a high-speed centrifuge at a rate of 11,000 revolutions to wash the pigment red 264 PSS dispersion with deionized water multiple times to remove the remaining PSS aqueous solution.

[0065] 4) By mass fraction, disperse the washed pigment red 264 PSS adsorbate into one portion of deionized water, and slowly pour one portion of PDADMAC aqueous solution while stirring and ultrasonically treating, then ultrasonically treat for 20 min and let stand for adsorption for 20 min.

[0066] 5) Use a high-speed centrifuge at a rate of 11,000 revolutions to wash the pigment red 264 PDADMAC dispersion with deionized water multiple times to remove the remaining PDADMAC aqueous solution.

[0067] 6) By mass fraction, disperse one portion of the washed pigment red 264 PDADMAC adsorbate into 50 portions of ethanol, then add 10 portions of water, and slowly dropwise add 40 portions of an ethanol solution of tetrabutyl titanate with a concentration of 0.020 mol / L within 2 h while stirring. Stir and react at room temperature for 18 h. Centrifuge, wash, and dry to obtain titanium dioxide-coated pigment red 264.

[0068] Example 3

[0069] In this example, the method of the present invention is used to prepare titanium dioxide-coated pigment, and the pigment used is phthalocyanine blue 15:3. The specific steps are as follows:

[0070] 1) By mass fraction, dissolve one portion of sodium polyacrylate in four portions of aqueous solution, and then add one portion of phthalocyanine blue 15:3 to prepare a pigment sodium polyacrylate dispersion.

[0071] 2) Grind the phthalocyanine blue 15:3 sodium polyacrylate dispersion of the pigment with a ball mill at a rate of 500 revolutions, test the particle size, and stabilize the particle size at about 100 nm.

[0072] 3) Use a high-speed centrifuge at a rate of 11,000 revolutions, and wash the phthalocyanine blue 15:3 sodium polyacrylate dispersion of the pigment with deionized water multiple times to remove the remaining aqueous sodium polyacrylate solution.

[0073] 4) By mass fraction, disperse the washed phthalocyanine blue 15:3 sodium polyacrylate adsorbate into one part of deionized water, slowly pour one part of the PDADMAC aqueous solution while stirring and ultrasonically treating, then ultrasonically treat for 20 min and statically adsorb for 20 min.

[0074] 5) Use a high-speed centrifuge at a rate of 11,000 revolutions, and wash the phthalocyanine blue 15:3 PDADMAC dispersion of the pigment with deionized water multiple times to remove the remaining PDADMAC aqueous solution.

[0075] 6) By mass fraction, disperse one part of the washed phthalocyanine blue 15:3 PDADMAC adsorbate into 50 parts of ethanol, add 10 parts of water, slowly dropwise add 40 parts of an ethanol solution of 0.025 mol / L tetrabutyl titanate within 2 h while stirring, and stir and react at room temperature for 10 h. Centrifuge, wash, and dry to obtain titanium dioxide-coated phthalocyanine blue 15:3.

[0076] Example 4

[0077] This example uses the method of the present invention to prepare titanium dioxide-coated pigments. The pigment used is pigment green 7. The specific steps are as follows:

[0078] 1) By mass fraction, fully dissolve one part of PSS in four parts of an aqueous solution, and then add one part of pigment green 7 to prepare a pigment PSS dispersion;

[0079] 2) Grind the pigment green 7 PSS dispersion with a ball mill at a rate of 500 revolutions, test the particle size, and stabilize the particle size at about 100 nm;

[0080] 3) Use a high-speed centrifuge at a rate of 11,000 revolutions, and wash the pigment green 7 PSS dispersion with deionized water multiple times to remove the remaining PSS aqueous solution;

[0081] 4) By mass fraction, disperse the washed pigment green 7 PSS adsorbate into one part of deionized water, slowly pour one part of the polyacrylamide aqueous solution while stirring and ultrasonically treating, then ultrasonically treat for 20 min and statically adsorb for 20 min;

[0082] 5) Use a high-speed centrifuge to wash the Pigment Green 7 polyacrylamide dispersion multiple times with deionized water at a rate of 11,000 revolutions to remove the remaining polyacrylamide aqueous solution;

[0083] 6) By mass, disperse one part of the washed Pigment Green 7 polyacrylamide adsorbate into 50 parts of ethanol, then add 10 parts of water, and slowly dropwise add 40 parts of a 0.011 mol / L tetrabutyl titanate ethanol solution within 2 h while stirring, and stir and react at room temperature for 12 h. Centrifuge, wash, and dry to obtain titanium dioxide-coated Pigment Green 7.

[0084] Example 5

[0085] In this example, the method of the present invention is used to prepare titanium dioxide-coated pigments, and the pigment used is Pigment Red 149. The specific steps are as follows:

[0086] 1) By mass, dissolve one part of PSS in four parts of an aqueous solution, and then add one part of Pigment Red 149 to prepare a pigment PSS dispersion.

[0087] 2) Grind the Pigment Red 149 PSS dispersion with a ball mill at a rate of 500 revolutions, test the particle size, and stabilize the particle size at about 100 nm.

[0088] 3) Use a high-speed centrifuge to wash the Pigment Red 149 PSS dispersion multiple times with deionized water at a rate of 11,000 revolutions to remove the remaining PSS aqueous solution.

[0089] 4) By mass, disperse the washed Pigment Red 149 PSS adsorbate into one part of deionized water, slowly pour one part of a polyvinylamide aqueous solution while stirring and ultrasonically, then ultrasonically for 20 min, and let stand for adsorption for 20 min.

[0090] 5) Use a high-speed centrifuge to wash the Pigment Red 149 polyvinylamide dispersion multiple times with deionized water at a rate of 11,000 revolutions to remove the remaining polyvinylamide aqueous solution.

[0091] 6) By mass, disperse one part of the washed Pigment Red 149 polyvinylamide adsorbate into 50 parts of ethanol, then add 10 parts of water, and slowly dropwise add 40 parts of a 0.018 mol / L tetrabutyl titanate ethanol solution within 2 h while stirring, and stir and react at room temperature for 18 h. Centrifuge, wash, and dry to obtain titanium dioxide-coated Pigment Red 149.

[0092] Comparative Example 1

[0093] 1) By mass, dissolve one part of PSS in four parts of an aqueous solution, and then add one part of Pigment Red 264 to prepare a pigment PSS dispersion;

[0094] 2) Use a high-speed centrifuge at a speed of 11,000 revolutions to wash the Pigment Red 264 PSS dispersion with deionized water multiple times to remove the remaining PSS aqueous solution.

[0095] 3) By mass fraction, disperse the washed Pigment Red 264 PSS adsorbate into one portion of deionized water, slowly pour one portion of PDADMAC aqueous solution while stirring and ultrasonically treating, then ultrasonically treat for 20 min and let it stand for adsorption for 20 min.

[0096] 4) Use a high-speed centrifuge at a speed of 11,000 revolutions to wash the Pigment Red 264 PDADMAC dispersion with deionized water multiple times to remove the remaining PDADMAC aqueous solution.

[0097] 5) By mass fraction, disperse one portion of the washed Pigment Red 264 PDADMAC adsorbate into 50 portions of ethanol, add 10 portions of water, slowly dropwise add 40 portions of a 0.011 mol / L tetrabutyl titanate ethanol solution while stirring within 2 h, and stir and react at room temperature for 12 h. Centrifuge, wash, and dry to obtain titanium dioxide-coated Pigment Red 264.

[0098] Comparative Example 2

[0099] 1) By mass fraction, fully dissolve one portion of PSS in four portions of aqueous solution, then add one portion of Pigment Red 264 to prepare a Pigment PSS dispersion;

[0100] 2) Grind the Pigment Red 264 PSS dispersion with a ball mill at a speed of 500 revolutions, test the particle size, and stabilize the particle size at about 100 nm.

[0101] 3) Use a high-speed centrifuge at a speed of 11,000 revolutions to wash the Pigment Red 264 PSS dispersion with deionized water multiple times to remove the remaining PSS aqueous solution.

[0102] 4) By mass fraction, disperse the washed Pigment Red 264 PSS adsorbate into one portion of deionized water, slowly add one portion of PDADMAC aqueous solution under vigorous stirring, then ultrasonically treat for 20 min and let it stand for adsorption for 20 min.

[0103] 5) Use a high-speed centrifuge at a speed of 11,000 revolutions to wash the Pigment Red 264 PDADMAC dispersion with deionized water multiple times to remove the remaining PDADMAC aqueous solution.

[0104] 6) By mass fraction, disperse one portion of the washed Pigment Red 264 PDADMAC adsorbate into 50 portions of ethanol, add 10 portions of water, slowly dropwise add 40 portions of a 0.011 mol / L tetrabutyl titanate ethanol solution while stirring within 2 h, and stir and react at room temperature for 12 h. Centrifuge, wash, and dry to obtain titanium dioxide-coated Pigment Red 264.

[0105] Ink was prepared using the pigments obtained in Example 2 and Comparative Examples 1 and 2 above, and then reflective film samples were prepared by manual coating and thermal transfer. The test results are shown in Table 1:

[0106] Table 1 Test Results of the Pigments in Example 2, Comparative Example 1, and Comparative Example 2

[0107]

[0108]

[0109] According to the test results in the above table and Figure 1 ˉ3, it can be seen that the ink prepared with the pigment of Example 2 has higher tinting strength and transparency.

[0110] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0111] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0112] In the present invention, unless otherwise clearly specified and limited, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "underneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature.

[0113] In the description of this specification, the description referring to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0114] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0115] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a transparent titanium dioxide coated pigment, characterized in that: The surface of the organic pigment particles is pre-adsorbed and modified at least once by using a polyelectrolyte, the particle size of the pigment dispersion is reduced to nanometer level by grinding with a ball mill, and a continuous titanium dioxide film is formed on the surface of the organic pigment particles by a sol-gel method to obtain the titanium dioxide coated pigment; The preparation method comprises the following steps: S1, dispersing the organic pigment in an anionic polyelectrolyte solution to obtain a first dispersion; S2, grinding the dispersion with a ball mill until the particle size of the dispersion is nanometer-scale; the particle size of the dispersion is 100 nm; S3, washing away the free anionic polyelectrolyte in the first dispersion to obtain a first paste; S4, dispersing the first paste in water, adding a cationic polyelectrolyte solution, and allowing to stand for adsorption to obtain a second dispersion; The specific method of adding the cationic polyelectrolyte solution is to perform ultrasonic treatment while stirring, and continue the ultrasonic treatment after the cationic polyelectrolyte solution is completely added; and perform the static adsorption after the ultrasonic treatment is completed; S5, washing away the free cationic polyelectrolyte in the second dispersion to obtain a second paste; S6, mixing the second paste with ethanol and water, and then adding tetrabutyl titanate solution, and obtaining the titanium dioxide coated pigment after reaction; The mass ratio of the second paste, ethanol, water and the tetrabutyl titanate ethanol solution is 1:50:10:40; the tetrabutyl titanate ethanol solution is slowly added dropwise while stirring, the addition time is 0.5 to 2 hours, and after the addition is completed, stirring and reacting, the reaction time is 10 to 18 hours; The particle size of the titanium dioxide coated pigment is 168 nm.

2. The method for preparing a transparent titanium dioxide coated pigment according to claim 1, characterized in that: The anionic polyelectrolyte solution is a sodium polystyrene sulfonate aqueous solution or a sodium polyacrylate aqueous solution; the cationic polyelectrolyte solution is one of a polydimethyldiallylammonium chloride aqueous solution, a polyvinylamide aqueous solution and a polyacrylamide aqueous solution.

3. The method for preparing a transparent titanium dioxide coated pigment according to claim 2, characterized in that: In the anionic polyelectrolyte aqueous solution, the mass percentage of the anionic polyelectrolyte is 20%.

4. The method for preparing a transparent titanium dioxide coated pigment according to claim 2, characterized in that: In the cationic polyelectrolyte aqueous solution, the mass fraction of the cationic polyelectrolyte is 5%-10%.

5. A method for preparing a transparent titanium dioxide coated pigment according to any one of claims 1 to 4, characterized in that: In step S6, the concentration of the tetrabutyl titanate ethanol solution is 0.011 mol / L to 0.025 mol / L.

6. A transparent titanium dioxide coated pigment, characterized in that: The method is prepared by any one of claims 1 to 5.

Images