Transparent titanium dioxide coated pigment and preparation method thereof

Abstract

The invention relates to the technical field of pigments, in particular to a transparent titanium dioxide coated pigment and a preparation method thereof. The preparation method comprises the following steps: carrying out at least one pre-adsorption modification on the particle surface of an organic pigment by using polyelectrolyte, grinding by using a ball mill to reduce the particle size of a pigment dispersion liquid to nanoscale, and carrying out a sol-gel method to obtain the transparent titanium dioxide coated pigment. According to the method, polyelectrolyte is used for carrying out pre-adsorption modification on the surface of the organic pigment, so that the surface of the pigment is charged, a layer of tetrabutyl titanate is adsorbed through the electrostatic adsorption effect, then a layer of continuous titanium dioxide film is formed on the surface of pigment particles through the hydrolysis effect of the tetrabutyl titanate, and therefore coating modification of the organic pigment is achieved. The method is simple in step, mild in condition and low in cost, the prepared pigment coating is good in transparency, and the application range of the coated pigment is expanded.

Description

Technical Field

[0001] The invention relates to the technical field of pigments, and in particular 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, a complete color spectrum, and bright tones.

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

[0004] At present, the research on the modification technology of organic pigments with inorganic materials mainly focuses on the following three directions: one is the simple blending of inorganic materials and organic pigments; the second is to use inorganic materials as the core to wrap the organic pigments on the surface of inorganic materials; the third is to use organic pigments as the core to wrap the inorganic materials on the surface of 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 the cumbersome and complicated steps. Although the sol-gel method is relatively mature, the pigment particle size obtained by the existing technical solution is relatively large and the dispersibility is poor, which makes it difficult to give full play to the original advantages of organic pigments.

[0005] In addition, the existing process for preparing inorganic material coated pigments still has defects such as complicated preparation operation process and too long cycle, which are not conducive to actual production. In particular, the particle size of pigments synthesized by current research methods is at the micron level, which makes it difficult to form a transparent pigment coating, limiting the application scope of the coated pigments. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method for preparing a transparent titanium dioxide coated pigment to solve the problems of poor weather resistance or poor dispersibility, low tinting power, and especially poor transparency of the pigment 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 method for preparing a transparent titanium dioxide coated pigment, comprising: performing at least one pre-adsorption modification on the particle surface of an organic pigment by using at least one polyelectrolyte, reducing the particle size of the pigment dispersion to nanometer level by grinding with a ball mill, and then coating the surface of the organic pigment particles with titanium dioxide by a sol-gel method to obtain the transparent titanium dioxide coated pigment.

[0009] Based on the above technical solution, the present invention can also be improved as follows.

[0010] Further, the following steps are included:

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

[0012] S2, grinding the dispersion with a ball mill until the particle size of the dispersion is nanometer-scale;

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

[0014] S4, dispersing the first paste in water, adding a cationic polyelectrolyte solution, and allowing to stand for adsorption to obtain a second dispersion;

[0015] S5, washing 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 tetrabutyl titanate ethanol solution to obtain the titanium dioxide coated pigment after reaction.

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

[0018] Furthermore, in the anionic polyelectrolyte aqueous solution, the mass percentage of 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, and after the second polyelectrolyte solution is completely added, continue the ultrasonic treatment; after the ultrasonic treatment is completed, perform the static adsorption.

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

[0023] Furthermore, 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 0.5-2h, and after the addition is completed, stirring and reacting, the reaction time is 10-18h.

[0024] The present invention also provides a transparent titanium dioxide coated pigment, which is prepared by the above method.

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

[0026] (1) The preparation method of the transparent titanium dioxide coated pigment of the present invention uses tetrabutyl titanate as a raw material and generates a titanium dioxide film by a sol-gel method to achieve inorganic material surface coating modification of the pigment;

[0027] (2) The method for preparing the transparent titanium dioxide coated pigment of the present invention controls the particle size of the pigment to 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A method for preparing a transparent titanium dioxide coated pigment is shown, and a sample is prepared using the pigment of Example 2;

[0031] Figure 2 A method for preparing a transparent titanium dioxide coated pigment, a sample diagram of the pigment prepared using Comparative Example 1;

[0032] Figure 3 This is a method for preparing a transparent titanium dioxide coated pigment, and a sample diagram of the pigment prepared using Comparative Example 2. DETAILED DESCRIPTION

[0033] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0034] The preparation method of the transparent titanium dioxide coated pigment of the present invention comprises the following steps: using at least one polyelectrolyte to pre-adsorb and modify the surface of the organic pigment particles at least once, and then forming a continuous titanium dioxide film on the surface of the organic pigment particles by a sol-gel method to obtain the titanium dioxide coated pigment. The titanium dioxide film has the function of isolating oxygen and reducing ultraviolet radiation, thereby effectively improving the light resistance, heat resistance, solvent resistance and other weather resistance properties of the modified pigment.

[0035] The prior art can only obtain covering type coated pigments due to the difficulty in controlling the pigment particle size, and the coloring power is low. The present invention controls the pigment particle size to nanometer level by grinding with a ball mill, and obtains transparent titanium dioxide coated pigments with higher coloring power.

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

[0037] S1. Dispersing an 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, wherein the mass percentage of the polyelectrolyte is 20%.

[0039] S2. Grind the dispersion using a ball mill until the particle size of the dispersion is nanometer-scale.

[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, dispersing the first paste in water, adding the cationic polyelectrolyte solution, and allowing to stand for adsorption to obtain a second dispersion.

[0043] Preferably, the cationic polyelectrolyte solution is a cationic polyelectrolyte solution of one of polydimethyldiallylammonium chloride (PDADMAC) aqueous solution, polyacrylamide aqueous solution and polyvinylamide aqueous solution, and 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, and continue the ultrasonic treatment after the PDADMAC is completely added; and perform static adsorption after the ultrasonic treatment is completed.

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

[0045] In the above steps, the two polyelectrolytes are adsorbed once. The interference of non-adsorbed polyelectrolytes is eliminated by multiple washings, which can effectively improve the adsorption degree and efficiency.

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

[0047] Preferably, the nano-titanium dioxide precursor solution is tetrabutyl titanate (TBOT) ethanol solution, and the concentration of TBOT is 0.011 mol / Lˉ0.025 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, the addition time is 0.5-2h, and after the addition is completed, stirring and reacting, the reaction time is 10-18h.

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

[0050] The titanium dioxide coated pigment of the present invention is prepared by the above method. The titanium dioxide coated pigment is a transparent coated pigment with good tinting power and transparency, and has good weather resistance properties such as light resistance, heat resistance, solvent resistance, etc.

[0051] The present invention is described in detail below through specific examples.

[0052] Example 1

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

[0054] 1) 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 500 rpm, test the particle size, and stabilize the particle size at about 100 nm.

[0056] 3) Wash the Pigment Yellow 150 PSS dispersion several times with deionized water using a high-speed centrifuge at 11,000 rpm to remove the remaining PSS aqueous solution.

[0057] 4) Disperse the washed Pigment Yellow PSS adsorbate into one portion of deionized water by mass, slowly pour one portion of PDADMAC aqueous solution into it while stirring and ultrasonicating, then ultrasonicate for 20 minutes and allow to stand for adsorption for 20 minutes.

[0058] 5) Wash the Pigment Yellow 150 PDADMAC dispersion several times with deionized water using a high-speed centrifuge at 11,000 rpm to remove the remaining PDADMAC aqueous solution.

[0059] 6) Disperse one portion of the washed Pigment Yellow PDADMAC adsorbent in 50 portions of ethanol by mass, add 10 portions of water, slowly dropwise add 40 portions of 0.011 mol / L tetrabutyl titanate ethanol solution within 2 hours while stirring, and react at room temperature for 12 hours. Centrifuge, wash, and dry to obtain titanium dioxide-coated Pigment Yellow 150.

[0060] Example 2

[0061] This embodiment adopts the method of the present invention to prepare titanium dioxide coated pigment, and the pigment used is Pigment Red 264. The specific steps are as follows:

[0062] 1) Prepare a pigment PSS dispersion by dissolving one part of PSS in four parts of aqueous solution and then adding one part of Pigment Red 264.

[0063] 2) Grind the Pigment Red 264PSS dispersion with a ball mill at 500 rpm, test the particle size, and stabilize the particle size at about 100 nm;

[0064] 3) Wash the Pigment Red 264 PSS dispersion several times with deionized water using a high-speed centrifuge at 11,000 rpm to remove the remaining PSS aqueous solution.

[0065] 4) Disperse the washed Pigment Red 264PSS adsorbate into one portion of deionized water by mass, slowly pour one portion of PDADMAC aqueous solution into it while stirring and ultrasonicating, then ultrasonicate for 20 minutes and allow to stand for adsorption for 20 minutes.

[0066] 5) Wash the Pigment Red 264 PDADMAC dispersion several times with deionized water using a high-speed centrifuge at 11,000 rpm to remove the remaining PDADMAC aqueous solution.

[0067] 6) Disperse one portion of the washed Pigment Red 264 PDADMAC adsorbate in 50 portions of ethanol by mass, add 10 portions of water, slowly dropwise add 40 portions of 0.020 mol / L ethanol solution of tetrabutyl titanate within 2 hours while stirring, react at room temperature with stirring for 18 hours, centrifuge, wash, and dry to obtain titanium dioxide-coated Pigment Red 264.

[0068] Example 3

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

[0070] 1) Dissolve one part of sodium polyacrylate in four parts of aqueous solution by mass, then add one part of phthalocyanine blue in a ratio of 15:3 to prepare a pigment sodium polyacrylate dispersion.

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

[0072] 3) Wash the pigment phthalocyanine blue 15:3 sodium polyacrylate dispersion with deionized water for multiple times at 11,000 rpm in a high-speed centrifuge to remove the remaining sodium polyacrylate aqueous solution.

[0073] 4) Disperse the washed phthalocyanine blue 15:3 sodium polyacrylate adsorbent into a portion of deionized water by mass, slowly pour in a portion of PDADMAC aqueous solution while stirring and ultrasonicating, then ultrasonicate for 20 minutes and allow to stand for adsorption for 20 minutes.

[0074] 5) Wash the pigment phthalocyanine blue 15:3 PDADMAC dispersion with deionized water for multiple times at 11,000 rpm using a high-speed centrifuge to remove the remaining PDADMAC aqueous solution.

[0075] 6) Disperse one portion of the washed phthalocyanine blue 15:3 PDADMAC adsorbent into 50 portions of ethanol by mass, add 10 portions of water, slowly dropwise add 40 portions of 0.025 mol / L tetrabutyl titanate ethanol solution within 2 hours while stirring, and react at room temperature for 10 hours. Centrifuge, wash, and dry to obtain titanium dioxide-coated phthalocyanine blue 15:3.

[0076] Example 4

[0077] This embodiment adopts the method of the present invention to prepare titanium dioxide coated pigment, and the pigment used is Pigment Green 7. The specific steps are as follows:

[0078] 1) Dissolve one part of PSS in four parts of aqueous solution by mass, and then add one part of Pigment Green 7 to prepare a pigment PSS dispersion;

[0079] 2) Grind the Pigment Green 7PSS dispersion with a ball mill at 500 rpm, test the particle size, and stabilize the particle size at about 100 nm;

[0080] 3) washing the Pigment Green 7 PSS dispersion with deionized water several times at 11,000 rpm using a high-speed centrifuge to remove the remaining PSS aqueous solution;

[0081] 4) Disperse the washed Pigment Green 7PSS adsorbate into one portion of deionized water by mass, slowly pour one portion of polyacrylamide aqueous solution into it while stirring and ultrasonicating, then ultrasonicate for 20 minutes and allow to stand for adsorption for 20 minutes;

[0082] 5) washing the Pigment Green 7 polyacrylamide dispersion with deionized water for multiple times at 11,000 rpm using a high-speed centrifuge to remove the remaining polyacrylamide aqueous solution;

[0083] 6) Disperse one portion of washed Pigment Green 7 polyacrylamide adsorbate in 50 portions of ethanol by mass, add 10 portions of water, slowly dropwise add 40 portions of 0.011 mol / L tetrabutyl titanate ethanol solution within 2 hours while stirring, and react at room temperature for 12 hours. Centrifuge, wash, and dry to obtain titanium dioxide-coated Pigment Green 7.

[0084] Example 5

[0085] This embodiment adopts the method of the present invention to prepare titanium dioxide coated pigment, and the pigment used is Pigment Red 149. The specific steps are as follows:

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

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

[0088] 3) Wash the Pigment Red 149 PSS dispersion several times with deionized water using a high-speed centrifuge at 11,000 rpm to remove the remaining PSS aqueous solution.

[0089] 4) Disperse the washed Pigment Red 149PSS adsorbate into one portion of deionized water by mass, slowly pour one portion of poly(ethylene amide) aqueous solution into it while stirring and ultrasonicating, then ultrasonicate for 20 minutes and allow to stand for adsorption for 20 minutes.

[0090] 5) Wash the Pigment Red 149 polyacrylamide dispersion several times with deionized water using a high-speed centrifuge at 11,000 rpm to remove the remaining polyacrylamide aqueous solution.

[0091] 6) Disperse one portion of washed Pigment Red 149 polyvinyl amide adsorbate in 50 portions of ethanol by mass, add 10 portions of water, slowly dropwise add 40 portions of 0.018 mol / L tetrabutyl titanate ethanol solution within 2 hours while stirring, and react at room temperature for 18 hours. Centrifuge, wash, and dry to obtain titanium dioxide-coated Pigment Red 149.

[0092] Comparative Example 1

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

[0094] 2) Wash the Pigment Red 264 PSS dispersion several times with deionized water using a high-speed centrifuge at 11,000 rpm to remove the remaining PSS aqueous solution.

[0095] 3) Disperse the washed Pigment Red 264PSS adsorbate into one portion of deionized water by mass, slowly pour one portion of PDADMAC aqueous solution into it while stirring and ultrasonicating, then ultrasonicate for 20 minutes and allow to stand for adsorption for 20 minutes.

[0096] 4) Wash the Pigment Red 264 PDADMAC dispersion several times with deionized water using a high-speed centrifuge at 11,000 rpm to remove the remaining PDADMAC aqueous solution.

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

[0098] Comparative Example 2

[0099] 1) Dissolve one part of PSS in four parts of aqueous solution by mass, and then add one part of Pigment Red 264 to prepare a pigment PSS dispersion;

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

[0101] 3) Wash the Pigment Red 264 PSS dispersion several times with deionized water using a high-speed centrifuge at 11,000 rpm to remove the remaining PSS aqueous solution.

[0102] 4) Disperse the washed Pigment Red 264PSS adsorbate into one portion of deionized water by mass, slowly add one portion of PDADMAC aqueous solution under vigorous stirring, then ultrasonicate for 20 minutes and allow to stand for adsorption for 20 minutes.

[0103] 5) Wash the Pigment Red 264 PDADMAC dispersion several times with deionized water using a high-speed centrifuge at 11,000 rpm to remove the remaining PDADMAC aqueous solution.

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

[0105] The pigments prepared in Example 2 and Comparative Examples 1 and 2 were used to prepare inks, and then reflective film samples were prepared by manual coating and thermal transfer. The test results are shown in Table 1:

[0106] Table 1 Pigment test results of Example 2, Comparative Examples 1 and 2

[0107]

[0108]

[0109] According to the test results in the above table and Figure 1 ˉ3It can be seen that the ink prepared with the pigment of Example 2 has higher tinting power and transparency.

[0110] In the description of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0111] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0112] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean 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, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

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

[0114] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, 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 a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0115] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a transparent titanium dioxide coated pigment, It is 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 generated on the surface of the organic pigment particles by a sol-gel method to obtain the titanium dioxide coated pigment.

2. A method for preparing a transparent titanium dioxide coated pigment according to claim 1, It is characterized in that The following steps are involved: 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; S3, washing away the free first 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; S5, washing away the free cationic polyelectrolyte in the second dispersion to obtain a second paste; S6. Mix the second paste with ethanol and water, and then add tetrabutyl titanate solution to obtain the titanium dioxide coated pigment after reaction.

3. A method for preparing a transparent titanium dioxide coated pigment according to claim 2, It is 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.

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

5. A method for preparing a transparent titanium dioxide coated pigment according to claim 3, It is characterized in that In the cationic polyelectrolyte aqueous solution, the mass fraction of the cationic polyelectrolyte is 5%-10%.

6. A method for preparing a transparent titanium dioxide coated pigment according to any one of claims 1 to 5, It is characterized in that In step S2, the particle size of the dispersion is 100-200 nm.

7. A method for preparing a transparent titanium dioxide coated pigment according to any one of claims 1 to 5, It is characterized in that In step S4, the specific method of adding the second polyelectrolyte solution is to perform ultrasonic treatment while stirring, and continue the ultrasonic treatment after the second polyelectrolyte solution is completely added; after the ultrasonic treatment is completed, the static adsorption is performed.

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

9. A method for preparing a transparent titanium dioxide coated pigment according to claim 8, It is characterized in that In step S6, 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 0.5-2h, and after the addition is completed, stirring and reacting, the reaction time is 10-18h.

10. A transparent titanium dioxide coated pigment, It is characterized in that The method is prepared according to any one of claims 1 to 9.

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