Titanium dioxide for high light-resistant laminated paper and preparation method thereof

Abstract

The present invention discloses a titanium dioxide powder for highly light-resistant laminated paper and a preparation method thereof. The titanium dioxide powder comprises a titanium dioxide substrate and a coating layer located on the surface of the titanium dioxide substrate. The coating layer comprises, from the inside out, a silicon phosphate film layer, a zinc phosphate film layer, and an aluminum oxide film layer. The titanium dioxide powder provided herein, with a three-layer coating of silicon phosphate, zinc phosphate, and aluminum oxide, significantly improves its dispersibility and light resistance, making it suitable for use in laminated paper.

Description

Technical Field

[0001] The invention belongs to the technical field of titanium dioxide preparation, and particularly relates to titanium dioxide for high-light-resistant laminated paper and a preparation method thereof. Background Art

[0002] Titanium dioxide pigments are widely used in coatings, plastics, papermaking, inks and other fields, and papermaking is one of its important application fields; paper is the third largest user of titanium dioxide. In the papermaking field, decorative paper is the one that uses the most titanium dioxide, and its titanium dioxide usage can reach 45%. Titanium dioxide for decorative paper should have good hiding power, weather resistance (anti-powdering ability), color fastness, and water dispersibility to ensure that the decorative paper has excellent performance. However, there are some photoactivated points on the surface of titanium dioxide powder particles. When exposed to sunlight (mainly in the near-ultraviolet spectrum) in the presence of moisture, the oxygen ions on its lattice will lose two electrons and become oxygen atoms, and the released electrons are Ti 4+ Captured and reduced to Ti 3+ The new ecological oxygen released by the above-mentioned photochemical reaction is extremely active and can oxidize the melamine in the laminated paper, causing the polymer chain to break and degrade. The photochemical activity of titanium dioxide is the inherent reason for the reduced weather resistance of decorative paper.

[0003] Publication No. CN108929574A discloses a method for preparing titanium dioxide specifically for papermaking. The titanium dioxide coating formed on the surface of the titanium dioxide has a three-layer structure, with the innermost layer being a cerium compound, the middle layer being zirconium oxide, and the outer layer being an aluminum oxide layer. Although the titanium dioxide pigment obtained by this method has high light resistance and hiding power, the coating process uses zirconium compounds, which is relatively costly.

[0004] Publication number CN102585559A discloses a method for preparing titanium dioxide for decorative paper. The coating layer of the method is composed of silicon oxide, aluminum phosphate, aluminum oxide and an organic treatment layer. Although the obtained titanium dioxide has high hiding power, its light resistance is poor. Summary of the Invention

[0005] The purpose of the present invention is to provide a titanium dioxide for high light-resistant laminated paper and a preparation method thereof in order to solve the deficiencies of the prior art.

[0006] The purpose of the present invention is achieved by the following technical solutions:

[0007] A titanium dioxide for highly light-resistant laminated paper comprises a titanium dioxide substrate and a coating layer located on the surface of the titanium dioxide substrate, wherein the coating layer comprises, from the inside to the outside, a silicon phosphate film layer, a zinc phosphate film layer and an aluminum oxide film layer.

[0008] Preferably, the silicon phosphate film layer is formed by reacting a silicon source and a phosphoric acid source in a titanium dioxide-based material slurry at a pH of 2 to 5.

[0009] Preferably, the amount of the silicon source is 2.0-3.0% of the mass of the titanium dioxide substrate in terms of SiO2; the amount of the phosphoric acid source is based on adjusting the pH of the titanium dioxide-based material slurry to which the silicon source is added to be 2-5.

[0010] Preferably, the zinc phosphate film layer is formed by reacting a zinc source and a phosphoric acid source in a titanium dioxide-based material slurry at a pH of 4 to 6.

[0011] Preferably, the amount of the zinc source, calculated as ZnO, is 1.0-2.0% of the mass of the titanium dioxide substrate; the amount of the phosphoric acid source, calculated as P2O5, is 1.0-3.0% of the mass of the titanium dioxide substrate.

[0012] Preferably, the aluminum oxide film layer is formed by first adjusting the pH of the titanium dioxide-based material slurry to 1.0-3.0 using an aluminum source at a temperature of 30-50° C., then adjusting the pH to 9.0-10.0 after aging, and then aging again.

[0013] The method for preparing the titanium dioxide for high lightfastness laminated paper as described above comprises the following steps:

[0014] An uncoated titanium dioxide-based material slurry is coated with a silicon phosphate film layer, a zinc phosphate film layer and an aluminum oxide film layer in sequence to obtain the titanium dioxide for high light-resistant laminated paper.

[0015] Preferably, the silicon phosphate film coating step is:

[0016] The temperature of the titanium dioxide-based material slurry is adjusted to 70-90°C, and then a silicon source is first added, and then a phosphoric acid source is added to adjust the pH of the slurry to 2-5, and the silicon phosphate film layer is formed after aging; the amount of the silicon source is calculated as SiO2, which is 2.0-3.0% of the mass of the titanium dioxide substrate; the amount of the phosphoric acid source is based on adjusting the pH of the titanium dioxide-based material slurry to 2-5 after adding the silicon source.

[0017] Preferably, the zinc phosphate film coating step is:

[0018] A zinc source and a phosphoric acid source are added simultaneously to a titanium dioxide-based material slurry coated with a silicon phosphate film layer, and then the pH of the slurry is adjusted to 4-6. The zinc phosphate film layer is formed after aging; the amount of the zinc source, calculated as ZnO, is 1.0-2.0% of the mass of the titanium dioxide substrate; the amount of the phosphoric acid source, calculated as P2O5, is 1.0-3.0% of the mass of the titanium dioxide substrate.

[0019] Preferably, the aluminum oxide film coating step is:

[0020] First, the temperature of the titanium dioxide-based material slurry coated with a silicon phosphate film layer and a zinc phosphate film layer is adjusted to 30-50°C, and then an aluminum source is added to adjust the slurry pH to 1.0-3.0. After aging, an aluminum source is added again to adjust the slurry pH to 9.0-10.0, and aging is performed again to form an aluminum oxide film layer.

[0021] The titanium dioxide provided in this application adopts a three-layer coating of silicon phosphate, zinc phosphate and aluminum oxide, which can significantly improve the dispersibility and light resistance of titanium dioxide and is suitable for use in laminated paper. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a graph showing the isoelectric point test results of the titanium dioxide obtained in Examples 1 to 5 and Comparative Examples 1 to 2 of the present application. DETAILED DESCRIPTION

[0023] The present invention provides a titanium dioxide for highly light-resistant laminated paper, comprising a titanium dioxide substrate and a coating layer located on the surface of the titanium dioxide substrate, wherein the coating layer comprises, from the inside to the outside, a silicon phosphate film layer, a zinc phosphate film layer and an aluminum oxide film layer.

[0024] The present invention adopts a three-layer hamburger-style coating. First, silicon phosphate is coated on the surface of the titanium dioxide substrate. On the one hand, it improves the dispersibility of titanium dioxide and enhances its dispersibility in water; on the other hand, it can block the photoactivated points of titanium dioxide and improve its light resistance; thirdly, the phosphate particles PO4 in the silicon phosphate 3- Will be generated during the exposure process Ti 3+ The reaction generates phosphite PO3 3- , phosphite and hydroxyl radicals react to form hydrogen phosphate ions HPO4 2- , thereby capturing highly active hydroxyl radicals, preventing hydroxyl radicals from degrading organic matter, and enhancing the light resistance of TiO2; secondly, it is coated with a layer of zinc phosphate film, which has good UV resistance and good adhesion, and can adhere to the surface of the titanium dioxide substrate to block oxygen from contacting the titanium dioxide surface; finally, the aluminum oxide film layer can improve the dispersibility of titanium dioxide, help to increase the retention rate of titanium dioxide, and thus improve the light resistance of the product.

[0025] In the prior art (such as CN102585559A, a method for preparing titanium dioxide for decorative paper, as described in the background art), a layer of silicon oxide is generally coated on the surface of the titanium dioxide substrate. Specifically, amorphous silicon oxide hydrate is generated, which is firmly bonded to the surface of the TiO2 particles with hydroxyl groups, thereby protecting the titanium dioxide from chemical erosion and improving its light resistance. The silicon phosphate coating of the present application can form short chains of -0-PO-Si-OP- in the slurry solution. As the film layer is deposited, these short chains aggregate into long chains to form a network. It has a high surface affinity for titanium dioxide pigment and completely covers it, which can improve the dispersibility and hiding power of titanium dioxide. In addition, as mentioned in the previous paragraph, the phosphate ion PO4 3- Will be generated during the exposure process Ti 3+ The reaction generates phosphite PO3 3- , phosphite and hydroxyl radicals react to form hydrogen phosphate ions HPO4 2- , thereby capturing highly active hydroxyl radicals, preventing them from degrading organic matter and enhancing the light resistance of TiO2. Therefore, the silicon phosphate film of this application can further improve the light resistance, dispersibility, and hiding power of titanium dioxide compared to conventional silicon oxide films.

[0026] The present application uses zinc phosphate on the outer surface of the silicon phosphate film layer to replace the aluminum phosphate recorded in the background technology CN102585559A. In addition to the function of aluminum phosphate in capturing hydroxyl radicals to prevent oxidative degradation, zinc phosphate also has good adhesion and can adhere to the surface of the titanium dioxide base material to block the contact between oxygen and the titanium dioxide surface. In addition, zinc phosphate also has good UV resistance. The electrons in its valence band can accept the energy in the ultraviolet light to undergo transition, absorb ultraviolet light, and further improve light resistance.

[0027] Preferably, the silicon phosphate film layer is formed by reacting a silicon source and a phosphoric acid source in a titanium dioxide-based material slurry at a pH of 2 to 5. More preferably, the silicon source is added first, followed by the phosphoric acid source. Silicic acid sources such as sodium silicate and potassium silicate are alkaline. After the phosphoric acid source is added to adjust the pH, the solution first generates silica hydroxide sol. As the pH decreases to below 5, the silica hydroxide sol reacts with phosphoric acid to generate silicon phosphate.

[0028] Preferably, the amount of silicon source is 2.0-3.0% of the mass of the titanium dioxide substrate in terms of SiO2; the amount of phosphoric acid source is based on adjusting the pH of the titanium dioxide-based material slurry to which the silicon source is added to be 2-5.

[0029] Preferably, the zinc phosphate film is formed by reacting a zinc source and a phosphate source in a titanium dioxide-based material slurry at a pH of 4 to 6. At a pH of 4 to 6, phosphate radicals and zinc ions react to form zinc phosphate precipitates, which are deposited on the surface of the silicon phosphate film to form the zinc phosphate film.

[0030] Preferably, the amount of the zinc source, calculated as ZnO, is 1.0-2.0% of the mass of the titanium dioxide substrate; the amount of the phosphoric acid source, calculated as P2O5, is 1.0-3.0% of the mass of the titanium dioxide substrate.

[0031] Preferably, the aluminum oxide film layer is formed by first adjusting the pH of the titanium dioxide-based material slurry to 1.0-3.0 using an aluminum source at a temperature of 30-50° C., then adjusting the pH to 9.0-10.0 after aging, and then aging again.

[0032] Under normal conditions, the outermost layer of titanium dioxide is generally coated with pseudo-boehmite alumina to improve the dispersibility of titanium dioxide. The coating temperature is generally greater than 50°C, and the coating is generally performed by adding aluminum salts and pH regulators in parallel to maintain the pH at 7.0-9.0. However, the present application preferably uses low-temperature, downstream, high-pH conditions to deposit the aluminum oxide film. Compared with the existing technology, this can form a more stable pseudo-boehmite alumina, avoid aggregation after coating, improve the covering power of the coated aluminum layer, and reduce the exposure of silicon phosphate and zinc phosphate. This can give full play to the advantage of the isoelectric point of Al(OH)3, increase the isoelectric point of titanium dioxide, improve retention rate, and thus improve the light resistance of the product.

[0033] Specifically, alumina is deposited under high pH conditions (9.5-10.0), because the particle surface adsorbs more OH - Negative charge is conducive to the growth and orderly increase of powder particles, and the high pH value of Al(OH)3 and OH - Reaction to form Al(OH)4 - , solubility increases, this process is similar to recrystallization, and thus is conducive to improving crystallinity. At low pH values, the particle surface is positively charged, which can separate the electrostatic repulsion and is not conducive to particle growth, resulting in the powder presenting small particles of amorphous precipitation. However, under high pH conditions (9.5-10.0), if high temperature deposition is performed, Bayerite crystals are likely to appear, which will deteriorate the performance of the pigment. Therefore, under high pH conditions, the temperature needs to be lowered to form pseudo-boehmite alumina to improve dispersibility.

[0034] The present application also provides a method for preparing the titanium dioxide for high lightfastness laminated paper as described above, comprising the following steps:

[0035] An uncoated titanium dioxide-based material slurry is coated with a silicon phosphate film layer, a zinc phosphate film layer and an aluminum oxide film layer in sequence to obtain titanium dioxide for highly light-resistant laminated paper.

[0036] Preferably, the concentration of the titanium dioxide-based material slurry is 300-350 g / L, and the titanium dioxide slurry can be prepared by sulfuric acid method or chloride method.

[0037] Preferably, the silicon phosphate film coating step is:

[0038] The temperature of the titanium dioxide-based material slurry is adjusted to 70-90°C, and then a silicon source is first added, followed by a phosphoric acid source to adjust the slurry pH to 2-5. After aging, a silicon phosphate film layer is formed; the silicon source is used in an amount of 2.0-3.0% of the mass of the titanium dioxide substrate, calculated as SiO2; the phosphoric acid source is used in an amount based on the pH of the titanium dioxide-based material slurry after the silicon source is added, adjusted to 2-5. The silicon source is preferably sodium silicate and / or potassium silicate, and is preferably added in the form of a solution with a concentration of 100-150 g / L, calculated as SiO2. The silicon source is preferably added for 20-40 minutes, and the aging time for forming the silicon phosphate film layer is preferably 20-40 minutes. Phosphoric acid is preferably used as the phosphoric acid source.

[0039] Preferably, the zinc phosphate film coating step is:

[0040] A zinc source and a phosphate source are simultaneously added to a titanium dioxide-based material slurry coated with a silicon phosphate film. The slurry pH is then adjusted to 4-6, and the zinc phosphate film is formed after aging. The zinc source is used in an amount of 1.0-2.0% by weight of the titanium dioxide substrate, calculated as ZnO; the phosphate source is used in an amount of 1.0-3.0% by weight of the titanium dioxide substrate, calculated as P2O5. The zinc source is preferably ZnCl2 or ZnSO4, and is preferably added as a solution. The concentration of the solution is preferably 100-120 g / L, calculated as ZnO. The phosphate source is preferably Na2HPO4, Na3PO4, (NaPO3)6, Na4P2O7, etc., and is preferably added as a solution. The concentration is preferably 100-120 g / L, calculated as P2O5. The zinc source and phosphate source are preferably added for 40-60 minutes, and the aging time for forming the zinc phosphate film is preferably 20-40 minutes.

[0041] Preferably, the aluminum oxide film coating step is:

[0042] First, the temperature of the titanium dioxide-based material slurry coated with a silicon phosphate film layer and a zinc phosphate film layer is adjusted to 30-50°C. Then, an aluminum source is added to adjust the slurry pH to 1.0-3.0. The aluminum source is preferably added for 30-60 minutes. After aging for 20-40 minutes, the aluminum source is added again to adjust the slurry pH to 9.0-10.0. The aluminum source is preferably added for 30-60 minutes, and aging is performed again to form an aluminum oxide film layer. The aluminum source is preferably aluminum sulfate or sodium metaaluminate. When added, it is preferably added in the form of a solution. The concentration of the solution is preferably 150-180 g / L in terms of Al2O3.

[0043] Preferably, after the aluminum oxide coating, the following steps are further included:

[0044] The pH of the slurry is adjusted to 5.0-6.0, and the slurry is aged for 1.5-2.5 hours. The aged slurry is then washed with water, flashed, and steam-powdered to obtain titanium dioxide. The pH of the slurry is adjusted to a weak acidic state to facilitate water washing.

[0045] Example 1

[0046] The slurry with qualified sand-milling particle size is introduced into the coating tank, and the slurry concentration is controlled to 300g / L (in terms of TiO2), and the temperature is raised to 80°C at the same time; 2.0% NaSiO3 (in terms of SiO2) is added within 40 minutes and homogenized for 30 minutes; H3PO4 is added to adjust the pH to 3.0, adjusted for 50 minutes, and homogenized for 30 minutes; 1.0% ZnCl2 and 1.5% Na2HPO4 solutions are added simultaneously within 60 minutes and homogenized for 20 minutes; H2SO4 is used to adjust the pH to 5.0, which is completed within 40 minutes and homogenized for 30 minutes; the temperature is lowered to 40°C; aluminum sulfate is added within 40 minutes to adjust the pH to 1.5, and homogenized for 30 minutes; sodium aluminate is added within 40 minutes to adjust the pH to 9.5, and homogenized for 30 minutes; pH is adjusted to 5.5 with dilute H2SO4, adjusted for 30 minutes, and homogenized for 120 minutes; the product is obtained by water washing, flash evaporation, and steam powder.

[0047] Example 2

[0048] The slurry with qualified sand-milling particle size is introduced into the coating tank, and the slurry concentration is controlled to 300g / L (in terms of TiO2), and the temperature is raised to 80°C at the same time; 2.5% NaSiO3 (in terms of SiO2) is added within 40 minutes and homogenized for 30 minutes; H3PO4 is added to adjust the pH to 3.0, adjusted for 50 minutes, and homogenized for 30 minutes; 1.5% ZnCl2 and 2.3% Na2HPO4 solutions are added simultaneously within 60 minutes and homogenized for 20 minutes; H2SO4 is used to adjust the pH to 5.0, which is completed within 40 minutes and homogenized for 30 minutes; the temperature is lowered to 40°C; aluminum sulfate is added within 40 minutes to adjust the pH to 2.0, and homogenized for 30 minutes; sodium aluminate is added within 40 minutes to adjust the pH to 9.5, and homogenized for 30 minutes; pH is adjusted to 5.5 with dilute H2SO4, adjusted for 30 minutes, and homogenized for 120 minutes; the product is obtained by water washing, flash evaporation, and steam powder.

[0049] Example 3

[0050] The slurry with qualified sand-milling particle size is introduced into the coating tank, and the slurry concentration is controlled to 300g / L (in terms of TiO2), and the temperature is raised to 80°C at the same time; 3.0% NaSiO3 (in terms of SiO2) is added within 40 minutes and homogenized for 30 minutes; H3PO4 is added to adjust the pH to 3.0, adjusted for 50 minutes, and homogenized for 30 minutes; 2.0% ZnCl2 and 3.0% Na2HPO4 solutions are added simultaneously within 60 minutes and homogenized for 20 minutes; H2SO4 is used to adjust the pH to 5.0, and the adjustment is completed within 40 minutes, and homogenized for 30 minutes; the temperature is lowered to 40°C; Al2(SO4)3 is added within 40 minutes to adjust the pH to 2.0, and homogenized for 30 minutes; NaAlO2 is added within 40 minutes to adjust the pH to 10.0, and homogenized for 30 minutes; pH is adjusted to 5.5 with dilute H2SO4, adjusted for 30 minutes, and homogenized for 120 minutes; the product is obtained by water washing, flash evaporation, and steam powder.

[0051] Example 4

[0052] The slurry with qualified sand-milling particle size is introduced into the coating tank, and the slurry concentration is controlled to 300g / L (in terms of TiO2), and the temperature is raised to 80°C at the same time; 2.5% NaSiO3 (in terms of SiO2) is added within 40 minutes and homogenized for 30 minutes; H3PO4 is added to adjust the pH to 2.0, adjusted for 50 minutes, and homogenized for 30 minutes; 1.5% ZnCl2 and 2.3% Na2HPO4 solutions are added simultaneously within 60 minutes and homogenized for 20 minutes; H2SO4 is used to adjust the pH to 4.0, which is completed within 40 minutes and homogenized for 30 minutes; the temperature is lowered to 40°C; aluminum sulfate is added within 40 minutes to adjust the pH to 2.0, and homogenized for 30 minutes; sodium metaaluminate is added within 40 minutes to adjust the pH to 9.5, and homogenized for 30 minutes; pH is adjusted to 5.5 with dilute H2SO4, adjusted for 30 minutes, and homogenized for 120 minutes; the product is obtained by water washing, flash evaporation, and steam powder.

[0053] Example 5

[0054] The slurry with qualified sand-milling particle size is introduced into the coating tank, and the slurry concentration is controlled to 300g / L (in terms of TiO2), and the temperature is raised to 80°C at the same time; 2.5% NaSiO3 (in terms of SiO2) is added within 40 minutes and homogenized for 30 minutes; H3PO4 is added to adjust the pH to 5.0, adjusted for 50 minutes, and homogenized for 30 minutes; 1.5% ZnCl2 and 2.3% Na2HPO4 solutions are added simultaneously within 60 minutes and homogenized for 20 minutes; H2SO4 is used to adjust the pH to 6.0, which is completed within 40 minutes and homogenized for 30 minutes; the temperature is lowered to 40°C; aluminum sulfate is added within 40 minutes to adjust the pH to 2.0, and homogenized for 30 minutes; sodium aluminate is added within 40 minutes to adjust the pH to 9.5, and homogenized for 30 minutes; pH is adjusted to 5.5 with dilute H2SO4, adjusted for 30 minutes, and homogenized for 120 minutes; the product is obtained by water washing, flash evaporation, and steam powder.

[0055] Comparative Example 1 (using silicon oxide, aluminum phosphate and aluminum oxide coating)

[0056] The slurry with qualified sand-grinding particle size is introduced into the coating tank, and the slurry concentration is controlled to 300g / L (calculated as TiO2). At the same time, the temperature is raised to 80℃; 2.0% NaSiO3 (calculated as SiO2) is added within 30min and homogenized for 30min; dilute H2SO4 solution is adjusted to pH = 7.0, adjusted for 60min, and homogenized for 30min; dilute H2SO4 solution is adjusted to pH = 6.0, adjusted for 20min, and homogenized for 30min; 1.5% H3PO4 is added within 45min. 4 solution and NaAlO2 solution, keep the pH = 6.0 in parallel, and homogenize for 30 minutes; adjust the pH of the slurry to 8.2 with dilute NaOH solution, adjust for 30 minutes, and homogenize for 30 minutes; add 3.5% NaAlO2 solution and dilute H2SO4 solution within 90 minutes, keep the pH = 8.2 in parallel, and homogenize for 30 minutes; adjust the pH = 5.5 with dilute H2SO4, adjust for 30 minutes, and homogenize for 120 minutes; wash with water, flash evaporation, and steam powder to obtain the product.

[0057] Comparative Example 2 (compared with Example 1, using conventional alumina coating)

[0058] The slurry with qualified sand-milling particle size is introduced into the coating tank, and the slurry concentration is controlled to 300g / L (in terms of TiO2), and the temperature is raised to 80°C at the same time; 2.0% NaSiO3 (in terms of SiO2) is added within 40 minutes and homogenized for 30 minutes; H3PO4 is added to adjust the pH to 3.0, adjusted for 50 minutes, and homogenized for 30 minutes; 1.0% ZnCl2 and 1.5% Na2HPO4 solutions are added simultaneously within 60 minutes and homogenized for 20 minutes; H2SO4 is used to adjust the pH to 5.0, which is completed within 40 minutes and homogenized for 30 minutes; the pH of the slurry is adjusted to 8.2 with dilute NaOH solution, adjusted for 30 minutes, and homogenized for 30 minutes; 3.5% NaAlO2 solution and dilute H2SO4 solution are added within 90 minutes, maintaining the pH at 8.2 in parallel, and homogenized for 30 minutes; the pH is adjusted to 5.5 with dilute H2SO4, adjusted for 30 minutes, and homogenized for 120 minutes; the product is obtained by water washing, flash evaporation, and steam powder.

[0059] The light resistance and isoelectric point of the titanium dioxide obtained in Examples 1 to 5 and Comparative Examples 1 to 2 of the present application were measured by conventional methods. The results are shown in Tables 1 and Figure 1 shown.

[0060] 1. Lightfastness results of Examples and Comparative Examples (Comparison of Examples and Comparative Papermaking):

[0061] Table 1

[0062] sample Average ΔE / 120h Comparative Example 1 3.52 Comparative Example 2 3.21 Example 1 2.88 Example 2 2.46 Comparative Example 3 2.05 Example 4 2.50 Comparative Example 5 2.37

[0063] 2. Isoelectric point of Examples and Comparative Examples:

[0064] from Figure 1 It can be seen that the isoelectric point of the titanium dioxide prepared by the present invention shifts to the right, which helps to improve the retention rate of titanium dioxide in papermaking. The data in Table 1 also proves that the light resistance of the titanium dioxide prepared by the present invention in papermaking is better than that of the control example.

[0065] Although preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they are aware of the basic inventive concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the invention. Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the invention. Thus, the present invention is intended to include such changes and modifications as fall within the scope of the claims and their equivalents.

Claims

1. A titanium dioxide for high lightfastness laminated paper, characterized in that: The invention comprises a titanium dioxide substrate and a coating layer located on the surface of the titanium dioxide substrate, wherein the coating layer comprises, from the inside to the outside, a silicon phosphate film layer, a zinc phosphate film layer and an aluminum oxide film layer; The aluminum oxide film layer is formed by the following steps: First, the temperature of the titanium dioxide-based material slurry coated with a silicon phosphate film layer and a zinc phosphate film layer is adjusted to 30~50°C, and then an aluminum source is added to adjust the slurry pH to 1.0~3.

0. After aging, an aluminum source is added again to adjust the slurry pH to 9.0~10.0, and aging is performed again.

2. The titanium dioxide for highly light-resistant laminated paper according to claim 1, wherein The silicon phosphate film layer is formed by reacting a silicon source and a phosphoric acid source in a titanium dioxide-based material slurry under a pH condition of 2-5.

3. The titanium dioxide for high lightfastness laminated paper according to claim 2, wherein: The amount of the silicon source is calculated as SiO2, which is 2.0-3.0% of the mass of the titanium dioxide substrate; the amount of the phosphoric acid source is based on adjusting the pH of the titanium dioxide-based material slurry to which the silicon source is added to be 2-5.

4. The titanium dioxide for high lightfastness laminated paper according to claim 1, wherein The zinc phosphate film layer is formed by the reaction of a zinc source and a phosphoric acid source in a titanium dioxide-based material slurry under a pH condition of 4-6.

5. The titanium dioxide for highly light-resistant laminated paper according to claim 4, wherein The amount of the zinc source, calculated as ZnO, is 1.0-2.0% of the mass of the titanium dioxide substrate; the amount of the phosphoric acid source, calculated as P2O5, is 1.0-3.0% of the mass of the titanium dioxide substrate.

6. The method for preparing titanium dioxide for highly light-resistant laminated paper according to any one of claims 1 to 5, wherein: The following steps are involved: An uncoated titanium dioxide-based material slurry is coated with a silicon phosphate film layer, a zinc phosphate film layer and an aluminum oxide film layer in sequence to obtain the titanium dioxide for high light-resistant laminated paper.

7. The method for preparing titanium dioxide for highly light-resistant laminated paper according to claim 6, wherein: The silicon phosphate film coating step is: The temperature of the titanium dioxide-based material slurry is adjusted to 70-90°C, and then a silicon source is added first, and then a phosphoric acid source is added to adjust the pH of the slurry to 2-5, and the silicon phosphate film layer is formed after aging; the amount of the silicon source is calculated as SiO2, which is 2.0-3.0% of the mass of the titanium dioxide substrate; the amount of the phosphoric acid source is based on adjusting the pH of the titanium dioxide-based material slurry to 2-5 after adding the silicon source.

8. The method for preparing titanium dioxide for highly light-resistant laminated paper according to claim 6, wherein: The zinc phosphate film coating step is: A zinc source and a phosphoric acid source are added simultaneously to a titanium dioxide-based material slurry coated with a silicon phosphate film layer, and then the pH of the slurry is adjusted to 4-6. After aging, the zinc phosphate film layer is formed; the amount of the zinc source, calculated as ZnO, is 1.0-2.0% of the mass of the titanium dioxide substrate; the amount of the phosphoric acid source, calculated as P2O5, is 1.0-3.0% of the mass of the titanium dioxide substrate.

9. The method for preparing titanium dioxide for highly light-resistant laminated paper according to claim 6, wherein: The aluminum oxide film coating step is: First, the temperature of the titanium dioxide-based material slurry coated with a silicon phosphate film layer and a zinc phosphate film layer is adjusted to 30~50°C, and then an aluminum source is added to adjust the slurry pH to 1.0~3.

0. After aging, an aluminum source is added again to adjust the slurry pH to 9.0~10.0, and then aging is performed again to form an aluminum oxide film layer.

Images