Preparation method of high light-resistant and high-hiding titanium dioxide pigment with flat gloss

Abstract

A method for preparing a matte, highly lightfast, and high-hiding titanium dioxide pigment comprises beating a primary rutile titanium dioxide product, dispersing it, and then grinding it. The ground slurry is heated to 70°C to 80°C and then coated. First, a first layer of dense hydrated aluminum oxide is coated on the titanium dioxide surface; second, a second layer of a mixed film of aluminum phosphate, hydrated silicon oxide, and aluminum oxide is coated on the surface of the first dense hydrated aluminum oxide film; and finally, a third layer of a reticulated boehmite hydrated aluminum oxide film is coated on the surface of the second mixed film of aluminum phosphate, hydrated silicon oxide, and aluminum oxide. The filter cake is washed, dried, and subjected to air-powder treatment to produce the product. Advantages of this method include: continuing the traditional heavy coating method for improving hiding power while also exhibiting excellent lightfastness. The resulting titanium dioxide pigment exhibits high hiding power, high lightfastness, good whiteness, and good dispersibility in water-based matte latex paints and matte printing inks.

Description

Technical Field

[0001] The present invention relates to a preparation method of a high-light-resistant and high-hiding titanium dioxide pigment with flat gloss in the field of chemical industry. Background Art

[0002] Titanium dioxide is one of the most important fine chemical raw materials. Due to its high refractive index, tinting power, and excellent hiding power, it is the most widely used white pigment, earning it the nickname "King of White Pigments." It is widely used in the production of coatings, plastics, papermaking, rubber, chemical fibers, and other industries. The coatings industry consumes the most titanium dioxide, accounting for over 60% of the total. Titanium dioxide pigment is a key component of coatings, providing coverage, color, and durability. The quality of coatings depends largely on the quality of the pigment.

[0003] Water-based matte latex paints and matte printing inks are green and environmentally friendly, and have become increasingly popular with customers in recent years. With the increasing use of water-based paints and inks, the requirements for pigment hiding power, lightfastness, whiteness, and other indicators are becoming increasingly stringent. Water-based matte latex paints and printing inks have high pigment volume concentrations, and their hiding power is determined by the refractive index differences between the titanium dioxide pigment and the air in the pores, as well as between the titanium dioxide pigment and the emulsion resin, and between the titanium dioxide pigment and water. Therefore, heavy coating of the titanium dioxide pigment to increase its surface porosity and improve its hiding performance in latex paints has become a widely used technology. However, products produced using this technology currently have serious lightfastness deficiencies in the matte water-based paint and ink applications, failing to meet the requirements of this field. In addition, titanium dioxide pigments, manufactured by coating them with variable-valence rare earth oxides, zirconium phosphate, and aluminum phosphate, have enhanced their lightfastness. These products are primarily used in decorative paper applications, but they suffer from insufficient hiding power in matte water-based coatings and inks. Therefore, the development of a high-lightfastness, high-hiding titanium dioxide pigment with matte properties to meet the needs of matte water-based coatings and inks is urgently needed.

[0004] US3510335 discloses a method for producing a discoloration-resistant, high-hiding titanium dioxide by coating a loose, porous silica film on a titanium dioxide-aluminum oxide surface and calcining it at 300-1000°C. The product produced by this method suffers from poor lightfastness and dispersibility in aqueous systems.

[0005] CN101885926 A discloses a method for producing high-hiding rutile titanium dioxide. The method improves the product's hiding power while maintaining high whiteness and basic weather resistance through acidic coating of a dense hydrated silicon oxide film, a loose hydrated silicon oxide film, and an aluminum oxide film. The product produced by this method exhibits excellent hiding power, weather resistance, and whiteness. However, the dense surface coating of titanium dioxide with a small amount of amorphous hydrated aluminum oxide has limited improvement in light resistance, resulting in poor light resistance.

[0006] CN 109705630 A discloses a method for preparing highly lightfast laminated titanium dioxide. The method involves sequentially coating the titanium dioxide surface with a dense aluminum phosphate coating, a loose aluminum silica coating, and a loose boehmite-type hydrated aluminum oxide coating to improve the product's lightfastness, dispersibility, and retention. This product is used in water-based matte latex paints and matte printing inks. While it improves the product's lightfastness, its lightfastness improvement is still somewhat inferior to that achieved in matte water-based coatings and inks. Furthermore, the loose aluminum silica coating does not provide sufficiently high dry hiding power, resulting in insufficient hiding power in the final product. Summary of the Invention

[0007] The main purpose of the present invention is to address the deficiencies of the existing technology and provide a method for preparing a high-light-resistant and high-hiding titanium dioxide pigment with matting properties. The method continues the traditional heavy coating to improve hiding power, while also having excellent light resistance. The prepared titanium dioxide pigment has the characteristics of high hiding power, high light resistance, good whiteness and dispersibility in water-based matte latex paint and matte printing ink.

[0008] The technical solution of the present invention is:

[0009] A method for preparing a high-lightfast and high-hiding titanium dioxide pigment with matting properties comprises beating a primary rutile titanium dioxide product, dispersing it, and then grinding it. The ground slurry is heated to 70°C to 80°C and coated, and the temperature is maintained at 70°C to 80°C throughout the coating process. After coating, the filter cake is washed with deionized water until the electrical conductivity is greater than 50,000 Ω·cm, and then dried and subjected to steam powder treatment to obtain a high-lightfast and high-hiding titanium dioxide pigment with matting properties. The method is special in that:

[0010] During the coating process, first, a first layer of dense hydrated aluminum oxide film is coated on the surface of titanium dioxide; secondly, a second layer of a mixed film of aluminum phosphate, hydrated silicon oxide and aluminum oxide is coated on the surface of the first layer of dense hydrated aluminum oxide film; finally, a third layer of a network boehmite-type hydrated aluminum oxide film is coated on the surface of the second layer of the mixed film of aluminum phosphate, hydrated silicon oxide and aluminum oxide, thereby ensuring that the titanium dioxide pigment has excellent dispersion and filtration properties;

[0011] The steps for the second layer of aluminum phosphate, hydrated silicon oxide and aluminum oxide mixed film are as follows:

[0012] A phosphorus-containing compound solution is added to the titanium dioxide slurry coated with the first layer at one time. The phosphorus-containing compound solution is an alkali metal phosphate solution, an alkali metal hydrogen phosphate solution or a hexametaphosphate solution, wherein the amount of the phosphorus-containing compound solution added is 2.0% to 3.0% by weight of P2O5 based on the weight of TiO2, and the slurry is matured for 20 minutes to 30 minutes. Within 120 minutes to 180 minutes, a water-soluble silicate and a water-soluble metaaluminate solution are added simultaneously, wherein the amount of the water-soluble silicate solution added is 6.0% to 10.0% by weight of SiO2 based on the weight of TiO2, and the amount of the water-soluble metaaluminate solution added is 2.0% to 4.0% by weight of Al2O3 based on the weight of TiO2, and an acidic aluminum salt solution is used to maintain the pH value of the slurry at 5.0 to 7.0, and the slurry is matured for 30 minutes to 60 minutes.

[0013] Further preferably, the phosphorus-containing compound solution is a sodium tripolyphosphate solution, a sodium pyrophosphate solution or a sodium hexametaphosphate solution, and the concentration of the phosphorus-containing compound solution is 150 g / L to 250 g / L in terms of P2O5.

[0014] Further preferably, the water-soluble silicate solution is at least one of a sodium silicate solution and a potassium silicate solution, and its concentration is 200 g / L to 250 g / L in terms of SiO2.

[0015] Further preferably, the water-soluble aluminate solution is at least one of a sodium aluminate solution and a potassium aluminate solution, and its concentration is 150 g / L to 200 g / L in terms of Al2O3.

[0016] Further preferably, the acidic aluminum salt solution is at least one of aluminum trichloride solution, aluminum nitrate solution, and aluminum sulfate solution, and its concentration is 80 g / L to 100 g / L in terms of Al2O3.

[0017] Further preference is given to coating the first layer of dense hydrated alumina film, adding a water-soluble alkaline aluminum salt solution to the titanium dioxide slurry after beating, dispersion and grinding within 30 minutes to 60 minutes, the amount of water-soluble alkaline aluminum salt solution added is 1.5% to 2.5% by weight of Al2O3 to TiO2, adding an inorganic acid solution to maintain the pH value of the slurry at 5.0 to 6.0, and aging for 30 minutes to 60 minutes.

[0018] As a further preference, the water-soluble alkaline aluminum salt solution is at least one of a water-soluble sodium aluminate solution and a water-soluble potassium aluminate solution, and the concentration of the water-soluble alkaline aluminum salt solution is 150 g / L to 200 g / L in terms of Al2O3.

[0019] Further preferably, when coating the third layer of reticulated boehmite-type hydrated alumina, water-soluble aluminate is added to the titanium dioxide slurry coated with the second layer within 60 to 90 minutes, and the amount of water-soluble aluminate solution added is 3.5% to 4.0% by weight of Al2O3 to TiO2. The pH value of the slurry is adjusted to 7.5 to 8.5 with an inorganic acid solution and matured for 60 to 120 minutes.

[0020] As a further preference, the inorganic acid solution is at least one of hydrochloric acid solution, sulfuric acid solution, and nitric acid solution, and its mass percentage concentration is 15% to 20%; the water-soluble aluminate is at least one of water-soluble sodium aluminate solution and water-soluble potassium aluminate solution, and the concentration of the water-soluble alkaline aluminum salt solution is 150g / L to 200g / L in terms of Al2O3.

[0021] Further preferably, during the dispersion treatment, the pH value of the slurry is adjusted to 9.8-10.5 with an inorganic alkaline solution, and a water-soluble silicate solution is added as a dispersant. The amount of water-soluble silicate solution added is 0.2%-0.3% by weight of SiO2 to TiO2, and the slurry is matured for 20min-40min.

[0022] As a further preference, the inorganic alkali solution is at least one of a sodium hydroxide solution or a potassium hydroxide solution, and its mass percentage concentration is 10% to 20%; the water-soluble silicate solution is a sodium silicate solution or a potassium silicate solution, and its concentration is 200g / L to 250g / L in terms of SiO2.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The product utilizes a three-layer coating. The first layer, a dense hydrated alumina coating, effectively blocks the product's photochemical sites, providing the foundation for its excellent lightfastness. A mixed coating of aluminum phosphate, hydrated silica, and alumina is successfully introduced as the second primary coating. This porous structure of aluminum phosphate and alumina effectively enhances the product's lightfastness due to its variable-valence phosphate compound and composite hydrated silica and hydrated alumina coating. This coating not only ensures high dry hiding power, but also effectively improves the product's lightfastness due to its presence. This continues the traditional heavy coating approach to enhance hiding power while also providing excellent lightfastness. The resulting titanium dioxide pigment exhibits high dry hiding power, lightfastness, excellent whiteness, and dispersibility. It can be widely used in matte and semi-gloss water-based architectural coatings and printing inks, among other applications requiring high lightfastness and high hiding power. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with specific embodiments, but the application scope of the present invention is not limited to the embodiments. Various replacements and changes made without departing from the technical concept of the present invention should be within the scope of the present invention.

[0026] Example 1

[0027] 1.1. Weigh 400 g of primary rutile titanium dioxide powder prepared by the chloride process and add deionized water to prepare a slurry with a mass concentration of 20%. The pH value of the slurry is detected by a pH meter throughout the coating process. The pH of the slurry is adjusted to 9.8 with a 10% mass concentration of sodium hydroxide solution. Sodium silicate solution is added. The concentration of the sodium silicate solution is 200 g / L in terms of SiO2. The amount of sodium silicate solution added is 0.2% by weight of SiO2 in the sodium silicate relative to the weight of TiO2. The mixture is aged for 20 minutes.

[0028] 1.2. Heat the ground slurry to 70°C and maintain this temperature throughout the coating process;

[0029] 1.3. Add water-soluble sodium aluminate within 30 minutes. The concentration of the water-soluble sodium aluminate solution is 150g / L based on Al2O3. The amount of water-soluble sodium aluminate solution added is 1.5% by weight based on Al2O3 to TiO2. Use 10% hydrochloric acid to adjust the pH value of the slurry to 5.0 and mature for 30 minutes.

[0030] 1.4. Add 2.0% (as P2O5 to TiO2 by weight) of sodium tripolyphosphate solution at one time, the concentration of the sodium tripolyphosphate solution being 150 g / L based on P2O5, and mature for 20 minutes; add water-soluble sodium silicate and sodium metaaluminate solutions simultaneously within 180 minutes, the concentration of the water-soluble sodium silicate solution being 200 g / L, the addition amount being 10% based on SiO2 to TiO2 by weight, the concentration of the water-soluble sodium metaaluminate solution being 150 g / L, the addition amount being 2.0% based on Al2O3 to TiO2 by weight, and maintain the slurry pH at 5.0 with an aluminum chloride solution having a concentration of 80 g / L (as Al2O3) and mature for 30 minutes;

[0031] 1.5. Add water-soluble sodium aluminate solution within 60 minutes. The concentration of the water-soluble sodium aluminate solution is 150 g / L based on Al2O3. The amount of sodium aluminate solution added is 3.5% by weight based on Al2O3 to TiO2. Add 10% hydrochloric acid to maintain the pH value of the slurry at 7.5 and mature for 60 minutes.

[0032] 1.6. The slurry matured in step 1.5 is washed with deionized water at 70° C. until the filter cake resistivity reaches 55,000 Ω·cm. The slurry is filtered, dried, and then subjected to steam-powder treatment to obtain a highly light-resistant and high-hiding titanium dioxide pigment.

[0033] Example 2

[0034] 1.1. Weigh 400 g of primary rutile titanium dioxide powder prepared by the chloride process and add deionized water to prepare a slurry with a mass concentration of 30%. The pH value of the slurry is detected by a pH meter during the entire coating process. The pH of the slurry is adjusted to 10.5 with a 20% mass concentration of potassium hydroxide solution. Potassium silicate solution is added. The concentration of the potassium silicate solution is 250 g / L in terms of SiO2. The amount of potassium silicate solution added is 0.3% by weight of SiO2 in the potassium silicate relative to the weight of TiO2. The mixture is aged for 40 min.

[0035] 1.2. Heat the ground slurry to 80°C and maintain this temperature throughout the coating process;

[0036] 1.3. Add water-soluble potassium aluminate within 60 minutes. The concentration of the water-soluble potassium aluminate solution is 200 g / L based on Al2O3. The amount of water-soluble potassium aluminate solution added is 2.5% by weight based on Al2O3 to TiO2. Use 20% sulfuric acid solution to adjust the pH value of the slurry to 6.0 and mature for 45 minutes.

[0037] 1.4. Add 3.0% (based on the weight of P2O5 in TiO2) of sodium pyrophosphate solution at one time, the concentration of the sodium pyrophosphate solution being 250g / L based on P2O5, and mature for 30 minutes; add potassium silicate and potassium metaaluminate solutions simultaneously within 120 minutes, the concentration of the water-soluble potassium silicate solution being 250g / L, the addition amount being 6% based on the weight of SiO2 in TiO2, and the concentration of the water-soluble potassium metaaluminate solution being 200g / L, the addition amount being 4.0% based on the weight of Al2O3 in TiO2, and maintain the slurry pH at 7.0 with aluminum nitrate solution having a concentration of 100g / L (based on Al2O3), and mature for 60 minutes;

[0038] 1.5. Add potassium aluminate solution within 90 minutes. The concentration of the water-soluble potassium aluminate solution is 200 g / L based on Al2O3. The amount of potassium aluminate solution added is 4.0% based on the weight of Al2O3 to TiO2. Add 20% sulfuric acid solution to maintain the pH value of the slurry at 8.5. Ripen for 120 minutes.

[0039] 1.6. The slurry matured in step 1.5 is washed with 80° C. deionized water until the filter cake resistivity reaches 60,000 Ω·cm. The slurry is filtered, dried, and then subjected to steam-powder treatment to obtain a highly light-resistant and high-hiding titanium dioxide pigment.

[0040] Example 3

[0041] 1.1. Weigh 400 g of primary rutile titanium dioxide powder prepared by the chloride process and add deionized water to prepare a slurry with a mass concentration of 25%. The pH value of the slurry is detected by a pH meter during the entire coating process. The pH of the slurry is adjusted to 10.0 with a 15% mass concentration of sodium hydroxide solution. Sodium silicate solution is added. The concentration of the sodium silicate solution is 220 g / L in terms of SiO2. The amount of sodium silicate solution added is 0.25% by weight of SiO2 in the sodium silicate relative to the weight of TiO2. The mixture is aged for 30 min.

[0042] 1.2. Heat the ground slurry to 75°C and maintain this temperature throughout the coating process;

[0043] 1.3. Add water-soluble sodium aluminate within 45 minutes. The concentration of the water-soluble sodium aluminate solution is 180 g / L based on Al2O3. The amount of water-soluble sodium aluminate solution added is 2.0% by weight based on Al2O3 to TiO2. Use 15% nitric acid to adjust the pH value of the slurry to 5.5 and mature for 45 minutes.

[0044] 1.4. Add 2.5% (based on the weight of P2O5 in TiO2) of sodium hexametaphosphate solution at one time, the concentration of the sodium hexametaphosphate solution is 200g / L based on P2O5, and mature for 30 minutes; add water-soluble sodium silicate and sodium metaaluminate solutions simultaneously within 150 minutes, the concentration of the water-soluble sodium silicate solution is 220g / L, the addition amount is 8% based on the weight of SiO2 in TiO2, the concentration of the water-soluble sodium metaaluminate solution is 180g / L, the addition amount is 3% based on the weight of Al2O3 in TiO2, and use aluminum sulfate solution with a concentration of 90g / L (based on Al2O3) to maintain the slurry pH value at 6.0, and mature for 60 minutes;

[0045] 1.5. Within 75 minutes, add water-soluble sodium aluminate solution, the concentration of which is 180 g / L in terms of Al2O3, and the amount of sodium aluminate solution added is 3.75% by weight of Al2O3 to TiO2. Add 15% nitric acid solution to maintain the pH value of the slurry at 8.0, and mature for 90 minutes;

[0046] 1.6. The slurry matured in step 1.5 is washed with deionized water at 75° C. until the filter cake resistivity reaches 58,000 Ω·cm. The slurry is filtered, dried, and then subjected to steam-powder treatment to obtain a highly light-resistant and high-hiding titanium dioxide pigment.

[0047] Comparative Example 1

[0048] Same as Example 3, except that step 1.3 is omitted.

[0049] 1.1. Weigh 400 g of primary rutile titanium dioxide powder prepared by the chloride process and add deionized water to prepare a slurry with a mass concentration of 25%. The pH value of the slurry is detected by a pH meter during the entire coating process. The pH of the slurry is adjusted to 10.0 with a 15% mass concentration of sodium hydroxide solution. Sodium silicate solution is added. The concentration of the sodium silicate solution is 220 g / L in terms of SiO2. The amount of sodium silicate solution added is 0.25% by weight of SiO2 in the sodium silicate relative to the weight of TiO2. The mixture is aged for 30 min.

[0050] 1.2. Heat the ground slurry to 75°C and maintain this temperature throughout the coating process;

[0051] 1.3. Add 2.5% (based on the weight of P2O5 in TiO2) of sodium hexametaphosphate solution at one time, the concentration of the sodium hexametaphosphate solution is 200g / L based on P2O5, and mature for 30 minutes; add water-soluble sodium silicate and sodium metaaluminate solutions simultaneously within 150 minutes, the concentration of the water-soluble sodium silicate solution is 220g / L, the addition amount is 8% based on the weight of SiO2 in TiO2, the concentration of the water-soluble sodium metaaluminate solution is 180g / L, the addition amount is 3% based on the weight of Al2O3 in TiO2, and use aluminum sulfate solution with a concentration of 90g / L (based on Al2O3) to maintain the slurry pH value at 6.0, and mature for 60 minutes;

[0052] 1.4. Within 75 minutes, add water-soluble sodium aluminate solution, the concentration of which is 180 g / L in terms of Al2O3, and the amount of sodium aluminate solution added is 3.75% by weight of Al2O3 to TiO2. Add 15% nitric acid solution to maintain the pH value of the slurry at 8.0, and mature for 90 minutes;

[0053] 1.5. The slurry matured in step 1.5 was washed with deionized water at 75° C. until the filter cake resistivity reached 58,000 Ω·cm. The slurry was filtered, dried, and then subjected to steam-powder treatment to obtain titanium dioxide pigment.

[0054] Comparative Example 2

[0055] The same as Example 3, except that step 1.4 is omitted: 2.5% (based on the weight of P2O5 to TiO2) of sodium hexametaphosphate solution is added at one time, the concentration of the sodium hexametaphosphate solution is 200 g / L based on P2O5, and the mixture is aged for 30 minutes.

[0056] 1.1. Weigh 400 g of primary rutile titanium dioxide powder prepared by the chloride process and add deionized water to prepare a slurry with a mass concentration of 25%. The pH value of the slurry is detected by a pH meter during the entire coating process. The pH of the slurry is adjusted to 10.0 with a 15% mass concentration of sodium hydroxide solution. Sodium silicate solution is added. The concentration of the sodium silicate solution is 220 g / L in terms of SiO2. The amount of sodium silicate solution added is 0.25% by weight of SiO2 in the sodium silicate relative to the weight of TiO2. The mixture is aged for 30 min.

[0057] 1.2. Heat the ground slurry to 75°C and maintain this temperature throughout the coating process;

[0058] 1.3. Add water-soluble sodium aluminate within 45 minutes. The concentration of the water-soluble sodium aluminate solution is 180 g / L based on Al2O3. The amount of water-soluble sodium aluminate solution added is 2.0% by weight based on Al2O3 to TiO2. Use 15% nitric acid to adjust the pH value of the slurry to 5.5 and mature for 45 minutes.

[0059] 1.4. Add water-soluble sodium silicate and sodium metaaluminate solutions simultaneously within 150 minutes. The concentration of the water-soluble sodium silicate solution is 220 g / L, and the amount added is 8% by weight based on SiO2 to TiO2. The concentration of the water-soluble sodium metaaluminate solution is 180 g / L, and the amount added is 3% by weight based on Al2O3 to TiO2. Aluminum sulfate solution with a concentration of 90 g / L (calculated as Al2O3) is used to maintain the slurry pH at 6.0. Ripen for 60 minutes.

[0060] 1.5. Within 75 minutes, add water-soluble sodium aluminate solution, the concentration of which is 180 g / L in terms of Al2O3, and the amount of sodium aluminate solution added is 3.75% by weight of Al2O3 to TiO2. Add 15% nitric acid solution to maintain the pH value of the slurry at 8.0, and mature for 90 minutes;

[0061] 1.6. The slurry matured in step 1.5 is washed with deionized water at 75° C. until the filter cake resistivity reaches 58,000 Ω·cm. The slurry is filtered, dried, and then subjected to steam-powder treatment to obtain a highly light-resistant and high-hiding titanium dioxide pigment.

[0062] Comparative Example 3

[0063] The same as Example 3, except that the addition of sodium metaaluminate solution is omitted in step 1.4. The specific steps of step 1.4 are: adding 2.5% (in terms of P2O5 to TiO2 weight) of sodium hexametaphosphate solution at one time, the concentration of sodium hexametaphosphate solution is 200g / L in terms of P2O5, and aging for 30min; adding water-soluble sodium silicate solution at the same time within 150min, the concentration of water-soluble sodium silicate solution is 220g / L, the addition amount is 8% in terms of SiO2 to TiO2 weight, and using aluminum sulfate solution with a concentration of 90g / L (in terms of Al2O3) to maintain the slurry pH value at 6.0, and aging for 60min.

[0064] 1.1. Weigh 400 g of primary rutile titanium dioxide powder prepared by the chloride process and add deionized water to prepare a slurry with a mass concentration of 25%. The pH value of the slurry is detected by a pH meter during the entire coating process. The pH of the slurry is adjusted to 10.0 with a 15% mass concentration of sodium hydroxide solution. Sodium silicate solution is added. The concentration of the sodium silicate solution is 220 g / L in terms of SiO2. The amount of sodium silicate solution added is 0.25% by weight of SiO2 in the sodium silicate relative to the weight of TiO2. The mixture is aged for 30 min.

[0065] 1.2. Heat the ground slurry to 75°C and maintain this temperature throughout the coating process;

[0066] 1.3. Add water-soluble sodium aluminate within 45 minutes. The concentration of the water-soluble sodium aluminate solution is 180 g / L based on Al2O3. The amount of water-soluble sodium aluminate solution added is 2.0% by weight based on Al2O3 to TiO2. Use 15% nitric acid to adjust the pH value of the slurry to 5.5 and mature for 45 minutes.

[0067] 1.4. Add 2.5% (based on the weight of P2O5 in TiO2) of sodium hexametaphosphate solution at one time, the concentration of the sodium hexametaphosphate solution is 200g / L based on P2O5, and mature for 30 minutes; add water-soluble sodium silicate solution within 150 minutes, the concentration of the water-soluble sodium silicate solution is 220g / L, the addition amount is 8% based on the weight of SiO2 in TiO2, and use aluminum sulfate solution with a concentration of 90g / L (based on Al2O3) to maintain the slurry pH value at 6.0, and mature for 60 minutes;

[0068] 1.5. Within 75 minutes, add water-soluble sodium aluminate solution, the concentration of which is 180 g / L in terms of Al2O3, and the amount of sodium aluminate solution added is 3.75% by weight of Al2O3 to TiO2. Add 15% nitric acid solution to maintain the pH value of the slurry at 8.0, and mature for 90 minutes;

[0069] 1.6. The slurry matured in step 1.5 is washed with deionized water at 75° C. until the filter cake resistivity reaches 58,000 Ω·cm. The slurry is filtered, dried, and then subjected to steam-powder treatment to obtain a highly light-resistant and high-hiding titanium dioxide pigment.

[0070] Comparative Example 4

[0071] The same as Example 3, except that the coated dense aluminum in step 1.3 is replaced by dense silicon. The specific steps of step 1.3 are: adding 2.0% (by weight of SiO2 to TiO2) of water-soluble sodium silicate solution at one time, the concentration of the water-soluble sodium silicate solution is 220 g / L in terms of SiO2, and uniformly adjusting the pH of the slurry to 6.5 with a hydrochloric acid solution with a mass percentage concentration of 10% within 90 minutes, and aging for 60 minutes.

[0072] 1.1. Weigh 400 g of primary rutile titanium dioxide powder prepared by the chloride process and add deionized water to prepare a slurry with a mass concentration of 25%. The pH value of the slurry is detected by a pH meter during the entire coating process. The pH of the slurry is adjusted to 10.0 with a 15% mass concentration of sodium hydroxide solution. Sodium silicate solution is added. The concentration of the sodium silicate solution is 220 g / L in terms of SiO2. The amount of sodium silicate solution added is 0.25% by weight of SiO2 in the sodium silicate relative to the weight of TiO2. The mixture is aged for 30 min.

[0073] 1.2. Heat the ground slurry to 75°C and maintain this temperature throughout the coating process;

[0074] 1.3. Add 2.0% (by weight of SiO2 to TiO2) of water-soluble sodium silicate solution at one time. The concentration of the water-soluble sodium silicate solution is 220g / L based on SiO2. Use 10% hydrochloric acid solution with a mass percentage concentration to evenly adjust the pH of the slurry to 6.5 within 90 minutes and mature for 60 minutes.

[0075] 1.4. Add 2.5% (based on the weight of P2O5 in TiO2) of sodium hexametaphosphate solution at one time, the concentration of the sodium hexametaphosphate solution is 200g / L based on P2O5, and mature for 30 minutes; add water-soluble sodium silicate and sodium metaaluminate solutions simultaneously within 150 minutes, the concentration of the water-soluble sodium silicate solution is 220g / L, the addition amount is 8% based on the weight of SiO2 in TiO2, the concentration of the water-soluble sodium metaaluminate solution is 180g / L, the addition amount is 3% based on the weight of Al2O3 in TiO2, and use aluminum sulfate solution with a concentration of 90g / L (based on Al2O3) to maintain the slurry pH value at 6.0, and mature for 60 minutes;

[0076] 1.5. Within 75 minutes, add water-soluble sodium aluminate solution, the concentration of which is 180 g / L in terms of Al2O3, and the amount of sodium aluminate solution added is 3.75% by weight of Al2O3 to TiO2. Add 15% nitric acid solution to maintain the pH value of the slurry at 8.0, and mature for 90 minutes;

[0077] 1.6. The slurry matured in step 1.5 is washed with deionized water at 75° C. until the filter cake resistivity reaches 58,000 Ω·cm. The slurry is filtered, dried, and then subjected to steam-powder treatment to obtain a highly light-resistant and high-hiding titanium dioxide pigment.

[0078] Comparative Example 5

[0079] The same as Example 3, except that step 1.4 only coats aluminum phosphate. The specific steps of step 1.4 are: adding 2.5% (in terms of P2O5 to TiO2 weight) sodium hexametaphosphate solution at one time, the concentration of sodium hexametaphosphate solution is 200 g / L in terms of P2O5, and aging for 30 minutes; adding sodium aluminate solution at the same time within 150 minutes, the concentration of water-soluble sodium aluminate solution is 180 g / L, the addition amount is 3% in terms of Al2O3 to TiO2 weight, and using aluminum sulfate solution with a concentration of 90 g / L (in terms of Al2O3) to maintain the slurry pH value at 6.0, and aging for 60 minutes.

[0080] 1.1. Weigh 400 g of primary rutile titanium dioxide powder prepared by the chloride process and add deionized water to prepare a slurry with a mass concentration of 25%. The pH value of the slurry is detected by a pH meter during the entire coating process. The pH of the slurry is adjusted to 10.0 with a 15% mass concentration of sodium hydroxide solution. Sodium silicate solution is added. The concentration of the sodium silicate solution is 220 g / L in terms of SiO2. The amount of sodium silicate solution added is 0.25% by weight of SiO2 in the sodium silicate relative to the weight of TiO2. The mixture is aged for 30 min.

[0081] 1.2. Heat the ground slurry to 75°C and maintain this temperature throughout the coating process;

[0082] 1.3. Add water-soluble sodium aluminate within 45 minutes. The concentration of the water-soluble sodium aluminate solution is 180 g / L based on Al2O3. The amount of water-soluble sodium aluminate solution added is 2.0% by weight based on Al2O3 to TiO2. Use 15% nitric acid to adjust the pH value of the slurry to 5.5 and mature for 45 minutes.

[0083] 1.4. Add 2.5% (based on the weight of P2O5 in TiO2) of sodium hexametaphosphate solution at one time, the concentration of the sodium hexametaphosphate solution is 200g / L based on P2O5, and mature for 30 minutes; simultaneously add sodium metaaluminate solution within 150 minutes, the concentration of the water-soluble sodium metaaluminate solution is 180g / L, the addition amount is 3% based on the weight of Al2O3 in TiO2, and use aluminum sulfate solution with a concentration of 90g / L (based on Al2O3) to maintain the slurry pH value at 6.0, and mature for 60 minutes;

[0084] 1.5. Within 75 minutes, add water-soluble sodium aluminate solution, the concentration of which is 180 g / L in terms of Al2O3, and the amount of sodium aluminate solution added is 3.75% by weight of Al2O3 to TiO2. Add 15% nitric acid solution to maintain the pH value of the slurry at 8.0, and mature for 90 minutes;

[0085] 1.6. The slurry matured in step 1.5 is washed with deionized water at 75° C. until the filter cake resistivity reaches 58,000 Ω·cm. The slurry is filtered, dried, and then subjected to steam-powder treatment to obtain a highly light-resistant and high-hiding titanium dioxide pigment.

[0086] The test results of the titanium dioxide pigments prepared in Examples 1 to 3 and Comparative Examples 1 to 5 are shown in Table 1. The hiding power is measured using the above-mentioned product in a latex paint formulation with a high pigment volume concentration to produce a paint panel; the lightfastness is measured using the prepared latex paint to produce a paint panel, and the color difference (ΔE) is measured after irradiation in an ultraviolet aging chamber for 1 hour.

[0087] Table 1 shows the relevant indicators and application indicators of the products in the examples.

[0088]

[0089] A comparison of Examples 1 and 3 in the table above shows that there are minimal differences in the relevant indicators and application parameters of the three samples, including brightness, acid solubility, specific surface area, hiding power, and light resistance. The light resistance is significantly superior to that of the foreign R931 sample. Acid solubility (i.e., weather resistance) is related to the density of the silica coating: a denser film layer indicates better weather resistance. Specific surface area is related to the density of the coating layer: a looser film layer and a larger specific surface area indicate better hiding power in latex paint preparation. Lower light resistance values indicate better light resistance.

[0090] From the comparison results of Comparative Example 1 and Example 3, it can be seen that after the dense aluminum film coating is removed, the light resistance of the product decreases; but the acid solubility is lower than that of Example 3, indicating that the innermost dense aluminum film can improve the light resistance of the product and have an adverse effect on the acid solubility of the product.

[0091] Comparison of the results of Comparative Example 2 and Example 3 shows that adding the aluminum phosphate mixed coating layer has a significant benefit in improving the light resistance of the product, and the other properties are basically equivalent.

[0092] Comparison of the results of Comparative Example 3 with Example 3 shows that the loose mixed film of aluminum phosphate, hydrated silicon silicate and hydrated aluminum oxide has better light resistance than the hydrated silicon oxide and aluminum silicate coated products with a network structure, and the other properties are basically equivalent.

[0093] Comparison of the results of Comparative Example 4 with Comparative Example 2 and Example 3 shows that coating the first layer of dense hydrated silicon oxide cannot improve the light resistance of the product.

[0094] Comparison of the results of Comparative Example 5 with Examples 1-3 shows that the coating of the dense aluminum phosphate coating layer can indeed improve the light resistance of the product, but the light resistance of the product is still somewhat lower than that of Example 3, and the hiding power of the product is also much lower than that of Example 3, which cannot meet the requirements of the field of water-based flat latex paint and printing ink.

[0095] It can be seen that the titanium dioxide pigment produced according to the specific preparation method of the present invention has the characteristics of high light resistance, high hiding power, high whiteness and excellent dispersibility in water-based matte latex paint and matte printing ink. In addition, the titanium dioxide pigment prepared by this method has low production cost and high raw material utilization rate, which is beneficial to energy conservation and environmental protection.

[0096] The above are merely specific embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing a high-lightfastness, high-hiding titanium dioxide pigment with matting properties, comprising: beating a primary rutile titanium dioxide product, dispersing it, and then grinding it; heating the ground slurry to 70°C to 80°C, coating it, and maintaining the temperature at 70°C to 80°C throughout the coating process; washing the filter cake with deionized water until the conductivity is greater than 50,000 Ω·cm, and then drying and steam-dusting it to obtain a high-lightfastness, high-hiding titanium dioxide pigment with matting properties; the method comprising: During the coating process, first, a first layer of dense hydrated aluminum oxide film is coated on the surface of titanium dioxide; secondly, a second layer of a mixed film of aluminum phosphate, hydrated silicon oxide and aluminum oxide is coated on the surface of the first layer of dense hydrated aluminum oxide film; finally, a third layer of a network boehmite-type hydrated aluminum oxide film is coated on the surface of the second layer of the mixed film of aluminum phosphate, hydrated silicon oxide and aluminum oxide; The steps for the second layer of aluminum phosphate, hydrated silicon oxide and aluminum oxide mixed film are as follows: A phosphorus-containing compound solution is added to the titanium dioxide slurry coated with the first layer at one time. The phosphorus-containing compound solution is an alkali metal phosphate solution, an alkali metal hydrogen phosphate solution or a hexametaphosphate solution, wherein the amount of the phosphorus-containing compound solution added is 2.0% to 3.0% by weight of P2O5 based on the weight of TiO2, and the slurry is aged for 20 min to 30 min. Within 120 min to 180 min, a water-soluble silicate and a water-soluble metaaluminate solution are added simultaneously, wherein the amount of the water-soluble silicate solution added is 6.0% to 10.0% by weight of SiO2 based on the weight of TiO2, and the amount of the water-soluble metaaluminate solution added is 2.0% to 4.0% by weight of Al2O3 based on the weight of TiO2, and an acidic aluminum salt solution is used to maintain the pH value of the slurry at 5.0 to 7.0, and the slurry is aged for 30 min to 60 min.

2. The method for preparing the high light-resistant and high-hiding titanium dioxide pigment with flat gloss according to claim 1, wherein: The phosphorus-containing compound solution is a sodium tripolyphosphate solution, a sodium pyrophosphate solution or a sodium hexametaphosphate solution; the concentration of the phosphorus-containing compound solution is 150 g / L to 250 g / L in terms of P2O5.

3. The method for preparing the high light-resistant and high-hiding titanium dioxide pigment with flat gloss according to claim 1, wherein: The water-soluble silicate solution is at least one of a sodium silicate solution and a potassium silicate solution, and its concentration is 200 g / L to 250 g / L in terms of SiO2.

4. The method for preparing the high light-resistant and high-hiding titanium dioxide pigment with flat gloss according to claim 1, wherein: The water-soluble metaaluminate solution is at least one of a sodium metaaluminate solution and a potassium metaaluminate solution, and its concentration is 150 g / L to 200 g / L in terms of Al2O3.

5. The method for preparing the high light-resistant and high-hiding titanium dioxide pigment with flat gloss according to claim 1, wherein: The acidic aluminum salt solution is at least one of aluminum trichloride solution, aluminum nitrate solution, and aluminum sulfate solution, and its concentration is 80 g / L to 100 g / L in terms of Al2O3.

6. The method for preparing the high light-resistant and high-hiding titanium dioxide pigment with flat gloss according to claim 1, wherein: When coating the first layer of dense hydrated alumina film, add a water-soluble alkaline aluminum salt solution to the titanium dioxide slurry after beating, dispersion and grinding within 30 minutes to 60 minutes. The amount of water-soluble alkaline aluminum salt solution added is 1.5% to 2.5% by weight of Al2O3 to TiO2. Add an inorganic acid solution to maintain the pH value of the slurry at 5.0 to 6.0 and mature for 30 minutes to 60 minutes.

7. The method for preparing the high light-resistant and high-hiding titanium dioxide pigment with flat gloss according to claim 6, characterized in that: The water-soluble alkaline aluminum salt solution is at least one of a water-soluble sodium aluminate solution and a water-soluble potassium aluminate solution, and the concentration of the water-soluble alkaline aluminum salt solution is 150 g / L to 200 g / L in terms of Al2O3.

8. The method for preparing the high light-resistant and high-hiding titanium dioxide pigment with flat gloss according to claim 1, wherein: When coating the third layer of reticulated boehmite-type hydrated alumina, add a water-soluble aluminate solution to the titanium dioxide slurry coated with the second layer within 60 to 90 minutes. The amount of water-soluble aluminate solution added is 3.5% to 4.0% by weight of Al2O3 to TiO2. Use an inorganic acid solution to adjust the pH value of the slurry to 7.5 to 8.5 and mature it for 60 to 120 minutes.

9. The method for preparing the high light-resistant and high-hiding titanium dioxide pigment with flat gloss according to claim 8, wherein: The inorganic acid solution is at least one of hydrochloric acid solution, sulfuric acid solution, and nitric acid solution, and its mass percentage concentration is 15% to 20%; the water-soluble aluminate solution is at least one of water-soluble sodium aluminate solution and water-soluble potassium aluminate solution, and the concentration of the water-soluble aluminate solution is 150 g / L to 200 g / L in terms of Al2O3.

10. The method for preparing the high light-resistant and high-hiding titanium dioxide pigment with flat gloss according to claim 1, wherein: During the dispersion treatment, the pH value of the slurry is adjusted to 9.8-10.5 with an inorganic alkali solution, and a water-soluble silicate solution is added as a dispersant. The amount of water-soluble silicate solution added is 0.2%-0.3% by weight of SiO2 to TiO2, and the slurry is aged for 20 min-40 min. The inorganic alkali solution is at least one of sodium hydroxide solution or potassium hydroxide solution, and its mass percentage concentration is 10%-20%. The water-soluble silicate solution is sodium silicate solution or potassium silicate solution, and its concentration is 200 g / L-250 g / L in terms of SiO2.

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