Preparation method of high-covering titanium dioxide for water-based ink

Abstract

The invention relates to the field of titanium dioxide preparation, and provides a preparation method of high-covering titanium dioxide for water-based ink, which comprises the following steps: adding 100g / L of sodium silicate solution into slurry before coating, adjusting the pH value to 8.5-11.5, stirring for 30 minutes, adjusting the pH value to 4.5-6, stirring for 60 minutes, coating a compact silicon oxide film, and ensuring that silicon oxide accounts for more than or equal to 2% and less than or equal to 3% of the mass of titanium dioxide; a sodium silicate solution with the concentration of 120-280 g / L is added, the PH value is adjusted to be 8-11.5, stirring is conducted for 30 min, the PH value is adjusted to be 4.5-5, stirring is conducted for 30 min, and a loose silicon oxide film with the concentration of 3% lt is coated; the silicon oxide film accounts for less than or equal to 8% of titanium dioxide; the pH value is adjusted to 9-10, the temperature is reduced to 60-65 DEG C, an aluminum-containing compound is added for reaction, the pH value is adjusted to 7.2-7.6, an aluminum oxide film is coated, and the mass of aluminum oxide accounts for not less than 2% and not more than 3% of the mass of titanium dioxide. According to the scheme, the raw material cost is reduced, the preparation process is simplified, and the environmental protection property is improved.

Description

Technical Field

[0001] The present invention relates to the field of titanium dioxide preparation, and particularly to a preparation method of high-covering titanium dioxide for water-based inks. Background Art

[0002] Titanium dioxide is the most important white pigment or brightening agent in water-based inks. Titanium dioxide has a high refractive index (2.7 for rutile type and 2.5 for anatase type), can effectively scatter light, cover the base material background color, and reduce the ink usage. The combination of the two is widely used in fields such as food packaging and label printing. Titanium dioxide needs to be coated with organic (such as silane, polyol) or inorganic (such as alumina, silica) coatings to improve its dispersibility in the water-based system and prevent agglomeration.

[0003] The existing patent CN111393876B discloses a preparation method of high-covering and high-gloss titanium dioxide. Among them, after slurry preparation, coating, filtration, washing, flash drying, calcination, and airflow pulverization, the finished product is obtained. In the process of coating, a small molecule template agent EDA is used. During the preparation process, more key raw materials are added, resulting in an increase in raw material costs and a long process. In addition, the introduction of the small molecule template agent EDA may pose an environmental protection risk.

[0004] Therefore, there is an urgent need for a preparation method of high-covering titanium dioxide for water-based inks that can reduce production costs, simplify the process flow, and do not increase environmental protection risks. Summary of the Invention

[0005] In view of the problem that in the prior art, after slurry preparation, coating, filtration, washing, flash drying, calcination, and airflow pulverization, the finished product is obtained, and a small molecule template agent EDA is used in the process of coating to prepare high-covering and high-gloss titanium dioxide, with more key raw materials added, an increase in raw material costs, the introduction of the small molecule template agent EDA, and possible environmental protection risks. The present disclosure provides a preparation method of high-covering titanium dioxide for water-based inks, including: Step a: Add water and a sodium silicate solution with a mass concentration of 0.2% to the initial product of rutile titanium dioxide particles, beat and disperse, and then screen to obtain a pre-coating slurry with a concentration of 450 - 680 g / L; Step b: Take an appropriate amount of the pre-coating slurry and dilute it to 400 - 450 g / L, heat it to 80 - 85 °C, and adjust the pH value to 9 - 10.5; Step c: Add a sodium silicate solution with a concentration of 100 g / L to the pre-coating slurry, adjust the pH value to 8.5 - 11.5, stir for 30 min, then adjust the pH value to 4.5 - 6, and stir for 60 min to coat a dense silica film on the particle surface, where 2% ≤ the mass of silica accounts for the mass of titanium dioxide ≤ 3%; Step d: Add a sodium silicate solution with a concentration of 120 - 280 g / L to the pre-coated slurry, adjust the pH value to 8 - 11.5, stir for 30 min, then adjust the pH value to 4.5 - 5 and stir for 30 min to coat a loose silica film on the particle surface, where 3% < mass of silica / mass of titanium dioxide ≤ 8%; Step e: Adjust the pH value of the pre-coated slurry to 9 - 10 and cool it down to 60 - 65 °C, add an aluminum-containing compound for reaction, then adjust the pH value to 7.2 - 7.6 to coat an alumina film on the particle surface and obtain the post-coated slurry, where 2% ≤ mass of alumina / mass of titanium dioxide ≤ 3%; Step f: Age, filter, wash, and perform surface organic treatment on the post-coated slurry to obtain high-coverage titanium dioxide for water-based inks.

[0006] In some embodiments, step a further includes: Add deionized water or distilled water and a sodium silicate solution with a mass concentration of 0.2% to the initial product of rutile titanium dioxide particles, add a sodium hydroxide solution with a mass concentration of 15%, adjust the pH value to 9 - 10, beat and disperse for 60 - 120 min, and then filter through a 100 - 600 mesh sieve to obtain a pre-coated slurry with a concentration of 450 - 680 g / L.

[0007] In some embodiments, step a further includes: Beat and disperse for 60 min, and then filter through a 325 mesh sieve to obtain a pre-coated slurry with a concentration of 450 - 620 g / L.

[0008] In some embodiments, step b includes: Take an appropriate amount of the pre-coated slurry, dilute it with deionized water or distilled water to 400 - 450 g / L, heat it to 80 - 85 °C, then add a sodium hydroxide solution with a mass concentration of 15%, and adjust the pH value to 9 - 10.5.

[0009] In some embodiments, step c includes: Uniformly add a sodium silicate solution with a concentration of 100 g / L to the pre-coated slurry within 30 min, control the pH value of the slurry after addition to 8.5 - 11.5, maintain the temperature at 80 - 85 °C and stir for 30 min, then uniformly add a dilute sulfuric acid solution with a mass concentration of 20% within 120 min, control the pH value after addition to 4.5 - 6, maintain the temperature at 80 - 85 °C and stir for 60 min to coat a dense silica film on the particle surface, where the mass of silica accounts for 3% of the mass of titanium dioxide.

[0010] In some embodiments, step d includes: Add a sodium silicate solution with a concentration of 120 - 280 g / L to the pre-coated slurry at a uniform rate within 30 min, control the pH value of the slurry after addition to be 8 - 11.5, maintain the temperature at 80 - 85 °C and stir for 30 min. Then, add a dilute sulfuric acid solution with a mass concentration of 20% at a uniform rate within 60 min, control the pH value after addition to be 4.5 - 5, maintain the temperature at 80 - 85 °C and stir for 30 min to coat a loose silica film on the particle surface, and the mass of silica accounts for 6% of the mass of titanium dioxide.

[0011] In some embodiments, step d further includes: Add a sodium silicate solution with a concentration of 200 g / L to the pre-coated slurry at a uniform rate within 30 min, control the pH value of the slurry after addition to be 8 - 11.5, maintain the temperature at 80 - 85 °C and stir for 30 min. Then, add a dilute sulfuric acid solution with a mass concentration of 20% at a uniform rate within 60 min, control the pH value after addition to be 4.5 - 5, maintain the temperature at 80 - 85 °C and stir for 30 min to coat a loose silica film on the particle surface, and the mass of silica accounts for 6% of the mass of titanium dioxide.

[0012] In some embodiments, step d further includes: Add a sodium silicate solution with a concentration of 160 g / L to the pre-coated slurry at a uniform rate within 30 min, control the pH value of the slurry after addition to be 8 - 11.5, maintain the temperature at 80 - 85 °C and stir for 30 min. Then, add a dilute sulfuric acid solution with a mass concentration of 20% at a uniform rate within 60 min, control the pH value after addition to be 4.5 - 5, maintain the temperature at 80 - 85 °C and stir for 30 min to coat a loose silica film on the particle surface, and the mass of silica accounts for 6% of the mass of titanium dioxide.

[0013] In some embodiments, step e includes: Add a sodium hydroxide solution with a mass concentration of 15% to the pre-coated slurry at a uniform rate within 30 min, adjust the pH value to 9 - 10, maintain the temperature at 80 - 85 °C and stir for 15 min. Then, add normal temperature demineralized water or pure water within 30 min, cool down to 60 - 65 °C and stir for 15 min. Then, uniformly add sodium aluminate with a concentration of 100 g / L and a dilute sulfuric acid solution with a mass concentration of 20% within 90 min, control the pH value during the addition process to be 9 - 10.5 and stir for 60 min. Then, add a dilute sulfuric acid solution with a concentration of 20% to adjust the pH value to 7.2 - 7.6 and stir for 90 min to coat an alumina film on the particle surface and obtain the post-coated slurry, and the mass of alumina is 2.5% of the mass of titanium dioxide.

[0014] In some embodiments, step f includes: The fully aged slurry after coating is filtered by suction, and washed repeatedly with deionized water or distilled water to obtain a qualified filter cake. A polyol with a mass concentration of 0.5% is added to the qualified filter cake for organic treatment, followed by drying and pulverization to obtain high-covering titanium dioxide for water-based ink.

[0015] The preparation method of the above-mentioned high-covering titanium dioxide for water-based ink uses the primary product of rutile-type titanium dioxide particles, and uses a sodium silicate solution with a mass concentration of 0.2% as a dispersant to assist in the dispersion of the primary product of titanium dioxide particles. By controlling the slurry concentration and sieving steps, the slurry before coating can be obtained, which can effectively improve the stability, uniformity and reactivity of the slurry before coating, and provide an ideal precursor for the preparation of high-covering titanium dioxide. By combining the dilution, heating and pH adjustment of the slurry before coating, conditions for efficient reaction, uniform coating and stable performance are provided for the subsequent organic and inorganic coating processes. Based on the slurry before coating, sodium silicate solution and aluminum-containing compound, the pH value, concentration, temperature and time are synergistically controlled to form a gradient coating design of dense silica film - loose silica film - alumina film on the surface of titanium dioxide. By controlling the relevant parameters in the coating process of each film, the finally obtained titanium dioxide has high covering power and durability. The slurry after coating is aged, filtered by suction, washed and surface-organically treated to obtain the final high-covering titanium dioxide for water-based ink. In the whole preparation process, the addition content of each raw material element is small, reducing the raw material preparation cost, and no polluting gas is generated during the preparation process, which is beneficial to improving environmental protection. At the same time, the preparation process is simplified and suitable for large-scale industrial production. Description of the Drawings

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other embodiments can also be obtained based on these drawings.

[0017] Figure 1 It is a flowchart of a preparation method of high-covering titanium dioxide for water-based ink provided by an embodiment of the present invention. Detailed Embodiments

[0018] The following will further describe the embodiments of the present disclosure in detail in conjunction with the drawings and embodiments. The detailed description and drawings of the following embodiments are used to exemplarily illustrate the principles of the present disclosure, but cannot be used to limit the scope of the present disclosure. The present disclosure can be implemented in many different forms, not limited to the specific embodiments disclosed in the text, but including all technical solutions falling within the scope of the claims.

[0019] These embodiments are provided to make the present disclosure thorough and complete, and to fully convey the scope of the present disclosure to those skilled in the art. It should be noted that: unless otherwise specifically stated, the relative arrangements of components and steps, the compositions of materials, numerical expressions, and numerical values set forth in these embodiments should be construed as merely exemplary, rather than as limitations.

[0020] In addition, the terms "first", "second", and similar terms used in the present disclosure do not denote any order, quantity, or importance, but are merely used to distinguish different parts. Words such as "comprising" or "including" mean that the elements before this word cover the elements listed after this word, and do not exclude the possibility of also covering other elements.

[0021] All terms used in the present disclosure have the same meanings as those understood by those of ordinary skill in the art to which the present disclosure pertains, unless otherwise specifically defined. It should also be understood that terms defined in a general dictionary, such as those, should be construed to have meanings consistent with their meanings in the context of the relevant art, and should not be interpreted in an idealized or overly formal sense, unless specifically defined as such here.

[0022] Technologies, methods, and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and devices should be regarded as part of the specification.

[0023] It should be understood that the embodiments of the present invention shown in the exemplary embodiments are merely illustrative. Although only a few embodiments of the present invention have been described in detail, those skilled in the art can easily appreciate that various modifications are feasible without substantially departing from the teachings of the subject matter of the present invention. Accordingly, all such modifications should be included within the scope of the present invention. Without departing from the gist of the present invention, other substitutions, modifications, variations, and deletions can be made to the design, operating conditions, parameters, etc. of the following exemplary embodiments.

[0024] Please refer to Figure 1 , Figure 1 which shows a flowchart of a preparation method of a high-coverage titanium dioxide for water-based ink provided by an embodiment of the present invention. A preparation method of a high-coverage titanium dioxide for water-based ink includes: Step a: Add water and a sodium silicate solution with a mass concentration of 0.2% to the initial product of rutile-type titanium dioxide particles, perform beating and dispersion, and then screen to obtain a pre-coated slurry with a concentration of 450 - 680 g / L; Among them, rutile titanium dioxide has excellent refractive index and can have a large refractive index difference with the surrounding medium. Rutile titanium dioxide can provide white pigments with the best covering power. The covering power of sulfuric acid process rutile titanium dioxide is affected by the particle size and uniformity of the particles themselves, and is also affected by particle surface treatment, dispersion uniformity in the application system, volume concentration, and refractive index difference between titanium dioxide and the surrounding substrate.

[0025] Specifically, deionized water or distilled water is added to the initial product of rutile titanium dioxide particles, and then a certain amount of sodium silicate solution with a mass concentration of 0.2% is added for pulping and dispersion to form a titanium dioxide slurry. The concentration of the slurry is controlled between 450 - 680 g / L, and the obtained slurry is sanded for 60 - 120 min. The sanded slurry is sieved through a 100 - 600 - mesh sieve to obtain the pre - coating slurry after filtration.

[0026] Step b: Take an appropriate amount of the pre - coating slurry and dilute it to 400 - 450 g / L, heat it to 80 - 85 °C and adjust the pH value to 9 - 10.5. Specifically, take an appropriate amount of the pre - coating slurry and put it into a coating device, add deionized water or distilled water to it, dilute the concentration of the pre - coating slurry to 400 - 450 g / L, heat it to 80 - 85 °C, add a dilute alkali solution, such as a 15% sodium hydroxide solution, and adjust the pH value to 9 - 10.5.

[0027] Step c: Add a 100 g / L sodium silicate solution to the pre - coating slurry and adjust the pH value to 8.5 - 11.5, stir for 30 min, then adjust the pH value to 4.5 - 6 and stir for 60 min to coat a dense silica film on the particle surface. 2% ≤ the mass of silica accounts for the mass of titanium dioxide ≤ 3%. Control the concentration, pH value and stirring time of the sodium silicate solution added to the slurry to coat a dense silica film on the surface of titanium dioxide particles. Step d: Add a 120 - 280 g / L sodium silicate solution to the pre - coating slurry and adjust the pH value to 8 - 11.5, stir for 30 min, then adjust the pH value to 4.5 - 5 and stir for 30 min to coat a loose silica film on the particle surface. 3% < the mass of silica accounts for the mass of titanium dioxide ≤ 8%. After fully coating a dense silica film on the surface of titanium dioxide particles, further control the concentration, pH value and stirring time of the sodium silicate solution added to the slurry to fully coat a loose silica film on the surface of titanium dioxide particles.

[0028] Step e: Adjust the pH value of the slurry before coating to 9 - 10 and cool it down to 60 - 65°C. Add an aluminum-containing compound for reaction, and then adjust the pH value to 7.2 - 7.6 to coat an alumina film on the particle surface and obtain the slurry after coating. 2% ≤ the mass of alumina ≤ 3% of the mass of titanium dioxide. After completely coating the loose silica film on the surface of titanium dioxide particles, adjust the pH value, temperature, and the added aluminum-containing compound of the slurry, and finally form a uniform and continuous alumina film on the surface of titanium dioxide particles to complete the inorganic coating on the surface of titanium dioxide particles.

[0029] Step f: Cure, filter, wash, and perform surface organic treatment on the slurry after coating to obtain high-covering titanium dioxide for water-based ink. Among them, the specific steps of curing, filtering, washing, and surface organic treatment of the slurry after coating belong to the content of the prior art and will not be elaborated here. When performing organic treatment on the surface of titanium dioxide particles, polyol with a mass concentration of 0.5% can be used for organic treatment.

[0030] The above preparation method of high-covering titanium dioxide for water-based ink uses the initial product of rutile-type titanium dioxide particles, uses sodium silicate solution with a mass concentration of 0.2% as a dispersant to assist in the dispersion of the initial product of titanium dioxide particles, and cooperates with controlling the slurry concentration and sieving steps to obtain the slurry before coating, which can effectively improve the stability, uniformity, and reactivity of the slurry before coating, and provide an ideal precursor for the preparation of high-covering titanium dioxide. By combining the dilution, heating, and pH value adjustment of the slurry before coating, it provides conditions for efficient reaction, uniform coating, and stable performance in the subsequent organic and inorganic coating processes. Based on the slurry before coating, sodium silicate solution, and aluminum-containing compound, synergistically control the pH value, concentration, temperature, and time to form a gradient coating design of a dense silica film - loose silica film - alumina film on the surface of titanium dioxide. By controlling the relevant parameters in each film coating process, the finally obtained titanium dioxide has high covering power and durability. Cure, filter, wash, and perform surface organic treatment on the slurry after coating to obtain the final high-covering titanium dioxide for water-based ink. The content of each raw material element added in the whole preparation process is small, reducing the raw material preparation cost, and no polluting gas is generated during the preparation process, which is beneficial to improving environmental protection. At the same time, the preparation process is simplified and suitable for large-scale industrial production.

[0031] For a further understanding of the preparation method of high-covering titanium dioxide for water-based ink of the present invention, the following will be further elaborated in detail in specific examples.

[0032] Example 1 (1) Take a certain amount of rutile titanium dioxide particles and put them into a stirring device. Add a certain amount of deionized water or distilled water, and add 0.2% sodium silicate as a dispersant. Adjust the pH value of the slurry to 9.0 with dilute alkali solution, beat and disperse for 60 minutes, and then filter through a 325-mesh sieve to obtain a pre-coated slurry with a concentration of 450 g / L.

[0033] (2) Take a certain amount of the pre-coated slurry dispersed in step (1) and put it into a coating tank. Add deionized water or distilled water to dilute the concentration of the pre-coated slurry to 420 g / L, and then turn on the heating device to control the temperature of the pre-coated slurry to be maintained between 80 - 85 °C.

[0034] (3) Add an appropriate amount of 15% sodium hydroxide solution by mass concentration to the pre-coated slurry, adjust the pH value of the pre-coated slurry to 9.0, and maintain the slurry temperature between 80 - 85 °C.

[0035] (4) Slowly add a 100 g / L sodium silicate solution uniformly within 30 minutes to make the resulting silicon dioxide:titanium dioxide = 3.0%. Control the pH value of the slurry after the addition to be 8.5, and then continue to stir for 30 minutes while maintaining the slurry temperature between 80 - 85 °C.

[0036] (5) Slowly add a 20% dilute sulfuric acid solution uniformly within 120 minutes. Control the pH value of the slurry after the addition to be 4.5, maintain the slurry temperature between 80 - 85 °C, and continue to stir for 60 minutes.

[0037] (6) Slowly add a 280 g / L sodium silicate solution uniformly within 30 minutes to make the resulting silicon dioxide:titanium dioxide = 6.0%. After the addition is completed, measure the pH value of the slurry to be 8.0, continue to stir for 30 minutes, and maintain the slurry temperature between 80 - 85 °C.

[0038] (7) Slowly add a 20% dilute sulfuric acid solution by mass concentration uniformly within 60 minutes. Control the pH value of the slurry after the addition to be 4.5, continue to maintain the slurry temperature between 80 - 85 °C, and continue to stir for 30 minutes.

[0039] (8) After the stirring is completed, adjust the pH value of the slurry to 9.0 with dilute alkali solution within 30 minutes, maintain the slurry temperature between 80 - 85 °C, and continue to stir for 15 minutes.

[0040] (9) Add a certain amount of normal-temperature demineralized water or pure water within 30 minutes to reduce the slurry temperature to between 60 - 65 °C, and continue to stir for 15 minutes.

[0041] (10) Sodium aluminate at 100 g / L was added uniformly within 90 min to obtain alumina:titanium dioxide = 2.5%, and 20% dilute sulfuric acid was added. The pH value during the addition process was controlled at 9.0, and stirring was continued for 60 min after the addition was completed.

[0042] (11) The pH value was adjusted to 7.2 with 20% dilute sulfuric acid, and stirring was continued for 90 min while maintaining the pH value range.

[0043] (12) The slurry was subjected to ripening treatment. The fully ripened slurry was filtered by suction and washed. After passing the inspection, 0.5% polyol was added for organic treatment. After stirring evenly, it was dried and pulverized to obtain high-coverage titanium dioxide for water-based ink.

[0044] Example 2 The differences from Example 1 are as follows: In step (1), the pH value of the slurry was adjusted to 10.0 with dilute alkali solution, and it was beaten and dispersed for 60 min. Then it was filtered through a 325-mesh sieve to obtain the pre-coated slurry at 620 g / L. In step (3), the pH value of the pre-coated slurry was adjusted to 10.5. In step (4), the pH value of the slurry after the addition was completed was controlled at 11.5. In step (5), the pH value of the slurry after the addition was completed was controlled at 6.0. In step (6), sodium silicate solution at 240 g / L was added uniformly within 30 min. After the addition was completed, the pH value of the slurry was measured to be 11.5. In step (7), the pH value of the slurry after the addition was completed was controlled at 5.0. In step (8), the pH value of the slurry was adjusted to 10.0 with dilute alkali solution within 30 min. In step (10), the pH value during the addition process was controlled at 10.5. In step (11), the pH value was adjusted to 7.6 with 20% dilute sulfuric acid.

[0045] Example 3 The differences from Example 1 are as follows: In step (1), the pH value of the slurry was adjusted to 9.5 with dilute alkali solution, and it was beaten and dispersed for 60 min. Then it was filtered through a 325-mesh sieve to obtain the pre-coated slurry at 500 g / L. In step (3), the pH value of the pre-coated slurry was adjusted to 10. In step (4), the pH value of the slurry after the addition was completed was controlled at 9. In step (5), the pH value of the slurry after the addition was completed was controlled at 5. In step (6), sodium silicate solution at 200 g / L was added uniformly within 30 min. After the addition was completed, the pH value of the slurry was measured to be 10. In step (7), the pH value of the slurry after the addition was completed was controlled at 4.7. In step (8), the pH value of the slurry was adjusted to 9.5 with dilute alkali solution within 30 min. In step (10), the pH value during the addition process was controlled at 10. In step (11), the pH value was adjusted to 7.4 with 20% dilute sulfuric acid.

[0046] Example 4 The differences from Example 1 are as follows: In step (1), the pH value of the slurry is adjusted to 9.2 with dilute alkali solution, beaten and dispersed for 60 min, and then filtered through a 325-mesh sieve to obtain the pre-coated slurry with a concentration of 550 g / L; in step (3), the pH value of the pre-coated slurry is adjusted to 10.2; in step (4), the pH value of the slurry after the addition is controlled to be 11; in step (5), the pH value of the slurry after the addition is controlled to be 5.5; in step (6), a sodium silicate solution with a concentration of 160 g / L is added uniformly within 30 min, and the pH value of the slurry is measured to be 10.5 after the addition; in step (7), the pH value of the slurry after the addition is controlled to be 4.8; in step (8), the pH value of the slurry is adjusted to 9.2 with dilute alkali solution within 30 min; in step (10), the pH value during the addition is controlled to be 10.2; in step (11), the pH value is adjusted to 7.3 with 20% dilute sulfuric acid.

[0047] Example 5 The differences from Example 1 are as follows: In step (1), the pH value of the slurry is adjusted to 9.2 with dilute alkali solution, beaten and dispersed for 60 min, and then filtered through a 325-mesh sieve to obtain the pre-coated slurry with a concentration of 600 g / L; in step (3), the pH value of the pre-coated slurry is adjusted to 10.5; in step (4), the pH value of the slurry after the addition is controlled to be 11.5; in step (5), the pH value of the slurry after the addition is controlled to be 5.5; in step (6), a sodium silicate solution with a concentration of 120 g / L is added uniformly within 30 min, and the pH value of the slurry is measured to be 11 after the addition; in step (7), the pH value of the slurry after the addition is controlled to be 5.0; in step (8), the pH value of the slurry is adjusted to 9.8 with dilute alkali solution within 30 min; in step (10), the pH value during the addition is controlled to be 10.4; in step (11), the pH value is adjusted to 7.5 with 20% dilute sulfuric acid.

[0048] Comparative Examples 1 - 5 Comparative Examples 1-5 are compared with Examples 1-5 respectively. The titanium dioxide in Comparative Examples 1-5 is prepared by the prior art titanium dioxide preparation method, which at least does not include steps (4)-(5) or (6)-(7). Even when a silica film is coated on the surface of titanium dioxide particles, only one of a dense silica film or a porous silica film is coated, and the concentration of the sodium silicate solution added during the whole preparation process remains unchanged at 100 g / L.

[0049] The hiding power of the titanium dioxide samples prepared from the above Examples 1-5 and Comparative Examples 1-5 was detected, and the hiding power of the titanium dioxide samples obtained in each example and comparative example is shown in Table 1 below: Table 1

[0050] As can be seen from Table 1 above, the hiding power of the titanium dioxide prepared by the preparation method of the high-hiding titanium dioxide for water-based inks according to the present application has increased by at least 1.4% compared with that of the titanium dioxide prepared by the conventional technology. In the whole preparation process of the present application, the addition content of each raw material element is small, reducing the raw material preparation cost, and no polluting gas is generated during the preparation process, which is beneficial to improving environmental protection. At the same time, the preparation process is simplified, which is suitable for large-scale industrial production. At the same time, it can also effectively improve the yellow-edge resistance of downstream products. Downstream factories can appropriately reduce the dosage of titanium dioxide without affecting the application performance, improving the economic benefits of the entire titanium dioxide production and use chain.

[0051] So far, the embodiments of the present disclosure have been described in detail. In order to avoid obscuring the concept of the present disclosure, some details well known in the art have not been described. Those skilled in the art can fully understand how to implement the technical solutions disclosed herein based on the above description.

[0052] Although some specific embodiments of the present disclosure have been described in detail by way of examples, those skilled in the art should understand that the above examples are only for illustration and not for limiting the scope of the present disclosure. Those skilled in the art should understand that the above embodiments can be modified or partial technical features can be equivalently replaced without departing from the scope and spirit of the present disclosure. In particular, as long as there is no structural conflict, the technical features mentioned in each embodiment can be combined in any way.

Claims

1. A preparation method of high-covering titanium dioxide for water-based ink, characterized in that, Including: Step a: Add water and a sodium silicate solution with a mass concentration of 0.2% to the initial product of rutile titanium dioxide particles, perform pulping and dispersion, and then screen to obtain a pre-coating slurry with a concentration of 450 - 680 g / L; Step b: Take an appropriate amount of the pre-coating slurry and dilute it to 400 - 450 g / L, heat it to 80 - 85 °C and adjust the pH value to 9 - 10.5; Step c: Add a sodium silicate solution with a concentration of 100 g / L to the pre-coating slurry and adjust the pH value to 8.5 - 11.5, stir for 30 min, then adjust the pH value to 4.5 - 6 and stir for 60 min to coat a dense silica film on the particle surface, where 2% ≤ the mass of silica accounts for the mass of titanium dioxide ≤ 3%; Step d: Add a sodium silicate solution with a concentration of 120 - 280 g / L to the pre-coating slurry and adjust the pH value to 8 - 11.5, stir for 30 min, then adjust the pH value to 4.5 - 5 and stir for 30 min to coat a porous silica film on the particle surface, where 3% < the mass of silica accounts for the mass of titanium dioxide ≤ 8%; Step e: Adjust the pH value of the pre-coating slurry to 9 - 10 and cool it down to 60 - 65 °C, add an aluminum-containing compound for reaction, then adjust the pH value to 7.2 - 7.6 to coat an alumina film on the particle surface and obtain a post-coating slurry, where 2% ≤ the mass of alumina accounts for the mass of titanium dioxide ≤ 3%; Step f: Cure, filter, wash and perform surface organic treatment on the post-coating slurry to obtain high-coverage titanium dioxide for water-based inks.

2. The preparation method of the high-covering titanium dioxide for water-based ink according to claim 1, characterized in that, The step a further includes: Add deionized water or distilled water and a sodium silicate solution with a mass concentration of 0.2% to the initial product of rutile titanium dioxide particles, add a sodium hydroxide solution with a mass concentration of 15%, adjust the pH value to 9 - 10, perform pulping and dispersion for 60 - 120 min, and then filter with a 100 - 600 mesh sieve to obtain a pre-coating slurry with a concentration of 450 - 680 g / L.

3. The preparation method of the high-covering titanium dioxide for water-based ink according to claim 2, characterized in that, The step a further includes: Perform pulping and dispersion for 60 min, and then filter with a 325 mesh sieve to obtain a pre-coating slurry with a concentration of 450 - 620 g / L.

4. The preparation method of the high-covering titanium dioxide for water-based ink according to claim 1, characterized in that, The step b includes: Take an appropriate amount of the pre-coating slurry, add deionized water or distilled water to dilute it to 400 - 450 g / L, heat it to 80 - 85 °C, and then add a sodium hydroxide solution with a mass concentration of 15% to adjust the pH value to 9 - 10.

5.

5. The preparation method of the high-coverage titanium dioxide for water-based inks according to claim 1, characterized in that, The step c includes: Uniformly add a sodium silicate solution with a concentration of 100 g / L to the pre-coating slurry within 30 min, control the pH value of the slurry after addition to 8.5 - 11.5, maintain the temperature at 80 - 85 °C and stir for 30 min, then uniformly add a dilute sulfuric acid solution with a mass concentration of 20% within 120 min, control the pH value after addition to 4.5 - 6, maintain the temperature at 80 - 85 °C and stir for 60 min to coat a dense silica film on the particle surface, and the mass of silica accounts for 3% of the mass of titanium dioxide.

6. The preparation method of the high-hiding titanium dioxide for water-based ink according to claim 5, characterized in that, The step d includes: Add a sodium silicate solution with a concentration of 120 - 280 g / L to the pre-coated slurry at a uniform speed within 30 min, control the pH value of the slurry after addition to be 8 - 11.5, maintain the temperature at 80 - 85 °C and stir for 30 min. Then, add a dilute sulfuric acid solution with a mass concentration of 20% at a uniform speed within 60 min, control the pH value after addition to be 4.5 - 5, maintain the temperature at 80 - 85 °C and stir for 30 min to coat a loose silica film on the particle surface, and the mass of silica accounts for 6% of the mass of titanium dioxide.

7. The preparation method of the high-covering titanium dioxide for water-based ink according to claim 6, characterized in that, Step d further includes: Add a sodium silicate solution with a concentration of 200 g / L to the pre-coated slurry at a uniform speed within 30 min, control the pH value of the slurry after addition to be 8 - 11.5, maintain the temperature at 80 - 85 °C and stir for 30 min. Then, add a dilute sulfuric acid solution with a mass concentration of 20% at a uniform speed within 60 min, control the pH value after addition to be 4.5 - 5, maintain the temperature at 80 - 85 °C and stir for 30 min to coat a loose silica film on the particle surface, and the mass of silica accounts for 6% of the mass of titanium dioxide.

8. The preparation method of the high-covering titanium dioxide for water-based ink according to claim 6, characterized in that, Step d further includes: Add a sodium silicate solution with a concentration of 160 g / L to the pre-coated slurry at a uniform speed within 30 min, control the pH value of the slurry after addition to be 8 - 11.5, maintain the temperature at 80 - 85 °C and stir for 30 min. Then, add a dilute sulfuric acid solution with a mass concentration of 20% at a uniform speed within 60 min, control the pH value after addition to be 4.5 - 5, maintain the temperature at 80 - 85 °C and stir for 30 min to coat a loose silica film on the particle surface, and the mass of silica accounts for 6% of the mass of titanium dioxide.

9. The preparation method of the high-coverage titanium dioxide for water-based ink according to claim 1, characterized in that, Step e includes: Add a sodium hydroxide solution with a mass concentration of 15% to the pre-coated slurry at a uniform speed within 30 min, adjust the pH value to 9 - 10, maintain the temperature at 80 - 85 °C and stir for 15 min. Then, add normal temperature demineralized water or pure water within 30 min, cool down to 60 - 65 °C and stir for 15 min. Then, uniformly add sodium aluminate with a concentration of 100 g / L and a dilute sulfuric acid solution with a mass concentration of 20% within 90 min, control the pH value during the addition process to be 9 - 10.5 and stir for 60 min. Then, add a dilute sulfuric acid solution with a concentration of 20% to adjust the pH value to 7.2 - 7.6 and stir for 90 min to coat an alumina film on the particle surface and obtain the post-coated slurry, and the mass of alumina is 2.5% of the mass of titanium dioxide.

10. The preparation method of the high-covering titanium dioxide for water-based ink according to claim 1, characterized in that, Step f includes: Filter the completely cured post-coated slurry by suction, and wash it with deionized water or distilled water multiple times to obtain a qualified filter cake. Add a polyol with a mass concentration of 0.5% to the qualified filter cake for organic treatment, and then perform drying and pulverization treatment to obtain high-coverage titanium dioxide for water-based inks.

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