High-weather-resistant flame-retardant titanium dioxide as well as preparation method and application thereof

Abstract

The invention relates to the technical field of titanium dioxide production, in particular to high-weather-resistance flame-retardant titanium dioxide as well as a preparation method and application thereof. The preparation method comprises the following steps: S1, adjusting the temperature and pH of titanium dioxide base material slurry, adding a phosphoric acid solution and an alkali solution in a parallel flow manner, introducing air at the same time, and curing; s2, adjusting the pH value of the slurry, adding an aluminum salt and a pH regulator in a parallel flow manner, introducing air at the same time, and curing; s3, adjusting the pH value of the slurry, washing with water, and drying to obtain a filter cake; s4, adding an organic alkaline acid-binding agent to adjust the pH value of the slurry, and then adding an acylation reagent to react; and S5, adjusting the temperature of the slurry, adding acetone cyanohydrin, reacting, adding organic acid to adjust the pH value of the slurry, and carrying out alcohol washing, flash evaporation and steam powder to obtain the high-weather-resistant flame-retardant titanium dioxide. According to the method, air-assisted inorganic coating is adopted, acetone cyanohydrin is adopted for organic modification,-CN groups are introduced to the surface of titanium dioxide, and the weather resistance and flame retardance of titanium dioxide are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of titanium dioxide production technology, and more specifically, to a high weather-resistant and flame-retardant titanium dioxide, its preparation method, and its application. Background Technology

[0002] In the modern papermaking industry, titanium dioxide is a highly favored key raw material. With its high hiding power, it can effectively cover up defects in the paper substrate, keeping the paper pure. Its excellent coloring power can give the paper vibrant colors, and it performs well in both packaging and printing paper. At the same time, its excellent optical properties can also add gloss and texture to the paper, meeting the stringent quality requirements of high-grade paper production.

[0003] However, traditional titanium dioxide has poor adhesion and abrasion resistance, and it is prone to peeling off when the paper is damp, heated, or rubbed, leading to discoloration and affecting its appearance. It also suffers from poor weather resistance; in harsh environments, ultraviolet rays and other factors can corrode its molecular structure, causing the paper's appearance to deteriorate and its lifespan to shorten, failing to meet market demands for high-quality paper. To address these issues, commonly used modification methods are inorganic coating and organic modification. Inorganic coating modification involves using oxides of elements such as aluminum, silicon, and zirconium to coat titanium dioxide particles, forming a protective layer that blocks external erosion, improves the weather resistance of titanium dioxide, and also enhances its dispersibility and stability. Organic modification, on the other hand, alters its surface properties at the molecular level, strengthening its bond with paper fibers and improving abrasion resistance and flexibility.

[0004] However, existing modification methods have limited effect on improving the weather resistance of titanium dioxide, and existing titanium dioxide usually does not have flame retardant properties. Paper is mainly composed of plant cellulose, which is flammable. Fire accidents occur frequently, threatening life and property safety. Developing flame retardant paper has become an urgent need in the industry. Therefore, providing a titanium dioxide with high weather resistance and flame retardant function is of great significance for the preparation of flame retardant paper.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The primary objective of this invention is to provide a method for preparing highly weather-resistant and flame-retardant titanium dioxide. This method introduces -CN groups onto the surface of titanium dioxide by air-assisted inorganic coating and organic modification with acetone cyanohydrin, which significantly improves the weather resistance and flame retardancy of titanium dioxide.

[0007] The second objective of this invention is to provide a high weather-resistant and flame-retardant titanium dioxide, which is prepared by the method described above.

[0008] The third objective of this invention is to provide an application of the high weather-resistant and flame-retardant titanium dioxide as described above in papermaking.

[0009] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: A method for preparing high weather-resistant and flame-retardant titanium dioxide includes the following steps: S1. Adjust the temperature and pH of the titanium dioxide base slurry, and add phosphoric acid solution and alkaline solution while simultaneously introducing air to mature the slurry and obtain the first slurry; S2. Adjust the pH of the first slurry, and add aluminum salt and pH adjuster while simultaneously introducing air to mature it, thus obtaining the second slurry; S3. Adjust the pH of the second slurry, wash with water, and dry to obtain a filter cake; S4. The filter cake is pulped using an organic solvent, an organic basic acid-binding agent is added to adjust the pH of the pulp, and then an acylation reagent is added to react and a third pulp is obtained. S5. Adjust the temperature of the third slurry, add acetone cyanohydrin to react, add organic acid to adjust the pH of the slurry after the reaction, and then wash with alcohol, flash evaporate and steam to obtain the high weather-resistant flame-retardant titanium dioxide.

[0010] Preferably, in step S1, the temperature of the adjusted slurry is 75-85℃ and the pH is 4.8-5.2.

[0011] Preferably, in step S1, the amount of phosphoric acid solution added is 1%-3% of the mass of TiO2 in the slurry, calculated as P2O5. Preferably, in step S2, the pH of the adjusted slurry is 6.8-7.2; the aluminum salt includes aluminum sulfate or aluminate, and the amount of aluminum salt added is 3%-6% of the mass of TiO2 in the slurry, calculated as Al2O3.

[0012] Preferably, the air velocity in steps S1 and S2 is independently controlled between 1.5 and 2.5 m / s.

[0013] Preferably, in step S4, the organic solvent includes THF and / or DMI, and the pulp temperature is controlled at 20-30℃ after pulping.

[0014] Preferably, in step S4, the organic basic acid-binding agent includes triethylamine and / or pyridine.

[0015] Preferably, in step S4, after adding the organic alkaline acid-binding agent, the pH of the slurry is 9.0~10.0.

[0016] Preferably, in step S4, the acylation reagent includes p-toluenesulfonyl chloride, and the amount added is 3%-6% of the mass of TiO2 in the slurry, and the reaction time is 1-3 hours.

[0017] Preferably, in step S5, the temperature of the slurry is adjusted to 50-60°C, and the reaction time after adding the acetone cyanohydrin is 3-4 hours.

[0018] Preferably, in step S5, the amount of acetone cyanohydrin added is 0.1%-0.3% of the mass of TiO2 in the slurry.

[0019] A high weather-resistant and flame-retardant titanium dioxide is prepared by the preparation method of high weather-resistant and flame-retardant titanium dioxide described in any one of the foregoing embodiments.

[0020] The application of the high weather-resistant and flame-retardant titanium dioxide described in the foregoing embodiments in papermaking.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention first employs phosphoric acid and aluminum salts to inorganically coat titanium dioxide base material, forming an aluminum phosphate film and an alumina film on the surface of the titanium dioxide base material. During the inorganic coating process, air is introduced into the slurry to make the coating layer denser, effectively enhancing the weather resistance of titanium dioxide. Then, organic modification is performed using acetone cyanohydrin to introduce cyano groups onto the surface of titanium dioxide. The synergistic effect of cyano groups and phosphorus significantly improves the flame retardancy of titanium dioxide. The titanium dioxide prepared by this invention has both excellent weather resistance and flame retardancy, and can be used to prepare flame-retardant paper, promoting the development of the papermaking industry towards high quality and safety. Detailed Implementation

[0022] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0023] The first aspect of this invention provides a method for preparing high weather-resistant and flame-retardant titanium dioxide, comprising the following steps: S1. Adjust the temperature and pH of the titanium dioxide base slurry, and add phosphoric acid solution and alkaline solution while simultaneously introducing air to mature the slurry and obtain the first slurry; S2. Adjust the pH of the first slurry, and add aluminum salt and pH adjuster while simultaneously introducing air to mature it, thus obtaining the second slurry; S3. Adjust the pH of the second slurry, wash with water, and dry to obtain filter cake; S4. The filter cake is pulped using an organic solvent, an organic basic acid-binding agent is added to adjust the pH of the pulp, and then an acylation reagent is added to react and obtain a third pulp. S5. Adjust the temperature of the third slurry, add acetone cyanohydrin to react, add organic acid to adjust the pH of the slurry after the reaction, and then wash with alcohol, flash evaporate and steam to obtain high weather-resistant and flame-retardant titanium dioxide.

[0024] This invention first employs a phosphoric acid solution and aluminum salts to inorganically coat titanium dioxide substrate, sequentially forming an aluminum phosphate film and an aluminum oxide film on the surface of the titanium dioxide substrate. Air is introduced during the inorganic coating process, significantly enhancing the coating effect through several mechanisms: First, the air bubbles, through mechanical stirring and dynamic covering, ensure uniform dispersion of the coating agent and complete coverage of the titanium dioxide surface, preventing uneven coating and improving film density. Second, airflow further densifies the film, reducing micropores and cracks on the filter cake surface, thus facilitating water removal during subsequent dehydration, shortening drying time, saving flash steam consumption, reducing costs, and improving production efficiency. Third, the air bubbles create steric hindrance between titanium dioxide particles, reducing direct contact and van der Waals forces, effectively inhibiting agglomeration. Finally, air assistance enhances the bonding force between the coating agent and the powder, improving adhesion through surface activation or mechanical anchoring.

[0025] Then, titanium dioxide is organically modified by acetone cyanohydrin to introduce cyano groups onto its surface to improve its flame retardancy. The reaction mechanism is as follows: Under alkaline conditions, TiO2-OH undergoes an esterification reaction with an acylation reagent (such as p-toluenesulfonyl chloride TsCl) to generate the intermediate p-toluenesulfonate (TiO2-OTs); then, under the action of an acid-binding agent, using acetone cyanohydrin as the cyanide source, the OTs group in the p-toluenesulfonate is replaced with a cyano group (-CN) through a nucleophilic substitution reaction to generate the final product TiO2-CN. The process is as follows: .

[0026] The introduction of cyano groups (-C≡N) can make titanium dioxide flame retardant. On the one hand, cyano groups can form a carbon-nitrogen alternating conjugated structure through cyclization and cross-linking reactions, constructing a dense char layer that effectively isolates oxygen and heat conduction, inhibiting the spread of combustion. On the other hand, cyano groups can hydrolyze to generate carboxyl groups, which combine with metal ions to form stable compounds, enhancing the adhesion of the char layer and further improving the flame retardant effect. In addition, cyano-containing compounds (-C≡N) decompose at high temperatures, releasing inert gases such as nitrogen and ammonia, diluting the concentration of combustibles and carrying away heat, slowing down the combustion rate, and achieving the purpose of flame retardancy.

[0027] Furthermore, the synergistic effect of cyano (-C≡N) and phosphorus (P) significantly enhances the flame retardant effect. First, during combustion, the two react to form an intermediate containing NP bonds, which enhances the activity of phosphorylation, accelerates polymer dehydration to char, and reduces the release of flammable volatiles. Phosphorus acts as an acid source to promote char layer formation, while inert gases such as nitrogen and ammonia produced by cyano decomposition act as a gas source, causing the char layer to expand and dilute oxygen and combustibles, forming a dual flame retardant barrier of "gas phase-condensed phase". Second, the introduction of cyano can delay the volatilization loss of phosphorus compounds in the condensed phase, enhance its oxidation effect, make the char layer denser and more thermally stable, and effectively isolate heat and oxygen transfer. In addition, the PN synergistic system can also reduce the density of combustion smoke and the amount of toxic gases (such as carbon monoxide) generated, improving safety.

[0028] The method of this invention has a simple preparation process, mild and controllable reaction conditions, and is easy to scale up for production. The composite modification process of introducing cyano groups through air-assisted inorganic coating and acetone cyanohydrin organic modification significantly improves the weather resistance and flame retardancy of titanium dioxide.

[0029] In some specific embodiments of the present invention, in step S1, the concentration of the titanium dioxide base slurry is 290-310 g / L, for example, it can be any one value or a range of any two values ​​among 290 g / L, 295 g / L, 300 g / L, 305 g / L, and 310 g / L; the temperature of the adjusted slurry is 75-85℃, for example, it can be any one value or a range of any two values ​​among 75℃, 78℃, 80℃, 82℃, and 85℃; the pH is 4.8-5.2, for example, it can be any one value or a range of any two values ​​among 4.8, 4.9, 5.0, 5.1, and 5.2.

[0030] In some specific embodiments of the present invention, in step S1, the amount of phosphoric acid solution added is 1%-3% of the mass of TiO2 in the slurry, calculated as P2O5. For example, it can be any one value or a range of any two values ​​from 1%, 1.5%, 2%, 2.5%, to 3%. As an example, the mass concentration of the phosphoric acid solution used can be 100±10g / L (calculated as P2O5).

[0031] In some specific embodiments of the present invention, in step S1, the alkaline solution used includes NaOH solution and / or KOH solution. The purpose of using the alkaline solution and phosphoric acid solution in parallel flow is to maintain the pH of the slurry stably at 5.0±0.2. As an example, the mass concentration of the alkaline solution used can be 200±10 g / L.

[0032] In some specific embodiments of the present invention, in step S1, the curing time is not less than 30 minutes. For example, it can be any one value among 30 minutes, 40 minutes, 50 minutes, and 60 minutes, or a range of any two values.

[0033] In some specific embodiments of the present invention, in step S2, the pH of the adjusted slurry is 6.8-7.2, for example, it can be any one value or a range of any two values ​​among 6.8, 6.9, 7.0, 7.1, and 7.2; the aluminum salt includes aluminum sulfate or aluminate, wherein the aluminate includes sodium aluminate and / or potassium aluminate; the pH adjuster is an acid solution (such as HCl, H2SO4) or an alkaline solution (such as NaOH, KOH) to stably maintain the pH of the slurry at 7.0±0.2 during the co-current feeding process. When aluminum sulfate is used as the aluminum salt, the pH adjuster is an alkaline solution; when the aluminum salt is aluminate, the pH adjuster is an acid solution; the amount of aluminum salt added is 3%-6% of the mass of TiO2 in the slurry, calculated as Al2O3, for example, it can be any one value or a range of any two values ​​among 3%, 4%, 5%, and 6%; as an example, the mass concentration of the aluminum salt used is 100±10 g / L (calculated as Al2O3).

[0034] In some specific embodiments of the present invention, in step S2, the curing time is not less than 60 minutes. For example, it can be any one value among 60 minutes, 70 minutes, 80 minutes, and 90 minutes, or a range of values ​​composed of any two points.

[0035] In some specific embodiments of the present invention, the air velocity in steps S1 and S2 is independently controlled between 1.5 and 2.5 m / s. For example, it can be any one value or a range of any two values ​​among 1.5 m / s, 1.8 m / s, 2 m / s, 2.3 m / s, and 2.5 m / s.

[0036] In some specific embodiments of the present invention, in steps S1 and S2, air may be introduced only during the parallel feeding process, or air may be introduced during both the parallel feeding and the curing process.

[0037] In some specific embodiments of the present invention, in step S3, an acid solution (such as H2SO4 or HCl) is added to adjust the pH of the slurry to 5.0±0.2, and then the slurry is washed and dried; as an example, the concentration of the acid solution can be 130±10 g / L.

[0038] In some specific embodiments of the present invention, in step S4, the organic solvent includes THF and / or DMI, and the concentration of the pulp after beating is 190-210 g / L. For example, it can be any one value or a range of any two values ​​among 190 g / L, 195 g / L, 200 g / L, 205 g / L, and 210 g / L. The temperature of the pulp is controlled at 20-30°C. For example, it can be any one value or a range of any two values ​​among 20°C, 22°C, 25°C, 28°C, and 30°C.

[0039] In some specific embodiments of the present invention, in step S4, the organic basic acid-binding agent includes triethylamine and / or pyridine, which serves two purposes: first, to adjust the pH, and second, to neutralize the H generated in the organic reaction. + .

[0040] In some specific embodiments of the present invention, in step S4, the pH of the slurry after adding the organic alkaline acid-binding agent is 9.0~10.0. For example, it can be any one value or a range of any two values ​​among 9.0, 9.2, 9.5, 9.8, and 10.0.

[0041] In some specific embodiments of the present invention, in step S4, the acylation reagent used includes p-toluenesulfonyl chloride, and the amount added is 3%-6% of the mass of TiO2 in the slurry. For example, it can be any one value or a range of any two values ​​from 3%, 4%, 5%, and 6%. The reaction time is 1-3 hours, for example, it can be any one value or a range of any two values ​​from 1 hour, 1.5 hours, 2 hours, 2.5 hours, and 3 hours.

[0042] In some specific embodiments of the present invention, in step S5, the temperature of the adjusted slurry is 50-60°C, for example, it can be any one value or a range of any two values ​​among 50°C, 52°C, 55°C, 58°C, and 60°C; the reaction time after adding acetone cyanohydrin is 3-4 hours, for example, it can be any one value or a range of any two values ​​among 3 hours, 3.2 hours, 3.5 hours, 3.8 hours, and 4 hours.

[0043] In some specific embodiments of the present invention, in step S5, the amount of acetone cyanohydrin added is 0.1%-0.3% of the mass of TiO2 in the slurry. For example, it can be any one value or a range of any two values ​​from 0.1%, 0.15%, 0.2%, 0.25%, and 0.3%.

[0044] In some specific embodiments of the present invention, in step S5, the organic acids used include acetic acid and / or citric acid, the pH of the slurry is adjusted to 5.0-6.0, and then alcohol washing, flash evaporation and steam evaporation are performed.

[0045] In some specific embodiments of the present invention, after adjusting the pH of the slurry in steps S1, S2, S3, S4, and S5, it is necessary to mature the slurry before proceeding to the next step. As an example, the maturation time is not less than 30 minutes.

[0046] A second aspect of the present invention provides a high weather-resistant and flame-retardant titanium dioxide, which is prepared by any one of the preparation methods described in the foregoing embodiments.

[0047] A third aspect of the present invention provides the application of high weather-resistant and flame-retardant titanium dioxide as described in the second aspect in papermaking. The titanium dioxide provided by the present invention can be used to prepare flame-retardant paper.

[0048] The embodiments of the present invention will be described in detail below with reference to specific examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified, specific conditions in the examples are performed under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products. The concentrations of NaOH solution, phosphoric acid solution, aluminum salt solution, and H2SO4 solution used in the examples and comparative examples are 200 g / L, 100 g / L, 100 g / L, and 130 g / L, respectively. Process parameters not mentioned are conventional process parameters and are the same in each example and comparative example.

[0049] Example 1 S1. Pour the slurry with qualified particle size from the sand mill into a coating tank, control the concentration at 300 g / L, and heat it to 80℃; within 40 min, add NaOH solution to adjust the pH of the slurry to 5.0, and mature for 30 min; within 60 min, add phosphoric acid solution and NaOH solution in parallel to control the pH of the slurry to 5.0 ± 0.2, and simultaneously introduce air. The amount of phosphoric acid added is 2% of the mass of TiO2 in the slurry, calculated as P2O5, and the air flow rate is 2.0 m / s. After the addition is completed, stop the aeration and mature for 30 min to obtain the first slurry. S2. Within 40 min, add NaOH solution to adjust the slurry pH to 7.0 and mature for 30 min; within 120 min, add Al2(SO4)3 and NaOH solution in parallel to control the slurry pH to 7.0±0.2, and simultaneously introduce air. The amount of Al2(SO4)3 added is 5.2% of the mass of TiO2 in the slurry, calculated as Al2O3, and the air flow rate is 2.0 m / s. After the addition is completed, stop the aeration and mature for 60 min to obtain the second slurry. S3. Within 40 minutes, add H2SO4 solution to adjust the pH of the slurry to 5.0 and mature for 30 minutes; wash the resulting slurry with water and dry it to obtain filter cake; S4. Use THF to slurry the above filter cake, control the concentration at 200 g / L, control the slurry temperature at 25℃, add triethylamine to adjust the pH of the slurry to 9.5, and mature for 30 min; add p-toluenesulfonyl chloride, the amount of which is 5% of the mass of TiO2 in the slurry, and react for 2 h to obtain the third slurry; S5. Heat to 55℃, add acetone cyanohydrin, the amount added is 0.1% of the mass of TiO2 in the slurry, react for 3h, add citric acid within 60min to adjust the pH of the slurry to 5.5, and mature for 30min; wash with alcohol, and the filter cake is flash-evaporated and steam-dried to obtain the target titanium dioxide.

[0050] Example 2 S1. Pour the slurry with qualified particle size from the sand mill into a coating tank, control the concentration at 300 g / L, and heat it to 80℃; within 40 min, add NaOH solution to adjust the pH of the slurry to 5.0, and mature for 30 min; within 60 min, add phosphoric acid solution and NaOH solution in parallel to control the pH of the slurry to 5.0 ± 0.2, and simultaneously introduce air. The amount of phosphoric acid added is 2% of the mass of TiO2 in the slurry, calculated as P2O5, and the air flow rate is 2.0 m / s. After the addition is completed, stop the aeration and mature for 30 min to obtain the first slurry. S2. Within 40 min, add NaOH solution to adjust the slurry pH to 7.0 and mature for 30 min; within 120 min, add Al2(SO4)3 and NaOH solution in parallel to control the slurry pH to 7.0±0.2, and simultaneously introduce air. The amount of Al2(SO4)3 added is 5.2% of the mass of TiO2 in the slurry, calculated as Al2O3, and the air flow rate is 2.0 m / s. After the addition is completed, stop the aeration and mature for 60 min to obtain the second slurry. S3. Within 40 minutes, add H2SO4 solution to adjust the pH of the slurry to 5.0 and mature for 30 minutes; wash the resulting slurry with water and dry it to obtain filter cake; S4. Use THF to slurry the above filter cake, control the concentration at 200 g / L, control the slurry temperature at 25℃, add triethylamine to adjust the pH of the slurry to 9.5, and mature for 30 min; add p-toluenesulfonyl chloride, the amount of which is 5% of the mass of TiO2 in the slurry, and react for 2 h to obtain the third slurry; S5. Heat to 55℃, add acetone cyanohydrin, the amount added is 0.2% of the mass of TiO2 in the slurry, react for 3h, add citric acid within 60min to adjust the pH of the slurry to 5.5, and mature for 30min; wash with alcohol, and the filter cake is flash-evaporated and steam-dried to obtain the target titanium dioxide.

[0051] Example 3 S1. Pour the slurry with qualified particle size from the sand mill into a coating tank, control the concentration at 300 g / L, and heat it to 80℃; within 40 min, add NaOH solution to adjust the pH of the slurry to 5.0, and mature for 30 min; within 60 min, add phosphoric acid solution and NaOH solution in parallel to control the pH of the slurry to 5.0 ± 0.2, and simultaneously introduce air. The amount of phosphoric acid added is 2% of the mass of TiO2 in the slurry, calculated as P2O5, and the air flow rate is 2.0 m / s. After the addition is completed, stop the aeration and mature for 30 min to obtain the first slurry. S2. Within 40 min, add NaOH solution to adjust the slurry pH to 7.0 and mature for 30 min; within 120 min, add Al2(SO4)3 and NaOH solution in parallel to control the slurry pH to 7.0±0.2, and simultaneously introduce air. The amount of Al2(SO4)3 added is 5.2% of the mass of TiO2 in the slurry, calculated as Al2O3, and the air flow rate is 2.0 m / s. After the addition is completed, stop the aeration and mature for 60 min to obtain the second slurry. S3. Within 40 minutes, add H2SO4 solution to adjust the pH of the slurry to 5.0 and mature for 30 minutes; wash the resulting slurry with water and dry it to obtain filter cake; S4. Use THF to slurry the above filter cake, control the concentration at 200 g / L, control the slurry temperature at 25℃, add triethylamine to adjust the pH of the slurry to 9.5, and mature for 30 min; add p-toluenesulfonyl chloride, the amount of which is 5% of the mass of TiO2 in the slurry, and react for 2 h to obtain the third slurry; S5. Heat to 55℃, add acetone cyanohydrin, the amount added is 0.3% of the mass of TiO2 in the slurry, react for 3h, add citric acid within 60min to adjust the pH of the slurry to 5.5, and mature for 30min; wash with alcohol, and the filter cake is flash-evaporated and steam-dried to obtain the target titanium dioxide.

[0052] Comparative Example 1 S1. Pour the slurry with qualified particle size from the sand mill into a coating tank, control the concentration at 300 g / L, and heat it to 80℃; within 40 min, add NaOH solution to adjust the pH of the slurry to 5.0, and let it mature for 30 min; within 60 min, add phosphoric acid solution and NaOH solution in parallel to control the pH of the slurry to 5.0 ± 0.2, wherein the amount of phosphoric acid added is 2% of the mass of TiO2 in the slurry based on P2O5, and mature for 30 min to obtain the first slurry; S2. Within 40 min, add NaOH solution to adjust the slurry pH to 7.0 and mature for 30 min; within 120 min, add Al2(SO4)3 and NaOH solution in parallel to control the slurry pH to 7.0 ± 0.2. The amount of Al2(SO4)3 added is 5.2% of the mass of TiO2 in the slurry, calculated as Al2O3. Mature for 60 min to obtain the second slurry. S3. Within 40 minutes, add H2SO4 solution to adjust the pH of the slurry to 5.0 and mature for 30 minutes; wash the resulting slurry with water, and flash-evaporate and steam-powder the filter cake to obtain the target titanium dioxide.

[0053] Comparative Example 2 S1. Pour the slurry with qualified particle size from the sand mill into a coating tank, control the concentration at 300 g / L, and heat it to 80℃; within 40 min, add NaOH solution to adjust the pH of the slurry to 5.0, and mature for 30 min; within 60 min, add phosphoric acid solution and NaOH solution in parallel to control the pH of the slurry to 5.0 ± 0.2, and simultaneously introduce air. The amount of phosphoric acid added is 2% of the mass of TiO2 in the slurry, calculated as P2O5, and the air flow rate is 2.0 m / s. After the addition is completed, stop the aeration and mature for 30 min to obtain the first slurry. S2. Within 40 min, add NaOH solution to adjust the pH of the slurry to 7.0 and mature for 30 min; within 120 min, add Al2(SO4)3 and NaOH solution in parallel to control the pH to 7.0±0.2, and simultaneously introduce air. The amount of Al2(SO4)3 added is 5.2% of the mass of TiO2 in the slurry, calculated as Al2O3, and the air flow rate is 2.0 m / s. After the addition is completed, stop the aeration and mature for 60 min to obtain the second slurry. S3. Within 40 minutes, add H2SO4 solution to adjust the pH of the slurry to 5.0 and mature for 30 minutes; wash the resulting slurry with water, and flash-evaporate and steam-powder the filter cake to obtain the target titanium dioxide.

[0054] Comparative Example 3 S1. Pour the slurry with qualified particle size from the sand mill into a coating tank, control the concentration at 300 g / L, and heat it to 80℃; within 40 min, add NaOH solution to adjust the pH of the slurry to 5.0, and let it mature for 30 min; within 60 min, add phosphoric acid solution and NaOH solution in parallel to control the pH of the slurry to 5.0 ± 0.2, wherein the amount of phosphoric acid added is 2% of the mass of TiO2 in the slurry based on P2O5, and mature for 30 min to obtain the first slurry; S2. Within 40 min, add NaOH solution to adjust the slurry pH to 7.0 and mature for 30 min; within 120 min, add Al2(SO4)3 and NaOH solution in parallel to control the slurry pH to 7.0 ± 0.2. The amount of Al2(SO4)3 added is 5.2% of the mass of TiO2 in the slurry, calculated as Al2O3. Mature for 60 min to obtain the second slurry. S3. Within 40 minutes, add H2SO4 solution to adjust the pH of the slurry to 5.0 and mature for 30 minutes; wash the resulting slurry with water and dry it to obtain filter cake; Steps S4 and S5 are the same as in Example 3.

[0055] Comparative Example 4 Comparative Example 4 is similar to Example 3, except that the P coating in step S1 was not performed, and all other conditions are the same as in Example 3.

[0056] Test case (a) The moisture content of the target titanium dioxide in each embodiment and each comparative example was tested, and the test method is as follows: Take 10g of finished titanium dioxide under the same flash evaporation and steam powder conditions, treat it in an oven at 105℃ for 4h, and calculate the mass loss ratio before and after treatment, which is the moisture content.

[0057] The test results are shown in Table 1.

[0058] Table 1

[0059] Data from Examples 1-3 and Comparative Example 1 show that introducing air and -CN groups during the coating process can accelerate the drying speed of titanium dioxide filter cake; data from Comparative Examples 1-4 show that the introduction of -CN groups has a relatively small effect on improving the drying speed of titanium dioxide, and introducing air during the coating process is the key to improving the drying speed of titanium dioxide.

[0060] (ii) The target titanium dioxide from each embodiment and each comparative example was used to make paper using the same process, and the application performance of the paper was tested.

[0061] Papermaking is performed using conventional techniques in this field, and the papermaking process is as follows: (1) Pulping: Mix coarse pulp, fine pulp, titanium dioxide and water, add wet strength agent and NaOH solution, continue pulping for 1 minute, transfer to a measuring cup and let stand for 40 minutes; (2) Sheet making: Wet paper sheets are formed using a sheet making machine and then dried; (3) Basis weight: Visually inspect the uniformity and smoothness of the dried paper; (4) Impregnation: Select paper with similar amount and ash content, impregnate the paper in melamine glue for 2 minutes, use a wire bar coater to remove excess glue, place it in a 135℃ oven for 2 minutes, and the paper surface is half dry. (5) Press plate: Place the black and white paper impregnated with glue, the paper impregnated with glue for the standard sample and the mirror steel plate on the OSB board in sequence; gently place the OSB board on the vulcanizing machine and press it at 160℃ and 7.5Mpa for 1 minute.

[0062] 1. Test the flame retardancy of paper. According to GB / T 14656-2009, the char length of the paper was tested using a horizontal and vertical burner, with the flame-retardant paper size being 70 mm × 210 mm; according to GB / T 5454—1997, the limiting oxygen index (LOI) of the paper was tested using an oxygen index tester, with the flame-retardant paper size being 38 mm × 140 mm.

[0063] The test results are shown in Table 2.

[0064] Table 2

[0065] The data in Table 1 show that introducing -CN groups onto the surface of titanium dioxide significantly improves the flame retardancy of paper, and the flame retardancy of paper exhibits a positive correlation with the increase of -CN groups. The data from Example 3 and Comparative Example 4 show that the flame retardant performance is better when both P and -CN are present, which is due to their synergistic effect.

[0066] 2. Test the paper's weather resistance. The paper weather resistance test method adopted was ASTM D4303 (xenon lamp irradiation for 120 hours), and the test results are shown in Table 3.

[0067] Table 3

[0068] The data from Examples 1-3 and Comparative Example 1 show that introducing air and -CN groups during the coating process can significantly improve the weather resistance of paper, with ΔE decreasing by approximately 60%; the data from Comparative Examples 1-3 show that the -CN groups improve the weather resistance of paper to a much lesser extent than introducing air during the coating process, indicating that introducing air during the coating process is the key to improving the weather resistance of titanium dioxide in this invention; the data from Comparative Example 4 show that aluminum phosphate coating also has an important impact on improving weather resistance.

[0069] Although the present invention has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and scope of the present invention; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such substitutions and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. A method for preparing a high-weather-resistant flame-retardant titanium white powder, characterized in that, The method comprises the following steps: S1. Adjusting the temperature and pH of a titanium dioxide base slurry, and adding phosphoric acid solution and alkali solution in a flow, while air is introduced, and aging to obtain a first slurry; S2. Adjusting the pH of the first slurry, and adding an aluminum salt and a pH regulator in a flow, while air is introduced, and aging to obtain a second slurry; S3. Adjusting the pH of the second slurry, and washing with water, drying to obtain a filter cake; S4. Pulp beating the filter cake with an organic solvent, adjusting the pH of the slurry by adding an organic alkaline acid-binding agent, and then adding an acylation reagent to react, to obtain a third slurry; S5. Adjusting the temperature of the third slurry, adding acetone cyanohydrin to react, and then adding an organic acid to adjust the pH of the slurry after the reaction, and then washing with alcohol, flash evaporation and steam powdering to obtain the high-weather-resistant flame-retardant titanium dioxide.

2. The method of preparing high weather resistant flame retardant titanium dioxide according to claim 1, characterized in that, In step S1, the temperature of the adjusted slurry is 75-85℃, and the pH is 4.8-5.

2.

3. The method for preparing high weather-resistant and flame-retardant titanium dioxide according to claim 1, characterized in that, In step S1, the amount of the added phosphoric acid solution is 1%-3% of the mass of TiO2 in the slurry in terms of P2O5.

4. The method of preparing high weather resistant flame retardant titanium dioxide according to claim 1, characterized in that, In step S2, the pH of the adjusted slurry is 6.8-7.2; the aluminum salt includes aluminum sulfate or metavanadate, and the amount of the added aluminum salt is 3%-6% of the mass of TiO2 in the slurry in terms of Al2O3.

5. The method of preparing high weather resistant flame retardant titanium dioxide according to claim 1, characterized in that, The air flow rate in steps S1 and S2 is independently controlled at 1.5-2.5 m / s.

6. The method of preparing high weather resistant flame retardant titanium dioxide according to claim 1, characterized in that, In step S4, at least one of the following characteristics is met: (1) the organic solvent includes THF and / or DMI, and the temperature of the slurry after pulp beating is controlled at 20-30℃; (2) the organic alkaline acid-binding agent includes triethylamine and / or pyridine; (3) after adding the organic alkaline acid-binding agent, the pH of the slurry is 9.0-10.0; (4) the acylation reagent includes p-toluenesulfonyl chloride, and the amount of the added acylation reagent is 3%-6% of the mass of TiO2 in the slurry, and the reaction time is 1-3h.

7. The method of preparing high weather resistant flame retardant titanium dioxide according to claim 1, characterized in that, In step S5, the temperature of the adjusted slurry is 50-60℃, and the reaction time after adding the acetone cyanohydrin is 3-4h.

8. The method of preparing high weather resistant flame retardant titanium dioxide according to claim 1, characterized in that, In step S5, the amount of the added acetone cyanohydrin is 0.1%-0.3% of the mass of TiO2 in the slurry.

9. A high weather resistant flame retardant titanium dioxide, characterized in that, The high-weather-resistant flame-retardant titanium dioxide is prepared by the method of any one of claims 1-8.

10. The high-weather-resistant flame-retardant titanium dioxide of claim 9 in papermaking.

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