Preparation method of high-conductivity chlorinated titanium dioxide

Abstract

This invention relates to the field of pigment preparation, specifically to a method for preparing highly conductive titanium dioxide using the chloride process. The method includes: reacting oxygen and titanium tetrachloride with an oxidation reaction to generate titanium dioxide particles, which are then introduced into a cooling conduit. A preheated coating agent is added for a coating reaction and slurry preparation. The slurry temperature is adjusted to 60-75°C and the pH to 2-3, and a phosphate-containing compound is added. The slurry temperature is adjusted to 80-90°C, and a sodium aluminate solution and an alkaline solution are added to adjust the pH of the slurry to 9.5-10.5, followed by a first homogenization treatment. A tin chloride solution and a sodium aluminate solution are added, and the pH of the slurry is adjusted to 7.5-8.5, followed by a second homogenization treatment. The pH of the slurry is adjusted to 4.5-5.5, followed by a third homogenization treatment. The pH of the slurry is adjusted to 5.5-6.5, followed by a fourth homogenization treatment. This method is low-cost, simple, and suitable for large-scale production, producing conductive titanium dioxide with excellent performance.

Description

Technical Field

[0001] This invention relates to the field of pigment preparation, and more specifically, to a method for preparing highly conductive chloride-process titanium dioxide. Background Technology

[0002] Conductive titanium dioxide (TID) is a novel type of electronically conductive functional semiconductor pigment (filler) made from titanium dioxide as a matrix using nanotechnology. Through surface treatment and semiconductor doping, a conductive oxide layer is formed on the matrix surface. Conductive titanium dioxide exhibits low light absorption and high light scattering, and possesses excellent optical properties such as gloss, whiteness, tinting strength, and hiding power. It can be used to produce near-white and other light-colored permanent conductive and antistatic products. It is particularly suitable for conductive and antistatic products and environments requiring high whiteness.

[0003] Currently, most conductive titanium dioxide on the market comes from abroad (e.g., Ishihara, Japan), and is very expensive (208,000-277,000 RMB / ton). General-purpose titanium dioxide is priced at 10,000-20,000 RMB / ton. Domestically produced conductive titanium dioxide is mostly in the research and development stage, with unstable conductivity and immature technology, making large-scale production impossible. Existing conductive titanium dioxide preparation technologies have several drawbacks. For example, the blending method, which mechanically mixes conductive materials with titanium dioxide, produces conductive titanium dioxide with uneven color and unstable conductivity. Another example is the coating method, which coats titanium dioxide with an ATO conductive layer. This method involves mixing tin and antimony salts before coating the titanium dioxide, making the operation complex. Furthermore, subsequent calcination leads to sintering, poor dispersibility, and consequently, poor conductivity. Finally, hydrothermal reaction coating in a liquid slurry state requires an additional hydrothermal reactor, resulting in a long reaction time, a lengthy process, and low production efficiency.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing highly conductive titanium dioxide by chloride process, so as to solve the technical problems of existing conductive titanium dioxide relying on imports and having high costs, as well as the difficulty of large-scale production of domestic products due to unstable conductivity and complex production processes.

[0006] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: A method for preparing highly conductive titanium dioxide by chloride process includes the following steps: (a) Oxygen and titanium tetrachloride are oxidized to produce titanium dioxide particles; the titanium dioxide particles enter a cooling conduit, and a preheated coating agent is added to the cooling conduit to carry out a coating reaction and slurry to obtain a slurry; (b) Adjust the temperature of the slurry to 60~75℃ and the pH to 2~3, and add a phosphate compound for a period of time; adjust the temperature of the slurry to 80~90℃, add sodium aluminate solution and alkaline solution to adjust the pH of the slurry to 9.5~10.5 and then perform the first homogenization treatment; (c) Add tin chloride solution and sodium aluminate solution, adjust the pH of the slurry after the first homogenization treatment to 7.5~8.5, and then perform a second homogenization treatment; (d) Adjust the pH of the slurry after the second homogenization treatment to 4.5~5.5 and maintain it for a period of time before performing the third homogenization treatment; (e) Adjust the pH of the slurry after the third homogenization treatment to 5.5~6.5 and maintain it for a period of time before performing the fourth homogenization treatment.

[0007] Preferably, in step (a), the molar ratio of oxygen to titanium tetrachloride is 1.05 to 1.35:1.

[0008] Preferably, in step (a), when the particle size of the titanium dioxide particles is 200~500nm, the preheated coating agent is added into the cooling conduit.

[0009] Preferably, in step (a), the amount of the coating agent added accounts for 3wt% to 25wt% of the mass of the titanium dioxide particles.

[0010] Preferably, in step (a), the preheating temperature of the coating agent is 150~250℃.

[0011] Preferably, the coating agent comprises: tin chloride, antimony chloride, and aluminum chloride; The mass ratio of tin chloride to antimony chloride is 1.05 to 9.9:1, and the mass of aluminum chloride is 25% to 150% of the total mass of tin chloride and antimony chloride.

[0012] Preferably, in step (b), the amount of the phosphate-containing compound added is 0.3wt%~0.6wt%, and the addition time is 40~60min.

[0013] Preferably, the phosphate-containing compound includes: phosphate and / or phosphoric acid.

[0014] Preferably, in step (b), the amount of sodium aluminate solution added is 0.5% to 1.5% of the dry weight of titanium dioxide, calculated as alumina; and the amount of alkaline solution added is 0.3% to 0.5% of the dry weight of titanium dioxide, calculated as alkali.

[0015] Preferably, in step (b), the sodium aluminate solution and the alkaline solution are added over a period of 60 to 80 minutes.

[0016] Preferably, in step (c), the amount of tin chloride added is 0.4% to 0.8% of the dry mass of titanium dioxide, calculated as tin dioxide; and the amount of sodium aluminate solution added is 0.5% to 1.0% of the dry mass of titanium dioxide, calculated as alumina.

[0017] Preferably, in step (c), the addition time of the tin chloride solution and the sodium aluminate solution is 30~60 min.

[0018] Preferably, in step (d), the pH of the slurry is maintained at 4.5-5.5 for 40-60 minutes.

[0019] Preferably, in step (e), the pH of the slurry is maintained at 5.5 to 6.5 for 20 to 30 minutes.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The titanium dioxide prepared by this invention is coated in an excess oxygen atmosphere during the initial stage of the chlorination cooling conduit, forming a more uniform and continuous coating layer of tin oxide, antimony oxide, and Al2O3. This prevents further growth of titanium dioxide particles, resulting in more uniform particle size and a more concentrated particle size distribution. Al2O3 is doped into the conductive layer, which is mainly composed of tin oxide and antimony oxide. Alumina is distributed in a dotted pattern on the surface of the titanium dioxide particles, bridging the coating of tin oxide and antimony oxide to form a network of conductive layers covering the surface of the titanium dioxide particles. High conductivity can be achieved with low tin oxide and antimony oxide coating amounts, reducing the amount of costly tin oxide and antimony oxide used without affecting conductivity. The excess oxygen ensures the deposition rate and uniformity of the conductive film layer. 2. The titanium dioxide prepared by this invention has an outermost layer coated with a mixed film of tin oxide and aluminum oxide. On the one hand, this solves the problems of difficult subsequent desalination washing and dispersion in the substrate; on the other hand, the mixed film is connected to the inner conductive film, so that the conductivity of the inner layer is not reduced by the outer aluminum oxide coating. 3. The preparation method of this invention does not require additional equipment, has a short process flow, is simple to operate, and has low production costs; 4. The titanium dioxide prepared by this invention has a uniform and continuous conductive film coating on its surface, resulting in good conductivity and excellent color. Attached Figure Description

[0021] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 The temperature range for the gas-phase preparation of TiO2; Figure 2 The process flow for preparing titanium dioxide via the chloride method; Figure 3 This is a flow chart of the coating process of the present invention. Detailed Implementation

[0023] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and 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.

[0024] One aspect of the present invention relates to a method for preparing highly conductive titanium dioxide produced by the chloride process, such as... Figure 3 As shown, it includes the following steps: (a) Oxygen and titanium tetrachloride are oxidized to produce titanium dioxide particles; the titanium dioxide particles enter a cooling conduit, and a preheated coating agent is added to the cooling conduit to carry out a coating reaction and slurry to obtain a slurry; (b) Adjust the temperature of the slurry to 60-75°C (e.g., any value of 60°C, 63°C, 65°C, 70°C, 73°C, or 75°C, or a range between any two), and the pH to 2-3 (e.g., any value of 2, 2.3, 2.5, 2.8, or 3, or a range between any two), and add a phosphate-containing compound for a period of time; adjust the temperature of the slurry to 80-90°C, add sodium aluminate solution and alkaline solution to adjust the pH of the slurry to 9.5-10.5, and then perform a first homogenization treatment; the acidic environment of 60-75°C and pH 2-3 ensures that the phosphate-containing compound can effectively anchor and stabilize the initial conductive layer of the vapor-phase deposition, while homogenizing the surface charge of the particles; then raise the temperature to 80-90°C to accelerate the reaction, and under strongly alkaline conditions of pH 9.5-10.5, promote the hydrolysis of sodium aluminate, and uniformly and densely deposit an alumina transition layer; (c) Add tin chloride solution and the sodium aluminate solution to adjust the pH of the slurry after the first homogenization treatment to 7.5~8.5 (for example, it can be any point value or any range between 7.5, 7.7, 7.9, 8.1, 8.3 or 8.5, or any value between two of them) and then perform a second homogenization treatment; in a weakly alkaline environment of pH 7.5~8.5, by simultaneously adding tin chloride solution and sodium aluminate solution, tin salt can be uniformly hydrolyzed and deposited on the surface of alumina transition layer, supplementing and extending the internal conductive network; aluminum salt further stabilizes the composite structure; (d) Adjust the pH of the slurry after the second homogenization treatment to 4.5~5.5 (for example, it can be a point value or a range between any two of 4.5, 4.7, 4.9, 5.1, 5.3 or 5.5) and maintain it for a period of time before performing the third homogenization treatment; (e) Adjust the pH of the slurry after the third homogenization treatment to 5.5 to 6.5 (for example, it can be a point value or a range between any two of 5.5, 5.7, 5.9, 6.1, 6.3 or 6.5) and maintain it for a period of time before performing the fourth homogenization treatment.

[0025] The process flow for preparing titanium dioxide via the chloride method is as follows: Figure 2 As shown, the oxidation stage of the typical chloride process for titanium dioxide involves the reaction of TiCl4 with O2. In this stage, TiCl4 is preheated to 350-500℃, and O2 is preheated to 700-1000℃. The reaction temperature is usually between 1500℃ and 2000℃. After the reaction, the mixture enters a cooling conduit with circulating water, where the temperature rapidly decreases to 300-350℃. The temperature range for the gas-phase TiO2 preparation process is as follows: Figure 1 As shown. In this stage, the titanium dioxide particles have completed crystal transformation and grain growth. This invention utilizes the high-temperature process of cooling conduits exceeding that of wet coating, and the excellent coating effect of highly dispersed particles in the gas phase state, which cannot be achieved by hydrothermal methods. Preheated tin chloride, antimony chloride, and aluminum chloride are added to form a more uniform and continuous coating layer of tin oxide, antimony oxide, and Al2O3, which prevents further growth of titanium dioxide particles, resulting in more uniform particle size and a more concentrated particle size distribution. Al2O3 is doped into the conductive layer mainly composed of tin oxide and antimony oxide, while aluminum oxide is distributed in a dotted pattern on the surface of titanium dioxide particles, building a bridge for the coating of tin oxide and antimony oxide, forming a network of conductive layers covering the surface of titanium dioxide particles, achieving high conductivity with low tin oxide and antimony oxide coating amounts.

[0026] The titanium dioxide prepared by this invention forms a more uniform and continuous coating layer of tin oxide and antimony oxide during the initial stage of the chlorination cooling conduit after the fumed titanium dioxide lattice growth is completed. This coating layer prevents further growth of titanium dioxide particles, resulting in more uniform particle size and a more concentrated particle size distribution. Furthermore, the conductive material is uniformly doped into the TiO2 lattice, providing high conductivity. The preparation method of this invention does not require additional equipment, has a short process flow, is simple to operate, and has low production costs. The titanium dioxide prepared by this invention has a uniform and continuous conductive film coating on its surface, resulting in good conductivity and a superior color.

[0027] The conductive titanium dioxide prepared by this invention possesses a unique three-layer gradient composite coating structure. The innermost layer, formed in situ in the cooling conduit during the vapor-phase coating stage, is a "conductive symbiotic base layer" composed of tin oxide, antimony oxide, and alumina, where alumina acts as a bridge connecting the conductive components, constructing an initial highly efficient conductive network. The middle layer is a dense alumina transition layer formed under strongly alkaline conditions by adding sodium aluminate solution; its main function is to protect the inner conductive structure and significantly improve powder dispersibility. The outermost layer is a tin oxide-alumina composite modification layer formed under weakly alkaline conditions by simultaneously adding tin chloride and sodium aluminate solution. This layer not only supplements the conductive pathways but also ensures effective extraction of internal conductivity. This three-layer structure is constructed in stages through a "vapor-phase deposition + liquid-phase composite" process, synergistically achieving a unified high conductivity, high dispersibility, and good stability in the product.

[0028] Further, in step (a), the molar ratio of oxygen to titanium tetrachloride is 1.05 to 1.35:1 (e.g., but not limited to 1.05:1, 1.10:1, 1.15:1, 1.20:1, 1.25:1, 1.30:1, or 1.35:1), preferably 1.15 to 1.25:1. Introducing excess oxygen can improve the deposition rate and uniformity of the subsequent vapor-coated conductive film.

[0029] Further, in step (a), when the particle size of the titanium dioxide particles is 200~500nm (for example, it can be any point value or a range between any two of 200nm, 230nm, 250nm, 280nm, 300nm, 330nm, 350nm, 380nm, 400nm, 430nm, 450nm, 480nm or 500nm), preferably 250~450nm, more preferably 280~360nm, the preheated coating agent is added into the cooling conduit. Within this particle size range, the particles have completed crystal transformation and initial growth, and the surface activity is moderate. At this time, coating can effectively prevent further sintering and growth of the particles, which is conducive to forming a product with concentrated particle size distribution and uniform coating.

[0030] Furthermore, feed pipes are added at approximately 1 / 6 to 1 / 3 of the total circumference of the cooling conduit near the oxidation zone. These feed pipes are spaced 3-5 times at equal intervals. The upper end of each feed pipe is connected to a preheating tank for the coating agent, with a volume of 1.5-3 m³. 3 It features a built-in circulating pump, and the preheating tank walls are preheated with hot air. Three coating agent storage tanks, each with a volume of 1.5~3m³, are connected to the upper end of the preheating tank. 3 Match the coating agent and preheating tank volume according to the production output.

[0031] Further, in step (a), the amount of the coating agent added is 3wt% to 25wt% of the mass of the titanium dioxide particles (for example, it can be any one of 3wt%, 5wt%, 10wt%, 15wt%, 20wt%, or 25wt%, or a range between any two), preferably 4.5wt% to 20wt%, more preferably 8.0wt% to 20wt%. This dosage range minimizes the consumption of expensive tin and antimony raw materials while ensuring the formation of a complete and continuous conductive network, achieving a balance of obtaining high conductivity at a lower cost.

[0032] Further, in step (a), the preheating temperature of the coating agent is 150~250℃, including but not limited to any one of 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 220℃, 230℃, 240℃, or 250℃, or a range between any two. Preheating prevents the coating agent from rapidly cooling and condensing when it enters the high-temperature conduit, ensuring its rapid vaporization and full contact and reaction with the titanium dioxide particles, which is an important process condition for achieving uniform vapor-phase coating.

[0033] Furthermore, the coating agent includes: tin chloride, antimony chloride, and aluminum chloride.

[0034] Further, the mass ratio of tin chloride to antimony chloride is 1.05 to 9.9:1 (e.g., but not limited to 1.05:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, or 9.9:1), and the mass of aluminum chloride is 25% to 150% of the total mass of tin chloride and antimony chloride (e.g., any one of 25%, 35%, 45%, 55%, 65%, 75%, 85%, 95%, 105%, 115%, 125%, 135%, 145%, or 150%, or a range between any two). This specific ratio results in the co-generation of a symbiotic coating layer of tin oxide (conductive host), antimony oxide (dopant), and aluminum oxide (structural bridge) in the gas phase. The aluminum oxide is distributed in a dotted pattern, building a network of connections for the conductive components, thereby constructing an efficient conductive pathway with less conductive material.

[0035] Furthermore, the feed rate of the coating agent is 26~225 kg / h (for example, it can be any one of 26 kg / h, 50 kg / h, 80 kg / h, 100 kg / h, 130 kg / h, 150 kg / h, 180 kg / h, 200 kg / h or 225 kg / h or any range between two), and the feed pressure is 1.5~2.8 bar (for example, it can be any one of 1.5 bar, 1.8 bar, 2.0 bar, 2.2 bar, 2.5 bar or 2.8 bar or any range between two).

[0036] Further, in step (b), the amount of the phosphate-containing compound added is 0.3wt% to 0.6wt% (for example, it can be any one of 0.3wt%, 0.4wt%, 0.5wt%, or 0.6wt%, or a range between any two), and the addition time is 40 to 60 min (for example, it can be any one of 40 min, 45 min, 50 min, 55 min, or 60 min, or a range between any two). Under strictly controlled time and dosage, phosphate ions can effectively anchor the primary conductive layer deposited in the vapor phase, enhance its adhesion to the substrate, and homogenize the surface charge of the particles, laying a stable foundation for subsequent liquid phase film formation.

[0037] Furthermore, the phosphate-containing compound includes: phosphate and / or phosphoric acid.

[0038] Furthermore, the phosphate includes at least one of sodium hexametaphosphate, potassium pyrophosphate, or disodium hydrogen phosphate.

[0039] Furthermore, the alkaline solution includes at least one of potassium hydroxide solution, ammonia solution, or sodium hydroxide solution.

[0040] Further, in step (b), the amount of sodium aluminate solution added, based on alumina, is 0.5% to 1.5% of the dry mass of titanium dioxide (for example, it can be any one of 0.5%, 1.0%, or 1.5%, or a range between any two); the amount of alkaline solution added, based on alkali content, is 0.3% to 0.5% of the dry mass of titanium dioxide (for example, it can be any one of 0.3%, 0.4%, or 0.5%, or a range between any two).

[0041] Furthermore, in step (b), the addition time of the sodium aluminate solution and the alkaline solution is 60~80 min, including but not limited to the point value of any one of 60 min, 65 min, 70 min, 75 min or 80 min or the range value between any two.

[0042] By co-adding sodium aluminate and an alkaline solution and controlling the addition time for a relatively long period, aluminum species can be slowly and uniformly hydrolyzed and deposited in an alkaline environment to form a dense outer film of alumina hydrate. This film can improve product dispersibility and provide a good interface for subsequent processing.

[0043] Furthermore, the first homogenization process takes 20 to 40 minutes, including but not limited to point values ​​or ranges between any one of 20 minutes, 25 minutes, 30 minutes, 35 minutes, or 40 minutes.

[0044] Furthermore, the solvent of the tin chloride solution is a 15wt% hydrochloric acid solution, and the total amount of tin in the solution, after being converted into tin oxide, has a concentration of 50~120g / L (for example, it can be any one of 50g / L, 60g / L, 70g / L, 80g / L, 90g / L, 100g / L, 110g / L or 120g / L or any range between two values).

[0045] Further, in step (c), the amount of tin chloride added, based on tin dioxide, is 0.4% to 0.8% of the oven-dry mass of titanium dioxide (e.g., it can be a point value or a range between any two of 0.4%, 0.5%, 0.6%, 0.7%, or 0.8%); the amount of sodium aluminate solution added, based on alumina, is 0.5% to 1.0% of the oven-dry mass of titanium dioxide (e.g., it can be a point value or a range between any two of 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1.0%).

[0046] Furthermore, in step (c), the addition time of the tin chloride solution and the sodium aluminate solution is 30 to 60 minutes, including but not limited to the point value of any one of 30 minutes, 40 minutes, 50 minutes or 60 minutes or the range value between any two.

[0047] By supplementing tin salts and simultaneously adding sodium aluminate under a weakly alkaline environment, the surface can be repaired and re-coated. This step further strengthens the conductive network and forms a good connection with the outer alumina film, ensuring that conductivity is not completely blocked by the outer insulating film.

[0048] Furthermore, the second homogenization process takes 20 to 40 minutes, including but not limited to point values ​​or ranges between any one of 20 minutes, 25 minutes, 30 minutes, 35 minutes, or 40 minutes.

[0049] Further, in step (d), the pH of the slurry is maintained at 4.5-5.5 for 40-60 minutes, including but not limited to any one of 40 minutes, 45 minutes, 50 minutes, 55 minutes, or 60 minutes, or a range between any two. Performing the first aging step within this weakly acidic range allows residual salts in the slurry to migrate and precipitate sufficiently to the particle surface. Extending the aging time ensures the thoroughness of the process and reduces interference from impurities on the conductive layer.

[0050] Furthermore, the time for the third homogenization process is 20 to 40 minutes, including but not limited to point values ​​or range values ​​between any one of 20 minutes, 25 minutes, 30 minutes, 35 minutes, or 40 minutes.

[0051] Further, in step (e), the pH of the slurry is maintained at 5.5-6.5 for 20-30 minutes, including but not limited to a point value or a range between any two of 20 minutes, 22 minutes, 24 minutes, 26 minutes, 28 minutes, or 30 minutes. Subsequently, a second aging process is carried out within a near-neutral pH range to further stabilize and homogenize the chemical composition and structure of the film. This stepwise pH aging process, working together, ultimately yields a complete coating layer with stable chemical properties and excellent conductivity.

[0052] Furthermore, the time for the fourth homogenization process is 20 to 30 minutes, including but not limited to point values ​​or range values ​​between any one of 20 minutes, 22 minutes, 24 minutes, 26 minutes, 28 minutes, or 30 minutes.

[0053] Steps (d) and (e) involve two-step pH adjustment. First, the aging time is extended, and the pH is kept at 4.5-5.5 to allow the salt to fully precipitate to the surface. Then, a second adjustment process is carried out to 5.5-6.5, which compensates for the changes in the chemical composition of the film. The two-step pH adjustment reduces the interference of salt on the conductive film, improves conductivity, and makes the chemical composition of the film more stable and complete.

[0054] Furthermore, the method for preparing the highly conductive chloride-process titanium dioxide also includes: (f) The slurry after the fourth homogenization treatment is washed, dried, crushed and packaged.

[0055] Furthermore, the washing is performed 3 to 5 times, and the temperature of the filter cake and washing water during the washing process is 70 to 95°C. The resistivity of the product after washing is >300Ω·m.

[0056] The embodiments of the present invention will be described in detail below with reference to 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 in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0057] Example 1 The method for preparing highly conductive titanium dioxide by chloride process provided in this embodiment includes the following steps: 1. Oxygen and titanium tetrachloride are oxidized to produce titanium dioxide particles, which enter the cooling conduit. The molar ratio of O2 to TiCl4 is 1.05:1. 2. Design five feed pipes at the 1 / 6 mark of the cooling duct near the oxidation zone, with the upper end of each feed pipe connected to a 1.5m section. 3 The coating agent preheating tank has a built-in circulating pump, and the tank walls are preheated with hot air. Three 1.5m... connections are made to the upper end of the preheating tank. 3 Coating agent storage tank; 3. When the titanium dioxide particle size is 200~500nm, add 3wt% coating agent with a preheated temperature of 150℃ through the feeding pipe. The mass ratio of tin chloride to antimony chloride in the coating agent is 1.05:1, and AlCl3 is 50% of the total mass of tin chloride and antimony chloride. The feeding rate is 26kg / h, and the feeding pressure is 1.5bar. The reacted material is then pulped to obtain a slurry. 4. Control the slurry temperature at 60℃, adjust the pH to 2, and add 0.3wt% sodium hexametaphosphate solution over a period of 40 minutes. 5. The slurry temperature is controlled at 85℃. Sodium aluminate solution and sodium hydroxide solution are added to adjust the pH of the slurry to 9.5. The amount of sodium aluminate solution added is 0.5% of the dry weight of titanium dioxide, calculated based on alumina. The amount of alkaline solution added is 0.3% of the dry weight of titanium dioxide, calculated based on 100% alkali. The addition time is 60 min, and homogenization is carried out for 20 min. 6. Add tin chloride solution and sodium aluminate solution to adjust the pH of the slurry to 7.5. The amount of tin chloride added is 0.8% of the dry weight of titanium dioxide, calculated as tin dioxide; the amount of sodium aluminate added is 0.5% of the dry weight of titanium dioxide, calculated as alumina. The addition time is 30 min, and homogenization is carried out for 20 min. 7. Adjust the pH of the slurry to 4.5 and maintain it for 40 minutes, then homogenize for 20 minutes; 8. Adjust the pH of the slurry to 5.5 and maintain it for 20 minutes, then homogenize for 20 minutes; 9. Wash and desalinate the product three times. The temperature of the filter cake and washing water during the washing process is 70℃. After washing, the resistivity of the product is >300Ω·m. Then dry and pulverize the product to obtain product #1.

[0058] Example 2 The method for preparing highly conductive titanium dioxide by chloride process provided in this embodiment includes the following steps: 1. Oxygen and titanium tetrachloride are oxidized to produce titanium dioxide particles, which enter the cooling conduit. The molar ratio of O2 to TiCl4 is 1.35:1. 2. Design three feed pipes at the 1 / 3 mark of the cooling duct near the oxidation zone, with the upper end of each feed pipe connected to a 3m... 3 The coating agent preheating tank has a built-in circulating pump, and the tank walls are preheated with hot air. Three 3m3 meters are connected to the top of the preheating tank. 3 Coating agent storage tank; 3. When the titanium dioxide particle size is 280-360nm, add 25wt% coating agent preheated to 250℃ through the feeding pipe. The mass ratio of tin chloride to antimony chloride in the coating agent is 9.9:1, and AlCl3 is 150% of the total mass of tin chloride and antimony chloride. The feeding rate is 225kg / h, and the feeding pressure is 2.8bar. The reacted material is then pulped to obtain a slurry. 4. Control the slurry temperature at 75℃, adjust the pH to 3, and add 0.6wt% disodium hydrogen phosphate solution over a period of 60 minutes. 5. The slurry temperature is controlled at 85℃. Sodium aluminate solution and ammonia are added to adjust the pH of the slurry to 10.5. The amount of sodium aluminate solution added is 1.5% of the dry weight of titanium dioxide, calculated based on alumina. The amount of alkaline solution added is 0.5% of the dry weight of titanium dioxide, calculated based on 100% alkali. The addition time is 80 min, and homogenization is carried out for 40 min. 6. Add tin chloride solution and sodium aluminate solution to adjust the pH of the slurry to 8.5. The amount of tin chloride added is 0.4% of the dry weight of titanium dioxide, calculated as tin dioxide; the amount of sodium aluminate added is 1.0% of the dry weight of titanium dioxide, calculated as alumina. The addition time is 60 min, and homogenization is 40 min. 7. Adjust the pH of the slurry to 5.5 and maintain it for 60 minutes, then homogenize for 40 minutes; 8. Adjust the pH of the slurry to 6.5 and maintain it for 30 minutes, then homogenize for 30 minutes; 9. Wash and desalinate the product 5 times. The temperature of the filter cake and washing water during the washing process is 95℃. After washing, the resistivity of the product is >300Ω·m. Then dry and pulverize to obtain product #2.

[0059] Example 3 The method for preparing highly conductive titanium dioxide by chloride process provided in this embodiment includes the following steps: 1. Oxygen and titanium tetrachloride are oxidized to produce titanium dioxide particles, which enter the cooling conduit. The molar ratio of O2 to TiCl4 is 1.25:1. 2. Design four feed pipes at the 1 / 4 mark of the cooling duct near the oxidation zone, with a 2m connection at the top of each feed pipe. 3 The coating agent preheating tank has a built-in circulating pump, and the tank walls are preheated with hot air. Three 1.8m... connections are made to the upper end of the preheating tank. 3 Coating agent storage tank; 3. When the titanium dioxide particle size is 250~450nm, add 10wt% coating agent with a preheated temperature of 200℃ through the feeding pipe. The mass ratio of tin chloride to antimony chloride in the coating agent is 5:1, and the total mass of AlCl3 is equal to that of tin chloride and antimony chloride. The feeding rate is 100kg / h, and the feeding pressure is 2.0bar. The reacted material is then pulped to obtain a slurry. 4. Control the slurry temperature at 65℃, adjust the pH to 2.5, add 0.5wt% potassium pyrophosphate solution, and add it over 50 minutes. 5. The slurry temperature is controlled at 85℃. Sodium aluminate solution and sodium hydroxide solution are added to adjust the pH of the slurry to 10. The amount of sodium aluminate solution added is 1.0% of the dry weight of titanium dioxide, calculated based on alumina. The amount of alkaline solution added is 0.4% of the dry weight of titanium dioxide, calculated based on 100% alkali. The addition time is 70 min, and homogenization is carried out for 30 min. 6. Add tin chloride solution and sodium aluminate solution to adjust the pH of the slurry to 8.0. The amount of tin chloride added is 0.6% of the dry weight of titanium dioxide, calculated as tin dioxide; the amount of sodium aluminate added is 0.75% of the dry weight of titanium dioxide, calculated as alumina. The addition time is 50 min, and homogenization is 30 min. 7. Adjust the pH of the slurry to 5.0 and maintain it for 50 minutes, then homogenize for 30 minutes; 8. Adjust the pH of the slurry to 6.0 and maintain it for 25 minutes, then homogenize for 25 minutes; 9. Wash and desalinate the product 4 times. The temperature of the filter cake and washing water during the washing process is 80℃. After washing, the resistivity of the product is >300Ω·m. Then dry and pulverize to obtain product #3.

[0060] Example 4 The method for preparing highly conductive titanium dioxide by chloride process provided in this embodiment includes the following steps: 1. Oxygen and titanium tetrachloride are oxidized to produce titanium dioxide particles, which enter the cooling conduit. The molar ratio of O2 to TiCl4 is 1.35:1. 2. Design four feed pipes at the 1 / 5 mark of the cooling duct near the oxidation zone, with a 2m connection at the top of each feed pipe. 3 The coating agent preheating tank has a built-in circulating pump, and the tank walls are preheated with hot air. Three 1.5m... connections are made to the upper end of the preheating tank. 3 Coating agent storage tank; 3. When the titanium dioxide particle size is 280~350nm, add 17wt% coating agent with a preheated temperature of 200℃ through the feeding pipe. The mass ratio of tin chloride to antimony chloride in the coating agent is 8:1, and AlCl3 is 80% of the total mass of tin chloride and antimony chloride. The feeding rate is 185kg / h, and the feeding pressure is 2.2bar. The reacted material is then pulped to obtain a slurry. 4. Control the slurry temperature at 75℃, adjust the pH to 2.7, add 0.5wt% phosphoric acid solution, and add over 60 minutes; 5. The slurry temperature is controlled at 85℃. The pH of the slurry is adjusted to 10.3 by adding sodium aluminate solution and potassium hydroxide. The amount of sodium aluminate solution added is 1.5% of the dry weight of titanium dioxide, calculated based on alumina. The amount of alkaline solution added is 0.5% of the dry weight of titanium dioxide, calculated based on 100% alkali. The addition time is 80 min, and homogenization is carried out for 40 min. 6. Add tin chloride solution and sodium aluminate solution to adjust the pH of the slurry to 8.5. The amount of tin chloride added is 0.7% of the dry weight of titanium dioxide, calculated as tin dioxide; the amount of sodium aluminate added is 1.0% of the dry weight of titanium dioxide, calculated as alumina. The addition time is 60 min, and homogenization is 40 min. 7. Adjust the pH of the slurry to 5.0 and maintain it for 60 minutes, then homogenize for 40 minutes; 8. Adjust the pH of the slurry to 6.5 and maintain it for 30 minutes, then homogenize for 30 minutes; 9. Wash and desalinate the product 5 times. The temperature of the filter cake and washing water during the washing process is 85℃. After washing, the resistivity of the product is >300Ω·m. Then dry and pulverize to obtain product #4.

[0061] Comparative Example 1 The titanium dioxide base material produced by the chloride process had a concentration of 300 g / L and a particle size of 200-500 nm. The slurry temperature was raised to 70°C. Simultaneously, 3.8 w% of a mixture of tin chloride and antimony chloride (tin chloride to antimony chloride mass ratio 1.05:1) was added, keeping the slurry pH constant at 2.3. The addition time was 40 min, followed by homogenization for 30 min. The pH of the slurry was adjusted to 6.0 with sodium hydroxide solution, and a hydrothermal reaction was carried out at 190°C for 3.6 h. After sieving, washing, drying, and pulverizing, comparative product 1# was obtained.

[0062] Comparative Example 2 The titanium dioxide base material produced by the chloride process had a concentration of 300 g / L and a particle size of 200-500 nm. The slurry temperature was raised to 70°C. Simultaneously, 3.8 w% of a mixture of tin chloride and antimony chloride (tin chloride to antimony chloride mass ratio 1.05:1) was added, keeping the slurry pH constant at 2.3. The addition time was 40 min, followed by homogenization for 30 min. The pH of the slurry was adjusted to 6.0 with sodium hydroxide solution, and then calcined at 540°C for 2 h. After sieving, washing with water, drying, and pulverizing, comparative product #2 was obtained.

[0063] Comparative Example 3 The titanium dioxide base material produced by the chloride process had a concentration of 300 g / L and a particle size of 200-500 nm. The slurry temperature was raised to 70°C. Simultaneously, a mixture of 26 wt% tin chloride and antimony chloride (tin chloride to antimony chloride mass ratio 1.05:1) was added, keeping the slurry pH constant at 2.3. The addition time was 40 min, followed by homogenization for 30 min. The pH of the slurry was adjusted to 6.0 with sodium hydroxide solution, and then calcined at 540°C for 2 h. After sieving, washing with water, drying, and pulverizing, the comparative product #3 was obtained.

[0064] Comparative Example 4 The titanium dioxide base material prepared by the chloride process was mixed with ATO dry powder prepared by 15% tin oxide and antimony oxide, washed with water, dried and pulverized to obtain the comparative product 4#.

[0065] The sample from the example and the comparative sample were analyzed for their properties. The powder resistivity was measured according to JB / T 13537-2018, the particle size was measured using an MS3000 laser particle size analyzer, the dispersibility was measured according to GB6753.1-1986, and the powder color was measured according to Q / BLL 21-2019. The results are shown in Table 1.

[0066] Table 1

[0067] PSD is a parameter used to describe the range of particle size distribution in a powder sample. Generally, the smaller the PSD value (closer to 1), the more concentrated and uniform the particle size distribution; conversely, the larger the PSD value, the wider the particle size distribution and the greater the difference in particle size.

[0068] The level of dispersibility in an aqueous system directly represents the ease and stability of dispersion of the conductive titanium dioxide in an aqueous medium. A low value indicates that the powder is easy to disperse, can be quickly opened up in water to form a uniform and stable suspension, with few particle agglomerations and little sedimentation. A high value indicates poor powder dispersibility, which easily forms large agglomerates in water and is difficult to distribute uniformly.

[0069] Oil system dispersibility indicates the ease and stability of dispersibility of the conductive titanium dioxide in an oily medium. A low value indicates excellent compatibility and dispersibility of the powder in an oily system. A high value indicates difficulty in dispersing the powder in an oily system and a tendency to agglomerate.

[0070] The "L" value of a powder directly represents its whiteness and brightness as a white pigment. A high L value (close to 100) indicates that the powder is extremely white, has very high brightness, and excellent optical properties. A low L value (far from 100) indicates that the powder is grayish, dark, or yellowish, has poor whiteness and brightness, and has defective optical properties.

[0071] The titanium dioxide prepared by this invention exhibits significantly superior electrical conductivity compared to samples prepared using existing hydrothermal technology (Comparative Example 1), wet coating technology (Comparative Example 2), and dry blending technology (Comparative Example 3), indicating that the titanium dioxide prepared by this invention has high electrical conductivity.

[0072] 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.

Claims

1. A method for preparing highly conductive titanium dioxide using the chloride process, characterized in that, Includes the following steps: (a) Oxygen and titanium tetrachloride are oxidized to produce titanium dioxide particles; the titanium dioxide particles enter a cooling conduit, and a preheated coating agent is added to the cooling conduit to carry out a coating reaction and slurry to obtain a slurry; (b) Adjust the temperature of the slurry to 60~75℃ and the pH to 2~3, and add a phosphate compound for a period of time; adjust the temperature of the slurry to 80~90℃, add sodium aluminate solution and alkaline solution to adjust the pH of the slurry to 9.5~10.5 and then perform the first homogenization treatment; (c) Add tin chloride solution and sodium aluminate solution, adjust the pH of the slurry after the first homogenization treatment to 7.5~8.5, and then perform a second homogenization treatment; (d) Adjust the pH of the slurry after the second homogenization treatment to 4.5~5.5 and maintain it for a period of time before performing the third homogenization treatment; (e) Adjust the pH of the slurry after the third homogenization treatment to 5.5~6.5 and maintain it for a period of time before performing the fourth homogenization treatment.

2. The method for preparing highly conductive titanium dioxide by chloride process according to claim 1, characterized in that, In step (a), the molar ratio of oxygen to titanium tetrachloride is 1.05 to 1.35:

1.

3. The method for preparing highly conductive titanium dioxide by chloride process according to claim 1, characterized in that, In step (a), when the particle size of the titanium dioxide particles is 200~500nm, the preheated coating agent is added into the cooling conduit.

4. The method for preparing highly conductive titanium dioxide by chloride process according to claim 1, characterized in that, In step (a), the amount of the coating agent added is 3wt% to 25wt% of the mass of the titanium dioxide particles; And / or, in step (a), the preheating temperature of the coating agent is 150~250°C.

5. The method for preparing highly conductive titanium dioxide by chloride process according to claim 1, characterized in that, The coating agent includes: tin chloride, antimony chloride, and aluminum chloride; The mass ratio of tin chloride to antimony chloride is 1.05 to 9.9:1, and the mass of aluminum chloride is 25% to 150% of the total mass of tin chloride and antimony chloride.

6. The method for preparing highly conductive titanium dioxide by chloride process according to claim 1, characterized in that, In step (b), the amount of the phosphate-containing compound added is 0.3wt%~0.6wt%, and the addition time is 40~60min; And / or, the phosphate-containing compound includes: phosphate and / or phosphoric acid.

7. The method for preparing highly conductive titanium dioxide by chloride process according to claim 1, characterized in that, In step (b), the amount of sodium aluminate solution added, calculated based on alumina, is 0.5% to 1.5% of the dry weight of titanium dioxide; the amount of alkaline solution added, calculated based on 100% alkali, is 0.3% to 0.5% of the dry weight of titanium dioxide. And / or, in step (b), the sodium aluminate solution and alkaline solution are added over a period of 60 to 80 minutes.

8. The method for preparing highly conductive titanium dioxide by chloride process according to claim 1, characterized in that, In step (c), the amount of tin chloride added, calculated as tin dioxide, is 0.4% to 0.8% of the oven-dry mass of titanium dioxide; the amount of sodium aluminate solution added, calculated as alumina, is 0.5% to 1.0% of the oven-dry mass of titanium dioxide. And / or, in step (c), the addition time of tin chloride solution and sodium aluminate solution is 30~60 min.

9. The method for preparing highly conductive titanium dioxide by chloride process according to claim 1, characterized in that, In step (d), the pH of the slurry is maintained at 4.5 to 5.5 for 40 to 60 minutes.

10. The method for preparing highly conductive titanium dioxide by chloride process according to claim 1, characterized in that, In step (e), the pH of the slurry is maintained at 5.5 to 6.5 for 20 to 30 minutes.

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