阅读说明：本技术 塑料专用型钛白粉的包膜处理方法 (Coating treatment method of special titanium dioxide for plastics ) 是由 胡井成 王雪峰 王志学 于 2021-08-31 设计创作，主要内容包括：本发明公开了一种塑料专用型钛白粉的包膜处理方法,涉及钛白粉制备技术领域。本发明提供的方法通过硅膜包覆处理和铝膜包覆处理显著提高了钛白粉的耐候性和分散性,并且利用有机硅膜包覆处理使钛白粉与树脂具有良好的兼容性。(The invention discloses a coating treatment method of special plastic titanium dioxide, and relates to the technical field of titanium dioxide preparation. The method provided by the invention obviously improves the weather resistance and the dispersibility of the titanium dioxide through the silicon film coating treatment and the aluminum film coating treatment, and ensures that the titanium dioxide and the resin have good compatibility by utilizing the organic silicon film coating treatment.)

1. A coating treatment method of special plastic titanium dioxide is characterized by comprising the following steps:

step one, dispersing and neutralizing treatment: mixing the initial slurry, a dispersing agent and a neutralizing agent, and adjusting the pH value of the slurry to 8-12 to obtain a mixed base material, wherein the viscosity of the mixed base material is less than 500mPa & s, and the concentration of the mixed base material is 300-700 g/L;

step two, wet grinding treatment: dispersing the mixed base material to obtain titanium dioxide particle size D₉₉Titanium dioxide slurry with particle size less than 1 μm;

step three, silicon film coating treatment: adding sodium silicate into titanium dioxide slurry under the heating condition while stirring to obtain first mixed slurry, continuously stirring to adjust the pH of the first mixed slurry to 10-12, and performing first curing treatment to obtain silicon-coated titanium dioxide particles;

step four, aluminum film coating treatment: adding an aluminum-containing compound and a pH regulator into the silicon-coated titanium dioxide particle slurry under the condition that the pH value is 7.5-8 to obtain a second mixed slurry, regulating the pH value of the second mixed slurry to 6.5-8, and performing second aging treatment to obtain titanium dioxide particles coated with aluminum films;

step five, filter pressing and drying treatment: carrying out filter pressing and drying treatment on the slurry subjected to the aluminum film coating treatment to obtain a titanium dioxide intermediate with the water content of less than or equal to 0.5%;

step six, organic silicon film coating treatment: and adding alkyl silicone oil in at least one process of drying and airflow crushing the titanium dioxide intermediate, and performing organic silicon film coating treatment to obtain the titanium dioxide.

2. The method for coating titanium dioxide powder specially used for plastics according to claim 1, wherein the initial slurry is prepared by the titanium dioxide chlorination process through TiCl₄The crystal form of the rutile titanium dioxide is obtained through oxidation reaction.

3. The method for coating the special titanium dioxide for the plastics according to claim 1, wherein the dispersant is one or more of sodium hexametaphosphate, sodium silicate, carboxylate and isopropanolamine, and the addition amount of the dispersant is 0.05-0.5% of the mass of the titanium dioxide; the neutralizer is sodium hydroxide or ammonia water.

4. The method for coating titanium dioxide powder special for plastics according to claim 1, wherein the wet grinding equipment is a vertical or horizontal sand mill, the sand milling medium is zirconium silicate beads, zirconium oxide beads or ottawa sand, the particle size of the sand milling medium is 1-5 μm, and the filling rate is controlled at 30-70%; the rotating speed is 1500 r/min-3000 r/min, and the sanding time is 5-30 min.

5. The method for coating the special titanium dioxide for plastics according to claim 1, wherein in the third step, the heating temperature is controlled to 60-90 ℃, the stirring speed is 200-300 r/min, the sodium silicate is added by a peristaltic pump or a metering pump, the adding time is controlled to 60-120 min, and the stirring is continued for 30-60 min after the adding is completed.

6. The method for coating the special titanium dioxide powder for plastics according to claim 1 or 5, wherein the time for adjusting the pH of the first mixed slurry is 10-60 min, and the stirring speed is 150-200 r/min; the first curing treatment is carried out at the rotating speed of 150 r/min-200 r/min, and the first curing time is 10-60 min.

7. The method for coating the special titanium dioxide for plastics according to claim 1, wherein the amount of sodium silicate added is 30-100 g per 1 kg of titanium dioxide, wherein the amount of sodium silicate added is SiO₂And (6) counting.

8. The method for coating the titanium dioxide powder for plastic according to claim 1, wherein the aluminum-containing compound is aluminum sulfate and/or sodium metaaluminate, and the amount of the aluminum-containing compound added is 10-30 g of aluminum oxide per 1 kg of titanium dioxide base material, calculated as aluminum oxide.

9. The method for coating titanium dioxide powder special for plastics according to claim 1, wherein in step four, the pH regulator is one of sulfuric acid and hydrochloric acid, and sodium hydroxide, the sulfuric acid is 98 wt% concentrated sulfuric acid, the hydrochloric acid is 36.5 wt% concentrated hydrochloric acid, and the sodium hydroxide is 50% by weight.

10. The method for coating the special titanium dioxide for plastics according to claim 1, wherein the addition amount of the alkyl silicone oil is 1-10 per mill of the mass of the titanium dioxide intermediate.

Technical Field

The invention relates to the technical field of titanium dioxide preparation, in particular to a coating treatment method of special plastic titanium dioxide.

Background

Titanium dioxide (TiO) with titanium dioxide name₂) Mainly has two crystal forms of rutile type and anatase type. Titanium dioxide has the advantages of excellent whiteness, tinting strength, covering power and the like, has the highest refractive index in all white pigments, is considered to be the best white pigment, and is widely applied to coatings, plastics, printing and rubberAnd the like.

When the titanium dioxide is applied to plastics, the titanium dioxide can improve the heat resistance, light resistance and weather resistance of plastic products besides utilizing the high covering power, high tinting strength and other pigment properties of the titanium dioxide. The requirements of plastics on whiteness, dispersibility, covering power, oil absorption performance and the like are higher, and the titanium dioxide obtained by the traditional process often cannot meet the requirements. Therefore, how to improve the existing process to obtain a titanium dioxide product with higher whiteness, dispersibility, covering power and oil absorption becomes a technical problem to be solved urgently.

Disclosure of Invention

In order to solve the technical problems, the invention provides a coating treatment method of special plastic titanium dioxide, which obviously improves the weather resistance and the dispersibility of the titanium dioxide through silicon film coating treatment and aluminum film coating treatment, and ensures that the titanium dioxide has good compatibility with resin through organic silicon film coating treatment.

In order to realize the technical purpose, the invention adopts the following scheme: the coating treatment method of the special plastic titanium dioxide comprises the following steps:

step one, dispersing and neutralizing treatment: and mixing the initial slurry, the dispersing agent and the neutralizing agent, and adjusting the pH value of the slurry to 8-12 to obtain a mixed base material, wherein the viscosity of the mixed base material is less than 500mPa & s, the concentration of the mixed base material is 300-700 g/L, the dispersibility of the titanium dioxide particles is better at the concentration, the formed coating is uniform, the coating is suitable for industrial production, and the energy consumption is lower.

Step two, wet grinding treatment: dispersing the mixed base material to obtain titanium dioxide particle size D₉₉The titanium dioxide slurry with particle size less than 1 μm, the aggregate of titanium dioxide particles in the titanium dioxide slurry after wet grinding is completely dispersed and is in the primary particle state, so that the subsequent silicon film, aluminum film and organic silicon film can be fully coated on the titanium dioxide particles.

Step three, silicon film coating treatment: adding sodium silicate into titanium dioxide slurry under the heating condition while stirring to obtain first mixed slurry, continuously stirring to adjust the pH of the first mixed slurry to 10-12, and performing first curing treatment to obtain silicon-coated titanium dioxide particles; through silicon film coating treatment, the surface of the titanium dioxide is coated into a compact and uniform silicon film, so that photochemical active points of the titanium dioxide can be effectively shielded, and the weather resistance of the titanium dioxide is remarkably improved.

Step four, aluminum film coating treatment: adding an aluminum-containing compound and a pH regulator into the silicon-coated titanium dioxide particle slurry under the condition that the pH value is 7.5-8 to obtain second mixed slurry, stirring the second mixed slurry for 10-60 min, regulating the pH value of the second mixed slurry to 6.5-8, and then carrying out second aging treatment to obtain titanium dioxide particles coated with the aluminum film; the aluminum film coating treatment forms a uniform boehmite type film on the surface of the titanium dioxide base material particles coated with the silicon film, thereby effectively solving the problem of agglomeration of the titanium dioxide and ensuring that the titanium dioxide has good dispersibility and fluidity in plastic processing.

Step five, filter pressing and drying treatment: and (3) carrying out filter pressing and drying treatment on the slurry subjected to the aluminum film coating treatment, and removing water in the slurry to obtain a titanium dioxide intermediate with the water content of less than or equal to 0.5%.

Step six, organic silicon film coating treatment: and adding alkyl silicone oil in at least one process of drying and airflow crushing the titanium dioxide intermediate, and performing organic silicon film coating treatment to obtain the titanium dioxide. The organic silicon film coating treatment is utilized to improve the dispersibility, wettability and rheological property of the titanium dioxide application, solve the compatibility of the titanium dioxide and resin, and enable the prepared titanium dioxide to be easy to process in plastics.

Compared with the prior art, the invention has the beneficial effects that: the silicon film coating treatment is carried out under the condition that the pH value is 10-12, so that the surface of the titanium dioxide is coated into a compact and uniform silicon film, photochemical active points on the surfaces of titanium dioxide particles are effectively shielded, and the weather resistance of the titanium dioxide is obviously improved. The surfaces of the titanium dioxide base material particles coated with the silicon film are coated with the aluminum films again through aluminum film coating treatment, and the feeding process of the aluminum film coating treatment is to control the pH to be stable at 6-8, so that the surfaces of the titanium dioxide particles are coated with the uniform crystal boehmite films, the agglomeration of the titanium dioxide is effectively solved, and the dispersibility of the titanium dioxide in plastic processing is guaranteed. In addition, the method utilizes the organic silicon film to coat and treat to solve the compatibility of the titanium dioxide and resin, so that the prepared titanium dioxide is easy to process in plastics.

The further scheme of the invention is as follows:

in the S100 neutralization and dispersion treatment:

the initial slurry is prepared by a titanium white chlorination process through TiCl₄Obtained by oxidation reaction, wherein the crystal form of the titanium dioxide is rutile type; from TiCl₄The titanium dioxide base material obtained by oxidation reaction has high rutile type conversion rate, good weather resistance, good granularity and good granularity distribution.

The dispersing agent is selected from at least one of sodium hexametaphosphate, sodium silicate, carboxylate and isopropanolamine, and the adding amount of the dispersing agent is 0.05-0.5% of the mass of the titanium dioxide. The dispersed mixed base material has good dispersibility and low viscosity. The neutralizer is sodium hydroxide or ammonia water. The viscosity of the titanium dioxide slurry treated in the first step is 30-100 mPa.s, and the agglomeration rate of the mixed slurry is low at the viscosity. Silicon films and aluminum films are easily coated on the titanium dioxide particles.

S200, wet grinding treatment:

and further dispersing the neutralized and dispersed titanium dioxide slurry to obtain the dispersed titanium dioxide slurry. Therefore, the aggregate of the titanium dioxide particles in the titanium dioxide slurry is completely dispersed, and the subsequent coating treatment is convenient.

The wet grinding equipment adopts a vertical or horizontal sand mill, the sand milling medium is zirconium silicate beads, zirconium oxide beads or Ottawa sand, the granularity of the sand milling medium is 1-5 mu m, and the filling rate is controlled at 30-70%. Furthermore, the rotating speed of the sand mill is 1500 r/min-3000 r/min, the sand milling time is 5-30 min, so that the aggregates of the titanium dioxide particles are fully dispersed, the titanium dioxide particles are in a primary particle state, and the dispersibility is good.

S300 silicon film coating treatment:

and performing silicon film coating treatment on the dispersed titanium dioxide slurry to coat silicon films on the surfaces of titanium dioxide particles in the dispersed titanium dioxide slurry to obtain silicon film-coated titanium dioxide particles, wherein the silicon film coating treatment is performed under the condition that the pH value is 10-12. Therefore, the silicon film is coated on the surface of the titanium dioxide base material particles through the silicon film coating treatment, and the silicon film coating treatment is carried out under the condition that the pH value is 10-12, so that the surface of the titanium dioxide is coated into a compact and uniform silicon film, the photochemical active points of the titanium dioxide can be effectively shielded, and the weather resistance of the titanium dioxide is remarkably improved.

The heating condition in the third step is realized by heating with steam or an electric heating jacket, and the temperature is controlled to be 60-90 ℃. Adding sodium silicate under the stirring condition, wherein the stirring speed is 200 r/min-300 r/min, fully mixing the sodium silicate with the slurry, and fully coating the silicon film on the surface of the titanium dioxide base material particles. Adding sodium silicate by adopting a peristaltic pump or a metering pump, keeping the sodium silicate to be stably added into the titanium dioxide slurry at a certain speed, wherein the adding is completed within 60-120 min, and continuously stirring uniformly for 30-60 min after the adding is completed, so that the sodium silicate is fully mixed with the slurry, and the silicon film is fully coated on the surface of the titanium dioxide base material particles.

The time for adjusting the pH value of the first mixed slurry is 10-60 min, the stirring speed is 150-200 r/min, so that the pH regulator and the first mixed slurry are uniformly mixed, and the pH value measurement deviation caused by nonuniform distribution of the pH regulator is avoided.

The first curing treatment is carried out at the rotating speed of 150 r/min-200 r/min, and the first curing time is 10-60 min.

The adding amount of the sodium silicate is 30-100 g of sodium silicate per 1 kg of titanium dioxide (referring to titanium dioxide dry basis), wherein the adding amount of the sodium silicate is SiO₂By the method, the silicon film formed by the sodium silicate is fully coated on the surface of the titanium dioxide base material particles, and the waste of raw materials caused by excessive sodium silicate is avoided.

The silicon film coated by the silicon-coated titanium dioxide particles is a hydrated silicon dioxide film which can effectively shield ultraviolet light and improve the weather resistance of the titanium dioxide.

In the S400 aluminum film coating treatment:

and carrying out aluminum film coating treatment on the slurry subjected to the silicon film coating treatment so as to coat aluminum films on the surfaces of the silicon-coated titanium dioxide particles to obtain aluminum-coated titanium dioxide particles, wherein the feeding process of the aluminum film coating treatment is carried out under the condition that the pH value is 6-8. Therefore, the surface of the titanium dioxide base material particle coated with the silicon film is coated with the aluminum film again through aluminum film coating treatment, and the feeding process of the aluminum film coating treatment is to coat the surface of the titanium dioxide particle with a single-crystal-form film type aluminum film under the condition that the pH value is 6-8, so that the agglomeration of the titanium dioxide is effectively solved, and the dispersibility of the titanium dioxide in plastic processing is ensured.

The aluminum-containing compound and the pH regulator are added under the stirring condition, wherein the stirring speed is 150 r/min-200 r/min, the adding time is 15-60 min, the aluminum-containing compound and the pH regulator are stably added into the slurry at a certain speed, the aluminum-containing compound and the pH regulator are fully mixed with the slurry, the pH value in the feeding process is kept stable, and the surface of the titanium dioxide base material particle coated by the silicon film is fully coated with the aluminum film.

The aluminum-containing compound is aluminum sulfate and/or sodium metaaluminate, and the aluminum sulfate and the sodium metaaluminate are easy to obtain, low in price and low in impurity content, have no influence on the pigment performance of the titanium dioxide, and are suitable for being used as the raw material of the aluminum film.

The adding amount of the aluminum-containing compound is calculated by aluminum oxide, and 10-30 g of aluminum oxide is added into every 1 kg of titanium dioxide base material (referring to titanium dioxide dry base). Not only the aluminum film formed by the aluminum-containing compound is fully coated on the surface of the titanium dioxide base material particles, but also the waste of raw materials caused by excessive aluminum-containing compound is avoided.

The aluminum film coated with the aluminum-coated titanium dioxide particles is a boehmite type aluminum film, and the aluminum film with the crystal structure improves the fluidity of the titanium dioxide in plastic processing.

The pH regulator in S400 is one of sulfuric acid and hydrochloric acid and sodium hydroxide, the sulfuric acid is 98 wt% of concentrated sulfuric acid, the hydrochloric acid is 36.5 wt% of concentrated hydrochloric acid, the mass fraction of the sodium hydroxide is 50%, and the pH value can be flexibly regulated only by a small amount of the pH regulator.

And adding an aluminum-containing compound and a pH regulator into the slurry after the silicon film coating treatment in a concurrent flow or parallel flow mode.

S500, in the filter pressing and drying treatment:

and carrying out filter pressing and drying treatment on the slurry subjected to the aluminum film coating treatment so as to obtain the coated titanium dioxide intermediate. Thus, removing the water in the slurry to obtain the dried coated titanium dioxide intermediate.

The filter pressing equipment is selected from one of a diaphragm filter press and a rotary drum filter, preferably, the high-cantilever diaphragm filter press is adopted, the equipment is simple to operate, the filter pressing effect is good, and chemical impurities remained on the surface of the coated titanium dioxide intermediate body can be washed and removed during filter pressing, so that the purity of the titanium dioxide is higher.

The drying equipment is selected from one of a rotary flash dryer, a spray dryer, a belt dryer and a boiling dryer, preferably, the rotary flash dryer is adopted, the crushing effect is good, the drying is complete, and the moisture content of the coated titanium dioxide intermediate obtained after the drying is less than or equal to 0.5 percent.

S600 organic silicon film coating treatment

And (4) performing organic silicon film coating treatment on the coated titanium dioxide intermediate to obtain the titanium dioxide. Therefore, the organic silicon film coating treatment is utilized to improve the dispersibility, wettability and rheological property of the titanium dioxide application, solve the compatibility of the titanium dioxide and resin, and enable the prepared titanium dioxide to be easy to process in plastics.

The organic silicon film coating treatment is carried out by using alkyl silicone oil, and the addition amount of the alkyl silicone oil is 1-10 per mill of the mass of the titanium dioxide intermediate. Not only the organic silicon film formed by the alkyl silicone oil is fully coated on the surface of the coated titanium dioxide intermediate, but also the waste of raw materials caused by the excessive alkyl silicone oil is avoided, and simultaneously the reduction of the whiteness of the titanium dioxide caused by the too thick coating of the alkyl silicone oil is also avoided.

The alkyl silicone oil is added in at least one process of drying and airflow pulverization of the coated titanium dioxide intermediate. Therefore, the alkyl silicone oil is uniformly coated on the surface of the coated titanium dioxide intermediate particles.

The carrier in the jet milling process is superheated steam, compressed air and compressed nitrogen. Preferably, superheated steam is used as a medium, so that the crushing effect is good.

Drawings

Fig. 1 is a process flow diagram provided in an embodiment of the present invention.

Detailed Description

The present invention will be described in detail with reference to the following embodiments in order to fully understand the objects, features and effects of the invention, but the present invention is not limited thereto.

The technological process of the coating treatment method of the special titanium dioxide for plastics is shown in figure 1.

Example 1

The method of the invention is utilized to treat the surface of the titanium dioxide, and the specific method is as follows:

(1) preparing 1L of initial slurry with the concentration of 400g/L, and adding 2 per mill of sodium hexametaphosphate (P ‰)₂O₅Calculating), dispersing for 10min by using a sand mill, placing in a single-layer glass reaction kettle, stirring, heating to 70 ℃, and adjusting the pH value to 10.0.

(2) Adding a sodium silicate solution with the concentration of 100g/L into the titanium dioxide slurry by adopting a peristaltic pump, wherein the total amount of the sodium silicate is SiO₂Calculated as 3.0 percent of the titanium dioxide, namely 120mL, the flow rate is 6mL/min, and after the addition is finished, the mixture is aged for 60min to obtain silicon-coated titanium dioxide particles.

(3) Adjusting the pH value of the slurry obtained in the step (2) to 7.5 by using sulfuric acid, adding a sodium metaaluminate solution with the concentration of 270g/L, wherein the total amount of the metaaluminate is Al₂O₃Calculated as 2.0 percent of the titanium dioxide, namely 29.6mL, the flow rate is 0.5mL/min, and the titanium dioxide is aged for 60min after the addition is finished. Adjusting the pH value to 7.3 by using sulfuric acid, and curing for 15min to obtain the aluminum-coated titanium dioxide particles.

(4) And (4) performing filter pressing washing on the slurry obtained in the step (3), drying the slurry in a vacuum drying oven at 105 ℃ until the water content is less than 0.5%, crushing the slurry by using an airflow crusher, adding alkyl silicone oil in the crushing process, wherein the addition amount of the alkyl silicone oil is 3 per mill of the titanium dioxide, and crushing the mixture to obtain the finished product of the titanium dioxide.

Example 2

The method of the invention is utilized to treat the surface of the titanium dioxide, and the specific method is as follows:

(1) preparing 1L of initial slurry with the concentration of 400g/L, and adding 2 per mill of sodium hexametaphosphate (P ‰)₂O₅Calculating), dispersing for 10min by sand mill, stirring in single-layer glass reaction kettle, heating to 70 deg.C, and adjusting pHWas 10.0.

(2) Adding a sodium silicate solution with the concentration of 100g/L into the titanium dioxide slurry by adopting a peristaltic pump, wherein the total amount of the sodium silicate is SiO₂Calculated as 3.5 percent of the titanium dioxide, namely 140mL, the flow rate is 7mL/min, and after the addition is finished, the mixture is aged for 60min to obtain silicon-coated titanium dioxide particles.

(3) Adjusting the pH value of the slurry obtained in the step (2) to 6.5 by using sulfuric acid, adding a sodium metaaluminate solution with the concentration of 270g/L, wherein the total amount of the metaaluminate is Al₂O₃Calculated as 2.0 percent of the titanium dioxide, namely 29.6mL, the flow rate is 0.5mL/min, and the titanium dioxide is aged for 60min after the addition is finished. Adjusting the pH value to 7.3 by using sulfuric acid, and curing for 15min to obtain the aluminum-coated titanium dioxide particles.

(4) And (4) performing filter pressing washing on the slurry obtained in the step (3), drying the slurry in a vacuum drying oven at 105 ℃ until the water content is less than 0.5%, crushing the slurry by using an airflow crusher, adding alkyl silicone oil in the crushing process, wherein the addition amount of the alkyl silicone oil is 3 per mill of the titanium dioxide, and crushing the mixture to obtain the finished product of the titanium dioxide.

Example 3

The method of the invention is utilized to treat the surface of the titanium dioxide, and the specific method is as follows:

(1) preparing 1L of initial slurry with the concentration of 400g/L, adding 2 thousandth of isopropanolamine, dispersing for 10min by using a sand mill, placing the mixture in a single-layer glass reaction kettle, stirring, heating to 70 ℃, and adjusting the pH value to 10.0.

(2) Adding a sodium silicate solution with the concentration of 100g/L into the titanium dioxide slurry by adopting a peristaltic pump, wherein the total amount of the sodium silicate is SiO₂Calculated as 3.0 percent of the titanium dioxide, namely 120mL, the flow rate is 6mL/min, and after the addition is finished, the mixture is aged for 60min to obtain silicon-coated titanium dioxide particles.

(3) Adjusting the pH value of the slurry obtained in the step (2) to 7.5 by using sulfuric acid, adding a sodium metaaluminate solution with the concentration of 270g/L, wherein the total amount of the metaaluminate is Al₂O₃Calculated as 3.0 percent of the titanium dioxide, namely 44.4mL, the flow rate is 0.74mL/min, and the titanium dioxide is aged for 60min after the addition is finished. Adjusting the pH value to 7.3 by using sulfuric acid, and curing for 15min to obtain the aluminum-coated titanium dioxide particles.

(4) And (4) performing filter pressing washing on the slurry obtained in the step (3), drying the slurry in a vacuum drying oven at 105 ℃ until the water content is less than 0.5%, crushing the slurry by using an airflow crusher, adding alkyl silicone oil in the crushing process, wherein the addition amount of the alkyl silicone oil is 3 per mill of the titanium dioxide, and crushing the mixture to obtain the finished product of the titanium dioxide.

Example 4

The method of the invention is utilized to treat the surface of the titanium dioxide, and the specific method is as follows:

(1) preparing 1L of initial slurry with the concentration of 400g/L, adding 2 thousandth of isopropanolamine, dispersing for 10min by using a sand mill, placing the mixture in a single-layer glass reaction kettle, stirring, heating to 70 ℃, and adjusting the pH value to 10.0.

(2) Adding a sodium silicate solution with the concentration of 100g/L into the titanium dioxide slurry by adopting a peristaltic pump, wherein the total amount of the sodium silicate is SiO₂Calculated as 3.0 percent of the titanium dioxide, namely 120mL, the flow rate is 6mL/min, and after the addition is finished, the mixture is aged for 60min to obtain silicon-coated titanium dioxide particles.

(3) Adjusting the pH value of the slurry obtained in the step (2) to 7.5 by using sulfuric acid, adding a sodium metaaluminate solution with the concentration of 270g/L, wherein the total amount of the metaaluminate is Al₂O₃Calculated as 3.0 percent of the titanium dioxide, namely 44.4mL, the flow rate is 0.74mL/min, and the titanium dioxide is aged for 60min after the addition is finished. Adjusting the pH value to 7.3 by using sulfuric acid, and curing for 15min to obtain the aluminum-coated titanium dioxide particles.

(4) And (4) performing filter pressing washing on the slurry obtained in the step (3), drying the slurry in a vacuum drying oven at 105 ℃ until the water content is less than 0.5%, crushing the slurry by using an airflow crusher, adding alkyl silicone oil in the crushing process, wherein the addition amount of the alkyl silicone oil is 5 per mill of the titanium dioxide, and crushing the mixture to obtain the finished product of the titanium dioxide.

Comparative example 1

Titanium white powder special for domestic famous brand plastics is sold.

Product characterization the titanium dioxide powders of examples 1-4 and comparative example 1 were tableted and tested for brightness and whiteness using a spectrocolorimeter (LabScanXE); testing the oil absorption according to item 7.9 in GB/T1706-2006; in the linseed oil system, after dispersion by a flat grinder, the dispersion was measured by a fine blade reader having a blackman number, and the results are shown in Table 1.

Table 1:

through tests, the brightness, whiteness, oil absorption and dispersibility of the special titanium dioxide powder for plastics are superior to those of products sold in the market, and the prepared titanium dioxide powder is easy to process in plastics.

Finally, it is noted that: the above-mentioned list is only the preferred embodiment of the present invention, and naturally those skilled in the art can make modifications and variations to the present invention, which should be considered as the protection scope of the present invention provided they are within the scope of the claims of the present invention and their equivalents.