JP2010208863A - Method for producing titanium oxide powder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for simply producing fine titanium oxide powders with high purity without refining treatment accompanying to the purity falling of an obtained cake (filtered substance) and controlling the additional amount of a pH adjusting agent when the titanium oxide powders are filtered from a dispersion liquid where crude titanium oxide powders produced by a liquid phase method are dispersed in water. <P>SOLUTION: The method for producing the titanium oxide powders is characterized in that the titanium oxide powders in a slurry obtained after the dispersion liquid where the crude titanium oxide powders produced by the liquid phase method are dispersed in water are contacted with carbonic acid are separated. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing titanium oxide powder.

  Titanium oxide is used in a wide range of applications such as photocatalysts, additives for solar cells, UV shielding materials and silicone rubber, dielectric materials, cosmetics, etc., for the purpose of decomposing organic substances by photocatalysis. It is also applied to antibacterial tiles, building materials, deodorant fibers, and paper.

  The photocatalytic action of titanium oxide is that titanium oxide absorbs ultraviolet rays and generates electrons and holes therein, and the generated holes react with the adsorbed water of titanium oxide to generate hydroxy radicals, which are oxidized. It is generated by decomposing organic substances adsorbed on the titanium surface into carbon dioxide gas or water.

  In addition, research on the application of titanium oxide to solar cells has been underway since 1991 when Gretzel et al. Of Lausanne University of Technology reported a dye-sensitized solar cell combining titanium oxide and a ruthenium-based dye. . A dye-sensitized solar cell has a structure in which an electrolytic layer is sandwiched between a conductive glass electrode on which a dye-supported titanium oxide layer is formed and a counter electrode, and the dye absorbs light to absorb electrons and holes. appear. The generated electrons reach the conductive glass electrode through the titanium oxide layer and are extracted to the outside. On the other hand, the generated holes are transported to the counter electrode through the electrolytic layer, and are combined with electrons supplied through the conductive glass electrode.

  Thus, when applying titanium oxide as a photocatalyst to a glass surface or the like, or when applying it to an electrode of a solar cell, etc., the transparency of the titanium oxide film is an important factor in increasing the catalyst efficiency and photoelectric conversion efficiency. It becomes.

  In general, it is said that light scattering (hiding power) is maximized when the particle size of titanium oxide particles is about ½ of the visible light wavelength, and light scattering is also weakened when the particle size is reduced. If the primary particle diameter of the powder is several nanometers to several tens of nanometers and the dispersibility is good, the influence on light scattering is reduced, and a highly transparent titanium oxide film is obtained. The transparency of the titanium oxide film is also affected by impurities in the titanium oxide, and when the titanium oxide contains impurities (for example, transition elements, nitrogen, sulfur, etc.), light coloration may occur.

  From the above, it is very important for the application of titanium oxide powder that the titanium oxide powder is fine and the content of impurities is small.

  The titanium oxide powder can be produced by vaporizing a titanium oxide raw material such as titanium chloride or an organic compound of titanium, and oxidizing or decomposing the raw material to obtain a titanium oxide powder, and titanium chloride or titanyl sulfate. There is a liquid phase method (wet method) in which a liquid in which a titanium oxide raw material is dissolved is hydrolyzed or neutralized.

  When producing titanium oxide powder by the liquid phase method, it is necessary to separate the titanium oxide powder from the titanium oxide powder-containing slurry. As one of the separation methods, the solid-liquid mixture (the titanium oxide powder-containing slurry) is filtered or filtered. And a filtration method in which the solid is separated into a wet solid (titanium oxide powder) and a dispersion medium.

  However, in general, when filtering a suspension in which fine titanium oxide powder is dispersed, filter media such as filter cloth and filter paper are generally clogged, and a long time is required for the filtration process. And

  In order to advance the filtration process economically, it is necessary to increase the filtration throughput, and the filtration throughput is increased by increasing the filtration rate or increasing the unit operation volume (the filtration volume per operation). be able to. As a method for improving the filtration rate, as a pretreatment, a method in which a filter aid is used for a solid-liquid mixture (a slurry containing titanium oxide powder) or a coagulation treatment is known.

  Filter aids are used for the purpose of reducing filtrate resistance, preventing clogging of filter media, and high-clarity filtrate separation. Examples include filter aids.

  Moreover, as a general method of the aggregation treatment, a method of adjusting the pH of the solid-liquid mixture or adding a flocculant can be mentioned (see Non-Patent Document 1).

  The method for adjusting the pH is to adjust the zeta potential of the metal oxide to near zero (isoelectric point) with a pH adjusting agent such as acid or base. Examples of the pH adjusting agent include hydrochloric acid, sulfuric acid, phosphoric acid, Examples thereof include acids such as acetic acid, citric acid and tartaric acid, and bases such as ammonia, sodium hydroxide and potassium hydroxide.

  The flocculants include polyacrylamide, polyethylene oxide, polyacrylamide partial hydrolyzed salts, organic polymer systems such as sodium polyacrylate, sodium alginate, polyacrylaminoacrylate, polyaminomethylacrylamide, activated silicic acid, aluminum sulfate, poly Inorganic materials such as aluminum chloride, ferrous sulfate, ferric chloride and the like can be mentioned.

Chemical Engineering Association, “Revised 5th edition, Chemical Engineering Handbook”, pages 745-747 (1988)

  However, when the present inventors examined, in the method using the said filter aid, and the method using a pH adjuster and a flocculant, the purity of the cake (filtrate) obtained will fall and it will be after filtration processing. It has been found that a purification treatment is necessary if necessary.

  In addition, in the method using a pH adjuster, if the pH adjuster is added excessively, the pH drops too much and cannot be effectively solid-liquid separated, so depending on the isoelectric point of the titanium oxide to be obtained. Therefore, there is a technical problem that it is necessary to appropriately adjust the addition amount of the pH adjusting agent, and the separation operation becomes complicated.

  Under such circumstances, it is an object of the present invention to provide a method for easily producing a fine particulate titanium oxide powder with high purity.

  In order to solve the above technical problem, the present inventors conducted extensive studies, and after bringing the crude titanium oxide powder and carbonic acid into contact with each other in water, the titanium oxide powder in the resulting slurry was separated. The present inventors have found that the above problems can be solved, and have completed the present invention.

That is, the present invention
(1) A method for producing a titanium oxide powder, comprising: bringing a crude titanium oxide powder and carbonic acid into contact with water; and separating the titanium oxide powder in the obtained slurry;
(2) In the above (1), the amount of carbonic acid in the slurry is controlled so that the pH of the slurry to be separated is within ± 1.5 at the isoelectric point of the titanium oxide powder to be obtained. A method for producing the described titanium oxide powder,
(3) The method for producing a titanium oxide powder according to (1) or (2) above, wherein the crude titanium oxide powder is obtained by neutralizing titanium tetrachloride with ammonia, and (4) The method for producing a titanium oxide powder according to any one of the above (1) to (3), wherein the separation treatment is a filtration treatment.

  According to the present invention, by using carbonic acid as a pH adjuster, it is possible to suppress a decrease in purity of the obtained titanium oxide powder and to perform a separation treatment while easily controlling the pH of the titanium oxide powder-containing slurry. Therefore, the particulate titanium oxide powder can be easily produced with high purity.

  The method for producing a titanium oxide powder according to the present invention is characterized in that after the crude titanium oxide powder and carbonic acid are brought into contact with each other in water, the titanium oxide powder in the obtained slurry is subjected to a separation treatment.

  In the present invention, the crude titanium oxide powder may be produced by a liquid phase method or may be produced by a vapor phase method.

  Examples of a method for producing a crude titanium oxide powder by a liquid phase method include a method in which titanium halide is hydrolyzed or a titanium halide-containing liquid is neutralized. For example, water is added to titanium halide. The method of hydrolyzing and the method of neutralizing by contacting an aqueous solution of titanium halide with an alkali include titanium chlorides such as titanium trichloride and titanium tetrachloride, And titanium tetraiodide and the like. Titanium tetrachloride is suitable as the titanium halide.

  The crude titanium oxide powder obtained by the above-mentioned method for producing crude titanium oxide powder by liquid phase method contains rutile or anatase type titanium oxide, orthotitanic acid, metatitanic acid, titanium hydroxide or titanium oxide hydrate. Things.

  As a method for producing the crude titanium oxide powder by the liquid phase method, a method for alkali neutralizing the aqueous titanium halide solution will be specifically described below.

As a method of performing alkali neutralization of titanium halide, an aqueous solution in which titanium halide is dissolved in water is prepared, and while stirring the aqueous solution, the alkali is mixed and the titanium halide and the alkali are brought into contact with each other. More specifically, the following neutralization method 1 to neutralization method 3, that is,
(Neutralization method 1) A method in which an alkaline aqueous solution is added dropwise to a titanium halide aqueous solution to bring them into contact with each other.
(Neutralization method 2) A method in which an aqueous solution of titanium halide is added dropwise to an alkaline aqueous solution to bring them into contact with each other.
(Neutralization method 3) A method in which water adjusted in pH is put in a reaction vessel, and a titanium halide aqueous solution and an alkaline aqueous solution are dropped therein, and both are brought into contact with each other.
Can be mentioned.

  It does not restrict | limit especially as an alkali used for the said alkaline aqueous solution, For example, ammonia etc. can be mentioned. When ammonia is used as the alkali, it is preferable because the obtained titanium oxide powder does not contain an alkali-derived metal component.

  In the above (neutralization method 1) to (neutralization method 3), the neutralization temperature is preferably 10 to 80 ° C, more preferably 30 to 80 ° C. When the neutralization temperature is less than 10 ° C., the neutralization reaction hardly occurs, and when it exceeds 80 ° C., it is difficult to obtain an alkali neutralized product having a small average particle size and a large specific surface area.

  When using ammonia as an alkali and neutralizing titanium halide in water to prepare a crude titanium oxide powder aqueous dispersion, the pH of the crude titanium oxide powder aqueous dispersion is obtained with aqueous ammonia. It is preferable to adjust the pH to be higher than the pH at the isoelectric point of the powder, for example, pH 6 or higher. Chlorine can be efficiently removed by setting the pH of the crude titanium oxide powder aqueous dispersion to pH 6 or higher, which is higher than the pH at the isoelectric point of the titanium oxide powder to be obtained.

On the other hand, as a method for producing the crude titanium oxide powder by a vapor phase method, the following vapor phase method 1 to vapor phase method 4, that is,
(Gas phase method 1) Gas phase oxidation method in which titanium halide gas is oxidized by contacting oxygen gas in the gas phase,
(Gas phase method 2) A flame hydrolysis method in which a flammable gas such as hydrogen gas and oxygen gas that generate water during combustion and an oxygen gas are supplied to a combustion burner to form a flame, and a titanium halide gas is introduced therein.
(Gas phase method 3) Gas phase oxidation method in which titanium halide gas is contacted with water vapor in the gas phase and oxidized,
(Gas phase method 4) A flame hydrolysis method in which a combustible gas such as hydrogen gas and oxygen gas that generate water at the time of combustion is supplied to a combustion burner to form a flame, and a titanium halide gas and water vapor are introduced into the flame.
And so on.

  Examples of the titanium halide gas include titanium chloride gas such as titanium trichloride gas and titanium tetrachloride gas, titanium tetrabromide gas, and titanium tetraiodide gas.

  In the liquid phase method, since impurity elements other than the halogen element derived from titanium halide as a raw material exist in the liquid, impurity elements other than halogen elements are mixed in or remain in the obtained crude titanium oxide powder. In the phase method, titanium halide gas is brought into contact with hydrogen gas, oxygen gas or water vapor in the gas phase to react, so that the resulting crude titanium oxide powder contains titanium halide in comparison with the liquid phase method. Impurity elements other than the contained elements are unlikely to enter or remain. However, even in the vapor phase method, there may be a case where a halogen element derived from a titanium halide or a carbon content in a combustible gas is mixed in the obtained crude titanium oxide. For such a crude titanium oxide powder, It is preferable to prepare titanium oxide powder by the method of the present invention.

Further, the specific surface area of the crude titanium oxide powder is not particularly limited, but the present invention can be effectively applied to a powder having a large specific surface area (small particle size). For example, the specific surface area of the crude titanium oxide powder is: preferably ^{30m 2 / g~300m 2 / g,} 80m 2 / g~300m 2 / g is more preferable.

  In the present invention, the crude titanium oxide powder and carbonic acid are contacted in water.

  At the time of the contact, the concentration of the crude titanium oxide powder in water is preferably adjusted to be 500 g / liter or less, and more preferably adjusted to be 10 to 500 g / liter. If it exceeds 500 g / liter, dispersion of the crude titanium oxide powder becomes difficult.

Method of contacting the crude titanium oxide powder and carbonate is not particularly limited, for example, to generate carbonic acid (H 2 _{CO 3)} in water by bubbling carbon dioxide gas (CO ₂₎ to the crude titanium oxide powder aqueous dispersion Then, it may be brought into contact with the crude titanium oxide powder, or after an aqueous solution (carbonated water) in which carbon dioxide gas is bubbled in advance to generate carbonic acid in water, the carbonated water and the crude titanium oxide powder aqueous dispersion The crude titanium oxide powder and carbonic acid may be brought into contact by mixing. Alternatively, carbonated water may be prepared in advance, and the carbonated water and the crude titanium oxide powder aqueous dispersion may be mixed, and the crude titanium oxide powder and carbonic acid may be brought into contact with each other by blowing carbon dioxide into the mixture. When carbon dioxide is bubbled to generate carbonic acid, the carbon dioxide gas may be blown while stirring the aqueous dispersion or water to be bubbled, or it may be blown into a fine foam with a filter or the like.

  By treating with an aqueous carbonate solution, the sedimentation rate of the alkali neutralized product is also increased. In addition, the reduction rate of impurities such as chlorine and nitrogen in the dispersion is increased.

  When the crude titanium oxide powder dispersion is in contact with carbonic acid, the concentration of carbonic acid in the contact liquid (crude titanium oxide powder-containing slurry) is the pH at the isoelectric point of the titanium oxide powder to be obtained as the pH of the contact liquid. Is preferably within a range of ± 1.5, more preferably until the carbonic acid concentration is saturated (until the pH becomes constant within the above pH range).

  The contact time between the crude titanium oxide powder and carbonic acid is preferably set to a time at which a desired pH or saturation concentration can be achieved.

  At the time of contact between the crude titanium oxide powder and carbonic acid, the temperature of the contact liquid (contact temperature) is not particularly limited, but it is economical that the temperature is from room temperature to 60 ° C.

  When carbon dioxide is generated by bubbling carbon dioxide in water, when carbon dioxide is bubbled in water, the concentration of carbonic acid in water will eventually reach a saturation concentration, and the pH in water will be at the isoelectric point of the titanium oxide powder. The pH is close to pH (pH 5 to 7). At this time, the titanium oxide powder becomes weakly aggregated and settles, so it is considered that impurities are easily taken up. However, according to the study by the present inventors, it has been surprisingly found that the present invention aggregates while suppressing the incorporation of impurities.

  In the present invention, since carbon dioxide is used to adjust the pH, there is no contamination with acid or alkali as in the case of using a normal pH adjusting agent, and a high-purity powder can be obtained.

  Furthermore, according to the study by the present inventors, it has been found that even when the crude titanium oxide powder and carbonic acid are brought into contact with each other in water, the pH is not reduced below a certain value. For example, by bubbling carbon dioxide in a liquid at room temperature and atmospheric pressure with respect to a 25 ° C. crude titanium oxide powder aqueous dispersion obtained by neutralizing titanium tetrachloride with ammonia by a liquid phase method. It was found that when the crude titanium oxide powder and carbonic acid were brought into contact with each other, the pH in the liquid was gradually reduced but not reduced to pH 5.8 or lower. For this reason, in the present invention, attention is paid to pH fluctuations caused by excessive addition of pH adjusters, as in the case of adding ordinary pH adjusters composed of acids such as hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, citric acid, and tartaric acid. This is not necessary, and the reaction can be performed easily.

  Further, according to the study by the present inventors, when carbon dioxide is supplied into water until the pH in the water in which the crude titanium oxide powder and carbonic acid are brought into contact is constant, impurities such as chlorine and nitrogen in the crude titanium oxide powder. It has been found that the reduction rate of can be improved.

  In the present invention, the pH of a slurry to be subjected to a separation treatment described later, that is, a slurry containing a crude titanium oxide powder obtained by contacting a crude titanium oxide powder and carbonic acid in water, immediately before being subjected to the separation treatment. It is preferable to control the amount of carbonic acid in the slurry so that the pH of the slurry is within ± 1.5 at the isoelectric point of the titanium oxide powder to be obtained.

  In this application, the isoelectric point means a state in which the zeta potential on the titanium oxide surface is zero. The zeta potential on the surface of titanium oxide varies depending on the pH of the system, and the pH at the isoelectric point (pH at which the zeta potential becomes zero) is, for example, 4.8 of natural rutile titanium oxide in an aqueous solution at 25 ° C. About 6.7 for synthetic rutile type titanium oxide and about 6.0 for synthetic anatase type titanium oxide.

  As described above, even when the crude titanium oxide powder and carbonic acid are brought into contact with each other in water, the pH of the slurry is not reduced below a certain value, and the pH in water changes around the isoelectric point of titanium oxide. For this reason, even if the pH of the slurry is, for example, when carbon dioxide gas is excessively supplied into water, the lower limit value is ± 1. With respect to the pH at the isoelectric point of the titanium oxide powder to be obtained. It can easily be within a range of 5 or less.

  By controlling the amount of carbonic acid in the slurry so that the pH of the slurry subjected to the separation treatment described later is within pH ± 1.5 at the isoelectric point of the titanium oxide powder to be obtained, the subsequent filtration The solid-liquid separation speed when performing solid-liquid separation such as the above can be improved.

  In the present invention, a slurry obtained by bringing a crude titanium oxide powder and carbonic acid into contact with each other in water is subjected to a separation treatment, whereby the titanium oxide powder is isolated.

  Examples of the separation treatment method include a normal solid-liquid separation method, and examples of the solid-liquid separation method include a precipitation separation method and a filtration method, and the separation treatment is more preferable by the filtration method.

  The separation process by the filtration method may be performed only once or may be performed a plurality of times. For example, after filtering a crude titanium oxide powder aqueous dispersion adjusted to a pH equal to or higher than the pH at the isoelectric point of the titanium oxide powder to be obtained, adding water to the resulting titanium oxide powder-containing cake and stirring, then again It may be carried out by repeating the filtration operation, or after bringing the crude titanium oxide powder and carbonic acid into contact with water and precipitating the titanium oxide powder, the supernatant is removed, and after adding water and stirring, the titanium oxide powder After repeating the operation of settling (sediment separation), filtration may be performed once.

  When the separation process is performed by repeating the filtration operation, the pH of the slurry provided for each filtration process is within ± 1.5 at the isoelectric point of the titanium oxide powder to be obtained for each filtration process. It is preferable to adjust so that.

  The filtration method is a method of passing the slurry through a porous material (filter material) provided with a large number of pores to separate a solid powder having a size larger than the size of the pores from the liquid. Natural filtration using gravity, reduced pressure filtration by filtering the lower surface of the filter medium by applying atmospheric pressure, pressure filtration that performs filtration by pressurizing the upper surface of the filtrate with compressed air or inert gas such as nitrogen, Centrifugal filtration which filters by differential pressure using centrifugal force is mentioned.

  Filter media include cellulose-based filter paper, cotton, woven fabric made of synthetic fiber, glass fiber filter made of glass fiber, membrane filter made of fluororesin and cellulose acetate, made of sintered metal or ceramic Examples thereof include a porous filter, and particulate substances such as charcoal, glass wool, and sand.

The titanium oxide powder obtained by the separation treatment is then dried as necessary.
The drying means is not particularly limited, and examples thereof include a drying device such as a dryer, and a firing furnace such as a muffle furnace and a cantal furnace.

  The drying temperature is preferably 60 ° C. or higher, more preferably 70 to 160 ° C., and still more preferably 110 to 150 ° C.

  By setting the drying temperature to 60 ° C. or higher, the carbon dioxide adsorbed on the surface of the titanium oxide powder can be removed, and a high-purity titanium oxide powder can be obtained. In particular, when the drying temperature is 110 to 150 ° C., it is possible to effectively remove alkalis such as ammonia used in the production of the crude titanium oxide powder, and to suppress the growth of the particle size, thereby reducing the ratio of the titanium oxide powder. Reduction in surface area can be suppressed.

  Furthermore, when a drying process is performed until the weight loss becomes 1% by mass or less, a titanium oxide powder having a low nitrogen content can be obtained.

In the present application, the weight loss means that the measurement powder is heated to 120 ° C. in the atmosphere and heated at 120 ° C., and the mass change of the measurement sample is 0.2 mass% / min or less. The mass of the measurement sample before measurement is X (g), and the mass of the measurement sample when heated at 120 ° C. and the mass change is 0.2 mass% / min or less is Y (g). As the following formula:
Weight loss of measurement sample (mass%) = {(XY) / X} × 100
It is the value calculated | required by.

  EXAMPLES Next, although an Example is given and this invention is demonstrated more concretely, this is only an illustration and does not restrict | limit this invention.

(Preparation of slurry containing crude titanium oxide powder)
A slurry containing crude titanium oxide powder was prepared by the following method.
In a storage tank equipped with a stirrer, a 1250 mL, 60 ° C. acidic aqueous solution adjusted to pH 4 with an aqueous titanium tetrachloride solution (titanium concentration: 5.9% by mass) was prepared as a starting solution.

  While stirring with a stirrer in the above-mentioned storage tank, an aqueous solution of titanium tetrachloride (titanium concentration: 5.9% by mass) and an aqueous ammonia solution (ammonia concentration: 5.6% by mass) were respectively adjusted to a neutralization equivalent. The slurry was added continuously and reacted so that the addition rates were 5.55 g / min and 5.47 g / min to produce a titanium tetrachloride neutralized reactant-containing slurry. At this time, the addition and reaction time were 5 hours, and the temperature of the reaction solution to which the titanium tetrachloride aqueous solution and the ammonia aqueous solution were added was adjusted to maintain 60 ° C.

  The pH of the solution obtained by adding the aqueous solution of titanium tetrachloride (titanium concentration: 5.9% by mass) and the aqueous ammonia solution (ammonia concentration: 5.6% by mass) used in this example so as to have a neutralization equivalent was 4 Therefore, the pH of the slurry during addition and reaction was maintained at pH 4.

  After cooling to room temperature, the resulting titanium tetrachloride neutralized reactant-containing slurry was filtered. Water and an aqueous ammonia solution (ammonia concentration: 5.6% by mass) were added to the cake obtained after filtration, and stirred for 30 minutes to obtain a slurry containing crude titanium oxide powder. The pH of this crude titanium oxide powder-containing slurry was 6.5, and the concentration of titanium contained in the slurry was 200 g / liter in terms of titanium oxide.

  Moreover, the isoelectric point of the titanium oxide contained in the said slurry containing a rough titanium oxide powder was measured by electrophoresis. A part of the crude titanium oxide-containing slurry was added to distilled water, and an aqueous sodium hydroxide solution was further added to adjust the pH to 10 to obtain a slurry for isoelectric point measurement. The concentration of titanium oxide in the isoelectric point measuring slurry is 1 g / liter. Dilute hydrochloric acid was sequentially added to the slurry to change the pH.

  When the pH at the isoelectric point of titanium oxide contained in the slurry was measured by a zeta potential measurement system (ELSZ-1) and a pH titrator system (ELSZ-PT) (manufactured by Otsuka Electronics Co., Ltd.), the pH was 5.4. there were.

  A part of the cake obtained by filtering the slurry containing the titanium tetrachloride neutralization reaction product was transferred to a vat, and then a natural convection dryer (manufactured by Yamato Scientific Co., Ltd., model number DX602) at 110 ° C. for 16 hours. After the time drying, when the titanium oxide crystal phase contained in the cake was identified, the rutile ratio was 0%, which was anatase type. In addition, the identification method of a crystal phase is as showing below.

(Identification of crystal phase)
According to ASTM D 3720-84, the peak area (Ir) of the strongest interference line (surface index 110) of rutile crystalline titanium oxide in the X-ray diffraction pattern and the peak of the strongest interference line (surface index 101) of anatase type titanium oxide powder The area (Id) was determined, and the rutile ratio was determined from the following calculation formula.
Rutile ratio (% by mass) = 100-100 / (1 + 1.2 × Ir / Id)

The X-ray diffraction measurement conditions are as follows.
Diffraction device RAD-1C (manufactured by Rigaku Corporation)
X-ray tube Cu
Tube voltage / tube current 40kV, 30mA
Slit DS-SS: 1 degree, RS: 0.15mm
Monochromator Graphite measurement interval 0.002 degree counting method Constant clock number method

Example 1
After stirring 10 liters of the above slurry containing titanium oxide powder (pH 6.5) in a container, carbon dioxide gas was bubbled to precipitate titanium oxide powder, and the oxidation was controlled so that the pH immediately before filtration was 6 A titanium powder-containing slurry was obtained. Next, the slurry was filtered twice to separate the titanium oxide powder in the slurry.
The conditions for the first filtration treatment are as follows.

(Filtration method)
Method: Vacuum filtration Filter media: Circular filter paper No. 5C (manufactured by ADVANTEC)
The obtained titanium oxide powder-containing cake was again poured into 10 liters of water, stirred, and then bubbled with carbon dioxide under the same conditions as above to control the titanium oxide so that the pH immediately before filtration was 6 A powder-containing slurry was obtained, and a second filtration treatment was performed under the same conditions as the first filtration treatment.
The obtained titanium oxide powder-containing cake was transferred to a vat and subjected to a drying treatment at 110 ° C. for 16 hours in a natural convection dryer (manufactured by Yamato Kagaku Co., Ltd., model number DX602) to obtain the target titanium oxide powder. .
When the moisture content of the titanium oxide powder obtained by the drying treatment was measured by the following method, the moisture content was 0.2% by mass or less.
Further, the chlorine content in the titanium oxide powder obtained (mass%), nitrogen content (mass%), the specific surface area (m 2 ^{/ g)} was measured by the following method. These measurement results are shown in Table 1 together with the crystal phase and rutile ratio of titanium oxide and the total filtration time (total of the first filtration time and the second filtration time) during the filtration treatment.

(amount of water)
With a heat drying moisture meter ML-50 (manufactured by A & D Co., Ltd.), 5 g of the measurement sample was heated and heated to 120 ° C. in the atmosphere, and the mass change of the measurement sample was 0.2 mass% / min or less. Then, the amount of mass decrease was measured, and the water content was calculated by the above formula (1).

(Chlorine content analysis method)
The obtained titanium oxide powder was dissolved in hydrofluoric acid, and the solution was analyzed by coulometric titration.

(Method for analyzing nitrogen content)
The obtained titanium oxide powder was dissolved in hydrofluoric acid, and the liquid was analyzed by ammonia distillation separation amide sulfuric acid titration method.

(Measurement of specific surface area)
It was measured by the BET method. The degassing conditions for the pretreatment were 110 ° C. and 30 minutes.

(Comparative Example 1)
Except that carbon dioxide bubbling was not performed, a titanium oxide powder-containing slurry was prepared in the same manner as in Example 1, and the titanium oxide powder-containing slurry was filtered twice in the same manner as in Example 1. A drying treatment was performed to obtain a comparative titanium oxide powder.
The pH of the slurry immediately before the first filtration treatment was 6.4, and the pH of the slurry immediately before the second filtration treatment was 6.9. The results of measuring the chlorine content, nitrogen content, and specific surface area of the comparative titanium oxide powder in the same manner as in Example 1 were used to obtain the titanium oxide crystal phase and rutile ratio, total filtration time (first filtration time and second filtration time). Table 1 together with

(Example 2)
In the same manner as in Example 1, a titanium oxide powder-containing slurry was prepared, and the slurry was filtered twice to obtain a titanium oxide powder-containing cake. This titanium oxide powder-containing cake was again put into water in the same manner as in the filtration treatment of Example 1, and after stirring and bubbling with carbon dioxide, the filtration operation was repeated twice to contain the titanium oxide powder. I got a cake.
The pH of the slurry containing titanium oxide powder immediately before the third and fourth (last) filtration was 6.
The obtained titanium oxide powder-containing cake was dried by the same method as in Example 1 to obtain the target titanium oxide powder.
The chlorine content (mass%), nitrogen content (mass%), and specific surface area (m ² / g) in the obtained titanium oxide powder were measured in the same manner as in Example 1. Moreover, the carbon content (mass%) in the obtained titanium oxide powder was measured by the following method. These measurement results are shown in Table 1 together with the crystal phase and rutile ratio of titanium oxide and the total filtration time (total of the first to fourth filtration times) during the filtration treatment.

(Method for analyzing carbon content)
It was analyzed by combustion-infrared absorption method.
From the results of Example 2, it is understood that the nitrogen content and the carbon content are reduced by treating the crude titanium oxide powder with carbon dioxide gas.

(Comparative Example 2)
In the same manner as in Comparative Example 1, a titanium oxide powder-containing slurry was prepared, and the slurry was filtered twice to obtain a comparative titanium oxide powder-containing cake. This comparative titanium oxide powder-containing cake was again poured into water and stirred in the same manner as in the filtration treatment of Comparative Example 1, and then the filtration operation was repeated twice to obtain a titanium oxide powder-containing cake.
The pH of the titanium oxide powder-containing slurry immediately before the third filtration was 7.5, and the pH of the titanium oxide powder-containing slurry immediately before the fourth (last) filtration was 8.0.
The titanium oxide powder-containing cake was dried by the same method as in Example 1 to obtain the target titanium oxide powder.
The chlorine content (mass%), nitrogen content (mass%), carbon content (mass%), and specific surface area (m ² / g) in the obtained titanium oxide powder were measured in the same manner as in Example 2. did. These measurement results are shown in Table 1 together with the crystal phase and rutile ratio of titanium oxide, and the total filtration time (total of the first to fourth filtration times) during the filtration treatment.
From the results of Example 2 and Comparative Example 2, the pH of the titanium oxide-containing slurry before filtration is within pH (5.4) ± 1.5 at the isoelectric point of the titanium oxide powder to be obtained. It turns out that the reduction effect of filtration time is large. Moreover, it turns out that nitrogen content is reducing more by processing a crude titanium oxide powder with a carbon dioxide gas.

(Comparative Example 3)
A titanium oxide powder-containing slurry was prepared in the same manner as in Example 1 except that an acetic acid aqueous solution (acetic acid concentration: 40%) was used instead of carbon dioxide gas. After four filtration treatments, a drying treatment was performed to obtain titanium oxide powder.
The pH of the slurry immediately before the first to fourth filtration treatments was adjusted to be 6.
The chlorine content (mass%), nitrogen content (mass%), carbon content (mass%), and specific surface area (m ² / g) in the obtained titanium oxide powder were measured in the same manner as in Example 2. did. These measurement results are shown in Table 1 together with the crystal phase and rutile ratio of titanium oxide and the total filtration time (total of the first to fourth filtration times) during the filtration treatment.
By comparing the results of Example 2 and Comparative Example 3, it can be seen that in the present invention, the carbon content of the obtained titanium oxide powder can be reduced by treating the crude titanium oxide powder with carbon dioxide gas.

Example 3
In Example 1, instead of bubbling carbon dioxide so that the pH of the crude titanium oxide powder-containing slurry immediately before the first and second filtration was 6, carbon dioxide was added at 10 liters / minute in each slurry. A titanium oxide powder was obtained in the same manner as in Example 1 except that bubbling was performed for a minute.
The pH of the slurry containing the crude titanium oxide powder did not become less than 5.8, and showed a constant value of about 5.8 to 5.9 (in addition, bubbling of carbon dioxide gas similarly to distilled water not containing titanium oxide) The pH is about 4.5).
The chlorine content (mass%), nitrogen content (mass%), carbon content (mass%), and specific surface area (m ² / g) in the obtained titanium oxide powder were measured in the same manner as in Example 2. did. These measurement results are shown in Table 1 together with the crystal phase and rutile ratio of titanium oxide and the total filtration time (total of the first filtration time and the second filtration time) during the filtration treatment.

  In the present Example, it turns out that the filtration rate is quicker than Example 1, and nitrogen content is reducing more.

(Comparative Example 4)
Instead of bubbling carbon dioxide gas, the same treatment as in Example 1 was conducted except that 100 g of a cationic polymer flocculant (trade name Sanfloc (manufactured by Sanyo Chemical Industries)) was added to the crude titanium oxide powder dispersion. Thus, a comparative titanium oxide powder was obtained.
The pH of the slurry immediately before the first and second filtration treatments was about 6.
The chlorine content (mass%), nitrogen content (mass%), carbon content (mass%), and specific surface area (m ² / g) in the obtained comparative titanium oxide powder were the same as in Example 2. It was measured. These measurement results are shown in Table 1 together with the crystal phase and rutile ratio of titanium oxide and the total filtration time (total of the first filtration time and the second filtration time) during the filtration treatment.

  By comparing the results of Example 1 and Comparative Example 4, it can be seen that the filtration time can be shortened by treating the crude titanium oxide powder with carbon dioxide gas in the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the method of manufacturing a particulate titanium oxide powder with high purity and simply can be provided.

Claims (4)

  A method for producing a titanium oxide powder, comprising: bringing a crude titanium oxide powder and carbonic acid into contact with each other in water; and separating the titanium oxide powder in the obtained slurry.   The titanium oxide according to claim 1, wherein the amount of carbonic acid in the slurry is controlled so that the pH of the slurry to be separated is within ± 1.5 at the isoelectric point of the titanium oxide powder to be obtained. Powder manufacturing method.   The method for producing a titanium oxide powder according to claim 1 or 2, wherein the crude titanium oxide powder is obtained by neutralizing titanium tetrachloride with ammonia.   The method for producing a titanium oxide powder according to any one of claims 1 to 3, wherein the separation treatment is a filtration treatment.