JPS62235215A - Production of rutile titanium oxide sol - Google Patents

Abstract

PURPOSE:To obtain the titled high-purity rutile titanium oxide sol with high efficiency by heating hydrated titanium oxide along with the hydroxide of an alkali metal, aging the material in an aq. hydrochloric acid soln. and washing the obtained rutile titanium oxide by using a filter membrane. CONSTITUTION:Hydrated titanium oxide obtained by the hydrolysis of titanyl sulfate aq. solution, for example, is heated along with the hydroxide of an alkali metal (e.g., NaOH). The heated material is then heated and aged in an aq. hydrochloric acid soln., or TiCl4 is dripped into an aq. hydrochloric acid soln., and the obtained soln. is hydrolyzed, to prepare a rutile titania sol. The obtained titania sol is desirable washed by using the filter membrane of a filter consisting of a circulating system. In this case, a permeable membrane having 10-5,000Angstrom , especially 30-2,000Angstrom , permeation pores is used. The high- purity rutile titania sol is stable for a long time even at high concn., and the fine powder of the rutile titanium oxide is obtained by drying the sol.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing titanium oxide, particularly rutile type titanium oxide sol.

Titanium oxide has a high refractive index, excellent coloring power and hiding power, and is chemically stable, so it is used as a white pigment in many fields. The high-purity sol provided by the present invention and the fine powder produced therefrom can be found to have further uses as described below. In other words, the sol or fine powder provided by the present invention is dispersed in a base material such as glass, plastic molded product, -/- sheet + film, or a coating film containing the sol or fine powder provided by the present invention is formed on the above base material. Film and UV shielding for the base material.

It is used to impart or improve functions such as light resistance, weather resistance, hardness reinforcement, heat resistance, and chemical resistance. In particular, when a sol or fine powder with excellent dispersibility and uniform particle size as seen in the present invention is applied to a transparent substrate, there is an advantage that the above-mentioned functions can be improved without impairing the transparency of the substrate.

[Conventional technology]

Hydrous titanium oxide obtained by heat treating a titanium sulfate solution or a titanium tetrachloride solution, etc. is treated with sodium hydroxide, etc., and then aged in hydrochloric acid, or titanium tetrachloride is added to a solution of hydrochloric acid, etc. It is known that a titania sol having a siltyl type crystal structure can be obtained by heating a solution added dropwise. Also, Tokukai Sho 5
Publication No. 9-223231 discloses that a free carboxylic acid or a polyvalent metal salt thereof is produced by reacting a carboxylic acid having 7 or more carbon atoms or an aqueous salt thereof with an acid or a polyvalent metal salt in a rutile type titania sol. A method for producing rutile-type fine particle titanium oxide having a particle size of 0.1 μm or less is disclosed by coating dispersed particles, then filtering and drying the dispersed particles, and optionally calcining the dispersed particles.

[Problem that the invention seeks to solve]

However, when applying the conventional hydrolysis method to obtain a rutile-type titania sol, the sol obtained after hydrolysis contains anions and metal ions, and the titania sol needs to be washed. The diameter of the particles is usually less than 0.1μ, so they have a strong affinity with water and form a strong water layer with water molecules, causing clogging of the filtration membrane during normal filtration operations. 4. When over-cleaning is extremely difficult, or when cleaning is performed using a tilting method, etc.

As cleaning progresses, the aquifer becomes peptized and the particles become isolated, but since these particles are small and stable in an aqueous solution, there has been no suitable method to capture them, and the efficiency of titania sol has been limited. It was difficult to perform a good cleaning.

The present inventors investigated the filtration and cleaning method for the rutile-type titania sol and found that titania sol can be cleaned extremely efficiently by employing a filtration method called ultrafiltration or molecular filtration. It has been found that rutile type titanium oxide particles can be obtained by preparing a high-purity rutile type titanium oxide sol using the filtration method, and then drying and calcining the sol.

〔means〕

The rutile titania sol targeted by the present invention is prepared by a known method. For example, a solution obtained by heat-treating hydrous titanium oxide obtained by hydrolysis of a titanyl sulfate solution with an alkali metal hydroxide and then heating and aging in an aqueous hydrochloric acid solution, or by dropping titanium tetrachloride into a hydrochloric acid solution. Rutile type titania sol is prepared by hydrolyzing . The sol thus obtained is then introduced into a filtration device and washed. It is preferable that the filtration device adopts a circulation system, in which water containing anions and metal ions is discharged from the system, and purified water is added to the concentrated sol to continuously wash it. At this time, the selection of the filtration membrane is important, and it is necessary to use a membrane that has permeable pores large enough to completely capture particles in the sol and allow only anions and metal ions to pass through. The highly purified rutile type titania sol obtained after washing is stable for a long period of time even at high concentrations, and can be used as a sol.

Further, by drying the sol, a rutile-type titanium oxide fine powder can be easily obtained, and the particle size can also be adjusted by firing this if necessary.

[Effect]

The filtration method used in the present invention is called ultrafiltration or single molecule filtration with a smaller permeation rate. There is a need for a method that can filter the sol while it is fluidized.

The circulation method of the present invention is preferable because it allows continuous filtration by introducing the sol to be filtered into the filtration device and returning the sol that has left the filtration device without being filtered. It is possible to carry out continuous and efficient filtration operations without substantially depositing particles, and it is also possible to concentrate the sol. Furthermore, the diameter of the permeation pores of the filtration membrane used in the present invention must be selected to be optimal; if the diameter is too large, particles may not be captured and cleaning may become impossible, or particles may be lost. If the number is too large, or if it is too small, anions and metal ions can pass through, making cleaning impossible or requiring a long time. In the present invention, IOX~500
A filtration membrane with a narrow pore size distribution width and permeation pores of 30□ to 2000X is preferable, and if the flow rate of the sol on the filtration membrane is 0.51 or more, the filtration operation can be carried out for a long time. No decrease in filtration ability due to particle deposition was observed. It is also advantageous to carry out the filtration operation under pressure in order to increase the filtration ability, but in this case a pressure of 6 kg/Crn2 or less is sufficient.

Furthermore, the cleaning method of the present invention can also be applied to the cleaning of hydrated titanium oxide obtained by hydrolysis of titanyl sulfate or tetra-f titanium, and the cleaning after heat-treating hydrated titanium oxide with an alkali metal hydroxide. By doing so, cleaning in a slurry state can be performed extremely efficiently, and in combination with the cleaning with the sol, a high purity rutile type titanium oxide sol can be easily and efficiently prepared.

To obtain rutile-type titanium oxide fine powder, high-purity rutile-type titanium oxide sol can be dried as is, or surface treated with surfactant, alumina, silica, etc., as is usually done, depending on the purpose. After drying, a rutile-type titanium oxide fine powder is obtained. The drying method may be normal heating drying, but dielectric heating drying, freeze drying,
Alternatively, fine rutile titanium oxide powder with good dispersibility can be obtained by spray drying, and if necessary, this can be calcined to obtain rutile titanium oxide with a larger particle size.

After concentrating the washed high-purity rutile titania sol, it is dispersed in an organic solvent such as alcohol, benzene, toluene, etc., and then heated and distilled to remove moisture. A rutile titanium oxide sol can be prepared. By drying and firing the organic solvent sol, a rutile-type titanium oxide fine powder with good dispersibility can be obtained.

Example 1 Hydrous titanium oxide obtained by boiling a titanyl sulfate solution was filtered and washed to prepare a slurry containing 500 g of T + 02. Next, caustic soda was added to the slurry under stirring, heat treatment was performed at 90 to 95°C, and 2 tons of 36% hydrochloric acid was added to the slurry obtained by thorough washing and heated at 98°C for 3 hours to prepare titania sol. . Then, the total filtration area is about 2 m2 and the average passage hole is about 100X.
The titania sol was pumped into a filtration device equipped with a filtration membrane and filtered. The filtrate that passed through the membrane was discharged, and the unfiltered sol was returned to its original state for continuous filtration and concentration. When the sol weighed about 4 tons, the filtrate was discharged while adding pure water, and the sol was subsequently washed.

When the chloride ion concentration in the sol became 2 PPM or less, the washing operation was stopped and the sol was concentrated to 5 tons. The cleaning required approximately 300 tons of pure water and took approximately 150 minutes.

The titania sol thus obtained was stable even when stored for a long time.

Further, a part of this sol was freeze-dried using liquid nitrogen to form a fine powder. The obtained fine powder showed a rutile crystal structure by X-ray diffraction, and its specific surface area was 140 m2.
/9.

Example 2 Ion exchange water 1t VC36% hydrochloric acid 40. After adding Iz, 95 g of titanium tetrachloride was added little by little while stirring while cooling in a water bath, and cooling was continued for 30 minutes even after the addition was completed. then 6
The mixture was heated at 0° C. for 3 hours to obtain titania sol. When this sol was allowed to stand and cool, the particles settled. While stirring the sol, the total filtration area is 4.000i and the average passing pore is about 6.
The sol was washed using the same filtration device as in Example 1 except that a 0X filtration membrane was used. When the chlorine ion concentration in the sol becomes 2 PPM or less, stop the cleaning operation and remove the sol.
It was concentrated to 50ml. The sol thus obtained is candy +
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About 30 tons of pure water was required for the Σ cleaning, and the time required was about 100 minutes. X-ray diffraction of the fine powder obtained by freeze-drying a part of the sol showed a rutile crystal structure, and the average crystal particle size was o, o o sμ. Further, the average crystal particle size of this rutile type titanium oxide fine powder after heat treatment at 500° C. for 1 hour was 0.04 μm and 8°.

When treated at ℃ for 1 hour, it was 0.18μ.

Claims (1)

[Claims] (1) A rutile-type titanium oxide sol is obtained by heat-treating hydrous titanium oxide with an alkali metal hydroxide and then aging in an aqueous hydrochloric acid solution, or by hydrolyzing a titanium tetrachloride solution, and then filtering the sol. A method for producing a high-purity rutile-type titanium oxide sol, which is characterized by using a membrane and cleaning it.