JPH0717377B2 - Method for producing spherical titanium dioxide powder - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing spherical titanium dioxide (hereinafter referred to as titanium oxide) powder having an optimum particle size as a filler.

[Prior Art and Problems] Titanium oxide has a high refractive index, is excellent in whiteness, hiding power, and coloring power, and is mainly used as a white pigment for paints, plastics, etc., but it has physical and chemical stability. Since it is excellent, it has recently been attracting attention as an electronic material such as a filler for a semiconductor encapsulating material in addition to the field of the above pigments.

Conventionally, the sulfuric acid method and the chlorine method are known as methods for producing titanium oxide. In the sulfuric acid method, the titanium oxide hydrate is precipitated by neutralizing or thermally hydrolyzing titanium sulfate or basic titanium sulfate. The titanium oxide powder is produced, separated, dried and fired to obtain a titanium oxide powder. In the chlorine method, titanium tetrachloride is oxidatively decomposed or an aqueous solution of titanium tetrachloride is hydrolyzed at a high temperature to precipitate a primary hydrate of titanium oxide, which is separated, dried and calcined to obtain titanium oxide powder. ing.

By the way, the titanium oxide powder obtained by the above-mentioned conventional manufacturing method has a particle diameter of 0.1 to 0.5 μm and is very fine. For this reason, it has excellent properties as a pigment, but when used as a filler, the particles are too fine, and when mixed in a large amount in the resin, the flexibility is lost and the resin becomes brittle.

[Findings on Problem Solving] When producing titanium oxide powder by the sulfuric acid method, the present inventor uses a titanium sulfate aqueous solution as an acidic solution and contains an excess of acid, and a relatively low concentration titanium sulfate aqueous solution is used at high temperature. , In-situ (in liquid) by adding ammonia instead of adding seed crystals
By generating and hydrolyzing and growing the precipitate,
It has been found that a spherical titanium oxide powder having a uniform and large growth can be obtained because the hydrolysis slowly progresses and the corners of the particles are removed by the acid.

[Structure of the Invention] The present invention provides a method for producing a titanium dioxide powder, which comprises hydrolyzing an aqueous solution of titanium sulfate and calcining a precipitated titanium dioxide hydrate, wherein the aqueous solution of titanium sulfate is titanium sulfate and acid. Is an acidic titanium sulfate aqueous solution having a weight ratio of 100: 5 to 100: 100, a weight ratio of water to titanium sulfate of 100: 5 to 100: 50, and hydrolysis at a temperature higher than 90 ° C. and a boiling point or less. By adding ammonia at a temperature, the number of particles within the particle size range of 10 to 20 μm is 90 after firing.
% Of spherical titanium dioxide powder is provided, and a method for producing spherical titanium dioxide powder is provided.

Here, the titanium sulfate refers to first titanium sulfate, second titanium sulfate, and titanium oxysulfate.

The present invention thermally hydrolyzes an acidic aqueous solution of titanium sulfate to produce a titanium oxide hydrate precipitate. Sulfuric acid second titanium Ti (SO ₄ ) ₂
In the case of using, the second titanium sulfate is dissolved in water to neutralize titanium oxysulfate (to form titanyl sulfate TiOSO ₄ ) or to undergo a thermal hydrolysis reaction to form a precipitate of titanium oxide hydrate TiO (OH) _2. To do. Separately, this is washed with water, dried and fired to obtain titanium oxide. Of course, titanium oxysulfate may be used in place of the second titanium sulfate. Incidentally, titanium oxysulfate can be industrially obtained from ilmenite, rutile ore, and synthetic rutile, and is therefore convenient as a raw material. On the other hand, primary titanium sulfate Ti ₂ (SO ₄ ) ₃ is liable to generate titanium trihydroxide TiO (OH) ₃ by thermal hydrolysis, and this precipitation is unstable. Whiteness is reduced. Next, the above-mentioned titanium sulfate aqueous solution is prepared by adding an acid to obtain a solution having a strong acidity of pH 1 or less. The titanium sulfate aqueous solution itself is an acidic solution with a pH of around 1, but an acid is further added to this to make an acidic solution with a strong acidity. If such an acidic solution is not used, a titanium oxide powder having a particle size of 10 to 20 μm suitable for a filler cannot be obtained. On the other hand, when the above acidic solution is used, the precipitation does not proceed rapidly when titanium oxide hydrate precipitates during thermal hydrolysis, and the formation of nuclei is suppressed. A powder with a large diameter is obtained.
If a strong acid such as hydrochloric acid, nitric acid, or sulfuric acid is used as the acid to be added, a large number of nuclei are avoided from being rapidly generated even if ammonia for forming nuclei is added, and large particles are easily grown. Further, by using an acidic solution, the reaction proceeds in an acidic region of pH 1 or less near the boiling point, so that the acid causes the particles to be sharpened and rounded into a spherical shape.

The precipitation of the acidic aqueous solution of titanium sulfate is allowed to proceed at a temperature higher than 90 ° C and lower than the boiling point. The boiling point of the acidic titanium sulfate solution is 103 ° C when the weight ratio of water to titanium sulfate is 100: 5.
It is 115 ° C at 100: 50. Therefore, thermal hydrolysis is preferably carried out above 90 ° C. If the hydrolysis temperature is 90 ° C. or lower, it is difficult to obtain large particles of 10 μm or more. On the other hand, at a temperature higher than the boiling point, it is necessary to use a pressurizing device such as an autoclave and a sealing device, and there are still problems such as degassing treatment. Therefore, it is preferable to carry out hydrolysis at atmospheric pressure.

Next, the ratio of water to titanium sulfate in the titanium sulfate aqueous solution is
Water: Titanium sulfate = 100: 5 to 100: 50 (weight ratio) is recommended. If the amount of titanium sulfate is less than 5 parts by weight, it is difficult to obtain large particles of 10 μm or more, and the number of particles of 5 μm or less increases. On the other hand, when the amount of titanium sulfate exceeds 50 parts by weight, the shape of the particles collapses into a lump and it is difficult to obtain spherical titanium oxide powder. Further, in this case, dispersibility is poor, primary particles are aggregated, secondary particles having a particle size of 30 μm or more are easily formed, and 90% or more of particles having a particle size of 10 to 20 μm do not easily form a desired particle size distribution.

The ratio of the acid added to the titanium sulfate aqueous solution is preferably titanium sulfate: acid = 100: 5 to 100: 100 (weight ratio). Acid is 5
If the amount is less than 10 parts by weight, it is difficult for the particles to become spherical, and 10 μm
The following particles increase. On the other hand, when the amount of the acid is equal to or more than that of titanium sulfate, the rate of titanium oxide hydrate precipitate formation becomes very slow, and the formation time of the precipitate becomes long. Further, when the precipitate is over-collected and then washed with water, the acid is not sufficiently removed and remains inside the particles, which causes volatilization of the acid during firing and causes cracking of the particles. In addition, the use of a large amount of acid causes corrosion of the apparatus, which is not preferable.

[Examples and Comparative Examples] Examples 1 to 13 According to the compounding ratio shown in Table 1, a predetermined amount of acid was added to the titanium sulfate aqueous solution, and further a predetermined amount of aqueous ammonia was added and mixed, and then the solution was heated to around the boiling point. The mixture was heated to 1, followed by thermal hydrolysis for 2 hours to obtain a titanium oxide hydrate precipitate. The precipitate was separated, thoroughly washed with water, dried, heated to 1050 ° C. at a rate of 100 ° C./hour, and further calcined at 1050 ° C. for 2 hours. The obtained powder, the particle size with a scanning electron microscope,
The shape was observed, the sedimentation of the particles was measured by the light transmission method to determine the particle size distribution, and further the specific surface area was determined by the BET method. The results are shown in Table 1 and the figures.

Comparative Examples 1 to 12 Titanium oxide powder was produced in the same manner as in Examples except that the compounding ratios and liquid temperatures shown in Table 2 were used, and the particle shape, particle size, specific surface area, and particle size distribution were determined. The results are shown in Table 2 and the figures.

As is clear from the above examples and comparative examples, the titanium oxide obtained by the method of the present invention has a particle size of 10 to 20 μm and 90%.
Although it is a spherical powder having a sharp particle size distribution as described above, the titanium oxide powders of Comparative Examples often have irregular particle shapes, and it is difficult to obtain spherical particles, and the particle size distribution is broadly spread. The proportion of ~ 20 μm is low.

[Effect of the Invention] According to the production method of the present invention, it is possible to easily produce a spherical titanium oxide powder having a particle size of 10 to 20 μm and an extremely sharp particle size distribution of 90% or more.

The titanium oxide powder having the above grain size is suitable as a sealing material for semiconductors and electronic materials, and can be widely used in this field and other fields.

Further, unlike the chlorine method, the present invention does not generate hydrochloric acid vapor during boiling, so that it is not necessary to treat waste gas, and there is no problem of equipment corrosion due to hydrochloric acid vapor. By the way, in the chlorine method, titanium tetrachloride and water react violently at high temperature to generate a large amount of hydrochloric acid vapor, so a facility for treating the hydrochloric acid vapor is required, and the hydrochloric acid vapor causes corrosion of the equipment. There are significant problems. In this respect, the method of the present invention does not cause the above problems,
The manufacturing cost can be kept low compared to the chlorine method.

[Brief description of drawings]

1 is a graph showing the particle size distribution of Example 4, FIG. 2 is a graph showing the particle size distribution of Comparative Example 2, and FIG. 3 is a graph showing the particle size distribution of Comparative Example 5.

Claims (1)

[Claims] 1. A method for producing a titanium dioxide powder, which comprises hydrolyzing an aqueous solution of titanium sulfate and calcining a precipitated titanium dioxide hydrate, wherein the aqueous solution of titanium sulfate is a weight ratio of titanium sulfate and acid. Is 100: 5 to 100: 100, and the weight ratio of water to titanium sulfate is 100: 5 to 100: 50, and the hydrolysis of ammonia is carried out at a temperature higher than 90 ° C and lower than the boiling point. By adding, the number of particles within the particle size range of 10 to 20 μm after firing is
A method for producing spherical titanium dioxide powder, characterized in that spherical titanium dioxide powder occupying 90% or more is obtained.