JPH07187676A - Titanium dioxide fine powder and its production - Google Patents

Abstract

PURPOSE:To produce a titanium dioxide fine powder entered with zirconium in solid solution excellent in dispersibility and light resistance, in more detail, a readily dispersable titanium dioxide fine powder entered with zirconium in solid solution useful to a food wrapping material, UV degradation preventing agent, UV shield sheet or film, and anti-suntan cosmetics or the like. CONSTITUTION:This powder has 0.007-0.1mum average grain size, and zirconium is entered in solid solution into its crystal structure. Moreover, this powder has a covering layer which is, for example, at least one kind of a hydrous oxide selected from a group consisting of e.g. a hydrous silicon oxide and a hydrous aluminum oxide on its surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fine powder of zirconium solid solution titanium dioxide excellent in dispersibility and light resistance, and more specifically, food packaging materials, ultraviolet ray deterioration preventive agents, ultraviolet ray shielding sheets and films, sun protection agents. The present invention relates to a readily dispersible zirconium solid solution titanium dioxide fine powder useful for cosmetics and the like.

[0002]

2. Description of the Related Art Titanium dioxide fine powder having a particle size of 0.1 .mu.m or less transmits visible light when blended with resin, for example, while blocking ultraviolet rays to protect substances that are discolored or deteriorated by ultraviolet rays. Therefore, it is used as a plastic packaging material for foods and pharmaceuticals, a plastic covering material for agricultural and horticultural use, and cosmetics. Since such fine particles of titanium dioxide are fine particles, they have extremely strong cohesive force and are difficult to disperse in a resin. Therefore, since undispersed aggregated particles remain in the dispersion medium resin when added to and mixed with the resin, the original high visible light transmittance and ultraviolet ray shielding ability of the titanium dioxide fine powder of the above size are substantially obtained. The reality is that it is not available. Further, since the fine powder of titanium dioxide having the above size has strong photoactivity, it has a problem that it oxidizes and deteriorates the dispersion medium resin.

In order to solve the above problems, a method of coating the surface of titanium dioxide to improve the dispersibility has been proposed. For example, Japanese Examined Patent Publication No. 63-51974 discloses a titanium dioxide composition in which the surface of fine titanium dioxide particles having a size substantially within the range of 0.01 to 0.1 μm is treated with an oxide of silicon and / or aluminum. is doing. Further, JP-A-2-194063 discloses a fine particle titanium oxide powder having excellent dispersibility and weather resistance, on the surface of fine particle titanium dioxide having a maximum particle diameter of 0.1 μm or less, which is the core, on the surface of fine particle titanium dioxide SnO 2. 0.1 to 5% tin hydroxide as ₂ and / or Zr
0.1 to 5% of zirconium hydroxide as O ₂ is coated on the innermost layer, and then 0.1 to 8% of silicon hydroxide as SiO ₂ relative to the weight of the particulate titanium dioxide is used as an intermediate layer. And finally, a fine particle titanium dioxide powder obtained by coating the outermost layer with a hydrous oxide of 0.1 to 10% as Al ₂ O _{3 based on} the weight of the titanium dioxide particles.

There are several other applications for improving dispersibility by surface treatment. In any case, when a coating layer is provided on the surface of titanium dioxide powder, first, fine titanium dioxide powder is dispersed in primary particles. Will be required. However, conventional titanium dioxide has a problem of dispersibility in water, and the operation itself of dispersing titanium dioxide in primary particles is difficult. Therefore, it is necessary to industrially produce titanium dioxide fine powder having excellent dispersibility. Was difficult.

Regarding the production of zirconium solid solution titanium dioxide fine particles, Suyama et al. Reported that they could be synthesized by a vapor phase method (Y. Suyama, M. Tanak).
a, A. Kata: Ceramurgia Inter
n. , Vo. 1, No. 2, pp. 84-88 (197
9)). However, the zirconium solid solution titanium dioxide fine particles synthesized by them contain coarse particles having a size of 0.3 μm or more, and they are inferior in high visible light transmittance and ultraviolet ray shielding ability.

[0006]

As described above, the conventional titanium dioxide fine powder has a problem that it is difficult to dispose the coating layer industrially stably with poor dispersibility and high photoactivity. It was Therefore, it has been desired to develop a novel titanium dioxide fine powder having excellent dispersibility and light resistance, which can be easily and stably produced industrially. With respect to zirconium solid solution titanium dioxide, there was no example of synthesizing fine powder having a size of 0.1 μm or less.

It is an object of the present invention to provide a novel zirconium solid-solution titanium dioxide fine powder which is improved in the above-mentioned drawbacks of the titanium dioxide fine powder and a method for producing the same.

[0008]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that the solid solution of zirconium in the crystal structure improves the dispersibility and the light resistance. Completed the invention. That is, the present invention provides a titanium dioxide fine powder characterized by having a size within the range of 0.007 to 0.1 µm and having zirconium in the crystal structure as a solid solution. The crystal form of titanium dioxide is preferably the rutile type. Zirconium is substantially uniformly solid-dissolved in the particles and is mainly present in the crystal lattice. Further, the present invention provides the above titanium dioxide, wherein a coating layer, preferably a coating layer of at least one hydrated hydroxide selected from the group consisting of hydrous oxides of silicon and hydrous oxide of aluminum, is provided on the surface of the particles. To do.

The particle size of titanium dioxide according to the present invention is 0.
It may be in the range of 007 to 0.1 μm, but 0.01
The range of up to 0.07 μm is more preferable. Further, the content of zirconium is 0.10 as ZrO _{2 with} respect to TiO ₂ .
5-25% by weight, preferably 1-15% by weight is suitable. When the content of ZrO ₂ is less than this range, it is difficult to obtain the effect of improving dispersibility and light resistance, and when it is too large, there is no particular difference in light resistance,
Dispersibility deteriorates.

The zirconium solid solution titanium dioxide fine powder of the present invention is excellent in dispersibility and dispersion stability in water, so that it can be easily mixed into various water-soluble resins to form a coating film. It is easy to disperse and mix with agents or other cosmetic ingredients. Further, since it does not substantially contain coarse agglomerated particles, it has a viscosity adjusting agent for paints, plastics, a silicone rubber filler for preventing physical property deterioration at high temperatures, a pigment, a charge control external additive for toner and a charge exchange aid. It can be suitably used as an agent, a frost color pigment of aluminum metallic paint, a solid lubricant such as fibers and films, and the like. In particular, since it has a better affinity with urethane than conventional titanium dioxide and has a low photoactivity, it is preferably used for polyurethane elastic fibers which are weak to ultraviolet rays.

The zirconium solid solution titanium dioxide fine powder according to the present invention has excellent dispersibility in water and can be easily dispersed in primary particles. Therefore, it is possible to use a hydrous oxide for improving dispersibility in a resin. Surface treatment can be carried out easily and uniformly, and titanium dioxide fine powder having a coating layer, which has excellent dispersibility in resin and light resistance, can be industrially easily and stably produced.

The zirconium solid solution titanium dioxide fine powder according to the present invention is obtained by, for example, hydrolyzing a mixed aqueous solution of a titanium compound and a zirconium compound to form an aggregate coprecipitate of hydrous titanium oxide and hydrous zirconium oxide. After washing, a monobasic acid was added to form a sol, and then an alkali was added to neutralize and wash by filtration.
It can be produced by firing at 0 ° C. for 30 minutes to 3 hours. When a coating layer of silicon and / or aluminum is provided, after the above firing, the fired product is dispersed in water to form an aqueous slurry, and the slurry contains a water-soluble silicon and / or aluminum compound, preferably water containing silicon. The oxide and / or aluminum hydrous oxide may be added in an amount such that the coating amount is 1 to 20% by weight in terms of SiO ₂ and Al ₂ O ₃ with respect to TiO ₂ and then neutralized.

Examples of the water-soluble titanium compound include titanium sulfate, titanium oxysulfate, titanium ammonium sulfate,
Titanium tetrachloride and the like can be used, and as the water-soluble zirconium compound, zirconium sulfate, zirconium oxysulfate, zirconium chloride, zirconium oxychloride and the like can be used.

For the hydrolysis, a known heating method or neutralization method can be effectively utilized. In addition, when adopting a method of adding a seed crystal during hydrolysis, only the seed crystal of hydrous titanium oxide may be added.

The concentration of TiO ₂ + ZrO _{2 in} the mixed aqueous solution of the water-soluble titanium compound and the water-soluble zirconium compound is 5 to
It is in the range of 350 g / liter, preferably 30 to 300 g / liter. That is, at a concentration lower than 5 g / liter and a concentration higher than 350 g / liter, particles having a size of 0.1 μm or more are easily generated, which is not preferable.

When the heating method is used for the hydrolysis, the hydrolysis rate of titanium oxide and the coprecipitation rate of zirconia into hydrous titanium oxide change significantly depending on the relative ratio between the acid concentration of the solution and the TiO ₂ + ZrO ₂ concentration. To do. That is, in order to increase the hydrolysis rate and the coprecipitation rate of zirconia in hydrous titanium oxide, the acid concentration with respect to the TiO ₂ + ZrO ₂ concentration may be lowered, but if this value is made too small, the stability of the solution deteriorates and Not relevant. For example, TiO ₂ + relative to the acid concentration (g / liter) when hydrolyzing in an acidic aqueous sulfuric acid solution
The ratio of ZrO ₂ concentration (g / liter) is TiO ₂ + ZrO
_{2 If the} concentration is 1, 1.3 to 1.9 is suitable,
Within this range, the coprecipitation rate of zirconia on hydrous titanium oxide is in the range of approximately 40 to 95%. Therefore, the addition ratio of the water-soluble zirconium compound to the water-soluble titanium compound is calculated in consideration of the coprecipitation rate of zirconia to hydrous titanium oxide during hydrolysis in the range where a product in the above-mentioned appropriate range is obtained. There is a need.

When the hydrolysis is carried out by the neutralization method, an alkali is added to the acidic aqueous solution to adjust the pH of the aqueous solution to 3 or more so that the coprecipitation rate of zirconia in hydrous titanium oxide is 100%. You can

Most of the added zirconium is present in the crystal lattice of titanium dioxide, but it is not necessary that the entire amount thereof be present in the crystal lattice, and a part of it is to the extent that the effect of the present invention is not impaired. Zirconium titanate (ZrTiO
₄ ) and zirconium oxide may be present.

Further, as is apparent from the above-mentioned manufacturing method, zirconium is present substantially uniformly not only in the vicinity of the surface of the particle but also inside the particle.

In order to make the aggregated precipitate obtained by hydrolyzing an acidic aqueous solution of sulfuric acid into a sol, the precipitate is washed, made into a slurry, and neutralized with an alkali such as aqueous sodium hydroxide solution or aqueous ammonia. Filter and wash to remove sulfate radicals. After that, it is made into a slurry, and a monobasic acid such as hydrochloric acid, nitric acid or trichloroacetic acid is added to the slurry,
The H may be adjusted to 3 or less, preferably 2-1 and then peptized. Further, in order to form a coagulated precipitate produced by hydrolyzing an acidic aqueous hydrochloric acid solution into a sol, after filtering and washing, it is made into a slurry, and the monobasic acid is added to adjust the pH of the slurry to 3 or less, preferably 2 It can be easily done by adjusting to ~ 1.

The firing temperature is in the range of 400 to 1000 ° C.,
The range of 600 to 950 ° C is suitable. That is, if the firing temperature is lower than this range, the amount of adsorbed water increases, which has an unfavorable effect such as difficulty in dispersion when mixed with a resin. On the other hand, if the temperature is too high, the titanium dioxide particles may adhere to each other or may be sintered to form coarse particles larger than 0.1 μm, which is not preferable.

The zirconium solid-solution titanium dioxide fine powder of the present invention is excellent in water dispersibility, but the dispersibility and dispersion stability in the coating material become a problem due to the compatibility with the dispersion medium resin and the solvent. Depending on the type of resin or solvent, problems may occur in dispersion stability. In such a case, it is preferable to coat the particle surface with a hydrous oxide of silicon or aluminum by a known method to improve the familiarity. The zirconium solid solution titanium dioxide fine powder of the present invention is excellent in water dispersibility, and thus such a coating treatment is effectively utilized. The type of coating material is not particularly limited, and it can be treated depending on the type of resin or solvent used. For example, the treatment with the hydrous oxide of silicon and / or aluminum described above may be performed, or the hydrous oxide of tin and / or the hydrous oxide of zirconium may be coated on the innermost layer, and then the hydrous oxide of silicon may be added. The intermediate layer may be coated, and finally a hydrous oxide of aluminum may be coated. In addition, it may be coated with a hydrous oxide such as titanium, cerium or zinc. Further, known organic coating materials such as aluminum stearate, dodecylbenzenesulfonic acid, surfactants such as alkanolamines, polyhydric alcohols, organosiloxane compounds, silane-based, titanate-based and aluminum-based coupling agents are also used. it can. Generally, a treatment with a hydrous oxide of silicon and / or aluminum is preferably performed.

This coating treatment can be performed by a known method. For example, in the case of treating with a hydrous oxide of silicon and / or aluminum, the zirconium solid solution titanium dioxide obtained in the above firing step is used as TiO _{2 in an amount} of 100 to 400 g / liter, preferably 200 to 3
It is made by dispersing in water to a concentration of 00 g / liter to form an aqueous slurry, adding a water-soluble silicate or an aluminum compound thereto, and then adding an alkali or an acid for neutralization. That is, when sodium silicate is used as the water-soluble silicate, an acid such as sulfuric acid, nitric acid or hydrochloric acid is added to the aqueous slurry to adjust the pH of the slurry to 7. When aluminum sulfate is used as the water-soluble aluminum compound, the pH of the aqueous slurry in which zirconium solid solution titanium dioxide is dispersed is adjusted to 7 by adding an alkali such as sodium hydroxide or potassium hydroxide.

For the treatment of hydrous oxide of silicon or aluminum, 1 to 20% by weight of each of TiO ₂ in terms of SiO ₂ and Al ₂ O ₃ is suitable. If the amount of treatment is too large, the ultraviolet ray shielding effect is lowered, which is not preferable.

Further, a treatment method using an organic coating material is also known, and it can be treated by an appropriate method if necessary.

The titanium compound produced by using naturally occurring ore such as rutile type titanium oxide or ilmenite as a TiO ₂ source contains various impurities derived from ores such as iron, niobium and tantalum. A part of them remains in the zirconium solid solution titanium dioxide, but there is no problem even if the impurities are contained in an amount that is acceptable for pigment use.

The present invention will be described in more detail below with reference to examples. The following examples are given for illustration only and the scope of the invention is not limited thereby.

Example 1 180 g / liter as TiO _{2 and 2} as H ₂ SO ₄
To 5 liters of a 90 g / liter titanium oxysulfate aqueous solution, 850 ml of a ZrO ₂ 200 g / liter and H ₂ SO ₄ 280 g / liter zirconium oxysulfate aqueous solution were added, and the mixture was stirred until the boiling point reached 3
The temperature was raised in 0 minutes and the temperature was maintained for 4 hours.

The aggregated precipitate obtained was washed with pure water until the electric conductivity of the supernatant reached 1000 μS / cm,
Add a sodium hydroxide aqueous solution to adjust the pH of the slurry.
Was adjusted to 9 and stirring was continued for 1 hour. Then, hydrochloric acid was added to adjust the pH of the slurry to 7, and the supernatant was washed with pure water until the electric conductivity of the supernatant was 260 μS / cm.

Thereafter, hydrochloric acid was added to the slurry to adjust the pH of the slurry to 1.5 and to peptize it to obtain a sol. The pH of the slurry was adjusted to 7 by adding an aqueous sodium hydroxide solution to the sol. The electric conductivity of the supernatant is 60 μS
It was washed with pure water until it became / cm, filtered and dried.
This dried product is calcined at 850 ° C. for 30 minutes to obtain 0.01-
A fine powder having a particle size of 0.07 μm was obtained.

When the fine powder was examined by X-ray diffraction, it showed a diffraction pattern similar to that of the anatase type titanium dioxide, but the position of the diffraction line was shifted to a lower angle side than that of the anatase type titanium dioxide. . Purity 99.
When the lattice spacing d corresponding to the (101) plane of the anatase type titanium dioxide was determined using 9% silicon powder as an internal standard, it was 3.528Å.

Comparative Example 1 180 g / liter as TiO _{2 and 2} as H ₂ SO ₄
With stirring, 5 liters of a 90 g / liter titanium oxysulfate aqueous solution was heated to the boiling point in 30 minutes and kept at the temperature for 4 hours. When the obtained coagulated precipitate was treated under the same conditions as in Example 1, fine powder having a particle size of 0.05 to 0.21 μm was obtained.

When this fine powder was examined by X-ray diffraction, it was found to be a single phase of anatase type titanium dioxide. The lattice spacing d corresponding to the (101) plane of the anatase type titanium dioxide was determined to be 3.519Å, using silicon powder having a purity of 99.9% as an internal standard. This value is smaller than that of the fine powder of Example 1 described above. From this, it is understood that the fine powder of Example 1 is a crystal in which Zr ⁴⁺ is substituted and solid-dissolved at the position of Ti ^{4+ in} the anatase type titanium dioxide crystal lattice.

COMPARATIVE EXAMPLE 2 In Comparative Example 1, the treatment was carried out under the same conditions except that the firing conditions were 700 ° C. and 30 minutes, and the result was 0.01-
Anatase type titanium dioxide having a particle size of 0.05 μm was obtained.

Example 2 50 g / liter as TiO _{2 and} 48 g as HCl
Zr to 10 liters of titanium tetrachloride aqueous solution / liter
150 g / l as O _{2 and} 98 g / l as HCl
165 ml of zirconium oxychloride was added, and then 25 g of hydrous titanium oxide having a rutile type structure synthesized by a known method as TiO _2.
Add and mix. The temperature was raised to the boiling point in 120 minutes with stirring, and the temperature was maintained for 3 hours.

The aggregated precipitate thus obtained was washed with pure water until the electric conductivity of the supernatant became 22 mμS / cm to obtain titania sol. The pH of the slurry was adjusted to 7 by adding an aqueous sodium hydroxide solution to the sol. The supernatant was washed with pure water until the electric conductivity of the supernatant became 60 μS / cm, filtered, and dried. The dried product was calcined at 850 ° C. for 30 minutes to obtain a fine powder having a particle diameter of 0.01 to 0.07 μm.

When this fine powder was examined by X-ray diffraction, it showed the same diffraction pattern as rutile type titanium dioxide, but the position of the diffraction line was shifted to a lower angle side than that of rutile type titanium dioxide. . Using silicon powder having a purity of 99.9% as an internal standard, the rutile type titanium dioxide (1
10) When the lattice spacing d corresponding to the plane was calculated, 3.
It was 263Å.

Comparative Example 3 50 g / liter as TiO _{2 and} 48 g as HCl
25 g of titanium oxide hydroxide having a rutile structure synthesized by a known method as TiO ₂ was added to 10 liters of a titanium tetrachloride aqueous solution of 1 / liter. The temperature was raised to the boiling point in 120 minutes with stirring, and the temperature was maintained for 3 hours.

The obtained coagulated precipitate was treated under the same conditions as in Example, and a fine powder having a particle diameter of 0.08 to 0.32 μm was obtained.

When this fine powder was examined by X-ray diffraction, it was found to be a single phase of rutile type titanium dioxide. When the lattice spacing d corresponding to the (110) plane of rutile titanium dioxide was determined with silicon powder having a purity of 99.9% as an internal standard, it was 3.249Å. This value is smaller than that of the fine powder of Example 2 described above. From this, it is understood that the fine powder of Example 2 is a crystal in which Zr ⁴⁺ is substituted and solid-dissolved at the Ti ⁴⁺ position of the rutile type titanium dioxide crystal lattice.

COMPARATIVE EXAMPLE 4 Comparative Example 3 was performed under the same conditions except that the firing conditions were 700 ° C. and 30 minutes, and the results were 0.02 to 0.02.
A rutile titanium dioxide having a particle size of 0.08 μm was obtained.

Example 3 350 g of the fine powder obtained in Example 1 was made into an aqueous slurry of 210 g / liter, 121 ml of a 180 g / liter sodium aluminate aqueous solution as Al ₂ O ₃ was added and mixed, and then sulfuric acid was added dropwise. Adjust the pH of the slurry to 7
Adjusted to. It was filtered, washed and dried at 120 ° C.

Example 4 450 g of the fine powder obtained in Example 2 was made into an aqueous slurry of 150 g / liter, 285 ml of an aqueous solution of sodium silicate of 85 g / liter as SiO ₂ was added, and 107 g as Al ₂ O ₃ was further added. / Ml aluminum sulfate aqueous solution of 220 ml was added. An aqueous sodium hydroxide solution was added dropwise to the slurry to adjust the pH to 7.5. It was filtered, washed and dried at 120 ° C.

When the fine powders obtained in Examples 1 to 4 and Comparative Examples 1 to 4 were exposed to sunlight for 8 hours, the color tones of the fine powders of Comparative Examples were all changed to bluish black, while those of the Examples were changed. That of the fine powder did not discolor in particular.

Further, the fine powders of Examples 1 and 2 and Comparative Examples 1 to 4 were dispersed in water so as to have a concentration of 0.01% by weight, put into a quartz cell having a thickness of 10 mm, and a visible light (550 n
Table 1 shows the results of measuring the transmittance of m) and ultraviolet rays (320 nm) with a spectrophotometer Ubest-50 type manufactured by JASCO Corporation. From this table, it can be seen that the dispersion liquid of the fine powder of the present invention has a high visible light transmittance. Further, when the dispersions of Examples 1 and 2 and Comparative Examples 2 and 4 were allowed to stand for 7 days, the above-mentioned characteristics were measured. The dispersions of the fine powders of Comparative Examples 2 and 4 had both visible light and ultraviolet transmittances. While the size of the fine powder of the example did not change, the fine powder of the present invention was excellent in dispersion stability in water.

When the fine powders of Examples 3 and 4 were mixed with a nitrocellulose solution to prepare a nitrocellulose coating, the coating was examined every 5 minutes with a grind gauge.
The dispersion time until it becomes 0 μm or less is 15 to 20 in all cases.
And the dispersibility was excellent.

[0047]

Claims (8)

[Claims] 1. A titanium dioxide fine powder having an average particle diameter of 0.007 to 0.1 μm and zirconium solid-dissolved in its crystal structure. 2. The titanium dioxide fine powder according to claim 1, wherein the crystal type is rutile type. 3. The titanium dioxide fine powder according to claim 1, wherein zirconium is substantially uniformly dissolved in the particles as a solid solution. 4. The titanium dioxide fine powder according to claim 1, wherein zirconium is present in the crystal lattice. 5. The titanium dioxide fine powder according to claim 1, which has a coating layer on the surface of the particles. 6. The titanium dioxide fine powder according to claim 5, wherein the coating layer is at least one kind of hydrous oxide selected from the group consisting of hydrous oxides of silicon and hydrous oxides of aluminum. . 7. A mixed aqueous solution of a titanium compound and a zirconium compound is hydrolyzed to form a coprecipitate of hydrous titanium oxide and hydrous zirconium oxide, and after washing the precipitate, a monobasic acid is added to form a sol. The method for producing fine titanium dioxide powder according to claim 1, characterized in that the titanium dioxide fine powder is calcined at 400 to 1000 ° C. after neutralization by adding a post-alkali, filtering and washing. 8. A mixed aqueous solution of a titanium compound and a zirconium compound is hydrolyzed to form a coprecipitate of hydrous titanium oxide and hydrous zirconium oxide, and after washing the precipitate, a monobasic acid is added to form a sol. Thereafter, an alkali is further added to neutralize the mixture, which is filtered and washed, and then calcined at 400 to 1000 ° C., after which the calcined product is dispersed in water to give an aqueous slurry, and the slurry is made of a water-soluble silicon compound and an aluminum compound. The method for producing fine titanium dioxide powder according to claim 6, wherein at least one compound selected from the above is added and then neutralized.