JPH0649388A - Production of titanium dioxide pigment - Google Patents

Abstract

PURPOSE:To produce simply and easily a titanium dioxide pigment excellent in weathering resistance and dispersibility and useful for a high-grade industrial coating material represented by an automotive coating material in virtue of its excellent pigment properties. CONSTITUTION:The production process relates to a process for surface-treating titanium dioxide comprising neutralizing a zirconium compound in the presence of at least one organic compound selected from the group consisting of a hydroxyfatty acid compound and a compound containing at least two hydroxyl groups on vicinal carbon atoms in the molecule in a dispersion of titanium dioxide to coat the surface of the titanium dioxide particle with an oxide of zirconium.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a titanium dioxide pigment having excellent weather resistance and dispersibility, and more particularly to a method for producing a titanium dioxide pigment coated with zirconium oxide or the like.

[0002]

BACKGROUND OF THE INVENTION Titanium dioxide pigments are used in a wide range of fields such as paints, plastics and inks as white pigments having excellent hiding power and coloring power, but the required pigment properties are becoming severer year by year. ing. Generally, a titanium dioxide pigment is obtained by coating the particle surface of a titanium dioxide crude pigment with, for example, a hydrous oxide such as aluminum, silicon, titanium, zirconium, or tin to obtain its pigment properties such as dispersibility, gloss, and weather resistance. Has improved. In particular, it is known that coating with a hydrous oxide of zirconium improves weather resistance.

[0003]

In order to coat the surface of titanium dioxide particles with a hydrous oxide of zirconium, etc., a method of neutralizing the zirconium compound by adding a zirconium compound and an alkali to a dispersion liquid of titanium dioxide. Is common. However, zirconium compounds are usually p
Since H is deposited in the range of about 1 to 2 or more, in the above method, the zirconium compound added to the titanium dioxide dispersion is immediately neutralized and deposited. Therefore, the formed zirconium precipitate may not exist on the surface of the titanium dioxide particles or may not exist uniformly. Therefore, even if the zirconium coating is applied, the weather resistance of the titanium dioxide pigment is not sufficiently improved, and there is a problem that it is difficult to obtain a pigment that satisfies the high weather resistance and dispersibility required in recent years.

[0004]

Means for Solving the Problems The present inventors have conducted various studies on a method of coating a hydrous oxide of zirconium or the like in order to improve the weather resistance of a titanium dioxide pigment, and as a result, in the presence of a specific organic compound. When the zirconium compound is neutralized, (1) the zirconium compound is gradually precipitated and the surface of the titanium dioxide particles can be uniformly coated, and (2) the titanium dioxide pigment coated as described above is used as a resin. When a coating film is formed by mixing with a medium, the holes generated inside the titanium dioxide particles by ultraviolet irradiation are blocked by this coating, or the reactivity of the holes is suppressed, and (3) Titanium dioxide face coated with zirconium oxide by the method of the present invention, in which the weatherability of the titanium dioxide pigment is remarkably improved because the degree of decomposition of the resin is reduced. Is also excellent in its dispersibility and luster, and when (4) zirconium oxide coating is applied, aluminum oxide coating is more excellent in weather resistance and dispersibility. The present invention has been completed by finding out that the above can be obtained. That is, the present invention is to provide a titanium dioxide pigment having a high degree of weather resistance and dispersibility.

The titanium dioxide used in the present invention is titanium dioxide having an average particle diameter of 0.01 to 1.0 μm.
The crystal form may be either anatase type or rutile type, and may be a mixture of anatase type titanium dioxide and rutile type titanium dioxide. The titanium dioxide pigment of the present invention is a pigment in which the surface of titanium dioxide particles is uniformly coated with zirconium oxide, and a pigment coated as a continuous coating layer is particularly desirable from the viewpoint of improving weather resistance.
In the present invention, the oxide of zirconium includes a case where a part or the whole of hydrous zirconium oxide is a hydrous zirconium oxide or a dried zirconium hydroxide, and therefore a part or the whole is hydrous zirconium oxide or a zirconium hydroxide. It is at least one selected from the group of zirconium and zirconium oxide, and its coating amount is 0.1 to 10.0% by weight, particularly 0.6 to 5.0% by weight (based on TiO ₂ ) in terms of ZrO _2. Is desirable. If the coating amount is less than 0.1% by weight, the weather resistance of the titanium dioxide pigment may not be sufficiently improved.
Even if it is more than 0.0% by weight, it is difficult to noticeably improve the weather resistance of the titanium dioxide pigment.

Furthermore, the present invention is a titanium dioxide pigment having an oxide coating of aluminum in addition to the above oxide coating of zirconium. In the present invention, the aluminum oxide, hydrous aluminum oxide is at least one selected from the group of aluminum oxide and aluminum hydroxide, the coating amount is in terms of Al ₂ O ₃ 0.1~4. 0% by weight, especially 1.0 to 2.0% by weight (T
iO ₂ standard) is preferable. If the coating amount is less than 0.1% by weight, the weather resistance and dispersibility of the titanium dioxide pigment may not be sufficiently improved, and if it is more than 4.0% by weight, the weather resistance and dispersion of the titanium dioxide pigment may be insufficient. It is difficult to notice a marked improvement in sex. In the present invention, instead of the aluminum oxide, or in addition to the aluminum oxide, further added to the aluminum oxide, silicon, titanium, antimony, hydrous oxide of a metal such as tin or cerium, You may coat at least 1 type, such as an oxide and a hydroxide. These coating amounts can be set appropriately.

Next, the method of the present invention will be described in detail. First, in the present invention, the titanium dioxide dispersion contains at least 2 oxy fatty acid compounds and adjacent carbon atoms in one molecule.
At least one organic compound selected from the group consisting of compounds having one hydroxyl group, a zirconium compound and a neutralizing agent are added to neutralize the zirconium compound in the presence of the organic compound. In the present invention, titanium dioxide (crude pigment) is, for example, titanyl sulfate, titanium tetrachloride,
A method of hydrolyzing a titanium compound such as an organic titanium compound in the presence of seeds for nucleation, if necessary, a method of adding an alkali to a titanium compound such as titanyl sulfate, titanium tetrachloride or organic titanium to neutralize the same. , Titanium tetrachloride,
A method of vapor-phase oxidizing an organic titanium compound or the like,
It can be produced by a method of calcining the hydrous titanium dioxide obtained by the above method. The titanium dioxide dispersion of the present invention has a TiO ₂ concentration of 50 to 600 g / l, preferably 100 to 500 g / l. When preparing a dispersion of titanium dioxide, it is preferable to add a dispersant and then wet pulverize or classify the dispersion to adjust the titanium dioxide in the dispersion as close as possible to single particles. preferable. The organic compound used in the present invention may be a compound capable of coordinating with zirconium, but is particularly preferably an oxyfatty acid compound or a compound having at least two hydroxyl groups on adjacent carbons in one molecule. ,
Examples of the oxyfatty acid compound include glycolic acid, lactic acid, hydroacrylic acid, oxybutyric acid, glyceric acid, tartronic acid, malic acid, tartaric acid, citric acid, salicylic acid, oxybenzoic acid, gallic acid, mandelic acid, tropic acid or the like. And salts thereof, and examples of the compound having at least two hydroxyl groups on adjacent carbons in one molecule include glycerin, glucose, catechol, and pyrogallol. Particularly, it is desirable to use malic acid, tartaric acid, citric acid or salts thereof. The compounding amount of the above organic compound is 1 m of zirconium metal atom in the added zirconium compound.
0.1 to 4.0 mol, particularly 0.2 to 1.
0 mol is preferred. If the blending amount is less than 0.1 mol, the effect of adding the organic compound may not be sufficient, and if it is more than 4.0 mol, further improvement is difficult to be recognized. Examples of the zirconium compound added to the titanium dioxide dispersion of the present invention include zirconium sulfate, zirconium chloride, zirconium oxychloride, zirconium nitrate and the like, and various zirconium compounds can be used alone or in combination. As the neutralizing agent, a commonly used alkali or acid can be used, and examples of the alkali include:
Examples thereof include sodium hydroxide, potassium hydroxide and ammonia, and examples of the acid include sulfuric acid, hydrochloric acid, nitric acid and the like.

The zirconium compound is neutralized in the presence of the above organic compound in a dispersion of titanium dioxide (crude pigment).
Examples of the neutralization method include (a) a titanium dioxide dispersion liquid or a solvent in which titanium dioxide is dispersed, in which the organic compound is dissolved in advance so that the organic compound is present in the titanium dioxide dispersion liquid, and then the titanium dioxide dispersion liquid is added. To the titanium dioxide dispersion containing the organic compound of the above (a), the zirconium compound and the neutralizing agent are added at the same time. Neutralization method, (c) an organic compound and a zirconium compound are simultaneously added to the titanium dioxide dispersion, and then a neutralizing agent is added to neutralize, and (d) the organic compound and the zirconium compound are mixed in advance. A method in which the mixed solution is added to the titanium dioxide dispersion, and then a neutralizing agent is added to neutralize, and (e) the zirconium compound is added to the titanium dioxide dispersion, and then the organic compound is added. After the compound was added, there is a method of neutralizing by adding a neutralizing agent, it is possible to select these methods appropriately. The temperature of the titanium dioxide dispersion at the time of neutralization can be set appropriately, but about 50 to 80 ° C. is suitable.
In the present invention, the above neutralization reaction product is then separated from the dispersion, dried and, if necessary, pulverized to obtain the surface-coated titanium dioxide pigment of the present invention. In particular,
The dispersion after the neutralization reaction is aged for a certain period of time, usually 10 to 60 minutes at a temperature of 40 to 90 ° C., then separated according to a known method, washed, and dried at a temperature of 100 to 200 ° C., if necessary. Titanium dioxide pigment product through dry grinding and other processes. The dry pulverization after the drying is usually performed by an air flow pulverizer such as a jet mill or a micro mill.

In the present invention, the oxide coating of aluminum can be carried out by a method similar to the above-mentioned method for neutralizing a zirconium compound. When coating aluminum oxide in addition to zirconium oxide, the zirconium compound is added to the titanium dioxide dispersion by appropriately setting the order of addition of zirconium compound, aluminum compound, and neutralizing agent to the surface of titanium dioxide particles. The aluminum coating may be applied after the above coating, the aluminum coating may be applied simultaneously with the zirconium coating, or the zirconium coating may be applied after the aluminum coating is applied in advance. Examples of the aluminum compound include aluminum chloride,
Examples include aluminum sulfate and sodium aluminate, and various aluminum compounds may be used alone or in combination. As the neutralizing agent, the above-mentioned alkali or acid can be appropriately used.

[0010]

【Example】

Example 1 Titanium dioxide obtained by oxidizing titanium tetrachloride in the gas phase was pulverized and classified to obtain an aqueous dispersion having a TiO ₂ concentration of 100 g / l. This aqueous dispersion is heated to 60 ° C. and then kept at this temperature under constant stirring while maintaining Zr based on TiO _2.
Zirconium sulfate corresponding to 1.2% by weight as O ₂ and 1 mol of zirconium metal atom in this zirconium sulfate
3 parts of a mixed solution with 0.25 mol of malic acid per 1
It was added in 0 minutes and aged for 30 minutes. Then, an aqueous sodium hydroxide solution was gradually added to adjust the pH of the aqueous dispersion to 7.0 in 30 minutes, and the mixture was aged for 30 minutes. Continue to T
An aqueous sodium aluminate solution corresponding to 2.0% by weight as Al ₂ O _{3 based on} iO ₂ and a dilute sulfuric acid solution were sufficiently stirred while maintaining the pH of the aqueous dispersion at 7.0.
Simultaneously added for 1 minute and then aged for 30 minutes. After this, it is filtered, washed and dried at a temperature of 120 ° C. for 5 hours,
Then, the mixture was ground in an agate mortar to obtain the titanium dioxide pigment of the present invention (Sample A).

Example 2 In Example 1, the amount of phosphorus acid added was 0.35 m.
The titanium dioxide pigment of the present invention (Sample B) was obtained by the same treatment as in Example 1 except that the sol was changed to ol.

Comparative Example Titanium dioxide obtained by oxidizing titanium tetrachloride in the gas phase was pulverized and classified to obtain an aqueous dispersion having a TiO ₂ concentration of 100 g / l. This aqueous dispersion was heated to 60 ° C. and then kept under constant stirring at this temperature while maintaining ZrO based on TiO _2.
An aqueous zirconium sulfate solution and an aqueous sodium hydroxide solution corresponding to 1.2% by weight as ₂ were simultaneously added for 30 minutes while maintaining the pH of the aqueous dispersion at 7.0, followed by aging for 30 minutes. Next, aluminum coating treatment was performed in the same manner as in Example 1 to obtain a titanium dioxide pigment (Sample C).

Samples obtained in Examples and Comparative Examples (A to
C) 200 mg of each was mixed with 1 ml of tetralin,
Next, 15 μl (microliter) of 5,5-dimethyl-1-pyrroline-1-oxide (DMPO, manufactured by Labotech) was added, and the mixture was dispersed for 5 minutes with an ultrasonic cleaner. An electron spin resonance device (JES-RE2X)
Type, manufactured by JEOL Ltd.) and placed in a measurement sample tube and irradiated with UV light generated by a UV light source (HLS200V, manufactured by HOYA). DMP that captured the radicals generated at this time
The increase in the intensity of the electron spin resonance signal of O was measured over time, and the initial slope thereof was calculated. The sample having a small inclination has a small amount of generated holes, that is, has good weather resistance. On the other hand, a sample having a large inclination has a large amount of holes generated, that is, has poor weather resistance. The results obtained are shown in Table 1. As is clear from Table 1, the sample of the present invention has a smaller inclination than that of the comparative example, and it is understood that the weather resistance is improved. In addition, these samples (A ~
C) was made into a paint according to the conventional method, the paint was baked on a steel plate to prepare a test plate, and then the test plate was accelerated exposed to examine the weather resistance of the sample. The weather resistance was improved as compared with the sample No.

Next, the respective samples (A to C) obtained in Examples and Comparative Examples were treated with coconut oil modified short oil alkyd resin / butylated melamine resin (7/3 wt. (Comparative) It was mixed in a varnish and dispersed by a paint shaker (# 5110 manufactured by Red Devil Co.) to form a paint.
This was applied on a glass plate (15 cm × 10 cm) to a thickness of about 45 μm (as a dry coating film) using a doctor blade, and baked at 120 ° C. for 30 minutes to prepare a test plate. The initial gloss of these test plates is 20 ° -20 ° and 6
The 0 ° -60 ° specular gloss was measured with a gloss meter (VG-1D manufactured by Nippon Denshoku Co., Ltd.). The results obtained are shown in Table 1.
As is clear from Table 1, the sample of the present invention has a gloss equivalent to that of the sample of Comparative Example and is excellent in dispersibility. When glycerin was used instead of malic acid of Example 1, a titanium dioxide pigment of the present invention having weather resistance and dispersibility comparable to those of Example 1 was obtained.

[0015]

[Table 1]

[0016]

INDUSTRIAL APPLICABILITY The present invention is a titanium dioxide pigment in which the surface of titanium dioxide particles is uniformly coated with zirconium oxide, and which has a high degree of weather resistance and dispersibility. In addition to being usable, it is particularly useful for high-grade industrial paints represented by automobile paints due to its excellent dispersibility, gloss and weather resistance.

Claims (3)

[Claims] 1. A titanium dioxide dispersion in the presence of an oxyfatty acid compound and at least one organic compound selected from the group consisting of compounds having at least two hydroxyl groups on adjacent carbons in one molecule. A method for producing a titanium dioxide pigment, in which a zirconium compound is neutralized, the obtained product is separated, and dried to coat particles of titanium dioxide with zirconium oxide. 2. An oxyfatty acid compound is malic acid, tartaric acid,
The method for producing a titanium dioxide pigment according to claim 1, which is citric acid or a salt thereof. 3. Zirconium in a titanium dioxide dispersion in the presence of at least one organic compound selected from the group consisting of oxyfatty acid compounds and compounds having at least two hydroxyl groups on adjacent carbons in one molecule. A method for producing a titanium dioxide pigment in which a compound and an aluminum compound are neutralized, the obtained product is fractionated, and dried to coat particles of titanium dioxide with oxides of zirconium and aluminum.