JPS5930749B2 - Titanium dioxide pigment composition and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a titanium dioxide pigment composition with improved dispersibility and heat resistance, and a method for surface treatment of coarse titanium dioxide pigment particles for obtaining the composition.

Demand for titanium dioxide pigments is still growing due to its excellent pigment properties such as high whiteness and hiding power.However, the demand for titanium dioxide pigments is wide-ranging, and the durability of the titanium dioxide pigments used is still growing. , improved stability, improved dispersibility, etc. are strongly desired. In order to improve the properties of titanium dioxide pigments, it is widely practiced to treat the surface of the particles with hydrated oxides of silicon, aluminum, etc. or phosphates.

For example, coating titanium dioxide particles with compact silica is described in US Pat. No. 2,885,366 and with aluminum phosphate in US Pat. No. 2,668,776. The present invention aims to further improve these conventional techniques and provide a titanium dioxide pigment composition that has particularly excellent weather resistance, high dispersibility, and heat resistance.

The pigment composition of the present invention is applied to rutile-type crystalline titanium dioxide particles having a particle size of 0.1 to 0.5 microns, and includes (1) a continuous coating of 1 to 10% silicate force in terms of SlO2 to coat the surface of the particles; and (2) Al2O3 covering the surface of the silica film.
It has an aluminum phosphate coating of 0.5 to 5% in terms of conversion.

A feature of this composition is that the titanium dioxide particles have two different coatings: a bottom silica coating and a top aluminum phosphate coating.

The silicone coating is 1 to 10% of the weight of TiO2 in terms of SlO2.
, preferably 1 to 5% silica precipitate, adheres closely to the surface of the titanium dioxide particles as a continuous coating of almost uniform thickness. In addition, the aluminum phosphate coating is Al2
0.5 to 5% of the weight of TiO2 in terms of O3, preferably 1
It consists of a precipitate mainly consisting of ~3 (!) aluminum phosphate, and adheres closely to the surface of the silica continuous coating. The method for producing the pigment assembly of the present invention includes (1) dispersing rutile-type crystalline titanium dioxide particles with a particle size of 0.1 to 0.5 microns in water to form a slurry, and (2) adjusting the pH to 8 or higher and temperature. 60℃
Add 1 to 10% water-soluble silicate in terms of SiO2 while maintaining the above, and add acid or ammonium salt while stirring sufficiently to react to bring the pH to 4 to 8, and remove the substance of the silica precipitate formed. (3) stabilize the coating by maintaining the same temperature; (4) reduce the temperature of the slurry to 60°C.
0.5 to 5% water-soluble aluminum compound and P2O5 in terms of Al2O3 while maintaining the temperature above ℃ and stirring thoroughly.
/Al2O3 molar ratio is 0 to 2 by adding phosphoric acid or a water-soluble phosphate to adjust the pH to 3 to 10, and substantially all of the resulting precipitate mainly composed of aluminum phosphate is coated with the silica. It is characterized in that it is deposited as a film that covers the surface of the particles, (5) the film is stabilized by maintaining it at the same temperature, and then the coated pigment is recovered by filtration and washing.

Titanium dioxide as core particles is produced by sintering hydrous titanium oxide obtained by hydrolyzing an aqueous titanium salt solution (sulfuric acid method) or by vapor phase oxidation of titanium halide (chlorine method). The rutile type crystals are crushed and classified in advance.

The particle size is adjusted to 1 to 0.5 micron, preferably 0.15 to 0.3 micron.

This crude pigment is first dispersed in water to form a slurry. The pH of the aqueous slurry is adjusted to 8 or higher, usually 8.5 to 10.
The TiO2 concentration is 100 to 6009/11, preferably 100 to 3009/11 for crude pigments obtained by the sulfuric acid method, and 100 to 5009/l for those obtained by the chlorine method. Add silicate to this slurry while maintaining the pH at 8 or higher and the temperature at 60°C or higher.

Silicates can be prepared using sodium silicate or potassium silicate.
It is preferable to use M2O (M is Na or K) with a molar ratio of 4 to 0.5 and add it as an aqueous solution of SlO25O to 3009/l. The amount added may be determined depending on the desired amount of silica coating, but the speed of addition may be determined by adjusting the amount of added SlO2 to 1% (T
The mixture is added for about 5 to 30 minutes per 1O2 (based on 1O2), with thorough stirring. Next, in order to bring the pH of this slurry to 8 or less and precipitate silica, an acid is added to neutralize it, or an ammonium salt is added to react and the ammonia produced is volatilized.

This operation must be carried out under well-controlled conditions to avoid the formation of free silica gel from the titanium dioxide particles and to completely coat the particles with silica. The acid used is commonly used sulfuric acid, hydrochloric acid, etc.
It is preferable to use one with a concentration of 0%.

Stir thoroughly to ensure a homogeneous system, and add acid at multiple locations if necessary to prevent local acid overconcentration.
An amount equivalent to 0.5 equivalent or more, preferably 1 to 2 equivalents, based on the silicate present is added. Ammonium salts include ammonium chloride, ammonium sulfate, etc.
009/11 It is preferably used as a solution with a concentration of 20 to 1009/l.

As with acids, while stirring thoroughly, gradually add 0.5 equivalent or more, usually 1 to 2 equivalents to the silicate, but since the reaction is slower than acids, it is difficult to make the system uniform. Relatively easy to maintain, 10-180 minutes, preferably 20-1
Add over 20 minutes. In order to volatilize and remove ammonia produced during the reaction, the slurry must be maintained at a temperature of 60° C. or higher, preferably 80° C. to boiling point. Note that the addition of this acid or ammonium salt can also be carried out simultaneously with the addition of the silicate.

The pH of the slurry after the reaction is adjusted to 4 to 8 if necessary, and held at a temperature of 60° C. or higher for 10 minutes or more, usually 30 to 120 minutes.

This aging makes the silica coating on the titanium dioxide particles uniform and stable. Next, an aluminum compound and phosphoric acid or a water-soluble phosphate are added to the obtained slurry to precipitate aluminum phosphate.

As the aluminum compound, sodium aluminate, aluminum chloride, aluminum sulfate, etc. are used, and as the phosphoric acid or water-soluble phosphate, orthophosphoric acid, metaphosphoric acid,
Pyrophosphoric acid, their soda salts, potassium salts, ammonium salts, etc. are used. While thoroughly stirring a slurry with a pH of 2 to 8, preferably 3 to 5, at a temperature of 60°C or higher, phosphoric acid or a water-soluble phosphate is usually added to uniformly dissolve the slurry, and then a water-soluble aluminum compound is added. , preferably A
Add as a solution with a concentration of 12O35O to 3009/l. If the aluminum compound is an alkaline source, the pH of the slurry will be 3-10, but if the aluminum compound is an acidic source, an alkali is added to adjust the pH of the slurry to 3-10. It is preferable to add phosphoric acid or a water-soluble phosphate first, but it is also possible to add the phosphoric acid or the water-soluble phosphate first, but it is also possible to add the aluminum compound simultaneously or first. The amount of aluminum compound is determined according to the desired amount of coating, and the amount of phosphoric acid or water-soluble phosphate is
The amount corresponds to a molar ratio of P2O5/Al2O3 of 1 to 2, preferably 1 to 1 with respect to the amount of aluminum. The precipitate that forms is mainly composed of aluminum phosphate.
The larger the molar ratio, the more uniform the aluminum phosphate, and the smaller the molar ratio, the more alumina is mixed in the aluminum phosphate. Maintain the temperature of the slurry above 60℃, and
When H is desirably set to 6 to 8 and stirred for 10 minutes or more and aged, the coating of aluminum phosphate deposited on the titanium dioxide particles becomes more uniform and stabilized.

If desired, one or more hydrated oxides such as aluminum, titanium, zirconium, cerium, zinc, etc. are subsequently precipitated in the slurry and incorporated into the composition by conventional means. You can also do that. Due to the aluminum phosphate coating treatment, the slurry exhibits thixotropic properties, so when it is to be rinsed immediately without adding other treatments, flocculants such as formic acid, polychloride, etc. aluminum, polymer flocculant,
It is preferable to add about 0.01 to 0.1% based on TlO2 in the slurry.

This slurry is filtered, washed, dried and pulverized according to a known method to obtain a product.

The resulting titanium dioxide pigment composition has excellent weather resistance, high dispersibility, and heat resistance, and can withstand heat processing and long-term exposure while maintaining good gloss.
Furthermore, as shown in the Examples below, the composition has good affinity for aqueous media and can be made into a free-flowing slurry with good dispersibility, and has high industrial utility value.
Example 1 A crude titanium dioxide pigment produced by vapor phase oxidation of titanium tetrachloride was hot-pulverized at pH 9 to a particle size of 0.15 to 0.45.
The particles were sized to micron size and made into an aqueous slurry of TiO225O9/l.

Dilute caustic soda solution was added to this slurry 11 to make the pH 9.
．． 5, and while keeping the temperature at 60°C, SiO2l equivalent to 4Cf) as SiO2 on the TiO2 weight basis.
100 cc of OO9/2 sodium silicate solution (SlO2/Na2O molar ratio 3.0) was added over 30 minutes under thorough stirring. This slurry was heated to 80° C., stirred for 10 minutes, and then 1009/11 sulfuric acid was added for 60 minutes to neutralize it to pH 4 and coat the silica hydrate. Add this slurry to 3
Aged for 0 minutes. Then, 70 CC (equivalent to the molar ratio of Al2O3/P2O) of 1009/l orthophosphoric acid solution was added as P2O5. Thereafter, a sodium aluminate solution of 2% as Al2O3 based on the weight of TiO2 was added over 20 minutes, and the pH was further adjusted to 6 with 1009/l sulfuric acid.
Coated with aluminum phosphate. After aging for 10 minutes, the slurry was neutralized to pH 7, then filtered and washed to remove soluble salts.

It was dried at 120° C. and ground in a fluid energy mill to obtain the titanium dioxide pigment composition of the present invention.

For comparison, a comparison titanium dioxide pigment was produced in the following manner according to the method described in Japanese Patent Publication No. 47-45173. That is, a sodium silicate solution corresponding to 24 l% of SiO was added in the same manner to the same crude pigment slurry as in the previous example. PH5 to slurry heated to 90℃
An amount of 1009/l sulfuric acid was added over a period of 5 hours under thorough stirring to neutralize and coat the hydrated silica.

This slurry was aged for 30 minutes, then 2% sodium aluminate was added as Al2O3, neutralized to pH 7 with 1009/l sulfuric acid, aged for 30 minutes, filtered, washed, dried and washed in the same manner as in the previous example. Pulverized. Example 2 In Example 1, 130 CC of orthophosphoric acid solution 1 50 CC of sodium aluminate solution (Al2O3 based on the weight of TiO2)
2%, equivalent to the molar ratio of Al2O3/P2O5)
A titanium dioxide pigment composition of the present invention was obtained by processing in the same manner as in the same example except for the addition.

The pigment performance of the titanium dioxide pigment compositions obtained in each of the above examples was tested, and the results shown in Table 1 were obtained. The test results in the table were measured as follows.

Weather resistance evaluation Titanium dioxide pigment was mixed into a varnish modified with short oil alkyd resin/butylated melamine resin ('!A weight ratio), dispersed with a sand mill to form a paint, and then coated on a mild steel plate (7CTrLX15cTrL). Approximately 50 microns thick (
A coating film was prepared by coating with a dry coating film) and baking at 120° C. for 30 minutes.

Accelerated exposure (Rainfall 12
60 min/60 min irradiation, relative humidity 53+3%, black panel temperature 600+5°C), and 60-60 gloss was measured at regular intervals for evaluation. The start time of chalking was defined as the time until the adhesion of chalk powder was observed by the finger touch method. (The degree of chalking is based on the coating film evaluation standards of the Japan Paint Inspection Association) Dispersibility evaluation weather resistance test: Apply the same paint used in the test to a thickness of 100 microns (wet) using a film applicator on a glass plate. After drying at room temperature for 30 minutes, it was baked at 120°C for 30 minutes, and then cumulatively baked at 200°C for 30 minutes each time. We conducted an evaluation.

Heat Resistance Evaluation The same paint used in the weather resistance test was applied to a glass plate with a film applicator to a thickness of 250 microns (wet), dried for 30 minutes at room temperature, baked at 120°C for 30 minutes, and further accumulated to 200 microns thick. Baking was carried out at .degree. C. for 30 minutes, and each time the L, a and b values of the coating film were measured, .DELTA.E was calculated, and the heat resistance was evaluated.

Water dispersibility evaluation 353 g of titanium dioxide pigment was added to 151 cc of deionized water with stirring and thoroughly mixed to prepare a slurry with a pigment concentration of 70%.

The slurry viscosity of this slurry was measured using a B-type rotational viscometer (B-8-H type) (25° C., 100 rpm). Next, a predetermined amount of a dispersant [25% solution of TAMOL-731 (polycarboxylate salt type) manufactured by Rohm & Hass Co., Ltd.] was added to this slurry, and after stirring for a certain period of time, the slurry viscosity was measured in the same manner as described above. The amount of the dispersant added is based on the weight of TiO2. Example 3 A crude titanium dioxide pigment produced by calcining hydrated titanium oxide obtained by hydrolysis of titanyl sulfate was used in Example 1.
It was crushed, classified and sized in the same manner as above to obtain a slurry of TlO225Oθ/l.

A titanium dioxide pigment composition of the present invention was obtained by processing in the same manner as in the same example except that the temperature during silica precipitation was 85° C., the sulfuric acid addition time was 40 minutes, and the pH was adjusted to 3 before addition of phosphoric acid.
The pigment performance of this composition was tested in the same manner as in the previous example, with the results shown in Table 2.

Claims (1)

[Scope of Claims] 1. A titanium dioxide pigment composition with improved dispersibility and heat resistance, which comprises: (1) a titanium dioxide pigment composition having improved dispersibility and heat resistance; A continuous silica film of 1 to 10% (based on TiO_2) in terms of SiO_2 that covers the surface, and (2) A that covers the surface of the silica film.
A titanium dioxide pigment composition having an aluminum phosphate coating of 0.5 to 5% (based on TiO_2) in terms of l_2O_3. 2 1 to 5% (based on TiO_2) of SiO_2 continuous silica coating and Al covering the surface of the silica continuous coating
The titanium dioxide pigment composition according to claim 1, which has an aluminum phosphate coating of 1 to 3% in terms of _2O_3. 3. A method for producing a titanium dioxide pigment composition with improved dispersibility and heat resistance, comprising: (1) dispersing rutile-type crystalline titanium dioxide particles having a particle size of 0.1 to 0.5 microns in water to form a slurry; (2) While maintaining the pH at 8 or above and the temperature at 60°C or above, add 1 to 10% (based on TiO_2 in the slurry) of water-soluble silicate in terms of SiO_2, and add acid or ammonium salt while stirring thoroughly. Add and react p
(3) maintaining the temperature at the same temperature to stabilize the coating;
4) While maintaining the temperature of the slurry at 60°C or higher and stirring sufficiently, add a water-soluble aluminum compound of 0.5 to 5% (based on TiO_2 in the slurry) in terms of Al_2O_3 and a P_2O_2/Al_2O_3 molar ratio of 1/ 4-2
Add an amount of phosphoric acid or water-soluble phosphate salt to pH
3 to 10, substantially all of the produced precipitate mainly consisting of aluminum phosphate is precipitated as a coating covering the surface of the silica-coated particles, and (5) maintaining the same temperature to stabilize the coating. , followed by filtration and washing to recover the coated pigment. 4. The titanium dioxide pigment composition according to claim 3, in which a water-soluble silicate and an ammonium salt are added to a titanium dioxide slurry and reacted at a boiling point of 80°C to volatilize the generated ammonia to precipitate a continuous silica film. How things are made. 5. To the silica-coated titanium dioxide slurry, add phosphoric acid or a water-soluble phosphate in an amount corresponding to a P_2O_5/Al_2O_3 molar ratio of 1/2 to 1 in the aluminum phosphate coating, followed by a corresponding amount of water-soluble phosphate. A method for producing a titanium dioxide pigment composition according to claim 3, 4, or 5, which comprises adding an aluminum compound and adjusting the pH to 3 to 10 to precipitate an aluminum phosphate film.