JPH09100120A - Green pigment and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a compound oxide green pigment excellent in transparency and durability, showing a yellowish green, by coprecipitating each salt from an aqueous solution of mixed salts of a cobalt salt, a chromium salt, a titanium compound and a zinc salt and baking. SOLUTION: Four components in a ratio of 1mol cobalt salt, 2.0-4.5mol chromium salt, 0.05-1.0mol titanium compound and 0.1-2.0mol zinc salt are dissolved in an aqueous medium so as to give 5-50wt.% concentration of the mixed salts. The aqueous solution of the mixed salts and an aqueous solution of an alkali are dripped into water to coprecipitate the salts at 0.1-0.5mol/L concentration at pH7-10 at 0-100 deg.C. The precipitate is washed, filtered, dried and baked at 600-1,000 deg.C to give a compound oxide green pigment. The pigment comprises cobalt oxide, chromium oxide and zinc oxide and has particle diameters of >=50m<2> /g by BET specific surface area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite oxide green pigment and a method for producing the same, and more particularly to a green pigment having good transparency and durability which is useful for a heat resistant color filter and the like and a method for producing the same.

[0002]

2. Description of the Related Art Composite oxide type inorganic pigments are excellent in heat resistance, weather resistance, chemical resistance and the like, and are therefore widely used as a very robust colorant in applications requiring durability such as special paints and glass enamel. Came. On the other hand, these composite oxide-based inorganic pigments are generally characterized by a large hiding power and low transparency as compared with organic pigments, but if hiding power is small and a high transparency can be obtained, durability is improved. It is expected that its application will be further expanded as a good transparent pigment.
Such applications that require both durability and transparency at the same time include, for example, heat-resistant color filter pigments.

As the pigment used for the color filter, coloring materials having respective color tones of blue, green and red are required. In recent years, Co-Al-based pigments have been used as blue-based and green-based pigments having excellent durability and transparency (Japanese Patent Application Laid-Open No. HEI 2-
283771), a Co-Al-Cr system (JP-A-4-5).
5322), a Co-Al-Cr-Ti system (JP-A-4-
55323) and a Co-Zn-Ni-Ti-based (Japanese Patent Laid-Open No. 3-8728) blue-comprising finely divided composite oxide.
Green pigments have been developed and are being used for these applications.

[0004]

However, among these conventional finely divided composite oxide pigments, Co--Al and C are used.
The o-Al-Cr and Co-Al-Cr-Ti systems are both blue to greenish blue, while Co-Zn-N
The i-Ti system was yellow green with no good green or yellowish green pigment present. Therefore, an object of the present invention is to provide a composite oxide pigment which is excellent in durability and transparency and exhibits a green color, and a method for producing the same.

[0005]

The inventors of the present invention have made various metal salts (compounds) into fine particles by a coprecipitation method and examined the transparency and the tint thereof. As a result, cobalt, chromium and titanium were obtained. The inventors have found that 4-component composite oxide fine particles of zinc and zinc are useful as a green pigment having excellent transparency, and have completed the present invention.

That is, the present invention comprises cobalt, chromium, titanium and zinc oxides and has a BET specific surface area of 50.
A composite oxide green pigment having a m ² / g or more is provided.

In the present invention, four components of cobalt salt, chromium salt, titanium compound and zinc salt are dissolved in an aqueous medium, and each salt is coprecipitated from the obtained mixed salt aqueous solution using an alkaline aqueous solution. The present invention provides a method for producing the above complex oxide green pigment, which comprises firing the coprecipitate.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The composition of the composite oxide in the composite oxide green pigment of the present invention is a composite oxide of cobalt (Co), chromium (Cr), titanium (Ti) and zinc (Zn). Its constituents are cobalt, chromium,
The compositional molar ratio of titanium and zinc is 1 for cobalt.
Chromium 2.0 to 4.5, titanium 0.05 to 1.0, and zinc 0.1 to 2.0 are preferable in terms of transparency and tint.

The particle size of the composite oxide green pigment of the present invention has a BET specific surface area of 50 m from the viewpoint of ensuring transparency.
² / g or more is necessary, especially 60 m ² / g
It is preferable that it is above.

The pigment of the present invention comprises a cobalt salt, a chromium salt, a titanium compound and a zinc salt, which are dissolved in an aqueous medium.
It is produced by coprecipitating each salt from the obtained mixed salt aqueous solution using an alkaline aqueous solution and then calcining the coprecipitate. As the cobalt salt, the chromium salt or the zinc salt used as a raw material, chloride is used. Compounds, inorganic acid salts such as nitrates and sulfates, and organic acid salts such as acetates. Also,
Examples of the titanium compound include titanium chloride and titanyl sulfate.

First, these raw materials are dissolved in an aqueous medium, and the aqueous medium is preferably water. An aqueous mixed salt solution of the above constituents is obtained by such a dissolving operation, and the concentration of the mixed salt is preferably 5 to 50% by weight as a whole.

When the oxidizing agent is added to the obtained mixed salt aqueous solution before the coprecipitation operation, the transparency of the obtained pigment is further improved. The oxidizing agent used here is preferably a peracid, and particularly preferably one or more selected from hydrogen peroxide, peroxo acids and peroxo acid salts. The amount of the oxidizing agent added is not particularly limited, but is preferably 0.05 mol or more per 1 mol of titanium.

The coprecipitation operation is carried out by dropping the mixed salt aqueous solution and the alkaline aqueous solution into the coprecipitation medium. Here, water is preferable as the coprecipitation medium. From the viewpoint of workability, the coprecipitation reaction concentration is preferably 0.1 to 0.5 mol / l. The pH during the coprecipitation reaction is preferably 7 to 10 and the temperature is preferably 0 to 100 ° C., since transparency is not particularly impaired.

The precipitate obtained by the coprecipitation reaction is washed if necessary, collected by means such as filtration, dried, and calcined. Firing is a normal metal oxide formation condition 600
It is preferably carried out at a temperature of ˜1000 ° C., especially 650˜850 ° C.

The composite oxide pigment thus obtained has the above-mentioned BET specific surface area, is excellent in transparency and exhibits a good green color.

[0016]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited to these examples.

Example 1 In a 500 ml beaker, 15.58 g of cobalt nitrate hexahydrate,
Chromium nitrate nonahydrate 85.25 g, zinc nitrate hexahydrate 20.
Weigh 40 g, 5.48 g of titanyl sulfate containing 32.1% in terms of titanium oxide, add water to completely dissolve it, add 0.2 ml of 35% hydrogen peroxide, and further add water. The total volume was about 500 ml. Next, weigh 50 g of caustic soda as a precipitant, add water, and add about 500 to the whole.
ml. Water 150 as a precipitation medium prepared in advance
A mixed salt aqueous solution and a caustic soda aqueous solution were simultaneously added dropwise to 0 ml to complete the neutralization reaction in about 1 hour. PH at this time
I was careful that it was 9. This was allowed to stand for a whole day and night, the supernatant was removed, and the precipitate slurry was sufficiently washed by decantation until the electric conductivity of the precipitate slurry reached 150 to 300 μS / cm, and then filtered. Then 100-140
It was dried at a temperature of ° C for 12 hours or more. 75 of this dried product
Firing was performed at 0 ° C. for 3 hours in an oxidizing atmosphere. The pigment thus obtained is a fine particle having a yellowish green color tone.
The T specific surface area was 78 m ² / g.

Comparative Example 1 Commercially available industrial chemical, 23.61 g of cobalt oxide containing 71% of Co content, 86.88 g of chromium oxide, 29.98 g of zinc oxide, 9.52 of titanium oxide (anatase).
g was weighed and thoroughly mixed with a tabletop high speed blender. Next, the pigment was obtained by baking at 1100 ° C. for 1 hour in an electric furnace.

Comparative Example 2 Al-Co according to Example 1 of JP-A-4-55323.
A -Cr-Ti-based fine particle composite oxide pigment was prepared.

Comparative Example 3 Ni-Co according to Example 1 of JP-A-3-8728.
A -Zn-Ti-based fine particle composite oxide pigment was prepared.

Test Example A sample pigment is dispersed in a melamine alkyd resin with a paint shaker to a pigment content of 5%. This was color-developed on a 1.5 mm-thick colorless and transparent plate glass with an applicator of 10 MIL and baked, and then the test piece was exposed to natural light to observe the surface color and transmitted color tone. Further, the transmitted light of 400 nm to 700 nm was measured with a scanning spectrophotometer and the wavelength showing the strongest transmission was observed. Table 1 shows the results.

[0022]

[Table 1]

As described above, the pigment obtained in Example 1 is greener than the pigment obtained in the conventional Comparative Example 2, and
It has a color less yellowed than the pigment obtained in Comparative Example 3 and has transparency as compared with the pigment obtained in Comparative Example 1. Also in the spectral transmission measurement, the transmission peak is located in the middle of the pigments obtained in the conventional Comparative Example 2 and Comparative Example 3.

[0024]

EFFECTS OF THE INVENTION Since the pigment of the present invention exhibits a yellowish green color, and has transparency and durability, it has a conventional fine particle composite oxide blue green pigment (Comparative Example 2) and a conventional fine particle composite oxide green. As an intermediate color of the pigment (Comparative Example 3), it is useful as a coloring material for conventional paints, synthetic resins, and the like, or a heat-resistant color filter, a phosphor, etc., which utilizes its transparency.

Claims (2)

[Claims] 1. A composite oxide green pigment comprising an oxide of cobalt, chromium, titanium and zinc and having a BET specific surface area of 50 m ² / g or more. 2. A cobalt salt, a chromium salt, a titanium compound and a zinc salt are dissolved in an aqueous medium, and the respective salts are coprecipitated from the resulting mixed salt aqueous solution using an alkaline aqueous solution.
Then, the coprecipitate is fired.
A method for producing the composite oxide green pigment described.