JP2869961B2 - Fine particle composite oxide green pigment and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fine particulate composite oxide green pigment, and more particularly, to an inorganic pigment which has excellent coloring properties, has a deep color as an inorganic pigment, exhibits a colored green color, and has transparency and dispersibility. Of fine-grained composite oxide green pigments with good properties and their production methods, by utilizing the new properties of pigments for ceramics as well as paints and inks, and also by making them into fine particles, by increasing their color developing properties However, for example, as a green pigment for color filters, as a pigment for metallic paint or color clear utilizing the color tone of the base material, further useful for pigments for phosphors, thin films, ultraviolet absorbers, printing inks and the like The present invention relates to a particulate composite oxide green pigment.

[0002]

2. Description of the Related Art Composite oxide green pigments are widely known as inorganic pigments having excellent heat resistance, weather resistance, and the like, and are widely used, for example, as colorants for paints and synthetic resins, and for ceramics. Among them, titanium-cobalt-nickel-based and aluminum-cobalt-chromium-based composite oxide green pigments are well known. These composite oxide green pigments are mainly produced by a dry method, and the pigments are produced through the steps of mixing, calcining and pulverizing an oxide or carbonate compound as a raw material. The dry method requires a large amount of energy for pulverization and has a problem that fine particles cannot be obtained because the sintered body is pulverized. For inorganic pigments, fine particle technology has been developed for single-component inorganic compounds such as titanium oxide and iron oxide for a long time.However, it is difficult to obtain transparent fine particle type pigments for composite oxide pigments. Have been.

[0003] However, with respect to the complex oxide green pigments of the above-mentioned system, the methods of making fine particles proposed by the present applicants (JP-B-4-55322, JP-B-4-55323, JP-B4-55323, No. 8728, etc.)
However, the complex oxide green pigments obtained by these methods are a yellowish green pigment and a bluish green pigment, and an intermediate color between them can be obtained by toning, but the transmittance is high. However, there is a problem of causing a decrease in color and saturation, and a single-phase fine particle pigment exhibiting an intermediate color without such a problem is eagerly desired.

[0004]

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a single-phase, fine-grained green pigment exhibiting an intermediate color of excellent transparency and saturation. The present inventors have conducted intensive studies in order to solve the above-mentioned problems of the prior art, and as a result, a pigment having a composition different from the constituents such as the green pigments shown above, that is, a pigment having a spinel structure composed of oxides of cobalt and chromium. Further, by forming a composite oxide pigment having a ternary spinel structure in which a part of the constituent elements is replaced with titanium, and further manufacturing the pigment by a wet precipitation method, It has been found that a fine particle composite oxide green pigment having excellent color development and coloring can be obtained.

[0005]

That is, the present invention provides a fine particle composite oxide green pigment comprising a composite oxide of cobalt, chromium and titanium and having a BET specific surface area of 30 m ² / g or more. The three components of cobalt salt, chromium salt and titanium compound are dissolved in water to form a mixed solution,
Each salt is co-precipitated using an aqueous alkali solution as a precipitant,
This is a method for producing a fine particulate composite oxide green pigment, which comprises aging, separating, washing, drying and calcining.

Heretofore, a cobalt-chromium-based spinel-type compound has a complex oxide green pigment in which part of aluminum is replaced by chromium and all of aluminum is replaced by chromium in a spinel-type compound composed of oxides of cobalt and aluminum. There is a composite oxide green pigment with a spinel structure, which is an inorganic pigment with excellent heat resistance and weather resistance, but is mainly used as a colorant for ceramics because its color tone is dark blue green and poor color development I was However,
Composite oxide pigments having a ternary spinel structure in which some of the constituent elements are replaced with titanium to the pigments having a spinel structure of cobalt and chromium oxides, and those produced using a wet precipitation method, It has been found that the composite oxide green pigment is excellent in transparency, heat resistance, and weather resistance and exhibits a colored green color. This fine-particle pigment is located almost in the middle of the hue of the yellow to bluish green pigment, shows a sharp waveform where the main wavelength of transmitted light is around 530 to 550 nm, and the main wavelength of reflected light is 520 to 550 nm.
It has a colored green color with a sharp waveform near 540 nm, and has a high coloring power. The BET specific surface area of the particles is 30 m
^Since it is ² / g or more, it is a pigment that can satisfy the above-mentioned desired properties.

[0007]

A titanium compound is further added to a mixed solution of a cobalt salt and a chromium salt to form a mixed solution of three components, which is co-precipitated using a precipitant such as an aqueous alkali solution.
A fine particle composite oxide green pigment which has good transparency and yet has a deep green color as an inorganic pigment and which sufficiently develops color even when fired at a relatively low temperature is obtained.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in more detail with reference to preferred embodiments. The cobalt and chromium salts used for producing the pigment of the present invention are sulfates, nitrates, carbonates,
All of those conventionally used in producing composite oxide pigments, such as chlorides and acetates, can be used. or,
In the case of titanium, a reagent such as titanium tetrachloride or titanyl sulfate or a titanium compound which is an industrial raw material can be used. These raw materials are such that the molar ratio of cobalt, chromium and titanium constituting the composite oxide pigment of the present invention is 1.0 to 3.0 for chromium and 0.01 to 1.0 for titanium with respect to cobalt 1.
It is preferable to use the pigment in such a ratio that the pigment has excellent transparency and the color tone can be easily changed from yellowish to bluish green. Cobalt and chromium spinel-type composite oxides have poor color development, exhibit a dull dark blue-green color, and have a tendency to become duller as the amount of chromium increases, and the transparency increases as the amount of titanium added exceeds the above ratio. Although the coloring tends to increase, the coloring with the depth decreases, and conversely, when the coloring decreases, the coloring tends to be dull. The molar ratio of cobalt: chromium: titanium is 1: 1.6 to 2.0: 0.2
A ratio of 0.6 is particularly preferable, and at this ratio, transparency and coloring are good, and a deep green color is exhibited.

The fine particle pigment comprising the composite oxide of each of the constituent elements in the above ratio can be produced by a wet precipitation method using the metal salts and compounds of the above constituent elements as raw materials. In the wet precipitation method, each raw material is dissolved in water to form a mixed salt aqueous solution. The concentration at this time is adjusted so that the molar ratio of each constituent element is within the above range, and it is appropriate to set the concentration as a whole to about 5 to 50% by weight. This mixed solution is dropped into a precipitation medium such as water at the same time as an alkaline aqueous solution such as caustic soda as a precipitant,
Each raw material is co-precipitated.

In this case, the reaction concentration (the concentration of all the constituent elements in the whole solution) does not have a particularly bad influence on the transparency.
Considering workability, etc., 0.05 mol / l to 0.5
The range of mol / liter is appropriate, and the lower the concentration, the better the transparency of the pigment. The reaction temperature (coprecipitation formation temperature) is in the range performed by a usual wet precipitation method, that is, 0 ° C.
If the temperature is within the range of from 100C to 100C, a pigment having excellent transparency can be obtained as described above. The pH at this time does not significantly impair the transparency as long as it is in the range of 7 to 12, but as the pH shifts to the alkali side, the transparency slightly increases and the transparency increases, and conversely, as the pH shifts to the acidic side. It tends to be whitish and the transparency is reduced. 30 minutes ~
After a precipitate is formed with stirring for about one hour, aging is performed for about one hour to complete the precipitation reaction.

Next, the separated coprecipitate is separated by filtration or the like. Since the separated coprecipitate usually has a water content of about 40% by weight to about 80% by weight,
After drying at a temperature of about 0 ° C, 500 ° C in an acidic atmosphere
To a temperature of 1000 ° C. for about 30 minutes to 1 hour to form a color. Thus, the BET specific surface area is 30 m ² /
g or more of the inorganic pigment of the present invention can be obtained.
The fine particle composite oxide green pigment of the present invention has a transparent and deep color tone as compared with those manufactured by a conventional dry method, is easily crushed as necessary, and furthermore, cobalt,
By making a three-component system that adds titanium to chromium,
It is a colored pigment that has excellent color developability and is deep as an inorganic pigment.

[0012]

Next, the present invention will be described more specifically with reference to examples and comparative examples. In the following, "parts" and "%" are based on weight unless otherwise specified. Example 1 29.10 parts of cobalt nitrate hexahydrate, chromium nitrate nonahydrate 7
2.03 parts and 11.54 parts of an aqueous solution of titanium tetrachloride having a titanium content of 16.6% were added to water and completely dissolved.
00 parts. Next, 37.0 parts of caustic soda is dissolved in water to make a precipitant solution having a total of about 400 parts. 1,200 parts of water as a precipitating medium is heated and maintained at 30 ° C., and an aqueous mixed salt solution and an aqueous caustic soda solution are simultaneously added dropwise thereto with stirring, and the precipitating reaction is completed in about 30 minutes to 1 hour. At this time, the pH was maintained at 9, and when the addition was completed, the pH was raised to about 10 so that precipitation was completely performed, and the liquid temperature was raised to 30.
Aging is performed for about 1 hour while maintaining the temperature at ° C.

After completion of aging, the coprecipitate is sufficiently washed with decantation to remove residual salts, and separated by filtration. Next, it is dried at a temperature of 100 ° C. to 120 ° C. for 12 hours or more. The dried product is fired at 800 ° C. for one hour in an oxidizing atmosphere. The pigment thus obtained had fine particles, a BET specific surface area of 60 m ² / g, and was transparent and deep. 30 parts of the above pigment was dispersed in 100 parts of melamine alkyd resin using a paint shaker. The hue, transparency, and dispersibility were visually observed with the naked eye with respect to a color obtained by applying this to art paper with a black belt using a 3 mil applicator. Further, the spectral reflectance and transmittance in the visible light region of a substrate coated with quartz glass at a film thickness of 50 μm were measured. FIG. 1 shows the measurement results.
The spectral reflectance shows a sharp reflectance curve (1-1) having a maximum peak near a wavelength of 530 nm, and the transmittance shows a transmittance curve (1-2) having a sharp maximum peak near a wavelength of 545 nm. Was. The wavelengths of these maximum peaks can be shifted to longer wavelengths and shorter wavelengths by improving the composition and synthesis conditions.

Example 2 5.69 parts of titanyl nitrate having a titanium content of 33.7% was added to water 20
Add 0 parts and stir to dissolve completely. Next, water is added to 80.03 parts of chromium nitrate nonahydrate and 29.10 parts of cobalt nitrate hexahydrate so that the total amount becomes 400 parts and completely dissolved to prepare a mixed salt aqueous solution. These solutions and the solution of the precipitant were simultaneously added to the aqueous medium in the same manner as in Example 1, and the following operation was carried out in the same manner as in Example 1 to prepare a pigment. The resulting pigment was colored green and transparent with fine particles and a large depth of specific surface area.

Comparative Example 1 29.10 parts of cobalt nitrate hexahydrate and 80.03 parts of chromium nitrate nonahydrate were added to water and completely dissolved to give a total of about 40 parts.
0 copies. The following operation was carried out in the same manner as in Example 1 to obtain a pigment. The obtained pigment had a dull blue-green color with poor coloring properties, was poor in transparency, and had no color.

Comparative Example 2 74.93 parts of cobalt monoxide, dichromium trioxide 151.
99 parts and 31.96 parts of titanium dioxide are thoroughly mixed,
It was baked at 1000 ° C., baked, and pulverized to obtain a pigment.
Thus, the pigment obtained by the dry method had insufficient color development as compared with the pigment obtained in Example 1, and was whitish as a whole and poor in transparency. The observation results of the color tone of the pigment obtained as described above are summarized in Table 1.

[0017]

[Table 1]

[0018]

As described above, according to the present invention, as an inorganic pigment having excellent coloring properties and excellent transparency, a fine-grained composite oxide green pigment having a deep green color can be obtained. The pigment is used not only as a colorant for simulated kilns as in the case of the conventional composite oxide green pigment, but also as a colorant for general paints and synthetic resins, which has been difficult to apply with the conventional pigments, Utilizing the characteristics, for example, as a green pigment for a color filter, or as a metallic paint or color clear pigment utilizing the color tone of the base material, as well as a phosphor pigment, an ultraviolet absorber, a thin film, a printing ink, It is expected to be applied to cosmetics and abrasives.

[Brief description of the drawings]

FIG. 1 shows a spectral reflectance curve (1-1) and a transmittance curve (1-2) in a visible light region of a typical fine particle composite oxide green pigment obtained in Example 1 of the present invention.

Continuation of the front page (72) Inventor Takahiro Ota 1-7-6 Nihonbashi Bakurocho, Chuo-ku, Tokyo Inside Dainichi Seika Kogyo Co., Ltd. (56) References JP-A-6-107417 (JP, A) JP-A-4 -55322 (JP, A) JP-A-3-8728 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C01G 51/00

Claims (5)

(57) [Claims] 1. A fine particle composite oxide green pigment comprising a composite oxide of cobalt, chromium and titanium and having a BET specific surface area of 30 m ² / g or more. 2. The molar ratio of the constituents cobalt, chromium and titanium is such that the chromium to cobalt 1 is 1.0 to 1.0.
2. The fine particle composite oxide green pigment according to claim 1, wherein the average particle diameter ranges from 3.0 to 0.01 to 1.0. 3. A mixed solution comprising three components of a cobalt salt, a chromium salt and a titanium compound dissolved in water to form a mixed solution. Each salt is coprecipitated using an aqueous alkali solution as a precipitant, and after ripening, separation,
A method for producing a fine particle composite oxide green pigment, which comprises washing, drying and firing. 4. The method according to claim 3, wherein the pH during coprecipitation is in the range of 7 to 12. 5. The method for producing a particulate composite oxide green pigment according to claim 3, wherein the firing is carried out at 500 ° C. to 1000 ° C. in an acidic atmosphere.