JPH08198629A - Green pigment of fine particulate multiple oxide and its production - Google Patents

Abstract

PURPOSE: To improve color developing property by controlling BET specific surface area to equal or above a specific value and being constituted of a multiple oxide of Co, Cr and Ti. CONSTITUTION: A mixed salt aq. solution having 5-50wt.% concn. is prepared by dissolving a Co salt such as C(MO3 )2 .6H2 O, a Cr salt such as Cr(NO3 )3 .9H2 O and a Ti compound such as TiCl4 in a prescribed ratio. Next, the mixed salt aq. solution is dropped simultaneously with an aq. solution of an alkali such as NaOH as a precipitant into a precitation solvent such as water, allowed to precipitation react in the range of pH7-12 and aged for about 1hr after the reaction is completed. After that, the fine particulate multiple oxide green pigment having >=30m<2> /g BET specific surface area and composed of the structural components having molar ratio of Co/Cr/Ti=1.0/(1.0-3.0)/(0.01-1.0) is obtained by firing the coprecipitated material under an acidic atmosphere at 500-1000 deg.C for 0.5-1hr after filtering, washing and drying at 100-120 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fine particle composite oxide green pigment, more specifically, it has excellent color developability, has a depth as an inorganic pigment, and exhibits a brilliant green color, and further has transparency and dispersion. Concerning the fine particle composite oxide green pigment with good properties and its manufacturing method, it can be used not only as a pigment for conventional ceramics due to its improved coloring property, but also as a paint or ink, and by utilizing the characteristics that newly appear by making it finer. However, for example, it is useful as a green pigment for color filters, as a metallic paint or a color clear pigment that makes the best use of the color tone of a substrate, and as a pigment for phosphors, thin films, ultraviolet absorbers, printing inks, etc. The present invention relates to a particulate composite oxide green pigment.

[0002]

BACKGROUND OF THE INVENTION Composite oxide green pigments are widely known as inorganic pigments having excellent heat resistance and weather resistance, and are widely used, for example, as coloring agents for paints and synthetic resins, and coloring agents for ceramics. Among them, titanium / cobalt / nickel-based and aluminum / cobalt / chromium-based composite oxide green pigments are well known. A dry method is mainly used for producing these composite oxide green pigments, and the pigment is produced through the steps of mixing raw material oxides and carbonate compounds, firing and pulverizing. The dry method has a problem that a large amount of energy is required for crushing and fine particles cannot be obtained because the sintered body is crushed. Even for inorganic pigments, fine particle technology has been developed for a long time for single composition inorganic compounds such as titanium oxide and iron oxide, but it is difficult to obtain transparent fine particle type pigments for complex oxide pigments. Came.

However, regarding the above-mentioned series of complex oxide green pigments, the method of forming fine particles proposed by the present applicants (Japanese Patent Publication No. 4-55322, Japanese Patent Publication No. 4-55323, and Japanese Patent Publication No. 3-53323). 8728 publication)
However, the complex oxide green pigments obtained by these methods are yellowish green pigments and bluish green pigments. However, there is a need for a single-phase fine particle pigment that exhibits a neutral color without such problems.

[0004]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a single phase particulate green pigment which exhibits an intermediate color of excellent transparency and saturation. As a result of intensive research to solve the above-mentioned problems of the prior art, the inventors of the present invention have a composition different from the constituents such as the above-described green pigment, that is, a pigment having a spinel structure composed of oxides of cobalt and chromium. In addition, a composite oxide pigment having a ternary spinel structure in which some of the constituent elements are replaced with titanium is prepared, and further, the pigment is produced by a wet precipitation method to obtain the desired excellent properties described above. It has been found that a fine particle composite oxide green pigment having excellent coloring and coloring can be obtained.

[0005]

That is, the present invention relates to 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. Three components of cobalt salt, chromium salt and titanium compound are dissolved in water to form a mixed solution,
Coprecipitate each salt using an aqueous alkaline solution as a precipitant,
After the aging, the method for producing a fine particle composite oxide green pigment is characterized in that it is separated, washed with water, dried and fired.

[0006] Conventionally, a cobalt-chromium spinel compound is a composite oxide green pigment obtained by substituting a part of aluminum of a spinel compound composed of an oxide of cobalt and aluminum with chromium, and all of the aluminum is replaced with chromium. There is a complex oxide green pigment with a spinel structure.The latter is an inorganic pigment with excellent heat resistance and weather resistance, but it is mainly used as a coloring agent for ceramics due to its dark blue green color and poor color development. Was there. However,
The composite oxide pigment having a ternary spinel structure in which some of the constituent elements are replaced by titanium is added to the pigment having the spinel structure formed by the oxides of cobalt and chromium, which is further manufactured by the wet precipitation method. It was found that the fine particle composite oxide green pigment is excellent in transparency, heat resistance, and weather resistance and exhibits a brilliant green color. This fine particle pigment is located approximately in the middle of the hues of yellowish to blueish green pigments, and the dominant wavelength of transmitted light shows a sharp waveform around 530 to 550 nm, and the dominant wavelength of reflected light is 520 to 520 nm.
It has a vivid green color with a sharp waveform around 540 nm and has high coloring power. Also, 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 properties required in the above.

[0007]

[Function] A titanium compound is further added to a mixed solution of cobalt salt and chromium salt to form a mixed solution of three components, and this is coprecipitated using a precipitating agent such as an alkaline aqueous solution.
It is possible to obtain a fine particle composite oxide green pigment which has good transparency, yet has a deep green color as an inorganic pigment, and sufficiently develops color even when fired at a relatively low temperature.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail with reference to the preferred embodiments. The cobalt and chromium salts used in the production of the pigments of the present invention include sulfates, nitrates, carbonates,
Any of those conventionally used for 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. In these raw materials, the molar ratio of cobalt, chromium and titanium constituting the composite oxide pigment of the present invention is 1.0 to 3.0 of chromium and 0.01 to 1.0 of titanium with respect to 1 cobalt.
It is preferable to use it in a ratio within the range since it is possible to impart excellent transparency to the pigment and easily change the color tone from yellowish to bluish green. Cobalt and chromium spinel type complex oxides have poor color development, exhibit a dull dark blue-green color, and tend to become dull as the amount of chromium increases, and as the amount of titanium added exceeds the above ratio, the transparency becomes Although it tends to increase, the coloration with depth decreases, and conversely when it decreases, it tends to become dull, and it is not suitable because it does not develop a deep green color. The molar ratio of cobalt: chromium: titanium is 1: 1.6 to 2.0: 0.2.
A ratio of up to 0.6 is particularly preferable, and in this ratio, both transparency and color development are good, and a deep green color is exhibited.

The fine particle pigment composed of the composite oxide of each constituent element in the above proportions can be produced by the 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 that time is adjusted so that the molar ratio of each constituent element is within the above range, and it is suitable that the concentration is about 5 to 50% by weight as a whole. This mixed solution is dropped into a precipitation medium such as water simultaneously with an alkaline aqueous solution such as caustic soda as a precipitant,
Co-precipitate each source material.

The reaction concentration (concentration of all the constituent elements in all the solutions) at this time does not particularly affect the transparency,
Considering workability, etc., 0.05 mol / liter to 0.5
The range of mol / liter is appropriate, and the tendency is that the thinner the concentration, the better the transparency of the pigment. The reaction temperature (coprecipitation formation temperature) is in the range that is usually used for wet precipitation, that is, 0.
When the temperature is in the range of 100 ° C to 100 ° C, a pigment having excellent transparency can be obtained as described above. Further, if the pH at this time is in the range of 7 to 12, the transparency is not greatly impaired, but as the pH shifts to the alkali side, the transparency increases slightly dull, and conversely as it shifts to the acidic side. It tends to become whitish and less transparent. 30 minutes ~
After forming a precipitate with stirring for about 1 hour, aging is carried out for about 1 hour to complete the precipitation reaction.

Next, the coprecipitate that has come out is separated by filtration or the like. Since the separated coprecipitate usually has a water content of about 40% to 80% by weight, the coprecipitate is 100 ° C to 12%.
After drying at a temperature of 0 ℃, 500 ℃ in an acidic atmosphere
To about 1000 ° C. for about 30 minutes to 1 hour for color development. In this way, the BET specific surface area is 30 m ² /
It is possible to obtain the fine particle composite oxide green pigment of the present invention having a color of not less than g and having a depth as an inorganic pigment.
The fine particle composite oxide green pigment of the present invention has a transparent and deep color tone as compared with that produced by a conventional dry method, and is easy to pulverize if necessary, and cobalt,
By using a three-component system in which titanium is added to chromium,
It is a pigment that is excellent in color development and has depth as an inorganic pigment.

[0012]

EXAMPLES Next, the present invention will be described more specifically with reference to Examples and Comparative Examples. In addition, unless otherwise specified, "parts" and "%" in the text are based on weight. Example 1 Cobalt nitrate 6-hydrate 29.10 parts, chromium nitrate 9-hydrate 7
2.03 parts and 11.54 parts of a titanium tetrachloride aqueous solution having a titanium content of 16.6% were added to water to completely dissolve it, and the whole solution was about 4
00 copies. Next, 37.0 parts of caustic soda is dissolved in water to prepare a precipitant solution having a total amount of about 400 parts. 1,200 parts of water, which is a precipitation medium, is heated and maintained at 30 ° C., and an aqueous mixed salt solution and an aqueous solution of sodium hydroxide are simultaneously added dropwise thereto with stirring to complete the precipitation reaction over about 30 minutes to 1 hour. At this time, the pH was kept at 9, and when the dropping was completed, the pH was raised to about 10 and the liquid temperature was raised to about 30 so that the precipitation was completed.
Aging is performed for about 1 hour while maintaining at ℃.

After completion of aging, the coprecipitate is thoroughly washed with water by decantation to wash away residual salts, and separated by filtration. Then, it is dried at a temperature of 100 ° C. to 120 ° C. for 12 hours or more. The dried product is baked at 800 ° C. for 1 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 had a depth. 30 parts of the above pigment was dispersed with 100 parts of melamine alkyd resin using a paint shaker. The color, transparency, and dispersibility of the product, which was developed by applying a 3 mil applicator to art paper with a black belt, were visually observed. Further, the spectral reflectance and the transmittance in the visible light region were measured for a quartz glass substrate coated with a film thickness of 50 μm. The measurement results are shown in FIG.
Spectral reflectance shows a sharp reflectance curve (1-1) with a maximum peak near a wavelength of 530 nm, and transmittance shows a transmittance curve (1-2) with a sharp maximum peak near a wavelength of 545 nm. It was The wavelengths of these maximum peaks can be moved to the long wavelength side and the short wavelength side by improving the composition and the synthesis conditions.

Example 2 5.69 parts of titanyl nitrate having a titanium content of 33.7% was added to 20 parts of water.
Add 0 parts and stir to dissolve completely. Next, water is added to 80.03 parts of chromium nitrate 9-hydrate 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. As in Example 1, these solutions and the solution of the precipitating agent were simultaneously added to the aqueous medium, and the following operations were performed in the same manner as in Example 1 to prepare a pigment. The resulting pigment was a fine green particle having a large depth of specific surface area and was colored green and transparent.

COMPARATIVE EXAMPLE 1 29.10 parts of cobalt nitrate hexahydrate and 80.03 parts of chromium nitrate 9-hydrate were added to water and completely dissolved to obtain a total of about 40 parts.
Set to 0. The following operations were carried out in the same manner as in Example 1 to obtain a pigment. The resulting pigment had a dull blue-green color with poor color development, had poor transparency, and had no color.

Comparative Example 2 74.93 parts of cobalt monoxide, dichromium trioxide 151.
Thoroughly mix 99 parts and 31.96 parts titanium dioxide,
The pigment was obtained by firing at 1000 ° C. and pulverizing after firing.
As described above, the pigment obtained by the dry method was insufficient in color development as compared with the pigment obtained in Example 1, and was entirely whitish and poor in transparency. The results of observing the color tone of the pigments obtained as described above are summarized in Table 1.

[0017]

[Table 1]

[0018]

As described above, according to the present invention, a fine particle composite oxide green pigment exhibiting a deep green color is obtained as an inorganic pigment excellent in color developability and transparency. The pigment is used as a coloring agent for kiln similar to the conventional composite oxide green pigment, and also as a coloring agent for general paints and synthetic resins, which are difficult to apply with the conventional pigment. Utilizing the characteristics, for example, as a green pigment for a color filter, or as a pigment for a metallic paint or a color clear that makes the best use of the color tone of a substrate, a pigment for a phosphor, an ultraviolet absorber, a thin film, a printing ink, It is expected to be applied to cosmetics and abrasives.

[Brief description of 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 Dainichi Seika Kogyo Co., Ltd.

Claims (5)

[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 constituent components cobalt, chromium and titanium is from 1.0 to 1.0 for cobalt.
The fine particle composite oxide green pigment according to claim 1, which has a range of 3.0 and titanium 0.01 to 1.0. 3. A cobalt solution, a chromium salt and a titanium compound are dissolved in water to form a mixed solution, and each salt is co-precipitated using an alkaline aqueous solution as a precipitant, and after aging, separation,
A method for producing a fine particle composite oxide green pigment, which comprises washing with water, drying and firing. 4. The method for producing a fine particle composite oxide green pigment according to claim 3, wherein the pH at the time of coprecipitation is in the range of 7 to 12. 5. The method for producing a fine particle composite oxide green pigment according to claim 3, which is fired at 500 ° C. to 1000 ° C. in an acidic atmosphere.