JPH0455322A - Blue-green pigment of multiple oxide fine particle and its production - Google Patents

Abstract

PURPOSE:To obtain a blue-green pigment comprising fine particles of multiple oxide, which is transparent and has large specific surface area and good dispersibility by applying a coprecipitaton method from an aq. soln. of aluminum salt, cobalt salt and chromium salt. CONSTITUTION:The blue-green pigment comprising fine particles of multiple oxide consists of oxides of Al, Co and Cr and has >=40 m<2>/g BET specific surface area. The molar ratio of Al and Cr to Co is preferably 0.5 - 2.0 of Al and 0.1 - 3 of Cr to 1 of Co. This pigment is obtained by dissolving the three components of aluminum salt, chromium salt and cobalt salt in water to prepare the mixture salt soln. and effecting the coprecipitation using an alkali aq. soln. as a precipitant. Then the precipitate is aged, filtered, washed with water, dried and calcined.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a fine particle composite oxide blue-green pigment and a method for producing the same, which is transparent and has a specific surface area of 40 d/
The object of the present invention is to provide a fine particle composite oxide blue-green pigment with good dispersibility of more than 100 g.

(Prior Art) Complex oxide blue-green pigments are widely known as inorganic pigments with excellent heat resistance, and are widely used, for example, as colorants for paints and synthetic resins, and colorants for ceramics.

The blue-green pigment mentioned above is a spinel-type compound made of oxides of aluminum, cobalt and chromium, and is mainly manufactured by a dry method by mixing oxides and carbonates such as aluminum oxide, cobalt oxide and chromium oxide, and firing and grinding. can get.

However, the dry method described above has the disadvantage that pulverization requires a large amount of energy, and fine particles cannot be obtained because the sintered body is pulverized. Furthermore, at present, industrial production of blue-green pigments by a wet method has not been carried out to date.

(Problem to be solved by the invention) The dry method mixes aluminum, cobalt, chromium oxides, etc.
This method involves firing at high temperature in the presence of flux, and then pulverizing the sintered particles using a powerful crusher to form pigments.However, unless the constituent oxides are fine particles, the fired product will not be transparent. It is difficult to form fine particles (even if such fine particles exist, they are sintered during firing and require a large amount of energy for pulverization, so it is difficult to obtain a fine particle composite oxide blue-green pigment with this method.

Therefore, an object of the present invention is to solve the problems of the prior art described above and to provide a fine particle composite oxide blue-green pigment that is transparent, has a large specific surface area, and has good dispersibility.

(Means for solving problems) The above objects are achieved by the present invention as described below.

That is, the present invention provides a fine particle composite oxide blue-green pigment comprising oxides of aluminum, cobalt and chromium, characterized in that it has a BET specific surface area of 40 rrr/g or more, and a fine particle composite oxide blue-green pigment comprising oxides of aluminum, cobalt and chromium. A fine particle composite oxide blue-green pigment characterized in that three components are dissolved in water to form a mixed salt solution, each salt is coprecipitated and aged using an aqueous alkali solution as a precipitant, and then filtered, washed with water, dried and fired. This is a manufacturing method.

(Function) By dissolving aluminum salt, cobalt salt, and chromium salt in water to form a mixed solution, and co-precipitating this using a precipitating agent such as an aqueous alkaline solution, each component is precipitated uniformly. Therefore, a soft and transparent microparticle composite oxide blue-green pigment that develops color sufficiently even when fired at a relatively low temperature can be obtained.

(Preferred Embodiments) Next, the present invention will be described in more detail by citing preferred embodiments.

The salts of each constituent element used in the present invention include sulfates, nitrates, carbonates, chlorides, acetates, etc., all of which are conventionally used in producing complex oxide blue-green pigments. .

In the above, the compositional ratio of each component is most preferably aluminum:cobalt nichrome = 2:1:2: in molar ratio of metals, and at this ratio, a bluish and transparent blue-green color is produced.

Furthermore, according to the results of the research conducted by the present inventors, the molar ratio of the above-mentioned constituents, aluminum (Al), cobalt (Co), and chromium (Cr), is 0.5 to 2.0 for aluminum to 1 cobalt. It was found that a change in composition within the range of 0.1 to 3 chromium did not significantly affect transparency.

Also, as the proportion of aluminum increases, it tends to become more bluish and hard, and conversely, as the proportion of chromium increases, it becomes greenish, but as the proportion of chromium increases, it tends to become more difficult.

The metal salts of the constituent elements as described above are dissolved in water to form a mixed aqueous solution. The concentration at this time is suitably about 5 to 50% by weight as a whole based on the above molar ratio. This mixed solution is simultaneously dropped into a precipitation medium prepared in advance using an alkaline aqueous solution such as caustic soda as a precipitant.

The reaction concentration at this time does not have a particularly bad effect on transparency, but considering workability, etc., the reaction concentration is 0.05 mol/ρ ~ 0.05 mol/ρ.
5 mol/ρ is suitable. Further, as long as the synthesis temperature is within the usual range, that is, 0°C to 100°C, it will not have a particularly bad effect on transparency. However, if the synthesis temperature is 70°C or higher, transparency tends to be slightly impaired compared to synthesis at lower temperatures, so it is desirable to carry out the synthesis within the range of 0°C to 70°C.

Also, if the pH at the time of synthesis is in the range of 7 to 10, transparency will not be significantly impaired, but as the pH shifts to the alkaline side, transparency increases but aggregation occurs and drying becomes hard. (As a result, dispersibility tends to deteriorate.

After forming a precipitate while stirring for 30 minutes to 1 hour in this manner, the mixture is aged for about 1 hour to complete the precipitation reaction.

Next, by filtering the precipitated coprecipitate, the water content will be about 40% to 80%, so it will be heated to 100°C to 12°C.
Dry at a temperature of about 0°C, and dry at 700°C in a warm atmosphere.
C. to 1100.degree. C. for 30 minutes to 1 hour to develop color. In this way, the fine particle composite oxide blue-green pigment of the present invention can be obtained.

The fine particle composite oxide blue-green pigment of the present invention obtained in this way had a clearer and deeper color tone than that obtained by the conventional dry method, and had good dispersibility.

(Example) Next, the present invention will be explained in more detail by giving examples and comparative examples. It should be noted that unless otherwise specified, the terms in the text or % are based on weight.

Example 1 75.02 parts of aluminum nitrate nonahydrate, 6 parts of cobalt nitrate
Measure out 29.10 parts of aqueous salt, 80.03 parts of chromium nitrate nonahydrate, and 4.31 parts of zinc sulfate heptahydrate, add to water, and dissolve completely to make a total of about 500 parts. Next, measure out 57.0 parts of caustic soda as a precipitant and add water to make a total of about 5.0 parts.
00 parts and Ya.

200 parts of water, which is a precipitation medium prepared in advance, is heated to about 30°C using a gas burner or electric heater, and mixed salt aqueous solution and caustic soda aqueous solution are simultaneously added dropwise thereto for about 30 minutes to 1 hour. to complete the precipitation reaction. At this time, care is taken to keep the pH at 9, and once the dropwise addition is complete, the pH is raised to about 10 to ensure complete precipitation, and the solution is aged for about 1 hour while maintaining the temperature at 30°C.

Next, when the ripening is completed, it is taken out, thoroughly washed with water by decantation, and filtered to remove residual salt.Then, it is dried at a temperature of 100 to 120°C for 12 hours or more. This dried product is fired at 1.000° C. for 1 hour in an oxidizing atmosphere.

When compared to conventional products, the pigment thus obtained has finer particles, a BET specific surface area of 40rrr/g or more, transparency, deep color tone, and good dispersibility. Ta.

The fired product is then dispersed in melamine alkyd resin (PHR40) using a paint shaker.

The color was then applied to black art paper using a 6 mil applicator and the color tone was observed.

Example 2 75.02 parts of aluminum nitrate nonahydrate, 7 parts of cobalt sulfate
Weigh out 28.10 parts of aqueous salt, 143.30 parts of chromium sulfate 18 hydrate, and 4.31 parts of zinc sulfate heptahydrate, and the total amount is 50 parts.
Add water to make 0 parts and dissolve completely to make a mixed salt aqueous solution.

The pigment obtained in the same manner as in Example 1 also had finer particles and a larger specific surface area than the conventional product, and was transparent and deep.

Comparative Example 1 203.92 parts of aluminum oxide, cobal oxide) 74.
Weigh and mix 93 parts of chromium oxide and 303.98 parts of chromium oxide.

This is fired at 1,000°C.

Next, this fired product was crushed to obtain a sample.

As described above, the pigment obtained by the dry method was less transparent than the pigment obtained in Example 1, and exhibited an overall bluish-green color. It was a dull blue-green color.

The above results are summarized in Table 1.

In addition, its properties are expected to be used in applications such as transparent paints, transparent thin films, printing inks, cosmetics, phosphors, and abrasives.

Claims (7)

[Claims] (1) A fine particle composite oxide blue-green pigment comprising oxides of aluminum, cobalt and chromium and having a BET specific surface area of 40 m^2/g or more. (2) The molar ratio of the constituent components aluminum (Al), cobalt (Co) and chromium (Cr) is 0.5 to 2.0 aluminum and 0.1 to 3 chromium to 1 cobalt.
The fine particulate composite oxide blue-green pigment according to claim 1, which is in the range of . (3) Dissolve the three components of aluminum salt, cobalt salt, and chromium salt in water to make a mixed salt solution, and use an aqueous alkali solution as a precipitant to coprecipitate and age each salt, followed by filtration, washing, drying, and baking. A method for producing a fine particulate composite oxide blue-green pigment, characterized by: (4) The method for producing a particulate composite oxide blue-green pigment according to claim 3, wherein coprecipitation is carried out by simultaneously adding a mixed salt solution and an alkaline solution to a coprecipitation medium. (5) The method for producing a particulate composite oxide blue-green pigment according to claim 3, wherein the firing temperature is 700°C or higher. (6) Claim 3, wherein the pH during coprecipitation is within the range of 7 to 10.
A method for producing a fine particle composite oxide blue-green pigment as described in . (7) The molar ratio of the constituent components aluminum (Al), cobalt (Co) and chromium (Cr) to cobalt 1: aluminum 0.5-2.0 and chromium 0.1-3
4. The method for producing a fine particulate composite oxide blue-green pigment according to claim 3.