JP2997206B2 - Fine particle composite oxide black 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 particle composite oxide black pigment and a method for producing the same. The primary particles are extremely small as compared with conventional pigments of the same type, and the degree of blackness, tinting strength, sharpness, and color development are high. And excellent heat resistance,
The present invention relates to a pigment useful for paints, thin films, printing inks and the like, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, composite oxide black pigments are widely known as inorganic pigments having excellent heat resistance, color separation properties, durability and the like. For example, they are widely used as colorants for paints and heat-resistant inks, and as colorants for the ceramic industry. It is used. Among the above black pigments, Cu-Cr-based, Cu-Cr-Mn-based, Cu
-Mn type, Cu-Fe-Mn type, etc., and the structure is generally a spinel structure. The method for producing these pigments is mainly a dry method, and pigments are produced by mixing, baking and pulverizing oxides and carbonates of each component.

On the other hand, there are not many types of copper oxide-containing composite oxide black pigments, and a Co-Fe-Cr-based so-called cobalt black pigment is known. The production method is a dry method like the black pigment containing copper. However, the above-mentioned dry method has a disadvantage that a large amount of energy is required for pulverizing a coarse pigment which is a sintered body, and a fine pigment cannot be obtained because the coarse pigment which is a sintered body is pulverized. Is the current situation. Further, in a wet method using an aqueous solution of each constituent element, there is a possibility that fine-particle pigments can be obtained. However, for Co-Fe-Cr-based pigments, production methods by the wet method have been completely reported and proposed. Absent.

[0004]

The dry method that has been practiced in the prior art is to mix oxides or carbonates of cobalt, iron and chromium, etc., sometimes in combination with a mineralizer, and after firing at a high temperature, It is a method of pulverizing the sintered particles with a powerful pulverizer, and as long as each component is not a fine particle,
The product after sintering is also unlikely to become transparent fine particles, and even if such fine particles are present, these fine particles sinter at the time of sintering and require a large amount of energy for fine pulverization.

On the other hand, it is expected that a cobalt black composite oxide black pigment can be obtained by a wet method. In this case, a simple method of mixing and precipitating a solution of a salt of each constituent element, that is, cobalt, divalent, is used. Or trivalent iron and 3
A mixed metal salt solution in which a valent chromium salt is dissolved is coprecipitated using an alkali such as caustic soda as a precipitant, washed with water,
After drying, a method of firing is considered. However, in this method, when the temperature at the time of precipitation is low, too fine particles are formed, and the pigment is not suitable. Further, under high temperature, the particle growth of only iron oxide is intense, and it is difficult to obtain fine-particle pigments.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to meet the above demand, and have found that a fine composite oxide black pigment (cobalt black) comprising cobalt, iron, chromium and, if necessary, manganese is produced. After the wet precipitation reaction, it was confirmed that the desired particulate pigment was obtained by subjecting the precipitate to air oxidation at 50 ° C. or lower.

That is, the present invention relates to cobalt, iron and chromium.
Having a spinel structure composed of an oxide of
The molar ratio of the metal is 0.5 to iron with respect to 1 cobalt.
1.2 and chromium are in the range of 0.8 to 1.4, and the BET specific surface area is 50 m ² / g or more and 100 m ² / g or less; A mixed solution of 3 or 4 components of divalent iron salt, trivalent chromium salt and, if necessary, divalent manganese salt
And the amount of alkali moles required for precipitation as a precipitant
An alkaline aqueous solution containing 1.1 to 1.5-fold excess of alkali, after generating the coprecipitate simultaneously added to the precipitation medium, blowing air in a temperature range of 50 ° C. or less, fine face
A fine particle composite oxide black pigment, which comprises producing a precursor of the pigment, drying and firing.

According to the present invention, a salt of a metal constituting the fine particulate composite oxide black pigment (cobalt black) is mixed and precipitated as a hydroxide of the metal with an alkali precipitant, and the precipitate is subjected to liquid phase air oxidation. By performing the treatment, the subsequent firing temperature can be extremely lowered, and a fine-grained composite oxide black pigment having fineness and a single spinel phase, excellent in blackness, coloring power and sharpness can be obtained. . Furthermore, the black pigment thus obtained is soft and excellent in dispersibility, despite being very fine particles.

An important point of the present invention is that the oxidation reaction after precipitation of each constituent metal salt of the fine particle cobalt black pigment as an alkali hydroxide is intended to oxidize iron and manganese. Fine particles are formed. For this purpose, the oxidizing agent used may be any oxidizing agent capable of oxidizing iron and manganese. For example, a strong oxidizing agent such as hydrogen peroxide may be used.
Since chromium having a valence of 6 is oxidized to hexavalent, it cannot be used in the production method of the present invention. In addition, an oxidizing agent that produces a residual insoluble matter by an oxidation reaction is not desirable because it adversely affects the obtained pigment. Because oxidation by air can prevent oxidation of iron and manganese under mild conditions while preventing oxidation of chromium to hexavalent,
The size of the obtained pigment particles can be appropriately controlled, and this is the most suitable oxidation method in the production method of the present invention.

[0010]

Next, the present invention will be described in more detail with reference to preferred embodiments. As the salts of the constituent elements used in the present invention, all of those conventionally used for producing complex oxide black pigments, such as sulfates, nitrates, chlorides and acetates, can be used.

The constituent ratio of each component in the pigment of the present invention is cobalt: iron: chromium = 1: 0.
9: 1.1 is most preferable, and when the pigment of the present invention contains manganese, cobalt: iron: chromium: manganese = 1: 1: 1.2: 0.25 is most preferable in terms of metal molar ratio. At this ratio, a black pigment excellent in blackness and coloring power can be obtained.

Further, according to the results of the study by the present inventors, when the molar ratio of the constituents cobalt (Co), iron (Fe), chromium (Cr) and manganese (Mn) does not contain manganese, The composition change in the range of 0.5 to 1.2 iron and 0.8 to 1.4 chromium per 1 cobalt, and when the pigment of the present invention contains manganese, 0 As long as the composition changes in the range of 0.6 to 1.3, chromium of 0.9 to 1.5 and manganese of 0.1 to 1.0, the resulting pigment is not significantly affected by blackness and tinting strength. Was observed. Further, as the proportion of iron in the pigment increases, the pigment obtained becomes reddish, and when iron exceeds 1.2 in molar ratio, the blackness of the pigment obtained decreases remarkably. On the other hand, when the amount of chromium increases, the redness of the obtained pigment tends to decrease, and the pigment tends to be slightly greenish. Further, when manganese is contained, the blackness of the obtained pigment increases, but when the manganese molar ratio exceeds 0.5, the blackness of the obtained pigment decreases, and when the manganese molar ratio exceeds 1.0, the obtained blackness decreases. The resulting pigment becomes reddish.

All the metal salts of the respective constituent elements as described above are dissolved in water to form a mixed salt aqueous solution. The concentration of the metal salt at that time is suitably about 5 to 50% by weight as a whole in the above molar ratio. This mixed solution is simultaneously dropped into a precipitating medium prepared in advance together with an aqueous alkali solution such as caustic soda as a precipitating agent. The concentration of the reactant at this time is not so great as to have a particularly bad influence on the precipitated product, but is preferably 0.05 mol / L to 0 mol in consideration of the workability and the subsequent oxidation step using air or the like. .2 mol / l is appropriate, and the tendency is that the lower the concentration of the reactant, the smaller the pigment particles obtained.

The synthesis temperature of the crude pigment is usually in the range of
That is, when the temperature is in the range of 0 ° C. to 100 ° C., the effect can be sufficiently exhibited. However, when the synthesis temperature exceeds 50 ° C., the growth of precipitated particles (coarse pigment) is large, and the coloring power of the obtained pigment is slightly impaired. There is a tendency. In addition, the pH at the time of synthesis
Does not significantly affect any pH range as long as it is an alkali side of 8 or more. However, as a general tendency, the precipitated particles tend to be large at low pH,
Also, when the pH is high, small precipitated particles are easily obtained.

For the above reasons, the pH at the time of synthesis of the crude pigment has a subtle effect on the ease of handling of the subsequent product and on the blackness and tinting strength of the final product, pigment. Excess alkali is added after precipitation. In this case, the excess amount of alkali is in the range of 1.1 to 1.5 times, preferably about 1.1 times, the number of moles of alkali required for precipitation, and the resulting pigment has the best blackness and coloring power. . When the amount of excess alkali is small, the growth of precipitated particles is suppressed, and although the pigment is finely made into fine particles, the blackness of the obtained pigment tends to be insufficient. In addition, when the amount of excess alkali is large, the growth of precipitated particles is intense, and it is difficult to obtain fine-particle pigments, chromium dissolves in excess alkali, and this may cause a change in the composition of the obtained pigment, or may be used in a subsequent treatment. Adversely affect. After the precipitate is formed while stirring the reaction mixture for 30 minutes to 1 hour in this way, aging is performed for about 5 to 20 minutes to complete the precipitation reaction.

Next, air is blown into the reaction solution containing the coprecipitate with stirring to completely oxidize divalent iron and manganese. The amount of air at this time is 1.0 to 2.0 liter / min. Within this range there is no significant effect on quality. However, it takes a long time to complete the reaction if the amount of blowing air is small, and at the same time, the precipitated particles are slightly large, and a pigment having insufficient coloring power is obtained.On the other hand, if the amount of blowing air is too large, the precipitated particles are too small,
The color tone of the obtained pigment becomes reddish, and a pigment having poor dispersibility is obtained. The temperature at the time of oxidation is preferably 50 ° C. or lower, and more preferably, 20 to 30 ° C. At a high temperature, the growth of precipitated particles is remarkable, and it is difficult to obtain a fine pigment.

Under the above reaction conditions, the air blowing time is approximately 3 to 4 hours. The end of the reaction can be known by measuring the oxidation-reduction potential of the solution. That is, under these conditions, at the start of the reaction, +600 to +500 mV
At the end of the reaction drops to around +50 mV. Under these conditions, trivalent chromium is hardly oxidized to hexavalent, and very little.

Next, the obtained precipitated particles are filtered, washed with water, and dried at a temperature of about 100 ° C. to 120 ° C. By firing the obtained dried product in an oxidizing atmosphere at a temperature of 600 ° C. to 800 ° C. for 30 minutes to 1 hour, the fine particle composite oxide black pigment of the present invention, that is, fine particle cobalt black can be obtained.

The fine particle composite oxide black pigment of the present invention thus obtained is excellent in blackness, coloring power and sharpness as compared with the pigment obtained by a conventional dry method, and has a BET.
By adjusting the specific surface area to be in the range of 50 to 100 m ² / g and adjusting the size of the pigment fine particles, the pigment can be well dispersed in the coating system.

[0020]

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 Cobalt chloride 6
57.1 parts of water salt, 62.5 parts of ferrous sulfate heptahydrate and 40
Weigh 124 parts of a chromium sulfate solution, add water and completely dissolve it to make about 500 parts in total. Next, 69 parts of caustic soda is weighed as a precipitant, and water is added to make about 500 parts.

About 1,000 parts of water as a precipitating medium prepared in advance is adjusted to a temperature of about 25 ° C. by a gas burner, an electric heater, or the like, and an aqueous mixed salt solution and an aqueous caustic soda solution are simultaneously dropped therein, The precipitation reaction is completed in about 30 minutes to 1 hour. At this time, care is taken so that the pH is about 11. When the dropping of the mixed salt aqueous solution is completed, an excess of aqueous sodium hydroxide solution is continuously added, and the mixture is aged for about 20 minutes.

Next, a glass tube processed into a thin capillary was prepared, and 1.2 l / min. Blow in air at the flow rate. During this time, stirring was continued, the rotation speed of the stirring blade was adjusted to about 300 rpm, the temperature was adjusted to 25 ° C., and air blowing was continued for about 3 hours. The initial greenish gray precipitate changes to a reddish brown precipitate at the end.

Next, the product is taken out, washed sufficiently with decantation to remove residual salts, and filtered. Next, it is dried at a temperature of 100 ° C. to 120 ° C. for 12 hours or more. The dried product was fired at 700 ° C. for 1 hour in an oxidizing atmosphere and then cooled. The pigment thus obtained has fine particles, a BET specific surface area of 75 m ² / g, a high blackness, excellent sharpness, high coloring power, and good dispersibility. Pigment (fine particle cobalt black).

The particulate composite oxide black pigment is sufficiently dispersed with a melamine / alkyd resin (PHR30) using a paint conditioner (manufactured by Red Devil Co., Ltd.). Then, the color was applied to art paper with a black belt using a 6-mil applicator, and the color tone was observed. In addition, the coloring power was observed for those diluted with titanium oxide.

Example 2 53.7 parts of cobalt chloride hexahydrate,
Weigh 62.5 parts of ferrous sulfate, 125 parts of a 40% chromium sulfate solution and 9.0 parts of manganese sulfate, add water, and add
00 parts. Next, 70 parts of caustic soda is measured as a precipitant, and water is added to make 300 parts. Hereinafter, the pigment obtained by the same method as in Example 1 has fine particles and a BET specific surface area of 70 m ² / g as in Example 1, and has a higher blackness than the pigment of Example 1. It was excellent in sharpness, high coloring power and good dispersibility.

Example 3 A pigment of the present invention was obtained in the same manner as in Example 1 except that the molar ratio of metals was changed to cobalt: iron: chromium = 1: 0.9: 1.1. The BET specific surface area of this pigment was 75 m ² / g, and the pigment was higher in blackness, superior in image clarity, higher in coloring power, and better in dispersibility than the pigment of Example 1.

Example 4 A pigment of the present invention was obtained in the same manner as in Example 2 except that the molar ratio of metals was changed to cobalt: iron: chromium: manganese = 1: 1: 1.2: 0.25. The BET specific surface area of this pigment was 75 m ² / g, and the pigment was higher in blackness, excellent in image clarity, higher in coloring power, and better in dispersibility than the pigment of Example 2.

Comparative Example 1 53.7 parts of cobalt chloride hexahydrate, ferrous sulfate heptahydrate 6
Weigh 2.5 parts, 125 parts of a 40% chromium sulfate solution and 9.0 parts of manganese sulfate, and add water to make about 500 parts. Next, measure 70 parts of caustic soda as a precipitant,
Add water to make 300 parts.

Water, which is a precipitating medium prepared in advance, is used.
Adjust 1,000 parts to about 25 ° C with a gas burner or electric heater.
And the mixed salt aqueous solution and caustic soda aqueous solution
Occasionally, the precipitation reaction is completed in about 30 minutes to 1 hour.
Complete. Make sure that the pH at this time is around 11.
When the addition of the mixed salt aqueous solution is complete,
After continuous addition of the aqueous solution, the mixture is aged for about 20 minutes.

An air blowing oxidation reaction after aging is performed below.
Fine particles obtained in the same manner as in Example 1 , except that
The composite oxide black pigment had a somewhat large particle size and high blackness, but lacked sharpness.

Comparative Example 2 Commercially available basic cobalt carbonate (18% as cobalt oxide)
Parts), 19.9 parts of needle-like hydrous ferric oxide pigment, and 19.5 parts of chromium oxide are weighed, and an appropriate amount of water is added thereto, and thoroughly wet-mixed. This was calcined at 1,000 ° C. for 1 hour and then pulverized according to a conventional method to obtain a pigment. The pigment obtained by the dry method obtained as described above has larger primary particles than the pigments obtained in Examples 1 to 4, and has insufficient coloration.
It was inferior in blackness, coloring power and sharpness. Table 1 summarizes the above results.

[0032]Table 1 Hue and blackness Dispersibility Specific surface area  Conventional product Brown black, poor image quality Poor 6m^Two/ G Example 1 High blackness, high coloring power, good clarity good 75m^Two/ G Example 2 High blackness, high tinting strength, good clarity good 70 m^Two/ G Example 3 High blackness, high coloring power, good clarity good 75 m^Two/ G Example 4 High blackness, high coloring power, good clarity good 75 m^Two/ G Comparative example1 Inferior in blackness and poor in sharpness than in Example 2.^Two/ G Comparative example2 Redness black, blackness, coloring power are both small.^Two/ G * Hue, sharpness, dispersibility: melamine alkyd / PHR30 The conventional products in Table 1 above are commercially available composite oxide black
Pigment (cobalt black).

[0033]

As described above, according to the present invention, there can be obtained a fine particle composite oxide black pigment having a smaller particle diameter than conventional conventional pigments and having excellent blackness, coloring power and sharpness.
The pigment is used as a general paint, a coloring agent for building materials and a synthetic resin, and a coloring agent for ceramics, as well as the conventional pigment. For example, application as a black pigment for a black matrix such as a color filter, a black pigment for an inkjet, a black pigment for a special paint, and particularly a black pigment in a portion which may come into contact with a phosphor is expected.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tohru Kawakami 1-7-6 Nihombashi Bakurocho, Chuo-ku, Tokyo Inside Dainichi Seika Kogyo Co., Ltd. (72) Inventor Kenichi Yamane 1-7 Nihonbashi Bakurocho, Chuo-ku, Tokyo No. 6 Within Dainichi Seika Kogyo Co., Ltd. (56) References JP-A-53-81536 (JP, A) JP-A-58-60623 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB Name) C09C 1/00-1/42

Claims (5)

(57) [Claims] 1. A metal having a spinel structure composed of oxides of cobalt, iron and chromium, wherein
The ratio is 0.5 to 1.2 iron and chromium to 1 cobalt.
Is in the range of 0.8 to 1.4, and the BET specific surface area is 50 m ² / g or more and 100 m ² / g or less. 2. The particulate composite oxide black pigment according to claim 1, further comprising a manganese oxide. 3. The fine particle composite oxide black pigment according to claim 2 , wherein the manganese content is 1 or less with respect to 1 mole of cobalt. 4. A mixed solution of a cobalt salt, a divalent iron salt and a trivalent chromium salt, and optionally a trivalent or quaternary component of a divalent manganese salt, and the number of moles of alkali required for forming a precipitate as a precipitant.
Of an alkaline aqueous solution containing 1.1 to 1.5-fold excess of alkali, after generating the coprecipitate simultaneously added to the precipitation medium, blowing air in a temperature range of 50 ° C. or less, the precursor of the particulate pigment A method for producing a fine particle composite oxide black pigment, comprising producing a body, drying and firing. 5. The method for producing a particulate composite oxide black pigment according to claim 5, wherein the firing temperature is in the range of 600 to 800 ° C.