JP2003138160A - Cobalt black pigment and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a black pigment having neither reddishness nor yellowishness and high coloring ability. SOLUTION: This black pigment which consists of tricobalt tetroxide powder obtained by baking cobalt hydroxycarbonate or cobalt hydroxide, has a specific surface area of >=1 m<2> /g, and L*-value of <=24, a*-value of -2.5 to 0 and b*- value of -2.5 to 0 in the L*a*b* color specification system and a 311 half-width index of <=0.30. A method for producing the black pigment is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cobalt-based black pigment used for coloring resins, glass, porcelains, etc., and in particular, it is excellent in colorability and jet blackness and is suitable for mechanical shearing force or high temperature heating. The present invention relates to a black pigment that enables stable coloring even under severe conditions of use and a method for producing the same.

[0002]

2. Description of the Related Art As black pigments, carbon black,
Copper / iron / manganese-based composite oxides and cobalt trioxide, which uses cobalt oxide as a starting material, are known, but all have a slight redness or low blackness (L ^*
It has a large value) or has a small specific surface area and is inferior in coloring property. Carbon black, magnetite-based black, copper / iron / manganese-based black, titanium black, etc. were used as black pigments used for coloring resins, glass, wares, etc., but black pigments with high jetness are few, especially A black pigment that can be used for resins, glass, wares, etc., often exhibits a reddish or yellowish color when subjected to mechanical shearing force or high heat, and a black pigment that can maintain a pure black color has not been heretofore known. In recent years, there has been an increasing demand for pure black pigments that do not exhibit reddish or yellowish colors in the form of resins, glass, burnt products, including electronic materials.

[0003]

In addition to the conventionally known black pigments, cobalt-based oxides, especially cobalt trioxide, are considered as black substances that may meet the above requirements. Cobalt trioxide was obtained by igniting cobalt-containing compounds such as cobalt monoxide, cobalt hydroxide, cobalt hydroxycarbonate, cobalt chloride, cobalt sulfate, cobalt nitrate, cobalt carbonate and cobalt acetate in the atmosphere. To obtain powder physical properties as a pigment, such as specific surface area of powder, blackness, and degree of crystallization, the specific surface area of the raw material cobalt-containing compound is large,
It has a high melting point, no sublimation property, is highly available on the market, and when used as a pigment, the powder has a large specific surface area in the sense that it has good coloring properties and does not exhibit redness or yellowness. ) Is excellent, and it is stable under heat and mechanically severe usage conditions, and many other conditions must be solved. The present invention intends to provide a black pigment that exhibits substantially no redness or yellowness and has a high degree of blackness and that is also excellent in colorability.

[0004]

Means for Solving the Problems As a result of intensive studies for solving the above-mentioned problems, the present inventor has found that cobalt trioxide powder obtained by firing cobalt hydroxycarbonate or cobalt hydroxide at a specific temperature is used. The present inventors have found that the pigment has a high degree of blackness, which has not been obtained with conventional black pigments, and has reached the present invention. That is, the present invention is a cobalt trioxide powder obtained by firing cobalt hydroxycarbonate or cobalt hydroxide, the specific surface area of which is 1 m ^2.
/ G or more, L ^* value is 24 or less in the L ^* a ^* b ^* color system, and both a ^* value and b ^* value are -2.5.
A black pigment characterized by being in the range of 0 to 0, and in particular, the 311 half-value width index of cobalt trioxide powder is 0.3.
It exists in the black pigment which is 0 or less. Further, the present invention resides in a method for producing a black pigment, which comprises heating cobalt hydroxycarbonate or cobalt hydroxide in an oxidizing atmosphere and firing at a temperature of 150 to 800 ° C.
A method of firing at a temperature of 50 to 800 ° C., and further, heating cobalt hydroxycarbonate or cobalt hydroxide in an oxidizing atmosphere to fire at a temperature of 200 ° C. or more and less than 500 ° C., and then cooling to a temperature of less than 200 ° C. Then, it is heated again in an oxidizing atmosphere and fired at a temperature of 500 to 800 ° C., which is a method for producing a black pigment.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The black pigment of the present invention comprises L ^* a ^* b
^{* In} color system, L ^* value is 24 or less, preferably 22
Below, it is usually 5 or more, and it is necessary that both the a ^* value and the b ^* value are in the range of −2.5 to 0. L ^* a ^*
The b ^* color system is a color system used to represent the color of an object, standardized by the International Commission on Illumination (CIE) in 1976, and adopted in JIS (Z8729) in Japan. In the L ^* a ^* b ^* color system, lightness is represented by L ^* , and chromaticity indicating hue and saturation is represented by a ^* and b ^* . If the value of L ^* a ^* b ^* is out of the above range, the blackness becomes insufficient.

The black pigment of the present invention must have a powder specific surface area of 1 m ² / g or more, and usually 140 m
² / g or less. If it is less than 1 m ² / g, the colorability will be poor.

In the present invention, in particular, in order to maintain the blackness even under severe conditions of use, such as the black pigment of the present invention being subjected to shearing force or being used at high temperature,
The value of L ^* a ^* b ^* is within the above range, and the 311 half-value width index of cobalt trioxide is 0.30 or less, preferably 0.24 or less, and usually 0.19 or more. is there. In the present invention, the 311 full width at half maximum refers to the full width at half maximum at the 311 lattice plane peak of cobalt tetraoxide when the diffraction angle (2θ) by the X-ray diffraction method is 36.850 degrees, and the crystallization, crystal It is a physical property value that depends on the degree of phase transition, crystal surface distortion, etc.The half-width index is the numerical value of the half-width when measured under the specific conditions described below. This is a parameter to be used as a guide.
If the parameter of the half-value width exceeds 0.30, the pigment may be slightly reddish or yellowish and may not maintain the blackness when it is subjected to shearing force during use or is baked at high temperature. .

The black pigment of the present invention is obtained as cobalt tetraoxide powder by heating cobalt hydroxycarbonate or cobalt hydroxide powder in an oxidizing atmosphere and oxidizing and firing. The firing temperature is appropriately in the temperature range of 150 to 800 ° C., and if it is less than 150 ° C., firing is insufficient,
If it exceeds 800 ° C, the L ^* value becomes high and the blackness decreases. The firing time is determined as appropriate depending on the firing temperature, the amount of firing, and the firing method. In particular, in order to obtain a black pigment that maintains blackness even under severe usage conditions such as being subjected to shearing force, the firing temperature needs to be as high as 650 to 800 ° C. If the temperature is lower than 650 ° C., a reddish or yellowish color is exhibited under heat or mechanically severe use conditions, and stable blackness cannot be maintained. The pigment must be in the form of fine powder, but when the raw material is fired at a high temperature of 500 to 800 ° C., solidification due to sintering is likely to occur, and the fine powder is not obtained, which is not preferable. In order to prevent solidification due to sintering, first, the raw material is preheated in an oxygen atmosphere and fired at a temperature of 200 ° C. or higher and lower than 500 ° C., preferably 300 to 450 ° C.,
It is desirable to cool to a temperature of less than 200 ° C., preferably 100 ° C. or less, heat again in an oxygen atmosphere and fire at a temperature of 500 to 800 ° C. In the cooling step, it is preferable that the preheated raw material is once transferred to another container and then consolidated and stirred. When firing is performed using an electric furnace capable of controlling the temperature in several stages, it is possible to set a temperature pattern and control the cooling process in-line using the same container.

[0009]

EXAMPLES Next, the contents of the present invention will be described in more detail by way of examples. In addition, each physical-property value of the black pigment shown in the Example and the comparative example was measured by the test method shown below.

(1) Specific surface area BET method Specific surface area was measured using a specific surface area measuring device Micromeritex "Asup 2010" (manufactured by Shimadzu Corporation).

(2) L ^* value, a ^* value, and b ^* value Using a spectrocolorimeter JS555 (manufactured by Color Techno System Co., Ltd.), each value at a color change angle of 10 ° was measured by a solid powder diffusion method using a D65 light source. Measured by

(3) Full width half-power index X-ray diffractometer ("Mini Flex" manufactured by Rigaku Denki Co., Ltd.,
X-ray tube: Cu bulb, output: 30 kV × 15 mA) was used to determine the half width at the peak of the 311 lattice plane of cobalt trioxide when the diffraction angle 2θ was 36.850 degrees.

(4) 2 g of the shear resistant black pigment sample was crushed 10 times in a mortar to obtain L ^* value, a
^* Changes in the value and b ^* values were measured. In addition, the change in color of the sample attached to the mortar was visually observed, and it was determined that the sample that retained the initial black color was ◯, and that that exhibited a slight reddish or yellowish pattern was x.

Example 1 10 g of cobalt hydroxycarbonate (manufactured by Nippon Kagaku Sangyo Co., Ltd.)
Was fired in an air furnace at temperatures of 400 ° C. and 725 ° C. for 1 hour, respectively, to obtain a highly pure cobalt trioxide powder containing substantially no other cobalt compound. The L ^* value, the a ^* value, the b ^* value, and the half-value width index of the obtained powder were measured, and further the shear resistance test was performed. The test results are shown in Table 1. The powders produced at the firing temperatures of 400 ° C. and 725 ° C. both showed good blackness, but when a shearing force was applied, the firing temperature of 400 ° C.
Those having a temperature of ℃ had a b ^* value exceeding the standard value and exhibited a slight yellowish tinge.

Comparative Example 1 10 g of cobalt hydroxycarbonate (manufactured by Nippon Kagaku Sangyo Co., Ltd.)
Was baked at a temperature of 100 ° C. for 24 hours and at a temperature of 850 ° C. for 1 hour in an atmospheric furnace. At a firing temperature of 100 ° C, it does not turn black even if it is burned for a long time (the raw material color remains pink), and at 850 ° C, it has a high L ^* value and exhibits a grayish color that cannot be said to be black. Was small.
Table 1 shows the test results of the powder obtained at the firing temperature of 850 ° C.

Example 2 10 g of cobalt hydroxide (manufactured by Ise Chemical Co., Ltd.) was baked in an atmospheric furnace at temperatures of 400 ° C. and 700 ° C. for 1 hour, respectively,
A high-purity cobalt trioxide powder containing substantially no other cobalt compound was obtained. The L ^* value, the a ^* value, the b ^* value, and the half-value width index of the obtained powder were measured, and further the shear resistance test was performed. The test results are shown in Table 1. The powders produced at the firing temperatures of 400 ° C. and 700 ° C. both showed good blackness, but when a shearing force was applied, those produced at a firing temperature of 400 ° C. b
^{* The} value exceeded the standard value and exhibited a slight yellowish tinge.

Example 3 Cobalt hydroxycarbonate (manufactured by Nippon Kagaku Sangyo Co., Ltd.) 700
g was calcined at a temperature of 400 ° C. for 6 hours in an atmospheric furnace, once cooled to a temperature of 150 ° C. or lower, and then calcined again at a temperature of 700 ° C. for 6 hours. The obtained trifluorocobalt oxide powder passed through a sieve having an opening of 600 μm in about 100%.

Comparative Example 2 Firing was performed under the same firing conditions (the same raw materials were used) as in Example 3 except that no heat treatment (preliminary firing) was performed. The amount of the obtained trisodium trioxide powder that passed through a sieve having an opening of 600 μm was about 30% of the whole.

[0019]

[Table 1]

[0020]

According to the present invention, the blackness is excellent,
It is possible to provide a black pigment which is capable of maintaining excellent blackness under heat or mechanically severe usage conditions and has good colorability.

Claims (5)

[Claims] 1. A cobalt trioxide powder obtained by firing cobalt hydroxycarbonate or cobalt hydroxide,
The specific surface area is 1 m ² / g or more, the L ^* value is 24 or less in the L ^* a ^* b ^* color system, and the a ^* value and b
^* A black pigment having a value in the range of -2.5 to 0. 2. The black pigment according to claim 1, wherein the trivalent cobalt oxide powder has a 311 full width at half maximum index of 0.30 or less. 3. The method for producing a black pigment according to claim 1, wherein cobalt hydroxycarbonate or cobalt hydroxide is heated in an oxidizing atmosphere and calcined at a temperature of 150 to 800 ° C. 4. The method for producing a black pigment according to claim 1, wherein cobalt hydroxycarbonate or cobalt hydroxide is heated in an oxidizing atmosphere and calcined at a temperature of 650 to 800 ° C. 5. Cobalt hydroxycarbonate or cobalt hydroxide is heated in an oxidizing atmosphere to 200 ° C. or above 500.
After firing at a temperature of less than ℃, cooled to a temperature of less than 200 ℃, heated again in an oxidizing atmosphere to 500 ~ 800 ℃
The method for producing a black pigment according to claim 1, wherein the black pigment is fired at the temperature of.