JP2872903B2 - Method for producing green pearlescent pigment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a pearlescent pigment,
More specifically, as compared with a conventional pearlescent pigment having a color tone of only an interference color of light, a green pearlescent pigment which exhibits a strong green color, particularly when the base is white, has a brilliant color, and has a more strongly developed color tone. , The fields seeking these colors,
For example, an object of the present invention is to provide a pearlescent pigment that is useful in fields requiring design, in addition to fields such as resins, paints, inks, and building materials.

[0002]

2. Description of the Related Art Among the known pearlescent pigments, the most popular one is a so-called iris color in which the color tone is changed by changing the film thickness of titanium dioxide coated on mica flakes. It is.
However, the hue of the pearlescent pigment obtained by these methods is generally pale and soft,
It cannot produce dark colors. This is because the light used as the interference color in the entire light is limited to only a small part.

[0003] When a paint using the above-mentioned conventional pearlescent pigment is applied, scattered light is removed by making the base black, so that the color tone becomes slightly stronger as a whole, but when the base is white, it is affected by confusion light. It is a situation where it becomes whitish and a slight iris color appears. Further, as a pigment having a relatively strong color tone, there is a pigment in which mica flakes are coated with iron oxide having a high concealing property like titanium dioxide, and this pearlescent pigment is a so-called gold to russet pigment of yellow to brown. Color tone and lacked strong color variations.

[0004]

As described above, the conventional pearlescent pigment based on titanium dioxide as a coating layer of mica flakes has a weak color tone only by using the iris color, and titanium dioxide is used as the coating layer. Other than the base, there was an iron oxide type having a relatively strong color, but the color tone was yellow or brown and there was a dislike for lack of color variation. Accordingly, an object of the present invention is to provide a green pearlescent pigment having a stronger color tone and a large variety of colors while maintaining the strong brilliancy of titanium dioxide in view of the above-mentioned state of the art.

[0005]

The above object is achieved by the present invention described below. That is, the present invention provides a titanium dioxide-coated mica flake having a titanium dioxide layer on the mica flake.
The click is suspended in an aqueous medium, on the surface thereof, by the precipitant
These metal Te cobalt salts, nickel salts and zinc salts
To precipitate a composite oxide or a hydrate thereof, followed by calcination
Cobalt oxide Te, in the manufacturing method of the green pearlescent pigments Ru to form a coating of the composite oxide layer made of nickel oxide and zinc oxide, as a precipitant of the metal salts, the use of a substance that generates ammonia by heating This is a method for producing a green pearlescent pigment.

[0006]

[Function] By coating a titanium dioxide layer on mica flakes and a composite oxide layer composed of cobalt oxide, nickel oxide and zinc oxide on the mica flakes, the titanium dioxide layer has a high hiding power and is easy to produce a glitter. While maintaining the brilliancy, the surface of the titanium dioxide layer is coated with a composite oxide layer of cobalt, nickel, and zinc exhibiting a stronger green color as a coloring component, and heat-treated to form a spinel phase in the composite oxide layer. By forming the pigment, properties as a green pearlescent pigment can be exhibited, and at the same time, various properties of the composite oxide layer can be obtained.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in more detail with reference to preferred embodiments. As the mica flakes which are the coating base used for the green pearlescent pigment of the present invention, commonly used muscovite can be used. However, the mica flakes that can be used as a coated mother body are not limited to muscovite, and other mica flakes can be used as long as the surface smoothness and aspect ratio are similar to the above muscovite. Needless to say, this is possible.
The muscovite having a particle size of about 1 to 100 [mu] m is used, and a thin one having a relatively uniform particle size of about 20 to 50 [mu] m and a thickness of about 0.1 [mu] m is preferable.

For the titanium dioxide to be coated on the surface of the mica flake, a titanium salt is used as a titanium source, and more specifically, a reagent such as titanyl sulfate, titanium tetrachloride or an industrial material can be used. As a method of coating titanium dioxide on muscovite flakes, a pre-dissolved titanium solution is added to a pre-heated muscovite suspension,
This is a method of depositing a hydrate or oxide of titanium on muscovite flakes by hydrolyzing a titanium salt, and this method is known per se.

[0009] The titanium dioxide-coated mica slurry thus obtained is washed with water, and further coated with cobalt oxide,
It is provided to a coating base for forming a composite oxide layer composed of nickel oxide and zinc oxide. At this time, the slurry is once filtered, and the obtained cake is dried at 120 ° C. for about 12 hours, and then the dried flakes are heat-treated at 700 to 900 ° C. for about 1 hour to be provided with the coating of the composite oxide. It is also possible.

[0010] The titanium dioxide-coated mica flakes obtained as described above emit a green iris color and exhibit excellent glitter regardless of whether they are heat-treated. As the composite oxide coated on the titanium dioxide layer on mica flakes,
Finally, it reacts with titanium dioxide to form a secondary composite oxide. As the composite oxide selected at that time, a combination of metals is selected which exhibits an unprecedented strong color development after its formation and has excellent various resistances, that is, excellent weather resistance and chemical resistance.

More specifically, cobalt-, nickel-, zinc- and titanium-based composite oxides exhibiting strong color development in the prior art composite oxide pigments and having a spinel crystal structure are selected. This system, as an inorganic pigment, not only has a stronger color development than other complex oxide systems, for example, rutile type titanium, antimony, nickel system, titanium, antimony, chromium system yellow pigments, as well as those systems Extremely excellent resistance to Also, because it is based on titanium dioxide,
Brightness is also sufficiently ensured.

In the present invention, a composite oxide of cobalt, nickel and zinc is selected as a coloring component in addition to titanium dioxide for the above reasons. The metal salts used for these coatings, sulfates, nitrates, chlorides, acetates, and the like used in the production of conventional composite oxide pigments can all be used, and the preferable ratio of these metals is Although the stoichiometric ratio is titanium: cobalt: nickel: zinc = 2: 1: 2: 1, the difference between the characteristics of coating on the pigment particle surface and the precipitation characteristics of each metal while securing the brilliancy. In consideration of the maximum, cobalt: nickel: zinc = 1: 2: 1 with respect to titanium.
it is conceivable that.

In other words, it is considered that the smaller the amount of the composite metal oxide newly coated after coating the mica flakes with titanium dioxide, the easier it is to adhere to the surface of the titanium dioxide layer of the mica flakes more effectively. . Therefore, the quantitative relation of metal to titanium dioxide is desirably 0.1 / 1 <(cobalt + nickel + zinc) / titanium <0.5 / 1 in consideration of the strength of the final color tone. If the amount is larger than this range, agglomeration of the mica flakes occurs during the coating reaction, and the glitter is significantly impaired. If the ratio is less than 0.1 / 1, a strong color tone cannot be obtained.

The mixing ratio of each metal except for titanium basically depends on the stoichiometric mixing ratio. However, even if the ratio slightly deviates from this ratio, the effect on the color tone is small. However, it should be noted that a large deviation may cause weak coloring or dullness.
Such a metal salt is introduced and dissolved in an aqueous suspension of bright green mica flakes previously coated with titanium dioxide, and the concentration of the green mica flake suspension is 100%.
g / liter or less is desirable. If the concentration is too high, the mica flakes agglomerate during the coating reaction, significantly impairing the glitter.

In the present invention, as a precipitating agent for depositing such a metal salt on the surface of the titanium dioxide layer of mica flakes, a compound which produces ammonia by heating, for example,
Urea or a derivative thereof is used. By introducing and dissolving urea or its derivative in the above mica flake suspension, no change occurs around room temperature, but when heated with stirring, urea or its derivative uniformly dissolved in the entire system Starts to decompose, and uniform and fine composite oxide or hydrate particles thereof are deposited on the mica flakes.
The reason for this is that urea or a derivative thereof as a precipitant has no local concentration odor in the solution, and the complete precipitant which can never be obtained by the method of successively adding the precipitant by a dropping method conventionally used is not obtained. Uniformity is assured.

The urea or its derivative as described above is preferably used in an amount of 1 to 5 mol per equivalent of the metal relative to the metal salt. If the amount is more than this range, the composite metal oxide film is cracked, the surface is roughened, and mica aggregates occur. In this way, the mixed suspension of the brilliant green mica flakes and the metal salt and urea or its derivative is preferably 70 to
By heating and stirring in a temperature range of 100 ° C. for 0.5 to 12 hours, metal oxides or hydrates thereof are deposited on the titanium dioxide layer on the mica flakes.

Next, the slurry on which the oxide or its hydrate is deposited is washed with water, filtered, and dried at 120 ° C. for about 12 hours.
By performing a heat treatment at 1,000 ° C. for 0.5 to 2 hours, a spinel phase is formed from the composite oxide containing titanium dioxide, and the bright pearlescent pigment of the present invention having a strong brilliant color can be obtained. .

[0018]

Next, the present invention will be described specifically with reference to examples and comparative examples. The parts or percentages in the text are based on weight unless otherwise specified. Example 1 45 parts of the bright green mica flake pigment of Comparative Example 1 below was suspended in 1,000 parts of water, and then 6.7 parts of nickel chloride hexahydrate, 4.2 parts of zinc nitrate hexahydrate and nitric acid 4.1 parts of cobalt hexahydrate are dissolved in 100 parts of water and added to the suspension. This mixed suspension is stirred well, and after each component is uniformly dissolved, temperature rise is started. When the temperature reaches 100 ° C., the temperature is kept constant, and the state is maintained as it is. After a while, a precipitate of an oxide or a hydrate of each metal starts to precipitate on the titanium dioxide-coated mica flakes. Thereafter, heating and stirring are continued, and after 3 hours, the reaction is terminated, followed by washing with water and filtration. The cake obtained is dried at 120 ° C. for at least 12 hours.

The dried mica flakes were heat-treated at 700 ° C. for 1 hour in an oxidizing atmosphere to obtain a bright green pearlescent pigment of the present invention. This was made into a paint with an acrylic cracker, and applied to art paper with a black band using a 6 mil film applicator. The black band developed the same brilliant green color as in Comparative Example 1, and the white base was A strong green color tone was exhibited while maintaining the brilliancy.

Comparative Example 1 550 parts of water was added to 20 parts of flaky muscovite having a thickness of 0.05 to 0.2 μm and an average particle diameter of 40 μm, and the mixture was suspended with stirring to obtain a liquid A. Next, 70 parts of titanyl sulfate (32% of titanium dioxide) and 150 parts of water were mixed to dissolve titanium, and 100 parts of 98% sulfuric acid was further added to obtain a liquid B. The solution A was heated with stirring, and when the temperature of the solution reached 95 ° C., the solution B was added and the mixture was aged by heating for 3 hours. The resulting titanium dioxide-coated mica slurry was washed with water and filtered. Dry for 12 hours.

Next, the dried cake is placed in an oxidizing atmosphere for 8 hours.
Heat treatment was performed at 00 ° C. for 1 hour to obtain a white mica flake pigment that generates a bright green iris color coated with titanium dioxide. This was made into a paint with an acrylic cracker and applied to art paper with a black belt using a 6 mil film applicator. The black band developed a bright green color, and the white background provided a glitter, The color was almost white.

Comparative Example 2 45 parts of the glittering white mica flake pigment prepared according to Comparative Example 1 were suspended in 1,000 parts of water, then 6.7 parts of nickel chloride hexahydrate and zinc nitrate hexahydrate. 2 parts and 4.1 parts of cobalt nitrate hexahydrate are dissolved in 100 parts of water, and 4.5 parts of caustic soda as a precipitant solution are dissolved in 100 parts of water. The metal salt solution and the caustic soda solution thus obtained are gradually and simultaneously dropped into the above mica flake suspension under stirring at PH8, and the metal oxide or its hydration is placed on the bright green mica flake pigment. Let the objects come out.

After completion of the dropping, the coated mica flakes are washed with water and filtered, and the obtained cake is dried at 120 ° C. for 12 hours or more. Metal oxide or coated titanium dioxide coated mica flakes with their hydrates are already fairly aggregated at this time, it was observed before dropping metal salt glitter was almost lost. This dried mica flake was heat-treated at 700 ° C. for 1 hour in an oxidizing atmosphere to obtain a glittering green pearlescent pigment of Comparative Example. This was made into a paint with an acrylic cracker and applied to art paper with a black belt using an art paper with a 6 mil film applicator. In the part, a whitish green color tone was shown.

[0024]

According to the present invention as described above, by covering a mica flake with a titanium dioxide layer and a composite oxide layer composed of cobalt oxide, nickel oxide and zinc oxide, a high hiding power and a high brilliancy can be obtained. Cobalt showing a stronger green color development as a coloring component on the surface of the titanium dioxide layer while maintaining the excellent glitter of the titanium dioxide layer,
Coating a composite oxide layer of nickel and zinc and heat treating,
By forming a spinel phase, characteristics as a green pearlescent pigment can be exhibited, and at the same time, various characteristics of the composite oxide layer can be obtained.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Mineki Machitori 1-7-6 Nihombashi Bakurocho, Chuo-ku, Tokyo Inside Dainichi Seika Kogyo Co., Ltd. (56) References JP-A-4-65741 (JP, A) JP-A-7-157688 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C09C 1/00-3-12

Claims (5)

(57) [Claims] 1. Titanium dioxide-coated mica flakes having a titanium dioxide layer on mica flakes are suspended in an aqueous medium and the composite oxides of these metals are precipitated from cobalt, nickel and zinc salts by means of a precipitant. Thing or its water
Precipitate and then bake to form a coating of a composite oxide layer consisting of cobalt oxide, nickel oxide and zinc oxide
The method of manufacturing a green pearlescent pigment was Ru is as precipitant of the metal salt, the manufacturing method of the green pearlescent pigment, characterized by using a substance that generates ammonia by heating. 2. The method for producing a green pearlescent pigment according to claim 1, wherein the precipitant is urea or a derivative thereof. 3. The method for producing a green pearlescent pigment according to claim 1, wherein the slurry concentration of the titanium dioxide-coated mica flake is 100 g / liter or less. 4. The method according to claim 1, wherein the amount of urea or a derivative thereof is the above-mentioned metal salt.
3. The method for producing a green pearlescent pigment according to claim 2 , wherein the amount is 1 to 5 mol per 1 equivalent of the metal. 5. Precipitation on mica flakes coated with titanium dioxide
The composite oxide or its hydrate of the who 600～1,0
The method for producing a green pearlescent pigment according to claim 1, wherein the heat treatment is performed at 00 ° C.