JPH07157689A - Production of green nacreous pigment - Google Patents

Abstract

PURPOSE:To obtain a green nacreous pigment retaining strong brilliancy inherent in titanium dioxide, having more intense hue, and being various in color. CONSTITUTION:This production method comprises suspending a white nacreous pigment prepared by coating mica flakes with a titanium dioxide layer in an aqueous medium and coating the surface with a compound oxide layer comprising cobalt oxide, nickel oxide and zinc oxide from a cobalt salt, a nickel salt and a zinc salt, and a substance which forms ammonia upon heating is used as the pricipitant for the metal salts.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a pearlescent pigment,
More specifically, compared with conventional pearlescent pigments having a color tone of only light interference color, it is a green pearlescent pigment that exhibits a strong green color particularly when the base is white, has a glitter and has a stronger color tone. , Fields that require these tones,
For example, it is an object of the present invention to provide a pearlescent pigment that is useful in fields such as resins, paints, inks and building materials, as well as in fields requiring designability.

[0002]

2. Description of the Related Art The most popular colored pearlescent pigments known so far are generally based on so-called iris colors, which change the color tone by changing the film thickness of titanium dioxide coated on mica flakes. Is.
However, the hue of the pearlescent pigment obtained by these methods is generally light and soft,
It is not possible to produce a dark color. The reason for this is that the light used as an interference color in the whole light is limited to only a part.

When a coating material using the above-mentioned conventional pearlescent pigment is applied, since the scattered light is removed by blackening the base, the color tone becomes slightly strong as a whole, but when the base is white, it is affected by confusion light. It becomes whitish and a slight iris color appears. Also, 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 similar to titanium dioxide, and this pearlescent pigment is a yellow to brown so-called gold to russet type. There was a lack of strong color variations.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention As described above, the conventional pearlescent pigment based on titanium dioxide as a coating layer for mica flakes has a weak color tone only by utilizing an iris color. Other than the base, there are iron oxides with a relatively strong color, but there is a dislike of lacking variation in the color with a yellow or brown color. Therefore, in view of the situation of the prior art, an object of the present invention is to provide a green pearl luster pigment having a stronger color tone and a large variation of colors while maintaining the strong glitter of titanium dioxide.

[0005]

The above object can be achieved by the present invention described below. That is, the present invention is to suspend a white pearlescent pigment having a titanium dioxide layer on mica flakes in an aqueous medium, and from the cobalt salt, nickel salt and zinc salt, cobalt oxide, nickel oxide and zinc oxide on the surface thereof. In the method for producing a green pearlescent pigment covering a composite oxide layer consisting of, a method for producing a green pearlescent pigment, characterized in that a substance that generates ammonia by heating is used as a precipitant for the metal salt. .

[0006]

[Function] By coating a titanium dioxide layer on mica flakes and a composite oxide layer consisting of cobalt oxide, nickel oxide and zinc oxide on the flakes, the titanium dioxide layer has high hiding power and is easy to produce glittering properties. The surface of the titanium dioxide layer is coated with a complex oxide layer of cobalt, nickel and zinc showing a stronger green coloration as a coloring component while being kept bright and heat treated to form a spinel phase of the complex oxide layer. By being formed, the properties as a green pearlescent pigment can be exhibited, and at the same time, the properties of the composite oxide layer can be provided.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail with reference to the preferred embodiments. Commonly used muscovite can be used as the mica flakes that are the coating matrix used for the green pearlescent pigment of the present invention. However, the mica flakes that can be used as the coated mica are not limited to this muscovite, and if the surface smoothness and aspect ratio are similar to those of the above muscovite, other mica flakes can be used as well. It goes without saying that it is possible.
The muscovite having a particle size of about 1 to 100 μm is used, but a thin mica having a particle size of about 20 to 50 μm and a relatively uniform thickness of about 0.1 μm is preferable.

The titanium dioxide coated on the surface of the mica flakes uses a titanium salt as a titanium source, and more specifically, a reagent such as titanyl sulfate or titanium tetrachloride or an industrial material can be used. As a method of coating muscovite flakes with titanium dioxide, a pre-dissolved titanium solution is added to a preheated 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 itself is known.

The titanium dioxide-coated mica slurry thus obtained was washed with water, and then cobalt oxide,
It is used as a coating base for forming a composite oxide layer composed of nickel oxide and zinc oxide. At this time, the slurry is once filtered, 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 used for coating the above-mentioned composite oxide. It is also possible.

The titanium dioxide-coated mica flakes obtained as described above emit a green iris color and exhibit excellent brilliance regardless of whether they are heat-treated. As the composite oxide coated on the titanium dioxide layer on the mica flakes,
Finally, it also reacts with titanium dioxide to form a secondary composite oxide. The composite oxide selected at that time is selected from a combination of metals that exhibits a strong coloration that has never been obtained after its formation and has various resistances, that is, excellent weather resistance and chemical resistance.

More specifically, cobalt, nickel, zinc, and titanium-based composite oxides which exhibit strong color development and have a spinel-based crystal structure among the prior art composite oxide-based pigments are selected. This system is an inorganic pigment that is not only stronger in color development than other complex oxide systems, for example, rutile type titanium, antimony, nickel and titanium, antimony, chromium type yellow pigments, but also similar to those systems. The various resistances are extremely excellent. Also, because it is a titanium dioxide base,
The glitter is sufficiently secured.

In the present invention, a complex oxide of cobalt, nickel and zinc is selected in addition to titanium dioxide as the coloring component for the above reasons. The metal salt used in these coatings can be any of the sulfates, nitrates, chlorides, acetates, etc. used in the production of conventional composite oxide pigments, and the preferred ratio of these metals is Stoichiometrically, titanium: cobalt: nickel: zinc = 2: 1: 2: 1, but with the characteristic that the pigment particles are coated on the surface of the pigment and the precipitation characteristics of each metal, while maintaining the glitter. Considering the above, the maximum of titanium is cobalt: nickel: zinc = 1: 2: 1.
it is conceivable that.

That is, it is considered that, when the amount of the composite metal oxide newly coated after coating titanium dioxide on the mica flakes is small, it is easier to effectively adhere to the surface of the titanium dioxide layer of the mica flakes. . Therefore, it is desirable that the quantitative relationship of the metal with respect to titanium dioxide be 0.1 / 1 <(cobalt + nickel + zinc) / titanium <0.5 / 1, considering the final color strength. If the amount is more than this range, agglomeration of mica flakes occurs during the coating reaction, and the glittering property is significantly impaired. If it is less than 0.1 / 1, a strong color tone cannot be obtained.

The mixing ratio of each metal other than titanium basically depends on the stoichiometric mixing, but even if it deviates a little from this ratio, it has little effect on the color tone. However, it is necessary to be careful because a large deviation causes weak coloration and causes dullness.
Such metal salts are introduced and dissolved in an aqueous suspension of bright green mica flakes previously coated with titanium dioxide, the concentration of this green mica flake suspension being 100%.
It is preferably g / liter or less. If the concentration is too high, agglomeration of mica flakes will occur during the coating reaction, and the glitter will be significantly impaired.

Further, in the present invention, as a precipitant for causing such a metal salt to be projected on the surface of the titanium dioxide layer of the mica flake, in the present invention, a compound which produces ammonia upon heating, for example,
Urea or its derivative is used. By adding and dissolving urea or its derivative in the above mica flake suspension, no change occurs at around room temperature, but when heated with stirring, urea or its derivative uniformly dissolved in the whole system. Starts to decompose, and composite oxide or its hydrate particles, which are uniform and fine throughout, are projected on the mica flakes.
The reason for this is that urea or its derivative, which is a precipitating agent, does not have a local concentration gradient in the solution, and it cannot be completely obtained by the method of sequentially adding the precipitating agent by the conventionally used dropping method. Uniform uniformity is guaranteed.

The above urea or its derivative is preferably used in an amount of 1 to 5 mol per 1 equivalent of metal with respect to the metal salt. If the amount is more than this range, the composite metal oxide film may be cracked, the surface may be roughened, or mica may be aggregated. In this way, the mixed suspension of the bright green mica flakes, the metal salt and urea or its derivative is preferably 70-
By heating and stirring in the temperature range of 100 ° C. for 0.5 to 12 hours, the metal oxide or its hydrate is deposited on the titanium dioxide layer on the mica flakes.

Next, the slurry in which the oxide or its hydrate is deposited is washed with water, filtered, and dried at 120 ° C. for about 12 hours, and the dried mica flakes are dried at 600 to 600 ° C. in an oxidizing atmosphere.
By heat-treating at 1,000 ° C. for 0.5 to 2 hours, a spinel phase can be formed from the composite oxide containing titanium dioxide, and the bright and strongly colored green pearlescent pigment of the present invention can be obtained. .

[0018]

EXAMPLES Next, the present invention will be specifically described with reference to Examples and Comparative Examples. The parts or% in the text are based on weight unless otherwise noted. 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. The mixed suspension is well stirred to uniformly dissolve each component, and then the temperature rise is started. When the temperature reaches 100 ° C., the temperature is kept constant, and the state is maintained. After a while, a precipitate of an oxide of each metal or a hydrate thereof is precipitated on the titanium dioxide-coated mica flakes, but after that, heating and stirring are continued, the reaction is terminated after 3 hours, and the mixture is washed with water and filtered. The cake obtained is dried at 120 ° C. for 12 hours or more.

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. When this product 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 part developed a brilliant green color similar to Comparative Example 1, and the white background part was While maintaining the glitter, a strong green color tone was exhibited.

COMPARATIVE EXAMPLE 1 550 parts of water was added to 20 parts of scaly 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 prepare a solution 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 prepare a liquid B. The solution A was heated with stirring, and when the temperature reached 95 ° C, the solution B was added and the mixture was heated and aged for 3 hours, then the produced titanium dioxide-coated mica slurry was washed with water and filtered, and the obtained cake was heated at 120 ° C. It was dried for 12 hours.

The dried cake is then placed in an oxidizing atmosphere for 8 hours.
Heat treatment was carried out at 00 ° C. for 1 hour to obtain a white mica flake pigment which was coated with titanium dioxide and which generated a bright green iris color. When 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 belt part developed a bright green color, and the white background part had a glitter property, The color tone was almost white.

Comparative Example 2 45 parts of the bright white mica flake pigment prepared according to Comparative Example 1 were suspended in 1,000 parts of water, and then 6.7 parts of nickel chloride hexahydrate and zinc nitrate hexahydrate 4. 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 were gradually dropped at the same time into the above mica flake suspension under stirring at PH8, and the metal oxide or its hydration was obtained on the bright green mica flake pigment. Make things stick 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. The titanium dioxide-coated mica flakes coated with metal oxides or hydrates were already highly agglomerated at this point, with most of the glitter observed before metal salt addition was lost. The dried mica flakes were placed in an oxidizing atmosphere for 7
It was heat-treated at 00 ° C. for 1 hour to obtain a bright green pearlescent pigment of Comparative Example. When this was made into a paint with an acrylic cracker and applied to art paper with a black belt with a 6 mil film applicator, no glitter was seen at both the black belt portion and the white background portion, and the base was white. In the part, a whitish green color tone was shown.

[0024]

[Effects] According to the present invention as described above, by coating a titanium dioxide layer and a layer composed of cobalt oxide, nickel oxide and zinc oxide on mica flakes, titanium dioxide having high concealing power and easily exhibiting glittering properties While maintaining the excellent brilliance of the layer, the surface of the titanium dioxide layer is coated with a complex oxide layer of cobalt, nickel and zinc showing a stronger green coloration as a coloring component and heat-treated to form a spinel phase. As a result, the properties of the green pearlescent pigment can be exhibited, and at the same time, the properties of the composite oxide layer can be provided.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mineki Matori 1-7-6 Nihonbashi-Bakurocho, Chuo-ku, Tokyo Dainichi Seika Kogyo Co., Ltd.

Claims (5)

[Claims] 1. A white pearlescent pigment having a titanium dioxide layer on mica flakes is suspended in an aqueous medium, and on its surface, from cobalt salt, nickel salt and zinc salt, from cobalt oxide, nickel oxide and zinc oxide. In the method for producing a green pearlescent pigment covering the complex oxide layer, the substance for producing ammonia by heating is used as a precipitant for the metal salt. 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 flakes is 100 g / liter or less. 4. The method for producing a green pearlescent pigment according to claim 1, wherein the amount of urea or its derivative is in the range of 1 to 5 mol per 1 equivalent of metal. 5. The method for producing a green pearlescent pigment according to claim 1, wherein the coated metal complex oxide or a hydrate thereof is heat-treated at 600 to 1,000 ° C.