JPS638221A - Production of zinc ferrite pigment - Google Patents

Abstract

PURPOSE:To produce zinc ferrite pigment having improved heat resistance, dispersibility and yellow clarity, by precipitating and depositing zinc hydroxide from a water-soluble zinc compound on yellow iron oxide pigment in an aqueous medium, calcining the pigment at high temperature and washing with water. CONSTITUTION:Yellow iron oxide pigment is dispersed into water and an aqueous solution of a water-soluble zinc compound such as zinc chloride, etc., and an aqueous solution of an alkalizing agent such as NaOH, etc., are simultaneously added to the dispersion. The mixed solution is adjusted to pH about 7.0-9.0, stirred and zinc hydroxide is precipitated and deposited on the surface of the pigment at about 0-40 deg.C. The prepared mixture is washed with water, dried, calcinied at about 900-1,050 deg.C and gradually cooled in a temperature range of about 300-600 deg.C for >=about 30min. Then the cooled calcined substance is washed with water into <=about 0.2wt% inorganic salt content in the formed pigment. By this method zinc ferrite pigment having improved dispersibility, heat resistance, strong yellow and high clarity is obtained.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a method for producing a zinc ferrite pigment, and more specifically, its purpose is to provide a zinc ferrite pigment that has excellent heat resistance, dispersibility, and yellow brightness. .

(Prior Art and its Problems) Hitherto, as yellow inorganic pigments, lead oxide, iron oxide, cadmium yellow, etc. have been widely used.

Since the pigments themselves have insufficient heat resistance, yellow lead and iron oxide yellow are difficult to use, for example, for coloring synthetic resins. Furthermore, although cadmium yellow has excellent heat resistance, its use may be restricted from the viewpoint of pollution.

Zinc ferrite pigments are also known as yellow inorganic pigments other than those mentioned above. Brown and yellow zinc ferrite pigments are known, but yellow zinc ferrite pigments have hard particles and insufficient dispersibility in synthetic resins. There is a disadvantage that a large amount of inorganic salt remains, and when the resin is colored at a relatively high temperature, the clarity of the color tone of the colored product decreases significantly, resulting in only a dull colored product. Furthermore, since this zinc ferrite pigment has a yellow color close to brown, there is a demand for a pigment with a brighter yellowish tone.

(Means for Solving the Problems) The present inventor has solved the problems of the prior art as described above, and as a result of intensive research in order to meet the demands of the above-mentioned prior art, has found that the dispersibility of the conventional yellow zinc ferrite pigment is It was discovered that the defect was due to the conditions during the production of this pigment, namely that the Fe component and Zn component were mixed in a dry process, and that the defect in heat resistance was caused by the inclusion of a relatively large amount of inorganic salt in the pigment. Furthermore, we found that this is due to the fact that these inorganic salts are tightly encapsulated in the pigment particles due to the dry synthesis method, and therefore cannot be sufficiently removed by washing with water, etc. .

Based on these findings, further research revealed that when manufacturing zinc ferrite pigments, the Fe and Zn components are mixed wetly, that is, using an aqueous medium.
It has been found that the resulting zinc ferrite pigment particles are soft and easily dispersible, and that the inorganic salts included as impurities are sufficiently removed by water washing in post-treatment, and that sufficient heat resistance can be imparted to the resulting pigment. .

Furthermore, the hue of the zinc ferrite pigment obtained is determined by the addition of aluminum, -
It has been found that by adding a rum compound and/or a titanium compound, the color tone becomes even more yellowish.

That is, the present invention is a method for producing a zinc ferrite pigment, which comprises depositing zinc hydroxide on a yellow iron oxide pigment from a water-soluble zinc compound in an aqueous medium, firing at a high temperature, and washing with water.

Next, to explain the present invention in more detail, the yellow iron oxide pigment used in the present invention may be a conventionally known yellow iron oxide pigment. Useful in methods.

In the production method of the present invention, a Zn component is incorporated into the yellow iron oxide pigment as described above, and the main feature is that the Zn component is incorporated in a wet manner, that is, using an aqueous medium.

Preferred zinc compounds for inclusion of the Zn component include any water-soluble zinc compound such as zinc chloride, zinc sulfate, zinc nitrate, etc. Particularly preferred among these water-soluble zinc compounds is zinc chloride; by using zinc chloride, a moderate amount of chlorine ions remain in the pigment, which can be used as a flux in the subsequent firing process. Because it works, too much;
Sufficient firing can be achieved without increasing the firing temperature, and a zinc ferrite pigment with a brighter yellow tint can be obtained.

The amount of water-soluble zinc compound used for yellow iron oxide pigment is:
The preferred range is 50 to 55 moles of Zn atoms per 100 moles of Fe atoms in terms of Fe atoms and Zn atoms;
If the amount of Zn atoms is less than the above range, iron oxides such as iron oxides such as iron oxides will be produced due to excess Fe, resulting in the problem of dull or reddish color tone.On the other hand, if the amount of Zn atoms exceeds the above range, chlorine If it is excessive, there will be a problem that uneven baking will easily occur, and the object of the present invention will not be achieved sufficiently, which is not preferable.

The method of incorporating the Zn component into the yellow iron oxide pigment may be any method as long as it is a method of depositing zinc hydroxide from a water-soluble zinc compound onto the surface of the yellow iron oxide pigment particles using an aqueous medium. (1) A method in which a yellow iron oxide pigment is dispersed in water, and an aqueous solution of a water-soluble zinc compound and an aqueous alkali agent solution are simultaneously injected into this dispersion.

(2) A method in which a water-soluble zinc compound is dissolved in an aqueous dispersion of a yellow iron oxide pigment, and then an alkaline agent or its aqueous solution is added gradually or all at once.

(3) A method in which an aqueous dispersion of a yellow iron oxide pigment is made alkaline and an aqueous solution of a water-soluble zinc compound is added thereto.

Either method can be used. In either method, sufficient stirring is desirable during deposition. A particularly preferred method is method (1) above, which allows the precipitation and attachment of zinc hydroxide to be carried out at a constant pH, thereby making it possible to most uniformly attach zinc hydroxide to the surface of the yellow iron oxide pigment particles. .

According to the method described above, zinc hydroxide and other impurities such as inorganic salts are attached to the surface of the yellow iron oxide pigment particles, so unlike the conventional dry method, the action and effect of the zinc compound is sufficient. Impurities such as unnecessary inorganic salts can be easily and sufficiently removed by washing with water.

In the above, the conditions for precipitation and attachment of zinc hydroxide also affect the effects of the present invention, and the dispersion concentration of the yellow iron oxide pigment is preferably about 1.5 to 8% by weight, for example.
The concentration of the aqueous solution of the water-soluble zinc compound is preferably about 10 to 70% by weight, and the concentration of the alkaline agent (for example, alkali metal hydroxide or ammonia) is preferably about 10 to 50% by weight.

When zinc hydroxide is precipitated and attached to the surface of the yellow iron oxide pigment particles, the pH of the aqueous medium is preferably in the range of 7.0 to 9.0. If the pH exceeds 9.0, the yellow color of the yellow iron oxide pigment obtained will not be sufficiently improved, and the chlorine content in the mixture will be insufficient, resulting in an insufficient amount of chloride to act as a flux during firing. , there is a risk of firing defects. If the pH is less than 7.0, precipitation of zinc hydroxide will be insufficient, the composition of Fe component and Zn component will be non-uniform, and the amount of chlorine in the mixture will be excessive, resulting in non-uniform firing during subsequent firing. This is not preferable because it causes

Further, the temperature at which zinc hydroxide is precipitated and attached to the surface of the yellow iron oxide pigment particles is preferably in the range of 0 to 40°C, and within this range, the best color tone and firing effect can be achieved during subsequent firing.

In the present invention, it has been found that by adding a third metal component at the time of mixing the Fe component and the Zn component described above, the yellow clarity of the resulting pigment is further improved. Such additives are aluminum compounds or titanium compounds or both.

As the aluminum compound, for example, common aluminum salts such as aluminum chloride, aluminum sulfate, and aluminum nitrate are preferred, and as the titanium compound, common titanium compounds such as titanium chloride, titanium sulfate, titanic acid, and metatitanic acid are preferred. These aluminum compounds and titanium compounds may be used simultaneously.

By adding such an aluminum compound and/or a titanium compound at the same time as or before or after depositing zinc hydroxide, the resulting pigment becomes more yellowish and its sharpness is improved. The yellowness of the pigment obtained can be improved depending on the amount of the aluminum compound and/or titanium compound added, but if the amount added is too large. Since the firing conditions may change and defective products may be produced, the amount used is preferably 1.35% by weight or less of the yellow iron oxide pigment when aluminum or titanium is a chloride; , +3.5ffif for substances other than chloride
It is preferably less than fi%. This is because if a large amount of chloride is used, a large amount of chlorine remains in the mixture, which may cause uneven firing during firing. The addition method is as described above (
In addition to methods 1) to (3), any method may be used as long as it is performed before firing.

The mixture obtained as described above is thoroughly washed with water and heated to a temperature of about 120°C for a sufficient temperature of 97°C. After drying, the next firing process is performed.

The firing process is performed at a temperature of about 900 to 1050°C and a temperature of about 0.5 to
It is preferable to carry out the reaction for 2 hours; at temperatures below 900°C, the color tone becomes brown and it is difficult to develop a clear yellow color;
At temperatures exceeding 0° C., sintering of particles may proceed, resulting in poor dispersion.

The same applies to the firing time.

Furthermore, although the reason is unknown, the color tone of the pigment obtained changes depending on the time for cooling the fired product after firing.Although rapid cooling may be used, slow cooling should be performed over 30 minutes or more after firing. As a result, the yellowness of the pigment obtained was increased and the color became clearer. Particularly in the present invention, it is preferable to slowly cool the product at a temperature of 600 to 300°C for 30 minutes or more after firing.

Next, the cooled baked product is dispersed in water to elute the remaining inorganic salts. This elution can be easily performed by stirring the pigment in water.

On the other hand, in the case of the conventional dry method, many of the pigment particles contain inorganic salts as impurities, so it is difficult to wash away the inorganic salts sufficiently by washing with water. When the resin is colored with a pigment, the salt acts as a catalyst for the deterioration of the resin, causing the color of the colored product to become dull.

However, in the present invention, the inorganic salt can be easily eluted for the above-mentioned reasons, and the inorganic salt in the pigment can be easily removed. According to the present invention, the heat resistance of the pigment (
It was discovered that the dullness of the color tone of the colored product due to the temperature when coloring the resin was rapidly improved, and the problem of dullness of color did not occur. Therefore, the amount of residual inorganic salt in the pigment of the present invention is preferably 0.2% by weight or less.

Thereafter, the pigment of the present invention is obtained according to conventional techniques such as washing with water, drying, and pulverization.

(Functions and Effects) According to the present invention as described above, as already mentioned, the pigments are significantly improved compared to conventional zinc ferrite pigments.

A zinc ferrite pigment with improved dispersibility and heat resistance, strong yellow color, and great clarity is provided.

Next, the present invention will be explained in more detail with reference to Examples.

In the text, parts and percentages are based on weight unless otherwise specified.

Example 1 40 parts of yellow iron oxide pigment were dispersed in 1500 parts of water,
While thoroughly stirring this dispersion, a solution of 30.7 parts of zinc chloride dissolved in 200 parts of water and a solution of 18 parts of caustic soda dissolved in 200 parts of water were simultaneously injected into the dispersion. The temperature during injection was 25°C, and the pH of the mixture was 7.0.
-9.0.

After thoroughly stirring the mixture for 30 minutes, it was filtered and washed with water.
It was dried at 20°C for 12 hours. Next, dry this product at 900℃
After firing for 1 hour at a temperature of ~1050°C, 40°C from the firing temperature
It took 6 hours to gradually cool down to 600 - 30℃.
It took 45 minutes to cool down to 0°C).

The cooled material was thoroughly dispersed in 100 times the volume of water, and the remaining inorganic salts were removed by filtration and washing with water. Thereafter, it was dried to obtain a bright yellow zinc ferrite pigment of the present invention. The residual amount of inorganic salt 1 in this product was 0.2% or less.

Example 2 In Example 1, 0.54 parts of aluminum chloride was added to an aqueous solution of zinc chloride, and the same procedure as in Example 1 was repeated to obtain a bright yellow zinc ferrite pigment of the present invention. The amount of inorganic salt present in this product was 0.2% or less.

Example 3 In Example 1, 1.7
4 parts of metatitanic acid was added, and the same procedure as in Example 1 was carried out to obtain a bright yellow zinc ferrite pigment of the present invention. The amount of inorganic salt present in this product was 0.2% or less.

Example 4 In Example 1, 1.7
4 parts of metatitanic acid was added, and 0.54 parts of aluminum chloride was added to the aqueous solution of zinc chloride to obtain a vivid yellow zinc ferrite pigment of the present invention in the same manner as in Example 1. The amount of inorganic salt present in this product was 0.2% or less.

The color tone, heat resistance and dispersibility of the yellow zinc ferrite pigment of the present invention obtained as described above were investigated.
Obtained the results in the table.

'7J 1 = = C Conventional product 3 2 2 Example 1
3-4 3-45 // 2 4 4 4-5 horns 454-55 The conventional products in Table 7gi above are zinc ferrite pigments produced by a dry method to which the method of the present invention was not applied.

The color tone was determined by placing each sample in soft polyvinyl chloride at a concentration of 1.
A sheet was formed by kneading at 45%, and the one with the clearest yellow color to the naked eye was evaluated as 5.

The heat resistance of each sample was 0.0% compared to polypropylene resin.
It was added at a rate of 3% and kneaded at 200° C. for 20 minutes to prepare a colored plate, and the degree of dullness of the color was judged with the naked eye, and the clearest one was evaluated as 5.

The dispersibility was evaluated using a 25 μm gauge, and the best one was evaluated as 5.

As mentioned above, the zinc ferrite pigment produced by the method of the present invention is
Compared to conventional zinc ferrite pigments, it is significantly superior in yellow clarity, heat resistance, and dispersibility.

Claims (8)

[Claims] (1) A method for producing a zinc ferrite pigment, which comprises depositing zinc hydroxide from a water-soluble zinc compound on a yellow iron oxide pigment in an aqueous medium, baking the pigment at a high temperature, and washing with water. (2) The method for producing a zinc ferrite pigment according to claim (1), wherein the water-soluble zinc compound is zinc chloride. (3) Precipitate adhesion of zinc hydroxide at a pH of 7.0 to 9.0.
A method for producing a zinc ferrite pigment according to claim (1). (4) The method for producing a zinc ferrite pigment according to claim (1), wherein the precipitation and attachment of zinc hydroxide is carried out at 0 to 40°C. (5) The method for producing a zinc ferrite pigment according to claim (1), wherein the firing temperature is 900 to 1050°C. (6) The method for producing a zinc ferrite pigment according to claim (1), wherein after firing, the zinc ferrite pigment is slowly cooled at a temperature in the range of 300 to 600°C for 30 minutes or more. (7) When washing with water, the inorganic salt in the produced pigment is 0.2 of the produced pigment.
The method for producing a zinc ferrite pigment according to claim (1), which is carried out until the zinc ferrite pigment is reduced to % by weight or less. (8) The method for producing a zinc ferrite pigment according to claim (1), further comprising adding an aluminum compound and/or a titanium compound as an additive.