JPH0357055B2 - - Google Patents

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 bright yellow color. .

(Prior Art and its Problems) Hitherto, yellow lead, iron oxide yellow, cadmium yellow, and the like have been widely used as yellow inorganic pigments.
Yellow lead and iron oxide yellow are difficult to use, for example, for coloring synthetic resins, because the pigments themselves have insufficient heat resistance. Further, 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 in the resin, and when the resin is colored at a relatively high temperature, the sharpness of the color tone of the colored product is significantly reduced and only a colored product with a very dull color is obtained. 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 to meet the demands of the prior art, has found that the dispersibility of the conventional yellow zinc ferrite pigment is The defect is due to the conditions during the production of this pigment, namely Fe
It was discovered that the poor heat resistance was due to the fact that the pigment contained a relatively large amount of inorganic salts, and that these inorganic salts were synthesized by the method of synthesis. It has been found that this is due to the fact that since it is a dry process, it is tightly encapsulated in the pigment particles and cannot be sufficiently removed by washing with water or the like.

Based on this knowledge, further research revealed that when manufacturing zinc ferrite pigments, Fe component and Zn
By mixing the ingredients wetly, that is, using a water-washing medium, the resulting zinc ferrite pigment particles become soft and easily dispersible, and inorganic salts included as impurities are removed by washing with water during post-treatment. It has been found that the pigments can be sufficiently removed and impart sufficient heat resistance to the resulting pigment.

Furthermore, it has been found that the hue of the resulting zinc ferrite pigment can be made more yellowish by adding an aluminum compound and/or a titanium compound as an additive during the production of the zinc ferrite pigment.

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 included in the yellow iron oxide pigment as described above,
The main feature is that the Zn component is incorporated in a wet manner, that is, using an aqueous medium.

Preferred zinc compounds for use in incorporating 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 is used as a flux during the subsequent firing process. Therefore, sufficient firing can be achieved without raising the firing temperature too much, and a zinc ferrite pigment with a brighter yellow color can be obtained.

The amount of water-soluble zinc compound used for yellow iron oxide pigment is 100 Fe atoms in terms of Fe atoms and Zn atoms.
A range of 50 to 55 moles of Zn atoms per mole is preferred; if the amount of Zn atoms is less than the above range, Fe will be excessive and iron oxides such as red pepper will be produced, causing problems such as dull or reddish color tone. , while Zn
If the amount of atoms exceeds the above range, the problem arises that chlorine becomes excessive and uneven baking is likely to occur.
This is not preferable because the object of the present invention cannot be sufficiently achieved.

The method of incorporating Zn component into yellow iron oxide pigment is as follows:
Any method may be used as long as it deposits zinc hydroxide from a water-soluble zinc compound onto the surface of yellow iron oxide pigment particles using an aqueous medium. For example, (1) dispersing yellow iron oxide pigment in water; , a method in which 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 added gradually or all at once to an alkaline agent or its aqueous solution.

(3) A method in which an aqueous dispersion of 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 zinc hydroxide to be precipitated and adhered at a constant pH, so that zinc hydroxide can be most uniformly adhered to the surface of 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, and the concentration of the aqueous solution of the water-soluble zinc compound is preferably about 10 to 70% by weight, and an alkaline agent (e.g., alkali metal hydroxide or ammonia)
The concentration of is preferably about 10 to 50%.

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, and the amount of chloride that will act as a flux during firing will be insufficient, resulting in poor firing. Failure to do so may result in defects. Also, if the pH is less than 7.0,
Precipitation of zinc hydroxide becomes insufficient, and Fe component and Zn
This is not preferable because the composition with the other components becomes non-uniform and the amount of chlorine in the mixture becomes excessive, resulting in non-uniform firing during subsequent firing.

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 when mixing the Fe component and Zn component described above, the yellow color 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 resulting pigment improves as the amount of the aluminum compound and/or titanium compound added increases, but if the amount added becomes too large. Since the firing conditions may change and produce defective products, the amount used is preferably 1.35% by weight or less of the yellow iron oxide pigment when aluminum or titanium is a chloride; In the case of something other than a thing
It is preferably 13.5% by weight or less. In the case of chloride,
This is because if a large amount is used, there will be a large amount of chlorine remaining in the mixture, which may cause uneven firing during firing. In addition to the methods (1) to (3) above, any method of addition may be used as long as it is performed before firing.

The mixture obtained as above is thoroughly washed with water, dried thoroughly at a temperature of, for example, about 120°C,
Perform the next firing process.

The firing process is about 0.5 to 2
It is preferable to carry out the dispersion for a certain period of time. At a temperature below 900°C, the color tone becomes brown and it is difficult to develop a clear yellow color. On the other hand, at a temperature exceeding 1050°C, sintering of particles may proceed and poor dispersion may occur. The same applies to the firing time.

In addition, 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,
By slowly cooling the pigment over a period of more than 1 minute, the yellowness of the resulting pigment increased and 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 carried out by stirring the pigment in water.
On the other hand, in the case of the conventional dry method, there are many portions where inorganic salts, which are impurities, are incorporated into the pigment particles, so it is difficult to sufficiently wash away the inorganic salts by washing with water. When the resin is colored with a pigment, this inorganic salt acts as a catalyst for resin deterioration, 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, by reducing the residual amount of such inorganic salts to 0.2% by weight or less of the pigment, the heat resistance of the pigment (dullness of the color tone of the colored product due to the temperature when coloring the resin) can be drastically reduced. It was discovered that the problem of dull 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.

(Function/Effect) According to the present invention, as described above, the dispersibility and heat resistance are significantly improved compared to conventional zinc ferrite pigments, and the zinc ferrite pigment has a strong yellow color and a high definition. A ferrite pigment 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 was dispersed in 1500 parts of water, and 200 parts of this dispersion was added to the water while stirring well.
A solution of 30.7 parts of zinc chloride in 1 part of water,
A solution of 18 parts of caustic soda in 200 parts of water was simultaneously injected. The temperature at the time of injection was 25°C, and the pH of the mixture was within the range of 7.0 to 9.0.

The mixture was thoroughly stirred for 30 minutes, filtered, washed with water, and dried at 120°C for 12 hours. Next, add this dried product
After firing at a temperature of 900°C to 1050°C for 1 hour, it took 6 hours to gradually cool from the firing temperature to 40°C.
It took 45 minutes to cool down between 600 and 300℃).

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 in this product is 0.2
% or less.

Example 2 In Example 1, 0.54
of aluminum chloride was added thereto to obtain a bright yellow zinc ferrite pigment of the present invention at the same time as in Example 1. The amount of inorganic salt present in this product was 0.2% or less.

Example 3 In Example 1, 1.74 parts of metatitanic acid was added to the yellow iron oxide pigment dispersion, and the same process 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 4 In Example 1, 1.74 parts of metatitanic acid was added to the dispersion of yellow iron oxide pigment, and 0.54 parts of aluminum chloride was added to the aqueous solution of zinc chloride. A zinc ferrite pigment of the present invention was obtained. 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, and the results shown in Table 1 below were obtained.

Table 1 Pigment Color Tone Heat resistance Dispersibility Conventional product 3 2 2 Example 1 3-4 3-4 5 〃 2 4 4 4-5 〃 3 4 5 5 〃 4 5 4-5 5 In addition, the above Table 1 The conventional product is a zinc ferrite pigment produced by a dry method to which the method of the present invention was not applied.

The color tone was evaluated by kneading each sample in soft polyvinyl chloride at a concentration of 1.45% to form a sheet, and grading the color tone with a score of 5 for the one that best explained the yellowness to the naked eye.

Heat resistance was determined by adding each sample to polypropylene resin at a ratio of 0.3% and kneading it at 200℃ for 20 minutes to create a colored plate.The degree of dullness of the color was judged with the naked eye, and the clearest one was scored as 5. evaluated.

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

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

Claims (1)

[Claims] 1. 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. 2. The method for producing a zinc ferrite pigment according to claim 1, wherein the water-soluble zinc compound is zinc chloride. 3. The method for producing a zinc ferrite pigment according to claim 1, wherein the precipitation and attachment of zinc hydroxide is carried out at a pH of 7.0 to 9.0. 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, which comprises slowly cooling at a temperature in the range of 300 to 600°C for 30 minutes or more after firing. 7 Inorganic salts in the pigment produced by washing with water
The method for producing a zinc ferrite pigment according to claim 1, which is carried out until the zinc ferrite pigment becomes 0.2% 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.