JPS6015580B2 - yellow iron oxide pigment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a yellow iron oxide pigment having a rice grain-like (ellipsoidal) particle shape and a narrow particle size distribution, and a method for producing the same.

The aim is to provide a yellow iron oxide pigment with excellent color tone, dispersibility, and heat resistance, further expand its existing uses, and create new uses such as heat-processable resins, cosmetics, and traffic paints. It's about to be explored. At present, the yellow acid pigments include chlorine lead, strontium yellow, cadmium yellow, and penzidine yellow. Since all of these are toxic or carcinogenic, their use has naturally been regulated in order to prevent environmental pollution and protect the health of the public. In view of this situation, the color material industry is eagerly awaiting the development of an excellent non-toxic yellow pigment to replace the above-mentioned toxic yellow pigment. Yellow iron oxide has a Goeite structure with a composition of Q-Fe00 days, is called goethite, loess, ocher, etc., and has been used as a coloring material since ancient times.

It is non-toxic, tear resistant and stable, and inexpensive. Its uses range from paints, printing inks, and building materials to coloring cosmetics, cigarette filter paper, and poultry feed because it is nontoxic. Also,
After the war, it began to be used as a raw material for magnetic powder for magnetic recording, and demand for it has increased markedly as magnetic recording methods have progressed and spread. However, its properties as a pigment are not satisfactory and there is much room for improvement. That is, they have drawbacks such as a slightly unclear color tone, high viscosity due to the acicular particle shape, and poor heat resistance. For this reason, substitution with the above-mentioned toxic yellow pigment has been restricted, and for some time,
There was a strong demand for improving the characteristics and quality of this pigment.
Currently, yellow iron oxide is produced by applying hydrolysis of an aqueous ferrous sulfate solution and air oxidation reaction to grow microcrystal nuclei to a desired particle size.

At this time, there are 20,000 methods, which are a method using iron scraps and a method using ammonia gas, as methods for very gently neutralizing the ferrous sulfate aqueous solution and promoting crystal growth. The former is described in detail in, for example, Nobuoka et al., Koka, 66, 412 (1963). Regarding the latter, see Yada, Electronic Ceramics '72, Kanade. 1, P. 15. From these documents and FIGS. 3 and 4 described below, conventional yellow iron oxide has an acicular tactid particle morphology, and its axial ratio:
Kunhan Jun is over 50. The manufacturing method involves crystal growth in an aqueous solution of an insoluble salt, and considering the formation mechanism, it is extremely difficult to make the particle size of the product more uniform or to obtain a more homogeneous product than at present, just by adjusting the manufacturing conditions. It is also impossible to change the shape or axial ratio of the particles. Therefore, as shown in FIGS. 3 and 4, currently commercially available iron oxide has a wide particle size distribution, with a mixture of large and small particles and uneven axial ratios of acicular particles. It is well known that the physical properties exhibited by a powder system are generally correlated with the particle morphology of the powder system. The particle morphology of pigments affects color tone, bay hiding power, oil absorption, coloring power, rheological properties when used as a paint, strength of paint film, etc. In the case of yellow iron oxide, if large particles and small particles coexist, the physical properties exhibited by the large particles are different from those exhibited by the small particles, but as a powder, they exhibit physical properties as a statistical average that cancel each other out. . Taking color tones as an example, Nobuoka, Carpenter Examination Report, No. 331, P. As described in 33 (Hisho 44), the color shown by large particles and the color shown by small particles are different, so when they are mixed, it becomes a subtractive color mixture like the color mixture of paints, which changes the brightness and saturation. becomes smaller and the color tone becomes darker. In other words, it is ideal for the pigment to be a woven material with a narrow particle size distribution. Furthermore, there is a demand for a pigment with a small axial ratio of acicular particles, good dispersibility, and low oil absorption. Through many years of research on yellow iron oxide, the present inventors have understood its essential drawbacks, and in response to the needs of this industry,
He has conducted extensive research and contributed to improving the quality of this product.

For example, in patents, Ando, Nobuoka, Hakama Kimishō 31-32
Group: Nobuoka, Asai, Ato, Special Public Service No. 53-28158; Nobuoka, Asai, Ato, U. S. Pat. , 3,969, Group 4:
Nobuoka et al., Special Publication No. 55-9016, etc. Some of these technologies have been contracted and implemented. This time, we have developed a new technology. They successfully improved the particle morphology of yellow iron oxide from needle-like to rice-grain-like and narrowed the particle size distribution. This made it possible to dramatically improve various properties as a pigment, such as color tone, dispersibility, and stability. Next, the configuration of the present invention will be explained.

First, a ferric salt aqueous solution and an alkaline aqueous solution are reacted to prepare an iron hydroxide precipitate. In this case, the iron salt used is a hydroxyl iron salt such as ferric sulfate, ferric chloride, and ferric nitrate. The concentration used is below 0.8M/〆, preferably around 0.2M/〆. On the other hand, alkalis include sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, and calcium hydroxide. The concentration used is 4M/lower, preferably around IM/〆. If the reaction is carried out at a concentration higher than a predetermined concentration, the product will become heterogeneous and the particle size distribution will become wider, resulting in unfavorable results. As mentioned above, the iron salt aqueous solution and the alkaline aqueous solution are reacted at -5 to 3000, but at this time, it is a necessary condition that the iron salt aqueous solution is added to the alkaline aqueous solution. If this is done in reverse, the particle morphology of the product will be acicular with a large axial ratio. Furthermore, the temperature at which the two liquids are reacted is an important factor that affects the size of the product particles and the axial ratio of the particles. If it is 3000 or more, the axial ratio becomes too large and tactoids are likely to be formed.

The iron hydroxide precipitate prepared as described above is aged for at least 3 days, preferably about 1 day, and then subjected to the next hydrothermal treatment.

This ripening results in homogeneous, well-ordered particles. The aged precipitate is subjected to hydrothermal treatment at a temperature in the range of 120 to 25,000, preferably 18,000 for about 1 hour. When the processing temperature is low, it takes a long time for crystallization, and when the temperature is higher than a predetermined temperature, red iron oxide Q-Fe203 is mixed. This hydrothermal treatment promotes the crystallization of the amorphous iron hydroxide precipitate, and the dissolution and precipitation action results in grain-like iron oxide hydroxide Q-Fe00.
In other words, yellow iron oxide is produced.

The outline of the present invention is as described above; that is, this technology relates to the adjustment of particle morphology.

The key point of this new technology was in the preparation conditions for iron hydroxide precipitation at the initial stage. This series of technologies is a collection of combinations of conditions at each stage. There are a huge number of combinations of conditions, but most of them yield ineffective results. However, since no theory regarding the adjustment of crystal morphology has yet been established, useful results can only be expected by carefully experimenting with many conditions. The inventors
Through many experiments, they finally found useful conditions for preparing rice grain-like yellow iron oxide. Next, the present invention will be explained by examples. Ferric chloride FeC as iron salt
13. Use a 5M aqueous solution (approximately 0.2M/so) of the mother LO, and use a 75/2 aqueous solution (approximately IM/so) of sodium hydroxide NaOH as the alkali. Both liquids -5~3
At 5° C., an aqueous FeC13 solution is added to an aqueous NaOH solution to perform a precipitation reaction to prepare an iron hydroxide precipitate. In this case, the excess free alkali concentration in the mother liquor is approximately 0.4 K/
It's a sleeve. If this free alkali concentration is too higher than IM/T, the particle morphology will collapse, which is not preferable. When the iron hydroxide precipitate is aged with the mother liquor for one day and then subjected to hydrothermal treatment at 180° C. for about one hour, iron hydroxide oxide Q-Fe00 day, that is, yellow iron oxide is produced. Table 1 shows typical pigment properties of the results of this experiment, with the reaction temperature for precipitation being a variable. Table 1 1) BET method, 2) JISK5101, 3) Volume of precipitate in water, 4) From the results in Table 1 (see Figure 1),
As the reaction temperature increases, both the long and short axes grow better.

However, since the growth of the long axis is greater than that of the short axis, the axial ratio increases with increasing temperature. And 300
The axial ratio increases rapidly from around 0. The specific surface area is approximately proportional to the oil absorption amount, and a smaller one is preferable, but it is not preferable that the axial ratio of the particles increases and the bulk increases when dispersing the particles. The settled volume or bulk increases in proportion to the axial ratio. The hidden Bey force increases almost in proportion to the short axis of the particle. Regarding the relationship between acicular particles and pigment properties, see Nobuoka, Carpentry Test Report, No. 331, P. 35 (1969);
This was reported in detail in Nobuoka, Ado, and Asai, Color Materials Research Presentation (1980). Generally, in terms of pigment properties, it is ideal for particles to have a spherical shape with the smallest surface energy. In the case of acicular particles, the color tone and hidden Bay force are mainly determined by the short axis (width).
is controlled by. From the results in Table 1, it is found that particles having a rice grain shape are suitable for use as pigments when the reaction temperature is 3000 or less, and in particular particles in the range of 15 to 20o0 have a mari ratio of about 3 or less. Pigments are used as coloring materials in paints, printing inks, cosmetics, etc.

Therefore, color tone, dispersibility in vehicles, and weather resistance are important properties. In the case of yellow iron oxide, the color tone changes depending on the long axis of the particles. In other words, there is a correlation between the minor axis diameter and brightness. Practically speaking, the desired brightness of yellow iron oxide varies depending on the application. In fact, each company offers several types of products. As shown in Table 1, the hidden bay power changes depending on the size of the short axis diameter, and pigments with a large value have a large brightness. Smaller pigments become transparent and are therefore used as transparent yellow pigments (low-oversity). As mentioned above, it goes without saying that spherical particles exhibiting the minimum surface energy are best for pigment dispersibility in a vehicle, but in the case of yellow iron oxide, a method for synthesizing spherical particles has not yet been invented. .

The present inventors improved the conventional acicular particles into rice grain-like particles and improved various properties. This is similar to considering a steel sewing needle and a ball bearing as powder and comparing their dispersion characteristics into a vehicle. The former is bulky (intertwined and difficult to disperse, but
The latter is easy to disperse at low altitudes. Rice grain-shaped yellow iron oxide is
Compared to needle-shaped ones of the same color, the oil absorption is lower,
It is easy to disperse and has a low viscosity when dispersed. These properties are very desirable as a pigment. Note that superiority resistance and heat resistance are inherent to the compound, but in the case of pigments, the homogeneity, crystallinity, particle size distribution, etc. of the powder affect them.
The yellow iron oxide of the present invention is particularly excellent in terms of these drawbacks because it is completely crystallized by hydrothermal treatment, as described above. Next, the present invention will be explained in more detail with reference to Examples. Example 1 Aqueous solutions of FeC13/Fine 2050/So and NaOH75/2 were prepared, and both solutions were cooled to -2°C.

Then, while praying carefully, I put Fe into the NaOH aqueous solution.
C13 aqueous solution is gradually added to form Fe(OH)3 precipitate. The liquid temperature after precipitation is approximately 0°C. This precipitate is aged with the mother liquor for one day, with occasional stirring. The sedimentation volume of the precipitate after aging is about 250 ml, so discard the top solution and transfer the top of the 300 ml precipitate containing the mother liquor to a Teflon beaker.
The mixture was placed in an autoclave and subjected to hydrothermal treatment at 180 qo for 6 minutes. The pressure at this time is the saturation pressure of water vapor.
By this treatment, the brown precipitate of amorphous Fe(OH)3 is completely crystallized and turns into a crystalline yellow precipitate. When this was washed with water, the settling volume of the precipitate was as low as 150'. When filtered and dried, iron hydroxide oxide in the form of rice grains yields -Fe00 days, that is, yellow iron oxide.

The pigment properties of this are as follows. Particle diameter, major axis: 13
4 nm, short European 5 m, axial ratio: 2.4, specific surface area: 35 / m, hidden bay power: 530 / m, yield: 15 m, sedimentation volume: 10 / m, (see Figure 1) ).

Example 2. Fe2 (S04) 336 evening/So and NaOH75 evening/
2. Prepare each aqueous solution and cool both solutions to 9°C.

Then, while praying well, Fe was added to the NaOH aqueous solution.
2(S04)3 aqueous solution was gradually added, Fe(OH)3
Make a precipitate. The liquid temperature after the precipitation is about 10 qo. Thereafter, rice grain-shaped yellow iron oxide is obtained in exactly the same manner as in Example 1. The pigment properties of this are as follows. Particle diameter, maximum axis: 194 nm, short axis: 7 mm, axial ratio: 2.8 Specific surface area:
30/evening, hidden power: 580/evening, yield: 15 evening.
Example 3 Fe (N03) 3 Group 2075 Yu/Soto KOHIOO
Prepare aqueous solutions of Tano 2 and keep both solutions at 1900.

Then, while often crossing the ocean, KOH and Fe(
N03)3 aqueous solution is gradually added to form Fe(OH)3 precipitate. The liquid temperature after the precipitation is about 20°C. Thereafter, semi-granular yellow iron oxide is obtained in exactly the same manner as in Example 1.
The pigment properties of this are as follows. Particle diameter, major axis: 26
Tsumugi m, short axis: 8 m, axial ratio: 3.2, specific surface area: 26 w/w, concealment power: 920 w/w, yield: 16 w/w, (Figure 2
reference).

[Brief explanation of the drawing]

1 and 2 are electron micrographs of a yellow iron oxide pigment obtained by the method of the present invention at a magnification of 40,000 times. 3 and 4 are 40,00 pm electron micrographs of a conventional yellow iron oxide pigment. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. Yellow iron oxide having an ellipsoidal (rice grain-like) particle shape,
Its long axis: 100-350 nm, axial ratio: long axis / short axis = 1
．． A yellow iron oxide pigment, characterized in that it is in the range of 5 to 3.2. 2 Prepare iron hydroxide by adding and mixing a ferric salt aqueous solution at a temperature of 30°C or less into an alkaline aqueous solution at a temperature of 30°C or less, and after aging it, add it at a temperature of 120 to 250°C. A method for producing a yellow iron oxide pigment, which comprises performing hydrothermal treatment to produce iron oxide hydroxide powder. 3. To prepare iron hydroxide, adjust the concentration of the ferric salt aqueous solution to 0.5.
3. The method according to item 2, characterized in that the reaction is carried out at an alkali aqueous solution concentration of 4 M/l or less. 4. Iron hydroxide is prepared by reacting with a pre-calculated amount of alkali in excess of the formula amounts of ferric salt and alkali required for stoichiometric neutralization. 3. The method according to item 2, wherein the free alkali concentration in the total liquid volume is 1.0 M/l or less after the reaction is completed. 5. The method according to item 2, wherein after the precipitation reaction of iron hydroxide is completed, the precipitate is aged together with the mother liquor for about 1 day, and then subjected to hydrothermal treatment.