Iron Oxide Pigment Development Overview and Related Applications (4)

2α-FeOOH=α-Fe2O3+H2O

2.3. Transparent Iron Black

Production of transparent iron black using coprecipitation. First, ferrous hydroxide and iron hydroxide were separately prepared, then mixed by equivalents, and dehydrated by heating to form transparent iron black.

The chemical reaction formula is as follows:

6FeSO4+NaClO3+3H2SO4=3Fe2(SO4)3+NaCl+3H2O

Fe2(SO4)3+6NaOH=2Fe(OH)3↓+3Na2SO4

FeSO4+2NaOH=Fe(OH)2↓+Na2SO4

Fe(OH)2+2Fe(OH)3=Fe3O4+4H2O

2.4. Other colors of transparent iron oxide

Transparent iron oxides in three colors of orange, brown and green are mixed pigments. Transparent iron orange is made of transparent iron red and transparent iron yellow; transparent iron brown is made of transparent iron red, transparent iron yellow and transparent iron black; transparent iron green is made of transparent iron yellow and organic pigment phthalocyanine blue. Mixed.

3. Zinc iron yellow pigment

Zinc-iron yellow chemical composition is zinc ferrite, the molecular formula is ZnFe2O4 or ZnO · Fe2O3, the color is brownish yellow, is produced by the calcination method. The world's major producers are Bayer AG and Columbia Chemicals, which are still blank in our country.

Zinc-iron yellow pigment has good heat resistance and rust-proof function, and its temperature is up to 300°C. It is non-toxic and has good light resistance, weather resistance and migration resistance. It can be used for hard polyvinyl chloride, high-density polyethylene, poly Polypropylene, polystyrene and other plastics that need to be processed at higher temperatures are also suitable for high-temperature coatings. They can also be used in plastics and coatings that come into contact with foods in formulations where cadmium pigments and lead pigments cannot be used. Zinc iron yellow can be used in combination with iron red to give orange or light brown chromatograms.

The zinc iron yellow is prepared by reacting an alkali with ferrous sulfate to form ferrous hydroxide, and oxidizing ferrous hydroxide with air to obtain an iron yellow seed. The iron yellow seed is washed and mixed with the zinc hydroxide according to a formula. Calcination, adding some trace elements to reduce the activation energy, zinc oxide replaces the water in the iron yellow lattice to form zinc ferrite. We already have mature technology for preparation of yellow crystalline seeds, as well as the calcination technology for rutile titanium dioxide, which has already provided the technical basis for the development of this product.

4. Composite iron green pigment

There are few types of green pigments in inorganic pigments, only chromium oxide green and lead chromium green. Chromium oxide green has good light resistance, weather resistance and chemical resistance, but it is dark in color, expensive and toxic, and can only be used in some special occasions; lead chromium green is mixed with blue pigment and lead chrome yellow. Into, it is relatively bright color, but the light, weather resistance is not good, poor alkali resistance, poor performance in aqueous systems, and the price is more expensive, but also have some toxicity. With the development of economy, people’s living standards have been continuously improved, the use of colored building materials has become larger and larger, and the requirements for chromatography have become more and more comprehensive. This requires a green colorant that can be used in aqueous systems. Compound iron green.

The complex iron green color is bright, similar to the natural grass green, has good light resistance, weather resistance, acid resistance, alkali resistance, non-toxicity, excellent dispersion in the aqueous system, the price is relatively cheap, therefore, can be used in large quantities for construction Materials, as a colorant for cement, floor tiles, and various waterborne coatings. Nowadays, in cities, the color sidewalks are popular, and the green color is iron green.

Compound iron green is made of iron oxide yellow and organic pigment phthalocyanine blue. It does not require high color of iron yellow, but phthalocyanine blue is very difficult to disperse in water. This requires special measures. The phthalocyanine blue was first dispersed in water to make an aqueous paste, which was then mixed with the hydrophilized iron yellow, followed by dry pulverization to obtain a composite ferric green.

5. Summary

The production of iron red by ferrous sulfate calcining method is of low quality, and it is not possible to obtain a neutral red color with high saturation and pure color of the wet iron red “130”. It is not appropriate to develop it until there is no breakthrough in theory and technology.

The production of iron red and iron yellow by liquid-phase precipitation method should be the long-term research direction. Among them, the production of iron yellow is less difficult than the production of iron red, and zinc iron yellow and compound iron green are developed on the basis of iron yellow, and iron yellow, zinc iron yellow, composite iron green can be developed together. The main task of Tiehe is to conduct application research and deep processing of the product.

Transparent iron oxide is a new type of material. With the development of applied research, its application range will become wider and wider, and the demand will increase.