A series of iron oxide series related to inorganic pigments

 Among all kinds of pigments, the production and sales of iron oxide pigments is second only to titanium dioxide, is the second large amount of inorganic pigments, is the first color pigments. The color of iron oxide pigment is many, the chromatogram is wide, the covering power is high, the coloring force is strong, the main color is three kinds of red, yellow and black, and the complex pigment of orange, brown, green and so on can be obtained by blending.

Iron oxide pigment has good light, weather resistance, acid resistance, alkali resistance and solvent resistance, and has the characteristics of non-toxic. It is widely used in building materials, coatings, ink, plastics, ceramics, paper making, magnetic recording materials and other industries. Ferrous sulfate, a byproduct of titanium dioxide, can be used as raw material to produce many kinds of ferric oxide products. It is the best way to treat ferrous sulfate.

1, the production of iron red by calcining

About 80 ferric oxide brands sold in the United States market, about 20 of them are calcined vitriol red, and the world's largest production of iron oxide by calcining method in Japan is about 200 thousand tons, but its products are mainly used as magnetic materials. In China, several factories with Zibo cobalt industry are produced by calcining method, but the quality of the products is low, the use is not wide, and the quality is far away from the nitrous acid method, which is widely used in China.

At present, 60% of the global iron oxide pigments are used for building materials and 30% for paints. These two types of iron oxide are required to have good color and dispersion. The iron oxide in the building material must also have high coloring force (low coloring force will increase the amount of pigment and affect the strength of the material. " ). The iron red particles produced by the calcination method are larger, the color is deep and the coloring force is not high, which is basically not used in the building materials, which makes their application range greatly reduced.

2. Production of iron red and iron yellow by liquid phase oxidation

Using caustic soda (or ammonia) and ferrous sulfate to produce ferrous hydroxide, oxidizing ferrous hydroxide with air, oxidizing ferrous sulfate with air in the presence of seeds, adding ferrous sulfate and alkali (or ammonia) continuously in the reaction process to maintain a certain ferrous concentration and pH value, and through the control of color light, it can be obtained from light color to the light color. A series of dark colored ferric oxide. The difference between iron red and iron yellow produced by this process lies in the different preparation conditions of crystal seeds. Iron yellow crystal seeds are obtained under acidic conditions and iron red crystal seeds are obtained under alkaline conditions. The production of 1 tons of iron oxide by air liquid phase oxidation requires about seven tons of ferrous sulfate 3.5~4 tons, 30% caustic soda 3 tons or liquid ammonia 0.45 tons.

The production of ferric oxide by liquid phase oxidation is still in the laboratory stage in China, and there is no industrial production device yet. The main reason is that there is a big gap between the quality of the product and the mature iron method. In addition, it needs to consume a lot of alkali or ammonia, and there is no advantage in the production cost. However, as one of the effective ways to deal with the by-product ferrous sulfate, it is a very worthwhile production process. The key is two points: one is to find an effective method to control the uniform growth of the particles and improve the quality of the product. Two, the recovery and utilization of the sodium or ammonia salt of the reaction and the reduction of the production cost.

3, ammonia process iron red

The primary seed gamma -FeOOH was obtained from ammonia neutralization of ferrous sulfate to alkaline (PH=8.5~9.5) and air oxidation, and gamma -FeOOH was transformed into true nucleation alpha -Fe2O3 under the induction of Fe2+, which is a process of re nucleation. In the presence of alpha -Fe2O3 nucleation and ferrous sulfate, ferric sulphate is oxidized with air in the air, and the produced iron oxide is deposited on the nucleus, and the sulphuric acid is neutralized by ammonia and continuously added to the ferrous sulfate and ammonia, and the nucleation is gradually grown to form iron red. The chemical reaction is as follows: FeSO4 + 2NH3. H2O = Fe (OH) 2 + (NH4) 2SO42Fe (OH) 2 + 1/2O2 = 2 gamma -FeOOH + H2O; crystal species conversion: 2 gamma -FeOOH to alpha and two step oxidation: 2

4. Ammoniacal ferric yellow

Neutralization of ferrous sulfate solution by ammonia to pH 5~6, and neutralization of the system still has a certain amount of ferrous sulfate. Iron oxide crystals are obtained by oxidizing ambient air at room temperature. The two step oxidation is carried out in the presence of crystal seeds. The two step oxidation process is similar to that of ammonia iron oxide, and is not repeated here. The chemical reaction is as follows: FeSO4 + 2NH3. H2O = Fe (OH) 2 + (NH4) 2SO4 2Fe (OH) 2 + 1/2O2 = Fe2O3 H2O + two steps of oxidation

5, ferrous hydroxide gel oxidation process to produce iron black

In the process of oxidizing ferrous hydroxide in the process of oxidizing ferrous hydroxide with the alkaline substance (NaOH, NH3 and so on) and ferrous sulfate and oxidizing ferrous hydroxide in the air, the particles are uniformly grown by changing the process conditions to obtain the iron black with very high particle size and uniform distribution.

The method has mature production technology, the product's coloring force is in the world leading level. The future research focuses on improving the application performance to make the comprehensive performance of the product reach the world level.

6. Granular iron black in water system

The main purpose of iron black is still used as building materials. In Europe and the United States, iron oxide for building materials requires no dust, which requires granulation of ferric oxide. If the iron black is directly made into granules, it will make it difficult to disperse and affect the performance. Granulation auxiliaries must be added. The granulation agent must meet three conditions: (1) it does not affect the performance of the system used in the iron black; (2) the hardness of the iron black in the dry particles; (3) the iron black particles can be rapidly dispersed in the water system. Granulation AIDS consist of wetting dispersants and adhesives

7. Ultrafine iron black for oil system

The iron black is superfine comminuted by an air pulverizer to crush the aggregate so that the fineness is below 5 m. Auxiliaries must also be added before air pulverization, otherwise the particles will re aggregate to meet the required fineness. Different types of iron black can also be obtained by changing the type of auxiliaries.

8. Heat resistant iron black

Because of the unstable nature of the two valence iron in iron black, it is oxidized to ferric iron at a temperature greater than 140 degrees, and the iron becomes black. The heat resistance of the black iron can be improved by special treatment, so that the iron black can be applied to some coatings and plastics and other occasions which need to be processed and used at higher temperatures.

The production of heat resistant iron black must choose the iron black variety with relatively stable heat performance. First, a dense aluminum and silicon coating is wrapped and a second layer coating is formed with a kind of organic matter with good heat resistance, and its performance is improved at the same time.

9, transparent iron oxide pigment

The original particle size of transparent iron oxide is only a few tens of nanometers. When it is fully dispersed in the transparent medium to form a continuous film, the light will diffract the pigment particles and make the film with good transparency. The chemical structure of transparent iron oxide determines that it has good light resistance, weather resistance, acid resistance, alkali resistance and solvent resistance, and has strong UV absorbability because of the very fine original size. The transparent iron yellow, transparent iron orange and transparent iron red per square meter of the film produced by BASF company contain 1., respectively. 7, 1.3 and 0.9 grams can absorb 99.5% of ultraviolet light.

Transparent iron oxide can be used for high grade car flash paint, hammer paint, wood coating colorant, imitating red wood paint, canned bottle inner wall paint, interior and exterior coatings for building, and also used for ink and plastic coloring. The transparent iron oxide, which strictly controls arsenic and heavy metals, can replace the gradually banned azo pigments, dyes and other synthetic pigments, and is used as a colorant for food, medicine and cosmetics.

The developed countries began to use transparent iron oxide pigments from the end of the 70s of the last century. The main factories are Bayer company, Bayer, Hilton Davies chemical company, Blythe Colours Ltd and Capel company, and so on. With the development of many years, its application field has been from the early advanced sedan. Lacquer has been extended to various fields.

At present, there are three main processes for producing transparent iron oxide, namely, air oxidation, carbonyl iron combustion and sodium chlorate oxidation-conversion. The product particles produced by air oxidation are acicular and the ratio of the long and short axis is 5~8; the carbonyl iron combustion method is a unique technology of the Basf Inc. The product particles are amorphous, the particle size is only a few nanometers; the sodium chlorate oxidation process is mainly used in our country, the product particles are spindle, the ratio of the long and short axis is 3~5, the short axis length is 10~20 nanoscale.

10, zinc iron yellow pigment

Zinc iron yellow chemical composition is zinc ferrite, the molecular formula is ZnFe2O4 or ZnO. Fe2O3, brown yellow color, is produced by calcination. The main producers in the world are Bayer and Columbian Chemical Company of the United States, which are still blank in our country.

Zinc iron yellow pigment has good heat resistance and antirust function, temperature resistant to 300 C, non-toxic, good light resistance, weatherability and mobility resistance, can be used for hard polyvinyl chloride, high density polyethylene, polypropylene, polystyrene and other plastic coloring at high temperature, also suitable for high temperature resistant coatings, and can also be used in high temperature resistant coatings. Plastics and coatings that can be used to make food contact can not be used in the formulation of cadmium pigments and lead pigments. Zinc iron yellow can be mixed with iron oxide to obtain orange or light brown chromatography.

The preparation method of zinc iron yellow is to produce ferrous hydroxide by the reaction of alkali and ferrous sulfate, and the iron yellow crystal is produced by oxidizing the iron oxide in air. After washing the iron yellow crystal and mixing zinc hydroxide with the formula of zinc hydroxide, some trace elements are added to reduce the activation energy, and the Zinc Oxide is replaced by the water in the iron yellow lattice to form ferric acid. Zinc. There are mature techniques for the preparation of iron xanthate seeds in China and the calcination of rutile titanium dioxide for reference, which lay the technical foundation for the development of the product.

11. Compound iron green pigment

There are few varieties of green pigments in inorganic pigments, only chrome oxide green and lead chrome green. Chromium oxide green has good light resistance, weather resistance and chemical resistance, but it is dark, expensive and poisonous. It can only be used in some special occasions; lead chrome green is mixed with blue pigment and lead chrome yellow. It is brighter in color, but not good in light, weatherability and alkali resistance. It is not used in water system. Yes, and the price is more expensive, and also has certain toxicity. With the development of the economy, people's living standards are increasing, the use of color building materials is becoming more and more large, and the requirements for chromatography are more and more comprehensive. This requires a green colorant which can be used in the water system, so the compound iron green appears.

The compound iron green is bright color, similar to the natural grass green, good light resistance, weather resistance, acid resistance, alkali resistance, non-toxic, in the water system is excellent dispersion, relatively cheap in price, so it can be used in building materials, as cement, floor tiles, various water-based coatings color agents. Now the city popularizes colored sidewalks, of which green is the use of iron green.

Composite iron green is a mixture 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.