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Introduction to iron oxide pigments

Sep 09,/2022

Inorganic pigment titanium dioxide application scope and dosage is the first, the second in the second inorganic pigment should be iron oxide series pigment, its pigment color, wide chromatography, high covering force, strong color force, the main color has red, yellow, black three, through the deployment can also get orange, brown, green and other series of chromatography composite pigments. Iron oxide pigment has a very good light resistance, weather resistance, acid resistance, alkali resistance and solvent resistance, but also has the characteristics of non-toxic, widely used in building materials, coatings, ink, plastics, ceramics, paper making, glass products, magnetic recording materials and other industries.
Performance of the iron oxide series of pigments

1. Acid and alkali resistance: it is very stable for any concentration of alkali and other kinds of alkaline substances, especially the cement and lime mortar commonly used in buildings, and it does not powder the cement building components, and it does not affect its strength. It has a certain resistance to the general weak acid and the dilute acid class, but it can also gradually dissolve in the strong acid, especially in the warm and concentrated cases.

2. Light and heat resistance: the color remains unchanged under the strong sunlight exposure, and the color of the exterior wall coating is iron oxide series. Due to the structural limitation, it is stable within a certain temperature limit, the color begins to change, as the temperature increases, the degree becomes more significantly, iron oxide over 130℃, dark red, 300℃, dark red, iron oxide over 1000℃, dark red. This is just the temperature limit of ordinary iron oxide pigment, and now many enterprises all have better performance products.
3. Weather resistance: Climate conditions such as atmospheric cold and heat, dry and wet have a very little impact on the pigment, and just because of the good weather resistance, the outdoor application is also used
a fat lot of.

4. Other properties: it is very stable in any dirty gas, such as hydrogen sulfide, carbon oxide, sulfur oxide, hydrogen chloride, nitrogen oxide and other gases. It is not dissolved in water, various mineral oils, vegetable oils and ethers, esters, ketones, and other organic solvents, and has no infiltration phenomenon.
Preparation Process of Iron Oxide Series Pigment
Iron oxide pigments are mainly iron red, iron yellow and iron black, these are brief descriptions of the three pigments from the iron oxide manufacturer.
1. Preparation process of red iron oxide
The traditional preparation method is dry, high temperature calcination; the other is wet, acid solution oxidation. The main raw material is limited to iron
Skin and iron chips, long production cycle, high energy consumption, high production cost. Some new approaches have been tried in recent years:

(1)After grinding FeSO4 7H2O into powder, NH4HCO3 and surfactant PEG (polyethylene glycol) -400 were added, 40min was ground at room temperature, washed, alcohol washed, pumped, dried to the precursor powder, and then pyrolysis to the nanoscale red iron oxide products. This room-temperature solid-phase synthesis method is easy to operate, cheap raw materials and easy to control the product particle size, which is a good new method to prepare nanograde Fe2O3 powder.
(2)Iron mud as raw material to prepare iron oxide red pigment: ① with industrial waste residue iron mud as raw material, prepared by acid oxidation
Material, the products meet the requirements of paint, paint and other iron red paint.➁ iron mud dry method of preparation of iron oxide red pigment: the raw material iron mud added to sulfuric acid as an oxidant, into the maver furnace calcined iron oxide red pigment. These two methods study the process route of preparing red iron oxide from industrial waste residue and iron mud, so as to eliminate the environmental pollution of iron mud, and turn waste into treasure, which has a certain practical feasibility.

(3)Preparation of iron oxide red product ferrous sulfate pigment: a certain amount of titanium dioxide byproduct ferrous sulfate heated to 500℃, thermal insulation for 2h, cooling after grinding, so that the particle size reaches the required range of iron oxide red, and then heated to 800℃ thermal insulation for 2h, fully calcination to obtain iron oxide red.
2. Preparation process of iron oxide yellow
Iron oxide yellow pigment is an important variety in the iron oxide pigment series. Because the iron yellow pigment has high purity, uniform particle size, easy to control, so its color phase is good, plus its non-toxic, its application scope is expanding. The existing preparation methods of yellow iron oxide are acid method (including iron sheet method and drip addition), alkali method, oxidation method (including air oxidation method, sodium chloride oxide oxidation method, hydroxyl iron oxide oxidation method), and glue dissolution method. In recent years, new achievements have been made in the preparation of iron oxide, and some new processes have been developed.

With ferrous sulfate as raw material, sodium hydroxide as the precipitant agent, adding dispersant and surfactant, first through nitrogen protection, and then into the air oxidation, made a particle composition, good crystallization, spindle shape of transparent iron oxide pigment, to avoid the filament light effect, its main performance reaches the standard of China’s chemical industry. This improved air oxidation process is simple (no need to prepare crystals), low production cost, has a good development future.
Huang Jian et al. prepared transparent iron oxide yellow pigment by using yellow sodium iron alum slag as raw material. The iron-yellow particles were prepared as needles

Form, no agglomeration phenomenon, monodispersion is good, the disadvantage is that there will appear filament light effect, color difference is larger. Kong Xianghua et al. used complexation precipitation method to prepare iron oxide yellow: F e C l 3 solution and N a F solution were gradually add N a O H solution to obtain yellow precipitation, and the samples were made by filtration, washing and drying. This method is a completely new complexation precipitation method, where F e C l 3 and N a O H as reaction reagents and N a F as complexation agent. Finally, the spherical iron oxide yellow particles were successfully prepared. The filament light effect of needle particles is overcome, the color difference is smaller, and the pigment quality is better.
3. Production red and yellow iron by liquid phase oxidation
With caustic soda (or ammonia) neutralizing ferrous sulfate to form ferrous iron hydroxide, with air oxidation of ferrous hydrogen oxide crystal species, in the presence of crystals
Oxide iron sulfate with air, continuously add iron sulfate and alkali (or ammonia) during the reaction process, maintain a certain iron concentration and P H value, through the control of color light progress, a series of iron oxide can be obtained from light to dark color. The difference between iron red and iron yellow production in this process is that the crystal preparation conditions are different, including iron yellow crystal under acid conditions, and iron red crystal under alkaline conditions. Compared with the current mature iron sheet method, there is still a big gap, in addition, it needs to consume a lot of alkali or ammonia, and the production cost has no advantage. However, as one of the effective ways to treat titanium dioxide byproduct ferrous sulfate, this is still a set of very worthy of research production technology.
4. Introduction to iron oxide black
(1)Water-borne system with granular iron black
The main use of iron black is still used as a building material. In Europe and the United States, iron oxide for building materials requires dust-free, which must grain iron oxide. If the iron black directly made into granular, it will be difficult to disperse and affect the performance, must be granulation additives must be added. Granulation additives must meet three conditions: ① does not affect the performance of the system used in iron black; ➁ hardness iron black in dry particles, and ③ distributes iron black particles in the water-based system. The granulation aid consists of wetting dispersers and adhesives.
(2)Oil system with ultrafine iron black
Use the airflow grinder to crush the iron black ultra-micro, break the aggregate, so that the fineness is below 5 m. An additives must also be added before the airflow crush, otherwise particles will reaggregate to the required fineness. It can also be different by changing the type of additives
Iron and black for use.
(3)Heat resistant iron black
Because the bivalent iron in the iron black is very unstable, it is oxidized to the trivalent iron when the temperature is greater than 140℃. Through the special treatment, the heat resistance of the iron black energy can be improved, so that the iron black energy can be applied to some coatings and plastics and other occasions that need to be processed and used at higher temperatures.The production of heat-resistant iron black must choose the particle size is relatively stable iron black varieties, first package it with a layer of dense aluminum, silicon envelope, and then use an organic matter with good heat resistance to form a second layer of envelope, and improve its use performance.

Finally, add to introduce the transparent iron oxide pigment, the more common is the wood coating, such as the wood paint used in the transparent iron oxide series. The primary particle size of transparent iron oxide is only a few dozen nanometers. When it is fully dispersed in the transparent medium to form a continuous membrane layer, the light will bypass the pigment particle and undergo diffraction phenomenon, so that the membrane layer has good transparency. The chemical structure of transparent iron oxide determines that it has a very good light resistance, weather resistance, acid resistance, alkali resistance and solvent resistance, and due to the very fine primary particle size and has a strong ultraviolet light absorption capacity, its light resistance is more excellent. It can be used for advanced car flash paint, hammer paint, wood paint colorant, imitation mahogany paint, can inner wall paint and building interior and exterior wall paint, but also for ink and plastic coloring. At present, there are three main process routes to produce transparent iron oxide, namely air oxidation method, base iron base combustion method and sodium chloride oxidation transformation
law. The product particles produced by air oxidation method are needle shape, length and length axis ratio of 5~8; base iron combustion method is BASF unique technology, product particles are uncertain shape, particle size is only a few nanometers; sodium chloride oxidation conversion method is mainly used in China, product particles
Children are spindle shaped, with the ratio of long and short axes 3 to 5 and short axes 10 to 20 nm.
With the improvement and development of iron oxide pigment preparation technology, there will be a better quality of iron oxide series pigment products appear, its application
The face will be wider. The colorful world needs more pigments to contribute to its gorgeous colors.Zhonglong manufacturers will provide more inorganic color pigment composites.

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