How are the iron oxide series pigments surface modified?

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　　Surface modification is considered to be one of the important processes used in the manufacture of pigments, and the surface treatment of the surface of the pigment particles can change the surface characteristics of the pigment and make it more in line with the requirements of the application.

　　

　　1. Surface modification technology of iron oxide red pigment

　　(1) Iron oxide red inorganic surface coating modification

　　Iron oxide has a certain catalyst activity in some polymers, which can cause early aging of the polymer, so its surface is reduced by alumina silica or silicone coating, which can improve the service life of plastic products. Iron oxide pigments coated with alumina or silicon oxide are also an anti-flocculation iron oxide pigment suitable for application in coatings.

　　(2) The surface coating modification of iron oxide red organic matter

　　The surface of iron oxide pigment particles is alkaline or acidic, and can be modified by treating the surface with organic compounds such as quaternary amine salts, stearic acid, and sulfonic acid.

　　The use of polymeric electrolytes such as polyacrylates, polyamines and other dispersants to change the application performance of pigments in aqueous system coatings, the reason is that the polymeric electrolyte molecules contain ionizable groups, easily soluble in water, very polar, can provide both electron layer stabilization and space estrhost effect, strong dispersion in aqueous systems.

　　(3) Modification of iron oxide red packet core method

　　At present, the nucleus-clad method uses kaolin or other inert materials as the nucleus, and the surface is activated by sodium polyphosphate, so that the α-FeOOH microcrystalline coating can be obtained after calcination.

　　2. Surface modification technology of iron oxide yellow pigment

　　(1) The surface coating modification of iron oxide yellow organic matter

　　In order to improve the dispersibility of iron yellow in organic solvents, it is usually used to add a dispersant to the system to control the size and uniformity of the particles, or to add a surfactant to change the iron yellow particles from hydrophilic with high surface tension to hydrophobicity. Among them, the most commonly used are sodium hexametaphosphate, sodium pyrophosphate, tartaric acid, sodium dodecylbenzenesulfonate and the like.

　　(2) Preparation of new pigments using surface modification technology

　　The color of iron yellow belongs to warm colors, the color is natural and soft, and the decoration is high, but the color is not bright enough. The organic pigment has good coloring power and bright color, and it can be compounded with iron oxide pigments to obtain pigments with good durability and strong coloring power. By the iron oxide yellow and phthalic blue two pigments for compounding can obtain composite iron green pigments, the production process is to add pigments in proportion to the high-speed disperser dispersion evenly, into the filtration, drying, crushing and preparation of finished products. The product can be used for cement coloring, and shows its unique lightfastness, weather resistance, alkali resistance and other properties, and because of the low price has become the preferred cement coloring green pigment, replacing the higher price of chromium oxide green pigment. It can also be used to formulate industrial coatings, but only in grass-green coatings.

　　(3) Iron oxide yellow inorganic surface coating modification

　　In order to improve the heat resistance and weather resistance of iron oxide yellow, researchers have also done a lot of work. Bayer prepares heat-resistant iron oxide pigments by the packing method, replaces the iron in the lattice with zinc and silicon in the preparation process, and produces iron-yellow pigments suitable for plastics and temperature-resistant coatings, the main ingredient of which is zinc ferrite.