Ammonium dichromate and sodium sulfate mixed crystal as well as preparation method and application thereof

Abstract

The invention provides an ammonium dichromate and sodium sulfate mixed crystal as well as a preparation method and application thereof. The preparation method comprises the following steps: heating amixed solution of sodium dichromate, ammonium sulfate and sodium sulfate, and conducting cooling and crystallizing to obtain a saturated salt solution; and heating the obtained saturated salt solution, then adding ammonium sulfate, then adding sodium dichromate, conducting stirring for reaction, and then conducting cooling for crystallization to obtain mixed crystals and crystallization mother liquor. According to the invention, the saturated salt solution is used as a reaction base solution, and then the mixed crystal with uniform, dispersed and non-sticky particle size is prepared by controlling the reactant adding mode and proportion, reaction and post-treatment process, so that the generation of double salt is avoided, and the composition of the mixed crystal is ensured to meet the requirements; meanwhile, due to the use of the reaction base solution, evaporation and concentration steps can be omitted, and the crystallization yield is increased; and a chromium oxide green pigment is prepared from the obtained mixed crystal, so that the problem of difficult feeding in industrial production can be effectively solved, and the obtained product has better chromaticity parameters andexcellent performance.

Description

technical field [0001] The invention belongs to the technical field of mixed crystal preparation, and relates to a mixed crystal of ammonium dichromate and sodium sulfate and its preparation method and application, in particular to a mixed crystal of ammonium dichromate and sodium sulfate, its preparation method and its use in the preparation of oxidized The use of chrome green pigment. Background technique [0002] Chromium oxide green is a commonly used pigment with good stability, acid and alkali resistance, high temperature resistance, light and weather resistance, etc. It can be used in paints, coatings, inks, plastics, rubber, chemical fibers, textiles, ceramics, glass, cement and other industries Among them, chromium oxide green has a color similar to plant chlorophyll, and has great advantages as a camouflage material; in addition, chromium oxide green is also used in cosmetics, tapes, food, adhesives, electrostatic copying and other fields . When used as a pigment...

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Problems solved by technology

[0003] At present, the production methods of chromium oxide green pigment mainly include chromic anhydride thermal decomposition method and sodium dichromate-ammonium sulfate thermal decomposition method. The former preparation method is simple, but there are The problem of high cost and serious environmental pollution, the latter method produces less harmful gas, and the product color parameters are easy to control, but its product performance still needs to be improved, such as water granulation or wet mixing measures

US 4067747A discloses that sodium dichromate solution and ammonium sulfate solution are mixed and reacted, and excess water is removed by evaporation to obtain a mixture of ammonium dichromate and sodium sulfate, which is heated and roasted in the presence of water to obtain a pigment product, but the method The mixture of ammonium dichromate and sodium sulfate obtained in the method has a relatively high viscosity, and in order to ensure continuous feeding during roasting, the feeding needs to be dispersed and non-bonding, so there is a problem of feeding difficulties, although spray drying to a certain extent This problem can be solved, but the energy consumption is high and the control is difficult

[0004] In order to obtain a dispersed mixture, it is a method to directly mix ammonium dichromate and sodium sulfate raw materials. However, ammonium dichromate and organic matter contact friction, The impact can cause combustion and explosion, and it will start to decompose at 170-185°C, which is not conducive to transportation; at the same time, in industrial production, ammonium dichromate is obtained by the double decomposition reaction of sodium dichromate and ammonium chloride, and sulfuric acid can also be used Ammonium is used instead of ammonium chloride to produce ammonium dichromate. It can be seen that it is more appropriate to use sodium dichromate and ammonium sulfate as raw materials to prepare a dispersed, non-bonding mixture of ammonium dichromate and sodium sulfate.

[0005]CN 108675353A discloses a production method of high-end pigment chromium oxide green, using sodium dichromate and ammonium sulfate or ammonium carbonate as raw materials, and first producing Mixed crystals of ammonium dichromate and sodium sulfate or ammonium dichromate and sodium carbonate, then add roasting additives and roast at high temperature in a rotary kiln, and finally wash and remove impurities, dry, and pulverize to obtain chromium oxide green products, but this method does not The control of the component ratio and particle size in the mixed crystal has not been realized, and the performance of the chromium oxide green pigment cannot be guaranteed

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