GYPSUM PRODUCT AND PREPARATION METHOD THEREOF Russian patent published in 2012 - IPC C01F11/46 C09C1/02 D21H17/67 

FIELD: chemistry.

SUBSTANCE: invention can be used in making paper products. The gypsum product essentially consists of undamaged crystals, having weight-average diameter D₅₀ 0.1 - 2.0 mcm and particle size distribution width less than 2.0. The shape factor of the crystals is equal to at least 2.0 and the aspect ratio is equal to 1.0-10. The gypsum product is obtained by reacting calcium sulphate hemihydrate and/or calcium sulphate anhydrite and water in the presence of a crystal habit modifier. The reaction mixture has dry substance content of 50-84 wt %. The crystal habit modifier is used in amount of 0.01-5.0% of the weight of the calcium sulphate hemihydrate and/or calcium sulpohate anhydrite and is selected from a group consisting of ethylenediamine succinic acid, iminodisuccinic acid, ethylenediamine tetraacetic acid, diethylenetriamine pentaacetic acid, nitrilotriacetic acid, N-bis-(2-(1,2-dicarboxyethoxy)ethylasparticacid, di-, tetra- and hexaaminostilbene sulphonic acid and salts thereof, such as sodium aminotriethoxy succinate (Na₆-TCA), as well as alkylbenzene sulphonates. The crystallised or extracted gypsum is dispersed, treated with biocides, sieved and bleached.

EFFECT: high lustre and opacity due to that the gypsum particles are flat and have equal size.

18 cl, 11 dwg, 5 ex