| 摘要 |
<p>Process for preparing dihydrous calcium sulphate with the appearance of elongated crystalline structures from hemihydrated calcium sulphate of the " beta " or " alpha " variety, characterized in that in order to obtain a controlled length and shape factor, it includes: (a) grinding and/or selecting said hemihydrated calcium sulphate within a given granulometric range such that the specific granulometric size to produce elongated crystalline structures with a predetermined length and shape factor is situated within the range delimited by extremes of 5 micrometers and 200 micrometers; (b) the presence of at least one recrystallization regulating agent, in the proportion of between 0.01 and 6.66 weight per cent, relative to the total mass of the suspension to be formed in stage (c); (c) preparing by dispersion from materials of stages (a) and (b) a water suspension at an isothermic transformation temperature set to a maximum of 60 DEG C, with a proportion of dry matter of no more than 33.33 weight per cent relative to the total mass of the suspension; (d) maintaining the temperature at the fixed level for no longer than 60 minutes and (e) possibly separating the elongated crystalline structures with controlled length and shape factor. The elongated crystalline structures obtained by said process are used in particular for a wide variety of fields of application, including those of paper, paints and synthetic materials.</p> |
