| 摘要 |
The present invention relates to the preparation of fine, particulate anhydrite gypsum for use as a filler in paper manufacture, or as a paper-coating agent. Sulphuric acid having a concentration of at least 35% by weight in water is heated to at least 60%, whereafter gypsum in the form of dihydrate and/or hemihydrate gypsum is dissolved to saturation in the acid, the gypsum being added in an amount of at least 100 grams per liter of sulphuric acid solution. Anhydrite gypsum is then permitted to precipitate, and the gypsum isolated and dried. The resultant gypsum has a particle size of less than 10 mu m. |
