| 摘要 |
<p>1. Calcitic calcium carbonate filler in needle, fibre and/or rod form, having a specific BET surface area of 15-200 m**2 /g, an average shape factor of > 5 and having a phosphate content of 2.5-25% by weight, calculated as PO4-3- and based on calcium carbonate, and prepared by precipitation of an aqueous 3-25% strength by weight calcium hydroxide suspension using carbon dioxide, if appropriate mixed with air or nitrogen, at temperatures of from 0-25 degrees C, where 3-25% by weight, based on the calcium hydroxide employed, of PO4-3- being added in the form of Ha Me3-a PO4 (a = 0-3; Me = H, NH4-+ (a Not= 0), Na**+ , or K**+ ) before commencement of the pH decrease, thorough mixing being ensured during the entire reaction, and, if appropriate, the finished product, being dried and/or coated in a known manner.</p> |
