DISPERSED CALCIUM CARBONATE CONTAINING MATERIAL FOR AN IMPROVED STABILITY UNDER ALKALINE CONDITIONS

摘要

The present invention relates to a method for preparing an aqueous calcium carbonate containing suspension, a suspension comprising a calcium carbonate containing material obtainable by said method as well as a calcium carbonate containing material obtainable by drying said suspension and to the use of the suspension or calcium carbonate containing material in paper, paper coating, plastic and/or paint applications and to the use of the suspension for stabilizing the rheology of a sodium silicate and/or sodium hydroxide containing coating formulations for paper applications.

主权项

1. A method for preparing an aqueous calcium carbonate containing suspension, comprising the following steps of:
a) providing a calcium carbonate containing material in the form of an aqueous cake or suspension having solids content of at least 45 wt.-%, based on the total weight of the aqueous cake or suspension; b) providing at least one alkali metal salt of a phosphonic acid in an amount from 0.01 to 5 wt.-%, based on the total dry weight of the calcium carbonate containing material; c) providing at least one phosphonic acid in an amount from 0.001 to 0.5 wt.-%, based on the total dry weight of the calcium carbonate containing material; d) contacting the calcium carbonate containing material of step a) with the at least one alkali metal salt of a phosphonic acid of step b) such as to obtain a suspension having a pH from 10 to 14; e) contacting the suspension of step d) with the at least one phosphonic acid of step c) such as to obtain a suspension having a pH from 8 to 10; and f) optionally grinding the suspension obtained in step e).