METHOD FOR PRODUCING HIGH SOLIDS AQUEOUS ACID-RESISTANT CALCIUM CARBONATE SUSPENSIONS AND PRODUCT THEREOF

摘要

A method of producing a high solids slurry of an acid-resistat precipitated calcium carbonate for shipping purposes is disclosed. A low solids of about 18 wt.% to 20 wt.% solids slurry is treated with a chemical additive, such as sodium aluminate, in order to impart acid resistance to the calcium carbonate, and is dewatered to form an intermediate solids slurry of about 44 wt%. This intermediate solids slurry is then diluted with a fraction of the low solids slurry which was treated with the chemical additive, in order to bring the intermediate slurry to a final high solids slurry of about 35 wt.%. Acid is added to the final product slurry in order to reduce the pH of the final slurry to within a buffering range of about 7.0 to 6.5. The final product slurry of about 35 wt.% comprises an acid-resistant calcium carbonate composition with a pH of about 7.0 which can be shipped for ultimate use when making paper under neutral pH conditions. The final product slurry has a Brookfield viscosity ranging from 200 to 500 centipoise at 100 rpm.