Precipitated calcium carbonate
AssigneeECC International Limited
InventorsIan S. Bleakley, Thomas R. Jones
Life of this patent
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Abstract
The calcium carbonate is prepared by: (a) slaking quicklime in an aqueous medium; (b) carbonating and neutralizing the suspension of slaked lime formed in step (a) using a gas comprising carbon dioxide; and (c) separating the precipitated calcium carbonate formed in step (b) from the aqueous medium in which it is suspended. There is added 0.01% to 15% by weight, based on the weight of dry calcium oxide, of a reagent having one or more active hydrogen atoms (or a salt thereof), to the aqueous medium in which the quicklime is slaked in step (a). The reagent is selected from the group consisting of triethanolamine, mannitol, diethanolamine, bicine, morpholine, tri-isopropanolamine, N-ethyl diethanolamine, N,N-diethylethanolamine and sodium boroheptonate.
Claims10
A process of preparing clusters of scalenohedral calcium carbonate, which give good light scattering properties when used as a paper filler or paper coating pigment, which process comprises the following steps:
- (a) adding to an aqueous medium, either a reagent having one or more hydrogen atoms which dissociate on addition of said reagent to said aqueous medium or a salt of said reagent, said reagent being selected from the group consisting of triethanolamine, mannitol, diethanolamine, bicine, morpholine, tri-isopropanolamine, N-ethyl diethanolamine, N,N-diethylethanolamine and sodium boroheptonate;
- (b) thereafter slaking quicklime in said aqueous medium;
- (c) carbonating the suspension of slaked lime formed in step (b) by passing therethrough a sufficient amount of a gas comprising carbon dioxide to cause the pH of the suspension to fall to substantially neutral;
- and
- (d) separating the precipitated calcium carbonate formed in step (c) from said aqueous medium;
- wherein said reagent or salt of said reagent is added to said aqueous medium in an amount equal to 1%, by weight of dry calcium oxide, in said quicklime.
Dependencies are inferred from the claim text.