Manufacture of precipitated calcium carbonate of improved color and stable crystalline form
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United States of America Patent
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Oct 17, 2000
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N/A
app pub date -
Jun 5, 1998
filing date -
Jun 18, 1997
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Abstract
A method for the manufacture of precipitated calcium carbonate from impure calcium oxide of improved color is disclosed. The method comprises admixing impure calcium oxide with an aqueous solution consisting essentially of a salt of at least one compound selected from the group consisting of organic amines of the formula RNH.sub.2 and alkanolamines of the formula NH.sub.2 (R.sup.1 OH), where R and R.sup.1 are alkyl groups of 1-4 carbon atoms, and hydrochloric or nitric acid. The solution obtained is treated with a reducing agent e.g. sodium hydrosulphite, separated from insoluble matter and then treated with carbon dioxide or the carbonate of the amine or alkanolamine at a temperature of at least 50.degree. C. Preferably, the amine of the salt and of the carbonate are the same, and the salt is used in at least the stoichiometric amount to dissolve the lime.
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