Process for producing .alpha.-type calcium sulfate hemihydrate
AssigneeTaki Chemical Co., Ltd.
InventorsHakuichi Akazawa, Kenichi Nishimura
Life of this patent
Estimating the term…
Abstract
A process for producing .alpha.-type hemihydrate calcium sulfate by oxidizing calcium sulfite with an oxidizing agent in a suspension containing at least one anionic, nonionic or amphoteric surface active agent.
Claims5
A process for producing .alpha.-type hemihydrate of calcium sulfate by oxidizing calcium sulfite with air or oxygen at a temperature in the range of from 90.degree. C to 130.degree. C in a suspension containing surface active agents, the suspension containing seed crystals of .alpha.-type hemihydrate of calcium sulfate and having a pH in the range of from 3 to 6 and the surface active agents being at least one agent selected from the group consisting of (a) anionic surface active agents having a sulfonic acid group as the hydrophilic atomic group and having an alkyl, alkyl-aryl or alkylallyl group as the hydrophobic atomic group;
- (b) non-ionic surface active agents having a polyoxyethylene chain as the hydrophilic atomic group and having an alkyl or alkylphenoxy group as the hydrophobic atomic group and (c) amphoteric surface active agents of a betaine.
Dependencies are inferred from the claim text.