PROCESS FOR PREPARING PYRROLIDONE-5,5-DIPHOSPHONIC ACIDS

• Main Authors: PLOGER, WALTER, SCHMIDT-DUNKER, MANFRED, GLOXHUBER, CHRISTIAN
• Format: Patent
• Language: English; French
• Published: 28.11.1978

Pyrrolidone-5,5-diphosphonic acids having the formula wherein R is a member selected from the group consisting of hydrogen and alkyl having from 1 to 6 carbon atoms; as well as their water-soluble salts. The pyrrolidone5,5-aiphosphonic acids are excellent sequestering agents especially for alkaline earth metal ions. They are stabilizers for percompounds and are useful in the delaying of the setting times for gypsum. This divisional application is particularly directed to the process of preparing said diphosphonic acids by(1) reacting a compound of the formulae and with at least the stoichiometric amount of a phosphorus reactant selected from the group consisting of phosphorus trihalide and a mixture of a phosphorus trihalide and phosphorous acid, (2) subjecting the resulting product of an aqueous hydrolysis at an elevated temperature and (3) recovering the desired diphosphonic acid derivative.