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US 4,828,766 AGranted
Process for the preparation of vinyldiphosphonic acid and salts thereof
AssigneeBenckiser-Knapsack GmbH
InventorsStephan Kleemann, Werner Ehret
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Abstract
An improved process for the preparation of vinyldiphosphonic acid is disclosed. The process involves elimination of a volatile acid from a 1-(O-acyl)-ethane-1,1-diphosphonic acid. The starting materials may be prepared by reacting 1-hydroxyethane-1,1-diphosphonic acid with the corresponding acid or directly by reacting the acid with phosphorous acid and an acyl anhydride.
Claims15
A process for forming vinyl-disphosphonic acid and salts thereof, comprising the steps of:
- forming 1-(O-acyl)-ethane-1,1-diphosphonic acid;
- and
- heating the 1-(O-acyl)-ethane-1,1-diphosphonic acid to about 200-300.degree. C. with or without alkali or ammonia to eliminate an alkylcarboxy acid having from 1 to 10 carbon atoms from the 1-(O-acyl)-ethane-1,1-diphosphonic acid to form vinyl diphosphonic acid when alkali or ammonia is not present or a salt of vinyl diphosphonic acid when alkali or ammonia is present.
Dependencies are inferred from the claim text.