Methods of Manufacturing

Metaldehyde is obtained in addition to large amounts of paraldehyde during polymerization of acetaldehyde in the presence of HBr and alkaline earth metal bromides, such as CaBr2, at temperatures below 0 deg C. However, yields are scarcely higher than 8%. Yields of 14 - 20% have been reported when working in the presence of 7 - 15% of an aliphatic or cyclic ether at 0 - 20 deg C. Insoluble metaldehyde is filtered out. Acetaldehyde is then distilled from the filtrate following depolymerization of the paraldehyde and is returned to the polymerization. Recycling of the large amounts of acetaldehyde results in losses that increase the process costs.
Prepd by polymerization of acetaldehyde in presence of hydrochloric acid, sulfuric acid @ low temp: Kekule, Zincke, Ann 162, 125 (1872); in presence of pyridine and hydrogen bromide: Wilder, US patent 2,426,961 (1947 to Publicker Ind).

U.S. Production

Production volumes for non-confidential chemicals reported under the Inventory Update Rule. Year Production Range (pounds) 1986 No Reports 1990 10 thousand - 500 thousand 1994 No Reports 1998 No Reports 2002 No Reports