Methyl methacrylate

Methyl methacrylate (MMA) is an organic compound with the formula CH2=C(CH3)COOCH3. This colorless liquid, the methyl ester of methacrylic acid (MAA), is a monomer produced on a large scale for the production of poly(methyl methacrylate) (PMMA).

History

MMA was discovered by Bernhard Tollens and his student W. A. Caspary in 1873, who noticed and described its tendency to change into a clear, hard, transparent substance especially in sunlight. Studies on acrylic esters slowly developed until Staudinger's theory of macromolecules and his research into the nature of polyacrylates allowed control over polymerization. The company Rohm and Haas, founded by German chemist Otto Röhm, who investigated the topic for three decades, was finally able to start its industrial production in 1931.

Production and properties

Given the scale of production, many methods have been developed starting from diverse two- to four-carbon precursors. Two principal routes appear to be commonly practiced.

Cyanohydrin route

The principal route begins with the condensation of acetone and hydrogen cyanide:

(CH3)2CO + HCN → (CH3)2C(OH)CN

Sulfuric acid then hydrolyzes acetone cyanohydrin (ACH) to a sulfate ester-adduct, which is cracked to the ester:

(CH3)2C(OH)CN + 2H2SO4 → ((CH3)2C(OSO3H)C(O)NH2·H2SO4

→ (CH3)2C(OSO3H)C(O)NH2 + H2SO4

Methanolysis gives ammonium bisulfate and MMA:

(CH3)2C(OSO3H)C(O)NH2 + CH3OH → CH2=C(CH3)C(O)OCH3 + NH4HSO4

Laboratory scale procedures are available for some of these steps.

This technology affords more than 3 billion kilograms per year, and the economics have been optimized. Nevertheless, the ACH route coproduces substantial amounts of ammonium bisulfate: roughly 1.1 kg/(kg MMA).