Properties of copolymers of aspartic acid and aliphatic dicarboxylic acids prepared by reactive extrusion

Aspartic acid is prepared chemically or by the fermentation of carbohydrates. Currently, low molecular weight polyaspartic acids are prepared commercially by heating aspartic acid at high temperatures (>220°C) for several hours in the solid state. In an effort to develop a more rapid, continuous, melt polymerization scheme, aspartic acid was copolymerized with adipic, azelaic, sebacic, and dodecanedioic acids using a vented twin‐screw extruder. Copolymers having ratios of aspartic/diacid ≤16 andMwup to 9100 were prepared at temperatures of 240–260°C and residence times of only about 5 min.Mwgenerally increased with aspartic/diacid ratio but melt viscosities became very high and processing became difficult at ratios >16. Most of the copolymers exhibited inhibition of calcium carbonate precipitation at concentrations similar to that of pure polyaspartic acid and thus may find application as antiscalants.