Polyurea compositions from polyaspartic esters and 2-substituted butanedioic acid esters

A method of preparing a polyurea coating comprising reacting a polyaspartic acid ester represented by the structure below:

• wherein Z=a cycloalkyl or alkyl group, R1, R2=alkyl groups containing 1-10 carbon atoms, and n=2-4,
• with a 2-substituted butanedioic acid ester prepared by reacting the fumaric ester in the polyaspartic acid ester solution with a cyanoacetate, a malononitrile or a 1,3-diketone in the presence of a base to form a mixture, and reacting the mixture with a polyisocyanate.

A process for preparing a polyaspartic ester/2-substituted butanedioic acid ester mixture comprising the steps of

• a) reacting an ester of fumaric acid or maleic acid with a polyamine;
• and
• b) reacting the residual ester of fumaric acid or maleic ester to completion with a cyanoacetate, a malononitrile or a 1,3-diketone.