Two-grid methods for mixed finite element approxi-mations of nonlinear parabolic equations

Polyaddition polymers comprising the reaction products of bis-epoxy compounds with poly-N-substituted polyamines or poly-N-substituted polyalkylene imines, wherein said poly-N-substituted polyamines and said polyalkylene imines contain at least two active hydrogens, and which polyamines and polyalkylene imines contain alkali metal salts or alkyl ester groups of carboxyalkyl groups or cyanoalkyl groups which are substituents on the nitrogen atoms of said polyamines of polyalkylene imines. The polymer is extremely useful for chelating and recovering heavy metal ions from industrial waste liquids and also effective as adhesives, resin for paint, electrostatic inhibitor for polymer, electro-conductive polymer, rust inhibitor ion-exchanging material and the like. The polymer may be obtained in the form of particles of a controlled particle size.