Process for the preparation of high purity 1,3-dialkyl-2-imidazolidinone

In a process for reacting N,N'-dialkylethylenediamine with urea in an aprotic polar solvent to prepare 1,3-dialkyl-2-imidazolidinone, a process comprising progressing the reaction while continuously adding N,N'-dialkylethylenediamine and urea into the aprotic polar solvent, is disclosed. The process is a high-yield manufacturing process in industry capable of efficiently producing very high purity 1,3-dialkyl-2-imidazolidinone which contains less than 0.1% by weight of by-product 1,3-dialkyl-2-imidazolidinimine derived from the raw materials.