| 摘要 |
PROBLEM TO BE SOLVED: To purify an N,N,N',N'-tetra(phosphomethyl)-diaminoalkane that is useful for a washing solution for washing the surfaces of semiconductors in high recovery yield with extremely reduced impurity contents, for example, chloride ions, and the like, by adding acetone, and the like, to an aqueous solution of a crude N,N,N',N'-tetra(phosphomethyl)-diaminoalkane to effect the recrystallization of the diaminoalkane. SOLUTION: An alcohol of 1-4 carbon atoms, for example, ethanol or a ketone, for example, acetone are added to an aqueous solution of a crude N,N,N ',N'-tetra(phosphomethyl)-diaminoalkane that is concentrated to 40-80 wt.% solution, and preferably cooled down to 0-10 deg.C to recrystallize the diaminoalkane. In a preferred embodiment, the resultant crystals are washed with a 1-3C alcohol, for example, ethanol, or the like, to purify the objective compound, for example, N,N,N',N'-tetramethylphosphonic acid-1,2- diaminopropane. The amount of the 1-4C alcohol or acetone to be added is preferably 0.2-4 liters per 1 kg of the diaminoalkane in the aqueous solution.
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