Sumitomo Chemical Company, Limited

Eiiti Yoneyama

Shinya Tanaka

Shinichi Yachigo

Manji Sasaki

Hiroki Yamamoto

Crude N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl)alkanediamine represented by the formula: ##STR1## wherein n is an integer of 2 to 10, is purified by crystallization from a ketone solvent of 3 to 9 carbon atoms. The purified product thus obtained has a purity of 98% by weight or more, a 2,2,6,6-tetramethyl-4-piperidone content of 150 ppm or less, and an initial APHA value of 30 or less. The purified product is also inhibited from discoloration with the passage of time.

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Niihama, Japan

Eiiti Yoneyama