Dear Zahra Pakdin-Parizi, I found some hint in the literature, that the reaction product of ethanolamine and formaldehyde is N,N',N''-1,3,5-tris-(2-hydroxyethyl)-hexahydrotriazine (see attached picture). Unfortunately the only reference I found was a patent written in German.

Hi Zahra Pakdin-Parizi , attached is a pdf of the German patent file which mentions the compound N,N',N''-1,3,5-tris-(2-hydroxyethyl)-hexahydrotriazine. I hope it helps.

Dear Frank T. Edelmann Thank you very much for your guidance.