| 摘要 |
1287192 Methylene-bridged di- and polyisocyanates BADISCHE ANILIN- & SODAFABRlK AG 15 Jan 1970 [16 Jan 1969] 2020/70 Heading C2C 4,41-Diphenylmethane diisocyanate and a mixture of methylene -bridged diisocyanates and polyisocyanates are prepared by condensing aniline with formaldehyde in a molar ratio of from 2:1 to 6:1 in the presence of strong mineral acids at temperatures of 10‹ to 90‹ C. at the start of the reaction rising to temperatures from 80‹ to 150‹ C. as condensation proceeds, distilling off from the mixture obtained after neutralization all or a portion of the diamines, separating from the distillate substantially pure 4,4<SP>1</SP>- diaminodiphenylmethane by crystallization from a solvent, reacting this with phosgene to form 4,4<SP>1</SP>-diphenylmethane diisocyanate, combining the distillation residue and the mother liquor from the crystallization step containing methylene-bridged primary diamines and polyamines and phosgenating this to the corresponding diisocyanates and polyisocyanates. |
