| 摘要 |
1,263,439. Polyphenyl-polymethylene-polyisocyanates. FARBENFABRIKEN BAYERA.G. 1 May, 1970 [7 May, 1969], No. 21035/70. Heading C2C. The invention comprises (1) a poly-/diisocyanate composition, I, in which the ratio between the concentrations of 2,4<SP>1</SP>-diphenylmethane diisocyanate (2,4<SP>1</SP>-MDI) and 4,4<SP>1</SP>-MDI is a, the ratio between the concentrations of 1-(4-isocyanatophenylmethyl) - 3 - (2 - isocyanatophenylmethyl)-4-isocyanatobenzene and 1,3- di - (4 - isocyanatophenylmethyl) - 4 - isocyanato benzene is b and the ratio a : b is greater than 1À3, (2) a process for the production both of pure 4,4<SP>1</SP>- MDI and a polyphenyl-polymethylene-polyisocyanate mixture which comprises separating the polyisocyanate mixture, obtained by phosgenation of an aniline-formaldehyde condensation mixture, by fractional distillation into a fraction A which consists mainly of isomeric MDI and a fraction B which, in addition to isomeric diphenyl diisocyanates consists of polyisocyanates containing more than two aromatic nuclei, and in which fraction A is then separated by fractional distillation into a fraction C consisting of 2,2<SP>1</SP>-, 2,41- and 4,4<SP>1</SP>-MDI, a fraction D consisting of at least 98 weight per cent pure 4,4<SP>1</SP>-MDI and a residue E formed as a result of high temperature polymerization. The composition, I, may be formed by the above process and is the fraction B either alone or to which has been added fraction C to adjust the ratio a : b to the correct value. |
