Nylon 6 is produced from polymerisation of caprolactam. Process steps involved in production of Nylon 6 involve the following steps
Caprolactam is polymerised to Nylon 6 polymer by ring opening polymerisation at 240-270 0C in presence of water, which opens the ring structure of the caprolactam to give amino caproic acid. Reacting SO2 with ammonium nitrite & ammonium carbonate which results in production of hydroxylamine disulphonate finally hydrolysis of hydroxylamine disulphonate at 95 oC to yield hydroxylamine sulphate & ammonium sulphate as by-product. Process flow diagram for nylon 6 manufacturing is shown in Figure M-VIII 5.4.
Figure M-VIII 5.4: Manufacture of Nylon 6
Nylon 66 is produced by polymerisation of adipic acid & hexamethylene diamine. Manufacturing process flow diagram for nylon 66 is shown in Figure M-VIII 5.5. Process step involved in manufacture of Nylon 66
Figure M-VIII 5.5: Process of Nylon 66 manufacture
Various routes of adipic acid manufacturing is shown in Figure M-VIII 5.6
Adipic acid Hexamethylenediamine Hexamethylene diammonium adipate
[-HN(CH2)6NHOC(CH2)4co-] + 2x.H2O
Poly (Hexamethylene Adipamide) or Nylon
Figure M-VIII 5.6: Various Routes for Manufacture of Adipic Acid
Cyclohexane is oxidised by air to form cyclohexanol &cyclohexanone in presence of cobalt naphthenate catalyst at temperature of 145-150 oC. The cyclohexanol and cyclohexanone mixture is oxidised to adipic acid in presence of nitric acid using ammonium metavanadate and copper scrap at 60-80 oC. The adipic acid formed is crystallised, centrifuged and finally dried with hot air.
Hexamethylene diamine is another intermediate for the manufacture of Nylon 66. Hexamethylene diamine is manufactured by the catalytic hydrogenation of adiponitrile. Hexamethylene diamine is manufactured by catalytic hydrogenation of adiponitrile in presence of catalyst either by high pressure process (60-65 MPa) or low pressure process (3 MPa). Catalyst in low pressure is nickel whereas in case of high pressure process it is cobalt and copper. Process flow diagram for the manufacture of Hexamethylene diamine is given in Figure M-VIII 5.7
NC(CH2)4CN + 2 H2 →HN=CH(CH2)4CH=NH
Figure M-VIII 5.7: Process flow diagram for Hexamethylene diamine