Process for continuously preparing copolyamides from lactams and salts of diamines and dicarboxylic acids

摘要

A process for continuously preparing copolyamides from lactams and salts of diamines and dicarboxylic acids, in which lactams together with salts of diamines and dicarboxylic acids are passed from the top downward through a vertical polymerization tube at polyamide-forming temperatures, which comprises
a) intensively mixing an aqueous solution of lactams with salts of diamines and dicarboxylic acids under elevated pressure which is greater than the vapor pressure of the mixture which arises in a mixing apparatus at a temperature of from 80 to 300° C.,b) feeding the mixture thus obtained to a heated helical tube evaporator in which a liquid phase and a vapor phase form at a temperature of from 140 to 300° C., a stream of water vapor and/or inert gas also being introduced into the mixture if appropriate upstream of the helical tube,c) removing the vapor phase formed in stage b) from the liquid phase and separating it in a column into water vapor and into organic components comprising diamines, dicarboxylic acids and lactams, and recycling the organic components into the polymerization,d) passing the liquid phase from the helical tube of stage b) mixed with the organic components of stage c) from the top downward through a vertical polymerization tube at polyamide-forming temperatures to obtain a copolyamide.

主权项

1. A process for continuously preparing copolyamides from lactams and salts of diamines and dicarboxylic acids, in which the lactams together with the salts of diamines and dicarboxylic acids are passed from the top downward through a vertical polymerization tube at polyamide-forming temperatures, which comprises
a) intensively mixing an aqueous solution of lactams with salts of diamines and dicarboxylic acids under elevated pressure which is greater than the vapor pressure of the mixture which arises in a mixing apparatus at a temperature of from 80 to 300° C., wherein the intensive mixing leads to substantial or complete homogenization of the aqueous starting monomer mixture, b) feeding the mixture thus obtained to a heated helical tube evaporator in which a liquid phase and a vapor phase form at a temperature of from 140 to 300° C., a stream of water vapor and/or inert gas also being introduced into the mixture if appropriate upstream of the helical tube, and a decompression to about atmospheric pressure is effected by passage through the helical tube evaporator, wherein no polymerization takes place in the helical tube evaporator, c) removing the vapor phase formed in stage b) from the liquid phase and separating it in a column into water vapor and into organic components comprising diamines, dicarboxylic acids and lactams, and recycling the organic components into the polymerization in stage d), d) passing the liquid phase from the helical tube of stage b) mixed with the organic components of stage c) from the top downward through a vertical polymerization tube at polyamide-forming temperatures to obtain a copolyamide,
wherein the vapor phase which forms from the mixture as it flows through the helical tube is separated from the liquid phase in the top of the vertical polymerization tube and the vapor phase from the top of the polymerization tube is separated in a column into water vapor and into an organic phase comprising diamines, dicarboxylic acids and lactams, and the organic phase is recycled into the top of the vertical polymerization tube.