Process for preparing polyamide 6 having a low dimer content

• Main Authors: TRIEBENECK, KONRAD, ULRICH, RALPH
• Format: Patent
• Language: Chinese; English
• Published: 01.10.2004
• Subjects: CHEMISTRY; COMPOSITIONS BASED THEREON; MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONSONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS; METALLURGY; ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP

The present invention relates to a process for preparing polyamide 6 (PA 6) by hydrolytic polymerization of -caprolactam. In a first reaction step, a first intermediate mixture is formed by ring opening -caprolactam in the presence of water, under conditions of increased pressure and temperature. The first intermediate mixture is then dehydrated to form a dehydrated intermediate having a water content of less than 0.5 wt.%. The dehydrated intermediate is subsequently polymerized to produce a polyamide 6 product having a low dimer content (e.g. of less than 0.3 wt.%). The invention also relates to an apparatus in which the process may be performed. The apparatus includes, in sequence, a pressure reactor (23) having heat exchange surfaces (36), a dehydration device (24) that is in fluid communication with the pressure reactor (23), and a main reactor (25) that is in fluid communication with the dehydration device (24).