Process for preparing pa 4x and pa 410 obtainable by the process

摘要

A process for preparation of a polyamide PA 4X containing monomer units of 1 4 diaminobutane and an aliphatic linear dicarboxylic acid X with at least 8 carbon atoms which contains the following steps: 1) making a solution comprising a salt of 1 4 diaminobutane and the aliphatic linear dicarboxylic acid and water at a temperature at which the salt dissolves; 2) concentrating the solution of the salt at a temperature above the crystallization temperature of the salt at a pressure of at most 7 barA to a water content of between 0 and 30 wt% based on the total amount of solution 3) producing a polymer from the solution obtained by step 2 while keeping the polymer in a melt and at a pressure of less than 18 barA 4) depressurizing the polymer obtained at step 3 while keeping the polymer in the melt to further polymerize the polymer. In an preferred embodiment the aliphatic linear dicarboxylic acid is 1 10 decanedioic acid. Also claimed is a polyamide 410 having a viscosity number (VN) of at least 100 ml/gram.