Process for preparing a diamine/dicarboxylic acid salt

A process for preparing a diamine/dicarboxylic acid salt comprising the steps of:

• (i) forming a reaction mixture by contacting a diamine liquid with a dicarboxylic acid powder comprising an aromatic dicarboxylic acid, wherein the dicarboxylic acid powder has a particle size distribution with a Span, defined by a ratio of (d84−d16)/d50, of at most 5;
• and
• (ii) allowing the diamine and the aromatic dicarboxylic acid in the reaction mixture to react to form a diamine/dicarboxylic acid salt, wherein
• step (i) comprises the steps of:
• (a) gradually dosing the diamine liquid to the aromatic dicarboxylic acid powder, while keeping the aromatic dicarboxylic acid powder in constant movement, and thereafter
• (b) keeping the reaction mixture in constant movement for a time period directly following completion of the dosing;
• wherein
• steps of (a) and (b) are carried out at a temperature above 0° C. and below all of the following:
• the boiling temperature of the diamine and the melting temperatures of the dicarboxylic acid, the diamine/dicarboxylic acid salt and any intermediate reaction product, and wherein
• the reaction mixture in steps (a) and (b) comprises at most 5 wt. % of water, relative to the total weight of the diamine and dicarboxylic acid;
• and wherein
• the diamine consists of a mixture of different diamines.