Process for the manufacture of a solution of salts of diacids/diamine(s)
A method for manufacturing a solution of a diacid and diamine salt for manufacturing polyamide is described. A method for manufacturing an aqueous solution of diacid and diamine salts produced by mixing at least two diacids and at least one diamine, with a weight concentration of salt between 40% and 70%, including, in a first step, preparing an aqueous solution of diacid(s) and diamine(s) with a diacid/diamine mole ratio of less than 1 using one diacid and one diamine, and in a second step, adjusting the mole ratio of diacids/diamine(s) to a value of between 0.9 and 1.1, and fixing the weight concentration of salt by adding another diacid and, optionally, additional water and/or diamine is also described.
1. A process for manufacturing an aqueous solution comprising salts of diacids and at least one diamine, the process comprising:
producing an aqueous solution (A′) of diamine(s) and diacid(s) having a diacid/diamine molar ratio of less than 1, by feeding into a reactor (a) a liquid comprising water and diamine at a temperature from 55° C. to 95° C., (b) a stream (B′) comprising an aliphatic or cycloaliphatic diacid comprising a number of carbon atoms of greater than 10 or an aromatic diacid, optionally (c) a stream comprising diamine, and optionally (d) a stream comprising water; wherein the flow rates of the feed stream or streams are controlled to always have a temperature of the solution in the reactor less than the boiling point of the solution under operating pressure; and the amounts of the water and diamine in the liquid and flow rates of the feed streams being controlled in order to always have a diacid(s)/diamine(s) molar ratio of less than 1;
mixing the aqueous solution (A′) resulting from the first stage with a stream (B″) comprising at least one diacid, the diacid being an aliphatic or cycloaliphatic diacid comprising a number of carbon atoms of less than or equal to 10, and optionally supplementary water and/or supplementary diamine; and obtaining an aqueous solution (resulting from the mixing of (A′) and (B″)) having a diacids/diamine(s) molar ratio of between 0.9 and 1.1;
bringing the solution to a temperature at most equal to the boiling point of the solution at operating pressure by at least a release of heat of reaction between the diamine(s) and the diacids; and
obtaining an aqueous solution (A) comprising salts of diacids and diamine(s) having a concentration by weight of salt of between 40 and 70%.
2. The process according to claim 1 , wherein the reactor is maintained under an atmosphere devoid of oxygen.
3. The process according to claim 1 , wherein the diamine of the solution (A′) and of the stream (B″) is hexamethylenediamine.
4. The process according to claim 1 , wherein the diacid of the stream (B′) is terephthalic acid.
5. The process according to claim 1 , wherein the diacid of the stream (B″) is adipic acid.
6. The process according to claim 1 , wherein the solution (A) exhibits a molar proportion of terephthalic acid, with respect to the diacids, of between 5% and 80%.
7. The process according to claim 1 , wherein the liquid comprises all the water and diamine of the solution (A′).
8. The process according to claim 1 , wherein the stream (B″) is an aqueous solution of diacid and of diamine with a diacid/diamine molar ratio of between 1.5 and 5 and a concentration in the water of the dissolved entities of between 40% and 75% by weight.
9. The process according to claim 1 , wherein the diacid/diamine molar ratio in the aqueous solution (A′) is less than or equal to 0.9.
10. The process according to claim 1 , wherein the liquid in the reactor in which aqueous solution (A′) is produced is at a temperature of from 60° C. to 90° C.
11. The process according to claim 1 , wherein the aqueous solution (resulting from the mixing of (A′) and (B′)) has a molar ratio from 0.98 to 1.02.
12. The process according to claim 6 , wherein the solution (A) has a molar proportion of terephthalic acid, with respect to the diacids, of between 20% and 50%.
13. The process according to claim 8 , wherein the concentration in the water of the dissolved entities is between 45% and 65% by weight.