MONOMERIC BALANCE CONTROL IN THE PREPARATION OF PRECURSORS FOR POLYAMIDATION PROCESSES

1 ) A process control method for measuring and controlling diacid-diamine balance of a polyamide precursor solution comprising:

a) creating a predictive model of Raman spectra for diacid-diamine balance by:

i) acquiring Raman spectra for a series of polyamide precursor solutions having different known molar ratios of diacid:diamine;

ii) modeling the relationship between the known molar ratios and the acquired Raman spectra;

b) applying the model of (a)(ii) to an observed Raman spectrum for a polyamide precursor solution in which the diacid:diamine balance is unknown; and

c) determining the diacid:diamine balance of the solution (b).

2 ) The process control method of claim 1 further comprising comparing the diacid:diamine balance determined in step (c) with a setpoint.

3 ) The process control method of claim 2 further comprising adjusting at least one process variable in response to the comparison of the determined diacid:diamine balance with the setpoint.

4 ) The method of claim 3 , wherein the process variable that is adjusted is selected from the group consisting of: flow rate of dicarboxylic acid or of a dicarboxylic acid-rich feed stream, flow rate of diamine or of a diamine-rich feed stream, residence time, and flow rate of additive.

5 ) The method of any one of the preceding claims wherein the modeling a (ii) comprises partial least squares statistical analysis.

6 ) The method of any one of the preceding claims, wherein the polyamide precursor solution comprises dicarboxylic acid, diamine and water.

7 ) The method of any one of the preceding claims, wherein the dicarboxylic acid comprises adipic acid.

8 ) The method of any one of the preceding claims, wherein the diamine comprises hexamethylenediamine.

9 ) A process of preparing a polyamide comprising the process control method of any one of the preceding claims.

10 ) The process of claim 9 , wherein the polyamide is nylon 6,6.