Abstract: Disclosed is a method for measuring and/or controlling salt balance in a feed to a condensation polymerization process for making nylon. The method employs Raman spectroscopy.

Abstract: Disclosed are nylon salt solution preparation processes including a trim diamine feed. The nylon salt solution is prepared by feeding a dicarboxylic acid monomer and a diamine monomer to a single continuous stirred tank reactor. The dicarboxylic acid is metered, based on weight, from a loss-in-weight feeder to the reactor. The nylon salt solution is formed continuously and has low variability from a target pH and/or a target salt solution concentration. The nylon salt solution is transferred directly to a storage tank, without further monomer addition, pH adjustment, or salt solution adjustment after exiting the continuous stirred tank reactor.

Abstract: Disclosed are process controls for controlling the continuous preparation of nylon salt solution. The process controls include feed forward controls. A model is generated to achieve a target pH and/or salt concentration. Feed rates are set for each of a dicarboxylic acid monomer, a diamine monomer, and/or water to a single continuous stirred tank reactor. The dicarboxylic acid is metered, based on weight, from a loss-in-weight feeder to the reactor. The nylon salt solution is formed continuously and has low variability from a target pH and/or a target salt solution concentration. The nylon salt solution is transferred directly to a storage tank, without further monomer addition, pH adjustment, or salt solution adjustment after exiting the continuous stirred tank reactor.

Abstract: The disclosures herein relate to a polymer such as nylon 66, having low yellowness and excellent whiteness retention for applications in melt extrusion and injection molding where an increase in molecular weight is not desirable. The polymer is prepared with a phosphorus compound content, e.g., a sodium hypophosphite (SHP) content, in an amount of 150 to 300 ppm by weight. The presence of an “end cap” additive such as one selected from acetic acid, propionic acid, benzoic acid, or succinic acid, added at the start of polymerization, effectively mitigates undesired molecular weight gain.

Abstract: The disclosures herein relate to a polymer such as nylon 66, having low yellowness and excellent whiteness retention for applications in melt extrusion and injection molding where an increase in molecular weight is not desirable. The polymer is prepared with a phosphorus compound content, e.g., a sodium hypophosphite (SHP) content, in an amount of 150 to 300 ppm by weight. The presence of an “end cap” additive such as one selected from acetic acid, propionic acid, benzoic acid, or succinic acid, added at the start of polymerization, effectively mitigates undesired molecular weight gain.