Identification of caprolactam oligomers and related compounds in aqueous extracts of nylon‐6

Abstract

Cyclic oligomers of caprolactam were isolated from a multilayered polyolefin plastic film containing a nylon-6 layer and subsequently characterized. Nylon-6 was extracted with aqueous solutions and the levels of the oligomers were measured in the resulting extracts. Oligomers up to n ϭ 5 were present at high and comparable levels in all the nylon-6 extracts. The levels of the oligomers dropped off rapidly with increased compound size after n ϭ 5, with the heptamer being barely observable in the extract chromatograms. The effect of extracting solution pH on the compound's concentration in the extract was small, except for the monomer, whose accumulation was significantly decreased at low pH.

Evaluation of the Chemical Compatibility of Plastic Contact Materials and Pharmaceutical Products; Safety Considerations Related to Extractables and Leachables

“…These cases include the extraction of zinc from stoppers used in diluent vials (resulting in the generation of particulate matter in phosphate‐containing diluents), an “impurity” peak in a LC/UV chromatogram for a drug product that was linked to BHT leached from a stopper, “impurity” peaks in a drug product manufactured in a new facility, which were subsequently linked to substances leached from the silicone tubing used at the new plant, and the release of particulate matter from a filtering device used in aseptic drug product processing. Jenke et al document the extraction of caprolactam and its related oligomers from Nylon 6, a material commonly used in multi‐layered structure used in container‐closure sytems 32. The leaching of organic acids (e.g., acetic formic, stearic, palmitic acids) from gamma‐irradiated EVA materials as a function of solution pH and polarity has been reported 33.…”

A Novel Synthetic Strategy for Preparing Polyamide 6 (PA6)-Based Polymer with Transesterification

“…Juncheng Huang and Ruchao Yuan et al [10,11] prepared a polyamide 6 elastomer by using adipic acid and terephthalic acid as blocking agents and esterification of polytetrahydrofuran under melt conditions, respectively. However, in the process of caprolactam hydrolysis polymerization, approximately 8%–10% of oligomers are inevitably formed, also known as hot water extractables [12,13]. Usually, the polyamide 6 slices are extracted with boiling water or superheated water before the product leaves the factory; otherwise, the quality of the material is affected.…”

Mathematical modeling of the extractables release from multi‐layered plastic films used in drug product containers

“…Caprolactam and its associated cyclic and linear oligomers were clearly associated with the film's nylon layer, which is a caprolactam‐based polymer. The correlation of caprolactam and its associated linear and cyclic oligomers with nylon materials has been previously reported …”

“…The correlation of caprolactam and its associated linear and cyclic oligomers with nylon materials has been previously reported. [27][28][29][30] Targeted extractables were chosen from the film's entire extractables profile based on two criteria, analytical expediency and the location of the extractable's source material within the film structure. Considering analytical expediency, the major considerations were sensitivity and simplicity of the required analytical method and the availability of reference standards.…”