Direct determination of isocyanates and amines as degradation products in the industrial production of polyurethane-coated wire

Abstract

Isocyanates and amines were analysed in the workplace atmosphere during the production of polyurethane-coated wire. Toluene diisocyanate and phenyl isocyanate were identified as the isocyanate monomers in the experimental thermodegradation of four different polyurethane varnishes. The formation of amines was also studied with dynamic simulation of workplace conditions. Isocyanates and the corresponding amines were detected at 220 °C. The isocyanates were determined as N-(4-nitrobenzyl)propylamine derivatives by high-performance liquid chromatography with ultraviolet detection. Additional qualitative information was acquired by on-line ultraviolet analysis. The amines were determined as fluorinated amides by capillary gas chromatography with electron-capture detection or alternatively as free amines with thermionic specific detection and packed columns.The toluene diisocyanate and toluenediamine concentrations found during the different stages of the coating process varied from below 0.001 to 0.74 mg m–3 and from below 0.0005 to 4.9 mg m–3, respectively. Corresponding values for aniline were 0.0005 and 0.18 mg m–3. No phenyl isocyanate was detected in the factory samples. The capillary gas-chromatographic determination of electron-capturing derivatives for amines was highly specific and sensitive and thus suitable for their quantification in routine work. Gas chromatography-mass spectrometry of the derivatives confirmed this view.