Reactive Trapping of 3,3′-Dichlorobenzidine Decomposition Products in Polyethylene-Based Diarylide Pigment Concentrates

Abstract

The last 10 years have seen a steady decline in the use of lead and cadmium-based pigments in the coloration of polyethylene and polypropylene packaging materials and durable goods. Concerns over the thermal decomposition products of diarylide pigments in polyethylene matrices have severely limited the use of this versatile and cost-effective pigment family in many colorant applications. Largely as a result of environmental concerns, these relatively inexpensive, highly opaque, lightfast pigments have been replaced with expensive organic alternatives. The replacement pigments are much more expensive, much less strongly colored, less opaque, and they possess poorer light fastness. A strategy for the reactive trapping of 3, 3’-dichlorobenzidine—a potential human carcinogen formed during the high temperature processing of polyethylene concentrates—is discussed is this chapter. Chemical trapping tests made using maleic anhydride modified polymer additives showed favorable reactivity towards 3, 3’-DCB in model systems. The results of laboratory screening trials with Pigment Yellow 13 and Pigment Yellow 83 are also reported. The apparent complexity of the diarylide pigment decomposition reaction in LLDPE at typical processing temperatures (> 200 °C) made isolation, analysis, and quantification of residual 3, 3’-DCB levels extremely difficult.