Chemicals & Polymers SOLVENT CLEANING : ZCZ ’ S NEW PRODUCT DEVELOPMENT

1. INTRODUCTION Over the past 60 years, for the reasons shown in Figure 1, the engineering industry has found halogen-containing cleaning solvents to be technically very effective. More recently, the chemical inertness, non-flammability, low toxicity and convenience of 1,1,2-trichlorotrifluoroethane, has led to the wide use of products based on CFC-113 in electronics applications. Evidence of their environmental impact has, however, brought about the need for greater efficiency in the use of halogen-containing materials, including improved containment and recycling technologies. In certain cases, such as CFC-113 and methyl chloroform, concerns regarding their impact on the ozone layer, arising from their relatively long atmospheric lifetime, has resulted in a phase out regulated by the Montreal Protocol. Relevant data are shown in Figure 2. Figure 3 shows some atmospheric lifetime and Ozone Depletion Potential (ODP) values for the two regulated materials, along with values for two alternatives, Several well established solvents, such as methylene chloride, trichloro-ethylene and tetrachloroethylene, have such short lifetimes in the atmosphere that their impact on the ozone layer is negligible compared with the estimated 3.5 million tons of naturally occuring organohalogen compounds, such as methyl chloride and methyl bromide, which are believed to be generated each year from sea weed and rotting wood (refs 1,2). Approaches to these challenges employed by solvent users and producers are summarised in Figure 4 and include: