Methanol Depletion in Solvents

The Materials and Processes Research Laboratory of the Electronics Manufacturing Productivity Facility (EMPF) is undertaking a research project to examine the use of solvents in a vapour decreasing process. Fourteen solvents are included in this project. During the research, it was found that the concentration of the denaturant Methanol (MEOH) in the trichlorotrifluoroethane/ethanol (TCF/ethanol) mixture in the vapour degreaser boil sump was being depleted. The fresh material had a concentration of 0 · 35 percent MEOH by volume but the test data showed that this concentration dropped to levels between 0·19 and 0·11 percent MEOH. MEOH depletion in trichlorotrifluoroethane/methanol (TCE/methanol) azeotrope was also detected. The alcohol depletion that was discovered is a concern because when one component of an azeotrope breaks down, the entire azeotrope is affected and the constant boiling feature is no longer present. MEOH separation may also be a flammability hazard and may decrease the Threshold Limit Value (TLV) of the solvent because of MEOH toxicity. It was determined that the MEOH depletion was caused by the molecular sieve or desiccant adsorbing the alcohol. Recommendations are offered to minimise the flammability hazard associated with a MEOH‐adsorbing molecular sieve.