CEH Report

Table of Contents

Abstract

This report covers the four chlorinated methanes: methyl chloride, methylene chloride, chloroform and carbon tetrachloride. Chlorinated methanes are used primarily as precursors—methyl chloride for silicones and other materials, methylene chloride for its solvent properties, chloroform for hydrochlorofluorocarbon-22 (HCFC-22) and carbon tetrachloride for chlorofluorocarbons-11 and 12 (CFC-11 and CFC-12). As CFCs are being phased out, use of carbon tetrachloride for newer HFCs such as HFC-245fa, HFC-365mfc, and HFO-1234yf/ze is growing.

The following pie charts show world consumption of the four chlorinated methanes.

The largest market for methyl chloride is the production of methyl chlorosilanes as an intermediate in the production of silicones, followed by use in methyl cellulose production, halobutyl rubber production and quaternary ammonium compounds. In 2011, it is estimated that over 84% of all methyl chloride consumption was used in the production of silicones. The United States is the world's largest consumer of methyl chloride in the production of silicones. The silicone market is growing faster in Asia and Europe than in the Americas.

The leading application for methylene chloride (MeC) is as a solvent, although usage in the production of HFC-32 has been growing. MeC is also used as an auxiliary foam blowing agent in the production of low-density and soft polyurethane foams, which are mainly used for furniture, transportation, bedding and carpet applications. This is not considered a solvent application for the purposes of the report. In addition, small but growing amounts of MeC are used as a feedstock for hydrofluorocarbon 32 (HFC-32), which is used as a substitute for HCFC-22 in certain refrigeration applications. MeC is used as a processing solvent in a variety of pharmaceutical applications, including use as a reaction medium, extraction solvent, and as a carrier solvent for polymeric barrier coatings applied to pharmaceutical tablets. In these applications, no residual MeC is left on the final product, or only in minor amounts.

For many years, there has been considerable debate over the toxicity of MeC. In the United States, OSHA considers MeC as a "potential human carcinogen." After some debate in the 1990s, OSHA lowered the 8-hour permissible exposure level for MeC to 25 ppm. In California, containers of paint strippers containing MeC must carry a strong warning about the risk of cancer, as required by Proposition 65, the California State law that requires strict labeling of containers of toxic materials.

The primary application for chloroform is the production of HCFC-22 (R-22), which is used as a refrigerant and an intermediate in the production of the fluoropolymer PTFE.

Demand for carbon tetrachloride is led by Western Europe and the United States with the production of HFC-245fa, HFC-365mfc and HFO-1234yf.

Consumption is forecast to grow at average annual rates of about 3% for methyl chloride, 1.5% for methylene chloride, 3.5% for chloroform, and 2.5% for carbon tetrachloride during 2011–2016.