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Vinyl chloride monomer (VCM), also known as chloroethene in IUPAC nomenclature, is an important industrial chemical chiefly used to produce its polymer, polyvinyl chloride (PVC). At room temperature, VCM is a toxic, colorless gas with a sickly sweet odor.
Additional recommended knowledge
Vinyl chloride was first produced in 1835 by Justus von Liebig and his student Henri Victor Regnault. They obtained it by treating ethylene dichloride with a solution of potassium hydroxide in ethanol.
In 1912, Frans, a German chemist working for Griesheim-Elektron, patented a means to produce vinyl chloride from acetylene and hydrogen chloride using mercuric chloride as a catalyst. While this method was widely used during the 1930s and 1940s, it has since been superseded by more economical processes
A vinyl chloride monomer manufacturing plant generally consists of seven (7) different plant areas, 1) the Ethylene Dichloride (EDC) production area; 2) the Reactors that convert EDC to VCM; 3) the Distillation towers that separate and purify the VCM product; 4) the Oxychlorination process area; 5) the By-product Recovery area; 6) the Environmental Protection area (Waste Treatment and Hazardous Waste storage); 7) the VCM and By-product storage .
STEP 1 - Create the raw material for the VCM reaction, ethylene dichloride (EDC), by reacting ethylene with chlorine
STEP 2 - React EDC to form VCM and hydrogen chloride (HCl)
STEP 3 - Cool the reactor effluent and purify products and by-products
STEP 4 - React recycled HCl to make more EDC which is sent back to STEP 2
STEP 5 - By-product Recovery
STEP 6 - Environmental Protection
STEP 7 - Product and By-product Storage
VCM is a chemical intermediate. It is not a final product. Due to the hazardous nature of VCM to human health there are no end products that use vinyl chloride in its monomer form. Once VCM has been polymerized it is very stable and non-hazardous and can be used for a great number of end products.
VCM liquid is fed to polymerization reactors where it is converted from a monomer to a polymer PVC . The final product of the polymerization process is PVC in either a flake or pellet form. Literally, tens of billions of pounds of PVC is sold on the global market each year. From its flake or pellet form PVC is sold to companies that heat and mold the PVC into end products such as PVC pipe and bottles.
Until 1974, VCM was used in aerosol spray propellant. Prior to the removal of VCM from hair spray the accumulation of vinyl chloride vapor in hair salons may have exceeded the NOAEL (NO Adverse Effect Level) exposure guidelines.
VCM was briefly used as an inhalational anaesthetic, in a similar vein to ethyl chloride, though its toxicity forced this practice to be abandoned.
Vinyl chloride depresses the central nervous system, and inhaling its vapors produces symptoms similar to alcohol intoxication. These include headache, dizziness, and loss of coordination, and in severe cases may progress to hallucination, unconsciousness, and death by respiratory failure.
In the late 1960s, Dr. John Creech and Dr. Maurice Johnson were the first to clearly link and recognize the carcinogenicity of VCM to humans when workers in the PVC section of a B.F. Goodrich plant near Louisville, Kentucky, were diagnosed with liver angiosarcoma, a rare disease. Since that time, studies of PVC workers in Australia, Italy, Germany, and the UK have all associated certain types of occupational cancers with exposure to vinyl chloride. The link between angiosarcoma of the liver and long-term exposure to vinyl chloride is the only one which has been confirmed by the International Agency for Research on Cancer. All the cases of angiosarcoma developed from exposure to vinyl chloride monomer, were in workers who were exposed to very high VCM levels, routinely, for many years.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Vinyl_chloride". A list of authors is available in Wikipedia.|