Trichloroethylene

• Trichlorethylene ( Tri )
• Ethylentrichlorid
• Acetylentrichlorid
• TCE
• R1120

Colorless liquid with a sweetish ethereal odor

Liquid

1.46 g · cm -3

-86 ° C

87 ° C

78 hPa ( 20 ° C)

Poorly in water (1 g · l -1)

1.4782 (20 ° C)

Risk

2402 mg · kg -1 ( LD50, mouse, oral)

-43.6 KJ / mol

Template: Infobox chemical / molecular formula search available

Trichloroethene (common name: trichlorethylene, trichloroethane, tri ) is a colorless, clear liquid. She smells like chloroform and is unentzündlich. It acts as a powerful solvent and therefore was formerly used in molds and rolling detergents in the printing industry and in metal processing plants as parts cleaner.

Trichloroethylene dissolves to polyolefins and chemically related plastics, making them soft and opaque.

Production and representation

Until the early 1970s, most trichlorethylene was produced in a two -step process from acetylene. First ethyne is reacted with chlorine and a ferric chloride catalyst at 90 ° C to 1,1,2,2- tetrachloroethane:

The 1,1,2,2- tetrachloroethane to trichlorethylene was then dehydrochlorinated. This can be either an aqueous solution of calcium hydroxide

Or in the gas phase done by heating to 300-500 ° C with a barium or calcium chloride catalyst:

Today trichloroethene is usually produced from ethene. This is first converted by means of an iron chloride catalyst is prepared by chlorination of 1,2-dichloroethane

And then converted at 400 ° C with additional chlorine in trichloroethene.

This reaction may be catalyzed by a variety of substances., The catalyst most commonly used is a mixture of potassium chloride and aluminum chloride. However, various forms of porous carbon can be used. This reaction produced as a by- product also tetrachloroethene, which, depending on the amount of added chlorine, also the main product can be. Typically, trichlorethylene and tetrachlorethylene are collected and then separated by distillation.

Use

Due to its good degreasing property, the volatility and non-flammability is trichloroethene, next to related compounds such as tetrachloroethene, been one of the most common cleaning, degreasing and extraction agent. It was used, for example in the metal and glass industry, in the dry-cleaning and textile processing. Even today, it is important as a heavy liquid with minerals and as an intermediate in chemical syntheses. It is also used in the bituminous and asphalt industry, as solvent for bitumen.

Safety

Trichloroethylene is harmful and strong narcotic effect: Inhalation of air with 200 ppm leads to fatigue. It was built by the MAK Commission as carcinogenic (especially kidney cancer) (category 2 ), and have mutagen (Category 3B). It is to be marked as " toxic".

Threshold Limit Values ​​at work: There is currently no binding limit in Germany. In the European Union of the Scientific Committee on Occupational Exposure Limits ( SCOEL) recommends an exposure limit for workers of 10 ppm ( 54.7 mg/m3) for an 8-hour TWA and 30 ppm ( 164.1 mg/m3) for STEL ( 15 min). In the U.S., the limit is 50 ppm.

Acute poisoning cause brain damage, blindness and repealing smell and taste sensation.

In the body it is converted by monooxygenases to Trichlorethenoxid, trichloroacetaldehyde, trichloroethanol and trichloroacetic acid. Trichloroethanol is glucuronidated and excreted in the urine, while the trichloroacetic acid because of their strong binding to proteins accumulate in blood plasma and is neurotoxic.

Legislation

Existing EU legislation on the protection of workers against possible health risks posed by chemical substances (including Chemical Agents Directive 98/24/EC and carcinogens Substances Directive 2004/37/EC ) be no mandatory minimum requirements for risk control employees during the use phase or throughout the life cycle of trichlorethylene. If, however, have the ongoing discussions within the Carcinogens Directive establishing a binding maximum workplace concentration for trichlorethylene for the protection of workers result, this conclusion can be checked.

The VOC Directive 1999/13/EC and Directive 2010/75/EU on industrial emissions make mandatory minimum requirements for emissions of trichlorethylene to the environment, including emissions for cleaning surface. Activities with a solvent consumption below a predetermined threshold are not covered by these minimum requirements.