International name: Perchloroethene (Tetrachloroethene)

Synonyms: tetrachlorethylene

Chemical formula: C2Cl4

Appearance: clear liquid without admixture of emulsified particles

Manufacturing: Russia

Packing and storage: metal barrel; up to 2 years

 

Organochlorine solvents. General information

Chlororganic solvents have the following valuable qualities: the ability to dissolve a variety of substances, easily mix with other organic solvents, considerable resistance to fire. Their combustibility decreases with increasing chlorine content in the molecule. The raw material for their production is chlorine, as well as the gases of oil cracking - ethylene and homologues.
Solvents are sufficiently stable with respect to oxidizing agents. Monochloroalkanes that do not oxidize under the influence of such strong oxidizing agents as potassium permanganate, concentrated nitric acid, organic peracids are particularly stable.
The organochlorine solvent has a low surface tension to ensure maximum wetting and penetration into the grooves, blind holes of a complex configuration product.
The main organochlorine solvents are methylene chloride, carbon tetrachloride, trichlorethylene, tetrachlorethylene and methyl chloroform. They are used for degreasing metals, dry cleaning clothes and fabrics, for the extraction of fats and oils
Solvents also interact with halogens (and hydrogen halides) in the liquid and gas phases over a wide range of temperatures.
The organochlorine solvent readily dissolves the impurities present on the surface. The dissolving power of any solvents is evaluated in Kauri-butanol values. The dissolving power of organochlorine solvents used for degreasing various materials is exceptionally high.
The ability of organochlorine solvents to decompose under the influence of light, heat, metals and other factors is different and depends on the structure of the solvent, including the number of chlorine atoms and the presence of a double bond

 

Description

Dichloromethane (methylene chloride, DCM, CH2Cl2) is a transparent, readily mobile and volatile liquid with a characteristic sweet odor for halogenated derivatives. It was first synthesized in 1840 by keeping a mixture of chlorine and methyl chloride in the light. In general, it is most safe among haloalkanes.

 

Properties

Virtually insoluble in water (2 g / l), mixed with most organic solvents. Light-weight (40 ° C) forms an azeotropic mixture with water (bp 38.1 ° C, 98.5%). Methylene chloride reacts with chlorine to form chloroform and carbon tetrachloride.

 

Receiving

It is obtained by direct chlorination of methane with chlorine under conditions of a radical mechanism at 400-500 ° C with a ratio of 5: 1. As a result, a mixture of all possible chlorides is obtained: chloromethane, dichloromethane, chloroform and carbon tetrachloride, which are then separated by distillation. After that, it has a purity of at least 99.7%. In 1995, annual production was estimated at 500 million tons.

Application

Methylene chloride is used in the production of chemical fibers, film films, plastics, perfumes, rubber products and in other industries; is a solvent of polymers (eg, cellulose ethers, rubbers); Extracting agent for extraction of essential oils, in metallurgy, radio industry is used for degreasing surfaces, in the paint and varnish industry - for making old paint washing.
In the European Union, paints with dichloromethane are prohibited, both for personal use and for professional use. For regular work with dichloromethane, latex gloves or nitrile gloves are not suitable.

 

Safety requirements

Organochlorine solvents, when inhaled in large concentrations, cause anesthetic effects, the symptoms of which quickly disappear in the open air, and the restoration of health is complete without consequences.
Although methylene chloride is the least poisonous among haloalkanes, but one must be careful when handling, as it is very volatile and can cause acute poisoning. Exhaust ventilation is necessary. In the body, dichloromethane is metabolized to carbon monoxide, which can cause poisoning. A prolonged cover contact with dichloromethane may cause accumulation in fatty tissues and lead to burns. Also, with prolonged use of it, liver damage and neuropathy are possible. In rats it is shown that it can cause lung, liver and pancreatic cancer. At the same time, there was no evidence of any effect on the development of embryos in women who had contact with DXM.
Methylene chloride is difficult to burn, it can form explosive mixtures with air.
When acute poisoning - fresh air, peace, warmth, alkaline drink.

 

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