2-хлор-1,3-бутадиен

Описание

Chloroprene, 2-chloro-1,3-butadiene, is a colorless, volatile synthetic liquid that has a pungent ether-like odor. Synthesis of chloroprene was first reported by chemists of the E. I. du Pont de Nemours Company in 1931 following studies of acetylene polymerization with the objective of producing synthetic rubber. The chloroprene monomer differs from isoprene, the fundamental monomer of natural rubber, only by substitution of chlorine for the methyl group of isoprene. Chloroprene was observed to polymerize much more quickly than did isoprene. In industrial processes prior to 1960, chloroprene was produced in relatively high yields by reacting vinyl acetylene with hydrogen chloride. Today, chloroprene is produced more efficiently by chlorination of 1,3-butadiene.
When compared with natural rubber the chloroprene synthetic polymer, polychloroprene, was noted to be much denser, more resistant to water and hydrocarbon solvents, less permeable to many gases, and was more resistant to degradation by oxygen, ozone, hydrogen chloride, hydrogen fluoride, and other chemicals. Due to desirable physical and chemical properties, polychloroprene and its latex polymers are produced in quantities exceeding 200 000 metric tons at a limited number of facilities around the world. Chloroprene production is closely tied to demand for polychloroprene.

Химические свойства

Chloroprene (2-chloro-1,3-butadiene) is a flammable, colorless liquid at room temperature with a characteristic ether-like odor. The Odor Threshold is 0.4 milligram per cubic meter. It is slightly soluble in water and more soluble in organic solvents. It has not been found to occur naturally. Chloroprene is very unstable and reacts in air with oxygen and other compounds to form epoxides, peroxides, and other hazardous compounds.

Использование

Manufacture of neoprene.

Методы производства

Chloroprene can be synthesized by addition of HCl to vinyl acetylene H2C=CH?C≡CH +HCl → H2C=CH?CCl=CH2, and by dehydrochlorination of dichlorobutenes or 2,2,3-trichlorobutane.

Определение

A colorless liquid derivative of butadiene used in the manufacture of neoprene rubber.

Подготовка

Preparation of chloroprene from butadiene In this method, the following route is used:

In the first step, butadiene is chlorinated in the vapour phase at 330-420?? and atmospheric pressure. The main products are 3,4-dichloro-l-butene and 1,4-dichloro-2-butene in approximately equal amounts. The latter material is then isomerized to the former by heating with a copper catalyst such as cuprous chloride. The 3,4-dichloro-l-butene is dehydrochlorinated by treatment with 10% aqueous sodium hydroxide at 85??. Chloroprene is isolated by distillation under reduced pressure in the presence of polymerization inhibitors.

Общее описание

A clear colorless liquid. Flash point -4°F. May polymerize exothermically if heated or contaminated. If polymerization takes place inside a container, the container may rupture violently. Less dense than water. Vapors heavier than air. Used to make neoprene rubber.

Реакции воздуха и воды

Highly flammable. Slightly soluble in water.

Профиль реактивности

CHLOROPRENE emits highly toxic fumes of chlorine gas when heated to decomposition. Autooxidizes very rapidly with air and, even at 0°C, produces unstable peroxides that catalyze exothermic polymerization [Bretherick, 5th ed., 1995, p. 507]. This reactivity is greatly slowed by presence of an inhibitor.

Опасность

Toxic by ingestion, inhalation, and skin absorption. Flammable, dangerous fire risk, explosive limits in air 4.0–20%. Eye and upper respiratory tract irritant. Possible carcinogen.

Угроза здоровью

INHALATION: Fatigue, psychic changes, irritability, oppression in chest, occasionally substernal pain, tachycardia upon exertion. EYES: Can cause conjunctivitis, corneal necrosis and edema of eyelids. SKIN: May cause dermatitis and temporary loss of hair. Rapidly absorbed by skin.

Возможный контакт

The major use of chloroprene is in the production of artificial rubber (Neoprene, duprene); polychloroprene elastomers. Chloroprene is extremely reactive, e.g., it can polymerize spontaneously at room temperatures; the process being catalyzed by light, peroxides, and other free radical initiators. It can also react with oxygen to form polymeric peroxides and because of its instability, flammability, and toxicity, chloroprene has no end-product uses as such.

Канцерогенность

Chloroprene is reasonably anticipated to be a human carcinogen based on evidence of carcinogenicity from studies in experimental animals.

Перевозки

UN1991 Chloroprene, stabilized, Hazard Class: 3; Labels: 3-Flammable liquid, 6.1-Poisonous material.

Несовместимости

Can form unstable peroxides; chloroprene may polymerize on standing with fire or explosion hazard. May form explosive mixture with air. Reacts with liquid or gaseous fluorine, alkali metals; metal powders, oxidizers, creating a fire or explosion hazard. Attacks some plastics, rubber, and coatings. May accumulate static electrical charges, and may cause ignition of its vapors.

Утилизация отходов

Incineration, preferably after mixing with another combustible fuel. Care must be exercised to assure complete combustion to prevent the formation of phosgene. An acid scrubber is necessary to remove the halo acids produced.