VINYL CHLORIDE

Description

Vinyl chloride is a colorless, flammable gas with a sweet ethereal odor. It is shipped as a liquefied compressed gas. Contact of the liquid with the skin can result in freezing or frostbite. Vinyl chloride has been established as a human carcinogen. In addition, acute effects of vinyl chloride exposure include irritation of the skin and eyes on contact. Inhalation of concentrations of more than 500 ppm produces mild anesthesia.
Anhydrous vinyl chloride does not corrode metals at normal temperatures and pressures, but in the presence of moisture and elevated temperatures, vinyl chloride accelerates the corrosion of iron and steel at elevated temperatures. Vinyl chloride polymerizes readily when exposed to air, sunlight, heat, or oxygen, although it is chemically stable as shipped with an inhibitor (phenol).

Description

Vinyl chloride is a colorless gas with a mild, sweet odor that belies how hazardous it is. (See the hazard information table.) It has been in the news lately because of the February 3 rail disaster in East Palestine, OH.
Vinyl chloride has been known since at least 1835, when Henri Victor Regnault at the University of Giessen (Germany)1 synthesized it via the reaction of 1,2-dichloroethane2 and potassium hydroxide in ethanol solution. 1,2-Dichloroethane, frequently called ethylene dichloride, is still the precursor to vinyl chloride today. In 2021, the worldwide market for vinyl chloride was 51 megatonnes.
By far the largest use of vinyl chloride is in the manufacture of poly(vinyl chloride)3 (PVC) plastics, which have a multitude of applications that range from pipes to packaging to phonograph records (“vinyls”). Until the 1970s, vinyl chloride was also a commercial refrigerant; its use was discontinued because of its virulent toxicity.
The train derailment in East Palestine included five railcars that carried almost 500,000 L of vinyl chloride as a liquefied gas. Only one of the cars released a small amount of its contents; but the authorities, fearing a vinyl chloride explosion caused by fires from other derailed cars, decided to conduct a controlled release and burn of the chemical in all five cars. This operation resulted not only in the release of highly toxic vinyl chloride but also in the formation of extremely hazardous combustion products, particularly the gases hydrogen chloride4 and phosgene5.
For other compounds released by the derailment, see the sidebar “Additional East Palestine chemical releases”. In the weeks after the accident, the handling of its effects on the residents was widely criticized, as reported in C&EN on February 17.
The authorities state that the cleanup is mostly complete; but air, soil, and water testing will continue indefinitely. Although the US Environmental Protection Agency states that the air quality is normal, residents continue to experience symptoms such as headaches and rashes. The release will likely cause long-term environmental damage.
EPA issues a daily update on its response to the derailment.
1. Regnault was a student of the renowned chemist Justus von Liebig, for whom the university is now named. 2. CA Reg. No. 107-06-2. 3. CA Reg. No. 9002-86-2. 4. CA Reg. No. 7647-01-0. 5. CA Reg. No. 75-44-5.

Chemical properties

Vinyl chloride is a flammable gas at room temperature, and is usually encountered as a cooled liquid. The colorless liquid forms a vapor which has a pleasant, ethereal odor. The odor threshold is variously given as 260 ppm, 3,000 ppm (NJ fact sheet), 4000 ppm (NY fact sheet) in air and 3.4 ppm in water (EPA Toxicological profile). Shipped as a liquefied compressed gas.

Physical properties

Colorless, liquefied compressed gas with a faint, sweetish odor

The Uses of VINYL CHLORIDE

In the plastics industry to manufacture of polyvinyl chloride; in organic syntheses. Has been used as refrigerant, spray can propellant.

The Uses of VINYL CHLORIDE

Vinyl chloride is used as a monomer inthe manufacture of polyvinyl chloride resinsand plastics, as a refrigerant, and in organicsynthesis.

The Uses of VINYL CHLORIDE

Vinyl chloride is polymerized in various ways to polyvinyl chloride (PVC). It is also copolymerized with various other monomers to make a variety of useful resins.

Definition

ChEBI: A monohaloethene that is ethene in which one of the hydrogens has been replaced by a chloro group.

Production Methods

VC was first synthesized in 1835 by Henri Victor Regnault in the laboratory of Justus von Liebig. Industrial production of VC began in 1930s. Ninety-eight percent is used for polyvinyl chloride (PVC) production and the remaining 2% for polyvinylidene chloride and chlorinated solvents. The most common method for the production ofVC monomer is based on cracking ethylene dichloride. Over 95% of VC produced worldwide in 2006 was made by this method. A less common method is by hydrochlorination of acetylene. VC has been produced commercially in the United States for over 70 years.

Production Methods

Vinyl Chloride is produced by alkaline dehydrochlorination of ethylene dichloride, or by thermal cracking of EDC, or 1,1-dichloroethane.

General Description

A colorless gas with a sweet odor. Easily ignited. Shipped as a liquefied gas under own vapor pressure. Contact with the unconfined liquid may cause frostbite by evaporative cooling. Leaks may be liquid or vapor. Vapors are heavier than air. May asphyxiate by the displacement of air. Under prolonged exposure to fire or intense heat the containers may rupture violently and rocket. Suspected carcinogen. Used to make plastics, adhesives, and other chemicals.

Air & Water Reactions

Highly flammable. Forms polymeric peroxides that are explosive [Bretherick 1979. p. 164].

Reactivity Profile

VINYL CHLORIDE is peroxidizable. Forms explosive polymeric peroxides in contact with air (in the presence of any of a variety of catalysts) [Bretherick 1979. p. 164]. Long storage in contact with air increases the concentration of the polyperoxides to hazardous levels [MCA Case History 1551. 1969]. The peroxides may initiate exothermic polymerization of the remaining material [Handling Chemicals Safely 1980.p. 958; Bretherick 1979. p. 160]. Light-sensitive. Many oxidizing agents apparently initiate polymerization (oxides of nitrogen, O2, etc.). May react with very hot water or steam to produce toxic fumes.

Hazard

The vapor density is 2.16, which is heavier than air. It is toxic by inhalation, ingestion, and skin absorption. Vinyl chloride is a known human carcinogen. The TLV is 5 ppm in air. The four-digit UN identification number is 1086. The NFPA 704 designation is health 2, flammability 4, and reactivity 2; uninhibited, the values would be higher for reactivity. The primary uses are in making polyvinyl chloride and as an additive in plastics.

Health Hazard

The acute inhalation toxicity is of low order.Since it is a gas, the route of exposure isprimarily inhalation. The target organs arethe liver, central nervous system, respiratorysystem, and blood. Exposure to high concen trations can produce narcosis. A 30-minuteexposure to 30% vinyl chloride in air wasfatal to experimental animals. Chronic expo sure produced minor injury to the liver andkidneys. Such effects were noted at a 7-hourexposure daily to 200 ppm for 6 months.
Vinyl chloride is an animal and humancarcinogen. Rats subjected to 12 months’inhalation developed tumors of the lungs,skin, and bones. Occupational exposure tothis compound demonstrated an increasedincidence of liver cancer. Tabershaw andGaffey (1974) conducted epidemiologicalstudies on workers who had at least 1 year ofoccupational exposure to vinyl chloride. Thestudy indicated that cancers of the digestivesystem, respiratory system, and brain, as wellas lymphomas, were greater among peoplewho had the greatest estimated exposure tovinyl chloride.

Fire Hazard

Flammable gas; heavier than air, density 2.2 (air=D 1), flame propagation and flash back fire hazard if the container is placed near a source of ignition; autoignition tem perature 472°C (882°F); polymerization may occur at elevated temperatures, which may cause possible rupture of containers; fire extinguishing measure: stop the flow of gas; water may be used to keep fire-exposed containers cool. Vinyl chloride may decom pose under fire conditions, producing the toxic gases carbon monoxide and hydrogen chloride.
Vinyl chloride forms explosive mixtures with air in a wide range; the LEL and UEL values are 3.6% and 33.0% by volume in air, respectively. It may undergo oxidation by atmospheric oxygen, producing an unstable polyperoxide that may explode (MCA 1969). Such a reaction is catalyzed by a variety of contaminants.

Materials Uses

Steel is recommended for all piping, storage tanks, and equipment used with vinyl chloride. However, at elevated temperatures, vinyl chloride in the presence of moisture speeds its corrosion. Stainless steel is also an acceptable material to use with vinyl chloride. Copper and copper alloys must not be used. Valves in vinyl chloride service must not contain copper or copper alloys. Acetylene may be present as an impurity in vinyl chloride and can form an explosive acetyl ide when exposed to copper.
Asbestos, Teflon, lead, and carbon are satisfactory gasket materials for fittings and connections.

Safety Profile

Confirmed human carcinogen producing liver and blood tumors. Moderately toxic by ingestion. Experimental teratogenic data. Experimental reproductive effects. Human reproductive effects by inhalation: changes in spermato- genesis. Human mutation data reported. A severe irritant to skin, eyes, and mucous membranes. Causes skin burns by rapid evaporation and consequent freezing. In high concentration it acts as an anesthetic. Chronic exposure has produced liver injury. Circulatory and bone changes in the fingertips have been reported in workers handling unpolymerized materials.A very dangerous fire hazard when exposed to heat, flame, or oxidzers. Large fires of ths material are practically inextinguishable. A severe explosion hazard in the form of vapor when exposed to heat or flame. Long-term exposure to air may result in formation of peroxides that can initiate explosive polymerization of the chloride. Can react vigorously with oxidizing materials. Can explode on contact with oxides of nitrogen. Obtain instructions for its use from the supplier before storing or handling ths material. To fight fire, stop flow of gas. When heated to decomposition it emits highly toxic fumes of Cl-. See also CHLORINATED HYDROCARBONS, ALIPHATIC.

Potential Exposure

Vinyl chloride is used as a vinyl monomer in the manufacture of polyvinyl chloride (vinyl chloride homopolymer) and other copolymer resins. It is also used as a chemical intermediate and as a solvent.

Physiological effects

Vinyl chloride is toxic and carcinogenic. ACGIH recommends a Threshold Limit ValueTime-Weighted Average (TLV-TWA) of 5 ppm (13 mg/m3) for vinyl chloride. The TLV-TWA is the time-weighted average concentration for a normal 8-hour workday and a 40-hour workweek, to which nearly all workers may be repeatedly exposed, day after day, without adverse effect.
OSHA lists an 8-hour Time-Weighted Average-Permissible Exposure Limit (TWA-PEL) of 1 ppm for vinyl chloride. TWA-PEL is the exposure limit that shall not be exceeded by the 8-hour TWAin any 8-hour work shift of a 40-hour workweek. Additionally, there shall not be exposure to concentrations greater than 5 ppm averaged over any period not exceeding 15 minutes. A complete standard describing control of employee exposure to vinyl chloride as required by OSHA is given in 29 CFR 1910.1017.
Vinyl chloride acts as a general anesthetic in concentrations over 500 ppm. It has been reported that acute exposures to vinyl chloride concentrations above 1000 ppm slowly produce mild disturbances such as drowsiness, blurred vision, staggering gait, and tingling and numbness in the feet and hands. The occurrence of acro-osteolysis and hepatic angiosarcoma have been associated with vinyl chloride exposure. Liver changes including hepatomegaly, liver function abnormalities, and parenchymal damage have been reported.
Vinyl chloride can irritate or damage the eyes on contact. Liquid vinyl chloride also irritates the skin and can freeze the skin on prolonged contact.

Carcinogenicity

Vinyl chloride is known to be a human carcinogen based on sufficient evidence of carcinogenicity from studies in humans.

Source

Vinyl chloride in soil and/or groundwater may form from the biotransformation of 1,1,1- trichloroethane (Lesage et al., 1990), trichloroethylene, 1,2-dichloroethylene (Smith and Dragun, 1984; Wilson et al., 1986), and from the chemical reduction of trichloroethylene by zero-valent iron (Orth and Gillham, 1996).
Drinking water standard (final): MCLG: zero; MCL: 2 μg/L (U.S. EPA, 2000).

Environmental Fate

Biological. Under anaerobic or aerobic conditions, degradation to carbon dioxide was reported in experimental systems containing mixed or pure cultures (Vogel et al., 1987). The anaerobic degradation of vinyl chloride dissolved in groundwater by static microcosms was enhanced by the presence of nutrients (methane, methanol, ammonium phosphate, phenol). Methane and ethylene were reported as the biodegradation end products (Barrio-Lage et al., 1990). When vinyl chloride (1 mM) was incubated with resting cells of Pseudomonas sp (0.1 g/L) in a 0.1 M phosphate buffer at pH 7.4, hydroxylation of the C-Cl bond occurred yielding acetaldehyde and chloride ions. Oxidation at both the methyl and carbonyl carbons produced acetic acid and hydroxyacetaldehyde, which underwent oxidation to give glycolic acid (hydroxyacetic acid). The acid was oxidized to carbon dioxide (Castro et al., 1992).
Surface Water. In natural surface waters, vinyl chloride was resistant to biological and chemical degradation (Hill et al., 1976).
Groundwater. Under aerobic conditions, >99% vinyl chloride degraded in shallow groundwater after 108 d and 65% was completely mineralized (Davis and Carpenter, 1990).
Photolytic. Irradiation of vinyl chloride in the presence of nitrogen dioxide for 160 min produced formic acid, HCl, carbon monoxide, formaldehyde, ozone, and trace amounts of formyl chloride and nitric acid. In the presence of ozone, however, vinyl chloride photooxidized to carbon monoxide, formaldehyde, formic acid, and small amounts of HCl (Gay et al., 1976). Reported photooxidation products in the troposphere include hydrogen chloride and/or formyl chloride (U.S. EPA, 1985). In the presence of moisture, formyl chloride will decompose to carbon monoxide and HCl (Morrison and Boyd, 1971). Vinyl chloride reacts rapidly with OH radicals in the atmosphere. Based on a reaction rate of 6.6 x 10^-12 cm³/molecule?sec, the estimated half-life for this reaction at 299 K is 1.5 d (Perry et al., 1977). Vinyl chloride reacts also with ozone and NO3 in the gas-phase. Sanhueza et al. (1976) reported a rate constant of 6.5 x 10^-21 cm³/molecule?sec for the reaction with OH radicals in air at 295 K. Atkinson et al. (1988) reported a rate constant of 4.45 x 10^-16 cm³/molecule?sec for the reaction with NO3 radicals in air at 298 K.
Chemical/Physical. In a laboratory experiment, it was observed that the leaching of a vinyl chloride monomer from a polyvinyl chloride pipe into water reacted with chlorine to form chloroacetaldehyde, chloroacetic acid, and other unidentified compounds (Ando and Sayato, 1984).

storage

Vinyl chloride should be used in a well-ventilated area, preferably using a hood with forced ventilation. Some authorities believe that the odor of vinyl chloride does not provide adequate warning of its presence in concentrations sufficient to produce dizziness and unconsciousness, so special caution is urged against leaks and poor ventilation.
Precautions required for the safe handling of all flammable gas must be observed with vinyl chloride. Adequate electrical grounding of all lines and equipment, and ditching or diking in storage tank areas to control the liquid in the event of vessel rupture are among recommended precautions. Ditching is preferable because the material should not be retained at a location directly beneath or surrounding the storage tanks. Installations must be designed to comply with requirements for unfired pressure vessels and all state, provincial, and local regulations. Personnel handling vinyl chloride should wear safety shoes, chemical safety goggles or a full face shield, and rubber gloves. An effective educational and training program must be instituted to inform the workers of the hazards involved in handling and using vinyl chloride and the first aid measures to be followed in the event of an emergency. For specific OSHA requirements, refer to 29 CFR 1910.1017.
For respiratory protection, SCBA, air-line cartridge-type respirators, and U.S. Bureau of Mines or NIOSH approved canister-type, cartridge-type respirators should be available in emergencies. Instant-acting safety showers and eyewash fountains should be conveniently located near the site ofthe operation.
Store and use cylinders of vinyl chloride in well-ventilated areas away from heat and all sources of ignition such as flames and sparks. Do not use vinyl chloride around sparking motors or other equipment that is not explosion-proof equipment. Do not store reserve cylinder stocks of vinyl chloride with cylinders containing oxygen, chlorine, or other highly oxidizing or combustible materials.

Shipping

UN1086 Vinyl chloride, stabilized, Hazard Class: 2.1; Labels: 2.1-Flammable gas. Cylinders must be transported in a secure upright position, in a well-ventilated truck. Protect cylinder and labels from physical damage. The owner of the compressed gas cylinder is the only entity allowed by federal law (49CFR) to transport and refill them. It is a violation of transportation regulations to refill compressed gas cylinders without the express written permission of the owner.

Toxicity evaluation

The mechanisms of toxicity for noncancer effects of VC have not been completely determined.
It is hypothesized that VC is metabolized to the reactive metabolites 2-chloroethylene oxide and, subsequently, 2-chloroacetaldehyde via mixed-function oxidases (MFOs), whose activity is primarily concentrated in the liver. The presence of the reactive 2-chloroacetaldehyde results in protein adduction, which interferes with normal cellular function, resulting in cytotoxicity. This is consistent with the progression of effects from hypertrophy to fatty changes, hyperplasia, and necrosis. Indications of binding to proteins such as immunoglobulin G (IgG) in occupationally exposed individuals show immune responses including B-cell proliferation, hyperimmunoglobulinemia, and complement activation and increased circulating immune complexes. It has been hypothesized that cardiac arrhythmia reported after VC exposure may result from sensitization of the heart to circulatory catecholamines, as occurs with other halogenated hydrocarbons.
VC is a known human and animal carcinogen including both increased incidence of hepatic angiosarcomas and hepatotoxicity. It is thought that the mechanism for these liver effects is that VC is metabolized by MFO to form an epoxide intermediate, 2-chloroethylene oxide, which rearranges to form 2-chloroacetaldehyde. These reactive metabolites are transported from parenchymal cells to the nonparenchymal cells forming four primary DNA adducts which produce base–pair transitions during transcription and DNA cross-links. Such mutations can result in the mutation of ras oncogenes and the p53 tumor suppressor gene which are found in VC-exposed individuals.
The metabolism of VC to highly reactive metabolites, the observance of DNA adduction in mechanistic studies, and the observed carcinogenicity resulting from a single, high-level inhalation exposure in animals suggest that the primary mechanism of VC carcinogenicity involves direct DNA interactions rather than secondary responses to cytotoxicity.

Incompatibilities

Copper, oxidizers, aluminum, peroxides, iron, steel. Polymerizes in air, sunlight, heat, and on contact with a catalyst, strong oxidizers; and metals, such as aluminum and copper unless stabilized by inhibitors, such as phenol. Attacks iron and steel in presence of moisture.

Waste Disposal

Return refillable compressed gas cylinders to supplier. Consult with environmental regulatory agencies for guidance on acceptable disposal practices. Generators of waste containing this contaminant (≥100 kg/mo) must conform to EPA regulations governing storage, transportation, treatment, and waste disposal. Incineration, preferably after mixing with another combustible fuel. Care must be exercised to assured to assure complete combustion to prevent the formation of phosgene. An acid scrubber is necessary to remove the halo acids produced. A variety of techniques have been described for vinyl chloride recovery from PVC latexes.

GRADES AVAILABLE

Vinyl chloride is available for commercial and industrial use in various grades having much the same composition from one producer to another. It typically has a minimum purity of 99.9 mole percent in the liquid phase.