What is Monoethylene Glycol ?

Monoethyleneglycol (MEG), also known as ethylene glycol or simply glycol, is a colorless, odorless, viscous liquid that is hygroscopic and miscible with water, alcohol, ether, and chloroform. It has a sweet taste, and its density is higher than that of water. MEG has important industrial and commercial uses, and it is mainly manufactured to produce polyester fibers and polyethylene terephthalate (PET) plastics.

Physical and Monoethylene Glycol

Some key physical and chemical properties of MEG include:

- Molecular formula: C2H6O2
- Molar mass: 62.07 g/mol
- Boiling point: 197.3 °C (387.1 °F)
- Melting point: -13 °C (8.6 °F)
- Density: 1.1135 g/cm3 at 20 °C
- Solubility: Highly soluble in water, alcohol, ether, and acetone. Insoluble in hydrocarbon solvents.
- pH: Neutral
- Toxicity: Highly toxic if ingested

MEG has two alcohol groups that make it hygroscopic. Its viscosity makes it well-suited as a heat transfer fluid. MEG can absorb up to 30% of its weight in moisture from the air. It forms an azeotrope with water, meaning it boils at a lower temperature when mixed with water.

Uses and Production

MEG is primarily used to produce polyester fibers, films, and containers through condensation polymerization reactions with terephthalic acid or its dimethyl ester. Around 60–70% of global MEG production is directed towards polyester production. Some key uses and end-use markets of MEG include:

Polyester Fiber Production

Approximately 65% of Monoethylene Glycol manufactured is used for polyethylene terephthalate (PET) and polyester fiber production. PET/polyester fibers are used in clothing, home furnishings like carpets, and nonwoven materials.

Antifreeze and Coolant Solutions

Due to its low freezing point and high boiling point, MEG is widely used as an antifreeze and coolant in automobile radiators and HVAC systems. 20-25% of MEG goes into making antifreeze solutions.

Polyester Resins

MEG is used to manufacture a variety of unsaturated polyester and alkyd resins used in industrial coatings, molded composites, Gelcoats, and anticorrosive applications.

De-icer Fluid

MEG solutions are used as runway de-icers at airports to prevent ice buildup during winter. MEG melts ice at temperatures as low as -60°C.

Other Uses

MEG finds some minor usage in brake fluids, textile printing, and as a solvent. It is also widely used as a humectant in personal care products like shampoos.

Commercially, MEG is produced via two routes:

1) Oxidation of Ethane or Ethylene

Higher temperatures (700-900°C) and oxygen are used to oxidize natural gas or petroleum-derived ethylene to produce MEG. Around 95% of global MEG is produced via this route.

2) Glycolysis of Ethylene Oxide

Ethylene oxide undergoes hydration in the presence of ion-exchange resins to form MEG. This process takes place at lower temperatures (200-250°C).

Health Effects and Regulations

Toxicity

While relatively non-toxic at low levels, ingesting high quantities of MEG can have serious adverse health effects. Symptoms include abdominal pain, central nervous system depression, kidney failure, and even death. Commercial-grade MEG contains bittering agents to prevent accidental ingestion.

Storage and Disposal

MEG needs to be stored and transported carefully according to fire and safety regulations due to its combustibility. The EPA regulates MEG disposal under the Resource Conservation and Recovery Act due to its toxicity. Contaminated MEG cannot be directly released into water bodies or sewers.

Exposure Limits

The US Occupational Safety and Health Administration (OSHA) has stipulated a permissible exposure limit (PEL) of 240 mg/m3 MEG vapor over an 8-hour workday. The National Institute for Occupational Safety and Health also recommends a short-term exposure limit of 60 mg/m3 over 15 minutes.

International Regulations

MEG manufacture and usage internationally are regulated by conventions like EU REACH and other country-specific workplace exposure limits and product safety standards. Testing and risk assessment are required to ensure safe handling and disposal.

With sizeable production capacity and critical usage throughout industries like textiles, automotive, and construction, Monoethyleneglycol will retain prominence as a key industrial and commercial chemical. While hazardous in concentration, continued compliance with evolving regulatory norms will help ensure MEG benefits society responsibly. Its widespread applications exemplify how chemistry improves modern lifestyles while industry growth circles back to create more jobs and wealth.

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 Money Singh is a seasoned content writer with over four years of experience in the market research sector. Her expertise spans various industries, including food and beverages, biotechnology, chemical and materials, defense and aerospace, consumer goods, etc. (https://www.linkedin.com/in/money-singh-590844163)