Glycols

Abstract

Glycols are diols, compounds containing two hydroxyl groups attached to separate carbon atoms. In an aliphatic chain, ethylene glycol, is the simplest glycol. Diethylene, triethylene, and tetraethylene glycols are oligomers of ethylene glycol. Polyglycols are higher molecular weight adducts of ethylene oxide and are distinguished by intervening ether linkages in the hydrocarbon chain. The first commercial application of the Lefort direct ethylene oxidation to ethylene oxide followed by hydrolysis of ethylene oxide remains the main commercial source of ethylene glycol production. The uses for ethylene glycol are numerous. Some of the applications are polyester resins for fiber, PET containers, and film applications; all‐weather automotive antifreeze and coolants, defrosting and deicing aircraft; heat‐transfer solutions for coolants for gas compressors, heating, ventilating, and air‐conditioning systems; water‐based formulations such as adhesives, latex paints, and asphalt emulsions; manufacture of capacitors; and unsaturated polyester resins. The oligomers also have excellent water solubility but are less hygroscopic and have somewhat different solvent properties. The largest commercial use of ethylene glycol is its reaction with dicarboxylic acids to form linear polyesters. In addition to oligomers ethylene glycol derivative classes include monoethers, diethers, esters, acetals, and ketals as well as numerous other organic and organometallic molecules. The propylene glycol family of chemical compounds consists of monopropylene glycol (PG), dipropylene glycol (DPG), and tripropylene glycol (TPG). These chemicals are manufactured as copoducts and are used commercially in a large variety of applications. They are available as highly purified products which meet well‐defined manufacturing and sales specifications. All commercial production is via the hydrolysis of propylene oxide. The propylene glycols are clear, viscous, colorless liquids that have very little odor, a slightly bittersweet taste, and low vapor pressures. The most important member of the family is monopropylene glycol. All of the glycols are totally miscible with water. Propylene glycol, when produced according to the U.S. Food and Drug Administration good manufacturing practice guidelines at a registered facility, meets the requirements of the U.S. Food, Drug, and Cosmetic Act. It is listed in the regulation as a direct additive for specified foods and is classified as generally recognized as safe (GRAS). Because of its low human toxicity and desirable formulation properties it has been an important ingredient for years in food, cosmetic, and pharmaceutical products. Glycols such as neopentyl glycol, 2,2,4‐trimethyl‐1,3‐pentanediol, 1,4‐cyclohexanedimethanol, and hydroxypivalyl hydroxypivalate are used in the synthesis of polyesters and urethane foams. Commercial preparation of neopentyl glycol can be via an alkali‐catalyzed condensation of isobutyraldehyde with 2 moles of formaldehyde (crossed Cannizzaro reaction). 2,2,4‐Trimethyl‐1,3‐pentanediol can be produced by hydrogenation of the aldehyde trimer resulting from the aldol condensation of isobutyraldehyde. The manufacture of 1,4‐cyclohexanedimethanol can be accomplished by the catalytic reduction under pressure of dimethyl terephthalate in a methanol solution. Hydroxypivalyl hydroxypivalate may be produced by the esterification of hydoxypivalic acid with neopentyl glycol or by the intermolecular oxidation–reduction (Tishchenko reaction) of hydroxypivaldehyde using an aluminum alkoxide catalyst. Polyester resins produced from of the glycols, are useful for preparation of coatings exhibiting a combination of hydrolytic stability, excellent weather resistance, and good flexibility.

Material characterization of polyamide 12 and related agents used in the multi-jet fusion process: complementary application of high-resolution mass spectrometry and other advanced instrumental techniques

“…In addition, triethylene glycol is a water soluble and colorless additive with low volatility and a very high boiling point (288 °C). Furthermore, the application of triethylene glycol in printing inks, cleaning compounds, and heat-transfer fluids is reported in the literature [21].…”

A Review of Recent Developments of Pervaporation Membranes for Ethylene Glycol Purification

“…Ethylene glycol (EG) is an essential reagent in the chemical industry. Among its main applications, worthy of mention are the production of polymers, namely, polyethylene terephthalate and polyester, as well as manufacture of nonvolatile antifreeze and brake fluids, and anti-icing additives [ 1 ]. In 2010, the global production and consumption of EG were about 20 million metric tons, with an estimated increase of 5–10% per year [ 2 ].…”

Molecular interaction study of glycols in water and sodium ethylparaben mixtures using acoustic method

“…Glycols are a type of chemical that belongs to the alcohol family, with two hydroxyl (-OH) groups linked to separate carbon atoms in each molecule. In 1859, a French scientist called Charles-Adolphe Wurtz saponified ethylene glycol diacetate with potassium hydroxide to make the most basic diol, ethylene glycol (EG) [10]. Binary liquid mixtures including poly(ethylene) glycols (PEGs) and glycols in non-aqueous solvents are used in the food industry [11].…”