Antifreeze propylene glycol

Propylene Glycol. Propylene glycol, the second largest use of propylene oxide, is produced by hydrolysis of the oxide with water. Propylene glycol has very low toxicity and is, therefore, used direcdy in foods, pharmaceuticals (qv), and cosmetics, and indirectly in packaging materials (qv). Propylene glycol also finds use as an intermediate for numerous chemicals, in hydrauhc fluids (qv), in heat-transfer fluids (antifreeze), and in many other apphcations (273). 

Higher alcohols have more than three carbon atoms. Examples are the dihydric alcohol, ethylene glycol used for antifreeze, brake fluids and as derivatives in resins, paints " " osives, and polyester fibers. Reactions with propylene make propylene glycol, a moistening ag foods and tobacco. 

It is prudent at this stage to briefly consider the problems that can be experienced in either refrigeration or heat recovery systems when water treatment is required to prevent freezing. The antifreeze treatment of pure water may be achieved by various means, typical ones being various brines, ethylene glycol, and propylene glycol. 

Ethylene glycol is common in automotive antifreeze mixtures. Because of its toxicity, it is sometimes replaced by propylene glycol, which is FDA approved for use in food, and is considered generally accepted as safe. Ethylene glycol has a sweet taste, and accidental poisoning in children is a danger. 

But diethylene glycol is not glycerin or propylene glycol, both of which are nontoxic toothpaste ingredients that also have antifreeze properties, in addition to the emulsifying and moisturizing properties that are useful in toothpastes, cosmetics, baby wipes, bubble baths, medicines, flavorings, and shampoos. 

So when someone warns that there is antifreeze in your toothpaste, ask which antifreeze. Some are illegal adulterants added by criminal cost-cutters, and their products are quickly recalled. Others (like glycerin, propylene glycol, or salt) are generally recognized as safe and are reasonable household ingredients. 

Diols are applied on a multimilhon ton scale as antifreezing agents and polyester monomers (ethylene and propylene glycol) [58]. In addition, they are starting materials for various fine chemicals. Intimately coimected with the epoxidation-hydrolysis process, dihydroxylation of C=C double bonds constitutes a shorter and more atom-efficient route to 1,2-diols. Although considerable advancements in the field of biomimetic nonheme complexes have been achieved in recent years, still osmium complexes remain the most efficient and reliable catalysts for dihydroxylation of olefins (reviews [59]). 

The aquatic toxicity of antifreeze agents is not strictly a function of the main component. Aquatic toxicity may come also from minor components in the formulation. Both ethylene glycol and propylene glycol are believed to be essentially nontoxic for aquatic life. 

Wyandotte A process for making a mixture of ethylene and propylene glycols, for use as antifreeze, from propane. The propane is cracked to a mixture of ethylene and propylene, which are not separated but converted to the corresponding glycols by chlorohydrination. Developed by the Wyandotte Chemicals Corporation. 

Uses. Polyester resins use up about 60% of the propylene glycol (and most of the dipropylene glycol) manufactured. The remainder is used as a tobacco and cosmetic humectant. (a chemical that keeps moisture around), automotive antifreeze and brake fluid ingredients, food additive, and plasticizers for various resins, and making nonionic detergents and coatings. Propylene glycol is an excellent solvent. 

Antifreeze. Any compound or mixture that lowers the freeing point of water can be referred to as antifreeze. The preponderant, commercial antifreeze is ethylene glycol diluted with water. Other organic compounds used occasionally are methanol, ethanol, and propylene glycol. The primary application is to protect automotive cooling systems from freezing. 

Unsaturated polyester resins account for the majority of the commercial use of propylene glycol (40%). Other uses include liquid and laundry detergent (15%), cosmetics and pharmaceuticals (12%), antifreeze and deicers (10%), pet food (6%), functional fluids (6%), paint and coatings (4%), and tobacco humectants (3%). 

Diethylene glycol or propylene glycol alone can also be used as antifreeze coolants, but they are more likely to be mixed with ethylene glycol. Their addition is usually restricted to a small percentage of the total glycol content. 

Aqueous solutions of propylene glycol display excellent antifreeze properties and are therefore valuable as low temperature heat-transfer fluids. For applications involving indirect food contact, heat-transfer fluids formulated with the USP grade product are preferred, since there could be inadvertent contact with a food product. These fluids are commonly used in the brewing and dairy industries as well as in refrigerated display cases in retail grocery stores. 

Glycols and Glycol Ethers. Ethylene and propylene glycols, for example, in antifreeze give rise to considerable exposure of the general public. Glycol ethers, such as methyl cellosolve, are also widely used. 

Glycol Solutions Ethylene glycol can be used in principle down to -35 °C, but in practice is limited to —10 °C because of high viscosity. Propylene glycol has the advantage of being nontoxic. Other antifreeze fluids, such as methanol and ethanol solutions raise safety and toxicity problems. 

Propanediols 1,2-Propanediol (propylene glycol) and 1,3-propanediol are important chemicals because of their use for the production of antifreezes and polyesters, respectively. Figure 2.2.10 shows the petrochemical route to both compounds... 

The common names of glycols can be awkward and confusing because the -ene portion of the name implies the presence of an alkene double bond, but the glycol does not contain a double bond. We will generally use the IUPAC dk>l nomenclature for diols, but be aware that the names ethylene glycol (automotive antifreeze) and propylene glycol (used in medicines and foods) are universally accepted for these common diols. 

Propylene glycol is commonly used to make antifreeze and deicing solutions for cars, airplanes, and boats to make polyester compounds and as solvents in the paint and plastics industries. It is used as a substitute for ethylene glycol mono-alkyl ethers in all-purpose cleaners, coatings, inks, nail polish, lacquers, latex paints, and adhesives. It is also used to create artificial smoke or fog used in fire-fighting training and in theatrical productions. 

---