Harry Harvey Monopropylene Glycol PG
By HH Industries From United Kingdom
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Monopropylene Glycol - PG - BP/USP
99.8 % Purity
Monopropylene Glycol is an effective aircraft de-icer and car antifreeze Monopropylene Glycol (or simply propylene glycol, HOCH2CHOHCH3) is a colourless viscous alcohol with a particularly sweet taste. It’s highly hygroscopic and soluble in many solvents, including water, chloroform and acetone. Its structure contains an asymmetrical carbon, which means two stereoisomers are possible. The standard commercial product is a racemic mixture of both versions, but pure isomers can be obtained by hydration of optically pure propylene oxide.
Monopropylene glycol is synthesised industrially by hydration of propylene oxide (CH3CHCH2O), in a non-catalytic reaction at 200 degree Celsius or catalysed by ion exchange resin or sulphuric acid at a lower temperature (150 degree Celsius). CH3CHCH2O + H2O ? HOCH2CHOHCH3 Subsequently, a purification process by distillation under reduced pressure is also required to remove propanediol, dipropylene glycol and minute amounts of other polypropylene glycols, also produced during the reaction.
The vast majority of monopropylene glycol manufactured is used in the production of unsaturated polyester resins (which include recurring –COO groups in the chain). This process involves a reaction between monopropylene glycol (100 parts by weight) with maleic anhydride (72 parts by weight) and isophthalic acid (54 parts by weight) to generate a co-polymer. It is essential that the ratio 1.2:0.67:0.33 is maintained. These components are mixed at 150 to 200 degree Celsius up to 16 hours, with water continuously distilled from the reaction. These polymers can be further used to produce thermoset plastics. Considered safe, this compound is also used as a tobacco and food additive (E1520); as well as in many personal hygiene and pharmaceutical products. In addition, as it lowers the water’s freezing point, it’s an effective aircraft de-icer and car antifreeze.
As mentioned previously, this compound has a low toxicity and high levels are needed to be detrimental to health. In the body, monopropylene glycol is simply converted mainly to pyruvic acid, which is a normal metabolic component in various pathways to produce energy; but acetic acid and lactic acid are also produced, as well as propionaldehyde. Of these, only the latter may be potentially dangerous if present in large quantities. As to achieve critical values, consumption would have to be over a very short period of time, it is highly unlikely that this threshold can be reached by consuming food with this additive. However, despite rare, case of poisoning with monopropylene glycol can occur, especially in children and pets, with accidental ingestion of antifreeze. Up until recently, it was generally accepted that this compound did not represent a risk following long-term exposure, but concerns with regards to its safe use in paints have questioned its original “Generally Recognised As Safe (GRAS)” classification.
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