Diethylene glycol, purification

The principal solvolysis reactions for PET are methanolysis with dimethyl terephthalate and ethylene glycol as products, glycolysis with a mixture of polyols and BHET as products, and hydrolysis to form terephthalic acid and ethylene glycol. The preferred route is methanolysis because the DMT is easily purified by distillation for subsequent repolymerization. However, because PET bottles are copolyesters, the products of the methanolysis of postconsumer PET are often a mixture of glycols, alcohols, and phthalate derivatives. The separation and purification of the various products make methanolysis a cosdy process. In addition to the major product DMT, methanol, ethylene glycol, diethylene glycol, and 1,4-cyclohexane dimethanol have to be recovered to make the process economical.1... 

The required working time is 3 to 4 hours. All equipment is thoroughly dried prior to use and is flushed with an inert gas (argon or nitrogen). Commercial sodium hydroborate is used without purification. The dimethyl ether of diethylene glycol (diglyme) is refluxed over calcium hydride for 8 hours and subsequently distilled over lithium tetrahydroaluminate (lithium aluminum hydride). Commercial tri-n-butylamine is refluxed with acetic anhydride and distilled at atmospheric pressure. 

A reactor was charged with poly[(R)-3-hydroxybutyrate], diethylene glycol, dibutyltin dilaurate, and diglyme and then heated overnight and the telechelic hydroxylated prepolymer isolated and used without further purification. 

Materials. Diethylene glycol divinyl ether, DEGDVE (GAF), butanediol divinyl ether, BDDVE (GAF) and 2-ethoxyethyl ether (Aldrich) were distilled from calcium hydride prior to gamma experiments. All starting materials for the synthesis of onium salts were obtained from Aldrich and used without further purification. 

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