Dimethyl terephthalate prepn. from polyester waste - by diolysis and methanolysis using magnesium methylate catalyst in anhydrous methanol

摘要

Bis-diol-terephthalate, (I) prepd. by diolysis of a (co) polyterephthalate, is converted to dimethyl terephthalate, (II), by methanolysis, which is carried out in anhydrous MeOH using Mg methylate catalyst. Process is used esp. for regenerating (co)polyterephthalate waste, e.g. of polyethylene-, -propylene-, -butylene-, -hexylene- and cyclohexyl dimethylene terephthalate or -terephthalate-isophthalate copolyesters. (II) can be obtd. in quantitative yields. By-prod. formation is minimised. Incineration of organic Mg salts is easier than that of the Na salts. In an example glycolysis of polyethylene terephthalate waste is carried out with Mg(AcO)2.4H2O and methanolysis of diglycol terephthalate in MeOH using 1000 ppm Mg as Mg methylate.