Patent ID: 6670503
Filing Date: 2003-12-30
Classification: C07C

Abstract:
A method of recovering terephthalic acid (TPA) from materials containing poly(ethylene terephthalate) (P.E.T.) through precipitation by acidification with a stronger acid than TPA of an aqueous solution comprising one or more water-soluble metal salts of the TPA and subsequent separation, washing and drying of the precipitated TPA, wherein said solution comprising one or more metal salts of the TPA is obtained by a process comprising the following steps:a) mixing, in the absence of water, a reaction mixture comprising said material containing P.E.T. and one or more water-soluble salts of acids weaker than TPA but stronger than water until a water-soluble reaction compound is obtained; said soluble compound being comprised of soluble chemical species obtained following interaction between P.E.T. and said metal salts of weaker acids than the TPA and possible parts of the unreacted P.E.T. or parts of material of different nature than P.E.T., present in the starting material; b) adding a fraction of water to the soluble compound obtained from step a), until a reaction of salifying the TPA contained in said soluble chemical species is carried out, so that an aqueous solution is obtained which comprises one or more metal salts of the TPA, ethylene glycol and possible parts of the unreacted starting material.