Abstract: The subject of the invention is a method to manufacture polyester resins using a by-product formed during a process of oxidizing cyclohexane to cyclohexanol and cyclohexanone, which contains a mixture of carboxyl acids; the method comprises a heating process with the removal of water and low-boiling residues as well as a polycondensation process with di- and polyhydroxy alcohols under a reduced pressure; the method described is characterized by that a water layer is applied as a baseline material in the synthesis; the said water layer is separated from the residues left over after the hydrolysis of cyclohexyl esters contained in the cyclohexane oxidation product, and after the main components, cyclohexanol and cyclohexanon, have been first separated from the said product: thereafter, the water layer is condensed.

Abstract: The subject of the invention is a method to manufacture polyester resins using a by-product formed during a process of oxidizing cyclohexane to cyclohexanol and, cyclohexanone, which contains a mixture of carboxyl acids; the method comprises a heating process with the removal of water and low-boiling residues as well as a polycondensation process with di- and polyhydroxy alcohols under a reduced pressure; the method described, is characterized by that a water layer is applied as a baseline material in the synthesis; the said water layer is separated from the residues left over after the hydrolysis of cyclohexyl esters contained in the cyclohexane oxidation product, and after the main components, cyclohexanol and cyclohexanon, have been first separated from the said product: thereafter, the water layer is condensed.