The present invention refers to an economical and ecological process for obtaining aromatic polyester-ether polyols suitable for rigid polyurethane foams formation, using as raw materials polyethylene terphthalate wastes and, in some alternatives, a material derived from biomass, consisting of: (1) glycolysis of polyethylene terephthalate wastes, resulted from soft-drink postconsuming bottles, with aliphatic polyols or polyoxyalkylene glycols with low molecular weights, in presence of transesterification catalysts; (2) partial esterification of aromatic polycarboxylic acids cyclic anhydrides with glycolysis products resulted from previous reaction stage (1), until the acid number reaches a particular value corresponding to a single carboxyl group full esterification (anhydride ring opening addition); (3) alcoxylation of the reaction mixture obtained in stage (2), up to a designed hydroxyl number, in presence of base catalysts (tertiary amines) and to an aromatic polyester-ether polyol obtained by some alternatives of the respective procedure, incorporating 20 - 30 % mol. moieties derived from PET wastes and 10-20% mol. moieties derived from isosorbide, and which can replace up to 30% wt. of the polyol component in rigid polyurethane foam formulations.
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