POLYOLS BY POLYESTERIFICATION OF GLYCOLYS IS PRODUCTS OF POLYETHYLENETEREPHTHALATE, THEIR PHYSICOCHEMICAL PROPERTIES AND RESULTANT POLYURETHANE FOAMS

Polyesterdiols suitable for the fabrication of PUR/PIR materials may b e obtained by alcoholysis of PET, in particular bottles wastes, with a mixture of DEG/DPG/MEG, followed by an esterification with adipic aci d and/or phtalic anhydride. The resultant polyols are consists of a mi xture of free glycols and alpha, omega-dihydroxy-polyesters built with the fragments resulting from the adipic and ortho or tere phtalic aci ds and from the diols (mono- and di- ethyleneglycol, dipropyleneglycol ). Their properties depend strongly on their raw chemical composition, their mean molecular weight and polydispersity. Tetrabutylorthotitana te catalysed reactions are rapidly going, at 200- 220 degrees C, to a system at thermodynamic equilibrium. In respect to the interchange equ ilibrium, the reactivity of DPG is only slightly less than the DEG's a nd MEG's, whereas the polycondensation equilibrium constant is sometim es higher than expected from the equireactivity concept and, thus, the higher molecular weight species are favoured. Crystallisation tendenc y is amplified by terephtalic groups, especially by ethyleneterephtala te groups. Long term homogeneous liquid character is only feasible by adjonction of other diacid fragments. Liquid polyols, with high aromat ic content, can be attained with orthophtalic moieties introduction. V iscosity is the more sensitive physicochemical property. Viscosity is highly affected by mean polymerisation degree and by acid fragments co mposition. Polydispersity, that can be only changed by synthesis proce ss modification, is also an important factor. The HCFC 141b compatibil ities are generally good. Enhancement is possible by the introduction of DPG fragments. When PVC contaminated samples are glycolised, hydroc hloric acid vapours are produced, but to a slight extent and, after so lid impurities filtration, the chemical characteristics of the polyol are not modified. Some polyurethane foams were synthesised. The semi-r igid foams obtained are characterised by a very fine cellularity, and after 70 degrees C ageing have a sufficient low thermal conductivity f or insulation applications.