Proprietes physicochimiques des polyols obtenus par polyestérification des produits de glycolyse du polyéthylènetéré phtalate et syntheses de polyurethanes

Polyesterdiols suitable for the fabrication of PUR/PIR materials may be obtained by alcoholysis of PET, in particular bottles wastes, with a mixture of DEG/DPG/MEG, followed by an esterification with adipic acid and/or phtalic anhydride. The resultant polyols are consists of a mixture of free glycols and α, ωdihydroxy-polyesters built with the fragments resulting from the adipic and ortho or tere phtalic acids and from the diols (mono- and di- ethyleneglycol, dipropyleneglycol). Their properties depend strongly on their raw chemical composition, their mean molecular weight and polydispersity. Tetrabutylorthotitanate catalysed reactions are rapidly going, at 200220°C, to a system at thermodynamic equilibrium. In respect to the interchange equilibrium, the reactivity of DPG is only slightly less than the DEG's and MEG's, whereas the polycondensation equilibrium constant is sometimes higher than expected from the equireactivity concept and, thus, the higher molecular weight species are favoured. Crystallisation tendency is amplified by terephtalic groups, especially by ethyleneterephtalate groups. Long term homogeneous liquid character is only feasible by adjonction of other diacid fragments. Liquid polyols, with high aromatic content, can be attained with orthophtalic moieties introduction. Viscosity is the more sensitive physicochemical property. Viscosity is highly affected by mean polymerisation degree and by acid fragments composition. Polydispersity, that can be only changed by synthesis process modification, is also an important factor. The HCFC 141b compatibilities are generally good. Enhancement is possible by the introduction of DPG fragments. When PVC contaminated samples are glycolised, hydrochloric acid vapours are produced, but to a slight extent and, after solid impurities filtration, the chemical characteristics of the polyol are not modified. Some polyurethane foams were synthesised. The semi-rigid foams obtained are characterised by a very fine cellularity, and after 70°C ageing have a sufficient low thermal conductivity for insulation applications