Abstract: The present invention refers to a process for manufacturing polyester comprising at least the following steps: (a) esterifying or transesterifying a carboxylic diacid or a dieester of a carboxylic diacid with a diol, (b) polymerizing in melt phase the esterification or transesterification product, (c) solidifying and granulating, (d) placing in contact the granules with a liquid swelling medium, and (e) post-condensing the granules in solid phase. The realization of the immersion step in a swelling medium permits increasing the kinetics of the solid phase post-condensation step.

Abstract: The present invention refers to the production of a polyester-type polymer and more particularly to the solid phase condensation of a polyester. The invention presents a process for manufacturing polyester which comprises at least the following steps: a) esterifying of transesterifying a carboxylic diacid or a carboxylic acid diester with a diol, b) prepolymerizing the esterification or transesterification product in liquid phase until an average degree of polymerization between 10 and 50, preferably between 20 and 45, c) preparing a dispersion of the prepolymer in a non-solvent of diol and non-swelling of the prepolymer liquid, the prepolymer being present in the dispersion in the form of solid particles having diameters under 2 mm and crystallized, with a crystalline lamella thickness under 17 nm, d) polymerizing in dispersed solid phase, e) recovering solid particles. The accomplishment of a dispersed solid phase polymerization permits improving the reaction kinetics.