Abstract: Polyester resins particularly suitable for extrusion and injection blow-molding contain from 20 to 1000 ppm of a dianhydride of an aromatic tetracarboxylic acid and show values of die swell less than 45%. The resins are obtained by solid state polycondensation of resin having intrinsic viscosity less than 0.7 dl/g, added with a dianhydride of an aromatic tetracarboxylic acid in amount between 0.02 and less than 0.05% by weight.

Abstract: Articles from a polyester resin obtained by melt-shaping of the resin added with a polyfunctional compound, capable of increasing the molecular weight of the resin by addition reaction in the solid state with the end groups of the resin and by upgrading treatment of the article, so as to increase by at least 0.1 dl/g the intrinsic viscosity of the starting resin.

Abstract: Process for the production of aromatic polyester resins starting from resins with an IV from 0.1 to 0.4 dl/g comprising the steps of blending the resin with a dianhydride of a tetracarboxylic acid, extruding the resin under the form of a strand, cooling the strand or the chips obtainable by cutting the strand, at a temperature between 150° C. and 210° C. and maintaining the same temperature for sufficient time to obtain a crystalline product wherein the DSC curves of the same do not show presence of premelt peaks or only so in a negligible amount.

Abstract: Process for the crystallization of aromatic polyester resins having IV between 0,5 and 0.7 dl/g wherein the resin is extruded in the form of a strand at extruder exit or the chips obtained by cutting the strand are crystallized maintaining them at temperature between 160° C. and 220° C. for sufficient time to obtain a crystallized product wherein the DSC curves do not show the presence of practically any premelt peaks.

Abstract: Aromatic polyester resins, having improved mechanical and hydrolysis resistant properties, by mixing said aromatic polyester resin with a phenoxy resin, a dianhydride of a tetracarboxylic acid and liquid crystals.

Abstract: Film obtained by blowing, using the bubble method from aromatic polyester resins containing a dianhydride of an aromatic tetracarboxylic acid, having thickness inferior to 10 .mu.m.

Abstract: Polyester resins containing up to 5% by weight of a polymeric liquid crystal and an upgrading agent capable of increasing the I.V. of the resin by polyaddition reaction in the solid state with the end groups of the resin. Fibers, films and biaxially oriented articles obtained from the resins.

Abstract: Process for the production of aromatic polyester resins starting from resins with an IV from 0.1 to 0.4 dl/g comprising the steps of blending the resin with a dianhydride of a tetracarboxylic acid, extruding the resin under the form of a strand, cooling the strand or the chips obtainable by cutting the strand, at a temperature between 150.degree. C. and 210.degree. C. and maintaining the same temperature for sufficient time to obtain a crystalline product wherein the DSC curves of the same do not show presence of premelt peaks or only in a negligible amount.

Abstract: Articles from a polyester resin reinforced with glass fiber obtained by melt-shaping of the resin mixed with the glass fiber and a polyfunctional compound capable of increasing the intrinsic viscosity of the resin by addition reactions with the end groups of the rein using melt residence times during the shaping phase lower than 120 sec. and temperatures lower than 300.degree. C.

Abstract: Process for the solid state polycondensation of polyamide resins by the use in the polycondensation reactor of a quantity of an inert gas such that the ratio by weight between the solid capacity/h at the reactor outlet and that one of gas fed into the reactor is lower than 0.5.

Abstract: A process for the preparation of polymeric alloys from polyester resins and polymers containing groups capable of giving addition reaction with functional compounds containing at least two reactive groups comprising the melt state mixture stage of polyester resin, reactive polymer and functional compound of mixture pelletizing and following polyaddition reaction in the solid state at temperatures between 150.degree. and 220.degree. C. to obtain an increase of the polymer intrinsic viscosity of 0.1 dl/g in comparison with the starting polyester resin.

Abstract: Cooling process for polyester and/or polyamide resins downstream of solid-state polycondensation plants in which the cooling is carried out by passing the solid material through two types of equipment in series, of which one is a fluid-bed, the other is a solid/wall cooling equipment. The fluid bed equipment is fed with a stream of inert-gas coming from the solid-state polycondensation reactor, previously subjected to by-products purification, drying and cooling.

Abstract: Concentrates of dianhydrides of tetracarboxylic acids in polycarbonate resins containing up to about 50% by weight of dianhydride. The concentrates can be added to aromatic polyester resins in the melt in quantities equivalent to contents of dianhydride from 0.05 to 2% by weight of the resin.

Abstract: Process for the production of aromatic polyester resins by polycondensation in the solid state of resins with intrinsic viscosity comprised between 0.1 and 0.45 dl/g, in which the ratio by weight between the hourly flow speed of the inert gas fed to the reactor and the hourly flow speed of the fed polymer is comprised between 0.1 and 0.6.

Abstract: Aromatic polyester resins are continuously crystallized in a fluid bed crystallizer, where the fluidizing gas (nitrogen) enters at a temperature not lower than 195.degree. C. and the average residence time is higher than 5 minutes.

Abstract: Process for the solid state polycondensation of polyester resins, where an inert gas is circulating in a moving bed of polymer at a temperature between 180.degree. and 230.degree. C., characterized by the fact that the ratio by weight between the gas rate of flow per hour and that one of the discharged polymer is lower than 0.6.

Abstract: Polyamide resins characterized in melt state by high sensitivity to shear forces and high visco-elasticity, obtained by polycondensation/polyaddition in the solid state in presence of polyfunctional compounds capable of reacting with resin terminal groups and/or in presence of polyester resins employed in quantity up to about 40% by weight of the resin mixtures.

Abstract: Filaments from a polyester resin having an elastic modulus higher than 30 GPa and stress at break greater than 300 MPa. The filaments are obtained by upgrading under stretch filaments prepared from polyester resin mixed in the melt with a polyfunctional compound able to increase the polymer intrinsic viscosity by addition reaction in the solid state with the terminal groups of the resin.

Abstract: Polyester resins containing up to 5% by weight of a polymeric liquid crystal and an upgrading agent capable of increasing the I. V. of the resin by polyaddition reaction in the solid state with the end groups of the resin. Fibres, films and biaxially oriented articles obtained from the resins.

Abstract: A new process has been developed for separating the water and acetic acid present in the aqueous phase contained in cellulose acetate flakes precipitated from esterification solutions of cellulose. The process includes the step of simultaneously extracting water and acetic acid from the aqueous phase with supercritical carbon dioxide until the content of water and acetic acid in the flakes is substantially reduced.