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: 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: 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: 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.

Abstract: A composition of polyester resins comprising diblock copolymers formed of two different polyester blocks joined by a bifunctional radical deriving from a dianhydride of a tetracarboxylic acid. The compositions are prepared by a reaction in the solid state of two different polyesters in the presence of a dianhydride of a tetracarboxylic acid.

Abstract: A method for recycling polyethyleneterephthalate beverage bottles comprises the removal of the contaminants with the use of supercritical carbon dioxide. The recycled material is placed in an autoclave and treated with carbon dioxide at a temperature greater than 31.degree. C. and a pressure greater than 50 bars.

Abstract: A method for purifying polyethyleneterephthalate reins by contacting the resins with an atmosphere containing carbon dioxide under supercritical conditions.

Abstract: A method of treating PET preforms and bottles consists of subjecting the preforms or the bottles to a carbon dioxide atmosphere at a higher temperature than the critical temperature of carbon dioxide, a higher pressure than ambient pressure, and for a set time period. The treatment reduces the acetaldehyde concentration in the head of the treated bottles or in the bottles obtained from the treated preforms by stretch-blowing, and also reduces the permeability of gases through the bottle walls.