Abstract: Polyamides, e.g., polyhexamethylene adipamide, are continuously produced via the following stages: Stage 1: into and through a reactor, polycondensing a liquid stream which contain the polyamide monomer(s) at a pressure P1 greater than atmospheric pressure, the stream of material at the outlet of the reactor including a vapor phase which contains steam and a liquid phase which at least contains the product of polycondensation; Stage 2: feeding the outlet stream of material into a chamber, evacuating at least a portion of the vapor phase therefrom and recovering at least the liquid phase which at least contains the product of polycondensation, the pressure P2 in the chamber being regulated at a set value such that it is greater than atmospheric pressure and the residence time of said liquid phase in the chamber being less than 5 minutes; and Stage 3: pressure reducing at least the liquid phase which at least contains the stream of polycondensation product recovered during Stage 2.

Abstract: This invention relates to a coil comprising a first helical tube segment (511) and a second helical tube segment (512, 513) extending, parallel to the first helical segment (511), between a distributor (53) and a manifold (54), said first and second helical segments (511, 512, 513) being centred on a common geometrical axis (X5), with substantially the same bending radius (R1) and nested, such that they form together a globally cylindrical bundle (51). The method comprises a step which consists in interleaving the helical tube segments (511-513) so as to form a globally cylindrical bundle. The invention also concerns a reactor equipped with such a coil which can be used for treating a viscous medium or for carrying out chemical reactions, such as 6-6 polyamide polymerization.

Abstract: The invention relates to wires, fibres and filaments having improved resistance to abrasion, which are suitable, for example, for the production of felts for papermaking machines. In particular, the invention relates to polyamide- or polyester-based wires, fibres and filaments.

Abstract: The invention relates to a process for preparing stabilized compositions based on polyamide. The stabilizer is a phosphorus stabilizer selected from phosphorous acid and hypophosphorous acid. It is introduced before or during the polymerization of the polyamide. The use of these stabilizers prevents foaming phenomena.

Abstract: The invention relates to a continuous process for manufacturing polyamides. The polyamides are of the type obtained from diacids and diamines. The process comprises an operation of continuous mixing of a compound which is rich in amine end groups and a compound which is rich in acid end groups and a polycondensation operation using the mixture. The invention relates to the starting phase of such a process, during which an aqueous solution comprising a mixture of monomers in substantially stoichiometric proportions is used.

Abstract: The invention relates to a process for preparing stabilized compositions based on polyamide. The stabilizer is a phosphorus stabilizer selected from phosphorous acid and hypophosphorous acid. It is introduced before or during the polymerization of the polyamide. The use of these stabilizers prevents foaming phenomena.

Abstract: The invention concerns a method for making polyamide. More particularly, the invention concerns a method for making polyamides derived from the reaction between a diacid and a diamine. It concerns a method for making a polyamide derived from the reaction of at least a diacid with at least a polyamide comprising the following steps: preparing a first mixture of diacid and diamine with a diacid/diamine molar ratio ranging between 0.8 and 0.995, preferably ranging between 0.95 and 0.99 in a first reactor (5); preparing a second mixture of diacid and diamine with a diacid/diamine molar ratio ranging between 1.005 and 1.2, preferably between 1.01 and 1.05, in a second reactor (4); introducing in melted form a first flow of the first mixture and a second flow of the second mixture in a stirred polymer reactor (7); drawing, preferably, continuously, from said reactor a flow of polyamide prepolymer; feeding said polyamide flow into a finishing step to obtain the desired degree of polymerisation.

Abstract: The invention relates to a continuous process for manufacturing polyamides. The polyamides are of the type obtained from diacids and diamines. The process comprises an operation of continuous mixing of a compound which is rich in amine end groups and a compound which is rich in acid end groups and a polycondensation operation using the mixture. The invention relates to the starting phase of such a process, during which an aqueous solution comprising a mixture of monomers in substantially stoichiometric proportions is used.

Abstract: (Co)polyamides, for example the polyamides 6 and 66, are prepared via the improvedly catalyzed polycondensation of (co)polyamide-forming (co)monomers, even in the presence of normally catalyst-inhibiting matting agents (e.g., microparticulate TiO2), the catalyst therefor comprising solid nanometric TiO2 particulates having diameters of less than 100 nm.

Abstract: (Co)polyamides, for example the polyamides 6 and 66, are prepared via the improvedly catalyzed polycondensation of (co)polyamide-forming (co)monomers, even in the presence of normally catalyst-inhibiting matting agents (e.g., microparticulate TiO2), the catalyst therefor comprising solid nanometric TiO2 particulates having diameters of less than 100 nm.

Abstract: L-aspartic acid is improvedly prepared in high yields by treating ammonium aspartate, advantageously in aqueous reaction medium, with an effective, aspartic acid-precipitating amount of fumaric acid.