Abstract: A continuous process for mixing polymer melts with additives, in particular polycarbonate melts with additives in liquid form, in solution or in dispersion is described. The additives are added to a main stream of polymer melt and are then mixed, preferably directly, with the main stream in a static mixer.

Abstract: An improvement in the continuous two-phase interfacial condensation process for preparing polycarbonate is disclosed. In the process that entails at least one diphenol, phosgene, at least one chain terminator, and optionally branching agents and is carried out in the presence of a catalyst the improvement comprising maintaining the concentration of the catalyst at a level of at least 0.012 mol per mol of diphenol.

Abstract: A motor-vehicle antenna has a monopole formed by a rigid circuit-board having a conductive trace, a socket for connecting a coaxial cable to the monopole, and a ground plane formed of rigid sheet metal or a circuit board and fixed to the monopole.

Abstract: A process for producing phosgene having low content of carbon tetrachloride is disclosed. The process entails reacting carbon monoxide with chlorine in the presence of elemental carbon, in a reactor. Critically the temperature of the gas stream emerging from the reactor is restricted to 30 to 80° C. and its pressure, measured directly downstream from said reactor is restricted to 120 to 400 kPaabs. The phosgene thus produced has a content of carbon tetrachloride that is less than 150 ppm.

Abstract: The present invention relates to a process for the treatment of waste waters containing common salt, characterised in that, by a specific sequence of acidification, extraction, alkalisation and stripping steps, an aqueous common salt solution is obtained, which can be used directly in chlor-alkali electrolysis.

Abstract: An apparatus for degassing plastic materials, e.g., high molecular weight polycarbonate solutions, is described. The apparatus includes a double-shaft extruder having a length-to-diameter ratio of less than or equal to 40, which comprises: (i) two co-rotating and meshing shafts; (ii) an intake opening; and (iii) upstream and downstream portions relative to the intake opening. The shafts of the extruder are designed with a double lead in a degassing zone, and with a triple lead in a pressure build-up zone. Each of the degassing and the pressure build-up zones are down-stream from the intake opening, and the pressure build-up zone is further down-stream than the degassing zone. Also described is a process for degassing plastic materials, which involves providing the described double-shaft co-rotating extruder, into which plastic material is fed, processed and degassed.

Abstract: A process for preparing an emulsion is disclosed. The process entails mixing an aqueous mineral acid that contains phosphorous in an organic solvent, the mixing being continuous and with the degree of intensity sufficient to form a homogeneous emulsion. The emulsion prepared by the process is useful in the process of preparing polycarbonate by the interfacial process. Accordingly the washed organic polycarbonate that has been washed without the use of a phosphorous containing mineral acid solution is mixed with the novel emulsion. The resulting polycarbonate is characterized by its improved thermal stability.

Abstract: A strand devolatilizer that includes a degassing container, a product inlet, a product distributor, a product outlet and a vapor outlet is disclosed. The product distributor is in the form of a tube distributor with at least one distributor tube (1) and a plurality of die tubes (2) arranged in parallel, each containing a plurality of apertures (15) in the tube wall. The die tubes (2) are preferably arranged in several planes one above the other and staggered laterally relative to one another.

Abstract: Nitrate-containing (contaminated) solutions are reduced with SO2 gas in the presence of an at least equimolar amount of NH4+ or ammonium salt.

Abstract: A process for producing polymer pellets is disclosed. The process that is particular suitable for making polycarbonate pellets entails extruding a polymer melt, cooling the extrudate by contacting it with a cooling fluid and pelletizing the solidified polymer. The process is characterized in that the cooling fluid has a solids particle content of at most 10 ppm.

Abstract: A device and process for the removal of volatile constituents from polymers is disclosed. The device entails a container having an inlet for a polymer solution, an outlet for the volatile components, an outflow for the polymer from which the volatile components have been removed and a heat exchanger. The heat exchanger is characterized in that it contains a plurality of specially structured channels.

Abstract: The present invention provides a polycarbonate having a low particle content, a process for producing high-purity polycarbonate and polycarbonate of maximum purity and molded products made from such polycarbonate.

Abstract: A process for the production of polycarbonate is disclosed. The process, representing an improvement over the known interfacial polycondensation process entails introducing into the loop of a circulating reactor that additionally contains, a residence tank, an optional mixer, a pump, and a heat exchanger (i) an organic phase that contains a solvent for polycarbonate and phosgene and (ii) an aqueous phase that contains an aqueous lye solution, a dihydroxy compound and an optional monophenol to form an emulsion. Maintaining specified temperature and process conditions results in polycarbonate resin having good properties and in waste water that are characterized by their purity.

Abstract: A process for preparing a vacuole-free polymer is disclosed. Extruded polymer resin is cooled at a rate of less than 50° C./sec. to a temperature that is 1 to 20° C. above the glass transition temperature of the polymer resin and the resin is then cut.

Abstract: Described is a multi-stage, continuous process for evaporating and concentrating feed polymer solutions. In a first stage (a) of the process, the feed polymer solution is concentrated by passing it through one of (i) a combination of a tubular heat exchanger with one of a thin-film evaporator and a coiled tube evaporator, and (ii) a tubular heat exchanger. Each evaporator of (i) having a downstream separator. In a further stage (b), the intermediate polymer solution of the first stage is further concentrated and degassed to form a product polymer in a tubular heat exchanger having a downstream separator. The tubular heat exchanger of the further stage has an inside diameter of from 5 to 30 mm, and a length of from 0.5 to 4 m, and the throughput per heat exchanger tube being from 5 to 30 kg/h, based on the polymer. An entrainer is introduced into a delivery device located downstream from the separator of further stage (b).

Abstract: This invention relates to a multistep process for evaporating polymer solutions of thermoplastic polymers and for removing volatile constituents from thermoplastic polymers by indirect heat exchange. The invention relates in particular to a process for evaporating volatile constituents out of polymer solutions using shell-and-tube heat exchangers having a special geometry, coiled-tube evaporators and extrusion evaporators.

Abstract: A process of evaporating a viscous polymer solution is described. The process includes: (a) providing a viscous polymer solution including at least 30 wt. % of solvents and monomers; (b) introducing the viscous polymer solution into a heated helix (5), the heated helix having a vapor exit velocity of 200 to 300 m/s, (a film flow including a two-phase mixture of polymer melt, and solvent vapors and monomer vapors being formed within the helix); (c) forwarding the film flow from helix (5) into a heated vapor separator (6); (d) expanding the two-phase mixture of polymer melt, and solvent vapors and monomer vapors of the film flow within vapor separator (6) at an absolute pressure of 10 mbar to 800 mbar, (a bottom product including a concentrated melt of the polymer is formed within the vapor separator); and (e) withdrawing the bottom product from vapor separator (6).

Abstract: A method for removing volatile components from polymer solutions is disclosed. The method, yielding products having low content of residual volatile components and causing no thermal damage to the polymer, entails using apparatuses in which surfaces which come into contact with the product are made from materials which are low in iron content.

Abstract: The production of polycarbonate by the phase boundary method is disclosed. In accordance with the inventive process, a solution that contains polycarbonate is repeatedly washed with a washing liquid and the washing liquid is separated from the solution that contains the polycarbonate by separating elements and the solvent is then evaporated. The process is characterized in that the organic solution that contains the polycarbonate and the washing liquid are separated from each other after the first washing stage in a coalescer that contains hydrophilic packing.