Abstract: A mixing apparatus suitable for mixing and conveying solid, particulate, polymeric materials, comprising a barrel that can be heated and cooled, at least two co-rotatable, self-wiping extruder screws located within the bore of the barrel, the screws being connected through a laterally flexible coupling to a drive means which can reverse the direction of rotation of the screws upon the occurrence of a predetermined event. The apparatus also comprises a closeable feed port and a closeable discharge port, both of which can be made gas-tight, the shafts of the screws being provided with seals capable of withstanding elevated gas pressures inside the barrel.

Abstract: A staged feeding process for preparing a composition by mixing at least a first polymer and a second, dissimilar polymer forms a final composition comprising a uniform, small-particle dispersion of the first polymer in a matrix of the second polymer. Preferably, the first polymer has a melt viscosity greater than the second polymer. The process comprises the steps of feeding the first polymer in a first feed stage and feeding all of the second polymer as a melt at least two feed stages to mix the first and second polymers. Alternatively, the process may comprise feeding the first polymer in a first feed stage and feeding all of the second polymer in at least two feed stages subsequent to the first feed stage. In either case, this mixing initiates a chemical reaction between the first and second polymers.

Abstract: A mixing apparatus suitable for mixing and conveying solid, particulate, polymeric materials, comprising a barrel that can be heated and cooled, at least two co-rotatable, self-wiping extruder screws located within the bore of the barrel, the screws being connected through a laterally flexible coupling to a dirve means which can reverse the direction of rotation of the screws upon the occurrence of a predetermined event. The apparatus also comprises a closeable feed port and a closeable discharge port, both of which can be made gas-tight, the shafts of the screws being provided with seals capable of withstanding elevated gas pressures inside the barrel.

Abstract: A linear polyamide having a weight average molecular weight above 200,000 is made by heating a lower molecular weight molten polyamide with thorough mixing at a temperature of about 265.degree.-300.degree. C. for at least 5 minutes while an inert gas is swept gently through the reactor, the increase of molecular weight of the polyamide being catalyzed by a particular phosphinic acid derivative.

Abstract: A continuous process for preparing particulate microporous, open-celled polymer structures in a co-rotating twin-screw processor comprising agitating normally solid organic polymer and chlorofluorocarbon in the melt zone of said processor, cooling the resulting solution under agitation in the cooling and milling zone, extruding a snow-like mass from the cooling and milling zone, and then removing the chlorofluorocarbon from the snow-like mass to leave the polymer structures.

Abstract: Clear, bubble-free acrylonitrile polymer solutions of high polymer concentration are rapidly prepared by feeding powdered acrylonitrile polymer to a cool zone of a twin-screw machine and injecting solvent to form a slurry at a temperature below 40.degree. C., advancing the cool slurry to a heated zone and converting the slurry into a concentrated solution at 110.degree. to 150.degree. C. while intermittently squeezing it in directions transverse to the axes of the screws, and discharging the hot solution continuously from the machine. A zone of reduced pressure is provided to remove gases trapped in the slurry. A twin-screw machine for carrying out the process is disclosed.