Abstract: A process is described for obtaining pure isocyanate isomers from a mixture of isocyanate isomers by suspension crystallization and the isolation of isomerically pure crystals, which is characterized in that, prior to the isolation of the crystals, 5 to 40% by weight of the crystals produced are remelted while simultaneously increasing the temperature of the crystal slurry by 4.5 to 9° C.

Abstract: The viscosity of a fluid liquid substance is first increased in a multiphase coil in the presence of a gas phase flowing at high speed and then, with separation of the gas phase, the substance is applied to a stirred bed consisting of a solid granular material where it is converted into a solid substance.

Abstract: A process and a device are described for separating a solid residue, after separation, from a solution of the residue in evaporable materials and/or solvents with the addition of up to 20% by weight of high-boiling hydrocarbons that are inert under evaporation conditions of the evaporable materials, heating the mixture to evaporation temperature under vacuum, whereby the evaporable materials evaporate, are drawn off and condensed, and the residue is obtained as a free-flowing solid, the residue solution being introduced onto a stirred bed of granular solid material kept at the evaporation temperature.

Abstract: Aromatic diamines and polyamines are produced by a continuous process for the catalytic hydrogenation of the corresponding dinitro and polynitro compounds at elevated temperature. Heat removed from the reaction mixture may be used to produce steam with an overpressure of .gtoreq.2 bar.

Abstract: A candle type precoated filter for residual volume filtration has a pressure vessel having a cylindrical upper part and a conical base, a plurality of filter elements arranged substantially vertically and including at least one residual filter element and other filter elements formed so that the at least one residual filter element is lengthened toward the base and is longer than the other filter elements and a separating wall which separates the residual filter element in an upper portion of the pressure vessel from the other filter elements so as to be tight against media and to project out in a lower portion of the pressure vessel beyond a length of the other filter element.

Abstract: The present invention relates to a filtering device with an agitator. The filtering device broadly consists of a horizontal filter plate with a central discharge opening and an agitator shaft disposed vertically and centrally to the filter plate. The agitator shaft has two agitator arms, with agitator blades being disposed on the agitator arms, pointing towards the filter plate and set at an angle to their circular path.

Abstract: A process for removing alkali material from a polyether polyol. From 1-20 wt. % water and 0-30 wt. % inert organic solvent are added to an alkaline polyether polyol. The resultant emulsion is maintained at a temperature of at least 70.degree. C. for a period of at least 30 minutes with little or no stirring to effect separation of the emulsion into an organic and an aqueous phase. The aqueous phase is then separated from the organic phase and the organic phase is treated by known methods to remove residual alkali material.

Abstract: The present invention is directed to a process for separating polyurethane hydrolyzates, preferably polyurethane foam hydrolyzates, into substantially amine-free foamable polyethers and diamines, comprising (a) (i) briefly expanding a hot polyurethane hydrolyzate obtained in a continuous screw extruder to normal pressure or in vacuo and, without using readily volatile components (ii) spraying said hydrolyzate directly into a tubular coil evaporator which is heated to 180.degree.-300.degree. C. and at the end of which a pressure of from 0.1 to 20 mbar is applied and (iii) separating a hydrolyzate containing less than 1% by weight of NH.sub.

Abstract: The invention relates to a multiple phase flow tube for evaporating and reacting components in compound mixtures in which a spiral pipe is arranged within a multiple phase flow pipe. The components are propelled by means of an internally flowing gas stream in an annular shaped passage formed by a spiral tube and a second tube arranged as a core of the spiral tube. The second tube contains a heat exchange medium. The spiral tube is arranged within a cylindrical casing which contains a heat exchange medium. A gaseous stream of a reduced amount is then sufficient for carrying out the particular chemical process desired.

Abstract: This invention relates to an improved process for the preparation of polyisocyanates which contain biuret groups by the direct reaction of polyamines in vapor form with polyisocyanates.

Abstract: This invention relates to a process for the removal of troublesome secondary products, particularly small quantities of water, solvents, low molecular weight glycols, and pungent-smelling substances, from polyethers by means of a tubular coil evaporator.

Abstract: An apparatus for hydrolytic degradation of plastics in which plastic material is deposited into a tubular housing via a feed hopper. An elongated screw shaft has a first section in the form of a high pitch screw thread disposed below the feed hopper to receive and advance the material to a second section. The second section of the screw shaft is in the form of a lower pitch thread for compressing the plastic material and transferring it to a longer, third section in the form of kneading discs, from which material passes through an outlet nozzle section to a cyclone separator where trapped gases and liquid may be withdrawn. The tubular housing is vented upstream of the feed hopper and a water inlet pipe is disposed adjacent to the second section of the screw shaft, downstream of the feed hopper. The outlet nozzle section is provided with pressure measuring and regulating means and a liquid level measuring and regulating device.

Abstract: The instant invention relates to a continuous process for the hydrolytic degradation of plastics wherein a hydrolyzable material is introduced with water into a screw machine, and is subjected therein to a temperature of 100 to 300.degree. C, and a pressure of 5 to 100 bars for 2 to 100 minutes. The invention also relates to an apparatus useful in conducting the process.

Abstract: The instant invention is directed to a process for the continuous production of aromatic polyisocyanates containing uretdione groups. The process broadly comprising dimerizing an aromatic polyisocyanate in a continuous, coolable screw reactor at a temperature of from -30.degree. to +70.degree. C.