Abstract: A sealable discharge die for thermoplastics, comprising a housing, a dieplate which closes the latter except for perforations for discharge of the plastic melt in strands or filaments, and a perforated plate located immediately below or above this dieplate, one of the plates being slidable or rotatable and the perforated plate having orifices which can be brought into alignment with the perforations of the dieplate.

Abstract: A process for removing caprolactam and its oligomers from cooling water containing these compounds, wherein gases are introduced into the cooling water and the foam which forms is separated off.

Abstract: A melt of synthetic material is forced through orifices of a die plate, and the resulting strands of melt are led into a trough, where they travel in counter-current to a stream of cooling water. At the end of the trough, the strands are discharged, for further processing. The bottom of the trough merges into a vertical pipe and the melt strands are led into this pipe and out again, in a variable loop, in order to obtain the desired length of cooling path.

Abstract: An improved process for the continuous preparation of polycaprolactam, in which .epsilon.-caprolactam is partially polymerized, with the addition of a water-containing agent and acetic acid or propionic acid as a chain regulator, at a nylon-forming temperature, in a mechanically mixed zone in a vertical tubular reactor through which the reaction mixture flows downwards, and is then polymerized further, in additional heat exchange zones, until the desired degree of polymerization is reached, and polycaprolactam is then discharged as a melt, wherein a gaseous mixture of caprolactam, water and acetic acid or propionic acid is removed at the top of the tubular reactor and is fed to the middle of a column, water is removed at the top of the column, the bottom of the column is maintained at from 125.degree. to 145.degree. C., and the mixture obtained at the bottom of the column, and comprising caprolactam, acetic acid or propionic acid and a small amount of water, is recycled to the top of the tubular reactor.

Abstract: Concentrates of from 20 to 50% by weight of titanium dioxide in polycaprolactam are produced by a process in which a 5-15% strength by weight aqueous suspension of titanium dioxide is metered into a solution of caprolactam in water at from 100.degree. to 150.degree. C. at the same rate at which water is distilled off, and after the water has been distilled off the resulting mixture is polymerized at from 240.degree. to 280.degree. C.

Abstract: A process for the continuous preparation of polycaprolactam, which comprises polymerizing .epsilon.-caprolactam in a vertical tubular reactor through which the .epsilon.-caprolactam flows downward, wherein the .epsilon.-caprolactam is partially polymerized, at a nylon-forming temperature, in a mechanically mixed zone, the reaction mixture is circulated through a heat exchange zone in the lower part of the mechanically mixed reaction zone, and is polymerized further, in additional heat exchange zones, until the desired degree of polymerization is reached, and poly-.epsilon.-caprolactam is then discharged as a melt, and an apparatus for carrying out the process.

Abstract: A process for discharging a granular organic polymer, which is sensitive to molecular oxygen at elevated temperatures, from a treatment zone in which it has been continuously treated, at above 70.degree. C., with an inert gas which is free from molecular oxygen, and has subsequently been cooled, which process comprises withdrawing the polymer at .ltoreq.50.degree. C. through a narrow elongate tubular discharge zone, the said zone always being filled with granular polymer.

Abstract: A process for removing volatile constituents which are evolved from plastic melts when extruding the latter and are drawn off together with the surrounding air. The volatile constituents are drawn off immediately as they are evolved by the plastic melt and the air containing such volatile constituents is heated immediately after entering the suction orifice, and an apparatus for carrying out this process.

Abstract: The continuous countercurrent extraction of polylactam granules with hot water in an extraction zone for the removal of monomer and/or oligomers, the extraction zone being subdivided into subzones by at least one heating zone. The density of the extract-containing water differs by at least 0.0002 between the subzones.

Abstract: An extraction tube for the continuous removal of low molecular weight components of polylactam granules by means of hot water by the countercurrent principle of operation, the water being fed upwardly and the granules downwardly, the tube being provided with inlets and outlets for the granules and the water and exhibiting baffles within the tube, wherein there is provided, within the tube, a heat exchanger whichA. divides the tube into two sections bearing a ratio to each other of from 50:50 to 85:15 by volume, the smaller section being at the top of the tube,B. exhibits ducts for the granules over the entire cross-section of the tube andC. has top surfaces facing the stream of granules, which surfaces are inclined toward the ducts to an angle .beta. to the horizontal, this angle being equal to or greater than the angle of repose of the granules but less than 90.degree.,Further similar heat exchangers being provided beneath said heat exchanger if desired.