Abstract: Aqueous suspensions of finely divided titanium dioxide are produced in the presence of dispersants by a process in which titanium dioxide powder and caprolactam are kneaded together in the dry state at from 15.degree. to 40.degree. C., the resulting mixture is kneaded with the addition of water, the paste thus obtained is suspended in water, the suspension is then allowed to sediment, and the resulting suspension containing finely divided titanium dioxide is decanted.

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: A vertical cylinder for drying and heating granules which includes an inlet at the top of the cylinder, a conically tapered outlet at the bottom of the cylinder, a rotatable screening ring beneath the inlet, a chute beneath the screening ring and a scraper above the ring inlets for gases in the downward extending section of the cylinder, a shell and tube heat exchanger located coaxially in the bottom quarter of the cylinder, a horizontally movable grid as flow control device below the heat exchange and a discharge zone below the grid.

Abstract: An improved process for the preparation of fiber-forming polycaprolactam by polymerizing .epsilon.-caprolactam, and an aqueous extract containing .epsilon.-caprolactam and caprolactam oligomers, which extract has been obtained by extracting polycaprolactam with water, wherein the aqueous extract contains from 0.1 to 5.0% by weight of oligomers of caprolactam, based on the monomeric caprolactam in the aqueous extract.

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: An improved process for the continuous polymerization of .epsilon.-caprolactam in the presence of water as initiator in a vertical downward-flow tubular reactor, in which the .epsilon.-caprolactam is partially polymerized at elevated temperature in a first, mechanically agitated reaction zone and is further polymerized in further reaction zones to the desired degree of polymerization. Poly-.epsilon.-caprolactam is discharged in the form of a melt. The polymerization is carried out at a gauge pressure of from 0.2 to 0.9 bar, constant in all reaction zones. The temperature in the first reaction zone is maintained according to the relationship t.ltoreq.265+43 p .degree.C., where p is the numerical value of the gauge pressure in bars which relationship is subject to the condition that the temperature be within the range of 260.degree. to 295.degree. C.

Abstract: A process for achieving a uniform flow profile of very viscous liquids when flowing through tubes or reaction chambers, wherein the very viscous liquid is passed through annular spaces extending concentrically with increasing diameter over the entire cross-section of the tubes or reaction chambers and having the same depth in the direction of flow, and this procedure is repeated once or several times, the annular spaces being staggered with respect to each other as viewed in the direction of flow, and an apparatus consisting of a combination of two or more discs arranged at axial intervals within a tube transversely to the direction of flow, each disc consisting of a plurality of ring-shaped bands of increasing diameter, the bands being arranged freely of one another and concentrically at intervals on a grid supporting means to provide correspondingly concentric open spaces between the bands over the entire cross-section of the tube, with the walls of the bands running parallel to the direction of flow, and t

Abstract: In a process for drying and heating nylon granules, in which the granules flow downwards through a vertical zone, hot inert gases which are free from molecular oxygen are passed in counter-current through the granules and the cooled granules are then intermittently discharged in part-streams, the improvement wherein the wet granules, or a suspension of the granules in water, are fed into the zone at the top, the granules are deposited as a layer, the water is led away, the layer of granules is then transferred into the next-lower part of the zone, the granules are there allowed to flow under gravity downwards through the zone, and inert gases which are free from molecular oxygen are passed in countercurrent upwards through the granules at from 70 to 200.degree.

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.