Abstract: The preparation of polyamides, their oligomers or mixtures thereof, where appropriate with other reaction products, takes place by reacting amino nitrites (A) and, where appropriate, other polyamide-forming monomers and/or oligomers with water (D) in a reactive distillation, wherein the reaction product (P) is discharged from the bottom of the reactive distillation apparatus, and ammonia (N) which is produced and, where appropriate, other low molecular weight compounds which are produced, and water, are taken off overhead.

Abstract: Continuous recovery of raw materials from coated films and apparatus for this purpose and film material recovered therewith. Large amounts of coated films can be fed to a continuous recycling process in which any pigments present in the coating and the substrate material are recovered. The treatment is carried out at room temperature in an alkaline medium consisting of soft soap, organic solvent and/or water, with or without the use of a catalyst. The solvent is recycled. After the first treatment stage, the film shreds can be treated in a second stage with a solvent/water mixture similarly to the first stage, and thorough final washing in a water or solvent circulation is effected in a third stage. The recovered film shreds are dried, pressed, milled and brought to the desired shape in a plastics agglomerator, and the recovered pigments are dried under reduced pressure (FIG. 1).

Abstract: A process for the continuous polymerization of vinyl monomers to form vinyl polymers having a molecular weight M.sub.n of from 1000 to 20,000 comprisesa. carrying out the polymerization within an annular gap from 0.5 to 10 mm in width,b. confining the annular gap on the inner surface with a rotor, andc. carrying out the polymerization at from 110.degree. to 270.degree. C.

Abstract: Aqueous non-self-emulsifying polymer dispersions having small particles and a long shelf life and based on highly viscous reaction resins are prepared without the addition of solvents, by means of an intensively dispersing screw apparatus, by a continuous process in which the preparation of the polymer dispersion is carried out in an intensive shear zone of the screw apparatus, the water/reaction resin ratio in this intensive shear zone corresponding to the phase inversion point or being close to it, and the specific energy supply is 0.01-0.15 kWh/kg, the residence time is 0.1-60 sec and the shear gradient is 2,000-20,000 sec.sup.-1.

Abstract: In order to compound organic materials which are crystalline under standard conditions, these materials, in the pulverulent and/or molten state, are processed in a self-purging, twin-screw extruder in which the screws rotate in the same direction, ejected through one or more narrow passages into a low pressure zone, cooled and comminuted to give particles. In order to improve the pourability and shelf life, the materials are completely crystallized by the time they reach the end of the screws, and are heated during discharge through the narrow passage, in order to form a melt film. Dust-free granules havig a smooth surface can be produced in this manner.

Abstract: When producing molded foam parts from liquid reaction components, the charge of gas in the initial components has a significant effect on the foam structure and quality of the molded part. This invention provides a process and apparatus for introducing a gas into at least one of the liquid reaction components prior to mixing said components for reaction. The component which is to be charged with gas is circulated from a feed tank through a recycle circuit to a compression zone which is maintained at a higher pressure than that of the feed tank. Said gas is admixed with said component at the point of initiation of the compression zone and the higher pressure is relieved through a throttle element prior to returning the gas-charged component to the feed tank. A finely divided stable gas dispersion which can be mixed with other components for reaction is obtained.

Abstract: A mixing apparatus for multi-component plastics, in particular polyurethane, possesses a mixing chamber (2) with inlet apertures (3) and (4) for the individual plastic components and an outlet aperture (8) for the mixture. In the mixing chamber, a control element (5), which has the same cross-section as the chamber and possesses overflow channels (6) and (7), can be moved to and fro for controlling the component streams. In order to avoid pressure peaks or pressure surges in the transport of the components when the control element passes from the closed position to the mixing position and vice versa, and to provide improved accuracy of metering, the inlet apertures in the inner wall of the mixing chamber, and the corresponding areas of the shell of the control element between its end face (13) and the overflow channels, are matched with one another with regard to their size.

Abstract: A sheet-like structure is produced from a vinyl alcohol polymer by a method wherein, in a self-cleaning multi-screw extruder, the polymer is mixed with a small amount of water, the mixture is melted, homogenized, devolatilized and finally extruded as a melt, and the extrudate is shaped in a conventional manner into the sheet-like structure.

Abstract: A mixing head for multicomponent plastics, especially polyurethane, in whose mixing chamber (2) a hollow piston (7) can be moved to and fro to control the component streams. The hollow piston contains an expulsion piston (8), which is movable independently of the hollow piston, and which can be passed through an outlet tube (3) which adjoins the outlet orifice (4). The end face (12) of the hollow piston forms, together with the mixing chamber wall (11) nearest the sprue, a shearing gap in which the components are mixed. As a result of the design and arrangement of the pistons (7) and (8), good mixing is achievable even under critical conditions, and the mixing chamber is also easily cleaned.