Hochpolymere Zusatzmittel für die PVC-Verarbeitung auf der Basis von Polymethylmethacrylat

High-molecular PMMA-based processing aids are used for rigid PVC for many years. Their possible performances are known. However, the mechanisms are largely unexplained. The improvement of plastifying behaviour of rigid PVC is based on the increase of friction coefficient PVC/metal and the transformation from a non-wall-adherent into a wall-adherent plastic. This transformation also explains the prevention of melt fracture. In the case of injection moulding, removes of melt are avoided not only by better adherence, but also by higher PMMA-agent concentrations in the outside layers of the injected melt.     

Dioxine – Eine Aufgabe für die Umwelttechnik

Dioxins – Task for Environmental Engineering Two decades of the environmental history of dioxins, i.e. of PCCDs and PCDFs, are examined, with the main emphasis being placed on developments in Germany. After a brief consideration of the important, environmentally relevant properties of dioxins, interest is focussed on the course of the Seveso incident of 1976. The environmental effects of dioxins observed in Seveso received global publicity. In the following years our knowledge of the analysis and toxicology of this group of substances greatly improved and the production of dioxins in the aromatics sector of the chemical industry was drastically reduced. In the 1980s, discussions concentrated on the formation of dioxins in waste incineration. The results obtained during this period led to the present situation in which waste incineration is no longer a significant source of dioxin emission in Germany. The greatest known source of dioxins in Germany is in the metallurgical industry. By the year 2000 this dioxin source will also have been largely eliminated.     

Auslegung von pulsierten Siebboden‐ und Sprühkolonnen für die Extraktion auf der Basis von Einzeltropfenuntersuchungen

The design of pulsed sieve‐plate extraction columns (PSE) on the basis of published data is not currently possible as it relais on additional and cost intensive laboratory experiments. This is due to the lack of knowledge about the complex mass transfer between two liquid phases which is strongly influenced by factors such as surface active impurities and the Marangoni‐effect. In order to reduce the experimental effort in the determination of the required design input data, several standard experimental test units have been developed at the Institut für Thermische Verfahrenstechnik that allow the determination of the needed fluiddynamic and mass transfer data. The test units are based on single drop experiments, and they use the technical mixture to be separated in practice. Finally, the meas ured mass transfer and fluiddynamic data are used to calculate the drop‐size‐, holdup‐ and concentration‐profiles for the systems toluene‐ace tone‐water and n‐butylacetate‐ace tone‐water in a PSE‐column and a spray‐column. The results are compared with experimental data reported in the literature and our own data obtained with a semi‐industrial PSE‐column.     

Neuartige Goldkatalysatoren auf Alumophosphat‐Basis für die direkte Propen‐Epoxidierung

Propene oxide is an important intermediate in chemical industry. Amongst others it is needed for the production of various plastics. As currently applied processes for the production of propene oxide either generate large amounts of undesired by‐products or are highly expensive regarding the reactants introduced to the process, it is desirable to epoxidate propene directly by aerial oxygen. It has been shown that this is possible by the use of supported gold catalysts. This contribution engages in the question to which extent titanium substituted alumophosphates are suitable as support for this kind of catalysts.     

Auswahl von Sorbenzien für die Gasphasenadsorption

Selection of Sorbents for Gas Phase Adsorption. For gas phase adsorption processes it is almost always necessary to select a suitable sorbent by experiment, i.e. a sorbent that is suitable for adsorption as well as for desorption. Therefore sorbents from the group of activated carbons, adsorbent resins and zeolites have been tested and compared with each other under adsorption and desorption conditions. The sorbents have also been checked for reliable function. Operational disturbances are often caused by components such as water vapor or (irreversibly adsorbing) high boiling components. In any case it is useful to select adsorbents which are not susceptible to interference by these components. The co-adsorption of water vapor, undesirable in practice, normally leads to a reduced adsorbent capacity. It is also shown that a single high boiling component, present in traces in the gas, loads the adsorbent to the same extent as the pure main component, so that there is hardly any capacity left for the main component. The range of investigation was insufficient to draw up general rules for the different groups of sorbents referring to the points considered.     

Produktdesign von Kunststoffen für die Waschmittelindustrie

Water soluble polymers in the detergent industry represent on the one hand parts of the formulations of washing powder to improve the washing result, and are used on the other hand as foils for the packaging of liquid detergent portions. Insoluble, thermoplastic polymers (PE, PP, PET) are needed as packaging materials for solids, pastes, suspensions and liquids in the form of laminated cardboard, boxes, bags, bottles, buckets and tubes. The polymers can be tailored to the application. For this purpose, not only the possibilities of the reaction and synthesis technology are available, but the addition of additives manages the adjustment of the required physical, technical and optical properties, such as color and durability. In an extrusion process, the plasticized or melted material gets the product shape; any form can be produced. The packaging should convince not only in forms and functions, but also throughout the aesthetics relating to the specific brand. The product design is the sum of these parameters.