Modifizierung der integralen form der Mayo-Lewis-Gleichung zur berechnung der copolymerzusammensetzung bei der semikontinuierlichen polymerisation

Equations for the mathematical simulation of the semicontinuous copolymerization are proposed. With these equations it is possible to calculate the composition course of the monomer phase and of the just formed polymer, as well as the integral composition of the polymer as a function of conversion. The proposed relations form a system of differential equations, which are calculated numerically by stepwise integration. This calculation process is demonstrated using semicontinuous emulsion polymerization of the styrene/acrylonitrile system. The calculated relations show, that after a quasi-stationary phase has been reached, the polymerization ratio must be higher than the ratio of the monomer dosage.     

Neues aus der Chemie der Iminiumsalze

Recent Developments in Iminium Salt Chemistry Iminium salts are of continuing interest as versatile building blocks in organic synthesis. This progress report from different laboratories highlights some current research activities in iminium salt chemistry. Several contributions focus on novel synthetic applications of isolable, functionalized iminium systems such as α,β-unsaturated iminium salts (e.g. vinamidinium, 3-trifloxy, 3-chloro-, 3-isocyanato- and 3-thiopropene iminium, as well as propyne iminium salts), furthermore on phosgene iminium chloride and trifluoromethyl-substituted iminium salts. Iminium intermediates occur in various synthetic transformations; for example, cyclopropane iminium ions are intermediates in nucleophilic substitution reactions at bicyclic aminocyclopropanes. Also reported is the synthesis of a variety of novel orthoamides and their use as synthetic building blocks. Research directed to the application of vinamidinium salts in materials science is also presented.     

Aufgaben der Produktionsleitebene in der chemischen Industrie

The plant management functions in chemical industry . The information flow can be structured by a layer model, comprising the plant management layer, the process control layer, and the field layer. The higher company management layer issues production orders which are detailed at the plant management layer with the aid of a formulation; amounts of materials required, equipment, personnel, and laboratory measurements are assigned as a prerequisite for production. These tasks are described in detail, the flow of information between the adjacent layers indicated, and the layer structure of other business units briefly considered.     

Strukturwandel in der Ingenieurtechnik der chemischen Industrie

Changes in the Structure of Engineering in the Chemical Industry. The poor profit situation has stimulated a discussion of the costs of engineering in the chemical industry. The allocation of engineering responsibilities to centralized organizational structures is at issue. This applies to planning just as much as to plant maintenance or to the workshops. These structures are regarded as inflexible, expensive and, in many cases, monopolistic. Decentralized units which are directly responsible to divisions or business units seem to be able to work more efficiently and cheaply. The best alternative, however, is considered to be the outsourcing of work to external firms on a far larger scale than up to now. The article deals with the reasons which have initiated the structural change and with the relating consequences thereto.     

Anwendung der UV-Spektrophotometrie bei der Untersuchung der Oxydation und Polymerisation von Fetten

Application of UV-Spectrophotometry in the Investigation of Oxidation and Polymerisation of Fats In the direct UV-method, the first maximum of extinction at wave-length 243 nm of heated sunflower oil is related to viscosity, refractive index and specific weight, but not related to peroxide value and aldehyde content. In these experiments the oils were heated in air, in air current and in current of nitrogen.     

Potenziale und Herausforderungen in der Implementierung der organophilen Nanofiltration in der Spezialchemie

Organic solvent nanofiltration (OSN) is a suitable tool for process intensification. For specialty chemicals production within a multi‐purpose environment, there are some specific concerns regarding membranes and equipment design that have to be considered. Process development for OSN to date is hampered by a lack of system characteristics and detailed transport models. Here, we present a systematic investigation with different membrane materials and solvents in order to define guidelines for a fast membrane selection.     

Bestimmung der Temperaturabhängigkeit der Inhibierungsperiode und der Radikalbildungskonstante von AIBN bei der Polymerisation von Methylmethacrylat

The dependence on temperature of the specific reaction rate quotient of the inhibition period has been determined as by dilatometric measurement of the inhibition period caused by dissolved oxygen, and by the initial rate of the methyl methacrylata polymerisation, using azoisobutyronitrile (AIBN) aa initiator. In the examined concentration range the initial polymerisation rate and the reciprocal of the inhibition period are strictly proportional to the root of the initiator concentration, the yield of free initiator radicals is thus independent of the initiator concentration. It is, therefore, possible to determine the radical forming constant k_R of AIBN represented by the equation The fraction of the radicals recombining in the cage can be determined from k_R and the decomposition constant k_z; at 60°C for example it amounts to 24%. This value corresponds very well to the value obtained by the gas-chromatographic investigation of the recombination products by VOGT and DULOG.