Zum mechanismus der inhibierenden reaktion phenolischer antioxydantien bei der verarbeitung von polypropylen. I. Modellreaktionen von 1,3,5-trimethyl-2,4,6-tris-(3,5-di-tert.-butyl-4-hydroxybenzyl)-benzol

The reaction mechanism of 1,3,5-trimethyl-2,4,6-tris-(3,5-di-tert.-butyl-4-hydroxybenzy1)-benzene (I) with tert.-buthylhydroperoxide was investigated and the following course of reaction was found: See (A) in the German summary. Whereas the fir partial step also occurs in case of other phenolic antioxidants, the decomposition of the intermediate product is evidently strongly influenced by the substituent in 4-position of the quinoidal ring. Thus, among others, 3,5-di-tert.-butyl-4-hydroxybenzaldehyde (XI) and tert.-butanol are obtained from the thermal decomposition of the reaction product (X) of 3,5-di-tert.-butyl-4-hydroxytoluene and tert.-butylhydroperoxide. See (B) in the German summary. The atmospheric oxidation of I leads to quinone methides (V) as well as 3,5-di-tert.-butyl-4-hydroxybenzaldehyde (XI) and 2,6-di-tert.-butyl-p-benzoquinone (VII) : See (C) in the German summary.     

Automatisierung bei der Raffination von Nahrungsfetten

Automation in the Refining of Edible Oils Automatic process control and regulation are now indispensable items in production plants and auxiliary equipment for the refining of edible oils. Their application is primarily aimed towards reduction of cost of wages, energy and raw materials as well as auxiliary materials, and towards maintenance of constant conditions of processing which ensures uniform and high quality product. In addition to classical instrumentation in individual production sections having independent regulating systems, emphasis is laid these days on centralization and coupling of the, various unit operations. Recent developments in the area of programmed control, microprocessors and minicomputers permit suitable and elegant solution of such tasks. Technically sophisticated signal processing shows distinctly that specific receivers of actual processing data are available to a rather limited extent. A few special developments in this area are discussed. In other cases, suitable combination of easily measurable data can be used for comparison.     

Fortschritte bei der Modellierung von Festbettreaktoren

Progress in the modeling of fixed bed reactors. Recent work on the modeling of catalytic fixed bed reactors have led to more realistic mathematical models and to a better understanding of problems connected with modeling. Nowadays standard routine computer programs are available for use in the design (and analysis) of catalytic fixed bed reactors for very complex reaction systems. The influence of bed structure on transport parameters was illustrated by experimental determination of axial and radial concentration and temperature distribution. Moreover the problem of multicomponent diffusion coupled with complex reactions in porous catalysts has been solved and can be included in the reactor model. However, the practical application of possible reactor models is limited by the availability of transport parameters for fixed beds.     

Einfluss der Feuchtebeladung bei der Druckbeanspruchung von Granulaten

The material behavior of γ‐Al₂O₃‐, zeolite 4A‐ und sodium benzoate granules at compression has been experimentally studied. The material behavior has been found to be dominant elastic, elastic‐plastic and dominant plastic. Additionally, the influence of moisture content on the material behavior has been investigated. The force‐displacement curves have been approximated using suitable mechanical models.     

Verpackungsprobleme bei der Strahlenkonservierung von Lebensmitteln

Packing Problems in the Food Preservation by Irradiation In the food preservation by irradiation differentiation is made between sterilization and pasteurization. Accordingly, requirements to be met by the packing materials are different. In the present paper the points involving the suitability of various materials as well as a few technological problems associated with the usual sources of irradiation are given. The basic problems of microbiological equilibrium after irradiation are then explained. Apart from the resistance of individual plastics towards radiation the problems involved in the detection of irradiation and induced radioactivity are dealt with. Finally, the transfer of foreign substances from the packing material to the foodstuff is discussed.     

Definition von Destillationslinien bei der Trennung von Mehrstoffgemischen

Definition of Distillation Lines in the Separation of Multicomponent Mixtures. In recent years “distillation lines” have been used for the assessment of the separation behaviour of multicomponent mixtures, with these distillation lines being defined differently by different authors. The theory of distillation of multicomponent mixtures shows that it is appropriate to distinguish between residue lines and rectification lines. While the profile of residue lines is determined solely by the thermodynamic phase equilibrium, that of rectification lines also depends upon the mass transfer model used. By analogy with VDI Guideline 2761: “Thermal Separation Processes in Process Engineering”, it is proposed that residue lines and rectification lines are designated by the collective term distillation lines.     

Fraktionierungserscheinungen bei der Entmischung von Ethylen-Polyethylen-Gemischen

During the separation of mixtures of monomers and polymers fractionation takes place. The polymers with high molecular weight can be found in the dense phase whereas the low molecular fraction is concentrated within the light phase. The polymers in both phases exhibit different molecular weight distributions which differ also from the distribution of the polymer in the homogeneous mixture. The influence of pressure, temperature and polymer concentration on the fractionation during phase separation was studied with mixtures of ethylene and commercial polyethylenes. Measurements were performed at pressures up to 200 MPa and temperatures between 383 and 473 K.     

Sicherheitstechnik bei der Handhabung von Wasserstoff

Safety engineering in the handling of hydrogen . After a survey of the handling of hydrogen as a gaseous or liquid industrial gas, possible safety risks are discussed in the light of its properties, and primary, secondary, and tertiary safety measures are deduced therefrom. The most important German regulations for stationary and mobile hydrogen installations are indicated. A comparison shows that hydrogen, which was introduced into industry decades ago, is no more dangerous than other inflammable gases and liquids freely available even to the public.     

Posteffekt bei der Radiolyse von Polystyrol

In polystyrene the major part of crosslinks is produced during irradiation in a “hot reaction”. 10% of the crosslinks are formed in a postreaction. A kinetic analysis of the experimental data showed the latter reaction to be first order. At larger storage times especially at higher temperatures the initial increase of crosslinks is followed by a decrease. This can only be explained if the crosslinks are formed during dissolution. We assume, that the posteffect is due to trapped cyclohexadienyl- and benzylradicals. The first order kinetics is ascribed to a transformation of cyclohexadienyl- to benzylradicals. By dissolution of the polymer after increasing storage time the reaction of cyclohexadienylradicals with benzylradicals, which leads predominantly to disproportionation, is replaced by recombination of two benzylradicals forming crosslinks. At higher temperatures and long storage times also benzylradicals must dissapear in the solid polymer by reactions not forming crosslinks. Additives like Anthracene and Naphthochinon suppress the posteffect. Based on the experimental results a reaction mechanism for the formation of crosslinks during irradiation and in the postreaction is proposed.