Über die katalytische wirkung des calciumacetats und des gemisches mangan-natriumacetat bei umesterung von dimethylterephthalat mit äthylenglykol

The products of the ester exchange of DMT with EG in the presence of two catalysts (calcium acetate and a mixture of manganese and sodium acetate) obtained under manufacturing conditions have been investigated. The ester exchange product and the distillate obtained during different reaction times were analysed. On the base of the obtained results of the effect of the duration and temperature the reaction was established as well as of the type of catalyst on the progress of the fundamental and by-reactions. It was found that the trans-esterification proceeds through a mixed ester of terephthalic acid, namely methylethylolterephthalate. After the trans-esterification of the methylester groups of methylethylolterephthalate and DMT the reaction does not stop, but continues with the oligomerization of the diethylterephthalate. At the end of the process about 82% of oligomers are obtained when the catalyst is calcium acetate and 93% with the mixed catalyst. The experimental results show that part of the initial monomers participate in undesired side-reactions (by-processes): hydrolysis of DMT to terephthalic acid and breaking down of EG to acetaldehyde. The results obtained indicate the greater effectiveness of the mixed catalyst.     

Weizenlipide: Funktion und Einfluß bei der Verarbeitung des Mehles

Wheat Lipids — Function and Effect in Flour Processing Bread volume and crumb quality are improved in standard baking experiments by extraction of non-polar lipids. Depending on the extracting agent the effect is more or less distinct, whereas the fat composition of the extracted lipids is essentially the same. Whereas lipases have only low influence on bread volume, phospho- or galactolipid fermenting enzymes from potatoes have very negative and irreversible effects on volume and crumb quality. Lecithin (in combination with glycerides) or ester of diacetyltartaric acid improve significantly the fermenting tolerance and volume yield. The different effects of lipids in dependence on the applied baking experiment are worth to be considered. Since defatting in rapid-mix-test has negative effects on roll volume and the lecithin effect is lower, too, it is supposed that fibrillar structures or lipoproteine membranes are destroyed by intensive mechanical working, which are necessary for an optimal dough structure formation.     

Molekulargewicht,umsatz und relative lösungsviskosität bei der hydrolytischen polymerisation von laurinlactam

Applying the relations for the calculation of an (AB+RA_f) system given by FLORY, molecular weights and polymer conversions for hydrolytically polymerized polylaurolactam are calculated dependent on the relative solution viscosity. It is shown that the moiety of molecules which does not contain any regulator molecule must also be considered calculating M?_v in the case of f≥2 and small regulator quantities even for high conversions. The relation for M?_v given by FLORY neglecting this moiety of molecules is valid only as a limiting value for higher quantities of regulator or quantitative polymer conversion. The results are compared with those determined by a former simplified model and with experimental values.     

Einfluß der Reaktionsbedingungen bei der Chlormethylierung von Styrol

The influence of trioxane, inhibitor (CuCl₂), solvent (isopropanol), water, and catalyst concentration, and temperature in the chloromethylation of styrene has been studied. A two level statistical design of experiments was used. Conversion and selectivity were fitted by multiple linear regression. Two equations have been obtained. The influence of the conditions in the reaction is shown in these two equations.     

Die polymerisation der lactame XIV. Einfluß des hexamethylguanidiniumchlorides auf die aktivierte anionische polymerisation der lactame

It was proved that hexamethylguanidiniumchloride (HMGC) exhibited a pronounced accelerating effect on the activated anionic polymerization of 2-pyrrolidone (40°C) and 6-caprolactam initiated by alkali metal salts of the corresponding lactams. The accelerating effect of HMGC was not specific for a certain type of alkali metal salt of lactams as initiator, it was proved that the effect is operative for polymerization of 6-caprolactam when using sodium or cesium salt of 6-caprolactam. It was proved that HMGC does not form growing centers under reaction conditions studied. The initial polymerization rate in the homogeneous phase is a linear function of square root of HMGC concentration at constant concentrations of initiator and activator. On the basis of this finding it was possible to suggest a plausible mechanism of HMGC influence on the polymerization process.     

Einfluß der Struktur und der Morphologie von Bleicherden auf die Bleichwirkung bei Ölen und Fetten

Influence of the Structure and Morphology of Bleaching Earths on Their Bleaching Action on Oils and Fats In the manufacture of highly active bleaching earths from bentonite, the acid activation causes alterations in the chemical composition and structural as well as morphological properties of bentonite, depending on the concentration of acid, temperature, time etc. This has been demonstrated by changes in specific surface, volume of the micropores, particle size distribution and proportion of soluble silicic acid, and the impact of these alterations on the bleaching of vegetable oils is discussed. The results are supported by electron optical and X-ray investigations. Studies on repeated removal of silicic acid formed by acid treatment of bentonite as well as repeated acid activation indicate that the bleaching action of these earths depends not only on specific surface, but also, to a considerable extent, on the volume of micropores.     

Einfluß der Linolsäurezufuhr auf Membranlipide und Enzymaktivitäten der Erythrozyten und Lebermitochondrien von Ratten

Effect of Linoleic Acid Supply on Membrane Lipids and Enzyme Activities of Erythrozytes und Liver Mitochondria of Rats The effects of different oral doses of linoleic acid (0 to 4% of energy intake) on membrane lipids and activities of membrane-bound enzymes of erythrocytes and liver mitochondria were tested in weanling male Wistar-rats. The osmotic resistance of red blood cells turned out to be clearly dependent on the level of linoleic acid intake after 2 weeks. This observation can partly be caused by changes in the cholesterolphospholipid-ratio found in the erythrocytes. The activity of the erythrocyte-acetylcholinesterase revealed no difference between the test groups. On the other hand the activity of the (Na⁺ + K⁺)-ATPase increased significantly in the group fed the linoleic acid-free diet after 14 weeks. In liver mitochondria the linoleic acid deficiency caused a decrease of the cardiolipin concentration and slight elevations in the concentrations of phosphatidylinositol and sphingomyelin. The activity of the Mg²⁺-ATPase of liver mitochondria was not influenced by the supply of linoleic acid. The activities of the succinate dehydrogenase and the cytochrom-c-oxidase decreased in the animals receiving the fat-free diet after 6 weeks.     

Einfluß des Verstreckens und Temperns auf das Dehnungs- und Bruchverhalten von Polyäthylenterephthalat

The stress-strain diagrams of undrawn and drawn polyethylene terephthalate were measured at room temperature and above the glass transition temperature. Before the stress-strain measurements the undrawn samples had been crystallized at various temperatures, whereas the drawn samples had been crystallized in the undrawn state, then were drawn at various temperatures and finally were crystallized again. The influence of the temperature of crystallization and the temperature of drawing on the Young's modulus, the tensile strength, and the fracture strain were of special interest. The fracture strain as a function of the crystallization temperature shows a minimum at room temperature. This minimum disappears above the glass transition temperature. Young's modulus and tensile strength generally are found the higher, the higher the degree of orientation in the sample. Crystallization of the undrawn samples therefore does not change these values significantly. But a drawing of the samples leads to a significant increase which is still more pronounced if the sample is crystallized after the drawing. Crystallization before drawing of a sample leads to a decrease of Young's modulus and tensile strength because in this case apparently the formation of a sufficient orientation during the drawing cannot take place. An increase of the drawing temperature above the glass transition temperature also leads to a decrease in the mentioned values.