Abstract: The invention relates to a process for obtaining extractive-material-reduced cellulose with a low LAL reaction, wherein cotton linters or wood pulps, subsequent to the customary digesting treatment, are subjected for 1 to 10 hours to hydraulic washing with water, lye with a concentration of less than 5 g/l alkali content, or with a diluted acid containing less than 5 g/l acid at temperatures of 120.degree. to 180.degree. C. and under a pressure of 2 to 20 bar.The resulting cellulose is used for the manufacture of hemodialysis and/or hemofiltration membranes in the form of flat membranes, tubular membranes or hollow filaments by regeneration of a cellulose solution containing the extractive-material-reduced cellulose with a low LAL reaction.The regeneration may be effected from solutions of cellulose cuoxam, cellulose xanthate, or solutions of cellulose in tertiary amine oxide or in an LiCl-containing solvent.

Abstract: The invention relates to a dialysis membrane of regenerated cellulose and to a process for its production. Isocyanate prepolymers with an average molecular weight of 300 to 50,000, which are soluble in organic solvents other than solvents reacting with isocyanate groups and dissolving cellulose, are bound chemically at least to one membrane surface of the dialysis membrane. The dialysis membrane of the present invention substantially eliminates the symptoms of leukopenia and complement activation.

Abstract: The invention relates to a method for the production of a dialysis membrane of regenerated cellulose. Isocyanate prepolymers with an average molecular weight of 300 to 50,000, which are soluble in organic solvents other than solvents reacting with isocyanate groups and dissolving cellulose, are bound chemically at least to one membrane surface of the dialysis membrane. The dialysis membrane made by the process of the present invention substantially eliminates the symptoms of leukopenia and complement activation.

Abstract: A dialysis membrane used for hemodialysis having a structure comprised of flat films, blown films or tubular threads of substitution-modified cellulose, in which the effects of complement activation and leukopenia are clearly reduced. The average degree of substitution of the modified cellulose is 0.02 to 0.07. Dialysis membranes, which have proven successful within the scope of the invention, contain modified cellulose, having a structure represented by the formula cellulose-Z, wherein Z represents the group --R'--X--Y.X is at least one member selected from the group consisting of ##STR1## Y is at least one member selected from the group consisting of --R, --NR.sub.2, --Si(OR").sub.3, --SO.sub.3 H, --COOH, --PO.sub.3 H.sub.2, --N.sup.+ HR.sub.2, --OR" and the salts thereof.R' is at least one member selected from the group consisting of an alkylenes cycloalkylenes and arylenes having a total of 1 to 25 carbon atoms.R" is a hydrogen atom or R.

Abstract: Embedding mass of polyurethane produced on the basis of castor oil, and a method for its production, wherein an aromatic diisocyanate is reacted with a mixture of castor oil and trimethylolpropane into an NCO-group displaying pre-adduct, the pre-adduct being mixed for network polymerization with castor oil or a mixture of castor oil and trimethylolpropane, and after embedding the mixture is hardened in the presence of catalyst, thereby characterized in that a titanium alkylate compound is used as catalyst in amounts from 7 to 700 ppm, calculated as elemental titanium. Preferably, the catalyst is a titanium tetraalkylate; in particular titanium tetrabutylate. Also, a titanium magnesium hexaalkylate may be used as titanium alkylate compound; preferably, titanium magnesium hexabutylate. Preferably the catalyst is present in amounts from 40 to 140 ppm, calculated as elemental titanium.

Abstract: The converter protection device has a number of controlled semiconductor elements. A control unit is connected to the semiconductor elements of the converter for forming firing pulses for the controlled semiconductor elements. Reference blocking intervals for the semiconductor elements are set and actual blocking intervals of the semiconductor elements are set and controlled. A comparator receives and compares the reference and actual blocking intervals. There are also provided a read-only memory for storing the reference blocking intervals, an event counter for counting disturbances detected by comparison of the reference and actual blocking intervals, a memory stage being connected to the event counter and being set if the event counter reaches a predetermined count, and a time-base device connected to the event counter and memory stage for resetting the event counter if the memory stage is not set at the end of a predetermined base time.

Abstract: Method for controlling the speed and torque of an asynchronous machine fed through a static frequency changer with impressed intermediate current link, a control variable for the frequency of the current delivered by the frequency changer being formed from an electrical variable corresponding to a slip frequency value and an electrical variable corresponding to actual value of a frequency proportional to the rotor speed of the asynchronous machine which includes operating the asynchronous machine with constant flux in a region of constant maximal torque, and adjusting the flux in the machine, in a region of constant maximal power, as a function both of voltage at commutating capacitors of a self-commutating inverter and of a respective load condition of the asynchronous machine.

Abstract: Polyurethanes prepared from macrodiols with an average molecular weight between about 800 and 4000, lower molecular weight chain extenders with at least two labile hydrogens, and cyclohexane-1,4-diisocyanate with a trans-isomer content of at least 90%, are described. These polyurethanes exhibit exceptional mechanical properties, high softening temperatures, and remarkable stability to light and to many common solvents.Methods for preparation of the novel polyurethanes, as well as for their use, are also disclosed.

Abstract: A process for the production of polyurethane solutions by reaction of a diisocyanate with a mixture of a glycol and a polymer bearing terminal hydroxy groups in a solvent medium under certain prescribed conditions. The resulting polyurethane solutions are especially valuable as impregnants or coating agents for textile substrates, for example in the preparation of a microporous synthetic leather.