Akzo N.v.

Akzona Incorporated

Joachim Behnke

Michael Wallrabenstein

Dieter Frank

Klaus Gerlach

Walter Brodowski

Helmut Schulze

Michael Pelger

Rolf Vollbrecht

Alfred Rasen

Klemens Schenesse

Hans-Jurgen Pitowski

Christoph Josefiak

Walter Loffelmann

Angelika Reiche

Dieter Huff

Wolfgang Rosener

Ernst Berg

Hans-Dieter Brauer

Marija Del Rio

Ewald Hohm

In a process for chlorine-free bleaching of cellulose with an .alpha.-cellulose content of more than 90%, preferably from boiled cotton linters, more than 75% whiteness is achieved in a single-stage process using oxygen. The bleaching is conducted using the oxygen obtained by disproportionation of peroxo compounds in the pH range from 6 to 13 and with the bleaching time, depending on the bleaching temperature of 35.degree. C. to 15.degree. C., being between 15 and 150 minutes.

Oxygen bleaching of cotton linters by disproportionation of hydrogen

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.

Process for producing extractive-material-reduced cellulose

In a process for the production of linear segmented polyurethane by simultaneous reaction of macrodiols, low-molecular diols as chain-lengthener and aromatic diisocyanate, in a solvent in the presence of catalyst, and in the presence of catalytic amounts of a magnesium or calcium salt, an aromatic carboxylic acid macrodiol, monomeric, lower-molecular diol and aromatic diisocyanate are reacted, the macrodiol being used in such amounts as to adjust in the prepared polyurethane a weight ratio of soft segment to hard segment of about 4:1 to 1:4. Preferred embodiments include reaction at temperature from about 70.degree. to 120.degree. C.; use of an inert solvent; and having the concentration of starting material amount to about 10-40% by weight relative to the mixture of starting material and solvent. Also provided are polyurethanes obtained according to this process, having a molecular non-uniformity from 2 to 7. Preferred embodiments include that the polyurethane have an average molecular weight from 60,000 to 250,000. The polyurethanes are useful for the production of membranes, specifically those to be used for sterile filtration or blood oxygenation.

Linear segmented polyurethane and process for its production

A method is provided for producing a membrane from polycarbonate-polyether-blockcopolymers with about 5 to 35 weight percent of repeating alkyleneethercarbonate units and about 95 to 65 weight percent of repeating bisphenol A-carbonate units, wherein the polyethyleneoxide blocks have a molecular weight from about 1,000 to 20,000, wherein the intrinsic viscosity of the copolymer is from about 180 to 300 ml/g as measured in chloroform at 25.degree. C. and wherein the ultrafiltration rate is from about 4 to 200 ml/h.m.sup.2.mm Hg. In a first dissolving step a polycarbonate-polyether-copolymer is homogeneously mixed with a solvent at a temperature from about 80.degree. to 120.degree. C. and in a second dissolving step the temperature is brought to about 140.degree. to 180.degree. C. to produce a true solution. The filtered solution is cooled to from about 20.degree. to 50.degree. C. and is then extruded through a nozzle into a bath comprising a nonsolvent for the polymer for precipitating the polymer. The precipitated polymer is then washed and dried. The resulting membranes improve the processes of hemodialyzing and of homofiltration.

Polycarbonate-polyether-copolymer membrane

A method for production of polycarbonate-polyether-blockcopolymers is provided. One or more solutions comprising bisphenol A and polyalkyleneglycol and a phosgene solution are added to a cooled initial reaction medium in a cooled reaction chamber in such a way that the phosgene contacts substantially the reaction partners from the one or more cooled solutions after they have spread in the reaction medium. Preferably the phosgene solution and the one or more solutions are added through tubes ending above the liquid level of the reaction medium such that the solutions added contact only within the stirred reaction mixture the reaction partner. The phosgene is employed in an excess of less than about 10 weight percent of the stochiometrically required weight amount relative to bisphenol A and polyalkyleneglycol. The polymer is useful in the production of membranes for dialysis, ultrafiltration and reverse osmosis.

Process for preparing polycarbonate-polyether-blockcopolymers

Process for the production of phosphazo polymers by thermal polymerization of a cyclic compound of the formula (NPCl.sub.2).sub.n in which n is an integer from 3 to 10 in the presence of a catalyst of the general formula R-O-SO.sub.2 -R.sup.1.

Process for the thermal polymerization of phosphazene polymers

A low density matting structure of improved transverse strength obtained by vertically laying continuous melt-spun thermoplastic macrofilaments (diameter=0.1-1.5 mm) onto a horizontally moving profiled support in overlapping rows of irregularly looped filaments to form a peak and valley three-dimensional structure undulating in its longitudinal and/or transverse direction. The matting articles consist essentially of the melt-spun filaments which are self-bonded or fused at random points of intersection without using any bonding agent or reinforcing inserts, and the resulting matting is especially distinguished by a high transverse strength per unit of surface weight of at least 2 Nm/g and preferably 4 Nm/g.

Low density matting and process

An ultrafiltration membrane comprised of a linear polyurethane having a hydraulic permeability for water of about 50 to 500 1/m.sup.2 .multidot. h and a separation factor .alpha. of about 2.times.10.sup.-3 to 1.times.10.sup.-4, the permeability being based on determination with a membrane of a thickness of about 0.02 mm, a pressure differential of 1 bar and a temperature of 20.degree. C. and the separation factor .alpha. being established with a 2% oil-water emulsion at 25.degree. C. The membrane is particularly suited for operation of oil-water mixtures or emulsions.

Linear polyurethane ultrafilter and processes for use thereof

A process for the production of high molecular weight, fiber- and film-trimming polyterephthaloyl oxalamidrazone and polydiphenylether-4,4'-dicarboxylic acid oxalamidrazone where a solution of pure terephtaloyl chloride or diphenyl-ether-4,4'-dicarboxylic acid dichloride in an inert solvent free from amines and water is slowly added, at a temperature between 10.degree. C. and 35.degree. C., to a solution of pure oxalic acid bisamidrazone in dimethyl acetamide and/or N-methyl pyrrolidone, free from amines and water, containing 4 to 6 percent by weight of anhydrous lithium chloride, the total quantity of the solvents used amounting to 1.25 to 3.30 liters per mole of oxalic acid bisamidrazone.

Process for the preparation of polyterephthaloyl-and polydiphenyl

A process for the stabilization of a polymer which is a barium, strontium and/or calcium complex of polyterephthaloyl oxalamidrazone or polydiphenylether-dicarboxylic acid-4,4'-oxalamidrazone wherein the polymer is treated in an acidic to neutral aqueous solution, e.g. at pH of 1 to 7, containing an acid or salt compound selected from the group consisting of oxalic acid, alkali oxalate, alkali sulfite, alkali hydrogen sulfite, alkali dithionite and alkali hydrogen sulfate. The resulting product has a much improved resistance to UV, oxidation and hydrolysis. Such polymers are especially useful in the form of flame-retardant threads, yarns, filaments, fibers, felts, fabrics and the like.

Stabilization of barium, strontium and calcium complexes of

A metal compound of a polyacyl-2,4-dihydrazino-s-triazine in which the metal is chemically bound in complex form to the polymer to provide dimensionally stable and heat-resistant polymeric compounds which are useful as pigments, catalysts and synthetic fibers.

Growing community of inventors

Amorbach, Germany

Joachim Behnke