Abstract: The present invention relates to a process for the preparation of colorless, storage-stable polyisocyanates containing biuret groups from di- or polyisocyanates using water and/or steam as a biuretizing agent, and an apparatus for this purpose and the use thereof.

Abstract: A process for the preparation of polyisocyanates which contain one or more biuret groups, by reacting a) an aliphatic or cycloaliphatic isocyanate containing two or more isocyanate groups (isocyanate a) with b) a tertiary alcohol or a mixture of water and a tertiary alcohol (biuretizing agent b) at from 100 to 250° C.

Abstract: A process for the preparation of polyisocyanates which contain one or more biuret groups, by reacting

Abstract: Mixtures comprise a) polyisocyanates (polyisocyanates A), comprising structural units selected from the isocyanurate and biuret group, derived from aliphatic or cycloaliphatic diisocyanates (diisocyanates C), b) non-A polyisocyanates (polyisocyanates B), comprising structural units selected from the allophanate and urethane group, derived from b1) aliphatic or cycloaliphatic diisocyanates (diisocyanates C) and b2) polyhydric aliphatic or cycloaliphatic alcohols (alcohols A), the molar ratio of the polyisocyanates A to the polyisocyanates B being from 200:1 to 5:1.

Abstract: A process for preparing biuret-functional polyisocyanates from at least one aliphatic or cycloaliphatic diisocyanate and from at least one amine or water or a mixture thereof as reactants involves mixing the reactants with one another in a mixing unit having a high shear action.

Abstract: A process for the preparation of polyester polyols having an acid number of less than 1, a hydroxyl number of approximately 20 to about 400, and having a functionality of efficaciously 2 to 3, wherein polycarboxylic acids and/or their anhydrides and multivalent alcohols are polycondensed, preferably in the absence of common esterification catalysts, at temperatures of from about 150.degree. to 250.degree. C., optionally under reduced pressure, up to an acid number of from 20 to 5. The resulting polycondensate is then oxyalkylated per carboxyl group using from 1 to 5 moles of an alkylene oxide, for example 1,2-propylene oxide and/or preferably ethylene oxide, in the presence of at least one tertiary amine catalyst from the group consisting of N-methylimidazole, diazabicyclo[2,2,2]octane, diazabicyclo[5,4,0]undec-7-ene and pentamethyldiethylenetriamine and mixtures thereof, in a quantity of from about 0.001 to 1.0 weight percent based on the weight of the polycondensate, at temperatures from about 100.degree.

Abstract: Optically active carboxylic acids ##STR1## where R.sup.1 is an organic radical which is linked to the asymmetric C' atom via a carbon atom and R.sup.2 is one of the radicals R.sup.1 (but not the same radical), halogen or an organic radical which is bonded to the asymmetric C' atom via an oxygen atom, are prepared by reacting a ketene II ##STR2## with an alcohol in a homogeneous liquid phase in the presence of a tertiary amine III and then converting the resulting ester into the acid, using an optically active alcohol IV.

Abstract: The invention relates to s-triazine radical-containing polyether polyol mixtures having functionalities of from 2 to 6 and hydroxyl numbers of from 210 to 640, prepared by the oxyalkylation of a mixture of one or more polyamino-1,3,5-triazines, preferably melamine, and an alkanol having a hydroxyl functionality of from 2 to 6 and having 2 to 18 carbon atoms, water, or their mixtures, in the absence of catalysts and conventional inert polar solvents. The resulting polyether polyol mixtures are suitable for the preparation of rigid polyurethane, polyisocyanurate, and urethane group-containing polyisocyanuate foams produced by means of the polyisocyanate polyaddition process.