Abstract: Aqueous dispersion of one or more polyurethane resins with a number average molecular weight (Mn) of 2500 to 1000000, a content of 2 to 150 mmol of siloxane linkages (--Si--O--Si--) per 100 g of solid resin, a hydroxyl value of 0 to 100 and a content of ionic groups, groups convertible into ionic groups and/or hydrophilic groups of 5 to 200 mEq per 100 g of solid resin and the process for the production thereof by chain extension of a polyurethane prepolymer containing ionic groups, groups capable of ion formation and/or hydrophilic groups which has at least one group R'OSi-- in whichR'=C.sub.1 to C.sub.8 alkyl or C(O)R"' andR"'=C.sub.1 to C.sub.10 alkylby the addition of water. The aqueous dispersion is suitable for aqueous coating compositions which are suitable in particular for multilayer lacquer coatings.

Abstract: A process and a coating medium for producing a decorative multilayer coating on a substrate, wherein a base lacquer coat is applied and is overpainted with a transparent lacquer coat, wherein an aqueous, self-crosslinking base lacquer is used, which contains, as a binder vehicle, an aqueous polyurethane resin dispersion based on a polyurethane resin having a number average molecular weight (Mn) of 2500 to 120,000, a content of 10 to 400 mmole of lateral and/or terminal hydroxyl and/or R'O groups bonded to silicon, whereR'=a C.sub.1 to C.sub.8 alkyl or C(O)R''', andR'''=a C.sub.1 to C.sub.10 alkyl,per 100 g solid resin, a hydroxyl number of 0 to 150, wherein hydroxyl groups bonded to silicon are not included in the calculation of the OH number, and a content of ionic groups, groups convertible into ionic groups and/or hydrophilic groups of 5 to 200 mEqu per 100 g solid resin.

Abstract: There are described aqueous dispersions of polyurethane resins, the production thereof and their use in aqueous coating agents, said dispersions being obtainable in aqueous or non-aqueous phase froma) polyurethane resins with at least one CH acidic group, an ionic or non-ionic hydrophilic group and, optionally, OH and/or NH groups, byb) introduction of olefinic double bonds by reaction withb.sub.1) compounds with a CH acidic group and an olefinic double bond, and/orb.sub.2) compounds with an olefinic double bond and also a group that is capable of reacting with CH acidic groups, and/orb.sub.3) compounds with an olefinic double bond and also a group that is capable of reacting with OH or NH groups, orb.sub.4) formaldehyde,whereupon, optionally, conversion into the aqueous phase and radical polymerization are effected.