Polyurethane heat-stabilizing agents may help resist temperature changes and preparations of an aqueous composition which may be resistant to temperature changes due to the use of such an agent (P). The viscosity may be thermally stabilized by such an aqueous composition in a wide temperature range and for many shear gradient values.

A reduction in the viscosity is achieved and improvements in the storage stability and the heat resistance of the coating film are achieved.

An aqueous dispersion of a polyurethane resin according to an embodiment is obtained by a reaction of a polyol (A), a polyisocyanate (B), and a chain extender (C). The polyol (A) includes an aromatic polyester polyol (A1), and an aliphatic diol (A2) having a hydrocarbon group in a side chain. The chain extender (C) includes a compound (C1) having three primary and/or secondary amino groups and not having hydroxy groups, and a compound (C2) having one or more hydroxy groups and two or more primary and/or secondary amino groups. The acid value is 11.0 to 23.0 mgKOH/g and the hydroxyl value is 8.0 to 23.0 mgKOH/g.

The present invention relates to a dimensionally stable adhesive compound which is formulated so as to be largely water- and solvent-free and can be brought into contact with the substrate to be bonded by being wiped on in the form of a thin adhesive film that is suitable in particular for bonding materials obtained from plant fibers. The organic constituent of the adhesive compound according to the invention consists predominantly of polyester polyurethanes, at least some of which are based on semi-crystalline polyester polyols. The invention also relates to a method for applying a tacky film to a planar substrate, preferably to paper, by wiping the adhesive compound onto the point of contact with the substrate.