Solvent-borne polyurethane adhesives with high molecular weight, high OH content and low solution viscosity

Abstract

An adhesive composition includes a polyurethane polymer, a solvent and a co-solvent. The polyurethane polymer is an internally and/or externally hydrophilized thermoplastic polyurethane having an Mw of ≥50000 g/mol. The solvent is a polar-aprotic solvent. The co-solvent is selected from water, a primary alcohol having ≤10 carbon atoms, a vicinal diol or a mixture of at least two of the aforementioned compounds. The solvent and the co-solvent are present in such amounts that they form a homogenous mixture without the formation of a second phase when combined together at 20° C. The hydroxyl group content is ≥1 weight-%, based on the total weight of the composition. The polyurethane polymer content is ≥10 weight-%, based on the total weight of the composition and the composition forms a single continuous liquid phase. Examples for solvent/co-solvent combinations are methylethyl ketone (MEK) and water or MEK and ethanol.

Dependencies are inferred from the claim text.