Polyurethanes including pendant hindered amines and compositions incorporating same

摘要

Ungelled, aqueous dispersions of silane-terminated partially crosslinked polyurethane polymers are described which are the reaction product of A) an isocyanate-containing prepolymer formed from: (i) a molar excess of organic polyisocyanate sufficient to promote substantially equal access to isocyanate groups; (ii) active hydrogen-containing material; (iii) sterically hindered amines; (iv) emulsifying monomer; B) chain-extending monomer; C) an organic compound having a pKb of at most about 7; and D) a silane coupling agent represented by the general formula ASi(OR2)3 and present in an amount sufficient to partially crosslink the polyurethane resin but insufficient to gel the dispersion, provide advantages over previously known polyurethanes used as surface coatings. The hindered amine allows surface coatings incorporating the polyurethanes to be easily removed by aqueous compositions having pH between about 2 and 5. Methods of making the prepolymers, polymers, and dispersions are also presented.