SULFONATE AND NON-SULFONATE THIOL HYDROXY FUNCTIONAL POLYURETHANE AND GRAFT COPOLYMER FABRICATED BY USING THE SAME

摘要

PROBLEM TO BE SOLVED: To provide a high Tg and satisfactory mechanical properties, allow a pigment to be well dispersed, and realize cross-linking with an isocyanate hardening agent by allowing a hardening dispersion body coating film applied on a surface of a substrate to contain a vinyl/sulfonate hydroxy functional polyurethane graft copolymer, a dispersive agent and a magnetic pigment dispersed in the hardening dispersion body. SOLUTION: A copolymer is made of a polyurethane main chain; three or more cross-linked hydroxy groups each suspending from the main chain and having a hydroxy equivalent of a main chain of about 500 to 50,000; and one or more univalent component suspending from the main chain and being represented in a formula of -S-B (where B represents a polymer segment containing polymerized radical-polymeric polymer which has a weight ratio of a main chain to OH and S with respect to B of about 5:95 to 95:5. In this copolymer, most portions of hard resin are grafted to sulfonate hydroxy functional polyurethane, and exhibit both satisfactory mechanical properties and satisfactory optical transparency as a binder to be used for a magnetic recording medium.