Blocked MDI Prepolymer BPI-80 Single-Component

BPI-80 uses methyl ethyl ketoxime (MEKO) as the blocking agent, which reacts reversibly with MDI prepolymer NCO groups below 60°C. During baking at 150–170°C, the equilibrium shifts: MEKO volatilizes and free NCO groups regenerate, reacting with hydroxyl-functional binders (polyester, acrylic) to form urethane crosslinks. The cured coating achieves pencil hardness ≥2H and MEK double-rub resistance >200 cycles within a 30-minute bake at 160°C. BPI-80 is favored over IPDI-based blocked systems in coil coating where higher reactivity and lower bake temperatures improve line speed economics. The residual MEKO must be vented from the oven; modern systems recover and recycle MEKO to meet VOC emission regulations.