The invention belongs to the technical field of preparation and surface protection of
polyurethane coatings, and particularly relates to weather-resistant
polyurethane and a preparation method thereof. The
coating provided by the invention is composed of a component A and a component B according to a weight ratio of 1: (0.2-0.4). The component A is prepared from water-based
fluorine-containing hydroxy acrylic dispersion resin with a high
hydroxyl value, GMA (
glycidyl methacrylate) grafted modified water-based acrylic dispersion resin, a
benzotriazole ultraviolet light absorber, a light hindered amine stabilizer,
rutile titanium dioxide, wet
sericite powder,
nano zinc oxide and auxiliaries; and the component B comprises an aliphatic
isocyanate curing agent and
propylene glycol diacetate. By constructing a quadruple synergistic weather-resistant mechanism of
ultraviolet absorption, free radical capture, physical shielding and structural densification, the
weather resistance and
corrosion resistance of the
coating are remarkably improved while the
coating keeps excellent
adhesive force (0-1 level) and
hardness (2H-3H), the color change
delta E is smaller than or equal to 1.8 after artificial
accelerated aging for 1000 hours, the gloss
loss rate is smaller than or equal to 23%, and the
weather resistance and
corrosion resistance of the coating are greatly improved. And the
corrosion spreading width of a 600-hour
salt spray test lineation is less than or equal to 2.3 mm.