Patent ID: 8138230

Claim:
A chi (x)-alumina dispersion characterized by subjecting gibbsite to thermal treating, physical wet-milling and/or mixing and pH adjusting processes, so as to obtain the x-alumina dispersion containing flaked porous x-alumina nanoparticles without gamma (y)-alumina, wherein the flaked porous x-alumina nanoparticles have a specific surface area of 100 m 2 /g to 220 m 2 /g, an average thickness of 10 nm to 200 nm, an average cross-sectional diameter of 20 nm to 1000 nm, pore size over a surface of the flaked porous x-alumina nanoparticles of 1 nm to 10 nm, a solid content of 20 wt. % to 40 wt. %, a pH value of 2 to 6, and a coating layer formed by the x-alumina dispersion without dyes and pigments has water resistance and an ink absorptivity of 1.5 mg/cm 2 to 1.8 mg/cm 2 .