A stable aqueous alumina sol and method for preparing the same.

摘要

A stable aqueous sol of amorphous alumina containing Al2O3 up to 15 % by weight and 0.1 to 0.5 gram equivalent of an anion of acid to 1 mol of aluminum in the sol, in which the colloidal particles of amorphous alumina have a controlled thickness in a range of 20 to 100 millimicrons and a uniform length in a range of 200 to 500 millimicrons is produced by a process comprising feeding an aqueous solution of an acid into an aqueous slurry containing 1 to 7 % by weight of metallic aluminum, 10 to 200 ppm by weight as SiO2 of a water-soluble silicate and 0 to 20 ppm by weight of a water-soluble sulfate as SO4 to the water in the slurry while maintaining the slurry at a temperature of 80 DEG C to boiling point under normal pressure, said acid being in an amount of 0.1 to 0.5 gram equivalent to 1 mol of the metallic aluminum in said slurry, at a rate of 0.001 to 0.03 gram equivalent of the acid to 1,000 g of the water in the slurry per minute, and continuing heating the slurry after completion of the feeding of the acid at a temperature of 80 DEG C to boiling point of the slurry until a sol of amorphous alumina having a uniform length of 200 to 500 millimicrons is formed.