| 摘要 |
PROBLEM TO BE SOLVED: To obtain an alumina sol having a large pore diameter, pore volume and high transparency from which an ink accepting layer for a recording medi um having good absorbency for ink and high transparency can be produced, by flocculating an alumina hydrate slurry of a specified solid concn. under specified pH region and stirring power, and then subjecting to deflocculating treatment with acid. SOLUTION: A slurry of alumina hydrate having 1 to 40wt.% solid density is stirred in pH 7 to 12 range with >0.5kW/m<3> effective energy consumption to flocculate. Then, the slurry is deflocculated by adding acid to obtain an alumina soln. In the flocculation treatment, an alkali metal hydroxide or alkali metal aluminate is preferably added to the alumina hydrate slurry to control pH 7 to 12. The alumina hydrate preferably has <=1μm average secondary particle size. The alumina hydrate powder can be obtd. by drying the slurry after the flocculation treatment, however, it is preferable to dry the slurry after deflocculation treatment. |
