| 摘要 |
PURPOSE: To obtain an ultrafiltration membrane having an alpha alumina sepn. layer having an average pore diameter of <=35 nm by applying an alumina hydrate gel dispersed with finely divided crystalline seed particles on a porous support and drying the coating, then heating the same at <1300 deg.C. CONSTITUTION: The alumina hydrate gel dispersed (about 0.05 to 1 wt.%) with the finely divided crystalline seed particles (a specification surface area of >=35 m<2> /g is preferable) is applied on the porous support, such as tubular microfilter, of alpha alumina. The coating is then dried and thereafter the dried gel is heated at <1300 deg.C for the time sufficient for converting the gel to the alpha alumina and to bond the same onto the support. As a result, the novel ultrafiltration membrane having the sepn. layer of which at least >=60 vol.% consists of the alpha alumina and which has the pore size of <=35 nm is obtd. The temp. necessary for conversion to the alpha alumina is higher and the pore size is larger if the seed crystals are not added. |
