| 摘要 |
PURPOSE:To provide a fluidity improver which allows the fluidity of powder to be greatly improved and retained over a long period of time, consisting of fine silica powder made hydrophobic with a specified diorganosiloxane oligomer. CONSTITUTION:1-50pts.wt. diorganosiloxane oligomer of the formula (wherein R is a monovalent hydrocarbon group; n is 1-15; Q is halogen, hydroxyl or OR<1>; and R<1> is a monovalent hydrocarbon group) is added to 100pts.wt. fine silica powder having a very low water content (e.g., fumed silica). The mixture is mixed until a homogeneous mixture is formed. The mixture is heated at 100-200 deg.C to make the powder hydrophobic, thus obtaining a fluidity improver having such characteristics that its specific surface area (BET method) is 180+ or -100m<2>; its carbon content is 5+ or -3wt%; its apparent density is 75+ or -35g/l; its compression density is 220+ or -35mg/cm<2> when 1.5g of a sample is placed under a pressure of 3.4kg/cm<2> for 4min; and its silanol titer is 1.0+ or -1.0ml; the titer being expressed by the titer of an aq. soln. of 0.1N-NaOH required for changing the pH of a dispersion from 4.0-9.0. The dispersion obtd. by dispersing 2.0g of a sample in a liquid mixture of 25ml of ethanol and 75ml of a 20wt% aq. soln. of NaCl. 0.2-0.3wt% said fluidity improver is added to powder. |
