| 摘要 |
PURPOSE: To provide an electroviscous fluid having an electroviscous effect superior to that of conventional products by using silica particles with a polyhydric alcohol bonded through an ester bond to a surface silanol group of each particle in an electroviscous fluid comprising an electrical insulating liq. and silica particles, ammonia and water incorporated into the liq. CONSTITUTION: A compd. having a b.p. of 100 deg.C or above, e.g. ethylene glycol, is used as the polyhydric alcohol, which may be bonded through an ester bond to a silanol group on the surface of silica by any conventional method. Since the silica particle usually has a surface area of tens to hundreds of m<2> /g, 2 to 20wt.% of the resultant silica particles having an ester bond may serve as a bonded group derived from the polyhydric alcohol. Any electrical insulating liq. may be used without limitation so far as it has a high insulating resistance. Examples thereof include mineral oils and synthetic lubricating oils and pref. they have a viscosity of 5 to 200cP at 25 deg.C. These components are mixed by means of a vibrating ball mill or the like. pref. heat treatment is conducted after the mixing. |
