| abstract |
1467003 Synthetic siliceous material; pressure sensitive copying paper UNILEVER Ltd 13 March 1974 [15 March 1973] 12514/73 Heading C4A A synthetic siliceous material, for use in paper coating compositions, comprises an amorphous silica/alumina mixture in which the proportion of Al 2 O 3 is between 7À5% and 28% on a dried weight basis, the surface area being in the range 300 to 800 m<SP>2</SP>/g., the mean pore diameter being in the range 40 to 100Š, the pore volume being in the range 0À5 to 1 c.c./g. and the average particle size as measured by a Coulter counter (R.T.M.), being in the range 15 to 3 microns. The material may be provided by milling certain silica/alumina materials which are available as petroleum cracking catalysts to reduce their particle size. The preferred milling technique is water wet milling. The material may contain small amounts of zinc oxide or magnesium oxide. Pressure-sensitive copying paper is coated with a composition comprising the material and a binder, e.g. a butadiene/styrene latex. The material may be used to replace all or part of the silton clay or phenolic resin in conventional coating systems. |