Patent GB-1026573-A (GB)
Title: Improvements in or relating to sheet materials
IPC: D21H13/36
Filed: 1963-07-24
Abstract: Sheet material is made by mixing sheetable particulate material with an aqueous solution of an organosilicon compound, the pH of the aqueous solution during at least part of the time of contact being such that organo-silicon compound is deposited upon the sheetable particles, allowing the coated particles to stand, without agitation, until they no longer coagulate when agitated, and then separating the particles from the water so that they are bound together as a sheet. The organo-silicon compound consists essentially of 70 to 100 mol. per cent of C6H5Si­ units, essentially all of any remaining organosilyl units being (C6H5)(CH3)Si= or (CH3)2Si=, essentially all of the remaining valencies of the silicon atoms being satisfied by oxygen atoms present in SiOSi or OH groups. The particulate material may be fibres, e.g. of asbestos, glass, quartz, polyamide, polyethylene terephthalate, polyacrylonitrile or alpha-cellulose or flakes, e.g. of mica or glass or mixtures thereof.  The pH may be adjusted by the addition of an alkaline substance, e.g. potassium hydroxide, ammonia or beta-hydroxyethyl-trimethyl-ammonium bicarbonate, or by the leaching out of alkali from the fibres, when these are of asbestos.  The slurry may be agitated after the standing period and before sheeting out.  The sheets may be consolidated by heat and pressure.  Laminates may be formed by pressing several such sheets together, before or after the removal of water, or by winding them round a mandrel and then applying heat and pressure. The particulate material may first be coated with a low-molecular weight hydroxyl-end-blocked phenylmethylsiloxane, and then treated with the organo-silicon compound as above.  The product may be thinner than tissue or thicker and of high opacity.  It has high thermal and electrical insulation.ALSO:Sheet material is made by mixing sheetable particulate material with an aqueous solution of an organosilicon compound, the pH of the aqueous solution during at least part of the time of contact being such that organo-silicon compound is deposited upon the sheetable particles, allowing the coated particles to stand, without agitation, until they no longer coagulate when agitated, and then separating the particles from the water so that they are bound together as a sheet.  The organosilicon compound consists essentially of 70 to 100 mol. per cent of C6H5Si ­ units, essentially all of any remaining organosily units being (C6H5)(CH3)Si = or (CH3)2Si =, essentially all of the remaining valancies of the silicon atoms being satisfied by oxygen atoms present in SiOSi or OH groups. The particulate material may be fibres e.g. of asbestos, glass, quartz, polyamide, polyethylene terephthalate, polyacrylonitrile or alpha-cellulose or flakes, e.g. of mica or glass or mixtures thereof. The pH may be adjusted by the addition of an alkaline substance, e.g. potassium hydroxide, ammonia or beta-hydroxy-ethyl-trimethyl-ammonium bicarbonate, or by the leading out of alkali from the fibres, when these are of asbestos. The slurry may be agitated after the standing period and before sheeting out.  The sheets may be consolidated by heat and pressure.  Laminates may be formed by pressing several such sheets together, before or after the removal of water, or by winding them round a mandrel and then applying heat and pressure. The particulate material may first be coated with a low-molecular weight hydroxyl-end-blocked phenylmethyl-siloxane, and then treated with the organo-silicon compound as above.  The product may be thinner than tissue or thicker and of high opacity.  It has high thermal and electrical insulation.