Patent GB-722012-A (GB)
Title: Improvements relating to thermal insulating material
Inventor: SMITH ERIC CHARLES WILLIAM
IPC: C04B28/22
Filed: 1951-07-20
Abstract: A thermal insulating material consists of inorganic fibre, especially artificially produced fibre, e.g. rock wool and/or glass fibre, and inorganic insulating binder comprising lime and a natural silica material, preferably kieselguhr preferably in equal proportions by weight, which have been finely ground and intimately mixed together preferably in the form of an aqueous paste before mixture with, or application to, the fibre and treatment of the composite material so produced in an autoclave, preferably in the proportions by weight of 60 per cent. fibre, this preferably being made of rock wool and glass fibre in the ratio of 55 to 40 per cent (preferably 50 to 45 per cent) rock wool to 5 to 20 per cent (preferably 10 to 15 per cent) glass fibre, and 40 per cent binder.  In one method of carrying out the invention 20 per cent by weight of each of lime and kieselguhr are mixed with water to form a thick paste and are then ground so that they will pass a screen of 150 meshes to the inch and the mixture is then fed into a drum mixer with paddles into which 55 to 40 per cent rock wool and 5 to 20 per cent glass fibres have first been mixed with at least about 50 times the weight of the fibre of water to produce effective dispersal of the fibre after which the mixture is run off into perforated moulds, drained and the moulded blocks thus obtained are treated in autoclaves under steam pressure of 100 to 150 lbs. per sq. in. for 1 to 5 hours, the treated blocks being then cut up into slabs and oven dried.  In another method in which light weight insulating material with included air cavities is formed, the fibre is dispersed in a large volume of foam produced by placing about 10 gallons of an aqueous solution of a foam-producing agent, for example that known under the R.T.M. "Cemor" in a tank provided with rotatble agitating paddles and with a pipe at the bottom having fine perforation, rotating the paddles and blowing air under pressure into the liquid through the pipe until the tank is full of foam when the fibre is introduced and is uniformly dispersed by the action of the paddles, followed by finely ground and mixed lime and kieselguhr and the agitation continued until all the constituents are uniformly mixed and the fibres are well coated with the binder.  The contents of the tank are then run off into non-perforated moulds of required shape and subjected to autoclave treatment and drying as previously described.  In a continuous method 20 lbs. each of hydrated lime and kieselguhr are mixed with 10 gallons of water to which may be added a dispersing agent or protective colloid suitably bentonite, and ground together to give to a suspension, which will pass a screen of 150 meshes to the inch, the aqueous dispersion so formed being sprayed into a chamber and caused to disperse in and intermingle with the fibre as it is blown at a steady rate into the chamber at whose bottom there is a moving conveyer upon which the fibre falls continuously preferably into trays which facilitate the removal of the mat of wet fibre in sections or when settled on the conveyer, the rates of feed being adjusted so that 40 lbs. of the solid constituents of the binder are introduced during the same period as 60 lbs. of fibre.  The wet fibre may be rolled to a required thickness before being removed from the trays, cut to required size before autoclaving and drying. Cylindrical sections can be produced by rolling or winding a mat of fibre e.g. glass fibre, which has been saturated with the binder as described above.  A similar but discontinuous method in which a mat of fibre is saturated with a suspension of the binder may be used for the direct production of slabs of required thickness or for producing a block of materials which is cut into slabs after treatment in the autoclave.  In a further method of producing cylindrical sections a continuous roll of glass fibre is saturated with a dispersion of the finely ground binder or of the binder mixed with rock wool, the saturated roll being then shaped or rolled on a mandrel treated in the autoclave and dried.