Patent GB-805807-A (GB)
Title: Improvements relating to axial-flow compressors
IPC: B05D3/02
Filed: 1956-12-17
Abstract: In a coating composition comprising a mixture of sodium silicate, or a thermo-setting synthetic resin, a filler material, and a volatile solvent, for application to the inner surface of a compressor casing for sealing purposes as in the parent Specification, the filler material is baked to reduce its moisture content before mixing with the other ingredients.  The filler material, for example asbestos, is spread on a metal sheet to a thickness of about half an inch and baked at a temperature of 950 DEG  to 1050 DEG  F. for about two hours, followed by one hour at about 200 DEG  F.  It is then mixed with the other ingredients at such a rate as to produce a homogeneous mixture without balling.  The synthetic resin, when used, may comprise phenol formaldehyde, urea formaldehyde, melamine formaldehyde, or a heat-hardenable silicone resin.  The filler material may comprise finelydivided graphite, asbestos, or both, or glass fibre or silica flour.  The volatile solvent may be toluene or secondary butyl acetate.  The mixture may comprise 15 to 55 per cent by weight of filler material, 7 to 45 per cent of a silicone resin, up to 75 per cent of a volatile solvent and, when desired, about 7 per cent to 12 per cent of finely-divided aluminium or other metallic powder.  A preferred composition comprises 96 to 104 fluid ounces of a silicone resin aluminium paint (which includes the resin, the solvent, and aluminium powder) and 1.9 to 2.1 lb. of asbestos fibre. After cleaning and degreasing, the metal surface to be coated is given a thin brush coating of the composition, followed by spray coating to a thickness of about 1/32 inch.  After baking at about 125 DEG  F. for about 30 minutes, followed by cooling to a maximum temperature of about 100 DEG  F., a further layer is applied to increase the thickness to about 5/64 inch.  This is followed by air-drying for about 16 to 20 hours and then baking for about two hours at about 125 degrees F.  If desired, the required thickness may be obtained in smaller increments by repeating the steps of spraying, baking and cooling prior to air-drying. Finally, the coating is cured by baking for at least one hour at about 125 DEG  F., followed by two hours each at 200 DEG , 300 DEG , 400 DEG  and 500 DEG  F.  The coating is then machined to the desired dimensions, and two thin coats of the silicone resin alone, in liquid form, are applied, the first coat being air-dried and the second coat being baked at about 625 DEG  F. for at least four hours.ALSO:In a composition comprising a mixture of sodium silicate or a heat-hardenable silicone resin or a thermosetting synthetic resin such as phenol formaldehyde, urea formaldehyde or melamine formaldehyde; a filler material such as finely-divided graphite, asbestos or both, or glass fibre or silica flour; and a volatile solvent such as toluene or secondary butyl acetate, the filler material is baked to reduce its moisture content before mixing with the other ingredients.  The mixture may comprise 15 to 55 per cent by weight of filler material, 7 to 45 per cent of a silicone resin, up to 75 per cent of a volatile solvent and, when desired, about 7 to 12 per cent by weight of finely-divided aluminium or other metallic powder.