Patent GB-984527-A (GB)
Title: Improvements in or relating to the manufacture of flexible sheet material for sound proofing and other purposes
IPC: D04H1/645
Filed: 1961-03-11
Abstract: 984,527. Sound insulating materials. EVERGLADES Ltd., W. TREUHERZ, S. WOLSTENHOLME, and S. HALLOWELL. March 7, 1962 [March 11, 1961], No. 8972/61. Heading B2E. [Also in Division D1] A sheet of flexible material for sound insulation is formed by impregnating a fibrous base with a bonding agent applied to fill the voids between the fibres of the base in the form of a liquid or paste containing a high proportion of lead or other heavy metal or compound thereof in powder form and which is non-brittle in its finished state. By high proportion of lead is meant a proportion of not less than 40% by weight of the whole, while by heavy metal or compound thereof is meant a metal or compound thereof having a density of not less than 3À5. The fibrous base may comprise a non- woven or a loosely woven fabric of glass, polyvinyl chloride, polyvinylidene chloride, wool, jute or other fibres. After impregnation the excess binder is squeezed out and solidified either by evaporation or by heat gelation. The added powder is preferably metallic lead, a heavy lead compound, e.g. lead sulphide, tungsten, a tungsten compound or a barium compound. The fibres may be bonded with a polymer, casein or starch or not bonded in the case of a non-woven woollen felt or glass fibre mat. For impregnation, the powder may be suspended in a pourable paste of a polymer with a plasticizer added, the metal powder may be added to a solution of a polymer in a suitable solvent or the bonding agent may be insoluble but dispersible in water so that an emulsion is formed. The polymeric binder may be polyvinyl chloride or polyvinyl acetate. The plasticizer may be dioctyl or dibutyl phthalate or a polyester. Flame resistant plasticizers, e.g. tritolyl phosphate or other alkyl aryl phosphates in conjunction with boric acid or antimony oxide, may be incorporated with the binding agent. Lead carbonate as a stabilizer and polyglycol oleate as a viscosity control may also be added. A solvent solution of rubber or synthetic rubber may be used with powdered lead or lead sulphide. The solution may contain crepe rubber, zinc oxide, stearic acid, antioxidant, sulphur, naphtha solvent and mercapto benzthiazole accelerator. Examples are given stating the proportions by weight of the constituents of the impregnating mixture. The fabric to be impregnated may be passed through an agitated bath of paste or a thin paste layer may be applied thereto by forcing the paste under pressure through a slot on to the fabric. As shown, fabric 10 from an idler roller 11 provided with a tension device 12 passes through an impregnating tank 15 containing a removable guide roller 14. The impregnating mixture is fed to the tank 15 from a feed tank 17 provided with an agitator 18. The impregnated fabric 10a passes between adjustable scrapers 21, 22 and through a heater or drier 23 having infra-red heaters 24 or gas heaters. The fabric 10b passes between embossing or smoothing rollers 25 and rollers 26, both pairs of which may be water cooled, to a take-up roller 27 driven by rollers 28. The rollers 25, 26, 28 are driven in synchronism from a variable speed gear 29. An extraction duct 30 for the removal of fumes is provided. The fabric 10a may pass between high pressure or hot rollers (not shown) after impregnation to densify the material. The finished fabric may be coated with a coloured lacquer by spreading or spraying or may be laminated with a pre-formed sheet, e.g. polyvinyl chloride.