Patent GB-562161-A (GB)
Title: Superfine asbestos and method of manufacture
IPC: C04B20/08
Filed: 1941-07-25
Abstract: 562,161. Paper. SCIENTIFIC & INDUSTRIAL RESEARCH, THE HONORARY ADVISORY COUNCIL FOR. July 25, 1941, No. 9489. Convention date, Aug. 4, 1940. [Class 96] [Also in Groups II and V] By bending and squeezing chrysotile asbestos repeatedly, restricting the action to a narrow area relatively to the length of the pencils of fibre, while permitting liberated fibre to spread in the neutral region of the stressed material, a mass is produced in which a substantial portion of the fibres is invisible at magnifications of 3000 diameters and have a ratio of length to diameter of not less than 100. The smallest of the fibres may be about 300 Angstrom units in diameter. A mass of such fibres has remarkable qualities ; great liquid holding capacity ; very little optical effect under the polariscope ; great flexibility when wet; useful laminaforming properties ; moulding properties when mixed with latex, oil, or bitumen to form thermo-plastic and thermo-setting material ; lubricating quality if mixed with graphite; and it has some apparently chemical and structural effect on the binding mass, for example, a latex product containing 70 per cent. of such fibre is insoluble in acetone. Various apparatus for forming the fibres is described and the'essential is that the fibrous body has freedom to expand and spread out at right angles to the applied force. The asbestos bundles are put in a cylinder 1, Fig. 1, with rubber lining 5 against which they are pressed by blunt edged spiral fins 7 on rollers 6 swinging on arms 8 pivoted near a sleeve 9 driven by a pulley 4. The cylinder is separately driven by a pulley 10. In another machine the spirally finned rollers 60, Fig. 8, work in a conical mantle 50 and swing by links 56 from arms 57 driven by a shaft 46 and pulley 59, the mantle 50 being driven by a pulley 54. A hopper 61 feeds the material to a bowl 62 fast on the shaft 46 and having a downwardly tapered rim 63 to direct the material between the rollers and mantle. Walls 64 and 65 confine and direct the treated material towards the discharge opening 66. In another form of apparatus the material is fed on to a rubber belt conveyer 11, Fig. 3, and passes under blunt edged blades 13 slanting across the belt and reciprocated vertically by a spring-mounted support 16, 18 controlled by an electromagnet 19. Another means of reducing the asbestos is a pebble mill which, rotated for 4 hours, produces a slurry of fibres about 95 per cent. of which are about 300 Angstrom units in diameter. Another suitable apparatus is a disc 23, Fig. 6, vibrated by an air driven piston 35 against a - serrated floating disc 24 with a control inlet hopper and feed pipes 27, 28 and a spring supporting means 31, 29 to adjust the pressure applied to the material. Or, a hollander type of pulp beating machine may be used where the beater roll 38, Fig. 7, co-operates with a knived bed plate 39 with the addition of a rubber surfaced roll 41 along the apex of the backfall 40. The fibres may be opened up still further after treatment by any of the above apparatus, by employing the spray device shown in Fig. 9 in which the asbestos sludge produced as above is put in a closed tank 67, through a filling plug 68, where air or steam from a pressure supply pipe 71 is applied to it through a submerged nozzle 73 and a pipe 76 from the bottom of the tank is led to a nozzle 78 in a second tank 74, open at the top ; a branch of the nozzle being fed with pressure air or steam from the supply pipe 71. Fibres produced by the above methods can be made into sheets using standard paper-making equipment without foreign bonding material. Thin sheets have great flexibility and smoothness and are practically transparent.