Patent GB-1129815-A (GB)
Title: Production of coherent bodies from asbestos dispersions
Inventor: DONALDSON WILLIAM KENNETH
IPC: D02G3/20
Filed: 1964-12-04
Abstract: 1,129,815. Papemaking; forming fibrous mats; spinning yarns; non-woven webs. TURNER BROS. ASBESTOS CO. Ltd. 25 Nov., 1965, [4 Dec., 1964; 7 May, 1965], Nos. 49445/64 and 19469/65..Headings D1F, DIN, D1R, D2A and D2B. A continuous coherent body of predominantly asbestos fibres e.g. a sheet or strip from which a yarn may be spun or a paper-like product, is produced by drawing a carrier surface e.g. of a drum 72 across a pool 73 of an aqueous dispersion of asbestos fibres. A reagent is provided in the dispersion and a coagulating liquid is placed on the carrier surface so that the .precipitate formed on the surface of - the carrier binds the fibres into a coherent mass. After the strip 79 is formed on the carrier surface the outer surface is also treated with coagulating liquid either by spraying or by causing the carrier surface to move into a bath of the coagulating liquid. The strip is then taken from the carrier surface e.g. while it is still below the surface of the coagulating liquid and lead away e.g. to a pot spinning device. The carrier surface may be the permeable or impermeable surface of a drum or belt or a wire gauge may be used. The carrier surface may, as in Fig. 8, form one end wall of a trough holding the dispersion or it may be the surface of a band touching the surface of a pool of dispersion (Figs: 1, 2 not shown) or the surface of a band dipping into the dispersion (Figs. 5 and 6 not shown) or as in Fig. 9 (not shown) the dispersion is passed by a tube (66) onto an inclined moving belt (60). In Figs. 3 and 4 (not shown) the wall of the trough 20 holding the dispersion which is adjacent the carrier surface is slotted so that side by side strips are formed. Alternatively a wide sheet may be cut into strips before or after the sheet has been completely coagulated.  At. ,the point of leaving the dispersion the carrier surface may be moving upwardly e.g. as in Fig. 9 (not shown) so that gravity tends to hold back the dispersion and allow only a thin film to be formed or as in Fig. 8. an air doctor, may be provided to hold back the body of the dispersion. At the point where the strip leaves the carrier surface a jet of coagulating fluid may be directed to prevent the strip sticking, particularly when the strip breaks or when the strip is being first passed through the apparatus. The coagulating fluid may also be used to clean the carrier surface.  Circulation systems are arranged to maintain the concentration of the dispersion and of the coagulating fluid constant. Doctor fluid or squeeze rollers may be provided to prevent excess coagulating liquid being carried by the carrier .surface into the pool of dispersion. The fibres are preferably: of chrysotile asbestos. and particles of polymers or graphite and glass fibres may be included in the dispersion. Emulsions and latices e.g. rubber may be incorporated. The reagent may be a sodium soap which is coagulated to a water insoluble soap or a fatty acid. An anionic surface-active dispersing agent may also be used. The coagulating liquid is preferably a solution having cations of a polyvalent metal or hydrogen. A solution of aluminium or zinc sulphate is preferred. An example is given showing the constitution of a particular dispersion and coagulating liquid.