GB889928A - Improvements in and relating to the production of fibres from lignocellulosic material - Google Patents

Abstract

Fibres suitable for dry forming into a mat <PICT:0889928/IV (a)/1> which may be consilidated to a board are produced by exposing lignocellulosic material, e.g. wood chips, to steam at a pressure, e.g. 25 to 100 p.s.i., and for a time, e.g. 1 to 6 minutes, sufficient to soften the chips, but insufficient to form appreciable quantities, e.g. greater than 5% by weight, of water-soluble compounds from constituents of the chips, hereafter pressing the softened chips before finally reducing them to fibres between a pair of rotating grinding discs. In the apparatus shown, chips stored in silos 12 are conveyed by an endless belt 13 to a surge chamber 4 and thence up an elevator 15 to an upper surge bin 16 from whence they are admitted in controlled quantities through a valve 18 into a cooker 19. Softened chips leave the cooker through a valve 21 and are moved by a conveyer 22 to screw conveyers 23 feeding screw presses 25 followed by refiners 26. One of the shafts carrying a grinding disc in the refiner is drilled axially to provide an opening through which resin may be introduced, if desired, to produce fibres having a resin content from 0,5 to 10%. A water-repellent, e.g. wax, may also be added in amount from 0,5 to 4%. After discharge from the refiner, the fibres are conveyed through conduits 65 by hot air streams which reduce their moisture content to 8 to 12%. Before final felting, the fibres may be subjected to air separation, classification and, if not effected in the refiners, resin binder mixing. The felted mat of fibres is then hot pressed p to cure the resin and form a board of S.G. 0,8 to 1,2.