GB809332A - Improvements in ligno-cellulosic fibre-board - Google Patents

Abstract

<PICT:0809332/IV (a)/1> <PICT:0809332/IV (a)/2> <PICT:0809332/IV (a)/3> In making low-density fibreboards, fibrous lignocellulosic particles of various sizes coated with a liquid binder are fed, from a hopper 4, through vibrating screens 4a, 4b and 4c of increasing coarseness to form a loose airfelted mat B on a series of smooth metal, e.g. stainless steel, plates 2 coated with a liquid binder moving along a conveyer 1. A sheet of absorbent paper may be applied to the coated plates. The binder may be applied to the plates by a spray 3 or by placing on the plates a sheet of absorbent paper saturated with the binder. The upper surface of the mat may be smoothed by a brush 5a. The mat may be compressed and made thinner by a moving endless belt 6. Upper plates 9 are applied to the mat and a part 10 of the conveyer is speeded up to form separate assemblies comprising portions of the mat sandwiched between individual plates 2 and 9. These assemblies are arranged in a loader 11 from which they are passed into a press 12 where they are heated and pressed to dry and set the binder and form fibreboards having fine particles on their front or under surfaces and coarse particles on their upper surfaces or backs. Two fibreboards may be bonded together back-to-back. Before the mat is heated and pressed, a layer 8 of the binder may be applied to its upper surface by a spray 7 or by coating the plates 9 with the binder. A layer of fine particles treated or untreated with binder may be deposited on the mat before it is heated and pressed. The ligno-cellulosic particles may be particles of wood, bamboo, straw or bagasse. The binder may be a synthetic resin or a protein, e.g. soyabean protein. Powdered nut shells and inorganic fillers and pigments may be incorporated in the binder.