GB803051A - Improvements in or relating to the manufacture of pressed sheets from comminuted wood - Google Patents

Abstract

<PICT:0803051/IV (a)/1> A pressed or moulded sheet is made from a loose layer of comminuted wood such as wood chips or wood shreds coated or impregnated with a hardenable adhesive resin binder by first compressing the layer to approximately its final thickness under high pressure sufficient to convert it into a coherent sheet without hardening the binder, and subsequently hardening the binder under low pressure. The loose layer 2, which may be formed by spreading the material on a paper sheet 1 and may be covered by a sheet 3, e.g. of resin-impregnated asbestos, may be reduced in thickness by feeding it through pressure rollers 5, or through successive pairs of rollers which reduce the thickness in stages. The coherent mat or sheet so produced is, if desired, moulded to a required shape, e.g. a motor car roof, under light pressure, and is heated whilst under pressure to cause hardening of the resin, e.g. between matched heated dies or between a heated forming tool and a compressed air bag. The resins employed may be phenol-or urea-formaldehyde, cold-setting or thermosetting, and in liquid or powdered form.