GB1099088A - Improvements in and relating to the manufacture of boards and other shaped articles from wood and other chips of vegetable origin - Google Patents

Abstract

<PICT:1099088/C3/1> In making chipboard and the like, chips of wood, wood wool, straw or chaff are treated with impregnating and/or binding agents in a solution, dispersion or emulsion and then partly dried in a centrifugal strainer. In Figure 2, the chips are added at 7 to a stream of impregnating agent entering the drum 2 by shoot 5 and partly dried before reaching pipes 11, 12 which deliver a binding agent and pipe 13 which delivers hot air. The impregnating agent may be a solution of urea and sodium fluoride with some ammonium dihydrogen phosphate as a fireproofing agent and hardener for the binder; which may be urea, melamine or phenol formaldehyde or cresol-resol resin. Movement along rotating perforate drum 2 is induced by reciprocating plate 4, and the drum may be of stepped construction to aid mixing and increase peripheral speed towards the open end. The impregnating and binding agents could be mixed before adding to the chips. In alternative methods the chips and liquor are mixed in a vat before entering the drum, or the chips may enter the drum dry in an air stream or vibrating trough, or the binder is added in a mixing step to impregnated and dried chips leaving the drum. Some constituents of the liquors may reduce adhesion to the drum wall. Other constituents such as chlorinated paraffin wax, sorbitol and resorcinol may be added to the liquors. The liquor withdrawn from the centrifugal strainer may be brought up to strength and recirculated.