METHOD OF APPLYING A POWDER COATING TO A LENGTH OF A LIGNOCELLULOSIC MATERIAL

摘要

A method of applying a powder coating to a length of lignocellulosic material such as for example a sheet of paper includes the steps of: (a) impregnating the length of lignocellulosic material with an impregnating composition comprising either: (i) a dicarboxylic anhydride or a tricarboxylic anhydride dissolved in a suitable non-aqueous solvent; or (ii) an isocyanate thermosetting resin dissolved in a suitable non-aqueous solvent; or (ii) a combination of a dicarboxylic anhydride or a tricarboxylic anhydride and an isocyanate thermosetting resin dissolved in a suitable non-aqueous solvent; (b) if necessary removing from the impregnated length of lignocellulosic material any excess of the impregnating composition; (c) removing the non-aqueous solvent or solvents; (d) placing the impregnated length of lignocellulosic material in an electrostatic field or in a fluidized bed and applying a powder coating composition thereto so that the powder coating composition adheres thereto; and (e) then subjecting the length of lignocellulosic material to elevated temperatures to polymerise and/or cross-link the resin or resins in the length of lignocellulosic material and to cure the powder coating composition to form the powder coating.