Process for treating a porous material

摘要

A method of treating a piece of porous cellulose and/or lignin based material by impregnating with a radiation polymerizable monomer comprising a vinylic grouping and comprising a grafting functional group reactive with the cellulose/lignin hydroxyl groups and/or a crosslinker and irradiation with high energy radiation. The thickness of the impregnation layer is 0.1-5 mm below the material surface and the quantity of impregnation monomer is 1-9 wt.% of the layer. The treatment is carried out at atmospheric pressure. The impregnation layer does not exceed in thickness 30% of the smallest dimension of the piece. The conditions governing the layer thickness are a temperature 10-80[deg]C and/or a duration 90 minutes or less and/or a moisture content 12% or less and/or a monomer viscosity at 25[deg]C 10-3000 mPa.s. It is disclosed that the minimum moisture content should be 5% or above. The radiation treatment is gamma radiation or bundles electrons or heavy ions. The energy employed is 20-100 kGy. The most preferred material is wood. An independent claim is also included for a piece of cellulose and/or lignin based porous material comprising for a thickness of 0.1-5 mm below its surface a moisture impermeable film of a polymer grafted to the material and/or crosslinked such that he moisture impermeability factor does not exceed 55. This factor is defined as the product of the weight of moisture (expressed as a percentage) re-taken up by the material after steeping for 48 hours in water at 20[deg]C by the amount (expressed as a percentage) of monomers constituting the polymer forming the impermeable film.