Unit for preserving wood - comprising wood preservative enclosed in thin casing of fibrous material sealed with coating of water-soluble or water-swellable material

摘要

In a unit for preserving wood, comprising a wood preservative enclosed in a casing, where the preservative can be given up when the unit comes into contact with water, the casing consists of a think envelope of fibrous material which has been sealed by a coating of water-soluble or swellable material. The thin envelope is of a non-woven material, pref. water-insol. and -nonswelling, and is surrounded in the middle of the unit by a water-impermeable screen, partic. of a synthetic film extending over 0.5-0.25 of the total length of the unit. The water-soluble material of the casing is of polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol, polyacrylamide, soluble cellulose derivs. or polyethylene oxides, and the water-swellable material is polyvinyl acetate or a polymer mixt.. Pref. the polymer or mixt. dissolves or swells to a max. extent at a moisture content not below 18 wt.%.