Method for the modification of wood

A process for the acetylation of wood elements comprising the following steps:

• (a) impregnating a plurality of batches of wood elements with an acetylation fluid comprising acetic anhydride and/or acetic acid so as to provide a plurality of batches of impregnated wood elements comprising acetylation fluid comprising acetic anhydride and/or acetic acid, wherein the impregnating step is carried out in an impregnation chamber, wherein the impregnation chamber is configured to be closed off;
• (b) collecting, combining and storing said plurality of batches of impregnated wood elements comprising acetylation fluid comprising acetic anhydride and/or acetic acid in a collection chamber in such a manner as to provide a continuous feed of impregnated wood elements to a reaction chamber, the collection chamber is a vessel having an inlet, a place to collect and store a buffer volume of impregnated wood elements, an outlet for impregnated wood elements and a drain for separation of excess liquid from the wood elements, wherein said outlet for impregnated wood elements allows a controlled amount of impregnated wood elements to be fed into the reaction chamber, wherein the volume of the collection chamber is 1 to 15 times the volume of the impregnation chamber;
• (c) subjecting a continuous flow of impregnated wood elements to acetylation reaction conditions in said reaction chamber so as to provide a continuous flow of acetylated wood elements exiting said reaction chamber, wherein
• excess impregnation liquid is removed from the impregnated wood elements by transport of the impregnated wood elements through an upward tilted transport screw.