A method for liquid treatment of a wood species

Abstract

The present invention relates to an improved method for impregnating a porous material, such as wood, more specifically a method in which an active ingredient to be deposited within the porous material is dissolved in condensed carbon dioxide and impregnated in the material

1 . A method for treating a porous material with an active ingredient comprising the steps of
 a. providing the porous material to a container;   b. applying pressure, in the container, by providing gaseous carbon dioxide to the container, said container comprising the porous material, at a temperature below the critical point of carbon dioxide;   c. applying further pressure to the container to provide condensed carbon dioxide;   d. providing an active ingredient, optionally solubilized, to the container, optionally premixed with carbon dioxide;   e. maintaining the pressure obtained in step c. for a predetermined period of time;   f. increasing the temperature in the container to a temperature above the critical point of carbon dioxide at the prevailing pressure to provide carbon dioxide in supercritical form;   g. maintaining the conditions obtained in step f. for a predetermined period of time; and   h. reducing the pressure to atmospheric to provide a treated porous material and carbon dioxide in gaseous form.   
     
     
         2 . A method according to  claim 1 , wherein the porous material is a wood species. 
     
     
         3 . A method according to any of the  claim 1  or  2 , wherein the active ingredient is added to the container at a pressure, which is higher than the pressure in the container. 
     
     
         4 . A method according to  claim 3 , wherein the active ingredient is added to the lower part of the container. 
     
     
         5 . A method according to any of the  claims 1  to  4 , wherein the active ingredient of step d. is added approximately at the point of condensation of carbon dioxide in step c. 
     
     
         6 . A method according to any of the  claims 1  to  5 , wherein the pressure in step c. reaches a pressure in the range 70-90 bar and the temperature is in the range 15 to 25° C., preferably 80 bar and 20° C. 
     
     
         7 . A method according to any of the  claims 1  to  6 , wherein the temperature in step f. is increased to a temperature in the range 20 to 70° C., preferably 60° C. 
     
     
         8 . A method according to any of the  claims 1  to  7 , wherein the density of carbon dioxide in step e. is above 750 kg/m 3 , preferably above 800 kg/m 3 . 
     
     
         9 . A method according to any of the preceding claims wherein the active ingredient is selected from the group consisting of polymers for increasing water resistance, modifiers of the building blocks of the porous material, organic and inorganic biocides, aromas, colorants and organic or inorganic salts. 
     
     
         10 . Method according to  claim 9  wherein the biocide is an organic biocide selected from the group consisting of triazoles, pyrotroides, carbamates and salts of organic acids. 
     
     
         11 . Method according to any one of the preceding claims, wherein the treatment is selected among impregnation, extraction, dying, improving water resistance or drying and any combination thereof.