Encapsulated Wood Preservatives

Abstract

A method of incorporating biocides into wood or a wood product, the method including the steps of synthesising a plurality of capsules each having an outer shell of polymer and incorporating within each said capsule an additive which includes an organic biocide, and then applying the said capsules to the wood or wood product in a manner whereby the capsules penetrate the wood or wood product.

What we claim is: 
     
         1 . A microencapsulated organic biocidal composition for impregnating a wood or timber product at a pressure not exceeding 1400 Kpa and formulated to retain a biocidally effective amount of one or more organic biocides selected from fungicides and insecticides, mouldicides, bactericides, algaecides, and a combination thereof within the inner ninth core of said product, the composition comprising a plurality of microcapsules having a mean diameter of between about 0.5 micron and about 20 microns, the microcapsules comprising a water immiscible solvent containing said one or more organic biocides surrounded by a polymeric outer shell, the microcapsules being further characterized in that they are prepared by dissolving the biocidal active in a water immiscible solvent containing a reactive, oil-soluble pre-polymer, emulsifying the solvent in an aqueous phase containing a reactive polymerization initiator to create the polymeric outer shell at the oil/water interface. 
     
     
         2 . The composition according to  claim 1  wherein the mean microcapsule diameter is less than about 9.2 microns. 
     
     
         3 . The composition according to  claim 1  wherein the preferred organic biocide is at least one insecticide or fungicide. 
     
     
         4 . The composition according to  claim 1  wherein the one or more insecticide or fungicide is selected from the group consisting of an isothiazolone, a benzothiazole, a pyrethroid, a neonicotinoid, a halogenated carbamate, an azole, a chloronitrile, or a combination thereof 
     
     
         5 . The composition according to  claim 1  wherein the one or more insecticide or fungicide is selected from the group consisting of 4,5-dichloro-2-n-octyle-4-isothiazoline-3-one (DCOIT), chlorothalonil, bifenthrin, and a combination thereof 
     
     
         6 . The composition according to  claim 1  wherein the microencapsulated organic biocide is diluted with water then applied to the wood or timber product using standard industry vacuum and or pressure treatment methods to force the microcapsules to penetrate into the inner ninth core to provide for a biocide retention within the inner ninth core exceeding 75% of the estimated average biocide retention. 
     
     
         7 . The composition according to  claim 1  wherein the microencapsulated organic biocide is made by:
 (a) dissolving the biocide in a water immiscible solvent, 
 (b) mixing a reactive oil-soluble pre-polymer into the water immiscible solvent, 
 (c) emulsifying the water immiscible solvent into an aqueous phase containing a reactive polymerisation initiator to create a microcapsule wall at the solvent-water interface. 
 
     
     
         8 . The composition according to  claim 1  wherein the microencapsulated organic biocide further comprises one or more additional water soluble biocides and/or other penetrating adjuvants. 
     
     
         9 . The composition according to  claim 8  wherein the additional water soluble biocides are quaternary ammonium compounds, metal salts or boron salts. 
     
     
         10 . The composition according  claim 1  wherein the wood or timber product is at least one of solid wood, orientated strand board, particle board, medium density fibrewood, plywood, laminated veneer lumber, and laminated strand lumber. 
     
     
         11 . A wood or timber product impregnated with the microencapsulated organic biocidal composition of  claim 1 .