Method for producing products based on wood as a raw material

Abstract

A method is disclosed for producing products based on wood as a raw material. The method includes wood, in the form of wood particles, being subjected to an extraction treatment using an extracting agent. The extracting agent may include one or more organic solvents in an organic-aqueous mixture of the solvent or solvents with water. A content of fatty acids in the wood particles is reduced, by the extraction treatment of the wood particles using the solvent, by at least 70%, measured as hexanal content in wt. % after accelerated aging for 72 h at 90° C., while the content of cellulose, hemicelluloses and lignin is largely maintained during this extraction treatment.

1 . A method for producing products based on wood as a raw material comprising:
 wood in the form of wood particles being subjected to an extraction treatment with an extracting agent,   wherein the extracting agent comprises one or more organic solvents in an organic-aqueous mixture of the solvent or solvents with water,   wherein the content of fatty acids in the wood particles is reduced by at least 70%, measured as the hexanal content in wt % after accelerated aging for 72 h at 90° C., by the extraction treatment of the wood particles with the extracting agent, and   wherein the content of cellulose, hemicelluloses and lignin is substantially maintained in the extraction treatment.   
     
     
         2 . The method according to  claim 1 , wherein the wood particles are present in a size of at most 2 mm, wherein the particle size is preferably defined according to the National Renewable Energy Laboratory (NREL) Laboratory Analytical Procedure (LAP) NREL/TP-510-42620 “Preparation of Samples for Compositional Analysis” by the screen mesh of 2 mm of the cutting mill for sample preparation, and wherein the wood particles are preferably present in the form of fibers, chips or mixtures thereof. 
     
     
         3 . The method according to  claim 1 , wherein the wood particles are wood frayed by mechanical and/or thermal and/or chemical digestion, in particular wood fibers with average fiber lengths between 0.5 and 2 mm and average fiber diameters between 10 and 50 μm, and wherein the average fiber length as well as the average fiber diameter relate to the length average determined by optical measurement of the suspended fibers. 
     
     
         4 . The method according to  claim 1 , wherein the solvent portion of the organic-aqueous mixture in the extracting agent, determined as the concentration of the liquid phase of the extract, is composed of 0-95 wt % of ethanol, preferably 50-90 wt % of ethanol, 0-99 wt % of acetone, preferably 30-90 wt % of acetone, 0-70 wt % of n-propanol, 0-85 wt % of iso-propanol and/or 0-99 wt % of methanol. 
     
     
         5 . The method according to  claim 1 , wherein the content of cellulose, hemicelluloses and lignin is reduced by less than 10%, preferably by less than 5%, in particular by less than 4%, in the extraction treatment, wherein this reduction is preferably ascertained as an extracted solid mass related to the basic material, the wood particles. 
     
     
         6 . The method according to  claim 1 , wherein the wood particles are selected from coniferous wood particles, preferably spruce wood particles, fir wood particles, pine wood particles or larch wood particles; deciduous wood particles, in particular beech wood particles, poplar wood particles, birch wood particles or  eucalyptus  wood particles; or mixtures thereof. 
     
     
         7 . The method according to  claim 1 , wherein the wood particles are purified once or multiple times with an extracting agent after the treatment with the extracting agent, preferably purified with an organic-aqueous solvent with a similar or identical concentration as that of the extracting agent. 
     
     
         8 . The method according to  claim 1 , wherein the content of fatty acids in the wood particles is reduced by at least 75%, preferably by at least 80%, in particular by at least 90%, measured as the hexanal content in wt % of the wood particles in the basic material compared to the extracted wood particles after accelerated aging for 72 h at 90° C., by extraction of the wood particles with the extracting agent. 
     
     
         9 . The method according to  claim 1 , wherein the content of fatty acids in the wood particles is reduced to a content below 2 mg/kg dry matter, preferably below 1 mg/kg dry matter, in particular of below 0.5 mg/kg dry matter, measured as the hexanal content as the mass portion of the extracted wood particles after accelerated aging for 72 h at 90° C., by extraction of the wood particles with the extracting agent. 
     
     
         10 . The method according to  claim 1 , wherein resin acids are also extracted with the extraction besides the fatty acids. 
     
     
         11 . The method according to  claim 10 , wherein the fatty acids, resin acids and/or optionally further extractives extracted with the extracting agent are supplied to a further purification method, preferably by mechanical separating technique after the thermal separation of the organic solvent from the organic-aqueous extracting agent, wherein lipophilic extractives, in particular fatty acids and resin acids, are precipitated and separated, and a liquid phase enriched with hydrophilic extractives, in particular lignans, is obtained, wherein the hydrophilic extractives are preferably further concentrated by subsequent treatment with thermal separating technique, in particular by means of membrane separating methods and/or adsorption. 
     
     
         12 . The method according to  claim 11 , wherein a preceding membrane filtration of the extracting agent is effected in the extractive enrichment. 
     
     
         13 . The method according to  claim 1 , wherein chelating agents, in particular chelating agents selected from multivalent and polyfunctional carboxylic acids, aminomethylcarboxylic acids, aminomethylphosphonic acids and the compounds thereof, EDTA, DTPA EGTA, EDDS and the salts thereof, polyphenols, tannins, amino acids, peptides, proteins, polycarboxylates, phosphates, polyphosphates, phosphonic acids, polyphosphonates, phosphated, phosphonylated, sulfated and sulfonated polymers are not added to the wood particles in the course of the extraction method, in particular in the course of the entire production method for the products produced from the wood particles. 
     
     
         14 . The method according to  claim 1 , wherein the extracting agent as well as optionally used washing liquids, in particular water, are regenerated for reuse. 
     
     
         15 . The method according to  claim 1 , wherein in addition to the reduction of the hexanal content, the mechanical strength of the extracted wood particles, measured as the tensile index of sample sheets in Nm/g, is also increased by at least 10%, preferably by at least 15%, in particular by at least 25%, by the extraction treatment, wherein the degree of grinding, measured in ° SR, therein changes by less than 10%. 
     
     
         16 . A use of the lipophilic extractive fraction obtained according to  claim 12  as an animal feed supplement.