US20240076831A1 - Method for producing products based on wood as a raw material - Google Patents

Method for producing products based on wood as a raw material Download PDF

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US20240076831A1
US20240076831A1 US18/259,700 US202118259700A US2024076831A1 US 20240076831 A1 US20240076831 A1 US 20240076831A1 US 202118259700 A US202118259700 A US 202118259700A US 2024076831 A1 US2024076831 A1 US 2024076831A1
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wood particles
wood
extraction
content
extracting agent
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Anton Friedl
Maximilian LEHR
Martin MILTNER
Walter WUKOVITS
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MM Board and Paper GmbH
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    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C3/00—Pulping cellulose-containing materials
    • D21C3/20—Pulping cellulose-containing materials with organic solvents or in solvent environment
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/08—Removal of fats, resins, pitch or waxes; Chemical or physical purification, i.e. refining, of crude cellulose by removing non-cellulosic contaminants, optionally combined with bleaching
    • D21C9/086—Removal of fats, resins, pitch or waxes; Chemical or physical purification, i.e. refining, of crude cellulose by removing non-cellulosic contaminants, optionally combined with bleaching with organic compounds or compositions comprising organic compounds
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/001—Modification of pulp properties
    • D21C9/007—Modification of pulp properties by mechanical or physical means
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/08—Removal of fats, resins, pitch or waxes; Chemical or physical purification, i.e. refining, of crude cellulose by removing non-cellulosic contaminants, optionally combined with bleaching

Definitions

  • the invention relates to methods for producing products based on wood, in particular methods for pretreatment of wood.
  • Wood as a raw material for the industrial processing to products based on wood contains—besides the main components cellulose, hemicelluloses and lignin—many different low- and high-molecular materials like fatty acids, resin acids, phenols and terpenes. These substances are subsumed as so-called extract materials (or extractives) since they can be extracted from wood with hot water and/or organic solvents (Koch, Raw Material for Pulp; in: Sixta (ed) Handbook of Pulp (2006), Weinheim: Wiley-VCH Verlag GmbH & Co. KGaA, p 21-68).
  • extractives are “organoleptically relevant substances”, since they can result in olfactory and flavor interactions and impairments in products based on wood particles with the environment relevant to the respective final application (for example food in case of packaging cardboard or room air in case of wood fiber boards).
  • extractives which inherently have characteristic odors as volatile hydrocarbons (e.g. terpenes), especially aldehydes (particularly hexanal) are responsible therefor, which are formed by an autocatalytic oxidation of fatty acids naturally occurring in the wood (Schreiner et al., Resolving the smell of wood-identification of odour-active compounds in Scots pine ( Pinus sylvestris L.) (2016), Scientific Reports 8:8294).
  • wood particles contain resins, which can coagulate to sticky particles in processing the wood particles, which is augmented by the fats and waxes also naturally occurring in the wood.
  • resinous particles also referred to as “pitch” or “stickies”, also cause disturbing effects on the paper/cardboard surface, which can entail problems in further processing the paper/cardboard (e.g. imprinting) in further consequence.
  • These materials can also have a disruptive effect on the production process in that they cause deposit on machine parts, rollers and covering parts and the like (Sixta et al., Chemical Pulping Processes; in: Sixta (ed) Handbook of Pulp (2006), Weinheim: Wiley-VCH Verlag GmbH & Co.
  • fatty acids are not removed from wood particles for products based on wood particles, such as for example cardboard or wood fiber boards. Instead, the autooxidation of these fatty acids is inhibited or delayed in that the heavy metal ions acting as a catalyst are bound in the wood particle products by the addition of chelating agents such as ethylenediaminetetraacetic acid (EDTA) or diethylenetriaminepentaacetic acid (DTPA).
  • EDTA ethylenediaminetetraacetic acid
  • DTPA diethylenetriaminepentaacetic acid
  • EDTA and its metal complexes are only poorly and slowly degradable in the wastewater purification and therefore are considered to be ecologically critical today, which in particular entails increasingly great problems for wastewater from production plants for products based on wood particles.
  • bleaching e.g. DE 10 2004 050 278 A1
  • delignifying e.g. DE 28 18 320 A1
  • oxidizing or reducing e.g. DE 33 44 239 C2
  • WO 2006/039914 A1 DE 10 2006 020 612 A1
  • DE 10 2014 114 921 A1 relates to a method for producing an “emission-reduced” solid wood product or an “emission-reduced” wood containing basic material, in which it is treated with a “buffer solution” with a pH of ⁇ 6 to precisely “reduce” the emissions (substantially of VOCs), however, wherein cellulose, hemicellulose and lignin are obviously not substantially maintained, and it is not disclosed, to which extent the content of fatty acids can be reduced with this method.
  • solid wood or wood particles are treated such that the fatty acid esters contained therein are “inhibited, cleaved or oxidized”, but not extracted.
  • WO 93/20279 A1 discloses the treatment of cellulose pulp (thus not wood particles) with organic solvents, which are to be again separated subsequent to this treatment.
  • WO 2020/000008 A1 discloses the production of lignin particles.
  • WO 00/34568 A1 relates to a method for producing chemical pulp from wood chips, wherein hemicellulose and lignin are separated.
  • EP 2 138 528 A1 relates to a method for producing a cellulose material with reduced content of wood extractive.
  • DE 10 2013 001 678 A1 discloses a method for treating wood with an oxidant.
  • EP 2 356 977 A1 relates to the use of honey locust wood extracts for treating cellulite.
  • a further object of the present invention is a significant improvement of the organoleptic characteristics of the wood particles as well as of aged wood particles, which are produced according to this method, such that the products produced therewith have no or only low odor loads also without the employment or addition of bleaching, delignifying, oxidating or reducing chemicals.
  • a preferred object of the present invention is in removing further ingredients from wood particles, which are undesired in the planned product, for example resin acids.
  • the present invention relates to a method for producing products based on wood as a raw material, in which wood in the form of wood particles is subjected to an extraction treatment with an extracting agent, which includes one or more organic solvents in an organic-aqueous mixture or the solvent or solvents with water, wherein the content of fatty acids in the wood particles is reduced by at least 70%, measured as a 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, but the content of cellulose, hemicelluloses and lignin is substantially maintained in this extraction treatment.
  • an extracting agent which includes one or more organic solvents in an organic-aqueous mixture or the solvent or solvents with water
  • the treatment according to the invention is preferably selected such that the desired reduction is thereby achieved anyway, and a reduction by at least 70%, preferably by at least 90%, in particular by at least 95%, is thus achieved.
  • the conditions to be applied according to the invention can then be selected e.g.
  • a preferred embodiment of the method according to the invention relates to an extraction of the wood particles to a hexanal content of 0.5 mg/kg TM or below.
  • hexanal contents of the wood particles >0.5 mg/kg TM it could be determined that the risk of an organoleptic impairment of the wood particles also increased here with increasing hexanal content.
  • the wood particles then have to be aged sealed in these vials at room temperature (ca. 20° C.) for six months to oxidize the fatty acids to hexanal. Since this takes very much time and thereby does not allow a soon assessment of the extraction success, the determination of the hexanal content is effected via the accelerated aging according to DIN ISO 5630-2 according to the present invention.
  • the hexanal content was performed in the experiments in the example part (unless explicitly otherwise indicated); this method is also relevant to the determination of the hexanal content for the purposes of the present invention in case of doubt.
  • the wood particles are sealed in HS-GC vials, aged for 72 h at 90° C. and the hexanal content was subsequently ascertained by means of HS-GC.
  • the wood particles are present in a size of less than 2 mm, preferably in the form of fibers, chips or mixtures thereof.
  • This particle feature (as “particle size”) is defined according to the National Renewable Energy Laboratory (NREL) Laboratory Analytical Procedure (LAP) NREL/TP-510-42620 “Preparation of Samples for Compositional Analysis”, to which the NREL LAP NREL/TP-510-42619 “Determination of Extractives in Biomass” also relates.
  • the particle feature of the particle size is accordingly formulated on the screen mesh (2 mm) of the cutting mill for sample preparation.
  • the wood particles are preferably present in the form of fibers, chips or mixtures thereof.
  • This limitation of the particle size to 2 mm as also preset in the NREL method NREL/TP-510-42620, entails the great advantage that besides the relatively well accessible resin channels, the comparatively difficultly accessible parenchyma cells, where the fatty acids are located, can also be extractively well reached (Lehr et al., Removal of wood extractives as pulp (pre-)treatment: a technological review (2021), SN Applied Sciences 3:886).
  • 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 ⁇ m.
  • average fiber length as well as average fiber diameter relate to the length average, determined by means of optical measurement of the suspended fibers. This optical measurement usually results in uniform results (independently of chosen methodology and analysis apparatus), however, the apparatuses PulpEye (http://www.pulpeye.com/products/pulpeye/) and in particular MorFi Fiber Analyzer (http://www.techpap.com/fiber-and-shive-analyzer-morfi-neo,lab-device,31.html) have proven to be particularly suitable.
  • the amount of organic compounds, which can be extracted with the method according to the invention, is different according to wood type and constituent of the tree, from which the wood particles are obtained (heartwood/sapwood).
  • wood type and constituent of the tree from which the wood particles are obtained (heartwood/sapwood).
  • pines contain up to 9 wt % of extractable material in the heartwood
  • fir sapwood usually only comprises up to 1% of extractable material (Bjorklund Jansson et al., Wood Extractives; in: Ek et al. (eds) Wood Chemistry and Wood Biotechnology, 1 (2009), Walter de Gruyter GmbH & Co.
  • VOC volatile organic compounds
  • aliphatic and aromatic aldehydes in particular hexanal and furfural
  • wood is treated with at least one compound for adjusting a neutral to alkaline pH value (like NaOH) and at least one chelating agent (like EDTA or DTPA).
  • at least one compound for adjusting a neutral to alkaline pH value like NaOH
  • at least one chelating agent like EDTA or DTPA
  • CTMP chemical-thermal-mechanical digestion
  • U.S. Pat. No. 5,698,667 A discloses a pretreatment of a lignin containing cellulose containing material by extraction with an organic solvent (e.g. acetone) to remove wood extractives like volatile organic compounds (VOC) and higher-molecular pitch components without substantially impairing the integrity of the lignocellulose constituents of the material.
  • an organic solvent e.g. acetone
  • this hexanal content is reduced by at least 70% related to the potential of the basic raw material (as well as—in absolute contents) preferably down to below 0.5 mg/kg TM.
  • the wood particles are not substantially changed in their composition by the pretreatment, that is cellulose, hemicelluloses and lignin are not extracted and/or degraded to appreciable extent (in any case not by more than 10%, preferably by not more than 6%, in particular by not more than 4%), wherein this reduction is preferably ascertained as an extracted solid mass related to the basic material, the wood particles.
  • this reduction is preferably ascertained as an extracted solid mass related to the basic material, the wood particles.
  • Pitch stickies, resins and the like
  • Pitch are removed from the process and thereby cannot have a disturbing effect on the production process such that no or a reduced deposition on machine parts, rollers and covering parts and the like occurs.
  • the CSB loads of the wastewater of the process are also highly reduced, whereby greater production capacities are allowed with consistent CSB load in the wastewater.
  • the release of odor- and flavor-active aldehydes in products based on wood particles like cardboard or wood fiber boards by autooxidation of fatty acids naturally occurring in the wood can be achieved according to the present invention also completely without the addition of chelating agents.
  • a chelating agent like EDTA or DTPA in the production of products based on wood particles for reducing the olfactory and flavor load of these products becomes unnecessary, whereby the EDTA/DTPA load of the wastewater is eliminated, and thus the (ground) water-related environmental effects of the production of products based on wood particles are decreased as well as the EDTA/DTPA load of the products themselves is avoided.
  • extractives are also significantly reduced and thereby unloaded from the process, which decreases the extractive load of the process water in the production of the wood particles and thus entails lower requirements to the wastewater purification/processing.
  • the reduced extractive load of the process water also has the advantage that problems in the production process of products based on wood particles can be reduced and the quality of the products can be increased (e.g. avoiding pitch/sticky problems in the cardboard production). Therefore, this variant is a particularly environment-friendly embodiment of the present invention.
  • the specific method conditions (like size, shape and dry substance content of the wood particles, choice of the extracting agent, water content, temperature, treatment duration, pH, amount of extracting agent (in proportion to wood), pressure, number of the extraction stages, variants of contacting between extracting agent and solid, operating mode etc.) required in practice for a certain wood type or for certain wood materials for an extraction of at least 70% of the fatty acids and for establishing a maximum absolute value of hexanal below 2 mg/kg dry matter, preferably below 1 mg/kg dry matter, in particular below 0.5 mg/kg dry matter (respectively measured as a hexanal content in wt % of the extracted wood particles after accelerated aging for 72 h at 90° C.), respectively, can be immediately determined based on the teaching disclosed herein, in particular considering the results set forth in the example part, without further inventive assistance, in particular in view of the (usually known) amounts of organic materials (like fatty acids, resin acids, phenols, terpenes etc.) of the wood basic material, of
  • the present invention can be relatively easily integrated in existing production plants and be operated with existing plants, respectively.
  • extracting agent liquid phase of the extract according to the invention
  • solvent or solvent mixture in the extracting agent also has to be selected such that a significant loss of cellulose, hemicelluloses and lignin does not occur and the treatment duration nevertheless is not unduly long.
  • mixtures according to the invention of ethanol, acetone and water with 0-95 wt % of ethanol, preferably 50-90 wt % of ethanol and 0-99 wt % of acetone, preferably 30-90 wt % of acetone, as the organic-aqueous solvent in the extracting agent have proven to be particularly advantageous.
  • Further organic solvents, which can be used in the extracting agent instead of (or for certain purposes optionally also together with) ethanol or acetone with regard to an industrial scale are for example methanol, n-propanol and iso-propanol.
  • Preferred ratios of extracting agent to solid dry substance are 5:1-25:1 (w/w), preferably 8:1-17:1 (w/w), in the method according to the invention.
  • the ratios and concentrations in the extracting agent indicated herein With 100% of extracting agent, the total amount of extracting agent, which is present after the extraction, is always meant, namely the extracting agent, including the materials extracted from the wood particles and the water contained in the wood basic material (in the wood particles).
  • the amounts of wood basic material are usually indicated as “wood dry matter” herein and the substances extracted from the wood are usually below 1% of the total mass of the extracting agent, the ratios before the extraction substantially (just +/ ⁇ 1%) also correspond to the ratios after the extraction (the optionally present water portion in the wood basic material, which mostly exists in the economical exploitation, is accordingly always already attributed to the extracting agent herein).
  • At least 10% of water, preferably at least 7.5% of water, in particular at least 5% of water, are preferably contained in the organic-aqueous mixture of the solvent or solvents according to the invention, preferably in any event in a method with a single extraction step or (e.g. in a method with at least two extraction steps) in the first extraction step.
  • the extraction temperatures can also be determined based on the remaining wood and process parameters, in particular also considering the energy input, which higher temperatures require.
  • the treatment is effected at an extraction temperature of 20-150° C., preferably 40-120° C., in particular 50-110° C.
  • the method according to the invention is operated at normal pressure; in certain cases, an extraction under pressure can be advantageous (despite of the energetic overhead of the pressure application). Therefore, the treatment is effected according to a preferred embodiment at an absolute extraction pressure of 1-5 bar, preferably 1-1.49 bar, according to the invention.
  • the duration of the extraction method according to the invention one can determine based on the remaining process parameters, which duration is required for the depletion of fatty acids to be achieved.
  • the treatment according to the invention is effected during an extraction time of 10 min-8 h, preferably 30 min-7 h, in particular 1-5 h.
  • the present method is principally suitable for all products based on wood, in which organoleptic characteristics play a role.
  • the method according to the invention is particularly suitable for products, which are in use for longer time, are used for the packaging of food or in interior rooms. Therefore, the method according to the invention is particularly suitable for (large-scale) production of cardboard, paper, wood fiber boards, chipboards, objects of utility (for example (or in case of doubt) according to the definition of the Austrian food safety and consumer protection law (LMSV, BGB1. I No. 13/2006, in the version of 01.10.2020)), medical products (for example (or in case of doubt) according to the definition of the Austrian medical product law (MPG, BGB1. No. 657/1996, in the version of 01.10.2020)), in particular for producing cardboard.
  • LMSV Austrian food safety and consumer protection law
  • MPG BGB1. No. 657/1996, in the version of 01.10.2020
  • the content of dry substance of the employed wood particles is reduced by less than 10%, preferably less than 5%, in particular less than 4%, in the treatment according to the invention, wherein this reduction is preferably ascertained as an extracted solid mass related to the basic material, namely the wood particles.
  • the wood particles can preferably be selected from the industrially relevant wood types, thus e.g. from coniferous wood particles, 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.
  • the wood particles are mixed during the treatment with the extracting agent.
  • a preferred embodiment of the method according to the invention is in that the wood particles are squeezed after the treatment with the extracting agent to remove the extracting agent.
  • the wood particles can be cleaned once or multiple times with an extracting agent, even more preferably with an organic-aqueous solvent with a similar or identical concentration as that of the extracting agent after the (extraction) treatment with the extracting agent.
  • the extracting agent used in the extraction and/or washing can be removed from the wood particles by multiple times of washing with water and/or water steam stripping and/or drying, wherein water steam stripping and/or drying are particularly preferred. Both extracting agents and washing waters are preferably regenerated subsequent to the method according to the invention for reuse.
  • the extractives particularly fatty acids and resin acids, can be separated from the extracting agent, as mentioned, and be used as byproducts.
  • the method according to the invention it is possible to prepare wood particles such that the content of fatty acids in the wood particles is reduced such that the product to be produced of the wood raw materials does not have organoleptically disadvantageous characteristics.
  • 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 respectively after accelerated aging for 72 h at 90° C., by extraction of the wood particles with the extracting agent according to the invention.
  • the wood particles thus obtained preferably have a content of fatty acids in the wood particles below 2 mg/kg dry matter, preferably below 1 mg/kg dry matter, in particular 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.
  • the method according to the invention to increase the mechanical strength of the extracted wood particles, measured as the tensile index of sample sheets in Nm/g, by at least 10%, preferably by at least 15%, in particular by at least 25%, wherein the degree of grinding, measured in ° SR, therein changes by less than 10%.
  • fatty acids besides other VOCs
  • resin acids can also be extracted.
  • the fatty acids, resin acids and/or optionally further extractives extracted into the extracting agent are supplied to a further purification method and can then be provided as byproducts of the production in extracted and optionally further purified form.
  • this can be effected by mechanical separation technique after the thermal separation of the organic solvent from the organic-aqueous extracting agent to thus separate the precipitated lipophilic extractives (such as fatty acids and resin acids), and to obtain an aqueous phase enriched with the hydrophilic extractives (such as lignans), wherein the hydrophilic extractives can be still further concentrated by subsequent treatment with thermal separation technique (e.g. membrane separation methods and/or adsorption) (Lindemann et al., Selective recovery of polyphenols from MDF process waters by adsorption on a macroporous, cross-linked pyrrolidone-based resin (2019), Holzforschung volume 74 magazine 2).
  • thermal separation technique e.g. membrane separation methods and/or adsorption
  • the achieved extractive enrichments can be still additionally increased by preceding membrane filtration of the extracting agent (Shi et al., Separation of vegetable oil compounds and solvent recovery using commercial organic solvent nanofiltration membranes (2019), Journal of Membrane Science 588; Weinwurm et al., Lignin Concentration by Nanofiltration and Precipitation in a Lignocellulose Biorefinery (2015), Chemical Engineering Transactions 45, pp. 901-906).
  • the employment of the lipophilic extractive fraction obtained according to this method lends itself as animal feed supplement (WO 2015/071534 A1, U.S. Pat. No.
  • 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.
  • the method according to the invention represents an extremely advantageous and practice-oriented variant already for ecological reasons
  • FIG. 1 is the hexanal content at 70° C. extraction temperature.
  • the x-axis shows the extraction time in h; the y-axis shows the hexanal content of the extracted groundwood in mg/kg TM.
  • FIG. 2 is the hexanal content at 90° C. extraction temperature.
  • the x-axis shows the extraction time in h; the y-axis shows the hexanal content of the extracted groundwood in mg/kg TM.
  • FIG. 3 is the hexanal content at 110° C. extraction temperature.
  • the x-axis shows the extraction time in h; the y-axis shows the hexanal content of the extracted groundwood in mg/kg TM.
  • FIG. 4 is the hexanal content reduction at 70° C. extraction temperature.
  • the x-axis shows the extraction time in h; the y-axis shows the reduction of the hexanal content in % related to dry basic material.
  • FIG. 5 is the hexanal content reduction at 90° C. extraction temperature.
  • the x-axis shows the extraction time in h; the y-axis shows the reduction of the hexanal content in % related to dry basic material.
  • FIG. 6 is the hexanal content reduction at 110° C. extraction temperature.
  • the x-axis shows the extraction time in h; the y-axis shows the reduction of the hexanal content in % related to dry basic material.
  • the goal of the developed method in this patent is a significant improvement of the organoleptic characteristics of the wood particles as well as of aged wood particles, which are produced according to this method.
  • This autocatalytic oxidation is, as above mentioned, currently industrially prevented or greatly decelerated by the complexation of the metal ions present in the wood particles, which act as a catalyst, by means of addition of chelating agents like for example ethylenediaminetetraacetic acid (EDTA).
  • EDTA ethylenediaminetetraacetic acid
  • hexanal content of the wood particles after aging was used for assessing the extraction success of the experiments of this patent. It is to be noted at this point that 0.5 mg/kg TM of hexanal (related to dry wood) mark that empirically ascertained value, below which organoleptic impairments are empirically no longer sensorially perceivable. For hexanal contents of the wood particles >0.5 mg/kg TM, it applies: the higher the hexanal content, the higher the organoleptic impairment of the wood particles.
  • the determination of the hexanal content can be effected via headspace gas chromatography (HS-GC) in that ca. 0.2 g of air-dry wood particles (90-95 wt % TSG) are filled into a headspace vial. In these vials, the wood particles then have to be aged sealed at room temperature (ca. 20° C.) for six months to oxidize the fatty acids to hexanal. Since this takes very much time and therefore does not allow soon assessment of the extraction success, the accelerated aging according to DIN ISO 5630-2 was performed for the present experiments (unless explicitly otherwise indicated). The wood particles were sealed in HS-GC vials, aged for 72 h at 90° C.
  • HS-GC headspace gas chromatography
  • the hexanal content was used since it empirically represents the main influencing factor of the organoleptic impairment of wood particles.
  • the extractive content by means of Soxhlet extraction according to the TAPPI standard T204 is too inaccurate hereto, as table 2 shows.
  • the NREL method NREL/TP-510-42619 very similar to the T204 was applied and groundwood or 2 mm sized wood particles were employed as the basic material instead of wood dust.
  • the Soxhlet extractions with ethanol significantly differ from those with acetone in the hexanal content, but not significantly in the extractive content.
  • the hexanal content of the wood particles after aging is thus a substantially stronger and more accurate indicator for the organoleptic impairment than the extractive content, and therefore was used for the extraction success according to the present invention.
  • the hexanal content of the basic material and the reduction of the hexanal content resulting from it was indicated for all of the experiments, since the basic materials are snapshots and the hexanal content therefore can possibly very greatly fluctuate.
  • the extracted extractive mass (ascertained as evaporation residue of the extract) is an important indicator for the solid mass loss of the extractions since it nearly includes the entire extractively removed solid mass—except for some few very volatile compounds.
  • the evaporation residue of the extract together with the hexanal content of the extracted wood particles is an important measure of the assessment of the selectivity of the extractions.
  • FIGS. 1 to 3 show that the extraction success at 70 or 90 wt % of ethanol is considerably improved with respect to that at 50 wt %— in particular at lower temperatures.
  • Ethanol concentrations of 70 or 90 wt % of ethanol decrease the hexanal content to a comparable level.
  • 90 and 110° C. approximately identically decrease the hexanal content, while it is not as greatly reduced at 70° C.
  • the hexanal content can even be decreased below the 0.5 mg/kg TM mark from 90° C., whereby the groundwood extracted under these conditions empirically does no longer have organoleptic impairments.
  • Experiment 3 was performed to test three different technically relevant solvents under real extraction conditions.
  • Ca. 450 g TM of mechanically dehydrated groundwood (ca. 25 wt % TSG; ca. 95% spruce and 5% pine) were extracted in a solvent-water mixture with a solid: extracting agent ratio of 1:10 w/w and a solvent concentration of 70 wt % at a temperature of 70° C. for 4 h in an autoclave.
  • the groundwood was squeezed, washed with extracting agent, again squeezed and once again washed with demineralized water before it was dried, aged and analyzed.
  • Table 6 shows the results of these extractions.
  • acetone extracts the unsaturated fatty acids, which are responsible for the hexanal formation, significantly better than non-denatured ethanol.
  • the best extraction results could be achieved with ethanol, which was incompletely denatured with butanone.
  • the hexanal content of 2.77 mg/kg TM achieved herein with 70 wt %, 70° C. and 4 h extraction time is still considerably above the 0.5 mg/kg TM limit, but corresponds to a reduction of 80%.
  • the evaporation residue of the extract is only between 2.2 and 2.4 wt % related to the basic material dry matter, which means with an ascertained extractive portion of 3.6 wt % that the wood main constituents cellulose, hemicelluloses and lignin de facto were not attacked and the extractions were thus very selective.
  • the abietinic acid content of the extractions of this experiment was reduced by 41-55% related to the basic material. Since abietinic acid was here selected as a lead substance for the content of resin acids, a reduction of the content by around 50% is an indication of the considerable reduction of resin by the method of this patent.
  • the hexanal content is reduced by over 80% in all extractions already after the first stage, however, is still considerably over 0.50 mg/kg TM in particular with a basic material with higher hexanal contents.
  • stage three the hexanal content is below 0.50 mg/kg TM, partially even below the determination limit of 0.20 mg/kg TM, with all extracted groundwoods of this experiment.
  • the evaporation residue of the extract is less than 3-5%, which is an evidence for the quantitative preservation of the lignocellulose constituents in this method with ascertained extractive contents of the basic material of 2.5-3.7 wt %.
  • This experiment too has shown that the method of this patent can significantly reduce resin, in particular with increasing extraction stage number, by the reduction of the abietinic acid content by 55-100% related to the basic material.
  • Ca. 650 g TM of woodchips (ca. 20 mm; ca. 55 wt % TSG; spruce), ca. 450 g TM of chopped woodchips (2 mm mesh of the cutting mill screen; ca. 60 wt % TSG; spruce) and ca. 400 g TM of mechanically dehydrated groundwood (ca. 25 wt % TSG; ca. 95% spruce and 5% fir) were extracted respectively in two stages (each one hour) at 50° C. as well as respectively in two stages (each 30 min) at 21° C. in an autoclave.
  • the multi-stage extractions were performed analogously to experiment 5 by squeezing the wood particles after each extraction stage and mixing with fresh unloaded extracting agent.
  • the extraction parameters were 50° C., extraction durations of each 1 h per extraction stage and acetone concentrations of 70 wt % in the extracting agent (extraction parameter 1) as well as 21° C., extraction durations of each 30 min per extraction stage and pure acetone as admixed extracting agent, which results in acetone concentrations of 70-99 wt % according to extraction stage and particle size (extraction parameter 2).
  • the solid: extracting agent ratios were selected such that the wood particles were just covered with extracting agent (1:6 with woodchips and ground woodchips and 1:10 with groundwood). After the extraction, the wood particles were squeezed (and washed with extracting agent with extraction parameter 1) and again squeezed before they were dried, aged and analyzed. The results of these results are listed in table 9.
  • the hexanal content of woodchips can only be decreased by ca. 20-30% with the method according to the invention.
  • the hexanal content can be decreased to ca. 1 mg/kg TM, which corresponds to a reduction of ca. 95% with the starting hexanal content of 21.36 mg/kg TM, with the method according to the invention.
  • the reduction of the hexanal content with ca. 97% is even higher.
  • the two extraction parameters provide comparable hexanal contents with larger particle size, whereas with smaller particle size, in particular groundwood, the extraction parameters 1 (higher temperature and longer extraction time) provide significantly better results.
  • the extraction parameters provide better results with all particle sizes.
  • table 9 it is additionally apparent that the reduction of the extract evaporation residue related to the extract evaporation residue of the basic material Soxhlet extraction cannot be used as an indicator for the extraction success of the intended method since for example with woodchips, even with high reduction of 73%, the hexanal content was only decreased by ca. 20, whereas with groundwood with a reduction of the extract evaporation residue related to the extract evaporation residue of the basic material Soxhlet extraction by 75%, the hexanal content could be decreased by ca. 96%.
  • the degree of grinding and thus the dehydration of the groundwood hardly alters by the extraction, which entails the advantage with regard to a possible further processing (for example to cardboard) that existing production plants do not have to be retrofitted or converted.
  • the stiffness index also only little alters by the extraction, whereas the tensile index as a measure of the breaking strength reproducibly highly increases.
  • the mass loss by the evaporation residue of the extract is very low with around 2%. This means that the wood particles over-proportionally highly gain strength by the extraction with low mass loss, which is in particular of great importance for the lightweighting trend in the packaging sector.
  • the acetone was separated by distillation in that the distillation flask was heated up to 108° C. and distilled under atmospheric pressure up to the equilibrium setting. The remaining residue was centrifugated with 7197 g for 10 min and the sediment was subsequently separated from the supernatant. The supernatant was weighed and the dry substance content thereof was ascertained by gently drying at room temperature, which substantially corresponds to the content of extracted extractives. The sediment was also weighed and dissolved in defined mass of pure acetone. Analogously to the supernatant, the dry substance content thereof was determined. The deposits already precipitated in the distillation were also dissolved in pure acetone. Thereof, the dry substance content was determined analogously to the sediment.
  • the predominant extractive mass arises as a centrifugated sediment.
  • the dry substance content (which here substantially corresponds to the extractive mass) in the supernatant is only at a similarly low level as in the extract ( ⁇ 1 wt %).
  • the portion of free fatty acids and resin acids could be decreased to a very low level in the supernatant, whereas the lignans were enriched.
  • extractives analyzed here (free fatty acids, resin acids and lignans) only represent a part of the extractives (and dry substance found here), thus, it is uniquely apparent that with the selected thermal and mechanical separating method (distillation and centrifugation), not only the liquid phase (extract and supernatant, respectively) can be most widely freed from fatty and resin acids, but also lipophilic extractives (e.g. fatty acids and resin acids) and hydrophilic extractives (e.g. lignans) can respectively be significantly concentrated and purified as byproducts.
  • lipophilic extractives e.g. fatty acids and resin acids
  • hydrophilic extractives e.g. lignans
  • a method for producing products based on wood as a raw material characterized in that wood in the form of wood particles is subjected to an extraction treatment with an extracting agent, which includes 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, but the content of cellulose, hemicelluloses and lignin is substantially maintained in this extraction treatment.
  • an extracting agent which includes one or more organic solvents in an organic-aqueous mixture of the solvent or solvents with water
  • 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.
  • NREL National Renewable Energy Laboratory
  • LAP Laboratory Analytical Procedure
  • wood particles are wood fibers with average fiber lengths between 0.5 and 2 mm and average fiber diameters between 10 and 50 ⁇ m, wherein the average fiber length as well as the average fiber diameter relate to the length average determined by means of optical measurement of the suspended fibers.
  • the solvent portion of the organic-aqueous solvent mixture in the extracting agent 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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,
  • a method for producing products based on wood as a raw material characterized in that wood in the form of wood particles is subjected to an extraction treatment with an extracting agent, which includes one or more organic solvents or 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, but the content of cellulose, hemicelluloses and lignin is substantially maintained in this extraction treatment.
  • an extracting agent which includes one or more organic solvents or an organic-aqueous mixture of the solvent or solvents with water
  • wood particles are present in the form of fibers, chips, strands, woodchips or mixtures thereof.
  • wood particles are wood fibers with average fiber lengths between 0.5 and 2 mm and average fiber diameters between 10 and 50 ⁇ m, wherein the average fiber length as well as the average fiber diameter relate to the length average determined by means of optical measurement of the suspended fibers.
  • the solvent portion of the organic-aqueous solvent mixture in the extracting agent 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.
  • 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.
  • 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.
  • 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.
  • 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,

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  • Wood Science & Technology (AREA)
  • Mechanical Engineering (AREA)
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  • Paper (AREA)
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JP2667058B2 (ja) * 1992-04-06 1997-10-22 エイ．アフルストロム コーポレーション パルプの製造方法
US5698667A (en) 1995-12-27 1997-12-16 Weyerhaeuser Company Pretreatment of wood particulates for removal of wood extractives
DE19856582C1 (de) * 1998-12-08 2001-03-15 Rhodia Acetow Ag Verfahren zur Gewinnung von Chemiezellstoff aus Hackschnitzeln
DE19916347C1 (de) * 1999-04-12 2000-11-09 Rhodia Acetow Ag Verfahren zum Auftrennen lignocellulosehaltiger Biomasse
EP1793972A1 (de) * 2004-09-21 2007-06-13 Institut für Holztechnologie Dresden gGmbH Holz oder holzwerkstoff, verfahren zu deren herstellung
DE102004050278A1 (de) 2004-10-14 2006-04-27 Basf Ag Helle bis weiße Holzwerkstoffplatten
DE502005010889D1 (de) 2004-10-15 2011-03-03 Fraunhofer Ges Forschung Verfahren zur verminderung der abgabe von flüchtigzzerkleinerungsprodukten und aus daraus hergestellten holzwerkstoffen, insbesondere holzspanplatten
DE102006020612B4 (de) 2006-05-02 2019-03-14 SWISS KRONO Tec AG Verfahren zur Herstellung von Holzwerkstoffen mit verringerter Emission an flüchtigen organischen Verbindungen, damit erhältliche Holzwerkstoffe sowie die Verwendung bestimmter Additive zur Verminderung der Freisetzung von flüchtigen organischen Verbindungen aus Holzwerkstoffen und Holzzerkleinerungsprodukten von Lignocellulosen
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EP2356977B1 (de) * 2011-02-02 2017-12-27 Symrise AG Zubereitungen mit Holzextrakten von Gleditschien
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FI124918B (fi) * 2013-05-14 2015-03-31 Hankkija Maatalous Oy Mäntyöljyrasvahappo
DE102014114921A1 (de) * 2013-10-14 2015-04-16 Hochschule für Nachhaltige Entwicklung Eberswalde Verfahren zur Herstellung eines emissionsreduzierten Massivholzproduktes oder eines emissionsreduzierten, holzhaltigen Ausgangsstoffes sowie emissionsreduzierte Massivholzprodukte oder emissionsreduzierte, holzhaltige Ausgangsstoffe
CN105764521A (zh) 2013-11-13 2016-07-13 汉克奇亚公司 包含基于树脂酸组合物的饲料补充剂和饲料组合物
NL2020102B1 (en) * 2017-12-15 2019-06-25 Miscancell B V Multi-step process for the isolation of components from Miscanthus
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