WO2022144377A1

WO2022144377A1 - Method for producing products based on wood as a raw materal

Info

Publication number: WO2022144377A1
Application number: PCT/EP2021/087767
Authority: WO
Inventors: Anton Friedl; Maximilian LEHR; Martin MILTNER; Walter WUKOVITS
Original assignee: Mm Board & Paper Gmbh
Priority date: 2020-12-29
Filing date: 2021-12-29
Publication date: 2022-07-07
Also published as: EP4271880A1; EP4023812A1; WO2022144176A1; EP4271879A1; JP2024501377A; CA3203411A1; US20240076831A1; CN116897233A

Abstract

The invention relates to a method for producing products based on wood as a raw material, characterised in that wood, in the form of wood particles, is subjected to extraction treatment using an extracting agent which 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 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, but the content of cellulose, hemicelluloses and lignin is largely maintained during this extraction treatment.

Description

Process for the manufacture of products based on wood as a raw material

The invention relates to methods for the manufacture of wood-based products, in particular methods for the pretreatment of wood.

Wood as a raw material for industrial processing into wood-based products (such as wood fiber boards or cardboard) contains - in addition to the main components cellulose, hemicelluloses and lignin - many different low and high molecular weight substances such as fatty acids, resin acids, phenols and terpenes. These substances are summarized as so-called extractive substances (or extractives) because 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) . Many of these extractive substances are "organoleptically relevant substances" since they can lead to odor and taste interactions and impairments in wood particle-based products with the environment relevant to the respective end use (e.g. food in the case of packaging cardboard or room air in the case of wood fiber boards). In addition to extractives, which, as volatile hydrocarbons, naturally have characteristic odors (e.g. terpenes), aldehydes (especially hexanal) are primarily responsible for this, which are formed by autocatalytic oxidation of fatty acids naturally occurring in wood (Schreiner et al., Resolving the smell of wood-identification of odor-active compounds in Scots pine (Pinus sylvestris L.) (2018) , Scientific Reports 8:8294).

Furthermore, wood particles contain resins that can coagulate into sticky particles during processing of the wood particles, which is intensified by the fats and waxes that also occur naturally in the wood. These resinous particles, also referred to as "pitch" or "stickles", also cause disruptive effects on the paper/cardboard surface, which can subsequently cause problems in the further processing of the paper/cardboard (e.g. printing). These substances can also have a disruptive effect on the production process by causing deposits on machine parts, rollers and clothing parts, etc. (Sixta et al., Chemical Pulping Processes; in: Sixta (ed) Handbook of Pulp (2006), Weinheim: Wiley-VCH Verlag GmbH & Co. KGaA, p 109-509; Björklund Jansson et al., Wood Extractives; in: Ek et al. (eds) Wood Chemistry and Wood Biotechnology, 1 (2009), Walter de Gruyter GmbH & Co. KG, , Berlin, pp 147-171).

At present, fatty acids are not removed from wood particles for wood particle-based products such as cardboard or fiberboard. Instead, the auto-oxidation of these fatty acids is inhibited or delayed by binding the heavy metal ions, which act as catalysts, in the wood particle products by adding complexing agents such as ethylenediaminetetraacetic acid (EDTA) or diethylenetriaminepentaacetic acid (DTPA). However, EDTA and its metal complexes are only poorly and slowly degradable in waste water treatment and are therefore considered ecologically questionable today, which entails increasing problems, especially for waste water from production plants for wood particle-based products.

Other processes that have been described to improve the organoleptic properties are 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) chemicals are used.

DE 10 2014 114 921 A1 relates to a method for producing a "reduced-emission" solid wood product or a "reduced-emission" wood-containing starting material, which is treated with a "buffer solution" with a pH of >6 in order to reduce the emission (essentially of VOCs) to "reduce", however cellulose, hemicellulose and lignin are apparently not substantially preserved and it is not disclosed to what extent the content of fatty acids can be reduced with this method. According to WO 2006/032267 A1, solid wood or wood particles are treated in such a way that the fatty acid esters contained therein are "inhibited, split or oxidized", but not extracted. WO 93/20279 A1 discloses the treatment of cellulose pulp (i.e. no wood particles) with organic solvents which are to be separated again following 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, with hemicellulose and lignin being separated. EP 2 138 528 A1 relates to a method for producing a cellulose material with a reduced content of wood extract . DE 10 2013 001 678 A1 discloses a method for treating wood with an oxidizing agent. EP 2 356 977 A1 relates to the use of Gliditsche wood extracts for the treatment of cellulite.

It is therefore an object of the present invention to reduce the content of releasable odor- and taste-active aldehydes in wood particle-based products such as cardboard or wood fiber boards by autoxidation of fatty acids naturally occurring in the wood. This should be done without the use or addition of complexing agents.

Another object of the present invention is a significant improvement in the organoleptic properties of the wood particles and aged wood particles that are produced by this method, so that the products produced with it have little or no odor even without the use of z or the addition of have bleaching, delignifying, oxidizing or reducing chemicals. In particular, with the method according to the invention, after aging of the wood particles (up to 6 months), an undesirable odor and taste changes occurring in the course of this aging in the foodstuffs coming into contact with them are to be prevented.

Finally, a preferred object of the present invention is to remove other ingredients from wood particles that are undesirable in the planned product, for example resin acids.

Accordingly, the present invention relates to a process for the manufacture of 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 extraction agent which contains one or more organic solvents in an organic-aqueous Mixture of the solvent or solvents with water, the content of fatty acids in the wood particles being reduced by at least 70% by the extraction treatment of the wood particles with the extractant, measured as the hexanal content in weight. -% after accelerated aging for 72 h at 90 °C, but the content of cellulose, hemicelluloses and lignin is essentially preserved in this extraction treatment.

As has been shown in the course of the present invention, the inventive extraction of the organoleptically questionable substances from the raw materials can result in a significant improvement in the organoleptic properties of the wood particles can be achieved without the addition of complexing agents, but by removing potential aldehyde sources, especially fatty acids. However , it is known that fatty acids as a source of aldehydes and subsequently as a source of organoleptic impairment of the wood particles can only be quantified satisfactorily with great effort . According to the invention, the hexanal content of the wood particles after aging was therefore used to assess the success of the extraction. This has proven to be a reliable parameter for the organoleptic properties of the products to be made from the raw material, such as paper, cardboard, fibreboard, etc. , which correlates excellently with the (very time-consuming) traditional aging tests (see the investigations and proofs in the example section below).

It was found that with the method according to the invention, a large part of the fatty acids and other disruptive substances (resin acids, etc.) can be extracted without the substance of the wood material (cellulose, hemicelluloses and lignin) being significantly impaired. While any improvement in the removal of fatty acids from the wood raw material will bring benefits, a substantial reduction of at least 70% for suitable large scale commercial use is readily achievable with the present process. However, the treatment according to the invention is preferably selected such that the desired reduction is achieved in any case, and a reduction of at least 70%, preferably at least 90%, in particular at least 95%, is achieved. Accordingly, the conditions to be applied according to the invention can then e.g. B. be chosen based on the nature of the wood or the extractant s so that the hexanal reduction according to the invention results in any case. In this way, it is also possible to set preferred maximum values in absolute hexanal contents. Although wood particles with a hexanal content of 2 mg/kg dry matter (DM) can also be used for certain applications, absolute values below 1 mg/kgDM are preferred. In the case of the particularly strict guidelines that were applied in the course of the examples of the present invention, a hexanal content of 0.5 mg/kgTM hexanal (based on dry wood) was marked as an empirically determined value below which experience has shown that there are no sensory organoleptic impairments are more noticeable. Accordingly, a preferred embodiment of the method according to the invention relates to extraction of the wood particles to a hexanal content of 0.5 mg/kg DM or below. For hexanal contents of the wood particles > 0.5 mg/kgTM it could be determined that the risk of an organoleptic impairment of the wood particles increased with increasing hexanal content.

For the purposes of the present invention, the hexanal content can be determined in case of doubt using headspace gas chromatography (HS-GC) by measuring approx. 0.2 g of air-dried wood particles (90-95 wt% (= wt. -%) Dry matter content (TSG) ) are filled into a headspace vial. In these vials, the sealed wood particles must then be aged for six months at room temperature (approx. 20 °C) in order to oxidize the fatty acids to hexanal. Since this takes a lot of time and therefore does not allow a timely assessment of the extraction success, the hexanal content is determined according to the present invention via accelerated aging according to DIN ISO 5630-2. This was used to determine the hexanal content in the experiments in the example section (unless explicitly stated otherwise); this method is also relevant in case of doubt for determining the hexanal content for the purposes of the present invention. The wood particles are sealed in HS-GC vials, aged for 72 h at 90 °C and then the hexanal content is determined using HS-GC.

The wood particles are preferably less than 2 mm in size, preferably in the form of fibers, chips or mixtures thereof. This particle characteristic (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". The particle characteristic of the particle size is therefore formulated on the sieve mesh size (2 mm) of the cutting mill for sample preparation.

The wood particles are preferably in the form of fibers, chips or mixtures thereof. This limitation of the particle size to 2 mm, as also specified in the NREL method NREL/TP-510-42620, brings with it the great advantage that, in addition to the relatively easily accessible resin channels, the comparatively difficult to accessible parenchyma cells, where the fatty acids are located, can be easily reached by extraction (Lehr et al., Removal of wood extractives as pulp (pre-) treatment: a technological review (2021), SN Applied Sciences 3:886).

According to a preferred embodiment, the wood particles are broken down into fibrous wood, in particular wood fibers with mean fiber lengths between 0.5 and 2 mm and mean fiber diameters between 10 and 50 μm, by mechanical and/or thermal and/or chemical digestion. Average fiber length and average fiber diameter relate to the average length, determined by optical measurement of the suspended fibers. This optical measurement usually leads to uniform results (regardless of the chosen methodology and analysis device), but the devices PulpEye (http://www.pulpeye.com/products/pulpeye/) and in particular MorFi Fiber have proven to be particularly suitable Analyzer (http://www.techpap.com/fiber-and-shive-analyzer-morf i-neo, lab-device, 31.html), proven.

The amount of organic compounds that can be extracted using the method according to the invention varies depending on the type of wood and part of the tree from which the wood particles are obtained (heartwood/sapwood). For example, pine heartwood contains up to 9% by weight of extractable material, whereas fir sapwood usually only has up to 1% extractable material (Björklund Jansson et al., Wood Extractives; in: Ek et al. (eds) Wood Chemistry and Wood Biotechnology, 1 (2009) , Walter de Gruyter GmbH & Co. KG, , Berlin, pp 147-171 Nisula Wood Extractives in Conifers: A Study of Stemwood and Knots of Industrially Important Species (2018) , Abo Akademi University Press, Abo ) . In particular, types of wood such as pine, birch, linden or poplar contain higher amounts of fatty acid esters (birch 2315 mg/kg, lime 7544 mg/kg or pine 5807 mg/kg of fatty acids; DE 10 2009 046 127 A1), which are caused by the manufacture of products can be broken down from these woods into aldehydes and organic acids without this being able to be prevented by changing technological parameters. In addition, there are larger fluctuations in the content of fatty acids and triglycerides depending on the location, tree age, height section of the individual tree and between heartwood and sapwood.

DE 10 2009 046 127 A1 describes a method for producing wood fiber materials in which volatile Organic compounds ("VOC"), aliphatic and aromatic aldehydes, in particular hexanal and furfural, are reduced, whereby wood is treated with at least one compound for setting a neutral to basic pH value (such as NaOH) and at least one complexing agent (such as EDTA or DTPA) It is emphasized that no bleaching, delignifying, oxidizing or reducing chemicals are used for such a production and that no liquid formulation is pressed out before the wood or wood chips are plasticized such as EDTA and DTPA, as mentioned above, a serious waste water and environmental problem.The present invention thus brings decisive advantages over a mere, known chemical-thermo-mechanical digestion (CTMP), wherein wood chips with sodium sulfite and EDTA are mixed, both in terms of Environmental aspects as well as with regard to the effect according to the invention in the ef fi cient depletion of fatty acids from the raw material.

US Pat. No. 5,698,667 A discloses a pretreatment of a lignocellulosic material by extraction with an organic solvent (e.g. acetone) in order to remove wood extractives, such as volatile organic compounds (VOC) and higher-molecular pitch components. without significantly affecting the integrity of the lignocellulosic components of the material. However, no industrially usable depletion of the undesirable ingredients could be achieved (the maximum depletion of pitch and VOCs was 54, 4 and 65% (after two extractions for acetone in water (80/20) and 100% acetone) or maximum 78.2% for pure acetone, although the methodology used there cannot ensure that volatile components pass into the gas phase when the solvent is removed from the extract and that the depletion when determined by the evaporation residue of the extract is to be set even lower.

In contrast, in the method according to the invention mith fe an extractive pretreatment of wood particles (such as wood z fibers) with organic solvents in an organic-aqueous mixture of the solvent or solvents with water, a large part of the fatty acids naturally occurring in the wood is already before further processing (e.g. to cardboard or wood fiber boards) removed. In addition, this pre-treatment greatly reduces other extractives such as resin acids, phenols and terpenes in the wood. According to the invention, the hexanal content has proven itself as an indicator for the auto-oxidation of naturally occurring fatty acids in the wood, especially when it is determined after accelerated aging of the wood particles (72 h at 90° C.). According to the invention, this hexanal content is reduced by at least 70%, based on the potential of the starting raw material (and--in absolute contents), preferably down to below 0.5 mg/kg DM. As a result, odor and taste interactions of wood particle-based products with the environment relevant to the respective end use (for example food in the case of packaging board or room air in the case of wood fiber boards) can be greatly reduced with the present invention. At the same time, the pre-treatment does not significantly change the composition of the wood particles, i.e. cellulose, hemicelluloses and lignin are not significantly reduced (at least by no more than 10%, preferably by no more than 6%, in particular by no more than 4 % reduced ) extracted and / or broken down , this reduction preferably being determined as the extracted solid mass , based on the starting material , the wood particles . In addition to reducing the proportion of organoleptically relevant components in the wood particles, the present invention results in further important product and process advantages, particularly for paper and cardboard production:

Pitch (stickles, resins, etc.) are removed from the process and can therefore not have a disruptive effect on the production process, so that there are no or reduced deposits on machine parts, rollers and clothing parts, etc. comes .

As a result, with the present invention, disruptive effects on the paper/cardboard surface can also be reduced, as a result of which problems in the further processing of the paper/cardboard (e.g. printing) are also significantly reduced. Due to the significantly lower proportion of these components on the surface and also inside the paper/cardboard, there is also increased product quality and an increase in mechanical strength.

Due to the improved product properties mentioned Products that are made from the wood particles extracted according to the invention can also open up new areas of application that can currently only be covered with paper/cardboard whose fiber components come from cellulose and/or treated BCTMP (bleached chemi-thermo-mechanical pulp) ( e.g. high-quality packaging boxes ) or for particularly delicate applications that can now only be served with cellulose.

In addition, the extractive pre-treatment according to the present invention also greatly reduces the COD loads of the waste water from the process, as a result of which larger production capacities are made possible with the same COD load in the waste water.

According to the present invention, the release of odor- and taste-active aldehydes in wood particle-based products such as cardboard or wood fiber boards by auto-oxidation of fatty acids naturally occurring in the wood can also be achieved entirely without the addition of complexing agents. The addition of a complexing agent such as EDTA or DTPA in the manufacture of wood particle-based products to reduce the odor and taste load of these products thus becomes superfluous, eliminating the EDTA/DTPA load in the effluent and thus the (reasonably) water-related environmental impact of production Wood particle-based products are reduced, and the EDTA/DTPA contamination of the products themselves is avoided. Furthermore, in addition to fatty acids, other extractives are also significantly reduced and thus removed from the process, which reduces the extractive loading of the process water in the production of the wood particles and thus results in lower demands on the waste water cleaning/treatment. The reduced extractive load in the process water also has the advantage that problems in the manufacturing process of wood particle-based products can be reduced and the quality of the products can be increased (e.g. avoidance of pitch/stickies problems in cardboard production). This variant is therefore a particularly environmentally friendly embodiment of the present invention.

The tender or in practice for a specific Hol. for certain heating materials for an extraction of at least 70 % of the fatty acids or . to establish a maximum absolute value of hexanal of less than 2 mg/kg dry matter, preferably less than 1 mg/kg dry matter, in particular less than 0.5 mg/kg dry matter (measured in each case as hexanal content in % by weight) the extracted Wood particles after accelerated aging for 72 h at 90°C), required specific process conditions (such as size, shape and dry matter content of the wood particles, choice of extractant, water content, temperature, treatment time, pH, amount of extractant (in relation to the wood), pressure, Number of extraction stages, variants of contacting between extractant and solid, mode of operation, etc.) can be determined directly and without further inventive step on the basis of the teaching disclosed herein, in particular taking into account the results presented in the example section, especially in view of the (usually known) amounts of organic substances (such as fatty acids, resin acids, phenols, terpenes, etc.) of the wood raw material, the nature of the wood (heartwood, sapwood, mixtures, etc.) and the requirements for the final product (cardboard, paper, fiberboard, application in certain areas (food, pharmaceuticals, animal feed, etc.) .

In particular, the present invention can be integrated relatively easily into existing production plants or operated with existing plants.

One or more of the objects set out above can be achieved according to the invention by a method having the features of patent claim 1 . Advantageous configurations with expedient developments of the invention are specified in the respective dependent claims.

The choice of the liquid phase of the extract according to the invention (referred to here as the extractant) also depends on the relevant type of wood (and its natural content of extractives). However, the solvent or solvent mixture in the extraction agent must also be chosen in such a way that there is no significant loss of cellulose, hemicelluloses and lignin and the treatment time is not excessively long. Mixtures of ethanol, acetone and water according to the invention with 0-95% by weight ethanol, preferably 50-90% by weight ethanol, and 0-99% by weight acetone, preferably 30-90% by weight -% acetone, exposed as organic-aqueous solvents in the extractant. Other organic solvents that can be used instead of (or for certain purposes also together with) ethanol or acetone with regard to an industrial scale in the extractant are, for example, methanol, n-propanol and iso- propanol .

In the process according to the invention, preferred ratios of extractant to solid/dry substance are 5:1-25:1 (w/w), preferably 8:1-17:1 (w/w).

The following considerations apply to the ratios and concentrations in the extractant given herein: 100% extractant always means the total amount of extractant present after extraction, namely the extractant, including the materials extracted from the wood particles and that in the wood raw material (in the wood particles) contained water. However, since the amounts of wood raw material are usually given here as "wood dry matter" and the substances extracted from the wood are usually less than 1% of the total mass of the extractant, the ratios before extraction essentially correspond (just + /- 1%) also the conditions after the extraction (the possibly existing water content in the wood starting material, which is usually given in the economic utilization, is accordingly always already included in the extraction agent). This results in the use of 100 wt. -% acetone concentration of the extractant at 1:10 (solid matter: extractant) thus 1 kg dry wood mass and 10 kg acetone. 70% by weight acetone concentration of the extractant at 1:10 (solid matter: extractant) would then be e.g. 1 kg wood dry mass, 7 kg acetone and 3 kg water The extracted material would, as mentioned, still be added, but experience has shown that it is around the concentration concentrations well below 1% by weight in the extractant and is therefore negligible. Due to the water content in the starting material, the organic-aqueous mixture of the solvent(s) preferably contains at least 10% water, preferably at least 7.5% water, in particular at least 5% water, preferably at least in a process 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 other wood and process parameters, in particular taking into account the energy consumption that higher temperatures require. According to the invention, the treatment preferably takes place at an extraction temperature of 20-150.degree. C., preferably 40-120.degree. C., in particular 50-110.degree. According to a preferred embodiment, the process according to the invention is operated at atmospheric pressure; in certain cases, extraction under pressure can be advantageous (despite the additional energy expenditure of the pressure application). Therefore, according to a preferred embodiment, the treatment according to the invention takes place at an absolute extraction pressure of 1-5 bar, preferably 1-1.49 bar.

The duration of the extraction process according to the invention can also be determined on the basis of the other process parameters, which duration is necessary for the depletion of fatty acids to be achieved. The treatment according to the invention preferably takes place during an extraction time of 10 minutes to 8 hours, preferably 30 minutes to 7 hours, in particular 1 to 5 hours.

In principle, the present method is suitable for all wood-based products in which organoleptic properties play a role. The method according to the invention is particularly suitable for products that are in use for a long time, for packaging foodstuffs or are used indoors. The method according to the invention is therefore particularly suitable for the (large-scale) production of cardboard, paper, wood fiber boards, chipboard, commodities (for example (or in case of doubt) according to the definition of the Austrian Food Safety and Consumer Protection Act (LMSV, BGBl. I No. 13/ 2006, idFv 01.10.2020) ), medical products (for example (or in case of doubt) according to the definition of the Austrian Medical Devices Act (MPG, Federal Law Gazette No. 657/1996, idFv 01.10.2020) ), in particular for the production of cardboard.

Particularly advantageous process parameters for the extraction treatment according to the present invention are selected from:

treatment with ethanol in a concentration of at least 65% by weight at at least 65°C for a period of at least 3 hours;

treatment with ethanol in a concentration of at least 65% by weight at at least 85°C for a period of at least 30 minutes;

treatment with ethanol in a concentration of at least 70% by weight at at least 105°C for a period of at least 30 minutes;

Treatment with ethanol in a concentration of at least 45% by weight at at least 105°C for a period of at least 5 H;

treatment with acetone in a concentration of at least 50% by weight at at least 40°C for a period of at least 30 minutes; or

Treatment with acetone in a concentration of at least 50% by weight at at least 20°C for a period of at least 15 minutes.

In the context of the present invention, it has been found that batch as well as continuous and semi-continuous extractions are possible and can even have an advantageous effect on the extraction result, particularly if the partial residence time per extraction step is a maximum of 1 hour.

When determining the process parameters, it is also essential that conditions are selected in which there are no significant losses of the wood substance (i.e. the content of cellulose, hemicelluloses and lignin). It can therefore also be provided that during the treatment according to the invention the dry substance content of the wood particles used is reduced by less than 10%, preferably by less than 5%, in particular by less than 4%, this reduction preferably being related to the extracted solid mass on the starting material, namely the wood particles, is determined.

As mentioned above, different types of wood vary in their VOC content. The specific process parameters according to the invention are also to be adjusted accordingly. However, since this is made possible with the disclosure of the invention contained herein for all industrially relevant types of wood, the wood particles can preferably be selected from the industrially relevant types of wood, e.g. 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.

According to a preferred embodiment, the wood particles are mixed with the extractant during the treatment.

As already mentioned above, a preferred embodiment of the method according to the invention is that the wood particles are pressed after treatment with the extractant in order to remove the extractant. Preferably, after the (extraction) treatment with the extractant, the wood particles can be treated once or several times with an extractant more preferably cleaned with an organic-aqueous solvent having a similar or the same concentration as that of the extraction agent. The extractant used in the extraction and/or washing can be removed from the wood particles by repeated washing with water and/or steam stripping and/or drying, with steam stripping and/or drying being particularly preferred. Both the extraction agent and the washing water are preferably regenerated for reuse after the process according to the invention. As mentioned, the extractives, especially fatty acids and resin acids, can be separated from the extractant and used as by-products.

With the method according to the invention it is possible to prepare wood particles in such a way that the content of fatty acids in the wood particles is reduced in such a way that the product to be produced from the wood raw materials does not have any organoleptically disadvantageous properties. According to the invention, the content of fatty acids in the wood particles is preferably 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 starting material compared to the extracted wood particles each after accelerated aging for 72 h at 90 °C.

The wood particles obtained in this way preferably have a fatty acid content in the wood particles of less than 2 mg/kg dry matter, preferably less than 1 mg/kg dry matter, in particular less than 0.5 mg/kg dry matter, measured as hexanal Content as mass fraction of extracted wood particles after accelerated aging for 72 h at 90 °C.

In addition to reducing the hexanal content, it is also possible with the method according to the invention to reduce the mechanical strength of the extracted wood particles, measured as Tensile Index of sample sheets in Nm/g, by at least 10%, preferably by at least 15%, in particular by at least 25 %, whereby the freeness, measured in ° SR, changes by less than 10%.

It has been shown according to the invention that, in addition to the extraction of fatty acids, resin acids (along with other VOCs) can also be extracted using the method according to the invention. As part of In a preferred embodiment, the fatty acids, resin acids and/or other extractives extracted into the extractant are subjected to a further purification process and can then be made available as by-products of the production in extracted and optionally further purified form. This can be done in particular by mechanical separation technology after the thermal separation of the organic solvent from the organic-aqueous extraction agent in order to separate the precipitated lipophilic extractives (such as fatty acids and resin acids) and an aqueous phase enriched with hydrophilic extractives (such as lignans). win, whereby the hydrophilic extractive substances can be further concentrated by subsequent treatment with thermal separation technology (e.g. membrane separation process 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) , Wood Research Volume 74 Issue 2) . The concentration of extractives achieved can be further increased by prior membrane filtration of the extraction 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 use of the lipophilic extractive fraction obtained by this method is suitable as a feed supplement (WO 2015/071534 A1, US Pat has already been shown in various studies, especially for poultry (Kettunen et al., Natural resin acid-enriched composition as a modulator of intestinal microbiota and performance enhancer in broiler chicken (2015), Journal of Applied Animal Nutrition Vol.3; Kettunen et al., nen et al., Dietary resin acid composition as a performance enhancer for broiler chickens (2017), Journal of Applied Animal Nutrition Vol 5, pp 349-355, Vienola et al., Tall oil fatty acid inclusion in the diet improves performance and increases ileal density of lactobacilli in broiler chickens (2018) British Poultry Science Vol. 59 No. 3) . According to a preferred embodiment no complexing agents are applied to the wood particles, in particular complexing agents selected from polybasic and polyfunctional carboxylic acids, aminomethylcarboxylic acids, aminomethylphosphonic acids and their compounds, EDTA, DTPA EGTA, EDDS and their salts, polyphenols, tannins, amino acids, peptides, proteins, polycarboxylates, phosphates, Polyphosphates, phosphonic acids, polyphosphonates, phosphated, phosphonylated, sulfated and sulfonated polymers, added during the extraction process, especially during the entire manufacturing process for the products made from the wood particles. In this embodiment, the method according to the invention represents an extremely advantageous and practice-relevant variant, if only for ecological reasons.

Further features of the invention result from the claims, the figures and the description of the figures. The features and feature combinations mentioned above in the description, as well as the features and feature combinations mentioned below in the description of the figures and/or shown alone in the figures, can be used not only in the combination specified in each case, but also in other combinations, without departing from the scope of the invention to leave . Therefore, the invention also includes and discloses embodiments that are not explicitly shown and explained in the figures, but that result from the explained embodiments and can be generated through separate combinations of features. There are also versions and combinations of features to be regarded as disclosed, which therefore do not have all the features of an originally formulated independent claim. In addition, there are versions and combinations of features, in particular through the above versions, to be regarded as disclosed, which go beyond or deviate from the combinations of features set out in the back references of the claims. In particular, the present invention is explained in more detail using the following examples and the figures, without of course being restricted thereto. Show it :

Fig. 1 the hexanal content at 70 °C extraction temperature. The x-axis shows the extraction time in h; the y-axis the hexanal content of the extracted wood pulp in mg/kgDM;

Fig. 2 the hexanal content at 90 °C extraction temperature. The x-axis shows the extraction time in h; the y-axis the hexanal content of the extracted wood pulp in mg/kgDM; 3 shows the hexanal content at an extraction temperature of 110°C. The x-axis shows the extraction time in h; the y-axis the hexanal content of the extracted wood pulp in mg/kgDM;

4 shows the reduction in hexanal content at an extraction temperature of 70.degree. The x-axis shows the extraction time in h; the y-axis the reduction of the hexanal content in % based on dry starting material;

5 shows the hexanal content reduction at 90° C. extraction temperature. The x-axis shows the extraction time in h; the y-axis the reduction of the hexanal content in % based on dry starting material;

6 shows the hexanal content reduction at 110° C. extraction temperature. The x-axis shows the extraction time in h; the y-axis the reduction of the hexanal content in % based on dry starting material.

Examples :

The aim of the process developed in this patent is a significant improvement in the organoleptic properties of the wood particles and aged wood particles produced by this process. The undesirable odor that occurs, especially after the wood particles have aged (up to 6 months), and the taste of the food that comes into contact with them, is mainly caused by aldehydes (especially hexanal), which are caused by autocatalytic oxidation of in the wood naturally occurring fatty acids are formed. As mentioned above, this autocatalytic oxidation is currently prevented or greatly slowed down industrially by complexing the metal ions present in the wood particles, which act as a catalyst, by adding complexing agents such as ethylenediaminetetraacetic acid (EDTA). The process of this patent achieves a significant improvement in the organoleptic properties of the wood particles without adding complexing agents, but by removing potential aldehyde sources, primarily fatty acids.

Since fatty acids as a source of aldehydes and subsequently as a source of organoleptic impairment of the wood particles can only be quantified satisfactorily with great effort, the hexanal content of the wood particles was used to assess the extraction success of the tests of this patent aging used. At this point it should be noted that 0.5 mg/kgTM Hexanal (relative to dry wood) marks the empirically determined value below which experience has shown that organoleptic impairments are no longer perceptible to the senses. The following applies to hexanal contents in the wood particles > 0.5 mg/kgTM: The higher the hexanal content, the greater the organoleptic impairment of the wood particles.

The hexanal content can be determined using headspace gas chromatography (HS-GC) by filling a headspace vial with approx. 0.2 g of air-dried wood particles (90-95 wt% TSG). In these vials, the sealed wood particles must then be aged for six months at room temperature (approx. 20 °C) in order to oxidize the fatty acids to hexanal. Since this takes a lot of time and therefore does not allow a timely assessment of the extraction success, accelerated aging according to DIN ISO 5630-2 was carried out for the present experiments (unless explicitly stated otherwise). The wood particles were sealed in HS-GC vials, aged for 72 h at 90° C. and then the hexanal content was determined using HS-GC. Although this standard for accelerated aging has been withdrawn, the extraction tests carried out in Table 1 show that the method of accelerated aging supplies comparable values and that the hexanal values for accelerated aging are on average even higher and are therefore even safer regarding the extraction success.

Table 1

The hexanal content was used for the extraction success of all experiments according to the present invention, since experience has shown that this is the main factor influencing the organoleptic impairment of wood particles. The extractive substance content using Soxhlet extraction according to the TAPPI standard T204 is too imprecise for this, as Table 2 shows. At this point it should be noted that the TAPPI standard T204 was not used to determine the extractive content of the wood particles in all of the tests in this patent, but rather the NREL method NREL/TP-510-42619, which is very similar to T204, and Hol z-grinding or . 2 mm large wood particles were used as the starting material instead of wood flour.

Table 2

As can be seen in Table 2, the Soxhlet extractions with ethanol differ significantly from those with acetone in terms of the hexanal content, but not significantly in terms of the extractive content. This means that, for example, two differently extracted wood particles can have different organoleptic properties despite not significantly different extractive content. The hexanal content of the wood particles after aging is therefore a much stronger and more accurate indicator of the organoleptic impairment than the extractive content, and was therefore used for the extraction success according to the present invention. In addition, the hexanal content of the starting material and the resulting reduction specify the hexanal content for all experiments, since the starting materials are snapshots and the hexanal content can therefore vary greatly from time to time.

Nevertheless, the extracted extractive mass (determined as the evaporation residue of the extract) is an important indicator for the solid mass loss of the extraction, since it - apart from a few very volatile compounds - includes almost the entire extractively removed solid mass. Thus, the evaporation residue of the extract together with the hexanal content of the extracted wood particles is an important measure for assessing the selectivity of the extraction.

Experiment: Comparison of solvents based on Soxhlet extractions

For the pre-selection of solvents, wood grinding samples were extracted with three different solvents. In each case 3 g of air-dried wood pulp were extracted for 24 hours using the Soxhlet method according to the NREL procedure NREL/TP-510-42619. The results are shown in Table 3.

Table 3

In Table 3 it can be seen that even with higher hexanal contents in the starting material, ethanol extracts best, followed by acetone. Cyclohexane extracts by far the worst, which means that completely non-polar solvents are unsuitable for the extraction of fatty acids. According to Reichardt and Welton (Reichardt and Welton, Solvents and Solvent Effects in Organic Chemistry ⁴ (2011), Weinheim: Wiley-VCH Verlag GmbH & Co. KGaA, pp 550-552) the empirically determined polarity of cyclohexane is 0 (very non-polar) compared to 0.355 of acetone and 0.654 of ethanol. Nevertheless, extraction with cyclohexane was also able to reduce the hexanal content by 79%.

Experiment 1: Extraction of dry wood pulp

The influence of the parameters solvent concentration, temperature and extraction time was examined on the basis of the extraction of air-dried groundwood (consisting of approx. 95% spruce and 5% pine) with ethanol (EtOH). For this purpose, approx. 2 g of air-dried groundwood were placed in an ethanol-water mixture with a solids:extractant ratio of 1:10 w/w and ethanol concentrations of 50, 70 and 90 wt% at temperatures of 70, 90 and 110 °C for 0.5, 1, 2, 4 and 8 h in small autoclaves. After extraction, the groundwood was pressed, washed with ethanol, pressed again and washed again with deionized water before it was dried, aged and analyzed. In FIGS. 1 to 3, the hexanal contents achieved by the extraction at the different extraction temperatures and solvent concentrations are plotted over the extraction time.

Figures 1 to 3 show that the extraction success with 70 or 90 wt% ethanol is significantly improved compared to enem at 50 wt% - especially at lower temperatures. Ethanol concentrations of 70 or 90 wt% ethanol reduce the hexanal content to a comparable level. With the extraction temperatures, it is apparent that 90 and 110°C reduce the hexanal content approximately equally, while it is not reduced as much at 70°C. With 90 wt% ethanol, the hexanal content can even drop below the 0.5 mg/kgTM mark from 90°C, which means that the groundwood extracted under these conditions no longer has any organoleptic impairments, according to experience. Based on the different extraction times, it can be seen that the hexanal content drops the most at the beginning of the extraction, and especially in the first 4 hours. This can also be seen in FIGS. 4 to 6. These figures reflect the extraction successes shown in FIGS. 1 to 3, since the same batch of starting material was used for all experiments in this series of experiments. It is clearly evident that in the worst case (0.5 h with 50 wt% ethanol at 70 wt% the hexanal content could only be reduced by approx. 20%, while this was reduced by more than 95% with 90 wt% ethanol from 90 °C.

Table 4 shows that despite the high hexanal content reductions achieved in this test series, the extracted solids mass is max. 7 wt% (based on the starting material) - but usually significantly lower. With a determined extractive content of the starting material of approx. 3 wt%, this means that neither hemicelluloses nor lignin are extracted to any significant extent.

Table 4

Experiment 2: Extraction of wet wood pulp with ethanol under different conditions

The extraction of moist groundwood represents real conditions much better, especially in cardboard production, than the extraction of dry groundwood, as in test 1. In addition, significantly more sample mass was taken for these tests (factor 225) than for test 1 in order to get a more meaningful to get result. Approx. 450 gTM mechanically dewatered groundwood (approx. 25 wt% TSG; approx. 95% spruce and 5% pine) in an ethanol-water mixture with a solids:solvent ratio of 1:10 w/w and ethanol concentrations of 60 wt% at temperatures of 70 and 90 °C for 2 and 4 hours in an autoclave. After the extraction, the ground wood was pressed, washed with ethanol, pressed again and again with full washed with deionized water before being dried, aged and analyzed. Table 5 shows the results of these extractions.

Table 5

The tests show that - compared to the extraction of a smaller and, above all, air-dry wood-pulp mass - the tests with mechanically dewatered wood-pulp and more sample mass show higher hexanal contents in the extracted wood-pulp. Nonetheless, over 73% reduction in hexanal content was achieved in each setting.

Experiment 3: Extraction of wet wood pulp with three different organic solvents

Experiment 3 was carried out to test three different technically relevant solvents under real extraction conditions. Approx. 450 gTM mechanically dewatered groundwood (approx. 25 wt% TSG; approx. 95% spruce and 5% pine) in a solvent-water mixture with a solids:extractant ratio of 1:10 w/w and a solvent concentration of 70 wt% at a temperature of 70 °C for 4 hours in an autoclave. After extraction, the groundwood was pressed, washed with extraction agent, pressed again and washed again with deionized water before it was dried, aged and analyzed. Table 6 shows the results of these extractions.

As can be seen in Table 6, acetone extracts the unsaturated fatty acids responsible for hexanal formation significantly better than undenatured ethanol. However, the best extraction results were achieved with ethanol that was incompletely denatured with butanone. The hexanal content of 2.77 mg/kgDM achieved with 70 wt%, 70°C and 4 h extraction time is still well above the 0.5 mg/kgDM limit, but corresponds to a reduction of 80%. With all extractions, the evaporation residue of the extract is only between 2.2 and 2.4 wt% based on the starting material dry mass, which means that with a determined extractive content of 3.6 wt%, the main wood components are cellulose, hemicelluloses and In fact, lignin was not attacked and the extractions were therefore very selective. The abietic acid content of the extractions in this experiment was reduced by 41-55%, based on the starting material. Since abietic acid was selected here as the key substance for the content of resin acids, a reduction in the content of around 50% is an indication of the clear reduction in resin through the

Method of this patent.

Experiment 4: Extraction of moist wood pulp with acetone at different solids/extractant ratios

The influence of different solids/extractant ratios was investigated in this experiment. Approx. 200 - 450 gTM (depending on the ratio of solids: extraction agent) mechanically dewatered groundwood (approx. 25 wt% TSG; approx. 95% spruce and 5% pine) were dissolved in an acetone-water mixture consisting of 70 wt% acetone and 30 wt% deionized water with solid:extractant ratios of 1:10, 1:15 and 1:25 w/w at a temperature of 50°C for 1, 2 and 4 hours in an autoclave. After extraction, the groundwood was pressed, washed with extraction agent, pressed again and washed again with deionized water before it was dried, aged and analyzed. The results of these extractions are listed in Table 7.

Table 7

As Table 7 shows, the hexanal content is reduced by over 80% in all extractions (except for the solid:extractant ratio of 1:10 (w/w) at a starting material hexanal content of 14.07 mg/kgDM). reduced. With extraction agent-solids ratios of more than 10:1 (w/w), the reduction in the hexanal content is comparably high and always well over 70% under the same extraction conditions, despite different starting material hexanal contents. The evaporation residue of the extract is less than 3%, which, given the extractive substance content of the starting material of 3.4 - 3.7 wt%, is proof of the quantitative preservation of the lignocellulose components in this process. By reducing the abietic acid content by 31-54%, based on the starting material, this test also showed that the process of this patent can significantly reduce resin.

Experiment 5: Multi-stage extraction of moist wood pulp with acetone

In this experiment, multi-stage extractions were carried out, with fresh, unloaded extraction agent being used for each stage (= one hour each). The wood pulp (approx. 400 - 450 gDM; approx. 25 wt% TSG) was pressed after each extraction stage (to approx. 30 wt% TSG) and with acetone and deionized water (both preheated to an extraction temperature of 50 °C) mixed in such a way that the solids:extractant ratio is 1:10 and the acetone concentration in the extractant is 70 wt%. The extractions were performed in an autoclave. After extraction, the groundwood was pressed, washed with extraction agent, pressed again and washed again with deionized water before it was dried, aged and analyzed. The results of these extractions are listed in Table 8.

Table 8

As Table 8 shows, the hexanal content is already reduced by more than 80% in all extractions after the first stage, but is still well above 0.50 mg/kgDM, especially in the case of a starting material with a higher hexanal content. After stage three, however, the hexanal content in all of the ground wood samples extracted from this test was below 0.50 mg/kgDM, in some cases even below the limit of quantification of 0.20 mg/kgDM. The evaporation residue of the extract is less than 3.5%, which, given the extractive substance content of the starting material of 2.5 - 3.7 wt%, is proof of the quantitative preservation of the lignocellulose components in this process. By reducing the abietic acid content by 55-100%, based on the starting material, this test has also shown that the process of this patent can significantly reduce resin, in particular with an increasing number of extraction stages. Experiment 6: Multi-stage extraction of moist wood particles of different particle sizes with acetone

The influence of the particle size was examined in this experiment with different extraction parameters. Approx. 650 gTM wood chips (approx. 20 mm; approx. 55 wt% TSG; spruce), approx. 450 gTM shredded wood chips (2 mm mesh size of the cutting mill sieve; approx. 60 wt% TSG; spruce) and approx. 400 gTM mechanically dewatered groundwood (approx. 25 wt% TSG; approx. 95% spruce and 5% fir) in two stages (one hour each) at 50°C and in two stages (30 minutes each) at 21°C extracted in an autoclave. The multi-stage extractions were carried out analogously to experiment 5 by pressing off the wood particles after each extraction stage and mixing them with fresh, unloaded extraction agent. The extraction parameters were 50 °C, extraction times of 1 h per extraction stage and acetone concentrations of 70 wt% in the extractant (extraction parameter 1) and 21 °C, extraction times of 30 min per extraction stage and pure acetone as the added extractant resulting in acetone Concentrations of 70 - 99 wt% depending on the extraction stage and particle size results (extraction parameter 2). The solids: extractant ratios were chosen so that the wood particles were just covered with extractant (1:6 for wood chips and ground wood chips and 1:10 for ground wood). After extraction, the wood particles were pressed (and washed with extractant at extraction parameter 1) and pressed again before being dried, aged and analyzed. The results of these extractions are listed in Table 9.

Table 9

As Table 9 shows, the hexanal content of wood chips can only be reduced by about 20-30% using the process according to the invention. On the other hand, when the wood chips are ground to a particle size of 2 mm, as also specified by the NREL method NREL/TP-510-42620, the hexanal content can be reduced to approx. 1 mg/kgTM using the process according to the invention, which is hexanal content of 21.36 mg/kgTM corresponds to a reduction of approx. 95%. With an even smaller particle size, such as groundwood, the reduction in the hexanal content is even higher at around 97%. The two extraction parameters deliver comparable hexanal contents with larger particle sizes, whereas with smaller ones Particle size, especially wood pulp, the extraction parameters 1 (higher temperature and longer extraction time) deliver significantly better results. When reducing the extract evaporation residue based on the extract evaporation residue of the starting material Soxhlet extraction, the extraction parameters deliver better results for all particle sizes. Table 9 also shows that the reduction of the extract evaporation residue based on the extract evaporation residue of the starting material Soxhlet extraction cannot be used as an indicator for the extraction success of the intended method, since, for example, with wood chips even at high Reduction of 73% of the hexanal content by only approx. 20 was lowered, whereas in the case of ground wood, with a reduction in the extract evaporation residue based on the extract evaporation residue of the starting material Soxhlet extraction by 75%, the hexanal content could be reduced by approx. 96%.

Experiment 7: Modification of the mechanical properties by the extractive treatment of groundwood according to the present invention

This experiment serves to investigate the effects of the extractive treatment on the mechanical properties of the extracted wood particles. For this purpose, approx. 300 - 450 g DM (depending on the solids: extractant ratio) mechanically dewatered groundwood (approx. 25 wt% TSG) were dissolved in a solvent-water mixture with solids: extractant ratios of 1:10 and 1: 15 w/w and a solvent concentration of 60 and 70 wt% at temperatures of 50 °C, 70 °C and 90 °C. Ethanol 96 fully undenatured (EtOH pure), ethanol 96 fully incompletely denatured with butanone (EtOH comp.) and acetone were used as solvents. After extraction, the ground wood was pressed, washed with extraction agent, pressed again and washed again with deionized water before sample sheets were formed from it, on the basis of which the mechanical properties were examined. The mass loss results from the evaporation residue of the extract and is related to the starting material dry mass. Table 10 lists the results.

Table 10

As can be seen in Table 10, the degree of grinding and thus the dewatering of the ground wood pulp hardly changes as a result of the extraction, which has the advantage with regard to any further processing (e.g. into cardboard) that existing production plants do not have to be converted or converted Need to become. The stiffness index also changes only slightly as a result of the extraction, whereas the tensile index, as a measure of the breaking force, rises sharply and reproducibly. Compared to this high increase of between 20 and 41% on average, the loss of mass due to the evaporation residue of the extract is very low at around 2%. This means that the wood particles gain disproportionately strong strength through the extraction with little mass loss, which is of great importance for the lightweighting trend in the packaging sector in particular.

Experiment 8: purification of the extracted extractives

In this test, mechanically dewatered groundwood (approx. 25 wt% TSG; approx. 95% spruce and 5% fir) with a solids/extractant ratio of 1:10 w/w at 50 °C for 1 h in extracted an autoclave, the extraction agent being composed of 70 wt% acetone and 30 wt% deionized water. After the extraction, the wood pulp was pressed out (to approx. 30 wt%) and the extract obtained in this way was worked up as follows: First, the acetone was separated off by distillation by heating the distillation flask to 108 °C and under atmospheric pressure until equilibrium was established was distilled . The remaining residue was centrifuged at 7197 g for 10 minutes and the sediment was then separated from the supernatant. The supernatant was weighed and its dry matter content determined by gentle drying at room temperature, which essentially corresponds to the content of extracted extractives. The sediment was also weighed and dissolved in a defined mass of pure acetone. From this, the dry matter content was determined analogously to the supernatant. The deposits that had already formed during the distillation were also dissolved in pure acetone. From this, the dry matter content was determined analogously to the sediment. The content of free fatty acids (linolenic acid, linoleic acid, oleic acid and stearic acid, each expressed in linoleic acid equivalents), resin acids (isopimaric acid, palustric acid, Dehydroabietic acid and abietic acid, each expressed in abietic acid equivalents) and lignans (isolariciresinol, secoisolariciresinol, conidendric acid, hydroxymatairesinol and matairesinol, each expressed in hydroxymatairesinol equivalents). The results of Experiment 1 and Experiment 2 (repetitions with identical parameters) are listed in Tables 11 and 12.

Table 11

Table 12

As can be seen in Tables 11 and 12, the bulk of the extractive substance accumulates as centrifuged sediment. Despite the reduction in the amount of liquid by approx. 80% (from extract to supernatant), the dry matter content (which here essentially corresponds to the mass of extractive substance) in the supernatant is only at a similarly low level as in the extract (< 1 wt%) due to the selected separation process. . However, the proportion of free fatty acids and resin acids in the supernatant could be reduced to a very low level, while the lignans were enriched. In contrast, the sediment and the deposits contain little or no lignans, but a high content of free fatty acids and resin acids. Although the extractive substances analyzed here (free fatty acids, resin acids and lignans) represent only part of the extractive substances (and dry substance found here), it is clearly evident that with the selected thermal and mechanical separation process (distillation and centrifugation), not only the liquid phase (extract or supernatant) can be largely freed from fatty and resin acids, but also lipophilic extractives (e.g. fatty acids and resin acids) and hydrophilic extractives (e.g. lignans) as by-products can each be significantly concentrated and purified.

Legend :

STDEV = standard deviation

TM = dry matter

TSG = dry matter content

Preferred embodiments:

In view of the above description of the present invention, the following preferred embodiments of the invention are disclosed herein:

1. 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 extraction agent which 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% by the extraction treatment of the wood particles with the extraction agent, measured as hexanal content in % by weight after accelerated aging for 72 h at 90°C, but the cellulose content , hemicelluloses and Lignin is essentially preserved in this extraction treatment.

2. The method according to embodiment 1, characterized in that the wood particles are present in a size of at most 2 mm, the particle size preferably according to the National Renewable Energy Laboratory (NREL) Laboratory Analytical Procedure (LAP) NREL/TP-510-42620 "Preparation of Samples for Compositional

Analysis" is defined by the sieve mesh width of 2 mm of the cutting mill for sample preparation.

3. Method according to embodiment 1 or 2, characterized in that the wood particles are in the form of fibers, chips or mixtures thereof.

4. The method according to one or more of embodiments 1 to 3, characterized in that the wood particles are fibrous wood by mechanical and/or thermal and/or chemical digestion.

5. The method according to one or more of embodiments 1 to 4, characterized in that the wood particles are wood fibers with average fiber lengths between 0.5 and 2 mm and average fiber diameters between 10 and 50 μm, with the average fiber length and the average Refer fiber diameter to the mean length, determined by optical measurement of the suspended fibers.

6. The method according to one or more of embodiments 1 to 5, characterized in that the proportion of solvent in the organic-aqueous solvent mixture in the extractant, determined as the concentration of the liquid phase of the extract, consists of 0-95% by weight ethanol, preferably 50-90% by weight ethanol, 0-99% by weight acetone, preferably 30-90% by weight acetone, 0-70% by weight n-propanol, 0-85% by weight iso-propanol and/or 0-99% by weight of methanol.

7. The method according to one or more of embodiments 1 to 6, characterized in that the ratio of extractant to solid dry substance is 5:1 - 25:1 (w/w), preferably 8:1 - 17:1 (w /w) is.

8. Process according to one or more of embodiments 1 to 7, characterized in that the extraction treatment is carried out at an extraction temperature of 20-150 °C, preferably 40-120 °C, in particular 50-110 °C.

9. Method according to one or more of the embodiments 1 to 8, characterized in that the extraction treatment is carried out at an absolute extraction pressure of 1-5 bar, preferably 1-1.49 bar.

10. The method according to one or more of embodiments 1 to 9, characterized in that the extraction treatment takes place during an extraction time of 10 minutes to 8 hours, preferably 30 minutes to 7 hours, in particular 1 to 5 hours.

11. The method according to one or more of embodiments 1 to 10, characterized in that the method is used to produce cardboard, paper, wood fiber boards, chipboard, articles of daily use, medical products, in particular to produce cardboard.

12. The method according to one or more of embodiments 1 to 11, characterized in that the extraction treatment is selected from:

treatment with ethanol in a concentration of at least 45% by weight at at least 105°C for a period of at least 5 hours;

13. The method according to one or more of embodiments 1 to 12, characterized in that the treatment with the extraction agent is carried out as a batch, continuous or semi-continuous extraction, preferably with a maximum partial residence time of 1 hour per extraction step.

14. The method according to one or more of embodiments 1 to 13, characterized in that the extraction treatment reduces the content of cellulose, hemicelluloses and lignin by less than 10%, preferably by less than 5%, in particular by less than 4%, this reduction preferably being determined as the extracted solid mass, based on the starting material, the wood particles.

15. The method according to one or more of embodiments 1 to 14, characterized in that the wood particles are selected from softwood 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.

16. The method according to one or more of embodiments 1 to 15, characterized in that the wood particles are mixed with the extraction agent during the treatment.

17. The method according to one or more of embodiments 1 to 16, characterized in that the wood particles are pressed after treatment with the extraction agent in order to remove the extraction agent.

18. The method according to one or more of embodiments 1 to 17, characterized in that after treatment with the extraction agent, the wood particles are cleaned one or more times with an extraction agent, preferably with an organic-aqueous solvent with a similar or the same concentration as that of the Extractant to be cleaned.

19. The method according to one or more of embodiments 1 to 18, characterized in that the extraction agent is removed from the wood particles by one or more washings with water and/or steam stripping and/or drying, preferably by steam stripping and/or drying Will get removed.

20. The method according to one or more of embodiments 1 to 19, characterized in that the content of fatty acids in the wood particles by extraction of the wood particles with the extraction agent by at least 75%, preferably by at least 80%, in particular by at least 90%, is reduced, measured as the hexanal content in % by weight of the wood particles in the starting material compared to the extracted wood particles after accelerated aging for 72 h at 90°C.

21. The method according to one or more of embodiments 1 to 20, characterized in that the content of fatty acids in the wood particles is reduced by extraction of the wood particles with the extraction agent to a content of less than 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 fraction of the extracted wood particles after accelerated aging for 72 hours at 90°C.

22 . Method according to one or more of embodiments 1 to 21, characterized in that resin acids are also extracted in addition to the fatty acids.

23 . Process according to one or more of embodiments 1 to 22, characterized in that the fatty acids, resin acids and/or other extractives extracted with the extraction agent are fed to a further purification process, preferably by mechanical separation technology after thermal separation of the organic solvent from the organic-aqueous extraction agent, with lipophilic extractives, in particular fatty acids and resin acids, being precipitated and separated, and an aqueous phase enriched with hydrophilic extractives, particularly lignans, being obtained, with the hydrophilic extractives preferably being separated by subsequent treatment with thermal separation technology , In particular by means of membrane separation processes and / or adsorption, are further concentrated.

24 . Method according to embodiment 23, characterized in that the extractant is preceded by membrane filtration of the extractant during enrichment of the extractant.

25 . Method according to one or more of embodiments 1 to 24, characterized in that the wood particles no complexing agents, in particular complexing agents selected from polybasic and polyfunctional carboxylic acids, aminomethyl carboxylic acids, aminomethyl phosphonic acids and their compounds, EDTA, DTPA EGTA, EDDS and their salt zen, polyphenols, tannins, amino acids, peptides, proteins, polycarboxylates, phosphates, polyphosphates, phosphonic acids, polyphosphonates, phosphated, phosphonylated, sulfated and sulfonated polymers, during the extraction process, especially during the entire manufacturing process for the from the Products made of wood particles are added.

26 . Process according to one or more of embodiments 1 to 25, characterized in that the extraction agent and any washing liquids used, in particular water, are regenerated for reuse. 27 . Method according to one or more of embodiments 1 to 26, characterized in that the extraction treatment, in addition to reducing the hexanal content, also reduces the mechanical strength of the extracted wood particles, measured as Tensile Index of test sheets in Nm/g, by at least 10% , preferably by at least 15%, in particular by at least 25%, with the freeness, measured in °SR, changing by less than 10%.

28 . Process according to one or more of embodiments 1 to 27, characterized in that the organic-aqueous mixture of the solvent or solvents contains at least 10% water, preferably at least 7.5% water, in particular at least 5% water.

Further preferred embodiments of the present invention are the following embodiments:

1 . Process for the manufacture of 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 extraction agent which comprises 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% by the extraction treatment of the wood particles with the extractant, measured as the hexanal content in wt. -% after accelerated aging for 72 h at 90 °C, but the content of cellulose, hemicelluloses and lignin is essentially preserved in this extraction treatment.

2 . Method according to embodiment 1, characterized in that the wood particles are present with a size of less than 5 cm, the particle size preferably being determined by sieving using a square mesh screen, in particular using a square mesh screen with a mesh size of 5 cm or less.

3 . Method according to embodiment 1 or 2, characterized in that the wood particles are present in the form of fibers, chips, strands, wood chips or mixtures thereof.

4 . Method according to one or more of embodiments 1 to 3, characterized in that the wood particles are fibrous wood by mechanical and/or thermal and/or chemical digestion.

5 . Process according to one or more of the embodiments 1 to 4, characterized in that the wood particles are wood fibers with average fiber lengths between 0.5 and 2 mm and average fiber diameters between 10 and 50 μm, the average fiber length and the average fiber diameter being based on the length average, determined using optical measurement of the suspended fibers.

9. Process according to one or more of embodiments 1 to 8, characterized in that the extraction treatment is carried out at an absolute extraction pressure of 1-5 bar, preferably 1-1.49 bar.

treatment with ethanol in a concentration of at least 65% by weight at at least 65°C for a period of at least 3 hours; treatment with ethanol in a concentration of at least 65% by weight at at least 85°C for a period of at least 30 minutes;

treatment with ethanol in a concentration of at least 70% by weight at at least 105°C for a period of at least 30 minutes; or

Treatment with ethanol in a concentration of at least 45% by weight at at least 105°C for a period of at least 5 hours.

Treatment with acetone in a concentration of at least 50% by weight at at least 40°C for a period of at least 30 minutes.

14. The method according to one or more of embodiments 1 to 13, characterized in that during the extraction treatment the content of cellulose, hemicelluloses and lignin is reduced by less than 10%, preferably by less than 5%, in particular by less than 4%, is reduced, this reduction preferably being determined as the extracted solid mass, based on the starting material, the wood particles.

18. The method according to one or more of embodiments 1 to 17, characterized in that the wood particles after Treatment with the extractant is cleaned one or more times with an extractant, preferably with an organic aqueous solvent having a concentration similar to or the same as that of the extractant.

19. The method according to one or more of embodiments 1 to 18, characterized in that the extraction agent is removed from the wood particles by one or more washings with water or drying, preferably by drying.

21. The method according to one or more of embodiments 1 to 20, characterized in that the content of fatty acids in the wood particles is reduced by extraction of the wood particles with the extraction agent to a content of less than 2 mg/kg dry matter, preferably less than 1 mg/kg. kg dry matter, in particular below 0.5 mg/kg dry matter, is reduced, measured as the hexanal content as the mass fraction of the extracted wood particles after accelerated aging for 72 h at 90°C.

22. The method according to one or more of embodiments 1 to 21, characterized in that resin acids are also extracted in addition to the fatty acids.

23. Process according to one or more of embodiments 1 to 22, characterized in that the fatty acids, resin acids and/or optionally other extractives extracted with the extraction agent are fed to a further purification process.

24. The method according to one or more of embodiments 1 to 23, characterized in that the wood particles no complexing agents, in particular complexing agents selected from polybasic and polyfunctional carboxylic acids, aminomethyl carboxylic acids, aminomethyl phosphonic acids and their compounds, EDTA, DTPA EGTA, EDDS and their salts, polyphenols, tannins, amino acids, peptides, proteins, polycarboxylates, phosphates, polyphospha- th, phosphonic acids, polyphosphonates, phosphated, phosphonylated, sulfated and sulfonated polymers, are added during the extraction process, especially during the entire manufacturing process for the products made from the wood particles.

25 . Process according to one or more of embodiments 1 to 24, characterized in that the extraction agent and any washing liquids used, in particular water, are regenerated for reuse.

26 . Method according to one or more of embodiments 1 to 25, characterized in that the extraction treatment, in addition to reducing the hexanal content, also reduces the mechanical strength of the extracted wood particles, measured as Tensile Index of test sheets in Nm/g, by at least 10% , preferably by at least 15%, in particular by at least 25%, with the freeness, measured in °SR, changing by less than 10%.

Claims

44 claims :

1. 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 extraction agent which 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% by the extraction treatment of the wood particles with the extraction agent, measured as hexanal content in % by weight after accelerated aging for 72 h at 90°C, but the content of cellulose, hemicelluloses and lignin is essentially retained in this extraction treatment.

2. The method according to claim 1, characterized in that the wood particles are present in a size of at most 2 mm, the particle size preferably according to the National Renewable Energy Laboratory (NREL) Laboratory Analytical Procedure (LAP) NREL/TP- 510-42620 "Preparation of Samples for Compositional Analysis" is defined by the sieve mesh size of 2 mm of the cutting mill for sample preparation, the wood particles preferably being present in the form of fibres, chips or mixtures thereof.

3. The method according to claim 1 or 2, characterized in that the wood particles by mechanical and / or thermal and / or chemical digestion to fibrous wood, in particular wood fibers with average fiber lengths between 0.5 and 2 mm and average fiber diameters between 10 and 50 pm , where the average fiber length and the average fiber diameter relate to the average length , determined by optical measurement of the suspended fibers.

4. The method according to one or more of claims 1 to 3, characterized in that the solvent content of the organic-aqueous solvent mixture in the extractant, determined as the concentration of the liquid phase of the extract, consists of 0-95% by weight ethanol, preferably 50 - 90% by weight ethanol, 0-99% by weight acetone, preferably 30-90% by weight acetone, 0-70% by weight n-propanol, 0-85% by weight iso-propanol and/or or 0-99% by weight methanol. 45

5. The method according to one or more of claims 1 to 4, characterized in that during the extraction treatment the content of cellulose, hemicelluloses and lignin is reduced by less than 10%, preferably by less than 5%, in particular by less than 4% , This reduction preferably being determined as the extracted solid mass, based on the starting material, the wood particles.

6. The method according to one or more of claims 1 to 5, characterized in that the wood particles are selected from softwood 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 one or more of claims 1 to 6, characterized in that the wood particles are cleaned one or more times with an extraction agent after treatment with the extraction agent, preferably with an organic-aqueous solvent with a similar or the same concentration as that of the Extractant to be cleaned.

8. The method according to one or more of claims 1 to 7, characterized in that 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%, by extraction of the wood particles with the extraction agent , measured as hexanal content in % by weight of the wood particles in the starting material compared to the extracted wood particles after accelerated aging for 72 h at 90°C.

9. The method according to one or more of claims 1 to 8, characterized in that the content of fatty acids in the wood particles by extraction of the wood particles with the extractant to a content of less than 2 mg / kg dry matter, preferably less than 1 mg / kg dry matter , in particular less than 0.5 mg / kg dry matter, is reduced, measured as a hexanal content as a mass fraction of the extracted wood particles after accelerated 46

Aging for 72 h at 90 °C.

10 . Process according to one or more of Claims 1 to 9, characterized in that the extraction not only extracts the fatty acids but also resin acids.

11 . Method according to one or more of Claims 1 to 10, characterized in that the fatty acids, resin acids and/or other extractives extracted with the extraction agent are fed to a further purification process, preferably by mechanical separation technology after the thermal separation of the organic solvent from the organic-aqueous extraction agent, with lipophilic extractives, in particular fatty acids and resin acids, being precipitated and separated, and an aqueous phase enriched with hydrophilic extractives, in particular lignans, is obtained, with the hydrophilic extractives preferably being separated by subsequent treatment with thermal separation technology, in particular by means of membrane separation processes and/or adsorption, are further concentrated.

12 . Method according to Claim 11, characterized in that the extractant is preceded by membrane filtration during the enrichment of the extractive substance.

13 . Method according to one or more of Claims 1 to 12, characterized in that the wood particles do not have any complexing agents, in particular complexing agents selected from polybasic and polyfunctional carboxylic acids, aminomethyl carboxylic acids, aminomethyl phosphonic acids and their compounds, EDTA, DTPA EGTA, EDDS and their salts, Polyphenols, tannins, amino acids, peptides, proteins, polycarboxylates, phosphates, polyphosphates, phosphonic acids, polyphosphonates, phosphated, phosphonylated, sulfated and sulfonated polymers, during the extraction process, in particular during the entire manufacturing process for the products made from the wood particles, be added.

14 . The method according to one or more of claims 1 to 13, characterized in that the extractant and any washing liquids used, in particular water, for be regenerated for reuse.

15. The method according to one or more of claims 1 to 14, characterized in that the extraction treatment, in addition to reducing the hexanal content, also reduces the mechanical strength of the extracted wood particles, measured as Tensile Index of sample sheets in Nm/g, by at least 10% , preferably by at least 15%, in particular by at least 25%, with the freeness, measured in °SR, changing by less than 10%.

16. Use of the lipophilic extractive substance fraction obtained according to claims 11 and 12 as a feed supplement.