EP4023812A1 - Method for producing wood-based products - Google Patents

Abstract

Described is a method for manufacturing 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 containing one or more organic solvents or an organic-aqueous mixture of the solvent or solvents with water comprises, 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 solvent, measured as 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.

Description

The invention relates to methods for the manufacture of wood-based products, in particular methods for the pre-treatment 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 known as "pitch" or "stickies", 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. cause ( 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 methods that have been described to improve organoleptic properties include bleaching (e.g DE 10 2004 050 278 A1 ), delignifying (eg DE 28 18 320 A1 ), oxidizing or reducing (eg DE 33 44 239 C2 , WO 2006/039914 A1 , DE 10 2006 020 612 A1 ) chemicals used.

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 auto-oxidation of fatty acids naturally occurring in 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 pollution even without the use or addition of 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 method for Manufacture of products based on wood as raw material, in which wood in the form of wood particles is subjected to an extraction treatment with an extraction agent comprising one or more organic solvents or an organic-aqueous mixture of the solvent or solvents with water, the content of fatty acids being reduced 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 at this Extraction treatment is essentially obtained.

As has been shown in the course of the present invention, a significant improvement in the organoleptic properties of the wood particles can be achieved with the inventive extraction of the organoleptically questionable substances from the raw materials without adding complexing agents, but by removing potential aldehyde sources, above all fatty acids. However, it is known that fatty acids as a source of aldehydes and subsequently as a source of organoleptic impairments of the wood particles can only be satisfactorily quantified 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 studies and evidence in the examples 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 has benefits, a significant reduction of at least 70% for suitable large scale commercial use is readily possible with the present process. However, the treatment according to the invention is preferably selected in such a way that the desired reduction is achieved in any case, and thus a reduction by at least 70%, preferably by at least 90%, in particular by at least 95%, is achieved. Accordingly, the conditions to be used according to the invention can then be selected, for example on the basis of the nature of the wood or the extractant, such that the hexanal reduction according to the invention results in any case. In this way, preferred maximum values in absolute contents of hexanal can also be set. 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/kg DM 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 organoleptic impairments are not sensory 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 5 cm in size, preferably in the form of fibers, chips, strands, wood chips or mixtures thereof. This particle feature (as "Particle size") can preferably be determined by sieve analysis using a square mesh sieve. Accordingly, the particle characteristic of the particle size is formulated in terms of the mesh size, preferably 5 cm (other sizes (depending on practical necessity), eg 4, 3, 2 or 1 cm (or possibly larger) can also be easily set with this). According to this preferred embodiment, the particles according to this size definition essentially correspond to the undersize of the sieve with mesh size as the particle feature.

The wood particles are preferably in the form of fibers, chips, strands, chips or mixtures thereof.

According to a preferred embodiment, the wood particles are wood that has been fiberized by mechanical and/or thermal and/or chemical digestion, in particular wood fibers with average fiber lengths between 0.5 and 2 mm and average fiber diameters between 10 and 50 μm. 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 Analyzer ( http://www.techpap.com/fiber-and-shive-analyzer-morfi-neo,labdevice,31.html).

The amount of organic compounds that can be extracted using the method according to the invention varies depending on the type of wood and the component of the tree from which the wood particles are obtained (heartwood/sapwood). For example, pine heartwood contains up to 9% extractables by weight, while fir sapwood typically has up to 1% extractables ( 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), Åbo Akademi University Press, Åbo ). In particular, types of wood such as pine, birch, lime 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 ) obtained through the manufacture of products from these Wood can be broken down 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.

In the DE 10 2009 046 127 A1 describes a process for the production of 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 the wood chips are plasticized. However, as mentioned above, the use of complexing agents such as EDTA and DTPA entails a serious waste water and environmental problem. The present invention thus brings decisive advantages over a mere chemical-thermo-mechanical digestion (CTMP) known per se, in which wood chips are mixed with sodium sulfite and EDTA, both with regard to environmental aspects and with regard to the inventive effect in the efficient depletion of fatty acids from the raw material.

the US 5,698,667A discloses a pretreatment of a lignocellulosic material by extraction with an organic solvent (e.g., acetone) to remove wood extractives such as volatile organic compounds (VOC) and higher molecular weight 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), although there The methodology used cannot ensure that volatile components pass into the gas phase when the solvent is removed from the extract and thus the depletion when determined by the evaporation residue of the extract are to be set even lower.

In contrast, in the method according to the invention using an extractive pretreatment of wood particles (such as wood fibers) with organic solvents or organic-aqueous mixtures of the solvent or solvents with water, a large part of the fatty acids naturally occurring in the wood are removed before further processing (e.g. to cardboard or wood fiber boards). In addition, other extractives such as resin acids, phenols and terpenes in the mechanical pulp are greatly reduced by this pre-treatment. According to the invention, the hexanal content has proven itself as an indicator for the auto-oxidation of naturally occurring fatty acids in 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 (as well as--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 pretreatment does not significantly change the composition of the wood particles, i.e. cellulose, hemicelluloses and lignin are not reduced to any significant extent (at least by no more than 10%, preferably by no more than 6%, in particular by no more than 4% reduced) extracted and/or degraded, 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 other important product and process advantages, especially for paper and cardboard production:
Pitch (stickies, 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, interference effects on the paper/cardboard surface can also be reduced with the present invention, which subsequently also causes problems in the further processing of the Paper/cardboard (e.g. printing) can be 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, surprisingly, an increase in mechanical strength.

The above-mentioned improved product properties of products 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 are cellulose and/or treated BCTMP (bleached chemi-thermo-mechanical pulp) (e.g. high-quality packaging boxes) or for particularly delicate applications that can only be served with cellulose today.

In addition, the COD loads of the waste water of the process are also greatly reduced by the extractive pretreatment according to the present invention, 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 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 waste water and thus the (ground)water-related environmental impact of the wood particle production -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 of 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.

In practice, for a certain type of wood or for certain wood materials for an extraction of at least 70% of the fatty acids or for establishing 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 of 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 based on the teaching disclosed herein, in particular under Considering the results presented in the example part, will be determined directly and without further inventive step n, especially considering 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 specific 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 according to the invention of ethanol, acetone and water with 0-95% by weight ethanol, preferably 50-90% by weight ethanol, and 0-99% by weight acetone have proven to be particularly advantageous. preferably 30-90% by weight of acetone, identified as the organic-aqueous solvent in the extractant. Other organic solvents which can be used instead of (or, for certain purposes, optionally also together with) ethanol or acetone in the extractant with a view to an industrial scale are, for example, methanol, n-propanol and isopropanol.

In the process according to the invention, preferred ratios of extractant to solid dry matter 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). When using an acetone concentration of 100% by weight of the extractant at 1:10 (solid matter: extractant), this results in 1 kg of dry wood mass and 10 kg of acetone. A 70% by weight acetone concentration of the extractant at 1:10 (solid matter: extractant) would then be, for example, 1 kg of dry wood mass, 7 kg of acetone and 3 kg of water. As mentioned, the extracted material would still be added, but experience has shown that it is at concentrations well below 1% by weight in the extraction agent and is therefore negligible.

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. Therefore, the method according to the invention is 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, Federal Law Gazette I No. 13/2006, idFv 01.10.2020)), medical devices (e.g. (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.

• Behandlung mit Ethanol in einer Konzentration von zumindest 65 Gew.-% bei zumindest 65°C für einen Zeitraum von zumindest 3 h;
• Behandlung mit Ethanol in einer Konzentration von zumindest 65 Gew.-% bei zumindest 85°C für einen Zeitraum von zumindest 30 min;
• Behandlung mit Ethanol in einer Konzentration von zumindest 70 Gew.-% bei zumindest 105°C für einen Zeitraum von zumindest 30 min; oder
• Behandlung mit Ethanol in einer Konzentration von zumindest 45 Gew.-% bei zumindest 105°C für einen Zeitraum von zumindest 5 h.
• Behandlung mit Aceton in einer Konzentration von zumindest 50 Gew.-% bei zumindest 40 °C für einen Zeitraum von zumindest 30 min.

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; 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 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.

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. After the (extraction) treatment with the extractant, the wood particles can preferably be treated one or more times with an extractant, even more preferably with an organic-aqueous solvent a concentration similar or equal to that of the extractant. The extractant used in the extraction and/or washing can be removed from the wood particles by repeated washing with water or drying, with 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, extraction of the wood particles with the extraction agent preferably reduces the content of fatty acids in the wood particles by at least 75%, preferably by at least 80%, in particular by at least 90%, measured as the hexanal content in % by weight of the wood particles in the starting material in comparison to the extracted wood particles 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 the 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 test 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. In a preferred embodiment, the fatty acids, resin acids and/or optionally further extractive substances are fed to a further purification process and can then be made available as by-products of the production in an extracted and optionally further purified form.

According to a preferred embodiment, 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, Added to phosphates, polyphosphates, phosphonic acids, polyphosphonates, phosphated, phosphonylated, sulfated and sulfonated polymers during the extraction process, particularly throughout the 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.

• Fig. 1 den Hexanal-Gehalt bei 70°C Extraktionstemperatur. Die x-Achse zeigt die Extraktionszeit in h; die y-Achse den Hexanal-Gehalt des extrahierten Holz-Schliffes in mg/kgTM;
• Fig. 2 den Hexanal-Gehalt bei 90°C Extraktionstemperatur. Die x-Achse zeigt die Extraktionszeit in h; die y-Achse den Hexanal-Gehalt des extrahierten Holz-Schliffes in mg/kgTM;
• Fig. 3 den Hexanal-Gehalt bei 110°C Extraktionstemperatur. Die x-Achse zeigt die Extraktionszeit in h; die y-Achse den Hexanal-Gehalt des extrahierten Holz-Schliffes in mg/kgTM;
• Fig. 4 die Hexanal-Gehalt-Reduktion bei 70°C Extraktionstemperatur. Die x-Achse zeigt die Extraktionszeit in h; die y-Achse die Reduktion des Hexanal-Gehaltes in % bezogen auf trockenem Ausgangsstoff;
• Fig. 5 die Hexanal-Gehalt-Reduktion bei 90°C Extraktionstemperatur. Die x-Achse zeigt die Extraktionszeit in h; die y-Achse die Reduktion des Hexanal-Gehaltes in % bezogen auf trockenem Ausgangsstoff;
• Fig. 6 die Hexanal-Gehalt-Reduktion bei 110°C Extraktionstemperatur. Die x-Achse zeigt die Extraktionszeit in h; die y-Achse die Reduktion des Hexanal-Gehaltes in % bezogen auf trockenem Ausgangsstoff.

Further features of the invention result from the claims, the figures and the description of the figures. The features and combinations of features mentioned above in the description, as well as the features and combinations of features 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 going beyond the scope of the invention leaving. The invention is therefore also to be considered to include and disclose embodiments that are not explicitly shown and explained in the figures, but that result from the explained embodiments and can be generated by separate combinations of features. Versions and combinations of features are also to be regarded as disclosed which therefore do not have all the features of an originally formulated independent claim. Furthermore, embodiments and combinations of features, in particular through the embodiments presented above, are to be regarded as disclosed which go beyond or deviate from the combinations of features presented 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:

• 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;
• 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/kgTM;
• 3 the hexanal content at 110°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/kgTM;
• 4 the hexanal content reduction at 70°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;
• figure 5 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 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.

Because fatty acids as a source of aldehydes, and subsequently source organoleptic impairments of the wood particles, can only be quantified satisfactorily with great effort, the hexanal content of the wood particles after aging was used to assess the extraction success of the tests of this patent. 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 at 90 °C for 72 h and then the hexanal content was determined by 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 delivers comparable values or that the hexanal values for accelerated aging are on average even higher and thus even provide security with regard to of extraction success. Table 1 Analyzed wood particles Hexanal content accelerated aged 72 h at 90 °C in mg/kgDM Hexanal content naturally aged 6M at 20°C in mg/kgTM raw material 11:37 10.62 Extracted wood particles 1 2:14 1.41 Extracted wood particles 2 2:17 1.52 Extracted wood particles 3 2.80 1.74 Extracted wood particles 4 3.32 2.57 Extracted wood particles 5 3.64 2.75 Extracted wood particles 6 1.34 2.72 Extracted wood particles 7 2.35 1.69 Extracted wood particles 8 2.86 2.83

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 for the determination of the extractive substance content of the wood particles in all tests of this patent, not the TAPPI standard T204, but the NREL method NREL/TP-510-42619, which is very similar to T204, was used and ground wood instead of wood Flour was used as the raw material. Table 2 solvent Hexanal content of the starting material in mg/kgDM Hexanal content of the extracted wood particles in mg/kgDM Determined extractive substance content of the extracted wood particles in wt% based on the starting material Average STAFF DEV Average STAFF DEV ethanol 14.07 1:13 < 0.20 - 3.4 ethanol 14.07 1:13 < 0.20 - 3.0 acetone 14.07 1:13 0.32 0.02 3.0 acetone 14.07 1:13 0.27 0.01 2.6

As can be seen in Table 2, the Soxhlet extractions with ethanol differ significantly from those with acetone in the hexanal content, but not significantly in 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 in the hexanal content were specified 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 substance mass (determined as the evaporation residue of the extract) is an important indicator for the solids mass loss of the extractions, since it includes almost the entire extractively removed solids mass - with the exception of a few very volatile compounds. 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, groundwood samples were extracted with three different solvents. In each case 3 g of air-dried groundwood 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 Solvent 1 (24 h) Solvent 2 (24 h) Hexanal content of the starting material in mg/kgDM Hexanal content of the extracted wood pulp in mg/kgDM Determined extractive substance content of the extracted wood particles in wt% based on the starting material cyclohexane - 11:32 2.36 1.0 ethanol cyclohexane 11:32 < 0.20 3.4 ethanol - 11:32 < 0.20 3.1 ethanol - 14.07 < 0.20 3.0 acetone - 14.07 0.32 3.0

Table 3 shows 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 Chemistry4 (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 wood pulp 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 the Figures 1 to 3 the hexanal contents achieved by the extraction at the different extraction temperatures and solvent concentrations are plotted against the extraction time.

the Figures 1 to 3 show that the extraction success with 70 or 90 wt% ethanol is significantly better than that with 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 is also in the Figures 4 to 6 evident. These figures reflect the extraction successes presented in the characters 1 to 3 reflected, 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 with 90 wt% ethanol from 90 °C it was over 95 % has been reduced.

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 Extracted solid mass in wt% (based on the starting material) extraction time in h 0.5 1.0 2.0 4.0 8.0 70℃ 50 wt% EtOH 4.3 4.6 4.4 4.0 3.6 70 wt% EtOH 4.9 5.1 4.8 5.6 4.2 90 wt% EtOH 4.5 5.5 5.7 5.3 6.1 90°C 50 wt% EtOH 3.7 3.5 4.0 4.7 5.1 70 wt% EtOH 4.0 4.4 4.8 4.8 5.4 90 wt% EtOH 5.5 5.6 5.9 5.8 5.6 110ºC 50 wt% EtOH 4.7 4.1 5.3 6.2 6.3 70 wt% EtOH 5.2 6.6 5.7 5.8 7.2 90 wt% EtOH 5.8 5.7 6.8 6.5 6.4

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

The extraction of moist groundwood represents real conditions much better than the extraction of dry groundwood, such as test 1, especially in cardboard production. 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) 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 extraction the ground wood was pressed, washed with ethanol, pressed again and washed again with deionized water before it was dried, aged and analyzed. Table 5 shows the results of these extractions. Table 5 EtOH concentration in wt% extraction conditions Hexanal content of the starting material in mg/kgDM Hexanal content of the extracted wood substance in mg/kgDM Reduction of the hexanal content in relation to the starting material Temperature in °C time in h Average STAFF DEV Average STAFF DEV 60 70 2 11:37 0.18 3.06 1:18 73% 60 70 4 11:37 0.18 2:15 1.00 81% 60 90 2 11:37 0.18 2.60 0.88 77% 60 90 4 11:37 0.18 2.49 1.50 78%

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) in a solvent-water mixture with a solids:extractant ratio of 1:10 w/w and a solvent concentration of 70 wt% extracted in an autoclave at a temperature of 70°C for 4 hours. 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. Table 6 solvent Hexanal content of the starting material in mg/kgDM Hexanal content of the extracted wood substance in mg/kgDM Reduction of the hexanal content in relation to the starting material Evaporation residue of the extract in wt% based on the starting material dry matter Reduction of the A-bietic acid content in relation to the starting material Average STAFF DEV Average STAFF DEV starting material Extracted wood pulp f Ethanol 96 vol% undenatured 14.07 1:13 4.92 0.40 65% 3.6 2.3 41% Ethanol 96 vol% incompletely denatured with butanone 14.07 1:13 2.77 0.04 80% 3.6 2.4 48% acetone 14.07 1:13 3.43 0.04 76% 3.6 2.2 55%

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 substance 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 were 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 chosen here as the key substance for the content of resin acids, a reduction in the content by around 50% is an indication of the clear reduction in resin through the process of this patent.

Experiment 4: Extraction of wet 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) were mixed with a solvent-water mixture consisting of 70 wt% acetone and 30 wt% deionized water 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 Solid: extractant ratio w/w Extraction s time in h Hexanal content of the starting material in mg/kgDM Hexanal content of the extracted wood substance in mg/kgDM Reduction of the hexanal content in relation to the starting material Evaporation residue of the extract in wt% based on the starting material dry matter Reduction of the abietic acid content in relation to the starting material Average STAB W Average STAB W 1:10 4 14.07 1:13 5.83 0.18 59% 2.0 31% 1:15 4 14.07 1:13 2.76 0.15 80% 2.5 54% 1:15 2 7.24 0.03 1:19 0.72 84% - 38% 1:25 2 7.24 0.03 0.94 0.23 87% - 52% 1:10 1 2.44 0.11 0.40 0.04 84% 2.2 - 1:10 2 2.44 0.11 0.40 0.05 84% 1.5 - 1:15 2 2.44 0.11 0.39 0.01 84% 2.5 - 1:25 2 2.44 0.11 0.33 0.01 86% 2.8 -

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: 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 gDM (depending on the solids:extractant ratio) mechanically dewatered groundwood (approx. 25 wt% TSG) were mixed in an extractant-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. as Solvents used were ethanol 96% by volume undenatured (EtOH pure), ethanol 96% by volume incompletely denatured with butanone (EtOH comp.) and acetone. 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 8 lists the results. Table 8 extraction conditions Average increase in mechanical properties Average mass loss through extraction solvent conc. Solvent-medium ratio temp time Stiffness index according to Nm ⁷ /kg ³ Tensile index according to Nm/g Freeness according to °SR EtOH neat 60 wt% 1:10 70℃ 2 hours 3% 25% 3% 2% 90°C 4 hours EtOH neat 70 wt% 1:10 70℃ 2 hours 3% 41% 0% 2% 4 hours 8 hours EtOH pure EtOH comp. acetone 70 wt% 1:10 50℃ 4 hours 4% 27% 6% 2% 1:15 70℃ 90°C

As can be seen in Table 8, the degree of grinding and thus the dewatering of the ground wood pulp hardly changes as a result of the extraction, which, with regard to any further processing (e.g. into cardboard), has the advantage 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 25 and 41% on average, the mass loss due to the evaporation residue of the extract is around 2% very low. 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.

Legend:

• TM = dry matter
• TSG = dry matter content

Preferred embodiments:

1. 1. Verfahren zur Herstellung von Produkten auf Basis von Holz als Rohstoff, dadurch gekennzeichnet, dass Holz in Form von Holzpartikeln einer Extraktionsbehandlung mit einem Extraktionsmittel unterzogen wird, das ein oder mehrere organische Lösungsmittel oder ein organisch-wässriges Gemisch des oder der Lösungsmittel mit Wasser umfasst, wobei der Gehalt an Fettsäuren in den Holzpartikeln durch die Extraktionsbehandlung der Holzpartikel mit dem Extraktionsmittel um mindestens 70 % verringert wird, gemessen als Hexanal-Gehalt in Gew.-% nach beschleunigter Alterung für 72 h bei 90°C, jedoch der Gehalt an Cellulose, Hemicellulosen und Lignin bei dieser Extraktionsbehandlung im Wesentlichen erhalten wird.
2. 2. Verfahren nach Ausführungsform 1, dadurch gekennzeichnet, dass die Holzpartikel in einer Größe von unter 5 cm vorliegen, wobei die Partikelgröße vorzugsweise durch eine Siebung mittels Quadratmaschensieb ermittelt wird, insbesondere mittels Quadratmaschensieb mit einer Maschenweite von 5 cm oder weniger.
3. 3. Verfahren nach Ausführungsform 1 oder 2, dadurch gekennzeichnet, dass die Holzpartikel in Form von Fasern, Spänen, Strands, Hackschnitzel oder Mischungen davon vorliegen.
4. 4. Verfahren nach einer oder mehreren der Ausführungsformen 1 bis 3, dadurch gekennzeichnet, dass die Holzpartikel durch mechanischen und/oder thermischen und/oder chemischen Aufschluss aufgefasertes Holz sind.
5. 5. Verfahren nach einer oder mehreren der Ausführungsformen 1 bis 4, dadurch gekennzeichnet, dass die Holzpartikel Holzfasern mit mittleren Faserlängen zwischen 0,5 und 2 mm und mittleren Faserdurchmessern zwischen 10 und 50 µm sind, wobei sich die mittlere Faserlänge sowie der mittlere Faserdurchmesser auf das Längen-Mittel, bestimmt mittels optischer Messung der suspendierten Fasern, beziehen.
6. 6. Verfahren nach einer oder mehreren der Ausführungsformen 1 bis 5, dadurch gekennzeichnet, dass der Lösungsmittelanteil des organisch-wässrigen Lösungsmittel-Gemisches im Extraktionsmittel, bestimmt als Konzentration der flüssigen Phase des Extraktes, aus 0 - 95 Gew.-% Ethanol, vorzugsweise 50 - 90 Gew.-% Ethanol, 0 - 99 Gew.-% Aceton, vorzugsweise 30 - 90 Gew.-% Aceton, 0 - 70 Gew.-% n-Propanol, 0-85 Gew.-% Iso-Propanol und/oder 0 - 99 Gew.-% Methanol besteht.
7. 7. Verfahren nach einer oder mehreren der Ausführungsformen 1 bis 6, dadurch gekennzeichnet, dass das Verhältnis von Extraktionsmittel zu Feststoff- Trockensubstanz 5:1 - 25:1 (w/w), vorzugsweise 8:1 - 17:1 (w/w) beträgt.
8. 8. Verfahren nach einer oder mehreren der Ausführungsformen 1 bis 7, dadurch gekennzeichnet, dass die Extraktionsbehandlung bei einer Extraktions-Temperatur von 20 - 150 °C, vorzugsweise 40 - 120 °C, insbesondere 50 - 110 °C, erfolgt.
9. 9. Verfahren nach einer oder mehreren der Ausführungsformen 1 bis 8, dadurch gekennzeichnet, dass die Extraktionsbehandlung bei einem absoluten Extraktionsdruck von 1 - 5 bar, vorzugsweise 1 - 1,49 bar, erfolgt.
10. 10. Verfahren nach einer oder mehreren der Ausführungsformen 1 bis 9, dadurch gekennzeichnet, dass die Extraktionsbehandlung während einer Extraktionszeit von 10 min - 8 h, vorzugsweise 30 min - 7 h, insbesondere 1 - 5 h, erfolgt.
11. 11. Verfahren nach einer oder mehreren der Ausführungsformen 1 bis 10, dadurch gekennzeichnet, dass das Verfahren zur Herstellung von Karton, Papier, Holzfaserplatten, Spanplatten, Gebrauchsgegenständen, Medizinprodukten, insbesondere zur Herstellung von Karton verwendet wird.
12. 12. Verfahren nach einer oder mehreren der Ausführungsformen 1 bis 11, dadurch gekennzeichnet, dass die Extraktionsbehandlung ausgewählt ist aus:
    • Behandlung mit Ethanol in einer Konzentration von zumindest 65 Gew.-% bei zumindest 65°C für einen Zeitraum von zumindest 3 h;
    • Behandlung mit Ethanol in einer Konzentration von zumindest 65 Gew.-% bei zumindest 85°C für einen Zeitraum von zumindest 30 min;
    • Behandlung mit Ethanol in einer Konzentration von zumindest 70 Gew.-% bei zumindest 105°C für einen Zeitraum von zumindest 30 min; oder
    • Behandlung mit Ethanol in einer Konzentration von zumindest 45 Gew.-% bei zumindest 105°C für einen Zeitraum von zumindest 5 h.
    • Behandlung mit Aceton in einer Konzentration von zumindest 50 Gew.-% bei zumindest 40 °C für einen Zeitraum von zumindest 30 min.
13. 13. Verfahren nach einer oder mehreren der Ausführungsformen 1 bis 12, dadurch gekennzeichnet, dass die Behandlung mit dem Extraktionsmittel als Batch, kontinuierliche oder semi-kontinuierliche Extraktion durchgeführt wird, vorzugsweise mit einer Teilverweilzeit von maximal 1h pro Extraktionsschritt.
14. 14. Verfahren nach einer oder mehreren der Ausführungsformen 1 bis 13, dadurch gekennzeichnet, dass bei der Extraktionsbehandlung der Gehalt an Cellulose, Hemicellulosen und Lignin um weniger als 10 %, vorzugsweise um weniger als 5 %, insbesondere um weniger als 4 %, verringert wird, wobei diese Verringerung vorzugsweise als extrahierte Feststoffmasse, bezogen auf den Ausgangsstoff, die Holzpartikel, ermittelt wird.
15. 15. Verfahren nach einer oder mehreren der Ausführungsformen 1 bis 14, dadurch gekennzeichnet, dass die Holzpartikel ausgewählt sind aus Nadelholzpartikel, vorzugsweise Fichtenholzpartikel, Tannenholzpartikel, Kiefernholzpartikel, oder Lärchenholzpartikel; Laubholzpartikel, insbesondere Buchenholzpartikel, Pappelholzpartikel, Birkenholzpartikel, oder Eukalyptusholzpartikel; oder Mischungen davon.
16. 16. Verfahren nach einer oder mehreren der Ausführungsformen 1 bis 15, dadurch gekennzeichnet, dass die Holzpartikel während der Behandlung mit dem Extraktionsmittel durchmischt werden.
17. 17. Verfahren nach einer oder mehreren der Ausführungsformen 1 bis 16, dadurch gekennzeichnet, dass die Holzpartikel nach der Behandlung mit dem Extraktionsmittel abgepresst werden, um das Extraktionsmittel zu entfernen.
18. 18. Verfahren nach einer oder mehreren der Ausführungsformen 1 bis 17, dadurch gekennzeichnet, dass die Holzpartikel nach der Behandlung mit dem Extraktionsmittel ein- oder mehrmals mit einem Extraktionsmittel gereinigt, vorzugsweise mit einem organisch-wässrigen Lösungsmittel mit einer ähnlichen oder gleichen Konzentration wie die des Extraktionsmittels, gereinigt werden.
19. 19. Verfahren nach einer oder mehreren der Ausführungsformen 1 bis 18, dadurch gekennzeichnet, dass das Extraktionsmittel durch ein- oder mehrmalige Waschung mit Wasser oder Trocknung, vorzugsweise durch eine Trocknung, aus den Holzpartikeln entfernt wird.
20. 20. Verfahren nach einer oder mehreren der Ausführungsformen 1 bis 19, dadurch gekennzeichnet, dass der Gehalt an Fettsäuren in den Holzpartikeln durch Extraktion der Holzpartikel mit dem Extraktionsmittel um mindestens 75 %, vorzugsweise um mindestens 80 %, insbesondere um mindestens 90 %, verringert wird, gemessen als Hexanal-Gehalt in Gew.-% der Holzpartikel im Ausgangsmaterial im Vergleich zu den extrahierten Holzpartikel nach beschleunigter Alterung für 72 h bei 90°C.
21. 21. Verfahren nach einer oder mehreren der Ausführungsformen 1 bis 20, dadurch gekennzeichnet, dass der Gehalt an Fettsäuren in den Holzpartikeln durch Extraktion der Holzpartikel mit dem Extraktionsmittel auf einen Gehalt von unter 2 mg/kg Trockenmasse, vorzugsweise von unter 1 mg/kg Trockenmasse, insbesondere von unter 0,5 mg/kg Trockenmasse, verringert wird, gemessen als Hexanal-Gehalt als Massenanteil der extrahierten Holzpartikel nach beschleunigter Alterung für 72 h bei 90°C.
22. 22. Verfahren nach einer oder mehreren der Ausführungsformen 1 bis 21, dadurch gekennzeichnet, dass mit der Extraktion neben den Fettsäuren auch Harzsäuren extrahiert werden.
23. 23. Verfahren nach einer oder mehreren der Ausführungsformen 1 bis 22, dadurch gekennzeichnet, dass die mit dem Extraktionsmittel extrahierten Fettsäuren, Harzsäuren und/oder gegebenenfalls weitere Extraktstoffe einem weiteren Aufreinigungsverfahren zugeführt werden.
24. 24. Verfahren nach einer oder mehreren der Ausführungsformen 1 bis 23, dadurch gekennzeichnet, dass den Holzpartikel keine Komplexbildner, insbesondere Komplexbildner ausgewählt aus mehrwertigen und polyfunktionellen Carbonsäuren, Aminomethylcarbonsäuren, Aminomethyl-phosphonsäuren und deren Verbindungen, EDTA, DTPA EGTA, EDDS und deren Salzen, Polyphenolen, Tanninen, Aminosäuren, Peptiden, Proteinen, Polycarboxylaten, Phosphaten, Polyphosphaten, Phosphonsäuren, Polyphosphonaten, phosphatierten, phosphonylierten, sulfatierten und sulfonierten Polymeren, im Verlauf des Extraktionsverfahrens, insbesondere im Verlauf des gesamten Herstellungsverfahrens für die aus den Holzpartikeln hergestellten Produkte, zugesetzt werden.
25. 25. Verfahren nach einer oder mehreren der Ausführungsformen 1 bis 24, dadurch gekennzeichnet, dass das Extraktionsmittel sowie gegebenenfalls verwendete Waschflüssigkeiten, insbesondere Wasser, für eine Wiederverwendung regeneriert werden.
26. 26. Verfahren nach einer oder mehreren der Ausführungsformen 1 bis 25, dadurch gekennzeichnet, dass durch die Extraktionsbehandlung zusätzlich zur Reduktion des Hexanal-Gehaltes auch die mechanische Festigkeit der extrahierten Holzpartikel, gemessen als Tensile Index von Probeblättern in Nm/g, um mindestens 10 %, vorzugsweise um mindestens 15 %, insbesondere um mindestens 25 %, erhöht wird, wobei sich der Mahlgrad, gemessen in °SR, dabei um weniger als 10 % ändert.

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

1. 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 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 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. 2. Method according to embodiment 1, characterized in that the wood particles are less than 5 cm in size, 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. 3. The method according to embodiment 1 or 2, characterized in that the wood particles are in the form of fibers, chips, strands, wood chips or mixtures thereof.
4. 4. The method according to one or more of embodiments 1 to 3, characterized in that the wood particles are wood that has been fiberized by mechanical and/or thermal and/or chemical digestion.
5. 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, the average fiber length and the average fiber diameter being based on the average length, determined by optical measurement of the suspended fibers.
6. 6. The method according to one or more of embodiments 1 to 5, 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.
7. 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 ) amounts to.
8. 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. 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.
10. 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. 11. The method according to one or more of embodiments 1 to 10, characterized in that the method is used for the production of cardboard, paper, wood fiber boards, chipboard, commodities, medical products, in particular for the production of cardboard.
12. 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 65% by weight at at least 65°C for a period of at least 3 hours;
    • Treatment with ethanol at 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.
13. 13. The method according to one or more of embodiments 1 to 12, characterized in that the treatment with the extractant 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. 14. The method according to one or more of embodiments 1 to 13, characterized in that the content of cellulose, hemicelluloses and lignin is reduced by less than 10%, preferably by less than 5%, in particular by less than 4% during the extraction treatment , This reduction preferably being determined as the extracted solid mass, based on the starting material, the wood particles.
15. 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. 16. The method according to one or more of embodiments 1 to 15, characterized in that the wood particles are mixed during the treatment with the extractant.
17. 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 extractant in order to remove the extractant.
18. 18. The method according to one or more of embodiments 1 to 17, characterized in that the wood particles after treatment with the extractant once or several times with a Extractant cleaned, preferably with an organic aqueous solvent having a similar or the same concentration as that of the extractant cleaned.
19. 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.
20. 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 is reduced by at least 75%, preferably by at least 80%, in particular by at least 90%, by extracting the wood particles with the extraction agent , 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. 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 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 below 0.5 mg/kg dry matter, measured as hexanal content as mass fraction of the extracted wood particles after accelerated aging for 72 h at 90°C.
22. 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 with the extraction.
23. 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. 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, polyphosphates, phosphonic acids, polyphosphonates, phosphated, phosphonylated, sulfated and sulfonated polymers, during the Extraction process, especially in the course of the entire manufacturing process for the products made from the wood particles, are added.
25. 25. The method according to one or more of embodiments 1 to 24, characterized in that the extractant and any washing liquids used, in particular water, are regenerated for reuse.
26. 26. The 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 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%.

Claims (14)

Process for the manufacture of products based on wood as 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 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 substantially preserved in this extraction treatment. A method according to claim 1, characterized in that the wood particles are less than 5 cm in size, the particle size preferably being determined by screening using a square mesh sieve, the wood particles preferably being in the form of fibres, chips, strands, chips or mixtures thereof . Method according to Claim 1 or 2, characterized in that the wood particles are wood that has been broken down into fibers by mechanical and/or thermal and/or chemical digestion, in particular wood fibers with average fiber lengths between 0.5 and 2 mm and average fiber diameters between 10 and 50 µm, where the average fiber length and the average fiber diameter relate to the average length, determined by optical measurement of the suspended fibers. Process according to one or more of Claims 1 to 3, 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 % 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. 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 expressed as extracted solid mass, based on the starting material , the wood particles, is determined. Method according to one or more of Claims 1 to 5, characterized in that the wood particles are selected from coniferous wood particles, preferably spruce wood particles, fir wood particles, pine wood particles or larch wood particles; Deciduous wood particles, in particular beech wood particles, poplar wood particles, birch wood particles, or eucalyptus wood particles; or mixtures thereof. Method according to one or more of Claims 1 to 6, characterized in that after the treatment with the extraction agent, the wood particles are cleaned one or more times with an extraction agent, preferably with an organic-aqueous solvent having a similar or the same concentration as that of the extraction agent, getting cleaned. 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 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. 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 below 0.5 mg/kg dry matter, measured as hexanal content as mass fraction of the extracted wood particles after accelerated aging for 72 h at 90°C. 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. Process according to one or more of Claims 1 to 10, 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. Method according to one or more of Claims 1 to 11, characterized in that the wood particles have 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, polyphosphates, 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. Process according to one or more of Claims 1 to 12, characterized in that the extraction agent and any washing liquids used, in particular water, are regenerated for reuse. The method according to one or more of claims 1 to 13, 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 is increased by at least 15%, in particular by at least 25%, with the freeness, measured in °SR, changing by less than 10%.

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