EP2181818A2 - Method for manufacturing wood fibre substances and wood fibre substances with lower emissions of volatile VOC - Google Patents

Abstract

Producing wood fiber materials with reduced emission of volatile organic compounds comprises chopping wood, cleaning, plasticizing the chopped wood under pressure and temperature and fraying in a refiner and coating and pressing wood fibers, where unchopped and/or chopped wood is contacted with a formulation containing a compound for adjusting neutral to alkaline pH value comprising e.g. alkali- and alkaline earth-carbonates, and a complexing agent comprising e.g. polyvalent and polyfunctional carboxylic acids aminomethyl carboxylic acids and aminomethyl phosphonic acids. Producing wood fiber materials with reduced emission of volatile organic compounds comprises chopping wood, cleaning, plasticizing the chopped wood under pressure and temperature and fraying in a refiner and coating and pressing wood fibers, where unchopped and/or chopped wood is contacted with a formulation containing at least a compound for adjusting neutral to alkaline pH value comprising alkali- and alkaline earth-carbonates, -phosphates, -dihydrogen phosphates, -hydrogen phosphates, -oxides, -hydroxides, or -silicates, and at least a complexing agent comprising polyvalent and polyfunctional carboxylic acids, aminomethyl carboxylic acids, aminomethyl phosphonic acids, ethylenediaminetetraacetic acid, diethylene triamine pentaacetic acid, ethylene glycol tetraacetic acid, ethylenediamine-N,N'-disuccinic acid or its salts, polyphenols, tannins, amino acids, peptides, proteins, polycarboxylates, phosphates, polyphosphates, phosphonic acids, polyphosphonates, or phosphated, phosphonylated, sulfated or sulfonated polymers. An independent claim is included for a wood fiber material made of plasticized fatty acid ester containing wood or wood particles, where: the wood fiber material exhibits no off-odor caused by furfural and degradation products of fatty acid esters and fatty acids, such as propanal, hexanal, nonanal, 2-octenal, 2-heptenal, 2-decenal, octanal, propionic acid, butyric acid or hexanoic acid; the wood fiber material, after 28 days test period under committee for the health-related evaluation of building products- or Natureplus(RTM: Eco-friendly volatile organic compound-free inks support for protecting nature, earth and health)-test conditions, no unsaturated aldehydes from the reduction of fatty acid esters and fatty acids at a concentration of greater than 5 mu g/m 3>, and no furfural at a concentration of greater than 10 mu g/m 3>are emitted and exhibits total emission of aldehydes, which lies at below 20 mu g/m 3>; and the wood fiber material contains a complexing agent at a concentration of at least 0.1 mg/g.

Description

The invention relates to processes for the production of wood fiber materials and wood fiber materials from wood fibers, which are obtained after plasticization of wood and have a reduced emission of volatile organic compounds (VOC), in particular aliphatic and aromatic aldehydes, in particular hexanal and furfural.

Wood fiber materials are z. B. so-called medium-density fiberboard (MDF plates), high-density fibreboard (HDF plates), fiber, Faserdämmplatten which are made of wood fibers by pressing with or without binder. These wood-based materials are used in a wide variety of areas. In Germany, mainly pine and spruce are used for such wood materials, while only up to about 15% hardwoods are used.

Wood fiber boards are usually produced in a continuous process. Crushed wood (wood chips) is washed, optionally preheated and plasticized in a cooking aggregate to temperatures up to 200 ° C, corresponding to 16 bar pressure. After that, these woodchips get into a refiner, where they are frayed between grinding discs and a metal tube, the so-called blowline, discharged. Here, a part of the water is discharged as steam, so that the wood fibers partially dry. At the same time the task of binders can take place here. In the main, these are urea-formaldehyde resins, urea-melamine-formaldehyde resins or isocyanates, which are applied together with other additives. The wood fibers then pass through a dryer. Subsequently, the task of said binder takes place.

The glued wood fibers are poured into mats (or fiber fleece), partially precompressed at ambient temperature and then pressed in hot presses to plates.

In addition to the physico-mechanical properties of these materials, residential hygiene parameters are increasingly influencing the possible uses of the materials prevail. This applies in particular to products that are used in the interior. These include z. As "classic" wood materials for partitions in house building and interior, products for the floor area, furniture and panels or insulation materials made of wood fibers.

The basis for the hygienic evaluation of such products are the concentrations of volatile organic compounds (VOC) determined under standardized conditions (DIN ISO 16000 parts 9 to 11 in conjunction with ISO 16000 parts 3 and 6).

The evaluation of these VOCs can be done as a sum parameter (total VOC, TVOC) and, depending on voluntary agreements (eco-labels and other quality labels), a certain concentration of VOCs should not be exceeded. Furthermore, "dangerous" substances, which include in particular the CMT substances of category 1 and 2, are to be excluded. Since October 2004, the emission of construction products has been toxicologically assessed according to the AgBB scheme based on NIK values (lowest concentration of interest). Exceeding the toxicological limit value leads to a non-admission of construction products subject to approval or to a restriction of the distribution of such wood-based materials in the area which is currently not subject to approval. For example, a wood fiber insulation material tested according to AgBB criteria emitted furfural in the amount of 57 μg / m ³ after a test period of 28 days.

All woods contain the main constituents cellulose, lignin and hemicelluloses as well as minor constituents, such as terpenes, salts and lipids, which include the fatty acids or their esters.

The proportions are different for individual woods and the composition of the hemicelluloses is different in particular between coniferous and hardwoods. The hemicelluloses contain varying amounts of acetyl groups, which are both acidic and basic hydrolyzable. This process leads to the formation of acetic acid in different processes. In addition, there are also relevant amounts of formic acid, which is a 10 times stronger acid than acetic acid.

The formation of furfural (NIK value 20 mg / m ³ ) takes place starting from the hemicelluloses in a multistage, continuously acid-catalyzed process.

In the first step, the hemicelluloses are hydrolyzed to the simple sugars, so that therefore pentoses (C ₅ sugar - xylose, arabinose) and hexoses (C ₆ - sugar - glucose, mannose, galactose, rhamnose) and uronic acids (glucuronic acid, galacturonic acid) arise. The acid-catalyzed dehydration of pentoses, uronic acids and hexoses produces furfural or hydroxymethylfurfural (HMF).

With increasing temperature and increasing time furfural increasingly forms from the pentoses of the wood. The reaction is catalyzed acid, so depends on the pH and the acidity, so z. B. from the acetyl group content, from.

Selected wood species such as pine, birch, linden or poplar contain higher levels of fatty acid esters, which can be broken down into aldehydes and organic acids during the manufacture of products, without this being able to be prevented by changing technological parameters. Own investigations have shown that z. B. in birch 2315 mg / kg, linden 7544 mg / kg or pine 5807 mg / kg of fatty acids may be included. In addition, larger variations in the levels of fatty acids and triglycerides depending on the location, tree age, height section of the individual tree and between core and sapwood.

Both classes of compounds, aldehydes and organic acids, are odor-intensive. For consumers, products with increased emissions of odor-intensive compounds have a negative impact, causing complaints and also adverse health effects, solely due to the smell. The odor thresholds in these compounds may be 20 μg / m ³ and below.

Wood-based materials that emit in particular furfural, saturated and unsaturated aldehydes, organic acids and other odorous compounds, are difficult to deduct.

Out DE 10 2004 050 278 A1 is a process for the preparation of light or white wood materials by bleaching known in the aqueous, 5 to 40 wt.% Wood fiber dispersions are continuously treated in countercurrent towers at temperatures of 90 to 150 ° C and pressures up to 3 bar with aqueous solutions or dispersions of bleach. In this case, in the presence of complexing agents, such as EDTA, worked to avoid the degradation of bleach by transition metal ions.

Especially with MDF / HDF boards, bleaching is done during plate making. The bleaches are added to the wood chips in the pre-heater or in the cooker. In this case, complexing agents are added.

DE 696 28 900 T2 describes a method of preserving plywood and chipboard against deterioration and mold, in which complexing agents are mixed into the adhesive or adhesive compound.

DE 28 18 320 A1 discloses a method of treating wood chips in which the wood chips are impregnated with a solution containing complexing agents and alkali and a heavy metal reducing agent prior to delignification or defibration treatment. Part of the impregnation solution is deposited before the delignification or defibration treatment.

Methods are known for reducing the VOC emissions from wood and wood-based materials.

DE 33 44 239 C2 discloses the use of ammonium carbonate [(NH ₄ ) ₂ CO ₃ ], - hydrogen carbonate [NH ₄ HCO ₃ ], urea, thiourea, melamine and dicyandiamide to reduce the emission of formaldehyde from particleboard.

WO 2006/039914 A1 describes the use of alkali metal hydroxides (especially of NaOH), alkali metal carbonates (especially of Na ₂ CO ₃ ), alkali metal sulfites (especially of Na ₂ SO ₃ ), alkali phosphates (especially of Na ₃ PO ₄ ), mixtures of the aforementioned compounds and ammonia gas (NH ₃ ) to reduce emissions of VOC from wood-based materials, especially from OSB. In the practical examples, it is possible to reduce the release of terpene; in heartwood, there is also a certain reduction in the release of products of oxidative fatty acid cleavage (aldehydes).

WO 2006/032267 A1 describes, inter alia, the use of alkaline compounds and antioxidants for the production of emission-reduced OSB from high-fat softwoods. The objective is to reduce emissions of fatty acid degradation products.

WO 2006/039914 A1 describes the use of alkali hydroxides, alkali metal carbonates, alkali metal sulfites, alkali metal phosphates, mixtures of the aforementioned compounds as well as gaseous ammonia to reduce emissions of VOC from wood-based materials, especially from OSB.

DE 10 2006 020 612 A1 describes the use of monounsaturated compounds (Ene) in combination with catalysts of the Diels-Alder reaction. Through certain combinations here a reduction of the release of terpenes is achieved by these to a significant extent on the Diels-Alder reaction to high molecular weight and so that virtually non-volatile compounds react.
Phenol, resorcinol and their precondensates with formaldehyde (including mixtures) are additionally used for this purpose.

CA 2034952 C describes the subsequent protection of wood surfaces against light-induced degradation. Protection is achieved by applying to a primer a coating of a synthetic resin containing sterically hindered phenols. In one embodiment, the primer may consist of a phenolic antioxidant dissolved in an organic solvent.

DE 3911 091 A1 discloses an impregnating solution which neutralizes or sets existing in wood or pulp organic acids, formaldehyde and other aldehydes and which causes a hydrophobization of the wood surface.

The neutralization of organic acids has the purpose to prevent corrosion of metals that are processed together with wood / wood materials. The treatment is intended for woods used for the production of packaging materials.

DD 257 607 A1 discloses a process for chemically dyeing veneers with soda solution. In this method, veneer, which is made of steamed wood by washing and drying, dyed with alkaline solutions such as sodium carbonate solution at elevated temperature in the dipping process.

DE 3 787 967 T2 relates to a method for protecting wood, in particular to prevent staining and decay and increase the fire resistance. This is achieved by superficially treating the wood with a solution containing at least sodium carbonate and sodium borate.

US 3,282,313 A relates to a method for plasticizing dried solid wood. The wood is treated with liquid or gaseous ammonia. Ammonia breaks down hydrogen bonds in the polysaccharides of the wood, resulting in plasticization of the wood.

DD 284 836 A5 discloses a process for the preparation and use of a phenolic drug for the treatment of mycologically stained woods. For the preparation of the active ingredient bark extracts are treated with industrial enzymes. The active ingredient is a wood preservative made from bark.

The previously known methods are inadequate in particular for reducing the furfural content of wood fiber materials made of wood fibers.

The object of the invention is therefore the provision of wood fiber materials with reduced emission of VOC, in particular with reduced delivery of furfural and reduced release of aldehydes from the oxidative degradation of fatty acids and fatty acid esters.

According to the invention the object is achieved by a process for the production of wood fiber materials with reduced emission of volatile organic compounds (VOC), in which crushed wood, cleaned, the so-shredded wood is plasticized under pressure and temperature and defibrated in the refiner and then glued the wood fibers and be pressed, with the uncrushed and / or crushed wood with a formulation containing at least one compound for adjusting a neutral to basic pH and at least one complexing agent, wherein the compounds for adjusting a neutral to basic pH are selected from alkali metal and alkaline earth metal carbonates, alkali metal and alkaline earth bicarbonates, phosphates, dihydrogen phosphates, hydrogen phosphates, oxides, hydroxides, and silicates and wherein the complexing agents are 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.

In addition, the formulation may contain antioxidants for additional antioxidant protection of fats. Antioxidants are phenolic compounds and reductones, especially extracts of bark, wood and other parts of tannin-containing plants, 2,6-di-tert-butyl-4-methylphenol (BHT), butylhydroxyanisole (BHA), gallic acid, salts and esters of gallic acid, z. As propyl gallate, octyl gallate, decyl gallate ascorbic acid and its salts, isoascorbic acid and its salts, 2,3-dihydroxy-2-cyclopentenone (reductic acid) but also hydroxypropanedial.

For the production of wood fiber materials according to the invention no bleaching, delignifying, oxidizing or reducing chemicals are used. Furthermore, no pressing liquid formulation takes place before the plasticization of wood or wood chips.

Wood fiber materials according to the invention are medium density fibreboard (medium density fibreboard, MDF boards), wood fiber boards, fiber insulation boards but also wood fiber molded parts.

The wood fiber materials are preferably produced from pine, spruce, birch and / or poplar wood, particularly preferably from pine, birch and poplar wood.

By the method according to the invention, wood fiber materials from pine, spruce-birch, or poplar wood can be produced, which have a reduced release of furfural and have no increased or even reduced emissions of degradation products of fatty acids and fatty acid esters.

The wood fiber materials according to the invention have no off-odor. Malodor means an odor impression, which is generally perceived as unpleasant and leads to product rejection or irritation.

The wood fiber materials according to the invention of plastified fatty acid ester-containing woods or wood particles are characterized in that the wood fiber material is not affected by furfural and by degradation products of the fatty acid esters and fatty acids such as propanal, hexanal, nonanal, 2-octenal, 2-heptenal, 2-decenal, octanal, propionic acid, Buttersäure or hexanoic acid caused bad odor that the wood fiber material after 28 days of testing under AgBB or Natureplus® test conditions no unsaturated aldehydes from the degradation of fatty acid esters and fatty acids in a concentration greater than 5μg / m ³ and no furfural in a concentration greater than 10μg / m ³ and has total emissions of aldehydes which are below 20 μg / m ³ , and that the wood fiber material contains complexing agents in a concentration of at least 0.1 mg / g.

In addition, the wood fiber material may contain antioxidants at a concentration of at least 0.1 μg / g ascorbic acid equivalents.

Wood fiber materials according to the invention are medium density fibreboard (medium density fibreboard, MDF boards), wood fiber boards, fiber insulation boards but also wood fiber molded parts.

The wood fiber materials preferably consist of pine, spruce, birch and / or poplar wood, particularly preferably pine, birch and poplar wood.

Decomposition products of the fatty acid esters are, in particular, organic acids such as propionic, butanoic and hexanoic acids and aldehydes such as propanal, butanal, pentanal, hexanal, heptanal, octanal, nonanal, 2-butenal, 2-octenal, 2-heptenal, 2-decenal or 2- octenal. These degradation products of fatty acid esters and fatty acids cause a bad smell. The odor thresholds in the saturated compounds are 20 μg / m ³ and below. Unsaturated aldehydes, such as. As 2-octenal, 2-decenal, 2-heptenal or 2-Nonenal set the Wood fiber materials according to the invention are free in maximum in a total concentration of 5 ug / m ³ .

Currently, the wood plasticization at higher temperatures (> 150 ° C) and thus higher digestion pressures (> 5 bar) is made, as this can reduce the use of mechanical and thus electrical energy in the refiner. However, this has the disadvantage that the decomposition reactions described proceed expeditiously and thus, in particular, the formation of furfural is promoted. This circumstance is counteracted by the invention.

According to the method of the invention, the debarked woods and / or wood chips are contacted with a formulation containing at least one compound for adjusting a neutral or alkaline pH and at least one complexing agent.

According to a preferred embodiment of the invention is carried out in the plasticization at a pressure of 8 to 16 bar and a temperature of 160 to 205 ° C.

According to the invention, the formulation contains compounds for adjusting a neutral to basic pH with a concentration of 0.1 to 50 g / kg wood or wood chips, preferably 1 to 10 g / kg and complexing agent with a concentration of 0.01 to 50 g / kg wood or wood chips, preferably 0.1 to 5 g / kg. In addition, the formulation may contain antioxidants or free-radical scavengers in a concentration of 0.01 to 50 g / kg, preferably from 0.1 to 5 g / kg wood or wood chips.

Essential to the invention with regard to avoiding the formation of furfural and the aldehydes from the fatty acid degradation is a common application of an alkaline-reacting compound and a complexing chemical or additionally with an antioxidant to the starting material wood or woodchips at neutral to basic pH.

The formulation may be in solid form, so z. B. as a powdery product or as a liquid formulation, preferably in aqueous solution, are applied. A Application as a solid can be done in very different ways, such. B. by blowing into technical equipment or by sprinkling, z. B. on conveyors.

An application as a liquid formulation can also be done in very different ways, such. As by Auf-, pouring, spraying, misting, dipping, spraying, flooding, with and without the use of overpressures or press-fit, especially in plants that are operated under pressure.

The contacting takes place before, but at the latest during the plasticization of the wood, so z. B. in storage facilities for wood chips (bunkers o. Ä.) On conveyors, in feeders of the digester.

Since the partial steps of the furfural formation, hydrolysis of polysaccharides and dehydration, are catalysed acidic, the addition of alkaline reacting compounds, the pH is shifted, at least temporarily, in the direction of a neutral or basic reaction.

The increase in the pH has the positive side effect of reducing the extraction of heavy metal ions of the metals iron, nickel and chromium from the system parts of the digester and the refiner and thereby reduced conversion of unsaturated fatty acids or their esters with oxygen to aldehydes and acids.

The formation of acetic and formic acid can thereby be accelerated, resulting in a consumption of alkaline chemicals due to salt formation with the acids mentioned. The uronic acids on the hemicelluloses also have a buffer effect. They are partially esterified with methanol, resulting in hydrolysis to release the uronic acids. Other, acid-forming processes can take place.

The unsaturated fatty acids of woodchips can react with oxygen due to the presence of heavy metal ions. This reaction leads to oxidative degradation of the unsaturated fatty acids and ultimately to the formation of volatile aldehydes and also acids.

In order to prevent this process, heavy-metal complexing compounds are added, whereby the emission level of aldehydes from the fatty acid degradation despite alkali use corresponds to the wood pulp without addition of chemicals or is lower.

As alkaline compounds alkali and alkaline earth metal carbonates, alkali and Erdalkalibicarbonate, phosphates, dihydrogen phosphates, hydrogen phosphates, oxides, silicates are used. Preferred are sodium hydroxide, sodium carbonate, sodium bicarbonate, ammonium hydroxide, ammonium carbonate, ammonium bicarbonate, calcium oxide, calcium hydroxide, calcium carbonate, calcium bicarbonate.

• Mehrwertige und polyfunktionelle Carbonsäuren, wie z. B. Citronensäure und Citrate sowie polymere Citronensäure-Derivate, Weinsäure und Tartrate einschließlich polymerer Derivate, Zuckersäuren (monomere, oligo- und polymere), z. B. Gluconsäure, Glucuronsäure, Glucarsäure, Polyglucuronsäure, Gellan, Pektine, Alginate, halbsynthetische carboxylgruppenhaltige Polysaccharidderivate wie Carboxymethylcellulosen oder Carboxymethylstärken.
• Aminomethylcarbonsäuren und ähnliche Verbindungen, auch oligomere und polymere Varianten, vor allem aber Ethylendiamintetraessigsäure (EDTA) und ihre Salze , wie z. B. Dinatrium-ethylendiamin-tetraacetat (Na₂EDTA, Natriumedetat), Tetranatriumethylendiamin-tetraacetat (Na₄EDTA), Calcium-dinatrium-ethylendiamin-tetraacetat (CaNa₂EDTA, E 385), Dieethylentriaminpentaessigsäure (DTPA) und ihre Salze, Nitrilotriessigsäure (NTA), Ethylenglykol-bis(aminoethylether)-N,N'-tetraessigsäure (EGTA), Ethylendiamindibernsteinsäure (EDDS), Iminodibernsteinsäure Natriumsalz (IDS Na-Salz).
• Aminomethylphosphonsäuren (AMPA) und ähnliche Verbindungen, auch oligomere und polymere Varianten, vor allem aber Hexaethylendiamin-tetra-methylenphosphonsäure (HDTMP), Ethylendiamin-tetra-methylenphosphonsäure (EDTMP), Amino-tris-methylenphosphonsäure (ATMP), Ethylendiamin-tetra-methylenphosphonsäure (DTPMP), Amino-tris-methylenphosphonsäure (NTMP), Glyphosat (N-(Phosphonomethyl)glycin), Aminomethylphosphonsäure (AMPA).
• Polyphenole / Tannine verschiedener Herkunft, auch in chemisch modifizierter Form.
• Aminosäuren / Peptide / Proteine
• Aminosäuren, Peptide und Proteine sind in der Lage, Schwermetalle zu komplexieren. Einige Organismen produzieren zu diesem Zweck spezielle metallbindende Proteine, welche reich an SH-Gruppen sind, also viele Cystein-Reste enthalten, z. B. die Metallothioneine.
• Polyasparaginsäure, chemisch modifizierte Aminosäuren, Peptide und Proteine.
• Polyamine, wie z. B. Polyethylenimin (PEI), Polyvinylamin (PVA) und deren Derivate, vor allem die Carboxymethylderivate. Aminogruppenhaltige Polysaccharide / -derivate wie deacetyliertes Chitin (Poly-2-aminodesoxyglucose) oder Chitin selbst sowie die entsprechenden Monomere, einschliesslich chemisch modifizierte Formen, vor allem veretherte, veresterte, alkylierte und oxidierte Varianten.
• Polyphosphonate, Polyphosphate, Phosphonsäuren, z. B. 1-Hydroxyethan-(1,1-diphosphonsäure) (HEDP), Phosphonobutantricarbonsäure (PBTC), anorganische Phosphate, z. B. Meta-, Di-, Tri- und Polyphosphate, z. B. Pentanatriumtriphosphat.
• Anorganische und organische Polymere, welche anionische Gruppen tragen oder aber in wässrigen Medien zu Anionen dissoziierende Gruppen tragen. Beispiele sind phosphatierte oder sulfatierte Polysaccharide, z. B. phosphatierte oder sulfatierte Stärke, Cellulose, Hemicellulosen. Weitere Beispiele sind Polymere, die Sulfonsäure- oder Phosphonsäurereste enthalten.
• Ionenaustauscher, Zeolithe, synthetische Silikate, Bentonite.

As complexing agents, the following compounds can be used:

• Polyvalent and polyfunctional carboxylic acids, such as. Citric acid and citrates as well as polymeric citric acid derivatives, tartaric acid and tartrates including polymeric derivatives, sugar acids (monomeric, oligomers and polymers), e.g. As gluconic acid, glucuronic acid, glucaric acid, polyglucuronic acid, gellan, pectins, alginates, semisynthetic carboxyl-containing polysaccharide derivatives such as carboxymethylcelluloses or carboxymethyl starches.
• Aminomethylcarbonsäuren and similar compounds, including oligomeric and polymeric variants, but especially ethylenediaminetetraacetic acid (EDTA) and their salts, such as. Disodium ethylenediamine tetraacetate (Na ₂ EDTA, sodium edetate), tetrasodium ethylenediamine tetraacetate (Na ₄ EDTA), calcium disodium ethylenediamine tetraacetate (CaNa ₂ EDTA, E 385), dieethylenetriamine pentaacetic acid (DTPA) and its salts, nitrilotriacetic acid ( NTA), ethylene glycol bis (aminoethyl ether) -N, N'-tetraacetic acid (EGTA), ethylenediamine disuccinic acid (EDDS), sodium iminodisuccinate (IDS Na salt).
• Aminomethylphosphonic acids (AMPA) and similar compounds, including oligomeric and polymeric variants, but especially hexaethylenediamine tetra-methylenephosphonic acid (HDTMP), ethylenediamine-tetra-methylenephosphonic acid (EDTMP), amino-tris-methylenephosphonic acid (ATMP), ethylenediamine-tetra-methylenephosphonic acid ( DTPMP), amino-tris-methylenephosphonic acid (NTMP), glyphosate (N- (phosphonomethyl) glycine), aminomethylphosphonic acid (AMPA).
• Polyphenols / tannins of various origins, also in chemically modified form.
• Amino acids / peptides / proteins
• Amino acids, peptides and proteins are able to complex heavy metals. Some organisms produce for this purpose special metal-binding proteins which are rich in SH groups, that is, contain many cysteine residues, e.g. For example, the metallothioneins.
• Polyaspartic acid, chemically modified amino acids, peptides and proteins.
• Polyamines, such as. As polyethyleneimine (PEI), polyvinylamine (PVA) and their derivatives, especially the carboxymethyl derivatives. Amino-containing polysaccharides / derivatives such as deacetylated chitin (poly-2-aminodeoxyglucose) or chitin itself and the corresponding monomers, including chemically modified forms, especially etherified, esterified, alkylated and oxidized variants.
• Polyphosphonates, polyphosphates, phosphonic acids, eg. 1-hydroxyethane- (1,1-diphosphonic acid) (HEDP), phosphonobutane tricarboxylic acid (PBTC), inorganic phosphates, e.g. As meta-, di-, tri- and polyphosphates, z. B. pentasodium triphosphate.
• Inorganic and organic polymers which carry anionic groups or which carry anion-dissociating groups in aqueous media. Examples are phosphated or sulfated polysaccharides, e.g. As phosphated or sulfated starch, cellulose, hemicelluloses. Further examples are polymers which contain sulfonic acid or phosphonic acid residues.
• Ion exchangers, zeolites, synthetic silicates, bentonites.

Mixtures and combinations of the aforementioned starting materials are also included. The number of combined feedstocks and their mixing ratios are not limited.

Preferred are EDTA, DPTA, the group of AMPA and the aminophosphonates.

The chemicals used can be used as solids, as solutions, preferably aqueous. The concentration ratios depend on the type of wood, the requirement for the final product and other boundary conditions, eg. Eg price. They can be in a very wide range to each other.

Aqueous solutions are used in the range of 0.01% to the respective saturation concentration, preferably at a higher concentration, in order to minimize the energy expenditure for subsequent drying processes.

Reference to subsequent embodiments, the invention is explained in more detail: Embodiment 1

30 kg fresh chips of the wood pine are applied in an open vessel with 2 liters of an aqueous solution of 150 g of NaOH and 50 g of EDTA (disodium salt) and mixed. Subsequently, these pretreated wood chips are introduced into the digester, where the plasticization of the wood is operated at a pressure of 15 bar (corresponding to about 200 ° C.). The residence time is 4 minutes, which is an industry-typical value. The subsequent grinding process in the refiner, however, is of a very short duration.

The moist wood pulp is transported via a blow pipe and dried. 2 samples of dried wood pulp (47 g each) are placed in wire cages (dimensions 20 x 10 x 6 cm) for emission testing. The material density thus obtained is 3.9 kg / m ³ .

Embodiment 2

30 kg fresh chips of the wood species pine are applied in an open vessel with 2 liters of an aqueous solution of 150 g of NaOH and mixed. Subsequently, these pretreated wood chips are introduced into the digester, where the plasticization of the wood is operated at a pressure of 15 bar (corresponding to about 200.degree. C.) becomes. The residence time is 4 minutes, which is an industry-typical value. The subsequent grinding process in the refiner, however, is of a very short duration.

The moist wood pulp is transported via a blow pipe and dried. 2 samples of dried wood pulp (47 g each) are placed in wire cages (dimensions 20 x 10 x 6 cm) for emission testing. The material density thus obtained is 3.9 kg / m ³ .

Embodiment 3

30 kg fresh chips of the wood species pine are applied in an open vessel with 2 liters of an aqueous solution of 150 g of NaOH and mixed. Subsequently, these pretreated wood chips are introduced into the digester, where the plasticization of the wood is operated at a pressure of 15 bar (corresponding to about 200 ° C.). The residence time is 4 minutes, which is an industry-typical value. The subsequent grinding process in the refiner, however, is of a very short duration.

The moist wood pulp is transported via a blow pipe and dried. 2 samples of dried wood pulp (47 g each) are placed in wire cages (dimensions 20 x 10 x 6 cm) for emission testing. The material density thus obtained is 3.9 kg / m ³ .

Embodiment 4

30 kg fresh wood chips of pine are applied in an open vessel with 2 liters of an aqueous solution of 150 g of NaOH and 50 g of EDTA (disodium salt) and with 10 g of finely powdered BHT and mixed. Subsequently, these pretreated wood chips are introduced into the digester, where the plasticization of the wood is operated at a pressure of 15 bar (corresponding to about 200 ° C.). The residence time is 4 minutes, which is an industry-typical value. The subsequent grinding process in the refiner, however, is of a very short duration.

The moist wood pulp is transported via a blow pipe and dried. 2 samples of dried wood pulp (47 g each) are placed in wire cages (dimensions 20 x 10 x 6 cm) for emission testing. The material density thus obtained is 3.9 kg / m ³ .

• Prüfbedingungen:

  Luftwechsel

  1

  Temperatur

  23°C

  Luftfeuchte

  50 %

  Kammervolumen

  0,1 m³

  Probenahme

  nach 1, 3, 7, 14 und 21 Tagen auf TENAX®

  Analytik

  mittels GC-MS

Ergebnisse Variante 1 (NaOH + EDTA) 2 (NaOH) 3 (-) 4 (NaOH + EDTA + BHT) Probe 1 Probe 2 Probe 1 Probe 1 Probe 1 Probe 2 Probe 1 Probe 2 Probenahmetag Furfural [µg/m³] 1 5 10 8 7 15 13 5 9 3 3 5 2 3 17 5 4 5 7 3 2 6 3 2 3 14 0 3 1 4 6 6 1 2 28 1 1 1 2 6 4 0 2 Probenahmetag Hexanal [µg/m³] 1 1 3 17 85 1 1 1 1 3 0 1 58 43 0 0 0 1 7 1 0 1 0 1 0 14 0 1 6 9 1 2 0 0 28 1 1 4 3 1 1 0 0 The wood fibers produced according to embodiments 1-4 are tested in the described embodiment in accordance with DIN ISO 16000-3, -6 and -9 to -11:

• test conditions:

  air exchange

  1

  temperature

  23 ° C

  humidity

  50%

  chamber volume

  0.1 m ³

  sampling

  after 1, 3, 7, 14 and 21 days on TENAX®

  analytics

  by GC-MS

Results variant 1 (NaOH + EDTA) 2 (NaOH) 3 (-) 4 (NaOH + EDTA + BHT) Sample 1 Sample 2 Sample 1 Sample 1 Sample 1 Sample 2 Sample 1 Sample 2 day of sampling Furfural [μg / m ³ ] 1 5 10 8th 7 15 13 5 9 3 3 5 2 3 17 5 4 5 7 3 2 6 3 2 3 14 0 3 1 4 6 6 1 2 28 1 1 1 2 6 4 0 2 day of sampling Hexanal [μg / m ³ ] 1 1 3 17 85 1 1 1 1 3 0 1 58 43 0 0 0 1 7 1 0 1 0 1 0 14 0 1 6 9 1 2 0 0 28 1 1 4 3 1 1 0 0

In Example 3 (without additives) emits significantly more furfural from the wood pulp than when using alkalis (Examples 1, 2 and 4).

In addition, Example 2 (NaOH only) leads to significantly increased emission of aldehydes from the oxidative degradation of fats and fatty acids. As an example, the emission values for the hexanal, the predominantly formed aldehyde, are given. In addition, aldehydes are formed with very low NIK values, eg. For example, 2-octenal, 2-butenal and other unsaturated aldehydes. The, in absolute terms, low emission levels of these aldehydes naturally cause larger measurement errors, which is why the hexanal is a more reliable indicator.

In Example 1, in addition to the alkali, the EDTA disodium salt is used, resulting in a strong suppression of aldehyde formation.

In Example 4, in addition to the alkali, the EDTA disodium salt and the radical scavenger BHT are used, resulting in the strongest suppression of aldehyde formation from the fatty acid degradation of all 4 embodiments.

Claims (10)

Process for the production of wood fiber materials with reduced emission of volatile organic compounds (VOC) in which wood is crushed, cleaned, the wood is crushed under pressure and temperature and plasticized in the refiner and then glued and pressed the wood fibers, characterized in that the uncrushed and / or the comminuted wood is contacted with a formulation containing at least one compound to establish a neutral to basic pH and at least one complexing agent, the compounds being selected to establish a neutral to basic pH of alkali and Alkaline earth carbonates, alkali and alkaline earth bicarbonates, phosphates, dihydrogen phosphates, hydrogen phosphates, oxides, hydroxides, and silicates, and wherein the complexing agents are selected from polyhydric and polyfunctional carboxylic acids, aminomethylcarboxylic acids, aminomethylphosphonic acids and theirs 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. A method according to claim 1, characterized in that the formulation additionally contains antioxidants. A method according to claim 1 or 2, characterized in that the formulation is used in solid or liquid form. Method according to one of claims 1 to 3, characterized in that the contacting of the wood or the wood particles takes place at the latest to their plasticization. Method according to one of claims 1 to 4, characterized in that the wood fiber materials are made of pine, spruce, birch and / or poplar wood. Method according to one of claims 1 to 5, characterized in that the plasticization of the wood is carried out at pressures of 2 to 16 bar. Method according to one of claims 1 to 6, characterized in that there is no preheating of the wood chips before the plasticization of the wood. Wood fiber material made of plasticized fatty acid ester wood or wood particles, characterized in that the wood fiber material by furfural and by degradation products of the fatty acid esters and fatty acids such as propanal, hexanal, nonanal, 2-octenal, 2-heptenal, 2-decenal, octanal, propionic acid, butyric acid, comprises or hexanoic off odor caused that the wood-fiber material after 28 days test period under AgBB or natureplus® test no unsaturated aldehydes from the reduction of the fatty acid ester and fatty acids in a concentration greater than 5 .mu.g / m ³ and no furfural in a concentration greater than 10 ug / m ³ emitted and has total emissions of aldehydes, which are below 20 ug / m ³ and that the wood material contains complexing agent in a concentration of at least 0.1 mg / g. Wood fiber material according to claim 8, characterized in that it contains antioxidants in a concentration of at least 0.1 μg / g ascorbic acid equivalents. Wood fiber material according to claim 8 or 9, characterized in that the wood fiber material consists of pine, spruce, birch and / or poplar wood and is an MDF board or wood fiber board or a Faserdämmplatte or a wood fiber molding.