FORMALDEHYDE-FREE WOOD BINDER

Abstract

The formaldehyde-free binder for cellulose-containing materials contains a polycondensed hydroxyaldehyde resin with an ammonium salt. In particularly preferred embodiments, the resin is obtained in situ from glycerin using hydrogen peroxide. A protein component consisting of animal blood is added. The binder is urea-free and can be used as a one- or two-component binder. It binds materials such as wood, paper, and other natural fibers to form high-quality composite products.<!--endfragment-->

Description

[0001] The invention relates to a formaldehyde-free binder for cellulose-containing materials, in particular for wood and paper, and to an associated composite material product, for example in the form of a board.

[0002] The term "binder" is frequently used for composite materials and refers to a substance or agent that bonds or "connects" different substrates or materials within the composite. The binder for cellulose-containing materials can also be synonymously called an adhesive; it bonds lumpy materials or more extensive substrates adhesively and / or cohesively, including reactively.

[0003] "Cellulose-containing materials" contain cellulose, hemicellulose, holocellulose, or lignocellulose, and therefore also lignin. Cellulose-containing materials include, among others, wood, pulp, straw, bagasse, kenaf, bamboo, sisal, hemp, coconut fiber, and paper, to name just a few. In Europe, wood and paper composite materials are currently the most important.

[0004] The main raw materials for composite products with the aforementioned materials and suitable binders are solid wood, wood chips, sawdust, wood pulp, wood flour, wood pulp, etc., also in the form of recycled materials such as waste wood or waste paper.

[0005] For wood-based composites, amine resins (also called amino resins or aminoplasts), amide resins, and resins of aromatic hydroxy compounds, such as phenolic resins, are used industrially on a large scale. These compounds are provided in the binder as relatively low-molecular-weight, curable resins that harden, among other things, under the influence of heat during processing into composite components. After curing, a thermosetting cross-linking is present. These widely used aminoplastic binder resins are obtained by polycondensation of carbonyl compounds and NH-containing compounds. The carbonyl compounds can be aldehydes or ketones, more commonly aldehydes, and the nitrogen compounds that cross-link them can be very diverse, with the most important resin groups being urea resins (UF), melamine resins (MF), and dicyandiamide resins (DD).Water-based resins – low-molecular-weight condensed, uncured resins of the aforementioned type in aqueous solution – are also called adhesive resins. This invention also primarily relates to binder adhesives, i.e., water-based binders or aqueous binder solutions. These can generally also be used as spray-dried powders in molding compounds.

[0006] Conventional aminoplast-based wood binders have several disadvantages. Curing requires a hardening process that, after activation, occurs within a specific timeframe. This timeframe is difficult to control, making production interruptions problematic. Another significant drawback is the emissions from the finished composite products. Even today, inexpensive and highly effective formaldehyde is widely used, particularly in UF and MF resins, which hold a large market share, despite the well-known emission problems associated with them. To address this issue, attempts are generally made to reduce formaldehyde emissions by binding it so tightly that it cannot escape. Success in this area has been limited.

[0007] Since April 1, 2015, EU Regulation 605 / 2014 has been in force, lowering the emission limits for formaldehyde, classified as a highly carcinogenic substance, in production facilities from 20 mg / m³ to 1 mg / m³. Implementation is expected by August 2017 (REACH Regulation). Binders without formaldehyde emissions are therefore of great interest.

[0008] For a long time, attempts have been made to replace formaldehyde with other aldehydes or ketones. The materials must not be too expensive, and the required material properties must be achievable with the substitute. Rapid setting and good mechanical stability are important.

[0009] Formaldehyde-free resins based on hydroxyaldehydes are known from WO 2015 / 086074 A1, in which a hydroxy monoaldehyde is reacted with an amine, an amide, or an aromatic hydroxy compound. Suitable amines or amides include, in particular, urea, melamine, benzoguanamine, dicyandiamide, acetylenediurea, aminotriacin, diaminoalkanes or diamidoalkanes, and polyacrylamide. Glycolaldehyde or glyceraldehyde, or a mixture of these aldehydes, is preferably used as the hydroxy monoaldehyde. The hydroxy monoaldehydes are generated separately in an upstream step, preferably by means of a so-called polarity reversal reaction from formaldehyde. The process is therefore relatively complex and expensive, and carries the risk of residual formaldehyde entering the mixture if a clearly separated two-stage process is not used, which in practice leads to further cost increases.

[0010] Glycolaldehyde and glyceraldehyde, with the molecular formula (CH₂O)ₙ, can be considered carbohydrate aldehydes. The use of such aldehydes in amino resins is also addressed in US Patent 4,172,057 A, which describes the incorporation of a hydroxyaldehyde or ketone into an amino resin, specifically a urea-formaldehyde resin or a melamine-formaldehyde resin. In this example, glucose is added to the conventional amino resins to modify the resin. The modified resin is then processed into fibers intended for use as adhesives in papermaking.

[0011] Finally, DE 10 2014 105 879 A1 discloses a process for producing a composite material comprising at least one cellulose-containing substrate and a multi-component binder. The first component of the binder comprises animal blood, and the second component comprises at least one additive from a list that includes, among others, urea, alum, glycerin, formaldehyde, isocyanate, hexamine, aluminum salts, acids and bases, and peroxide. These substances, referred to as additives, can be used individually or in mixtures and applied in combination with the first component. This allows for a wide variety of possibilities. The examples given are very diverse and lead to highly heterogeneous results. The products are not formaldehyde-free, i.e., not emission-free.

[0012] In contrast, the invention is based on the objective of providing an ecologically sound, strictly formaldehyde-free and therefore emission-free binder that can be used for a wide variety of composite materials and in particular wood and paper composite materials.

[0013] The agent is intended to ensure compliance with emission standards in the production of end products such as composite materials. The setting process should be as controlled and rapid as possible to deliver good and reproducible results within continuous manufacturing processes. The new binder should be available from cost-effective base raw materials and preferably be available as a single-component system for easy storage and transport.

[0014] These problems are solved with a binder according to claim 1 and the associated composite material product obtained therefrom according to claim 12.

[0015] According to the invention, a hydroxyaldehyde, which includes mixtures of several hydroxyaldehydes, is polycondensed and cross-linked with an ammonium salt. The binding possibilities in the complex system between ammonium (NH₄⁺), aldehyde, and cellulose structures are manifold. In the presence of a protein component, it also interacts with the system. The binding possibilities are explained in more detail below with reference to the figures.

[0016] Surprisingly, it was found that ammonium salts condense with hydroxyaldehydes to form excellent binder resins that effectively bond cellulose-containing materials and, particularly in composite materials with cellulose, result in good mechanical strength and overall very satisfactory product qualities. Until now, the extent to which ammonium salts can be used in binder resins, especially as a replacement for urea, and the advantages this offers, had not been recognized.

[0017] The fundamental reactivity of carbonyl compounds with ammonia and ammonium cations has been known for a long time, for example from the production of urotropin or through formol titration. However, this principle has not yet been used in the sense described here.

[0018] The crosslinking possibilities of glyceraldehyde and, correspondingly (not shown separately), of dihydroxyacetone, which can be present as a co-product in mixtures, as described in more detail below, are derived from the Figures 1 to 3 Sure. Other hydroxy aldehydes and related ketones would react accordingly. Figure 1 The diagram schematically shows the binding of glycol to a peptide surface. Binding to cellulose-containing substrates occurs via OH groups on the cellulose. The diagram in Figure 2 is dedicated to further condensation possibilities. Figure 3 schematically acknowledges in particular the influence of the ammonium salt, which forms a central component of the invention.

[0019] The binder according to the invention can replace the widely used UF and MF resins with emission-free, environmentally friendly products. Certain suitable ammonium salts are commercially available and inexpensive in large quantities.

[0020] In many embodiments, the relatively high ammonium salt content is also responsible for a high solids content in the binder. The associated low water content, which should preferably be below 50 wt.%, is essential or advantageous for some binder applications.

[0021] In preferred embodiments, the ammonium salt or the several ammonium salts are used in the mixture in a stoichiometric ratio to the hydroxyaldehyde. In addition to the ammonium salts, any amines or amides present in subordinate amounts – including amines or amides contained within a protein component – ​​are taken into account in the stoichiometric ratio, as necessary.

[0022] Preferred hydroxyaldehydes are the carbohydrate aldehydes of the molecular formula (CH₂O)ₙ, which include glycolaldehyde, glyceraldehyde, trioses, and higher aldoses. Glyceraldehyde is particularly preferred.

[0023] Within the scope of the invention, it was surprisingly discovered that these hydroxyaldehydes, and especially glyceraldehyde, can be very advantageously generated within the binder, i.e., in situ, using a mild oxidizing agent from at least difunctional hydroxy compounds (polyols). Hydrogen peroxide is preferred as the oxidizing agent. In a particularly preferred embodiment, the binder contains at least one at least difunctional hydroxy compound, preferably glycerol, and the oxidizing agent, preferably hydrogen peroxide, to form the hydroxyaldehyde, preferably glyceraldehyde, in situ. This then reacts with the ammonium salt and optionally other substances present in the binder mixture to form the hydroxyaldehyde resin. This resin hardens during the overall reaction under heat and pressure.

[0024] It is particularly remarkable that the binder, with all its ingredients including diol or polyol and peroxide, or other oxidizing agent, can be stored for a long time, e.g. over a year.

[0025] Glyceraldehyde and dihydroxyacetone are formed from glycerol using a suitable mild oxidizing agent, preferably hydrogen peroxide. The co-formed dihydroxyacetone polycondenses with NH-reactive components (ammonium salts, melamine, urea) in a manner similar to that of the aldehyde (see Figure 1These two compounds can interconvert via an enediol group (Lobry-de Bruyn-van Ekenstein rearrangement). Therefore, it is not necessary to first synthesize a pure aldehyde. The combination of an ammonium salt, a polyol (preferably glycerol), and an oxidizing agent (preferably hydrogen peroxide) already yields a glue resin. The optimal proportions can be easily determined. The chemical structure of the substrate also plays a role in this.

[0026] In preferred embodiments, the binder is urea-free. Using urea but without formaldehyde results in only a weaker adhesive strength.

[0027] In a further development of the invention, it is provided that, in addition to the components described so far, a protein component is included in the binder. Proteins in this context comprise polypeptides. This protein component further strengthens the cross-linked molecular structure that forms in the binder and between the binder and the cellulose-containing material or substrate. At the same time, it gives the adhesive structure and can serve as a filler. When the aldehyde (and / or ketone) comes into contact with the protein component, its carbonyl and hydroxyl groups react with functional groups of the protein. This results in condensation and esterification reactions.

[0028] The chemical relationships are summarized and greatly simplified in the diagrams shown in Figures 1 to 3. The reaction processes in nature are much more complex – also due to variations in composition – and can only be represented here in a very simplified way; this is intended only to facilitate a basic understanding of the invention.

[0029] The presence of the protein offers crucial advantages. As a macromolecule, the protein provides a surface to which numerous glycerol units can bind, which in turn cross-link with the help of the NH component, ammonium. Additionally, amine and amide groups of the protein can react with the carbonyl groups of the aldehyde / ketone. Hydroxyl groups of the aldehyde or ketone can esterify with acidic groups of the protein, and so on. This increases the stiffness of the cross-linked molecular structures in the binder, or rather, the overall degree of cross-linking.

[0030] The protein(s) of the protein component are preferably present in a denatured form within the binder. This is achieved through various ingredients and the pH value. Hydrogen peroxide is particularly effective in denaturing the protein, but surfactant additives, if present, also contribute to this effect.

[0031] The protein component improves the cross-linking with the cellulose-containing material that is to be bound.

[0032] For the protein component, basically any readily available and inexpensive substance with a predominantly or sufficiently high protein content can be used. Preferably, the protein component is based on animal blood, i.e., it is derived from animal blood, although other admixtures may be present, and preferably contains hemoglobin from animal blood or protein concentrate from animal blood. Particularly preferred is animal blood powder, e.g., whole animal blood powder, i.e., dried animal blood, and especially animal blood powder from Category 3 animal blood, plasma powder, or hemoglobin powder.

[0033] Hemoglobin promotes the oxidation process of the polyol with the oxidizing agent through the presence of iron(II). Starting from the peptide surface, a binding network forms via the aldehyde and / or ketone with the NH component.

[0034] According to the invention, ammonium compounds are used as NH-reactive compounds that add to carbonyl groups in the following manner:

[0035] These initial primary products condense, also in the network with the other partners, to form the binder resin.

[0036] Preferred ammonium salts for the purposes of this invention are salts from the group consisting of: ammonium sulfate, ammonium alums, in particular ammonium aluminum double salt, which crystallizes as a dodecahydrate in a cubic form, like all alums, ammonium lignosulfonate, and ammonium hydrogen phosphate. All these salts are commercially available and not too expensive.

[0037] Either a salt from this group is selected for the binding agent, or a mixture of salts from the aforementioned group is used.

[0038] In a particularly preferred embodiment, the ammonium salt content is at least 50 wt.% based on all nitrogen-containing components capable of crosslinking with hydroxyaldehydes—i.e., the NH-reactive components as described above—but excluding the optionally present protein component. When the protein component is included within the amount of the remaining NH-reactive components, other than ammonium, the ammonium salt content is at least 25 wt.%.

[0039] The ammonium salt used according to the invention can be supplemented or partially replaced, up to a maximum of 50 wt.%, by an additional amine or amide component. Preferably, this supplementation is made with melamine. Urea, on the other hand, is not preferred as a supplement to the ammonium salt; rather, the binder is preferably urea-free.

[0040] The weight fraction of the sum of all nitrogen-containing components capable of combination (addition) and cross-linking with hydroxyaldehydes, including the ammonium salt, excluding proteins, is at least 15 wt.% of the binder.

[0041] According to a particularly preferred, special embodiment, the binder consists of the following components: Water, with a maximum content of 48 wt.%, at least one ammonium salt, glycerol, hydrogen peroxide, a protein component, optionally an additional amine or amide, and optionally additives and excipients.

[0042] In preferred embodiments, the glycerin content is between 5 and 40 wt.% based on the undiluted binder, as illustrated below by means of examples.

[0043] Hydrogen peroxide is used in the examples in a 35% solution. Preferably, the hydrogen peroxide content is between 1 and 10 wt% in the undiluted binder (all percentages are weight percentages unless otherwise stated).

[0044] The protein component is preferably present in an amount of up to 20% by weight, and more preferably up to 15% by weight. In the examples, amounts between 4% and 10% by weight are used. Of course, smaller amounts, for example less than 1% or 1% to 4%, may also be suitable for certain applications.

[0045] Additives, such as wetting agents, defoamers, thickeners, smoothing agents, flame retardants, etc., can be added to the binder in suitable quantities, which typically do not exceed 5% by weight. The addition of additives can be left to a person skilled in the art; suitable products are commercially available.

[0046] Possible specific additives include: surfactants, polyasparaginate as a surfactant additive, defoaming mixtures, paraffins, thickeners such as gelatin or 2-hydroxyethyl methyl ether. Dyes.

[0047] The binder is ready-to-use, i.e., pre-mixed with all its components, and suitable for storage and transport. It has a shelf life of several months. The binder—a binder glue or "glue resin"—is therefore fundamentally a one-component adhesive. However, a person skilled in the art may divide the components of the binder into two components to create a two-component adhesive. An example of this is shown in Application Example 6.

[0048] The binder is preferably used in its undiluted, basic glue form. The examples illustrate this without limitation. For certain purposes—for example, as a primer—the binder can also be diluted. It can also be supplied in a dried form.

[0049] The binder can be used on all common processing machines, automated production lines, and also hand presses. It bonds with the cellulose-containing components under heat and, if necessary, pressure applied during processing. Pressing preferably takes place at temperatures above 100 °C to 250 °C and in pressure ranges typical for the respective processing methods, preferably up to approximately 180 bar.

[0050] The processing time and setting behavior can be precisely controlled by adjusting heat and pressure. For example, the pressing time for boards depends on the type of cellulose-containing substrate, the pressing temperature, the pressing pressure, and also the thickness (height) of the composite boards to be produced. All these relationships are well known to experts and therefore do not need to be explained in detail.

[0051] A particular advantage of the invention is the reduction of pressing times on continuous presses. Pressing times of less than 10 seconds per 1 mm of sheet thickness are achievable.

[0052] The binder according to the invention can also be used in the craft sector as a wood glue, as described above as a 1K glue, but also as a 2K glue.

[0053] The invention also encompasses the composite products themselves, which can be obtained by bonding a cellulose-containing starting material with the new binder and shaping it into a product. This includes all such product forms as are available with conventional adhesive resins. Examples include products for the furniture industry, e.g., furniture panels, building material panels and thermal insulation panels, dust-bonded recycled products, and recycled paper panels.

[0054] The composite products according to this invention are generally obtainable by bonding a cellulose-containing starting material with the binder according to the invention and molding it into a product. This generally results in a molded body. All processes known and commonly used in the prior art can also be carried out with the binder according to this invention. Existing processing plants can be used without special modifications. Molding is generally carried out as is currently customary, under heat and pressure. This process yields, for example, the sheets mentioned above or other bodies such as bricks, etc.

[0055] The cellulose-containing starting material for the composite product is preferably wood and / or paper. The composite product is in particular in the form of boards, wood panels, pressed boards made from wood chips, flakes and the like, especially particleboard, laminates, MDF, OSB and plywood, but also straw boards (see example) or other natural fiber boards, e.g., in the construction sector as insulation material (hemp boards, etc.).

[0056] The invention will be explained in more detail below using examples that are purely illustrative and intended to provide a better understanding of the invention. EXAMPLES

[0057] Nine binder glues are prepared. The compositions are in Table 1 shown. Table 1 Example 1 2 3 4 5 6 7 8 9 1) 60% aqueous salt solution for ... wt% content in the binder glue Ammonium sulfate 41,4 - 9,3 28,8 15,0 9,6 25,8 32,4 - Ammonium alum - 41,4 9,3 - - 9,6 - - - 2) binder glue with the following components: Solution from 1) (wt%) 69 69 31 48 25 32 43 54 25 H 2 O other N-components: Ammonium ligninsulfonate 14 20 25 10 40 Ammonium hydrogen phosphate 20 melamine 20 Glycerin (85%) 15 15 38 12 10 40 10 8 15 Hydrogen peroxide (35% iq) 12 12 20 14 10 20 12 6 10 Protein component (solid) 4 4 8 10 10 8 10 4 10 Additives: Surfactant, Schwego foam 6305® (with polyasparaginate) 2 1 1 Paraffin solution (ethanolic) Hydro Wax Fa. Sasol 1 1 2 1 2 gelatin 3 (all figures in wt.%)

[0058] First, a 60% (w / w) aqueous ammonium salt solution is prepared, provided the recipe calls for ammonium sulfate or ammonium aluminum sulfate dodecahydrate (or another ammonium alum). For higher ammonium salt concentrations, this can be done using heat. Table 1 lists, under 1), the ammonium sulfate and / or ammonium alum concentrations in the binder adhesive that result when the quantity of aqueous solution from 1) specified below is used in the composition.

[0059] For example 6, which does not contain ammonium sulfate or ammonium alum, the ammonium ligninsulfonate is first dissolved in water, then the other components are added.

[0060] The binder-glue examples listed in Table 1 have a wide range of applications. They bind wood, paper, and other cellulose-containing natural fibers, as well as synthetic pulp products. Some possible uses are given in the application examples below. APPLICATION EXAMPLES Application example 1

[0061] To produce a particleboard, spruce wood chips with a residual moisture content of 2% are mixed with a formaldehyde-free binder according to this invention.

[0062] The mass fraction of the chips is 92% (wt%).

[0063] The binder mixture is a single-component compound. In all examples, the solids content is above 50%, meaning the water content of the binder adhesive is below 50%. The solids content includes all inorganic and organic components of the adhesive, including glycerin, but excluding hydrogen peroxide and water. Mixing is carried out by spraying to achieve uniform wetting. The binder content, based on the solids content, is 8% of the specific gravity of the board.

[0064] The wood chips, coated with the binding agent, are evenly spread onto a press plate to form a chip sheet. This chip sheet is then pressed in a panel press at a temperature of 180 °C for 180 seconds to produce a 12 mm thick particleboard. The pressing pressure is set to 150 bar. Particleboard produced in this way is emission-free.

[0065] The technical specifications of DIN ISO EN 312:210 type P2 have been achieved. variant

[0066] Up to a maximum of 10 wt% of a 1 molar solution of potassium hydroxide (KOH), sodium hydroxide (NaOH) or calcium hydroxide (Ca(OH) 2 ) can be added to the binder. Application example 2

[0067] To produce a 12 mm thick OSB (oriented strand board), "flakes" with a wood moisture content of 2-4% are required, which are wetted with a one-component binder from the example part (see Table 1) using a drum process.

[0068] Based on the specific weight of the flakes and the solids content of the binder, 10% binder is processed.

[0069] The flakes, moistened with the liquid, are spread into a cake and placed in a plate press for compression. The flake cake is then pressed into an OSB board at a temperature of 180 °C and a pressure of 165 bar for 180 seconds.

[0070] The technical specifications of DIN ISO EN 312:210 type P2 have been achieved. Application example 3

[0071] To produce a thin particleboard, e.g., using the Mende process on a calender, with a specific gravity of < 780 kg / m³, the chips are mixed in a Lödige drum mixer with 143 kg of binder from the sample part. To achieve the technical values ​​of the EN standard, a binder content of 11%, based on the solids content, must be reached.

[0072] The 3.0 mm plate is pressed in 30 seconds at 140 bar pressure and a temperature of 175 °C.

[0073] The technical specifications of DIN ISO EN 312:210 type P2 have been achieved. Application example 4

[0074] To manufacture particleboard, a chip sheet is formed. The mass fraction of moist chips is 92%, with a residual moisture content of 2%. A binder with a water content of less than 40% is selected. The binder is applied by spraying. The binder content, based on the solids content, is 8% of the specific gravity of the board. At a temperature of 200 °C, a pressure of 155 bar, and a pressing time of 12 seconds per mm of board thickness, the chip sheet is pressed in a single-stage press.

[0075] The technical specifications of DIN ISO EN 312:210 type P2 have been achieved. Application example 5

[0076] To produce an MDF board, wood fibers dried via a refiner (1% wood moisture content) are wetted with a one-component, formaldehyde-free binder according to the invention by means of drum gluing in a spray process. The mass fraction of the wood fibers is 90%; the binder fraction is 10% based on the solids content.

[0077] The moistened wood fibers are pressed at 185 °C and a pressure of 140 bar. The pressing time in a continuous press is 8 seconds per 1 mm of board thickness. (A 6 mm board is produced in 48 seconds.) Application example 6

[0078] The binder adhesive from Example 1 is produced as a two-component product. Adhesive component 1: Mixture of aqueous ammonium alum solution and hydrogen peroxide; Adhesive component 2: Mixture of 85% glycerin and protein concentrate from Saval®.

[0079] To produce plywood (layered wood), 2 mm thick birch veneers are provided. Adhesive component 1, which is very low in viscosity, is sprayed onto one side of a birch veneer. Adhesive component 2 is then rolled onto another top side of a second birch veneer at a rate of 40 g / m². The two top sides of the birch veneers are then placed crosswise on top of each other and pressed together at a pressing temperature of 170 °C and a pressure of 65 bar for approximately 120 seconds. Application example 7

[0080] To produce a veneered surface, a one-component binder according to the invention is applied to the substrate, in this case a chipboard, with a density of 80 g / m²< using a single-sided glue application roller.

[0081] The veneer, in this case oak veneer with a thickness of 0.6 mm, is laid across the entire surface of the glued substrate and pressed in a veneer press with a pressure of 70 N / mm² for 90 seconds. variant

[0082] The binder is added before application at a rate of up to 10% by weight.

[0083] Wheat flour or starch (preferably corn or soy starch) is added to increase the solids content and prevent the so-called "glue bleed-through". Application example 8

[0084] To produce a 22 mm chipboard, a chip sheet is formed.

[0085] The mass fraction of the moist chips is 90%, with a residual moisture content of 2-4%. The binder has a solids content of approximately 63%.

[0086] The binder content is 10% of the specific weight of the board based on the solids content (680 kg / m³ < weight of the finished board, 68 kg solids content of the binder, 108 kg liquid binder).

[0087] The binding agent is applied using a spray method.

[0088] The chip cake is pressed in a single-stage press at a temperature of 210 °C, a pressure of 150 bar, and a pressing time of 220 seconds. Application example 9 (straw board)

[0089] A one-component binder is used, as shown in Example 9.

[0090] The length of the straw fibers should be a maximum of 20 mm.

[0091] The liquid is applied using a Lödige plowshare mixer.

[0092] The mass fraction of straw fibers is 90%; the binder, based on the solids content, is 10%.

[0093] The moistened straw fibers are pressed at 165 °C and a pressure of 160 bar. The pressing time in a single-stage press is 15 seconds per 1 mm of sheet thickness.

[0094] A lightweight panel 30 mm thick with a specific weight of 280 kg / m 3< was manufactured.

[0095] Instead of straw, other cellulose-containing fibers (preferably from young plants) or recycled paper can also be used. Note:

[0096] Straw boards cannot be bonded with conventional urea-formaldehyde binders because the outer layer of the straw contains paraffin and exhibits a high release effect against this binder. Therefore, straw boards are manufactured using isocyanates (PDMI).

[0097] The formaldehyde-free binder according to the invention, in particular according to Example 9, dissolves the paraffin structure of the straws and enables crosslinking to form a sheet. Formaldehyde test:

[0098] A formaldehyde test was carried out at the Institute of Wood Technology in Poznań.

[0099] Test Report No.: 371 / 2016 / SF dated 25.02.2016

[0100] The six three-layer chipboard panels had a format of 290 mm x 290 mm x 6 mm and were manufactured with a binder of example no. 4.

[0101] Three-layer particleboard (EO P1 CE) was tested for 10 days according to EN 717-1:2006 (chamber method).

[0102] The 9 measurements yielded the following values: 0.022 / 0.017 / 0.013 / 0.008 / 0.007 / 0.008 / 0.008 / 0.008 / 0.008 ppm formaldehyde emission.

[0103] According to the standard (EN 120 / CARB standard), formaldehyde emissions under these conditions must not exceed 0.1 ppm (ml / m 3< ).

[0104] The measured values ​​were far below that and originate from the organic matter in the wood.

[0105] This shows that no fission reactions can take place during the setting process, releasing formaldehyde or other harmful emissions.

[0106] The new panel received is completely formaldehyde-free in accordance with the EN 120 / CARB standard.

Claims

1. Formaldehyde-free binder for cellulose-containing materials, characterized in that it contains a hydroxyaldehyde resin which is polycondensed with an ammonium salt.

2. Formaldehyde-free binder according to claim 1, characterized in that the hydroxyaldehyde for the binder resin is a carbohydrate aldehyde and in particular glyceraldehyde.

3. Formaldehyde-free binder according to claim 1 or 2 characterized in that the hydroxyaldehyde is formed from at least one difunctional hydroxy compound with an oxidizing agent, such as in particular a peroxide.

4. Formaldehyde-free binder according to any one of claims 1 to 3, characterized in that it is free of urea.

5. Formaldehyde-free binder according to any one of claims 1 to 4, characterized in that it contains a protein component.

6. Formaldehyde-free binder according to claim 5, characterized in that the protein component is based on animal blood and in particular contains hemoglobin from animal blood or protein concentrate from animal blood.

7. Formaldehyde-free binder according to any one of claims 1 to 6, characterized in that the ammonium salt is a single salt or a mixture of salts selected from the group of ammonium sulfate, ammonium aluminum sulfate, in particular ammonium aluminum double salt, ammonium lignosulphonate and ammonium hydrogen phosphate.

8. Formaldehyde-free binder according to any one of claims 1 to 7, characterized in that the ammonium salt is at least 50 wt.-% relative to all nitrogen-containing components capable to cross-link with hydroxyaldehydes without considering the optionally present protein component, wherein in particular a melamine portion may be present.

9. Formaldehyde-free binder according to claim 8, characterized in that the weight portion of the sum of all nitrogen-containing components which are capable to cross-link with hydroxyaldehydes, including the ammonium salt and excluding proteins, is at least 15 wt.-% of the binder.

10. Formaldehyde-free binder according to claim 8 or 9, characterized in that it contains water in an amount of about 48 wt.-%, at least one ammonium salt, glycerol, hydrogen peroxide, the protein component, optionally an additional amine or amide as well as optionally additives and auxiliaries.

11. Formaldehyde-free binder according to any one of claims 1 to 10, characterized in that it is a two or multi-component binder, the components of which are mixed directly before its use or are applied separately.

12. Composite material product obtainable by binding a cellulose-containing starting material with a binder according to any one of claims 1 to 11 and shaping to a product.

13. Composite material product according to claim 12, characterized in that the starting material is wood and / or paper.

14. Composite material product according to claim 12 or 13, characterized in that it is plate-shaped, preferably a compressed board or a laminate.