EP3080204A1 - Wood product or natural fiber composite material product and use of a formaldehyde-free amino- and amide resin based on glyoxylic acid esters for the production thereof - Google Patents

Abstract

The invention relates to a wood product or natural fiber composite material product made from at least one lignocellulose- and/or cellulose-containing material that is provided with an adhesive and is cured or crosslinked in the desired shape, the adhesive being in the form of a formaldehyde-free amino- or amide resin based on glyoxylic acid esters as an aldehyde component, and to the use of such an adhesive for producing a wood product or a natural fiber composite material product.

Description

 Wood-based product or natural fiber composite product and use of a formaldehyde-free amino and amide resin based on glyoxylic esters for their preparation

The invention relates to a wood-based product or natural fiber composite product comprising at least one lignocellulosic and / or cellulose-containing material which has been provided with an adhesive or a polymer or a matrix and cured or crosslinked in the desired form, and the use of a formaldehyde-free amino or amide resin based on glyoxylic acid ester for the production of such a material. Other aldehydes which can be processed with the aldehyde component can be glyoxylic acid, glycolaldehyde, glyoxal, furfural or glutaraldehyde. Instead of amino or amido resins, imino resins can also be used.

Composite or composite materials are materials made of different materials. Natural fiber composites, or natural fiber reinforced plastics (NFK), are composites of a polymer or a matrix (thermosets, thermoplastics or combinations) and natural fibers and / or synthetic fibers. Natural fiber-reinforced composite materials or plastics have considerable market potential in vehicle construction (passenger cars, commercial vehicles, rail-bound vehicles), boat building, furniture and interior fittings. In the German automotive industry, the production of large-area natural fiber reinforced plastics for the interior takes place more than 90% after the compression molding process. About 60% of these natural fiber molded parts have a duroplastic matrix. Thermosets include the aminoplasts (e.g., urea and melamine-formaldehyde resins), phenolic resins (e.g., phenol-formaldehyde resins), epoxy resins, polyacrylates, polyurethanes, and other crosslinked polymers.

Wood-based materials are mainly used in the construction and furniture industry. In addition, wood-based materials are used in vehicle construction and as packaging material. The wood materials include e.g. Plywood, particleboard and fibreboard, scrims, wood-polymer materials (WPC), engineered wood products such as Oriented Strand Boards (OSB), Laminated Veneer Lumber (LVL), Veneer Strip Wood (Parallel Strand Lumber [PSL]), carrier

CONFIRMATION COPY Systems, I-beams and honeycomb panels with a core of paper, aluminum etc. and a cover layer, eg of plywood or fiberboard.

The starting material for lignocellulose composites and possibly natural fiber composites are particles of wood, annual and perennial plants, secondary residues such as waste wood, waste paper, production residues and lignocellulose-containing residues from agriculture, e.g. Used straw or hemp shives. The particles are usually joined by means of an adhesive to a wood material or with a polymer (duroplastic or thermoplastic) to form a natural fiber composite material. In addition to the lignocellulosic raw material and the adhesive or the polymer, the composites usually contain additives such as water repellents, flame retardants, curing accelerators, adhesion promoters, formaldehyde scavengers, dyes and surface-active substances to obtain certain properties of the material.

Amino resins and amide resins are relatively low molecular weight, curable materials obtained by reacting carbonyl compounds (especially aldehydes such as formaldehyde) with compounds having NH groups. Subsequent crosslinking (i.e., curing) of the amino or amide resin yields a thermoset.

As components with amine or amide functionality z. As urea, melamine, benzoguanamine, dicyandiamide and Acetylendihamstoff used, in particular urea and melamine resins are of industrial importance. As aldehyde component is preferably due to its high reactivity and low raw material price formaldehyde used. Resin synthesis often involves an excess of aldehyde to aid in the reactions between the two components. The residual contents of formaldehyde are correspondingly high. Formaldehyde can also be released by hydrolysis of the polycondensates.

The most widely used adhesive for wood-based materials is urea-formaldehyde resin (UF resin). Inside, more than 90% of the wood materials are bound with UF resin. UF resins, in addition to many positive properties such as There are also disadvantages such as increased brittleness, limited moisture resistance and formaldehyde emission. In order to meet the legal requirements for the formaldehyde emission of wood-based materials of the emission class E1, usually low-formaldehyde, but less reactive UF resins are used. In certain applications, therefore, is a modification of the UF resins, eg with Me-Iamin (mUF or MUF resins) or the use of resin combinations (eg UF resin and polymeric diphenylmethane-4,4'-diisocyanate [PMDI] ) required.

For moisture-resistant gluing especially alkaline-curing phenol-formaldehyde resins (PF resins), MUF resins and adhesives based on polymeric diisocyanate (PMDI) are used. The PF resins release formaldehyde in small amounts. Also, wood materials with mixed resins of various reaction components containing phenol (e.g., MUPF resins) have very low formaldehyde release. PMDI is formaldehyde-free and suitable for the bonding of particles, but not without modification for surface bonding.

Furthermore, combinations of formaldehyde with melamine (MF resins), resorcinol (RF resins), tannin (TF resins) and mixed resins with additional components for use in composites are possible. Melamine-formaldehyde resins are widely used as impregnating resins for decorative paper coating of wood-based materials.

Adhesives based on renewable raw materials, such as e.g. Lignins, tannins, polysaccharides, e.g. Starch, fatty acids, proteins have so far not been able to assert themselves for reasons of both technology and availability; to a lesser extent, they are useful as extenders for synthetic resins (e.g., tannin or lignin in phenol-formaldehyde resin, soy protein in combination with polyamidoamine-epichlorohydrin resin [PAE resin]).

Cement-bonded chipboard according to DIN EN 634-2 consist of about 60% by volume of wood chips and about 40% by volume of cement and additives. The composite of the wood chips takes place by the setting of the mineral substance components. The same applies to chipboard and fibreboard, the gypsum or magnesite as inorganic Component included. Another inorganic binder for chipboard and fiberboard is waterglass, which are sodium and potassium silicates or their aqueous solutions.

According to O ^' Carrol, cited in Kandelbauer, A., Petek, P., Med ed, S., Pizzi, A. Teischinger, A. 2010: On the Performance of a melamine-urea-formaldehyde resin for decorative paper coatings , Eur. J. Wood Prod. 68; 63-75, 70% of the chipboard and medium-density fibreboard for furniture and flooring (laminate flooring) are treated with resin-impregnated paper, the rest are finished with wood veneer or thermoplastic foil, varnished or printed. Laminate flooring elements consist of at least four layers, a chipboard support, a high-density (HDF) or medium-density fiberboard (MDF), as well as a room-side coating of the panels, typically consisting of several layers of high-grade paper impregnated with a transparent melamine resin. Furthermore, there is a so-called Gegenzugpapier back. For cost-effectiveness, urea-formaldehyde resin (UF resin) and then melamine-formaldehyde resin are often used in a two-stage process for the impregnation of decorative paper. The surface film (protective function) is usually melamine-formaldehyde resin.

The adhesives may contribute directly (formaldehyde-containing adhesives) and / or indirectly through interaction between the adhesive and the lignocellulose to emit formaldehyde and other volatile organic compounds (VOCs). As described above, the wood-based materials currently contain predominantly formaldehyde-containing adhesives. The formaldehyde release of wood-based materials and products made from them is currently regulated by law in Germany to a compensation concentration of max. 1, 2 mg / m ³ (= 0.1 ppm) in the test chamber, determined in accordance with DIN EN 717-1 (emission class - E1 -) , The reduction in permissible formaldehyde emission of wood-based materials with formaldehyde-containing adhesives and products made therefrom has been taking place for years (eg, Adhanassiadou, E., Tsiantzii, S., Markessini, C. 2009: Producing Panels with Formaldehyde Emission at Wood Level, Forest Products Society, International Conference on Wood Adhesives, Session 2B Composites, http://legacv.forestproud.org/adhesives09powerpoints.htm). Thus, in addition to the legal provisions, voluntary, stricter limits have been established, such as For example, the Ecolabel RAL-ZU 76 for low-emission uncoated and coated wood-based panels (Blue Angel) to 0.05 ppm, and the value of 0.03 ppm required by the German Association of prefabricated construction (BDF). Furthermore, regulations in Japan and the US led to reflections in Europe concerning one. Reduction of the limit below the E1 standard.

To reduce the formaldehyde emission of wood materials - preferably to the level of wood or wood particles - is the 2004 recommendation by the International Commission for Research on Cancer (IARC) WHO, formaldehyde of "presumably carcinogenic to humans" (Class 2A ) to "carcinogenic to humans" (Class 1) (IARC, 2004: International Agency for Research on Cancer (IARC), Press Release Number 153, 15th June 2004). In 2011, formaldehyde was approved by the U.S. Department of Health and Human Services © (News Releases: New Substances Added to HHS Report on Carcinogens, 10 June 20,

http://www.niehs.nih.gov/news/newsroom/releases/2011/june10/) as "carcinogenic to humans".

Formaldehyde has been classified by the European Union in the regulation on the classification, packaging and labeling of hazardous substances from category 3 (substances with possible carcinogenic effects) to category 2 (substances that are considered to be carcinogenic) (EU Directives, 2004 / 73 / EC 2004, EU Regulation No. 1272/2008).

In December 2012, the European Chemicals Agency (ECHA) Risk Assessment Committee (RAC) approved a reclassification of formaldehyde as Category 2 mutagen according to the CLP Regulation (substance may cause hereditary damage) and Carcinogen category B (substance likely to cause cancer in humans). From March 2013 to September 2013, the review of the REACH committee on the inclusion of formaldehyde was foreseen in the 6th update of the CLP Regulation. For the beginning of 2014, the publication of the new classification is planned. With the approval of the European Commission, the new classification of formaldehyde would be expected from April 2015 at the earliest. Although possible effects of a Revaluing formaldehyde to the production of wood-based materials is currently not possible, formaldehyde-free adhesives for the production of wood-based materials with extremely low formaldehyde release in the near future can gain in importance.

Formaldehyde-free adhesives which are already used or can be used in composite materials include, for example, polymeric diphenylmethane-4,4'-diisocyanate (PMDI), polyurethanes, EPI adhesives, adhesives based on polyamides, polyacrylamides, polyethylene, polyesters, polyvinyl acetates, epoxides organo-functional silanes, cyclic urea, renewable raw materials such as starch, protein, lignin, fatty acids, latex or other biopolymers and inorganic binders.

The disadvantage of PMDI is the high price, the necessary use of emulsifiers or special dosing and gluing techniques and release agents, the need for higher occupational safety measures and limited availability. One-component polyurethanes are often highly viscous, need to be diluted with organic solvents, and exposed to high temperatures for curing. 2-component polyurethanes require a complex working behavior due to two components and have a very short service life. Overall, the costs are high and there is the security risk of unbound isocyanate monomers.

For polyacrylamides, the safety risk is due to unpolymerized acrylamide, which is toxic.

Polyvinyl acetates (PVAC) have a thermoplastic behavior and are sensitive to creep of the bondline. Curing can only take place at relatively low temperatures, so that PVAC can only be used in the cover layer or in thin plates. Epoxies require resin and hardener, which must be present in an exact Mischungsver ratio, also the polyaddition is highly exothermic, so that a fire hazard is given. The service life is very short, epoxies are irritating, environmentally hazardous, so that a special protective equipment when handling is lent. The adhesive is not recyclable, the applications are limited.

The processing of silanvernetzten polymer adhesives or organofunctional silanes is difficult because of the viscoelastic property. Renewable raw materials have varying properties with mostly low reactivity. Availability is not always guaranteed, the costs are comparatively high and ready-to-use forms of delivery are rare.

Since primarily amino resins (UF, mUF or MUF resins) based on an amine and formaldehyde are used as adhesives for wood-based materials and composite materials, the object of the invention was to develop wood-based products with formaldehyde-free amino resins, in which the production conditions and the mechanical and hygric material properties correspond as possible to the materials bound with formaldehyde-containing aminoplast resin.

As an alternative to formaldehyde, other aldehydes are available in principle for the preparation of formaldehyde-free aminoplast resins, such as, for example, Acetaldehyde, propionaldehyde, acrolein, crotonaldehyde, glutaraldehyde, glyoxal, furfuraldehyde, etc. (Adam, 1988: Melaminharze In: Kunststoff-Handbuch 10: Duroplaste, eds .: Woebcken, W, Adam, W. ISBN-3-446- 14418-8).

Formaldehyde-free resins as adhesives for wood-based materials or decorative papers based on urea or cyclic urea (ethyleneurea) are listed in some patents.

US-A-4,395,504 discloses a formaldehyde-free binder for making particleboard from a cyclic urea, e.g. Ethylene urea and glyoxal in a molar ratio of 1, 1 1, 5: 1 described.

In US-A-4,906,727 a urea-aldehyde condensate for surface coatings is listed, which was obtained by reacting urea or certain alkylene ureas with certain aldehydes (including formaldehyde). US Pat. No. 4,220,751 relates to a resin for surface coatings of urea. As urea derivatives and certain monoaldehydes (eg alkyl, aryl aldehyde) specified.

DE 691 03 847 T2 describes the preparation and use of ethyleneurea / glutaraldehyde resin or urea / ethyleneurea / glutaraldehyde resin in wood-based materials. The molar ratio of ethylene urea to glutaraldehyde can vary between 0.3 and 3.5. With this resin, a catalyst is not required to achieve the appropriate cure and bond strength.

US-A-4,906,726 describes resins for surface coatings of two components, on the one hand a mixture of polyaldehydes (glyoxal or glutaraldehyde or derivatives thereof) and a water-dispersible component (e.g., epoxy resin emulsion, synthetic latex) and on the other hand a reaction product of e.g. Urea-formaldehyde ether monomer, a polyamine and calcium, strontium or barium oxide or hydroxide.

Wang, S. and Pizzi, A. 1997: Succinaldehyde-induced water resistance improvements of UF wood adhesives. Wood Raw 55: 9-12 replace formaldehyde with succinaldehyde, a dialdehyde with a short hydrocarbon chain. Furthermore, propionaldehyde (Mansouri, HR and Pizzi, A. 2006: urea-formaldehyde-propionaldehyde physical gelation resins for improved swelling in water, J. Appl. Polym., Sci. 102 (6): 5131-5136) and glutaraldehyde (US Pat. Maminski, M.L., Borysiuk, P., Parzuchowski, PG 2008; Improved water resistance of particleboards bonded with glutaraldehyde-blended UF resin, wood raw material 66: 381-383) in combination with UF resin for the production of chipboard used. Several references include the replacement of formaldehyde by furfural or furfuryl alcohol (see Dunky, M., Niemz, P. 2002: Wood Materials and Glues - Technology and Influencing Factors Springer Verlag, ISBN 3-540-42980-8).

Ballerini, A., Despres, A. Pizzi, A. 2005: Non-toxic zero emission tannin-glyoxal adhesives for wood panels. Holz Roh-Werkstoff 63: 477-478 replaced formaldehyde with glyoxal in tannin formaldehyde resins. In these tests, 9% glyoxal (% based on tannin) is added to a 45% tannin solution, the action of glyoxal with tannin takes place during hot pressing. Laboratory particle boards made with this glue resin exhibited lower transverse tensile strength and lower formaldehyde release than comparable plates made with tannin-formaldehyde resin.

For the preparation of formaldehyde-free melamine resins, the use of alternative mono- and dialdehydes is described. In the past, both the use of α-keto aldehydes, e.g. in DE 103 22 107 B4, as well as dialdehydes, e.g. in DE 10 2006 029 408 A1, described and discussed as Formaldehydersatz. The practical application, however, failed due to the rate of dissolution of the melamine in these aldehydes. Even during the long dissolution time, the products that have already gone into solution condense on and then precipitate out again.

Another conceivable alternative is the glyoxal. Due to the structure, similarly high crosslinking densities are to be expected as in the previously known formaldehyde-based melamine resins. Reactions of glyoxal with melamine, however, lead to a cross-linked product during the addition, since up to 3 molecules of aldehyde can attach to one molecule of melamine under similar reaction conditions. Dialdehyde-based resins, which by themselves promise high network density with melamine, are not storable and unsuitable for commercial use in relevant applications. Optionally, the literature discusses the possibility of unilaterally providing glyoxal with protecting groups, e.g. in DE 103 22 107 B4. However, the introduction of such protective groups is expensive and only partially conceivable for commercial products for the production of wood-based materials.

Formaldehyde-free urea and melamine adhesives based on dimethoxyglyoxal (also referred to as dimethoxyethanal [DME]) were used for laboratory particle board (Despres A., Pizzi, A., Vu C, Delmotte L. 2010: Colourless formaldehyde-free urea resin adhesives for wood panels: Eur. J. Wood Prod. 68: 13-20, Properzi M., Wieland, S., Pichelin, F., Pizzi, A., Vu C. 2009: Dimethoxyethanal-derived resins for wood based panels In: Processing of the International Panel Products Symposium 2009, 16- 18 September 2009, La Cite International de Congres Nanes, France. ISBN: 978-1-184220-118-3). Dimethoxyethanal is a derivative of glyoxal that is colorless and non-volatile. By adding DME to urea or melamine, precursors of amino resin were prepared. Although the crosslinking reaction of urea with DME was present, it was too slow to meet the requirements for adhesives for wood-based materials. Crosslinking was improved by adding 14% to 20% polymeric diisocyanate (PMDI). With a relatively high pressing time of 17 s / mm ... 42 s / mm plate thickness, an adhesive content of 7% ... 10% (solid resin based on dry wood) and a pressing temperature of 193 ° C chipboard was produced Transverse tensile strength meet the requirements of the standard for indoor panels. In further studies, melamine-DME precursors were mixed with 5% ... 16.5% PMDI, 26.5% latex or 16.5% PMDI and 5% glyoxylic acid (based on melamine-DME + latex) as Adhesive used for chipboard. The manufacturing conditions for the plates were 8% ... 9% adhesive, 20 s / mm ... 43 s / mm plate thickness pressing time, 193 ° C pressing temperature. A sufficient transverse tensile strength was only achieved with very long process times of 34 s / mm, which are not acceptable for the industry.

In practical application, urea resins based on glyoxal, e.g. for crease-resistant finishing of textiles, described in DE 30 41 580 12. But here, too, there are limitations due to the bifunctionality of the glyoxal compared to urea resins based on formaldehyde. This particularly concerns discolorations and problems with the stability of the resins. In order to improve the storage stability, protective groups are frequently used here in order to limit the reactivity (Despres A., Pizzi, A., Vu C, Delmotte L. 2010: Colourless Formaldehyde-Free Urea Resin Adhesives for Wood Panels. Eur Wood Prod. 68: 13-20).

The only besides formaldehyde for the preparation of melamine resins practically used monoaldehyde is the glyoxylic acid. Melamine resins prepared from glyoxylic acid and its salts are used, inter alia, as flow aids in concrete processing or as an additive for hydraulic binders, for example in DE 196 27 531 B4 and in tanning, for example in DE 39 35 879 A1 and DE 10 2005 032 585 A1 discloses application. However, such resins were for use in wood-based materials not yet suitable because they can lead to swelling in the final products due to the high salt content in the presence of water. DE 41 40 899 A1 describes a condensation product of a mixture of, for example, melamine or urea, glyoxylic acid and glyoxal, which is likewise used as tanning agent. In this case, part of the glyoxal is oxidized to glyoxylic acid. This mixture is reacted with melamine. The problem with this approach is that the melamine must be brought into solution during the addition of the aldehydes and glyoxal can already build oligomeric units in this phase. Such resins are correspondingly difficult to stabilize.

Pure glyoxylic acid-based amino resins also provide stable resins, but carry a high salt load since, prior to synthesis, they need to be neutralized to the amino resins with a base to cure. These salts easily absorb water and lead to increased swellability of the end products when used in wood-based materials. However, since the acid group forms water-insoluble salts with calcium ions, such systems are used as a concrete consolidator and flow aid in the construction industry (e.g., US-A-2008/108732, DE 2004050395 A1, US-A-5750634, US-A-5891983).

Furthermore, water-soluble formaldehyde-free polycondensation products based on aminotriazines, glyoxylic acid and an amino compound are known as additives for aqueous suspensions based on inorganic binders from DE 196 27 531 B4.

Some alternative aldehydes to formaldehyde have the disadvantage of causing discoloration, to some extent being toxic, volatile and / or non-reactive, their solubility in water causing problems, the manufacturing conditions for the wood-based materials unacceptable to the industry, or the like End product does not have the required properties in terms of standard strength requirements. The problems described in connection with wood-based materials can accordingly also arise for natural-fiber composite products. Amino resins based on glyoxylic acid methyl ester hemiacetal are described in DE 10322107 B4, the synthesis being carried out in alcohols. Resin systems based on glyoxylic acid esters with urea and / or melamine and / or dicyandiamide or other aminic components are not described in the patent literature and other publications.

The object of the present invention is to provide a wood-based product or natural fiber composite product which contains a formaldehyde-free adhesive with high reactivity and sufficient storage stability and which meets the requirements of use in terms of mechanical and hygric properties and emissions of volatile organic compounds.

According to the invention, this object is achieved by a wood-based product or natural fiber composite product having the features of the main claim and the use of formaldehyde-free amino and amide resins based on glyoxylic esters as the aldehyde component. Advantageous embodiments and further developments of the invention are disclosed in the subclaims, the description and the tables.

The wood-based product or natural fiber composite product of at least one lignocellulosic and / or cellulose-containing material, which is provided with an adhesive and cured or crosslinked in the desired form, provides that the adhesive is a formaldehyde-free amino or amido resin based on glyoxylic esters as aldehyde Component is formed. Plywood, chipboard and fibreboard, scrimber, wood-polymer materials (WPC), engineered wood products such as Oriented Strand Boards (OSB), Laminated Veneer Lumber (LVL) "Parallel Strand Lumber [PSL]", carrier systems, I-Beams and honeycomb panels having a core of paper, aluminum, etc. and a cover layer, eg of plywood or fiberboard, and other than plate-shaped products, such as molded products Natural fiber composites, or natural fiber reinforced plastics (NFK), are composites of a polymer or a matrix (thermosets, Thermoplastics or combinations) and natural fibers and / or synthetic fibers. If the following is spoken of a wood-based product, the statements apply accordingly to products that have natural fiber composites, or natural fiber reinforced plastics, ie for natural fiber composite products. Natural fiber composites may also be formed as plates or shaped bodies.

In the synthesis of amino or amide resins based on Glyoxylsäu- reestern the reaction is chosen so that premature curing of the resin can be excluded. Due to the partial hydrolysis of the ester, the pH must constantly be controlled in the reaction to the resins in order to counteract a decrease in the pH value and thus to avoid premature acidic hardening.

To increase the crosslink density, these resins can be reacted with glyoxal. The glyoxylic acid esters serve as a protective group of the amide functions. When the glyoxal is added, resins are then produced which have a high free aldehyde content and therefore increase the reactivity by addition reactions. Resins could be synthesized whose reactivity to urea resins was comparable or even higher.

With these resins, even after curing, many condensable groups are retained. This results in further advantages for different applications. Thus, e.g. It is expected that when recycling materials based on the resins described herein after processing the products by e.g. Milling a direct grouting without or with a reduced amount of glue can take place.

Furthermore, amino resins based on glyoxylic acid esters offer the advantage over prior art amino resins that the hydrophobicity of the resins can be adjusted by the type of ester. Since no glyoxylic acid is used, these resins bring no salt load in the end products compared to the Glyoxylsäureharzen. Another advantage of using glyoxylic acid esters is that a small amount of glyoxylic acid is released upon curing by hydrolysis. This can act as a catalyst, so that no further catalysts must be added during curing.

Another advantageous aspect of these resins is that by adjusting the hydrophobicity, a reduction of the thickness swelling of the end products can be achieved.

The wood-based product or natural fiber composite product may be single-layered or multi-layered or formed as a multi-layer composite material, wherein the amino or amide resin is used in at least one layer. This makes it possible to produce composites that are made of cellulose-containing or lignocellulose-containing materials and other materials or to produce multilayer lignocel lulosehaltige or cellulose-containing materials, with the use of formaldehyde-free amino or amide resin a significant reduction of formaldehyde emissions on the level of wood particles can be achieved.

The formaldehyde-free amino or amide resin can be used as a decor or surface coating or for fixing a decorative layer or a wear-resistant layer. This makes it possible to glue decors, such as decorative films or decor papers or cover a decor. The formaldehyde-free amino or amide resins can also be used after the printing of decors as wear protection layer, optionally with the addition of wear protection components, such as corundum.

The wood-based product or natural fiber composite product may also contain materials which are not made from renewable raw materials, for example polystyrenes, polyurethane foams, plastics, synthetic fibers, aramids or intumescent elements, in addition to ligno-cellulosic or cellulose-containing components.

To provide lignocellulosic and cellulosic materials Wood, annual and perennial crops as well as residual and recycling materials, such as paper are used. The wood-based product or natural fiber composite product may also be designed as a single-layer or multi-layer, wherein layers of non-cellulose-containing or non-lignocellulose-containing materials can be provided in multilayer wood-based products or natural fiber composite products, so that a total of a composite material from the wood-based product or natural fiber composite product and the other materials. The design as a composite material increases the possible uses of the end product.

A variant of the invention provides that the amino or amide resin is used as the sole adhesive. As a result, the Formaldehydeinsatz is excluded.

Alternatively to a sole use of the formaldehyde-free amino or amide resin, it is provided that a combination with formaldehyde-containing or formaldehyde-free other organic adhesives is used. As formaldehyde-containing adhesives z. For example, urea, melamine, phenol or resorcinol formaldehyde resins are used. Likewise, fomaldehyde-containing adhesives based on renewable raw materials such as lignin, tannin, protein, starch, fatty acids, latex or mixtures thereof can be used. The formaldehyde-free organic adhesives may be e.g. as polymeric diisocyanate (PMDI), emulsion polymer isocyanate (EPI), polyurethane, epoxy resin, polyvinyl acetate, silane crosslinked polymers and adhesives based on renewable raw materials or mixtures thereof may be formed.

It is also possible that the amino or amide resin based on a reactive protective group and a dialdehyde is used as a network former in combination with an inorganic binder such as gypsum, magnisite, cement and / or water glass, the amino or amide resin so at least one inorganic Binder has.

The formaldehyde-free amino or amide resin based on a reactive protective group and a dialdehyde as a network former can be used in solid, liquid, foamed or intumescent form. Functional additives such as water repellents, flame retardants, curing accelerators, adhesion promoters, formaldehyde scavengers, dyes and / or surface-active substances may be added to the wood-base product or natural-fiber composite product.

The invention also relates to the use of a formaldehyde-free resin for producing a wood-based product or natural fiber composite product as described above, prepared by a process in which a glyoxylic acid ester is reacted with an amine, an amide or an aromatic hydroxy compound.

Glyoxylic acid ester based resins offer the advantage, compared to known resins, that the hydrophobicity of the resins can be adjusted by the type of ester. Since glyoxylic acid is either not or optionally used only in minor amounts, bring these resins in comparison to the Glyoxylsäureharzen no or only a very low salt load in the final products. Another advantage of using glyoxylic acid esters is that a small amount of glyoxylic acid is released upon curing by hydrolysis. This can act as a catalyst, so that no further catalysts must be added during curing. The reactivity of the resins based on glyoxalic acid esters is comparable to that of UF resins, making them more reactive than the classic formaldehyde-based melamine resins.

The glyoxylic acid ester is preferably a glyoxylic acid alkyl ester, in particular a glyoxylic acid C _-4 -alkyl ester. By way of example, at this point methyl glyoxylate, ethyl glyoxylate, propyl glyoxylate, glyoxylic acid isopropyl or Glyoxylsäurebutylester or mixtures thereof may be mentioned.

Glyoxylic acid esters can be prepared by conventional synthesis methods known to those skilled in the art or are commercially available.

For example, glyoxylic acid esters can be obtained by esterification of the glyoxylic acid with an alcohol. If the esterification does not proceed quantitatively, glyoxylic acid is present in addition to the glyoxylic acid ester. In the process according to the invention, it is also possible to use a mixture of glyoxylic acid ester and glyoxylic acid for the reaction with the amine, the amide or the aromatic hydroxy compound without impairing the advantageous properties of the resin, for example good storage stability. If glyoxylic acid is still present in the resin, in a preferred embodiment it can be neutralized with a base.

The amine, amide or aromatic hydroxy compound which is reacted with the glyoxylic acid ester to produce a formaldehyde-free resin may be those usually used for the production of resins.

The starting amine or Ausgangssamid can for example 2-3 amine or

Amide groups (i.e., diamines or diamide or triamine or triamide). However, within the scope of the present invention it is also possible to use amines or amides having more than 3 amine or amide groups (for example polyamide, polyacrylamide).

As the amine or amide, there are, for example, an amino triazine, urea, a urea derivative, thiourea, a thiourea derivative, imino urea (i.e., guanidine), an imino urea derivative, a cyanamide, a diaminoalkane, a diamidoalkane, a polyacrylamide, or a mixture of these compounds. Furthermore, vegetable / animal amines / amides (such as proteins, gelatin) can be used.

Suitable aminotriazines are in particular amino-1, 3,5-triazines such as melamine, acetoguanamine and benzoguanamine. As suitable urea derivatives, there may be mentioned, for example, alkylated ureas such as methyl urea or cyclic ureas such as acetylene diurea or ethylene urea. Suitable thiourea derivatives include, for example, cyclic thioureas such as ethylene thiourea. As suitable imino urea derivatives, for example, cyclic imino ureas can be mentioned. As a suitable cyanamide, for example, dicyandiamide or cyanamide may be mentioned. Suitable diaminoalkanes, for example diamino-Ci-s-alkanes may be mentioned. As suitable diamido alkanes for example diamido Ci _-8 are called alkanes.

Suitable aromatic hydroxy compounds are, for example, phenol (i.e., only one hydroxy group) or phenolic compounds having at least two hydroxy groups. For example, catechol, resorcinol, hydroquinone, phloroglucinol, hydroxyhydroquinone, pyrogallol or a mixture of at least two of these phenol compounds may be mentioned as preferred phenolic compounds.

If the resin synthesis is with an amine or amide, the molar ratio of the glyoxylic ester to the amine groups of the amine or the amide groups of the amide can be varied over a wide range.

For example, when the amine or amide has 3 amine or amide groups, the molar ratio of the glyoxylic ester to the amine groups of the amine or amide groups of the amide is preferably in the range of 0.5 / 3 to 3/3, more preferably 1/5 / 3 to 2.5 / 3 or 1, 8/3 to 2.2 / 3. If the amine or amide has, for example, 2 amine or amide groups, the molar ratio of the glyoxylic acid ester to the amine groups of the amine or the amide groups of the amide is preferably in the range from 0.2 / 2 to 2/2, more preferably 0.3 / 2 to 1, 5/2, more preferably 0.5 / 2 to 1, 5/2.

If the resin synthesis is with an aromatic hydroxy compound, the molar ratio of the glyoxylic ester to the hydroxy aromatic compound can be varied over a wide range.

For example, when the aromatic hydroxy compound has 3 hydroxy groups, the molar ratio of the glyoxylic acid ester to the aromatic hydroxy compound is preferably in the range of 0.5 / 1 to 1/3, more preferably 1/1 to 1/2. For example, when the aromatic hydroxy compound has 2 hydroxy groups, the molar ratio of the glyoxylic acid ester to the aromatic hydroxy compound is preferably in the range of 0.5 / 1 to 1/4, more preferably 1/1 to 1/2.

In the process according to the invention, it is in principle possible for each amine group of the starting amine or each amide group of the starting amide or for phenols each ring position of the aromatic ring ortho or para to the OH group (hereinafter also referred to as reactive ring positions of the aromatic hydroxy compound) reacts with at least one glyoxylic acid ester. Alternatively, however, it may be preferable that at least one amine group of the amine or an amide group of the amide or a reactive ring position of the aromatic hydroxy compound is not reacted with the glyoxylic acid ester.

As will be described in more detail below, in a preferred embodiment, the product obtained from the reaction of the glyoxylic ester with the amine, the amide or the aromatic hydroxy compound can then be reacted with a further aldehyde, preferably a dialdehyde or a trialdehyde. In a preferred embodiment, this gives a resin which still has free aldehyde groups. If, after the reaction of the glyoxylic acid ester with the amine, the amide or the aromatic hydroxy compound, free amine or amide groups or reactive ring positions are still present, they would be directly accessible for reaction with the dialdehyde or trialdehyde in a subsequent reaction step. Suitable process conditions to ensure this are known to those skilled in the art. For example, the glyoxylic acid ester can be added in molar deficiency based on the number of amine groups of the amine or amide groups of the amide or reactive ring positions of the hydroxyaromatic compound.

Suitable solvents for the reaction of the glyoxylic acid ester with the amine, the amide or the aromatic hydroxy compound are known in principle to the person skilled in the art. Preferably, an aqueous solvent is used. Further, hydrogen bond-breaking polar solvents can be used.

Suitable reaction conditions (such as reaction temperature and pH) for the reaction of the glyoxylic acid ester with the amine, amide or hydroxy aromatic compound are known in the art.

The reaction temperature may be, for example, in the range of 20 ° C to 00 ° C, more preferably in the range of 40 to 65 ° C. Depending on the amine or amide or aromatic hydroxy compound and the glyoxylic acid ester used, the pH may vary over a wide range. The pH may be, for example, in the range of 6 to 10, more preferably 7 to 8.5.

With the method according to the invention oligomers are formed with very short sequences. These resins can be readily stabilized even at high solids levels (e.g., 60% by weight) (i.e., high storage stability). The addition of stabilizing additives is not required. The resin of the invention may, for example, have a solids content of at least 40% by weight or even at least 55% by weight.

In a preferred embodiment, the product obtained from the reaction of the glyoxylic acid ester with the amine, the amide or the aromatic hydroxy compound is subsequently reacted with a further aldehyde, wherein the aldehyde is preferably a dialdehyde, a trialdehyde, glyoxylic acid, glycolaldehyde or furfural or a mixture of at least two of these aldehydes.

In this preferred embodiment, it has been found that storage-stable resins can also be prepared with dialdehydes or trialdehydes when the amine or amide or the aromatic hydroxy compound is first reacted with the glyoxylic acid ester. In a known manner, the aldehyde group reacts with the nitrogen of the amine or amide group or with a reactive ring position (i.e., a position of the aromatic ring which is ortho or para to the OH group) of the hydroxy aromatic compound. The residue covalently bonded as a consequence of this reaction to the nitrogen atom of the amine or amide group or the aromatic ring and derived from the glyoxylic acid ester then functions as a protective group which, in the subsequent process step, prevents it from reacting with the dialdehyde or trialdehyde leads to an undesirable significant networking.

As in the addition of an aldehyde, for example, to an amine or amide according to the reaction equation -NHR + OHC- NR-CH (OH) - the aldehyde group is converted into a hemiacetal group and this hemiacetal group is a reactive group that can be used for a later crosslinking reaction becomes a "reactive protecting group" in this first reaction step attached to the amine or amide group (ie, a group on the one hand in a subsequent reaction with a di- or trialdehyde initially prevents unwanted premature crosslinking, but on the other hand has a reactive group, which later support the desired crosslinking or curing to a crosslinked material can).

In this preferred embodiment, therefore, after the first step, one or more amine groups of the amine or amide groups of the amide or one or more positions of the aromatic phenol ring are initially blocked by a reactive protective group derived from the glyoxylic acid ester. If, in a further step, the dialdehyde or trialdehyde is added, it can initially react only with N atoms or reactive positions of the aromatic ring which have not yet been blocked with a protective group in the first step. In addition, since the reaction of the glyoxylic acid ester with the amine or amide is an equilibrium reaction in the first step, the dialdehyde or trialdehyde in the second step can partially replace the protective groups derived from the glyoxylic acid ester.

In a preferred embodiment, the resin has free aldehyde groups. The presence of free aldehyde groups can increase the reactivity in setting appropriate conditions and thus assist in the preparation of a final crosslinked product.

By still possible in the second step reaction of the dialdehyde or Trialde- hyds with the nitrogen of the amine or amide may on the one hand according to the equation Re ^¬ action

 -NHR + OHC-R-CHO-> -NR-CH (OH) -R-CHO

free aldehyde groups are formed, but no significant premature (and thus undesirable) crosslinking occurs. The same applies to the resins based on an aromatic hydroxy compound. The reactivity of the resin is also increased by the presence of the reactive protecting group. As already explained above, the residue derived from the glyoxylic acid ester and functioning as a protective group for the amine or amide group or the aromatic ring position contains a reactive hemiacetal group which, when appropriate conditions are set, is available for a subsequent crosslinking reaction.

Dialdehydes or trialdehydes which can be reacted with amines or amides or aromatic hydroxy compounds are known per se to the person skilled in the art.

By way of example, glyoxal or a dialdehyde of the formula OHC- (CH ₂ ) i-3-CHO (ie malonaldehyde, succinic dialdehyde, glutaraldehyde) may be mentioned in this context.

As a suitable trialdehyde, for example, 2,4,6-tris (p-formylphenoxy) -1, 3,5-triazine can be mentioned.

In the context of the present invention, it is possible for the dialdehyde or trialdehyde to be added to the product from the first step, which is preferably present in an aqueous solution. Alternatively, it is also possible for the product from the first step (for example in the form of an aqueous solution) to be added to the dialdehyde or trialdehyde. In both cases, it is preferred that one component of the other component is continuously metered. While in the first case is added slowly enough, so that in the reaction medium during the reaction is always a low concentration of unreacted dialdehyde or trialdehyde, is rapidly dosed in the case of good water-soluble products to stabilize the resin by cooling after the reaction.

If a reaction is carried out with a further aldehyde, the product from the first step is preferably not isolated, but used in the form of the aqueous solution in which it was prepared in the first step, for the reaction with the dialdehyde or trialdehyde in the second step.

The amount of dialdehyde or trialdehyde added in the second step can be varied over a wide range.

If the amine or amide has 3 amine or amide groups, the molar ratio of the dialdehyde or trialdehyde to the amine groups or amide groups is preferably in the range from 0.1 / 3 to 5/3, more preferably 0.5 / 3 to 3 / 3 or 0.8 / 3 to 2.2 / 3. If the starting amine or parent amide has 2 amine or amide groups, the molar ratio of the dialdehyde or trialdehyde to the amine groups or amide groups is preferably in the range from 0.1 / 3.9 to 3.9 / 0.1, more preferably 0, 3/1, 7 to 1, 7 / 0.3, more preferably 0.5 / 1, 5 to 1, 5 / 0.5.

If the amine or amide has two amine or amide groups, the molar ratio of the dialdehyde or trialdehyde added in the second step to the glyoxylic acid ester added in the first step can be, for example, in the range from 1 / 0.01 to 1/3 or 1/0, 2 to 1/2 or 1 / 0.5 to 1/1, 5 are. If the amine or amide has three amine or amide groups, then the molar ratio of the dialdehyde or trialdehyde added in the second step to the glyoxylic acid ester added in the first step can be in the range from 1 / 0.01 to 1/5 or 1.5 / 0.2 to 1, 5/2 or even 2 / 0.3 to 2/1.

When the aromatic hydroxy compound has 3 hydroxy groups, the molar ratio of the dialdehyde or trialdehyde to the aromatic hydroxy compound is preferably in the range of 1 / 0.1 to 1 / 2.5, more preferably 1 / 0.1 to 1/1, 5. When the aromatic hydroxy compound has 2 hydroxy groups, the molar ratio of the dialdehyde or trialdehyde to the aromatic hydroxy compound is preferably in the range of 1 / 0.1 to 1 / 3.5, more preferably 1 / 0.1 to 1/2.

Suitable reaction conditions (such as reaction temperature and pH) for the reaction of an amine or amide or an aromatic hydroxy compound with the dialdehyde or trialdehyde are known in the art.

The reaction temperature in the second step may be, for example, in the range of 20 ° C to 100 ° C, more preferably 40 ° C to 65 ° C. The pH may be, for example, in the range of 6 to 10, more preferably 7 to 8.5. In this preferred embodiment (ie reaction with a further aldehyde, in particular a di- or trialdehyde, in a second step) oligomers can be formed with very short sequences and the resins can also be stabilized without problems even at high solids contents (eg 60% by weight) , Even in the case of readily soluble compounds such as urea or guanidine, the reaction products remain so low in viscosity due to the reactive protective group derived from the glyoxylic ester that stabilization is very well possible even at high solids contents.

Furthermore, in a preferred embodiment, the resin is characterized by having free aldehyde groups which increase the reactivity in setting suitable conditions and thus assist in the production of a crosslinked final product.

The reactivity of the resin is also increased by the presence of the reactive protecting group.

This achieves a reactivity which is equal to or even exceeds that of formaldehyde-based resins.

The produced resins can be stabilized, for example by

 Cooling (e.g., to a temperature below 30 ° C, more preferably below 25 ° C) and / or

 Addition of alcohols and / or

 Adjusting the pH to a value in the range of 7.0-9.0, more preferably 7.5-8.5.

In another aspect, the present invention relates to a method for

Preparation of a crosslinked material comprising

 the provision of a formaldehyde-free resin according to the method described above and

 the crosslinking or curing of the resin.

Suitable conditions for the crosslinking of a resin for the production of a crosslinked material are basically known to the person skilled in the art. As already mentioned above, another advantage of using glyoxylic acid esters is that a small amount of glyoxylic acid is liberated by hydrolysis during curing. This can act as a catalyst, so that no further catalysts must be added during curing.

In a preferred embodiment, therefore, no external catalyst is supplied to the curing resin obtained by the process of the present invention.

Since there are many hydrogen bonds in the material, it is also suitable for microwave treatment during the crosslinking step (e.g., in the form of a microwell post-cure).

Crosslinked materials are also referred to as thermosets.

The presence of free primary amide groups can increase the reactivity of the resin. In a preferred embodiment, urea or polyamide or polyacrylamide (preferably in each case in the form of a solution) is therefore added to the formaldehyde-free resin before and / or during the crosslinking. Preferably, the addition of the amide is carried out in an amount such that the number of free primary amide groups is less than the number of free aldehyde groups.

In another aspect, the present invention relates to a formaldehyde-free resin obtainable by the above-described process, that is, by reacting a glyoxylic acid ester with an amine or an amide or an aromatic hydroxy compound.

With regard to preferred glyoxylic acid esters, amines, amides or aromatic hydroxy compounds, reference may be made to the statements made above.

Preferably, the resin has free aldehyde groups.

In a preferred embodiment, in the resin according to the invention: Amine groups or amide groups or aromatic rings to which residues are derived which are derived from the reaction with the glyoxylic acid ester from the first step, ie the reactive protective group,

 and amine groups or amide groups or aromatic rings to which residues are attached, which are derived from the reaction with the dialdehyde or trialdehyde in the second step and, in a preferred embodiment, may have free aldehyde groups.

The solids content of the resin can be varied over a wide range. The solids content is at least 40% by weight. Preferably, the concentration or the solids content of the resin is in the range of 40 to 80% by weight or 55 to 70% by weight. The resin of the invention shows good storage stability even at high solids content. Stabilizing additives are not required. Preferably, the resin does not contain a polymeric additive.

In another aspect, the present invention relates to a crosslinked material obtainable from the above-described resin.

The crosslinked material is obtained by curing the resin appropriately, i. is subjected to crosslinking.

As exemplary crosslinked materials which can be produced from the resin according to the invention, foams or foamed materials or also fibers can be mentioned.

In the case of the materials according to the invention, many condensable groups remain even after curing. This results in further advantages for different applications.

In a recycling of materials based on the resins described here can take place after the preparation of the products by, for example, grinding direct compression without or with a reduced amount of glue. A further advantage of products based on the glyoxylic acid ester resins is that the partial hydrolysis of the ester groups can generate acidic and thus fungicidally active surfaces.

At the same time, this acidic surface can catalyze the resin system because the condensation catalyst (acid) is permanently present in the final products. In the case of mechanical damage or hydrolysis in the event of water, a self-healing effect can therefore be achieved by renewed condensation even at room temperature.

Another advantageous aspect of these resins is that by adjusting the hydrophobicity, a reduction of the thickness swelling of the end products can be achieved. The remarks on the amines and amides apply accordingly to imines.

The invention will be explained in more detail with reference to the following examples.

Examples

Example 1 :

 Preparation of glyoxylic acid ethyl ester

To 421.4 g of 50% glyoxylic acid (2.85 mol) is added 462 g of ethanol. After addition of 40 g (0.406 mol) of 37% hydrochloric acid is heated to 55 ° C for 20min. heated. Then the solution is neutralized with 111 g (0.80 mol) of potassium carbonate. From the amount of potassium carbonate required for neutralization, the degree of esterification can be calculated. This is 57.89% here.

In order to separate off the potassium chloride which forms, a further 400 g of ethanol are added in order to reduce the solubility in salt, and the salt is then filtered off. Finally, the ethanol is distilled off.

This gives 496 g of a solution of glyoxylic acid and ethyl glyoxylate, which was used in Example 3 or 4 directly for resin synthesis. Example 2:

 Preparation of isobutyric acid ester

To 191.4 g of 50% glyoxylic acid (1.29 mol) are added 197.4 g of isopropanol. After addition of 12.7 g (0.13 mol) of 37% hydrochloric acid is heated to 55 ° C for 20min. heated. Then the solution is neutralized with 61.7 g (0.447 mol) of potassium carbonate. 32% of the glyoxylic acid was esterified.

After neutralization and addition of 100 g of isopropanol, 2 phases were formed.

For the resin syntheses in Examples 5 and 6, both phases were prepared by distilling off the isopropanol and water and diluting with 50 ml of water. The ester is initially much in solid form.

For the resin synthesis in Example 7, the isopropanol of the organic phase was distilled off after the phase separation. The product was overcoated with 100 g of water to bring melamine into the aqueous phase in the synthesis of the resin (see Example 7).

Example 3:

 Synthesis of Resin 1-Glivoxylic Acid Ethyl Ester / Glivoxylic Acid Resins Based on Melamine (Ester from Example 1)

119.5 g (0.95 mol) of melamine are added to 496 g of the solution from Example 1. After neutralization with potassium carbonate (pH 7.5) at 60 ° C for 60min. heated. Here, the resin clears up completely.

For this resin, the viscosity curve was determined as a function of the temperature. This is shown in FIG. The resin had a pH of 6.3. No catalyst was added in the form of an acid. Curing started at a temperature of 92 ° C.

The temperature-dependent viscosity curve of a conventional melamine-formaldehyde Resin (MF resin) is shown in FIG. After addition of an acid catalyst

 (pH = 5) began curing at a temperature of 1 0 ° C.

Thus, with the composition according to the invention, the onset of the cure could be shifted to a distinctly low temperature, although no acid was used

 Curing catalyst was added.

Example 4:

 Resin Synthesis 2 - Glyoxylic Acid Ethyl Ester / Glivoxylic Acid / Glivoxal Resins Based on i o Melamine (Esters from Example 1)

To 496 g of the solution from Example 1 are added 79.7 g (0.63 mol) of melamine. After neutralization with potassium carbonate (pH 7.3) at 60 ° C for 30min. heated. This dissolves much of the melamine. Then 68.59g glyoxal within 20 min. 15 dropped. After another 5 min. The resin is cooled in a water bath (15 ° C) to room temperature.

The resin contains free aldehyde groups and has a high storage stability at room temperature. The free aldehyde groups in the curing of these resins 0 in addition to the condensation and an addition reaction allows, which increases the reactivity.

Example 5:

 Harzsvnthese 3 - Glvoxylsäureisopropylester- / Glvoxylsäureharze based on melamine 5 (ester from Example 2)

After neutralization, 26.46 g (0.21 mol) of melamine were added to the ester from Example 2 and heated at 60 ° C. for 30 min. touched. A clear resin was obtained, which was cooled down to room temperature in a water bath.

0

 Example 6:

Resin Synthesis 4 - Glvoxylic Acid Ester / Glivoxylic Acid / Glvoxal Resins Based on Melamine (Ester from Example 2) After neutralization, 53.95 g (0.428 mol) of melamine were added to the ester from Example 2 and stirred at 60 ° C. for 30 min. touched. Then 31.3 g of glyoxal were added. After 12min. a clear resin was obtained, which was cooled down to room temperature in a water bath.

The resin contains free aldehyde groups and has a high storage stability at room temperature. The free aldehyde groups in the curing of these resins in addition to the condensation and an addition reaction allows, which increases the reactivity.

Example 7:

 Resin Synthesis 5 - Gliboxylic Acid Ester Resins Based on Melamine (Esters from Example 2)

The concentrated organic phase from Example 2 was neutralized after addition with 100 g of water with potassium carbonate solution and admixed with 8.46 g (0.067 mol) of melamine. After stirring for 1.5 h at 56 ° C., a highly viscous resin was obtained.

Hereinafter, an embodiment of wood-based products will be described.

Example 8 Particleboard with a formaldehyde-free amino resin based on

 Glyoxylic / glyoxylic

The glue resin was prepared as described in Example 1:

To 421.4 g of 50% glyoxylic acid (2.85 mol) is added 462 g of ethanol. After addition of 40 g (0.406 mol) of 37% hydrochloric acid is heated to 55 ° C for 20min. heated. Then the solution is neutralized with 111 g (0.80 mol) of potassium carbonate. From the amount of potassium carbonate, which was needed for neutralization, the degree of esterification can be calculated. This is 57.89% here.

In order to separate off the potassium chloride which forms, a further 400 g of ethanol are added in order to reduce the solubility in salt, and the salt is then filtered off. Finally, the ethanol is distilled off. There are 496g of a solution of glyoxyl acid and glyoxylic acid ethyl ester, which is used directly for resin synthesis. In addition, 19.5 g (0.95 mol) of melamine are added to the solution. After neutralization with potassium carbonate (pH 7.5) at 60 ° C for 60min. heated. Here, the resin clears up completely.

Single-layer chipboards were produced under the following conditions:

Plate structure: single-layered

 Chips: spruce chips (sieve fraction: 0.6> x <5 mm)

 Adhesive: melamine-glyoxylic acid / glyoxylic acid ester resin

Adhesive content: 12% (solid resin based on atro wood)

 Curing accelerator: 2.5% ammonium sulfate: (solid / solid resin)

 Paraffin dispersion: 1, 5% (solid based on atro wood)

 Plate thickness: 13 mm (unpolished)

Target density: 650 kg / m ³

 Pressing temperature: 200 ° C

 Press time: 22 s / mm plate thickness

After preparation, the plates were formatted and conditioned in the normal climate (20 ° C and 65% relative humidity) to equilibrium moisture content. Bulk density, flexural strength and flexural modulus of elasticity (DIN EN 310: 1993), transverse tensile strength (DIN EN 319: 1993) and thickness swelling (EN 317) after 24 h of water storage were determined on the air-conditioned panels. The formaldehyde release of the chipboard was determined by the bottle method according to EN 717-3 after 3 h and 24 h storage and according to the test chamber method (EN 717-1 The results of the mechanical plate properties and the formaldehyde release are listed in Table 1. Mechanical and Hygric Properties of Particle Boards with a Melamine Glyoxylic Acid / Glyoxylic Acid Ester Resin

* Requirements for the mechanical properties of panels for the interior (including furniture) for use in dry areas (type P2)

Table 2: Formaldehyde release (bottle and test chamber method) of chipboard with a melamine-glyoxylic acid / glyoxylic acid ester resin

With the melamine resin, the requirements for the mechanical properties of particleboard type P2 have not yet been reached under the specified production conditions. Since the strength properties of particleboard depend on the density, increasing the plate density can improve the mechanical properties and meet the standard requirements. The formaldehyde release of the panels was very low. With an emission value of 0.02 ppm (EN 717-1, test chamber method), the current limit value of 0.1 ppm set by the Deutsches Institut für Bautechnik (DIBt) in 1994 was clearly undercut.

Claims

Patent claims:

1. Wood-based product or natural fiber composite product made of at least one lignocellulose and / or cellulose-containing material, which is provided with an adhesive and cured or crosslinked in the desired form, characterized in that the adhesive is in the form of an idehyde-free amino, imine and / or Amide component based on glyoxylic acid ester is formed as the aldehydic main component.

2. Wood material product or natural fiber composite material product according to claim 1, characterized in that it is designed in one or more layers or is designed as a multi-layer composite material and the amino, imine and / or amide resin is used in at least one layer.

3. Wood material product or natural fiber composite material product according to claim 1 or 2, characterized in that the amino, imine and / or amide resin is used as a decoration or surface coating or for fastening a decorative layer or wear protection layer.

4. Wood material product or natural fiber composite material product according to one of the preceding claims, characterized in that in addition to lignocellulose and / or cellulose-containing materials, other materials are present.

5. Wood material product or natural fiber composite material product according to one of the preceding claims, characterized in that the amino, imine and / or amide resin is used as the sole adhesive.

6. Wood material product or natural fiber composite material product according to one of claims 1 to 4, characterized in that the amino, imine and / or amide resin is used in combination with formaldehyde-containing or formaldehyde-free organic adhesives.

7. Wood material product or natural fiber composite product according to one of the preceding claims, characterized in that the amino, imine and / or amide resin is used in combination with an inorganic binder.

8. Wood material product or natural fiber composite material product according to one of the preceding claims, characterized in that the wood material product or natural fiber composite material product has functional additives.

Wood product and wood material and natural fiber composite product according to one of the preceding claims, characterized in that the products consist of lignocelluloses chemically modified with these formaldehyde-free amino, imino and / or amide resins.

10. Use of a formaldehyde-free amino resin for producing a wood material product or natural fiber composite product according to one of the preceding claims, produced by a process in which a glyoxylic acid ester is reacted with an amine, an amide or an aromatic hydroxy compound.

11. Use according to claim 10, wherein the glyoxylic acid ester is a glyoxylic acid C-alkyl ester.

12. Use according to claim 10 or 11, wherein the amine or amide is an aminotriazine, urea, a urea derivative, thiourea, a thiourea derivative,

Iminourea, an iminourea derivative, a cyanamide, a diaminoalkane, a diamidoalkane, a polyacrylamide, a plant or animal amine or amide, or a mixture of at least two of these compounds; or the aromatic hydroxy compound is a phenol compound having at least two hydroxy groups.

13. Use according to one of claims 10 to 12, wherein the reaction of the glyoxylic acid ester with the amine, the amide or the aromatic The product obtained from the hydroxy compound is then reacted with a further aldehyde, the aldehyde preferably being a dialdehyde, a trialdehyde, a monoaldehyde such as glyoxylic acid, glycolaldehyde, furfural, or a mixture of at least two of these aldehydes.

5

14. Use according to claim 13, wherein the dialdehyde is glyoxal or a dialdehyde of the formula OHC-(CH ₂ )i- ₃ -CHO.

15. Use according to claim 13 or 14, wherein the amine or amide is a triamino or triamide and the molar ratio of the dialdehyde or trialdehyde to the amine groups or amide groups is in the range of 0.1/3 to 5/3; or the amine or amide is a diamine or diamide and the molar ratio of the dialdehyde or trialdehyde to the amine groups or amide groups is in the range from 0.1/3.9 to 3.9/0.1.

5

16. Use according to one of claims 13 to 15, wherein the resin has free aldehyde groups.

17. Use according to one of claims 10 to 16, comprising

0 - the provision of a formaldehyde-free resin according to one of claims 10 to 16 and

the crosslinking of the resin.

18. Use according to claim 17, wherein no external catalyst is added to the formaldehyde-free resin for crosslinking.

19. Use according to claim 17 or 18, wherein the crosslinking of the resin comprises microwave treatment. 0